Mon, 06 Aug 2012 12:20:14 -0700
6818524: G1: use ergonomic resizing of PLABs
Summary: Employ PLABStats instances to record information about survivor and old PLABs, and use the recorded stats to adjust the sizes of survivor and old PLABS.
Reviewed-by: johnc, ysr
Contributed-by: Brandon Mitchell <brandon@twitter.com>
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.
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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/g1GCPhaseTimes.hpp"
37 #include "gc_implementation/g1/g1Log.hpp"
38 #include "gc_implementation/g1/g1MarkSweep.hpp"
39 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
40 #include "gc_implementation/g1/g1RemSet.inline.hpp"
41 #include "gc_implementation/g1/heapRegion.inline.hpp"
42 #include "gc_implementation/g1/heapRegionRemSet.hpp"
43 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
44 #include "gc_implementation/g1/vm_operations_g1.hpp"
45 #include "gc_implementation/shared/isGCActiveMark.hpp"
46 #include "memory/gcLocker.inline.hpp"
47 #include "memory/genOopClosures.inline.hpp"
48 #include "memory/generationSpec.hpp"
49 #include "memory/referenceProcessor.hpp"
50 #include "oops/oop.inline.hpp"
51 #include "oops/oop.pcgc.inline.hpp"
52 #include "runtime/aprofiler.hpp"
53 #include "runtime/vmThread.hpp"
55 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
57 // turn it on so that the contents of the young list (scan-only /
58 // to-be-collected) are printed at "strategic" points before / during
59 // / after the collection --- this is useful for debugging
60 #define YOUNG_LIST_VERBOSE 0
61 // CURRENT STATUS
62 // This file is under construction. Search for "FIXME".
64 // INVARIANTS/NOTES
65 //
66 // All allocation activity covered by the G1CollectedHeap interface is
67 // serialized by acquiring the HeapLock. This happens in mem_allocate
68 // and allocate_new_tlab, which are the "entry" points to the
69 // allocation code from the rest of the JVM. (Note that this does not
70 // apply to TLAB allocation, which is not part of this interface: it
71 // is done by clients of this interface.)
73 // Notes on implementation of parallelism in different tasks.
74 //
75 // G1ParVerifyTask uses heap_region_par_iterate_chunked() for parallelism.
76 // The number of GC workers is passed to heap_region_par_iterate_chunked().
77 // It does use run_task() which sets _n_workers in the task.
78 // G1ParTask executes g1_process_strong_roots() ->
79 // SharedHeap::process_strong_roots() which calls eventuall to
80 // CardTableModRefBS::par_non_clean_card_iterate_work() which uses
81 // SequentialSubTasksDone. SharedHeap::process_strong_roots() also
82 // directly uses SubTasksDone (_process_strong_tasks field in SharedHeap).
83 //
85 // Local to this file.
87 class RefineCardTableEntryClosure: public CardTableEntryClosure {
88 SuspendibleThreadSet* _sts;
89 G1RemSet* _g1rs;
90 ConcurrentG1Refine* _cg1r;
91 bool _concurrent;
92 public:
93 RefineCardTableEntryClosure(SuspendibleThreadSet* sts,
94 G1RemSet* g1rs,
95 ConcurrentG1Refine* cg1r) :
96 _sts(sts), _g1rs(g1rs), _cg1r(cg1r), _concurrent(true)
97 {}
98 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
99 bool oops_into_cset = _g1rs->concurrentRefineOneCard(card_ptr, worker_i, false);
100 // This path is executed by the concurrent refine or mutator threads,
101 // concurrently, and so we do not care if card_ptr contains references
102 // that point into the collection set.
103 assert(!oops_into_cset, "should be");
105 if (_concurrent && _sts->should_yield()) {
106 // Caller will actually yield.
107 return false;
108 }
109 // Otherwise, we finished successfully; return true.
110 return true;
111 }
112 void set_concurrent(bool b) { _concurrent = b; }
113 };
116 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure {
117 int _calls;
118 G1CollectedHeap* _g1h;
119 CardTableModRefBS* _ctbs;
120 int _histo[256];
121 public:
122 ClearLoggedCardTableEntryClosure() :
123 _calls(0)
124 {
125 _g1h = G1CollectedHeap::heap();
126 _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
127 for (int i = 0; i < 256; i++) _histo[i] = 0;
128 }
129 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
130 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
131 _calls++;
132 unsigned char* ujb = (unsigned char*)card_ptr;
133 int ind = (int)(*ujb);
134 _histo[ind]++;
135 *card_ptr = -1;
136 }
137 return true;
138 }
139 int calls() { return _calls; }
140 void print_histo() {
141 gclog_or_tty->print_cr("Card table value histogram:");
142 for (int i = 0; i < 256; i++) {
143 if (_histo[i] != 0) {
144 gclog_or_tty->print_cr(" %d: %d", i, _histo[i]);
145 }
146 }
147 }
148 };
150 class RedirtyLoggedCardTableEntryClosure: public CardTableEntryClosure {
151 int _calls;
152 G1CollectedHeap* _g1h;
153 CardTableModRefBS* _ctbs;
154 public:
155 RedirtyLoggedCardTableEntryClosure() :
156 _calls(0)
157 {
158 _g1h = G1CollectedHeap::heap();
159 _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
160 }
161 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
162 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
163 _calls++;
164 *card_ptr = 0;
165 }
166 return true;
167 }
168 int calls() { return _calls; }
169 };
171 class RedirtyLoggedCardTableEntryFastClosure : public CardTableEntryClosure {
172 public:
173 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
174 *card_ptr = CardTableModRefBS::dirty_card_val();
175 return true;
176 }
177 };
179 YoungList::YoungList(G1CollectedHeap* g1h) :
180 _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0),
181 _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) {
182 guarantee(check_list_empty(false), "just making sure...");
183 }
185 void YoungList::push_region(HeapRegion *hr) {
186 assert(!hr->is_young(), "should not already be young");
187 assert(hr->get_next_young_region() == NULL, "cause it should!");
189 hr->set_next_young_region(_head);
190 _head = hr;
192 _g1h->g1_policy()->set_region_eden(hr, (int) _length);
193 ++_length;
194 }
196 void YoungList::add_survivor_region(HeapRegion* hr) {
197 assert(hr->is_survivor(), "should be flagged as survivor region");
198 assert(hr->get_next_young_region() == NULL, "cause it should!");
200 hr->set_next_young_region(_survivor_head);
201 if (_survivor_head == NULL) {
202 _survivor_tail = hr;
203 }
204 _survivor_head = hr;
205 ++_survivor_length;
206 }
208 void YoungList::empty_list(HeapRegion* list) {
209 while (list != NULL) {
210 HeapRegion* next = list->get_next_young_region();
211 list->set_next_young_region(NULL);
212 list->uninstall_surv_rate_group();
213 list->set_not_young();
214 list = next;
215 }
216 }
218 void YoungList::empty_list() {
219 assert(check_list_well_formed(), "young list should be well formed");
221 empty_list(_head);
222 _head = NULL;
223 _length = 0;
225 empty_list(_survivor_head);
226 _survivor_head = NULL;
227 _survivor_tail = NULL;
228 _survivor_length = 0;
230 _last_sampled_rs_lengths = 0;
232 assert(check_list_empty(false), "just making sure...");
233 }
235 bool YoungList::check_list_well_formed() {
236 bool ret = true;
238 uint length = 0;
239 HeapRegion* curr = _head;
240 HeapRegion* last = NULL;
241 while (curr != NULL) {
242 if (!curr->is_young()) {
243 gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
244 "incorrectly tagged (y: %d, surv: %d)",
245 curr->bottom(), curr->end(),
246 curr->is_young(), curr->is_survivor());
247 ret = false;
248 }
249 ++length;
250 last = curr;
251 curr = curr->get_next_young_region();
252 }
253 ret = ret && (length == _length);
255 if (!ret) {
256 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
257 gclog_or_tty->print_cr("### list has %u entries, _length is %u",
258 length, _length);
259 }
261 return ret;
262 }
264 bool YoungList::check_list_empty(bool check_sample) {
265 bool ret = true;
267 if (_length != 0) {
268 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u",
269 _length);
270 ret = false;
271 }
272 if (check_sample && _last_sampled_rs_lengths != 0) {
273 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
274 ret = false;
275 }
276 if (_head != NULL) {
277 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
278 ret = false;
279 }
280 if (!ret) {
281 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
282 }
284 return ret;
285 }
287 void
288 YoungList::rs_length_sampling_init() {
289 _sampled_rs_lengths = 0;
290 _curr = _head;
291 }
293 bool
294 YoungList::rs_length_sampling_more() {
295 return _curr != NULL;
296 }
298 void
299 YoungList::rs_length_sampling_next() {
300 assert( _curr != NULL, "invariant" );
301 size_t rs_length = _curr->rem_set()->occupied();
303 _sampled_rs_lengths += rs_length;
305 // The current region may not yet have been added to the
306 // incremental collection set (it gets added when it is
307 // retired as the current allocation region).
308 if (_curr->in_collection_set()) {
309 // Update the collection set policy information for this region
310 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
311 }
313 _curr = _curr->get_next_young_region();
314 if (_curr == NULL) {
315 _last_sampled_rs_lengths = _sampled_rs_lengths;
316 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
317 }
318 }
320 void
321 YoungList::reset_auxilary_lists() {
322 guarantee( is_empty(), "young list should be empty" );
323 assert(check_list_well_formed(), "young list should be well formed");
325 // Add survivor regions to SurvRateGroup.
326 _g1h->g1_policy()->note_start_adding_survivor_regions();
327 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
329 int young_index_in_cset = 0;
330 for (HeapRegion* curr = _survivor_head;
331 curr != NULL;
332 curr = curr->get_next_young_region()) {
333 _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
335 // The region is a non-empty survivor so let's add it to
336 // the incremental collection set for the next evacuation
337 // pause.
338 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
339 young_index_in_cset += 1;
340 }
341 assert((uint) young_index_in_cset == _survivor_length, "post-condition");
342 _g1h->g1_policy()->note_stop_adding_survivor_regions();
344 _head = _survivor_head;
345 _length = _survivor_length;
346 if (_survivor_head != NULL) {
347 assert(_survivor_tail != NULL, "cause it shouldn't be");
348 assert(_survivor_length > 0, "invariant");
349 _survivor_tail->set_next_young_region(NULL);
350 }
352 // Don't clear the survivor list handles until the start of
353 // the next evacuation pause - we need it in order to re-tag
354 // the survivor regions from this evacuation pause as 'young'
355 // at the start of the next.
357 _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
359 assert(check_list_well_formed(), "young list should be well formed");
360 }
362 void YoungList::print() {
363 HeapRegion* lists[] = {_head, _survivor_head};
364 const char* names[] = {"YOUNG", "SURVIVOR"};
366 for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) {
367 gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
368 HeapRegion *curr = lists[list];
369 if (curr == NULL)
370 gclog_or_tty->print_cr(" empty");
371 while (curr != NULL) {
372 gclog_or_tty->print_cr(" "HR_FORMAT", P: "PTR_FORMAT "N: "PTR_FORMAT", age: %4d",
373 HR_FORMAT_PARAMS(curr),
374 curr->prev_top_at_mark_start(),
375 curr->next_top_at_mark_start(),
376 curr->age_in_surv_rate_group_cond());
377 curr = curr->get_next_young_region();
378 }
379 }
381 gclog_or_tty->print_cr("");
382 }
384 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
385 {
386 // Claim the right to put the region on the dirty cards region list
387 // by installing a self pointer.
388 HeapRegion* next = hr->get_next_dirty_cards_region();
389 if (next == NULL) {
390 HeapRegion* res = (HeapRegion*)
391 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
392 NULL);
393 if (res == NULL) {
394 HeapRegion* head;
395 do {
396 // Put the region to the dirty cards region list.
397 head = _dirty_cards_region_list;
398 next = (HeapRegion*)
399 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
400 if (next == head) {
401 assert(hr->get_next_dirty_cards_region() == hr,
402 "hr->get_next_dirty_cards_region() != hr");
403 if (next == NULL) {
404 // The last region in the list points to itself.
405 hr->set_next_dirty_cards_region(hr);
406 } else {
407 hr->set_next_dirty_cards_region(next);
408 }
409 }
410 } while (next != head);
411 }
412 }
413 }
415 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
416 {
417 HeapRegion* head;
418 HeapRegion* hr;
419 do {
420 head = _dirty_cards_region_list;
421 if (head == NULL) {
422 return NULL;
423 }
424 HeapRegion* new_head = head->get_next_dirty_cards_region();
425 if (head == new_head) {
426 // The last region.
427 new_head = NULL;
428 }
429 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
430 head);
431 } while (hr != head);
432 assert(hr != NULL, "invariant");
433 hr->set_next_dirty_cards_region(NULL);
434 return hr;
435 }
437 void G1CollectedHeap::stop_conc_gc_threads() {
438 _cg1r->stop();
439 _cmThread->stop();
440 }
442 #ifdef ASSERT
443 // A region is added to the collection set as it is retired
444 // so an address p can point to a region which will be in the
445 // collection set but has not yet been retired. This method
446 // therefore is only accurate during a GC pause after all
447 // regions have been retired. It is used for debugging
448 // to check if an nmethod has references to objects that can
449 // be move during a partial collection. Though it can be
450 // inaccurate, it is sufficient for G1 because the conservative
451 // implementation of is_scavengable() for G1 will indicate that
452 // all nmethods must be scanned during a partial collection.
453 bool G1CollectedHeap::is_in_partial_collection(const void* p) {
454 HeapRegion* hr = heap_region_containing(p);
455 return hr != NULL && hr->in_collection_set();
456 }
457 #endif
459 // Returns true if the reference points to an object that
460 // can move in an incremental collecction.
461 bool G1CollectedHeap::is_scavengable(const void* p) {
462 G1CollectedHeap* g1h = G1CollectedHeap::heap();
463 G1CollectorPolicy* g1p = g1h->g1_policy();
464 HeapRegion* hr = heap_region_containing(p);
465 if (hr == NULL) {
466 // perm gen (or null)
467 return false;
468 } else {
469 return !hr->isHumongous();
470 }
471 }
473 void G1CollectedHeap::check_ct_logs_at_safepoint() {
474 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
475 CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
477 // Count the dirty cards at the start.
478 CountNonCleanMemRegionClosure count1(this);
479 ct_bs->mod_card_iterate(&count1);
480 int orig_count = count1.n();
482 // First clear the logged cards.
483 ClearLoggedCardTableEntryClosure clear;
484 dcqs.set_closure(&clear);
485 dcqs.apply_closure_to_all_completed_buffers();
486 dcqs.iterate_closure_all_threads(false);
487 clear.print_histo();
489 // Now ensure that there's no dirty cards.
490 CountNonCleanMemRegionClosure count2(this);
491 ct_bs->mod_card_iterate(&count2);
492 if (count2.n() != 0) {
493 gclog_or_tty->print_cr("Card table has %d entries; %d originally",
494 count2.n(), orig_count);
495 }
496 guarantee(count2.n() == 0, "Card table should be clean.");
498 RedirtyLoggedCardTableEntryClosure redirty;
499 JavaThread::dirty_card_queue_set().set_closure(&redirty);
500 dcqs.apply_closure_to_all_completed_buffers();
501 dcqs.iterate_closure_all_threads(false);
502 gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
503 clear.calls(), orig_count);
504 guarantee(redirty.calls() == clear.calls(),
505 "Or else mechanism is broken.");
507 CountNonCleanMemRegionClosure count3(this);
508 ct_bs->mod_card_iterate(&count3);
509 if (count3.n() != orig_count) {
510 gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
511 orig_count, count3.n());
512 guarantee(count3.n() >= orig_count, "Should have restored them all.");
513 }
515 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
516 }
518 // Private class members.
520 G1CollectedHeap* G1CollectedHeap::_g1h;
522 // Private methods.
524 HeapRegion*
525 G1CollectedHeap::new_region_try_secondary_free_list() {
526 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
527 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
528 if (!_secondary_free_list.is_empty()) {
529 if (G1ConcRegionFreeingVerbose) {
530 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
531 "secondary_free_list has %u entries",
532 _secondary_free_list.length());
533 }
534 // It looks as if there are free regions available on the
535 // secondary_free_list. Let's move them to the free_list and try
536 // again to allocate from it.
537 append_secondary_free_list();
539 assert(!_free_list.is_empty(), "if the secondary_free_list was not "
540 "empty we should have moved at least one entry to the free_list");
541 HeapRegion* res = _free_list.remove_head();
542 if (G1ConcRegionFreeingVerbose) {
543 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
544 "allocated "HR_FORMAT" from secondary_free_list",
545 HR_FORMAT_PARAMS(res));
546 }
547 return res;
548 }
550 // Wait here until we get notifed either when (a) there are no
551 // more free regions coming or (b) some regions have been moved on
552 // the secondary_free_list.
553 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
554 }
556 if (G1ConcRegionFreeingVerbose) {
557 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
558 "could not allocate from secondary_free_list");
559 }
560 return NULL;
561 }
563 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool do_expand) {
564 assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords,
565 "the only time we use this to allocate a humongous region is "
566 "when we are allocating a single humongous region");
568 HeapRegion* res;
569 if (G1StressConcRegionFreeing) {
570 if (!_secondary_free_list.is_empty()) {
571 if (G1ConcRegionFreeingVerbose) {
572 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
573 "forced to look at the secondary_free_list");
574 }
575 res = new_region_try_secondary_free_list();
576 if (res != NULL) {
577 return res;
578 }
579 }
580 }
581 res = _free_list.remove_head_or_null();
582 if (res == NULL) {
583 if (G1ConcRegionFreeingVerbose) {
584 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
585 "res == NULL, trying the secondary_free_list");
586 }
587 res = new_region_try_secondary_free_list();
588 }
589 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
590 // Currently, only attempts to allocate GC alloc regions set
591 // do_expand to true. So, we should only reach here during a
592 // safepoint. If this assumption changes we might have to
593 // reconsider the use of _expand_heap_after_alloc_failure.
594 assert(SafepointSynchronize::is_at_safepoint(), "invariant");
596 ergo_verbose1(ErgoHeapSizing,
597 "attempt heap expansion",
598 ergo_format_reason("region allocation request failed")
599 ergo_format_byte("allocation request"),
600 word_size * HeapWordSize);
601 if (expand(word_size * HeapWordSize)) {
602 // Given that expand() succeeded in expanding the heap, and we
603 // always expand the heap by an amount aligned to the heap
604 // region size, the free list should in theory not be empty. So
605 // it would probably be OK to use remove_head(). But the extra
606 // check for NULL is unlikely to be a performance issue here (we
607 // just expanded the heap!) so let's just be conservative and
608 // use remove_head_or_null().
609 res = _free_list.remove_head_or_null();
610 } else {
611 _expand_heap_after_alloc_failure = false;
612 }
613 }
614 return res;
615 }
617 uint G1CollectedHeap::humongous_obj_allocate_find_first(uint num_regions,
618 size_t word_size) {
619 assert(isHumongous(word_size), "word_size should be humongous");
620 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
622 uint first = G1_NULL_HRS_INDEX;
623 if (num_regions == 1) {
624 // Only one region to allocate, no need to go through the slower
625 // path. The caller will attempt the expasion if this fails, so
626 // let's not try to expand here too.
627 HeapRegion* hr = new_region(word_size, false /* do_expand */);
628 if (hr != NULL) {
629 first = hr->hrs_index();
630 } else {
631 first = G1_NULL_HRS_INDEX;
632 }
633 } else {
634 // We can't allocate humongous regions while cleanupComplete() is
635 // running, since some of the regions we find to be empty might not
636 // yet be added to the free list and it is not straightforward to
637 // know which list they are on so that we can remove them. Note
638 // that we only need to do this if we need to allocate more than
639 // one region to satisfy the current humongous allocation
640 // request. If we are only allocating one region we use the common
641 // region allocation code (see above).
642 wait_while_free_regions_coming();
643 append_secondary_free_list_if_not_empty_with_lock();
645 if (free_regions() >= num_regions) {
646 first = _hrs.find_contiguous(num_regions);
647 if (first != G1_NULL_HRS_INDEX) {
648 for (uint i = first; i < first + num_regions; ++i) {
649 HeapRegion* hr = region_at(i);
650 assert(hr->is_empty(), "sanity");
651 assert(is_on_master_free_list(hr), "sanity");
652 hr->set_pending_removal(true);
653 }
654 _free_list.remove_all_pending(num_regions);
655 }
656 }
657 }
658 return first;
659 }
661 HeapWord*
662 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
663 uint num_regions,
664 size_t word_size) {
665 assert(first != G1_NULL_HRS_INDEX, "pre-condition");
666 assert(isHumongous(word_size), "word_size should be humongous");
667 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
669 // Index of last region in the series + 1.
670 uint last = first + num_regions;
672 // We need to initialize the region(s) we just discovered. This is
673 // a bit tricky given that it can happen concurrently with
674 // refinement threads refining cards on these regions and
675 // potentially wanting to refine the BOT as they are scanning
676 // those cards (this can happen shortly after a cleanup; see CR
677 // 6991377). So we have to set up the region(s) carefully and in
678 // a specific order.
680 // The word size sum of all the regions we will allocate.
681 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
682 assert(word_size <= word_size_sum, "sanity");
684 // This will be the "starts humongous" region.
685 HeapRegion* first_hr = region_at(first);
686 // The header of the new object will be placed at the bottom of
687 // the first region.
688 HeapWord* new_obj = first_hr->bottom();
689 // This will be the new end of the first region in the series that
690 // should also match the end of the last region in the seriers.
691 HeapWord* new_end = new_obj + word_size_sum;
692 // This will be the new top of the first region that will reflect
693 // this allocation.
694 HeapWord* new_top = new_obj + word_size;
696 // First, we need to zero the header of the space that we will be
697 // allocating. When we update top further down, some refinement
698 // threads might try to scan the region. By zeroing the header we
699 // ensure that any thread that will try to scan the region will
700 // come across the zero klass word and bail out.
701 //
702 // NOTE: It would not have been correct to have used
703 // CollectedHeap::fill_with_object() and make the space look like
704 // an int array. The thread that is doing the allocation will
705 // later update the object header to a potentially different array
706 // type and, for a very short period of time, the klass and length
707 // fields will be inconsistent. This could cause a refinement
708 // thread to calculate the object size incorrectly.
709 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
711 // We will set up the first region as "starts humongous". This
712 // will also update the BOT covering all the regions to reflect
713 // that there is a single object that starts at the bottom of the
714 // first region.
715 first_hr->set_startsHumongous(new_top, new_end);
717 // Then, if there are any, we will set up the "continues
718 // humongous" regions.
719 HeapRegion* hr = NULL;
720 for (uint i = first + 1; i < last; ++i) {
721 hr = region_at(i);
722 hr->set_continuesHumongous(first_hr);
723 }
724 // If we have "continues humongous" regions (hr != NULL), then the
725 // end of the last one should match new_end.
726 assert(hr == NULL || hr->end() == new_end, "sanity");
728 // Up to this point no concurrent thread would have been able to
729 // do any scanning on any region in this series. All the top
730 // fields still point to bottom, so the intersection between
731 // [bottom,top] and [card_start,card_end] will be empty. Before we
732 // update the top fields, we'll do a storestore to make sure that
733 // no thread sees the update to top before the zeroing of the
734 // object header and the BOT initialization.
735 OrderAccess::storestore();
737 // Now that the BOT and the object header have been initialized,
738 // we can update top of the "starts humongous" region.
739 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
740 "new_top should be in this region");
741 first_hr->set_top(new_top);
742 if (_hr_printer.is_active()) {
743 HeapWord* bottom = first_hr->bottom();
744 HeapWord* end = first_hr->orig_end();
745 if ((first + 1) == last) {
746 // the series has a single humongous region
747 _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
748 } else {
749 // the series has more than one humongous regions
750 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
751 }
752 }
754 // Now, we will update the top fields of the "continues humongous"
755 // regions. The reason we need to do this is that, otherwise,
756 // these regions would look empty and this will confuse parts of
757 // G1. For example, the code that looks for a consecutive number
758 // of empty regions will consider them empty and try to
759 // re-allocate them. We can extend is_empty() to also include
760 // !continuesHumongous(), but it is easier to just update the top
761 // fields here. The way we set top for all regions (i.e., top ==
762 // end for all regions but the last one, top == new_top for the
763 // last one) is actually used when we will free up the humongous
764 // region in free_humongous_region().
765 hr = NULL;
766 for (uint i = first + 1; i < last; ++i) {
767 hr = region_at(i);
768 if ((i + 1) == last) {
769 // last continues humongous region
770 assert(hr->bottom() < new_top && new_top <= hr->end(),
771 "new_top should fall on this region");
772 hr->set_top(new_top);
773 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
774 } else {
775 // not last one
776 assert(new_top > hr->end(), "new_top should be above this region");
777 hr->set_top(hr->end());
778 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
779 }
780 }
781 // If we have continues humongous regions (hr != NULL), then the
782 // end of the last one should match new_end and its top should
783 // match new_top.
784 assert(hr == NULL ||
785 (hr->end() == new_end && hr->top() == new_top), "sanity");
787 assert(first_hr->used() == word_size * HeapWordSize, "invariant");
788 _summary_bytes_used += first_hr->used();
789 _humongous_set.add(first_hr);
791 return new_obj;
792 }
794 // If could fit into free regions w/o expansion, try.
795 // Otherwise, if can expand, do so.
796 // Otherwise, if using ex regions might help, try with ex given back.
797 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
798 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
800 verify_region_sets_optional();
802 size_t word_size_rounded = round_to(word_size, HeapRegion::GrainWords);
803 uint num_regions = (uint) (word_size_rounded / HeapRegion::GrainWords);
804 uint x_num = expansion_regions();
805 uint fs = _hrs.free_suffix();
806 uint first = humongous_obj_allocate_find_first(num_regions, word_size);
807 if (first == G1_NULL_HRS_INDEX) {
808 // The only thing we can do now is attempt expansion.
809 if (fs + x_num >= num_regions) {
810 // If the number of regions we're trying to allocate for this
811 // object is at most the number of regions in the free suffix,
812 // then the call to humongous_obj_allocate_find_first() above
813 // should have succeeded and we wouldn't be here.
814 //
815 // We should only be trying to expand when the free suffix is
816 // not sufficient for the object _and_ we have some expansion
817 // room available.
818 assert(num_regions > fs, "earlier allocation should have succeeded");
820 ergo_verbose1(ErgoHeapSizing,
821 "attempt heap expansion",
822 ergo_format_reason("humongous allocation request failed")
823 ergo_format_byte("allocation request"),
824 word_size * HeapWordSize);
825 if (expand((num_regions - fs) * HeapRegion::GrainBytes)) {
826 // Even though the heap was expanded, it might not have
827 // reached the desired size. So, we cannot assume that the
828 // allocation will succeed.
829 first = humongous_obj_allocate_find_first(num_regions, word_size);
830 }
831 }
832 }
834 HeapWord* result = NULL;
835 if (first != G1_NULL_HRS_INDEX) {
836 result =
837 humongous_obj_allocate_initialize_regions(first, num_regions, word_size);
838 assert(result != NULL, "it should always return a valid result");
840 // A successful humongous object allocation changes the used space
841 // information of the old generation so we need to recalculate the
842 // sizes and update the jstat counters here.
843 g1mm()->update_sizes();
844 }
846 verify_region_sets_optional();
848 return result;
849 }
851 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
852 assert_heap_not_locked_and_not_at_safepoint();
853 assert(!isHumongous(word_size), "we do not allow humongous TLABs");
855 unsigned int dummy_gc_count_before;
856 return attempt_allocation(word_size, &dummy_gc_count_before);
857 }
859 HeapWord*
860 G1CollectedHeap::mem_allocate(size_t word_size,
861 bool* gc_overhead_limit_was_exceeded) {
862 assert_heap_not_locked_and_not_at_safepoint();
864 // Loop until the allocation is satisified, or unsatisfied after GC.
865 for (int try_count = 1; /* we'll return */; try_count += 1) {
866 unsigned int gc_count_before;
868 HeapWord* result = NULL;
869 if (!isHumongous(word_size)) {
870 result = attempt_allocation(word_size, &gc_count_before);
871 } else {
872 result = attempt_allocation_humongous(word_size, &gc_count_before);
873 }
874 if (result != NULL) {
875 return result;
876 }
878 // Create the garbage collection operation...
879 VM_G1CollectForAllocation op(gc_count_before, word_size);
880 // ...and get the VM thread to execute it.
881 VMThread::execute(&op);
883 if (op.prologue_succeeded() && op.pause_succeeded()) {
884 // If the operation was successful we'll return the result even
885 // if it is NULL. If the allocation attempt failed immediately
886 // after a Full GC, it's unlikely we'll be able to allocate now.
887 HeapWord* result = op.result();
888 if (result != NULL && !isHumongous(word_size)) {
889 // Allocations that take place on VM operations do not do any
890 // card dirtying and we have to do it here. We only have to do
891 // this for non-humongous allocations, though.
892 dirty_young_block(result, word_size);
893 }
894 return result;
895 } else {
896 assert(op.result() == NULL,
897 "the result should be NULL if the VM op did not succeed");
898 }
900 // Give a warning if we seem to be looping forever.
901 if ((QueuedAllocationWarningCount > 0) &&
902 (try_count % QueuedAllocationWarningCount == 0)) {
903 warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
904 }
905 }
907 ShouldNotReachHere();
908 return NULL;
909 }
911 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
912 unsigned int *gc_count_before_ret) {
913 // Make sure you read the note in attempt_allocation_humongous().
915 assert_heap_not_locked_and_not_at_safepoint();
916 assert(!isHumongous(word_size), "attempt_allocation_slow() should not "
917 "be called for humongous allocation requests");
919 // We should only get here after the first-level allocation attempt
920 // (attempt_allocation()) failed to allocate.
922 // We will loop until a) we manage to successfully perform the
923 // allocation or b) we successfully schedule a collection which
924 // fails to perform the allocation. b) is the only case when we'll
925 // return NULL.
926 HeapWord* result = NULL;
927 for (int try_count = 1; /* we'll return */; try_count += 1) {
928 bool should_try_gc;
929 unsigned int gc_count_before;
931 {
932 MutexLockerEx x(Heap_lock);
934 result = _mutator_alloc_region.attempt_allocation_locked(word_size,
935 false /* bot_updates */);
936 if (result != NULL) {
937 return result;
938 }
940 // If we reach here, attempt_allocation_locked() above failed to
941 // allocate a new region. So the mutator alloc region should be NULL.
942 assert(_mutator_alloc_region.get() == NULL, "only way to get here");
944 if (GC_locker::is_active_and_needs_gc()) {
945 if (g1_policy()->can_expand_young_list()) {
946 // No need for an ergo verbose message here,
947 // can_expand_young_list() does this when it returns true.
948 result = _mutator_alloc_region.attempt_allocation_force(word_size,
949 false /* bot_updates */);
950 if (result != NULL) {
951 return result;
952 }
953 }
954 should_try_gc = false;
955 } else {
956 // The GCLocker may not be active but the GCLocker initiated
957 // GC may not yet have been performed (GCLocker::needs_gc()
958 // returns true). In this case we do not try this GC and
959 // wait until the GCLocker initiated GC is performed, and
960 // then retry the allocation.
961 if (GC_locker::needs_gc()) {
962 should_try_gc = false;
963 } else {
964 // Read the GC count while still holding the Heap_lock.
965 gc_count_before = total_collections();
966 should_try_gc = true;
967 }
968 }
969 }
971 if (should_try_gc) {
972 bool succeeded;
973 result = do_collection_pause(word_size, gc_count_before, &succeeded);
974 if (result != NULL) {
975 assert(succeeded, "only way to get back a non-NULL result");
976 return result;
977 }
979 if (succeeded) {
980 // If we get here we successfully scheduled a collection which
981 // failed to allocate. No point in trying to allocate
982 // further. We'll just return NULL.
983 MutexLockerEx x(Heap_lock);
984 *gc_count_before_ret = total_collections();
985 return NULL;
986 }
987 } else {
988 // The GCLocker is either active or the GCLocker initiated
989 // GC has not yet been performed. Stall until it is and
990 // then retry the allocation.
991 GC_locker::stall_until_clear();
992 }
994 // We can reach here if we were unsuccessul in scheduling a
995 // collection (because another thread beat us to it) or if we were
996 // stalled due to the GC locker. In either can we should retry the
997 // allocation attempt in case another thread successfully
998 // performed a collection and reclaimed enough space. We do the
999 // first attempt (without holding the Heap_lock) here and the
1000 // follow-on attempt will be at the start of the next loop
1001 // iteration (after taking the Heap_lock).
1002 result = _mutator_alloc_region.attempt_allocation(word_size,
1003 false /* bot_updates */);
1004 if (result != NULL) {
1005 return result;
1006 }
1008 // Give a warning if we seem to be looping forever.
1009 if ((QueuedAllocationWarningCount > 0) &&
1010 (try_count % QueuedAllocationWarningCount == 0)) {
1011 warning("G1CollectedHeap::attempt_allocation_slow() "
1012 "retries %d times", try_count);
1013 }
1014 }
1016 ShouldNotReachHere();
1017 return NULL;
1018 }
1020 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
1021 unsigned int * gc_count_before_ret) {
1022 // The structure of this method has a lot of similarities to
1023 // attempt_allocation_slow(). The reason these two were not merged
1024 // into a single one is that such a method would require several "if
1025 // allocation is not humongous do this, otherwise do that"
1026 // conditional paths which would obscure its flow. In fact, an early
1027 // version of this code did use a unified method which was harder to
1028 // follow and, as a result, it had subtle bugs that were hard to
1029 // track down. So keeping these two methods separate allows each to
1030 // be more readable. It will be good to keep these two in sync as
1031 // much as possible.
1033 assert_heap_not_locked_and_not_at_safepoint();
1034 assert(isHumongous(word_size), "attempt_allocation_humongous() "
1035 "should only be called for humongous allocations");
1037 // Humongous objects can exhaust the heap quickly, so we should check if we
1038 // need to start a marking cycle at each humongous object allocation. We do
1039 // the check before we do the actual allocation. The reason for doing it
1040 // before the allocation is that we avoid having to keep track of the newly
1041 // allocated memory while we do a GC.
1042 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
1043 word_size)) {
1044 collect(GCCause::_g1_humongous_allocation);
1045 }
1047 // We will loop until a) we manage to successfully perform the
1048 // allocation or b) we successfully schedule a collection which
1049 // fails to perform the allocation. b) is the only case when we'll
1050 // return NULL.
1051 HeapWord* result = NULL;
1052 for (int try_count = 1; /* we'll return */; try_count += 1) {
1053 bool should_try_gc;
1054 unsigned int gc_count_before;
1056 {
1057 MutexLockerEx x(Heap_lock);
1059 // Given that humongous objects are not allocated in young
1060 // regions, we'll first try to do the allocation without doing a
1061 // collection hoping that there's enough space in the heap.
1062 result = humongous_obj_allocate(word_size);
1063 if (result != NULL) {
1064 return result;
1065 }
1067 if (GC_locker::is_active_and_needs_gc()) {
1068 should_try_gc = false;
1069 } else {
1070 // The GCLocker may not be active but the GCLocker initiated
1071 // GC may not yet have been performed (GCLocker::needs_gc()
1072 // returns true). In this case we do not try this GC and
1073 // wait until the GCLocker initiated GC is performed, and
1074 // then retry the allocation.
1075 if (GC_locker::needs_gc()) {
1076 should_try_gc = false;
1077 } else {
1078 // Read the GC count while still holding the Heap_lock.
1079 gc_count_before = total_collections();
1080 should_try_gc = true;
1081 }
1082 }
1083 }
1085 if (should_try_gc) {
1086 // If we failed to allocate the humongous object, we should try to
1087 // do a collection pause (if we're allowed) in case it reclaims
1088 // enough space for the allocation to succeed after the pause.
1090 bool succeeded;
1091 result = do_collection_pause(word_size, gc_count_before, &succeeded);
1092 if (result != NULL) {
1093 assert(succeeded, "only way to get back a non-NULL result");
1094 return result;
1095 }
1097 if (succeeded) {
1098 // If we get here we successfully scheduled a collection which
1099 // failed to allocate. No point in trying to allocate
1100 // further. We'll just return NULL.
1101 MutexLockerEx x(Heap_lock);
1102 *gc_count_before_ret = total_collections();
1103 return NULL;
1104 }
1105 } else {
1106 // The GCLocker is either active or the GCLocker initiated
1107 // GC has not yet been performed. Stall until it is and
1108 // then retry the allocation.
1109 GC_locker::stall_until_clear();
1110 }
1112 // We can reach here if we were unsuccessul in scheduling a
1113 // collection (because another thread beat us to it) or if we were
1114 // stalled due to the GC locker. In either can we should retry the
1115 // allocation attempt in case another thread successfully
1116 // performed a collection and reclaimed enough space. Give a
1117 // warning if we seem to be looping forever.
1119 if ((QueuedAllocationWarningCount > 0) &&
1120 (try_count % QueuedAllocationWarningCount == 0)) {
1121 warning("G1CollectedHeap::attempt_allocation_humongous() "
1122 "retries %d times", try_count);
1123 }
1124 }
1126 ShouldNotReachHere();
1127 return NULL;
1128 }
1130 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1131 bool expect_null_mutator_alloc_region) {
1132 assert_at_safepoint(true /* should_be_vm_thread */);
1133 assert(_mutator_alloc_region.get() == NULL ||
1134 !expect_null_mutator_alloc_region,
1135 "the current alloc region was unexpectedly found to be non-NULL");
1137 if (!isHumongous(word_size)) {
1138 return _mutator_alloc_region.attempt_allocation_locked(word_size,
1139 false /* bot_updates */);
1140 } else {
1141 HeapWord* result = humongous_obj_allocate(word_size);
1142 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1143 g1_policy()->set_initiate_conc_mark_if_possible();
1144 }
1145 return result;
1146 }
1148 ShouldNotReachHere();
1149 }
1151 class PostMCRemSetClearClosure: public HeapRegionClosure {
1152 G1CollectedHeap* _g1h;
1153 ModRefBarrierSet* _mr_bs;
1154 public:
1155 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1156 _g1h(g1h), _mr_bs(mr_bs) { }
1157 bool doHeapRegion(HeapRegion* r) {
1158 if (r->continuesHumongous()) {
1159 return false;
1160 }
1161 _g1h->reset_gc_time_stamps(r);
1162 HeapRegionRemSet* hrrs = r->rem_set();
1163 if (hrrs != NULL) hrrs->clear();
1164 // You might think here that we could clear just the cards
1165 // corresponding to the used region. But no: if we leave a dirty card
1166 // in a region we might allocate into, then it would prevent that card
1167 // from being enqueued, and cause it to be missed.
1168 // Re: the performance cost: we shouldn't be doing full GC anyway!
1169 _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1170 return false;
1171 }
1172 };
1174 void G1CollectedHeap::clear_rsets_post_compaction() {
1175 PostMCRemSetClearClosure rs_clear(this, mr_bs());
1176 heap_region_iterate(&rs_clear);
1177 }
1179 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1180 G1CollectedHeap* _g1h;
1181 UpdateRSOopClosure _cl;
1182 int _worker_i;
1183 public:
1184 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1185 _cl(g1->g1_rem_set(), worker_i),
1186 _worker_i(worker_i),
1187 _g1h(g1)
1188 { }
1190 bool doHeapRegion(HeapRegion* r) {
1191 if (!r->continuesHumongous()) {
1192 _cl.set_from(r);
1193 r->oop_iterate(&_cl);
1194 }
1195 return false;
1196 }
1197 };
1199 class ParRebuildRSTask: public AbstractGangTask {
1200 G1CollectedHeap* _g1;
1201 public:
1202 ParRebuildRSTask(G1CollectedHeap* g1)
1203 : AbstractGangTask("ParRebuildRSTask"),
1204 _g1(g1)
1205 { }
1207 void work(uint worker_id) {
1208 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1209 _g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id,
1210 _g1->workers()->active_workers(),
1211 HeapRegion::RebuildRSClaimValue);
1212 }
1213 };
1215 class PostCompactionPrinterClosure: public HeapRegionClosure {
1216 private:
1217 G1HRPrinter* _hr_printer;
1218 public:
1219 bool doHeapRegion(HeapRegion* hr) {
1220 assert(!hr->is_young(), "not expecting to find young regions");
1221 // We only generate output for non-empty regions.
1222 if (!hr->is_empty()) {
1223 if (!hr->isHumongous()) {
1224 _hr_printer->post_compaction(hr, G1HRPrinter::Old);
1225 } else if (hr->startsHumongous()) {
1226 if (hr->region_num() == 1) {
1227 // single humongous region
1228 _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
1229 } else {
1230 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
1231 }
1232 } else {
1233 assert(hr->continuesHumongous(), "only way to get here");
1234 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1235 }
1236 }
1237 return false;
1238 }
1240 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1241 : _hr_printer(hr_printer) { }
1242 };
1244 void G1CollectedHeap::print_hrs_post_compaction() {
1245 PostCompactionPrinterClosure cl(hr_printer());
1246 heap_region_iterate(&cl);
1247 }
1249 bool G1CollectedHeap::do_collection(bool explicit_gc,
1250 bool clear_all_soft_refs,
1251 size_t word_size) {
1252 assert_at_safepoint(true /* should_be_vm_thread */);
1254 if (GC_locker::check_active_before_gc()) {
1255 return false;
1256 }
1258 SvcGCMarker sgcm(SvcGCMarker::FULL);
1259 ResourceMark rm;
1261 print_heap_before_gc();
1263 HRSPhaseSetter x(HRSPhaseFullGC);
1264 verify_region_sets_optional();
1266 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1267 collector_policy()->should_clear_all_soft_refs();
1269 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1271 {
1272 IsGCActiveMark x;
1274 // Timing
1275 assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant");
1276 gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps);
1277 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
1279 TraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, gclog_or_tty);
1280 TraceCollectorStats tcs(g1mm()->full_collection_counters());
1281 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1283 double start = os::elapsedTime();
1284 g1_policy()->record_full_collection_start();
1286 // Note: When we have a more flexible GC logging framework that
1287 // allows us to add optional attributes to a GC log record we
1288 // could consider timing and reporting how long we wait in the
1289 // following two methods.
1290 wait_while_free_regions_coming();
1291 // If we start the compaction before the CM threads finish
1292 // scanning the root regions we might trip them over as we'll
1293 // be moving objects / updating references. So let's wait until
1294 // they are done. By telling them to abort, they should complete
1295 // early.
1296 _cm->root_regions()->abort();
1297 _cm->root_regions()->wait_until_scan_finished();
1298 append_secondary_free_list_if_not_empty_with_lock();
1300 gc_prologue(true);
1301 increment_total_collections(true /* full gc */);
1302 increment_old_marking_cycles_started();
1304 size_t g1h_prev_used = used();
1305 assert(used() == recalculate_used(), "Should be equal");
1307 if (VerifyBeforeGC && total_collections() >= VerifyGCStartAt) {
1308 HandleMark hm; // Discard invalid handles created during verification
1309 gclog_or_tty->print(" VerifyBeforeGC:");
1310 prepare_for_verify();
1311 Universe::verify(/* silent */ false,
1312 /* option */ VerifyOption_G1UsePrevMarking);
1314 }
1315 pre_full_gc_dump();
1317 COMPILER2_PRESENT(DerivedPointerTable::clear());
1319 // Disable discovery and empty the discovered lists
1320 // for the CM ref processor.
1321 ref_processor_cm()->disable_discovery();
1322 ref_processor_cm()->abandon_partial_discovery();
1323 ref_processor_cm()->verify_no_references_recorded();
1325 // Abandon current iterations of concurrent marking and concurrent
1326 // refinement, if any are in progress. We have to do this before
1327 // wait_until_scan_finished() below.
1328 concurrent_mark()->abort();
1330 // Make sure we'll choose a new allocation region afterwards.
1331 release_mutator_alloc_region();
1332 abandon_gc_alloc_regions();
1333 g1_rem_set()->cleanupHRRS();
1335 // We should call this after we retire any currently active alloc
1336 // regions so that all the ALLOC / RETIRE events are generated
1337 // before the start GC event.
1338 _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1340 // We may have added regions to the current incremental collection
1341 // set between the last GC or pause and now. We need to clear the
1342 // incremental collection set and then start rebuilding it afresh
1343 // after this full GC.
1344 abandon_collection_set(g1_policy()->inc_cset_head());
1345 g1_policy()->clear_incremental_cset();
1346 g1_policy()->stop_incremental_cset_building();
1348 tear_down_region_sets(false /* free_list_only */);
1349 g1_policy()->set_gcs_are_young(true);
1351 // See the comments in g1CollectedHeap.hpp and
1352 // G1CollectedHeap::ref_processing_init() about
1353 // how reference processing currently works in G1.
1355 // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1356 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1358 // Temporarily clear the STW ref processor's _is_alive_non_header field.
1359 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1361 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
1362 ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1364 // Do collection work
1365 {
1366 HandleMark hm; // Discard invalid handles created during gc
1367 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1368 }
1370 assert(free_regions() == 0, "we should not have added any free regions");
1371 rebuild_region_sets(false /* free_list_only */);
1373 // Enqueue any discovered reference objects that have
1374 // not been removed from the discovered lists.
1375 ref_processor_stw()->enqueue_discovered_references();
1377 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1379 MemoryService::track_memory_usage();
1381 if (VerifyAfterGC && total_collections() >= VerifyGCStartAt) {
1382 HandleMark hm; // Discard invalid handles created during verification
1383 gclog_or_tty->print(" VerifyAfterGC:");
1384 prepare_for_verify();
1385 Universe::verify(/* silent */ false,
1386 /* option */ VerifyOption_G1UsePrevMarking);
1388 }
1390 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1391 ref_processor_stw()->verify_no_references_recorded();
1393 // Note: since we've just done a full GC, concurrent
1394 // marking is no longer active. Therefore we need not
1395 // re-enable reference discovery for the CM ref processor.
1396 // That will be done at the start of the next marking cycle.
1397 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1398 ref_processor_cm()->verify_no_references_recorded();
1400 reset_gc_time_stamp();
1401 // Since everything potentially moved, we will clear all remembered
1402 // sets, and clear all cards. Later we will rebuild remebered
1403 // sets. We will also reset the GC time stamps of the regions.
1404 clear_rsets_post_compaction();
1405 check_gc_time_stamps();
1407 // Resize the heap if necessary.
1408 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1410 if (_hr_printer.is_active()) {
1411 // We should do this after we potentially resize the heap so
1412 // that all the COMMIT / UNCOMMIT events are generated before
1413 // the end GC event.
1415 print_hrs_post_compaction();
1416 _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1417 }
1419 if (_cg1r->use_cache()) {
1420 _cg1r->clear_and_record_card_counts();
1421 _cg1r->clear_hot_cache();
1422 }
1424 // Rebuild remembered sets of all regions.
1425 if (G1CollectedHeap::use_parallel_gc_threads()) {
1426 uint n_workers =
1427 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1428 workers()->active_workers(),
1429 Threads::number_of_non_daemon_threads());
1430 assert(UseDynamicNumberOfGCThreads ||
1431 n_workers == workers()->total_workers(),
1432 "If not dynamic should be using all the workers");
1433 workers()->set_active_workers(n_workers);
1434 // Set parallel threads in the heap (_n_par_threads) only
1435 // before a parallel phase and always reset it to 0 after
1436 // the phase so that the number of parallel threads does
1437 // no get carried forward to a serial phase where there
1438 // may be code that is "possibly_parallel".
1439 set_par_threads(n_workers);
1441 ParRebuildRSTask rebuild_rs_task(this);
1442 assert(check_heap_region_claim_values(
1443 HeapRegion::InitialClaimValue), "sanity check");
1444 assert(UseDynamicNumberOfGCThreads ||
1445 workers()->active_workers() == workers()->total_workers(),
1446 "Unless dynamic should use total workers");
1447 // Use the most recent number of active workers
1448 assert(workers()->active_workers() > 0,
1449 "Active workers not properly set");
1450 set_par_threads(workers()->active_workers());
1451 workers()->run_task(&rebuild_rs_task);
1452 set_par_threads(0);
1453 assert(check_heap_region_claim_values(
1454 HeapRegion::RebuildRSClaimValue), "sanity check");
1455 reset_heap_region_claim_values();
1456 } else {
1457 RebuildRSOutOfRegionClosure rebuild_rs(this);
1458 heap_region_iterate(&rebuild_rs);
1459 }
1461 if (G1Log::fine()) {
1462 print_size_transition(gclog_or_tty, g1h_prev_used, used(), capacity());
1463 }
1465 if (true) { // FIXME
1466 // Ask the permanent generation to adjust size for full collections
1467 perm()->compute_new_size();
1468 }
1470 // Start a new incremental collection set for the next pause
1471 assert(g1_policy()->collection_set() == NULL, "must be");
1472 g1_policy()->start_incremental_cset_building();
1474 // Clear the _cset_fast_test bitmap in anticipation of adding
1475 // regions to the incremental collection set for the next
1476 // evacuation pause.
1477 clear_cset_fast_test();
1479 init_mutator_alloc_region();
1481 double end = os::elapsedTime();
1482 g1_policy()->record_full_collection_end();
1484 #ifdef TRACESPINNING
1485 ParallelTaskTerminator::print_termination_counts();
1486 #endif
1488 gc_epilogue(true);
1490 // Discard all rset updates
1491 JavaThread::dirty_card_queue_set().abandon_logs();
1492 assert(!G1DeferredRSUpdate
1493 || (G1DeferredRSUpdate && (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any");
1495 _young_list->reset_sampled_info();
1496 // At this point there should be no regions in the
1497 // entire heap tagged as young.
1498 assert( check_young_list_empty(true /* check_heap */),
1499 "young list should be empty at this point");
1501 // Update the number of full collections that have been completed.
1502 increment_old_marking_cycles_completed(false /* concurrent */);
1504 _hrs.verify_optional();
1505 verify_region_sets_optional();
1507 print_heap_after_gc();
1509 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1510 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1511 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1512 // before any GC notifications are raised.
1513 g1mm()->update_sizes();
1514 }
1516 post_full_gc_dump();
1518 return true;
1519 }
1521 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1522 // do_collection() will return whether it succeeded in performing
1523 // the GC. Currently, there is no facility on the
1524 // do_full_collection() API to notify the caller than the collection
1525 // did not succeed (e.g., because it was locked out by the GC
1526 // locker). So, right now, we'll ignore the return value.
1527 bool dummy = do_collection(true, /* explicit_gc */
1528 clear_all_soft_refs,
1529 0 /* word_size */);
1530 }
1532 // This code is mostly copied from TenuredGeneration.
1533 void
1534 G1CollectedHeap::
1535 resize_if_necessary_after_full_collection(size_t word_size) {
1536 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, "sanity check");
1538 // Include the current allocation, if any, and bytes that will be
1539 // pre-allocated to support collections, as "used".
1540 const size_t used_after_gc = used();
1541 const size_t capacity_after_gc = capacity();
1542 const size_t free_after_gc = capacity_after_gc - used_after_gc;
1544 // This is enforced in arguments.cpp.
1545 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1546 "otherwise the code below doesn't make sense");
1548 // We don't have floating point command-line arguments
1549 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1550 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1551 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1552 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1554 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1555 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1557 // We have to be careful here as these two calculations can overflow
1558 // 32-bit size_t's.
1559 double used_after_gc_d = (double) used_after_gc;
1560 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1561 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1563 // Let's make sure that they are both under the max heap size, which
1564 // by default will make them fit into a size_t.
1565 double desired_capacity_upper_bound = (double) max_heap_size;
1566 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1567 desired_capacity_upper_bound);
1568 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1569 desired_capacity_upper_bound);
1571 // We can now safely turn them into size_t's.
1572 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1573 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1575 // This assert only makes sense here, before we adjust them
1576 // with respect to the min and max heap size.
1577 assert(minimum_desired_capacity <= maximum_desired_capacity,
1578 err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1579 "maximum_desired_capacity = "SIZE_FORMAT,
1580 minimum_desired_capacity, maximum_desired_capacity));
1582 // Should not be greater than the heap max size. No need to adjust
1583 // it with respect to the heap min size as it's a lower bound (i.e.,
1584 // we'll try to make the capacity larger than it, not smaller).
1585 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1586 // Should not be less than the heap min size. No need to adjust it
1587 // with respect to the heap max size as it's an upper bound (i.e.,
1588 // we'll try to make the capacity smaller than it, not greater).
1589 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1591 if (capacity_after_gc < minimum_desired_capacity) {
1592 // Don't expand unless it's significant
1593 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1594 ergo_verbose4(ErgoHeapSizing,
1595 "attempt heap expansion",
1596 ergo_format_reason("capacity lower than "
1597 "min desired capacity after Full GC")
1598 ergo_format_byte("capacity")
1599 ergo_format_byte("occupancy")
1600 ergo_format_byte_perc("min desired capacity"),
1601 capacity_after_gc, used_after_gc,
1602 minimum_desired_capacity, (double) MinHeapFreeRatio);
1603 expand(expand_bytes);
1605 // No expansion, now see if we want to shrink
1606 } else if (capacity_after_gc > maximum_desired_capacity) {
1607 // Capacity too large, compute shrinking size
1608 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1609 ergo_verbose4(ErgoHeapSizing,
1610 "attempt heap shrinking",
1611 ergo_format_reason("capacity higher than "
1612 "max desired capacity after Full GC")
1613 ergo_format_byte("capacity")
1614 ergo_format_byte("occupancy")
1615 ergo_format_byte_perc("max desired capacity"),
1616 capacity_after_gc, used_after_gc,
1617 maximum_desired_capacity, (double) MaxHeapFreeRatio);
1618 shrink(shrink_bytes);
1619 }
1620 }
1623 HeapWord*
1624 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1625 bool* succeeded) {
1626 assert_at_safepoint(true /* should_be_vm_thread */);
1628 *succeeded = true;
1629 // Let's attempt the allocation first.
1630 HeapWord* result =
1631 attempt_allocation_at_safepoint(word_size,
1632 false /* expect_null_mutator_alloc_region */);
1633 if (result != NULL) {
1634 assert(*succeeded, "sanity");
1635 return result;
1636 }
1638 // In a G1 heap, we're supposed to keep allocation from failing by
1639 // incremental pauses. Therefore, at least for now, we'll favor
1640 // expansion over collection. (This might change in the future if we can
1641 // do something smarter than full collection to satisfy a failed alloc.)
1642 result = expand_and_allocate(word_size);
1643 if (result != NULL) {
1644 assert(*succeeded, "sanity");
1645 return result;
1646 }
1648 // Expansion didn't work, we'll try to do a Full GC.
1649 bool gc_succeeded = do_collection(false, /* explicit_gc */
1650 false, /* clear_all_soft_refs */
1651 word_size);
1652 if (!gc_succeeded) {
1653 *succeeded = false;
1654 return NULL;
1655 }
1657 // Retry the allocation
1658 result = attempt_allocation_at_safepoint(word_size,
1659 true /* expect_null_mutator_alloc_region */);
1660 if (result != NULL) {
1661 assert(*succeeded, "sanity");
1662 return result;
1663 }
1665 // Then, try a Full GC that will collect all soft references.
1666 gc_succeeded = do_collection(false, /* explicit_gc */
1667 true, /* clear_all_soft_refs */
1668 word_size);
1669 if (!gc_succeeded) {
1670 *succeeded = false;
1671 return NULL;
1672 }
1674 // Retry the allocation once more
1675 result = attempt_allocation_at_safepoint(word_size,
1676 true /* expect_null_mutator_alloc_region */);
1677 if (result != NULL) {
1678 assert(*succeeded, "sanity");
1679 return result;
1680 }
1682 assert(!collector_policy()->should_clear_all_soft_refs(),
1683 "Flag should have been handled and cleared prior to this point");
1685 // What else? We might try synchronous finalization later. If the total
1686 // space available is large enough for the allocation, then a more
1687 // complete compaction phase than we've tried so far might be
1688 // appropriate.
1689 assert(*succeeded, "sanity");
1690 return NULL;
1691 }
1693 // Attempting to expand the heap sufficiently
1694 // to support an allocation of the given "word_size". If
1695 // successful, perform the allocation and return the address of the
1696 // allocated block, or else "NULL".
1698 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1699 assert_at_safepoint(true /* should_be_vm_thread */);
1701 verify_region_sets_optional();
1703 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1704 ergo_verbose1(ErgoHeapSizing,
1705 "attempt heap expansion",
1706 ergo_format_reason("allocation request failed")
1707 ergo_format_byte("allocation request"),
1708 word_size * HeapWordSize);
1709 if (expand(expand_bytes)) {
1710 _hrs.verify_optional();
1711 verify_region_sets_optional();
1712 return attempt_allocation_at_safepoint(word_size,
1713 false /* expect_null_mutator_alloc_region */);
1714 }
1715 return NULL;
1716 }
1718 void G1CollectedHeap::update_committed_space(HeapWord* old_end,
1719 HeapWord* new_end) {
1720 assert(old_end != new_end, "don't call this otherwise");
1721 assert((HeapWord*) _g1_storage.high() == new_end, "invariant");
1723 // Update the committed mem region.
1724 _g1_committed.set_end(new_end);
1725 // Tell the card table about the update.
1726 Universe::heap()->barrier_set()->resize_covered_region(_g1_committed);
1727 // Tell the BOT about the update.
1728 _bot_shared->resize(_g1_committed.word_size());
1729 }
1731 bool G1CollectedHeap::expand(size_t expand_bytes) {
1732 size_t old_mem_size = _g1_storage.committed_size();
1733 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1734 aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1735 HeapRegion::GrainBytes);
1736 ergo_verbose2(ErgoHeapSizing,
1737 "expand the heap",
1738 ergo_format_byte("requested expansion amount")
1739 ergo_format_byte("attempted expansion amount"),
1740 expand_bytes, aligned_expand_bytes);
1742 // First commit the memory.
1743 HeapWord* old_end = (HeapWord*) _g1_storage.high();
1744 bool successful = _g1_storage.expand_by(aligned_expand_bytes);
1745 if (successful) {
1746 // Then propagate this update to the necessary data structures.
1747 HeapWord* new_end = (HeapWord*) _g1_storage.high();
1748 update_committed_space(old_end, new_end);
1750 FreeRegionList expansion_list("Local Expansion List");
1751 MemRegion mr = _hrs.expand_by(old_end, new_end, &expansion_list);
1752 assert(mr.start() == old_end, "post-condition");
1753 // mr might be a smaller region than what was requested if
1754 // expand_by() was unable to allocate the HeapRegion instances
1755 assert(mr.end() <= new_end, "post-condition");
1757 size_t actual_expand_bytes = mr.byte_size();
1758 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1759 assert(actual_expand_bytes == expansion_list.total_capacity_bytes(),
1760 "post-condition");
1761 if (actual_expand_bytes < aligned_expand_bytes) {
1762 // We could not expand _hrs to the desired size. In this case we
1763 // need to shrink the committed space accordingly.
1764 assert(mr.end() < new_end, "invariant");
1766 size_t diff_bytes = aligned_expand_bytes - actual_expand_bytes;
1767 // First uncommit the memory.
1768 _g1_storage.shrink_by(diff_bytes);
1769 // Then propagate this update to the necessary data structures.
1770 update_committed_space(new_end, mr.end());
1771 }
1772 _free_list.add_as_tail(&expansion_list);
1774 if (_hr_printer.is_active()) {
1775 HeapWord* curr = mr.start();
1776 while (curr < mr.end()) {
1777 HeapWord* curr_end = curr + HeapRegion::GrainWords;
1778 _hr_printer.commit(curr, curr_end);
1779 curr = curr_end;
1780 }
1781 assert(curr == mr.end(), "post-condition");
1782 }
1783 g1_policy()->record_new_heap_size(n_regions());
1784 } else {
1785 ergo_verbose0(ErgoHeapSizing,
1786 "did not expand the heap",
1787 ergo_format_reason("heap expansion operation failed"));
1788 // The expansion of the virtual storage space was unsuccessful.
1789 // Let's see if it was because we ran out of swap.
1790 if (G1ExitOnExpansionFailure &&
1791 _g1_storage.uncommitted_size() >= aligned_expand_bytes) {
1792 // We had head room...
1793 vm_exit_out_of_memory(aligned_expand_bytes, "G1 heap expansion");
1794 }
1795 }
1796 return successful;
1797 }
1799 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1800 size_t old_mem_size = _g1_storage.committed_size();
1801 size_t aligned_shrink_bytes =
1802 ReservedSpace::page_align_size_down(shrink_bytes);
1803 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1804 HeapRegion::GrainBytes);
1805 uint num_regions_deleted = 0;
1806 MemRegion mr = _hrs.shrink_by(aligned_shrink_bytes, &num_regions_deleted);
1807 HeapWord* old_end = (HeapWord*) _g1_storage.high();
1808 assert(mr.end() == old_end, "post-condition");
1810 ergo_verbose3(ErgoHeapSizing,
1811 "shrink the heap",
1812 ergo_format_byte("requested shrinking amount")
1813 ergo_format_byte("aligned shrinking amount")
1814 ergo_format_byte("attempted shrinking amount"),
1815 shrink_bytes, aligned_shrink_bytes, mr.byte_size());
1816 if (mr.byte_size() > 0) {
1817 if (_hr_printer.is_active()) {
1818 HeapWord* curr = mr.end();
1819 while (curr > mr.start()) {
1820 HeapWord* curr_end = curr;
1821 curr -= HeapRegion::GrainWords;
1822 _hr_printer.uncommit(curr, curr_end);
1823 }
1824 assert(curr == mr.start(), "post-condition");
1825 }
1827 _g1_storage.shrink_by(mr.byte_size());
1828 HeapWord* new_end = (HeapWord*) _g1_storage.high();
1829 assert(mr.start() == new_end, "post-condition");
1831 _expansion_regions += num_regions_deleted;
1832 update_committed_space(old_end, new_end);
1833 HeapRegionRemSet::shrink_heap(n_regions());
1834 g1_policy()->record_new_heap_size(n_regions());
1835 } else {
1836 ergo_verbose0(ErgoHeapSizing,
1837 "did not shrink the heap",
1838 ergo_format_reason("heap shrinking operation failed"));
1839 }
1840 }
1842 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1843 verify_region_sets_optional();
1845 // We should only reach here at the end of a Full GC which means we
1846 // should not not be holding to any GC alloc regions. The method
1847 // below will make sure of that and do any remaining clean up.
1848 abandon_gc_alloc_regions();
1850 // Instead of tearing down / rebuilding the free lists here, we
1851 // could instead use the remove_all_pending() method on free_list to
1852 // remove only the ones that we need to remove.
1853 tear_down_region_sets(true /* free_list_only */);
1854 shrink_helper(shrink_bytes);
1855 rebuild_region_sets(true /* free_list_only */);
1857 _hrs.verify_optional();
1858 verify_region_sets_optional();
1859 }
1861 // Public methods.
1863 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1864 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1865 #endif // _MSC_VER
1868 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1869 SharedHeap(policy_),
1870 _g1_policy(policy_),
1871 _dirty_card_queue_set(false),
1872 _into_cset_dirty_card_queue_set(false),
1873 _is_alive_closure_cm(this),
1874 _is_alive_closure_stw(this),
1875 _ref_processor_cm(NULL),
1876 _ref_processor_stw(NULL),
1877 _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
1878 _bot_shared(NULL),
1879 _objs_with_preserved_marks(NULL), _preserved_marks_of_objs(NULL),
1880 _evac_failure_scan_stack(NULL) ,
1881 _mark_in_progress(false),
1882 _cg1r(NULL), _summary_bytes_used(0),
1883 _g1mm(NULL),
1884 _refine_cte_cl(NULL),
1885 _full_collection(false),
1886 _free_list("Master Free List"),
1887 _secondary_free_list("Secondary Free List"),
1888 _old_set("Old Set"),
1889 _humongous_set("Master Humongous Set"),
1890 _free_regions_coming(false),
1891 _young_list(new YoungList(this)),
1892 _gc_time_stamp(0),
1893 _retained_old_gc_alloc_region(NULL),
1894 _survivor_plab_stats(YoungPLABSize, PLABWeight),
1895 _old_plab_stats(OldPLABSize, PLABWeight),
1896 _expand_heap_after_alloc_failure(true),
1897 _surviving_young_words(NULL),
1898 _old_marking_cycles_started(0),
1899 _old_marking_cycles_completed(0),
1900 _in_cset_fast_test(NULL),
1901 _in_cset_fast_test_base(NULL),
1902 _dirty_cards_region_list(NULL),
1903 _worker_cset_start_region(NULL),
1904 _worker_cset_start_region_time_stamp(NULL) {
1905 _g1h = this; // To catch bugs.
1906 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
1907 vm_exit_during_initialization("Failed necessary allocation.");
1908 }
1910 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1912 int n_queues = MAX2((int)ParallelGCThreads, 1);
1913 _task_queues = new RefToScanQueueSet(n_queues);
1915 int n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1916 assert(n_rem_sets > 0, "Invariant.");
1918 HeapRegionRemSetIterator** iter_arr =
1919 NEW_C_HEAP_ARRAY(HeapRegionRemSetIterator*, n_queues, mtGC);
1920 for (int i = 0; i < n_queues; i++) {
1921 iter_arr[i] = new HeapRegionRemSetIterator();
1922 }
1923 _rem_set_iterator = iter_arr;
1925 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1926 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC);
1928 for (int i = 0; i < n_queues; i++) {
1929 RefToScanQueue* q = new RefToScanQueue();
1930 q->initialize();
1931 _task_queues->register_queue(i, q);
1932 }
1934 clear_cset_start_regions();
1936 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1937 }
1939 jint G1CollectedHeap::initialize() {
1940 CollectedHeap::pre_initialize();
1941 os::enable_vtime();
1943 G1Log::init();
1945 // Necessary to satisfy locking discipline assertions.
1947 MutexLocker x(Heap_lock);
1949 // We have to initialize the printer before committing the heap, as
1950 // it will be used then.
1951 _hr_printer.set_active(G1PrintHeapRegions);
1953 // While there are no constraints in the GC code that HeapWordSize
1954 // be any particular value, there are multiple other areas in the
1955 // system which believe this to be true (e.g. oop->object_size in some
1956 // cases incorrectly returns the size in wordSize units rather than
1957 // HeapWordSize).
1958 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1960 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1961 size_t max_byte_size = collector_policy()->max_heap_byte_size();
1963 // Ensure that the sizes are properly aligned.
1964 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1965 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1967 _cg1r = new ConcurrentG1Refine();
1969 // Reserve the maximum.
1970 PermanentGenerationSpec* pgs = collector_policy()->permanent_generation();
1971 // Includes the perm-gen.
1973 // When compressed oops are enabled, the preferred heap base
1974 // is calculated by subtracting the requested size from the
1975 // 32Gb boundary and using the result as the base address for
1976 // heap reservation. If the requested size is not aligned to
1977 // HeapRegion::GrainBytes (i.e. the alignment that is passed
1978 // into the ReservedHeapSpace constructor) then the actual
1979 // base of the reserved heap may end up differing from the
1980 // address that was requested (i.e. the preferred heap base).
1981 // If this happens then we could end up using a non-optimal
1982 // compressed oops mode.
1984 // Since max_byte_size is aligned to the size of a heap region (checked
1985 // above), we also need to align the perm gen size as it might not be.
1986 const size_t total_reserved = max_byte_size +
1987 align_size_up(pgs->max_size(), HeapRegion::GrainBytes);
1988 Universe::check_alignment(total_reserved, HeapRegion::GrainBytes, "g1 heap and perm");
1990 char* addr = Universe::preferred_heap_base(total_reserved, Universe::UnscaledNarrowOop);
1992 ReservedHeapSpace heap_rs(total_reserved, HeapRegion::GrainBytes,
1993 UseLargePages, addr);
1995 if (UseCompressedOops) {
1996 if (addr != NULL && !heap_rs.is_reserved()) {
1997 // Failed to reserve at specified address - the requested memory
1998 // region is taken already, for example, by 'java' launcher.
1999 // Try again to reserver heap higher.
2000 addr = Universe::preferred_heap_base(total_reserved, Universe::ZeroBasedNarrowOop);
2002 ReservedHeapSpace heap_rs0(total_reserved, HeapRegion::GrainBytes,
2003 UseLargePages, addr);
2005 if (addr != NULL && !heap_rs0.is_reserved()) {
2006 // Failed to reserve at specified address again - give up.
2007 addr = Universe::preferred_heap_base(total_reserved, Universe::HeapBasedNarrowOop);
2008 assert(addr == NULL, "");
2010 ReservedHeapSpace heap_rs1(total_reserved, HeapRegion::GrainBytes,
2011 UseLargePages, addr);
2012 heap_rs = heap_rs1;
2013 } else {
2014 heap_rs = heap_rs0;
2015 }
2016 }
2017 }
2019 if (!heap_rs.is_reserved()) {
2020 vm_exit_during_initialization("Could not reserve enough space for object heap");
2021 return JNI_ENOMEM;
2022 }
2024 // It is important to do this in a way such that concurrent readers can't
2025 // temporarily think somethings in the heap. (I've actually seen this
2026 // happen in asserts: DLD.)
2027 _reserved.set_word_size(0);
2028 _reserved.set_start((HeapWord*)heap_rs.base());
2029 _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size()));
2031 _expansion_regions = (uint) (max_byte_size / HeapRegion::GrainBytes);
2033 // Create the gen rem set (and barrier set) for the entire reserved region.
2034 _rem_set = collector_policy()->create_rem_set(_reserved, 2);
2035 set_barrier_set(rem_set()->bs());
2036 if (barrier_set()->is_a(BarrierSet::ModRef)) {
2037 _mr_bs = (ModRefBarrierSet*)_barrier_set;
2038 } else {
2039 vm_exit_during_initialization("G1 requires a mod ref bs.");
2040 return JNI_ENOMEM;
2041 }
2043 // Also create a G1 rem set.
2044 if (mr_bs()->is_a(BarrierSet::CardTableModRef)) {
2045 _g1_rem_set = new G1RemSet(this, (CardTableModRefBS*)mr_bs());
2046 } else {
2047 vm_exit_during_initialization("G1 requires a cardtable mod ref bs.");
2048 return JNI_ENOMEM;
2049 }
2051 // Carve out the G1 part of the heap.
2053 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
2054 _g1_reserved = MemRegion((HeapWord*)g1_rs.base(),
2055 g1_rs.size()/HeapWordSize);
2056 ReservedSpace perm_gen_rs = heap_rs.last_part(max_byte_size);
2058 _perm_gen = pgs->init(perm_gen_rs, pgs->init_size(), rem_set());
2060 _g1_storage.initialize(g1_rs, 0);
2061 _g1_committed = MemRegion((HeapWord*)_g1_storage.low(), (size_t) 0);
2062 _hrs.initialize((HeapWord*) _g1_reserved.start(),
2063 (HeapWord*) _g1_reserved.end(),
2064 _expansion_regions);
2066 // 6843694 - ensure that the maximum region index can fit
2067 // in the remembered set structures.
2068 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
2069 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
2071 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
2072 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
2073 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
2074 "too many cards per region");
2076 HeapRegionSet::set_unrealistically_long_length(max_regions() + 1);
2078 _bot_shared = new G1BlockOffsetSharedArray(_reserved,
2079 heap_word_size(init_byte_size));
2081 _g1h = this;
2083 _in_cset_fast_test_length = max_regions();
2084 _in_cset_fast_test_base =
2085 NEW_C_HEAP_ARRAY(bool, (size_t) _in_cset_fast_test_length, mtGC);
2087 // We're biasing _in_cset_fast_test to avoid subtracting the
2088 // beginning of the heap every time we want to index; basically
2089 // it's the same with what we do with the card table.
2090 _in_cset_fast_test = _in_cset_fast_test_base -
2091 ((uintx) _g1_reserved.start() >> HeapRegion::LogOfHRGrainBytes);
2093 // Clear the _cset_fast_test bitmap in anticipation of adding
2094 // regions to the incremental collection set for the first
2095 // evacuation pause.
2096 clear_cset_fast_test();
2098 // Create the ConcurrentMark data structure and thread.
2099 // (Must do this late, so that "max_regions" is defined.)
2100 _cm = new ConcurrentMark(heap_rs, max_regions());
2101 _cmThread = _cm->cmThread();
2103 // Initialize the from_card cache structure of HeapRegionRemSet.
2104 HeapRegionRemSet::init_heap(max_regions());
2106 // Now expand into the initial heap size.
2107 if (!expand(init_byte_size)) {
2108 vm_exit_during_initialization("Failed to allocate initial heap.");
2109 return JNI_ENOMEM;
2110 }
2112 // Perform any initialization actions delegated to the policy.
2113 g1_policy()->init();
2115 _refine_cte_cl =
2116 new RefineCardTableEntryClosure(ConcurrentG1RefineThread::sts(),
2117 g1_rem_set(),
2118 concurrent_g1_refine());
2119 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
2121 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
2122 SATB_Q_FL_lock,
2123 G1SATBProcessCompletedThreshold,
2124 Shared_SATB_Q_lock);
2126 JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
2127 DirtyCardQ_FL_lock,
2128 concurrent_g1_refine()->yellow_zone(),
2129 concurrent_g1_refine()->red_zone(),
2130 Shared_DirtyCardQ_lock);
2132 if (G1DeferredRSUpdate) {
2133 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
2134 DirtyCardQ_FL_lock,
2135 -1, // never trigger processing
2136 -1, // no limit on length
2137 Shared_DirtyCardQ_lock,
2138 &JavaThread::dirty_card_queue_set());
2139 }
2141 // Initialize the card queue set used to hold cards containing
2142 // references into the collection set.
2143 _into_cset_dirty_card_queue_set.initialize(DirtyCardQ_CBL_mon,
2144 DirtyCardQ_FL_lock,
2145 -1, // never trigger processing
2146 -1, // no limit on length
2147 Shared_DirtyCardQ_lock,
2148 &JavaThread::dirty_card_queue_set());
2150 // In case we're keeping closure specialization stats, initialize those
2151 // counts and that mechanism.
2152 SpecializationStats::clear();
2154 // Do later initialization work for concurrent refinement.
2155 _cg1r->init();
2157 // Here we allocate the dummy full region that is required by the
2158 // G1AllocRegion class. If we don't pass an address in the reserved
2159 // space here, lots of asserts fire.
2161 HeapRegion* dummy_region = new_heap_region(0 /* index of bottom region */,
2162 _g1_reserved.start());
2163 // We'll re-use the same region whether the alloc region will
2164 // require BOT updates or not and, if it doesn't, then a non-young
2165 // region will complain that it cannot support allocations without
2166 // BOT updates. So we'll tag the dummy region as young to avoid that.
2167 dummy_region->set_young();
2168 // Make sure it's full.
2169 dummy_region->set_top(dummy_region->end());
2170 G1AllocRegion::setup(this, dummy_region);
2172 init_mutator_alloc_region();
2174 // Do create of the monitoring and management support so that
2175 // values in the heap have been properly initialized.
2176 _g1mm = new G1MonitoringSupport(this);
2178 return JNI_OK;
2179 }
2181 void G1CollectedHeap::ref_processing_init() {
2182 // Reference processing in G1 currently works as follows:
2183 //
2184 // * There are two reference processor instances. One is
2185 // used to record and process discovered references
2186 // during concurrent marking; the other is used to
2187 // record and process references during STW pauses
2188 // (both full and incremental).
2189 // * Both ref processors need to 'span' the entire heap as
2190 // the regions in the collection set may be dotted around.
2191 //
2192 // * For the concurrent marking ref processor:
2193 // * Reference discovery is enabled at initial marking.
2194 // * Reference discovery is disabled and the discovered
2195 // references processed etc during remarking.
2196 // * Reference discovery is MT (see below).
2197 // * Reference discovery requires a barrier (see below).
2198 // * Reference processing may or may not be MT
2199 // (depending on the value of ParallelRefProcEnabled
2200 // and ParallelGCThreads).
2201 // * A full GC disables reference discovery by the CM
2202 // ref processor and abandons any entries on it's
2203 // discovered lists.
2204 //
2205 // * For the STW processor:
2206 // * Non MT discovery is enabled at the start of a full GC.
2207 // * Processing and enqueueing during a full GC is non-MT.
2208 // * During a full GC, references are processed after marking.
2209 //
2210 // * Discovery (may or may not be MT) is enabled at the start
2211 // of an incremental evacuation pause.
2212 // * References are processed near the end of a STW evacuation pause.
2213 // * For both types of GC:
2214 // * Discovery is atomic - i.e. not concurrent.
2215 // * Reference discovery will not need a barrier.
2217 SharedHeap::ref_processing_init();
2218 MemRegion mr = reserved_region();
2220 // Concurrent Mark ref processor
2221 _ref_processor_cm =
2222 new ReferenceProcessor(mr, // span
2223 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2224 // mt processing
2225 (int) ParallelGCThreads,
2226 // degree of mt processing
2227 (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2228 // mt discovery
2229 (int) MAX2(ParallelGCThreads, ConcGCThreads),
2230 // degree of mt discovery
2231 false,
2232 // Reference discovery is not atomic
2233 &_is_alive_closure_cm,
2234 // is alive closure
2235 // (for efficiency/performance)
2236 true);
2237 // Setting next fields of discovered
2238 // lists requires a barrier.
2240 // STW ref processor
2241 _ref_processor_stw =
2242 new ReferenceProcessor(mr, // span
2243 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2244 // mt processing
2245 MAX2((int)ParallelGCThreads, 1),
2246 // degree of mt processing
2247 (ParallelGCThreads > 1),
2248 // mt discovery
2249 MAX2((int)ParallelGCThreads, 1),
2250 // degree of mt discovery
2251 true,
2252 // Reference discovery is atomic
2253 &_is_alive_closure_stw,
2254 // is alive closure
2255 // (for efficiency/performance)
2256 false);
2257 // Setting next fields of discovered
2258 // lists requires a barrier.
2259 }
2261 size_t G1CollectedHeap::capacity() const {
2262 return _g1_committed.byte_size();
2263 }
2265 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2266 assert(!hr->continuesHumongous(), "pre-condition");
2267 hr->reset_gc_time_stamp();
2268 if (hr->startsHumongous()) {
2269 uint first_index = hr->hrs_index() + 1;
2270 uint last_index = hr->last_hc_index();
2271 for (uint i = first_index; i < last_index; i += 1) {
2272 HeapRegion* chr = region_at(i);
2273 assert(chr->continuesHumongous(), "sanity");
2274 chr->reset_gc_time_stamp();
2275 }
2276 }
2277 }
2279 #ifndef PRODUCT
2280 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2281 private:
2282 unsigned _gc_time_stamp;
2283 bool _failures;
2285 public:
2286 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2287 _gc_time_stamp(gc_time_stamp), _failures(false) { }
2289 virtual bool doHeapRegion(HeapRegion* hr) {
2290 unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2291 if (_gc_time_stamp != region_gc_time_stamp) {
2292 gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, "
2293 "expected %d", HR_FORMAT_PARAMS(hr),
2294 region_gc_time_stamp, _gc_time_stamp);
2295 _failures = true;
2296 }
2297 return false;
2298 }
2300 bool failures() { return _failures; }
2301 };
2303 void G1CollectedHeap::check_gc_time_stamps() {
2304 CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2305 heap_region_iterate(&cl);
2306 guarantee(!cl.failures(), "all GC time stamps should have been reset");
2307 }
2308 #endif // PRODUCT
2310 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2311 DirtyCardQueue* into_cset_dcq,
2312 bool concurrent,
2313 int worker_i) {
2314 // Clean cards in the hot card cache
2315 concurrent_g1_refine()->clean_up_cache(worker_i, g1_rem_set(), into_cset_dcq);
2317 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2318 int n_completed_buffers = 0;
2319 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2320 n_completed_buffers++;
2321 }
2322 g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i,
2323 (double) n_completed_buffers);
2324 dcqs.clear_n_completed_buffers();
2325 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2326 }
2329 // Computes the sum of the storage used by the various regions.
2331 size_t G1CollectedHeap::used() const {
2332 assert(Heap_lock->owner() != NULL,
2333 "Should be owned on this thread's behalf.");
2334 size_t result = _summary_bytes_used;
2335 // Read only once in case it is set to NULL concurrently
2336 HeapRegion* hr = _mutator_alloc_region.get();
2337 if (hr != NULL)
2338 result += hr->used();
2339 return result;
2340 }
2342 size_t G1CollectedHeap::used_unlocked() const {
2343 size_t result = _summary_bytes_used;
2344 return result;
2345 }
2347 class SumUsedClosure: public HeapRegionClosure {
2348 size_t _used;
2349 public:
2350 SumUsedClosure() : _used(0) {}
2351 bool doHeapRegion(HeapRegion* r) {
2352 if (!r->continuesHumongous()) {
2353 _used += r->used();
2354 }
2355 return false;
2356 }
2357 size_t result() { return _used; }
2358 };
2360 size_t G1CollectedHeap::recalculate_used() const {
2361 SumUsedClosure blk;
2362 heap_region_iterate(&blk);
2363 return blk.result();
2364 }
2366 size_t G1CollectedHeap::unsafe_max_alloc() {
2367 if (free_regions() > 0) return HeapRegion::GrainBytes;
2368 // otherwise, is there space in the current allocation region?
2370 // We need to store the current allocation region in a local variable
2371 // here. The problem is that this method doesn't take any locks and
2372 // there may be other threads which overwrite the current allocation
2373 // region field. attempt_allocation(), for example, sets it to NULL
2374 // and this can happen *after* the NULL check here but before the call
2375 // to free(), resulting in a SIGSEGV. Note that this doesn't appear
2376 // to be a problem in the optimized build, since the two loads of the
2377 // current allocation region field are optimized away.
2378 HeapRegion* hr = _mutator_alloc_region.get();
2379 if (hr == NULL) {
2380 return 0;
2381 }
2382 return hr->free();
2383 }
2385 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2386 switch (cause) {
2387 case GCCause::_gc_locker: return GCLockerInvokesConcurrent;
2388 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
2389 case GCCause::_g1_humongous_allocation: return true;
2390 default: return false;
2391 }
2392 }
2394 #ifndef PRODUCT
2395 void G1CollectedHeap::allocate_dummy_regions() {
2396 // Let's fill up most of the region
2397 size_t word_size = HeapRegion::GrainWords - 1024;
2398 // And as a result the region we'll allocate will be humongous.
2399 guarantee(isHumongous(word_size), "sanity");
2401 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2402 // Let's use the existing mechanism for the allocation
2403 HeapWord* dummy_obj = humongous_obj_allocate(word_size);
2404 if (dummy_obj != NULL) {
2405 MemRegion mr(dummy_obj, word_size);
2406 CollectedHeap::fill_with_object(mr);
2407 } else {
2408 // If we can't allocate once, we probably cannot allocate
2409 // again. Let's get out of the loop.
2410 break;
2411 }
2412 }
2413 }
2414 #endif // !PRODUCT
2416 void G1CollectedHeap::increment_old_marking_cycles_started() {
2417 assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2418 _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2419 err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2420 _old_marking_cycles_started, _old_marking_cycles_completed));
2422 _old_marking_cycles_started++;
2423 }
2425 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2426 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2428 // We assume that if concurrent == true, then the caller is a
2429 // concurrent thread that was joined the Suspendible Thread
2430 // Set. If there's ever a cheap way to check this, we should add an
2431 // assert here.
2433 // Given that this method is called at the end of a Full GC or of a
2434 // concurrent cycle, and those can be nested (i.e., a Full GC can
2435 // interrupt a concurrent cycle), the number of full collections
2436 // completed should be either one (in the case where there was no
2437 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2438 // behind the number of full collections started.
2440 // This is the case for the inner caller, i.e. a Full GC.
2441 assert(concurrent ||
2442 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2443 (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2444 err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
2445 "is inconsistent with _old_marking_cycles_completed = %u",
2446 _old_marking_cycles_started, _old_marking_cycles_completed));
2448 // This is the case for the outer caller, i.e. the concurrent cycle.
2449 assert(!concurrent ||
2450 (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2451 err_msg("for outer caller (concurrent cycle): "
2452 "_old_marking_cycles_started = %u "
2453 "is inconsistent with _old_marking_cycles_completed = %u",
2454 _old_marking_cycles_started, _old_marking_cycles_completed));
2456 _old_marking_cycles_completed += 1;
2458 // We need to clear the "in_progress" flag in the CM thread before
2459 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2460 // is set) so that if a waiter requests another System.gc() it doesn't
2461 // incorrectly see that a marking cyle is still in progress.
2462 if (concurrent) {
2463 _cmThread->clear_in_progress();
2464 }
2466 // This notify_all() will ensure that a thread that called
2467 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2468 // and it's waiting for a full GC to finish will be woken up. It is
2469 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2470 FullGCCount_lock->notify_all();
2471 }
2473 void G1CollectedHeap::collect_as_vm_thread(GCCause::Cause cause) {
2474 assert_at_safepoint(true /* should_be_vm_thread */);
2475 GCCauseSetter gcs(this, cause);
2476 switch (cause) {
2477 case GCCause::_heap_inspection:
2478 case GCCause::_heap_dump: {
2479 HandleMark hm;
2480 do_full_collection(false); // don't clear all soft refs
2481 break;
2482 }
2483 default: // XXX FIX ME
2484 ShouldNotReachHere(); // Unexpected use of this function
2485 }
2486 }
2488 void G1CollectedHeap::collect(GCCause::Cause cause) {
2489 assert_heap_not_locked();
2491 unsigned int gc_count_before;
2492 unsigned int old_marking_count_before;
2493 bool retry_gc;
2495 do {
2496 retry_gc = false;
2498 {
2499 MutexLocker ml(Heap_lock);
2501 // Read the GC count while holding the Heap_lock
2502 gc_count_before = total_collections();
2503 old_marking_count_before = _old_marking_cycles_started;
2504 }
2506 if (should_do_concurrent_full_gc(cause)) {
2507 // Schedule an initial-mark evacuation pause that will start a
2508 // concurrent cycle. We're setting word_size to 0 which means that
2509 // we are not requesting a post-GC allocation.
2510 VM_G1IncCollectionPause op(gc_count_before,
2511 0, /* word_size */
2512 true, /* should_initiate_conc_mark */
2513 g1_policy()->max_pause_time_ms(),
2514 cause);
2516 VMThread::execute(&op);
2517 if (!op.pause_succeeded()) {
2518 if (old_marking_count_before == _old_marking_cycles_started) {
2519 retry_gc = op.should_retry_gc();
2520 } else {
2521 // A Full GC happened while we were trying to schedule the
2522 // initial-mark GC. No point in starting a new cycle given
2523 // that the whole heap was collected anyway.
2524 }
2526 if (retry_gc) {
2527 if (GC_locker::is_active_and_needs_gc()) {
2528 GC_locker::stall_until_clear();
2529 }
2530 }
2531 }
2532 } else {
2533 if (cause == GCCause::_gc_locker
2534 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2536 // Schedule a standard evacuation pause. We're setting word_size
2537 // to 0 which means that we are not requesting a post-GC allocation.
2538 VM_G1IncCollectionPause op(gc_count_before,
2539 0, /* word_size */
2540 false, /* should_initiate_conc_mark */
2541 g1_policy()->max_pause_time_ms(),
2542 cause);
2543 VMThread::execute(&op);
2544 } else {
2545 // Schedule a Full GC.
2546 VM_G1CollectFull op(gc_count_before, old_marking_count_before, cause);
2547 VMThread::execute(&op);
2548 }
2549 }
2550 } while (retry_gc);
2551 }
2553 bool G1CollectedHeap::is_in(const void* p) const {
2554 if (_g1_committed.contains(p)) {
2555 // Given that we know that p is in the committed space,
2556 // heap_region_containing_raw() should successfully
2557 // return the containing region.
2558 HeapRegion* hr = heap_region_containing_raw(p);
2559 return hr->is_in(p);
2560 } else {
2561 return _perm_gen->as_gen()->is_in(p);
2562 }
2563 }
2565 // Iteration functions.
2567 // Iterates an OopClosure over all ref-containing fields of objects
2568 // within a HeapRegion.
2570 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2571 MemRegion _mr;
2572 OopClosure* _cl;
2573 public:
2574 IterateOopClosureRegionClosure(MemRegion mr, OopClosure* cl)
2575 : _mr(mr), _cl(cl) {}
2576 bool doHeapRegion(HeapRegion* r) {
2577 if (!r->continuesHumongous()) {
2578 r->oop_iterate(_cl);
2579 }
2580 return false;
2581 }
2582 };
2584 void G1CollectedHeap::oop_iterate(OopClosure* cl, bool do_perm) {
2585 IterateOopClosureRegionClosure blk(_g1_committed, cl);
2586 heap_region_iterate(&blk);
2587 if (do_perm) {
2588 perm_gen()->oop_iterate(cl);
2589 }
2590 }
2592 void G1CollectedHeap::oop_iterate(MemRegion mr, OopClosure* cl, bool do_perm) {
2593 IterateOopClosureRegionClosure blk(mr, cl);
2594 heap_region_iterate(&blk);
2595 if (do_perm) {
2596 perm_gen()->oop_iterate(cl);
2597 }
2598 }
2600 // Iterates an ObjectClosure over all objects within a HeapRegion.
2602 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2603 ObjectClosure* _cl;
2604 public:
2605 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2606 bool doHeapRegion(HeapRegion* r) {
2607 if (! r->continuesHumongous()) {
2608 r->object_iterate(_cl);
2609 }
2610 return false;
2611 }
2612 };
2614 void G1CollectedHeap::object_iterate(ObjectClosure* cl, bool do_perm) {
2615 IterateObjectClosureRegionClosure blk(cl);
2616 heap_region_iterate(&blk);
2617 if (do_perm) {
2618 perm_gen()->object_iterate(cl);
2619 }
2620 }
2622 void G1CollectedHeap::object_iterate_since_last_GC(ObjectClosure* cl) {
2623 // FIXME: is this right?
2624 guarantee(false, "object_iterate_since_last_GC not supported by G1 heap");
2625 }
2627 // Calls a SpaceClosure on a HeapRegion.
2629 class SpaceClosureRegionClosure: public HeapRegionClosure {
2630 SpaceClosure* _cl;
2631 public:
2632 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2633 bool doHeapRegion(HeapRegion* r) {
2634 _cl->do_space(r);
2635 return false;
2636 }
2637 };
2639 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2640 SpaceClosureRegionClosure blk(cl);
2641 heap_region_iterate(&blk);
2642 }
2644 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2645 _hrs.iterate(cl);
2646 }
2648 void
2649 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
2650 uint worker_id,
2651 uint no_of_par_workers,
2652 jint claim_value) {
2653 const uint regions = n_regions();
2654 const uint max_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
2655 no_of_par_workers :
2656 1);
2657 assert(UseDynamicNumberOfGCThreads ||
2658 no_of_par_workers == workers()->total_workers(),
2659 "Non dynamic should use fixed number of workers");
2660 // try to spread out the starting points of the workers
2661 const HeapRegion* start_hr =
2662 start_region_for_worker(worker_id, no_of_par_workers);
2663 const uint start_index = start_hr->hrs_index();
2665 // each worker will actually look at all regions
2666 for (uint count = 0; count < regions; ++count) {
2667 const uint index = (start_index + count) % regions;
2668 assert(0 <= index && index < regions, "sanity");
2669 HeapRegion* r = region_at(index);
2670 // we'll ignore "continues humongous" regions (we'll process them
2671 // when we come across their corresponding "start humongous"
2672 // region) and regions already claimed
2673 if (r->claim_value() == claim_value || r->continuesHumongous()) {
2674 continue;
2675 }
2676 // OK, try to claim it
2677 if (r->claimHeapRegion(claim_value)) {
2678 // success!
2679 assert(!r->continuesHumongous(), "sanity");
2680 if (r->startsHumongous()) {
2681 // If the region is "starts humongous" we'll iterate over its
2682 // "continues humongous" first; in fact we'll do them
2683 // first. The order is important. In on case, calling the
2684 // closure on the "starts humongous" region might de-allocate
2685 // and clear all its "continues humongous" regions and, as a
2686 // result, we might end up processing them twice. So, we'll do
2687 // them first (notice: most closures will ignore them anyway) and
2688 // then we'll do the "starts humongous" region.
2689 for (uint ch_index = index + 1; ch_index < regions; ++ch_index) {
2690 HeapRegion* chr = region_at(ch_index);
2692 // if the region has already been claimed or it's not
2693 // "continues humongous" we're done
2694 if (chr->claim_value() == claim_value ||
2695 !chr->continuesHumongous()) {
2696 break;
2697 }
2699 // Noone should have claimed it directly. We can given
2700 // that we claimed its "starts humongous" region.
2701 assert(chr->claim_value() != claim_value, "sanity");
2702 assert(chr->humongous_start_region() == r, "sanity");
2704 if (chr->claimHeapRegion(claim_value)) {
2705 // we should always be able to claim it; noone else should
2706 // be trying to claim this region
2708 bool res2 = cl->doHeapRegion(chr);
2709 assert(!res2, "Should not abort");
2711 // Right now, this holds (i.e., no closure that actually
2712 // does something with "continues humongous" regions
2713 // clears them). We might have to weaken it in the future,
2714 // but let's leave these two asserts here for extra safety.
2715 assert(chr->continuesHumongous(), "should still be the case");
2716 assert(chr->humongous_start_region() == r, "sanity");
2717 } else {
2718 guarantee(false, "we should not reach here");
2719 }
2720 }
2721 }
2723 assert(!r->continuesHumongous(), "sanity");
2724 bool res = cl->doHeapRegion(r);
2725 assert(!res, "Should not abort");
2726 }
2727 }
2728 }
2730 class ResetClaimValuesClosure: public HeapRegionClosure {
2731 public:
2732 bool doHeapRegion(HeapRegion* r) {
2733 r->set_claim_value(HeapRegion::InitialClaimValue);
2734 return false;
2735 }
2736 };
2738 void G1CollectedHeap::reset_heap_region_claim_values() {
2739 ResetClaimValuesClosure blk;
2740 heap_region_iterate(&blk);
2741 }
2743 void G1CollectedHeap::reset_cset_heap_region_claim_values() {
2744 ResetClaimValuesClosure blk;
2745 collection_set_iterate(&blk);
2746 }
2748 #ifdef ASSERT
2749 // This checks whether all regions in the heap have the correct claim
2750 // value. I also piggy-backed on this a check to ensure that the
2751 // humongous_start_region() information on "continues humongous"
2752 // regions is correct.
2754 class CheckClaimValuesClosure : public HeapRegionClosure {
2755 private:
2756 jint _claim_value;
2757 uint _failures;
2758 HeapRegion* _sh_region;
2760 public:
2761 CheckClaimValuesClosure(jint claim_value) :
2762 _claim_value(claim_value), _failures(0), _sh_region(NULL) { }
2763 bool doHeapRegion(HeapRegion* r) {
2764 if (r->claim_value() != _claim_value) {
2765 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2766 "claim value = %d, should be %d",
2767 HR_FORMAT_PARAMS(r),
2768 r->claim_value(), _claim_value);
2769 ++_failures;
2770 }
2771 if (!r->isHumongous()) {
2772 _sh_region = NULL;
2773 } else if (r->startsHumongous()) {
2774 _sh_region = r;
2775 } else if (r->continuesHumongous()) {
2776 if (r->humongous_start_region() != _sh_region) {
2777 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2778 "HS = "PTR_FORMAT", should be "PTR_FORMAT,
2779 HR_FORMAT_PARAMS(r),
2780 r->humongous_start_region(),
2781 _sh_region);
2782 ++_failures;
2783 }
2784 }
2785 return false;
2786 }
2787 uint failures() { return _failures; }
2788 };
2790 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
2791 CheckClaimValuesClosure cl(claim_value);
2792 heap_region_iterate(&cl);
2793 return cl.failures() == 0;
2794 }
2796 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure {
2797 private:
2798 jint _claim_value;
2799 uint _failures;
2801 public:
2802 CheckClaimValuesInCSetHRClosure(jint claim_value) :
2803 _claim_value(claim_value), _failures(0) { }
2805 uint failures() { return _failures; }
2807 bool doHeapRegion(HeapRegion* hr) {
2808 assert(hr->in_collection_set(), "how?");
2809 assert(!hr->isHumongous(), "H-region in CSet");
2810 if (hr->claim_value() != _claim_value) {
2811 gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", "
2812 "claim value = %d, should be %d",
2813 HR_FORMAT_PARAMS(hr),
2814 hr->claim_value(), _claim_value);
2815 _failures += 1;
2816 }
2817 return false;
2818 }
2819 };
2821 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) {
2822 CheckClaimValuesInCSetHRClosure cl(claim_value);
2823 collection_set_iterate(&cl);
2824 return cl.failures() == 0;
2825 }
2826 #endif // ASSERT
2828 // Clear the cached CSet starting regions and (more importantly)
2829 // the time stamps. Called when we reset the GC time stamp.
2830 void G1CollectedHeap::clear_cset_start_regions() {
2831 assert(_worker_cset_start_region != NULL, "sanity");
2832 assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2834 int n_queues = MAX2((int)ParallelGCThreads, 1);
2835 for (int i = 0; i < n_queues; i++) {
2836 _worker_cset_start_region[i] = NULL;
2837 _worker_cset_start_region_time_stamp[i] = 0;
2838 }
2839 }
2841 // Given the id of a worker, obtain or calculate a suitable
2842 // starting region for iterating over the current collection set.
2843 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(int worker_i) {
2844 assert(get_gc_time_stamp() > 0, "should have been updated by now");
2846 HeapRegion* result = NULL;
2847 unsigned gc_time_stamp = get_gc_time_stamp();
2849 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2850 // Cached starting region for current worker was set
2851 // during the current pause - so it's valid.
2852 // Note: the cached starting heap region may be NULL
2853 // (when the collection set is empty).
2854 result = _worker_cset_start_region[worker_i];
2855 assert(result == NULL || result->in_collection_set(), "sanity");
2856 return result;
2857 }
2859 // The cached entry was not valid so let's calculate
2860 // a suitable starting heap region for this worker.
2862 // We want the parallel threads to start their collection
2863 // set iteration at different collection set regions to
2864 // avoid contention.
2865 // If we have:
2866 // n collection set regions
2867 // p threads
2868 // Then thread t will start at region floor ((t * n) / p)
2870 result = g1_policy()->collection_set();
2871 if (G1CollectedHeap::use_parallel_gc_threads()) {
2872 uint cs_size = g1_policy()->cset_region_length();
2873 uint active_workers = workers()->active_workers();
2874 assert(UseDynamicNumberOfGCThreads ||
2875 active_workers == workers()->total_workers(),
2876 "Unless dynamic should use total workers");
2878 uint end_ind = (cs_size * worker_i) / active_workers;
2879 uint start_ind = 0;
2881 if (worker_i > 0 &&
2882 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2883 // Previous workers starting region is valid
2884 // so let's iterate from there
2885 start_ind = (cs_size * (worker_i - 1)) / active_workers;
2886 result = _worker_cset_start_region[worker_i - 1];
2887 }
2889 for (uint i = start_ind; i < end_ind; i++) {
2890 result = result->next_in_collection_set();
2891 }
2892 }
2894 // Note: the calculated starting heap region may be NULL
2895 // (when the collection set is empty).
2896 assert(result == NULL || result->in_collection_set(), "sanity");
2897 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2898 "should be updated only once per pause");
2899 _worker_cset_start_region[worker_i] = result;
2900 OrderAccess::storestore();
2901 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2902 return result;
2903 }
2905 HeapRegion* G1CollectedHeap::start_region_for_worker(uint worker_i,
2906 uint no_of_par_workers) {
2907 uint worker_num =
2908 G1CollectedHeap::use_parallel_gc_threads() ? no_of_par_workers : 1U;
2909 assert(UseDynamicNumberOfGCThreads ||
2910 no_of_par_workers == workers()->total_workers(),
2911 "Non dynamic should use fixed number of workers");
2912 const uint start_index = n_regions() * worker_i / worker_num;
2913 return region_at(start_index);
2914 }
2916 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2917 HeapRegion* r = g1_policy()->collection_set();
2918 while (r != NULL) {
2919 HeapRegion* next = r->next_in_collection_set();
2920 if (cl->doHeapRegion(r)) {
2921 cl->incomplete();
2922 return;
2923 }
2924 r = next;
2925 }
2926 }
2928 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2929 HeapRegionClosure *cl) {
2930 if (r == NULL) {
2931 // The CSet is empty so there's nothing to do.
2932 return;
2933 }
2935 assert(r->in_collection_set(),
2936 "Start region must be a member of the collection set.");
2937 HeapRegion* cur = r;
2938 while (cur != NULL) {
2939 HeapRegion* next = cur->next_in_collection_set();
2940 if (cl->doHeapRegion(cur) && false) {
2941 cl->incomplete();
2942 return;
2943 }
2944 cur = next;
2945 }
2946 cur = g1_policy()->collection_set();
2947 while (cur != r) {
2948 HeapRegion* next = cur->next_in_collection_set();
2949 if (cl->doHeapRegion(cur) && false) {
2950 cl->incomplete();
2951 return;
2952 }
2953 cur = next;
2954 }
2955 }
2957 CompactibleSpace* G1CollectedHeap::first_compactible_space() {
2958 return n_regions() > 0 ? region_at(0) : NULL;
2959 }
2962 Space* G1CollectedHeap::space_containing(const void* addr) const {
2963 Space* res = heap_region_containing(addr);
2964 if (res == NULL)
2965 res = perm_gen()->space_containing(addr);
2966 return res;
2967 }
2969 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2970 Space* sp = space_containing(addr);
2971 if (sp != NULL) {
2972 return sp->block_start(addr);
2973 }
2974 return NULL;
2975 }
2977 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2978 Space* sp = space_containing(addr);
2979 assert(sp != NULL, "block_size of address outside of heap");
2980 return sp->block_size(addr);
2981 }
2983 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2984 Space* sp = space_containing(addr);
2985 return sp->block_is_obj(addr);
2986 }
2988 bool G1CollectedHeap::supports_tlab_allocation() const {
2989 return true;
2990 }
2992 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2993 return HeapRegion::GrainBytes;
2994 }
2996 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2997 // Return the remaining space in the cur alloc region, but not less than
2998 // the min TLAB size.
3000 // Also, this value can be at most the humongous object threshold,
3001 // since we can't allow tlabs to grow big enough to accomodate
3002 // humongous objects.
3004 HeapRegion* hr = _mutator_alloc_region.get();
3005 size_t max_tlab_size = _humongous_object_threshold_in_words * wordSize;
3006 if (hr == NULL) {
3007 return max_tlab_size;
3008 } else {
3009 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab_size);
3010 }
3011 }
3013 size_t G1CollectedHeap::max_capacity() const {
3014 return _g1_reserved.byte_size();
3015 }
3017 jlong G1CollectedHeap::millis_since_last_gc() {
3018 // assert(false, "NYI");
3019 return 0;
3020 }
3022 void G1CollectedHeap::prepare_for_verify() {
3023 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
3024 ensure_parsability(false);
3025 }
3026 g1_rem_set()->prepare_for_verify();
3027 }
3029 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr,
3030 VerifyOption vo) {
3031 switch (vo) {
3032 case VerifyOption_G1UsePrevMarking:
3033 return hr->obj_allocated_since_prev_marking(obj);
3034 case VerifyOption_G1UseNextMarking:
3035 return hr->obj_allocated_since_next_marking(obj);
3036 case VerifyOption_G1UseMarkWord:
3037 return false;
3038 default:
3039 ShouldNotReachHere();
3040 }
3041 return false; // keep some compilers happy
3042 }
3044 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) {
3045 switch (vo) {
3046 case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start();
3047 case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start();
3048 case VerifyOption_G1UseMarkWord: return NULL;
3049 default: ShouldNotReachHere();
3050 }
3051 return NULL; // keep some compilers happy
3052 }
3054 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) {
3055 switch (vo) {
3056 case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj);
3057 case VerifyOption_G1UseNextMarking: return isMarkedNext(obj);
3058 case VerifyOption_G1UseMarkWord: return obj->is_gc_marked();
3059 default: ShouldNotReachHere();
3060 }
3061 return false; // keep some compilers happy
3062 }
3064 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) {
3065 switch (vo) {
3066 case VerifyOption_G1UsePrevMarking: return "PTAMS";
3067 case VerifyOption_G1UseNextMarking: return "NTAMS";
3068 case VerifyOption_G1UseMarkWord: return "NONE";
3069 default: ShouldNotReachHere();
3070 }
3071 return NULL; // keep some compilers happy
3072 }
3074 class VerifyLivenessOopClosure: public OopClosure {
3075 G1CollectedHeap* _g1h;
3076 VerifyOption _vo;
3077 public:
3078 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
3079 _g1h(g1h), _vo(vo)
3080 { }
3081 void do_oop(narrowOop *p) { do_oop_work(p); }
3082 void do_oop( oop *p) { do_oop_work(p); }
3084 template <class T> void do_oop_work(T *p) {
3085 oop obj = oopDesc::load_decode_heap_oop(p);
3086 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
3087 "Dead object referenced by a not dead object");
3088 }
3089 };
3091 class VerifyObjsInRegionClosure: public ObjectClosure {
3092 private:
3093 G1CollectedHeap* _g1h;
3094 size_t _live_bytes;
3095 HeapRegion *_hr;
3096 VerifyOption _vo;
3097 public:
3098 // _vo == UsePrevMarking -> use "prev" marking information,
3099 // _vo == UseNextMarking -> use "next" marking information,
3100 // _vo == UseMarkWord -> use mark word from object header.
3101 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
3102 : _live_bytes(0), _hr(hr), _vo(vo) {
3103 _g1h = G1CollectedHeap::heap();
3104 }
3105 void do_object(oop o) {
3106 VerifyLivenessOopClosure isLive(_g1h, _vo);
3107 assert(o != NULL, "Huh?");
3108 if (!_g1h->is_obj_dead_cond(o, _vo)) {
3109 // If the object is alive according to the mark word,
3110 // then verify that the marking information agrees.
3111 // Note we can't verify the contra-positive of the
3112 // above: if the object is dead (according to the mark
3113 // word), it may not be marked, or may have been marked
3114 // but has since became dead, or may have been allocated
3115 // since the last marking.
3116 if (_vo == VerifyOption_G1UseMarkWord) {
3117 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
3118 }
3120 o->oop_iterate(&isLive);
3121 if (!_hr->obj_allocated_since_prev_marking(o)) {
3122 size_t obj_size = o->size(); // Make sure we don't overflow
3123 _live_bytes += (obj_size * HeapWordSize);
3124 }
3125 }
3126 }
3127 size_t live_bytes() { return _live_bytes; }
3128 };
3130 class PrintObjsInRegionClosure : public ObjectClosure {
3131 HeapRegion *_hr;
3132 G1CollectedHeap *_g1;
3133 public:
3134 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
3135 _g1 = G1CollectedHeap::heap();
3136 };
3138 void do_object(oop o) {
3139 if (o != NULL) {
3140 HeapWord *start = (HeapWord *) o;
3141 size_t word_sz = o->size();
3142 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
3143 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
3144 (void*) o, word_sz,
3145 _g1->isMarkedPrev(o),
3146 _g1->isMarkedNext(o),
3147 _hr->obj_allocated_since_prev_marking(o));
3148 HeapWord *end = start + word_sz;
3149 HeapWord *cur;
3150 int *val;
3151 for (cur = start; cur < end; cur++) {
3152 val = (int *) cur;
3153 gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val);
3154 }
3155 }
3156 }
3157 };
3159 class VerifyRegionClosure: public HeapRegionClosure {
3160 private:
3161 bool _par;
3162 VerifyOption _vo;
3163 bool _failures;
3164 public:
3165 // _vo == UsePrevMarking -> use "prev" marking information,
3166 // _vo == UseNextMarking -> use "next" marking information,
3167 // _vo == UseMarkWord -> use mark word from object header.
3168 VerifyRegionClosure(bool par, VerifyOption vo)
3169 : _par(par),
3170 _vo(vo),
3171 _failures(false) {}
3173 bool failures() {
3174 return _failures;
3175 }
3177 bool doHeapRegion(HeapRegion* r) {
3178 if (!r->continuesHumongous()) {
3179 bool failures = false;
3180 r->verify(_vo, &failures);
3181 if (failures) {
3182 _failures = true;
3183 } else {
3184 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
3185 r->object_iterate(¬_dead_yet_cl);
3186 if (_vo != VerifyOption_G1UseNextMarking) {
3187 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
3188 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
3189 "max_live_bytes "SIZE_FORMAT" "
3190 "< calculated "SIZE_FORMAT,
3191 r->bottom(), r->end(),
3192 r->max_live_bytes(),
3193 not_dead_yet_cl.live_bytes());
3194 _failures = true;
3195 }
3196 } else {
3197 // When vo == UseNextMarking we cannot currently do a sanity
3198 // check on the live bytes as the calculation has not been
3199 // finalized yet.
3200 }
3201 }
3202 }
3203 return false; // stop the region iteration if we hit a failure
3204 }
3205 };
3207 class VerifyRootsClosure: public OopsInGenClosure {
3208 private:
3209 G1CollectedHeap* _g1h;
3210 VerifyOption _vo;
3211 bool _failures;
3212 public:
3213 // _vo == UsePrevMarking -> use "prev" marking information,
3214 // _vo == UseNextMarking -> use "next" marking information,
3215 // _vo == UseMarkWord -> use mark word from object header.
3216 VerifyRootsClosure(VerifyOption vo) :
3217 _g1h(G1CollectedHeap::heap()),
3218 _vo(vo),
3219 _failures(false) { }
3221 bool failures() { return _failures; }
3223 template <class T> void do_oop_nv(T* p) {
3224 T heap_oop = oopDesc::load_heap_oop(p);
3225 if (!oopDesc::is_null(heap_oop)) {
3226 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3227 if (_g1h->is_obj_dead_cond(obj, _vo)) {
3228 gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
3229 "points to dead obj "PTR_FORMAT, p, (void*) obj);
3230 if (_vo == VerifyOption_G1UseMarkWord) {
3231 gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark()));
3232 }
3233 obj->print_on(gclog_or_tty);
3234 _failures = true;
3235 }
3236 }
3237 }
3239 void do_oop(oop* p) { do_oop_nv(p); }
3240 void do_oop(narrowOop* p) { do_oop_nv(p); }
3241 };
3243 // This is the task used for parallel heap verification.
3245 class G1ParVerifyTask: public AbstractGangTask {
3246 private:
3247 G1CollectedHeap* _g1h;
3248 VerifyOption _vo;
3249 bool _failures;
3251 public:
3252 // _vo == UsePrevMarking -> use "prev" marking information,
3253 // _vo == UseNextMarking -> use "next" marking information,
3254 // _vo == UseMarkWord -> use mark word from object header.
3255 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
3256 AbstractGangTask("Parallel verify task"),
3257 _g1h(g1h),
3258 _vo(vo),
3259 _failures(false) { }
3261 bool failures() {
3262 return _failures;
3263 }
3265 void work(uint worker_id) {
3266 HandleMark hm;
3267 VerifyRegionClosure blk(true, _vo);
3268 _g1h->heap_region_par_iterate_chunked(&blk, worker_id,
3269 _g1h->workers()->active_workers(),
3270 HeapRegion::ParVerifyClaimValue);
3271 if (blk.failures()) {
3272 _failures = true;
3273 }
3274 }
3275 };
3277 void G1CollectedHeap::verify(bool silent) {
3278 verify(silent, VerifyOption_G1UsePrevMarking);
3279 }
3281 void G1CollectedHeap::verify(bool silent,
3282 VerifyOption vo) {
3283 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
3284 if (!silent) { gclog_or_tty->print("Roots (excluding permgen) "); }
3285 VerifyRootsClosure rootsCl(vo);
3287 assert(Thread::current()->is_VM_thread(),
3288 "Expected to be executed serially by the VM thread at this point");
3290 CodeBlobToOopClosure blobsCl(&rootsCl, /*do_marking=*/ false);
3292 // We apply the relevant closures to all the oops in the
3293 // system dictionary, the string table and the code cache.
3294 const int so = SO_AllClasses | SO_Strings | SO_CodeCache;
3296 process_strong_roots(true, // activate StrongRootsScope
3297 true, // we set "collecting perm gen" to true,
3298 // so we don't reset the dirty cards in the perm gen.
3299 ScanningOption(so), // roots scanning options
3300 &rootsCl,
3301 &blobsCl,
3302 &rootsCl);
3304 // If we're verifying after the marking phase of a Full GC then we can't
3305 // treat the perm gen as roots into the G1 heap. Some of the objects in
3306 // the perm gen may be dead and hence not marked. If one of these dead
3307 // objects is considered to be a root then we may end up with a false
3308 // "Root location <x> points to dead ob <y>" failure.
3309 if (vo != VerifyOption_G1UseMarkWord) {
3310 // Since we used "collecting_perm_gen" == true above, we will not have
3311 // checked the refs from perm into the G1-collected heap. We check those
3312 // references explicitly below. Whether the relevant cards are dirty
3313 // is checked further below in the rem set verification.
3314 if (!silent) { gclog_or_tty->print("Permgen roots "); }
3315 perm_gen()->oop_iterate(&rootsCl);
3316 }
3317 bool failures = rootsCl.failures();
3319 if (vo != VerifyOption_G1UseMarkWord) {
3320 // If we're verifying during a full GC then the region sets
3321 // will have been torn down at the start of the GC. Therefore
3322 // verifying the region sets will fail. So we only verify
3323 // the region sets when not in a full GC.
3324 if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3325 verify_region_sets();
3326 }
3328 if (!silent) { gclog_or_tty->print("HeapRegions "); }
3329 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3330 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3331 "sanity check");
3333 G1ParVerifyTask task(this, vo);
3334 assert(UseDynamicNumberOfGCThreads ||
3335 workers()->active_workers() == workers()->total_workers(),
3336 "If not dynamic should be using all the workers");
3337 int n_workers = workers()->active_workers();
3338 set_par_threads(n_workers);
3339 workers()->run_task(&task);
3340 set_par_threads(0);
3341 if (task.failures()) {
3342 failures = true;
3343 }
3345 // Checks that the expected amount of parallel work was done.
3346 // The implication is that n_workers is > 0.
3347 assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
3348 "sanity check");
3350 reset_heap_region_claim_values();
3352 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3353 "sanity check");
3354 } else {
3355 VerifyRegionClosure blk(false, vo);
3356 heap_region_iterate(&blk);
3357 if (blk.failures()) {
3358 failures = true;
3359 }
3360 }
3361 if (!silent) gclog_or_tty->print("RemSet ");
3362 rem_set()->verify();
3364 if (failures) {
3365 gclog_or_tty->print_cr("Heap:");
3366 // It helps to have the per-region information in the output to
3367 // help us track down what went wrong. This is why we call
3368 // print_extended_on() instead of print_on().
3369 print_extended_on(gclog_or_tty);
3370 gclog_or_tty->print_cr("");
3371 #ifndef PRODUCT
3372 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3373 concurrent_mark()->print_reachable("at-verification-failure",
3374 vo, false /* all */);
3375 }
3376 #endif
3377 gclog_or_tty->flush();
3378 }
3379 guarantee(!failures, "there should not have been any failures");
3380 } else {
3381 if (!silent) gclog_or_tty->print("(SKIPPING roots, heapRegions, remset) ");
3382 }
3383 }
3385 class PrintRegionClosure: public HeapRegionClosure {
3386 outputStream* _st;
3387 public:
3388 PrintRegionClosure(outputStream* st) : _st(st) {}
3389 bool doHeapRegion(HeapRegion* r) {
3390 r->print_on(_st);
3391 return false;
3392 }
3393 };
3395 void G1CollectedHeap::print_on(outputStream* st) const {
3396 st->print(" %-20s", "garbage-first heap");
3397 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3398 capacity()/K, used_unlocked()/K);
3399 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3400 _g1_storage.low_boundary(),
3401 _g1_storage.high(),
3402 _g1_storage.high_boundary());
3403 st->cr();
3404 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3405 uint young_regions = _young_list->length();
3406 st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3407 (size_t) young_regions * HeapRegion::GrainBytes / K);
3408 uint survivor_regions = g1_policy()->recorded_survivor_regions();
3409 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3410 (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3411 st->cr();
3412 perm()->as_gen()->print_on(st);
3413 }
3415 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3416 print_on(st);
3418 // Print the per-region information.
3419 st->cr();
3420 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3421 "HS=humongous(starts), HC=humongous(continues), "
3422 "CS=collection set, F=free, TS=gc time stamp, "
3423 "PTAMS=previous top-at-mark-start, "
3424 "NTAMS=next top-at-mark-start)");
3425 PrintRegionClosure blk(st);
3426 heap_region_iterate(&blk);
3427 }
3429 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3430 if (G1CollectedHeap::use_parallel_gc_threads()) {
3431 workers()->print_worker_threads_on(st);
3432 }
3433 _cmThread->print_on(st);
3434 st->cr();
3435 _cm->print_worker_threads_on(st);
3436 _cg1r->print_worker_threads_on(st);
3437 st->cr();
3438 }
3440 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3441 if (G1CollectedHeap::use_parallel_gc_threads()) {
3442 workers()->threads_do(tc);
3443 }
3444 tc->do_thread(_cmThread);
3445 _cg1r->threads_do(tc);
3446 }
3448 void G1CollectedHeap::print_tracing_info() const {
3449 // We'll overload this to mean "trace GC pause statistics."
3450 if (TraceGen0Time || TraceGen1Time) {
3451 // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3452 // to that.
3453 g1_policy()->print_tracing_info();
3454 }
3455 if (G1SummarizeRSetStats) {
3456 g1_rem_set()->print_summary_info();
3457 }
3458 if (G1SummarizeConcMark) {
3459 concurrent_mark()->print_summary_info();
3460 }
3461 g1_policy()->print_yg_surv_rate_info();
3462 SpecializationStats::print();
3463 }
3465 #ifndef PRODUCT
3466 // Helpful for debugging RSet issues.
3468 class PrintRSetsClosure : public HeapRegionClosure {
3469 private:
3470 const char* _msg;
3471 size_t _occupied_sum;
3473 public:
3474 bool doHeapRegion(HeapRegion* r) {
3475 HeapRegionRemSet* hrrs = r->rem_set();
3476 size_t occupied = hrrs->occupied();
3477 _occupied_sum += occupied;
3479 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3480 HR_FORMAT_PARAMS(r));
3481 if (occupied == 0) {
3482 gclog_or_tty->print_cr(" RSet is empty");
3483 } else {
3484 hrrs->print();
3485 }
3486 gclog_or_tty->print_cr("----------");
3487 return false;
3488 }
3490 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3491 gclog_or_tty->cr();
3492 gclog_or_tty->print_cr("========================================");
3493 gclog_or_tty->print_cr(msg);
3494 gclog_or_tty->cr();
3495 }
3497 ~PrintRSetsClosure() {
3498 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3499 gclog_or_tty->print_cr("========================================");
3500 gclog_or_tty->cr();
3501 }
3502 };
3504 void G1CollectedHeap::print_cset_rsets() {
3505 PrintRSetsClosure cl("Printing CSet RSets");
3506 collection_set_iterate(&cl);
3507 }
3509 void G1CollectedHeap::print_all_rsets() {
3510 PrintRSetsClosure cl("Printing All RSets");;
3511 heap_region_iterate(&cl);
3512 }
3513 #endif // PRODUCT
3515 G1CollectedHeap* G1CollectedHeap::heap() {
3516 assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3517 "not a garbage-first heap");
3518 return _g1h;
3519 }
3521 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3522 // always_do_update_barrier = false;
3523 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3524 // Call allocation profiler
3525 AllocationProfiler::iterate_since_last_gc();
3526 // Fill TLAB's and such
3527 ensure_parsability(true);
3528 }
3530 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) {
3531 // FIXME: what is this about?
3532 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3533 // is set.
3534 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3535 "derived pointer present"));
3536 // always_do_update_barrier = true;
3538 // We have just completed a GC. Update the soft reference
3539 // policy with the new heap occupancy
3540 Universe::update_heap_info_at_gc();
3541 }
3543 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3544 unsigned int gc_count_before,
3545 bool* succeeded) {
3546 assert_heap_not_locked_and_not_at_safepoint();
3547 g1_policy()->record_stop_world_start();
3548 VM_G1IncCollectionPause op(gc_count_before,
3549 word_size,
3550 false, /* should_initiate_conc_mark */
3551 g1_policy()->max_pause_time_ms(),
3552 GCCause::_g1_inc_collection_pause);
3553 VMThread::execute(&op);
3555 HeapWord* result = op.result();
3556 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3557 assert(result == NULL || ret_succeeded,
3558 "the result should be NULL if the VM did not succeed");
3559 *succeeded = ret_succeeded;
3561 assert_heap_not_locked();
3562 return result;
3563 }
3565 void
3566 G1CollectedHeap::doConcurrentMark() {
3567 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3568 if (!_cmThread->in_progress()) {
3569 _cmThread->set_started();
3570 CGC_lock->notify();
3571 }
3572 }
3574 size_t G1CollectedHeap::pending_card_num() {
3575 size_t extra_cards = 0;
3576 JavaThread *curr = Threads::first();
3577 while (curr != NULL) {
3578 DirtyCardQueue& dcq = curr->dirty_card_queue();
3579 extra_cards += dcq.size();
3580 curr = curr->next();
3581 }
3582 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3583 size_t buffer_size = dcqs.buffer_size();
3584 size_t buffer_num = dcqs.completed_buffers_num();
3585 return buffer_size * buffer_num + extra_cards;
3586 }
3588 size_t G1CollectedHeap::max_pending_card_num() {
3589 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3590 size_t buffer_size = dcqs.buffer_size();
3591 size_t buffer_num = dcqs.completed_buffers_num();
3592 int thread_num = Threads::number_of_threads();
3593 return (buffer_num + thread_num) * buffer_size;
3594 }
3596 size_t G1CollectedHeap::cards_scanned() {
3597 return g1_rem_set()->cardsScanned();
3598 }
3600 void
3601 G1CollectedHeap::setup_surviving_young_words() {
3602 assert(_surviving_young_words == NULL, "pre-condition");
3603 uint array_length = g1_policy()->young_cset_region_length();
3604 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3605 if (_surviving_young_words == NULL) {
3606 vm_exit_out_of_memory(sizeof(size_t) * array_length,
3607 "Not enough space for young surv words summary.");
3608 }
3609 memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3610 #ifdef ASSERT
3611 for (uint i = 0; i < array_length; ++i) {
3612 assert( _surviving_young_words[i] == 0, "memset above" );
3613 }
3614 #endif // !ASSERT
3615 }
3617 void
3618 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3619 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3620 uint array_length = g1_policy()->young_cset_region_length();
3621 for (uint i = 0; i < array_length; ++i) {
3622 _surviving_young_words[i] += surv_young_words[i];
3623 }
3624 }
3626 void
3627 G1CollectedHeap::cleanup_surviving_young_words() {
3628 guarantee( _surviving_young_words != NULL, "pre-condition" );
3629 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC);
3630 _surviving_young_words = NULL;
3631 }
3633 #ifdef ASSERT
3634 class VerifyCSetClosure: public HeapRegionClosure {
3635 public:
3636 bool doHeapRegion(HeapRegion* hr) {
3637 // Here we check that the CSet region's RSet is ready for parallel
3638 // iteration. The fields that we'll verify are only manipulated
3639 // when the region is part of a CSet and is collected. Afterwards,
3640 // we reset these fields when we clear the region's RSet (when the
3641 // region is freed) so they are ready when the region is
3642 // re-allocated. The only exception to this is if there's an
3643 // evacuation failure and instead of freeing the region we leave
3644 // it in the heap. In that case, we reset these fields during
3645 // evacuation failure handling.
3646 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3648 // Here's a good place to add any other checks we'd like to
3649 // perform on CSet regions.
3650 return false;
3651 }
3652 };
3653 #endif // ASSERT
3655 #if TASKQUEUE_STATS
3656 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3657 st->print_raw_cr("GC Task Stats");
3658 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3659 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3660 }
3662 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3663 print_taskqueue_stats_hdr(st);
3665 TaskQueueStats totals;
3666 const int n = workers() != NULL ? workers()->total_workers() : 1;
3667 for (int i = 0; i < n; ++i) {
3668 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3669 totals += task_queue(i)->stats;
3670 }
3671 st->print_raw("tot "); totals.print(st); st->cr();
3673 DEBUG_ONLY(totals.verify());
3674 }
3676 void G1CollectedHeap::reset_taskqueue_stats() {
3677 const int n = workers() != NULL ? workers()->total_workers() : 1;
3678 for (int i = 0; i < n; ++i) {
3679 task_queue(i)->stats.reset();
3680 }
3681 }
3682 #endif // TASKQUEUE_STATS
3684 bool
3685 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3686 assert_at_safepoint(true /* should_be_vm_thread */);
3687 guarantee(!is_gc_active(), "collection is not reentrant");
3689 if (GC_locker::check_active_before_gc()) {
3690 return false;
3691 }
3693 SvcGCMarker sgcm(SvcGCMarker::MINOR);
3694 ResourceMark rm;
3696 print_heap_before_gc();
3698 HRSPhaseSetter x(HRSPhaseEvacuation);
3699 verify_region_sets_optional();
3700 verify_dirty_young_regions();
3702 // This call will decide whether this pause is an initial-mark
3703 // pause. If it is, during_initial_mark_pause() will return true
3704 // for the duration of this pause.
3705 g1_policy()->decide_on_conc_mark_initiation();
3707 // We do not allow initial-mark to be piggy-backed on a mixed GC.
3708 assert(!g1_policy()->during_initial_mark_pause() ||
3709 g1_policy()->gcs_are_young(), "sanity");
3711 // We also do not allow mixed GCs during marking.
3712 assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3714 // Record whether this pause is an initial mark. When the current
3715 // thread has completed its logging output and it's safe to signal
3716 // the CM thread, the flag's value in the policy has been reset.
3717 bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3719 // Inner scope for scope based logging, timers, and stats collection
3720 {
3721 if (g1_policy()->during_initial_mark_pause()) {
3722 // We are about to start a marking cycle, so we increment the
3723 // full collection counter.
3724 increment_old_marking_cycles_started();
3725 }
3726 // if the log level is "finer" is on, we'll print long statistics information
3727 // in the collector policy code, so let's not print this as the output
3728 // is messy if we do.
3729 gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps);
3730 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3732 int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
3733 workers()->active_workers() : 1);
3734 g1_policy()->phase_times()->note_gc_start(os::elapsedTime(), active_workers,
3735 g1_policy()->gcs_are_young(), g1_policy()->during_initial_mark_pause(), gc_cause());
3737 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3738 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3740 // If the secondary_free_list is not empty, append it to the
3741 // free_list. No need to wait for the cleanup operation to finish;
3742 // the region allocation code will check the secondary_free_list
3743 // and wait if necessary. If the G1StressConcRegionFreeing flag is
3744 // set, skip this step so that the region allocation code has to
3745 // get entries from the secondary_free_list.
3746 if (!G1StressConcRegionFreeing) {
3747 append_secondary_free_list_if_not_empty_with_lock();
3748 }
3750 assert(check_young_list_well_formed(),
3751 "young list should be well formed");
3753 // Don't dynamically change the number of GC threads this early. A value of
3754 // 0 is used to indicate serial work. When parallel work is done,
3755 // it will be set.
3757 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3758 IsGCActiveMark x;
3760 gc_prologue(false);
3761 increment_total_collections(false /* full gc */);
3762 increment_gc_time_stamp();
3764 if (VerifyBeforeGC && total_collections() >= VerifyGCStartAt) {
3765 HandleMark hm; // Discard invalid handles created during verification
3766 gclog_or_tty->print(" VerifyBeforeGC:");
3767 prepare_for_verify();
3768 Universe::verify(/* silent */ false,
3769 /* option */ VerifyOption_G1UsePrevMarking);
3770 }
3772 COMPILER2_PRESENT(DerivedPointerTable::clear());
3774 // Please see comment in g1CollectedHeap.hpp and
3775 // G1CollectedHeap::ref_processing_init() to see how
3776 // reference processing currently works in G1.
3778 // Enable discovery in the STW reference processor
3779 ref_processor_stw()->enable_discovery(true /*verify_disabled*/,
3780 true /*verify_no_refs*/);
3782 {
3783 // We want to temporarily turn off discovery by the
3784 // CM ref processor, if necessary, and turn it back on
3785 // on again later if we do. Using a scoped
3786 // NoRefDiscovery object will do this.
3787 NoRefDiscovery no_cm_discovery(ref_processor_cm());
3789 // Forget the current alloc region (we might even choose it to be part
3790 // of the collection set!).
3791 release_mutator_alloc_region();
3793 // We should call this after we retire the mutator alloc
3794 // region(s) so that all the ALLOC / RETIRE events are generated
3795 // before the start GC event.
3796 _hr_printer.start_gc(false /* full */, (size_t) total_collections());
3798 // This timing is only used by the ergonomics to handle our pause target.
3799 // It is unclear why this should not include the full pause. We will
3800 // investigate this in CR 7178365.
3801 //
3802 // Preserving the old comment here if that helps the investigation:
3803 //
3804 // The elapsed time induced by the start time below deliberately elides
3805 // the possible verification above.
3806 double sample_start_time_sec = os::elapsedTime();
3807 size_t start_used_bytes = used();
3809 #if YOUNG_LIST_VERBOSE
3810 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
3811 _young_list->print();
3812 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3813 #endif // YOUNG_LIST_VERBOSE
3815 g1_policy()->record_collection_pause_start(sample_start_time_sec,
3816 start_used_bytes);
3818 double scan_wait_start = os::elapsedTime();
3819 // We have to wait until the CM threads finish scanning the
3820 // root regions as it's the only way to ensure that all the
3821 // objects on them have been correctly scanned before we start
3822 // moving them during the GC.
3823 bool waited = _cm->root_regions()->wait_until_scan_finished();
3824 double wait_time_ms = 0.0;
3825 if (waited) {
3826 double scan_wait_end = os::elapsedTime();
3827 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
3828 }
3829 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
3831 #if YOUNG_LIST_VERBOSE
3832 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
3833 _young_list->print();
3834 #endif // YOUNG_LIST_VERBOSE
3836 if (g1_policy()->during_initial_mark_pause()) {
3837 concurrent_mark()->checkpointRootsInitialPre();
3838 }
3839 perm_gen()->save_marks();
3841 #if YOUNG_LIST_VERBOSE
3842 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
3843 _young_list->print();
3844 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3845 #endif // YOUNG_LIST_VERBOSE
3847 g1_policy()->finalize_cset(target_pause_time_ms);
3849 _cm->note_start_of_gc();
3850 // We should not verify the per-thread SATB buffers given that
3851 // we have not filtered them yet (we'll do so during the
3852 // GC). We also call this after finalize_cset() to
3853 // ensure that the CSet has been finalized.
3854 _cm->verify_no_cset_oops(true /* verify_stacks */,
3855 true /* verify_enqueued_buffers */,
3856 false /* verify_thread_buffers */,
3857 true /* verify_fingers */);
3859 if (_hr_printer.is_active()) {
3860 HeapRegion* hr = g1_policy()->collection_set();
3861 while (hr != NULL) {
3862 G1HRPrinter::RegionType type;
3863 if (!hr->is_young()) {
3864 type = G1HRPrinter::Old;
3865 } else if (hr->is_survivor()) {
3866 type = G1HRPrinter::Survivor;
3867 } else {
3868 type = G1HRPrinter::Eden;
3869 }
3870 _hr_printer.cset(hr);
3871 hr = hr->next_in_collection_set();
3872 }
3873 }
3875 #ifdef ASSERT
3876 VerifyCSetClosure cl;
3877 collection_set_iterate(&cl);
3878 #endif // ASSERT
3880 setup_surviving_young_words();
3882 // Initialize the GC alloc regions.
3883 init_gc_alloc_regions();
3885 // Actually do the work...
3886 evacuate_collection_set();
3888 // We do this to mainly verify the per-thread SATB buffers
3889 // (which have been filtered by now) since we didn't verify
3890 // them earlier. No point in re-checking the stacks / enqueued
3891 // buffers given that the CSet has not changed since last time
3892 // we checked.
3893 _cm->verify_no_cset_oops(false /* verify_stacks */,
3894 false /* verify_enqueued_buffers */,
3895 true /* verify_thread_buffers */,
3896 true /* verify_fingers */);
3898 free_collection_set(g1_policy()->collection_set());
3899 g1_policy()->clear_collection_set();
3901 cleanup_surviving_young_words();
3903 // Start a new incremental collection set for the next pause.
3904 g1_policy()->start_incremental_cset_building();
3906 // Clear the _cset_fast_test bitmap in anticipation of adding
3907 // regions to the incremental collection set for the next
3908 // evacuation pause.
3909 clear_cset_fast_test();
3911 _young_list->reset_sampled_info();
3913 // Don't check the whole heap at this point as the
3914 // GC alloc regions from this pause have been tagged
3915 // as survivors and moved on to the survivor list.
3916 // Survivor regions will fail the !is_young() check.
3917 assert(check_young_list_empty(false /* check_heap */),
3918 "young list should be empty");
3920 #if YOUNG_LIST_VERBOSE
3921 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
3922 _young_list->print();
3923 #endif // YOUNG_LIST_VERBOSE
3925 g1_policy()->record_survivor_regions(_young_list->survivor_length(),
3926 _young_list->first_survivor_region(),
3927 _young_list->last_survivor_region());
3929 _young_list->reset_auxilary_lists();
3931 if (evacuation_failed()) {
3932 _summary_bytes_used = recalculate_used();
3933 } else {
3934 // The "used" of the the collection set have already been subtracted
3935 // when they were freed. Add in the bytes evacuated.
3936 _summary_bytes_used += g1_policy()->bytes_copied_during_gc();
3937 }
3939 if (g1_policy()->during_initial_mark_pause()) {
3940 // We have to do this before we notify the CM threads that
3941 // they can start working to make sure that all the
3942 // appropriate initialization is done on the CM object.
3943 concurrent_mark()->checkpointRootsInitialPost();
3944 set_marking_started();
3945 // Note that we don't actually trigger the CM thread at
3946 // this point. We do that later when we're sure that
3947 // the current thread has completed its logging output.
3948 }
3950 allocate_dummy_regions();
3952 #if YOUNG_LIST_VERBOSE
3953 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
3954 _young_list->print();
3955 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3956 #endif // YOUNG_LIST_VERBOSE
3958 init_mutator_alloc_region();
3960 {
3961 size_t expand_bytes = g1_policy()->expansion_amount();
3962 if (expand_bytes > 0) {
3963 size_t bytes_before = capacity();
3964 // No need for an ergo verbose message here,
3965 // expansion_amount() does this when it returns a value > 0.
3966 if (!expand(expand_bytes)) {
3967 // We failed to expand the heap so let's verify that
3968 // committed/uncommitted amount match the backing store
3969 assert(capacity() == _g1_storage.committed_size(), "committed size mismatch");
3970 assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch");
3971 }
3972 }
3973 }
3975 // We redo the verificaiton but now wrt to the new CSet which
3976 // has just got initialized after the previous CSet was freed.
3977 _cm->verify_no_cset_oops(true /* verify_stacks */,
3978 true /* verify_enqueued_buffers */,
3979 true /* verify_thread_buffers */,
3980 true /* verify_fingers */);
3981 _cm->note_end_of_gc();
3983 // Collect thread local data to allow the ergonomics to use
3984 // the collected information
3985 g1_policy()->phase_times()->collapse_par_times();
3987 // This timing is only used by the ergonomics to handle our pause target.
3988 // It is unclear why this should not include the full pause. We will
3989 // investigate this in CR 7178365.
3990 double sample_end_time_sec = os::elapsedTime();
3991 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3992 g1_policy()->record_collection_pause_end(pause_time_ms);
3994 MemoryService::track_memory_usage();
3996 // In prepare_for_verify() below we'll need to scan the deferred
3997 // update buffers to bring the RSets up-to-date if
3998 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
3999 // the update buffers we'll probably need to scan cards on the
4000 // regions we just allocated to (i.e., the GC alloc
4001 // regions). However, during the last GC we called
4002 // set_saved_mark() on all the GC alloc regions, so card
4003 // scanning might skip the [saved_mark_word()...top()] area of
4004 // those regions (i.e., the area we allocated objects into
4005 // during the last GC). But it shouldn't. Given that
4006 // saved_mark_word() is conditional on whether the GC time stamp
4007 // on the region is current or not, by incrementing the GC time
4008 // stamp here we invalidate all the GC time stamps on all the
4009 // regions and saved_mark_word() will simply return top() for
4010 // all the regions. This is a nicer way of ensuring this rather
4011 // than iterating over the regions and fixing them. In fact, the
4012 // GC time stamp increment here also ensures that
4013 // saved_mark_word() will return top() between pauses, i.e.,
4014 // during concurrent refinement. So we don't need the
4015 // is_gc_active() check to decided which top to use when
4016 // scanning cards (see CR 7039627).
4017 increment_gc_time_stamp();
4019 if (VerifyAfterGC && total_collections() >= VerifyGCStartAt) {
4020 HandleMark hm; // Discard invalid handles created during verification
4021 gclog_or_tty->print(" VerifyAfterGC:");
4022 prepare_for_verify();
4023 Universe::verify(/* silent */ false,
4024 /* option */ VerifyOption_G1UsePrevMarking);
4025 }
4027 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
4028 ref_processor_stw()->verify_no_references_recorded();
4030 // CM reference discovery will be re-enabled if necessary.
4031 }
4033 // We should do this after we potentially expand the heap so
4034 // that all the COMMIT events are generated before the end GC
4035 // event, and after we retire the GC alloc regions so that all
4036 // RETIRE events are generated before the end GC event.
4037 _hr_printer.end_gc(false /* full */, (size_t) total_collections());
4039 if (mark_in_progress()) {
4040 concurrent_mark()->update_g1_committed();
4041 }
4043 #ifdef TRACESPINNING
4044 ParallelTaskTerminator::print_termination_counts();
4045 #endif
4047 gc_epilogue(false);
4049 g1_policy()->phase_times()->note_gc_end(os::elapsedTime());
4051 // We have to do this after we decide whether to expand the heap or not.
4052 g1_policy()->print_heap_transition();
4053 }
4055 // It is not yet to safe to tell the concurrent mark to
4056 // start as we have some optional output below. We don't want the
4057 // output from the concurrent mark thread interfering with this
4058 // logging output either.
4060 _hrs.verify_optional();
4061 verify_region_sets_optional();
4063 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
4064 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
4066 print_heap_after_gc();
4068 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
4069 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
4070 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
4071 // before any GC notifications are raised.
4072 g1mm()->update_sizes();
4073 }
4075 if (G1SummarizeRSetStats &&
4076 (G1SummarizeRSetStatsPeriod > 0) &&
4077 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
4078 g1_rem_set()->print_summary_info();
4079 }
4081 // It should now be safe to tell the concurrent mark thread to start
4082 // without its logging output interfering with the logging output
4083 // that came from the pause.
4085 if (should_start_conc_mark) {
4086 // CAUTION: after the doConcurrentMark() call below,
4087 // the concurrent marking thread(s) could be running
4088 // concurrently with us. Make sure that anything after
4089 // this point does not assume that we are the only GC thread
4090 // running. Note: of course, the actual marking work will
4091 // not start until the safepoint itself is released in
4092 // ConcurrentGCThread::safepoint_desynchronize().
4093 doConcurrentMark();
4094 }
4096 return true;
4097 }
4099 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
4100 {
4101 size_t gclab_word_size;
4102 switch (purpose) {
4103 case GCAllocForSurvived:
4104 gclab_word_size = _survivor_plab_stats.desired_plab_sz();
4105 break;
4106 case GCAllocForTenured:
4107 gclab_word_size = _old_plab_stats.desired_plab_sz();
4108 break;
4109 default:
4110 assert(false, "unknown GCAllocPurpose");
4111 gclab_word_size = _old_plab_stats.desired_plab_sz();
4112 break;
4113 }
4115 // Prevent humongous PLAB sizes for two reasons:
4116 // * PLABs are allocated using a similar paths as oops, but should
4117 // never be in a humongous region
4118 // * Allowing humongous PLABs needlessly churns the region free lists
4119 return MIN2(_humongous_object_threshold_in_words, gclab_word_size);
4120 }
4122 void G1CollectedHeap::init_mutator_alloc_region() {
4123 assert(_mutator_alloc_region.get() == NULL, "pre-condition");
4124 _mutator_alloc_region.init();
4125 }
4127 void G1CollectedHeap::release_mutator_alloc_region() {
4128 _mutator_alloc_region.release();
4129 assert(_mutator_alloc_region.get() == NULL, "post-condition");
4130 }
4132 void G1CollectedHeap::init_gc_alloc_regions() {
4133 assert_at_safepoint(true /* should_be_vm_thread */);
4135 _survivor_gc_alloc_region.init();
4136 _old_gc_alloc_region.init();
4137 HeapRegion* retained_region = _retained_old_gc_alloc_region;
4138 _retained_old_gc_alloc_region = NULL;
4140 // We will discard the current GC alloc region if:
4141 // a) it's in the collection set (it can happen!),
4142 // b) it's already full (no point in using it),
4143 // c) it's empty (this means that it was emptied during
4144 // a cleanup and it should be on the free list now), or
4145 // d) it's humongous (this means that it was emptied
4146 // during a cleanup and was added to the free list, but
4147 // has been subseqently used to allocate a humongous
4148 // object that may be less than the region size).
4149 if (retained_region != NULL &&
4150 !retained_region->in_collection_set() &&
4151 !(retained_region->top() == retained_region->end()) &&
4152 !retained_region->is_empty() &&
4153 !retained_region->isHumongous()) {
4154 retained_region->set_saved_mark();
4155 // The retained region was added to the old region set when it was
4156 // retired. We have to remove it now, since we don't allow regions
4157 // we allocate to in the region sets. We'll re-add it later, when
4158 // it's retired again.
4159 _old_set.remove(retained_region);
4160 bool during_im = g1_policy()->during_initial_mark_pause();
4161 retained_region->note_start_of_copying(during_im);
4162 _old_gc_alloc_region.set(retained_region);
4163 _hr_printer.reuse(retained_region);
4164 }
4165 }
4167 void G1CollectedHeap::release_gc_alloc_regions() {
4168 _survivor_gc_alloc_region.release();
4169 // If we have an old GC alloc region to release, we'll save it in
4170 // _retained_old_gc_alloc_region. If we don't
4171 // _retained_old_gc_alloc_region will become NULL. This is what we
4172 // want either way so no reason to check explicitly for either
4173 // condition.
4174 _retained_old_gc_alloc_region = _old_gc_alloc_region.release();
4176 if (ResizePLAB) {
4177 _survivor_plab_stats.adjust_desired_plab_sz();
4178 _old_plab_stats.adjust_desired_plab_sz();
4179 }
4180 }
4182 void G1CollectedHeap::abandon_gc_alloc_regions() {
4183 assert(_survivor_gc_alloc_region.get() == NULL, "pre-condition");
4184 assert(_old_gc_alloc_region.get() == NULL, "pre-condition");
4185 _retained_old_gc_alloc_region = NULL;
4186 }
4188 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4189 _drain_in_progress = false;
4190 set_evac_failure_closure(cl);
4191 _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4192 }
4194 void G1CollectedHeap::finalize_for_evac_failure() {
4195 assert(_evac_failure_scan_stack != NULL &&
4196 _evac_failure_scan_stack->length() == 0,
4197 "Postcondition");
4198 assert(!_drain_in_progress, "Postcondition");
4199 delete _evac_failure_scan_stack;
4200 _evac_failure_scan_stack = NULL;
4201 }
4203 void G1CollectedHeap::remove_self_forwarding_pointers() {
4204 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4206 G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4208 if (G1CollectedHeap::use_parallel_gc_threads()) {
4209 set_par_threads();
4210 workers()->run_task(&rsfp_task);
4211 set_par_threads(0);
4212 } else {
4213 rsfp_task.work(0);
4214 }
4216 assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity");
4218 // Reset the claim values in the regions in the collection set.
4219 reset_cset_heap_region_claim_values();
4221 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4223 // Now restore saved marks, if any.
4224 if (_objs_with_preserved_marks != NULL) {
4225 assert(_preserved_marks_of_objs != NULL, "Both or none.");
4226 guarantee(_objs_with_preserved_marks->length() ==
4227 _preserved_marks_of_objs->length(), "Both or none.");
4228 for (int i = 0; i < _objs_with_preserved_marks->length(); i++) {
4229 oop obj = _objs_with_preserved_marks->at(i);
4230 markOop m = _preserved_marks_of_objs->at(i);
4231 obj->set_mark(m);
4232 }
4234 // Delete the preserved marks growable arrays (allocated on the C heap).
4235 delete _objs_with_preserved_marks;
4236 delete _preserved_marks_of_objs;
4237 _objs_with_preserved_marks = NULL;
4238 _preserved_marks_of_objs = NULL;
4239 }
4240 }
4242 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4243 _evac_failure_scan_stack->push(obj);
4244 }
4246 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4247 assert(_evac_failure_scan_stack != NULL, "precondition");
4249 while (_evac_failure_scan_stack->length() > 0) {
4250 oop obj = _evac_failure_scan_stack->pop();
4251 _evac_failure_closure->set_region(heap_region_containing(obj));
4252 obj->oop_iterate_backwards(_evac_failure_closure);
4253 }
4254 }
4256 oop
4257 G1CollectedHeap::handle_evacuation_failure_par(OopsInHeapRegionClosure* cl,
4258 oop old) {
4259 assert(obj_in_cs(old),
4260 err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4261 (HeapWord*) old));
4262 markOop m = old->mark();
4263 oop forward_ptr = old->forward_to_atomic(old);
4264 if (forward_ptr == NULL) {
4265 // Forward-to-self succeeded.
4267 if (_evac_failure_closure != cl) {
4268 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4269 assert(!_drain_in_progress,
4270 "Should only be true while someone holds the lock.");
4271 // Set the global evac-failure closure to the current thread's.
4272 assert(_evac_failure_closure == NULL, "Or locking has failed.");
4273 set_evac_failure_closure(cl);
4274 // Now do the common part.
4275 handle_evacuation_failure_common(old, m);
4276 // Reset to NULL.
4277 set_evac_failure_closure(NULL);
4278 } else {
4279 // The lock is already held, and this is recursive.
4280 assert(_drain_in_progress, "This should only be the recursive case.");
4281 handle_evacuation_failure_common(old, m);
4282 }
4283 return old;
4284 } else {
4285 // Forward-to-self failed. Either someone else managed to allocate
4286 // space for this object (old != forward_ptr) or they beat us in
4287 // self-forwarding it (old == forward_ptr).
4288 assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4289 err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4290 "should not be in the CSet",
4291 (HeapWord*) old, (HeapWord*) forward_ptr));
4292 return forward_ptr;
4293 }
4294 }
4296 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4297 set_evacuation_failed(true);
4299 preserve_mark_if_necessary(old, m);
4301 HeapRegion* r = heap_region_containing(old);
4302 if (!r->evacuation_failed()) {
4303 r->set_evacuation_failed(true);
4304 _hr_printer.evac_failure(r);
4305 }
4307 push_on_evac_failure_scan_stack(old);
4309 if (!_drain_in_progress) {
4310 // prevent recursion in copy_to_survivor_space()
4311 _drain_in_progress = true;
4312 drain_evac_failure_scan_stack();
4313 _drain_in_progress = false;
4314 }
4315 }
4317 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4318 assert(evacuation_failed(), "Oversaving!");
4319 // We want to call the "for_promotion_failure" version only in the
4320 // case of a promotion failure.
4321 if (m->must_be_preserved_for_promotion_failure(obj)) {
4322 if (_objs_with_preserved_marks == NULL) {
4323 assert(_preserved_marks_of_objs == NULL, "Both or none.");
4324 _objs_with_preserved_marks =
4325 new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4326 _preserved_marks_of_objs =
4327 new (ResourceObj::C_HEAP, mtGC) GrowableArray<markOop>(40, true);
4328 }
4329 _objs_with_preserved_marks->push(obj);
4330 _preserved_marks_of_objs->push(m);
4331 }
4332 }
4334 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
4335 size_t word_size) {
4336 if (purpose == GCAllocForSurvived) {
4337 HeapWord* result = survivor_attempt_allocation(word_size);
4338 if (result != NULL) {
4339 return result;
4340 } else {
4341 // Let's try to allocate in the old gen in case we can fit the
4342 // object there.
4343 return old_attempt_allocation(word_size);
4344 }
4345 } else {
4346 assert(purpose == GCAllocForTenured, "sanity");
4347 HeapWord* result = old_attempt_allocation(word_size);
4348 if (result != NULL) {
4349 return result;
4350 } else {
4351 // Let's try to allocate in the survivors in case we can fit the
4352 // object there.
4353 return survivor_attempt_allocation(word_size);
4354 }
4355 }
4357 ShouldNotReachHere();
4358 // Trying to keep some compilers happy.
4359 return NULL;
4360 }
4362 G1ParGCAllocBuffer::G1ParGCAllocBuffer(size_t gclab_word_size) :
4363 ParGCAllocBuffer(gclab_word_size), _retired(false) { }
4365 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, uint queue_num)
4366 : _g1h(g1h),
4367 _refs(g1h->task_queue(queue_num)),
4368 _dcq(&g1h->dirty_card_queue_set()),
4369 _ct_bs((CardTableModRefBS*)_g1h->barrier_set()),
4370 _g1_rem(g1h->g1_rem_set()),
4371 _hash_seed(17), _queue_num(queue_num),
4372 _term_attempts(0),
4373 _surviving_alloc_buffer(g1h->desired_plab_sz(GCAllocForSurvived)),
4374 _tenured_alloc_buffer(g1h->desired_plab_sz(GCAllocForTenured)),
4375 _age_table(false),
4376 _strong_roots_time(0), _term_time(0),
4377 _alloc_buffer_waste(0), _undo_waste(0) {
4378 // we allocate G1YoungSurvRateNumRegions plus one entries, since
4379 // we "sacrifice" entry 0 to keep track of surviving bytes for
4380 // non-young regions (where the age is -1)
4381 // We also add a few elements at the beginning and at the end in
4382 // an attempt to eliminate cache contention
4383 uint real_length = 1 + _g1h->g1_policy()->young_cset_region_length();
4384 uint array_length = PADDING_ELEM_NUM +
4385 real_length +
4386 PADDING_ELEM_NUM;
4387 _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length, mtGC);
4388 if (_surviving_young_words_base == NULL)
4389 vm_exit_out_of_memory(array_length * sizeof(size_t),
4390 "Not enough space for young surv histo.");
4391 _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM;
4392 memset(_surviving_young_words, 0, (size_t) real_length * sizeof(size_t));
4394 _alloc_buffers[GCAllocForSurvived] = &_surviving_alloc_buffer;
4395 _alloc_buffers[GCAllocForTenured] = &_tenured_alloc_buffer;
4397 _start = os::elapsedTime();
4398 }
4400 void
4401 G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st)
4402 {
4403 st->print_raw_cr("GC Termination Stats");
4404 st->print_raw_cr(" elapsed --strong roots-- -------termination-------"
4405 " ------waste (KiB)------");
4406 st->print_raw_cr("thr ms ms % ms % attempts"
4407 " total alloc undo");
4408 st->print_raw_cr("--- --------- --------- ------ --------- ------ --------"
4409 " ------- ------- -------");
4410 }
4412 void
4413 G1ParScanThreadState::print_termination_stats(int i,
4414 outputStream* const st) const
4415 {
4416 const double elapsed_ms = elapsed_time() * 1000.0;
4417 const double s_roots_ms = strong_roots_time() * 1000.0;
4418 const double term_ms = term_time() * 1000.0;
4419 st->print_cr("%3d %9.2f %9.2f %6.2f "
4420 "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
4421 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
4422 i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms,
4423 term_ms, term_ms * 100 / elapsed_ms, term_attempts(),
4424 (alloc_buffer_waste() + undo_waste()) * HeapWordSize / K,
4425 alloc_buffer_waste() * HeapWordSize / K,
4426 undo_waste() * HeapWordSize / K);
4427 }
4429 #ifdef ASSERT
4430 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const {
4431 assert(ref != NULL, "invariant");
4432 assert(UseCompressedOops, "sanity");
4433 assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, ref));
4434 oop p = oopDesc::load_decode_heap_oop(ref);
4435 assert(_g1h->is_in_g1_reserved(p),
4436 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4437 return true;
4438 }
4440 bool G1ParScanThreadState::verify_ref(oop* ref) const {
4441 assert(ref != NULL, "invariant");
4442 if (has_partial_array_mask(ref)) {
4443 // Must be in the collection set--it's already been copied.
4444 oop p = clear_partial_array_mask(ref);
4445 assert(_g1h->obj_in_cs(p),
4446 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4447 } else {
4448 oop p = oopDesc::load_decode_heap_oop(ref);
4449 assert(_g1h->is_in_g1_reserved(p),
4450 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4451 }
4452 return true;
4453 }
4455 bool G1ParScanThreadState::verify_task(StarTask ref) const {
4456 if (ref.is_narrow()) {
4457 return verify_ref((narrowOop*) ref);
4458 } else {
4459 return verify_ref((oop*) ref);
4460 }
4461 }
4462 #endif // ASSERT
4464 void G1ParScanThreadState::trim_queue() {
4465 assert(_evac_cl != NULL, "not set");
4466 assert(_evac_failure_cl != NULL, "not set");
4467 assert(_partial_scan_cl != NULL, "not set");
4469 StarTask ref;
4470 do {
4471 // Drain the overflow stack first, so other threads can steal.
4472 while (refs()->pop_overflow(ref)) {
4473 deal_with_reference(ref);
4474 }
4476 while (refs()->pop_local(ref)) {
4477 deal_with_reference(ref);
4478 }
4479 } while (!refs()->is_empty());
4480 }
4482 G1ParClosureSuper::G1ParClosureSuper(G1CollectedHeap* g1,
4483 G1ParScanThreadState* par_scan_state) :
4484 _g1(g1), _g1_rem(_g1->g1_rem_set()), _cm(_g1->concurrent_mark()),
4485 _par_scan_state(par_scan_state),
4486 _worker_id(par_scan_state->queue_num()),
4487 _during_initial_mark(_g1->g1_policy()->during_initial_mark_pause()),
4488 _mark_in_progress(_g1->mark_in_progress()) { }
4490 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4491 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>::mark_object(oop obj) {
4492 #ifdef ASSERT
4493 HeapRegion* hr = _g1->heap_region_containing(obj);
4494 assert(hr != NULL, "sanity");
4495 assert(!hr->in_collection_set(), "should not mark objects in the CSet");
4496 #endif // ASSERT
4498 // We know that the object is not moving so it's safe to read its size.
4499 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4500 }
4502 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4503 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4504 ::mark_forwarded_object(oop from_obj, oop to_obj) {
4505 #ifdef ASSERT
4506 assert(from_obj->is_forwarded(), "from obj should be forwarded");
4507 assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4508 assert(from_obj != to_obj, "should not be self-forwarded");
4510 HeapRegion* from_hr = _g1->heap_region_containing(from_obj);
4511 assert(from_hr != NULL, "sanity");
4512 assert(from_hr->in_collection_set(), "from obj should be in the CSet");
4514 HeapRegion* to_hr = _g1->heap_region_containing(to_obj);
4515 assert(to_hr != NULL, "sanity");
4516 assert(!to_hr->in_collection_set(), "should not mark objects in the CSet");
4517 #endif // ASSERT
4519 // The object might be in the process of being copied by another
4520 // worker so we cannot trust that its to-space image is
4521 // well-formed. So we have to read its size from its from-space
4522 // image which we know should not be changing.
4523 _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4524 }
4526 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4527 oop G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4528 ::copy_to_survivor_space(oop old) {
4529 size_t word_sz = old->size();
4530 HeapRegion* from_region = _g1->heap_region_containing_raw(old);
4531 // +1 to make the -1 indexes valid...
4532 int young_index = from_region->young_index_in_cset()+1;
4533 assert( (from_region->is_young() && young_index > 0) ||
4534 (!from_region->is_young() && young_index == 0), "invariant" );
4535 G1CollectorPolicy* g1p = _g1->g1_policy();
4536 markOop m = old->mark();
4537 int age = m->has_displaced_mark_helper() ? m->displaced_mark_helper()->age()
4538 : m->age();
4539 GCAllocPurpose alloc_purpose = g1p->evacuation_destination(from_region, age,
4540 word_sz);
4541 HeapWord* obj_ptr = _par_scan_state->allocate(alloc_purpose, word_sz);
4542 oop obj = oop(obj_ptr);
4544 if (obj_ptr == NULL) {
4545 // This will either forward-to-self, or detect that someone else has
4546 // installed a forwarding pointer.
4547 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4548 return _g1->handle_evacuation_failure_par(cl, old);
4549 }
4551 // We're going to allocate linearly, so might as well prefetch ahead.
4552 Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
4554 oop forward_ptr = old->forward_to_atomic(obj);
4555 if (forward_ptr == NULL) {
4556 Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
4557 if (g1p->track_object_age(alloc_purpose)) {
4558 // We could simply do obj->incr_age(). However, this causes a
4559 // performance issue. obj->incr_age() will first check whether
4560 // the object has a displaced mark by checking its mark word;
4561 // getting the mark word from the new location of the object
4562 // stalls. So, given that we already have the mark word and we
4563 // are about to install it anyway, it's better to increase the
4564 // age on the mark word, when the object does not have a
4565 // displaced mark word. We're not expecting many objects to have
4566 // a displaced marked word, so that case is not optimized
4567 // further (it could be...) and we simply call obj->incr_age().
4569 if (m->has_displaced_mark_helper()) {
4570 // in this case, we have to install the mark word first,
4571 // otherwise obj looks to be forwarded (the old mark word,
4572 // which contains the forward pointer, was copied)
4573 obj->set_mark(m);
4574 obj->incr_age();
4575 } else {
4576 m = m->incr_age();
4577 obj->set_mark(m);
4578 }
4579 _par_scan_state->age_table()->add(obj, word_sz);
4580 } else {
4581 obj->set_mark(m);
4582 }
4584 size_t* surv_young_words = _par_scan_state->surviving_young_words();
4585 surv_young_words[young_index] += word_sz;
4587 if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
4588 // We keep track of the next start index in the length field of
4589 // the to-space object. The actual length can be found in the
4590 // length field of the from-space object.
4591 arrayOop(obj)->set_length(0);
4592 oop* old_p = set_partial_array_mask(old);
4593 _par_scan_state->push_on_queue(old_p);
4594 } else {
4595 // No point in using the slower heap_region_containing() method,
4596 // given that we know obj is in the heap.
4597 _scanner.set_region(_g1->heap_region_containing_raw(obj));
4598 obj->oop_iterate_backwards(&_scanner);
4599 }
4600 } else {
4601 _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz);
4602 obj = forward_ptr;
4603 }
4604 return obj;
4605 }
4607 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4608 template <class T>
4609 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4610 ::do_oop_work(T* p) {
4611 oop obj = oopDesc::load_decode_heap_oop(p);
4612 assert(barrier != G1BarrierRS || obj != NULL,
4613 "Precondition: G1BarrierRS implies obj is non-NULL");
4615 assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4617 // here the null check is implicit in the cset_fast_test() test
4618 if (_g1->in_cset_fast_test(obj)) {
4619 oop forwardee;
4620 if (obj->is_forwarded()) {
4621 forwardee = obj->forwardee();
4622 } else {
4623 forwardee = copy_to_survivor_space(obj);
4624 }
4625 assert(forwardee != NULL, "forwardee should not be NULL");
4626 oopDesc::encode_store_heap_oop(p, forwardee);
4627 if (do_mark_object && forwardee != obj) {
4628 // If the object is self-forwarded we don't need to explicitly
4629 // mark it, the evacuation failure protocol will do so.
4630 mark_forwarded_object(obj, forwardee);
4631 }
4633 // When scanning the RS, we only care about objs in CS.
4634 if (barrier == G1BarrierRS) {
4635 _par_scan_state->update_rs(_from, p, _worker_id);
4636 }
4637 } else {
4638 // The object is not in collection set. If we're a root scanning
4639 // closure during an initial mark pause (i.e. do_mark_object will
4640 // be true) then attempt to mark the object.
4641 if (do_mark_object && _g1->is_in_g1_reserved(obj)) {
4642 mark_object(obj);
4643 }
4644 }
4646 if (barrier == G1BarrierEvac && obj != NULL) {
4647 _par_scan_state->update_rs(_from, p, _worker_id);
4648 }
4650 if (do_gen_barrier && obj != NULL) {
4651 par_do_barrier(p);
4652 }
4653 }
4655 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(oop* p);
4656 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(narrowOop* p);
4658 template <class T> void G1ParScanPartialArrayClosure::do_oop_nv(T* p) {
4659 assert(has_partial_array_mask(p), "invariant");
4660 oop from_obj = clear_partial_array_mask(p);
4662 assert(Universe::heap()->is_in_reserved(from_obj), "must be in heap.");
4663 assert(from_obj->is_objArray(), "must be obj array");
4664 objArrayOop from_obj_array = objArrayOop(from_obj);
4665 // The from-space object contains the real length.
4666 int length = from_obj_array->length();
4668 assert(from_obj->is_forwarded(), "must be forwarded");
4669 oop to_obj = from_obj->forwardee();
4670 assert(from_obj != to_obj, "should not be chunking self-forwarded objects");
4671 objArrayOop to_obj_array = objArrayOop(to_obj);
4672 // We keep track of the next start index in the length field of the
4673 // to-space object.
4674 int next_index = to_obj_array->length();
4675 assert(0 <= next_index && next_index < length,
4676 err_msg("invariant, next index: %d, length: %d", next_index, length));
4678 int start = next_index;
4679 int end = length;
4680 int remainder = end - start;
4681 // We'll try not to push a range that's smaller than ParGCArrayScanChunk.
4682 if (remainder > 2 * ParGCArrayScanChunk) {
4683 end = start + ParGCArrayScanChunk;
4684 to_obj_array->set_length(end);
4685 // Push the remainder before we process the range in case another
4686 // worker has run out of things to do and can steal it.
4687 oop* from_obj_p = set_partial_array_mask(from_obj);
4688 _par_scan_state->push_on_queue(from_obj_p);
4689 } else {
4690 assert(length == end, "sanity");
4691 // We'll process the final range for this object. Restore the length
4692 // so that the heap remains parsable in case of evacuation failure.
4693 to_obj_array->set_length(end);
4694 }
4695 _scanner.set_region(_g1->heap_region_containing_raw(to_obj));
4696 // Process indexes [start,end). It will also process the header
4697 // along with the first chunk (i.e., the chunk with start == 0).
4698 // Note that at this point the length field of to_obj_array is not
4699 // correct given that we are using it to keep track of the next
4700 // start index. oop_iterate_range() (thankfully!) ignores the length
4701 // field and only relies on the start / end parameters. It does
4702 // however return the size of the object which will be incorrect. So
4703 // we have to ignore it even if we wanted to use it.
4704 to_obj_array->oop_iterate_range(&_scanner, start, end);
4705 }
4707 class G1ParEvacuateFollowersClosure : public VoidClosure {
4708 protected:
4709 G1CollectedHeap* _g1h;
4710 G1ParScanThreadState* _par_scan_state;
4711 RefToScanQueueSet* _queues;
4712 ParallelTaskTerminator* _terminator;
4714 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
4715 RefToScanQueueSet* queues() { return _queues; }
4716 ParallelTaskTerminator* terminator() { return _terminator; }
4718 public:
4719 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4720 G1ParScanThreadState* par_scan_state,
4721 RefToScanQueueSet* queues,
4722 ParallelTaskTerminator* terminator)
4723 : _g1h(g1h), _par_scan_state(par_scan_state),
4724 _queues(queues), _terminator(terminator) {}
4726 void do_void();
4728 private:
4729 inline bool offer_termination();
4730 };
4732 bool G1ParEvacuateFollowersClosure::offer_termination() {
4733 G1ParScanThreadState* const pss = par_scan_state();
4734 pss->start_term_time();
4735 const bool res = terminator()->offer_termination();
4736 pss->end_term_time();
4737 return res;
4738 }
4740 void G1ParEvacuateFollowersClosure::do_void() {
4741 StarTask stolen_task;
4742 G1ParScanThreadState* const pss = par_scan_state();
4743 pss->trim_queue();
4745 do {
4746 while (queues()->steal(pss->queue_num(), pss->hash_seed(), stolen_task)) {
4747 assert(pss->verify_task(stolen_task), "sanity");
4748 if (stolen_task.is_narrow()) {
4749 pss->deal_with_reference((narrowOop*) stolen_task);
4750 } else {
4751 pss->deal_with_reference((oop*) stolen_task);
4752 }
4754 // We've just processed a reference and we might have made
4755 // available new entries on the queues. So we have to make sure
4756 // we drain the queues as necessary.
4757 pss->trim_queue();
4758 }
4759 } while (!offer_termination());
4761 pss->retire_alloc_buffers();
4762 }
4764 class G1ParTask : public AbstractGangTask {
4765 protected:
4766 G1CollectedHeap* _g1h;
4767 RefToScanQueueSet *_queues;
4768 ParallelTaskTerminator _terminator;
4769 uint _n_workers;
4771 Mutex _stats_lock;
4772 Mutex* stats_lock() { return &_stats_lock; }
4774 size_t getNCards() {
4775 return (_g1h->capacity() + G1BlockOffsetSharedArray::N_bytes - 1)
4776 / G1BlockOffsetSharedArray::N_bytes;
4777 }
4779 public:
4780 G1ParTask(G1CollectedHeap* g1h,
4781 RefToScanQueueSet *task_queues)
4782 : AbstractGangTask("G1 collection"),
4783 _g1h(g1h),
4784 _queues(task_queues),
4785 _terminator(0, _queues),
4786 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4787 {}
4789 RefToScanQueueSet* queues() { return _queues; }
4791 RefToScanQueue *work_queue(int i) {
4792 return queues()->queue(i);
4793 }
4795 ParallelTaskTerminator* terminator() { return &_terminator; }
4797 virtual void set_for_termination(int active_workers) {
4798 // This task calls set_n_termination() in par_non_clean_card_iterate_work()
4799 // in the young space (_par_seq_tasks) in the G1 heap
4800 // for SequentialSubTasksDone.
4801 // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap
4802 // both of which need setting by set_n_termination().
4803 _g1h->SharedHeap::set_n_termination(active_workers);
4804 _g1h->set_n_termination(active_workers);
4805 terminator()->reset_for_reuse(active_workers);
4806 _n_workers = active_workers;
4807 }
4809 void work(uint worker_id) {
4810 if (worker_id >= _n_workers) return; // no work needed this round
4812 double start_time_ms = os::elapsedTime() * 1000.0;
4813 _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms);
4815 {
4816 ResourceMark rm;
4817 HandleMark hm;
4819 ReferenceProcessor* rp = _g1h->ref_processor_stw();
4821 G1ParScanThreadState pss(_g1h, worker_id);
4822 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, rp);
4823 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
4824 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, rp);
4826 pss.set_evac_closure(&scan_evac_cl);
4827 pss.set_evac_failure_closure(&evac_failure_cl);
4828 pss.set_partial_scan_closure(&partial_scan_cl);
4830 G1ParScanExtRootClosure only_scan_root_cl(_g1h, &pss, rp);
4831 G1ParScanPermClosure only_scan_perm_cl(_g1h, &pss, rp);
4833 G1ParScanAndMarkExtRootClosure scan_mark_root_cl(_g1h, &pss, rp);
4834 G1ParScanAndMarkPermClosure scan_mark_perm_cl(_g1h, &pss, rp);
4836 OopClosure* scan_root_cl = &only_scan_root_cl;
4837 OopsInHeapRegionClosure* scan_perm_cl = &only_scan_perm_cl;
4839 if (_g1h->g1_policy()->during_initial_mark_pause()) {
4840 // We also need to mark copied objects.
4841 scan_root_cl = &scan_mark_root_cl;
4842 scan_perm_cl = &scan_mark_perm_cl;
4843 }
4845 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss);
4847 pss.start_strong_roots();
4848 _g1h->g1_process_strong_roots(/* not collecting perm */ false,
4849 SharedHeap::SO_AllClasses,
4850 scan_root_cl,
4851 &push_heap_rs_cl,
4852 scan_perm_cl,
4853 worker_id);
4854 pss.end_strong_roots();
4856 {
4857 double start = os::elapsedTime();
4858 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4859 evac.do_void();
4860 double elapsed_ms = (os::elapsedTime()-start)*1000.0;
4861 double term_ms = pss.term_time()*1000.0;
4862 _g1h->g1_policy()->phase_times()->record_obj_copy_time(worker_id, elapsed_ms-term_ms);
4863 _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts());
4864 }
4865 _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4866 _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4868 if (ParallelGCVerbose) {
4869 MutexLocker x(stats_lock());
4870 pss.print_termination_stats(worker_id);
4871 }
4873 assert(pss.refs()->is_empty(), "should be empty");
4875 // Close the inner scope so that the ResourceMark and HandleMark
4876 // destructors are executed here and are included as part of the
4877 // "GC Worker Time".
4878 }
4880 double end_time_ms = os::elapsedTime() * 1000.0;
4881 _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms);
4882 }
4883 };
4885 // *** Common G1 Evacuation Stuff
4887 // Closures that support the filtering of CodeBlobs scanned during
4888 // external root scanning.
4890 // Closure applied to reference fields in code blobs (specifically nmethods)
4891 // to determine whether an nmethod contains references that point into
4892 // the collection set. Used as a predicate when walking code roots so
4893 // that only nmethods that point into the collection set are added to the
4894 // 'marked' list.
4896 class G1FilteredCodeBlobToOopClosure : public CodeBlobToOopClosure {
4898 class G1PointsIntoCSOopClosure : public OopClosure {
4899 G1CollectedHeap* _g1;
4900 bool _points_into_cs;
4901 public:
4902 G1PointsIntoCSOopClosure(G1CollectedHeap* g1) :
4903 _g1(g1), _points_into_cs(false) { }
4905 bool points_into_cs() const { return _points_into_cs; }
4907 template <class T>
4908 void do_oop_nv(T* p) {
4909 if (!_points_into_cs) {
4910 T heap_oop = oopDesc::load_heap_oop(p);
4911 if (!oopDesc::is_null(heap_oop) &&
4912 _g1->in_cset_fast_test(oopDesc::decode_heap_oop_not_null(heap_oop))) {
4913 _points_into_cs = true;
4914 }
4915 }
4916 }
4918 virtual void do_oop(oop* p) { do_oop_nv(p); }
4919 virtual void do_oop(narrowOop* p) { do_oop_nv(p); }
4920 };
4922 G1CollectedHeap* _g1;
4924 public:
4925 G1FilteredCodeBlobToOopClosure(G1CollectedHeap* g1, OopClosure* cl) :
4926 CodeBlobToOopClosure(cl, true), _g1(g1) { }
4928 virtual void do_code_blob(CodeBlob* cb) {
4929 nmethod* nm = cb->as_nmethod_or_null();
4930 if (nm != NULL && !(nm->test_oops_do_mark())) {
4931 G1PointsIntoCSOopClosure predicate_cl(_g1);
4932 nm->oops_do(&predicate_cl);
4934 if (predicate_cl.points_into_cs()) {
4935 // At least one of the reference fields or the oop relocations
4936 // in the nmethod points into the collection set. We have to
4937 // 'mark' this nmethod.
4938 // Note: Revisit the following if CodeBlobToOopClosure::do_code_blob()
4939 // or MarkingCodeBlobClosure::do_code_blob() change.
4940 if (!nm->test_set_oops_do_mark()) {
4941 do_newly_marked_nmethod(nm);
4942 }
4943 }
4944 }
4945 }
4946 };
4948 // This method is run in a GC worker.
4950 void
4951 G1CollectedHeap::
4952 g1_process_strong_roots(bool collecting_perm_gen,
4953 ScanningOption so,
4954 OopClosure* scan_non_heap_roots,
4955 OopsInHeapRegionClosure* scan_rs,
4956 OopsInGenClosure* scan_perm,
4957 int worker_i) {
4959 // First scan the strong roots, including the perm gen.
4960 double ext_roots_start = os::elapsedTime();
4961 double closure_app_time_sec = 0.0;
4963 BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
4964 BufferingOopsInGenClosure buf_scan_perm(scan_perm);
4965 buf_scan_perm.set_generation(perm_gen());
4967 // Walk the code cache w/o buffering, because StarTask cannot handle
4968 // unaligned oop locations.
4969 G1FilteredCodeBlobToOopClosure eager_scan_code_roots(this, scan_non_heap_roots);
4971 process_strong_roots(false, // no scoping; this is parallel code
4972 collecting_perm_gen, so,
4973 &buf_scan_non_heap_roots,
4974 &eager_scan_code_roots,
4975 &buf_scan_perm);
4977 // Now the CM ref_processor roots.
4978 if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
4979 // We need to treat the discovered reference lists of the
4980 // concurrent mark ref processor as roots and keep entries
4981 // (which are added by the marking threads) on them live
4982 // until they can be processed at the end of marking.
4983 ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
4984 }
4986 // Finish up any enqueued closure apps (attributed as object copy time).
4987 buf_scan_non_heap_roots.done();
4988 buf_scan_perm.done();
4990 double ext_roots_end = os::elapsedTime();
4992 g1_policy()->phase_times()->reset_obj_copy_time(worker_i);
4993 double obj_copy_time_sec = buf_scan_perm.closure_app_seconds() +
4994 buf_scan_non_heap_roots.closure_app_seconds();
4995 g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
4997 double ext_root_time_ms =
4998 ((ext_roots_end - ext_roots_start) - obj_copy_time_sec) * 1000.0;
5000 g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
5002 // During conc marking we have to filter the per-thread SATB buffers
5003 // to make sure we remove any oops into the CSet (which will show up
5004 // as implicitly live).
5005 if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) {
5006 if (mark_in_progress()) {
5007 JavaThread::satb_mark_queue_set().filter_thread_buffers();
5008 }
5009 }
5010 double satb_filtering_ms = (os::elapsedTime() - ext_roots_end) * 1000.0;
5011 g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms);
5013 // Now scan the complement of the collection set.
5014 if (scan_rs != NULL) {
5015 g1_rem_set()->oops_into_collection_set_do(scan_rs, worker_i);
5016 }
5018 _process_strong_tasks->all_tasks_completed();
5019 }
5021 void
5022 G1CollectedHeap::g1_process_weak_roots(OopClosure* root_closure,
5023 OopClosure* non_root_closure) {
5024 CodeBlobToOopClosure roots_in_blobs(root_closure, /*do_marking=*/ false);
5025 SharedHeap::process_weak_roots(root_closure, &roots_in_blobs, non_root_closure);
5026 }
5028 // Weak Reference Processing support
5030 // An always "is_alive" closure that is used to preserve referents.
5031 // If the object is non-null then it's alive. Used in the preservation
5032 // of referent objects that are pointed to by reference objects
5033 // discovered by the CM ref processor.
5034 class G1AlwaysAliveClosure: public BoolObjectClosure {
5035 G1CollectedHeap* _g1;
5036 public:
5037 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5038 void do_object(oop p) { assert(false, "Do not call."); }
5039 bool do_object_b(oop p) {
5040 if (p != NULL) {
5041 return true;
5042 }
5043 return false;
5044 }
5045 };
5047 bool G1STWIsAliveClosure::do_object_b(oop p) {
5048 // An object is reachable if it is outside the collection set,
5049 // or is inside and copied.
5050 return !_g1->obj_in_cs(p) || p->is_forwarded();
5051 }
5053 // Non Copying Keep Alive closure
5054 class G1KeepAliveClosure: public OopClosure {
5055 G1CollectedHeap* _g1;
5056 public:
5057 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5058 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
5059 void do_oop( oop* p) {
5060 oop obj = *p;
5062 if (_g1->obj_in_cs(obj)) {
5063 assert( obj->is_forwarded(), "invariant" );
5064 *p = obj->forwardee();
5065 }
5066 }
5067 };
5069 // Copying Keep Alive closure - can be called from both
5070 // serial and parallel code as long as different worker
5071 // threads utilize different G1ParScanThreadState instances
5072 // and different queues.
5074 class G1CopyingKeepAliveClosure: public OopClosure {
5075 G1CollectedHeap* _g1h;
5076 OopClosure* _copy_non_heap_obj_cl;
5077 OopsInHeapRegionClosure* _copy_perm_obj_cl;
5078 G1ParScanThreadState* _par_scan_state;
5080 public:
5081 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
5082 OopClosure* non_heap_obj_cl,
5083 OopsInHeapRegionClosure* perm_obj_cl,
5084 G1ParScanThreadState* pss):
5085 _g1h(g1h),
5086 _copy_non_heap_obj_cl(non_heap_obj_cl),
5087 _copy_perm_obj_cl(perm_obj_cl),
5088 _par_scan_state(pss)
5089 {}
5091 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
5092 virtual void do_oop( oop* p) { do_oop_work(p); }
5094 template <class T> void do_oop_work(T* p) {
5095 oop obj = oopDesc::load_decode_heap_oop(p);
5097 if (_g1h->obj_in_cs(obj)) {
5098 // If the referent object has been forwarded (either copied
5099 // to a new location or to itself in the event of an
5100 // evacuation failure) then we need to update the reference
5101 // field and, if both reference and referent are in the G1
5102 // heap, update the RSet for the referent.
5103 //
5104 // If the referent has not been forwarded then we have to keep
5105 // it alive by policy. Therefore we have copy the referent.
5106 //
5107 // If the reference field is in the G1 heap then we can push
5108 // on the PSS queue. When the queue is drained (after each
5109 // phase of reference processing) the object and it's followers
5110 // will be copied, the reference field set to point to the
5111 // new location, and the RSet updated. Otherwise we need to
5112 // use the the non-heap or perm closures directly to copy
5113 // the refernt object and update the pointer, while avoiding
5114 // updating the RSet.
5116 if (_g1h->is_in_g1_reserved(p)) {
5117 _par_scan_state->push_on_queue(p);
5118 } else {
5119 // The reference field is not in the G1 heap.
5120 if (_g1h->perm_gen()->is_in(p)) {
5121 _copy_perm_obj_cl->do_oop(p);
5122 } else {
5123 _copy_non_heap_obj_cl->do_oop(p);
5124 }
5125 }
5126 }
5127 }
5128 };
5130 // Serial drain queue closure. Called as the 'complete_gc'
5131 // closure for each discovered list in some of the
5132 // reference processing phases.
5134 class G1STWDrainQueueClosure: public VoidClosure {
5135 protected:
5136 G1CollectedHeap* _g1h;
5137 G1ParScanThreadState* _par_scan_state;
5139 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
5141 public:
5142 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
5143 _g1h(g1h),
5144 _par_scan_state(pss)
5145 { }
5147 void do_void() {
5148 G1ParScanThreadState* const pss = par_scan_state();
5149 pss->trim_queue();
5150 }
5151 };
5153 // Parallel Reference Processing closures
5155 // Implementation of AbstractRefProcTaskExecutor for parallel reference
5156 // processing during G1 evacuation pauses.
5158 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5159 private:
5160 G1CollectedHeap* _g1h;
5161 RefToScanQueueSet* _queues;
5162 FlexibleWorkGang* _workers;
5163 int _active_workers;
5165 public:
5166 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5167 FlexibleWorkGang* workers,
5168 RefToScanQueueSet *task_queues,
5169 int n_workers) :
5170 _g1h(g1h),
5171 _queues(task_queues),
5172 _workers(workers),
5173 _active_workers(n_workers)
5174 {
5175 assert(n_workers > 0, "shouldn't call this otherwise");
5176 }
5178 // Executes the given task using concurrent marking worker threads.
5179 virtual void execute(ProcessTask& task);
5180 virtual void execute(EnqueueTask& task);
5181 };
5183 // Gang task for possibly parallel reference processing
5185 class G1STWRefProcTaskProxy: public AbstractGangTask {
5186 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5187 ProcessTask& _proc_task;
5188 G1CollectedHeap* _g1h;
5189 RefToScanQueueSet *_task_queues;
5190 ParallelTaskTerminator* _terminator;
5192 public:
5193 G1STWRefProcTaskProxy(ProcessTask& proc_task,
5194 G1CollectedHeap* g1h,
5195 RefToScanQueueSet *task_queues,
5196 ParallelTaskTerminator* terminator) :
5197 AbstractGangTask("Process reference objects in parallel"),
5198 _proc_task(proc_task),
5199 _g1h(g1h),
5200 _task_queues(task_queues),
5201 _terminator(terminator)
5202 {}
5204 virtual void work(uint worker_id) {
5205 // The reference processing task executed by a single worker.
5206 ResourceMark rm;
5207 HandleMark hm;
5209 G1STWIsAliveClosure is_alive(_g1h);
5211 G1ParScanThreadState pss(_g1h, worker_id);
5213 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, NULL);
5214 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5215 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, NULL);
5217 pss.set_evac_closure(&scan_evac_cl);
5218 pss.set_evac_failure_closure(&evac_failure_cl);
5219 pss.set_partial_scan_closure(&partial_scan_cl);
5221 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5222 G1ParScanPermClosure only_copy_perm_cl(_g1h, &pss, NULL);
5224 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5225 G1ParScanAndMarkPermClosure copy_mark_perm_cl(_g1h, &pss, NULL);
5227 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5228 OopsInHeapRegionClosure* copy_perm_cl = &only_copy_perm_cl;
5230 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5231 // We also need to mark copied objects.
5232 copy_non_heap_cl = ©_mark_non_heap_cl;
5233 copy_perm_cl = ©_mark_perm_cl;
5234 }
5236 // Keep alive closure.
5237 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_perm_cl, &pss);
5239 // Complete GC closure
5240 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5242 // Call the reference processing task's work routine.
5243 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5245 // Note we cannot assert that the refs array is empty here as not all
5246 // of the processing tasks (specifically phase2 - pp2_work) execute
5247 // the complete_gc closure (which ordinarily would drain the queue) so
5248 // the queue may not be empty.
5249 }
5250 };
5252 // Driver routine for parallel reference processing.
5253 // Creates an instance of the ref processing gang
5254 // task and has the worker threads execute it.
5255 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5256 assert(_workers != NULL, "Need parallel worker threads.");
5258 ParallelTaskTerminator terminator(_active_workers, _queues);
5259 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5261 _g1h->set_par_threads(_active_workers);
5262 _workers->run_task(&proc_task_proxy);
5263 _g1h->set_par_threads(0);
5264 }
5266 // Gang task for parallel reference enqueueing.
5268 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5269 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5270 EnqueueTask& _enq_task;
5272 public:
5273 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5274 AbstractGangTask("Enqueue reference objects in parallel"),
5275 _enq_task(enq_task)
5276 { }
5278 virtual void work(uint worker_id) {
5279 _enq_task.work(worker_id);
5280 }
5281 };
5283 // Driver routine for parallel reference enqueing.
5284 // Creates an instance of the ref enqueueing gang
5285 // task and has the worker threads execute it.
5287 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5288 assert(_workers != NULL, "Need parallel worker threads.");
5290 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5292 _g1h->set_par_threads(_active_workers);
5293 _workers->run_task(&enq_task_proxy);
5294 _g1h->set_par_threads(0);
5295 }
5297 // End of weak reference support closures
5299 // Abstract task used to preserve (i.e. copy) any referent objects
5300 // that are in the collection set and are pointed to by reference
5301 // objects discovered by the CM ref processor.
5303 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5304 protected:
5305 G1CollectedHeap* _g1h;
5306 RefToScanQueueSet *_queues;
5307 ParallelTaskTerminator _terminator;
5308 uint _n_workers;
5310 public:
5311 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
5312 AbstractGangTask("ParPreserveCMReferents"),
5313 _g1h(g1h),
5314 _queues(task_queues),
5315 _terminator(workers, _queues),
5316 _n_workers(workers)
5317 { }
5319 void work(uint worker_id) {
5320 ResourceMark rm;
5321 HandleMark hm;
5323 G1ParScanThreadState pss(_g1h, worker_id);
5324 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, NULL);
5325 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5326 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, NULL);
5328 pss.set_evac_closure(&scan_evac_cl);
5329 pss.set_evac_failure_closure(&evac_failure_cl);
5330 pss.set_partial_scan_closure(&partial_scan_cl);
5332 assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5335 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5336 G1ParScanPermClosure only_copy_perm_cl(_g1h, &pss, NULL);
5338 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5339 G1ParScanAndMarkPermClosure copy_mark_perm_cl(_g1h, &pss, NULL);
5341 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5342 OopsInHeapRegionClosure* copy_perm_cl = &only_copy_perm_cl;
5344 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5345 // We also need to mark copied objects.
5346 copy_non_heap_cl = ©_mark_non_heap_cl;
5347 copy_perm_cl = ©_mark_perm_cl;
5348 }
5350 // Is alive closure
5351 G1AlwaysAliveClosure always_alive(_g1h);
5353 // Copying keep alive closure. Applied to referent objects that need
5354 // to be copied.
5355 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_perm_cl, &pss);
5357 ReferenceProcessor* rp = _g1h->ref_processor_cm();
5359 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5360 uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5362 // limit is set using max_num_q() - which was set using ParallelGCThreads.
5363 // So this must be true - but assert just in case someone decides to
5364 // change the worker ids.
5365 assert(0 <= worker_id && worker_id < limit, "sanity");
5366 assert(!rp->discovery_is_atomic(), "check this code");
5368 // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5369 for (uint idx = worker_id; idx < limit; idx += stride) {
5370 DiscoveredList& ref_list = rp->discovered_refs()[idx];
5372 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5373 while (iter.has_next()) {
5374 // Since discovery is not atomic for the CM ref processor, we
5375 // can see some null referent objects.
5376 iter.load_ptrs(DEBUG_ONLY(true));
5377 oop ref = iter.obj();
5379 // This will filter nulls.
5380 if (iter.is_referent_alive()) {
5381 iter.make_referent_alive();
5382 }
5383 iter.move_to_next();
5384 }
5385 }
5387 // Drain the queue - which may cause stealing
5388 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5389 drain_queue.do_void();
5390 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5391 assert(pss.refs()->is_empty(), "should be");
5392 }
5393 };
5395 // Weak Reference processing during an evacuation pause (part 1).
5396 void G1CollectedHeap::process_discovered_references() {
5397 double ref_proc_start = os::elapsedTime();
5399 ReferenceProcessor* rp = _ref_processor_stw;
5400 assert(rp->discovery_enabled(), "should have been enabled");
5402 // Any reference objects, in the collection set, that were 'discovered'
5403 // by the CM ref processor should have already been copied (either by
5404 // applying the external root copy closure to the discovered lists, or
5405 // by following an RSet entry).
5406 //
5407 // But some of the referents, that are in the collection set, that these
5408 // reference objects point to may not have been copied: the STW ref
5409 // processor would have seen that the reference object had already
5410 // been 'discovered' and would have skipped discovering the reference,
5411 // but would not have treated the reference object as a regular oop.
5412 // As a reult the copy closure would not have been applied to the
5413 // referent object.
5414 //
5415 // We need to explicitly copy these referent objects - the references
5416 // will be processed at the end of remarking.
5417 //
5418 // We also need to do this copying before we process the reference
5419 // objects discovered by the STW ref processor in case one of these
5420 // referents points to another object which is also referenced by an
5421 // object discovered by the STW ref processor.
5423 uint active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5424 workers()->active_workers() : 1);
5426 assert(!G1CollectedHeap::use_parallel_gc_threads() ||
5427 active_workers == workers()->active_workers(),
5428 "Need to reset active_workers");
5430 set_par_threads(active_workers);
5431 G1ParPreserveCMReferentsTask keep_cm_referents(this, active_workers, _task_queues);
5433 if (G1CollectedHeap::use_parallel_gc_threads()) {
5434 workers()->run_task(&keep_cm_referents);
5435 } else {
5436 keep_cm_referents.work(0);
5437 }
5439 set_par_threads(0);
5441 // Closure to test whether a referent is alive.
5442 G1STWIsAliveClosure is_alive(this);
5444 // Even when parallel reference processing is enabled, the processing
5445 // of JNI refs is serial and performed serially by the current thread
5446 // rather than by a worker. The following PSS will be used for processing
5447 // JNI refs.
5449 // Use only a single queue for this PSS.
5450 G1ParScanThreadState pss(this, 0);
5452 // We do not embed a reference processor in the copying/scanning
5453 // closures while we're actually processing the discovered
5454 // reference objects.
5455 G1ParScanHeapEvacClosure scan_evac_cl(this, &pss, NULL);
5456 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5457 G1ParScanPartialArrayClosure partial_scan_cl(this, &pss, NULL);
5459 pss.set_evac_closure(&scan_evac_cl);
5460 pss.set_evac_failure_closure(&evac_failure_cl);
5461 pss.set_partial_scan_closure(&partial_scan_cl);
5463 assert(pss.refs()->is_empty(), "pre-condition");
5465 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL);
5466 G1ParScanPermClosure only_copy_perm_cl(this, &pss, NULL);
5468 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5469 G1ParScanAndMarkPermClosure copy_mark_perm_cl(this, &pss, NULL);
5471 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5472 OopsInHeapRegionClosure* copy_perm_cl = &only_copy_perm_cl;
5474 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5475 // We also need to mark copied objects.
5476 copy_non_heap_cl = ©_mark_non_heap_cl;
5477 copy_perm_cl = ©_mark_perm_cl;
5478 }
5480 // Keep alive closure.
5481 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, copy_perm_cl, &pss);
5483 // Serial Complete GC closure
5484 G1STWDrainQueueClosure drain_queue(this, &pss);
5486 // Setup the soft refs policy...
5487 rp->setup_policy(false);
5489 if (!rp->processing_is_mt()) {
5490 // Serial reference processing...
5491 rp->process_discovered_references(&is_alive,
5492 &keep_alive,
5493 &drain_queue,
5494 NULL);
5495 } else {
5496 // Parallel reference processing
5497 assert(rp->num_q() == active_workers, "sanity");
5498 assert(active_workers <= rp->max_num_q(), "sanity");
5500 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, active_workers);
5501 rp->process_discovered_references(&is_alive, &keep_alive, &drain_queue, &par_task_executor);
5502 }
5504 // We have completed copying any necessary live referent objects
5505 // (that were not copied during the actual pause) so we can
5506 // retire any active alloc buffers
5507 pss.retire_alloc_buffers();
5508 assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5510 double ref_proc_time = os::elapsedTime() - ref_proc_start;
5511 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5512 }
5514 // Weak Reference processing during an evacuation pause (part 2).
5515 void G1CollectedHeap::enqueue_discovered_references() {
5516 double ref_enq_start = os::elapsedTime();
5518 ReferenceProcessor* rp = _ref_processor_stw;
5519 assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5521 // Now enqueue any remaining on the discovered lists on to
5522 // the pending list.
5523 if (!rp->processing_is_mt()) {
5524 // Serial reference processing...
5525 rp->enqueue_discovered_references();
5526 } else {
5527 // Parallel reference enqueuing
5529 uint active_workers = (ParallelGCThreads > 0 ? workers()->active_workers() : 1);
5530 assert(active_workers == workers()->active_workers(),
5531 "Need to reset active_workers");
5532 assert(rp->num_q() == active_workers, "sanity");
5533 assert(active_workers <= rp->max_num_q(), "sanity");
5535 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, active_workers);
5536 rp->enqueue_discovered_references(&par_task_executor);
5537 }
5539 rp->verify_no_references_recorded();
5540 assert(!rp->discovery_enabled(), "should have been disabled");
5542 // FIXME
5543 // CM's reference processing also cleans up the string and symbol tables.
5544 // Should we do that here also? We could, but it is a serial operation
5545 // and could signicantly increase the pause time.
5547 double ref_enq_time = os::elapsedTime() - ref_enq_start;
5548 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5549 }
5551 void G1CollectedHeap::evacuate_collection_set() {
5552 _expand_heap_after_alloc_failure = true;
5553 set_evacuation_failed(false);
5555 g1_rem_set()->prepare_for_oops_into_collection_set_do();
5556 concurrent_g1_refine()->set_use_cache(false);
5557 concurrent_g1_refine()->clear_hot_cache_claimed_index();
5559 uint n_workers;
5560 if (G1CollectedHeap::use_parallel_gc_threads()) {
5561 n_workers =
5562 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
5563 workers()->active_workers(),
5564 Threads::number_of_non_daemon_threads());
5565 assert(UseDynamicNumberOfGCThreads ||
5566 n_workers == workers()->total_workers(),
5567 "If not dynamic should be using all the workers");
5568 workers()->set_active_workers(n_workers);
5569 set_par_threads(n_workers);
5570 } else {
5571 assert(n_par_threads() == 0,
5572 "Should be the original non-parallel value");
5573 n_workers = 1;
5574 }
5576 G1ParTask g1_par_task(this, _task_queues);
5578 init_for_evac_failure(NULL);
5580 rem_set()->prepare_for_younger_refs_iterate(true);
5582 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5583 double start_par_time_sec = os::elapsedTime();
5584 double end_par_time_sec;
5586 {
5587 StrongRootsScope srs(this);
5589 if (G1CollectedHeap::use_parallel_gc_threads()) {
5590 // The individual threads will set their evac-failure closures.
5591 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
5592 // These tasks use ShareHeap::_process_strong_tasks
5593 assert(UseDynamicNumberOfGCThreads ||
5594 workers()->active_workers() == workers()->total_workers(),
5595 "If not dynamic should be using all the workers");
5596 workers()->run_task(&g1_par_task);
5597 } else {
5598 g1_par_task.set_for_termination(n_workers);
5599 g1_par_task.work(0);
5600 }
5601 end_par_time_sec = os::elapsedTime();
5603 // Closing the inner scope will execute the destructor
5604 // for the StrongRootsScope object. We record the current
5605 // elapsed time before closing the scope so that time
5606 // taken for the SRS destructor is NOT included in the
5607 // reported parallel time.
5608 }
5610 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5611 g1_policy()->phase_times()->record_par_time(par_time_ms);
5613 double code_root_fixup_time_ms =
5614 (os::elapsedTime() - end_par_time_sec) * 1000.0;
5615 g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms);
5617 set_par_threads(0);
5619 // Process any discovered reference objects - we have
5620 // to do this _before_ we retire the GC alloc regions
5621 // as we may have to copy some 'reachable' referent
5622 // objects (and their reachable sub-graphs) that were
5623 // not copied during the pause.
5624 process_discovered_references();
5626 // Weak root processing.
5627 // Note: when JSR 292 is enabled and code blobs can contain
5628 // non-perm oops then we will need to process the code blobs
5629 // here too.
5630 {
5631 G1STWIsAliveClosure is_alive(this);
5632 G1KeepAliveClosure keep_alive(this);
5633 JNIHandles::weak_oops_do(&is_alive, &keep_alive);
5634 }
5636 release_gc_alloc_regions();
5637 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5639 concurrent_g1_refine()->clear_hot_cache();
5640 concurrent_g1_refine()->set_use_cache(true);
5642 finalize_for_evac_failure();
5644 if (evacuation_failed()) {
5645 remove_self_forwarding_pointers();
5646 if (G1Log::finer()) {
5647 gclog_or_tty->print(" (to-space exhausted)");
5648 } else if (G1Log::fine()) {
5649 gclog_or_tty->print("--");
5650 }
5651 }
5653 // Enqueue any remaining references remaining on the STW
5654 // reference processor's discovered lists. We need to do
5655 // this after the card table is cleaned (and verified) as
5656 // the act of enqueuing entries on to the pending list
5657 // will log these updates (and dirty their associated
5658 // cards). We need these updates logged to update any
5659 // RSets.
5660 enqueue_discovered_references();
5662 if (G1DeferredRSUpdate) {
5663 RedirtyLoggedCardTableEntryFastClosure redirty;
5664 dirty_card_queue_set().set_closure(&redirty);
5665 dirty_card_queue_set().apply_closure_to_all_completed_buffers();
5667 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5668 dcq.merge_bufferlists(&dirty_card_queue_set());
5669 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5670 }
5671 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5672 }
5674 void G1CollectedHeap::free_region_if_empty(HeapRegion* hr,
5675 size_t* pre_used,
5676 FreeRegionList* free_list,
5677 OldRegionSet* old_proxy_set,
5678 HumongousRegionSet* humongous_proxy_set,
5679 HRRSCleanupTask* hrrs_cleanup_task,
5680 bool par) {
5681 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) {
5682 if (hr->isHumongous()) {
5683 assert(hr->startsHumongous(), "we should only see starts humongous");
5684 free_humongous_region(hr, pre_used, free_list, humongous_proxy_set, par);
5685 } else {
5686 _old_set.remove_with_proxy(hr, old_proxy_set);
5687 free_region(hr, pre_used, free_list, par);
5688 }
5689 } else {
5690 hr->rem_set()->do_cleanup_work(hrrs_cleanup_task);
5691 }
5692 }
5694 void G1CollectedHeap::free_region(HeapRegion* hr,
5695 size_t* pre_used,
5696 FreeRegionList* free_list,
5697 bool par) {
5698 assert(!hr->isHumongous(), "this is only for non-humongous regions");
5699 assert(!hr->is_empty(), "the region should not be empty");
5700 assert(free_list != NULL, "pre-condition");
5702 *pre_used += hr->used();
5703 hr->hr_clear(par, true /* clear_space */);
5704 free_list->add_as_head(hr);
5705 }
5707 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
5708 size_t* pre_used,
5709 FreeRegionList* free_list,
5710 HumongousRegionSet* humongous_proxy_set,
5711 bool par) {
5712 assert(hr->startsHumongous(), "this is only for starts humongous regions");
5713 assert(free_list != NULL, "pre-condition");
5714 assert(humongous_proxy_set != NULL, "pre-condition");
5716 size_t hr_used = hr->used();
5717 size_t hr_capacity = hr->capacity();
5718 size_t hr_pre_used = 0;
5719 _humongous_set.remove_with_proxy(hr, humongous_proxy_set);
5720 // We need to read this before we make the region non-humongous,
5721 // otherwise the information will be gone.
5722 uint last_index = hr->last_hc_index();
5723 hr->set_notHumongous();
5724 free_region(hr, &hr_pre_used, free_list, par);
5726 uint i = hr->hrs_index() + 1;
5727 while (i < last_index) {
5728 HeapRegion* curr_hr = region_at(i);
5729 assert(curr_hr->continuesHumongous(), "invariant");
5730 curr_hr->set_notHumongous();
5731 free_region(curr_hr, &hr_pre_used, free_list, par);
5732 i += 1;
5733 }
5734 assert(hr_pre_used == hr_used,
5735 err_msg("hr_pre_used: "SIZE_FORMAT" and hr_used: "SIZE_FORMAT" "
5736 "should be the same", hr_pre_used, hr_used));
5737 *pre_used += hr_pre_used;
5738 }
5740 void G1CollectedHeap::update_sets_after_freeing_regions(size_t pre_used,
5741 FreeRegionList* free_list,
5742 OldRegionSet* old_proxy_set,
5743 HumongousRegionSet* humongous_proxy_set,
5744 bool par) {
5745 if (pre_used > 0) {
5746 Mutex* lock = (par) ? ParGCRareEvent_lock : NULL;
5747 MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag);
5748 assert(_summary_bytes_used >= pre_used,
5749 err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" "
5750 "should be >= pre_used: "SIZE_FORMAT,
5751 _summary_bytes_used, pre_used));
5752 _summary_bytes_used -= pre_used;
5753 }
5754 if (free_list != NULL && !free_list->is_empty()) {
5755 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
5756 _free_list.add_as_head(free_list);
5757 }
5758 if (old_proxy_set != NULL && !old_proxy_set->is_empty()) {
5759 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5760 _old_set.update_from_proxy(old_proxy_set);
5761 }
5762 if (humongous_proxy_set != NULL && !humongous_proxy_set->is_empty()) {
5763 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5764 _humongous_set.update_from_proxy(humongous_proxy_set);
5765 }
5766 }
5768 class G1ParCleanupCTTask : public AbstractGangTask {
5769 CardTableModRefBS* _ct_bs;
5770 G1CollectedHeap* _g1h;
5771 HeapRegion* volatile _su_head;
5772 public:
5773 G1ParCleanupCTTask(CardTableModRefBS* ct_bs,
5774 G1CollectedHeap* g1h) :
5775 AbstractGangTask("G1 Par Cleanup CT Task"),
5776 _ct_bs(ct_bs), _g1h(g1h) { }
5778 void work(uint worker_id) {
5779 HeapRegion* r;
5780 while (r = _g1h->pop_dirty_cards_region()) {
5781 clear_cards(r);
5782 }
5783 }
5785 void clear_cards(HeapRegion* r) {
5786 // Cards of the survivors should have already been dirtied.
5787 if (!r->is_survivor()) {
5788 _ct_bs->clear(MemRegion(r->bottom(), r->end()));
5789 }
5790 }
5791 };
5793 #ifndef PRODUCT
5794 class G1VerifyCardTableCleanup: public HeapRegionClosure {
5795 G1CollectedHeap* _g1h;
5796 CardTableModRefBS* _ct_bs;
5797 public:
5798 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, CardTableModRefBS* ct_bs)
5799 : _g1h(g1h), _ct_bs(ct_bs) { }
5800 virtual bool doHeapRegion(HeapRegion* r) {
5801 if (r->is_survivor()) {
5802 _g1h->verify_dirty_region(r);
5803 } else {
5804 _g1h->verify_not_dirty_region(r);
5805 }
5806 return false;
5807 }
5808 };
5810 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
5811 // All of the region should be clean.
5812 CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
5813 MemRegion mr(hr->bottom(), hr->end());
5814 ct_bs->verify_not_dirty_region(mr);
5815 }
5817 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
5818 // We cannot guarantee that [bottom(),end()] is dirty. Threads
5819 // dirty allocated blocks as they allocate them. The thread that
5820 // retires each region and replaces it with a new one will do a
5821 // maximal allocation to fill in [pre_dummy_top(),end()] but will
5822 // not dirty that area (one less thing to have to do while holding
5823 // a lock). So we can only verify that [bottom(),pre_dummy_top()]
5824 // is dirty.
5825 CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set();
5826 MemRegion mr(hr->bottom(), hr->pre_dummy_top());
5827 ct_bs->verify_dirty_region(mr);
5828 }
5830 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
5831 CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set();
5832 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
5833 verify_dirty_region(hr);
5834 }
5835 }
5837 void G1CollectedHeap::verify_dirty_young_regions() {
5838 verify_dirty_young_list(_young_list->first_region());
5839 }
5840 #endif
5842 void G1CollectedHeap::cleanUpCardTable() {
5843 CardTableModRefBS* ct_bs = (CardTableModRefBS*) (barrier_set());
5844 double start = os::elapsedTime();
5846 {
5847 // Iterate over the dirty cards region list.
5848 G1ParCleanupCTTask cleanup_task(ct_bs, this);
5850 if (G1CollectedHeap::use_parallel_gc_threads()) {
5851 set_par_threads();
5852 workers()->run_task(&cleanup_task);
5853 set_par_threads(0);
5854 } else {
5855 while (_dirty_cards_region_list) {
5856 HeapRegion* r = _dirty_cards_region_list;
5857 cleanup_task.clear_cards(r);
5858 _dirty_cards_region_list = r->get_next_dirty_cards_region();
5859 if (_dirty_cards_region_list == r) {
5860 // The last region.
5861 _dirty_cards_region_list = NULL;
5862 }
5863 r->set_next_dirty_cards_region(NULL);
5864 }
5865 }
5866 #ifndef PRODUCT
5867 if (G1VerifyCTCleanup || VerifyAfterGC) {
5868 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
5869 heap_region_iterate(&cleanup_verifier);
5870 }
5871 #endif
5872 }
5874 double elapsed = os::elapsedTime() - start;
5875 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
5876 }
5878 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head) {
5879 size_t pre_used = 0;
5880 FreeRegionList local_free_list("Local List for CSet Freeing");
5882 double young_time_ms = 0.0;
5883 double non_young_time_ms = 0.0;
5885 // Since the collection set is a superset of the the young list,
5886 // all we need to do to clear the young list is clear its
5887 // head and length, and unlink any young regions in the code below
5888 _young_list->clear();
5890 G1CollectorPolicy* policy = g1_policy();
5892 double start_sec = os::elapsedTime();
5893 bool non_young = true;
5895 HeapRegion* cur = cs_head;
5896 int age_bound = -1;
5897 size_t rs_lengths = 0;
5899 while (cur != NULL) {
5900 assert(!is_on_master_free_list(cur), "sanity");
5901 if (non_young) {
5902 if (cur->is_young()) {
5903 double end_sec = os::elapsedTime();
5904 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5905 non_young_time_ms += elapsed_ms;
5907 start_sec = os::elapsedTime();
5908 non_young = false;
5909 }
5910 } else {
5911 if (!cur->is_young()) {
5912 double end_sec = os::elapsedTime();
5913 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5914 young_time_ms += elapsed_ms;
5916 start_sec = os::elapsedTime();
5917 non_young = true;
5918 }
5919 }
5921 rs_lengths += cur->rem_set()->occupied();
5923 HeapRegion* next = cur->next_in_collection_set();
5924 assert(cur->in_collection_set(), "bad CS");
5925 cur->set_next_in_collection_set(NULL);
5926 cur->set_in_collection_set(false);
5928 if (cur->is_young()) {
5929 int index = cur->young_index_in_cset();
5930 assert(index != -1, "invariant");
5931 assert((uint) index < policy->young_cset_region_length(), "invariant");
5932 size_t words_survived = _surviving_young_words[index];
5933 cur->record_surv_words_in_group(words_survived);
5935 // At this point the we have 'popped' cur from the collection set
5936 // (linked via next_in_collection_set()) but it is still in the
5937 // young list (linked via next_young_region()). Clear the
5938 // _next_young_region field.
5939 cur->set_next_young_region(NULL);
5940 } else {
5941 int index = cur->young_index_in_cset();
5942 assert(index == -1, "invariant");
5943 }
5945 assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
5946 (!cur->is_young() && cur->young_index_in_cset() == -1),
5947 "invariant" );
5949 if (!cur->evacuation_failed()) {
5950 MemRegion used_mr = cur->used_region();
5952 // And the region is empty.
5953 assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
5954 free_region(cur, &pre_used, &local_free_list, false /* par */);
5955 } else {
5956 cur->uninstall_surv_rate_group();
5957 if (cur->is_young()) {
5958 cur->set_young_index_in_cset(-1);
5959 }
5960 cur->set_not_young();
5961 cur->set_evacuation_failed(false);
5962 // The region is now considered to be old.
5963 _old_set.add(cur);
5964 }
5965 cur = next;
5966 }
5968 policy->record_max_rs_lengths(rs_lengths);
5969 policy->cset_regions_freed();
5971 double end_sec = os::elapsedTime();
5972 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5974 if (non_young) {
5975 non_young_time_ms += elapsed_ms;
5976 } else {
5977 young_time_ms += elapsed_ms;
5978 }
5980 update_sets_after_freeing_regions(pre_used, &local_free_list,
5981 NULL /* old_proxy_set */,
5982 NULL /* humongous_proxy_set */,
5983 false /* par */);
5984 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
5985 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
5986 }
5988 // This routine is similar to the above but does not record
5989 // any policy statistics or update free lists; we are abandoning
5990 // the current incremental collection set in preparation of a
5991 // full collection. After the full GC we will start to build up
5992 // the incremental collection set again.
5993 // This is only called when we're doing a full collection
5994 // and is immediately followed by the tearing down of the young list.
5996 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
5997 HeapRegion* cur = cs_head;
5999 while (cur != NULL) {
6000 HeapRegion* next = cur->next_in_collection_set();
6001 assert(cur->in_collection_set(), "bad CS");
6002 cur->set_next_in_collection_set(NULL);
6003 cur->set_in_collection_set(false);
6004 cur->set_young_index_in_cset(-1);
6005 cur = next;
6006 }
6007 }
6009 void G1CollectedHeap::set_free_regions_coming() {
6010 if (G1ConcRegionFreeingVerbose) {
6011 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6012 "setting free regions coming");
6013 }
6015 assert(!free_regions_coming(), "pre-condition");
6016 _free_regions_coming = true;
6017 }
6019 void G1CollectedHeap::reset_free_regions_coming() {
6020 assert(free_regions_coming(), "pre-condition");
6022 {
6023 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6024 _free_regions_coming = false;
6025 SecondaryFreeList_lock->notify_all();
6026 }
6028 if (G1ConcRegionFreeingVerbose) {
6029 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6030 "reset free regions coming");
6031 }
6032 }
6034 void G1CollectedHeap::wait_while_free_regions_coming() {
6035 // Most of the time we won't have to wait, so let's do a quick test
6036 // first before we take the lock.
6037 if (!free_regions_coming()) {
6038 return;
6039 }
6041 if (G1ConcRegionFreeingVerbose) {
6042 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6043 "waiting for free regions");
6044 }
6046 {
6047 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6048 while (free_regions_coming()) {
6049 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
6050 }
6051 }
6053 if (G1ConcRegionFreeingVerbose) {
6054 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6055 "done waiting for free regions");
6056 }
6057 }
6059 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
6060 assert(heap_lock_held_for_gc(),
6061 "the heap lock should already be held by or for this thread");
6062 _young_list->push_region(hr);
6063 }
6065 class NoYoungRegionsClosure: public HeapRegionClosure {
6066 private:
6067 bool _success;
6068 public:
6069 NoYoungRegionsClosure() : _success(true) { }
6070 bool doHeapRegion(HeapRegion* r) {
6071 if (r->is_young()) {
6072 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
6073 r->bottom(), r->end());
6074 _success = false;
6075 }
6076 return false;
6077 }
6078 bool success() { return _success; }
6079 };
6081 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
6082 bool ret = _young_list->check_list_empty(check_sample);
6084 if (check_heap) {
6085 NoYoungRegionsClosure closure;
6086 heap_region_iterate(&closure);
6087 ret = ret && closure.success();
6088 }
6090 return ret;
6091 }
6093 class TearDownRegionSetsClosure : public HeapRegionClosure {
6094 private:
6095 OldRegionSet *_old_set;
6097 public:
6098 TearDownRegionSetsClosure(OldRegionSet* old_set) : _old_set(old_set) { }
6100 bool doHeapRegion(HeapRegion* r) {
6101 if (r->is_empty()) {
6102 // We ignore empty regions, we'll empty the free list afterwards
6103 } else if (r->is_young()) {
6104 // We ignore young regions, we'll empty the young list afterwards
6105 } else if (r->isHumongous()) {
6106 // We ignore humongous regions, we're not tearing down the
6107 // humongous region set
6108 } else {
6109 // The rest should be old
6110 _old_set->remove(r);
6111 }
6112 return false;
6113 }
6115 ~TearDownRegionSetsClosure() {
6116 assert(_old_set->is_empty(), "post-condition");
6117 }
6118 };
6120 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6121 assert_at_safepoint(true /* should_be_vm_thread */);
6123 if (!free_list_only) {
6124 TearDownRegionSetsClosure cl(&_old_set);
6125 heap_region_iterate(&cl);
6127 // Need to do this after the heap iteration to be able to
6128 // recognize the young regions and ignore them during the iteration.
6129 _young_list->empty_list();
6130 }
6131 _free_list.remove_all();
6132 }
6134 class RebuildRegionSetsClosure : public HeapRegionClosure {
6135 private:
6136 bool _free_list_only;
6137 OldRegionSet* _old_set;
6138 FreeRegionList* _free_list;
6139 size_t _total_used;
6141 public:
6142 RebuildRegionSetsClosure(bool free_list_only,
6143 OldRegionSet* old_set, FreeRegionList* free_list) :
6144 _free_list_only(free_list_only),
6145 _old_set(old_set), _free_list(free_list), _total_used(0) {
6146 assert(_free_list->is_empty(), "pre-condition");
6147 if (!free_list_only) {
6148 assert(_old_set->is_empty(), "pre-condition");
6149 }
6150 }
6152 bool doHeapRegion(HeapRegion* r) {
6153 if (r->continuesHumongous()) {
6154 return false;
6155 }
6157 if (r->is_empty()) {
6158 // Add free regions to the free list
6159 _free_list->add_as_tail(r);
6160 } else if (!_free_list_only) {
6161 assert(!r->is_young(), "we should not come across young regions");
6163 if (r->isHumongous()) {
6164 // We ignore humongous regions, we left the humongous set unchanged
6165 } else {
6166 // The rest should be old, add them to the old set
6167 _old_set->add(r);
6168 }
6169 _total_used += r->used();
6170 }
6172 return false;
6173 }
6175 size_t total_used() {
6176 return _total_used;
6177 }
6178 };
6180 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6181 assert_at_safepoint(true /* should_be_vm_thread */);
6183 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_free_list);
6184 heap_region_iterate(&cl);
6186 if (!free_list_only) {
6187 _summary_bytes_used = cl.total_used();
6188 }
6189 assert(_summary_bytes_used == recalculate_used(),
6190 err_msg("inconsistent _summary_bytes_used, "
6191 "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6192 _summary_bytes_used, recalculate_used()));
6193 }
6195 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6196 _refine_cte_cl->set_concurrent(concurrent);
6197 }
6199 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6200 HeapRegion* hr = heap_region_containing(p);
6201 if (hr == NULL) {
6202 return is_in_permanent(p);
6203 } else {
6204 return hr->is_in(p);
6205 }
6206 }
6208 // Methods for the mutator alloc region
6210 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6211 bool force) {
6212 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6213 assert(!force || g1_policy()->can_expand_young_list(),
6214 "if force is true we should be able to expand the young list");
6215 bool young_list_full = g1_policy()->is_young_list_full();
6216 if (force || !young_list_full) {
6217 HeapRegion* new_alloc_region = new_region(word_size,
6218 false /* do_expand */);
6219 if (new_alloc_region != NULL) {
6220 set_region_short_lived_locked(new_alloc_region);
6221 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6222 return new_alloc_region;
6223 }
6224 }
6225 return NULL;
6226 }
6228 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6229 size_t allocated_bytes) {
6230 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6231 assert(alloc_region->is_young(), "all mutator alloc regions should be young");
6233 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6234 _summary_bytes_used += allocated_bytes;
6235 _hr_printer.retire(alloc_region);
6236 // We update the eden sizes here, when the region is retired,
6237 // instead of when it's allocated, since this is the point that its
6238 // used space has been recored in _summary_bytes_used.
6239 g1mm()->update_eden_size();
6240 }
6242 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
6243 bool force) {
6244 return _g1h->new_mutator_alloc_region(word_size, force);
6245 }
6247 void G1CollectedHeap::set_par_threads() {
6248 // Don't change the number of workers. Use the value previously set
6249 // in the workgroup.
6250 assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise");
6251 uint n_workers = workers()->active_workers();
6252 assert(UseDynamicNumberOfGCThreads ||
6253 n_workers == workers()->total_workers(),
6254 "Otherwise should be using the total number of workers");
6255 if (n_workers == 0) {
6256 assert(false, "Should have been set in prior evacuation pause.");
6257 n_workers = ParallelGCThreads;
6258 workers()->set_active_workers(n_workers);
6259 }
6260 set_par_threads(n_workers);
6261 }
6263 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
6264 size_t allocated_bytes) {
6265 _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
6266 }
6268 // Methods for the GC alloc regions
6270 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6271 uint count,
6272 GCAllocPurpose ap) {
6273 assert(FreeList_lock->owned_by_self(), "pre-condition");
6275 if (count < g1_policy()->max_regions(ap)) {
6276 HeapRegion* new_alloc_region = new_region(word_size,
6277 true /* do_expand */);
6278 if (new_alloc_region != NULL) {
6279 // We really only need to do this for old regions given that we
6280 // should never scan survivors. But it doesn't hurt to do it
6281 // for survivors too.
6282 new_alloc_region->set_saved_mark();
6283 if (ap == GCAllocForSurvived) {
6284 new_alloc_region->set_survivor();
6285 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6286 } else {
6287 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6288 }
6289 bool during_im = g1_policy()->during_initial_mark_pause();
6290 new_alloc_region->note_start_of_copying(during_im);
6291 return new_alloc_region;
6292 } else {
6293 g1_policy()->note_alloc_region_limit_reached(ap);
6294 }
6295 }
6296 return NULL;
6297 }
6299 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6300 size_t allocated_bytes,
6301 GCAllocPurpose ap) {
6302 bool during_im = g1_policy()->during_initial_mark_pause();
6303 alloc_region->note_end_of_copying(during_im);
6304 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6305 if (ap == GCAllocForSurvived) {
6306 young_list()->add_survivor_region(alloc_region);
6307 } else {
6308 _old_set.add(alloc_region);
6309 }
6310 _hr_printer.retire(alloc_region);
6311 }
6313 HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size,
6314 bool force) {
6315 assert(!force, "not supported for GC alloc regions");
6316 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForSurvived);
6317 }
6319 void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region,
6320 size_t allocated_bytes) {
6321 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6322 GCAllocForSurvived);
6323 }
6325 HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size,
6326 bool force) {
6327 assert(!force, "not supported for GC alloc regions");
6328 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForTenured);
6329 }
6331 void OldGCAllocRegion::retire_region(HeapRegion* alloc_region,
6332 size_t allocated_bytes) {
6333 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6334 GCAllocForTenured);
6335 }
6336 // Heap region set verification
6338 class VerifyRegionListsClosure : public HeapRegionClosure {
6339 private:
6340 FreeRegionList* _free_list;
6341 OldRegionSet* _old_set;
6342 HumongousRegionSet* _humongous_set;
6343 uint _region_count;
6345 public:
6346 VerifyRegionListsClosure(OldRegionSet* old_set,
6347 HumongousRegionSet* humongous_set,
6348 FreeRegionList* free_list) :
6349 _old_set(old_set), _humongous_set(humongous_set),
6350 _free_list(free_list), _region_count(0) { }
6352 uint region_count() { return _region_count; }
6354 bool doHeapRegion(HeapRegion* hr) {
6355 _region_count += 1;
6357 if (hr->continuesHumongous()) {
6358 return false;
6359 }
6361 if (hr->is_young()) {
6362 // TODO
6363 } else if (hr->startsHumongous()) {
6364 _humongous_set->verify_next_region(hr);
6365 } else if (hr->is_empty()) {
6366 _free_list->verify_next_region(hr);
6367 } else {
6368 _old_set->verify_next_region(hr);
6369 }
6370 return false;
6371 }
6372 };
6374 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
6375 HeapWord* bottom) {
6376 HeapWord* end = bottom + HeapRegion::GrainWords;
6377 MemRegion mr(bottom, end);
6378 assert(_g1_reserved.contains(mr), "invariant");
6379 // This might return NULL if the allocation fails
6380 return new HeapRegion(hrs_index, _bot_shared, mr, true /* is_zeroed */);
6381 }
6383 void G1CollectedHeap::verify_region_sets() {
6384 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6386 // First, check the explicit lists.
6387 _free_list.verify();
6388 {
6389 // Given that a concurrent operation might be adding regions to
6390 // the secondary free list we have to take the lock before
6391 // verifying it.
6392 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6393 _secondary_free_list.verify();
6394 }
6395 _old_set.verify();
6396 _humongous_set.verify();
6398 // If a concurrent region freeing operation is in progress it will
6399 // be difficult to correctly attributed any free regions we come
6400 // across to the correct free list given that they might belong to
6401 // one of several (free_list, secondary_free_list, any local lists,
6402 // etc.). So, if that's the case we will skip the rest of the
6403 // verification operation. Alternatively, waiting for the concurrent
6404 // operation to complete will have a non-trivial effect on the GC's
6405 // operation (no concurrent operation will last longer than the
6406 // interval between two calls to verification) and it might hide
6407 // any issues that we would like to catch during testing.
6408 if (free_regions_coming()) {
6409 return;
6410 }
6412 // Make sure we append the secondary_free_list on the free_list so
6413 // that all free regions we will come across can be safely
6414 // attributed to the free_list.
6415 append_secondary_free_list_if_not_empty_with_lock();
6417 // Finally, make sure that the region accounting in the lists is
6418 // consistent with what we see in the heap.
6419 _old_set.verify_start();
6420 _humongous_set.verify_start();
6421 _free_list.verify_start();
6423 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_free_list);
6424 heap_region_iterate(&cl);
6426 _old_set.verify_end();
6427 _humongous_set.verify_end();
6428 _free_list.verify_end();
6429 }