Thu, 28 Jun 2012 17:03:16 -0400
6995781: Native Memory Tracking (Phase 1)
7151532: DCmd for hotspot native memory tracking
Summary: Implementation of native memory tracking phase 1, which tracks VM native memory usage, and related DCmd
Reviewed-by: acorn, coleenp, fparain
1 /*
2 * Copyright (c) 2001, 2012, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
25 #include "precompiled.hpp"
26 #include "code/icBuffer.hpp"
27 #include "gc_implementation/g1/bufferingOopClosure.hpp"
28 #include "gc_implementation/g1/concurrentG1Refine.hpp"
29 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
30 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
31 #include "gc_implementation/g1/g1AllocRegion.inline.hpp"
32 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
33 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
34 #include "gc_implementation/g1/g1ErgoVerbose.hpp"
35 #include "gc_implementation/g1/g1EvacFailure.hpp"
36 #include "gc_implementation/g1/g1Log.hpp"
37 #include "gc_implementation/g1/g1MarkSweep.hpp"
38 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
39 #include "gc_implementation/g1/g1RemSet.inline.hpp"
40 #include "gc_implementation/g1/heapRegion.inline.hpp"
41 #include "gc_implementation/g1/heapRegionRemSet.hpp"
42 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
43 #include "gc_implementation/g1/vm_operations_g1.hpp"
44 #include "gc_implementation/shared/isGCActiveMark.hpp"
45 #include "memory/gcLocker.inline.hpp"
46 #include "memory/genOopClosures.inline.hpp"
47 #include "memory/generationSpec.hpp"
48 #include "memory/referenceProcessor.hpp"
49 #include "oops/oop.inline.hpp"
50 #include "oops/oop.pcgc.inline.hpp"
51 #include "runtime/aprofiler.hpp"
52 #include "runtime/vmThread.hpp"
54 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
56 // turn it on so that the contents of the young list (scan-only /
57 // to-be-collected) are printed at "strategic" points before / during
58 // / after the collection --- this is useful for debugging
59 #define YOUNG_LIST_VERBOSE 0
60 // CURRENT STATUS
61 // This file is under construction. Search for "FIXME".
63 // INVARIANTS/NOTES
64 //
65 // All allocation activity covered by the G1CollectedHeap interface is
66 // serialized by acquiring the HeapLock. This happens in mem_allocate
67 // and allocate_new_tlab, which are the "entry" points to the
68 // allocation code from the rest of the JVM. (Note that this does not
69 // apply to TLAB allocation, which is not part of this interface: it
70 // is done by clients of this interface.)
72 // Notes on implementation of parallelism in different tasks.
73 //
74 // G1ParVerifyTask uses heap_region_par_iterate_chunked() for parallelism.
75 // The number of GC workers is passed to heap_region_par_iterate_chunked().
76 // It does use run_task() which sets _n_workers in the task.
77 // G1ParTask executes g1_process_strong_roots() ->
78 // SharedHeap::process_strong_roots() which calls eventuall to
79 // CardTableModRefBS::par_non_clean_card_iterate_work() which uses
80 // SequentialSubTasksDone. SharedHeap::process_strong_roots() also
81 // directly uses SubTasksDone (_process_strong_tasks field in SharedHeap).
82 //
84 // Local to this file.
86 class RefineCardTableEntryClosure: public CardTableEntryClosure {
87 SuspendibleThreadSet* _sts;
88 G1RemSet* _g1rs;
89 ConcurrentG1Refine* _cg1r;
90 bool _concurrent;
91 public:
92 RefineCardTableEntryClosure(SuspendibleThreadSet* sts,
93 G1RemSet* g1rs,
94 ConcurrentG1Refine* cg1r) :
95 _sts(sts), _g1rs(g1rs), _cg1r(cg1r), _concurrent(true)
96 {}
97 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
98 bool oops_into_cset = _g1rs->concurrentRefineOneCard(card_ptr, worker_i, false);
99 // This path is executed by the concurrent refine or mutator threads,
100 // concurrently, and so we do not care if card_ptr contains references
101 // that point into the collection set.
102 assert(!oops_into_cset, "should be");
104 if (_concurrent && _sts->should_yield()) {
105 // Caller will actually yield.
106 return false;
107 }
108 // Otherwise, we finished successfully; return true.
109 return true;
110 }
111 void set_concurrent(bool b) { _concurrent = b; }
112 };
115 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure {
116 int _calls;
117 G1CollectedHeap* _g1h;
118 CardTableModRefBS* _ctbs;
119 int _histo[256];
120 public:
121 ClearLoggedCardTableEntryClosure() :
122 _calls(0)
123 {
124 _g1h = G1CollectedHeap::heap();
125 _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
126 for (int i = 0; i < 256; i++) _histo[i] = 0;
127 }
128 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
129 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
130 _calls++;
131 unsigned char* ujb = (unsigned char*)card_ptr;
132 int ind = (int)(*ujb);
133 _histo[ind]++;
134 *card_ptr = -1;
135 }
136 return true;
137 }
138 int calls() { return _calls; }
139 void print_histo() {
140 gclog_or_tty->print_cr("Card table value histogram:");
141 for (int i = 0; i < 256; i++) {
142 if (_histo[i] != 0) {
143 gclog_or_tty->print_cr(" %d: %d", i, _histo[i]);
144 }
145 }
146 }
147 };
149 class RedirtyLoggedCardTableEntryClosure: public CardTableEntryClosure {
150 int _calls;
151 G1CollectedHeap* _g1h;
152 CardTableModRefBS* _ctbs;
153 public:
154 RedirtyLoggedCardTableEntryClosure() :
155 _calls(0)
156 {
157 _g1h = G1CollectedHeap::heap();
158 _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
159 }
160 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
161 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
162 _calls++;
163 *card_ptr = 0;
164 }
165 return true;
166 }
167 int calls() { return _calls; }
168 };
170 class RedirtyLoggedCardTableEntryFastClosure : public CardTableEntryClosure {
171 public:
172 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
173 *card_ptr = CardTableModRefBS::dirty_card_val();
174 return true;
175 }
176 };
178 YoungList::YoungList(G1CollectedHeap* g1h) :
179 _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0),
180 _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) {
181 guarantee(check_list_empty(false), "just making sure...");
182 }
184 void YoungList::push_region(HeapRegion *hr) {
185 assert(!hr->is_young(), "should not already be young");
186 assert(hr->get_next_young_region() == NULL, "cause it should!");
188 hr->set_next_young_region(_head);
189 _head = hr;
191 _g1h->g1_policy()->set_region_eden(hr, (int) _length);
192 ++_length;
193 }
195 void YoungList::add_survivor_region(HeapRegion* hr) {
196 assert(hr->is_survivor(), "should be flagged as survivor region");
197 assert(hr->get_next_young_region() == NULL, "cause it should!");
199 hr->set_next_young_region(_survivor_head);
200 if (_survivor_head == NULL) {
201 _survivor_tail = hr;
202 }
203 _survivor_head = hr;
204 ++_survivor_length;
205 }
207 void YoungList::empty_list(HeapRegion* list) {
208 while (list != NULL) {
209 HeapRegion* next = list->get_next_young_region();
210 list->set_next_young_region(NULL);
211 list->uninstall_surv_rate_group();
212 list->set_not_young();
213 list = next;
214 }
215 }
217 void YoungList::empty_list() {
218 assert(check_list_well_formed(), "young list should be well formed");
220 empty_list(_head);
221 _head = NULL;
222 _length = 0;
224 empty_list(_survivor_head);
225 _survivor_head = NULL;
226 _survivor_tail = NULL;
227 _survivor_length = 0;
229 _last_sampled_rs_lengths = 0;
231 assert(check_list_empty(false), "just making sure...");
232 }
234 bool YoungList::check_list_well_formed() {
235 bool ret = true;
237 uint length = 0;
238 HeapRegion* curr = _head;
239 HeapRegion* last = NULL;
240 while (curr != NULL) {
241 if (!curr->is_young()) {
242 gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
243 "incorrectly tagged (y: %d, surv: %d)",
244 curr->bottom(), curr->end(),
245 curr->is_young(), curr->is_survivor());
246 ret = false;
247 }
248 ++length;
249 last = curr;
250 curr = curr->get_next_young_region();
251 }
252 ret = ret && (length == _length);
254 if (!ret) {
255 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
256 gclog_or_tty->print_cr("### list has %u entries, _length is %u",
257 length, _length);
258 }
260 return ret;
261 }
263 bool YoungList::check_list_empty(bool check_sample) {
264 bool ret = true;
266 if (_length != 0) {
267 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u",
268 _length);
269 ret = false;
270 }
271 if (check_sample && _last_sampled_rs_lengths != 0) {
272 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
273 ret = false;
274 }
275 if (_head != NULL) {
276 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
277 ret = false;
278 }
279 if (!ret) {
280 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
281 }
283 return ret;
284 }
286 void
287 YoungList::rs_length_sampling_init() {
288 _sampled_rs_lengths = 0;
289 _curr = _head;
290 }
292 bool
293 YoungList::rs_length_sampling_more() {
294 return _curr != NULL;
295 }
297 void
298 YoungList::rs_length_sampling_next() {
299 assert( _curr != NULL, "invariant" );
300 size_t rs_length = _curr->rem_set()->occupied();
302 _sampled_rs_lengths += rs_length;
304 // The current region may not yet have been added to the
305 // incremental collection set (it gets added when it is
306 // retired as the current allocation region).
307 if (_curr->in_collection_set()) {
308 // Update the collection set policy information for this region
309 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
310 }
312 _curr = _curr->get_next_young_region();
313 if (_curr == NULL) {
314 _last_sampled_rs_lengths = _sampled_rs_lengths;
315 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
316 }
317 }
319 void
320 YoungList::reset_auxilary_lists() {
321 guarantee( is_empty(), "young list should be empty" );
322 assert(check_list_well_formed(), "young list should be well formed");
324 // Add survivor regions to SurvRateGroup.
325 _g1h->g1_policy()->note_start_adding_survivor_regions();
326 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
328 int young_index_in_cset = 0;
329 for (HeapRegion* curr = _survivor_head;
330 curr != NULL;
331 curr = curr->get_next_young_region()) {
332 _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
334 // The region is a non-empty survivor so let's add it to
335 // the incremental collection set for the next evacuation
336 // pause.
337 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
338 young_index_in_cset += 1;
339 }
340 assert((uint) young_index_in_cset == _survivor_length, "post-condition");
341 _g1h->g1_policy()->note_stop_adding_survivor_regions();
343 _head = _survivor_head;
344 _length = _survivor_length;
345 if (_survivor_head != NULL) {
346 assert(_survivor_tail != NULL, "cause it shouldn't be");
347 assert(_survivor_length > 0, "invariant");
348 _survivor_tail->set_next_young_region(NULL);
349 }
351 // Don't clear the survivor list handles until the start of
352 // the next evacuation pause - we need it in order to re-tag
353 // the survivor regions from this evacuation pause as 'young'
354 // at the start of the next.
356 _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
358 assert(check_list_well_formed(), "young list should be well formed");
359 }
361 void YoungList::print() {
362 HeapRegion* lists[] = {_head, _survivor_head};
363 const char* names[] = {"YOUNG", "SURVIVOR"};
365 for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) {
366 gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
367 HeapRegion *curr = lists[list];
368 if (curr == NULL)
369 gclog_or_tty->print_cr(" empty");
370 while (curr != NULL) {
371 gclog_or_tty->print_cr(" "HR_FORMAT", P: "PTR_FORMAT "N: "PTR_FORMAT", age: %4d",
372 HR_FORMAT_PARAMS(curr),
373 curr->prev_top_at_mark_start(),
374 curr->next_top_at_mark_start(),
375 curr->age_in_surv_rate_group_cond());
376 curr = curr->get_next_young_region();
377 }
378 }
380 gclog_or_tty->print_cr("");
381 }
383 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
384 {
385 // Claim the right to put the region on the dirty cards region list
386 // by installing a self pointer.
387 HeapRegion* next = hr->get_next_dirty_cards_region();
388 if (next == NULL) {
389 HeapRegion* res = (HeapRegion*)
390 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
391 NULL);
392 if (res == NULL) {
393 HeapRegion* head;
394 do {
395 // Put the region to the dirty cards region list.
396 head = _dirty_cards_region_list;
397 next = (HeapRegion*)
398 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
399 if (next == head) {
400 assert(hr->get_next_dirty_cards_region() == hr,
401 "hr->get_next_dirty_cards_region() != hr");
402 if (next == NULL) {
403 // The last region in the list points to itself.
404 hr->set_next_dirty_cards_region(hr);
405 } else {
406 hr->set_next_dirty_cards_region(next);
407 }
408 }
409 } while (next != head);
410 }
411 }
412 }
414 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
415 {
416 HeapRegion* head;
417 HeapRegion* hr;
418 do {
419 head = _dirty_cards_region_list;
420 if (head == NULL) {
421 return NULL;
422 }
423 HeapRegion* new_head = head->get_next_dirty_cards_region();
424 if (head == new_head) {
425 // The last region.
426 new_head = NULL;
427 }
428 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
429 head);
430 } while (hr != head);
431 assert(hr != NULL, "invariant");
432 hr->set_next_dirty_cards_region(NULL);
433 return hr;
434 }
436 void G1CollectedHeap::stop_conc_gc_threads() {
437 _cg1r->stop();
438 _cmThread->stop();
439 }
441 #ifdef ASSERT
442 // A region is added to the collection set as it is retired
443 // so an address p can point to a region which will be in the
444 // collection set but has not yet been retired. This method
445 // therefore is only accurate during a GC pause after all
446 // regions have been retired. It is used for debugging
447 // to check if an nmethod has references to objects that can
448 // be move during a partial collection. Though it can be
449 // inaccurate, it is sufficient for G1 because the conservative
450 // implementation of is_scavengable() for G1 will indicate that
451 // all nmethods must be scanned during a partial collection.
452 bool G1CollectedHeap::is_in_partial_collection(const void* p) {
453 HeapRegion* hr = heap_region_containing(p);
454 return hr != NULL && hr->in_collection_set();
455 }
456 #endif
458 // Returns true if the reference points to an object that
459 // can move in an incremental collecction.
460 bool G1CollectedHeap::is_scavengable(const void* p) {
461 G1CollectedHeap* g1h = G1CollectedHeap::heap();
462 G1CollectorPolicy* g1p = g1h->g1_policy();
463 HeapRegion* hr = heap_region_containing(p);
464 if (hr == NULL) {
465 // perm gen (or null)
466 return false;
467 } else {
468 return !hr->isHumongous();
469 }
470 }
472 void G1CollectedHeap::check_ct_logs_at_safepoint() {
473 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
474 CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
476 // Count the dirty cards at the start.
477 CountNonCleanMemRegionClosure count1(this);
478 ct_bs->mod_card_iterate(&count1);
479 int orig_count = count1.n();
481 // First clear the logged cards.
482 ClearLoggedCardTableEntryClosure clear;
483 dcqs.set_closure(&clear);
484 dcqs.apply_closure_to_all_completed_buffers();
485 dcqs.iterate_closure_all_threads(false);
486 clear.print_histo();
488 // Now ensure that there's no dirty cards.
489 CountNonCleanMemRegionClosure count2(this);
490 ct_bs->mod_card_iterate(&count2);
491 if (count2.n() != 0) {
492 gclog_or_tty->print_cr("Card table has %d entries; %d originally",
493 count2.n(), orig_count);
494 }
495 guarantee(count2.n() == 0, "Card table should be clean.");
497 RedirtyLoggedCardTableEntryClosure redirty;
498 JavaThread::dirty_card_queue_set().set_closure(&redirty);
499 dcqs.apply_closure_to_all_completed_buffers();
500 dcqs.iterate_closure_all_threads(false);
501 gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
502 clear.calls(), orig_count);
503 guarantee(redirty.calls() == clear.calls(),
504 "Or else mechanism is broken.");
506 CountNonCleanMemRegionClosure count3(this);
507 ct_bs->mod_card_iterate(&count3);
508 if (count3.n() != orig_count) {
509 gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
510 orig_count, count3.n());
511 guarantee(count3.n() >= orig_count, "Should have restored them all.");
512 }
514 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
515 }
517 // Private class members.
519 G1CollectedHeap* G1CollectedHeap::_g1h;
521 // Private methods.
523 HeapRegion*
524 G1CollectedHeap::new_region_try_secondary_free_list() {
525 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
526 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
527 if (!_secondary_free_list.is_empty()) {
528 if (G1ConcRegionFreeingVerbose) {
529 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
530 "secondary_free_list has %u entries",
531 _secondary_free_list.length());
532 }
533 // It looks as if there are free regions available on the
534 // secondary_free_list. Let's move them to the free_list and try
535 // again to allocate from it.
536 append_secondary_free_list();
538 assert(!_free_list.is_empty(), "if the secondary_free_list was not "
539 "empty we should have moved at least one entry to the free_list");
540 HeapRegion* res = _free_list.remove_head();
541 if (G1ConcRegionFreeingVerbose) {
542 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
543 "allocated "HR_FORMAT" from secondary_free_list",
544 HR_FORMAT_PARAMS(res));
545 }
546 return res;
547 }
549 // Wait here until we get notifed either when (a) there are no
550 // more free regions coming or (b) some regions have been moved on
551 // the secondary_free_list.
552 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
553 }
555 if (G1ConcRegionFreeingVerbose) {
556 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
557 "could not allocate from secondary_free_list");
558 }
559 return NULL;
560 }
562 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool do_expand) {
563 assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords,
564 "the only time we use this to allocate a humongous region is "
565 "when we are allocating a single humongous region");
567 HeapRegion* res;
568 if (G1StressConcRegionFreeing) {
569 if (!_secondary_free_list.is_empty()) {
570 if (G1ConcRegionFreeingVerbose) {
571 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
572 "forced to look at the secondary_free_list");
573 }
574 res = new_region_try_secondary_free_list();
575 if (res != NULL) {
576 return res;
577 }
578 }
579 }
580 res = _free_list.remove_head_or_null();
581 if (res == NULL) {
582 if (G1ConcRegionFreeingVerbose) {
583 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
584 "res == NULL, trying the secondary_free_list");
585 }
586 res = new_region_try_secondary_free_list();
587 }
588 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
589 // Currently, only attempts to allocate GC alloc regions set
590 // do_expand to true. So, we should only reach here during a
591 // safepoint. If this assumption changes we might have to
592 // reconsider the use of _expand_heap_after_alloc_failure.
593 assert(SafepointSynchronize::is_at_safepoint(), "invariant");
595 ergo_verbose1(ErgoHeapSizing,
596 "attempt heap expansion",
597 ergo_format_reason("region allocation request failed")
598 ergo_format_byte("allocation request"),
599 word_size * HeapWordSize);
600 if (expand(word_size * HeapWordSize)) {
601 // Given that expand() succeeded in expanding the heap, and we
602 // always expand the heap by an amount aligned to the heap
603 // region size, the free list should in theory not be empty. So
604 // it would probably be OK to use remove_head(). But the extra
605 // check for NULL is unlikely to be a performance issue here (we
606 // just expanded the heap!) so let's just be conservative and
607 // use remove_head_or_null().
608 res = _free_list.remove_head_or_null();
609 } else {
610 _expand_heap_after_alloc_failure = false;
611 }
612 }
613 return res;
614 }
616 uint G1CollectedHeap::humongous_obj_allocate_find_first(uint num_regions,
617 size_t word_size) {
618 assert(isHumongous(word_size), "word_size should be humongous");
619 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
621 uint first = G1_NULL_HRS_INDEX;
622 if (num_regions == 1) {
623 // Only one region to allocate, no need to go through the slower
624 // path. The caller will attempt the expasion if this fails, so
625 // let's not try to expand here too.
626 HeapRegion* hr = new_region(word_size, false /* do_expand */);
627 if (hr != NULL) {
628 first = hr->hrs_index();
629 } else {
630 first = G1_NULL_HRS_INDEX;
631 }
632 } else {
633 // We can't allocate humongous regions while cleanupComplete() is
634 // running, since some of the regions we find to be empty might not
635 // yet be added to the free list and it is not straightforward to
636 // know which list they are on so that we can remove them. Note
637 // that we only need to do this if we need to allocate more than
638 // one region to satisfy the current humongous allocation
639 // request. If we are only allocating one region we use the common
640 // region allocation code (see above).
641 wait_while_free_regions_coming();
642 append_secondary_free_list_if_not_empty_with_lock();
644 if (free_regions() >= num_regions) {
645 first = _hrs.find_contiguous(num_regions);
646 if (first != G1_NULL_HRS_INDEX) {
647 for (uint i = first; i < first + num_regions; ++i) {
648 HeapRegion* hr = region_at(i);
649 assert(hr->is_empty(), "sanity");
650 assert(is_on_master_free_list(hr), "sanity");
651 hr->set_pending_removal(true);
652 }
653 _free_list.remove_all_pending(num_regions);
654 }
655 }
656 }
657 return first;
658 }
660 HeapWord*
661 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
662 uint num_regions,
663 size_t word_size) {
664 assert(first != G1_NULL_HRS_INDEX, "pre-condition");
665 assert(isHumongous(word_size), "word_size should be humongous");
666 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
668 // Index of last region in the series + 1.
669 uint last = first + num_regions;
671 // We need to initialize the region(s) we just discovered. This is
672 // a bit tricky given that it can happen concurrently with
673 // refinement threads refining cards on these regions and
674 // potentially wanting to refine the BOT as they are scanning
675 // those cards (this can happen shortly after a cleanup; see CR
676 // 6991377). So we have to set up the region(s) carefully and in
677 // a specific order.
679 // The word size sum of all the regions we will allocate.
680 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
681 assert(word_size <= word_size_sum, "sanity");
683 // This will be the "starts humongous" region.
684 HeapRegion* first_hr = region_at(first);
685 // The header of the new object will be placed at the bottom of
686 // the first region.
687 HeapWord* new_obj = first_hr->bottom();
688 // This will be the new end of the first region in the series that
689 // should also match the end of the last region in the seriers.
690 HeapWord* new_end = new_obj + word_size_sum;
691 // This will be the new top of the first region that will reflect
692 // this allocation.
693 HeapWord* new_top = new_obj + word_size;
695 // First, we need to zero the header of the space that we will be
696 // allocating. When we update top further down, some refinement
697 // threads might try to scan the region. By zeroing the header we
698 // ensure that any thread that will try to scan the region will
699 // come across the zero klass word and bail out.
700 //
701 // NOTE: It would not have been correct to have used
702 // CollectedHeap::fill_with_object() and make the space look like
703 // an int array. The thread that is doing the allocation will
704 // later update the object header to a potentially different array
705 // type and, for a very short period of time, the klass and length
706 // fields will be inconsistent. This could cause a refinement
707 // thread to calculate the object size incorrectly.
708 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
710 // We will set up the first region as "starts humongous". This
711 // will also update the BOT covering all the regions to reflect
712 // that there is a single object that starts at the bottom of the
713 // first region.
714 first_hr->set_startsHumongous(new_top, new_end);
716 // Then, if there are any, we will set up the "continues
717 // humongous" regions.
718 HeapRegion* hr = NULL;
719 for (uint i = first + 1; i < last; ++i) {
720 hr = region_at(i);
721 hr->set_continuesHumongous(first_hr);
722 }
723 // If we have "continues humongous" regions (hr != NULL), then the
724 // end of the last one should match new_end.
725 assert(hr == NULL || hr->end() == new_end, "sanity");
727 // Up to this point no concurrent thread would have been able to
728 // do any scanning on any region in this series. All the top
729 // fields still point to bottom, so the intersection between
730 // [bottom,top] and [card_start,card_end] will be empty. Before we
731 // update the top fields, we'll do a storestore to make sure that
732 // no thread sees the update to top before the zeroing of the
733 // object header and the BOT initialization.
734 OrderAccess::storestore();
736 // Now that the BOT and the object header have been initialized,
737 // we can update top of the "starts humongous" region.
738 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
739 "new_top should be in this region");
740 first_hr->set_top(new_top);
741 if (_hr_printer.is_active()) {
742 HeapWord* bottom = first_hr->bottom();
743 HeapWord* end = first_hr->orig_end();
744 if ((first + 1) == last) {
745 // the series has a single humongous region
746 _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
747 } else {
748 // the series has more than one humongous regions
749 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
750 }
751 }
753 // Now, we will update the top fields of the "continues humongous"
754 // regions. The reason we need to do this is that, otherwise,
755 // these regions would look empty and this will confuse parts of
756 // G1. For example, the code that looks for a consecutive number
757 // of empty regions will consider them empty and try to
758 // re-allocate them. We can extend is_empty() to also include
759 // !continuesHumongous(), but it is easier to just update the top
760 // fields here. The way we set top for all regions (i.e., top ==
761 // end for all regions but the last one, top == new_top for the
762 // last one) is actually used when we will free up the humongous
763 // region in free_humongous_region().
764 hr = NULL;
765 for (uint i = first + 1; i < last; ++i) {
766 hr = region_at(i);
767 if ((i + 1) == last) {
768 // last continues humongous region
769 assert(hr->bottom() < new_top && new_top <= hr->end(),
770 "new_top should fall on this region");
771 hr->set_top(new_top);
772 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
773 } else {
774 // not last one
775 assert(new_top > hr->end(), "new_top should be above this region");
776 hr->set_top(hr->end());
777 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
778 }
779 }
780 // If we have continues humongous regions (hr != NULL), then the
781 // end of the last one should match new_end and its top should
782 // match new_top.
783 assert(hr == NULL ||
784 (hr->end() == new_end && hr->top() == new_top), "sanity");
786 assert(first_hr->used() == word_size * HeapWordSize, "invariant");
787 _summary_bytes_used += first_hr->used();
788 _humongous_set.add(first_hr);
790 return new_obj;
791 }
793 // If could fit into free regions w/o expansion, try.
794 // Otherwise, if can expand, do so.
795 // Otherwise, if using ex regions might help, try with ex given back.
796 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
797 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
799 verify_region_sets_optional();
801 size_t word_size_rounded = round_to(word_size, HeapRegion::GrainWords);
802 uint num_regions = (uint) (word_size_rounded / HeapRegion::GrainWords);
803 uint x_num = expansion_regions();
804 uint fs = _hrs.free_suffix();
805 uint first = humongous_obj_allocate_find_first(num_regions, word_size);
806 if (first == G1_NULL_HRS_INDEX) {
807 // The only thing we can do now is attempt expansion.
808 if (fs + x_num >= num_regions) {
809 // If the number of regions we're trying to allocate for this
810 // object is at most the number of regions in the free suffix,
811 // then the call to humongous_obj_allocate_find_first() above
812 // should have succeeded and we wouldn't be here.
813 //
814 // We should only be trying to expand when the free suffix is
815 // not sufficient for the object _and_ we have some expansion
816 // room available.
817 assert(num_regions > fs, "earlier allocation should have succeeded");
819 ergo_verbose1(ErgoHeapSizing,
820 "attempt heap expansion",
821 ergo_format_reason("humongous allocation request failed")
822 ergo_format_byte("allocation request"),
823 word_size * HeapWordSize);
824 if (expand((num_regions - fs) * HeapRegion::GrainBytes)) {
825 // Even though the heap was expanded, it might not have
826 // reached the desired size. So, we cannot assume that the
827 // allocation will succeed.
828 first = humongous_obj_allocate_find_first(num_regions, word_size);
829 }
830 }
831 }
833 HeapWord* result = NULL;
834 if (first != G1_NULL_HRS_INDEX) {
835 result =
836 humongous_obj_allocate_initialize_regions(first, num_regions, word_size);
837 assert(result != NULL, "it should always return a valid result");
839 // A successful humongous object allocation changes the used space
840 // information of the old generation so we need to recalculate the
841 // sizes and update the jstat counters here.
842 g1mm()->update_sizes();
843 }
845 verify_region_sets_optional();
847 return result;
848 }
850 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
851 assert_heap_not_locked_and_not_at_safepoint();
852 assert(!isHumongous(word_size), "we do not allow humongous TLABs");
854 unsigned int dummy_gc_count_before;
855 return attempt_allocation(word_size, &dummy_gc_count_before);
856 }
858 HeapWord*
859 G1CollectedHeap::mem_allocate(size_t word_size,
860 bool* gc_overhead_limit_was_exceeded) {
861 assert_heap_not_locked_and_not_at_safepoint();
863 // Loop until the allocation is satisified, or unsatisfied after GC.
864 for (int try_count = 1; /* we'll return */; try_count += 1) {
865 unsigned int gc_count_before;
867 HeapWord* result = NULL;
868 if (!isHumongous(word_size)) {
869 result = attempt_allocation(word_size, &gc_count_before);
870 } else {
871 result = attempt_allocation_humongous(word_size, &gc_count_before);
872 }
873 if (result != NULL) {
874 return result;
875 }
877 // Create the garbage collection operation...
878 VM_G1CollectForAllocation op(gc_count_before, word_size);
879 // ...and get the VM thread to execute it.
880 VMThread::execute(&op);
882 if (op.prologue_succeeded() && op.pause_succeeded()) {
883 // If the operation was successful we'll return the result even
884 // if it is NULL. If the allocation attempt failed immediately
885 // after a Full GC, it's unlikely we'll be able to allocate now.
886 HeapWord* result = op.result();
887 if (result != NULL && !isHumongous(word_size)) {
888 // Allocations that take place on VM operations do not do any
889 // card dirtying and we have to do it here. We only have to do
890 // this for non-humongous allocations, though.
891 dirty_young_block(result, word_size);
892 }
893 return result;
894 } else {
895 assert(op.result() == NULL,
896 "the result should be NULL if the VM op did not succeed");
897 }
899 // Give a warning if we seem to be looping forever.
900 if ((QueuedAllocationWarningCount > 0) &&
901 (try_count % QueuedAllocationWarningCount == 0)) {
902 warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
903 }
904 }
906 ShouldNotReachHere();
907 return NULL;
908 }
910 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
911 unsigned int *gc_count_before_ret) {
912 // Make sure you read the note in attempt_allocation_humongous().
914 assert_heap_not_locked_and_not_at_safepoint();
915 assert(!isHumongous(word_size), "attempt_allocation_slow() should not "
916 "be called for humongous allocation requests");
918 // We should only get here after the first-level allocation attempt
919 // (attempt_allocation()) failed to allocate.
921 // We will loop until a) we manage to successfully perform the
922 // allocation or b) we successfully schedule a collection which
923 // fails to perform the allocation. b) is the only case when we'll
924 // return NULL.
925 HeapWord* result = NULL;
926 for (int try_count = 1; /* we'll return */; try_count += 1) {
927 bool should_try_gc;
928 unsigned int gc_count_before;
930 {
931 MutexLockerEx x(Heap_lock);
933 result = _mutator_alloc_region.attempt_allocation_locked(word_size,
934 false /* bot_updates */);
935 if (result != NULL) {
936 return result;
937 }
939 // If we reach here, attempt_allocation_locked() above failed to
940 // allocate a new region. So the mutator alloc region should be NULL.
941 assert(_mutator_alloc_region.get() == NULL, "only way to get here");
943 if (GC_locker::is_active_and_needs_gc()) {
944 if (g1_policy()->can_expand_young_list()) {
945 // No need for an ergo verbose message here,
946 // can_expand_young_list() does this when it returns true.
947 result = _mutator_alloc_region.attempt_allocation_force(word_size,
948 false /* bot_updates */);
949 if (result != NULL) {
950 return result;
951 }
952 }
953 should_try_gc = false;
954 } else {
955 // The GCLocker may not be active but the GCLocker initiated
956 // GC may not yet have been performed (GCLocker::needs_gc()
957 // returns true). In this case we do not try this GC and
958 // wait until the GCLocker initiated GC is performed, and
959 // then retry the allocation.
960 if (GC_locker::needs_gc()) {
961 should_try_gc = false;
962 } else {
963 // Read the GC count while still holding the Heap_lock.
964 gc_count_before = total_collections();
965 should_try_gc = true;
966 }
967 }
968 }
970 if (should_try_gc) {
971 bool succeeded;
972 result = do_collection_pause(word_size, gc_count_before, &succeeded);
973 if (result != NULL) {
974 assert(succeeded, "only way to get back a non-NULL result");
975 return result;
976 }
978 if (succeeded) {
979 // If we get here we successfully scheduled a collection which
980 // failed to allocate. No point in trying to allocate
981 // further. We'll just return NULL.
982 MutexLockerEx x(Heap_lock);
983 *gc_count_before_ret = total_collections();
984 return NULL;
985 }
986 } else {
987 // The GCLocker is either active or the GCLocker initiated
988 // GC has not yet been performed. Stall until it is and
989 // then retry the allocation.
990 GC_locker::stall_until_clear();
991 }
993 // We can reach here if we were unsuccessul in scheduling a
994 // collection (because another thread beat us to it) or if we were
995 // stalled due to the GC locker. In either can we should retry the
996 // allocation attempt in case another thread successfully
997 // performed a collection and reclaimed enough space. We do the
998 // first attempt (without holding the Heap_lock) here and the
999 // follow-on attempt will be at the start of the next loop
1000 // iteration (after taking the Heap_lock).
1001 result = _mutator_alloc_region.attempt_allocation(word_size,
1002 false /* bot_updates */);
1003 if (result != NULL) {
1004 return result;
1005 }
1007 // Give a warning if we seem to be looping forever.
1008 if ((QueuedAllocationWarningCount > 0) &&
1009 (try_count % QueuedAllocationWarningCount == 0)) {
1010 warning("G1CollectedHeap::attempt_allocation_slow() "
1011 "retries %d times", try_count);
1012 }
1013 }
1015 ShouldNotReachHere();
1016 return NULL;
1017 }
1019 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
1020 unsigned int * gc_count_before_ret) {
1021 // The structure of this method has a lot of similarities to
1022 // attempt_allocation_slow(). The reason these two were not merged
1023 // into a single one is that such a method would require several "if
1024 // allocation is not humongous do this, otherwise do that"
1025 // conditional paths which would obscure its flow. In fact, an early
1026 // version of this code did use a unified method which was harder to
1027 // follow and, as a result, it had subtle bugs that were hard to
1028 // track down. So keeping these two methods separate allows each to
1029 // be more readable. It will be good to keep these two in sync as
1030 // much as possible.
1032 assert_heap_not_locked_and_not_at_safepoint();
1033 assert(isHumongous(word_size), "attempt_allocation_humongous() "
1034 "should only be called for humongous allocations");
1036 // Humongous objects can exhaust the heap quickly, so we should check if we
1037 // need to start a marking cycle at each humongous object allocation. We do
1038 // the check before we do the actual allocation. The reason for doing it
1039 // before the allocation is that we avoid having to keep track of the newly
1040 // allocated memory while we do a GC.
1041 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
1042 word_size)) {
1043 collect(GCCause::_g1_humongous_allocation);
1044 }
1046 // We will loop until a) we manage to successfully perform the
1047 // allocation or b) we successfully schedule a collection which
1048 // fails to perform the allocation. b) is the only case when we'll
1049 // return NULL.
1050 HeapWord* result = NULL;
1051 for (int try_count = 1; /* we'll return */; try_count += 1) {
1052 bool should_try_gc;
1053 unsigned int gc_count_before;
1055 {
1056 MutexLockerEx x(Heap_lock);
1058 // Given that humongous objects are not allocated in young
1059 // regions, we'll first try to do the allocation without doing a
1060 // collection hoping that there's enough space in the heap.
1061 result = humongous_obj_allocate(word_size);
1062 if (result != NULL) {
1063 return result;
1064 }
1066 if (GC_locker::is_active_and_needs_gc()) {
1067 should_try_gc = false;
1068 } else {
1069 // The GCLocker may not be active but the GCLocker initiated
1070 // GC may not yet have been performed (GCLocker::needs_gc()
1071 // returns true). In this case we do not try this GC and
1072 // wait until the GCLocker initiated GC is performed, and
1073 // then retry the allocation.
1074 if (GC_locker::needs_gc()) {
1075 should_try_gc = false;
1076 } else {
1077 // Read the GC count while still holding the Heap_lock.
1078 gc_count_before = total_collections();
1079 should_try_gc = true;
1080 }
1081 }
1082 }
1084 if (should_try_gc) {
1085 // If we failed to allocate the humongous object, we should try to
1086 // do a collection pause (if we're allowed) in case it reclaims
1087 // enough space for the allocation to succeed after the pause.
1089 bool succeeded;
1090 result = do_collection_pause(word_size, gc_count_before, &succeeded);
1091 if (result != NULL) {
1092 assert(succeeded, "only way to get back a non-NULL result");
1093 return result;
1094 }
1096 if (succeeded) {
1097 // If we get here we successfully scheduled a collection which
1098 // failed to allocate. No point in trying to allocate
1099 // further. We'll just return NULL.
1100 MutexLockerEx x(Heap_lock);
1101 *gc_count_before_ret = total_collections();
1102 return NULL;
1103 }
1104 } else {
1105 // The GCLocker is either active or the GCLocker initiated
1106 // GC has not yet been performed. Stall until it is and
1107 // then retry the allocation.
1108 GC_locker::stall_until_clear();
1109 }
1111 // We can reach here if we were unsuccessul in scheduling a
1112 // collection (because another thread beat us to it) or if we were
1113 // stalled due to the GC locker. In either can we should retry the
1114 // allocation attempt in case another thread successfully
1115 // performed a collection and reclaimed enough space. Give a
1116 // warning if we seem to be looping forever.
1118 if ((QueuedAllocationWarningCount > 0) &&
1119 (try_count % QueuedAllocationWarningCount == 0)) {
1120 warning("G1CollectedHeap::attempt_allocation_humongous() "
1121 "retries %d times", try_count);
1122 }
1123 }
1125 ShouldNotReachHere();
1126 return NULL;
1127 }
1129 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1130 bool expect_null_mutator_alloc_region) {
1131 assert_at_safepoint(true /* should_be_vm_thread */);
1132 assert(_mutator_alloc_region.get() == NULL ||
1133 !expect_null_mutator_alloc_region,
1134 "the current alloc region was unexpectedly found to be non-NULL");
1136 if (!isHumongous(word_size)) {
1137 return _mutator_alloc_region.attempt_allocation_locked(word_size,
1138 false /* bot_updates */);
1139 } else {
1140 HeapWord* result = humongous_obj_allocate(word_size);
1141 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1142 g1_policy()->set_initiate_conc_mark_if_possible();
1143 }
1144 return result;
1145 }
1147 ShouldNotReachHere();
1148 }
1150 class PostMCRemSetClearClosure: public HeapRegionClosure {
1151 ModRefBarrierSet* _mr_bs;
1152 public:
1153 PostMCRemSetClearClosure(ModRefBarrierSet* mr_bs) : _mr_bs(mr_bs) {}
1154 bool doHeapRegion(HeapRegion* r) {
1155 r->reset_gc_time_stamp();
1156 if (r->continuesHumongous())
1157 return false;
1158 HeapRegionRemSet* hrrs = r->rem_set();
1159 if (hrrs != NULL) hrrs->clear();
1160 // You might think here that we could clear just the cards
1161 // corresponding to the used region. But no: if we leave a dirty card
1162 // in a region we might allocate into, then it would prevent that card
1163 // from being enqueued, and cause it to be missed.
1164 // Re: the performance cost: we shouldn't be doing full GC anyway!
1165 _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1166 return false;
1167 }
1168 };
1171 class PostMCRemSetInvalidateClosure: public HeapRegionClosure {
1172 ModRefBarrierSet* _mr_bs;
1173 public:
1174 PostMCRemSetInvalidateClosure(ModRefBarrierSet* mr_bs) : _mr_bs(mr_bs) {}
1175 bool doHeapRegion(HeapRegion* r) {
1176 if (r->continuesHumongous()) return false;
1177 if (r->used_region().word_size() != 0) {
1178 _mr_bs->invalidate(r->used_region(), true /*whole heap*/);
1179 }
1180 return false;
1181 }
1182 };
1184 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1185 G1CollectedHeap* _g1h;
1186 UpdateRSOopClosure _cl;
1187 int _worker_i;
1188 public:
1189 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1190 _cl(g1->g1_rem_set(), worker_i),
1191 _worker_i(worker_i),
1192 _g1h(g1)
1193 { }
1195 bool doHeapRegion(HeapRegion* r) {
1196 if (!r->continuesHumongous()) {
1197 _cl.set_from(r);
1198 r->oop_iterate(&_cl);
1199 }
1200 return false;
1201 }
1202 };
1204 class ParRebuildRSTask: public AbstractGangTask {
1205 G1CollectedHeap* _g1;
1206 public:
1207 ParRebuildRSTask(G1CollectedHeap* g1)
1208 : AbstractGangTask("ParRebuildRSTask"),
1209 _g1(g1)
1210 { }
1212 void work(uint worker_id) {
1213 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1214 _g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id,
1215 _g1->workers()->active_workers(),
1216 HeapRegion::RebuildRSClaimValue);
1217 }
1218 };
1220 class PostCompactionPrinterClosure: public HeapRegionClosure {
1221 private:
1222 G1HRPrinter* _hr_printer;
1223 public:
1224 bool doHeapRegion(HeapRegion* hr) {
1225 assert(!hr->is_young(), "not expecting to find young regions");
1226 // We only generate output for non-empty regions.
1227 if (!hr->is_empty()) {
1228 if (!hr->isHumongous()) {
1229 _hr_printer->post_compaction(hr, G1HRPrinter::Old);
1230 } else if (hr->startsHumongous()) {
1231 if (hr->capacity() == HeapRegion::GrainBytes) {
1232 // single humongous region
1233 _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
1234 } else {
1235 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
1236 }
1237 } else {
1238 assert(hr->continuesHumongous(), "only way to get here");
1239 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1240 }
1241 }
1242 return false;
1243 }
1245 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1246 : _hr_printer(hr_printer) { }
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 PostMCRemSetClearClosure rs_clear(mr_bs());
1405 heap_region_iterate(&rs_clear);
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 PostCompactionPrinterClosure cl(hr_printer());
1416 heap_region_iterate(&cl);
1418 _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1419 }
1421 if (_cg1r->use_cache()) {
1422 _cg1r->clear_and_record_card_counts();
1423 _cg1r->clear_hot_cache();
1424 }
1426 // Rebuild remembered sets of all regions.
1427 if (G1CollectedHeap::use_parallel_gc_threads()) {
1428 uint n_workers =
1429 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1430 workers()->active_workers(),
1431 Threads::number_of_non_daemon_threads());
1432 assert(UseDynamicNumberOfGCThreads ||
1433 n_workers == workers()->total_workers(),
1434 "If not dynamic should be using all the workers");
1435 workers()->set_active_workers(n_workers);
1436 // Set parallel threads in the heap (_n_par_threads) only
1437 // before a parallel phase and always reset it to 0 after
1438 // the phase so that the number of parallel threads does
1439 // no get carried forward to a serial phase where there
1440 // may be code that is "possibly_parallel".
1441 set_par_threads(n_workers);
1443 ParRebuildRSTask rebuild_rs_task(this);
1444 assert(check_heap_region_claim_values(
1445 HeapRegion::InitialClaimValue), "sanity check");
1446 assert(UseDynamicNumberOfGCThreads ||
1447 workers()->active_workers() == workers()->total_workers(),
1448 "Unless dynamic should use total workers");
1449 // Use the most recent number of active workers
1450 assert(workers()->active_workers() > 0,
1451 "Active workers not properly set");
1452 set_par_threads(workers()->active_workers());
1453 workers()->run_task(&rebuild_rs_task);
1454 set_par_threads(0);
1455 assert(check_heap_region_claim_values(
1456 HeapRegion::RebuildRSClaimValue), "sanity check");
1457 reset_heap_region_claim_values();
1458 } else {
1459 RebuildRSOutOfRegionClosure rebuild_rs(this);
1460 heap_region_iterate(&rebuild_rs);
1461 }
1463 if (G1Log::fine()) {
1464 print_size_transition(gclog_or_tty, g1h_prev_used, used(), capacity());
1465 }
1467 if (true) { // FIXME
1468 // Ask the permanent generation to adjust size for full collections
1469 perm()->compute_new_size();
1470 }
1472 // Start a new incremental collection set for the next pause
1473 assert(g1_policy()->collection_set() == NULL, "must be");
1474 g1_policy()->start_incremental_cset_building();
1476 // Clear the _cset_fast_test bitmap in anticipation of adding
1477 // regions to the incremental collection set for the next
1478 // evacuation pause.
1479 clear_cset_fast_test();
1481 init_mutator_alloc_region();
1483 double end = os::elapsedTime();
1484 g1_policy()->record_full_collection_end();
1486 #ifdef TRACESPINNING
1487 ParallelTaskTerminator::print_termination_counts();
1488 #endif
1490 gc_epilogue(true);
1492 // Discard all rset updates
1493 JavaThread::dirty_card_queue_set().abandon_logs();
1494 assert(!G1DeferredRSUpdate
1495 || (G1DeferredRSUpdate && (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any");
1497 _young_list->reset_sampled_info();
1498 // At this point there should be no regions in the
1499 // entire heap tagged as young.
1500 assert( check_young_list_empty(true /* check_heap */),
1501 "young list should be empty at this point");
1503 // Update the number of full collections that have been completed.
1504 increment_old_marking_cycles_completed(false /* concurrent */);
1506 _hrs.verify_optional();
1507 verify_region_sets_optional();
1509 print_heap_after_gc();
1511 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1512 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1513 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1514 // before any GC notifications are raised.
1515 g1mm()->update_sizes();
1516 }
1518 post_full_gc_dump();
1520 return true;
1521 }
1523 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1524 // do_collection() will return whether it succeeded in performing
1525 // the GC. Currently, there is no facility on the
1526 // do_full_collection() API to notify the caller than the collection
1527 // did not succeed (e.g., because it was locked out by the GC
1528 // locker). So, right now, we'll ignore the return value.
1529 bool dummy = do_collection(true, /* explicit_gc */
1530 clear_all_soft_refs,
1531 0 /* word_size */);
1532 }
1534 // This code is mostly copied from TenuredGeneration.
1535 void
1536 G1CollectedHeap::
1537 resize_if_necessary_after_full_collection(size_t word_size) {
1538 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, "sanity check");
1540 // Include the current allocation, if any, and bytes that will be
1541 // pre-allocated to support collections, as "used".
1542 const size_t used_after_gc = used();
1543 const size_t capacity_after_gc = capacity();
1544 const size_t free_after_gc = capacity_after_gc - used_after_gc;
1546 // This is enforced in arguments.cpp.
1547 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1548 "otherwise the code below doesn't make sense");
1550 // We don't have floating point command-line arguments
1551 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1552 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1553 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1554 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1556 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1557 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1559 // We have to be careful here as these two calculations can overflow
1560 // 32-bit size_t's.
1561 double used_after_gc_d = (double) used_after_gc;
1562 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1563 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1565 // Let's make sure that they are both under the max heap size, which
1566 // by default will make them fit into a size_t.
1567 double desired_capacity_upper_bound = (double) max_heap_size;
1568 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1569 desired_capacity_upper_bound);
1570 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1571 desired_capacity_upper_bound);
1573 // We can now safely turn them into size_t's.
1574 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1575 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1577 // This assert only makes sense here, before we adjust them
1578 // with respect to the min and max heap size.
1579 assert(minimum_desired_capacity <= maximum_desired_capacity,
1580 err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1581 "maximum_desired_capacity = "SIZE_FORMAT,
1582 minimum_desired_capacity, maximum_desired_capacity));
1584 // Should not be greater than the heap max size. No need to adjust
1585 // it with respect to the heap min size as it's a lower bound (i.e.,
1586 // we'll try to make the capacity larger than it, not smaller).
1587 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1588 // Should not be less than the heap min size. No need to adjust it
1589 // with respect to the heap max size as it's an upper bound (i.e.,
1590 // we'll try to make the capacity smaller than it, not greater).
1591 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1593 if (capacity_after_gc < minimum_desired_capacity) {
1594 // Don't expand unless it's significant
1595 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1596 ergo_verbose4(ErgoHeapSizing,
1597 "attempt heap expansion",
1598 ergo_format_reason("capacity lower than "
1599 "min desired capacity after Full GC")
1600 ergo_format_byte("capacity")
1601 ergo_format_byte("occupancy")
1602 ergo_format_byte_perc("min desired capacity"),
1603 capacity_after_gc, used_after_gc,
1604 minimum_desired_capacity, (double) MinHeapFreeRatio);
1605 expand(expand_bytes);
1607 // No expansion, now see if we want to shrink
1608 } else if (capacity_after_gc > maximum_desired_capacity) {
1609 // Capacity too large, compute shrinking size
1610 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1611 ergo_verbose4(ErgoHeapSizing,
1612 "attempt heap shrinking",
1613 ergo_format_reason("capacity higher than "
1614 "max desired capacity after Full GC")
1615 ergo_format_byte("capacity")
1616 ergo_format_byte("occupancy")
1617 ergo_format_byte_perc("max desired capacity"),
1618 capacity_after_gc, used_after_gc,
1619 maximum_desired_capacity, (double) MaxHeapFreeRatio);
1620 shrink(shrink_bytes);
1621 }
1622 }
1625 HeapWord*
1626 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1627 bool* succeeded) {
1628 assert_at_safepoint(true /* should_be_vm_thread */);
1630 *succeeded = true;
1631 // Let's attempt the allocation first.
1632 HeapWord* result =
1633 attempt_allocation_at_safepoint(word_size,
1634 false /* expect_null_mutator_alloc_region */);
1635 if (result != NULL) {
1636 assert(*succeeded, "sanity");
1637 return result;
1638 }
1640 // In a G1 heap, we're supposed to keep allocation from failing by
1641 // incremental pauses. Therefore, at least for now, we'll favor
1642 // expansion over collection. (This might change in the future if we can
1643 // do something smarter than full collection to satisfy a failed alloc.)
1644 result = expand_and_allocate(word_size);
1645 if (result != NULL) {
1646 assert(*succeeded, "sanity");
1647 return result;
1648 }
1650 // Expansion didn't work, we'll try to do a Full GC.
1651 bool gc_succeeded = do_collection(false, /* explicit_gc */
1652 false, /* clear_all_soft_refs */
1653 word_size);
1654 if (!gc_succeeded) {
1655 *succeeded = false;
1656 return NULL;
1657 }
1659 // Retry the allocation
1660 result = attempt_allocation_at_safepoint(word_size,
1661 true /* expect_null_mutator_alloc_region */);
1662 if (result != NULL) {
1663 assert(*succeeded, "sanity");
1664 return result;
1665 }
1667 // Then, try a Full GC that will collect all soft references.
1668 gc_succeeded = do_collection(false, /* explicit_gc */
1669 true, /* clear_all_soft_refs */
1670 word_size);
1671 if (!gc_succeeded) {
1672 *succeeded = false;
1673 return NULL;
1674 }
1676 // Retry the allocation once more
1677 result = attempt_allocation_at_safepoint(word_size,
1678 true /* expect_null_mutator_alloc_region */);
1679 if (result != NULL) {
1680 assert(*succeeded, "sanity");
1681 return result;
1682 }
1684 assert(!collector_policy()->should_clear_all_soft_refs(),
1685 "Flag should have been handled and cleared prior to this point");
1687 // What else? We might try synchronous finalization later. If the total
1688 // space available is large enough for the allocation, then a more
1689 // complete compaction phase than we've tried so far might be
1690 // appropriate.
1691 assert(*succeeded, "sanity");
1692 return NULL;
1693 }
1695 // Attempting to expand the heap sufficiently
1696 // to support an allocation of the given "word_size". If
1697 // successful, perform the allocation and return the address of the
1698 // allocated block, or else "NULL".
1700 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1701 assert_at_safepoint(true /* should_be_vm_thread */);
1703 verify_region_sets_optional();
1705 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1706 ergo_verbose1(ErgoHeapSizing,
1707 "attempt heap expansion",
1708 ergo_format_reason("allocation request failed")
1709 ergo_format_byte("allocation request"),
1710 word_size * HeapWordSize);
1711 if (expand(expand_bytes)) {
1712 _hrs.verify_optional();
1713 verify_region_sets_optional();
1714 return attempt_allocation_at_safepoint(word_size,
1715 false /* expect_null_mutator_alloc_region */);
1716 }
1717 return NULL;
1718 }
1720 void G1CollectedHeap::update_committed_space(HeapWord* old_end,
1721 HeapWord* new_end) {
1722 assert(old_end != new_end, "don't call this otherwise");
1723 assert((HeapWord*) _g1_storage.high() == new_end, "invariant");
1725 // Update the committed mem region.
1726 _g1_committed.set_end(new_end);
1727 // Tell the card table about the update.
1728 Universe::heap()->barrier_set()->resize_covered_region(_g1_committed);
1729 // Tell the BOT about the update.
1730 _bot_shared->resize(_g1_committed.word_size());
1731 }
1733 bool G1CollectedHeap::expand(size_t expand_bytes) {
1734 size_t old_mem_size = _g1_storage.committed_size();
1735 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1736 aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1737 HeapRegion::GrainBytes);
1738 ergo_verbose2(ErgoHeapSizing,
1739 "expand the heap",
1740 ergo_format_byte("requested expansion amount")
1741 ergo_format_byte("attempted expansion amount"),
1742 expand_bytes, aligned_expand_bytes);
1744 // First commit the memory.
1745 HeapWord* old_end = (HeapWord*) _g1_storage.high();
1746 bool successful = _g1_storage.expand_by(aligned_expand_bytes);
1747 if (successful) {
1748 // Then propagate this update to the necessary data structures.
1749 HeapWord* new_end = (HeapWord*) _g1_storage.high();
1750 update_committed_space(old_end, new_end);
1752 FreeRegionList expansion_list("Local Expansion List");
1753 MemRegion mr = _hrs.expand_by(old_end, new_end, &expansion_list);
1754 assert(mr.start() == old_end, "post-condition");
1755 // mr might be a smaller region than what was requested if
1756 // expand_by() was unable to allocate the HeapRegion instances
1757 assert(mr.end() <= new_end, "post-condition");
1759 size_t actual_expand_bytes = mr.byte_size();
1760 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1761 assert(actual_expand_bytes == expansion_list.total_capacity_bytes(),
1762 "post-condition");
1763 if (actual_expand_bytes < aligned_expand_bytes) {
1764 // We could not expand _hrs to the desired size. In this case we
1765 // need to shrink the committed space accordingly.
1766 assert(mr.end() < new_end, "invariant");
1768 size_t diff_bytes = aligned_expand_bytes - actual_expand_bytes;
1769 // First uncommit the memory.
1770 _g1_storage.shrink_by(diff_bytes);
1771 // Then propagate this update to the necessary data structures.
1772 update_committed_space(new_end, mr.end());
1773 }
1774 _free_list.add_as_tail(&expansion_list);
1776 if (_hr_printer.is_active()) {
1777 HeapWord* curr = mr.start();
1778 while (curr < mr.end()) {
1779 HeapWord* curr_end = curr + HeapRegion::GrainWords;
1780 _hr_printer.commit(curr, curr_end);
1781 curr = curr_end;
1782 }
1783 assert(curr == mr.end(), "post-condition");
1784 }
1785 g1_policy()->record_new_heap_size(n_regions());
1786 } else {
1787 ergo_verbose0(ErgoHeapSizing,
1788 "did not expand the heap",
1789 ergo_format_reason("heap expansion operation failed"));
1790 // The expansion of the virtual storage space was unsuccessful.
1791 // Let's see if it was because we ran out of swap.
1792 if (G1ExitOnExpansionFailure &&
1793 _g1_storage.uncommitted_size() >= aligned_expand_bytes) {
1794 // We had head room...
1795 vm_exit_out_of_memory(aligned_expand_bytes, "G1 heap expansion");
1796 }
1797 }
1798 return successful;
1799 }
1801 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1802 size_t old_mem_size = _g1_storage.committed_size();
1803 size_t aligned_shrink_bytes =
1804 ReservedSpace::page_align_size_down(shrink_bytes);
1805 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1806 HeapRegion::GrainBytes);
1807 uint num_regions_deleted = 0;
1808 MemRegion mr = _hrs.shrink_by(aligned_shrink_bytes, &num_regions_deleted);
1809 HeapWord* old_end = (HeapWord*) _g1_storage.high();
1810 assert(mr.end() == old_end, "post-condition");
1812 ergo_verbose3(ErgoHeapSizing,
1813 "shrink the heap",
1814 ergo_format_byte("requested shrinking amount")
1815 ergo_format_byte("aligned shrinking amount")
1816 ergo_format_byte("attempted shrinking amount"),
1817 shrink_bytes, aligned_shrink_bytes, mr.byte_size());
1818 if (mr.byte_size() > 0) {
1819 if (_hr_printer.is_active()) {
1820 HeapWord* curr = mr.end();
1821 while (curr > mr.start()) {
1822 HeapWord* curr_end = curr;
1823 curr -= HeapRegion::GrainWords;
1824 _hr_printer.uncommit(curr, curr_end);
1825 }
1826 assert(curr == mr.start(), "post-condition");
1827 }
1829 _g1_storage.shrink_by(mr.byte_size());
1830 HeapWord* new_end = (HeapWord*) _g1_storage.high();
1831 assert(mr.start() == new_end, "post-condition");
1833 _expansion_regions += num_regions_deleted;
1834 update_committed_space(old_end, new_end);
1835 HeapRegionRemSet::shrink_heap(n_regions());
1836 g1_policy()->record_new_heap_size(n_regions());
1837 } else {
1838 ergo_verbose0(ErgoHeapSizing,
1839 "did not shrink the heap",
1840 ergo_format_reason("heap shrinking operation failed"));
1841 }
1842 }
1844 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1845 verify_region_sets_optional();
1847 // We should only reach here at the end of a Full GC which means we
1848 // should not not be holding to any GC alloc regions. The method
1849 // below will make sure of that and do any remaining clean up.
1850 abandon_gc_alloc_regions();
1852 // Instead of tearing down / rebuilding the free lists here, we
1853 // could instead use the remove_all_pending() method on free_list to
1854 // remove only the ones that we need to remove.
1855 tear_down_region_sets(true /* free_list_only */);
1856 shrink_helper(shrink_bytes);
1857 rebuild_region_sets(true /* free_list_only */);
1859 _hrs.verify_optional();
1860 verify_region_sets_optional();
1861 }
1863 // Public methods.
1865 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1866 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1867 #endif // _MSC_VER
1870 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1871 SharedHeap(policy_),
1872 _g1_policy(policy_),
1873 _dirty_card_queue_set(false),
1874 _into_cset_dirty_card_queue_set(false),
1875 _is_alive_closure_cm(this),
1876 _is_alive_closure_stw(this),
1877 _ref_processor_cm(NULL),
1878 _ref_processor_stw(NULL),
1879 _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
1880 _bot_shared(NULL),
1881 _objs_with_preserved_marks(NULL), _preserved_marks_of_objs(NULL),
1882 _evac_failure_scan_stack(NULL) ,
1883 _mark_in_progress(false),
1884 _cg1r(NULL), _summary_bytes_used(0),
1885 _g1mm(NULL),
1886 _refine_cte_cl(NULL),
1887 _full_collection(false),
1888 _free_list("Master Free List"),
1889 _secondary_free_list("Secondary Free List"),
1890 _old_set("Old Set"),
1891 _humongous_set("Master Humongous Set"),
1892 _free_regions_coming(false),
1893 _young_list(new YoungList(this)),
1894 _gc_time_stamp(0),
1895 _retained_old_gc_alloc_region(NULL),
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::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2266 DirtyCardQueue* into_cset_dcq,
2267 bool concurrent,
2268 int worker_i) {
2269 // Clean cards in the hot card cache
2270 concurrent_g1_refine()->clean_up_cache(worker_i, g1_rem_set(), into_cset_dcq);
2272 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2273 int n_completed_buffers = 0;
2274 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2275 n_completed_buffers++;
2276 }
2277 g1_policy()->record_update_rs_processed_buffers(worker_i,
2278 (double) n_completed_buffers);
2279 dcqs.clear_n_completed_buffers();
2280 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2281 }
2284 // Computes the sum of the storage used by the various regions.
2286 size_t G1CollectedHeap::used() const {
2287 assert(Heap_lock->owner() != NULL,
2288 "Should be owned on this thread's behalf.");
2289 size_t result = _summary_bytes_used;
2290 // Read only once in case it is set to NULL concurrently
2291 HeapRegion* hr = _mutator_alloc_region.get();
2292 if (hr != NULL)
2293 result += hr->used();
2294 return result;
2295 }
2297 size_t G1CollectedHeap::used_unlocked() const {
2298 size_t result = _summary_bytes_used;
2299 return result;
2300 }
2302 class SumUsedClosure: public HeapRegionClosure {
2303 size_t _used;
2304 public:
2305 SumUsedClosure() : _used(0) {}
2306 bool doHeapRegion(HeapRegion* r) {
2307 if (!r->continuesHumongous()) {
2308 _used += r->used();
2309 }
2310 return false;
2311 }
2312 size_t result() { return _used; }
2313 };
2315 size_t G1CollectedHeap::recalculate_used() const {
2316 SumUsedClosure blk;
2317 heap_region_iterate(&blk);
2318 return blk.result();
2319 }
2321 size_t G1CollectedHeap::unsafe_max_alloc() {
2322 if (free_regions() > 0) return HeapRegion::GrainBytes;
2323 // otherwise, is there space in the current allocation region?
2325 // We need to store the current allocation region in a local variable
2326 // here. The problem is that this method doesn't take any locks and
2327 // there may be other threads which overwrite the current allocation
2328 // region field. attempt_allocation(), for example, sets it to NULL
2329 // and this can happen *after* the NULL check here but before the call
2330 // to free(), resulting in a SIGSEGV. Note that this doesn't appear
2331 // to be a problem in the optimized build, since the two loads of the
2332 // current allocation region field are optimized away.
2333 HeapRegion* hr = _mutator_alloc_region.get();
2334 if (hr == NULL) {
2335 return 0;
2336 }
2337 return hr->free();
2338 }
2340 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2341 switch (cause) {
2342 case GCCause::_gc_locker: return GCLockerInvokesConcurrent;
2343 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
2344 case GCCause::_g1_humongous_allocation: return true;
2345 default: return false;
2346 }
2347 }
2349 #ifndef PRODUCT
2350 void G1CollectedHeap::allocate_dummy_regions() {
2351 // Let's fill up most of the region
2352 size_t word_size = HeapRegion::GrainWords - 1024;
2353 // And as a result the region we'll allocate will be humongous.
2354 guarantee(isHumongous(word_size), "sanity");
2356 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2357 // Let's use the existing mechanism for the allocation
2358 HeapWord* dummy_obj = humongous_obj_allocate(word_size);
2359 if (dummy_obj != NULL) {
2360 MemRegion mr(dummy_obj, word_size);
2361 CollectedHeap::fill_with_object(mr);
2362 } else {
2363 // If we can't allocate once, we probably cannot allocate
2364 // again. Let's get out of the loop.
2365 break;
2366 }
2367 }
2368 }
2369 #endif // !PRODUCT
2371 void G1CollectedHeap::increment_old_marking_cycles_started() {
2372 assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2373 _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2374 err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2375 _old_marking_cycles_started, _old_marking_cycles_completed));
2377 _old_marking_cycles_started++;
2378 }
2380 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2381 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2383 // We assume that if concurrent == true, then the caller is a
2384 // concurrent thread that was joined the Suspendible Thread
2385 // Set. If there's ever a cheap way to check this, we should add an
2386 // assert here.
2388 // Given that this method is called at the end of a Full GC or of a
2389 // concurrent cycle, and those can be nested (i.e., a Full GC can
2390 // interrupt a concurrent cycle), the number of full collections
2391 // completed should be either one (in the case where there was no
2392 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2393 // behind the number of full collections started.
2395 // This is the case for the inner caller, i.e. a Full GC.
2396 assert(concurrent ||
2397 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2398 (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2399 err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
2400 "is inconsistent with _old_marking_cycles_completed = %u",
2401 _old_marking_cycles_started, _old_marking_cycles_completed));
2403 // This is the case for the outer caller, i.e. the concurrent cycle.
2404 assert(!concurrent ||
2405 (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2406 err_msg("for outer caller (concurrent cycle): "
2407 "_old_marking_cycles_started = %u "
2408 "is inconsistent with _old_marking_cycles_completed = %u",
2409 _old_marking_cycles_started, _old_marking_cycles_completed));
2411 _old_marking_cycles_completed += 1;
2413 // We need to clear the "in_progress" flag in the CM thread before
2414 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2415 // is set) so that if a waiter requests another System.gc() it doesn't
2416 // incorrectly see that a marking cyle is still in progress.
2417 if (concurrent) {
2418 _cmThread->clear_in_progress();
2419 }
2421 // This notify_all() will ensure that a thread that called
2422 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2423 // and it's waiting for a full GC to finish will be woken up. It is
2424 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2425 FullGCCount_lock->notify_all();
2426 }
2428 void G1CollectedHeap::collect_as_vm_thread(GCCause::Cause cause) {
2429 assert_at_safepoint(true /* should_be_vm_thread */);
2430 GCCauseSetter gcs(this, cause);
2431 switch (cause) {
2432 case GCCause::_heap_inspection:
2433 case GCCause::_heap_dump: {
2434 HandleMark hm;
2435 do_full_collection(false); // don't clear all soft refs
2436 break;
2437 }
2438 default: // XXX FIX ME
2439 ShouldNotReachHere(); // Unexpected use of this function
2440 }
2441 }
2443 void G1CollectedHeap::collect(GCCause::Cause cause) {
2444 assert_heap_not_locked();
2446 unsigned int gc_count_before;
2447 unsigned int old_marking_count_before;
2448 bool retry_gc;
2450 do {
2451 retry_gc = false;
2453 {
2454 MutexLocker ml(Heap_lock);
2456 // Read the GC count while holding the Heap_lock
2457 gc_count_before = total_collections();
2458 old_marking_count_before = _old_marking_cycles_started;
2459 }
2461 if (should_do_concurrent_full_gc(cause)) {
2462 // Schedule an initial-mark evacuation pause that will start a
2463 // concurrent cycle. We're setting word_size to 0 which means that
2464 // we are not requesting a post-GC allocation.
2465 VM_G1IncCollectionPause op(gc_count_before,
2466 0, /* word_size */
2467 true, /* should_initiate_conc_mark */
2468 g1_policy()->max_pause_time_ms(),
2469 cause);
2471 VMThread::execute(&op);
2472 if (!op.pause_succeeded()) {
2473 if (old_marking_count_before == _old_marking_cycles_started) {
2474 retry_gc = op.should_retry_gc();
2475 } else {
2476 // A Full GC happened while we were trying to schedule the
2477 // initial-mark GC. No point in starting a new cycle given
2478 // that the whole heap was collected anyway.
2479 }
2481 if (retry_gc) {
2482 if (GC_locker::is_active_and_needs_gc()) {
2483 GC_locker::stall_until_clear();
2484 }
2485 }
2486 }
2487 } else {
2488 if (cause == GCCause::_gc_locker
2489 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2491 // Schedule a standard evacuation pause. We're setting word_size
2492 // to 0 which means that we are not requesting a post-GC allocation.
2493 VM_G1IncCollectionPause op(gc_count_before,
2494 0, /* word_size */
2495 false, /* should_initiate_conc_mark */
2496 g1_policy()->max_pause_time_ms(),
2497 cause);
2498 VMThread::execute(&op);
2499 } else {
2500 // Schedule a Full GC.
2501 VM_G1CollectFull op(gc_count_before, old_marking_count_before, cause);
2502 VMThread::execute(&op);
2503 }
2504 }
2505 } while (retry_gc);
2506 }
2508 bool G1CollectedHeap::is_in(const void* p) const {
2509 if (_g1_committed.contains(p)) {
2510 // Given that we know that p is in the committed space,
2511 // heap_region_containing_raw() should successfully
2512 // return the containing region.
2513 HeapRegion* hr = heap_region_containing_raw(p);
2514 return hr->is_in(p);
2515 } else {
2516 return _perm_gen->as_gen()->is_in(p);
2517 }
2518 }
2520 // Iteration functions.
2522 // Iterates an OopClosure over all ref-containing fields of objects
2523 // within a HeapRegion.
2525 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2526 MemRegion _mr;
2527 OopClosure* _cl;
2528 public:
2529 IterateOopClosureRegionClosure(MemRegion mr, OopClosure* cl)
2530 : _mr(mr), _cl(cl) {}
2531 bool doHeapRegion(HeapRegion* r) {
2532 if (! r->continuesHumongous()) {
2533 r->oop_iterate(_cl);
2534 }
2535 return false;
2536 }
2537 };
2539 void G1CollectedHeap::oop_iterate(OopClosure* cl, bool do_perm) {
2540 IterateOopClosureRegionClosure blk(_g1_committed, cl);
2541 heap_region_iterate(&blk);
2542 if (do_perm) {
2543 perm_gen()->oop_iterate(cl);
2544 }
2545 }
2547 void G1CollectedHeap::oop_iterate(MemRegion mr, OopClosure* cl, bool do_perm) {
2548 IterateOopClosureRegionClosure blk(mr, cl);
2549 heap_region_iterate(&blk);
2550 if (do_perm) {
2551 perm_gen()->oop_iterate(cl);
2552 }
2553 }
2555 // Iterates an ObjectClosure over all objects within a HeapRegion.
2557 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2558 ObjectClosure* _cl;
2559 public:
2560 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2561 bool doHeapRegion(HeapRegion* r) {
2562 if (! r->continuesHumongous()) {
2563 r->object_iterate(_cl);
2564 }
2565 return false;
2566 }
2567 };
2569 void G1CollectedHeap::object_iterate(ObjectClosure* cl, bool do_perm) {
2570 IterateObjectClosureRegionClosure blk(cl);
2571 heap_region_iterate(&blk);
2572 if (do_perm) {
2573 perm_gen()->object_iterate(cl);
2574 }
2575 }
2577 void G1CollectedHeap::object_iterate_since_last_GC(ObjectClosure* cl) {
2578 // FIXME: is this right?
2579 guarantee(false, "object_iterate_since_last_GC not supported by G1 heap");
2580 }
2582 // Calls a SpaceClosure on a HeapRegion.
2584 class SpaceClosureRegionClosure: public HeapRegionClosure {
2585 SpaceClosure* _cl;
2586 public:
2587 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2588 bool doHeapRegion(HeapRegion* r) {
2589 _cl->do_space(r);
2590 return false;
2591 }
2592 };
2594 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2595 SpaceClosureRegionClosure blk(cl);
2596 heap_region_iterate(&blk);
2597 }
2599 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2600 _hrs.iterate(cl);
2601 }
2603 void G1CollectedHeap::heap_region_iterate_from(HeapRegion* r,
2604 HeapRegionClosure* cl) const {
2605 _hrs.iterate_from(r, cl);
2606 }
2608 void
2609 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
2610 uint worker,
2611 uint no_of_par_workers,
2612 jint claim_value) {
2613 const uint regions = n_regions();
2614 const uint max_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
2615 no_of_par_workers :
2616 1);
2617 assert(UseDynamicNumberOfGCThreads ||
2618 no_of_par_workers == workers()->total_workers(),
2619 "Non dynamic should use fixed number of workers");
2620 // try to spread out the starting points of the workers
2621 const uint start_index = regions / max_workers * worker;
2623 // each worker will actually look at all regions
2624 for (uint count = 0; count < regions; ++count) {
2625 const uint index = (start_index + count) % regions;
2626 assert(0 <= index && index < regions, "sanity");
2627 HeapRegion* r = region_at(index);
2628 // we'll ignore "continues humongous" regions (we'll process them
2629 // when we come across their corresponding "start humongous"
2630 // region) and regions already claimed
2631 if (r->claim_value() == claim_value || r->continuesHumongous()) {
2632 continue;
2633 }
2634 // OK, try to claim it
2635 if (r->claimHeapRegion(claim_value)) {
2636 // success!
2637 assert(!r->continuesHumongous(), "sanity");
2638 if (r->startsHumongous()) {
2639 // If the region is "starts humongous" we'll iterate over its
2640 // "continues humongous" first; in fact we'll do them
2641 // first. The order is important. In on case, calling the
2642 // closure on the "starts humongous" region might de-allocate
2643 // and clear all its "continues humongous" regions and, as a
2644 // result, we might end up processing them twice. So, we'll do
2645 // them first (notice: most closures will ignore them anyway) and
2646 // then we'll do the "starts humongous" region.
2647 for (uint ch_index = index + 1; ch_index < regions; ++ch_index) {
2648 HeapRegion* chr = region_at(ch_index);
2650 // if the region has already been claimed or it's not
2651 // "continues humongous" we're done
2652 if (chr->claim_value() == claim_value ||
2653 !chr->continuesHumongous()) {
2654 break;
2655 }
2657 // Noone should have claimed it directly. We can given
2658 // that we claimed its "starts humongous" region.
2659 assert(chr->claim_value() != claim_value, "sanity");
2660 assert(chr->humongous_start_region() == r, "sanity");
2662 if (chr->claimHeapRegion(claim_value)) {
2663 // we should always be able to claim it; noone else should
2664 // be trying to claim this region
2666 bool res2 = cl->doHeapRegion(chr);
2667 assert(!res2, "Should not abort");
2669 // Right now, this holds (i.e., no closure that actually
2670 // does something with "continues humongous" regions
2671 // clears them). We might have to weaken it in the future,
2672 // but let's leave these two asserts here for extra safety.
2673 assert(chr->continuesHumongous(), "should still be the case");
2674 assert(chr->humongous_start_region() == r, "sanity");
2675 } else {
2676 guarantee(false, "we should not reach here");
2677 }
2678 }
2679 }
2681 assert(!r->continuesHumongous(), "sanity");
2682 bool res = cl->doHeapRegion(r);
2683 assert(!res, "Should not abort");
2684 }
2685 }
2686 }
2688 class ResetClaimValuesClosure: public HeapRegionClosure {
2689 public:
2690 bool doHeapRegion(HeapRegion* r) {
2691 r->set_claim_value(HeapRegion::InitialClaimValue);
2692 return false;
2693 }
2694 };
2696 void G1CollectedHeap::reset_heap_region_claim_values() {
2697 ResetClaimValuesClosure blk;
2698 heap_region_iterate(&blk);
2699 }
2701 void G1CollectedHeap::reset_cset_heap_region_claim_values() {
2702 ResetClaimValuesClosure blk;
2703 collection_set_iterate(&blk);
2704 }
2706 #ifdef ASSERT
2707 // This checks whether all regions in the heap have the correct claim
2708 // value. I also piggy-backed on this a check to ensure that the
2709 // humongous_start_region() information on "continues humongous"
2710 // regions is correct.
2712 class CheckClaimValuesClosure : public HeapRegionClosure {
2713 private:
2714 jint _claim_value;
2715 uint _failures;
2716 HeapRegion* _sh_region;
2718 public:
2719 CheckClaimValuesClosure(jint claim_value) :
2720 _claim_value(claim_value), _failures(0), _sh_region(NULL) { }
2721 bool doHeapRegion(HeapRegion* r) {
2722 if (r->claim_value() != _claim_value) {
2723 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2724 "claim value = %d, should be %d",
2725 HR_FORMAT_PARAMS(r),
2726 r->claim_value(), _claim_value);
2727 ++_failures;
2728 }
2729 if (!r->isHumongous()) {
2730 _sh_region = NULL;
2731 } else if (r->startsHumongous()) {
2732 _sh_region = r;
2733 } else if (r->continuesHumongous()) {
2734 if (r->humongous_start_region() != _sh_region) {
2735 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2736 "HS = "PTR_FORMAT", should be "PTR_FORMAT,
2737 HR_FORMAT_PARAMS(r),
2738 r->humongous_start_region(),
2739 _sh_region);
2740 ++_failures;
2741 }
2742 }
2743 return false;
2744 }
2745 uint failures() { return _failures; }
2746 };
2748 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
2749 CheckClaimValuesClosure cl(claim_value);
2750 heap_region_iterate(&cl);
2751 return cl.failures() == 0;
2752 }
2754 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure {
2755 private:
2756 jint _claim_value;
2757 uint _failures;
2759 public:
2760 CheckClaimValuesInCSetHRClosure(jint claim_value) :
2761 _claim_value(claim_value), _failures(0) { }
2763 uint failures() { return _failures; }
2765 bool doHeapRegion(HeapRegion* hr) {
2766 assert(hr->in_collection_set(), "how?");
2767 assert(!hr->isHumongous(), "H-region in CSet");
2768 if (hr->claim_value() != _claim_value) {
2769 gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", "
2770 "claim value = %d, should be %d",
2771 HR_FORMAT_PARAMS(hr),
2772 hr->claim_value(), _claim_value);
2773 _failures += 1;
2774 }
2775 return false;
2776 }
2777 };
2779 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) {
2780 CheckClaimValuesInCSetHRClosure cl(claim_value);
2781 collection_set_iterate(&cl);
2782 return cl.failures() == 0;
2783 }
2784 #endif // ASSERT
2786 // Clear the cached CSet starting regions and (more importantly)
2787 // the time stamps. Called when we reset the GC time stamp.
2788 void G1CollectedHeap::clear_cset_start_regions() {
2789 assert(_worker_cset_start_region != NULL, "sanity");
2790 assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2792 int n_queues = MAX2((int)ParallelGCThreads, 1);
2793 for (int i = 0; i < n_queues; i++) {
2794 _worker_cset_start_region[i] = NULL;
2795 _worker_cset_start_region_time_stamp[i] = 0;
2796 }
2797 }
2799 // Given the id of a worker, obtain or calculate a suitable
2800 // starting region for iterating over the current collection set.
2801 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(int worker_i) {
2802 assert(get_gc_time_stamp() > 0, "should have been updated by now");
2804 HeapRegion* result = NULL;
2805 unsigned gc_time_stamp = get_gc_time_stamp();
2807 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2808 // Cached starting region for current worker was set
2809 // during the current pause - so it's valid.
2810 // Note: the cached starting heap region may be NULL
2811 // (when the collection set is empty).
2812 result = _worker_cset_start_region[worker_i];
2813 assert(result == NULL || result->in_collection_set(), "sanity");
2814 return result;
2815 }
2817 // The cached entry was not valid so let's calculate
2818 // a suitable starting heap region for this worker.
2820 // We want the parallel threads to start their collection
2821 // set iteration at different collection set regions to
2822 // avoid contention.
2823 // If we have:
2824 // n collection set regions
2825 // p threads
2826 // Then thread t will start at region floor ((t * n) / p)
2828 result = g1_policy()->collection_set();
2829 if (G1CollectedHeap::use_parallel_gc_threads()) {
2830 uint cs_size = g1_policy()->cset_region_length();
2831 uint active_workers = workers()->active_workers();
2832 assert(UseDynamicNumberOfGCThreads ||
2833 active_workers == workers()->total_workers(),
2834 "Unless dynamic should use total workers");
2836 uint end_ind = (cs_size * worker_i) / active_workers;
2837 uint start_ind = 0;
2839 if (worker_i > 0 &&
2840 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2841 // Previous workers starting region is valid
2842 // so let's iterate from there
2843 start_ind = (cs_size * (worker_i - 1)) / active_workers;
2844 result = _worker_cset_start_region[worker_i - 1];
2845 }
2847 for (uint i = start_ind; i < end_ind; i++) {
2848 result = result->next_in_collection_set();
2849 }
2850 }
2852 // Note: the calculated starting heap region may be NULL
2853 // (when the collection set is empty).
2854 assert(result == NULL || result->in_collection_set(), "sanity");
2855 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2856 "should be updated only once per pause");
2857 _worker_cset_start_region[worker_i] = result;
2858 OrderAccess::storestore();
2859 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2860 return result;
2861 }
2863 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2864 HeapRegion* r = g1_policy()->collection_set();
2865 while (r != NULL) {
2866 HeapRegion* next = r->next_in_collection_set();
2867 if (cl->doHeapRegion(r)) {
2868 cl->incomplete();
2869 return;
2870 }
2871 r = next;
2872 }
2873 }
2875 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2876 HeapRegionClosure *cl) {
2877 if (r == NULL) {
2878 // The CSet is empty so there's nothing to do.
2879 return;
2880 }
2882 assert(r->in_collection_set(),
2883 "Start region must be a member of the collection set.");
2884 HeapRegion* cur = r;
2885 while (cur != NULL) {
2886 HeapRegion* next = cur->next_in_collection_set();
2887 if (cl->doHeapRegion(cur) && false) {
2888 cl->incomplete();
2889 return;
2890 }
2891 cur = next;
2892 }
2893 cur = g1_policy()->collection_set();
2894 while (cur != r) {
2895 HeapRegion* next = cur->next_in_collection_set();
2896 if (cl->doHeapRegion(cur) && false) {
2897 cl->incomplete();
2898 return;
2899 }
2900 cur = next;
2901 }
2902 }
2904 CompactibleSpace* G1CollectedHeap::first_compactible_space() {
2905 return n_regions() > 0 ? region_at(0) : NULL;
2906 }
2909 Space* G1CollectedHeap::space_containing(const void* addr) const {
2910 Space* res = heap_region_containing(addr);
2911 if (res == NULL)
2912 res = perm_gen()->space_containing(addr);
2913 return res;
2914 }
2916 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2917 Space* sp = space_containing(addr);
2918 if (sp != NULL) {
2919 return sp->block_start(addr);
2920 }
2921 return NULL;
2922 }
2924 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2925 Space* sp = space_containing(addr);
2926 assert(sp != NULL, "block_size of address outside of heap");
2927 return sp->block_size(addr);
2928 }
2930 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2931 Space* sp = space_containing(addr);
2932 return sp->block_is_obj(addr);
2933 }
2935 bool G1CollectedHeap::supports_tlab_allocation() const {
2936 return true;
2937 }
2939 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2940 return HeapRegion::GrainBytes;
2941 }
2943 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2944 // Return the remaining space in the cur alloc region, but not less than
2945 // the min TLAB size.
2947 // Also, this value can be at most the humongous object threshold,
2948 // since we can't allow tlabs to grow big enough to accomodate
2949 // humongous objects.
2951 HeapRegion* hr = _mutator_alloc_region.get();
2952 size_t max_tlab_size = _humongous_object_threshold_in_words * wordSize;
2953 if (hr == NULL) {
2954 return max_tlab_size;
2955 } else {
2956 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab_size);
2957 }
2958 }
2960 size_t G1CollectedHeap::max_capacity() const {
2961 return _g1_reserved.byte_size();
2962 }
2964 jlong G1CollectedHeap::millis_since_last_gc() {
2965 // assert(false, "NYI");
2966 return 0;
2967 }
2969 void G1CollectedHeap::prepare_for_verify() {
2970 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
2971 ensure_parsability(false);
2972 }
2973 g1_rem_set()->prepare_for_verify();
2974 }
2976 class VerifyLivenessOopClosure: public OopClosure {
2977 G1CollectedHeap* _g1h;
2978 VerifyOption _vo;
2979 public:
2980 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
2981 _g1h(g1h), _vo(vo)
2982 { }
2983 void do_oop(narrowOop *p) { do_oop_work(p); }
2984 void do_oop( oop *p) { do_oop_work(p); }
2986 template <class T> void do_oop_work(T *p) {
2987 oop obj = oopDesc::load_decode_heap_oop(p);
2988 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
2989 "Dead object referenced by a not dead object");
2990 }
2991 };
2993 class VerifyObjsInRegionClosure: public ObjectClosure {
2994 private:
2995 G1CollectedHeap* _g1h;
2996 size_t _live_bytes;
2997 HeapRegion *_hr;
2998 VerifyOption _vo;
2999 public:
3000 // _vo == UsePrevMarking -> use "prev" marking information,
3001 // _vo == UseNextMarking -> use "next" marking information,
3002 // _vo == UseMarkWord -> use mark word from object header.
3003 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
3004 : _live_bytes(0), _hr(hr), _vo(vo) {
3005 _g1h = G1CollectedHeap::heap();
3006 }
3007 void do_object(oop o) {
3008 VerifyLivenessOopClosure isLive(_g1h, _vo);
3009 assert(o != NULL, "Huh?");
3010 if (!_g1h->is_obj_dead_cond(o, _vo)) {
3011 // If the object is alive according to the mark word,
3012 // then verify that the marking information agrees.
3013 // Note we can't verify the contra-positive of the
3014 // above: if the object is dead (according to the mark
3015 // word), it may not be marked, or may have been marked
3016 // but has since became dead, or may have been allocated
3017 // since the last marking.
3018 if (_vo == VerifyOption_G1UseMarkWord) {
3019 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
3020 }
3022 o->oop_iterate(&isLive);
3023 if (!_hr->obj_allocated_since_prev_marking(o)) {
3024 size_t obj_size = o->size(); // Make sure we don't overflow
3025 _live_bytes += (obj_size * HeapWordSize);
3026 }
3027 }
3028 }
3029 size_t live_bytes() { return _live_bytes; }
3030 };
3032 class PrintObjsInRegionClosure : public ObjectClosure {
3033 HeapRegion *_hr;
3034 G1CollectedHeap *_g1;
3035 public:
3036 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
3037 _g1 = G1CollectedHeap::heap();
3038 };
3040 void do_object(oop o) {
3041 if (o != NULL) {
3042 HeapWord *start = (HeapWord *) o;
3043 size_t word_sz = o->size();
3044 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
3045 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
3046 (void*) o, word_sz,
3047 _g1->isMarkedPrev(o),
3048 _g1->isMarkedNext(o),
3049 _hr->obj_allocated_since_prev_marking(o));
3050 HeapWord *end = start + word_sz;
3051 HeapWord *cur;
3052 int *val;
3053 for (cur = start; cur < end; cur++) {
3054 val = (int *) cur;
3055 gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val);
3056 }
3057 }
3058 }
3059 };
3061 class VerifyRegionClosure: public HeapRegionClosure {
3062 private:
3063 bool _par;
3064 VerifyOption _vo;
3065 bool _failures;
3066 public:
3067 // _vo == UsePrevMarking -> use "prev" marking information,
3068 // _vo == UseNextMarking -> use "next" marking information,
3069 // _vo == UseMarkWord -> use mark word from object header.
3070 VerifyRegionClosure(bool par, VerifyOption vo)
3071 : _par(par),
3072 _vo(vo),
3073 _failures(false) {}
3075 bool failures() {
3076 return _failures;
3077 }
3079 bool doHeapRegion(HeapRegion* r) {
3080 guarantee(_par || r->claim_value() == HeapRegion::InitialClaimValue,
3081 "Should be unclaimed at verify points.");
3082 if (!r->continuesHumongous()) {
3083 bool failures = false;
3084 r->verify(_vo, &failures);
3085 if (failures) {
3086 _failures = true;
3087 } else {
3088 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
3089 r->object_iterate(¬_dead_yet_cl);
3090 if (_vo != VerifyOption_G1UseNextMarking) {
3091 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
3092 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
3093 "max_live_bytes "SIZE_FORMAT" "
3094 "< calculated "SIZE_FORMAT,
3095 r->bottom(), r->end(),
3096 r->max_live_bytes(),
3097 not_dead_yet_cl.live_bytes());
3098 _failures = true;
3099 }
3100 } else {
3101 // When vo == UseNextMarking we cannot currently do a sanity
3102 // check on the live bytes as the calculation has not been
3103 // finalized yet.
3104 }
3105 }
3106 }
3107 return false; // stop the region iteration if we hit a failure
3108 }
3109 };
3111 class VerifyRootsClosure: public OopsInGenClosure {
3112 private:
3113 G1CollectedHeap* _g1h;
3114 VerifyOption _vo;
3115 bool _failures;
3116 public:
3117 // _vo == UsePrevMarking -> use "prev" marking information,
3118 // _vo == UseNextMarking -> use "next" marking information,
3119 // _vo == UseMarkWord -> use mark word from object header.
3120 VerifyRootsClosure(VerifyOption vo) :
3121 _g1h(G1CollectedHeap::heap()),
3122 _vo(vo),
3123 _failures(false) { }
3125 bool failures() { return _failures; }
3127 template <class T> void do_oop_nv(T* p) {
3128 T heap_oop = oopDesc::load_heap_oop(p);
3129 if (!oopDesc::is_null(heap_oop)) {
3130 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3131 if (_g1h->is_obj_dead_cond(obj, _vo)) {
3132 gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
3133 "points to dead obj "PTR_FORMAT, p, (void*) obj);
3134 if (_vo == VerifyOption_G1UseMarkWord) {
3135 gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark()));
3136 }
3137 obj->print_on(gclog_or_tty);
3138 _failures = true;
3139 }
3140 }
3141 }
3143 void do_oop(oop* p) { do_oop_nv(p); }
3144 void do_oop(narrowOop* p) { do_oop_nv(p); }
3145 };
3147 // This is the task used for parallel heap verification.
3149 class G1ParVerifyTask: public AbstractGangTask {
3150 private:
3151 G1CollectedHeap* _g1h;
3152 VerifyOption _vo;
3153 bool _failures;
3155 public:
3156 // _vo == UsePrevMarking -> use "prev" marking information,
3157 // _vo == UseNextMarking -> use "next" marking information,
3158 // _vo == UseMarkWord -> use mark word from object header.
3159 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
3160 AbstractGangTask("Parallel verify task"),
3161 _g1h(g1h),
3162 _vo(vo),
3163 _failures(false) { }
3165 bool failures() {
3166 return _failures;
3167 }
3169 void work(uint worker_id) {
3170 HandleMark hm;
3171 VerifyRegionClosure blk(true, _vo);
3172 _g1h->heap_region_par_iterate_chunked(&blk, worker_id,
3173 _g1h->workers()->active_workers(),
3174 HeapRegion::ParVerifyClaimValue);
3175 if (blk.failures()) {
3176 _failures = true;
3177 }
3178 }
3179 };
3181 void G1CollectedHeap::verify(bool silent) {
3182 verify(silent, VerifyOption_G1UsePrevMarking);
3183 }
3185 void G1CollectedHeap::verify(bool silent,
3186 VerifyOption vo) {
3187 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
3188 if (!silent) { gclog_or_tty->print("Roots (excluding permgen) "); }
3189 VerifyRootsClosure rootsCl(vo);
3191 assert(Thread::current()->is_VM_thread(),
3192 "Expected to be executed serially by the VM thread at this point");
3194 CodeBlobToOopClosure blobsCl(&rootsCl, /*do_marking=*/ false);
3196 // We apply the relevant closures to all the oops in the
3197 // system dictionary, the string table and the code cache.
3198 const int so = SO_AllClasses | SO_Strings | SO_CodeCache;
3200 process_strong_roots(true, // activate StrongRootsScope
3201 true, // we set "collecting perm gen" to true,
3202 // so we don't reset the dirty cards in the perm gen.
3203 ScanningOption(so), // roots scanning options
3204 &rootsCl,
3205 &blobsCl,
3206 &rootsCl);
3208 // If we're verifying after the marking phase of a Full GC then we can't
3209 // treat the perm gen as roots into the G1 heap. Some of the objects in
3210 // the perm gen may be dead and hence not marked. If one of these dead
3211 // objects is considered to be a root then we may end up with a false
3212 // "Root location <x> points to dead ob <y>" failure.
3213 if (vo != VerifyOption_G1UseMarkWord) {
3214 // Since we used "collecting_perm_gen" == true above, we will not have
3215 // checked the refs from perm into the G1-collected heap. We check those
3216 // references explicitly below. Whether the relevant cards are dirty
3217 // is checked further below in the rem set verification.
3218 if (!silent) { gclog_or_tty->print("Permgen roots "); }
3219 perm_gen()->oop_iterate(&rootsCl);
3220 }
3221 bool failures = rootsCl.failures();
3223 if (vo != VerifyOption_G1UseMarkWord) {
3224 // If we're verifying during a full GC then the region sets
3225 // will have been torn down at the start of the GC. Therefore
3226 // verifying the region sets will fail. So we only verify
3227 // the region sets when not in a full GC.
3228 if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3229 verify_region_sets();
3230 }
3232 if (!silent) { gclog_or_tty->print("HeapRegions "); }
3233 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3234 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3235 "sanity check");
3237 G1ParVerifyTask task(this, vo);
3238 assert(UseDynamicNumberOfGCThreads ||
3239 workers()->active_workers() == workers()->total_workers(),
3240 "If not dynamic should be using all the workers");
3241 int n_workers = workers()->active_workers();
3242 set_par_threads(n_workers);
3243 workers()->run_task(&task);
3244 set_par_threads(0);
3245 if (task.failures()) {
3246 failures = true;
3247 }
3249 // Checks that the expected amount of parallel work was done.
3250 // The implication is that n_workers is > 0.
3251 assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
3252 "sanity check");
3254 reset_heap_region_claim_values();
3256 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3257 "sanity check");
3258 } else {
3259 VerifyRegionClosure blk(false, vo);
3260 heap_region_iterate(&blk);
3261 if (blk.failures()) {
3262 failures = true;
3263 }
3264 }
3265 if (!silent) gclog_or_tty->print("RemSet ");
3266 rem_set()->verify();
3268 if (failures) {
3269 gclog_or_tty->print_cr("Heap:");
3270 // It helps to have the per-region information in the output to
3271 // help us track down what went wrong. This is why we call
3272 // print_extended_on() instead of print_on().
3273 print_extended_on(gclog_or_tty);
3274 gclog_or_tty->print_cr("");
3275 #ifndef PRODUCT
3276 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3277 concurrent_mark()->print_reachable("at-verification-failure",
3278 vo, false /* all */);
3279 }
3280 #endif
3281 gclog_or_tty->flush();
3282 }
3283 guarantee(!failures, "there should not have been any failures");
3284 } else {
3285 if (!silent) gclog_or_tty->print("(SKIPPING roots, heapRegions, remset) ");
3286 }
3287 }
3289 class PrintRegionClosure: public HeapRegionClosure {
3290 outputStream* _st;
3291 public:
3292 PrintRegionClosure(outputStream* st) : _st(st) {}
3293 bool doHeapRegion(HeapRegion* r) {
3294 r->print_on(_st);
3295 return false;
3296 }
3297 };
3299 void G1CollectedHeap::print_on(outputStream* st) const {
3300 st->print(" %-20s", "garbage-first heap");
3301 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3302 capacity()/K, used_unlocked()/K);
3303 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3304 _g1_storage.low_boundary(),
3305 _g1_storage.high(),
3306 _g1_storage.high_boundary());
3307 st->cr();
3308 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3309 uint young_regions = _young_list->length();
3310 st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3311 (size_t) young_regions * HeapRegion::GrainBytes / K);
3312 uint survivor_regions = g1_policy()->recorded_survivor_regions();
3313 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3314 (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3315 st->cr();
3316 perm()->as_gen()->print_on(st);
3317 }
3319 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3320 print_on(st);
3322 // Print the per-region information.
3323 st->cr();
3324 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3325 "HS=humongous(starts), HC=humongous(continues), "
3326 "CS=collection set, F=free, TS=gc time stamp, "
3327 "PTAMS=previous top-at-mark-start, "
3328 "NTAMS=next top-at-mark-start)");
3329 PrintRegionClosure blk(st);
3330 heap_region_iterate(&blk);
3331 }
3333 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3334 if (G1CollectedHeap::use_parallel_gc_threads()) {
3335 workers()->print_worker_threads_on(st);
3336 }
3337 _cmThread->print_on(st);
3338 st->cr();
3339 _cm->print_worker_threads_on(st);
3340 _cg1r->print_worker_threads_on(st);
3341 st->cr();
3342 }
3344 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3345 if (G1CollectedHeap::use_parallel_gc_threads()) {
3346 workers()->threads_do(tc);
3347 }
3348 tc->do_thread(_cmThread);
3349 _cg1r->threads_do(tc);
3350 }
3352 void G1CollectedHeap::print_tracing_info() const {
3353 // We'll overload this to mean "trace GC pause statistics."
3354 if (TraceGen0Time || TraceGen1Time) {
3355 // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3356 // to that.
3357 g1_policy()->print_tracing_info();
3358 }
3359 if (G1SummarizeRSetStats) {
3360 g1_rem_set()->print_summary_info();
3361 }
3362 if (G1SummarizeConcMark) {
3363 concurrent_mark()->print_summary_info();
3364 }
3365 g1_policy()->print_yg_surv_rate_info();
3366 SpecializationStats::print();
3367 }
3369 #ifndef PRODUCT
3370 // Helpful for debugging RSet issues.
3372 class PrintRSetsClosure : public HeapRegionClosure {
3373 private:
3374 const char* _msg;
3375 size_t _occupied_sum;
3377 public:
3378 bool doHeapRegion(HeapRegion* r) {
3379 HeapRegionRemSet* hrrs = r->rem_set();
3380 size_t occupied = hrrs->occupied();
3381 _occupied_sum += occupied;
3383 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3384 HR_FORMAT_PARAMS(r));
3385 if (occupied == 0) {
3386 gclog_or_tty->print_cr(" RSet is empty");
3387 } else {
3388 hrrs->print();
3389 }
3390 gclog_or_tty->print_cr("----------");
3391 return false;
3392 }
3394 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3395 gclog_or_tty->cr();
3396 gclog_or_tty->print_cr("========================================");
3397 gclog_or_tty->print_cr(msg);
3398 gclog_or_tty->cr();
3399 }
3401 ~PrintRSetsClosure() {
3402 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3403 gclog_or_tty->print_cr("========================================");
3404 gclog_or_tty->cr();
3405 }
3406 };
3408 void G1CollectedHeap::print_cset_rsets() {
3409 PrintRSetsClosure cl("Printing CSet RSets");
3410 collection_set_iterate(&cl);
3411 }
3413 void G1CollectedHeap::print_all_rsets() {
3414 PrintRSetsClosure cl("Printing All RSets");;
3415 heap_region_iterate(&cl);
3416 }
3417 #endif // PRODUCT
3419 G1CollectedHeap* G1CollectedHeap::heap() {
3420 assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3421 "not a garbage-first heap");
3422 return _g1h;
3423 }
3425 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3426 // always_do_update_barrier = false;
3427 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3428 // Call allocation profiler
3429 AllocationProfiler::iterate_since_last_gc();
3430 // Fill TLAB's and such
3431 ensure_parsability(true);
3432 }
3434 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) {
3435 // FIXME: what is this about?
3436 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3437 // is set.
3438 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3439 "derived pointer present"));
3440 // always_do_update_barrier = true;
3442 // We have just completed a GC. Update the soft reference
3443 // policy with the new heap occupancy
3444 Universe::update_heap_info_at_gc();
3445 }
3447 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3448 unsigned int gc_count_before,
3449 bool* succeeded) {
3450 assert_heap_not_locked_and_not_at_safepoint();
3451 g1_policy()->record_stop_world_start();
3452 VM_G1IncCollectionPause op(gc_count_before,
3453 word_size,
3454 false, /* should_initiate_conc_mark */
3455 g1_policy()->max_pause_time_ms(),
3456 GCCause::_g1_inc_collection_pause);
3457 VMThread::execute(&op);
3459 HeapWord* result = op.result();
3460 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3461 assert(result == NULL || ret_succeeded,
3462 "the result should be NULL if the VM did not succeed");
3463 *succeeded = ret_succeeded;
3465 assert_heap_not_locked();
3466 return result;
3467 }
3469 void
3470 G1CollectedHeap::doConcurrentMark() {
3471 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3472 if (!_cmThread->in_progress()) {
3473 _cmThread->set_started();
3474 CGC_lock->notify();
3475 }
3476 }
3478 size_t G1CollectedHeap::pending_card_num() {
3479 size_t extra_cards = 0;
3480 JavaThread *curr = Threads::first();
3481 while (curr != NULL) {
3482 DirtyCardQueue& dcq = curr->dirty_card_queue();
3483 extra_cards += dcq.size();
3484 curr = curr->next();
3485 }
3486 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3487 size_t buffer_size = dcqs.buffer_size();
3488 size_t buffer_num = dcqs.completed_buffers_num();
3489 return buffer_size * buffer_num + extra_cards;
3490 }
3492 size_t G1CollectedHeap::max_pending_card_num() {
3493 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3494 size_t buffer_size = dcqs.buffer_size();
3495 size_t buffer_num = dcqs.completed_buffers_num();
3496 int thread_num = Threads::number_of_threads();
3497 return (buffer_num + thread_num) * buffer_size;
3498 }
3500 size_t G1CollectedHeap::cards_scanned() {
3501 return g1_rem_set()->cardsScanned();
3502 }
3504 void
3505 G1CollectedHeap::setup_surviving_young_words() {
3506 assert(_surviving_young_words == NULL, "pre-condition");
3507 uint array_length = g1_policy()->young_cset_region_length();
3508 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3509 if (_surviving_young_words == NULL) {
3510 vm_exit_out_of_memory(sizeof(size_t) * array_length,
3511 "Not enough space for young surv words summary.");
3512 }
3513 memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3514 #ifdef ASSERT
3515 for (uint i = 0; i < array_length; ++i) {
3516 assert( _surviving_young_words[i] == 0, "memset above" );
3517 }
3518 #endif // !ASSERT
3519 }
3521 void
3522 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3523 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3524 uint array_length = g1_policy()->young_cset_region_length();
3525 for (uint i = 0; i < array_length; ++i) {
3526 _surviving_young_words[i] += surv_young_words[i];
3527 }
3528 }
3530 void
3531 G1CollectedHeap::cleanup_surviving_young_words() {
3532 guarantee( _surviving_young_words != NULL, "pre-condition" );
3533 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC);
3534 _surviving_young_words = NULL;
3535 }
3537 #ifdef ASSERT
3538 class VerifyCSetClosure: public HeapRegionClosure {
3539 public:
3540 bool doHeapRegion(HeapRegion* hr) {
3541 // Here we check that the CSet region's RSet is ready for parallel
3542 // iteration. The fields that we'll verify are only manipulated
3543 // when the region is part of a CSet and is collected. Afterwards,
3544 // we reset these fields when we clear the region's RSet (when the
3545 // region is freed) so they are ready when the region is
3546 // re-allocated. The only exception to this is if there's an
3547 // evacuation failure and instead of freeing the region we leave
3548 // it in the heap. In that case, we reset these fields during
3549 // evacuation failure handling.
3550 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3552 // Here's a good place to add any other checks we'd like to
3553 // perform on CSet regions.
3554 return false;
3555 }
3556 };
3557 #endif // ASSERT
3559 #if TASKQUEUE_STATS
3560 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3561 st->print_raw_cr("GC Task Stats");
3562 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3563 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3564 }
3566 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3567 print_taskqueue_stats_hdr(st);
3569 TaskQueueStats totals;
3570 const int n = workers() != NULL ? workers()->total_workers() : 1;
3571 for (int i = 0; i < n; ++i) {
3572 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3573 totals += task_queue(i)->stats;
3574 }
3575 st->print_raw("tot "); totals.print(st); st->cr();
3577 DEBUG_ONLY(totals.verify());
3578 }
3580 void G1CollectedHeap::reset_taskqueue_stats() {
3581 const int n = workers() != NULL ? workers()->total_workers() : 1;
3582 for (int i = 0; i < n; ++i) {
3583 task_queue(i)->stats.reset();
3584 }
3585 }
3586 #endif // TASKQUEUE_STATS
3588 bool
3589 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3590 assert_at_safepoint(true /* should_be_vm_thread */);
3591 guarantee(!is_gc_active(), "collection is not reentrant");
3593 if (GC_locker::check_active_before_gc()) {
3594 return false;
3595 }
3597 SvcGCMarker sgcm(SvcGCMarker::MINOR);
3598 ResourceMark rm;
3600 print_heap_before_gc();
3602 HRSPhaseSetter x(HRSPhaseEvacuation);
3603 verify_region_sets_optional();
3604 verify_dirty_young_regions();
3606 // This call will decide whether this pause is an initial-mark
3607 // pause. If it is, during_initial_mark_pause() will return true
3608 // for the duration of this pause.
3609 g1_policy()->decide_on_conc_mark_initiation();
3611 // We do not allow initial-mark to be piggy-backed on a mixed GC.
3612 assert(!g1_policy()->during_initial_mark_pause() ||
3613 g1_policy()->gcs_are_young(), "sanity");
3615 // We also do not allow mixed GCs during marking.
3616 assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3618 // Record whether this pause is an initial mark. When the current
3619 // thread has completed its logging output and it's safe to signal
3620 // the CM thread, the flag's value in the policy has been reset.
3621 bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3623 // Inner scope for scope based logging, timers, and stats collection
3624 {
3625 if (g1_policy()->during_initial_mark_pause()) {
3626 // We are about to start a marking cycle, so we increment the
3627 // full collection counter.
3628 increment_old_marking_cycles_started();
3629 }
3630 // if the log level is "finer" is on, we'll print long statistics information
3631 // in the collector policy code, so let's not print this as the output
3632 // is messy if we do.
3633 gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps);
3634 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3636 GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
3637 .append(g1_policy()->gcs_are_young() ? " (young)" : " (mixed)")
3638 .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : "");
3639 TraceTime t(gc_cause_str, G1Log::fine() && !G1Log::finer(), true, gclog_or_tty);
3641 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3642 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3644 // If the secondary_free_list is not empty, append it to the
3645 // free_list. No need to wait for the cleanup operation to finish;
3646 // the region allocation code will check the secondary_free_list
3647 // and wait if necessary. If the G1StressConcRegionFreeing flag is
3648 // set, skip this step so that the region allocation code has to
3649 // get entries from the secondary_free_list.
3650 if (!G1StressConcRegionFreeing) {
3651 append_secondary_free_list_if_not_empty_with_lock();
3652 }
3654 assert(check_young_list_well_formed(),
3655 "young list should be well formed");
3657 // Don't dynamically change the number of GC threads this early. A value of
3658 // 0 is used to indicate serial work. When parallel work is done,
3659 // it will be set.
3661 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3662 IsGCActiveMark x;
3664 gc_prologue(false);
3665 increment_total_collections(false /* full gc */);
3666 increment_gc_time_stamp();
3668 if (VerifyBeforeGC && total_collections() >= VerifyGCStartAt) {
3669 HandleMark hm; // Discard invalid handles created during verification
3670 gclog_or_tty->print(" VerifyBeforeGC:");
3671 prepare_for_verify();
3672 Universe::verify(/* silent */ false,
3673 /* option */ VerifyOption_G1UsePrevMarking);
3674 }
3676 COMPILER2_PRESENT(DerivedPointerTable::clear());
3678 // Please see comment in g1CollectedHeap.hpp and
3679 // G1CollectedHeap::ref_processing_init() to see how
3680 // reference processing currently works in G1.
3682 // Enable discovery in the STW reference processor
3683 ref_processor_stw()->enable_discovery(true /*verify_disabled*/,
3684 true /*verify_no_refs*/);
3686 {
3687 // We want to temporarily turn off discovery by the
3688 // CM ref processor, if necessary, and turn it back on
3689 // on again later if we do. Using a scoped
3690 // NoRefDiscovery object will do this.
3691 NoRefDiscovery no_cm_discovery(ref_processor_cm());
3693 // Forget the current alloc region (we might even choose it to be part
3694 // of the collection set!).
3695 release_mutator_alloc_region();
3697 // We should call this after we retire the mutator alloc
3698 // region(s) so that all the ALLOC / RETIRE events are generated
3699 // before the start GC event.
3700 _hr_printer.start_gc(false /* full */, (size_t) total_collections());
3702 // The elapsed time induced by the start time below deliberately elides
3703 // the possible verification above.
3704 double start_time_sec = os::elapsedTime();
3705 size_t start_used_bytes = used();
3707 #if YOUNG_LIST_VERBOSE
3708 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
3709 _young_list->print();
3710 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3711 #endif // YOUNG_LIST_VERBOSE
3713 g1_policy()->record_collection_pause_start(start_time_sec,
3714 start_used_bytes);
3716 double scan_wait_start = os::elapsedTime();
3717 // We have to wait until the CM threads finish scanning the
3718 // root regions as it's the only way to ensure that all the
3719 // objects on them have been correctly scanned before we start
3720 // moving them during the GC.
3721 bool waited = _cm->root_regions()->wait_until_scan_finished();
3722 if (waited) {
3723 double scan_wait_end = os::elapsedTime();
3724 double wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
3725 g1_policy()->record_root_region_scan_wait_time(wait_time_ms);
3726 }
3728 #if YOUNG_LIST_VERBOSE
3729 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
3730 _young_list->print();
3731 #endif // YOUNG_LIST_VERBOSE
3733 if (g1_policy()->during_initial_mark_pause()) {
3734 concurrent_mark()->checkpointRootsInitialPre();
3735 }
3736 perm_gen()->save_marks();
3738 #if YOUNG_LIST_VERBOSE
3739 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
3740 _young_list->print();
3741 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3742 #endif // YOUNG_LIST_VERBOSE
3744 g1_policy()->finalize_cset(target_pause_time_ms);
3746 _cm->note_start_of_gc();
3747 // We should not verify the per-thread SATB buffers given that
3748 // we have not filtered them yet (we'll do so during the
3749 // GC). We also call this after finalize_cset() to
3750 // ensure that the CSet has been finalized.
3751 _cm->verify_no_cset_oops(true /* verify_stacks */,
3752 true /* verify_enqueued_buffers */,
3753 false /* verify_thread_buffers */,
3754 true /* verify_fingers */);
3756 if (_hr_printer.is_active()) {
3757 HeapRegion* hr = g1_policy()->collection_set();
3758 while (hr != NULL) {
3759 G1HRPrinter::RegionType type;
3760 if (!hr->is_young()) {
3761 type = G1HRPrinter::Old;
3762 } else if (hr->is_survivor()) {
3763 type = G1HRPrinter::Survivor;
3764 } else {
3765 type = G1HRPrinter::Eden;
3766 }
3767 _hr_printer.cset(hr);
3768 hr = hr->next_in_collection_set();
3769 }
3770 }
3772 #ifdef ASSERT
3773 VerifyCSetClosure cl;
3774 collection_set_iterate(&cl);
3775 #endif // ASSERT
3777 setup_surviving_young_words();
3779 // Initialize the GC alloc regions.
3780 init_gc_alloc_regions();
3782 // Actually do the work...
3783 evacuate_collection_set();
3785 // We do this to mainly verify the per-thread SATB buffers
3786 // (which have been filtered by now) since we didn't verify
3787 // them earlier. No point in re-checking the stacks / enqueued
3788 // buffers given that the CSet has not changed since last time
3789 // we checked.
3790 _cm->verify_no_cset_oops(false /* verify_stacks */,
3791 false /* verify_enqueued_buffers */,
3792 true /* verify_thread_buffers */,
3793 true /* verify_fingers */);
3795 free_collection_set(g1_policy()->collection_set());
3796 g1_policy()->clear_collection_set();
3798 cleanup_surviving_young_words();
3800 // Start a new incremental collection set for the next pause.
3801 g1_policy()->start_incremental_cset_building();
3803 // Clear the _cset_fast_test bitmap in anticipation of adding
3804 // regions to the incremental collection set for the next
3805 // evacuation pause.
3806 clear_cset_fast_test();
3808 _young_list->reset_sampled_info();
3810 // Don't check the whole heap at this point as the
3811 // GC alloc regions from this pause have been tagged
3812 // as survivors and moved on to the survivor list.
3813 // Survivor regions will fail the !is_young() check.
3814 assert(check_young_list_empty(false /* check_heap */),
3815 "young list should be empty");
3817 #if YOUNG_LIST_VERBOSE
3818 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
3819 _young_list->print();
3820 #endif // YOUNG_LIST_VERBOSE
3822 g1_policy()->record_survivor_regions(_young_list->survivor_length(),
3823 _young_list->first_survivor_region(),
3824 _young_list->last_survivor_region());
3826 _young_list->reset_auxilary_lists();
3828 if (evacuation_failed()) {
3829 _summary_bytes_used = recalculate_used();
3830 } else {
3831 // The "used" of the the collection set have already been subtracted
3832 // when they were freed. Add in the bytes evacuated.
3833 _summary_bytes_used += g1_policy()->bytes_copied_during_gc();
3834 }
3836 if (g1_policy()->during_initial_mark_pause()) {
3837 // We have to do this before we notify the CM threads that
3838 // they can start working to make sure that all the
3839 // appropriate initialization is done on the CM object.
3840 concurrent_mark()->checkpointRootsInitialPost();
3841 set_marking_started();
3842 // Note that we don't actually trigger the CM thread at
3843 // this point. We do that later when we're sure that
3844 // the current thread has completed its logging output.
3845 }
3847 allocate_dummy_regions();
3849 #if YOUNG_LIST_VERBOSE
3850 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
3851 _young_list->print();
3852 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3853 #endif // YOUNG_LIST_VERBOSE
3855 init_mutator_alloc_region();
3857 {
3858 size_t expand_bytes = g1_policy()->expansion_amount();
3859 if (expand_bytes > 0) {
3860 size_t bytes_before = capacity();
3861 // No need for an ergo verbose message here,
3862 // expansion_amount() does this when it returns a value > 0.
3863 if (!expand(expand_bytes)) {
3864 // We failed to expand the heap so let's verify that
3865 // committed/uncommitted amount match the backing store
3866 assert(capacity() == _g1_storage.committed_size(), "committed size mismatch");
3867 assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch");
3868 }
3869 }
3870 }
3872 // We redo the verificaiton but now wrt to the new CSet which
3873 // has just got initialized after the previous CSet was freed.
3874 _cm->verify_no_cset_oops(true /* verify_stacks */,
3875 true /* verify_enqueued_buffers */,
3876 true /* verify_thread_buffers */,
3877 true /* verify_fingers */);
3878 _cm->note_end_of_gc();
3880 double end_time_sec = os::elapsedTime();
3881 double pause_time_ms = (end_time_sec - start_time_sec) * MILLIUNITS;
3882 g1_policy()->record_pause_time_ms(pause_time_ms);
3883 int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
3884 workers()->active_workers() : 1);
3885 g1_policy()->record_collection_pause_end(active_workers);
3887 MemoryService::track_memory_usage();
3889 // In prepare_for_verify() below we'll need to scan the deferred
3890 // update buffers to bring the RSets up-to-date if
3891 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
3892 // the update buffers we'll probably need to scan cards on the
3893 // regions we just allocated to (i.e., the GC alloc
3894 // regions). However, during the last GC we called
3895 // set_saved_mark() on all the GC alloc regions, so card
3896 // scanning might skip the [saved_mark_word()...top()] area of
3897 // those regions (i.e., the area we allocated objects into
3898 // during the last GC). But it shouldn't. Given that
3899 // saved_mark_word() is conditional on whether the GC time stamp
3900 // on the region is current or not, by incrementing the GC time
3901 // stamp here we invalidate all the GC time stamps on all the
3902 // regions and saved_mark_word() will simply return top() for
3903 // all the regions. This is a nicer way of ensuring this rather
3904 // than iterating over the regions and fixing them. In fact, the
3905 // GC time stamp increment here also ensures that
3906 // saved_mark_word() will return top() between pauses, i.e.,
3907 // during concurrent refinement. So we don't need the
3908 // is_gc_active() check to decided which top to use when
3909 // scanning cards (see CR 7039627).
3910 increment_gc_time_stamp();
3912 if (VerifyAfterGC && total_collections() >= VerifyGCStartAt) {
3913 HandleMark hm; // Discard invalid handles created during verification
3914 gclog_or_tty->print(" VerifyAfterGC:");
3915 prepare_for_verify();
3916 Universe::verify(/* silent */ false,
3917 /* option */ VerifyOption_G1UsePrevMarking);
3918 }
3920 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
3921 ref_processor_stw()->verify_no_references_recorded();
3923 // CM reference discovery will be re-enabled if necessary.
3924 }
3926 // We should do this after we potentially expand the heap so
3927 // that all the COMMIT events are generated before the end GC
3928 // event, and after we retire the GC alloc regions so that all
3929 // RETIRE events are generated before the end GC event.
3930 _hr_printer.end_gc(false /* full */, (size_t) total_collections());
3932 // We have to do this after we decide whether to expand the heap or not.
3933 g1_policy()->print_heap_transition();
3935 if (mark_in_progress()) {
3936 concurrent_mark()->update_g1_committed();
3937 }
3939 #ifdef TRACESPINNING
3940 ParallelTaskTerminator::print_termination_counts();
3941 #endif
3943 gc_epilogue(false);
3944 }
3946 // The closing of the inner scope, immediately above, will complete
3947 // logging at the "fine" level. The record_collection_pause_end() call
3948 // above will complete logging at the "finer" level.
3949 //
3950 // It is not yet to safe, however, to tell the concurrent mark to
3951 // start as we have some optional output below. We don't want the
3952 // output from the concurrent mark thread interfering with this
3953 // logging output either.
3955 _hrs.verify_optional();
3956 verify_region_sets_optional();
3958 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
3959 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3961 print_heap_after_gc();
3963 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3964 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3965 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3966 // before any GC notifications are raised.
3967 g1mm()->update_sizes();
3968 }
3970 if (G1SummarizeRSetStats &&
3971 (G1SummarizeRSetStatsPeriod > 0) &&
3972 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3973 g1_rem_set()->print_summary_info();
3974 }
3976 // It should now be safe to tell the concurrent mark thread to start
3977 // without its logging output interfering with the logging output
3978 // that came from the pause.
3980 if (should_start_conc_mark) {
3981 // CAUTION: after the doConcurrentMark() call below,
3982 // the concurrent marking thread(s) could be running
3983 // concurrently with us. Make sure that anything after
3984 // this point does not assume that we are the only GC thread
3985 // running. Note: of course, the actual marking work will
3986 // not start until the safepoint itself is released in
3987 // ConcurrentGCThread::safepoint_desynchronize().
3988 doConcurrentMark();
3989 }
3991 return true;
3992 }
3994 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
3995 {
3996 size_t gclab_word_size;
3997 switch (purpose) {
3998 case GCAllocForSurvived:
3999 gclab_word_size = YoungPLABSize;
4000 break;
4001 case GCAllocForTenured:
4002 gclab_word_size = OldPLABSize;
4003 break;
4004 default:
4005 assert(false, "unknown GCAllocPurpose");
4006 gclab_word_size = OldPLABSize;
4007 break;
4008 }
4009 return gclab_word_size;
4010 }
4012 void G1CollectedHeap::init_mutator_alloc_region() {
4013 assert(_mutator_alloc_region.get() == NULL, "pre-condition");
4014 _mutator_alloc_region.init();
4015 }
4017 void G1CollectedHeap::release_mutator_alloc_region() {
4018 _mutator_alloc_region.release();
4019 assert(_mutator_alloc_region.get() == NULL, "post-condition");
4020 }
4022 void G1CollectedHeap::init_gc_alloc_regions() {
4023 assert_at_safepoint(true /* should_be_vm_thread */);
4025 _survivor_gc_alloc_region.init();
4026 _old_gc_alloc_region.init();
4027 HeapRegion* retained_region = _retained_old_gc_alloc_region;
4028 _retained_old_gc_alloc_region = NULL;
4030 // We will discard the current GC alloc region if:
4031 // a) it's in the collection set (it can happen!),
4032 // b) it's already full (no point in using it),
4033 // c) it's empty (this means that it was emptied during
4034 // a cleanup and it should be on the free list now), or
4035 // d) it's humongous (this means that it was emptied
4036 // during a cleanup and was added to the free list, but
4037 // has been subseqently used to allocate a humongous
4038 // object that may be less than the region size).
4039 if (retained_region != NULL &&
4040 !retained_region->in_collection_set() &&
4041 !(retained_region->top() == retained_region->end()) &&
4042 !retained_region->is_empty() &&
4043 !retained_region->isHumongous()) {
4044 retained_region->set_saved_mark();
4045 // The retained region was added to the old region set when it was
4046 // retired. We have to remove it now, since we don't allow regions
4047 // we allocate to in the region sets. We'll re-add it later, when
4048 // it's retired again.
4049 _old_set.remove(retained_region);
4050 bool during_im = g1_policy()->during_initial_mark_pause();
4051 retained_region->note_start_of_copying(during_im);
4052 _old_gc_alloc_region.set(retained_region);
4053 _hr_printer.reuse(retained_region);
4054 }
4055 }
4057 void G1CollectedHeap::release_gc_alloc_regions() {
4058 _survivor_gc_alloc_region.release();
4059 // If we have an old GC alloc region to release, we'll save it in
4060 // _retained_old_gc_alloc_region. If we don't
4061 // _retained_old_gc_alloc_region will become NULL. This is what we
4062 // want either way so no reason to check explicitly for either
4063 // condition.
4064 _retained_old_gc_alloc_region = _old_gc_alloc_region.release();
4065 }
4067 void G1CollectedHeap::abandon_gc_alloc_regions() {
4068 assert(_survivor_gc_alloc_region.get() == NULL, "pre-condition");
4069 assert(_old_gc_alloc_region.get() == NULL, "pre-condition");
4070 _retained_old_gc_alloc_region = NULL;
4071 }
4073 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4074 _drain_in_progress = false;
4075 set_evac_failure_closure(cl);
4076 _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4077 }
4079 void G1CollectedHeap::finalize_for_evac_failure() {
4080 assert(_evac_failure_scan_stack != NULL &&
4081 _evac_failure_scan_stack->length() == 0,
4082 "Postcondition");
4083 assert(!_drain_in_progress, "Postcondition");
4084 delete _evac_failure_scan_stack;
4085 _evac_failure_scan_stack = NULL;
4086 }
4088 void G1CollectedHeap::remove_self_forwarding_pointers() {
4089 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4091 G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4093 if (G1CollectedHeap::use_parallel_gc_threads()) {
4094 set_par_threads();
4095 workers()->run_task(&rsfp_task);
4096 set_par_threads(0);
4097 } else {
4098 rsfp_task.work(0);
4099 }
4101 assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity");
4103 // Reset the claim values in the regions in the collection set.
4104 reset_cset_heap_region_claim_values();
4106 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4108 // Now restore saved marks, if any.
4109 if (_objs_with_preserved_marks != NULL) {
4110 assert(_preserved_marks_of_objs != NULL, "Both or none.");
4111 guarantee(_objs_with_preserved_marks->length() ==
4112 _preserved_marks_of_objs->length(), "Both or none.");
4113 for (int i = 0; i < _objs_with_preserved_marks->length(); i++) {
4114 oop obj = _objs_with_preserved_marks->at(i);
4115 markOop m = _preserved_marks_of_objs->at(i);
4116 obj->set_mark(m);
4117 }
4119 // Delete the preserved marks growable arrays (allocated on the C heap).
4120 delete _objs_with_preserved_marks;
4121 delete _preserved_marks_of_objs;
4122 _objs_with_preserved_marks = NULL;
4123 _preserved_marks_of_objs = NULL;
4124 }
4125 }
4127 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4128 _evac_failure_scan_stack->push(obj);
4129 }
4131 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4132 assert(_evac_failure_scan_stack != NULL, "precondition");
4134 while (_evac_failure_scan_stack->length() > 0) {
4135 oop obj = _evac_failure_scan_stack->pop();
4136 _evac_failure_closure->set_region(heap_region_containing(obj));
4137 obj->oop_iterate_backwards(_evac_failure_closure);
4138 }
4139 }
4141 oop
4142 G1CollectedHeap::handle_evacuation_failure_par(OopsInHeapRegionClosure* cl,
4143 oop old) {
4144 assert(obj_in_cs(old),
4145 err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4146 (HeapWord*) old));
4147 markOop m = old->mark();
4148 oop forward_ptr = old->forward_to_atomic(old);
4149 if (forward_ptr == NULL) {
4150 // Forward-to-self succeeded.
4152 if (_evac_failure_closure != cl) {
4153 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4154 assert(!_drain_in_progress,
4155 "Should only be true while someone holds the lock.");
4156 // Set the global evac-failure closure to the current thread's.
4157 assert(_evac_failure_closure == NULL, "Or locking has failed.");
4158 set_evac_failure_closure(cl);
4159 // Now do the common part.
4160 handle_evacuation_failure_common(old, m);
4161 // Reset to NULL.
4162 set_evac_failure_closure(NULL);
4163 } else {
4164 // The lock is already held, and this is recursive.
4165 assert(_drain_in_progress, "This should only be the recursive case.");
4166 handle_evacuation_failure_common(old, m);
4167 }
4168 return old;
4169 } else {
4170 // Forward-to-self failed. Either someone else managed to allocate
4171 // space for this object (old != forward_ptr) or they beat us in
4172 // self-forwarding it (old == forward_ptr).
4173 assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4174 err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4175 "should not be in the CSet",
4176 (HeapWord*) old, (HeapWord*) forward_ptr));
4177 return forward_ptr;
4178 }
4179 }
4181 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4182 set_evacuation_failed(true);
4184 preserve_mark_if_necessary(old, m);
4186 HeapRegion* r = heap_region_containing(old);
4187 if (!r->evacuation_failed()) {
4188 r->set_evacuation_failed(true);
4189 _hr_printer.evac_failure(r);
4190 }
4192 push_on_evac_failure_scan_stack(old);
4194 if (!_drain_in_progress) {
4195 // prevent recursion in copy_to_survivor_space()
4196 _drain_in_progress = true;
4197 drain_evac_failure_scan_stack();
4198 _drain_in_progress = false;
4199 }
4200 }
4202 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4203 assert(evacuation_failed(), "Oversaving!");
4204 // We want to call the "for_promotion_failure" version only in the
4205 // case of a promotion failure.
4206 if (m->must_be_preserved_for_promotion_failure(obj)) {
4207 if (_objs_with_preserved_marks == NULL) {
4208 assert(_preserved_marks_of_objs == NULL, "Both or none.");
4209 _objs_with_preserved_marks =
4210 new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4211 _preserved_marks_of_objs =
4212 new (ResourceObj::C_HEAP, mtGC) GrowableArray<markOop>(40, true);
4213 }
4214 _objs_with_preserved_marks->push(obj);
4215 _preserved_marks_of_objs->push(m);
4216 }
4217 }
4219 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
4220 size_t word_size) {
4221 if (purpose == GCAllocForSurvived) {
4222 HeapWord* result = survivor_attempt_allocation(word_size);
4223 if (result != NULL) {
4224 return result;
4225 } else {
4226 // Let's try to allocate in the old gen in case we can fit the
4227 // object there.
4228 return old_attempt_allocation(word_size);
4229 }
4230 } else {
4231 assert(purpose == GCAllocForTenured, "sanity");
4232 HeapWord* result = old_attempt_allocation(word_size);
4233 if (result != NULL) {
4234 return result;
4235 } else {
4236 // Let's try to allocate in the survivors in case we can fit the
4237 // object there.
4238 return survivor_attempt_allocation(word_size);
4239 }
4240 }
4242 ShouldNotReachHere();
4243 // Trying to keep some compilers happy.
4244 return NULL;
4245 }
4247 G1ParGCAllocBuffer::G1ParGCAllocBuffer(size_t gclab_word_size) :
4248 ParGCAllocBuffer(gclab_word_size), _retired(false) { }
4250 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, uint queue_num)
4251 : _g1h(g1h),
4252 _refs(g1h->task_queue(queue_num)),
4253 _dcq(&g1h->dirty_card_queue_set()),
4254 _ct_bs((CardTableModRefBS*)_g1h->barrier_set()),
4255 _g1_rem(g1h->g1_rem_set()),
4256 _hash_seed(17), _queue_num(queue_num),
4257 _term_attempts(0),
4258 _surviving_alloc_buffer(g1h->desired_plab_sz(GCAllocForSurvived)),
4259 _tenured_alloc_buffer(g1h->desired_plab_sz(GCAllocForTenured)),
4260 _age_table(false),
4261 _strong_roots_time(0), _term_time(0),
4262 _alloc_buffer_waste(0), _undo_waste(0) {
4263 // we allocate G1YoungSurvRateNumRegions plus one entries, since
4264 // we "sacrifice" entry 0 to keep track of surviving bytes for
4265 // non-young regions (where the age is -1)
4266 // We also add a few elements at the beginning and at the end in
4267 // an attempt to eliminate cache contention
4268 uint real_length = 1 + _g1h->g1_policy()->young_cset_region_length();
4269 uint array_length = PADDING_ELEM_NUM +
4270 real_length +
4271 PADDING_ELEM_NUM;
4272 _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length, mtGC);
4273 if (_surviving_young_words_base == NULL)
4274 vm_exit_out_of_memory(array_length * sizeof(size_t),
4275 "Not enough space for young surv histo.");
4276 _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM;
4277 memset(_surviving_young_words, 0, (size_t) real_length * sizeof(size_t));
4279 _alloc_buffers[GCAllocForSurvived] = &_surviving_alloc_buffer;
4280 _alloc_buffers[GCAllocForTenured] = &_tenured_alloc_buffer;
4282 _start = os::elapsedTime();
4283 }
4285 void
4286 G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st)
4287 {
4288 st->print_raw_cr("GC Termination Stats");
4289 st->print_raw_cr(" elapsed --strong roots-- -------termination-------"
4290 " ------waste (KiB)------");
4291 st->print_raw_cr("thr ms ms % ms % attempts"
4292 " total alloc undo");
4293 st->print_raw_cr("--- --------- --------- ------ --------- ------ --------"
4294 " ------- ------- -------");
4295 }
4297 void
4298 G1ParScanThreadState::print_termination_stats(int i,
4299 outputStream* const st) const
4300 {
4301 const double elapsed_ms = elapsed_time() * 1000.0;
4302 const double s_roots_ms = strong_roots_time() * 1000.0;
4303 const double term_ms = term_time() * 1000.0;
4304 st->print_cr("%3d %9.2f %9.2f %6.2f "
4305 "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
4306 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
4307 i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms,
4308 term_ms, term_ms * 100 / elapsed_ms, term_attempts(),
4309 (alloc_buffer_waste() + undo_waste()) * HeapWordSize / K,
4310 alloc_buffer_waste() * HeapWordSize / K,
4311 undo_waste() * HeapWordSize / K);
4312 }
4314 #ifdef ASSERT
4315 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const {
4316 assert(ref != NULL, "invariant");
4317 assert(UseCompressedOops, "sanity");
4318 assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, ref));
4319 oop p = oopDesc::load_decode_heap_oop(ref);
4320 assert(_g1h->is_in_g1_reserved(p),
4321 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4322 return true;
4323 }
4325 bool G1ParScanThreadState::verify_ref(oop* ref) const {
4326 assert(ref != NULL, "invariant");
4327 if (has_partial_array_mask(ref)) {
4328 // Must be in the collection set--it's already been copied.
4329 oop p = clear_partial_array_mask(ref);
4330 assert(_g1h->obj_in_cs(p),
4331 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4332 } else {
4333 oop p = oopDesc::load_decode_heap_oop(ref);
4334 assert(_g1h->is_in_g1_reserved(p),
4335 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4336 }
4337 return true;
4338 }
4340 bool G1ParScanThreadState::verify_task(StarTask ref) const {
4341 if (ref.is_narrow()) {
4342 return verify_ref((narrowOop*) ref);
4343 } else {
4344 return verify_ref((oop*) ref);
4345 }
4346 }
4347 #endif // ASSERT
4349 void G1ParScanThreadState::trim_queue() {
4350 assert(_evac_cl != NULL, "not set");
4351 assert(_evac_failure_cl != NULL, "not set");
4352 assert(_partial_scan_cl != NULL, "not set");
4354 StarTask ref;
4355 do {
4356 // Drain the overflow stack first, so other threads can steal.
4357 while (refs()->pop_overflow(ref)) {
4358 deal_with_reference(ref);
4359 }
4361 while (refs()->pop_local(ref)) {
4362 deal_with_reference(ref);
4363 }
4364 } while (!refs()->is_empty());
4365 }
4367 G1ParClosureSuper::G1ParClosureSuper(G1CollectedHeap* g1,
4368 G1ParScanThreadState* par_scan_state) :
4369 _g1(g1), _g1_rem(_g1->g1_rem_set()), _cm(_g1->concurrent_mark()),
4370 _par_scan_state(par_scan_state),
4371 _worker_id(par_scan_state->queue_num()),
4372 _during_initial_mark(_g1->g1_policy()->during_initial_mark_pause()),
4373 _mark_in_progress(_g1->mark_in_progress()) { }
4375 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4376 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>::mark_object(oop obj) {
4377 #ifdef ASSERT
4378 HeapRegion* hr = _g1->heap_region_containing(obj);
4379 assert(hr != NULL, "sanity");
4380 assert(!hr->in_collection_set(), "should not mark objects in the CSet");
4381 #endif // ASSERT
4383 // We know that the object is not moving so it's safe to read its size.
4384 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4385 }
4387 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4388 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4389 ::mark_forwarded_object(oop from_obj, oop to_obj) {
4390 #ifdef ASSERT
4391 assert(from_obj->is_forwarded(), "from obj should be forwarded");
4392 assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4393 assert(from_obj != to_obj, "should not be self-forwarded");
4395 HeapRegion* from_hr = _g1->heap_region_containing(from_obj);
4396 assert(from_hr != NULL, "sanity");
4397 assert(from_hr->in_collection_set(), "from obj should be in the CSet");
4399 HeapRegion* to_hr = _g1->heap_region_containing(to_obj);
4400 assert(to_hr != NULL, "sanity");
4401 assert(!to_hr->in_collection_set(), "should not mark objects in the CSet");
4402 #endif // ASSERT
4404 // The object might be in the process of being copied by another
4405 // worker so we cannot trust that its to-space image is
4406 // well-formed. So we have to read its size from its from-space
4407 // image which we know should not be changing.
4408 _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4409 }
4411 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4412 oop G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4413 ::copy_to_survivor_space(oop old) {
4414 size_t word_sz = old->size();
4415 HeapRegion* from_region = _g1->heap_region_containing_raw(old);
4416 // +1 to make the -1 indexes valid...
4417 int young_index = from_region->young_index_in_cset()+1;
4418 assert( (from_region->is_young() && young_index > 0) ||
4419 (!from_region->is_young() && young_index == 0), "invariant" );
4420 G1CollectorPolicy* g1p = _g1->g1_policy();
4421 markOop m = old->mark();
4422 int age = m->has_displaced_mark_helper() ? m->displaced_mark_helper()->age()
4423 : m->age();
4424 GCAllocPurpose alloc_purpose = g1p->evacuation_destination(from_region, age,
4425 word_sz);
4426 HeapWord* obj_ptr = _par_scan_state->allocate(alloc_purpose, word_sz);
4427 oop obj = oop(obj_ptr);
4429 if (obj_ptr == NULL) {
4430 // This will either forward-to-self, or detect that someone else has
4431 // installed a forwarding pointer.
4432 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4433 return _g1->handle_evacuation_failure_par(cl, old);
4434 }
4436 // We're going to allocate linearly, so might as well prefetch ahead.
4437 Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
4439 oop forward_ptr = old->forward_to_atomic(obj);
4440 if (forward_ptr == NULL) {
4441 Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
4442 if (g1p->track_object_age(alloc_purpose)) {
4443 // We could simply do obj->incr_age(). However, this causes a
4444 // performance issue. obj->incr_age() will first check whether
4445 // the object has a displaced mark by checking its mark word;
4446 // getting the mark word from the new location of the object
4447 // stalls. So, given that we already have the mark word and we
4448 // are about to install it anyway, it's better to increase the
4449 // age on the mark word, when the object does not have a
4450 // displaced mark word. We're not expecting many objects to have
4451 // a displaced marked word, so that case is not optimized
4452 // further (it could be...) and we simply call obj->incr_age().
4454 if (m->has_displaced_mark_helper()) {
4455 // in this case, we have to install the mark word first,
4456 // otherwise obj looks to be forwarded (the old mark word,
4457 // which contains the forward pointer, was copied)
4458 obj->set_mark(m);
4459 obj->incr_age();
4460 } else {
4461 m = m->incr_age();
4462 obj->set_mark(m);
4463 }
4464 _par_scan_state->age_table()->add(obj, word_sz);
4465 } else {
4466 obj->set_mark(m);
4467 }
4469 size_t* surv_young_words = _par_scan_state->surviving_young_words();
4470 surv_young_words[young_index] += word_sz;
4472 if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
4473 // We keep track of the next start index in the length field of
4474 // the to-space object. The actual length can be found in the
4475 // length field of the from-space object.
4476 arrayOop(obj)->set_length(0);
4477 oop* old_p = set_partial_array_mask(old);
4478 _par_scan_state->push_on_queue(old_p);
4479 } else {
4480 // No point in using the slower heap_region_containing() method,
4481 // given that we know obj is in the heap.
4482 _scanner.set_region(_g1->heap_region_containing_raw(obj));
4483 obj->oop_iterate_backwards(&_scanner);
4484 }
4485 } else {
4486 _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz);
4487 obj = forward_ptr;
4488 }
4489 return obj;
4490 }
4492 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4493 template <class T>
4494 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4495 ::do_oop_work(T* p) {
4496 oop obj = oopDesc::load_decode_heap_oop(p);
4497 assert(barrier != G1BarrierRS || obj != NULL,
4498 "Precondition: G1BarrierRS implies obj is non-NULL");
4500 assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4502 // here the null check is implicit in the cset_fast_test() test
4503 if (_g1->in_cset_fast_test(obj)) {
4504 oop forwardee;
4505 if (obj->is_forwarded()) {
4506 forwardee = obj->forwardee();
4507 } else {
4508 forwardee = copy_to_survivor_space(obj);
4509 }
4510 assert(forwardee != NULL, "forwardee should not be NULL");
4511 oopDesc::encode_store_heap_oop(p, forwardee);
4512 if (do_mark_object && forwardee != obj) {
4513 // If the object is self-forwarded we don't need to explicitly
4514 // mark it, the evacuation failure protocol will do so.
4515 mark_forwarded_object(obj, forwardee);
4516 }
4518 // When scanning the RS, we only care about objs in CS.
4519 if (barrier == G1BarrierRS) {
4520 _par_scan_state->update_rs(_from, p, _worker_id);
4521 }
4522 } else {
4523 // The object is not in collection set. If we're a root scanning
4524 // closure during an initial mark pause (i.e. do_mark_object will
4525 // be true) then attempt to mark the object.
4526 if (do_mark_object && _g1->is_in_g1_reserved(obj)) {
4527 mark_object(obj);
4528 }
4529 }
4531 if (barrier == G1BarrierEvac && obj != NULL) {
4532 _par_scan_state->update_rs(_from, p, _worker_id);
4533 }
4535 if (do_gen_barrier && obj != NULL) {
4536 par_do_barrier(p);
4537 }
4538 }
4540 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(oop* p);
4541 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(narrowOop* p);
4543 template <class T> void G1ParScanPartialArrayClosure::do_oop_nv(T* p) {
4544 assert(has_partial_array_mask(p), "invariant");
4545 oop from_obj = clear_partial_array_mask(p);
4547 assert(Universe::heap()->is_in_reserved(from_obj), "must be in heap.");
4548 assert(from_obj->is_objArray(), "must be obj array");
4549 objArrayOop from_obj_array = objArrayOop(from_obj);
4550 // The from-space object contains the real length.
4551 int length = from_obj_array->length();
4553 assert(from_obj->is_forwarded(), "must be forwarded");
4554 oop to_obj = from_obj->forwardee();
4555 assert(from_obj != to_obj, "should not be chunking self-forwarded objects");
4556 objArrayOop to_obj_array = objArrayOop(to_obj);
4557 // We keep track of the next start index in the length field of the
4558 // to-space object.
4559 int next_index = to_obj_array->length();
4560 assert(0 <= next_index && next_index < length,
4561 err_msg("invariant, next index: %d, length: %d", next_index, length));
4563 int start = next_index;
4564 int end = length;
4565 int remainder = end - start;
4566 // We'll try not to push a range that's smaller than ParGCArrayScanChunk.
4567 if (remainder > 2 * ParGCArrayScanChunk) {
4568 end = start + ParGCArrayScanChunk;
4569 to_obj_array->set_length(end);
4570 // Push the remainder before we process the range in case another
4571 // worker has run out of things to do and can steal it.
4572 oop* from_obj_p = set_partial_array_mask(from_obj);
4573 _par_scan_state->push_on_queue(from_obj_p);
4574 } else {
4575 assert(length == end, "sanity");
4576 // We'll process the final range for this object. Restore the length
4577 // so that the heap remains parsable in case of evacuation failure.
4578 to_obj_array->set_length(end);
4579 }
4580 _scanner.set_region(_g1->heap_region_containing_raw(to_obj));
4581 // Process indexes [start,end). It will also process the header
4582 // along with the first chunk (i.e., the chunk with start == 0).
4583 // Note that at this point the length field of to_obj_array is not
4584 // correct given that we are using it to keep track of the next
4585 // start index. oop_iterate_range() (thankfully!) ignores the length
4586 // field and only relies on the start / end parameters. It does
4587 // however return the size of the object which will be incorrect. So
4588 // we have to ignore it even if we wanted to use it.
4589 to_obj_array->oop_iterate_range(&_scanner, start, end);
4590 }
4592 class G1ParEvacuateFollowersClosure : public VoidClosure {
4593 protected:
4594 G1CollectedHeap* _g1h;
4595 G1ParScanThreadState* _par_scan_state;
4596 RefToScanQueueSet* _queues;
4597 ParallelTaskTerminator* _terminator;
4599 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
4600 RefToScanQueueSet* queues() { return _queues; }
4601 ParallelTaskTerminator* terminator() { return _terminator; }
4603 public:
4604 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4605 G1ParScanThreadState* par_scan_state,
4606 RefToScanQueueSet* queues,
4607 ParallelTaskTerminator* terminator)
4608 : _g1h(g1h), _par_scan_state(par_scan_state),
4609 _queues(queues), _terminator(terminator) {}
4611 void do_void();
4613 private:
4614 inline bool offer_termination();
4615 };
4617 bool G1ParEvacuateFollowersClosure::offer_termination() {
4618 G1ParScanThreadState* const pss = par_scan_state();
4619 pss->start_term_time();
4620 const bool res = terminator()->offer_termination();
4621 pss->end_term_time();
4622 return res;
4623 }
4625 void G1ParEvacuateFollowersClosure::do_void() {
4626 StarTask stolen_task;
4627 G1ParScanThreadState* const pss = par_scan_state();
4628 pss->trim_queue();
4630 do {
4631 while (queues()->steal(pss->queue_num(), pss->hash_seed(), stolen_task)) {
4632 assert(pss->verify_task(stolen_task), "sanity");
4633 if (stolen_task.is_narrow()) {
4634 pss->deal_with_reference((narrowOop*) stolen_task);
4635 } else {
4636 pss->deal_with_reference((oop*) stolen_task);
4637 }
4639 // We've just processed a reference and we might have made
4640 // available new entries on the queues. So we have to make sure
4641 // we drain the queues as necessary.
4642 pss->trim_queue();
4643 }
4644 } while (!offer_termination());
4646 pss->retire_alloc_buffers();
4647 }
4649 class G1ParTask : public AbstractGangTask {
4650 protected:
4651 G1CollectedHeap* _g1h;
4652 RefToScanQueueSet *_queues;
4653 ParallelTaskTerminator _terminator;
4654 uint _n_workers;
4656 Mutex _stats_lock;
4657 Mutex* stats_lock() { return &_stats_lock; }
4659 size_t getNCards() {
4660 return (_g1h->capacity() + G1BlockOffsetSharedArray::N_bytes - 1)
4661 / G1BlockOffsetSharedArray::N_bytes;
4662 }
4664 public:
4665 G1ParTask(G1CollectedHeap* g1h,
4666 RefToScanQueueSet *task_queues)
4667 : AbstractGangTask("G1 collection"),
4668 _g1h(g1h),
4669 _queues(task_queues),
4670 _terminator(0, _queues),
4671 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4672 {}
4674 RefToScanQueueSet* queues() { return _queues; }
4676 RefToScanQueue *work_queue(int i) {
4677 return queues()->queue(i);
4678 }
4680 ParallelTaskTerminator* terminator() { return &_terminator; }
4682 virtual void set_for_termination(int active_workers) {
4683 // This task calls set_n_termination() in par_non_clean_card_iterate_work()
4684 // in the young space (_par_seq_tasks) in the G1 heap
4685 // for SequentialSubTasksDone.
4686 // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap
4687 // both of which need setting by set_n_termination().
4688 _g1h->SharedHeap::set_n_termination(active_workers);
4689 _g1h->set_n_termination(active_workers);
4690 terminator()->reset_for_reuse(active_workers);
4691 _n_workers = active_workers;
4692 }
4694 void work(uint worker_id) {
4695 if (worker_id >= _n_workers) return; // no work needed this round
4697 double start_time_ms = os::elapsedTime() * 1000.0;
4698 _g1h->g1_policy()->record_gc_worker_start_time(worker_id, start_time_ms);
4700 {
4701 ResourceMark rm;
4702 HandleMark hm;
4704 ReferenceProcessor* rp = _g1h->ref_processor_stw();
4706 G1ParScanThreadState pss(_g1h, worker_id);
4707 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, rp);
4708 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
4709 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, rp);
4711 pss.set_evac_closure(&scan_evac_cl);
4712 pss.set_evac_failure_closure(&evac_failure_cl);
4713 pss.set_partial_scan_closure(&partial_scan_cl);
4715 G1ParScanExtRootClosure only_scan_root_cl(_g1h, &pss, rp);
4716 G1ParScanPermClosure only_scan_perm_cl(_g1h, &pss, rp);
4718 G1ParScanAndMarkExtRootClosure scan_mark_root_cl(_g1h, &pss, rp);
4719 G1ParScanAndMarkPermClosure scan_mark_perm_cl(_g1h, &pss, rp);
4721 OopClosure* scan_root_cl = &only_scan_root_cl;
4722 OopsInHeapRegionClosure* scan_perm_cl = &only_scan_perm_cl;
4724 if (_g1h->g1_policy()->during_initial_mark_pause()) {
4725 // We also need to mark copied objects.
4726 scan_root_cl = &scan_mark_root_cl;
4727 scan_perm_cl = &scan_mark_perm_cl;
4728 }
4730 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss);
4732 pss.start_strong_roots();
4733 _g1h->g1_process_strong_roots(/* not collecting perm */ false,
4734 SharedHeap::SO_AllClasses,
4735 scan_root_cl,
4736 &push_heap_rs_cl,
4737 scan_perm_cl,
4738 worker_id);
4739 pss.end_strong_roots();
4741 {
4742 double start = os::elapsedTime();
4743 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4744 evac.do_void();
4745 double elapsed_ms = (os::elapsedTime()-start)*1000.0;
4746 double term_ms = pss.term_time()*1000.0;
4747 _g1h->g1_policy()->record_obj_copy_time(worker_id, elapsed_ms-term_ms);
4748 _g1h->g1_policy()->record_termination(worker_id, term_ms, pss.term_attempts());
4749 }
4750 _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4751 _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4753 // Clean up any par-expanded rem sets.
4754 HeapRegionRemSet::par_cleanup();
4756 if (ParallelGCVerbose) {
4757 MutexLocker x(stats_lock());
4758 pss.print_termination_stats(worker_id);
4759 }
4761 assert(pss.refs()->is_empty(), "should be empty");
4763 // Close the inner scope so that the ResourceMark and HandleMark
4764 // destructors are executed here and are included as part of the
4765 // "GC Worker Time".
4766 }
4768 double end_time_ms = os::elapsedTime() * 1000.0;
4769 _g1h->g1_policy()->record_gc_worker_end_time(worker_id, end_time_ms);
4770 }
4771 };
4773 // *** Common G1 Evacuation Stuff
4775 // Closures that support the filtering of CodeBlobs scanned during
4776 // external root scanning.
4778 // Closure applied to reference fields in code blobs (specifically nmethods)
4779 // to determine whether an nmethod contains references that point into
4780 // the collection set. Used as a predicate when walking code roots so
4781 // that only nmethods that point into the collection set are added to the
4782 // 'marked' list.
4784 class G1FilteredCodeBlobToOopClosure : public CodeBlobToOopClosure {
4786 class G1PointsIntoCSOopClosure : public OopClosure {
4787 G1CollectedHeap* _g1;
4788 bool _points_into_cs;
4789 public:
4790 G1PointsIntoCSOopClosure(G1CollectedHeap* g1) :
4791 _g1(g1), _points_into_cs(false) { }
4793 bool points_into_cs() const { return _points_into_cs; }
4795 template <class T>
4796 void do_oop_nv(T* p) {
4797 if (!_points_into_cs) {
4798 T heap_oop = oopDesc::load_heap_oop(p);
4799 if (!oopDesc::is_null(heap_oop) &&
4800 _g1->in_cset_fast_test(oopDesc::decode_heap_oop_not_null(heap_oop))) {
4801 _points_into_cs = true;
4802 }
4803 }
4804 }
4806 virtual void do_oop(oop* p) { do_oop_nv(p); }
4807 virtual void do_oop(narrowOop* p) { do_oop_nv(p); }
4808 };
4810 G1CollectedHeap* _g1;
4812 public:
4813 G1FilteredCodeBlobToOopClosure(G1CollectedHeap* g1, OopClosure* cl) :
4814 CodeBlobToOopClosure(cl, true), _g1(g1) { }
4816 virtual void do_code_blob(CodeBlob* cb) {
4817 nmethod* nm = cb->as_nmethod_or_null();
4818 if (nm != NULL && !(nm->test_oops_do_mark())) {
4819 G1PointsIntoCSOopClosure predicate_cl(_g1);
4820 nm->oops_do(&predicate_cl);
4822 if (predicate_cl.points_into_cs()) {
4823 // At least one of the reference fields or the oop relocations
4824 // in the nmethod points into the collection set. We have to
4825 // 'mark' this nmethod.
4826 // Note: Revisit the following if CodeBlobToOopClosure::do_code_blob()
4827 // or MarkingCodeBlobClosure::do_code_blob() change.
4828 if (!nm->test_set_oops_do_mark()) {
4829 do_newly_marked_nmethod(nm);
4830 }
4831 }
4832 }
4833 }
4834 };
4836 // This method is run in a GC worker.
4838 void
4839 G1CollectedHeap::
4840 g1_process_strong_roots(bool collecting_perm_gen,
4841 ScanningOption so,
4842 OopClosure* scan_non_heap_roots,
4843 OopsInHeapRegionClosure* scan_rs,
4844 OopsInGenClosure* scan_perm,
4845 int worker_i) {
4847 // First scan the strong roots, including the perm gen.
4848 double ext_roots_start = os::elapsedTime();
4849 double closure_app_time_sec = 0.0;
4851 BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
4852 BufferingOopsInGenClosure buf_scan_perm(scan_perm);
4853 buf_scan_perm.set_generation(perm_gen());
4855 // Walk the code cache w/o buffering, because StarTask cannot handle
4856 // unaligned oop locations.
4857 G1FilteredCodeBlobToOopClosure eager_scan_code_roots(this, scan_non_heap_roots);
4859 process_strong_roots(false, // no scoping; this is parallel code
4860 collecting_perm_gen, so,
4861 &buf_scan_non_heap_roots,
4862 &eager_scan_code_roots,
4863 &buf_scan_perm);
4865 // Now the CM ref_processor roots.
4866 if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
4867 // We need to treat the discovered reference lists of the
4868 // concurrent mark ref processor as roots and keep entries
4869 // (which are added by the marking threads) on them live
4870 // until they can be processed at the end of marking.
4871 ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
4872 }
4874 // Finish up any enqueued closure apps (attributed as object copy time).
4875 buf_scan_non_heap_roots.done();
4876 buf_scan_perm.done();
4878 double ext_roots_end = os::elapsedTime();
4880 g1_policy()->reset_obj_copy_time(worker_i);
4881 double obj_copy_time_sec = buf_scan_perm.closure_app_seconds() +
4882 buf_scan_non_heap_roots.closure_app_seconds();
4883 g1_policy()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
4885 double ext_root_time_ms =
4886 ((ext_roots_end - ext_roots_start) - obj_copy_time_sec) * 1000.0;
4888 g1_policy()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
4890 // During conc marking we have to filter the per-thread SATB buffers
4891 // to make sure we remove any oops into the CSet (which will show up
4892 // as implicitly live).
4893 if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) {
4894 if (mark_in_progress()) {
4895 JavaThread::satb_mark_queue_set().filter_thread_buffers();
4896 }
4897 }
4898 double satb_filtering_ms = (os::elapsedTime() - ext_roots_end) * 1000.0;
4899 g1_policy()->record_satb_filtering_time(worker_i, satb_filtering_ms);
4901 // Now scan the complement of the collection set.
4902 if (scan_rs != NULL) {
4903 g1_rem_set()->oops_into_collection_set_do(scan_rs, worker_i);
4904 }
4906 _process_strong_tasks->all_tasks_completed();
4907 }
4909 void
4910 G1CollectedHeap::g1_process_weak_roots(OopClosure* root_closure,
4911 OopClosure* non_root_closure) {
4912 CodeBlobToOopClosure roots_in_blobs(root_closure, /*do_marking=*/ false);
4913 SharedHeap::process_weak_roots(root_closure, &roots_in_blobs, non_root_closure);
4914 }
4916 // Weak Reference Processing support
4918 // An always "is_alive" closure that is used to preserve referents.
4919 // If the object is non-null then it's alive. Used in the preservation
4920 // of referent objects that are pointed to by reference objects
4921 // discovered by the CM ref processor.
4922 class G1AlwaysAliveClosure: public BoolObjectClosure {
4923 G1CollectedHeap* _g1;
4924 public:
4925 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
4926 void do_object(oop p) { assert(false, "Do not call."); }
4927 bool do_object_b(oop p) {
4928 if (p != NULL) {
4929 return true;
4930 }
4931 return false;
4932 }
4933 };
4935 bool G1STWIsAliveClosure::do_object_b(oop p) {
4936 // An object is reachable if it is outside the collection set,
4937 // or is inside and copied.
4938 return !_g1->obj_in_cs(p) || p->is_forwarded();
4939 }
4941 // Non Copying Keep Alive closure
4942 class G1KeepAliveClosure: public OopClosure {
4943 G1CollectedHeap* _g1;
4944 public:
4945 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
4946 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
4947 void do_oop( oop* p) {
4948 oop obj = *p;
4950 if (_g1->obj_in_cs(obj)) {
4951 assert( obj->is_forwarded(), "invariant" );
4952 *p = obj->forwardee();
4953 }
4954 }
4955 };
4957 // Copying Keep Alive closure - can be called from both
4958 // serial and parallel code as long as different worker
4959 // threads utilize different G1ParScanThreadState instances
4960 // and different queues.
4962 class G1CopyingKeepAliveClosure: public OopClosure {
4963 G1CollectedHeap* _g1h;
4964 OopClosure* _copy_non_heap_obj_cl;
4965 OopsInHeapRegionClosure* _copy_perm_obj_cl;
4966 G1ParScanThreadState* _par_scan_state;
4968 public:
4969 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
4970 OopClosure* non_heap_obj_cl,
4971 OopsInHeapRegionClosure* perm_obj_cl,
4972 G1ParScanThreadState* pss):
4973 _g1h(g1h),
4974 _copy_non_heap_obj_cl(non_heap_obj_cl),
4975 _copy_perm_obj_cl(perm_obj_cl),
4976 _par_scan_state(pss)
4977 {}
4979 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
4980 virtual void do_oop( oop* p) { do_oop_work(p); }
4982 template <class T> void do_oop_work(T* p) {
4983 oop obj = oopDesc::load_decode_heap_oop(p);
4985 if (_g1h->obj_in_cs(obj)) {
4986 // If the referent object has been forwarded (either copied
4987 // to a new location or to itself in the event of an
4988 // evacuation failure) then we need to update the reference
4989 // field and, if both reference and referent are in the G1
4990 // heap, update the RSet for the referent.
4991 //
4992 // If the referent has not been forwarded then we have to keep
4993 // it alive by policy. Therefore we have copy the referent.
4994 //
4995 // If the reference field is in the G1 heap then we can push
4996 // on the PSS queue. When the queue is drained (after each
4997 // phase of reference processing) the object and it's followers
4998 // will be copied, the reference field set to point to the
4999 // new location, and the RSet updated. Otherwise we need to
5000 // use the the non-heap or perm closures directly to copy
5001 // the refernt object and update the pointer, while avoiding
5002 // updating the RSet.
5004 if (_g1h->is_in_g1_reserved(p)) {
5005 _par_scan_state->push_on_queue(p);
5006 } else {
5007 // The reference field is not in the G1 heap.
5008 if (_g1h->perm_gen()->is_in(p)) {
5009 _copy_perm_obj_cl->do_oop(p);
5010 } else {
5011 _copy_non_heap_obj_cl->do_oop(p);
5012 }
5013 }
5014 }
5015 }
5016 };
5018 // Serial drain queue closure. Called as the 'complete_gc'
5019 // closure for each discovered list in some of the
5020 // reference processing phases.
5022 class G1STWDrainQueueClosure: public VoidClosure {
5023 protected:
5024 G1CollectedHeap* _g1h;
5025 G1ParScanThreadState* _par_scan_state;
5027 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
5029 public:
5030 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
5031 _g1h(g1h),
5032 _par_scan_state(pss)
5033 { }
5035 void do_void() {
5036 G1ParScanThreadState* const pss = par_scan_state();
5037 pss->trim_queue();
5038 }
5039 };
5041 // Parallel Reference Processing closures
5043 // Implementation of AbstractRefProcTaskExecutor for parallel reference
5044 // processing during G1 evacuation pauses.
5046 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5047 private:
5048 G1CollectedHeap* _g1h;
5049 RefToScanQueueSet* _queues;
5050 FlexibleWorkGang* _workers;
5051 int _active_workers;
5053 public:
5054 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5055 FlexibleWorkGang* workers,
5056 RefToScanQueueSet *task_queues,
5057 int n_workers) :
5058 _g1h(g1h),
5059 _queues(task_queues),
5060 _workers(workers),
5061 _active_workers(n_workers)
5062 {
5063 assert(n_workers > 0, "shouldn't call this otherwise");
5064 }
5066 // Executes the given task using concurrent marking worker threads.
5067 virtual void execute(ProcessTask& task);
5068 virtual void execute(EnqueueTask& task);
5069 };
5071 // Gang task for possibly parallel reference processing
5073 class G1STWRefProcTaskProxy: public AbstractGangTask {
5074 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5075 ProcessTask& _proc_task;
5076 G1CollectedHeap* _g1h;
5077 RefToScanQueueSet *_task_queues;
5078 ParallelTaskTerminator* _terminator;
5080 public:
5081 G1STWRefProcTaskProxy(ProcessTask& proc_task,
5082 G1CollectedHeap* g1h,
5083 RefToScanQueueSet *task_queues,
5084 ParallelTaskTerminator* terminator) :
5085 AbstractGangTask("Process reference objects in parallel"),
5086 _proc_task(proc_task),
5087 _g1h(g1h),
5088 _task_queues(task_queues),
5089 _terminator(terminator)
5090 {}
5092 virtual void work(uint worker_id) {
5093 // The reference processing task executed by a single worker.
5094 ResourceMark rm;
5095 HandleMark hm;
5097 G1STWIsAliveClosure is_alive(_g1h);
5099 G1ParScanThreadState pss(_g1h, worker_id);
5101 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, NULL);
5102 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5103 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, NULL);
5105 pss.set_evac_closure(&scan_evac_cl);
5106 pss.set_evac_failure_closure(&evac_failure_cl);
5107 pss.set_partial_scan_closure(&partial_scan_cl);
5109 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5110 G1ParScanPermClosure only_copy_perm_cl(_g1h, &pss, NULL);
5112 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5113 G1ParScanAndMarkPermClosure copy_mark_perm_cl(_g1h, &pss, NULL);
5115 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5116 OopsInHeapRegionClosure* copy_perm_cl = &only_copy_perm_cl;
5118 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5119 // We also need to mark copied objects.
5120 copy_non_heap_cl = ©_mark_non_heap_cl;
5121 copy_perm_cl = ©_mark_perm_cl;
5122 }
5124 // Keep alive closure.
5125 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_perm_cl, &pss);
5127 // Complete GC closure
5128 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5130 // Call the reference processing task's work routine.
5131 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5133 // Note we cannot assert that the refs array is empty here as not all
5134 // of the processing tasks (specifically phase2 - pp2_work) execute
5135 // the complete_gc closure (which ordinarily would drain the queue) so
5136 // the queue may not be empty.
5137 }
5138 };
5140 // Driver routine for parallel reference processing.
5141 // Creates an instance of the ref processing gang
5142 // task and has the worker threads execute it.
5143 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5144 assert(_workers != NULL, "Need parallel worker threads.");
5146 ParallelTaskTerminator terminator(_active_workers, _queues);
5147 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5149 _g1h->set_par_threads(_active_workers);
5150 _workers->run_task(&proc_task_proxy);
5151 _g1h->set_par_threads(0);
5152 }
5154 // Gang task for parallel reference enqueueing.
5156 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5157 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5158 EnqueueTask& _enq_task;
5160 public:
5161 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5162 AbstractGangTask("Enqueue reference objects in parallel"),
5163 _enq_task(enq_task)
5164 { }
5166 virtual void work(uint worker_id) {
5167 _enq_task.work(worker_id);
5168 }
5169 };
5171 // Driver routine for parallel reference enqueing.
5172 // Creates an instance of the ref enqueueing gang
5173 // task and has the worker threads execute it.
5175 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5176 assert(_workers != NULL, "Need parallel worker threads.");
5178 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5180 _g1h->set_par_threads(_active_workers);
5181 _workers->run_task(&enq_task_proxy);
5182 _g1h->set_par_threads(0);
5183 }
5185 // End of weak reference support closures
5187 // Abstract task used to preserve (i.e. copy) any referent objects
5188 // that are in the collection set and are pointed to by reference
5189 // objects discovered by the CM ref processor.
5191 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5192 protected:
5193 G1CollectedHeap* _g1h;
5194 RefToScanQueueSet *_queues;
5195 ParallelTaskTerminator _terminator;
5196 uint _n_workers;
5198 public:
5199 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
5200 AbstractGangTask("ParPreserveCMReferents"),
5201 _g1h(g1h),
5202 _queues(task_queues),
5203 _terminator(workers, _queues),
5204 _n_workers(workers)
5205 { }
5207 void work(uint worker_id) {
5208 ResourceMark rm;
5209 HandleMark hm;
5211 G1ParScanThreadState pss(_g1h, worker_id);
5212 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, NULL);
5213 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5214 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, NULL);
5216 pss.set_evac_closure(&scan_evac_cl);
5217 pss.set_evac_failure_closure(&evac_failure_cl);
5218 pss.set_partial_scan_closure(&partial_scan_cl);
5220 assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5223 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5224 G1ParScanPermClosure only_copy_perm_cl(_g1h, &pss, NULL);
5226 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5227 G1ParScanAndMarkPermClosure copy_mark_perm_cl(_g1h, &pss, NULL);
5229 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5230 OopsInHeapRegionClosure* copy_perm_cl = &only_copy_perm_cl;
5232 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5233 // We also need to mark copied objects.
5234 copy_non_heap_cl = ©_mark_non_heap_cl;
5235 copy_perm_cl = ©_mark_perm_cl;
5236 }
5238 // Is alive closure
5239 G1AlwaysAliveClosure always_alive(_g1h);
5241 // Copying keep alive closure. Applied to referent objects that need
5242 // to be copied.
5243 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_perm_cl, &pss);
5245 ReferenceProcessor* rp = _g1h->ref_processor_cm();
5247 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5248 uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5250 // limit is set using max_num_q() - which was set using ParallelGCThreads.
5251 // So this must be true - but assert just in case someone decides to
5252 // change the worker ids.
5253 assert(0 <= worker_id && worker_id < limit, "sanity");
5254 assert(!rp->discovery_is_atomic(), "check this code");
5256 // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5257 for (uint idx = worker_id; idx < limit; idx += stride) {
5258 DiscoveredList& ref_list = rp->discovered_refs()[idx];
5260 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5261 while (iter.has_next()) {
5262 // Since discovery is not atomic for the CM ref processor, we
5263 // can see some null referent objects.
5264 iter.load_ptrs(DEBUG_ONLY(true));
5265 oop ref = iter.obj();
5267 // This will filter nulls.
5268 if (iter.is_referent_alive()) {
5269 iter.make_referent_alive();
5270 }
5271 iter.move_to_next();
5272 }
5273 }
5275 // Drain the queue - which may cause stealing
5276 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5277 drain_queue.do_void();
5278 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5279 assert(pss.refs()->is_empty(), "should be");
5280 }
5281 };
5283 // Weak Reference processing during an evacuation pause (part 1).
5284 void G1CollectedHeap::process_discovered_references() {
5285 double ref_proc_start = os::elapsedTime();
5287 ReferenceProcessor* rp = _ref_processor_stw;
5288 assert(rp->discovery_enabled(), "should have been enabled");
5290 // Any reference objects, in the collection set, that were 'discovered'
5291 // by the CM ref processor should have already been copied (either by
5292 // applying the external root copy closure to the discovered lists, or
5293 // by following an RSet entry).
5294 //
5295 // But some of the referents, that are in the collection set, that these
5296 // reference objects point to may not have been copied: the STW ref
5297 // processor would have seen that the reference object had already
5298 // been 'discovered' and would have skipped discovering the reference,
5299 // but would not have treated the reference object as a regular oop.
5300 // As a reult the copy closure would not have been applied to the
5301 // referent object.
5302 //
5303 // We need to explicitly copy these referent objects - the references
5304 // will be processed at the end of remarking.
5305 //
5306 // We also need to do this copying before we process the reference
5307 // objects discovered by the STW ref processor in case one of these
5308 // referents points to another object which is also referenced by an
5309 // object discovered by the STW ref processor.
5311 uint active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5312 workers()->active_workers() : 1);
5314 assert(!G1CollectedHeap::use_parallel_gc_threads() ||
5315 active_workers == workers()->active_workers(),
5316 "Need to reset active_workers");
5318 set_par_threads(active_workers);
5319 G1ParPreserveCMReferentsTask keep_cm_referents(this, active_workers, _task_queues);
5321 if (G1CollectedHeap::use_parallel_gc_threads()) {
5322 workers()->run_task(&keep_cm_referents);
5323 } else {
5324 keep_cm_referents.work(0);
5325 }
5327 set_par_threads(0);
5329 // Closure to test whether a referent is alive.
5330 G1STWIsAliveClosure is_alive(this);
5332 // Even when parallel reference processing is enabled, the processing
5333 // of JNI refs is serial and performed serially by the current thread
5334 // rather than by a worker. The following PSS will be used for processing
5335 // JNI refs.
5337 // Use only a single queue for this PSS.
5338 G1ParScanThreadState pss(this, 0);
5340 // We do not embed a reference processor in the copying/scanning
5341 // closures while we're actually processing the discovered
5342 // reference objects.
5343 G1ParScanHeapEvacClosure scan_evac_cl(this, &pss, NULL);
5344 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5345 G1ParScanPartialArrayClosure partial_scan_cl(this, &pss, NULL);
5347 pss.set_evac_closure(&scan_evac_cl);
5348 pss.set_evac_failure_closure(&evac_failure_cl);
5349 pss.set_partial_scan_closure(&partial_scan_cl);
5351 assert(pss.refs()->is_empty(), "pre-condition");
5353 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL);
5354 G1ParScanPermClosure only_copy_perm_cl(this, &pss, NULL);
5356 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5357 G1ParScanAndMarkPermClosure copy_mark_perm_cl(this, &pss, NULL);
5359 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5360 OopsInHeapRegionClosure* copy_perm_cl = &only_copy_perm_cl;
5362 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5363 // We also need to mark copied objects.
5364 copy_non_heap_cl = ©_mark_non_heap_cl;
5365 copy_perm_cl = ©_mark_perm_cl;
5366 }
5368 // Keep alive closure.
5369 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, copy_perm_cl, &pss);
5371 // Serial Complete GC closure
5372 G1STWDrainQueueClosure drain_queue(this, &pss);
5374 // Setup the soft refs policy...
5375 rp->setup_policy(false);
5377 if (!rp->processing_is_mt()) {
5378 // Serial reference processing...
5379 rp->process_discovered_references(&is_alive,
5380 &keep_alive,
5381 &drain_queue,
5382 NULL);
5383 } else {
5384 // Parallel reference processing
5385 assert(rp->num_q() == active_workers, "sanity");
5386 assert(active_workers <= rp->max_num_q(), "sanity");
5388 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, active_workers);
5389 rp->process_discovered_references(&is_alive, &keep_alive, &drain_queue, &par_task_executor);
5390 }
5392 // We have completed copying any necessary live referent objects
5393 // (that were not copied during the actual pause) so we can
5394 // retire any active alloc buffers
5395 pss.retire_alloc_buffers();
5396 assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5398 double ref_proc_time = os::elapsedTime() - ref_proc_start;
5399 g1_policy()->record_ref_proc_time(ref_proc_time * 1000.0);
5400 }
5402 // Weak Reference processing during an evacuation pause (part 2).
5403 void G1CollectedHeap::enqueue_discovered_references() {
5404 double ref_enq_start = os::elapsedTime();
5406 ReferenceProcessor* rp = _ref_processor_stw;
5407 assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5409 // Now enqueue any remaining on the discovered lists on to
5410 // the pending list.
5411 if (!rp->processing_is_mt()) {
5412 // Serial reference processing...
5413 rp->enqueue_discovered_references();
5414 } else {
5415 // Parallel reference enqueuing
5417 uint active_workers = (ParallelGCThreads > 0 ? workers()->active_workers() : 1);
5418 assert(active_workers == workers()->active_workers(),
5419 "Need to reset active_workers");
5420 assert(rp->num_q() == active_workers, "sanity");
5421 assert(active_workers <= rp->max_num_q(), "sanity");
5423 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, active_workers);
5424 rp->enqueue_discovered_references(&par_task_executor);
5425 }
5427 rp->verify_no_references_recorded();
5428 assert(!rp->discovery_enabled(), "should have been disabled");
5430 // FIXME
5431 // CM's reference processing also cleans up the string and symbol tables.
5432 // Should we do that here also? We could, but it is a serial operation
5433 // and could signicantly increase the pause time.
5435 double ref_enq_time = os::elapsedTime() - ref_enq_start;
5436 g1_policy()->record_ref_enq_time(ref_enq_time * 1000.0);
5437 }
5439 void G1CollectedHeap::evacuate_collection_set() {
5440 _expand_heap_after_alloc_failure = true;
5441 set_evacuation_failed(false);
5443 g1_rem_set()->prepare_for_oops_into_collection_set_do();
5444 concurrent_g1_refine()->set_use_cache(false);
5445 concurrent_g1_refine()->clear_hot_cache_claimed_index();
5447 uint n_workers;
5448 if (G1CollectedHeap::use_parallel_gc_threads()) {
5449 n_workers =
5450 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
5451 workers()->active_workers(),
5452 Threads::number_of_non_daemon_threads());
5453 assert(UseDynamicNumberOfGCThreads ||
5454 n_workers == workers()->total_workers(),
5455 "If not dynamic should be using all the workers");
5456 workers()->set_active_workers(n_workers);
5457 set_par_threads(n_workers);
5458 } else {
5459 assert(n_par_threads() == 0,
5460 "Should be the original non-parallel value");
5461 n_workers = 1;
5462 }
5464 G1ParTask g1_par_task(this, _task_queues);
5466 init_for_evac_failure(NULL);
5468 rem_set()->prepare_for_younger_refs_iterate(true);
5470 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5471 double start_par_time_sec = os::elapsedTime();
5472 double end_par_time_sec;
5474 {
5475 StrongRootsScope srs(this);
5477 if (G1CollectedHeap::use_parallel_gc_threads()) {
5478 // The individual threads will set their evac-failure closures.
5479 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
5480 // These tasks use ShareHeap::_process_strong_tasks
5481 assert(UseDynamicNumberOfGCThreads ||
5482 workers()->active_workers() == workers()->total_workers(),
5483 "If not dynamic should be using all the workers");
5484 workers()->run_task(&g1_par_task);
5485 } else {
5486 g1_par_task.set_for_termination(n_workers);
5487 g1_par_task.work(0);
5488 }
5489 end_par_time_sec = os::elapsedTime();
5491 // Closing the inner scope will execute the destructor
5492 // for the StrongRootsScope object. We record the current
5493 // elapsed time before closing the scope so that time
5494 // taken for the SRS destructor is NOT included in the
5495 // reported parallel time.
5496 }
5498 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5499 g1_policy()->record_par_time(par_time_ms);
5501 double code_root_fixup_time_ms =
5502 (os::elapsedTime() - end_par_time_sec) * 1000.0;
5503 g1_policy()->record_code_root_fixup_time(code_root_fixup_time_ms);
5505 set_par_threads(0);
5507 // Process any discovered reference objects - we have
5508 // to do this _before_ we retire the GC alloc regions
5509 // as we may have to copy some 'reachable' referent
5510 // objects (and their reachable sub-graphs) that were
5511 // not copied during the pause.
5512 process_discovered_references();
5514 // Weak root processing.
5515 // Note: when JSR 292 is enabled and code blobs can contain
5516 // non-perm oops then we will need to process the code blobs
5517 // here too.
5518 {
5519 G1STWIsAliveClosure is_alive(this);
5520 G1KeepAliveClosure keep_alive(this);
5521 JNIHandles::weak_oops_do(&is_alive, &keep_alive);
5522 }
5524 release_gc_alloc_regions();
5525 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5527 concurrent_g1_refine()->clear_hot_cache();
5528 concurrent_g1_refine()->set_use_cache(true);
5530 finalize_for_evac_failure();
5532 if (evacuation_failed()) {
5533 remove_self_forwarding_pointers();
5534 if (G1Log::finer()) {
5535 gclog_or_tty->print(" (to-space exhausted)");
5536 } else if (G1Log::fine()) {
5537 gclog_or_tty->print("--");
5538 }
5539 }
5541 // Enqueue any remaining references remaining on the STW
5542 // reference processor's discovered lists. We need to do
5543 // this after the card table is cleaned (and verified) as
5544 // the act of enqueuing entries on to the pending list
5545 // will log these updates (and dirty their associated
5546 // cards). We need these updates logged to update any
5547 // RSets.
5548 enqueue_discovered_references();
5550 if (G1DeferredRSUpdate) {
5551 RedirtyLoggedCardTableEntryFastClosure redirty;
5552 dirty_card_queue_set().set_closure(&redirty);
5553 dirty_card_queue_set().apply_closure_to_all_completed_buffers();
5555 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5556 dcq.merge_bufferlists(&dirty_card_queue_set());
5557 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5558 }
5559 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5560 }
5562 void G1CollectedHeap::free_region_if_empty(HeapRegion* hr,
5563 size_t* pre_used,
5564 FreeRegionList* free_list,
5565 OldRegionSet* old_proxy_set,
5566 HumongousRegionSet* humongous_proxy_set,
5567 HRRSCleanupTask* hrrs_cleanup_task,
5568 bool par) {
5569 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) {
5570 if (hr->isHumongous()) {
5571 assert(hr->startsHumongous(), "we should only see starts humongous");
5572 free_humongous_region(hr, pre_used, free_list, humongous_proxy_set, par);
5573 } else {
5574 _old_set.remove_with_proxy(hr, old_proxy_set);
5575 free_region(hr, pre_used, free_list, par);
5576 }
5577 } else {
5578 hr->rem_set()->do_cleanup_work(hrrs_cleanup_task);
5579 }
5580 }
5582 void G1CollectedHeap::free_region(HeapRegion* hr,
5583 size_t* pre_used,
5584 FreeRegionList* free_list,
5585 bool par) {
5586 assert(!hr->isHumongous(), "this is only for non-humongous regions");
5587 assert(!hr->is_empty(), "the region should not be empty");
5588 assert(free_list != NULL, "pre-condition");
5590 *pre_used += hr->used();
5591 hr->hr_clear(par, true /* clear_space */);
5592 free_list->add_as_head(hr);
5593 }
5595 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
5596 size_t* pre_used,
5597 FreeRegionList* free_list,
5598 HumongousRegionSet* humongous_proxy_set,
5599 bool par) {
5600 assert(hr->startsHumongous(), "this is only for starts humongous regions");
5601 assert(free_list != NULL, "pre-condition");
5602 assert(humongous_proxy_set != NULL, "pre-condition");
5604 size_t hr_used = hr->used();
5605 size_t hr_capacity = hr->capacity();
5606 size_t hr_pre_used = 0;
5607 _humongous_set.remove_with_proxy(hr, humongous_proxy_set);
5608 hr->set_notHumongous();
5609 free_region(hr, &hr_pre_used, free_list, par);
5611 uint i = hr->hrs_index() + 1;
5612 uint num = 1;
5613 while (i < n_regions()) {
5614 HeapRegion* curr_hr = region_at(i);
5615 if (!curr_hr->continuesHumongous()) {
5616 break;
5617 }
5618 curr_hr->set_notHumongous();
5619 free_region(curr_hr, &hr_pre_used, free_list, par);
5620 num += 1;
5621 i += 1;
5622 }
5623 assert(hr_pre_used == hr_used,
5624 err_msg("hr_pre_used: "SIZE_FORMAT" and hr_used: "SIZE_FORMAT" "
5625 "should be the same", hr_pre_used, hr_used));
5626 *pre_used += hr_pre_used;
5627 }
5629 void G1CollectedHeap::update_sets_after_freeing_regions(size_t pre_used,
5630 FreeRegionList* free_list,
5631 OldRegionSet* old_proxy_set,
5632 HumongousRegionSet* humongous_proxy_set,
5633 bool par) {
5634 if (pre_used > 0) {
5635 Mutex* lock = (par) ? ParGCRareEvent_lock : NULL;
5636 MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag);
5637 assert(_summary_bytes_used >= pre_used,
5638 err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" "
5639 "should be >= pre_used: "SIZE_FORMAT,
5640 _summary_bytes_used, pre_used));
5641 _summary_bytes_used -= pre_used;
5642 }
5643 if (free_list != NULL && !free_list->is_empty()) {
5644 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
5645 _free_list.add_as_head(free_list);
5646 }
5647 if (old_proxy_set != NULL && !old_proxy_set->is_empty()) {
5648 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5649 _old_set.update_from_proxy(old_proxy_set);
5650 }
5651 if (humongous_proxy_set != NULL && !humongous_proxy_set->is_empty()) {
5652 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5653 _humongous_set.update_from_proxy(humongous_proxy_set);
5654 }
5655 }
5657 class G1ParCleanupCTTask : public AbstractGangTask {
5658 CardTableModRefBS* _ct_bs;
5659 G1CollectedHeap* _g1h;
5660 HeapRegion* volatile _su_head;
5661 public:
5662 G1ParCleanupCTTask(CardTableModRefBS* ct_bs,
5663 G1CollectedHeap* g1h) :
5664 AbstractGangTask("G1 Par Cleanup CT Task"),
5665 _ct_bs(ct_bs), _g1h(g1h) { }
5667 void work(uint worker_id) {
5668 HeapRegion* r;
5669 while (r = _g1h->pop_dirty_cards_region()) {
5670 clear_cards(r);
5671 }
5672 }
5674 void clear_cards(HeapRegion* r) {
5675 // Cards of the survivors should have already been dirtied.
5676 if (!r->is_survivor()) {
5677 _ct_bs->clear(MemRegion(r->bottom(), r->end()));
5678 }
5679 }
5680 };
5682 #ifndef PRODUCT
5683 class G1VerifyCardTableCleanup: public HeapRegionClosure {
5684 G1CollectedHeap* _g1h;
5685 CardTableModRefBS* _ct_bs;
5686 public:
5687 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, CardTableModRefBS* ct_bs)
5688 : _g1h(g1h), _ct_bs(ct_bs) { }
5689 virtual bool doHeapRegion(HeapRegion* r) {
5690 if (r->is_survivor()) {
5691 _g1h->verify_dirty_region(r);
5692 } else {
5693 _g1h->verify_not_dirty_region(r);
5694 }
5695 return false;
5696 }
5697 };
5699 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
5700 // All of the region should be clean.
5701 CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
5702 MemRegion mr(hr->bottom(), hr->end());
5703 ct_bs->verify_not_dirty_region(mr);
5704 }
5706 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
5707 // We cannot guarantee that [bottom(),end()] is dirty. Threads
5708 // dirty allocated blocks as they allocate them. The thread that
5709 // retires each region and replaces it with a new one will do a
5710 // maximal allocation to fill in [pre_dummy_top(),end()] but will
5711 // not dirty that area (one less thing to have to do while holding
5712 // a lock). So we can only verify that [bottom(),pre_dummy_top()]
5713 // is dirty.
5714 CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set();
5715 MemRegion mr(hr->bottom(), hr->pre_dummy_top());
5716 ct_bs->verify_dirty_region(mr);
5717 }
5719 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
5720 CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set();
5721 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
5722 verify_dirty_region(hr);
5723 }
5724 }
5726 void G1CollectedHeap::verify_dirty_young_regions() {
5727 verify_dirty_young_list(_young_list->first_region());
5728 verify_dirty_young_list(_young_list->first_survivor_region());
5729 }
5730 #endif
5732 void G1CollectedHeap::cleanUpCardTable() {
5733 CardTableModRefBS* ct_bs = (CardTableModRefBS*) (barrier_set());
5734 double start = os::elapsedTime();
5736 {
5737 // Iterate over the dirty cards region list.
5738 G1ParCleanupCTTask cleanup_task(ct_bs, this);
5740 if (G1CollectedHeap::use_parallel_gc_threads()) {
5741 set_par_threads();
5742 workers()->run_task(&cleanup_task);
5743 set_par_threads(0);
5744 } else {
5745 while (_dirty_cards_region_list) {
5746 HeapRegion* r = _dirty_cards_region_list;
5747 cleanup_task.clear_cards(r);
5748 _dirty_cards_region_list = r->get_next_dirty_cards_region();
5749 if (_dirty_cards_region_list == r) {
5750 // The last region.
5751 _dirty_cards_region_list = NULL;
5752 }
5753 r->set_next_dirty_cards_region(NULL);
5754 }
5755 }
5756 #ifndef PRODUCT
5757 if (G1VerifyCTCleanup || VerifyAfterGC) {
5758 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
5759 heap_region_iterate(&cleanup_verifier);
5760 }
5761 #endif
5762 }
5764 double elapsed = os::elapsedTime() - start;
5765 g1_policy()->record_clear_ct_time(elapsed * 1000.0);
5766 }
5768 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head) {
5769 size_t pre_used = 0;
5770 FreeRegionList local_free_list("Local List for CSet Freeing");
5772 double young_time_ms = 0.0;
5773 double non_young_time_ms = 0.0;
5775 // Since the collection set is a superset of the the young list,
5776 // all we need to do to clear the young list is clear its
5777 // head and length, and unlink any young regions in the code below
5778 _young_list->clear();
5780 G1CollectorPolicy* policy = g1_policy();
5782 double start_sec = os::elapsedTime();
5783 bool non_young = true;
5785 HeapRegion* cur = cs_head;
5786 int age_bound = -1;
5787 size_t rs_lengths = 0;
5789 while (cur != NULL) {
5790 assert(!is_on_master_free_list(cur), "sanity");
5791 if (non_young) {
5792 if (cur->is_young()) {
5793 double end_sec = os::elapsedTime();
5794 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5795 non_young_time_ms += elapsed_ms;
5797 start_sec = os::elapsedTime();
5798 non_young = false;
5799 }
5800 } else {
5801 if (!cur->is_young()) {
5802 double end_sec = os::elapsedTime();
5803 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5804 young_time_ms += elapsed_ms;
5806 start_sec = os::elapsedTime();
5807 non_young = true;
5808 }
5809 }
5811 rs_lengths += cur->rem_set()->occupied();
5813 HeapRegion* next = cur->next_in_collection_set();
5814 assert(cur->in_collection_set(), "bad CS");
5815 cur->set_next_in_collection_set(NULL);
5816 cur->set_in_collection_set(false);
5818 if (cur->is_young()) {
5819 int index = cur->young_index_in_cset();
5820 assert(index != -1, "invariant");
5821 assert((uint) index < policy->young_cset_region_length(), "invariant");
5822 size_t words_survived = _surviving_young_words[index];
5823 cur->record_surv_words_in_group(words_survived);
5825 // At this point the we have 'popped' cur from the collection set
5826 // (linked via next_in_collection_set()) but it is still in the
5827 // young list (linked via next_young_region()). Clear the
5828 // _next_young_region field.
5829 cur->set_next_young_region(NULL);
5830 } else {
5831 int index = cur->young_index_in_cset();
5832 assert(index == -1, "invariant");
5833 }
5835 assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
5836 (!cur->is_young() && cur->young_index_in_cset() == -1),
5837 "invariant" );
5839 if (!cur->evacuation_failed()) {
5840 MemRegion used_mr = cur->used_region();
5842 // And the region is empty.
5843 assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
5844 free_region(cur, &pre_used, &local_free_list, false /* par */);
5845 } else {
5846 cur->uninstall_surv_rate_group();
5847 if (cur->is_young()) {
5848 cur->set_young_index_in_cset(-1);
5849 }
5850 cur->set_not_young();
5851 cur->set_evacuation_failed(false);
5852 // The region is now considered to be old.
5853 _old_set.add(cur);
5854 }
5855 cur = next;
5856 }
5858 policy->record_max_rs_lengths(rs_lengths);
5859 policy->cset_regions_freed();
5861 double end_sec = os::elapsedTime();
5862 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5864 if (non_young) {
5865 non_young_time_ms += elapsed_ms;
5866 } else {
5867 young_time_ms += elapsed_ms;
5868 }
5870 update_sets_after_freeing_regions(pre_used, &local_free_list,
5871 NULL /* old_proxy_set */,
5872 NULL /* humongous_proxy_set */,
5873 false /* par */);
5874 policy->record_young_free_cset_time_ms(young_time_ms);
5875 policy->record_non_young_free_cset_time_ms(non_young_time_ms);
5876 }
5878 // This routine is similar to the above but does not record
5879 // any policy statistics or update free lists; we are abandoning
5880 // the current incremental collection set in preparation of a
5881 // full collection. After the full GC we will start to build up
5882 // the incremental collection set again.
5883 // This is only called when we're doing a full collection
5884 // and is immediately followed by the tearing down of the young list.
5886 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
5887 HeapRegion* cur = cs_head;
5889 while (cur != NULL) {
5890 HeapRegion* next = cur->next_in_collection_set();
5891 assert(cur->in_collection_set(), "bad CS");
5892 cur->set_next_in_collection_set(NULL);
5893 cur->set_in_collection_set(false);
5894 cur->set_young_index_in_cset(-1);
5895 cur = next;
5896 }
5897 }
5899 void G1CollectedHeap::set_free_regions_coming() {
5900 if (G1ConcRegionFreeingVerbose) {
5901 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
5902 "setting free regions coming");
5903 }
5905 assert(!free_regions_coming(), "pre-condition");
5906 _free_regions_coming = true;
5907 }
5909 void G1CollectedHeap::reset_free_regions_coming() {
5910 assert(free_regions_coming(), "pre-condition");
5912 {
5913 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5914 _free_regions_coming = false;
5915 SecondaryFreeList_lock->notify_all();
5916 }
5918 if (G1ConcRegionFreeingVerbose) {
5919 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
5920 "reset free regions coming");
5921 }
5922 }
5924 void G1CollectedHeap::wait_while_free_regions_coming() {
5925 // Most of the time we won't have to wait, so let's do a quick test
5926 // first before we take the lock.
5927 if (!free_regions_coming()) {
5928 return;
5929 }
5931 if (G1ConcRegionFreeingVerbose) {
5932 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
5933 "waiting for free regions");
5934 }
5936 {
5937 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5938 while (free_regions_coming()) {
5939 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
5940 }
5941 }
5943 if (G1ConcRegionFreeingVerbose) {
5944 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
5945 "done waiting for free regions");
5946 }
5947 }
5949 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
5950 assert(heap_lock_held_for_gc(),
5951 "the heap lock should already be held by or for this thread");
5952 _young_list->push_region(hr);
5953 }
5955 class NoYoungRegionsClosure: public HeapRegionClosure {
5956 private:
5957 bool _success;
5958 public:
5959 NoYoungRegionsClosure() : _success(true) { }
5960 bool doHeapRegion(HeapRegion* r) {
5961 if (r->is_young()) {
5962 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
5963 r->bottom(), r->end());
5964 _success = false;
5965 }
5966 return false;
5967 }
5968 bool success() { return _success; }
5969 };
5971 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
5972 bool ret = _young_list->check_list_empty(check_sample);
5974 if (check_heap) {
5975 NoYoungRegionsClosure closure;
5976 heap_region_iterate(&closure);
5977 ret = ret && closure.success();
5978 }
5980 return ret;
5981 }
5983 class TearDownRegionSetsClosure : public HeapRegionClosure {
5984 private:
5985 OldRegionSet *_old_set;
5987 public:
5988 TearDownRegionSetsClosure(OldRegionSet* old_set) : _old_set(old_set) { }
5990 bool doHeapRegion(HeapRegion* r) {
5991 if (r->is_empty()) {
5992 // We ignore empty regions, we'll empty the free list afterwards
5993 } else if (r->is_young()) {
5994 // We ignore young regions, we'll empty the young list afterwards
5995 } else if (r->isHumongous()) {
5996 // We ignore humongous regions, we're not tearing down the
5997 // humongous region set
5998 } else {
5999 // The rest should be old
6000 _old_set->remove(r);
6001 }
6002 return false;
6003 }
6005 ~TearDownRegionSetsClosure() {
6006 assert(_old_set->is_empty(), "post-condition");
6007 }
6008 };
6010 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6011 assert_at_safepoint(true /* should_be_vm_thread */);
6013 if (!free_list_only) {
6014 TearDownRegionSetsClosure cl(&_old_set);
6015 heap_region_iterate(&cl);
6017 // Need to do this after the heap iteration to be able to
6018 // recognize the young regions and ignore them during the iteration.
6019 _young_list->empty_list();
6020 }
6021 _free_list.remove_all();
6022 }
6024 class RebuildRegionSetsClosure : public HeapRegionClosure {
6025 private:
6026 bool _free_list_only;
6027 OldRegionSet* _old_set;
6028 FreeRegionList* _free_list;
6029 size_t _total_used;
6031 public:
6032 RebuildRegionSetsClosure(bool free_list_only,
6033 OldRegionSet* old_set, FreeRegionList* free_list) :
6034 _free_list_only(free_list_only),
6035 _old_set(old_set), _free_list(free_list), _total_used(0) {
6036 assert(_free_list->is_empty(), "pre-condition");
6037 if (!free_list_only) {
6038 assert(_old_set->is_empty(), "pre-condition");
6039 }
6040 }
6042 bool doHeapRegion(HeapRegion* r) {
6043 if (r->continuesHumongous()) {
6044 return false;
6045 }
6047 if (r->is_empty()) {
6048 // Add free regions to the free list
6049 _free_list->add_as_tail(r);
6050 } else if (!_free_list_only) {
6051 assert(!r->is_young(), "we should not come across young regions");
6053 if (r->isHumongous()) {
6054 // We ignore humongous regions, we left the humongous set unchanged
6055 } else {
6056 // The rest should be old, add them to the old set
6057 _old_set->add(r);
6058 }
6059 _total_used += r->used();
6060 }
6062 return false;
6063 }
6065 size_t total_used() {
6066 return _total_used;
6067 }
6068 };
6070 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6071 assert_at_safepoint(true /* should_be_vm_thread */);
6073 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_free_list);
6074 heap_region_iterate(&cl);
6076 if (!free_list_only) {
6077 _summary_bytes_used = cl.total_used();
6078 }
6079 assert(_summary_bytes_used == recalculate_used(),
6080 err_msg("inconsistent _summary_bytes_used, "
6081 "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6082 _summary_bytes_used, recalculate_used()));
6083 }
6085 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6086 _refine_cte_cl->set_concurrent(concurrent);
6087 }
6089 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6090 HeapRegion* hr = heap_region_containing(p);
6091 if (hr == NULL) {
6092 return is_in_permanent(p);
6093 } else {
6094 return hr->is_in(p);
6095 }
6096 }
6098 // Methods for the mutator alloc region
6100 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6101 bool force) {
6102 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6103 assert(!force || g1_policy()->can_expand_young_list(),
6104 "if force is true we should be able to expand the young list");
6105 bool young_list_full = g1_policy()->is_young_list_full();
6106 if (force || !young_list_full) {
6107 HeapRegion* new_alloc_region = new_region(word_size,
6108 false /* do_expand */);
6109 if (new_alloc_region != NULL) {
6110 set_region_short_lived_locked(new_alloc_region);
6111 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6112 return new_alloc_region;
6113 }
6114 }
6115 return NULL;
6116 }
6118 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6119 size_t allocated_bytes) {
6120 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6121 assert(alloc_region->is_young(), "all mutator alloc regions should be young");
6123 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6124 _summary_bytes_used += allocated_bytes;
6125 _hr_printer.retire(alloc_region);
6126 // We update the eden sizes here, when the region is retired,
6127 // instead of when it's allocated, since this is the point that its
6128 // used space has been recored in _summary_bytes_used.
6129 g1mm()->update_eden_size();
6130 }
6132 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
6133 bool force) {
6134 return _g1h->new_mutator_alloc_region(word_size, force);
6135 }
6137 void G1CollectedHeap::set_par_threads() {
6138 // Don't change the number of workers. Use the value previously set
6139 // in the workgroup.
6140 assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise");
6141 uint n_workers = workers()->active_workers();
6142 assert(UseDynamicNumberOfGCThreads ||
6143 n_workers == workers()->total_workers(),
6144 "Otherwise should be using the total number of workers");
6145 if (n_workers == 0) {
6146 assert(false, "Should have been set in prior evacuation pause.");
6147 n_workers = ParallelGCThreads;
6148 workers()->set_active_workers(n_workers);
6149 }
6150 set_par_threads(n_workers);
6151 }
6153 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
6154 size_t allocated_bytes) {
6155 _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
6156 }
6158 // Methods for the GC alloc regions
6160 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6161 uint count,
6162 GCAllocPurpose ap) {
6163 assert(FreeList_lock->owned_by_self(), "pre-condition");
6165 if (count < g1_policy()->max_regions(ap)) {
6166 HeapRegion* new_alloc_region = new_region(word_size,
6167 true /* do_expand */);
6168 if (new_alloc_region != NULL) {
6169 // We really only need to do this for old regions given that we
6170 // should never scan survivors. But it doesn't hurt to do it
6171 // for survivors too.
6172 new_alloc_region->set_saved_mark();
6173 if (ap == GCAllocForSurvived) {
6174 new_alloc_region->set_survivor();
6175 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6176 } else {
6177 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6178 }
6179 bool during_im = g1_policy()->during_initial_mark_pause();
6180 new_alloc_region->note_start_of_copying(during_im);
6181 return new_alloc_region;
6182 } else {
6183 g1_policy()->note_alloc_region_limit_reached(ap);
6184 }
6185 }
6186 return NULL;
6187 }
6189 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6190 size_t allocated_bytes,
6191 GCAllocPurpose ap) {
6192 bool during_im = g1_policy()->during_initial_mark_pause();
6193 alloc_region->note_end_of_copying(during_im);
6194 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6195 if (ap == GCAllocForSurvived) {
6196 young_list()->add_survivor_region(alloc_region);
6197 } else {
6198 _old_set.add(alloc_region);
6199 }
6200 _hr_printer.retire(alloc_region);
6201 }
6203 HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size,
6204 bool force) {
6205 assert(!force, "not supported for GC alloc regions");
6206 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForSurvived);
6207 }
6209 void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region,
6210 size_t allocated_bytes) {
6211 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6212 GCAllocForSurvived);
6213 }
6215 HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size,
6216 bool force) {
6217 assert(!force, "not supported for GC alloc regions");
6218 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForTenured);
6219 }
6221 void OldGCAllocRegion::retire_region(HeapRegion* alloc_region,
6222 size_t allocated_bytes) {
6223 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6224 GCAllocForTenured);
6225 }
6226 // Heap region set verification
6228 class VerifyRegionListsClosure : public HeapRegionClosure {
6229 private:
6230 FreeRegionList* _free_list;
6231 OldRegionSet* _old_set;
6232 HumongousRegionSet* _humongous_set;
6233 uint _region_count;
6235 public:
6236 VerifyRegionListsClosure(OldRegionSet* old_set,
6237 HumongousRegionSet* humongous_set,
6238 FreeRegionList* free_list) :
6239 _old_set(old_set), _humongous_set(humongous_set),
6240 _free_list(free_list), _region_count(0) { }
6242 uint region_count() { return _region_count; }
6244 bool doHeapRegion(HeapRegion* hr) {
6245 _region_count += 1;
6247 if (hr->continuesHumongous()) {
6248 return false;
6249 }
6251 if (hr->is_young()) {
6252 // TODO
6253 } else if (hr->startsHumongous()) {
6254 _humongous_set->verify_next_region(hr);
6255 } else if (hr->is_empty()) {
6256 _free_list->verify_next_region(hr);
6257 } else {
6258 _old_set->verify_next_region(hr);
6259 }
6260 return false;
6261 }
6262 };
6264 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
6265 HeapWord* bottom) {
6266 HeapWord* end = bottom + HeapRegion::GrainWords;
6267 MemRegion mr(bottom, end);
6268 assert(_g1_reserved.contains(mr), "invariant");
6269 // This might return NULL if the allocation fails
6270 return new HeapRegion(hrs_index, _bot_shared, mr, true /* is_zeroed */);
6271 }
6273 void G1CollectedHeap::verify_region_sets() {
6274 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6276 // First, check the explicit lists.
6277 _free_list.verify();
6278 {
6279 // Given that a concurrent operation might be adding regions to
6280 // the secondary free list we have to take the lock before
6281 // verifying it.
6282 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6283 _secondary_free_list.verify();
6284 }
6285 _old_set.verify();
6286 _humongous_set.verify();
6288 // If a concurrent region freeing operation is in progress it will
6289 // be difficult to correctly attributed any free regions we come
6290 // across to the correct free list given that they might belong to
6291 // one of several (free_list, secondary_free_list, any local lists,
6292 // etc.). So, if that's the case we will skip the rest of the
6293 // verification operation. Alternatively, waiting for the concurrent
6294 // operation to complete will have a non-trivial effect on the GC's
6295 // operation (no concurrent operation will last longer than the
6296 // interval between two calls to verification) and it might hide
6297 // any issues that we would like to catch during testing.
6298 if (free_regions_coming()) {
6299 return;
6300 }
6302 // Make sure we append the secondary_free_list on the free_list so
6303 // that all free regions we will come across can be safely
6304 // attributed to the free_list.
6305 append_secondary_free_list_if_not_empty_with_lock();
6307 // Finally, make sure that the region accounting in the lists is
6308 // consistent with what we see in the heap.
6309 _old_set.verify_start();
6310 _humongous_set.verify_start();
6311 _free_list.verify_start();
6313 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_free_list);
6314 heap_region_iterate(&cl);
6316 _old_set.verify_end();
6317 _humongous_set.verify_end();
6318 _free_list.verify_end();
6319 }