Mon, 23 Jun 2014 16:43:41 +0200
8046231: G1: Code root location ... from nmethod ... not in strong code roots for region
Reviewed-by: tschatzl, ehelin
1 /*
2 * Copyright (c) 2001, 2014, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
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23 */
25 #if !defined(__clang_major__) && defined(__GNUC__)
26 #define ATTRIBUTE_PRINTF(x,y) // FIXME, formats are a mess.
27 #endif
29 #include "precompiled.hpp"
30 #include "code/codeCache.hpp"
31 #include "code/icBuffer.hpp"
32 #include "gc_implementation/g1/bufferingOopClosure.hpp"
33 #include "gc_implementation/g1/concurrentG1Refine.hpp"
34 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
35 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
36 #include "gc_implementation/g1/g1AllocRegion.inline.hpp"
37 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
38 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
39 #include "gc_implementation/g1/g1ErgoVerbose.hpp"
40 #include "gc_implementation/g1/g1EvacFailure.hpp"
41 #include "gc_implementation/g1/g1GCPhaseTimes.hpp"
42 #include "gc_implementation/g1/g1Log.hpp"
43 #include "gc_implementation/g1/g1MarkSweep.hpp"
44 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
45 #include "gc_implementation/g1/g1RemSet.inline.hpp"
46 #include "gc_implementation/g1/g1StringDedup.hpp"
47 #include "gc_implementation/g1/g1YCTypes.hpp"
48 #include "gc_implementation/g1/heapRegion.inline.hpp"
49 #include "gc_implementation/g1/heapRegionRemSet.hpp"
50 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
51 #include "gc_implementation/g1/vm_operations_g1.hpp"
52 #include "gc_implementation/shared/gcHeapSummary.hpp"
53 #include "gc_implementation/shared/gcTimer.hpp"
54 #include "gc_implementation/shared/gcTrace.hpp"
55 #include "gc_implementation/shared/gcTraceTime.hpp"
56 #include "gc_implementation/shared/isGCActiveMark.hpp"
57 #include "memory/gcLocker.inline.hpp"
58 #include "memory/generationSpec.hpp"
59 #include "memory/iterator.hpp"
60 #include "memory/referenceProcessor.hpp"
61 #include "oops/oop.inline.hpp"
62 #include "oops/oop.pcgc.inline.hpp"
63 #include "runtime/vmThread.hpp"
64 #include "utilities/ticks.hpp"
66 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
68 // turn it on so that the contents of the young list (scan-only /
69 // to-be-collected) are printed at "strategic" points before / during
70 // / after the collection --- this is useful for debugging
71 #define YOUNG_LIST_VERBOSE 0
72 // CURRENT STATUS
73 // This file is under construction. Search for "FIXME".
75 // INVARIANTS/NOTES
76 //
77 // All allocation activity covered by the G1CollectedHeap interface is
78 // serialized by acquiring the HeapLock. This happens in mem_allocate
79 // and allocate_new_tlab, which are the "entry" points to the
80 // allocation code from the rest of the JVM. (Note that this does not
81 // apply to TLAB allocation, which is not part of this interface: it
82 // is done by clients of this interface.)
84 // Notes on implementation of parallelism in different tasks.
85 //
86 // G1ParVerifyTask uses heap_region_par_iterate_chunked() for parallelism.
87 // The number of GC workers is passed to heap_region_par_iterate_chunked().
88 // It does use run_task() which sets _n_workers in the task.
89 // G1ParTask executes g1_process_strong_roots() ->
90 // SharedHeap::process_strong_roots() which calls eventually to
91 // CardTableModRefBS::par_non_clean_card_iterate_work() which uses
92 // SequentialSubTasksDone. SharedHeap::process_strong_roots() also
93 // directly uses SubTasksDone (_process_strong_tasks field in SharedHeap).
94 //
96 // Local to this file.
98 class RefineCardTableEntryClosure: public CardTableEntryClosure {
99 SuspendibleThreadSet* _sts;
100 G1RemSet* _g1rs;
101 ConcurrentG1Refine* _cg1r;
102 bool _concurrent;
103 public:
104 RefineCardTableEntryClosure(SuspendibleThreadSet* sts,
105 G1RemSet* g1rs,
106 ConcurrentG1Refine* cg1r) :
107 _sts(sts), _g1rs(g1rs), _cg1r(cg1r), _concurrent(true)
108 {}
109 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
110 bool oops_into_cset = _g1rs->refine_card(card_ptr, worker_i, false);
111 // This path is executed by the concurrent refine or mutator threads,
112 // concurrently, and so we do not care if card_ptr contains references
113 // that point into the collection set.
114 assert(!oops_into_cset, "should be");
116 if (_concurrent && _sts->should_yield()) {
117 // Caller will actually yield.
118 return false;
119 }
120 // Otherwise, we finished successfully; return true.
121 return true;
122 }
123 void set_concurrent(bool b) { _concurrent = b; }
124 };
127 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure {
128 int _calls;
129 G1CollectedHeap* _g1h;
130 CardTableModRefBS* _ctbs;
131 int _histo[256];
132 public:
133 ClearLoggedCardTableEntryClosure() :
134 _calls(0), _g1h(G1CollectedHeap::heap()), _ctbs(_g1h->g1_barrier_set())
135 {
136 for (int i = 0; i < 256; i++) _histo[i] = 0;
137 }
138 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
139 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
140 _calls++;
141 unsigned char* ujb = (unsigned char*)card_ptr;
142 int ind = (int)(*ujb);
143 _histo[ind]++;
144 *card_ptr = -1;
145 }
146 return true;
147 }
148 int calls() { return _calls; }
149 void print_histo() {
150 gclog_or_tty->print_cr("Card table value histogram:");
151 for (int i = 0; i < 256; i++) {
152 if (_histo[i] != 0) {
153 gclog_or_tty->print_cr(" %d: %d", i, _histo[i]);
154 }
155 }
156 }
157 };
159 class RedirtyLoggedCardTableEntryClosure: public CardTableEntryClosure {
160 int _calls;
161 G1CollectedHeap* _g1h;
162 CardTableModRefBS* _ctbs;
163 public:
164 RedirtyLoggedCardTableEntryClosure() :
165 _calls(0), _g1h(G1CollectedHeap::heap()), _ctbs(_g1h->g1_barrier_set()) {}
167 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
168 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
169 _calls++;
170 *card_ptr = 0;
171 }
172 return true;
173 }
174 int calls() { return _calls; }
175 };
177 YoungList::YoungList(G1CollectedHeap* g1h) :
178 _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0),
179 _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) {
180 guarantee(check_list_empty(false), "just making sure...");
181 }
183 void YoungList::push_region(HeapRegion *hr) {
184 assert(!hr->is_young(), "should not already be young");
185 assert(hr->get_next_young_region() == NULL, "cause it should!");
187 hr->set_next_young_region(_head);
188 _head = hr;
190 _g1h->g1_policy()->set_region_eden(hr, (int) _length);
191 ++_length;
192 }
194 void YoungList::add_survivor_region(HeapRegion* hr) {
195 assert(hr->is_survivor(), "should be flagged as survivor region");
196 assert(hr->get_next_young_region() == NULL, "cause it should!");
198 hr->set_next_young_region(_survivor_head);
199 if (_survivor_head == NULL) {
200 _survivor_tail = hr;
201 }
202 _survivor_head = hr;
203 ++_survivor_length;
204 }
206 void YoungList::empty_list(HeapRegion* list) {
207 while (list != NULL) {
208 HeapRegion* next = list->get_next_young_region();
209 list->set_next_young_region(NULL);
210 list->uninstall_surv_rate_group();
211 list->set_not_young();
212 list = next;
213 }
214 }
216 void YoungList::empty_list() {
217 assert(check_list_well_formed(), "young list should be well formed");
219 empty_list(_head);
220 _head = NULL;
221 _length = 0;
223 empty_list(_survivor_head);
224 _survivor_head = NULL;
225 _survivor_tail = NULL;
226 _survivor_length = 0;
228 _last_sampled_rs_lengths = 0;
230 assert(check_list_empty(false), "just making sure...");
231 }
233 bool YoungList::check_list_well_formed() {
234 bool ret = true;
236 uint length = 0;
237 HeapRegion* curr = _head;
238 HeapRegion* last = NULL;
239 while (curr != NULL) {
240 if (!curr->is_young()) {
241 gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
242 "incorrectly tagged (y: %d, surv: %d)",
243 curr->bottom(), curr->end(),
244 curr->is_young(), curr->is_survivor());
245 ret = false;
246 }
247 ++length;
248 last = curr;
249 curr = curr->get_next_young_region();
250 }
251 ret = ret && (length == _length);
253 if (!ret) {
254 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
255 gclog_or_tty->print_cr("### list has %u entries, _length is %u",
256 length, _length);
257 }
259 return ret;
260 }
262 bool YoungList::check_list_empty(bool check_sample) {
263 bool ret = true;
265 if (_length != 0) {
266 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u",
267 _length);
268 ret = false;
269 }
270 if (check_sample && _last_sampled_rs_lengths != 0) {
271 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
272 ret = false;
273 }
274 if (_head != NULL) {
275 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
276 ret = false;
277 }
278 if (!ret) {
279 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
280 }
282 return ret;
283 }
285 void
286 YoungList::rs_length_sampling_init() {
287 _sampled_rs_lengths = 0;
288 _curr = _head;
289 }
291 bool
292 YoungList::rs_length_sampling_more() {
293 return _curr != NULL;
294 }
296 void
297 YoungList::rs_length_sampling_next() {
298 assert( _curr != NULL, "invariant" );
299 size_t rs_length = _curr->rem_set()->occupied();
301 _sampled_rs_lengths += rs_length;
303 // The current region may not yet have been added to the
304 // incremental collection set (it gets added when it is
305 // retired as the current allocation region).
306 if (_curr->in_collection_set()) {
307 // Update the collection set policy information for this region
308 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
309 }
311 _curr = _curr->get_next_young_region();
312 if (_curr == NULL) {
313 _last_sampled_rs_lengths = _sampled_rs_lengths;
314 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
315 }
316 }
318 void
319 YoungList::reset_auxilary_lists() {
320 guarantee( is_empty(), "young list should be empty" );
321 assert(check_list_well_formed(), "young list should be well formed");
323 // Add survivor regions to SurvRateGroup.
324 _g1h->g1_policy()->note_start_adding_survivor_regions();
325 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
327 int young_index_in_cset = 0;
328 for (HeapRegion* curr = _survivor_head;
329 curr != NULL;
330 curr = curr->get_next_young_region()) {
331 _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
333 // The region is a non-empty survivor so let's add it to
334 // the incremental collection set for the next evacuation
335 // pause.
336 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
337 young_index_in_cset += 1;
338 }
339 assert((uint) young_index_in_cset == _survivor_length, "post-condition");
340 _g1h->g1_policy()->note_stop_adding_survivor_regions();
342 _head = _survivor_head;
343 _length = _survivor_length;
344 if (_survivor_head != NULL) {
345 assert(_survivor_tail != NULL, "cause it shouldn't be");
346 assert(_survivor_length > 0, "invariant");
347 _survivor_tail->set_next_young_region(NULL);
348 }
350 // Don't clear the survivor list handles until the start of
351 // the next evacuation pause - we need it in order to re-tag
352 // the survivor regions from this evacuation pause as 'young'
353 // at the start of the next.
355 _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
357 assert(check_list_well_formed(), "young list should be well formed");
358 }
360 void YoungList::print() {
361 HeapRegion* lists[] = {_head, _survivor_head};
362 const char* names[] = {"YOUNG", "SURVIVOR"};
364 for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) {
365 gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
366 HeapRegion *curr = lists[list];
367 if (curr == NULL)
368 gclog_or_tty->print_cr(" empty");
369 while (curr != NULL) {
370 gclog_or_tty->print_cr(" "HR_FORMAT", P: "PTR_FORMAT "N: "PTR_FORMAT", age: %4d",
371 HR_FORMAT_PARAMS(curr),
372 curr->prev_top_at_mark_start(),
373 curr->next_top_at_mark_start(),
374 curr->age_in_surv_rate_group_cond());
375 curr = curr->get_next_young_region();
376 }
377 }
379 gclog_or_tty->cr();
380 }
382 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
383 {
384 // Claim the right to put the region on the dirty cards region list
385 // by installing a self pointer.
386 HeapRegion* next = hr->get_next_dirty_cards_region();
387 if (next == NULL) {
388 HeapRegion* res = (HeapRegion*)
389 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
390 NULL);
391 if (res == NULL) {
392 HeapRegion* head;
393 do {
394 // Put the region to the dirty cards region list.
395 head = _dirty_cards_region_list;
396 next = (HeapRegion*)
397 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
398 if (next == head) {
399 assert(hr->get_next_dirty_cards_region() == hr,
400 "hr->get_next_dirty_cards_region() != hr");
401 if (next == NULL) {
402 // The last region in the list points to itself.
403 hr->set_next_dirty_cards_region(hr);
404 } else {
405 hr->set_next_dirty_cards_region(next);
406 }
407 }
408 } while (next != head);
409 }
410 }
411 }
413 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
414 {
415 HeapRegion* head;
416 HeapRegion* hr;
417 do {
418 head = _dirty_cards_region_list;
419 if (head == NULL) {
420 return NULL;
421 }
422 HeapRegion* new_head = head->get_next_dirty_cards_region();
423 if (head == new_head) {
424 // The last region.
425 new_head = NULL;
426 }
427 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
428 head);
429 } while (hr != head);
430 assert(hr != NULL, "invariant");
431 hr->set_next_dirty_cards_region(NULL);
432 return hr;
433 }
435 #ifdef ASSERT
436 // A region is added to the collection set as it is retired
437 // so an address p can point to a region which will be in the
438 // collection set but has not yet been retired. This method
439 // therefore is only accurate during a GC pause after all
440 // regions have been retired. It is used for debugging
441 // to check if an nmethod has references to objects that can
442 // be move during a partial collection. Though it can be
443 // inaccurate, it is sufficient for G1 because the conservative
444 // implementation of is_scavengable() for G1 will indicate that
445 // all nmethods must be scanned during a partial collection.
446 bool G1CollectedHeap::is_in_partial_collection(const void* p) {
447 HeapRegion* hr = heap_region_containing(p);
448 return hr != NULL && hr->in_collection_set();
449 }
450 #endif
452 // Returns true if the reference points to an object that
453 // can move in an incremental collection.
454 bool G1CollectedHeap::is_scavengable(const void* p) {
455 G1CollectedHeap* g1h = G1CollectedHeap::heap();
456 G1CollectorPolicy* g1p = g1h->g1_policy();
457 HeapRegion* hr = heap_region_containing(p);
458 if (hr == NULL) {
459 // null
460 assert(p == NULL, err_msg("Not NULL " PTR_FORMAT ,p));
461 return false;
462 } else {
463 return !hr->isHumongous();
464 }
465 }
467 void G1CollectedHeap::check_ct_logs_at_safepoint() {
468 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
469 CardTableModRefBS* ct_bs = g1_barrier_set();
471 // Count the dirty cards at the start.
472 CountNonCleanMemRegionClosure count1(this);
473 ct_bs->mod_card_iterate(&count1);
474 int orig_count = count1.n();
476 // First clear the logged cards.
477 ClearLoggedCardTableEntryClosure clear;
478 dcqs.set_closure(&clear);
479 dcqs.apply_closure_to_all_completed_buffers();
480 dcqs.iterate_closure_all_threads(false);
481 clear.print_histo();
483 // Now ensure that there's no dirty cards.
484 CountNonCleanMemRegionClosure count2(this);
485 ct_bs->mod_card_iterate(&count2);
486 if (count2.n() != 0) {
487 gclog_or_tty->print_cr("Card table has %d entries; %d originally",
488 count2.n(), orig_count);
489 }
490 guarantee(count2.n() == 0, "Card table should be clean.");
492 RedirtyLoggedCardTableEntryClosure redirty;
493 JavaThread::dirty_card_queue_set().set_closure(&redirty);
494 dcqs.apply_closure_to_all_completed_buffers();
495 dcqs.iterate_closure_all_threads(false);
496 gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
497 clear.calls(), orig_count);
498 guarantee(redirty.calls() == clear.calls(),
499 "Or else mechanism is broken.");
501 CountNonCleanMemRegionClosure count3(this);
502 ct_bs->mod_card_iterate(&count3);
503 if (count3.n() != orig_count) {
504 gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
505 orig_count, count3.n());
506 guarantee(count3.n() >= orig_count, "Should have restored them all.");
507 }
509 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
510 }
512 // Private class members.
514 G1CollectedHeap* G1CollectedHeap::_g1h;
516 // Private methods.
518 HeapRegion*
519 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
520 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
521 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
522 if (!_secondary_free_list.is_empty()) {
523 if (G1ConcRegionFreeingVerbose) {
524 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
525 "secondary_free_list has %u entries",
526 _secondary_free_list.length());
527 }
528 // It looks as if there are free regions available on the
529 // secondary_free_list. Let's move them to the free_list and try
530 // again to allocate from it.
531 append_secondary_free_list();
533 assert(!_free_list.is_empty(), "if the secondary_free_list was not "
534 "empty we should have moved at least one entry to the free_list");
535 HeapRegion* res = _free_list.remove_region(is_old);
536 if (G1ConcRegionFreeingVerbose) {
537 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
538 "allocated "HR_FORMAT" from secondary_free_list",
539 HR_FORMAT_PARAMS(res));
540 }
541 return res;
542 }
544 // Wait here until we get notified either when (a) there are no
545 // more free regions coming or (b) some regions have been moved on
546 // the secondary_free_list.
547 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
548 }
550 if (G1ConcRegionFreeingVerbose) {
551 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
552 "could not allocate from secondary_free_list");
553 }
554 return NULL;
555 }
557 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
558 assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords,
559 "the only time we use this to allocate a humongous region is "
560 "when we are allocating a single humongous region");
562 HeapRegion* res;
563 if (G1StressConcRegionFreeing) {
564 if (!_secondary_free_list.is_empty()) {
565 if (G1ConcRegionFreeingVerbose) {
566 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
567 "forced to look at the secondary_free_list");
568 }
569 res = new_region_try_secondary_free_list(is_old);
570 if (res != NULL) {
571 return res;
572 }
573 }
574 }
576 res = _free_list.remove_region(is_old);
578 if (res == NULL) {
579 if (G1ConcRegionFreeingVerbose) {
580 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
581 "res == NULL, trying the secondary_free_list");
582 }
583 res = new_region_try_secondary_free_list(is_old);
584 }
585 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
586 // Currently, only attempts to allocate GC alloc regions set
587 // do_expand to true. So, we should only reach here during a
588 // safepoint. If this assumption changes we might have to
589 // reconsider the use of _expand_heap_after_alloc_failure.
590 assert(SafepointSynchronize::is_at_safepoint(), "invariant");
592 ergo_verbose1(ErgoHeapSizing,
593 "attempt heap expansion",
594 ergo_format_reason("region allocation request failed")
595 ergo_format_byte("allocation request"),
596 word_size * HeapWordSize);
597 if (expand(word_size * HeapWordSize)) {
598 // Given that expand() succeeded in expanding the heap, and we
599 // always expand the heap by an amount aligned to the heap
600 // region size, the free list should in theory not be empty.
601 // In either case remove_region() will check for NULL.
602 res = _free_list.remove_region(is_old);
603 } else {
604 _expand_heap_after_alloc_failure = false;
605 }
606 }
607 return res;
608 }
610 uint G1CollectedHeap::humongous_obj_allocate_find_first(uint num_regions,
611 size_t word_size) {
612 assert(isHumongous(word_size), "word_size should be humongous");
613 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
615 uint first = G1_NULL_HRS_INDEX;
616 if (num_regions == 1) {
617 // Only one region to allocate, no need to go through the slower
618 // path. The caller will attempt the expansion if this fails, so
619 // let's not try to expand here too.
620 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
621 if (hr != NULL) {
622 first = hr->hrs_index();
623 } else {
624 first = G1_NULL_HRS_INDEX;
625 }
626 } else {
627 // We can't allocate humongous regions while cleanupComplete() is
628 // running, since some of the regions we find to be empty might not
629 // yet be added to the free list and it is not straightforward to
630 // know which list they are on so that we can remove them. Note
631 // that we only need to do this if we need to allocate more than
632 // one region to satisfy the current humongous allocation
633 // request. If we are only allocating one region we use the common
634 // region allocation code (see above).
635 wait_while_free_regions_coming();
636 append_secondary_free_list_if_not_empty_with_lock();
638 if (free_regions() >= num_regions) {
639 first = _hrs.find_contiguous(num_regions);
640 if (first != G1_NULL_HRS_INDEX) {
641 for (uint i = first; i < first + num_regions; ++i) {
642 HeapRegion* hr = region_at(i);
643 assert(hr->is_empty(), "sanity");
644 assert(is_on_master_free_list(hr), "sanity");
645 hr->set_pending_removal(true);
646 }
647 _free_list.remove_all_pending(num_regions);
648 }
649 }
650 }
651 return first;
652 }
654 HeapWord*
655 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
656 uint num_regions,
657 size_t word_size) {
658 assert(first != G1_NULL_HRS_INDEX, "pre-condition");
659 assert(isHumongous(word_size), "word_size should be humongous");
660 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
662 // Index of last region in the series + 1.
663 uint last = first + num_regions;
665 // We need to initialize the region(s) we just discovered. This is
666 // a bit tricky given that it can happen concurrently with
667 // refinement threads refining cards on these regions and
668 // potentially wanting to refine the BOT as they are scanning
669 // those cards (this can happen shortly after a cleanup; see CR
670 // 6991377). So we have to set up the region(s) carefully and in
671 // a specific order.
673 // The word size sum of all the regions we will allocate.
674 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
675 assert(word_size <= word_size_sum, "sanity");
677 // This will be the "starts humongous" region.
678 HeapRegion* first_hr = region_at(first);
679 // The header of the new object will be placed at the bottom of
680 // the first region.
681 HeapWord* new_obj = first_hr->bottom();
682 // This will be the new end of the first region in the series that
683 // should also match the end of the last region in the series.
684 HeapWord* new_end = new_obj + word_size_sum;
685 // This will be the new top of the first region that will reflect
686 // this allocation.
687 HeapWord* new_top = new_obj + word_size;
689 // First, we need to zero the header of the space that we will be
690 // allocating. When we update top further down, some refinement
691 // threads might try to scan the region. By zeroing the header we
692 // ensure that any thread that will try to scan the region will
693 // come across the zero klass word and bail out.
694 //
695 // NOTE: It would not have been correct to have used
696 // CollectedHeap::fill_with_object() and make the space look like
697 // an int array. The thread that is doing the allocation will
698 // later update the object header to a potentially different array
699 // type and, for a very short period of time, the klass and length
700 // fields will be inconsistent. This could cause a refinement
701 // thread to calculate the object size incorrectly.
702 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
704 // We will set up the first region as "starts humongous". This
705 // will also update the BOT covering all the regions to reflect
706 // that there is a single object that starts at the bottom of the
707 // first region.
708 first_hr->set_startsHumongous(new_top, new_end);
710 // Then, if there are any, we will set up the "continues
711 // humongous" regions.
712 HeapRegion* hr = NULL;
713 for (uint i = first + 1; i < last; ++i) {
714 hr = region_at(i);
715 hr->set_continuesHumongous(first_hr);
716 }
717 // If we have "continues humongous" regions (hr != NULL), then the
718 // end of the last one should match new_end.
719 assert(hr == NULL || hr->end() == new_end, "sanity");
721 // Up to this point no concurrent thread would have been able to
722 // do any scanning on any region in this series. All the top
723 // fields still point to bottom, so the intersection between
724 // [bottom,top] and [card_start,card_end] will be empty. Before we
725 // update the top fields, we'll do a storestore to make sure that
726 // no thread sees the update to top before the zeroing of the
727 // object header and the BOT initialization.
728 OrderAccess::storestore();
730 // Now that the BOT and the object header have been initialized,
731 // we can update top of the "starts humongous" region.
732 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
733 "new_top should be in this region");
734 first_hr->set_top(new_top);
735 if (_hr_printer.is_active()) {
736 HeapWord* bottom = first_hr->bottom();
737 HeapWord* end = first_hr->orig_end();
738 if ((first + 1) == last) {
739 // the series has a single humongous region
740 _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
741 } else {
742 // the series has more than one humongous regions
743 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
744 }
745 }
747 // Now, we will update the top fields of the "continues humongous"
748 // regions. The reason we need to do this is that, otherwise,
749 // these regions would look empty and this will confuse parts of
750 // G1. For example, the code that looks for a consecutive number
751 // of empty regions will consider them empty and try to
752 // re-allocate them. We can extend is_empty() to also include
753 // !continuesHumongous(), but it is easier to just update the top
754 // fields here. The way we set top for all regions (i.e., top ==
755 // end for all regions but the last one, top == new_top for the
756 // last one) is actually used when we will free up the humongous
757 // region in free_humongous_region().
758 hr = NULL;
759 for (uint i = first + 1; i < last; ++i) {
760 hr = region_at(i);
761 if ((i + 1) == last) {
762 // last continues humongous region
763 assert(hr->bottom() < new_top && new_top <= hr->end(),
764 "new_top should fall on this region");
765 hr->set_top(new_top);
766 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
767 } else {
768 // not last one
769 assert(new_top > hr->end(), "new_top should be above this region");
770 hr->set_top(hr->end());
771 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
772 }
773 }
774 // If we have continues humongous regions (hr != NULL), then the
775 // end of the last one should match new_end and its top should
776 // match new_top.
777 assert(hr == NULL ||
778 (hr->end() == new_end && hr->top() == new_top), "sanity");
780 assert(first_hr->used() == word_size * HeapWordSize, "invariant");
781 _summary_bytes_used += first_hr->used();
782 _humongous_set.add(first_hr);
784 return new_obj;
785 }
787 // If could fit into free regions w/o expansion, try.
788 // Otherwise, if can expand, do so.
789 // Otherwise, if using ex regions might help, try with ex given back.
790 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
791 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
793 verify_region_sets_optional();
795 size_t word_size_rounded = round_to(word_size, HeapRegion::GrainWords);
796 uint num_regions = (uint) (word_size_rounded / HeapRegion::GrainWords);
797 uint x_num = expansion_regions();
798 uint fs = _hrs.free_suffix();
799 uint first = humongous_obj_allocate_find_first(num_regions, word_size);
800 if (first == G1_NULL_HRS_INDEX) {
801 // The only thing we can do now is attempt expansion.
802 if (fs + x_num >= num_regions) {
803 // If the number of regions we're trying to allocate for this
804 // object is at most the number of regions in the free suffix,
805 // then the call to humongous_obj_allocate_find_first() above
806 // should have succeeded and we wouldn't be here.
807 //
808 // We should only be trying to expand when the free suffix is
809 // not sufficient for the object _and_ we have some expansion
810 // room available.
811 assert(num_regions > fs, "earlier allocation should have succeeded");
813 ergo_verbose1(ErgoHeapSizing,
814 "attempt heap expansion",
815 ergo_format_reason("humongous allocation request failed")
816 ergo_format_byte("allocation request"),
817 word_size * HeapWordSize);
818 if (expand((num_regions - fs) * HeapRegion::GrainBytes)) {
819 // Even though the heap was expanded, it might not have
820 // reached the desired size. So, we cannot assume that the
821 // allocation will succeed.
822 first = humongous_obj_allocate_find_first(num_regions, word_size);
823 }
824 }
825 }
827 HeapWord* result = NULL;
828 if (first != G1_NULL_HRS_INDEX) {
829 result =
830 humongous_obj_allocate_initialize_regions(first, num_regions, word_size);
831 assert(result != NULL, "it should always return a valid result");
833 // A successful humongous object allocation changes the used space
834 // information of the old generation so we need to recalculate the
835 // sizes and update the jstat counters here.
836 g1mm()->update_sizes();
837 }
839 verify_region_sets_optional();
841 return result;
842 }
844 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
845 assert_heap_not_locked_and_not_at_safepoint();
846 assert(!isHumongous(word_size), "we do not allow humongous TLABs");
848 unsigned int dummy_gc_count_before;
849 int dummy_gclocker_retry_count = 0;
850 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
851 }
853 HeapWord*
854 G1CollectedHeap::mem_allocate(size_t word_size,
855 bool* gc_overhead_limit_was_exceeded) {
856 assert_heap_not_locked_and_not_at_safepoint();
858 // Loop until the allocation is satisfied, or unsatisfied after GC.
859 for (int try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
860 unsigned int gc_count_before;
862 HeapWord* result = NULL;
863 if (!isHumongous(word_size)) {
864 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
865 } else {
866 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
867 }
868 if (result != NULL) {
869 return result;
870 }
872 // Create the garbage collection operation...
873 VM_G1CollectForAllocation op(gc_count_before, word_size);
874 // ...and get the VM thread to execute it.
875 VMThread::execute(&op);
877 if (op.prologue_succeeded() && op.pause_succeeded()) {
878 // If the operation was successful we'll return the result even
879 // if it is NULL. If the allocation attempt failed immediately
880 // after a Full GC, it's unlikely we'll be able to allocate now.
881 HeapWord* result = op.result();
882 if (result != NULL && !isHumongous(word_size)) {
883 // Allocations that take place on VM operations do not do any
884 // card dirtying and we have to do it here. We only have to do
885 // this for non-humongous allocations, though.
886 dirty_young_block(result, word_size);
887 }
888 return result;
889 } else {
890 if (gclocker_retry_count > GCLockerRetryAllocationCount) {
891 return NULL;
892 }
893 assert(op.result() == NULL,
894 "the result should be NULL if the VM op did not succeed");
895 }
897 // Give a warning if we seem to be looping forever.
898 if ((QueuedAllocationWarningCount > 0) &&
899 (try_count % QueuedAllocationWarningCount == 0)) {
900 warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
901 }
902 }
904 ShouldNotReachHere();
905 return NULL;
906 }
908 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
909 unsigned int *gc_count_before_ret,
910 int* gclocker_retry_count_ret) {
911 // Make sure you read the note in attempt_allocation_humongous().
913 assert_heap_not_locked_and_not_at_safepoint();
914 assert(!isHumongous(word_size), "attempt_allocation_slow() should not "
915 "be called for humongous allocation requests");
917 // We should only get here after the first-level allocation attempt
918 // (attempt_allocation()) failed to allocate.
920 // We will loop until a) we manage to successfully perform the
921 // allocation or b) we successfully schedule a collection which
922 // fails to perform the allocation. b) is the only case when we'll
923 // return NULL.
924 HeapWord* result = NULL;
925 for (int try_count = 1; /* we'll return */; try_count += 1) {
926 bool should_try_gc;
927 unsigned int gc_count_before;
929 {
930 MutexLockerEx x(Heap_lock);
932 result = _mutator_alloc_region.attempt_allocation_locked(word_size,
933 false /* bot_updates */);
934 if (result != NULL) {
935 return result;
936 }
938 // If we reach here, attempt_allocation_locked() above failed to
939 // allocate a new region. So the mutator alloc region should be NULL.
940 assert(_mutator_alloc_region.get() == NULL, "only way to get here");
942 if (GC_locker::is_active_and_needs_gc()) {
943 if (g1_policy()->can_expand_young_list()) {
944 // No need for an ergo verbose message here,
945 // can_expand_young_list() does this when it returns true.
946 result = _mutator_alloc_region.attempt_allocation_force(word_size,
947 false /* bot_updates */);
948 if (result != NULL) {
949 return result;
950 }
951 }
952 should_try_gc = false;
953 } else {
954 // The GCLocker may not be active but the GCLocker initiated
955 // GC may not yet have been performed (GCLocker::needs_gc()
956 // returns true). In this case we do not try this GC and
957 // wait until the GCLocker initiated GC is performed, and
958 // then retry the allocation.
959 if (GC_locker::needs_gc()) {
960 should_try_gc = false;
961 } else {
962 // Read the GC count while still holding the Heap_lock.
963 gc_count_before = total_collections();
964 should_try_gc = true;
965 }
966 }
967 }
969 if (should_try_gc) {
970 bool succeeded;
971 result = do_collection_pause(word_size, gc_count_before, &succeeded,
972 GCCause::_g1_inc_collection_pause);
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 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
988 MutexLockerEx x(Heap_lock);
989 *gc_count_before_ret = total_collections();
990 return NULL;
991 }
992 // The GCLocker is either active or the GCLocker initiated
993 // GC has not yet been performed. Stall until it is and
994 // then retry the allocation.
995 GC_locker::stall_until_clear();
996 (*gclocker_retry_count_ret) += 1;
997 }
999 // We can reach here if we were unsuccessful in scheduling a
1000 // collection (because another thread beat us to it) or if we were
1001 // stalled due to the GC locker. In either can we should retry the
1002 // allocation attempt in case another thread successfully
1003 // performed a collection and reclaimed enough space. We do the
1004 // first attempt (without holding the Heap_lock) here and the
1005 // follow-on attempt will be at the start of the next loop
1006 // iteration (after taking the Heap_lock).
1007 result = _mutator_alloc_region.attempt_allocation(word_size,
1008 false /* bot_updates */);
1009 if (result != NULL) {
1010 return result;
1011 }
1013 // Give a warning if we seem to be looping forever.
1014 if ((QueuedAllocationWarningCount > 0) &&
1015 (try_count % QueuedAllocationWarningCount == 0)) {
1016 warning("G1CollectedHeap::attempt_allocation_slow() "
1017 "retries %d times", try_count);
1018 }
1019 }
1021 ShouldNotReachHere();
1022 return NULL;
1023 }
1025 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
1026 unsigned int * gc_count_before_ret,
1027 int* gclocker_retry_count_ret) {
1028 // The structure of this method has a lot of similarities to
1029 // attempt_allocation_slow(). The reason these two were not merged
1030 // into a single one is that such a method would require several "if
1031 // allocation is not humongous do this, otherwise do that"
1032 // conditional paths which would obscure its flow. In fact, an early
1033 // version of this code did use a unified method which was harder to
1034 // follow and, as a result, it had subtle bugs that were hard to
1035 // track down. So keeping these two methods separate allows each to
1036 // be more readable. It will be good to keep these two in sync as
1037 // much as possible.
1039 assert_heap_not_locked_and_not_at_safepoint();
1040 assert(isHumongous(word_size), "attempt_allocation_humongous() "
1041 "should only be called for humongous allocations");
1043 // Humongous objects can exhaust the heap quickly, so we should check if we
1044 // need to start a marking cycle at each humongous object allocation. We do
1045 // the check before we do the actual allocation. The reason for doing it
1046 // before the allocation is that we avoid having to keep track of the newly
1047 // allocated memory while we do a GC.
1048 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
1049 word_size)) {
1050 collect(GCCause::_g1_humongous_allocation);
1051 }
1053 // We will loop until a) we manage to successfully perform the
1054 // allocation or b) we successfully schedule a collection which
1055 // fails to perform the allocation. b) is the only case when we'll
1056 // return NULL.
1057 HeapWord* result = NULL;
1058 for (int try_count = 1; /* we'll return */; try_count += 1) {
1059 bool should_try_gc;
1060 unsigned int gc_count_before;
1062 {
1063 MutexLockerEx x(Heap_lock);
1065 // Given that humongous objects are not allocated in young
1066 // regions, we'll first try to do the allocation without doing a
1067 // collection hoping that there's enough space in the heap.
1068 result = humongous_obj_allocate(word_size);
1069 if (result != NULL) {
1070 return result;
1071 }
1073 if (GC_locker::is_active_and_needs_gc()) {
1074 should_try_gc = false;
1075 } else {
1076 // The GCLocker may not be active but the GCLocker initiated
1077 // GC may not yet have been performed (GCLocker::needs_gc()
1078 // returns true). In this case we do not try this GC and
1079 // wait until the GCLocker initiated GC is performed, and
1080 // then retry the allocation.
1081 if (GC_locker::needs_gc()) {
1082 should_try_gc = false;
1083 } else {
1084 // Read the GC count while still holding the Heap_lock.
1085 gc_count_before = total_collections();
1086 should_try_gc = true;
1087 }
1088 }
1089 }
1091 if (should_try_gc) {
1092 // If we failed to allocate the humongous object, we should try to
1093 // do a collection pause (if we're allowed) in case it reclaims
1094 // enough space for the allocation to succeed after the pause.
1096 bool succeeded;
1097 result = do_collection_pause(word_size, gc_count_before, &succeeded,
1098 GCCause::_g1_humongous_allocation);
1099 if (result != NULL) {
1100 assert(succeeded, "only way to get back a non-NULL result");
1101 return result;
1102 }
1104 if (succeeded) {
1105 // If we get here we successfully scheduled a collection which
1106 // failed to allocate. No point in trying to allocate
1107 // further. We'll just return NULL.
1108 MutexLockerEx x(Heap_lock);
1109 *gc_count_before_ret = total_collections();
1110 return NULL;
1111 }
1112 } else {
1113 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1114 MutexLockerEx x(Heap_lock);
1115 *gc_count_before_ret = total_collections();
1116 return NULL;
1117 }
1118 // The GCLocker is either active or the GCLocker initiated
1119 // GC has not yet been performed. Stall until it is and
1120 // then retry the allocation.
1121 GC_locker::stall_until_clear();
1122 (*gclocker_retry_count_ret) += 1;
1123 }
1125 // We can reach here if we were unsuccessful in scheduling a
1126 // collection (because another thread beat us to it) or if we were
1127 // stalled due to the GC locker. In either can we should retry the
1128 // allocation attempt in case another thread successfully
1129 // performed a collection and reclaimed enough space. Give a
1130 // warning if we seem to be looping forever.
1132 if ((QueuedAllocationWarningCount > 0) &&
1133 (try_count % QueuedAllocationWarningCount == 0)) {
1134 warning("G1CollectedHeap::attempt_allocation_humongous() "
1135 "retries %d times", try_count);
1136 }
1137 }
1139 ShouldNotReachHere();
1140 return NULL;
1141 }
1143 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1144 bool expect_null_mutator_alloc_region) {
1145 assert_at_safepoint(true /* should_be_vm_thread */);
1146 assert(_mutator_alloc_region.get() == NULL ||
1147 !expect_null_mutator_alloc_region,
1148 "the current alloc region was unexpectedly found to be non-NULL");
1150 if (!isHumongous(word_size)) {
1151 return _mutator_alloc_region.attempt_allocation_locked(word_size,
1152 false /* bot_updates */);
1153 } else {
1154 HeapWord* result = humongous_obj_allocate(word_size);
1155 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1156 g1_policy()->set_initiate_conc_mark_if_possible();
1157 }
1158 return result;
1159 }
1161 ShouldNotReachHere();
1162 }
1164 class PostMCRemSetClearClosure: public HeapRegionClosure {
1165 G1CollectedHeap* _g1h;
1166 ModRefBarrierSet* _mr_bs;
1167 public:
1168 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1169 _g1h(g1h), _mr_bs(mr_bs) {}
1171 bool doHeapRegion(HeapRegion* r) {
1172 HeapRegionRemSet* hrrs = r->rem_set();
1174 if (r->continuesHumongous()) {
1175 // We'll assert that the strong code root list and RSet is empty
1176 assert(hrrs->strong_code_roots_list_length() == 0, "sanity");
1177 assert(hrrs->occupied() == 0, "RSet should be empty");
1178 return false;
1179 }
1181 _g1h->reset_gc_time_stamps(r);
1182 hrrs->clear();
1183 // You might think here that we could clear just the cards
1184 // corresponding to the used region. But no: if we leave a dirty card
1185 // in a region we might allocate into, then it would prevent that card
1186 // from being enqueued, and cause it to be missed.
1187 // Re: the performance cost: we shouldn't be doing full GC anyway!
1188 _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1190 return false;
1191 }
1192 };
1194 void G1CollectedHeap::clear_rsets_post_compaction() {
1195 PostMCRemSetClearClosure rs_clear(this, g1_barrier_set());
1196 heap_region_iterate(&rs_clear);
1197 }
1199 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1200 G1CollectedHeap* _g1h;
1201 UpdateRSOopClosure _cl;
1202 int _worker_i;
1203 public:
1204 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1205 _cl(g1->g1_rem_set(), worker_i),
1206 _worker_i(worker_i),
1207 _g1h(g1)
1208 { }
1210 bool doHeapRegion(HeapRegion* r) {
1211 if (!r->continuesHumongous()) {
1212 _cl.set_from(r);
1213 r->oop_iterate(&_cl);
1214 }
1215 return false;
1216 }
1217 };
1219 class ParRebuildRSTask: public AbstractGangTask {
1220 G1CollectedHeap* _g1;
1221 public:
1222 ParRebuildRSTask(G1CollectedHeap* g1)
1223 : AbstractGangTask("ParRebuildRSTask"),
1224 _g1(g1)
1225 { }
1227 void work(uint worker_id) {
1228 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1229 _g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id,
1230 _g1->workers()->active_workers(),
1231 HeapRegion::RebuildRSClaimValue);
1232 }
1233 };
1235 class PostCompactionPrinterClosure: public HeapRegionClosure {
1236 private:
1237 G1HRPrinter* _hr_printer;
1238 public:
1239 bool doHeapRegion(HeapRegion* hr) {
1240 assert(!hr->is_young(), "not expecting to find young regions");
1241 // We only generate output for non-empty regions.
1242 if (!hr->is_empty()) {
1243 if (!hr->isHumongous()) {
1244 _hr_printer->post_compaction(hr, G1HRPrinter::Old);
1245 } else if (hr->startsHumongous()) {
1246 if (hr->region_num() == 1) {
1247 // single humongous region
1248 _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
1249 } else {
1250 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
1251 }
1252 } else {
1253 assert(hr->continuesHumongous(), "only way to get here");
1254 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1255 }
1256 }
1257 return false;
1258 }
1260 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1261 : _hr_printer(hr_printer) { }
1262 };
1264 void G1CollectedHeap::print_hrs_post_compaction() {
1265 PostCompactionPrinterClosure cl(hr_printer());
1266 heap_region_iterate(&cl);
1267 }
1269 bool G1CollectedHeap::do_collection(bool explicit_gc,
1270 bool clear_all_soft_refs,
1271 size_t word_size) {
1272 assert_at_safepoint(true /* should_be_vm_thread */);
1274 if (GC_locker::check_active_before_gc()) {
1275 return false;
1276 }
1278 STWGCTimer* gc_timer = G1MarkSweep::gc_timer();
1279 gc_timer->register_gc_start();
1281 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer();
1282 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start());
1284 SvcGCMarker sgcm(SvcGCMarker::FULL);
1285 ResourceMark rm;
1287 print_heap_before_gc();
1288 trace_heap_before_gc(gc_tracer);
1290 size_t metadata_prev_used = MetaspaceAux::used_bytes();
1292 verify_region_sets_optional();
1294 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1295 collector_policy()->should_clear_all_soft_refs();
1297 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1299 {
1300 IsGCActiveMark x;
1302 // Timing
1303 assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant");
1304 gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps);
1305 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
1307 {
1308 GCTraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, NULL, gc_tracer->gc_id());
1309 TraceCollectorStats tcs(g1mm()->full_collection_counters());
1310 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1312 double start = os::elapsedTime();
1313 g1_policy()->record_full_collection_start();
1315 // Note: When we have a more flexible GC logging framework that
1316 // allows us to add optional attributes to a GC log record we
1317 // could consider timing and reporting how long we wait in the
1318 // following two methods.
1319 wait_while_free_regions_coming();
1320 // If we start the compaction before the CM threads finish
1321 // scanning the root regions we might trip them over as we'll
1322 // be moving objects / updating references. So let's wait until
1323 // they are done. By telling them to abort, they should complete
1324 // early.
1325 _cm->root_regions()->abort();
1326 _cm->root_regions()->wait_until_scan_finished();
1327 append_secondary_free_list_if_not_empty_with_lock();
1329 gc_prologue(true);
1330 increment_total_collections(true /* full gc */);
1331 increment_old_marking_cycles_started();
1333 assert(used() == recalculate_used(), "Should be equal");
1335 verify_before_gc();
1337 pre_full_gc_dump(gc_timer);
1339 COMPILER2_PRESENT(DerivedPointerTable::clear());
1341 // Disable discovery and empty the discovered lists
1342 // for the CM ref processor.
1343 ref_processor_cm()->disable_discovery();
1344 ref_processor_cm()->abandon_partial_discovery();
1345 ref_processor_cm()->verify_no_references_recorded();
1347 // Abandon current iterations of concurrent marking and concurrent
1348 // refinement, if any are in progress. We have to do this before
1349 // wait_until_scan_finished() below.
1350 concurrent_mark()->abort();
1352 // Make sure we'll choose a new allocation region afterwards.
1353 release_mutator_alloc_region();
1354 abandon_gc_alloc_regions();
1355 g1_rem_set()->cleanupHRRS();
1357 // We should call this after we retire any currently active alloc
1358 // regions so that all the ALLOC / RETIRE events are generated
1359 // before the start GC event.
1360 _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1362 // We may have added regions to the current incremental collection
1363 // set between the last GC or pause and now. We need to clear the
1364 // incremental collection set and then start rebuilding it afresh
1365 // after this full GC.
1366 abandon_collection_set(g1_policy()->inc_cset_head());
1367 g1_policy()->clear_incremental_cset();
1368 g1_policy()->stop_incremental_cset_building();
1370 tear_down_region_sets(false /* free_list_only */);
1371 g1_policy()->set_gcs_are_young(true);
1373 // See the comments in g1CollectedHeap.hpp and
1374 // G1CollectedHeap::ref_processing_init() about
1375 // how reference processing currently works in G1.
1377 // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1378 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1380 // Temporarily clear the STW ref processor's _is_alive_non_header field.
1381 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1383 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
1384 ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1386 // Do collection work
1387 {
1388 HandleMark hm; // Discard invalid handles created during gc
1389 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1390 }
1392 assert(free_regions() == 0, "we should not have added any free regions");
1393 rebuild_region_sets(false /* free_list_only */);
1395 // Enqueue any discovered reference objects that have
1396 // not been removed from the discovered lists.
1397 ref_processor_stw()->enqueue_discovered_references();
1399 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1401 MemoryService::track_memory_usage();
1403 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1404 ref_processor_stw()->verify_no_references_recorded();
1406 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1407 ClassLoaderDataGraph::purge();
1408 MetaspaceAux::verify_metrics();
1410 // Note: since we've just done a full GC, concurrent
1411 // marking is no longer active. Therefore we need not
1412 // re-enable reference discovery for the CM ref processor.
1413 // That will be done at the start of the next marking cycle.
1414 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1415 ref_processor_cm()->verify_no_references_recorded();
1417 reset_gc_time_stamp();
1418 // Since everything potentially moved, we will clear all remembered
1419 // sets, and clear all cards. Later we will rebuild remembered
1420 // sets. We will also reset the GC time stamps of the regions.
1421 clear_rsets_post_compaction();
1422 check_gc_time_stamps();
1424 // Resize the heap if necessary.
1425 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1427 if (_hr_printer.is_active()) {
1428 // We should do this after we potentially resize the heap so
1429 // that all the COMMIT / UNCOMMIT events are generated before
1430 // the end GC event.
1432 print_hrs_post_compaction();
1433 _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1434 }
1436 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
1437 if (hot_card_cache->use_cache()) {
1438 hot_card_cache->reset_card_counts();
1439 hot_card_cache->reset_hot_cache();
1440 }
1442 // Rebuild remembered sets of all regions.
1443 if (G1CollectedHeap::use_parallel_gc_threads()) {
1444 uint n_workers =
1445 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1446 workers()->active_workers(),
1447 Threads::number_of_non_daemon_threads());
1448 assert(UseDynamicNumberOfGCThreads ||
1449 n_workers == workers()->total_workers(),
1450 "If not dynamic should be using all the workers");
1451 workers()->set_active_workers(n_workers);
1452 // Set parallel threads in the heap (_n_par_threads) only
1453 // before a parallel phase and always reset it to 0 after
1454 // the phase so that the number of parallel threads does
1455 // no get carried forward to a serial phase where there
1456 // may be code that is "possibly_parallel".
1457 set_par_threads(n_workers);
1459 ParRebuildRSTask rebuild_rs_task(this);
1460 assert(check_heap_region_claim_values(
1461 HeapRegion::InitialClaimValue), "sanity check");
1462 assert(UseDynamicNumberOfGCThreads ||
1463 workers()->active_workers() == workers()->total_workers(),
1464 "Unless dynamic should use total workers");
1465 // Use the most recent number of active workers
1466 assert(workers()->active_workers() > 0,
1467 "Active workers not properly set");
1468 set_par_threads(workers()->active_workers());
1469 workers()->run_task(&rebuild_rs_task);
1470 set_par_threads(0);
1471 assert(check_heap_region_claim_values(
1472 HeapRegion::RebuildRSClaimValue), "sanity check");
1473 reset_heap_region_claim_values();
1474 } else {
1475 RebuildRSOutOfRegionClosure rebuild_rs(this);
1476 heap_region_iterate(&rebuild_rs);
1477 }
1479 // Rebuild the strong code root lists for each region
1480 rebuild_strong_code_roots();
1482 if (true) { // FIXME
1483 MetaspaceGC::compute_new_size();
1484 }
1486 #ifdef TRACESPINNING
1487 ParallelTaskTerminator::print_termination_counts();
1488 #endif
1490 // Discard all rset updates
1491 JavaThread::dirty_card_queue_set().abandon_logs();
1492 assert(!G1DeferredRSUpdate
1493 || (G1DeferredRSUpdate &&
1494 (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any");
1496 _young_list->reset_sampled_info();
1497 // At this point there should be no regions in the
1498 // entire heap tagged as young.
1499 assert(check_young_list_empty(true /* check_heap */),
1500 "young list should be empty at this point");
1502 // Update the number of full collections that have been completed.
1503 increment_old_marking_cycles_completed(false /* concurrent */);
1505 _hrs.verify_optional();
1506 verify_region_sets_optional();
1508 verify_after_gc();
1510 // Start a new incremental collection set for the next pause
1511 assert(g1_policy()->collection_set() == NULL, "must be");
1512 g1_policy()->start_incremental_cset_building();
1514 // Clear the _cset_fast_test bitmap in anticipation of adding
1515 // regions to the incremental collection set for the next
1516 // evacuation pause.
1517 clear_cset_fast_test();
1519 init_mutator_alloc_region();
1521 double end = os::elapsedTime();
1522 g1_policy()->record_full_collection_end();
1524 if (G1Log::fine()) {
1525 g1_policy()->print_heap_transition();
1526 }
1528 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1529 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1530 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1531 // before any GC notifications are raised.
1532 g1mm()->update_sizes();
1534 gc_epilogue(true);
1535 }
1537 if (G1Log::finer()) {
1538 g1_policy()->print_detailed_heap_transition(true /* full */);
1539 }
1541 print_heap_after_gc();
1542 trace_heap_after_gc(gc_tracer);
1544 post_full_gc_dump(gc_timer);
1546 gc_timer->register_gc_end();
1547 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
1548 }
1550 return true;
1551 }
1553 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1554 // do_collection() will return whether it succeeded in performing
1555 // the GC. Currently, there is no facility on the
1556 // do_full_collection() API to notify the caller than the collection
1557 // did not succeed (e.g., because it was locked out by the GC
1558 // locker). So, right now, we'll ignore the return value.
1559 bool dummy = do_collection(true, /* explicit_gc */
1560 clear_all_soft_refs,
1561 0 /* word_size */);
1562 }
1564 // This code is mostly copied from TenuredGeneration.
1565 void
1566 G1CollectedHeap::
1567 resize_if_necessary_after_full_collection(size_t word_size) {
1568 // Include the current allocation, if any, and bytes that will be
1569 // pre-allocated to support collections, as "used".
1570 const size_t used_after_gc = used();
1571 const size_t capacity_after_gc = capacity();
1572 const size_t free_after_gc = capacity_after_gc - used_after_gc;
1574 // This is enforced in arguments.cpp.
1575 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1576 "otherwise the code below doesn't make sense");
1578 // We don't have floating point command-line arguments
1579 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1580 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1581 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1582 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1584 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1585 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1587 // We have to be careful here as these two calculations can overflow
1588 // 32-bit size_t's.
1589 double used_after_gc_d = (double) used_after_gc;
1590 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1591 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1593 // Let's make sure that they are both under the max heap size, which
1594 // by default will make them fit into a size_t.
1595 double desired_capacity_upper_bound = (double) max_heap_size;
1596 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1597 desired_capacity_upper_bound);
1598 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1599 desired_capacity_upper_bound);
1601 // We can now safely turn them into size_t's.
1602 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1603 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1605 // This assert only makes sense here, before we adjust them
1606 // with respect to the min and max heap size.
1607 assert(minimum_desired_capacity <= maximum_desired_capacity,
1608 err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1609 "maximum_desired_capacity = "SIZE_FORMAT,
1610 minimum_desired_capacity, maximum_desired_capacity));
1612 // Should not be greater than the heap max size. No need to adjust
1613 // it with respect to the heap min size as it's a lower bound (i.e.,
1614 // we'll try to make the capacity larger than it, not smaller).
1615 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1616 // Should not be less than the heap min size. No need to adjust it
1617 // with respect to the heap max size as it's an upper bound (i.e.,
1618 // we'll try to make the capacity smaller than it, not greater).
1619 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1621 if (capacity_after_gc < minimum_desired_capacity) {
1622 // Don't expand unless it's significant
1623 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1624 ergo_verbose4(ErgoHeapSizing,
1625 "attempt heap expansion",
1626 ergo_format_reason("capacity lower than "
1627 "min desired capacity after Full GC")
1628 ergo_format_byte("capacity")
1629 ergo_format_byte("occupancy")
1630 ergo_format_byte_perc("min desired capacity"),
1631 capacity_after_gc, used_after_gc,
1632 minimum_desired_capacity, (double) MinHeapFreeRatio);
1633 expand(expand_bytes);
1635 // No expansion, now see if we want to shrink
1636 } else if (capacity_after_gc > maximum_desired_capacity) {
1637 // Capacity too large, compute shrinking size
1638 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1639 ergo_verbose4(ErgoHeapSizing,
1640 "attempt heap shrinking",
1641 ergo_format_reason("capacity higher than "
1642 "max desired capacity after Full GC")
1643 ergo_format_byte("capacity")
1644 ergo_format_byte("occupancy")
1645 ergo_format_byte_perc("max desired capacity"),
1646 capacity_after_gc, used_after_gc,
1647 maximum_desired_capacity, (double) MaxHeapFreeRatio);
1648 shrink(shrink_bytes);
1649 }
1650 }
1653 HeapWord*
1654 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1655 bool* succeeded) {
1656 assert_at_safepoint(true /* should_be_vm_thread */);
1658 *succeeded = true;
1659 // Let's attempt the allocation first.
1660 HeapWord* result =
1661 attempt_allocation_at_safepoint(word_size,
1662 false /* expect_null_mutator_alloc_region */);
1663 if (result != NULL) {
1664 assert(*succeeded, "sanity");
1665 return result;
1666 }
1668 // In a G1 heap, we're supposed to keep allocation from failing by
1669 // incremental pauses. Therefore, at least for now, we'll favor
1670 // expansion over collection. (This might change in the future if we can
1671 // do something smarter than full collection to satisfy a failed alloc.)
1672 result = expand_and_allocate(word_size);
1673 if (result != NULL) {
1674 assert(*succeeded, "sanity");
1675 return result;
1676 }
1678 // Expansion didn't work, we'll try to do a Full GC.
1679 bool gc_succeeded = do_collection(false, /* explicit_gc */
1680 false, /* clear_all_soft_refs */
1681 word_size);
1682 if (!gc_succeeded) {
1683 *succeeded = false;
1684 return NULL;
1685 }
1687 // Retry the allocation
1688 result = attempt_allocation_at_safepoint(word_size,
1689 true /* expect_null_mutator_alloc_region */);
1690 if (result != NULL) {
1691 assert(*succeeded, "sanity");
1692 return result;
1693 }
1695 // Then, try a Full GC that will collect all soft references.
1696 gc_succeeded = do_collection(false, /* explicit_gc */
1697 true, /* clear_all_soft_refs */
1698 word_size);
1699 if (!gc_succeeded) {
1700 *succeeded = false;
1701 return NULL;
1702 }
1704 // Retry the allocation once more
1705 result = attempt_allocation_at_safepoint(word_size,
1706 true /* expect_null_mutator_alloc_region */);
1707 if (result != NULL) {
1708 assert(*succeeded, "sanity");
1709 return result;
1710 }
1712 assert(!collector_policy()->should_clear_all_soft_refs(),
1713 "Flag should have been handled and cleared prior to this point");
1715 // What else? We might try synchronous finalization later. If the total
1716 // space available is large enough for the allocation, then a more
1717 // complete compaction phase than we've tried so far might be
1718 // appropriate.
1719 assert(*succeeded, "sanity");
1720 return NULL;
1721 }
1723 // Attempting to expand the heap sufficiently
1724 // to support an allocation of the given "word_size". If
1725 // successful, perform the allocation and return the address of the
1726 // allocated block, or else "NULL".
1728 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1729 assert_at_safepoint(true /* should_be_vm_thread */);
1731 verify_region_sets_optional();
1733 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1734 ergo_verbose1(ErgoHeapSizing,
1735 "attempt heap expansion",
1736 ergo_format_reason("allocation request failed")
1737 ergo_format_byte("allocation request"),
1738 word_size * HeapWordSize);
1739 if (expand(expand_bytes)) {
1740 _hrs.verify_optional();
1741 verify_region_sets_optional();
1742 return attempt_allocation_at_safepoint(word_size,
1743 false /* expect_null_mutator_alloc_region */);
1744 }
1745 return NULL;
1746 }
1748 void G1CollectedHeap::update_committed_space(HeapWord* old_end,
1749 HeapWord* new_end) {
1750 assert(old_end != new_end, "don't call this otherwise");
1751 assert((HeapWord*) _g1_storage.high() == new_end, "invariant");
1753 // Update the committed mem region.
1754 _g1_committed.set_end(new_end);
1755 // Tell the card table about the update.
1756 Universe::heap()->barrier_set()->resize_covered_region(_g1_committed);
1757 // Tell the BOT about the update.
1758 _bot_shared->resize(_g1_committed.word_size());
1759 // Tell the hot card cache about the update
1760 _cg1r->hot_card_cache()->resize_card_counts(capacity());
1761 }
1763 bool G1CollectedHeap::expand(size_t expand_bytes) {
1764 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1765 aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1766 HeapRegion::GrainBytes);
1767 ergo_verbose2(ErgoHeapSizing,
1768 "expand the heap",
1769 ergo_format_byte("requested expansion amount")
1770 ergo_format_byte("attempted expansion amount"),
1771 expand_bytes, aligned_expand_bytes);
1773 if (_g1_storage.uncommitted_size() == 0) {
1774 ergo_verbose0(ErgoHeapSizing,
1775 "did not expand the heap",
1776 ergo_format_reason("heap already fully expanded"));
1777 return false;
1778 }
1780 // First commit the memory.
1781 HeapWord* old_end = (HeapWord*) _g1_storage.high();
1782 bool successful = _g1_storage.expand_by(aligned_expand_bytes);
1783 if (successful) {
1784 // Then propagate this update to the necessary data structures.
1785 HeapWord* new_end = (HeapWord*) _g1_storage.high();
1786 update_committed_space(old_end, new_end);
1788 FreeRegionList expansion_list("Local Expansion List");
1789 MemRegion mr = _hrs.expand_by(old_end, new_end, &expansion_list);
1790 assert(mr.start() == old_end, "post-condition");
1791 // mr might be a smaller region than what was requested if
1792 // expand_by() was unable to allocate the HeapRegion instances
1793 assert(mr.end() <= new_end, "post-condition");
1795 size_t actual_expand_bytes = mr.byte_size();
1796 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1797 assert(actual_expand_bytes == expansion_list.total_capacity_bytes(),
1798 "post-condition");
1799 if (actual_expand_bytes < aligned_expand_bytes) {
1800 // We could not expand _hrs to the desired size. In this case we
1801 // need to shrink the committed space accordingly.
1802 assert(mr.end() < new_end, "invariant");
1804 size_t diff_bytes = aligned_expand_bytes - actual_expand_bytes;
1805 // First uncommit the memory.
1806 _g1_storage.shrink_by(diff_bytes);
1807 // Then propagate this update to the necessary data structures.
1808 update_committed_space(new_end, mr.end());
1809 }
1810 _free_list.add_as_tail(&expansion_list);
1812 if (_hr_printer.is_active()) {
1813 HeapWord* curr = mr.start();
1814 while (curr < mr.end()) {
1815 HeapWord* curr_end = curr + HeapRegion::GrainWords;
1816 _hr_printer.commit(curr, curr_end);
1817 curr = curr_end;
1818 }
1819 assert(curr == mr.end(), "post-condition");
1820 }
1821 g1_policy()->record_new_heap_size(n_regions());
1822 } else {
1823 ergo_verbose0(ErgoHeapSizing,
1824 "did not expand the heap",
1825 ergo_format_reason("heap expansion operation failed"));
1826 // The expansion of the virtual storage space was unsuccessful.
1827 // Let's see if it was because we ran out of swap.
1828 if (G1ExitOnExpansionFailure &&
1829 _g1_storage.uncommitted_size() >= aligned_expand_bytes) {
1830 // We had head room...
1831 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1832 }
1833 }
1834 return successful;
1835 }
1837 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1838 size_t aligned_shrink_bytes =
1839 ReservedSpace::page_align_size_down(shrink_bytes);
1840 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1841 HeapRegion::GrainBytes);
1842 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1844 uint num_regions_removed = _hrs.shrink_by(num_regions_to_remove);
1845 HeapWord* old_end = (HeapWord*) _g1_storage.high();
1846 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1848 ergo_verbose3(ErgoHeapSizing,
1849 "shrink the heap",
1850 ergo_format_byte("requested shrinking amount")
1851 ergo_format_byte("aligned shrinking amount")
1852 ergo_format_byte("attempted shrinking amount"),
1853 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1854 if (num_regions_removed > 0) {
1855 _g1_storage.shrink_by(shrunk_bytes);
1856 HeapWord* new_end = (HeapWord*) _g1_storage.high();
1858 if (_hr_printer.is_active()) {
1859 HeapWord* curr = old_end;
1860 while (curr > new_end) {
1861 HeapWord* curr_end = curr;
1862 curr -= HeapRegion::GrainWords;
1863 _hr_printer.uncommit(curr, curr_end);
1864 }
1865 }
1867 _expansion_regions += num_regions_removed;
1868 update_committed_space(old_end, new_end);
1869 HeapRegionRemSet::shrink_heap(n_regions());
1870 g1_policy()->record_new_heap_size(n_regions());
1871 } else {
1872 ergo_verbose0(ErgoHeapSizing,
1873 "did not shrink the heap",
1874 ergo_format_reason("heap shrinking operation failed"));
1875 }
1876 }
1878 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1879 verify_region_sets_optional();
1881 // We should only reach here at the end of a Full GC which means we
1882 // should not not be holding to any GC alloc regions. The method
1883 // below will make sure of that and do any remaining clean up.
1884 abandon_gc_alloc_regions();
1886 // Instead of tearing down / rebuilding the free lists here, we
1887 // could instead use the remove_all_pending() method on free_list to
1888 // remove only the ones that we need to remove.
1889 tear_down_region_sets(true /* free_list_only */);
1890 shrink_helper(shrink_bytes);
1891 rebuild_region_sets(true /* free_list_only */);
1893 _hrs.verify_optional();
1894 verify_region_sets_optional();
1895 }
1897 // Public methods.
1899 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1900 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1901 #endif // _MSC_VER
1904 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1905 SharedHeap(policy_),
1906 _g1_policy(policy_),
1907 _dirty_card_queue_set(false),
1908 _into_cset_dirty_card_queue_set(false),
1909 _is_alive_closure_cm(this),
1910 _is_alive_closure_stw(this),
1911 _ref_processor_cm(NULL),
1912 _ref_processor_stw(NULL),
1913 _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
1914 _bot_shared(NULL),
1915 _evac_failure_scan_stack(NULL),
1916 _mark_in_progress(false),
1917 _cg1r(NULL), _summary_bytes_used(0),
1918 _g1mm(NULL),
1919 _refine_cte_cl(NULL),
1920 _full_collection(false),
1921 _free_list("Master Free List", new MasterFreeRegionListMtSafeChecker()),
1922 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1923 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1924 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1925 _free_regions_coming(false),
1926 _young_list(new YoungList(this)),
1927 _gc_time_stamp(0),
1928 _retained_old_gc_alloc_region(NULL),
1929 _survivor_plab_stats(YoungPLABSize, PLABWeight),
1930 _old_plab_stats(OldPLABSize, PLABWeight),
1931 _expand_heap_after_alloc_failure(true),
1932 _surviving_young_words(NULL),
1933 _old_marking_cycles_started(0),
1934 _old_marking_cycles_completed(0),
1935 _concurrent_cycle_started(false),
1936 _in_cset_fast_test(NULL),
1937 _in_cset_fast_test_base(NULL),
1938 _dirty_cards_region_list(NULL),
1939 _worker_cset_start_region(NULL),
1940 _worker_cset_start_region_time_stamp(NULL),
1941 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1942 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
1943 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1944 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) {
1946 _g1h = this;
1947 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
1948 vm_exit_during_initialization("Failed necessary allocation.");
1949 }
1951 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1953 int n_queues = MAX2((int)ParallelGCThreads, 1);
1954 _task_queues = new RefToScanQueueSet(n_queues);
1956 uint n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1957 assert(n_rem_sets > 0, "Invariant.");
1959 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1960 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC);
1961 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1963 for (int i = 0; i < n_queues; i++) {
1964 RefToScanQueue* q = new RefToScanQueue();
1965 q->initialize();
1966 _task_queues->register_queue(i, q);
1967 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1968 }
1969 clear_cset_start_regions();
1971 // Initialize the G1EvacuationFailureALot counters and flags.
1972 NOT_PRODUCT(reset_evacuation_should_fail();)
1974 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1975 }
1977 jint G1CollectedHeap::initialize() {
1978 CollectedHeap::pre_initialize();
1979 os::enable_vtime();
1981 G1Log::init();
1983 // Necessary to satisfy locking discipline assertions.
1985 MutexLocker x(Heap_lock);
1987 // We have to initialize the printer before committing the heap, as
1988 // it will be used then.
1989 _hr_printer.set_active(G1PrintHeapRegions);
1991 // While there are no constraints in the GC code that HeapWordSize
1992 // be any particular value, there are multiple other areas in the
1993 // system which believe this to be true (e.g. oop->object_size in some
1994 // cases incorrectly returns the size in wordSize units rather than
1995 // HeapWordSize).
1996 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1998 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1999 size_t max_byte_size = collector_policy()->max_heap_byte_size();
2000 size_t heap_alignment = collector_policy()->heap_alignment();
2002 // Ensure that the sizes are properly aligned.
2003 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
2004 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
2005 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
2007 _cg1r = new ConcurrentG1Refine(this);
2009 // Reserve the maximum.
2011 // When compressed oops are enabled, the preferred heap base
2012 // is calculated by subtracting the requested size from the
2013 // 32Gb boundary and using the result as the base address for
2014 // heap reservation. If the requested size is not aligned to
2015 // HeapRegion::GrainBytes (i.e. the alignment that is passed
2016 // into the ReservedHeapSpace constructor) then the actual
2017 // base of the reserved heap may end up differing from the
2018 // address that was requested (i.e. the preferred heap base).
2019 // If this happens then we could end up using a non-optimal
2020 // compressed oops mode.
2022 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
2023 heap_alignment);
2025 // It is important to do this in a way such that concurrent readers can't
2026 // temporarily think something is in the heap. (I've actually seen this
2027 // happen in asserts: DLD.)
2028 _reserved.set_word_size(0);
2029 _reserved.set_start((HeapWord*)heap_rs.base());
2030 _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size()));
2032 _expansion_regions = (uint) (max_byte_size / HeapRegion::GrainBytes);
2034 // Create the gen rem set (and barrier set) for the entire reserved region.
2035 _rem_set = collector_policy()->create_rem_set(_reserved, 2);
2036 set_barrier_set(rem_set()->bs());
2037 if (!barrier_set()->is_a(BarrierSet::G1SATBCTLogging)) {
2038 vm_exit_during_initialization("G1 requires a G1SATBLoggingCardTableModRefBS");
2039 return JNI_ENOMEM;
2040 }
2042 // Also create a G1 rem set.
2043 _g1_rem_set = new G1RemSet(this, g1_barrier_set());
2045 // Carve out the G1 part of the heap.
2047 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
2048 _g1_reserved = MemRegion((HeapWord*)g1_rs.base(),
2049 g1_rs.size()/HeapWordSize);
2051 _g1_storage.initialize(g1_rs, 0);
2052 _g1_committed = MemRegion((HeapWord*)_g1_storage.low(), (size_t) 0);
2053 _hrs.initialize((HeapWord*) _g1_reserved.start(),
2054 (HeapWord*) _g1_reserved.end());
2055 assert(_hrs.max_length() == _expansion_regions,
2056 err_msg("max length: %u expansion regions: %u",
2057 _hrs.max_length(), _expansion_regions));
2059 // Do later initialization work for concurrent refinement.
2060 _cg1r->init();
2062 // 6843694 - ensure that the maximum region index can fit
2063 // in the remembered set structures.
2064 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
2065 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
2067 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
2068 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
2069 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
2070 "too many cards per region");
2072 FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
2074 _bot_shared = new G1BlockOffsetSharedArray(_reserved,
2075 heap_word_size(init_byte_size));
2077 _g1h = this;
2079 _in_cset_fast_test_length = max_regions();
2080 _in_cset_fast_test_base =
2081 NEW_C_HEAP_ARRAY(bool, (size_t) _in_cset_fast_test_length, mtGC);
2083 // We're biasing _in_cset_fast_test to avoid subtracting the
2084 // beginning of the heap every time we want to index; basically
2085 // it's the same with what we do with the card table.
2086 _in_cset_fast_test = _in_cset_fast_test_base -
2087 ((uintx) _g1_reserved.start() >> HeapRegion::LogOfHRGrainBytes);
2089 // Clear the _cset_fast_test bitmap in anticipation of adding
2090 // regions to the incremental collection set for the first
2091 // evacuation pause.
2092 clear_cset_fast_test();
2094 // Create the ConcurrentMark data structure and thread.
2095 // (Must do this late, so that "max_regions" is defined.)
2096 _cm = new ConcurrentMark(this, heap_rs);
2097 if (_cm == NULL || !_cm->completed_initialization()) {
2098 vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark");
2099 return JNI_ENOMEM;
2100 }
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_shutdown_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 // Here we allocate the dummy full region that is required by the
2155 // G1AllocRegion class. If we don't pass an address in the reserved
2156 // space here, lots of asserts fire.
2158 HeapRegion* dummy_region = new_heap_region(0 /* index of bottom region */,
2159 _g1_reserved.start());
2160 // We'll re-use the same region whether the alloc region will
2161 // require BOT updates or not and, if it doesn't, then a non-young
2162 // region will complain that it cannot support allocations without
2163 // BOT updates. So we'll tag the dummy region as young to avoid that.
2164 dummy_region->set_young();
2165 // Make sure it's full.
2166 dummy_region->set_top(dummy_region->end());
2167 G1AllocRegion::setup(this, dummy_region);
2169 init_mutator_alloc_region();
2171 // Do create of the monitoring and management support so that
2172 // values in the heap have been properly initialized.
2173 _g1mm = new G1MonitoringSupport(this);
2175 G1StringDedup::initialize();
2177 return JNI_OK;
2178 }
2180 void G1CollectedHeap::stop() {
2181 // Stop all concurrent threads. We do this to make sure these threads
2182 // do not continue to execute and access resources (e.g. gclog_or_tty)
2183 // that are destroyed during shutdown.
2184 _cg1r->stop();
2185 _cmThread->stop();
2186 if (G1StringDedup::is_enabled()) {
2187 G1StringDedup::stop();
2188 }
2189 }
2191 size_t G1CollectedHeap::conservative_max_heap_alignment() {
2192 return HeapRegion::max_region_size();
2193 }
2195 void G1CollectedHeap::ref_processing_init() {
2196 // Reference processing in G1 currently works as follows:
2197 //
2198 // * There are two reference processor instances. One is
2199 // used to record and process discovered references
2200 // during concurrent marking; the other is used to
2201 // record and process references during STW pauses
2202 // (both full and incremental).
2203 // * Both ref processors need to 'span' the entire heap as
2204 // the regions in the collection set may be dotted around.
2205 //
2206 // * For the concurrent marking ref processor:
2207 // * Reference discovery is enabled at initial marking.
2208 // * Reference discovery is disabled and the discovered
2209 // references processed etc during remarking.
2210 // * Reference discovery is MT (see below).
2211 // * Reference discovery requires a barrier (see below).
2212 // * Reference processing may or may not be MT
2213 // (depending on the value of ParallelRefProcEnabled
2214 // and ParallelGCThreads).
2215 // * A full GC disables reference discovery by the CM
2216 // ref processor and abandons any entries on it's
2217 // discovered lists.
2218 //
2219 // * For the STW processor:
2220 // * Non MT discovery is enabled at the start of a full GC.
2221 // * Processing and enqueueing during a full GC is non-MT.
2222 // * During a full GC, references are processed after marking.
2223 //
2224 // * Discovery (may or may not be MT) is enabled at the start
2225 // of an incremental evacuation pause.
2226 // * References are processed near the end of a STW evacuation pause.
2227 // * For both types of GC:
2228 // * Discovery is atomic - i.e. not concurrent.
2229 // * Reference discovery will not need a barrier.
2231 SharedHeap::ref_processing_init();
2232 MemRegion mr = reserved_region();
2234 // Concurrent Mark ref processor
2235 _ref_processor_cm =
2236 new ReferenceProcessor(mr, // span
2237 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2238 // mt processing
2239 (int) ParallelGCThreads,
2240 // degree of mt processing
2241 (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2242 // mt discovery
2243 (int) MAX2(ParallelGCThreads, ConcGCThreads),
2244 // degree of mt discovery
2245 false,
2246 // Reference discovery is not atomic
2247 &_is_alive_closure_cm);
2248 // is alive closure
2249 // (for efficiency/performance)
2251 // STW ref processor
2252 _ref_processor_stw =
2253 new ReferenceProcessor(mr, // span
2254 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2255 // mt processing
2256 MAX2((int)ParallelGCThreads, 1),
2257 // degree of mt processing
2258 (ParallelGCThreads > 1),
2259 // mt discovery
2260 MAX2((int)ParallelGCThreads, 1),
2261 // degree of mt discovery
2262 true,
2263 // Reference discovery is atomic
2264 &_is_alive_closure_stw);
2265 // is alive closure
2266 // (for efficiency/performance)
2267 }
2269 size_t G1CollectedHeap::capacity() const {
2270 return _g1_committed.byte_size();
2271 }
2273 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2274 assert(!hr->continuesHumongous(), "pre-condition");
2275 hr->reset_gc_time_stamp();
2276 if (hr->startsHumongous()) {
2277 uint first_index = hr->hrs_index() + 1;
2278 uint last_index = hr->last_hc_index();
2279 for (uint i = first_index; i < last_index; i += 1) {
2280 HeapRegion* chr = region_at(i);
2281 assert(chr->continuesHumongous(), "sanity");
2282 chr->reset_gc_time_stamp();
2283 }
2284 }
2285 }
2287 #ifndef PRODUCT
2288 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2289 private:
2290 unsigned _gc_time_stamp;
2291 bool _failures;
2293 public:
2294 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2295 _gc_time_stamp(gc_time_stamp), _failures(false) { }
2297 virtual bool doHeapRegion(HeapRegion* hr) {
2298 unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2299 if (_gc_time_stamp != region_gc_time_stamp) {
2300 gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, "
2301 "expected %d", HR_FORMAT_PARAMS(hr),
2302 region_gc_time_stamp, _gc_time_stamp);
2303 _failures = true;
2304 }
2305 return false;
2306 }
2308 bool failures() { return _failures; }
2309 };
2311 void G1CollectedHeap::check_gc_time_stamps() {
2312 CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2313 heap_region_iterate(&cl);
2314 guarantee(!cl.failures(), "all GC time stamps should have been reset");
2315 }
2316 #endif // PRODUCT
2318 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2319 DirtyCardQueue* into_cset_dcq,
2320 bool concurrent,
2321 uint worker_i) {
2322 // Clean cards in the hot card cache
2323 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
2324 hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq);
2326 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2327 int n_completed_buffers = 0;
2328 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2329 n_completed_buffers++;
2330 }
2331 g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers);
2332 dcqs.clear_n_completed_buffers();
2333 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2334 }
2337 // Computes the sum of the storage used by the various regions.
2339 size_t G1CollectedHeap::used() const {
2340 assert(Heap_lock->owner() != NULL,
2341 "Should be owned on this thread's behalf.");
2342 size_t result = _summary_bytes_used;
2343 // Read only once in case it is set to NULL concurrently
2344 HeapRegion* hr = _mutator_alloc_region.get();
2345 if (hr != NULL)
2346 result += hr->used();
2347 return result;
2348 }
2350 size_t G1CollectedHeap::used_unlocked() const {
2351 size_t result = _summary_bytes_used;
2352 return result;
2353 }
2355 class SumUsedClosure: public HeapRegionClosure {
2356 size_t _used;
2357 public:
2358 SumUsedClosure() : _used(0) {}
2359 bool doHeapRegion(HeapRegion* r) {
2360 if (!r->continuesHumongous()) {
2361 _used += r->used();
2362 }
2363 return false;
2364 }
2365 size_t result() { return _used; }
2366 };
2368 size_t G1CollectedHeap::recalculate_used() const {
2369 double recalculate_used_start = os::elapsedTime();
2371 SumUsedClosure blk;
2372 heap_region_iterate(&blk);
2374 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2375 return blk.result();
2376 }
2378 size_t G1CollectedHeap::unsafe_max_alloc() {
2379 if (free_regions() > 0) return HeapRegion::GrainBytes;
2380 // otherwise, is there space in the current allocation region?
2382 // We need to store the current allocation region in a local variable
2383 // here. The problem is that this method doesn't take any locks and
2384 // there may be other threads which overwrite the current allocation
2385 // region field. attempt_allocation(), for example, sets it to NULL
2386 // and this can happen *after* the NULL check here but before the call
2387 // to free(), resulting in a SIGSEGV. Note that this doesn't appear
2388 // to be a problem in the optimized build, since the two loads of the
2389 // current allocation region field are optimized away.
2390 HeapRegion* hr = _mutator_alloc_region.get();
2391 if (hr == NULL) {
2392 return 0;
2393 }
2394 return hr->free();
2395 }
2397 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2398 switch (cause) {
2399 case GCCause::_gc_locker: return GCLockerInvokesConcurrent;
2400 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
2401 case GCCause::_g1_humongous_allocation: return true;
2402 default: return false;
2403 }
2404 }
2406 #ifndef PRODUCT
2407 void G1CollectedHeap::allocate_dummy_regions() {
2408 // Let's fill up most of the region
2409 size_t word_size = HeapRegion::GrainWords - 1024;
2410 // And as a result the region we'll allocate will be humongous.
2411 guarantee(isHumongous(word_size), "sanity");
2413 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2414 // Let's use the existing mechanism for the allocation
2415 HeapWord* dummy_obj = humongous_obj_allocate(word_size);
2416 if (dummy_obj != NULL) {
2417 MemRegion mr(dummy_obj, word_size);
2418 CollectedHeap::fill_with_object(mr);
2419 } else {
2420 // If we can't allocate once, we probably cannot allocate
2421 // again. Let's get out of the loop.
2422 break;
2423 }
2424 }
2425 }
2426 #endif // !PRODUCT
2428 void G1CollectedHeap::increment_old_marking_cycles_started() {
2429 assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2430 _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2431 err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2432 _old_marking_cycles_started, _old_marking_cycles_completed));
2434 _old_marking_cycles_started++;
2435 }
2437 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2438 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2440 // We assume that if concurrent == true, then the caller is a
2441 // concurrent thread that was joined the Suspendible Thread
2442 // Set. If there's ever a cheap way to check this, we should add an
2443 // assert here.
2445 // Given that this method is called at the end of a Full GC or of a
2446 // concurrent cycle, and those can be nested (i.e., a Full GC can
2447 // interrupt a concurrent cycle), the number of full collections
2448 // completed should be either one (in the case where there was no
2449 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2450 // behind the number of full collections started.
2452 // This is the case for the inner caller, i.e. a Full GC.
2453 assert(concurrent ||
2454 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2455 (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2456 err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
2457 "is inconsistent with _old_marking_cycles_completed = %u",
2458 _old_marking_cycles_started, _old_marking_cycles_completed));
2460 // This is the case for the outer caller, i.e. the concurrent cycle.
2461 assert(!concurrent ||
2462 (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2463 err_msg("for outer caller (concurrent cycle): "
2464 "_old_marking_cycles_started = %u "
2465 "is inconsistent with _old_marking_cycles_completed = %u",
2466 _old_marking_cycles_started, _old_marking_cycles_completed));
2468 _old_marking_cycles_completed += 1;
2470 // We need to clear the "in_progress" flag in the CM thread before
2471 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2472 // is set) so that if a waiter requests another System.gc() it doesn't
2473 // incorrectly see that a marking cycle is still in progress.
2474 if (concurrent) {
2475 _cmThread->clear_in_progress();
2476 }
2478 // This notify_all() will ensure that a thread that called
2479 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2480 // and it's waiting for a full GC to finish will be woken up. It is
2481 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2482 FullGCCount_lock->notify_all();
2483 }
2485 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) {
2486 _concurrent_cycle_started = true;
2487 _gc_timer_cm->register_gc_start(start_time);
2489 _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start());
2490 trace_heap_before_gc(_gc_tracer_cm);
2491 }
2493 void G1CollectedHeap::register_concurrent_cycle_end() {
2494 if (_concurrent_cycle_started) {
2495 if (_cm->has_aborted()) {
2496 _gc_tracer_cm->report_concurrent_mode_failure();
2497 }
2499 _gc_timer_cm->register_gc_end();
2500 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
2502 _concurrent_cycle_started = false;
2503 }
2504 }
2506 void G1CollectedHeap::trace_heap_after_concurrent_cycle() {
2507 if (_concurrent_cycle_started) {
2508 trace_heap_after_gc(_gc_tracer_cm);
2509 }
2510 }
2512 G1YCType G1CollectedHeap::yc_type() {
2513 bool is_young = g1_policy()->gcs_are_young();
2514 bool is_initial_mark = g1_policy()->during_initial_mark_pause();
2515 bool is_during_mark = mark_in_progress();
2517 if (is_initial_mark) {
2518 return InitialMark;
2519 } else if (is_during_mark) {
2520 return DuringMark;
2521 } else if (is_young) {
2522 return Normal;
2523 } else {
2524 return Mixed;
2525 }
2526 }
2528 void G1CollectedHeap::collect(GCCause::Cause cause) {
2529 assert_heap_not_locked();
2531 unsigned int gc_count_before;
2532 unsigned int old_marking_count_before;
2533 bool retry_gc;
2535 do {
2536 retry_gc = false;
2538 {
2539 MutexLocker ml(Heap_lock);
2541 // Read the GC count while holding the Heap_lock
2542 gc_count_before = total_collections();
2543 old_marking_count_before = _old_marking_cycles_started;
2544 }
2546 if (should_do_concurrent_full_gc(cause)) {
2547 // Schedule an initial-mark evacuation pause that will start a
2548 // concurrent cycle. We're setting word_size to 0 which means that
2549 // we are not requesting a post-GC allocation.
2550 VM_G1IncCollectionPause op(gc_count_before,
2551 0, /* word_size */
2552 true, /* should_initiate_conc_mark */
2553 g1_policy()->max_pause_time_ms(),
2554 cause);
2556 VMThread::execute(&op);
2557 if (!op.pause_succeeded()) {
2558 if (old_marking_count_before == _old_marking_cycles_started) {
2559 retry_gc = op.should_retry_gc();
2560 } else {
2561 // A Full GC happened while we were trying to schedule the
2562 // initial-mark GC. No point in starting a new cycle given
2563 // that the whole heap was collected anyway.
2564 }
2566 if (retry_gc) {
2567 if (GC_locker::is_active_and_needs_gc()) {
2568 GC_locker::stall_until_clear();
2569 }
2570 }
2571 }
2572 } else {
2573 if (cause == GCCause::_gc_locker
2574 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2576 // Schedule a standard evacuation pause. We're setting word_size
2577 // to 0 which means that we are not requesting a post-GC allocation.
2578 VM_G1IncCollectionPause op(gc_count_before,
2579 0, /* word_size */
2580 false, /* should_initiate_conc_mark */
2581 g1_policy()->max_pause_time_ms(),
2582 cause);
2583 VMThread::execute(&op);
2584 } else {
2585 // Schedule a Full GC.
2586 VM_G1CollectFull op(gc_count_before, old_marking_count_before, cause);
2587 VMThread::execute(&op);
2588 }
2589 }
2590 } while (retry_gc);
2591 }
2593 bool G1CollectedHeap::is_in(const void* p) const {
2594 if (_g1_committed.contains(p)) {
2595 // Given that we know that p is in the committed space,
2596 // heap_region_containing_raw() should successfully
2597 // return the containing region.
2598 HeapRegion* hr = heap_region_containing_raw(p);
2599 return hr->is_in(p);
2600 } else {
2601 return false;
2602 }
2603 }
2605 // Iteration functions.
2607 // Iterates an OopClosure over all ref-containing fields of objects
2608 // within a HeapRegion.
2610 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2611 MemRegion _mr;
2612 ExtendedOopClosure* _cl;
2613 public:
2614 IterateOopClosureRegionClosure(MemRegion mr, ExtendedOopClosure* cl)
2615 : _mr(mr), _cl(cl) {}
2616 bool doHeapRegion(HeapRegion* r) {
2617 if (!r->continuesHumongous()) {
2618 r->oop_iterate(_cl);
2619 }
2620 return false;
2621 }
2622 };
2624 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) {
2625 IterateOopClosureRegionClosure blk(_g1_committed, cl);
2626 heap_region_iterate(&blk);
2627 }
2629 void G1CollectedHeap::oop_iterate(MemRegion mr, ExtendedOopClosure* cl) {
2630 IterateOopClosureRegionClosure blk(mr, cl);
2631 heap_region_iterate(&blk);
2632 }
2634 // Iterates an ObjectClosure over all objects within a HeapRegion.
2636 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2637 ObjectClosure* _cl;
2638 public:
2639 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2640 bool doHeapRegion(HeapRegion* r) {
2641 if (! r->continuesHumongous()) {
2642 r->object_iterate(_cl);
2643 }
2644 return false;
2645 }
2646 };
2648 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2649 IterateObjectClosureRegionClosure blk(cl);
2650 heap_region_iterate(&blk);
2651 }
2653 // Calls a SpaceClosure on a HeapRegion.
2655 class SpaceClosureRegionClosure: public HeapRegionClosure {
2656 SpaceClosure* _cl;
2657 public:
2658 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2659 bool doHeapRegion(HeapRegion* r) {
2660 _cl->do_space(r);
2661 return false;
2662 }
2663 };
2665 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2666 SpaceClosureRegionClosure blk(cl);
2667 heap_region_iterate(&blk);
2668 }
2670 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2671 _hrs.iterate(cl);
2672 }
2674 void
2675 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
2676 uint worker_id,
2677 uint no_of_par_workers,
2678 jint claim_value) {
2679 const uint regions = n_regions();
2680 const uint max_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
2681 no_of_par_workers :
2682 1);
2683 assert(UseDynamicNumberOfGCThreads ||
2684 no_of_par_workers == workers()->total_workers(),
2685 "Non dynamic should use fixed number of workers");
2686 // try to spread out the starting points of the workers
2687 const HeapRegion* start_hr =
2688 start_region_for_worker(worker_id, no_of_par_workers);
2689 const uint start_index = start_hr->hrs_index();
2691 // each worker will actually look at all regions
2692 for (uint count = 0; count < regions; ++count) {
2693 const uint index = (start_index + count) % regions;
2694 assert(0 <= index && index < regions, "sanity");
2695 HeapRegion* r = region_at(index);
2696 // we'll ignore "continues humongous" regions (we'll process them
2697 // when we come across their corresponding "start humongous"
2698 // region) and regions already claimed
2699 if (r->claim_value() == claim_value || r->continuesHumongous()) {
2700 continue;
2701 }
2702 // OK, try to claim it
2703 if (r->claimHeapRegion(claim_value)) {
2704 // success!
2705 assert(!r->continuesHumongous(), "sanity");
2706 if (r->startsHumongous()) {
2707 // If the region is "starts humongous" we'll iterate over its
2708 // "continues humongous" first; in fact we'll do them
2709 // first. The order is important. In on case, calling the
2710 // closure on the "starts humongous" region might de-allocate
2711 // and clear all its "continues humongous" regions and, as a
2712 // result, we might end up processing them twice. So, we'll do
2713 // them first (notice: most closures will ignore them anyway) and
2714 // then we'll do the "starts humongous" region.
2715 for (uint ch_index = index + 1; ch_index < regions; ++ch_index) {
2716 HeapRegion* chr = region_at(ch_index);
2718 // if the region has already been claimed or it's not
2719 // "continues humongous" we're done
2720 if (chr->claim_value() == claim_value ||
2721 !chr->continuesHumongous()) {
2722 break;
2723 }
2725 // No one should have claimed it directly. We can given
2726 // that we claimed its "starts humongous" region.
2727 assert(chr->claim_value() != claim_value, "sanity");
2728 assert(chr->humongous_start_region() == r, "sanity");
2730 if (chr->claimHeapRegion(claim_value)) {
2731 // we should always be able to claim it; no one else should
2732 // be trying to claim this region
2734 bool res2 = cl->doHeapRegion(chr);
2735 assert(!res2, "Should not abort");
2737 // Right now, this holds (i.e., no closure that actually
2738 // does something with "continues humongous" regions
2739 // clears them). We might have to weaken it in the future,
2740 // but let's leave these two asserts here for extra safety.
2741 assert(chr->continuesHumongous(), "should still be the case");
2742 assert(chr->humongous_start_region() == r, "sanity");
2743 } else {
2744 guarantee(false, "we should not reach here");
2745 }
2746 }
2747 }
2749 assert(!r->continuesHumongous(), "sanity");
2750 bool res = cl->doHeapRegion(r);
2751 assert(!res, "Should not abort");
2752 }
2753 }
2754 }
2756 class ResetClaimValuesClosure: public HeapRegionClosure {
2757 public:
2758 bool doHeapRegion(HeapRegion* r) {
2759 r->set_claim_value(HeapRegion::InitialClaimValue);
2760 return false;
2761 }
2762 };
2764 void G1CollectedHeap::reset_heap_region_claim_values() {
2765 ResetClaimValuesClosure blk;
2766 heap_region_iterate(&blk);
2767 }
2769 void G1CollectedHeap::reset_cset_heap_region_claim_values() {
2770 ResetClaimValuesClosure blk;
2771 collection_set_iterate(&blk);
2772 }
2774 #ifdef ASSERT
2775 // This checks whether all regions in the heap have the correct claim
2776 // value. I also piggy-backed on this a check to ensure that the
2777 // humongous_start_region() information on "continues humongous"
2778 // regions is correct.
2780 class CheckClaimValuesClosure : public HeapRegionClosure {
2781 private:
2782 jint _claim_value;
2783 uint _failures;
2784 HeapRegion* _sh_region;
2786 public:
2787 CheckClaimValuesClosure(jint claim_value) :
2788 _claim_value(claim_value), _failures(0), _sh_region(NULL) { }
2789 bool doHeapRegion(HeapRegion* r) {
2790 if (r->claim_value() != _claim_value) {
2791 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2792 "claim value = %d, should be %d",
2793 HR_FORMAT_PARAMS(r),
2794 r->claim_value(), _claim_value);
2795 ++_failures;
2796 }
2797 if (!r->isHumongous()) {
2798 _sh_region = NULL;
2799 } else if (r->startsHumongous()) {
2800 _sh_region = r;
2801 } else if (r->continuesHumongous()) {
2802 if (r->humongous_start_region() != _sh_region) {
2803 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2804 "HS = "PTR_FORMAT", should be "PTR_FORMAT,
2805 HR_FORMAT_PARAMS(r),
2806 r->humongous_start_region(),
2807 _sh_region);
2808 ++_failures;
2809 }
2810 }
2811 return false;
2812 }
2813 uint failures() { return _failures; }
2814 };
2816 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
2817 CheckClaimValuesClosure cl(claim_value);
2818 heap_region_iterate(&cl);
2819 return cl.failures() == 0;
2820 }
2822 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure {
2823 private:
2824 jint _claim_value;
2825 uint _failures;
2827 public:
2828 CheckClaimValuesInCSetHRClosure(jint claim_value) :
2829 _claim_value(claim_value), _failures(0) { }
2831 uint failures() { return _failures; }
2833 bool doHeapRegion(HeapRegion* hr) {
2834 assert(hr->in_collection_set(), "how?");
2835 assert(!hr->isHumongous(), "H-region in CSet");
2836 if (hr->claim_value() != _claim_value) {
2837 gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", "
2838 "claim value = %d, should be %d",
2839 HR_FORMAT_PARAMS(hr),
2840 hr->claim_value(), _claim_value);
2841 _failures += 1;
2842 }
2843 return false;
2844 }
2845 };
2847 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) {
2848 CheckClaimValuesInCSetHRClosure cl(claim_value);
2849 collection_set_iterate(&cl);
2850 return cl.failures() == 0;
2851 }
2852 #endif // ASSERT
2854 // Clear the cached CSet starting regions and (more importantly)
2855 // the time stamps. Called when we reset the GC time stamp.
2856 void G1CollectedHeap::clear_cset_start_regions() {
2857 assert(_worker_cset_start_region != NULL, "sanity");
2858 assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2860 int n_queues = MAX2((int)ParallelGCThreads, 1);
2861 for (int i = 0; i < n_queues; i++) {
2862 _worker_cset_start_region[i] = NULL;
2863 _worker_cset_start_region_time_stamp[i] = 0;
2864 }
2865 }
2867 // Given the id of a worker, obtain or calculate a suitable
2868 // starting region for iterating over the current collection set.
2869 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) {
2870 assert(get_gc_time_stamp() > 0, "should have been updated by now");
2872 HeapRegion* result = NULL;
2873 unsigned gc_time_stamp = get_gc_time_stamp();
2875 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2876 // Cached starting region for current worker was set
2877 // during the current pause - so it's valid.
2878 // Note: the cached starting heap region may be NULL
2879 // (when the collection set is empty).
2880 result = _worker_cset_start_region[worker_i];
2881 assert(result == NULL || result->in_collection_set(), "sanity");
2882 return result;
2883 }
2885 // The cached entry was not valid so let's calculate
2886 // a suitable starting heap region for this worker.
2888 // We want the parallel threads to start their collection
2889 // set iteration at different collection set regions to
2890 // avoid contention.
2891 // If we have:
2892 // n collection set regions
2893 // p threads
2894 // Then thread t will start at region floor ((t * n) / p)
2896 result = g1_policy()->collection_set();
2897 if (G1CollectedHeap::use_parallel_gc_threads()) {
2898 uint cs_size = g1_policy()->cset_region_length();
2899 uint active_workers = workers()->active_workers();
2900 assert(UseDynamicNumberOfGCThreads ||
2901 active_workers == workers()->total_workers(),
2902 "Unless dynamic should use total workers");
2904 uint end_ind = (cs_size * worker_i) / active_workers;
2905 uint start_ind = 0;
2907 if (worker_i > 0 &&
2908 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2909 // Previous workers starting region is valid
2910 // so let's iterate from there
2911 start_ind = (cs_size * (worker_i - 1)) / active_workers;
2912 result = _worker_cset_start_region[worker_i - 1];
2913 }
2915 for (uint i = start_ind; i < end_ind; i++) {
2916 result = result->next_in_collection_set();
2917 }
2918 }
2920 // Note: the calculated starting heap region may be NULL
2921 // (when the collection set is empty).
2922 assert(result == NULL || result->in_collection_set(), "sanity");
2923 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2924 "should be updated only once per pause");
2925 _worker_cset_start_region[worker_i] = result;
2926 OrderAccess::storestore();
2927 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2928 return result;
2929 }
2931 HeapRegion* G1CollectedHeap::start_region_for_worker(uint worker_i,
2932 uint no_of_par_workers) {
2933 uint worker_num =
2934 G1CollectedHeap::use_parallel_gc_threads() ? no_of_par_workers : 1U;
2935 assert(UseDynamicNumberOfGCThreads ||
2936 no_of_par_workers == workers()->total_workers(),
2937 "Non dynamic should use fixed number of workers");
2938 const uint start_index = n_regions() * worker_i / worker_num;
2939 return region_at(start_index);
2940 }
2942 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2943 HeapRegion* r = g1_policy()->collection_set();
2944 while (r != NULL) {
2945 HeapRegion* next = r->next_in_collection_set();
2946 if (cl->doHeapRegion(r)) {
2947 cl->incomplete();
2948 return;
2949 }
2950 r = next;
2951 }
2952 }
2954 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2955 HeapRegionClosure *cl) {
2956 if (r == NULL) {
2957 // The CSet is empty so there's nothing to do.
2958 return;
2959 }
2961 assert(r->in_collection_set(),
2962 "Start region must be a member of the collection set.");
2963 HeapRegion* cur = r;
2964 while (cur != NULL) {
2965 HeapRegion* next = cur->next_in_collection_set();
2966 if (cl->doHeapRegion(cur) && false) {
2967 cl->incomplete();
2968 return;
2969 }
2970 cur = next;
2971 }
2972 cur = g1_policy()->collection_set();
2973 while (cur != r) {
2974 HeapRegion* next = cur->next_in_collection_set();
2975 if (cl->doHeapRegion(cur) && false) {
2976 cl->incomplete();
2977 return;
2978 }
2979 cur = next;
2980 }
2981 }
2983 CompactibleSpace* G1CollectedHeap::first_compactible_space() {
2984 return n_regions() > 0 ? region_at(0) : NULL;
2985 }
2988 Space* G1CollectedHeap::space_containing(const void* addr) const {
2989 Space* res = heap_region_containing(addr);
2990 return res;
2991 }
2993 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2994 Space* sp = space_containing(addr);
2995 if (sp != NULL) {
2996 return sp->block_start(addr);
2997 }
2998 return NULL;
2999 }
3001 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
3002 Space* sp = space_containing(addr);
3003 assert(sp != NULL, "block_size of address outside of heap");
3004 return sp->block_size(addr);
3005 }
3007 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
3008 Space* sp = space_containing(addr);
3009 return sp->block_is_obj(addr);
3010 }
3012 bool G1CollectedHeap::supports_tlab_allocation() const {
3013 return true;
3014 }
3016 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
3017 return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes;
3018 }
3020 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
3021 return young_list()->eden_used_bytes();
3022 }
3024 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
3025 // must be smaller than the humongous object limit.
3026 size_t G1CollectedHeap::max_tlab_size() const {
3027 return align_size_down(_humongous_object_threshold_in_words - 1, MinObjAlignment);
3028 }
3030 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
3031 // Return the remaining space in the cur alloc region, but not less than
3032 // the min TLAB size.
3034 // Also, this value can be at most the humongous object threshold,
3035 // since we can't allow tlabs to grow big enough to accommodate
3036 // humongous objects.
3038 HeapRegion* hr = _mutator_alloc_region.get();
3039 size_t max_tlab = max_tlab_size() * wordSize;
3040 if (hr == NULL) {
3041 return max_tlab;
3042 } else {
3043 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab);
3044 }
3045 }
3047 size_t G1CollectedHeap::max_capacity() const {
3048 return _g1_reserved.byte_size();
3049 }
3051 jlong G1CollectedHeap::millis_since_last_gc() {
3052 // assert(false, "NYI");
3053 return 0;
3054 }
3056 void G1CollectedHeap::prepare_for_verify() {
3057 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
3058 ensure_parsability(false);
3059 }
3060 g1_rem_set()->prepare_for_verify();
3061 }
3063 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr,
3064 VerifyOption vo) {
3065 switch (vo) {
3066 case VerifyOption_G1UsePrevMarking:
3067 return hr->obj_allocated_since_prev_marking(obj);
3068 case VerifyOption_G1UseNextMarking:
3069 return hr->obj_allocated_since_next_marking(obj);
3070 case VerifyOption_G1UseMarkWord:
3071 return false;
3072 default:
3073 ShouldNotReachHere();
3074 }
3075 return false; // keep some compilers happy
3076 }
3078 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) {
3079 switch (vo) {
3080 case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start();
3081 case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start();
3082 case VerifyOption_G1UseMarkWord: return NULL;
3083 default: ShouldNotReachHere();
3084 }
3085 return NULL; // keep some compilers happy
3086 }
3088 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) {
3089 switch (vo) {
3090 case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj);
3091 case VerifyOption_G1UseNextMarking: return isMarkedNext(obj);
3092 case VerifyOption_G1UseMarkWord: return obj->is_gc_marked();
3093 default: ShouldNotReachHere();
3094 }
3095 return false; // keep some compilers happy
3096 }
3098 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) {
3099 switch (vo) {
3100 case VerifyOption_G1UsePrevMarking: return "PTAMS";
3101 case VerifyOption_G1UseNextMarking: return "NTAMS";
3102 case VerifyOption_G1UseMarkWord: return "NONE";
3103 default: ShouldNotReachHere();
3104 }
3105 return NULL; // keep some compilers happy
3106 }
3108 class VerifyRootsClosure: public OopClosure {
3109 private:
3110 G1CollectedHeap* _g1h;
3111 VerifyOption _vo;
3112 bool _failures;
3113 public:
3114 // _vo == UsePrevMarking -> use "prev" marking information,
3115 // _vo == UseNextMarking -> use "next" marking information,
3116 // _vo == UseMarkWord -> use mark word from object header.
3117 VerifyRootsClosure(VerifyOption vo) :
3118 _g1h(G1CollectedHeap::heap()),
3119 _vo(vo),
3120 _failures(false) { }
3122 bool failures() { return _failures; }
3124 template <class T> void do_oop_nv(T* p) {
3125 T heap_oop = oopDesc::load_heap_oop(p);
3126 if (!oopDesc::is_null(heap_oop)) {
3127 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3128 if (_g1h->is_obj_dead_cond(obj, _vo)) {
3129 gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
3130 "points to dead obj "PTR_FORMAT, p, (void*) obj);
3131 if (_vo == VerifyOption_G1UseMarkWord) {
3132 gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark()));
3133 }
3134 obj->print_on(gclog_or_tty);
3135 _failures = true;
3136 }
3137 }
3138 }
3140 void do_oop(oop* p) { do_oop_nv(p); }
3141 void do_oop(narrowOop* p) { do_oop_nv(p); }
3142 };
3144 class G1VerifyCodeRootOopClosure: public OopClosure {
3145 G1CollectedHeap* _g1h;
3146 OopClosure* _root_cl;
3147 nmethod* _nm;
3148 VerifyOption _vo;
3149 bool _failures;
3151 template <class T> void do_oop_work(T* p) {
3152 // First verify that this root is live
3153 _root_cl->do_oop(p);
3155 if (!G1VerifyHeapRegionCodeRoots) {
3156 // We're not verifying the code roots attached to heap region.
3157 return;
3158 }
3160 // Don't check the code roots during marking verification in a full GC
3161 if (_vo == VerifyOption_G1UseMarkWord) {
3162 return;
3163 }
3165 // Now verify that the current nmethod (which contains p) is
3166 // in the code root list of the heap region containing the
3167 // object referenced by p.
3169 T heap_oop = oopDesc::load_heap_oop(p);
3170 if (!oopDesc::is_null(heap_oop)) {
3171 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3173 // Now fetch the region containing the object
3174 HeapRegion* hr = _g1h->heap_region_containing(obj);
3175 HeapRegionRemSet* hrrs = hr->rem_set();
3176 // Verify that the strong code root list for this region
3177 // contains the nmethod
3178 if (!hrrs->strong_code_roots_list_contains(_nm)) {
3179 gclog_or_tty->print_cr("Code root location "PTR_FORMAT" "
3180 "from nmethod "PTR_FORMAT" not in strong "
3181 "code roots for region ["PTR_FORMAT","PTR_FORMAT")",
3182 p, _nm, hr->bottom(), hr->end());
3183 _failures = true;
3184 }
3185 }
3186 }
3188 public:
3189 G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo):
3190 _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {}
3192 void do_oop(oop* p) { do_oop_work(p); }
3193 void do_oop(narrowOop* p) { do_oop_work(p); }
3195 void set_nmethod(nmethod* nm) { _nm = nm; }
3196 bool failures() { return _failures; }
3197 };
3199 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure {
3200 G1VerifyCodeRootOopClosure* _oop_cl;
3202 public:
3203 G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl):
3204 _oop_cl(oop_cl) {}
3206 void do_code_blob(CodeBlob* cb) {
3207 nmethod* nm = cb->as_nmethod_or_null();
3208 if (nm != NULL) {
3209 _oop_cl->set_nmethod(nm);
3210 nm->oops_do(_oop_cl);
3211 }
3212 }
3213 };
3215 class YoungRefCounterClosure : public OopClosure {
3216 G1CollectedHeap* _g1h;
3217 int _count;
3218 public:
3219 YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {}
3220 void do_oop(oop* p) { if (_g1h->is_in_young(*p)) { _count++; } }
3221 void do_oop(narrowOop* p) { ShouldNotReachHere(); }
3223 int count() { return _count; }
3224 void reset_count() { _count = 0; };
3225 };
3227 class VerifyKlassClosure: public KlassClosure {
3228 YoungRefCounterClosure _young_ref_counter_closure;
3229 OopClosure *_oop_closure;
3230 public:
3231 VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {}
3232 void do_klass(Klass* k) {
3233 k->oops_do(_oop_closure);
3235 _young_ref_counter_closure.reset_count();
3236 k->oops_do(&_young_ref_counter_closure);
3237 if (_young_ref_counter_closure.count() > 0) {
3238 guarantee(k->has_modified_oops(), err_msg("Klass %p, has young refs but is not dirty.", k));
3239 }
3240 }
3241 };
3243 class VerifyLivenessOopClosure: public OopClosure {
3244 G1CollectedHeap* _g1h;
3245 VerifyOption _vo;
3246 public:
3247 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
3248 _g1h(g1h), _vo(vo)
3249 { }
3250 void do_oop(narrowOop *p) { do_oop_work(p); }
3251 void do_oop( oop *p) { do_oop_work(p); }
3253 template <class T> void do_oop_work(T *p) {
3254 oop obj = oopDesc::load_decode_heap_oop(p);
3255 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
3256 "Dead object referenced by a not dead object");
3257 }
3258 };
3260 class VerifyObjsInRegionClosure: public ObjectClosure {
3261 private:
3262 G1CollectedHeap* _g1h;
3263 size_t _live_bytes;
3264 HeapRegion *_hr;
3265 VerifyOption _vo;
3266 public:
3267 // _vo == UsePrevMarking -> use "prev" marking information,
3268 // _vo == UseNextMarking -> use "next" marking information,
3269 // _vo == UseMarkWord -> use mark word from object header.
3270 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
3271 : _live_bytes(0), _hr(hr), _vo(vo) {
3272 _g1h = G1CollectedHeap::heap();
3273 }
3274 void do_object(oop o) {
3275 VerifyLivenessOopClosure isLive(_g1h, _vo);
3276 assert(o != NULL, "Huh?");
3277 if (!_g1h->is_obj_dead_cond(o, _vo)) {
3278 // If the object is alive according to the mark word,
3279 // then verify that the marking information agrees.
3280 // Note we can't verify the contra-positive of the
3281 // above: if the object is dead (according to the mark
3282 // word), it may not be marked, or may have been marked
3283 // but has since became dead, or may have been allocated
3284 // since the last marking.
3285 if (_vo == VerifyOption_G1UseMarkWord) {
3286 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
3287 }
3289 o->oop_iterate_no_header(&isLive);
3290 if (!_hr->obj_allocated_since_prev_marking(o)) {
3291 size_t obj_size = o->size(); // Make sure we don't overflow
3292 _live_bytes += (obj_size * HeapWordSize);
3293 }
3294 }
3295 }
3296 size_t live_bytes() { return _live_bytes; }
3297 };
3299 class PrintObjsInRegionClosure : public ObjectClosure {
3300 HeapRegion *_hr;
3301 G1CollectedHeap *_g1;
3302 public:
3303 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
3304 _g1 = G1CollectedHeap::heap();
3305 };
3307 void do_object(oop o) {
3308 if (o != NULL) {
3309 HeapWord *start = (HeapWord *) o;
3310 size_t word_sz = o->size();
3311 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
3312 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
3313 (void*) o, word_sz,
3314 _g1->isMarkedPrev(o),
3315 _g1->isMarkedNext(o),
3316 _hr->obj_allocated_since_prev_marking(o));
3317 HeapWord *end = start + word_sz;
3318 HeapWord *cur;
3319 int *val;
3320 for (cur = start; cur < end; cur++) {
3321 val = (int *) cur;
3322 gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val);
3323 }
3324 }
3325 }
3326 };
3328 class VerifyRegionClosure: public HeapRegionClosure {
3329 private:
3330 bool _par;
3331 VerifyOption _vo;
3332 bool _failures;
3333 public:
3334 // _vo == UsePrevMarking -> use "prev" marking information,
3335 // _vo == UseNextMarking -> use "next" marking information,
3336 // _vo == UseMarkWord -> use mark word from object header.
3337 VerifyRegionClosure(bool par, VerifyOption vo)
3338 : _par(par),
3339 _vo(vo),
3340 _failures(false) {}
3342 bool failures() {
3343 return _failures;
3344 }
3346 bool doHeapRegion(HeapRegion* r) {
3347 if (!r->continuesHumongous()) {
3348 bool failures = false;
3349 r->verify(_vo, &failures);
3350 if (failures) {
3351 _failures = true;
3352 } else {
3353 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
3354 r->object_iterate(¬_dead_yet_cl);
3355 if (_vo != VerifyOption_G1UseNextMarking) {
3356 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
3357 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
3358 "max_live_bytes "SIZE_FORMAT" "
3359 "< calculated "SIZE_FORMAT,
3360 r->bottom(), r->end(),
3361 r->max_live_bytes(),
3362 not_dead_yet_cl.live_bytes());
3363 _failures = true;
3364 }
3365 } else {
3366 // When vo == UseNextMarking we cannot currently do a sanity
3367 // check on the live bytes as the calculation has not been
3368 // finalized yet.
3369 }
3370 }
3371 }
3372 return false; // stop the region iteration if we hit a failure
3373 }
3374 };
3376 // This is the task used for parallel verification of the heap regions
3378 class G1ParVerifyTask: public AbstractGangTask {
3379 private:
3380 G1CollectedHeap* _g1h;
3381 VerifyOption _vo;
3382 bool _failures;
3384 public:
3385 // _vo == UsePrevMarking -> use "prev" marking information,
3386 // _vo == UseNextMarking -> use "next" marking information,
3387 // _vo == UseMarkWord -> use mark word from object header.
3388 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
3389 AbstractGangTask("Parallel verify task"),
3390 _g1h(g1h),
3391 _vo(vo),
3392 _failures(false) { }
3394 bool failures() {
3395 return _failures;
3396 }
3398 void work(uint worker_id) {
3399 HandleMark hm;
3400 VerifyRegionClosure blk(true, _vo);
3401 _g1h->heap_region_par_iterate_chunked(&blk, worker_id,
3402 _g1h->workers()->active_workers(),
3403 HeapRegion::ParVerifyClaimValue);
3404 if (blk.failures()) {
3405 _failures = true;
3406 }
3407 }
3408 };
3410 void G1CollectedHeap::verify(bool silent, VerifyOption vo) {
3411 if (SafepointSynchronize::is_at_safepoint()) {
3412 assert(Thread::current()->is_VM_thread(),
3413 "Expected to be executed serially by the VM thread at this point");
3415 if (!silent) { gclog_or_tty->print("Roots "); }
3416 VerifyRootsClosure rootsCl(vo);
3417 G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo);
3418 G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl);
3419 VerifyKlassClosure klassCl(this, &rootsCl);
3421 // We apply the relevant closures to all the oops in the
3422 // system dictionary, the string table and the code cache.
3423 const int so = SO_AllClasses | SO_Strings | SO_CodeCache;
3425 // Need cleared claim bits for the strong roots processing
3426 ClassLoaderDataGraph::clear_claimed_marks();
3428 process_strong_roots(true, // activate StrongRootsScope
3429 false, // we set "is scavenging" to false,
3430 // so we don't reset the dirty cards.
3431 ScanningOption(so), // roots scanning options
3432 &rootsCl,
3433 &blobsCl,
3434 &klassCl
3435 );
3437 bool failures = rootsCl.failures() || codeRootsCl.failures();
3439 if (vo != VerifyOption_G1UseMarkWord) {
3440 // If we're verifying during a full GC then the region sets
3441 // will have been torn down at the start of the GC. Therefore
3442 // verifying the region sets will fail. So we only verify
3443 // the region sets when not in a full GC.
3444 if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3445 verify_region_sets();
3446 }
3448 if (!silent) { gclog_or_tty->print("HeapRegions "); }
3449 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3450 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3451 "sanity check");
3453 G1ParVerifyTask task(this, vo);
3454 assert(UseDynamicNumberOfGCThreads ||
3455 workers()->active_workers() == workers()->total_workers(),
3456 "If not dynamic should be using all the workers");
3457 int n_workers = workers()->active_workers();
3458 set_par_threads(n_workers);
3459 workers()->run_task(&task);
3460 set_par_threads(0);
3461 if (task.failures()) {
3462 failures = true;
3463 }
3465 // Checks that the expected amount of parallel work was done.
3466 // The implication is that n_workers is > 0.
3467 assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
3468 "sanity check");
3470 reset_heap_region_claim_values();
3472 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3473 "sanity check");
3474 } else {
3475 VerifyRegionClosure blk(false, vo);
3476 heap_region_iterate(&blk);
3477 if (blk.failures()) {
3478 failures = true;
3479 }
3480 }
3481 if (!silent) gclog_or_tty->print("RemSet ");
3482 rem_set()->verify();
3484 if (G1StringDedup::is_enabled()) {
3485 if (!silent) gclog_or_tty->print("StrDedup ");
3486 G1StringDedup::verify();
3487 }
3489 if (failures) {
3490 gclog_or_tty->print_cr("Heap:");
3491 // It helps to have the per-region information in the output to
3492 // help us track down what went wrong. This is why we call
3493 // print_extended_on() instead of print_on().
3494 print_extended_on(gclog_or_tty);
3495 gclog_or_tty->cr();
3496 #ifndef PRODUCT
3497 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3498 concurrent_mark()->print_reachable("at-verification-failure",
3499 vo, false /* all */);
3500 }
3501 #endif
3502 gclog_or_tty->flush();
3503 }
3504 guarantee(!failures, "there should not have been any failures");
3505 } else {
3506 if (!silent) {
3507 gclog_or_tty->print("(SKIPPING Roots, HeapRegionSets, HeapRegions, RemSet");
3508 if (G1StringDedup::is_enabled()) {
3509 gclog_or_tty->print(", StrDedup");
3510 }
3511 gclog_or_tty->print(") ");
3512 }
3513 }
3514 }
3516 void G1CollectedHeap::verify(bool silent) {
3517 verify(silent, VerifyOption_G1UsePrevMarking);
3518 }
3520 double G1CollectedHeap::verify(bool guard, const char* msg) {
3521 double verify_time_ms = 0.0;
3523 if (guard && total_collections() >= VerifyGCStartAt) {
3524 double verify_start = os::elapsedTime();
3525 HandleMark hm; // Discard invalid handles created during verification
3526 prepare_for_verify();
3527 Universe::verify(VerifyOption_G1UsePrevMarking, msg);
3528 verify_time_ms = (os::elapsedTime() - verify_start) * 1000;
3529 }
3531 return verify_time_ms;
3532 }
3534 void G1CollectedHeap::verify_before_gc() {
3535 double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:");
3536 g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms);
3537 }
3539 void G1CollectedHeap::verify_after_gc() {
3540 double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:");
3541 g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms);
3542 }
3544 class PrintRegionClosure: public HeapRegionClosure {
3545 outputStream* _st;
3546 public:
3547 PrintRegionClosure(outputStream* st) : _st(st) {}
3548 bool doHeapRegion(HeapRegion* r) {
3549 r->print_on(_st);
3550 return false;
3551 }
3552 };
3554 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3555 const HeapRegion* hr,
3556 const VerifyOption vo) const {
3557 switch (vo) {
3558 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
3559 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
3560 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked();
3561 default: ShouldNotReachHere();
3562 }
3563 return false; // keep some compilers happy
3564 }
3566 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3567 const VerifyOption vo) const {
3568 switch (vo) {
3569 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
3570 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
3571 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked();
3572 default: ShouldNotReachHere();
3573 }
3574 return false; // keep some compilers happy
3575 }
3577 void G1CollectedHeap::print_on(outputStream* st) const {
3578 st->print(" %-20s", "garbage-first heap");
3579 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3580 capacity()/K, used_unlocked()/K);
3581 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3582 _g1_storage.low_boundary(),
3583 _g1_storage.high(),
3584 _g1_storage.high_boundary());
3585 st->cr();
3586 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3587 uint young_regions = _young_list->length();
3588 st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3589 (size_t) young_regions * HeapRegion::GrainBytes / K);
3590 uint survivor_regions = g1_policy()->recorded_survivor_regions();
3591 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3592 (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3593 st->cr();
3594 MetaspaceAux::print_on(st);
3595 }
3597 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3598 print_on(st);
3600 // Print the per-region information.
3601 st->cr();
3602 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3603 "HS=humongous(starts), HC=humongous(continues), "
3604 "CS=collection set, F=free, TS=gc time stamp, "
3605 "PTAMS=previous top-at-mark-start, "
3606 "NTAMS=next top-at-mark-start)");
3607 PrintRegionClosure blk(st);
3608 heap_region_iterate(&blk);
3609 }
3611 void G1CollectedHeap::print_on_error(outputStream* st) const {
3612 this->CollectedHeap::print_on_error(st);
3614 if (_cm != NULL) {
3615 st->cr();
3616 _cm->print_on_error(st);
3617 }
3618 }
3620 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3621 if (G1CollectedHeap::use_parallel_gc_threads()) {
3622 workers()->print_worker_threads_on(st);
3623 }
3624 _cmThread->print_on(st);
3625 st->cr();
3626 _cm->print_worker_threads_on(st);
3627 _cg1r->print_worker_threads_on(st);
3628 if (G1StringDedup::is_enabled()) {
3629 G1StringDedup::print_worker_threads_on(st);
3630 }
3631 }
3633 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3634 if (G1CollectedHeap::use_parallel_gc_threads()) {
3635 workers()->threads_do(tc);
3636 }
3637 tc->do_thread(_cmThread);
3638 _cg1r->threads_do(tc);
3639 if (G1StringDedup::is_enabled()) {
3640 G1StringDedup::threads_do(tc);
3641 }
3642 }
3644 void G1CollectedHeap::print_tracing_info() const {
3645 // We'll overload this to mean "trace GC pause statistics."
3646 if (TraceGen0Time || TraceGen1Time) {
3647 // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3648 // to that.
3649 g1_policy()->print_tracing_info();
3650 }
3651 if (G1SummarizeRSetStats) {
3652 g1_rem_set()->print_summary_info();
3653 }
3654 if (G1SummarizeConcMark) {
3655 concurrent_mark()->print_summary_info();
3656 }
3657 g1_policy()->print_yg_surv_rate_info();
3658 SpecializationStats::print();
3659 }
3661 #ifndef PRODUCT
3662 // Helpful for debugging RSet issues.
3664 class PrintRSetsClosure : public HeapRegionClosure {
3665 private:
3666 const char* _msg;
3667 size_t _occupied_sum;
3669 public:
3670 bool doHeapRegion(HeapRegion* r) {
3671 HeapRegionRemSet* hrrs = r->rem_set();
3672 size_t occupied = hrrs->occupied();
3673 _occupied_sum += occupied;
3675 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3676 HR_FORMAT_PARAMS(r));
3677 if (occupied == 0) {
3678 gclog_or_tty->print_cr(" RSet is empty");
3679 } else {
3680 hrrs->print();
3681 }
3682 gclog_or_tty->print_cr("----------");
3683 return false;
3684 }
3686 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3687 gclog_or_tty->cr();
3688 gclog_or_tty->print_cr("========================================");
3689 gclog_or_tty->print_cr("%s", msg);
3690 gclog_or_tty->cr();
3691 }
3693 ~PrintRSetsClosure() {
3694 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3695 gclog_or_tty->print_cr("========================================");
3696 gclog_or_tty->cr();
3697 }
3698 };
3700 void G1CollectedHeap::print_cset_rsets() {
3701 PrintRSetsClosure cl("Printing CSet RSets");
3702 collection_set_iterate(&cl);
3703 }
3705 void G1CollectedHeap::print_all_rsets() {
3706 PrintRSetsClosure cl("Printing All RSets");;
3707 heap_region_iterate(&cl);
3708 }
3709 #endif // PRODUCT
3711 G1CollectedHeap* G1CollectedHeap::heap() {
3712 assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3713 "not a garbage-first heap");
3714 return _g1h;
3715 }
3717 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3718 // always_do_update_barrier = false;
3719 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3720 // Fill TLAB's and such
3721 accumulate_statistics_all_tlabs();
3722 ensure_parsability(true);
3724 if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) &&
3725 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3726 g1_rem_set()->print_periodic_summary_info("Before GC RS summary");
3727 }
3728 }
3730 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) {
3732 if (G1SummarizeRSetStats &&
3733 (G1SummarizeRSetStatsPeriod > 0) &&
3734 // we are at the end of the GC. Total collections has already been increased.
3735 ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) {
3736 g1_rem_set()->print_periodic_summary_info("After GC RS summary");
3737 }
3739 // FIXME: what is this about?
3740 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3741 // is set.
3742 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3743 "derived pointer present"));
3744 // always_do_update_barrier = true;
3746 resize_all_tlabs();
3748 // We have just completed a GC. Update the soft reference
3749 // policy with the new heap occupancy
3750 Universe::update_heap_info_at_gc();
3751 }
3753 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3754 unsigned int gc_count_before,
3755 bool* succeeded,
3756 GCCause::Cause gc_cause) {
3757 assert_heap_not_locked_and_not_at_safepoint();
3758 g1_policy()->record_stop_world_start();
3759 VM_G1IncCollectionPause op(gc_count_before,
3760 word_size,
3761 false, /* should_initiate_conc_mark */
3762 g1_policy()->max_pause_time_ms(),
3763 gc_cause);
3764 VMThread::execute(&op);
3766 HeapWord* result = op.result();
3767 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3768 assert(result == NULL || ret_succeeded,
3769 "the result should be NULL if the VM did not succeed");
3770 *succeeded = ret_succeeded;
3772 assert_heap_not_locked();
3773 return result;
3774 }
3776 void
3777 G1CollectedHeap::doConcurrentMark() {
3778 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3779 if (!_cmThread->in_progress()) {
3780 _cmThread->set_started();
3781 CGC_lock->notify();
3782 }
3783 }
3785 size_t G1CollectedHeap::pending_card_num() {
3786 size_t extra_cards = 0;
3787 JavaThread *curr = Threads::first();
3788 while (curr != NULL) {
3789 DirtyCardQueue& dcq = curr->dirty_card_queue();
3790 extra_cards += dcq.size();
3791 curr = curr->next();
3792 }
3793 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3794 size_t buffer_size = dcqs.buffer_size();
3795 size_t buffer_num = dcqs.completed_buffers_num();
3797 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
3798 // in bytes - not the number of 'entries'. We need to convert
3799 // into a number of cards.
3800 return (buffer_size * buffer_num + extra_cards) / oopSize;
3801 }
3803 size_t G1CollectedHeap::cards_scanned() {
3804 return g1_rem_set()->cardsScanned();
3805 }
3807 void
3808 G1CollectedHeap::setup_surviving_young_words() {
3809 assert(_surviving_young_words == NULL, "pre-condition");
3810 uint array_length = g1_policy()->young_cset_region_length();
3811 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3812 if (_surviving_young_words == NULL) {
3813 vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR,
3814 "Not enough space for young surv words summary.");
3815 }
3816 memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3817 #ifdef ASSERT
3818 for (uint i = 0; i < array_length; ++i) {
3819 assert( _surviving_young_words[i] == 0, "memset above" );
3820 }
3821 #endif // !ASSERT
3822 }
3824 void
3825 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3826 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3827 uint array_length = g1_policy()->young_cset_region_length();
3828 for (uint i = 0; i < array_length; ++i) {
3829 _surviving_young_words[i] += surv_young_words[i];
3830 }
3831 }
3833 void
3834 G1CollectedHeap::cleanup_surviving_young_words() {
3835 guarantee( _surviving_young_words != NULL, "pre-condition" );
3836 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC);
3837 _surviving_young_words = NULL;
3838 }
3840 #ifdef ASSERT
3841 class VerifyCSetClosure: public HeapRegionClosure {
3842 public:
3843 bool doHeapRegion(HeapRegion* hr) {
3844 // Here we check that the CSet region's RSet is ready for parallel
3845 // iteration. The fields that we'll verify are only manipulated
3846 // when the region is part of a CSet and is collected. Afterwards,
3847 // we reset these fields when we clear the region's RSet (when the
3848 // region is freed) so they are ready when the region is
3849 // re-allocated. The only exception to this is if there's an
3850 // evacuation failure and instead of freeing the region we leave
3851 // it in the heap. In that case, we reset these fields during
3852 // evacuation failure handling.
3853 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3855 // Here's a good place to add any other checks we'd like to
3856 // perform on CSet regions.
3857 return false;
3858 }
3859 };
3860 #endif // ASSERT
3862 #if TASKQUEUE_STATS
3863 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3864 st->print_raw_cr("GC Task Stats");
3865 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3866 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3867 }
3869 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3870 print_taskqueue_stats_hdr(st);
3872 TaskQueueStats totals;
3873 const int n = workers() != NULL ? workers()->total_workers() : 1;
3874 for (int i = 0; i < n; ++i) {
3875 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3876 totals += task_queue(i)->stats;
3877 }
3878 st->print_raw("tot "); totals.print(st); st->cr();
3880 DEBUG_ONLY(totals.verify());
3881 }
3883 void G1CollectedHeap::reset_taskqueue_stats() {
3884 const int n = workers() != NULL ? workers()->total_workers() : 1;
3885 for (int i = 0; i < n; ++i) {
3886 task_queue(i)->stats.reset();
3887 }
3888 }
3889 #endif // TASKQUEUE_STATS
3891 void G1CollectedHeap::log_gc_header() {
3892 if (!G1Log::fine()) {
3893 return;
3894 }
3896 gclog_or_tty->gclog_stamp(_gc_tracer_stw->gc_id());
3898 GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
3899 .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)")
3900 .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : "");
3902 gclog_or_tty->print("[%s", (const char*)gc_cause_str);
3903 }
3905 void G1CollectedHeap::log_gc_footer(double pause_time_sec) {
3906 if (!G1Log::fine()) {
3907 return;
3908 }
3910 if (G1Log::finer()) {
3911 if (evacuation_failed()) {
3912 gclog_or_tty->print(" (to-space exhausted)");
3913 }
3914 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3915 g1_policy()->phase_times()->note_gc_end();
3916 g1_policy()->phase_times()->print(pause_time_sec);
3917 g1_policy()->print_detailed_heap_transition();
3918 } else {
3919 if (evacuation_failed()) {
3920 gclog_or_tty->print("--");
3921 }
3922 g1_policy()->print_heap_transition();
3923 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3924 }
3925 gclog_or_tty->flush();
3926 }
3928 bool
3929 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3930 assert_at_safepoint(true /* should_be_vm_thread */);
3931 guarantee(!is_gc_active(), "collection is not reentrant");
3933 if (GC_locker::check_active_before_gc()) {
3934 return false;
3935 }
3937 _gc_timer_stw->register_gc_start();
3939 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3941 SvcGCMarker sgcm(SvcGCMarker::MINOR);
3942 ResourceMark rm;
3944 print_heap_before_gc();
3945 trace_heap_before_gc(_gc_tracer_stw);
3947 verify_region_sets_optional();
3948 verify_dirty_young_regions();
3950 // This call will decide whether this pause is an initial-mark
3951 // pause. If it is, during_initial_mark_pause() will return true
3952 // for the duration of this pause.
3953 g1_policy()->decide_on_conc_mark_initiation();
3955 // We do not allow initial-mark to be piggy-backed on a mixed GC.
3956 assert(!g1_policy()->during_initial_mark_pause() ||
3957 g1_policy()->gcs_are_young(), "sanity");
3959 // We also do not allow mixed GCs during marking.
3960 assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3962 // Record whether this pause is an initial mark. When the current
3963 // thread has completed its logging output and it's safe to signal
3964 // the CM thread, the flag's value in the policy has been reset.
3965 bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3967 // Inner scope for scope based logging, timers, and stats collection
3968 {
3969 EvacuationInfo evacuation_info;
3971 if (g1_policy()->during_initial_mark_pause()) {
3972 // We are about to start a marking cycle, so we increment the
3973 // full collection counter.
3974 increment_old_marking_cycles_started();
3975 register_concurrent_cycle_start(_gc_timer_stw->gc_start());
3976 }
3978 _gc_tracer_stw->report_yc_type(yc_type());
3980 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3982 int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
3983 workers()->active_workers() : 1);
3984 double pause_start_sec = os::elapsedTime();
3985 g1_policy()->phase_times()->note_gc_start(active_workers);
3986 log_gc_header();
3988 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3989 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3991 // If the secondary_free_list is not empty, append it to the
3992 // free_list. No need to wait for the cleanup operation to finish;
3993 // the region allocation code will check the secondary_free_list
3994 // and wait if necessary. If the G1StressConcRegionFreeing flag is
3995 // set, skip this step so that the region allocation code has to
3996 // get entries from the secondary_free_list.
3997 if (!G1StressConcRegionFreeing) {
3998 append_secondary_free_list_if_not_empty_with_lock();
3999 }
4001 assert(check_young_list_well_formed(), "young list should be well formed");
4002 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
4003 "sanity check");
4005 // Don't dynamically change the number of GC threads this early. A value of
4006 // 0 is used to indicate serial work. When parallel work is done,
4007 // it will be set.
4009 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
4010 IsGCActiveMark x;
4012 gc_prologue(false);
4013 increment_total_collections(false /* full gc */);
4014 increment_gc_time_stamp();
4016 verify_before_gc();
4018 COMPILER2_PRESENT(DerivedPointerTable::clear());
4020 // Please see comment in g1CollectedHeap.hpp and
4021 // G1CollectedHeap::ref_processing_init() to see how
4022 // reference processing currently works in G1.
4024 // Enable discovery in the STW reference processor
4025 ref_processor_stw()->enable_discovery(true /*verify_disabled*/,
4026 true /*verify_no_refs*/);
4028 {
4029 // We want to temporarily turn off discovery by the
4030 // CM ref processor, if necessary, and turn it back on
4031 // on again later if we do. Using a scoped
4032 // NoRefDiscovery object will do this.
4033 NoRefDiscovery no_cm_discovery(ref_processor_cm());
4035 // Forget the current alloc region (we might even choose it to be part
4036 // of the collection set!).
4037 release_mutator_alloc_region();
4039 // We should call this after we retire the mutator alloc
4040 // region(s) so that all the ALLOC / RETIRE events are generated
4041 // before the start GC event.
4042 _hr_printer.start_gc(false /* full */, (size_t) total_collections());
4044 // This timing is only used by the ergonomics to handle our pause target.
4045 // It is unclear why this should not include the full pause. We will
4046 // investigate this in CR 7178365.
4047 //
4048 // Preserving the old comment here if that helps the investigation:
4049 //
4050 // The elapsed time induced by the start time below deliberately elides
4051 // the possible verification above.
4052 double sample_start_time_sec = os::elapsedTime();
4054 #if YOUNG_LIST_VERBOSE
4055 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
4056 _young_list->print();
4057 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4058 #endif // YOUNG_LIST_VERBOSE
4060 g1_policy()->record_collection_pause_start(sample_start_time_sec);
4062 double scan_wait_start = os::elapsedTime();
4063 // We have to wait until the CM threads finish scanning the
4064 // root regions as it's the only way to ensure that all the
4065 // objects on them have been correctly scanned before we start
4066 // moving them during the GC.
4067 bool waited = _cm->root_regions()->wait_until_scan_finished();
4068 double wait_time_ms = 0.0;
4069 if (waited) {
4070 double scan_wait_end = os::elapsedTime();
4071 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
4072 }
4073 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
4075 #if YOUNG_LIST_VERBOSE
4076 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
4077 _young_list->print();
4078 #endif // YOUNG_LIST_VERBOSE
4080 if (g1_policy()->during_initial_mark_pause()) {
4081 concurrent_mark()->checkpointRootsInitialPre();
4082 }
4084 #if YOUNG_LIST_VERBOSE
4085 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
4086 _young_list->print();
4087 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4088 #endif // YOUNG_LIST_VERBOSE
4090 g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info);
4092 _cm->note_start_of_gc();
4093 // We should not verify the per-thread SATB buffers given that
4094 // we have not filtered them yet (we'll do so during the
4095 // GC). We also call this after finalize_cset() to
4096 // ensure that the CSet has been finalized.
4097 _cm->verify_no_cset_oops(true /* verify_stacks */,
4098 true /* verify_enqueued_buffers */,
4099 false /* verify_thread_buffers */,
4100 true /* verify_fingers */);
4102 if (_hr_printer.is_active()) {
4103 HeapRegion* hr = g1_policy()->collection_set();
4104 while (hr != NULL) {
4105 G1HRPrinter::RegionType type;
4106 if (!hr->is_young()) {
4107 type = G1HRPrinter::Old;
4108 } else if (hr->is_survivor()) {
4109 type = G1HRPrinter::Survivor;
4110 } else {
4111 type = G1HRPrinter::Eden;
4112 }
4113 _hr_printer.cset(hr);
4114 hr = hr->next_in_collection_set();
4115 }
4116 }
4118 #ifdef ASSERT
4119 VerifyCSetClosure cl;
4120 collection_set_iterate(&cl);
4121 #endif // ASSERT
4123 setup_surviving_young_words();
4125 // Initialize the GC alloc regions.
4126 init_gc_alloc_regions(evacuation_info);
4128 // Actually do the work...
4129 evacuate_collection_set(evacuation_info);
4131 // We do this to mainly verify the per-thread SATB buffers
4132 // (which have been filtered by now) since we didn't verify
4133 // them earlier. No point in re-checking the stacks / enqueued
4134 // buffers given that the CSet has not changed since last time
4135 // we checked.
4136 _cm->verify_no_cset_oops(false /* verify_stacks */,
4137 false /* verify_enqueued_buffers */,
4138 true /* verify_thread_buffers */,
4139 true /* verify_fingers */);
4141 free_collection_set(g1_policy()->collection_set(), evacuation_info);
4142 g1_policy()->clear_collection_set();
4144 cleanup_surviving_young_words();
4146 // Start a new incremental collection set for the next pause.
4147 g1_policy()->start_incremental_cset_building();
4149 // Clear the _cset_fast_test bitmap in anticipation of adding
4150 // regions to the incremental collection set for the next
4151 // evacuation pause.
4152 clear_cset_fast_test();
4154 _young_list->reset_sampled_info();
4156 // Don't check the whole heap at this point as the
4157 // GC alloc regions from this pause have been tagged
4158 // as survivors and moved on to the survivor list.
4159 // Survivor regions will fail the !is_young() check.
4160 assert(check_young_list_empty(false /* check_heap */),
4161 "young list should be empty");
4163 #if YOUNG_LIST_VERBOSE
4164 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
4165 _young_list->print();
4166 #endif // YOUNG_LIST_VERBOSE
4168 g1_policy()->record_survivor_regions(_young_list->survivor_length(),
4169 _young_list->first_survivor_region(),
4170 _young_list->last_survivor_region());
4172 _young_list->reset_auxilary_lists();
4174 if (evacuation_failed()) {
4175 _summary_bytes_used = recalculate_used();
4176 uint n_queues = MAX2((int)ParallelGCThreads, 1);
4177 for (uint i = 0; i < n_queues; i++) {
4178 if (_evacuation_failed_info_array[i].has_failed()) {
4179 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
4180 }
4181 }
4182 } else {
4183 // The "used" of the the collection set have already been subtracted
4184 // when they were freed. Add in the bytes evacuated.
4185 _summary_bytes_used += g1_policy()->bytes_copied_during_gc();
4186 }
4188 if (g1_policy()->during_initial_mark_pause()) {
4189 // We have to do this before we notify the CM threads that
4190 // they can start working to make sure that all the
4191 // appropriate initialization is done on the CM object.
4192 concurrent_mark()->checkpointRootsInitialPost();
4193 set_marking_started();
4194 // Note that we don't actually trigger the CM thread at
4195 // this point. We do that later when we're sure that
4196 // the current thread has completed its logging output.
4197 }
4199 allocate_dummy_regions();
4201 #if YOUNG_LIST_VERBOSE
4202 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
4203 _young_list->print();
4204 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4205 #endif // YOUNG_LIST_VERBOSE
4207 init_mutator_alloc_region();
4209 {
4210 size_t expand_bytes = g1_policy()->expansion_amount();
4211 if (expand_bytes > 0) {
4212 size_t bytes_before = capacity();
4213 // No need for an ergo verbose message here,
4214 // expansion_amount() does this when it returns a value > 0.
4215 if (!expand(expand_bytes)) {
4216 // We failed to expand the heap so let's verify that
4217 // committed/uncommitted amount match the backing store
4218 assert(capacity() == _g1_storage.committed_size(), "committed size mismatch");
4219 assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch");
4220 }
4221 }
4222 }
4224 // We redo the verification but now wrt to the new CSet which
4225 // has just got initialized after the previous CSet was freed.
4226 _cm->verify_no_cset_oops(true /* verify_stacks */,
4227 true /* verify_enqueued_buffers */,
4228 true /* verify_thread_buffers */,
4229 true /* verify_fingers */);
4230 _cm->note_end_of_gc();
4232 // This timing is only used by the ergonomics to handle our pause target.
4233 // It is unclear why this should not include the full pause. We will
4234 // investigate this in CR 7178365.
4235 double sample_end_time_sec = os::elapsedTime();
4236 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
4237 g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info);
4239 MemoryService::track_memory_usage();
4241 // In prepare_for_verify() below we'll need to scan the deferred
4242 // update buffers to bring the RSets up-to-date if
4243 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
4244 // the update buffers we'll probably need to scan cards on the
4245 // regions we just allocated to (i.e., the GC alloc
4246 // regions). However, during the last GC we called
4247 // set_saved_mark() on all the GC alloc regions, so card
4248 // scanning might skip the [saved_mark_word()...top()] area of
4249 // those regions (i.e., the area we allocated objects into
4250 // during the last GC). But it shouldn't. Given that
4251 // saved_mark_word() is conditional on whether the GC time stamp
4252 // on the region is current or not, by incrementing the GC time
4253 // stamp here we invalidate all the GC time stamps on all the
4254 // regions and saved_mark_word() will simply return top() for
4255 // all the regions. This is a nicer way of ensuring this rather
4256 // than iterating over the regions and fixing them. In fact, the
4257 // GC time stamp increment here also ensures that
4258 // saved_mark_word() will return top() between pauses, i.e.,
4259 // during concurrent refinement. So we don't need the
4260 // is_gc_active() check to decided which top to use when
4261 // scanning cards (see CR 7039627).
4262 increment_gc_time_stamp();
4264 verify_after_gc();
4266 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
4267 ref_processor_stw()->verify_no_references_recorded();
4269 // CM reference discovery will be re-enabled if necessary.
4270 }
4272 // We should do this after we potentially expand the heap so
4273 // that all the COMMIT events are generated before the end GC
4274 // event, and after we retire the GC alloc regions so that all
4275 // RETIRE events are generated before the end GC event.
4276 _hr_printer.end_gc(false /* full */, (size_t) total_collections());
4278 if (mark_in_progress()) {
4279 concurrent_mark()->update_g1_committed();
4280 }
4282 #ifdef TRACESPINNING
4283 ParallelTaskTerminator::print_termination_counts();
4284 #endif
4286 gc_epilogue(false);
4287 }
4289 // Print the remainder of the GC log output.
4290 log_gc_footer(os::elapsedTime() - pause_start_sec);
4292 // It is not yet to safe to tell the concurrent mark to
4293 // start as we have some optional output below. We don't want the
4294 // output from the concurrent mark thread interfering with this
4295 // logging output either.
4297 _hrs.verify_optional();
4298 verify_region_sets_optional();
4300 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
4301 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
4303 print_heap_after_gc();
4304 trace_heap_after_gc(_gc_tracer_stw);
4306 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
4307 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
4308 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
4309 // before any GC notifications are raised.
4310 g1mm()->update_sizes();
4312 _gc_tracer_stw->report_evacuation_info(&evacuation_info);
4313 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
4314 _gc_timer_stw->register_gc_end();
4315 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
4316 }
4317 // It should now be safe to tell the concurrent mark thread to start
4318 // without its logging output interfering with the logging output
4319 // that came from the pause.
4321 if (should_start_conc_mark) {
4322 // CAUTION: after the doConcurrentMark() call below,
4323 // the concurrent marking thread(s) could be running
4324 // concurrently with us. Make sure that anything after
4325 // this point does not assume that we are the only GC thread
4326 // running. Note: of course, the actual marking work will
4327 // not start until the safepoint itself is released in
4328 // ConcurrentGCThread::safepoint_desynchronize().
4329 doConcurrentMark();
4330 }
4332 return true;
4333 }
4335 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
4336 {
4337 size_t gclab_word_size;
4338 switch (purpose) {
4339 case GCAllocForSurvived:
4340 gclab_word_size = _survivor_plab_stats.desired_plab_sz();
4341 break;
4342 case GCAllocForTenured:
4343 gclab_word_size = _old_plab_stats.desired_plab_sz();
4344 break;
4345 default:
4346 assert(false, "unknown GCAllocPurpose");
4347 gclab_word_size = _old_plab_stats.desired_plab_sz();
4348 break;
4349 }
4351 // Prevent humongous PLAB sizes for two reasons:
4352 // * PLABs are allocated using a similar paths as oops, but should
4353 // never be in a humongous region
4354 // * Allowing humongous PLABs needlessly churns the region free lists
4355 return MIN2(_humongous_object_threshold_in_words, gclab_word_size);
4356 }
4358 void G1CollectedHeap::init_mutator_alloc_region() {
4359 assert(_mutator_alloc_region.get() == NULL, "pre-condition");
4360 _mutator_alloc_region.init();
4361 }
4363 void G1CollectedHeap::release_mutator_alloc_region() {
4364 _mutator_alloc_region.release();
4365 assert(_mutator_alloc_region.get() == NULL, "post-condition");
4366 }
4368 void G1CollectedHeap::init_gc_alloc_regions(EvacuationInfo& evacuation_info) {
4369 assert_at_safepoint(true /* should_be_vm_thread */);
4371 _survivor_gc_alloc_region.init();
4372 _old_gc_alloc_region.init();
4373 HeapRegion* retained_region = _retained_old_gc_alloc_region;
4374 _retained_old_gc_alloc_region = NULL;
4376 // We will discard the current GC alloc region if:
4377 // a) it's in the collection set (it can happen!),
4378 // b) it's already full (no point in using it),
4379 // c) it's empty (this means that it was emptied during
4380 // a cleanup and it should be on the free list now), or
4381 // d) it's humongous (this means that it was emptied
4382 // during a cleanup and was added to the free list, but
4383 // has been subsequently used to allocate a humongous
4384 // object that may be less than the region size).
4385 if (retained_region != NULL &&
4386 !retained_region->in_collection_set() &&
4387 !(retained_region->top() == retained_region->end()) &&
4388 !retained_region->is_empty() &&
4389 !retained_region->isHumongous()) {
4390 retained_region->set_saved_mark();
4391 // The retained region was added to the old region set when it was
4392 // retired. We have to remove it now, since we don't allow regions
4393 // we allocate to in the region sets. We'll re-add it later, when
4394 // it's retired again.
4395 _old_set.remove(retained_region);
4396 bool during_im = g1_policy()->during_initial_mark_pause();
4397 retained_region->note_start_of_copying(during_im);
4398 _old_gc_alloc_region.set(retained_region);
4399 _hr_printer.reuse(retained_region);
4400 evacuation_info.set_alloc_regions_used_before(retained_region->used());
4401 }
4402 }
4404 void G1CollectedHeap::release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info) {
4405 evacuation_info.set_allocation_regions(_survivor_gc_alloc_region.count() +
4406 _old_gc_alloc_region.count());
4407 _survivor_gc_alloc_region.release();
4408 // If we have an old GC alloc region to release, we'll save it in
4409 // _retained_old_gc_alloc_region. If we don't
4410 // _retained_old_gc_alloc_region will become NULL. This is what we
4411 // want either way so no reason to check explicitly for either
4412 // condition.
4413 _retained_old_gc_alloc_region = _old_gc_alloc_region.release();
4415 if (ResizePLAB) {
4416 _survivor_plab_stats.adjust_desired_plab_sz(no_of_gc_workers);
4417 _old_plab_stats.adjust_desired_plab_sz(no_of_gc_workers);
4418 }
4419 }
4421 void G1CollectedHeap::abandon_gc_alloc_regions() {
4422 assert(_survivor_gc_alloc_region.get() == NULL, "pre-condition");
4423 assert(_old_gc_alloc_region.get() == NULL, "pre-condition");
4424 _retained_old_gc_alloc_region = NULL;
4425 }
4427 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4428 _drain_in_progress = false;
4429 set_evac_failure_closure(cl);
4430 _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4431 }
4433 void G1CollectedHeap::finalize_for_evac_failure() {
4434 assert(_evac_failure_scan_stack != NULL &&
4435 _evac_failure_scan_stack->length() == 0,
4436 "Postcondition");
4437 assert(!_drain_in_progress, "Postcondition");
4438 delete _evac_failure_scan_stack;
4439 _evac_failure_scan_stack = NULL;
4440 }
4442 void G1CollectedHeap::remove_self_forwarding_pointers() {
4443 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4445 double remove_self_forwards_start = os::elapsedTime();
4447 G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4449 if (G1CollectedHeap::use_parallel_gc_threads()) {
4450 set_par_threads();
4451 workers()->run_task(&rsfp_task);
4452 set_par_threads(0);
4453 } else {
4454 rsfp_task.work(0);
4455 }
4457 assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity");
4459 // Reset the claim values in the regions in the collection set.
4460 reset_cset_heap_region_claim_values();
4462 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4464 // Now restore saved marks, if any.
4465 assert(_objs_with_preserved_marks.size() ==
4466 _preserved_marks_of_objs.size(), "Both or none.");
4467 while (!_objs_with_preserved_marks.is_empty()) {
4468 oop obj = _objs_with_preserved_marks.pop();
4469 markOop m = _preserved_marks_of_objs.pop();
4470 obj->set_mark(m);
4471 }
4472 _objs_with_preserved_marks.clear(true);
4473 _preserved_marks_of_objs.clear(true);
4475 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
4476 }
4478 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4479 _evac_failure_scan_stack->push(obj);
4480 }
4482 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4483 assert(_evac_failure_scan_stack != NULL, "precondition");
4485 while (_evac_failure_scan_stack->length() > 0) {
4486 oop obj = _evac_failure_scan_stack->pop();
4487 _evac_failure_closure->set_region(heap_region_containing(obj));
4488 obj->oop_iterate_backwards(_evac_failure_closure);
4489 }
4490 }
4492 oop
4493 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state,
4494 oop old) {
4495 assert(obj_in_cs(old),
4496 err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4497 (HeapWord*) old));
4498 markOop m = old->mark();
4499 oop forward_ptr = old->forward_to_atomic(old);
4500 if (forward_ptr == NULL) {
4501 // Forward-to-self succeeded.
4502 assert(_par_scan_state != NULL, "par scan state");
4503 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4504 uint queue_num = _par_scan_state->queue_num();
4506 _evacuation_failed = true;
4507 _evacuation_failed_info_array[queue_num].register_copy_failure(old->size());
4508 if (_evac_failure_closure != cl) {
4509 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4510 assert(!_drain_in_progress,
4511 "Should only be true while someone holds the lock.");
4512 // Set the global evac-failure closure to the current thread's.
4513 assert(_evac_failure_closure == NULL, "Or locking has failed.");
4514 set_evac_failure_closure(cl);
4515 // Now do the common part.
4516 handle_evacuation_failure_common(old, m);
4517 // Reset to NULL.
4518 set_evac_failure_closure(NULL);
4519 } else {
4520 // The lock is already held, and this is recursive.
4521 assert(_drain_in_progress, "This should only be the recursive case.");
4522 handle_evacuation_failure_common(old, m);
4523 }
4524 return old;
4525 } else {
4526 // Forward-to-self failed. Either someone else managed to allocate
4527 // space for this object (old != forward_ptr) or they beat us in
4528 // self-forwarding it (old == forward_ptr).
4529 assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4530 err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4531 "should not be in the CSet",
4532 (HeapWord*) old, (HeapWord*) forward_ptr));
4533 return forward_ptr;
4534 }
4535 }
4537 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4538 preserve_mark_if_necessary(old, m);
4540 HeapRegion* r = heap_region_containing(old);
4541 if (!r->evacuation_failed()) {
4542 r->set_evacuation_failed(true);
4543 _hr_printer.evac_failure(r);
4544 }
4546 push_on_evac_failure_scan_stack(old);
4548 if (!_drain_in_progress) {
4549 // prevent recursion in copy_to_survivor_space()
4550 _drain_in_progress = true;
4551 drain_evac_failure_scan_stack();
4552 _drain_in_progress = false;
4553 }
4554 }
4556 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4557 assert(evacuation_failed(), "Oversaving!");
4558 // We want to call the "for_promotion_failure" version only in the
4559 // case of a promotion failure.
4560 if (m->must_be_preserved_for_promotion_failure(obj)) {
4561 _objs_with_preserved_marks.push(obj);
4562 _preserved_marks_of_objs.push(m);
4563 }
4564 }
4566 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
4567 size_t word_size) {
4568 if (purpose == GCAllocForSurvived) {
4569 HeapWord* result = survivor_attempt_allocation(word_size);
4570 if (result != NULL) {
4571 return result;
4572 } else {
4573 // Let's try to allocate in the old gen in case we can fit the
4574 // object there.
4575 return old_attempt_allocation(word_size);
4576 }
4577 } else {
4578 assert(purpose == GCAllocForTenured, "sanity");
4579 HeapWord* result = old_attempt_allocation(word_size);
4580 if (result != NULL) {
4581 return result;
4582 } else {
4583 // Let's try to allocate in the survivors in case we can fit the
4584 // object there.
4585 return survivor_attempt_allocation(word_size);
4586 }
4587 }
4589 ShouldNotReachHere();
4590 // Trying to keep some compilers happy.
4591 return NULL;
4592 }
4594 G1ParGCAllocBuffer::G1ParGCAllocBuffer(size_t gclab_word_size) :
4595 ParGCAllocBuffer(gclab_word_size), _retired(false) { }
4597 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, uint queue_num, ReferenceProcessor* rp)
4598 : _g1h(g1h),
4599 _refs(g1h->task_queue(queue_num)),
4600 _dcq(&g1h->dirty_card_queue_set()),
4601 _ct_bs(g1h->g1_barrier_set()),
4602 _g1_rem(g1h->g1_rem_set()),
4603 _hash_seed(17), _queue_num(queue_num),
4604 _term_attempts(0),
4605 _surviving_alloc_buffer(g1h->desired_plab_sz(GCAllocForSurvived)),
4606 _tenured_alloc_buffer(g1h->desired_plab_sz(GCAllocForTenured)),
4607 _age_table(false), _scanner(g1h, this, rp),
4608 _strong_roots_time(0), _term_time(0),
4609 _alloc_buffer_waste(0), _undo_waste(0) {
4610 // we allocate G1YoungSurvRateNumRegions plus one entries, since
4611 // we "sacrifice" entry 0 to keep track of surviving bytes for
4612 // non-young regions (where the age is -1)
4613 // We also add a few elements at the beginning and at the end in
4614 // an attempt to eliminate cache contention
4615 uint real_length = 1 + _g1h->g1_policy()->young_cset_region_length();
4616 uint array_length = PADDING_ELEM_NUM +
4617 real_length +
4618 PADDING_ELEM_NUM;
4619 _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length, mtGC);
4620 if (_surviving_young_words_base == NULL)
4621 vm_exit_out_of_memory(array_length * sizeof(size_t), OOM_MALLOC_ERROR,
4622 "Not enough space for young surv histo.");
4623 _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM;
4624 memset(_surviving_young_words, 0, (size_t) real_length * sizeof(size_t));
4626 _alloc_buffers[GCAllocForSurvived] = &_surviving_alloc_buffer;
4627 _alloc_buffers[GCAllocForTenured] = &_tenured_alloc_buffer;
4629 _start = os::elapsedTime();
4630 }
4632 void
4633 G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st)
4634 {
4635 st->print_raw_cr("GC Termination Stats");
4636 st->print_raw_cr(" elapsed --strong roots-- -------termination-------"
4637 " ------waste (KiB)------");
4638 st->print_raw_cr("thr ms ms % ms % attempts"
4639 " total alloc undo");
4640 st->print_raw_cr("--- --------- --------- ------ --------- ------ --------"
4641 " ------- ------- -------");
4642 }
4644 void
4645 G1ParScanThreadState::print_termination_stats(int i,
4646 outputStream* const st) const
4647 {
4648 const double elapsed_ms = elapsed_time() * 1000.0;
4649 const double s_roots_ms = strong_roots_time() * 1000.0;
4650 const double term_ms = term_time() * 1000.0;
4651 st->print_cr("%3d %9.2f %9.2f %6.2f "
4652 "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
4653 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
4654 i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms,
4655 term_ms, term_ms * 100 / elapsed_ms, term_attempts(),
4656 (alloc_buffer_waste() + undo_waste()) * HeapWordSize / K,
4657 alloc_buffer_waste() * HeapWordSize / K,
4658 undo_waste() * HeapWordSize / K);
4659 }
4661 #ifdef ASSERT
4662 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const {
4663 assert(ref != NULL, "invariant");
4664 assert(UseCompressedOops, "sanity");
4665 assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, ref));
4666 oop p = oopDesc::load_decode_heap_oop(ref);
4667 assert(_g1h->is_in_g1_reserved(p),
4668 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, (void *)p));
4669 return true;
4670 }
4672 bool G1ParScanThreadState::verify_ref(oop* ref) const {
4673 assert(ref != NULL, "invariant");
4674 if (has_partial_array_mask(ref)) {
4675 // Must be in the collection set--it's already been copied.
4676 oop p = clear_partial_array_mask(ref);
4677 assert(_g1h->obj_in_cs(p),
4678 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, (void *)p));
4679 } else {
4680 oop p = oopDesc::load_decode_heap_oop(ref);
4681 assert(_g1h->is_in_g1_reserved(p),
4682 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, (void *)p));
4683 }
4684 return true;
4685 }
4687 bool G1ParScanThreadState::verify_task(StarTask ref) const {
4688 if (ref.is_narrow()) {
4689 return verify_ref((narrowOop*) ref);
4690 } else {
4691 return verify_ref((oop*) ref);
4692 }
4693 }
4694 #endif // ASSERT
4696 void G1ParScanThreadState::trim_queue() {
4697 assert(_evac_failure_cl != NULL, "not set");
4699 StarTask ref;
4700 do {
4701 // Drain the overflow stack first, so other threads can steal.
4702 while (refs()->pop_overflow(ref)) {
4703 deal_with_reference(ref);
4704 }
4706 while (refs()->pop_local(ref)) {
4707 deal_with_reference(ref);
4708 }
4709 } while (!refs()->is_empty());
4710 }
4712 G1ParClosureSuper::G1ParClosureSuper(G1CollectedHeap* g1,
4713 G1ParScanThreadState* par_scan_state) :
4714 _g1(g1), _par_scan_state(par_scan_state),
4715 _worker_id(par_scan_state->queue_num()) { }
4717 void G1ParCopyHelper::mark_object(oop obj) {
4718 #ifdef ASSERT
4719 HeapRegion* hr = _g1->heap_region_containing(obj);
4720 assert(hr != NULL, "sanity");
4721 assert(!hr->in_collection_set(), "should not mark objects in the CSet");
4722 #endif // ASSERT
4724 // We know that the object is not moving so it's safe to read its size.
4725 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4726 }
4728 void G1ParCopyHelper::mark_forwarded_object(oop from_obj, oop to_obj) {
4729 #ifdef ASSERT
4730 assert(from_obj->is_forwarded(), "from obj should be forwarded");
4731 assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4732 assert(from_obj != to_obj, "should not be self-forwarded");
4734 HeapRegion* from_hr = _g1->heap_region_containing(from_obj);
4735 assert(from_hr != NULL, "sanity");
4736 assert(from_hr->in_collection_set(), "from obj should be in the CSet");
4738 HeapRegion* to_hr = _g1->heap_region_containing(to_obj);
4739 assert(to_hr != NULL, "sanity");
4740 assert(!to_hr->in_collection_set(), "should not mark objects in the CSet");
4741 #endif // ASSERT
4743 // The object might be in the process of being copied by another
4744 // worker so we cannot trust that its to-space image is
4745 // well-formed. So we have to read its size from its from-space
4746 // image which we know should not be changing.
4747 _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4748 }
4750 oop G1ParScanThreadState::copy_to_survivor_space(oop const old) {
4751 size_t word_sz = old->size();
4752 HeapRegion* from_region = _g1h->heap_region_containing_raw(old);
4753 // +1 to make the -1 indexes valid...
4754 int young_index = from_region->young_index_in_cset()+1;
4755 assert( (from_region->is_young() && young_index > 0) ||
4756 (!from_region->is_young() && young_index == 0), "invariant" );
4757 G1CollectorPolicy* g1p = _g1h->g1_policy();
4758 markOop m = old->mark();
4759 int age = m->has_displaced_mark_helper() ? m->displaced_mark_helper()->age()
4760 : m->age();
4761 GCAllocPurpose alloc_purpose = g1p->evacuation_destination(from_region, age,
4762 word_sz);
4763 HeapWord* obj_ptr = allocate(alloc_purpose, word_sz);
4764 #ifndef PRODUCT
4765 // Should this evacuation fail?
4766 if (_g1h->evacuation_should_fail()) {
4767 if (obj_ptr != NULL) {
4768 undo_allocation(alloc_purpose, obj_ptr, word_sz);
4769 obj_ptr = NULL;
4770 }
4771 }
4772 #endif // !PRODUCT
4774 if (obj_ptr == NULL) {
4775 // This will either forward-to-self, or detect that someone else has
4776 // installed a forwarding pointer.
4777 return _g1h->handle_evacuation_failure_par(this, old);
4778 }
4780 oop obj = oop(obj_ptr);
4782 // We're going to allocate linearly, so might as well prefetch ahead.
4783 Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
4785 oop forward_ptr = old->forward_to_atomic(obj);
4786 if (forward_ptr == NULL) {
4787 Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
4789 // alloc_purpose is just a hint to allocate() above, recheck the type of region
4790 // we actually allocated from and update alloc_purpose accordingly
4791 HeapRegion* to_region = _g1h->heap_region_containing_raw(obj_ptr);
4792 alloc_purpose = to_region->is_young() ? GCAllocForSurvived : GCAllocForTenured;
4794 if (g1p->track_object_age(alloc_purpose)) {
4795 // We could simply do obj->incr_age(). However, this causes a
4796 // performance issue. obj->incr_age() will first check whether
4797 // the object has a displaced mark by checking its mark word;
4798 // getting the mark word from the new location of the object
4799 // stalls. So, given that we already have the mark word and we
4800 // are about to install it anyway, it's better to increase the
4801 // age on the mark word, when the object does not have a
4802 // displaced mark word. We're not expecting many objects to have
4803 // a displaced marked word, so that case is not optimized
4804 // further (it could be...) and we simply call obj->incr_age().
4806 if (m->has_displaced_mark_helper()) {
4807 // in this case, we have to install the mark word first,
4808 // otherwise obj looks to be forwarded (the old mark word,
4809 // which contains the forward pointer, was copied)
4810 obj->set_mark(m);
4811 obj->incr_age();
4812 } else {
4813 m = m->incr_age();
4814 obj->set_mark(m);
4815 }
4816 age_table()->add(obj, word_sz);
4817 } else {
4818 obj->set_mark(m);
4819 }
4821 if (G1StringDedup::is_enabled()) {
4822 G1StringDedup::enqueue_from_evacuation(from_region->is_young(),
4823 to_region->is_young(),
4824 queue_num(),
4825 obj);
4826 }
4828 size_t* surv_young_words = surviving_young_words();
4829 surv_young_words[young_index] += word_sz;
4831 if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
4832 // We keep track of the next start index in the length field of
4833 // the to-space object. The actual length can be found in the
4834 // length field of the from-space object.
4835 arrayOop(obj)->set_length(0);
4836 oop* old_p = set_partial_array_mask(old);
4837 push_on_queue(old_p);
4838 } else {
4839 // No point in using the slower heap_region_containing() method,
4840 // given that we know obj is in the heap.
4841 _scanner.set_region(_g1h->heap_region_containing_raw(obj));
4842 obj->oop_iterate_backwards(&_scanner);
4843 }
4844 } else {
4845 undo_allocation(alloc_purpose, obj_ptr, word_sz);
4846 obj = forward_ptr;
4847 }
4848 return obj;
4849 }
4851 template <class T>
4852 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) {
4853 if (_g1->heap_region_containing_raw(new_obj)->is_young()) {
4854 _scanned_klass->record_modified_oops();
4855 }
4856 }
4858 template <G1Barrier barrier, bool do_mark_object>
4859 template <class T>
4860 void G1ParCopyClosure<barrier, do_mark_object>::do_oop_work(T* p) {
4861 T heap_oop = oopDesc::load_heap_oop(p);
4863 if (oopDesc::is_null(heap_oop)) {
4864 return;
4865 }
4867 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
4869 assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4871 if (_g1->in_cset_fast_test(obj)) {
4872 oop forwardee;
4873 if (obj->is_forwarded()) {
4874 forwardee = obj->forwardee();
4875 } else {
4876 forwardee = _par_scan_state->copy_to_survivor_space(obj);
4877 }
4878 assert(forwardee != NULL, "forwardee should not be NULL");
4879 oopDesc::encode_store_heap_oop(p, forwardee);
4880 if (do_mark_object && forwardee != obj) {
4881 // If the object is self-forwarded we don't need to explicitly
4882 // mark it, the evacuation failure protocol will do so.
4883 mark_forwarded_object(obj, forwardee);
4884 }
4886 if (barrier == G1BarrierKlass) {
4887 do_klass_barrier(p, forwardee);
4888 }
4889 } else {
4890 // The object is not in collection set. If we're a root scanning
4891 // closure during an initial mark pause (i.e. do_mark_object will
4892 // be true) then attempt to mark the object.
4893 if (do_mark_object) {
4894 mark_object(obj);
4895 }
4896 }
4898 if (barrier == G1BarrierEvac) {
4899 _par_scan_state->update_rs(_from, p, _worker_id);
4900 }
4901 }
4903 template void G1ParCopyClosure<G1BarrierEvac, false>::do_oop_work(oop* p);
4904 template void G1ParCopyClosure<G1BarrierEvac, false>::do_oop_work(narrowOop* p);
4906 class G1ParEvacuateFollowersClosure : public VoidClosure {
4907 protected:
4908 G1CollectedHeap* _g1h;
4909 G1ParScanThreadState* _par_scan_state;
4910 RefToScanQueueSet* _queues;
4911 ParallelTaskTerminator* _terminator;
4913 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
4914 RefToScanQueueSet* queues() { return _queues; }
4915 ParallelTaskTerminator* terminator() { return _terminator; }
4917 public:
4918 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4919 G1ParScanThreadState* par_scan_state,
4920 RefToScanQueueSet* queues,
4921 ParallelTaskTerminator* terminator)
4922 : _g1h(g1h), _par_scan_state(par_scan_state),
4923 _queues(queues), _terminator(terminator) {}
4925 void do_void();
4927 private:
4928 inline bool offer_termination();
4929 };
4931 bool G1ParEvacuateFollowersClosure::offer_termination() {
4932 G1ParScanThreadState* const pss = par_scan_state();
4933 pss->start_term_time();
4934 const bool res = terminator()->offer_termination();
4935 pss->end_term_time();
4936 return res;
4937 }
4939 void G1ParEvacuateFollowersClosure::do_void() {
4940 StarTask stolen_task;
4941 G1ParScanThreadState* const pss = par_scan_state();
4942 pss->trim_queue();
4944 do {
4945 while (queues()->steal(pss->queue_num(), pss->hash_seed(), stolen_task)) {
4946 assert(pss->verify_task(stolen_task), "sanity");
4947 if (stolen_task.is_narrow()) {
4948 pss->deal_with_reference((narrowOop*) stolen_task);
4949 } else {
4950 pss->deal_with_reference((oop*) stolen_task);
4951 }
4953 // We've just processed a reference and we might have made
4954 // available new entries on the queues. So we have to make sure
4955 // we drain the queues as necessary.
4956 pss->trim_queue();
4957 }
4958 } while (!offer_termination());
4960 pss->retire_alloc_buffers();
4961 }
4963 class G1KlassScanClosure : public KlassClosure {
4964 G1ParCopyHelper* _closure;
4965 bool _process_only_dirty;
4966 int _count;
4967 public:
4968 G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty)
4969 : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {}
4970 void do_klass(Klass* klass) {
4971 // If the klass has not been dirtied we know that there's
4972 // no references into the young gen and we can skip it.
4973 if (!_process_only_dirty || klass->has_modified_oops()) {
4974 // Clean the klass since we're going to scavenge all the metadata.
4975 klass->clear_modified_oops();
4977 // Tell the closure that this klass is the Klass to scavenge
4978 // and is the one to dirty if oops are left pointing into the young gen.
4979 _closure->set_scanned_klass(klass);
4981 klass->oops_do(_closure);
4983 _closure->set_scanned_klass(NULL);
4984 }
4985 _count++;
4986 }
4987 };
4989 class G1ParTask : public AbstractGangTask {
4990 protected:
4991 G1CollectedHeap* _g1h;
4992 RefToScanQueueSet *_queues;
4993 ParallelTaskTerminator _terminator;
4994 uint _n_workers;
4996 Mutex _stats_lock;
4997 Mutex* stats_lock() { return &_stats_lock; }
4999 size_t getNCards() {
5000 return (_g1h->capacity() + G1BlockOffsetSharedArray::N_bytes - 1)
5001 / G1BlockOffsetSharedArray::N_bytes;
5002 }
5004 public:
5005 G1ParTask(G1CollectedHeap* g1h,
5006 RefToScanQueueSet *task_queues)
5007 : AbstractGangTask("G1 collection"),
5008 _g1h(g1h),
5009 _queues(task_queues),
5010 _terminator(0, _queues),
5011 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
5012 {}
5014 RefToScanQueueSet* queues() { return _queues; }
5016 RefToScanQueue *work_queue(int i) {
5017 return queues()->queue(i);
5018 }
5020 ParallelTaskTerminator* terminator() { return &_terminator; }
5022 virtual void set_for_termination(int active_workers) {
5023 // This task calls set_n_termination() in par_non_clean_card_iterate_work()
5024 // in the young space (_par_seq_tasks) in the G1 heap
5025 // for SequentialSubTasksDone.
5026 // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap
5027 // both of which need setting by set_n_termination().
5028 _g1h->SharedHeap::set_n_termination(active_workers);
5029 _g1h->set_n_termination(active_workers);
5030 terminator()->reset_for_reuse(active_workers);
5031 _n_workers = active_workers;
5032 }
5034 void work(uint worker_id) {
5035 if (worker_id >= _n_workers) return; // no work needed this round
5037 double start_time_ms = os::elapsedTime() * 1000.0;
5038 _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms);
5040 {
5041 ResourceMark rm;
5042 HandleMark hm;
5044 ReferenceProcessor* rp = _g1h->ref_processor_stw();
5046 G1ParScanThreadState pss(_g1h, worker_id, rp);
5047 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
5049 pss.set_evac_failure_closure(&evac_failure_cl);
5051 G1ParScanExtRootClosure only_scan_root_cl(_g1h, &pss, rp);
5052 G1ParScanMetadataClosure only_scan_metadata_cl(_g1h, &pss, rp);
5054 G1ParScanAndMarkExtRootClosure scan_mark_root_cl(_g1h, &pss, rp);
5055 G1ParScanAndMarkMetadataClosure scan_mark_metadata_cl(_g1h, &pss, rp);
5057 bool only_young = _g1h->g1_policy()->gcs_are_young();
5058 G1KlassScanClosure scan_mark_klasses_cl_s(&scan_mark_metadata_cl, false);
5059 G1KlassScanClosure only_scan_klasses_cl_s(&only_scan_metadata_cl, only_young);
5061 OopClosure* scan_root_cl = &only_scan_root_cl;
5062 G1KlassScanClosure* scan_klasses_cl = &only_scan_klasses_cl_s;
5064 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5065 // We also need to mark copied objects.
5066 scan_root_cl = &scan_mark_root_cl;
5067 scan_klasses_cl = &scan_mark_klasses_cl_s;
5068 }
5070 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss);
5072 // Don't scan the scavengable methods in the code cache as part
5073 // of strong root scanning. The code roots that point into a
5074 // region in the collection set are scanned when we scan the
5075 // region's RSet.
5076 int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings;
5078 pss.start_strong_roots();
5079 _g1h->g1_process_strong_roots(/* is scavenging */ true,
5080 SharedHeap::ScanningOption(so),
5081 scan_root_cl,
5082 &push_heap_rs_cl,
5083 scan_klasses_cl,
5084 worker_id);
5085 pss.end_strong_roots();
5087 {
5088 double start = os::elapsedTime();
5089 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
5090 evac.do_void();
5091 double elapsed_ms = (os::elapsedTime()-start)*1000.0;
5092 double term_ms = pss.term_time()*1000.0;
5093 _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms);
5094 _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts());
5095 }
5096 _g1h->g1_policy()->record_thread_age_table(pss.age_table());
5097 _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
5099 if (ParallelGCVerbose) {
5100 MutexLocker x(stats_lock());
5101 pss.print_termination_stats(worker_id);
5102 }
5104 assert(pss.refs()->is_empty(), "should be empty");
5106 // Close the inner scope so that the ResourceMark and HandleMark
5107 // destructors are executed here and are included as part of the
5108 // "GC Worker Time".
5109 }
5111 double end_time_ms = os::elapsedTime() * 1000.0;
5112 _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms);
5113 }
5114 };
5116 // *** Common G1 Evacuation Stuff
5118 // This method is run in a GC worker.
5120 void
5121 G1CollectedHeap::
5122 g1_process_strong_roots(bool is_scavenging,
5123 ScanningOption so,
5124 OopClosure* scan_non_heap_roots,
5125 OopsInHeapRegionClosure* scan_rs,
5126 G1KlassScanClosure* scan_klasses,
5127 uint worker_i) {
5129 // First scan the strong roots
5130 double ext_roots_start = os::elapsedTime();
5131 double closure_app_time_sec = 0.0;
5133 BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
5135 assert(so & SO_CodeCache || scan_rs != NULL, "must scan code roots somehow");
5136 // Walk the code cache/strong code roots w/o buffering, because StarTask
5137 // cannot handle unaligned oop locations.
5138 CodeBlobToOopClosure eager_scan_code_roots(scan_non_heap_roots, true /* do_marking */);
5140 process_strong_roots(false, // no scoping; this is parallel code
5141 is_scavenging, so,
5142 &buf_scan_non_heap_roots,
5143 &eager_scan_code_roots,
5144 scan_klasses
5145 );
5147 // Now the CM ref_processor roots.
5148 if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
5149 // We need to treat the discovered reference lists of the
5150 // concurrent mark ref processor as roots and keep entries
5151 // (which are added by the marking threads) on them live
5152 // until they can be processed at the end of marking.
5153 ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
5154 }
5156 // Finish up any enqueued closure apps (attributed as object copy time).
5157 buf_scan_non_heap_roots.done();
5159 double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds();
5161 g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
5163 double ext_root_time_ms =
5164 ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0;
5166 g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
5168 // During conc marking we have to filter the per-thread SATB buffers
5169 // to make sure we remove any oops into the CSet (which will show up
5170 // as implicitly live).
5171 double satb_filtering_ms = 0.0;
5172 if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) {
5173 if (mark_in_progress()) {
5174 double satb_filter_start = os::elapsedTime();
5176 JavaThread::satb_mark_queue_set().filter_thread_buffers();
5178 satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0;
5179 }
5180 }
5181 g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms);
5183 // If this is an initial mark pause, and we're not scanning
5184 // the entire code cache, we need to mark the oops in the
5185 // strong code root lists for the regions that are not in
5186 // the collection set.
5187 // Note all threads participate in this set of root tasks.
5188 double mark_strong_code_roots_ms = 0.0;
5189 if (g1_policy()->during_initial_mark_pause() && !(so & SO_CodeCache)) {
5190 double mark_strong_roots_start = os::elapsedTime();
5191 mark_strong_code_roots(worker_i);
5192 mark_strong_code_roots_ms = (os::elapsedTime() - mark_strong_roots_start) * 1000.0;
5193 }
5194 g1_policy()->phase_times()->record_strong_code_root_mark_time(worker_i, mark_strong_code_roots_ms);
5196 // Now scan the complement of the collection set.
5197 if (scan_rs != NULL) {
5198 g1_rem_set()->oops_into_collection_set_do(scan_rs, &eager_scan_code_roots, worker_i);
5199 }
5200 _process_strong_tasks->all_tasks_completed();
5201 }
5203 void
5204 G1CollectedHeap::g1_process_weak_roots(OopClosure* root_closure) {
5205 CodeBlobToOopClosure roots_in_blobs(root_closure, /*do_marking=*/ false);
5206 SharedHeap::process_weak_roots(root_closure, &roots_in_blobs);
5207 }
5209 class G1StringSymbolTableUnlinkTask : public AbstractGangTask {
5210 private:
5211 BoolObjectClosure* _is_alive;
5212 int _initial_string_table_size;
5213 int _initial_symbol_table_size;
5215 bool _process_strings;
5216 int _strings_processed;
5217 int _strings_removed;
5219 bool _process_symbols;
5220 int _symbols_processed;
5221 int _symbols_removed;
5223 bool _do_in_parallel;
5224 public:
5225 G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) :
5226 AbstractGangTask("Par String/Symbol table unlink"), _is_alive(is_alive),
5227 _do_in_parallel(G1CollectedHeap::use_parallel_gc_threads()),
5228 _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
5229 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) {
5231 _initial_string_table_size = StringTable::the_table()->table_size();
5232 _initial_symbol_table_size = SymbolTable::the_table()->table_size();
5233 if (process_strings) {
5234 StringTable::clear_parallel_claimed_index();
5235 }
5236 if (process_symbols) {
5237 SymbolTable::clear_parallel_claimed_index();
5238 }
5239 }
5241 ~G1StringSymbolTableUnlinkTask() {
5242 guarantee(!_process_strings || !_do_in_parallel || StringTable::parallel_claimed_index() >= _initial_string_table_size,
5243 err_msg("claim value "INT32_FORMAT" after unlink less than initial string table size "INT32_FORMAT,
5244 StringTable::parallel_claimed_index(), _initial_string_table_size));
5245 guarantee(!_process_symbols || !_do_in_parallel || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
5246 err_msg("claim value "INT32_FORMAT" after unlink less than initial symbol table size "INT32_FORMAT,
5247 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size));
5248 }
5250 void work(uint worker_id) {
5251 if (_do_in_parallel) {
5252 int strings_processed = 0;
5253 int strings_removed = 0;
5254 int symbols_processed = 0;
5255 int symbols_removed = 0;
5256 if (_process_strings) {
5257 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
5258 Atomic::add(strings_processed, &_strings_processed);
5259 Atomic::add(strings_removed, &_strings_removed);
5260 }
5261 if (_process_symbols) {
5262 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
5263 Atomic::add(symbols_processed, &_symbols_processed);
5264 Atomic::add(symbols_removed, &_symbols_removed);
5265 }
5266 } else {
5267 if (_process_strings) {
5268 StringTable::unlink(_is_alive, &_strings_processed, &_strings_removed);
5269 }
5270 if (_process_symbols) {
5271 SymbolTable::unlink(&_symbols_processed, &_symbols_removed);
5272 }
5273 }
5274 }
5276 size_t strings_processed() const { return (size_t)_strings_processed; }
5277 size_t strings_removed() const { return (size_t)_strings_removed; }
5279 size_t symbols_processed() const { return (size_t)_symbols_processed; }
5280 size_t symbols_removed() const { return (size_t)_symbols_removed; }
5281 };
5283 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive,
5284 bool process_strings, bool process_symbols) {
5285 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5286 _g1h->workers()->active_workers() : 1);
5288 G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols);
5289 if (G1CollectedHeap::use_parallel_gc_threads()) {
5290 set_par_threads(n_workers);
5291 workers()->run_task(&g1_unlink_task);
5292 set_par_threads(0);
5293 } else {
5294 g1_unlink_task.work(0);
5295 }
5296 if (G1TraceStringSymbolTableScrubbing) {
5297 gclog_or_tty->print_cr("Cleaned string and symbol table, "
5298 "strings: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed, "
5299 "symbols: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed",
5300 g1_unlink_task.strings_processed(), g1_unlink_task.strings_removed(),
5301 g1_unlink_task.symbols_processed(), g1_unlink_task.symbols_removed());
5302 }
5304 if (G1StringDedup::is_enabled()) {
5305 G1StringDedup::unlink(is_alive);
5306 }
5307 }
5309 class RedirtyLoggedCardTableEntryFastClosure : public CardTableEntryClosure {
5310 public:
5311 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
5312 *card_ptr = CardTableModRefBS::dirty_card_val();
5313 return true;
5314 }
5315 };
5317 void G1CollectedHeap::redirty_logged_cards() {
5318 guarantee(G1DeferredRSUpdate, "Must only be called when using deferred RS updates.");
5319 double redirty_logged_cards_start = os::elapsedTime();
5321 RedirtyLoggedCardTableEntryFastClosure redirty;
5322 dirty_card_queue_set().set_closure(&redirty);
5323 dirty_card_queue_set().apply_closure_to_all_completed_buffers();
5325 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5326 dcq.merge_bufferlists(&dirty_card_queue_set());
5327 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5329 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
5330 }
5332 // Weak Reference Processing support
5334 // An always "is_alive" closure that is used to preserve referents.
5335 // If the object is non-null then it's alive. Used in the preservation
5336 // of referent objects that are pointed to by reference objects
5337 // discovered by the CM ref processor.
5338 class G1AlwaysAliveClosure: public BoolObjectClosure {
5339 G1CollectedHeap* _g1;
5340 public:
5341 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5342 bool do_object_b(oop p) {
5343 if (p != NULL) {
5344 return true;
5345 }
5346 return false;
5347 }
5348 };
5350 bool G1STWIsAliveClosure::do_object_b(oop p) {
5351 // An object is reachable if it is outside the collection set,
5352 // or is inside and copied.
5353 return !_g1->obj_in_cs(p) || p->is_forwarded();
5354 }
5356 // Non Copying Keep Alive closure
5357 class G1KeepAliveClosure: public OopClosure {
5358 G1CollectedHeap* _g1;
5359 public:
5360 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5361 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
5362 void do_oop( oop* p) {
5363 oop obj = *p;
5365 if (_g1->obj_in_cs(obj)) {
5366 assert( obj->is_forwarded(), "invariant" );
5367 *p = obj->forwardee();
5368 }
5369 }
5370 };
5372 // Copying Keep Alive closure - can be called from both
5373 // serial and parallel code as long as different worker
5374 // threads utilize different G1ParScanThreadState instances
5375 // and different queues.
5377 class G1CopyingKeepAliveClosure: public OopClosure {
5378 G1CollectedHeap* _g1h;
5379 OopClosure* _copy_non_heap_obj_cl;
5380 OopsInHeapRegionClosure* _copy_metadata_obj_cl;
5381 G1ParScanThreadState* _par_scan_state;
5383 public:
5384 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
5385 OopClosure* non_heap_obj_cl,
5386 OopsInHeapRegionClosure* metadata_obj_cl,
5387 G1ParScanThreadState* pss):
5388 _g1h(g1h),
5389 _copy_non_heap_obj_cl(non_heap_obj_cl),
5390 _copy_metadata_obj_cl(metadata_obj_cl),
5391 _par_scan_state(pss)
5392 {}
5394 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
5395 virtual void do_oop( oop* p) { do_oop_work(p); }
5397 template <class T> void do_oop_work(T* p) {
5398 oop obj = oopDesc::load_decode_heap_oop(p);
5400 if (_g1h->obj_in_cs(obj)) {
5401 // If the referent object has been forwarded (either copied
5402 // to a new location or to itself in the event of an
5403 // evacuation failure) then we need to update the reference
5404 // field and, if both reference and referent are in the G1
5405 // heap, update the RSet for the referent.
5406 //
5407 // If the referent has not been forwarded then we have to keep
5408 // it alive by policy. Therefore we have copy the referent.
5409 //
5410 // If the reference field is in the G1 heap then we can push
5411 // on the PSS queue. When the queue is drained (after each
5412 // phase of reference processing) the object and it's followers
5413 // will be copied, the reference field set to point to the
5414 // new location, and the RSet updated. Otherwise we need to
5415 // use the the non-heap or metadata closures directly to copy
5416 // the referent object and update the pointer, while avoiding
5417 // updating the RSet.
5419 if (_g1h->is_in_g1_reserved(p)) {
5420 _par_scan_state->push_on_queue(p);
5421 } else {
5422 assert(!Metaspace::contains((const void*)p),
5423 err_msg("Otherwise need to call _copy_metadata_obj_cl->do_oop(p) "
5424 PTR_FORMAT, p));
5425 _copy_non_heap_obj_cl->do_oop(p);
5426 }
5427 }
5428 }
5429 };
5431 // Serial drain queue closure. Called as the 'complete_gc'
5432 // closure for each discovered list in some of the
5433 // reference processing phases.
5435 class G1STWDrainQueueClosure: public VoidClosure {
5436 protected:
5437 G1CollectedHeap* _g1h;
5438 G1ParScanThreadState* _par_scan_state;
5440 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
5442 public:
5443 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
5444 _g1h(g1h),
5445 _par_scan_state(pss)
5446 { }
5448 void do_void() {
5449 G1ParScanThreadState* const pss = par_scan_state();
5450 pss->trim_queue();
5451 }
5452 };
5454 // Parallel Reference Processing closures
5456 // Implementation of AbstractRefProcTaskExecutor for parallel reference
5457 // processing during G1 evacuation pauses.
5459 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5460 private:
5461 G1CollectedHeap* _g1h;
5462 RefToScanQueueSet* _queues;
5463 FlexibleWorkGang* _workers;
5464 int _active_workers;
5466 public:
5467 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5468 FlexibleWorkGang* workers,
5469 RefToScanQueueSet *task_queues,
5470 int n_workers) :
5471 _g1h(g1h),
5472 _queues(task_queues),
5473 _workers(workers),
5474 _active_workers(n_workers)
5475 {
5476 assert(n_workers > 0, "shouldn't call this otherwise");
5477 }
5479 // Executes the given task using concurrent marking worker threads.
5480 virtual void execute(ProcessTask& task);
5481 virtual void execute(EnqueueTask& task);
5482 };
5484 // Gang task for possibly parallel reference processing
5486 class G1STWRefProcTaskProxy: public AbstractGangTask {
5487 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5488 ProcessTask& _proc_task;
5489 G1CollectedHeap* _g1h;
5490 RefToScanQueueSet *_task_queues;
5491 ParallelTaskTerminator* _terminator;
5493 public:
5494 G1STWRefProcTaskProxy(ProcessTask& proc_task,
5495 G1CollectedHeap* g1h,
5496 RefToScanQueueSet *task_queues,
5497 ParallelTaskTerminator* terminator) :
5498 AbstractGangTask("Process reference objects in parallel"),
5499 _proc_task(proc_task),
5500 _g1h(g1h),
5501 _task_queues(task_queues),
5502 _terminator(terminator)
5503 {}
5505 virtual void work(uint worker_id) {
5506 // The reference processing task executed by a single worker.
5507 ResourceMark rm;
5508 HandleMark hm;
5510 G1STWIsAliveClosure is_alive(_g1h);
5512 G1ParScanThreadState pss(_g1h, worker_id, NULL);
5513 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5515 pss.set_evac_failure_closure(&evac_failure_cl);
5517 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5518 G1ParScanMetadataClosure only_copy_metadata_cl(_g1h, &pss, NULL);
5520 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5521 G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(_g1h, &pss, NULL);
5523 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5524 OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl;
5526 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5527 // We also need to mark copied objects.
5528 copy_non_heap_cl = ©_mark_non_heap_cl;
5529 copy_metadata_cl = ©_mark_metadata_cl;
5530 }
5532 // Keep alive closure.
5533 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_metadata_cl, &pss);
5535 // Complete GC closure
5536 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5538 // Call the reference processing task's work routine.
5539 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5541 // Note we cannot assert that the refs array is empty here as not all
5542 // of the processing tasks (specifically phase2 - pp2_work) execute
5543 // the complete_gc closure (which ordinarily would drain the queue) so
5544 // the queue may not be empty.
5545 }
5546 };
5548 // Driver routine for parallel reference processing.
5549 // Creates an instance of the ref processing gang
5550 // task and has the worker threads execute it.
5551 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5552 assert(_workers != NULL, "Need parallel worker threads.");
5554 ParallelTaskTerminator terminator(_active_workers, _queues);
5555 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5557 _g1h->set_par_threads(_active_workers);
5558 _workers->run_task(&proc_task_proxy);
5559 _g1h->set_par_threads(0);
5560 }
5562 // Gang task for parallel reference enqueueing.
5564 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5565 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5566 EnqueueTask& _enq_task;
5568 public:
5569 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5570 AbstractGangTask("Enqueue reference objects in parallel"),
5571 _enq_task(enq_task)
5572 { }
5574 virtual void work(uint worker_id) {
5575 _enq_task.work(worker_id);
5576 }
5577 };
5579 // Driver routine for parallel reference enqueueing.
5580 // Creates an instance of the ref enqueueing gang
5581 // task and has the worker threads execute it.
5583 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5584 assert(_workers != NULL, "Need parallel worker threads.");
5586 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5588 _g1h->set_par_threads(_active_workers);
5589 _workers->run_task(&enq_task_proxy);
5590 _g1h->set_par_threads(0);
5591 }
5593 // End of weak reference support closures
5595 // Abstract task used to preserve (i.e. copy) any referent objects
5596 // that are in the collection set and are pointed to by reference
5597 // objects discovered by the CM ref processor.
5599 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5600 protected:
5601 G1CollectedHeap* _g1h;
5602 RefToScanQueueSet *_queues;
5603 ParallelTaskTerminator _terminator;
5604 uint _n_workers;
5606 public:
5607 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
5608 AbstractGangTask("ParPreserveCMReferents"),
5609 _g1h(g1h),
5610 _queues(task_queues),
5611 _terminator(workers, _queues),
5612 _n_workers(workers)
5613 { }
5615 void work(uint worker_id) {
5616 ResourceMark rm;
5617 HandleMark hm;
5619 G1ParScanThreadState pss(_g1h, worker_id, NULL);
5620 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5622 pss.set_evac_failure_closure(&evac_failure_cl);
5624 assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5627 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5628 G1ParScanMetadataClosure only_copy_metadata_cl(_g1h, &pss, NULL);
5630 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5631 G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(_g1h, &pss, NULL);
5633 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5634 OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl;
5636 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5637 // We also need to mark copied objects.
5638 copy_non_heap_cl = ©_mark_non_heap_cl;
5639 copy_metadata_cl = ©_mark_metadata_cl;
5640 }
5642 // Is alive closure
5643 G1AlwaysAliveClosure always_alive(_g1h);
5645 // Copying keep alive closure. Applied to referent objects that need
5646 // to be copied.
5647 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_metadata_cl, &pss);
5649 ReferenceProcessor* rp = _g1h->ref_processor_cm();
5651 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5652 uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5654 // limit is set using max_num_q() - which was set using ParallelGCThreads.
5655 // So this must be true - but assert just in case someone decides to
5656 // change the worker ids.
5657 assert(0 <= worker_id && worker_id < limit, "sanity");
5658 assert(!rp->discovery_is_atomic(), "check this code");
5660 // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5661 for (uint idx = worker_id; idx < limit; idx += stride) {
5662 DiscoveredList& ref_list = rp->discovered_refs()[idx];
5664 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5665 while (iter.has_next()) {
5666 // Since discovery is not atomic for the CM ref processor, we
5667 // can see some null referent objects.
5668 iter.load_ptrs(DEBUG_ONLY(true));
5669 oop ref = iter.obj();
5671 // This will filter nulls.
5672 if (iter.is_referent_alive()) {
5673 iter.make_referent_alive();
5674 }
5675 iter.move_to_next();
5676 }
5677 }
5679 // Drain the queue - which may cause stealing
5680 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5681 drain_queue.do_void();
5682 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5683 assert(pss.refs()->is_empty(), "should be");
5684 }
5685 };
5687 // Weak Reference processing during an evacuation pause (part 1).
5688 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) {
5689 double ref_proc_start = os::elapsedTime();
5691 ReferenceProcessor* rp = _ref_processor_stw;
5692 assert(rp->discovery_enabled(), "should have been enabled");
5694 // Any reference objects, in the collection set, that were 'discovered'
5695 // by the CM ref processor should have already been copied (either by
5696 // applying the external root copy closure to the discovered lists, or
5697 // by following an RSet entry).
5698 //
5699 // But some of the referents, that are in the collection set, that these
5700 // reference objects point to may not have been copied: the STW ref
5701 // processor would have seen that the reference object had already
5702 // been 'discovered' and would have skipped discovering the reference,
5703 // but would not have treated the reference object as a regular oop.
5704 // As a result the copy closure would not have been applied to the
5705 // referent object.
5706 //
5707 // We need to explicitly copy these referent objects - the references
5708 // will be processed at the end of remarking.
5709 //
5710 // We also need to do this copying before we process the reference
5711 // objects discovered by the STW ref processor in case one of these
5712 // referents points to another object which is also referenced by an
5713 // object discovered by the STW ref processor.
5715 assert(!G1CollectedHeap::use_parallel_gc_threads() ||
5716 no_of_gc_workers == workers()->active_workers(),
5717 "Need to reset active GC workers");
5719 set_par_threads(no_of_gc_workers);
5720 G1ParPreserveCMReferentsTask keep_cm_referents(this,
5721 no_of_gc_workers,
5722 _task_queues);
5724 if (G1CollectedHeap::use_parallel_gc_threads()) {
5725 workers()->run_task(&keep_cm_referents);
5726 } else {
5727 keep_cm_referents.work(0);
5728 }
5730 set_par_threads(0);
5732 // Closure to test whether a referent is alive.
5733 G1STWIsAliveClosure is_alive(this);
5735 // Even when parallel reference processing is enabled, the processing
5736 // of JNI refs is serial and performed serially by the current thread
5737 // rather than by a worker. The following PSS will be used for processing
5738 // JNI refs.
5740 // Use only a single queue for this PSS.
5741 G1ParScanThreadState pss(this, 0, NULL);
5743 // We do not embed a reference processor in the copying/scanning
5744 // closures while we're actually processing the discovered
5745 // reference objects.
5746 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5748 pss.set_evac_failure_closure(&evac_failure_cl);
5750 assert(pss.refs()->is_empty(), "pre-condition");
5752 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL);
5753 G1ParScanMetadataClosure only_copy_metadata_cl(this, &pss, NULL);
5755 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5756 G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(this, &pss, NULL);
5758 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5759 OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl;
5761 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5762 // We also need to mark copied objects.
5763 copy_non_heap_cl = ©_mark_non_heap_cl;
5764 copy_metadata_cl = ©_mark_metadata_cl;
5765 }
5767 // Keep alive closure.
5768 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, copy_metadata_cl, &pss);
5770 // Serial Complete GC closure
5771 G1STWDrainQueueClosure drain_queue(this, &pss);
5773 // Setup the soft refs policy...
5774 rp->setup_policy(false);
5776 ReferenceProcessorStats stats;
5777 if (!rp->processing_is_mt()) {
5778 // Serial reference processing...
5779 stats = rp->process_discovered_references(&is_alive,
5780 &keep_alive,
5781 &drain_queue,
5782 NULL,
5783 _gc_timer_stw,
5784 _gc_tracer_stw->gc_id());
5785 } else {
5786 // Parallel reference processing
5787 assert(rp->num_q() == no_of_gc_workers, "sanity");
5788 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5790 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5791 stats = rp->process_discovered_references(&is_alive,
5792 &keep_alive,
5793 &drain_queue,
5794 &par_task_executor,
5795 _gc_timer_stw,
5796 _gc_tracer_stw->gc_id());
5797 }
5799 _gc_tracer_stw->report_gc_reference_stats(stats);
5800 // We have completed copying any necessary live referent objects
5801 // (that were not copied during the actual pause) so we can
5802 // retire any active alloc buffers
5803 pss.retire_alloc_buffers();
5804 assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5806 double ref_proc_time = os::elapsedTime() - ref_proc_start;
5807 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5808 }
5810 // Weak Reference processing during an evacuation pause (part 2).
5811 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) {
5812 double ref_enq_start = os::elapsedTime();
5814 ReferenceProcessor* rp = _ref_processor_stw;
5815 assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5817 // Now enqueue any remaining on the discovered lists on to
5818 // the pending list.
5819 if (!rp->processing_is_mt()) {
5820 // Serial reference processing...
5821 rp->enqueue_discovered_references();
5822 } else {
5823 // Parallel reference enqueueing
5825 assert(no_of_gc_workers == workers()->active_workers(),
5826 "Need to reset active workers");
5827 assert(rp->num_q() == no_of_gc_workers, "sanity");
5828 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5830 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5831 rp->enqueue_discovered_references(&par_task_executor);
5832 }
5834 rp->verify_no_references_recorded();
5835 assert(!rp->discovery_enabled(), "should have been disabled");
5837 // FIXME
5838 // CM's reference processing also cleans up the string and symbol tables.
5839 // Should we do that here also? We could, but it is a serial operation
5840 // and could significantly increase the pause time.
5842 double ref_enq_time = os::elapsedTime() - ref_enq_start;
5843 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5844 }
5846 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) {
5847 _expand_heap_after_alloc_failure = true;
5848 _evacuation_failed = false;
5850 // Should G1EvacuationFailureALot be in effect for this GC?
5851 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
5853 g1_rem_set()->prepare_for_oops_into_collection_set_do();
5855 // Disable the hot card cache.
5856 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
5857 hot_card_cache->reset_hot_cache_claimed_index();
5858 hot_card_cache->set_use_cache(false);
5860 uint n_workers;
5861 if (G1CollectedHeap::use_parallel_gc_threads()) {
5862 n_workers =
5863 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
5864 workers()->active_workers(),
5865 Threads::number_of_non_daemon_threads());
5866 assert(UseDynamicNumberOfGCThreads ||
5867 n_workers == workers()->total_workers(),
5868 "If not dynamic should be using all the workers");
5869 workers()->set_active_workers(n_workers);
5870 set_par_threads(n_workers);
5871 } else {
5872 assert(n_par_threads() == 0,
5873 "Should be the original non-parallel value");
5874 n_workers = 1;
5875 }
5877 G1ParTask g1_par_task(this, _task_queues);
5879 init_for_evac_failure(NULL);
5881 rem_set()->prepare_for_younger_refs_iterate(true);
5883 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5884 double start_par_time_sec = os::elapsedTime();
5885 double end_par_time_sec;
5887 {
5888 StrongRootsScope srs(this);
5890 if (G1CollectedHeap::use_parallel_gc_threads()) {
5891 // The individual threads will set their evac-failure closures.
5892 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
5893 // These tasks use ShareHeap::_process_strong_tasks
5894 assert(UseDynamicNumberOfGCThreads ||
5895 workers()->active_workers() == workers()->total_workers(),
5896 "If not dynamic should be using all the workers");
5897 workers()->run_task(&g1_par_task);
5898 } else {
5899 g1_par_task.set_for_termination(n_workers);
5900 g1_par_task.work(0);
5901 }
5902 end_par_time_sec = os::elapsedTime();
5904 // Closing the inner scope will execute the destructor
5905 // for the StrongRootsScope object. We record the current
5906 // elapsed time before closing the scope so that time
5907 // taken for the SRS destructor is NOT included in the
5908 // reported parallel time.
5909 }
5911 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5912 g1_policy()->phase_times()->record_par_time(par_time_ms);
5914 double code_root_fixup_time_ms =
5915 (os::elapsedTime() - end_par_time_sec) * 1000.0;
5916 g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms);
5918 set_par_threads(0);
5920 // Process any discovered reference objects - we have
5921 // to do this _before_ we retire the GC alloc regions
5922 // as we may have to copy some 'reachable' referent
5923 // objects (and their reachable sub-graphs) that were
5924 // not copied during the pause.
5925 process_discovered_references(n_workers);
5927 // Weak root processing.
5928 {
5929 G1STWIsAliveClosure is_alive(this);
5930 G1KeepAliveClosure keep_alive(this);
5931 JNIHandles::weak_oops_do(&is_alive, &keep_alive);
5932 if (G1StringDedup::is_enabled()) {
5933 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive);
5934 }
5935 }
5937 release_gc_alloc_regions(n_workers, evacuation_info);
5938 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5940 // Reset and re-enable the hot card cache.
5941 // Note the counts for the cards in the regions in the
5942 // collection set are reset when the collection set is freed.
5943 hot_card_cache->reset_hot_cache();
5944 hot_card_cache->set_use_cache(true);
5946 // Migrate the strong code roots attached to each region in
5947 // the collection set. Ideally we would like to do this
5948 // after we have finished the scanning/evacuation of the
5949 // strong code roots for a particular heap region.
5950 migrate_strong_code_roots();
5952 purge_code_root_memory();
5954 if (g1_policy()->during_initial_mark_pause()) {
5955 // Reset the claim values set during marking the strong code roots
5956 reset_heap_region_claim_values();
5957 }
5959 finalize_for_evac_failure();
5961 if (evacuation_failed()) {
5962 remove_self_forwarding_pointers();
5964 // Reset the G1EvacuationFailureALot counters and flags
5965 // Note: the values are reset only when an actual
5966 // evacuation failure occurs.
5967 NOT_PRODUCT(reset_evacuation_should_fail();)
5968 }
5970 // Enqueue any remaining references remaining on the STW
5971 // reference processor's discovered lists. We need to do
5972 // this after the card table is cleaned (and verified) as
5973 // the act of enqueueing entries on to the pending list
5974 // will log these updates (and dirty their associated
5975 // cards). We need these updates logged to update any
5976 // RSets.
5977 enqueue_discovered_references(n_workers);
5979 if (G1DeferredRSUpdate) {
5980 redirty_logged_cards();
5981 }
5982 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5983 }
5985 void G1CollectedHeap::free_region(HeapRegion* hr,
5986 FreeRegionList* free_list,
5987 bool par,
5988 bool locked) {
5989 assert(!hr->isHumongous(), "this is only for non-humongous regions");
5990 assert(!hr->is_empty(), "the region should not be empty");
5991 assert(free_list != NULL, "pre-condition");
5993 // Clear the card counts for this region.
5994 // Note: we only need to do this if the region is not young
5995 // (since we don't refine cards in young regions).
5996 if (!hr->is_young()) {
5997 _cg1r->hot_card_cache()->reset_card_counts(hr);
5998 }
5999 hr->hr_clear(par, true /* clear_space */, locked /* locked */);
6000 free_list->add_ordered(hr);
6001 }
6003 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
6004 FreeRegionList* free_list,
6005 bool par) {
6006 assert(hr->startsHumongous(), "this is only for starts humongous regions");
6007 assert(free_list != NULL, "pre-condition");
6009 size_t hr_capacity = hr->capacity();
6010 // We need to read this before we make the region non-humongous,
6011 // otherwise the information will be gone.
6012 uint last_index = hr->last_hc_index();
6013 hr->set_notHumongous();
6014 free_region(hr, free_list, par);
6016 uint i = hr->hrs_index() + 1;
6017 while (i < last_index) {
6018 HeapRegion* curr_hr = region_at(i);
6019 assert(curr_hr->continuesHumongous(), "invariant");
6020 curr_hr->set_notHumongous();
6021 free_region(curr_hr, free_list, par);
6022 i += 1;
6023 }
6024 }
6026 void G1CollectedHeap::remove_from_old_sets(const HeapRegionSetCount& old_regions_removed,
6027 const HeapRegionSetCount& humongous_regions_removed) {
6028 if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 0) {
6029 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
6030 _old_set.bulk_remove(old_regions_removed);
6031 _humongous_set.bulk_remove(humongous_regions_removed);
6032 }
6034 }
6036 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
6037 assert(list != NULL, "list can't be null");
6038 if (!list->is_empty()) {
6039 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
6040 _free_list.add_ordered(list);
6041 }
6042 }
6044 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
6045 assert(_summary_bytes_used >= bytes,
6046 err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" should be >= bytes: "SIZE_FORMAT,
6047 _summary_bytes_used, bytes));
6048 _summary_bytes_used -= bytes;
6049 }
6051 class G1ParCleanupCTTask : public AbstractGangTask {
6052 G1SATBCardTableModRefBS* _ct_bs;
6053 G1CollectedHeap* _g1h;
6054 HeapRegion* volatile _su_head;
6055 public:
6056 G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs,
6057 G1CollectedHeap* g1h) :
6058 AbstractGangTask("G1 Par Cleanup CT Task"),
6059 _ct_bs(ct_bs), _g1h(g1h) { }
6061 void work(uint worker_id) {
6062 HeapRegion* r;
6063 while (r = _g1h->pop_dirty_cards_region()) {
6064 clear_cards(r);
6065 }
6066 }
6068 void clear_cards(HeapRegion* r) {
6069 // Cards of the survivors should have already been dirtied.
6070 if (!r->is_survivor()) {
6071 _ct_bs->clear(MemRegion(r->bottom(), r->end()));
6072 }
6073 }
6074 };
6076 #ifndef PRODUCT
6077 class G1VerifyCardTableCleanup: public HeapRegionClosure {
6078 G1CollectedHeap* _g1h;
6079 G1SATBCardTableModRefBS* _ct_bs;
6080 public:
6081 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs)
6082 : _g1h(g1h), _ct_bs(ct_bs) { }
6083 virtual bool doHeapRegion(HeapRegion* r) {
6084 if (r->is_survivor()) {
6085 _g1h->verify_dirty_region(r);
6086 } else {
6087 _g1h->verify_not_dirty_region(r);
6088 }
6089 return false;
6090 }
6091 };
6093 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
6094 // All of the region should be clean.
6095 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6096 MemRegion mr(hr->bottom(), hr->end());
6097 ct_bs->verify_not_dirty_region(mr);
6098 }
6100 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
6101 // We cannot guarantee that [bottom(),end()] is dirty. Threads
6102 // dirty allocated blocks as they allocate them. The thread that
6103 // retires each region and replaces it with a new one will do a
6104 // maximal allocation to fill in [pre_dummy_top(),end()] but will
6105 // not dirty that area (one less thing to have to do while holding
6106 // a lock). So we can only verify that [bottom(),pre_dummy_top()]
6107 // is dirty.
6108 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6109 MemRegion mr(hr->bottom(), hr->pre_dummy_top());
6110 if (hr->is_young()) {
6111 ct_bs->verify_g1_young_region(mr);
6112 } else {
6113 ct_bs->verify_dirty_region(mr);
6114 }
6115 }
6117 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
6118 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6119 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
6120 verify_dirty_region(hr);
6121 }
6122 }
6124 void G1CollectedHeap::verify_dirty_young_regions() {
6125 verify_dirty_young_list(_young_list->first_region());
6126 }
6127 #endif
6129 void G1CollectedHeap::cleanUpCardTable() {
6130 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6131 double start = os::elapsedTime();
6133 {
6134 // Iterate over the dirty cards region list.
6135 G1ParCleanupCTTask cleanup_task(ct_bs, this);
6137 if (G1CollectedHeap::use_parallel_gc_threads()) {
6138 set_par_threads();
6139 workers()->run_task(&cleanup_task);
6140 set_par_threads(0);
6141 } else {
6142 while (_dirty_cards_region_list) {
6143 HeapRegion* r = _dirty_cards_region_list;
6144 cleanup_task.clear_cards(r);
6145 _dirty_cards_region_list = r->get_next_dirty_cards_region();
6146 if (_dirty_cards_region_list == r) {
6147 // The last region.
6148 _dirty_cards_region_list = NULL;
6149 }
6150 r->set_next_dirty_cards_region(NULL);
6151 }
6152 }
6153 #ifndef PRODUCT
6154 if (G1VerifyCTCleanup || VerifyAfterGC) {
6155 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
6156 heap_region_iterate(&cleanup_verifier);
6157 }
6158 #endif
6159 }
6161 double elapsed = os::elapsedTime() - start;
6162 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
6163 }
6165 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) {
6166 size_t pre_used = 0;
6167 FreeRegionList local_free_list("Local List for CSet Freeing");
6169 double young_time_ms = 0.0;
6170 double non_young_time_ms = 0.0;
6172 // Since the collection set is a superset of the the young list,
6173 // all we need to do to clear the young list is clear its
6174 // head and length, and unlink any young regions in the code below
6175 _young_list->clear();
6177 G1CollectorPolicy* policy = g1_policy();
6179 double start_sec = os::elapsedTime();
6180 bool non_young = true;
6182 HeapRegion* cur = cs_head;
6183 int age_bound = -1;
6184 size_t rs_lengths = 0;
6186 while (cur != NULL) {
6187 assert(!is_on_master_free_list(cur), "sanity");
6188 if (non_young) {
6189 if (cur->is_young()) {
6190 double end_sec = os::elapsedTime();
6191 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6192 non_young_time_ms += elapsed_ms;
6194 start_sec = os::elapsedTime();
6195 non_young = false;
6196 }
6197 } else {
6198 if (!cur->is_young()) {
6199 double end_sec = os::elapsedTime();
6200 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6201 young_time_ms += elapsed_ms;
6203 start_sec = os::elapsedTime();
6204 non_young = true;
6205 }
6206 }
6208 rs_lengths += cur->rem_set()->occupied_locked();
6210 HeapRegion* next = cur->next_in_collection_set();
6211 assert(cur->in_collection_set(), "bad CS");
6212 cur->set_next_in_collection_set(NULL);
6213 cur->set_in_collection_set(false);
6215 if (cur->is_young()) {
6216 int index = cur->young_index_in_cset();
6217 assert(index != -1, "invariant");
6218 assert((uint) index < policy->young_cset_region_length(), "invariant");
6219 size_t words_survived = _surviving_young_words[index];
6220 cur->record_surv_words_in_group(words_survived);
6222 // At this point the we have 'popped' cur from the collection set
6223 // (linked via next_in_collection_set()) but it is still in the
6224 // young list (linked via next_young_region()). Clear the
6225 // _next_young_region field.
6226 cur->set_next_young_region(NULL);
6227 } else {
6228 int index = cur->young_index_in_cset();
6229 assert(index == -1, "invariant");
6230 }
6232 assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
6233 (!cur->is_young() && cur->young_index_in_cset() == -1),
6234 "invariant" );
6236 if (!cur->evacuation_failed()) {
6237 MemRegion used_mr = cur->used_region();
6239 // And the region is empty.
6240 assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
6241 pre_used += cur->used();
6242 free_region(cur, &local_free_list, false /* par */, true /* locked */);
6243 } else {
6244 cur->uninstall_surv_rate_group();
6245 if (cur->is_young()) {
6246 cur->set_young_index_in_cset(-1);
6247 }
6248 cur->set_not_young();
6249 cur->set_evacuation_failed(false);
6250 // The region is now considered to be old.
6251 _old_set.add(cur);
6252 evacuation_info.increment_collectionset_used_after(cur->used());
6253 }
6254 cur = next;
6255 }
6257 evacuation_info.set_regions_freed(local_free_list.length());
6258 policy->record_max_rs_lengths(rs_lengths);
6259 policy->cset_regions_freed();
6261 double end_sec = os::elapsedTime();
6262 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6264 if (non_young) {
6265 non_young_time_ms += elapsed_ms;
6266 } else {
6267 young_time_ms += elapsed_ms;
6268 }
6270 prepend_to_freelist(&local_free_list);
6271 decrement_summary_bytes(pre_used);
6272 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
6273 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
6274 }
6276 // This routine is similar to the above but does not record
6277 // any policy statistics or update free lists; we are abandoning
6278 // the current incremental collection set in preparation of a
6279 // full collection. After the full GC we will start to build up
6280 // the incremental collection set again.
6281 // This is only called when we're doing a full collection
6282 // and is immediately followed by the tearing down of the young list.
6284 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
6285 HeapRegion* cur = cs_head;
6287 while (cur != NULL) {
6288 HeapRegion* next = cur->next_in_collection_set();
6289 assert(cur->in_collection_set(), "bad CS");
6290 cur->set_next_in_collection_set(NULL);
6291 cur->set_in_collection_set(false);
6292 cur->set_young_index_in_cset(-1);
6293 cur = next;
6294 }
6295 }
6297 void G1CollectedHeap::set_free_regions_coming() {
6298 if (G1ConcRegionFreeingVerbose) {
6299 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6300 "setting free regions coming");
6301 }
6303 assert(!free_regions_coming(), "pre-condition");
6304 _free_regions_coming = true;
6305 }
6307 void G1CollectedHeap::reset_free_regions_coming() {
6308 assert(free_regions_coming(), "pre-condition");
6310 {
6311 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6312 _free_regions_coming = false;
6313 SecondaryFreeList_lock->notify_all();
6314 }
6316 if (G1ConcRegionFreeingVerbose) {
6317 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6318 "reset free regions coming");
6319 }
6320 }
6322 void G1CollectedHeap::wait_while_free_regions_coming() {
6323 // Most of the time we won't have to wait, so let's do a quick test
6324 // first before we take the lock.
6325 if (!free_regions_coming()) {
6326 return;
6327 }
6329 if (G1ConcRegionFreeingVerbose) {
6330 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6331 "waiting for free regions");
6332 }
6334 {
6335 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6336 while (free_regions_coming()) {
6337 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
6338 }
6339 }
6341 if (G1ConcRegionFreeingVerbose) {
6342 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6343 "done waiting for free regions");
6344 }
6345 }
6347 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
6348 assert(heap_lock_held_for_gc(),
6349 "the heap lock should already be held by or for this thread");
6350 _young_list->push_region(hr);
6351 }
6353 class NoYoungRegionsClosure: public HeapRegionClosure {
6354 private:
6355 bool _success;
6356 public:
6357 NoYoungRegionsClosure() : _success(true) { }
6358 bool doHeapRegion(HeapRegion* r) {
6359 if (r->is_young()) {
6360 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
6361 r->bottom(), r->end());
6362 _success = false;
6363 }
6364 return false;
6365 }
6366 bool success() { return _success; }
6367 };
6369 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
6370 bool ret = _young_list->check_list_empty(check_sample);
6372 if (check_heap) {
6373 NoYoungRegionsClosure closure;
6374 heap_region_iterate(&closure);
6375 ret = ret && closure.success();
6376 }
6378 return ret;
6379 }
6381 class TearDownRegionSetsClosure : public HeapRegionClosure {
6382 private:
6383 HeapRegionSet *_old_set;
6385 public:
6386 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
6388 bool doHeapRegion(HeapRegion* r) {
6389 if (r->is_empty()) {
6390 // We ignore empty regions, we'll empty the free list afterwards
6391 } else if (r->is_young()) {
6392 // We ignore young regions, we'll empty the young list afterwards
6393 } else if (r->isHumongous()) {
6394 // We ignore humongous regions, we're not tearing down the
6395 // humongous region set
6396 } else {
6397 // The rest should be old
6398 _old_set->remove(r);
6399 }
6400 return false;
6401 }
6403 ~TearDownRegionSetsClosure() {
6404 assert(_old_set->is_empty(), "post-condition");
6405 }
6406 };
6408 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6409 assert_at_safepoint(true /* should_be_vm_thread */);
6411 if (!free_list_only) {
6412 TearDownRegionSetsClosure cl(&_old_set);
6413 heap_region_iterate(&cl);
6415 // Note that emptying the _young_list is postponed and instead done as
6416 // the first step when rebuilding the regions sets again. The reason for
6417 // this is that during a full GC string deduplication needs to know if
6418 // a collected region was young or old when the full GC was initiated.
6419 }
6420 _free_list.remove_all();
6421 }
6423 class RebuildRegionSetsClosure : public HeapRegionClosure {
6424 private:
6425 bool _free_list_only;
6426 HeapRegionSet* _old_set;
6427 FreeRegionList* _free_list;
6428 size_t _total_used;
6430 public:
6431 RebuildRegionSetsClosure(bool free_list_only,
6432 HeapRegionSet* old_set, FreeRegionList* free_list) :
6433 _free_list_only(free_list_only),
6434 _old_set(old_set), _free_list(free_list), _total_used(0) {
6435 assert(_free_list->is_empty(), "pre-condition");
6436 if (!free_list_only) {
6437 assert(_old_set->is_empty(), "pre-condition");
6438 }
6439 }
6441 bool doHeapRegion(HeapRegion* r) {
6442 if (r->continuesHumongous()) {
6443 return false;
6444 }
6446 if (r->is_empty()) {
6447 // Add free regions to the free list
6448 _free_list->add_as_tail(r);
6449 } else if (!_free_list_only) {
6450 assert(!r->is_young(), "we should not come across young regions");
6452 if (r->isHumongous()) {
6453 // We ignore humongous regions, we left the humongous set unchanged
6454 } else {
6455 // The rest should be old, add them to the old set
6456 _old_set->add(r);
6457 }
6458 _total_used += r->used();
6459 }
6461 return false;
6462 }
6464 size_t total_used() {
6465 return _total_used;
6466 }
6467 };
6469 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6470 assert_at_safepoint(true /* should_be_vm_thread */);
6472 if (!free_list_only) {
6473 _young_list->empty_list();
6474 }
6476 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_free_list);
6477 heap_region_iterate(&cl);
6479 if (!free_list_only) {
6480 _summary_bytes_used = cl.total_used();
6481 }
6482 assert(_summary_bytes_used == recalculate_used(),
6483 err_msg("inconsistent _summary_bytes_used, "
6484 "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6485 _summary_bytes_used, recalculate_used()));
6486 }
6488 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6489 _refine_cte_cl->set_concurrent(concurrent);
6490 }
6492 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6493 HeapRegion* hr = heap_region_containing(p);
6494 if (hr == NULL) {
6495 return false;
6496 } else {
6497 return hr->is_in(p);
6498 }
6499 }
6501 // Methods for the mutator alloc region
6503 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6504 bool force) {
6505 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6506 assert(!force || g1_policy()->can_expand_young_list(),
6507 "if force is true we should be able to expand the young list");
6508 bool young_list_full = g1_policy()->is_young_list_full();
6509 if (force || !young_list_full) {
6510 HeapRegion* new_alloc_region = new_region(word_size,
6511 false /* is_old */,
6512 false /* do_expand */);
6513 if (new_alloc_region != NULL) {
6514 set_region_short_lived_locked(new_alloc_region);
6515 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6516 return new_alloc_region;
6517 }
6518 }
6519 return NULL;
6520 }
6522 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6523 size_t allocated_bytes) {
6524 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6525 assert(alloc_region->is_young(), "all mutator alloc regions should be young");
6527 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6528 _summary_bytes_used += allocated_bytes;
6529 _hr_printer.retire(alloc_region);
6530 // We update the eden sizes here, when the region is retired,
6531 // instead of when it's allocated, since this is the point that its
6532 // used space has been recored in _summary_bytes_used.
6533 g1mm()->update_eden_size();
6534 }
6536 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
6537 bool force) {
6538 return _g1h->new_mutator_alloc_region(word_size, force);
6539 }
6541 void G1CollectedHeap::set_par_threads() {
6542 // Don't change the number of workers. Use the value previously set
6543 // in the workgroup.
6544 assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise");
6545 uint n_workers = workers()->active_workers();
6546 assert(UseDynamicNumberOfGCThreads ||
6547 n_workers == workers()->total_workers(),
6548 "Otherwise should be using the total number of workers");
6549 if (n_workers == 0) {
6550 assert(false, "Should have been set in prior evacuation pause.");
6551 n_workers = ParallelGCThreads;
6552 workers()->set_active_workers(n_workers);
6553 }
6554 set_par_threads(n_workers);
6555 }
6557 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
6558 size_t allocated_bytes) {
6559 _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
6560 }
6562 // Methods for the GC alloc regions
6564 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6565 uint count,
6566 GCAllocPurpose ap) {
6567 assert(FreeList_lock->owned_by_self(), "pre-condition");
6569 if (count < g1_policy()->max_regions(ap)) {
6570 bool survivor = (ap == GCAllocForSurvived);
6571 HeapRegion* new_alloc_region = new_region(word_size,
6572 !survivor,
6573 true /* do_expand */);
6574 if (new_alloc_region != NULL) {
6575 // We really only need to do this for old regions given that we
6576 // should never scan survivors. But it doesn't hurt to do it
6577 // for survivors too.
6578 new_alloc_region->set_saved_mark();
6579 if (survivor) {
6580 new_alloc_region->set_survivor();
6581 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6582 } else {
6583 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6584 }
6585 bool during_im = g1_policy()->during_initial_mark_pause();
6586 new_alloc_region->note_start_of_copying(during_im);
6587 return new_alloc_region;
6588 } else {
6589 g1_policy()->note_alloc_region_limit_reached(ap);
6590 }
6591 }
6592 return NULL;
6593 }
6595 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6596 size_t allocated_bytes,
6597 GCAllocPurpose ap) {
6598 bool during_im = g1_policy()->during_initial_mark_pause();
6599 alloc_region->note_end_of_copying(during_im);
6600 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6601 if (ap == GCAllocForSurvived) {
6602 young_list()->add_survivor_region(alloc_region);
6603 } else {
6604 _old_set.add(alloc_region);
6605 }
6606 _hr_printer.retire(alloc_region);
6607 }
6609 HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size,
6610 bool force) {
6611 assert(!force, "not supported for GC alloc regions");
6612 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForSurvived);
6613 }
6615 void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region,
6616 size_t allocated_bytes) {
6617 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6618 GCAllocForSurvived);
6619 }
6621 HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size,
6622 bool force) {
6623 assert(!force, "not supported for GC alloc regions");
6624 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForTenured);
6625 }
6627 void OldGCAllocRegion::retire_region(HeapRegion* alloc_region,
6628 size_t allocated_bytes) {
6629 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6630 GCAllocForTenured);
6631 }
6632 // Heap region set verification
6634 class VerifyRegionListsClosure : public HeapRegionClosure {
6635 private:
6636 HeapRegionSet* _old_set;
6637 HeapRegionSet* _humongous_set;
6638 FreeRegionList* _free_list;
6640 public:
6641 HeapRegionSetCount _old_count;
6642 HeapRegionSetCount _humongous_count;
6643 HeapRegionSetCount _free_count;
6645 VerifyRegionListsClosure(HeapRegionSet* old_set,
6646 HeapRegionSet* humongous_set,
6647 FreeRegionList* free_list) :
6648 _old_set(old_set), _humongous_set(humongous_set), _free_list(free_list),
6649 _old_count(), _humongous_count(), _free_count(){ }
6651 bool doHeapRegion(HeapRegion* hr) {
6652 if (hr->continuesHumongous()) {
6653 return false;
6654 }
6656 if (hr->is_young()) {
6657 // TODO
6658 } else if (hr->startsHumongous()) {
6659 assert(hr->containing_set() == _humongous_set, err_msg("Heap region %u is starts humongous but not in humongous set.", hr->region_num()));
6660 _humongous_count.increment(1u, hr->capacity());
6661 } else if (hr->is_empty()) {
6662 assert(hr->containing_set() == _free_list, err_msg("Heap region %u is empty but not on the free list.", hr->region_num()));
6663 _free_count.increment(1u, hr->capacity());
6664 } else {
6665 assert(hr->containing_set() == _old_set, err_msg("Heap region %u is old but not in the old set.", hr->region_num()));
6666 _old_count.increment(1u, hr->capacity());
6667 }
6668 return false;
6669 }
6671 void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, FreeRegionList* free_list) {
6672 guarantee(old_set->length() == _old_count.length(), err_msg("Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length()));
6673 guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), err_msg("Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6674 old_set->total_capacity_bytes(), _old_count.capacity()));
6676 guarantee(humongous_set->length() == _humongous_count.length(), err_msg("Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length()));
6677 guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), err_msg("Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6678 humongous_set->total_capacity_bytes(), _humongous_count.capacity()));
6680 guarantee(free_list->length() == _free_count.length(), err_msg("Free list count mismatch. Expected %u, actual %u.", free_list->length(), _free_count.length()));
6681 guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), err_msg("Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6682 free_list->total_capacity_bytes(), _free_count.capacity()));
6683 }
6684 };
6686 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
6687 HeapWord* bottom) {
6688 HeapWord* end = bottom + HeapRegion::GrainWords;
6689 MemRegion mr(bottom, end);
6690 assert(_g1_reserved.contains(mr), "invariant");
6691 // This might return NULL if the allocation fails
6692 return new HeapRegion(hrs_index, _bot_shared, mr);
6693 }
6695 void G1CollectedHeap::verify_region_sets() {
6696 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6698 // First, check the explicit lists.
6699 _free_list.verify_list();
6700 {
6701 // Given that a concurrent operation might be adding regions to
6702 // the secondary free list we have to take the lock before
6703 // verifying it.
6704 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6705 _secondary_free_list.verify_list();
6706 }
6708 // If a concurrent region freeing operation is in progress it will
6709 // be difficult to correctly attributed any free regions we come
6710 // across to the correct free list given that they might belong to
6711 // one of several (free_list, secondary_free_list, any local lists,
6712 // etc.). So, if that's the case we will skip the rest of the
6713 // verification operation. Alternatively, waiting for the concurrent
6714 // operation to complete will have a non-trivial effect on the GC's
6715 // operation (no concurrent operation will last longer than the
6716 // interval between two calls to verification) and it might hide
6717 // any issues that we would like to catch during testing.
6718 if (free_regions_coming()) {
6719 return;
6720 }
6722 // Make sure we append the secondary_free_list on the free_list so
6723 // that all free regions we will come across can be safely
6724 // attributed to the free_list.
6725 append_secondary_free_list_if_not_empty_with_lock();
6727 // Finally, make sure that the region accounting in the lists is
6728 // consistent with what we see in the heap.
6730 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_free_list);
6731 heap_region_iterate(&cl);
6732 cl.verify_counts(&_old_set, &_humongous_set, &_free_list);
6733 }
6735 // Optimized nmethod scanning
6737 class RegisterNMethodOopClosure: public OopClosure {
6738 G1CollectedHeap* _g1h;
6739 nmethod* _nm;
6741 template <class T> void do_oop_work(T* p) {
6742 T heap_oop = oopDesc::load_heap_oop(p);
6743 if (!oopDesc::is_null(heap_oop)) {
6744 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6745 HeapRegion* hr = _g1h->heap_region_containing(obj);
6746 assert(!hr->continuesHumongous(),
6747 err_msg("trying to add code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6748 " starting at "HR_FORMAT,
6749 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6751 // HeapRegion::add_strong_code_root() avoids adding duplicate
6752 // entries but having duplicates is OK since we "mark" nmethods
6753 // as visited when we scan the strong code root lists during the GC.
6754 hr->add_strong_code_root(_nm);
6755 assert(hr->rem_set()->strong_code_roots_list_contains(_nm),
6756 err_msg("failed to add code root "PTR_FORMAT" to remembered set of region "HR_FORMAT,
6757 _nm, HR_FORMAT_PARAMS(hr)));
6758 }
6759 }
6761 public:
6762 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6763 _g1h(g1h), _nm(nm) {}
6765 void do_oop(oop* p) { do_oop_work(p); }
6766 void do_oop(narrowOop* p) { do_oop_work(p); }
6767 };
6769 class UnregisterNMethodOopClosure: public OopClosure {
6770 G1CollectedHeap* _g1h;
6771 nmethod* _nm;
6773 template <class T> void do_oop_work(T* p) {
6774 T heap_oop = oopDesc::load_heap_oop(p);
6775 if (!oopDesc::is_null(heap_oop)) {
6776 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6777 HeapRegion* hr = _g1h->heap_region_containing(obj);
6778 assert(!hr->continuesHumongous(),
6779 err_msg("trying to remove code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6780 " starting at "HR_FORMAT,
6781 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6783 hr->remove_strong_code_root(_nm);
6784 assert(!hr->rem_set()->strong_code_roots_list_contains(_nm),
6785 err_msg("failed to remove code root "PTR_FORMAT" of region "HR_FORMAT,
6786 _nm, HR_FORMAT_PARAMS(hr)));
6787 }
6788 }
6790 public:
6791 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6792 _g1h(g1h), _nm(nm) {}
6794 void do_oop(oop* p) { do_oop_work(p); }
6795 void do_oop(narrowOop* p) { do_oop_work(p); }
6796 };
6798 void G1CollectedHeap::register_nmethod(nmethod* nm) {
6799 CollectedHeap::register_nmethod(nm);
6801 guarantee(nm != NULL, "sanity");
6802 RegisterNMethodOopClosure reg_cl(this, nm);
6803 nm->oops_do(®_cl);
6804 }
6806 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
6807 CollectedHeap::unregister_nmethod(nm);
6809 guarantee(nm != NULL, "sanity");
6810 UnregisterNMethodOopClosure reg_cl(this, nm);
6811 nm->oops_do(®_cl, true);
6812 }
6814 class MigrateCodeRootsHeapRegionClosure: public HeapRegionClosure {
6815 public:
6816 bool doHeapRegion(HeapRegion *hr) {
6817 assert(!hr->isHumongous(),
6818 err_msg("humongous region "HR_FORMAT" should not have been added to collection set",
6819 HR_FORMAT_PARAMS(hr)));
6820 hr->migrate_strong_code_roots();
6821 return false;
6822 }
6823 };
6825 void G1CollectedHeap::migrate_strong_code_roots() {
6826 MigrateCodeRootsHeapRegionClosure cl;
6827 double migrate_start = os::elapsedTime();
6828 collection_set_iterate(&cl);
6829 double migration_time_ms = (os::elapsedTime() - migrate_start) * 1000.0;
6830 g1_policy()->phase_times()->record_strong_code_root_migration_time(migration_time_ms);
6831 }
6833 void G1CollectedHeap::purge_code_root_memory() {
6834 double purge_start = os::elapsedTime();
6835 G1CodeRootSet::purge_chunks(G1CodeRootsChunkCacheKeepPercent);
6836 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
6837 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
6838 }
6840 // Mark all the code roots that point into regions *not* in the
6841 // collection set.
6842 //
6843 // Note we do not want to use a "marking" CodeBlobToOopClosure while
6844 // walking the the code roots lists of regions not in the collection
6845 // set. Suppose we have an nmethod (M) that points to objects in two
6846 // separate regions - one in the collection set (R1) and one not (R2).
6847 // Using a "marking" CodeBlobToOopClosure here would result in "marking"
6848 // nmethod M when walking the code roots for R1. When we come to scan
6849 // the code roots for R2, we would see that M is already marked and it
6850 // would be skipped and the objects in R2 that are referenced from M
6851 // would not be evacuated.
6853 class MarkStrongCodeRootCodeBlobClosure: public CodeBlobClosure {
6855 class MarkStrongCodeRootOopClosure: public OopClosure {
6856 ConcurrentMark* _cm;
6857 HeapRegion* _hr;
6858 uint _worker_id;
6860 template <class T> void do_oop_work(T* p) {
6861 T heap_oop = oopDesc::load_heap_oop(p);
6862 if (!oopDesc::is_null(heap_oop)) {
6863 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6864 // Only mark objects in the region (which is assumed
6865 // to be not in the collection set).
6866 if (_hr->is_in(obj)) {
6867 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
6868 }
6869 }
6870 }
6872 public:
6873 MarkStrongCodeRootOopClosure(ConcurrentMark* cm, HeapRegion* hr, uint worker_id) :
6874 _cm(cm), _hr(hr), _worker_id(worker_id) {
6875 assert(!_hr->in_collection_set(), "sanity");
6876 }
6878 void do_oop(narrowOop* p) { do_oop_work(p); }
6879 void do_oop(oop* p) { do_oop_work(p); }
6880 };
6882 MarkStrongCodeRootOopClosure _oop_cl;
6884 public:
6885 MarkStrongCodeRootCodeBlobClosure(ConcurrentMark* cm, HeapRegion* hr, uint worker_id):
6886 _oop_cl(cm, hr, worker_id) {}
6888 void do_code_blob(CodeBlob* cb) {
6889 nmethod* nm = (cb == NULL) ? NULL : cb->as_nmethod_or_null();
6890 if (nm != NULL) {
6891 nm->oops_do(&_oop_cl);
6892 }
6893 }
6894 };
6896 class MarkStrongCodeRootsHRClosure: public HeapRegionClosure {
6897 G1CollectedHeap* _g1h;
6898 uint _worker_id;
6900 public:
6901 MarkStrongCodeRootsHRClosure(G1CollectedHeap* g1h, uint worker_id) :
6902 _g1h(g1h), _worker_id(worker_id) {}
6904 bool doHeapRegion(HeapRegion *hr) {
6905 HeapRegionRemSet* hrrs = hr->rem_set();
6906 if (hr->continuesHumongous()) {
6907 // Code roots should never be attached to a continuation of a humongous region
6908 assert(hrrs->strong_code_roots_list_length() == 0,
6909 err_msg("code roots should never be attached to continuations of humongous region "HR_FORMAT
6910 " starting at "HR_FORMAT", but has "SIZE_FORMAT,
6911 HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()),
6912 hrrs->strong_code_roots_list_length()));
6913 return false;
6914 }
6916 if (hr->in_collection_set()) {
6917 // Don't mark code roots into regions in the collection set here.
6918 // They will be marked when we scan them.
6919 return false;
6920 }
6922 MarkStrongCodeRootCodeBlobClosure cb_cl(_g1h->concurrent_mark(), hr, _worker_id);
6923 hr->strong_code_roots_do(&cb_cl);
6924 return false;
6925 }
6926 };
6928 void G1CollectedHeap::mark_strong_code_roots(uint worker_id) {
6929 MarkStrongCodeRootsHRClosure cl(this, worker_id);
6930 if (G1CollectedHeap::use_parallel_gc_threads()) {
6931 heap_region_par_iterate_chunked(&cl,
6932 worker_id,
6933 workers()->active_workers(),
6934 HeapRegion::ParMarkRootClaimValue);
6935 } else {
6936 heap_region_iterate(&cl);
6937 }
6938 }
6940 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
6941 G1CollectedHeap* _g1h;
6943 public:
6944 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
6945 _g1h(g1h) {}
6947 void do_code_blob(CodeBlob* cb) {
6948 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
6949 if (nm == NULL) {
6950 return;
6951 }
6953 if (ScavengeRootsInCode) {
6954 _g1h->register_nmethod(nm);
6955 }
6956 }
6957 };
6959 void G1CollectedHeap::rebuild_strong_code_roots() {
6960 RebuildStrongCodeRootClosure blob_cl(this);
6961 CodeCache::blobs_do(&blob_cl);
6962 }