Thu, 26 Sep 2013 10:25:02 -0400
7195622: CheckUnhandledOops has limited usefulness now
Summary: Enable CHECK_UNHANDLED_OOPS in fastdebug builds across all supported platforms.
Reviewed-by: coleenp, hseigel, dholmes, stefank, twisti, ihse, rdurbin
Contributed-by: lois.foltan@oracle.com
1 /*
2 * Copyright (c) 2001, 2013, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
25 #include "precompiled.hpp"
26 #include "code/codeCache.hpp"
27 #include "code/icBuffer.hpp"
28 #include "gc_implementation/g1/bufferingOopClosure.hpp"
29 #include "gc_implementation/g1/concurrentG1Refine.hpp"
30 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
31 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
32 #include "gc_implementation/g1/g1AllocRegion.inline.hpp"
33 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
34 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
35 #include "gc_implementation/g1/g1ErgoVerbose.hpp"
36 #include "gc_implementation/g1/g1EvacFailure.hpp"
37 #include "gc_implementation/g1/g1GCPhaseTimes.hpp"
38 #include "gc_implementation/g1/g1Log.hpp"
39 #include "gc_implementation/g1/g1MarkSweep.hpp"
40 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
41 #include "gc_implementation/g1/g1RemSet.inline.hpp"
42 #include "gc_implementation/g1/g1YCTypes.hpp"
43 #include "gc_implementation/g1/heapRegion.inline.hpp"
44 #include "gc_implementation/g1/heapRegionRemSet.hpp"
45 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
46 #include "gc_implementation/g1/vm_operations_g1.hpp"
47 #include "gc_implementation/shared/gcHeapSummary.hpp"
48 #include "gc_implementation/shared/gcTimer.hpp"
49 #include "gc_implementation/shared/gcTrace.hpp"
50 #include "gc_implementation/shared/gcTraceTime.hpp"
51 #include "gc_implementation/shared/isGCActiveMark.hpp"
52 #include "memory/gcLocker.inline.hpp"
53 #include "memory/genOopClosures.inline.hpp"
54 #include "memory/generationSpec.hpp"
55 #include "memory/referenceProcessor.hpp"
56 #include "oops/oop.inline.hpp"
57 #include "oops/oop.pcgc.inline.hpp"
58 #include "runtime/vmThread.hpp"
60 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
62 // turn it on so that the contents of the young list (scan-only /
63 // to-be-collected) are printed at "strategic" points before / during
64 // / after the collection --- this is useful for debugging
65 #define YOUNG_LIST_VERBOSE 0
66 // CURRENT STATUS
67 // This file is under construction. Search for "FIXME".
69 // INVARIANTS/NOTES
70 //
71 // All allocation activity covered by the G1CollectedHeap interface is
72 // serialized by acquiring the HeapLock. This happens in mem_allocate
73 // and allocate_new_tlab, which are the "entry" points to the
74 // allocation code from the rest of the JVM. (Note that this does not
75 // apply to TLAB allocation, which is not part of this interface: it
76 // is done by clients of this interface.)
78 // Notes on implementation of parallelism in different tasks.
79 //
80 // G1ParVerifyTask uses heap_region_par_iterate_chunked() for parallelism.
81 // The number of GC workers is passed to heap_region_par_iterate_chunked().
82 // It does use run_task() which sets _n_workers in the task.
83 // G1ParTask executes g1_process_strong_roots() ->
84 // SharedHeap::process_strong_roots() which calls eventually to
85 // CardTableModRefBS::par_non_clean_card_iterate_work() which uses
86 // SequentialSubTasksDone. SharedHeap::process_strong_roots() also
87 // directly uses SubTasksDone (_process_strong_tasks field in SharedHeap).
88 //
90 // Local to this file.
92 class RefineCardTableEntryClosure: public CardTableEntryClosure {
93 SuspendibleThreadSet* _sts;
94 G1RemSet* _g1rs;
95 ConcurrentG1Refine* _cg1r;
96 bool _concurrent;
97 public:
98 RefineCardTableEntryClosure(SuspendibleThreadSet* sts,
99 G1RemSet* g1rs,
100 ConcurrentG1Refine* cg1r) :
101 _sts(sts), _g1rs(g1rs), _cg1r(cg1r), _concurrent(true)
102 {}
103 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
104 bool oops_into_cset = _g1rs->refine_card(card_ptr, worker_i, false);
105 // This path is executed by the concurrent refine or mutator threads,
106 // concurrently, and so we do not care if card_ptr contains references
107 // that point into the collection set.
108 assert(!oops_into_cset, "should be");
110 if (_concurrent && _sts->should_yield()) {
111 // Caller will actually yield.
112 return false;
113 }
114 // Otherwise, we finished successfully; return true.
115 return true;
116 }
117 void set_concurrent(bool b) { _concurrent = b; }
118 };
121 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure {
122 int _calls;
123 G1CollectedHeap* _g1h;
124 CardTableModRefBS* _ctbs;
125 int _histo[256];
126 public:
127 ClearLoggedCardTableEntryClosure() :
128 _calls(0)
129 {
130 _g1h = G1CollectedHeap::heap();
131 _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
132 for (int i = 0; i < 256; i++) _histo[i] = 0;
133 }
134 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
135 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
136 _calls++;
137 unsigned char* ujb = (unsigned char*)card_ptr;
138 int ind = (int)(*ujb);
139 _histo[ind]++;
140 *card_ptr = -1;
141 }
142 return true;
143 }
144 int calls() { return _calls; }
145 void print_histo() {
146 gclog_or_tty->print_cr("Card table value histogram:");
147 for (int i = 0; i < 256; i++) {
148 if (_histo[i] != 0) {
149 gclog_or_tty->print_cr(" %d: %d", i, _histo[i]);
150 }
151 }
152 }
153 };
155 class RedirtyLoggedCardTableEntryClosure: public CardTableEntryClosure {
156 int _calls;
157 G1CollectedHeap* _g1h;
158 CardTableModRefBS* _ctbs;
159 public:
160 RedirtyLoggedCardTableEntryClosure() :
161 _calls(0)
162 {
163 _g1h = G1CollectedHeap::heap();
164 _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
165 }
166 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
167 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
168 _calls++;
169 *card_ptr = 0;
170 }
171 return true;
172 }
173 int calls() { return _calls; }
174 };
176 class RedirtyLoggedCardTableEntryFastClosure : public CardTableEntryClosure {
177 public:
178 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
179 *card_ptr = CardTableModRefBS::dirty_card_val();
180 return true;
181 }
182 };
184 YoungList::YoungList(G1CollectedHeap* g1h) :
185 _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0),
186 _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) {
187 guarantee(check_list_empty(false), "just making sure...");
188 }
190 void YoungList::push_region(HeapRegion *hr) {
191 assert(!hr->is_young(), "should not already be young");
192 assert(hr->get_next_young_region() == NULL, "cause it should!");
194 hr->set_next_young_region(_head);
195 _head = hr;
197 _g1h->g1_policy()->set_region_eden(hr, (int) _length);
198 ++_length;
199 }
201 void YoungList::add_survivor_region(HeapRegion* hr) {
202 assert(hr->is_survivor(), "should be flagged as survivor region");
203 assert(hr->get_next_young_region() == NULL, "cause it should!");
205 hr->set_next_young_region(_survivor_head);
206 if (_survivor_head == NULL) {
207 _survivor_tail = hr;
208 }
209 _survivor_head = hr;
210 ++_survivor_length;
211 }
213 void YoungList::empty_list(HeapRegion* list) {
214 while (list != NULL) {
215 HeapRegion* next = list->get_next_young_region();
216 list->set_next_young_region(NULL);
217 list->uninstall_surv_rate_group();
218 list->set_not_young();
219 list = next;
220 }
221 }
223 void YoungList::empty_list() {
224 assert(check_list_well_formed(), "young list should be well formed");
226 empty_list(_head);
227 _head = NULL;
228 _length = 0;
230 empty_list(_survivor_head);
231 _survivor_head = NULL;
232 _survivor_tail = NULL;
233 _survivor_length = 0;
235 _last_sampled_rs_lengths = 0;
237 assert(check_list_empty(false), "just making sure...");
238 }
240 bool YoungList::check_list_well_formed() {
241 bool ret = true;
243 uint length = 0;
244 HeapRegion* curr = _head;
245 HeapRegion* last = NULL;
246 while (curr != NULL) {
247 if (!curr->is_young()) {
248 gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
249 "incorrectly tagged (y: %d, surv: %d)",
250 curr->bottom(), curr->end(),
251 curr->is_young(), curr->is_survivor());
252 ret = false;
253 }
254 ++length;
255 last = curr;
256 curr = curr->get_next_young_region();
257 }
258 ret = ret && (length == _length);
260 if (!ret) {
261 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
262 gclog_or_tty->print_cr("### list has %u entries, _length is %u",
263 length, _length);
264 }
266 return ret;
267 }
269 bool YoungList::check_list_empty(bool check_sample) {
270 bool ret = true;
272 if (_length != 0) {
273 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u",
274 _length);
275 ret = false;
276 }
277 if (check_sample && _last_sampled_rs_lengths != 0) {
278 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
279 ret = false;
280 }
281 if (_head != NULL) {
282 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
283 ret = false;
284 }
285 if (!ret) {
286 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
287 }
289 return ret;
290 }
292 void
293 YoungList::rs_length_sampling_init() {
294 _sampled_rs_lengths = 0;
295 _curr = _head;
296 }
298 bool
299 YoungList::rs_length_sampling_more() {
300 return _curr != NULL;
301 }
303 void
304 YoungList::rs_length_sampling_next() {
305 assert( _curr != NULL, "invariant" );
306 size_t rs_length = _curr->rem_set()->occupied();
308 _sampled_rs_lengths += rs_length;
310 // The current region may not yet have been added to the
311 // incremental collection set (it gets added when it is
312 // retired as the current allocation region).
313 if (_curr->in_collection_set()) {
314 // Update the collection set policy information for this region
315 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
316 }
318 _curr = _curr->get_next_young_region();
319 if (_curr == NULL) {
320 _last_sampled_rs_lengths = _sampled_rs_lengths;
321 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
322 }
323 }
325 void
326 YoungList::reset_auxilary_lists() {
327 guarantee( is_empty(), "young list should be empty" );
328 assert(check_list_well_formed(), "young list should be well formed");
330 // Add survivor regions to SurvRateGroup.
331 _g1h->g1_policy()->note_start_adding_survivor_regions();
332 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
334 int young_index_in_cset = 0;
335 for (HeapRegion* curr = _survivor_head;
336 curr != NULL;
337 curr = curr->get_next_young_region()) {
338 _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
340 // The region is a non-empty survivor so let's add it to
341 // the incremental collection set for the next evacuation
342 // pause.
343 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
344 young_index_in_cset += 1;
345 }
346 assert((uint) young_index_in_cset == _survivor_length, "post-condition");
347 _g1h->g1_policy()->note_stop_adding_survivor_regions();
349 _head = _survivor_head;
350 _length = _survivor_length;
351 if (_survivor_head != NULL) {
352 assert(_survivor_tail != NULL, "cause it shouldn't be");
353 assert(_survivor_length > 0, "invariant");
354 _survivor_tail->set_next_young_region(NULL);
355 }
357 // Don't clear the survivor list handles until the start of
358 // the next evacuation pause - we need it in order to re-tag
359 // the survivor regions from this evacuation pause as 'young'
360 // at the start of the next.
362 _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
364 assert(check_list_well_formed(), "young list should be well formed");
365 }
367 void YoungList::print() {
368 HeapRegion* lists[] = {_head, _survivor_head};
369 const char* names[] = {"YOUNG", "SURVIVOR"};
371 for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) {
372 gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
373 HeapRegion *curr = lists[list];
374 if (curr == NULL)
375 gclog_or_tty->print_cr(" empty");
376 while (curr != NULL) {
377 gclog_or_tty->print_cr(" "HR_FORMAT", P: "PTR_FORMAT "N: "PTR_FORMAT", age: %4d",
378 HR_FORMAT_PARAMS(curr),
379 curr->prev_top_at_mark_start(),
380 curr->next_top_at_mark_start(),
381 curr->age_in_surv_rate_group_cond());
382 curr = curr->get_next_young_region();
383 }
384 }
386 gclog_or_tty->print_cr("");
387 }
389 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
390 {
391 // Claim the right to put the region on the dirty cards region list
392 // by installing a self pointer.
393 HeapRegion* next = hr->get_next_dirty_cards_region();
394 if (next == NULL) {
395 HeapRegion* res = (HeapRegion*)
396 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
397 NULL);
398 if (res == NULL) {
399 HeapRegion* head;
400 do {
401 // Put the region to the dirty cards region list.
402 head = _dirty_cards_region_list;
403 next = (HeapRegion*)
404 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
405 if (next == head) {
406 assert(hr->get_next_dirty_cards_region() == hr,
407 "hr->get_next_dirty_cards_region() != hr");
408 if (next == NULL) {
409 // The last region in the list points to itself.
410 hr->set_next_dirty_cards_region(hr);
411 } else {
412 hr->set_next_dirty_cards_region(next);
413 }
414 }
415 } while (next != head);
416 }
417 }
418 }
420 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
421 {
422 HeapRegion* head;
423 HeapRegion* hr;
424 do {
425 head = _dirty_cards_region_list;
426 if (head == NULL) {
427 return NULL;
428 }
429 HeapRegion* new_head = head->get_next_dirty_cards_region();
430 if (head == new_head) {
431 // The last region.
432 new_head = NULL;
433 }
434 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
435 head);
436 } while (hr != head);
437 assert(hr != NULL, "invariant");
438 hr->set_next_dirty_cards_region(NULL);
439 return hr;
440 }
442 void G1CollectedHeap::stop_conc_gc_threads() {
443 _cg1r->stop();
444 _cmThread->stop();
445 }
447 #ifdef ASSERT
448 // A region is added to the collection set as it is retired
449 // so an address p can point to a region which will be in the
450 // collection set but has not yet been retired. This method
451 // therefore is only accurate during a GC pause after all
452 // regions have been retired. It is used for debugging
453 // to check if an nmethod has references to objects that can
454 // be move during a partial collection. Though it can be
455 // inaccurate, it is sufficient for G1 because the conservative
456 // implementation of is_scavengable() for G1 will indicate that
457 // all nmethods must be scanned during a partial collection.
458 bool G1CollectedHeap::is_in_partial_collection(const void* p) {
459 HeapRegion* hr = heap_region_containing(p);
460 return hr != NULL && hr->in_collection_set();
461 }
462 #endif
464 // Returns true if the reference points to an object that
465 // can move in an incremental collection.
466 bool G1CollectedHeap::is_scavengable(const void* p) {
467 G1CollectedHeap* g1h = G1CollectedHeap::heap();
468 G1CollectorPolicy* g1p = g1h->g1_policy();
469 HeapRegion* hr = heap_region_containing(p);
470 if (hr == NULL) {
471 // null
472 assert(p == NULL, err_msg("Not NULL " PTR_FORMAT ,p));
473 return false;
474 } else {
475 return !hr->isHumongous();
476 }
477 }
479 void G1CollectedHeap::check_ct_logs_at_safepoint() {
480 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
481 CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
483 // Count the dirty cards at the start.
484 CountNonCleanMemRegionClosure count1(this);
485 ct_bs->mod_card_iterate(&count1);
486 int orig_count = count1.n();
488 // First clear the logged cards.
489 ClearLoggedCardTableEntryClosure clear;
490 dcqs.set_closure(&clear);
491 dcqs.apply_closure_to_all_completed_buffers();
492 dcqs.iterate_closure_all_threads(false);
493 clear.print_histo();
495 // Now ensure that there's no dirty cards.
496 CountNonCleanMemRegionClosure count2(this);
497 ct_bs->mod_card_iterate(&count2);
498 if (count2.n() != 0) {
499 gclog_or_tty->print_cr("Card table has %d entries; %d originally",
500 count2.n(), orig_count);
501 }
502 guarantee(count2.n() == 0, "Card table should be clean.");
504 RedirtyLoggedCardTableEntryClosure redirty;
505 JavaThread::dirty_card_queue_set().set_closure(&redirty);
506 dcqs.apply_closure_to_all_completed_buffers();
507 dcqs.iterate_closure_all_threads(false);
508 gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
509 clear.calls(), orig_count);
510 guarantee(redirty.calls() == clear.calls(),
511 "Or else mechanism is broken.");
513 CountNonCleanMemRegionClosure count3(this);
514 ct_bs->mod_card_iterate(&count3);
515 if (count3.n() != orig_count) {
516 gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
517 orig_count, count3.n());
518 guarantee(count3.n() >= orig_count, "Should have restored them all.");
519 }
521 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
522 }
524 // Private class members.
526 G1CollectedHeap* G1CollectedHeap::_g1h;
528 // Private methods.
530 HeapRegion*
531 G1CollectedHeap::new_region_try_secondary_free_list() {
532 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
533 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
534 if (!_secondary_free_list.is_empty()) {
535 if (G1ConcRegionFreeingVerbose) {
536 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
537 "secondary_free_list has %u entries",
538 _secondary_free_list.length());
539 }
540 // It looks as if there are free regions available on the
541 // secondary_free_list. Let's move them to the free_list and try
542 // again to allocate from it.
543 append_secondary_free_list();
545 assert(!_free_list.is_empty(), "if the secondary_free_list was not "
546 "empty we should have moved at least one entry to the free_list");
547 HeapRegion* res = _free_list.remove_head();
548 if (G1ConcRegionFreeingVerbose) {
549 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
550 "allocated "HR_FORMAT" from secondary_free_list",
551 HR_FORMAT_PARAMS(res));
552 }
553 return res;
554 }
556 // Wait here until we get notified either when (a) there are no
557 // more free regions coming or (b) some regions have been moved on
558 // the secondary_free_list.
559 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
560 }
562 if (G1ConcRegionFreeingVerbose) {
563 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
564 "could not allocate from secondary_free_list");
565 }
566 return NULL;
567 }
569 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool do_expand) {
570 assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords,
571 "the only time we use this to allocate a humongous region is "
572 "when we are allocating a single humongous region");
574 HeapRegion* res;
575 if (G1StressConcRegionFreeing) {
576 if (!_secondary_free_list.is_empty()) {
577 if (G1ConcRegionFreeingVerbose) {
578 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
579 "forced to look at the secondary_free_list");
580 }
581 res = new_region_try_secondary_free_list();
582 if (res != NULL) {
583 return res;
584 }
585 }
586 }
587 res = _free_list.remove_head_or_null();
588 if (res == NULL) {
589 if (G1ConcRegionFreeingVerbose) {
590 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
591 "res == NULL, trying the secondary_free_list");
592 }
593 res = new_region_try_secondary_free_list();
594 }
595 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
596 // Currently, only attempts to allocate GC alloc regions set
597 // do_expand to true. So, we should only reach here during a
598 // safepoint. If this assumption changes we might have to
599 // reconsider the use of _expand_heap_after_alloc_failure.
600 assert(SafepointSynchronize::is_at_safepoint(), "invariant");
602 ergo_verbose1(ErgoHeapSizing,
603 "attempt heap expansion",
604 ergo_format_reason("region allocation request failed")
605 ergo_format_byte("allocation request"),
606 word_size * HeapWordSize);
607 if (expand(word_size * HeapWordSize)) {
608 // Given that expand() succeeded in expanding the heap, and we
609 // always expand the heap by an amount aligned to the heap
610 // region size, the free list should in theory not be empty. So
611 // it would probably be OK to use remove_head(). But the extra
612 // check for NULL is unlikely to be a performance issue here (we
613 // just expanded the heap!) so let's just be conservative and
614 // use remove_head_or_null().
615 res = _free_list.remove_head_or_null();
616 } else {
617 _expand_heap_after_alloc_failure = false;
618 }
619 }
620 return res;
621 }
623 uint G1CollectedHeap::humongous_obj_allocate_find_first(uint num_regions,
624 size_t word_size) {
625 assert(isHumongous(word_size), "word_size should be humongous");
626 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
628 uint first = G1_NULL_HRS_INDEX;
629 if (num_regions == 1) {
630 // Only one region to allocate, no need to go through the slower
631 // path. The caller will attempt the expansion if this fails, so
632 // let's not try to expand here too.
633 HeapRegion* hr = new_region(word_size, false /* do_expand */);
634 if (hr != NULL) {
635 first = hr->hrs_index();
636 } else {
637 first = G1_NULL_HRS_INDEX;
638 }
639 } else {
640 // We can't allocate humongous regions while cleanupComplete() is
641 // running, since some of the regions we find to be empty might not
642 // yet be added to the free list and it is not straightforward to
643 // know which list they are on so that we can remove them. Note
644 // that we only need to do this if we need to allocate more than
645 // one region to satisfy the current humongous allocation
646 // request. If we are only allocating one region we use the common
647 // region allocation code (see above).
648 wait_while_free_regions_coming();
649 append_secondary_free_list_if_not_empty_with_lock();
651 if (free_regions() >= num_regions) {
652 first = _hrs.find_contiguous(num_regions);
653 if (first != G1_NULL_HRS_INDEX) {
654 for (uint i = first; i < first + num_regions; ++i) {
655 HeapRegion* hr = region_at(i);
656 assert(hr->is_empty(), "sanity");
657 assert(is_on_master_free_list(hr), "sanity");
658 hr->set_pending_removal(true);
659 }
660 _free_list.remove_all_pending(num_regions);
661 }
662 }
663 }
664 return first;
665 }
667 HeapWord*
668 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
669 uint num_regions,
670 size_t word_size) {
671 assert(first != G1_NULL_HRS_INDEX, "pre-condition");
672 assert(isHumongous(word_size), "word_size should be humongous");
673 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
675 // Index of last region in the series + 1.
676 uint last = first + num_regions;
678 // We need to initialize the region(s) we just discovered. This is
679 // a bit tricky given that it can happen concurrently with
680 // refinement threads refining cards on these regions and
681 // potentially wanting to refine the BOT as they are scanning
682 // those cards (this can happen shortly after a cleanup; see CR
683 // 6991377). So we have to set up the region(s) carefully and in
684 // a specific order.
686 // The word size sum of all the regions we will allocate.
687 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
688 assert(word_size <= word_size_sum, "sanity");
690 // This will be the "starts humongous" region.
691 HeapRegion* first_hr = region_at(first);
692 // The header of the new object will be placed at the bottom of
693 // the first region.
694 HeapWord* new_obj = first_hr->bottom();
695 // This will be the new end of the first region in the series that
696 // should also match the end of the last region in the series.
697 HeapWord* new_end = new_obj + word_size_sum;
698 // This will be the new top of the first region that will reflect
699 // this allocation.
700 HeapWord* new_top = new_obj + word_size;
702 // First, we need to zero the header of the space that we will be
703 // allocating. When we update top further down, some refinement
704 // threads might try to scan the region. By zeroing the header we
705 // ensure that any thread that will try to scan the region will
706 // come across the zero klass word and bail out.
707 //
708 // NOTE: It would not have been correct to have used
709 // CollectedHeap::fill_with_object() and make the space look like
710 // an int array. The thread that is doing the allocation will
711 // later update the object header to a potentially different array
712 // type and, for a very short period of time, the klass and length
713 // fields will be inconsistent. This could cause a refinement
714 // thread to calculate the object size incorrectly.
715 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
717 // We will set up the first region as "starts humongous". This
718 // will also update the BOT covering all the regions to reflect
719 // that there is a single object that starts at the bottom of the
720 // first region.
721 first_hr->set_startsHumongous(new_top, new_end);
723 // Then, if there are any, we will set up the "continues
724 // humongous" regions.
725 HeapRegion* hr = NULL;
726 for (uint i = first + 1; i < last; ++i) {
727 hr = region_at(i);
728 hr->set_continuesHumongous(first_hr);
729 }
730 // If we have "continues humongous" regions (hr != NULL), then the
731 // end of the last one should match new_end.
732 assert(hr == NULL || hr->end() == new_end, "sanity");
734 // Up to this point no concurrent thread would have been able to
735 // do any scanning on any region in this series. All the top
736 // fields still point to bottom, so the intersection between
737 // [bottom,top] and [card_start,card_end] will be empty. Before we
738 // update the top fields, we'll do a storestore to make sure that
739 // no thread sees the update to top before the zeroing of the
740 // object header and the BOT initialization.
741 OrderAccess::storestore();
743 // Now that the BOT and the object header have been initialized,
744 // we can update top of the "starts humongous" region.
745 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
746 "new_top should be in this region");
747 first_hr->set_top(new_top);
748 if (_hr_printer.is_active()) {
749 HeapWord* bottom = first_hr->bottom();
750 HeapWord* end = first_hr->orig_end();
751 if ((first + 1) == last) {
752 // the series has a single humongous region
753 _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
754 } else {
755 // the series has more than one humongous regions
756 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
757 }
758 }
760 // Now, we will update the top fields of the "continues humongous"
761 // regions. The reason we need to do this is that, otherwise,
762 // these regions would look empty and this will confuse parts of
763 // G1. For example, the code that looks for a consecutive number
764 // of empty regions will consider them empty and try to
765 // re-allocate them. We can extend is_empty() to also include
766 // !continuesHumongous(), but it is easier to just update the top
767 // fields here. The way we set top for all regions (i.e., top ==
768 // end for all regions but the last one, top == new_top for the
769 // last one) is actually used when we will free up the humongous
770 // region in free_humongous_region().
771 hr = NULL;
772 for (uint i = first + 1; i < last; ++i) {
773 hr = region_at(i);
774 if ((i + 1) == last) {
775 // last continues humongous region
776 assert(hr->bottom() < new_top && new_top <= hr->end(),
777 "new_top should fall on this region");
778 hr->set_top(new_top);
779 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
780 } else {
781 // not last one
782 assert(new_top > hr->end(), "new_top should be above this region");
783 hr->set_top(hr->end());
784 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
785 }
786 }
787 // If we have continues humongous regions (hr != NULL), then the
788 // end of the last one should match new_end and its top should
789 // match new_top.
790 assert(hr == NULL ||
791 (hr->end() == new_end && hr->top() == new_top), "sanity");
793 assert(first_hr->used() == word_size * HeapWordSize, "invariant");
794 _summary_bytes_used += first_hr->used();
795 _humongous_set.add(first_hr);
797 return new_obj;
798 }
800 // If could fit into free regions w/o expansion, try.
801 // Otherwise, if can expand, do so.
802 // Otherwise, if using ex regions might help, try with ex given back.
803 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
804 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
806 verify_region_sets_optional();
808 size_t word_size_rounded = round_to(word_size, HeapRegion::GrainWords);
809 uint num_regions = (uint) (word_size_rounded / HeapRegion::GrainWords);
810 uint x_num = expansion_regions();
811 uint fs = _hrs.free_suffix();
812 uint first = humongous_obj_allocate_find_first(num_regions, word_size);
813 if (first == G1_NULL_HRS_INDEX) {
814 // The only thing we can do now is attempt expansion.
815 if (fs + x_num >= num_regions) {
816 // If the number of regions we're trying to allocate for this
817 // object is at most the number of regions in the free suffix,
818 // then the call to humongous_obj_allocate_find_first() above
819 // should have succeeded and we wouldn't be here.
820 //
821 // We should only be trying to expand when the free suffix is
822 // not sufficient for the object _and_ we have some expansion
823 // room available.
824 assert(num_regions > fs, "earlier allocation should have succeeded");
826 ergo_verbose1(ErgoHeapSizing,
827 "attempt heap expansion",
828 ergo_format_reason("humongous allocation request failed")
829 ergo_format_byte("allocation request"),
830 word_size * HeapWordSize);
831 if (expand((num_regions - fs) * HeapRegion::GrainBytes)) {
832 // Even though the heap was expanded, it might not have
833 // reached the desired size. So, we cannot assume that the
834 // allocation will succeed.
835 first = humongous_obj_allocate_find_first(num_regions, word_size);
836 }
837 }
838 }
840 HeapWord* result = NULL;
841 if (first != G1_NULL_HRS_INDEX) {
842 result =
843 humongous_obj_allocate_initialize_regions(first, num_regions, word_size);
844 assert(result != NULL, "it should always return a valid result");
846 // A successful humongous object allocation changes the used space
847 // information of the old generation so we need to recalculate the
848 // sizes and update the jstat counters here.
849 g1mm()->update_sizes();
850 }
852 verify_region_sets_optional();
854 return result;
855 }
857 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
858 assert_heap_not_locked_and_not_at_safepoint();
859 assert(!isHumongous(word_size), "we do not allow humongous TLABs");
861 unsigned int dummy_gc_count_before;
862 int dummy_gclocker_retry_count = 0;
863 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
864 }
866 HeapWord*
867 G1CollectedHeap::mem_allocate(size_t word_size,
868 bool* gc_overhead_limit_was_exceeded) {
869 assert_heap_not_locked_and_not_at_safepoint();
871 // Loop until the allocation is satisfied, or unsatisfied after GC.
872 for (int try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
873 unsigned int gc_count_before;
875 HeapWord* result = NULL;
876 if (!isHumongous(word_size)) {
877 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
878 } else {
879 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
880 }
881 if (result != NULL) {
882 return result;
883 }
885 // Create the garbage collection operation...
886 VM_G1CollectForAllocation op(gc_count_before, word_size);
887 // ...and get the VM thread to execute it.
888 VMThread::execute(&op);
890 if (op.prologue_succeeded() && op.pause_succeeded()) {
891 // If the operation was successful we'll return the result even
892 // if it is NULL. If the allocation attempt failed immediately
893 // after a Full GC, it's unlikely we'll be able to allocate now.
894 HeapWord* result = op.result();
895 if (result != NULL && !isHumongous(word_size)) {
896 // Allocations that take place on VM operations do not do any
897 // card dirtying and we have to do it here. We only have to do
898 // this for non-humongous allocations, though.
899 dirty_young_block(result, word_size);
900 }
901 return result;
902 } else {
903 if (gclocker_retry_count > GCLockerRetryAllocationCount) {
904 return NULL;
905 }
906 assert(op.result() == NULL,
907 "the result should be NULL if the VM op did not succeed");
908 }
910 // Give a warning if we seem to be looping forever.
911 if ((QueuedAllocationWarningCount > 0) &&
912 (try_count % QueuedAllocationWarningCount == 0)) {
913 warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
914 }
915 }
917 ShouldNotReachHere();
918 return NULL;
919 }
921 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
922 unsigned int *gc_count_before_ret,
923 int* gclocker_retry_count_ret) {
924 // Make sure you read the note in attempt_allocation_humongous().
926 assert_heap_not_locked_and_not_at_safepoint();
927 assert(!isHumongous(word_size), "attempt_allocation_slow() should not "
928 "be called for humongous allocation requests");
930 // We should only get here after the first-level allocation attempt
931 // (attempt_allocation()) failed to allocate.
933 // We will loop until a) we manage to successfully perform the
934 // allocation or b) we successfully schedule a collection which
935 // fails to perform the allocation. b) is the only case when we'll
936 // return NULL.
937 HeapWord* result = NULL;
938 for (int try_count = 1; /* we'll return */; try_count += 1) {
939 bool should_try_gc;
940 unsigned int gc_count_before;
942 {
943 MutexLockerEx x(Heap_lock);
945 result = _mutator_alloc_region.attempt_allocation_locked(word_size,
946 false /* bot_updates */);
947 if (result != NULL) {
948 return result;
949 }
951 // If we reach here, attempt_allocation_locked() above failed to
952 // allocate a new region. So the mutator alloc region should be NULL.
953 assert(_mutator_alloc_region.get() == NULL, "only way to get here");
955 if (GC_locker::is_active_and_needs_gc()) {
956 if (g1_policy()->can_expand_young_list()) {
957 // No need for an ergo verbose message here,
958 // can_expand_young_list() does this when it returns true.
959 result = _mutator_alloc_region.attempt_allocation_force(word_size,
960 false /* bot_updates */);
961 if (result != NULL) {
962 return result;
963 }
964 }
965 should_try_gc = false;
966 } else {
967 // The GCLocker may not be active but the GCLocker initiated
968 // GC may not yet have been performed (GCLocker::needs_gc()
969 // returns true). In this case we do not try this GC and
970 // wait until the GCLocker initiated GC is performed, and
971 // then retry the allocation.
972 if (GC_locker::needs_gc()) {
973 should_try_gc = false;
974 } else {
975 // Read the GC count while still holding the Heap_lock.
976 gc_count_before = total_collections();
977 should_try_gc = true;
978 }
979 }
980 }
982 if (should_try_gc) {
983 bool succeeded;
984 result = do_collection_pause(word_size, gc_count_before, &succeeded,
985 GCCause::_g1_inc_collection_pause);
986 if (result != NULL) {
987 assert(succeeded, "only way to get back a non-NULL result");
988 return result;
989 }
991 if (succeeded) {
992 // If we get here we successfully scheduled a collection which
993 // failed to allocate. No point in trying to allocate
994 // further. We'll just return NULL.
995 MutexLockerEx x(Heap_lock);
996 *gc_count_before_ret = total_collections();
997 return NULL;
998 }
999 } else {
1000 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1001 MutexLockerEx x(Heap_lock);
1002 *gc_count_before_ret = total_collections();
1003 return NULL;
1004 }
1005 // The GCLocker is either active or the GCLocker initiated
1006 // GC has not yet been performed. Stall until it is and
1007 // then retry the allocation.
1008 GC_locker::stall_until_clear();
1009 (*gclocker_retry_count_ret) += 1;
1010 }
1012 // We can reach here if we were unsuccessful in scheduling a
1013 // collection (because another thread beat us to it) or if we were
1014 // stalled due to the GC locker. In either can we should retry the
1015 // allocation attempt in case another thread successfully
1016 // performed a collection and reclaimed enough space. We do the
1017 // first attempt (without holding the Heap_lock) here and the
1018 // follow-on attempt will be at the start of the next loop
1019 // iteration (after taking the Heap_lock).
1020 result = _mutator_alloc_region.attempt_allocation(word_size,
1021 false /* bot_updates */);
1022 if (result != NULL) {
1023 return result;
1024 }
1026 // Give a warning if we seem to be looping forever.
1027 if ((QueuedAllocationWarningCount > 0) &&
1028 (try_count % QueuedAllocationWarningCount == 0)) {
1029 warning("G1CollectedHeap::attempt_allocation_slow() "
1030 "retries %d times", try_count);
1031 }
1032 }
1034 ShouldNotReachHere();
1035 return NULL;
1036 }
1038 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
1039 unsigned int * gc_count_before_ret,
1040 int* gclocker_retry_count_ret) {
1041 // The structure of this method has a lot of similarities to
1042 // attempt_allocation_slow(). The reason these two were not merged
1043 // into a single one is that such a method would require several "if
1044 // allocation is not humongous do this, otherwise do that"
1045 // conditional paths which would obscure its flow. In fact, an early
1046 // version of this code did use a unified method which was harder to
1047 // follow and, as a result, it had subtle bugs that were hard to
1048 // track down. So keeping these two methods separate allows each to
1049 // be more readable. It will be good to keep these two in sync as
1050 // much as possible.
1052 assert_heap_not_locked_and_not_at_safepoint();
1053 assert(isHumongous(word_size), "attempt_allocation_humongous() "
1054 "should only be called for humongous allocations");
1056 // Humongous objects can exhaust the heap quickly, so we should check if we
1057 // need to start a marking cycle at each humongous object allocation. We do
1058 // the check before we do the actual allocation. The reason for doing it
1059 // before the allocation is that we avoid having to keep track of the newly
1060 // allocated memory while we do a GC.
1061 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
1062 word_size)) {
1063 collect(GCCause::_g1_humongous_allocation);
1064 }
1066 // We will loop until a) we manage to successfully perform the
1067 // allocation or b) we successfully schedule a collection which
1068 // fails to perform the allocation. b) is the only case when we'll
1069 // return NULL.
1070 HeapWord* result = NULL;
1071 for (int try_count = 1; /* we'll return */; try_count += 1) {
1072 bool should_try_gc;
1073 unsigned int gc_count_before;
1075 {
1076 MutexLockerEx x(Heap_lock);
1078 // Given that humongous objects are not allocated in young
1079 // regions, we'll first try to do the allocation without doing a
1080 // collection hoping that there's enough space in the heap.
1081 result = humongous_obj_allocate(word_size);
1082 if (result != NULL) {
1083 return result;
1084 }
1086 if (GC_locker::is_active_and_needs_gc()) {
1087 should_try_gc = false;
1088 } else {
1089 // The GCLocker may not be active but the GCLocker initiated
1090 // GC may not yet have been performed (GCLocker::needs_gc()
1091 // returns true). In this case we do not try this GC and
1092 // wait until the GCLocker initiated GC is performed, and
1093 // then retry the allocation.
1094 if (GC_locker::needs_gc()) {
1095 should_try_gc = false;
1096 } else {
1097 // Read the GC count while still holding the Heap_lock.
1098 gc_count_before = total_collections();
1099 should_try_gc = true;
1100 }
1101 }
1102 }
1104 if (should_try_gc) {
1105 // If we failed to allocate the humongous object, we should try to
1106 // do a collection pause (if we're allowed) in case it reclaims
1107 // enough space for the allocation to succeed after the pause.
1109 bool succeeded;
1110 result = do_collection_pause(word_size, gc_count_before, &succeeded,
1111 GCCause::_g1_humongous_allocation);
1112 if (result != NULL) {
1113 assert(succeeded, "only way to get back a non-NULL result");
1114 return result;
1115 }
1117 if (succeeded) {
1118 // If we get here we successfully scheduled a collection which
1119 // failed to allocate. No point in trying to allocate
1120 // further. We'll just return NULL.
1121 MutexLockerEx x(Heap_lock);
1122 *gc_count_before_ret = total_collections();
1123 return NULL;
1124 }
1125 } else {
1126 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1127 MutexLockerEx x(Heap_lock);
1128 *gc_count_before_ret = total_collections();
1129 return NULL;
1130 }
1131 // The GCLocker is either active or the GCLocker initiated
1132 // GC has not yet been performed. Stall until it is and
1133 // then retry the allocation.
1134 GC_locker::stall_until_clear();
1135 (*gclocker_retry_count_ret) += 1;
1136 }
1138 // We can reach here if we were unsuccessful in scheduling a
1139 // collection (because another thread beat us to it) or if we were
1140 // stalled due to the GC locker. In either can we should retry the
1141 // allocation attempt in case another thread successfully
1142 // performed a collection and reclaimed enough space. Give a
1143 // warning if we seem to be looping forever.
1145 if ((QueuedAllocationWarningCount > 0) &&
1146 (try_count % QueuedAllocationWarningCount == 0)) {
1147 warning("G1CollectedHeap::attempt_allocation_humongous() "
1148 "retries %d times", try_count);
1149 }
1150 }
1152 ShouldNotReachHere();
1153 return NULL;
1154 }
1156 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1157 bool expect_null_mutator_alloc_region) {
1158 assert_at_safepoint(true /* should_be_vm_thread */);
1159 assert(_mutator_alloc_region.get() == NULL ||
1160 !expect_null_mutator_alloc_region,
1161 "the current alloc region was unexpectedly found to be non-NULL");
1163 if (!isHumongous(word_size)) {
1164 return _mutator_alloc_region.attempt_allocation_locked(word_size,
1165 false /* bot_updates */);
1166 } else {
1167 HeapWord* result = humongous_obj_allocate(word_size);
1168 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1169 g1_policy()->set_initiate_conc_mark_if_possible();
1170 }
1171 return result;
1172 }
1174 ShouldNotReachHere();
1175 }
1177 class PostMCRemSetClearClosure: public HeapRegionClosure {
1178 G1CollectedHeap* _g1h;
1179 ModRefBarrierSet* _mr_bs;
1180 public:
1181 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1182 _g1h(g1h), _mr_bs(mr_bs) {}
1184 bool doHeapRegion(HeapRegion* r) {
1185 HeapRegionRemSet* hrrs = r->rem_set();
1187 if (r->continuesHumongous()) {
1188 // We'll assert that the strong code root list and RSet is empty
1189 assert(hrrs->strong_code_roots_list_length() == 0, "sanity");
1190 assert(hrrs->occupied() == 0, "RSet should be empty");
1191 return false;
1192 }
1194 _g1h->reset_gc_time_stamps(r);
1195 hrrs->clear();
1196 // You might think here that we could clear just the cards
1197 // corresponding to the used region. But no: if we leave a dirty card
1198 // in a region we might allocate into, then it would prevent that card
1199 // from being enqueued, and cause it to be missed.
1200 // Re: the performance cost: we shouldn't be doing full GC anyway!
1201 _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1203 return false;
1204 }
1205 };
1207 void G1CollectedHeap::clear_rsets_post_compaction() {
1208 PostMCRemSetClearClosure rs_clear(this, mr_bs());
1209 heap_region_iterate(&rs_clear);
1210 }
1212 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1213 G1CollectedHeap* _g1h;
1214 UpdateRSOopClosure _cl;
1215 int _worker_i;
1216 public:
1217 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1218 _cl(g1->g1_rem_set(), worker_i),
1219 _worker_i(worker_i),
1220 _g1h(g1)
1221 { }
1223 bool doHeapRegion(HeapRegion* r) {
1224 if (!r->continuesHumongous()) {
1225 _cl.set_from(r);
1226 r->oop_iterate(&_cl);
1227 }
1228 return false;
1229 }
1230 };
1232 class ParRebuildRSTask: public AbstractGangTask {
1233 G1CollectedHeap* _g1;
1234 public:
1235 ParRebuildRSTask(G1CollectedHeap* g1)
1236 : AbstractGangTask("ParRebuildRSTask"),
1237 _g1(g1)
1238 { }
1240 void work(uint worker_id) {
1241 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1242 _g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id,
1243 _g1->workers()->active_workers(),
1244 HeapRegion::RebuildRSClaimValue);
1245 }
1246 };
1248 class PostCompactionPrinterClosure: public HeapRegionClosure {
1249 private:
1250 G1HRPrinter* _hr_printer;
1251 public:
1252 bool doHeapRegion(HeapRegion* hr) {
1253 assert(!hr->is_young(), "not expecting to find young regions");
1254 // We only generate output for non-empty regions.
1255 if (!hr->is_empty()) {
1256 if (!hr->isHumongous()) {
1257 _hr_printer->post_compaction(hr, G1HRPrinter::Old);
1258 } else if (hr->startsHumongous()) {
1259 if (hr->region_num() == 1) {
1260 // single humongous region
1261 _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
1262 } else {
1263 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
1264 }
1265 } else {
1266 assert(hr->continuesHumongous(), "only way to get here");
1267 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1268 }
1269 }
1270 return false;
1271 }
1273 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1274 : _hr_printer(hr_printer) { }
1275 };
1277 void G1CollectedHeap::print_hrs_post_compaction() {
1278 PostCompactionPrinterClosure cl(hr_printer());
1279 heap_region_iterate(&cl);
1280 }
1282 bool G1CollectedHeap::do_collection(bool explicit_gc,
1283 bool clear_all_soft_refs,
1284 size_t word_size) {
1285 assert_at_safepoint(true /* should_be_vm_thread */);
1287 if (GC_locker::check_active_before_gc()) {
1288 return false;
1289 }
1291 STWGCTimer* gc_timer = G1MarkSweep::gc_timer();
1292 gc_timer->register_gc_start(os::elapsed_counter());
1294 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer();
1295 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start());
1297 SvcGCMarker sgcm(SvcGCMarker::FULL);
1298 ResourceMark rm;
1300 print_heap_before_gc();
1301 trace_heap_before_gc(gc_tracer);
1303 size_t metadata_prev_used = MetaspaceAux::allocated_used_bytes();
1305 HRSPhaseSetter x(HRSPhaseFullGC);
1306 verify_region_sets_optional();
1308 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1309 collector_policy()->should_clear_all_soft_refs();
1311 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1313 {
1314 IsGCActiveMark x;
1316 // Timing
1317 assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant");
1318 gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps);
1319 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
1321 {
1322 GCTraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, NULL);
1323 TraceCollectorStats tcs(g1mm()->full_collection_counters());
1324 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1326 double start = os::elapsedTime();
1327 g1_policy()->record_full_collection_start();
1329 // Note: When we have a more flexible GC logging framework that
1330 // allows us to add optional attributes to a GC log record we
1331 // could consider timing and reporting how long we wait in the
1332 // following two methods.
1333 wait_while_free_regions_coming();
1334 // If we start the compaction before the CM threads finish
1335 // scanning the root regions we might trip them over as we'll
1336 // be moving objects / updating references. So let's wait until
1337 // they are done. By telling them to abort, they should complete
1338 // early.
1339 _cm->root_regions()->abort();
1340 _cm->root_regions()->wait_until_scan_finished();
1341 append_secondary_free_list_if_not_empty_with_lock();
1343 gc_prologue(true);
1344 increment_total_collections(true /* full gc */);
1345 increment_old_marking_cycles_started();
1347 assert(used() == recalculate_used(), "Should be equal");
1349 verify_before_gc();
1351 pre_full_gc_dump(gc_timer);
1353 COMPILER2_PRESENT(DerivedPointerTable::clear());
1355 // Disable discovery and empty the discovered lists
1356 // for the CM ref processor.
1357 ref_processor_cm()->disable_discovery();
1358 ref_processor_cm()->abandon_partial_discovery();
1359 ref_processor_cm()->verify_no_references_recorded();
1361 // Abandon current iterations of concurrent marking and concurrent
1362 // refinement, if any are in progress. We have to do this before
1363 // wait_until_scan_finished() below.
1364 concurrent_mark()->abort();
1366 // Make sure we'll choose a new allocation region afterwards.
1367 release_mutator_alloc_region();
1368 abandon_gc_alloc_regions();
1369 g1_rem_set()->cleanupHRRS();
1371 // We should call this after we retire any currently active alloc
1372 // regions so that all the ALLOC / RETIRE events are generated
1373 // before the start GC event.
1374 _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1376 // We may have added regions to the current incremental collection
1377 // set between the last GC or pause and now. We need to clear the
1378 // incremental collection set and then start rebuilding it afresh
1379 // after this full GC.
1380 abandon_collection_set(g1_policy()->inc_cset_head());
1381 g1_policy()->clear_incremental_cset();
1382 g1_policy()->stop_incremental_cset_building();
1384 tear_down_region_sets(false /* free_list_only */);
1385 g1_policy()->set_gcs_are_young(true);
1387 // See the comments in g1CollectedHeap.hpp and
1388 // G1CollectedHeap::ref_processing_init() about
1389 // how reference processing currently works in G1.
1391 // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1392 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1394 // Temporarily clear the STW ref processor's _is_alive_non_header field.
1395 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1397 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
1398 ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1400 // Do collection work
1401 {
1402 HandleMark hm; // Discard invalid handles created during gc
1403 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1404 }
1406 assert(free_regions() == 0, "we should not have added any free regions");
1407 rebuild_region_sets(false /* free_list_only */);
1409 // Enqueue any discovered reference objects that have
1410 // not been removed from the discovered lists.
1411 ref_processor_stw()->enqueue_discovered_references();
1413 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1415 MemoryService::track_memory_usage();
1417 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1418 ref_processor_stw()->verify_no_references_recorded();
1420 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1421 ClassLoaderDataGraph::purge();
1422 MetaspaceAux::verify_metrics();
1424 // Note: since we've just done a full GC, concurrent
1425 // marking is no longer active. Therefore we need not
1426 // re-enable reference discovery for the CM ref processor.
1427 // That will be done at the start of the next marking cycle.
1428 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1429 ref_processor_cm()->verify_no_references_recorded();
1431 reset_gc_time_stamp();
1432 // Since everything potentially moved, we will clear all remembered
1433 // sets, and clear all cards. Later we will rebuild remembered
1434 // sets. We will also reset the GC time stamps of the regions.
1435 clear_rsets_post_compaction();
1436 check_gc_time_stamps();
1438 // Resize the heap if necessary.
1439 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1441 if (_hr_printer.is_active()) {
1442 // We should do this after we potentially resize the heap so
1443 // that all the COMMIT / UNCOMMIT events are generated before
1444 // the end GC event.
1446 print_hrs_post_compaction();
1447 _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1448 }
1450 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
1451 if (hot_card_cache->use_cache()) {
1452 hot_card_cache->reset_card_counts();
1453 hot_card_cache->reset_hot_cache();
1454 }
1456 // Rebuild remembered sets of all regions.
1457 if (G1CollectedHeap::use_parallel_gc_threads()) {
1458 uint n_workers =
1459 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1460 workers()->active_workers(),
1461 Threads::number_of_non_daemon_threads());
1462 assert(UseDynamicNumberOfGCThreads ||
1463 n_workers == workers()->total_workers(),
1464 "If not dynamic should be using all the workers");
1465 workers()->set_active_workers(n_workers);
1466 // Set parallel threads in the heap (_n_par_threads) only
1467 // before a parallel phase and always reset it to 0 after
1468 // the phase so that the number of parallel threads does
1469 // no get carried forward to a serial phase where there
1470 // may be code that is "possibly_parallel".
1471 set_par_threads(n_workers);
1473 ParRebuildRSTask rebuild_rs_task(this);
1474 assert(check_heap_region_claim_values(
1475 HeapRegion::InitialClaimValue), "sanity check");
1476 assert(UseDynamicNumberOfGCThreads ||
1477 workers()->active_workers() == workers()->total_workers(),
1478 "Unless dynamic should use total workers");
1479 // Use the most recent number of active workers
1480 assert(workers()->active_workers() > 0,
1481 "Active workers not properly set");
1482 set_par_threads(workers()->active_workers());
1483 workers()->run_task(&rebuild_rs_task);
1484 set_par_threads(0);
1485 assert(check_heap_region_claim_values(
1486 HeapRegion::RebuildRSClaimValue), "sanity check");
1487 reset_heap_region_claim_values();
1488 } else {
1489 RebuildRSOutOfRegionClosure rebuild_rs(this);
1490 heap_region_iterate(&rebuild_rs);
1491 }
1493 // Rebuild the strong code root lists for each region
1494 rebuild_strong_code_roots();
1496 if (true) { // FIXME
1497 MetaspaceGC::compute_new_size();
1498 }
1500 #ifdef TRACESPINNING
1501 ParallelTaskTerminator::print_termination_counts();
1502 #endif
1504 // Discard all rset updates
1505 JavaThread::dirty_card_queue_set().abandon_logs();
1506 assert(!G1DeferredRSUpdate
1507 || (G1DeferredRSUpdate &&
1508 (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any");
1510 _young_list->reset_sampled_info();
1511 // At this point there should be no regions in the
1512 // entire heap tagged as young.
1513 assert(check_young_list_empty(true /* check_heap */),
1514 "young list should be empty at this point");
1516 // Update the number of full collections that have been completed.
1517 increment_old_marking_cycles_completed(false /* concurrent */);
1519 _hrs.verify_optional();
1520 verify_region_sets_optional();
1522 verify_after_gc();
1524 // Start a new incremental collection set for the next pause
1525 assert(g1_policy()->collection_set() == NULL, "must be");
1526 g1_policy()->start_incremental_cset_building();
1528 // Clear the _cset_fast_test bitmap in anticipation of adding
1529 // regions to the incremental collection set for the next
1530 // evacuation pause.
1531 clear_cset_fast_test();
1533 init_mutator_alloc_region();
1535 double end = os::elapsedTime();
1536 g1_policy()->record_full_collection_end();
1538 if (G1Log::fine()) {
1539 g1_policy()->print_heap_transition();
1540 }
1542 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1543 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1544 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1545 // before any GC notifications are raised.
1546 g1mm()->update_sizes();
1548 gc_epilogue(true);
1549 }
1551 if (G1Log::finer()) {
1552 g1_policy()->print_detailed_heap_transition(true /* full */);
1553 }
1555 print_heap_after_gc();
1556 trace_heap_after_gc(gc_tracer);
1558 post_full_gc_dump(gc_timer);
1560 gc_timer->register_gc_end(os::elapsed_counter());
1561 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
1562 }
1564 return true;
1565 }
1567 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1568 // do_collection() will return whether it succeeded in performing
1569 // the GC. Currently, there is no facility on the
1570 // do_full_collection() API to notify the caller than the collection
1571 // did not succeed (e.g., because it was locked out by the GC
1572 // locker). So, right now, we'll ignore the return value.
1573 bool dummy = do_collection(true, /* explicit_gc */
1574 clear_all_soft_refs,
1575 0 /* word_size */);
1576 }
1578 // This code is mostly copied from TenuredGeneration.
1579 void
1580 G1CollectedHeap::
1581 resize_if_necessary_after_full_collection(size_t word_size) {
1582 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, "sanity check");
1584 // Include the current allocation, if any, and bytes that will be
1585 // pre-allocated to support collections, as "used".
1586 const size_t used_after_gc = used();
1587 const size_t capacity_after_gc = capacity();
1588 const size_t free_after_gc = capacity_after_gc - used_after_gc;
1590 // This is enforced in arguments.cpp.
1591 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1592 "otherwise the code below doesn't make sense");
1594 // We don't have floating point command-line arguments
1595 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1596 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1597 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1598 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1600 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1601 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1603 // We have to be careful here as these two calculations can overflow
1604 // 32-bit size_t's.
1605 double used_after_gc_d = (double) used_after_gc;
1606 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1607 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1609 // Let's make sure that they are both under the max heap size, which
1610 // by default will make them fit into a size_t.
1611 double desired_capacity_upper_bound = (double) max_heap_size;
1612 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1613 desired_capacity_upper_bound);
1614 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1615 desired_capacity_upper_bound);
1617 // We can now safely turn them into size_t's.
1618 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1619 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1621 // This assert only makes sense here, before we adjust them
1622 // with respect to the min and max heap size.
1623 assert(minimum_desired_capacity <= maximum_desired_capacity,
1624 err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1625 "maximum_desired_capacity = "SIZE_FORMAT,
1626 minimum_desired_capacity, maximum_desired_capacity));
1628 // Should not be greater than the heap max size. No need to adjust
1629 // it with respect to the heap min size as it's a lower bound (i.e.,
1630 // we'll try to make the capacity larger than it, not smaller).
1631 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1632 // Should not be less than the heap min size. No need to adjust it
1633 // with respect to the heap max size as it's an upper bound (i.e.,
1634 // we'll try to make the capacity smaller than it, not greater).
1635 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1637 if (capacity_after_gc < minimum_desired_capacity) {
1638 // Don't expand unless it's significant
1639 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1640 ergo_verbose4(ErgoHeapSizing,
1641 "attempt heap expansion",
1642 ergo_format_reason("capacity lower than "
1643 "min desired capacity after Full GC")
1644 ergo_format_byte("capacity")
1645 ergo_format_byte("occupancy")
1646 ergo_format_byte_perc("min desired capacity"),
1647 capacity_after_gc, used_after_gc,
1648 minimum_desired_capacity, (double) MinHeapFreeRatio);
1649 expand(expand_bytes);
1651 // No expansion, now see if we want to shrink
1652 } else if (capacity_after_gc > maximum_desired_capacity) {
1653 // Capacity too large, compute shrinking size
1654 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1655 ergo_verbose4(ErgoHeapSizing,
1656 "attempt heap shrinking",
1657 ergo_format_reason("capacity higher than "
1658 "max desired capacity after Full GC")
1659 ergo_format_byte("capacity")
1660 ergo_format_byte("occupancy")
1661 ergo_format_byte_perc("max desired capacity"),
1662 capacity_after_gc, used_after_gc,
1663 maximum_desired_capacity, (double) MaxHeapFreeRatio);
1664 shrink(shrink_bytes);
1665 }
1666 }
1669 HeapWord*
1670 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1671 bool* succeeded) {
1672 assert_at_safepoint(true /* should_be_vm_thread */);
1674 *succeeded = true;
1675 // Let's attempt the allocation first.
1676 HeapWord* result =
1677 attempt_allocation_at_safepoint(word_size,
1678 false /* expect_null_mutator_alloc_region */);
1679 if (result != NULL) {
1680 assert(*succeeded, "sanity");
1681 return result;
1682 }
1684 // In a G1 heap, we're supposed to keep allocation from failing by
1685 // incremental pauses. Therefore, at least for now, we'll favor
1686 // expansion over collection. (This might change in the future if we can
1687 // do something smarter than full collection to satisfy a failed alloc.)
1688 result = expand_and_allocate(word_size);
1689 if (result != NULL) {
1690 assert(*succeeded, "sanity");
1691 return result;
1692 }
1694 // Expansion didn't work, we'll try to do a Full GC.
1695 bool gc_succeeded = do_collection(false, /* explicit_gc */
1696 false, /* clear_all_soft_refs */
1697 word_size);
1698 if (!gc_succeeded) {
1699 *succeeded = false;
1700 return NULL;
1701 }
1703 // Retry the allocation
1704 result = attempt_allocation_at_safepoint(word_size,
1705 true /* expect_null_mutator_alloc_region */);
1706 if (result != NULL) {
1707 assert(*succeeded, "sanity");
1708 return result;
1709 }
1711 // Then, try a Full GC that will collect all soft references.
1712 gc_succeeded = do_collection(false, /* explicit_gc */
1713 true, /* clear_all_soft_refs */
1714 word_size);
1715 if (!gc_succeeded) {
1716 *succeeded = false;
1717 return NULL;
1718 }
1720 // Retry the allocation once more
1721 result = attempt_allocation_at_safepoint(word_size,
1722 true /* expect_null_mutator_alloc_region */);
1723 if (result != NULL) {
1724 assert(*succeeded, "sanity");
1725 return result;
1726 }
1728 assert(!collector_policy()->should_clear_all_soft_refs(),
1729 "Flag should have been handled and cleared prior to this point");
1731 // What else? We might try synchronous finalization later. If the total
1732 // space available is large enough for the allocation, then a more
1733 // complete compaction phase than we've tried so far might be
1734 // appropriate.
1735 assert(*succeeded, "sanity");
1736 return NULL;
1737 }
1739 // Attempting to expand the heap sufficiently
1740 // to support an allocation of the given "word_size". If
1741 // successful, perform the allocation and return the address of the
1742 // allocated block, or else "NULL".
1744 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1745 assert_at_safepoint(true /* should_be_vm_thread */);
1747 verify_region_sets_optional();
1749 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1750 ergo_verbose1(ErgoHeapSizing,
1751 "attempt heap expansion",
1752 ergo_format_reason("allocation request failed")
1753 ergo_format_byte("allocation request"),
1754 word_size * HeapWordSize);
1755 if (expand(expand_bytes)) {
1756 _hrs.verify_optional();
1757 verify_region_sets_optional();
1758 return attempt_allocation_at_safepoint(word_size,
1759 false /* expect_null_mutator_alloc_region */);
1760 }
1761 return NULL;
1762 }
1764 void G1CollectedHeap::update_committed_space(HeapWord* old_end,
1765 HeapWord* new_end) {
1766 assert(old_end != new_end, "don't call this otherwise");
1767 assert((HeapWord*) _g1_storage.high() == new_end, "invariant");
1769 // Update the committed mem region.
1770 _g1_committed.set_end(new_end);
1771 // Tell the card table about the update.
1772 Universe::heap()->barrier_set()->resize_covered_region(_g1_committed);
1773 // Tell the BOT about the update.
1774 _bot_shared->resize(_g1_committed.word_size());
1775 // Tell the hot card cache about the update
1776 _cg1r->hot_card_cache()->resize_card_counts(capacity());
1777 }
1779 bool G1CollectedHeap::expand(size_t expand_bytes) {
1780 size_t old_mem_size = _g1_storage.committed_size();
1781 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1782 aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1783 HeapRegion::GrainBytes);
1784 ergo_verbose2(ErgoHeapSizing,
1785 "expand the heap",
1786 ergo_format_byte("requested expansion amount")
1787 ergo_format_byte("attempted expansion amount"),
1788 expand_bytes, aligned_expand_bytes);
1790 // First commit the memory.
1791 HeapWord* old_end = (HeapWord*) _g1_storage.high();
1792 bool successful = _g1_storage.expand_by(aligned_expand_bytes);
1793 if (successful) {
1794 // Then propagate this update to the necessary data structures.
1795 HeapWord* new_end = (HeapWord*) _g1_storage.high();
1796 update_committed_space(old_end, new_end);
1798 FreeRegionList expansion_list("Local Expansion List");
1799 MemRegion mr = _hrs.expand_by(old_end, new_end, &expansion_list);
1800 assert(mr.start() == old_end, "post-condition");
1801 // mr might be a smaller region than what was requested if
1802 // expand_by() was unable to allocate the HeapRegion instances
1803 assert(mr.end() <= new_end, "post-condition");
1805 size_t actual_expand_bytes = mr.byte_size();
1806 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1807 assert(actual_expand_bytes == expansion_list.total_capacity_bytes(),
1808 "post-condition");
1809 if (actual_expand_bytes < aligned_expand_bytes) {
1810 // We could not expand _hrs to the desired size. In this case we
1811 // need to shrink the committed space accordingly.
1812 assert(mr.end() < new_end, "invariant");
1814 size_t diff_bytes = aligned_expand_bytes - actual_expand_bytes;
1815 // First uncommit the memory.
1816 _g1_storage.shrink_by(diff_bytes);
1817 // Then propagate this update to the necessary data structures.
1818 update_committed_space(new_end, mr.end());
1819 }
1820 _free_list.add_as_tail(&expansion_list);
1822 if (_hr_printer.is_active()) {
1823 HeapWord* curr = mr.start();
1824 while (curr < mr.end()) {
1825 HeapWord* curr_end = curr + HeapRegion::GrainWords;
1826 _hr_printer.commit(curr, curr_end);
1827 curr = curr_end;
1828 }
1829 assert(curr == mr.end(), "post-condition");
1830 }
1831 g1_policy()->record_new_heap_size(n_regions());
1832 } else {
1833 ergo_verbose0(ErgoHeapSizing,
1834 "did not expand the heap",
1835 ergo_format_reason("heap expansion operation failed"));
1836 // The expansion of the virtual storage space was unsuccessful.
1837 // Let's see if it was because we ran out of swap.
1838 if (G1ExitOnExpansionFailure &&
1839 _g1_storage.uncommitted_size() >= aligned_expand_bytes) {
1840 // We had head room...
1841 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1842 }
1843 }
1844 return successful;
1845 }
1847 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1848 size_t old_mem_size = _g1_storage.committed_size();
1849 size_t aligned_shrink_bytes =
1850 ReservedSpace::page_align_size_down(shrink_bytes);
1851 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1852 HeapRegion::GrainBytes);
1853 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1855 uint num_regions_removed = _hrs.shrink_by(num_regions_to_remove);
1856 HeapWord* old_end = (HeapWord*) _g1_storage.high();
1857 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1859 ergo_verbose3(ErgoHeapSizing,
1860 "shrink the heap",
1861 ergo_format_byte("requested shrinking amount")
1862 ergo_format_byte("aligned shrinking amount")
1863 ergo_format_byte("attempted shrinking amount"),
1864 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1865 if (num_regions_removed > 0) {
1866 _g1_storage.shrink_by(shrunk_bytes);
1867 HeapWord* new_end = (HeapWord*) _g1_storage.high();
1869 if (_hr_printer.is_active()) {
1870 HeapWord* curr = old_end;
1871 while (curr > new_end) {
1872 HeapWord* curr_end = curr;
1873 curr -= HeapRegion::GrainWords;
1874 _hr_printer.uncommit(curr, curr_end);
1875 }
1876 }
1878 _expansion_regions += num_regions_removed;
1879 update_committed_space(old_end, new_end);
1880 HeapRegionRemSet::shrink_heap(n_regions());
1881 g1_policy()->record_new_heap_size(n_regions());
1882 } else {
1883 ergo_verbose0(ErgoHeapSizing,
1884 "did not shrink the heap",
1885 ergo_format_reason("heap shrinking operation failed"));
1886 }
1887 }
1889 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1890 verify_region_sets_optional();
1892 // We should only reach here at the end of a Full GC which means we
1893 // should not not be holding to any GC alloc regions. The method
1894 // below will make sure of that and do any remaining clean up.
1895 abandon_gc_alloc_regions();
1897 // Instead of tearing down / rebuilding the free lists here, we
1898 // could instead use the remove_all_pending() method on free_list to
1899 // remove only the ones that we need to remove.
1900 tear_down_region_sets(true /* free_list_only */);
1901 shrink_helper(shrink_bytes);
1902 rebuild_region_sets(true /* free_list_only */);
1904 _hrs.verify_optional();
1905 verify_region_sets_optional();
1906 }
1908 // Public methods.
1910 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1911 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1912 #endif // _MSC_VER
1915 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1916 SharedHeap(policy_),
1917 _g1_policy(policy_),
1918 _dirty_card_queue_set(false),
1919 _into_cset_dirty_card_queue_set(false),
1920 _is_alive_closure_cm(this),
1921 _is_alive_closure_stw(this),
1922 _ref_processor_cm(NULL),
1923 _ref_processor_stw(NULL),
1924 _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
1925 _bot_shared(NULL),
1926 _evac_failure_scan_stack(NULL),
1927 _mark_in_progress(false),
1928 _cg1r(NULL), _summary_bytes_used(0),
1929 _g1mm(NULL),
1930 _refine_cte_cl(NULL),
1931 _full_collection(false),
1932 _free_list("Master Free List"),
1933 _secondary_free_list("Secondary Free List"),
1934 _old_set("Old Set"),
1935 _humongous_set("Master Humongous Set"),
1936 _free_regions_coming(false),
1937 _young_list(new YoungList(this)),
1938 _gc_time_stamp(0),
1939 _retained_old_gc_alloc_region(NULL),
1940 _survivor_plab_stats(YoungPLABSize, PLABWeight),
1941 _old_plab_stats(OldPLABSize, PLABWeight),
1942 _expand_heap_after_alloc_failure(true),
1943 _surviving_young_words(NULL),
1944 _old_marking_cycles_started(0),
1945 _old_marking_cycles_completed(0),
1946 _concurrent_cycle_started(false),
1947 _in_cset_fast_test(NULL),
1948 _in_cset_fast_test_base(NULL),
1949 _dirty_cards_region_list(NULL),
1950 _worker_cset_start_region(NULL),
1951 _worker_cset_start_region_time_stamp(NULL),
1952 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1953 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
1954 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1955 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) {
1957 _g1h = this;
1958 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
1959 vm_exit_during_initialization("Failed necessary allocation.");
1960 }
1962 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1964 int n_queues = MAX2((int)ParallelGCThreads, 1);
1965 _task_queues = new RefToScanQueueSet(n_queues);
1967 int n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1968 assert(n_rem_sets > 0, "Invariant.");
1970 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1971 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC);
1972 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1974 for (int i = 0; i < n_queues; i++) {
1975 RefToScanQueue* q = new RefToScanQueue();
1976 q->initialize();
1977 _task_queues->register_queue(i, q);
1978 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1979 }
1980 clear_cset_start_regions();
1982 // Initialize the G1EvacuationFailureALot counters and flags.
1983 NOT_PRODUCT(reset_evacuation_should_fail();)
1985 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1986 }
1988 jint G1CollectedHeap::initialize() {
1989 CollectedHeap::pre_initialize();
1990 os::enable_vtime();
1992 G1Log::init();
1994 // Necessary to satisfy locking discipline assertions.
1996 MutexLocker x(Heap_lock);
1998 // We have to initialize the printer before committing the heap, as
1999 // it will be used then.
2000 _hr_printer.set_active(G1PrintHeapRegions);
2002 // While there are no constraints in the GC code that HeapWordSize
2003 // be any particular value, there are multiple other areas in the
2004 // system which believe this to be true (e.g. oop->object_size in some
2005 // cases incorrectly returns the size in wordSize units rather than
2006 // HeapWordSize).
2007 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
2009 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
2010 size_t max_byte_size = collector_policy()->max_heap_byte_size();
2011 size_t heap_alignment = collector_policy()->max_alignment();
2013 // Ensure that the sizes are properly aligned.
2014 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
2015 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
2016 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
2018 _cg1r = new ConcurrentG1Refine(this);
2020 // Reserve the maximum.
2022 // When compressed oops are enabled, the preferred heap base
2023 // is calculated by subtracting the requested size from the
2024 // 32Gb boundary and using the result as the base address for
2025 // heap reservation. If the requested size is not aligned to
2026 // HeapRegion::GrainBytes (i.e. the alignment that is passed
2027 // into the ReservedHeapSpace constructor) then the actual
2028 // base of the reserved heap may end up differing from the
2029 // address that was requested (i.e. the preferred heap base).
2030 // If this happens then we could end up using a non-optimal
2031 // compressed oops mode.
2033 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
2034 heap_alignment);
2036 // It is important to do this in a way such that concurrent readers can't
2037 // temporarily think something is in the heap. (I've actually seen this
2038 // happen in asserts: DLD.)
2039 _reserved.set_word_size(0);
2040 _reserved.set_start((HeapWord*)heap_rs.base());
2041 _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size()));
2043 _expansion_regions = (uint) (max_byte_size / HeapRegion::GrainBytes);
2045 // Create the gen rem set (and barrier set) for the entire reserved region.
2046 _rem_set = collector_policy()->create_rem_set(_reserved, 2);
2047 set_barrier_set(rem_set()->bs());
2048 if (barrier_set()->is_a(BarrierSet::ModRef)) {
2049 _mr_bs = (ModRefBarrierSet*)_barrier_set;
2050 } else {
2051 vm_exit_during_initialization("G1 requires a mod ref bs.");
2052 return JNI_ENOMEM;
2053 }
2055 // Also create a G1 rem set.
2056 if (mr_bs()->is_a(BarrierSet::CardTableModRef)) {
2057 _g1_rem_set = new G1RemSet(this, (CardTableModRefBS*)mr_bs());
2058 } else {
2059 vm_exit_during_initialization("G1 requires a cardtable mod ref bs.");
2060 return JNI_ENOMEM;
2061 }
2063 // Carve out the G1 part of the heap.
2065 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
2066 _g1_reserved = MemRegion((HeapWord*)g1_rs.base(),
2067 g1_rs.size()/HeapWordSize);
2069 _g1_storage.initialize(g1_rs, 0);
2070 _g1_committed = MemRegion((HeapWord*)_g1_storage.low(), (size_t) 0);
2071 _hrs.initialize((HeapWord*) _g1_reserved.start(),
2072 (HeapWord*) _g1_reserved.end(),
2073 _expansion_regions);
2075 // Do later initialization work for concurrent refinement.
2076 _cg1r->init();
2078 // 6843694 - ensure that the maximum region index can fit
2079 // in the remembered set structures.
2080 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
2081 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
2083 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
2084 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
2085 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
2086 "too many cards per region");
2088 HeapRegionSet::set_unrealistically_long_length(max_regions() + 1);
2090 _bot_shared = new G1BlockOffsetSharedArray(_reserved,
2091 heap_word_size(init_byte_size));
2093 _g1h = this;
2095 _in_cset_fast_test_length = max_regions();
2096 _in_cset_fast_test_base =
2097 NEW_C_HEAP_ARRAY(bool, (size_t) _in_cset_fast_test_length, mtGC);
2099 // We're biasing _in_cset_fast_test to avoid subtracting the
2100 // beginning of the heap every time we want to index; basically
2101 // it's the same with what we do with the card table.
2102 _in_cset_fast_test = _in_cset_fast_test_base -
2103 ((uintx) _g1_reserved.start() >> HeapRegion::LogOfHRGrainBytes);
2105 // Clear the _cset_fast_test bitmap in anticipation of adding
2106 // regions to the incremental collection set for the first
2107 // evacuation pause.
2108 clear_cset_fast_test();
2110 // Create the ConcurrentMark data structure and thread.
2111 // (Must do this late, so that "max_regions" is defined.)
2112 _cm = new ConcurrentMark(this, heap_rs);
2113 if (_cm == NULL || !_cm->completed_initialization()) {
2114 vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark");
2115 return JNI_ENOMEM;
2116 }
2117 _cmThread = _cm->cmThread();
2119 // Initialize the from_card cache structure of HeapRegionRemSet.
2120 HeapRegionRemSet::init_heap(max_regions());
2122 // Now expand into the initial heap size.
2123 if (!expand(init_byte_size)) {
2124 vm_shutdown_during_initialization("Failed to allocate initial heap.");
2125 return JNI_ENOMEM;
2126 }
2128 // Perform any initialization actions delegated to the policy.
2129 g1_policy()->init();
2131 _refine_cte_cl =
2132 new RefineCardTableEntryClosure(ConcurrentG1RefineThread::sts(),
2133 g1_rem_set(),
2134 concurrent_g1_refine());
2135 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
2137 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
2138 SATB_Q_FL_lock,
2139 G1SATBProcessCompletedThreshold,
2140 Shared_SATB_Q_lock);
2142 JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
2143 DirtyCardQ_FL_lock,
2144 concurrent_g1_refine()->yellow_zone(),
2145 concurrent_g1_refine()->red_zone(),
2146 Shared_DirtyCardQ_lock);
2148 if (G1DeferredRSUpdate) {
2149 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
2150 DirtyCardQ_FL_lock,
2151 -1, // never trigger processing
2152 -1, // no limit on length
2153 Shared_DirtyCardQ_lock,
2154 &JavaThread::dirty_card_queue_set());
2155 }
2157 // Initialize the card queue set used to hold cards containing
2158 // references into the collection set.
2159 _into_cset_dirty_card_queue_set.initialize(DirtyCardQ_CBL_mon,
2160 DirtyCardQ_FL_lock,
2161 -1, // never trigger processing
2162 -1, // no limit on length
2163 Shared_DirtyCardQ_lock,
2164 &JavaThread::dirty_card_queue_set());
2166 // In case we're keeping closure specialization stats, initialize those
2167 // counts and that mechanism.
2168 SpecializationStats::clear();
2170 // Here we allocate the dummy full region that is required by the
2171 // G1AllocRegion class. If we don't pass an address in the reserved
2172 // space here, lots of asserts fire.
2174 HeapRegion* dummy_region = new_heap_region(0 /* index of bottom region */,
2175 _g1_reserved.start());
2176 // We'll re-use the same region whether the alloc region will
2177 // require BOT updates or not and, if it doesn't, then a non-young
2178 // region will complain that it cannot support allocations without
2179 // BOT updates. So we'll tag the dummy region as young to avoid that.
2180 dummy_region->set_young();
2181 // Make sure it's full.
2182 dummy_region->set_top(dummy_region->end());
2183 G1AllocRegion::setup(this, dummy_region);
2185 init_mutator_alloc_region();
2187 // Do create of the monitoring and management support so that
2188 // values in the heap have been properly initialized.
2189 _g1mm = new G1MonitoringSupport(this);
2191 return JNI_OK;
2192 }
2194 size_t G1CollectedHeap::conservative_max_heap_alignment() {
2195 return HeapRegion::max_region_size();
2196 }
2198 void G1CollectedHeap::ref_processing_init() {
2199 // Reference processing in G1 currently works as follows:
2200 //
2201 // * There are two reference processor instances. One is
2202 // used to record and process discovered references
2203 // during concurrent marking; the other is used to
2204 // record and process references during STW pauses
2205 // (both full and incremental).
2206 // * Both ref processors need to 'span' the entire heap as
2207 // the regions in the collection set may be dotted around.
2208 //
2209 // * For the concurrent marking ref processor:
2210 // * Reference discovery is enabled at initial marking.
2211 // * Reference discovery is disabled and the discovered
2212 // references processed etc during remarking.
2213 // * Reference discovery is MT (see below).
2214 // * Reference discovery requires a barrier (see below).
2215 // * Reference processing may or may not be MT
2216 // (depending on the value of ParallelRefProcEnabled
2217 // and ParallelGCThreads).
2218 // * A full GC disables reference discovery by the CM
2219 // ref processor and abandons any entries on it's
2220 // discovered lists.
2221 //
2222 // * For the STW processor:
2223 // * Non MT discovery is enabled at the start of a full GC.
2224 // * Processing and enqueueing during a full GC is non-MT.
2225 // * During a full GC, references are processed after marking.
2226 //
2227 // * Discovery (may or may not be MT) is enabled at the start
2228 // of an incremental evacuation pause.
2229 // * References are processed near the end of a STW evacuation pause.
2230 // * For both types of GC:
2231 // * Discovery is atomic - i.e. not concurrent.
2232 // * Reference discovery will not need a barrier.
2234 SharedHeap::ref_processing_init();
2235 MemRegion mr = reserved_region();
2237 // Concurrent Mark ref processor
2238 _ref_processor_cm =
2239 new ReferenceProcessor(mr, // span
2240 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2241 // mt processing
2242 (int) ParallelGCThreads,
2243 // degree of mt processing
2244 (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2245 // mt discovery
2246 (int) MAX2(ParallelGCThreads, ConcGCThreads),
2247 // degree of mt discovery
2248 false,
2249 // Reference discovery is not atomic
2250 &_is_alive_closure_cm,
2251 // is alive closure
2252 // (for efficiency/performance)
2253 true);
2254 // Setting next fields of discovered
2255 // lists requires a barrier.
2257 // STW ref processor
2258 _ref_processor_stw =
2259 new ReferenceProcessor(mr, // span
2260 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2261 // mt processing
2262 MAX2((int)ParallelGCThreads, 1),
2263 // degree of mt processing
2264 (ParallelGCThreads > 1),
2265 // mt discovery
2266 MAX2((int)ParallelGCThreads, 1),
2267 // degree of mt discovery
2268 true,
2269 // Reference discovery is atomic
2270 &_is_alive_closure_stw,
2271 // is alive closure
2272 // (for efficiency/performance)
2273 false);
2274 // Setting next fields of discovered
2275 // lists requires a barrier.
2276 }
2278 size_t G1CollectedHeap::capacity() const {
2279 return _g1_committed.byte_size();
2280 }
2282 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2283 assert(!hr->continuesHumongous(), "pre-condition");
2284 hr->reset_gc_time_stamp();
2285 if (hr->startsHumongous()) {
2286 uint first_index = hr->hrs_index() + 1;
2287 uint last_index = hr->last_hc_index();
2288 for (uint i = first_index; i < last_index; i += 1) {
2289 HeapRegion* chr = region_at(i);
2290 assert(chr->continuesHumongous(), "sanity");
2291 chr->reset_gc_time_stamp();
2292 }
2293 }
2294 }
2296 #ifndef PRODUCT
2297 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2298 private:
2299 unsigned _gc_time_stamp;
2300 bool _failures;
2302 public:
2303 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2304 _gc_time_stamp(gc_time_stamp), _failures(false) { }
2306 virtual bool doHeapRegion(HeapRegion* hr) {
2307 unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2308 if (_gc_time_stamp != region_gc_time_stamp) {
2309 gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, "
2310 "expected %d", HR_FORMAT_PARAMS(hr),
2311 region_gc_time_stamp, _gc_time_stamp);
2312 _failures = true;
2313 }
2314 return false;
2315 }
2317 bool failures() { return _failures; }
2318 };
2320 void G1CollectedHeap::check_gc_time_stamps() {
2321 CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2322 heap_region_iterate(&cl);
2323 guarantee(!cl.failures(), "all GC time stamps should have been reset");
2324 }
2325 #endif // PRODUCT
2327 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2328 DirtyCardQueue* into_cset_dcq,
2329 bool concurrent,
2330 int worker_i) {
2331 // Clean cards in the hot card cache
2332 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
2333 hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq);
2335 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2336 int n_completed_buffers = 0;
2337 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2338 n_completed_buffers++;
2339 }
2340 g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers);
2341 dcqs.clear_n_completed_buffers();
2342 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2343 }
2346 // Computes the sum of the storage used by the various regions.
2348 size_t G1CollectedHeap::used() const {
2349 assert(Heap_lock->owner() != NULL,
2350 "Should be owned on this thread's behalf.");
2351 size_t result = _summary_bytes_used;
2352 // Read only once in case it is set to NULL concurrently
2353 HeapRegion* hr = _mutator_alloc_region.get();
2354 if (hr != NULL)
2355 result += hr->used();
2356 return result;
2357 }
2359 size_t G1CollectedHeap::used_unlocked() const {
2360 size_t result = _summary_bytes_used;
2361 return result;
2362 }
2364 class SumUsedClosure: public HeapRegionClosure {
2365 size_t _used;
2366 public:
2367 SumUsedClosure() : _used(0) {}
2368 bool doHeapRegion(HeapRegion* r) {
2369 if (!r->continuesHumongous()) {
2370 _used += r->used();
2371 }
2372 return false;
2373 }
2374 size_t result() { return _used; }
2375 };
2377 size_t G1CollectedHeap::recalculate_used() const {
2378 SumUsedClosure blk;
2379 heap_region_iterate(&blk);
2380 return blk.result();
2381 }
2383 size_t G1CollectedHeap::unsafe_max_alloc() {
2384 if (free_regions() > 0) return HeapRegion::GrainBytes;
2385 // otherwise, is there space in the current allocation region?
2387 // We need to store the current allocation region in a local variable
2388 // here. The problem is that this method doesn't take any locks and
2389 // there may be other threads which overwrite the current allocation
2390 // region field. attempt_allocation(), for example, sets it to NULL
2391 // and this can happen *after* the NULL check here but before the call
2392 // to free(), resulting in a SIGSEGV. Note that this doesn't appear
2393 // to be a problem in the optimized build, since the two loads of the
2394 // current allocation region field are optimized away.
2395 HeapRegion* hr = _mutator_alloc_region.get();
2396 if (hr == NULL) {
2397 return 0;
2398 }
2399 return hr->free();
2400 }
2402 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2403 switch (cause) {
2404 case GCCause::_gc_locker: return GCLockerInvokesConcurrent;
2405 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
2406 case GCCause::_g1_humongous_allocation: return true;
2407 default: return false;
2408 }
2409 }
2411 #ifndef PRODUCT
2412 void G1CollectedHeap::allocate_dummy_regions() {
2413 // Let's fill up most of the region
2414 size_t word_size = HeapRegion::GrainWords - 1024;
2415 // And as a result the region we'll allocate will be humongous.
2416 guarantee(isHumongous(word_size), "sanity");
2418 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2419 // Let's use the existing mechanism for the allocation
2420 HeapWord* dummy_obj = humongous_obj_allocate(word_size);
2421 if (dummy_obj != NULL) {
2422 MemRegion mr(dummy_obj, word_size);
2423 CollectedHeap::fill_with_object(mr);
2424 } else {
2425 // If we can't allocate once, we probably cannot allocate
2426 // again. Let's get out of the loop.
2427 break;
2428 }
2429 }
2430 }
2431 #endif // !PRODUCT
2433 void G1CollectedHeap::increment_old_marking_cycles_started() {
2434 assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2435 _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2436 err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2437 _old_marking_cycles_started, _old_marking_cycles_completed));
2439 _old_marking_cycles_started++;
2440 }
2442 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2443 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2445 // We assume that if concurrent == true, then the caller is a
2446 // concurrent thread that was joined the Suspendible Thread
2447 // Set. If there's ever a cheap way to check this, we should add an
2448 // assert here.
2450 // Given that this method is called at the end of a Full GC or of a
2451 // concurrent cycle, and those can be nested (i.e., a Full GC can
2452 // interrupt a concurrent cycle), the number of full collections
2453 // completed should be either one (in the case where there was no
2454 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2455 // behind the number of full collections started.
2457 // This is the case for the inner caller, i.e. a Full GC.
2458 assert(concurrent ||
2459 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2460 (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2461 err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
2462 "is inconsistent with _old_marking_cycles_completed = %u",
2463 _old_marking_cycles_started, _old_marking_cycles_completed));
2465 // This is the case for the outer caller, i.e. the concurrent cycle.
2466 assert(!concurrent ||
2467 (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2468 err_msg("for outer caller (concurrent cycle): "
2469 "_old_marking_cycles_started = %u "
2470 "is inconsistent with _old_marking_cycles_completed = %u",
2471 _old_marking_cycles_started, _old_marking_cycles_completed));
2473 _old_marking_cycles_completed += 1;
2475 // We need to clear the "in_progress" flag in the CM thread before
2476 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2477 // is set) so that if a waiter requests another System.gc() it doesn't
2478 // incorrectly see that a marking cycle is still in progress.
2479 if (concurrent) {
2480 _cmThread->clear_in_progress();
2481 }
2483 // This notify_all() will ensure that a thread that called
2484 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2485 // and it's waiting for a full GC to finish will be woken up. It is
2486 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2487 FullGCCount_lock->notify_all();
2488 }
2490 void G1CollectedHeap::register_concurrent_cycle_start(jlong start_time) {
2491 _concurrent_cycle_started = true;
2492 _gc_timer_cm->register_gc_start(start_time);
2494 _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start());
2495 trace_heap_before_gc(_gc_tracer_cm);
2496 }
2498 void G1CollectedHeap::register_concurrent_cycle_end() {
2499 if (_concurrent_cycle_started) {
2500 if (_cm->has_aborted()) {
2501 _gc_tracer_cm->report_concurrent_mode_failure();
2502 }
2504 _gc_timer_cm->register_gc_end(os::elapsed_counter());
2505 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
2507 _concurrent_cycle_started = false;
2508 }
2509 }
2511 void G1CollectedHeap::trace_heap_after_concurrent_cycle() {
2512 if (_concurrent_cycle_started) {
2513 trace_heap_after_gc(_gc_tracer_cm);
2514 }
2515 }
2517 G1YCType G1CollectedHeap::yc_type() {
2518 bool is_young = g1_policy()->gcs_are_young();
2519 bool is_initial_mark = g1_policy()->during_initial_mark_pause();
2520 bool is_during_mark = mark_in_progress();
2522 if (is_initial_mark) {
2523 return InitialMark;
2524 } else if (is_during_mark) {
2525 return DuringMark;
2526 } else if (is_young) {
2527 return Normal;
2528 } else {
2529 return Mixed;
2530 }
2531 }
2533 void G1CollectedHeap::collect(GCCause::Cause cause) {
2534 assert_heap_not_locked();
2536 unsigned int gc_count_before;
2537 unsigned int old_marking_count_before;
2538 bool retry_gc;
2540 do {
2541 retry_gc = false;
2543 {
2544 MutexLocker ml(Heap_lock);
2546 // Read the GC count while holding the Heap_lock
2547 gc_count_before = total_collections();
2548 old_marking_count_before = _old_marking_cycles_started;
2549 }
2551 if (should_do_concurrent_full_gc(cause)) {
2552 // Schedule an initial-mark evacuation pause that will start a
2553 // concurrent cycle. We're setting word_size to 0 which means that
2554 // we are not requesting a post-GC allocation.
2555 VM_G1IncCollectionPause op(gc_count_before,
2556 0, /* word_size */
2557 true, /* should_initiate_conc_mark */
2558 g1_policy()->max_pause_time_ms(),
2559 cause);
2561 VMThread::execute(&op);
2562 if (!op.pause_succeeded()) {
2563 if (old_marking_count_before == _old_marking_cycles_started) {
2564 retry_gc = op.should_retry_gc();
2565 } else {
2566 // A Full GC happened while we were trying to schedule the
2567 // initial-mark GC. No point in starting a new cycle given
2568 // that the whole heap was collected anyway.
2569 }
2571 if (retry_gc) {
2572 if (GC_locker::is_active_and_needs_gc()) {
2573 GC_locker::stall_until_clear();
2574 }
2575 }
2576 }
2577 } else {
2578 if (cause == GCCause::_gc_locker
2579 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2581 // Schedule a standard evacuation pause. We're setting word_size
2582 // to 0 which means that we are not requesting a post-GC allocation.
2583 VM_G1IncCollectionPause op(gc_count_before,
2584 0, /* word_size */
2585 false, /* should_initiate_conc_mark */
2586 g1_policy()->max_pause_time_ms(),
2587 cause);
2588 VMThread::execute(&op);
2589 } else {
2590 // Schedule a Full GC.
2591 VM_G1CollectFull op(gc_count_before, old_marking_count_before, cause);
2592 VMThread::execute(&op);
2593 }
2594 }
2595 } while (retry_gc);
2596 }
2598 bool G1CollectedHeap::is_in(const void* p) const {
2599 if (_g1_committed.contains(p)) {
2600 // Given that we know that p is in the committed space,
2601 // heap_region_containing_raw() should successfully
2602 // return the containing region.
2603 HeapRegion* hr = heap_region_containing_raw(p);
2604 return hr->is_in(p);
2605 } else {
2606 return false;
2607 }
2608 }
2610 // Iteration functions.
2612 // Iterates an OopClosure over all ref-containing fields of objects
2613 // within a HeapRegion.
2615 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2616 MemRegion _mr;
2617 ExtendedOopClosure* _cl;
2618 public:
2619 IterateOopClosureRegionClosure(MemRegion mr, ExtendedOopClosure* cl)
2620 : _mr(mr), _cl(cl) {}
2621 bool doHeapRegion(HeapRegion* r) {
2622 if (!r->continuesHumongous()) {
2623 r->oop_iterate(_cl);
2624 }
2625 return false;
2626 }
2627 };
2629 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) {
2630 IterateOopClosureRegionClosure blk(_g1_committed, cl);
2631 heap_region_iterate(&blk);
2632 }
2634 void G1CollectedHeap::oop_iterate(MemRegion mr, ExtendedOopClosure* cl) {
2635 IterateOopClosureRegionClosure blk(mr, cl);
2636 heap_region_iterate(&blk);
2637 }
2639 // Iterates an ObjectClosure over all objects within a HeapRegion.
2641 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2642 ObjectClosure* _cl;
2643 public:
2644 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2645 bool doHeapRegion(HeapRegion* r) {
2646 if (! r->continuesHumongous()) {
2647 r->object_iterate(_cl);
2648 }
2649 return false;
2650 }
2651 };
2653 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2654 IterateObjectClosureRegionClosure blk(cl);
2655 heap_region_iterate(&blk);
2656 }
2658 // Calls a SpaceClosure on a HeapRegion.
2660 class SpaceClosureRegionClosure: public HeapRegionClosure {
2661 SpaceClosure* _cl;
2662 public:
2663 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2664 bool doHeapRegion(HeapRegion* r) {
2665 _cl->do_space(r);
2666 return false;
2667 }
2668 };
2670 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2671 SpaceClosureRegionClosure blk(cl);
2672 heap_region_iterate(&blk);
2673 }
2675 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2676 _hrs.iterate(cl);
2677 }
2679 void
2680 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
2681 uint worker_id,
2682 uint no_of_par_workers,
2683 jint claim_value) {
2684 const uint regions = n_regions();
2685 const uint max_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
2686 no_of_par_workers :
2687 1);
2688 assert(UseDynamicNumberOfGCThreads ||
2689 no_of_par_workers == workers()->total_workers(),
2690 "Non dynamic should use fixed number of workers");
2691 // try to spread out the starting points of the workers
2692 const HeapRegion* start_hr =
2693 start_region_for_worker(worker_id, no_of_par_workers);
2694 const uint start_index = start_hr->hrs_index();
2696 // each worker will actually look at all regions
2697 for (uint count = 0; count < regions; ++count) {
2698 const uint index = (start_index + count) % regions;
2699 assert(0 <= index && index < regions, "sanity");
2700 HeapRegion* r = region_at(index);
2701 // we'll ignore "continues humongous" regions (we'll process them
2702 // when we come across their corresponding "start humongous"
2703 // region) and regions already claimed
2704 if (r->claim_value() == claim_value || r->continuesHumongous()) {
2705 continue;
2706 }
2707 // OK, try to claim it
2708 if (r->claimHeapRegion(claim_value)) {
2709 // success!
2710 assert(!r->continuesHumongous(), "sanity");
2711 if (r->startsHumongous()) {
2712 // If the region is "starts humongous" we'll iterate over its
2713 // "continues humongous" first; in fact we'll do them
2714 // first. The order is important. In on case, calling the
2715 // closure on the "starts humongous" region might de-allocate
2716 // and clear all its "continues humongous" regions and, as a
2717 // result, we might end up processing them twice. So, we'll do
2718 // them first (notice: most closures will ignore them anyway) and
2719 // then we'll do the "starts humongous" region.
2720 for (uint ch_index = index + 1; ch_index < regions; ++ch_index) {
2721 HeapRegion* chr = region_at(ch_index);
2723 // if the region has already been claimed or it's not
2724 // "continues humongous" we're done
2725 if (chr->claim_value() == claim_value ||
2726 !chr->continuesHumongous()) {
2727 break;
2728 }
2730 // No one should have claimed it directly. We can given
2731 // that we claimed its "starts humongous" region.
2732 assert(chr->claim_value() != claim_value, "sanity");
2733 assert(chr->humongous_start_region() == r, "sanity");
2735 if (chr->claimHeapRegion(claim_value)) {
2736 // we should always be able to claim it; no one else should
2737 // be trying to claim this region
2739 bool res2 = cl->doHeapRegion(chr);
2740 assert(!res2, "Should not abort");
2742 // Right now, this holds (i.e., no closure that actually
2743 // does something with "continues humongous" regions
2744 // clears them). We might have to weaken it in the future,
2745 // but let's leave these two asserts here for extra safety.
2746 assert(chr->continuesHumongous(), "should still be the case");
2747 assert(chr->humongous_start_region() == r, "sanity");
2748 } else {
2749 guarantee(false, "we should not reach here");
2750 }
2751 }
2752 }
2754 assert(!r->continuesHumongous(), "sanity");
2755 bool res = cl->doHeapRegion(r);
2756 assert(!res, "Should not abort");
2757 }
2758 }
2759 }
2761 class ResetClaimValuesClosure: public HeapRegionClosure {
2762 public:
2763 bool doHeapRegion(HeapRegion* r) {
2764 r->set_claim_value(HeapRegion::InitialClaimValue);
2765 return false;
2766 }
2767 };
2769 void G1CollectedHeap::reset_heap_region_claim_values() {
2770 ResetClaimValuesClosure blk;
2771 heap_region_iterate(&blk);
2772 }
2774 void G1CollectedHeap::reset_cset_heap_region_claim_values() {
2775 ResetClaimValuesClosure blk;
2776 collection_set_iterate(&blk);
2777 }
2779 #ifdef ASSERT
2780 // This checks whether all regions in the heap have the correct claim
2781 // value. I also piggy-backed on this a check to ensure that the
2782 // humongous_start_region() information on "continues humongous"
2783 // regions is correct.
2785 class CheckClaimValuesClosure : public HeapRegionClosure {
2786 private:
2787 jint _claim_value;
2788 uint _failures;
2789 HeapRegion* _sh_region;
2791 public:
2792 CheckClaimValuesClosure(jint claim_value) :
2793 _claim_value(claim_value), _failures(0), _sh_region(NULL) { }
2794 bool doHeapRegion(HeapRegion* r) {
2795 if (r->claim_value() != _claim_value) {
2796 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2797 "claim value = %d, should be %d",
2798 HR_FORMAT_PARAMS(r),
2799 r->claim_value(), _claim_value);
2800 ++_failures;
2801 }
2802 if (!r->isHumongous()) {
2803 _sh_region = NULL;
2804 } else if (r->startsHumongous()) {
2805 _sh_region = r;
2806 } else if (r->continuesHumongous()) {
2807 if (r->humongous_start_region() != _sh_region) {
2808 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2809 "HS = "PTR_FORMAT", should be "PTR_FORMAT,
2810 HR_FORMAT_PARAMS(r),
2811 r->humongous_start_region(),
2812 _sh_region);
2813 ++_failures;
2814 }
2815 }
2816 return false;
2817 }
2818 uint failures() { return _failures; }
2819 };
2821 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
2822 CheckClaimValuesClosure cl(claim_value);
2823 heap_region_iterate(&cl);
2824 return cl.failures() == 0;
2825 }
2827 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure {
2828 private:
2829 jint _claim_value;
2830 uint _failures;
2832 public:
2833 CheckClaimValuesInCSetHRClosure(jint claim_value) :
2834 _claim_value(claim_value), _failures(0) { }
2836 uint failures() { return _failures; }
2838 bool doHeapRegion(HeapRegion* hr) {
2839 assert(hr->in_collection_set(), "how?");
2840 assert(!hr->isHumongous(), "H-region in CSet");
2841 if (hr->claim_value() != _claim_value) {
2842 gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", "
2843 "claim value = %d, should be %d",
2844 HR_FORMAT_PARAMS(hr),
2845 hr->claim_value(), _claim_value);
2846 _failures += 1;
2847 }
2848 return false;
2849 }
2850 };
2852 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) {
2853 CheckClaimValuesInCSetHRClosure cl(claim_value);
2854 collection_set_iterate(&cl);
2855 return cl.failures() == 0;
2856 }
2857 #endif // ASSERT
2859 // Clear the cached CSet starting regions and (more importantly)
2860 // the time stamps. Called when we reset the GC time stamp.
2861 void G1CollectedHeap::clear_cset_start_regions() {
2862 assert(_worker_cset_start_region != NULL, "sanity");
2863 assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2865 int n_queues = MAX2((int)ParallelGCThreads, 1);
2866 for (int i = 0; i < n_queues; i++) {
2867 _worker_cset_start_region[i] = NULL;
2868 _worker_cset_start_region_time_stamp[i] = 0;
2869 }
2870 }
2872 // Given the id of a worker, obtain or calculate a suitable
2873 // starting region for iterating over the current collection set.
2874 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(int worker_i) {
2875 assert(get_gc_time_stamp() > 0, "should have been updated by now");
2877 HeapRegion* result = NULL;
2878 unsigned gc_time_stamp = get_gc_time_stamp();
2880 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2881 // Cached starting region for current worker was set
2882 // during the current pause - so it's valid.
2883 // Note: the cached starting heap region may be NULL
2884 // (when the collection set is empty).
2885 result = _worker_cset_start_region[worker_i];
2886 assert(result == NULL || result->in_collection_set(), "sanity");
2887 return result;
2888 }
2890 // The cached entry was not valid so let's calculate
2891 // a suitable starting heap region for this worker.
2893 // We want the parallel threads to start their collection
2894 // set iteration at different collection set regions to
2895 // avoid contention.
2896 // If we have:
2897 // n collection set regions
2898 // p threads
2899 // Then thread t will start at region floor ((t * n) / p)
2901 result = g1_policy()->collection_set();
2902 if (G1CollectedHeap::use_parallel_gc_threads()) {
2903 uint cs_size = g1_policy()->cset_region_length();
2904 uint active_workers = workers()->active_workers();
2905 assert(UseDynamicNumberOfGCThreads ||
2906 active_workers == workers()->total_workers(),
2907 "Unless dynamic should use total workers");
2909 uint end_ind = (cs_size * worker_i) / active_workers;
2910 uint start_ind = 0;
2912 if (worker_i > 0 &&
2913 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2914 // Previous workers starting region is valid
2915 // so let's iterate from there
2916 start_ind = (cs_size * (worker_i - 1)) / active_workers;
2917 result = _worker_cset_start_region[worker_i - 1];
2918 }
2920 for (uint i = start_ind; i < end_ind; i++) {
2921 result = result->next_in_collection_set();
2922 }
2923 }
2925 // Note: the calculated starting heap region may be NULL
2926 // (when the collection set is empty).
2927 assert(result == NULL || result->in_collection_set(), "sanity");
2928 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2929 "should be updated only once per pause");
2930 _worker_cset_start_region[worker_i] = result;
2931 OrderAccess::storestore();
2932 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2933 return result;
2934 }
2936 HeapRegion* G1CollectedHeap::start_region_for_worker(uint worker_i,
2937 uint no_of_par_workers) {
2938 uint worker_num =
2939 G1CollectedHeap::use_parallel_gc_threads() ? no_of_par_workers : 1U;
2940 assert(UseDynamicNumberOfGCThreads ||
2941 no_of_par_workers == workers()->total_workers(),
2942 "Non dynamic should use fixed number of workers");
2943 const uint start_index = n_regions() * worker_i / worker_num;
2944 return region_at(start_index);
2945 }
2947 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2948 HeapRegion* r = g1_policy()->collection_set();
2949 while (r != NULL) {
2950 HeapRegion* next = r->next_in_collection_set();
2951 if (cl->doHeapRegion(r)) {
2952 cl->incomplete();
2953 return;
2954 }
2955 r = next;
2956 }
2957 }
2959 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2960 HeapRegionClosure *cl) {
2961 if (r == NULL) {
2962 // The CSet is empty so there's nothing to do.
2963 return;
2964 }
2966 assert(r->in_collection_set(),
2967 "Start region must be a member of the collection set.");
2968 HeapRegion* cur = r;
2969 while (cur != NULL) {
2970 HeapRegion* next = cur->next_in_collection_set();
2971 if (cl->doHeapRegion(cur) && false) {
2972 cl->incomplete();
2973 return;
2974 }
2975 cur = next;
2976 }
2977 cur = g1_policy()->collection_set();
2978 while (cur != r) {
2979 HeapRegion* next = cur->next_in_collection_set();
2980 if (cl->doHeapRegion(cur) && false) {
2981 cl->incomplete();
2982 return;
2983 }
2984 cur = next;
2985 }
2986 }
2988 CompactibleSpace* G1CollectedHeap::first_compactible_space() {
2989 return n_regions() > 0 ? region_at(0) : NULL;
2990 }
2993 Space* G1CollectedHeap::space_containing(const void* addr) const {
2994 Space* res = heap_region_containing(addr);
2995 return res;
2996 }
2998 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2999 Space* sp = space_containing(addr);
3000 if (sp != NULL) {
3001 return sp->block_start(addr);
3002 }
3003 return NULL;
3004 }
3006 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
3007 Space* sp = space_containing(addr);
3008 assert(sp != NULL, "block_size of address outside of heap");
3009 return sp->block_size(addr);
3010 }
3012 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
3013 Space* sp = space_containing(addr);
3014 return sp->block_is_obj(addr);
3015 }
3017 bool G1CollectedHeap::supports_tlab_allocation() const {
3018 return true;
3019 }
3021 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
3022 return HeapRegion::GrainBytes;
3023 }
3025 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
3026 // Return the remaining space in the cur alloc region, but not less than
3027 // the min TLAB size.
3029 // Also, this value can be at most the humongous object threshold,
3030 // since we can't allow tlabs to grow big enough to accommodate
3031 // humongous objects.
3033 HeapRegion* hr = _mutator_alloc_region.get();
3034 size_t max_tlab_size = _humongous_object_threshold_in_words * wordSize;
3035 if (hr == NULL) {
3036 return max_tlab_size;
3037 } else {
3038 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab_size);
3039 }
3040 }
3042 size_t G1CollectedHeap::max_capacity() const {
3043 return _g1_reserved.byte_size();
3044 }
3046 jlong G1CollectedHeap::millis_since_last_gc() {
3047 // assert(false, "NYI");
3048 return 0;
3049 }
3051 void G1CollectedHeap::prepare_for_verify() {
3052 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
3053 ensure_parsability(false);
3054 }
3055 g1_rem_set()->prepare_for_verify();
3056 }
3058 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr,
3059 VerifyOption vo) {
3060 switch (vo) {
3061 case VerifyOption_G1UsePrevMarking:
3062 return hr->obj_allocated_since_prev_marking(obj);
3063 case VerifyOption_G1UseNextMarking:
3064 return hr->obj_allocated_since_next_marking(obj);
3065 case VerifyOption_G1UseMarkWord:
3066 return false;
3067 default:
3068 ShouldNotReachHere();
3069 }
3070 return false; // keep some compilers happy
3071 }
3073 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) {
3074 switch (vo) {
3075 case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start();
3076 case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start();
3077 case VerifyOption_G1UseMarkWord: return NULL;
3078 default: ShouldNotReachHere();
3079 }
3080 return NULL; // keep some compilers happy
3081 }
3083 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) {
3084 switch (vo) {
3085 case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj);
3086 case VerifyOption_G1UseNextMarking: return isMarkedNext(obj);
3087 case VerifyOption_G1UseMarkWord: return obj->is_gc_marked();
3088 default: ShouldNotReachHere();
3089 }
3090 return false; // keep some compilers happy
3091 }
3093 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) {
3094 switch (vo) {
3095 case VerifyOption_G1UsePrevMarking: return "PTAMS";
3096 case VerifyOption_G1UseNextMarking: return "NTAMS";
3097 case VerifyOption_G1UseMarkWord: return "NONE";
3098 default: ShouldNotReachHere();
3099 }
3100 return NULL; // keep some compilers happy
3101 }
3103 // TODO: VerifyRootsClosure extends OopsInGenClosure so that we can
3104 // pass it as the perm_blk to SharedHeap::process_strong_roots.
3105 // When process_strong_roots stop calling perm_blk->younger_refs_iterate
3106 // we can change this closure to extend the simpler OopClosure.
3107 class VerifyRootsClosure: public OopsInGenClosure {
3108 private:
3109 G1CollectedHeap* _g1h;
3110 VerifyOption _vo;
3111 bool _failures;
3112 public:
3113 // _vo == UsePrevMarking -> use "prev" marking information,
3114 // _vo == UseNextMarking -> use "next" marking information,
3115 // _vo == UseMarkWord -> use mark word from object header.
3116 VerifyRootsClosure(VerifyOption vo) :
3117 _g1h(G1CollectedHeap::heap()),
3118 _vo(vo),
3119 _failures(false) { }
3121 bool failures() { return _failures; }
3123 template <class T> void do_oop_nv(T* p) {
3124 T heap_oop = oopDesc::load_heap_oop(p);
3125 if (!oopDesc::is_null(heap_oop)) {
3126 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3127 if (_g1h->is_obj_dead_cond(obj, _vo)) {
3128 gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
3129 "points to dead obj "PTR_FORMAT, p, (void*) obj);
3130 if (_vo == VerifyOption_G1UseMarkWord) {
3131 gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark()));
3132 }
3133 obj->print_on(gclog_or_tty);
3134 _failures = true;
3135 }
3136 }
3137 }
3139 void do_oop(oop* p) { do_oop_nv(p); }
3140 void do_oop(narrowOop* p) { do_oop_nv(p); }
3141 };
3143 class G1VerifyCodeRootOopClosure: public OopsInGenClosure {
3144 G1CollectedHeap* _g1h;
3145 OopClosure* _root_cl;
3146 nmethod* _nm;
3147 VerifyOption _vo;
3148 bool _failures;
3150 template <class T> void do_oop_work(T* p) {
3151 // First verify that this root is live
3152 _root_cl->do_oop(p);
3154 if (!G1VerifyHeapRegionCodeRoots) {
3155 // We're not verifying the code roots attached to heap region.
3156 return;
3157 }
3159 // Don't check the code roots during marking verification in a full GC
3160 if (_vo == VerifyOption_G1UseMarkWord) {
3161 return;
3162 }
3164 // Now verify that the current nmethod (which contains p) is
3165 // in the code root list of the heap region containing the
3166 // object referenced by p.
3168 T heap_oop = oopDesc::load_heap_oop(p);
3169 if (!oopDesc::is_null(heap_oop)) {
3170 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3172 // Now fetch the region containing the object
3173 HeapRegion* hr = _g1h->heap_region_containing(obj);
3174 HeapRegionRemSet* hrrs = hr->rem_set();
3175 // Verify that the strong code root list for this region
3176 // contains the nmethod
3177 if (!hrrs->strong_code_roots_list_contains(_nm)) {
3178 gclog_or_tty->print_cr("Code root location "PTR_FORMAT" "
3179 "from nmethod "PTR_FORMAT" not in strong "
3180 "code roots for region ["PTR_FORMAT","PTR_FORMAT")",
3181 p, _nm, hr->bottom(), hr->end());
3182 _failures = true;
3183 }
3184 }
3185 }
3187 public:
3188 G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo):
3189 _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {}
3191 void do_oop(oop* p) { do_oop_work(p); }
3192 void do_oop(narrowOop* p) { do_oop_work(p); }
3194 void set_nmethod(nmethod* nm) { _nm = nm; }
3195 bool failures() { return _failures; }
3196 };
3198 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure {
3199 G1VerifyCodeRootOopClosure* _oop_cl;
3201 public:
3202 G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl):
3203 _oop_cl(oop_cl) {}
3205 void do_code_blob(CodeBlob* cb) {
3206 nmethod* nm = cb->as_nmethod_or_null();
3207 if (nm != NULL) {
3208 _oop_cl->set_nmethod(nm);
3209 nm->oops_do(_oop_cl);
3210 }
3211 }
3212 };
3214 class YoungRefCounterClosure : public OopClosure {
3215 G1CollectedHeap* _g1h;
3216 int _count;
3217 public:
3218 YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {}
3219 void do_oop(oop* p) { if (_g1h->is_in_young(*p)) { _count++; } }
3220 void do_oop(narrowOop* p) { ShouldNotReachHere(); }
3222 int count() { return _count; }
3223 void reset_count() { _count = 0; };
3224 };
3226 class VerifyKlassClosure: public KlassClosure {
3227 YoungRefCounterClosure _young_ref_counter_closure;
3228 OopClosure *_oop_closure;
3229 public:
3230 VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {}
3231 void do_klass(Klass* k) {
3232 k->oops_do(_oop_closure);
3234 _young_ref_counter_closure.reset_count();
3235 k->oops_do(&_young_ref_counter_closure);
3236 if (_young_ref_counter_closure.count() > 0) {
3237 guarantee(k->has_modified_oops(), err_msg("Klass %p, has young refs but is not dirty.", k));
3238 }
3239 }
3240 };
3242 class VerifyLivenessOopClosure: public OopClosure {
3243 G1CollectedHeap* _g1h;
3244 VerifyOption _vo;
3245 public:
3246 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
3247 _g1h(g1h), _vo(vo)
3248 { }
3249 void do_oop(narrowOop *p) { do_oop_work(p); }
3250 void do_oop( oop *p) { do_oop_work(p); }
3252 template <class T> void do_oop_work(T *p) {
3253 oop obj = oopDesc::load_decode_heap_oop(p);
3254 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
3255 "Dead object referenced by a not dead object");
3256 }
3257 };
3259 class VerifyObjsInRegionClosure: public ObjectClosure {
3260 private:
3261 G1CollectedHeap* _g1h;
3262 size_t _live_bytes;
3263 HeapRegion *_hr;
3264 VerifyOption _vo;
3265 public:
3266 // _vo == UsePrevMarking -> use "prev" marking information,
3267 // _vo == UseNextMarking -> use "next" marking information,
3268 // _vo == UseMarkWord -> use mark word from object header.
3269 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
3270 : _live_bytes(0), _hr(hr), _vo(vo) {
3271 _g1h = G1CollectedHeap::heap();
3272 }
3273 void do_object(oop o) {
3274 VerifyLivenessOopClosure isLive(_g1h, _vo);
3275 assert(o != NULL, "Huh?");
3276 if (!_g1h->is_obj_dead_cond(o, _vo)) {
3277 // If the object is alive according to the mark word,
3278 // then verify that the marking information agrees.
3279 // Note we can't verify the contra-positive of the
3280 // above: if the object is dead (according to the mark
3281 // word), it may not be marked, or may have been marked
3282 // but has since became dead, or may have been allocated
3283 // since the last marking.
3284 if (_vo == VerifyOption_G1UseMarkWord) {
3285 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
3286 }
3288 o->oop_iterate_no_header(&isLive);
3289 if (!_hr->obj_allocated_since_prev_marking(o)) {
3290 size_t obj_size = o->size(); // Make sure we don't overflow
3291 _live_bytes += (obj_size * HeapWordSize);
3292 }
3293 }
3294 }
3295 size_t live_bytes() { return _live_bytes; }
3296 };
3298 class PrintObjsInRegionClosure : public ObjectClosure {
3299 HeapRegion *_hr;
3300 G1CollectedHeap *_g1;
3301 public:
3302 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
3303 _g1 = G1CollectedHeap::heap();
3304 };
3306 void do_object(oop o) {
3307 if (o != NULL) {
3308 HeapWord *start = (HeapWord *) o;
3309 size_t word_sz = o->size();
3310 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
3311 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
3312 (void*) o, word_sz,
3313 _g1->isMarkedPrev(o),
3314 _g1->isMarkedNext(o),
3315 _hr->obj_allocated_since_prev_marking(o));
3316 HeapWord *end = start + word_sz;
3317 HeapWord *cur;
3318 int *val;
3319 for (cur = start; cur < end; cur++) {
3320 val = (int *) cur;
3321 gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val);
3322 }
3323 }
3324 }
3325 };
3327 class VerifyRegionClosure: public HeapRegionClosure {
3328 private:
3329 bool _par;
3330 VerifyOption _vo;
3331 bool _failures;
3332 public:
3333 // _vo == UsePrevMarking -> use "prev" marking information,
3334 // _vo == UseNextMarking -> use "next" marking information,
3335 // _vo == UseMarkWord -> use mark word from object header.
3336 VerifyRegionClosure(bool par, VerifyOption vo)
3337 : _par(par),
3338 _vo(vo),
3339 _failures(false) {}
3341 bool failures() {
3342 return _failures;
3343 }
3345 bool doHeapRegion(HeapRegion* r) {
3346 if (!r->continuesHumongous()) {
3347 bool failures = false;
3348 r->verify(_vo, &failures);
3349 if (failures) {
3350 _failures = true;
3351 } else {
3352 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
3353 r->object_iterate(¬_dead_yet_cl);
3354 if (_vo != VerifyOption_G1UseNextMarking) {
3355 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
3356 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
3357 "max_live_bytes "SIZE_FORMAT" "
3358 "< calculated "SIZE_FORMAT,
3359 r->bottom(), r->end(),
3360 r->max_live_bytes(),
3361 not_dead_yet_cl.live_bytes());
3362 _failures = true;
3363 }
3364 } else {
3365 // When vo == UseNextMarking we cannot currently do a sanity
3366 // check on the live bytes as the calculation has not been
3367 // finalized yet.
3368 }
3369 }
3370 }
3371 return false; // stop the region iteration if we hit a failure
3372 }
3373 };
3375 // This is the task used for parallel verification of the heap regions
3377 class G1ParVerifyTask: public AbstractGangTask {
3378 private:
3379 G1CollectedHeap* _g1h;
3380 VerifyOption _vo;
3381 bool _failures;
3383 public:
3384 // _vo == UsePrevMarking -> use "prev" marking information,
3385 // _vo == UseNextMarking -> use "next" marking information,
3386 // _vo == UseMarkWord -> use mark word from object header.
3387 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
3388 AbstractGangTask("Parallel verify task"),
3389 _g1h(g1h),
3390 _vo(vo),
3391 _failures(false) { }
3393 bool failures() {
3394 return _failures;
3395 }
3397 void work(uint worker_id) {
3398 HandleMark hm;
3399 VerifyRegionClosure blk(true, _vo);
3400 _g1h->heap_region_par_iterate_chunked(&blk, worker_id,
3401 _g1h->workers()->active_workers(),
3402 HeapRegion::ParVerifyClaimValue);
3403 if (blk.failures()) {
3404 _failures = true;
3405 }
3406 }
3407 };
3409 void G1CollectedHeap::verify(bool silent, VerifyOption vo) {
3410 if (SafepointSynchronize::is_at_safepoint()) {
3411 assert(Thread::current()->is_VM_thread(),
3412 "Expected to be executed serially by the VM thread at this point");
3414 if (!silent) { gclog_or_tty->print("Roots "); }
3415 VerifyRootsClosure rootsCl(vo);
3416 G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo);
3417 G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl);
3418 VerifyKlassClosure klassCl(this, &rootsCl);
3420 // We apply the relevant closures to all the oops in the
3421 // system dictionary, the string table and the code cache.
3422 const int so = SO_AllClasses | SO_Strings | SO_CodeCache;
3424 // Need cleared claim bits for the strong roots processing
3425 ClassLoaderDataGraph::clear_claimed_marks();
3427 process_strong_roots(true, // activate StrongRootsScope
3428 false, // we set "is scavenging" to false,
3429 // so we don't reset the dirty cards.
3430 ScanningOption(so), // roots scanning options
3431 &rootsCl,
3432 &blobsCl,
3433 &klassCl
3434 );
3436 bool failures = rootsCl.failures() || codeRootsCl.failures();
3438 if (vo != VerifyOption_G1UseMarkWord) {
3439 // If we're verifying during a full GC then the region sets
3440 // will have been torn down at the start of the GC. Therefore
3441 // verifying the region sets will fail. So we only verify
3442 // the region sets when not in a full GC.
3443 if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3444 verify_region_sets();
3445 }
3447 if (!silent) { gclog_or_tty->print("HeapRegions "); }
3448 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3449 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3450 "sanity check");
3452 G1ParVerifyTask task(this, vo);
3453 assert(UseDynamicNumberOfGCThreads ||
3454 workers()->active_workers() == workers()->total_workers(),
3455 "If not dynamic should be using all the workers");
3456 int n_workers = workers()->active_workers();
3457 set_par_threads(n_workers);
3458 workers()->run_task(&task);
3459 set_par_threads(0);
3460 if (task.failures()) {
3461 failures = true;
3462 }
3464 // Checks that the expected amount of parallel work was done.
3465 // The implication is that n_workers is > 0.
3466 assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
3467 "sanity check");
3469 reset_heap_region_claim_values();
3471 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3472 "sanity check");
3473 } else {
3474 VerifyRegionClosure blk(false, vo);
3475 heap_region_iterate(&blk);
3476 if (blk.failures()) {
3477 failures = true;
3478 }
3479 }
3480 if (!silent) gclog_or_tty->print("RemSet ");
3481 rem_set()->verify();
3483 if (failures) {
3484 gclog_or_tty->print_cr("Heap:");
3485 // It helps to have the per-region information in the output to
3486 // help us track down what went wrong. This is why we call
3487 // print_extended_on() instead of print_on().
3488 print_extended_on(gclog_or_tty);
3489 gclog_or_tty->print_cr("");
3490 #ifndef PRODUCT
3491 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3492 concurrent_mark()->print_reachable("at-verification-failure",
3493 vo, false /* all */);
3494 }
3495 #endif
3496 gclog_or_tty->flush();
3497 }
3498 guarantee(!failures, "there should not have been any failures");
3499 } else {
3500 if (!silent)
3501 gclog_or_tty->print("(SKIPPING roots, heapRegionSets, heapRegions, remset) ");
3502 }
3503 }
3505 void G1CollectedHeap::verify(bool silent) {
3506 verify(silent, VerifyOption_G1UsePrevMarking);
3507 }
3509 double G1CollectedHeap::verify(bool guard, const char* msg) {
3510 double verify_time_ms = 0.0;
3512 if (guard && total_collections() >= VerifyGCStartAt) {
3513 double verify_start = os::elapsedTime();
3514 HandleMark hm; // Discard invalid handles created during verification
3515 prepare_for_verify();
3516 Universe::verify(VerifyOption_G1UsePrevMarking, msg);
3517 verify_time_ms = (os::elapsedTime() - verify_start) * 1000;
3518 }
3520 return verify_time_ms;
3521 }
3523 void G1CollectedHeap::verify_before_gc() {
3524 double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:");
3525 g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms);
3526 }
3528 void G1CollectedHeap::verify_after_gc() {
3529 double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:");
3530 g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms);
3531 }
3533 class PrintRegionClosure: public HeapRegionClosure {
3534 outputStream* _st;
3535 public:
3536 PrintRegionClosure(outputStream* st) : _st(st) {}
3537 bool doHeapRegion(HeapRegion* r) {
3538 r->print_on(_st);
3539 return false;
3540 }
3541 };
3543 void G1CollectedHeap::print_on(outputStream* st) const {
3544 st->print(" %-20s", "garbage-first heap");
3545 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3546 capacity()/K, used_unlocked()/K);
3547 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3548 _g1_storage.low_boundary(),
3549 _g1_storage.high(),
3550 _g1_storage.high_boundary());
3551 st->cr();
3552 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3553 uint young_regions = _young_list->length();
3554 st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3555 (size_t) young_regions * HeapRegion::GrainBytes / K);
3556 uint survivor_regions = g1_policy()->recorded_survivor_regions();
3557 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3558 (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3559 st->cr();
3560 MetaspaceAux::print_on(st);
3561 }
3563 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3564 print_on(st);
3566 // Print the per-region information.
3567 st->cr();
3568 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3569 "HS=humongous(starts), HC=humongous(continues), "
3570 "CS=collection set, F=free, TS=gc time stamp, "
3571 "PTAMS=previous top-at-mark-start, "
3572 "NTAMS=next top-at-mark-start)");
3573 PrintRegionClosure blk(st);
3574 heap_region_iterate(&blk);
3575 }
3577 void G1CollectedHeap::print_on_error(outputStream* st) const {
3578 this->CollectedHeap::print_on_error(st);
3580 if (_cm != NULL) {
3581 st->cr();
3582 _cm->print_on_error(st);
3583 }
3584 }
3586 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3587 if (G1CollectedHeap::use_parallel_gc_threads()) {
3588 workers()->print_worker_threads_on(st);
3589 }
3590 _cmThread->print_on(st);
3591 st->cr();
3592 _cm->print_worker_threads_on(st);
3593 _cg1r->print_worker_threads_on(st);
3594 }
3596 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3597 if (G1CollectedHeap::use_parallel_gc_threads()) {
3598 workers()->threads_do(tc);
3599 }
3600 tc->do_thread(_cmThread);
3601 _cg1r->threads_do(tc);
3602 }
3604 void G1CollectedHeap::print_tracing_info() const {
3605 // We'll overload this to mean "trace GC pause statistics."
3606 if (TraceGen0Time || TraceGen1Time) {
3607 // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3608 // to that.
3609 g1_policy()->print_tracing_info();
3610 }
3611 if (G1SummarizeRSetStats) {
3612 g1_rem_set()->print_summary_info();
3613 }
3614 if (G1SummarizeConcMark) {
3615 concurrent_mark()->print_summary_info();
3616 }
3617 g1_policy()->print_yg_surv_rate_info();
3618 SpecializationStats::print();
3619 }
3621 #ifndef PRODUCT
3622 // Helpful for debugging RSet issues.
3624 class PrintRSetsClosure : public HeapRegionClosure {
3625 private:
3626 const char* _msg;
3627 size_t _occupied_sum;
3629 public:
3630 bool doHeapRegion(HeapRegion* r) {
3631 HeapRegionRemSet* hrrs = r->rem_set();
3632 size_t occupied = hrrs->occupied();
3633 _occupied_sum += occupied;
3635 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3636 HR_FORMAT_PARAMS(r));
3637 if (occupied == 0) {
3638 gclog_or_tty->print_cr(" RSet is empty");
3639 } else {
3640 hrrs->print();
3641 }
3642 gclog_or_tty->print_cr("----------");
3643 return false;
3644 }
3646 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3647 gclog_or_tty->cr();
3648 gclog_or_tty->print_cr("========================================");
3649 gclog_or_tty->print_cr(msg);
3650 gclog_or_tty->cr();
3651 }
3653 ~PrintRSetsClosure() {
3654 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3655 gclog_or_tty->print_cr("========================================");
3656 gclog_or_tty->cr();
3657 }
3658 };
3660 void G1CollectedHeap::print_cset_rsets() {
3661 PrintRSetsClosure cl("Printing CSet RSets");
3662 collection_set_iterate(&cl);
3663 }
3665 void G1CollectedHeap::print_all_rsets() {
3666 PrintRSetsClosure cl("Printing All RSets");;
3667 heap_region_iterate(&cl);
3668 }
3669 #endif // PRODUCT
3671 G1CollectedHeap* G1CollectedHeap::heap() {
3672 assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3673 "not a garbage-first heap");
3674 return _g1h;
3675 }
3677 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3678 // always_do_update_barrier = false;
3679 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3680 // Fill TLAB's and such
3681 ensure_parsability(true);
3682 }
3684 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) {
3686 if (G1SummarizeRSetStats &&
3687 (G1SummarizeRSetStatsPeriod > 0) &&
3688 // we are at the end of the GC. Total collections has already been increased.
3689 ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) {
3690 g1_rem_set()->print_periodic_summary_info();
3691 }
3693 // FIXME: what is this about?
3694 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3695 // is set.
3696 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3697 "derived pointer present"));
3698 // always_do_update_barrier = true;
3700 // We have just completed a GC. Update the soft reference
3701 // policy with the new heap occupancy
3702 Universe::update_heap_info_at_gc();
3703 }
3705 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3706 unsigned int gc_count_before,
3707 bool* succeeded,
3708 GCCause::Cause gc_cause) {
3709 assert_heap_not_locked_and_not_at_safepoint();
3710 g1_policy()->record_stop_world_start();
3711 VM_G1IncCollectionPause op(gc_count_before,
3712 word_size,
3713 false, /* should_initiate_conc_mark */
3714 g1_policy()->max_pause_time_ms(),
3715 gc_cause);
3716 VMThread::execute(&op);
3718 HeapWord* result = op.result();
3719 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3720 assert(result == NULL || ret_succeeded,
3721 "the result should be NULL if the VM did not succeed");
3722 *succeeded = ret_succeeded;
3724 assert_heap_not_locked();
3725 return result;
3726 }
3728 void
3729 G1CollectedHeap::doConcurrentMark() {
3730 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3731 if (!_cmThread->in_progress()) {
3732 _cmThread->set_started();
3733 CGC_lock->notify();
3734 }
3735 }
3737 size_t G1CollectedHeap::pending_card_num() {
3738 size_t extra_cards = 0;
3739 JavaThread *curr = Threads::first();
3740 while (curr != NULL) {
3741 DirtyCardQueue& dcq = curr->dirty_card_queue();
3742 extra_cards += dcq.size();
3743 curr = curr->next();
3744 }
3745 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3746 size_t buffer_size = dcqs.buffer_size();
3747 size_t buffer_num = dcqs.completed_buffers_num();
3749 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
3750 // in bytes - not the number of 'entries'. We need to convert
3751 // into a number of cards.
3752 return (buffer_size * buffer_num + extra_cards) / oopSize;
3753 }
3755 size_t G1CollectedHeap::cards_scanned() {
3756 return g1_rem_set()->cardsScanned();
3757 }
3759 void
3760 G1CollectedHeap::setup_surviving_young_words() {
3761 assert(_surviving_young_words == NULL, "pre-condition");
3762 uint array_length = g1_policy()->young_cset_region_length();
3763 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3764 if (_surviving_young_words == NULL) {
3765 vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR,
3766 "Not enough space for young surv words summary.");
3767 }
3768 memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3769 #ifdef ASSERT
3770 for (uint i = 0; i < array_length; ++i) {
3771 assert( _surviving_young_words[i] == 0, "memset above" );
3772 }
3773 #endif // !ASSERT
3774 }
3776 void
3777 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3778 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3779 uint array_length = g1_policy()->young_cset_region_length();
3780 for (uint i = 0; i < array_length; ++i) {
3781 _surviving_young_words[i] += surv_young_words[i];
3782 }
3783 }
3785 void
3786 G1CollectedHeap::cleanup_surviving_young_words() {
3787 guarantee( _surviving_young_words != NULL, "pre-condition" );
3788 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC);
3789 _surviving_young_words = NULL;
3790 }
3792 #ifdef ASSERT
3793 class VerifyCSetClosure: public HeapRegionClosure {
3794 public:
3795 bool doHeapRegion(HeapRegion* hr) {
3796 // Here we check that the CSet region's RSet is ready for parallel
3797 // iteration. The fields that we'll verify are only manipulated
3798 // when the region is part of a CSet and is collected. Afterwards,
3799 // we reset these fields when we clear the region's RSet (when the
3800 // region is freed) so they are ready when the region is
3801 // re-allocated. The only exception to this is if there's an
3802 // evacuation failure and instead of freeing the region we leave
3803 // it in the heap. In that case, we reset these fields during
3804 // evacuation failure handling.
3805 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3807 // Here's a good place to add any other checks we'd like to
3808 // perform on CSet regions.
3809 return false;
3810 }
3811 };
3812 #endif // ASSERT
3814 #if TASKQUEUE_STATS
3815 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3816 st->print_raw_cr("GC Task Stats");
3817 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3818 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3819 }
3821 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3822 print_taskqueue_stats_hdr(st);
3824 TaskQueueStats totals;
3825 const int n = workers() != NULL ? workers()->total_workers() : 1;
3826 for (int i = 0; i < n; ++i) {
3827 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3828 totals += task_queue(i)->stats;
3829 }
3830 st->print_raw("tot "); totals.print(st); st->cr();
3832 DEBUG_ONLY(totals.verify());
3833 }
3835 void G1CollectedHeap::reset_taskqueue_stats() {
3836 const int n = workers() != NULL ? workers()->total_workers() : 1;
3837 for (int i = 0; i < n; ++i) {
3838 task_queue(i)->stats.reset();
3839 }
3840 }
3841 #endif // TASKQUEUE_STATS
3843 void G1CollectedHeap::log_gc_header() {
3844 if (!G1Log::fine()) {
3845 return;
3846 }
3848 gclog_or_tty->date_stamp(PrintGCDateStamps);
3849 gclog_or_tty->stamp(PrintGCTimeStamps);
3851 GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
3852 .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)")
3853 .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : "");
3855 gclog_or_tty->print("[%s", (const char*)gc_cause_str);
3856 }
3858 void G1CollectedHeap::log_gc_footer(double pause_time_sec) {
3859 if (!G1Log::fine()) {
3860 return;
3861 }
3863 if (G1Log::finer()) {
3864 if (evacuation_failed()) {
3865 gclog_or_tty->print(" (to-space exhausted)");
3866 }
3867 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3868 g1_policy()->phase_times()->note_gc_end();
3869 g1_policy()->phase_times()->print(pause_time_sec);
3870 g1_policy()->print_detailed_heap_transition();
3871 } else {
3872 if (evacuation_failed()) {
3873 gclog_or_tty->print("--");
3874 }
3875 g1_policy()->print_heap_transition();
3876 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3877 }
3878 gclog_or_tty->flush();
3879 }
3881 bool
3882 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3883 assert_at_safepoint(true /* should_be_vm_thread */);
3884 guarantee(!is_gc_active(), "collection is not reentrant");
3886 if (GC_locker::check_active_before_gc()) {
3887 return false;
3888 }
3890 _gc_timer_stw->register_gc_start(os::elapsed_counter());
3892 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3894 SvcGCMarker sgcm(SvcGCMarker::MINOR);
3895 ResourceMark rm;
3897 print_heap_before_gc();
3898 trace_heap_before_gc(_gc_tracer_stw);
3900 HRSPhaseSetter x(HRSPhaseEvacuation);
3901 verify_region_sets_optional();
3902 verify_dirty_young_regions();
3904 // This call will decide whether this pause is an initial-mark
3905 // pause. If it is, during_initial_mark_pause() will return true
3906 // for the duration of this pause.
3907 g1_policy()->decide_on_conc_mark_initiation();
3909 // We do not allow initial-mark to be piggy-backed on a mixed GC.
3910 assert(!g1_policy()->during_initial_mark_pause() ||
3911 g1_policy()->gcs_are_young(), "sanity");
3913 // We also do not allow mixed GCs during marking.
3914 assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3916 // Record whether this pause is an initial mark. When the current
3917 // thread has completed its logging output and it's safe to signal
3918 // the CM thread, the flag's value in the policy has been reset.
3919 bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3921 // Inner scope for scope based logging, timers, and stats collection
3922 {
3923 EvacuationInfo evacuation_info;
3925 if (g1_policy()->during_initial_mark_pause()) {
3926 // We are about to start a marking cycle, so we increment the
3927 // full collection counter.
3928 increment_old_marking_cycles_started();
3929 register_concurrent_cycle_start(_gc_timer_stw->gc_start());
3930 }
3932 _gc_tracer_stw->report_yc_type(yc_type());
3934 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3936 int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
3937 workers()->active_workers() : 1);
3938 double pause_start_sec = os::elapsedTime();
3939 g1_policy()->phase_times()->note_gc_start(active_workers);
3940 log_gc_header();
3942 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3943 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3945 // If the secondary_free_list is not empty, append it to the
3946 // free_list. No need to wait for the cleanup operation to finish;
3947 // the region allocation code will check the secondary_free_list
3948 // and wait if necessary. If the G1StressConcRegionFreeing flag is
3949 // set, skip this step so that the region allocation code has to
3950 // get entries from the secondary_free_list.
3951 if (!G1StressConcRegionFreeing) {
3952 append_secondary_free_list_if_not_empty_with_lock();
3953 }
3955 assert(check_young_list_well_formed(), "young list should be well formed");
3956 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3957 "sanity check");
3959 // Don't dynamically change the number of GC threads this early. A value of
3960 // 0 is used to indicate serial work. When parallel work is done,
3961 // it will be set.
3963 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3964 IsGCActiveMark x;
3966 gc_prologue(false);
3967 increment_total_collections(false /* full gc */);
3968 increment_gc_time_stamp();
3970 verify_before_gc();
3972 COMPILER2_PRESENT(DerivedPointerTable::clear());
3974 // Please see comment in g1CollectedHeap.hpp and
3975 // G1CollectedHeap::ref_processing_init() to see how
3976 // reference processing currently works in G1.
3978 // Enable discovery in the STW reference processor
3979 ref_processor_stw()->enable_discovery(true /*verify_disabled*/,
3980 true /*verify_no_refs*/);
3982 {
3983 // We want to temporarily turn off discovery by the
3984 // CM ref processor, if necessary, and turn it back on
3985 // on again later if we do. Using a scoped
3986 // NoRefDiscovery object will do this.
3987 NoRefDiscovery no_cm_discovery(ref_processor_cm());
3989 // Forget the current alloc region (we might even choose it to be part
3990 // of the collection set!).
3991 release_mutator_alloc_region();
3993 // We should call this after we retire the mutator alloc
3994 // region(s) so that all the ALLOC / RETIRE events are generated
3995 // before the start GC event.
3996 _hr_printer.start_gc(false /* full */, (size_t) total_collections());
3998 // This timing is only used by the ergonomics to handle our pause target.
3999 // It is unclear why this should not include the full pause. We will
4000 // investigate this in CR 7178365.
4001 //
4002 // Preserving the old comment here if that helps the investigation:
4003 //
4004 // The elapsed time induced by the start time below deliberately elides
4005 // the possible verification above.
4006 double sample_start_time_sec = os::elapsedTime();
4008 #if YOUNG_LIST_VERBOSE
4009 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
4010 _young_list->print();
4011 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4012 #endif // YOUNG_LIST_VERBOSE
4014 g1_policy()->record_collection_pause_start(sample_start_time_sec);
4016 double scan_wait_start = os::elapsedTime();
4017 // We have to wait until the CM threads finish scanning the
4018 // root regions as it's the only way to ensure that all the
4019 // objects on them have been correctly scanned before we start
4020 // moving them during the GC.
4021 bool waited = _cm->root_regions()->wait_until_scan_finished();
4022 double wait_time_ms = 0.0;
4023 if (waited) {
4024 double scan_wait_end = os::elapsedTime();
4025 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
4026 }
4027 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
4029 #if YOUNG_LIST_VERBOSE
4030 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
4031 _young_list->print();
4032 #endif // YOUNG_LIST_VERBOSE
4034 if (g1_policy()->during_initial_mark_pause()) {
4035 concurrent_mark()->checkpointRootsInitialPre();
4036 }
4038 #if YOUNG_LIST_VERBOSE
4039 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
4040 _young_list->print();
4041 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4042 #endif // YOUNG_LIST_VERBOSE
4044 g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info);
4046 _cm->note_start_of_gc();
4047 // We should not verify the per-thread SATB buffers given that
4048 // we have not filtered them yet (we'll do so during the
4049 // GC). We also call this after finalize_cset() to
4050 // ensure that the CSet has been finalized.
4051 _cm->verify_no_cset_oops(true /* verify_stacks */,
4052 true /* verify_enqueued_buffers */,
4053 false /* verify_thread_buffers */,
4054 true /* verify_fingers */);
4056 if (_hr_printer.is_active()) {
4057 HeapRegion* hr = g1_policy()->collection_set();
4058 while (hr != NULL) {
4059 G1HRPrinter::RegionType type;
4060 if (!hr->is_young()) {
4061 type = G1HRPrinter::Old;
4062 } else if (hr->is_survivor()) {
4063 type = G1HRPrinter::Survivor;
4064 } else {
4065 type = G1HRPrinter::Eden;
4066 }
4067 _hr_printer.cset(hr);
4068 hr = hr->next_in_collection_set();
4069 }
4070 }
4072 #ifdef ASSERT
4073 VerifyCSetClosure cl;
4074 collection_set_iterate(&cl);
4075 #endif // ASSERT
4077 setup_surviving_young_words();
4079 // Initialize the GC alloc regions.
4080 init_gc_alloc_regions(evacuation_info);
4082 // Actually do the work...
4083 evacuate_collection_set(evacuation_info);
4085 // We do this to mainly verify the per-thread SATB buffers
4086 // (which have been filtered by now) since we didn't verify
4087 // them earlier. No point in re-checking the stacks / enqueued
4088 // buffers given that the CSet has not changed since last time
4089 // we checked.
4090 _cm->verify_no_cset_oops(false /* verify_stacks */,
4091 false /* verify_enqueued_buffers */,
4092 true /* verify_thread_buffers */,
4093 true /* verify_fingers */);
4095 free_collection_set(g1_policy()->collection_set(), evacuation_info);
4096 g1_policy()->clear_collection_set();
4098 cleanup_surviving_young_words();
4100 // Start a new incremental collection set for the next pause.
4101 g1_policy()->start_incremental_cset_building();
4103 // Clear the _cset_fast_test bitmap in anticipation of adding
4104 // regions to the incremental collection set for the next
4105 // evacuation pause.
4106 clear_cset_fast_test();
4108 _young_list->reset_sampled_info();
4110 // Don't check the whole heap at this point as the
4111 // GC alloc regions from this pause have been tagged
4112 // as survivors and moved on to the survivor list.
4113 // Survivor regions will fail the !is_young() check.
4114 assert(check_young_list_empty(false /* check_heap */),
4115 "young list should be empty");
4117 #if YOUNG_LIST_VERBOSE
4118 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
4119 _young_list->print();
4120 #endif // YOUNG_LIST_VERBOSE
4122 g1_policy()->record_survivor_regions(_young_list->survivor_length(),
4123 _young_list->first_survivor_region(),
4124 _young_list->last_survivor_region());
4126 _young_list->reset_auxilary_lists();
4128 if (evacuation_failed()) {
4129 _summary_bytes_used = recalculate_used();
4130 uint n_queues = MAX2((int)ParallelGCThreads, 1);
4131 for (uint i = 0; i < n_queues; i++) {
4132 if (_evacuation_failed_info_array[i].has_failed()) {
4133 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
4134 }
4135 }
4136 } else {
4137 // The "used" of the the collection set have already been subtracted
4138 // when they were freed. Add in the bytes evacuated.
4139 _summary_bytes_used += g1_policy()->bytes_copied_during_gc();
4140 }
4142 if (g1_policy()->during_initial_mark_pause()) {
4143 // We have to do this before we notify the CM threads that
4144 // they can start working to make sure that all the
4145 // appropriate initialization is done on the CM object.
4146 concurrent_mark()->checkpointRootsInitialPost();
4147 set_marking_started();
4148 // Note that we don't actually trigger the CM thread at
4149 // this point. We do that later when we're sure that
4150 // the current thread has completed its logging output.
4151 }
4153 allocate_dummy_regions();
4155 #if YOUNG_LIST_VERBOSE
4156 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
4157 _young_list->print();
4158 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4159 #endif // YOUNG_LIST_VERBOSE
4161 init_mutator_alloc_region();
4163 {
4164 size_t expand_bytes = g1_policy()->expansion_amount();
4165 if (expand_bytes > 0) {
4166 size_t bytes_before = capacity();
4167 // No need for an ergo verbose message here,
4168 // expansion_amount() does this when it returns a value > 0.
4169 if (!expand(expand_bytes)) {
4170 // We failed to expand the heap so let's verify that
4171 // committed/uncommitted amount match the backing store
4172 assert(capacity() == _g1_storage.committed_size(), "committed size mismatch");
4173 assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch");
4174 }
4175 }
4176 }
4178 // We redo the verification but now wrt to the new CSet which
4179 // has just got initialized after the previous CSet was freed.
4180 _cm->verify_no_cset_oops(true /* verify_stacks */,
4181 true /* verify_enqueued_buffers */,
4182 true /* verify_thread_buffers */,
4183 true /* verify_fingers */);
4184 _cm->note_end_of_gc();
4186 // This timing is only used by the ergonomics to handle our pause target.
4187 // It is unclear why this should not include the full pause. We will
4188 // investigate this in CR 7178365.
4189 double sample_end_time_sec = os::elapsedTime();
4190 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
4191 g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info);
4193 MemoryService::track_memory_usage();
4195 // In prepare_for_verify() below we'll need to scan the deferred
4196 // update buffers to bring the RSets up-to-date if
4197 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
4198 // the update buffers we'll probably need to scan cards on the
4199 // regions we just allocated to (i.e., the GC alloc
4200 // regions). However, during the last GC we called
4201 // set_saved_mark() on all the GC alloc regions, so card
4202 // scanning might skip the [saved_mark_word()...top()] area of
4203 // those regions (i.e., the area we allocated objects into
4204 // during the last GC). But it shouldn't. Given that
4205 // saved_mark_word() is conditional on whether the GC time stamp
4206 // on the region is current or not, by incrementing the GC time
4207 // stamp here we invalidate all the GC time stamps on all the
4208 // regions and saved_mark_word() will simply return top() for
4209 // all the regions. This is a nicer way of ensuring this rather
4210 // than iterating over the regions and fixing them. In fact, the
4211 // GC time stamp increment here also ensures that
4212 // saved_mark_word() will return top() between pauses, i.e.,
4213 // during concurrent refinement. So we don't need the
4214 // is_gc_active() check to decided which top to use when
4215 // scanning cards (see CR 7039627).
4216 increment_gc_time_stamp();
4218 verify_after_gc();
4220 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
4221 ref_processor_stw()->verify_no_references_recorded();
4223 // CM reference discovery will be re-enabled if necessary.
4224 }
4226 // We should do this after we potentially expand the heap so
4227 // that all the COMMIT events are generated before the end GC
4228 // event, and after we retire the GC alloc regions so that all
4229 // RETIRE events are generated before the end GC event.
4230 _hr_printer.end_gc(false /* full */, (size_t) total_collections());
4232 if (mark_in_progress()) {
4233 concurrent_mark()->update_g1_committed();
4234 }
4236 #ifdef TRACESPINNING
4237 ParallelTaskTerminator::print_termination_counts();
4238 #endif
4240 gc_epilogue(false);
4241 }
4243 // Print the remainder of the GC log output.
4244 log_gc_footer(os::elapsedTime() - pause_start_sec);
4246 // It is not yet to safe to tell the concurrent mark to
4247 // start as we have some optional output below. We don't want the
4248 // output from the concurrent mark thread interfering with this
4249 // logging output either.
4251 _hrs.verify_optional();
4252 verify_region_sets_optional();
4254 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
4255 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
4257 print_heap_after_gc();
4258 trace_heap_after_gc(_gc_tracer_stw);
4260 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
4261 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
4262 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
4263 // before any GC notifications are raised.
4264 g1mm()->update_sizes();
4266 _gc_tracer_stw->report_evacuation_info(&evacuation_info);
4267 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
4268 _gc_timer_stw->register_gc_end(os::elapsed_counter());
4269 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
4270 }
4271 // It should now be safe to tell the concurrent mark thread to start
4272 // without its logging output interfering with the logging output
4273 // that came from the pause.
4275 if (should_start_conc_mark) {
4276 // CAUTION: after the doConcurrentMark() call below,
4277 // the concurrent marking thread(s) could be running
4278 // concurrently with us. Make sure that anything after
4279 // this point does not assume that we are the only GC thread
4280 // running. Note: of course, the actual marking work will
4281 // not start until the safepoint itself is released in
4282 // ConcurrentGCThread::safepoint_desynchronize().
4283 doConcurrentMark();
4284 }
4286 return true;
4287 }
4289 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
4290 {
4291 size_t gclab_word_size;
4292 switch (purpose) {
4293 case GCAllocForSurvived:
4294 gclab_word_size = _survivor_plab_stats.desired_plab_sz();
4295 break;
4296 case GCAllocForTenured:
4297 gclab_word_size = _old_plab_stats.desired_plab_sz();
4298 break;
4299 default:
4300 assert(false, "unknown GCAllocPurpose");
4301 gclab_word_size = _old_plab_stats.desired_plab_sz();
4302 break;
4303 }
4305 // Prevent humongous PLAB sizes for two reasons:
4306 // * PLABs are allocated using a similar paths as oops, but should
4307 // never be in a humongous region
4308 // * Allowing humongous PLABs needlessly churns the region free lists
4309 return MIN2(_humongous_object_threshold_in_words, gclab_word_size);
4310 }
4312 void G1CollectedHeap::init_mutator_alloc_region() {
4313 assert(_mutator_alloc_region.get() == NULL, "pre-condition");
4314 _mutator_alloc_region.init();
4315 }
4317 void G1CollectedHeap::release_mutator_alloc_region() {
4318 _mutator_alloc_region.release();
4319 assert(_mutator_alloc_region.get() == NULL, "post-condition");
4320 }
4322 void G1CollectedHeap::init_gc_alloc_regions(EvacuationInfo& evacuation_info) {
4323 assert_at_safepoint(true /* should_be_vm_thread */);
4325 _survivor_gc_alloc_region.init();
4326 _old_gc_alloc_region.init();
4327 HeapRegion* retained_region = _retained_old_gc_alloc_region;
4328 _retained_old_gc_alloc_region = NULL;
4330 // We will discard the current GC alloc region if:
4331 // a) it's in the collection set (it can happen!),
4332 // b) it's already full (no point in using it),
4333 // c) it's empty (this means that it was emptied during
4334 // a cleanup and it should be on the free list now), or
4335 // d) it's humongous (this means that it was emptied
4336 // during a cleanup and was added to the free list, but
4337 // has been subsequently used to allocate a humongous
4338 // object that may be less than the region size).
4339 if (retained_region != NULL &&
4340 !retained_region->in_collection_set() &&
4341 !(retained_region->top() == retained_region->end()) &&
4342 !retained_region->is_empty() &&
4343 !retained_region->isHumongous()) {
4344 retained_region->set_saved_mark();
4345 // The retained region was added to the old region set when it was
4346 // retired. We have to remove it now, since we don't allow regions
4347 // we allocate to in the region sets. We'll re-add it later, when
4348 // it's retired again.
4349 _old_set.remove(retained_region);
4350 bool during_im = g1_policy()->during_initial_mark_pause();
4351 retained_region->note_start_of_copying(during_im);
4352 _old_gc_alloc_region.set(retained_region);
4353 _hr_printer.reuse(retained_region);
4354 evacuation_info.set_alloc_regions_used_before(retained_region->used());
4355 }
4356 }
4358 void G1CollectedHeap::release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info) {
4359 evacuation_info.set_allocation_regions(_survivor_gc_alloc_region.count() +
4360 _old_gc_alloc_region.count());
4361 _survivor_gc_alloc_region.release();
4362 // If we have an old GC alloc region to release, we'll save it in
4363 // _retained_old_gc_alloc_region. If we don't
4364 // _retained_old_gc_alloc_region will become NULL. This is what we
4365 // want either way so no reason to check explicitly for either
4366 // condition.
4367 _retained_old_gc_alloc_region = _old_gc_alloc_region.release();
4369 if (ResizePLAB) {
4370 _survivor_plab_stats.adjust_desired_plab_sz(no_of_gc_workers);
4371 _old_plab_stats.adjust_desired_plab_sz(no_of_gc_workers);
4372 }
4373 }
4375 void G1CollectedHeap::abandon_gc_alloc_regions() {
4376 assert(_survivor_gc_alloc_region.get() == NULL, "pre-condition");
4377 assert(_old_gc_alloc_region.get() == NULL, "pre-condition");
4378 _retained_old_gc_alloc_region = NULL;
4379 }
4381 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4382 _drain_in_progress = false;
4383 set_evac_failure_closure(cl);
4384 _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4385 }
4387 void G1CollectedHeap::finalize_for_evac_failure() {
4388 assert(_evac_failure_scan_stack != NULL &&
4389 _evac_failure_scan_stack->length() == 0,
4390 "Postcondition");
4391 assert(!_drain_in_progress, "Postcondition");
4392 delete _evac_failure_scan_stack;
4393 _evac_failure_scan_stack = NULL;
4394 }
4396 void G1CollectedHeap::remove_self_forwarding_pointers() {
4397 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4399 G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4401 if (G1CollectedHeap::use_parallel_gc_threads()) {
4402 set_par_threads();
4403 workers()->run_task(&rsfp_task);
4404 set_par_threads(0);
4405 } else {
4406 rsfp_task.work(0);
4407 }
4409 assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity");
4411 // Reset the claim values in the regions in the collection set.
4412 reset_cset_heap_region_claim_values();
4414 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4416 // Now restore saved marks, if any.
4417 assert(_objs_with_preserved_marks.size() ==
4418 _preserved_marks_of_objs.size(), "Both or none.");
4419 while (!_objs_with_preserved_marks.is_empty()) {
4420 oop obj = _objs_with_preserved_marks.pop();
4421 markOop m = _preserved_marks_of_objs.pop();
4422 obj->set_mark(m);
4423 }
4424 _objs_with_preserved_marks.clear(true);
4425 _preserved_marks_of_objs.clear(true);
4426 }
4428 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4429 _evac_failure_scan_stack->push(obj);
4430 }
4432 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4433 assert(_evac_failure_scan_stack != NULL, "precondition");
4435 while (_evac_failure_scan_stack->length() > 0) {
4436 oop obj = _evac_failure_scan_stack->pop();
4437 _evac_failure_closure->set_region(heap_region_containing(obj));
4438 obj->oop_iterate_backwards(_evac_failure_closure);
4439 }
4440 }
4442 oop
4443 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state,
4444 oop old) {
4445 assert(obj_in_cs(old),
4446 err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4447 (HeapWord*) old));
4448 markOop m = old->mark();
4449 oop forward_ptr = old->forward_to_atomic(old);
4450 if (forward_ptr == NULL) {
4451 // Forward-to-self succeeded.
4452 assert(_par_scan_state != NULL, "par scan state");
4453 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4454 uint queue_num = _par_scan_state->queue_num();
4456 _evacuation_failed = true;
4457 _evacuation_failed_info_array[queue_num].register_copy_failure(old->size());
4458 if (_evac_failure_closure != cl) {
4459 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4460 assert(!_drain_in_progress,
4461 "Should only be true while someone holds the lock.");
4462 // Set the global evac-failure closure to the current thread's.
4463 assert(_evac_failure_closure == NULL, "Or locking has failed.");
4464 set_evac_failure_closure(cl);
4465 // Now do the common part.
4466 handle_evacuation_failure_common(old, m);
4467 // Reset to NULL.
4468 set_evac_failure_closure(NULL);
4469 } else {
4470 // The lock is already held, and this is recursive.
4471 assert(_drain_in_progress, "This should only be the recursive case.");
4472 handle_evacuation_failure_common(old, m);
4473 }
4474 return old;
4475 } else {
4476 // Forward-to-self failed. Either someone else managed to allocate
4477 // space for this object (old != forward_ptr) or they beat us in
4478 // self-forwarding it (old == forward_ptr).
4479 assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4480 err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4481 "should not be in the CSet",
4482 (HeapWord*) old, (HeapWord*) forward_ptr));
4483 return forward_ptr;
4484 }
4485 }
4487 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4488 preserve_mark_if_necessary(old, m);
4490 HeapRegion* r = heap_region_containing(old);
4491 if (!r->evacuation_failed()) {
4492 r->set_evacuation_failed(true);
4493 _hr_printer.evac_failure(r);
4494 }
4496 push_on_evac_failure_scan_stack(old);
4498 if (!_drain_in_progress) {
4499 // prevent recursion in copy_to_survivor_space()
4500 _drain_in_progress = true;
4501 drain_evac_failure_scan_stack();
4502 _drain_in_progress = false;
4503 }
4504 }
4506 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4507 assert(evacuation_failed(), "Oversaving!");
4508 // We want to call the "for_promotion_failure" version only in the
4509 // case of a promotion failure.
4510 if (m->must_be_preserved_for_promotion_failure(obj)) {
4511 _objs_with_preserved_marks.push(obj);
4512 _preserved_marks_of_objs.push(m);
4513 }
4514 }
4516 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
4517 size_t word_size) {
4518 if (purpose == GCAllocForSurvived) {
4519 HeapWord* result = survivor_attempt_allocation(word_size);
4520 if (result != NULL) {
4521 return result;
4522 } else {
4523 // Let's try to allocate in the old gen in case we can fit the
4524 // object there.
4525 return old_attempt_allocation(word_size);
4526 }
4527 } else {
4528 assert(purpose == GCAllocForTenured, "sanity");
4529 HeapWord* result = old_attempt_allocation(word_size);
4530 if (result != NULL) {
4531 return result;
4532 } else {
4533 // Let's try to allocate in the survivors in case we can fit the
4534 // object there.
4535 return survivor_attempt_allocation(word_size);
4536 }
4537 }
4539 ShouldNotReachHere();
4540 // Trying to keep some compilers happy.
4541 return NULL;
4542 }
4544 G1ParGCAllocBuffer::G1ParGCAllocBuffer(size_t gclab_word_size) :
4545 ParGCAllocBuffer(gclab_word_size), _retired(false) { }
4547 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, uint queue_num)
4548 : _g1h(g1h),
4549 _refs(g1h->task_queue(queue_num)),
4550 _dcq(&g1h->dirty_card_queue_set()),
4551 _ct_bs((CardTableModRefBS*)_g1h->barrier_set()),
4552 _g1_rem(g1h->g1_rem_set()),
4553 _hash_seed(17), _queue_num(queue_num),
4554 _term_attempts(0),
4555 _surviving_alloc_buffer(g1h->desired_plab_sz(GCAllocForSurvived)),
4556 _tenured_alloc_buffer(g1h->desired_plab_sz(GCAllocForTenured)),
4557 _age_table(false),
4558 _strong_roots_time(0), _term_time(0),
4559 _alloc_buffer_waste(0), _undo_waste(0) {
4560 // we allocate G1YoungSurvRateNumRegions plus one entries, since
4561 // we "sacrifice" entry 0 to keep track of surviving bytes for
4562 // non-young regions (where the age is -1)
4563 // We also add a few elements at the beginning and at the end in
4564 // an attempt to eliminate cache contention
4565 uint real_length = 1 + _g1h->g1_policy()->young_cset_region_length();
4566 uint array_length = PADDING_ELEM_NUM +
4567 real_length +
4568 PADDING_ELEM_NUM;
4569 _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length, mtGC);
4570 if (_surviving_young_words_base == NULL)
4571 vm_exit_out_of_memory(array_length * sizeof(size_t), OOM_MALLOC_ERROR,
4572 "Not enough space for young surv histo.");
4573 _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM;
4574 memset(_surviving_young_words, 0, (size_t) real_length * sizeof(size_t));
4576 _alloc_buffers[GCAllocForSurvived] = &_surviving_alloc_buffer;
4577 _alloc_buffers[GCAllocForTenured] = &_tenured_alloc_buffer;
4579 _start = os::elapsedTime();
4580 }
4582 void
4583 G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st)
4584 {
4585 st->print_raw_cr("GC Termination Stats");
4586 st->print_raw_cr(" elapsed --strong roots-- -------termination-------"
4587 " ------waste (KiB)------");
4588 st->print_raw_cr("thr ms ms % ms % attempts"
4589 " total alloc undo");
4590 st->print_raw_cr("--- --------- --------- ------ --------- ------ --------"
4591 " ------- ------- -------");
4592 }
4594 void
4595 G1ParScanThreadState::print_termination_stats(int i,
4596 outputStream* const st) const
4597 {
4598 const double elapsed_ms = elapsed_time() * 1000.0;
4599 const double s_roots_ms = strong_roots_time() * 1000.0;
4600 const double term_ms = term_time() * 1000.0;
4601 st->print_cr("%3d %9.2f %9.2f %6.2f "
4602 "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
4603 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
4604 i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms,
4605 term_ms, term_ms * 100 / elapsed_ms, term_attempts(),
4606 (alloc_buffer_waste() + undo_waste()) * HeapWordSize / K,
4607 alloc_buffer_waste() * HeapWordSize / K,
4608 undo_waste() * HeapWordSize / K);
4609 }
4611 #ifdef ASSERT
4612 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const {
4613 assert(ref != NULL, "invariant");
4614 assert(UseCompressedOops, "sanity");
4615 assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, ref));
4616 oop p = oopDesc::load_decode_heap_oop(ref);
4617 assert(_g1h->is_in_g1_reserved(p),
4618 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, (void *)p));
4619 return true;
4620 }
4622 bool G1ParScanThreadState::verify_ref(oop* ref) const {
4623 assert(ref != NULL, "invariant");
4624 if (has_partial_array_mask(ref)) {
4625 // Must be in the collection set--it's already been copied.
4626 oop p = clear_partial_array_mask(ref);
4627 assert(_g1h->obj_in_cs(p),
4628 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, (void *)p));
4629 } else {
4630 oop p = oopDesc::load_decode_heap_oop(ref);
4631 assert(_g1h->is_in_g1_reserved(p),
4632 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, (void *)p));
4633 }
4634 return true;
4635 }
4637 bool G1ParScanThreadState::verify_task(StarTask ref) const {
4638 if (ref.is_narrow()) {
4639 return verify_ref((narrowOop*) ref);
4640 } else {
4641 return verify_ref((oop*) ref);
4642 }
4643 }
4644 #endif // ASSERT
4646 void G1ParScanThreadState::trim_queue() {
4647 assert(_evac_cl != NULL, "not set");
4648 assert(_evac_failure_cl != NULL, "not set");
4649 assert(_partial_scan_cl != NULL, "not set");
4651 StarTask ref;
4652 do {
4653 // Drain the overflow stack first, so other threads can steal.
4654 while (refs()->pop_overflow(ref)) {
4655 deal_with_reference(ref);
4656 }
4658 while (refs()->pop_local(ref)) {
4659 deal_with_reference(ref);
4660 }
4661 } while (!refs()->is_empty());
4662 }
4664 G1ParClosureSuper::G1ParClosureSuper(G1CollectedHeap* g1,
4665 G1ParScanThreadState* par_scan_state) :
4666 _g1(g1), _g1_rem(_g1->g1_rem_set()), _cm(_g1->concurrent_mark()),
4667 _par_scan_state(par_scan_state),
4668 _worker_id(par_scan_state->queue_num()),
4669 _during_initial_mark(_g1->g1_policy()->during_initial_mark_pause()),
4670 _mark_in_progress(_g1->mark_in_progress()) { }
4672 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4673 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>::mark_object(oop obj) {
4674 #ifdef ASSERT
4675 HeapRegion* hr = _g1->heap_region_containing(obj);
4676 assert(hr != NULL, "sanity");
4677 assert(!hr->in_collection_set(), "should not mark objects in the CSet");
4678 #endif // ASSERT
4680 // We know that the object is not moving so it's safe to read its size.
4681 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4682 }
4684 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4685 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4686 ::mark_forwarded_object(oop from_obj, oop to_obj) {
4687 #ifdef ASSERT
4688 assert(from_obj->is_forwarded(), "from obj should be forwarded");
4689 assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4690 assert(from_obj != to_obj, "should not be self-forwarded");
4692 HeapRegion* from_hr = _g1->heap_region_containing(from_obj);
4693 assert(from_hr != NULL, "sanity");
4694 assert(from_hr->in_collection_set(), "from obj should be in the CSet");
4696 HeapRegion* to_hr = _g1->heap_region_containing(to_obj);
4697 assert(to_hr != NULL, "sanity");
4698 assert(!to_hr->in_collection_set(), "should not mark objects in the CSet");
4699 #endif // ASSERT
4701 // The object might be in the process of being copied by another
4702 // worker so we cannot trust that its to-space image is
4703 // well-formed. So we have to read its size from its from-space
4704 // image which we know should not be changing.
4705 _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4706 }
4708 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4709 oop G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4710 ::copy_to_survivor_space(oop old) {
4711 size_t word_sz = old->size();
4712 HeapRegion* from_region = _g1->heap_region_containing_raw(old);
4713 // +1 to make the -1 indexes valid...
4714 int young_index = from_region->young_index_in_cset()+1;
4715 assert( (from_region->is_young() && young_index > 0) ||
4716 (!from_region->is_young() && young_index == 0), "invariant" );
4717 G1CollectorPolicy* g1p = _g1->g1_policy();
4718 markOop m = old->mark();
4719 int age = m->has_displaced_mark_helper() ? m->displaced_mark_helper()->age()
4720 : m->age();
4721 GCAllocPurpose alloc_purpose = g1p->evacuation_destination(from_region, age,
4722 word_sz);
4723 HeapWord* obj_ptr = _par_scan_state->allocate(alloc_purpose, word_sz);
4724 #ifndef PRODUCT
4725 // Should this evacuation fail?
4726 if (_g1->evacuation_should_fail()) {
4727 if (obj_ptr != NULL) {
4728 _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz);
4729 obj_ptr = NULL;
4730 }
4731 }
4732 #endif // !PRODUCT
4734 if (obj_ptr == NULL) {
4735 // This will either forward-to-self, or detect that someone else has
4736 // installed a forwarding pointer.
4737 return _g1->handle_evacuation_failure_par(_par_scan_state, old);
4738 }
4740 oop obj = oop(obj_ptr);
4742 // We're going to allocate linearly, so might as well prefetch ahead.
4743 Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
4745 oop forward_ptr = old->forward_to_atomic(obj);
4746 if (forward_ptr == NULL) {
4747 Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
4748 if (g1p->track_object_age(alloc_purpose)) {
4749 // We could simply do obj->incr_age(). However, this causes a
4750 // performance issue. obj->incr_age() will first check whether
4751 // the object has a displaced mark by checking its mark word;
4752 // getting the mark word from the new location of the object
4753 // stalls. So, given that we already have the mark word and we
4754 // are about to install it anyway, it's better to increase the
4755 // age on the mark word, when the object does not have a
4756 // displaced mark word. We're not expecting many objects to have
4757 // a displaced marked word, so that case is not optimized
4758 // further (it could be...) and we simply call obj->incr_age().
4760 if (m->has_displaced_mark_helper()) {
4761 // in this case, we have to install the mark word first,
4762 // otherwise obj looks to be forwarded (the old mark word,
4763 // which contains the forward pointer, was copied)
4764 obj->set_mark(m);
4765 obj->incr_age();
4766 } else {
4767 m = m->incr_age();
4768 obj->set_mark(m);
4769 }
4770 _par_scan_state->age_table()->add(obj, word_sz);
4771 } else {
4772 obj->set_mark(m);
4773 }
4775 size_t* surv_young_words = _par_scan_state->surviving_young_words();
4776 surv_young_words[young_index] += word_sz;
4778 if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
4779 // We keep track of the next start index in the length field of
4780 // the to-space object. The actual length can be found in the
4781 // length field of the from-space object.
4782 arrayOop(obj)->set_length(0);
4783 oop* old_p = set_partial_array_mask(old);
4784 _par_scan_state->push_on_queue(old_p);
4785 } else {
4786 // No point in using the slower heap_region_containing() method,
4787 // given that we know obj is in the heap.
4788 _scanner.set_region(_g1->heap_region_containing_raw(obj));
4789 obj->oop_iterate_backwards(&_scanner);
4790 }
4791 } else {
4792 _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz);
4793 obj = forward_ptr;
4794 }
4795 return obj;
4796 }
4798 template <class T>
4799 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) {
4800 if (_g1->heap_region_containing_raw(new_obj)->is_young()) {
4801 _scanned_klass->record_modified_oops();
4802 }
4803 }
4805 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4806 template <class T>
4807 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4808 ::do_oop_work(T* p) {
4809 oop obj = oopDesc::load_decode_heap_oop(p);
4810 assert(barrier != G1BarrierRS || obj != NULL,
4811 "Precondition: G1BarrierRS implies obj is non-NULL");
4813 assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4815 // here the null check is implicit in the cset_fast_test() test
4816 if (_g1->in_cset_fast_test(obj)) {
4817 oop forwardee;
4818 if (obj->is_forwarded()) {
4819 forwardee = obj->forwardee();
4820 } else {
4821 forwardee = copy_to_survivor_space(obj);
4822 }
4823 assert(forwardee != NULL, "forwardee should not be NULL");
4824 oopDesc::encode_store_heap_oop(p, forwardee);
4825 if (do_mark_object && forwardee != obj) {
4826 // If the object is self-forwarded we don't need to explicitly
4827 // mark it, the evacuation failure protocol will do so.
4828 mark_forwarded_object(obj, forwardee);
4829 }
4831 // When scanning the RS, we only care about objs in CS.
4832 if (barrier == G1BarrierRS) {
4833 _par_scan_state->update_rs(_from, p, _worker_id);
4834 } else if (barrier == G1BarrierKlass) {
4835 do_klass_barrier(p, forwardee);
4836 }
4837 } else {
4838 // The object is not in collection set. If we're a root scanning
4839 // closure during an initial mark pause (i.e. do_mark_object will
4840 // be true) then attempt to mark the object.
4841 if (do_mark_object && _g1->is_in_g1_reserved(obj)) {
4842 mark_object(obj);
4843 }
4844 }
4846 if (barrier == G1BarrierEvac && obj != NULL) {
4847 _par_scan_state->update_rs(_from, p, _worker_id);
4848 }
4850 if (do_gen_barrier && obj != NULL) {
4851 par_do_barrier(p);
4852 }
4853 }
4855 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(oop* p);
4856 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(narrowOop* p);
4858 template <class T> void G1ParScanPartialArrayClosure::do_oop_nv(T* p) {
4859 assert(has_partial_array_mask(p), "invariant");
4860 oop from_obj = clear_partial_array_mask(p);
4862 assert(Universe::heap()->is_in_reserved(from_obj), "must be in heap.");
4863 assert(from_obj->is_objArray(), "must be obj array");
4864 objArrayOop from_obj_array = objArrayOop(from_obj);
4865 // The from-space object contains the real length.
4866 int length = from_obj_array->length();
4868 assert(from_obj->is_forwarded(), "must be forwarded");
4869 oop to_obj = from_obj->forwardee();
4870 assert(from_obj != to_obj, "should not be chunking self-forwarded objects");
4871 objArrayOop to_obj_array = objArrayOop(to_obj);
4872 // We keep track of the next start index in the length field of the
4873 // to-space object.
4874 int next_index = to_obj_array->length();
4875 assert(0 <= next_index && next_index < length,
4876 err_msg("invariant, next index: %d, length: %d", next_index, length));
4878 int start = next_index;
4879 int end = length;
4880 int remainder = end - start;
4881 // We'll try not to push a range that's smaller than ParGCArrayScanChunk.
4882 if (remainder > 2 * ParGCArrayScanChunk) {
4883 end = start + ParGCArrayScanChunk;
4884 to_obj_array->set_length(end);
4885 // Push the remainder before we process the range in case another
4886 // worker has run out of things to do and can steal it.
4887 oop* from_obj_p = set_partial_array_mask(from_obj);
4888 _par_scan_state->push_on_queue(from_obj_p);
4889 } else {
4890 assert(length == end, "sanity");
4891 // We'll process the final range for this object. Restore the length
4892 // so that the heap remains parsable in case of evacuation failure.
4893 to_obj_array->set_length(end);
4894 }
4895 _scanner.set_region(_g1->heap_region_containing_raw(to_obj));
4896 // Process indexes [start,end). It will also process the header
4897 // along with the first chunk (i.e., the chunk with start == 0).
4898 // Note that at this point the length field of to_obj_array is not
4899 // correct given that we are using it to keep track of the next
4900 // start index. oop_iterate_range() (thankfully!) ignores the length
4901 // field and only relies on the start / end parameters. It does
4902 // however return the size of the object which will be incorrect. So
4903 // we have to ignore it even if we wanted to use it.
4904 to_obj_array->oop_iterate_range(&_scanner, start, end);
4905 }
4907 class G1ParEvacuateFollowersClosure : public VoidClosure {
4908 protected:
4909 G1CollectedHeap* _g1h;
4910 G1ParScanThreadState* _par_scan_state;
4911 RefToScanQueueSet* _queues;
4912 ParallelTaskTerminator* _terminator;
4914 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
4915 RefToScanQueueSet* queues() { return _queues; }
4916 ParallelTaskTerminator* terminator() { return _terminator; }
4918 public:
4919 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4920 G1ParScanThreadState* par_scan_state,
4921 RefToScanQueueSet* queues,
4922 ParallelTaskTerminator* terminator)
4923 : _g1h(g1h), _par_scan_state(par_scan_state),
4924 _queues(queues), _terminator(terminator) {}
4926 void do_void();
4928 private:
4929 inline bool offer_termination();
4930 };
4932 bool G1ParEvacuateFollowersClosure::offer_termination() {
4933 G1ParScanThreadState* const pss = par_scan_state();
4934 pss->start_term_time();
4935 const bool res = terminator()->offer_termination();
4936 pss->end_term_time();
4937 return res;
4938 }
4940 void G1ParEvacuateFollowersClosure::do_void() {
4941 StarTask stolen_task;
4942 G1ParScanThreadState* const pss = par_scan_state();
4943 pss->trim_queue();
4945 do {
4946 while (queues()->steal(pss->queue_num(), pss->hash_seed(), stolen_task)) {
4947 assert(pss->verify_task(stolen_task), "sanity");
4948 if (stolen_task.is_narrow()) {
4949 pss->deal_with_reference((narrowOop*) stolen_task);
4950 } else {
4951 pss->deal_with_reference((oop*) stolen_task);
4952 }
4954 // We've just processed a reference and we might have made
4955 // available new entries on the queues. So we have to make sure
4956 // we drain the queues as necessary.
4957 pss->trim_queue();
4958 }
4959 } while (!offer_termination());
4961 pss->retire_alloc_buffers();
4962 }
4964 class G1KlassScanClosure : public KlassClosure {
4965 G1ParCopyHelper* _closure;
4966 bool _process_only_dirty;
4967 int _count;
4968 public:
4969 G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty)
4970 : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {}
4971 void do_klass(Klass* klass) {
4972 // If the klass has not been dirtied we know that there's
4973 // no references into the young gen and we can skip it.
4974 if (!_process_only_dirty || klass->has_modified_oops()) {
4975 // Clean the klass since we're going to scavenge all the metadata.
4976 klass->clear_modified_oops();
4978 // Tell the closure that this klass is the Klass to scavenge
4979 // and is the one to dirty if oops are left pointing into the young gen.
4980 _closure->set_scanned_klass(klass);
4982 klass->oops_do(_closure);
4984 _closure->set_scanned_klass(NULL);
4985 }
4986 _count++;
4987 }
4988 };
4990 class G1ParTask : public AbstractGangTask {
4991 protected:
4992 G1CollectedHeap* _g1h;
4993 RefToScanQueueSet *_queues;
4994 ParallelTaskTerminator _terminator;
4995 uint _n_workers;
4997 Mutex _stats_lock;
4998 Mutex* stats_lock() { return &_stats_lock; }
5000 size_t getNCards() {
5001 return (_g1h->capacity() + G1BlockOffsetSharedArray::N_bytes - 1)
5002 / G1BlockOffsetSharedArray::N_bytes;
5003 }
5005 public:
5006 G1ParTask(G1CollectedHeap* g1h,
5007 RefToScanQueueSet *task_queues)
5008 : AbstractGangTask("G1 collection"),
5009 _g1h(g1h),
5010 _queues(task_queues),
5011 _terminator(0, _queues),
5012 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
5013 {}
5015 RefToScanQueueSet* queues() { return _queues; }
5017 RefToScanQueue *work_queue(int i) {
5018 return queues()->queue(i);
5019 }
5021 ParallelTaskTerminator* terminator() { return &_terminator; }
5023 virtual void set_for_termination(int active_workers) {
5024 // This task calls set_n_termination() in par_non_clean_card_iterate_work()
5025 // in the young space (_par_seq_tasks) in the G1 heap
5026 // for SequentialSubTasksDone.
5027 // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap
5028 // both of which need setting by set_n_termination().
5029 _g1h->SharedHeap::set_n_termination(active_workers);
5030 _g1h->set_n_termination(active_workers);
5031 terminator()->reset_for_reuse(active_workers);
5032 _n_workers = active_workers;
5033 }
5035 void work(uint worker_id) {
5036 if (worker_id >= _n_workers) return; // no work needed this round
5038 double start_time_ms = os::elapsedTime() * 1000.0;
5039 _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms);
5041 {
5042 ResourceMark rm;
5043 HandleMark hm;
5045 ReferenceProcessor* rp = _g1h->ref_processor_stw();
5047 G1ParScanThreadState pss(_g1h, worker_id);
5048 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, rp);
5049 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
5050 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, rp);
5052 pss.set_evac_closure(&scan_evac_cl);
5053 pss.set_evac_failure_closure(&evac_failure_cl);
5054 pss.set_partial_scan_closure(&partial_scan_cl);
5056 G1ParScanExtRootClosure only_scan_root_cl(_g1h, &pss, rp);
5057 G1ParScanMetadataClosure only_scan_metadata_cl(_g1h, &pss, rp);
5059 G1ParScanAndMarkExtRootClosure scan_mark_root_cl(_g1h, &pss, rp);
5060 G1ParScanAndMarkMetadataClosure scan_mark_metadata_cl(_g1h, &pss, rp);
5062 bool only_young = _g1h->g1_policy()->gcs_are_young();
5063 G1KlassScanClosure scan_mark_klasses_cl_s(&scan_mark_metadata_cl, false);
5064 G1KlassScanClosure only_scan_klasses_cl_s(&only_scan_metadata_cl, only_young);
5066 OopClosure* scan_root_cl = &only_scan_root_cl;
5067 G1KlassScanClosure* scan_klasses_cl = &only_scan_klasses_cl_s;
5069 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5070 // We also need to mark copied objects.
5071 scan_root_cl = &scan_mark_root_cl;
5072 scan_klasses_cl = &scan_mark_klasses_cl_s;
5073 }
5075 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss);
5077 // Don't scan the scavengable methods in the code cache as part
5078 // of strong root scanning. The code roots that point into a
5079 // region in the collection set are scanned when we scan the
5080 // region's RSet.
5081 int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings;
5083 pss.start_strong_roots();
5084 _g1h->g1_process_strong_roots(/* is scavenging */ true,
5085 SharedHeap::ScanningOption(so),
5086 scan_root_cl,
5087 &push_heap_rs_cl,
5088 scan_klasses_cl,
5089 worker_id);
5090 pss.end_strong_roots();
5092 {
5093 double start = os::elapsedTime();
5094 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
5095 evac.do_void();
5096 double elapsed_ms = (os::elapsedTime()-start)*1000.0;
5097 double term_ms = pss.term_time()*1000.0;
5098 _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms);
5099 _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts());
5100 }
5101 _g1h->g1_policy()->record_thread_age_table(pss.age_table());
5102 _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
5104 if (ParallelGCVerbose) {
5105 MutexLocker x(stats_lock());
5106 pss.print_termination_stats(worker_id);
5107 }
5109 assert(pss.refs()->is_empty(), "should be empty");
5111 // Close the inner scope so that the ResourceMark and HandleMark
5112 // destructors are executed here and are included as part of the
5113 // "GC Worker Time".
5114 }
5116 double end_time_ms = os::elapsedTime() * 1000.0;
5117 _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms);
5118 }
5119 };
5121 // *** Common G1 Evacuation Stuff
5123 // This method is run in a GC worker.
5125 void
5126 G1CollectedHeap::
5127 g1_process_strong_roots(bool is_scavenging,
5128 ScanningOption so,
5129 OopClosure* scan_non_heap_roots,
5130 OopsInHeapRegionClosure* scan_rs,
5131 G1KlassScanClosure* scan_klasses,
5132 int worker_i) {
5134 // First scan the strong roots
5135 double ext_roots_start = os::elapsedTime();
5136 double closure_app_time_sec = 0.0;
5138 BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
5140 assert(so & SO_CodeCache || scan_rs != NULL, "must scan code roots somehow");
5141 // Walk the code cache/strong code roots w/o buffering, because StarTask
5142 // cannot handle unaligned oop locations.
5143 CodeBlobToOopClosure eager_scan_code_roots(scan_non_heap_roots, true /* do_marking */);
5145 process_strong_roots(false, // no scoping; this is parallel code
5146 is_scavenging, so,
5147 &buf_scan_non_heap_roots,
5148 &eager_scan_code_roots,
5149 scan_klasses
5150 );
5152 // Now the CM ref_processor roots.
5153 if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
5154 // We need to treat the discovered reference lists of the
5155 // concurrent mark ref processor as roots and keep entries
5156 // (which are added by the marking threads) on them live
5157 // until they can be processed at the end of marking.
5158 ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
5159 }
5161 // Finish up any enqueued closure apps (attributed as object copy time).
5162 buf_scan_non_heap_roots.done();
5164 double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds();
5166 g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
5168 double ext_root_time_ms =
5169 ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0;
5171 g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
5173 // During conc marking we have to filter the per-thread SATB buffers
5174 // to make sure we remove any oops into the CSet (which will show up
5175 // as implicitly live).
5176 double satb_filtering_ms = 0.0;
5177 if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) {
5178 if (mark_in_progress()) {
5179 double satb_filter_start = os::elapsedTime();
5181 JavaThread::satb_mark_queue_set().filter_thread_buffers();
5183 satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0;
5184 }
5185 }
5186 g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms);
5188 // If this is an initial mark pause, and we're not scanning
5189 // the entire code cache, we need to mark the oops in the
5190 // strong code root lists for the regions that are not in
5191 // the collection set.
5192 // Note all threads participate in this set of root tasks.
5193 double mark_strong_code_roots_ms = 0.0;
5194 if (g1_policy()->during_initial_mark_pause() && !(so & SO_CodeCache)) {
5195 double mark_strong_roots_start = os::elapsedTime();
5196 mark_strong_code_roots(worker_i);
5197 mark_strong_code_roots_ms = (os::elapsedTime() - mark_strong_roots_start) * 1000.0;
5198 }
5199 g1_policy()->phase_times()->record_strong_code_root_mark_time(worker_i, mark_strong_code_roots_ms);
5201 // Now scan the complement of the collection set.
5202 if (scan_rs != NULL) {
5203 g1_rem_set()->oops_into_collection_set_do(scan_rs, &eager_scan_code_roots, worker_i);
5204 }
5205 _process_strong_tasks->all_tasks_completed();
5206 }
5208 void
5209 G1CollectedHeap::g1_process_weak_roots(OopClosure* root_closure) {
5210 CodeBlobToOopClosure roots_in_blobs(root_closure, /*do_marking=*/ false);
5211 SharedHeap::process_weak_roots(root_closure, &roots_in_blobs);
5212 }
5214 // Weak Reference Processing support
5216 // An always "is_alive" closure that is used to preserve referents.
5217 // If the object is non-null then it's alive. Used in the preservation
5218 // of referent objects that are pointed to by reference objects
5219 // discovered by the CM ref processor.
5220 class G1AlwaysAliveClosure: public BoolObjectClosure {
5221 G1CollectedHeap* _g1;
5222 public:
5223 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5224 bool do_object_b(oop p) {
5225 if (p != NULL) {
5226 return true;
5227 }
5228 return false;
5229 }
5230 };
5232 bool G1STWIsAliveClosure::do_object_b(oop p) {
5233 // An object is reachable if it is outside the collection set,
5234 // or is inside and copied.
5235 return !_g1->obj_in_cs(p) || p->is_forwarded();
5236 }
5238 // Non Copying Keep Alive closure
5239 class G1KeepAliveClosure: public OopClosure {
5240 G1CollectedHeap* _g1;
5241 public:
5242 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5243 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
5244 void do_oop( oop* p) {
5245 oop obj = *p;
5247 if (_g1->obj_in_cs(obj)) {
5248 assert( obj->is_forwarded(), "invariant" );
5249 *p = obj->forwardee();
5250 }
5251 }
5252 };
5254 // Copying Keep Alive closure - can be called from both
5255 // serial and parallel code as long as different worker
5256 // threads utilize different G1ParScanThreadState instances
5257 // and different queues.
5259 class G1CopyingKeepAliveClosure: public OopClosure {
5260 G1CollectedHeap* _g1h;
5261 OopClosure* _copy_non_heap_obj_cl;
5262 OopsInHeapRegionClosure* _copy_metadata_obj_cl;
5263 G1ParScanThreadState* _par_scan_state;
5265 public:
5266 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
5267 OopClosure* non_heap_obj_cl,
5268 OopsInHeapRegionClosure* metadata_obj_cl,
5269 G1ParScanThreadState* pss):
5270 _g1h(g1h),
5271 _copy_non_heap_obj_cl(non_heap_obj_cl),
5272 _copy_metadata_obj_cl(metadata_obj_cl),
5273 _par_scan_state(pss)
5274 {}
5276 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
5277 virtual void do_oop( oop* p) { do_oop_work(p); }
5279 template <class T> void do_oop_work(T* p) {
5280 oop obj = oopDesc::load_decode_heap_oop(p);
5282 if (_g1h->obj_in_cs(obj)) {
5283 // If the referent object has been forwarded (either copied
5284 // to a new location or to itself in the event of an
5285 // evacuation failure) then we need to update the reference
5286 // field and, if both reference and referent are in the G1
5287 // heap, update the RSet for the referent.
5288 //
5289 // If the referent has not been forwarded then we have to keep
5290 // it alive by policy. Therefore we have copy the referent.
5291 //
5292 // If the reference field is in the G1 heap then we can push
5293 // on the PSS queue. When the queue is drained (after each
5294 // phase of reference processing) the object and it's followers
5295 // will be copied, the reference field set to point to the
5296 // new location, and the RSet updated. Otherwise we need to
5297 // use the the non-heap or metadata closures directly to copy
5298 // the referent object and update the pointer, while avoiding
5299 // updating the RSet.
5301 if (_g1h->is_in_g1_reserved(p)) {
5302 _par_scan_state->push_on_queue(p);
5303 } else {
5304 assert(!ClassLoaderDataGraph::contains((address)p),
5305 err_msg("Otherwise need to call _copy_metadata_obj_cl->do_oop(p) "
5306 PTR_FORMAT, p));
5307 _copy_non_heap_obj_cl->do_oop(p);
5308 }
5309 }
5310 }
5311 };
5313 // Serial drain queue closure. Called as the 'complete_gc'
5314 // closure for each discovered list in some of the
5315 // reference processing phases.
5317 class G1STWDrainQueueClosure: public VoidClosure {
5318 protected:
5319 G1CollectedHeap* _g1h;
5320 G1ParScanThreadState* _par_scan_state;
5322 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
5324 public:
5325 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
5326 _g1h(g1h),
5327 _par_scan_state(pss)
5328 { }
5330 void do_void() {
5331 G1ParScanThreadState* const pss = par_scan_state();
5332 pss->trim_queue();
5333 }
5334 };
5336 // Parallel Reference Processing closures
5338 // Implementation of AbstractRefProcTaskExecutor for parallel reference
5339 // processing during G1 evacuation pauses.
5341 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5342 private:
5343 G1CollectedHeap* _g1h;
5344 RefToScanQueueSet* _queues;
5345 FlexibleWorkGang* _workers;
5346 int _active_workers;
5348 public:
5349 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5350 FlexibleWorkGang* workers,
5351 RefToScanQueueSet *task_queues,
5352 int n_workers) :
5353 _g1h(g1h),
5354 _queues(task_queues),
5355 _workers(workers),
5356 _active_workers(n_workers)
5357 {
5358 assert(n_workers > 0, "shouldn't call this otherwise");
5359 }
5361 // Executes the given task using concurrent marking worker threads.
5362 virtual void execute(ProcessTask& task);
5363 virtual void execute(EnqueueTask& task);
5364 };
5366 // Gang task for possibly parallel reference processing
5368 class G1STWRefProcTaskProxy: public AbstractGangTask {
5369 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5370 ProcessTask& _proc_task;
5371 G1CollectedHeap* _g1h;
5372 RefToScanQueueSet *_task_queues;
5373 ParallelTaskTerminator* _terminator;
5375 public:
5376 G1STWRefProcTaskProxy(ProcessTask& proc_task,
5377 G1CollectedHeap* g1h,
5378 RefToScanQueueSet *task_queues,
5379 ParallelTaskTerminator* terminator) :
5380 AbstractGangTask("Process reference objects in parallel"),
5381 _proc_task(proc_task),
5382 _g1h(g1h),
5383 _task_queues(task_queues),
5384 _terminator(terminator)
5385 {}
5387 virtual void work(uint worker_id) {
5388 // The reference processing task executed by a single worker.
5389 ResourceMark rm;
5390 HandleMark hm;
5392 G1STWIsAliveClosure is_alive(_g1h);
5394 G1ParScanThreadState pss(_g1h, worker_id);
5396 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, NULL);
5397 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5398 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, NULL);
5400 pss.set_evac_closure(&scan_evac_cl);
5401 pss.set_evac_failure_closure(&evac_failure_cl);
5402 pss.set_partial_scan_closure(&partial_scan_cl);
5404 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5405 G1ParScanMetadataClosure only_copy_metadata_cl(_g1h, &pss, NULL);
5407 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5408 G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(_g1h, &pss, NULL);
5410 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5411 OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl;
5413 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5414 // We also need to mark copied objects.
5415 copy_non_heap_cl = ©_mark_non_heap_cl;
5416 copy_metadata_cl = ©_mark_metadata_cl;
5417 }
5419 // Keep alive closure.
5420 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_metadata_cl, &pss);
5422 // Complete GC closure
5423 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5425 // Call the reference processing task's work routine.
5426 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5428 // Note we cannot assert that the refs array is empty here as not all
5429 // of the processing tasks (specifically phase2 - pp2_work) execute
5430 // the complete_gc closure (which ordinarily would drain the queue) so
5431 // the queue may not be empty.
5432 }
5433 };
5435 // Driver routine for parallel reference processing.
5436 // Creates an instance of the ref processing gang
5437 // task and has the worker threads execute it.
5438 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5439 assert(_workers != NULL, "Need parallel worker threads.");
5441 ParallelTaskTerminator terminator(_active_workers, _queues);
5442 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5444 _g1h->set_par_threads(_active_workers);
5445 _workers->run_task(&proc_task_proxy);
5446 _g1h->set_par_threads(0);
5447 }
5449 // Gang task for parallel reference enqueueing.
5451 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5452 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5453 EnqueueTask& _enq_task;
5455 public:
5456 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5457 AbstractGangTask("Enqueue reference objects in parallel"),
5458 _enq_task(enq_task)
5459 { }
5461 virtual void work(uint worker_id) {
5462 _enq_task.work(worker_id);
5463 }
5464 };
5466 // Driver routine for parallel reference enqueueing.
5467 // Creates an instance of the ref enqueueing gang
5468 // task and has the worker threads execute it.
5470 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5471 assert(_workers != NULL, "Need parallel worker threads.");
5473 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5475 _g1h->set_par_threads(_active_workers);
5476 _workers->run_task(&enq_task_proxy);
5477 _g1h->set_par_threads(0);
5478 }
5480 // End of weak reference support closures
5482 // Abstract task used to preserve (i.e. copy) any referent objects
5483 // that are in the collection set and are pointed to by reference
5484 // objects discovered by the CM ref processor.
5486 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5487 protected:
5488 G1CollectedHeap* _g1h;
5489 RefToScanQueueSet *_queues;
5490 ParallelTaskTerminator _terminator;
5491 uint _n_workers;
5493 public:
5494 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
5495 AbstractGangTask("ParPreserveCMReferents"),
5496 _g1h(g1h),
5497 _queues(task_queues),
5498 _terminator(workers, _queues),
5499 _n_workers(workers)
5500 { }
5502 void work(uint worker_id) {
5503 ResourceMark rm;
5504 HandleMark hm;
5506 G1ParScanThreadState pss(_g1h, worker_id);
5507 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss, NULL);
5508 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5509 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss, NULL);
5511 pss.set_evac_closure(&scan_evac_cl);
5512 pss.set_evac_failure_closure(&evac_failure_cl);
5513 pss.set_partial_scan_closure(&partial_scan_cl);
5515 assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5518 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5519 G1ParScanMetadataClosure only_copy_metadata_cl(_g1h, &pss, NULL);
5521 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5522 G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(_g1h, &pss, NULL);
5524 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5525 OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl;
5527 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5528 // We also need to mark copied objects.
5529 copy_non_heap_cl = ©_mark_non_heap_cl;
5530 copy_metadata_cl = ©_mark_metadata_cl;
5531 }
5533 // Is alive closure
5534 G1AlwaysAliveClosure always_alive(_g1h);
5536 // Copying keep alive closure. Applied to referent objects that need
5537 // to be copied.
5538 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_metadata_cl, &pss);
5540 ReferenceProcessor* rp = _g1h->ref_processor_cm();
5542 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5543 uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5545 // limit is set using max_num_q() - which was set using ParallelGCThreads.
5546 // So this must be true - but assert just in case someone decides to
5547 // change the worker ids.
5548 assert(0 <= worker_id && worker_id < limit, "sanity");
5549 assert(!rp->discovery_is_atomic(), "check this code");
5551 // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5552 for (uint idx = worker_id; idx < limit; idx += stride) {
5553 DiscoveredList& ref_list = rp->discovered_refs()[idx];
5555 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5556 while (iter.has_next()) {
5557 // Since discovery is not atomic for the CM ref processor, we
5558 // can see some null referent objects.
5559 iter.load_ptrs(DEBUG_ONLY(true));
5560 oop ref = iter.obj();
5562 // This will filter nulls.
5563 if (iter.is_referent_alive()) {
5564 iter.make_referent_alive();
5565 }
5566 iter.move_to_next();
5567 }
5568 }
5570 // Drain the queue - which may cause stealing
5571 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5572 drain_queue.do_void();
5573 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5574 assert(pss.refs()->is_empty(), "should be");
5575 }
5576 };
5578 // Weak Reference processing during an evacuation pause (part 1).
5579 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) {
5580 double ref_proc_start = os::elapsedTime();
5582 ReferenceProcessor* rp = _ref_processor_stw;
5583 assert(rp->discovery_enabled(), "should have been enabled");
5585 // Any reference objects, in the collection set, that were 'discovered'
5586 // by the CM ref processor should have already been copied (either by
5587 // applying the external root copy closure to the discovered lists, or
5588 // by following an RSet entry).
5589 //
5590 // But some of the referents, that are in the collection set, that these
5591 // reference objects point to may not have been copied: the STW ref
5592 // processor would have seen that the reference object had already
5593 // been 'discovered' and would have skipped discovering the reference,
5594 // but would not have treated the reference object as a regular oop.
5595 // As a result the copy closure would not have been applied to the
5596 // referent object.
5597 //
5598 // We need to explicitly copy these referent objects - the references
5599 // will be processed at the end of remarking.
5600 //
5601 // We also need to do this copying before we process the reference
5602 // objects discovered by the STW ref processor in case one of these
5603 // referents points to another object which is also referenced by an
5604 // object discovered by the STW ref processor.
5606 assert(!G1CollectedHeap::use_parallel_gc_threads() ||
5607 no_of_gc_workers == workers()->active_workers(),
5608 "Need to reset active GC workers");
5610 set_par_threads(no_of_gc_workers);
5611 G1ParPreserveCMReferentsTask keep_cm_referents(this,
5612 no_of_gc_workers,
5613 _task_queues);
5615 if (G1CollectedHeap::use_parallel_gc_threads()) {
5616 workers()->run_task(&keep_cm_referents);
5617 } else {
5618 keep_cm_referents.work(0);
5619 }
5621 set_par_threads(0);
5623 // Closure to test whether a referent is alive.
5624 G1STWIsAliveClosure is_alive(this);
5626 // Even when parallel reference processing is enabled, the processing
5627 // of JNI refs is serial and performed serially by the current thread
5628 // rather than by a worker. The following PSS will be used for processing
5629 // JNI refs.
5631 // Use only a single queue for this PSS.
5632 G1ParScanThreadState pss(this, 0);
5634 // We do not embed a reference processor in the copying/scanning
5635 // closures while we're actually processing the discovered
5636 // reference objects.
5637 G1ParScanHeapEvacClosure scan_evac_cl(this, &pss, NULL);
5638 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5639 G1ParScanPartialArrayClosure partial_scan_cl(this, &pss, NULL);
5641 pss.set_evac_closure(&scan_evac_cl);
5642 pss.set_evac_failure_closure(&evac_failure_cl);
5643 pss.set_partial_scan_closure(&partial_scan_cl);
5645 assert(pss.refs()->is_empty(), "pre-condition");
5647 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL);
5648 G1ParScanMetadataClosure only_copy_metadata_cl(this, &pss, NULL);
5650 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5651 G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(this, &pss, NULL);
5653 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5654 OopsInHeapRegionClosure* copy_metadata_cl = &only_copy_metadata_cl;
5656 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5657 // We also need to mark copied objects.
5658 copy_non_heap_cl = ©_mark_non_heap_cl;
5659 copy_metadata_cl = ©_mark_metadata_cl;
5660 }
5662 // Keep alive closure.
5663 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, copy_metadata_cl, &pss);
5665 // Serial Complete GC closure
5666 G1STWDrainQueueClosure drain_queue(this, &pss);
5668 // Setup the soft refs policy...
5669 rp->setup_policy(false);
5671 ReferenceProcessorStats stats;
5672 if (!rp->processing_is_mt()) {
5673 // Serial reference processing...
5674 stats = rp->process_discovered_references(&is_alive,
5675 &keep_alive,
5676 &drain_queue,
5677 NULL,
5678 _gc_timer_stw);
5679 } else {
5680 // Parallel reference processing
5681 assert(rp->num_q() == no_of_gc_workers, "sanity");
5682 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5684 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5685 stats = rp->process_discovered_references(&is_alive,
5686 &keep_alive,
5687 &drain_queue,
5688 &par_task_executor,
5689 _gc_timer_stw);
5690 }
5692 _gc_tracer_stw->report_gc_reference_stats(stats);
5693 // We have completed copying any necessary live referent objects
5694 // (that were not copied during the actual pause) so we can
5695 // retire any active alloc buffers
5696 pss.retire_alloc_buffers();
5697 assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5699 double ref_proc_time = os::elapsedTime() - ref_proc_start;
5700 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5701 }
5703 // Weak Reference processing during an evacuation pause (part 2).
5704 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) {
5705 double ref_enq_start = os::elapsedTime();
5707 ReferenceProcessor* rp = _ref_processor_stw;
5708 assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5710 // Now enqueue any remaining on the discovered lists on to
5711 // the pending list.
5712 if (!rp->processing_is_mt()) {
5713 // Serial reference processing...
5714 rp->enqueue_discovered_references();
5715 } else {
5716 // Parallel reference enqueueing
5718 assert(no_of_gc_workers == workers()->active_workers(),
5719 "Need to reset active workers");
5720 assert(rp->num_q() == no_of_gc_workers, "sanity");
5721 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5723 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5724 rp->enqueue_discovered_references(&par_task_executor);
5725 }
5727 rp->verify_no_references_recorded();
5728 assert(!rp->discovery_enabled(), "should have been disabled");
5730 // FIXME
5731 // CM's reference processing also cleans up the string and symbol tables.
5732 // Should we do that here also? We could, but it is a serial operation
5733 // and could significantly increase the pause time.
5735 double ref_enq_time = os::elapsedTime() - ref_enq_start;
5736 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5737 }
5739 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) {
5740 _expand_heap_after_alloc_failure = true;
5741 _evacuation_failed = false;
5743 // Should G1EvacuationFailureALot be in effect for this GC?
5744 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
5746 g1_rem_set()->prepare_for_oops_into_collection_set_do();
5748 // Disable the hot card cache.
5749 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
5750 hot_card_cache->reset_hot_cache_claimed_index();
5751 hot_card_cache->set_use_cache(false);
5753 uint n_workers;
5754 if (G1CollectedHeap::use_parallel_gc_threads()) {
5755 n_workers =
5756 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
5757 workers()->active_workers(),
5758 Threads::number_of_non_daemon_threads());
5759 assert(UseDynamicNumberOfGCThreads ||
5760 n_workers == workers()->total_workers(),
5761 "If not dynamic should be using all the workers");
5762 workers()->set_active_workers(n_workers);
5763 set_par_threads(n_workers);
5764 } else {
5765 assert(n_par_threads() == 0,
5766 "Should be the original non-parallel value");
5767 n_workers = 1;
5768 }
5770 G1ParTask g1_par_task(this, _task_queues);
5772 init_for_evac_failure(NULL);
5774 rem_set()->prepare_for_younger_refs_iterate(true);
5776 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5777 double start_par_time_sec = os::elapsedTime();
5778 double end_par_time_sec;
5780 {
5781 StrongRootsScope srs(this);
5783 if (G1CollectedHeap::use_parallel_gc_threads()) {
5784 // The individual threads will set their evac-failure closures.
5785 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
5786 // These tasks use ShareHeap::_process_strong_tasks
5787 assert(UseDynamicNumberOfGCThreads ||
5788 workers()->active_workers() == workers()->total_workers(),
5789 "If not dynamic should be using all the workers");
5790 workers()->run_task(&g1_par_task);
5791 } else {
5792 g1_par_task.set_for_termination(n_workers);
5793 g1_par_task.work(0);
5794 }
5795 end_par_time_sec = os::elapsedTime();
5797 // Closing the inner scope will execute the destructor
5798 // for the StrongRootsScope object. We record the current
5799 // elapsed time before closing the scope so that time
5800 // taken for the SRS destructor is NOT included in the
5801 // reported parallel time.
5802 }
5804 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5805 g1_policy()->phase_times()->record_par_time(par_time_ms);
5807 double code_root_fixup_time_ms =
5808 (os::elapsedTime() - end_par_time_sec) * 1000.0;
5809 g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms);
5811 set_par_threads(0);
5813 // Process any discovered reference objects - we have
5814 // to do this _before_ we retire the GC alloc regions
5815 // as we may have to copy some 'reachable' referent
5816 // objects (and their reachable sub-graphs) that were
5817 // not copied during the pause.
5818 process_discovered_references(n_workers);
5820 // Weak root processing.
5821 {
5822 G1STWIsAliveClosure is_alive(this);
5823 G1KeepAliveClosure keep_alive(this);
5824 JNIHandles::weak_oops_do(&is_alive, &keep_alive);
5825 }
5827 release_gc_alloc_regions(n_workers, evacuation_info);
5828 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5830 // Reset and re-enable the hot card cache.
5831 // Note the counts for the cards in the regions in the
5832 // collection set are reset when the collection set is freed.
5833 hot_card_cache->reset_hot_cache();
5834 hot_card_cache->set_use_cache(true);
5836 // Migrate the strong code roots attached to each region in
5837 // the collection set. Ideally we would like to do this
5838 // after we have finished the scanning/evacuation of the
5839 // strong code roots for a particular heap region.
5840 migrate_strong_code_roots();
5842 if (g1_policy()->during_initial_mark_pause()) {
5843 // Reset the claim values set during marking the strong code roots
5844 reset_heap_region_claim_values();
5845 }
5847 finalize_for_evac_failure();
5849 if (evacuation_failed()) {
5850 remove_self_forwarding_pointers();
5852 // Reset the G1EvacuationFailureALot counters and flags
5853 // Note: the values are reset only when an actual
5854 // evacuation failure occurs.
5855 NOT_PRODUCT(reset_evacuation_should_fail();)
5856 }
5858 // Enqueue any remaining references remaining on the STW
5859 // reference processor's discovered lists. We need to do
5860 // this after the card table is cleaned (and verified) as
5861 // the act of enqueueing entries on to the pending list
5862 // will log these updates (and dirty their associated
5863 // cards). We need these updates logged to update any
5864 // RSets.
5865 enqueue_discovered_references(n_workers);
5867 if (G1DeferredRSUpdate) {
5868 RedirtyLoggedCardTableEntryFastClosure redirty;
5869 dirty_card_queue_set().set_closure(&redirty);
5870 dirty_card_queue_set().apply_closure_to_all_completed_buffers();
5872 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5873 dcq.merge_bufferlists(&dirty_card_queue_set());
5874 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5875 }
5876 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5877 }
5879 void G1CollectedHeap::free_region_if_empty(HeapRegion* hr,
5880 size_t* pre_used,
5881 FreeRegionList* free_list,
5882 OldRegionSet* old_proxy_set,
5883 HumongousRegionSet* humongous_proxy_set,
5884 HRRSCleanupTask* hrrs_cleanup_task,
5885 bool par) {
5886 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) {
5887 if (hr->isHumongous()) {
5888 assert(hr->startsHumongous(), "we should only see starts humongous");
5889 free_humongous_region(hr, pre_used, free_list, humongous_proxy_set, par);
5890 } else {
5891 _old_set.remove_with_proxy(hr, old_proxy_set);
5892 free_region(hr, pre_used, free_list, par);
5893 }
5894 } else {
5895 hr->rem_set()->do_cleanup_work(hrrs_cleanup_task);
5896 }
5897 }
5899 void G1CollectedHeap::free_region(HeapRegion* hr,
5900 size_t* pre_used,
5901 FreeRegionList* free_list,
5902 bool par) {
5903 assert(!hr->isHumongous(), "this is only for non-humongous regions");
5904 assert(!hr->is_empty(), "the region should not be empty");
5905 assert(free_list != NULL, "pre-condition");
5907 // Clear the card counts for this region.
5908 // Note: we only need to do this if the region is not young
5909 // (since we don't refine cards in young regions).
5910 if (!hr->is_young()) {
5911 _cg1r->hot_card_cache()->reset_card_counts(hr);
5912 }
5913 *pre_used += hr->used();
5914 hr->hr_clear(par, true /* clear_space */);
5915 free_list->add_as_head(hr);
5916 }
5918 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
5919 size_t* pre_used,
5920 FreeRegionList* free_list,
5921 HumongousRegionSet* humongous_proxy_set,
5922 bool par) {
5923 assert(hr->startsHumongous(), "this is only for starts humongous regions");
5924 assert(free_list != NULL, "pre-condition");
5925 assert(humongous_proxy_set != NULL, "pre-condition");
5927 size_t hr_used = hr->used();
5928 size_t hr_capacity = hr->capacity();
5929 size_t hr_pre_used = 0;
5930 _humongous_set.remove_with_proxy(hr, humongous_proxy_set);
5931 // We need to read this before we make the region non-humongous,
5932 // otherwise the information will be gone.
5933 uint last_index = hr->last_hc_index();
5934 hr->set_notHumongous();
5935 free_region(hr, &hr_pre_used, free_list, par);
5937 uint i = hr->hrs_index() + 1;
5938 while (i < last_index) {
5939 HeapRegion* curr_hr = region_at(i);
5940 assert(curr_hr->continuesHumongous(), "invariant");
5941 curr_hr->set_notHumongous();
5942 free_region(curr_hr, &hr_pre_used, free_list, par);
5943 i += 1;
5944 }
5945 assert(hr_pre_used == hr_used,
5946 err_msg("hr_pre_used: "SIZE_FORMAT" and hr_used: "SIZE_FORMAT" "
5947 "should be the same", hr_pre_used, hr_used));
5948 *pre_used += hr_pre_used;
5949 }
5951 void G1CollectedHeap::update_sets_after_freeing_regions(size_t pre_used,
5952 FreeRegionList* free_list,
5953 OldRegionSet* old_proxy_set,
5954 HumongousRegionSet* humongous_proxy_set,
5955 bool par) {
5956 if (pre_used > 0) {
5957 Mutex* lock = (par) ? ParGCRareEvent_lock : NULL;
5958 MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag);
5959 assert(_summary_bytes_used >= pre_used,
5960 err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" "
5961 "should be >= pre_used: "SIZE_FORMAT,
5962 _summary_bytes_used, pre_used));
5963 _summary_bytes_used -= pre_used;
5964 }
5965 if (free_list != NULL && !free_list->is_empty()) {
5966 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
5967 _free_list.add_as_head(free_list);
5968 }
5969 if (old_proxy_set != NULL && !old_proxy_set->is_empty()) {
5970 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5971 _old_set.update_from_proxy(old_proxy_set);
5972 }
5973 if (humongous_proxy_set != NULL && !humongous_proxy_set->is_empty()) {
5974 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5975 _humongous_set.update_from_proxy(humongous_proxy_set);
5976 }
5977 }
5979 class G1ParCleanupCTTask : public AbstractGangTask {
5980 CardTableModRefBS* _ct_bs;
5981 G1CollectedHeap* _g1h;
5982 HeapRegion* volatile _su_head;
5983 public:
5984 G1ParCleanupCTTask(CardTableModRefBS* ct_bs,
5985 G1CollectedHeap* g1h) :
5986 AbstractGangTask("G1 Par Cleanup CT Task"),
5987 _ct_bs(ct_bs), _g1h(g1h) { }
5989 void work(uint worker_id) {
5990 HeapRegion* r;
5991 while (r = _g1h->pop_dirty_cards_region()) {
5992 clear_cards(r);
5993 }
5994 }
5996 void clear_cards(HeapRegion* r) {
5997 // Cards of the survivors should have already been dirtied.
5998 if (!r->is_survivor()) {
5999 _ct_bs->clear(MemRegion(r->bottom(), r->end()));
6000 }
6001 }
6002 };
6004 #ifndef PRODUCT
6005 class G1VerifyCardTableCleanup: public HeapRegionClosure {
6006 G1CollectedHeap* _g1h;
6007 CardTableModRefBS* _ct_bs;
6008 public:
6009 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, CardTableModRefBS* ct_bs)
6010 : _g1h(g1h), _ct_bs(ct_bs) { }
6011 virtual bool doHeapRegion(HeapRegion* r) {
6012 if (r->is_survivor()) {
6013 _g1h->verify_dirty_region(r);
6014 } else {
6015 _g1h->verify_not_dirty_region(r);
6016 }
6017 return false;
6018 }
6019 };
6021 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
6022 // All of the region should be clean.
6023 CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
6024 MemRegion mr(hr->bottom(), hr->end());
6025 ct_bs->verify_not_dirty_region(mr);
6026 }
6028 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
6029 // We cannot guarantee that [bottom(),end()] is dirty. Threads
6030 // dirty allocated blocks as they allocate them. The thread that
6031 // retires each region and replaces it with a new one will do a
6032 // maximal allocation to fill in [pre_dummy_top(),end()] but will
6033 // not dirty that area (one less thing to have to do while holding
6034 // a lock). So we can only verify that [bottom(),pre_dummy_top()]
6035 // is dirty.
6036 CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set();
6037 MemRegion mr(hr->bottom(), hr->pre_dummy_top());
6038 ct_bs->verify_dirty_region(mr);
6039 }
6041 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
6042 CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set();
6043 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
6044 verify_dirty_region(hr);
6045 }
6046 }
6048 void G1CollectedHeap::verify_dirty_young_regions() {
6049 verify_dirty_young_list(_young_list->first_region());
6050 }
6051 #endif
6053 void G1CollectedHeap::cleanUpCardTable() {
6054 CardTableModRefBS* ct_bs = (CardTableModRefBS*) (barrier_set());
6055 double start = os::elapsedTime();
6057 {
6058 // Iterate over the dirty cards region list.
6059 G1ParCleanupCTTask cleanup_task(ct_bs, this);
6061 if (G1CollectedHeap::use_parallel_gc_threads()) {
6062 set_par_threads();
6063 workers()->run_task(&cleanup_task);
6064 set_par_threads(0);
6065 } else {
6066 while (_dirty_cards_region_list) {
6067 HeapRegion* r = _dirty_cards_region_list;
6068 cleanup_task.clear_cards(r);
6069 _dirty_cards_region_list = r->get_next_dirty_cards_region();
6070 if (_dirty_cards_region_list == r) {
6071 // The last region.
6072 _dirty_cards_region_list = NULL;
6073 }
6074 r->set_next_dirty_cards_region(NULL);
6075 }
6076 }
6077 #ifndef PRODUCT
6078 if (G1VerifyCTCleanup || VerifyAfterGC) {
6079 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
6080 heap_region_iterate(&cleanup_verifier);
6081 }
6082 #endif
6083 }
6085 double elapsed = os::elapsedTime() - start;
6086 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
6087 }
6089 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) {
6090 size_t pre_used = 0;
6091 FreeRegionList local_free_list("Local List for CSet Freeing");
6093 double young_time_ms = 0.0;
6094 double non_young_time_ms = 0.0;
6096 // Since the collection set is a superset of the the young list,
6097 // all we need to do to clear the young list is clear its
6098 // head and length, and unlink any young regions in the code below
6099 _young_list->clear();
6101 G1CollectorPolicy* policy = g1_policy();
6103 double start_sec = os::elapsedTime();
6104 bool non_young = true;
6106 HeapRegion* cur = cs_head;
6107 int age_bound = -1;
6108 size_t rs_lengths = 0;
6110 while (cur != NULL) {
6111 assert(!is_on_master_free_list(cur), "sanity");
6112 if (non_young) {
6113 if (cur->is_young()) {
6114 double end_sec = os::elapsedTime();
6115 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6116 non_young_time_ms += elapsed_ms;
6118 start_sec = os::elapsedTime();
6119 non_young = false;
6120 }
6121 } else {
6122 if (!cur->is_young()) {
6123 double end_sec = os::elapsedTime();
6124 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6125 young_time_ms += elapsed_ms;
6127 start_sec = os::elapsedTime();
6128 non_young = true;
6129 }
6130 }
6132 rs_lengths += cur->rem_set()->occupied();
6134 HeapRegion* next = cur->next_in_collection_set();
6135 assert(cur->in_collection_set(), "bad CS");
6136 cur->set_next_in_collection_set(NULL);
6137 cur->set_in_collection_set(false);
6139 if (cur->is_young()) {
6140 int index = cur->young_index_in_cset();
6141 assert(index != -1, "invariant");
6142 assert((uint) index < policy->young_cset_region_length(), "invariant");
6143 size_t words_survived = _surviving_young_words[index];
6144 cur->record_surv_words_in_group(words_survived);
6146 // At this point the we have 'popped' cur from the collection set
6147 // (linked via next_in_collection_set()) but it is still in the
6148 // young list (linked via next_young_region()). Clear the
6149 // _next_young_region field.
6150 cur->set_next_young_region(NULL);
6151 } else {
6152 int index = cur->young_index_in_cset();
6153 assert(index == -1, "invariant");
6154 }
6156 assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
6157 (!cur->is_young() && cur->young_index_in_cset() == -1),
6158 "invariant" );
6160 if (!cur->evacuation_failed()) {
6161 MemRegion used_mr = cur->used_region();
6163 // And the region is empty.
6164 assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
6165 free_region(cur, &pre_used, &local_free_list, false /* par */);
6166 } else {
6167 cur->uninstall_surv_rate_group();
6168 if (cur->is_young()) {
6169 cur->set_young_index_in_cset(-1);
6170 }
6171 cur->set_not_young();
6172 cur->set_evacuation_failed(false);
6173 // The region is now considered to be old.
6174 _old_set.add(cur);
6175 evacuation_info.increment_collectionset_used_after(cur->used());
6176 }
6177 cur = next;
6178 }
6180 evacuation_info.set_regions_freed(local_free_list.length());
6181 policy->record_max_rs_lengths(rs_lengths);
6182 policy->cset_regions_freed();
6184 double end_sec = os::elapsedTime();
6185 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6187 if (non_young) {
6188 non_young_time_ms += elapsed_ms;
6189 } else {
6190 young_time_ms += elapsed_ms;
6191 }
6193 update_sets_after_freeing_regions(pre_used, &local_free_list,
6194 NULL /* old_proxy_set */,
6195 NULL /* humongous_proxy_set */,
6196 false /* par */);
6197 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
6198 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
6199 }
6201 // This routine is similar to the above but does not record
6202 // any policy statistics or update free lists; we are abandoning
6203 // the current incremental collection set in preparation of a
6204 // full collection. After the full GC we will start to build up
6205 // the incremental collection set again.
6206 // This is only called when we're doing a full collection
6207 // and is immediately followed by the tearing down of the young list.
6209 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
6210 HeapRegion* cur = cs_head;
6212 while (cur != NULL) {
6213 HeapRegion* next = cur->next_in_collection_set();
6214 assert(cur->in_collection_set(), "bad CS");
6215 cur->set_next_in_collection_set(NULL);
6216 cur->set_in_collection_set(false);
6217 cur->set_young_index_in_cset(-1);
6218 cur = next;
6219 }
6220 }
6222 void G1CollectedHeap::set_free_regions_coming() {
6223 if (G1ConcRegionFreeingVerbose) {
6224 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6225 "setting free regions coming");
6226 }
6228 assert(!free_regions_coming(), "pre-condition");
6229 _free_regions_coming = true;
6230 }
6232 void G1CollectedHeap::reset_free_regions_coming() {
6233 assert(free_regions_coming(), "pre-condition");
6235 {
6236 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6237 _free_regions_coming = false;
6238 SecondaryFreeList_lock->notify_all();
6239 }
6241 if (G1ConcRegionFreeingVerbose) {
6242 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6243 "reset free regions coming");
6244 }
6245 }
6247 void G1CollectedHeap::wait_while_free_regions_coming() {
6248 // Most of the time we won't have to wait, so let's do a quick test
6249 // first before we take the lock.
6250 if (!free_regions_coming()) {
6251 return;
6252 }
6254 if (G1ConcRegionFreeingVerbose) {
6255 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6256 "waiting for free regions");
6257 }
6259 {
6260 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6261 while (free_regions_coming()) {
6262 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
6263 }
6264 }
6266 if (G1ConcRegionFreeingVerbose) {
6267 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6268 "done waiting for free regions");
6269 }
6270 }
6272 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
6273 assert(heap_lock_held_for_gc(),
6274 "the heap lock should already be held by or for this thread");
6275 _young_list->push_region(hr);
6276 }
6278 class NoYoungRegionsClosure: public HeapRegionClosure {
6279 private:
6280 bool _success;
6281 public:
6282 NoYoungRegionsClosure() : _success(true) { }
6283 bool doHeapRegion(HeapRegion* r) {
6284 if (r->is_young()) {
6285 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
6286 r->bottom(), r->end());
6287 _success = false;
6288 }
6289 return false;
6290 }
6291 bool success() { return _success; }
6292 };
6294 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
6295 bool ret = _young_list->check_list_empty(check_sample);
6297 if (check_heap) {
6298 NoYoungRegionsClosure closure;
6299 heap_region_iterate(&closure);
6300 ret = ret && closure.success();
6301 }
6303 return ret;
6304 }
6306 class TearDownRegionSetsClosure : public HeapRegionClosure {
6307 private:
6308 OldRegionSet *_old_set;
6310 public:
6311 TearDownRegionSetsClosure(OldRegionSet* old_set) : _old_set(old_set) { }
6313 bool doHeapRegion(HeapRegion* r) {
6314 if (r->is_empty()) {
6315 // We ignore empty regions, we'll empty the free list afterwards
6316 } else if (r->is_young()) {
6317 // We ignore young regions, we'll empty the young list afterwards
6318 } else if (r->isHumongous()) {
6319 // We ignore humongous regions, we're not tearing down the
6320 // humongous region set
6321 } else {
6322 // The rest should be old
6323 _old_set->remove(r);
6324 }
6325 return false;
6326 }
6328 ~TearDownRegionSetsClosure() {
6329 assert(_old_set->is_empty(), "post-condition");
6330 }
6331 };
6333 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6334 assert_at_safepoint(true /* should_be_vm_thread */);
6336 if (!free_list_only) {
6337 TearDownRegionSetsClosure cl(&_old_set);
6338 heap_region_iterate(&cl);
6340 // Need to do this after the heap iteration to be able to
6341 // recognize the young regions and ignore them during the iteration.
6342 _young_list->empty_list();
6343 }
6344 _free_list.remove_all();
6345 }
6347 class RebuildRegionSetsClosure : public HeapRegionClosure {
6348 private:
6349 bool _free_list_only;
6350 OldRegionSet* _old_set;
6351 FreeRegionList* _free_list;
6352 size_t _total_used;
6354 public:
6355 RebuildRegionSetsClosure(bool free_list_only,
6356 OldRegionSet* old_set, FreeRegionList* free_list) :
6357 _free_list_only(free_list_only),
6358 _old_set(old_set), _free_list(free_list), _total_used(0) {
6359 assert(_free_list->is_empty(), "pre-condition");
6360 if (!free_list_only) {
6361 assert(_old_set->is_empty(), "pre-condition");
6362 }
6363 }
6365 bool doHeapRegion(HeapRegion* r) {
6366 if (r->continuesHumongous()) {
6367 return false;
6368 }
6370 if (r->is_empty()) {
6371 // Add free regions to the free list
6372 _free_list->add_as_tail(r);
6373 } else if (!_free_list_only) {
6374 assert(!r->is_young(), "we should not come across young regions");
6376 if (r->isHumongous()) {
6377 // We ignore humongous regions, we left the humongous set unchanged
6378 } else {
6379 // The rest should be old, add them to the old set
6380 _old_set->add(r);
6381 }
6382 _total_used += r->used();
6383 }
6385 return false;
6386 }
6388 size_t total_used() {
6389 return _total_used;
6390 }
6391 };
6393 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6394 assert_at_safepoint(true /* should_be_vm_thread */);
6396 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_free_list);
6397 heap_region_iterate(&cl);
6399 if (!free_list_only) {
6400 _summary_bytes_used = cl.total_used();
6401 }
6402 assert(_summary_bytes_used == recalculate_used(),
6403 err_msg("inconsistent _summary_bytes_used, "
6404 "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6405 _summary_bytes_used, recalculate_used()));
6406 }
6408 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6409 _refine_cte_cl->set_concurrent(concurrent);
6410 }
6412 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6413 HeapRegion* hr = heap_region_containing(p);
6414 if (hr == NULL) {
6415 return false;
6416 } else {
6417 return hr->is_in(p);
6418 }
6419 }
6421 // Methods for the mutator alloc region
6423 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6424 bool force) {
6425 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6426 assert(!force || g1_policy()->can_expand_young_list(),
6427 "if force is true we should be able to expand the young list");
6428 bool young_list_full = g1_policy()->is_young_list_full();
6429 if (force || !young_list_full) {
6430 HeapRegion* new_alloc_region = new_region(word_size,
6431 false /* do_expand */);
6432 if (new_alloc_region != NULL) {
6433 set_region_short_lived_locked(new_alloc_region);
6434 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6435 return new_alloc_region;
6436 }
6437 }
6438 return NULL;
6439 }
6441 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6442 size_t allocated_bytes) {
6443 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6444 assert(alloc_region->is_young(), "all mutator alloc regions should be young");
6446 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6447 _summary_bytes_used += allocated_bytes;
6448 _hr_printer.retire(alloc_region);
6449 // We update the eden sizes here, when the region is retired,
6450 // instead of when it's allocated, since this is the point that its
6451 // used space has been recored in _summary_bytes_used.
6452 g1mm()->update_eden_size();
6453 }
6455 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
6456 bool force) {
6457 return _g1h->new_mutator_alloc_region(word_size, force);
6458 }
6460 void G1CollectedHeap::set_par_threads() {
6461 // Don't change the number of workers. Use the value previously set
6462 // in the workgroup.
6463 assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise");
6464 uint n_workers = workers()->active_workers();
6465 assert(UseDynamicNumberOfGCThreads ||
6466 n_workers == workers()->total_workers(),
6467 "Otherwise should be using the total number of workers");
6468 if (n_workers == 0) {
6469 assert(false, "Should have been set in prior evacuation pause.");
6470 n_workers = ParallelGCThreads;
6471 workers()->set_active_workers(n_workers);
6472 }
6473 set_par_threads(n_workers);
6474 }
6476 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
6477 size_t allocated_bytes) {
6478 _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
6479 }
6481 // Methods for the GC alloc regions
6483 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6484 uint count,
6485 GCAllocPurpose ap) {
6486 assert(FreeList_lock->owned_by_self(), "pre-condition");
6488 if (count < g1_policy()->max_regions(ap)) {
6489 HeapRegion* new_alloc_region = new_region(word_size,
6490 true /* do_expand */);
6491 if (new_alloc_region != NULL) {
6492 // We really only need to do this for old regions given that we
6493 // should never scan survivors. But it doesn't hurt to do it
6494 // for survivors too.
6495 new_alloc_region->set_saved_mark();
6496 if (ap == GCAllocForSurvived) {
6497 new_alloc_region->set_survivor();
6498 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6499 } else {
6500 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6501 }
6502 bool during_im = g1_policy()->during_initial_mark_pause();
6503 new_alloc_region->note_start_of_copying(during_im);
6504 return new_alloc_region;
6505 } else {
6506 g1_policy()->note_alloc_region_limit_reached(ap);
6507 }
6508 }
6509 return NULL;
6510 }
6512 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6513 size_t allocated_bytes,
6514 GCAllocPurpose ap) {
6515 bool during_im = g1_policy()->during_initial_mark_pause();
6516 alloc_region->note_end_of_copying(during_im);
6517 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6518 if (ap == GCAllocForSurvived) {
6519 young_list()->add_survivor_region(alloc_region);
6520 } else {
6521 _old_set.add(alloc_region);
6522 }
6523 _hr_printer.retire(alloc_region);
6524 }
6526 HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size,
6527 bool force) {
6528 assert(!force, "not supported for GC alloc regions");
6529 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForSurvived);
6530 }
6532 void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region,
6533 size_t allocated_bytes) {
6534 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6535 GCAllocForSurvived);
6536 }
6538 HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size,
6539 bool force) {
6540 assert(!force, "not supported for GC alloc regions");
6541 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForTenured);
6542 }
6544 void OldGCAllocRegion::retire_region(HeapRegion* alloc_region,
6545 size_t allocated_bytes) {
6546 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6547 GCAllocForTenured);
6548 }
6549 // Heap region set verification
6551 class VerifyRegionListsClosure : public HeapRegionClosure {
6552 private:
6553 FreeRegionList* _free_list;
6554 OldRegionSet* _old_set;
6555 HumongousRegionSet* _humongous_set;
6556 uint _region_count;
6558 public:
6559 VerifyRegionListsClosure(OldRegionSet* old_set,
6560 HumongousRegionSet* humongous_set,
6561 FreeRegionList* free_list) :
6562 _old_set(old_set), _humongous_set(humongous_set),
6563 _free_list(free_list), _region_count(0) { }
6565 uint region_count() { return _region_count; }
6567 bool doHeapRegion(HeapRegion* hr) {
6568 _region_count += 1;
6570 if (hr->continuesHumongous()) {
6571 return false;
6572 }
6574 if (hr->is_young()) {
6575 // TODO
6576 } else if (hr->startsHumongous()) {
6577 _humongous_set->verify_next_region(hr);
6578 } else if (hr->is_empty()) {
6579 _free_list->verify_next_region(hr);
6580 } else {
6581 _old_set->verify_next_region(hr);
6582 }
6583 return false;
6584 }
6585 };
6587 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
6588 HeapWord* bottom) {
6589 HeapWord* end = bottom + HeapRegion::GrainWords;
6590 MemRegion mr(bottom, end);
6591 assert(_g1_reserved.contains(mr), "invariant");
6592 // This might return NULL if the allocation fails
6593 return new HeapRegion(hrs_index, _bot_shared, mr);
6594 }
6596 void G1CollectedHeap::verify_region_sets() {
6597 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6599 // First, check the explicit lists.
6600 _free_list.verify();
6601 {
6602 // Given that a concurrent operation might be adding regions to
6603 // the secondary free list we have to take the lock before
6604 // verifying it.
6605 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6606 _secondary_free_list.verify();
6607 }
6608 _old_set.verify();
6609 _humongous_set.verify();
6611 // If a concurrent region freeing operation is in progress it will
6612 // be difficult to correctly attributed any free regions we come
6613 // across to the correct free list given that they might belong to
6614 // one of several (free_list, secondary_free_list, any local lists,
6615 // etc.). So, if that's the case we will skip the rest of the
6616 // verification operation. Alternatively, waiting for the concurrent
6617 // operation to complete will have a non-trivial effect on the GC's
6618 // operation (no concurrent operation will last longer than the
6619 // interval between two calls to verification) and it might hide
6620 // any issues that we would like to catch during testing.
6621 if (free_regions_coming()) {
6622 return;
6623 }
6625 // Make sure we append the secondary_free_list on the free_list so
6626 // that all free regions we will come across can be safely
6627 // attributed to the free_list.
6628 append_secondary_free_list_if_not_empty_with_lock();
6630 // Finally, make sure that the region accounting in the lists is
6631 // consistent with what we see in the heap.
6632 _old_set.verify_start();
6633 _humongous_set.verify_start();
6634 _free_list.verify_start();
6636 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_free_list);
6637 heap_region_iterate(&cl);
6639 _old_set.verify_end();
6640 _humongous_set.verify_end();
6641 _free_list.verify_end();
6642 }
6644 // Optimized nmethod scanning
6646 class RegisterNMethodOopClosure: public OopClosure {
6647 G1CollectedHeap* _g1h;
6648 nmethod* _nm;
6650 template <class T> void do_oop_work(T* p) {
6651 T heap_oop = oopDesc::load_heap_oop(p);
6652 if (!oopDesc::is_null(heap_oop)) {
6653 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6654 HeapRegion* hr = _g1h->heap_region_containing(obj);
6655 assert(!hr->isHumongous(), "code root in humongous region?");
6657 // HeapRegion::add_strong_code_root() avoids adding duplicate
6658 // entries but having duplicates is OK since we "mark" nmethods
6659 // as visited when we scan the strong code root lists during the GC.
6660 hr->add_strong_code_root(_nm);
6661 assert(hr->rem_set()->strong_code_roots_list_contains(_nm), "add failed?");
6662 }
6663 }
6665 public:
6666 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6667 _g1h(g1h), _nm(nm) {}
6669 void do_oop(oop* p) { do_oop_work(p); }
6670 void do_oop(narrowOop* p) { do_oop_work(p); }
6671 };
6673 class UnregisterNMethodOopClosure: public OopClosure {
6674 G1CollectedHeap* _g1h;
6675 nmethod* _nm;
6677 template <class T> void do_oop_work(T* p) {
6678 T heap_oop = oopDesc::load_heap_oop(p);
6679 if (!oopDesc::is_null(heap_oop)) {
6680 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6681 HeapRegion* hr = _g1h->heap_region_containing(obj);
6682 assert(!hr->isHumongous(), "code root in humongous region?");
6683 hr->remove_strong_code_root(_nm);
6684 assert(!hr->rem_set()->strong_code_roots_list_contains(_nm), "remove failed?");
6685 }
6686 }
6688 public:
6689 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6690 _g1h(g1h), _nm(nm) {}
6692 void do_oop(oop* p) { do_oop_work(p); }
6693 void do_oop(narrowOop* p) { do_oop_work(p); }
6694 };
6696 void G1CollectedHeap::register_nmethod(nmethod* nm) {
6697 CollectedHeap::register_nmethod(nm);
6699 guarantee(nm != NULL, "sanity");
6700 RegisterNMethodOopClosure reg_cl(this, nm);
6701 nm->oops_do(®_cl);
6702 }
6704 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
6705 CollectedHeap::unregister_nmethod(nm);
6707 guarantee(nm != NULL, "sanity");
6708 UnregisterNMethodOopClosure reg_cl(this, nm);
6709 nm->oops_do(®_cl, true);
6710 }
6712 class MigrateCodeRootsHeapRegionClosure: public HeapRegionClosure {
6713 public:
6714 bool doHeapRegion(HeapRegion *hr) {
6715 assert(!hr->isHumongous(), "humongous region in collection set?");
6716 hr->migrate_strong_code_roots();
6717 return false;
6718 }
6719 };
6721 void G1CollectedHeap::migrate_strong_code_roots() {
6722 MigrateCodeRootsHeapRegionClosure cl;
6723 double migrate_start = os::elapsedTime();
6724 collection_set_iterate(&cl);
6725 double migration_time_ms = (os::elapsedTime() - migrate_start) * 1000.0;
6726 g1_policy()->phase_times()->record_strong_code_root_migration_time(migration_time_ms);
6727 }
6729 // Mark all the code roots that point into regions *not* in the
6730 // collection set.
6731 //
6732 // Note we do not want to use a "marking" CodeBlobToOopClosure while
6733 // walking the the code roots lists of regions not in the collection
6734 // set. Suppose we have an nmethod (M) that points to objects in two
6735 // separate regions - one in the collection set (R1) and one not (R2).
6736 // Using a "marking" CodeBlobToOopClosure here would result in "marking"
6737 // nmethod M when walking the code roots for R1. When we come to scan
6738 // the code roots for R2, we would see that M is already marked and it
6739 // would be skipped and the objects in R2 that are referenced from M
6740 // would not be evacuated.
6742 class MarkStrongCodeRootCodeBlobClosure: public CodeBlobClosure {
6744 class MarkStrongCodeRootOopClosure: public OopClosure {
6745 ConcurrentMark* _cm;
6746 HeapRegion* _hr;
6747 uint _worker_id;
6749 template <class T> void do_oop_work(T* p) {
6750 T heap_oop = oopDesc::load_heap_oop(p);
6751 if (!oopDesc::is_null(heap_oop)) {
6752 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6753 // Only mark objects in the region (which is assumed
6754 // to be not in the collection set).
6755 if (_hr->is_in(obj)) {
6756 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
6757 }
6758 }
6759 }
6761 public:
6762 MarkStrongCodeRootOopClosure(ConcurrentMark* cm, HeapRegion* hr, uint worker_id) :
6763 _cm(cm), _hr(hr), _worker_id(worker_id) {
6764 assert(!_hr->in_collection_set(), "sanity");
6765 }
6767 void do_oop(narrowOop* p) { do_oop_work(p); }
6768 void do_oop(oop* p) { do_oop_work(p); }
6769 };
6771 MarkStrongCodeRootOopClosure _oop_cl;
6773 public:
6774 MarkStrongCodeRootCodeBlobClosure(ConcurrentMark* cm, HeapRegion* hr, uint worker_id):
6775 _oop_cl(cm, hr, worker_id) {}
6777 void do_code_blob(CodeBlob* cb) {
6778 nmethod* nm = (cb == NULL) ? NULL : cb->as_nmethod_or_null();
6779 if (nm != NULL) {
6780 nm->oops_do(&_oop_cl);
6781 }
6782 }
6783 };
6785 class MarkStrongCodeRootsHRClosure: public HeapRegionClosure {
6786 G1CollectedHeap* _g1h;
6787 uint _worker_id;
6789 public:
6790 MarkStrongCodeRootsHRClosure(G1CollectedHeap* g1h, uint worker_id) :
6791 _g1h(g1h), _worker_id(worker_id) {}
6793 bool doHeapRegion(HeapRegion *hr) {
6794 HeapRegionRemSet* hrrs = hr->rem_set();
6795 if (hr->isHumongous()) {
6796 // Code roots should never be attached to a humongous region
6797 assert(hrrs->strong_code_roots_list_length() == 0, "sanity");
6798 return false;
6799 }
6801 if (hr->in_collection_set()) {
6802 // Don't mark code roots into regions in the collection set here.
6803 // They will be marked when we scan them.
6804 return false;
6805 }
6807 MarkStrongCodeRootCodeBlobClosure cb_cl(_g1h->concurrent_mark(), hr, _worker_id);
6808 hr->strong_code_roots_do(&cb_cl);
6809 return false;
6810 }
6811 };
6813 void G1CollectedHeap::mark_strong_code_roots(uint worker_id) {
6814 MarkStrongCodeRootsHRClosure cl(this, worker_id);
6815 if (G1CollectedHeap::use_parallel_gc_threads()) {
6816 heap_region_par_iterate_chunked(&cl,
6817 worker_id,
6818 workers()->active_workers(),
6819 HeapRegion::ParMarkRootClaimValue);
6820 } else {
6821 heap_region_iterate(&cl);
6822 }
6823 }
6825 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
6826 G1CollectedHeap* _g1h;
6828 public:
6829 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
6830 _g1h(g1h) {}
6832 void do_code_blob(CodeBlob* cb) {
6833 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
6834 if (nm == NULL) {
6835 return;
6836 }
6838 if (ScavengeRootsInCode && nm->detect_scavenge_root_oops()) {
6839 _g1h->register_nmethod(nm);
6840 }
6841 }
6842 };
6844 void G1CollectedHeap::rebuild_strong_code_roots() {
6845 RebuildStrongCodeRootClosure blob_cl(this);
6846 CodeCache::blobs_do(&blob_cl);
6847 }