1 /*
2 * Copyright (c) 2001, 2015, 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 */
24
25 #include "precompiled.hpp"
26 #include "classfile/metadataOnStackMark.hpp"
27 #include "classfile/stringTable.hpp"
28 #include "code/codeCache.hpp"
29 #include "code/icBuffer.hpp"
30 #include "gc/g1/bufferingOopClosure.hpp"
31 #include "gc/g1/concurrentG1Refine.hpp"
32 #include "gc/g1/concurrentG1RefineThread.hpp"
33 #include "gc/g1/concurrentMarkThread.inline.hpp"
34 #include "gc/g1/g1AllocRegion.inline.hpp"
35 #include "gc/g1/g1CollectedHeap.inline.hpp"
36 #include "gc/g1/g1CollectorPolicy.hpp"
37 #include "gc/g1/g1ErgoVerbose.hpp"
38 #include "gc/g1/g1EvacFailure.hpp"
39 #include "gc/g1/g1GCPhaseTimes.hpp"
40 #include "gc/g1/g1Log.hpp"
41 #include "gc/g1/g1MarkSweep.hpp"
42 #include "gc/g1/g1OopClosures.inline.hpp"
43 #include "gc/g1/g1ParScanThreadState.inline.hpp"
44 #include "gc/g1/g1RegionToSpaceMapper.hpp"
45 #include "gc/g1/g1RemSet.inline.hpp"
46 #include "gc/g1/g1RootProcessor.hpp"
47 #include "gc/g1/g1StringDedup.hpp"
48 #include "gc/g1/g1YCTypes.hpp"
49 #include "gc/g1/heapRegion.inline.hpp"
50 #include "gc/g1/heapRegionRemSet.hpp"
51 #include "gc/g1/heapRegionSet.inline.hpp"
52 #include "gc/g1/suspendibleThreadSet.hpp"
53 #include "gc/g1/vm_operations_g1.hpp"
54 #include "gc/shared/gcHeapSummary.hpp"
55 #include "gc/shared/gcLocker.inline.hpp"
56 #include "gc/shared/gcTimer.hpp"
57 #include "gc/shared/gcTrace.hpp"
58 #include "gc/shared/gcTraceTime.hpp"
59 #include "gc/shared/generationSpec.hpp"
60 #include "gc/shared/isGCActiveMark.hpp"
61 #include "gc/shared/referenceProcessor.hpp"
62 #include "gc/shared/taskqueue.inline.hpp"
63 #include "memory/allocation.hpp"
64 #include "memory/iterator.hpp"
65 #include "oops/oop.inline.hpp"
66 #include "runtime/atomic.inline.hpp"
67 #include "runtime/orderAccess.inline.hpp"
68 #include "runtime/vmThread.hpp"
69 #include "utilities/globalDefinitions.hpp"
70 #include "utilities/stack.inline.hpp"
71
72 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
73
74 // turn it on so that the contents of the young list (scan-only /
75 // to-be-collected) are printed at "strategic" points before / during
76 // / after the collection --- this is useful for debugging
77 #define YOUNG_LIST_VERBOSE 0
78 // CURRENT STATUS
79 // This file is under construction. Search for "FIXME".
80
81 // INVARIANTS/NOTES
82 //
83 // All allocation activity covered by the G1CollectedHeap interface is
84 // serialized by acquiring the HeapLock. This happens in mem_allocate
85 // and allocate_new_tlab, which are the "entry" points to the
86 // allocation code from the rest of the JVM. (Note that this does not
87 // apply to TLAB allocation, which is not part of this interface: it
88 // is done by clients of this interface.)
89
90 // Local to this file.
91
92 class RefineCardTableEntryClosure: public CardTableEntryClosure {
93 bool _concurrent;
94 public:
95 RefineCardTableEntryClosure() : _concurrent(true) { }
96
97 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
98 bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, false);
99 // This path is executed by the concurrent refine or mutator threads,
100 // concurrently, and so we do not care if card_ptr contains references
101 // that point into the collection set.
102 assert(!oops_into_cset, "should be");
103
104 if (_concurrent && SuspendibleThreadSet::should_yield()) {
105 // Caller will actually yield.
106 return false;
107 }
108 // Otherwise, we finished successfully; return true.
109 return true;
110 }
111
112 void set_concurrent(bool b) { _concurrent = b; }
113 };
114
115
116 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
117 private:
118 size_t _num_processed;
119
120 public:
121 RedirtyLoggedCardTableEntryClosure() : CardTableEntryClosure(), _num_processed(0) { }
122
123 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
124 *card_ptr = CardTableModRefBS::dirty_card_val();
125 _num_processed++;
126 return true;
127 }
128
129 size_t num_processed() const { return _num_processed; }
130 };
131
132 YoungList::YoungList(G1CollectedHeap* g1h) :
133 _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0),
134 _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) {
135 guarantee(check_list_empty(false), "just making sure...");
136 }
137
138 void YoungList::push_region(HeapRegion *hr) {
139 assert(!hr->is_young(), "should not already be young");
140 assert(hr->get_next_young_region() == NULL, "cause it should!");
141
142 hr->set_next_young_region(_head);
143 _head = hr;
144
145 _g1h->g1_policy()->set_region_eden(hr, (int) _length);
146 ++_length;
147 }
148
149 void YoungList::add_survivor_region(HeapRegion* hr) {
150 assert(hr->is_survivor(), "should be flagged as survivor region");
151 assert(hr->get_next_young_region() == NULL, "cause it should!");
152
153 hr->set_next_young_region(_survivor_head);
154 if (_survivor_head == NULL) {
155 _survivor_tail = hr;
156 }
157 _survivor_head = hr;
158 ++_survivor_length;
159 }
160
161 void YoungList::empty_list(HeapRegion* list) {
162 while (list != NULL) {
163 HeapRegion* next = list->get_next_young_region();
164 list->set_next_young_region(NULL);
165 list->uninstall_surv_rate_group();
166 // This is called before a Full GC and all the non-empty /
167 // non-humongous regions at the end of the Full GC will end up as
168 // old anyway.
169 list->set_old();
170 list = next;
171 }
172 }
173
174 void YoungList::empty_list() {
175 assert(check_list_well_formed(), "young list should be well formed");
176
177 empty_list(_head);
178 _head = NULL;
179 _length = 0;
180
181 empty_list(_survivor_head);
182 _survivor_head = NULL;
183 _survivor_tail = NULL;
184 _survivor_length = 0;
185
186 _last_sampled_rs_lengths = 0;
187
188 assert(check_list_empty(false), "just making sure...");
189 }
190
191 bool YoungList::check_list_well_formed() {
192 bool ret = true;
193
194 uint length = 0;
195 HeapRegion* curr = _head;
196 HeapRegion* last = NULL;
197 while (curr != NULL) {
198 if (!curr->is_young()) {
199 gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
200 "incorrectly tagged (y: %d, surv: %d)",
201 p2i(curr->bottom()), p2i(curr->end()),
202 curr->is_young(), curr->is_survivor());
203 ret = false;
204 }
205 ++length;
206 last = curr;
207 curr = curr->get_next_young_region();
208 }
209 ret = ret && (length == _length);
210
211 if (!ret) {
212 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
213 gclog_or_tty->print_cr("### list has %u entries, _length is %u",
214 length, _length);
215 }
216
217 return ret;
218 }
219
220 bool YoungList::check_list_empty(bool check_sample) {
221 bool ret = true;
222
223 if (_length != 0) {
224 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u",
225 _length);
226 ret = false;
227 }
228 if (check_sample && _last_sampled_rs_lengths != 0) {
229 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
230 ret = false;
231 }
232 if (_head != NULL) {
233 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
234 ret = false;
235 }
236 if (!ret) {
237 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
238 }
239
240 return ret;
241 }
242
243 void
244 YoungList::rs_length_sampling_init() {
245 _sampled_rs_lengths = 0;
246 _curr = _head;
247 }
248
249 bool
250 YoungList::rs_length_sampling_more() {
251 return _curr != NULL;
252 }
253
254 void
255 YoungList::rs_length_sampling_next() {
256 assert( _curr != NULL, "invariant" );
257 size_t rs_length = _curr->rem_set()->occupied();
258
259 _sampled_rs_lengths += rs_length;
260
261 // The current region may not yet have been added to the
262 // incremental collection set (it gets added when it is
263 // retired as the current allocation region).
264 if (_curr->in_collection_set()) {
265 // Update the collection set policy information for this region
266 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
267 }
268
269 _curr = _curr->get_next_young_region();
270 if (_curr == NULL) {
271 _last_sampled_rs_lengths = _sampled_rs_lengths;
272 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
273 }
274 }
275
276 void
277 YoungList::reset_auxilary_lists() {
278 guarantee( is_empty(), "young list should be empty" );
279 assert(check_list_well_formed(), "young list should be well formed");
280
281 // Add survivor regions to SurvRateGroup.
282 _g1h->g1_policy()->note_start_adding_survivor_regions();
283 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
284
285 int young_index_in_cset = 0;
286 for (HeapRegion* curr = _survivor_head;
287 curr != NULL;
288 curr = curr->get_next_young_region()) {
289 _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
290
291 // The region is a non-empty survivor so let's add it to
292 // the incremental collection set for the next evacuation
293 // pause.
294 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
295 young_index_in_cset += 1;
296 }
297 assert((uint) young_index_in_cset == _survivor_length, "post-condition");
298 _g1h->g1_policy()->note_stop_adding_survivor_regions();
299
300 _head = _survivor_head;
301 _length = _survivor_length;
302 if (_survivor_head != NULL) {
303 assert(_survivor_tail != NULL, "cause it shouldn't be");
304 assert(_survivor_length > 0, "invariant");
305 _survivor_tail->set_next_young_region(NULL);
306 }
307
308 // Don't clear the survivor list handles until the start of
309 // the next evacuation pause - we need it in order to re-tag
310 // the survivor regions from this evacuation pause as 'young'
311 // at the start of the next.
312
313 _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
314
315 assert(check_list_well_formed(), "young list should be well formed");
316 }
317
318 void YoungList::print() {
319 HeapRegion* lists[] = {_head, _survivor_head};
320 const char* names[] = {"YOUNG", "SURVIVOR"};
321
322 for (uint list = 0; list < ARRAY_SIZE(lists); ++list) {
323 gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
324 HeapRegion *curr = lists[list];
325 if (curr == NULL)
326 gclog_or_tty->print_cr(" empty");
327 while (curr != NULL) {
328 gclog_or_tty->print_cr(" "HR_FORMAT", P: "PTR_FORMAT ", N: "PTR_FORMAT", age: %4d",
329 HR_FORMAT_PARAMS(curr),
330 p2i(curr->prev_top_at_mark_start()),
331 p2i(curr->next_top_at_mark_start()),
332 curr->age_in_surv_rate_group_cond());
333 curr = curr->get_next_young_region();
334 }
335 }
336
337 gclog_or_tty->cr();
338 }
339
340 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
341 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
342 }
343
344 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
345 // The from card cache is not the memory that is actually committed. So we cannot
346 // take advantage of the zero_filled parameter.
347 reset_from_card_cache(start_idx, num_regions);
348 }
349
350 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
351 {
352 // Claim the right to put the region on the dirty cards region list
353 // by installing a self pointer.
354 HeapRegion* next = hr->get_next_dirty_cards_region();
355 if (next == NULL) {
356 HeapRegion* res = (HeapRegion*)
357 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
358 NULL);
359 if (res == NULL) {
360 HeapRegion* head;
361 do {
362 // Put the region to the dirty cards region list.
363 head = _dirty_cards_region_list;
364 next = (HeapRegion*)
365 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
366 if (next == head) {
367 assert(hr->get_next_dirty_cards_region() == hr,
368 "hr->get_next_dirty_cards_region() != hr");
369 if (next == NULL) {
370 // The last region in the list points to itself.
371 hr->set_next_dirty_cards_region(hr);
372 } else {
373 hr->set_next_dirty_cards_region(next);
374 }
375 }
376 } while (next != head);
377 }
378 }
379 }
380
381 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
382 {
383 HeapRegion* head;
384 HeapRegion* hr;
385 do {
386 head = _dirty_cards_region_list;
387 if (head == NULL) {
388 return NULL;
389 }
390 HeapRegion* new_head = head->get_next_dirty_cards_region();
391 if (head == new_head) {
392 // The last region.
393 new_head = NULL;
394 }
395 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
396 head);
397 } while (hr != head);
398 assert(hr != NULL, "invariant");
399 hr->set_next_dirty_cards_region(NULL);
400 return hr;
401 }
402
403 // Returns true if the reference points to an object that
404 // can move in an incremental collection.
405 bool G1CollectedHeap::is_scavengable(const void* p) {
406 HeapRegion* hr = heap_region_containing(p);
407 return !hr->is_humongous();
408 }
409
410 // Private methods.
411
412 HeapRegion*
413 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
414 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
415 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
416 if (!_secondary_free_list.is_empty()) {
417 if (G1ConcRegionFreeingVerbose) {
418 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
419 "secondary_free_list has %u entries",
420 _secondary_free_list.length());
421 }
422 // It looks as if there are free regions available on the
423 // secondary_free_list. Let's move them to the free_list and try
424 // again to allocate from it.
425 append_secondary_free_list();
426
427 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not "
428 "empty we should have moved at least one entry to the free_list");
429 HeapRegion* res = _hrm.allocate_free_region(is_old);
430 if (G1ConcRegionFreeingVerbose) {
431 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
432 "allocated "HR_FORMAT" from secondary_free_list",
433 HR_FORMAT_PARAMS(res));
434 }
435 return res;
436 }
437
438 // Wait here until we get notified either when (a) there are no
439 // more free regions coming or (b) some regions have been moved on
440 // the secondary_free_list.
441 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
442 }
443
444 if (G1ConcRegionFreeingVerbose) {
445 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
446 "could not allocate from secondary_free_list");
447 }
448 return NULL;
449 }
450
451 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
452 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
453 "the only time we use this to allocate a humongous region is "
454 "when we are allocating a single humongous region");
455
456 HeapRegion* res;
457 if (G1StressConcRegionFreeing) {
458 if (!_secondary_free_list.is_empty()) {
459 if (G1ConcRegionFreeingVerbose) {
460 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
461 "forced to look at the secondary_free_list");
462 }
463 res = new_region_try_secondary_free_list(is_old);
464 if (res != NULL) {
465 return res;
466 }
467 }
468 }
469
470 res = _hrm.allocate_free_region(is_old);
471
472 if (res == NULL) {
473 if (G1ConcRegionFreeingVerbose) {
474 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
475 "res == NULL, trying the secondary_free_list");
476 }
477 res = new_region_try_secondary_free_list(is_old);
478 }
479 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
480 // Currently, only attempts to allocate GC alloc regions set
481 // do_expand to true. So, we should only reach here during a
482 // safepoint. If this assumption changes we might have to
483 // reconsider the use of _expand_heap_after_alloc_failure.
484 assert(SafepointSynchronize::is_at_safepoint(), "invariant");
485
486 ergo_verbose1(ErgoHeapSizing,
487 "attempt heap expansion",
488 ergo_format_reason("region allocation request failed")
489 ergo_format_byte("allocation request"),
490 word_size * HeapWordSize);
491 if (expand(word_size * HeapWordSize)) {
492 // Given that expand() succeeded in expanding the heap, and we
493 // always expand the heap by an amount aligned to the heap
494 // region size, the free list should in theory not be empty.
495 // In either case allocate_free_region() will check for NULL.
496 res = _hrm.allocate_free_region(is_old);
497 } else {
498 _expand_heap_after_alloc_failure = false;
499 }
500 }
501 return res;
502 }
503
504 HeapWord*
505 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
506 uint num_regions,
507 size_t word_size,
508 AllocationContext_t context) {
509 assert(first != G1_NO_HRM_INDEX, "pre-condition");
510 assert(is_humongous(word_size), "word_size should be humongous");
511 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
512
513 // Index of last region in the series + 1.
514 uint last = first + num_regions;
515
516 // We need to initialize the region(s) we just discovered. This is
517 // a bit tricky given that it can happen concurrently with
518 // refinement threads refining cards on these regions and
519 // potentially wanting to refine the BOT as they are scanning
520 // those cards (this can happen shortly after a cleanup; see CR
521 // 6991377). So we have to set up the region(s) carefully and in
522 // a specific order.
523
524 // The word size sum of all the regions we will allocate.
525 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
526 assert(word_size <= word_size_sum, "sanity");
527
528 // This will be the "starts humongous" region.
529 HeapRegion* first_hr = region_at(first);
530 // The header of the new object will be placed at the bottom of
531 // the first region.
532 HeapWord* new_obj = first_hr->bottom();
533 // This will be the new end of the first region in the series that
534 // should also match the end of the last region in the series.
535 HeapWord* new_end = new_obj + word_size_sum;
536 // This will be the new top of the first region that will reflect
537 // this allocation.
538 HeapWord* new_top = new_obj + word_size;
539
540 // First, we need to zero the header of the space that we will be
541 // allocating. When we update top further down, some refinement
542 // threads might try to scan the region. By zeroing the header we
543 // ensure that any thread that will try to scan the region will
544 // come across the zero klass word and bail out.
545 //
546 // NOTE: It would not have been correct to have used
547 // CollectedHeap::fill_with_object() and make the space look like
548 // an int array. The thread that is doing the allocation will
549 // later update the object header to a potentially different array
550 // type and, for a very short period of time, the klass and length
551 // fields will be inconsistent. This could cause a refinement
552 // thread to calculate the object size incorrectly.
553 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
554
555 // We will set up the first region as "starts humongous". This
556 // will also update the BOT covering all the regions to reflect
557 // that there is a single object that starts at the bottom of the
558 // first region.
559 first_hr->set_starts_humongous(new_top, new_end);
560 first_hr->set_allocation_context(context);
561 // Then, if there are any, we will set up the "continues
562 // humongous" regions.
563 HeapRegion* hr = NULL;
564 for (uint i = first + 1; i < last; ++i) {
565 hr = region_at(i);
566 hr->set_continues_humongous(first_hr);
567 hr->set_allocation_context(context);
568 }
569 // If we have "continues humongous" regions (hr != NULL), then the
570 // end of the last one should match new_end.
571 assert(hr == NULL || hr->end() == new_end, "sanity");
572
573 // Up to this point no concurrent thread would have been able to
574 // do any scanning on any region in this series. All the top
575 // fields still point to bottom, so the intersection between
576 // [bottom,top] and [card_start,card_end] will be empty. Before we
577 // update the top fields, we'll do a storestore to make sure that
578 // no thread sees the update to top before the zeroing of the
579 // object header and the BOT initialization.
580 OrderAccess::storestore();
581
582 // Now that the BOT and the object header have been initialized,
583 // we can update top of the "starts humongous" region.
584 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
585 "new_top should be in this region");
586 first_hr->set_top(new_top);
587 if (_hr_printer.is_active()) {
588 HeapWord* bottom = first_hr->bottom();
589 HeapWord* end = first_hr->orig_end();
590 if ((first + 1) == last) {
591 // the series has a single humongous region
592 _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
593 } else {
594 // the series has more than one humongous regions
595 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
596 }
597 }
598
599 // Now, we will update the top fields of the "continues humongous"
600 // regions. The reason we need to do this is that, otherwise,
601 // these regions would look empty and this will confuse parts of
602 // G1. For example, the code that looks for a consecutive number
603 // of empty regions will consider them empty and try to
604 // re-allocate them. We can extend is_empty() to also include
605 // !is_continues_humongous(), but it is easier to just update the top
606 // fields here. The way we set top for all regions (i.e., top ==
607 // end for all regions but the last one, top == new_top for the
608 // last one) is actually used when we will free up the humongous
609 // region in free_humongous_region().
610 hr = NULL;
611 for (uint i = first + 1; i < last; ++i) {
612 hr = region_at(i);
613 if ((i + 1) == last) {
614 // last continues humongous region
615 assert(hr->bottom() < new_top && new_top <= hr->end(),
616 "new_top should fall on this region");
617 hr->set_top(new_top);
618 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
619 } else {
620 // not last one
621 assert(new_top > hr->end(), "new_top should be above this region");
622 hr->set_top(hr->end());
623 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
624 }
625 }
626 // If we have continues humongous regions (hr != NULL), then the
627 // end of the last one should match new_end and its top should
628 // match new_top.
629 assert(hr == NULL ||
630 (hr->end() == new_end && hr->top() == new_top), "sanity");
631 check_bitmaps("Humongous Region Allocation", first_hr);
632
633 assert(first_hr->used() == word_size * HeapWordSize, "invariant");
634 _allocator->increase_used(first_hr->used());
635 _humongous_set.add(first_hr);
636
637 return new_obj;
638 }
639
640 // If could fit into free regions w/o expansion, try.
641 // Otherwise, if can expand, do so.
642 // Otherwise, if using ex regions might help, try with ex given back.
643 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) {
644 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
645
646 verify_region_sets_optional();
647
648 uint first = G1_NO_HRM_INDEX;
649 uint obj_regions = (uint)(align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords);
650
651 if (obj_regions == 1) {
652 // Only one region to allocate, try to use a fast path by directly allocating
653 // from the free lists. Do not try to expand here, we will potentially do that
654 // later.
655 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
656 if (hr != NULL) {
657 first = hr->hrm_index();
658 }
659 } else {
660 // We can't allocate humongous regions spanning more than one region while
661 // cleanupComplete() is running, since some of the regions we find to be
662 // empty might not yet be added to the free list. It is not straightforward
663 // to know in which list they are on so that we can remove them. We only
664 // need to do this if we need to allocate more than one region to satisfy the
665 // current humongous allocation request. If we are only allocating one region
666 // we use the one-region region allocation code (see above), that already
667 // potentially waits for regions from the secondary free list.
668 wait_while_free_regions_coming();
669 append_secondary_free_list_if_not_empty_with_lock();
670
671 // Policy: Try only empty regions (i.e. already committed first). Maybe we
672 // are lucky enough to find some.
673 first = _hrm.find_contiguous_only_empty(obj_regions);
674 if (first != G1_NO_HRM_INDEX) {
675 _hrm.allocate_free_regions_starting_at(first, obj_regions);
676 }
677 }
678
679 if (first == G1_NO_HRM_INDEX) {
680 // Policy: We could not find enough regions for the humongous object in the
681 // free list. Look through the heap to find a mix of free and uncommitted regions.
682 // If so, try expansion.
683 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
684 if (first != G1_NO_HRM_INDEX) {
685 // We found something. Make sure these regions are committed, i.e. expand
686 // the heap. Alternatively we could do a defragmentation GC.
687 ergo_verbose1(ErgoHeapSizing,
688 "attempt heap expansion",
689 ergo_format_reason("humongous allocation request failed")
690 ergo_format_byte("allocation request"),
691 word_size * HeapWordSize);
692
693 _hrm.expand_at(first, obj_regions);
694 g1_policy()->record_new_heap_size(num_regions());
695
696 #ifdef ASSERT
697 for (uint i = first; i < first + obj_regions; ++i) {
698 HeapRegion* hr = region_at(i);
699 assert(hr->is_free(), "sanity");
700 assert(hr->is_empty(), "sanity");
701 assert(is_on_master_free_list(hr), "sanity");
702 }
703 #endif
704 _hrm.allocate_free_regions_starting_at(first, obj_regions);
705 } else {
706 // Policy: Potentially trigger a defragmentation GC.
707 }
708 }
709
710 HeapWord* result = NULL;
711 if (first != G1_NO_HRM_INDEX) {
712 result = humongous_obj_allocate_initialize_regions(first, obj_regions,
713 word_size, context);
714 assert(result != NULL, "it should always return a valid result");
715
716 // A successful humongous object allocation changes the used space
717 // information of the old generation so we need to recalculate the
718 // sizes and update the jstat counters here.
719 g1mm()->update_sizes();
720 }
721
722 verify_region_sets_optional();
723
724 return result;
725 }
726
727 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
728 assert_heap_not_locked_and_not_at_safepoint();
729 assert(!is_humongous(word_size), "we do not allow humongous TLABs");
730
731 uint dummy_gc_count_before;
732 uint dummy_gclocker_retry_count = 0;
733 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
734 }
735
736 HeapWord*
737 G1CollectedHeap::mem_allocate(size_t word_size,
738 bool* gc_overhead_limit_was_exceeded) {
739 assert_heap_not_locked_and_not_at_safepoint();
740
741 // Loop until the allocation is satisfied, or unsatisfied after GC.
742 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
743 uint gc_count_before;
744
745 HeapWord* result = NULL;
746 if (!is_humongous(word_size)) {
747 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
748 } else {
749 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
750 }
751 if (result != NULL) {
752 return result;
753 }
754
755 // Create the garbage collection operation...
756 VM_G1CollectForAllocation op(gc_count_before, word_size);
757 op.set_allocation_context(AllocationContext::current());
758
759 // ...and get the VM thread to execute it.
760 VMThread::execute(&op);
761
762 if (op.prologue_succeeded() && op.pause_succeeded()) {
763 // If the operation was successful we'll return the result even
764 // if it is NULL. If the allocation attempt failed immediately
765 // after a Full GC, it's unlikely we'll be able to allocate now.
766 HeapWord* result = op.result();
767 if (result != NULL && !is_humongous(word_size)) {
768 // Allocations that take place on VM operations do not do any
769 // card dirtying and we have to do it here. We only have to do
770 // this for non-humongous allocations, though.
771 dirty_young_block(result, word_size);
772 }
773 return result;
774 } else {
775 if (gclocker_retry_count > GCLockerRetryAllocationCount) {
776 return NULL;
777 }
778 assert(op.result() == NULL,
779 "the result should be NULL if the VM op did not succeed");
780 }
781
782 // Give a warning if we seem to be looping forever.
783 if ((QueuedAllocationWarningCount > 0) &&
784 (try_count % QueuedAllocationWarningCount == 0)) {
785 warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
786 }
787 }
788
789 ShouldNotReachHere();
790 return NULL;
791 }
792
793 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
794 AllocationContext_t context,
795 uint* gc_count_before_ret,
796 uint* gclocker_retry_count_ret) {
797 // Make sure you read the note in attempt_allocation_humongous().
798
799 assert_heap_not_locked_and_not_at_safepoint();
800 assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
801 "be called for humongous allocation requests");
802
803 // We should only get here after the first-level allocation attempt
804 // (attempt_allocation()) failed to allocate.
805
806 // We will loop until a) we manage to successfully perform the
807 // allocation or b) we successfully schedule a collection which
808 // fails to perform the allocation. b) is the only case when we'll
809 // return NULL.
810 HeapWord* result = NULL;
811 for (int try_count = 1; /* we'll return */; try_count += 1) {
812 bool should_try_gc;
813 uint gc_count_before;
814
815 {
816 MutexLockerEx x(Heap_lock);
817 result = _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size,
818 false /* bot_updates */);
819 if (result != NULL) {
820 return result;
821 }
822
823 // If we reach here, attempt_allocation_locked() above failed to
824 // allocate a new region. So the mutator alloc region should be NULL.
825 assert(_allocator->mutator_alloc_region(context)->get() == NULL, "only way to get here");
826
827 if (GC_locker::is_active_and_needs_gc()) {
828 if (g1_policy()->can_expand_young_list()) {
829 // No need for an ergo verbose message here,
830 // can_expand_young_list() does this when it returns true.
831 result = _allocator->mutator_alloc_region(context)->attempt_allocation_force(word_size,
832 false /* bot_updates */);
833 if (result != NULL) {
834 return result;
835 }
836 }
837 should_try_gc = false;
838 } else {
839 // The GCLocker may not be active but the GCLocker initiated
840 // GC may not yet have been performed (GCLocker::needs_gc()
841 // returns true). In this case we do not try this GC and
842 // wait until the GCLocker initiated GC is performed, and
843 // then retry the allocation.
844 if (GC_locker::needs_gc()) {
845 should_try_gc = false;
846 } else {
847 // Read the GC count while still holding the Heap_lock.
848 gc_count_before = total_collections();
849 should_try_gc = true;
850 }
851 }
852 }
853
854 if (should_try_gc) {
855 bool succeeded;
856 result = do_collection_pause(word_size, gc_count_before, &succeeded,
857 GCCause::_g1_inc_collection_pause);
858 if (result != NULL) {
859 assert(succeeded, "only way to get back a non-NULL result");
860 return result;
861 }
862
863 if (succeeded) {
864 // If we get here we successfully scheduled a collection which
865 // failed to allocate. No point in trying to allocate
866 // further. We'll just return NULL.
867 MutexLockerEx x(Heap_lock);
868 *gc_count_before_ret = total_collections();
869 return NULL;
870 }
871 } else {
872 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
873 MutexLockerEx x(Heap_lock);
874 *gc_count_before_ret = total_collections();
875 return NULL;
876 }
877 // The GCLocker is either active or the GCLocker initiated
878 // GC has not yet been performed. Stall until it is and
879 // then retry the allocation.
880 GC_locker::stall_until_clear();
881 (*gclocker_retry_count_ret) += 1;
882 }
883
884 // We can reach here if we were unsuccessful in scheduling a
885 // collection (because another thread beat us to it) or if we were
886 // stalled due to the GC locker. In either can we should retry the
887 // allocation attempt in case another thread successfully
888 // performed a collection and reclaimed enough space. We do the
889 // first attempt (without holding the Heap_lock) here and the
890 // follow-on attempt will be at the start of the next loop
891 // iteration (after taking the Heap_lock).
892 result = _allocator->mutator_alloc_region(context)->attempt_allocation(word_size,
893 false /* bot_updates */);
894 if (result != NULL) {
895 return result;
896 }
897
898 // Give a warning if we seem to be looping forever.
899 if ((QueuedAllocationWarningCount > 0) &&
900 (try_count % QueuedAllocationWarningCount == 0)) {
901 warning("G1CollectedHeap::attempt_allocation_slow() "
902 "retries %d times", try_count);
903 }
904 }
905
906 ShouldNotReachHere();
907 return NULL;
908 }
909
910 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
911 uint* gc_count_before_ret,
912 uint* gclocker_retry_count_ret) {
913 // The structure of this method has a lot of similarities to
914 // attempt_allocation_slow(). The reason these two were not merged
915 // into a single one is that such a method would require several "if
916 // allocation is not humongous do this, otherwise do that"
917 // conditional paths which would obscure its flow. In fact, an early
918 // version of this code did use a unified method which was harder to
919 // follow and, as a result, it had subtle bugs that were hard to
920 // track down. So keeping these two methods separate allows each to
921 // be more readable. It will be good to keep these two in sync as
922 // much as possible.
923
924 assert_heap_not_locked_and_not_at_safepoint();
925 assert(is_humongous(word_size), "attempt_allocation_humongous() "
926 "should only be called for humongous allocations");
927
928 // Humongous objects can exhaust the heap quickly, so we should check if we
929 // need to start a marking cycle at each humongous object allocation. We do
930 // the check before we do the actual allocation. The reason for doing it
931 // before the allocation is that we avoid having to keep track of the newly
932 // allocated memory while we do a GC.
933 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
934 word_size)) {
935 collect(GCCause::_g1_humongous_allocation);
936 }
937
938 // We will loop until a) we manage to successfully perform the
939 // allocation or b) we successfully schedule a collection which
940 // fails to perform the allocation. b) is the only case when we'll
941 // return NULL.
942 HeapWord* result = NULL;
943 for (int try_count = 1; /* we'll return */; try_count += 1) {
944 bool should_try_gc;
945 uint gc_count_before;
946
947 {
948 MutexLockerEx x(Heap_lock);
949
950 // Given that humongous objects are not allocated in young
951 // regions, we'll first try to do the allocation without doing a
952 // collection hoping that there's enough space in the heap.
953 result = humongous_obj_allocate(word_size, AllocationContext::current());
954 if (result != NULL) {
955 return result;
956 }
957
958 if (GC_locker::is_active_and_needs_gc()) {
959 should_try_gc = false;
960 } else {
961 // The GCLocker may not be active but the GCLocker initiated
962 // GC may not yet have been performed (GCLocker::needs_gc()
963 // returns true). In this case we do not try this GC and
964 // wait until the GCLocker initiated GC is performed, and
965 // then retry the allocation.
966 if (GC_locker::needs_gc()) {
967 should_try_gc = false;
968 } else {
969 // Read the GC count while still holding the Heap_lock.
970 gc_count_before = total_collections();
971 should_try_gc = true;
972 }
973 }
974 }
975
976 if (should_try_gc) {
977 // If we failed to allocate the humongous object, we should try to
978 // do a collection pause (if we're allowed) in case it reclaims
979 // enough space for the allocation to succeed after the pause.
980
981 bool succeeded;
982 result = do_collection_pause(word_size, gc_count_before, &succeeded,
983 GCCause::_g1_humongous_allocation);
984 if (result != NULL) {
985 assert(succeeded, "only way to get back a non-NULL result");
986 return result;
987 }
988
989 if (succeeded) {
990 // If we get here we successfully scheduled a collection which
991 // failed to allocate. No point in trying to allocate
992 // further. We'll just return NULL.
993 MutexLockerEx x(Heap_lock);
994 *gc_count_before_ret = total_collections();
995 return NULL;
996 }
997 } else {
998 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
999 MutexLockerEx x(Heap_lock);
1000 *gc_count_before_ret = total_collections();
1001 return NULL;
1002 }
1003 // The GCLocker is either active or the GCLocker initiated
1004 // GC has not yet been performed. Stall until it is and
1005 // then retry the allocation.
1006 GC_locker::stall_until_clear();
1007 (*gclocker_retry_count_ret) += 1;
1008 }
1009
1010 // We can reach here if we were unsuccessful in scheduling a
1011 // collection (because another thread beat us to it) or if we were
1012 // stalled due to the GC locker. In either can we should retry the
1013 // allocation attempt in case another thread successfully
1014 // performed a collection and reclaimed enough space. Give a
1015 // warning if we seem to be looping forever.
1016
1017 if ((QueuedAllocationWarningCount > 0) &&
1018 (try_count % QueuedAllocationWarningCount == 0)) {
1019 warning("G1CollectedHeap::attempt_allocation_humongous() "
1020 "retries %d times", try_count);
1021 }
1022 }
1023
1024 ShouldNotReachHere();
1025 return NULL;
1026 }
1027
1028 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1029 AllocationContext_t context,
1030 bool expect_null_mutator_alloc_region) {
1031 assert_at_safepoint(true /* should_be_vm_thread */);
1032 assert(_allocator->mutator_alloc_region(context)->get() == NULL ||
1033 !expect_null_mutator_alloc_region,
1034 "the current alloc region was unexpectedly found to be non-NULL");
1035
1036 if (!is_humongous(word_size)) {
1037 return _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size,
1038 false /* bot_updates */);
1039 } else {
1040 HeapWord* result = humongous_obj_allocate(word_size, context);
1041 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1042 g1_policy()->set_initiate_conc_mark_if_possible();
1043 }
1044 return result;
1045 }
1046
1047 ShouldNotReachHere();
1048 }
1049
1050 class PostMCRemSetClearClosure: public HeapRegionClosure {
1051 G1CollectedHeap* _g1h;
1052 ModRefBarrierSet* _mr_bs;
1053 public:
1054 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1055 _g1h(g1h), _mr_bs(mr_bs) {}
1056
1057 bool doHeapRegion(HeapRegion* r) {
1058 HeapRegionRemSet* hrrs = r->rem_set();
1059
1060 if (r->is_continues_humongous()) {
1061 // We'll assert that the strong code root list and RSet is empty
1062 assert(hrrs->strong_code_roots_list_length() == 0, "sanity");
1063 assert(hrrs->occupied() == 0, "RSet should be empty");
1064 return false;
1065 }
1066
1067 _g1h->reset_gc_time_stamps(r);
1068 hrrs->clear();
1069 // You might think here that we could clear just the cards
1070 // corresponding to the used region. But no: if we leave a dirty card
1071 // in a region we might allocate into, then it would prevent that card
1072 // from being enqueued, and cause it to be missed.
1073 // Re: the performance cost: we shouldn't be doing full GC anyway!
1074 _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1075
1076 return false;
1077 }
1078 };
1079
1080 void G1CollectedHeap::clear_rsets_post_compaction() {
1081 PostMCRemSetClearClosure rs_clear(this, g1_barrier_set());
1082 heap_region_iterate(&rs_clear);
1083 }
1084
1085 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1086 G1CollectedHeap* _g1h;
1087 UpdateRSOopClosure _cl;
1088 public:
1089 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, uint worker_i = 0) :
1090 _cl(g1->g1_rem_set(), worker_i),
1091 _g1h(g1)
1092 { }
1093
1094 bool doHeapRegion(HeapRegion* r) {
1095 if (!r->is_continues_humongous()) {
1096 _cl.set_from(r);
1097 r->oop_iterate(&_cl);
1098 }
1099 return false;
1100 }
1101 };
1102
1103 class ParRebuildRSTask: public AbstractGangTask {
1104 G1CollectedHeap* _g1;
1105 HeapRegionClaimer _hrclaimer;
1106
1107 public:
1108 ParRebuildRSTask(G1CollectedHeap* g1) :
1109 AbstractGangTask("ParRebuildRSTask"), _g1(g1), _hrclaimer(g1->workers()->active_workers()) {}
1110
1111 void work(uint worker_id) {
1112 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1113 _g1->heap_region_par_iterate(&rebuild_rs, worker_id, &_hrclaimer);
1114 }
1115 };
1116
1117 class PostCompactionPrinterClosure: public HeapRegionClosure {
1118 private:
1119 G1HRPrinter* _hr_printer;
1120 public:
1121 bool doHeapRegion(HeapRegion* hr) {
1122 assert(!hr->is_young(), "not expecting to find young regions");
1123 if (hr->is_free()) {
1124 // We only generate output for non-empty regions.
1125 } else if (hr->is_starts_humongous()) {
1126 if (hr->region_num() == 1) {
1127 // single humongous region
1128 _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
1129 } else {
1130 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
1131 }
1132 } else if (hr->is_continues_humongous()) {
1133 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1134 } else if (hr->is_old()) {
1135 _hr_printer->post_compaction(hr, G1HRPrinter::Old);
1136 } else {
1137 ShouldNotReachHere();
1138 }
1139 return false;
1140 }
1141
1142 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1143 : _hr_printer(hr_printer) { }
1144 };
1145
1146 void G1CollectedHeap::print_hrm_post_compaction() {
1147 PostCompactionPrinterClosure cl(hr_printer());
1148 heap_region_iterate(&cl);
1149 }
1150
1151 bool G1CollectedHeap::do_collection(bool explicit_gc,
1152 bool clear_all_soft_refs,
1153 size_t word_size) {
1154 assert_at_safepoint(true /* should_be_vm_thread */);
1155
1156 if (GC_locker::check_active_before_gc()) {
1157 return false;
1158 }
1159
1160 STWGCTimer* gc_timer = G1MarkSweep::gc_timer();
1161 gc_timer->register_gc_start();
1162
1163 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer();
1164 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start());
1165
1166 SvcGCMarker sgcm(SvcGCMarker::FULL);
1167 ResourceMark rm;
1168
1169 G1Log::update_level();
1170 print_heap_before_gc();
1171 trace_heap_before_gc(gc_tracer);
1172
1173 size_t metadata_prev_used = MetaspaceAux::used_bytes();
1174
1175 verify_region_sets_optional();
1176
1177 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1178 collector_policy()->should_clear_all_soft_refs();
1179
1180 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1181
1182 {
1183 IsGCActiveMark x;
1184
1185 // Timing
1186 assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant");
1187 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
1188
1189 {
1190 GCTraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, NULL, gc_tracer->gc_id());
1191 TraceCollectorStats tcs(g1mm()->full_collection_counters());
1192 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1193
1194 g1_policy()->record_full_collection_start();
1195
1196 // Note: When we have a more flexible GC logging framework that
1197 // allows us to add optional attributes to a GC log record we
1198 // could consider timing and reporting how long we wait in the
1199 // following two methods.
1200 wait_while_free_regions_coming();
1201 // If we start the compaction before the CM threads finish
1202 // scanning the root regions we might trip them over as we'll
1203 // be moving objects / updating references. So let's wait until
1204 // they are done. By telling them to abort, they should complete
1205 // early.
1206 _cm->root_regions()->abort();
1207 _cm->root_regions()->wait_until_scan_finished();
1208 append_secondary_free_list_if_not_empty_with_lock();
1209
1210 gc_prologue(true);
1211 increment_total_collections(true /* full gc */);
1212 increment_old_marking_cycles_started();
1213
1214 assert(used() == recalculate_used(), "Should be equal");
1215
1216 verify_before_gc();
1217
1218 check_bitmaps("Full GC Start");
1219 pre_full_gc_dump(gc_timer);
1220
1221 COMPILER2_PRESENT(DerivedPointerTable::clear());
1222
1223 // Disable discovery and empty the discovered lists
1224 // for the CM ref processor.
1225 ref_processor_cm()->disable_discovery();
1226 ref_processor_cm()->abandon_partial_discovery();
1227 ref_processor_cm()->verify_no_references_recorded();
1228
1229 // Abandon current iterations of concurrent marking and concurrent
1230 // refinement, if any are in progress. We have to do this before
1231 // wait_until_scan_finished() below.
1232 concurrent_mark()->abort();
1233
1234 // Make sure we'll choose a new allocation region afterwards.
1235 _allocator->release_mutator_alloc_region();
1236 _allocator->abandon_gc_alloc_regions();
1237 g1_rem_set()->cleanupHRRS();
1238
1239 // We should call this after we retire any currently active alloc
1240 // regions so that all the ALLOC / RETIRE events are generated
1241 // before the start GC event.
1242 _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1243
1244 // We may have added regions to the current incremental collection
1245 // set between the last GC or pause and now. We need to clear the
1246 // incremental collection set and then start rebuilding it afresh
1247 // after this full GC.
1248 abandon_collection_set(g1_policy()->inc_cset_head());
1249 g1_policy()->clear_incremental_cset();
1250 g1_policy()->stop_incremental_cset_building();
1251
1252 tear_down_region_sets(false /* free_list_only */);
1253 g1_policy()->set_gcs_are_young(true);
1254
1255 // See the comments in g1CollectedHeap.hpp and
1256 // G1CollectedHeap::ref_processing_init() about
1257 // how reference processing currently works in G1.
1258
1259 // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1260 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1261
1262 // Temporarily clear the STW ref processor's _is_alive_non_header field.
1263 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1264
1265 ref_processor_stw()->enable_discovery();
1266 ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1267
1268 // Do collection work
1269 {
1270 HandleMark hm; // Discard invalid handles created during gc
1271 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1272 }
1273
1274 assert(num_free_regions() == 0, "we should not have added any free regions");
1275 rebuild_region_sets(false /* free_list_only */);
1276
1277 // Enqueue any discovered reference objects that have
1278 // not been removed from the discovered lists.
1279 ref_processor_stw()->enqueue_discovered_references();
1280
1281 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1282
1283 MemoryService::track_memory_usage();
1284
1285 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1286 ref_processor_stw()->verify_no_references_recorded();
1287
1288 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1289 ClassLoaderDataGraph::purge();
1290 MetaspaceAux::verify_metrics();
1291
1292 // Note: since we've just done a full GC, concurrent
1293 // marking is no longer active. Therefore we need not
1294 // re-enable reference discovery for the CM ref processor.
1295 // That will be done at the start of the next marking cycle.
1296 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1297 ref_processor_cm()->verify_no_references_recorded();
1298
1299 reset_gc_time_stamp();
1300 // Since everything potentially moved, we will clear all remembered
1301 // sets, and clear all cards. Later we will rebuild remembered
1302 // sets. We will also reset the GC time stamps of the regions.
1303 clear_rsets_post_compaction();
1304 check_gc_time_stamps();
1305
1306 // Resize the heap if necessary.
1307 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1308
1309 if (_hr_printer.is_active()) {
1310 // We should do this after we potentially resize the heap so
1311 // that all the COMMIT / UNCOMMIT events are generated before
1312 // the end GC event.
1313
1314 print_hrm_post_compaction();
1315 _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1316 }
1317
1318 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
1319 if (hot_card_cache->use_cache()) {
1320 hot_card_cache->reset_card_counts();
1321 hot_card_cache->reset_hot_cache();
1322 }
1323
1324 // Rebuild remembered sets of all regions.
1325 uint n_workers =
1326 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1327 workers()->active_workers(),
1328 Threads::number_of_non_daemon_threads());
1329 workers()->set_active_workers(n_workers);
1330
1331 ParRebuildRSTask rebuild_rs_task(this);
1332 workers()->run_task(&rebuild_rs_task);
1333
1334 // Rebuild the strong code root lists for each region
1335 rebuild_strong_code_roots();
1336
1337 if (true) { // FIXME
1338 MetaspaceGC::compute_new_size();
1339 }
1340
1341 #ifdef TRACESPINNING
1342 ParallelTaskTerminator::print_termination_counts();
1343 #endif
1344
1345 // Discard all rset updates
1346 JavaThread::dirty_card_queue_set().abandon_logs();
1347 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1348
1349 _young_list->reset_sampled_info();
1350 // At this point there should be no regions in the
1351 // entire heap tagged as young.
1352 assert(check_young_list_empty(true /* check_heap */),
1353 "young list should be empty at this point");
1354
1355 // Update the number of full collections that have been completed.
1356 increment_old_marking_cycles_completed(false /* concurrent */);
1357
1358 _hrm.verify_optional();
1359 verify_region_sets_optional();
1360
1361 verify_after_gc();
1362
1363 // Clear the previous marking bitmap, if needed for bitmap verification.
1364 // Note we cannot do this when we clear the next marking bitmap in
1365 // ConcurrentMark::abort() above since VerifyDuringGC verifies the
1366 // objects marked during a full GC against the previous bitmap.
1367 // But we need to clear it before calling check_bitmaps below since
1368 // the full GC has compacted objects and updated TAMS but not updated
1369 // the prev bitmap.
1370 if (G1VerifyBitmaps) {
1371 ((CMBitMap*) concurrent_mark()->prevMarkBitMap())->clearAll();
1372 }
1373 check_bitmaps("Full GC End");
1374
1375 // Start a new incremental collection set for the next pause
1376 assert(g1_policy()->collection_set() == NULL, "must be");
1377 g1_policy()->start_incremental_cset_building();
1378
1379 clear_cset_fast_test();
1380
1381 _allocator->init_mutator_alloc_region();
1382
1383 g1_policy()->record_full_collection_end();
1384
1385 if (G1Log::fine()) {
1386 g1_policy()->print_heap_transition();
1387 }
1388
1389 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1390 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1391 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1392 // before any GC notifications are raised.
1393 g1mm()->update_sizes();
1394
1395 gc_epilogue(true);
1396 }
1397
1398 if (G1Log::finer()) {
1399 g1_policy()->print_detailed_heap_transition(true /* full */);
1400 }
1401
1402 print_heap_after_gc();
1403 trace_heap_after_gc(gc_tracer);
1404
1405 post_full_gc_dump(gc_timer);
1406
1407 gc_timer->register_gc_end();
1408 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
1409 }
1410
1411 return true;
1412 }
1413
1414 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1415 // do_collection() will return whether it succeeded in performing
1416 // the GC. Currently, there is no facility on the
1417 // do_full_collection() API to notify the caller than the collection
1418 // did not succeed (e.g., because it was locked out by the GC
1419 // locker). So, right now, we'll ignore the return value.
1420 bool dummy = do_collection(true, /* explicit_gc */
1421 clear_all_soft_refs,
1422 0 /* word_size */);
1423 }
1424
1425 // This code is mostly copied from TenuredGeneration.
1426 void
1427 G1CollectedHeap::
1428 resize_if_necessary_after_full_collection(size_t word_size) {
1429 // Include the current allocation, if any, and bytes that will be
1430 // pre-allocated to support collections, as "used".
1431 const size_t used_after_gc = used();
1432 const size_t capacity_after_gc = capacity();
1433 const size_t free_after_gc = capacity_after_gc - used_after_gc;
1434
1435 // This is enforced in arguments.cpp.
1436 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1437 "otherwise the code below doesn't make sense");
1438
1439 // We don't have floating point command-line arguments
1440 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1441 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1442 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1443 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1444
1445 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1446 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1447
1448 // We have to be careful here as these two calculations can overflow
1449 // 32-bit size_t's.
1450 double used_after_gc_d = (double) used_after_gc;
1451 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1452 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1453
1454 // Let's make sure that they are both under the max heap size, which
1455 // by default will make them fit into a size_t.
1456 double desired_capacity_upper_bound = (double) max_heap_size;
1457 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1458 desired_capacity_upper_bound);
1459 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1460 desired_capacity_upper_bound);
1461
1462 // We can now safely turn them into size_t's.
1463 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1464 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1465
1466 // This assert only makes sense here, before we adjust them
1467 // with respect to the min and max heap size.
1468 assert(minimum_desired_capacity <= maximum_desired_capacity,
1469 err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1470 "maximum_desired_capacity = "SIZE_FORMAT,
1471 minimum_desired_capacity, maximum_desired_capacity));
1472
1473 // Should not be greater than the heap max size. No need to adjust
1474 // it with respect to the heap min size as it's a lower bound (i.e.,
1475 // we'll try to make the capacity larger than it, not smaller).
1476 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1477 // Should not be less than the heap min size. No need to adjust it
1478 // with respect to the heap max size as it's an upper bound (i.e.,
1479 // we'll try to make the capacity smaller than it, not greater).
1480 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1481
1482 if (capacity_after_gc < minimum_desired_capacity) {
1483 // Don't expand unless it's significant
1484 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1485 ergo_verbose4(ErgoHeapSizing,
1486 "attempt heap expansion",
1487 ergo_format_reason("capacity lower than "
1488 "min desired capacity after Full GC")
1489 ergo_format_byte("capacity")
1490 ergo_format_byte("occupancy")
1491 ergo_format_byte_perc("min desired capacity"),
1492 capacity_after_gc, used_after_gc,
1493 minimum_desired_capacity, (double) MinHeapFreeRatio);
1494 expand(expand_bytes);
1495
1496 // No expansion, now see if we want to shrink
1497 } else if (capacity_after_gc > maximum_desired_capacity) {
1498 // Capacity too large, compute shrinking size
1499 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1500 ergo_verbose4(ErgoHeapSizing,
1501 "attempt heap shrinking",
1502 ergo_format_reason("capacity higher than "
1503 "max desired capacity after Full GC")
1504 ergo_format_byte("capacity")
1505 ergo_format_byte("occupancy")
1506 ergo_format_byte_perc("max desired capacity"),
1507 capacity_after_gc, used_after_gc,
1508 maximum_desired_capacity, (double) MaxHeapFreeRatio);
1509 shrink(shrink_bytes);
1510 }
1511 }
1512
1513
1514 HeapWord*
1515 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1516 AllocationContext_t context,
1517 bool* succeeded) {
1518 assert_at_safepoint(true /* should_be_vm_thread */);
1519
1520 *succeeded = true;
1521 // Let's attempt the allocation first.
1522 HeapWord* result =
1523 attempt_allocation_at_safepoint(word_size,
1524 context,
1525 false /* expect_null_mutator_alloc_region */);
1526 if (result != NULL) {
1527 assert(*succeeded, "sanity");
1528 return result;
1529 }
1530
1531 // In a G1 heap, we're supposed to keep allocation from failing by
1532 // incremental pauses. Therefore, at least for now, we'll favor
1533 // expansion over collection. (This might change in the future if we can
1534 // do something smarter than full collection to satisfy a failed alloc.)
1535 result = expand_and_allocate(word_size, context);
1536 if (result != NULL) {
1537 assert(*succeeded, "sanity");
1538 return result;
1539 }
1540
1541 // Expansion didn't work, we'll try to do a Full GC.
1542 bool gc_succeeded = do_collection(false, /* explicit_gc */
1543 false, /* clear_all_soft_refs */
1544 word_size);
1545 if (!gc_succeeded) {
1546 *succeeded = false;
1547 return NULL;
1548 }
1549
1550 // Retry the allocation
1551 result = attempt_allocation_at_safepoint(word_size,
1552 context,
1553 true /* expect_null_mutator_alloc_region */);
1554 if (result != NULL) {
1555 assert(*succeeded, "sanity");
1556 return result;
1557 }
1558
1559 // Then, try a Full GC that will collect all soft references.
1560 gc_succeeded = do_collection(false, /* explicit_gc */
1561 true, /* clear_all_soft_refs */
1562 word_size);
1563 if (!gc_succeeded) {
1564 *succeeded = false;
1565 return NULL;
1566 }
1567
1568 // Retry the allocation once more
1569 result = attempt_allocation_at_safepoint(word_size,
1570 context,
1571 true /* expect_null_mutator_alloc_region */);
1572 if (result != NULL) {
1573 assert(*succeeded, "sanity");
1574 return result;
1575 }
1576
1577 assert(!collector_policy()->should_clear_all_soft_refs(),
1578 "Flag should have been handled and cleared prior to this point");
1579
1580 // What else? We might try synchronous finalization later. If the total
1581 // space available is large enough for the allocation, then a more
1582 // complete compaction phase than we've tried so far might be
1583 // appropriate.
1584 assert(*succeeded, "sanity");
1585 return NULL;
1586 }
1587
1588 // Attempting to expand the heap sufficiently
1589 // to support an allocation of the given "word_size". If
1590 // successful, perform the allocation and return the address of the
1591 // allocated block, or else "NULL".
1592
1593 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) {
1594 assert_at_safepoint(true /* should_be_vm_thread */);
1595
1596 verify_region_sets_optional();
1597
1598 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1599 ergo_verbose1(ErgoHeapSizing,
1600 "attempt heap expansion",
1601 ergo_format_reason("allocation request failed")
1602 ergo_format_byte("allocation request"),
1603 word_size * HeapWordSize);
1604 if (expand(expand_bytes)) {
1605 _hrm.verify_optional();
1606 verify_region_sets_optional();
1607 return attempt_allocation_at_safepoint(word_size,
1608 context,
1609 false /* expect_null_mutator_alloc_region */);
1610 }
1611 return NULL;
1612 }
1613
1614 bool G1CollectedHeap::expand(size_t expand_bytes) {
1615 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1616 aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1617 HeapRegion::GrainBytes);
1618 ergo_verbose2(ErgoHeapSizing,
1619 "expand the heap",
1620 ergo_format_byte("requested expansion amount")
1621 ergo_format_byte("attempted expansion amount"),
1622 expand_bytes, aligned_expand_bytes);
1623
1624 if (is_maximal_no_gc()) {
1625 ergo_verbose0(ErgoHeapSizing,
1626 "did not expand the heap",
1627 ergo_format_reason("heap already fully expanded"));
1628 return false;
1629 }
1630
1631 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1632 assert(regions_to_expand > 0, "Must expand by at least one region");
1633
1634 uint expanded_by = _hrm.expand_by(regions_to_expand);
1635
1636 if (expanded_by > 0) {
1637 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1638 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1639 g1_policy()->record_new_heap_size(num_regions());
1640 } else {
1641 ergo_verbose0(ErgoHeapSizing,
1642 "did not expand the heap",
1643 ergo_format_reason("heap expansion operation failed"));
1644 // The expansion of the virtual storage space was unsuccessful.
1645 // Let's see if it was because we ran out of swap.
1646 if (G1ExitOnExpansionFailure &&
1647 _hrm.available() >= regions_to_expand) {
1648 // We had head room...
1649 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1650 }
1651 }
1652 return regions_to_expand > 0;
1653 }
1654
1655 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1656 size_t aligned_shrink_bytes =
1657 ReservedSpace::page_align_size_down(shrink_bytes);
1658 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1659 HeapRegion::GrainBytes);
1660 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1661
1662 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1663 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1664
1665 ergo_verbose3(ErgoHeapSizing,
1666 "shrink the heap",
1667 ergo_format_byte("requested shrinking amount")
1668 ergo_format_byte("aligned shrinking amount")
1669 ergo_format_byte("attempted shrinking amount"),
1670 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1671 if (num_regions_removed > 0) {
1672 g1_policy()->record_new_heap_size(num_regions());
1673 } else {
1674 ergo_verbose0(ErgoHeapSizing,
1675 "did not shrink the heap",
1676 ergo_format_reason("heap shrinking operation failed"));
1677 }
1678 }
1679
1680 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1681 verify_region_sets_optional();
1682
1683 // We should only reach here at the end of a Full GC which means we
1684 // should not not be holding to any GC alloc regions. The method
1685 // below will make sure of that and do any remaining clean up.
1686 _allocator->abandon_gc_alloc_regions();
1687
1688 // Instead of tearing down / rebuilding the free lists here, we
1689 // could instead use the remove_all_pending() method on free_list to
1690 // remove only the ones that we need to remove.
1691 tear_down_region_sets(true /* free_list_only */);
1692 shrink_helper(shrink_bytes);
1693 rebuild_region_sets(true /* free_list_only */);
1694
1695 _hrm.verify_optional();
1696 verify_region_sets_optional();
1697 }
1698
1699 // Public methods.
1700
1701 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1702 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1703 #endif // _MSC_VER
1704
1705
1706 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1707 CollectedHeap(),
1708 _g1_policy(policy_),
1709 _dirty_card_queue_set(false),
1710 _into_cset_dirty_card_queue_set(false),
1711 _is_alive_closure_cm(this),
1712 _is_alive_closure_stw(this),
1713 _ref_processor_cm(NULL),
1714 _ref_processor_stw(NULL),
1715 _bot_shared(NULL),
1716 _evac_failure_scan_stack(NULL),
1717 _mark_in_progress(false),
1718 _cg1r(NULL),
1719 _g1mm(NULL),
1720 _refine_cte_cl(NULL),
1721 _full_collection(false),
1722 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1723 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1724 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1725 _humongous_reclaim_candidates(),
1726 _has_humongous_reclaim_candidates(false),
1727 _free_regions_coming(false),
1728 _young_list(new YoungList(this)),
1729 _gc_time_stamp(0),
1730 _survivor_plab_stats(YoungPLABSize, PLABWeight),
1731 _old_plab_stats(OldPLABSize, PLABWeight),
1732 _expand_heap_after_alloc_failure(true),
1733 _surviving_young_words(NULL),
1734 _old_marking_cycles_started(0),
1735 _old_marking_cycles_completed(0),
1736 _concurrent_cycle_started(false),
1737 _heap_summary_sent(false),
1738 _in_cset_fast_test(),
1739 _dirty_cards_region_list(NULL),
1740 _worker_cset_start_region(NULL),
1741 _worker_cset_start_region_time_stamp(NULL),
1742 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1743 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
1744 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1745 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) {
1746
1747 _workers = new FlexibleWorkGang("GC Thread", ParallelGCThreads,
1748 /* are_GC_task_threads */true,
1749 /* are_ConcurrentGC_threads */false);
1750 _workers->initialize_workers();
1751
1752 _allocator = G1Allocator::create_allocator(this);
1753 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1754
1755 int n_queues = (int)ParallelGCThreads;
1756 _task_queues = new RefToScanQueueSet(n_queues);
1757
1758 uint n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1759 assert(n_rem_sets > 0, "Invariant.");
1760
1761 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1762 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(uint, n_queues, mtGC);
1763 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1764
1765 for (int i = 0; i < n_queues; i++) {
1766 RefToScanQueue* q = new RefToScanQueue();
1767 q->initialize();
1768 _task_queues->register_queue(i, q);
1769 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1770 }
1771 clear_cset_start_regions();
1772
1773 // Initialize the G1EvacuationFailureALot counters and flags.
1774 NOT_PRODUCT(reset_evacuation_should_fail();)
1775
1776 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1777 }
1778
1779 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1780 size_t size,
1781 size_t translation_factor) {
1782 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1783 // Allocate a new reserved space, preferring to use large pages.
1784 ReservedSpace rs(size, preferred_page_size);
1785 G1RegionToSpaceMapper* result =
1786 G1RegionToSpaceMapper::create_mapper(rs,
1787 size,
1788 rs.alignment(),
1789 HeapRegion::GrainBytes,
1790 translation_factor,
1791 mtGC);
1792 if (TracePageSizes) {
1793 gclog_or_tty->print_cr("G1 '%s': pg_sz=" SIZE_FORMAT " base=" PTR_FORMAT " size=" SIZE_FORMAT " alignment=" SIZE_FORMAT " reqsize=" SIZE_FORMAT,
1794 description, preferred_page_size, p2i(rs.base()), rs.size(), rs.alignment(), size);
1795 }
1796 return result;
1797 }
1798
1799 jint G1CollectedHeap::initialize() {
1800 CollectedHeap::pre_initialize();
1801 os::enable_vtime();
1802
1803 G1Log::init();
1804
1805 // Necessary to satisfy locking discipline assertions.
1806
1807 MutexLocker x(Heap_lock);
1808
1809 // We have to initialize the printer before committing the heap, as
1810 // it will be used then.
1811 _hr_printer.set_active(G1PrintHeapRegions);
1812
1813 // While there are no constraints in the GC code that HeapWordSize
1814 // be any particular value, there are multiple other areas in the
1815 // system which believe this to be true (e.g. oop->object_size in some
1816 // cases incorrectly returns the size in wordSize units rather than
1817 // HeapWordSize).
1818 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1819
1820 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1821 size_t max_byte_size = collector_policy()->max_heap_byte_size();
1822 size_t heap_alignment = collector_policy()->heap_alignment();
1823
1824 // Ensure that the sizes are properly aligned.
1825 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1826 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1827 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1828
1829 _refine_cte_cl = new RefineCardTableEntryClosure();
1830
1831 _cg1r = new ConcurrentG1Refine(this, _refine_cte_cl);
1832
1833 // Reserve the maximum.
1834
1835 // When compressed oops are enabled, the preferred heap base
1836 // is calculated by subtracting the requested size from the
1837 // 32Gb boundary and using the result as the base address for
1838 // heap reservation. If the requested size is not aligned to
1839 // HeapRegion::GrainBytes (i.e. the alignment that is passed
1840 // into the ReservedHeapSpace constructor) then the actual
1841 // base of the reserved heap may end up differing from the
1842 // address that was requested (i.e. the preferred heap base).
1843 // If this happens then we could end up using a non-optimal
1844 // compressed oops mode.
1845
1846 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1847 heap_alignment);
1848
1849 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
1850
1851 // Create the barrier set for the entire reserved region.
1852 G1SATBCardTableLoggingModRefBS* bs
1853 = new G1SATBCardTableLoggingModRefBS(reserved_region());
1854 bs->initialize();
1855 assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity");
1856 set_barrier_set(bs);
1857
1858 // Also create a G1 rem set.
1859 _g1_rem_set = new G1RemSet(this, g1_barrier_set());
1860
1861 // Carve out the G1 part of the heap.
1862
1863 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1864 size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
1865 G1RegionToSpaceMapper* heap_storage =
1866 G1RegionToSpaceMapper::create_mapper(g1_rs,
1867 g1_rs.size(),
1868 page_size,
1869 HeapRegion::GrainBytes,
1870 1,
1871 mtJavaHeap);
1872 os::trace_page_sizes("G1 Heap", collector_policy()->min_heap_byte_size(),
1873 max_byte_size, page_size,
1874 heap_rs.base(),
1875 heap_rs.size());
1876 heap_storage->set_mapping_changed_listener(&_listener);
1877
1878 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1879 G1RegionToSpaceMapper* bot_storage =
1880 create_aux_memory_mapper("Block offset table",
1881 G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize),
1882 G1BlockOffsetSharedArray::heap_map_factor());
1883
1884 ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize));
1885 G1RegionToSpaceMapper* cardtable_storage =
1886 create_aux_memory_mapper("Card table",
1887 G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize),
1888 G1SATBCardTableLoggingModRefBS::heap_map_factor());
1889
1890 G1RegionToSpaceMapper* card_counts_storage =
1891 create_aux_memory_mapper("Card counts table",
1892 G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1893 G1CardCounts::heap_map_factor());
1894
1895 size_t bitmap_size = CMBitMap::compute_size(g1_rs.size());
1896 G1RegionToSpaceMapper* prev_bitmap_storage =
1897 create_aux_memory_mapper("Prev Bitmap", bitmap_size, CMBitMap::heap_map_factor());
1898 G1RegionToSpaceMapper* next_bitmap_storage =
1899 create_aux_memory_mapper("Next Bitmap", bitmap_size, CMBitMap::heap_map_factor());
1900
1901 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1902 g1_barrier_set()->initialize(cardtable_storage);
1903 // Do later initialization work for concurrent refinement.
1904 _cg1r->init(card_counts_storage);
1905
1906 // 6843694 - ensure that the maximum region index can fit
1907 // in the remembered set structures.
1908 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1909 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1910
1911 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1912 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1913 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1914 "too many cards per region");
1915
1916 FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
1917
1918 _bot_shared = new G1BlockOffsetSharedArray(reserved_region(), bot_storage);
1919
1920 {
1921 HeapWord* start = _hrm.reserved().start();
1922 HeapWord* end = _hrm.reserved().end();
1923 size_t granularity = HeapRegion::GrainBytes;
1924
1925 _in_cset_fast_test.initialize(start, end, granularity);
1926 _humongous_reclaim_candidates.initialize(start, end, granularity);
1927 }
1928
1929 // Create the ConcurrentMark data structure and thread.
1930 // (Must do this late, so that "max_regions" is defined.)
1931 _cm = new ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1932 if (_cm == NULL || !_cm->completed_initialization()) {
1933 vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark");
1934 return JNI_ENOMEM;
1935 }
1936 _cmThread = _cm->cmThread();
1937
1938 // Initialize the from_card cache structure of HeapRegionRemSet.
1939 HeapRegionRemSet::init_heap(max_regions());
1940
1941 // Now expand into the initial heap size.
1942 if (!expand(init_byte_size)) {
1943 vm_shutdown_during_initialization("Failed to allocate initial heap.");
1944 return JNI_ENOMEM;
1945 }
1946
1947 // Perform any initialization actions delegated to the policy.
1948 g1_policy()->init();
1949
1950 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
1951 SATB_Q_FL_lock,
1952 G1SATBProcessCompletedThreshold,
1953 Shared_SATB_Q_lock);
1954
1955 JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl,
1956 DirtyCardQ_CBL_mon,
1957 DirtyCardQ_FL_lock,
1958 concurrent_g1_refine()->yellow_zone(),
1959 concurrent_g1_refine()->red_zone(),
1960 Shared_DirtyCardQ_lock);
1961
1962 dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code
1963 DirtyCardQ_CBL_mon,
1964 DirtyCardQ_FL_lock,
1965 -1, // never trigger processing
1966 -1, // no limit on length
1967 Shared_DirtyCardQ_lock,
1968 &JavaThread::dirty_card_queue_set());
1969
1970 // Initialize the card queue set used to hold cards containing
1971 // references into the collection set.
1972 _into_cset_dirty_card_queue_set.initialize(NULL, // Should never be called by the Java code
1973 DirtyCardQ_CBL_mon,
1974 DirtyCardQ_FL_lock,
1975 -1, // never trigger processing
1976 -1, // no limit on length
1977 Shared_DirtyCardQ_lock,
1978 &JavaThread::dirty_card_queue_set());
1979
1980 // Here we allocate the dummy HeapRegion that is required by the
1981 // G1AllocRegion class.
1982 HeapRegion* dummy_region = _hrm.get_dummy_region();
1983
1984 // We'll re-use the same region whether the alloc region will
1985 // require BOT updates or not and, if it doesn't, then a non-young
1986 // region will complain that it cannot support allocations without
1987 // BOT updates. So we'll tag the dummy region as eden to avoid that.
1988 dummy_region->set_eden();
1989 // Make sure it's full.
1990 dummy_region->set_top(dummy_region->end());
1991 G1AllocRegion::setup(this, dummy_region);
1992
1993 _allocator->init_mutator_alloc_region();
1994
1995 // Do create of the monitoring and management support so that
1996 // values in the heap have been properly initialized.
1997 _g1mm = new G1MonitoringSupport(this);
1998
1999 G1StringDedup::initialize();
2000
2001 return JNI_OK;
2002 }
2003
2004 void G1CollectedHeap::stop() {
2005 // Stop all concurrent threads. We do this to make sure these threads
2006 // do not continue to execute and access resources (e.g. gclog_or_tty)
2007 // that are destroyed during shutdown.
2008 _cg1r->stop();
2009 _cmThread->stop();
2010 if (G1StringDedup::is_enabled()) {
2011 G1StringDedup::stop();
2012 }
2013 }
2014
2015 size_t G1CollectedHeap::conservative_max_heap_alignment() {
2016 return HeapRegion::max_region_size();
2017 }
2018
2019 void G1CollectedHeap::post_initialize() {
2020 CollectedHeap::post_initialize();
2021 ref_processing_init();
2022 }
2023
2024 void G1CollectedHeap::ref_processing_init() {
2025 // Reference processing in G1 currently works as follows:
2026 //
2027 // * There are two reference processor instances. One is
2028 // used to record and process discovered references
2029 // during concurrent marking; the other is used to
2030 // record and process references during STW pauses
2031 // (both full and incremental).
2032 // * Both ref processors need to 'span' the entire heap as
2033 // the regions in the collection set may be dotted around.
2034 //
2035 // * For the concurrent marking ref processor:
2036 // * Reference discovery is enabled at initial marking.
2037 // * Reference discovery is disabled and the discovered
2038 // references processed etc during remarking.
2039 // * Reference discovery is MT (see below).
2040 // * Reference discovery requires a barrier (see below).
2041 // * Reference processing may or may not be MT
2042 // (depending on the value of ParallelRefProcEnabled
2043 // and ParallelGCThreads).
2044 // * A full GC disables reference discovery by the CM
2045 // ref processor and abandons any entries on it's
2046 // discovered lists.
2047 //
2048 // * For the STW processor:
2049 // * Non MT discovery is enabled at the start of a full GC.
2050 // * Processing and enqueueing during a full GC is non-MT.
2051 // * During a full GC, references are processed after marking.
2052 //
2053 // * Discovery (may or may not be MT) is enabled at the start
2054 // of an incremental evacuation pause.
2055 // * References are processed near the end of a STW evacuation pause.
2056 // * For both types of GC:
2057 // * Discovery is atomic - i.e. not concurrent.
2058 // * Reference discovery will not need a barrier.
2059
2060 MemRegion mr = reserved_region();
2061
2062 // Concurrent Mark ref processor
2063 _ref_processor_cm =
2064 new ReferenceProcessor(mr, // span
2065 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2066 // mt processing
2067 (uint) ParallelGCThreads,
2068 // degree of mt processing
2069 (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2070 // mt discovery
2071 (uint) MAX2(ParallelGCThreads, ConcGCThreads),
2072 // degree of mt discovery
2073 false,
2074 // Reference discovery is not atomic
2075 &_is_alive_closure_cm);
2076 // is alive closure
2077 // (for efficiency/performance)
2078
2079 // STW ref processor
2080 _ref_processor_stw =
2081 new ReferenceProcessor(mr, // span
2082 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2083 // mt processing
2084 (uint) ParallelGCThreads,
2085 // degree of mt processing
2086 (ParallelGCThreads > 1),
2087 // mt discovery
2088 (uint) ParallelGCThreads,
2089 // degree of mt discovery
2090 true,
2091 // Reference discovery is atomic
2092 &_is_alive_closure_stw);
2093 // is alive closure
2094 // (for efficiency/performance)
2095 }
2096
2097 size_t G1CollectedHeap::capacity() const {
2098 return _hrm.length() * HeapRegion::GrainBytes;
2099 }
2100
2101 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2102 assert(!hr->is_continues_humongous(), "pre-condition");
2103 hr->reset_gc_time_stamp();
2104 if (hr->is_starts_humongous()) {
2105 uint first_index = hr->hrm_index() + 1;
2106 uint last_index = hr->last_hc_index();
2107 for (uint i = first_index; i < last_index; i += 1) {
2108 HeapRegion* chr = region_at(i);
2109 assert(chr->is_continues_humongous(), "sanity");
2110 chr->reset_gc_time_stamp();
2111 }
2112 }
2113 }
2114
2115 #ifndef PRODUCT
2116
2117 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2118 private:
2119 unsigned _gc_time_stamp;
2120 bool _failures;
2121
2122 public:
2123 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2124 _gc_time_stamp(gc_time_stamp), _failures(false) { }
2125
2126 virtual bool doHeapRegion(HeapRegion* hr) {
2127 unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2128 if (_gc_time_stamp != region_gc_time_stamp) {
2129 gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, "
2130 "expected %d", HR_FORMAT_PARAMS(hr),
2131 region_gc_time_stamp, _gc_time_stamp);
2132 _failures = true;
2133 }
2134 return false;
2135 }
2136
2137 bool failures() { return _failures; }
2138 };
2139
2140 void G1CollectedHeap::check_gc_time_stamps() {
2141 CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2142 heap_region_iterate(&cl);
2143 guarantee(!cl.failures(), "all GC time stamps should have been reset");
2144 }
2145 #endif // PRODUCT
2146
2147 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2148 DirtyCardQueue* into_cset_dcq,
2149 bool concurrent,
2150 uint worker_i) {
2151 // Clean cards in the hot card cache
2152 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
2153 hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq);
2154
2155 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2156 size_t n_completed_buffers = 0;
2157 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2158 n_completed_buffers++;
2159 }
2160 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers);
2161 dcqs.clear_n_completed_buffers();
2162 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2163 }
2164
2165
2166 // Computes the sum of the storage used by the various regions.
2167 size_t G1CollectedHeap::used() const {
2168 return _allocator->used();
2169 }
2170
2171 size_t G1CollectedHeap::used_unlocked() const {
2172 return _allocator->used_unlocked();
2173 }
2174
2175 class SumUsedClosure: public HeapRegionClosure {
2176 size_t _used;
2177 public:
2178 SumUsedClosure() : _used(0) {}
2179 bool doHeapRegion(HeapRegion* r) {
2180 if (!r->is_continues_humongous()) {
2181 _used += r->used();
2182 }
2183 return false;
2184 }
2185 size_t result() { return _used; }
2186 };
2187
2188 size_t G1CollectedHeap::recalculate_used() const {
2189 double recalculate_used_start = os::elapsedTime();
2190
2191 SumUsedClosure blk;
2192 heap_region_iterate(&blk);
2193
2194 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2195 return blk.result();
2196 }
2197
2198 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2199 switch (cause) {
2200 case GCCause::_gc_locker: return GCLockerInvokesConcurrent;
2201 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
2202 case GCCause::_g1_humongous_allocation: return true;
2203 case GCCause::_update_allocation_context_stats_inc: return true;
2204 case GCCause::_wb_conc_mark: return true;
2205 default: return false;
2206 }
2207 }
2208
2209 #ifndef PRODUCT
2210 void G1CollectedHeap::allocate_dummy_regions() {
2211 // Let's fill up most of the region
2212 size_t word_size = HeapRegion::GrainWords - 1024;
2213 // And as a result the region we'll allocate will be humongous.
2214 guarantee(is_humongous(word_size), "sanity");
2215
2216 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2217 // Let's use the existing mechanism for the allocation
2218 HeapWord* dummy_obj = humongous_obj_allocate(word_size,
2219 AllocationContext::system());
2220 if (dummy_obj != NULL) {
2221 MemRegion mr(dummy_obj, word_size);
2222 CollectedHeap::fill_with_object(mr);
2223 } else {
2224 // If we can't allocate once, we probably cannot allocate
2225 // again. Let's get out of the loop.
2226 break;
2227 }
2228 }
2229 }
2230 #endif // !PRODUCT
2231
2232 void G1CollectedHeap::increment_old_marking_cycles_started() {
2233 assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2234 _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2235 err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2236 _old_marking_cycles_started, _old_marking_cycles_completed));
2237
2238 _old_marking_cycles_started++;
2239 }
2240
2241 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2242 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2243
2244 // We assume that if concurrent == true, then the caller is a
2245 // concurrent thread that was joined the Suspendible Thread
2246 // Set. If there's ever a cheap way to check this, we should add an
2247 // assert here.
2248
2249 // Given that this method is called at the end of a Full GC or of a
2250 // concurrent cycle, and those can be nested (i.e., a Full GC can
2251 // interrupt a concurrent cycle), the number of full collections
2252 // completed should be either one (in the case where there was no
2253 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2254 // behind the number of full collections started.
2255
2256 // This is the case for the inner caller, i.e. a Full GC.
2257 assert(concurrent ||
2258 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2259 (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2260 err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
2261 "is inconsistent with _old_marking_cycles_completed = %u",
2262 _old_marking_cycles_started, _old_marking_cycles_completed));
2263
2264 // This is the case for the outer caller, i.e. the concurrent cycle.
2265 assert(!concurrent ||
2266 (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2267 err_msg("for outer caller (concurrent cycle): "
2268 "_old_marking_cycles_started = %u "
2269 "is inconsistent with _old_marking_cycles_completed = %u",
2270 _old_marking_cycles_started, _old_marking_cycles_completed));
2271
2272 _old_marking_cycles_completed += 1;
2273
2274 // We need to clear the "in_progress" flag in the CM thread before
2275 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2276 // is set) so that if a waiter requests another System.gc() it doesn't
2277 // incorrectly see that a marking cycle is still in progress.
2278 if (concurrent) {
2279 _cmThread->clear_in_progress();
2280 }
2281
2282 // This notify_all() will ensure that a thread that called
2283 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2284 // and it's waiting for a full GC to finish will be woken up. It is
2285 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2286 FullGCCount_lock->notify_all();
2287 }
2288
2289 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) {
2290 _concurrent_cycle_started = true;
2291 _gc_timer_cm->register_gc_start(start_time);
2292
2293 _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start());
2294 trace_heap_before_gc(_gc_tracer_cm);
2295 }
2296
2297 void G1CollectedHeap::register_concurrent_cycle_end() {
2298 if (_concurrent_cycle_started) {
2299 if (_cm->has_aborted()) {
2300 _gc_tracer_cm->report_concurrent_mode_failure();
2301 }
2302
2303 _gc_timer_cm->register_gc_end();
2304 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
2305
2306 // Clear state variables to prepare for the next concurrent cycle.
2307 _concurrent_cycle_started = false;
2308 _heap_summary_sent = false;
2309 }
2310 }
2311
2312 void G1CollectedHeap::trace_heap_after_concurrent_cycle() {
2313 if (_concurrent_cycle_started) {
2314 // This function can be called when:
2315 // the cleanup pause is run
2316 // the concurrent cycle is aborted before the cleanup pause.
2317 // the concurrent cycle is aborted after the cleanup pause,
2318 // but before the concurrent cycle end has been registered.
2319 // Make sure that we only send the heap information once.
2320 if (!_heap_summary_sent) {
2321 trace_heap_after_gc(_gc_tracer_cm);
2322 _heap_summary_sent = true;
2323 }
2324 }
2325 }
2326
2327 G1YCType G1CollectedHeap::yc_type() {
2328 bool is_young = g1_policy()->gcs_are_young();
2329 bool is_initial_mark = g1_policy()->during_initial_mark_pause();
2330 bool is_during_mark = mark_in_progress();
2331
2332 if (is_initial_mark) {
2333 return InitialMark;
2334 } else if (is_during_mark) {
2335 return DuringMark;
2336 } else if (is_young) {
2337 return Normal;
2338 } else {
2339 return Mixed;
2340 }
2341 }
2342
2343 void G1CollectedHeap::collect(GCCause::Cause cause) {
2344 assert_heap_not_locked();
2345
2346 uint gc_count_before;
2347 uint old_marking_count_before;
2348 uint full_gc_count_before;
2349 bool retry_gc;
2350
2351 do {
2352 retry_gc = false;
2353
2354 {
2355 MutexLocker ml(Heap_lock);
2356
2357 // Read the GC count while holding the Heap_lock
2358 gc_count_before = total_collections();
2359 full_gc_count_before = total_full_collections();
2360 old_marking_count_before = _old_marking_cycles_started;
2361 }
2362
2363 if (should_do_concurrent_full_gc(cause)) {
2364 // Schedule an initial-mark evacuation pause that will start a
2365 // concurrent cycle. We're setting word_size to 0 which means that
2366 // we are not requesting a post-GC allocation.
2367 VM_G1IncCollectionPause op(gc_count_before,
2368 0, /* word_size */
2369 true, /* should_initiate_conc_mark */
2370 g1_policy()->max_pause_time_ms(),
2371 cause);
2372 op.set_allocation_context(AllocationContext::current());
2373
2374 VMThread::execute(&op);
2375 if (!op.pause_succeeded()) {
2376 if (old_marking_count_before == _old_marking_cycles_started) {
2377 retry_gc = op.should_retry_gc();
2378 } else {
2379 // A Full GC happened while we were trying to schedule the
2380 // initial-mark GC. No point in starting a new cycle given
2381 // that the whole heap was collected anyway.
2382 }
2383
2384 if (retry_gc) {
2385 if (GC_locker::is_active_and_needs_gc()) {
2386 GC_locker::stall_until_clear();
2387 }
2388 }
2389 }
2390 } else {
2391 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2392 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2393
2394 // Schedule a standard evacuation pause. We're setting word_size
2395 // to 0 which means that we are not requesting a post-GC allocation.
2396 VM_G1IncCollectionPause op(gc_count_before,
2397 0, /* word_size */
2398 false, /* should_initiate_conc_mark */
2399 g1_policy()->max_pause_time_ms(),
2400 cause);
2401 VMThread::execute(&op);
2402 } else {
2403 // Schedule a Full GC.
2404 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2405 VMThread::execute(&op);
2406 }
2407 }
2408 } while (retry_gc);
2409 }
2410
2411 bool G1CollectedHeap::is_in(const void* p) const {
2412 if (_hrm.reserved().contains(p)) {
2413 // Given that we know that p is in the reserved space,
2414 // heap_region_containing_raw() should successfully
2415 // return the containing region.
2416 HeapRegion* hr = heap_region_containing_raw(p);
2417 return hr->is_in(p);
2418 } else {
2419 return false;
2420 }
2421 }
2422
2423 #ifdef ASSERT
2424 bool G1CollectedHeap::is_in_exact(const void* p) const {
2425 bool contains = reserved_region().contains(p);
2426 bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2427 if (contains && available) {
2428 return true;
2429 } else {
2430 return false;
2431 }
2432 }
2433 #endif
2434
2435 // Iteration functions.
2436
2437 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion.
2438
2439 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2440 ExtendedOopClosure* _cl;
2441 public:
2442 IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {}
2443 bool doHeapRegion(HeapRegion* r) {
2444 if (!r->is_continues_humongous()) {
2445 r->oop_iterate(_cl);
2446 }
2447 return false;
2448 }
2449 };
2450
2451 // Iterates an ObjectClosure over all objects within a HeapRegion.
2452
2453 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2454 ObjectClosure* _cl;
2455 public:
2456 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2457 bool doHeapRegion(HeapRegion* r) {
2458 if (!r->is_continues_humongous()) {
2459 r->object_iterate(_cl);
2460 }
2461 return false;
2462 }
2463 };
2464
2465 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2466 IterateObjectClosureRegionClosure blk(cl);
2467 heap_region_iterate(&blk);
2468 }
2469
2470 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2471 _hrm.iterate(cl);
2472 }
2473
2474 void
2475 G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl,
2476 uint worker_id,
2477 HeapRegionClaimer *hrclaimer,
2478 bool concurrent) const {
2479 _hrm.par_iterate(cl, worker_id, hrclaimer, concurrent);
2480 }
2481
2482 // Clear the cached CSet starting regions and (more importantly)
2483 // the time stamps. Called when we reset the GC time stamp.
2484 void G1CollectedHeap::clear_cset_start_regions() {
2485 assert(_worker_cset_start_region != NULL, "sanity");
2486 assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2487
2488 for (uint i = 0; i < ParallelGCThreads; i++) {
2489 _worker_cset_start_region[i] = NULL;
2490 _worker_cset_start_region_time_stamp[i] = 0;
2491 }
2492 }
2493
2494 // Given the id of a worker, obtain or calculate a suitable
2495 // starting region for iterating over the current collection set.
2496 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) {
2497 assert(get_gc_time_stamp() > 0, "should have been updated by now");
2498
2499 HeapRegion* result = NULL;
2500 unsigned gc_time_stamp = get_gc_time_stamp();
2501
2502 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2503 // Cached starting region for current worker was set
2504 // during the current pause - so it's valid.
2505 // Note: the cached starting heap region may be NULL
2506 // (when the collection set is empty).
2507 result = _worker_cset_start_region[worker_i];
2508 assert(result == NULL || result->in_collection_set(), "sanity");
2509 return result;
2510 }
2511
2512 // The cached entry was not valid so let's calculate
2513 // a suitable starting heap region for this worker.
2514
2515 // We want the parallel threads to start their collection
2516 // set iteration at different collection set regions to
2517 // avoid contention.
2518 // If we have:
2519 // n collection set regions
2520 // p threads
2521 // Then thread t will start at region floor ((t * n) / p)
2522
2523 result = g1_policy()->collection_set();
2524 uint cs_size = g1_policy()->cset_region_length();
2525 uint active_workers = workers()->active_workers();
2526
2527 uint end_ind = (cs_size * worker_i) / active_workers;
2528 uint start_ind = 0;
2529
2530 if (worker_i > 0 &&
2531 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2532 // Previous workers starting region is valid
2533 // so let's iterate from there
2534 start_ind = (cs_size * (worker_i - 1)) / active_workers;
2535 result = _worker_cset_start_region[worker_i - 1];
2536 }
2537
2538 for (uint i = start_ind; i < end_ind; i++) {
2539 result = result->next_in_collection_set();
2540 }
2541
2542 // Note: the calculated starting heap region may be NULL
2543 // (when the collection set is empty).
2544 assert(result == NULL || result->in_collection_set(), "sanity");
2545 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2546 "should be updated only once per pause");
2547 _worker_cset_start_region[worker_i] = result;
2548 OrderAccess::storestore();
2549 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2550 return result;
2551 }
2552
2553 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2554 HeapRegion* r = g1_policy()->collection_set();
2555 while (r != NULL) {
2556 HeapRegion* next = r->next_in_collection_set();
2557 if (cl->doHeapRegion(r)) {
2558 cl->incomplete();
2559 return;
2560 }
2561 r = next;
2562 }
2563 }
2564
2565 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2566 HeapRegionClosure *cl) {
2567 if (r == NULL) {
2568 // The CSet is empty so there's nothing to do.
2569 return;
2570 }
2571
2572 assert(r->in_collection_set(),
2573 "Start region must be a member of the collection set.");
2574 HeapRegion* cur = r;
2575 while (cur != NULL) {
2576 HeapRegion* next = cur->next_in_collection_set();
2577 if (cl->doHeapRegion(cur) && false) {
2578 cl->incomplete();
2579 return;
2580 }
2581 cur = next;
2582 }
2583 cur = g1_policy()->collection_set();
2584 while (cur != r) {
2585 HeapRegion* next = cur->next_in_collection_set();
2586 if (cl->doHeapRegion(cur) && false) {
2587 cl->incomplete();
2588 return;
2589 }
2590 cur = next;
2591 }
2592 }
2593
2594 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const {
2595 HeapRegion* result = _hrm.next_region_in_heap(from);
2596 while (result != NULL && result->is_humongous()) {
2597 result = _hrm.next_region_in_heap(result);
2598 }
2599 return result;
2600 }
2601
2602 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2603 HeapRegion* hr = heap_region_containing(addr);
2604 return hr->block_start(addr);
2605 }
2606
2607 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2608 HeapRegion* hr = heap_region_containing(addr);
2609 return hr->block_size(addr);
2610 }
2611
2612 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2613 HeapRegion* hr = heap_region_containing(addr);
2614 return hr->block_is_obj(addr);
2615 }
2616
2617 bool G1CollectedHeap::supports_tlab_allocation() const {
2618 return true;
2619 }
2620
2621 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2622 return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes;
2623 }
2624
2625 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2626 return young_list()->eden_used_bytes();
2627 }
2628
2629 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2630 // must be smaller than the humongous object limit.
2631 size_t G1CollectedHeap::max_tlab_size() const {
2632 return align_size_down(_humongous_object_threshold_in_words - 1, MinObjAlignment);
2633 }
2634
2635 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2636 // Return the remaining space in the cur alloc region, but not less than
2637 // the min TLAB size.
2638
2639 // Also, this value can be at most the humongous object threshold,
2640 // since we can't allow tlabs to grow big enough to accommodate
2641 // humongous objects.
2642
2643 HeapRegion* hr = _allocator->mutator_alloc_region(AllocationContext::current())->get();
2644 size_t max_tlab = max_tlab_size() * wordSize;
2645 if (hr == NULL) {
2646 return max_tlab;
2647 } else {
2648 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab);
2649 }
2650 }
2651
2652 size_t G1CollectedHeap::max_capacity() const {
2653 return _hrm.reserved().byte_size();
2654 }
2655
2656 jlong G1CollectedHeap::millis_since_last_gc() {
2657 // assert(false, "NYI");
2658 return 0;
2659 }
2660
2661 void G1CollectedHeap::prepare_for_verify() {
2662 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
2663 ensure_parsability(false);
2664 }
2665 g1_rem_set()->prepare_for_verify();
2666 }
2667
2668 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr,
2669 VerifyOption vo) {
2670 switch (vo) {
2671 case VerifyOption_G1UsePrevMarking:
2672 return hr->obj_allocated_since_prev_marking(obj);
2673 case VerifyOption_G1UseNextMarking:
2674 return hr->obj_allocated_since_next_marking(obj);
2675 case VerifyOption_G1UseMarkWord:
2676 return false;
2677 default:
2678 ShouldNotReachHere();
2679 }
2680 return false; // keep some compilers happy
2681 }
2682
2683 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) {
2684 switch (vo) {
2685 case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start();
2686 case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start();
2687 case VerifyOption_G1UseMarkWord: return NULL;
2688 default: ShouldNotReachHere();
2689 }
2690 return NULL; // keep some compilers happy
2691 }
2692
2693 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) {
2694 switch (vo) {
2695 case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj);
2696 case VerifyOption_G1UseNextMarking: return isMarkedNext(obj);
2697 case VerifyOption_G1UseMarkWord: return obj->is_gc_marked();
2698 default: ShouldNotReachHere();
2699 }
2700 return false; // keep some compilers happy
2701 }
2702
2703 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) {
2704 switch (vo) {
2705 case VerifyOption_G1UsePrevMarking: return "PTAMS";
2706 case VerifyOption_G1UseNextMarking: return "NTAMS";
2707 case VerifyOption_G1UseMarkWord: return "NONE";
2708 default: ShouldNotReachHere();
2709 }
2710 return NULL; // keep some compilers happy
2711 }
2712
2713 class VerifyRootsClosure: public OopClosure {
2714 private:
2715 G1CollectedHeap* _g1h;
2716 VerifyOption _vo;
2717 bool _failures;
2718 public:
2719 // _vo == UsePrevMarking -> use "prev" marking information,
2720 // _vo == UseNextMarking -> use "next" marking information,
2721 // _vo == UseMarkWord -> use mark word from object header.
2722 VerifyRootsClosure(VerifyOption vo) :
2723 _g1h(G1CollectedHeap::heap()),
2724 _vo(vo),
2725 _failures(false) { }
2726
2727 bool failures() { return _failures; }
2728
2729 template <class T> void do_oop_nv(T* p) {
2730 T heap_oop = oopDesc::load_heap_oop(p);
2731 if (!oopDesc::is_null(heap_oop)) {
2732 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2733 if (_g1h->is_obj_dead_cond(obj, _vo)) {
2734 gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
2735 "points to dead obj "PTR_FORMAT, p2i(p), p2i(obj));
2736 if (_vo == VerifyOption_G1UseMarkWord) {
2737 gclog_or_tty->print_cr(" Mark word: "INTPTR_FORMAT, (intptr_t)obj->mark());
2738 }
2739 obj->print_on(gclog_or_tty);
2740 _failures = true;
2741 }
2742 }
2743 }
2744
2745 void do_oop(oop* p) { do_oop_nv(p); }
2746 void do_oop(narrowOop* p) { do_oop_nv(p); }
2747 };
2748
2749 class G1VerifyCodeRootOopClosure: public OopClosure {
2750 G1CollectedHeap* _g1h;
2751 OopClosure* _root_cl;
2752 nmethod* _nm;
2753 VerifyOption _vo;
2754 bool _failures;
2755
2756 template <class T> void do_oop_work(T* p) {
2757 // First verify that this root is live
2758 _root_cl->do_oop(p);
2759
2760 if (!G1VerifyHeapRegionCodeRoots) {
2761 // We're not verifying the code roots attached to heap region.
2762 return;
2763 }
2764
2765 // Don't check the code roots during marking verification in a full GC
2766 if (_vo == VerifyOption_G1UseMarkWord) {
2767 return;
2768 }
2769
2770 // Now verify that the current nmethod (which contains p) is
2771 // in the code root list of the heap region containing the
2772 // object referenced by p.
2773
2774 T heap_oop = oopDesc::load_heap_oop(p);
2775 if (!oopDesc::is_null(heap_oop)) {
2776 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2777
2778 // Now fetch the region containing the object
2779 HeapRegion* hr = _g1h->heap_region_containing(obj);
2780 HeapRegionRemSet* hrrs = hr->rem_set();
2781 // Verify that the strong code root list for this region
2782 // contains the nmethod
2783 if (!hrrs->strong_code_roots_list_contains(_nm)) {
2784 gclog_or_tty->print_cr("Code root location "PTR_FORMAT" "
2785 "from nmethod "PTR_FORMAT" not in strong "
2786 "code roots for region ["PTR_FORMAT","PTR_FORMAT")",
2787 p2i(p), p2i(_nm), p2i(hr->bottom()), p2i(hr->end()));
2788 _failures = true;
2789 }
2790 }
2791 }
2792
2793 public:
2794 G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo):
2795 _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {}
2796
2797 void do_oop(oop* p) { do_oop_work(p); }
2798 void do_oop(narrowOop* p) { do_oop_work(p); }
2799
2800 void set_nmethod(nmethod* nm) { _nm = nm; }
2801 bool failures() { return _failures; }
2802 };
2803
2804 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure {
2805 G1VerifyCodeRootOopClosure* _oop_cl;
2806
2807 public:
2808 G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl):
2809 _oop_cl(oop_cl) {}
2810
2811 void do_code_blob(CodeBlob* cb) {
2812 nmethod* nm = cb->as_nmethod_or_null();
2813 if (nm != NULL) {
2814 _oop_cl->set_nmethod(nm);
2815 nm->oops_do(_oop_cl);
2816 }
2817 }
2818 };
2819
2820 class YoungRefCounterClosure : public OopClosure {
2821 G1CollectedHeap* _g1h;
2822 int _count;
2823 public:
2824 YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {}
2825 void do_oop(oop* p) { if (_g1h->is_in_young(*p)) { _count++; } }
2826 void do_oop(narrowOop* p) { ShouldNotReachHere(); }
2827
2828 int count() { return _count; }
2829 void reset_count() { _count = 0; };
2830 };
2831
2832 class VerifyKlassClosure: public KlassClosure {
2833 YoungRefCounterClosure _young_ref_counter_closure;
2834 OopClosure *_oop_closure;
2835 public:
2836 VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {}
2837 void do_klass(Klass* k) {
2838 k->oops_do(_oop_closure);
2839
2840 _young_ref_counter_closure.reset_count();
2841 k->oops_do(&_young_ref_counter_closure);
2842 if (_young_ref_counter_closure.count() > 0) {
2843 guarantee(k->has_modified_oops(), err_msg("Klass " PTR_FORMAT ", has young refs but is not dirty.", p2i(k)));
2844 }
2845 }
2846 };
2847
2848 class VerifyLivenessOopClosure: public OopClosure {
2849 G1CollectedHeap* _g1h;
2850 VerifyOption _vo;
2851 public:
2852 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
2853 _g1h(g1h), _vo(vo)
2854 { }
2855 void do_oop(narrowOop *p) { do_oop_work(p); }
2856 void do_oop( oop *p) { do_oop_work(p); }
2857
2858 template <class T> void do_oop_work(T *p) {
2859 oop obj = oopDesc::load_decode_heap_oop(p);
2860 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
2861 "Dead object referenced by a not dead object");
2862 }
2863 };
2864
2865 class VerifyObjsInRegionClosure: public ObjectClosure {
2866 private:
2867 G1CollectedHeap* _g1h;
2868 size_t _live_bytes;
2869 HeapRegion *_hr;
2870 VerifyOption _vo;
2871 public:
2872 // _vo == UsePrevMarking -> use "prev" marking information,
2873 // _vo == UseNextMarking -> use "next" marking information,
2874 // _vo == UseMarkWord -> use mark word from object header.
2875 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
2876 : _live_bytes(0), _hr(hr), _vo(vo) {
2877 _g1h = G1CollectedHeap::heap();
2878 }
2879 void do_object(oop o) {
2880 VerifyLivenessOopClosure isLive(_g1h, _vo);
2881 assert(o != NULL, "Huh?");
2882 if (!_g1h->is_obj_dead_cond(o, _vo)) {
2883 // If the object is alive according to the mark word,
2884 // then verify that the marking information agrees.
2885 // Note we can't verify the contra-positive of the
2886 // above: if the object is dead (according to the mark
2887 // word), it may not be marked, or may have been marked
2888 // but has since became dead, or may have been allocated
2889 // since the last marking.
2890 if (_vo == VerifyOption_G1UseMarkWord) {
2891 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
2892 }
2893
2894 o->oop_iterate_no_header(&isLive);
2895 if (!_hr->obj_allocated_since_prev_marking(o)) {
2896 size_t obj_size = o->size(); // Make sure we don't overflow
2897 _live_bytes += (obj_size * HeapWordSize);
2898 }
2899 }
2900 }
2901 size_t live_bytes() { return _live_bytes; }
2902 };
2903
2904 class VerifyRegionClosure: public HeapRegionClosure {
2905 private:
2906 bool _par;
2907 VerifyOption _vo;
2908 bool _failures;
2909 public:
2910 // _vo == UsePrevMarking -> use "prev" marking information,
2911 // _vo == UseNextMarking -> use "next" marking information,
2912 // _vo == UseMarkWord -> use mark word from object header.
2913 VerifyRegionClosure(bool par, VerifyOption vo)
2914 : _par(par),
2915 _vo(vo),
2916 _failures(false) {}
2917
2918 bool failures() {
2919 return _failures;
2920 }
2921
2922 bool doHeapRegion(HeapRegion* r) {
2923 if (!r->is_continues_humongous()) {
2924 bool failures = false;
2925 r->verify(_vo, &failures);
2926 if (failures) {
2927 _failures = true;
2928 } else {
2929 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
2930 r->object_iterate(¬_dead_yet_cl);
2931 if (_vo != VerifyOption_G1UseNextMarking) {
2932 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
2933 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
2934 "max_live_bytes "SIZE_FORMAT" "
2935 "< calculated "SIZE_FORMAT,
2936 p2i(r->bottom()), p2i(r->end()),
2937 r->max_live_bytes(),
2938 not_dead_yet_cl.live_bytes());
2939 _failures = true;
2940 }
2941 } else {
2942 // When vo == UseNextMarking we cannot currently do a sanity
2943 // check on the live bytes as the calculation has not been
2944 // finalized yet.
2945 }
2946 }
2947 }
2948 return false; // stop the region iteration if we hit a failure
2949 }
2950 };
2951
2952 // This is the task used for parallel verification of the heap regions
2953
2954 class G1ParVerifyTask: public AbstractGangTask {
2955 private:
2956 G1CollectedHeap* _g1h;
2957 VerifyOption _vo;
2958 bool _failures;
2959 HeapRegionClaimer _hrclaimer;
2960
2961 public:
2962 // _vo == UsePrevMarking -> use "prev" marking information,
2963 // _vo == UseNextMarking -> use "next" marking information,
2964 // _vo == UseMarkWord -> use mark word from object header.
2965 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
2966 AbstractGangTask("Parallel verify task"),
2967 _g1h(g1h),
2968 _vo(vo),
2969 _failures(false),
2970 _hrclaimer(g1h->workers()->active_workers()) {}
2971
2972 bool failures() {
2973 return _failures;
2974 }
2975
2976 void work(uint worker_id) {
2977 HandleMark hm;
2978 VerifyRegionClosure blk(true, _vo);
2979 _g1h->heap_region_par_iterate(&blk, worker_id, &_hrclaimer);
2980 if (blk.failures()) {
2981 _failures = true;
2982 }
2983 }
2984 };
2985
2986 void G1CollectedHeap::verify(bool silent, VerifyOption vo) {
2987 if (SafepointSynchronize::is_at_safepoint()) {
2988 assert(Thread::current()->is_VM_thread(),
2989 "Expected to be executed serially by the VM thread at this point");
2990
2991 if (!silent) { gclog_or_tty->print("Roots "); }
2992 VerifyRootsClosure rootsCl(vo);
2993 VerifyKlassClosure klassCl(this, &rootsCl);
2994 CLDToKlassAndOopClosure cldCl(&klassCl, &rootsCl, false);
2995
2996 // We apply the relevant closures to all the oops in the
2997 // system dictionary, class loader data graph, the string table
2998 // and the nmethods in the code cache.
2999 G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo);
3000 G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl);
3001
3002 {
3003 G1RootProcessor root_processor(this, 1);
3004 root_processor.process_all_roots(&rootsCl,
3005 &cldCl,
3006 &blobsCl);
3007 }
3008
3009 bool failures = rootsCl.failures() || codeRootsCl.failures();
3010
3011 if (vo != VerifyOption_G1UseMarkWord) {
3012 // If we're verifying during a full GC then the region sets
3013 // will have been torn down at the start of the GC. Therefore
3014 // verifying the region sets will fail. So we only verify
3015 // the region sets when not in a full GC.
3016 if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3017 verify_region_sets();
3018 }
3019
3020 if (!silent) { gclog_or_tty->print("HeapRegions "); }
3021 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3022
3023 G1ParVerifyTask task(this, vo);
3024 workers()->run_task(&task);
3025 if (task.failures()) {
3026 failures = true;
3027 }
3028
3029 } else {
3030 VerifyRegionClosure blk(false, vo);
3031 heap_region_iterate(&blk);
3032 if (blk.failures()) {
3033 failures = true;
3034 }
3035 }
3036
3037 if (G1StringDedup::is_enabled()) {
3038 if (!silent) gclog_or_tty->print("StrDedup ");
3039 G1StringDedup::verify();
3040 }
3041
3042 if (failures) {
3043 gclog_or_tty->print_cr("Heap:");
3044 // It helps to have the per-region information in the output to
3045 // help us track down what went wrong. This is why we call
3046 // print_extended_on() instead of print_on().
3047 print_extended_on(gclog_or_tty);
3048 gclog_or_tty->cr();
3049 gclog_or_tty->flush();
3050 }
3051 guarantee(!failures, "there should not have been any failures");
3052 } else {
3053 if (!silent) {
3054 gclog_or_tty->print("(SKIPPING Roots, HeapRegionSets, HeapRegions, RemSet");
3055 if (G1StringDedup::is_enabled()) {
3056 gclog_or_tty->print(", StrDedup");
3057 }
3058 gclog_or_tty->print(") ");
3059 }
3060 }
3061 }
3062
3063 void G1CollectedHeap::verify(bool silent) {
3064 verify(silent, VerifyOption_G1UsePrevMarking);
3065 }
3066
3067 double G1CollectedHeap::verify(bool guard, const char* msg) {
3068 double verify_time_ms = 0.0;
3069
3070 if (guard && total_collections() >= VerifyGCStartAt) {
3071 double verify_start = os::elapsedTime();
3072 HandleMark hm; // Discard invalid handles created during verification
3073 prepare_for_verify();
3074 Universe::verify(VerifyOption_G1UsePrevMarking, msg);
3075 verify_time_ms = (os::elapsedTime() - verify_start) * 1000;
3076 }
3077
3078 return verify_time_ms;
3079 }
3080
3081 void G1CollectedHeap::verify_before_gc() {
3082 double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:");
3083 g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms);
3084 }
3085
3086 void G1CollectedHeap::verify_after_gc() {
3087 double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:");
3088 g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms);
3089 }
3090
3091 class PrintRegionClosure: public HeapRegionClosure {
3092 outputStream* _st;
3093 public:
3094 PrintRegionClosure(outputStream* st) : _st(st) {}
3095 bool doHeapRegion(HeapRegion* r) {
3096 r->print_on(_st);
3097 return false;
3098 }
3099 };
3100
3101 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3102 const HeapRegion* hr,
3103 const VerifyOption vo) const {
3104 switch (vo) {
3105 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
3106 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
3107 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked();
3108 default: ShouldNotReachHere();
3109 }
3110 return false; // keep some compilers happy
3111 }
3112
3113 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3114 const VerifyOption vo) const {
3115 switch (vo) {
3116 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
3117 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
3118 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked();
3119 default: ShouldNotReachHere();
3120 }
3121 return false; // keep some compilers happy
3122 }
3123
3124 void G1CollectedHeap::print_on(outputStream* st) const {
3125 st->print(" %-20s", "garbage-first heap");
3126 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3127 capacity()/K, used_unlocked()/K);
3128 st->print(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")",
3129 p2i(_hrm.reserved().start()),
3130 p2i(_hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords),
3131 p2i(_hrm.reserved().end()));
3132 st->cr();
3133 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3134 uint young_regions = _young_list->length();
3135 st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3136 (size_t) young_regions * HeapRegion::GrainBytes / K);
3137 uint survivor_regions = g1_policy()->recorded_survivor_regions();
3138 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3139 (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3140 st->cr();
3141 MetaspaceAux::print_on(st);
3142 }
3143
3144 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3145 print_on(st);
3146
3147 // Print the per-region information.
3148 st->cr();
3149 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3150 "HS=humongous(starts), HC=humongous(continues), "
3151 "CS=collection set, F=free, TS=gc time stamp, "
3152 "PTAMS=previous top-at-mark-start, "
3153 "NTAMS=next top-at-mark-start)");
3154 PrintRegionClosure blk(st);
3155 heap_region_iterate(&blk);
3156 }
3157
3158 void G1CollectedHeap::print_on_error(outputStream* st) const {
3159 this->CollectedHeap::print_on_error(st);
3160
3161 if (_cm != NULL) {
3162 st->cr();
3163 _cm->print_on_error(st);
3164 }
3165 }
3166
3167 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3168 workers()->print_worker_threads_on(st);
3169 _cmThread->print_on(st);
3170 st->cr();
3171 _cm->print_worker_threads_on(st);
3172 _cg1r->print_worker_threads_on(st);
3173 if (G1StringDedup::is_enabled()) {
3174 G1StringDedup::print_worker_threads_on(st);
3175 }
3176 }
3177
3178 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3179 workers()->threads_do(tc);
3180 tc->do_thread(_cmThread);
3181 _cg1r->threads_do(tc);
3182 if (G1StringDedup::is_enabled()) {
3183 G1StringDedup::threads_do(tc);
3184 }
3185 }
3186
3187 void G1CollectedHeap::print_tracing_info() const {
3188 // We'll overload this to mean "trace GC pause statistics."
3189 if (TraceYoungGenTime || TraceOldGenTime) {
3190 // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3191 // to that.
3192 g1_policy()->print_tracing_info();
3193 }
3194 if (G1SummarizeRSetStats) {
3195 g1_rem_set()->print_summary_info();
3196 }
3197 if (G1SummarizeConcMark) {
3198 concurrent_mark()->print_summary_info();
3199 }
3200 g1_policy()->print_yg_surv_rate_info();
3201 }
3202
3203 #ifndef PRODUCT
3204 // Helpful for debugging RSet issues.
3205
3206 class PrintRSetsClosure : public HeapRegionClosure {
3207 private:
3208 const char* _msg;
3209 size_t _occupied_sum;
3210
3211 public:
3212 bool doHeapRegion(HeapRegion* r) {
3213 HeapRegionRemSet* hrrs = r->rem_set();
3214 size_t occupied = hrrs->occupied();
3215 _occupied_sum += occupied;
3216
3217 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3218 HR_FORMAT_PARAMS(r));
3219 if (occupied == 0) {
3220 gclog_or_tty->print_cr(" RSet is empty");
3221 } else {
3222 hrrs->print();
3223 }
3224 gclog_or_tty->print_cr("----------");
3225 return false;
3226 }
3227
3228 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3229 gclog_or_tty->cr();
3230 gclog_or_tty->print_cr("========================================");
3231 gclog_or_tty->print_cr("%s", msg);
3232 gclog_or_tty->cr();
3233 }
3234
3235 ~PrintRSetsClosure() {
3236 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3237 gclog_or_tty->print_cr("========================================");
3238 gclog_or_tty->cr();
3239 }
3240 };
3241
3242 void G1CollectedHeap::print_cset_rsets() {
3243 PrintRSetsClosure cl("Printing CSet RSets");
3244 collection_set_iterate(&cl);
3245 }
3246
3247 void G1CollectedHeap::print_all_rsets() {
3248 PrintRSetsClosure cl("Printing All RSets");;
3249 heap_region_iterate(&cl);
3250 }
3251 #endif // PRODUCT
3252
3253 G1CollectedHeap* G1CollectedHeap::heap() {
3254 CollectedHeap* heap = Universe::heap();
3255 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
3256 assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap");
3257 return (G1CollectedHeap*)heap;
3258 }
3259
3260 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3261 // always_do_update_barrier = false;
3262 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3263 // Fill TLAB's and such
3264 accumulate_statistics_all_tlabs();
3265 ensure_parsability(true);
3266
3267 if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) &&
3268 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3269 g1_rem_set()->print_periodic_summary_info("Before GC RS summary");
3270 }
3271 }
3272
3273 void G1CollectedHeap::gc_epilogue(bool full) {
3274
3275 if (G1SummarizeRSetStats &&
3276 (G1SummarizeRSetStatsPeriod > 0) &&
3277 // we are at the end of the GC. Total collections has already been increased.
3278 ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) {
3279 g1_rem_set()->print_periodic_summary_info("After GC RS summary");
3280 }
3281
3282 // FIXME: what is this about?
3283 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3284 // is set.
3285 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3286 "derived pointer present"));
3287 // always_do_update_barrier = true;
3288
3289 resize_all_tlabs();
3290 allocation_context_stats().update(full);
3291
3292 // We have just completed a GC. Update the soft reference
3293 // policy with the new heap occupancy
3294 Universe::update_heap_info_at_gc();
3295 }
3296
3297 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3298 uint gc_count_before,
3299 bool* succeeded,
3300 GCCause::Cause gc_cause) {
3301 assert_heap_not_locked_and_not_at_safepoint();
3302 g1_policy()->record_stop_world_start();
3303 VM_G1IncCollectionPause op(gc_count_before,
3304 word_size,
3305 false, /* should_initiate_conc_mark */
3306 g1_policy()->max_pause_time_ms(),
3307 gc_cause);
3308
3309 op.set_allocation_context(AllocationContext::current());
3310 VMThread::execute(&op);
3311
3312 HeapWord* result = op.result();
3313 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3314 assert(result == NULL || ret_succeeded,
3315 "the result should be NULL if the VM did not succeed");
3316 *succeeded = ret_succeeded;
3317
3318 assert_heap_not_locked();
3319 return result;
3320 }
3321
3322 void
3323 G1CollectedHeap::doConcurrentMark() {
3324 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3325 if (!_cmThread->in_progress()) {
3326 _cmThread->set_started();
3327 CGC_lock->notify();
3328 }
3329 }
3330
3331 size_t G1CollectedHeap::pending_card_num() {
3332 size_t extra_cards = 0;
3333 JavaThread *curr = Threads::first();
3334 while (curr != NULL) {
3335 DirtyCardQueue& dcq = curr->dirty_card_queue();
3336 extra_cards += dcq.size();
3337 curr = curr->next();
3338 }
3339 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3340 size_t buffer_size = dcqs.buffer_size();
3341 size_t buffer_num = dcqs.completed_buffers_num();
3342
3343 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
3344 // in bytes - not the number of 'entries'. We need to convert
3345 // into a number of cards.
3346 return (buffer_size * buffer_num + extra_cards) / oopSize;
3347 }
3348
3349 size_t G1CollectedHeap::cards_scanned() {
3350 return g1_rem_set()->cardsScanned();
3351 }
3352
3353 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
3354 private:
3355 size_t _total_humongous;
3356 size_t _candidate_humongous;
3357
3358 DirtyCardQueue _dcq;
3359
3360 // We don't nominate objects with many remembered set entries, on
3361 // the assumption that such objects are likely still live.
3362 bool is_remset_small(HeapRegion* region) const {
3363 HeapRegionRemSet* const rset = region->rem_set();
3364 return G1EagerReclaimHumongousObjectsWithStaleRefs
3365 ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries)
3366 : rset->is_empty();
3367 }
3368
3369 bool is_typeArray_region(HeapRegion* region) const {
3370 return oop(region->bottom())->is_typeArray();
3371 }
3372
3373 bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const {
3374 assert(region->is_starts_humongous(), "Must start a humongous object");
3375
3376 // Candidate selection must satisfy the following constraints
3377 // while concurrent marking is in progress:
3378 //
3379 // * In order to maintain SATB invariants, an object must not be
3380 // reclaimed if it was allocated before the start of marking and
3381 // has not had its references scanned. Such an object must have
3382 // its references (including type metadata) scanned to ensure no
3383 // live objects are missed by the marking process. Objects
3384 // allocated after the start of concurrent marking don't need to
3385 // be scanned.
3386 //
3387 // * An object must not be reclaimed if it is on the concurrent
3388 // mark stack. Objects allocated after the start of concurrent
3389 // marking are never pushed on the mark stack.
3390 //
3391 // Nominating only objects allocated after the start of concurrent
3392 // marking is sufficient to meet both constraints. This may miss
3393 // some objects that satisfy the constraints, but the marking data
3394 // structures don't support efficiently performing the needed
3395 // additional tests or scrubbing of the mark stack.
3396 //
3397 // However, we presently only nominate is_typeArray() objects.
3398 // A humongous object containing references induces remembered
3399 // set entries on other regions. In order to reclaim such an
3400 // object, those remembered sets would need to be cleaned up.
3401 //
3402 // We also treat is_typeArray() objects specially, allowing them
3403 // to be reclaimed even if allocated before the start of
3404 // concurrent mark. For this we rely on mark stack insertion to
3405 // exclude is_typeArray() objects, preventing reclaiming an object
3406 // that is in the mark stack. We also rely on the metadata for
3407 // such objects to be built-in and so ensured to be kept live.
3408 // Frequent allocation and drop of large binary blobs is an
3409 // important use case for eager reclaim, and this special handling
3410 // may reduce needed headroom.
3411
3412 return is_typeArray_region(region) && is_remset_small(region);
3413 }
3414
3415 public:
3416 RegisterHumongousWithInCSetFastTestClosure()
3417 : _total_humongous(0),
3418 _candidate_humongous(0),
3419 _dcq(&JavaThread::dirty_card_queue_set()) {
3420 }
3421
3422 virtual bool doHeapRegion(HeapRegion* r) {
3423 if (!r->is_starts_humongous()) {
3424 return false;
3425 }
3426 G1CollectedHeap* g1h = G1CollectedHeap::heap();
3427
3428 bool is_candidate = humongous_region_is_candidate(g1h, r);
3429 uint rindex = r->hrm_index();
3430 g1h->set_humongous_reclaim_candidate(rindex, is_candidate);
3431 if (is_candidate) {
3432 _candidate_humongous++;
3433 g1h->register_humongous_region_with_cset(rindex);
3434 // Is_candidate already filters out humongous object with large remembered sets.
3435 // If we have a humongous object with a few remembered sets, we simply flush these
3436 // remembered set entries into the DCQS. That will result in automatic
3437 // re-evaluation of their remembered set entries during the following evacuation
3438 // phase.
3439 if (!r->rem_set()->is_empty()) {
3440 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
3441 "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
3442 G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set();
3443 HeapRegionRemSetIterator hrrs(r->rem_set());
3444 size_t card_index;
3445 while (hrrs.has_next(card_index)) {
3446 jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index);
3447 // The remembered set might contain references to already freed
3448 // regions. Filter out such entries to avoid failing card table
3449 // verification.
3450 if (!g1h->heap_region_containing(bs->addr_for(card_ptr))->is_free()) {
3451 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
3452 *card_ptr = CardTableModRefBS::dirty_card_val();
3453 _dcq.enqueue(card_ptr);
3454 }
3455 }
3456 }
3457 r->rem_set()->clear_locked();
3458 }
3459 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
3460 }
3461 _total_humongous++;
3462
3463 return false;
3464 }
3465
3466 size_t total_humongous() const { return _total_humongous; }
3467 size_t candidate_humongous() const { return _candidate_humongous; }
3468
3469 void flush_rem_set_entries() { _dcq.flush(); }
3470 };
3471
3472 void G1CollectedHeap::register_humongous_regions_with_cset() {
3473 if (!G1EagerReclaimHumongousObjects) {
3474 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
3475 return;
3476 }
3477 double time = os::elapsed_counter();
3478
3479 // Collect reclaim candidate information and register candidates with cset.
3480 RegisterHumongousWithInCSetFastTestClosure cl;
3481 heap_region_iterate(&cl);
3482
3483 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
3484 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
3485 cl.total_humongous(),
3486 cl.candidate_humongous());
3487 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
3488
3489 // Finally flush all remembered set entries to re-check into the global DCQS.
3490 cl.flush_rem_set_entries();
3491 }
3492
3493 void
3494 G1CollectedHeap::setup_surviving_young_words() {
3495 assert(_surviving_young_words == NULL, "pre-condition");
3496 uint array_length = g1_policy()->young_cset_region_length();
3497 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3498 if (_surviving_young_words == NULL) {
3499 vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR,
3500 "Not enough space for young surv words summary.");
3501 }
3502 memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3503 #ifdef ASSERT
3504 for (uint i = 0; i < array_length; ++i) {
3505 assert( _surviving_young_words[i] == 0, "memset above" );
3506 }
3507 #endif // !ASSERT
3508 }
3509
3510 void
3511 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3512 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3513 uint array_length = g1_policy()->young_cset_region_length();
3514 for (uint i = 0; i < array_length; ++i) {
3515 _surviving_young_words[i] += surv_young_words[i];
3516 }
3517 }
3518
3519 void
3520 G1CollectedHeap::cleanup_surviving_young_words() {
3521 guarantee( _surviving_young_words != NULL, "pre-condition" );
3522 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words);
3523 _surviving_young_words = NULL;
3524 }
3525
3526 #ifdef ASSERT
3527 class VerifyCSetClosure: public HeapRegionClosure {
3528 public:
3529 bool doHeapRegion(HeapRegion* hr) {
3530 // Here we check that the CSet region's RSet is ready for parallel
3531 // iteration. The fields that we'll verify are only manipulated
3532 // when the region is part of a CSet and is collected. Afterwards,
3533 // we reset these fields when we clear the region's RSet (when the
3534 // region is freed) so they are ready when the region is
3535 // re-allocated. The only exception to this is if there's an
3536 // evacuation failure and instead of freeing the region we leave
3537 // it in the heap. In that case, we reset these fields during
3538 // evacuation failure handling.
3539 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3540
3541 // Here's a good place to add any other checks we'd like to
3542 // perform on CSet regions.
3543 return false;
3544 }
3545 };
3546 #endif // ASSERT
3547
3548 uint G1CollectedHeap::num_task_queues() const {
3549 return _task_queues->size();
3550 }
3551
3552 #if TASKQUEUE_STATS
3553 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3554 st->print_raw_cr("GC Task Stats");
3555 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3556 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3557 }
3558
3559 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3560 print_taskqueue_stats_hdr(st);
3561
3562 TaskQueueStats totals;
3563 const uint n = num_task_queues();
3564 for (uint i = 0; i < n; ++i) {
3565 st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
3566 totals += task_queue(i)->stats;
3567 }
3568 st->print_raw("tot "); totals.print(st); st->cr();
3569
3570 DEBUG_ONLY(totals.verify());
3571 }
3572
3573 void G1CollectedHeap::reset_taskqueue_stats() {
3574 const uint n = num_task_queues();
3575 for (uint i = 0; i < n; ++i) {
3576 task_queue(i)->stats.reset();
3577 }
3578 }
3579 #endif // TASKQUEUE_STATS
3580
3581 void G1CollectedHeap::log_gc_header() {
3582 if (!G1Log::fine()) {
3583 return;
3584 }
3585
3586 gclog_or_tty->gclog_stamp(_gc_tracer_stw->gc_id());
3587
3588 GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
3589 .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)")
3590 .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : "");
3591
3592 gclog_or_tty->print("[%s", (const char*)gc_cause_str);
3593 }
3594
3595 void G1CollectedHeap::log_gc_footer(double pause_time_sec) {
3596 if (!G1Log::fine()) {
3597 return;
3598 }
3599
3600 if (G1Log::finer()) {
3601 if (evacuation_failed()) {
3602 gclog_or_tty->print(" (to-space exhausted)");
3603 }
3604 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3605 g1_policy()->phase_times()->note_gc_end();
3606 g1_policy()->phase_times()->print(pause_time_sec);
3607 g1_policy()->print_detailed_heap_transition();
3608 } else {
3609 if (evacuation_failed()) {
3610 gclog_or_tty->print("--");
3611 }
3612 g1_policy()->print_heap_transition();
3613 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3614 }
3615 gclog_or_tty->flush();
3616 }
3617
3618 bool
3619 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3620 assert_at_safepoint(true /* should_be_vm_thread */);
3621 guarantee(!is_gc_active(), "collection is not reentrant");
3622
3623 if (GC_locker::check_active_before_gc()) {
3624 return false;
3625 }
3626
3627 _gc_timer_stw->register_gc_start();
3628
3629 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3630
3631 SvcGCMarker sgcm(SvcGCMarker::MINOR);
3632 ResourceMark rm;
3633
3634 G1Log::update_level();
3635 print_heap_before_gc();
3636 trace_heap_before_gc(_gc_tracer_stw);
3637
3638 verify_region_sets_optional();
3639 verify_dirty_young_regions();
3640
3641 // This call will decide whether this pause is an initial-mark
3642 // pause. If it is, during_initial_mark_pause() will return true
3643 // for the duration of this pause.
3644 g1_policy()->decide_on_conc_mark_initiation();
3645
3646 // We do not allow initial-mark to be piggy-backed on a mixed GC.
3647 assert(!g1_policy()->during_initial_mark_pause() ||
3648 g1_policy()->gcs_are_young(), "sanity");
3649
3650 // We also do not allow mixed GCs during marking.
3651 assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3652
3653 // Record whether this pause is an initial mark. When the current
3654 // thread has completed its logging output and it's safe to signal
3655 // the CM thread, the flag's value in the policy has been reset.
3656 bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3657
3658 // Inner scope for scope based logging, timers, and stats collection
3659 {
3660 EvacuationInfo evacuation_info;
3661
3662 if (g1_policy()->during_initial_mark_pause()) {
3663 // We are about to start a marking cycle, so we increment the
3664 // full collection counter.
3665 increment_old_marking_cycles_started();
3666 register_concurrent_cycle_start(_gc_timer_stw->gc_start());
3667 }
3668
3669 _gc_tracer_stw->report_yc_type(yc_type());
3670
3671 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3672
3673 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
3674 workers()->active_workers(),
3675 Threads::number_of_non_daemon_threads());
3676 workers()->set_active_workers(active_workers);
3677
3678 double pause_start_sec = os::elapsedTime();
3679 g1_policy()->phase_times()->note_gc_start(active_workers, mark_in_progress());
3680 log_gc_header();
3681
3682 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3683 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3684
3685 // If the secondary_free_list is not empty, append it to the
3686 // free_list. No need to wait for the cleanup operation to finish;
3687 // the region allocation code will check the secondary_free_list
3688 // and wait if necessary. If the G1StressConcRegionFreeing flag is
3689 // set, skip this step so that the region allocation code has to
3690 // get entries from the secondary_free_list.
3691 if (!G1StressConcRegionFreeing) {
3692 append_secondary_free_list_if_not_empty_with_lock();
3693 }
3694
3695 assert(check_young_list_well_formed(), "young list should be well formed");
3696
3697 // Don't dynamically change the number of GC threads this early. A value of
3698 // 0 is used to indicate serial work. When parallel work is done,
3699 // it will be set.
3700
3701 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3702 IsGCActiveMark x;
3703
3704 gc_prologue(false);
3705 increment_total_collections(false /* full gc */);
3706 increment_gc_time_stamp();
3707
3708 verify_before_gc();
3709
3710 check_bitmaps("GC Start");
3711
3712 COMPILER2_PRESENT(DerivedPointerTable::clear());
3713
3714 // Please see comment in g1CollectedHeap.hpp and
3715 // G1CollectedHeap::ref_processing_init() to see how
3716 // reference processing currently works in G1.
3717
3718 // Enable discovery in the STW reference processor
3719 ref_processor_stw()->enable_discovery();
3720
3721 {
3722 // We want to temporarily turn off discovery by the
3723 // CM ref processor, if necessary, and turn it back on
3724 // on again later if we do. Using a scoped
3725 // NoRefDiscovery object will do this.
3726 NoRefDiscovery no_cm_discovery(ref_processor_cm());
3727
3728 // Forget the current alloc region (we might even choose it to be part
3729 // of the collection set!).
3730 _allocator->release_mutator_alloc_region();
3731
3732 // We should call this after we retire the mutator alloc
3733 // region(s) so that all the ALLOC / RETIRE events are generated
3734 // before the start GC event.
3735 _hr_printer.start_gc(false /* full */, (size_t) total_collections());
3736
3737 // This timing is only used by the ergonomics to handle our pause target.
3738 // It is unclear why this should not include the full pause. We will
3739 // investigate this in CR 7178365.
3740 //
3741 // Preserving the old comment here if that helps the investigation:
3742 //
3743 // The elapsed time induced by the start time below deliberately elides
3744 // the possible verification above.
3745 double sample_start_time_sec = os::elapsedTime();
3746
3747 #if YOUNG_LIST_VERBOSE
3748 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
3749 _young_list->print();
3750 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3751 #endif // YOUNG_LIST_VERBOSE
3752
3753 g1_policy()->record_collection_pause_start(sample_start_time_sec);
3754
3755 double scan_wait_start = os::elapsedTime();
3756 // We have to wait until the CM threads finish scanning the
3757 // root regions as it's the only way to ensure that all the
3758 // objects on them have been correctly scanned before we start
3759 // moving them during the GC.
3760 bool waited = _cm->root_regions()->wait_until_scan_finished();
3761 double wait_time_ms = 0.0;
3762 if (waited) {
3763 double scan_wait_end = os::elapsedTime();
3764 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
3765 }
3766 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
3767
3768 #if YOUNG_LIST_VERBOSE
3769 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
3770 _young_list->print();
3771 #endif // YOUNG_LIST_VERBOSE
3772
3773 if (g1_policy()->during_initial_mark_pause()) {
3774 concurrent_mark()->checkpointRootsInitialPre();
3775 }
3776
3777 #if YOUNG_LIST_VERBOSE
3778 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
3779 _young_list->print();
3780 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3781 #endif // YOUNG_LIST_VERBOSE
3782
3783 g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info);
3784
3785 register_humongous_regions_with_cset();
3786
3787 assert(check_cset_fast_test(), "Inconsistency in the InCSetState table.");
3788
3789 _cm->note_start_of_gc();
3790 // We call this after finalize_cset() to
3791 // ensure that the CSet has been finalized.
3792 _cm->verify_no_cset_oops();
3793
3794 if (_hr_printer.is_active()) {
3795 HeapRegion* hr = g1_policy()->collection_set();
3796 while (hr != NULL) {
3797 _hr_printer.cset(hr);
3798 hr = hr->next_in_collection_set();
3799 }
3800 }
3801
3802 #ifdef ASSERT
3803 VerifyCSetClosure cl;
3804 collection_set_iterate(&cl);
3805 #endif // ASSERT
3806
3807 setup_surviving_young_words();
3808
3809 // Initialize the GC alloc regions.
3810 _allocator->init_gc_alloc_regions(evacuation_info);
3811
3812 // Actually do the work...
3813 evacuate_collection_set(evacuation_info);
3814
3815 free_collection_set(g1_policy()->collection_set(), evacuation_info);
3816
3817 eagerly_reclaim_humongous_regions();
3818
3819 g1_policy()->clear_collection_set();
3820
3821 cleanup_surviving_young_words();
3822
3823 // Start a new incremental collection set for the next pause.
3824 g1_policy()->start_incremental_cset_building();
3825
3826 clear_cset_fast_test();
3827
3828 _young_list->reset_sampled_info();
3829
3830 // Don't check the whole heap at this point as the
3831 // GC alloc regions from this pause have been tagged
3832 // as survivors and moved on to the survivor list.
3833 // Survivor regions will fail the !is_young() check.
3834 assert(check_young_list_empty(false /* check_heap */),
3835 "young list should be empty");
3836
3837 #if YOUNG_LIST_VERBOSE
3838 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
3839 _young_list->print();
3840 #endif // YOUNG_LIST_VERBOSE
3841
3842 g1_policy()->record_survivor_regions(_young_list->survivor_length(),
3843 _young_list->first_survivor_region(),
3844 _young_list->last_survivor_region());
3845
3846 _young_list->reset_auxilary_lists();
3847
3848 if (evacuation_failed()) {
3849 _allocator->set_used(recalculate_used());
3850 for (uint i = 0; i < ParallelGCThreads; i++) {
3851 if (_evacuation_failed_info_array[i].has_failed()) {
3852 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
3853 }
3854 }
3855 } else {
3856 // The "used" of the the collection set have already been subtracted
3857 // when they were freed. Add in the bytes evacuated.
3858 _allocator->increase_used(g1_policy()->bytes_copied_during_gc());
3859 }
3860
3861 if (g1_policy()->during_initial_mark_pause()) {
3862 // We have to do this before we notify the CM threads that
3863 // they can start working to make sure that all the
3864 // appropriate initialization is done on the CM object.
3865 concurrent_mark()->checkpointRootsInitialPost();
3866 set_marking_started();
3867 // Note that we don't actually trigger the CM thread at
3868 // this point. We do that later when we're sure that
3869 // the current thread has completed its logging output.
3870 }
3871
3872 allocate_dummy_regions();
3873
3874 #if YOUNG_LIST_VERBOSE
3875 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
3876 _young_list->print();
3877 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3878 #endif // YOUNG_LIST_VERBOSE
3879
3880 _allocator->init_mutator_alloc_region();
3881
3882 {
3883 size_t expand_bytes = g1_policy()->expansion_amount();
3884 if (expand_bytes > 0) {
3885 size_t bytes_before = capacity();
3886 // No need for an ergo verbose message here,
3887 // expansion_amount() does this when it returns a value > 0.
3888 if (!expand(expand_bytes)) {
3889 // We failed to expand the heap. Cannot do anything about it.
3890 }
3891 }
3892 }
3893
3894 // We redo the verification but now wrt to the new CSet which
3895 // has just got initialized after the previous CSet was freed.
3896 _cm->verify_no_cset_oops();
3897 _cm->note_end_of_gc();
3898
3899 // This timing is only used by the ergonomics to handle our pause target.
3900 // It is unclear why this should not include the full pause. We will
3901 // investigate this in CR 7178365.
3902 double sample_end_time_sec = os::elapsedTime();
3903 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3904 g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info);
3905
3906 MemoryService::track_memory_usage();
3907
3908 // In prepare_for_verify() below we'll need to scan the deferred
3909 // update buffers to bring the RSets up-to-date if
3910 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
3911 // the update buffers we'll probably need to scan cards on the
3912 // regions we just allocated to (i.e., the GC alloc
3913 // regions). However, during the last GC we called
3914 // set_saved_mark() on all the GC alloc regions, so card
3915 // scanning might skip the [saved_mark_word()...top()] area of
3916 // those regions (i.e., the area we allocated objects into
3917 // during the last GC). But it shouldn't. Given that
3918 // saved_mark_word() is conditional on whether the GC time stamp
3919 // on the region is current or not, by incrementing the GC time
3920 // stamp here we invalidate all the GC time stamps on all the
3921 // regions and saved_mark_word() will simply return top() for
3922 // all the regions. This is a nicer way of ensuring this rather
3923 // than iterating over the regions and fixing them. In fact, the
3924 // GC time stamp increment here also ensures that
3925 // saved_mark_word() will return top() between pauses, i.e.,
3926 // during concurrent refinement. So we don't need the
3927 // is_gc_active() check to decided which top to use when
3928 // scanning cards (see CR 7039627).
3929 increment_gc_time_stamp();
3930
3931 verify_after_gc();
3932 check_bitmaps("GC End");
3933
3934 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
3935 ref_processor_stw()->verify_no_references_recorded();
3936
3937 // CM reference discovery will be re-enabled if necessary.
3938 }
3939
3940 // We should do this after we potentially expand the heap so
3941 // that all the COMMIT events are generated before the end GC
3942 // event, and after we retire the GC alloc regions so that all
3943 // RETIRE events are generated before the end GC event.
3944 _hr_printer.end_gc(false /* full */, (size_t) total_collections());
3945
3946 #ifdef TRACESPINNING
3947 ParallelTaskTerminator::print_termination_counts();
3948 #endif
3949
3950 gc_epilogue(false);
3951 }
3952
3953 // Print the remainder of the GC log output.
3954 log_gc_footer(os::elapsedTime() - pause_start_sec);
3955
3956 // It is not yet to safe to tell the concurrent mark to
3957 // start as we have some optional output below. We don't want the
3958 // output from the concurrent mark thread interfering with this
3959 // logging output either.
3960
3961 _hrm.verify_optional();
3962 verify_region_sets_optional();
3963
3964 TASKQUEUE_STATS_ONLY(if (PrintTaskqueue) print_taskqueue_stats());
3965 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3966
3967 print_heap_after_gc();
3968 trace_heap_after_gc(_gc_tracer_stw);
3969
3970 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3971 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3972 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3973 // before any GC notifications are raised.
3974 g1mm()->update_sizes();
3975
3976 _gc_tracer_stw->report_evacuation_info(&evacuation_info);
3977 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
3978 _gc_timer_stw->register_gc_end();
3979 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
3980 }
3981 // It should now be safe to tell the concurrent mark thread to start
3982 // without its logging output interfering with the logging output
3983 // that came from the pause.
3984
3985 if (should_start_conc_mark) {
3986 // CAUTION: after the doConcurrentMark() call below,
3987 // the concurrent marking thread(s) could be running
3988 // concurrently with us. Make sure that anything after
3989 // this point does not assume that we are the only GC thread
3990 // running. Note: of course, the actual marking work will
3991 // not start until the safepoint itself is released in
3992 // SuspendibleThreadSet::desynchronize().
3993 doConcurrentMark();
3994 }
3995
3996 return true;
3997 }
3998
3999 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4000 _drain_in_progress = false;
4001 set_evac_failure_closure(cl);
4002 _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4003 }
4004
4005 void G1CollectedHeap::finalize_for_evac_failure() {
4006 assert(_evac_failure_scan_stack != NULL &&
4007 _evac_failure_scan_stack->length() == 0,
4008 "Postcondition");
4009 assert(!_drain_in_progress, "Postcondition");
4010 delete _evac_failure_scan_stack;
4011 _evac_failure_scan_stack = NULL;
4012 }
4013
4014 void G1CollectedHeap::remove_self_forwarding_pointers() {
4015 double remove_self_forwards_start = os::elapsedTime();
4016
4017 G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4018 workers()->run_task(&rsfp_task);
4019
4020 // Now restore saved marks, if any.
4021 assert(_objs_with_preserved_marks.size() ==
4022 _preserved_marks_of_objs.size(), "Both or none.");
4023 while (!_objs_with_preserved_marks.is_empty()) {
4024 oop obj = _objs_with_preserved_marks.pop();
4025 markOop m = _preserved_marks_of_objs.pop();
4026 obj->set_mark(m);
4027 }
4028 _objs_with_preserved_marks.clear(true);
4029 _preserved_marks_of_objs.clear(true);
4030
4031 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
4032 }
4033
4034 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4035 _evac_failure_scan_stack->push(obj);
4036 }
4037
4038 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4039 assert(_evac_failure_scan_stack != NULL, "precondition");
4040
4041 while (_evac_failure_scan_stack->length() > 0) {
4042 oop obj = _evac_failure_scan_stack->pop();
4043 _evac_failure_closure->set_region(heap_region_containing(obj));
4044 obj->oop_iterate_backwards(_evac_failure_closure);
4045 }
4046 }
4047
4048 oop
4049 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state,
4050 oop old) {
4051 assert(obj_in_cs(old),
4052 err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4053 p2i(old)));
4054 markOop m = old->mark();
4055 oop forward_ptr = old->forward_to_atomic(old);
4056 if (forward_ptr == NULL) {
4057 // Forward-to-self succeeded.
4058 assert(_par_scan_state != NULL, "par scan state");
4059 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4060 uint queue_num = _par_scan_state->queue_num();
4061
4062 _evacuation_failed = true;
4063 _evacuation_failed_info_array[queue_num].register_copy_failure(old->size());
4064 if (_evac_failure_closure != cl) {
4065 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4066 assert(!_drain_in_progress,
4067 "Should only be true while someone holds the lock.");
4068 // Set the global evac-failure closure to the current thread's.
4069 assert(_evac_failure_closure == NULL, "Or locking has failed.");
4070 set_evac_failure_closure(cl);
4071 // Now do the common part.
4072 handle_evacuation_failure_common(old, m);
4073 // Reset to NULL.
4074 set_evac_failure_closure(NULL);
4075 } else {
4076 // The lock is already held, and this is recursive.
4077 assert(_drain_in_progress, "This should only be the recursive case.");
4078 handle_evacuation_failure_common(old, m);
4079 }
4080 return old;
4081 } else {
4082 // Forward-to-self failed. Either someone else managed to allocate
4083 // space for this object (old != forward_ptr) or they beat us in
4084 // self-forwarding it (old == forward_ptr).
4085 assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4086 err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4087 "should not be in the CSet",
4088 p2i(old), p2i(forward_ptr)));
4089 return forward_ptr;
4090 }
4091 }
4092
4093 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4094 preserve_mark_if_necessary(old, m);
4095
4096 HeapRegion* r = heap_region_containing(old);
4097 if (!r->evacuation_failed()) {
4098 r->set_evacuation_failed(true);
4099 _hr_printer.evac_failure(r);
4100 }
4101
4102 push_on_evac_failure_scan_stack(old);
4103
4104 if (!_drain_in_progress) {
4105 // prevent recursion in copy_to_survivor_space()
4106 _drain_in_progress = true;
4107 drain_evac_failure_scan_stack();
4108 _drain_in_progress = false;
4109 }
4110 }
4111
4112 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4113 assert(evacuation_failed(), "Oversaving!");
4114 // We want to call the "for_promotion_failure" version only in the
4115 // case of a promotion failure.
4116 if (m->must_be_preserved_for_promotion_failure(obj)) {
4117 _objs_with_preserved_marks.push(obj);
4118 _preserved_marks_of_objs.push(m);
4119 }
4120 }
4121
4122 void G1ParCopyHelper::mark_object(oop obj) {
4123 assert(!_g1->heap_region_containing(obj)->in_collection_set(), "should not mark objects in the CSet");
4124
4125 // We know that the object is not moving so it's safe to read its size.
4126 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4127 }
4128
4129 void G1ParCopyHelper::mark_forwarded_object(oop from_obj, oop to_obj) {
4130 assert(from_obj->is_forwarded(), "from obj should be forwarded");
4131 assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4132 assert(from_obj != to_obj, "should not be self-forwarded");
4133
4134 assert(_g1->heap_region_containing(from_obj)->in_collection_set(), "from obj should be in the CSet");
4135 assert(!_g1->heap_region_containing(to_obj)->in_collection_set(), "should not mark objects in the CSet");
4136
4137 // The object might be in the process of being copied by another
4138 // worker so we cannot trust that its to-space image is
4139 // well-formed. So we have to read its size from its from-space
4140 // image which we know should not be changing.
4141 _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4142 }
4143
4144 template <class T>
4145 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) {
4146 if (_g1->heap_region_containing_raw(new_obj)->is_young()) {
4147 _scanned_klass->record_modified_oops();
4148 }
4149 }
4150
4151 template <G1Barrier barrier, G1Mark do_mark_object>
4152 template <class T>
4153 void G1ParCopyClosure<barrier, do_mark_object>::do_oop_work(T* p) {
4154 T heap_oop = oopDesc::load_heap_oop(p);
4155
4156 if (oopDesc::is_null(heap_oop)) {
4157 return;
4158 }
4159
4160 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
4161
4162 assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4163
4164 const InCSetState state = _g1->in_cset_state(obj);
4165 if (state.is_in_cset()) {
4166 oop forwardee;
4167 markOop m = obj->mark();
4168 if (m->is_marked()) {
4169 forwardee = (oop) m->decode_pointer();
4170 } else {
4171 forwardee = _par_scan_state->copy_to_survivor_space(state, obj, m);
4172 }
4173 assert(forwardee != NULL, "forwardee should not be NULL");
4174 oopDesc::encode_store_heap_oop(p, forwardee);
4175 if (do_mark_object != G1MarkNone && forwardee != obj) {
4176 // If the object is self-forwarded we don't need to explicitly
4177 // mark it, the evacuation failure protocol will do so.
4178 mark_forwarded_object(obj, forwardee);
4179 }
4180
4181 if (barrier == G1BarrierKlass) {
4182 do_klass_barrier(p, forwardee);
4183 }
4184 } else {
4185 if (state.is_humongous()) {
4186 _g1->set_humongous_is_live(obj);
4187 }
4188 // The object is not in collection set. If we're a root scanning
4189 // closure during an initial mark pause then attempt to mark the object.
4190 if (do_mark_object == G1MarkFromRoot) {
4191 mark_object(obj);
4192 }
4193 }
4194
4195 if (barrier == G1BarrierEvac) {
4196 _par_scan_state->update_rs(_from, p, _worker_id);
4197 }
4198 }
4199
4200 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(oop* p);
4201 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(narrowOop* p);
4202
4203 class G1ParEvacuateFollowersClosure : public VoidClosure {
4204 protected:
4205 G1CollectedHeap* _g1h;
4206 G1ParScanThreadState* _par_scan_state;
4207 RefToScanQueueSet* _queues;
4208 ParallelTaskTerminator* _terminator;
4209
4210 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
4211 RefToScanQueueSet* queues() { return _queues; }
4212 ParallelTaskTerminator* terminator() { return _terminator; }
4213
4214 public:
4215 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4216 G1ParScanThreadState* par_scan_state,
4217 RefToScanQueueSet* queues,
4218 ParallelTaskTerminator* terminator)
4219 : _g1h(g1h), _par_scan_state(par_scan_state),
4220 _queues(queues), _terminator(terminator) {}
4221
4222 void do_void();
4223
4224 private:
4225 inline bool offer_termination();
4226 };
4227
4228 bool G1ParEvacuateFollowersClosure::offer_termination() {
4229 G1ParScanThreadState* const pss = par_scan_state();
4230 pss->start_term_time();
4231 const bool res = terminator()->offer_termination();
4232 pss->end_term_time();
4233 return res;
4234 }
4235
4236 void G1ParEvacuateFollowersClosure::do_void() {
4237 G1ParScanThreadState* const pss = par_scan_state();
4238 pss->trim_queue();
4239 do {
4240 pss->steal_and_trim_queue(queues());
4241 } while (!offer_termination());
4242 }
4243
4244 class G1KlassScanClosure : public KlassClosure {
4245 G1ParCopyHelper* _closure;
4246 bool _process_only_dirty;
4247 int _count;
4248 public:
4249 G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty)
4250 : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {}
4251 void do_klass(Klass* klass) {
4252 // If the klass has not been dirtied we know that there's
4253 // no references into the young gen and we can skip it.
4254 if (!_process_only_dirty || klass->has_modified_oops()) {
4255 // Clean the klass since we're going to scavenge all the metadata.
4256 klass->clear_modified_oops();
4257
4258 // Tell the closure that this klass is the Klass to scavenge
4259 // and is the one to dirty if oops are left pointing into the young gen.
4260 _closure->set_scanned_klass(klass);
4261
4262 klass->oops_do(_closure);
4263
4264 _closure->set_scanned_klass(NULL);
4265 }
4266 _count++;
4267 }
4268 };
4269
4270 class G1ParTask : public AbstractGangTask {
4271 protected:
4272 G1CollectedHeap* _g1h;
4273 RefToScanQueueSet *_queues;
4274 G1RootProcessor* _root_processor;
4275 ParallelTaskTerminator _terminator;
4276 uint _n_workers;
4277
4278 Mutex _stats_lock;
4279 Mutex* stats_lock() { return &_stats_lock; }
4280
4281 public:
4282 G1ParTask(G1CollectedHeap* g1h, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers)
4283 : AbstractGangTask("G1 collection"),
4284 _g1h(g1h),
4285 _queues(task_queues),
4286 _root_processor(root_processor),
4287 _terminator(n_workers, _queues),
4288 _n_workers(n_workers),
4289 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4290 {}
4291
4292 RefToScanQueueSet* queues() { return _queues; }
4293
4294 RefToScanQueue *work_queue(int i) {
4295 return queues()->queue(i);
4296 }
4297
4298 ParallelTaskTerminator* terminator() { return &_terminator; }
4299
4300 // Helps out with CLD processing.
4301 //
4302 // During InitialMark we need to:
4303 // 1) Scavenge all CLDs for the young GC.
4304 // 2) Mark all objects directly reachable from strong CLDs.
4305 template <G1Mark do_mark_object>
4306 class G1CLDClosure : public CLDClosure {
4307 G1ParCopyClosure<G1BarrierNone, do_mark_object>* _oop_closure;
4308 G1ParCopyClosure<G1BarrierKlass, do_mark_object> _oop_in_klass_closure;
4309 G1KlassScanClosure _klass_in_cld_closure;
4310 bool _claim;
4311
4312 public:
4313 G1CLDClosure(G1ParCopyClosure<G1BarrierNone, do_mark_object>* oop_closure,
4314 bool only_young, bool claim)
4315 : _oop_closure(oop_closure),
4316 _oop_in_klass_closure(oop_closure->g1(),
4317 oop_closure->pss(),
4318 oop_closure->rp()),
4319 _klass_in_cld_closure(&_oop_in_klass_closure, only_young),
4320 _claim(claim) {
4321
4322 }
4323
4324 void do_cld(ClassLoaderData* cld) {
4325 cld->oops_do(_oop_closure, &_klass_in_cld_closure, _claim);
4326 }
4327 };
4328
4329 void work(uint worker_id) {
4330 if (worker_id >= _n_workers) return; // no work needed this round
4331
4332 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, os::elapsedTime());
4333
4334 {
4335 ResourceMark rm;
4336 HandleMark hm;
4337
4338 ReferenceProcessor* rp = _g1h->ref_processor_stw();
4339
4340 G1ParScanThreadState pss(_g1h, worker_id, rp);
4341 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
4342
4343 pss.set_evac_failure_closure(&evac_failure_cl);
4344
4345 bool only_young = _g1h->g1_policy()->gcs_are_young();
4346
4347 // Non-IM young GC.
4348 G1ParCopyClosure<G1BarrierNone, G1MarkNone> scan_only_root_cl(_g1h, &pss, rp);
4349 G1CLDClosure<G1MarkNone> scan_only_cld_cl(&scan_only_root_cl,
4350 only_young, // Only process dirty klasses.
4351 false); // No need to claim CLDs.
4352 // IM young GC.
4353 // Strong roots closures.
4354 G1ParCopyClosure<G1BarrierNone, G1MarkFromRoot> scan_mark_root_cl(_g1h, &pss, rp);
4355 G1CLDClosure<G1MarkFromRoot> scan_mark_cld_cl(&scan_mark_root_cl,
4356 false, // Process all klasses.
4357 true); // Need to claim CLDs.
4358 // Weak roots closures.
4359 G1ParCopyClosure<G1BarrierNone, G1MarkPromotedFromRoot> scan_mark_weak_root_cl(_g1h, &pss, rp);
4360 G1CLDClosure<G1MarkPromotedFromRoot> scan_mark_weak_cld_cl(&scan_mark_weak_root_cl,
4361 false, // Process all klasses.
4362 true); // Need to claim CLDs.
4363
4364 OopClosure* strong_root_cl;
4365 OopClosure* weak_root_cl;
4366 CLDClosure* strong_cld_cl;
4367 CLDClosure* weak_cld_cl;
4368
4369 bool trace_metadata = false;
4370
4371 if (_g1h->g1_policy()->during_initial_mark_pause()) {
4372 // We also need to mark copied objects.
4373 strong_root_cl = &scan_mark_root_cl;
4374 strong_cld_cl = &scan_mark_cld_cl;
4375 if (ClassUnloadingWithConcurrentMark) {
4376 weak_root_cl = &scan_mark_weak_root_cl;
4377 weak_cld_cl = &scan_mark_weak_cld_cl;
4378 trace_metadata = true;
4379 } else {
4380 weak_root_cl = &scan_mark_root_cl;
4381 weak_cld_cl = &scan_mark_cld_cl;
4382 }
4383 } else {
4384 strong_root_cl = &scan_only_root_cl;
4385 weak_root_cl = &scan_only_root_cl;
4386 strong_cld_cl = &scan_only_cld_cl;
4387 weak_cld_cl = &scan_only_cld_cl;
4388 }
4389
4390 pss.start_strong_roots();
4391
4392 _root_processor->evacuate_roots(strong_root_cl,
4393 weak_root_cl,
4394 strong_cld_cl,
4395 weak_cld_cl,
4396 trace_metadata,
4397 worker_id);
4398
4399 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss);
4400 _root_processor->scan_remembered_sets(&push_heap_rs_cl,
4401 weak_root_cl,
4402 worker_id);
4403 pss.end_strong_roots();
4404
4405 {
4406 double start = os::elapsedTime();
4407 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4408 evac.do_void();
4409 double elapsed_sec = os::elapsedTime() - start;
4410 double term_sec = pss.term_time();
4411 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec);
4412 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec);
4413 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, pss.term_attempts());
4414 }
4415 _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4416 _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4417
4418 if (PrintTerminationStats) {
4419 MutexLocker x(stats_lock());
4420 pss.print_termination_stats(worker_id);
4421 }
4422
4423 assert(pss.queue_is_empty(), "should be empty");
4424
4425 // Close the inner scope so that the ResourceMark and HandleMark
4426 // destructors are executed here and are included as part of the
4427 // "GC Worker Time".
4428 }
4429 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime());
4430 }
4431 };
4432
4433 class G1StringSymbolTableUnlinkTask : public AbstractGangTask {
4434 private:
4435 BoolObjectClosure* _is_alive;
4436 int _initial_string_table_size;
4437 int _initial_symbol_table_size;
4438
4439 bool _process_strings;
4440 int _strings_processed;
4441 int _strings_removed;
4442
4443 bool _process_symbols;
4444 int _symbols_processed;
4445 int _symbols_removed;
4446
4447 public:
4448 G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) :
4449 AbstractGangTask("String/Symbol Unlinking"),
4450 _is_alive(is_alive),
4451 _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
4452 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) {
4453
4454 _initial_string_table_size = StringTable::the_table()->table_size();
4455 _initial_symbol_table_size = SymbolTable::the_table()->table_size();
4456 if (process_strings) {
4457 StringTable::clear_parallel_claimed_index();
4458 }
4459 if (process_symbols) {
4460 SymbolTable::clear_parallel_claimed_index();
4461 }
4462 }
4463
4464 ~G1StringSymbolTableUnlinkTask() {
4465 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size,
4466 err_msg("claim value %d after unlink less than initial string table size %d",
4467 StringTable::parallel_claimed_index(), _initial_string_table_size));
4468 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
4469 err_msg("claim value %d after unlink less than initial symbol table size %d",
4470 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size));
4471
4472 if (G1TraceStringSymbolTableScrubbing) {
4473 gclog_or_tty->print_cr("Cleaned string and symbol table, "
4474 "strings: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed, "
4475 "symbols: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed",
4476 strings_processed(), strings_removed(),
4477 symbols_processed(), symbols_removed());
4478 }
4479 }
4480
4481 void work(uint worker_id) {
4482 int strings_processed = 0;
4483 int strings_removed = 0;
4484 int symbols_processed = 0;
4485 int symbols_removed = 0;
4486 if (_process_strings) {
4487 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
4488 Atomic::add(strings_processed, &_strings_processed);
4489 Atomic::add(strings_removed, &_strings_removed);
4490 }
4491 if (_process_symbols) {
4492 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
4493 Atomic::add(symbols_processed, &_symbols_processed);
4494 Atomic::add(symbols_removed, &_symbols_removed);
4495 }
4496 }
4497
4498 size_t strings_processed() const { return (size_t)_strings_processed; }
4499 size_t strings_removed() const { return (size_t)_strings_removed; }
4500
4501 size_t symbols_processed() const { return (size_t)_symbols_processed; }
4502 size_t symbols_removed() const { return (size_t)_symbols_removed; }
4503 };
4504
4505 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
4506 private:
4507 static Monitor* _lock;
4508
4509 BoolObjectClosure* const _is_alive;
4510 const bool _unloading_occurred;
4511 const uint _num_workers;
4512
4513 // Variables used to claim nmethods.
4514 nmethod* _first_nmethod;
4515 volatile nmethod* _claimed_nmethod;
4516
4517 // The list of nmethods that need to be processed by the second pass.
4518 volatile nmethod* _postponed_list;
4519 volatile uint _num_entered_barrier;
4520
4521 public:
4522 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
4523 _is_alive(is_alive),
4524 _unloading_occurred(unloading_occurred),
4525 _num_workers(num_workers),
4526 _first_nmethod(NULL),
4527 _claimed_nmethod(NULL),
4528 _postponed_list(NULL),
4529 _num_entered_barrier(0)
4530 {
4531 nmethod::increase_unloading_clock();
4532 // Get first alive nmethod
4533 NMethodIterator iter = NMethodIterator();
4534 if(iter.next_alive()) {
4535 _first_nmethod = iter.method();
4536 }
4537 _claimed_nmethod = (volatile nmethod*)_first_nmethod;
4538 }
4539
4540 ~G1CodeCacheUnloadingTask() {
4541 CodeCache::verify_clean_inline_caches();
4542
4543 CodeCache::set_needs_cache_clean(false);
4544 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
4545
4546 CodeCache::verify_icholder_relocations();
4547 }
4548
4549 private:
4550 void add_to_postponed_list(nmethod* nm) {
4551 nmethod* old;
4552 do {
4553 old = (nmethod*)_postponed_list;
4554 nm->set_unloading_next(old);
4555 } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old);
4556 }
4557
4558 void clean_nmethod(nmethod* nm) {
4559 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
4560
4561 if (postponed) {
4562 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
4563 add_to_postponed_list(nm);
4564 }
4565
4566 // Mark that this thread has been cleaned/unloaded.
4567 // After this call, it will be safe to ask if this nmethod was unloaded or not.
4568 nm->set_unloading_clock(nmethod::global_unloading_clock());
4569 }
4570
4571 void clean_nmethod_postponed(nmethod* nm) {
4572 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
4573 }
4574
4575 static const int MaxClaimNmethods = 16;
4576
4577 void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) {
4578 nmethod* first;
4579 NMethodIterator last;
4580
4581 do {
4582 *num_claimed_nmethods = 0;
4583
4584 first = (nmethod*)_claimed_nmethod;
4585 last = NMethodIterator(first);
4586
4587 if (first != NULL) {
4588
4589 for (int i = 0; i < MaxClaimNmethods; i++) {
4590 if (!last.next_alive()) {
4591 break;
4592 }
4593 claimed_nmethods[i] = last.method();
4594 (*num_claimed_nmethods)++;
4595 }
4596 }
4597
4598 } while ((nmethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first);
4599 }
4600
4601 nmethod* claim_postponed_nmethod() {
4602 nmethod* claim;
4603 nmethod* next;
4604
4605 do {
4606 claim = (nmethod*)_postponed_list;
4607 if (claim == NULL) {
4608 return NULL;
4609 }
4610
4611 next = claim->unloading_next();
4612
4613 } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim);
4614
4615 return claim;
4616 }
4617
4618 public:
4619 // Mark that we're done with the first pass of nmethod cleaning.
4620 void barrier_mark(uint worker_id) {
4621 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
4622 _num_entered_barrier++;
4623 if (_num_entered_barrier == _num_workers) {
4624 ml.notify_all();
4625 }
4626 }
4627
4628 // See if we have to wait for the other workers to
4629 // finish their first-pass nmethod cleaning work.
4630 void barrier_wait(uint worker_id) {
4631 if (_num_entered_barrier < _num_workers) {
4632 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
4633 while (_num_entered_barrier < _num_workers) {
4634 ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
4635 }
4636 }
4637 }
4638
4639 // Cleaning and unloading of nmethods. Some work has to be postponed
4640 // to the second pass, when we know which nmethods survive.
4641 void work_first_pass(uint worker_id) {
4642 // The first nmethods is claimed by the first worker.
4643 if (worker_id == 0 && _first_nmethod != NULL) {
4644 clean_nmethod(_first_nmethod);
4645 _first_nmethod = NULL;
4646 }
4647
4648 int num_claimed_nmethods;
4649 nmethod* claimed_nmethods[MaxClaimNmethods];
4650
4651 while (true) {
4652 claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
4653
4654 if (num_claimed_nmethods == 0) {
4655 break;
4656 }
4657
4658 for (int i = 0; i < num_claimed_nmethods; i++) {
4659 clean_nmethod(claimed_nmethods[i]);
4660 }
4661 }
4662 }
4663
4664 void work_second_pass(uint worker_id) {
4665 nmethod* nm;
4666 // Take care of postponed nmethods.
4667 while ((nm = claim_postponed_nmethod()) != NULL) {
4668 clean_nmethod_postponed(nm);
4669 }
4670 }
4671 };
4672
4673 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never);
4674
4675 class G1KlassCleaningTask : public StackObj {
4676 BoolObjectClosure* _is_alive;
4677 volatile jint _clean_klass_tree_claimed;
4678 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
4679
4680 public:
4681 G1KlassCleaningTask(BoolObjectClosure* is_alive) :
4682 _is_alive(is_alive),
4683 _clean_klass_tree_claimed(0),
4684 _klass_iterator() {
4685 }
4686
4687 private:
4688 bool claim_clean_klass_tree_task() {
4689 if (_clean_klass_tree_claimed) {
4690 return false;
4691 }
4692
4693 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0;
4694 }
4695
4696 InstanceKlass* claim_next_klass() {
4697 Klass* klass;
4698 do {
4699 klass =_klass_iterator.next_klass();
4700 } while (klass != NULL && !klass->oop_is_instance());
4701
4702 return (InstanceKlass*)klass;
4703 }
4704
4705 public:
4706
4707 void clean_klass(InstanceKlass* ik) {
4708 ik->clean_implementors_list(_is_alive);
4709 ik->clean_method_data(_is_alive);
4710
4711 // G1 specific cleanup work that has
4712 // been moved here to be done in parallel.
4713 ik->clean_dependent_nmethods();
4714 }
4715
4716 void work() {
4717 ResourceMark rm;
4718
4719 // One worker will clean the subklass/sibling klass tree.
4720 if (claim_clean_klass_tree_task()) {
4721 Klass::clean_subklass_tree(_is_alive);
4722 }
4723
4724 // All workers will help cleaning the classes,
4725 InstanceKlass* klass;
4726 while ((klass = claim_next_klass()) != NULL) {
4727 clean_klass(klass);
4728 }
4729 }
4730 };
4731
4732 // To minimize the remark pause times, the tasks below are done in parallel.
4733 class G1ParallelCleaningTask : public AbstractGangTask {
4734 private:
4735 G1StringSymbolTableUnlinkTask _string_symbol_task;
4736 G1CodeCacheUnloadingTask _code_cache_task;
4737 G1KlassCleaningTask _klass_cleaning_task;
4738
4739 public:
4740 // The constructor is run in the VMThread.
4741 G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) :
4742 AbstractGangTask("Parallel Cleaning"),
4743 _string_symbol_task(is_alive, process_strings, process_symbols),
4744 _code_cache_task(num_workers, is_alive, unloading_occurred),
4745 _klass_cleaning_task(is_alive) {
4746 }
4747
4748 // The parallel work done by all worker threads.
4749 void work(uint worker_id) {
4750 // Do first pass of code cache cleaning.
4751 _code_cache_task.work_first_pass(worker_id);
4752
4753 // Let the threads mark that the first pass is done.
4754 _code_cache_task.barrier_mark(worker_id);
4755
4756 // Clean the Strings and Symbols.
4757 _string_symbol_task.work(worker_id);
4758
4759 // Wait for all workers to finish the first code cache cleaning pass.
4760 _code_cache_task.barrier_wait(worker_id);
4761
4762 // Do the second code cache cleaning work, which realize on
4763 // the liveness information gathered during the first pass.
4764 _code_cache_task.work_second_pass(worker_id);
4765
4766 // Clean all klasses that were not unloaded.
4767 _klass_cleaning_task.work();
4768 }
4769 };
4770
4771
4772 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive,
4773 bool process_strings,
4774 bool process_symbols,
4775 bool class_unloading_occurred) {
4776 uint n_workers = workers()->active_workers();
4777
4778 G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols,
4779 n_workers, class_unloading_occurred);
4780 workers()->run_task(&g1_unlink_task);
4781 }
4782
4783 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive,
4784 bool process_strings, bool process_symbols) {
4785 {
4786 G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols);
4787 workers()->run_task(&g1_unlink_task);
4788 }
4789
4790 if (G1StringDedup::is_enabled()) {
4791 G1StringDedup::unlink(is_alive);
4792 }
4793 }
4794
4795 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
4796 private:
4797 DirtyCardQueueSet* _queue;
4798 public:
4799 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue) : AbstractGangTask("Redirty Cards"), _queue(queue) { }
4800
4801 virtual void work(uint worker_id) {
4802 G1GCPhaseTimes* phase_times = G1CollectedHeap::heap()->g1_policy()->phase_times();
4803 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id);
4804
4805 RedirtyLoggedCardTableEntryClosure cl;
4806 _queue->par_apply_closure_to_all_completed_buffers(&cl);
4807
4808 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_processed());
4809 }
4810 };
4811
4812 void G1CollectedHeap::redirty_logged_cards() {
4813 double redirty_logged_cards_start = os::elapsedTime();
4814
4815 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set());
4816 dirty_card_queue_set().reset_for_par_iteration();
4817 workers()->run_task(&redirty_task);
4818
4819 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
4820 dcq.merge_bufferlists(&dirty_card_queue_set());
4821 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
4822
4823 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
4824 }
4825
4826 // Weak Reference Processing support
4827
4828 // An always "is_alive" closure that is used to preserve referents.
4829 // If the object is non-null then it's alive. Used in the preservation
4830 // of referent objects that are pointed to by reference objects
4831 // discovered by the CM ref processor.
4832 class G1AlwaysAliveClosure: public BoolObjectClosure {
4833 G1CollectedHeap* _g1;
4834 public:
4835 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
4836 bool do_object_b(oop p) {
4837 if (p != NULL) {
4838 return true;
4839 }
4840 return false;
4841 }
4842 };
4843
4844 bool G1STWIsAliveClosure::do_object_b(oop p) {
4845 // An object is reachable if it is outside the collection set,
4846 // or is inside and copied.
4847 return !_g1->obj_in_cs(p) || p->is_forwarded();
4848 }
4849
4850 // Non Copying Keep Alive closure
4851 class G1KeepAliveClosure: public OopClosure {
4852 G1CollectedHeap* _g1;
4853 public:
4854 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
4855 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
4856 void do_oop(oop* p) {
4857 oop obj = *p;
4858 assert(obj != NULL, "the caller should have filtered out NULL values");
4859
4860 const InCSetState cset_state = _g1->in_cset_state(obj);
4861 if (!cset_state.is_in_cset_or_humongous()) {
4862 return;
4863 }
4864 if (cset_state.is_in_cset()) {
4865 assert( obj->is_forwarded(), "invariant" );
4866 *p = obj->forwardee();
4867 } else {
4868 assert(!obj->is_forwarded(), "invariant" );
4869 assert(cset_state.is_humongous(),
4870 err_msg("Only allowed InCSet state is IsHumongous, but is %d", cset_state.value()));
4871 _g1->set_humongous_is_live(obj);
4872 }
4873 }
4874 };
4875
4876 // Copying Keep Alive closure - can be called from both
4877 // serial and parallel code as long as different worker
4878 // threads utilize different G1ParScanThreadState instances
4879 // and different queues.
4880
4881 class G1CopyingKeepAliveClosure: public OopClosure {
4882 G1CollectedHeap* _g1h;
4883 OopClosure* _copy_non_heap_obj_cl;
4884 G1ParScanThreadState* _par_scan_state;
4885
4886 public:
4887 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
4888 OopClosure* non_heap_obj_cl,
4889 G1ParScanThreadState* pss):
4890 _g1h(g1h),
4891 _copy_non_heap_obj_cl(non_heap_obj_cl),
4892 _par_scan_state(pss)
4893 {}
4894
4895 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
4896 virtual void do_oop( oop* p) { do_oop_work(p); }
4897
4898 template <class T> void do_oop_work(T* p) {
4899 oop obj = oopDesc::load_decode_heap_oop(p);
4900
4901 if (_g1h->is_in_cset_or_humongous(obj)) {
4902 // If the referent object has been forwarded (either copied
4903 // to a new location or to itself in the event of an
4904 // evacuation failure) then we need to update the reference
4905 // field and, if both reference and referent are in the G1
4906 // heap, update the RSet for the referent.
4907 //
4908 // If the referent has not been forwarded then we have to keep
4909 // it alive by policy. Therefore we have copy the referent.
4910 //
4911 // If the reference field is in the G1 heap then we can push
4912 // on the PSS queue. When the queue is drained (after each
4913 // phase of reference processing) the object and it's followers
4914 // will be copied, the reference field set to point to the
4915 // new location, and the RSet updated. Otherwise we need to
4916 // use the the non-heap or metadata closures directly to copy
4917 // the referent object and update the pointer, while avoiding
4918 // updating the RSet.
4919
4920 if (_g1h->is_in_g1_reserved(p)) {
4921 _par_scan_state->push_on_queue(p);
4922 } else {
4923 assert(!Metaspace::contains((const void*)p),
4924 err_msg("Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p)));
4925 _copy_non_heap_obj_cl->do_oop(p);
4926 }
4927 }
4928 }
4929 };
4930
4931 // Serial drain queue closure. Called as the 'complete_gc'
4932 // closure for each discovered list in some of the
4933 // reference processing phases.
4934
4935 class G1STWDrainQueueClosure: public VoidClosure {
4936 protected:
4937 G1CollectedHeap* _g1h;
4938 G1ParScanThreadState* _par_scan_state;
4939
4940 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
4941
4942 public:
4943 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
4944 _g1h(g1h),
4945 _par_scan_state(pss)
4946 { }
4947
4948 void do_void() {
4949 G1ParScanThreadState* const pss = par_scan_state();
4950 pss->trim_queue();
4951 }
4952 };
4953
4954 // Parallel Reference Processing closures
4955
4956 // Implementation of AbstractRefProcTaskExecutor for parallel reference
4957 // processing during G1 evacuation pauses.
4958
4959 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
4960 private:
4961 G1CollectedHeap* _g1h;
4962 RefToScanQueueSet* _queues;
4963 FlexibleWorkGang* _workers;
4964 uint _active_workers;
4965
4966 public:
4967 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
4968 FlexibleWorkGang* workers,
4969 RefToScanQueueSet *task_queues,
4970 uint n_workers) :
4971 _g1h(g1h),
4972 _queues(task_queues),
4973 _workers(workers),
4974 _active_workers(n_workers)
4975 {
4976 assert(n_workers > 0, "shouldn't call this otherwise");
4977 }
4978
4979 // Executes the given task using concurrent marking worker threads.
4980 virtual void execute(ProcessTask& task);
4981 virtual void execute(EnqueueTask& task);
4982 };
4983
4984 // Gang task for possibly parallel reference processing
4985
4986 class G1STWRefProcTaskProxy: public AbstractGangTask {
4987 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
4988 ProcessTask& _proc_task;
4989 G1CollectedHeap* _g1h;
4990 RefToScanQueueSet *_task_queues;
4991 ParallelTaskTerminator* _terminator;
4992
4993 public:
4994 G1STWRefProcTaskProxy(ProcessTask& proc_task,
4995 G1CollectedHeap* g1h,
4996 RefToScanQueueSet *task_queues,
4997 ParallelTaskTerminator* terminator) :
4998 AbstractGangTask("Process reference objects in parallel"),
4999 _proc_task(proc_task),
5000 _g1h(g1h),
5001 _task_queues(task_queues),
5002 _terminator(terminator)
5003 {}
5004
5005 virtual void work(uint worker_id) {
5006 // The reference processing task executed by a single worker.
5007 ResourceMark rm;
5008 HandleMark hm;
5009
5010 G1STWIsAliveClosure is_alive(_g1h);
5011
5012 G1ParScanThreadState pss(_g1h, worker_id, NULL);
5013 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5014
5015 pss.set_evac_failure_closure(&evac_failure_cl);
5016
5017 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5018
5019 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5020
5021 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5022
5023 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5024 // We also need to mark copied objects.
5025 copy_non_heap_cl = ©_mark_non_heap_cl;
5026 }
5027
5028 // Keep alive closure.
5029 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5030
5031 // Complete GC closure
5032 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5033
5034 // Call the reference processing task's work routine.
5035 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5036
5037 // Note we cannot assert that the refs array is empty here as not all
5038 // of the processing tasks (specifically phase2 - pp2_work) execute
5039 // the complete_gc closure (which ordinarily would drain the queue) so
5040 // the queue may not be empty.
5041 }
5042 };
5043
5044 // Driver routine for parallel reference processing.
5045 // Creates an instance of the ref processing gang
5046 // task and has the worker threads execute it.
5047 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5048 assert(_workers != NULL, "Need parallel worker threads.");
5049
5050 ParallelTaskTerminator terminator(_active_workers, _queues);
5051 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5052
5053 _workers->run_task(&proc_task_proxy);
5054 }
5055
5056 // Gang task for parallel reference enqueueing.
5057
5058 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5059 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5060 EnqueueTask& _enq_task;
5061
5062 public:
5063 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5064 AbstractGangTask("Enqueue reference objects in parallel"),
5065 _enq_task(enq_task)
5066 { }
5067
5068 virtual void work(uint worker_id) {
5069 _enq_task.work(worker_id);
5070 }
5071 };
5072
5073 // Driver routine for parallel reference enqueueing.
5074 // Creates an instance of the ref enqueueing gang
5075 // task and has the worker threads execute it.
5076
5077 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5078 assert(_workers != NULL, "Need parallel worker threads.");
5079
5080 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5081
5082 _workers->run_task(&enq_task_proxy);
5083 }
5084
5085 // End of weak reference support closures
5086
5087 // Abstract task used to preserve (i.e. copy) any referent objects
5088 // that are in the collection set and are pointed to by reference
5089 // objects discovered by the CM ref processor.
5090
5091 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5092 protected:
5093 G1CollectedHeap* _g1h;
5094 RefToScanQueueSet *_queues;
5095 ParallelTaskTerminator _terminator;
5096 uint _n_workers;
5097
5098 public:
5099 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, uint workers, RefToScanQueueSet *task_queues) :
5100 AbstractGangTask("ParPreserveCMReferents"),
5101 _g1h(g1h),
5102 _queues(task_queues),
5103 _terminator(workers, _queues),
5104 _n_workers(workers)
5105 { }
5106
5107 void work(uint worker_id) {
5108 ResourceMark rm;
5109 HandleMark hm;
5110
5111 G1ParScanThreadState pss(_g1h, worker_id, NULL);
5112 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5113
5114 pss.set_evac_failure_closure(&evac_failure_cl);
5115
5116 assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5117
5118 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5119
5120 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5121
5122 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5123
5124 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5125 // We also need to mark copied objects.
5126 copy_non_heap_cl = ©_mark_non_heap_cl;
5127 }
5128
5129 // Is alive closure
5130 G1AlwaysAliveClosure always_alive(_g1h);
5131
5132 // Copying keep alive closure. Applied to referent objects that need
5133 // to be copied.
5134 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5135
5136 ReferenceProcessor* rp = _g1h->ref_processor_cm();
5137
5138 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5139 uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5140
5141 // limit is set using max_num_q() - which was set using ParallelGCThreads.
5142 // So this must be true - but assert just in case someone decides to
5143 // change the worker ids.
5144 assert(worker_id < limit, "sanity");
5145 assert(!rp->discovery_is_atomic(), "check this code");
5146
5147 // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5148 for (uint idx = worker_id; idx < limit; idx += stride) {
5149 DiscoveredList& ref_list = rp->discovered_refs()[idx];
5150
5151 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5152 while (iter.has_next()) {
5153 // Since discovery is not atomic for the CM ref processor, we
5154 // can see some null referent objects.
5155 iter.load_ptrs(DEBUG_ONLY(true));
5156 oop ref = iter.obj();
5157
5158 // This will filter nulls.
5159 if (iter.is_referent_alive()) {
5160 iter.make_referent_alive();
5161 }
5162 iter.move_to_next();
5163 }
5164 }
5165
5166 // Drain the queue - which may cause stealing
5167 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5168 drain_queue.do_void();
5169 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5170 assert(pss.queue_is_empty(), "should be");
5171 }
5172 };
5173
5174 // Weak Reference processing during an evacuation pause (part 1).
5175 void G1CollectedHeap::process_discovered_references() {
5176 double ref_proc_start = os::elapsedTime();
5177
5178 ReferenceProcessor* rp = _ref_processor_stw;
5179 assert(rp->discovery_enabled(), "should have been enabled");
5180
5181 // Any reference objects, in the collection set, that were 'discovered'
5182 // by the CM ref processor should have already been copied (either by
5183 // applying the external root copy closure to the discovered lists, or
5184 // by following an RSet entry).
5185 //
5186 // But some of the referents, that are in the collection set, that these
5187 // reference objects point to may not have been copied: the STW ref
5188 // processor would have seen that the reference object had already
5189 // been 'discovered' and would have skipped discovering the reference,
5190 // but would not have treated the reference object as a regular oop.
5191 // As a result the copy closure would not have been applied to the
5192 // referent object.
5193 //
5194 // We need to explicitly copy these referent objects - the references
5195 // will be processed at the end of remarking.
5196 //
5197 // We also need to do this copying before we process the reference
5198 // objects discovered by the STW ref processor in case one of these
5199 // referents points to another object which is also referenced by an
5200 // object discovered by the STW ref processor.
5201
5202 uint no_of_gc_workers = workers()->active_workers();
5203
5204 G1ParPreserveCMReferentsTask keep_cm_referents(this,
5205 no_of_gc_workers,
5206 _task_queues);
5207
5208 workers()->run_task(&keep_cm_referents);
5209
5210 // Closure to test whether a referent is alive.
5211 G1STWIsAliveClosure is_alive(this);
5212
5213 // Even when parallel reference processing is enabled, the processing
5214 // of JNI refs is serial and performed serially by the current thread
5215 // rather than by a worker. The following PSS will be used for processing
5216 // JNI refs.
5217
5218 // Use only a single queue for this PSS.
5219 G1ParScanThreadState pss(this, 0, NULL);
5220
5221 // We do not embed a reference processor in the copying/scanning
5222 // closures while we're actually processing the discovered
5223 // reference objects.
5224 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5225
5226 pss.set_evac_failure_closure(&evac_failure_cl);
5227
5228 assert(pss.queue_is_empty(), "pre-condition");
5229
5230 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL);
5231
5232 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5233
5234 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5235
5236 if (g1_policy()->during_initial_mark_pause()) {
5237 // We also need to mark copied objects.
5238 copy_non_heap_cl = ©_mark_non_heap_cl;
5239 }
5240
5241 // Keep alive closure.
5242 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, &pss);
5243
5244 // Serial Complete GC closure
5245 G1STWDrainQueueClosure drain_queue(this, &pss);
5246
5247 // Setup the soft refs policy...
5248 rp->setup_policy(false);
5249
5250 ReferenceProcessorStats stats;
5251 if (!rp->processing_is_mt()) {
5252 // Serial reference processing...
5253 stats = rp->process_discovered_references(&is_alive,
5254 &keep_alive,
5255 &drain_queue,
5256 NULL,
5257 _gc_timer_stw,
5258 _gc_tracer_stw->gc_id());
5259 } else {
5260 // Parallel reference processing
5261 assert(rp->num_q() == no_of_gc_workers, "sanity");
5262 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5263
5264 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5265 stats = rp->process_discovered_references(&is_alive,
5266 &keep_alive,
5267 &drain_queue,
5268 &par_task_executor,
5269 _gc_timer_stw,
5270 _gc_tracer_stw->gc_id());
5271 }
5272
5273 _gc_tracer_stw->report_gc_reference_stats(stats);
5274
5275 // We have completed copying any necessary live referent objects.
5276 assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5277
5278 double ref_proc_time = os::elapsedTime() - ref_proc_start;
5279 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5280 }
5281
5282 // Weak Reference processing during an evacuation pause (part 2).
5283 void G1CollectedHeap::enqueue_discovered_references() {
5284 double ref_enq_start = os::elapsedTime();
5285
5286 ReferenceProcessor* rp = _ref_processor_stw;
5287 assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5288
5289 // Now enqueue any remaining on the discovered lists on to
5290 // the pending list.
5291 if (!rp->processing_is_mt()) {
5292 // Serial reference processing...
5293 rp->enqueue_discovered_references();
5294 } else {
5295 // Parallel reference enqueueing
5296
5297 uint n_workers = workers()->active_workers();
5298
5299 assert(rp->num_q() == n_workers, "sanity");
5300 assert(n_workers <= rp->max_num_q(), "sanity");
5301
5302 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, n_workers);
5303 rp->enqueue_discovered_references(&par_task_executor);
5304 }
5305
5306 rp->verify_no_references_recorded();
5307 assert(!rp->discovery_enabled(), "should have been disabled");
5308
5309 // FIXME
5310 // CM's reference processing also cleans up the string and symbol tables.
5311 // Should we do that here also? We could, but it is a serial operation
5312 // and could significantly increase the pause time.
5313
5314 double ref_enq_time = os::elapsedTime() - ref_enq_start;
5315 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5316 }
5317
5318 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) {
5319 _expand_heap_after_alloc_failure = true;
5320 _evacuation_failed = false;
5321
5322 // Should G1EvacuationFailureALot be in effect for this GC?
5323 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
5324
5325 g1_rem_set()->prepare_for_oops_into_collection_set_do();
5326
5327 // Disable the hot card cache.
5328 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
5329 hot_card_cache->reset_hot_cache_claimed_index();
5330 hot_card_cache->set_use_cache(false);
5331
5332 const uint n_workers = workers()->active_workers();
5333
5334 init_for_evac_failure(NULL);
5335
5336 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5337 double start_par_time_sec = os::elapsedTime();
5338 double end_par_time_sec;
5339
5340 {
5341 G1RootProcessor root_processor(this, n_workers);
5342 G1ParTask g1_par_task(this, _task_queues, &root_processor, n_workers);
5343 // InitialMark needs claim bits to keep track of the marked-through CLDs.
5344 if (g1_policy()->during_initial_mark_pause()) {
5345 ClassLoaderDataGraph::clear_claimed_marks();
5346 }
5347
5348 // The individual threads will set their evac-failure closures.
5349 if (PrintTerminationStats) G1ParScanThreadState::print_termination_stats_hdr();
5350
5351 workers()->run_task(&g1_par_task);
5352 end_par_time_sec = os::elapsedTime();
5353
5354 // Closing the inner scope will execute the destructor
5355 // for the G1RootProcessor object. We record the current
5356 // elapsed time before closing the scope so that time
5357 // taken for the destructor is NOT included in the
5358 // reported parallel time.
5359 }
5360
5361 G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
5362
5363 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5364 phase_times->record_par_time(par_time_ms);
5365
5366 double code_root_fixup_time_ms =
5367 (os::elapsedTime() - end_par_time_sec) * 1000.0;
5368 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms);
5369
5370 // Process any discovered reference objects - we have
5371 // to do this _before_ we retire the GC alloc regions
5372 // as we may have to copy some 'reachable' referent
5373 // objects (and their reachable sub-graphs) that were
5374 // not copied during the pause.
5375 process_discovered_references();
5376
5377 if (G1StringDedup::is_enabled()) {
5378 double fixup_start = os::elapsedTime();
5379
5380 G1STWIsAliveClosure is_alive(this);
5381 G1KeepAliveClosure keep_alive(this);
5382 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, phase_times);
5383
5384 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
5385 phase_times->record_string_dedup_fixup_time(fixup_time_ms);
5386 }
5387
5388 _allocator->release_gc_alloc_regions(n_workers, evacuation_info);
5389 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5390
5391 // Reset and re-enable the hot card cache.
5392 // Note the counts for the cards in the regions in the
5393 // collection set are reset when the collection set is freed.
5394 hot_card_cache->reset_hot_cache();
5395 hot_card_cache->set_use_cache(true);
5396
5397 purge_code_root_memory();
5398
5399 finalize_for_evac_failure();
5400
5401 if (evacuation_failed()) {
5402 remove_self_forwarding_pointers();
5403
5404 // Reset the G1EvacuationFailureALot counters and flags
5405 // Note: the values are reset only when an actual
5406 // evacuation failure occurs.
5407 NOT_PRODUCT(reset_evacuation_should_fail();)
5408 }
5409
5410 // Enqueue any remaining references remaining on the STW
5411 // reference processor's discovered lists. We need to do
5412 // this after the card table is cleaned (and verified) as
5413 // the act of enqueueing entries on to the pending list
5414 // will log these updates (and dirty their associated
5415 // cards). We need these updates logged to update any
5416 // RSets.
5417 enqueue_discovered_references();
5418
5419 redirty_logged_cards();
5420 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5421 }
5422
5423 void G1CollectedHeap::free_region(HeapRegion* hr,
5424 FreeRegionList* free_list,
5425 bool par,
5426 bool locked) {
5427 assert(!hr->is_free(), "the region should not be free");
5428 assert(!hr->is_empty(), "the region should not be empty");
5429 assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
5430 assert(free_list != NULL, "pre-condition");
5431
5432 if (G1VerifyBitmaps) {
5433 MemRegion mr(hr->bottom(), hr->end());
5434 concurrent_mark()->clearRangePrevBitmap(mr);
5435 }
5436
5437 // Clear the card counts for this region.
5438 // Note: we only need to do this if the region is not young
5439 // (since we don't refine cards in young regions).
5440 if (!hr->is_young()) {
5441 _cg1r->hot_card_cache()->reset_card_counts(hr);
5442 }
5443 hr->hr_clear(par, true /* clear_space */, locked /* locked */);
5444 free_list->add_ordered(hr);
5445 }
5446
5447 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
5448 FreeRegionList* free_list,
5449 bool par) {
5450 assert(hr->is_starts_humongous(), "this is only for starts humongous regions");
5451 assert(free_list != NULL, "pre-condition");
5452
5453 size_t hr_capacity = hr->capacity();
5454 // We need to read this before we make the region non-humongous,
5455 // otherwise the information will be gone.
5456 uint last_index = hr->last_hc_index();
5457 hr->clear_humongous();
5458 free_region(hr, free_list, par);
5459
5460 uint i = hr->hrm_index() + 1;
5461 while (i < last_index) {
5462 HeapRegion* curr_hr = region_at(i);
5463 assert(curr_hr->is_continues_humongous(), "invariant");
5464 curr_hr->clear_humongous();
5465 free_region(curr_hr, free_list, par);
5466 i += 1;
5467 }
5468 }
5469
5470 void G1CollectedHeap::remove_from_old_sets(const HeapRegionSetCount& old_regions_removed,
5471 const HeapRegionSetCount& humongous_regions_removed) {
5472 if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 0) {
5473 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5474 _old_set.bulk_remove(old_regions_removed);
5475 _humongous_set.bulk_remove(humongous_regions_removed);
5476 }
5477
5478 }
5479
5480 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
5481 assert(list != NULL, "list can't be null");
5482 if (!list->is_empty()) {
5483 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
5484 _hrm.insert_list_into_free_list(list);
5485 }
5486 }
5487
5488 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
5489 _allocator->decrease_used(bytes);
5490 }
5491
5492 class G1ParCleanupCTTask : public AbstractGangTask {
5493 G1SATBCardTableModRefBS* _ct_bs;
5494 G1CollectedHeap* _g1h;
5495 HeapRegion* volatile _su_head;
5496 public:
5497 G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs,
5498 G1CollectedHeap* g1h) :
5499 AbstractGangTask("G1 Par Cleanup CT Task"),
5500 _ct_bs(ct_bs), _g1h(g1h) { }
5501
5502 void work(uint worker_id) {
5503 HeapRegion* r;
5504 while (r = _g1h->pop_dirty_cards_region()) {
5505 clear_cards(r);
5506 }
5507 }
5508
5509 void clear_cards(HeapRegion* r) {
5510 // Cards of the survivors should have already been dirtied.
5511 if (!r->is_survivor()) {
5512 _ct_bs->clear(MemRegion(r->bottom(), r->end()));
5513 }
5514 }
5515 };
5516
5517 #ifndef PRODUCT
5518 class G1VerifyCardTableCleanup: public HeapRegionClosure {
5519 G1CollectedHeap* _g1h;
5520 G1SATBCardTableModRefBS* _ct_bs;
5521 public:
5522 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs)
5523 : _g1h(g1h), _ct_bs(ct_bs) { }
5524 virtual bool doHeapRegion(HeapRegion* r) {
5525 if (r->is_survivor()) {
5526 _g1h->verify_dirty_region(r);
5527 } else {
5528 _g1h->verify_not_dirty_region(r);
5529 }
5530 return false;
5531 }
5532 };
5533
5534 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
5535 // All of the region should be clean.
5536 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5537 MemRegion mr(hr->bottom(), hr->end());
5538 ct_bs->verify_not_dirty_region(mr);
5539 }
5540
5541 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
5542 // We cannot guarantee that [bottom(),end()] is dirty. Threads
5543 // dirty allocated blocks as they allocate them. The thread that
5544 // retires each region and replaces it with a new one will do a
5545 // maximal allocation to fill in [pre_dummy_top(),end()] but will
5546 // not dirty that area (one less thing to have to do while holding
5547 // a lock). So we can only verify that [bottom(),pre_dummy_top()]
5548 // is dirty.
5549 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5550 MemRegion mr(hr->bottom(), hr->pre_dummy_top());
5551 if (hr->is_young()) {
5552 ct_bs->verify_g1_young_region(mr);
5553 } else {
5554 ct_bs->verify_dirty_region(mr);
5555 }
5556 }
5557
5558 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
5559 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5560 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
5561 verify_dirty_region(hr);
5562 }
5563 }
5564
5565 void G1CollectedHeap::verify_dirty_young_regions() {
5566 verify_dirty_young_list(_young_list->first_region());
5567 }
5568
5569 bool G1CollectedHeap::verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
5570 HeapWord* tams, HeapWord* end) {
5571 guarantee(tams <= end,
5572 err_msg("tams: "PTR_FORMAT" end: "PTR_FORMAT, p2i(tams), p2i(end)));
5573 HeapWord* result = bitmap->getNextMarkedWordAddress(tams, end);
5574 if (result < end) {
5575 gclog_or_tty->cr();
5576 gclog_or_tty->print_cr("## wrong marked address on %s bitmap: "PTR_FORMAT,
5577 bitmap_name, p2i(result));
5578 gclog_or_tty->print_cr("## %s tams: "PTR_FORMAT" end: "PTR_FORMAT,
5579 bitmap_name, p2i(tams), p2i(end));
5580 return false;
5581 }
5582 return true;
5583 }
5584
5585 bool G1CollectedHeap::verify_bitmaps(const char* caller, HeapRegion* hr) {
5586 CMBitMapRO* prev_bitmap = concurrent_mark()->prevMarkBitMap();
5587 CMBitMapRO* next_bitmap = (CMBitMapRO*) concurrent_mark()->nextMarkBitMap();
5588
5589 HeapWord* bottom = hr->bottom();
5590 HeapWord* ptams = hr->prev_top_at_mark_start();
5591 HeapWord* ntams = hr->next_top_at_mark_start();
5592 HeapWord* end = hr->end();
5593
5594 bool res_p = verify_no_bits_over_tams("prev", prev_bitmap, ptams, end);
5595
5596 bool res_n = true;
5597 // We reset mark_in_progress() before we reset _cmThread->in_progress() and in this window
5598 // we do the clearing of the next bitmap concurrently. Thus, we can not verify the bitmap
5599 // if we happen to be in that state.
5600 if (mark_in_progress() || !_cmThread->in_progress()) {
5601 res_n = verify_no_bits_over_tams("next", next_bitmap, ntams, end);
5602 }
5603 if (!res_p || !res_n) {
5604 gclog_or_tty->print_cr("#### Bitmap verification failed for "HR_FORMAT,
5605 HR_FORMAT_PARAMS(hr));
5606 gclog_or_tty->print_cr("#### Caller: %s", caller);
5607 return false;
5608 }
5609 return true;
5610 }
5611
5612 void G1CollectedHeap::check_bitmaps(const char* caller, HeapRegion* hr) {
5613 if (!G1VerifyBitmaps) return;
5614
5615 guarantee(verify_bitmaps(caller, hr), "bitmap verification");
5616 }
5617
5618 class G1VerifyBitmapClosure : public HeapRegionClosure {
5619 private:
5620 const char* _caller;
5621 G1CollectedHeap* _g1h;
5622 bool _failures;
5623
5624 public:
5625 G1VerifyBitmapClosure(const char* caller, G1CollectedHeap* g1h) :
5626 _caller(caller), _g1h(g1h), _failures(false) { }
5627
5628 bool failures() { return _failures; }
5629
5630 virtual bool doHeapRegion(HeapRegion* hr) {
5631 if (hr->is_continues_humongous()) return false;
5632
5633 bool result = _g1h->verify_bitmaps(_caller, hr);
5634 if (!result) {
5635 _failures = true;
5636 }
5637 return false;
5638 }
5639 };
5640
5641 void G1CollectedHeap::check_bitmaps(const char* caller) {
5642 if (!G1VerifyBitmaps) return;
5643
5644 G1VerifyBitmapClosure cl(caller, this);
5645 heap_region_iterate(&cl);
5646 guarantee(!cl.failures(), "bitmap verification");
5647 }
5648
5649 class G1CheckCSetFastTableClosure : public HeapRegionClosure {
5650 private:
5651 bool _failures;
5652 public:
5653 G1CheckCSetFastTableClosure() : HeapRegionClosure(), _failures(false) { }
5654
5655 virtual bool doHeapRegion(HeapRegion* hr) {
5656 uint i = hr->hrm_index();
5657 InCSetState cset_state = (InCSetState) G1CollectedHeap::heap()->_in_cset_fast_test.get_by_index(i);
5658 if (hr->is_humongous()) {
5659 if (hr->in_collection_set()) {
5660 gclog_or_tty->print_cr("\n## humongous region %u in CSet", i);
5661 _failures = true;
5662 return true;
5663 }
5664 if (cset_state.is_in_cset()) {
5665 gclog_or_tty->print_cr("\n## inconsistent cset state %d for humongous region %u", cset_state.value(), i);
5666 _failures = true;
5667 return true;
5668 }
5669 if (hr->is_continues_humongous() && cset_state.is_humongous()) {
5670 gclog_or_tty->print_cr("\n## inconsistent cset state %d for continues humongous region %u", cset_state.value(), i);
5671 _failures = true;
5672 return true;
5673 }
5674 } else {
5675 if (cset_state.is_humongous()) {
5676 gclog_or_tty->print_cr("\n## inconsistent cset state %d for non-humongous region %u", cset_state.value(), i);
5677 _failures = true;
5678 return true;
5679 }
5680 if (hr->in_collection_set() != cset_state.is_in_cset()) {
5681 gclog_or_tty->print_cr("\n## in CSet %d / cset state %d inconsistency for region %u",
5682 hr->in_collection_set(), cset_state.value(), i);
5683 _failures = true;
5684 return true;
5685 }
5686 if (cset_state.is_in_cset()) {
5687 if (hr->is_young() != (cset_state.is_young())) {
5688 gclog_or_tty->print_cr("\n## is_young %d / cset state %d inconsistency for region %u",
5689 hr->is_young(), cset_state.value(), i);
5690 _failures = true;
5691 return true;
5692 }
5693 if (hr->is_old() != (cset_state.is_old())) {
5694 gclog_or_tty->print_cr("\n## is_old %d / cset state %d inconsistency for region %u",
5695 hr->is_old(), cset_state.value(), i);
5696 _failures = true;
5697 return true;
5698 }
5699 }
5700 }
5701 return false;
5702 }
5703
5704 bool failures() const { return _failures; }
5705 };
5706
5707 bool G1CollectedHeap::check_cset_fast_test() {
5708 G1CheckCSetFastTableClosure cl;
5709 _hrm.iterate(&cl);
5710 return !cl.failures();
5711 }
5712 #endif // PRODUCT
5713
5714 void G1CollectedHeap::cleanUpCardTable() {
5715 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5716 double start = os::elapsedTime();
5717
5718 {
5719 // Iterate over the dirty cards region list.
5720 G1ParCleanupCTTask cleanup_task(ct_bs, this);
5721
5722 workers()->run_task(&cleanup_task);
5723 #ifndef PRODUCT
5724 if (G1VerifyCTCleanup || VerifyAfterGC) {
5725 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
5726 heap_region_iterate(&cleanup_verifier);
5727 }
5728 #endif
5729 }
5730
5731 double elapsed = os::elapsedTime() - start;
5732 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
5733 }
5734
5735 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) {
5736 size_t pre_used = 0;
5737 FreeRegionList local_free_list("Local List for CSet Freeing");
5738
5739 double young_time_ms = 0.0;
5740 double non_young_time_ms = 0.0;
5741
5742 // Since the collection set is a superset of the the young list,
5743 // all we need to do to clear the young list is clear its
5744 // head and length, and unlink any young regions in the code below
5745 _young_list->clear();
5746
5747 G1CollectorPolicy* policy = g1_policy();
5748
5749 double start_sec = os::elapsedTime();
5750 bool non_young = true;
5751
5752 HeapRegion* cur = cs_head;
5753 int age_bound = -1;
5754 size_t rs_lengths = 0;
5755
5756 while (cur != NULL) {
5757 assert(!is_on_master_free_list(cur), "sanity");
5758 if (non_young) {
5759 if (cur->is_young()) {
5760 double end_sec = os::elapsedTime();
5761 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5762 non_young_time_ms += elapsed_ms;
5763
5764 start_sec = os::elapsedTime();
5765 non_young = false;
5766 }
5767 } else {
5768 if (!cur->is_young()) {
5769 double end_sec = os::elapsedTime();
5770 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5771 young_time_ms += elapsed_ms;
5772
5773 start_sec = os::elapsedTime();
5774 non_young = true;
5775 }
5776 }
5777
5778 rs_lengths += cur->rem_set()->occupied_locked();
5779
5780 HeapRegion* next = cur->next_in_collection_set();
5781 assert(cur->in_collection_set(), "bad CS");
5782 cur->set_next_in_collection_set(NULL);
5783 clear_in_cset(cur);
5784
5785 if (cur->is_young()) {
5786 int index = cur->young_index_in_cset();
5787 assert(index != -1, "invariant");
5788 assert((uint) index < policy->young_cset_region_length(), "invariant");
5789 size_t words_survived = _surviving_young_words[index];
5790 cur->record_surv_words_in_group(words_survived);
5791
5792 // At this point the we have 'popped' cur from the collection set
5793 // (linked via next_in_collection_set()) but it is still in the
5794 // young list (linked via next_young_region()). Clear the
5795 // _next_young_region field.
5796 cur->set_next_young_region(NULL);
5797 } else {
5798 int index = cur->young_index_in_cset();
5799 assert(index == -1, "invariant");
5800 }
5801
5802 assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
5803 (!cur->is_young() && cur->young_index_in_cset() == -1),
5804 "invariant" );
5805
5806 if (!cur->evacuation_failed()) {
5807 MemRegion used_mr = cur->used_region();
5808
5809 // And the region is empty.
5810 assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
5811 pre_used += cur->used();
5812 free_region(cur, &local_free_list, false /* par */, true /* locked */);
5813 } else {
5814 cur->uninstall_surv_rate_group();
5815 if (cur->is_young()) {
5816 cur->set_young_index_in_cset(-1);
5817 }
5818 cur->set_evacuation_failed(false);
5819 // The region is now considered to be old.
5820 cur->set_old();
5821 _old_set.add(cur);
5822 evacuation_info.increment_collectionset_used_after(cur->used());
5823 }
5824 cur = next;
5825 }
5826
5827 evacuation_info.set_regions_freed(local_free_list.length());
5828 policy->record_max_rs_lengths(rs_lengths);
5829 policy->cset_regions_freed();
5830
5831 double end_sec = os::elapsedTime();
5832 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5833
5834 if (non_young) {
5835 non_young_time_ms += elapsed_ms;
5836 } else {
5837 young_time_ms += elapsed_ms;
5838 }
5839
5840 prepend_to_freelist(&local_free_list);
5841 decrement_summary_bytes(pre_used);
5842 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
5843 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
5844 }
5845
5846 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
5847 private:
5848 FreeRegionList* _free_region_list;
5849 HeapRegionSet* _proxy_set;
5850 HeapRegionSetCount _humongous_regions_removed;
5851 size_t _freed_bytes;
5852 public:
5853
5854 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
5855 _free_region_list(free_region_list), _humongous_regions_removed(), _freed_bytes(0) {
5856 }
5857
5858 virtual bool doHeapRegion(HeapRegion* r) {
5859 if (!r->is_starts_humongous()) {
5860 return false;
5861 }
5862
5863 G1CollectedHeap* g1h = G1CollectedHeap::heap();
5864
5865 oop obj = (oop)r->bottom();
5866 CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap();
5867
5868 // The following checks whether the humongous object is live are sufficient.
5869 // The main additional check (in addition to having a reference from the roots
5870 // or the young gen) is whether the humongous object has a remembered set entry.
5871 //
5872 // A humongous object cannot be live if there is no remembered set for it
5873 // because:
5874 // - there can be no references from within humongous starts regions referencing
5875 // the object because we never allocate other objects into them.
5876 // (I.e. there are no intra-region references that may be missed by the
5877 // remembered set)
5878 // - as soon there is a remembered set entry to the humongous starts region
5879 // (i.e. it has "escaped" to an old object) this remembered set entry will stay
5880 // until the end of a concurrent mark.
5881 //
5882 // It is not required to check whether the object has been found dead by marking
5883 // or not, in fact it would prevent reclamation within a concurrent cycle, as
5884 // all objects allocated during that time are considered live.
5885 // SATB marking is even more conservative than the remembered set.
5886 // So if at this point in the collection there is no remembered set entry,
5887 // nobody has a reference to it.
5888 // At the start of collection we flush all refinement logs, and remembered sets
5889 // are completely up-to-date wrt to references to the humongous object.
5890 //
5891 // Other implementation considerations:
5892 // - never consider object arrays at this time because they would pose
5893 // considerable effort for cleaning up the the remembered sets. This is
5894 // required because stale remembered sets might reference locations that
5895 // are currently allocated into.
5896 uint region_idx = r->hrm_index();
5897 if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
5898 !r->rem_set()->is_empty()) {
5899
5900 if (G1TraceEagerReclaimHumongousObjects) {
5901 gclog_or_tty->print_cr("Live humongous region %u size "SIZE_FORMAT" start "PTR_FORMAT" length %u with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is marked %d reclaim candidate %d type array %d",
5902 region_idx,
5903 (size_t)obj->size() * HeapWordSize,
5904 p2i(r->bottom()),
5905 r->region_num(),
5906 r->rem_set()->occupied(),
5907 r->rem_set()->strong_code_roots_list_length(),
5908 next_bitmap->isMarked(r->bottom()),
5909 g1h->is_humongous_reclaim_candidate(region_idx),
5910 obj->is_typeArray()
5911 );
5912 }
5913
5914 return false;
5915 }
5916
5917 guarantee(obj->is_typeArray(),
5918 err_msg("Only eagerly reclaiming type arrays is supported, but the object "
5919 PTR_FORMAT " is not.",
5920 p2i(r->bottom())));
5921
5922 if (G1TraceEagerReclaimHumongousObjects) {
5923 gclog_or_tty->print_cr("Dead humongous region %u size "SIZE_FORMAT" start "PTR_FORMAT" length %u with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is marked %d reclaim candidate %d type array %d",
5924 region_idx,
5925 (size_t)obj->size() * HeapWordSize,
5926 p2i(r->bottom()),
5927 r->region_num(),
5928 r->rem_set()->occupied(),
5929 r->rem_set()->strong_code_roots_list_length(),
5930 next_bitmap->isMarked(r->bottom()),
5931 g1h->is_humongous_reclaim_candidate(region_idx),
5932 obj->is_typeArray()
5933 );
5934 }
5935 // Need to clear mark bit of the humongous object if already set.
5936 if (next_bitmap->isMarked(r->bottom())) {
5937 next_bitmap->clear(r->bottom());
5938 }
5939 _freed_bytes += r->used();
5940 r->set_containing_set(NULL);
5941 _humongous_regions_removed.increment(1u, r->capacity());
5942 g1h->free_humongous_region(r, _free_region_list, false);
5943
5944 return false;
5945 }
5946
5947 HeapRegionSetCount& humongous_free_count() {
5948 return _humongous_regions_removed;
5949 }
5950
5951 size_t bytes_freed() const {
5952 return _freed_bytes;
5953 }
5954
5955 size_t humongous_reclaimed() const {
5956 return _humongous_regions_removed.length();
5957 }
5958 };
5959
5960 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
5961 assert_at_safepoint(true);
5962
5963 if (!G1EagerReclaimHumongousObjects ||
5964 (!_has_humongous_reclaim_candidates && !G1TraceEagerReclaimHumongousObjects)) {
5965 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
5966 return;
5967 }
5968
5969 double start_time = os::elapsedTime();
5970
5971 FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
5972
5973 G1FreeHumongousRegionClosure cl(&local_cleanup_list);
5974 heap_region_iterate(&cl);
5975
5976 HeapRegionSetCount empty_set;
5977 remove_from_old_sets(empty_set, cl.humongous_free_count());
5978
5979 G1HRPrinter* hrp = hr_printer();
5980 if (hrp->is_active()) {
5981 FreeRegionListIterator iter(&local_cleanup_list);
5982 while (iter.more_available()) {
5983 HeapRegion* hr = iter.get_next();
5984 hrp->cleanup(hr);
5985 }
5986 }
5987
5988 prepend_to_freelist(&local_cleanup_list);
5989 decrement_summary_bytes(cl.bytes_freed());
5990
5991 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
5992 cl.humongous_reclaimed());
5993 }
5994
5995 // This routine is similar to the above but does not record
5996 // any policy statistics or update free lists; we are abandoning
5997 // the current incremental collection set in preparation of a
5998 // full collection. After the full GC we will start to build up
5999 // the incremental collection set again.
6000 // This is only called when we're doing a full collection
6001 // and is immediately followed by the tearing down of the young list.
6002
6003 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
6004 HeapRegion* cur = cs_head;
6005
6006 while (cur != NULL) {
6007 HeapRegion* next = cur->next_in_collection_set();
6008 assert(cur->in_collection_set(), "bad CS");
6009 cur->set_next_in_collection_set(NULL);
6010 clear_in_cset(cur);
6011 cur->set_young_index_in_cset(-1);
6012 cur = next;
6013 }
6014 }
6015
6016 void G1CollectedHeap::set_free_regions_coming() {
6017 if (G1ConcRegionFreeingVerbose) {
6018 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6019 "setting free regions coming");
6020 }
6021
6022 assert(!free_regions_coming(), "pre-condition");
6023 _free_regions_coming = true;
6024 }
6025
6026 void G1CollectedHeap::reset_free_regions_coming() {
6027 assert(free_regions_coming(), "pre-condition");
6028
6029 {
6030 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6031 _free_regions_coming = false;
6032 SecondaryFreeList_lock->notify_all();
6033 }
6034
6035 if (G1ConcRegionFreeingVerbose) {
6036 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6037 "reset free regions coming");
6038 }
6039 }
6040
6041 void G1CollectedHeap::wait_while_free_regions_coming() {
6042 // Most of the time we won't have to wait, so let's do a quick test
6043 // first before we take the lock.
6044 if (!free_regions_coming()) {
6045 return;
6046 }
6047
6048 if (G1ConcRegionFreeingVerbose) {
6049 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6050 "waiting for free regions");
6051 }
6052
6053 {
6054 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6055 while (free_regions_coming()) {
6056 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
6057 }
6058 }
6059
6060 if (G1ConcRegionFreeingVerbose) {
6061 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6062 "done waiting for free regions");
6063 }
6064 }
6065
6066 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
6067 _young_list->push_region(hr);
6068 }
6069
6070 class NoYoungRegionsClosure: public HeapRegionClosure {
6071 private:
6072 bool _success;
6073 public:
6074 NoYoungRegionsClosure() : _success(true) { }
6075 bool doHeapRegion(HeapRegion* r) {
6076 if (r->is_young()) {
6077 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
6078 p2i(r->bottom()), p2i(r->end()));
6079 _success = false;
6080 }
6081 return false;
6082 }
6083 bool success() { return _success; }
6084 };
6085
6086 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
6087 bool ret = _young_list->check_list_empty(check_sample);
6088
6089 if (check_heap) {
6090 NoYoungRegionsClosure closure;
6091 heap_region_iterate(&closure);
6092 ret = ret && closure.success();
6093 }
6094
6095 return ret;
6096 }
6097
6098 class TearDownRegionSetsClosure : public HeapRegionClosure {
6099 private:
6100 HeapRegionSet *_old_set;
6101
6102 public:
6103 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
6104
6105 bool doHeapRegion(HeapRegion* r) {
6106 if (r->is_old()) {
6107 _old_set->remove(r);
6108 } else {
6109 // We ignore free regions, we'll empty the free list afterwards.
6110 // We ignore young regions, we'll empty the young list afterwards.
6111 // We ignore humongous regions, we're not tearing down the
6112 // humongous regions set.
6113 assert(r->is_free() || r->is_young() || r->is_humongous(),
6114 "it cannot be another type");
6115 }
6116 return false;
6117 }
6118
6119 ~TearDownRegionSetsClosure() {
6120 assert(_old_set->is_empty(), "post-condition");
6121 }
6122 };
6123
6124 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6125 assert_at_safepoint(true /* should_be_vm_thread */);
6126
6127 if (!free_list_only) {
6128 TearDownRegionSetsClosure cl(&_old_set);
6129 heap_region_iterate(&cl);
6130
6131 // Note that emptying the _young_list is postponed and instead done as
6132 // the first step when rebuilding the regions sets again. The reason for
6133 // this is that during a full GC string deduplication needs to know if
6134 // a collected region was young or old when the full GC was initiated.
6135 }
6136 _hrm.remove_all_free_regions();
6137 }
6138
6139 class RebuildRegionSetsClosure : public HeapRegionClosure {
6140 private:
6141 bool _free_list_only;
6142 HeapRegionSet* _old_set;
6143 HeapRegionManager* _hrm;
6144 size_t _total_used;
6145
6146 public:
6147 RebuildRegionSetsClosure(bool free_list_only,
6148 HeapRegionSet* old_set, HeapRegionManager* hrm) :
6149 _free_list_only(free_list_only),
6150 _old_set(old_set), _hrm(hrm), _total_used(0) {
6151 assert(_hrm->num_free_regions() == 0, "pre-condition");
6152 if (!free_list_only) {
6153 assert(_old_set->is_empty(), "pre-condition");
6154 }
6155 }
6156
6157 bool doHeapRegion(HeapRegion* r) {
6158 if (r->is_continues_humongous()) {
6159 return false;
6160 }
6161
6162 if (r->is_empty()) {
6163 // Add free regions to the free list
6164 r->set_free();
6165 r->set_allocation_context(AllocationContext::system());
6166 _hrm->insert_into_free_list(r);
6167 } else if (!_free_list_only) {
6168 assert(!r->is_young(), "we should not come across young regions");
6169
6170 if (r->is_humongous()) {
6171 // We ignore humongous regions, we left the humongous set unchanged
6172 } else {
6173 // Objects that were compacted would have ended up on regions
6174 // that were previously old or free.
6175 assert(r->is_free() || r->is_old(), "invariant");
6176 // We now consider them old, so register as such.
6177 r->set_old();
6178 _old_set->add(r);
6179 }
6180 _total_used += r->used();
6181 }
6182
6183 return false;
6184 }
6185
6186 size_t total_used() {
6187 return _total_used;
6188 }
6189 };
6190
6191 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6192 assert_at_safepoint(true /* should_be_vm_thread */);
6193
6194 if (!free_list_only) {
6195 _young_list->empty_list();
6196 }
6197
6198 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
6199 heap_region_iterate(&cl);
6200
6201 if (!free_list_only) {
6202 _allocator->set_used(cl.total_used());
6203 }
6204 assert(_allocator->used_unlocked() == recalculate_used(),
6205 err_msg("inconsistent _allocator->used_unlocked(), "
6206 "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6207 _allocator->used_unlocked(), recalculate_used()));
6208 }
6209
6210 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6211 _refine_cte_cl->set_concurrent(concurrent);
6212 }
6213
6214 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6215 HeapRegion* hr = heap_region_containing(p);
6216 return hr->is_in(p);
6217 }
6218
6219 // Methods for the mutator alloc region
6220
6221 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6222 bool force) {
6223 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6224 assert(!force || g1_policy()->can_expand_young_list(),
6225 "if force is true we should be able to expand the young list");
6226 bool young_list_full = g1_policy()->is_young_list_full();
6227 if (force || !young_list_full) {
6228 HeapRegion* new_alloc_region = new_region(word_size,
6229 false /* is_old */,
6230 false /* do_expand */);
6231 if (new_alloc_region != NULL) {
6232 set_region_short_lived_locked(new_alloc_region);
6233 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6234 check_bitmaps("Mutator Region Allocation", new_alloc_region);
6235 return new_alloc_region;
6236 }
6237 }
6238 return NULL;
6239 }
6240
6241 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6242 size_t allocated_bytes) {
6243 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6244 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
6245
6246 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6247 _allocator->increase_used(allocated_bytes);
6248 _hr_printer.retire(alloc_region);
6249 // We update the eden sizes here, when the region is retired,
6250 // instead of when it's allocated, since this is the point that its
6251 // used space has been recored in _summary_bytes_used.
6252 g1mm()->update_eden_size();
6253 }
6254
6255 // Methods for the GC alloc regions
6256
6257 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6258 uint count,
6259 InCSetState dest) {
6260 assert(FreeList_lock->owned_by_self(), "pre-condition");
6261
6262 if (count < g1_policy()->max_regions(dest)) {
6263 const bool is_survivor = (dest.is_young());
6264 HeapRegion* new_alloc_region = new_region(word_size,
6265 !is_survivor,
6266 true /* do_expand */);
6267 if (new_alloc_region != NULL) {
6268 // We really only need to do this for old regions given that we
6269 // should never scan survivors. But it doesn't hurt to do it
6270 // for survivors too.
6271 new_alloc_region->record_timestamp();
6272 if (is_survivor) {
6273 new_alloc_region->set_survivor();
6274 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6275 check_bitmaps("Survivor Region Allocation", new_alloc_region);
6276 } else {
6277 new_alloc_region->set_old();
6278 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6279 check_bitmaps("Old Region Allocation", new_alloc_region);
6280 }
6281 bool during_im = g1_policy()->during_initial_mark_pause();
6282 new_alloc_region->note_start_of_copying(during_im);
6283 return new_alloc_region;
6284 }
6285 }
6286 return NULL;
6287 }
6288
6289 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6290 size_t allocated_bytes,
6291 InCSetState dest) {
6292 bool during_im = g1_policy()->during_initial_mark_pause();
6293 alloc_region->note_end_of_copying(during_im);
6294 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6295 if (dest.is_young()) {
6296 young_list()->add_survivor_region(alloc_region);
6297 } else {
6298 _old_set.add(alloc_region);
6299 }
6300 _hr_printer.retire(alloc_region);
6301 }
6302
6303 // Heap region set verification
6304
6305 class VerifyRegionListsClosure : public HeapRegionClosure {
6306 private:
6307 HeapRegionSet* _old_set;
6308 HeapRegionSet* _humongous_set;
6309 HeapRegionManager* _hrm;
6310
6311 public:
6312 HeapRegionSetCount _old_count;
6313 HeapRegionSetCount _humongous_count;
6314 HeapRegionSetCount _free_count;
6315
6316 VerifyRegionListsClosure(HeapRegionSet* old_set,
6317 HeapRegionSet* humongous_set,
6318 HeapRegionManager* hrm) :
6319 _old_set(old_set), _humongous_set(humongous_set), _hrm(hrm),
6320 _old_count(), _humongous_count(), _free_count(){ }
6321
6322 bool doHeapRegion(HeapRegion* hr) {
6323 if (hr->is_continues_humongous()) {
6324 return false;
6325 }
6326
6327 if (hr->is_young()) {
6328 // TODO
6329 } else if (hr->is_starts_humongous()) {
6330 assert(hr->containing_set() == _humongous_set, err_msg("Heap region %u is starts humongous but not in humongous set.", hr->hrm_index()));
6331 _humongous_count.increment(1u, hr->capacity());
6332 } else if (hr->is_empty()) {
6333 assert(_hrm->is_free(hr), err_msg("Heap region %u is empty but not on the free list.", hr->hrm_index()));
6334 _free_count.increment(1u, hr->capacity());
6335 } else if (hr->is_old()) {
6336 assert(hr->containing_set() == _old_set, err_msg("Heap region %u is old but not in the old set.", hr->hrm_index()));
6337 _old_count.increment(1u, hr->capacity());
6338 } else {
6339 ShouldNotReachHere();
6340 }
6341 return false;
6342 }
6343
6344 void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, HeapRegionManager* free_list) {
6345 guarantee(old_set->length() == _old_count.length(), err_msg("Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length()));
6346 guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), err_msg("Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6347 old_set->total_capacity_bytes(), _old_count.capacity()));
6348
6349 guarantee(humongous_set->length() == _humongous_count.length(), err_msg("Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length()));
6350 guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), err_msg("Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6351 humongous_set->total_capacity_bytes(), _humongous_count.capacity()));
6352
6353 guarantee(free_list->num_free_regions() == _free_count.length(), err_msg("Free list count mismatch. Expected %u, actual %u.", free_list->num_free_regions(), _free_count.length()));
6354 guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), err_msg("Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6355 free_list->total_capacity_bytes(), _free_count.capacity()));
6356 }
6357 };
6358
6359 void G1CollectedHeap::verify_region_sets() {
6360 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6361
6362 // First, check the explicit lists.
6363 _hrm.verify();
6364 {
6365 // Given that a concurrent operation might be adding regions to
6366 // the secondary free list we have to take the lock before
6367 // verifying it.
6368 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6369 _secondary_free_list.verify_list();
6370 }
6371
6372 // If a concurrent region freeing operation is in progress it will
6373 // be difficult to correctly attributed any free regions we come
6374 // across to the correct free list given that they might belong to
6375 // one of several (free_list, secondary_free_list, any local lists,
6376 // etc.). So, if that's the case we will skip the rest of the
6377 // verification operation. Alternatively, waiting for the concurrent
6378 // operation to complete will have a non-trivial effect on the GC's
6379 // operation (no concurrent operation will last longer than the
6380 // interval between two calls to verification) and it might hide
6381 // any issues that we would like to catch during testing.
6382 if (free_regions_coming()) {
6383 return;
6384 }
6385
6386 // Make sure we append the secondary_free_list on the free_list so
6387 // that all free regions we will come across can be safely
6388 // attributed to the free_list.
6389 append_secondary_free_list_if_not_empty_with_lock();
6390
6391 // Finally, make sure that the region accounting in the lists is
6392 // consistent with what we see in the heap.
6393
6394 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_hrm);
6395 heap_region_iterate(&cl);
6396 cl.verify_counts(&_old_set, &_humongous_set, &_hrm);
6397 }
6398
6399 // Optimized nmethod scanning
6400
6401 class RegisterNMethodOopClosure: public OopClosure {
6402 G1CollectedHeap* _g1h;
6403 nmethod* _nm;
6404
6405 template <class T> void do_oop_work(T* p) {
6406 T heap_oop = oopDesc::load_heap_oop(p);
6407 if (!oopDesc::is_null(heap_oop)) {
6408 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6409 HeapRegion* hr = _g1h->heap_region_containing(obj);
6410 assert(!hr->is_continues_humongous(),
6411 err_msg("trying to add code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6412 " starting at "HR_FORMAT,
6413 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6414
6415 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
6416 hr->add_strong_code_root_locked(_nm);
6417 }
6418 }
6419
6420 public:
6421 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6422 _g1h(g1h), _nm(nm) {}
6423
6424 void do_oop(oop* p) { do_oop_work(p); }
6425 void do_oop(narrowOop* p) { do_oop_work(p); }
6426 };
6427
6428 class UnregisterNMethodOopClosure: public OopClosure {
6429 G1CollectedHeap* _g1h;
6430 nmethod* _nm;
6431
6432 template <class T> void do_oop_work(T* p) {
6433 T heap_oop = oopDesc::load_heap_oop(p);
6434 if (!oopDesc::is_null(heap_oop)) {
6435 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6436 HeapRegion* hr = _g1h->heap_region_containing(obj);
6437 assert(!hr->is_continues_humongous(),
6438 err_msg("trying to remove code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6439 " starting at "HR_FORMAT,
6440 p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6441
6442 hr->remove_strong_code_root(_nm);
6443 }
6444 }
6445
6446 public:
6447 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6448 _g1h(g1h), _nm(nm) {}
6449
6450 void do_oop(oop* p) { do_oop_work(p); }
6451 void do_oop(narrowOop* p) { do_oop_work(p); }
6452 };
6453
6454 void G1CollectedHeap::register_nmethod(nmethod* nm) {
6455 CollectedHeap::register_nmethod(nm);
6456
6457 guarantee(nm != NULL, "sanity");
6458 RegisterNMethodOopClosure reg_cl(this, nm);
6459 nm->oops_do(®_cl);
6460 }
6461
6462 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
6463 CollectedHeap::unregister_nmethod(nm);
6464
6465 guarantee(nm != NULL, "sanity");
6466 UnregisterNMethodOopClosure reg_cl(this, nm);
6467 nm->oops_do(®_cl, true);
6468 }
6469
6470 void G1CollectedHeap::purge_code_root_memory() {
6471 double purge_start = os::elapsedTime();
6472 G1CodeRootSet::purge();
6473 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
6474 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
6475 }
6476
6477 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
6478 G1CollectedHeap* _g1h;
6479
6480 public:
6481 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
6482 _g1h(g1h) {}
6483
6484 void do_code_blob(CodeBlob* cb) {
6485 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
6486 if (nm == NULL) {
6487 return;
6488 }
6489
6490 if (ScavengeRootsInCode) {
6491 _g1h->register_nmethod(nm);
6492 }
6493 }
6494 };
6495
6496 void G1CollectedHeap::rebuild_strong_code_roots() {
6497 RebuildStrongCodeRootClosure blob_cl(this);
6498 CodeCache::blobs_do(&blob_cl);
6499 }