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 #if !defined(__clang_major__) && defined(__GNUC__)
26 // FIXME, formats have issues. Disable this macro definition, compile, and study warnings for more information.
27 #define ATTRIBUTE_PRINTF(x,y)
28 #endif
29
30 #include "precompiled.hpp"
31 #include "classfile/metadataOnStackMark.hpp"
32 #include "classfile/stringTable.hpp"
33 #include "code/codeCache.hpp"
34 #include "code/icBuffer.hpp"
35 #include "gc_implementation/g1/bufferingOopClosure.hpp"
36 #include "gc_implementation/g1/concurrentG1Refine.hpp"
37 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
38 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
39 #include "gc_implementation/g1/g1AllocRegion.inline.hpp"
40 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
41 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
42 #include "gc_implementation/g1/g1ErgoVerbose.hpp"
43 #include "gc_implementation/g1/g1EvacFailure.hpp"
44 #include "gc_implementation/g1/g1GCPhaseTimes.hpp"
45 #include "gc_implementation/g1/g1Log.hpp"
46 #include "gc_implementation/g1/g1MarkSweep.hpp"
47 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
48 #include "gc_implementation/g1/g1ParScanThreadState.inline.hpp"
49 #include "gc_implementation/g1/g1RegionToSpaceMapper.hpp"
50 #include "gc_implementation/g1/g1RemSet.inline.hpp"
51 #include "gc_implementation/g1/g1RootProcessor.hpp"
52 #include "gc_implementation/g1/g1StringDedup.hpp"
53 #include "gc_implementation/g1/g1YCTypes.hpp"
54 #include "gc_implementation/g1/heapRegion.inline.hpp"
55 #include "gc_implementation/g1/heapRegionRemSet.hpp"
56 #include "gc_implementation/g1/heapRegionSet.inline.hpp"
57 #include "gc_implementation/g1/vm_operations_g1.hpp"
58 #include "gc_implementation/shared/gcHeapSummary.hpp"
59 #include "gc_implementation/shared/gcTimer.hpp"
60 #include "gc_implementation/shared/gcTrace.hpp"
61 #include "gc_implementation/shared/gcTraceTime.hpp"
62 #include "gc_implementation/shared/isGCActiveMark.hpp"
63 #include "memory/allocation.hpp"
64 #include "memory/gcLocker.inline.hpp"
65 #include "memory/generationSpec.hpp"
66 #include "memory/iterator.hpp"
67 #include "memory/referenceProcessor.hpp"
68 #include "oops/oop.inline.hpp"
69 #include "runtime/atomic.inline.hpp"
70 #include "runtime/orderAccess.inline.hpp"
71 #include "runtime/vmThread.hpp"
72 #include "utilities/globalDefinitions.hpp"
73 #include "utilities/stack.inline.hpp"
74
75 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
76
77 // turn it on so that the contents of the young list (scan-only /
78 // to-be-collected) are printed at "strategic" points before / during
79 // / after the collection --- this is useful for debugging
80 #define YOUNG_LIST_VERBOSE 0
81 // CURRENT STATUS
82 // This file is under construction. Search for "FIXME".
83
84 // INVARIANTS/NOTES
85 //
86 // All allocation activity covered by the G1CollectedHeap interface is
87 // serialized by acquiring the HeapLock. This happens in mem_allocate
88 // and allocate_new_tlab, which are the "entry" points to the
89 // allocation code from the rest of the JVM. (Note that this does not
90 // apply to TLAB allocation, which is not part of this interface: it
91 // is done by clients of this interface.)
92
93 // Local to this file.
94
95 class RefineCardTableEntryClosure: public CardTableEntryClosure {
96 bool _concurrent;
97 public:
98 RefineCardTableEntryClosure() : _concurrent(true) { }
99
100 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
101 bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, false);
102 // This path is executed by the concurrent refine or mutator threads,
103 // concurrently, and so we do not care if card_ptr contains references
104 // that point into the collection set.
105 assert(!oops_into_cset, "should be");
106
107 if (_concurrent && SuspendibleThreadSet::should_yield()) {
108 // Caller will actually yield.
109 return false;
110 }
111 // Otherwise, we finished successfully; return true.
112 return true;
113 }
114
115 void set_concurrent(bool b) { _concurrent = b; }
116 };
117
118
119 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
120 private:
121 size_t _num_processed;
122
123 public:
124 RedirtyLoggedCardTableEntryClosure() : CardTableEntryClosure(), _num_processed(0) { }
125
126 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
127 *card_ptr = CardTableModRefBS::dirty_card_val();
128 _num_processed++;
129 return true;
130 }
131
132 size_t num_processed() const { return _num_processed; }
133 };
134
135 YoungList::YoungList(G1CollectedHeap* g1h) :
136 _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0),
137 _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) {
138 guarantee(check_list_empty(false), "just making sure...");
139 }
140
141 void YoungList::push_region(HeapRegion *hr) {
142 assert(!hr->is_young(), "should not already be young");
143 assert(hr->get_next_young_region() == NULL, "cause it should!");
144
145 hr->set_next_young_region(_head);
146 _head = hr;
147
148 _g1h->g1_policy()->set_region_eden(hr, (int) _length);
149 ++_length;
150 }
151
152 void YoungList::add_survivor_region(HeapRegion* hr) {
153 assert(hr->is_survivor(), "should be flagged as survivor region");
154 assert(hr->get_next_young_region() == NULL, "cause it should!");
155
156 hr->set_next_young_region(_survivor_head);
157 if (_survivor_head == NULL) {
158 _survivor_tail = hr;
159 }
160 _survivor_head = hr;
161 ++_survivor_length;
162 }
163
164 void YoungList::empty_list(HeapRegion* list) {
165 while (list != NULL) {
166 HeapRegion* next = list->get_next_young_region();
167 list->set_next_young_region(NULL);
168 list->uninstall_surv_rate_group();
169 // This is called before a Full GC and all the non-empty /
170 // non-humongous regions at the end of the Full GC will end up as
171 // old anyway.
172 list->set_old();
173 list = next;
174 }
175 }
176
177 void YoungList::empty_list() {
178 assert(check_list_well_formed(), "young list should be well formed");
179
180 empty_list(_head);
181 _head = NULL;
182 _length = 0;
183
184 empty_list(_survivor_head);
185 _survivor_head = NULL;
186 _survivor_tail = NULL;
187 _survivor_length = 0;
188
189 _last_sampled_rs_lengths = 0;
190
191 assert(check_list_empty(false), "just making sure...");
192 }
193
194 bool YoungList::check_list_well_formed() {
195 bool ret = true;
196
197 uint length = 0;
198 HeapRegion* curr = _head;
199 HeapRegion* last = NULL;
200 while (curr != NULL) {
201 if (!curr->is_young()) {
202 gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
203 "incorrectly tagged (y: %d, surv: %d)",
204 curr->bottom(), curr->end(),
205 curr->is_young(), curr->is_survivor());
206 ret = false;
207 }
208 ++length;
209 last = curr;
210 curr = curr->get_next_young_region();
211 }
212 ret = ret && (length == _length);
213
214 if (!ret) {
215 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
216 gclog_or_tty->print_cr("### list has %u entries, _length is %u",
217 length, _length);
218 }
219
220 return ret;
221 }
222
223 bool YoungList::check_list_empty(bool check_sample) {
224 bool ret = true;
225
226 if (_length != 0) {
227 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u",
228 _length);
229 ret = false;
230 }
231 if (check_sample && _last_sampled_rs_lengths != 0) {
232 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
233 ret = false;
234 }
235 if (_head != NULL) {
236 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
237 ret = false;
238 }
239 if (!ret) {
240 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
241 }
242
243 return ret;
244 }
245
246 void
247 YoungList::rs_length_sampling_init() {
248 _sampled_rs_lengths = 0;
249 _curr = _head;
250 }
251
252 bool
253 YoungList::rs_length_sampling_more() {
254 return _curr != NULL;
255 }
256
257 void
258 YoungList::rs_length_sampling_next() {
259 assert( _curr != NULL, "invariant" );
260 size_t rs_length = _curr->rem_set()->occupied();
261
262 _sampled_rs_lengths += rs_length;
263
264 // The current region may not yet have been added to the
265 // incremental collection set (it gets added when it is
266 // retired as the current allocation region).
267 if (_curr->in_collection_set()) {
268 // Update the collection set policy information for this region
269 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
270 }
271
272 _curr = _curr->get_next_young_region();
273 if (_curr == NULL) {
274 _last_sampled_rs_lengths = _sampled_rs_lengths;
275 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
276 }
277 }
278
279 void
280 YoungList::reset_auxilary_lists() {
281 guarantee( is_empty(), "young list should be empty" );
282 assert(check_list_well_formed(), "young list should be well formed");
283
284 // Add survivor regions to SurvRateGroup.
285 _g1h->g1_policy()->note_start_adding_survivor_regions();
286 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
287
288 int young_index_in_cset = 0;
289 for (HeapRegion* curr = _survivor_head;
290 curr != NULL;
291 curr = curr->get_next_young_region()) {
292 _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
293
294 // The region is a non-empty survivor so let's add it to
295 // the incremental collection set for the next evacuation
296 // pause.
297 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
298 young_index_in_cset += 1;
299 }
300 assert((uint) young_index_in_cset == _survivor_length, "post-condition");
301 _g1h->g1_policy()->note_stop_adding_survivor_regions();
302
303 _head = _survivor_head;
304 _length = _survivor_length;
305 if (_survivor_head != NULL) {
306 assert(_survivor_tail != NULL, "cause it shouldn't be");
307 assert(_survivor_length > 0, "invariant");
308 _survivor_tail->set_next_young_region(NULL);
309 }
310
311 // Don't clear the survivor list handles until the start of
312 // the next evacuation pause - we need it in order to re-tag
313 // the survivor regions from this evacuation pause as 'young'
314 // at the start of the next.
315
316 _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
317
318 assert(check_list_well_formed(), "young list should be well formed");
319 }
320
321 void YoungList::print() {
322 HeapRegion* lists[] = {_head, _survivor_head};
323 const char* names[] = {"YOUNG", "SURVIVOR"};
324
325 for (uint list = 0; list < ARRAY_SIZE(lists); ++list) {
326 gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
327 HeapRegion *curr = lists[list];
328 if (curr == NULL)
329 gclog_or_tty->print_cr(" empty");
330 while (curr != NULL) {
331 gclog_or_tty->print_cr(" "HR_FORMAT", P: "PTR_FORMAT ", N: "PTR_FORMAT", age: %4d",
332 HR_FORMAT_PARAMS(curr),
333 curr->prev_top_at_mark_start(),
334 curr->next_top_at_mark_start(),
335 curr->age_in_surv_rate_group_cond());
336 curr = curr->get_next_young_region();
337 }
338 }
339
340 gclog_or_tty->cr();
341 }
342
343 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
344 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
345 }
346
347 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
348 // The from card cache is not the memory that is actually committed. So we cannot
349 // take advantage of the zero_filled parameter.
350 reset_from_card_cache(start_idx, num_regions);
351 }
352
353 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
354 {
355 // Claim the right to put the region on the dirty cards region list
356 // by installing a self pointer.
357 HeapRegion* next = hr->get_next_dirty_cards_region();
358 if (next == NULL) {
359 HeapRegion* res = (HeapRegion*)
360 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
361 NULL);
362 if (res == NULL) {
363 HeapRegion* head;
364 do {
365 // Put the region to the dirty cards region list.
366 head = _dirty_cards_region_list;
367 next = (HeapRegion*)
368 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
369 if (next == head) {
370 assert(hr->get_next_dirty_cards_region() == hr,
371 "hr->get_next_dirty_cards_region() != hr");
372 if (next == NULL) {
373 // The last region in the list points to itself.
374 hr->set_next_dirty_cards_region(hr);
375 } else {
376 hr->set_next_dirty_cards_region(next);
377 }
378 }
379 } while (next != head);
380 }
381 }
382 }
383
384 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
385 {
386 HeapRegion* head;
387 HeapRegion* hr;
388 do {
389 head = _dirty_cards_region_list;
390 if (head == NULL) {
391 return NULL;
392 }
393 HeapRegion* new_head = head->get_next_dirty_cards_region();
394 if (head == new_head) {
395 // The last region.
396 new_head = NULL;
397 }
398 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
399 head);
400 } while (hr != head);
401 assert(hr != NULL, "invariant");
402 hr->set_next_dirty_cards_region(NULL);
403 return hr;
404 }
405
406 // Returns true if the reference points to an object that
407 // can move in an incremental collection.
408 bool G1CollectedHeap::is_scavengable(const void* p) {
409 HeapRegion* hr = heap_region_containing(p);
410 return !hr->is_humongous();
411 }
412
413 // Private methods.
414
415 HeapRegion*
416 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
417 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
418 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
419 if (!_secondary_free_list.is_empty()) {
420 if (G1ConcRegionFreeingVerbose) {
421 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
422 "secondary_free_list has %u entries",
423 _secondary_free_list.length());
424 }
425 // It looks as if there are free regions available on the
426 // secondary_free_list. Let's move them to the free_list and try
427 // again to allocate from it.
428 append_secondary_free_list();
429
430 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not "
431 "empty we should have moved at least one entry to the free_list");
432 HeapRegion* res = _hrm.allocate_free_region(is_old);
433 if (G1ConcRegionFreeingVerbose) {
434 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
435 "allocated "HR_FORMAT" from secondary_free_list",
436 HR_FORMAT_PARAMS(res));
437 }
438 return res;
439 }
440
441 // Wait here until we get notified either when (a) there are no
442 // more free regions coming or (b) some regions have been moved on
443 // the secondary_free_list.
444 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
445 }
446
447 if (G1ConcRegionFreeingVerbose) {
448 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
449 "could not allocate from secondary_free_list");
450 }
451 return NULL;
452 }
453
454 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
455 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
456 "the only time we use this to allocate a humongous region is "
457 "when we are allocating a single humongous region");
458
459 HeapRegion* res;
460 if (G1StressConcRegionFreeing) {
461 if (!_secondary_free_list.is_empty()) {
462 if (G1ConcRegionFreeingVerbose) {
463 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
464 "forced to look at the secondary_free_list");
465 }
466 res = new_region_try_secondary_free_list(is_old);
467 if (res != NULL) {
468 return res;
469 }
470 }
471 }
472
473 res = _hrm.allocate_free_region(is_old);
474
475 if (res == NULL) {
476 if (G1ConcRegionFreeingVerbose) {
477 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
478 "res == NULL, trying the secondary_free_list");
479 }
480 res = new_region_try_secondary_free_list(is_old);
481 }
482 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
483 // Currently, only attempts to allocate GC alloc regions set
484 // do_expand to true. So, we should only reach here during a
485 // safepoint. If this assumption changes we might have to
486 // reconsider the use of _expand_heap_after_alloc_failure.
487 assert(SafepointSynchronize::is_at_safepoint(), "invariant");
488
489 ergo_verbose1(ErgoHeapSizing,
490 "attempt heap expansion",
491 ergo_format_reason("region allocation request failed")
492 ergo_format_byte("allocation request"),
493 word_size * HeapWordSize);
494 if (expand(word_size * HeapWordSize)) {
495 // Given that expand() succeeded in expanding the heap, and we
496 // always expand the heap by an amount aligned to the heap
497 // region size, the free list should in theory not be empty.
498 // In either case allocate_free_region() will check for NULL.
499 res = _hrm.allocate_free_region(is_old);
500 } else {
501 _expand_heap_after_alloc_failure = false;
502 }
503 }
504 return res;
505 }
506
507 HeapWord*
508 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
509 uint num_regions,
510 size_t word_size,
511 AllocationContext_t context) {
512 assert(first != G1_NO_HRM_INDEX, "pre-condition");
513 assert(is_humongous(word_size), "word_size should be humongous");
514 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
515
516 // Index of last region in the series + 1.
517 uint last = first + num_regions;
518
519 // We need to initialize the region(s) we just discovered. This is
520 // a bit tricky given that it can happen concurrently with
521 // refinement threads refining cards on these regions and
522 // potentially wanting to refine the BOT as they are scanning
523 // those cards (this can happen shortly after a cleanup; see CR
524 // 6991377). So we have to set up the region(s) carefully and in
525 // a specific order.
526
527 // The word size sum of all the regions we will allocate.
528 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
529 assert(word_size <= word_size_sum, "sanity");
530
531 // This will be the "starts humongous" region.
532 HeapRegion* first_hr = region_at(first);
533 // The header of the new object will be placed at the bottom of
534 // the first region.
535 HeapWord* new_obj = first_hr->bottom();
536 // This will be the new end of the first region in the series that
537 // should also match the end of the last region in the series.
538 HeapWord* new_end = new_obj + word_size_sum;
539 // This will be the new top of the first region that will reflect
540 // this allocation.
541 HeapWord* new_top = new_obj + word_size;
542
543 // First, we need to zero the header of the space that we will be
544 // allocating. When we update top further down, some refinement
545 // threads might try to scan the region. By zeroing the header we
546 // ensure that any thread that will try to scan the region will
547 // come across the zero klass word and bail out.
548 //
549 // NOTE: It would not have been correct to have used
550 // CollectedHeap::fill_with_object() and make the space look like
551 // an int array. The thread that is doing the allocation will
552 // later update the object header to a potentially different array
553 // type and, for a very short period of time, the klass and length
554 // fields will be inconsistent. This could cause a refinement
555 // thread to calculate the object size incorrectly.
556 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
557
558 // We will set up the first region as "starts humongous". This
559 // will also update the BOT covering all the regions to reflect
560 // that there is a single object that starts at the bottom of the
561 // first region.
562 first_hr->set_starts_humongous(new_top, new_end);
563 first_hr->set_allocation_context(context);
564 // Then, if there are any, we will set up the "continues
565 // humongous" regions.
566 HeapRegion* hr = NULL;
567 for (uint i = first + 1; i < last; ++i) {
568 hr = region_at(i);
569 hr->set_continues_humongous(first_hr);
570 hr->set_allocation_context(context);
571 }
572 // If we have "continues humongous" regions (hr != NULL), then the
573 // end of the last one should match new_end.
574 assert(hr == NULL || hr->end() == new_end, "sanity");
575
576 // Up to this point no concurrent thread would have been able to
577 // do any scanning on any region in this series. All the top
578 // fields still point to bottom, so the intersection between
579 // [bottom,top] and [card_start,card_end] will be empty. Before we
580 // update the top fields, we'll do a storestore to make sure that
581 // no thread sees the update to top before the zeroing of the
582 // object header and the BOT initialization.
583 OrderAccess::storestore();
584
585 // Now that the BOT and the object header have been initialized,
586 // we can update top of the "starts humongous" region.
587 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
588 "new_top should be in this region");
589 first_hr->set_top(new_top);
590 if (_hr_printer.is_active()) {
591 HeapWord* bottom = first_hr->bottom();
592 HeapWord* end = first_hr->orig_end();
593 if ((first + 1) == last) {
594 // the series has a single humongous region
595 _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
596 } else {
597 // the series has more than one humongous regions
598 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
599 }
600 }
601
602 // Now, we will update the top fields of the "continues humongous"
603 // regions. The reason we need to do this is that, otherwise,
604 // these regions would look empty and this will confuse parts of
605 // G1. For example, the code that looks for a consecutive number
606 // of empty regions will consider them empty and try to
607 // re-allocate them. We can extend is_empty() to also include
608 // !is_continues_humongous(), but it is easier to just update the top
609 // fields here. The way we set top for all regions (i.e., top ==
610 // end for all regions but the last one, top == new_top for the
611 // last one) is actually used when we will free up the humongous
612 // region in free_humongous_region().
613 hr = NULL;
614 for (uint i = first + 1; i < last; ++i) {
615 hr = region_at(i);
616 if ((i + 1) == last) {
617 // last continues humongous region
618 assert(hr->bottom() < new_top && new_top <= hr->end(),
619 "new_top should fall on this region");
620 hr->set_top(new_top);
621 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
622 } else {
623 // not last one
624 assert(new_top > hr->end(), "new_top should be above this region");
625 hr->set_top(hr->end());
626 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
627 }
628 }
629 // If we have continues humongous regions (hr != NULL), then the
630 // end of the last one should match new_end and its top should
631 // match new_top.
632 assert(hr == NULL ||
633 (hr->end() == new_end && hr->top() == new_top), "sanity");
634 check_bitmaps("Humongous Region Allocation", first_hr);
635
636 assert(first_hr->used() == word_size * HeapWordSize, "invariant");
637 _allocator->increase_used(first_hr->used());
638 _humongous_set.add(first_hr);
639
640 return new_obj;
641 }
642
643 // If could fit into free regions w/o expansion, try.
644 // Otherwise, if can expand, do so.
645 // Otherwise, if using ex regions might help, try with ex given back.
646 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) {
647 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
648
649 verify_region_sets_optional();
650
651 uint first = G1_NO_HRM_INDEX;
652 uint obj_regions = (uint)(align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords);
653
654 if (obj_regions == 1) {
655 // Only one region to allocate, try to use a fast path by directly allocating
656 // from the free lists. Do not try to expand here, we will potentially do that
657 // later.
658 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
659 if (hr != NULL) {
660 first = hr->hrm_index();
661 }
662 } else {
663 // We can't allocate humongous regions spanning more than one region while
664 // cleanupComplete() is running, since some of the regions we find to be
665 // empty might not yet be added to the free list. It is not straightforward
666 // to know in which list they are on so that we can remove them. We only
667 // need to do this if we need to allocate more than one region to satisfy the
668 // current humongous allocation request. If we are only allocating one region
669 // we use the one-region region allocation code (see above), that already
670 // potentially waits for regions from the secondary free list.
671 wait_while_free_regions_coming();
672 append_secondary_free_list_if_not_empty_with_lock();
673
674 // Policy: Try only empty regions (i.e. already committed first). Maybe we
675 // are lucky enough to find some.
676 first = _hrm.find_contiguous_only_empty(obj_regions);
677 if (first != G1_NO_HRM_INDEX) {
678 _hrm.allocate_free_regions_starting_at(first, obj_regions);
679 }
680 }
681
682 if (first == G1_NO_HRM_INDEX) {
683 // Policy: We could not find enough regions for the humongous object in the
684 // free list. Look through the heap to find a mix of free and uncommitted regions.
685 // If so, try expansion.
686 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
687 if (first != G1_NO_HRM_INDEX) {
688 // We found something. Make sure these regions are committed, i.e. expand
689 // the heap. Alternatively we could do a defragmentation GC.
690 ergo_verbose1(ErgoHeapSizing,
691 "attempt heap expansion",
692 ergo_format_reason("humongous allocation request failed")
693 ergo_format_byte("allocation request"),
694 word_size * HeapWordSize);
695
696 _hrm.expand_at(first, obj_regions);
697 g1_policy()->record_new_heap_size(num_regions());
698
699 #ifdef ASSERT
700 for (uint i = first; i < first + obj_regions; ++i) {
701 HeapRegion* hr = region_at(i);
702 assert(hr->is_free(), "sanity");
703 assert(hr->is_empty(), "sanity");
704 assert(is_on_master_free_list(hr), "sanity");
705 }
706 #endif
707 _hrm.allocate_free_regions_starting_at(first, obj_regions);
708 } else {
709 // Policy: Potentially trigger a defragmentation GC.
710 }
711 }
712
713 HeapWord* result = NULL;
714 if (first != G1_NO_HRM_INDEX) {
715 result = humongous_obj_allocate_initialize_regions(first, obj_regions,
716 word_size, context);
717 assert(result != NULL, "it should always return a valid result");
718
719 // A successful humongous object allocation changes the used space
720 // information of the old generation so we need to recalculate the
721 // sizes and update the jstat counters here.
722 g1mm()->update_sizes();
723 }
724
725 verify_region_sets_optional();
726
727 return result;
728 }
729
730 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
731 assert_heap_not_locked_and_not_at_safepoint();
732 assert(!is_humongous(word_size), "we do not allow humongous TLABs");
733
734 uint dummy_gc_count_before;
735 uint dummy_gclocker_retry_count = 0;
736 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
737 }
738
739 HeapWord*
740 G1CollectedHeap::mem_allocate(size_t word_size,
741 bool* gc_overhead_limit_was_exceeded) {
742 assert_heap_not_locked_and_not_at_safepoint();
743
744 // Loop until the allocation is satisfied, or unsatisfied after GC.
745 for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
746 uint gc_count_before;
747
748 HeapWord* result = NULL;
749 if (!is_humongous(word_size)) {
750 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
751 } else {
752 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
753 }
754 if (result != NULL) {
755 return result;
756 }
757
758 // Create the garbage collection operation...
759 VM_G1CollectForAllocation op(gc_count_before, word_size);
760 op.set_allocation_context(AllocationContext::current());
761
762 // ...and get the VM thread to execute it.
763 VMThread::execute(&op);
764
765 if (op.prologue_succeeded() && op.pause_succeeded()) {
766 // If the operation was successful we'll return the result even
767 // if it is NULL. If the allocation attempt failed immediately
768 // after a Full GC, it's unlikely we'll be able to allocate now.
769 HeapWord* result = op.result();
770 if (result != NULL && !is_humongous(word_size)) {
771 // Allocations that take place on VM operations do not do any
772 // card dirtying and we have to do it here. We only have to do
773 // this for non-humongous allocations, though.
774 dirty_young_block(result, word_size);
775 }
776 return result;
777 } else {
778 if (gclocker_retry_count > GCLockerRetryAllocationCount) {
779 return NULL;
780 }
781 assert(op.result() == NULL,
782 "the result should be NULL if the VM op did not succeed");
783 }
784
785 // Give a warning if we seem to be looping forever.
786 if ((QueuedAllocationWarningCount > 0) &&
787 (try_count % QueuedAllocationWarningCount == 0)) {
788 warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
789 }
790 }
791
792 ShouldNotReachHere();
793 return NULL;
794 }
795
796 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
797 AllocationContext_t context,
798 uint* gc_count_before_ret,
799 uint* gclocker_retry_count_ret) {
800 // Make sure you read the note in attempt_allocation_humongous().
801
802 assert_heap_not_locked_and_not_at_safepoint();
803 assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
804 "be called for humongous allocation requests");
805
806 // We should only get here after the first-level allocation attempt
807 // (attempt_allocation()) failed to allocate.
808
809 // We will loop until a) we manage to successfully perform the
810 // allocation or b) we successfully schedule a collection which
811 // fails to perform the allocation. b) is the only case when we'll
812 // return NULL.
813 HeapWord* result = NULL;
814 for (int try_count = 1; /* we'll return */; try_count += 1) {
815 bool should_try_gc;
816 uint gc_count_before;
817
818 {
819 MutexLockerEx x(Heap_lock);
820 result = _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size,
821 false /* bot_updates */);
822 if (result != NULL) {
823 return result;
824 }
825
826 // If we reach here, attempt_allocation_locked() above failed to
827 // allocate a new region. So the mutator alloc region should be NULL.
828 assert(_allocator->mutator_alloc_region(context)->get() == NULL, "only way to get here");
829
830 if (GC_locker::is_active_and_needs_gc()) {
831 if (g1_policy()->can_expand_young_list()) {
832 // No need for an ergo verbose message here,
833 // can_expand_young_list() does this when it returns true.
834 result = _allocator->mutator_alloc_region(context)->attempt_allocation_force(word_size,
835 false /* bot_updates */);
836 if (result != NULL) {
837 return result;
838 }
839 }
840 should_try_gc = false;
841 } else {
842 // The GCLocker may not be active but the GCLocker initiated
843 // GC may not yet have been performed (GCLocker::needs_gc()
844 // returns true). In this case we do not try this GC and
845 // wait until the GCLocker initiated GC is performed, and
846 // then retry the allocation.
847 if (GC_locker::needs_gc()) {
848 should_try_gc = false;
849 } else {
850 // Read the GC count while still holding the Heap_lock.
851 gc_count_before = total_collections();
852 should_try_gc = true;
853 }
854 }
855 }
856
857 if (should_try_gc) {
858 bool succeeded;
859 result = do_collection_pause(word_size, gc_count_before, &succeeded,
860 GCCause::_g1_inc_collection_pause);
861 if (result != NULL) {
862 assert(succeeded, "only way to get back a non-NULL result");
863 return result;
864 }
865
866 if (succeeded) {
867 // If we get here we successfully scheduled a collection which
868 // failed to allocate. No point in trying to allocate
869 // further. We'll just return NULL.
870 MutexLockerEx x(Heap_lock);
871 *gc_count_before_ret = total_collections();
872 return NULL;
873 }
874 } else {
875 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
876 MutexLockerEx x(Heap_lock);
877 *gc_count_before_ret = total_collections();
878 return NULL;
879 }
880 // The GCLocker is either active or the GCLocker initiated
881 // GC has not yet been performed. Stall until it is and
882 // then retry the allocation.
883 GC_locker::stall_until_clear();
884 (*gclocker_retry_count_ret) += 1;
885 }
886
887 // We can reach here if we were unsuccessful in scheduling a
888 // collection (because another thread beat us to it) or if we were
889 // stalled due to the GC locker. In either can we should retry the
890 // allocation attempt in case another thread successfully
891 // performed a collection and reclaimed enough space. We do the
892 // first attempt (without holding the Heap_lock) here and the
893 // follow-on attempt will be at the start of the next loop
894 // iteration (after taking the Heap_lock).
895 result = _allocator->mutator_alloc_region(context)->attempt_allocation(word_size,
896 false /* bot_updates */);
897 if (result != NULL) {
898 return result;
899 }
900
901 // Give a warning if we seem to be looping forever.
902 if ((QueuedAllocationWarningCount > 0) &&
903 (try_count % QueuedAllocationWarningCount == 0)) {
904 warning("G1CollectedHeap::attempt_allocation_slow() "
905 "retries %d times", try_count);
906 }
907 }
908
909 ShouldNotReachHere();
910 return NULL;
911 }
912
913 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
914 uint* gc_count_before_ret,
915 uint* gclocker_retry_count_ret) {
916 // The structure of this method has a lot of similarities to
917 // attempt_allocation_slow(). The reason these two were not merged
918 // into a single one is that such a method would require several "if
919 // allocation is not humongous do this, otherwise do that"
920 // conditional paths which would obscure its flow. In fact, an early
921 // version of this code did use a unified method which was harder to
922 // follow and, as a result, it had subtle bugs that were hard to
923 // track down. So keeping these two methods separate allows each to
924 // be more readable. It will be good to keep these two in sync as
925 // much as possible.
926
927 assert_heap_not_locked_and_not_at_safepoint();
928 assert(is_humongous(word_size), "attempt_allocation_humongous() "
929 "should only be called for humongous allocations");
930
931 // Humongous objects can exhaust the heap quickly, so we should check if we
932 // need to start a marking cycle at each humongous object allocation. We do
933 // the check before we do the actual allocation. The reason for doing it
934 // before the allocation is that we avoid having to keep track of the newly
935 // allocated memory while we do a GC.
936 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
937 word_size)) {
938 collect(GCCause::_g1_humongous_allocation);
939 }
940
941 // We will loop until a) we manage to successfully perform the
942 // allocation or b) we successfully schedule a collection which
943 // fails to perform the allocation. b) is the only case when we'll
944 // return NULL.
945 HeapWord* result = NULL;
946 for (int try_count = 1; /* we'll return */; try_count += 1) {
947 bool should_try_gc;
948 uint gc_count_before;
949
950 {
951 MutexLockerEx x(Heap_lock);
952
953 // Given that humongous objects are not allocated in young
954 // regions, we'll first try to do the allocation without doing a
955 // collection hoping that there's enough space in the heap.
956 result = humongous_obj_allocate(word_size, AllocationContext::current());
957 if (result != NULL) {
958 return result;
959 }
960
961 if (GC_locker::is_active_and_needs_gc()) {
962 should_try_gc = false;
963 } else {
964 // The GCLocker may not be active but the GCLocker initiated
965 // GC may not yet have been performed (GCLocker::needs_gc()
966 // returns true). In this case we do not try this GC and
967 // wait until the GCLocker initiated GC is performed, and
968 // then retry the allocation.
969 if (GC_locker::needs_gc()) {
970 should_try_gc = false;
971 } else {
972 // Read the GC count while still holding the Heap_lock.
973 gc_count_before = total_collections();
974 should_try_gc = true;
975 }
976 }
977 }
978
979 if (should_try_gc) {
980 // If we failed to allocate the humongous object, we should try to
981 // do a collection pause (if we're allowed) in case it reclaims
982 // enough space for the allocation to succeed after the pause.
983
984 bool succeeded;
985 result = do_collection_pause(word_size, gc_count_before, &succeeded,
986 GCCause::_g1_humongous_allocation);
987 if (result != NULL) {
988 assert(succeeded, "only way to get back a non-NULL result");
989 return result;
990 }
991
992 if (succeeded) {
993 // If we get here we successfully scheduled a collection which
994 // failed to allocate. No point in trying to allocate
995 // further. We'll just return NULL.
996 MutexLockerEx x(Heap_lock);
997 *gc_count_before_ret = total_collections();
998 return NULL;
999 }
1000 } else {
1001 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1002 MutexLockerEx x(Heap_lock);
1003 *gc_count_before_ret = total_collections();
1004 return NULL;
1005 }
1006 // The GCLocker is either active or the GCLocker initiated
1007 // GC has not yet been performed. Stall until it is and
1008 // then retry the allocation.
1009 GC_locker::stall_until_clear();
1010 (*gclocker_retry_count_ret) += 1;
1011 }
1012
1013 // We can reach here if we were unsuccessful in scheduling a
1014 // collection (because another thread beat us to it) or if we were
1015 // stalled due to the GC locker. In either can we should retry the
1016 // allocation attempt in case another thread successfully
1017 // performed a collection and reclaimed enough space. Give a
1018 // warning if we seem to be looping forever.
1019
1020 if ((QueuedAllocationWarningCount > 0) &&
1021 (try_count % QueuedAllocationWarningCount == 0)) {
1022 warning("G1CollectedHeap::attempt_allocation_humongous() "
1023 "retries %d times", try_count);
1024 }
1025 }
1026
1027 ShouldNotReachHere();
1028 return NULL;
1029 }
1030
1031 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1032 AllocationContext_t context,
1033 bool expect_null_mutator_alloc_region) {
1034 assert_at_safepoint(true /* should_be_vm_thread */);
1035 assert(_allocator->mutator_alloc_region(context)->get() == NULL ||
1036 !expect_null_mutator_alloc_region,
1037 "the current alloc region was unexpectedly found to be non-NULL");
1038
1039 if (!is_humongous(word_size)) {
1040 return _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size,
1041 false /* bot_updates */);
1042 } else {
1043 HeapWord* result = humongous_obj_allocate(word_size, context);
1044 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1045 g1_policy()->set_initiate_conc_mark_if_possible();
1046 }
1047 return result;
1048 }
1049
1050 ShouldNotReachHere();
1051 }
1052
1053 class PostMCRemSetClearClosure: public HeapRegionClosure {
1054 G1CollectedHeap* _g1h;
1055 ModRefBarrierSet* _mr_bs;
1056 public:
1057 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1058 _g1h(g1h), _mr_bs(mr_bs) {}
1059
1060 bool doHeapRegion(HeapRegion* r) {
1061 HeapRegionRemSet* hrrs = r->rem_set();
1062
1063 if (r->is_continues_humongous()) {
1064 // We'll assert that the strong code root list and RSet is empty
1065 assert(hrrs->strong_code_roots_list_length() == 0, "sanity");
1066 assert(hrrs->occupied() == 0, "RSet should be empty");
1067 return false;
1068 }
1069
1070 _g1h->reset_gc_time_stamps(r);
1071 hrrs->clear();
1072 // You might think here that we could clear just the cards
1073 // corresponding to the used region. But no: if we leave a dirty card
1074 // in a region we might allocate into, then it would prevent that card
1075 // from being enqueued, and cause it to be missed.
1076 // Re: the performance cost: we shouldn't be doing full GC anyway!
1077 _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1078
1079 return false;
1080 }
1081 };
1082
1083 void G1CollectedHeap::clear_rsets_post_compaction() {
1084 PostMCRemSetClearClosure rs_clear(this, g1_barrier_set());
1085 heap_region_iterate(&rs_clear);
1086 }
1087
1088 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1089 G1CollectedHeap* _g1h;
1090 UpdateRSOopClosure _cl;
1091 int _worker_i;
1092 public:
1093 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1094 _cl(g1->g1_rem_set(), worker_i),
1095 _worker_i(worker_i),
1096 _g1h(g1)
1097 { }
1098
1099 bool doHeapRegion(HeapRegion* r) {
1100 if (!r->is_continues_humongous()) {
1101 _cl.set_from(r);
1102 r->oop_iterate(&_cl);
1103 }
1104 return false;
1105 }
1106 };
1107
1108 class ParRebuildRSTask: public AbstractGangTask {
1109 G1CollectedHeap* _g1;
1110 HeapRegionClaimer _hrclaimer;
1111
1112 public:
1113 ParRebuildRSTask(G1CollectedHeap* g1) :
1114 AbstractGangTask("ParRebuildRSTask"), _g1(g1), _hrclaimer(g1->workers()->active_workers()) {}
1115
1116 void work(uint worker_id) {
1117 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1118 _g1->heap_region_par_iterate(&rebuild_rs, worker_id, &_hrclaimer);
1119 }
1120 };
1121
1122 class PostCompactionPrinterClosure: public HeapRegionClosure {
1123 private:
1124 G1HRPrinter* _hr_printer;
1125 public:
1126 bool doHeapRegion(HeapRegion* hr) {
1127 assert(!hr->is_young(), "not expecting to find young regions");
1128 if (hr->is_free()) {
1129 // We only generate output for non-empty regions.
1130 } else if (hr->is_starts_humongous()) {
1131 if (hr->region_num() == 1) {
1132 // single humongous region
1133 _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
1134 } else {
1135 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
1136 }
1137 } else if (hr->is_continues_humongous()) {
1138 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1139 } else if (hr->is_old()) {
1140 _hr_printer->post_compaction(hr, G1HRPrinter::Old);
1141 } else {
1142 ShouldNotReachHere();
1143 }
1144 return false;
1145 }
1146
1147 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1148 : _hr_printer(hr_printer) { }
1149 };
1150
1151 void G1CollectedHeap::print_hrm_post_compaction() {
1152 PostCompactionPrinterClosure cl(hr_printer());
1153 heap_region_iterate(&cl);
1154 }
1155
1156 bool G1CollectedHeap::do_collection(bool explicit_gc,
1157 bool clear_all_soft_refs,
1158 size_t word_size) {
1159 assert_at_safepoint(true /* should_be_vm_thread */);
1160
1161 if (GC_locker::check_active_before_gc()) {
1162 return false;
1163 }
1164
1165 STWGCTimer* gc_timer = G1MarkSweep::gc_timer();
1166 gc_timer->register_gc_start();
1167
1168 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer();
1169 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start());
1170
1171 SvcGCMarker sgcm(SvcGCMarker::FULL);
1172 ResourceMark rm;
1173
1174 print_heap_before_gc();
1175 trace_heap_before_gc(gc_tracer);
1176
1177 size_t metadata_prev_used = MetaspaceAux::used_bytes();
1178
1179 verify_region_sets_optional();
1180
1181 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1182 collector_policy()->should_clear_all_soft_refs();
1183
1184 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1185
1186 {
1187 IsGCActiveMark x;
1188
1189 // Timing
1190 assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant");
1191 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
1192
1193 {
1194 GCTraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, NULL, gc_tracer->gc_id());
1195 TraceCollectorStats tcs(g1mm()->full_collection_counters());
1196 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1197
1198 g1_policy()->record_full_collection_start();
1199
1200 // Note: When we have a more flexible GC logging framework that
1201 // allows us to add optional attributes to a GC log record we
1202 // could consider timing and reporting how long we wait in the
1203 // following two methods.
1204 wait_while_free_regions_coming();
1205 // If we start the compaction before the CM threads finish
1206 // scanning the root regions we might trip them over as we'll
1207 // be moving objects / updating references. So let's wait until
1208 // they are done. By telling them to abort, they should complete
1209 // early.
1210 _cm->root_regions()->abort();
1211 _cm->root_regions()->wait_until_scan_finished();
1212 append_secondary_free_list_if_not_empty_with_lock();
1213
1214 gc_prologue(true);
1215 increment_total_collections(true /* full gc */);
1216 increment_old_marking_cycles_started();
1217
1218 assert(used() == recalculate_used(), "Should be equal");
1219
1220 verify_before_gc();
1221
1222 check_bitmaps("Full GC Start");
1223 pre_full_gc_dump(gc_timer);
1224
1225 COMPILER2_PRESENT(DerivedPointerTable::clear());
1226
1227 // Disable discovery and empty the discovered lists
1228 // for the CM ref processor.
1229 ref_processor_cm()->disable_discovery();
1230 ref_processor_cm()->abandon_partial_discovery();
1231 ref_processor_cm()->verify_no_references_recorded();
1232
1233 // Abandon current iterations of concurrent marking and concurrent
1234 // refinement, if any are in progress. We have to do this before
1235 // wait_until_scan_finished() below.
1236 concurrent_mark()->abort();
1237
1238 // Make sure we'll choose a new allocation region afterwards.
1239 _allocator->release_mutator_alloc_region();
1240 _allocator->abandon_gc_alloc_regions();
1241 g1_rem_set()->cleanupHRRS();
1242
1243 // We should call this after we retire any currently active alloc
1244 // regions so that all the ALLOC / RETIRE events are generated
1245 // before the start GC event.
1246 _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1247
1248 // We may have added regions to the current incremental collection
1249 // set between the last GC or pause and now. We need to clear the
1250 // incremental collection set and then start rebuilding it afresh
1251 // after this full GC.
1252 abandon_collection_set(g1_policy()->inc_cset_head());
1253 g1_policy()->clear_incremental_cset();
1254 g1_policy()->stop_incremental_cset_building();
1255
1256 tear_down_region_sets(false /* free_list_only */);
1257 g1_policy()->set_gcs_are_young(true);
1258
1259 // See the comments in g1CollectedHeap.hpp and
1260 // G1CollectedHeap::ref_processing_init() about
1261 // how reference processing currently works in G1.
1262
1263 // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1264 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1265
1266 // Temporarily clear the STW ref processor's _is_alive_non_header field.
1267 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1268
1269 ref_processor_stw()->enable_discovery();
1270 ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1271
1272 // Do collection work
1273 {
1274 HandleMark hm; // Discard invalid handles created during gc
1275 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1276 }
1277
1278 assert(num_free_regions() == 0, "we should not have added any free regions");
1279 rebuild_region_sets(false /* free_list_only */);
1280
1281 // Enqueue any discovered reference objects that have
1282 // not been removed from the discovered lists.
1283 ref_processor_stw()->enqueue_discovered_references();
1284
1285 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1286
1287 MemoryService::track_memory_usage();
1288
1289 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1290 ref_processor_stw()->verify_no_references_recorded();
1291
1292 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1293 ClassLoaderDataGraph::purge();
1294 MetaspaceAux::verify_metrics();
1295
1296 // Note: since we've just done a full GC, concurrent
1297 // marking is no longer active. Therefore we need not
1298 // re-enable reference discovery for the CM ref processor.
1299 // That will be done at the start of the next marking cycle.
1300 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1301 ref_processor_cm()->verify_no_references_recorded();
1302
1303 reset_gc_time_stamp();
1304 // Since everything potentially moved, we will clear all remembered
1305 // sets, and clear all cards. Later we will rebuild remembered
1306 // sets. We will also reset the GC time stamps of the regions.
1307 clear_rsets_post_compaction();
1308 check_gc_time_stamps();
1309
1310 // Resize the heap if necessary.
1311 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1312
1313 if (_hr_printer.is_active()) {
1314 // We should do this after we potentially resize the heap so
1315 // that all the COMMIT / UNCOMMIT events are generated before
1316 // the end GC event.
1317
1318 print_hrm_post_compaction();
1319 _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1320 }
1321
1322 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
1323 if (hot_card_cache->use_cache()) {
1324 hot_card_cache->reset_card_counts();
1325 hot_card_cache->reset_hot_cache();
1326 }
1327
1328 // Rebuild remembered sets of all regions.
1329 uint n_workers =
1330 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1331 workers()->active_workers(),
1332 Threads::number_of_non_daemon_threads());
1333 assert(UseDynamicNumberOfGCThreads ||
1334 n_workers == workers()->total_workers(),
1335 "If not dynamic should be using all the workers");
1336 workers()->set_active_workers(n_workers);
1337 // Set parallel threads in the heap (_n_par_threads) only
1338 // before a parallel phase and always reset it to 0 after
1339 // the phase so that the number of parallel threads does
1340 // no get carried forward to a serial phase where there
1341 // may be code that is "possibly_parallel".
1342 set_par_threads(n_workers);
1343
1344 ParRebuildRSTask rebuild_rs_task(this);
1345 assert(UseDynamicNumberOfGCThreads ||
1346 workers()->active_workers() == workers()->total_workers(),
1347 "Unless dynamic should use total workers");
1348 // Use the most recent number of active workers
1349 assert(workers()->active_workers() > 0,
1350 "Active workers not properly set");
1351 set_par_threads(workers()->active_workers());
1352 workers()->run_task(&rebuild_rs_task);
1353 set_par_threads(0);
1354
1355 // Rebuild the strong code root lists for each region
1356 rebuild_strong_code_roots();
1357
1358 if (true) { // FIXME
1359 MetaspaceGC::compute_new_size();
1360 }
1361
1362 #ifdef TRACESPINNING
1363 ParallelTaskTerminator::print_termination_counts();
1364 #endif
1365
1366 // Discard all rset updates
1367 JavaThread::dirty_card_queue_set().abandon_logs();
1368 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1369
1370 _young_list->reset_sampled_info();
1371 // At this point there should be no regions in the
1372 // entire heap tagged as young.
1373 assert(check_young_list_empty(true /* check_heap */),
1374 "young list should be empty at this point");
1375
1376 // Update the number of full collections that have been completed.
1377 increment_old_marking_cycles_completed(false /* concurrent */);
1378
1379 _hrm.verify_optional();
1380 verify_region_sets_optional();
1381
1382 verify_after_gc();
1383
1384 // Clear the previous marking bitmap, if needed for bitmap verification.
1385 // Note we cannot do this when we clear the next marking bitmap in
1386 // ConcurrentMark::abort() above since VerifyDuringGC verifies the
1387 // objects marked during a full GC against the previous bitmap.
1388 // But we need to clear it before calling check_bitmaps below since
1389 // the full GC has compacted objects and updated TAMS but not updated
1390 // the prev bitmap.
1391 if (G1VerifyBitmaps) {
1392 ((CMBitMap*) concurrent_mark()->prevMarkBitMap())->clearAll();
1393 }
1394 check_bitmaps("Full GC End");
1395
1396 // Start a new incremental collection set for the next pause
1397 assert(g1_policy()->collection_set() == NULL, "must be");
1398 g1_policy()->start_incremental_cset_building();
1399
1400 clear_cset_fast_test();
1401
1402 _allocator->init_mutator_alloc_region();
1403
1404 g1_policy()->record_full_collection_end();
1405
1406 if (G1Log::fine()) {
1407 g1_policy()->print_heap_transition();
1408 }
1409
1410 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1411 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1412 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1413 // before any GC notifications are raised.
1414 g1mm()->update_sizes();
1415
1416 gc_epilogue(true);
1417 }
1418
1419 if (G1Log::finer()) {
1420 g1_policy()->print_detailed_heap_transition(true /* full */);
1421 }
1422
1423 print_heap_after_gc();
1424 trace_heap_after_gc(gc_tracer);
1425
1426 post_full_gc_dump(gc_timer);
1427
1428 gc_timer->register_gc_end();
1429 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
1430 }
1431
1432 return true;
1433 }
1434
1435 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1436 // do_collection() will return whether it succeeded in performing
1437 // the GC. Currently, there is no facility on the
1438 // do_full_collection() API to notify the caller than the collection
1439 // did not succeed (e.g., because it was locked out by the GC
1440 // locker). So, right now, we'll ignore the return value.
1441 bool dummy = do_collection(true, /* explicit_gc */
1442 clear_all_soft_refs,
1443 0 /* word_size */);
1444 }
1445
1446 // This code is mostly copied from TenuredGeneration.
1447 void
1448 G1CollectedHeap::
1449 resize_if_necessary_after_full_collection(size_t word_size) {
1450 // Include the current allocation, if any, and bytes that will be
1451 // pre-allocated to support collections, as "used".
1452 const size_t used_after_gc = used();
1453 const size_t capacity_after_gc = capacity();
1454 const size_t free_after_gc = capacity_after_gc - used_after_gc;
1455
1456 // This is enforced in arguments.cpp.
1457 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1458 "otherwise the code below doesn't make sense");
1459
1460 // We don't have floating point command-line arguments
1461 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1462 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1463 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1464 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1465
1466 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1467 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1468
1469 // We have to be careful here as these two calculations can overflow
1470 // 32-bit size_t's.
1471 double used_after_gc_d = (double) used_after_gc;
1472 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1473 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1474
1475 // Let's make sure that they are both under the max heap size, which
1476 // by default will make them fit into a size_t.
1477 double desired_capacity_upper_bound = (double) max_heap_size;
1478 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1479 desired_capacity_upper_bound);
1480 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1481 desired_capacity_upper_bound);
1482
1483 // We can now safely turn them into size_t's.
1484 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1485 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1486
1487 // This assert only makes sense here, before we adjust them
1488 // with respect to the min and max heap size.
1489 assert(minimum_desired_capacity <= maximum_desired_capacity,
1490 err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1491 "maximum_desired_capacity = "SIZE_FORMAT,
1492 minimum_desired_capacity, maximum_desired_capacity));
1493
1494 // Should not be greater than the heap max size. No need to adjust
1495 // it with respect to the heap min size as it's a lower bound (i.e.,
1496 // we'll try to make the capacity larger than it, not smaller).
1497 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1498 // Should not be less than the heap min size. No need to adjust it
1499 // with respect to the heap max size as it's an upper bound (i.e.,
1500 // we'll try to make the capacity smaller than it, not greater).
1501 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1502
1503 if (capacity_after_gc < minimum_desired_capacity) {
1504 // Don't expand unless it's significant
1505 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1506 ergo_verbose4(ErgoHeapSizing,
1507 "attempt heap expansion",
1508 ergo_format_reason("capacity lower than "
1509 "min desired capacity after Full GC")
1510 ergo_format_byte("capacity")
1511 ergo_format_byte("occupancy")
1512 ergo_format_byte_perc("min desired capacity"),
1513 capacity_after_gc, used_after_gc,
1514 minimum_desired_capacity, (double) MinHeapFreeRatio);
1515 expand(expand_bytes);
1516
1517 // No expansion, now see if we want to shrink
1518 } else if (capacity_after_gc > maximum_desired_capacity) {
1519 // Capacity too large, compute shrinking size
1520 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1521 ergo_verbose4(ErgoHeapSizing,
1522 "attempt heap shrinking",
1523 ergo_format_reason("capacity higher than "
1524 "max desired capacity after Full GC")
1525 ergo_format_byte("capacity")
1526 ergo_format_byte("occupancy")
1527 ergo_format_byte_perc("max desired capacity"),
1528 capacity_after_gc, used_after_gc,
1529 maximum_desired_capacity, (double) MaxHeapFreeRatio);
1530 shrink(shrink_bytes);
1531 }
1532 }
1533
1534
1535 HeapWord*
1536 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1537 AllocationContext_t context,
1538 bool* succeeded) {
1539 assert_at_safepoint(true /* should_be_vm_thread */);
1540
1541 *succeeded = true;
1542 // Let's attempt the allocation first.
1543 HeapWord* result =
1544 attempt_allocation_at_safepoint(word_size,
1545 context,
1546 false /* expect_null_mutator_alloc_region */);
1547 if (result != NULL) {
1548 assert(*succeeded, "sanity");
1549 return result;
1550 }
1551
1552 // In a G1 heap, we're supposed to keep allocation from failing by
1553 // incremental pauses. Therefore, at least for now, we'll favor
1554 // expansion over collection. (This might change in the future if we can
1555 // do something smarter than full collection to satisfy a failed alloc.)
1556 result = expand_and_allocate(word_size, context);
1557 if (result != NULL) {
1558 assert(*succeeded, "sanity");
1559 return result;
1560 }
1561
1562 // Expansion didn't work, we'll try to do a Full GC.
1563 bool gc_succeeded = do_collection(false, /* explicit_gc */
1564 false, /* clear_all_soft_refs */
1565 word_size);
1566 if (!gc_succeeded) {
1567 *succeeded = false;
1568 return NULL;
1569 }
1570
1571 // Retry the allocation
1572 result = attempt_allocation_at_safepoint(word_size,
1573 context,
1574 true /* expect_null_mutator_alloc_region */);
1575 if (result != NULL) {
1576 assert(*succeeded, "sanity");
1577 return result;
1578 }
1579
1580 // Then, try a Full GC that will collect all soft references.
1581 gc_succeeded = do_collection(false, /* explicit_gc */
1582 true, /* clear_all_soft_refs */
1583 word_size);
1584 if (!gc_succeeded) {
1585 *succeeded = false;
1586 return NULL;
1587 }
1588
1589 // Retry the allocation once more
1590 result = attempt_allocation_at_safepoint(word_size,
1591 context,
1592 true /* expect_null_mutator_alloc_region */);
1593 if (result != NULL) {
1594 assert(*succeeded, "sanity");
1595 return result;
1596 }
1597
1598 assert(!collector_policy()->should_clear_all_soft_refs(),
1599 "Flag should have been handled and cleared prior to this point");
1600
1601 // What else? We might try synchronous finalization later. If the total
1602 // space available is large enough for the allocation, then a more
1603 // complete compaction phase than we've tried so far might be
1604 // appropriate.
1605 assert(*succeeded, "sanity");
1606 return NULL;
1607 }
1608
1609 // Attempting to expand the heap sufficiently
1610 // to support an allocation of the given "word_size". If
1611 // successful, perform the allocation and return the address of the
1612 // allocated block, or else "NULL".
1613
1614 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) {
1615 assert_at_safepoint(true /* should_be_vm_thread */);
1616
1617 verify_region_sets_optional();
1618
1619 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1620 ergo_verbose1(ErgoHeapSizing,
1621 "attempt heap expansion",
1622 ergo_format_reason("allocation request failed")
1623 ergo_format_byte("allocation request"),
1624 word_size * HeapWordSize);
1625 if (expand(expand_bytes)) {
1626 _hrm.verify_optional();
1627 verify_region_sets_optional();
1628 return attempt_allocation_at_safepoint(word_size,
1629 context,
1630 false /* expect_null_mutator_alloc_region */);
1631 }
1632 return NULL;
1633 }
1634
1635 bool G1CollectedHeap::expand(size_t expand_bytes) {
1636 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1637 aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1638 HeapRegion::GrainBytes);
1639 ergo_verbose2(ErgoHeapSizing,
1640 "expand the heap",
1641 ergo_format_byte("requested expansion amount")
1642 ergo_format_byte("attempted expansion amount"),
1643 expand_bytes, aligned_expand_bytes);
1644
1645 if (is_maximal_no_gc()) {
1646 ergo_verbose0(ErgoHeapSizing,
1647 "did not expand the heap",
1648 ergo_format_reason("heap already fully expanded"));
1649 return false;
1650 }
1651
1652 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1653 assert(regions_to_expand > 0, "Must expand by at least one region");
1654
1655 uint expanded_by = _hrm.expand_by(regions_to_expand);
1656
1657 if (expanded_by > 0) {
1658 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1659 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1660 g1_policy()->record_new_heap_size(num_regions());
1661 } else {
1662 ergo_verbose0(ErgoHeapSizing,
1663 "did not expand the heap",
1664 ergo_format_reason("heap expansion operation failed"));
1665 // The expansion of the virtual storage space was unsuccessful.
1666 // Let's see if it was because we ran out of swap.
1667 if (G1ExitOnExpansionFailure &&
1668 _hrm.available() >= regions_to_expand) {
1669 // We had head room...
1670 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1671 }
1672 }
1673 return regions_to_expand > 0;
1674 }
1675
1676 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1677 size_t aligned_shrink_bytes =
1678 ReservedSpace::page_align_size_down(shrink_bytes);
1679 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1680 HeapRegion::GrainBytes);
1681 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1682
1683 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1684 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1685
1686 ergo_verbose3(ErgoHeapSizing,
1687 "shrink the heap",
1688 ergo_format_byte("requested shrinking amount")
1689 ergo_format_byte("aligned shrinking amount")
1690 ergo_format_byte("attempted shrinking amount"),
1691 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1692 if (num_regions_removed > 0) {
1693 g1_policy()->record_new_heap_size(num_regions());
1694 } else {
1695 ergo_verbose0(ErgoHeapSizing,
1696 "did not shrink the heap",
1697 ergo_format_reason("heap shrinking operation failed"));
1698 }
1699 }
1700
1701 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1702 verify_region_sets_optional();
1703
1704 // We should only reach here at the end of a Full GC which means we
1705 // should not not be holding to any GC alloc regions. The method
1706 // below will make sure of that and do any remaining clean up.
1707 _allocator->abandon_gc_alloc_regions();
1708
1709 // Instead of tearing down / rebuilding the free lists here, we
1710 // could instead use the remove_all_pending() method on free_list to
1711 // remove only the ones that we need to remove.
1712 tear_down_region_sets(true /* free_list_only */);
1713 shrink_helper(shrink_bytes);
1714 rebuild_region_sets(true /* free_list_only */);
1715
1716 _hrm.verify_optional();
1717 verify_region_sets_optional();
1718 }
1719
1720 // Public methods.
1721
1722 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1723 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1724 #endif // _MSC_VER
1725
1726
1727 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1728 CollectedHeap(),
1729 _g1_policy(policy_),
1730 _dirty_card_queue_set(false),
1731 _into_cset_dirty_card_queue_set(false),
1732 _is_alive_closure_cm(this),
1733 _is_alive_closure_stw(this),
1734 _ref_processor_cm(NULL),
1735 _ref_processor_stw(NULL),
1736 _bot_shared(NULL),
1737 _evac_failure_scan_stack(NULL),
1738 _mark_in_progress(false),
1739 _cg1r(NULL),
1740 _g1mm(NULL),
1741 _refine_cte_cl(NULL),
1742 _full_collection(false),
1743 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1744 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1745 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1746 _humongous_reclaim_candidates(),
1747 _has_humongous_reclaim_candidates(false),
1748 _free_regions_coming(false),
1749 _young_list(new YoungList(this)),
1750 _gc_time_stamp(0),
1751 _survivor_plab_stats(YoungPLABSize, PLABWeight),
1752 _old_plab_stats(OldPLABSize, PLABWeight),
1753 _expand_heap_after_alloc_failure(true),
1754 _surviving_young_words(NULL),
1755 _old_marking_cycles_started(0),
1756 _old_marking_cycles_completed(0),
1757 _concurrent_cycle_started(false),
1758 _heap_summary_sent(false),
1759 _in_cset_fast_test(),
1760 _dirty_cards_region_list(NULL),
1761 _worker_cset_start_region(NULL),
1762 _worker_cset_start_region_time_stamp(NULL),
1763 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1764 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
1765 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1766 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) {
1767
1768 _workers = new FlexibleWorkGang("GC Thread", ParallelGCThreads,
1769 /* are_GC_task_threads */true,
1770 /* are_ConcurrentGC_threads */false);
1771 _workers->initialize_workers();
1772
1773 _allocator = G1Allocator::create_allocator(this);
1774 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1775
1776 int n_queues = MAX2((int)ParallelGCThreads, 1);
1777 _task_queues = new RefToScanQueueSet(n_queues);
1778
1779 uint n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1780 assert(n_rem_sets > 0, "Invariant.");
1781
1782 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1783 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(uint, n_queues, mtGC);
1784 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1785
1786 for (int i = 0; i < n_queues; i++) {
1787 RefToScanQueue* q = new RefToScanQueue();
1788 q->initialize();
1789 _task_queues->register_queue(i, q);
1790 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1791 }
1792 clear_cset_start_regions();
1793
1794 // Initialize the G1EvacuationFailureALot counters and flags.
1795 NOT_PRODUCT(reset_evacuation_should_fail();)
1796
1797 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1798 }
1799
1800 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1801 size_t size,
1802 size_t translation_factor) {
1803 size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1804 // Allocate a new reserved space, preferring to use large pages.
1805 ReservedSpace rs(size, preferred_page_size);
1806 G1RegionToSpaceMapper* result =
1807 G1RegionToSpaceMapper::create_mapper(rs,
1808 size,
1809 rs.alignment(),
1810 HeapRegion::GrainBytes,
1811 translation_factor,
1812 mtGC);
1813 if (TracePageSizes) {
1814 gclog_or_tty->print_cr("G1 '%s': pg_sz=" SIZE_FORMAT " base=" PTR_FORMAT " size=" SIZE_FORMAT " alignment=" SIZE_FORMAT " reqsize=" SIZE_FORMAT,
1815 description, preferred_page_size, p2i(rs.base()), rs.size(), rs.alignment(), size);
1816 }
1817 return result;
1818 }
1819
1820 jint G1CollectedHeap::initialize() {
1821 CollectedHeap::pre_initialize();
1822 os::enable_vtime();
1823
1824 G1Log::init();
1825
1826 // Necessary to satisfy locking discipline assertions.
1827
1828 MutexLocker x(Heap_lock);
1829
1830 // We have to initialize the printer before committing the heap, as
1831 // it will be used then.
1832 _hr_printer.set_active(G1PrintHeapRegions);
1833
1834 // While there are no constraints in the GC code that HeapWordSize
1835 // be any particular value, there are multiple other areas in the
1836 // system which believe this to be true (e.g. oop->object_size in some
1837 // cases incorrectly returns the size in wordSize units rather than
1838 // HeapWordSize).
1839 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1840
1841 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1842 size_t max_byte_size = collector_policy()->max_heap_byte_size();
1843 size_t heap_alignment = collector_policy()->heap_alignment();
1844
1845 // Ensure that the sizes are properly aligned.
1846 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1847 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1848 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1849
1850 _refine_cte_cl = new RefineCardTableEntryClosure();
1851
1852 _cg1r = new ConcurrentG1Refine(this, _refine_cte_cl);
1853
1854 // Reserve the maximum.
1855
1856 // When compressed oops are enabled, the preferred heap base
1857 // is calculated by subtracting the requested size from the
1858 // 32Gb boundary and using the result as the base address for
1859 // heap reservation. If the requested size is not aligned to
1860 // HeapRegion::GrainBytes (i.e. the alignment that is passed
1861 // into the ReservedHeapSpace constructor) then the actual
1862 // base of the reserved heap may end up differing from the
1863 // address that was requested (i.e. the preferred heap base).
1864 // If this happens then we could end up using a non-optimal
1865 // compressed oops mode.
1866
1867 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1868 heap_alignment);
1869
1870 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
1871
1872 // Create the barrier set for the entire reserved region.
1873 G1SATBCardTableLoggingModRefBS* bs
1874 = new G1SATBCardTableLoggingModRefBS(reserved_region());
1875 bs->initialize();
1876 assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity");
1877 set_barrier_set(bs);
1878
1879 // Also create a G1 rem set.
1880 _g1_rem_set = new G1RemSet(this, g1_barrier_set());
1881
1882 // Carve out the G1 part of the heap.
1883
1884 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1885 G1RegionToSpaceMapper* heap_storage =
1886 G1RegionToSpaceMapper::create_mapper(g1_rs,
1887 g1_rs.size(),
1888 UseLargePages ? os::large_page_size() : os::vm_page_size(),
1889 HeapRegion::GrainBytes,
1890 1,
1891 mtJavaHeap);
1892 heap_storage->set_mapping_changed_listener(&_listener);
1893
1894 // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1895 G1RegionToSpaceMapper* bot_storage =
1896 create_aux_memory_mapper("Block offset table",
1897 G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize),
1898 G1BlockOffsetSharedArray::N_bytes);
1899
1900 ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize));
1901 G1RegionToSpaceMapper* cardtable_storage =
1902 create_aux_memory_mapper("Card table",
1903 G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize),
1904 G1BlockOffsetSharedArray::N_bytes);
1905
1906 G1RegionToSpaceMapper* card_counts_storage =
1907 create_aux_memory_mapper("Card counts table",
1908 G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize),
1909 G1BlockOffsetSharedArray::N_bytes);
1910
1911 size_t bitmap_size = CMBitMap::compute_size(g1_rs.size());
1912 G1RegionToSpaceMapper* prev_bitmap_storage =
1913 create_aux_memory_mapper("Prev Bitmap", bitmap_size, CMBitMap::mark_distance());
1914 G1RegionToSpaceMapper* next_bitmap_storage =
1915 create_aux_memory_mapper("Next Bitmap", bitmap_size, CMBitMap::mark_distance());
1916
1917 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1918 g1_barrier_set()->initialize(cardtable_storage);
1919 // Do later initialization work for concurrent refinement.
1920 _cg1r->init(card_counts_storage);
1921
1922 // 6843694 - ensure that the maximum region index can fit
1923 // in the remembered set structures.
1924 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1925 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1926
1927 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1928 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1929 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1930 "too many cards per region");
1931
1932 FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
1933
1934 _bot_shared = new G1BlockOffsetSharedArray(reserved_region(), bot_storage);
1935
1936 {
1937 HeapWord* start = _hrm.reserved().start();
1938 HeapWord* end = _hrm.reserved().end();
1939 size_t granularity = HeapRegion::GrainBytes;
1940
1941 _in_cset_fast_test.initialize(start, end, granularity);
1942 _humongous_reclaim_candidates.initialize(start, end, granularity);
1943 }
1944
1945 // Create the ConcurrentMark data structure and thread.
1946 // (Must do this late, so that "max_regions" is defined.)
1947 _cm = new ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1948 if (_cm == NULL || !_cm->completed_initialization()) {
1949 vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark");
1950 return JNI_ENOMEM;
1951 }
1952 _cmThread = _cm->cmThread();
1953
1954 // Initialize the from_card cache structure of HeapRegionRemSet.
1955 HeapRegionRemSet::init_heap(max_regions());
1956
1957 // Now expand into the initial heap size.
1958 if (!expand(init_byte_size)) {
1959 vm_shutdown_during_initialization("Failed to allocate initial heap.");
1960 return JNI_ENOMEM;
1961 }
1962
1963 // Perform any initialization actions delegated to the policy.
1964 g1_policy()->init();
1965
1966 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
1967 SATB_Q_FL_lock,
1968 G1SATBProcessCompletedThreshold,
1969 Shared_SATB_Q_lock);
1970
1971 JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl,
1972 DirtyCardQ_CBL_mon,
1973 DirtyCardQ_FL_lock,
1974 concurrent_g1_refine()->yellow_zone(),
1975 concurrent_g1_refine()->red_zone(),
1976 Shared_DirtyCardQ_lock);
1977
1978 dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code
1979 DirtyCardQ_CBL_mon,
1980 DirtyCardQ_FL_lock,
1981 -1, // never trigger processing
1982 -1, // no limit on length
1983 Shared_DirtyCardQ_lock,
1984 &JavaThread::dirty_card_queue_set());
1985
1986 // Initialize the card queue set used to hold cards containing
1987 // references into the collection set.
1988 _into_cset_dirty_card_queue_set.initialize(NULL, // Should never be called by the Java code
1989 DirtyCardQ_CBL_mon,
1990 DirtyCardQ_FL_lock,
1991 -1, // never trigger processing
1992 -1, // no limit on length
1993 Shared_DirtyCardQ_lock,
1994 &JavaThread::dirty_card_queue_set());
1995
1996 // Here we allocate the dummy HeapRegion that is required by the
1997 // G1AllocRegion class.
1998 HeapRegion* dummy_region = _hrm.get_dummy_region();
1999
2000 // We'll re-use the same region whether the alloc region will
2001 // require BOT updates or not and, if it doesn't, then a non-young
2002 // region will complain that it cannot support allocations without
2003 // BOT updates. So we'll tag the dummy region as eden to avoid that.
2004 dummy_region->set_eden();
2005 // Make sure it's full.
2006 dummy_region->set_top(dummy_region->end());
2007 G1AllocRegion::setup(this, dummy_region);
2008
2009 _allocator->init_mutator_alloc_region();
2010
2011 // Do create of the monitoring and management support so that
2012 // values in the heap have been properly initialized.
2013 _g1mm = new G1MonitoringSupport(this);
2014
2015 G1StringDedup::initialize();
2016
2017 return JNI_OK;
2018 }
2019
2020 void G1CollectedHeap::stop() {
2021 // Stop all concurrent threads. We do this to make sure these threads
2022 // do not continue to execute and access resources (e.g. gclog_or_tty)
2023 // that are destroyed during shutdown.
2024 _cg1r->stop();
2025 _cmThread->stop();
2026 if (G1StringDedup::is_enabled()) {
2027 G1StringDedup::stop();
2028 }
2029 }
2030
2031 size_t G1CollectedHeap::conservative_max_heap_alignment() {
2032 return HeapRegion::max_region_size();
2033 }
2034
2035 void G1CollectedHeap::post_initialize() {
2036 CollectedHeap::post_initialize();
2037 ref_processing_init();
2038 }
2039
2040 void G1CollectedHeap::ref_processing_init() {
2041 // Reference processing in G1 currently works as follows:
2042 //
2043 // * There are two reference processor instances. One is
2044 // used to record and process discovered references
2045 // during concurrent marking; the other is used to
2046 // record and process references during STW pauses
2047 // (both full and incremental).
2048 // * Both ref processors need to 'span' the entire heap as
2049 // the regions in the collection set may be dotted around.
2050 //
2051 // * For the concurrent marking ref processor:
2052 // * Reference discovery is enabled at initial marking.
2053 // * Reference discovery is disabled and the discovered
2054 // references processed etc during remarking.
2055 // * Reference discovery is MT (see below).
2056 // * Reference discovery requires a barrier (see below).
2057 // * Reference processing may or may not be MT
2058 // (depending on the value of ParallelRefProcEnabled
2059 // and ParallelGCThreads).
2060 // * A full GC disables reference discovery by the CM
2061 // ref processor and abandons any entries on it's
2062 // discovered lists.
2063 //
2064 // * For the STW processor:
2065 // * Non MT discovery is enabled at the start of a full GC.
2066 // * Processing and enqueueing during a full GC is non-MT.
2067 // * During a full GC, references are processed after marking.
2068 //
2069 // * Discovery (may or may not be MT) is enabled at the start
2070 // of an incremental evacuation pause.
2071 // * References are processed near the end of a STW evacuation pause.
2072 // * For both types of GC:
2073 // * Discovery is atomic - i.e. not concurrent.
2074 // * Reference discovery will not need a barrier.
2075
2076 MemRegion mr = reserved_region();
2077
2078 // Concurrent Mark ref processor
2079 _ref_processor_cm =
2080 new ReferenceProcessor(mr, // span
2081 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2082 // mt processing
2083 (int) ParallelGCThreads,
2084 // degree of mt processing
2085 (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2086 // mt discovery
2087 (int) MAX2(ParallelGCThreads, ConcGCThreads),
2088 // degree of mt discovery
2089 false,
2090 // Reference discovery is not atomic
2091 &_is_alive_closure_cm);
2092 // is alive closure
2093 // (for efficiency/performance)
2094
2095 // STW ref processor
2096 _ref_processor_stw =
2097 new ReferenceProcessor(mr, // span
2098 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2099 // mt processing
2100 MAX2((int)ParallelGCThreads, 1),
2101 // degree of mt processing
2102 (ParallelGCThreads > 1),
2103 // mt discovery
2104 MAX2((int)ParallelGCThreads, 1),
2105 // degree of mt discovery
2106 true,
2107 // Reference discovery is atomic
2108 &_is_alive_closure_stw);
2109 // is alive closure
2110 // (for efficiency/performance)
2111 }
2112
2113 size_t G1CollectedHeap::capacity() const {
2114 return _hrm.length() * HeapRegion::GrainBytes;
2115 }
2116
2117 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2118 assert(!hr->is_continues_humongous(), "pre-condition");
2119 hr->reset_gc_time_stamp();
2120 if (hr->is_starts_humongous()) {
2121 uint first_index = hr->hrm_index() + 1;
2122 uint last_index = hr->last_hc_index();
2123 for (uint i = first_index; i < last_index; i += 1) {
2124 HeapRegion* chr = region_at(i);
2125 assert(chr->is_continues_humongous(), "sanity");
2126 chr->reset_gc_time_stamp();
2127 }
2128 }
2129 }
2130
2131 #ifndef PRODUCT
2132
2133 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2134 private:
2135 unsigned _gc_time_stamp;
2136 bool _failures;
2137
2138 public:
2139 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2140 _gc_time_stamp(gc_time_stamp), _failures(false) { }
2141
2142 virtual bool doHeapRegion(HeapRegion* hr) {
2143 unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2144 if (_gc_time_stamp != region_gc_time_stamp) {
2145 gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, "
2146 "expected %d", HR_FORMAT_PARAMS(hr),
2147 region_gc_time_stamp, _gc_time_stamp);
2148 _failures = true;
2149 }
2150 return false;
2151 }
2152
2153 bool failures() { return _failures; }
2154 };
2155
2156 void G1CollectedHeap::check_gc_time_stamps() {
2157 CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2158 heap_region_iterate(&cl);
2159 guarantee(!cl.failures(), "all GC time stamps should have been reset");
2160 }
2161 #endif // PRODUCT
2162
2163 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2164 DirtyCardQueue* into_cset_dcq,
2165 bool concurrent,
2166 uint worker_i) {
2167 // Clean cards in the hot card cache
2168 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
2169 hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq);
2170
2171 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2172 size_t n_completed_buffers = 0;
2173 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2174 n_completed_buffers++;
2175 }
2176 g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers);
2177 dcqs.clear_n_completed_buffers();
2178 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2179 }
2180
2181
2182 // Computes the sum of the storage used by the various regions.
2183 size_t G1CollectedHeap::used() const {
2184 return _allocator->used();
2185 }
2186
2187 size_t G1CollectedHeap::used_unlocked() const {
2188 return _allocator->used_unlocked();
2189 }
2190
2191 class SumUsedClosure: public HeapRegionClosure {
2192 size_t _used;
2193 public:
2194 SumUsedClosure() : _used(0) {}
2195 bool doHeapRegion(HeapRegion* r) {
2196 if (!r->is_continues_humongous()) {
2197 _used += r->used();
2198 }
2199 return false;
2200 }
2201 size_t result() { return _used; }
2202 };
2203
2204 size_t G1CollectedHeap::recalculate_used() const {
2205 double recalculate_used_start = os::elapsedTime();
2206
2207 SumUsedClosure blk;
2208 heap_region_iterate(&blk);
2209
2210 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2211 return blk.result();
2212 }
2213
2214 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2215 switch (cause) {
2216 case GCCause::_gc_locker: return GCLockerInvokesConcurrent;
2217 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
2218 case GCCause::_g1_humongous_allocation: return true;
2219 case GCCause::_update_allocation_context_stats_inc: return true;
2220 case GCCause::_wb_conc_mark: return true;
2221 default: return false;
2222 }
2223 }
2224
2225 #ifndef PRODUCT
2226 void G1CollectedHeap::allocate_dummy_regions() {
2227 // Let's fill up most of the region
2228 size_t word_size = HeapRegion::GrainWords - 1024;
2229 // And as a result the region we'll allocate will be humongous.
2230 guarantee(is_humongous(word_size), "sanity");
2231
2232 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2233 // Let's use the existing mechanism for the allocation
2234 HeapWord* dummy_obj = humongous_obj_allocate(word_size,
2235 AllocationContext::system());
2236 if (dummy_obj != NULL) {
2237 MemRegion mr(dummy_obj, word_size);
2238 CollectedHeap::fill_with_object(mr);
2239 } else {
2240 // If we can't allocate once, we probably cannot allocate
2241 // again. Let's get out of the loop.
2242 break;
2243 }
2244 }
2245 }
2246 #endif // !PRODUCT
2247
2248 void G1CollectedHeap::increment_old_marking_cycles_started() {
2249 assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2250 _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2251 err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2252 _old_marking_cycles_started, _old_marking_cycles_completed));
2253
2254 _old_marking_cycles_started++;
2255 }
2256
2257 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2258 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2259
2260 // We assume that if concurrent == true, then the caller is a
2261 // concurrent thread that was joined the Suspendible Thread
2262 // Set. If there's ever a cheap way to check this, we should add an
2263 // assert here.
2264
2265 // Given that this method is called at the end of a Full GC or of a
2266 // concurrent cycle, and those can be nested (i.e., a Full GC can
2267 // interrupt a concurrent cycle), the number of full collections
2268 // completed should be either one (in the case where there was no
2269 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2270 // behind the number of full collections started.
2271
2272 // This is the case for the inner caller, i.e. a Full GC.
2273 assert(concurrent ||
2274 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2275 (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2276 err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
2277 "is inconsistent with _old_marking_cycles_completed = %u",
2278 _old_marking_cycles_started, _old_marking_cycles_completed));
2279
2280 // This is the case for the outer caller, i.e. the concurrent cycle.
2281 assert(!concurrent ||
2282 (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2283 err_msg("for outer caller (concurrent cycle): "
2284 "_old_marking_cycles_started = %u "
2285 "is inconsistent with _old_marking_cycles_completed = %u",
2286 _old_marking_cycles_started, _old_marking_cycles_completed));
2287
2288 _old_marking_cycles_completed += 1;
2289
2290 // We need to clear the "in_progress" flag in the CM thread before
2291 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2292 // is set) so that if a waiter requests another System.gc() it doesn't
2293 // incorrectly see that a marking cycle is still in progress.
2294 if (concurrent) {
2295 _cmThread->clear_in_progress();
2296 }
2297
2298 // This notify_all() will ensure that a thread that called
2299 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2300 // and it's waiting for a full GC to finish will be woken up. It is
2301 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2302 FullGCCount_lock->notify_all();
2303 }
2304
2305 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) {
2306 _concurrent_cycle_started = true;
2307 _gc_timer_cm->register_gc_start(start_time);
2308
2309 _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start());
2310 trace_heap_before_gc(_gc_tracer_cm);
2311 }
2312
2313 void G1CollectedHeap::register_concurrent_cycle_end() {
2314 if (_concurrent_cycle_started) {
2315 if (_cm->has_aborted()) {
2316 _gc_tracer_cm->report_concurrent_mode_failure();
2317 }
2318
2319 _gc_timer_cm->register_gc_end();
2320 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
2321
2322 // Clear state variables to prepare for the next concurrent cycle.
2323 _concurrent_cycle_started = false;
2324 _heap_summary_sent = false;
2325 }
2326 }
2327
2328 void G1CollectedHeap::trace_heap_after_concurrent_cycle() {
2329 if (_concurrent_cycle_started) {
2330 // This function can be called when:
2331 // the cleanup pause is run
2332 // the concurrent cycle is aborted before the cleanup pause.
2333 // the concurrent cycle is aborted after the cleanup pause,
2334 // but before the concurrent cycle end has been registered.
2335 // Make sure that we only send the heap information once.
2336 if (!_heap_summary_sent) {
2337 trace_heap_after_gc(_gc_tracer_cm);
2338 _heap_summary_sent = true;
2339 }
2340 }
2341 }
2342
2343 G1YCType G1CollectedHeap::yc_type() {
2344 bool is_young = g1_policy()->gcs_are_young();
2345 bool is_initial_mark = g1_policy()->during_initial_mark_pause();
2346 bool is_during_mark = mark_in_progress();
2347
2348 if (is_initial_mark) {
2349 return InitialMark;
2350 } else if (is_during_mark) {
2351 return DuringMark;
2352 } else if (is_young) {
2353 return Normal;
2354 } else {
2355 return Mixed;
2356 }
2357 }
2358
2359 void G1CollectedHeap::collect(GCCause::Cause cause) {
2360 assert_heap_not_locked();
2361
2362 uint gc_count_before;
2363 uint old_marking_count_before;
2364 uint full_gc_count_before;
2365 bool retry_gc;
2366
2367 do {
2368 retry_gc = false;
2369
2370 {
2371 MutexLocker ml(Heap_lock);
2372
2373 // Read the GC count while holding the Heap_lock
2374 gc_count_before = total_collections();
2375 full_gc_count_before = total_full_collections();
2376 old_marking_count_before = _old_marking_cycles_started;
2377 }
2378
2379 if (should_do_concurrent_full_gc(cause)) {
2380 // Schedule an initial-mark evacuation pause that will start a
2381 // concurrent cycle. We're setting word_size to 0 which means that
2382 // we are not requesting a post-GC allocation.
2383 VM_G1IncCollectionPause op(gc_count_before,
2384 0, /* word_size */
2385 true, /* should_initiate_conc_mark */
2386 g1_policy()->max_pause_time_ms(),
2387 cause);
2388 op.set_allocation_context(AllocationContext::current());
2389
2390 VMThread::execute(&op);
2391 if (!op.pause_succeeded()) {
2392 if (old_marking_count_before == _old_marking_cycles_started) {
2393 retry_gc = op.should_retry_gc();
2394 } else {
2395 // A Full GC happened while we were trying to schedule the
2396 // initial-mark GC. No point in starting a new cycle given
2397 // that the whole heap was collected anyway.
2398 }
2399
2400 if (retry_gc) {
2401 if (GC_locker::is_active_and_needs_gc()) {
2402 GC_locker::stall_until_clear();
2403 }
2404 }
2405 }
2406 } else {
2407 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2408 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2409
2410 // Schedule a standard evacuation pause. We're setting word_size
2411 // to 0 which means that we are not requesting a post-GC allocation.
2412 VM_G1IncCollectionPause op(gc_count_before,
2413 0, /* word_size */
2414 false, /* should_initiate_conc_mark */
2415 g1_policy()->max_pause_time_ms(),
2416 cause);
2417 VMThread::execute(&op);
2418 } else {
2419 // Schedule a Full GC.
2420 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2421 VMThread::execute(&op);
2422 }
2423 }
2424 } while (retry_gc);
2425 }
2426
2427 bool G1CollectedHeap::is_in(const void* p) const {
2428 if (_hrm.reserved().contains(p)) {
2429 // Given that we know that p is in the reserved space,
2430 // heap_region_containing_raw() should successfully
2431 // return the containing region.
2432 HeapRegion* hr = heap_region_containing_raw(p);
2433 return hr->is_in(p);
2434 } else {
2435 return false;
2436 }
2437 }
2438
2439 #ifdef ASSERT
2440 bool G1CollectedHeap::is_in_exact(const void* p) const {
2441 bool contains = reserved_region().contains(p);
2442 bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2443 if (contains && available) {
2444 return true;
2445 } else {
2446 return false;
2447 }
2448 }
2449 #endif
2450
2451 // Iteration functions.
2452
2453 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion.
2454
2455 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2456 ExtendedOopClosure* _cl;
2457 public:
2458 IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {}
2459 bool doHeapRegion(HeapRegion* r) {
2460 if (!r->is_continues_humongous()) {
2461 r->oop_iterate(_cl);
2462 }
2463 return false;
2464 }
2465 };
2466
2467 // Iterates an ObjectClosure over all objects within a HeapRegion.
2468
2469 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2470 ObjectClosure* _cl;
2471 public:
2472 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2473 bool doHeapRegion(HeapRegion* r) {
2474 if (!r->is_continues_humongous()) {
2475 r->object_iterate(_cl);
2476 }
2477 return false;
2478 }
2479 };
2480
2481 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2482 IterateObjectClosureRegionClosure blk(cl);
2483 heap_region_iterate(&blk);
2484 }
2485
2486 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2487 _hrm.iterate(cl);
2488 }
2489
2490 void
2491 G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl,
2492 uint worker_id,
2493 HeapRegionClaimer *hrclaimer,
2494 bool concurrent) const {
2495 _hrm.par_iterate(cl, worker_id, hrclaimer, concurrent);
2496 }
2497
2498 // Clear the cached CSet starting regions and (more importantly)
2499 // the time stamps. Called when we reset the GC time stamp.
2500 void G1CollectedHeap::clear_cset_start_regions() {
2501 assert(_worker_cset_start_region != NULL, "sanity");
2502 assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2503
2504 int n_queues = MAX2((int)ParallelGCThreads, 1);
2505 for (int i = 0; i < n_queues; i++) {
2506 _worker_cset_start_region[i] = NULL;
2507 _worker_cset_start_region_time_stamp[i] = 0;
2508 }
2509 }
2510
2511 // Given the id of a worker, obtain or calculate a suitable
2512 // starting region for iterating over the current collection set.
2513 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) {
2514 assert(get_gc_time_stamp() > 0, "should have been updated by now");
2515
2516 HeapRegion* result = NULL;
2517 unsigned gc_time_stamp = get_gc_time_stamp();
2518
2519 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2520 // Cached starting region for current worker was set
2521 // during the current pause - so it's valid.
2522 // Note: the cached starting heap region may be NULL
2523 // (when the collection set is empty).
2524 result = _worker_cset_start_region[worker_i];
2525 assert(result == NULL || result->in_collection_set(), "sanity");
2526 return result;
2527 }
2528
2529 // The cached entry was not valid so let's calculate
2530 // a suitable starting heap region for this worker.
2531
2532 // We want the parallel threads to start their collection
2533 // set iteration at different collection set regions to
2534 // avoid contention.
2535 // If we have:
2536 // n collection set regions
2537 // p threads
2538 // Then thread t will start at region floor ((t * n) / p)
2539
2540 result = g1_policy()->collection_set();
2541 uint cs_size = g1_policy()->cset_region_length();
2542 uint active_workers = workers()->active_workers();
2543 assert(UseDynamicNumberOfGCThreads ||
2544 active_workers == workers()->total_workers(),
2545 "Unless dynamic should use total workers");
2546
2547 uint end_ind = (cs_size * worker_i) / active_workers;
2548 uint start_ind = 0;
2549
2550 if (worker_i > 0 &&
2551 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2552 // Previous workers starting region is valid
2553 // so let's iterate from there
2554 start_ind = (cs_size * (worker_i - 1)) / active_workers;
2555 result = _worker_cset_start_region[worker_i - 1];
2556 }
2557
2558 for (uint i = start_ind; i < end_ind; i++) {
2559 result = result->next_in_collection_set();
2560 }
2561
2562 // Note: the calculated starting heap region may be NULL
2563 // (when the collection set is empty).
2564 assert(result == NULL || result->in_collection_set(), "sanity");
2565 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2566 "should be updated only once per pause");
2567 _worker_cset_start_region[worker_i] = result;
2568 OrderAccess::storestore();
2569 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2570 return result;
2571 }
2572
2573 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2574 HeapRegion* r = g1_policy()->collection_set();
2575 while (r != NULL) {
2576 HeapRegion* next = r->next_in_collection_set();
2577 if (cl->doHeapRegion(r)) {
2578 cl->incomplete();
2579 return;
2580 }
2581 r = next;
2582 }
2583 }
2584
2585 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2586 HeapRegionClosure *cl) {
2587 if (r == NULL) {
2588 // The CSet is empty so there's nothing to do.
2589 return;
2590 }
2591
2592 assert(r->in_collection_set(),
2593 "Start region must be a member of the collection set.");
2594 HeapRegion* cur = r;
2595 while (cur != NULL) {
2596 HeapRegion* next = cur->next_in_collection_set();
2597 if (cl->doHeapRegion(cur) && false) {
2598 cl->incomplete();
2599 return;
2600 }
2601 cur = next;
2602 }
2603 cur = g1_policy()->collection_set();
2604 while (cur != r) {
2605 HeapRegion* next = cur->next_in_collection_set();
2606 if (cl->doHeapRegion(cur) && false) {
2607 cl->incomplete();
2608 return;
2609 }
2610 cur = next;
2611 }
2612 }
2613
2614 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const {
2615 HeapRegion* result = _hrm.next_region_in_heap(from);
2616 while (result != NULL && result->is_humongous()) {
2617 result = _hrm.next_region_in_heap(result);
2618 }
2619 return result;
2620 }
2621
2622 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2623 HeapRegion* hr = heap_region_containing(addr);
2624 return hr->block_start(addr);
2625 }
2626
2627 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2628 HeapRegion* hr = heap_region_containing(addr);
2629 return hr->block_size(addr);
2630 }
2631
2632 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2633 HeapRegion* hr = heap_region_containing(addr);
2634 return hr->block_is_obj(addr);
2635 }
2636
2637 bool G1CollectedHeap::supports_tlab_allocation() const {
2638 return true;
2639 }
2640
2641 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2642 return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes;
2643 }
2644
2645 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2646 return young_list()->eden_used_bytes();
2647 }
2648
2649 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2650 // must be smaller than the humongous object limit.
2651 size_t G1CollectedHeap::max_tlab_size() const {
2652 return align_size_down(_humongous_object_threshold_in_words - 1, MinObjAlignment);
2653 }
2654
2655 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2656 // Return the remaining space in the cur alloc region, but not less than
2657 // the min TLAB size.
2658
2659 // Also, this value can be at most the humongous object threshold,
2660 // since we can't allow tlabs to grow big enough to accommodate
2661 // humongous objects.
2662
2663 HeapRegion* hr = _allocator->mutator_alloc_region(AllocationContext::current())->get();
2664 size_t max_tlab = max_tlab_size() * wordSize;
2665 if (hr == NULL) {
2666 return max_tlab;
2667 } else {
2668 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab);
2669 }
2670 }
2671
2672 size_t G1CollectedHeap::max_capacity() const {
2673 return _hrm.reserved().byte_size();
2674 }
2675
2676 jlong G1CollectedHeap::millis_since_last_gc() {
2677 // assert(false, "NYI");
2678 return 0;
2679 }
2680
2681 void G1CollectedHeap::prepare_for_verify() {
2682 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
2683 ensure_parsability(false);
2684 }
2685 g1_rem_set()->prepare_for_verify();
2686 }
2687
2688 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr,
2689 VerifyOption vo) {
2690 switch (vo) {
2691 case VerifyOption_G1UsePrevMarking:
2692 return hr->obj_allocated_since_prev_marking(obj);
2693 case VerifyOption_G1UseNextMarking:
2694 return hr->obj_allocated_since_next_marking(obj);
2695 case VerifyOption_G1UseMarkWord:
2696 return false;
2697 default:
2698 ShouldNotReachHere();
2699 }
2700 return false; // keep some compilers happy
2701 }
2702
2703 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) {
2704 switch (vo) {
2705 case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start();
2706 case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start();
2707 case VerifyOption_G1UseMarkWord: return NULL;
2708 default: ShouldNotReachHere();
2709 }
2710 return NULL; // keep some compilers happy
2711 }
2712
2713 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) {
2714 switch (vo) {
2715 case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj);
2716 case VerifyOption_G1UseNextMarking: return isMarkedNext(obj);
2717 case VerifyOption_G1UseMarkWord: return obj->is_gc_marked();
2718 default: ShouldNotReachHere();
2719 }
2720 return false; // keep some compilers happy
2721 }
2722
2723 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) {
2724 switch (vo) {
2725 case VerifyOption_G1UsePrevMarking: return "PTAMS";
2726 case VerifyOption_G1UseNextMarking: return "NTAMS";
2727 case VerifyOption_G1UseMarkWord: return "NONE";
2728 default: ShouldNotReachHere();
2729 }
2730 return NULL; // keep some compilers happy
2731 }
2732
2733 class VerifyRootsClosure: public OopClosure {
2734 private:
2735 G1CollectedHeap* _g1h;
2736 VerifyOption _vo;
2737 bool _failures;
2738 public:
2739 // _vo == UsePrevMarking -> use "prev" marking information,
2740 // _vo == UseNextMarking -> use "next" marking information,
2741 // _vo == UseMarkWord -> use mark word from object header.
2742 VerifyRootsClosure(VerifyOption vo) :
2743 _g1h(G1CollectedHeap::heap()),
2744 _vo(vo),
2745 _failures(false) { }
2746
2747 bool failures() { return _failures; }
2748
2749 template <class T> void do_oop_nv(T* p) {
2750 T heap_oop = oopDesc::load_heap_oop(p);
2751 if (!oopDesc::is_null(heap_oop)) {
2752 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2753 if (_g1h->is_obj_dead_cond(obj, _vo)) {
2754 gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
2755 "points to dead obj "PTR_FORMAT, p, (void*) obj);
2756 if (_vo == VerifyOption_G1UseMarkWord) {
2757 gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark()));
2758 }
2759 obj->print_on(gclog_or_tty);
2760 _failures = true;
2761 }
2762 }
2763 }
2764
2765 void do_oop(oop* p) { do_oop_nv(p); }
2766 void do_oop(narrowOop* p) { do_oop_nv(p); }
2767 };
2768
2769 class G1VerifyCodeRootOopClosure: public OopClosure {
2770 G1CollectedHeap* _g1h;
2771 OopClosure* _root_cl;
2772 nmethod* _nm;
2773 VerifyOption _vo;
2774 bool _failures;
2775
2776 template <class T> void do_oop_work(T* p) {
2777 // First verify that this root is live
2778 _root_cl->do_oop(p);
2779
2780 if (!G1VerifyHeapRegionCodeRoots) {
2781 // We're not verifying the code roots attached to heap region.
2782 return;
2783 }
2784
2785 // Don't check the code roots during marking verification in a full GC
2786 if (_vo == VerifyOption_G1UseMarkWord) {
2787 return;
2788 }
2789
2790 // Now verify that the current nmethod (which contains p) is
2791 // in the code root list of the heap region containing the
2792 // object referenced by p.
2793
2794 T heap_oop = oopDesc::load_heap_oop(p);
2795 if (!oopDesc::is_null(heap_oop)) {
2796 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2797
2798 // Now fetch the region containing the object
2799 HeapRegion* hr = _g1h->heap_region_containing(obj);
2800 HeapRegionRemSet* hrrs = hr->rem_set();
2801 // Verify that the strong code root list for this region
2802 // contains the nmethod
2803 if (!hrrs->strong_code_roots_list_contains(_nm)) {
2804 gclog_or_tty->print_cr("Code root location "PTR_FORMAT" "
2805 "from nmethod "PTR_FORMAT" not in strong "
2806 "code roots for region ["PTR_FORMAT","PTR_FORMAT")",
2807 p, _nm, hr->bottom(), hr->end());
2808 _failures = true;
2809 }
2810 }
2811 }
2812
2813 public:
2814 G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo):
2815 _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {}
2816
2817 void do_oop(oop* p) { do_oop_work(p); }
2818 void do_oop(narrowOop* p) { do_oop_work(p); }
2819
2820 void set_nmethod(nmethod* nm) { _nm = nm; }
2821 bool failures() { return _failures; }
2822 };
2823
2824 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure {
2825 G1VerifyCodeRootOopClosure* _oop_cl;
2826
2827 public:
2828 G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl):
2829 _oop_cl(oop_cl) {}
2830
2831 void do_code_blob(CodeBlob* cb) {
2832 nmethod* nm = cb->as_nmethod_or_null();
2833 if (nm != NULL) {
2834 _oop_cl->set_nmethod(nm);
2835 nm->oops_do(_oop_cl);
2836 }
2837 }
2838 };
2839
2840 class YoungRefCounterClosure : public OopClosure {
2841 G1CollectedHeap* _g1h;
2842 int _count;
2843 public:
2844 YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {}
2845 void do_oop(oop* p) { if (_g1h->is_in_young(*p)) { _count++; } }
2846 void do_oop(narrowOop* p) { ShouldNotReachHere(); }
2847
2848 int count() { return _count; }
2849 void reset_count() { _count = 0; };
2850 };
2851
2852 class VerifyKlassClosure: public KlassClosure {
2853 YoungRefCounterClosure _young_ref_counter_closure;
2854 OopClosure *_oop_closure;
2855 public:
2856 VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {}
2857 void do_klass(Klass* k) {
2858 k->oops_do(_oop_closure);
2859
2860 _young_ref_counter_closure.reset_count();
2861 k->oops_do(&_young_ref_counter_closure);
2862 if (_young_ref_counter_closure.count() > 0) {
2863 guarantee(k->has_modified_oops(), err_msg("Klass " PTR_FORMAT ", has young refs but is not dirty.", k));
2864 }
2865 }
2866 };
2867
2868 class VerifyLivenessOopClosure: public OopClosure {
2869 G1CollectedHeap* _g1h;
2870 VerifyOption _vo;
2871 public:
2872 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
2873 _g1h(g1h), _vo(vo)
2874 { }
2875 void do_oop(narrowOop *p) { do_oop_work(p); }
2876 void do_oop( oop *p) { do_oop_work(p); }
2877
2878 template <class T> void do_oop_work(T *p) {
2879 oop obj = oopDesc::load_decode_heap_oop(p);
2880 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
2881 "Dead object referenced by a not dead object");
2882 }
2883 };
2884
2885 class VerifyObjsInRegionClosure: public ObjectClosure {
2886 private:
2887 G1CollectedHeap* _g1h;
2888 size_t _live_bytes;
2889 HeapRegion *_hr;
2890 VerifyOption _vo;
2891 public:
2892 // _vo == UsePrevMarking -> use "prev" marking information,
2893 // _vo == UseNextMarking -> use "next" marking information,
2894 // _vo == UseMarkWord -> use mark word from object header.
2895 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
2896 : _live_bytes(0), _hr(hr), _vo(vo) {
2897 _g1h = G1CollectedHeap::heap();
2898 }
2899 void do_object(oop o) {
2900 VerifyLivenessOopClosure isLive(_g1h, _vo);
2901 assert(o != NULL, "Huh?");
2902 if (!_g1h->is_obj_dead_cond(o, _vo)) {
2903 // If the object is alive according to the mark word,
2904 // then verify that the marking information agrees.
2905 // Note we can't verify the contra-positive of the
2906 // above: if the object is dead (according to the mark
2907 // word), it may not be marked, or may have been marked
2908 // but has since became dead, or may have been allocated
2909 // since the last marking.
2910 if (_vo == VerifyOption_G1UseMarkWord) {
2911 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
2912 }
2913
2914 o->oop_iterate_no_header(&isLive);
2915 if (!_hr->obj_allocated_since_prev_marking(o)) {
2916 size_t obj_size = o->size(); // Make sure we don't overflow
2917 _live_bytes += (obj_size * HeapWordSize);
2918 }
2919 }
2920 }
2921 size_t live_bytes() { return _live_bytes; }
2922 };
2923
2924 class VerifyRegionClosure: public HeapRegionClosure {
2925 private:
2926 bool _par;
2927 VerifyOption _vo;
2928 bool _failures;
2929 public:
2930 // _vo == UsePrevMarking -> use "prev" marking information,
2931 // _vo == UseNextMarking -> use "next" marking information,
2932 // _vo == UseMarkWord -> use mark word from object header.
2933 VerifyRegionClosure(bool par, VerifyOption vo)
2934 : _par(par),
2935 _vo(vo),
2936 _failures(false) {}
2937
2938 bool failures() {
2939 return _failures;
2940 }
2941
2942 bool doHeapRegion(HeapRegion* r) {
2943 if (!r->is_continues_humongous()) {
2944 bool failures = false;
2945 r->verify(_vo, &failures);
2946 if (failures) {
2947 _failures = true;
2948 } else {
2949 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
2950 r->object_iterate(¬_dead_yet_cl);
2951 if (_vo != VerifyOption_G1UseNextMarking) {
2952 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
2953 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
2954 "max_live_bytes "SIZE_FORMAT" "
2955 "< calculated "SIZE_FORMAT,
2956 r->bottom(), r->end(),
2957 r->max_live_bytes(),
2958 not_dead_yet_cl.live_bytes());
2959 _failures = true;
2960 }
2961 } else {
2962 // When vo == UseNextMarking we cannot currently do a sanity
2963 // check on the live bytes as the calculation has not been
2964 // finalized yet.
2965 }
2966 }
2967 }
2968 return false; // stop the region iteration if we hit a failure
2969 }
2970 };
2971
2972 // This is the task used for parallel verification of the heap regions
2973
2974 class G1ParVerifyTask: public AbstractGangTask {
2975 private:
2976 G1CollectedHeap* _g1h;
2977 VerifyOption _vo;
2978 bool _failures;
2979 HeapRegionClaimer _hrclaimer;
2980
2981 public:
2982 // _vo == UsePrevMarking -> use "prev" marking information,
2983 // _vo == UseNextMarking -> use "next" marking information,
2984 // _vo == UseMarkWord -> use mark word from object header.
2985 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
2986 AbstractGangTask("Parallel verify task"),
2987 _g1h(g1h),
2988 _vo(vo),
2989 _failures(false),
2990 _hrclaimer(g1h->workers()->active_workers()) {}
2991
2992 bool failures() {
2993 return _failures;
2994 }
2995
2996 void work(uint worker_id) {
2997 HandleMark hm;
2998 VerifyRegionClosure blk(true, _vo);
2999 _g1h->heap_region_par_iterate(&blk, worker_id, &_hrclaimer);
3000 if (blk.failures()) {
3001 _failures = true;
3002 }
3003 }
3004 };
3005
3006 void G1CollectedHeap::verify(bool silent, VerifyOption vo) {
3007 if (SafepointSynchronize::is_at_safepoint()) {
3008 assert(Thread::current()->is_VM_thread(),
3009 "Expected to be executed serially by the VM thread at this point");
3010
3011 if (!silent) { gclog_or_tty->print("Roots "); }
3012 VerifyRootsClosure rootsCl(vo);
3013 VerifyKlassClosure klassCl(this, &rootsCl);
3014 CLDToKlassAndOopClosure cldCl(&klassCl, &rootsCl, false);
3015
3016 // We apply the relevant closures to all the oops in the
3017 // system dictionary, class loader data graph, the string table
3018 // and the nmethods in the code cache.
3019 G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo);
3020 G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl);
3021
3022 {
3023 G1RootProcessor root_processor(this);
3024 root_processor.process_all_roots(&rootsCl,
3025 &cldCl,
3026 &blobsCl);
3027 }
3028
3029 bool failures = rootsCl.failures() || codeRootsCl.failures();
3030
3031 if (vo != VerifyOption_G1UseMarkWord) {
3032 // If we're verifying during a full GC then the region sets
3033 // will have been torn down at the start of the GC. Therefore
3034 // verifying the region sets will fail. So we only verify
3035 // the region sets when not in a full GC.
3036 if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3037 verify_region_sets();
3038 }
3039
3040 if (!silent) { gclog_or_tty->print("HeapRegions "); }
3041 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3042
3043 G1ParVerifyTask task(this, vo);
3044 assert(UseDynamicNumberOfGCThreads ||
3045 workers()->active_workers() == workers()->total_workers(),
3046 "If not dynamic should be using all the workers");
3047 int n_workers = workers()->active_workers();
3048 set_par_threads(n_workers);
3049 workers()->run_task(&task);
3050 set_par_threads(0);
3051 if (task.failures()) {
3052 failures = true;
3053 }
3054
3055 } else {
3056 VerifyRegionClosure blk(false, vo);
3057 heap_region_iterate(&blk);
3058 if (blk.failures()) {
3059 failures = true;
3060 }
3061 }
3062
3063 if (G1StringDedup::is_enabled()) {
3064 if (!silent) gclog_or_tty->print("StrDedup ");
3065 G1StringDedup::verify();
3066 }
3067
3068 if (failures) {
3069 gclog_or_tty->print_cr("Heap:");
3070 // It helps to have the per-region information in the output to
3071 // help us track down what went wrong. This is why we call
3072 // print_extended_on() instead of print_on().
3073 print_extended_on(gclog_or_tty);
3074 gclog_or_tty->cr();
3075 gclog_or_tty->flush();
3076 }
3077 guarantee(!failures, "there should not have been any failures");
3078 } else {
3079 if (!silent) {
3080 gclog_or_tty->print("(SKIPPING Roots, HeapRegionSets, HeapRegions, RemSet");
3081 if (G1StringDedup::is_enabled()) {
3082 gclog_or_tty->print(", StrDedup");
3083 }
3084 gclog_or_tty->print(") ");
3085 }
3086 }
3087 }
3088
3089 void G1CollectedHeap::verify(bool silent) {
3090 verify(silent, VerifyOption_G1UsePrevMarking);
3091 }
3092
3093 double G1CollectedHeap::verify(bool guard, const char* msg) {
3094 double verify_time_ms = 0.0;
3095
3096 if (guard && total_collections() >= VerifyGCStartAt) {
3097 double verify_start = os::elapsedTime();
3098 HandleMark hm; // Discard invalid handles created during verification
3099 prepare_for_verify();
3100 Universe::verify(VerifyOption_G1UsePrevMarking, msg);
3101 verify_time_ms = (os::elapsedTime() - verify_start) * 1000;
3102 }
3103
3104 return verify_time_ms;
3105 }
3106
3107 void G1CollectedHeap::verify_before_gc() {
3108 double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:");
3109 g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms);
3110 }
3111
3112 void G1CollectedHeap::verify_after_gc() {
3113 double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:");
3114 g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms);
3115 }
3116
3117 class PrintRegionClosure: public HeapRegionClosure {
3118 outputStream* _st;
3119 public:
3120 PrintRegionClosure(outputStream* st) : _st(st) {}
3121 bool doHeapRegion(HeapRegion* r) {
3122 r->print_on(_st);
3123 return false;
3124 }
3125 };
3126
3127 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3128 const HeapRegion* hr,
3129 const VerifyOption vo) const {
3130 switch (vo) {
3131 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
3132 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
3133 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked();
3134 default: ShouldNotReachHere();
3135 }
3136 return false; // keep some compilers happy
3137 }
3138
3139 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3140 const VerifyOption vo) const {
3141 switch (vo) {
3142 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
3143 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
3144 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked();
3145 default: ShouldNotReachHere();
3146 }
3147 return false; // keep some compilers happy
3148 }
3149
3150 void G1CollectedHeap::print_on(outputStream* st) const {
3151 st->print(" %-20s", "garbage-first heap");
3152 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3153 capacity()/K, used_unlocked()/K);
3154 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3155 _hrm.reserved().start(),
3156 _hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords,
3157 _hrm.reserved().end());
3158 st->cr();
3159 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3160 uint young_regions = _young_list->length();
3161 st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3162 (size_t) young_regions * HeapRegion::GrainBytes / K);
3163 uint survivor_regions = g1_policy()->recorded_survivor_regions();
3164 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3165 (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3166 st->cr();
3167 MetaspaceAux::print_on(st);
3168 }
3169
3170 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3171 print_on(st);
3172
3173 // Print the per-region information.
3174 st->cr();
3175 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3176 "HS=humongous(starts), HC=humongous(continues), "
3177 "CS=collection set, F=free, TS=gc time stamp, "
3178 "PTAMS=previous top-at-mark-start, "
3179 "NTAMS=next top-at-mark-start)");
3180 PrintRegionClosure blk(st);
3181 heap_region_iterate(&blk);
3182 }
3183
3184 void G1CollectedHeap::print_on_error(outputStream* st) const {
3185 this->CollectedHeap::print_on_error(st);
3186
3187 if (_cm != NULL) {
3188 st->cr();
3189 _cm->print_on_error(st);
3190 }
3191 }
3192
3193 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3194 workers()->print_worker_threads_on(st);
3195 _cmThread->print_on(st);
3196 st->cr();
3197 _cm->print_worker_threads_on(st);
3198 _cg1r->print_worker_threads_on(st);
3199 if (G1StringDedup::is_enabled()) {
3200 G1StringDedup::print_worker_threads_on(st);
3201 }
3202 }
3203
3204 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3205 workers()->threads_do(tc);
3206 tc->do_thread(_cmThread);
3207 _cg1r->threads_do(tc);
3208 if (G1StringDedup::is_enabled()) {
3209 G1StringDedup::threads_do(tc);
3210 }
3211 }
3212
3213 void G1CollectedHeap::print_tracing_info() const {
3214 // We'll overload this to mean "trace GC pause statistics."
3215 if (TraceYoungGenTime || TraceOldGenTime) {
3216 // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3217 // to that.
3218 g1_policy()->print_tracing_info();
3219 }
3220 if (G1SummarizeRSetStats) {
3221 g1_rem_set()->print_summary_info();
3222 }
3223 if (G1SummarizeConcMark) {
3224 concurrent_mark()->print_summary_info();
3225 }
3226 g1_policy()->print_yg_surv_rate_info();
3227 }
3228
3229 #ifndef PRODUCT
3230 // Helpful for debugging RSet issues.
3231
3232 class PrintRSetsClosure : public HeapRegionClosure {
3233 private:
3234 const char* _msg;
3235 size_t _occupied_sum;
3236
3237 public:
3238 bool doHeapRegion(HeapRegion* r) {
3239 HeapRegionRemSet* hrrs = r->rem_set();
3240 size_t occupied = hrrs->occupied();
3241 _occupied_sum += occupied;
3242
3243 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3244 HR_FORMAT_PARAMS(r));
3245 if (occupied == 0) {
3246 gclog_or_tty->print_cr(" RSet is empty");
3247 } else {
3248 hrrs->print();
3249 }
3250 gclog_or_tty->print_cr("----------");
3251 return false;
3252 }
3253
3254 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3255 gclog_or_tty->cr();
3256 gclog_or_tty->print_cr("========================================");
3257 gclog_or_tty->print_cr("%s", msg);
3258 gclog_or_tty->cr();
3259 }
3260
3261 ~PrintRSetsClosure() {
3262 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3263 gclog_or_tty->print_cr("========================================");
3264 gclog_or_tty->cr();
3265 }
3266 };
3267
3268 void G1CollectedHeap::print_cset_rsets() {
3269 PrintRSetsClosure cl("Printing CSet RSets");
3270 collection_set_iterate(&cl);
3271 }
3272
3273 void G1CollectedHeap::print_all_rsets() {
3274 PrintRSetsClosure cl("Printing All RSets");;
3275 heap_region_iterate(&cl);
3276 }
3277 #endif // PRODUCT
3278
3279 G1CollectedHeap* G1CollectedHeap::heap() {
3280 CollectedHeap* heap = Universe::heap();
3281 assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
3282 assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap");
3283 return (G1CollectedHeap*)heap;
3284 }
3285
3286 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3287 // always_do_update_barrier = false;
3288 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3289 // Fill TLAB's and such
3290 accumulate_statistics_all_tlabs();
3291 ensure_parsability(true);
3292
3293 if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) &&
3294 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3295 g1_rem_set()->print_periodic_summary_info("Before GC RS summary");
3296 }
3297 }
3298
3299 void G1CollectedHeap::gc_epilogue(bool full) {
3300
3301 if (G1SummarizeRSetStats &&
3302 (G1SummarizeRSetStatsPeriod > 0) &&
3303 // we are at the end of the GC. Total collections has already been increased.
3304 ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) {
3305 g1_rem_set()->print_periodic_summary_info("After GC RS summary");
3306 }
3307
3308 // FIXME: what is this about?
3309 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3310 // is set.
3311 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3312 "derived pointer present"));
3313 // always_do_update_barrier = true;
3314
3315 resize_all_tlabs();
3316 allocation_context_stats().update(full);
3317
3318 // We have just completed a GC. Update the soft reference
3319 // policy with the new heap occupancy
3320 Universe::update_heap_info_at_gc();
3321 }
3322
3323 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3324 uint gc_count_before,
3325 bool* succeeded,
3326 GCCause::Cause gc_cause) {
3327 assert_heap_not_locked_and_not_at_safepoint();
3328 g1_policy()->record_stop_world_start();
3329 VM_G1IncCollectionPause op(gc_count_before,
3330 word_size,
3331 false, /* should_initiate_conc_mark */
3332 g1_policy()->max_pause_time_ms(),
3333 gc_cause);
3334
3335 op.set_allocation_context(AllocationContext::current());
3336 VMThread::execute(&op);
3337
3338 HeapWord* result = op.result();
3339 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3340 assert(result == NULL || ret_succeeded,
3341 "the result should be NULL if the VM did not succeed");
3342 *succeeded = ret_succeeded;
3343
3344 assert_heap_not_locked();
3345 return result;
3346 }
3347
3348 void
3349 G1CollectedHeap::doConcurrentMark() {
3350 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3351 if (!_cmThread->in_progress()) {
3352 _cmThread->set_started();
3353 CGC_lock->notify();
3354 }
3355 }
3356
3357 size_t G1CollectedHeap::pending_card_num() {
3358 size_t extra_cards = 0;
3359 JavaThread *curr = Threads::first();
3360 while (curr != NULL) {
3361 DirtyCardQueue& dcq = curr->dirty_card_queue();
3362 extra_cards += dcq.size();
3363 curr = curr->next();
3364 }
3365 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3366 size_t buffer_size = dcqs.buffer_size();
3367 size_t buffer_num = dcqs.completed_buffers_num();
3368
3369 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
3370 // in bytes - not the number of 'entries'. We need to convert
3371 // into a number of cards.
3372 return (buffer_size * buffer_num + extra_cards) / oopSize;
3373 }
3374
3375 size_t G1CollectedHeap::cards_scanned() {
3376 return g1_rem_set()->cardsScanned();
3377 }
3378
3379 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
3380 private:
3381 size_t _total_humongous;
3382 size_t _candidate_humongous;
3383
3384 DirtyCardQueue _dcq;
3385
3386 // We don't nominate objects with many remembered set entries, on
3387 // the assumption that such objects are likely still live.
3388 bool is_remset_small(HeapRegion* region) const {
3389 HeapRegionRemSet* const rset = region->rem_set();
3390 return G1EagerReclaimHumongousObjectsWithStaleRefs
3391 ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries)
3392 : rset->is_empty();
3393 }
3394
3395 bool is_typeArray_region(HeapRegion* region) const {
3396 return oop(region->bottom())->is_typeArray();
3397 }
3398
3399 bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const {
3400 assert(region->is_starts_humongous(), "Must start a humongous object");
3401
3402 // Candidate selection must satisfy the following constraints
3403 // while concurrent marking is in progress:
3404 //
3405 // * In order to maintain SATB invariants, an object must not be
3406 // reclaimed if it was allocated before the start of marking and
3407 // has not had its references scanned. Such an object must have
3408 // its references (including type metadata) scanned to ensure no
3409 // live objects are missed by the marking process. Objects
3410 // allocated after the start of concurrent marking don't need to
3411 // be scanned.
3412 //
3413 // * An object must not be reclaimed if it is on the concurrent
3414 // mark stack. Objects allocated after the start of concurrent
3415 // marking are never pushed on the mark stack.
3416 //
3417 // Nominating only objects allocated after the start of concurrent
3418 // marking is sufficient to meet both constraints. This may miss
3419 // some objects that satisfy the constraints, but the marking data
3420 // structures don't support efficiently performing the needed
3421 // additional tests or scrubbing of the mark stack.
3422 //
3423 // However, we presently only nominate is_typeArray() objects.
3424 // A humongous object containing references induces remembered
3425 // set entries on other regions. In order to reclaim such an
3426 // object, those remembered sets would need to be cleaned up.
3427 //
3428 // We also treat is_typeArray() objects specially, allowing them
3429 // to be reclaimed even if allocated before the start of
3430 // concurrent mark. For this we rely on mark stack insertion to
3431 // exclude is_typeArray() objects, preventing reclaiming an object
3432 // that is in the mark stack. We also rely on the metadata for
3433 // such objects to be built-in and so ensured to be kept live.
3434 // Frequent allocation and drop of large binary blobs is an
3435 // important use case for eager reclaim, and this special handling
3436 // may reduce needed headroom.
3437
3438 return is_typeArray_region(region) && is_remset_small(region);
3439 }
3440
3441 public:
3442 RegisterHumongousWithInCSetFastTestClosure()
3443 : _total_humongous(0),
3444 _candidate_humongous(0),
3445 _dcq(&JavaThread::dirty_card_queue_set()) {
3446 }
3447
3448 virtual bool doHeapRegion(HeapRegion* r) {
3449 if (!r->is_starts_humongous()) {
3450 return false;
3451 }
3452 G1CollectedHeap* g1h = G1CollectedHeap::heap();
3453
3454 bool is_candidate = humongous_region_is_candidate(g1h, r);
3455 uint rindex = r->hrm_index();
3456 g1h->set_humongous_reclaim_candidate(rindex, is_candidate);
3457 if (is_candidate) {
3458 _candidate_humongous++;
3459 g1h->register_humongous_region_with_cset(rindex);
3460 // Is_candidate already filters out humongous object with large remembered sets.
3461 // If we have a humongous object with a few remembered sets, we simply flush these
3462 // remembered set entries into the DCQS. That will result in automatic
3463 // re-evaluation of their remembered set entries during the following evacuation
3464 // phase.
3465 if (!r->rem_set()->is_empty()) {
3466 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
3467 "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
3468 G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set();
3469 HeapRegionRemSetIterator hrrs(r->rem_set());
3470 size_t card_index;
3471 while (hrrs.has_next(card_index)) {
3472 jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index);
3473 // The remembered set might contain references to already freed
3474 // regions. Filter out such entries to avoid failing card table
3475 // verification.
3476 if (!g1h->heap_region_containing(bs->addr_for(card_ptr))->is_free()) {
3477 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
3478 *card_ptr = CardTableModRefBS::dirty_card_val();
3479 _dcq.enqueue(card_ptr);
3480 }
3481 }
3482 }
3483 r->rem_set()->clear_locked();
3484 }
3485 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
3486 }
3487 _total_humongous++;
3488
3489 return false;
3490 }
3491
3492 size_t total_humongous() const { return _total_humongous; }
3493 size_t candidate_humongous() const { return _candidate_humongous; }
3494
3495 void flush_rem_set_entries() { _dcq.flush(); }
3496 };
3497
3498 void G1CollectedHeap::register_humongous_regions_with_cset() {
3499 if (!G1EagerReclaimHumongousObjects) {
3500 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
3501 return;
3502 }
3503 double time = os::elapsed_counter();
3504
3505 // Collect reclaim candidate information and register candidates with cset.
3506 RegisterHumongousWithInCSetFastTestClosure cl;
3507 heap_region_iterate(&cl);
3508
3509 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
3510 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
3511 cl.total_humongous(),
3512 cl.candidate_humongous());
3513 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
3514
3515 // Finally flush all remembered set entries to re-check into the global DCQS.
3516 cl.flush_rem_set_entries();
3517 }
3518
3519 void
3520 G1CollectedHeap::setup_surviving_young_words() {
3521 assert(_surviving_young_words == NULL, "pre-condition");
3522 uint array_length = g1_policy()->young_cset_region_length();
3523 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3524 if (_surviving_young_words == NULL) {
3525 vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR,
3526 "Not enough space for young surv words summary.");
3527 }
3528 memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3529 #ifdef ASSERT
3530 for (uint i = 0; i < array_length; ++i) {
3531 assert( _surviving_young_words[i] == 0, "memset above" );
3532 }
3533 #endif // !ASSERT
3534 }
3535
3536 void
3537 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3538 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3539 uint array_length = g1_policy()->young_cset_region_length();
3540 for (uint i = 0; i < array_length; ++i) {
3541 _surviving_young_words[i] += surv_young_words[i];
3542 }
3543 }
3544
3545 void
3546 G1CollectedHeap::cleanup_surviving_young_words() {
3547 guarantee( _surviving_young_words != NULL, "pre-condition" );
3548 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words);
3549 _surviving_young_words = NULL;
3550 }
3551
3552 #ifdef ASSERT
3553 class VerifyCSetClosure: public HeapRegionClosure {
3554 public:
3555 bool doHeapRegion(HeapRegion* hr) {
3556 // Here we check that the CSet region's RSet is ready for parallel
3557 // iteration. The fields that we'll verify are only manipulated
3558 // when the region is part of a CSet and is collected. Afterwards,
3559 // we reset these fields when we clear the region's RSet (when the
3560 // region is freed) so they are ready when the region is
3561 // re-allocated. The only exception to this is if there's an
3562 // evacuation failure and instead of freeing the region we leave
3563 // it in the heap. In that case, we reset these fields during
3564 // evacuation failure handling.
3565 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3566
3567 // Here's a good place to add any other checks we'd like to
3568 // perform on CSet regions.
3569 return false;
3570 }
3571 };
3572 #endif // ASSERT
3573
3574 #if TASKQUEUE_STATS
3575 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3576 st->print_raw_cr("GC Task Stats");
3577 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3578 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3579 }
3580
3581 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3582 print_taskqueue_stats_hdr(st);
3583
3584 TaskQueueStats totals;
3585 const int n = workers()->total_workers();
3586 for (int i = 0; i < n; ++i) {
3587 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3588 totals += task_queue(i)->stats;
3589 }
3590 st->print_raw("tot "); totals.print(st); st->cr();
3591
3592 DEBUG_ONLY(totals.verify());
3593 }
3594
3595 void G1CollectedHeap::reset_taskqueue_stats() {
3596 const int n = workers()->total_workers();
3597 for (int i = 0; i < n; ++i) {
3598 task_queue(i)->stats.reset();
3599 }
3600 }
3601 #endif // TASKQUEUE_STATS
3602
3603 void G1CollectedHeap::log_gc_header() {
3604 if (!G1Log::fine()) {
3605 return;
3606 }
3607
3608 gclog_or_tty->gclog_stamp(_gc_tracer_stw->gc_id());
3609
3610 GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
3611 .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)")
3612 .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : "");
3613
3614 gclog_or_tty->print("[%s", (const char*)gc_cause_str);
3615 }
3616
3617 void G1CollectedHeap::log_gc_footer(double pause_time_sec) {
3618 if (!G1Log::fine()) {
3619 return;
3620 }
3621
3622 if (G1Log::finer()) {
3623 if (evacuation_failed()) {
3624 gclog_or_tty->print(" (to-space exhausted)");
3625 }
3626 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3627 g1_policy()->phase_times()->note_gc_end();
3628 g1_policy()->phase_times()->print(pause_time_sec);
3629 g1_policy()->print_detailed_heap_transition();
3630 } else {
3631 if (evacuation_failed()) {
3632 gclog_or_tty->print("--");
3633 }
3634 g1_policy()->print_heap_transition();
3635 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3636 }
3637 gclog_or_tty->flush();
3638 }
3639
3640 bool
3641 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3642 assert_at_safepoint(true /* should_be_vm_thread */);
3643 guarantee(!is_gc_active(), "collection is not reentrant");
3644
3645 if (GC_locker::check_active_before_gc()) {
3646 return false;
3647 }
3648
3649 _gc_timer_stw->register_gc_start();
3650
3651 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3652
3653 SvcGCMarker sgcm(SvcGCMarker::MINOR);
3654 ResourceMark rm;
3655
3656 print_heap_before_gc();
3657 trace_heap_before_gc(_gc_tracer_stw);
3658
3659 verify_region_sets_optional();
3660 verify_dirty_young_regions();
3661
3662 // This call will decide whether this pause is an initial-mark
3663 // pause. If it is, during_initial_mark_pause() will return true
3664 // for the duration of this pause.
3665 g1_policy()->decide_on_conc_mark_initiation();
3666
3667 // We do not allow initial-mark to be piggy-backed on a mixed GC.
3668 assert(!g1_policy()->during_initial_mark_pause() ||
3669 g1_policy()->gcs_are_young(), "sanity");
3670
3671 // We also do not allow mixed GCs during marking.
3672 assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3673
3674 // Record whether this pause is an initial mark. When the current
3675 // thread has completed its logging output and it's safe to signal
3676 // the CM thread, the flag's value in the policy has been reset.
3677 bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3678
3679 // Inner scope for scope based logging, timers, and stats collection
3680 {
3681 EvacuationInfo evacuation_info;
3682
3683 if (g1_policy()->during_initial_mark_pause()) {
3684 // We are about to start a marking cycle, so we increment the
3685 // full collection counter.
3686 increment_old_marking_cycles_started();
3687 register_concurrent_cycle_start(_gc_timer_stw->gc_start());
3688 }
3689
3690 _gc_tracer_stw->report_yc_type(yc_type());
3691
3692 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3693
3694 uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
3695 workers()->active_workers(),
3696 Threads::number_of_non_daemon_threads());
3697 assert(UseDynamicNumberOfGCThreads ||
3698 active_workers == workers()->total_workers(),
3699 "If not dynamic should be using all the workers");
3700 workers()->set_active_workers(active_workers);
3701
3702 double pause_start_sec = os::elapsedTime();
3703 g1_policy()->phase_times()->note_gc_start(active_workers, mark_in_progress());
3704 log_gc_header();
3705
3706 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3707 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3708
3709 // If the secondary_free_list is not empty, append it to the
3710 // free_list. No need to wait for the cleanup operation to finish;
3711 // the region allocation code will check the secondary_free_list
3712 // and wait if necessary. If the G1StressConcRegionFreeing flag is
3713 // set, skip this step so that the region allocation code has to
3714 // get entries from the secondary_free_list.
3715 if (!G1StressConcRegionFreeing) {
3716 append_secondary_free_list_if_not_empty_with_lock();
3717 }
3718
3719 assert(check_young_list_well_formed(), "young list should be well formed");
3720
3721 // Don't dynamically change the number of GC threads this early. A value of
3722 // 0 is used to indicate serial work. When parallel work is done,
3723 // it will be set.
3724
3725 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3726 IsGCActiveMark x;
3727
3728 gc_prologue(false);
3729 increment_total_collections(false /* full gc */);
3730 increment_gc_time_stamp();
3731
3732 verify_before_gc();
3733
3734 check_bitmaps("GC Start");
3735
3736 COMPILER2_PRESENT(DerivedPointerTable::clear());
3737
3738 // Please see comment in g1CollectedHeap.hpp and
3739 // G1CollectedHeap::ref_processing_init() to see how
3740 // reference processing currently works in G1.
3741
3742 // Enable discovery in the STW reference processor
3743 ref_processor_stw()->enable_discovery();
3744
3745 {
3746 // We want to temporarily turn off discovery by the
3747 // CM ref processor, if necessary, and turn it back on
3748 // on again later if we do. Using a scoped
3749 // NoRefDiscovery object will do this.
3750 NoRefDiscovery no_cm_discovery(ref_processor_cm());
3751
3752 // Forget the current alloc region (we might even choose it to be part
3753 // of the collection set!).
3754 _allocator->release_mutator_alloc_region();
3755
3756 // We should call this after we retire the mutator alloc
3757 // region(s) so that all the ALLOC / RETIRE events are generated
3758 // before the start GC event.
3759 _hr_printer.start_gc(false /* full */, (size_t) total_collections());
3760
3761 // This timing is only used by the ergonomics to handle our pause target.
3762 // It is unclear why this should not include the full pause. We will
3763 // investigate this in CR 7178365.
3764 //
3765 // Preserving the old comment here if that helps the investigation:
3766 //
3767 // The elapsed time induced by the start time below deliberately elides
3768 // the possible verification above.
3769 double sample_start_time_sec = os::elapsedTime();
3770
3771 #if YOUNG_LIST_VERBOSE
3772 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
3773 _young_list->print();
3774 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3775 #endif // YOUNG_LIST_VERBOSE
3776
3777 g1_policy()->record_collection_pause_start(sample_start_time_sec);
3778
3779 double scan_wait_start = os::elapsedTime();
3780 // We have to wait until the CM threads finish scanning the
3781 // root regions as it's the only way to ensure that all the
3782 // objects on them have been correctly scanned before we start
3783 // moving them during the GC.
3784 bool waited = _cm->root_regions()->wait_until_scan_finished();
3785 double wait_time_ms = 0.0;
3786 if (waited) {
3787 double scan_wait_end = os::elapsedTime();
3788 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
3789 }
3790 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
3791
3792 #if YOUNG_LIST_VERBOSE
3793 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
3794 _young_list->print();
3795 #endif // YOUNG_LIST_VERBOSE
3796
3797 if (g1_policy()->during_initial_mark_pause()) {
3798 concurrent_mark()->checkpointRootsInitialPre();
3799 }
3800
3801 #if YOUNG_LIST_VERBOSE
3802 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
3803 _young_list->print();
3804 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3805 #endif // YOUNG_LIST_VERBOSE
3806
3807 g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info);
3808
3809 register_humongous_regions_with_cset();
3810
3811 assert(check_cset_fast_test(), "Inconsistency in the InCSetState table.");
3812
3813 _cm->note_start_of_gc();
3814 // We should not verify the per-thread SATB buffers given that
3815 // we have not filtered them yet (we'll do so during the
3816 // GC). We also call this after finalize_cset() to
3817 // ensure that the CSet has been finalized.
3818 _cm->verify_no_cset_oops(true /* verify_stacks */,
3819 true /* verify_enqueued_buffers */,
3820 false /* verify_thread_buffers */,
3821 true /* verify_fingers */);
3822
3823 if (_hr_printer.is_active()) {
3824 HeapRegion* hr = g1_policy()->collection_set();
3825 while (hr != NULL) {
3826 _hr_printer.cset(hr);
3827 hr = hr->next_in_collection_set();
3828 }
3829 }
3830
3831 #ifdef ASSERT
3832 VerifyCSetClosure cl;
3833 collection_set_iterate(&cl);
3834 #endif // ASSERT
3835
3836 setup_surviving_young_words();
3837
3838 // Initialize the GC alloc regions.
3839 _allocator->init_gc_alloc_regions(evacuation_info);
3840
3841 // Actually do the work...
3842 evacuate_collection_set(evacuation_info);
3843
3844 // We do this to mainly verify the per-thread SATB buffers
3845 // (which have been filtered by now) since we didn't verify
3846 // them earlier. No point in re-checking the stacks / enqueued
3847 // buffers given that the CSet has not changed since last time
3848 // we checked.
3849 _cm->verify_no_cset_oops(false /* verify_stacks */,
3850 false /* verify_enqueued_buffers */,
3851 true /* verify_thread_buffers */,
3852 true /* verify_fingers */);
3853
3854 free_collection_set(g1_policy()->collection_set(), evacuation_info);
3855
3856 eagerly_reclaim_humongous_regions();
3857
3858 g1_policy()->clear_collection_set();
3859
3860 cleanup_surviving_young_words();
3861
3862 // Start a new incremental collection set for the next pause.
3863 g1_policy()->start_incremental_cset_building();
3864
3865 clear_cset_fast_test();
3866
3867 _young_list->reset_sampled_info();
3868
3869 // Don't check the whole heap at this point as the
3870 // GC alloc regions from this pause have been tagged
3871 // as survivors and moved on to the survivor list.
3872 // Survivor regions will fail the !is_young() check.
3873 assert(check_young_list_empty(false /* check_heap */),
3874 "young list should be empty");
3875
3876 #if YOUNG_LIST_VERBOSE
3877 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
3878 _young_list->print();
3879 #endif // YOUNG_LIST_VERBOSE
3880
3881 g1_policy()->record_survivor_regions(_young_list->survivor_length(),
3882 _young_list->first_survivor_region(),
3883 _young_list->last_survivor_region());
3884
3885 _young_list->reset_auxilary_lists();
3886
3887 if (evacuation_failed()) {
3888 _allocator->set_used(recalculate_used());
3889 uint n_queues = MAX2((int)ParallelGCThreads, 1);
3890 for (uint i = 0; i < n_queues; i++) {
3891 if (_evacuation_failed_info_array[i].has_failed()) {
3892 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
3893 }
3894 }
3895 } else {
3896 // The "used" of the the collection set have already been subtracted
3897 // when they were freed. Add in the bytes evacuated.
3898 _allocator->increase_used(g1_policy()->bytes_copied_during_gc());
3899 }
3900
3901 if (g1_policy()->during_initial_mark_pause()) {
3902 // We have to do this before we notify the CM threads that
3903 // they can start working to make sure that all the
3904 // appropriate initialization is done on the CM object.
3905 concurrent_mark()->checkpointRootsInitialPost();
3906 set_marking_started();
3907 // Note that we don't actually trigger the CM thread at
3908 // this point. We do that later when we're sure that
3909 // the current thread has completed its logging output.
3910 }
3911
3912 allocate_dummy_regions();
3913
3914 #if YOUNG_LIST_VERBOSE
3915 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
3916 _young_list->print();
3917 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3918 #endif // YOUNG_LIST_VERBOSE
3919
3920 _allocator->init_mutator_alloc_region();
3921
3922 {
3923 size_t expand_bytes = g1_policy()->expansion_amount();
3924 if (expand_bytes > 0) {
3925 size_t bytes_before = capacity();
3926 // No need for an ergo verbose message here,
3927 // expansion_amount() does this when it returns a value > 0.
3928 if (!expand(expand_bytes)) {
3929 // We failed to expand the heap. Cannot do anything about it.
3930 }
3931 }
3932 }
3933
3934 // We redo the verification but now wrt to the new CSet which
3935 // has just got initialized after the previous CSet was freed.
3936 _cm->verify_no_cset_oops(true /* verify_stacks */,
3937 true /* verify_enqueued_buffers */,
3938 true /* verify_thread_buffers */,
3939 true /* verify_fingers */);
3940 _cm->note_end_of_gc();
3941
3942 // This timing is only used by the ergonomics to handle our pause target.
3943 // It is unclear why this should not include the full pause. We will
3944 // investigate this in CR 7178365.
3945 double sample_end_time_sec = os::elapsedTime();
3946 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3947 g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info);
3948
3949 MemoryService::track_memory_usage();
3950
3951 // In prepare_for_verify() below we'll need to scan the deferred
3952 // update buffers to bring the RSets up-to-date if
3953 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
3954 // the update buffers we'll probably need to scan cards on the
3955 // regions we just allocated to (i.e., the GC alloc
3956 // regions). However, during the last GC we called
3957 // set_saved_mark() on all the GC alloc regions, so card
3958 // scanning might skip the [saved_mark_word()...top()] area of
3959 // those regions (i.e., the area we allocated objects into
3960 // during the last GC). But it shouldn't. Given that
3961 // saved_mark_word() is conditional on whether the GC time stamp
3962 // on the region is current or not, by incrementing the GC time
3963 // stamp here we invalidate all the GC time stamps on all the
3964 // regions and saved_mark_word() will simply return top() for
3965 // all the regions. This is a nicer way of ensuring this rather
3966 // than iterating over the regions and fixing them. In fact, the
3967 // GC time stamp increment here also ensures that
3968 // saved_mark_word() will return top() between pauses, i.e.,
3969 // during concurrent refinement. So we don't need the
3970 // is_gc_active() check to decided which top to use when
3971 // scanning cards (see CR 7039627).
3972 increment_gc_time_stamp();
3973
3974 verify_after_gc();
3975 check_bitmaps("GC End");
3976
3977 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
3978 ref_processor_stw()->verify_no_references_recorded();
3979
3980 // CM reference discovery will be re-enabled if necessary.
3981 }
3982
3983 // We should do this after we potentially expand the heap so
3984 // that all the COMMIT events are generated before the end GC
3985 // event, and after we retire the GC alloc regions so that all
3986 // RETIRE events are generated before the end GC event.
3987 _hr_printer.end_gc(false /* full */, (size_t) total_collections());
3988
3989 #ifdef TRACESPINNING
3990 ParallelTaskTerminator::print_termination_counts();
3991 #endif
3992
3993 gc_epilogue(false);
3994 }
3995
3996 // Print the remainder of the GC log output.
3997 log_gc_footer(os::elapsedTime() - pause_start_sec);
3998
3999 // It is not yet to safe to tell the concurrent mark to
4000 // start as we have some optional output below. We don't want the
4001 // output from the concurrent mark thread interfering with this
4002 // logging output either.
4003
4004 _hrm.verify_optional();
4005 verify_region_sets_optional();
4006
4007 TASKQUEUE_STATS_ONLY(if (PrintTaskqueue) print_taskqueue_stats());
4008 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
4009
4010 print_heap_after_gc();
4011 trace_heap_after_gc(_gc_tracer_stw);
4012
4013 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
4014 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
4015 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
4016 // before any GC notifications are raised.
4017 g1mm()->update_sizes();
4018
4019 _gc_tracer_stw->report_evacuation_info(&evacuation_info);
4020 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
4021 _gc_timer_stw->register_gc_end();
4022 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
4023 }
4024 // It should now be safe to tell the concurrent mark thread to start
4025 // without its logging output interfering with the logging output
4026 // that came from the pause.
4027
4028 if (should_start_conc_mark) {
4029 // CAUTION: after the doConcurrentMark() call below,
4030 // the concurrent marking thread(s) could be running
4031 // concurrently with us. Make sure that anything after
4032 // this point does not assume that we are the only GC thread
4033 // running. Note: of course, the actual marking work will
4034 // not start until the safepoint itself is released in
4035 // SuspendibleThreadSet::desynchronize().
4036 doConcurrentMark();
4037 }
4038
4039 return true;
4040 }
4041
4042 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4043 _drain_in_progress = false;
4044 set_evac_failure_closure(cl);
4045 _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4046 }
4047
4048 void G1CollectedHeap::finalize_for_evac_failure() {
4049 assert(_evac_failure_scan_stack != NULL &&
4050 _evac_failure_scan_stack->length() == 0,
4051 "Postcondition");
4052 assert(!_drain_in_progress, "Postcondition");
4053 delete _evac_failure_scan_stack;
4054 _evac_failure_scan_stack = NULL;
4055 }
4056
4057 void G1CollectedHeap::remove_self_forwarding_pointers() {
4058 double remove_self_forwards_start = os::elapsedTime();
4059
4060 set_par_threads();
4061 G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4062 workers()->run_task(&rsfp_task);
4063 set_par_threads(0);
4064
4065 // Now restore saved marks, if any.
4066 assert(_objs_with_preserved_marks.size() ==
4067 _preserved_marks_of_objs.size(), "Both or none.");
4068 while (!_objs_with_preserved_marks.is_empty()) {
4069 oop obj = _objs_with_preserved_marks.pop();
4070 markOop m = _preserved_marks_of_objs.pop();
4071 obj->set_mark(m);
4072 }
4073 _objs_with_preserved_marks.clear(true);
4074 _preserved_marks_of_objs.clear(true);
4075
4076 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
4077 }
4078
4079 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4080 _evac_failure_scan_stack->push(obj);
4081 }
4082
4083 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4084 assert(_evac_failure_scan_stack != NULL, "precondition");
4085
4086 while (_evac_failure_scan_stack->length() > 0) {
4087 oop obj = _evac_failure_scan_stack->pop();
4088 _evac_failure_closure->set_region(heap_region_containing(obj));
4089 obj->oop_iterate_backwards(_evac_failure_closure);
4090 }
4091 }
4092
4093 oop
4094 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state,
4095 oop old) {
4096 assert(obj_in_cs(old),
4097 err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4098 (HeapWord*) old));
4099 markOop m = old->mark();
4100 oop forward_ptr = old->forward_to_atomic(old);
4101 if (forward_ptr == NULL) {
4102 // Forward-to-self succeeded.
4103 assert(_par_scan_state != NULL, "par scan state");
4104 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4105 uint queue_num = _par_scan_state->queue_num();
4106
4107 _evacuation_failed = true;
4108 _evacuation_failed_info_array[queue_num].register_copy_failure(old->size());
4109 if (_evac_failure_closure != cl) {
4110 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4111 assert(!_drain_in_progress,
4112 "Should only be true while someone holds the lock.");
4113 // Set the global evac-failure closure to the current thread's.
4114 assert(_evac_failure_closure == NULL, "Or locking has failed.");
4115 set_evac_failure_closure(cl);
4116 // Now do the common part.
4117 handle_evacuation_failure_common(old, m);
4118 // Reset to NULL.
4119 set_evac_failure_closure(NULL);
4120 } else {
4121 // The lock is already held, and this is recursive.
4122 assert(_drain_in_progress, "This should only be the recursive case.");
4123 handle_evacuation_failure_common(old, m);
4124 }
4125 return old;
4126 } else {
4127 // Forward-to-self failed. Either someone else managed to allocate
4128 // space for this object (old != forward_ptr) or they beat us in
4129 // self-forwarding it (old == forward_ptr).
4130 assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4131 err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4132 "should not be in the CSet",
4133 (HeapWord*) old, (HeapWord*) forward_ptr));
4134 return forward_ptr;
4135 }
4136 }
4137
4138 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4139 preserve_mark_if_necessary(old, m);
4140
4141 HeapRegion* r = heap_region_containing(old);
4142 if (!r->evacuation_failed()) {
4143 r->set_evacuation_failed(true);
4144 _hr_printer.evac_failure(r);
4145 }
4146
4147 push_on_evac_failure_scan_stack(old);
4148
4149 if (!_drain_in_progress) {
4150 // prevent recursion in copy_to_survivor_space()
4151 _drain_in_progress = true;
4152 drain_evac_failure_scan_stack();
4153 _drain_in_progress = false;
4154 }
4155 }
4156
4157 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4158 assert(evacuation_failed(), "Oversaving!");
4159 // We want to call the "for_promotion_failure" version only in the
4160 // case of a promotion failure.
4161 if (m->must_be_preserved_for_promotion_failure(obj)) {
4162 _objs_with_preserved_marks.push(obj);
4163 _preserved_marks_of_objs.push(m);
4164 }
4165 }
4166
4167 void G1ParCopyHelper::mark_object(oop obj) {
4168 assert(!_g1->heap_region_containing(obj)->in_collection_set(), "should not mark objects in the CSet");
4169
4170 // We know that the object is not moving so it's safe to read its size.
4171 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4172 }
4173
4174 void G1ParCopyHelper::mark_forwarded_object(oop from_obj, oop to_obj) {
4175 assert(from_obj->is_forwarded(), "from obj should be forwarded");
4176 assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4177 assert(from_obj != to_obj, "should not be self-forwarded");
4178
4179 assert(_g1->heap_region_containing(from_obj)->in_collection_set(), "from obj should be in the CSet");
4180 assert(!_g1->heap_region_containing(to_obj)->in_collection_set(), "should not mark objects in the CSet");
4181
4182 // The object might be in the process of being copied by another
4183 // worker so we cannot trust that its to-space image is
4184 // well-formed. So we have to read its size from its from-space
4185 // image which we know should not be changing.
4186 _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4187 }
4188
4189 template <class T>
4190 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) {
4191 if (_g1->heap_region_containing_raw(new_obj)->is_young()) {
4192 _scanned_klass->record_modified_oops();
4193 }
4194 }
4195
4196 template <G1Barrier barrier, G1Mark do_mark_object>
4197 template <class T>
4198 void G1ParCopyClosure<barrier, do_mark_object>::do_oop_work(T* p) {
4199 T heap_oop = oopDesc::load_heap_oop(p);
4200
4201 if (oopDesc::is_null(heap_oop)) {
4202 return;
4203 }
4204
4205 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
4206
4207 assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4208
4209 const InCSetState state = _g1->in_cset_state(obj);
4210 if (state.is_in_cset()) {
4211 oop forwardee;
4212 markOop m = obj->mark();
4213 if (m->is_marked()) {
4214 forwardee = (oop) m->decode_pointer();
4215 } else {
4216 forwardee = _par_scan_state->copy_to_survivor_space(state, obj, m);
4217 }
4218 assert(forwardee != NULL, "forwardee should not be NULL");
4219 oopDesc::encode_store_heap_oop(p, forwardee);
4220 if (do_mark_object != G1MarkNone && forwardee != obj) {
4221 // If the object is self-forwarded we don't need to explicitly
4222 // mark it, the evacuation failure protocol will do so.
4223 mark_forwarded_object(obj, forwardee);
4224 }
4225
4226 if (barrier == G1BarrierKlass) {
4227 do_klass_barrier(p, forwardee);
4228 }
4229 } else {
4230 if (state.is_humongous()) {
4231 _g1->set_humongous_is_live(obj);
4232 }
4233 // The object is not in collection set. If we're a root scanning
4234 // closure during an initial mark pause then attempt to mark the object.
4235 if (do_mark_object == G1MarkFromRoot) {
4236 mark_object(obj);
4237 }
4238 }
4239
4240 if (barrier == G1BarrierEvac) {
4241 _par_scan_state->update_rs(_from, p, _worker_id);
4242 }
4243 }
4244
4245 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(oop* p);
4246 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(narrowOop* p);
4247
4248 class G1ParEvacuateFollowersClosure : public VoidClosure {
4249 protected:
4250 G1CollectedHeap* _g1h;
4251 G1ParScanThreadState* _par_scan_state;
4252 RefToScanQueueSet* _queues;
4253 ParallelTaskTerminator* _terminator;
4254
4255 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
4256 RefToScanQueueSet* queues() { return _queues; }
4257 ParallelTaskTerminator* terminator() { return _terminator; }
4258
4259 public:
4260 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4261 G1ParScanThreadState* par_scan_state,
4262 RefToScanQueueSet* queues,
4263 ParallelTaskTerminator* terminator)
4264 : _g1h(g1h), _par_scan_state(par_scan_state),
4265 _queues(queues), _terminator(terminator) {}
4266
4267 void do_void();
4268
4269 private:
4270 inline bool offer_termination();
4271 };
4272
4273 bool G1ParEvacuateFollowersClosure::offer_termination() {
4274 G1ParScanThreadState* const pss = par_scan_state();
4275 pss->start_term_time();
4276 const bool res = terminator()->offer_termination();
4277 pss->end_term_time();
4278 return res;
4279 }
4280
4281 void G1ParEvacuateFollowersClosure::do_void() {
4282 G1ParScanThreadState* const pss = par_scan_state();
4283 pss->trim_queue();
4284 do {
4285 pss->steal_and_trim_queue(queues());
4286 } while (!offer_termination());
4287 }
4288
4289 class G1KlassScanClosure : public KlassClosure {
4290 G1ParCopyHelper* _closure;
4291 bool _process_only_dirty;
4292 int _count;
4293 public:
4294 G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty)
4295 : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {}
4296 void do_klass(Klass* klass) {
4297 // If the klass has not been dirtied we know that there's
4298 // no references into the young gen and we can skip it.
4299 if (!_process_only_dirty || klass->has_modified_oops()) {
4300 // Clean the klass since we're going to scavenge all the metadata.
4301 klass->clear_modified_oops();
4302
4303 // Tell the closure that this klass is the Klass to scavenge
4304 // and is the one to dirty if oops are left pointing into the young gen.
4305 _closure->set_scanned_klass(klass);
4306
4307 klass->oops_do(_closure);
4308
4309 _closure->set_scanned_klass(NULL);
4310 }
4311 _count++;
4312 }
4313 };
4314
4315 class G1ParTask : public AbstractGangTask {
4316 protected:
4317 G1CollectedHeap* _g1h;
4318 RefToScanQueueSet *_queues;
4319 G1RootProcessor* _root_processor;
4320 ParallelTaskTerminator _terminator;
4321 uint _n_workers;
4322
4323 Mutex _stats_lock;
4324 Mutex* stats_lock() { return &_stats_lock; }
4325
4326 public:
4327 G1ParTask(G1CollectedHeap* g1h, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor)
4328 : AbstractGangTask("G1 collection"),
4329 _g1h(g1h),
4330 _queues(task_queues),
4331 _root_processor(root_processor),
4332 _terminator(0, _queues),
4333 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4334 {}
4335
4336 RefToScanQueueSet* queues() { return _queues; }
4337
4338 RefToScanQueue *work_queue(int i) {
4339 return queues()->queue(i);
4340 }
4341
4342 ParallelTaskTerminator* terminator() { return &_terminator; }
4343
4344 virtual void set_for_termination(int active_workers) {
4345 _root_processor->set_num_workers(active_workers);
4346 terminator()->reset_for_reuse(active_workers);
4347 _n_workers = active_workers;
4348 }
4349
4350 // Helps out with CLD processing.
4351 //
4352 // During InitialMark we need to:
4353 // 1) Scavenge all CLDs for the young GC.
4354 // 2) Mark all objects directly reachable from strong CLDs.
4355 template <G1Mark do_mark_object>
4356 class G1CLDClosure : public CLDClosure {
4357 G1ParCopyClosure<G1BarrierNone, do_mark_object>* _oop_closure;
4358 G1ParCopyClosure<G1BarrierKlass, do_mark_object> _oop_in_klass_closure;
4359 G1KlassScanClosure _klass_in_cld_closure;
4360 bool _claim;
4361
4362 public:
4363 G1CLDClosure(G1ParCopyClosure<G1BarrierNone, do_mark_object>* oop_closure,
4364 bool only_young, bool claim)
4365 : _oop_closure(oop_closure),
4366 _oop_in_klass_closure(oop_closure->g1(),
4367 oop_closure->pss(),
4368 oop_closure->rp()),
4369 _klass_in_cld_closure(&_oop_in_klass_closure, only_young),
4370 _claim(claim) {
4371
4372 }
4373
4374 void do_cld(ClassLoaderData* cld) {
4375 cld->oops_do(_oop_closure, &_klass_in_cld_closure, _claim);
4376 }
4377 };
4378
4379 void work(uint worker_id) {
4380 if (worker_id >= _n_workers) return; // no work needed this round
4381
4382 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, os::elapsedTime());
4383
4384 {
4385 ResourceMark rm;
4386 HandleMark hm;
4387
4388 ReferenceProcessor* rp = _g1h->ref_processor_stw();
4389
4390 G1ParScanThreadState pss(_g1h, worker_id, rp);
4391 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
4392
4393 pss.set_evac_failure_closure(&evac_failure_cl);
4394
4395 bool only_young = _g1h->g1_policy()->gcs_are_young();
4396
4397 // Non-IM young GC.
4398 G1ParCopyClosure<G1BarrierNone, G1MarkNone> scan_only_root_cl(_g1h, &pss, rp);
4399 G1CLDClosure<G1MarkNone> scan_only_cld_cl(&scan_only_root_cl,
4400 only_young, // Only process dirty klasses.
4401 false); // No need to claim CLDs.
4402 // IM young GC.
4403 // Strong roots closures.
4404 G1ParCopyClosure<G1BarrierNone, G1MarkFromRoot> scan_mark_root_cl(_g1h, &pss, rp);
4405 G1CLDClosure<G1MarkFromRoot> scan_mark_cld_cl(&scan_mark_root_cl,
4406 false, // Process all klasses.
4407 true); // Need to claim CLDs.
4408 // Weak roots closures.
4409 G1ParCopyClosure<G1BarrierNone, G1MarkPromotedFromRoot> scan_mark_weak_root_cl(_g1h, &pss, rp);
4410 G1CLDClosure<G1MarkPromotedFromRoot> scan_mark_weak_cld_cl(&scan_mark_weak_root_cl,
4411 false, // Process all klasses.
4412 true); // Need to claim CLDs.
4413
4414 OopClosure* strong_root_cl;
4415 OopClosure* weak_root_cl;
4416 CLDClosure* strong_cld_cl;
4417 CLDClosure* weak_cld_cl;
4418
4419 bool trace_metadata = false;
4420
4421 if (_g1h->g1_policy()->during_initial_mark_pause()) {
4422 // We also need to mark copied objects.
4423 strong_root_cl = &scan_mark_root_cl;
4424 strong_cld_cl = &scan_mark_cld_cl;
4425 if (ClassUnloadingWithConcurrentMark) {
4426 weak_root_cl = &scan_mark_weak_root_cl;
4427 weak_cld_cl = &scan_mark_weak_cld_cl;
4428 trace_metadata = true;
4429 } else {
4430 weak_root_cl = &scan_mark_root_cl;
4431 weak_cld_cl = &scan_mark_cld_cl;
4432 }
4433 } else {
4434 strong_root_cl = &scan_only_root_cl;
4435 weak_root_cl = &scan_only_root_cl;
4436 strong_cld_cl = &scan_only_cld_cl;
4437 weak_cld_cl = &scan_only_cld_cl;
4438 }
4439
4440 pss.start_strong_roots();
4441
4442 _root_processor->evacuate_roots(strong_root_cl,
4443 weak_root_cl,
4444 strong_cld_cl,
4445 weak_cld_cl,
4446 trace_metadata,
4447 worker_id);
4448
4449 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss);
4450 _root_processor->scan_remembered_sets(&push_heap_rs_cl,
4451 weak_root_cl,
4452 worker_id);
4453 pss.end_strong_roots();
4454
4455 {
4456 double start = os::elapsedTime();
4457 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4458 evac.do_void();
4459 double elapsed_sec = os::elapsedTime() - start;
4460 double term_sec = pss.term_time();
4461 _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec);
4462 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec);
4463 _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, pss.term_attempts());
4464 }
4465 _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4466 _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4467
4468 if (PrintTerminationStats) {
4469 MutexLocker x(stats_lock());
4470 pss.print_termination_stats(worker_id);
4471 }
4472
4473 assert(pss.queue_is_empty(), "should be empty");
4474
4475 // Close the inner scope so that the ResourceMark and HandleMark
4476 // destructors are executed here and are included as part of the
4477 // "GC Worker Time".
4478 }
4479 _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime());
4480 }
4481 };
4482
4483 class G1StringSymbolTableUnlinkTask : public AbstractGangTask {
4484 private:
4485 BoolObjectClosure* _is_alive;
4486 int _initial_string_table_size;
4487 int _initial_symbol_table_size;
4488
4489 bool _process_strings;
4490 int _strings_processed;
4491 int _strings_removed;
4492
4493 bool _process_symbols;
4494 int _symbols_processed;
4495 int _symbols_removed;
4496
4497 public:
4498 G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) :
4499 AbstractGangTask("String/Symbol Unlinking"),
4500 _is_alive(is_alive),
4501 _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
4502 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) {
4503
4504 _initial_string_table_size = StringTable::the_table()->table_size();
4505 _initial_symbol_table_size = SymbolTable::the_table()->table_size();
4506 if (process_strings) {
4507 StringTable::clear_parallel_claimed_index();
4508 }
4509 if (process_symbols) {
4510 SymbolTable::clear_parallel_claimed_index();
4511 }
4512 }
4513
4514 ~G1StringSymbolTableUnlinkTask() {
4515 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size,
4516 err_msg("claim value %d after unlink less than initial string table size %d",
4517 StringTable::parallel_claimed_index(), _initial_string_table_size));
4518 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
4519 err_msg("claim value %d after unlink less than initial symbol table size %d",
4520 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size));
4521
4522 if (G1TraceStringSymbolTableScrubbing) {
4523 gclog_or_tty->print_cr("Cleaned string and symbol table, "
4524 "strings: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed, "
4525 "symbols: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed",
4526 strings_processed(), strings_removed(),
4527 symbols_processed(), symbols_removed());
4528 }
4529 }
4530
4531 void work(uint worker_id) {
4532 int strings_processed = 0;
4533 int strings_removed = 0;
4534 int symbols_processed = 0;
4535 int symbols_removed = 0;
4536 if (_process_strings) {
4537 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
4538 Atomic::add(strings_processed, &_strings_processed);
4539 Atomic::add(strings_removed, &_strings_removed);
4540 }
4541 if (_process_symbols) {
4542 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
4543 Atomic::add(symbols_processed, &_symbols_processed);
4544 Atomic::add(symbols_removed, &_symbols_removed);
4545 }
4546 }
4547
4548 size_t strings_processed() const { return (size_t)_strings_processed; }
4549 size_t strings_removed() const { return (size_t)_strings_removed; }
4550
4551 size_t symbols_processed() const { return (size_t)_symbols_processed; }
4552 size_t symbols_removed() const { return (size_t)_symbols_removed; }
4553 };
4554
4555 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
4556 private:
4557 static Monitor* _lock;
4558
4559 BoolObjectClosure* const _is_alive;
4560 const bool _unloading_occurred;
4561 const uint _num_workers;
4562
4563 // Variables used to claim nmethods.
4564 nmethod* _first_nmethod;
4565 volatile nmethod* _claimed_nmethod;
4566
4567 // The list of nmethods that need to be processed by the second pass.
4568 volatile nmethod* _postponed_list;
4569 volatile uint _num_entered_barrier;
4570
4571 public:
4572 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
4573 _is_alive(is_alive),
4574 _unloading_occurred(unloading_occurred),
4575 _num_workers(num_workers),
4576 _first_nmethod(NULL),
4577 _claimed_nmethod(NULL),
4578 _postponed_list(NULL),
4579 _num_entered_barrier(0)
4580 {
4581 nmethod::increase_unloading_clock();
4582 // Get first alive nmethod
4583 NMethodIterator iter = NMethodIterator();
4584 if(iter.next_alive()) {
4585 _first_nmethod = iter.method();
4586 }
4587 _claimed_nmethod = (volatile nmethod*)_first_nmethod;
4588 }
4589
4590 ~G1CodeCacheUnloadingTask() {
4591 CodeCache::verify_clean_inline_caches();
4592
4593 CodeCache::set_needs_cache_clean(false);
4594 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
4595
4596 CodeCache::verify_icholder_relocations();
4597 }
4598
4599 private:
4600 void add_to_postponed_list(nmethod* nm) {
4601 nmethod* old;
4602 do {
4603 old = (nmethod*)_postponed_list;
4604 nm->set_unloading_next(old);
4605 } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old);
4606 }
4607
4608 void clean_nmethod(nmethod* nm) {
4609 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
4610
4611 if (postponed) {
4612 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
4613 add_to_postponed_list(nm);
4614 }
4615
4616 // Mark that this thread has been cleaned/unloaded.
4617 // After this call, it will be safe to ask if this nmethod was unloaded or not.
4618 nm->set_unloading_clock(nmethod::global_unloading_clock());
4619 }
4620
4621 void clean_nmethod_postponed(nmethod* nm) {
4622 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
4623 }
4624
4625 static const int MaxClaimNmethods = 16;
4626
4627 void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) {
4628 nmethod* first;
4629 NMethodIterator last;
4630
4631 do {
4632 *num_claimed_nmethods = 0;
4633
4634 first = (nmethod*)_claimed_nmethod;
4635 last = NMethodIterator(first);
4636
4637 if (first != NULL) {
4638
4639 for (int i = 0; i < MaxClaimNmethods; i++) {
4640 if (!last.next_alive()) {
4641 break;
4642 }
4643 claimed_nmethods[i] = last.method();
4644 (*num_claimed_nmethods)++;
4645 }
4646 }
4647
4648 } while ((nmethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first);
4649 }
4650
4651 nmethod* claim_postponed_nmethod() {
4652 nmethod* claim;
4653 nmethod* next;
4654
4655 do {
4656 claim = (nmethod*)_postponed_list;
4657 if (claim == NULL) {
4658 return NULL;
4659 }
4660
4661 next = claim->unloading_next();
4662
4663 } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim);
4664
4665 return claim;
4666 }
4667
4668 public:
4669 // Mark that we're done with the first pass of nmethod cleaning.
4670 void barrier_mark(uint worker_id) {
4671 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
4672 _num_entered_barrier++;
4673 if (_num_entered_barrier == _num_workers) {
4674 ml.notify_all();
4675 }
4676 }
4677
4678 // See if we have to wait for the other workers to
4679 // finish their first-pass nmethod cleaning work.
4680 void barrier_wait(uint worker_id) {
4681 if (_num_entered_barrier < _num_workers) {
4682 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
4683 while (_num_entered_barrier < _num_workers) {
4684 ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
4685 }
4686 }
4687 }
4688
4689 // Cleaning and unloading of nmethods. Some work has to be postponed
4690 // to the second pass, when we know which nmethods survive.
4691 void work_first_pass(uint worker_id) {
4692 // The first nmethods is claimed by the first worker.
4693 if (worker_id == 0 && _first_nmethod != NULL) {
4694 clean_nmethod(_first_nmethod);
4695 _first_nmethod = NULL;
4696 }
4697
4698 int num_claimed_nmethods;
4699 nmethod* claimed_nmethods[MaxClaimNmethods];
4700
4701 while (true) {
4702 claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
4703
4704 if (num_claimed_nmethods == 0) {
4705 break;
4706 }
4707
4708 for (int i = 0; i < num_claimed_nmethods; i++) {
4709 clean_nmethod(claimed_nmethods[i]);
4710 }
4711 }
4712 }
4713
4714 void work_second_pass(uint worker_id) {
4715 nmethod* nm;
4716 // Take care of postponed nmethods.
4717 while ((nm = claim_postponed_nmethod()) != NULL) {
4718 clean_nmethod_postponed(nm);
4719 }
4720 }
4721 };
4722
4723 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never);
4724
4725 class G1KlassCleaningTask : public StackObj {
4726 BoolObjectClosure* _is_alive;
4727 volatile jint _clean_klass_tree_claimed;
4728 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
4729
4730 public:
4731 G1KlassCleaningTask(BoolObjectClosure* is_alive) :
4732 _is_alive(is_alive),
4733 _clean_klass_tree_claimed(0),
4734 _klass_iterator() {
4735 }
4736
4737 private:
4738 bool claim_clean_klass_tree_task() {
4739 if (_clean_klass_tree_claimed) {
4740 return false;
4741 }
4742
4743 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0;
4744 }
4745
4746 InstanceKlass* claim_next_klass() {
4747 Klass* klass;
4748 do {
4749 klass =_klass_iterator.next_klass();
4750 } while (klass != NULL && !klass->oop_is_instance());
4751
4752 return (InstanceKlass*)klass;
4753 }
4754
4755 public:
4756
4757 void clean_klass(InstanceKlass* ik) {
4758 ik->clean_implementors_list(_is_alive);
4759 ik->clean_method_data(_is_alive);
4760
4761 // G1 specific cleanup work that has
4762 // been moved here to be done in parallel.
4763 ik->clean_dependent_nmethods();
4764 }
4765
4766 void work() {
4767 ResourceMark rm;
4768
4769 // One worker will clean the subklass/sibling klass tree.
4770 if (claim_clean_klass_tree_task()) {
4771 Klass::clean_subklass_tree(_is_alive);
4772 }
4773
4774 // All workers will help cleaning the classes,
4775 InstanceKlass* klass;
4776 while ((klass = claim_next_klass()) != NULL) {
4777 clean_klass(klass);
4778 }
4779 }
4780 };
4781
4782 // To minimize the remark pause times, the tasks below are done in parallel.
4783 class G1ParallelCleaningTask : public AbstractGangTask {
4784 private:
4785 G1StringSymbolTableUnlinkTask _string_symbol_task;
4786 G1CodeCacheUnloadingTask _code_cache_task;
4787 G1KlassCleaningTask _klass_cleaning_task;
4788
4789 public:
4790 // The constructor is run in the VMThread.
4791 G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) :
4792 AbstractGangTask("Parallel Cleaning"),
4793 _string_symbol_task(is_alive, process_strings, process_symbols),
4794 _code_cache_task(num_workers, is_alive, unloading_occurred),
4795 _klass_cleaning_task(is_alive) {
4796 }
4797
4798 // The parallel work done by all worker threads.
4799 void work(uint worker_id) {
4800 // Do first pass of code cache cleaning.
4801 _code_cache_task.work_first_pass(worker_id);
4802
4803 // Let the threads mark that the first pass is done.
4804 _code_cache_task.barrier_mark(worker_id);
4805
4806 // Clean the Strings and Symbols.
4807 _string_symbol_task.work(worker_id);
4808
4809 // Wait for all workers to finish the first code cache cleaning pass.
4810 _code_cache_task.barrier_wait(worker_id);
4811
4812 // Do the second code cache cleaning work, which realize on
4813 // the liveness information gathered during the first pass.
4814 _code_cache_task.work_second_pass(worker_id);
4815
4816 // Clean all klasses that were not unloaded.
4817 _klass_cleaning_task.work();
4818 }
4819 };
4820
4821
4822 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive,
4823 bool process_strings,
4824 bool process_symbols,
4825 bool class_unloading_occurred) {
4826 uint n_workers = workers()->active_workers();
4827
4828 G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols,
4829 n_workers, class_unloading_occurred);
4830 set_par_threads(n_workers);
4831 workers()->run_task(&g1_unlink_task);
4832 set_par_threads(0);
4833 }
4834
4835 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive,
4836 bool process_strings, bool process_symbols) {
4837 {
4838 uint n_workers = workers()->active_workers();
4839 G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols);
4840 set_par_threads(n_workers);
4841 workers()->run_task(&g1_unlink_task);
4842 set_par_threads(0);
4843 }
4844
4845 if (G1StringDedup::is_enabled()) {
4846 G1StringDedup::unlink(is_alive);
4847 }
4848 }
4849
4850 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
4851 private:
4852 DirtyCardQueueSet* _queue;
4853 public:
4854 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue) : AbstractGangTask("Redirty Cards"), _queue(queue) { }
4855
4856 virtual void work(uint worker_id) {
4857 G1GCPhaseTimes* phase_times = G1CollectedHeap::heap()->g1_policy()->phase_times();
4858 G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id);
4859
4860 RedirtyLoggedCardTableEntryClosure cl;
4861 _queue->par_apply_closure_to_all_completed_buffers(&cl);
4862
4863 phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_processed());
4864 }
4865 };
4866
4867 void G1CollectedHeap::redirty_logged_cards() {
4868 double redirty_logged_cards_start = os::elapsedTime();
4869
4870 uint n_workers = workers()->active_workers();
4871
4872 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set());
4873 dirty_card_queue_set().reset_for_par_iteration();
4874 set_par_threads(n_workers);
4875 workers()->run_task(&redirty_task);
4876 set_par_threads(0);
4877
4878 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
4879 dcq.merge_bufferlists(&dirty_card_queue_set());
4880 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
4881
4882 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
4883 }
4884
4885 // Weak Reference Processing support
4886
4887 // An always "is_alive" closure that is used to preserve referents.
4888 // If the object is non-null then it's alive. Used in the preservation
4889 // of referent objects that are pointed to by reference objects
4890 // discovered by the CM ref processor.
4891 class G1AlwaysAliveClosure: public BoolObjectClosure {
4892 G1CollectedHeap* _g1;
4893 public:
4894 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
4895 bool do_object_b(oop p) {
4896 if (p != NULL) {
4897 return true;
4898 }
4899 return false;
4900 }
4901 };
4902
4903 bool G1STWIsAliveClosure::do_object_b(oop p) {
4904 // An object is reachable if it is outside the collection set,
4905 // or is inside and copied.
4906 return !_g1->obj_in_cs(p) || p->is_forwarded();
4907 }
4908
4909 // Non Copying Keep Alive closure
4910 class G1KeepAliveClosure: public OopClosure {
4911 G1CollectedHeap* _g1;
4912 public:
4913 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
4914 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
4915 void do_oop(oop* p) {
4916 oop obj = *p;
4917 assert(obj != NULL, "the caller should have filtered out NULL values");
4918
4919 const InCSetState cset_state = _g1->in_cset_state(obj);
4920 if (!cset_state.is_in_cset_or_humongous()) {
4921 return;
4922 }
4923 if (cset_state.is_in_cset()) {
4924 assert( obj->is_forwarded(), "invariant" );
4925 *p = obj->forwardee();
4926 } else {
4927 assert(!obj->is_forwarded(), "invariant" );
4928 assert(cset_state.is_humongous(),
4929 err_msg("Only allowed InCSet state is IsHumongous, but is %d", cset_state.value()));
4930 _g1->set_humongous_is_live(obj);
4931 }
4932 }
4933 };
4934
4935 // Copying Keep Alive closure - can be called from both
4936 // serial and parallel code as long as different worker
4937 // threads utilize different G1ParScanThreadState instances
4938 // and different queues.
4939
4940 class G1CopyingKeepAliveClosure: public OopClosure {
4941 G1CollectedHeap* _g1h;
4942 OopClosure* _copy_non_heap_obj_cl;
4943 G1ParScanThreadState* _par_scan_state;
4944
4945 public:
4946 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
4947 OopClosure* non_heap_obj_cl,
4948 G1ParScanThreadState* pss):
4949 _g1h(g1h),
4950 _copy_non_heap_obj_cl(non_heap_obj_cl),
4951 _par_scan_state(pss)
4952 {}
4953
4954 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
4955 virtual void do_oop( oop* p) { do_oop_work(p); }
4956
4957 template <class T> void do_oop_work(T* p) {
4958 oop obj = oopDesc::load_decode_heap_oop(p);
4959
4960 if (_g1h->is_in_cset_or_humongous(obj)) {
4961 // If the referent object has been forwarded (either copied
4962 // to a new location or to itself in the event of an
4963 // evacuation failure) then we need to update the reference
4964 // field and, if both reference and referent are in the G1
4965 // heap, update the RSet for the referent.
4966 //
4967 // If the referent has not been forwarded then we have to keep
4968 // it alive by policy. Therefore we have copy the referent.
4969 //
4970 // If the reference field is in the G1 heap then we can push
4971 // on the PSS queue. When the queue is drained (after each
4972 // phase of reference processing) the object and it's followers
4973 // will be copied, the reference field set to point to the
4974 // new location, and the RSet updated. Otherwise we need to
4975 // use the the non-heap or metadata closures directly to copy
4976 // the referent object and update the pointer, while avoiding
4977 // updating the RSet.
4978
4979 if (_g1h->is_in_g1_reserved(p)) {
4980 _par_scan_state->push_on_queue(p);
4981 } else {
4982 assert(!Metaspace::contains((const void*)p),
4983 err_msg("Unexpectedly found a pointer from metadata: "
4984 PTR_FORMAT, p));
4985 _copy_non_heap_obj_cl->do_oop(p);
4986 }
4987 }
4988 }
4989 };
4990
4991 // Serial drain queue closure. Called as the 'complete_gc'
4992 // closure for each discovered list in some of the
4993 // reference processing phases.
4994
4995 class G1STWDrainQueueClosure: public VoidClosure {
4996 protected:
4997 G1CollectedHeap* _g1h;
4998 G1ParScanThreadState* _par_scan_state;
4999
5000 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
5001
5002 public:
5003 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
5004 _g1h(g1h),
5005 _par_scan_state(pss)
5006 { }
5007
5008 void do_void() {
5009 G1ParScanThreadState* const pss = par_scan_state();
5010 pss->trim_queue();
5011 }
5012 };
5013
5014 // Parallel Reference Processing closures
5015
5016 // Implementation of AbstractRefProcTaskExecutor for parallel reference
5017 // processing during G1 evacuation pauses.
5018
5019 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5020 private:
5021 G1CollectedHeap* _g1h;
5022 RefToScanQueueSet* _queues;
5023 FlexibleWorkGang* _workers;
5024 int _active_workers;
5025
5026 public:
5027 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5028 FlexibleWorkGang* workers,
5029 RefToScanQueueSet *task_queues,
5030 int n_workers) :
5031 _g1h(g1h),
5032 _queues(task_queues),
5033 _workers(workers),
5034 _active_workers(n_workers)
5035 {
5036 assert(n_workers > 0, "shouldn't call this otherwise");
5037 }
5038
5039 // Executes the given task using concurrent marking worker threads.
5040 virtual void execute(ProcessTask& task);
5041 virtual void execute(EnqueueTask& task);
5042 };
5043
5044 // Gang task for possibly parallel reference processing
5045
5046 class G1STWRefProcTaskProxy: public AbstractGangTask {
5047 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5048 ProcessTask& _proc_task;
5049 G1CollectedHeap* _g1h;
5050 RefToScanQueueSet *_task_queues;
5051 ParallelTaskTerminator* _terminator;
5052
5053 public:
5054 G1STWRefProcTaskProxy(ProcessTask& proc_task,
5055 G1CollectedHeap* g1h,
5056 RefToScanQueueSet *task_queues,
5057 ParallelTaskTerminator* terminator) :
5058 AbstractGangTask("Process reference objects in parallel"),
5059 _proc_task(proc_task),
5060 _g1h(g1h),
5061 _task_queues(task_queues),
5062 _terminator(terminator)
5063 {}
5064
5065 virtual void work(uint worker_id) {
5066 // The reference processing task executed by a single worker.
5067 ResourceMark rm;
5068 HandleMark hm;
5069
5070 G1STWIsAliveClosure is_alive(_g1h);
5071
5072 G1ParScanThreadState pss(_g1h, worker_id, NULL);
5073 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5074
5075 pss.set_evac_failure_closure(&evac_failure_cl);
5076
5077 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5078
5079 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5080
5081 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5082
5083 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5084 // We also need to mark copied objects.
5085 copy_non_heap_cl = ©_mark_non_heap_cl;
5086 }
5087
5088 // Keep alive closure.
5089 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5090
5091 // Complete GC closure
5092 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5093
5094 // Call the reference processing task's work routine.
5095 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5096
5097 // Note we cannot assert that the refs array is empty here as not all
5098 // of the processing tasks (specifically phase2 - pp2_work) execute
5099 // the complete_gc closure (which ordinarily would drain the queue) so
5100 // the queue may not be empty.
5101 }
5102 };
5103
5104 // Driver routine for parallel reference processing.
5105 // Creates an instance of the ref processing gang
5106 // task and has the worker threads execute it.
5107 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5108 assert(_workers != NULL, "Need parallel worker threads.");
5109
5110 ParallelTaskTerminator terminator(_active_workers, _queues);
5111 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5112
5113 _g1h->set_par_threads(_active_workers);
5114 _workers->run_task(&proc_task_proxy);
5115 _g1h->set_par_threads(0);
5116 }
5117
5118 // Gang task for parallel reference enqueueing.
5119
5120 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5121 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5122 EnqueueTask& _enq_task;
5123
5124 public:
5125 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5126 AbstractGangTask("Enqueue reference objects in parallel"),
5127 _enq_task(enq_task)
5128 { }
5129
5130 virtual void work(uint worker_id) {
5131 _enq_task.work(worker_id);
5132 }
5133 };
5134
5135 // Driver routine for parallel reference enqueueing.
5136 // Creates an instance of the ref enqueueing gang
5137 // task and has the worker threads execute it.
5138
5139 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5140 assert(_workers != NULL, "Need parallel worker threads.");
5141
5142 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5143
5144 _g1h->set_par_threads(_active_workers);
5145 _workers->run_task(&enq_task_proxy);
5146 _g1h->set_par_threads(0);
5147 }
5148
5149 // End of weak reference support closures
5150
5151 // Abstract task used to preserve (i.e. copy) any referent objects
5152 // that are in the collection set and are pointed to by reference
5153 // objects discovered by the CM ref processor.
5154
5155 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5156 protected:
5157 G1CollectedHeap* _g1h;
5158 RefToScanQueueSet *_queues;
5159 ParallelTaskTerminator _terminator;
5160 uint _n_workers;
5161
5162 public:
5163 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
5164 AbstractGangTask("ParPreserveCMReferents"),
5165 _g1h(g1h),
5166 _queues(task_queues),
5167 _terminator(workers, _queues),
5168 _n_workers(workers)
5169 { }
5170
5171 void work(uint worker_id) {
5172 ResourceMark rm;
5173 HandleMark hm;
5174
5175 G1ParScanThreadState pss(_g1h, worker_id, NULL);
5176 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5177
5178 pss.set_evac_failure_closure(&evac_failure_cl);
5179
5180 assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5181
5182 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5183
5184 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5185
5186 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5187
5188 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5189 // We also need to mark copied objects.
5190 copy_non_heap_cl = ©_mark_non_heap_cl;
5191 }
5192
5193 // Is alive closure
5194 G1AlwaysAliveClosure always_alive(_g1h);
5195
5196 // Copying keep alive closure. Applied to referent objects that need
5197 // to be copied.
5198 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5199
5200 ReferenceProcessor* rp = _g1h->ref_processor_cm();
5201
5202 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5203 uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5204
5205 // limit is set using max_num_q() - which was set using ParallelGCThreads.
5206 // So this must be true - but assert just in case someone decides to
5207 // change the worker ids.
5208 assert(worker_id < limit, "sanity");
5209 assert(!rp->discovery_is_atomic(), "check this code");
5210
5211 // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5212 for (uint idx = worker_id; idx < limit; idx += stride) {
5213 DiscoveredList& ref_list = rp->discovered_refs()[idx];
5214
5215 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5216 while (iter.has_next()) {
5217 // Since discovery is not atomic for the CM ref processor, we
5218 // can see some null referent objects.
5219 iter.load_ptrs(DEBUG_ONLY(true));
5220 oop ref = iter.obj();
5221
5222 // This will filter nulls.
5223 if (iter.is_referent_alive()) {
5224 iter.make_referent_alive();
5225 }
5226 iter.move_to_next();
5227 }
5228 }
5229
5230 // Drain the queue - which may cause stealing
5231 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5232 drain_queue.do_void();
5233 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5234 assert(pss.queue_is_empty(), "should be");
5235 }
5236 };
5237
5238 // Weak Reference processing during an evacuation pause (part 1).
5239 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) {
5240 double ref_proc_start = os::elapsedTime();
5241
5242 ReferenceProcessor* rp = _ref_processor_stw;
5243 assert(rp->discovery_enabled(), "should have been enabled");
5244
5245 // Any reference objects, in the collection set, that were 'discovered'
5246 // by the CM ref processor should have already been copied (either by
5247 // applying the external root copy closure to the discovered lists, or
5248 // by following an RSet entry).
5249 //
5250 // But some of the referents, that are in the collection set, that these
5251 // reference objects point to may not have been copied: the STW ref
5252 // processor would have seen that the reference object had already
5253 // been 'discovered' and would have skipped discovering the reference,
5254 // but would not have treated the reference object as a regular oop.
5255 // As a result the copy closure would not have been applied to the
5256 // referent object.
5257 //
5258 // We need to explicitly copy these referent objects - the references
5259 // will be processed at the end of remarking.
5260 //
5261 // We also need to do this copying before we process the reference
5262 // objects discovered by the STW ref processor in case one of these
5263 // referents points to another object which is also referenced by an
5264 // object discovered by the STW ref processor.
5265
5266 assert(no_of_gc_workers == workers()->active_workers(), "Need to reset active GC workers");
5267
5268 set_par_threads(no_of_gc_workers);
5269 G1ParPreserveCMReferentsTask keep_cm_referents(this,
5270 no_of_gc_workers,
5271 _task_queues);
5272
5273 workers()->run_task(&keep_cm_referents);
5274
5275 set_par_threads(0);
5276
5277 // Closure to test whether a referent is alive.
5278 G1STWIsAliveClosure is_alive(this);
5279
5280 // Even when parallel reference processing is enabled, the processing
5281 // of JNI refs is serial and performed serially by the current thread
5282 // rather than by a worker. The following PSS will be used for processing
5283 // JNI refs.
5284
5285 // Use only a single queue for this PSS.
5286 G1ParScanThreadState pss(this, 0, NULL);
5287
5288 // We do not embed a reference processor in the copying/scanning
5289 // closures while we're actually processing the discovered
5290 // reference objects.
5291 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5292
5293 pss.set_evac_failure_closure(&evac_failure_cl);
5294
5295 assert(pss.queue_is_empty(), "pre-condition");
5296
5297 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL);
5298
5299 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5300
5301 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5302
5303 if (g1_policy()->during_initial_mark_pause()) {
5304 // We also need to mark copied objects.
5305 copy_non_heap_cl = ©_mark_non_heap_cl;
5306 }
5307
5308 // Keep alive closure.
5309 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, &pss);
5310
5311 // Serial Complete GC closure
5312 G1STWDrainQueueClosure drain_queue(this, &pss);
5313
5314 // Setup the soft refs policy...
5315 rp->setup_policy(false);
5316
5317 ReferenceProcessorStats stats;
5318 if (!rp->processing_is_mt()) {
5319 // Serial reference processing...
5320 stats = rp->process_discovered_references(&is_alive,
5321 &keep_alive,
5322 &drain_queue,
5323 NULL,
5324 _gc_timer_stw,
5325 _gc_tracer_stw->gc_id());
5326 } else {
5327 // Parallel reference processing
5328 assert(rp->num_q() == no_of_gc_workers, "sanity");
5329 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5330
5331 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5332 stats = rp->process_discovered_references(&is_alive,
5333 &keep_alive,
5334 &drain_queue,
5335 &par_task_executor,
5336 _gc_timer_stw,
5337 _gc_tracer_stw->gc_id());
5338 }
5339
5340 _gc_tracer_stw->report_gc_reference_stats(stats);
5341
5342 // We have completed copying any necessary live referent objects.
5343 assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5344
5345 double ref_proc_time = os::elapsedTime() - ref_proc_start;
5346 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5347 }
5348
5349 // Weak Reference processing during an evacuation pause (part 2).
5350 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) {
5351 double ref_enq_start = os::elapsedTime();
5352
5353 ReferenceProcessor* rp = _ref_processor_stw;
5354 assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5355
5356 // Now enqueue any remaining on the discovered lists on to
5357 // the pending list.
5358 if (!rp->processing_is_mt()) {
5359 // Serial reference processing...
5360 rp->enqueue_discovered_references();
5361 } else {
5362 // Parallel reference enqueueing
5363
5364 assert(no_of_gc_workers == workers()->active_workers(),
5365 "Need to reset active workers");
5366 assert(rp->num_q() == no_of_gc_workers, "sanity");
5367 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5368
5369 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5370 rp->enqueue_discovered_references(&par_task_executor);
5371 }
5372
5373 rp->verify_no_references_recorded();
5374 assert(!rp->discovery_enabled(), "should have been disabled");
5375
5376 // FIXME
5377 // CM's reference processing also cleans up the string and symbol tables.
5378 // Should we do that here also? We could, but it is a serial operation
5379 // and could significantly increase the pause time.
5380
5381 double ref_enq_time = os::elapsedTime() - ref_enq_start;
5382 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5383 }
5384
5385 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) {
5386 _expand_heap_after_alloc_failure = true;
5387 _evacuation_failed = false;
5388
5389 // Should G1EvacuationFailureALot be in effect for this GC?
5390 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
5391
5392 g1_rem_set()->prepare_for_oops_into_collection_set_do();
5393
5394 // Disable the hot card cache.
5395 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
5396 hot_card_cache->reset_hot_cache_claimed_index();
5397 hot_card_cache->set_use_cache(false);
5398
5399 const uint n_workers = workers()->active_workers();
5400 assert(UseDynamicNumberOfGCThreads ||
5401 n_workers == workers()->total_workers(),
5402 "If not dynamic should be using all the workers");
5403 set_par_threads(n_workers);
5404
5405
5406 init_for_evac_failure(NULL);
5407
5408 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5409 double start_par_time_sec = os::elapsedTime();
5410 double end_par_time_sec;
5411
5412 {
5413 G1RootProcessor root_processor(this);
5414 G1ParTask g1_par_task(this, _task_queues, &root_processor);
5415 // InitialMark needs claim bits to keep track of the marked-through CLDs.
5416 if (g1_policy()->during_initial_mark_pause()) {
5417 ClassLoaderDataGraph::clear_claimed_marks();
5418 }
5419
5420 // The individual threads will set their evac-failure closures.
5421 if (PrintTerminationStats) G1ParScanThreadState::print_termination_stats_hdr();
5422 // These tasks use ShareHeap::_process_strong_tasks
5423 assert(UseDynamicNumberOfGCThreads ||
5424 workers()->active_workers() == workers()->total_workers(),
5425 "If not dynamic should be using all the workers");
5426 workers()->run_task(&g1_par_task);
5427 end_par_time_sec = os::elapsedTime();
5428
5429 // Closing the inner scope will execute the destructor
5430 // for the G1RootProcessor object. We record the current
5431 // elapsed time before closing the scope so that time
5432 // taken for the destructor is NOT included in the
5433 // reported parallel time.
5434 }
5435
5436 G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
5437
5438 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5439 phase_times->record_par_time(par_time_ms);
5440
5441 double code_root_fixup_time_ms =
5442 (os::elapsedTime() - end_par_time_sec) * 1000.0;
5443 phase_times->record_code_root_fixup_time(code_root_fixup_time_ms);
5444
5445 set_par_threads(0);
5446
5447 // Process any discovered reference objects - we have
5448 // to do this _before_ we retire the GC alloc regions
5449 // as we may have to copy some 'reachable' referent
5450 // objects (and their reachable sub-graphs) that were
5451 // not copied during the pause.
5452 process_discovered_references(n_workers);
5453
5454 if (G1StringDedup::is_enabled()) {
5455 double fixup_start = os::elapsedTime();
5456
5457 G1STWIsAliveClosure is_alive(this);
5458 G1KeepAliveClosure keep_alive(this);
5459 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, phase_times);
5460
5461 double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
5462 phase_times->record_string_dedup_fixup_time(fixup_time_ms);
5463 }
5464
5465 _allocator->release_gc_alloc_regions(n_workers, evacuation_info);
5466 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5467
5468 // Reset and re-enable the hot card cache.
5469 // Note the counts for the cards in the regions in the
5470 // collection set are reset when the collection set is freed.
5471 hot_card_cache->reset_hot_cache();
5472 hot_card_cache->set_use_cache(true);
5473
5474 purge_code_root_memory();
5475
5476 finalize_for_evac_failure();
5477
5478 if (evacuation_failed()) {
5479 remove_self_forwarding_pointers();
5480
5481 // Reset the G1EvacuationFailureALot counters and flags
5482 // Note: the values are reset only when an actual
5483 // evacuation failure occurs.
5484 NOT_PRODUCT(reset_evacuation_should_fail();)
5485 }
5486
5487 // Enqueue any remaining references remaining on the STW
5488 // reference processor's discovered lists. We need to do
5489 // this after the card table is cleaned (and verified) as
5490 // the act of enqueueing entries on to the pending list
5491 // will log these updates (and dirty their associated
5492 // cards). We need these updates logged to update any
5493 // RSets.
5494 enqueue_discovered_references(n_workers);
5495
5496 redirty_logged_cards();
5497 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5498 }
5499
5500 void G1CollectedHeap::free_region(HeapRegion* hr,
5501 FreeRegionList* free_list,
5502 bool par,
5503 bool locked) {
5504 assert(!hr->is_free(), "the region should not be free");
5505 assert(!hr->is_empty(), "the region should not be empty");
5506 assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
5507 assert(free_list != NULL, "pre-condition");
5508
5509 if (G1VerifyBitmaps) {
5510 MemRegion mr(hr->bottom(), hr->end());
5511 concurrent_mark()->clearRangePrevBitmap(mr);
5512 }
5513
5514 // Clear the card counts for this region.
5515 // Note: we only need to do this if the region is not young
5516 // (since we don't refine cards in young regions).
5517 if (!hr->is_young()) {
5518 _cg1r->hot_card_cache()->reset_card_counts(hr);
5519 }
5520 hr->hr_clear(par, true /* clear_space */, locked /* locked */);
5521 free_list->add_ordered(hr);
5522 }
5523
5524 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
5525 FreeRegionList* free_list,
5526 bool par) {
5527 assert(hr->is_starts_humongous(), "this is only for starts humongous regions");
5528 assert(free_list != NULL, "pre-condition");
5529
5530 size_t hr_capacity = hr->capacity();
5531 // We need to read this before we make the region non-humongous,
5532 // otherwise the information will be gone.
5533 uint last_index = hr->last_hc_index();
5534 hr->clear_humongous();
5535 free_region(hr, free_list, par);
5536
5537 uint i = hr->hrm_index() + 1;
5538 while (i < last_index) {
5539 HeapRegion* curr_hr = region_at(i);
5540 assert(curr_hr->is_continues_humongous(), "invariant");
5541 curr_hr->clear_humongous();
5542 free_region(curr_hr, free_list, par);
5543 i += 1;
5544 }
5545 }
5546
5547 void G1CollectedHeap::remove_from_old_sets(const HeapRegionSetCount& old_regions_removed,
5548 const HeapRegionSetCount& humongous_regions_removed) {
5549 if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 0) {
5550 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5551 _old_set.bulk_remove(old_regions_removed);
5552 _humongous_set.bulk_remove(humongous_regions_removed);
5553 }
5554
5555 }
5556
5557 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
5558 assert(list != NULL, "list can't be null");
5559 if (!list->is_empty()) {
5560 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
5561 _hrm.insert_list_into_free_list(list);
5562 }
5563 }
5564
5565 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
5566 _allocator->decrease_used(bytes);
5567 }
5568
5569 class G1ParCleanupCTTask : public AbstractGangTask {
5570 G1SATBCardTableModRefBS* _ct_bs;
5571 G1CollectedHeap* _g1h;
5572 HeapRegion* volatile _su_head;
5573 public:
5574 G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs,
5575 G1CollectedHeap* g1h) :
5576 AbstractGangTask("G1 Par Cleanup CT Task"),
5577 _ct_bs(ct_bs), _g1h(g1h) { }
5578
5579 void work(uint worker_id) {
5580 HeapRegion* r;
5581 while (r = _g1h->pop_dirty_cards_region()) {
5582 clear_cards(r);
5583 }
5584 }
5585
5586 void clear_cards(HeapRegion* r) {
5587 // Cards of the survivors should have already been dirtied.
5588 if (!r->is_survivor()) {
5589 _ct_bs->clear(MemRegion(r->bottom(), r->end()));
5590 }
5591 }
5592 };
5593
5594 #ifndef PRODUCT
5595 class G1VerifyCardTableCleanup: public HeapRegionClosure {
5596 G1CollectedHeap* _g1h;
5597 G1SATBCardTableModRefBS* _ct_bs;
5598 public:
5599 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs)
5600 : _g1h(g1h), _ct_bs(ct_bs) { }
5601 virtual bool doHeapRegion(HeapRegion* r) {
5602 if (r->is_survivor()) {
5603 _g1h->verify_dirty_region(r);
5604 } else {
5605 _g1h->verify_not_dirty_region(r);
5606 }
5607 return false;
5608 }
5609 };
5610
5611 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
5612 // All of the region should be clean.
5613 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5614 MemRegion mr(hr->bottom(), hr->end());
5615 ct_bs->verify_not_dirty_region(mr);
5616 }
5617
5618 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
5619 // We cannot guarantee that [bottom(),end()] is dirty. Threads
5620 // dirty allocated blocks as they allocate them. The thread that
5621 // retires each region and replaces it with a new one will do a
5622 // maximal allocation to fill in [pre_dummy_top(),end()] but will
5623 // not dirty that area (one less thing to have to do while holding
5624 // a lock). So we can only verify that [bottom(),pre_dummy_top()]
5625 // is dirty.
5626 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5627 MemRegion mr(hr->bottom(), hr->pre_dummy_top());
5628 if (hr->is_young()) {
5629 ct_bs->verify_g1_young_region(mr);
5630 } else {
5631 ct_bs->verify_dirty_region(mr);
5632 }
5633 }
5634
5635 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
5636 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5637 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
5638 verify_dirty_region(hr);
5639 }
5640 }
5641
5642 void G1CollectedHeap::verify_dirty_young_regions() {
5643 verify_dirty_young_list(_young_list->first_region());
5644 }
5645
5646 bool G1CollectedHeap::verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
5647 HeapWord* tams, HeapWord* end) {
5648 guarantee(tams <= end,
5649 err_msg("tams: "PTR_FORMAT" end: "PTR_FORMAT, tams, end));
5650 HeapWord* result = bitmap->getNextMarkedWordAddress(tams, end);
5651 if (result < end) {
5652 gclog_or_tty->cr();
5653 gclog_or_tty->print_cr("## wrong marked address on %s bitmap: "PTR_FORMAT,
5654 bitmap_name, result);
5655 gclog_or_tty->print_cr("## %s tams: "PTR_FORMAT" end: "PTR_FORMAT,
5656 bitmap_name, tams, end);
5657 return false;
5658 }
5659 return true;
5660 }
5661
5662 bool G1CollectedHeap::verify_bitmaps(const char* caller, HeapRegion* hr) {
5663 CMBitMapRO* prev_bitmap = concurrent_mark()->prevMarkBitMap();
5664 CMBitMapRO* next_bitmap = (CMBitMapRO*) concurrent_mark()->nextMarkBitMap();
5665
5666 HeapWord* bottom = hr->bottom();
5667 HeapWord* ptams = hr->prev_top_at_mark_start();
5668 HeapWord* ntams = hr->next_top_at_mark_start();
5669 HeapWord* end = hr->end();
5670
5671 bool res_p = verify_no_bits_over_tams("prev", prev_bitmap, ptams, end);
5672
5673 bool res_n = true;
5674 // We reset mark_in_progress() before we reset _cmThread->in_progress() and in this window
5675 // we do the clearing of the next bitmap concurrently. Thus, we can not verify the bitmap
5676 // if we happen to be in that state.
5677 if (mark_in_progress() || !_cmThread->in_progress()) {
5678 res_n = verify_no_bits_over_tams("next", next_bitmap, ntams, end);
5679 }
5680 if (!res_p || !res_n) {
5681 gclog_or_tty->print_cr("#### Bitmap verification failed for "HR_FORMAT,
5682 HR_FORMAT_PARAMS(hr));
5683 gclog_or_tty->print_cr("#### Caller: %s", caller);
5684 return false;
5685 }
5686 return true;
5687 }
5688
5689 void G1CollectedHeap::check_bitmaps(const char* caller, HeapRegion* hr) {
5690 if (!G1VerifyBitmaps) return;
5691
5692 guarantee(verify_bitmaps(caller, hr), "bitmap verification");
5693 }
5694
5695 class G1VerifyBitmapClosure : public HeapRegionClosure {
5696 private:
5697 const char* _caller;
5698 G1CollectedHeap* _g1h;
5699 bool _failures;
5700
5701 public:
5702 G1VerifyBitmapClosure(const char* caller, G1CollectedHeap* g1h) :
5703 _caller(caller), _g1h(g1h), _failures(false) { }
5704
5705 bool failures() { return _failures; }
5706
5707 virtual bool doHeapRegion(HeapRegion* hr) {
5708 if (hr->is_continues_humongous()) return false;
5709
5710 bool result = _g1h->verify_bitmaps(_caller, hr);
5711 if (!result) {
5712 _failures = true;
5713 }
5714 return false;
5715 }
5716 };
5717
5718 void G1CollectedHeap::check_bitmaps(const char* caller) {
5719 if (!G1VerifyBitmaps) return;
5720
5721 G1VerifyBitmapClosure cl(caller, this);
5722 heap_region_iterate(&cl);
5723 guarantee(!cl.failures(), "bitmap verification");
5724 }
5725
5726 class G1CheckCSetFastTableClosure : public HeapRegionClosure {
5727 private:
5728 bool _failures;
5729 public:
5730 G1CheckCSetFastTableClosure() : HeapRegionClosure(), _failures(false) { }
5731
5732 virtual bool doHeapRegion(HeapRegion* hr) {
5733 uint i = hr->hrm_index();
5734 InCSetState cset_state = (InCSetState) G1CollectedHeap::heap()->_in_cset_fast_test.get_by_index(i);
5735 if (hr->is_humongous()) {
5736 if (hr->in_collection_set()) {
5737 gclog_or_tty->print_cr("\n## humongous region %u in CSet", i);
5738 _failures = true;
5739 return true;
5740 }
5741 if (cset_state.is_in_cset()) {
5742 gclog_or_tty->print_cr("\n## inconsistent cset state %d for humongous region %u", cset_state.value(), i);
5743 _failures = true;
5744 return true;
5745 }
5746 if (hr->is_continues_humongous() && cset_state.is_humongous()) {
5747 gclog_or_tty->print_cr("\n## inconsistent cset state %d for continues humongous region %u", cset_state.value(), i);
5748 _failures = true;
5749 return true;
5750 }
5751 } else {
5752 if (cset_state.is_humongous()) {
5753 gclog_or_tty->print_cr("\n## inconsistent cset state %d for non-humongous region %u", cset_state.value(), i);
5754 _failures = true;
5755 return true;
5756 }
5757 if (hr->in_collection_set() != cset_state.is_in_cset()) {
5758 gclog_or_tty->print_cr("\n## in CSet %d / cset state %d inconsistency for region %u",
5759 hr->in_collection_set(), cset_state.value(), i);
5760 _failures = true;
5761 return true;
5762 }
5763 if (cset_state.is_in_cset()) {
5764 if (hr->is_young() != (cset_state.is_young())) {
5765 gclog_or_tty->print_cr("\n## is_young %d / cset state %d inconsistency for region %u",
5766 hr->is_young(), cset_state.value(), i);
5767 _failures = true;
5768 return true;
5769 }
5770 if (hr->is_old() != (cset_state.is_old())) {
5771 gclog_or_tty->print_cr("\n## is_old %d / cset state %d inconsistency for region %u",
5772 hr->is_old(), cset_state.value(), i);
5773 _failures = true;
5774 return true;
5775 }
5776 }
5777 }
5778 return false;
5779 }
5780
5781 bool failures() const { return _failures; }
5782 };
5783
5784 bool G1CollectedHeap::check_cset_fast_test() {
5785 G1CheckCSetFastTableClosure cl;
5786 _hrm.iterate(&cl);
5787 return !cl.failures();
5788 }
5789 #endif // PRODUCT
5790
5791 void G1CollectedHeap::cleanUpCardTable() {
5792 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5793 double start = os::elapsedTime();
5794
5795 {
5796 // Iterate over the dirty cards region list.
5797 G1ParCleanupCTTask cleanup_task(ct_bs, this);
5798
5799 set_par_threads();
5800 workers()->run_task(&cleanup_task);
5801 set_par_threads(0);
5802 #ifndef PRODUCT
5803 if (G1VerifyCTCleanup || VerifyAfterGC) {
5804 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
5805 heap_region_iterate(&cleanup_verifier);
5806 }
5807 #endif
5808 }
5809
5810 double elapsed = os::elapsedTime() - start;
5811 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
5812 }
5813
5814 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) {
5815 size_t pre_used = 0;
5816 FreeRegionList local_free_list("Local List for CSet Freeing");
5817
5818 double young_time_ms = 0.0;
5819 double non_young_time_ms = 0.0;
5820
5821 // Since the collection set is a superset of the the young list,
5822 // all we need to do to clear the young list is clear its
5823 // head and length, and unlink any young regions in the code below
5824 _young_list->clear();
5825
5826 G1CollectorPolicy* policy = g1_policy();
5827
5828 double start_sec = os::elapsedTime();
5829 bool non_young = true;
5830
5831 HeapRegion* cur = cs_head;
5832 int age_bound = -1;
5833 size_t rs_lengths = 0;
5834
5835 while (cur != NULL) {
5836 assert(!is_on_master_free_list(cur), "sanity");
5837 if (non_young) {
5838 if (cur->is_young()) {
5839 double end_sec = os::elapsedTime();
5840 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5841 non_young_time_ms += elapsed_ms;
5842
5843 start_sec = os::elapsedTime();
5844 non_young = false;
5845 }
5846 } else {
5847 if (!cur->is_young()) {
5848 double end_sec = os::elapsedTime();
5849 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5850 young_time_ms += elapsed_ms;
5851
5852 start_sec = os::elapsedTime();
5853 non_young = true;
5854 }
5855 }
5856
5857 rs_lengths += cur->rem_set()->occupied_locked();
5858
5859 HeapRegion* next = cur->next_in_collection_set();
5860 assert(cur->in_collection_set(), "bad CS");
5861 cur->set_next_in_collection_set(NULL);
5862 clear_in_cset(cur);
5863
5864 if (cur->is_young()) {
5865 int index = cur->young_index_in_cset();
5866 assert(index != -1, "invariant");
5867 assert((uint) index < policy->young_cset_region_length(), "invariant");
5868 size_t words_survived = _surviving_young_words[index];
5869 cur->record_surv_words_in_group(words_survived);
5870
5871 // At this point the we have 'popped' cur from the collection set
5872 // (linked via next_in_collection_set()) but it is still in the
5873 // young list (linked via next_young_region()). Clear the
5874 // _next_young_region field.
5875 cur->set_next_young_region(NULL);
5876 } else {
5877 int index = cur->young_index_in_cset();
5878 assert(index == -1, "invariant");
5879 }
5880
5881 assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
5882 (!cur->is_young() && cur->young_index_in_cset() == -1),
5883 "invariant" );
5884
5885 if (!cur->evacuation_failed()) {
5886 MemRegion used_mr = cur->used_region();
5887
5888 // And the region is empty.
5889 assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
5890 pre_used += cur->used();
5891 free_region(cur, &local_free_list, false /* par */, true /* locked */);
5892 } else {
5893 cur->uninstall_surv_rate_group();
5894 if (cur->is_young()) {
5895 cur->set_young_index_in_cset(-1);
5896 }
5897 cur->set_evacuation_failed(false);
5898 // The region is now considered to be old.
5899 cur->set_old();
5900 _old_set.add(cur);
5901 evacuation_info.increment_collectionset_used_after(cur->used());
5902 }
5903 cur = next;
5904 }
5905
5906 evacuation_info.set_regions_freed(local_free_list.length());
5907 policy->record_max_rs_lengths(rs_lengths);
5908 policy->cset_regions_freed();
5909
5910 double end_sec = os::elapsedTime();
5911 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5912
5913 if (non_young) {
5914 non_young_time_ms += elapsed_ms;
5915 } else {
5916 young_time_ms += elapsed_ms;
5917 }
5918
5919 prepend_to_freelist(&local_free_list);
5920 decrement_summary_bytes(pre_used);
5921 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
5922 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
5923 }
5924
5925 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
5926 private:
5927 FreeRegionList* _free_region_list;
5928 HeapRegionSet* _proxy_set;
5929 HeapRegionSetCount _humongous_regions_removed;
5930 size_t _freed_bytes;
5931 public:
5932
5933 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
5934 _free_region_list(free_region_list), _humongous_regions_removed(), _freed_bytes(0) {
5935 }
5936
5937 virtual bool doHeapRegion(HeapRegion* r) {
5938 if (!r->is_starts_humongous()) {
5939 return false;
5940 }
5941
5942 G1CollectedHeap* g1h = G1CollectedHeap::heap();
5943
5944 oop obj = (oop)r->bottom();
5945 CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap();
5946
5947 // The following checks whether the humongous object is live are sufficient.
5948 // The main additional check (in addition to having a reference from the roots
5949 // or the young gen) is whether the humongous object has a remembered set entry.
5950 //
5951 // A humongous object cannot be live if there is no remembered set for it
5952 // because:
5953 // - there can be no references from within humongous starts regions referencing
5954 // the object because we never allocate other objects into them.
5955 // (I.e. there are no intra-region references that may be missed by the
5956 // remembered set)
5957 // - as soon there is a remembered set entry to the humongous starts region
5958 // (i.e. it has "escaped" to an old object) this remembered set entry will stay
5959 // until the end of a concurrent mark.
5960 //
5961 // It is not required to check whether the object has been found dead by marking
5962 // or not, in fact it would prevent reclamation within a concurrent cycle, as
5963 // all objects allocated during that time are considered live.
5964 // SATB marking is even more conservative than the remembered set.
5965 // So if at this point in the collection there is no remembered set entry,
5966 // nobody has a reference to it.
5967 // At the start of collection we flush all refinement logs, and remembered sets
5968 // are completely up-to-date wrt to references to the humongous object.
5969 //
5970 // Other implementation considerations:
5971 // - never consider object arrays at this time because they would pose
5972 // considerable effort for cleaning up the the remembered sets. This is
5973 // required because stale remembered sets might reference locations that
5974 // are currently allocated into.
5975 uint region_idx = r->hrm_index();
5976 if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
5977 !r->rem_set()->is_empty()) {
5978
5979 if (G1TraceEagerReclaimHumongousObjects) {
5980 gclog_or_tty->print_cr("Live humongous region %u size "SIZE_FORMAT" start "PTR_FORMAT" length "UINT32_FORMAT" with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is marked %d reclaim candidate %d type array %d",
5981 region_idx,
5982 obj->size()*HeapWordSize,
5983 r->bottom(),
5984 r->region_num(),
5985 r->rem_set()->occupied(),
5986 r->rem_set()->strong_code_roots_list_length(),
5987 next_bitmap->isMarked(r->bottom()),
5988 g1h->is_humongous_reclaim_candidate(region_idx),
5989 obj->is_typeArray()
5990 );
5991 }
5992
5993 return false;
5994 }
5995
5996 guarantee(obj->is_typeArray(),
5997 err_msg("Only eagerly reclaiming type arrays is supported, but the object "
5998 PTR_FORMAT " is not.",
5999 r->bottom()));
6000
6001 if (G1TraceEagerReclaimHumongousObjects) {
6002 gclog_or_tty->print_cr("Dead humongous region %u size "SIZE_FORMAT" start "PTR_FORMAT" length "UINT32_FORMAT" with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is marked %d reclaim candidate %d type array %d",
6003 region_idx,
6004 obj->size()*HeapWordSize,
6005 r->bottom(),
6006 r->region_num(),
6007 r->rem_set()->occupied(),
6008 r->rem_set()->strong_code_roots_list_length(),
6009 next_bitmap->isMarked(r->bottom()),
6010 g1h->is_humongous_reclaim_candidate(region_idx),
6011 obj->is_typeArray()
6012 );
6013 }
6014 // Need to clear mark bit of the humongous object if already set.
6015 if (next_bitmap->isMarked(r->bottom())) {
6016 next_bitmap->clear(r->bottom());
6017 }
6018 _freed_bytes += r->used();
6019 r->set_containing_set(NULL);
6020 _humongous_regions_removed.increment(1u, r->capacity());
6021 g1h->free_humongous_region(r, _free_region_list, false);
6022
6023 return false;
6024 }
6025
6026 HeapRegionSetCount& humongous_free_count() {
6027 return _humongous_regions_removed;
6028 }
6029
6030 size_t bytes_freed() const {
6031 return _freed_bytes;
6032 }
6033
6034 size_t humongous_reclaimed() const {
6035 return _humongous_regions_removed.length();
6036 }
6037 };
6038
6039 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
6040 assert_at_safepoint(true);
6041
6042 if (!G1EagerReclaimHumongousObjects ||
6043 (!_has_humongous_reclaim_candidates && !G1TraceEagerReclaimHumongousObjects)) {
6044 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
6045 return;
6046 }
6047
6048 double start_time = os::elapsedTime();
6049
6050 FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
6051
6052 G1FreeHumongousRegionClosure cl(&local_cleanup_list);
6053 heap_region_iterate(&cl);
6054
6055 HeapRegionSetCount empty_set;
6056 remove_from_old_sets(empty_set, cl.humongous_free_count());
6057
6058 G1HRPrinter* hrp = hr_printer();
6059 if (hrp->is_active()) {
6060 FreeRegionListIterator iter(&local_cleanup_list);
6061 while (iter.more_available()) {
6062 HeapRegion* hr = iter.get_next();
6063 hrp->cleanup(hr);
6064 }
6065 }
6066
6067 prepend_to_freelist(&local_cleanup_list);
6068 decrement_summary_bytes(cl.bytes_freed());
6069
6070 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
6071 cl.humongous_reclaimed());
6072 }
6073
6074 // This routine is similar to the above but does not record
6075 // any policy statistics or update free lists; we are abandoning
6076 // the current incremental collection set in preparation of a
6077 // full collection. After the full GC we will start to build up
6078 // the incremental collection set again.
6079 // This is only called when we're doing a full collection
6080 // and is immediately followed by the tearing down of the young list.
6081
6082 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
6083 HeapRegion* cur = cs_head;
6084
6085 while (cur != NULL) {
6086 HeapRegion* next = cur->next_in_collection_set();
6087 assert(cur->in_collection_set(), "bad CS");
6088 cur->set_next_in_collection_set(NULL);
6089 clear_in_cset(cur);
6090 cur->set_young_index_in_cset(-1);
6091 cur = next;
6092 }
6093 }
6094
6095 void G1CollectedHeap::set_free_regions_coming() {
6096 if (G1ConcRegionFreeingVerbose) {
6097 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6098 "setting free regions coming");
6099 }
6100
6101 assert(!free_regions_coming(), "pre-condition");
6102 _free_regions_coming = true;
6103 }
6104
6105 void G1CollectedHeap::reset_free_regions_coming() {
6106 assert(free_regions_coming(), "pre-condition");
6107
6108 {
6109 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6110 _free_regions_coming = false;
6111 SecondaryFreeList_lock->notify_all();
6112 }
6113
6114 if (G1ConcRegionFreeingVerbose) {
6115 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6116 "reset free regions coming");
6117 }
6118 }
6119
6120 void G1CollectedHeap::wait_while_free_regions_coming() {
6121 // Most of the time we won't have to wait, so let's do a quick test
6122 // first before we take the lock.
6123 if (!free_regions_coming()) {
6124 return;
6125 }
6126
6127 if (G1ConcRegionFreeingVerbose) {
6128 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6129 "waiting for free regions");
6130 }
6131
6132 {
6133 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6134 while (free_regions_coming()) {
6135 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
6136 }
6137 }
6138
6139 if (G1ConcRegionFreeingVerbose) {
6140 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6141 "done waiting for free regions");
6142 }
6143 }
6144
6145 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
6146 _young_list->push_region(hr);
6147 }
6148
6149 class NoYoungRegionsClosure: public HeapRegionClosure {
6150 private:
6151 bool _success;
6152 public:
6153 NoYoungRegionsClosure() : _success(true) { }
6154 bool doHeapRegion(HeapRegion* r) {
6155 if (r->is_young()) {
6156 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
6157 r->bottom(), r->end());
6158 _success = false;
6159 }
6160 return false;
6161 }
6162 bool success() { return _success; }
6163 };
6164
6165 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
6166 bool ret = _young_list->check_list_empty(check_sample);
6167
6168 if (check_heap) {
6169 NoYoungRegionsClosure closure;
6170 heap_region_iterate(&closure);
6171 ret = ret && closure.success();
6172 }
6173
6174 return ret;
6175 }
6176
6177 class TearDownRegionSetsClosure : public HeapRegionClosure {
6178 private:
6179 HeapRegionSet *_old_set;
6180
6181 public:
6182 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
6183
6184 bool doHeapRegion(HeapRegion* r) {
6185 if (r->is_old()) {
6186 _old_set->remove(r);
6187 } else {
6188 // We ignore free regions, we'll empty the free list afterwards.
6189 // We ignore young regions, we'll empty the young list afterwards.
6190 // We ignore humongous regions, we're not tearing down the
6191 // humongous regions set.
6192 assert(r->is_free() || r->is_young() || r->is_humongous(),
6193 "it cannot be another type");
6194 }
6195 return false;
6196 }
6197
6198 ~TearDownRegionSetsClosure() {
6199 assert(_old_set->is_empty(), "post-condition");
6200 }
6201 };
6202
6203 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6204 assert_at_safepoint(true /* should_be_vm_thread */);
6205
6206 if (!free_list_only) {
6207 TearDownRegionSetsClosure cl(&_old_set);
6208 heap_region_iterate(&cl);
6209
6210 // Note that emptying the _young_list is postponed and instead done as
6211 // the first step when rebuilding the regions sets again. The reason for
6212 // this is that during a full GC string deduplication needs to know if
6213 // a collected region was young or old when the full GC was initiated.
6214 }
6215 _hrm.remove_all_free_regions();
6216 }
6217
6218 class RebuildRegionSetsClosure : public HeapRegionClosure {
6219 private:
6220 bool _free_list_only;
6221 HeapRegionSet* _old_set;
6222 HeapRegionManager* _hrm;
6223 size_t _total_used;
6224
6225 public:
6226 RebuildRegionSetsClosure(bool free_list_only,
6227 HeapRegionSet* old_set, HeapRegionManager* hrm) :
6228 _free_list_only(free_list_only),
6229 _old_set(old_set), _hrm(hrm), _total_used(0) {
6230 assert(_hrm->num_free_regions() == 0, "pre-condition");
6231 if (!free_list_only) {
6232 assert(_old_set->is_empty(), "pre-condition");
6233 }
6234 }
6235
6236 bool doHeapRegion(HeapRegion* r) {
6237 if (r->is_continues_humongous()) {
6238 return false;
6239 }
6240
6241 if (r->is_empty()) {
6242 // Add free regions to the free list
6243 r->set_free();
6244 r->set_allocation_context(AllocationContext::system());
6245 _hrm->insert_into_free_list(r);
6246 } else if (!_free_list_only) {
6247 assert(!r->is_young(), "we should not come across young regions");
6248
6249 if (r->is_humongous()) {
6250 // We ignore humongous regions, we left the humongous set unchanged
6251 } else {
6252 // Objects that were compacted would have ended up on regions
6253 // that were previously old or free.
6254 assert(r->is_free() || r->is_old(), "invariant");
6255 // We now consider them old, so register as such.
6256 r->set_old();
6257 _old_set->add(r);
6258 }
6259 _total_used += r->used();
6260 }
6261
6262 return false;
6263 }
6264
6265 size_t total_used() {
6266 return _total_used;
6267 }
6268 };
6269
6270 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6271 assert_at_safepoint(true /* should_be_vm_thread */);
6272
6273 if (!free_list_only) {
6274 _young_list->empty_list();
6275 }
6276
6277 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
6278 heap_region_iterate(&cl);
6279
6280 if (!free_list_only) {
6281 _allocator->set_used(cl.total_used());
6282 }
6283 assert(_allocator->used_unlocked() == recalculate_used(),
6284 err_msg("inconsistent _allocator->used_unlocked(), "
6285 "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6286 _allocator->used_unlocked(), recalculate_used()));
6287 }
6288
6289 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6290 _refine_cte_cl->set_concurrent(concurrent);
6291 }
6292
6293 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6294 HeapRegion* hr = heap_region_containing(p);
6295 return hr->is_in(p);
6296 }
6297
6298 // Methods for the mutator alloc region
6299
6300 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6301 bool force) {
6302 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6303 assert(!force || g1_policy()->can_expand_young_list(),
6304 "if force is true we should be able to expand the young list");
6305 bool young_list_full = g1_policy()->is_young_list_full();
6306 if (force || !young_list_full) {
6307 HeapRegion* new_alloc_region = new_region(word_size,
6308 false /* is_old */,
6309 false /* do_expand */);
6310 if (new_alloc_region != NULL) {
6311 set_region_short_lived_locked(new_alloc_region);
6312 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6313 check_bitmaps("Mutator Region Allocation", new_alloc_region);
6314 return new_alloc_region;
6315 }
6316 }
6317 return NULL;
6318 }
6319
6320 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6321 size_t allocated_bytes) {
6322 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6323 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
6324
6325 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6326 _allocator->increase_used(allocated_bytes);
6327 _hr_printer.retire(alloc_region);
6328 // We update the eden sizes here, when the region is retired,
6329 // instead of when it's allocated, since this is the point that its
6330 // used space has been recored in _summary_bytes_used.
6331 g1mm()->update_eden_size();
6332 }
6333
6334 void G1CollectedHeap::set_par_threads() {
6335 // Don't change the number of workers. Use the value previously set
6336 // in the workgroup.
6337 uint n_workers = workers()->active_workers();
6338 assert(UseDynamicNumberOfGCThreads ||
6339 n_workers == workers()->total_workers(),
6340 "Otherwise should be using the total number of workers");
6341 if (n_workers == 0) {
6342 assert(false, "Should have been set in prior evacuation pause.");
6343 n_workers = ParallelGCThreads;
6344 workers()->set_active_workers(n_workers);
6345 }
6346 set_par_threads(n_workers);
6347 }
6348
6349 // Methods for the GC alloc regions
6350
6351 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6352 uint count,
6353 InCSetState dest) {
6354 assert(FreeList_lock->owned_by_self(), "pre-condition");
6355
6356 if (count < g1_policy()->max_regions(dest)) {
6357 const bool is_survivor = (dest.is_young());
6358 HeapRegion* new_alloc_region = new_region(word_size,
6359 !is_survivor,
6360 true /* do_expand */);
6361 if (new_alloc_region != NULL) {
6362 // We really only need to do this for old regions given that we
6363 // should never scan survivors. But it doesn't hurt to do it
6364 // for survivors too.
6365 new_alloc_region->record_timestamp();
6366 if (is_survivor) {
6367 new_alloc_region->set_survivor();
6368 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6369 check_bitmaps("Survivor Region Allocation", new_alloc_region);
6370 } else {
6371 new_alloc_region->set_old();
6372 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6373 check_bitmaps("Old Region Allocation", new_alloc_region);
6374 }
6375 bool during_im = g1_policy()->during_initial_mark_pause();
6376 new_alloc_region->note_start_of_copying(during_im);
6377 return new_alloc_region;
6378 }
6379 }
6380 return NULL;
6381 }
6382
6383 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6384 size_t allocated_bytes,
6385 InCSetState dest) {
6386 bool during_im = g1_policy()->during_initial_mark_pause();
6387 alloc_region->note_end_of_copying(during_im);
6388 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6389 if (dest.is_young()) {
6390 young_list()->add_survivor_region(alloc_region);
6391 } else {
6392 _old_set.add(alloc_region);
6393 }
6394 _hr_printer.retire(alloc_region);
6395 }
6396
6397 // Heap region set verification
6398
6399 class VerifyRegionListsClosure : public HeapRegionClosure {
6400 private:
6401 HeapRegionSet* _old_set;
6402 HeapRegionSet* _humongous_set;
6403 HeapRegionManager* _hrm;
6404
6405 public:
6406 HeapRegionSetCount _old_count;
6407 HeapRegionSetCount _humongous_count;
6408 HeapRegionSetCount _free_count;
6409
6410 VerifyRegionListsClosure(HeapRegionSet* old_set,
6411 HeapRegionSet* humongous_set,
6412 HeapRegionManager* hrm) :
6413 _old_set(old_set), _humongous_set(humongous_set), _hrm(hrm),
6414 _old_count(), _humongous_count(), _free_count(){ }
6415
6416 bool doHeapRegion(HeapRegion* hr) {
6417 if (hr->is_continues_humongous()) {
6418 return false;
6419 }
6420
6421 if (hr->is_young()) {
6422 // TODO
6423 } else if (hr->is_starts_humongous()) {
6424 assert(hr->containing_set() == _humongous_set, err_msg("Heap region %u is starts humongous but not in humongous set.", hr->hrm_index()));
6425 _humongous_count.increment(1u, hr->capacity());
6426 } else if (hr->is_empty()) {
6427 assert(_hrm->is_free(hr), err_msg("Heap region %u is empty but not on the free list.", hr->hrm_index()));
6428 _free_count.increment(1u, hr->capacity());
6429 } else if (hr->is_old()) {
6430 assert(hr->containing_set() == _old_set, err_msg("Heap region %u is old but not in the old set.", hr->hrm_index()));
6431 _old_count.increment(1u, hr->capacity());
6432 } else {
6433 ShouldNotReachHere();
6434 }
6435 return false;
6436 }
6437
6438 void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, HeapRegionManager* free_list) {
6439 guarantee(old_set->length() == _old_count.length(), err_msg("Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length()));
6440 guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), err_msg("Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6441 old_set->total_capacity_bytes(), _old_count.capacity()));
6442
6443 guarantee(humongous_set->length() == _humongous_count.length(), err_msg("Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length()));
6444 guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), err_msg("Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6445 humongous_set->total_capacity_bytes(), _humongous_count.capacity()));
6446
6447 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()));
6448 guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), err_msg("Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6449 free_list->total_capacity_bytes(), _free_count.capacity()));
6450 }
6451 };
6452
6453 void G1CollectedHeap::verify_region_sets() {
6454 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6455
6456 // First, check the explicit lists.
6457 _hrm.verify();
6458 {
6459 // Given that a concurrent operation might be adding regions to
6460 // the secondary free list we have to take the lock before
6461 // verifying it.
6462 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6463 _secondary_free_list.verify_list();
6464 }
6465
6466 // If a concurrent region freeing operation is in progress it will
6467 // be difficult to correctly attributed any free regions we come
6468 // across to the correct free list given that they might belong to
6469 // one of several (free_list, secondary_free_list, any local lists,
6470 // etc.). So, if that's the case we will skip the rest of the
6471 // verification operation. Alternatively, waiting for the concurrent
6472 // operation to complete will have a non-trivial effect on the GC's
6473 // operation (no concurrent operation will last longer than the
6474 // interval between two calls to verification) and it might hide
6475 // any issues that we would like to catch during testing.
6476 if (free_regions_coming()) {
6477 return;
6478 }
6479
6480 // Make sure we append the secondary_free_list on the free_list so
6481 // that all free regions we will come across can be safely
6482 // attributed to the free_list.
6483 append_secondary_free_list_if_not_empty_with_lock();
6484
6485 // Finally, make sure that the region accounting in the lists is
6486 // consistent with what we see in the heap.
6487
6488 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_hrm);
6489 heap_region_iterate(&cl);
6490 cl.verify_counts(&_old_set, &_humongous_set, &_hrm);
6491 }
6492
6493 // Optimized nmethod scanning
6494
6495 class RegisterNMethodOopClosure: public OopClosure {
6496 G1CollectedHeap* _g1h;
6497 nmethod* _nm;
6498
6499 template <class T> void do_oop_work(T* p) {
6500 T heap_oop = oopDesc::load_heap_oop(p);
6501 if (!oopDesc::is_null(heap_oop)) {
6502 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6503 HeapRegion* hr = _g1h->heap_region_containing(obj);
6504 assert(!hr->is_continues_humongous(),
6505 err_msg("trying to add code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6506 " starting at "HR_FORMAT,
6507 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6508
6509 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
6510 hr->add_strong_code_root_locked(_nm);
6511 }
6512 }
6513
6514 public:
6515 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6516 _g1h(g1h), _nm(nm) {}
6517
6518 void do_oop(oop* p) { do_oop_work(p); }
6519 void do_oop(narrowOop* p) { do_oop_work(p); }
6520 };
6521
6522 class UnregisterNMethodOopClosure: public OopClosure {
6523 G1CollectedHeap* _g1h;
6524 nmethod* _nm;
6525
6526 template <class T> void do_oop_work(T* p) {
6527 T heap_oop = oopDesc::load_heap_oop(p);
6528 if (!oopDesc::is_null(heap_oop)) {
6529 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6530 HeapRegion* hr = _g1h->heap_region_containing(obj);
6531 assert(!hr->is_continues_humongous(),
6532 err_msg("trying to remove code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6533 " starting at "HR_FORMAT,
6534 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6535
6536 hr->remove_strong_code_root(_nm);
6537 }
6538 }
6539
6540 public:
6541 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6542 _g1h(g1h), _nm(nm) {}
6543
6544 void do_oop(oop* p) { do_oop_work(p); }
6545 void do_oop(narrowOop* p) { do_oop_work(p); }
6546 };
6547
6548 void G1CollectedHeap::register_nmethod(nmethod* nm) {
6549 CollectedHeap::register_nmethod(nm);
6550
6551 guarantee(nm != NULL, "sanity");
6552 RegisterNMethodOopClosure reg_cl(this, nm);
6553 nm->oops_do(®_cl);
6554 }
6555
6556 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
6557 CollectedHeap::unregister_nmethod(nm);
6558
6559 guarantee(nm != NULL, "sanity");
6560 UnregisterNMethodOopClosure reg_cl(this, nm);
6561 nm->oops_do(®_cl, true);
6562 }
6563
6564 void G1CollectedHeap::purge_code_root_memory() {
6565 double purge_start = os::elapsedTime();
6566 G1CodeRootSet::purge();
6567 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
6568 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
6569 }
6570
6571 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
6572 G1CollectedHeap* _g1h;
6573
6574 public:
6575 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
6576 _g1h(g1h) {}
6577
6578 void do_code_blob(CodeBlob* cb) {
6579 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
6580 if (nm == NULL) {
6581 return;
6582 }
6583
6584 if (ScavengeRootsInCode) {
6585 _g1h->register_nmethod(nm);
6586 }
6587 }
6588 };
6589
6590 void G1CollectedHeap::rebuild_strong_code_roots() {
6591 RebuildStrongCodeRootClosure blob_cl(this);
6592 CodeCache::blobs_do(&blob_cl);
6593 }