1 /*
2 * Copyright (c) 2001, 2014, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
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/g1StringDedup.hpp"
52 #include "gc_implementation/g1/g1YCTypes.hpp"
53 #include "gc_implementation/g1/heapRegion.inline.hpp"
54 #include "gc_implementation/g1/heapRegionRemSet.hpp"
55 #include "gc_implementation/g1/heapRegionSet.inline.hpp"
56 #include "gc_implementation/g1/vm_operations_g1.hpp"
57 #include "gc_implementation/shared/gcHeapSummary.hpp"
58 #include "gc_implementation/shared/gcTimer.hpp"
59 #include "gc_implementation/shared/gcTrace.hpp"
60 #include "gc_implementation/shared/gcTraceTime.hpp"
61 #include "gc_implementation/shared/isGCActiveMark.hpp"
62 #include "memory/allocation.hpp"
63 #include "memory/gcLocker.inline.hpp"
64 #include "memory/generationSpec.hpp"
65 #include "memory/iterator.hpp"
66 #include "memory/referenceProcessor.hpp"
67 #include "oops/oop.inline.hpp"
68 #include "oops/oop.pcgc.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
74 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
75
76 // turn it on so that the contents of the young list (scan-only /
77 // to-be-collected) are printed at "strategic" points before / during
78 // / after the collection --- this is useful for debugging
79 #define YOUNG_LIST_VERBOSE 0
80 // CURRENT STATUS
81 // This file is under construction. Search for "FIXME".
82
83 // INVARIANTS/NOTES
84 //
85 // All allocation activity covered by the G1CollectedHeap interface is
86 // serialized by acquiring the HeapLock. This happens in mem_allocate
87 // and allocate_new_tlab, which are the "entry" points to the
88 // allocation code from the rest of the JVM. (Note that this does not
89 // apply to TLAB allocation, which is not part of this interface: it
90 // is done by clients of this interface.)
91
92 // Notes on implementation of parallelism in different tasks.
93 //
94 // G1ParVerifyTask uses heap_region_par_iterate() for parallelism.
95 // The number of GC workers is passed to heap_region_par_iterate().
96 // It does use run_task() which sets _n_workers in the task.
97 // G1ParTask executes g1_process_roots() ->
98 // SharedHeap::process_roots() which calls eventually to
99 // CardTableModRefBS::par_non_clean_card_iterate_work() which uses
100 // SequentialSubTasksDone. SharedHeap::process_roots() also
101 // directly uses SubTasksDone (_process_strong_tasks field in SharedHeap).
102 //
103
104 // Local to this file.
105
106 class RefineCardTableEntryClosure: public CardTableEntryClosure {
107 bool _concurrent;
108 public:
109 RefineCardTableEntryClosure() : _concurrent(true) { }
110
111 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
112 bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, false);
113 // This path is executed by the concurrent refine or mutator threads,
114 // concurrently, and so we do not care if card_ptr contains references
115 // that point into the collection set.
116 assert(!oops_into_cset, "should be");
117
118 if (_concurrent && SuspendibleThreadSet::should_yield()) {
119 // Caller will actually yield.
120 return false;
121 }
122 // Otherwise, we finished successfully; return true.
123 return true;
124 }
125
126 void set_concurrent(bool b) { _concurrent = b; }
127 };
128
129
130 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
131 private:
132 size_t _num_processed;
133
134 public:
135 RedirtyLoggedCardTableEntryClosure() : CardTableEntryClosure(), _num_processed(0) { }
136
137 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
138 *card_ptr = CardTableModRefBS::dirty_card_val();
139 _num_processed++;
140 return true;
141 }
142
143 size_t num_processed() const { return _num_processed; }
144 };
145
146 YoungList::YoungList(G1CollectedHeap* g1h) :
147 _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0),
148 _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) {
149 guarantee(check_list_empty(false), "just making sure...");
150 }
151
152 void YoungList::push_region(HeapRegion *hr) {
153 assert(!hr->is_young(), "should not already be young");
154 assert(hr->get_next_young_region() == NULL, "cause it should!");
155
156 hr->set_next_young_region(_head);
157 _head = hr;
158
159 _g1h->g1_policy()->set_region_eden(hr, (int) _length);
160 ++_length;
161 }
162
163 void YoungList::add_survivor_region(HeapRegion* hr) {
164 assert(hr->is_survivor(), "should be flagged as survivor region");
165 assert(hr->get_next_young_region() == NULL, "cause it should!");
166
167 hr->set_next_young_region(_survivor_head);
168 if (_survivor_head == NULL) {
169 _survivor_tail = hr;
170 }
171 _survivor_head = hr;
172 ++_survivor_length;
173 }
174
175 void YoungList::empty_list(HeapRegion* list) {
176 while (list != NULL) {
177 HeapRegion* next = list->get_next_young_region();
178 list->set_next_young_region(NULL);
179 list->uninstall_surv_rate_group();
180 // This is called before a Full GC and all the non-empty /
181 // non-humongous regions at the end of the Full GC will end up as
182 // old anyway.
183 list->set_old();
184 list = next;
185 }
186 }
187
188 void YoungList::empty_list() {
189 assert(check_list_well_formed(), "young list should be well formed");
190
191 empty_list(_head);
192 _head = NULL;
193 _length = 0;
194
195 empty_list(_survivor_head);
196 _survivor_head = NULL;
197 _survivor_tail = NULL;
198 _survivor_length = 0;
199
200 _last_sampled_rs_lengths = 0;
201
202 assert(check_list_empty(false), "just making sure...");
203 }
204
205 bool YoungList::check_list_well_formed() {
206 bool ret = true;
207
208 uint length = 0;
209 HeapRegion* curr = _head;
210 HeapRegion* last = NULL;
211 while (curr != NULL) {
212 if (!curr->is_young()) {
213 gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
214 "incorrectly tagged (y: %d, surv: %d)",
215 curr->bottom(), curr->end(),
216 curr->is_young(), curr->is_survivor());
217 ret = false;
218 }
219 ++length;
220 last = curr;
221 curr = curr->get_next_young_region();
222 }
223 ret = ret && (length == _length);
224
225 if (!ret) {
226 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
227 gclog_or_tty->print_cr("### list has %u entries, _length is %u",
228 length, _length);
229 }
230
231 return ret;
232 }
233
234 bool YoungList::check_list_empty(bool check_sample) {
235 bool ret = true;
236
237 if (_length != 0) {
238 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u",
239 _length);
240 ret = false;
241 }
242 if (check_sample && _last_sampled_rs_lengths != 0) {
243 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
244 ret = false;
245 }
246 if (_head != NULL) {
247 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
248 ret = false;
249 }
250 if (!ret) {
251 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
252 }
253
254 return ret;
255 }
256
257 void
258 YoungList::rs_length_sampling_init() {
259 _sampled_rs_lengths = 0;
260 _curr = _head;
261 }
262
263 bool
264 YoungList::rs_length_sampling_more() {
265 return _curr != NULL;
266 }
267
268 void
269 YoungList::rs_length_sampling_next() {
270 assert( _curr != NULL, "invariant" );
271 size_t rs_length = _curr->rem_set()->occupied();
272
273 _sampled_rs_lengths += rs_length;
274
275 // The current region may not yet have been added to the
276 // incremental collection set (it gets added when it is
277 // retired as the current allocation region).
278 if (_curr->in_collection_set()) {
279 // Update the collection set policy information for this region
280 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
281 }
282
283 _curr = _curr->get_next_young_region();
284 if (_curr == NULL) {
285 _last_sampled_rs_lengths = _sampled_rs_lengths;
286 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
287 }
288 }
289
290 void
291 YoungList::reset_auxilary_lists() {
292 guarantee( is_empty(), "young list should be empty" );
293 assert(check_list_well_formed(), "young list should be well formed");
294
295 // Add survivor regions to SurvRateGroup.
296 _g1h->g1_policy()->note_start_adding_survivor_regions();
297 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
298
299 int young_index_in_cset = 0;
300 for (HeapRegion* curr = _survivor_head;
301 curr != NULL;
302 curr = curr->get_next_young_region()) {
303 _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
304
305 // The region is a non-empty survivor so let's add it to
306 // the incremental collection set for the next evacuation
307 // pause.
308 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
309 young_index_in_cset += 1;
310 }
311 assert((uint) young_index_in_cset == _survivor_length, "post-condition");
312 _g1h->g1_policy()->note_stop_adding_survivor_regions();
313
314 _head = _survivor_head;
315 _length = _survivor_length;
316 if (_survivor_head != NULL) {
317 assert(_survivor_tail != NULL, "cause it shouldn't be");
318 assert(_survivor_length > 0, "invariant");
319 _survivor_tail->set_next_young_region(NULL);
320 }
321
322 // Don't clear the survivor list handles until the start of
323 // the next evacuation pause - we need it in order to re-tag
324 // the survivor regions from this evacuation pause as 'young'
325 // at the start of the next.
326
327 _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
328
329 assert(check_list_well_formed(), "young list should be well formed");
330 }
331
332 void YoungList::print() {
333 HeapRegion* lists[] = {_head, _survivor_head};
334 const char* names[] = {"YOUNG", "SURVIVOR"};
335
336 for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) {
337 gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
338 HeapRegion *curr = lists[list];
339 if (curr == NULL)
340 gclog_or_tty->print_cr(" empty");
341 while (curr != NULL) {
342 gclog_or_tty->print_cr(" "HR_FORMAT", P: "PTR_FORMAT ", N: "PTR_FORMAT", age: %4d",
343 HR_FORMAT_PARAMS(curr),
344 curr->prev_top_at_mark_start(),
345 curr->next_top_at_mark_start(),
346 curr->age_in_surv_rate_group_cond());
347 curr = curr->get_next_young_region();
348 }
349 }
350
351 gclog_or_tty->cr();
352 }
353
354 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
355 HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
356 }
357
358 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
359 // The from card cache is not the memory that is actually committed. So we cannot
360 // take advantage of the zero_filled parameter.
361 reset_from_card_cache(start_idx, num_regions);
362 }
363
364 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
365 {
366 // Claim the right to put the region on the dirty cards region list
367 // by installing a self pointer.
368 HeapRegion* next = hr->get_next_dirty_cards_region();
369 if (next == NULL) {
370 HeapRegion* res = (HeapRegion*)
371 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
372 NULL);
373 if (res == NULL) {
374 HeapRegion* head;
375 do {
376 // Put the region to the dirty cards region list.
377 head = _dirty_cards_region_list;
378 next = (HeapRegion*)
379 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
380 if (next == head) {
381 assert(hr->get_next_dirty_cards_region() == hr,
382 "hr->get_next_dirty_cards_region() != hr");
383 if (next == NULL) {
384 // The last region in the list points to itself.
385 hr->set_next_dirty_cards_region(hr);
386 } else {
387 hr->set_next_dirty_cards_region(next);
388 }
389 }
390 } while (next != head);
391 }
392 }
393 }
394
395 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
396 {
397 HeapRegion* head;
398 HeapRegion* hr;
399 do {
400 head = _dirty_cards_region_list;
401 if (head == NULL) {
402 return NULL;
403 }
404 HeapRegion* new_head = head->get_next_dirty_cards_region();
405 if (head == new_head) {
406 // The last region.
407 new_head = NULL;
408 }
409 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
410 head);
411 } while (hr != head);
412 assert(hr != NULL, "invariant");
413 hr->set_next_dirty_cards_region(NULL);
414 return hr;
415 }
416
417 #ifdef ASSERT
418 // A region is added to the collection set as it is retired
419 // so an address p can point to a region which will be in the
420 // collection set but has not yet been retired. This method
421 // therefore is only accurate during a GC pause after all
422 // regions have been retired. It is used for debugging
423 // to check if an nmethod has references to objects that can
424 // be move during a partial collection. Though it can be
425 // inaccurate, it is sufficient for G1 because the conservative
426 // implementation of is_scavengable() for G1 will indicate that
427 // all nmethods must be scanned during a partial collection.
428 bool G1CollectedHeap::is_in_partial_collection(const void* p) {
429 if (p == NULL) {
430 return false;
431 }
432 return heap_region_containing(p)->in_collection_set();
433 }
434 #endif
435
436 // Returns true if the reference points to an object that
437 // can move in an incremental collection.
438 bool G1CollectedHeap::is_scavengable(const void* p) {
439 HeapRegion* hr = heap_region_containing(p);
440 return !hr->is_humongous();
441 }
442
443 // Private class members.
444
445 G1CollectedHeap* G1CollectedHeap::_g1h;
446
447 // Private methods.
448
449 HeapRegion*
450 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
451 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
452 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
453 if (!_secondary_free_list.is_empty()) {
454 if (G1ConcRegionFreeingVerbose) {
455 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
456 "secondary_free_list has %u entries",
457 _secondary_free_list.length());
458 }
459 // It looks as if there are free regions available on the
460 // secondary_free_list. Let's move them to the free_list and try
461 // again to allocate from it.
462 append_secondary_free_list();
463
464 assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not "
465 "empty we should have moved at least one entry to the free_list");
466 HeapRegion* res = _hrm.allocate_free_region(is_old);
467 if (G1ConcRegionFreeingVerbose) {
468 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
469 "allocated "HR_FORMAT" from secondary_free_list",
470 HR_FORMAT_PARAMS(res));
471 }
472 return res;
473 }
474
475 // Wait here until we get notified either when (a) there are no
476 // more free regions coming or (b) some regions have been moved on
477 // the secondary_free_list.
478 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
479 }
480
481 if (G1ConcRegionFreeingVerbose) {
482 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
483 "could not allocate from secondary_free_list");
484 }
485 return NULL;
486 }
487
488 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
489 assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
490 "the only time we use this to allocate a humongous region is "
491 "when we are allocating a single humongous region");
492
493 HeapRegion* res;
494 if (G1StressConcRegionFreeing) {
495 if (!_secondary_free_list.is_empty()) {
496 if (G1ConcRegionFreeingVerbose) {
497 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
498 "forced to look at the secondary_free_list");
499 }
500 res = new_region_try_secondary_free_list(is_old);
501 if (res != NULL) {
502 return res;
503 }
504 }
505 }
506
507 res = _hrm.allocate_free_region(is_old);
508
509 if (res == NULL) {
510 if (G1ConcRegionFreeingVerbose) {
511 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
512 "res == NULL, trying the secondary_free_list");
513 }
514 res = new_region_try_secondary_free_list(is_old);
515 }
516 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
517 // Currently, only attempts to allocate GC alloc regions set
518 // do_expand to true. So, we should only reach here during a
519 // safepoint. If this assumption changes we might have to
520 // reconsider the use of _expand_heap_after_alloc_failure.
521 assert(SafepointSynchronize::is_at_safepoint(), "invariant");
522
523 ergo_verbose1(ErgoHeapSizing,
524 "attempt heap expansion",
525 ergo_format_reason("region allocation request failed")
526 ergo_format_byte("allocation request"),
527 word_size * HeapWordSize);
528 if (expand(word_size * HeapWordSize)) {
529 // Given that expand() succeeded in expanding the heap, and we
530 // always expand the heap by an amount aligned to the heap
531 // region size, the free list should in theory not be empty.
532 // In either case allocate_free_region() will check for NULL.
533 res = _hrm.allocate_free_region(is_old);
534 } else {
535 _expand_heap_after_alloc_failure = false;
536 }
537 }
538 return res;
539 }
540
541 HeapWord*
542 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
543 uint num_regions,
544 size_t word_size,
545 AllocationContext_t context) {
546 assert(first != G1_NO_HRM_INDEX, "pre-condition");
547 assert(is_humongous(word_size), "word_size should be humongous");
548 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
549
550 // Index of last region in the series + 1.
551 uint last = first + num_regions;
552
553 // We need to initialize the region(s) we just discovered. This is
554 // a bit tricky given that it can happen concurrently with
555 // refinement threads refining cards on these regions and
556 // potentially wanting to refine the BOT as they are scanning
557 // those cards (this can happen shortly after a cleanup; see CR
558 // 6991377). So we have to set up the region(s) carefully and in
559 // a specific order.
560
561 // The word size sum of all the regions we will allocate.
562 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
563 assert(word_size <= word_size_sum, "sanity");
564
565 // This will be the "starts humongous" region.
566 HeapRegion* first_hr = region_at(first);
567 // The header of the new object will be placed at the bottom of
568 // the first region.
569 HeapWord* new_obj = first_hr->bottom();
570 // This will be the new end of the first region in the series that
571 // should also match the end of the last region in the series.
572 HeapWord* new_end = new_obj + word_size_sum;
573 // This will be the new top of the first region that will reflect
574 // this allocation.
575 HeapWord* new_top = new_obj + word_size;
576
577 // First, we need to zero the header of the space that we will be
578 // allocating. When we update top further down, some refinement
579 // threads might try to scan the region. By zeroing the header we
580 // ensure that any thread that will try to scan the region will
581 // come across the zero klass word and bail out.
582 //
583 // NOTE: It would not have been correct to have used
584 // CollectedHeap::fill_with_object() and make the space look like
585 // an int array. The thread that is doing the allocation will
586 // later update the object header to a potentially different array
587 // type and, for a very short period of time, the klass and length
588 // fields will be inconsistent. This could cause a refinement
589 // thread to calculate the object size incorrectly.
590 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
591
592 // We will set up the first region as "starts humongous". This
593 // will also update the BOT covering all the regions to reflect
594 // that there is a single object that starts at the bottom of the
595 // first region.
596 first_hr->set_starts_humongous(new_top, new_end);
597 first_hr->set_allocation_context(context);
598 // Then, if there are any, we will set up the "continues
599 // humongous" regions.
600 HeapRegion* hr = NULL;
601 for (uint i = first + 1; i < last; ++i) {
602 hr = region_at(i);
603 hr->set_continues_humongous(first_hr);
604 hr->set_allocation_context(context);
605 }
606 // If we have "continues humongous" regions (hr != NULL), then the
607 // end of the last one should match new_end.
608 assert(hr == NULL || hr->end() == new_end, "sanity");
609
610 // Up to this point no concurrent thread would have been able to
611 // do any scanning on any region in this series. All the top
612 // fields still point to bottom, so the intersection between
613 // [bottom,top] and [card_start,card_end] will be empty. Before we
614 // update the top fields, we'll do a storestore to make sure that
615 // no thread sees the update to top before the zeroing of the
616 // object header and the BOT initialization.
617 OrderAccess::storestore();
618
619 // Now that the BOT and the object header have been initialized,
620 // we can update top of the "starts humongous" region.
621 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
622 "new_top should be in this region");
623 first_hr->set_top(new_top);
624 if (_hr_printer.is_active()) {
625 HeapWord* bottom = first_hr->bottom();
626 HeapWord* end = first_hr->orig_end();
627 if ((first + 1) == last) {
628 // the series has a single humongous region
629 _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
630 } else {
631 // the series has more than one humongous regions
632 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
633 }
634 }
635
636 // Now, we will update the top fields of the "continues humongous"
637 // regions. The reason we need to do this is that, otherwise,
638 // these regions would look empty and this will confuse parts of
639 // G1. For example, the code that looks for a consecutive number
640 // of empty regions will consider them empty and try to
641 // re-allocate them. We can extend is_empty() to also include
642 // !is_continues_humongous(), but it is easier to just update the top
643 // fields here. The way we set top for all regions (i.e., top ==
644 // end for all regions but the last one, top == new_top for the
645 // last one) is actually used when we will free up the humongous
646 // region in free_humongous_region().
647 hr = NULL;
648 for (uint i = first + 1; i < last; ++i) {
649 hr = region_at(i);
650 if ((i + 1) == last) {
651 // last continues humongous region
652 assert(hr->bottom() < new_top && new_top <= hr->end(),
653 "new_top should fall on this region");
654 hr->set_top(new_top);
655 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
656 } else {
657 // not last one
658 assert(new_top > hr->end(), "new_top should be above this region");
659 hr->set_top(hr->end());
660 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
661 }
662 }
663 // If we have continues humongous regions (hr != NULL), then the
664 // end of the last one should match new_end and its top should
665 // match new_top.
666 assert(hr == NULL ||
667 (hr->end() == new_end && hr->top() == new_top), "sanity");
668 check_bitmaps("Humongous Region Allocation", first_hr);
669
670 assert(first_hr->used() == word_size * HeapWordSize, "invariant");
671 _allocator->increase_used(first_hr->used());
672 _humongous_set.add(first_hr);
673
674 return new_obj;
675 }
676
677 // If could fit into free regions w/o expansion, try.
678 // Otherwise, if can expand, do so.
679 // Otherwise, if using ex regions might help, try with ex given back.
680 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) {
681 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
682
683 verify_region_sets_optional();
684
685 uint first = G1_NO_HRM_INDEX;
686 uint obj_regions = (uint)(align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords);
687
688 if (obj_regions == 1) {
689 // Only one region to allocate, try to use a fast path by directly allocating
690 // from the free lists. Do not try to expand here, we will potentially do that
691 // later.
692 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
693 if (hr != NULL) {
694 first = hr->hrm_index();
695 }
696 } else {
697 // We can't allocate humongous regions spanning more than one region while
698 // cleanupComplete() is running, since some of the regions we find to be
699 // empty might not yet be added to the free list. It is not straightforward
700 // to know in which list they are on so that we can remove them. We only
701 // need to do this if we need to allocate more than one region to satisfy the
702 // current humongous allocation request. If we are only allocating one region
703 // we use the one-region region allocation code (see above), that already
704 // potentially waits for regions from the secondary free list.
705 wait_while_free_regions_coming();
706 append_secondary_free_list_if_not_empty_with_lock();
707
708 // Policy: Try only empty regions (i.e. already committed first). Maybe we
709 // are lucky enough to find some.
710 first = _hrm.find_contiguous_only_empty(obj_regions);
711 if (first != G1_NO_HRM_INDEX) {
712 _hrm.allocate_free_regions_starting_at(first, obj_regions);
713 }
714 }
715
716 if (first == G1_NO_HRM_INDEX) {
717 // Policy: We could not find enough regions for the humongous object in the
718 // free list. Look through the heap to find a mix of free and uncommitted regions.
719 // If so, try expansion.
720 first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
721 if (first != G1_NO_HRM_INDEX) {
722 // We found something. Make sure these regions are committed, i.e. expand
723 // the heap. Alternatively we could do a defragmentation GC.
724 ergo_verbose1(ErgoHeapSizing,
725 "attempt heap expansion",
726 ergo_format_reason("humongous allocation request failed")
727 ergo_format_byte("allocation request"),
728 word_size * HeapWordSize);
729
730 _hrm.expand_at(first, obj_regions);
731 g1_policy()->record_new_heap_size(num_regions());
732
733 #ifdef ASSERT
734 for (uint i = first; i < first + obj_regions; ++i) {
735 HeapRegion* hr = region_at(i);
736 assert(hr->is_free(), "sanity");
737 assert(hr->is_empty(), "sanity");
738 assert(is_on_master_free_list(hr), "sanity");
739 }
740 #endif
741 _hrm.allocate_free_regions_starting_at(first, obj_regions);
742 } else {
743 // Policy: Potentially trigger a defragmentation GC.
744 }
745 }
746
747 HeapWord* result = NULL;
748 if (first != G1_NO_HRM_INDEX) {
749 result = humongous_obj_allocate_initialize_regions(first, obj_regions,
750 word_size, context);
751 assert(result != NULL, "it should always return a valid result");
752
753 // A successful humongous object allocation changes the used space
754 // information of the old generation so we need to recalculate the
755 // sizes and update the jstat counters here.
756 g1mm()->update_sizes();
757 }
758
759 verify_region_sets_optional();
760
761 return result;
762 }
763
764 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
765 assert_heap_not_locked_and_not_at_safepoint();
766 assert(!is_humongous(word_size), "we do not allow humongous TLABs");
767
768 unsigned int dummy_gc_count_before;
769 int dummy_gclocker_retry_count = 0;
770 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
771 }
772
773 HeapWord*
774 G1CollectedHeap::mem_allocate(size_t word_size,
775 bool* gc_overhead_limit_was_exceeded) {
776 assert_heap_not_locked_and_not_at_safepoint();
777
778 // Loop until the allocation is satisfied, or unsatisfied after GC.
779 for (int try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
780 unsigned int gc_count_before;
781
782 HeapWord* result = NULL;
783 if (!is_humongous(word_size)) {
784 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
785 } else {
786 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
787 }
788 if (result != NULL) {
789 return result;
790 }
791
792 // Create the garbage collection operation...
793 VM_G1CollectForAllocation op(gc_count_before, word_size);
794 op.set_allocation_context(AllocationContext::current());
795
796 // ...and get the VM thread to execute it.
797 VMThread::execute(&op);
798
799 if (op.prologue_succeeded() && op.pause_succeeded()) {
800 // If the operation was successful we'll return the result even
801 // if it is NULL. If the allocation attempt failed immediately
802 // after a Full GC, it's unlikely we'll be able to allocate now.
803 HeapWord* result = op.result();
804 if (result != NULL && !is_humongous(word_size)) {
805 // Allocations that take place on VM operations do not do any
806 // card dirtying and we have to do it here. We only have to do
807 // this for non-humongous allocations, though.
808 dirty_young_block(result, word_size);
809 }
810 return result;
811 } else {
812 if (gclocker_retry_count > GCLockerRetryAllocationCount) {
813 return NULL;
814 }
815 assert(op.result() == NULL,
816 "the result should be NULL if the VM op did not succeed");
817 }
818
819 // Give a warning if we seem to be looping forever.
820 if ((QueuedAllocationWarningCount > 0) &&
821 (try_count % QueuedAllocationWarningCount == 0)) {
822 warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
823 }
824 }
825
826 ShouldNotReachHere();
827 return NULL;
828 }
829
830 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
831 AllocationContext_t context,
832 unsigned int *gc_count_before_ret,
833 int* gclocker_retry_count_ret) {
834 // Make sure you read the note in attempt_allocation_humongous().
835
836 assert_heap_not_locked_and_not_at_safepoint();
837 assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
838 "be called for humongous allocation requests");
839
840 // We should only get here after the first-level allocation attempt
841 // (attempt_allocation()) failed to allocate.
842
843 // We will loop until a) we manage to successfully perform the
844 // allocation or b) we successfully schedule a collection which
845 // fails to perform the allocation. b) is the only case when we'll
846 // return NULL.
847 HeapWord* result = NULL;
848 for (int try_count = 1; /* we'll return */; try_count += 1) {
849 bool should_try_gc;
850 unsigned int gc_count_before;
851
852 {
853 MutexLockerEx x(Heap_lock);
854 result = _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size,
855 false /* bot_updates */);
856 if (result != NULL) {
857 return result;
858 }
859
860 // If we reach here, attempt_allocation_locked() above failed to
861 // allocate a new region. So the mutator alloc region should be NULL.
862 assert(_allocator->mutator_alloc_region(context)->get() == NULL, "only way to get here");
863
864 if (GC_locker::is_active_and_needs_gc()) {
865 if (g1_policy()->can_expand_young_list()) {
866 // No need for an ergo verbose message here,
867 // can_expand_young_list() does this when it returns true.
868 result = _allocator->mutator_alloc_region(context)->attempt_allocation_force(word_size,
869 false /* bot_updates */);
870 if (result != NULL) {
871 return result;
872 }
873 }
874 should_try_gc = false;
875 } else {
876 // The GCLocker may not be active but the GCLocker initiated
877 // GC may not yet have been performed (GCLocker::needs_gc()
878 // returns true). In this case we do not try this GC and
879 // wait until the GCLocker initiated GC is performed, and
880 // then retry the allocation.
881 if (GC_locker::needs_gc()) {
882 should_try_gc = false;
883 } else {
884 // Read the GC count while still holding the Heap_lock.
885 gc_count_before = total_collections();
886 should_try_gc = true;
887 }
888 }
889 }
890
891 if (should_try_gc) {
892 bool succeeded;
893 result = do_collection_pause(word_size, gc_count_before, &succeeded,
894 GCCause::_g1_inc_collection_pause);
895 if (result != NULL) {
896 assert(succeeded, "only way to get back a non-NULL result");
897 return result;
898 }
899
900 if (succeeded) {
901 // If we get here we successfully scheduled a collection which
902 // failed to allocate. No point in trying to allocate
903 // further. We'll just return NULL.
904 MutexLockerEx x(Heap_lock);
905 *gc_count_before_ret = total_collections();
906 return NULL;
907 }
908 } else {
909 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
910 MutexLockerEx x(Heap_lock);
911 *gc_count_before_ret = total_collections();
912 return NULL;
913 }
914 // The GCLocker is either active or the GCLocker initiated
915 // GC has not yet been performed. Stall until it is and
916 // then retry the allocation.
917 GC_locker::stall_until_clear();
918 (*gclocker_retry_count_ret) += 1;
919 }
920
921 // We can reach here if we were unsuccessful in scheduling a
922 // collection (because another thread beat us to it) or if we were
923 // stalled due to the GC locker. In either can we should retry the
924 // allocation attempt in case another thread successfully
925 // performed a collection and reclaimed enough space. We do the
926 // first attempt (without holding the Heap_lock) here and the
927 // follow-on attempt will be at the start of the next loop
928 // iteration (after taking the Heap_lock).
929 result = _allocator->mutator_alloc_region(context)->attempt_allocation(word_size,
930 false /* bot_updates */);
931 if (result != NULL) {
932 return result;
933 }
934
935 // Give a warning if we seem to be looping forever.
936 if ((QueuedAllocationWarningCount > 0) &&
937 (try_count % QueuedAllocationWarningCount == 0)) {
938 warning("G1CollectedHeap::attempt_allocation_slow() "
939 "retries %d times", try_count);
940 }
941 }
942
943 ShouldNotReachHere();
944 return NULL;
945 }
946
947 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
948 unsigned int * gc_count_before_ret,
949 int* gclocker_retry_count_ret) {
950 // The structure of this method has a lot of similarities to
951 // attempt_allocation_slow(). The reason these two were not merged
952 // into a single one is that such a method would require several "if
953 // allocation is not humongous do this, otherwise do that"
954 // conditional paths which would obscure its flow. In fact, an early
955 // version of this code did use a unified method which was harder to
956 // follow and, as a result, it had subtle bugs that were hard to
957 // track down. So keeping these two methods separate allows each to
958 // be more readable. It will be good to keep these two in sync as
959 // much as possible.
960
961 assert_heap_not_locked_and_not_at_safepoint();
962 assert(is_humongous(word_size), "attempt_allocation_humongous() "
963 "should only be called for humongous allocations");
964
965 // Humongous objects can exhaust the heap quickly, so we should check if we
966 // need to start a marking cycle at each humongous object allocation. We do
967 // the check before we do the actual allocation. The reason for doing it
968 // before the allocation is that we avoid having to keep track of the newly
969 // allocated memory while we do a GC.
970 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
971 word_size)) {
972 collect(GCCause::_g1_humongous_allocation);
973 }
974
975 // We will loop until a) we manage to successfully perform the
976 // allocation or b) we successfully schedule a collection which
977 // fails to perform the allocation. b) is the only case when we'll
978 // return NULL.
979 HeapWord* result = NULL;
980 for (int try_count = 1; /* we'll return */; try_count += 1) {
981 bool should_try_gc;
982 unsigned int gc_count_before;
983
984 {
985 MutexLockerEx x(Heap_lock);
986
987 // Given that humongous objects are not allocated in young
988 // regions, we'll first try to do the allocation without doing a
989 // collection hoping that there's enough space in the heap.
990 result = humongous_obj_allocate(word_size, AllocationContext::current());
991 if (result != NULL) {
992 return result;
993 }
994
995 if (GC_locker::is_active_and_needs_gc()) {
996 should_try_gc = false;
997 } else {
998 // The GCLocker may not be active but the GCLocker initiated
999 // GC may not yet have been performed (GCLocker::needs_gc()
1000 // returns true). In this case we do not try this GC and
1001 // wait until the GCLocker initiated GC is performed, and
1002 // then retry the allocation.
1003 if (GC_locker::needs_gc()) {
1004 should_try_gc = false;
1005 } else {
1006 // Read the GC count while still holding the Heap_lock.
1007 gc_count_before = total_collections();
1008 should_try_gc = true;
1009 }
1010 }
1011 }
1012
1013 if (should_try_gc) {
1014 // If we failed to allocate the humongous object, we should try to
1015 // do a collection pause (if we're allowed) in case it reclaims
1016 // enough space for the allocation to succeed after the pause.
1017
1018 bool succeeded;
1019 result = do_collection_pause(word_size, gc_count_before, &succeeded,
1020 GCCause::_g1_humongous_allocation);
1021 if (result != NULL) {
1022 assert(succeeded, "only way to get back a non-NULL result");
1023 return result;
1024 }
1025
1026 if (succeeded) {
1027 // If we get here we successfully scheduled a collection which
1028 // failed to allocate. No point in trying to allocate
1029 // further. We'll just return NULL.
1030 MutexLockerEx x(Heap_lock);
1031 *gc_count_before_ret = total_collections();
1032 return NULL;
1033 }
1034 } else {
1035 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1036 MutexLockerEx x(Heap_lock);
1037 *gc_count_before_ret = total_collections();
1038 return NULL;
1039 }
1040 // The GCLocker is either active or the GCLocker initiated
1041 // GC has not yet been performed. Stall until it is and
1042 // then retry the allocation.
1043 GC_locker::stall_until_clear();
1044 (*gclocker_retry_count_ret) += 1;
1045 }
1046
1047 // We can reach here if we were unsuccessful in scheduling a
1048 // collection (because another thread beat us to it) or if we were
1049 // stalled due to the GC locker. In either can we should retry the
1050 // allocation attempt in case another thread successfully
1051 // performed a collection and reclaimed enough space. Give a
1052 // warning if we seem to be looping forever.
1053
1054 if ((QueuedAllocationWarningCount > 0) &&
1055 (try_count % QueuedAllocationWarningCount == 0)) {
1056 warning("G1CollectedHeap::attempt_allocation_humongous() "
1057 "retries %d times", try_count);
1058 }
1059 }
1060
1061 ShouldNotReachHere();
1062 return NULL;
1063 }
1064
1065 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1066 AllocationContext_t context,
1067 bool expect_null_mutator_alloc_region) {
1068 assert_at_safepoint(true /* should_be_vm_thread */);
1069 assert(_allocator->mutator_alloc_region(context)->get() == NULL ||
1070 !expect_null_mutator_alloc_region,
1071 "the current alloc region was unexpectedly found to be non-NULL");
1072
1073 if (!is_humongous(word_size)) {
1074 return _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size,
1075 false /* bot_updates */);
1076 } else {
1077 HeapWord* result = humongous_obj_allocate(word_size, context);
1078 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1079 g1_policy()->set_initiate_conc_mark_if_possible();
1080 }
1081 return result;
1082 }
1083
1084 ShouldNotReachHere();
1085 }
1086
1087 class PostMCRemSetClearClosure: public HeapRegionClosure {
1088 G1CollectedHeap* _g1h;
1089 ModRefBarrierSet* _mr_bs;
1090 public:
1091 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1092 _g1h(g1h), _mr_bs(mr_bs) {}
1093
1094 bool doHeapRegion(HeapRegion* r) {
1095 HeapRegionRemSet* hrrs = r->rem_set();
1096
1097 if (r->is_continues_humongous()) {
1098 // We'll assert that the strong code root list and RSet is empty
1099 assert(hrrs->strong_code_roots_list_length() == 0, "sanity");
1100 assert(hrrs->occupied() == 0, "RSet should be empty");
1101 return false;
1102 }
1103
1104 _g1h->reset_gc_time_stamps(r);
1105 hrrs->clear();
1106 // You might think here that we could clear just the cards
1107 // corresponding to the used region. But no: if we leave a dirty card
1108 // in a region we might allocate into, then it would prevent that card
1109 // from being enqueued, and cause it to be missed.
1110 // Re: the performance cost: we shouldn't be doing full GC anyway!
1111 _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1112
1113 return false;
1114 }
1115 };
1116
1117 void G1CollectedHeap::clear_rsets_post_compaction() {
1118 PostMCRemSetClearClosure rs_clear(this, g1_barrier_set());
1119 heap_region_iterate(&rs_clear);
1120 }
1121
1122 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1123 G1CollectedHeap* _g1h;
1124 UpdateRSOopClosure _cl;
1125 int _worker_i;
1126 public:
1127 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1128 _cl(g1->g1_rem_set(), worker_i),
1129 _worker_i(worker_i),
1130 _g1h(g1)
1131 { }
1132
1133 bool doHeapRegion(HeapRegion* r) {
1134 if (!r->is_continues_humongous()) {
1135 _cl.set_from(r);
1136 r->oop_iterate(&_cl);
1137 }
1138 return false;
1139 }
1140 };
1141
1142 class ParRebuildRSTask: public AbstractGangTask {
1143 G1CollectedHeap* _g1;
1144 HeapRegionClaimer _hrclaimer;
1145
1146 public:
1147 ParRebuildRSTask(G1CollectedHeap* g1) :
1148 AbstractGangTask("ParRebuildRSTask"), _g1(g1), _hrclaimer(g1->workers()->active_workers()) {}
1149
1150 void work(uint worker_id) {
1151 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1152 _g1->heap_region_par_iterate(&rebuild_rs, worker_id, &_hrclaimer);
1153 }
1154 };
1155
1156 class PostCompactionPrinterClosure: public HeapRegionClosure {
1157 private:
1158 G1HRPrinter* _hr_printer;
1159 public:
1160 bool doHeapRegion(HeapRegion* hr) {
1161 assert(!hr->is_young(), "not expecting to find young regions");
1162 if (hr->is_free()) {
1163 // We only generate output for non-empty regions.
1164 } else if (hr->is_starts_humongous()) {
1165 if (hr->region_num() == 1) {
1166 // single humongous region
1167 _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
1168 } else {
1169 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
1170 }
1171 } else if (hr->is_continues_humongous()) {
1172 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1173 } else if (hr->is_old()) {
1174 _hr_printer->post_compaction(hr, G1HRPrinter::Old);
1175 } else {
1176 ShouldNotReachHere();
1177 }
1178 return false;
1179 }
1180
1181 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1182 : _hr_printer(hr_printer) { }
1183 };
1184
1185 void G1CollectedHeap::print_hrm_post_compaction() {
1186 PostCompactionPrinterClosure cl(hr_printer());
1187 heap_region_iterate(&cl);
1188 }
1189
1190 bool G1CollectedHeap::do_collection(bool explicit_gc,
1191 bool clear_all_soft_refs,
1192 size_t word_size) {
1193 assert_at_safepoint(true /* should_be_vm_thread */);
1194
1195 if (GC_locker::check_active_before_gc()) {
1196 return false;
1197 }
1198
1199 STWGCTimer* gc_timer = G1MarkSweep::gc_timer();
1200 gc_timer->register_gc_start();
1201
1202 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer();
1203 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start());
1204
1205 SvcGCMarker sgcm(SvcGCMarker::FULL);
1206 ResourceMark rm;
1207
1208 print_heap_before_gc();
1209 trace_heap_before_gc(gc_tracer);
1210
1211 size_t metadata_prev_used = MetaspaceAux::used_bytes();
1212
1213 verify_region_sets_optional();
1214
1215 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1216 collector_policy()->should_clear_all_soft_refs();
1217
1218 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1219
1220 {
1221 IsGCActiveMark x;
1222
1223 // Timing
1224 assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant");
1225 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
1226
1227 {
1228 GCTraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, NULL, gc_tracer->gc_id());
1229 TraceCollectorStats tcs(g1mm()->full_collection_counters());
1230 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1231
1232 g1_policy()->record_full_collection_start();
1233
1234 // Note: When we have a more flexible GC logging framework that
1235 // allows us to add optional attributes to a GC log record we
1236 // could consider timing and reporting how long we wait in the
1237 // following two methods.
1238 wait_while_free_regions_coming();
1239 // If we start the compaction before the CM threads finish
1240 // scanning the root regions we might trip them over as we'll
1241 // be moving objects / updating references. So let's wait until
1242 // they are done. By telling them to abort, they should complete
1243 // early.
1244 _cm->root_regions()->abort();
1245 _cm->root_regions()->wait_until_scan_finished();
1246 append_secondary_free_list_if_not_empty_with_lock();
1247
1248 gc_prologue(true);
1249 increment_total_collections(true /* full gc */);
1250 increment_old_marking_cycles_started();
1251
1252 assert(used() == recalculate_used(), "Should be equal");
1253
1254 verify_before_gc();
1255
1256 check_bitmaps("Full GC Start");
1257 pre_full_gc_dump(gc_timer);
1258
1259 COMPILER2_PRESENT(DerivedPointerTable::clear());
1260
1261 // Disable discovery and empty the discovered lists
1262 // for the CM ref processor.
1263 ref_processor_cm()->disable_discovery();
1264 ref_processor_cm()->abandon_partial_discovery();
1265 ref_processor_cm()->verify_no_references_recorded();
1266
1267 // Abandon current iterations of concurrent marking and concurrent
1268 // refinement, if any are in progress. We have to do this before
1269 // wait_until_scan_finished() below.
1270 concurrent_mark()->abort();
1271
1272 // Make sure we'll choose a new allocation region afterwards.
1273 _allocator->release_mutator_alloc_region();
1274 _allocator->abandon_gc_alloc_regions();
1275 g1_rem_set()->cleanupHRRS();
1276
1277 // We should call this after we retire any currently active alloc
1278 // regions so that all the ALLOC / RETIRE events are generated
1279 // before the start GC event.
1280 _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1281
1282 // We may have added regions to the current incremental collection
1283 // set between the last GC or pause and now. We need to clear the
1284 // incremental collection set and then start rebuilding it afresh
1285 // after this full GC.
1286 abandon_collection_set(g1_policy()->inc_cset_head());
1287 g1_policy()->clear_incremental_cset();
1288 g1_policy()->stop_incremental_cset_building();
1289
1290 tear_down_region_sets(false /* free_list_only */);
1291 g1_policy()->set_gcs_are_young(true);
1292
1293 // See the comments in g1CollectedHeap.hpp and
1294 // G1CollectedHeap::ref_processing_init() about
1295 // how reference processing currently works in G1.
1296
1297 // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1298 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1299
1300 // Temporarily clear the STW ref processor's _is_alive_non_header field.
1301 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1302
1303 ref_processor_stw()->enable_discovery();
1304 ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1305
1306 // Do collection work
1307 {
1308 HandleMark hm; // Discard invalid handles created during gc
1309 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1310 }
1311
1312 assert(num_free_regions() == 0, "we should not have added any free regions");
1313 rebuild_region_sets(false /* free_list_only */);
1314
1315 // Enqueue any discovered reference objects that have
1316 // not been removed from the discovered lists.
1317 ref_processor_stw()->enqueue_discovered_references();
1318
1319 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1320
1321 MemoryService::track_memory_usage();
1322
1323 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1324 ref_processor_stw()->verify_no_references_recorded();
1325
1326 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1327 ClassLoaderDataGraph::purge();
1328 MetaspaceAux::verify_metrics();
1329
1330 // Note: since we've just done a full GC, concurrent
1331 // marking is no longer active. Therefore we need not
1332 // re-enable reference discovery for the CM ref processor.
1333 // That will be done at the start of the next marking cycle.
1334 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1335 ref_processor_cm()->verify_no_references_recorded();
1336
1337 reset_gc_time_stamp();
1338 // Since everything potentially moved, we will clear all remembered
1339 // sets, and clear all cards. Later we will rebuild remembered
1340 // sets. We will also reset the GC time stamps of the regions.
1341 clear_rsets_post_compaction();
1342 check_gc_time_stamps();
1343
1344 // Resize the heap if necessary.
1345 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1346
1347 if (_hr_printer.is_active()) {
1348 // We should do this after we potentially resize the heap so
1349 // that all the COMMIT / UNCOMMIT events are generated before
1350 // the end GC event.
1351
1352 print_hrm_post_compaction();
1353 _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1354 }
1355
1356 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
1357 if (hot_card_cache->use_cache()) {
1358 hot_card_cache->reset_card_counts();
1359 hot_card_cache->reset_hot_cache();
1360 }
1361
1362 // Rebuild remembered sets of all regions.
1363 uint n_workers =
1364 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1365 workers()->active_workers(),
1366 Threads::number_of_non_daemon_threads());
1367 assert(UseDynamicNumberOfGCThreads ||
1368 n_workers == workers()->total_workers(),
1369 "If not dynamic should be using all the workers");
1370 workers()->set_active_workers(n_workers);
1371 // Set parallel threads in the heap (_n_par_threads) only
1372 // before a parallel phase and always reset it to 0 after
1373 // the phase so that the number of parallel threads does
1374 // no get carried forward to a serial phase where there
1375 // may be code that is "possibly_parallel".
1376 set_par_threads(n_workers);
1377
1378 ParRebuildRSTask rebuild_rs_task(this);
1379 assert(UseDynamicNumberOfGCThreads ||
1380 workers()->active_workers() == workers()->total_workers(),
1381 "Unless dynamic should use total workers");
1382 // Use the most recent number of active workers
1383 assert(workers()->active_workers() > 0,
1384 "Active workers not properly set");
1385 set_par_threads(workers()->active_workers());
1386 workers()->run_task(&rebuild_rs_task);
1387 set_par_threads(0);
1388
1389 // Rebuild the strong code root lists for each region
1390 rebuild_strong_code_roots();
1391
1392 if (true) { // FIXME
1393 MetaspaceGC::compute_new_size();
1394 }
1395
1396 #ifdef TRACESPINNING
1397 ParallelTaskTerminator::print_termination_counts();
1398 #endif
1399
1400 // Discard all rset updates
1401 JavaThread::dirty_card_queue_set().abandon_logs();
1402 assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1403
1404 _young_list->reset_sampled_info();
1405 // At this point there should be no regions in the
1406 // entire heap tagged as young.
1407 assert(check_young_list_empty(true /* check_heap */),
1408 "young list should be empty at this point");
1409
1410 // Update the number of full collections that have been completed.
1411 increment_old_marking_cycles_completed(false /* concurrent */);
1412
1413 _hrm.verify_optional();
1414 verify_region_sets_optional();
1415
1416 verify_after_gc();
1417
1418 // Clear the previous marking bitmap, if needed for bitmap verification.
1419 // Note we cannot do this when we clear the next marking bitmap in
1420 // ConcurrentMark::abort() above since VerifyDuringGC verifies the
1421 // objects marked during a full GC against the previous bitmap.
1422 // But we need to clear it before calling check_bitmaps below since
1423 // the full GC has compacted objects and updated TAMS but not updated
1424 // the prev bitmap.
1425 if (G1VerifyBitmaps) {
1426 ((CMBitMap*) concurrent_mark()->prevMarkBitMap())->clearAll();
1427 }
1428 check_bitmaps("Full GC End");
1429
1430 // Start a new incremental collection set for the next pause
1431 assert(g1_policy()->collection_set() == NULL, "must be");
1432 g1_policy()->start_incremental_cset_building();
1433
1434 clear_cset_fast_test();
1435
1436 _allocator->init_mutator_alloc_region();
1437
1438 g1_policy()->record_full_collection_end();
1439
1440 if (G1Log::fine()) {
1441 g1_policy()->print_heap_transition();
1442 }
1443
1444 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1445 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1446 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1447 // before any GC notifications are raised.
1448 g1mm()->update_sizes();
1449
1450 gc_epilogue(true);
1451 }
1452
1453 if (G1Log::finer()) {
1454 g1_policy()->print_detailed_heap_transition(true /* full */);
1455 }
1456
1457 print_heap_after_gc();
1458 trace_heap_after_gc(gc_tracer);
1459
1460 post_full_gc_dump(gc_timer);
1461
1462 gc_timer->register_gc_end();
1463 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
1464 }
1465
1466 return true;
1467 }
1468
1469 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1470 // do_collection() will return whether it succeeded in performing
1471 // the GC. Currently, there is no facility on the
1472 // do_full_collection() API to notify the caller than the collection
1473 // did not succeed (e.g., because it was locked out by the GC
1474 // locker). So, right now, we'll ignore the return value.
1475 bool dummy = do_collection(true, /* explicit_gc */
1476 clear_all_soft_refs,
1477 0 /* word_size */);
1478 }
1479
1480 // This code is mostly copied from TenuredGeneration.
1481 void
1482 G1CollectedHeap::
1483 resize_if_necessary_after_full_collection(size_t word_size) {
1484 // Include the current allocation, if any, and bytes that will be
1485 // pre-allocated to support collections, as "used".
1486 const size_t used_after_gc = used();
1487 const size_t capacity_after_gc = capacity();
1488 const size_t free_after_gc = capacity_after_gc - used_after_gc;
1489
1490 // This is enforced in arguments.cpp.
1491 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1492 "otherwise the code below doesn't make sense");
1493
1494 // We don't have floating point command-line arguments
1495 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1496 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1497 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1498 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1499
1500 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1501 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1502
1503 // We have to be careful here as these two calculations can overflow
1504 // 32-bit size_t's.
1505 double used_after_gc_d = (double) used_after_gc;
1506 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1507 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1508
1509 // Let's make sure that they are both under the max heap size, which
1510 // by default will make them fit into a size_t.
1511 double desired_capacity_upper_bound = (double) max_heap_size;
1512 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1513 desired_capacity_upper_bound);
1514 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1515 desired_capacity_upper_bound);
1516
1517 // We can now safely turn them into size_t's.
1518 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1519 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1520
1521 // This assert only makes sense here, before we adjust them
1522 // with respect to the min and max heap size.
1523 assert(minimum_desired_capacity <= maximum_desired_capacity,
1524 err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1525 "maximum_desired_capacity = "SIZE_FORMAT,
1526 minimum_desired_capacity, maximum_desired_capacity));
1527
1528 // Should not be greater than the heap max size. No need to adjust
1529 // it with respect to the heap min size as it's a lower bound (i.e.,
1530 // we'll try to make the capacity larger than it, not smaller).
1531 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1532 // Should not be less than the heap min size. No need to adjust it
1533 // with respect to the heap max size as it's an upper bound (i.e.,
1534 // we'll try to make the capacity smaller than it, not greater).
1535 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1536
1537 if (capacity_after_gc < minimum_desired_capacity) {
1538 // Don't expand unless it's significant
1539 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1540 ergo_verbose4(ErgoHeapSizing,
1541 "attempt heap expansion",
1542 ergo_format_reason("capacity lower than "
1543 "min desired capacity after Full GC")
1544 ergo_format_byte("capacity")
1545 ergo_format_byte("occupancy")
1546 ergo_format_byte_perc("min desired capacity"),
1547 capacity_after_gc, used_after_gc,
1548 minimum_desired_capacity, (double) MinHeapFreeRatio);
1549 expand(expand_bytes);
1550
1551 // No expansion, now see if we want to shrink
1552 } else if (capacity_after_gc > maximum_desired_capacity) {
1553 // Capacity too large, compute shrinking size
1554 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1555 ergo_verbose4(ErgoHeapSizing,
1556 "attempt heap shrinking",
1557 ergo_format_reason("capacity higher than "
1558 "max desired capacity after Full GC")
1559 ergo_format_byte("capacity")
1560 ergo_format_byte("occupancy")
1561 ergo_format_byte_perc("max desired capacity"),
1562 capacity_after_gc, used_after_gc,
1563 maximum_desired_capacity, (double) MaxHeapFreeRatio);
1564 shrink(shrink_bytes);
1565 }
1566 }
1567
1568
1569 HeapWord*
1570 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1571 AllocationContext_t context,
1572 bool* succeeded) {
1573 assert_at_safepoint(true /* should_be_vm_thread */);
1574
1575 *succeeded = true;
1576 // Let's attempt the allocation first.
1577 HeapWord* result =
1578 attempt_allocation_at_safepoint(word_size,
1579 context,
1580 false /* expect_null_mutator_alloc_region */);
1581 if (result != NULL) {
1582 assert(*succeeded, "sanity");
1583 return result;
1584 }
1585
1586 // In a G1 heap, we're supposed to keep allocation from failing by
1587 // incremental pauses. Therefore, at least for now, we'll favor
1588 // expansion over collection. (This might change in the future if we can
1589 // do something smarter than full collection to satisfy a failed alloc.)
1590 result = expand_and_allocate(word_size, context);
1591 if (result != NULL) {
1592 assert(*succeeded, "sanity");
1593 return result;
1594 }
1595
1596 // Expansion didn't work, we'll try to do a Full GC.
1597 bool gc_succeeded = do_collection(false, /* explicit_gc */
1598 false, /* clear_all_soft_refs */
1599 word_size);
1600 if (!gc_succeeded) {
1601 *succeeded = false;
1602 return NULL;
1603 }
1604
1605 // Retry the allocation
1606 result = attempt_allocation_at_safepoint(word_size,
1607 context,
1608 true /* expect_null_mutator_alloc_region */);
1609 if (result != NULL) {
1610 assert(*succeeded, "sanity");
1611 return result;
1612 }
1613
1614 // Then, try a Full GC that will collect all soft references.
1615 gc_succeeded = do_collection(false, /* explicit_gc */
1616 true, /* clear_all_soft_refs */
1617 word_size);
1618 if (!gc_succeeded) {
1619 *succeeded = false;
1620 return NULL;
1621 }
1622
1623 // Retry the allocation once more
1624 result = attempt_allocation_at_safepoint(word_size,
1625 context,
1626 true /* expect_null_mutator_alloc_region */);
1627 if (result != NULL) {
1628 assert(*succeeded, "sanity");
1629 return result;
1630 }
1631
1632 assert(!collector_policy()->should_clear_all_soft_refs(),
1633 "Flag should have been handled and cleared prior to this point");
1634
1635 // What else? We might try synchronous finalization later. If the total
1636 // space available is large enough for the allocation, then a more
1637 // complete compaction phase than we've tried so far might be
1638 // appropriate.
1639 assert(*succeeded, "sanity");
1640 return NULL;
1641 }
1642
1643 // Attempting to expand the heap sufficiently
1644 // to support an allocation of the given "word_size". If
1645 // successful, perform the allocation and return the address of the
1646 // allocated block, or else "NULL".
1647
1648 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) {
1649 assert_at_safepoint(true /* should_be_vm_thread */);
1650
1651 verify_region_sets_optional();
1652
1653 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1654 ergo_verbose1(ErgoHeapSizing,
1655 "attempt heap expansion",
1656 ergo_format_reason("allocation request failed")
1657 ergo_format_byte("allocation request"),
1658 word_size * HeapWordSize);
1659 if (expand(expand_bytes)) {
1660 _hrm.verify_optional();
1661 verify_region_sets_optional();
1662 return attempt_allocation_at_safepoint(word_size,
1663 context,
1664 false /* expect_null_mutator_alloc_region */);
1665 }
1666 return NULL;
1667 }
1668
1669 bool G1CollectedHeap::expand(size_t expand_bytes) {
1670 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1671 aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1672 HeapRegion::GrainBytes);
1673 ergo_verbose2(ErgoHeapSizing,
1674 "expand the heap",
1675 ergo_format_byte("requested expansion amount")
1676 ergo_format_byte("attempted expansion amount"),
1677 expand_bytes, aligned_expand_bytes);
1678
1679 if (is_maximal_no_gc()) {
1680 ergo_verbose0(ErgoHeapSizing,
1681 "did not expand the heap",
1682 ergo_format_reason("heap already fully expanded"));
1683 return false;
1684 }
1685
1686 uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1687 assert(regions_to_expand > 0, "Must expand by at least one region");
1688
1689 uint expanded_by = _hrm.expand_by(regions_to_expand);
1690
1691 if (expanded_by > 0) {
1692 size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1693 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1694 g1_policy()->record_new_heap_size(num_regions());
1695 } else {
1696 ergo_verbose0(ErgoHeapSizing,
1697 "did not expand the heap",
1698 ergo_format_reason("heap expansion operation failed"));
1699 // The expansion of the virtual storage space was unsuccessful.
1700 // Let's see if it was because we ran out of swap.
1701 if (G1ExitOnExpansionFailure &&
1702 _hrm.available() >= regions_to_expand) {
1703 // We had head room...
1704 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1705 }
1706 }
1707 return regions_to_expand > 0;
1708 }
1709
1710 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1711 size_t aligned_shrink_bytes =
1712 ReservedSpace::page_align_size_down(shrink_bytes);
1713 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1714 HeapRegion::GrainBytes);
1715 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1716
1717 uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1718 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1719
1720 ergo_verbose3(ErgoHeapSizing,
1721 "shrink the heap",
1722 ergo_format_byte("requested shrinking amount")
1723 ergo_format_byte("aligned shrinking amount")
1724 ergo_format_byte("attempted shrinking amount"),
1725 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1726 if (num_regions_removed > 0) {
1727 g1_policy()->record_new_heap_size(num_regions());
1728 } else {
1729 ergo_verbose0(ErgoHeapSizing,
1730 "did not shrink the heap",
1731 ergo_format_reason("heap shrinking operation failed"));
1732 }
1733 }
1734
1735 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1736 verify_region_sets_optional();
1737
1738 // We should only reach here at the end of a Full GC which means we
1739 // should not not be holding to any GC alloc regions. The method
1740 // below will make sure of that and do any remaining clean up.
1741 _allocator->abandon_gc_alloc_regions();
1742
1743 // Instead of tearing down / rebuilding the free lists here, we
1744 // could instead use the remove_all_pending() method on free_list to
1745 // remove only the ones that we need to remove.
1746 tear_down_region_sets(true /* free_list_only */);
1747 shrink_helper(shrink_bytes);
1748 rebuild_region_sets(true /* free_list_only */);
1749
1750 _hrm.verify_optional();
1751 verify_region_sets_optional();
1752 }
1753
1754 // Public methods.
1755
1756 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1757 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1758 #endif // _MSC_VER
1759
1760
1761 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1762 SharedHeap(policy_),
1763 _g1_policy(policy_),
1764 _dirty_card_queue_set(false),
1765 _into_cset_dirty_card_queue_set(false),
1766 _is_alive_closure_cm(this),
1767 _is_alive_closure_stw(this),
1768 _ref_processor_cm(NULL),
1769 _ref_processor_stw(NULL),
1770 _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
1771 _bot_shared(NULL),
1772 _evac_failure_scan_stack(NULL),
1773 _mark_in_progress(false),
1774 _cg1r(NULL),
1775 _g1mm(NULL),
1776 _refine_cte_cl(NULL),
1777 _full_collection(false),
1778 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1779 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1780 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1781 _humongous_is_live(),
1782 _has_humongous_reclaim_candidates(false),
1783 _free_regions_coming(false),
1784 _young_list(new YoungList(this)),
1785 _gc_time_stamp(0),
1786 _survivor_plab_stats(YoungPLABSize, PLABWeight),
1787 _old_plab_stats(OldPLABSize, PLABWeight),
1788 _expand_heap_after_alloc_failure(true),
1789 _surviving_young_words(NULL),
1790 _old_marking_cycles_started(0),
1791 _old_marking_cycles_completed(0),
1792 _concurrent_cycle_started(false),
1793 _heap_summary_sent(false),
1794 _in_cset_fast_test(),
1795 _dirty_cards_region_list(NULL),
1796 _worker_cset_start_region(NULL),
1797 _worker_cset_start_region_time_stamp(NULL),
1798 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1799 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
1800 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1801 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) {
1802
1803 _g1h = this;
1804 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
1805 vm_exit_during_initialization("Failed necessary allocation.");
1806 }
1807
1808 _allocator = G1Allocator::create_allocator(_g1h);
1809 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1810
1811 int n_queues = MAX2((int)ParallelGCThreads, 1);
1812 _task_queues = new RefToScanQueueSet(n_queues);
1813
1814 uint n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1815 assert(n_rem_sets > 0, "Invariant.");
1816
1817 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1818 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC);
1819 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1820
1821 for (int i = 0; i < n_queues; i++) {
1822 RefToScanQueue* q = new RefToScanQueue();
1823 q->initialize();
1824 _task_queues->register_queue(i, q);
1825 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1826 }
1827 clear_cset_start_regions();
1828
1829 // Initialize the G1EvacuationFailureALot counters and flags.
1830 NOT_PRODUCT(reset_evacuation_should_fail();)
1831
1832 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1833 }
1834
1835 jint G1CollectedHeap::initialize() {
1836 CollectedHeap::pre_initialize();
1837 os::enable_vtime();
1838
1839 G1Log::init();
1840
1841 // Necessary to satisfy locking discipline assertions.
1842
1843 MutexLocker x(Heap_lock);
1844
1845 // We have to initialize the printer before committing the heap, as
1846 // it will be used then.
1847 _hr_printer.set_active(G1PrintHeapRegions);
1848
1849 // While there are no constraints in the GC code that HeapWordSize
1850 // be any particular value, there are multiple other areas in the
1851 // system which believe this to be true (e.g. oop->object_size in some
1852 // cases incorrectly returns the size in wordSize units rather than
1853 // HeapWordSize).
1854 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1855
1856 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1857 size_t max_byte_size = collector_policy()->max_heap_byte_size();
1858 size_t heap_alignment = collector_policy()->heap_alignment();
1859
1860 // Ensure that the sizes are properly aligned.
1861 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1862 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1863 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1864
1865 _refine_cte_cl = new RefineCardTableEntryClosure();
1866
1867 _cg1r = new ConcurrentG1Refine(this, _refine_cte_cl);
1868
1869 // Reserve the maximum.
1870
1871 // When compressed oops are enabled, the preferred heap base
1872 // is calculated by subtracting the requested size from the
1873 // 32Gb boundary and using the result as the base address for
1874 // heap reservation. If the requested size is not aligned to
1875 // HeapRegion::GrainBytes (i.e. the alignment that is passed
1876 // into the ReservedHeapSpace constructor) then the actual
1877 // base of the reserved heap may end up differing from the
1878 // address that was requested (i.e. the preferred heap base).
1879 // If this happens then we could end up using a non-optimal
1880 // compressed oops mode.
1881
1882 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1883 heap_alignment);
1884
1885 initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
1886
1887 // Create the barrier set for the entire reserved region.
1888 G1SATBCardTableLoggingModRefBS* bs
1889 = new G1SATBCardTableLoggingModRefBS(reserved_region());
1890 bs->initialize();
1891 assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity");
1892 set_barrier_set(bs);
1893
1894 // Also create a G1 rem set.
1895 _g1_rem_set = new G1RemSet(this, g1_barrier_set());
1896
1897 // Carve out the G1 part of the heap.
1898
1899 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1900 G1RegionToSpaceMapper* heap_storage =
1901 G1RegionToSpaceMapper::create_mapper(g1_rs,
1902 UseLargePages ? os::large_page_size() : os::vm_page_size(),
1903 HeapRegion::GrainBytes,
1904 1,
1905 mtJavaHeap);
1906 heap_storage->set_mapping_changed_listener(&_listener);
1907
1908 // Reserve space for the block offset table. We do not support automatic uncommit
1909 // for the card table at this time. BOT only.
1910 ReservedSpace bot_rs(G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize));
1911 G1RegionToSpaceMapper* bot_storage =
1912 G1RegionToSpaceMapper::create_mapper(bot_rs,
1913 os::vm_page_size(),
1914 HeapRegion::GrainBytes,
1915 G1BlockOffsetSharedArray::N_bytes,
1916 mtGC);
1917
1918 ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize));
1919 G1RegionToSpaceMapper* cardtable_storage =
1920 G1RegionToSpaceMapper::create_mapper(cardtable_rs,
1921 os::vm_page_size(),
1922 HeapRegion::GrainBytes,
1923 G1BlockOffsetSharedArray::N_bytes,
1924 mtGC);
1925
1926 // Reserve space for the card counts table.
1927 ReservedSpace card_counts_rs(G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize));
1928 G1RegionToSpaceMapper* card_counts_storage =
1929 G1RegionToSpaceMapper::create_mapper(card_counts_rs,
1930 os::vm_page_size(),
1931 HeapRegion::GrainBytes,
1932 G1BlockOffsetSharedArray::N_bytes,
1933 mtGC);
1934
1935 // Reserve space for prev and next bitmap.
1936 size_t bitmap_size = CMBitMap::compute_size(g1_rs.size());
1937
1938 ReservedSpace prev_bitmap_rs(ReservedSpace::allocation_align_size_up(bitmap_size));
1939 G1RegionToSpaceMapper* prev_bitmap_storage =
1940 G1RegionToSpaceMapper::create_mapper(prev_bitmap_rs,
1941 os::vm_page_size(),
1942 HeapRegion::GrainBytes,
1943 CMBitMap::mark_distance(),
1944 mtGC);
1945
1946 ReservedSpace next_bitmap_rs(ReservedSpace::allocation_align_size_up(bitmap_size));
1947 G1RegionToSpaceMapper* next_bitmap_storage =
1948 G1RegionToSpaceMapper::create_mapper(next_bitmap_rs,
1949 os::vm_page_size(),
1950 HeapRegion::GrainBytes,
1951 CMBitMap::mark_distance(),
1952 mtGC);
1953
1954 _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1955 g1_barrier_set()->initialize(cardtable_storage);
1956 // Do later initialization work for concurrent refinement.
1957 _cg1r->init(card_counts_storage);
1958
1959 // 6843694 - ensure that the maximum region index can fit
1960 // in the remembered set structures.
1961 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1962 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1963
1964 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1965 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1966 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1967 "too many cards per region");
1968
1969 FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
1970
1971 _bot_shared = new G1BlockOffsetSharedArray(reserved_region(), bot_storage);
1972
1973 _g1h = this;
1974
1975 _in_cset_fast_test.initialize(_hrm.reserved().start(), _hrm.reserved().end(), HeapRegion::GrainBytes);
1976 _humongous_is_live.initialize(_hrm.reserved().start(), _hrm.reserved().end(), HeapRegion::GrainBytes);
1977
1978 // Create the ConcurrentMark data structure and thread.
1979 // (Must do this late, so that "max_regions" is defined.)
1980 _cm = new ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1981 if (_cm == NULL || !_cm->completed_initialization()) {
1982 vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark");
1983 return JNI_ENOMEM;
1984 }
1985 _cmThread = _cm->cmThread();
1986
1987 // Initialize the from_card cache structure of HeapRegionRemSet.
1988 HeapRegionRemSet::init_heap(max_regions());
1989
1990 // Now expand into the initial heap size.
1991 if (!expand(init_byte_size)) {
1992 vm_shutdown_during_initialization("Failed to allocate initial heap.");
1993 return JNI_ENOMEM;
1994 }
1995
1996 // Perform any initialization actions delegated to the policy.
1997 g1_policy()->init();
1998
1999 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
2000 SATB_Q_FL_lock,
2001 G1SATBProcessCompletedThreshold,
2002 Shared_SATB_Q_lock);
2003
2004 JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl,
2005 DirtyCardQ_CBL_mon,
2006 DirtyCardQ_FL_lock,
2007 concurrent_g1_refine()->yellow_zone(),
2008 concurrent_g1_refine()->red_zone(),
2009 Shared_DirtyCardQ_lock);
2010
2011 dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code
2012 DirtyCardQ_CBL_mon,
2013 DirtyCardQ_FL_lock,
2014 -1, // never trigger processing
2015 -1, // no limit on length
2016 Shared_DirtyCardQ_lock,
2017 &JavaThread::dirty_card_queue_set());
2018
2019 // Initialize the card queue set used to hold cards containing
2020 // references into the collection set.
2021 _into_cset_dirty_card_queue_set.initialize(NULL, // Should never be called by the Java code
2022 DirtyCardQ_CBL_mon,
2023 DirtyCardQ_FL_lock,
2024 -1, // never trigger processing
2025 -1, // no limit on length
2026 Shared_DirtyCardQ_lock,
2027 &JavaThread::dirty_card_queue_set());
2028
2029 // In case we're keeping closure specialization stats, initialize those
2030 // counts and that mechanism.
2031 SpecializationStats::clear();
2032
2033 // Here we allocate the dummy HeapRegion that is required by the
2034 // G1AllocRegion class.
2035 HeapRegion* dummy_region = _hrm.get_dummy_region();
2036
2037 // We'll re-use the same region whether the alloc region will
2038 // require BOT updates or not and, if it doesn't, then a non-young
2039 // region will complain that it cannot support allocations without
2040 // BOT updates. So we'll tag the dummy region as eden to avoid that.
2041 dummy_region->set_eden();
2042 // Make sure it's full.
2043 dummy_region->set_top(dummy_region->end());
2044 G1AllocRegion::setup(this, dummy_region);
2045
2046 _allocator->init_mutator_alloc_region();
2047
2048 // Do create of the monitoring and management support so that
2049 // values in the heap have been properly initialized.
2050 _g1mm = new G1MonitoringSupport(this);
2051
2052 G1StringDedup::initialize();
2053
2054 return JNI_OK;
2055 }
2056
2057 void G1CollectedHeap::stop() {
2058 // Stop all concurrent threads. We do this to make sure these threads
2059 // do not continue to execute and access resources (e.g. gclog_or_tty)
2060 // that are destroyed during shutdown.
2061 _cg1r->stop();
2062 _cmThread->stop();
2063 if (G1StringDedup::is_enabled()) {
2064 G1StringDedup::stop();
2065 }
2066 }
2067
2068 void G1CollectedHeap::clear_humongous_is_live_table() {
2069 guarantee(G1EagerReclaimHumongousObjects, "Should only be called if true");
2070 _humongous_is_live.clear();
2071 }
2072
2073 size_t G1CollectedHeap::conservative_max_heap_alignment() {
2074 return HeapRegion::max_region_size();
2075 }
2076
2077 void G1CollectedHeap::ref_processing_init() {
2078 // Reference processing in G1 currently works as follows:
2079 //
2080 // * There are two reference processor instances. One is
2081 // used to record and process discovered references
2082 // during concurrent marking; the other is used to
2083 // record and process references during STW pauses
2084 // (both full and incremental).
2085 // * Both ref processors need to 'span' the entire heap as
2086 // the regions in the collection set may be dotted around.
2087 //
2088 // * For the concurrent marking ref processor:
2089 // * Reference discovery is enabled at initial marking.
2090 // * Reference discovery is disabled and the discovered
2091 // references processed etc during remarking.
2092 // * Reference discovery is MT (see below).
2093 // * Reference discovery requires a barrier (see below).
2094 // * Reference processing may or may not be MT
2095 // (depending on the value of ParallelRefProcEnabled
2096 // and ParallelGCThreads).
2097 // * A full GC disables reference discovery by the CM
2098 // ref processor and abandons any entries on it's
2099 // discovered lists.
2100 //
2101 // * For the STW processor:
2102 // * Non MT discovery is enabled at the start of a full GC.
2103 // * Processing and enqueueing during a full GC is non-MT.
2104 // * During a full GC, references are processed after marking.
2105 //
2106 // * Discovery (may or may not be MT) is enabled at the start
2107 // of an incremental evacuation pause.
2108 // * References are processed near the end of a STW evacuation pause.
2109 // * For both types of GC:
2110 // * Discovery is atomic - i.e. not concurrent.
2111 // * Reference discovery will not need a barrier.
2112
2113 SharedHeap::ref_processing_init();
2114 MemRegion mr = reserved_region();
2115
2116 // Concurrent Mark ref processor
2117 _ref_processor_cm =
2118 new ReferenceProcessor(mr, // span
2119 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2120 // mt processing
2121 (int) ParallelGCThreads,
2122 // degree of mt processing
2123 (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2124 // mt discovery
2125 (int) MAX2(ParallelGCThreads, ConcGCThreads),
2126 // degree of mt discovery
2127 false,
2128 // Reference discovery is not atomic
2129 &_is_alive_closure_cm);
2130 // is alive closure
2131 // (for efficiency/performance)
2132
2133 // STW ref processor
2134 _ref_processor_stw =
2135 new ReferenceProcessor(mr, // span
2136 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2137 // mt processing
2138 MAX2((int)ParallelGCThreads, 1),
2139 // degree of mt processing
2140 (ParallelGCThreads > 1),
2141 // mt discovery
2142 MAX2((int)ParallelGCThreads, 1),
2143 // degree of mt discovery
2144 true,
2145 // Reference discovery is atomic
2146 &_is_alive_closure_stw);
2147 // is alive closure
2148 // (for efficiency/performance)
2149 }
2150
2151 size_t G1CollectedHeap::capacity() const {
2152 return _hrm.length() * HeapRegion::GrainBytes;
2153 }
2154
2155 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2156 assert(!hr->is_continues_humongous(), "pre-condition");
2157 hr->reset_gc_time_stamp();
2158 if (hr->is_starts_humongous()) {
2159 uint first_index = hr->hrm_index() + 1;
2160 uint last_index = hr->last_hc_index();
2161 for (uint i = first_index; i < last_index; i += 1) {
2162 HeapRegion* chr = region_at(i);
2163 assert(chr->is_continues_humongous(), "sanity");
2164 chr->reset_gc_time_stamp();
2165 }
2166 }
2167 }
2168
2169 #ifndef PRODUCT
2170 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2171 private:
2172 unsigned _gc_time_stamp;
2173 bool _failures;
2174
2175 public:
2176 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2177 _gc_time_stamp(gc_time_stamp), _failures(false) { }
2178
2179 virtual bool doHeapRegion(HeapRegion* hr) {
2180 unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2181 if (_gc_time_stamp != region_gc_time_stamp) {
2182 gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, "
2183 "expected %d", HR_FORMAT_PARAMS(hr),
2184 region_gc_time_stamp, _gc_time_stamp);
2185 _failures = true;
2186 }
2187 return false;
2188 }
2189
2190 bool failures() { return _failures; }
2191 };
2192
2193 void G1CollectedHeap::check_gc_time_stamps() {
2194 CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2195 heap_region_iterate(&cl);
2196 guarantee(!cl.failures(), "all GC time stamps should have been reset");
2197 }
2198 #endif // PRODUCT
2199
2200 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2201 DirtyCardQueue* into_cset_dcq,
2202 bool concurrent,
2203 uint worker_i) {
2204 // Clean cards in the hot card cache
2205 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
2206 hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq);
2207
2208 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2209 int n_completed_buffers = 0;
2210 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2211 n_completed_buffers++;
2212 }
2213 g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers);
2214 dcqs.clear_n_completed_buffers();
2215 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2216 }
2217
2218
2219 // Computes the sum of the storage used by the various regions.
2220 size_t G1CollectedHeap::used() const {
2221 return _allocator->used();
2222 }
2223
2224 size_t G1CollectedHeap::used_unlocked() const {
2225 return _allocator->used_unlocked();
2226 }
2227
2228 class SumUsedClosure: public HeapRegionClosure {
2229 size_t _used;
2230 public:
2231 SumUsedClosure() : _used(0) {}
2232 bool doHeapRegion(HeapRegion* r) {
2233 if (!r->is_continues_humongous()) {
2234 _used += r->used();
2235 }
2236 return false;
2237 }
2238 size_t result() { return _used; }
2239 };
2240
2241 size_t G1CollectedHeap::recalculate_used() const {
2242 double recalculate_used_start = os::elapsedTime();
2243
2244 SumUsedClosure blk;
2245 heap_region_iterate(&blk);
2246
2247 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2248 return blk.result();
2249 }
2250
2251 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2252 switch (cause) {
2253 case GCCause::_gc_locker: return GCLockerInvokesConcurrent;
2254 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
2255 case GCCause::_g1_humongous_allocation: return true;
2256 case GCCause::_update_allocation_context_stats_inc: return true;
2257 case GCCause::_wb_conc_mark: return true;
2258 default: return false;
2259 }
2260 }
2261
2262 #ifndef PRODUCT
2263 void G1CollectedHeap::allocate_dummy_regions() {
2264 // Let's fill up most of the region
2265 size_t word_size = HeapRegion::GrainWords - 1024;
2266 // And as a result the region we'll allocate will be humongous.
2267 guarantee(is_humongous(word_size), "sanity");
2268
2269 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2270 // Let's use the existing mechanism for the allocation
2271 HeapWord* dummy_obj = humongous_obj_allocate(word_size,
2272 AllocationContext::system());
2273 if (dummy_obj != NULL) {
2274 MemRegion mr(dummy_obj, word_size);
2275 CollectedHeap::fill_with_object(mr);
2276 } else {
2277 // If we can't allocate once, we probably cannot allocate
2278 // again. Let's get out of the loop.
2279 break;
2280 }
2281 }
2282 }
2283 #endif // !PRODUCT
2284
2285 void G1CollectedHeap::increment_old_marking_cycles_started() {
2286 assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2287 _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2288 err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2289 _old_marking_cycles_started, _old_marking_cycles_completed));
2290
2291 _old_marking_cycles_started++;
2292 }
2293
2294 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2295 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2296
2297 // We assume that if concurrent == true, then the caller is a
2298 // concurrent thread that was joined the Suspendible Thread
2299 // Set. If there's ever a cheap way to check this, we should add an
2300 // assert here.
2301
2302 // Given that this method is called at the end of a Full GC or of a
2303 // concurrent cycle, and those can be nested (i.e., a Full GC can
2304 // interrupt a concurrent cycle), the number of full collections
2305 // completed should be either one (in the case where there was no
2306 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2307 // behind the number of full collections started.
2308
2309 // This is the case for the inner caller, i.e. a Full GC.
2310 assert(concurrent ||
2311 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2312 (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2313 err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
2314 "is inconsistent with _old_marking_cycles_completed = %u",
2315 _old_marking_cycles_started, _old_marking_cycles_completed));
2316
2317 // This is the case for the outer caller, i.e. the concurrent cycle.
2318 assert(!concurrent ||
2319 (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2320 err_msg("for outer caller (concurrent cycle): "
2321 "_old_marking_cycles_started = %u "
2322 "is inconsistent with _old_marking_cycles_completed = %u",
2323 _old_marking_cycles_started, _old_marking_cycles_completed));
2324
2325 _old_marking_cycles_completed += 1;
2326
2327 // We need to clear the "in_progress" flag in the CM thread before
2328 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2329 // is set) so that if a waiter requests another System.gc() it doesn't
2330 // incorrectly see that a marking cycle is still in progress.
2331 if (concurrent) {
2332 _cmThread->clear_in_progress();
2333 }
2334
2335 // This notify_all() will ensure that a thread that called
2336 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2337 // and it's waiting for a full GC to finish will be woken up. It is
2338 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2339 FullGCCount_lock->notify_all();
2340 }
2341
2342 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) {
2343 _concurrent_cycle_started = true;
2344 _gc_timer_cm->register_gc_start(start_time);
2345
2346 _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start());
2347 trace_heap_before_gc(_gc_tracer_cm);
2348 }
2349
2350 void G1CollectedHeap::register_concurrent_cycle_end() {
2351 if (_concurrent_cycle_started) {
2352 if (_cm->has_aborted()) {
2353 _gc_tracer_cm->report_concurrent_mode_failure();
2354 }
2355
2356 _gc_timer_cm->register_gc_end();
2357 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
2358
2359 // Clear state variables to prepare for the next concurrent cycle.
2360 _concurrent_cycle_started = false;
2361 _heap_summary_sent = false;
2362 }
2363 }
2364
2365 void G1CollectedHeap::trace_heap_after_concurrent_cycle() {
2366 if (_concurrent_cycle_started) {
2367 // This function can be called when:
2368 // the cleanup pause is run
2369 // the concurrent cycle is aborted before the cleanup pause.
2370 // the concurrent cycle is aborted after the cleanup pause,
2371 // but before the concurrent cycle end has been registered.
2372 // Make sure that we only send the heap information once.
2373 if (!_heap_summary_sent) {
2374 trace_heap_after_gc(_gc_tracer_cm);
2375 _heap_summary_sent = true;
2376 }
2377 }
2378 }
2379
2380 G1YCType G1CollectedHeap::yc_type() {
2381 bool is_young = g1_policy()->gcs_are_young();
2382 bool is_initial_mark = g1_policy()->during_initial_mark_pause();
2383 bool is_during_mark = mark_in_progress();
2384
2385 if (is_initial_mark) {
2386 return InitialMark;
2387 } else if (is_during_mark) {
2388 return DuringMark;
2389 } else if (is_young) {
2390 return Normal;
2391 } else {
2392 return Mixed;
2393 }
2394 }
2395
2396 void G1CollectedHeap::collect(GCCause::Cause cause) {
2397 assert_heap_not_locked();
2398
2399 unsigned int gc_count_before;
2400 unsigned int old_marking_count_before;
2401 unsigned int full_gc_count_before;
2402 bool retry_gc;
2403
2404 do {
2405 retry_gc = false;
2406
2407 {
2408 MutexLocker ml(Heap_lock);
2409
2410 // Read the GC count while holding the Heap_lock
2411 gc_count_before = total_collections();
2412 full_gc_count_before = total_full_collections();
2413 old_marking_count_before = _old_marking_cycles_started;
2414 }
2415
2416 if (should_do_concurrent_full_gc(cause)) {
2417 // Schedule an initial-mark evacuation pause that will start a
2418 // concurrent cycle. We're setting word_size to 0 which means that
2419 // we are not requesting a post-GC allocation.
2420 VM_G1IncCollectionPause op(gc_count_before,
2421 0, /* word_size */
2422 true, /* should_initiate_conc_mark */
2423 g1_policy()->max_pause_time_ms(),
2424 cause);
2425 op.set_allocation_context(AllocationContext::current());
2426
2427 VMThread::execute(&op);
2428 if (!op.pause_succeeded()) {
2429 if (old_marking_count_before == _old_marking_cycles_started) {
2430 retry_gc = op.should_retry_gc();
2431 } else {
2432 // A Full GC happened while we were trying to schedule the
2433 // initial-mark GC. No point in starting a new cycle given
2434 // that the whole heap was collected anyway.
2435 }
2436
2437 if (retry_gc) {
2438 if (GC_locker::is_active_and_needs_gc()) {
2439 GC_locker::stall_until_clear();
2440 }
2441 }
2442 }
2443 } else {
2444 if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2445 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2446
2447 // Schedule a standard evacuation pause. We're setting word_size
2448 // to 0 which means that we are not requesting a post-GC allocation.
2449 VM_G1IncCollectionPause op(gc_count_before,
2450 0, /* word_size */
2451 false, /* should_initiate_conc_mark */
2452 g1_policy()->max_pause_time_ms(),
2453 cause);
2454 VMThread::execute(&op);
2455 } else {
2456 // Schedule a Full GC.
2457 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2458 VMThread::execute(&op);
2459 }
2460 }
2461 } while (retry_gc);
2462 }
2463
2464 bool G1CollectedHeap::is_in(const void* p) const {
2465 if (_hrm.reserved().contains(p)) {
2466 // Given that we know that p is in the reserved space,
2467 // heap_region_containing_raw() should successfully
2468 // return the containing region.
2469 HeapRegion* hr = heap_region_containing_raw(p);
2470 return hr->is_in(p);
2471 } else {
2472 return false;
2473 }
2474 }
2475
2476 #ifdef ASSERT
2477 bool G1CollectedHeap::is_in_exact(const void* p) const {
2478 bool contains = reserved_region().contains(p);
2479 bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2480 if (contains && available) {
2481 return true;
2482 } else {
2483 return false;
2484 }
2485 }
2486 #endif
2487
2488 // Iteration functions.
2489
2490 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion.
2491
2492 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2493 ExtendedOopClosure* _cl;
2494 public:
2495 IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {}
2496 bool doHeapRegion(HeapRegion* r) {
2497 if (!r->is_continues_humongous()) {
2498 r->oop_iterate(_cl);
2499 }
2500 return false;
2501 }
2502 };
2503
2504 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) {
2505 IterateOopClosureRegionClosure blk(cl);
2506 heap_region_iterate(&blk);
2507 }
2508
2509 // Iterates an ObjectClosure over all objects within a HeapRegion.
2510
2511 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2512 ObjectClosure* _cl;
2513 public:
2514 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2515 bool doHeapRegion(HeapRegion* r) {
2516 if (!r->is_continues_humongous()) {
2517 r->object_iterate(_cl);
2518 }
2519 return false;
2520 }
2521 };
2522
2523 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2524 IterateObjectClosureRegionClosure blk(cl);
2525 heap_region_iterate(&blk);
2526 }
2527
2528 // Calls a SpaceClosure on a HeapRegion.
2529
2530 class SpaceClosureRegionClosure: public HeapRegionClosure {
2531 SpaceClosure* _cl;
2532 public:
2533 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2534 bool doHeapRegion(HeapRegion* r) {
2535 _cl->do_space(r);
2536 return false;
2537 }
2538 };
2539
2540 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2541 SpaceClosureRegionClosure blk(cl);
2542 heap_region_iterate(&blk);
2543 }
2544
2545 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2546 _hrm.iterate(cl);
2547 }
2548
2549 void
2550 G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl,
2551 uint worker_id,
2552 HeapRegionClaimer *hrclaimer,
2553 bool concurrent) const {
2554 _hrm.par_iterate(cl, worker_id, hrclaimer, concurrent);
2555 }
2556
2557 // Clear the cached CSet starting regions and (more importantly)
2558 // the time stamps. Called when we reset the GC time stamp.
2559 void G1CollectedHeap::clear_cset_start_regions() {
2560 assert(_worker_cset_start_region != NULL, "sanity");
2561 assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2562
2563 int n_queues = MAX2((int)ParallelGCThreads, 1);
2564 for (int i = 0; i < n_queues; i++) {
2565 _worker_cset_start_region[i] = NULL;
2566 _worker_cset_start_region_time_stamp[i] = 0;
2567 }
2568 }
2569
2570 // Given the id of a worker, obtain or calculate a suitable
2571 // starting region for iterating over the current collection set.
2572 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) {
2573 assert(get_gc_time_stamp() > 0, "should have been updated by now");
2574
2575 HeapRegion* result = NULL;
2576 unsigned gc_time_stamp = get_gc_time_stamp();
2577
2578 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2579 // Cached starting region for current worker was set
2580 // during the current pause - so it's valid.
2581 // Note: the cached starting heap region may be NULL
2582 // (when the collection set is empty).
2583 result = _worker_cset_start_region[worker_i];
2584 assert(result == NULL || result->in_collection_set(), "sanity");
2585 return result;
2586 }
2587
2588 // The cached entry was not valid so let's calculate
2589 // a suitable starting heap region for this worker.
2590
2591 // We want the parallel threads to start their collection
2592 // set iteration at different collection set regions to
2593 // avoid contention.
2594 // If we have:
2595 // n collection set regions
2596 // p threads
2597 // Then thread t will start at region floor ((t * n) / p)
2598
2599 result = g1_policy()->collection_set();
2600 uint cs_size = g1_policy()->cset_region_length();
2601 uint active_workers = workers()->active_workers();
2602 assert(UseDynamicNumberOfGCThreads ||
2603 active_workers == workers()->total_workers(),
2604 "Unless dynamic should use total workers");
2605
2606 uint end_ind = (cs_size * worker_i) / active_workers;
2607 uint start_ind = 0;
2608
2609 if (worker_i > 0 &&
2610 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2611 // Previous workers starting region is valid
2612 // so let's iterate from there
2613 start_ind = (cs_size * (worker_i - 1)) / active_workers;
2614 result = _worker_cset_start_region[worker_i - 1];
2615 }
2616
2617 for (uint i = start_ind; i < end_ind; i++) {
2618 result = result->next_in_collection_set();
2619 }
2620
2621 // Note: the calculated starting heap region may be NULL
2622 // (when the collection set is empty).
2623 assert(result == NULL || result->in_collection_set(), "sanity");
2624 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2625 "should be updated only once per pause");
2626 _worker_cset_start_region[worker_i] = result;
2627 OrderAccess::storestore();
2628 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2629 return result;
2630 }
2631
2632 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2633 HeapRegion* r = g1_policy()->collection_set();
2634 while (r != NULL) {
2635 HeapRegion* next = r->next_in_collection_set();
2636 if (cl->doHeapRegion(r)) {
2637 cl->incomplete();
2638 return;
2639 }
2640 r = next;
2641 }
2642 }
2643
2644 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2645 HeapRegionClosure *cl) {
2646 if (r == NULL) {
2647 // The CSet is empty so there's nothing to do.
2648 return;
2649 }
2650
2651 assert(r->in_collection_set(),
2652 "Start region must be a member of the collection set.");
2653 HeapRegion* cur = r;
2654 while (cur != NULL) {
2655 HeapRegion* next = cur->next_in_collection_set();
2656 if (cl->doHeapRegion(cur) && false) {
2657 cl->incomplete();
2658 return;
2659 }
2660 cur = next;
2661 }
2662 cur = g1_policy()->collection_set();
2663 while (cur != r) {
2664 HeapRegion* next = cur->next_in_collection_set();
2665 if (cl->doHeapRegion(cur) && false) {
2666 cl->incomplete();
2667 return;
2668 }
2669 cur = next;
2670 }
2671 }
2672
2673 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const {
2674 HeapRegion* result = _hrm.next_region_in_heap(from);
2675 while (result != NULL && result->is_humongous()) {
2676 result = _hrm.next_region_in_heap(result);
2677 }
2678 return result;
2679 }
2680
2681 Space* G1CollectedHeap::space_containing(const void* addr) const {
2682 return heap_region_containing(addr);
2683 }
2684
2685 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2686 Space* sp = space_containing(addr);
2687 return sp->block_start(addr);
2688 }
2689
2690 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2691 Space* sp = space_containing(addr);
2692 return sp->block_size(addr);
2693 }
2694
2695 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2696 Space* sp = space_containing(addr);
2697 return sp->block_is_obj(addr);
2698 }
2699
2700 bool G1CollectedHeap::supports_tlab_allocation() const {
2701 return true;
2702 }
2703
2704 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2705 return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes;
2706 }
2707
2708 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2709 return young_list()->eden_used_bytes();
2710 }
2711
2712 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2713 // must be smaller than the humongous object limit.
2714 size_t G1CollectedHeap::max_tlab_size() const {
2715 return align_size_down(_humongous_object_threshold_in_words - 1, MinObjAlignment);
2716 }
2717
2718 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2719 // Return the remaining space in the cur alloc region, but not less than
2720 // the min TLAB size.
2721
2722 // Also, this value can be at most the humongous object threshold,
2723 // since we can't allow tlabs to grow big enough to accommodate
2724 // humongous objects.
2725
2726 HeapRegion* hr = _allocator->mutator_alloc_region(AllocationContext::current())->get();
2727 size_t max_tlab = max_tlab_size() * wordSize;
2728 if (hr == NULL) {
2729 return max_tlab;
2730 } else {
2731 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab);
2732 }
2733 }
2734
2735 size_t G1CollectedHeap::max_capacity() const {
2736 return _hrm.reserved().byte_size();
2737 }
2738
2739 jlong G1CollectedHeap::millis_since_last_gc() {
2740 // assert(false, "NYI");
2741 return 0;
2742 }
2743
2744 void G1CollectedHeap::prepare_for_verify() {
2745 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
2746 ensure_parsability(false);
2747 }
2748 g1_rem_set()->prepare_for_verify();
2749 }
2750
2751 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr,
2752 VerifyOption vo) {
2753 switch (vo) {
2754 case VerifyOption_G1UsePrevMarking:
2755 return hr->obj_allocated_since_prev_marking(obj);
2756 case VerifyOption_G1UseNextMarking:
2757 return hr->obj_allocated_since_next_marking(obj);
2758 case VerifyOption_G1UseMarkWord:
2759 return false;
2760 default:
2761 ShouldNotReachHere();
2762 }
2763 return false; // keep some compilers happy
2764 }
2765
2766 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) {
2767 switch (vo) {
2768 case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start();
2769 case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start();
2770 case VerifyOption_G1UseMarkWord: return NULL;
2771 default: ShouldNotReachHere();
2772 }
2773 return NULL; // keep some compilers happy
2774 }
2775
2776 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) {
2777 switch (vo) {
2778 case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj);
2779 case VerifyOption_G1UseNextMarking: return isMarkedNext(obj);
2780 case VerifyOption_G1UseMarkWord: return obj->is_gc_marked();
2781 default: ShouldNotReachHere();
2782 }
2783 return false; // keep some compilers happy
2784 }
2785
2786 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) {
2787 switch (vo) {
2788 case VerifyOption_G1UsePrevMarking: return "PTAMS";
2789 case VerifyOption_G1UseNextMarking: return "NTAMS";
2790 case VerifyOption_G1UseMarkWord: return "NONE";
2791 default: ShouldNotReachHere();
2792 }
2793 return NULL; // keep some compilers happy
2794 }
2795
2796 class VerifyRootsClosure: public OopClosure {
2797 private:
2798 G1CollectedHeap* _g1h;
2799 VerifyOption _vo;
2800 bool _failures;
2801 public:
2802 // _vo == UsePrevMarking -> use "prev" marking information,
2803 // _vo == UseNextMarking -> use "next" marking information,
2804 // _vo == UseMarkWord -> use mark word from object header.
2805 VerifyRootsClosure(VerifyOption vo) :
2806 _g1h(G1CollectedHeap::heap()),
2807 _vo(vo),
2808 _failures(false) { }
2809
2810 bool failures() { return _failures; }
2811
2812 template <class T> void do_oop_nv(T* p) {
2813 T heap_oop = oopDesc::load_heap_oop(p);
2814 if (!oopDesc::is_null(heap_oop)) {
2815 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2816 if (_g1h->is_obj_dead_cond(obj, _vo)) {
2817 gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
2818 "points to dead obj "PTR_FORMAT, p, (void*) obj);
2819 if (_vo == VerifyOption_G1UseMarkWord) {
2820 gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark()));
2821 }
2822 obj->print_on(gclog_or_tty);
2823 _failures = true;
2824 }
2825 }
2826 }
2827
2828 void do_oop(oop* p) { do_oop_nv(p); }
2829 void do_oop(narrowOop* p) { do_oop_nv(p); }
2830 };
2831
2832 class G1VerifyCodeRootOopClosure: public OopClosure {
2833 G1CollectedHeap* _g1h;
2834 OopClosure* _root_cl;
2835 nmethod* _nm;
2836 VerifyOption _vo;
2837 bool _failures;
2838
2839 template <class T> void do_oop_work(T* p) {
2840 // First verify that this root is live
2841 _root_cl->do_oop(p);
2842
2843 if (!G1VerifyHeapRegionCodeRoots) {
2844 // We're not verifying the code roots attached to heap region.
2845 return;
2846 }
2847
2848 // Don't check the code roots during marking verification in a full GC
2849 if (_vo == VerifyOption_G1UseMarkWord) {
2850 return;
2851 }
2852
2853 // Now verify that the current nmethod (which contains p) is
2854 // in the code root list of the heap region containing the
2855 // object referenced by p.
2856
2857 T heap_oop = oopDesc::load_heap_oop(p);
2858 if (!oopDesc::is_null(heap_oop)) {
2859 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2860
2861 // Now fetch the region containing the object
2862 HeapRegion* hr = _g1h->heap_region_containing(obj);
2863 HeapRegionRemSet* hrrs = hr->rem_set();
2864 // Verify that the strong code root list for this region
2865 // contains the nmethod
2866 if (!hrrs->strong_code_roots_list_contains(_nm)) {
2867 gclog_or_tty->print_cr("Code root location "PTR_FORMAT" "
2868 "from nmethod "PTR_FORMAT" not in strong "
2869 "code roots for region ["PTR_FORMAT","PTR_FORMAT")",
2870 p, _nm, hr->bottom(), hr->end());
2871 _failures = true;
2872 }
2873 }
2874 }
2875
2876 public:
2877 G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo):
2878 _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {}
2879
2880 void do_oop(oop* p) { do_oop_work(p); }
2881 void do_oop(narrowOop* p) { do_oop_work(p); }
2882
2883 void set_nmethod(nmethod* nm) { _nm = nm; }
2884 bool failures() { return _failures; }
2885 };
2886
2887 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure {
2888 G1VerifyCodeRootOopClosure* _oop_cl;
2889
2890 public:
2891 G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl):
2892 _oop_cl(oop_cl) {}
2893
2894 void do_code_blob(CodeBlob* cb) {
2895 nmethod* nm = cb->as_nmethod_or_null();
2896 if (nm != NULL) {
2897 _oop_cl->set_nmethod(nm);
2898 nm->oops_do(_oop_cl);
2899 }
2900 }
2901 };
2902
2903 class YoungRefCounterClosure : public OopClosure {
2904 G1CollectedHeap* _g1h;
2905 int _count;
2906 public:
2907 YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {}
2908 void do_oop(oop* p) { if (_g1h->is_in_young(*p)) { _count++; } }
2909 void do_oop(narrowOop* p) { ShouldNotReachHere(); }
2910
2911 int count() { return _count; }
2912 void reset_count() { _count = 0; };
2913 };
2914
2915 class VerifyKlassClosure: public KlassClosure {
2916 YoungRefCounterClosure _young_ref_counter_closure;
2917 OopClosure *_oop_closure;
2918 public:
2919 VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {}
2920 void do_klass(Klass* k) {
2921 k->oops_do(_oop_closure);
2922
2923 _young_ref_counter_closure.reset_count();
2924 k->oops_do(&_young_ref_counter_closure);
2925 if (_young_ref_counter_closure.count() > 0) {
2926 guarantee(k->has_modified_oops(), err_msg("Klass " PTR_FORMAT ", has young refs but is not dirty.", k));
2927 }
2928 }
2929 };
2930
2931 class VerifyLivenessOopClosure: public OopClosure {
2932 G1CollectedHeap* _g1h;
2933 VerifyOption _vo;
2934 public:
2935 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
2936 _g1h(g1h), _vo(vo)
2937 { }
2938 void do_oop(narrowOop *p) { do_oop_work(p); }
2939 void do_oop( oop *p) { do_oop_work(p); }
2940
2941 template <class T> void do_oop_work(T *p) {
2942 oop obj = oopDesc::load_decode_heap_oop(p);
2943 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
2944 "Dead object referenced by a not dead object");
2945 }
2946 };
2947
2948 class VerifyObjsInRegionClosure: public ObjectClosure {
2949 private:
2950 G1CollectedHeap* _g1h;
2951 size_t _live_bytes;
2952 HeapRegion *_hr;
2953 VerifyOption _vo;
2954 public:
2955 // _vo == UsePrevMarking -> use "prev" marking information,
2956 // _vo == UseNextMarking -> use "next" marking information,
2957 // _vo == UseMarkWord -> use mark word from object header.
2958 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
2959 : _live_bytes(0), _hr(hr), _vo(vo) {
2960 _g1h = G1CollectedHeap::heap();
2961 }
2962 void do_object(oop o) {
2963 VerifyLivenessOopClosure isLive(_g1h, _vo);
2964 assert(o != NULL, "Huh?");
2965 if (!_g1h->is_obj_dead_cond(o, _vo)) {
2966 // If the object is alive according to the mark word,
2967 // then verify that the marking information agrees.
2968 // Note we can't verify the contra-positive of the
2969 // above: if the object is dead (according to the mark
2970 // word), it may not be marked, or may have been marked
2971 // but has since became dead, or may have been allocated
2972 // since the last marking.
2973 if (_vo == VerifyOption_G1UseMarkWord) {
2974 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
2975 }
2976
2977 o->oop_iterate_no_header(&isLive);
2978 if (!_hr->obj_allocated_since_prev_marking(o)) {
2979 size_t obj_size = o->size(); // Make sure we don't overflow
2980 _live_bytes += (obj_size * HeapWordSize);
2981 }
2982 }
2983 }
2984 size_t live_bytes() { return _live_bytes; }
2985 };
2986
2987 class PrintObjsInRegionClosure : public ObjectClosure {
2988 HeapRegion *_hr;
2989 G1CollectedHeap *_g1;
2990 public:
2991 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
2992 _g1 = G1CollectedHeap::heap();
2993 };
2994
2995 void do_object(oop o) {
2996 if (o != NULL) {
2997 HeapWord *start = (HeapWord *) o;
2998 size_t word_sz = o->size();
2999 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
3000 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
3001 (void*) o, word_sz,
3002 _g1->isMarkedPrev(o),
3003 _g1->isMarkedNext(o),
3004 _hr->obj_allocated_since_prev_marking(o));
3005 HeapWord *end = start + word_sz;
3006 HeapWord *cur;
3007 int *val;
3008 for (cur = start; cur < end; cur++) {
3009 val = (int *) cur;
3010 gclog_or_tty->print("\t "PTR_FORMAT":%d\n", val, *val);
3011 }
3012 }
3013 }
3014 };
3015
3016 class VerifyRegionClosure: public HeapRegionClosure {
3017 private:
3018 bool _par;
3019 VerifyOption _vo;
3020 bool _failures;
3021 public:
3022 // _vo == UsePrevMarking -> use "prev" marking information,
3023 // _vo == UseNextMarking -> use "next" marking information,
3024 // _vo == UseMarkWord -> use mark word from object header.
3025 VerifyRegionClosure(bool par, VerifyOption vo)
3026 : _par(par),
3027 _vo(vo),
3028 _failures(false) {}
3029
3030 bool failures() {
3031 return _failures;
3032 }
3033
3034 bool doHeapRegion(HeapRegion* r) {
3035 if (!r->is_continues_humongous()) {
3036 bool failures = false;
3037 r->verify(_vo, &failures);
3038 if (failures) {
3039 _failures = true;
3040 } else {
3041 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
3042 r->object_iterate(¬_dead_yet_cl);
3043 if (_vo != VerifyOption_G1UseNextMarking) {
3044 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
3045 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
3046 "max_live_bytes "SIZE_FORMAT" "
3047 "< calculated "SIZE_FORMAT,
3048 r->bottom(), r->end(),
3049 r->max_live_bytes(),
3050 not_dead_yet_cl.live_bytes());
3051 _failures = true;
3052 }
3053 } else {
3054 // When vo == UseNextMarking we cannot currently do a sanity
3055 // check on the live bytes as the calculation has not been
3056 // finalized yet.
3057 }
3058 }
3059 }
3060 return false; // stop the region iteration if we hit a failure
3061 }
3062 };
3063
3064 // This is the task used for parallel verification of the heap regions
3065
3066 class G1ParVerifyTask: public AbstractGangTask {
3067 private:
3068 G1CollectedHeap* _g1h;
3069 VerifyOption _vo;
3070 bool _failures;
3071 HeapRegionClaimer _hrclaimer;
3072
3073 public:
3074 // _vo == UsePrevMarking -> use "prev" marking information,
3075 // _vo == UseNextMarking -> use "next" marking information,
3076 // _vo == UseMarkWord -> use mark word from object header.
3077 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
3078 AbstractGangTask("Parallel verify task"),
3079 _g1h(g1h),
3080 _vo(vo),
3081 _failures(false),
3082 _hrclaimer(g1h->workers()->active_workers()) {}
3083
3084 bool failures() {
3085 return _failures;
3086 }
3087
3088 void work(uint worker_id) {
3089 HandleMark hm;
3090 VerifyRegionClosure blk(true, _vo);
3091 _g1h->heap_region_par_iterate(&blk, worker_id, &_hrclaimer);
3092 if (blk.failures()) {
3093 _failures = true;
3094 }
3095 }
3096 };
3097
3098 void G1CollectedHeap::verify(bool silent, VerifyOption vo) {
3099 if (SafepointSynchronize::is_at_safepoint()) {
3100 assert(Thread::current()->is_VM_thread(),
3101 "Expected to be executed serially by the VM thread at this point");
3102
3103 if (!silent) { gclog_or_tty->print("Roots "); }
3104 VerifyRootsClosure rootsCl(vo);
3105 VerifyKlassClosure klassCl(this, &rootsCl);
3106 CLDToKlassAndOopClosure cldCl(&klassCl, &rootsCl, false);
3107
3108 // We apply the relevant closures to all the oops in the
3109 // system dictionary, class loader data graph, the string table
3110 // and the nmethods in the code cache.
3111 G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo);
3112 G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl);
3113
3114 process_all_roots(true, // activate StrongRootsScope
3115 SO_AllCodeCache, // roots scanning options
3116 &rootsCl,
3117 &cldCl,
3118 &blobsCl);
3119
3120 bool failures = rootsCl.failures() || codeRootsCl.failures();
3121
3122 if (vo != VerifyOption_G1UseMarkWord) {
3123 // If we're verifying during a full GC then the region sets
3124 // will have been torn down at the start of the GC. Therefore
3125 // verifying the region sets will fail. So we only verify
3126 // the region sets when not in a full GC.
3127 if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3128 verify_region_sets();
3129 }
3130
3131 if (!silent) { gclog_or_tty->print("HeapRegions "); }
3132 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3133
3134 G1ParVerifyTask task(this, vo);
3135 assert(UseDynamicNumberOfGCThreads ||
3136 workers()->active_workers() == workers()->total_workers(),
3137 "If not dynamic should be using all the workers");
3138 int n_workers = workers()->active_workers();
3139 set_par_threads(n_workers);
3140 workers()->run_task(&task);
3141 set_par_threads(0);
3142 if (task.failures()) {
3143 failures = true;
3144 }
3145
3146 } else {
3147 VerifyRegionClosure blk(false, vo);
3148 heap_region_iterate(&blk);
3149 if (blk.failures()) {
3150 failures = true;
3151 }
3152 }
3153
3154 if (G1StringDedup::is_enabled()) {
3155 if (!silent) gclog_or_tty->print("StrDedup ");
3156 G1StringDedup::verify();
3157 }
3158
3159 if (failures) {
3160 gclog_or_tty->print_cr("Heap:");
3161 // It helps to have the per-region information in the output to
3162 // help us track down what went wrong. This is why we call
3163 // print_extended_on() instead of print_on().
3164 print_extended_on(gclog_or_tty);
3165 gclog_or_tty->cr();
3166 #ifndef PRODUCT
3167 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3168 concurrent_mark()->print_reachable("at-verification-failure",
3169 vo, false /* all */);
3170 }
3171 #endif
3172 gclog_or_tty->flush();
3173 }
3174 guarantee(!failures, "there should not have been any failures");
3175 } else {
3176 if (!silent) {
3177 gclog_or_tty->print("(SKIPPING Roots, HeapRegionSets, HeapRegions, RemSet");
3178 if (G1StringDedup::is_enabled()) {
3179 gclog_or_tty->print(", StrDedup");
3180 }
3181 gclog_or_tty->print(") ");
3182 }
3183 }
3184 }
3185
3186 void G1CollectedHeap::verify(bool silent) {
3187 verify(silent, VerifyOption_G1UsePrevMarking);
3188 }
3189
3190 double G1CollectedHeap::verify(bool guard, const char* msg) {
3191 double verify_time_ms = 0.0;
3192
3193 if (guard && total_collections() >= VerifyGCStartAt) {
3194 double verify_start = os::elapsedTime();
3195 HandleMark hm; // Discard invalid handles created during verification
3196 prepare_for_verify();
3197 Universe::verify(VerifyOption_G1UsePrevMarking, msg);
3198 verify_time_ms = (os::elapsedTime() - verify_start) * 1000;
3199 }
3200
3201 return verify_time_ms;
3202 }
3203
3204 void G1CollectedHeap::verify_before_gc() {
3205 double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:");
3206 g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms);
3207 }
3208
3209 void G1CollectedHeap::verify_after_gc() {
3210 double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:");
3211 g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms);
3212 }
3213
3214 class PrintRegionClosure: public HeapRegionClosure {
3215 outputStream* _st;
3216 public:
3217 PrintRegionClosure(outputStream* st) : _st(st) {}
3218 bool doHeapRegion(HeapRegion* r) {
3219 r->print_on(_st);
3220 return false;
3221 }
3222 };
3223
3224 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3225 const HeapRegion* hr,
3226 const VerifyOption vo) const {
3227 switch (vo) {
3228 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
3229 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
3230 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked();
3231 default: ShouldNotReachHere();
3232 }
3233 return false; // keep some compilers happy
3234 }
3235
3236 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3237 const VerifyOption vo) const {
3238 switch (vo) {
3239 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
3240 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
3241 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked();
3242 default: ShouldNotReachHere();
3243 }
3244 return false; // keep some compilers happy
3245 }
3246
3247 void G1CollectedHeap::print_on(outputStream* st) const {
3248 st->print(" %-20s", "garbage-first heap");
3249 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3250 capacity()/K, used_unlocked()/K);
3251 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3252 _hrm.reserved().start(),
3253 _hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords,
3254 _hrm.reserved().end());
3255 st->cr();
3256 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3257 uint young_regions = _young_list->length();
3258 st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3259 (size_t) young_regions * HeapRegion::GrainBytes / K);
3260 uint survivor_regions = g1_policy()->recorded_survivor_regions();
3261 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3262 (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3263 st->cr();
3264 MetaspaceAux::print_on(st);
3265 }
3266
3267 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3268 print_on(st);
3269
3270 // Print the per-region information.
3271 st->cr();
3272 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3273 "HS=humongous(starts), HC=humongous(continues), "
3274 "CS=collection set, F=free, TS=gc time stamp, "
3275 "PTAMS=previous top-at-mark-start, "
3276 "NTAMS=next top-at-mark-start)");
3277 PrintRegionClosure blk(st);
3278 heap_region_iterate(&blk);
3279 }
3280
3281 void G1CollectedHeap::print_on_error(outputStream* st) const {
3282 this->CollectedHeap::print_on_error(st);
3283
3284 if (_cm != NULL) {
3285 st->cr();
3286 _cm->print_on_error(st);
3287 }
3288 }
3289
3290 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3291 workers()->print_worker_threads_on(st);
3292 _cmThread->print_on(st);
3293 st->cr();
3294 _cm->print_worker_threads_on(st);
3295 _cg1r->print_worker_threads_on(st);
3296 if (G1StringDedup::is_enabled()) {
3297 G1StringDedup::print_worker_threads_on(st);
3298 }
3299 }
3300
3301 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3302 workers()->threads_do(tc);
3303 tc->do_thread(_cmThread);
3304 _cg1r->threads_do(tc);
3305 if (G1StringDedup::is_enabled()) {
3306 G1StringDedup::threads_do(tc);
3307 }
3308 }
3309
3310 void G1CollectedHeap::print_tracing_info() const {
3311 // We'll overload this to mean "trace GC pause statistics."
3312 if (TraceYoungGenTime || TraceOldGenTime) {
3313 // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3314 // to that.
3315 g1_policy()->print_tracing_info();
3316 }
3317 if (G1SummarizeRSetStats) {
3318 g1_rem_set()->print_summary_info();
3319 }
3320 if (G1SummarizeConcMark) {
3321 concurrent_mark()->print_summary_info();
3322 }
3323 g1_policy()->print_yg_surv_rate_info();
3324 SpecializationStats::print();
3325 }
3326
3327 #ifndef PRODUCT
3328 // Helpful for debugging RSet issues.
3329
3330 class PrintRSetsClosure : public HeapRegionClosure {
3331 private:
3332 const char* _msg;
3333 size_t _occupied_sum;
3334
3335 public:
3336 bool doHeapRegion(HeapRegion* r) {
3337 HeapRegionRemSet* hrrs = r->rem_set();
3338 size_t occupied = hrrs->occupied();
3339 _occupied_sum += occupied;
3340
3341 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3342 HR_FORMAT_PARAMS(r));
3343 if (occupied == 0) {
3344 gclog_or_tty->print_cr(" RSet is empty");
3345 } else {
3346 hrrs->print();
3347 }
3348 gclog_or_tty->print_cr("----------");
3349 return false;
3350 }
3351
3352 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3353 gclog_or_tty->cr();
3354 gclog_or_tty->print_cr("========================================");
3355 gclog_or_tty->print_cr("%s", msg);
3356 gclog_or_tty->cr();
3357 }
3358
3359 ~PrintRSetsClosure() {
3360 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3361 gclog_or_tty->print_cr("========================================");
3362 gclog_or_tty->cr();
3363 }
3364 };
3365
3366 void G1CollectedHeap::print_cset_rsets() {
3367 PrintRSetsClosure cl("Printing CSet RSets");
3368 collection_set_iterate(&cl);
3369 }
3370
3371 void G1CollectedHeap::print_all_rsets() {
3372 PrintRSetsClosure cl("Printing All RSets");;
3373 heap_region_iterate(&cl);
3374 }
3375 #endif // PRODUCT
3376
3377 G1CollectedHeap* G1CollectedHeap::heap() {
3378 assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3379 "not a garbage-first heap");
3380 return _g1h;
3381 }
3382
3383 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3384 // always_do_update_barrier = false;
3385 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3386 // Fill TLAB's and such
3387 accumulate_statistics_all_tlabs();
3388 ensure_parsability(true);
3389
3390 if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) &&
3391 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3392 g1_rem_set()->print_periodic_summary_info("Before GC RS summary");
3393 }
3394 }
3395
3396 void G1CollectedHeap::gc_epilogue(bool full) {
3397
3398 if (G1SummarizeRSetStats &&
3399 (G1SummarizeRSetStatsPeriod > 0) &&
3400 // we are at the end of the GC. Total collections has already been increased.
3401 ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) {
3402 g1_rem_set()->print_periodic_summary_info("After GC RS summary");
3403 }
3404
3405 // FIXME: what is this about?
3406 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3407 // is set.
3408 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3409 "derived pointer present"));
3410 // always_do_update_barrier = true;
3411
3412 resize_all_tlabs();
3413 allocation_context_stats().update(full);
3414
3415 // We have just completed a GC. Update the soft reference
3416 // policy with the new heap occupancy
3417 Universe::update_heap_info_at_gc();
3418 }
3419
3420 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3421 unsigned int gc_count_before,
3422 bool* succeeded,
3423 GCCause::Cause gc_cause) {
3424 assert_heap_not_locked_and_not_at_safepoint();
3425 g1_policy()->record_stop_world_start();
3426 VM_G1IncCollectionPause op(gc_count_before,
3427 word_size,
3428 false, /* should_initiate_conc_mark */
3429 g1_policy()->max_pause_time_ms(),
3430 gc_cause);
3431
3432 op.set_allocation_context(AllocationContext::current());
3433 VMThread::execute(&op);
3434
3435 HeapWord* result = op.result();
3436 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3437 assert(result == NULL || ret_succeeded,
3438 "the result should be NULL if the VM did not succeed");
3439 *succeeded = ret_succeeded;
3440
3441 assert_heap_not_locked();
3442 return result;
3443 }
3444
3445 void
3446 G1CollectedHeap::doConcurrentMark() {
3447 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3448 if (!_cmThread->in_progress()) {
3449 _cmThread->set_started();
3450 CGC_lock->notify();
3451 }
3452 }
3453
3454 size_t G1CollectedHeap::pending_card_num() {
3455 size_t extra_cards = 0;
3456 JavaThread *curr = Threads::first();
3457 while (curr != NULL) {
3458 DirtyCardQueue& dcq = curr->dirty_card_queue();
3459 extra_cards += dcq.size();
3460 curr = curr->next();
3461 }
3462 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3463 size_t buffer_size = dcqs.buffer_size();
3464 size_t buffer_num = dcqs.completed_buffers_num();
3465
3466 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
3467 // in bytes - not the number of 'entries'. We need to convert
3468 // into a number of cards.
3469 return (buffer_size * buffer_num + extra_cards) / oopSize;
3470 }
3471
3472 size_t G1CollectedHeap::cards_scanned() {
3473 return g1_rem_set()->cardsScanned();
3474 }
3475
3476 bool G1CollectedHeap::humongous_region_is_always_live(uint index) {
3477 HeapRegion* region = region_at(index);
3478 assert(region->is_starts_humongous(), "Must start a humongous object");
3479 return oop(region->bottom())->is_objArray() || !region->rem_set()->is_empty();
3480 }
3481
3482 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
3483 private:
3484 size_t _total_humongous;
3485 size_t _candidate_humongous;
3486
3487 DirtyCardQueue _dcq;
3488
3489 bool humongous_region_is_candidate(uint index) {
3490 HeapRegion* region = G1CollectedHeap::heap()->region_at(index);
3491 assert(region->is_starts_humongous(), "Must start a humongous object");
3492 HeapRegionRemSet* const rset = region->rem_set();
3493 bool const allow_stale_refs = G1EagerReclaimHumongousObjectsWithStaleRefs;
3494 return !oop(region->bottom())->is_objArray() &&
3495 ((allow_stale_refs && rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries)) ||
3496 (!allow_stale_refs && rset->is_empty()));
3497 }
3498
3499 public:
3500 RegisterHumongousWithInCSetFastTestClosure()
3501 : _total_humongous(0),
3502 _candidate_humongous(0),
3503 _dcq(&JavaThread::dirty_card_queue_set()) {
3504 }
3505
3506 virtual bool doHeapRegion(HeapRegion* r) {
3507 if (!r->is_starts_humongous()) {
3508 return false;
3509 }
3510 G1CollectedHeap* g1h = G1CollectedHeap::heap();
3511
3512 uint region_idx = r->hrm_index();
3513 bool is_candidate = humongous_region_is_candidate(region_idx);
3514 // Is_candidate already filters out humongous object with large remembered sets.
3515 // If we have a humongous object with a few remembered sets, we simply flush these
3516 // remembered set entries into the DCQS. That will result in automatic
3517 // re-evaluation of their remembered set entries during the following evacuation
3518 // phase.
3519 if (is_candidate) {
3520 if (!r->rem_set()->is_empty()) {
3521 guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
3522 "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
3523 G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set();
3524 HeapRegionRemSetIterator hrrs(r->rem_set());
3525 size_t card_index;
3526 while (hrrs.has_next(card_index)) {
3527 jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index);
3528 if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
3529 *card_ptr = CardTableModRefBS::dirty_card_val();
3530 _dcq.enqueue(card_ptr);
3531 }
3532 }
3533 r->rem_set()->clear_locked();
3534 }
3535 assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
3536 g1h->register_humongous_region_with_in_cset_fast_test(region_idx);
3537 _candidate_humongous++;
3538 }
3539 _total_humongous++;
3540
3541 return false;
3542 }
3543
3544 size_t total_humongous() const { return _total_humongous; }
3545 size_t candidate_humongous() const { return _candidate_humongous; }
3546
3547 void flush_rem_set_entries() { _dcq.flush(); }
3548 };
3549
3550 void G1CollectedHeap::register_humongous_regions_with_in_cset_fast_test() {
3551 if (!G1EagerReclaimHumongousObjects) {
3552 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
3553 return;
3554 }
3555 double time = os::elapsed_counter();
3556
3557 RegisterHumongousWithInCSetFastTestClosure cl;
3558 heap_region_iterate(&cl);
3559
3560 time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
3561 g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
3562 cl.total_humongous(),
3563 cl.candidate_humongous());
3564 _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
3565
3566 if (_has_humongous_reclaim_candidates || G1TraceEagerReclaimHumongousObjects) {
3567 clear_humongous_is_live_table();
3568 }
3569
3570 // Finally flush all remembered set entries to re-check into the global DCQS.
3571 cl.flush_rem_set_entries();
3572 }
3573
3574 void
3575 G1CollectedHeap::setup_surviving_young_words() {
3576 assert(_surviving_young_words == NULL, "pre-condition");
3577 uint array_length = g1_policy()->young_cset_region_length();
3578 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3579 if (_surviving_young_words == NULL) {
3580 vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR,
3581 "Not enough space for young surv words summary.");
3582 }
3583 memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3584 #ifdef ASSERT
3585 for (uint i = 0; i < array_length; ++i) {
3586 assert( _surviving_young_words[i] == 0, "memset above" );
3587 }
3588 #endif // !ASSERT
3589 }
3590
3591 void
3592 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3593 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3594 uint array_length = g1_policy()->young_cset_region_length();
3595 for (uint i = 0; i < array_length; ++i) {
3596 _surviving_young_words[i] += surv_young_words[i];
3597 }
3598 }
3599
3600 void
3601 G1CollectedHeap::cleanup_surviving_young_words() {
3602 guarantee( _surviving_young_words != NULL, "pre-condition" );
3603 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words);
3604 _surviving_young_words = NULL;
3605 }
3606
3607 #ifdef ASSERT
3608 class VerifyCSetClosure: public HeapRegionClosure {
3609 public:
3610 bool doHeapRegion(HeapRegion* hr) {
3611 // Here we check that the CSet region's RSet is ready for parallel
3612 // iteration. The fields that we'll verify are only manipulated
3613 // when the region is part of a CSet and is collected. Afterwards,
3614 // we reset these fields when we clear the region's RSet (when the
3615 // region is freed) so they are ready when the region is
3616 // re-allocated. The only exception to this is if there's an
3617 // evacuation failure and instead of freeing the region we leave
3618 // it in the heap. In that case, we reset these fields during
3619 // evacuation failure handling.
3620 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3621
3622 // Here's a good place to add any other checks we'd like to
3623 // perform on CSet regions.
3624 return false;
3625 }
3626 };
3627 #endif // ASSERT
3628
3629 #if TASKQUEUE_STATS
3630 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3631 st->print_raw_cr("GC Task Stats");
3632 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3633 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3634 }
3635
3636 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3637 print_taskqueue_stats_hdr(st);
3638
3639 TaskQueueStats totals;
3640 const int n = workers()->total_workers();
3641 for (int i = 0; i < n; ++i) {
3642 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3643 totals += task_queue(i)->stats;
3644 }
3645 st->print_raw("tot "); totals.print(st); st->cr();
3646
3647 DEBUG_ONLY(totals.verify());
3648 }
3649
3650 void G1CollectedHeap::reset_taskqueue_stats() {
3651 const int n = workers()->total_workers();
3652 for (int i = 0; i < n; ++i) {
3653 task_queue(i)->stats.reset();
3654 }
3655 }
3656 #endif // TASKQUEUE_STATS
3657
3658 void G1CollectedHeap::log_gc_header() {
3659 if (!G1Log::fine()) {
3660 return;
3661 }
3662
3663 gclog_or_tty->gclog_stamp(_gc_tracer_stw->gc_id());
3664
3665 GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
3666 .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)")
3667 .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : "");
3668
3669 gclog_or_tty->print("[%s", (const char*)gc_cause_str);
3670 }
3671
3672 void G1CollectedHeap::log_gc_footer(double pause_time_sec) {
3673 if (!G1Log::fine()) {
3674 return;
3675 }
3676
3677 if (G1Log::finer()) {
3678 if (evacuation_failed()) {
3679 gclog_or_tty->print(" (to-space exhausted)");
3680 }
3681 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3682 g1_policy()->phase_times()->note_gc_end();
3683 g1_policy()->phase_times()->print(pause_time_sec);
3684 g1_policy()->print_detailed_heap_transition();
3685 } else {
3686 if (evacuation_failed()) {
3687 gclog_or_tty->print("--");
3688 }
3689 g1_policy()->print_heap_transition();
3690 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3691 }
3692 gclog_or_tty->flush();
3693 }
3694
3695 bool
3696 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3697 assert_at_safepoint(true /* should_be_vm_thread */);
3698 guarantee(!is_gc_active(), "collection is not reentrant");
3699
3700 if (GC_locker::check_active_before_gc()) {
3701 return false;
3702 }
3703
3704 _gc_timer_stw->register_gc_start();
3705
3706 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3707
3708 SvcGCMarker sgcm(SvcGCMarker::MINOR);
3709 ResourceMark rm;
3710
3711 print_heap_before_gc();
3712 trace_heap_before_gc(_gc_tracer_stw);
3713
3714 verify_region_sets_optional();
3715 verify_dirty_young_regions();
3716
3717 // This call will decide whether this pause is an initial-mark
3718 // pause. If it is, during_initial_mark_pause() will return true
3719 // for the duration of this pause.
3720 g1_policy()->decide_on_conc_mark_initiation();
3721
3722 // We do not allow initial-mark to be piggy-backed on a mixed GC.
3723 assert(!g1_policy()->during_initial_mark_pause() ||
3724 g1_policy()->gcs_are_young(), "sanity");
3725
3726 // We also do not allow mixed GCs during marking.
3727 assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3728
3729 // Record whether this pause is an initial mark. When the current
3730 // thread has completed its logging output and it's safe to signal
3731 // the CM thread, the flag's value in the policy has been reset.
3732 bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3733
3734 // Inner scope for scope based logging, timers, and stats collection
3735 {
3736 EvacuationInfo evacuation_info;
3737
3738 if (g1_policy()->during_initial_mark_pause()) {
3739 // We are about to start a marking cycle, so we increment the
3740 // full collection counter.
3741 increment_old_marking_cycles_started();
3742 register_concurrent_cycle_start(_gc_timer_stw->gc_start());
3743 }
3744
3745 _gc_tracer_stw->report_yc_type(yc_type());
3746
3747 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3748
3749 int active_workers = workers()->active_workers();
3750 double pause_start_sec = os::elapsedTime();
3751 g1_policy()->phase_times()->note_gc_start(active_workers);
3752 log_gc_header();
3753
3754 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3755 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3756
3757 // If the secondary_free_list is not empty, append it to the
3758 // free_list. No need to wait for the cleanup operation to finish;
3759 // the region allocation code will check the secondary_free_list
3760 // and wait if necessary. If the G1StressConcRegionFreeing flag is
3761 // set, skip this step so that the region allocation code has to
3762 // get entries from the secondary_free_list.
3763 if (!G1StressConcRegionFreeing) {
3764 append_secondary_free_list_if_not_empty_with_lock();
3765 }
3766
3767 assert(check_young_list_well_formed(), "young list should be well formed");
3768
3769 // Don't dynamically change the number of GC threads this early. A value of
3770 // 0 is used to indicate serial work. When parallel work is done,
3771 // it will be set.
3772
3773 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3774 IsGCActiveMark x;
3775
3776 gc_prologue(false);
3777 increment_total_collections(false /* full gc */);
3778 increment_gc_time_stamp();
3779
3780 verify_before_gc();
3781
3782 check_bitmaps("GC Start");
3783
3784 COMPILER2_PRESENT(DerivedPointerTable::clear());
3785
3786 // Please see comment in g1CollectedHeap.hpp and
3787 // G1CollectedHeap::ref_processing_init() to see how
3788 // reference processing currently works in G1.
3789
3790 // Enable discovery in the STW reference processor
3791 ref_processor_stw()->enable_discovery();
3792
3793 {
3794 // We want to temporarily turn off discovery by the
3795 // CM ref processor, if necessary, and turn it back on
3796 // on again later if we do. Using a scoped
3797 // NoRefDiscovery object will do this.
3798 NoRefDiscovery no_cm_discovery(ref_processor_cm());
3799
3800 // Forget the current alloc region (we might even choose it to be part
3801 // of the collection set!).
3802 _allocator->release_mutator_alloc_region();
3803
3804 // We should call this after we retire the mutator alloc
3805 // region(s) so that all the ALLOC / RETIRE events are generated
3806 // before the start GC event.
3807 _hr_printer.start_gc(false /* full */, (size_t) total_collections());
3808
3809 // This timing is only used by the ergonomics to handle our pause target.
3810 // It is unclear why this should not include the full pause. We will
3811 // investigate this in CR 7178365.
3812 //
3813 // Preserving the old comment here if that helps the investigation:
3814 //
3815 // The elapsed time induced by the start time below deliberately elides
3816 // the possible verification above.
3817 double sample_start_time_sec = os::elapsedTime();
3818
3819 #if YOUNG_LIST_VERBOSE
3820 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
3821 _young_list->print();
3822 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3823 #endif // YOUNG_LIST_VERBOSE
3824
3825 g1_policy()->record_collection_pause_start(sample_start_time_sec);
3826
3827 double scan_wait_start = os::elapsedTime();
3828 // We have to wait until the CM threads finish scanning the
3829 // root regions as it's the only way to ensure that all the
3830 // objects on them have been correctly scanned before we start
3831 // moving them during the GC.
3832 bool waited = _cm->root_regions()->wait_until_scan_finished();
3833 double wait_time_ms = 0.0;
3834 if (waited) {
3835 double scan_wait_end = os::elapsedTime();
3836 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
3837 }
3838 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
3839
3840 #if YOUNG_LIST_VERBOSE
3841 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
3842 _young_list->print();
3843 #endif // YOUNG_LIST_VERBOSE
3844
3845 if (g1_policy()->during_initial_mark_pause()) {
3846 concurrent_mark()->checkpointRootsInitialPre();
3847 }
3848
3849 #if YOUNG_LIST_VERBOSE
3850 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
3851 _young_list->print();
3852 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3853 #endif // YOUNG_LIST_VERBOSE
3854
3855 g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info);
3856
3857 register_humongous_regions_with_in_cset_fast_test();
3858
3859 assert(check_cset_fast_test(), "Inconsistency in the InCSetState table.");
3860
3861 _cm->note_start_of_gc();
3862 // We should not verify the per-thread SATB buffers given that
3863 // we have not filtered them yet (we'll do so during the
3864 // GC). We also call this after finalize_cset() to
3865 // ensure that the CSet has been finalized.
3866 _cm->verify_no_cset_oops(true /* verify_stacks */,
3867 true /* verify_enqueued_buffers */,
3868 false /* verify_thread_buffers */,
3869 true /* verify_fingers */);
3870
3871 if (_hr_printer.is_active()) {
3872 HeapRegion* hr = g1_policy()->collection_set();
3873 while (hr != NULL) {
3874 _hr_printer.cset(hr);
3875 hr = hr->next_in_collection_set();
3876 }
3877 }
3878
3879 #ifdef ASSERT
3880 VerifyCSetClosure cl;
3881 collection_set_iterate(&cl);
3882 #endif // ASSERT
3883
3884 setup_surviving_young_words();
3885
3886 // Initialize the GC alloc regions.
3887 _allocator->init_gc_alloc_regions(evacuation_info);
3888
3889 // Actually do the work...
3890 evacuate_collection_set(evacuation_info);
3891
3892 // We do this to mainly verify the per-thread SATB buffers
3893 // (which have been filtered by now) since we didn't verify
3894 // them earlier. No point in re-checking the stacks / enqueued
3895 // buffers given that the CSet has not changed since last time
3896 // we checked.
3897 _cm->verify_no_cset_oops(false /* verify_stacks */,
3898 false /* verify_enqueued_buffers */,
3899 true /* verify_thread_buffers */,
3900 true /* verify_fingers */);
3901
3902 free_collection_set(g1_policy()->collection_set(), evacuation_info);
3903
3904 eagerly_reclaim_humongous_regions();
3905
3906 g1_policy()->clear_collection_set();
3907
3908 cleanup_surviving_young_words();
3909
3910 // Start a new incremental collection set for the next pause.
3911 g1_policy()->start_incremental_cset_building();
3912
3913 clear_cset_fast_test();
3914
3915 _young_list->reset_sampled_info();
3916
3917 // Don't check the whole heap at this point as the
3918 // GC alloc regions from this pause have been tagged
3919 // as survivors and moved on to the survivor list.
3920 // Survivor regions will fail the !is_young() check.
3921 assert(check_young_list_empty(false /* check_heap */),
3922 "young list should be empty");
3923
3924 #if YOUNG_LIST_VERBOSE
3925 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
3926 _young_list->print();
3927 #endif // YOUNG_LIST_VERBOSE
3928
3929 g1_policy()->record_survivor_regions(_young_list->survivor_length(),
3930 _young_list->first_survivor_region(),
3931 _young_list->last_survivor_region());
3932
3933 _young_list->reset_auxilary_lists();
3934
3935 if (evacuation_failed()) {
3936 _allocator->set_used(recalculate_used());
3937 uint n_queues = MAX2((int)ParallelGCThreads, 1);
3938 for (uint i = 0; i < n_queues; i++) {
3939 if (_evacuation_failed_info_array[i].has_failed()) {
3940 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
3941 }
3942 }
3943 } else {
3944 // The "used" of the the collection set have already been subtracted
3945 // when they were freed. Add in the bytes evacuated.
3946 _allocator->increase_used(g1_policy()->bytes_copied_during_gc());
3947 }
3948
3949 if (g1_policy()->during_initial_mark_pause()) {
3950 // We have to do this before we notify the CM threads that
3951 // they can start working to make sure that all the
3952 // appropriate initialization is done on the CM object.
3953 concurrent_mark()->checkpointRootsInitialPost();
3954 set_marking_started();
3955 // Note that we don't actually trigger the CM thread at
3956 // this point. We do that later when we're sure that
3957 // the current thread has completed its logging output.
3958 }
3959
3960 allocate_dummy_regions();
3961
3962 #if YOUNG_LIST_VERBOSE
3963 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
3964 _young_list->print();
3965 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3966 #endif // YOUNG_LIST_VERBOSE
3967
3968 _allocator->init_mutator_alloc_region();
3969
3970 {
3971 size_t expand_bytes = g1_policy()->expansion_amount();
3972 if (expand_bytes > 0) {
3973 size_t bytes_before = capacity();
3974 // No need for an ergo verbose message here,
3975 // expansion_amount() does this when it returns a value > 0.
3976 if (!expand(expand_bytes)) {
3977 // We failed to expand the heap. Cannot do anything about it.
3978 }
3979 }
3980 }
3981
3982 // We redo the verification but now wrt to the new CSet which
3983 // has just got initialized after the previous CSet was freed.
3984 _cm->verify_no_cset_oops(true /* verify_stacks */,
3985 true /* verify_enqueued_buffers */,
3986 true /* verify_thread_buffers */,
3987 true /* verify_fingers */);
3988 _cm->note_end_of_gc();
3989
3990 // This timing is only used by the ergonomics to handle our pause target.
3991 // It is unclear why this should not include the full pause. We will
3992 // investigate this in CR 7178365.
3993 double sample_end_time_sec = os::elapsedTime();
3994 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3995 g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info);
3996
3997 MemoryService::track_memory_usage();
3998
3999 // In prepare_for_verify() below we'll need to scan the deferred
4000 // update buffers to bring the RSets up-to-date if
4001 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
4002 // the update buffers we'll probably need to scan cards on the
4003 // regions we just allocated to (i.e., the GC alloc
4004 // regions). However, during the last GC we called
4005 // set_saved_mark() on all the GC alloc regions, so card
4006 // scanning might skip the [saved_mark_word()...top()] area of
4007 // those regions (i.e., the area we allocated objects into
4008 // during the last GC). But it shouldn't. Given that
4009 // saved_mark_word() is conditional on whether the GC time stamp
4010 // on the region is current or not, by incrementing the GC time
4011 // stamp here we invalidate all the GC time stamps on all the
4012 // regions and saved_mark_word() will simply return top() for
4013 // all the regions. This is a nicer way of ensuring this rather
4014 // than iterating over the regions and fixing them. In fact, the
4015 // GC time stamp increment here also ensures that
4016 // saved_mark_word() will return top() between pauses, i.e.,
4017 // during concurrent refinement. So we don't need the
4018 // is_gc_active() check to decided which top to use when
4019 // scanning cards (see CR 7039627).
4020 increment_gc_time_stamp();
4021
4022 verify_after_gc();
4023 check_bitmaps("GC End");
4024
4025 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
4026 ref_processor_stw()->verify_no_references_recorded();
4027
4028 // CM reference discovery will be re-enabled if necessary.
4029 }
4030
4031 // We should do this after we potentially expand the heap so
4032 // that all the COMMIT events are generated before the end GC
4033 // event, and after we retire the GC alloc regions so that all
4034 // RETIRE events are generated before the end GC event.
4035 _hr_printer.end_gc(false /* full */, (size_t) total_collections());
4036
4037 #ifdef TRACESPINNING
4038 ParallelTaskTerminator::print_termination_counts();
4039 #endif
4040
4041 gc_epilogue(false);
4042 }
4043
4044 // Print the remainder of the GC log output.
4045 log_gc_footer(os::elapsedTime() - pause_start_sec);
4046
4047 // It is not yet to safe to tell the concurrent mark to
4048 // start as we have some optional output below. We don't want the
4049 // output from the concurrent mark thread interfering with this
4050 // logging output either.
4051
4052 _hrm.verify_optional();
4053 verify_region_sets_optional();
4054
4055 TASKQUEUE_STATS_ONLY(if (PrintTaskqueue) print_taskqueue_stats());
4056 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
4057
4058 print_heap_after_gc();
4059 trace_heap_after_gc(_gc_tracer_stw);
4060
4061 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
4062 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
4063 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
4064 // before any GC notifications are raised.
4065 g1mm()->update_sizes();
4066
4067 _gc_tracer_stw->report_evacuation_info(&evacuation_info);
4068 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
4069 _gc_timer_stw->register_gc_end();
4070 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
4071 }
4072 // It should now be safe to tell the concurrent mark thread to start
4073 // without its logging output interfering with the logging output
4074 // that came from the pause.
4075
4076 if (should_start_conc_mark) {
4077 // CAUTION: after the doConcurrentMark() call below,
4078 // the concurrent marking thread(s) could be running
4079 // concurrently with us. Make sure that anything after
4080 // this point does not assume that we are the only GC thread
4081 // running. Note: of course, the actual marking work will
4082 // not start until the safepoint itself is released in
4083 // SuspendibleThreadSet::desynchronize().
4084 doConcurrentMark();
4085 }
4086
4087 return true;
4088 }
4089
4090 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4091 _drain_in_progress = false;
4092 set_evac_failure_closure(cl);
4093 _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4094 }
4095
4096 void G1CollectedHeap::finalize_for_evac_failure() {
4097 assert(_evac_failure_scan_stack != NULL &&
4098 _evac_failure_scan_stack->length() == 0,
4099 "Postcondition");
4100 assert(!_drain_in_progress, "Postcondition");
4101 delete _evac_failure_scan_stack;
4102 _evac_failure_scan_stack = NULL;
4103 }
4104
4105 void G1CollectedHeap::remove_self_forwarding_pointers() {
4106 double remove_self_forwards_start = os::elapsedTime();
4107
4108 set_par_threads();
4109 G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4110 workers()->run_task(&rsfp_task);
4111 set_par_threads(0);
4112
4113 // Now restore saved marks, if any.
4114 assert(_objs_with_preserved_marks.size() ==
4115 _preserved_marks_of_objs.size(), "Both or none.");
4116 while (!_objs_with_preserved_marks.is_empty()) {
4117 oop obj = _objs_with_preserved_marks.pop();
4118 markOop m = _preserved_marks_of_objs.pop();
4119 obj->set_mark(m);
4120 }
4121 _objs_with_preserved_marks.clear(true);
4122 _preserved_marks_of_objs.clear(true);
4123
4124 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
4125 }
4126
4127 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4128 _evac_failure_scan_stack->push(obj);
4129 }
4130
4131 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4132 assert(_evac_failure_scan_stack != NULL, "precondition");
4133
4134 while (_evac_failure_scan_stack->length() > 0) {
4135 oop obj = _evac_failure_scan_stack->pop();
4136 _evac_failure_closure->set_region(heap_region_containing(obj));
4137 obj->oop_iterate_backwards(_evac_failure_closure);
4138 }
4139 }
4140
4141 oop
4142 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state,
4143 oop old) {
4144 assert(obj_in_cs(old),
4145 err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4146 (HeapWord*) old));
4147 markOop m = old->mark();
4148 oop forward_ptr = old->forward_to_atomic(old);
4149 if (forward_ptr == NULL) {
4150 // Forward-to-self succeeded.
4151 assert(_par_scan_state != NULL, "par scan state");
4152 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4153 uint queue_num = _par_scan_state->queue_num();
4154
4155 _evacuation_failed = true;
4156 _evacuation_failed_info_array[queue_num].register_copy_failure(old->size());
4157 if (_evac_failure_closure != cl) {
4158 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4159 assert(!_drain_in_progress,
4160 "Should only be true while someone holds the lock.");
4161 // Set the global evac-failure closure to the current thread's.
4162 assert(_evac_failure_closure == NULL, "Or locking has failed.");
4163 set_evac_failure_closure(cl);
4164 // Now do the common part.
4165 handle_evacuation_failure_common(old, m);
4166 // Reset to NULL.
4167 set_evac_failure_closure(NULL);
4168 } else {
4169 // The lock is already held, and this is recursive.
4170 assert(_drain_in_progress, "This should only be the recursive case.");
4171 handle_evacuation_failure_common(old, m);
4172 }
4173 return old;
4174 } else {
4175 // Forward-to-self failed. Either someone else managed to allocate
4176 // space for this object (old != forward_ptr) or they beat us in
4177 // self-forwarding it (old == forward_ptr).
4178 assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4179 err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4180 "should not be in the CSet",
4181 (HeapWord*) old, (HeapWord*) forward_ptr));
4182 return forward_ptr;
4183 }
4184 }
4185
4186 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4187 preserve_mark_if_necessary(old, m);
4188
4189 HeapRegion* r = heap_region_containing(old);
4190 if (!r->evacuation_failed()) {
4191 r->set_evacuation_failed(true);
4192 _hr_printer.evac_failure(r);
4193 }
4194
4195 push_on_evac_failure_scan_stack(old);
4196
4197 if (!_drain_in_progress) {
4198 // prevent recursion in copy_to_survivor_space()
4199 _drain_in_progress = true;
4200 drain_evac_failure_scan_stack();
4201 _drain_in_progress = false;
4202 }
4203 }
4204
4205 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4206 assert(evacuation_failed(), "Oversaving!");
4207 // We want to call the "for_promotion_failure" version only in the
4208 // case of a promotion failure.
4209 if (m->must_be_preserved_for_promotion_failure(obj)) {
4210 _objs_with_preserved_marks.push(obj);
4211 _preserved_marks_of_objs.push(m);
4212 }
4213 }
4214
4215 void G1ParCopyHelper::mark_object(oop obj) {
4216 assert(!_g1->heap_region_containing(obj)->in_collection_set(), "should not mark objects in the CSet");
4217
4218 // We know that the object is not moving so it's safe to read its size.
4219 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4220 }
4221
4222 void G1ParCopyHelper::mark_forwarded_object(oop from_obj, oop to_obj) {
4223 assert(from_obj->is_forwarded(), "from obj should be forwarded");
4224 assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4225 assert(from_obj != to_obj, "should not be self-forwarded");
4226
4227 assert(_g1->heap_region_containing(from_obj)->in_collection_set(), "from obj should be in the CSet");
4228 assert(!_g1->heap_region_containing(to_obj)->in_collection_set(), "should not mark objects in the CSet");
4229
4230 // The object might be in the process of being copied by another
4231 // worker so we cannot trust that its to-space image is
4232 // well-formed. So we have to read its size from its from-space
4233 // image which we know should not be changing.
4234 _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4235 }
4236
4237 template <class T>
4238 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) {
4239 if (_g1->heap_region_containing_raw(new_obj)->is_young()) {
4240 _scanned_klass->record_modified_oops();
4241 }
4242 }
4243
4244 template <G1Barrier barrier, G1Mark do_mark_object>
4245 template <class T>
4246 void G1ParCopyClosure<barrier, do_mark_object>::do_oop_work(T* p) {
4247 T heap_oop = oopDesc::load_heap_oop(p);
4248
4249 if (oopDesc::is_null(heap_oop)) {
4250 return;
4251 }
4252
4253 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
4254
4255 assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4256
4257 const InCSetState state = _g1->in_cset_state(obj);
4258 if (state.is_in_cset()) {
4259 oop forwardee;
4260 markOop m = obj->mark();
4261 if (m->is_marked()) {
4262 forwardee = (oop) m->decode_pointer();
4263 } else {
4264 forwardee = _par_scan_state->copy_to_survivor_space(state, obj, m);
4265 }
4266 assert(forwardee != NULL, "forwardee should not be NULL");
4267 oopDesc::encode_store_heap_oop(p, forwardee);
4268 if (do_mark_object != G1MarkNone && forwardee != obj) {
4269 // If the object is self-forwarded we don't need to explicitly
4270 // mark it, the evacuation failure protocol will do so.
4271 mark_forwarded_object(obj, forwardee);
4272 }
4273
4274 if (barrier == G1BarrierKlass) {
4275 do_klass_barrier(p, forwardee);
4276 }
4277 } else {
4278 if (state.is_humongous()) {
4279 _g1->set_humongous_is_live(obj);
4280 }
4281 // The object is not in collection set. If we're a root scanning
4282 // closure during an initial mark pause then attempt to mark the object.
4283 if (do_mark_object == G1MarkFromRoot) {
4284 mark_object(obj);
4285 }
4286 }
4287
4288 if (barrier == G1BarrierEvac) {
4289 _par_scan_state->update_rs(_from, p, _worker_id);
4290 }
4291 }
4292
4293 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(oop* p);
4294 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(narrowOop* p);
4295
4296 class G1ParEvacuateFollowersClosure : public VoidClosure {
4297 protected:
4298 G1CollectedHeap* _g1h;
4299 G1ParScanThreadState* _par_scan_state;
4300 RefToScanQueueSet* _queues;
4301 ParallelTaskTerminator* _terminator;
4302
4303 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
4304 RefToScanQueueSet* queues() { return _queues; }
4305 ParallelTaskTerminator* terminator() { return _terminator; }
4306
4307 public:
4308 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4309 G1ParScanThreadState* par_scan_state,
4310 RefToScanQueueSet* queues,
4311 ParallelTaskTerminator* terminator)
4312 : _g1h(g1h), _par_scan_state(par_scan_state),
4313 _queues(queues), _terminator(terminator) {}
4314
4315 void do_void();
4316
4317 private:
4318 inline bool offer_termination();
4319 };
4320
4321 bool G1ParEvacuateFollowersClosure::offer_termination() {
4322 G1ParScanThreadState* const pss = par_scan_state();
4323 pss->start_term_time();
4324 const bool res = terminator()->offer_termination();
4325 pss->end_term_time();
4326 return res;
4327 }
4328
4329 void G1ParEvacuateFollowersClosure::do_void() {
4330 G1ParScanThreadState* const pss = par_scan_state();
4331 pss->trim_queue();
4332 do {
4333 pss->steal_and_trim_queue(queues());
4334 } while (!offer_termination());
4335 }
4336
4337 class G1KlassScanClosure : public KlassClosure {
4338 G1ParCopyHelper* _closure;
4339 bool _process_only_dirty;
4340 int _count;
4341 public:
4342 G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty)
4343 : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {}
4344 void do_klass(Klass* klass) {
4345 // If the klass has not been dirtied we know that there's
4346 // no references into the young gen and we can skip it.
4347 if (!_process_only_dirty || klass->has_modified_oops()) {
4348 // Clean the klass since we're going to scavenge all the metadata.
4349 klass->clear_modified_oops();
4350
4351 // Tell the closure that this klass is the Klass to scavenge
4352 // and is the one to dirty if oops are left pointing into the young gen.
4353 _closure->set_scanned_klass(klass);
4354
4355 klass->oops_do(_closure);
4356
4357 _closure->set_scanned_klass(NULL);
4358 }
4359 _count++;
4360 }
4361 };
4362
4363 class G1CodeBlobClosure : public CodeBlobClosure {
4364 class HeapRegionGatheringOopClosure : public OopClosure {
4365 G1CollectedHeap* _g1h;
4366 OopClosure* _work;
4367 nmethod* _nm;
4368
4369 template <typename T>
4370 void do_oop_work(T* p) {
4371 _work->do_oop(p);
4372 T oop_or_narrowoop = oopDesc::load_heap_oop(p);
4373 if (!oopDesc::is_null(oop_or_narrowoop)) {
4374 oop o = oopDesc::decode_heap_oop_not_null(oop_or_narrowoop);
4375 HeapRegion* hr = _g1h->heap_region_containing_raw(o);
4376 assert(!_g1h->obj_in_cs(o) || hr->rem_set()->strong_code_roots_list_contains(_nm), "if o still in CS then evacuation failed and nm must already be in the remset");
4377 hr->add_strong_code_root(_nm);
4378 }
4379 }
4380
4381 public:
4382 HeapRegionGatheringOopClosure(OopClosure* oc) : _g1h(G1CollectedHeap::heap()), _work(oc), _nm(NULL) {}
4383
4384 void do_oop(oop* o) {
4385 do_oop_work(o);
4386 }
4387
4388 void do_oop(narrowOop* o) {
4389 do_oop_work(o);
4390 }
4391
4392 void set_nm(nmethod* nm) {
4393 _nm = nm;
4394 }
4395 };
4396
4397 HeapRegionGatheringOopClosure _oc;
4398 public:
4399 G1CodeBlobClosure(OopClosure* oc) : _oc(oc) {}
4400
4401 void do_code_blob(CodeBlob* cb) {
4402 nmethod* nm = cb->as_nmethod_or_null();
4403 if (nm != NULL) {
4404 if (!nm->test_set_oops_do_mark()) {
4405 _oc.set_nm(nm);
4406 nm->oops_do(&_oc);
4407 nm->fix_oop_relocations();
4408 }
4409 }
4410 }
4411 };
4412
4413 class G1ParTask : public AbstractGangTask {
4414 protected:
4415 G1CollectedHeap* _g1h;
4416 RefToScanQueueSet *_queues;
4417 ParallelTaskTerminator _terminator;
4418 uint _n_workers;
4419
4420 Mutex _stats_lock;
4421 Mutex* stats_lock() { return &_stats_lock; }
4422
4423 public:
4424 G1ParTask(G1CollectedHeap* g1h, RefToScanQueueSet *task_queues)
4425 : AbstractGangTask("G1 collection"),
4426 _g1h(g1h),
4427 _queues(task_queues),
4428 _terminator(0, _queues),
4429 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4430 {}
4431
4432 RefToScanQueueSet* queues() { return _queues; }
4433
4434 RefToScanQueue *work_queue(int i) {
4435 return queues()->queue(i);
4436 }
4437
4438 ParallelTaskTerminator* terminator() { return &_terminator; }
4439
4440 virtual void set_for_termination(int active_workers) {
4441 // This task calls set_n_termination() in par_non_clean_card_iterate_work()
4442 // in the young space (_par_seq_tasks) in the G1 heap
4443 // for SequentialSubTasksDone.
4444 // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap
4445 // both of which need setting by set_n_termination().
4446 _g1h->SharedHeap::set_n_termination(active_workers);
4447 _g1h->set_n_termination(active_workers);
4448 terminator()->reset_for_reuse(active_workers);
4449 _n_workers = active_workers;
4450 }
4451
4452 // Helps out with CLD processing.
4453 //
4454 // During InitialMark we need to:
4455 // 1) Scavenge all CLDs for the young GC.
4456 // 2) Mark all objects directly reachable from strong CLDs.
4457 template <G1Mark do_mark_object>
4458 class G1CLDClosure : public CLDClosure {
4459 G1ParCopyClosure<G1BarrierNone, do_mark_object>* _oop_closure;
4460 G1ParCopyClosure<G1BarrierKlass, do_mark_object> _oop_in_klass_closure;
4461 G1KlassScanClosure _klass_in_cld_closure;
4462 bool _claim;
4463
4464 public:
4465 G1CLDClosure(G1ParCopyClosure<G1BarrierNone, do_mark_object>* oop_closure,
4466 bool only_young, bool claim)
4467 : _oop_closure(oop_closure),
4468 _oop_in_klass_closure(oop_closure->g1(),
4469 oop_closure->pss(),
4470 oop_closure->rp()),
4471 _klass_in_cld_closure(&_oop_in_klass_closure, only_young),
4472 _claim(claim) {
4473
4474 }
4475
4476 void do_cld(ClassLoaderData* cld) {
4477 cld->oops_do(_oop_closure, &_klass_in_cld_closure, _claim);
4478 }
4479 };
4480
4481 void work(uint worker_id) {
4482 if (worker_id >= _n_workers) return; // no work needed this round
4483
4484 double start_time_ms = os::elapsedTime() * 1000.0;
4485 _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms);
4486
4487 {
4488 ResourceMark rm;
4489 HandleMark hm;
4490
4491 ReferenceProcessor* rp = _g1h->ref_processor_stw();
4492
4493 G1ParScanThreadState pss(_g1h, worker_id, rp);
4494 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
4495
4496 pss.set_evac_failure_closure(&evac_failure_cl);
4497
4498 bool only_young = _g1h->g1_policy()->gcs_are_young();
4499
4500 // Non-IM young GC.
4501 G1ParCopyClosure<G1BarrierNone, G1MarkNone> scan_only_root_cl(_g1h, &pss, rp);
4502 G1CLDClosure<G1MarkNone> scan_only_cld_cl(&scan_only_root_cl,
4503 only_young, // Only process dirty klasses.
4504 false); // No need to claim CLDs.
4505 // IM young GC.
4506 // Strong roots closures.
4507 G1ParCopyClosure<G1BarrierNone, G1MarkFromRoot> scan_mark_root_cl(_g1h, &pss, rp);
4508 G1CLDClosure<G1MarkFromRoot> scan_mark_cld_cl(&scan_mark_root_cl,
4509 false, // Process all klasses.
4510 true); // Need to claim CLDs.
4511 // Weak roots closures.
4512 G1ParCopyClosure<G1BarrierNone, G1MarkPromotedFromRoot> scan_mark_weak_root_cl(_g1h, &pss, rp);
4513 G1CLDClosure<G1MarkPromotedFromRoot> scan_mark_weak_cld_cl(&scan_mark_weak_root_cl,
4514 false, // Process all klasses.
4515 true); // Need to claim CLDs.
4516
4517 G1CodeBlobClosure scan_only_code_cl(&scan_only_root_cl);
4518 G1CodeBlobClosure scan_mark_code_cl(&scan_mark_root_cl);
4519 // IM Weak code roots are handled later.
4520
4521 OopClosure* strong_root_cl;
4522 OopClosure* weak_root_cl;
4523 CLDClosure* strong_cld_cl;
4524 CLDClosure* weak_cld_cl;
4525 CodeBlobClosure* strong_code_cl;
4526
4527 if (_g1h->g1_policy()->during_initial_mark_pause()) {
4528 // We also need to mark copied objects.
4529 strong_root_cl = &scan_mark_root_cl;
4530 strong_cld_cl = &scan_mark_cld_cl;
4531 strong_code_cl = &scan_mark_code_cl;
4532 if (ClassUnloadingWithConcurrentMark) {
4533 weak_root_cl = &scan_mark_weak_root_cl;
4534 weak_cld_cl = &scan_mark_weak_cld_cl;
4535 } else {
4536 weak_root_cl = &scan_mark_root_cl;
4537 weak_cld_cl = &scan_mark_cld_cl;
4538 }
4539 } else {
4540 strong_root_cl = &scan_only_root_cl;
4541 weak_root_cl = &scan_only_root_cl;
4542 strong_cld_cl = &scan_only_cld_cl;
4543 weak_cld_cl = &scan_only_cld_cl;
4544 strong_code_cl = &scan_only_code_cl;
4545 }
4546
4547
4548 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss);
4549
4550 pss.start_strong_roots();
4551 _g1h->g1_process_roots(strong_root_cl,
4552 weak_root_cl,
4553 &push_heap_rs_cl,
4554 strong_cld_cl,
4555 weak_cld_cl,
4556 strong_code_cl,
4557 worker_id);
4558
4559 pss.end_strong_roots();
4560
4561 {
4562 double start = os::elapsedTime();
4563 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4564 evac.do_void();
4565 double elapsed_ms = (os::elapsedTime()-start)*1000.0;
4566 double term_ms = pss.term_time()*1000.0;
4567 _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms);
4568 _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts());
4569 }
4570 _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4571 _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4572
4573 if (PrintTerminationStats) {
4574 MutexLocker x(stats_lock());
4575 pss.print_termination_stats(worker_id);
4576 }
4577
4578 assert(pss.queue_is_empty(), "should be empty");
4579
4580 // Close the inner scope so that the ResourceMark and HandleMark
4581 // destructors are executed here and are included as part of the
4582 // "GC Worker Time".
4583 }
4584
4585 double end_time_ms = os::elapsedTime() * 1000.0;
4586 _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms);
4587 }
4588 };
4589
4590 // *** Common G1 Evacuation Stuff
4591
4592 // This method is run in a GC worker.
4593
4594 void
4595 G1CollectedHeap::
4596 g1_process_roots(OopClosure* scan_non_heap_roots,
4597 OopClosure* scan_non_heap_weak_roots,
4598 G1ParPushHeapRSClosure* scan_rs,
4599 CLDClosure* scan_strong_clds,
4600 CLDClosure* scan_weak_clds,
4601 CodeBlobClosure* scan_strong_code,
4602 uint worker_i) {
4603
4604 // First scan the shared roots.
4605 double ext_roots_start = os::elapsedTime();
4606 double closure_app_time_sec = 0.0;
4607
4608 bool during_im = _g1h->g1_policy()->during_initial_mark_pause();
4609 bool trace_metadata = during_im && ClassUnloadingWithConcurrentMark;
4610
4611 BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
4612 BufferingOopClosure buf_scan_non_heap_weak_roots(scan_non_heap_weak_roots);
4613
4614 process_roots(false, // no scoping; this is parallel code
4615 SharedHeap::SO_None,
4616 &buf_scan_non_heap_roots,
4617 &buf_scan_non_heap_weak_roots,
4618 scan_strong_clds,
4619 // Unloading Initial Marks handle the weak CLDs separately.
4620 (trace_metadata ? NULL : scan_weak_clds),
4621 scan_strong_code);
4622
4623 // Now the CM ref_processor roots.
4624 if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
4625 // We need to treat the discovered reference lists of the
4626 // concurrent mark ref processor as roots and keep entries
4627 // (which are added by the marking threads) on them live
4628 // until they can be processed at the end of marking.
4629 ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
4630 }
4631
4632 if (trace_metadata) {
4633 // Barrier to make sure all workers passed
4634 // the strong CLD and strong nmethods phases.
4635 active_strong_roots_scope()->wait_until_all_workers_done_with_threads(n_par_threads());
4636
4637 // Now take the complement of the strong CLDs.
4638 ClassLoaderDataGraph::roots_cld_do(NULL, scan_weak_clds);
4639 }
4640
4641 // Finish up any enqueued closure apps (attributed as object copy time).
4642 buf_scan_non_heap_roots.done();
4643 buf_scan_non_heap_weak_roots.done();
4644
4645 double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds()
4646 + buf_scan_non_heap_weak_roots.closure_app_seconds();
4647
4648 g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
4649
4650 double ext_root_time_ms =
4651 ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0;
4652
4653 g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
4654
4655 // During conc marking we have to filter the per-thread SATB buffers
4656 // to make sure we remove any oops into the CSet (which will show up
4657 // as implicitly live).
4658 double satb_filtering_ms = 0.0;
4659 if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) {
4660 if (mark_in_progress()) {
4661 double satb_filter_start = os::elapsedTime();
4662
4663 JavaThread::satb_mark_queue_set().filter_thread_buffers();
4664
4665 satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0;
4666 }
4667 }
4668 g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms);
4669
4670 // Now scan the complement of the collection set.
4671 G1CodeBlobClosure scavenge_cs_nmethods(scan_non_heap_weak_roots);
4672
4673 g1_rem_set()->oops_into_collection_set_do(scan_rs, &scavenge_cs_nmethods, worker_i);
4674
4675 _process_strong_tasks->all_tasks_completed();
4676 }
4677
4678 class G1StringSymbolTableUnlinkTask : public AbstractGangTask {
4679 private:
4680 BoolObjectClosure* _is_alive;
4681 int _initial_string_table_size;
4682 int _initial_symbol_table_size;
4683
4684 bool _process_strings;
4685 int _strings_processed;
4686 int _strings_removed;
4687
4688 bool _process_symbols;
4689 int _symbols_processed;
4690 int _symbols_removed;
4691
4692 public:
4693 G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) :
4694 AbstractGangTask("String/Symbol Unlinking"),
4695 _is_alive(is_alive),
4696 _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
4697 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) {
4698
4699 _initial_string_table_size = StringTable::the_table()->table_size();
4700 _initial_symbol_table_size = SymbolTable::the_table()->table_size();
4701 if (process_strings) {
4702 StringTable::clear_parallel_claimed_index();
4703 }
4704 if (process_symbols) {
4705 SymbolTable::clear_parallel_claimed_index();
4706 }
4707 }
4708
4709 ~G1StringSymbolTableUnlinkTask() {
4710 guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size,
4711 err_msg("claim value %d after unlink less than initial string table size %d",
4712 StringTable::parallel_claimed_index(), _initial_string_table_size));
4713 guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
4714 err_msg("claim value %d after unlink less than initial symbol table size %d",
4715 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size));
4716
4717 if (G1TraceStringSymbolTableScrubbing) {
4718 gclog_or_tty->print_cr("Cleaned string and symbol table, "
4719 "strings: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed, "
4720 "symbols: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed",
4721 strings_processed(), strings_removed(),
4722 symbols_processed(), symbols_removed());
4723 }
4724 }
4725
4726 void work(uint worker_id) {
4727 int strings_processed = 0;
4728 int strings_removed = 0;
4729 int symbols_processed = 0;
4730 int symbols_removed = 0;
4731 if (_process_strings) {
4732 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
4733 Atomic::add(strings_processed, &_strings_processed);
4734 Atomic::add(strings_removed, &_strings_removed);
4735 }
4736 if (_process_symbols) {
4737 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
4738 Atomic::add(symbols_processed, &_symbols_processed);
4739 Atomic::add(symbols_removed, &_symbols_removed);
4740 }
4741 }
4742
4743 size_t strings_processed() const { return (size_t)_strings_processed; }
4744 size_t strings_removed() const { return (size_t)_strings_removed; }
4745
4746 size_t symbols_processed() const { return (size_t)_symbols_processed; }
4747 size_t symbols_removed() const { return (size_t)_symbols_removed; }
4748 };
4749
4750 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
4751 private:
4752 static Monitor* _lock;
4753
4754 BoolObjectClosure* const _is_alive;
4755 const bool _unloading_occurred;
4756 const uint _num_workers;
4757
4758 // Variables used to claim nmethods.
4759 nmethod* _first_nmethod;
4760 volatile nmethod* _claimed_nmethod;
4761
4762 // The list of nmethods that need to be processed by the second pass.
4763 volatile nmethod* _postponed_list;
4764 volatile uint _num_entered_barrier;
4765
4766 public:
4767 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
4768 _is_alive(is_alive),
4769 _unloading_occurred(unloading_occurred),
4770 _num_workers(num_workers),
4771 _first_nmethod(NULL),
4772 _claimed_nmethod(NULL),
4773 _postponed_list(NULL),
4774 _num_entered_barrier(0)
4775 {
4776 nmethod::increase_unloading_clock();
4777 // Get first alive nmethod
4778 NMethodIterator iter = NMethodIterator();
4779 if(iter.next_alive()) {
4780 _first_nmethod = iter.method();
4781 }
4782 _claimed_nmethod = (volatile nmethod*)_first_nmethod;
4783 }
4784
4785 ~G1CodeCacheUnloadingTask() {
4786 CodeCache::verify_clean_inline_caches();
4787
4788 CodeCache::set_needs_cache_clean(false);
4789 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
4790
4791 CodeCache::verify_icholder_relocations();
4792 }
4793
4794 private:
4795 void add_to_postponed_list(nmethod* nm) {
4796 nmethod* old;
4797 do {
4798 old = (nmethod*)_postponed_list;
4799 nm->set_unloading_next(old);
4800 } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old);
4801 }
4802
4803 void clean_nmethod(nmethod* nm) {
4804 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
4805
4806 if (postponed) {
4807 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
4808 add_to_postponed_list(nm);
4809 }
4810
4811 // Mark that this thread has been cleaned/unloaded.
4812 // After this call, it will be safe to ask if this nmethod was unloaded or not.
4813 nm->set_unloading_clock(nmethod::global_unloading_clock());
4814 }
4815
4816 void clean_nmethod_postponed(nmethod* nm) {
4817 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
4818 }
4819
4820 static const int MaxClaimNmethods = 16;
4821
4822 void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) {
4823 nmethod* first;
4824 NMethodIterator last;
4825
4826 do {
4827 *num_claimed_nmethods = 0;
4828
4829 first = (nmethod*)_claimed_nmethod;
4830 last = NMethodIterator(first);
4831
4832 if (first != NULL) {
4833
4834 for (int i = 0; i < MaxClaimNmethods; i++) {
4835 if (!last.next_alive()) {
4836 break;
4837 }
4838 claimed_nmethods[i] = last.method();
4839 (*num_claimed_nmethods)++;
4840 }
4841 }
4842
4843 } while ((nmethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first);
4844 }
4845
4846 nmethod* claim_postponed_nmethod() {
4847 nmethod* claim;
4848 nmethod* next;
4849
4850 do {
4851 claim = (nmethod*)_postponed_list;
4852 if (claim == NULL) {
4853 return NULL;
4854 }
4855
4856 next = claim->unloading_next();
4857
4858 } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim);
4859
4860 return claim;
4861 }
4862
4863 public:
4864 // Mark that we're done with the first pass of nmethod cleaning.
4865 void barrier_mark(uint worker_id) {
4866 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
4867 _num_entered_barrier++;
4868 if (_num_entered_barrier == _num_workers) {
4869 ml.notify_all();
4870 }
4871 }
4872
4873 // See if we have to wait for the other workers to
4874 // finish their first-pass nmethod cleaning work.
4875 void barrier_wait(uint worker_id) {
4876 if (_num_entered_barrier < _num_workers) {
4877 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
4878 while (_num_entered_barrier < _num_workers) {
4879 ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
4880 }
4881 }
4882 }
4883
4884 // Cleaning and unloading of nmethods. Some work has to be postponed
4885 // to the second pass, when we know which nmethods survive.
4886 void work_first_pass(uint worker_id) {
4887 // The first nmethods is claimed by the first worker.
4888 if (worker_id == 0 && _first_nmethod != NULL) {
4889 clean_nmethod(_first_nmethod);
4890 _first_nmethod = NULL;
4891 }
4892
4893 int num_claimed_nmethods;
4894 nmethod* claimed_nmethods[MaxClaimNmethods];
4895
4896 while (true) {
4897 claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
4898
4899 if (num_claimed_nmethods == 0) {
4900 break;
4901 }
4902
4903 for (int i = 0; i < num_claimed_nmethods; i++) {
4904 clean_nmethod(claimed_nmethods[i]);
4905 }
4906 }
4907
4908 // The nmethod cleaning helps out and does the CodeCache part of MetadataOnStackMark.
4909 // Need to retire the buffers now that this thread has stopped cleaning nmethods.
4910 MetadataOnStackMark::retire_buffer_for_thread(Thread::current());
4911 }
4912
4913 void work_second_pass(uint worker_id) {
4914 nmethod* nm;
4915 // Take care of postponed nmethods.
4916 while ((nm = claim_postponed_nmethod()) != NULL) {
4917 clean_nmethod_postponed(nm);
4918 }
4919 }
4920 };
4921
4922 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never);
4923
4924 class G1KlassCleaningTask : public StackObj {
4925 BoolObjectClosure* _is_alive;
4926 volatile jint _clean_klass_tree_claimed;
4927 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
4928
4929 public:
4930 G1KlassCleaningTask(BoolObjectClosure* is_alive) :
4931 _is_alive(is_alive),
4932 _clean_klass_tree_claimed(0),
4933 _klass_iterator() {
4934 }
4935
4936 private:
4937 bool claim_clean_klass_tree_task() {
4938 if (_clean_klass_tree_claimed) {
4939 return false;
4940 }
4941
4942 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0;
4943 }
4944
4945 InstanceKlass* claim_next_klass() {
4946 Klass* klass;
4947 do {
4948 klass =_klass_iterator.next_klass();
4949 } while (klass != NULL && !klass->oop_is_instance());
4950
4951 return (InstanceKlass*)klass;
4952 }
4953
4954 public:
4955
4956 void clean_klass(InstanceKlass* ik) {
4957 ik->clean_implementors_list(_is_alive);
4958 ik->clean_method_data(_is_alive);
4959
4960 // G1 specific cleanup work that has
4961 // been moved here to be done in parallel.
4962 ik->clean_dependent_nmethods();
4963 if (JvmtiExport::has_redefined_a_class()) {
4964 InstanceKlass::purge_previous_versions(ik);
4965 }
4966 }
4967
4968 void work() {
4969 ResourceMark rm;
4970
4971 // One worker will clean the subklass/sibling klass tree.
4972 if (claim_clean_klass_tree_task()) {
4973 Klass::clean_subklass_tree(_is_alive);
4974 }
4975
4976 // All workers will help cleaning the classes,
4977 InstanceKlass* klass;
4978 while ((klass = claim_next_klass()) != NULL) {
4979 clean_klass(klass);
4980 }
4981 }
4982 };
4983
4984 // To minimize the remark pause times, the tasks below are done in parallel.
4985 class G1ParallelCleaningTask : public AbstractGangTask {
4986 private:
4987 G1StringSymbolTableUnlinkTask _string_symbol_task;
4988 G1CodeCacheUnloadingTask _code_cache_task;
4989 G1KlassCleaningTask _klass_cleaning_task;
4990
4991 public:
4992 // The constructor is run in the VMThread.
4993 G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) :
4994 AbstractGangTask("Parallel Cleaning"),
4995 _string_symbol_task(is_alive, process_strings, process_symbols),
4996 _code_cache_task(num_workers, is_alive, unloading_occurred),
4997 _klass_cleaning_task(is_alive) {
4998 }
4999
5000 void pre_work_verification() {
5001 assert(!MetadataOnStackMark::has_buffer_for_thread(Thread::current()), "Should be empty");
5002 }
5003
5004 void post_work_verification() {
5005 assert(!MetadataOnStackMark::has_buffer_for_thread(Thread::current()), "Should be empty");
5006 }
5007
5008 // The parallel work done by all worker threads.
5009 void work(uint worker_id) {
5010 pre_work_verification();
5011
5012 // Do first pass of code cache cleaning.
5013 _code_cache_task.work_first_pass(worker_id);
5014
5015 // Let the threads mark that the first pass is done.
5016 _code_cache_task.barrier_mark(worker_id);
5017
5018 // Clean the Strings and Symbols.
5019 _string_symbol_task.work(worker_id);
5020
5021 // Wait for all workers to finish the first code cache cleaning pass.
5022 _code_cache_task.barrier_wait(worker_id);
5023
5024 // Do the second code cache cleaning work, which realize on
5025 // the liveness information gathered during the first pass.
5026 _code_cache_task.work_second_pass(worker_id);
5027
5028 // Clean all klasses that were not unloaded.
5029 _klass_cleaning_task.work();
5030
5031 post_work_verification();
5032 }
5033 };
5034
5035
5036 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive,
5037 bool process_strings,
5038 bool process_symbols,
5039 bool class_unloading_occurred) {
5040 uint n_workers = workers()->active_workers();
5041
5042 G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols,
5043 n_workers, class_unloading_occurred);
5044 set_par_threads(n_workers);
5045 workers()->run_task(&g1_unlink_task);
5046 set_par_threads(0);
5047 }
5048
5049 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive,
5050 bool process_strings, bool process_symbols) {
5051 {
5052 uint n_workers = _g1h->workers()->active_workers();
5053 G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols);
5054 set_par_threads(n_workers);
5055 workers()->run_task(&g1_unlink_task);
5056 set_par_threads(0);
5057 }
5058
5059 if (G1StringDedup::is_enabled()) {
5060 G1StringDedup::unlink(is_alive);
5061 }
5062 }
5063
5064 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
5065 private:
5066 DirtyCardQueueSet* _queue;
5067 public:
5068 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue) : AbstractGangTask("Redirty Cards"), _queue(queue) { }
5069
5070 virtual void work(uint worker_id) {
5071 double start_time = os::elapsedTime();
5072
5073 RedirtyLoggedCardTableEntryClosure cl;
5074 _queue->par_apply_closure_to_all_completed_buffers(&cl);
5075
5076 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
5077 timer->record_redirty_logged_cards_time_ms(worker_id, (os::elapsedTime() - start_time) * 1000.0);
5078 timer->record_redirty_logged_cards_processed_cards(worker_id, cl.num_processed());
5079 }
5080 };
5081
5082 void G1CollectedHeap::redirty_logged_cards() {
5083 double redirty_logged_cards_start = os::elapsedTime();
5084
5085 uint n_workers = _g1h->workers()->active_workers();
5086
5087 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set());
5088 dirty_card_queue_set().reset_for_par_iteration();
5089 set_par_threads(n_workers);
5090 workers()->run_task(&redirty_task);
5091 set_par_threads(0);
5092
5093 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5094 dcq.merge_bufferlists(&dirty_card_queue_set());
5095 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5096
5097 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
5098 }
5099
5100 // Weak Reference Processing support
5101
5102 // An always "is_alive" closure that is used to preserve referents.
5103 // If the object is non-null then it's alive. Used in the preservation
5104 // of referent objects that are pointed to by reference objects
5105 // discovered by the CM ref processor.
5106 class G1AlwaysAliveClosure: public BoolObjectClosure {
5107 G1CollectedHeap* _g1;
5108 public:
5109 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5110 bool do_object_b(oop p) {
5111 if (p != NULL) {
5112 return true;
5113 }
5114 return false;
5115 }
5116 };
5117
5118 bool G1STWIsAliveClosure::do_object_b(oop p) {
5119 // An object is reachable if it is outside the collection set,
5120 // or is inside and copied.
5121 return !_g1->obj_in_cs(p) || p->is_forwarded();
5122 }
5123
5124 // Non Copying Keep Alive closure
5125 class G1KeepAliveClosure: public OopClosure {
5126 G1CollectedHeap* _g1;
5127 public:
5128 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5129 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
5130 void do_oop(oop* p) {
5131 oop obj = *p;
5132 assert(obj != NULL, "the caller should have filtered out NULL values");
5133
5134 const InCSetState cset_state = _g1->in_cset_state(obj);
5135 if (!cset_state.is_in_cset_or_humongous()) {
5136 return;
5137 }
5138 if (cset_state.is_in_cset()) {
5139 assert( obj->is_forwarded(), "invariant" );
5140 *p = obj->forwardee();
5141 } else {
5142 assert(!obj->is_forwarded(), "invariant" );
5143 assert(cset_state.is_humongous(),
5144 err_msg("Only allowed InCSet state is IsHumongous, but is %d", cset_state.value()));
5145 _g1->set_humongous_is_live(obj);
5146 }
5147 }
5148 };
5149
5150 // Copying Keep Alive closure - can be called from both
5151 // serial and parallel code as long as different worker
5152 // threads utilize different G1ParScanThreadState instances
5153 // and different queues.
5154
5155 class G1CopyingKeepAliveClosure: public OopClosure {
5156 G1CollectedHeap* _g1h;
5157 OopClosure* _copy_non_heap_obj_cl;
5158 G1ParScanThreadState* _par_scan_state;
5159
5160 public:
5161 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
5162 OopClosure* non_heap_obj_cl,
5163 G1ParScanThreadState* pss):
5164 _g1h(g1h),
5165 _copy_non_heap_obj_cl(non_heap_obj_cl),
5166 _par_scan_state(pss)
5167 {}
5168
5169 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
5170 virtual void do_oop( oop* p) { do_oop_work(p); }
5171
5172 template <class T> void do_oop_work(T* p) {
5173 oop obj = oopDesc::load_decode_heap_oop(p);
5174
5175 if (_g1h->is_in_cset_or_humongous(obj)) {
5176 // If the referent object has been forwarded (either copied
5177 // to a new location or to itself in the event of an
5178 // evacuation failure) then we need to update the reference
5179 // field and, if both reference and referent are in the G1
5180 // heap, update the RSet for the referent.
5181 //
5182 // If the referent has not been forwarded then we have to keep
5183 // it alive by policy. Therefore we have copy the referent.
5184 //
5185 // If the reference field is in the G1 heap then we can push
5186 // on the PSS queue. When the queue is drained (after each
5187 // phase of reference processing) the object and it's followers
5188 // will be copied, the reference field set to point to the
5189 // new location, and the RSet updated. Otherwise we need to
5190 // use the the non-heap or metadata closures directly to copy
5191 // the referent object and update the pointer, while avoiding
5192 // updating the RSet.
5193
5194 if (_g1h->is_in_g1_reserved(p)) {
5195 _par_scan_state->push_on_queue(p);
5196 } else {
5197 assert(!Metaspace::contains((const void*)p),
5198 err_msg("Unexpectedly found a pointer from metadata: "
5199 PTR_FORMAT, p));
5200 _copy_non_heap_obj_cl->do_oop(p);
5201 }
5202 }
5203 }
5204 };
5205
5206 // Serial drain queue closure. Called as the 'complete_gc'
5207 // closure for each discovered list in some of the
5208 // reference processing phases.
5209
5210 class G1STWDrainQueueClosure: public VoidClosure {
5211 protected:
5212 G1CollectedHeap* _g1h;
5213 G1ParScanThreadState* _par_scan_state;
5214
5215 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
5216
5217 public:
5218 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
5219 _g1h(g1h),
5220 _par_scan_state(pss)
5221 { }
5222
5223 void do_void() {
5224 G1ParScanThreadState* const pss = par_scan_state();
5225 pss->trim_queue();
5226 }
5227 };
5228
5229 // Parallel Reference Processing closures
5230
5231 // Implementation of AbstractRefProcTaskExecutor for parallel reference
5232 // processing during G1 evacuation pauses.
5233
5234 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5235 private:
5236 G1CollectedHeap* _g1h;
5237 RefToScanQueueSet* _queues;
5238 FlexibleWorkGang* _workers;
5239 int _active_workers;
5240
5241 public:
5242 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5243 FlexibleWorkGang* workers,
5244 RefToScanQueueSet *task_queues,
5245 int n_workers) :
5246 _g1h(g1h),
5247 _queues(task_queues),
5248 _workers(workers),
5249 _active_workers(n_workers)
5250 {
5251 assert(n_workers > 0, "shouldn't call this otherwise");
5252 }
5253
5254 // Executes the given task using concurrent marking worker threads.
5255 virtual void execute(ProcessTask& task);
5256 virtual void execute(EnqueueTask& task);
5257 };
5258
5259 // Gang task for possibly parallel reference processing
5260
5261 class G1STWRefProcTaskProxy: public AbstractGangTask {
5262 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5263 ProcessTask& _proc_task;
5264 G1CollectedHeap* _g1h;
5265 RefToScanQueueSet *_task_queues;
5266 ParallelTaskTerminator* _terminator;
5267
5268 public:
5269 G1STWRefProcTaskProxy(ProcessTask& proc_task,
5270 G1CollectedHeap* g1h,
5271 RefToScanQueueSet *task_queues,
5272 ParallelTaskTerminator* terminator) :
5273 AbstractGangTask("Process reference objects in parallel"),
5274 _proc_task(proc_task),
5275 _g1h(g1h),
5276 _task_queues(task_queues),
5277 _terminator(terminator)
5278 {}
5279
5280 virtual void work(uint worker_id) {
5281 // The reference processing task executed by a single worker.
5282 ResourceMark rm;
5283 HandleMark hm;
5284
5285 G1STWIsAliveClosure is_alive(_g1h);
5286
5287 G1ParScanThreadState pss(_g1h, worker_id, NULL);
5288 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5289
5290 pss.set_evac_failure_closure(&evac_failure_cl);
5291
5292 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5293
5294 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5295
5296 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5297
5298 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5299 // We also need to mark copied objects.
5300 copy_non_heap_cl = ©_mark_non_heap_cl;
5301 }
5302
5303 // Keep alive closure.
5304 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5305
5306 // Complete GC closure
5307 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5308
5309 // Call the reference processing task's work routine.
5310 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5311
5312 // Note we cannot assert that the refs array is empty here as not all
5313 // of the processing tasks (specifically phase2 - pp2_work) execute
5314 // the complete_gc closure (which ordinarily would drain the queue) so
5315 // the queue may not be empty.
5316 }
5317 };
5318
5319 // Driver routine for parallel reference processing.
5320 // Creates an instance of the ref processing gang
5321 // task and has the worker threads execute it.
5322 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5323 assert(_workers != NULL, "Need parallel worker threads.");
5324
5325 ParallelTaskTerminator terminator(_active_workers, _queues);
5326 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5327
5328 _g1h->set_par_threads(_active_workers);
5329 _workers->run_task(&proc_task_proxy);
5330 _g1h->set_par_threads(0);
5331 }
5332
5333 // Gang task for parallel reference enqueueing.
5334
5335 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5336 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5337 EnqueueTask& _enq_task;
5338
5339 public:
5340 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5341 AbstractGangTask("Enqueue reference objects in parallel"),
5342 _enq_task(enq_task)
5343 { }
5344
5345 virtual void work(uint worker_id) {
5346 _enq_task.work(worker_id);
5347 }
5348 };
5349
5350 // Driver routine for parallel reference enqueueing.
5351 // Creates an instance of the ref enqueueing gang
5352 // task and has the worker threads execute it.
5353
5354 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5355 assert(_workers != NULL, "Need parallel worker threads.");
5356
5357 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5358
5359 _g1h->set_par_threads(_active_workers);
5360 _workers->run_task(&enq_task_proxy);
5361 _g1h->set_par_threads(0);
5362 }
5363
5364 // End of weak reference support closures
5365
5366 // Abstract task used to preserve (i.e. copy) any referent objects
5367 // that are in the collection set and are pointed to by reference
5368 // objects discovered by the CM ref processor.
5369
5370 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5371 protected:
5372 G1CollectedHeap* _g1h;
5373 RefToScanQueueSet *_queues;
5374 ParallelTaskTerminator _terminator;
5375 uint _n_workers;
5376
5377 public:
5378 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
5379 AbstractGangTask("ParPreserveCMReferents"),
5380 _g1h(g1h),
5381 _queues(task_queues),
5382 _terminator(workers, _queues),
5383 _n_workers(workers)
5384 { }
5385
5386 void work(uint worker_id) {
5387 ResourceMark rm;
5388 HandleMark hm;
5389
5390 G1ParScanThreadState pss(_g1h, worker_id, NULL);
5391 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5392
5393 pss.set_evac_failure_closure(&evac_failure_cl);
5394
5395 assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5396
5397 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5398
5399 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5400
5401 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5402
5403 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5404 // We also need to mark copied objects.
5405 copy_non_heap_cl = ©_mark_non_heap_cl;
5406 }
5407
5408 // Is alive closure
5409 G1AlwaysAliveClosure always_alive(_g1h);
5410
5411 // Copying keep alive closure. Applied to referent objects that need
5412 // to be copied.
5413 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5414
5415 ReferenceProcessor* rp = _g1h->ref_processor_cm();
5416
5417 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5418 uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5419
5420 // limit is set using max_num_q() - which was set using ParallelGCThreads.
5421 // So this must be true - but assert just in case someone decides to
5422 // change the worker ids.
5423 assert(0 <= worker_id && worker_id < limit, "sanity");
5424 assert(!rp->discovery_is_atomic(), "check this code");
5425
5426 // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5427 for (uint idx = worker_id; idx < limit; idx += stride) {
5428 DiscoveredList& ref_list = rp->discovered_refs()[idx];
5429
5430 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5431 while (iter.has_next()) {
5432 // Since discovery is not atomic for the CM ref processor, we
5433 // can see some null referent objects.
5434 iter.load_ptrs(DEBUG_ONLY(true));
5435 oop ref = iter.obj();
5436
5437 // This will filter nulls.
5438 if (iter.is_referent_alive()) {
5439 iter.make_referent_alive();
5440 }
5441 iter.move_to_next();
5442 }
5443 }
5444
5445 // Drain the queue - which may cause stealing
5446 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5447 drain_queue.do_void();
5448 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5449 assert(pss.queue_is_empty(), "should be");
5450 }
5451 };
5452
5453 // Weak Reference processing during an evacuation pause (part 1).
5454 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) {
5455 double ref_proc_start = os::elapsedTime();
5456
5457 ReferenceProcessor* rp = _ref_processor_stw;
5458 assert(rp->discovery_enabled(), "should have been enabled");
5459
5460 // Any reference objects, in the collection set, that were 'discovered'
5461 // by the CM ref processor should have already been copied (either by
5462 // applying the external root copy closure to the discovered lists, or
5463 // by following an RSet entry).
5464 //
5465 // But some of the referents, that are in the collection set, that these
5466 // reference objects point to may not have been copied: the STW ref
5467 // processor would have seen that the reference object had already
5468 // been 'discovered' and would have skipped discovering the reference,
5469 // but would not have treated the reference object as a regular oop.
5470 // As a result the copy closure would not have been applied to the
5471 // referent object.
5472 //
5473 // We need to explicitly copy these referent objects - the references
5474 // will be processed at the end of remarking.
5475 //
5476 // We also need to do this copying before we process the reference
5477 // objects discovered by the STW ref processor in case one of these
5478 // referents points to another object which is also referenced by an
5479 // object discovered by the STW ref processor.
5480
5481 assert(no_of_gc_workers == workers()->active_workers(), "Need to reset active GC workers");
5482
5483 set_par_threads(no_of_gc_workers);
5484 G1ParPreserveCMReferentsTask keep_cm_referents(this,
5485 no_of_gc_workers,
5486 _task_queues);
5487
5488 workers()->run_task(&keep_cm_referents);
5489
5490 set_par_threads(0);
5491
5492 // Closure to test whether a referent is alive.
5493 G1STWIsAliveClosure is_alive(this);
5494
5495 // Even when parallel reference processing is enabled, the processing
5496 // of JNI refs is serial and performed serially by the current thread
5497 // rather than by a worker. The following PSS will be used for processing
5498 // JNI refs.
5499
5500 // Use only a single queue for this PSS.
5501 G1ParScanThreadState pss(this, 0, NULL);
5502
5503 // We do not embed a reference processor in the copying/scanning
5504 // closures while we're actually processing the discovered
5505 // reference objects.
5506 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5507
5508 pss.set_evac_failure_closure(&evac_failure_cl);
5509
5510 assert(pss.queue_is_empty(), "pre-condition");
5511
5512 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL);
5513
5514 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5515
5516 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5517
5518 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5519 // We also need to mark copied objects.
5520 copy_non_heap_cl = ©_mark_non_heap_cl;
5521 }
5522
5523 // Keep alive closure.
5524 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, &pss);
5525
5526 // Serial Complete GC closure
5527 G1STWDrainQueueClosure drain_queue(this, &pss);
5528
5529 // Setup the soft refs policy...
5530 rp->setup_policy(false);
5531
5532 ReferenceProcessorStats stats;
5533 if (!rp->processing_is_mt()) {
5534 // Serial reference processing...
5535 stats = rp->process_discovered_references(&is_alive,
5536 &keep_alive,
5537 &drain_queue,
5538 NULL,
5539 _gc_timer_stw,
5540 _gc_tracer_stw->gc_id());
5541 } else {
5542 // Parallel reference processing
5543 assert(rp->num_q() == no_of_gc_workers, "sanity");
5544 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5545
5546 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5547 stats = rp->process_discovered_references(&is_alive,
5548 &keep_alive,
5549 &drain_queue,
5550 &par_task_executor,
5551 _gc_timer_stw,
5552 _gc_tracer_stw->gc_id());
5553 }
5554
5555 _gc_tracer_stw->report_gc_reference_stats(stats);
5556
5557 // We have completed copying any necessary live referent objects.
5558 assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5559
5560 double ref_proc_time = os::elapsedTime() - ref_proc_start;
5561 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5562 }
5563
5564 // Weak Reference processing during an evacuation pause (part 2).
5565 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) {
5566 double ref_enq_start = os::elapsedTime();
5567
5568 ReferenceProcessor* rp = _ref_processor_stw;
5569 assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5570
5571 // Now enqueue any remaining on the discovered lists on to
5572 // the pending list.
5573 if (!rp->processing_is_mt()) {
5574 // Serial reference processing...
5575 rp->enqueue_discovered_references();
5576 } else {
5577 // Parallel reference enqueueing
5578
5579 assert(no_of_gc_workers == workers()->active_workers(),
5580 "Need to reset active workers");
5581 assert(rp->num_q() == no_of_gc_workers, "sanity");
5582 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5583
5584 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5585 rp->enqueue_discovered_references(&par_task_executor);
5586 }
5587
5588 rp->verify_no_references_recorded();
5589 assert(!rp->discovery_enabled(), "should have been disabled");
5590
5591 // FIXME
5592 // CM's reference processing also cleans up the string and symbol tables.
5593 // Should we do that here also? We could, but it is a serial operation
5594 // and could significantly increase the pause time.
5595
5596 double ref_enq_time = os::elapsedTime() - ref_enq_start;
5597 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5598 }
5599
5600 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) {
5601 _expand_heap_after_alloc_failure = true;
5602 _evacuation_failed = false;
5603
5604 // Should G1EvacuationFailureALot be in effect for this GC?
5605 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
5606
5607 g1_rem_set()->prepare_for_oops_into_collection_set_do();
5608
5609 // Disable the hot card cache.
5610 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
5611 hot_card_cache->reset_hot_cache_claimed_index();
5612 hot_card_cache->set_use_cache(false);
5613
5614 uint n_workers;
5615 n_workers =
5616 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
5617 workers()->active_workers(),
5618 Threads::number_of_non_daemon_threads());
5619 assert(UseDynamicNumberOfGCThreads ||
5620 n_workers == workers()->total_workers(),
5621 "If not dynamic should be using all the workers");
5622 workers()->set_active_workers(n_workers);
5623 set_par_threads(n_workers);
5624
5625 G1ParTask g1_par_task(this, _task_queues);
5626
5627 init_for_evac_failure(NULL);
5628
5629 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5630 double start_par_time_sec = os::elapsedTime();
5631 double end_par_time_sec;
5632
5633 {
5634 StrongRootsScope srs(this);
5635 // InitialMark needs claim bits to keep track of the marked-through CLDs.
5636 if (g1_policy()->during_initial_mark_pause()) {
5637 ClassLoaderDataGraph::clear_claimed_marks();
5638 }
5639
5640 // The individual threads will set their evac-failure closures.
5641 if (PrintTerminationStats) G1ParScanThreadState::print_termination_stats_hdr();
5642 // These tasks use ShareHeap::_process_strong_tasks
5643 assert(UseDynamicNumberOfGCThreads ||
5644 workers()->active_workers() == workers()->total_workers(),
5645 "If not dynamic should be using all the workers");
5646 workers()->run_task(&g1_par_task);
5647 end_par_time_sec = os::elapsedTime();
5648
5649 // Closing the inner scope will execute the destructor
5650 // for the StrongRootsScope object. We record the current
5651 // elapsed time before closing the scope so that time
5652 // taken for the SRS destructor is NOT included in the
5653 // reported parallel time.
5654 }
5655
5656 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5657 g1_policy()->phase_times()->record_par_time(par_time_ms);
5658
5659 double code_root_fixup_time_ms =
5660 (os::elapsedTime() - end_par_time_sec) * 1000.0;
5661 g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms);
5662
5663 set_par_threads(0);
5664
5665 // Process any discovered reference objects - we have
5666 // to do this _before_ we retire the GC alloc regions
5667 // as we may have to copy some 'reachable' referent
5668 // objects (and their reachable sub-graphs) that were
5669 // not copied during the pause.
5670 process_discovered_references(n_workers);
5671
5672 if (G1StringDedup::is_enabled()) {
5673 G1STWIsAliveClosure is_alive(this);
5674 G1KeepAliveClosure keep_alive(this);
5675 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive);
5676 }
5677
5678 _allocator->release_gc_alloc_regions(n_workers, evacuation_info);
5679 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5680
5681 // Reset and re-enable the hot card cache.
5682 // Note the counts for the cards in the regions in the
5683 // collection set are reset when the collection set is freed.
5684 hot_card_cache->reset_hot_cache();
5685 hot_card_cache->set_use_cache(true);
5686
5687 purge_code_root_memory();
5688
5689 finalize_for_evac_failure();
5690
5691 if (evacuation_failed()) {
5692 remove_self_forwarding_pointers();
5693
5694 // Reset the G1EvacuationFailureALot counters and flags
5695 // Note: the values are reset only when an actual
5696 // evacuation failure occurs.
5697 NOT_PRODUCT(reset_evacuation_should_fail();)
5698 }
5699
5700 // Enqueue any remaining references remaining on the STW
5701 // reference processor's discovered lists. We need to do
5702 // this after the card table is cleaned (and verified) as
5703 // the act of enqueueing entries on to the pending list
5704 // will log these updates (and dirty their associated
5705 // cards). We need these updates logged to update any
5706 // RSets.
5707 enqueue_discovered_references(n_workers);
5708
5709 redirty_logged_cards();
5710 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5711 }
5712
5713 void G1CollectedHeap::free_region(HeapRegion* hr,
5714 FreeRegionList* free_list,
5715 bool par,
5716 bool locked) {
5717 assert(!hr->is_free(), "the region should not be free");
5718 assert(!hr->is_empty(), "the region should not be empty");
5719 assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
5720 assert(free_list != NULL, "pre-condition");
5721
5722 if (G1VerifyBitmaps) {
5723 MemRegion mr(hr->bottom(), hr->end());
5724 concurrent_mark()->clearRangePrevBitmap(mr);
5725 }
5726
5727 // Clear the card counts for this region.
5728 // Note: we only need to do this if the region is not young
5729 // (since we don't refine cards in young regions).
5730 if (!hr->is_young()) {
5731 _cg1r->hot_card_cache()->reset_card_counts(hr);
5732 }
5733 hr->hr_clear(par, true /* clear_space */, locked /* locked */);
5734 free_list->add_ordered(hr);
5735 }
5736
5737 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
5738 FreeRegionList* free_list,
5739 bool par) {
5740 assert(hr->is_starts_humongous(), "this is only for starts humongous regions");
5741 assert(free_list != NULL, "pre-condition");
5742
5743 size_t hr_capacity = hr->capacity();
5744 // We need to read this before we make the region non-humongous,
5745 // otherwise the information will be gone.
5746 uint last_index = hr->last_hc_index();
5747 hr->clear_humongous();
5748 free_region(hr, free_list, par);
5749
5750 uint i = hr->hrm_index() + 1;
5751 while (i < last_index) {
5752 HeapRegion* curr_hr = region_at(i);
5753 assert(curr_hr->is_continues_humongous(), "invariant");
5754 curr_hr->clear_humongous();
5755 free_region(curr_hr, free_list, par);
5756 i += 1;
5757 }
5758 }
5759
5760 void G1CollectedHeap::remove_from_old_sets(const HeapRegionSetCount& old_regions_removed,
5761 const HeapRegionSetCount& humongous_regions_removed) {
5762 if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 0) {
5763 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5764 _old_set.bulk_remove(old_regions_removed);
5765 _humongous_set.bulk_remove(humongous_regions_removed);
5766 }
5767
5768 }
5769
5770 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
5771 assert(list != NULL, "list can't be null");
5772 if (!list->is_empty()) {
5773 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
5774 _hrm.insert_list_into_free_list(list);
5775 }
5776 }
5777
5778 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
5779 _allocator->decrease_used(bytes);
5780 }
5781
5782 class G1ParCleanupCTTask : public AbstractGangTask {
5783 G1SATBCardTableModRefBS* _ct_bs;
5784 G1CollectedHeap* _g1h;
5785 HeapRegion* volatile _su_head;
5786 public:
5787 G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs,
5788 G1CollectedHeap* g1h) :
5789 AbstractGangTask("G1 Par Cleanup CT Task"),
5790 _ct_bs(ct_bs), _g1h(g1h) { }
5791
5792 void work(uint worker_id) {
5793 HeapRegion* r;
5794 while (r = _g1h->pop_dirty_cards_region()) {
5795 clear_cards(r);
5796 }
5797 }
5798
5799 void clear_cards(HeapRegion* r) {
5800 // Cards of the survivors should have already been dirtied.
5801 if (!r->is_survivor()) {
5802 _ct_bs->clear(MemRegion(r->bottom(), r->end()));
5803 }
5804 }
5805 };
5806
5807 #ifndef PRODUCT
5808 class G1VerifyCardTableCleanup: public HeapRegionClosure {
5809 G1CollectedHeap* _g1h;
5810 G1SATBCardTableModRefBS* _ct_bs;
5811 public:
5812 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs)
5813 : _g1h(g1h), _ct_bs(ct_bs) { }
5814 virtual bool doHeapRegion(HeapRegion* r) {
5815 if (r->is_survivor()) {
5816 _g1h->verify_dirty_region(r);
5817 } else {
5818 _g1h->verify_not_dirty_region(r);
5819 }
5820 return false;
5821 }
5822 };
5823
5824 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
5825 // All of the region should be clean.
5826 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5827 MemRegion mr(hr->bottom(), hr->end());
5828 ct_bs->verify_not_dirty_region(mr);
5829 }
5830
5831 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
5832 // We cannot guarantee that [bottom(),end()] is dirty. Threads
5833 // dirty allocated blocks as they allocate them. The thread that
5834 // retires each region and replaces it with a new one will do a
5835 // maximal allocation to fill in [pre_dummy_top(),end()] but will
5836 // not dirty that area (one less thing to have to do while holding
5837 // a lock). So we can only verify that [bottom(),pre_dummy_top()]
5838 // is dirty.
5839 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5840 MemRegion mr(hr->bottom(), hr->pre_dummy_top());
5841 if (hr->is_young()) {
5842 ct_bs->verify_g1_young_region(mr);
5843 } else {
5844 ct_bs->verify_dirty_region(mr);
5845 }
5846 }
5847
5848 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
5849 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5850 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
5851 verify_dirty_region(hr);
5852 }
5853 }
5854
5855 void G1CollectedHeap::verify_dirty_young_regions() {
5856 verify_dirty_young_list(_young_list->first_region());
5857 }
5858
5859 bool G1CollectedHeap::verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
5860 HeapWord* tams, HeapWord* end) {
5861 guarantee(tams <= end,
5862 err_msg("tams: "PTR_FORMAT" end: "PTR_FORMAT, tams, end));
5863 HeapWord* result = bitmap->getNextMarkedWordAddress(tams, end);
5864 if (result < end) {
5865 gclog_or_tty->cr();
5866 gclog_or_tty->print_cr("## wrong marked address on %s bitmap: "PTR_FORMAT,
5867 bitmap_name, result);
5868 gclog_or_tty->print_cr("## %s tams: "PTR_FORMAT" end: "PTR_FORMAT,
5869 bitmap_name, tams, end);
5870 return false;
5871 }
5872 return true;
5873 }
5874
5875 bool G1CollectedHeap::verify_bitmaps(const char* caller, HeapRegion* hr) {
5876 CMBitMapRO* prev_bitmap = concurrent_mark()->prevMarkBitMap();
5877 CMBitMapRO* next_bitmap = (CMBitMapRO*) concurrent_mark()->nextMarkBitMap();
5878
5879 HeapWord* bottom = hr->bottom();
5880 HeapWord* ptams = hr->prev_top_at_mark_start();
5881 HeapWord* ntams = hr->next_top_at_mark_start();
5882 HeapWord* end = hr->end();
5883
5884 bool res_p = verify_no_bits_over_tams("prev", prev_bitmap, ptams, end);
5885
5886 bool res_n = true;
5887 // We reset mark_in_progress() before we reset _cmThread->in_progress() and in this window
5888 // we do the clearing of the next bitmap concurrently. Thus, we can not verify the bitmap
5889 // if we happen to be in that state.
5890 if (mark_in_progress() || !_cmThread->in_progress()) {
5891 res_n = verify_no_bits_over_tams("next", next_bitmap, ntams, end);
5892 }
5893 if (!res_p || !res_n) {
5894 gclog_or_tty->print_cr("#### Bitmap verification failed for "HR_FORMAT,
5895 HR_FORMAT_PARAMS(hr));
5896 gclog_or_tty->print_cr("#### Caller: %s", caller);
5897 return false;
5898 }
5899 return true;
5900 }
5901
5902 void G1CollectedHeap::check_bitmaps(const char* caller, HeapRegion* hr) {
5903 if (!G1VerifyBitmaps) return;
5904
5905 guarantee(verify_bitmaps(caller, hr), "bitmap verification");
5906 }
5907
5908 class G1VerifyBitmapClosure : public HeapRegionClosure {
5909 private:
5910 const char* _caller;
5911 G1CollectedHeap* _g1h;
5912 bool _failures;
5913
5914 public:
5915 G1VerifyBitmapClosure(const char* caller, G1CollectedHeap* g1h) :
5916 _caller(caller), _g1h(g1h), _failures(false) { }
5917
5918 bool failures() { return _failures; }
5919
5920 virtual bool doHeapRegion(HeapRegion* hr) {
5921 if (hr->is_continues_humongous()) return false;
5922
5923 bool result = _g1h->verify_bitmaps(_caller, hr);
5924 if (!result) {
5925 _failures = true;
5926 }
5927 return false;
5928 }
5929 };
5930
5931 void G1CollectedHeap::check_bitmaps(const char* caller) {
5932 if (!G1VerifyBitmaps) return;
5933
5934 G1VerifyBitmapClosure cl(caller, this);
5935 heap_region_iterate(&cl);
5936 guarantee(!cl.failures(), "bitmap verification");
5937 }
5938
5939 class G1CheckCSetFastTableClosure : public HeapRegionClosure {
5940 private:
5941 bool _failures;
5942 public:
5943 G1CheckCSetFastTableClosure() : HeapRegionClosure(), _failures(false) { }
5944
5945 virtual bool doHeapRegion(HeapRegion* hr) {
5946 uint i = hr->hrm_index();
5947 InCSetState cset_state = (InCSetState) G1CollectedHeap::heap()->_in_cset_fast_test.get_by_index(i);
5948 if (hr->is_humongous()) {
5949 if (hr->in_collection_set()) {
5950 gclog_or_tty->print_cr("\n## humongous region %u in CSet", i);
5951 _failures = true;
5952 return true;
5953 }
5954 if (cset_state.is_in_cset()) {
5955 gclog_or_tty->print_cr("\n## inconsistent cset state %d for humongous region %u", cset_state.value(), i);
5956 _failures = true;
5957 return true;
5958 }
5959 if (hr->is_continues_humongous() && cset_state.is_humongous()) {
5960 gclog_or_tty->print_cr("\n## inconsistent cset state %d for continues humongous region %u", cset_state.value(), i);
5961 _failures = true;
5962 return true;
5963 }
5964 } else {
5965 if (cset_state.is_humongous()) {
5966 gclog_or_tty->print_cr("\n## inconsistent cset state %d for non-humongous region %u", cset_state.value(), i);
5967 _failures = true;
5968 return true;
5969 }
5970 if (hr->in_collection_set() != cset_state.is_in_cset()) {
5971 gclog_or_tty->print_cr("\n## in CSet %d / cset state %d inconsistency for region %u",
5972 hr->in_collection_set(), cset_state.value(), i);
5973 _failures = true;
5974 return true;
5975 }
5976 if (cset_state.is_in_cset()) {
5977 if (hr->is_young() != (cset_state.is_young())) {
5978 gclog_or_tty->print_cr("\n## is_young %d / cset state %d inconsistency for region %u",
5979 hr->is_young(), cset_state.value(), i);
5980 _failures = true;
5981 return true;
5982 }
5983 if (hr->is_old() != (cset_state.is_old())) {
5984 gclog_or_tty->print_cr("\n## is_old %d / cset state %d inconsistency for region %u",
5985 hr->is_old(), cset_state.value(), i);
5986 _failures = true;
5987 return true;
5988 }
5989 }
5990 }
5991 return false;
5992 }
5993
5994 bool failures() const { return _failures; }
5995 };
5996
5997 bool G1CollectedHeap::check_cset_fast_test() {
5998 G1CheckCSetFastTableClosure cl;
5999 _hrm.iterate(&cl);
6000 return !cl.failures();
6001 }
6002 #endif // PRODUCT
6003
6004 void G1CollectedHeap::cleanUpCardTable() {
6005 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6006 double start = os::elapsedTime();
6007
6008 {
6009 // Iterate over the dirty cards region list.
6010 G1ParCleanupCTTask cleanup_task(ct_bs, this);
6011
6012 set_par_threads();
6013 workers()->run_task(&cleanup_task);
6014 set_par_threads(0);
6015 #ifndef PRODUCT
6016 if (G1VerifyCTCleanup || VerifyAfterGC) {
6017 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
6018 heap_region_iterate(&cleanup_verifier);
6019 }
6020 #endif
6021 }
6022
6023 double elapsed = os::elapsedTime() - start;
6024 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
6025 }
6026
6027 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) {
6028 size_t pre_used = 0;
6029 FreeRegionList local_free_list("Local List for CSet Freeing");
6030
6031 double young_time_ms = 0.0;
6032 double non_young_time_ms = 0.0;
6033
6034 // Since the collection set is a superset of the the young list,
6035 // all we need to do to clear the young list is clear its
6036 // head and length, and unlink any young regions in the code below
6037 _young_list->clear();
6038
6039 G1CollectorPolicy* policy = g1_policy();
6040
6041 double start_sec = os::elapsedTime();
6042 bool non_young = true;
6043
6044 HeapRegion* cur = cs_head;
6045 int age_bound = -1;
6046 size_t rs_lengths = 0;
6047
6048 while (cur != NULL) {
6049 assert(!is_on_master_free_list(cur), "sanity");
6050 if (non_young) {
6051 if (cur->is_young()) {
6052 double end_sec = os::elapsedTime();
6053 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6054 non_young_time_ms += elapsed_ms;
6055
6056 start_sec = os::elapsedTime();
6057 non_young = false;
6058 }
6059 } else {
6060 if (!cur->is_young()) {
6061 double end_sec = os::elapsedTime();
6062 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6063 young_time_ms += elapsed_ms;
6064
6065 start_sec = os::elapsedTime();
6066 non_young = true;
6067 }
6068 }
6069
6070 rs_lengths += cur->rem_set()->occupied_locked();
6071
6072 HeapRegion* next = cur->next_in_collection_set();
6073 assert(cur->in_collection_set(), "bad CS");
6074 cur->set_next_in_collection_set(NULL);
6075 cur->set_in_collection_set(false);
6076
6077 if (cur->is_young()) {
6078 int index = cur->young_index_in_cset();
6079 assert(index != -1, "invariant");
6080 assert((uint) index < policy->young_cset_region_length(), "invariant");
6081 size_t words_survived = _surviving_young_words[index];
6082 cur->record_surv_words_in_group(words_survived);
6083
6084 // At this point the we have 'popped' cur from the collection set
6085 // (linked via next_in_collection_set()) but it is still in the
6086 // young list (linked via next_young_region()). Clear the
6087 // _next_young_region field.
6088 cur->set_next_young_region(NULL);
6089 } else {
6090 int index = cur->young_index_in_cset();
6091 assert(index == -1, "invariant");
6092 }
6093
6094 assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
6095 (!cur->is_young() && cur->young_index_in_cset() == -1),
6096 "invariant" );
6097
6098 if (!cur->evacuation_failed()) {
6099 MemRegion used_mr = cur->used_region();
6100
6101 // And the region is empty.
6102 assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
6103 pre_used += cur->used();
6104 free_region(cur, &local_free_list, false /* par */, true /* locked */);
6105 } else {
6106 cur->uninstall_surv_rate_group();
6107 if (cur->is_young()) {
6108 cur->set_young_index_in_cset(-1);
6109 }
6110 cur->set_evacuation_failed(false);
6111 // The region is now considered to be old.
6112 cur->set_old();
6113 _old_set.add(cur);
6114 evacuation_info.increment_collectionset_used_after(cur->used());
6115 }
6116 cur = next;
6117 }
6118
6119 evacuation_info.set_regions_freed(local_free_list.length());
6120 policy->record_max_rs_lengths(rs_lengths);
6121 policy->cset_regions_freed();
6122
6123 double end_sec = os::elapsedTime();
6124 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6125
6126 if (non_young) {
6127 non_young_time_ms += elapsed_ms;
6128 } else {
6129 young_time_ms += elapsed_ms;
6130 }
6131
6132 prepend_to_freelist(&local_free_list);
6133 decrement_summary_bytes(pre_used);
6134 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
6135 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
6136 }
6137
6138 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
6139 private:
6140 FreeRegionList* _free_region_list;
6141 HeapRegionSet* _proxy_set;
6142 HeapRegionSetCount _humongous_regions_removed;
6143 size_t _freed_bytes;
6144 public:
6145
6146 G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
6147 _free_region_list(free_region_list), _humongous_regions_removed(), _freed_bytes(0) {
6148 }
6149
6150 virtual bool doHeapRegion(HeapRegion* r) {
6151 if (!r->is_starts_humongous()) {
6152 return false;
6153 }
6154
6155 G1CollectedHeap* g1h = G1CollectedHeap::heap();
6156
6157 oop obj = (oop)r->bottom();
6158 CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap();
6159
6160 // The following checks whether the humongous object is live are sufficient.
6161 // The main additional check (in addition to having a reference from the roots
6162 // or the young gen) is whether the humongous object has a remembered set entry.
6163 //
6164 // A humongous object cannot be live if there is no remembered set for it
6165 // because:
6166 // - there can be no references from within humongous starts regions referencing
6167 // the object because we never allocate other objects into them.
6168 // (I.e. there are no intra-region references that may be missed by the
6169 // remembered set)
6170 // - as soon there is a remembered set entry to the humongous starts region
6171 // (i.e. it has "escaped" to an old object) this remembered set entry will stay
6172 // until the end of a concurrent mark.
6173 //
6174 // It is not required to check whether the object has been found dead by marking
6175 // or not, in fact it would prevent reclamation within a concurrent cycle, as
6176 // all objects allocated during that time are considered live.
6177 // SATB marking is even more conservative than the remembered set.
6178 // So if at this point in the collection there is no remembered set entry,
6179 // nobody has a reference to it.
6180 // At the start of collection we flush all refinement logs, and remembered sets
6181 // are completely up-to-date wrt to references to the humongous object.
6182 //
6183 // Other implementation considerations:
6184 // - never consider object arrays at this time because they would pose
6185 // considerable effort for cleaning up the the remembered sets. This is
6186 // required because stale remembered sets might reference locations that
6187 // are currently allocated into.
6188 uint region_idx = r->hrm_index();
6189 if (g1h->humongous_is_live(region_idx) ||
6190 g1h->humongous_region_is_always_live(region_idx)) {
6191
6192 if (G1TraceEagerReclaimHumongousObjects) {
6193 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 live-other %d obj array %d",
6194 region_idx,
6195 obj->size()*HeapWordSize,
6196 r->bottom(),
6197 r->region_num(),
6198 r->rem_set()->occupied(),
6199 r->rem_set()->strong_code_roots_list_length(),
6200 next_bitmap->isMarked(r->bottom()),
6201 g1h->humongous_is_live(region_idx),
6202 obj->is_objArray()
6203 );
6204 }
6205
6206 return false;
6207 }
6208
6209 guarantee(!obj->is_objArray(),
6210 err_msg("Eagerly reclaiming object arrays is not supported, but the object "PTR_FORMAT" is.",
6211 r->bottom()));
6212
6213 if (G1TraceEagerReclaimHumongousObjects) {
6214 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 live-other %d obj array %d",
6215 region_idx,
6216 obj->size()*HeapWordSize,
6217 r->bottom(),
6218 r->region_num(),
6219 r->rem_set()->occupied(),
6220 r->rem_set()->strong_code_roots_list_length(),
6221 next_bitmap->isMarked(r->bottom()),
6222 g1h->humongous_is_live(region_idx),
6223 obj->is_objArray()
6224 );
6225 }
6226 // Need to clear mark bit of the humongous object if already set.
6227 if (next_bitmap->isMarked(r->bottom())) {
6228 next_bitmap->clear(r->bottom());
6229 }
6230 _freed_bytes += r->used();
6231 r->set_containing_set(NULL);
6232 _humongous_regions_removed.increment(1u, r->capacity());
6233 g1h->free_humongous_region(r, _free_region_list, false);
6234
6235 return false;
6236 }
6237
6238 HeapRegionSetCount& humongous_free_count() {
6239 return _humongous_regions_removed;
6240 }
6241
6242 size_t bytes_freed() const {
6243 return _freed_bytes;
6244 }
6245
6246 size_t humongous_reclaimed() const {
6247 return _humongous_regions_removed.length();
6248 }
6249 };
6250
6251 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
6252 assert_at_safepoint(true);
6253
6254 if (!G1EagerReclaimHumongousObjects ||
6255 (!_has_humongous_reclaim_candidates && !G1TraceEagerReclaimHumongousObjects)) {
6256 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
6257 return;
6258 }
6259
6260 double start_time = os::elapsedTime();
6261
6262 FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
6263
6264 G1FreeHumongousRegionClosure cl(&local_cleanup_list);
6265 heap_region_iterate(&cl);
6266
6267 HeapRegionSetCount empty_set;
6268 remove_from_old_sets(empty_set, cl.humongous_free_count());
6269
6270 G1HRPrinter* hr_printer = _g1h->hr_printer();
6271 if (hr_printer->is_active()) {
6272 FreeRegionListIterator iter(&local_cleanup_list);
6273 while (iter.more_available()) {
6274 HeapRegion* hr = iter.get_next();
6275 hr_printer->cleanup(hr);
6276 }
6277 }
6278
6279 prepend_to_freelist(&local_cleanup_list);
6280 decrement_summary_bytes(cl.bytes_freed());
6281
6282 g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
6283 cl.humongous_reclaimed());
6284 }
6285
6286 // This routine is similar to the above but does not record
6287 // any policy statistics or update free lists; we are abandoning
6288 // the current incremental collection set in preparation of a
6289 // full collection. After the full GC we will start to build up
6290 // the incremental collection set again.
6291 // This is only called when we're doing a full collection
6292 // and is immediately followed by the tearing down of the young list.
6293
6294 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
6295 HeapRegion* cur = cs_head;
6296
6297 while (cur != NULL) {
6298 HeapRegion* next = cur->next_in_collection_set();
6299 assert(cur->in_collection_set(), "bad CS");
6300 cur->set_next_in_collection_set(NULL);
6301 cur->set_in_collection_set(false);
6302 cur->set_young_index_in_cset(-1);
6303 cur = next;
6304 }
6305 }
6306
6307 void G1CollectedHeap::set_free_regions_coming() {
6308 if (G1ConcRegionFreeingVerbose) {
6309 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6310 "setting free regions coming");
6311 }
6312
6313 assert(!free_regions_coming(), "pre-condition");
6314 _free_regions_coming = true;
6315 }
6316
6317 void G1CollectedHeap::reset_free_regions_coming() {
6318 assert(free_regions_coming(), "pre-condition");
6319
6320 {
6321 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6322 _free_regions_coming = false;
6323 SecondaryFreeList_lock->notify_all();
6324 }
6325
6326 if (G1ConcRegionFreeingVerbose) {
6327 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6328 "reset free regions coming");
6329 }
6330 }
6331
6332 void G1CollectedHeap::wait_while_free_regions_coming() {
6333 // Most of the time we won't have to wait, so let's do a quick test
6334 // first before we take the lock.
6335 if (!free_regions_coming()) {
6336 return;
6337 }
6338
6339 if (G1ConcRegionFreeingVerbose) {
6340 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6341 "waiting for free regions");
6342 }
6343
6344 {
6345 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6346 while (free_regions_coming()) {
6347 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
6348 }
6349 }
6350
6351 if (G1ConcRegionFreeingVerbose) {
6352 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6353 "done waiting for free regions");
6354 }
6355 }
6356
6357 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
6358 assert(heap_lock_held_for_gc(),
6359 "the heap lock should already be held by or for this thread");
6360 _young_list->push_region(hr);
6361 }
6362
6363 class NoYoungRegionsClosure: public HeapRegionClosure {
6364 private:
6365 bool _success;
6366 public:
6367 NoYoungRegionsClosure() : _success(true) { }
6368 bool doHeapRegion(HeapRegion* r) {
6369 if (r->is_young()) {
6370 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
6371 r->bottom(), r->end());
6372 _success = false;
6373 }
6374 return false;
6375 }
6376 bool success() { return _success; }
6377 };
6378
6379 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
6380 bool ret = _young_list->check_list_empty(check_sample);
6381
6382 if (check_heap) {
6383 NoYoungRegionsClosure closure;
6384 heap_region_iterate(&closure);
6385 ret = ret && closure.success();
6386 }
6387
6388 return ret;
6389 }
6390
6391 class TearDownRegionSetsClosure : public HeapRegionClosure {
6392 private:
6393 HeapRegionSet *_old_set;
6394
6395 public:
6396 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
6397
6398 bool doHeapRegion(HeapRegion* r) {
6399 if (r->is_old()) {
6400 _old_set->remove(r);
6401 } else {
6402 // We ignore free regions, we'll empty the free list afterwards.
6403 // We ignore young regions, we'll empty the young list afterwards.
6404 // We ignore humongous regions, we're not tearing down the
6405 // humongous regions set.
6406 assert(r->is_free() || r->is_young() || r->is_humongous(),
6407 "it cannot be another type");
6408 }
6409 return false;
6410 }
6411
6412 ~TearDownRegionSetsClosure() {
6413 assert(_old_set->is_empty(), "post-condition");
6414 }
6415 };
6416
6417 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6418 assert_at_safepoint(true /* should_be_vm_thread */);
6419
6420 if (!free_list_only) {
6421 TearDownRegionSetsClosure cl(&_old_set);
6422 heap_region_iterate(&cl);
6423
6424 // Note that emptying the _young_list is postponed and instead done as
6425 // the first step when rebuilding the regions sets again. The reason for
6426 // this is that during a full GC string deduplication needs to know if
6427 // a collected region was young or old when the full GC was initiated.
6428 }
6429 _hrm.remove_all_free_regions();
6430 }
6431
6432 class RebuildRegionSetsClosure : public HeapRegionClosure {
6433 private:
6434 bool _free_list_only;
6435 HeapRegionSet* _old_set;
6436 HeapRegionManager* _hrm;
6437 size_t _total_used;
6438
6439 public:
6440 RebuildRegionSetsClosure(bool free_list_only,
6441 HeapRegionSet* old_set, HeapRegionManager* hrm) :
6442 _free_list_only(free_list_only),
6443 _old_set(old_set), _hrm(hrm), _total_used(0) {
6444 assert(_hrm->num_free_regions() == 0, "pre-condition");
6445 if (!free_list_only) {
6446 assert(_old_set->is_empty(), "pre-condition");
6447 }
6448 }
6449
6450 bool doHeapRegion(HeapRegion* r) {
6451 if (r->is_continues_humongous()) {
6452 return false;
6453 }
6454
6455 if (r->is_empty()) {
6456 // Add free regions to the free list
6457 r->set_free();
6458 r->set_allocation_context(AllocationContext::system());
6459 _hrm->insert_into_free_list(r);
6460 } else if (!_free_list_only) {
6461 assert(!r->is_young(), "we should not come across young regions");
6462
6463 if (r->is_humongous()) {
6464 // We ignore humongous regions, we left the humongous set unchanged
6465 } else {
6466 // Objects that were compacted would have ended up on regions
6467 // that were previously old or free.
6468 assert(r->is_free() || r->is_old(), "invariant");
6469 // We now consider them old, so register as such.
6470 r->set_old();
6471 _old_set->add(r);
6472 }
6473 _total_used += r->used();
6474 }
6475
6476 return false;
6477 }
6478
6479 size_t total_used() {
6480 return _total_used;
6481 }
6482 };
6483
6484 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6485 assert_at_safepoint(true /* should_be_vm_thread */);
6486
6487 if (!free_list_only) {
6488 _young_list->empty_list();
6489 }
6490
6491 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
6492 heap_region_iterate(&cl);
6493
6494 if (!free_list_only) {
6495 _allocator->set_used(cl.total_used());
6496 }
6497 assert(_allocator->used_unlocked() == recalculate_used(),
6498 err_msg("inconsistent _allocator->used_unlocked(), "
6499 "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6500 _allocator->used_unlocked(), recalculate_used()));
6501 }
6502
6503 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6504 _refine_cte_cl->set_concurrent(concurrent);
6505 }
6506
6507 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6508 HeapRegion* hr = heap_region_containing(p);
6509 return hr->is_in(p);
6510 }
6511
6512 // Methods for the mutator alloc region
6513
6514 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6515 bool force) {
6516 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6517 assert(!force || g1_policy()->can_expand_young_list(),
6518 "if force is true we should be able to expand the young list");
6519 bool young_list_full = g1_policy()->is_young_list_full();
6520 if (force || !young_list_full) {
6521 HeapRegion* new_alloc_region = new_region(word_size,
6522 false /* is_old */,
6523 false /* do_expand */);
6524 if (new_alloc_region != NULL) {
6525 set_region_short_lived_locked(new_alloc_region);
6526 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6527 check_bitmaps("Mutator Region Allocation", new_alloc_region);
6528 return new_alloc_region;
6529 }
6530 }
6531 return NULL;
6532 }
6533
6534 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6535 size_t allocated_bytes) {
6536 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6537 assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
6538
6539 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6540 _allocator->increase_used(allocated_bytes);
6541 _hr_printer.retire(alloc_region);
6542 // We update the eden sizes here, when the region is retired,
6543 // instead of when it's allocated, since this is the point that its
6544 // used space has been recored in _summary_bytes_used.
6545 g1mm()->update_eden_size();
6546 }
6547
6548 void G1CollectedHeap::set_par_threads() {
6549 // Don't change the number of workers. Use the value previously set
6550 // in the workgroup.
6551 uint n_workers = workers()->active_workers();
6552 assert(UseDynamicNumberOfGCThreads ||
6553 n_workers == workers()->total_workers(),
6554 "Otherwise should be using the total number of workers");
6555 if (n_workers == 0) {
6556 assert(false, "Should have been set in prior evacuation pause.");
6557 n_workers = ParallelGCThreads;
6558 workers()->set_active_workers(n_workers);
6559 }
6560 set_par_threads(n_workers);
6561 }
6562
6563 // Methods for the GC alloc regions
6564
6565 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6566 uint count,
6567 InCSetState dest) {
6568 assert(FreeList_lock->owned_by_self(), "pre-condition");
6569
6570 if (count < g1_policy()->max_regions(dest)) {
6571 const bool is_survivor = (dest.is_young());
6572 HeapRegion* new_alloc_region = new_region(word_size,
6573 !is_survivor,
6574 true /* do_expand */);
6575 if (new_alloc_region != NULL) {
6576 // We really only need to do this for old regions given that we
6577 // should never scan survivors. But it doesn't hurt to do it
6578 // for survivors too.
6579 new_alloc_region->record_timestamp();
6580 if (is_survivor) {
6581 new_alloc_region->set_survivor();
6582 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6583 check_bitmaps("Survivor Region Allocation", new_alloc_region);
6584 } else {
6585 new_alloc_region->set_old();
6586 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6587 check_bitmaps("Old Region Allocation", new_alloc_region);
6588 }
6589 bool during_im = g1_policy()->during_initial_mark_pause();
6590 new_alloc_region->note_start_of_copying(during_im);
6591 return new_alloc_region;
6592 }
6593 }
6594 return NULL;
6595 }
6596
6597 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6598 size_t allocated_bytes,
6599 InCSetState dest) {
6600 bool during_im = g1_policy()->during_initial_mark_pause();
6601 alloc_region->note_end_of_copying(during_im);
6602 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6603 if (dest.is_young()) {
6604 young_list()->add_survivor_region(alloc_region);
6605 } else {
6606 _old_set.add(alloc_region);
6607 }
6608 _hr_printer.retire(alloc_region);
6609 }
6610
6611 // Heap region set verification
6612
6613 class VerifyRegionListsClosure : public HeapRegionClosure {
6614 private:
6615 HeapRegionSet* _old_set;
6616 HeapRegionSet* _humongous_set;
6617 HeapRegionManager* _hrm;
6618
6619 public:
6620 HeapRegionSetCount _old_count;
6621 HeapRegionSetCount _humongous_count;
6622 HeapRegionSetCount _free_count;
6623
6624 VerifyRegionListsClosure(HeapRegionSet* old_set,
6625 HeapRegionSet* humongous_set,
6626 HeapRegionManager* hrm) :
6627 _old_set(old_set), _humongous_set(humongous_set), _hrm(hrm),
6628 _old_count(), _humongous_count(), _free_count(){ }
6629
6630 bool doHeapRegion(HeapRegion* hr) {
6631 if (hr->is_continues_humongous()) {
6632 return false;
6633 }
6634
6635 if (hr->is_young()) {
6636 // TODO
6637 } else if (hr->is_starts_humongous()) {
6638 assert(hr->containing_set() == _humongous_set, err_msg("Heap region %u is starts humongous but not in humongous set.", hr->hrm_index()));
6639 _humongous_count.increment(1u, hr->capacity());
6640 } else if (hr->is_empty()) {
6641 assert(_hrm->is_free(hr), err_msg("Heap region %u is empty but not on the free list.", hr->hrm_index()));
6642 _free_count.increment(1u, hr->capacity());
6643 } else if (hr->is_old()) {
6644 assert(hr->containing_set() == _old_set, err_msg("Heap region %u is old but not in the old set.", hr->hrm_index()));
6645 _old_count.increment(1u, hr->capacity());
6646 } else {
6647 ShouldNotReachHere();
6648 }
6649 return false;
6650 }
6651
6652 void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, HeapRegionManager* free_list) {
6653 guarantee(old_set->length() == _old_count.length(), err_msg("Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length()));
6654 guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), err_msg("Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6655 old_set->total_capacity_bytes(), _old_count.capacity()));
6656
6657 guarantee(humongous_set->length() == _humongous_count.length(), err_msg("Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length()));
6658 guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), err_msg("Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6659 humongous_set->total_capacity_bytes(), _humongous_count.capacity()));
6660
6661 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()));
6662 guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), err_msg("Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6663 free_list->total_capacity_bytes(), _free_count.capacity()));
6664 }
6665 };
6666
6667 void G1CollectedHeap::verify_region_sets() {
6668 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6669
6670 // First, check the explicit lists.
6671 _hrm.verify();
6672 {
6673 // Given that a concurrent operation might be adding regions to
6674 // the secondary free list we have to take the lock before
6675 // verifying it.
6676 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6677 _secondary_free_list.verify_list();
6678 }
6679
6680 // If a concurrent region freeing operation is in progress it will
6681 // be difficult to correctly attributed any free regions we come
6682 // across to the correct free list given that they might belong to
6683 // one of several (free_list, secondary_free_list, any local lists,
6684 // etc.). So, if that's the case we will skip the rest of the
6685 // verification operation. Alternatively, waiting for the concurrent
6686 // operation to complete will have a non-trivial effect on the GC's
6687 // operation (no concurrent operation will last longer than the
6688 // interval between two calls to verification) and it might hide
6689 // any issues that we would like to catch during testing.
6690 if (free_regions_coming()) {
6691 return;
6692 }
6693
6694 // Make sure we append the secondary_free_list on the free_list so
6695 // that all free regions we will come across can be safely
6696 // attributed to the free_list.
6697 append_secondary_free_list_if_not_empty_with_lock();
6698
6699 // Finally, make sure that the region accounting in the lists is
6700 // consistent with what we see in the heap.
6701
6702 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_hrm);
6703 heap_region_iterate(&cl);
6704 cl.verify_counts(&_old_set, &_humongous_set, &_hrm);
6705 }
6706
6707 // Optimized nmethod scanning
6708
6709 class RegisterNMethodOopClosure: public OopClosure {
6710 G1CollectedHeap* _g1h;
6711 nmethod* _nm;
6712
6713 template <class T> void do_oop_work(T* p) {
6714 T heap_oop = oopDesc::load_heap_oop(p);
6715 if (!oopDesc::is_null(heap_oop)) {
6716 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6717 HeapRegion* hr = _g1h->heap_region_containing(obj);
6718 assert(!hr->is_continues_humongous(),
6719 err_msg("trying to add code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6720 " starting at "HR_FORMAT,
6721 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6722
6723 // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
6724 hr->add_strong_code_root_locked(_nm);
6725 }
6726 }
6727
6728 public:
6729 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6730 _g1h(g1h), _nm(nm) {}
6731
6732 void do_oop(oop* p) { do_oop_work(p); }
6733 void do_oop(narrowOop* p) { do_oop_work(p); }
6734 };
6735
6736 class UnregisterNMethodOopClosure: public OopClosure {
6737 G1CollectedHeap* _g1h;
6738 nmethod* _nm;
6739
6740 template <class T> void do_oop_work(T* p) {
6741 T heap_oop = oopDesc::load_heap_oop(p);
6742 if (!oopDesc::is_null(heap_oop)) {
6743 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6744 HeapRegion* hr = _g1h->heap_region_containing(obj);
6745 assert(!hr->is_continues_humongous(),
6746 err_msg("trying to remove code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6747 " starting at "HR_FORMAT,
6748 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6749
6750 hr->remove_strong_code_root(_nm);
6751 }
6752 }
6753
6754 public:
6755 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6756 _g1h(g1h), _nm(nm) {}
6757
6758 void do_oop(oop* p) { do_oop_work(p); }
6759 void do_oop(narrowOop* p) { do_oop_work(p); }
6760 };
6761
6762 void G1CollectedHeap::register_nmethod(nmethod* nm) {
6763 CollectedHeap::register_nmethod(nm);
6764
6765 guarantee(nm != NULL, "sanity");
6766 RegisterNMethodOopClosure reg_cl(this, nm);
6767 nm->oops_do(®_cl);
6768 }
6769
6770 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
6771 CollectedHeap::unregister_nmethod(nm);
6772
6773 guarantee(nm != NULL, "sanity");
6774 UnregisterNMethodOopClosure reg_cl(this, nm);
6775 nm->oops_do(®_cl, true);
6776 }
6777
6778 void G1CollectedHeap::purge_code_root_memory() {
6779 double purge_start = os::elapsedTime();
6780 G1CodeRootSet::purge();
6781 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
6782 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
6783 }
6784
6785 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
6786 G1CollectedHeap* _g1h;
6787
6788 public:
6789 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
6790 _g1h(g1h) {}
6791
6792 void do_code_blob(CodeBlob* cb) {
6793 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
6794 if (nm == NULL) {
6795 return;
6796 }
6797
6798 if (ScavengeRootsInCode) {
6799 _g1h->register_nmethod(nm);
6800 }
6801 }
6802 };
6803
6804 void G1CollectedHeap::rebuild_strong_code_roots() {
6805 RebuildStrongCodeRootClosure blob_cl(this);
6806 CodeCache::blobs_do(&blob_cl);
6807 }