Tue, 26 Apr 2011 21:17:24 -0700
7039089: G1: changeset for 7037276 broke heap verification, and related cleanups
Summary: In G1 heap verification, we no longer scan perm to G1-collected heap refs as part of process_strong_roots() but rather in a separate explicit oop iteration over the perm gen. This preserves the original perm card-marks. Added a new assertion in younger_refs_iterate() to catch a simple subcase where the user may have forgotten a prior save_marks() call, as happened in the case of G1's attempt to iterate perm to G1 refs when verifying the heap before exit. The assert was deliberately weakened for ParNew+CMS and will be fixed for that combination in a future CR. Also made some (non-G1) cleanups related to code and comments obsoleted by the migration of Symbols to the native heap.
Reviewed-by: iveresov, jmasa, tonyp
1 /*
2 * Copyright (c) 2001, 2011, 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
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7 * published by the Free Software Foundation.
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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).
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17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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23 */
25 #include "precompiled.hpp"
26 #include "code/icBuffer.hpp"
27 #include "gc_implementation/g1/bufferingOopClosure.hpp"
28 #include "gc_implementation/g1/concurrentG1Refine.hpp"
29 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
30 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
31 #include "gc_implementation/g1/g1AllocRegion.inline.hpp"
32 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
33 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
34 #include "gc_implementation/g1/g1MarkSweep.hpp"
35 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
36 #include "gc_implementation/g1/g1RemSet.inline.hpp"
37 #include "gc_implementation/g1/heapRegionRemSet.hpp"
38 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
39 #include "gc_implementation/g1/vm_operations_g1.hpp"
40 #include "gc_implementation/shared/isGCActiveMark.hpp"
41 #include "memory/gcLocker.inline.hpp"
42 #include "memory/genOopClosures.inline.hpp"
43 #include "memory/generationSpec.hpp"
44 #include "oops/oop.inline.hpp"
45 #include "oops/oop.pcgc.inline.hpp"
46 #include "runtime/aprofiler.hpp"
47 #include "runtime/vmThread.hpp"
49 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
51 // turn it on so that the contents of the young list (scan-only /
52 // to-be-collected) are printed at "strategic" points before / during
53 // / after the collection --- this is useful for debugging
54 #define YOUNG_LIST_VERBOSE 0
55 // CURRENT STATUS
56 // This file is under construction. Search for "FIXME".
58 // INVARIANTS/NOTES
59 //
60 // All allocation activity covered by the G1CollectedHeap interface is
61 // serialized by acquiring the HeapLock. This happens in mem_allocate
62 // and allocate_new_tlab, which are the "entry" points to the
63 // allocation code from the rest of the JVM. (Note that this does not
64 // apply to TLAB allocation, which is not part of this interface: it
65 // is done by clients of this interface.)
67 // Local to this file.
69 class RefineCardTableEntryClosure: public CardTableEntryClosure {
70 SuspendibleThreadSet* _sts;
71 G1RemSet* _g1rs;
72 ConcurrentG1Refine* _cg1r;
73 bool _concurrent;
74 public:
75 RefineCardTableEntryClosure(SuspendibleThreadSet* sts,
76 G1RemSet* g1rs,
77 ConcurrentG1Refine* cg1r) :
78 _sts(sts), _g1rs(g1rs), _cg1r(cg1r), _concurrent(true)
79 {}
80 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
81 bool oops_into_cset = _g1rs->concurrentRefineOneCard(card_ptr, worker_i, false);
82 // This path is executed by the concurrent refine or mutator threads,
83 // concurrently, and so we do not care if card_ptr contains references
84 // that point into the collection set.
85 assert(!oops_into_cset, "should be");
87 if (_concurrent && _sts->should_yield()) {
88 // Caller will actually yield.
89 return false;
90 }
91 // Otherwise, we finished successfully; return true.
92 return true;
93 }
94 void set_concurrent(bool b) { _concurrent = b; }
95 };
98 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure {
99 int _calls;
100 G1CollectedHeap* _g1h;
101 CardTableModRefBS* _ctbs;
102 int _histo[256];
103 public:
104 ClearLoggedCardTableEntryClosure() :
105 _calls(0)
106 {
107 _g1h = G1CollectedHeap::heap();
108 _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
109 for (int i = 0; i < 256; i++) _histo[i] = 0;
110 }
111 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
112 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
113 _calls++;
114 unsigned char* ujb = (unsigned char*)card_ptr;
115 int ind = (int)(*ujb);
116 _histo[ind]++;
117 *card_ptr = -1;
118 }
119 return true;
120 }
121 int calls() { return _calls; }
122 void print_histo() {
123 gclog_or_tty->print_cr("Card table value histogram:");
124 for (int i = 0; i < 256; i++) {
125 if (_histo[i] != 0) {
126 gclog_or_tty->print_cr(" %d: %d", i, _histo[i]);
127 }
128 }
129 }
130 };
132 class RedirtyLoggedCardTableEntryClosure: public CardTableEntryClosure {
133 int _calls;
134 G1CollectedHeap* _g1h;
135 CardTableModRefBS* _ctbs;
136 public:
137 RedirtyLoggedCardTableEntryClosure() :
138 _calls(0)
139 {
140 _g1h = G1CollectedHeap::heap();
141 _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
142 }
143 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
144 if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
145 _calls++;
146 *card_ptr = 0;
147 }
148 return true;
149 }
150 int calls() { return _calls; }
151 };
153 class RedirtyLoggedCardTableEntryFastClosure : public CardTableEntryClosure {
154 public:
155 bool do_card_ptr(jbyte* card_ptr, int worker_i) {
156 *card_ptr = CardTableModRefBS::dirty_card_val();
157 return true;
158 }
159 };
161 YoungList::YoungList(G1CollectedHeap* g1h)
162 : _g1h(g1h), _head(NULL),
163 _length(0),
164 _last_sampled_rs_lengths(0),
165 _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0)
166 {
167 guarantee( check_list_empty(false), "just making sure..." );
168 }
170 void YoungList::push_region(HeapRegion *hr) {
171 assert(!hr->is_young(), "should not already be young");
172 assert(hr->get_next_young_region() == NULL, "cause it should!");
174 hr->set_next_young_region(_head);
175 _head = hr;
177 hr->set_young();
178 double yg_surv_rate = _g1h->g1_policy()->predict_yg_surv_rate((int)_length);
179 ++_length;
180 }
182 void YoungList::add_survivor_region(HeapRegion* hr) {
183 assert(hr->is_survivor(), "should be flagged as survivor region");
184 assert(hr->get_next_young_region() == NULL, "cause it should!");
186 hr->set_next_young_region(_survivor_head);
187 if (_survivor_head == NULL) {
188 _survivor_tail = hr;
189 }
190 _survivor_head = hr;
192 ++_survivor_length;
193 }
195 void YoungList::empty_list(HeapRegion* list) {
196 while (list != NULL) {
197 HeapRegion* next = list->get_next_young_region();
198 list->set_next_young_region(NULL);
199 list->uninstall_surv_rate_group();
200 list->set_not_young();
201 list = next;
202 }
203 }
205 void YoungList::empty_list() {
206 assert(check_list_well_formed(), "young list should be well formed");
208 empty_list(_head);
209 _head = NULL;
210 _length = 0;
212 empty_list(_survivor_head);
213 _survivor_head = NULL;
214 _survivor_tail = NULL;
215 _survivor_length = 0;
217 _last_sampled_rs_lengths = 0;
219 assert(check_list_empty(false), "just making sure...");
220 }
222 bool YoungList::check_list_well_formed() {
223 bool ret = true;
225 size_t length = 0;
226 HeapRegion* curr = _head;
227 HeapRegion* last = NULL;
228 while (curr != NULL) {
229 if (!curr->is_young()) {
230 gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
231 "incorrectly tagged (y: %d, surv: %d)",
232 curr->bottom(), curr->end(),
233 curr->is_young(), curr->is_survivor());
234 ret = false;
235 }
236 ++length;
237 last = curr;
238 curr = curr->get_next_young_region();
239 }
240 ret = ret && (length == _length);
242 if (!ret) {
243 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
244 gclog_or_tty->print_cr("### list has %d entries, _length is %d",
245 length, _length);
246 }
248 return ret;
249 }
251 bool YoungList::check_list_empty(bool check_sample) {
252 bool ret = true;
254 if (_length != 0) {
255 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %d",
256 _length);
257 ret = false;
258 }
259 if (check_sample && _last_sampled_rs_lengths != 0) {
260 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
261 ret = false;
262 }
263 if (_head != NULL) {
264 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
265 ret = false;
266 }
267 if (!ret) {
268 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
269 }
271 return ret;
272 }
274 void
275 YoungList::rs_length_sampling_init() {
276 _sampled_rs_lengths = 0;
277 _curr = _head;
278 }
280 bool
281 YoungList::rs_length_sampling_more() {
282 return _curr != NULL;
283 }
285 void
286 YoungList::rs_length_sampling_next() {
287 assert( _curr != NULL, "invariant" );
288 size_t rs_length = _curr->rem_set()->occupied();
290 _sampled_rs_lengths += rs_length;
292 // The current region may not yet have been added to the
293 // incremental collection set (it gets added when it is
294 // retired as the current allocation region).
295 if (_curr->in_collection_set()) {
296 // Update the collection set policy information for this region
297 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
298 }
300 _curr = _curr->get_next_young_region();
301 if (_curr == NULL) {
302 _last_sampled_rs_lengths = _sampled_rs_lengths;
303 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
304 }
305 }
307 void
308 YoungList::reset_auxilary_lists() {
309 guarantee( is_empty(), "young list should be empty" );
310 assert(check_list_well_formed(), "young list should be well formed");
312 // Add survivor regions to SurvRateGroup.
313 _g1h->g1_policy()->note_start_adding_survivor_regions();
314 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
316 for (HeapRegion* curr = _survivor_head;
317 curr != NULL;
318 curr = curr->get_next_young_region()) {
319 _g1h->g1_policy()->set_region_survivors(curr);
321 // The region is a non-empty survivor so let's add it to
322 // the incremental collection set for the next evacuation
323 // pause.
324 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
325 }
326 _g1h->g1_policy()->note_stop_adding_survivor_regions();
328 _head = _survivor_head;
329 _length = _survivor_length;
330 if (_survivor_head != NULL) {
331 assert(_survivor_tail != NULL, "cause it shouldn't be");
332 assert(_survivor_length > 0, "invariant");
333 _survivor_tail->set_next_young_region(NULL);
334 }
336 // Don't clear the survivor list handles until the start of
337 // the next evacuation pause - we need it in order to re-tag
338 // the survivor regions from this evacuation pause as 'young'
339 // at the start of the next.
341 _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
343 assert(check_list_well_formed(), "young list should be well formed");
344 }
346 void YoungList::print() {
347 HeapRegion* lists[] = {_head, _survivor_head};
348 const char* names[] = {"YOUNG", "SURVIVOR"};
350 for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) {
351 gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
352 HeapRegion *curr = lists[list];
353 if (curr == NULL)
354 gclog_or_tty->print_cr(" empty");
355 while (curr != NULL) {
356 gclog_or_tty->print_cr(" [%08x-%08x], t: %08x, P: %08x, N: %08x, C: %08x, "
357 "age: %4d, y: %d, surv: %d",
358 curr->bottom(), curr->end(),
359 curr->top(),
360 curr->prev_top_at_mark_start(),
361 curr->next_top_at_mark_start(),
362 curr->top_at_conc_mark_count(),
363 curr->age_in_surv_rate_group_cond(),
364 curr->is_young(),
365 curr->is_survivor());
366 curr = curr->get_next_young_region();
367 }
368 }
370 gclog_or_tty->print_cr("");
371 }
373 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
374 {
375 // Claim the right to put the region on the dirty cards region list
376 // by installing a self pointer.
377 HeapRegion* next = hr->get_next_dirty_cards_region();
378 if (next == NULL) {
379 HeapRegion* res = (HeapRegion*)
380 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
381 NULL);
382 if (res == NULL) {
383 HeapRegion* head;
384 do {
385 // Put the region to the dirty cards region list.
386 head = _dirty_cards_region_list;
387 next = (HeapRegion*)
388 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
389 if (next == head) {
390 assert(hr->get_next_dirty_cards_region() == hr,
391 "hr->get_next_dirty_cards_region() != hr");
392 if (next == NULL) {
393 // The last region in the list points to itself.
394 hr->set_next_dirty_cards_region(hr);
395 } else {
396 hr->set_next_dirty_cards_region(next);
397 }
398 }
399 } while (next != head);
400 }
401 }
402 }
404 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
405 {
406 HeapRegion* head;
407 HeapRegion* hr;
408 do {
409 head = _dirty_cards_region_list;
410 if (head == NULL) {
411 return NULL;
412 }
413 HeapRegion* new_head = head->get_next_dirty_cards_region();
414 if (head == new_head) {
415 // The last region.
416 new_head = NULL;
417 }
418 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
419 head);
420 } while (hr != head);
421 assert(hr != NULL, "invariant");
422 hr->set_next_dirty_cards_region(NULL);
423 return hr;
424 }
426 void G1CollectedHeap::stop_conc_gc_threads() {
427 _cg1r->stop();
428 _cmThread->stop();
429 }
431 void G1CollectedHeap::check_ct_logs_at_safepoint() {
432 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
433 CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
435 // Count the dirty cards at the start.
436 CountNonCleanMemRegionClosure count1(this);
437 ct_bs->mod_card_iterate(&count1);
438 int orig_count = count1.n();
440 // First clear the logged cards.
441 ClearLoggedCardTableEntryClosure clear;
442 dcqs.set_closure(&clear);
443 dcqs.apply_closure_to_all_completed_buffers();
444 dcqs.iterate_closure_all_threads(false);
445 clear.print_histo();
447 // Now ensure that there's no dirty cards.
448 CountNonCleanMemRegionClosure count2(this);
449 ct_bs->mod_card_iterate(&count2);
450 if (count2.n() != 0) {
451 gclog_or_tty->print_cr("Card table has %d entries; %d originally",
452 count2.n(), orig_count);
453 }
454 guarantee(count2.n() == 0, "Card table should be clean.");
456 RedirtyLoggedCardTableEntryClosure redirty;
457 JavaThread::dirty_card_queue_set().set_closure(&redirty);
458 dcqs.apply_closure_to_all_completed_buffers();
459 dcqs.iterate_closure_all_threads(false);
460 gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
461 clear.calls(), orig_count);
462 guarantee(redirty.calls() == clear.calls(),
463 "Or else mechanism is broken.");
465 CountNonCleanMemRegionClosure count3(this);
466 ct_bs->mod_card_iterate(&count3);
467 if (count3.n() != orig_count) {
468 gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
469 orig_count, count3.n());
470 guarantee(count3.n() >= orig_count, "Should have restored them all.");
471 }
473 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
474 }
476 // Private class members.
478 G1CollectedHeap* G1CollectedHeap::_g1h;
480 // Private methods.
482 HeapRegion*
483 G1CollectedHeap::new_region_try_secondary_free_list() {
484 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
485 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
486 if (!_secondary_free_list.is_empty()) {
487 if (G1ConcRegionFreeingVerbose) {
488 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
489 "secondary_free_list has "SIZE_FORMAT" entries",
490 _secondary_free_list.length());
491 }
492 // It looks as if there are free regions available on the
493 // secondary_free_list. Let's move them to the free_list and try
494 // again to allocate from it.
495 append_secondary_free_list();
497 assert(!_free_list.is_empty(), "if the secondary_free_list was not "
498 "empty we should have moved at least one entry to the free_list");
499 HeapRegion* res = _free_list.remove_head();
500 if (G1ConcRegionFreeingVerbose) {
501 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
502 "allocated "HR_FORMAT" from secondary_free_list",
503 HR_FORMAT_PARAMS(res));
504 }
505 return res;
506 }
508 // Wait here until we get notifed either when (a) there are no
509 // more free regions coming or (b) some regions have been moved on
510 // the secondary_free_list.
511 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
512 }
514 if (G1ConcRegionFreeingVerbose) {
515 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
516 "could not allocate from secondary_free_list");
517 }
518 return NULL;
519 }
521 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool do_expand) {
522 assert(!isHumongous(word_size) ||
523 word_size <= (size_t) HeapRegion::GrainWords,
524 "the only time we use this to allocate a humongous region is "
525 "when we are allocating a single humongous region");
527 HeapRegion* res;
528 if (G1StressConcRegionFreeing) {
529 if (!_secondary_free_list.is_empty()) {
530 if (G1ConcRegionFreeingVerbose) {
531 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
532 "forced to look at the secondary_free_list");
533 }
534 res = new_region_try_secondary_free_list();
535 if (res != NULL) {
536 return res;
537 }
538 }
539 }
540 res = _free_list.remove_head_or_null();
541 if (res == NULL) {
542 if (G1ConcRegionFreeingVerbose) {
543 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
544 "res == NULL, trying the secondary_free_list");
545 }
546 res = new_region_try_secondary_free_list();
547 }
548 if (res == NULL && do_expand) {
549 if (expand(word_size * HeapWordSize)) {
550 // The expansion succeeded and so we should have at least one
551 // region on the free list.
552 res = _free_list.remove_head();
553 }
554 }
555 if (res != NULL) {
556 if (G1PrintHeapRegions) {
557 gclog_or_tty->print_cr("new alloc region %d:["PTR_FORMAT","PTR_FORMAT"], "
558 "top "PTR_FORMAT, res->hrs_index(),
559 res->bottom(), res->end(), res->top());
560 }
561 }
562 return res;
563 }
565 HeapRegion* G1CollectedHeap::new_gc_alloc_region(int purpose,
566 size_t word_size) {
567 HeapRegion* alloc_region = NULL;
568 if (_gc_alloc_region_counts[purpose] < g1_policy()->max_regions(purpose)) {
569 alloc_region = new_region(word_size, true /* do_expand */);
570 if (purpose == GCAllocForSurvived && alloc_region != NULL) {
571 alloc_region->set_survivor();
572 }
573 ++_gc_alloc_region_counts[purpose];
574 } else {
575 g1_policy()->note_alloc_region_limit_reached(purpose);
576 }
577 return alloc_region;
578 }
580 int G1CollectedHeap::humongous_obj_allocate_find_first(size_t num_regions,
581 size_t word_size) {
582 assert(isHumongous(word_size), "word_size should be humongous");
583 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
585 int first = -1;
586 if (num_regions == 1) {
587 // Only one region to allocate, no need to go through the slower
588 // path. The caller will attempt the expasion if this fails, so
589 // let's not try to expand here too.
590 HeapRegion* hr = new_region(word_size, false /* do_expand */);
591 if (hr != NULL) {
592 first = hr->hrs_index();
593 } else {
594 first = -1;
595 }
596 } else {
597 // We can't allocate humongous regions while cleanupComplete() is
598 // running, since some of the regions we find to be empty might not
599 // yet be added to the free list and it is not straightforward to
600 // know which list they are on so that we can remove them. Note
601 // that we only need to do this if we need to allocate more than
602 // one region to satisfy the current humongous allocation
603 // request. If we are only allocating one region we use the common
604 // region allocation code (see above).
605 wait_while_free_regions_coming();
606 append_secondary_free_list_if_not_empty_with_lock();
608 if (free_regions() >= num_regions) {
609 first = _hrs->find_contiguous(num_regions);
610 if (first != -1) {
611 for (int i = first; i < first + (int) num_regions; ++i) {
612 HeapRegion* hr = _hrs->at(i);
613 assert(hr->is_empty(), "sanity");
614 assert(is_on_master_free_list(hr), "sanity");
615 hr->set_pending_removal(true);
616 }
617 _free_list.remove_all_pending(num_regions);
618 }
619 }
620 }
621 return first;
622 }
624 HeapWord*
625 G1CollectedHeap::humongous_obj_allocate_initialize_regions(int first,
626 size_t num_regions,
627 size_t word_size) {
628 assert(first != -1, "pre-condition");
629 assert(isHumongous(word_size), "word_size should be humongous");
630 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
632 // Index of last region in the series + 1.
633 int last = first + (int) num_regions;
635 // We need to initialize the region(s) we just discovered. This is
636 // a bit tricky given that it can happen concurrently with
637 // refinement threads refining cards on these regions and
638 // potentially wanting to refine the BOT as they are scanning
639 // those cards (this can happen shortly after a cleanup; see CR
640 // 6991377). So we have to set up the region(s) carefully and in
641 // a specific order.
643 // The word size sum of all the regions we will allocate.
644 size_t word_size_sum = num_regions * HeapRegion::GrainWords;
645 assert(word_size <= word_size_sum, "sanity");
647 // This will be the "starts humongous" region.
648 HeapRegion* first_hr = _hrs->at(first);
649 // The header of the new object will be placed at the bottom of
650 // the first region.
651 HeapWord* new_obj = first_hr->bottom();
652 // This will be the new end of the first region in the series that
653 // should also match the end of the last region in the seriers.
654 HeapWord* new_end = new_obj + word_size_sum;
655 // This will be the new top of the first region that will reflect
656 // this allocation.
657 HeapWord* new_top = new_obj + word_size;
659 // First, we need to zero the header of the space that we will be
660 // allocating. When we update top further down, some refinement
661 // threads might try to scan the region. By zeroing the header we
662 // ensure that any thread that will try to scan the region will
663 // come across the zero klass word and bail out.
664 //
665 // NOTE: It would not have been correct to have used
666 // CollectedHeap::fill_with_object() and make the space look like
667 // an int array. The thread that is doing the allocation will
668 // later update the object header to a potentially different array
669 // type and, for a very short period of time, the klass and length
670 // fields will be inconsistent. This could cause a refinement
671 // thread to calculate the object size incorrectly.
672 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
674 // We will set up the first region as "starts humongous". This
675 // will also update the BOT covering all the regions to reflect
676 // that there is a single object that starts at the bottom of the
677 // first region.
678 first_hr->set_startsHumongous(new_top, new_end);
680 // Then, if there are any, we will set up the "continues
681 // humongous" regions.
682 HeapRegion* hr = NULL;
683 for (int i = first + 1; i < last; ++i) {
684 hr = _hrs->at(i);
685 hr->set_continuesHumongous(first_hr);
686 }
687 // If we have "continues humongous" regions (hr != NULL), then the
688 // end of the last one should match new_end.
689 assert(hr == NULL || hr->end() == new_end, "sanity");
691 // Up to this point no concurrent thread would have been able to
692 // do any scanning on any region in this series. All the top
693 // fields still point to bottom, so the intersection between
694 // [bottom,top] and [card_start,card_end] will be empty. Before we
695 // update the top fields, we'll do a storestore to make sure that
696 // no thread sees the update to top before the zeroing of the
697 // object header and the BOT initialization.
698 OrderAccess::storestore();
700 // Now that the BOT and the object header have been initialized,
701 // we can update top of the "starts humongous" region.
702 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
703 "new_top should be in this region");
704 first_hr->set_top(new_top);
706 // Now, we will update the top fields of the "continues humongous"
707 // regions. The reason we need to do this is that, otherwise,
708 // these regions would look empty and this will confuse parts of
709 // G1. For example, the code that looks for a consecutive number
710 // of empty regions will consider them empty and try to
711 // re-allocate them. We can extend is_empty() to also include
712 // !continuesHumongous(), but it is easier to just update the top
713 // fields here. The way we set top for all regions (i.e., top ==
714 // end for all regions but the last one, top == new_top for the
715 // last one) is actually used when we will free up the humongous
716 // region in free_humongous_region().
717 hr = NULL;
718 for (int i = first + 1; i < last; ++i) {
719 hr = _hrs->at(i);
720 if ((i + 1) == last) {
721 // last continues humongous region
722 assert(hr->bottom() < new_top && new_top <= hr->end(),
723 "new_top should fall on this region");
724 hr->set_top(new_top);
725 } else {
726 // not last one
727 assert(new_top > hr->end(), "new_top should be above this region");
728 hr->set_top(hr->end());
729 }
730 }
731 // If we have continues humongous regions (hr != NULL), then the
732 // end of the last one should match new_end and its top should
733 // match new_top.
734 assert(hr == NULL ||
735 (hr->end() == new_end && hr->top() == new_top), "sanity");
737 assert(first_hr->used() == word_size * HeapWordSize, "invariant");
738 _summary_bytes_used += first_hr->used();
739 _humongous_set.add(first_hr);
741 return new_obj;
742 }
744 // If could fit into free regions w/o expansion, try.
745 // Otherwise, if can expand, do so.
746 // Otherwise, if using ex regions might help, try with ex given back.
747 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
748 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
750 verify_region_sets_optional();
752 size_t num_regions =
753 round_to(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
754 size_t x_size = expansion_regions();
755 size_t fs = _hrs->free_suffix();
756 int first = humongous_obj_allocate_find_first(num_regions, word_size);
757 if (first == -1) {
758 // The only thing we can do now is attempt expansion.
759 if (fs + x_size >= num_regions) {
760 // If the number of regions we're trying to allocate for this
761 // object is at most the number of regions in the free suffix,
762 // then the call to humongous_obj_allocate_find_first() above
763 // should have succeeded and we wouldn't be here.
764 //
765 // We should only be trying to expand when the free suffix is
766 // not sufficient for the object _and_ we have some expansion
767 // room available.
768 assert(num_regions > fs, "earlier allocation should have succeeded");
770 if (expand((num_regions - fs) * HeapRegion::GrainBytes)) {
771 first = humongous_obj_allocate_find_first(num_regions, word_size);
772 // If the expansion was successful then the allocation
773 // should have been successful.
774 assert(first != -1, "this should have worked");
775 }
776 }
777 }
779 HeapWord* result = NULL;
780 if (first != -1) {
781 result =
782 humongous_obj_allocate_initialize_regions(first, num_regions, word_size);
783 assert(result != NULL, "it should always return a valid result");
784 }
786 verify_region_sets_optional();
788 return result;
789 }
791 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
792 assert_heap_not_locked_and_not_at_safepoint();
793 assert(!isHumongous(word_size), "we do not allow humongous TLABs");
795 unsigned int dummy_gc_count_before;
796 return attempt_allocation(word_size, &dummy_gc_count_before);
797 }
799 HeapWord*
800 G1CollectedHeap::mem_allocate(size_t word_size,
801 bool is_noref,
802 bool is_tlab,
803 bool* gc_overhead_limit_was_exceeded) {
804 assert_heap_not_locked_and_not_at_safepoint();
805 assert(!is_tlab, "mem_allocate() this should not be called directly "
806 "to allocate TLABs");
808 // Loop until the allocation is satisified, or unsatisfied after GC.
809 for (int try_count = 1; /* we'll return */; try_count += 1) {
810 unsigned int gc_count_before;
812 HeapWord* result = NULL;
813 if (!isHumongous(word_size)) {
814 result = attempt_allocation(word_size, &gc_count_before);
815 } else {
816 result = attempt_allocation_humongous(word_size, &gc_count_before);
817 }
818 if (result != NULL) {
819 return result;
820 }
822 // Create the garbage collection operation...
823 VM_G1CollectForAllocation op(gc_count_before, word_size);
824 // ...and get the VM thread to execute it.
825 VMThread::execute(&op);
827 if (op.prologue_succeeded() && op.pause_succeeded()) {
828 // If the operation was successful we'll return the result even
829 // if it is NULL. If the allocation attempt failed immediately
830 // after a Full GC, it's unlikely we'll be able to allocate now.
831 HeapWord* result = op.result();
832 if (result != NULL && !isHumongous(word_size)) {
833 // Allocations that take place on VM operations do not do any
834 // card dirtying and we have to do it here. We only have to do
835 // this for non-humongous allocations, though.
836 dirty_young_block(result, word_size);
837 }
838 return result;
839 } else {
840 assert(op.result() == NULL,
841 "the result should be NULL if the VM op did not succeed");
842 }
844 // Give a warning if we seem to be looping forever.
845 if ((QueuedAllocationWarningCount > 0) &&
846 (try_count % QueuedAllocationWarningCount == 0)) {
847 warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
848 }
849 }
851 ShouldNotReachHere();
852 return NULL;
853 }
855 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
856 unsigned int *gc_count_before_ret) {
857 // Make sure you read the note in attempt_allocation_humongous().
859 assert_heap_not_locked_and_not_at_safepoint();
860 assert(!isHumongous(word_size), "attempt_allocation_slow() should not "
861 "be called for humongous allocation requests");
863 // We should only get here after the first-level allocation attempt
864 // (attempt_allocation()) failed to allocate.
866 // We will loop until a) we manage to successfully perform the
867 // allocation or b) we successfully schedule a collection which
868 // fails to perform the allocation. b) is the only case when we'll
869 // return NULL.
870 HeapWord* result = NULL;
871 for (int try_count = 1; /* we'll return */; try_count += 1) {
872 bool should_try_gc;
873 unsigned int gc_count_before;
875 {
876 MutexLockerEx x(Heap_lock);
878 result = _mutator_alloc_region.attempt_allocation_locked(word_size,
879 false /* bot_updates */);
880 if (result != NULL) {
881 return result;
882 }
884 // If we reach here, attempt_allocation_locked() above failed to
885 // allocate a new region. So the mutator alloc region should be NULL.
886 assert(_mutator_alloc_region.get() == NULL, "only way to get here");
888 if (GC_locker::is_active_and_needs_gc()) {
889 if (g1_policy()->can_expand_young_list()) {
890 result = _mutator_alloc_region.attempt_allocation_force(word_size,
891 false /* bot_updates */);
892 if (result != NULL) {
893 return result;
894 }
895 }
896 should_try_gc = false;
897 } else {
898 // Read the GC count while still holding the Heap_lock.
899 gc_count_before = SharedHeap::heap()->total_collections();
900 should_try_gc = true;
901 }
902 }
904 if (should_try_gc) {
905 bool succeeded;
906 result = do_collection_pause(word_size, gc_count_before, &succeeded);
907 if (result != NULL) {
908 assert(succeeded, "only way to get back a non-NULL result");
909 return result;
910 }
912 if (succeeded) {
913 // If we get here we successfully scheduled a collection which
914 // failed to allocate. No point in trying to allocate
915 // further. We'll just return NULL.
916 MutexLockerEx x(Heap_lock);
917 *gc_count_before_ret = SharedHeap::heap()->total_collections();
918 return NULL;
919 }
920 } else {
921 GC_locker::stall_until_clear();
922 }
924 // We can reach here if we were unsuccessul in scheduling a
925 // collection (because another thread beat us to it) or if we were
926 // stalled due to the GC locker. In either can we should retry the
927 // allocation attempt in case another thread successfully
928 // performed a collection and reclaimed enough space. We do the
929 // first attempt (without holding the Heap_lock) here and the
930 // follow-on attempt will be at the start of the next loop
931 // iteration (after taking the Heap_lock).
932 result = _mutator_alloc_region.attempt_allocation(word_size,
933 false /* bot_updates */);
934 if (result != NULL ){
935 return result;
936 }
938 // Give a warning if we seem to be looping forever.
939 if ((QueuedAllocationWarningCount > 0) &&
940 (try_count % QueuedAllocationWarningCount == 0)) {
941 warning("G1CollectedHeap::attempt_allocation_slow() "
942 "retries %d times", try_count);
943 }
944 }
946 ShouldNotReachHere();
947 return NULL;
948 }
950 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
951 unsigned int * gc_count_before_ret) {
952 // The structure of this method has a lot of similarities to
953 // attempt_allocation_slow(). The reason these two were not merged
954 // into a single one is that such a method would require several "if
955 // allocation is not humongous do this, otherwise do that"
956 // conditional paths which would obscure its flow. In fact, an early
957 // version of this code did use a unified method which was harder to
958 // follow and, as a result, it had subtle bugs that were hard to
959 // track down. So keeping these two methods separate allows each to
960 // be more readable. It will be good to keep these two in sync as
961 // much as possible.
963 assert_heap_not_locked_and_not_at_safepoint();
964 assert(isHumongous(word_size), "attempt_allocation_humongous() "
965 "should only be called for humongous allocations");
967 // We will loop until a) we manage to successfully perform the
968 // allocation or b) we successfully schedule a collection which
969 // fails to perform the allocation. b) is the only case when we'll
970 // return NULL.
971 HeapWord* result = NULL;
972 for (int try_count = 1; /* we'll return */; try_count += 1) {
973 bool should_try_gc;
974 unsigned int gc_count_before;
976 {
977 MutexLockerEx x(Heap_lock);
979 // Given that humongous objects are not allocated in young
980 // regions, we'll first try to do the allocation without doing a
981 // collection hoping that there's enough space in the heap.
982 result = humongous_obj_allocate(word_size);
983 if (result != NULL) {
984 return result;
985 }
987 if (GC_locker::is_active_and_needs_gc()) {
988 should_try_gc = false;
989 } else {
990 // Read the GC count while still holding the Heap_lock.
991 gc_count_before = SharedHeap::heap()->total_collections();
992 should_try_gc = true;
993 }
994 }
996 if (should_try_gc) {
997 // If we failed to allocate the humongous object, we should try to
998 // do a collection pause (if we're allowed) in case it reclaims
999 // enough space for the allocation to succeed after the pause.
1001 bool succeeded;
1002 result = do_collection_pause(word_size, gc_count_before, &succeeded);
1003 if (result != NULL) {
1004 assert(succeeded, "only way to get back a non-NULL result");
1005 return result;
1006 }
1008 if (succeeded) {
1009 // If we get here we successfully scheduled a collection which
1010 // failed to allocate. No point in trying to allocate
1011 // further. We'll just return NULL.
1012 MutexLockerEx x(Heap_lock);
1013 *gc_count_before_ret = SharedHeap::heap()->total_collections();
1014 return NULL;
1015 }
1016 } else {
1017 GC_locker::stall_until_clear();
1018 }
1020 // We can reach here if we were unsuccessul in scheduling a
1021 // collection (because another thread beat us to it) or if we were
1022 // stalled due to the GC locker. In either can we should retry the
1023 // allocation attempt in case another thread successfully
1024 // performed a collection and reclaimed enough space. Give a
1025 // warning if we seem to be looping forever.
1027 if ((QueuedAllocationWarningCount > 0) &&
1028 (try_count % QueuedAllocationWarningCount == 0)) {
1029 warning("G1CollectedHeap::attempt_allocation_humongous() "
1030 "retries %d times", try_count);
1031 }
1032 }
1034 ShouldNotReachHere();
1035 return NULL;
1036 }
1038 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1039 bool expect_null_mutator_alloc_region) {
1040 assert_at_safepoint(true /* should_be_vm_thread */);
1041 assert(_mutator_alloc_region.get() == NULL ||
1042 !expect_null_mutator_alloc_region,
1043 "the current alloc region was unexpectedly found to be non-NULL");
1045 if (!isHumongous(word_size)) {
1046 return _mutator_alloc_region.attempt_allocation_locked(word_size,
1047 false /* bot_updates */);
1048 } else {
1049 return humongous_obj_allocate(word_size);
1050 }
1052 ShouldNotReachHere();
1053 }
1055 void G1CollectedHeap::abandon_gc_alloc_regions() {
1056 // first, make sure that the GC alloc region list is empty (it should!)
1057 assert(_gc_alloc_region_list == NULL, "invariant");
1058 release_gc_alloc_regions(true /* totally */);
1059 }
1061 class PostMCRemSetClearClosure: public HeapRegionClosure {
1062 ModRefBarrierSet* _mr_bs;
1063 public:
1064 PostMCRemSetClearClosure(ModRefBarrierSet* mr_bs) : _mr_bs(mr_bs) {}
1065 bool doHeapRegion(HeapRegion* r) {
1066 r->reset_gc_time_stamp();
1067 if (r->continuesHumongous())
1068 return false;
1069 HeapRegionRemSet* hrrs = r->rem_set();
1070 if (hrrs != NULL) hrrs->clear();
1071 // You might think here that we could clear just the cards
1072 // corresponding to the used region. But no: if we leave a dirty card
1073 // in a region we might allocate into, then it would prevent that card
1074 // from being enqueued, and cause it to be missed.
1075 // Re: the performance cost: we shouldn't be doing full GC anyway!
1076 _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1077 return false;
1078 }
1079 };
1082 class PostMCRemSetInvalidateClosure: public HeapRegionClosure {
1083 ModRefBarrierSet* _mr_bs;
1084 public:
1085 PostMCRemSetInvalidateClosure(ModRefBarrierSet* mr_bs) : _mr_bs(mr_bs) {}
1086 bool doHeapRegion(HeapRegion* r) {
1087 if (r->continuesHumongous()) return false;
1088 if (r->used_region().word_size() != 0) {
1089 _mr_bs->invalidate(r->used_region(), true /*whole heap*/);
1090 }
1091 return false;
1092 }
1093 };
1095 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1096 G1CollectedHeap* _g1h;
1097 UpdateRSOopClosure _cl;
1098 int _worker_i;
1099 public:
1100 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1101 _cl(g1->g1_rem_set(), worker_i),
1102 _worker_i(worker_i),
1103 _g1h(g1)
1104 { }
1106 bool doHeapRegion(HeapRegion* r) {
1107 if (!r->continuesHumongous()) {
1108 _cl.set_from(r);
1109 r->oop_iterate(&_cl);
1110 }
1111 return false;
1112 }
1113 };
1115 class ParRebuildRSTask: public AbstractGangTask {
1116 G1CollectedHeap* _g1;
1117 public:
1118 ParRebuildRSTask(G1CollectedHeap* g1)
1119 : AbstractGangTask("ParRebuildRSTask"),
1120 _g1(g1)
1121 { }
1123 void work(int i) {
1124 RebuildRSOutOfRegionClosure rebuild_rs(_g1, i);
1125 _g1->heap_region_par_iterate_chunked(&rebuild_rs, i,
1126 HeapRegion::RebuildRSClaimValue);
1127 }
1128 };
1130 bool G1CollectedHeap::do_collection(bool explicit_gc,
1131 bool clear_all_soft_refs,
1132 size_t word_size) {
1133 assert_at_safepoint(true /* should_be_vm_thread */);
1135 if (GC_locker::check_active_before_gc()) {
1136 return false;
1137 }
1139 SvcGCMarker sgcm(SvcGCMarker::FULL);
1140 ResourceMark rm;
1142 if (PrintHeapAtGC) {
1143 Universe::print_heap_before_gc();
1144 }
1146 verify_region_sets_optional();
1148 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1149 collector_policy()->should_clear_all_soft_refs();
1151 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1153 {
1154 IsGCActiveMark x;
1156 // Timing
1157 bool system_gc = (gc_cause() == GCCause::_java_lang_system_gc);
1158 assert(!system_gc || explicit_gc, "invariant");
1159 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
1160 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
1161 TraceTime t(system_gc ? "Full GC (System.gc())" : "Full GC",
1162 PrintGC, true, gclog_or_tty);
1164 TraceCollectorStats tcs(g1mm()->full_collection_counters());
1165 TraceMemoryManagerStats tms(true /* fullGC */);
1167 double start = os::elapsedTime();
1168 g1_policy()->record_full_collection_start();
1170 wait_while_free_regions_coming();
1171 append_secondary_free_list_if_not_empty_with_lock();
1173 gc_prologue(true);
1174 increment_total_collections(true /* full gc */);
1176 size_t g1h_prev_used = used();
1177 assert(used() == recalculate_used(), "Should be equal");
1179 if (VerifyBeforeGC && total_collections() >= VerifyGCStartAt) {
1180 HandleMark hm; // Discard invalid handles created during verification
1181 gclog_or_tty->print(" VerifyBeforeGC:");
1182 prepare_for_verify();
1183 Universe::verify(true);
1184 }
1186 COMPILER2_PRESENT(DerivedPointerTable::clear());
1188 // We want to discover references, but not process them yet.
1189 // This mode is disabled in
1190 // instanceRefKlass::process_discovered_references if the
1191 // generation does some collection work, or
1192 // instanceRefKlass::enqueue_discovered_references if the
1193 // generation returns without doing any work.
1194 ref_processor()->disable_discovery();
1195 ref_processor()->abandon_partial_discovery();
1196 ref_processor()->verify_no_references_recorded();
1198 // Abandon current iterations of concurrent marking and concurrent
1199 // refinement, if any are in progress.
1200 concurrent_mark()->abort();
1202 // Make sure we'll choose a new allocation region afterwards.
1203 release_mutator_alloc_region();
1204 abandon_gc_alloc_regions();
1205 g1_rem_set()->cleanupHRRS();
1206 tear_down_region_lists();
1208 // We may have added regions to the current incremental collection
1209 // set between the last GC or pause and now. We need to clear the
1210 // incremental collection set and then start rebuilding it afresh
1211 // after this full GC.
1212 abandon_collection_set(g1_policy()->inc_cset_head());
1213 g1_policy()->clear_incremental_cset();
1214 g1_policy()->stop_incremental_cset_building();
1216 if (g1_policy()->in_young_gc_mode()) {
1217 empty_young_list();
1218 g1_policy()->set_full_young_gcs(true);
1219 }
1221 // See the comment in G1CollectedHeap::ref_processing_init() about
1222 // how reference processing currently works in G1.
1224 // Temporarily make reference _discovery_ single threaded (non-MT).
1225 ReferenceProcessorMTDiscoveryMutator rp_disc_ser(ref_processor(), false);
1227 // Temporarily make refs discovery atomic
1228 ReferenceProcessorAtomicMutator rp_disc_atomic(ref_processor(), true);
1230 // Temporarily clear _is_alive_non_header
1231 ReferenceProcessorIsAliveMutator rp_is_alive_null(ref_processor(), NULL);
1233 ref_processor()->enable_discovery();
1234 ref_processor()->setup_policy(do_clear_all_soft_refs);
1236 // Do collection work
1237 {
1238 HandleMark hm; // Discard invalid handles created during gc
1239 G1MarkSweep::invoke_at_safepoint(ref_processor(), do_clear_all_soft_refs);
1240 }
1241 assert(free_regions() == 0, "we should not have added any free regions");
1242 rebuild_region_lists();
1244 _summary_bytes_used = recalculate_used();
1246 ref_processor()->enqueue_discovered_references();
1248 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1250 MemoryService::track_memory_usage();
1252 if (VerifyAfterGC && total_collections() >= VerifyGCStartAt) {
1253 HandleMark hm; // Discard invalid handles created during verification
1254 gclog_or_tty->print(" VerifyAfterGC:");
1255 prepare_for_verify();
1256 Universe::verify(false);
1257 }
1258 NOT_PRODUCT(ref_processor()->verify_no_references_recorded());
1260 reset_gc_time_stamp();
1261 // Since everything potentially moved, we will clear all remembered
1262 // sets, and clear all cards. Later we will rebuild remebered
1263 // sets. We will also reset the GC time stamps of the regions.
1264 PostMCRemSetClearClosure rs_clear(mr_bs());
1265 heap_region_iterate(&rs_clear);
1267 // Resize the heap if necessary.
1268 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1270 if (_cg1r->use_cache()) {
1271 _cg1r->clear_and_record_card_counts();
1272 _cg1r->clear_hot_cache();
1273 }
1275 // Rebuild remembered sets of all regions.
1277 if (G1CollectedHeap::use_parallel_gc_threads()) {
1278 ParRebuildRSTask rebuild_rs_task(this);
1279 assert(check_heap_region_claim_values(
1280 HeapRegion::InitialClaimValue), "sanity check");
1281 set_par_threads(workers()->total_workers());
1282 workers()->run_task(&rebuild_rs_task);
1283 set_par_threads(0);
1284 assert(check_heap_region_claim_values(
1285 HeapRegion::RebuildRSClaimValue), "sanity check");
1286 reset_heap_region_claim_values();
1287 } else {
1288 RebuildRSOutOfRegionClosure rebuild_rs(this);
1289 heap_region_iterate(&rebuild_rs);
1290 }
1292 if (PrintGC) {
1293 print_size_transition(gclog_or_tty, g1h_prev_used, used(), capacity());
1294 }
1296 if (true) { // FIXME
1297 // Ask the permanent generation to adjust size for full collections
1298 perm()->compute_new_size();
1299 }
1301 // Start a new incremental collection set for the next pause
1302 assert(g1_policy()->collection_set() == NULL, "must be");
1303 g1_policy()->start_incremental_cset_building();
1305 // Clear the _cset_fast_test bitmap in anticipation of adding
1306 // regions to the incremental collection set for the next
1307 // evacuation pause.
1308 clear_cset_fast_test();
1310 init_mutator_alloc_region();
1312 double end = os::elapsedTime();
1313 g1_policy()->record_full_collection_end();
1315 #ifdef TRACESPINNING
1316 ParallelTaskTerminator::print_termination_counts();
1317 #endif
1319 gc_epilogue(true);
1321 // Discard all rset updates
1322 JavaThread::dirty_card_queue_set().abandon_logs();
1323 assert(!G1DeferredRSUpdate
1324 || (G1DeferredRSUpdate && (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any");
1325 }
1327 if (g1_policy()->in_young_gc_mode()) {
1328 _young_list->reset_sampled_info();
1329 // At this point there should be no regions in the
1330 // entire heap tagged as young.
1331 assert( check_young_list_empty(true /* check_heap */),
1332 "young list should be empty at this point");
1333 }
1335 // Update the number of full collections that have been completed.
1336 increment_full_collections_completed(false /* concurrent */);
1338 verify_region_sets_optional();
1340 if (PrintHeapAtGC) {
1341 Universe::print_heap_after_gc();
1342 }
1343 g1mm()->update_counters();
1345 return true;
1346 }
1348 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1349 // do_collection() will return whether it succeeded in performing
1350 // the GC. Currently, there is no facility on the
1351 // do_full_collection() API to notify the caller than the collection
1352 // did not succeed (e.g., because it was locked out by the GC
1353 // locker). So, right now, we'll ignore the return value.
1354 bool dummy = do_collection(true, /* explicit_gc */
1355 clear_all_soft_refs,
1356 0 /* word_size */);
1357 }
1359 // This code is mostly copied from TenuredGeneration.
1360 void
1361 G1CollectedHeap::
1362 resize_if_necessary_after_full_collection(size_t word_size) {
1363 assert(MinHeapFreeRatio <= MaxHeapFreeRatio, "sanity check");
1365 // Include the current allocation, if any, and bytes that will be
1366 // pre-allocated to support collections, as "used".
1367 const size_t used_after_gc = used();
1368 const size_t capacity_after_gc = capacity();
1369 const size_t free_after_gc = capacity_after_gc - used_after_gc;
1371 // This is enforced in arguments.cpp.
1372 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1373 "otherwise the code below doesn't make sense");
1375 // We don't have floating point command-line arguments
1376 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1377 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1378 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1379 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1381 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1382 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1384 // We have to be careful here as these two calculations can overflow
1385 // 32-bit size_t's.
1386 double used_after_gc_d = (double) used_after_gc;
1387 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1388 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1390 // Let's make sure that they are both under the max heap size, which
1391 // by default will make them fit into a size_t.
1392 double desired_capacity_upper_bound = (double) max_heap_size;
1393 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1394 desired_capacity_upper_bound);
1395 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1396 desired_capacity_upper_bound);
1398 // We can now safely turn them into size_t's.
1399 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1400 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1402 // This assert only makes sense here, before we adjust them
1403 // with respect to the min and max heap size.
1404 assert(minimum_desired_capacity <= maximum_desired_capacity,
1405 err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1406 "maximum_desired_capacity = "SIZE_FORMAT,
1407 minimum_desired_capacity, maximum_desired_capacity));
1409 // Should not be greater than the heap max size. No need to adjust
1410 // it with respect to the heap min size as it's a lower bound (i.e.,
1411 // we'll try to make the capacity larger than it, not smaller).
1412 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1413 // Should not be less than the heap min size. No need to adjust it
1414 // with respect to the heap max size as it's an upper bound (i.e.,
1415 // we'll try to make the capacity smaller than it, not greater).
1416 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1418 if (PrintGC && Verbose) {
1419 const double free_percentage =
1420 (double) free_after_gc / (double) capacity_after_gc;
1421 gclog_or_tty->print_cr("Computing new size after full GC ");
1422 gclog_or_tty->print_cr(" "
1423 " minimum_free_percentage: %6.2f",
1424 minimum_free_percentage);
1425 gclog_or_tty->print_cr(" "
1426 " maximum_free_percentage: %6.2f",
1427 maximum_free_percentage);
1428 gclog_or_tty->print_cr(" "
1429 " capacity: %6.1fK"
1430 " minimum_desired_capacity: %6.1fK"
1431 " maximum_desired_capacity: %6.1fK",
1432 (double) capacity_after_gc / (double) K,
1433 (double) minimum_desired_capacity / (double) K,
1434 (double) maximum_desired_capacity / (double) K);
1435 gclog_or_tty->print_cr(" "
1436 " free_after_gc: %6.1fK"
1437 " used_after_gc: %6.1fK",
1438 (double) free_after_gc / (double) K,
1439 (double) used_after_gc / (double) K);
1440 gclog_or_tty->print_cr(" "
1441 " free_percentage: %6.2f",
1442 free_percentage);
1443 }
1444 if (capacity_after_gc < minimum_desired_capacity) {
1445 // Don't expand unless it's significant
1446 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1447 if (expand(expand_bytes)) {
1448 if (PrintGC && Verbose) {
1449 gclog_or_tty->print_cr(" "
1450 " expanding:"
1451 " max_heap_size: %6.1fK"
1452 " minimum_desired_capacity: %6.1fK"
1453 " expand_bytes: %6.1fK",
1454 (double) max_heap_size / (double) K,
1455 (double) minimum_desired_capacity / (double) K,
1456 (double) expand_bytes / (double) K);
1457 }
1458 }
1460 // No expansion, now see if we want to shrink
1461 } else if (capacity_after_gc > maximum_desired_capacity) {
1462 // Capacity too large, compute shrinking size
1463 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1464 shrink(shrink_bytes);
1465 if (PrintGC && Verbose) {
1466 gclog_or_tty->print_cr(" "
1467 " shrinking:"
1468 " min_heap_size: %6.1fK"
1469 " maximum_desired_capacity: %6.1fK"
1470 " shrink_bytes: %6.1fK",
1471 (double) min_heap_size / (double) K,
1472 (double) maximum_desired_capacity / (double) K,
1473 (double) shrink_bytes / (double) K);
1474 }
1475 }
1476 }
1479 HeapWord*
1480 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1481 bool* succeeded) {
1482 assert_at_safepoint(true /* should_be_vm_thread */);
1484 *succeeded = true;
1485 // Let's attempt the allocation first.
1486 HeapWord* result =
1487 attempt_allocation_at_safepoint(word_size,
1488 false /* expect_null_mutator_alloc_region */);
1489 if (result != NULL) {
1490 assert(*succeeded, "sanity");
1491 return result;
1492 }
1494 // In a G1 heap, we're supposed to keep allocation from failing by
1495 // incremental pauses. Therefore, at least for now, we'll favor
1496 // expansion over collection. (This might change in the future if we can
1497 // do something smarter than full collection to satisfy a failed alloc.)
1498 result = expand_and_allocate(word_size);
1499 if (result != NULL) {
1500 assert(*succeeded, "sanity");
1501 return result;
1502 }
1504 // Expansion didn't work, we'll try to do a Full GC.
1505 bool gc_succeeded = do_collection(false, /* explicit_gc */
1506 false, /* clear_all_soft_refs */
1507 word_size);
1508 if (!gc_succeeded) {
1509 *succeeded = false;
1510 return NULL;
1511 }
1513 // Retry the allocation
1514 result = attempt_allocation_at_safepoint(word_size,
1515 true /* expect_null_mutator_alloc_region */);
1516 if (result != NULL) {
1517 assert(*succeeded, "sanity");
1518 return result;
1519 }
1521 // Then, try a Full GC that will collect all soft references.
1522 gc_succeeded = do_collection(false, /* explicit_gc */
1523 true, /* clear_all_soft_refs */
1524 word_size);
1525 if (!gc_succeeded) {
1526 *succeeded = false;
1527 return NULL;
1528 }
1530 // Retry the allocation once more
1531 result = attempt_allocation_at_safepoint(word_size,
1532 true /* expect_null_mutator_alloc_region */);
1533 if (result != NULL) {
1534 assert(*succeeded, "sanity");
1535 return result;
1536 }
1538 assert(!collector_policy()->should_clear_all_soft_refs(),
1539 "Flag should have been handled and cleared prior to this point");
1541 // What else? We might try synchronous finalization later. If the total
1542 // space available is large enough for the allocation, then a more
1543 // complete compaction phase than we've tried so far might be
1544 // appropriate.
1545 assert(*succeeded, "sanity");
1546 return NULL;
1547 }
1549 // Attempting to expand the heap sufficiently
1550 // to support an allocation of the given "word_size". If
1551 // successful, perform the allocation and return the address of the
1552 // allocated block, or else "NULL".
1554 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1555 assert_at_safepoint(true /* should_be_vm_thread */);
1557 verify_region_sets_optional();
1559 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1560 if (expand(expand_bytes)) {
1561 verify_region_sets_optional();
1562 return attempt_allocation_at_safepoint(word_size,
1563 false /* expect_null_mutator_alloc_region */);
1564 }
1565 return NULL;
1566 }
1568 bool G1CollectedHeap::expand(size_t expand_bytes) {
1569 size_t old_mem_size = _g1_storage.committed_size();
1570 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1571 aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1572 HeapRegion::GrainBytes);
1574 if (Verbose && PrintGC) {
1575 gclog_or_tty->print("Expanding garbage-first heap from %ldK by %ldK",
1576 old_mem_size/K, aligned_expand_bytes/K);
1577 }
1579 HeapWord* old_end = (HeapWord*)_g1_storage.high();
1580 bool successful = _g1_storage.expand_by(aligned_expand_bytes);
1581 if (successful) {
1582 HeapWord* new_end = (HeapWord*)_g1_storage.high();
1584 // Expand the committed region.
1585 _g1_committed.set_end(new_end);
1587 // Tell the cardtable about the expansion.
1588 Universe::heap()->barrier_set()->resize_covered_region(_g1_committed);
1590 // And the offset table as well.
1591 _bot_shared->resize(_g1_committed.word_size());
1593 expand_bytes = aligned_expand_bytes;
1594 HeapWord* base = old_end;
1596 // Create the heap regions for [old_end, new_end)
1597 while (expand_bytes > 0) {
1598 HeapWord* high = base + HeapRegion::GrainWords;
1600 // Create a new HeapRegion.
1601 MemRegion mr(base, high);
1602 bool is_zeroed = !_g1_max_committed.contains(base);
1603 HeapRegion* hr = new HeapRegion(_bot_shared, mr, is_zeroed);
1605 // Add it to the HeapRegionSeq.
1606 _hrs->insert(hr);
1607 _free_list.add_as_tail(hr);
1609 // And we used up an expansion region to create it.
1610 _expansion_regions--;
1612 expand_bytes -= HeapRegion::GrainBytes;
1613 base += HeapRegion::GrainWords;
1614 }
1615 assert(base == new_end, "sanity");
1617 // Now update max_committed if necessary.
1618 _g1_max_committed.set_end(MAX2(_g1_max_committed.end(), new_end));
1620 } else {
1621 // The expansion of the virtual storage space was unsuccessful.
1622 // Let's see if it was because we ran out of swap.
1623 if (G1ExitOnExpansionFailure &&
1624 _g1_storage.uncommitted_size() >= aligned_expand_bytes) {
1625 // We had head room...
1626 vm_exit_out_of_memory(aligned_expand_bytes, "G1 heap expansion");
1627 }
1628 }
1630 if (Verbose && PrintGC) {
1631 size_t new_mem_size = _g1_storage.committed_size();
1632 gclog_or_tty->print_cr("...%s, expanded to %ldK",
1633 (successful ? "Successful" : "Failed"),
1634 new_mem_size/K);
1635 }
1636 return successful;
1637 }
1639 void G1CollectedHeap::shrink_helper(size_t shrink_bytes)
1640 {
1641 size_t old_mem_size = _g1_storage.committed_size();
1642 size_t aligned_shrink_bytes =
1643 ReservedSpace::page_align_size_down(shrink_bytes);
1644 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1645 HeapRegion::GrainBytes);
1646 size_t num_regions_deleted = 0;
1647 MemRegion mr = _hrs->shrink_by(aligned_shrink_bytes, num_regions_deleted);
1649 assert(mr.end() == (HeapWord*)_g1_storage.high(), "Bad shrink!");
1650 if (mr.byte_size() > 0)
1651 _g1_storage.shrink_by(mr.byte_size());
1652 assert(mr.start() == (HeapWord*)_g1_storage.high(), "Bad shrink!");
1654 _g1_committed.set_end(mr.start());
1655 _expansion_regions += num_regions_deleted;
1657 // Tell the cardtable about it.
1658 Universe::heap()->barrier_set()->resize_covered_region(_g1_committed);
1660 // And the offset table as well.
1661 _bot_shared->resize(_g1_committed.word_size());
1663 HeapRegionRemSet::shrink_heap(n_regions());
1665 if (Verbose && PrintGC) {
1666 size_t new_mem_size = _g1_storage.committed_size();
1667 gclog_or_tty->print_cr("Shrinking garbage-first heap from %ldK by %ldK to %ldK",
1668 old_mem_size/K, aligned_shrink_bytes/K,
1669 new_mem_size/K);
1670 }
1671 }
1673 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1674 verify_region_sets_optional();
1676 release_gc_alloc_regions(true /* totally */);
1677 // Instead of tearing down / rebuilding the free lists here, we
1678 // could instead use the remove_all_pending() method on free_list to
1679 // remove only the ones that we need to remove.
1680 tear_down_region_lists(); // We will rebuild them in a moment.
1681 shrink_helper(shrink_bytes);
1682 rebuild_region_lists();
1684 verify_region_sets_optional();
1685 }
1687 // Public methods.
1689 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1690 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1691 #endif // _MSC_VER
1694 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1695 SharedHeap(policy_),
1696 _g1_policy(policy_),
1697 _dirty_card_queue_set(false),
1698 _into_cset_dirty_card_queue_set(false),
1699 _is_alive_closure(this),
1700 _ref_processor(NULL),
1701 _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
1702 _bot_shared(NULL),
1703 _objs_with_preserved_marks(NULL), _preserved_marks_of_objs(NULL),
1704 _evac_failure_scan_stack(NULL) ,
1705 _mark_in_progress(false),
1706 _cg1r(NULL), _summary_bytes_used(0),
1707 _refine_cte_cl(NULL),
1708 _full_collection(false),
1709 _free_list("Master Free List"),
1710 _secondary_free_list("Secondary Free List"),
1711 _humongous_set("Master Humongous Set"),
1712 _free_regions_coming(false),
1713 _young_list(new YoungList(this)),
1714 _gc_time_stamp(0),
1715 _surviving_young_words(NULL),
1716 _full_collections_completed(0),
1717 _in_cset_fast_test(NULL),
1718 _in_cset_fast_test_base(NULL),
1719 _dirty_cards_region_list(NULL) {
1720 _g1h = this; // To catch bugs.
1721 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
1722 vm_exit_during_initialization("Failed necessary allocation.");
1723 }
1725 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1727 int n_queues = MAX2((int)ParallelGCThreads, 1);
1728 _task_queues = new RefToScanQueueSet(n_queues);
1730 int n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1731 assert(n_rem_sets > 0, "Invariant.");
1733 HeapRegionRemSetIterator** iter_arr =
1734 NEW_C_HEAP_ARRAY(HeapRegionRemSetIterator*, n_queues);
1735 for (int i = 0; i < n_queues; i++) {
1736 iter_arr[i] = new HeapRegionRemSetIterator();
1737 }
1738 _rem_set_iterator = iter_arr;
1740 for (int i = 0; i < n_queues; i++) {
1741 RefToScanQueue* q = new RefToScanQueue();
1742 q->initialize();
1743 _task_queues->register_queue(i, q);
1744 }
1746 for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
1747 _gc_alloc_regions[ap] = NULL;
1748 _gc_alloc_region_counts[ap] = 0;
1749 _retained_gc_alloc_regions[ap] = NULL;
1750 // by default, we do not retain a GC alloc region for each ap;
1751 // we'll override this, when appropriate, below
1752 _retain_gc_alloc_region[ap] = false;
1753 }
1755 // We will try to remember the last half-full tenured region we
1756 // allocated to at the end of a collection so that we can re-use it
1757 // during the next collection.
1758 _retain_gc_alloc_region[GCAllocForTenured] = true;
1760 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1761 }
1763 jint G1CollectedHeap::initialize() {
1764 CollectedHeap::pre_initialize();
1765 os::enable_vtime();
1767 // Necessary to satisfy locking discipline assertions.
1769 MutexLocker x(Heap_lock);
1771 // While there are no constraints in the GC code that HeapWordSize
1772 // be any particular value, there are multiple other areas in the
1773 // system which believe this to be true (e.g. oop->object_size in some
1774 // cases incorrectly returns the size in wordSize units rather than
1775 // HeapWordSize).
1776 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1778 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1779 size_t max_byte_size = collector_policy()->max_heap_byte_size();
1781 // Ensure that the sizes are properly aligned.
1782 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1783 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1785 _cg1r = new ConcurrentG1Refine();
1787 // Reserve the maximum.
1788 PermanentGenerationSpec* pgs = collector_policy()->permanent_generation();
1789 // Includes the perm-gen.
1791 const size_t total_reserved = max_byte_size + pgs->max_size();
1792 char* addr = Universe::preferred_heap_base(total_reserved, Universe::UnscaledNarrowOop);
1794 ReservedSpace heap_rs(max_byte_size + pgs->max_size(),
1795 HeapRegion::GrainBytes,
1796 UseLargePages, addr);
1798 if (UseCompressedOops) {
1799 if (addr != NULL && !heap_rs.is_reserved()) {
1800 // Failed to reserve at specified address - the requested memory
1801 // region is taken already, for example, by 'java' launcher.
1802 // Try again to reserver heap higher.
1803 addr = Universe::preferred_heap_base(total_reserved, Universe::ZeroBasedNarrowOop);
1804 ReservedSpace heap_rs0(total_reserved, HeapRegion::GrainBytes,
1805 UseLargePages, addr);
1806 if (addr != NULL && !heap_rs0.is_reserved()) {
1807 // Failed to reserve at specified address again - give up.
1808 addr = Universe::preferred_heap_base(total_reserved, Universe::HeapBasedNarrowOop);
1809 assert(addr == NULL, "");
1810 ReservedSpace heap_rs1(total_reserved, HeapRegion::GrainBytes,
1811 UseLargePages, addr);
1812 heap_rs = heap_rs1;
1813 } else {
1814 heap_rs = heap_rs0;
1815 }
1816 }
1817 }
1819 if (!heap_rs.is_reserved()) {
1820 vm_exit_during_initialization("Could not reserve enough space for object heap");
1821 return JNI_ENOMEM;
1822 }
1824 // It is important to do this in a way such that concurrent readers can't
1825 // temporarily think somethings in the heap. (I've actually seen this
1826 // happen in asserts: DLD.)
1827 _reserved.set_word_size(0);
1828 _reserved.set_start((HeapWord*)heap_rs.base());
1829 _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size()));
1831 _expansion_regions = max_byte_size/HeapRegion::GrainBytes;
1833 // Create the gen rem set (and barrier set) for the entire reserved region.
1834 _rem_set = collector_policy()->create_rem_set(_reserved, 2);
1835 set_barrier_set(rem_set()->bs());
1836 if (barrier_set()->is_a(BarrierSet::ModRef)) {
1837 _mr_bs = (ModRefBarrierSet*)_barrier_set;
1838 } else {
1839 vm_exit_during_initialization("G1 requires a mod ref bs.");
1840 return JNI_ENOMEM;
1841 }
1843 // Also create a G1 rem set.
1844 if (mr_bs()->is_a(BarrierSet::CardTableModRef)) {
1845 _g1_rem_set = new G1RemSet(this, (CardTableModRefBS*)mr_bs());
1846 } else {
1847 vm_exit_during_initialization("G1 requires a cardtable mod ref bs.");
1848 return JNI_ENOMEM;
1849 }
1851 // Carve out the G1 part of the heap.
1853 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1854 _g1_reserved = MemRegion((HeapWord*)g1_rs.base(),
1855 g1_rs.size()/HeapWordSize);
1856 ReservedSpace perm_gen_rs = heap_rs.last_part(max_byte_size);
1858 _perm_gen = pgs->init(perm_gen_rs, pgs->init_size(), rem_set());
1860 _g1_storage.initialize(g1_rs, 0);
1861 _g1_committed = MemRegion((HeapWord*)_g1_storage.low(), (size_t) 0);
1862 _g1_max_committed = _g1_committed;
1863 _hrs = new HeapRegionSeq(_expansion_regions);
1864 guarantee(_hrs != NULL, "Couldn't allocate HeapRegionSeq");
1866 // 6843694 - ensure that the maximum region index can fit
1867 // in the remembered set structures.
1868 const size_t max_region_idx = ((size_t)1 << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1869 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1871 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1872 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1873 guarantee((size_t) HeapRegion::CardsPerRegion < max_cards_per_region,
1874 "too many cards per region");
1876 HeapRegionSet::set_unrealistically_long_length(max_regions() + 1);
1878 _bot_shared = new G1BlockOffsetSharedArray(_reserved,
1879 heap_word_size(init_byte_size));
1881 _g1h = this;
1883 _in_cset_fast_test_length = max_regions();
1884 _in_cset_fast_test_base = NEW_C_HEAP_ARRAY(bool, _in_cset_fast_test_length);
1886 // We're biasing _in_cset_fast_test to avoid subtracting the
1887 // beginning of the heap every time we want to index; basically
1888 // it's the same with what we do with the card table.
1889 _in_cset_fast_test = _in_cset_fast_test_base -
1890 ((size_t) _g1_reserved.start() >> HeapRegion::LogOfHRGrainBytes);
1892 // Clear the _cset_fast_test bitmap in anticipation of adding
1893 // regions to the incremental collection set for the first
1894 // evacuation pause.
1895 clear_cset_fast_test();
1897 // Create the ConcurrentMark data structure and thread.
1898 // (Must do this late, so that "max_regions" is defined.)
1899 _cm = new ConcurrentMark(heap_rs, (int) max_regions());
1900 _cmThread = _cm->cmThread();
1902 // Initialize the from_card cache structure of HeapRegionRemSet.
1903 HeapRegionRemSet::init_heap(max_regions());
1905 // Now expand into the initial heap size.
1906 if (!expand(init_byte_size)) {
1907 vm_exit_during_initialization("Failed to allocate initial heap.");
1908 return JNI_ENOMEM;
1909 }
1911 // Perform any initialization actions delegated to the policy.
1912 g1_policy()->init();
1914 g1_policy()->note_start_of_mark_thread();
1916 _refine_cte_cl =
1917 new RefineCardTableEntryClosure(ConcurrentG1RefineThread::sts(),
1918 g1_rem_set(),
1919 concurrent_g1_refine());
1920 JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
1922 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
1923 SATB_Q_FL_lock,
1924 G1SATBProcessCompletedThreshold,
1925 Shared_SATB_Q_lock);
1927 JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1928 DirtyCardQ_FL_lock,
1929 concurrent_g1_refine()->yellow_zone(),
1930 concurrent_g1_refine()->red_zone(),
1931 Shared_DirtyCardQ_lock);
1933 if (G1DeferredRSUpdate) {
1934 dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1935 DirtyCardQ_FL_lock,
1936 -1, // never trigger processing
1937 -1, // no limit on length
1938 Shared_DirtyCardQ_lock,
1939 &JavaThread::dirty_card_queue_set());
1940 }
1942 // Initialize the card queue set used to hold cards containing
1943 // references into the collection set.
1944 _into_cset_dirty_card_queue_set.initialize(DirtyCardQ_CBL_mon,
1945 DirtyCardQ_FL_lock,
1946 -1, // never trigger processing
1947 -1, // no limit on length
1948 Shared_DirtyCardQ_lock,
1949 &JavaThread::dirty_card_queue_set());
1951 // In case we're keeping closure specialization stats, initialize those
1952 // counts and that mechanism.
1953 SpecializationStats::clear();
1955 _gc_alloc_region_list = NULL;
1957 // Do later initialization work for concurrent refinement.
1958 _cg1r->init();
1960 // Here we allocate the dummy full region that is required by the
1961 // G1AllocRegion class. If we don't pass an address in the reserved
1962 // space here, lots of asserts fire.
1963 MemRegion mr(_g1_reserved.start(), HeapRegion::GrainWords);
1964 HeapRegion* dummy_region = new HeapRegion(_bot_shared, mr, true);
1965 // We'll re-use the same region whether the alloc region will
1966 // require BOT updates or not and, if it doesn't, then a non-young
1967 // region will complain that it cannot support allocations without
1968 // BOT updates. So we'll tag the dummy region as young to avoid that.
1969 dummy_region->set_young();
1970 // Make sure it's full.
1971 dummy_region->set_top(dummy_region->end());
1972 G1AllocRegion::setup(this, dummy_region);
1974 init_mutator_alloc_region();
1976 // Do create of the monitoring and management support so that
1977 // values in the heap have been properly initialized.
1978 _g1mm = new G1MonitoringSupport(this, &_g1_storage);
1980 return JNI_OK;
1981 }
1983 void G1CollectedHeap::ref_processing_init() {
1984 // Reference processing in G1 currently works as follows:
1985 //
1986 // * There is only one reference processor instance that
1987 // 'spans' the entire heap. It is created by the code
1988 // below.
1989 // * Reference discovery is not enabled during an incremental
1990 // pause (see 6484982).
1991 // * Discoverered refs are not enqueued nor are they processed
1992 // during an incremental pause (see 6484982).
1993 // * Reference discovery is enabled at initial marking.
1994 // * Reference discovery is disabled and the discovered
1995 // references processed etc during remarking.
1996 // * Reference discovery is MT (see below).
1997 // * Reference discovery requires a barrier (see below).
1998 // * Reference processing is currently not MT (see 6608385).
1999 // * A full GC enables (non-MT) reference discovery and
2000 // processes any discovered references.
2002 SharedHeap::ref_processing_init();
2003 MemRegion mr = reserved_region();
2004 _ref_processor =
2005 new ReferenceProcessor(mr, // span
2006 ParallelRefProcEnabled && (ParallelGCThreads > 1), // mt processing
2007 (int) ParallelGCThreads, // degree of mt processing
2008 ParallelGCThreads > 1 || ConcGCThreads > 1, // mt discovery
2009 (int) MAX2(ParallelGCThreads, ConcGCThreads), // degree of mt discovery
2010 false, // Reference discovery is not atomic
2011 &_is_alive_closure, // is alive closure for efficiency
2012 true); // Setting next fields of discovered
2013 // lists requires a barrier.
2014 }
2016 size_t G1CollectedHeap::capacity() const {
2017 return _g1_committed.byte_size();
2018 }
2020 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2021 DirtyCardQueue* into_cset_dcq,
2022 bool concurrent,
2023 int worker_i) {
2024 // Clean cards in the hot card cache
2025 concurrent_g1_refine()->clean_up_cache(worker_i, g1_rem_set(), into_cset_dcq);
2027 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2028 int n_completed_buffers = 0;
2029 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2030 n_completed_buffers++;
2031 }
2032 g1_policy()->record_update_rs_processed_buffers(worker_i,
2033 (double) n_completed_buffers);
2034 dcqs.clear_n_completed_buffers();
2035 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2036 }
2039 // Computes the sum of the storage used by the various regions.
2041 size_t G1CollectedHeap::used() const {
2042 assert(Heap_lock->owner() != NULL,
2043 "Should be owned on this thread's behalf.");
2044 size_t result = _summary_bytes_used;
2045 // Read only once in case it is set to NULL concurrently
2046 HeapRegion* hr = _mutator_alloc_region.get();
2047 if (hr != NULL)
2048 result += hr->used();
2049 return result;
2050 }
2052 size_t G1CollectedHeap::used_unlocked() const {
2053 size_t result = _summary_bytes_used;
2054 return result;
2055 }
2057 class SumUsedClosure: public HeapRegionClosure {
2058 size_t _used;
2059 public:
2060 SumUsedClosure() : _used(0) {}
2061 bool doHeapRegion(HeapRegion* r) {
2062 if (!r->continuesHumongous()) {
2063 _used += r->used();
2064 }
2065 return false;
2066 }
2067 size_t result() { return _used; }
2068 };
2070 size_t G1CollectedHeap::recalculate_used() const {
2071 SumUsedClosure blk;
2072 _hrs->iterate(&blk);
2073 return blk.result();
2074 }
2076 #ifndef PRODUCT
2077 class SumUsedRegionsClosure: public HeapRegionClosure {
2078 size_t _num;
2079 public:
2080 SumUsedRegionsClosure() : _num(0) {}
2081 bool doHeapRegion(HeapRegion* r) {
2082 if (r->continuesHumongous() || r->used() > 0 || r->is_gc_alloc_region()) {
2083 _num += 1;
2084 }
2085 return false;
2086 }
2087 size_t result() { return _num; }
2088 };
2090 size_t G1CollectedHeap::recalculate_used_regions() const {
2091 SumUsedRegionsClosure blk;
2092 _hrs->iterate(&blk);
2093 return blk.result();
2094 }
2095 #endif // PRODUCT
2097 size_t G1CollectedHeap::unsafe_max_alloc() {
2098 if (free_regions() > 0) return HeapRegion::GrainBytes;
2099 // otherwise, is there space in the current allocation region?
2101 // We need to store the current allocation region in a local variable
2102 // here. The problem is that this method doesn't take any locks and
2103 // there may be other threads which overwrite the current allocation
2104 // region field. attempt_allocation(), for example, sets it to NULL
2105 // and this can happen *after* the NULL check here but before the call
2106 // to free(), resulting in a SIGSEGV. Note that this doesn't appear
2107 // to be a problem in the optimized build, since the two loads of the
2108 // current allocation region field are optimized away.
2109 HeapRegion* hr = _mutator_alloc_region.get();
2110 if (hr == NULL) {
2111 return 0;
2112 }
2113 return hr->free();
2114 }
2116 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2117 return
2118 ((cause == GCCause::_gc_locker && GCLockerInvokesConcurrent) ||
2119 (cause == GCCause::_java_lang_system_gc && ExplicitGCInvokesConcurrent));
2120 }
2122 #ifndef PRODUCT
2123 void G1CollectedHeap::allocate_dummy_regions() {
2124 // Let's fill up most of the region
2125 size_t word_size = HeapRegion::GrainWords - 1024;
2126 // And as a result the region we'll allocate will be humongous.
2127 guarantee(isHumongous(word_size), "sanity");
2129 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2130 // Let's use the existing mechanism for the allocation
2131 HeapWord* dummy_obj = humongous_obj_allocate(word_size);
2132 if (dummy_obj != NULL) {
2133 MemRegion mr(dummy_obj, word_size);
2134 CollectedHeap::fill_with_object(mr);
2135 } else {
2136 // If we can't allocate once, we probably cannot allocate
2137 // again. Let's get out of the loop.
2138 break;
2139 }
2140 }
2141 }
2142 #endif // !PRODUCT
2144 void G1CollectedHeap::increment_full_collections_completed(bool concurrent) {
2145 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2147 // We assume that if concurrent == true, then the caller is a
2148 // concurrent thread that was joined the Suspendible Thread
2149 // Set. If there's ever a cheap way to check this, we should add an
2150 // assert here.
2152 // We have already incremented _total_full_collections at the start
2153 // of the GC, so total_full_collections() represents how many full
2154 // collections have been started.
2155 unsigned int full_collections_started = total_full_collections();
2157 // Given that this method is called at the end of a Full GC or of a
2158 // concurrent cycle, and those can be nested (i.e., a Full GC can
2159 // interrupt a concurrent cycle), the number of full collections
2160 // completed should be either one (in the case where there was no
2161 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2162 // behind the number of full collections started.
2164 // This is the case for the inner caller, i.e. a Full GC.
2165 assert(concurrent ||
2166 (full_collections_started == _full_collections_completed + 1) ||
2167 (full_collections_started == _full_collections_completed + 2),
2168 err_msg("for inner caller (Full GC): full_collections_started = %u "
2169 "is inconsistent with _full_collections_completed = %u",
2170 full_collections_started, _full_collections_completed));
2172 // This is the case for the outer caller, i.e. the concurrent cycle.
2173 assert(!concurrent ||
2174 (full_collections_started == _full_collections_completed + 1),
2175 err_msg("for outer caller (concurrent cycle): "
2176 "full_collections_started = %u "
2177 "is inconsistent with _full_collections_completed = %u",
2178 full_collections_started, _full_collections_completed));
2180 _full_collections_completed += 1;
2182 // We need to clear the "in_progress" flag in the CM thread before
2183 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2184 // is set) so that if a waiter requests another System.gc() it doesn't
2185 // incorrectly see that a marking cyle is still in progress.
2186 if (concurrent) {
2187 _cmThread->clear_in_progress();
2188 }
2190 // This notify_all() will ensure that a thread that called
2191 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2192 // and it's waiting for a full GC to finish will be woken up. It is
2193 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2194 FullGCCount_lock->notify_all();
2195 }
2197 void G1CollectedHeap::collect_as_vm_thread(GCCause::Cause cause) {
2198 assert_at_safepoint(true /* should_be_vm_thread */);
2199 GCCauseSetter gcs(this, cause);
2200 switch (cause) {
2201 case GCCause::_heap_inspection:
2202 case GCCause::_heap_dump: {
2203 HandleMark hm;
2204 do_full_collection(false); // don't clear all soft refs
2205 break;
2206 }
2207 default: // XXX FIX ME
2208 ShouldNotReachHere(); // Unexpected use of this function
2209 }
2210 }
2212 void G1CollectedHeap::collect(GCCause::Cause cause) {
2213 // The caller doesn't have the Heap_lock
2214 assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock");
2216 unsigned int gc_count_before;
2217 unsigned int full_gc_count_before;
2218 {
2219 MutexLocker ml(Heap_lock);
2221 // Read the GC count while holding the Heap_lock
2222 gc_count_before = SharedHeap::heap()->total_collections();
2223 full_gc_count_before = SharedHeap::heap()->total_full_collections();
2224 }
2226 if (should_do_concurrent_full_gc(cause)) {
2227 // Schedule an initial-mark evacuation pause that will start a
2228 // concurrent cycle. We're setting word_size to 0 which means that
2229 // we are not requesting a post-GC allocation.
2230 VM_G1IncCollectionPause op(gc_count_before,
2231 0, /* word_size */
2232 true, /* should_initiate_conc_mark */
2233 g1_policy()->max_pause_time_ms(),
2234 cause);
2235 VMThread::execute(&op);
2236 } else {
2237 if (cause == GCCause::_gc_locker
2238 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2240 // Schedule a standard evacuation pause. We're setting word_size
2241 // to 0 which means that we are not requesting a post-GC allocation.
2242 VM_G1IncCollectionPause op(gc_count_before,
2243 0, /* word_size */
2244 false, /* should_initiate_conc_mark */
2245 g1_policy()->max_pause_time_ms(),
2246 cause);
2247 VMThread::execute(&op);
2248 } else {
2249 // Schedule a Full GC.
2250 VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2251 VMThread::execute(&op);
2252 }
2253 }
2254 }
2256 bool G1CollectedHeap::is_in(const void* p) const {
2257 if (_g1_committed.contains(p)) {
2258 HeapRegion* hr = _hrs->addr_to_region(p);
2259 return hr->is_in(p);
2260 } else {
2261 return _perm_gen->as_gen()->is_in(p);
2262 }
2263 }
2265 // Iteration functions.
2267 // Iterates an OopClosure over all ref-containing fields of objects
2268 // within a HeapRegion.
2270 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2271 MemRegion _mr;
2272 OopClosure* _cl;
2273 public:
2274 IterateOopClosureRegionClosure(MemRegion mr, OopClosure* cl)
2275 : _mr(mr), _cl(cl) {}
2276 bool doHeapRegion(HeapRegion* r) {
2277 if (! r->continuesHumongous()) {
2278 r->oop_iterate(_cl);
2279 }
2280 return false;
2281 }
2282 };
2284 void G1CollectedHeap::oop_iterate(OopClosure* cl, bool do_perm) {
2285 IterateOopClosureRegionClosure blk(_g1_committed, cl);
2286 _hrs->iterate(&blk);
2287 if (do_perm) {
2288 perm_gen()->oop_iterate(cl);
2289 }
2290 }
2292 void G1CollectedHeap::oop_iterate(MemRegion mr, OopClosure* cl, bool do_perm) {
2293 IterateOopClosureRegionClosure blk(mr, cl);
2294 _hrs->iterate(&blk);
2295 if (do_perm) {
2296 perm_gen()->oop_iterate(cl);
2297 }
2298 }
2300 // Iterates an ObjectClosure over all objects within a HeapRegion.
2302 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2303 ObjectClosure* _cl;
2304 public:
2305 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2306 bool doHeapRegion(HeapRegion* r) {
2307 if (! r->continuesHumongous()) {
2308 r->object_iterate(_cl);
2309 }
2310 return false;
2311 }
2312 };
2314 void G1CollectedHeap::object_iterate(ObjectClosure* cl, bool do_perm) {
2315 IterateObjectClosureRegionClosure blk(cl);
2316 _hrs->iterate(&blk);
2317 if (do_perm) {
2318 perm_gen()->object_iterate(cl);
2319 }
2320 }
2322 void G1CollectedHeap::object_iterate_since_last_GC(ObjectClosure* cl) {
2323 // FIXME: is this right?
2324 guarantee(false, "object_iterate_since_last_GC not supported by G1 heap");
2325 }
2327 // Calls a SpaceClosure on a HeapRegion.
2329 class SpaceClosureRegionClosure: public HeapRegionClosure {
2330 SpaceClosure* _cl;
2331 public:
2332 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2333 bool doHeapRegion(HeapRegion* r) {
2334 _cl->do_space(r);
2335 return false;
2336 }
2337 };
2339 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2340 SpaceClosureRegionClosure blk(cl);
2341 _hrs->iterate(&blk);
2342 }
2344 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) {
2345 _hrs->iterate(cl);
2346 }
2348 void G1CollectedHeap::heap_region_iterate_from(HeapRegion* r,
2349 HeapRegionClosure* cl) {
2350 _hrs->iterate_from(r, cl);
2351 }
2353 void
2354 G1CollectedHeap::heap_region_iterate_from(int idx, HeapRegionClosure* cl) {
2355 _hrs->iterate_from(idx, cl);
2356 }
2358 HeapRegion* G1CollectedHeap::region_at(size_t idx) { return _hrs->at(idx); }
2360 void
2361 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
2362 int worker,
2363 jint claim_value) {
2364 const size_t regions = n_regions();
2365 const size_t worker_num = (G1CollectedHeap::use_parallel_gc_threads() ? ParallelGCThreads : 1);
2366 // try to spread out the starting points of the workers
2367 const size_t start_index = regions / worker_num * (size_t) worker;
2369 // each worker will actually look at all regions
2370 for (size_t count = 0; count < regions; ++count) {
2371 const size_t index = (start_index + count) % regions;
2372 assert(0 <= index && index < regions, "sanity");
2373 HeapRegion* r = region_at(index);
2374 // we'll ignore "continues humongous" regions (we'll process them
2375 // when we come across their corresponding "start humongous"
2376 // region) and regions already claimed
2377 if (r->claim_value() == claim_value || r->continuesHumongous()) {
2378 continue;
2379 }
2380 // OK, try to claim it
2381 if (r->claimHeapRegion(claim_value)) {
2382 // success!
2383 assert(!r->continuesHumongous(), "sanity");
2384 if (r->startsHumongous()) {
2385 // If the region is "starts humongous" we'll iterate over its
2386 // "continues humongous" first; in fact we'll do them
2387 // first. The order is important. In on case, calling the
2388 // closure on the "starts humongous" region might de-allocate
2389 // and clear all its "continues humongous" regions and, as a
2390 // result, we might end up processing them twice. So, we'll do
2391 // them first (notice: most closures will ignore them anyway) and
2392 // then we'll do the "starts humongous" region.
2393 for (size_t ch_index = index + 1; ch_index < regions; ++ch_index) {
2394 HeapRegion* chr = region_at(ch_index);
2396 // if the region has already been claimed or it's not
2397 // "continues humongous" we're done
2398 if (chr->claim_value() == claim_value ||
2399 !chr->continuesHumongous()) {
2400 break;
2401 }
2403 // Noone should have claimed it directly. We can given
2404 // that we claimed its "starts humongous" region.
2405 assert(chr->claim_value() != claim_value, "sanity");
2406 assert(chr->humongous_start_region() == r, "sanity");
2408 if (chr->claimHeapRegion(claim_value)) {
2409 // we should always be able to claim it; noone else should
2410 // be trying to claim this region
2412 bool res2 = cl->doHeapRegion(chr);
2413 assert(!res2, "Should not abort");
2415 // Right now, this holds (i.e., no closure that actually
2416 // does something with "continues humongous" regions
2417 // clears them). We might have to weaken it in the future,
2418 // but let's leave these two asserts here for extra safety.
2419 assert(chr->continuesHumongous(), "should still be the case");
2420 assert(chr->humongous_start_region() == r, "sanity");
2421 } else {
2422 guarantee(false, "we should not reach here");
2423 }
2424 }
2425 }
2427 assert(!r->continuesHumongous(), "sanity");
2428 bool res = cl->doHeapRegion(r);
2429 assert(!res, "Should not abort");
2430 }
2431 }
2432 }
2434 class ResetClaimValuesClosure: public HeapRegionClosure {
2435 public:
2436 bool doHeapRegion(HeapRegion* r) {
2437 r->set_claim_value(HeapRegion::InitialClaimValue);
2438 return false;
2439 }
2440 };
2442 void
2443 G1CollectedHeap::reset_heap_region_claim_values() {
2444 ResetClaimValuesClosure blk;
2445 heap_region_iterate(&blk);
2446 }
2448 #ifdef ASSERT
2449 // This checks whether all regions in the heap have the correct claim
2450 // value. I also piggy-backed on this a check to ensure that the
2451 // humongous_start_region() information on "continues humongous"
2452 // regions is correct.
2454 class CheckClaimValuesClosure : public HeapRegionClosure {
2455 private:
2456 jint _claim_value;
2457 size_t _failures;
2458 HeapRegion* _sh_region;
2459 public:
2460 CheckClaimValuesClosure(jint claim_value) :
2461 _claim_value(claim_value), _failures(0), _sh_region(NULL) { }
2462 bool doHeapRegion(HeapRegion* r) {
2463 if (r->claim_value() != _claim_value) {
2464 gclog_or_tty->print_cr("Region ["PTR_FORMAT","PTR_FORMAT"), "
2465 "claim value = %d, should be %d",
2466 r->bottom(), r->end(), r->claim_value(),
2467 _claim_value);
2468 ++_failures;
2469 }
2470 if (!r->isHumongous()) {
2471 _sh_region = NULL;
2472 } else if (r->startsHumongous()) {
2473 _sh_region = r;
2474 } else if (r->continuesHumongous()) {
2475 if (r->humongous_start_region() != _sh_region) {
2476 gclog_or_tty->print_cr("Region ["PTR_FORMAT","PTR_FORMAT"), "
2477 "HS = "PTR_FORMAT", should be "PTR_FORMAT,
2478 r->bottom(), r->end(),
2479 r->humongous_start_region(),
2480 _sh_region);
2481 ++_failures;
2482 }
2483 }
2484 return false;
2485 }
2486 size_t failures() {
2487 return _failures;
2488 }
2489 };
2491 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
2492 CheckClaimValuesClosure cl(claim_value);
2493 heap_region_iterate(&cl);
2494 return cl.failures() == 0;
2495 }
2496 #endif // ASSERT
2498 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2499 HeapRegion* r = g1_policy()->collection_set();
2500 while (r != NULL) {
2501 HeapRegion* next = r->next_in_collection_set();
2502 if (cl->doHeapRegion(r)) {
2503 cl->incomplete();
2504 return;
2505 }
2506 r = next;
2507 }
2508 }
2510 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2511 HeapRegionClosure *cl) {
2512 if (r == NULL) {
2513 // The CSet is empty so there's nothing to do.
2514 return;
2515 }
2517 assert(r->in_collection_set(),
2518 "Start region must be a member of the collection set.");
2519 HeapRegion* cur = r;
2520 while (cur != NULL) {
2521 HeapRegion* next = cur->next_in_collection_set();
2522 if (cl->doHeapRegion(cur) && false) {
2523 cl->incomplete();
2524 return;
2525 }
2526 cur = next;
2527 }
2528 cur = g1_policy()->collection_set();
2529 while (cur != r) {
2530 HeapRegion* next = cur->next_in_collection_set();
2531 if (cl->doHeapRegion(cur) && false) {
2532 cl->incomplete();
2533 return;
2534 }
2535 cur = next;
2536 }
2537 }
2539 CompactibleSpace* G1CollectedHeap::first_compactible_space() {
2540 return _hrs->length() > 0 ? _hrs->at(0) : NULL;
2541 }
2544 Space* G1CollectedHeap::space_containing(const void* addr) const {
2545 Space* res = heap_region_containing(addr);
2546 if (res == NULL)
2547 res = perm_gen()->space_containing(addr);
2548 return res;
2549 }
2551 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2552 Space* sp = space_containing(addr);
2553 if (sp != NULL) {
2554 return sp->block_start(addr);
2555 }
2556 return NULL;
2557 }
2559 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2560 Space* sp = space_containing(addr);
2561 assert(sp != NULL, "block_size of address outside of heap");
2562 return sp->block_size(addr);
2563 }
2565 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2566 Space* sp = space_containing(addr);
2567 return sp->block_is_obj(addr);
2568 }
2570 bool G1CollectedHeap::supports_tlab_allocation() const {
2571 return true;
2572 }
2574 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2575 return HeapRegion::GrainBytes;
2576 }
2578 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2579 // Return the remaining space in the cur alloc region, but not less than
2580 // the min TLAB size.
2582 // Also, this value can be at most the humongous object threshold,
2583 // since we can't allow tlabs to grow big enough to accomodate
2584 // humongous objects.
2586 HeapRegion* hr = _mutator_alloc_region.get();
2587 size_t max_tlab_size = _humongous_object_threshold_in_words * wordSize;
2588 if (hr == NULL) {
2589 return max_tlab_size;
2590 } else {
2591 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab_size);
2592 }
2593 }
2595 size_t G1CollectedHeap::large_typearray_limit() {
2596 // FIXME
2597 return HeapRegion::GrainBytes/HeapWordSize;
2598 }
2600 size_t G1CollectedHeap::max_capacity() const {
2601 return _g1_reserved.byte_size();
2602 }
2604 jlong G1CollectedHeap::millis_since_last_gc() {
2605 // assert(false, "NYI");
2606 return 0;
2607 }
2609 void G1CollectedHeap::prepare_for_verify() {
2610 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
2611 ensure_parsability(false);
2612 }
2613 g1_rem_set()->prepare_for_verify();
2614 }
2616 class VerifyLivenessOopClosure: public OopClosure {
2617 G1CollectedHeap* g1h;
2618 public:
2619 VerifyLivenessOopClosure(G1CollectedHeap* _g1h) {
2620 g1h = _g1h;
2621 }
2622 void do_oop(narrowOop *p) { do_oop_work(p); }
2623 void do_oop( oop *p) { do_oop_work(p); }
2625 template <class T> void do_oop_work(T *p) {
2626 oop obj = oopDesc::load_decode_heap_oop(p);
2627 guarantee(obj == NULL || !g1h->is_obj_dead(obj),
2628 "Dead object referenced by a not dead object");
2629 }
2630 };
2632 class VerifyObjsInRegionClosure: public ObjectClosure {
2633 private:
2634 G1CollectedHeap* _g1h;
2635 size_t _live_bytes;
2636 HeapRegion *_hr;
2637 bool _use_prev_marking;
2638 public:
2639 // use_prev_marking == true -> use "prev" marking information,
2640 // use_prev_marking == false -> use "next" marking information
2641 VerifyObjsInRegionClosure(HeapRegion *hr, bool use_prev_marking)
2642 : _live_bytes(0), _hr(hr), _use_prev_marking(use_prev_marking) {
2643 _g1h = G1CollectedHeap::heap();
2644 }
2645 void do_object(oop o) {
2646 VerifyLivenessOopClosure isLive(_g1h);
2647 assert(o != NULL, "Huh?");
2648 if (!_g1h->is_obj_dead_cond(o, _use_prev_marking)) {
2649 o->oop_iterate(&isLive);
2650 if (!_hr->obj_allocated_since_prev_marking(o)) {
2651 size_t obj_size = o->size(); // Make sure we don't overflow
2652 _live_bytes += (obj_size * HeapWordSize);
2653 }
2654 }
2655 }
2656 size_t live_bytes() { return _live_bytes; }
2657 };
2659 class PrintObjsInRegionClosure : public ObjectClosure {
2660 HeapRegion *_hr;
2661 G1CollectedHeap *_g1;
2662 public:
2663 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
2664 _g1 = G1CollectedHeap::heap();
2665 };
2667 void do_object(oop o) {
2668 if (o != NULL) {
2669 HeapWord *start = (HeapWord *) o;
2670 size_t word_sz = o->size();
2671 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
2672 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
2673 (void*) o, word_sz,
2674 _g1->isMarkedPrev(o),
2675 _g1->isMarkedNext(o),
2676 _hr->obj_allocated_since_prev_marking(o));
2677 HeapWord *end = start + word_sz;
2678 HeapWord *cur;
2679 int *val;
2680 for (cur = start; cur < end; cur++) {
2681 val = (int *) cur;
2682 gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val);
2683 }
2684 }
2685 }
2686 };
2688 class VerifyRegionClosure: public HeapRegionClosure {
2689 private:
2690 bool _allow_dirty;
2691 bool _par;
2692 bool _use_prev_marking;
2693 bool _failures;
2694 public:
2695 // use_prev_marking == true -> use "prev" marking information,
2696 // use_prev_marking == false -> use "next" marking information
2697 VerifyRegionClosure(bool allow_dirty, bool par, bool use_prev_marking)
2698 : _allow_dirty(allow_dirty),
2699 _par(par),
2700 _use_prev_marking(use_prev_marking),
2701 _failures(false) {}
2703 bool failures() {
2704 return _failures;
2705 }
2707 bool doHeapRegion(HeapRegion* r) {
2708 guarantee(_par || r->claim_value() == HeapRegion::InitialClaimValue,
2709 "Should be unclaimed at verify points.");
2710 if (!r->continuesHumongous()) {
2711 bool failures = false;
2712 r->verify(_allow_dirty, _use_prev_marking, &failures);
2713 if (failures) {
2714 _failures = true;
2715 } else {
2716 VerifyObjsInRegionClosure not_dead_yet_cl(r, _use_prev_marking);
2717 r->object_iterate(¬_dead_yet_cl);
2718 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
2719 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
2720 "max_live_bytes "SIZE_FORMAT" "
2721 "< calculated "SIZE_FORMAT,
2722 r->bottom(), r->end(),
2723 r->max_live_bytes(),
2724 not_dead_yet_cl.live_bytes());
2725 _failures = true;
2726 }
2727 }
2728 }
2729 return false; // stop the region iteration if we hit a failure
2730 }
2731 };
2733 class VerifyRootsClosure: public OopsInGenClosure {
2734 private:
2735 G1CollectedHeap* _g1h;
2736 bool _use_prev_marking;
2737 bool _failures;
2738 public:
2739 // use_prev_marking == true -> use "prev" marking information,
2740 // use_prev_marking == false -> use "next" marking information
2741 VerifyRootsClosure(bool use_prev_marking) :
2742 _g1h(G1CollectedHeap::heap()),
2743 _use_prev_marking(use_prev_marking),
2744 _failures(false) { }
2746 bool failures() { return _failures; }
2748 template <class T> void do_oop_nv(T* p) {
2749 T heap_oop = oopDesc::load_heap_oop(p);
2750 if (!oopDesc::is_null(heap_oop)) {
2751 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2752 if (_g1h->is_obj_dead_cond(obj, _use_prev_marking)) {
2753 gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
2754 "points to dead obj "PTR_FORMAT, p, (void*) obj);
2755 obj->print_on(gclog_or_tty);
2756 _failures = true;
2757 }
2758 }
2759 }
2761 void do_oop(oop* p) { do_oop_nv(p); }
2762 void do_oop(narrowOop* p) { do_oop_nv(p); }
2763 };
2765 // This is the task used for parallel heap verification.
2767 class G1ParVerifyTask: public AbstractGangTask {
2768 private:
2769 G1CollectedHeap* _g1h;
2770 bool _allow_dirty;
2771 bool _use_prev_marking;
2772 bool _failures;
2774 public:
2775 // use_prev_marking == true -> use "prev" marking information,
2776 // use_prev_marking == false -> use "next" marking information
2777 G1ParVerifyTask(G1CollectedHeap* g1h, bool allow_dirty,
2778 bool use_prev_marking) :
2779 AbstractGangTask("Parallel verify task"),
2780 _g1h(g1h),
2781 _allow_dirty(allow_dirty),
2782 _use_prev_marking(use_prev_marking),
2783 _failures(false) { }
2785 bool failures() {
2786 return _failures;
2787 }
2789 void work(int worker_i) {
2790 HandleMark hm;
2791 VerifyRegionClosure blk(_allow_dirty, true, _use_prev_marking);
2792 _g1h->heap_region_par_iterate_chunked(&blk, worker_i,
2793 HeapRegion::ParVerifyClaimValue);
2794 if (blk.failures()) {
2795 _failures = true;
2796 }
2797 }
2798 };
2800 void G1CollectedHeap::verify(bool allow_dirty, bool silent) {
2801 verify(allow_dirty, silent, /* use_prev_marking */ true);
2802 }
2804 void G1CollectedHeap::verify(bool allow_dirty,
2805 bool silent,
2806 bool use_prev_marking) {
2807 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
2808 if (!silent) { gclog_or_tty->print("Roots (excluding permgen) "); }
2809 VerifyRootsClosure rootsCl(use_prev_marking);
2810 CodeBlobToOopClosure blobsCl(&rootsCl, /*do_marking=*/ false);
2811 // We apply the relevant closures to all the oops in the
2812 // system dictionary, the string table and the code cache.
2813 const int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings | SharedHeap::SO_CodeCache;
2814 process_strong_roots(true, // activate StrongRootsScope
2815 true, // we set "collecting perm gen" to true,
2816 // so we don't reset the dirty cards in the perm gen.
2817 SharedHeap::ScanningOption(so), // roots scanning options
2818 &rootsCl,
2819 &blobsCl,
2820 &rootsCl);
2821 // Since we used "collecting_perm_gen" == true above, we will not have
2822 // checked the refs from perm into the G1-collected heap. We check those
2823 // references explicitly below. Whether the relevant cards are dirty
2824 // is checked further below in the rem set verification.
2825 if (!silent) { gclog_or_tty->print("Permgen roots "); }
2826 perm_gen()->oop_iterate(&rootsCl);
2827 bool failures = rootsCl.failures();
2828 if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
2829 verify_region_sets();
2830 if (!silent) { gclog_or_tty->print("HeapRegions "); }
2831 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
2832 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
2833 "sanity check");
2835 G1ParVerifyTask task(this, allow_dirty, use_prev_marking);
2836 int n_workers = workers()->total_workers();
2837 set_par_threads(n_workers);
2838 workers()->run_task(&task);
2839 set_par_threads(0);
2840 if (task.failures()) {
2841 failures = true;
2842 }
2844 assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
2845 "sanity check");
2847 reset_heap_region_claim_values();
2849 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
2850 "sanity check");
2851 } else {
2852 VerifyRegionClosure blk(allow_dirty, false, use_prev_marking);
2853 _hrs->iterate(&blk);
2854 if (blk.failures()) {
2855 failures = true;
2856 }
2857 }
2858 if (!silent) gclog_or_tty->print("RemSet ");
2859 rem_set()->verify();
2861 if (failures) {
2862 gclog_or_tty->print_cr("Heap:");
2863 print_on(gclog_or_tty, true /* extended */);
2864 gclog_or_tty->print_cr("");
2865 #ifndef PRODUCT
2866 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
2867 concurrent_mark()->print_reachable("at-verification-failure",
2868 use_prev_marking, false /* all */);
2869 }
2870 #endif
2871 gclog_or_tty->flush();
2872 }
2873 guarantee(!failures, "there should not have been any failures");
2874 } else {
2875 if (!silent) gclog_or_tty->print("(SKIPPING roots, heapRegions, remset) ");
2876 }
2877 }
2879 class PrintRegionClosure: public HeapRegionClosure {
2880 outputStream* _st;
2881 public:
2882 PrintRegionClosure(outputStream* st) : _st(st) {}
2883 bool doHeapRegion(HeapRegion* r) {
2884 r->print_on(_st);
2885 return false;
2886 }
2887 };
2889 void G1CollectedHeap::print() const { print_on(tty); }
2891 void G1CollectedHeap::print_on(outputStream* st) const {
2892 print_on(st, PrintHeapAtGCExtended);
2893 }
2895 void G1CollectedHeap::print_on(outputStream* st, bool extended) const {
2896 st->print(" %-20s", "garbage-first heap");
2897 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
2898 capacity()/K, used_unlocked()/K);
2899 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
2900 _g1_storage.low_boundary(),
2901 _g1_storage.high(),
2902 _g1_storage.high_boundary());
2903 st->cr();
2904 st->print(" region size " SIZE_FORMAT "K, ",
2905 HeapRegion::GrainBytes/K);
2906 size_t young_regions = _young_list->length();
2907 st->print(SIZE_FORMAT " young (" SIZE_FORMAT "K), ",
2908 young_regions, young_regions * HeapRegion::GrainBytes / K);
2909 size_t survivor_regions = g1_policy()->recorded_survivor_regions();
2910 st->print(SIZE_FORMAT " survivors (" SIZE_FORMAT "K)",
2911 survivor_regions, survivor_regions * HeapRegion::GrainBytes / K);
2912 st->cr();
2913 perm()->as_gen()->print_on(st);
2914 if (extended) {
2915 st->cr();
2916 print_on_extended(st);
2917 }
2918 }
2920 void G1CollectedHeap::print_on_extended(outputStream* st) const {
2921 PrintRegionClosure blk(st);
2922 _hrs->iterate(&blk);
2923 }
2925 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
2926 if (G1CollectedHeap::use_parallel_gc_threads()) {
2927 workers()->print_worker_threads_on(st);
2928 }
2929 _cmThread->print_on(st);
2930 st->cr();
2931 _cm->print_worker_threads_on(st);
2932 _cg1r->print_worker_threads_on(st);
2933 st->cr();
2934 }
2936 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2937 if (G1CollectedHeap::use_parallel_gc_threads()) {
2938 workers()->threads_do(tc);
2939 }
2940 tc->do_thread(_cmThread);
2941 _cg1r->threads_do(tc);
2942 }
2944 void G1CollectedHeap::print_tracing_info() const {
2945 // We'll overload this to mean "trace GC pause statistics."
2946 if (TraceGen0Time || TraceGen1Time) {
2947 // The "G1CollectorPolicy" is keeping track of these stats, so delegate
2948 // to that.
2949 g1_policy()->print_tracing_info();
2950 }
2951 if (G1SummarizeRSetStats) {
2952 g1_rem_set()->print_summary_info();
2953 }
2954 if (G1SummarizeConcMark) {
2955 concurrent_mark()->print_summary_info();
2956 }
2957 g1_policy()->print_yg_surv_rate_info();
2958 SpecializationStats::print();
2959 }
2961 int G1CollectedHeap::addr_to_arena_id(void* addr) const {
2962 HeapRegion* hr = heap_region_containing(addr);
2963 if (hr == NULL) {
2964 return 0;
2965 } else {
2966 return 1;
2967 }
2968 }
2970 G1CollectedHeap* G1CollectedHeap::heap() {
2971 assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
2972 "not a garbage-first heap");
2973 return _g1h;
2974 }
2976 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
2977 // always_do_update_barrier = false;
2978 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
2979 // Call allocation profiler
2980 AllocationProfiler::iterate_since_last_gc();
2981 // Fill TLAB's and such
2982 ensure_parsability(true);
2983 }
2985 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) {
2986 // FIXME: what is this about?
2987 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
2988 // is set.
2989 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
2990 "derived pointer present"));
2991 // always_do_update_barrier = true;
2992 }
2994 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2995 unsigned int gc_count_before,
2996 bool* succeeded) {
2997 assert_heap_not_locked_and_not_at_safepoint();
2998 g1_policy()->record_stop_world_start();
2999 VM_G1IncCollectionPause op(gc_count_before,
3000 word_size,
3001 false, /* should_initiate_conc_mark */
3002 g1_policy()->max_pause_time_ms(),
3003 GCCause::_g1_inc_collection_pause);
3004 VMThread::execute(&op);
3006 HeapWord* result = op.result();
3007 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3008 assert(result == NULL || ret_succeeded,
3009 "the result should be NULL if the VM did not succeed");
3010 *succeeded = ret_succeeded;
3012 assert_heap_not_locked();
3013 return result;
3014 }
3016 void
3017 G1CollectedHeap::doConcurrentMark() {
3018 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3019 if (!_cmThread->in_progress()) {
3020 _cmThread->set_started();
3021 CGC_lock->notify();
3022 }
3023 }
3025 class VerifyMarkedObjsClosure: public ObjectClosure {
3026 G1CollectedHeap* _g1h;
3027 public:
3028 VerifyMarkedObjsClosure(G1CollectedHeap* g1h) : _g1h(g1h) {}
3029 void do_object(oop obj) {
3030 assert(obj->mark()->is_marked() ? !_g1h->is_obj_dead(obj) : true,
3031 "markandsweep mark should agree with concurrent deadness");
3032 }
3033 };
3035 void
3036 G1CollectedHeap::checkConcurrentMark() {
3037 VerifyMarkedObjsClosure verifycl(this);
3038 // MutexLockerEx x(getMarkBitMapLock(),
3039 // Mutex::_no_safepoint_check_flag);
3040 object_iterate(&verifycl, false);
3041 }
3043 void G1CollectedHeap::do_sync_mark() {
3044 _cm->checkpointRootsInitial();
3045 _cm->markFromRoots();
3046 _cm->checkpointRootsFinal(false);
3047 }
3049 // <NEW PREDICTION>
3051 double G1CollectedHeap::predict_region_elapsed_time_ms(HeapRegion *hr,
3052 bool young) {
3053 return _g1_policy->predict_region_elapsed_time_ms(hr, young);
3054 }
3056 void G1CollectedHeap::check_if_region_is_too_expensive(double
3057 predicted_time_ms) {
3058 _g1_policy->check_if_region_is_too_expensive(predicted_time_ms);
3059 }
3061 size_t G1CollectedHeap::pending_card_num() {
3062 size_t extra_cards = 0;
3063 JavaThread *curr = Threads::first();
3064 while (curr != NULL) {
3065 DirtyCardQueue& dcq = curr->dirty_card_queue();
3066 extra_cards += dcq.size();
3067 curr = curr->next();
3068 }
3069 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3070 size_t buffer_size = dcqs.buffer_size();
3071 size_t buffer_num = dcqs.completed_buffers_num();
3072 return buffer_size * buffer_num + extra_cards;
3073 }
3075 size_t G1CollectedHeap::max_pending_card_num() {
3076 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3077 size_t buffer_size = dcqs.buffer_size();
3078 size_t buffer_num = dcqs.completed_buffers_num();
3079 int thread_num = Threads::number_of_threads();
3080 return (buffer_num + thread_num) * buffer_size;
3081 }
3083 size_t G1CollectedHeap::cards_scanned() {
3084 return g1_rem_set()->cardsScanned();
3085 }
3087 void
3088 G1CollectedHeap::setup_surviving_young_words() {
3089 guarantee( _surviving_young_words == NULL, "pre-condition" );
3090 size_t array_length = g1_policy()->young_cset_length();
3091 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, array_length);
3092 if (_surviving_young_words == NULL) {
3093 vm_exit_out_of_memory(sizeof(size_t) * array_length,
3094 "Not enough space for young surv words summary.");
3095 }
3096 memset(_surviving_young_words, 0, array_length * sizeof(size_t));
3097 #ifdef ASSERT
3098 for (size_t i = 0; i < array_length; ++i) {
3099 assert( _surviving_young_words[i] == 0, "memset above" );
3100 }
3101 #endif // !ASSERT
3102 }
3104 void
3105 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3106 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3107 size_t array_length = g1_policy()->young_cset_length();
3108 for (size_t i = 0; i < array_length; ++i)
3109 _surviving_young_words[i] += surv_young_words[i];
3110 }
3112 void
3113 G1CollectedHeap::cleanup_surviving_young_words() {
3114 guarantee( _surviving_young_words != NULL, "pre-condition" );
3115 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words);
3116 _surviving_young_words = NULL;
3117 }
3119 // </NEW PREDICTION>
3121 struct PrepareForRSScanningClosure : public HeapRegionClosure {
3122 bool doHeapRegion(HeapRegion *r) {
3123 r->rem_set()->set_iter_claimed(0);
3124 return false;
3125 }
3126 };
3128 #if TASKQUEUE_STATS
3129 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3130 st->print_raw_cr("GC Task Stats");
3131 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3132 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3133 }
3135 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3136 print_taskqueue_stats_hdr(st);
3138 TaskQueueStats totals;
3139 const int n = workers() != NULL ? workers()->total_workers() : 1;
3140 for (int i = 0; i < n; ++i) {
3141 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3142 totals += task_queue(i)->stats;
3143 }
3144 st->print_raw("tot "); totals.print(st); st->cr();
3146 DEBUG_ONLY(totals.verify());
3147 }
3149 void G1CollectedHeap::reset_taskqueue_stats() {
3150 const int n = workers() != NULL ? workers()->total_workers() : 1;
3151 for (int i = 0; i < n; ++i) {
3152 task_queue(i)->stats.reset();
3153 }
3154 }
3155 #endif // TASKQUEUE_STATS
3157 bool
3158 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3159 assert_at_safepoint(true /* should_be_vm_thread */);
3160 guarantee(!is_gc_active(), "collection is not reentrant");
3162 if (GC_locker::check_active_before_gc()) {
3163 return false;
3164 }
3166 SvcGCMarker sgcm(SvcGCMarker::MINOR);
3167 ResourceMark rm;
3169 if (PrintHeapAtGC) {
3170 Universe::print_heap_before_gc();
3171 }
3173 verify_region_sets_optional();
3174 verify_dirty_young_regions();
3176 {
3177 // This call will decide whether this pause is an initial-mark
3178 // pause. If it is, during_initial_mark_pause() will return true
3179 // for the duration of this pause.
3180 g1_policy()->decide_on_conc_mark_initiation();
3182 char verbose_str[128];
3183 sprintf(verbose_str, "GC pause ");
3184 if (g1_policy()->in_young_gc_mode()) {
3185 if (g1_policy()->full_young_gcs())
3186 strcat(verbose_str, "(young)");
3187 else
3188 strcat(verbose_str, "(partial)");
3189 }
3190 if (g1_policy()->during_initial_mark_pause()) {
3191 strcat(verbose_str, " (initial-mark)");
3192 // We are about to start a marking cycle, so we increment the
3193 // full collection counter.
3194 increment_total_full_collections();
3195 }
3197 // if PrintGCDetails is on, we'll print long statistics information
3198 // in the collector policy code, so let's not print this as the output
3199 // is messy if we do.
3200 gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
3201 TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
3202 TraceTime t(verbose_str, PrintGC && !PrintGCDetails, true, gclog_or_tty);
3204 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3205 TraceMemoryManagerStats tms(false /* fullGC */);
3207 // If the secondary_free_list is not empty, append it to the
3208 // free_list. No need to wait for the cleanup operation to finish;
3209 // the region allocation code will check the secondary_free_list
3210 // and wait if necessary. If the G1StressConcRegionFreeing flag is
3211 // set, skip this step so that the region allocation code has to
3212 // get entries from the secondary_free_list.
3213 if (!G1StressConcRegionFreeing) {
3214 append_secondary_free_list_if_not_empty_with_lock();
3215 }
3217 increment_gc_time_stamp();
3219 if (g1_policy()->in_young_gc_mode()) {
3220 assert(check_young_list_well_formed(),
3221 "young list should be well formed");
3222 }
3224 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3225 IsGCActiveMark x;
3227 gc_prologue(false);
3228 increment_total_collections(false /* full gc */);
3230 #if G1_REM_SET_LOGGING
3231 gclog_or_tty->print_cr("\nJust chose CS, heap:");
3232 print();
3233 #endif
3235 if (VerifyBeforeGC && total_collections() >= VerifyGCStartAt) {
3236 HandleMark hm; // Discard invalid handles created during verification
3237 gclog_or_tty->print(" VerifyBeforeGC:");
3238 prepare_for_verify();
3239 Universe::verify(false);
3240 }
3242 COMPILER2_PRESENT(DerivedPointerTable::clear());
3244 // Please see comment in G1CollectedHeap::ref_processing_init()
3245 // to see how reference processing currently works in G1.
3246 //
3247 // We want to turn off ref discovery, if necessary, and turn it back on
3248 // on again later if we do. XXX Dubious: why is discovery disabled?
3249 bool was_enabled = ref_processor()->discovery_enabled();
3250 if (was_enabled) ref_processor()->disable_discovery();
3252 // Forget the current alloc region (we might even choose it to be part
3253 // of the collection set!).
3254 release_mutator_alloc_region();
3256 // The elapsed time induced by the start time below deliberately elides
3257 // the possible verification above.
3258 double start_time_sec = os::elapsedTime();
3259 size_t start_used_bytes = used();
3261 #if YOUNG_LIST_VERBOSE
3262 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
3263 _young_list->print();
3264 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3265 #endif // YOUNG_LIST_VERBOSE
3267 g1_policy()->record_collection_pause_start(start_time_sec,
3268 start_used_bytes);
3270 #if YOUNG_LIST_VERBOSE
3271 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
3272 _young_list->print();
3273 #endif // YOUNG_LIST_VERBOSE
3275 if (g1_policy()->during_initial_mark_pause()) {
3276 concurrent_mark()->checkpointRootsInitialPre();
3277 }
3278 save_marks();
3280 // We must do this before any possible evacuation that should propagate
3281 // marks.
3282 if (mark_in_progress()) {
3283 double start_time_sec = os::elapsedTime();
3285 _cm->drainAllSATBBuffers();
3286 double finish_mark_ms = (os::elapsedTime() - start_time_sec) * 1000.0;
3287 g1_policy()->record_satb_drain_time(finish_mark_ms);
3288 }
3289 // Record the number of elements currently on the mark stack, so we
3290 // only iterate over these. (Since evacuation may add to the mark
3291 // stack, doing more exposes race conditions.) If no mark is in
3292 // progress, this will be zero.
3293 _cm->set_oops_do_bound();
3295 if (mark_in_progress())
3296 concurrent_mark()->newCSet();
3298 #if YOUNG_LIST_VERBOSE
3299 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
3300 _young_list->print();
3301 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3302 #endif // YOUNG_LIST_VERBOSE
3304 g1_policy()->choose_collection_set(target_pause_time_ms);
3306 // Nothing to do if we were unable to choose a collection set.
3307 #if G1_REM_SET_LOGGING
3308 gclog_or_tty->print_cr("\nAfter pause, heap:");
3309 print();
3310 #endif
3311 PrepareForRSScanningClosure prepare_for_rs_scan;
3312 collection_set_iterate(&prepare_for_rs_scan);
3314 setup_surviving_young_words();
3316 // Set up the gc allocation regions.
3317 get_gc_alloc_regions();
3319 // Actually do the work...
3320 evacuate_collection_set();
3322 free_collection_set(g1_policy()->collection_set());
3323 g1_policy()->clear_collection_set();
3325 cleanup_surviving_young_words();
3327 // Start a new incremental collection set for the next pause.
3328 g1_policy()->start_incremental_cset_building();
3330 // Clear the _cset_fast_test bitmap in anticipation of adding
3331 // regions to the incremental collection set for the next
3332 // evacuation pause.
3333 clear_cset_fast_test();
3335 if (g1_policy()->in_young_gc_mode()) {
3336 _young_list->reset_sampled_info();
3338 // Don't check the whole heap at this point as the
3339 // GC alloc regions from this pause have been tagged
3340 // as survivors and moved on to the survivor list.
3341 // Survivor regions will fail the !is_young() check.
3342 assert(check_young_list_empty(false /* check_heap */),
3343 "young list should be empty");
3345 #if YOUNG_LIST_VERBOSE
3346 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
3347 _young_list->print();
3348 #endif // YOUNG_LIST_VERBOSE
3350 g1_policy()->record_survivor_regions(_young_list->survivor_length(),
3351 _young_list->first_survivor_region(),
3352 _young_list->last_survivor_region());
3354 _young_list->reset_auxilary_lists();
3355 }
3357 if (evacuation_failed()) {
3358 _summary_bytes_used = recalculate_used();
3359 } else {
3360 // The "used" of the the collection set have already been subtracted
3361 // when they were freed. Add in the bytes evacuated.
3362 _summary_bytes_used += g1_policy()->bytes_in_to_space();
3363 }
3365 if (g1_policy()->in_young_gc_mode() &&
3366 g1_policy()->during_initial_mark_pause()) {
3367 concurrent_mark()->checkpointRootsInitialPost();
3368 set_marking_started();
3369 // CAUTION: after the doConcurrentMark() call below,
3370 // the concurrent marking thread(s) could be running
3371 // concurrently with us. Make sure that anything after
3372 // this point does not assume that we are the only GC thread
3373 // running. Note: of course, the actual marking work will
3374 // not start until the safepoint itself is released in
3375 // ConcurrentGCThread::safepoint_desynchronize().
3376 doConcurrentMark();
3377 }
3379 allocate_dummy_regions();
3381 #if YOUNG_LIST_VERBOSE
3382 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
3383 _young_list->print();
3384 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3385 #endif // YOUNG_LIST_VERBOSE
3387 init_mutator_alloc_region();
3389 double end_time_sec = os::elapsedTime();
3390 double pause_time_ms = (end_time_sec - start_time_sec) * MILLIUNITS;
3391 g1_policy()->record_pause_time_ms(pause_time_ms);
3392 g1_policy()->record_collection_pause_end();
3394 MemoryService::track_memory_usage();
3396 if (VerifyAfterGC && total_collections() >= VerifyGCStartAt) {
3397 HandleMark hm; // Discard invalid handles created during verification
3398 gclog_or_tty->print(" VerifyAfterGC:");
3399 prepare_for_verify();
3400 Universe::verify(false);
3401 }
3403 if (was_enabled) ref_processor()->enable_discovery();
3405 {
3406 size_t expand_bytes = g1_policy()->expansion_amount();
3407 if (expand_bytes > 0) {
3408 size_t bytes_before = capacity();
3409 if (!expand(expand_bytes)) {
3410 // We failed to expand the heap so let's verify that
3411 // committed/uncommitted amount match the backing store
3412 assert(capacity() == _g1_storage.committed_size(), "committed size mismatch");
3413 assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch");
3414 }
3415 }
3416 }
3418 if (mark_in_progress()) {
3419 concurrent_mark()->update_g1_committed();
3420 }
3422 #ifdef TRACESPINNING
3423 ParallelTaskTerminator::print_termination_counts();
3424 #endif
3426 gc_epilogue(false);
3427 }
3429 if (ExitAfterGCNum > 0 && total_collections() == ExitAfterGCNum) {
3430 gclog_or_tty->print_cr("Stopping after GC #%d", ExitAfterGCNum);
3431 print_tracing_info();
3432 vm_exit(-1);
3433 }
3434 }
3436 verify_region_sets_optional();
3438 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
3439 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3441 if (PrintHeapAtGC) {
3442 Universe::print_heap_after_gc();
3443 }
3444 g1mm()->update_counters();
3446 if (G1SummarizeRSetStats &&
3447 (G1SummarizeRSetStatsPeriod > 0) &&
3448 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3449 g1_rem_set()->print_summary_info();
3450 }
3452 return true;
3453 }
3455 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
3456 {
3457 size_t gclab_word_size;
3458 switch (purpose) {
3459 case GCAllocForSurvived:
3460 gclab_word_size = YoungPLABSize;
3461 break;
3462 case GCAllocForTenured:
3463 gclab_word_size = OldPLABSize;
3464 break;
3465 default:
3466 assert(false, "unknown GCAllocPurpose");
3467 gclab_word_size = OldPLABSize;
3468 break;
3469 }
3470 return gclab_word_size;
3471 }
3473 void G1CollectedHeap::init_mutator_alloc_region() {
3474 assert(_mutator_alloc_region.get() == NULL, "pre-condition");
3475 _mutator_alloc_region.init();
3476 }
3478 void G1CollectedHeap::release_mutator_alloc_region() {
3479 _mutator_alloc_region.release();
3480 assert(_mutator_alloc_region.get() == NULL, "post-condition");
3481 }
3483 void G1CollectedHeap::set_gc_alloc_region(int purpose, HeapRegion* r) {
3484 assert(purpose >= 0 && purpose < GCAllocPurposeCount, "invalid purpose");
3485 // make sure we don't call set_gc_alloc_region() multiple times on
3486 // the same region
3487 assert(r == NULL || !r->is_gc_alloc_region(),
3488 "shouldn't already be a GC alloc region");
3489 assert(r == NULL || !r->isHumongous(),
3490 "humongous regions shouldn't be used as GC alloc regions");
3492 HeapWord* original_top = NULL;
3493 if (r != NULL)
3494 original_top = r->top();
3496 // We will want to record the used space in r as being there before gc.
3497 // One we install it as a GC alloc region it's eligible for allocation.
3498 // So record it now and use it later.
3499 size_t r_used = 0;
3500 if (r != NULL) {
3501 r_used = r->used();
3503 if (G1CollectedHeap::use_parallel_gc_threads()) {
3504 // need to take the lock to guard against two threads calling
3505 // get_gc_alloc_region concurrently (very unlikely but...)
3506 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3507 r->save_marks();
3508 }
3509 }
3510 HeapRegion* old_alloc_region = _gc_alloc_regions[purpose];
3511 _gc_alloc_regions[purpose] = r;
3512 if (old_alloc_region != NULL) {
3513 // Replace aliases too.
3514 for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
3515 if (_gc_alloc_regions[ap] == old_alloc_region) {
3516 _gc_alloc_regions[ap] = r;
3517 }
3518 }
3519 }
3520 if (r != NULL) {
3521 push_gc_alloc_region(r);
3522 if (mark_in_progress() && original_top != r->next_top_at_mark_start()) {
3523 // We are using a region as a GC alloc region after it has been used
3524 // as a mutator allocation region during the current marking cycle.
3525 // The mutator-allocated objects are currently implicitly marked, but
3526 // when we move hr->next_top_at_mark_start() forward at the the end
3527 // of the GC pause, they won't be. We therefore mark all objects in
3528 // the "gap". We do this object-by-object, since marking densely
3529 // does not currently work right with marking bitmap iteration. This
3530 // means we rely on TLAB filling at the start of pauses, and no
3531 // "resuscitation" of filled TLAB's. If we want to do this, we need
3532 // to fix the marking bitmap iteration.
3533 HeapWord* curhw = r->next_top_at_mark_start();
3534 HeapWord* t = original_top;
3536 while (curhw < t) {
3537 oop cur = (oop)curhw;
3538 // We'll assume parallel for generality. This is rare code.
3539 concurrent_mark()->markAndGrayObjectIfNecessary(cur); // can't we just mark them?
3540 curhw = curhw + cur->size();
3541 }
3542 assert(curhw == t, "Should have parsed correctly.");
3543 }
3544 if (G1PolicyVerbose > 1) {
3545 gclog_or_tty->print("New alloc region ["PTR_FORMAT", "PTR_FORMAT", " PTR_FORMAT") "
3546 "for survivors:", r->bottom(), original_top, r->end());
3547 r->print();
3548 }
3549 g1_policy()->record_before_bytes(r_used);
3550 }
3551 }
3553 void G1CollectedHeap::push_gc_alloc_region(HeapRegion* hr) {
3554 assert(Thread::current()->is_VM_thread() ||
3555 FreeList_lock->owned_by_self(), "Precondition");
3556 assert(!hr->is_gc_alloc_region() && !hr->in_collection_set(),
3557 "Precondition.");
3558 hr->set_is_gc_alloc_region(true);
3559 hr->set_next_gc_alloc_region(_gc_alloc_region_list);
3560 _gc_alloc_region_list = hr;
3561 }
3563 #ifdef G1_DEBUG
3564 class FindGCAllocRegion: public HeapRegionClosure {
3565 public:
3566 bool doHeapRegion(HeapRegion* r) {
3567 if (r->is_gc_alloc_region()) {
3568 gclog_or_tty->print_cr("Region %d ["PTR_FORMAT"...] is still a gc_alloc_region.",
3569 r->hrs_index(), r->bottom());
3570 }
3571 return false;
3572 }
3573 };
3574 #endif // G1_DEBUG
3576 void G1CollectedHeap::forget_alloc_region_list() {
3577 assert_at_safepoint(true /* should_be_vm_thread */);
3578 while (_gc_alloc_region_list != NULL) {
3579 HeapRegion* r = _gc_alloc_region_list;
3580 assert(r->is_gc_alloc_region(), "Invariant.");
3581 // We need HeapRegion::oops_on_card_seq_iterate_careful() to work on
3582 // newly allocated data in order to be able to apply deferred updates
3583 // before the GC is done for verification purposes (i.e to allow
3584 // G1HRRSFlushLogBuffersOnVerify). It's safe thing to do after the
3585 // collection.
3586 r->ContiguousSpace::set_saved_mark();
3587 _gc_alloc_region_list = r->next_gc_alloc_region();
3588 r->set_next_gc_alloc_region(NULL);
3589 r->set_is_gc_alloc_region(false);
3590 if (r->is_survivor()) {
3591 if (r->is_empty()) {
3592 r->set_not_young();
3593 } else {
3594 _young_list->add_survivor_region(r);
3595 }
3596 }
3597 }
3598 #ifdef G1_DEBUG
3599 FindGCAllocRegion fa;
3600 heap_region_iterate(&fa);
3601 #endif // G1_DEBUG
3602 }
3605 bool G1CollectedHeap::check_gc_alloc_regions() {
3606 // TODO: allocation regions check
3607 return true;
3608 }
3610 void G1CollectedHeap::get_gc_alloc_regions() {
3611 // First, let's check that the GC alloc region list is empty (it should)
3612 assert(_gc_alloc_region_list == NULL, "invariant");
3614 for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
3615 assert(_gc_alloc_regions[ap] == NULL, "invariant");
3616 assert(_gc_alloc_region_counts[ap] == 0, "invariant");
3618 // Create new GC alloc regions.
3619 HeapRegion* alloc_region = _retained_gc_alloc_regions[ap];
3620 _retained_gc_alloc_regions[ap] = NULL;
3622 if (alloc_region != NULL) {
3623 assert(_retain_gc_alloc_region[ap], "only way to retain a GC region");
3625 // let's make sure that the GC alloc region is not tagged as such
3626 // outside a GC operation
3627 assert(!alloc_region->is_gc_alloc_region(), "sanity");
3629 if (alloc_region->in_collection_set() ||
3630 alloc_region->top() == alloc_region->end() ||
3631 alloc_region->top() == alloc_region->bottom() ||
3632 alloc_region->isHumongous()) {
3633 // we will discard the current GC alloc region if
3634 // * it's in the collection set (it can happen!),
3635 // * it's already full (no point in using it),
3636 // * it's empty (this means that it was emptied during
3637 // a cleanup and it should be on the free list now), or
3638 // * it's humongous (this means that it was emptied
3639 // during a cleanup and was added to the free list, but
3640 // has been subseqently used to allocate a humongous
3641 // object that may be less than the region size).
3643 alloc_region = NULL;
3644 }
3645 }
3647 if (alloc_region == NULL) {
3648 // we will get a new GC alloc region
3649 alloc_region = new_gc_alloc_region(ap, HeapRegion::GrainWords);
3650 } else {
3651 // the region was retained from the last collection
3652 ++_gc_alloc_region_counts[ap];
3653 if (G1PrintHeapRegions) {
3654 gclog_or_tty->print_cr("new alloc region %d:["PTR_FORMAT", "PTR_FORMAT"], "
3655 "top "PTR_FORMAT,
3656 alloc_region->hrs_index(), alloc_region->bottom(), alloc_region->end(), alloc_region->top());
3657 }
3658 }
3660 if (alloc_region != NULL) {
3661 assert(_gc_alloc_regions[ap] == NULL, "pre-condition");
3662 set_gc_alloc_region(ap, alloc_region);
3663 }
3665 assert(_gc_alloc_regions[ap] == NULL ||
3666 _gc_alloc_regions[ap]->is_gc_alloc_region(),
3667 "the GC alloc region should be tagged as such");
3668 assert(_gc_alloc_regions[ap] == NULL ||
3669 _gc_alloc_regions[ap] == _gc_alloc_region_list,
3670 "the GC alloc region should be the same as the GC alloc list head");
3671 }
3672 // Set alternative regions for allocation purposes that have reached
3673 // their limit.
3674 for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
3675 GCAllocPurpose alt_purpose = g1_policy()->alternative_purpose(ap);
3676 if (_gc_alloc_regions[ap] == NULL && alt_purpose != ap) {
3677 _gc_alloc_regions[ap] = _gc_alloc_regions[alt_purpose];
3678 }
3679 }
3680 assert(check_gc_alloc_regions(), "alloc regions messed up");
3681 }
3683 void G1CollectedHeap::release_gc_alloc_regions(bool totally) {
3684 // We keep a separate list of all regions that have been alloc regions in
3685 // the current collection pause. Forget that now. This method will
3686 // untag the GC alloc regions and tear down the GC alloc region
3687 // list. It's desirable that no regions are tagged as GC alloc
3688 // outside GCs.
3690 forget_alloc_region_list();
3692 // The current alloc regions contain objs that have survived
3693 // collection. Make them no longer GC alloc regions.
3694 for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
3695 HeapRegion* r = _gc_alloc_regions[ap];
3696 _retained_gc_alloc_regions[ap] = NULL;
3697 _gc_alloc_region_counts[ap] = 0;
3699 if (r != NULL) {
3700 // we retain nothing on _gc_alloc_regions between GCs
3701 set_gc_alloc_region(ap, NULL);
3703 if (r->is_empty()) {
3704 // We didn't actually allocate anything in it; let's just put
3705 // it back on the free list.
3706 _free_list.add_as_head(r);
3707 } else if (_retain_gc_alloc_region[ap] && !totally) {
3708 // retain it so that we can use it at the beginning of the next GC
3709 _retained_gc_alloc_regions[ap] = r;
3710 }
3711 }
3712 }
3713 }
3715 #ifndef PRODUCT
3716 // Useful for debugging
3718 void G1CollectedHeap::print_gc_alloc_regions() {
3719 gclog_or_tty->print_cr("GC alloc regions");
3720 for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
3721 HeapRegion* r = _gc_alloc_regions[ap];
3722 if (r == NULL) {
3723 gclog_or_tty->print_cr(" %2d : "PTR_FORMAT, ap, NULL);
3724 } else {
3725 gclog_or_tty->print_cr(" %2d : "PTR_FORMAT" "SIZE_FORMAT,
3726 ap, r->bottom(), r->used());
3727 }
3728 }
3729 }
3730 #endif // PRODUCT
3732 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
3733 _drain_in_progress = false;
3734 set_evac_failure_closure(cl);
3735 _evac_failure_scan_stack = new (ResourceObj::C_HEAP) GrowableArray<oop>(40, true);
3736 }
3738 void G1CollectedHeap::finalize_for_evac_failure() {
3739 assert(_evac_failure_scan_stack != NULL &&
3740 _evac_failure_scan_stack->length() == 0,
3741 "Postcondition");
3742 assert(!_drain_in_progress, "Postcondition");
3743 delete _evac_failure_scan_stack;
3744 _evac_failure_scan_stack = NULL;
3745 }
3749 // *** Sequential G1 Evacuation
3751 class G1IsAliveClosure: public BoolObjectClosure {
3752 G1CollectedHeap* _g1;
3753 public:
3754 G1IsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3755 void do_object(oop p) { assert(false, "Do not call."); }
3756 bool do_object_b(oop p) {
3757 // It is reachable if it is outside the collection set, or is inside
3758 // and forwarded.
3760 #ifdef G1_DEBUG
3761 gclog_or_tty->print_cr("is alive "PTR_FORMAT" in CS %d forwarded %d overall %d",
3762 (void*) p, _g1->obj_in_cs(p), p->is_forwarded(),
3763 !_g1->obj_in_cs(p) || p->is_forwarded());
3764 #endif // G1_DEBUG
3766 return !_g1->obj_in_cs(p) || p->is_forwarded();
3767 }
3768 };
3770 class G1KeepAliveClosure: public OopClosure {
3771 G1CollectedHeap* _g1;
3772 public:
3773 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3774 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
3775 void do_oop( oop* p) {
3776 oop obj = *p;
3777 #ifdef G1_DEBUG
3778 if (PrintGC && Verbose) {
3779 gclog_or_tty->print_cr("keep alive *"PTR_FORMAT" = "PTR_FORMAT" "PTR_FORMAT,
3780 p, (void*) obj, (void*) *p);
3781 }
3782 #endif // G1_DEBUG
3784 if (_g1->obj_in_cs(obj)) {
3785 assert( obj->is_forwarded(), "invariant" );
3786 *p = obj->forwardee();
3787 #ifdef G1_DEBUG
3788 gclog_or_tty->print_cr(" in CSet: moved "PTR_FORMAT" -> "PTR_FORMAT,
3789 (void*) obj, (void*) *p);
3790 #endif // G1_DEBUG
3791 }
3792 }
3793 };
3795 class UpdateRSetDeferred : public OopsInHeapRegionClosure {
3796 private:
3797 G1CollectedHeap* _g1;
3798 DirtyCardQueue *_dcq;
3799 CardTableModRefBS* _ct_bs;
3801 public:
3802 UpdateRSetDeferred(G1CollectedHeap* g1, DirtyCardQueue* dcq) :
3803 _g1(g1), _ct_bs((CardTableModRefBS*)_g1->barrier_set()), _dcq(dcq) {}
3805 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
3806 virtual void do_oop( oop* p) { do_oop_work(p); }
3807 template <class T> void do_oop_work(T* p) {
3808 assert(_from->is_in_reserved(p), "paranoia");
3809 if (!_from->is_in_reserved(oopDesc::load_decode_heap_oop(p)) &&
3810 !_from->is_survivor()) {
3811 size_t card_index = _ct_bs->index_for(p);
3812 if (_ct_bs->mark_card_deferred(card_index)) {
3813 _dcq->enqueue((jbyte*)_ct_bs->byte_for_index(card_index));
3814 }
3815 }
3816 }
3817 };
3819 class RemoveSelfPointerClosure: public ObjectClosure {
3820 private:
3821 G1CollectedHeap* _g1;
3822 ConcurrentMark* _cm;
3823 HeapRegion* _hr;
3824 size_t _prev_marked_bytes;
3825 size_t _next_marked_bytes;
3826 OopsInHeapRegionClosure *_cl;
3827 public:
3828 RemoveSelfPointerClosure(G1CollectedHeap* g1, HeapRegion* hr,
3829 OopsInHeapRegionClosure* cl) :
3830 _g1(g1), _hr(hr), _cm(_g1->concurrent_mark()), _prev_marked_bytes(0),
3831 _next_marked_bytes(0), _cl(cl) {}
3833 size_t prev_marked_bytes() { return _prev_marked_bytes; }
3834 size_t next_marked_bytes() { return _next_marked_bytes; }
3836 // <original comment>
3837 // The original idea here was to coalesce evacuated and dead objects.
3838 // However that caused complications with the block offset table (BOT).
3839 // In particular if there were two TLABs, one of them partially refined.
3840 // |----- TLAB_1--------|----TLAB_2-~~~(partially refined part)~~~|
3841 // The BOT entries of the unrefined part of TLAB_2 point to the start
3842 // of TLAB_2. If the last object of the TLAB_1 and the first object
3843 // of TLAB_2 are coalesced, then the cards of the unrefined part
3844 // would point into middle of the filler object.
3845 // The current approach is to not coalesce and leave the BOT contents intact.
3846 // </original comment>
3847 //
3848 // We now reset the BOT when we start the object iteration over the
3849 // region and refine its entries for every object we come across. So
3850 // the above comment is not really relevant and we should be able
3851 // to coalesce dead objects if we want to.
3852 void do_object(oop obj) {
3853 HeapWord* obj_addr = (HeapWord*) obj;
3854 assert(_hr->is_in(obj_addr), "sanity");
3855 size_t obj_size = obj->size();
3856 _hr->update_bot_for_object(obj_addr, obj_size);
3857 if (obj->is_forwarded() && obj->forwardee() == obj) {
3858 // The object failed to move.
3859 assert(!_g1->is_obj_dead(obj), "We should not be preserving dead objs.");
3860 _cm->markPrev(obj);
3861 assert(_cm->isPrevMarked(obj), "Should be marked!");
3862 _prev_marked_bytes += (obj_size * HeapWordSize);
3863 if (_g1->mark_in_progress() && !_g1->is_obj_ill(obj)) {
3864 _cm->markAndGrayObjectIfNecessary(obj);
3865 }
3866 obj->set_mark(markOopDesc::prototype());
3867 // While we were processing RSet buffers during the
3868 // collection, we actually didn't scan any cards on the
3869 // collection set, since we didn't want to update remebered
3870 // sets with entries that point into the collection set, given
3871 // that live objects fromthe collection set are about to move
3872 // and such entries will be stale very soon. This change also
3873 // dealt with a reliability issue which involved scanning a
3874 // card in the collection set and coming across an array that
3875 // was being chunked and looking malformed. The problem is
3876 // that, if evacuation fails, we might have remembered set
3877 // entries missing given that we skipped cards on the
3878 // collection set. So, we'll recreate such entries now.
3879 obj->oop_iterate(_cl);
3880 assert(_cm->isPrevMarked(obj), "Should be marked!");
3881 } else {
3882 // The object has been either evacuated or is dead. Fill it with a
3883 // dummy object.
3884 MemRegion mr((HeapWord*)obj, obj_size);
3885 CollectedHeap::fill_with_object(mr);
3886 _cm->clearRangeBothMaps(mr);
3887 }
3888 }
3889 };
3891 void G1CollectedHeap::remove_self_forwarding_pointers() {
3892 UpdateRSetImmediate immediate_update(_g1h->g1_rem_set());
3893 DirtyCardQueue dcq(&_g1h->dirty_card_queue_set());
3894 UpdateRSetDeferred deferred_update(_g1h, &dcq);
3895 OopsInHeapRegionClosure *cl;
3896 if (G1DeferredRSUpdate) {
3897 cl = &deferred_update;
3898 } else {
3899 cl = &immediate_update;
3900 }
3901 HeapRegion* cur = g1_policy()->collection_set();
3902 while (cur != NULL) {
3903 assert(g1_policy()->assertMarkedBytesDataOK(), "Should be!");
3904 assert(!cur->isHumongous(), "sanity");
3906 if (cur->evacuation_failed()) {
3907 assert(cur->in_collection_set(), "bad CS");
3908 RemoveSelfPointerClosure rspc(_g1h, cur, cl);
3910 cur->reset_bot();
3911 cl->set_region(cur);
3912 cur->object_iterate(&rspc);
3914 // A number of manipulations to make the TAMS be the current top,
3915 // and the marked bytes be the ones observed in the iteration.
3916 if (_g1h->concurrent_mark()->at_least_one_mark_complete()) {
3917 // The comments below are the postconditions achieved by the
3918 // calls. Note especially the last such condition, which says that
3919 // the count of marked bytes has been properly restored.
3920 cur->note_start_of_marking(false);
3921 // _next_top_at_mark_start == top, _next_marked_bytes == 0
3922 cur->add_to_marked_bytes(rspc.prev_marked_bytes());
3923 // _next_marked_bytes == prev_marked_bytes.
3924 cur->note_end_of_marking();
3925 // _prev_top_at_mark_start == top(),
3926 // _prev_marked_bytes == prev_marked_bytes
3927 }
3928 // If there is no mark in progress, we modified the _next variables
3929 // above needlessly, but harmlessly.
3930 if (_g1h->mark_in_progress()) {
3931 cur->note_start_of_marking(false);
3932 // _next_top_at_mark_start == top, _next_marked_bytes == 0
3933 // _next_marked_bytes == next_marked_bytes.
3934 }
3936 // Now make sure the region has the right index in the sorted array.
3937 g1_policy()->note_change_in_marked_bytes(cur);
3938 }
3939 cur = cur->next_in_collection_set();
3940 }
3941 assert(g1_policy()->assertMarkedBytesDataOK(), "Should be!");
3943 // Now restore saved marks, if any.
3944 if (_objs_with_preserved_marks != NULL) {
3945 assert(_preserved_marks_of_objs != NULL, "Both or none.");
3946 guarantee(_objs_with_preserved_marks->length() ==
3947 _preserved_marks_of_objs->length(), "Both or none.");
3948 for (int i = 0; i < _objs_with_preserved_marks->length(); i++) {
3949 oop obj = _objs_with_preserved_marks->at(i);
3950 markOop m = _preserved_marks_of_objs->at(i);
3951 obj->set_mark(m);
3952 }
3953 // Delete the preserved marks growable arrays (allocated on the C heap).
3954 delete _objs_with_preserved_marks;
3955 delete _preserved_marks_of_objs;
3956 _objs_with_preserved_marks = NULL;
3957 _preserved_marks_of_objs = NULL;
3958 }
3959 }
3961 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
3962 _evac_failure_scan_stack->push(obj);
3963 }
3965 void G1CollectedHeap::drain_evac_failure_scan_stack() {
3966 assert(_evac_failure_scan_stack != NULL, "precondition");
3968 while (_evac_failure_scan_stack->length() > 0) {
3969 oop obj = _evac_failure_scan_stack->pop();
3970 _evac_failure_closure->set_region(heap_region_containing(obj));
3971 obj->oop_iterate_backwards(_evac_failure_closure);
3972 }
3973 }
3975 oop
3976 G1CollectedHeap::handle_evacuation_failure_par(OopsInHeapRegionClosure* cl,
3977 oop old) {
3978 markOop m = old->mark();
3979 oop forward_ptr = old->forward_to_atomic(old);
3980 if (forward_ptr == NULL) {
3981 // Forward-to-self succeeded.
3982 if (_evac_failure_closure != cl) {
3983 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
3984 assert(!_drain_in_progress,
3985 "Should only be true while someone holds the lock.");
3986 // Set the global evac-failure closure to the current thread's.
3987 assert(_evac_failure_closure == NULL, "Or locking has failed.");
3988 set_evac_failure_closure(cl);
3989 // Now do the common part.
3990 handle_evacuation_failure_common(old, m);
3991 // Reset to NULL.
3992 set_evac_failure_closure(NULL);
3993 } else {
3994 // The lock is already held, and this is recursive.
3995 assert(_drain_in_progress, "This should only be the recursive case.");
3996 handle_evacuation_failure_common(old, m);
3997 }
3998 return old;
3999 } else {
4000 // Someone else had a place to copy it.
4001 return forward_ptr;
4002 }
4003 }
4005 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4006 set_evacuation_failed(true);
4008 preserve_mark_if_necessary(old, m);
4010 HeapRegion* r = heap_region_containing(old);
4011 if (!r->evacuation_failed()) {
4012 r->set_evacuation_failed(true);
4013 if (G1PrintHeapRegions) {
4014 gclog_or_tty->print("overflow in heap region "PTR_FORMAT" "
4015 "["PTR_FORMAT","PTR_FORMAT")\n",
4016 r, r->bottom(), r->end());
4017 }
4018 }
4020 push_on_evac_failure_scan_stack(old);
4022 if (!_drain_in_progress) {
4023 // prevent recursion in copy_to_survivor_space()
4024 _drain_in_progress = true;
4025 drain_evac_failure_scan_stack();
4026 _drain_in_progress = false;
4027 }
4028 }
4030 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4031 assert(evacuation_failed(), "Oversaving!");
4032 // We want to call the "for_promotion_failure" version only in the
4033 // case of a promotion failure.
4034 if (m->must_be_preserved_for_promotion_failure(obj)) {
4035 if (_objs_with_preserved_marks == NULL) {
4036 assert(_preserved_marks_of_objs == NULL, "Both or none.");
4037 _objs_with_preserved_marks =
4038 new (ResourceObj::C_HEAP) GrowableArray<oop>(40, true);
4039 _preserved_marks_of_objs =
4040 new (ResourceObj::C_HEAP) GrowableArray<markOop>(40, true);
4041 }
4042 _objs_with_preserved_marks->push(obj);
4043 _preserved_marks_of_objs->push(m);
4044 }
4045 }
4047 // *** Parallel G1 Evacuation
4049 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
4050 size_t word_size) {
4051 assert(!isHumongous(word_size),
4052 err_msg("we should not be seeing humongous allocation requests "
4053 "during GC, word_size = "SIZE_FORMAT, word_size));
4055 HeapRegion* alloc_region = _gc_alloc_regions[purpose];
4056 // let the caller handle alloc failure
4057 if (alloc_region == NULL) return NULL;
4059 HeapWord* block = alloc_region->par_allocate(word_size);
4060 if (block == NULL) {
4061 block = allocate_during_gc_slow(purpose, alloc_region, true, word_size);
4062 }
4063 return block;
4064 }
4066 void G1CollectedHeap::retire_alloc_region(HeapRegion* alloc_region,
4067 bool par) {
4068 // Another thread might have obtained alloc_region for the given
4069 // purpose, and might be attempting to allocate in it, and might
4070 // succeed. Therefore, we can't do the "finalization" stuff on the
4071 // region below until we're sure the last allocation has happened.
4072 // We ensure this by allocating the remaining space with a garbage
4073 // object.
4074 if (par) par_allocate_remaining_space(alloc_region);
4075 // Now we can do the post-GC stuff on the region.
4076 alloc_region->note_end_of_copying();
4077 g1_policy()->record_after_bytes(alloc_region->used());
4078 }
4080 HeapWord*
4081 G1CollectedHeap::allocate_during_gc_slow(GCAllocPurpose purpose,
4082 HeapRegion* alloc_region,
4083 bool par,
4084 size_t word_size) {
4085 assert(!isHumongous(word_size),
4086 err_msg("we should not be seeing humongous allocation requests "
4087 "during GC, word_size = "SIZE_FORMAT, word_size));
4089 // We need to make sure we serialize calls to this method. Given
4090 // that the FreeList_lock guards accesses to the free_list anyway,
4091 // and we need to potentially remove a region from it, we'll use it
4092 // to protect the whole call.
4093 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4095 HeapWord* block = NULL;
4096 // In the parallel case, a previous thread to obtain the lock may have
4097 // already assigned a new gc_alloc_region.
4098 if (alloc_region != _gc_alloc_regions[purpose]) {
4099 assert(par, "But should only happen in parallel case.");
4100 alloc_region = _gc_alloc_regions[purpose];
4101 if (alloc_region == NULL) return NULL;
4102 block = alloc_region->par_allocate(word_size);
4103 if (block != NULL) return block;
4104 // Otherwise, continue; this new region is empty, too.
4105 }
4106 assert(alloc_region != NULL, "We better have an allocation region");
4107 retire_alloc_region(alloc_region, par);
4109 if (_gc_alloc_region_counts[purpose] >= g1_policy()->max_regions(purpose)) {
4110 // Cannot allocate more regions for the given purpose.
4111 GCAllocPurpose alt_purpose = g1_policy()->alternative_purpose(purpose);
4112 // Is there an alternative?
4113 if (purpose != alt_purpose) {
4114 HeapRegion* alt_region = _gc_alloc_regions[alt_purpose];
4115 // Has not the alternative region been aliased?
4116 if (alloc_region != alt_region && alt_region != NULL) {
4117 // Try to allocate in the alternative region.
4118 if (par) {
4119 block = alt_region->par_allocate(word_size);
4120 } else {
4121 block = alt_region->allocate(word_size);
4122 }
4123 // Make an alias.
4124 _gc_alloc_regions[purpose] = _gc_alloc_regions[alt_purpose];
4125 if (block != NULL) {
4126 return block;
4127 }
4128 retire_alloc_region(alt_region, par);
4129 }
4130 // Both the allocation region and the alternative one are full
4131 // and aliased, replace them with a new allocation region.
4132 purpose = alt_purpose;
4133 } else {
4134 set_gc_alloc_region(purpose, NULL);
4135 return NULL;
4136 }
4137 }
4139 // Now allocate a new region for allocation.
4140 alloc_region = new_gc_alloc_region(purpose, word_size);
4142 // let the caller handle alloc failure
4143 if (alloc_region != NULL) {
4145 assert(check_gc_alloc_regions(), "alloc regions messed up");
4146 assert(alloc_region->saved_mark_at_top(),
4147 "Mark should have been saved already.");
4148 // This must be done last: once it's installed, other regions may
4149 // allocate in it (without holding the lock.)
4150 set_gc_alloc_region(purpose, alloc_region);
4152 if (par) {
4153 block = alloc_region->par_allocate(word_size);
4154 } else {
4155 block = alloc_region->allocate(word_size);
4156 }
4157 // Caller handles alloc failure.
4158 } else {
4159 // This sets other apis using the same old alloc region to NULL, also.
4160 set_gc_alloc_region(purpose, NULL);
4161 }
4162 return block; // May be NULL.
4163 }
4165 void G1CollectedHeap::par_allocate_remaining_space(HeapRegion* r) {
4166 HeapWord* block = NULL;
4167 size_t free_words;
4168 do {
4169 free_words = r->free()/HeapWordSize;
4170 // If there's too little space, no one can allocate, so we're done.
4171 if (free_words < CollectedHeap::min_fill_size()) return;
4172 // Otherwise, try to claim it.
4173 block = r->par_allocate(free_words);
4174 } while (block == NULL);
4175 fill_with_object(block, free_words);
4176 }
4178 #ifndef PRODUCT
4179 bool GCLabBitMapClosure::do_bit(size_t offset) {
4180 HeapWord* addr = _bitmap->offsetToHeapWord(offset);
4181 guarantee(_cm->isMarked(oop(addr)), "it should be!");
4182 return true;
4183 }
4184 #endif // PRODUCT
4186 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, int queue_num)
4187 : _g1h(g1h),
4188 _refs(g1h->task_queue(queue_num)),
4189 _dcq(&g1h->dirty_card_queue_set()),
4190 _ct_bs((CardTableModRefBS*)_g1h->barrier_set()),
4191 _g1_rem(g1h->g1_rem_set()),
4192 _hash_seed(17), _queue_num(queue_num),
4193 _term_attempts(0),
4194 _surviving_alloc_buffer(g1h->desired_plab_sz(GCAllocForSurvived)),
4195 _tenured_alloc_buffer(g1h->desired_plab_sz(GCAllocForTenured)),
4196 _age_table(false),
4197 _strong_roots_time(0), _term_time(0),
4198 _alloc_buffer_waste(0), _undo_waste(0)
4199 {
4200 // we allocate G1YoungSurvRateNumRegions plus one entries, since
4201 // we "sacrifice" entry 0 to keep track of surviving bytes for
4202 // non-young regions (where the age is -1)
4203 // We also add a few elements at the beginning and at the end in
4204 // an attempt to eliminate cache contention
4205 size_t real_length = 1 + _g1h->g1_policy()->young_cset_length();
4206 size_t array_length = PADDING_ELEM_NUM +
4207 real_length +
4208 PADDING_ELEM_NUM;
4209 _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length);
4210 if (_surviving_young_words_base == NULL)
4211 vm_exit_out_of_memory(array_length * sizeof(size_t),
4212 "Not enough space for young surv histo.");
4213 _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM;
4214 memset(_surviving_young_words, 0, real_length * sizeof(size_t));
4216 _alloc_buffers[GCAllocForSurvived] = &_surviving_alloc_buffer;
4217 _alloc_buffers[GCAllocForTenured] = &_tenured_alloc_buffer;
4219 _start = os::elapsedTime();
4220 }
4222 void
4223 G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st)
4224 {
4225 st->print_raw_cr("GC Termination Stats");
4226 st->print_raw_cr(" elapsed --strong roots-- -------termination-------"
4227 " ------waste (KiB)------");
4228 st->print_raw_cr("thr ms ms % ms % attempts"
4229 " total alloc undo");
4230 st->print_raw_cr("--- --------- --------- ------ --------- ------ --------"
4231 " ------- ------- -------");
4232 }
4234 void
4235 G1ParScanThreadState::print_termination_stats(int i,
4236 outputStream* const st) const
4237 {
4238 const double elapsed_ms = elapsed_time() * 1000.0;
4239 const double s_roots_ms = strong_roots_time() * 1000.0;
4240 const double term_ms = term_time() * 1000.0;
4241 st->print_cr("%3d %9.2f %9.2f %6.2f "
4242 "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
4243 SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
4244 i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms,
4245 term_ms, term_ms * 100 / elapsed_ms, term_attempts(),
4246 (alloc_buffer_waste() + undo_waste()) * HeapWordSize / K,
4247 alloc_buffer_waste() * HeapWordSize / K,
4248 undo_waste() * HeapWordSize / K);
4249 }
4251 #ifdef ASSERT
4252 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const {
4253 assert(ref != NULL, "invariant");
4254 assert(UseCompressedOops, "sanity");
4255 assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, ref));
4256 oop p = oopDesc::load_decode_heap_oop(ref);
4257 assert(_g1h->is_in_g1_reserved(p),
4258 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4259 return true;
4260 }
4262 bool G1ParScanThreadState::verify_ref(oop* ref) const {
4263 assert(ref != NULL, "invariant");
4264 if (has_partial_array_mask(ref)) {
4265 // Must be in the collection set--it's already been copied.
4266 oop p = clear_partial_array_mask(ref);
4267 assert(_g1h->obj_in_cs(p),
4268 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4269 } else {
4270 oop p = oopDesc::load_decode_heap_oop(ref);
4271 assert(_g1h->is_in_g1_reserved(p),
4272 err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4273 }
4274 return true;
4275 }
4277 bool G1ParScanThreadState::verify_task(StarTask ref) const {
4278 if (ref.is_narrow()) {
4279 return verify_ref((narrowOop*) ref);
4280 } else {
4281 return verify_ref((oop*) ref);
4282 }
4283 }
4284 #endif // ASSERT
4286 void G1ParScanThreadState::trim_queue() {
4287 StarTask ref;
4288 do {
4289 // Drain the overflow stack first, so other threads can steal.
4290 while (refs()->pop_overflow(ref)) {
4291 deal_with_reference(ref);
4292 }
4293 while (refs()->pop_local(ref)) {
4294 deal_with_reference(ref);
4295 }
4296 } while (!refs()->is_empty());
4297 }
4299 G1ParClosureSuper::G1ParClosureSuper(G1CollectedHeap* g1, G1ParScanThreadState* par_scan_state) :
4300 _g1(g1), _g1_rem(_g1->g1_rem_set()), _cm(_g1->concurrent_mark()),
4301 _par_scan_state(par_scan_state) { }
4303 template <class T> void G1ParCopyHelper::mark_forwardee(T* p) {
4304 // This is called _after_ do_oop_work has been called, hence after
4305 // the object has been relocated to its new location and *p points
4306 // to its new location.
4308 T heap_oop = oopDesc::load_heap_oop(p);
4309 if (!oopDesc::is_null(heap_oop)) {
4310 oop obj = oopDesc::decode_heap_oop(heap_oop);
4311 assert((_g1->evacuation_failed()) || (!_g1->obj_in_cs(obj)),
4312 "shouldn't still be in the CSet if evacuation didn't fail.");
4313 HeapWord* addr = (HeapWord*)obj;
4314 if (_g1->is_in_g1_reserved(addr))
4315 _cm->grayRoot(oop(addr));
4316 }
4317 }
4319 oop G1ParCopyHelper::copy_to_survivor_space(oop old) {
4320 size_t word_sz = old->size();
4321 HeapRegion* from_region = _g1->heap_region_containing_raw(old);
4322 // +1 to make the -1 indexes valid...
4323 int young_index = from_region->young_index_in_cset()+1;
4324 assert( (from_region->is_young() && young_index > 0) ||
4325 (!from_region->is_young() && young_index == 0), "invariant" );
4326 G1CollectorPolicy* g1p = _g1->g1_policy();
4327 markOop m = old->mark();
4328 int age = m->has_displaced_mark_helper() ? m->displaced_mark_helper()->age()
4329 : m->age();
4330 GCAllocPurpose alloc_purpose = g1p->evacuation_destination(from_region, age,
4331 word_sz);
4332 HeapWord* obj_ptr = _par_scan_state->allocate(alloc_purpose, word_sz);
4333 oop obj = oop(obj_ptr);
4335 if (obj_ptr == NULL) {
4336 // This will either forward-to-self, or detect that someone else has
4337 // installed a forwarding pointer.
4338 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4339 return _g1->handle_evacuation_failure_par(cl, old);
4340 }
4342 // We're going to allocate linearly, so might as well prefetch ahead.
4343 Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
4345 oop forward_ptr = old->forward_to_atomic(obj);
4346 if (forward_ptr == NULL) {
4347 Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
4348 if (g1p->track_object_age(alloc_purpose)) {
4349 // We could simply do obj->incr_age(). However, this causes a
4350 // performance issue. obj->incr_age() will first check whether
4351 // the object has a displaced mark by checking its mark word;
4352 // getting the mark word from the new location of the object
4353 // stalls. So, given that we already have the mark word and we
4354 // are about to install it anyway, it's better to increase the
4355 // age on the mark word, when the object does not have a
4356 // displaced mark word. We're not expecting many objects to have
4357 // a displaced marked word, so that case is not optimized
4358 // further (it could be...) and we simply call obj->incr_age().
4360 if (m->has_displaced_mark_helper()) {
4361 // in this case, we have to install the mark word first,
4362 // otherwise obj looks to be forwarded (the old mark word,
4363 // which contains the forward pointer, was copied)
4364 obj->set_mark(m);
4365 obj->incr_age();
4366 } else {
4367 m = m->incr_age();
4368 obj->set_mark(m);
4369 }
4370 _par_scan_state->age_table()->add(obj, word_sz);
4371 } else {
4372 obj->set_mark(m);
4373 }
4375 // preserve "next" mark bit
4376 if (_g1->mark_in_progress() && !_g1->is_obj_ill(old)) {
4377 if (!use_local_bitmaps ||
4378 !_par_scan_state->alloc_buffer(alloc_purpose)->mark(obj_ptr)) {
4379 // if we couldn't mark it on the local bitmap (this happens when
4380 // the object was not allocated in the GCLab), we have to bite
4381 // the bullet and do the standard parallel mark
4382 _cm->markAndGrayObjectIfNecessary(obj);
4383 }
4384 #if 1
4385 if (_g1->isMarkedNext(old)) {
4386 _cm->nextMarkBitMap()->parClear((HeapWord*)old);
4387 }
4388 #endif
4389 }
4391 size_t* surv_young_words = _par_scan_state->surviving_young_words();
4392 surv_young_words[young_index] += word_sz;
4394 if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
4395 arrayOop(old)->set_length(0);
4396 oop* old_p = set_partial_array_mask(old);
4397 _par_scan_state->push_on_queue(old_p);
4398 } else {
4399 // No point in using the slower heap_region_containing() method,
4400 // given that we know obj is in the heap.
4401 _scanner->set_region(_g1->heap_region_containing_raw(obj));
4402 obj->oop_iterate_backwards(_scanner);
4403 }
4404 } else {
4405 _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz);
4406 obj = forward_ptr;
4407 }
4408 return obj;
4409 }
4411 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_forwardee>
4412 template <class T>
4413 void G1ParCopyClosure <do_gen_barrier, barrier, do_mark_forwardee>
4414 ::do_oop_work(T* p) {
4415 oop obj = oopDesc::load_decode_heap_oop(p);
4416 assert(barrier != G1BarrierRS || obj != NULL,
4417 "Precondition: G1BarrierRS implies obj is nonNull");
4419 // here the null check is implicit in the cset_fast_test() test
4420 if (_g1->in_cset_fast_test(obj)) {
4421 #if G1_REM_SET_LOGGING
4422 gclog_or_tty->print_cr("Loc "PTR_FORMAT" contains pointer "PTR_FORMAT" "
4423 "into CS.", p, (void*) obj);
4424 #endif
4425 if (obj->is_forwarded()) {
4426 oopDesc::encode_store_heap_oop(p, obj->forwardee());
4427 } else {
4428 oop copy_oop = copy_to_survivor_space(obj);
4429 oopDesc::encode_store_heap_oop(p, copy_oop);
4430 }
4431 // When scanning the RS, we only care about objs in CS.
4432 if (barrier == G1BarrierRS) {
4433 _par_scan_state->update_rs(_from, p, _par_scan_state->queue_num());
4434 }
4435 }
4437 if (barrier == G1BarrierEvac && obj != NULL) {
4438 _par_scan_state->update_rs(_from, p, _par_scan_state->queue_num());
4439 }
4441 if (do_gen_barrier && obj != NULL) {
4442 par_do_barrier(p);
4443 }
4444 }
4446 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(oop* p);
4447 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(narrowOop* p);
4449 template <class T> void G1ParScanPartialArrayClosure::do_oop_nv(T* p) {
4450 assert(has_partial_array_mask(p), "invariant");
4451 oop old = clear_partial_array_mask(p);
4452 assert(old->is_objArray(), "must be obj array");
4453 assert(old->is_forwarded(), "must be forwarded");
4454 assert(Universe::heap()->is_in_reserved(old), "must be in heap.");
4456 objArrayOop obj = objArrayOop(old->forwardee());
4457 assert((void*)old != (void*)old->forwardee(), "self forwarding here?");
4458 // Process ParGCArrayScanChunk elements now
4459 // and push the remainder back onto queue
4460 int start = arrayOop(old)->length();
4461 int end = obj->length();
4462 int remainder = end - start;
4463 assert(start <= end, "just checking");
4464 if (remainder > 2 * ParGCArrayScanChunk) {
4465 // Test above combines last partial chunk with a full chunk
4466 end = start + ParGCArrayScanChunk;
4467 arrayOop(old)->set_length(end);
4468 // Push remainder.
4469 oop* old_p = set_partial_array_mask(old);
4470 assert(arrayOop(old)->length() < obj->length(), "Empty push?");
4471 _par_scan_state->push_on_queue(old_p);
4472 } else {
4473 // Restore length so that the heap remains parsable in
4474 // case of evacuation failure.
4475 arrayOop(old)->set_length(end);
4476 }
4477 _scanner.set_region(_g1->heap_region_containing_raw(obj));
4478 // process our set of indices (include header in first chunk)
4479 obj->oop_iterate_range(&_scanner, start, end);
4480 }
4482 class G1ParEvacuateFollowersClosure : public VoidClosure {
4483 protected:
4484 G1CollectedHeap* _g1h;
4485 G1ParScanThreadState* _par_scan_state;
4486 RefToScanQueueSet* _queues;
4487 ParallelTaskTerminator* _terminator;
4489 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
4490 RefToScanQueueSet* queues() { return _queues; }
4491 ParallelTaskTerminator* terminator() { return _terminator; }
4493 public:
4494 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4495 G1ParScanThreadState* par_scan_state,
4496 RefToScanQueueSet* queues,
4497 ParallelTaskTerminator* terminator)
4498 : _g1h(g1h), _par_scan_state(par_scan_state),
4499 _queues(queues), _terminator(terminator) {}
4501 void do_void();
4503 private:
4504 inline bool offer_termination();
4505 };
4507 bool G1ParEvacuateFollowersClosure::offer_termination() {
4508 G1ParScanThreadState* const pss = par_scan_state();
4509 pss->start_term_time();
4510 const bool res = terminator()->offer_termination();
4511 pss->end_term_time();
4512 return res;
4513 }
4515 void G1ParEvacuateFollowersClosure::do_void() {
4516 StarTask stolen_task;
4517 G1ParScanThreadState* const pss = par_scan_state();
4518 pss->trim_queue();
4520 do {
4521 while (queues()->steal(pss->queue_num(), pss->hash_seed(), stolen_task)) {
4522 assert(pss->verify_task(stolen_task), "sanity");
4523 if (stolen_task.is_narrow()) {
4524 pss->deal_with_reference((narrowOop*) stolen_task);
4525 } else {
4526 pss->deal_with_reference((oop*) stolen_task);
4527 }
4529 // We've just processed a reference and we might have made
4530 // available new entries on the queues. So we have to make sure
4531 // we drain the queues as necessary.
4532 pss->trim_queue();
4533 }
4534 } while (!offer_termination());
4536 pss->retire_alloc_buffers();
4537 }
4539 class G1ParTask : public AbstractGangTask {
4540 protected:
4541 G1CollectedHeap* _g1h;
4542 RefToScanQueueSet *_queues;
4543 ParallelTaskTerminator _terminator;
4544 int _n_workers;
4546 Mutex _stats_lock;
4547 Mutex* stats_lock() { return &_stats_lock; }
4549 size_t getNCards() {
4550 return (_g1h->capacity() + G1BlockOffsetSharedArray::N_bytes - 1)
4551 / G1BlockOffsetSharedArray::N_bytes;
4552 }
4554 public:
4555 G1ParTask(G1CollectedHeap* g1h, int workers, RefToScanQueueSet *task_queues)
4556 : AbstractGangTask("G1 collection"),
4557 _g1h(g1h),
4558 _queues(task_queues),
4559 _terminator(workers, _queues),
4560 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true),
4561 _n_workers(workers)
4562 {}
4564 RefToScanQueueSet* queues() { return _queues; }
4566 RefToScanQueue *work_queue(int i) {
4567 return queues()->queue(i);
4568 }
4570 void work(int i) {
4571 if (i >= _n_workers) return; // no work needed this round
4573 double start_time_ms = os::elapsedTime() * 1000.0;
4574 _g1h->g1_policy()->record_gc_worker_start_time(i, start_time_ms);
4576 ResourceMark rm;
4577 HandleMark hm;
4579 G1ParScanThreadState pss(_g1h, i);
4580 G1ParScanHeapEvacClosure scan_evac_cl(_g1h, &pss);
4581 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss);
4582 G1ParScanPartialArrayClosure partial_scan_cl(_g1h, &pss);
4584 pss.set_evac_closure(&scan_evac_cl);
4585 pss.set_evac_failure_closure(&evac_failure_cl);
4586 pss.set_partial_scan_closure(&partial_scan_cl);
4588 G1ParScanExtRootClosure only_scan_root_cl(_g1h, &pss);
4589 G1ParScanPermClosure only_scan_perm_cl(_g1h, &pss);
4590 G1ParScanHeapRSClosure only_scan_heap_rs_cl(_g1h, &pss);
4591 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss);
4593 G1ParScanAndMarkExtRootClosure scan_mark_root_cl(_g1h, &pss);
4594 G1ParScanAndMarkPermClosure scan_mark_perm_cl(_g1h, &pss);
4595 G1ParScanAndMarkHeapRSClosure scan_mark_heap_rs_cl(_g1h, &pss);
4597 OopsInHeapRegionClosure *scan_root_cl;
4598 OopsInHeapRegionClosure *scan_perm_cl;
4600 if (_g1h->g1_policy()->during_initial_mark_pause()) {
4601 scan_root_cl = &scan_mark_root_cl;
4602 scan_perm_cl = &scan_mark_perm_cl;
4603 } else {
4604 scan_root_cl = &only_scan_root_cl;
4605 scan_perm_cl = &only_scan_perm_cl;
4606 }
4608 pss.start_strong_roots();
4609 _g1h->g1_process_strong_roots(/* not collecting perm */ false,
4610 SharedHeap::SO_AllClasses,
4611 scan_root_cl,
4612 &push_heap_rs_cl,
4613 scan_perm_cl,
4614 i);
4615 pss.end_strong_roots();
4616 {
4617 double start = os::elapsedTime();
4618 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4619 evac.do_void();
4620 double elapsed_ms = (os::elapsedTime()-start)*1000.0;
4621 double term_ms = pss.term_time()*1000.0;
4622 _g1h->g1_policy()->record_obj_copy_time(i, elapsed_ms-term_ms);
4623 _g1h->g1_policy()->record_termination(i, term_ms, pss.term_attempts());
4624 }
4625 _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4626 _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4628 // Clean up any par-expanded rem sets.
4629 HeapRegionRemSet::par_cleanup();
4631 if (ParallelGCVerbose) {
4632 MutexLocker x(stats_lock());
4633 pss.print_termination_stats(i);
4634 }
4636 assert(pss.refs()->is_empty(), "should be empty");
4637 double end_time_ms = os::elapsedTime() * 1000.0;
4638 _g1h->g1_policy()->record_gc_worker_end_time(i, end_time_ms);
4639 }
4640 };
4642 // *** Common G1 Evacuation Stuff
4644 // This method is run in a GC worker.
4646 void
4647 G1CollectedHeap::
4648 g1_process_strong_roots(bool collecting_perm_gen,
4649 SharedHeap::ScanningOption so,
4650 OopClosure* scan_non_heap_roots,
4651 OopsInHeapRegionClosure* scan_rs,
4652 OopsInGenClosure* scan_perm,
4653 int worker_i) {
4654 // First scan the strong roots, including the perm gen.
4655 double ext_roots_start = os::elapsedTime();
4656 double closure_app_time_sec = 0.0;
4658 BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
4659 BufferingOopsInGenClosure buf_scan_perm(scan_perm);
4660 buf_scan_perm.set_generation(perm_gen());
4662 // Walk the code cache w/o buffering, because StarTask cannot handle
4663 // unaligned oop locations.
4664 CodeBlobToOopClosure eager_scan_code_roots(scan_non_heap_roots, /*do_marking=*/ true);
4666 process_strong_roots(false, // no scoping; this is parallel code
4667 collecting_perm_gen, so,
4668 &buf_scan_non_heap_roots,
4669 &eager_scan_code_roots,
4670 &buf_scan_perm);
4672 // Finish up any enqueued closure apps.
4673 buf_scan_non_heap_roots.done();
4674 buf_scan_perm.done();
4675 double ext_roots_end = os::elapsedTime();
4676 g1_policy()->reset_obj_copy_time(worker_i);
4677 double obj_copy_time_sec =
4678 buf_scan_non_heap_roots.closure_app_seconds() +
4679 buf_scan_perm.closure_app_seconds();
4680 g1_policy()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
4681 double ext_root_time_ms =
4682 ((ext_roots_end - ext_roots_start) - obj_copy_time_sec) * 1000.0;
4683 g1_policy()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
4685 // Scan strong roots in mark stack.
4686 if (!_process_strong_tasks->is_task_claimed(G1H_PS_mark_stack_oops_do)) {
4687 concurrent_mark()->oops_do(scan_non_heap_roots);
4688 }
4689 double mark_stack_scan_ms = (os::elapsedTime() - ext_roots_end) * 1000.0;
4690 g1_policy()->record_mark_stack_scan_time(worker_i, mark_stack_scan_ms);
4692 // XXX What should this be doing in the parallel case?
4693 g1_policy()->record_collection_pause_end_CH_strong_roots();
4694 // Now scan the complement of the collection set.
4695 if (scan_rs != NULL) {
4696 g1_rem_set()->oops_into_collection_set_do(scan_rs, worker_i);
4697 }
4698 // Finish with the ref_processor roots.
4699 if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
4700 // We need to treat the discovered reference lists as roots and
4701 // keep entries (which are added by the marking threads) on them
4702 // live until they can be processed at the end of marking.
4703 ref_processor()->weak_oops_do(scan_non_heap_roots);
4704 ref_processor()->oops_do(scan_non_heap_roots);
4705 }
4706 g1_policy()->record_collection_pause_end_G1_strong_roots();
4707 _process_strong_tasks->all_tasks_completed();
4708 }
4710 void
4711 G1CollectedHeap::g1_process_weak_roots(OopClosure* root_closure,
4712 OopClosure* non_root_closure) {
4713 CodeBlobToOopClosure roots_in_blobs(root_closure, /*do_marking=*/ false);
4714 SharedHeap::process_weak_roots(root_closure, &roots_in_blobs, non_root_closure);
4715 }
4718 class SaveMarksClosure: public HeapRegionClosure {
4719 public:
4720 bool doHeapRegion(HeapRegion* r) {
4721 r->save_marks();
4722 return false;
4723 }
4724 };
4726 void G1CollectedHeap::save_marks() {
4727 if (!CollectedHeap::use_parallel_gc_threads()) {
4728 SaveMarksClosure sm;
4729 heap_region_iterate(&sm);
4730 }
4731 // We do this even in the parallel case
4732 perm_gen()->save_marks();
4733 }
4735 void G1CollectedHeap::evacuate_collection_set() {
4736 set_evacuation_failed(false);
4738 g1_rem_set()->prepare_for_oops_into_collection_set_do();
4739 concurrent_g1_refine()->set_use_cache(false);
4740 concurrent_g1_refine()->clear_hot_cache_claimed_index();
4742 int n_workers = (ParallelGCThreads > 0 ? workers()->total_workers() : 1);
4743 set_par_threads(n_workers);
4744 G1ParTask g1_par_task(this, n_workers, _task_queues);
4746 init_for_evac_failure(NULL);
4748 rem_set()->prepare_for_younger_refs_iterate(true);
4750 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
4751 double start_par = os::elapsedTime();
4752 if (G1CollectedHeap::use_parallel_gc_threads()) {
4753 // The individual threads will set their evac-failure closures.
4754 StrongRootsScope srs(this);
4755 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
4756 workers()->run_task(&g1_par_task);
4757 } else {
4758 StrongRootsScope srs(this);
4759 g1_par_task.work(0);
4760 }
4762 double par_time = (os::elapsedTime() - start_par) * 1000.0;
4763 g1_policy()->record_par_time(par_time);
4764 set_par_threads(0);
4765 // Is this the right thing to do here? We don't save marks
4766 // on individual heap regions when we allocate from
4767 // them in parallel, so this seems like the correct place for this.
4768 retire_all_alloc_regions();
4770 // Weak root processing.
4771 // Note: when JSR 292 is enabled and code blobs can contain
4772 // non-perm oops then we will need to process the code blobs
4773 // here too.
4774 {
4775 G1IsAliveClosure is_alive(this);
4776 G1KeepAliveClosure keep_alive(this);
4777 JNIHandles::weak_oops_do(&is_alive, &keep_alive);
4778 }
4779 release_gc_alloc_regions(false /* totally */);
4780 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
4782 concurrent_g1_refine()->clear_hot_cache();
4783 concurrent_g1_refine()->set_use_cache(true);
4785 finalize_for_evac_failure();
4787 // Must do this before removing self-forwarding pointers, which clears
4788 // the per-region evac-failure flags.
4789 concurrent_mark()->complete_marking_in_collection_set();
4791 if (evacuation_failed()) {
4792 remove_self_forwarding_pointers();
4793 if (PrintGCDetails) {
4794 gclog_or_tty->print(" (to-space overflow)");
4795 } else if (PrintGC) {
4796 gclog_or_tty->print("--");
4797 }
4798 }
4800 if (G1DeferredRSUpdate) {
4801 RedirtyLoggedCardTableEntryFastClosure redirty;
4802 dirty_card_queue_set().set_closure(&redirty);
4803 dirty_card_queue_set().apply_closure_to_all_completed_buffers();
4805 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
4806 dcq.merge_bufferlists(&dirty_card_queue_set());
4807 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
4808 }
4809 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
4810 }
4812 void G1CollectedHeap::free_region_if_empty(HeapRegion* hr,
4813 size_t* pre_used,
4814 FreeRegionList* free_list,
4815 HumongousRegionSet* humongous_proxy_set,
4816 HRRSCleanupTask* hrrs_cleanup_task,
4817 bool par) {
4818 if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) {
4819 if (hr->isHumongous()) {
4820 assert(hr->startsHumongous(), "we should only see starts humongous");
4821 free_humongous_region(hr, pre_used, free_list, humongous_proxy_set, par);
4822 } else {
4823 free_region(hr, pre_used, free_list, par);
4824 }
4825 } else {
4826 hr->rem_set()->do_cleanup_work(hrrs_cleanup_task);
4827 }
4828 }
4830 void G1CollectedHeap::free_region(HeapRegion* hr,
4831 size_t* pre_used,
4832 FreeRegionList* free_list,
4833 bool par) {
4834 assert(!hr->isHumongous(), "this is only for non-humongous regions");
4835 assert(!hr->is_empty(), "the region should not be empty");
4836 assert(free_list != NULL, "pre-condition");
4838 *pre_used += hr->used();
4839 hr->hr_clear(par, true /* clear_space */);
4840 free_list->add_as_head(hr);
4841 }
4843 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
4844 size_t* pre_used,
4845 FreeRegionList* free_list,
4846 HumongousRegionSet* humongous_proxy_set,
4847 bool par) {
4848 assert(hr->startsHumongous(), "this is only for starts humongous regions");
4849 assert(free_list != NULL, "pre-condition");
4850 assert(humongous_proxy_set != NULL, "pre-condition");
4852 size_t hr_used = hr->used();
4853 size_t hr_capacity = hr->capacity();
4854 size_t hr_pre_used = 0;
4855 _humongous_set.remove_with_proxy(hr, humongous_proxy_set);
4856 hr->set_notHumongous();
4857 free_region(hr, &hr_pre_used, free_list, par);
4859 int i = hr->hrs_index() + 1;
4860 size_t num = 1;
4861 while ((size_t) i < n_regions()) {
4862 HeapRegion* curr_hr = _hrs->at(i);
4863 if (!curr_hr->continuesHumongous()) {
4864 break;
4865 }
4866 curr_hr->set_notHumongous();
4867 free_region(curr_hr, &hr_pre_used, free_list, par);
4868 num += 1;
4869 i += 1;
4870 }
4871 assert(hr_pre_used == hr_used,
4872 err_msg("hr_pre_used: "SIZE_FORMAT" and hr_used: "SIZE_FORMAT" "
4873 "should be the same", hr_pre_used, hr_used));
4874 *pre_used += hr_pre_used;
4875 }
4877 void G1CollectedHeap::update_sets_after_freeing_regions(size_t pre_used,
4878 FreeRegionList* free_list,
4879 HumongousRegionSet* humongous_proxy_set,
4880 bool par) {
4881 if (pre_used > 0) {
4882 Mutex* lock = (par) ? ParGCRareEvent_lock : NULL;
4883 MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag);
4884 assert(_summary_bytes_used >= pre_used,
4885 err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" "
4886 "should be >= pre_used: "SIZE_FORMAT,
4887 _summary_bytes_used, pre_used));
4888 _summary_bytes_used -= pre_used;
4889 }
4890 if (free_list != NULL && !free_list->is_empty()) {
4891 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4892 _free_list.add_as_head(free_list);
4893 }
4894 if (humongous_proxy_set != NULL && !humongous_proxy_set->is_empty()) {
4895 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4896 _humongous_set.update_from_proxy(humongous_proxy_set);
4897 }
4898 }
4900 void G1CollectedHeap::dirtyCardsForYoungRegions(CardTableModRefBS* ct_bs, HeapRegion* list) {
4901 while (list != NULL) {
4902 guarantee( list->is_young(), "invariant" );
4904 HeapWord* bottom = list->bottom();
4905 HeapWord* end = list->end();
4906 MemRegion mr(bottom, end);
4907 ct_bs->dirty(mr);
4909 list = list->get_next_young_region();
4910 }
4911 }
4914 class G1ParCleanupCTTask : public AbstractGangTask {
4915 CardTableModRefBS* _ct_bs;
4916 G1CollectedHeap* _g1h;
4917 HeapRegion* volatile _su_head;
4918 public:
4919 G1ParCleanupCTTask(CardTableModRefBS* ct_bs,
4920 G1CollectedHeap* g1h,
4921 HeapRegion* survivor_list) :
4922 AbstractGangTask("G1 Par Cleanup CT Task"),
4923 _ct_bs(ct_bs),
4924 _g1h(g1h),
4925 _su_head(survivor_list)
4926 { }
4928 void work(int i) {
4929 HeapRegion* r;
4930 while (r = _g1h->pop_dirty_cards_region()) {
4931 clear_cards(r);
4932 }
4933 // Redirty the cards of the survivor regions.
4934 dirty_list(&this->_su_head);
4935 }
4937 void clear_cards(HeapRegion* r) {
4938 // Cards for Survivor regions will be dirtied later.
4939 if (!r->is_survivor()) {
4940 _ct_bs->clear(MemRegion(r->bottom(), r->end()));
4941 }
4942 }
4944 void dirty_list(HeapRegion* volatile * head_ptr) {
4945 HeapRegion* head;
4946 do {
4947 // Pop region off the list.
4948 head = *head_ptr;
4949 if (head != NULL) {
4950 HeapRegion* r = (HeapRegion*)
4951 Atomic::cmpxchg_ptr(head->get_next_young_region(), head_ptr, head);
4952 if (r == head) {
4953 assert(!r->isHumongous(), "Humongous regions shouldn't be on survivor list");
4954 _ct_bs->dirty(MemRegion(r->bottom(), r->end()));
4955 }
4956 }
4957 } while (*head_ptr != NULL);
4958 }
4959 };
4962 #ifndef PRODUCT
4963 class G1VerifyCardTableCleanup: public HeapRegionClosure {
4964 CardTableModRefBS* _ct_bs;
4965 public:
4966 G1VerifyCardTableCleanup(CardTableModRefBS* ct_bs)
4967 : _ct_bs(ct_bs) { }
4968 virtual bool doHeapRegion(HeapRegion* r) {
4969 MemRegion mr(r->bottom(), r->end());
4970 if (r->is_survivor()) {
4971 _ct_bs->verify_dirty_region(mr);
4972 } else {
4973 _ct_bs->verify_clean_region(mr);
4974 }
4975 return false;
4976 }
4977 };
4979 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
4980 CardTableModRefBS* ct_bs = (CardTableModRefBS*) (barrier_set());
4981 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
4982 // We cannot guarantee that [bottom(),end()] is dirty. Threads
4983 // dirty allocated blocks as they allocate them. The thread that
4984 // retires each region and replaces it with a new one will do a
4985 // maximal allocation to fill in [pre_dummy_top(),end()] but will
4986 // not dirty that area (one less thing to have to do while holding
4987 // a lock). So we can only verify that [bottom(),pre_dummy_top()]
4988 // is dirty. Also note that verify_dirty_region() requires
4989 // mr.start() and mr.end() to be card aligned and pre_dummy_top()
4990 // is not guaranteed to be.
4991 MemRegion mr(hr->bottom(),
4992 ct_bs->align_to_card_boundary(hr->pre_dummy_top()));
4993 ct_bs->verify_dirty_region(mr);
4994 }
4995 }
4997 void G1CollectedHeap::verify_dirty_young_regions() {
4998 verify_dirty_young_list(_young_list->first_region());
4999 verify_dirty_young_list(_young_list->first_survivor_region());
5000 }
5001 #endif
5003 void G1CollectedHeap::cleanUpCardTable() {
5004 CardTableModRefBS* ct_bs = (CardTableModRefBS*) (barrier_set());
5005 double start = os::elapsedTime();
5007 // Iterate over the dirty cards region list.
5008 G1ParCleanupCTTask cleanup_task(ct_bs, this,
5009 _young_list->first_survivor_region());
5011 if (ParallelGCThreads > 0) {
5012 set_par_threads(workers()->total_workers());
5013 workers()->run_task(&cleanup_task);
5014 set_par_threads(0);
5015 } else {
5016 while (_dirty_cards_region_list) {
5017 HeapRegion* r = _dirty_cards_region_list;
5018 cleanup_task.clear_cards(r);
5019 _dirty_cards_region_list = r->get_next_dirty_cards_region();
5020 if (_dirty_cards_region_list == r) {
5021 // The last region.
5022 _dirty_cards_region_list = NULL;
5023 }
5024 r->set_next_dirty_cards_region(NULL);
5025 }
5026 // now, redirty the cards of the survivor regions
5027 // (it seemed faster to do it this way, instead of iterating over
5028 // all regions and then clearing / dirtying as appropriate)
5029 dirtyCardsForYoungRegions(ct_bs, _young_list->first_survivor_region());
5030 }
5032 double elapsed = os::elapsedTime() - start;
5033 g1_policy()->record_clear_ct_time( elapsed * 1000.0);
5034 #ifndef PRODUCT
5035 if (G1VerifyCTCleanup || VerifyAfterGC) {
5036 G1VerifyCardTableCleanup cleanup_verifier(ct_bs);
5037 heap_region_iterate(&cleanup_verifier);
5038 }
5039 #endif
5040 }
5042 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head) {
5043 size_t pre_used = 0;
5044 FreeRegionList local_free_list("Local List for CSet Freeing");
5046 double young_time_ms = 0.0;
5047 double non_young_time_ms = 0.0;
5049 // Since the collection set is a superset of the the young list,
5050 // all we need to do to clear the young list is clear its
5051 // head and length, and unlink any young regions in the code below
5052 _young_list->clear();
5054 G1CollectorPolicy* policy = g1_policy();
5056 double start_sec = os::elapsedTime();
5057 bool non_young = true;
5059 HeapRegion* cur = cs_head;
5060 int age_bound = -1;
5061 size_t rs_lengths = 0;
5063 while (cur != NULL) {
5064 assert(!is_on_master_free_list(cur), "sanity");
5066 if (non_young) {
5067 if (cur->is_young()) {
5068 double end_sec = os::elapsedTime();
5069 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5070 non_young_time_ms += elapsed_ms;
5072 start_sec = os::elapsedTime();
5073 non_young = false;
5074 }
5075 } else {
5076 double end_sec = os::elapsedTime();
5077 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5078 young_time_ms += elapsed_ms;
5080 start_sec = os::elapsedTime();
5081 non_young = true;
5082 }
5084 rs_lengths += cur->rem_set()->occupied();
5086 HeapRegion* next = cur->next_in_collection_set();
5087 assert(cur->in_collection_set(), "bad CS");
5088 cur->set_next_in_collection_set(NULL);
5089 cur->set_in_collection_set(false);
5091 if (cur->is_young()) {
5092 int index = cur->young_index_in_cset();
5093 guarantee( index != -1, "invariant" );
5094 guarantee( (size_t)index < policy->young_cset_length(), "invariant" );
5095 size_t words_survived = _surviving_young_words[index];
5096 cur->record_surv_words_in_group(words_survived);
5098 // At this point the we have 'popped' cur from the collection set
5099 // (linked via next_in_collection_set()) but it is still in the
5100 // young list (linked via next_young_region()). Clear the
5101 // _next_young_region field.
5102 cur->set_next_young_region(NULL);
5103 } else {
5104 int index = cur->young_index_in_cset();
5105 guarantee( index == -1, "invariant" );
5106 }
5108 assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
5109 (!cur->is_young() && cur->young_index_in_cset() == -1),
5110 "invariant" );
5112 if (!cur->evacuation_failed()) {
5113 // And the region is empty.
5114 assert(!cur->is_empty(), "Should not have empty regions in a CS.");
5115 free_region(cur, &pre_used, &local_free_list, false /* par */);
5116 } else {
5117 cur->uninstall_surv_rate_group();
5118 if (cur->is_young())
5119 cur->set_young_index_in_cset(-1);
5120 cur->set_not_young();
5121 cur->set_evacuation_failed(false);
5122 }
5123 cur = next;
5124 }
5126 policy->record_max_rs_lengths(rs_lengths);
5127 policy->cset_regions_freed();
5129 double end_sec = os::elapsedTime();
5130 double elapsed_ms = (end_sec - start_sec) * 1000.0;
5131 if (non_young)
5132 non_young_time_ms += elapsed_ms;
5133 else
5134 young_time_ms += elapsed_ms;
5136 update_sets_after_freeing_regions(pre_used, &local_free_list,
5137 NULL /* humongous_proxy_set */,
5138 false /* par */);
5139 policy->record_young_free_cset_time_ms(young_time_ms);
5140 policy->record_non_young_free_cset_time_ms(non_young_time_ms);
5141 }
5143 // This routine is similar to the above but does not record
5144 // any policy statistics or update free lists; we are abandoning
5145 // the current incremental collection set in preparation of a
5146 // full collection. After the full GC we will start to build up
5147 // the incremental collection set again.
5148 // This is only called when we're doing a full collection
5149 // and is immediately followed by the tearing down of the young list.
5151 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
5152 HeapRegion* cur = cs_head;
5154 while (cur != NULL) {
5155 HeapRegion* next = cur->next_in_collection_set();
5156 assert(cur->in_collection_set(), "bad CS");
5157 cur->set_next_in_collection_set(NULL);
5158 cur->set_in_collection_set(false);
5159 cur->set_young_index_in_cset(-1);
5160 cur = next;
5161 }
5162 }
5164 void G1CollectedHeap::set_free_regions_coming() {
5165 if (G1ConcRegionFreeingVerbose) {
5166 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
5167 "setting free regions coming");
5168 }
5170 assert(!free_regions_coming(), "pre-condition");
5171 _free_regions_coming = true;
5172 }
5174 void G1CollectedHeap::reset_free_regions_coming() {
5175 {
5176 assert(free_regions_coming(), "pre-condition");
5177 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5178 _free_regions_coming = false;
5179 SecondaryFreeList_lock->notify_all();
5180 }
5182 if (G1ConcRegionFreeingVerbose) {
5183 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
5184 "reset free regions coming");
5185 }
5186 }
5188 void G1CollectedHeap::wait_while_free_regions_coming() {
5189 // Most of the time we won't have to wait, so let's do a quick test
5190 // first before we take the lock.
5191 if (!free_regions_coming()) {
5192 return;
5193 }
5195 if (G1ConcRegionFreeingVerbose) {
5196 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
5197 "waiting for free regions");
5198 }
5200 {
5201 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5202 while (free_regions_coming()) {
5203 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
5204 }
5205 }
5207 if (G1ConcRegionFreeingVerbose) {
5208 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
5209 "done waiting for free regions");
5210 }
5211 }
5213 size_t G1CollectedHeap::n_regions() {
5214 return _hrs->length();
5215 }
5217 size_t G1CollectedHeap::max_regions() {
5218 return
5219 (size_t)align_size_up(max_capacity(), HeapRegion::GrainBytes) /
5220 HeapRegion::GrainBytes;
5221 }
5223 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
5224 assert(heap_lock_held_for_gc(),
5225 "the heap lock should already be held by or for this thread");
5226 _young_list->push_region(hr);
5227 g1_policy()->set_region_short_lived(hr);
5228 }
5230 class NoYoungRegionsClosure: public HeapRegionClosure {
5231 private:
5232 bool _success;
5233 public:
5234 NoYoungRegionsClosure() : _success(true) { }
5235 bool doHeapRegion(HeapRegion* r) {
5236 if (r->is_young()) {
5237 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
5238 r->bottom(), r->end());
5239 _success = false;
5240 }
5241 return false;
5242 }
5243 bool success() { return _success; }
5244 };
5246 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
5247 bool ret = _young_list->check_list_empty(check_sample);
5249 if (check_heap) {
5250 NoYoungRegionsClosure closure;
5251 heap_region_iterate(&closure);
5252 ret = ret && closure.success();
5253 }
5255 return ret;
5256 }
5258 void G1CollectedHeap::empty_young_list() {
5259 assert(heap_lock_held_for_gc(),
5260 "the heap lock should already be held by or for this thread");
5261 assert(g1_policy()->in_young_gc_mode(), "should be in young GC mode");
5263 _young_list->empty_list();
5264 }
5266 bool G1CollectedHeap::all_alloc_regions_no_allocs_since_save_marks() {
5267 bool no_allocs = true;
5268 for (int ap = 0; ap < GCAllocPurposeCount && no_allocs; ++ap) {
5269 HeapRegion* r = _gc_alloc_regions[ap];
5270 no_allocs = r == NULL || r->saved_mark_at_top();
5271 }
5272 return no_allocs;
5273 }
5275 void G1CollectedHeap::retire_all_alloc_regions() {
5276 for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
5277 HeapRegion* r = _gc_alloc_regions[ap];
5278 if (r != NULL) {
5279 // Check for aliases.
5280 bool has_processed_alias = false;
5281 for (int i = 0; i < ap; ++i) {
5282 if (_gc_alloc_regions[i] == r) {
5283 has_processed_alias = true;
5284 break;
5285 }
5286 }
5287 if (!has_processed_alias) {
5288 retire_alloc_region(r, false /* par */);
5289 }
5290 }
5291 }
5292 }
5294 // Done at the start of full GC.
5295 void G1CollectedHeap::tear_down_region_lists() {
5296 _free_list.remove_all();
5297 }
5299 class RegionResetter: public HeapRegionClosure {
5300 G1CollectedHeap* _g1h;
5301 FreeRegionList _local_free_list;
5303 public:
5304 RegionResetter() : _g1h(G1CollectedHeap::heap()),
5305 _local_free_list("Local Free List for RegionResetter") { }
5307 bool doHeapRegion(HeapRegion* r) {
5308 if (r->continuesHumongous()) return false;
5309 if (r->top() > r->bottom()) {
5310 if (r->top() < r->end()) {
5311 Copy::fill_to_words(r->top(),
5312 pointer_delta(r->end(), r->top()));
5313 }
5314 } else {
5315 assert(r->is_empty(), "tautology");
5316 _local_free_list.add_as_tail(r);
5317 }
5318 return false;
5319 }
5321 void update_free_lists() {
5322 _g1h->update_sets_after_freeing_regions(0, &_local_free_list, NULL,
5323 false /* par */);
5324 }
5325 };
5327 // Done at the end of full GC.
5328 void G1CollectedHeap::rebuild_region_lists() {
5329 // This needs to go at the end of the full GC.
5330 RegionResetter rs;
5331 heap_region_iterate(&rs);
5332 rs.update_free_lists();
5333 }
5335 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
5336 _refine_cte_cl->set_concurrent(concurrent);
5337 }
5339 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
5340 HeapRegion* hr = heap_region_containing(p);
5341 if (hr == NULL) {
5342 return is_in_permanent(p);
5343 } else {
5344 return hr->is_in(p);
5345 }
5346 }
5348 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
5349 bool force) {
5350 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5351 assert(!force || g1_policy()->can_expand_young_list(),
5352 "if force is true we should be able to expand the young list");
5353 if (force || !g1_policy()->is_young_list_full()) {
5354 HeapRegion* new_alloc_region = new_region(word_size,
5355 false /* do_expand */);
5356 if (new_alloc_region != NULL) {
5357 g1_policy()->update_region_num(true /* next_is_young */);
5358 set_region_short_lived_locked(new_alloc_region);
5359 g1mm()->update_eden_counters();
5360 return new_alloc_region;
5361 }
5362 }
5363 return NULL;
5364 }
5366 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
5367 size_t allocated_bytes) {
5368 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5369 assert(alloc_region->is_young(), "all mutator alloc regions should be young");
5371 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
5372 _summary_bytes_used += allocated_bytes;
5373 }
5375 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
5376 bool force) {
5377 return _g1h->new_mutator_alloc_region(word_size, force);
5378 }
5380 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
5381 size_t allocated_bytes) {
5382 _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
5383 }
5385 // Heap region set verification
5387 class VerifyRegionListsClosure : public HeapRegionClosure {
5388 private:
5389 HumongousRegionSet* _humongous_set;
5390 FreeRegionList* _free_list;
5391 size_t _region_count;
5393 public:
5394 VerifyRegionListsClosure(HumongousRegionSet* humongous_set,
5395 FreeRegionList* free_list) :
5396 _humongous_set(humongous_set), _free_list(free_list),
5397 _region_count(0) { }
5399 size_t region_count() { return _region_count; }
5401 bool doHeapRegion(HeapRegion* hr) {
5402 _region_count += 1;
5404 if (hr->continuesHumongous()) {
5405 return false;
5406 }
5408 if (hr->is_young()) {
5409 // TODO
5410 } else if (hr->startsHumongous()) {
5411 _humongous_set->verify_next_region(hr);
5412 } else if (hr->is_empty()) {
5413 _free_list->verify_next_region(hr);
5414 }
5415 return false;
5416 }
5417 };
5419 void G1CollectedHeap::verify_region_sets() {
5420 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5422 // First, check the explicit lists.
5423 _free_list.verify();
5424 {
5425 // Given that a concurrent operation might be adding regions to
5426 // the secondary free list we have to take the lock before
5427 // verifying it.
5428 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5429 _secondary_free_list.verify();
5430 }
5431 _humongous_set.verify();
5433 // If a concurrent region freeing operation is in progress it will
5434 // be difficult to correctly attributed any free regions we come
5435 // across to the correct free list given that they might belong to
5436 // one of several (free_list, secondary_free_list, any local lists,
5437 // etc.). So, if that's the case we will skip the rest of the
5438 // verification operation. Alternatively, waiting for the concurrent
5439 // operation to complete will have a non-trivial effect on the GC's
5440 // operation (no concurrent operation will last longer than the
5441 // interval between two calls to verification) and it might hide
5442 // any issues that we would like to catch during testing.
5443 if (free_regions_coming()) {
5444 return;
5445 }
5447 // Make sure we append the secondary_free_list on the free_list so
5448 // that all free regions we will come across can be safely
5449 // attributed to the free_list.
5450 append_secondary_free_list_if_not_empty_with_lock();
5452 // Finally, make sure that the region accounting in the lists is
5453 // consistent with what we see in the heap.
5454 _humongous_set.verify_start();
5455 _free_list.verify_start();
5457 VerifyRegionListsClosure cl(&_humongous_set, &_free_list);
5458 heap_region_iterate(&cl);
5460 _humongous_set.verify_end();
5461 _free_list.verify_end();
5462 }