Mon, 21 Jul 2014 09:59:46 +0200
8048085: Aborting marking just before remark results in useless additional clearing of the next mark bitmap
Summary: Skip clearing the next bitmap if we just recently aborted since the full GC already clears this bitmap.
Reviewed-by: brutisso
1 /*
2 * Copyright (c) 2001, 2014, Oracle and/or its affiliates. All rights reserved.
3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
4 *
5 * This code is free software; you can redistribute it and/or modify it
6 * under the terms of the GNU General Public License version 2 only, as
7 * published by the Free Software Foundation.
8 *
9 * This code is distributed in the hope that it will be useful, but WITHOUT
10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
12 * version 2 for more details (a copy is included in the LICENSE file that
13 * accompanied this code).
14 *
15 * You should have received a copy of the GNU General Public License version
16 * 2 along with this work; if not, write to the Free Software Foundation,
17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
18 *
19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
20 * or visit www.oracle.com if you need additional information or have any
21 * questions.
22 *
23 */
25 #if !defined(__clang_major__) && defined(__GNUC__)
26 #define ATTRIBUTE_PRINTF(x,y) // FIXME, formats are a mess.
27 #endif
29 #include "precompiled.hpp"
30 #include "code/codeCache.hpp"
31 #include "code/icBuffer.hpp"
32 #include "gc_implementation/g1/bufferingOopClosure.hpp"
33 #include "gc_implementation/g1/concurrentG1Refine.hpp"
34 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
35 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
36 #include "gc_implementation/g1/g1AllocRegion.inline.hpp"
37 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
38 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
39 #include "gc_implementation/g1/g1ErgoVerbose.hpp"
40 #include "gc_implementation/g1/g1EvacFailure.hpp"
41 #include "gc_implementation/g1/g1GCPhaseTimes.hpp"
42 #include "gc_implementation/g1/g1Log.hpp"
43 #include "gc_implementation/g1/g1MarkSweep.hpp"
44 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
45 #include "gc_implementation/g1/g1ParScanThreadState.inline.hpp"
46 #include "gc_implementation/g1/g1RemSet.inline.hpp"
47 #include "gc_implementation/g1/g1StringDedup.hpp"
48 #include "gc_implementation/g1/g1YCTypes.hpp"
49 #include "gc_implementation/g1/heapRegion.inline.hpp"
50 #include "gc_implementation/g1/heapRegionRemSet.hpp"
51 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
52 #include "gc_implementation/g1/vm_operations_g1.hpp"
53 #include "gc_implementation/shared/gcHeapSummary.hpp"
54 #include "gc_implementation/shared/gcTimer.hpp"
55 #include "gc_implementation/shared/gcTrace.hpp"
56 #include "gc_implementation/shared/gcTraceTime.hpp"
57 #include "gc_implementation/shared/isGCActiveMark.hpp"
58 #include "memory/allocation.hpp"
59 #include "memory/gcLocker.inline.hpp"
60 #include "memory/generationSpec.hpp"
61 #include "memory/iterator.hpp"
62 #include "memory/referenceProcessor.hpp"
63 #include "oops/oop.inline.hpp"
64 #include "oops/oop.pcgc.inline.hpp"
65 #include "runtime/orderAccess.inline.hpp"
66 #include "runtime/vmThread.hpp"
68 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
70 // turn it on so that the contents of the young list (scan-only /
71 // to-be-collected) are printed at "strategic" points before / during
72 // / after the collection --- this is useful for debugging
73 #define YOUNG_LIST_VERBOSE 0
74 // CURRENT STATUS
75 // This file is under construction. Search for "FIXME".
77 // INVARIANTS/NOTES
78 //
79 // All allocation activity covered by the G1CollectedHeap interface is
80 // serialized by acquiring the HeapLock. This happens in mem_allocate
81 // and allocate_new_tlab, which are the "entry" points to the
82 // allocation code from the rest of the JVM. (Note that this does not
83 // apply to TLAB allocation, which is not part of this interface: it
84 // is done by clients of this interface.)
86 // Notes on implementation of parallelism in different tasks.
87 //
88 // G1ParVerifyTask uses heap_region_par_iterate_chunked() for parallelism.
89 // The number of GC workers is passed to heap_region_par_iterate_chunked().
90 // It does use run_task() which sets _n_workers in the task.
91 // G1ParTask executes g1_process_roots() ->
92 // SharedHeap::process_roots() which calls eventually to
93 // CardTableModRefBS::par_non_clean_card_iterate_work() which uses
94 // SequentialSubTasksDone. SharedHeap::process_roots() also
95 // directly uses SubTasksDone (_process_strong_tasks field in SharedHeap).
96 //
98 // Local to this file.
100 class RefineCardTableEntryClosure: public CardTableEntryClosure {
101 bool _concurrent;
102 public:
103 RefineCardTableEntryClosure() : _concurrent(true) { }
105 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
106 bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, false);
107 // This path is executed by the concurrent refine or mutator threads,
108 // concurrently, and so we do not care if card_ptr contains references
109 // that point into the collection set.
110 assert(!oops_into_cset, "should be");
112 if (_concurrent && SuspendibleThreadSet::should_yield()) {
113 // Caller will actually yield.
114 return false;
115 }
116 // Otherwise, we finished successfully; return true.
117 return true;
118 }
120 void set_concurrent(bool b) { _concurrent = b; }
121 };
124 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure {
125 size_t _num_processed;
126 CardTableModRefBS* _ctbs;
127 int _histo[256];
129 public:
130 ClearLoggedCardTableEntryClosure() :
131 _num_processed(0), _ctbs(G1CollectedHeap::heap()->g1_barrier_set())
132 {
133 for (int i = 0; i < 256; i++) _histo[i] = 0;
134 }
136 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
137 unsigned char* ujb = (unsigned char*)card_ptr;
138 int ind = (int)(*ujb);
139 _histo[ind]++;
141 *card_ptr = (jbyte)CardTableModRefBS::clean_card_val();
142 _num_processed++;
144 return true;
145 }
147 size_t num_processed() { return _num_processed; }
149 void print_histo() {
150 gclog_or_tty->print_cr("Card table value histogram:");
151 for (int i = 0; i < 256; i++) {
152 if (_histo[i] != 0) {
153 gclog_or_tty->print_cr(" %d: %d", i, _histo[i]);
154 }
155 }
156 }
157 };
159 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
160 private:
161 size_t _num_processed;
163 public:
164 RedirtyLoggedCardTableEntryClosure() : CardTableEntryClosure(), _num_processed(0) { }
166 bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
167 *card_ptr = CardTableModRefBS::dirty_card_val();
168 _num_processed++;
169 return true;
170 }
172 size_t num_processed() const { return _num_processed; }
173 };
175 YoungList::YoungList(G1CollectedHeap* g1h) :
176 _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0),
177 _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) {
178 guarantee(check_list_empty(false), "just making sure...");
179 }
181 void YoungList::push_region(HeapRegion *hr) {
182 assert(!hr->is_young(), "should not already be young");
183 assert(hr->get_next_young_region() == NULL, "cause it should!");
185 hr->set_next_young_region(_head);
186 _head = hr;
188 _g1h->g1_policy()->set_region_eden(hr, (int) _length);
189 ++_length;
190 }
192 void YoungList::add_survivor_region(HeapRegion* hr) {
193 assert(hr->is_survivor(), "should be flagged as survivor region");
194 assert(hr->get_next_young_region() == NULL, "cause it should!");
196 hr->set_next_young_region(_survivor_head);
197 if (_survivor_head == NULL) {
198 _survivor_tail = hr;
199 }
200 _survivor_head = hr;
201 ++_survivor_length;
202 }
204 void YoungList::empty_list(HeapRegion* list) {
205 while (list != NULL) {
206 HeapRegion* next = list->get_next_young_region();
207 list->set_next_young_region(NULL);
208 list->uninstall_surv_rate_group();
209 list->set_not_young();
210 list = next;
211 }
212 }
214 void YoungList::empty_list() {
215 assert(check_list_well_formed(), "young list should be well formed");
217 empty_list(_head);
218 _head = NULL;
219 _length = 0;
221 empty_list(_survivor_head);
222 _survivor_head = NULL;
223 _survivor_tail = NULL;
224 _survivor_length = 0;
226 _last_sampled_rs_lengths = 0;
228 assert(check_list_empty(false), "just making sure...");
229 }
231 bool YoungList::check_list_well_formed() {
232 bool ret = true;
234 uint length = 0;
235 HeapRegion* curr = _head;
236 HeapRegion* last = NULL;
237 while (curr != NULL) {
238 if (!curr->is_young()) {
239 gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
240 "incorrectly tagged (y: %d, surv: %d)",
241 curr->bottom(), curr->end(),
242 curr->is_young(), curr->is_survivor());
243 ret = false;
244 }
245 ++length;
246 last = curr;
247 curr = curr->get_next_young_region();
248 }
249 ret = ret && (length == _length);
251 if (!ret) {
252 gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
253 gclog_or_tty->print_cr("### list has %u entries, _length is %u",
254 length, _length);
255 }
257 return ret;
258 }
260 bool YoungList::check_list_empty(bool check_sample) {
261 bool ret = true;
263 if (_length != 0) {
264 gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u",
265 _length);
266 ret = false;
267 }
268 if (check_sample && _last_sampled_rs_lengths != 0) {
269 gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
270 ret = false;
271 }
272 if (_head != NULL) {
273 gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
274 ret = false;
275 }
276 if (!ret) {
277 gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
278 }
280 return ret;
281 }
283 void
284 YoungList::rs_length_sampling_init() {
285 _sampled_rs_lengths = 0;
286 _curr = _head;
287 }
289 bool
290 YoungList::rs_length_sampling_more() {
291 return _curr != NULL;
292 }
294 void
295 YoungList::rs_length_sampling_next() {
296 assert( _curr != NULL, "invariant" );
297 size_t rs_length = _curr->rem_set()->occupied();
299 _sampled_rs_lengths += rs_length;
301 // The current region may not yet have been added to the
302 // incremental collection set (it gets added when it is
303 // retired as the current allocation region).
304 if (_curr->in_collection_set()) {
305 // Update the collection set policy information for this region
306 _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
307 }
309 _curr = _curr->get_next_young_region();
310 if (_curr == NULL) {
311 _last_sampled_rs_lengths = _sampled_rs_lengths;
312 // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
313 }
314 }
316 void
317 YoungList::reset_auxilary_lists() {
318 guarantee( is_empty(), "young list should be empty" );
319 assert(check_list_well_formed(), "young list should be well formed");
321 // Add survivor regions to SurvRateGroup.
322 _g1h->g1_policy()->note_start_adding_survivor_regions();
323 _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
325 int young_index_in_cset = 0;
326 for (HeapRegion* curr = _survivor_head;
327 curr != NULL;
328 curr = curr->get_next_young_region()) {
329 _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
331 // The region is a non-empty survivor so let's add it to
332 // the incremental collection set for the next evacuation
333 // pause.
334 _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
335 young_index_in_cset += 1;
336 }
337 assert((uint) young_index_in_cset == _survivor_length, "post-condition");
338 _g1h->g1_policy()->note_stop_adding_survivor_regions();
340 _head = _survivor_head;
341 _length = _survivor_length;
342 if (_survivor_head != NULL) {
343 assert(_survivor_tail != NULL, "cause it shouldn't be");
344 assert(_survivor_length > 0, "invariant");
345 _survivor_tail->set_next_young_region(NULL);
346 }
348 // Don't clear the survivor list handles until the start of
349 // the next evacuation pause - we need it in order to re-tag
350 // the survivor regions from this evacuation pause as 'young'
351 // at the start of the next.
353 _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
355 assert(check_list_well_formed(), "young list should be well formed");
356 }
358 void YoungList::print() {
359 HeapRegion* lists[] = {_head, _survivor_head};
360 const char* names[] = {"YOUNG", "SURVIVOR"};
362 for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) {
363 gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
364 HeapRegion *curr = lists[list];
365 if (curr == NULL)
366 gclog_or_tty->print_cr(" empty");
367 while (curr != NULL) {
368 gclog_or_tty->print_cr(" "HR_FORMAT", P: "PTR_FORMAT "N: "PTR_FORMAT", age: %4d",
369 HR_FORMAT_PARAMS(curr),
370 curr->prev_top_at_mark_start(),
371 curr->next_top_at_mark_start(),
372 curr->age_in_surv_rate_group_cond());
373 curr = curr->get_next_young_region();
374 }
375 }
377 gclog_or_tty->cr();
378 }
380 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
381 {
382 // Claim the right to put the region on the dirty cards region list
383 // by installing a self pointer.
384 HeapRegion* next = hr->get_next_dirty_cards_region();
385 if (next == NULL) {
386 HeapRegion* res = (HeapRegion*)
387 Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
388 NULL);
389 if (res == NULL) {
390 HeapRegion* head;
391 do {
392 // Put the region to the dirty cards region list.
393 head = _dirty_cards_region_list;
394 next = (HeapRegion*)
395 Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
396 if (next == head) {
397 assert(hr->get_next_dirty_cards_region() == hr,
398 "hr->get_next_dirty_cards_region() != hr");
399 if (next == NULL) {
400 // The last region in the list points to itself.
401 hr->set_next_dirty_cards_region(hr);
402 } else {
403 hr->set_next_dirty_cards_region(next);
404 }
405 }
406 } while (next != head);
407 }
408 }
409 }
411 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
412 {
413 HeapRegion* head;
414 HeapRegion* hr;
415 do {
416 head = _dirty_cards_region_list;
417 if (head == NULL) {
418 return NULL;
419 }
420 HeapRegion* new_head = head->get_next_dirty_cards_region();
421 if (head == new_head) {
422 // The last region.
423 new_head = NULL;
424 }
425 hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
426 head);
427 } while (hr != head);
428 assert(hr != NULL, "invariant");
429 hr->set_next_dirty_cards_region(NULL);
430 return hr;
431 }
433 #ifdef ASSERT
434 // A region is added to the collection set as it is retired
435 // so an address p can point to a region which will be in the
436 // collection set but has not yet been retired. This method
437 // therefore is only accurate during a GC pause after all
438 // regions have been retired. It is used for debugging
439 // to check if an nmethod has references to objects that can
440 // be move during a partial collection. Though it can be
441 // inaccurate, it is sufficient for G1 because the conservative
442 // implementation of is_scavengable() for G1 will indicate that
443 // all nmethods must be scanned during a partial collection.
444 bool G1CollectedHeap::is_in_partial_collection(const void* p) {
445 HeapRegion* hr = heap_region_containing(p);
446 return hr != NULL && hr->in_collection_set();
447 }
448 #endif
450 // Returns true if the reference points to an object that
451 // can move in an incremental collection.
452 bool G1CollectedHeap::is_scavengable(const void* p) {
453 G1CollectedHeap* g1h = G1CollectedHeap::heap();
454 G1CollectorPolicy* g1p = g1h->g1_policy();
455 HeapRegion* hr = heap_region_containing(p);
456 if (hr == NULL) {
457 // null
458 assert(p == NULL, err_msg("Not NULL " PTR_FORMAT ,p));
459 return false;
460 } else {
461 return !hr->isHumongous();
462 }
463 }
465 void G1CollectedHeap::check_ct_logs_at_safepoint() {
466 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
467 CardTableModRefBS* ct_bs = g1_barrier_set();
469 // Count the dirty cards at the start.
470 CountNonCleanMemRegionClosure count1(this);
471 ct_bs->mod_card_iterate(&count1);
472 int orig_count = count1.n();
474 // First clear the logged cards.
475 ClearLoggedCardTableEntryClosure clear;
476 dcqs.apply_closure_to_all_completed_buffers(&clear);
477 dcqs.iterate_closure_all_threads(&clear, false);
478 clear.print_histo();
480 // Now ensure that there's no dirty cards.
481 CountNonCleanMemRegionClosure count2(this);
482 ct_bs->mod_card_iterate(&count2);
483 if (count2.n() != 0) {
484 gclog_or_tty->print_cr("Card table has %d entries; %d originally",
485 count2.n(), orig_count);
486 }
487 guarantee(count2.n() == 0, "Card table should be clean.");
489 RedirtyLoggedCardTableEntryClosure redirty;
490 dcqs.apply_closure_to_all_completed_buffers(&redirty);
491 dcqs.iterate_closure_all_threads(&redirty, false);
492 gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
493 clear.num_processed(), orig_count);
494 guarantee(redirty.num_processed() == clear.num_processed(),
495 err_msg("Redirtied "SIZE_FORMAT" cards, bug cleared "SIZE_FORMAT,
496 redirty.num_processed(), clear.num_processed()));
498 CountNonCleanMemRegionClosure count3(this);
499 ct_bs->mod_card_iterate(&count3);
500 if (count3.n() != orig_count) {
501 gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
502 orig_count, count3.n());
503 guarantee(count3.n() >= orig_count, "Should have restored them all.");
504 }
505 }
507 // Private class members.
509 G1CollectedHeap* G1CollectedHeap::_g1h;
511 // Private methods.
513 HeapRegion*
514 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
515 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
516 while (!_secondary_free_list.is_empty() || free_regions_coming()) {
517 if (!_secondary_free_list.is_empty()) {
518 if (G1ConcRegionFreeingVerbose) {
519 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
520 "secondary_free_list has %u entries",
521 _secondary_free_list.length());
522 }
523 // It looks as if there are free regions available on the
524 // secondary_free_list. Let's move them to the free_list and try
525 // again to allocate from it.
526 append_secondary_free_list();
528 assert(!_free_list.is_empty(), "if the secondary_free_list was not "
529 "empty we should have moved at least one entry to the free_list");
530 HeapRegion* res = _free_list.remove_region(is_old);
531 if (G1ConcRegionFreeingVerbose) {
532 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
533 "allocated "HR_FORMAT" from secondary_free_list",
534 HR_FORMAT_PARAMS(res));
535 }
536 return res;
537 }
539 // Wait here until we get notified either when (a) there are no
540 // more free regions coming or (b) some regions have been moved on
541 // the secondary_free_list.
542 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
543 }
545 if (G1ConcRegionFreeingVerbose) {
546 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
547 "could not allocate from secondary_free_list");
548 }
549 return NULL;
550 }
552 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
553 assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords,
554 "the only time we use this to allocate a humongous region is "
555 "when we are allocating a single humongous region");
557 HeapRegion* res;
558 if (G1StressConcRegionFreeing) {
559 if (!_secondary_free_list.is_empty()) {
560 if (G1ConcRegionFreeingVerbose) {
561 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
562 "forced to look at the secondary_free_list");
563 }
564 res = new_region_try_secondary_free_list(is_old);
565 if (res != NULL) {
566 return res;
567 }
568 }
569 }
571 res = _free_list.remove_region(is_old);
573 if (res == NULL) {
574 if (G1ConcRegionFreeingVerbose) {
575 gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
576 "res == NULL, trying the secondary_free_list");
577 }
578 res = new_region_try_secondary_free_list(is_old);
579 }
580 if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
581 // Currently, only attempts to allocate GC alloc regions set
582 // do_expand to true. So, we should only reach here during a
583 // safepoint. If this assumption changes we might have to
584 // reconsider the use of _expand_heap_after_alloc_failure.
585 assert(SafepointSynchronize::is_at_safepoint(), "invariant");
587 ergo_verbose1(ErgoHeapSizing,
588 "attempt heap expansion",
589 ergo_format_reason("region allocation request failed")
590 ergo_format_byte("allocation request"),
591 word_size * HeapWordSize);
592 if (expand(word_size * HeapWordSize)) {
593 // Given that expand() succeeded in expanding the heap, and we
594 // always expand the heap by an amount aligned to the heap
595 // region size, the free list should in theory not be empty.
596 // In either case remove_region() will check for NULL.
597 res = _free_list.remove_region(is_old);
598 } else {
599 _expand_heap_after_alloc_failure = false;
600 }
601 }
602 return res;
603 }
605 uint G1CollectedHeap::humongous_obj_allocate_find_first(uint num_regions,
606 size_t word_size) {
607 assert(isHumongous(word_size), "word_size should be humongous");
608 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
610 uint first = G1_NULL_HRS_INDEX;
611 if (num_regions == 1) {
612 // Only one region to allocate, no need to go through the slower
613 // path. The caller will attempt the expansion if this fails, so
614 // let's not try to expand here too.
615 HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
616 if (hr != NULL) {
617 first = hr->hrs_index();
618 } else {
619 first = G1_NULL_HRS_INDEX;
620 }
621 } else {
622 // We can't allocate humongous regions while cleanupComplete() is
623 // running, since some of the regions we find to be empty might not
624 // yet be added to the free list and it is not straightforward to
625 // know which list they are on so that we can remove them. Note
626 // that we only need to do this if we need to allocate more than
627 // one region to satisfy the current humongous allocation
628 // request. If we are only allocating one region we use the common
629 // region allocation code (see above).
630 wait_while_free_regions_coming();
631 append_secondary_free_list_if_not_empty_with_lock();
633 if (free_regions() >= num_regions) {
634 first = _hrs.find_contiguous(num_regions);
635 if (first != G1_NULL_HRS_INDEX) {
636 for (uint i = first; i < first + num_regions; ++i) {
637 HeapRegion* hr = region_at(i);
638 assert(hr->is_empty(), "sanity");
639 assert(is_on_master_free_list(hr), "sanity");
640 hr->set_pending_removal(true);
641 }
642 _free_list.remove_all_pending(num_regions);
643 }
644 }
645 }
646 return first;
647 }
649 HeapWord*
650 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
651 uint num_regions,
652 size_t word_size) {
653 assert(first != G1_NULL_HRS_INDEX, "pre-condition");
654 assert(isHumongous(word_size), "word_size should be humongous");
655 assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
657 // Index of last region in the series + 1.
658 uint last = first + num_regions;
660 // We need to initialize the region(s) we just discovered. This is
661 // a bit tricky given that it can happen concurrently with
662 // refinement threads refining cards on these regions and
663 // potentially wanting to refine the BOT as they are scanning
664 // those cards (this can happen shortly after a cleanup; see CR
665 // 6991377). So we have to set up the region(s) carefully and in
666 // a specific order.
668 // The word size sum of all the regions we will allocate.
669 size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
670 assert(word_size <= word_size_sum, "sanity");
672 // This will be the "starts humongous" region.
673 HeapRegion* first_hr = region_at(first);
674 // The header of the new object will be placed at the bottom of
675 // the first region.
676 HeapWord* new_obj = first_hr->bottom();
677 // This will be the new end of the first region in the series that
678 // should also match the end of the last region in the series.
679 HeapWord* new_end = new_obj + word_size_sum;
680 // This will be the new top of the first region that will reflect
681 // this allocation.
682 HeapWord* new_top = new_obj + word_size;
684 // First, we need to zero the header of the space that we will be
685 // allocating. When we update top further down, some refinement
686 // threads might try to scan the region. By zeroing the header we
687 // ensure that any thread that will try to scan the region will
688 // come across the zero klass word and bail out.
689 //
690 // NOTE: It would not have been correct to have used
691 // CollectedHeap::fill_with_object() and make the space look like
692 // an int array. The thread that is doing the allocation will
693 // later update the object header to a potentially different array
694 // type and, for a very short period of time, the klass and length
695 // fields will be inconsistent. This could cause a refinement
696 // thread to calculate the object size incorrectly.
697 Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
699 // We will set up the first region as "starts humongous". This
700 // will also update the BOT covering all the regions to reflect
701 // that there is a single object that starts at the bottom of the
702 // first region.
703 first_hr->set_startsHumongous(new_top, new_end);
705 // Then, if there are any, we will set up the "continues
706 // humongous" regions.
707 HeapRegion* hr = NULL;
708 for (uint i = first + 1; i < last; ++i) {
709 hr = region_at(i);
710 hr->set_continuesHumongous(first_hr);
711 }
712 // If we have "continues humongous" regions (hr != NULL), then the
713 // end of the last one should match new_end.
714 assert(hr == NULL || hr->end() == new_end, "sanity");
716 // Up to this point no concurrent thread would have been able to
717 // do any scanning on any region in this series. All the top
718 // fields still point to bottom, so the intersection between
719 // [bottom,top] and [card_start,card_end] will be empty. Before we
720 // update the top fields, we'll do a storestore to make sure that
721 // no thread sees the update to top before the zeroing of the
722 // object header and the BOT initialization.
723 OrderAccess::storestore();
725 // Now that the BOT and the object header have been initialized,
726 // we can update top of the "starts humongous" region.
727 assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
728 "new_top should be in this region");
729 first_hr->set_top(new_top);
730 if (_hr_printer.is_active()) {
731 HeapWord* bottom = first_hr->bottom();
732 HeapWord* end = first_hr->orig_end();
733 if ((first + 1) == last) {
734 // the series has a single humongous region
735 _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
736 } else {
737 // the series has more than one humongous regions
738 _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
739 }
740 }
742 // Now, we will update the top fields of the "continues humongous"
743 // regions. The reason we need to do this is that, otherwise,
744 // these regions would look empty and this will confuse parts of
745 // G1. For example, the code that looks for a consecutive number
746 // of empty regions will consider them empty and try to
747 // re-allocate them. We can extend is_empty() to also include
748 // !continuesHumongous(), but it is easier to just update the top
749 // fields here. The way we set top for all regions (i.e., top ==
750 // end for all regions but the last one, top == new_top for the
751 // last one) is actually used when we will free up the humongous
752 // region in free_humongous_region().
753 hr = NULL;
754 for (uint i = first + 1; i < last; ++i) {
755 hr = region_at(i);
756 if ((i + 1) == last) {
757 // last continues humongous region
758 assert(hr->bottom() < new_top && new_top <= hr->end(),
759 "new_top should fall on this region");
760 hr->set_top(new_top);
761 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
762 } else {
763 // not last one
764 assert(new_top > hr->end(), "new_top should be above this region");
765 hr->set_top(hr->end());
766 _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
767 }
768 }
769 // If we have continues humongous regions (hr != NULL), then the
770 // end of the last one should match new_end and its top should
771 // match new_top.
772 assert(hr == NULL ||
773 (hr->end() == new_end && hr->top() == new_top), "sanity");
774 check_bitmaps("Humongous Region Allocation", first_hr);
776 assert(first_hr->used() == word_size * HeapWordSize, "invariant");
777 _summary_bytes_used += first_hr->used();
778 _humongous_set.add(first_hr);
780 return new_obj;
781 }
783 // If could fit into free regions w/o expansion, try.
784 // Otherwise, if can expand, do so.
785 // Otherwise, if using ex regions might help, try with ex given back.
786 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
787 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
789 verify_region_sets_optional();
791 size_t word_size_rounded = round_to(word_size, HeapRegion::GrainWords);
792 uint num_regions = (uint) (word_size_rounded / HeapRegion::GrainWords);
793 uint x_num = expansion_regions();
794 uint fs = _hrs.free_suffix();
795 uint first = humongous_obj_allocate_find_first(num_regions, word_size);
796 if (first == G1_NULL_HRS_INDEX) {
797 // The only thing we can do now is attempt expansion.
798 if (fs + x_num >= num_regions) {
799 // If the number of regions we're trying to allocate for this
800 // object is at most the number of regions in the free suffix,
801 // then the call to humongous_obj_allocate_find_first() above
802 // should have succeeded and we wouldn't be here.
803 //
804 // We should only be trying to expand when the free suffix is
805 // not sufficient for the object _and_ we have some expansion
806 // room available.
807 assert(num_regions > fs, "earlier allocation should have succeeded");
809 ergo_verbose1(ErgoHeapSizing,
810 "attempt heap expansion",
811 ergo_format_reason("humongous allocation request failed")
812 ergo_format_byte("allocation request"),
813 word_size * HeapWordSize);
814 if (expand((num_regions - fs) * HeapRegion::GrainBytes)) {
815 // Even though the heap was expanded, it might not have
816 // reached the desired size. So, we cannot assume that the
817 // allocation will succeed.
818 first = humongous_obj_allocate_find_first(num_regions, word_size);
819 }
820 }
821 }
823 HeapWord* result = NULL;
824 if (first != G1_NULL_HRS_INDEX) {
825 result =
826 humongous_obj_allocate_initialize_regions(first, num_regions, word_size);
827 assert(result != NULL, "it should always return a valid result");
829 // A successful humongous object allocation changes the used space
830 // information of the old generation so we need to recalculate the
831 // sizes and update the jstat counters here.
832 g1mm()->update_sizes();
833 }
835 verify_region_sets_optional();
837 return result;
838 }
840 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
841 assert_heap_not_locked_and_not_at_safepoint();
842 assert(!isHumongous(word_size), "we do not allow humongous TLABs");
844 unsigned int dummy_gc_count_before;
845 int dummy_gclocker_retry_count = 0;
846 return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
847 }
849 HeapWord*
850 G1CollectedHeap::mem_allocate(size_t word_size,
851 bool* gc_overhead_limit_was_exceeded) {
852 assert_heap_not_locked_and_not_at_safepoint();
854 // Loop until the allocation is satisfied, or unsatisfied after GC.
855 for (int try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
856 unsigned int gc_count_before;
858 HeapWord* result = NULL;
859 if (!isHumongous(word_size)) {
860 result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
861 } else {
862 result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
863 }
864 if (result != NULL) {
865 return result;
866 }
868 // Create the garbage collection operation...
869 VM_G1CollectForAllocation op(gc_count_before, word_size);
870 // ...and get the VM thread to execute it.
871 VMThread::execute(&op);
873 if (op.prologue_succeeded() && op.pause_succeeded()) {
874 // If the operation was successful we'll return the result even
875 // if it is NULL. If the allocation attempt failed immediately
876 // after a Full GC, it's unlikely we'll be able to allocate now.
877 HeapWord* result = op.result();
878 if (result != NULL && !isHumongous(word_size)) {
879 // Allocations that take place on VM operations do not do any
880 // card dirtying and we have to do it here. We only have to do
881 // this for non-humongous allocations, though.
882 dirty_young_block(result, word_size);
883 }
884 return result;
885 } else {
886 if (gclocker_retry_count > GCLockerRetryAllocationCount) {
887 return NULL;
888 }
889 assert(op.result() == NULL,
890 "the result should be NULL if the VM op did not succeed");
891 }
893 // Give a warning if we seem to be looping forever.
894 if ((QueuedAllocationWarningCount > 0) &&
895 (try_count % QueuedAllocationWarningCount == 0)) {
896 warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
897 }
898 }
900 ShouldNotReachHere();
901 return NULL;
902 }
904 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
905 unsigned int *gc_count_before_ret,
906 int* gclocker_retry_count_ret) {
907 // Make sure you read the note in attempt_allocation_humongous().
909 assert_heap_not_locked_and_not_at_safepoint();
910 assert(!isHumongous(word_size), "attempt_allocation_slow() should not "
911 "be called for humongous allocation requests");
913 // We should only get here after the first-level allocation attempt
914 // (attempt_allocation()) failed to allocate.
916 // We will loop until a) we manage to successfully perform the
917 // allocation or b) we successfully schedule a collection which
918 // fails to perform the allocation. b) is the only case when we'll
919 // return NULL.
920 HeapWord* result = NULL;
921 for (int try_count = 1; /* we'll return */; try_count += 1) {
922 bool should_try_gc;
923 unsigned int gc_count_before;
925 {
926 MutexLockerEx x(Heap_lock);
928 result = _mutator_alloc_region.attempt_allocation_locked(word_size,
929 false /* bot_updates */);
930 if (result != NULL) {
931 return result;
932 }
934 // If we reach here, attempt_allocation_locked() above failed to
935 // allocate a new region. So the mutator alloc region should be NULL.
936 assert(_mutator_alloc_region.get() == NULL, "only way to get here");
938 if (GC_locker::is_active_and_needs_gc()) {
939 if (g1_policy()->can_expand_young_list()) {
940 // No need for an ergo verbose message here,
941 // can_expand_young_list() does this when it returns true.
942 result = _mutator_alloc_region.attempt_allocation_force(word_size,
943 false /* bot_updates */);
944 if (result != NULL) {
945 return result;
946 }
947 }
948 should_try_gc = false;
949 } else {
950 // The GCLocker may not be active but the GCLocker initiated
951 // GC may not yet have been performed (GCLocker::needs_gc()
952 // returns true). In this case we do not try this GC and
953 // wait until the GCLocker initiated GC is performed, and
954 // then retry the allocation.
955 if (GC_locker::needs_gc()) {
956 should_try_gc = false;
957 } else {
958 // Read the GC count while still holding the Heap_lock.
959 gc_count_before = total_collections();
960 should_try_gc = true;
961 }
962 }
963 }
965 if (should_try_gc) {
966 bool succeeded;
967 result = do_collection_pause(word_size, gc_count_before, &succeeded,
968 GCCause::_g1_inc_collection_pause);
969 if (result != NULL) {
970 assert(succeeded, "only way to get back a non-NULL result");
971 return result;
972 }
974 if (succeeded) {
975 // If we get here we successfully scheduled a collection which
976 // failed to allocate. No point in trying to allocate
977 // further. We'll just return NULL.
978 MutexLockerEx x(Heap_lock);
979 *gc_count_before_ret = total_collections();
980 return NULL;
981 }
982 } else {
983 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
984 MutexLockerEx x(Heap_lock);
985 *gc_count_before_ret = total_collections();
986 return NULL;
987 }
988 // The GCLocker is either active or the GCLocker initiated
989 // GC has not yet been performed. Stall until it is and
990 // then retry the allocation.
991 GC_locker::stall_until_clear();
992 (*gclocker_retry_count_ret) += 1;
993 }
995 // We can reach here if we were unsuccessful in scheduling a
996 // collection (because another thread beat us to it) or if we were
997 // stalled due to the GC locker. In either can we should retry the
998 // allocation attempt in case another thread successfully
999 // performed a collection and reclaimed enough space. We do the
1000 // first attempt (without holding the Heap_lock) here and the
1001 // follow-on attempt will be at the start of the next loop
1002 // iteration (after taking the Heap_lock).
1003 result = _mutator_alloc_region.attempt_allocation(word_size,
1004 false /* bot_updates */);
1005 if (result != NULL) {
1006 return result;
1007 }
1009 // Give a warning if we seem to be looping forever.
1010 if ((QueuedAllocationWarningCount > 0) &&
1011 (try_count % QueuedAllocationWarningCount == 0)) {
1012 warning("G1CollectedHeap::attempt_allocation_slow() "
1013 "retries %d times", try_count);
1014 }
1015 }
1017 ShouldNotReachHere();
1018 return NULL;
1019 }
1021 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
1022 unsigned int * gc_count_before_ret,
1023 int* gclocker_retry_count_ret) {
1024 // The structure of this method has a lot of similarities to
1025 // attempt_allocation_slow(). The reason these two were not merged
1026 // into a single one is that such a method would require several "if
1027 // allocation is not humongous do this, otherwise do that"
1028 // conditional paths which would obscure its flow. In fact, an early
1029 // version of this code did use a unified method which was harder to
1030 // follow and, as a result, it had subtle bugs that were hard to
1031 // track down. So keeping these two methods separate allows each to
1032 // be more readable. It will be good to keep these two in sync as
1033 // much as possible.
1035 assert_heap_not_locked_and_not_at_safepoint();
1036 assert(isHumongous(word_size), "attempt_allocation_humongous() "
1037 "should only be called for humongous allocations");
1039 // Humongous objects can exhaust the heap quickly, so we should check if we
1040 // need to start a marking cycle at each humongous object allocation. We do
1041 // the check before we do the actual allocation. The reason for doing it
1042 // before the allocation is that we avoid having to keep track of the newly
1043 // allocated memory while we do a GC.
1044 if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
1045 word_size)) {
1046 collect(GCCause::_g1_humongous_allocation);
1047 }
1049 // We will loop until a) we manage to successfully perform the
1050 // allocation or b) we successfully schedule a collection which
1051 // fails to perform the allocation. b) is the only case when we'll
1052 // return NULL.
1053 HeapWord* result = NULL;
1054 for (int try_count = 1; /* we'll return */; try_count += 1) {
1055 bool should_try_gc;
1056 unsigned int gc_count_before;
1058 {
1059 MutexLockerEx x(Heap_lock);
1061 // Given that humongous objects are not allocated in young
1062 // regions, we'll first try to do the allocation without doing a
1063 // collection hoping that there's enough space in the heap.
1064 result = humongous_obj_allocate(word_size);
1065 if (result != NULL) {
1066 return result;
1067 }
1069 if (GC_locker::is_active_and_needs_gc()) {
1070 should_try_gc = false;
1071 } else {
1072 // The GCLocker may not be active but the GCLocker initiated
1073 // GC may not yet have been performed (GCLocker::needs_gc()
1074 // returns true). In this case we do not try this GC and
1075 // wait until the GCLocker initiated GC is performed, and
1076 // then retry the allocation.
1077 if (GC_locker::needs_gc()) {
1078 should_try_gc = false;
1079 } else {
1080 // Read the GC count while still holding the Heap_lock.
1081 gc_count_before = total_collections();
1082 should_try_gc = true;
1083 }
1084 }
1085 }
1087 if (should_try_gc) {
1088 // If we failed to allocate the humongous object, we should try to
1089 // do a collection pause (if we're allowed) in case it reclaims
1090 // enough space for the allocation to succeed after the pause.
1092 bool succeeded;
1093 result = do_collection_pause(word_size, gc_count_before, &succeeded,
1094 GCCause::_g1_humongous_allocation);
1095 if (result != NULL) {
1096 assert(succeeded, "only way to get back a non-NULL result");
1097 return result;
1098 }
1100 if (succeeded) {
1101 // If we get here we successfully scheduled a collection which
1102 // failed to allocate. No point in trying to allocate
1103 // further. We'll just return NULL.
1104 MutexLockerEx x(Heap_lock);
1105 *gc_count_before_ret = total_collections();
1106 return NULL;
1107 }
1108 } else {
1109 if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1110 MutexLockerEx x(Heap_lock);
1111 *gc_count_before_ret = total_collections();
1112 return NULL;
1113 }
1114 // The GCLocker is either active or the GCLocker initiated
1115 // GC has not yet been performed. Stall until it is and
1116 // then retry the allocation.
1117 GC_locker::stall_until_clear();
1118 (*gclocker_retry_count_ret) += 1;
1119 }
1121 // We can reach here if we were unsuccessful in scheduling a
1122 // collection (because another thread beat us to it) or if we were
1123 // stalled due to the GC locker. In either can we should retry the
1124 // allocation attempt in case another thread successfully
1125 // performed a collection and reclaimed enough space. Give a
1126 // warning if we seem to be looping forever.
1128 if ((QueuedAllocationWarningCount > 0) &&
1129 (try_count % QueuedAllocationWarningCount == 0)) {
1130 warning("G1CollectedHeap::attempt_allocation_humongous() "
1131 "retries %d times", try_count);
1132 }
1133 }
1135 ShouldNotReachHere();
1136 return NULL;
1137 }
1139 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1140 bool expect_null_mutator_alloc_region) {
1141 assert_at_safepoint(true /* should_be_vm_thread */);
1142 assert(_mutator_alloc_region.get() == NULL ||
1143 !expect_null_mutator_alloc_region,
1144 "the current alloc region was unexpectedly found to be non-NULL");
1146 if (!isHumongous(word_size)) {
1147 return _mutator_alloc_region.attempt_allocation_locked(word_size,
1148 false /* bot_updates */);
1149 } else {
1150 HeapWord* result = humongous_obj_allocate(word_size);
1151 if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1152 g1_policy()->set_initiate_conc_mark_if_possible();
1153 }
1154 return result;
1155 }
1157 ShouldNotReachHere();
1158 }
1160 class PostMCRemSetClearClosure: public HeapRegionClosure {
1161 G1CollectedHeap* _g1h;
1162 ModRefBarrierSet* _mr_bs;
1163 public:
1164 PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1165 _g1h(g1h), _mr_bs(mr_bs) {}
1167 bool doHeapRegion(HeapRegion* r) {
1168 HeapRegionRemSet* hrrs = r->rem_set();
1170 if (r->continuesHumongous()) {
1171 // We'll assert that the strong code root list and RSet is empty
1172 assert(hrrs->strong_code_roots_list_length() == 0, "sanity");
1173 assert(hrrs->occupied() == 0, "RSet should be empty");
1174 return false;
1175 }
1177 _g1h->reset_gc_time_stamps(r);
1178 hrrs->clear();
1179 // You might think here that we could clear just the cards
1180 // corresponding to the used region. But no: if we leave a dirty card
1181 // in a region we might allocate into, then it would prevent that card
1182 // from being enqueued, and cause it to be missed.
1183 // Re: the performance cost: we shouldn't be doing full GC anyway!
1184 _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1186 return false;
1187 }
1188 };
1190 void G1CollectedHeap::clear_rsets_post_compaction() {
1191 PostMCRemSetClearClosure rs_clear(this, g1_barrier_set());
1192 heap_region_iterate(&rs_clear);
1193 }
1195 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1196 G1CollectedHeap* _g1h;
1197 UpdateRSOopClosure _cl;
1198 int _worker_i;
1199 public:
1200 RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1201 _cl(g1->g1_rem_set(), worker_i),
1202 _worker_i(worker_i),
1203 _g1h(g1)
1204 { }
1206 bool doHeapRegion(HeapRegion* r) {
1207 if (!r->continuesHumongous()) {
1208 _cl.set_from(r);
1209 r->oop_iterate(&_cl);
1210 }
1211 return false;
1212 }
1213 };
1215 class ParRebuildRSTask: public AbstractGangTask {
1216 G1CollectedHeap* _g1;
1217 public:
1218 ParRebuildRSTask(G1CollectedHeap* g1)
1219 : AbstractGangTask("ParRebuildRSTask"),
1220 _g1(g1)
1221 { }
1223 void work(uint worker_id) {
1224 RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1225 _g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id,
1226 _g1->workers()->active_workers(),
1227 HeapRegion::RebuildRSClaimValue);
1228 }
1229 };
1231 class PostCompactionPrinterClosure: public HeapRegionClosure {
1232 private:
1233 G1HRPrinter* _hr_printer;
1234 public:
1235 bool doHeapRegion(HeapRegion* hr) {
1236 assert(!hr->is_young(), "not expecting to find young regions");
1237 // We only generate output for non-empty regions.
1238 if (!hr->is_empty()) {
1239 if (!hr->isHumongous()) {
1240 _hr_printer->post_compaction(hr, G1HRPrinter::Old);
1241 } else if (hr->startsHumongous()) {
1242 if (hr->region_num() == 1) {
1243 // single humongous region
1244 _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
1245 } else {
1246 _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
1247 }
1248 } else {
1249 assert(hr->continuesHumongous(), "only way to get here");
1250 _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1251 }
1252 }
1253 return false;
1254 }
1256 PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1257 : _hr_printer(hr_printer) { }
1258 };
1260 void G1CollectedHeap::print_hrs_post_compaction() {
1261 PostCompactionPrinterClosure cl(hr_printer());
1262 heap_region_iterate(&cl);
1263 }
1265 bool G1CollectedHeap::do_collection(bool explicit_gc,
1266 bool clear_all_soft_refs,
1267 size_t word_size) {
1268 assert_at_safepoint(true /* should_be_vm_thread */);
1270 if (GC_locker::check_active_before_gc()) {
1271 return false;
1272 }
1274 STWGCTimer* gc_timer = G1MarkSweep::gc_timer();
1275 gc_timer->register_gc_start();
1277 SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer();
1278 gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start());
1280 SvcGCMarker sgcm(SvcGCMarker::FULL);
1281 ResourceMark rm;
1283 print_heap_before_gc();
1284 trace_heap_before_gc(gc_tracer);
1286 size_t metadata_prev_used = MetaspaceAux::used_bytes();
1288 verify_region_sets_optional();
1290 const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1291 collector_policy()->should_clear_all_soft_refs();
1293 ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1295 {
1296 IsGCActiveMark x;
1298 // Timing
1299 assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant");
1300 gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps);
1301 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
1303 {
1304 GCTraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, NULL, gc_tracer->gc_id());
1305 TraceCollectorStats tcs(g1mm()->full_collection_counters());
1306 TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1308 double start = os::elapsedTime();
1309 g1_policy()->record_full_collection_start();
1311 // Note: When we have a more flexible GC logging framework that
1312 // allows us to add optional attributes to a GC log record we
1313 // could consider timing and reporting how long we wait in the
1314 // following two methods.
1315 wait_while_free_regions_coming();
1316 // If we start the compaction before the CM threads finish
1317 // scanning the root regions we might trip them over as we'll
1318 // be moving objects / updating references. So let's wait until
1319 // they are done. By telling them to abort, they should complete
1320 // early.
1321 _cm->root_regions()->abort();
1322 _cm->root_regions()->wait_until_scan_finished();
1323 append_secondary_free_list_if_not_empty_with_lock();
1325 gc_prologue(true);
1326 increment_total_collections(true /* full gc */);
1327 increment_old_marking_cycles_started();
1329 assert(used() == recalculate_used(), "Should be equal");
1331 verify_before_gc();
1333 check_bitmaps("Full GC Start");
1334 pre_full_gc_dump(gc_timer);
1336 COMPILER2_PRESENT(DerivedPointerTable::clear());
1338 // Disable discovery and empty the discovered lists
1339 // for the CM ref processor.
1340 ref_processor_cm()->disable_discovery();
1341 ref_processor_cm()->abandon_partial_discovery();
1342 ref_processor_cm()->verify_no_references_recorded();
1344 // Abandon current iterations of concurrent marking and concurrent
1345 // refinement, if any are in progress. We have to do this before
1346 // wait_until_scan_finished() below.
1347 concurrent_mark()->abort();
1349 // Make sure we'll choose a new allocation region afterwards.
1350 release_mutator_alloc_region();
1351 abandon_gc_alloc_regions();
1352 g1_rem_set()->cleanupHRRS();
1354 // We should call this after we retire any currently active alloc
1355 // regions so that all the ALLOC / RETIRE events are generated
1356 // before the start GC event.
1357 _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1359 // We may have added regions to the current incremental collection
1360 // set between the last GC or pause and now. We need to clear the
1361 // incremental collection set and then start rebuilding it afresh
1362 // after this full GC.
1363 abandon_collection_set(g1_policy()->inc_cset_head());
1364 g1_policy()->clear_incremental_cset();
1365 g1_policy()->stop_incremental_cset_building();
1367 tear_down_region_sets(false /* free_list_only */);
1368 g1_policy()->set_gcs_are_young(true);
1370 // See the comments in g1CollectedHeap.hpp and
1371 // G1CollectedHeap::ref_processing_init() about
1372 // how reference processing currently works in G1.
1374 // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1375 ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1377 // Temporarily clear the STW ref processor's _is_alive_non_header field.
1378 ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1380 ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
1381 ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1383 // Do collection work
1384 {
1385 HandleMark hm; // Discard invalid handles created during gc
1386 G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1387 }
1389 assert(free_regions() == 0, "we should not have added any free regions");
1390 rebuild_region_sets(false /* free_list_only */);
1392 // Enqueue any discovered reference objects that have
1393 // not been removed from the discovered lists.
1394 ref_processor_stw()->enqueue_discovered_references();
1396 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1398 MemoryService::track_memory_usage();
1400 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1401 ref_processor_stw()->verify_no_references_recorded();
1403 // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1404 ClassLoaderDataGraph::purge();
1405 MetaspaceAux::verify_metrics();
1407 // Note: since we've just done a full GC, concurrent
1408 // marking is no longer active. Therefore we need not
1409 // re-enable reference discovery for the CM ref processor.
1410 // That will be done at the start of the next marking cycle.
1411 assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1412 ref_processor_cm()->verify_no_references_recorded();
1414 reset_gc_time_stamp();
1415 // Since everything potentially moved, we will clear all remembered
1416 // sets, and clear all cards. Later we will rebuild remembered
1417 // sets. We will also reset the GC time stamps of the regions.
1418 clear_rsets_post_compaction();
1419 check_gc_time_stamps();
1421 // Resize the heap if necessary.
1422 resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1424 if (_hr_printer.is_active()) {
1425 // We should do this after we potentially resize the heap so
1426 // that all the COMMIT / UNCOMMIT events are generated before
1427 // the end GC event.
1429 print_hrs_post_compaction();
1430 _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1431 }
1433 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
1434 if (hot_card_cache->use_cache()) {
1435 hot_card_cache->reset_card_counts();
1436 hot_card_cache->reset_hot_cache();
1437 }
1439 // Rebuild remembered sets of all regions.
1440 if (G1CollectedHeap::use_parallel_gc_threads()) {
1441 uint n_workers =
1442 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1443 workers()->active_workers(),
1444 Threads::number_of_non_daemon_threads());
1445 assert(UseDynamicNumberOfGCThreads ||
1446 n_workers == workers()->total_workers(),
1447 "If not dynamic should be using all the workers");
1448 workers()->set_active_workers(n_workers);
1449 // Set parallel threads in the heap (_n_par_threads) only
1450 // before a parallel phase and always reset it to 0 after
1451 // the phase so that the number of parallel threads does
1452 // no get carried forward to a serial phase where there
1453 // may be code that is "possibly_parallel".
1454 set_par_threads(n_workers);
1456 ParRebuildRSTask rebuild_rs_task(this);
1457 assert(check_heap_region_claim_values(
1458 HeapRegion::InitialClaimValue), "sanity check");
1459 assert(UseDynamicNumberOfGCThreads ||
1460 workers()->active_workers() == workers()->total_workers(),
1461 "Unless dynamic should use total workers");
1462 // Use the most recent number of active workers
1463 assert(workers()->active_workers() > 0,
1464 "Active workers not properly set");
1465 set_par_threads(workers()->active_workers());
1466 workers()->run_task(&rebuild_rs_task);
1467 set_par_threads(0);
1468 assert(check_heap_region_claim_values(
1469 HeapRegion::RebuildRSClaimValue), "sanity check");
1470 reset_heap_region_claim_values();
1471 } else {
1472 RebuildRSOutOfRegionClosure rebuild_rs(this);
1473 heap_region_iterate(&rebuild_rs);
1474 }
1476 // Rebuild the strong code root lists for each region
1477 rebuild_strong_code_roots();
1479 if (true) { // FIXME
1480 MetaspaceGC::compute_new_size();
1481 }
1483 #ifdef TRACESPINNING
1484 ParallelTaskTerminator::print_termination_counts();
1485 #endif
1487 // Discard all rset updates
1488 JavaThread::dirty_card_queue_set().abandon_logs();
1489 assert(!G1DeferredRSUpdate
1490 || (G1DeferredRSUpdate &&
1491 (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any");
1493 _young_list->reset_sampled_info();
1494 // At this point there should be no regions in the
1495 // entire heap tagged as young.
1496 assert(check_young_list_empty(true /* check_heap */),
1497 "young list should be empty at this point");
1499 // Update the number of full collections that have been completed.
1500 increment_old_marking_cycles_completed(false /* concurrent */);
1502 _hrs.verify_optional();
1503 verify_region_sets_optional();
1505 verify_after_gc();
1507 // Clear the previous marking bitmap, if needed for bitmap verification.
1508 // Note we cannot do this when we clear the next marking bitmap in
1509 // ConcurrentMark::abort() above since VerifyDuringGC verifies the
1510 // objects marked during a full GC against the previous bitmap.
1511 // But we need to clear it before calling check_bitmaps below since
1512 // the full GC has compacted objects and updated TAMS but not updated
1513 // the prev bitmap.
1514 if (G1VerifyBitmaps) {
1515 ((CMBitMap*) concurrent_mark()->prevMarkBitMap())->clearAll();
1516 }
1517 check_bitmaps("Full GC End");
1519 // Start a new incremental collection set for the next pause
1520 assert(g1_policy()->collection_set() == NULL, "must be");
1521 g1_policy()->start_incremental_cset_building();
1523 clear_cset_fast_test();
1525 init_mutator_alloc_region();
1527 double end = os::elapsedTime();
1528 g1_policy()->record_full_collection_end();
1530 if (G1Log::fine()) {
1531 g1_policy()->print_heap_transition();
1532 }
1534 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1535 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1536 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1537 // before any GC notifications are raised.
1538 g1mm()->update_sizes();
1540 gc_epilogue(true);
1541 }
1543 if (G1Log::finer()) {
1544 g1_policy()->print_detailed_heap_transition(true /* full */);
1545 }
1547 print_heap_after_gc();
1548 trace_heap_after_gc(gc_tracer);
1550 post_full_gc_dump(gc_timer);
1552 gc_timer->register_gc_end();
1553 gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
1554 }
1556 return true;
1557 }
1559 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1560 // do_collection() will return whether it succeeded in performing
1561 // the GC. Currently, there is no facility on the
1562 // do_full_collection() API to notify the caller than the collection
1563 // did not succeed (e.g., because it was locked out by the GC
1564 // locker). So, right now, we'll ignore the return value.
1565 bool dummy = do_collection(true, /* explicit_gc */
1566 clear_all_soft_refs,
1567 0 /* word_size */);
1568 }
1570 // This code is mostly copied from TenuredGeneration.
1571 void
1572 G1CollectedHeap::
1573 resize_if_necessary_after_full_collection(size_t word_size) {
1574 // Include the current allocation, if any, and bytes that will be
1575 // pre-allocated to support collections, as "used".
1576 const size_t used_after_gc = used();
1577 const size_t capacity_after_gc = capacity();
1578 const size_t free_after_gc = capacity_after_gc - used_after_gc;
1580 // This is enforced in arguments.cpp.
1581 assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1582 "otherwise the code below doesn't make sense");
1584 // We don't have floating point command-line arguments
1585 const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1586 const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1587 const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1588 const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1590 const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1591 const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1593 // We have to be careful here as these two calculations can overflow
1594 // 32-bit size_t's.
1595 double used_after_gc_d = (double) used_after_gc;
1596 double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1597 double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1599 // Let's make sure that they are both under the max heap size, which
1600 // by default will make them fit into a size_t.
1601 double desired_capacity_upper_bound = (double) max_heap_size;
1602 minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1603 desired_capacity_upper_bound);
1604 maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1605 desired_capacity_upper_bound);
1607 // We can now safely turn them into size_t's.
1608 size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1609 size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1611 // This assert only makes sense here, before we adjust them
1612 // with respect to the min and max heap size.
1613 assert(minimum_desired_capacity <= maximum_desired_capacity,
1614 err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1615 "maximum_desired_capacity = "SIZE_FORMAT,
1616 minimum_desired_capacity, maximum_desired_capacity));
1618 // Should not be greater than the heap max size. No need to adjust
1619 // it with respect to the heap min size as it's a lower bound (i.e.,
1620 // we'll try to make the capacity larger than it, not smaller).
1621 minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1622 // Should not be less than the heap min size. No need to adjust it
1623 // with respect to the heap max size as it's an upper bound (i.e.,
1624 // we'll try to make the capacity smaller than it, not greater).
1625 maximum_desired_capacity = MAX2(maximum_desired_capacity, min_heap_size);
1627 if (capacity_after_gc < minimum_desired_capacity) {
1628 // Don't expand unless it's significant
1629 size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1630 ergo_verbose4(ErgoHeapSizing,
1631 "attempt heap expansion",
1632 ergo_format_reason("capacity lower than "
1633 "min desired capacity after Full GC")
1634 ergo_format_byte("capacity")
1635 ergo_format_byte("occupancy")
1636 ergo_format_byte_perc("min desired capacity"),
1637 capacity_after_gc, used_after_gc,
1638 minimum_desired_capacity, (double) MinHeapFreeRatio);
1639 expand(expand_bytes);
1641 // No expansion, now see if we want to shrink
1642 } else if (capacity_after_gc > maximum_desired_capacity) {
1643 // Capacity too large, compute shrinking size
1644 size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1645 ergo_verbose4(ErgoHeapSizing,
1646 "attempt heap shrinking",
1647 ergo_format_reason("capacity higher than "
1648 "max desired capacity after Full GC")
1649 ergo_format_byte("capacity")
1650 ergo_format_byte("occupancy")
1651 ergo_format_byte_perc("max desired capacity"),
1652 capacity_after_gc, used_after_gc,
1653 maximum_desired_capacity, (double) MaxHeapFreeRatio);
1654 shrink(shrink_bytes);
1655 }
1656 }
1659 HeapWord*
1660 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1661 bool* succeeded) {
1662 assert_at_safepoint(true /* should_be_vm_thread */);
1664 *succeeded = true;
1665 // Let's attempt the allocation first.
1666 HeapWord* result =
1667 attempt_allocation_at_safepoint(word_size,
1668 false /* expect_null_mutator_alloc_region */);
1669 if (result != NULL) {
1670 assert(*succeeded, "sanity");
1671 return result;
1672 }
1674 // In a G1 heap, we're supposed to keep allocation from failing by
1675 // incremental pauses. Therefore, at least for now, we'll favor
1676 // expansion over collection. (This might change in the future if we can
1677 // do something smarter than full collection to satisfy a failed alloc.)
1678 result = expand_and_allocate(word_size);
1679 if (result != NULL) {
1680 assert(*succeeded, "sanity");
1681 return result;
1682 }
1684 // Expansion didn't work, we'll try to do a Full GC.
1685 bool gc_succeeded = do_collection(false, /* explicit_gc */
1686 false, /* clear_all_soft_refs */
1687 word_size);
1688 if (!gc_succeeded) {
1689 *succeeded = false;
1690 return NULL;
1691 }
1693 // Retry the allocation
1694 result = attempt_allocation_at_safepoint(word_size,
1695 true /* expect_null_mutator_alloc_region */);
1696 if (result != NULL) {
1697 assert(*succeeded, "sanity");
1698 return result;
1699 }
1701 // Then, try a Full GC that will collect all soft references.
1702 gc_succeeded = do_collection(false, /* explicit_gc */
1703 true, /* clear_all_soft_refs */
1704 word_size);
1705 if (!gc_succeeded) {
1706 *succeeded = false;
1707 return NULL;
1708 }
1710 // Retry the allocation once more
1711 result = attempt_allocation_at_safepoint(word_size,
1712 true /* expect_null_mutator_alloc_region */);
1713 if (result != NULL) {
1714 assert(*succeeded, "sanity");
1715 return result;
1716 }
1718 assert(!collector_policy()->should_clear_all_soft_refs(),
1719 "Flag should have been handled and cleared prior to this point");
1721 // What else? We might try synchronous finalization later. If the total
1722 // space available is large enough for the allocation, then a more
1723 // complete compaction phase than we've tried so far might be
1724 // appropriate.
1725 assert(*succeeded, "sanity");
1726 return NULL;
1727 }
1729 // Attempting to expand the heap sufficiently
1730 // to support an allocation of the given "word_size". If
1731 // successful, perform the allocation and return the address of the
1732 // allocated block, or else "NULL".
1734 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1735 assert_at_safepoint(true /* should_be_vm_thread */);
1737 verify_region_sets_optional();
1739 size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1740 ergo_verbose1(ErgoHeapSizing,
1741 "attempt heap expansion",
1742 ergo_format_reason("allocation request failed")
1743 ergo_format_byte("allocation request"),
1744 word_size * HeapWordSize);
1745 if (expand(expand_bytes)) {
1746 _hrs.verify_optional();
1747 verify_region_sets_optional();
1748 return attempt_allocation_at_safepoint(word_size,
1749 false /* expect_null_mutator_alloc_region */);
1750 }
1751 return NULL;
1752 }
1754 void G1CollectedHeap::update_committed_space(HeapWord* old_end,
1755 HeapWord* new_end) {
1756 assert(old_end != new_end, "don't call this otherwise");
1757 assert((HeapWord*) _g1_storage.high() == new_end, "invariant");
1759 // Update the committed mem region.
1760 _g1_committed.set_end(new_end);
1761 // Tell the card table about the update.
1762 Universe::heap()->barrier_set()->resize_covered_region(_g1_committed);
1763 // Tell the BOT about the update.
1764 _bot_shared->resize(_g1_committed.word_size());
1765 // Tell the hot card cache about the update
1766 _cg1r->hot_card_cache()->resize_card_counts(capacity());
1767 }
1769 bool G1CollectedHeap::expand(size_t expand_bytes) {
1770 size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1771 aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1772 HeapRegion::GrainBytes);
1773 ergo_verbose2(ErgoHeapSizing,
1774 "expand the heap",
1775 ergo_format_byte("requested expansion amount")
1776 ergo_format_byte("attempted expansion amount"),
1777 expand_bytes, aligned_expand_bytes);
1779 if (_g1_storage.uncommitted_size() == 0) {
1780 ergo_verbose0(ErgoHeapSizing,
1781 "did not expand the heap",
1782 ergo_format_reason("heap already fully expanded"));
1783 return false;
1784 }
1786 // First commit the memory.
1787 HeapWord* old_end = (HeapWord*) _g1_storage.high();
1788 bool successful = _g1_storage.expand_by(aligned_expand_bytes);
1789 if (successful) {
1790 // Then propagate this update to the necessary data structures.
1791 HeapWord* new_end = (HeapWord*) _g1_storage.high();
1792 update_committed_space(old_end, new_end);
1794 FreeRegionList expansion_list("Local Expansion List");
1795 MemRegion mr = _hrs.expand_by(old_end, new_end, &expansion_list);
1796 assert(mr.start() == old_end, "post-condition");
1797 // mr might be a smaller region than what was requested if
1798 // expand_by() was unable to allocate the HeapRegion instances
1799 assert(mr.end() <= new_end, "post-condition");
1801 size_t actual_expand_bytes = mr.byte_size();
1802 assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1803 assert(actual_expand_bytes == expansion_list.total_capacity_bytes(),
1804 "post-condition");
1805 if (actual_expand_bytes < aligned_expand_bytes) {
1806 // We could not expand _hrs to the desired size. In this case we
1807 // need to shrink the committed space accordingly.
1808 assert(mr.end() < new_end, "invariant");
1810 size_t diff_bytes = aligned_expand_bytes - actual_expand_bytes;
1811 // First uncommit the memory.
1812 _g1_storage.shrink_by(diff_bytes);
1813 // Then propagate this update to the necessary data structures.
1814 update_committed_space(new_end, mr.end());
1815 }
1816 _free_list.add_as_tail(&expansion_list);
1818 if (_hr_printer.is_active()) {
1819 HeapWord* curr = mr.start();
1820 while (curr < mr.end()) {
1821 HeapWord* curr_end = curr + HeapRegion::GrainWords;
1822 _hr_printer.commit(curr, curr_end);
1823 curr = curr_end;
1824 }
1825 assert(curr == mr.end(), "post-condition");
1826 }
1827 g1_policy()->record_new_heap_size(n_regions());
1828 } else {
1829 ergo_verbose0(ErgoHeapSizing,
1830 "did not expand the heap",
1831 ergo_format_reason("heap expansion operation failed"));
1832 // The expansion of the virtual storage space was unsuccessful.
1833 // Let's see if it was because we ran out of swap.
1834 if (G1ExitOnExpansionFailure &&
1835 _g1_storage.uncommitted_size() >= aligned_expand_bytes) {
1836 // We had head room...
1837 vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1838 }
1839 }
1840 return successful;
1841 }
1843 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1844 size_t aligned_shrink_bytes =
1845 ReservedSpace::page_align_size_down(shrink_bytes);
1846 aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1847 HeapRegion::GrainBytes);
1848 uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1850 uint num_regions_removed = _hrs.shrink_by(num_regions_to_remove);
1851 HeapWord* old_end = (HeapWord*) _g1_storage.high();
1852 size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1854 ergo_verbose3(ErgoHeapSizing,
1855 "shrink the heap",
1856 ergo_format_byte("requested shrinking amount")
1857 ergo_format_byte("aligned shrinking amount")
1858 ergo_format_byte("attempted shrinking amount"),
1859 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1860 if (num_regions_removed > 0) {
1861 _g1_storage.shrink_by(shrunk_bytes);
1862 HeapWord* new_end = (HeapWord*) _g1_storage.high();
1864 if (_hr_printer.is_active()) {
1865 HeapWord* curr = old_end;
1866 while (curr > new_end) {
1867 HeapWord* curr_end = curr;
1868 curr -= HeapRegion::GrainWords;
1869 _hr_printer.uncommit(curr, curr_end);
1870 }
1871 }
1873 _expansion_regions += num_regions_removed;
1874 update_committed_space(old_end, new_end);
1875 HeapRegionRemSet::shrink_heap(n_regions());
1876 g1_policy()->record_new_heap_size(n_regions());
1877 } else {
1878 ergo_verbose0(ErgoHeapSizing,
1879 "did not shrink the heap",
1880 ergo_format_reason("heap shrinking operation failed"));
1881 }
1882 }
1884 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1885 verify_region_sets_optional();
1887 // We should only reach here at the end of a Full GC which means we
1888 // should not not be holding to any GC alloc regions. The method
1889 // below will make sure of that and do any remaining clean up.
1890 abandon_gc_alloc_regions();
1892 // Instead of tearing down / rebuilding the free lists here, we
1893 // could instead use the remove_all_pending() method on free_list to
1894 // remove only the ones that we need to remove.
1895 tear_down_region_sets(true /* free_list_only */);
1896 shrink_helper(shrink_bytes);
1897 rebuild_region_sets(true /* free_list_only */);
1899 _hrs.verify_optional();
1900 verify_region_sets_optional();
1901 }
1903 // Public methods.
1905 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1906 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1907 #endif // _MSC_VER
1910 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1911 SharedHeap(policy_),
1912 _g1_policy(policy_),
1913 _dirty_card_queue_set(false),
1914 _into_cset_dirty_card_queue_set(false),
1915 _is_alive_closure_cm(this),
1916 _is_alive_closure_stw(this),
1917 _ref_processor_cm(NULL),
1918 _ref_processor_stw(NULL),
1919 _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
1920 _bot_shared(NULL),
1921 _evac_failure_scan_stack(NULL),
1922 _mark_in_progress(false),
1923 _cg1r(NULL), _summary_bytes_used(0),
1924 _g1mm(NULL),
1925 _refine_cte_cl(NULL),
1926 _full_collection(false),
1927 _free_list("Master Free List", new MasterFreeRegionListMtSafeChecker()),
1928 _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1929 _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1930 _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1931 _free_regions_coming(false),
1932 _young_list(new YoungList(this)),
1933 _gc_time_stamp(0),
1934 _retained_old_gc_alloc_region(NULL),
1935 _survivor_plab_stats(YoungPLABSize, PLABWeight),
1936 _old_plab_stats(OldPLABSize, PLABWeight),
1937 _expand_heap_after_alloc_failure(true),
1938 _surviving_young_words(NULL),
1939 _old_marking_cycles_started(0),
1940 _old_marking_cycles_completed(0),
1941 _concurrent_cycle_started(false),
1942 _in_cset_fast_test(),
1943 _dirty_cards_region_list(NULL),
1944 _worker_cset_start_region(NULL),
1945 _worker_cset_start_region_time_stamp(NULL),
1946 _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1947 _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
1948 _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1949 _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) {
1951 _g1h = this;
1952 if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
1953 vm_exit_during_initialization("Failed necessary allocation.");
1954 }
1956 _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1958 int n_queues = MAX2((int)ParallelGCThreads, 1);
1959 _task_queues = new RefToScanQueueSet(n_queues);
1961 uint n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1962 assert(n_rem_sets > 0, "Invariant.");
1964 _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1965 _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC);
1966 _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1968 for (int i = 0; i < n_queues; i++) {
1969 RefToScanQueue* q = new RefToScanQueue();
1970 q->initialize();
1971 _task_queues->register_queue(i, q);
1972 ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1973 }
1974 clear_cset_start_regions();
1976 // Initialize the G1EvacuationFailureALot counters and flags.
1977 NOT_PRODUCT(reset_evacuation_should_fail();)
1979 guarantee(_task_queues != NULL, "task_queues allocation failure.");
1980 }
1982 jint G1CollectedHeap::initialize() {
1983 CollectedHeap::pre_initialize();
1984 os::enable_vtime();
1986 G1Log::init();
1988 // Necessary to satisfy locking discipline assertions.
1990 MutexLocker x(Heap_lock);
1992 // We have to initialize the printer before committing the heap, as
1993 // it will be used then.
1994 _hr_printer.set_active(G1PrintHeapRegions);
1996 // While there are no constraints in the GC code that HeapWordSize
1997 // be any particular value, there are multiple other areas in the
1998 // system which believe this to be true (e.g. oop->object_size in some
1999 // cases incorrectly returns the size in wordSize units rather than
2000 // HeapWordSize).
2001 guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
2003 size_t init_byte_size = collector_policy()->initial_heap_byte_size();
2004 size_t max_byte_size = collector_policy()->max_heap_byte_size();
2005 size_t heap_alignment = collector_policy()->heap_alignment();
2007 // Ensure that the sizes are properly aligned.
2008 Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
2009 Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
2010 Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
2012 _refine_cte_cl = new RefineCardTableEntryClosure();
2014 _cg1r = new ConcurrentG1Refine(this, _refine_cte_cl);
2016 // Reserve the maximum.
2018 // When compressed oops are enabled, the preferred heap base
2019 // is calculated by subtracting the requested size from the
2020 // 32Gb boundary and using the result as the base address for
2021 // heap reservation. If the requested size is not aligned to
2022 // HeapRegion::GrainBytes (i.e. the alignment that is passed
2023 // into the ReservedHeapSpace constructor) then the actual
2024 // base of the reserved heap may end up differing from the
2025 // address that was requested (i.e. the preferred heap base).
2026 // If this happens then we could end up using a non-optimal
2027 // compressed oops mode.
2029 ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
2030 heap_alignment);
2032 // It is important to do this in a way such that concurrent readers can't
2033 // temporarily think something is in the heap. (I've actually seen this
2034 // happen in asserts: DLD.)
2035 _reserved.set_word_size(0);
2036 _reserved.set_start((HeapWord*)heap_rs.base());
2037 _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size()));
2039 _expansion_regions = (uint) (max_byte_size / HeapRegion::GrainBytes);
2041 // Create the gen rem set (and barrier set) for the entire reserved region.
2042 _rem_set = collector_policy()->create_rem_set(_reserved, 2);
2043 set_barrier_set(rem_set()->bs());
2044 if (!barrier_set()->is_a(BarrierSet::G1SATBCTLogging)) {
2045 vm_exit_during_initialization("G1 requires a G1SATBLoggingCardTableModRefBS");
2046 return JNI_ENOMEM;
2047 }
2049 // Also create a G1 rem set.
2050 _g1_rem_set = new G1RemSet(this, g1_barrier_set());
2052 // Carve out the G1 part of the heap.
2054 ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
2055 _g1_reserved = MemRegion((HeapWord*)g1_rs.base(),
2056 g1_rs.size()/HeapWordSize);
2058 _g1_storage.initialize(g1_rs, 0);
2059 _g1_committed = MemRegion((HeapWord*)_g1_storage.low(), (size_t) 0);
2060 _hrs.initialize((HeapWord*) _g1_reserved.start(),
2061 (HeapWord*) _g1_reserved.end());
2062 assert(_hrs.max_length() == _expansion_regions,
2063 err_msg("max length: %u expansion regions: %u",
2064 _hrs.max_length(), _expansion_regions));
2066 // Do later initialization work for concurrent refinement.
2067 _cg1r->init();
2069 // 6843694 - ensure that the maximum region index can fit
2070 // in the remembered set structures.
2071 const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
2072 guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
2074 size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
2075 guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
2076 guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
2077 "too many cards per region");
2079 FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
2081 _bot_shared = new G1BlockOffsetSharedArray(_reserved,
2082 heap_word_size(init_byte_size));
2084 _g1h = this;
2086 _in_cset_fast_test.initialize(_g1_reserved.start(), _g1_reserved.end(), HeapRegion::GrainBytes);
2088 // Create the ConcurrentMark data structure and thread.
2089 // (Must do this late, so that "max_regions" is defined.)
2090 _cm = new ConcurrentMark(this, heap_rs);
2091 if (_cm == NULL || !_cm->completed_initialization()) {
2092 vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark");
2093 return JNI_ENOMEM;
2094 }
2095 _cmThread = _cm->cmThread();
2097 // Initialize the from_card cache structure of HeapRegionRemSet.
2098 HeapRegionRemSet::init_heap(max_regions());
2100 // Now expand into the initial heap size.
2101 if (!expand(init_byte_size)) {
2102 vm_shutdown_during_initialization("Failed to allocate initial heap.");
2103 return JNI_ENOMEM;
2104 }
2106 // Perform any initialization actions delegated to the policy.
2107 g1_policy()->init();
2109 JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
2110 SATB_Q_FL_lock,
2111 G1SATBProcessCompletedThreshold,
2112 Shared_SATB_Q_lock);
2114 JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl,
2115 DirtyCardQ_CBL_mon,
2116 DirtyCardQ_FL_lock,
2117 concurrent_g1_refine()->yellow_zone(),
2118 concurrent_g1_refine()->red_zone(),
2119 Shared_DirtyCardQ_lock);
2121 if (G1DeferredRSUpdate) {
2122 dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code
2123 DirtyCardQ_CBL_mon,
2124 DirtyCardQ_FL_lock,
2125 -1, // never trigger processing
2126 -1, // no limit on length
2127 Shared_DirtyCardQ_lock,
2128 &JavaThread::dirty_card_queue_set());
2129 }
2131 // Initialize the card queue set used to hold cards containing
2132 // references into the collection set.
2133 _into_cset_dirty_card_queue_set.initialize(NULL, // Should never be called by the Java code
2134 DirtyCardQ_CBL_mon,
2135 DirtyCardQ_FL_lock,
2136 -1, // never trigger processing
2137 -1, // no limit on length
2138 Shared_DirtyCardQ_lock,
2139 &JavaThread::dirty_card_queue_set());
2141 // In case we're keeping closure specialization stats, initialize those
2142 // counts and that mechanism.
2143 SpecializationStats::clear();
2145 // Here we allocate the dummy full region that is required by the
2146 // G1AllocRegion class. If we don't pass an address in the reserved
2147 // space here, lots of asserts fire.
2149 HeapRegion* dummy_region = new_heap_region(0 /* index of bottom region */,
2150 _g1_reserved.start());
2151 // We'll re-use the same region whether the alloc region will
2152 // require BOT updates or not and, if it doesn't, then a non-young
2153 // region will complain that it cannot support allocations without
2154 // BOT updates. So we'll tag the dummy region as young to avoid that.
2155 dummy_region->set_young();
2156 // Make sure it's full.
2157 dummy_region->set_top(dummy_region->end());
2158 G1AllocRegion::setup(this, dummy_region);
2160 init_mutator_alloc_region();
2162 // Do create of the monitoring and management support so that
2163 // values in the heap have been properly initialized.
2164 _g1mm = new G1MonitoringSupport(this);
2166 G1StringDedup::initialize();
2168 return JNI_OK;
2169 }
2171 void G1CollectedHeap::stop() {
2172 // Stop all concurrent threads. We do this to make sure these threads
2173 // do not continue to execute and access resources (e.g. gclog_or_tty)
2174 // that are destroyed during shutdown.
2175 _cg1r->stop();
2176 _cmThread->stop();
2177 if (G1StringDedup::is_enabled()) {
2178 G1StringDedup::stop();
2179 }
2180 }
2182 size_t G1CollectedHeap::conservative_max_heap_alignment() {
2183 return HeapRegion::max_region_size();
2184 }
2186 void G1CollectedHeap::ref_processing_init() {
2187 // Reference processing in G1 currently works as follows:
2188 //
2189 // * There are two reference processor instances. One is
2190 // used to record and process discovered references
2191 // during concurrent marking; the other is used to
2192 // record and process references during STW pauses
2193 // (both full and incremental).
2194 // * Both ref processors need to 'span' the entire heap as
2195 // the regions in the collection set may be dotted around.
2196 //
2197 // * For the concurrent marking ref processor:
2198 // * Reference discovery is enabled at initial marking.
2199 // * Reference discovery is disabled and the discovered
2200 // references processed etc during remarking.
2201 // * Reference discovery is MT (see below).
2202 // * Reference discovery requires a barrier (see below).
2203 // * Reference processing may or may not be MT
2204 // (depending on the value of ParallelRefProcEnabled
2205 // and ParallelGCThreads).
2206 // * A full GC disables reference discovery by the CM
2207 // ref processor and abandons any entries on it's
2208 // discovered lists.
2209 //
2210 // * For the STW processor:
2211 // * Non MT discovery is enabled at the start of a full GC.
2212 // * Processing and enqueueing during a full GC is non-MT.
2213 // * During a full GC, references are processed after marking.
2214 //
2215 // * Discovery (may or may not be MT) is enabled at the start
2216 // of an incremental evacuation pause.
2217 // * References are processed near the end of a STW evacuation pause.
2218 // * For both types of GC:
2219 // * Discovery is atomic - i.e. not concurrent.
2220 // * Reference discovery will not need a barrier.
2222 SharedHeap::ref_processing_init();
2223 MemRegion mr = reserved_region();
2225 // Concurrent Mark ref processor
2226 _ref_processor_cm =
2227 new ReferenceProcessor(mr, // span
2228 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2229 // mt processing
2230 (int) ParallelGCThreads,
2231 // degree of mt processing
2232 (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2233 // mt discovery
2234 (int) MAX2(ParallelGCThreads, ConcGCThreads),
2235 // degree of mt discovery
2236 false,
2237 // Reference discovery is not atomic
2238 &_is_alive_closure_cm);
2239 // is alive closure
2240 // (for efficiency/performance)
2242 // STW ref processor
2243 _ref_processor_stw =
2244 new ReferenceProcessor(mr, // span
2245 ParallelRefProcEnabled && (ParallelGCThreads > 1),
2246 // mt processing
2247 MAX2((int)ParallelGCThreads, 1),
2248 // degree of mt processing
2249 (ParallelGCThreads > 1),
2250 // mt discovery
2251 MAX2((int)ParallelGCThreads, 1),
2252 // degree of mt discovery
2253 true,
2254 // Reference discovery is atomic
2255 &_is_alive_closure_stw);
2256 // is alive closure
2257 // (for efficiency/performance)
2258 }
2260 size_t G1CollectedHeap::capacity() const {
2261 return _g1_committed.byte_size();
2262 }
2264 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2265 assert(!hr->continuesHumongous(), "pre-condition");
2266 hr->reset_gc_time_stamp();
2267 if (hr->startsHumongous()) {
2268 uint first_index = hr->hrs_index() + 1;
2269 uint last_index = hr->last_hc_index();
2270 for (uint i = first_index; i < last_index; i += 1) {
2271 HeapRegion* chr = region_at(i);
2272 assert(chr->continuesHumongous(), "sanity");
2273 chr->reset_gc_time_stamp();
2274 }
2275 }
2276 }
2278 #ifndef PRODUCT
2279 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2280 private:
2281 unsigned _gc_time_stamp;
2282 bool _failures;
2284 public:
2285 CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2286 _gc_time_stamp(gc_time_stamp), _failures(false) { }
2288 virtual bool doHeapRegion(HeapRegion* hr) {
2289 unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2290 if (_gc_time_stamp != region_gc_time_stamp) {
2291 gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, "
2292 "expected %d", HR_FORMAT_PARAMS(hr),
2293 region_gc_time_stamp, _gc_time_stamp);
2294 _failures = true;
2295 }
2296 return false;
2297 }
2299 bool failures() { return _failures; }
2300 };
2302 void G1CollectedHeap::check_gc_time_stamps() {
2303 CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2304 heap_region_iterate(&cl);
2305 guarantee(!cl.failures(), "all GC time stamps should have been reset");
2306 }
2307 #endif // PRODUCT
2309 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2310 DirtyCardQueue* into_cset_dcq,
2311 bool concurrent,
2312 uint worker_i) {
2313 // Clean cards in the hot card cache
2314 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
2315 hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq);
2317 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2318 int n_completed_buffers = 0;
2319 while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2320 n_completed_buffers++;
2321 }
2322 g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers);
2323 dcqs.clear_n_completed_buffers();
2324 assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2325 }
2328 // Computes the sum of the storage used by the various regions.
2330 size_t G1CollectedHeap::used() const {
2331 assert(Heap_lock->owner() != NULL,
2332 "Should be owned on this thread's behalf.");
2333 size_t result = _summary_bytes_used;
2334 // Read only once in case it is set to NULL concurrently
2335 HeapRegion* hr = _mutator_alloc_region.get();
2336 if (hr != NULL)
2337 result += hr->used();
2338 return result;
2339 }
2341 size_t G1CollectedHeap::used_unlocked() const {
2342 size_t result = _summary_bytes_used;
2343 return result;
2344 }
2346 class SumUsedClosure: public HeapRegionClosure {
2347 size_t _used;
2348 public:
2349 SumUsedClosure() : _used(0) {}
2350 bool doHeapRegion(HeapRegion* r) {
2351 if (!r->continuesHumongous()) {
2352 _used += r->used();
2353 }
2354 return false;
2355 }
2356 size_t result() { return _used; }
2357 };
2359 size_t G1CollectedHeap::recalculate_used() const {
2360 double recalculate_used_start = os::elapsedTime();
2362 SumUsedClosure blk;
2363 heap_region_iterate(&blk);
2365 g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2366 return blk.result();
2367 }
2369 size_t G1CollectedHeap::unsafe_max_alloc() {
2370 if (free_regions() > 0) return HeapRegion::GrainBytes;
2371 // otherwise, is there space in the current allocation region?
2373 // We need to store the current allocation region in a local variable
2374 // here. The problem is that this method doesn't take any locks and
2375 // there may be other threads which overwrite the current allocation
2376 // region field. attempt_allocation(), for example, sets it to NULL
2377 // and this can happen *after* the NULL check here but before the call
2378 // to free(), resulting in a SIGSEGV. Note that this doesn't appear
2379 // to be a problem in the optimized build, since the two loads of the
2380 // current allocation region field are optimized away.
2381 HeapRegion* hr = _mutator_alloc_region.get();
2382 if (hr == NULL) {
2383 return 0;
2384 }
2385 return hr->free();
2386 }
2388 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2389 switch (cause) {
2390 case GCCause::_gc_locker: return GCLockerInvokesConcurrent;
2391 case GCCause::_java_lang_system_gc: return ExplicitGCInvokesConcurrent;
2392 case GCCause::_g1_humongous_allocation: return true;
2393 default: return false;
2394 }
2395 }
2397 #ifndef PRODUCT
2398 void G1CollectedHeap::allocate_dummy_regions() {
2399 // Let's fill up most of the region
2400 size_t word_size = HeapRegion::GrainWords - 1024;
2401 // And as a result the region we'll allocate will be humongous.
2402 guarantee(isHumongous(word_size), "sanity");
2404 for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2405 // Let's use the existing mechanism for the allocation
2406 HeapWord* dummy_obj = humongous_obj_allocate(word_size);
2407 if (dummy_obj != NULL) {
2408 MemRegion mr(dummy_obj, word_size);
2409 CollectedHeap::fill_with_object(mr);
2410 } else {
2411 // If we can't allocate once, we probably cannot allocate
2412 // again. Let's get out of the loop.
2413 break;
2414 }
2415 }
2416 }
2417 #endif // !PRODUCT
2419 void G1CollectedHeap::increment_old_marking_cycles_started() {
2420 assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2421 _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2422 err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2423 _old_marking_cycles_started, _old_marking_cycles_completed));
2425 _old_marking_cycles_started++;
2426 }
2428 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2429 MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2431 // We assume that if concurrent == true, then the caller is a
2432 // concurrent thread that was joined the Suspendible Thread
2433 // Set. If there's ever a cheap way to check this, we should add an
2434 // assert here.
2436 // Given that this method is called at the end of a Full GC or of a
2437 // concurrent cycle, and those can be nested (i.e., a Full GC can
2438 // interrupt a concurrent cycle), the number of full collections
2439 // completed should be either one (in the case where there was no
2440 // nesting) or two (when a Full GC interrupted a concurrent cycle)
2441 // behind the number of full collections started.
2443 // This is the case for the inner caller, i.e. a Full GC.
2444 assert(concurrent ||
2445 (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2446 (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2447 err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
2448 "is inconsistent with _old_marking_cycles_completed = %u",
2449 _old_marking_cycles_started, _old_marking_cycles_completed));
2451 // This is the case for the outer caller, i.e. the concurrent cycle.
2452 assert(!concurrent ||
2453 (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2454 err_msg("for outer caller (concurrent cycle): "
2455 "_old_marking_cycles_started = %u "
2456 "is inconsistent with _old_marking_cycles_completed = %u",
2457 _old_marking_cycles_started, _old_marking_cycles_completed));
2459 _old_marking_cycles_completed += 1;
2461 // We need to clear the "in_progress" flag in the CM thread before
2462 // we wake up any waiters (especially when ExplicitInvokesConcurrent
2463 // is set) so that if a waiter requests another System.gc() it doesn't
2464 // incorrectly see that a marking cycle is still in progress.
2465 if (concurrent) {
2466 _cmThread->clear_in_progress();
2467 }
2469 // This notify_all() will ensure that a thread that called
2470 // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2471 // and it's waiting for a full GC to finish will be woken up. It is
2472 // waiting in VM_G1IncCollectionPause::doit_epilogue().
2473 FullGCCount_lock->notify_all();
2474 }
2476 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) {
2477 _concurrent_cycle_started = true;
2478 _gc_timer_cm->register_gc_start(start_time);
2480 _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start());
2481 trace_heap_before_gc(_gc_tracer_cm);
2482 }
2484 void G1CollectedHeap::register_concurrent_cycle_end() {
2485 if (_concurrent_cycle_started) {
2486 if (_cm->has_aborted()) {
2487 _gc_tracer_cm->report_concurrent_mode_failure();
2488 }
2490 _gc_timer_cm->register_gc_end();
2491 _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
2493 _concurrent_cycle_started = false;
2494 }
2495 }
2497 void G1CollectedHeap::trace_heap_after_concurrent_cycle() {
2498 if (_concurrent_cycle_started) {
2499 trace_heap_after_gc(_gc_tracer_cm);
2500 }
2501 }
2503 G1YCType G1CollectedHeap::yc_type() {
2504 bool is_young = g1_policy()->gcs_are_young();
2505 bool is_initial_mark = g1_policy()->during_initial_mark_pause();
2506 bool is_during_mark = mark_in_progress();
2508 if (is_initial_mark) {
2509 return InitialMark;
2510 } else if (is_during_mark) {
2511 return DuringMark;
2512 } else if (is_young) {
2513 return Normal;
2514 } else {
2515 return Mixed;
2516 }
2517 }
2519 void G1CollectedHeap::collect(GCCause::Cause cause) {
2520 assert_heap_not_locked();
2522 unsigned int gc_count_before;
2523 unsigned int old_marking_count_before;
2524 bool retry_gc;
2526 do {
2527 retry_gc = false;
2529 {
2530 MutexLocker ml(Heap_lock);
2532 // Read the GC count while holding the Heap_lock
2533 gc_count_before = total_collections();
2534 old_marking_count_before = _old_marking_cycles_started;
2535 }
2537 if (should_do_concurrent_full_gc(cause)) {
2538 // Schedule an initial-mark evacuation pause that will start a
2539 // concurrent cycle. We're setting word_size to 0 which means that
2540 // we are not requesting a post-GC allocation.
2541 VM_G1IncCollectionPause op(gc_count_before,
2542 0, /* word_size */
2543 true, /* should_initiate_conc_mark */
2544 g1_policy()->max_pause_time_ms(),
2545 cause);
2547 VMThread::execute(&op);
2548 if (!op.pause_succeeded()) {
2549 if (old_marking_count_before == _old_marking_cycles_started) {
2550 retry_gc = op.should_retry_gc();
2551 } else {
2552 // A Full GC happened while we were trying to schedule the
2553 // initial-mark GC. No point in starting a new cycle given
2554 // that the whole heap was collected anyway.
2555 }
2557 if (retry_gc) {
2558 if (GC_locker::is_active_and_needs_gc()) {
2559 GC_locker::stall_until_clear();
2560 }
2561 }
2562 }
2563 } else {
2564 if (cause == GCCause::_gc_locker
2565 DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2567 // Schedule a standard evacuation pause. We're setting word_size
2568 // to 0 which means that we are not requesting a post-GC allocation.
2569 VM_G1IncCollectionPause op(gc_count_before,
2570 0, /* word_size */
2571 false, /* should_initiate_conc_mark */
2572 g1_policy()->max_pause_time_ms(),
2573 cause);
2574 VMThread::execute(&op);
2575 } else {
2576 // Schedule a Full GC.
2577 VM_G1CollectFull op(gc_count_before, old_marking_count_before, cause);
2578 VMThread::execute(&op);
2579 }
2580 }
2581 } while (retry_gc);
2582 }
2584 bool G1CollectedHeap::is_in(const void* p) const {
2585 if (_g1_committed.contains(p)) {
2586 // Given that we know that p is in the committed space,
2587 // heap_region_containing_raw() should successfully
2588 // return the containing region.
2589 HeapRegion* hr = heap_region_containing_raw(p);
2590 return hr->is_in(p);
2591 } else {
2592 return false;
2593 }
2594 }
2596 // Iteration functions.
2598 // Iterates an OopClosure over all ref-containing fields of objects
2599 // within a HeapRegion.
2601 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2602 MemRegion _mr;
2603 ExtendedOopClosure* _cl;
2604 public:
2605 IterateOopClosureRegionClosure(MemRegion mr, ExtendedOopClosure* cl)
2606 : _mr(mr), _cl(cl) {}
2607 bool doHeapRegion(HeapRegion* r) {
2608 if (!r->continuesHumongous()) {
2609 r->oop_iterate(_cl);
2610 }
2611 return false;
2612 }
2613 };
2615 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) {
2616 IterateOopClosureRegionClosure blk(_g1_committed, cl);
2617 heap_region_iterate(&blk);
2618 }
2620 void G1CollectedHeap::oop_iterate(MemRegion mr, ExtendedOopClosure* cl) {
2621 IterateOopClosureRegionClosure blk(mr, cl);
2622 heap_region_iterate(&blk);
2623 }
2625 // Iterates an ObjectClosure over all objects within a HeapRegion.
2627 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2628 ObjectClosure* _cl;
2629 public:
2630 IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2631 bool doHeapRegion(HeapRegion* r) {
2632 if (! r->continuesHumongous()) {
2633 r->object_iterate(_cl);
2634 }
2635 return false;
2636 }
2637 };
2639 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2640 IterateObjectClosureRegionClosure blk(cl);
2641 heap_region_iterate(&blk);
2642 }
2644 // Calls a SpaceClosure on a HeapRegion.
2646 class SpaceClosureRegionClosure: public HeapRegionClosure {
2647 SpaceClosure* _cl;
2648 public:
2649 SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2650 bool doHeapRegion(HeapRegion* r) {
2651 _cl->do_space(r);
2652 return false;
2653 }
2654 };
2656 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2657 SpaceClosureRegionClosure blk(cl);
2658 heap_region_iterate(&blk);
2659 }
2661 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2662 _hrs.iterate(cl);
2663 }
2665 void
2666 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
2667 uint worker_id,
2668 uint no_of_par_workers,
2669 jint claim_value) {
2670 const uint regions = n_regions();
2671 const uint max_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
2672 no_of_par_workers :
2673 1);
2674 assert(UseDynamicNumberOfGCThreads ||
2675 no_of_par_workers == workers()->total_workers(),
2676 "Non dynamic should use fixed number of workers");
2677 // try to spread out the starting points of the workers
2678 const HeapRegion* start_hr =
2679 start_region_for_worker(worker_id, no_of_par_workers);
2680 const uint start_index = start_hr->hrs_index();
2682 // each worker will actually look at all regions
2683 for (uint count = 0; count < regions; ++count) {
2684 const uint index = (start_index + count) % regions;
2685 assert(0 <= index && index < regions, "sanity");
2686 HeapRegion* r = region_at(index);
2687 // we'll ignore "continues humongous" regions (we'll process them
2688 // when we come across their corresponding "start humongous"
2689 // region) and regions already claimed
2690 if (r->claim_value() == claim_value || r->continuesHumongous()) {
2691 continue;
2692 }
2693 // OK, try to claim it
2694 if (r->claimHeapRegion(claim_value)) {
2695 // success!
2696 assert(!r->continuesHumongous(), "sanity");
2697 if (r->startsHumongous()) {
2698 // If the region is "starts humongous" we'll iterate over its
2699 // "continues humongous" first; in fact we'll do them
2700 // first. The order is important. In on case, calling the
2701 // closure on the "starts humongous" region might de-allocate
2702 // and clear all its "continues humongous" regions and, as a
2703 // result, we might end up processing them twice. So, we'll do
2704 // them first (notice: most closures will ignore them anyway) and
2705 // then we'll do the "starts humongous" region.
2706 for (uint ch_index = index + 1; ch_index < regions; ++ch_index) {
2707 HeapRegion* chr = region_at(ch_index);
2709 // if the region has already been claimed or it's not
2710 // "continues humongous" we're done
2711 if (chr->claim_value() == claim_value ||
2712 !chr->continuesHumongous()) {
2713 break;
2714 }
2716 // No one should have claimed it directly. We can given
2717 // that we claimed its "starts humongous" region.
2718 assert(chr->claim_value() != claim_value, "sanity");
2719 assert(chr->humongous_start_region() == r, "sanity");
2721 if (chr->claimHeapRegion(claim_value)) {
2722 // we should always be able to claim it; no one else should
2723 // be trying to claim this region
2725 bool res2 = cl->doHeapRegion(chr);
2726 assert(!res2, "Should not abort");
2728 // Right now, this holds (i.e., no closure that actually
2729 // does something with "continues humongous" regions
2730 // clears them). We might have to weaken it in the future,
2731 // but let's leave these two asserts here for extra safety.
2732 assert(chr->continuesHumongous(), "should still be the case");
2733 assert(chr->humongous_start_region() == r, "sanity");
2734 } else {
2735 guarantee(false, "we should not reach here");
2736 }
2737 }
2738 }
2740 assert(!r->continuesHumongous(), "sanity");
2741 bool res = cl->doHeapRegion(r);
2742 assert(!res, "Should not abort");
2743 }
2744 }
2745 }
2747 class ResetClaimValuesClosure: public HeapRegionClosure {
2748 public:
2749 bool doHeapRegion(HeapRegion* r) {
2750 r->set_claim_value(HeapRegion::InitialClaimValue);
2751 return false;
2752 }
2753 };
2755 void G1CollectedHeap::reset_heap_region_claim_values() {
2756 ResetClaimValuesClosure blk;
2757 heap_region_iterate(&blk);
2758 }
2760 void G1CollectedHeap::reset_cset_heap_region_claim_values() {
2761 ResetClaimValuesClosure blk;
2762 collection_set_iterate(&blk);
2763 }
2765 #ifdef ASSERT
2766 // This checks whether all regions in the heap have the correct claim
2767 // value. I also piggy-backed on this a check to ensure that the
2768 // humongous_start_region() information on "continues humongous"
2769 // regions is correct.
2771 class CheckClaimValuesClosure : public HeapRegionClosure {
2772 private:
2773 jint _claim_value;
2774 uint _failures;
2775 HeapRegion* _sh_region;
2777 public:
2778 CheckClaimValuesClosure(jint claim_value) :
2779 _claim_value(claim_value), _failures(0), _sh_region(NULL) { }
2780 bool doHeapRegion(HeapRegion* r) {
2781 if (r->claim_value() != _claim_value) {
2782 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2783 "claim value = %d, should be %d",
2784 HR_FORMAT_PARAMS(r),
2785 r->claim_value(), _claim_value);
2786 ++_failures;
2787 }
2788 if (!r->isHumongous()) {
2789 _sh_region = NULL;
2790 } else if (r->startsHumongous()) {
2791 _sh_region = r;
2792 } else if (r->continuesHumongous()) {
2793 if (r->humongous_start_region() != _sh_region) {
2794 gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2795 "HS = "PTR_FORMAT", should be "PTR_FORMAT,
2796 HR_FORMAT_PARAMS(r),
2797 r->humongous_start_region(),
2798 _sh_region);
2799 ++_failures;
2800 }
2801 }
2802 return false;
2803 }
2804 uint failures() { return _failures; }
2805 };
2807 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
2808 CheckClaimValuesClosure cl(claim_value);
2809 heap_region_iterate(&cl);
2810 return cl.failures() == 0;
2811 }
2813 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure {
2814 private:
2815 jint _claim_value;
2816 uint _failures;
2818 public:
2819 CheckClaimValuesInCSetHRClosure(jint claim_value) :
2820 _claim_value(claim_value), _failures(0) { }
2822 uint failures() { return _failures; }
2824 bool doHeapRegion(HeapRegion* hr) {
2825 assert(hr->in_collection_set(), "how?");
2826 assert(!hr->isHumongous(), "H-region in CSet");
2827 if (hr->claim_value() != _claim_value) {
2828 gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", "
2829 "claim value = %d, should be %d",
2830 HR_FORMAT_PARAMS(hr),
2831 hr->claim_value(), _claim_value);
2832 _failures += 1;
2833 }
2834 return false;
2835 }
2836 };
2838 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) {
2839 CheckClaimValuesInCSetHRClosure cl(claim_value);
2840 collection_set_iterate(&cl);
2841 return cl.failures() == 0;
2842 }
2843 #endif // ASSERT
2845 // Clear the cached CSet starting regions and (more importantly)
2846 // the time stamps. Called when we reset the GC time stamp.
2847 void G1CollectedHeap::clear_cset_start_regions() {
2848 assert(_worker_cset_start_region != NULL, "sanity");
2849 assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2851 int n_queues = MAX2((int)ParallelGCThreads, 1);
2852 for (int i = 0; i < n_queues; i++) {
2853 _worker_cset_start_region[i] = NULL;
2854 _worker_cset_start_region_time_stamp[i] = 0;
2855 }
2856 }
2858 // Given the id of a worker, obtain or calculate a suitable
2859 // starting region for iterating over the current collection set.
2860 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) {
2861 assert(get_gc_time_stamp() > 0, "should have been updated by now");
2863 HeapRegion* result = NULL;
2864 unsigned gc_time_stamp = get_gc_time_stamp();
2866 if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2867 // Cached starting region for current worker was set
2868 // during the current pause - so it's valid.
2869 // Note: the cached starting heap region may be NULL
2870 // (when the collection set is empty).
2871 result = _worker_cset_start_region[worker_i];
2872 assert(result == NULL || result->in_collection_set(), "sanity");
2873 return result;
2874 }
2876 // The cached entry was not valid so let's calculate
2877 // a suitable starting heap region for this worker.
2879 // We want the parallel threads to start their collection
2880 // set iteration at different collection set regions to
2881 // avoid contention.
2882 // If we have:
2883 // n collection set regions
2884 // p threads
2885 // Then thread t will start at region floor ((t * n) / p)
2887 result = g1_policy()->collection_set();
2888 if (G1CollectedHeap::use_parallel_gc_threads()) {
2889 uint cs_size = g1_policy()->cset_region_length();
2890 uint active_workers = workers()->active_workers();
2891 assert(UseDynamicNumberOfGCThreads ||
2892 active_workers == workers()->total_workers(),
2893 "Unless dynamic should use total workers");
2895 uint end_ind = (cs_size * worker_i) / active_workers;
2896 uint start_ind = 0;
2898 if (worker_i > 0 &&
2899 _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2900 // Previous workers starting region is valid
2901 // so let's iterate from there
2902 start_ind = (cs_size * (worker_i - 1)) / active_workers;
2903 result = _worker_cset_start_region[worker_i - 1];
2904 }
2906 for (uint i = start_ind; i < end_ind; i++) {
2907 result = result->next_in_collection_set();
2908 }
2909 }
2911 // Note: the calculated starting heap region may be NULL
2912 // (when the collection set is empty).
2913 assert(result == NULL || result->in_collection_set(), "sanity");
2914 assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2915 "should be updated only once per pause");
2916 _worker_cset_start_region[worker_i] = result;
2917 OrderAccess::storestore();
2918 _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2919 return result;
2920 }
2922 HeapRegion* G1CollectedHeap::start_region_for_worker(uint worker_i,
2923 uint no_of_par_workers) {
2924 uint worker_num =
2925 G1CollectedHeap::use_parallel_gc_threads() ? no_of_par_workers : 1U;
2926 assert(UseDynamicNumberOfGCThreads ||
2927 no_of_par_workers == workers()->total_workers(),
2928 "Non dynamic should use fixed number of workers");
2929 const uint start_index = n_regions() * worker_i / worker_num;
2930 return region_at(start_index);
2931 }
2933 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2934 HeapRegion* r = g1_policy()->collection_set();
2935 while (r != NULL) {
2936 HeapRegion* next = r->next_in_collection_set();
2937 if (cl->doHeapRegion(r)) {
2938 cl->incomplete();
2939 return;
2940 }
2941 r = next;
2942 }
2943 }
2945 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2946 HeapRegionClosure *cl) {
2947 if (r == NULL) {
2948 // The CSet is empty so there's nothing to do.
2949 return;
2950 }
2952 assert(r->in_collection_set(),
2953 "Start region must be a member of the collection set.");
2954 HeapRegion* cur = r;
2955 while (cur != NULL) {
2956 HeapRegion* next = cur->next_in_collection_set();
2957 if (cl->doHeapRegion(cur) && false) {
2958 cl->incomplete();
2959 return;
2960 }
2961 cur = next;
2962 }
2963 cur = g1_policy()->collection_set();
2964 while (cur != r) {
2965 HeapRegion* next = cur->next_in_collection_set();
2966 if (cl->doHeapRegion(cur) && false) {
2967 cl->incomplete();
2968 return;
2969 }
2970 cur = next;
2971 }
2972 }
2974 CompactibleSpace* G1CollectedHeap::first_compactible_space() {
2975 return n_regions() > 0 ? region_at(0) : NULL;
2976 }
2979 Space* G1CollectedHeap::space_containing(const void* addr) const {
2980 Space* res = heap_region_containing(addr);
2981 return res;
2982 }
2984 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2985 Space* sp = space_containing(addr);
2986 if (sp != NULL) {
2987 return sp->block_start(addr);
2988 }
2989 return NULL;
2990 }
2992 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2993 Space* sp = space_containing(addr);
2994 assert(sp != NULL, "block_size of address outside of heap");
2995 return sp->block_size(addr);
2996 }
2998 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2999 Space* sp = space_containing(addr);
3000 return sp->block_is_obj(addr);
3001 }
3003 bool G1CollectedHeap::supports_tlab_allocation() const {
3004 return true;
3005 }
3007 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
3008 return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes;
3009 }
3011 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
3012 return young_list()->eden_used_bytes();
3013 }
3015 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
3016 // must be smaller than the humongous object limit.
3017 size_t G1CollectedHeap::max_tlab_size() const {
3018 return align_size_down(_humongous_object_threshold_in_words - 1, MinObjAlignment);
3019 }
3021 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
3022 // Return the remaining space in the cur alloc region, but not less than
3023 // the min TLAB size.
3025 // Also, this value can be at most the humongous object threshold,
3026 // since we can't allow tlabs to grow big enough to accommodate
3027 // humongous objects.
3029 HeapRegion* hr = _mutator_alloc_region.get();
3030 size_t max_tlab = max_tlab_size() * wordSize;
3031 if (hr == NULL) {
3032 return max_tlab;
3033 } else {
3034 return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab);
3035 }
3036 }
3038 size_t G1CollectedHeap::max_capacity() const {
3039 return _g1_reserved.byte_size();
3040 }
3042 jlong G1CollectedHeap::millis_since_last_gc() {
3043 // assert(false, "NYI");
3044 return 0;
3045 }
3047 void G1CollectedHeap::prepare_for_verify() {
3048 if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
3049 ensure_parsability(false);
3050 }
3051 g1_rem_set()->prepare_for_verify();
3052 }
3054 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr,
3055 VerifyOption vo) {
3056 switch (vo) {
3057 case VerifyOption_G1UsePrevMarking:
3058 return hr->obj_allocated_since_prev_marking(obj);
3059 case VerifyOption_G1UseNextMarking:
3060 return hr->obj_allocated_since_next_marking(obj);
3061 case VerifyOption_G1UseMarkWord:
3062 return false;
3063 default:
3064 ShouldNotReachHere();
3065 }
3066 return false; // keep some compilers happy
3067 }
3069 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) {
3070 switch (vo) {
3071 case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start();
3072 case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start();
3073 case VerifyOption_G1UseMarkWord: return NULL;
3074 default: ShouldNotReachHere();
3075 }
3076 return NULL; // keep some compilers happy
3077 }
3079 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) {
3080 switch (vo) {
3081 case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj);
3082 case VerifyOption_G1UseNextMarking: return isMarkedNext(obj);
3083 case VerifyOption_G1UseMarkWord: return obj->is_gc_marked();
3084 default: ShouldNotReachHere();
3085 }
3086 return false; // keep some compilers happy
3087 }
3089 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) {
3090 switch (vo) {
3091 case VerifyOption_G1UsePrevMarking: return "PTAMS";
3092 case VerifyOption_G1UseNextMarking: return "NTAMS";
3093 case VerifyOption_G1UseMarkWord: return "NONE";
3094 default: ShouldNotReachHere();
3095 }
3096 return NULL; // keep some compilers happy
3097 }
3099 class VerifyRootsClosure: public OopClosure {
3100 private:
3101 G1CollectedHeap* _g1h;
3102 VerifyOption _vo;
3103 bool _failures;
3104 public:
3105 // _vo == UsePrevMarking -> use "prev" marking information,
3106 // _vo == UseNextMarking -> use "next" marking information,
3107 // _vo == UseMarkWord -> use mark word from object header.
3108 VerifyRootsClosure(VerifyOption vo) :
3109 _g1h(G1CollectedHeap::heap()),
3110 _vo(vo),
3111 _failures(false) { }
3113 bool failures() { return _failures; }
3115 template <class T> void do_oop_nv(T* p) {
3116 T heap_oop = oopDesc::load_heap_oop(p);
3117 if (!oopDesc::is_null(heap_oop)) {
3118 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3119 if (_g1h->is_obj_dead_cond(obj, _vo)) {
3120 gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
3121 "points to dead obj "PTR_FORMAT, p, (void*) obj);
3122 if (_vo == VerifyOption_G1UseMarkWord) {
3123 gclog_or_tty->print_cr(" Mark word: "PTR_FORMAT, (void*)(obj->mark()));
3124 }
3125 obj->print_on(gclog_or_tty);
3126 _failures = true;
3127 }
3128 }
3129 }
3131 void do_oop(oop* p) { do_oop_nv(p); }
3132 void do_oop(narrowOop* p) { do_oop_nv(p); }
3133 };
3135 class G1VerifyCodeRootOopClosure: public OopClosure {
3136 G1CollectedHeap* _g1h;
3137 OopClosure* _root_cl;
3138 nmethod* _nm;
3139 VerifyOption _vo;
3140 bool _failures;
3142 template <class T> void do_oop_work(T* p) {
3143 // First verify that this root is live
3144 _root_cl->do_oop(p);
3146 if (!G1VerifyHeapRegionCodeRoots) {
3147 // We're not verifying the code roots attached to heap region.
3148 return;
3149 }
3151 // Don't check the code roots during marking verification in a full GC
3152 if (_vo == VerifyOption_G1UseMarkWord) {
3153 return;
3154 }
3156 // Now verify that the current nmethod (which contains p) is
3157 // in the code root list of the heap region containing the
3158 // object referenced by p.
3160 T heap_oop = oopDesc::load_heap_oop(p);
3161 if (!oopDesc::is_null(heap_oop)) {
3162 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3164 // Now fetch the region containing the object
3165 HeapRegion* hr = _g1h->heap_region_containing(obj);
3166 HeapRegionRemSet* hrrs = hr->rem_set();
3167 // Verify that the strong code root list for this region
3168 // contains the nmethod
3169 if (!hrrs->strong_code_roots_list_contains(_nm)) {
3170 gclog_or_tty->print_cr("Code root location "PTR_FORMAT" "
3171 "from nmethod "PTR_FORMAT" not in strong "
3172 "code roots for region ["PTR_FORMAT","PTR_FORMAT")",
3173 p, _nm, hr->bottom(), hr->end());
3174 _failures = true;
3175 }
3176 }
3177 }
3179 public:
3180 G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo):
3181 _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {}
3183 void do_oop(oop* p) { do_oop_work(p); }
3184 void do_oop(narrowOop* p) { do_oop_work(p); }
3186 void set_nmethod(nmethod* nm) { _nm = nm; }
3187 bool failures() { return _failures; }
3188 };
3190 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure {
3191 G1VerifyCodeRootOopClosure* _oop_cl;
3193 public:
3194 G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl):
3195 _oop_cl(oop_cl) {}
3197 void do_code_blob(CodeBlob* cb) {
3198 nmethod* nm = cb->as_nmethod_or_null();
3199 if (nm != NULL) {
3200 _oop_cl->set_nmethod(nm);
3201 nm->oops_do(_oop_cl);
3202 }
3203 }
3204 };
3206 class YoungRefCounterClosure : public OopClosure {
3207 G1CollectedHeap* _g1h;
3208 int _count;
3209 public:
3210 YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {}
3211 void do_oop(oop* p) { if (_g1h->is_in_young(*p)) { _count++; } }
3212 void do_oop(narrowOop* p) { ShouldNotReachHere(); }
3214 int count() { return _count; }
3215 void reset_count() { _count = 0; };
3216 };
3218 class VerifyKlassClosure: public KlassClosure {
3219 YoungRefCounterClosure _young_ref_counter_closure;
3220 OopClosure *_oop_closure;
3221 public:
3222 VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {}
3223 void do_klass(Klass* k) {
3224 k->oops_do(_oop_closure);
3226 _young_ref_counter_closure.reset_count();
3227 k->oops_do(&_young_ref_counter_closure);
3228 if (_young_ref_counter_closure.count() > 0) {
3229 guarantee(k->has_modified_oops(), err_msg("Klass %p, has young refs but is not dirty.", k));
3230 }
3231 }
3232 };
3234 class VerifyLivenessOopClosure: public OopClosure {
3235 G1CollectedHeap* _g1h;
3236 VerifyOption _vo;
3237 public:
3238 VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
3239 _g1h(g1h), _vo(vo)
3240 { }
3241 void do_oop(narrowOop *p) { do_oop_work(p); }
3242 void do_oop( oop *p) { do_oop_work(p); }
3244 template <class T> void do_oop_work(T *p) {
3245 oop obj = oopDesc::load_decode_heap_oop(p);
3246 guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
3247 "Dead object referenced by a not dead object");
3248 }
3249 };
3251 class VerifyObjsInRegionClosure: public ObjectClosure {
3252 private:
3253 G1CollectedHeap* _g1h;
3254 size_t _live_bytes;
3255 HeapRegion *_hr;
3256 VerifyOption _vo;
3257 public:
3258 // _vo == UsePrevMarking -> use "prev" marking information,
3259 // _vo == UseNextMarking -> use "next" marking information,
3260 // _vo == UseMarkWord -> use mark word from object header.
3261 VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
3262 : _live_bytes(0), _hr(hr), _vo(vo) {
3263 _g1h = G1CollectedHeap::heap();
3264 }
3265 void do_object(oop o) {
3266 VerifyLivenessOopClosure isLive(_g1h, _vo);
3267 assert(o != NULL, "Huh?");
3268 if (!_g1h->is_obj_dead_cond(o, _vo)) {
3269 // If the object is alive according to the mark word,
3270 // then verify that the marking information agrees.
3271 // Note we can't verify the contra-positive of the
3272 // above: if the object is dead (according to the mark
3273 // word), it may not be marked, or may have been marked
3274 // but has since became dead, or may have been allocated
3275 // since the last marking.
3276 if (_vo == VerifyOption_G1UseMarkWord) {
3277 guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
3278 }
3280 o->oop_iterate_no_header(&isLive);
3281 if (!_hr->obj_allocated_since_prev_marking(o)) {
3282 size_t obj_size = o->size(); // Make sure we don't overflow
3283 _live_bytes += (obj_size * HeapWordSize);
3284 }
3285 }
3286 }
3287 size_t live_bytes() { return _live_bytes; }
3288 };
3290 class PrintObjsInRegionClosure : public ObjectClosure {
3291 HeapRegion *_hr;
3292 G1CollectedHeap *_g1;
3293 public:
3294 PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
3295 _g1 = G1CollectedHeap::heap();
3296 };
3298 void do_object(oop o) {
3299 if (o != NULL) {
3300 HeapWord *start = (HeapWord *) o;
3301 size_t word_sz = o->size();
3302 gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
3303 " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
3304 (void*) o, word_sz,
3305 _g1->isMarkedPrev(o),
3306 _g1->isMarkedNext(o),
3307 _hr->obj_allocated_since_prev_marking(o));
3308 HeapWord *end = start + word_sz;
3309 HeapWord *cur;
3310 int *val;
3311 for (cur = start; cur < end; cur++) {
3312 val = (int *) cur;
3313 gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val);
3314 }
3315 }
3316 }
3317 };
3319 class VerifyRegionClosure: public HeapRegionClosure {
3320 private:
3321 bool _par;
3322 VerifyOption _vo;
3323 bool _failures;
3324 public:
3325 // _vo == UsePrevMarking -> use "prev" marking information,
3326 // _vo == UseNextMarking -> use "next" marking information,
3327 // _vo == UseMarkWord -> use mark word from object header.
3328 VerifyRegionClosure(bool par, VerifyOption vo)
3329 : _par(par),
3330 _vo(vo),
3331 _failures(false) {}
3333 bool failures() {
3334 return _failures;
3335 }
3337 bool doHeapRegion(HeapRegion* r) {
3338 if (!r->continuesHumongous()) {
3339 bool failures = false;
3340 r->verify(_vo, &failures);
3341 if (failures) {
3342 _failures = true;
3343 } else {
3344 VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
3345 r->object_iterate(¬_dead_yet_cl);
3346 if (_vo != VerifyOption_G1UseNextMarking) {
3347 if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
3348 gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
3349 "max_live_bytes "SIZE_FORMAT" "
3350 "< calculated "SIZE_FORMAT,
3351 r->bottom(), r->end(),
3352 r->max_live_bytes(),
3353 not_dead_yet_cl.live_bytes());
3354 _failures = true;
3355 }
3356 } else {
3357 // When vo == UseNextMarking we cannot currently do a sanity
3358 // check on the live bytes as the calculation has not been
3359 // finalized yet.
3360 }
3361 }
3362 }
3363 return false; // stop the region iteration if we hit a failure
3364 }
3365 };
3367 // This is the task used for parallel verification of the heap regions
3369 class G1ParVerifyTask: public AbstractGangTask {
3370 private:
3371 G1CollectedHeap* _g1h;
3372 VerifyOption _vo;
3373 bool _failures;
3375 public:
3376 // _vo == UsePrevMarking -> use "prev" marking information,
3377 // _vo == UseNextMarking -> use "next" marking information,
3378 // _vo == UseMarkWord -> use mark word from object header.
3379 G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
3380 AbstractGangTask("Parallel verify task"),
3381 _g1h(g1h),
3382 _vo(vo),
3383 _failures(false) { }
3385 bool failures() {
3386 return _failures;
3387 }
3389 void work(uint worker_id) {
3390 HandleMark hm;
3391 VerifyRegionClosure blk(true, _vo);
3392 _g1h->heap_region_par_iterate_chunked(&blk, worker_id,
3393 _g1h->workers()->active_workers(),
3394 HeapRegion::ParVerifyClaimValue);
3395 if (blk.failures()) {
3396 _failures = true;
3397 }
3398 }
3399 };
3401 void G1CollectedHeap::verify(bool silent, VerifyOption vo) {
3402 if (SafepointSynchronize::is_at_safepoint()) {
3403 assert(Thread::current()->is_VM_thread(),
3404 "Expected to be executed serially by the VM thread at this point");
3406 if (!silent) { gclog_or_tty->print("Roots "); }
3407 VerifyRootsClosure rootsCl(vo);
3408 VerifyKlassClosure klassCl(this, &rootsCl);
3409 CLDToKlassAndOopClosure cldCl(&klassCl, &rootsCl, false);
3411 // We apply the relevant closures to all the oops in the
3412 // system dictionary, class loader data graph, the string table
3413 // and the nmethods in the code cache.
3414 G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo);
3415 G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl);
3417 process_all_roots(true, // activate StrongRootsScope
3418 SO_AllCodeCache, // roots scanning options
3419 &rootsCl,
3420 &cldCl,
3421 &blobsCl);
3423 bool failures = rootsCl.failures() || codeRootsCl.failures();
3425 if (vo != VerifyOption_G1UseMarkWord) {
3426 // If we're verifying during a full GC then the region sets
3427 // will have been torn down at the start of the GC. Therefore
3428 // verifying the region sets will fail. So we only verify
3429 // the region sets when not in a full GC.
3430 if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3431 verify_region_sets();
3432 }
3434 if (!silent) { gclog_or_tty->print("HeapRegions "); }
3435 if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3436 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3437 "sanity check");
3439 G1ParVerifyTask task(this, vo);
3440 assert(UseDynamicNumberOfGCThreads ||
3441 workers()->active_workers() == workers()->total_workers(),
3442 "If not dynamic should be using all the workers");
3443 int n_workers = workers()->active_workers();
3444 set_par_threads(n_workers);
3445 workers()->run_task(&task);
3446 set_par_threads(0);
3447 if (task.failures()) {
3448 failures = true;
3449 }
3451 // Checks that the expected amount of parallel work was done.
3452 // The implication is that n_workers is > 0.
3453 assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
3454 "sanity check");
3456 reset_heap_region_claim_values();
3458 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3459 "sanity check");
3460 } else {
3461 VerifyRegionClosure blk(false, vo);
3462 heap_region_iterate(&blk);
3463 if (blk.failures()) {
3464 failures = true;
3465 }
3466 }
3467 if (!silent) gclog_or_tty->print("RemSet ");
3468 rem_set()->verify();
3470 if (G1StringDedup::is_enabled()) {
3471 if (!silent) gclog_or_tty->print("StrDedup ");
3472 G1StringDedup::verify();
3473 }
3475 if (failures) {
3476 gclog_or_tty->print_cr("Heap:");
3477 // It helps to have the per-region information in the output to
3478 // help us track down what went wrong. This is why we call
3479 // print_extended_on() instead of print_on().
3480 print_extended_on(gclog_or_tty);
3481 gclog_or_tty->cr();
3482 #ifndef PRODUCT
3483 if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3484 concurrent_mark()->print_reachable("at-verification-failure",
3485 vo, false /* all */);
3486 }
3487 #endif
3488 gclog_or_tty->flush();
3489 }
3490 guarantee(!failures, "there should not have been any failures");
3491 } else {
3492 if (!silent) {
3493 gclog_or_tty->print("(SKIPPING Roots, HeapRegionSets, HeapRegions, RemSet");
3494 if (G1StringDedup::is_enabled()) {
3495 gclog_or_tty->print(", StrDedup");
3496 }
3497 gclog_or_tty->print(") ");
3498 }
3499 }
3500 }
3502 void G1CollectedHeap::verify(bool silent) {
3503 verify(silent, VerifyOption_G1UsePrevMarking);
3504 }
3506 double G1CollectedHeap::verify(bool guard, const char* msg) {
3507 double verify_time_ms = 0.0;
3509 if (guard && total_collections() >= VerifyGCStartAt) {
3510 double verify_start = os::elapsedTime();
3511 HandleMark hm; // Discard invalid handles created during verification
3512 prepare_for_verify();
3513 Universe::verify(VerifyOption_G1UsePrevMarking, msg);
3514 verify_time_ms = (os::elapsedTime() - verify_start) * 1000;
3515 }
3517 return verify_time_ms;
3518 }
3520 void G1CollectedHeap::verify_before_gc() {
3521 double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:");
3522 g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms);
3523 }
3525 void G1CollectedHeap::verify_after_gc() {
3526 double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:");
3527 g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms);
3528 }
3530 class PrintRegionClosure: public HeapRegionClosure {
3531 outputStream* _st;
3532 public:
3533 PrintRegionClosure(outputStream* st) : _st(st) {}
3534 bool doHeapRegion(HeapRegion* r) {
3535 r->print_on(_st);
3536 return false;
3537 }
3538 };
3540 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3541 const HeapRegion* hr,
3542 const VerifyOption vo) const {
3543 switch (vo) {
3544 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
3545 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
3546 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked();
3547 default: ShouldNotReachHere();
3548 }
3549 return false; // keep some compilers happy
3550 }
3552 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3553 const VerifyOption vo) const {
3554 switch (vo) {
3555 case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
3556 case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
3557 case VerifyOption_G1UseMarkWord: return !obj->is_gc_marked();
3558 default: ShouldNotReachHere();
3559 }
3560 return false; // keep some compilers happy
3561 }
3563 void G1CollectedHeap::print_on(outputStream* st) const {
3564 st->print(" %-20s", "garbage-first heap");
3565 st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3566 capacity()/K, used_unlocked()/K);
3567 st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3568 _g1_storage.low_boundary(),
3569 _g1_storage.high(),
3570 _g1_storage.high_boundary());
3571 st->cr();
3572 st->print(" region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3573 uint young_regions = _young_list->length();
3574 st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3575 (size_t) young_regions * HeapRegion::GrainBytes / K);
3576 uint survivor_regions = g1_policy()->recorded_survivor_regions();
3577 st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3578 (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3579 st->cr();
3580 MetaspaceAux::print_on(st);
3581 }
3583 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3584 print_on(st);
3586 // Print the per-region information.
3587 st->cr();
3588 st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3589 "HS=humongous(starts), HC=humongous(continues), "
3590 "CS=collection set, F=free, TS=gc time stamp, "
3591 "PTAMS=previous top-at-mark-start, "
3592 "NTAMS=next top-at-mark-start)");
3593 PrintRegionClosure blk(st);
3594 heap_region_iterate(&blk);
3595 }
3597 void G1CollectedHeap::print_on_error(outputStream* st) const {
3598 this->CollectedHeap::print_on_error(st);
3600 if (_cm != NULL) {
3601 st->cr();
3602 _cm->print_on_error(st);
3603 }
3604 }
3606 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3607 if (G1CollectedHeap::use_parallel_gc_threads()) {
3608 workers()->print_worker_threads_on(st);
3609 }
3610 _cmThread->print_on(st);
3611 st->cr();
3612 _cm->print_worker_threads_on(st);
3613 _cg1r->print_worker_threads_on(st);
3614 if (G1StringDedup::is_enabled()) {
3615 G1StringDedup::print_worker_threads_on(st);
3616 }
3617 }
3619 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3620 if (G1CollectedHeap::use_parallel_gc_threads()) {
3621 workers()->threads_do(tc);
3622 }
3623 tc->do_thread(_cmThread);
3624 _cg1r->threads_do(tc);
3625 if (G1StringDedup::is_enabled()) {
3626 G1StringDedup::threads_do(tc);
3627 }
3628 }
3630 void G1CollectedHeap::print_tracing_info() const {
3631 // We'll overload this to mean "trace GC pause statistics."
3632 if (TraceGen0Time || TraceGen1Time) {
3633 // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3634 // to that.
3635 g1_policy()->print_tracing_info();
3636 }
3637 if (G1SummarizeRSetStats) {
3638 g1_rem_set()->print_summary_info();
3639 }
3640 if (G1SummarizeConcMark) {
3641 concurrent_mark()->print_summary_info();
3642 }
3643 g1_policy()->print_yg_surv_rate_info();
3644 SpecializationStats::print();
3645 }
3647 #ifndef PRODUCT
3648 // Helpful for debugging RSet issues.
3650 class PrintRSetsClosure : public HeapRegionClosure {
3651 private:
3652 const char* _msg;
3653 size_t _occupied_sum;
3655 public:
3656 bool doHeapRegion(HeapRegion* r) {
3657 HeapRegionRemSet* hrrs = r->rem_set();
3658 size_t occupied = hrrs->occupied();
3659 _occupied_sum += occupied;
3661 gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3662 HR_FORMAT_PARAMS(r));
3663 if (occupied == 0) {
3664 gclog_or_tty->print_cr(" RSet is empty");
3665 } else {
3666 hrrs->print();
3667 }
3668 gclog_or_tty->print_cr("----------");
3669 return false;
3670 }
3672 PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3673 gclog_or_tty->cr();
3674 gclog_or_tty->print_cr("========================================");
3675 gclog_or_tty->print_cr("%s", msg);
3676 gclog_or_tty->cr();
3677 }
3679 ~PrintRSetsClosure() {
3680 gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3681 gclog_or_tty->print_cr("========================================");
3682 gclog_or_tty->cr();
3683 }
3684 };
3686 void G1CollectedHeap::print_cset_rsets() {
3687 PrintRSetsClosure cl("Printing CSet RSets");
3688 collection_set_iterate(&cl);
3689 }
3691 void G1CollectedHeap::print_all_rsets() {
3692 PrintRSetsClosure cl("Printing All RSets");;
3693 heap_region_iterate(&cl);
3694 }
3695 #endif // PRODUCT
3697 G1CollectedHeap* G1CollectedHeap::heap() {
3698 assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3699 "not a garbage-first heap");
3700 return _g1h;
3701 }
3703 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3704 // always_do_update_barrier = false;
3705 assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3706 // Fill TLAB's and such
3707 accumulate_statistics_all_tlabs();
3708 ensure_parsability(true);
3710 if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) &&
3711 (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3712 g1_rem_set()->print_periodic_summary_info("Before GC RS summary");
3713 }
3714 }
3716 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) {
3718 if (G1SummarizeRSetStats &&
3719 (G1SummarizeRSetStatsPeriod > 0) &&
3720 // we are at the end of the GC. Total collections has already been increased.
3721 ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) {
3722 g1_rem_set()->print_periodic_summary_info("After GC RS summary");
3723 }
3725 // FIXME: what is this about?
3726 // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3727 // is set.
3728 COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3729 "derived pointer present"));
3730 // always_do_update_barrier = true;
3732 resize_all_tlabs();
3734 // We have just completed a GC. Update the soft reference
3735 // policy with the new heap occupancy
3736 Universe::update_heap_info_at_gc();
3737 }
3739 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3740 unsigned int gc_count_before,
3741 bool* succeeded,
3742 GCCause::Cause gc_cause) {
3743 assert_heap_not_locked_and_not_at_safepoint();
3744 g1_policy()->record_stop_world_start();
3745 VM_G1IncCollectionPause op(gc_count_before,
3746 word_size,
3747 false, /* should_initiate_conc_mark */
3748 g1_policy()->max_pause_time_ms(),
3749 gc_cause);
3750 VMThread::execute(&op);
3752 HeapWord* result = op.result();
3753 bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3754 assert(result == NULL || ret_succeeded,
3755 "the result should be NULL if the VM did not succeed");
3756 *succeeded = ret_succeeded;
3758 assert_heap_not_locked();
3759 return result;
3760 }
3762 void
3763 G1CollectedHeap::doConcurrentMark() {
3764 MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3765 if (!_cmThread->in_progress()) {
3766 _cmThread->set_started();
3767 CGC_lock->notify();
3768 }
3769 }
3771 size_t G1CollectedHeap::pending_card_num() {
3772 size_t extra_cards = 0;
3773 JavaThread *curr = Threads::first();
3774 while (curr != NULL) {
3775 DirtyCardQueue& dcq = curr->dirty_card_queue();
3776 extra_cards += dcq.size();
3777 curr = curr->next();
3778 }
3779 DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3780 size_t buffer_size = dcqs.buffer_size();
3781 size_t buffer_num = dcqs.completed_buffers_num();
3783 // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
3784 // in bytes - not the number of 'entries'. We need to convert
3785 // into a number of cards.
3786 return (buffer_size * buffer_num + extra_cards) / oopSize;
3787 }
3789 size_t G1CollectedHeap::cards_scanned() {
3790 return g1_rem_set()->cardsScanned();
3791 }
3793 void
3794 G1CollectedHeap::setup_surviving_young_words() {
3795 assert(_surviving_young_words == NULL, "pre-condition");
3796 uint array_length = g1_policy()->young_cset_region_length();
3797 _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3798 if (_surviving_young_words == NULL) {
3799 vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR,
3800 "Not enough space for young surv words summary.");
3801 }
3802 memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3803 #ifdef ASSERT
3804 for (uint i = 0; i < array_length; ++i) {
3805 assert( _surviving_young_words[i] == 0, "memset above" );
3806 }
3807 #endif // !ASSERT
3808 }
3810 void
3811 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3812 MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3813 uint array_length = g1_policy()->young_cset_region_length();
3814 for (uint i = 0; i < array_length; ++i) {
3815 _surviving_young_words[i] += surv_young_words[i];
3816 }
3817 }
3819 void
3820 G1CollectedHeap::cleanup_surviving_young_words() {
3821 guarantee( _surviving_young_words != NULL, "pre-condition" );
3822 FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC);
3823 _surviving_young_words = NULL;
3824 }
3826 #ifdef ASSERT
3827 class VerifyCSetClosure: public HeapRegionClosure {
3828 public:
3829 bool doHeapRegion(HeapRegion* hr) {
3830 // Here we check that the CSet region's RSet is ready for parallel
3831 // iteration. The fields that we'll verify are only manipulated
3832 // when the region is part of a CSet and is collected. Afterwards,
3833 // we reset these fields when we clear the region's RSet (when the
3834 // region is freed) so they are ready when the region is
3835 // re-allocated. The only exception to this is if there's an
3836 // evacuation failure and instead of freeing the region we leave
3837 // it in the heap. In that case, we reset these fields during
3838 // evacuation failure handling.
3839 guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3841 // Here's a good place to add any other checks we'd like to
3842 // perform on CSet regions.
3843 return false;
3844 }
3845 };
3846 #endif // ASSERT
3848 #if TASKQUEUE_STATS
3849 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3850 st->print_raw_cr("GC Task Stats");
3851 st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3852 st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3853 }
3855 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3856 print_taskqueue_stats_hdr(st);
3858 TaskQueueStats totals;
3859 const int n = workers() != NULL ? workers()->total_workers() : 1;
3860 for (int i = 0; i < n; ++i) {
3861 st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3862 totals += task_queue(i)->stats;
3863 }
3864 st->print_raw("tot "); totals.print(st); st->cr();
3866 DEBUG_ONLY(totals.verify());
3867 }
3869 void G1CollectedHeap::reset_taskqueue_stats() {
3870 const int n = workers() != NULL ? workers()->total_workers() : 1;
3871 for (int i = 0; i < n; ++i) {
3872 task_queue(i)->stats.reset();
3873 }
3874 }
3875 #endif // TASKQUEUE_STATS
3877 void G1CollectedHeap::log_gc_header() {
3878 if (!G1Log::fine()) {
3879 return;
3880 }
3882 gclog_or_tty->gclog_stamp(_gc_tracer_stw->gc_id());
3884 GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
3885 .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)")
3886 .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : "");
3888 gclog_or_tty->print("[%s", (const char*)gc_cause_str);
3889 }
3891 void G1CollectedHeap::log_gc_footer(double pause_time_sec) {
3892 if (!G1Log::fine()) {
3893 return;
3894 }
3896 if (G1Log::finer()) {
3897 if (evacuation_failed()) {
3898 gclog_or_tty->print(" (to-space exhausted)");
3899 }
3900 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3901 g1_policy()->phase_times()->note_gc_end();
3902 g1_policy()->phase_times()->print(pause_time_sec);
3903 g1_policy()->print_detailed_heap_transition();
3904 } else {
3905 if (evacuation_failed()) {
3906 gclog_or_tty->print("--");
3907 }
3908 g1_policy()->print_heap_transition();
3909 gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3910 }
3911 gclog_or_tty->flush();
3912 }
3914 bool
3915 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3916 assert_at_safepoint(true /* should_be_vm_thread */);
3917 guarantee(!is_gc_active(), "collection is not reentrant");
3919 if (GC_locker::check_active_before_gc()) {
3920 return false;
3921 }
3923 _gc_timer_stw->register_gc_start();
3925 _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3927 SvcGCMarker sgcm(SvcGCMarker::MINOR);
3928 ResourceMark rm;
3930 print_heap_before_gc();
3931 trace_heap_before_gc(_gc_tracer_stw);
3933 verify_region_sets_optional();
3934 verify_dirty_young_regions();
3936 // This call will decide whether this pause is an initial-mark
3937 // pause. If it is, during_initial_mark_pause() will return true
3938 // for the duration of this pause.
3939 g1_policy()->decide_on_conc_mark_initiation();
3941 // We do not allow initial-mark to be piggy-backed on a mixed GC.
3942 assert(!g1_policy()->during_initial_mark_pause() ||
3943 g1_policy()->gcs_are_young(), "sanity");
3945 // We also do not allow mixed GCs during marking.
3946 assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3948 // Record whether this pause is an initial mark. When the current
3949 // thread has completed its logging output and it's safe to signal
3950 // the CM thread, the flag's value in the policy has been reset.
3951 bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3953 // Inner scope for scope based logging, timers, and stats collection
3954 {
3955 EvacuationInfo evacuation_info;
3957 if (g1_policy()->during_initial_mark_pause()) {
3958 // We are about to start a marking cycle, so we increment the
3959 // full collection counter.
3960 increment_old_marking_cycles_started();
3961 register_concurrent_cycle_start(_gc_timer_stw->gc_start());
3962 }
3964 _gc_tracer_stw->report_yc_type(yc_type());
3966 TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3968 int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
3969 workers()->active_workers() : 1);
3970 double pause_start_sec = os::elapsedTime();
3971 g1_policy()->phase_times()->note_gc_start(active_workers);
3972 log_gc_header();
3974 TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3975 TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3977 // If the secondary_free_list is not empty, append it to the
3978 // free_list. No need to wait for the cleanup operation to finish;
3979 // the region allocation code will check the secondary_free_list
3980 // and wait if necessary. If the G1StressConcRegionFreeing flag is
3981 // set, skip this step so that the region allocation code has to
3982 // get entries from the secondary_free_list.
3983 if (!G1StressConcRegionFreeing) {
3984 append_secondary_free_list_if_not_empty_with_lock();
3985 }
3987 assert(check_young_list_well_formed(), "young list should be well formed");
3988 assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3989 "sanity check");
3991 // Don't dynamically change the number of GC threads this early. A value of
3992 // 0 is used to indicate serial work. When parallel work is done,
3993 // it will be set.
3995 { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3996 IsGCActiveMark x;
3998 gc_prologue(false);
3999 increment_total_collections(false /* full gc */);
4000 increment_gc_time_stamp();
4002 verify_before_gc();
4003 check_bitmaps("GC Start");
4005 COMPILER2_PRESENT(DerivedPointerTable::clear());
4007 // Please see comment in g1CollectedHeap.hpp and
4008 // G1CollectedHeap::ref_processing_init() to see how
4009 // reference processing currently works in G1.
4011 // Enable discovery in the STW reference processor
4012 ref_processor_stw()->enable_discovery(true /*verify_disabled*/,
4013 true /*verify_no_refs*/);
4015 {
4016 // We want to temporarily turn off discovery by the
4017 // CM ref processor, if necessary, and turn it back on
4018 // on again later if we do. Using a scoped
4019 // NoRefDiscovery object will do this.
4020 NoRefDiscovery no_cm_discovery(ref_processor_cm());
4022 // Forget the current alloc region (we might even choose it to be part
4023 // of the collection set!).
4024 release_mutator_alloc_region();
4026 // We should call this after we retire the mutator alloc
4027 // region(s) so that all the ALLOC / RETIRE events are generated
4028 // before the start GC event.
4029 _hr_printer.start_gc(false /* full */, (size_t) total_collections());
4031 // This timing is only used by the ergonomics to handle our pause target.
4032 // It is unclear why this should not include the full pause. We will
4033 // investigate this in CR 7178365.
4034 //
4035 // Preserving the old comment here if that helps the investigation:
4036 //
4037 // The elapsed time induced by the start time below deliberately elides
4038 // the possible verification above.
4039 double sample_start_time_sec = os::elapsedTime();
4041 #if YOUNG_LIST_VERBOSE
4042 gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
4043 _young_list->print();
4044 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4045 #endif // YOUNG_LIST_VERBOSE
4047 g1_policy()->record_collection_pause_start(sample_start_time_sec);
4049 double scan_wait_start = os::elapsedTime();
4050 // We have to wait until the CM threads finish scanning the
4051 // root regions as it's the only way to ensure that all the
4052 // objects on them have been correctly scanned before we start
4053 // moving them during the GC.
4054 bool waited = _cm->root_regions()->wait_until_scan_finished();
4055 double wait_time_ms = 0.0;
4056 if (waited) {
4057 double scan_wait_end = os::elapsedTime();
4058 wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
4059 }
4060 g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
4062 #if YOUNG_LIST_VERBOSE
4063 gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
4064 _young_list->print();
4065 #endif // YOUNG_LIST_VERBOSE
4067 if (g1_policy()->during_initial_mark_pause()) {
4068 concurrent_mark()->checkpointRootsInitialPre();
4069 }
4071 #if YOUNG_LIST_VERBOSE
4072 gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
4073 _young_list->print();
4074 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4075 #endif // YOUNG_LIST_VERBOSE
4077 g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info);
4079 _cm->note_start_of_gc();
4080 // We should not verify the per-thread SATB buffers given that
4081 // we have not filtered them yet (we'll do so during the
4082 // GC). We also call this after finalize_cset() to
4083 // ensure that the CSet has been finalized.
4084 _cm->verify_no_cset_oops(true /* verify_stacks */,
4085 true /* verify_enqueued_buffers */,
4086 false /* verify_thread_buffers */,
4087 true /* verify_fingers */);
4089 if (_hr_printer.is_active()) {
4090 HeapRegion* hr = g1_policy()->collection_set();
4091 while (hr != NULL) {
4092 G1HRPrinter::RegionType type;
4093 if (!hr->is_young()) {
4094 type = G1HRPrinter::Old;
4095 } else if (hr->is_survivor()) {
4096 type = G1HRPrinter::Survivor;
4097 } else {
4098 type = G1HRPrinter::Eden;
4099 }
4100 _hr_printer.cset(hr);
4101 hr = hr->next_in_collection_set();
4102 }
4103 }
4105 #ifdef ASSERT
4106 VerifyCSetClosure cl;
4107 collection_set_iterate(&cl);
4108 #endif // ASSERT
4110 setup_surviving_young_words();
4112 // Initialize the GC alloc regions.
4113 init_gc_alloc_regions(evacuation_info);
4115 // Actually do the work...
4116 evacuate_collection_set(evacuation_info);
4118 // We do this to mainly verify the per-thread SATB buffers
4119 // (which have been filtered by now) since we didn't verify
4120 // them earlier. No point in re-checking the stacks / enqueued
4121 // buffers given that the CSet has not changed since last time
4122 // we checked.
4123 _cm->verify_no_cset_oops(false /* verify_stacks */,
4124 false /* verify_enqueued_buffers */,
4125 true /* verify_thread_buffers */,
4126 true /* verify_fingers */);
4128 free_collection_set(g1_policy()->collection_set(), evacuation_info);
4129 g1_policy()->clear_collection_set();
4131 cleanup_surviving_young_words();
4133 // Start a new incremental collection set for the next pause.
4134 g1_policy()->start_incremental_cset_building();
4136 clear_cset_fast_test();
4138 _young_list->reset_sampled_info();
4140 // Don't check the whole heap at this point as the
4141 // GC alloc regions from this pause have been tagged
4142 // as survivors and moved on to the survivor list.
4143 // Survivor regions will fail the !is_young() check.
4144 assert(check_young_list_empty(false /* check_heap */),
4145 "young list should be empty");
4147 #if YOUNG_LIST_VERBOSE
4148 gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
4149 _young_list->print();
4150 #endif // YOUNG_LIST_VERBOSE
4152 g1_policy()->record_survivor_regions(_young_list->survivor_length(),
4153 _young_list->first_survivor_region(),
4154 _young_list->last_survivor_region());
4156 _young_list->reset_auxilary_lists();
4158 if (evacuation_failed()) {
4159 _summary_bytes_used = recalculate_used();
4160 uint n_queues = MAX2((int)ParallelGCThreads, 1);
4161 for (uint i = 0; i < n_queues; i++) {
4162 if (_evacuation_failed_info_array[i].has_failed()) {
4163 _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
4164 }
4165 }
4166 } else {
4167 // The "used" of the the collection set have already been subtracted
4168 // when they were freed. Add in the bytes evacuated.
4169 _summary_bytes_used += g1_policy()->bytes_copied_during_gc();
4170 }
4172 if (g1_policy()->during_initial_mark_pause()) {
4173 // We have to do this before we notify the CM threads that
4174 // they can start working to make sure that all the
4175 // appropriate initialization is done on the CM object.
4176 concurrent_mark()->checkpointRootsInitialPost();
4177 set_marking_started();
4178 // Note that we don't actually trigger the CM thread at
4179 // this point. We do that later when we're sure that
4180 // the current thread has completed its logging output.
4181 }
4183 allocate_dummy_regions();
4185 #if YOUNG_LIST_VERBOSE
4186 gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
4187 _young_list->print();
4188 g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4189 #endif // YOUNG_LIST_VERBOSE
4191 init_mutator_alloc_region();
4193 {
4194 size_t expand_bytes = g1_policy()->expansion_amount();
4195 if (expand_bytes > 0) {
4196 size_t bytes_before = capacity();
4197 // No need for an ergo verbose message here,
4198 // expansion_amount() does this when it returns a value > 0.
4199 if (!expand(expand_bytes)) {
4200 // We failed to expand the heap so let's verify that
4201 // committed/uncommitted amount match the backing store
4202 assert(capacity() == _g1_storage.committed_size(), "committed size mismatch");
4203 assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch");
4204 }
4205 }
4206 }
4208 // We redo the verification but now wrt to the new CSet which
4209 // has just got initialized after the previous CSet was freed.
4210 _cm->verify_no_cset_oops(true /* verify_stacks */,
4211 true /* verify_enqueued_buffers */,
4212 true /* verify_thread_buffers */,
4213 true /* verify_fingers */);
4214 _cm->note_end_of_gc();
4216 // This timing is only used by the ergonomics to handle our pause target.
4217 // It is unclear why this should not include the full pause. We will
4218 // investigate this in CR 7178365.
4219 double sample_end_time_sec = os::elapsedTime();
4220 double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
4221 g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info);
4223 MemoryService::track_memory_usage();
4225 // In prepare_for_verify() below we'll need to scan the deferred
4226 // update buffers to bring the RSets up-to-date if
4227 // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
4228 // the update buffers we'll probably need to scan cards on the
4229 // regions we just allocated to (i.e., the GC alloc
4230 // regions). However, during the last GC we called
4231 // set_saved_mark() on all the GC alloc regions, so card
4232 // scanning might skip the [saved_mark_word()...top()] area of
4233 // those regions (i.e., the area we allocated objects into
4234 // during the last GC). But it shouldn't. Given that
4235 // saved_mark_word() is conditional on whether the GC time stamp
4236 // on the region is current or not, by incrementing the GC time
4237 // stamp here we invalidate all the GC time stamps on all the
4238 // regions and saved_mark_word() will simply return top() for
4239 // all the regions. This is a nicer way of ensuring this rather
4240 // than iterating over the regions and fixing them. In fact, the
4241 // GC time stamp increment here also ensures that
4242 // saved_mark_word() will return top() between pauses, i.e.,
4243 // during concurrent refinement. So we don't need the
4244 // is_gc_active() check to decided which top to use when
4245 // scanning cards (see CR 7039627).
4246 increment_gc_time_stamp();
4248 verify_after_gc();
4249 check_bitmaps("GC End");
4251 assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
4252 ref_processor_stw()->verify_no_references_recorded();
4254 // CM reference discovery will be re-enabled if necessary.
4255 }
4257 // We should do this after we potentially expand the heap so
4258 // that all the COMMIT events are generated before the end GC
4259 // event, and after we retire the GC alloc regions so that all
4260 // RETIRE events are generated before the end GC event.
4261 _hr_printer.end_gc(false /* full */, (size_t) total_collections());
4263 if (mark_in_progress()) {
4264 concurrent_mark()->update_g1_committed();
4265 }
4267 #ifdef TRACESPINNING
4268 ParallelTaskTerminator::print_termination_counts();
4269 #endif
4271 gc_epilogue(false);
4272 }
4274 // Print the remainder of the GC log output.
4275 log_gc_footer(os::elapsedTime() - pause_start_sec);
4277 // It is not yet to safe to tell the concurrent mark to
4278 // start as we have some optional output below. We don't want the
4279 // output from the concurrent mark thread interfering with this
4280 // logging output either.
4282 _hrs.verify_optional();
4283 verify_region_sets_optional();
4285 TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
4286 TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
4288 print_heap_after_gc();
4289 trace_heap_after_gc(_gc_tracer_stw);
4291 // We must call G1MonitoringSupport::update_sizes() in the same scoping level
4292 // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
4293 // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
4294 // before any GC notifications are raised.
4295 g1mm()->update_sizes();
4297 _gc_tracer_stw->report_evacuation_info(&evacuation_info);
4298 _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
4299 _gc_timer_stw->register_gc_end();
4300 _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
4301 }
4302 // It should now be safe to tell the concurrent mark thread to start
4303 // without its logging output interfering with the logging output
4304 // that came from the pause.
4306 if (should_start_conc_mark) {
4307 // CAUTION: after the doConcurrentMark() call below,
4308 // the concurrent marking thread(s) could be running
4309 // concurrently with us. Make sure that anything after
4310 // this point does not assume that we are the only GC thread
4311 // running. Note: of course, the actual marking work will
4312 // not start until the safepoint itself is released in
4313 // SuspendibleThreadSet::desynchronize().
4314 doConcurrentMark();
4315 }
4317 return true;
4318 }
4320 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
4321 {
4322 size_t gclab_word_size;
4323 switch (purpose) {
4324 case GCAllocForSurvived:
4325 gclab_word_size = _survivor_plab_stats.desired_plab_sz();
4326 break;
4327 case GCAllocForTenured:
4328 gclab_word_size = _old_plab_stats.desired_plab_sz();
4329 break;
4330 default:
4331 assert(false, "unknown GCAllocPurpose");
4332 gclab_word_size = _old_plab_stats.desired_plab_sz();
4333 break;
4334 }
4336 // Prevent humongous PLAB sizes for two reasons:
4337 // * PLABs are allocated using a similar paths as oops, but should
4338 // never be in a humongous region
4339 // * Allowing humongous PLABs needlessly churns the region free lists
4340 return MIN2(_humongous_object_threshold_in_words, gclab_word_size);
4341 }
4343 void G1CollectedHeap::init_mutator_alloc_region() {
4344 assert(_mutator_alloc_region.get() == NULL, "pre-condition");
4345 _mutator_alloc_region.init();
4346 }
4348 void G1CollectedHeap::release_mutator_alloc_region() {
4349 _mutator_alloc_region.release();
4350 assert(_mutator_alloc_region.get() == NULL, "post-condition");
4351 }
4353 void G1CollectedHeap::use_retained_old_gc_alloc_region(EvacuationInfo& evacuation_info) {
4354 HeapRegion* retained_region = _retained_old_gc_alloc_region;
4355 _retained_old_gc_alloc_region = NULL;
4357 // We will discard the current GC alloc region if:
4358 // a) it's in the collection set (it can happen!),
4359 // b) it's already full (no point in using it),
4360 // c) it's empty (this means that it was emptied during
4361 // a cleanup and it should be on the free list now), or
4362 // d) it's humongous (this means that it was emptied
4363 // during a cleanup and was added to the free list, but
4364 // has been subsequently used to allocate a humongous
4365 // object that may be less than the region size).
4366 if (retained_region != NULL &&
4367 !retained_region->in_collection_set() &&
4368 !(retained_region->top() == retained_region->end()) &&
4369 !retained_region->is_empty() &&
4370 !retained_region->isHumongous()) {
4371 retained_region->record_top_and_timestamp();
4372 // The retained region was added to the old region set when it was
4373 // retired. We have to remove it now, since we don't allow regions
4374 // we allocate to in the region sets. We'll re-add it later, when
4375 // it's retired again.
4376 _old_set.remove(retained_region);
4377 bool during_im = g1_policy()->during_initial_mark_pause();
4378 retained_region->note_start_of_copying(during_im);
4379 _old_gc_alloc_region.set(retained_region);
4380 _hr_printer.reuse(retained_region);
4381 evacuation_info.set_alloc_regions_used_before(retained_region->used());
4382 }
4383 }
4385 void G1CollectedHeap::init_gc_alloc_regions(EvacuationInfo& evacuation_info) {
4386 assert_at_safepoint(true /* should_be_vm_thread */);
4388 _survivor_gc_alloc_region.init();
4389 _old_gc_alloc_region.init();
4391 use_retained_old_gc_alloc_region(evacuation_info);
4392 }
4394 void G1CollectedHeap::release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info) {
4395 evacuation_info.set_allocation_regions(_survivor_gc_alloc_region.count() +
4396 _old_gc_alloc_region.count());
4397 _survivor_gc_alloc_region.release();
4398 // If we have an old GC alloc region to release, we'll save it in
4399 // _retained_old_gc_alloc_region. If we don't
4400 // _retained_old_gc_alloc_region will become NULL. This is what we
4401 // want either way so no reason to check explicitly for either
4402 // condition.
4403 _retained_old_gc_alloc_region = _old_gc_alloc_region.release();
4405 if (ResizePLAB) {
4406 _survivor_plab_stats.adjust_desired_plab_sz(no_of_gc_workers);
4407 _old_plab_stats.adjust_desired_plab_sz(no_of_gc_workers);
4408 }
4409 }
4411 void G1CollectedHeap::abandon_gc_alloc_regions() {
4412 assert(_survivor_gc_alloc_region.get() == NULL, "pre-condition");
4413 assert(_old_gc_alloc_region.get() == NULL, "pre-condition");
4414 _retained_old_gc_alloc_region = NULL;
4415 }
4417 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4418 _drain_in_progress = false;
4419 set_evac_failure_closure(cl);
4420 _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4421 }
4423 void G1CollectedHeap::finalize_for_evac_failure() {
4424 assert(_evac_failure_scan_stack != NULL &&
4425 _evac_failure_scan_stack->length() == 0,
4426 "Postcondition");
4427 assert(!_drain_in_progress, "Postcondition");
4428 delete _evac_failure_scan_stack;
4429 _evac_failure_scan_stack = NULL;
4430 }
4432 void G1CollectedHeap::remove_self_forwarding_pointers() {
4433 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4435 double remove_self_forwards_start = os::elapsedTime();
4437 G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4439 if (G1CollectedHeap::use_parallel_gc_threads()) {
4440 set_par_threads();
4441 workers()->run_task(&rsfp_task);
4442 set_par_threads(0);
4443 } else {
4444 rsfp_task.work(0);
4445 }
4447 assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity");
4449 // Reset the claim values in the regions in the collection set.
4450 reset_cset_heap_region_claim_values();
4452 assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4454 // Now restore saved marks, if any.
4455 assert(_objs_with_preserved_marks.size() ==
4456 _preserved_marks_of_objs.size(), "Both or none.");
4457 while (!_objs_with_preserved_marks.is_empty()) {
4458 oop obj = _objs_with_preserved_marks.pop();
4459 markOop m = _preserved_marks_of_objs.pop();
4460 obj->set_mark(m);
4461 }
4462 _objs_with_preserved_marks.clear(true);
4463 _preserved_marks_of_objs.clear(true);
4465 g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
4466 }
4468 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4469 _evac_failure_scan_stack->push(obj);
4470 }
4472 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4473 assert(_evac_failure_scan_stack != NULL, "precondition");
4475 while (_evac_failure_scan_stack->length() > 0) {
4476 oop obj = _evac_failure_scan_stack->pop();
4477 _evac_failure_closure->set_region(heap_region_containing(obj));
4478 obj->oop_iterate_backwards(_evac_failure_closure);
4479 }
4480 }
4482 oop
4483 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state,
4484 oop old) {
4485 assert(obj_in_cs(old),
4486 err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4487 (HeapWord*) old));
4488 markOop m = old->mark();
4489 oop forward_ptr = old->forward_to_atomic(old);
4490 if (forward_ptr == NULL) {
4491 // Forward-to-self succeeded.
4492 assert(_par_scan_state != NULL, "par scan state");
4493 OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4494 uint queue_num = _par_scan_state->queue_num();
4496 _evacuation_failed = true;
4497 _evacuation_failed_info_array[queue_num].register_copy_failure(old->size());
4498 if (_evac_failure_closure != cl) {
4499 MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4500 assert(!_drain_in_progress,
4501 "Should only be true while someone holds the lock.");
4502 // Set the global evac-failure closure to the current thread's.
4503 assert(_evac_failure_closure == NULL, "Or locking has failed.");
4504 set_evac_failure_closure(cl);
4505 // Now do the common part.
4506 handle_evacuation_failure_common(old, m);
4507 // Reset to NULL.
4508 set_evac_failure_closure(NULL);
4509 } else {
4510 // The lock is already held, and this is recursive.
4511 assert(_drain_in_progress, "This should only be the recursive case.");
4512 handle_evacuation_failure_common(old, m);
4513 }
4514 return old;
4515 } else {
4516 // Forward-to-self failed. Either someone else managed to allocate
4517 // space for this object (old != forward_ptr) or they beat us in
4518 // self-forwarding it (old == forward_ptr).
4519 assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4520 err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4521 "should not be in the CSet",
4522 (HeapWord*) old, (HeapWord*) forward_ptr));
4523 return forward_ptr;
4524 }
4525 }
4527 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4528 preserve_mark_if_necessary(old, m);
4530 HeapRegion* r = heap_region_containing(old);
4531 if (!r->evacuation_failed()) {
4532 r->set_evacuation_failed(true);
4533 _hr_printer.evac_failure(r);
4534 }
4536 push_on_evac_failure_scan_stack(old);
4538 if (!_drain_in_progress) {
4539 // prevent recursion in copy_to_survivor_space()
4540 _drain_in_progress = true;
4541 drain_evac_failure_scan_stack();
4542 _drain_in_progress = false;
4543 }
4544 }
4546 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4547 assert(evacuation_failed(), "Oversaving!");
4548 // We want to call the "for_promotion_failure" version only in the
4549 // case of a promotion failure.
4550 if (m->must_be_preserved_for_promotion_failure(obj)) {
4551 _objs_with_preserved_marks.push(obj);
4552 _preserved_marks_of_objs.push(m);
4553 }
4554 }
4556 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
4557 size_t word_size) {
4558 if (purpose == GCAllocForSurvived) {
4559 HeapWord* result = survivor_attempt_allocation(word_size);
4560 if (result != NULL) {
4561 return result;
4562 } else {
4563 // Let's try to allocate in the old gen in case we can fit the
4564 // object there.
4565 return old_attempt_allocation(word_size);
4566 }
4567 } else {
4568 assert(purpose == GCAllocForTenured, "sanity");
4569 HeapWord* result = old_attempt_allocation(word_size);
4570 if (result != NULL) {
4571 return result;
4572 } else {
4573 // Let's try to allocate in the survivors in case we can fit the
4574 // object there.
4575 return survivor_attempt_allocation(word_size);
4576 }
4577 }
4579 ShouldNotReachHere();
4580 // Trying to keep some compilers happy.
4581 return NULL;
4582 }
4584 G1ParGCAllocBuffer::G1ParGCAllocBuffer(size_t gclab_word_size) :
4585 ParGCAllocBuffer(gclab_word_size), _retired(true) { }
4587 void G1ParCopyHelper::mark_object(oop obj) {
4588 #ifdef ASSERT
4589 HeapRegion* hr = _g1->heap_region_containing(obj);
4590 assert(hr != NULL, "sanity");
4591 assert(!hr->in_collection_set(), "should not mark objects in the CSet");
4592 #endif // ASSERT
4594 // We know that the object is not moving so it's safe to read its size.
4595 _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4596 }
4598 void G1ParCopyHelper::mark_forwarded_object(oop from_obj, oop to_obj) {
4599 #ifdef ASSERT
4600 assert(from_obj->is_forwarded(), "from obj should be forwarded");
4601 assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4602 assert(from_obj != to_obj, "should not be self-forwarded");
4604 HeapRegion* from_hr = _g1->heap_region_containing(from_obj);
4605 assert(from_hr != NULL, "sanity");
4606 assert(from_hr->in_collection_set(), "from obj should be in the CSet");
4608 HeapRegion* to_hr = _g1->heap_region_containing(to_obj);
4609 assert(to_hr != NULL, "sanity");
4610 assert(!to_hr->in_collection_set(), "should not mark objects in the CSet");
4611 #endif // ASSERT
4613 // The object might be in the process of being copied by another
4614 // worker so we cannot trust that its to-space image is
4615 // well-formed. So we have to read its size from its from-space
4616 // image which we know should not be changing.
4617 _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4618 }
4620 template <class T>
4621 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) {
4622 if (_g1->heap_region_containing_raw(new_obj)->is_young()) {
4623 _scanned_klass->record_modified_oops();
4624 }
4625 }
4627 template <G1Barrier barrier, G1Mark do_mark_object>
4628 template <class T>
4629 void G1ParCopyClosure<barrier, do_mark_object>::do_oop_work(T* p) {
4630 T heap_oop = oopDesc::load_heap_oop(p);
4632 if (oopDesc::is_null(heap_oop)) {
4633 return;
4634 }
4636 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
4638 assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4640 if (_g1->in_cset_fast_test(obj)) {
4641 oop forwardee;
4642 if (obj->is_forwarded()) {
4643 forwardee = obj->forwardee();
4644 } else {
4645 forwardee = _par_scan_state->copy_to_survivor_space(obj);
4646 }
4647 assert(forwardee != NULL, "forwardee should not be NULL");
4648 oopDesc::encode_store_heap_oop(p, forwardee);
4649 if (do_mark_object != G1MarkNone && forwardee != obj) {
4650 // If the object is self-forwarded we don't need to explicitly
4651 // mark it, the evacuation failure protocol will do so.
4652 mark_forwarded_object(obj, forwardee);
4653 }
4655 if (barrier == G1BarrierKlass) {
4656 do_klass_barrier(p, forwardee);
4657 }
4658 } else {
4659 // The object is not in collection set. If we're a root scanning
4660 // closure during an initial mark pause then attempt to mark the object.
4661 if (do_mark_object == G1MarkFromRoot) {
4662 mark_object(obj);
4663 }
4664 }
4666 if (barrier == G1BarrierEvac) {
4667 _par_scan_state->update_rs(_from, p, _worker_id);
4668 }
4669 }
4671 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(oop* p);
4672 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(narrowOop* p);
4674 class G1ParEvacuateFollowersClosure : public VoidClosure {
4675 protected:
4676 G1CollectedHeap* _g1h;
4677 G1ParScanThreadState* _par_scan_state;
4678 RefToScanQueueSet* _queues;
4679 ParallelTaskTerminator* _terminator;
4681 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
4682 RefToScanQueueSet* queues() { return _queues; }
4683 ParallelTaskTerminator* terminator() { return _terminator; }
4685 public:
4686 G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4687 G1ParScanThreadState* par_scan_state,
4688 RefToScanQueueSet* queues,
4689 ParallelTaskTerminator* terminator)
4690 : _g1h(g1h), _par_scan_state(par_scan_state),
4691 _queues(queues), _terminator(terminator) {}
4693 void do_void();
4695 private:
4696 inline bool offer_termination();
4697 };
4699 bool G1ParEvacuateFollowersClosure::offer_termination() {
4700 G1ParScanThreadState* const pss = par_scan_state();
4701 pss->start_term_time();
4702 const bool res = terminator()->offer_termination();
4703 pss->end_term_time();
4704 return res;
4705 }
4707 void G1ParEvacuateFollowersClosure::do_void() {
4708 G1ParScanThreadState* const pss = par_scan_state();
4709 pss->trim_queue();
4710 do {
4711 pss->steal_and_trim_queue(queues());
4712 } while (!offer_termination());
4713 }
4715 class G1KlassScanClosure : public KlassClosure {
4716 G1ParCopyHelper* _closure;
4717 bool _process_only_dirty;
4718 int _count;
4719 public:
4720 G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty)
4721 : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {}
4722 void do_klass(Klass* klass) {
4723 // If the klass has not been dirtied we know that there's
4724 // no references into the young gen and we can skip it.
4725 if (!_process_only_dirty || klass->has_modified_oops()) {
4726 // Clean the klass since we're going to scavenge all the metadata.
4727 klass->clear_modified_oops();
4729 // Tell the closure that this klass is the Klass to scavenge
4730 // and is the one to dirty if oops are left pointing into the young gen.
4731 _closure->set_scanned_klass(klass);
4733 klass->oops_do(_closure);
4735 _closure->set_scanned_klass(NULL);
4736 }
4737 _count++;
4738 }
4739 };
4741 class G1ParTask : public AbstractGangTask {
4742 protected:
4743 G1CollectedHeap* _g1h;
4744 RefToScanQueueSet *_queues;
4745 ParallelTaskTerminator _terminator;
4746 uint _n_workers;
4748 Mutex _stats_lock;
4749 Mutex* stats_lock() { return &_stats_lock; }
4751 size_t getNCards() {
4752 return (_g1h->capacity() + G1BlockOffsetSharedArray::N_bytes - 1)
4753 / G1BlockOffsetSharedArray::N_bytes;
4754 }
4756 public:
4757 G1ParTask(G1CollectedHeap* g1h, RefToScanQueueSet *task_queues)
4758 : AbstractGangTask("G1 collection"),
4759 _g1h(g1h),
4760 _queues(task_queues),
4761 _terminator(0, _queues),
4762 _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4763 {}
4765 RefToScanQueueSet* queues() { return _queues; }
4767 RefToScanQueue *work_queue(int i) {
4768 return queues()->queue(i);
4769 }
4771 ParallelTaskTerminator* terminator() { return &_terminator; }
4773 virtual void set_for_termination(int active_workers) {
4774 // This task calls set_n_termination() in par_non_clean_card_iterate_work()
4775 // in the young space (_par_seq_tasks) in the G1 heap
4776 // for SequentialSubTasksDone.
4777 // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap
4778 // both of which need setting by set_n_termination().
4779 _g1h->SharedHeap::set_n_termination(active_workers);
4780 _g1h->set_n_termination(active_workers);
4781 terminator()->reset_for_reuse(active_workers);
4782 _n_workers = active_workers;
4783 }
4785 // Helps out with CLD processing.
4786 //
4787 // During InitialMark we need to:
4788 // 1) Scavenge all CLDs for the young GC.
4789 // 2) Mark all objects directly reachable from strong CLDs.
4790 template <G1Mark do_mark_object>
4791 class G1CLDClosure : public CLDClosure {
4792 G1ParCopyClosure<G1BarrierNone, do_mark_object>* _oop_closure;
4793 G1ParCopyClosure<G1BarrierKlass, do_mark_object> _oop_in_klass_closure;
4794 G1KlassScanClosure _klass_in_cld_closure;
4795 bool _claim;
4797 public:
4798 G1CLDClosure(G1ParCopyClosure<G1BarrierNone, do_mark_object>* oop_closure,
4799 bool only_young, bool claim)
4800 : _oop_closure(oop_closure),
4801 _oop_in_klass_closure(oop_closure->g1(),
4802 oop_closure->pss(),
4803 oop_closure->rp()),
4804 _klass_in_cld_closure(&_oop_in_klass_closure, only_young),
4805 _claim(claim) {
4807 }
4809 void do_cld(ClassLoaderData* cld) {
4810 cld->oops_do(_oop_closure, &_klass_in_cld_closure, _claim);
4811 }
4812 };
4814 class G1CodeBlobClosure: public CodeBlobClosure {
4815 OopClosure* _f;
4817 public:
4818 G1CodeBlobClosure(OopClosure* f) : _f(f) {}
4819 void do_code_blob(CodeBlob* blob) {
4820 nmethod* that = blob->as_nmethod_or_null();
4821 if (that != NULL) {
4822 if (!that->test_set_oops_do_mark()) {
4823 that->oops_do(_f);
4824 that->fix_oop_relocations();
4825 }
4826 }
4827 }
4828 };
4830 void work(uint worker_id) {
4831 if (worker_id >= _n_workers) return; // no work needed this round
4833 double start_time_ms = os::elapsedTime() * 1000.0;
4834 _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms);
4836 {
4837 ResourceMark rm;
4838 HandleMark hm;
4840 ReferenceProcessor* rp = _g1h->ref_processor_stw();
4842 G1ParScanThreadState pss(_g1h, worker_id, rp);
4843 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
4845 pss.set_evac_failure_closure(&evac_failure_cl);
4847 bool only_young = _g1h->g1_policy()->gcs_are_young();
4849 // Non-IM young GC.
4850 G1ParCopyClosure<G1BarrierNone, G1MarkNone> scan_only_root_cl(_g1h, &pss, rp);
4851 G1CLDClosure<G1MarkNone> scan_only_cld_cl(&scan_only_root_cl,
4852 only_young, // Only process dirty klasses.
4853 false); // No need to claim CLDs.
4854 // IM young GC.
4855 // Strong roots closures.
4856 G1ParCopyClosure<G1BarrierNone, G1MarkFromRoot> scan_mark_root_cl(_g1h, &pss, rp);
4857 G1CLDClosure<G1MarkFromRoot> scan_mark_cld_cl(&scan_mark_root_cl,
4858 false, // Process all klasses.
4859 true); // Need to claim CLDs.
4860 // Weak roots closures.
4861 G1ParCopyClosure<G1BarrierNone, G1MarkPromotedFromRoot> scan_mark_weak_root_cl(_g1h, &pss, rp);
4862 G1CLDClosure<G1MarkPromotedFromRoot> scan_mark_weak_cld_cl(&scan_mark_weak_root_cl,
4863 false, // Process all klasses.
4864 true); // Need to claim CLDs.
4866 G1CodeBlobClosure scan_only_code_cl(&scan_only_root_cl);
4867 G1CodeBlobClosure scan_mark_code_cl(&scan_mark_root_cl);
4868 // IM Weak code roots are handled later.
4870 OopClosure* strong_root_cl;
4871 OopClosure* weak_root_cl;
4872 CLDClosure* strong_cld_cl;
4873 CLDClosure* weak_cld_cl;
4874 CodeBlobClosure* strong_code_cl;
4876 if (_g1h->g1_policy()->during_initial_mark_pause()) {
4877 // We also need to mark copied objects.
4878 strong_root_cl = &scan_mark_root_cl;
4879 strong_cld_cl = &scan_mark_cld_cl;
4880 strong_code_cl = &scan_mark_code_cl;
4881 if (ClassUnloadingWithConcurrentMark) {
4882 weak_root_cl = &scan_mark_weak_root_cl;
4883 weak_cld_cl = &scan_mark_weak_cld_cl;
4884 } else {
4885 weak_root_cl = &scan_mark_root_cl;
4886 weak_cld_cl = &scan_mark_cld_cl;
4887 }
4888 } else {
4889 strong_root_cl = &scan_only_root_cl;
4890 weak_root_cl = &scan_only_root_cl;
4891 strong_cld_cl = &scan_only_cld_cl;
4892 weak_cld_cl = &scan_only_cld_cl;
4893 strong_code_cl = &scan_only_code_cl;
4894 }
4897 G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss);
4899 pss.start_strong_roots();
4900 _g1h->g1_process_roots(strong_root_cl,
4901 weak_root_cl,
4902 &push_heap_rs_cl,
4903 strong_cld_cl,
4904 weak_cld_cl,
4905 strong_code_cl,
4906 worker_id);
4908 pss.end_strong_roots();
4910 {
4911 double start = os::elapsedTime();
4912 G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4913 evac.do_void();
4914 double elapsed_ms = (os::elapsedTime()-start)*1000.0;
4915 double term_ms = pss.term_time()*1000.0;
4916 _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms);
4917 _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts());
4918 }
4919 _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4920 _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4922 if (ParallelGCVerbose) {
4923 MutexLocker x(stats_lock());
4924 pss.print_termination_stats(worker_id);
4925 }
4927 assert(pss.queue_is_empty(), "should be empty");
4929 // Close the inner scope so that the ResourceMark and HandleMark
4930 // destructors are executed here and are included as part of the
4931 // "GC Worker Time".
4932 }
4934 double end_time_ms = os::elapsedTime() * 1000.0;
4935 _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms);
4936 }
4937 };
4939 // *** Common G1 Evacuation Stuff
4941 // This method is run in a GC worker.
4943 void
4944 G1CollectedHeap::
4945 g1_process_roots(OopClosure* scan_non_heap_roots,
4946 OopClosure* scan_non_heap_weak_roots,
4947 OopsInHeapRegionClosure* scan_rs,
4948 CLDClosure* scan_strong_clds,
4949 CLDClosure* scan_weak_clds,
4950 CodeBlobClosure* scan_strong_code,
4951 uint worker_i) {
4953 // First scan the shared roots.
4954 double ext_roots_start = os::elapsedTime();
4955 double closure_app_time_sec = 0.0;
4957 bool during_im = _g1h->g1_policy()->during_initial_mark_pause();
4958 bool trace_metadata = during_im && ClassUnloadingWithConcurrentMark;
4960 BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
4961 BufferingOopClosure buf_scan_non_heap_weak_roots(scan_non_heap_weak_roots);
4963 process_roots(false, // no scoping; this is parallel code
4964 SharedHeap::SO_None,
4965 &buf_scan_non_heap_roots,
4966 &buf_scan_non_heap_weak_roots,
4967 scan_strong_clds,
4968 // Unloading Initial Marks handle the weak CLDs separately.
4969 (trace_metadata ? NULL : scan_weak_clds),
4970 scan_strong_code);
4972 // Now the CM ref_processor roots.
4973 if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
4974 // We need to treat the discovered reference lists of the
4975 // concurrent mark ref processor as roots and keep entries
4976 // (which are added by the marking threads) on them live
4977 // until they can be processed at the end of marking.
4978 ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
4979 }
4981 if (trace_metadata) {
4982 // Barrier to make sure all workers passed
4983 // the strong CLD and strong nmethods phases.
4984 active_strong_roots_scope()->wait_until_all_workers_done_with_threads(n_par_threads());
4986 // Now take the complement of the strong CLDs.
4987 ClassLoaderDataGraph::roots_cld_do(NULL, scan_weak_clds);
4988 }
4990 // Finish up any enqueued closure apps (attributed as object copy time).
4991 buf_scan_non_heap_roots.done();
4992 buf_scan_non_heap_weak_roots.done();
4994 double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds()
4995 + buf_scan_non_heap_weak_roots.closure_app_seconds();
4997 g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
4999 double ext_root_time_ms =
5000 ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0;
5002 g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
5004 // During conc marking we have to filter the per-thread SATB buffers
5005 // to make sure we remove any oops into the CSet (which will show up
5006 // as implicitly live).
5007 double satb_filtering_ms = 0.0;
5008 if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) {
5009 if (mark_in_progress()) {
5010 double satb_filter_start = os::elapsedTime();
5012 JavaThread::satb_mark_queue_set().filter_thread_buffers();
5014 satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0;
5015 }
5016 }
5017 g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms);
5019 // Now scan the complement of the collection set.
5020 MarkingCodeBlobClosure scavenge_cs_nmethods(scan_non_heap_weak_roots, CodeBlobToOopClosure::FixRelocations);
5022 g1_rem_set()->oops_into_collection_set_do(scan_rs, &scavenge_cs_nmethods, worker_i);
5024 _process_strong_tasks->all_tasks_completed();
5025 }
5027 class G1StringSymbolTableUnlinkTask : public AbstractGangTask {
5028 private:
5029 BoolObjectClosure* _is_alive;
5030 int _initial_string_table_size;
5031 int _initial_symbol_table_size;
5033 bool _process_strings;
5034 int _strings_processed;
5035 int _strings_removed;
5037 bool _process_symbols;
5038 int _symbols_processed;
5039 int _symbols_removed;
5041 bool _do_in_parallel;
5042 public:
5043 G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) :
5044 AbstractGangTask("String/Symbol Unlinking"),
5045 _is_alive(is_alive),
5046 _do_in_parallel(G1CollectedHeap::use_parallel_gc_threads()),
5047 _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
5048 _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) {
5050 _initial_string_table_size = StringTable::the_table()->table_size();
5051 _initial_symbol_table_size = SymbolTable::the_table()->table_size();
5052 if (process_strings) {
5053 StringTable::clear_parallel_claimed_index();
5054 }
5055 if (process_symbols) {
5056 SymbolTable::clear_parallel_claimed_index();
5057 }
5058 }
5060 ~G1StringSymbolTableUnlinkTask() {
5061 guarantee(!_process_strings || !_do_in_parallel || StringTable::parallel_claimed_index() >= _initial_string_table_size,
5062 err_msg("claim value "INT32_FORMAT" after unlink less than initial string table size "INT32_FORMAT,
5063 StringTable::parallel_claimed_index(), _initial_string_table_size));
5064 guarantee(!_process_symbols || !_do_in_parallel || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
5065 err_msg("claim value "INT32_FORMAT" after unlink less than initial symbol table size "INT32_FORMAT,
5066 SymbolTable::parallel_claimed_index(), _initial_symbol_table_size));
5068 if (G1TraceStringSymbolTableScrubbing) {
5069 gclog_or_tty->print_cr("Cleaned string and symbol table, "
5070 "strings: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed, "
5071 "symbols: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed",
5072 strings_processed(), strings_removed(),
5073 symbols_processed(), symbols_removed());
5074 }
5075 }
5077 void work(uint worker_id) {
5078 if (_do_in_parallel) {
5079 int strings_processed = 0;
5080 int strings_removed = 0;
5081 int symbols_processed = 0;
5082 int symbols_removed = 0;
5083 if (_process_strings) {
5084 StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
5085 Atomic::add(strings_processed, &_strings_processed);
5086 Atomic::add(strings_removed, &_strings_removed);
5087 }
5088 if (_process_symbols) {
5089 SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
5090 Atomic::add(symbols_processed, &_symbols_processed);
5091 Atomic::add(symbols_removed, &_symbols_removed);
5092 }
5093 } else {
5094 if (_process_strings) {
5095 StringTable::unlink(_is_alive, &_strings_processed, &_strings_removed);
5096 }
5097 if (_process_symbols) {
5098 SymbolTable::unlink(&_symbols_processed, &_symbols_removed);
5099 }
5100 }
5101 }
5103 size_t strings_processed() const { return (size_t)_strings_processed; }
5104 size_t strings_removed() const { return (size_t)_strings_removed; }
5106 size_t symbols_processed() const { return (size_t)_symbols_processed; }
5107 size_t symbols_removed() const { return (size_t)_symbols_removed; }
5108 };
5110 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
5111 private:
5112 static Monitor* _lock;
5114 BoolObjectClosure* const _is_alive;
5115 const bool _unloading_occurred;
5116 const uint _num_workers;
5118 // Variables used to claim nmethods.
5119 nmethod* _first_nmethod;
5120 volatile nmethod* _claimed_nmethod;
5122 // The list of nmethods that need to be processed by the second pass.
5123 volatile nmethod* _postponed_list;
5124 volatile uint _num_entered_barrier;
5126 public:
5127 G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
5128 _is_alive(is_alive),
5129 _unloading_occurred(unloading_occurred),
5130 _num_workers(num_workers),
5131 _first_nmethod(NULL),
5132 _claimed_nmethod(NULL),
5133 _postponed_list(NULL),
5134 _num_entered_barrier(0)
5135 {
5136 nmethod::increase_unloading_clock();
5137 _first_nmethod = CodeCache::alive_nmethod(CodeCache::first());
5138 _claimed_nmethod = (volatile nmethod*)_first_nmethod;
5139 }
5141 ~G1CodeCacheUnloadingTask() {
5142 CodeCache::verify_clean_inline_caches();
5144 CodeCache::set_needs_cache_clean(false);
5145 guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
5147 CodeCache::verify_icholder_relocations();
5148 }
5150 private:
5151 void add_to_postponed_list(nmethod* nm) {
5152 nmethod* old;
5153 do {
5154 old = (nmethod*)_postponed_list;
5155 nm->set_unloading_next(old);
5156 } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old);
5157 }
5159 void clean_nmethod(nmethod* nm) {
5160 bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
5162 if (postponed) {
5163 // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
5164 add_to_postponed_list(nm);
5165 }
5167 // Mark that this thread has been cleaned/unloaded.
5168 // After this call, it will be safe to ask if this nmethod was unloaded or not.
5169 nm->set_unloading_clock(nmethod::global_unloading_clock());
5170 }
5172 void clean_nmethod_postponed(nmethod* nm) {
5173 nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
5174 }
5176 static const int MaxClaimNmethods = 16;
5178 void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) {
5179 nmethod* first;
5180 nmethod* last;
5182 do {
5183 *num_claimed_nmethods = 0;
5185 first = last = (nmethod*)_claimed_nmethod;
5187 if (first != NULL) {
5188 for (int i = 0; i < MaxClaimNmethods; i++) {
5189 last = CodeCache::alive_nmethod(CodeCache::next(last));
5191 if (last == NULL) {
5192 break;
5193 }
5195 claimed_nmethods[i] = last;
5196 (*num_claimed_nmethods)++;
5197 }
5198 }
5200 } while ((nmethod*)Atomic::cmpxchg_ptr(last, &_claimed_nmethod, first) != first);
5201 }
5203 nmethod* claim_postponed_nmethod() {
5204 nmethod* claim;
5205 nmethod* next;
5207 do {
5208 claim = (nmethod*)_postponed_list;
5209 if (claim == NULL) {
5210 return NULL;
5211 }
5213 next = claim->unloading_next();
5215 } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim);
5217 return claim;
5218 }
5220 public:
5221 // Mark that we're done with the first pass of nmethod cleaning.
5222 void barrier_mark(uint worker_id) {
5223 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
5224 _num_entered_barrier++;
5225 if (_num_entered_barrier == _num_workers) {
5226 ml.notify_all();
5227 }
5228 }
5230 // See if we have to wait for the other workers to
5231 // finish their first-pass nmethod cleaning work.
5232 void barrier_wait(uint worker_id) {
5233 if (_num_entered_barrier < _num_workers) {
5234 MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
5235 while (_num_entered_barrier < _num_workers) {
5236 ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
5237 }
5238 }
5239 }
5241 // Cleaning and unloading of nmethods. Some work has to be postponed
5242 // to the second pass, when we know which nmethods survive.
5243 void work_first_pass(uint worker_id) {
5244 // The first nmethods is claimed by the first worker.
5245 if (worker_id == 0 && _first_nmethod != NULL) {
5246 clean_nmethod(_first_nmethod);
5247 _first_nmethod = NULL;
5248 }
5250 int num_claimed_nmethods;
5251 nmethod* claimed_nmethods[MaxClaimNmethods];
5253 while (true) {
5254 claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
5256 if (num_claimed_nmethods == 0) {
5257 break;
5258 }
5260 for (int i = 0; i < num_claimed_nmethods; i++) {
5261 clean_nmethod(claimed_nmethods[i]);
5262 }
5263 }
5264 }
5266 void work_second_pass(uint worker_id) {
5267 nmethod* nm;
5268 // Take care of postponed nmethods.
5269 while ((nm = claim_postponed_nmethod()) != NULL) {
5270 clean_nmethod_postponed(nm);
5271 }
5272 }
5273 };
5275 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock");
5277 class G1KlassCleaningTask : public StackObj {
5278 BoolObjectClosure* _is_alive;
5279 volatile jint _clean_klass_tree_claimed;
5280 ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
5282 public:
5283 G1KlassCleaningTask(BoolObjectClosure* is_alive) :
5284 _is_alive(is_alive),
5285 _clean_klass_tree_claimed(0),
5286 _klass_iterator() {
5287 }
5289 private:
5290 bool claim_clean_klass_tree_task() {
5291 if (_clean_klass_tree_claimed) {
5292 return false;
5293 }
5295 return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0;
5296 }
5298 InstanceKlass* claim_next_klass() {
5299 Klass* klass;
5300 do {
5301 klass =_klass_iterator.next_klass();
5302 } while (klass != NULL && !klass->oop_is_instance());
5304 return (InstanceKlass*)klass;
5305 }
5307 public:
5309 void clean_klass(InstanceKlass* ik) {
5310 ik->clean_implementors_list(_is_alive);
5311 ik->clean_method_data(_is_alive);
5313 // G1 specific cleanup work that has
5314 // been moved here to be done in parallel.
5315 ik->clean_dependent_nmethods();
5316 }
5318 void work() {
5319 ResourceMark rm;
5321 // One worker will clean the subklass/sibling klass tree.
5322 if (claim_clean_klass_tree_task()) {
5323 Klass::clean_subklass_tree(_is_alive);
5324 }
5326 // All workers will help cleaning the classes,
5327 InstanceKlass* klass;
5328 while ((klass = claim_next_klass()) != NULL) {
5329 clean_klass(klass);
5330 }
5331 }
5332 };
5334 // To minimize the remark pause times, the tasks below are done in parallel.
5335 class G1ParallelCleaningTask : public AbstractGangTask {
5336 private:
5337 G1StringSymbolTableUnlinkTask _string_symbol_task;
5338 G1CodeCacheUnloadingTask _code_cache_task;
5339 G1KlassCleaningTask _klass_cleaning_task;
5341 public:
5342 // The constructor is run in the VMThread.
5343 G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) :
5344 AbstractGangTask("Parallel Cleaning"),
5345 _string_symbol_task(is_alive, process_strings, process_symbols),
5346 _code_cache_task(num_workers, is_alive, unloading_occurred),
5347 _klass_cleaning_task(is_alive) {
5348 }
5350 // The parallel work done by all worker threads.
5351 void work(uint worker_id) {
5352 // Do first pass of code cache cleaning.
5353 _code_cache_task.work_first_pass(worker_id);
5355 // Let the threads mark that the first pass is done.
5356 _code_cache_task.barrier_mark(worker_id);
5358 // Clean the Strings and Symbols.
5359 _string_symbol_task.work(worker_id);
5361 // Wait for all workers to finish the first code cache cleaning pass.
5362 _code_cache_task.barrier_wait(worker_id);
5364 // Do the second code cache cleaning work, which realize on
5365 // the liveness information gathered during the first pass.
5366 _code_cache_task.work_second_pass(worker_id);
5368 // Clean all klasses that were not unloaded.
5369 _klass_cleaning_task.work();
5370 }
5371 };
5374 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive,
5375 bool process_strings,
5376 bool process_symbols,
5377 bool class_unloading_occurred) {
5378 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5379 workers()->active_workers() : 1);
5381 G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols,
5382 n_workers, class_unloading_occurred);
5383 if (G1CollectedHeap::use_parallel_gc_threads()) {
5384 set_par_threads(n_workers);
5385 workers()->run_task(&g1_unlink_task);
5386 set_par_threads(0);
5387 } else {
5388 g1_unlink_task.work(0);
5389 }
5390 }
5392 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive,
5393 bool process_strings, bool process_symbols) {
5394 {
5395 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5396 _g1h->workers()->active_workers() : 1);
5397 G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols);
5398 if (G1CollectedHeap::use_parallel_gc_threads()) {
5399 set_par_threads(n_workers);
5400 workers()->run_task(&g1_unlink_task);
5401 set_par_threads(0);
5402 } else {
5403 g1_unlink_task.work(0);
5404 }
5405 }
5407 if (G1StringDedup::is_enabled()) {
5408 G1StringDedup::unlink(is_alive);
5409 }
5410 }
5412 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
5413 private:
5414 DirtyCardQueueSet* _queue;
5415 public:
5416 G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue) : AbstractGangTask("Redirty Cards"), _queue(queue) { }
5418 virtual void work(uint worker_id) {
5419 double start_time = os::elapsedTime();
5421 RedirtyLoggedCardTableEntryClosure cl;
5422 if (G1CollectedHeap::heap()->use_parallel_gc_threads()) {
5423 _queue->par_apply_closure_to_all_completed_buffers(&cl);
5424 } else {
5425 _queue->apply_closure_to_all_completed_buffers(&cl);
5426 }
5428 G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
5429 timer->record_redirty_logged_cards_time_ms(worker_id, (os::elapsedTime() - start_time) * 1000.0);
5430 timer->record_redirty_logged_cards_processed_cards(worker_id, cl.num_processed());
5431 }
5432 };
5434 void G1CollectedHeap::redirty_logged_cards() {
5435 guarantee(G1DeferredRSUpdate, "Must only be called when using deferred RS updates.");
5436 double redirty_logged_cards_start = os::elapsedTime();
5438 uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5439 _g1h->workers()->active_workers() : 1);
5441 G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set());
5442 dirty_card_queue_set().reset_for_par_iteration();
5443 if (use_parallel_gc_threads()) {
5444 set_par_threads(n_workers);
5445 workers()->run_task(&redirty_task);
5446 set_par_threads(0);
5447 } else {
5448 redirty_task.work(0);
5449 }
5451 DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5452 dcq.merge_bufferlists(&dirty_card_queue_set());
5453 assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5455 g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
5456 }
5458 // Weak Reference Processing support
5460 // An always "is_alive" closure that is used to preserve referents.
5461 // If the object is non-null then it's alive. Used in the preservation
5462 // of referent objects that are pointed to by reference objects
5463 // discovered by the CM ref processor.
5464 class G1AlwaysAliveClosure: public BoolObjectClosure {
5465 G1CollectedHeap* _g1;
5466 public:
5467 G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5468 bool do_object_b(oop p) {
5469 if (p != NULL) {
5470 return true;
5471 }
5472 return false;
5473 }
5474 };
5476 bool G1STWIsAliveClosure::do_object_b(oop p) {
5477 // An object is reachable if it is outside the collection set,
5478 // or is inside and copied.
5479 return !_g1->obj_in_cs(p) || p->is_forwarded();
5480 }
5482 // Non Copying Keep Alive closure
5483 class G1KeepAliveClosure: public OopClosure {
5484 G1CollectedHeap* _g1;
5485 public:
5486 G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5487 void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
5488 void do_oop( oop* p) {
5489 oop obj = *p;
5491 if (_g1->obj_in_cs(obj)) {
5492 assert( obj->is_forwarded(), "invariant" );
5493 *p = obj->forwardee();
5494 }
5495 }
5496 };
5498 // Copying Keep Alive closure - can be called from both
5499 // serial and parallel code as long as different worker
5500 // threads utilize different G1ParScanThreadState instances
5501 // and different queues.
5503 class G1CopyingKeepAliveClosure: public OopClosure {
5504 G1CollectedHeap* _g1h;
5505 OopClosure* _copy_non_heap_obj_cl;
5506 G1ParScanThreadState* _par_scan_state;
5508 public:
5509 G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
5510 OopClosure* non_heap_obj_cl,
5511 G1ParScanThreadState* pss):
5512 _g1h(g1h),
5513 _copy_non_heap_obj_cl(non_heap_obj_cl),
5514 _par_scan_state(pss)
5515 {}
5517 virtual void do_oop(narrowOop* p) { do_oop_work(p); }
5518 virtual void do_oop( oop* p) { do_oop_work(p); }
5520 template <class T> void do_oop_work(T* p) {
5521 oop obj = oopDesc::load_decode_heap_oop(p);
5523 if (_g1h->obj_in_cs(obj)) {
5524 // If the referent object has been forwarded (either copied
5525 // to a new location or to itself in the event of an
5526 // evacuation failure) then we need to update the reference
5527 // field and, if both reference and referent are in the G1
5528 // heap, update the RSet for the referent.
5529 //
5530 // If the referent has not been forwarded then we have to keep
5531 // it alive by policy. Therefore we have copy the referent.
5532 //
5533 // If the reference field is in the G1 heap then we can push
5534 // on the PSS queue. When the queue is drained (after each
5535 // phase of reference processing) the object and it's followers
5536 // will be copied, the reference field set to point to the
5537 // new location, and the RSet updated. Otherwise we need to
5538 // use the the non-heap or metadata closures directly to copy
5539 // the referent object and update the pointer, while avoiding
5540 // updating the RSet.
5542 if (_g1h->is_in_g1_reserved(p)) {
5543 _par_scan_state->push_on_queue(p);
5544 } else {
5545 assert(!Metaspace::contains((const void*)p),
5546 err_msg("Unexpectedly found a pointer from metadata: "
5547 PTR_FORMAT, p));
5548 _copy_non_heap_obj_cl->do_oop(p);
5549 }
5550 }
5551 }
5552 };
5554 // Serial drain queue closure. Called as the 'complete_gc'
5555 // closure for each discovered list in some of the
5556 // reference processing phases.
5558 class G1STWDrainQueueClosure: public VoidClosure {
5559 protected:
5560 G1CollectedHeap* _g1h;
5561 G1ParScanThreadState* _par_scan_state;
5563 G1ParScanThreadState* par_scan_state() { return _par_scan_state; }
5565 public:
5566 G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
5567 _g1h(g1h),
5568 _par_scan_state(pss)
5569 { }
5571 void do_void() {
5572 G1ParScanThreadState* const pss = par_scan_state();
5573 pss->trim_queue();
5574 }
5575 };
5577 // Parallel Reference Processing closures
5579 // Implementation of AbstractRefProcTaskExecutor for parallel reference
5580 // processing during G1 evacuation pauses.
5582 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5583 private:
5584 G1CollectedHeap* _g1h;
5585 RefToScanQueueSet* _queues;
5586 FlexibleWorkGang* _workers;
5587 int _active_workers;
5589 public:
5590 G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5591 FlexibleWorkGang* workers,
5592 RefToScanQueueSet *task_queues,
5593 int n_workers) :
5594 _g1h(g1h),
5595 _queues(task_queues),
5596 _workers(workers),
5597 _active_workers(n_workers)
5598 {
5599 assert(n_workers > 0, "shouldn't call this otherwise");
5600 }
5602 // Executes the given task using concurrent marking worker threads.
5603 virtual void execute(ProcessTask& task);
5604 virtual void execute(EnqueueTask& task);
5605 };
5607 // Gang task for possibly parallel reference processing
5609 class G1STWRefProcTaskProxy: public AbstractGangTask {
5610 typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5611 ProcessTask& _proc_task;
5612 G1CollectedHeap* _g1h;
5613 RefToScanQueueSet *_task_queues;
5614 ParallelTaskTerminator* _terminator;
5616 public:
5617 G1STWRefProcTaskProxy(ProcessTask& proc_task,
5618 G1CollectedHeap* g1h,
5619 RefToScanQueueSet *task_queues,
5620 ParallelTaskTerminator* terminator) :
5621 AbstractGangTask("Process reference objects in parallel"),
5622 _proc_task(proc_task),
5623 _g1h(g1h),
5624 _task_queues(task_queues),
5625 _terminator(terminator)
5626 {}
5628 virtual void work(uint worker_id) {
5629 // The reference processing task executed by a single worker.
5630 ResourceMark rm;
5631 HandleMark hm;
5633 G1STWIsAliveClosure is_alive(_g1h);
5635 G1ParScanThreadState pss(_g1h, worker_id, NULL);
5636 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5638 pss.set_evac_failure_closure(&evac_failure_cl);
5640 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5642 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5644 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5646 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5647 // We also need to mark copied objects.
5648 copy_non_heap_cl = ©_mark_non_heap_cl;
5649 }
5651 // Keep alive closure.
5652 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5654 // Complete GC closure
5655 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5657 // Call the reference processing task's work routine.
5658 _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5660 // Note we cannot assert that the refs array is empty here as not all
5661 // of the processing tasks (specifically phase2 - pp2_work) execute
5662 // the complete_gc closure (which ordinarily would drain the queue) so
5663 // the queue may not be empty.
5664 }
5665 };
5667 // Driver routine for parallel reference processing.
5668 // Creates an instance of the ref processing gang
5669 // task and has the worker threads execute it.
5670 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5671 assert(_workers != NULL, "Need parallel worker threads.");
5673 ParallelTaskTerminator terminator(_active_workers, _queues);
5674 G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5676 _g1h->set_par_threads(_active_workers);
5677 _workers->run_task(&proc_task_proxy);
5678 _g1h->set_par_threads(0);
5679 }
5681 // Gang task for parallel reference enqueueing.
5683 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5684 typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5685 EnqueueTask& _enq_task;
5687 public:
5688 G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5689 AbstractGangTask("Enqueue reference objects in parallel"),
5690 _enq_task(enq_task)
5691 { }
5693 virtual void work(uint worker_id) {
5694 _enq_task.work(worker_id);
5695 }
5696 };
5698 // Driver routine for parallel reference enqueueing.
5699 // Creates an instance of the ref enqueueing gang
5700 // task and has the worker threads execute it.
5702 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5703 assert(_workers != NULL, "Need parallel worker threads.");
5705 G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5707 _g1h->set_par_threads(_active_workers);
5708 _workers->run_task(&enq_task_proxy);
5709 _g1h->set_par_threads(0);
5710 }
5712 // End of weak reference support closures
5714 // Abstract task used to preserve (i.e. copy) any referent objects
5715 // that are in the collection set and are pointed to by reference
5716 // objects discovered by the CM ref processor.
5718 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5719 protected:
5720 G1CollectedHeap* _g1h;
5721 RefToScanQueueSet *_queues;
5722 ParallelTaskTerminator _terminator;
5723 uint _n_workers;
5725 public:
5726 G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
5727 AbstractGangTask("ParPreserveCMReferents"),
5728 _g1h(g1h),
5729 _queues(task_queues),
5730 _terminator(workers, _queues),
5731 _n_workers(workers)
5732 { }
5734 void work(uint worker_id) {
5735 ResourceMark rm;
5736 HandleMark hm;
5738 G1ParScanThreadState pss(_g1h, worker_id, NULL);
5739 G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5741 pss.set_evac_failure_closure(&evac_failure_cl);
5743 assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5745 G1ParScanExtRootClosure only_copy_non_heap_cl(_g1h, &pss, NULL);
5747 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5749 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5751 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5752 // We also need to mark copied objects.
5753 copy_non_heap_cl = ©_mark_non_heap_cl;
5754 }
5756 // Is alive closure
5757 G1AlwaysAliveClosure always_alive(_g1h);
5759 // Copying keep alive closure. Applied to referent objects that need
5760 // to be copied.
5761 G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5763 ReferenceProcessor* rp = _g1h->ref_processor_cm();
5765 uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5766 uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5768 // limit is set using max_num_q() - which was set using ParallelGCThreads.
5769 // So this must be true - but assert just in case someone decides to
5770 // change the worker ids.
5771 assert(0 <= worker_id && worker_id < limit, "sanity");
5772 assert(!rp->discovery_is_atomic(), "check this code");
5774 // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5775 for (uint idx = worker_id; idx < limit; idx += stride) {
5776 DiscoveredList& ref_list = rp->discovered_refs()[idx];
5778 DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5779 while (iter.has_next()) {
5780 // Since discovery is not atomic for the CM ref processor, we
5781 // can see some null referent objects.
5782 iter.load_ptrs(DEBUG_ONLY(true));
5783 oop ref = iter.obj();
5785 // This will filter nulls.
5786 if (iter.is_referent_alive()) {
5787 iter.make_referent_alive();
5788 }
5789 iter.move_to_next();
5790 }
5791 }
5793 // Drain the queue - which may cause stealing
5794 G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5795 drain_queue.do_void();
5796 // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5797 assert(pss.queue_is_empty(), "should be");
5798 }
5799 };
5801 // Weak Reference processing during an evacuation pause (part 1).
5802 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) {
5803 double ref_proc_start = os::elapsedTime();
5805 ReferenceProcessor* rp = _ref_processor_stw;
5806 assert(rp->discovery_enabled(), "should have been enabled");
5808 // Any reference objects, in the collection set, that were 'discovered'
5809 // by the CM ref processor should have already been copied (either by
5810 // applying the external root copy closure to the discovered lists, or
5811 // by following an RSet entry).
5812 //
5813 // But some of the referents, that are in the collection set, that these
5814 // reference objects point to may not have been copied: the STW ref
5815 // processor would have seen that the reference object had already
5816 // been 'discovered' and would have skipped discovering the reference,
5817 // but would not have treated the reference object as a regular oop.
5818 // As a result the copy closure would not have been applied to the
5819 // referent object.
5820 //
5821 // We need to explicitly copy these referent objects - the references
5822 // will be processed at the end of remarking.
5823 //
5824 // We also need to do this copying before we process the reference
5825 // objects discovered by the STW ref processor in case one of these
5826 // referents points to another object which is also referenced by an
5827 // object discovered by the STW ref processor.
5829 assert(!G1CollectedHeap::use_parallel_gc_threads() ||
5830 no_of_gc_workers == workers()->active_workers(),
5831 "Need to reset active GC workers");
5833 set_par_threads(no_of_gc_workers);
5834 G1ParPreserveCMReferentsTask keep_cm_referents(this,
5835 no_of_gc_workers,
5836 _task_queues);
5838 if (G1CollectedHeap::use_parallel_gc_threads()) {
5839 workers()->run_task(&keep_cm_referents);
5840 } else {
5841 keep_cm_referents.work(0);
5842 }
5844 set_par_threads(0);
5846 // Closure to test whether a referent is alive.
5847 G1STWIsAliveClosure is_alive(this);
5849 // Even when parallel reference processing is enabled, the processing
5850 // of JNI refs is serial and performed serially by the current thread
5851 // rather than by a worker. The following PSS will be used for processing
5852 // JNI refs.
5854 // Use only a single queue for this PSS.
5855 G1ParScanThreadState pss(this, 0, NULL);
5857 // We do not embed a reference processor in the copying/scanning
5858 // closures while we're actually processing the discovered
5859 // reference objects.
5860 G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5862 pss.set_evac_failure_closure(&evac_failure_cl);
5864 assert(pss.queue_is_empty(), "pre-condition");
5866 G1ParScanExtRootClosure only_copy_non_heap_cl(this, &pss, NULL);
5868 G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5870 OopClosure* copy_non_heap_cl = &only_copy_non_heap_cl;
5872 if (_g1h->g1_policy()->during_initial_mark_pause()) {
5873 // We also need to mark copied objects.
5874 copy_non_heap_cl = ©_mark_non_heap_cl;
5875 }
5877 // Keep alive closure.
5878 G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, &pss);
5880 // Serial Complete GC closure
5881 G1STWDrainQueueClosure drain_queue(this, &pss);
5883 // Setup the soft refs policy...
5884 rp->setup_policy(false);
5886 ReferenceProcessorStats stats;
5887 if (!rp->processing_is_mt()) {
5888 // Serial reference processing...
5889 stats = rp->process_discovered_references(&is_alive,
5890 &keep_alive,
5891 &drain_queue,
5892 NULL,
5893 _gc_timer_stw,
5894 _gc_tracer_stw->gc_id());
5895 } else {
5896 // Parallel reference processing
5897 assert(rp->num_q() == no_of_gc_workers, "sanity");
5898 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5900 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5901 stats = rp->process_discovered_references(&is_alive,
5902 &keep_alive,
5903 &drain_queue,
5904 &par_task_executor,
5905 _gc_timer_stw,
5906 _gc_tracer_stw->gc_id());
5907 }
5909 _gc_tracer_stw->report_gc_reference_stats(stats);
5911 // We have completed copying any necessary live referent objects.
5912 assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5914 double ref_proc_time = os::elapsedTime() - ref_proc_start;
5915 g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5916 }
5918 // Weak Reference processing during an evacuation pause (part 2).
5919 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) {
5920 double ref_enq_start = os::elapsedTime();
5922 ReferenceProcessor* rp = _ref_processor_stw;
5923 assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5925 // Now enqueue any remaining on the discovered lists on to
5926 // the pending list.
5927 if (!rp->processing_is_mt()) {
5928 // Serial reference processing...
5929 rp->enqueue_discovered_references();
5930 } else {
5931 // Parallel reference enqueueing
5933 assert(no_of_gc_workers == workers()->active_workers(),
5934 "Need to reset active workers");
5935 assert(rp->num_q() == no_of_gc_workers, "sanity");
5936 assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5938 G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5939 rp->enqueue_discovered_references(&par_task_executor);
5940 }
5942 rp->verify_no_references_recorded();
5943 assert(!rp->discovery_enabled(), "should have been disabled");
5945 // FIXME
5946 // CM's reference processing also cleans up the string and symbol tables.
5947 // Should we do that here also? We could, but it is a serial operation
5948 // and could significantly increase the pause time.
5950 double ref_enq_time = os::elapsedTime() - ref_enq_start;
5951 g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5952 }
5954 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) {
5955 _expand_heap_after_alloc_failure = true;
5956 _evacuation_failed = false;
5958 // Should G1EvacuationFailureALot be in effect for this GC?
5959 NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
5961 g1_rem_set()->prepare_for_oops_into_collection_set_do();
5963 // Disable the hot card cache.
5964 G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
5965 hot_card_cache->reset_hot_cache_claimed_index();
5966 hot_card_cache->set_use_cache(false);
5968 uint n_workers;
5969 if (G1CollectedHeap::use_parallel_gc_threads()) {
5970 n_workers =
5971 AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
5972 workers()->active_workers(),
5973 Threads::number_of_non_daemon_threads());
5974 assert(UseDynamicNumberOfGCThreads ||
5975 n_workers == workers()->total_workers(),
5976 "If not dynamic should be using all the workers");
5977 workers()->set_active_workers(n_workers);
5978 set_par_threads(n_workers);
5979 } else {
5980 assert(n_par_threads() == 0,
5981 "Should be the original non-parallel value");
5982 n_workers = 1;
5983 }
5985 G1ParTask g1_par_task(this, _task_queues);
5987 init_for_evac_failure(NULL);
5989 rem_set()->prepare_for_younger_refs_iterate(true);
5991 assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5992 double start_par_time_sec = os::elapsedTime();
5993 double end_par_time_sec;
5995 {
5996 StrongRootsScope srs(this);
5997 // InitialMark needs claim bits to keep track of the marked-through CLDs.
5998 if (g1_policy()->during_initial_mark_pause()) {
5999 ClassLoaderDataGraph::clear_claimed_marks();
6000 }
6002 if (G1CollectedHeap::use_parallel_gc_threads()) {
6003 // The individual threads will set their evac-failure closures.
6004 if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
6005 // These tasks use ShareHeap::_process_strong_tasks
6006 assert(UseDynamicNumberOfGCThreads ||
6007 workers()->active_workers() == workers()->total_workers(),
6008 "If not dynamic should be using all the workers");
6009 workers()->run_task(&g1_par_task);
6010 } else {
6011 g1_par_task.set_for_termination(n_workers);
6012 g1_par_task.work(0);
6013 }
6014 end_par_time_sec = os::elapsedTime();
6016 // Closing the inner scope will execute the destructor
6017 // for the StrongRootsScope object. We record the current
6018 // elapsed time before closing the scope so that time
6019 // taken for the SRS destructor is NOT included in the
6020 // reported parallel time.
6021 }
6023 double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
6024 g1_policy()->phase_times()->record_par_time(par_time_ms);
6026 double code_root_fixup_time_ms =
6027 (os::elapsedTime() - end_par_time_sec) * 1000.0;
6028 g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms);
6030 set_par_threads(0);
6032 // Process any discovered reference objects - we have
6033 // to do this _before_ we retire the GC alloc regions
6034 // as we may have to copy some 'reachable' referent
6035 // objects (and their reachable sub-graphs) that were
6036 // not copied during the pause.
6037 process_discovered_references(n_workers);
6039 // Weak root processing.
6040 {
6041 G1STWIsAliveClosure is_alive(this);
6042 G1KeepAliveClosure keep_alive(this);
6043 JNIHandles::weak_oops_do(&is_alive, &keep_alive);
6044 if (G1StringDedup::is_enabled()) {
6045 G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive);
6046 }
6047 }
6049 release_gc_alloc_regions(n_workers, evacuation_info);
6050 g1_rem_set()->cleanup_after_oops_into_collection_set_do();
6052 // Reset and re-enable the hot card cache.
6053 // Note the counts for the cards in the regions in the
6054 // collection set are reset when the collection set is freed.
6055 hot_card_cache->reset_hot_cache();
6056 hot_card_cache->set_use_cache(true);
6058 // Migrate the strong code roots attached to each region in
6059 // the collection set. Ideally we would like to do this
6060 // after we have finished the scanning/evacuation of the
6061 // strong code roots for a particular heap region.
6062 migrate_strong_code_roots();
6064 purge_code_root_memory();
6066 if (g1_policy()->during_initial_mark_pause()) {
6067 // Reset the claim values set during marking the strong code roots
6068 reset_heap_region_claim_values();
6069 }
6071 finalize_for_evac_failure();
6073 if (evacuation_failed()) {
6074 remove_self_forwarding_pointers();
6076 // Reset the G1EvacuationFailureALot counters and flags
6077 // Note: the values are reset only when an actual
6078 // evacuation failure occurs.
6079 NOT_PRODUCT(reset_evacuation_should_fail();)
6080 }
6082 // Enqueue any remaining references remaining on the STW
6083 // reference processor's discovered lists. We need to do
6084 // this after the card table is cleaned (and verified) as
6085 // the act of enqueueing entries on to the pending list
6086 // will log these updates (and dirty their associated
6087 // cards). We need these updates logged to update any
6088 // RSets.
6089 enqueue_discovered_references(n_workers);
6091 if (G1DeferredRSUpdate) {
6092 redirty_logged_cards();
6093 }
6094 COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
6095 }
6097 void G1CollectedHeap::free_region(HeapRegion* hr,
6098 FreeRegionList* free_list,
6099 bool par,
6100 bool locked) {
6101 assert(!hr->isHumongous(), "this is only for non-humongous regions");
6102 assert(!hr->is_empty(), "the region should not be empty");
6103 assert(free_list != NULL, "pre-condition");
6105 if (G1VerifyBitmaps) {
6106 MemRegion mr(hr->bottom(), hr->end());
6107 concurrent_mark()->clearRangePrevBitmap(mr);
6108 }
6110 // Clear the card counts for this region.
6111 // Note: we only need to do this if the region is not young
6112 // (since we don't refine cards in young regions).
6113 if (!hr->is_young()) {
6114 _cg1r->hot_card_cache()->reset_card_counts(hr);
6115 }
6116 hr->hr_clear(par, true /* clear_space */, locked /* locked */);
6117 free_list->add_ordered(hr);
6118 }
6120 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
6121 FreeRegionList* free_list,
6122 bool par) {
6123 assert(hr->startsHumongous(), "this is only for starts humongous regions");
6124 assert(free_list != NULL, "pre-condition");
6126 size_t hr_capacity = hr->capacity();
6127 // We need to read this before we make the region non-humongous,
6128 // otherwise the information will be gone.
6129 uint last_index = hr->last_hc_index();
6130 hr->set_notHumongous();
6131 free_region(hr, free_list, par);
6133 uint i = hr->hrs_index() + 1;
6134 while (i < last_index) {
6135 HeapRegion* curr_hr = region_at(i);
6136 assert(curr_hr->continuesHumongous(), "invariant");
6137 curr_hr->set_notHumongous();
6138 free_region(curr_hr, free_list, par);
6139 i += 1;
6140 }
6141 }
6143 void G1CollectedHeap::remove_from_old_sets(const HeapRegionSetCount& old_regions_removed,
6144 const HeapRegionSetCount& humongous_regions_removed) {
6145 if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 0) {
6146 MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
6147 _old_set.bulk_remove(old_regions_removed);
6148 _humongous_set.bulk_remove(humongous_regions_removed);
6149 }
6151 }
6153 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
6154 assert(list != NULL, "list can't be null");
6155 if (!list->is_empty()) {
6156 MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
6157 _free_list.add_ordered(list);
6158 }
6159 }
6161 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
6162 assert(_summary_bytes_used >= bytes,
6163 err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" should be >= bytes: "SIZE_FORMAT,
6164 _summary_bytes_used, bytes));
6165 _summary_bytes_used -= bytes;
6166 }
6168 class G1ParCleanupCTTask : public AbstractGangTask {
6169 G1SATBCardTableModRefBS* _ct_bs;
6170 G1CollectedHeap* _g1h;
6171 HeapRegion* volatile _su_head;
6172 public:
6173 G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs,
6174 G1CollectedHeap* g1h) :
6175 AbstractGangTask("G1 Par Cleanup CT Task"),
6176 _ct_bs(ct_bs), _g1h(g1h) { }
6178 void work(uint worker_id) {
6179 HeapRegion* r;
6180 while (r = _g1h->pop_dirty_cards_region()) {
6181 clear_cards(r);
6182 }
6183 }
6185 void clear_cards(HeapRegion* r) {
6186 // Cards of the survivors should have already been dirtied.
6187 if (!r->is_survivor()) {
6188 _ct_bs->clear(MemRegion(r->bottom(), r->end()));
6189 }
6190 }
6191 };
6193 #ifndef PRODUCT
6194 class G1VerifyCardTableCleanup: public HeapRegionClosure {
6195 G1CollectedHeap* _g1h;
6196 G1SATBCardTableModRefBS* _ct_bs;
6197 public:
6198 G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs)
6199 : _g1h(g1h), _ct_bs(ct_bs) { }
6200 virtual bool doHeapRegion(HeapRegion* r) {
6201 if (r->is_survivor()) {
6202 _g1h->verify_dirty_region(r);
6203 } else {
6204 _g1h->verify_not_dirty_region(r);
6205 }
6206 return false;
6207 }
6208 };
6210 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
6211 // All of the region should be clean.
6212 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6213 MemRegion mr(hr->bottom(), hr->end());
6214 ct_bs->verify_not_dirty_region(mr);
6215 }
6217 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
6218 // We cannot guarantee that [bottom(),end()] is dirty. Threads
6219 // dirty allocated blocks as they allocate them. The thread that
6220 // retires each region and replaces it with a new one will do a
6221 // maximal allocation to fill in [pre_dummy_top(),end()] but will
6222 // not dirty that area (one less thing to have to do while holding
6223 // a lock). So we can only verify that [bottom(),pre_dummy_top()]
6224 // is dirty.
6225 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6226 MemRegion mr(hr->bottom(), hr->pre_dummy_top());
6227 if (hr->is_young()) {
6228 ct_bs->verify_g1_young_region(mr);
6229 } else {
6230 ct_bs->verify_dirty_region(mr);
6231 }
6232 }
6234 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
6235 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6236 for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
6237 verify_dirty_region(hr);
6238 }
6239 }
6241 void G1CollectedHeap::verify_dirty_young_regions() {
6242 verify_dirty_young_list(_young_list->first_region());
6243 }
6245 bool G1CollectedHeap::verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
6246 HeapWord* tams, HeapWord* end) {
6247 guarantee(tams <= end,
6248 err_msg("tams: "PTR_FORMAT" end: "PTR_FORMAT, tams, end));
6249 HeapWord* result = bitmap->getNextMarkedWordAddress(tams, end);
6250 if (result < end) {
6251 gclog_or_tty->cr();
6252 gclog_or_tty->print_cr("## wrong marked address on %s bitmap: "PTR_FORMAT,
6253 bitmap_name, result);
6254 gclog_or_tty->print_cr("## %s tams: "PTR_FORMAT" end: "PTR_FORMAT,
6255 bitmap_name, tams, end);
6256 return false;
6257 }
6258 return true;
6259 }
6261 bool G1CollectedHeap::verify_bitmaps(const char* caller, HeapRegion* hr) {
6262 CMBitMapRO* prev_bitmap = concurrent_mark()->prevMarkBitMap();
6263 CMBitMapRO* next_bitmap = (CMBitMapRO*) concurrent_mark()->nextMarkBitMap();
6265 HeapWord* bottom = hr->bottom();
6266 HeapWord* ptams = hr->prev_top_at_mark_start();
6267 HeapWord* ntams = hr->next_top_at_mark_start();
6268 HeapWord* end = hr->end();
6270 bool res_p = verify_no_bits_over_tams("prev", prev_bitmap, ptams, end);
6272 bool res_n = true;
6273 // We reset mark_in_progress() before we reset _cmThread->in_progress() and in this window
6274 // we do the clearing of the next bitmap concurrently. Thus, we can not verify the bitmap
6275 // if we happen to be in that state.
6276 if (mark_in_progress() || !_cmThread->in_progress()) {
6277 res_n = verify_no_bits_over_tams("next", next_bitmap, ntams, end);
6278 }
6279 if (!res_p || !res_n) {
6280 gclog_or_tty->print_cr("#### Bitmap verification failed for "HR_FORMAT,
6281 HR_FORMAT_PARAMS(hr));
6282 gclog_or_tty->print_cr("#### Caller: %s", caller);
6283 return false;
6284 }
6285 return true;
6286 }
6288 void G1CollectedHeap::check_bitmaps(const char* caller, HeapRegion* hr) {
6289 if (!G1VerifyBitmaps) return;
6291 guarantee(verify_bitmaps(caller, hr), "bitmap verification");
6292 }
6294 class G1VerifyBitmapClosure : public HeapRegionClosure {
6295 private:
6296 const char* _caller;
6297 G1CollectedHeap* _g1h;
6298 bool _failures;
6300 public:
6301 G1VerifyBitmapClosure(const char* caller, G1CollectedHeap* g1h) :
6302 _caller(caller), _g1h(g1h), _failures(false) { }
6304 bool failures() { return _failures; }
6306 virtual bool doHeapRegion(HeapRegion* hr) {
6307 if (hr->continuesHumongous()) return false;
6309 bool result = _g1h->verify_bitmaps(_caller, hr);
6310 if (!result) {
6311 _failures = true;
6312 }
6313 return false;
6314 }
6315 };
6317 void G1CollectedHeap::check_bitmaps(const char* caller) {
6318 if (!G1VerifyBitmaps) return;
6320 G1VerifyBitmapClosure cl(caller, this);
6321 heap_region_iterate(&cl);
6322 guarantee(!cl.failures(), "bitmap verification");
6323 }
6324 #endif // PRODUCT
6326 void G1CollectedHeap::cleanUpCardTable() {
6327 G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6328 double start = os::elapsedTime();
6330 {
6331 // Iterate over the dirty cards region list.
6332 G1ParCleanupCTTask cleanup_task(ct_bs, this);
6334 if (G1CollectedHeap::use_parallel_gc_threads()) {
6335 set_par_threads();
6336 workers()->run_task(&cleanup_task);
6337 set_par_threads(0);
6338 } else {
6339 while (_dirty_cards_region_list) {
6340 HeapRegion* r = _dirty_cards_region_list;
6341 cleanup_task.clear_cards(r);
6342 _dirty_cards_region_list = r->get_next_dirty_cards_region();
6343 if (_dirty_cards_region_list == r) {
6344 // The last region.
6345 _dirty_cards_region_list = NULL;
6346 }
6347 r->set_next_dirty_cards_region(NULL);
6348 }
6349 }
6350 #ifndef PRODUCT
6351 if (G1VerifyCTCleanup || VerifyAfterGC) {
6352 G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
6353 heap_region_iterate(&cleanup_verifier);
6354 }
6355 #endif
6356 }
6358 double elapsed = os::elapsedTime() - start;
6359 g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
6360 }
6362 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) {
6363 size_t pre_used = 0;
6364 FreeRegionList local_free_list("Local List for CSet Freeing");
6366 double young_time_ms = 0.0;
6367 double non_young_time_ms = 0.0;
6369 // Since the collection set is a superset of the the young list,
6370 // all we need to do to clear the young list is clear its
6371 // head and length, and unlink any young regions in the code below
6372 _young_list->clear();
6374 G1CollectorPolicy* policy = g1_policy();
6376 double start_sec = os::elapsedTime();
6377 bool non_young = true;
6379 HeapRegion* cur = cs_head;
6380 int age_bound = -1;
6381 size_t rs_lengths = 0;
6383 while (cur != NULL) {
6384 assert(!is_on_master_free_list(cur), "sanity");
6385 if (non_young) {
6386 if (cur->is_young()) {
6387 double end_sec = os::elapsedTime();
6388 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6389 non_young_time_ms += elapsed_ms;
6391 start_sec = os::elapsedTime();
6392 non_young = false;
6393 }
6394 } else {
6395 if (!cur->is_young()) {
6396 double end_sec = os::elapsedTime();
6397 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6398 young_time_ms += elapsed_ms;
6400 start_sec = os::elapsedTime();
6401 non_young = true;
6402 }
6403 }
6405 rs_lengths += cur->rem_set()->occupied_locked();
6407 HeapRegion* next = cur->next_in_collection_set();
6408 assert(cur->in_collection_set(), "bad CS");
6409 cur->set_next_in_collection_set(NULL);
6410 cur->set_in_collection_set(false);
6412 if (cur->is_young()) {
6413 int index = cur->young_index_in_cset();
6414 assert(index != -1, "invariant");
6415 assert((uint) index < policy->young_cset_region_length(), "invariant");
6416 size_t words_survived = _surviving_young_words[index];
6417 cur->record_surv_words_in_group(words_survived);
6419 // At this point the we have 'popped' cur from the collection set
6420 // (linked via next_in_collection_set()) but it is still in the
6421 // young list (linked via next_young_region()). Clear the
6422 // _next_young_region field.
6423 cur->set_next_young_region(NULL);
6424 } else {
6425 int index = cur->young_index_in_cset();
6426 assert(index == -1, "invariant");
6427 }
6429 assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
6430 (!cur->is_young() && cur->young_index_in_cset() == -1),
6431 "invariant" );
6433 if (!cur->evacuation_failed()) {
6434 MemRegion used_mr = cur->used_region();
6436 // And the region is empty.
6437 assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
6438 pre_used += cur->used();
6439 free_region(cur, &local_free_list, false /* par */, true /* locked */);
6440 } else {
6441 cur->uninstall_surv_rate_group();
6442 if (cur->is_young()) {
6443 cur->set_young_index_in_cset(-1);
6444 }
6445 cur->set_not_young();
6446 cur->set_evacuation_failed(false);
6447 // The region is now considered to be old.
6448 _old_set.add(cur);
6449 evacuation_info.increment_collectionset_used_after(cur->used());
6450 }
6451 cur = next;
6452 }
6454 evacuation_info.set_regions_freed(local_free_list.length());
6455 policy->record_max_rs_lengths(rs_lengths);
6456 policy->cset_regions_freed();
6458 double end_sec = os::elapsedTime();
6459 double elapsed_ms = (end_sec - start_sec) * 1000.0;
6461 if (non_young) {
6462 non_young_time_ms += elapsed_ms;
6463 } else {
6464 young_time_ms += elapsed_ms;
6465 }
6467 prepend_to_freelist(&local_free_list);
6468 decrement_summary_bytes(pre_used);
6469 policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
6470 policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
6471 }
6473 // This routine is similar to the above but does not record
6474 // any policy statistics or update free lists; we are abandoning
6475 // the current incremental collection set in preparation of a
6476 // full collection. After the full GC we will start to build up
6477 // the incremental collection set again.
6478 // This is only called when we're doing a full collection
6479 // and is immediately followed by the tearing down of the young list.
6481 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
6482 HeapRegion* cur = cs_head;
6484 while (cur != NULL) {
6485 HeapRegion* next = cur->next_in_collection_set();
6486 assert(cur->in_collection_set(), "bad CS");
6487 cur->set_next_in_collection_set(NULL);
6488 cur->set_in_collection_set(false);
6489 cur->set_young_index_in_cset(-1);
6490 cur = next;
6491 }
6492 }
6494 void G1CollectedHeap::set_free_regions_coming() {
6495 if (G1ConcRegionFreeingVerbose) {
6496 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6497 "setting free regions coming");
6498 }
6500 assert(!free_regions_coming(), "pre-condition");
6501 _free_regions_coming = true;
6502 }
6504 void G1CollectedHeap::reset_free_regions_coming() {
6505 assert(free_regions_coming(), "pre-condition");
6507 {
6508 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6509 _free_regions_coming = false;
6510 SecondaryFreeList_lock->notify_all();
6511 }
6513 if (G1ConcRegionFreeingVerbose) {
6514 gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6515 "reset free regions coming");
6516 }
6517 }
6519 void G1CollectedHeap::wait_while_free_regions_coming() {
6520 // Most of the time we won't have to wait, so let's do a quick test
6521 // first before we take the lock.
6522 if (!free_regions_coming()) {
6523 return;
6524 }
6526 if (G1ConcRegionFreeingVerbose) {
6527 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6528 "waiting for free regions");
6529 }
6531 {
6532 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6533 while (free_regions_coming()) {
6534 SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
6535 }
6536 }
6538 if (G1ConcRegionFreeingVerbose) {
6539 gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6540 "done waiting for free regions");
6541 }
6542 }
6544 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
6545 assert(heap_lock_held_for_gc(),
6546 "the heap lock should already be held by or for this thread");
6547 _young_list->push_region(hr);
6548 }
6550 class NoYoungRegionsClosure: public HeapRegionClosure {
6551 private:
6552 bool _success;
6553 public:
6554 NoYoungRegionsClosure() : _success(true) { }
6555 bool doHeapRegion(HeapRegion* r) {
6556 if (r->is_young()) {
6557 gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
6558 r->bottom(), r->end());
6559 _success = false;
6560 }
6561 return false;
6562 }
6563 bool success() { return _success; }
6564 };
6566 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
6567 bool ret = _young_list->check_list_empty(check_sample);
6569 if (check_heap) {
6570 NoYoungRegionsClosure closure;
6571 heap_region_iterate(&closure);
6572 ret = ret && closure.success();
6573 }
6575 return ret;
6576 }
6578 class TearDownRegionSetsClosure : public HeapRegionClosure {
6579 private:
6580 HeapRegionSet *_old_set;
6582 public:
6583 TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
6585 bool doHeapRegion(HeapRegion* r) {
6586 if (r->is_empty()) {
6587 // We ignore empty regions, we'll empty the free list afterwards
6588 } else if (r->is_young()) {
6589 // We ignore young regions, we'll empty the young list afterwards
6590 } else if (r->isHumongous()) {
6591 // We ignore humongous regions, we're not tearing down the
6592 // humongous region set
6593 } else {
6594 // The rest should be old
6595 _old_set->remove(r);
6596 }
6597 return false;
6598 }
6600 ~TearDownRegionSetsClosure() {
6601 assert(_old_set->is_empty(), "post-condition");
6602 }
6603 };
6605 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6606 assert_at_safepoint(true /* should_be_vm_thread */);
6608 if (!free_list_only) {
6609 TearDownRegionSetsClosure cl(&_old_set);
6610 heap_region_iterate(&cl);
6612 // Note that emptying the _young_list is postponed and instead done as
6613 // the first step when rebuilding the regions sets again. The reason for
6614 // this is that during a full GC string deduplication needs to know if
6615 // a collected region was young or old when the full GC was initiated.
6616 }
6617 _free_list.remove_all();
6618 }
6620 class RebuildRegionSetsClosure : public HeapRegionClosure {
6621 private:
6622 bool _free_list_only;
6623 HeapRegionSet* _old_set;
6624 FreeRegionList* _free_list;
6625 size_t _total_used;
6627 public:
6628 RebuildRegionSetsClosure(bool free_list_only,
6629 HeapRegionSet* old_set, FreeRegionList* free_list) :
6630 _free_list_only(free_list_only),
6631 _old_set(old_set), _free_list(free_list), _total_used(0) {
6632 assert(_free_list->is_empty(), "pre-condition");
6633 if (!free_list_only) {
6634 assert(_old_set->is_empty(), "pre-condition");
6635 }
6636 }
6638 bool doHeapRegion(HeapRegion* r) {
6639 if (r->continuesHumongous()) {
6640 return false;
6641 }
6643 if (r->is_empty()) {
6644 // Add free regions to the free list
6645 _free_list->add_as_tail(r);
6646 } else if (!_free_list_only) {
6647 assert(!r->is_young(), "we should not come across young regions");
6649 if (r->isHumongous()) {
6650 // We ignore humongous regions, we left the humongous set unchanged
6651 } else {
6652 // The rest should be old, add them to the old set
6653 _old_set->add(r);
6654 }
6655 _total_used += r->used();
6656 }
6658 return false;
6659 }
6661 size_t total_used() {
6662 return _total_used;
6663 }
6664 };
6666 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6667 assert_at_safepoint(true /* should_be_vm_thread */);
6669 if (!free_list_only) {
6670 _young_list->empty_list();
6671 }
6673 RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_free_list);
6674 heap_region_iterate(&cl);
6676 if (!free_list_only) {
6677 _summary_bytes_used = cl.total_used();
6678 }
6679 assert(_summary_bytes_used == recalculate_used(),
6680 err_msg("inconsistent _summary_bytes_used, "
6681 "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6682 _summary_bytes_used, recalculate_used()));
6683 }
6685 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6686 _refine_cte_cl->set_concurrent(concurrent);
6687 }
6689 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6690 HeapRegion* hr = heap_region_containing(p);
6691 if (hr == NULL) {
6692 return false;
6693 } else {
6694 return hr->is_in(p);
6695 }
6696 }
6698 // Methods for the mutator alloc region
6700 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6701 bool force) {
6702 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6703 assert(!force || g1_policy()->can_expand_young_list(),
6704 "if force is true we should be able to expand the young list");
6705 bool young_list_full = g1_policy()->is_young_list_full();
6706 if (force || !young_list_full) {
6707 HeapRegion* new_alloc_region = new_region(word_size,
6708 false /* is_old */,
6709 false /* do_expand */);
6710 if (new_alloc_region != NULL) {
6711 set_region_short_lived_locked(new_alloc_region);
6712 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6713 check_bitmaps("Mutator Region Allocation", new_alloc_region);
6714 return new_alloc_region;
6715 }
6716 }
6717 return NULL;
6718 }
6720 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6721 size_t allocated_bytes) {
6722 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6723 assert(alloc_region->is_young(), "all mutator alloc regions should be young");
6725 g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6726 _summary_bytes_used += allocated_bytes;
6727 _hr_printer.retire(alloc_region);
6728 // We update the eden sizes here, when the region is retired,
6729 // instead of when it's allocated, since this is the point that its
6730 // used space has been recored in _summary_bytes_used.
6731 g1mm()->update_eden_size();
6732 }
6734 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
6735 bool force) {
6736 return _g1h->new_mutator_alloc_region(word_size, force);
6737 }
6739 void G1CollectedHeap::set_par_threads() {
6740 // Don't change the number of workers. Use the value previously set
6741 // in the workgroup.
6742 assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise");
6743 uint n_workers = workers()->active_workers();
6744 assert(UseDynamicNumberOfGCThreads ||
6745 n_workers == workers()->total_workers(),
6746 "Otherwise should be using the total number of workers");
6747 if (n_workers == 0) {
6748 assert(false, "Should have been set in prior evacuation pause.");
6749 n_workers = ParallelGCThreads;
6750 workers()->set_active_workers(n_workers);
6751 }
6752 set_par_threads(n_workers);
6753 }
6755 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
6756 size_t allocated_bytes) {
6757 _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
6758 }
6760 // Methods for the GC alloc regions
6762 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6763 uint count,
6764 GCAllocPurpose ap) {
6765 assert(FreeList_lock->owned_by_self(), "pre-condition");
6767 if (count < g1_policy()->max_regions(ap)) {
6768 bool survivor = (ap == GCAllocForSurvived);
6769 HeapRegion* new_alloc_region = new_region(word_size,
6770 !survivor,
6771 true /* do_expand */);
6772 if (new_alloc_region != NULL) {
6773 // We really only need to do this for old regions given that we
6774 // should never scan survivors. But it doesn't hurt to do it
6775 // for survivors too.
6776 new_alloc_region->record_top_and_timestamp();
6777 if (survivor) {
6778 new_alloc_region->set_survivor();
6779 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6780 check_bitmaps("Survivor Region Allocation", new_alloc_region);
6781 } else {
6782 _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6783 check_bitmaps("Old Region Allocation", new_alloc_region);
6784 }
6785 bool during_im = g1_policy()->during_initial_mark_pause();
6786 new_alloc_region->note_start_of_copying(during_im);
6787 return new_alloc_region;
6788 } else {
6789 g1_policy()->note_alloc_region_limit_reached(ap);
6790 }
6791 }
6792 return NULL;
6793 }
6795 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6796 size_t allocated_bytes,
6797 GCAllocPurpose ap) {
6798 bool during_im = g1_policy()->during_initial_mark_pause();
6799 alloc_region->note_end_of_copying(during_im);
6800 g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6801 if (ap == GCAllocForSurvived) {
6802 young_list()->add_survivor_region(alloc_region);
6803 } else {
6804 _old_set.add(alloc_region);
6805 }
6806 _hr_printer.retire(alloc_region);
6807 }
6809 HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size,
6810 bool force) {
6811 assert(!force, "not supported for GC alloc regions");
6812 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForSurvived);
6813 }
6815 void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region,
6816 size_t allocated_bytes) {
6817 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6818 GCAllocForSurvived);
6819 }
6821 HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size,
6822 bool force) {
6823 assert(!force, "not supported for GC alloc regions");
6824 return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForTenured);
6825 }
6827 void OldGCAllocRegion::retire_region(HeapRegion* alloc_region,
6828 size_t allocated_bytes) {
6829 _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6830 GCAllocForTenured);
6831 }
6832 // Heap region set verification
6834 class VerifyRegionListsClosure : public HeapRegionClosure {
6835 private:
6836 HeapRegionSet* _old_set;
6837 HeapRegionSet* _humongous_set;
6838 FreeRegionList* _free_list;
6840 public:
6841 HeapRegionSetCount _old_count;
6842 HeapRegionSetCount _humongous_count;
6843 HeapRegionSetCount _free_count;
6845 VerifyRegionListsClosure(HeapRegionSet* old_set,
6846 HeapRegionSet* humongous_set,
6847 FreeRegionList* free_list) :
6848 _old_set(old_set), _humongous_set(humongous_set), _free_list(free_list),
6849 _old_count(), _humongous_count(), _free_count(){ }
6851 bool doHeapRegion(HeapRegion* hr) {
6852 if (hr->continuesHumongous()) {
6853 return false;
6854 }
6856 if (hr->is_young()) {
6857 // TODO
6858 } else if (hr->startsHumongous()) {
6859 assert(hr->containing_set() == _humongous_set, err_msg("Heap region %u is starts humongous but not in humongous set.", hr->region_num()));
6860 _humongous_count.increment(1u, hr->capacity());
6861 } else if (hr->is_empty()) {
6862 assert(hr->containing_set() == _free_list, err_msg("Heap region %u is empty but not on the free list.", hr->region_num()));
6863 _free_count.increment(1u, hr->capacity());
6864 } else {
6865 assert(hr->containing_set() == _old_set, err_msg("Heap region %u is old but not in the old set.", hr->region_num()));
6866 _old_count.increment(1u, hr->capacity());
6867 }
6868 return false;
6869 }
6871 void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, FreeRegionList* free_list) {
6872 guarantee(old_set->length() == _old_count.length(), err_msg("Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length()));
6873 guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), err_msg("Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6874 old_set->total_capacity_bytes(), _old_count.capacity()));
6876 guarantee(humongous_set->length() == _humongous_count.length(), err_msg("Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length()));
6877 guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), err_msg("Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6878 humongous_set->total_capacity_bytes(), _humongous_count.capacity()));
6880 guarantee(free_list->length() == _free_count.length(), err_msg("Free list count mismatch. Expected %u, actual %u.", free_list->length(), _free_count.length()));
6881 guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), err_msg("Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6882 free_list->total_capacity_bytes(), _free_count.capacity()));
6883 }
6884 };
6886 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
6887 HeapWord* bottom) {
6888 HeapWord* end = bottom + HeapRegion::GrainWords;
6889 MemRegion mr(bottom, end);
6890 assert(_g1_reserved.contains(mr), "invariant");
6891 // This might return NULL if the allocation fails
6892 return new HeapRegion(hrs_index, _bot_shared, mr);
6893 }
6895 void G1CollectedHeap::verify_region_sets() {
6896 assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6898 // First, check the explicit lists.
6899 _free_list.verify_list();
6900 {
6901 // Given that a concurrent operation might be adding regions to
6902 // the secondary free list we have to take the lock before
6903 // verifying it.
6904 MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6905 _secondary_free_list.verify_list();
6906 }
6908 // If a concurrent region freeing operation is in progress it will
6909 // be difficult to correctly attributed any free regions we come
6910 // across to the correct free list given that they might belong to
6911 // one of several (free_list, secondary_free_list, any local lists,
6912 // etc.). So, if that's the case we will skip the rest of the
6913 // verification operation. Alternatively, waiting for the concurrent
6914 // operation to complete will have a non-trivial effect on the GC's
6915 // operation (no concurrent operation will last longer than the
6916 // interval between two calls to verification) and it might hide
6917 // any issues that we would like to catch during testing.
6918 if (free_regions_coming()) {
6919 return;
6920 }
6922 // Make sure we append the secondary_free_list on the free_list so
6923 // that all free regions we will come across can be safely
6924 // attributed to the free_list.
6925 append_secondary_free_list_if_not_empty_with_lock();
6927 // Finally, make sure that the region accounting in the lists is
6928 // consistent with what we see in the heap.
6930 VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_free_list);
6931 heap_region_iterate(&cl);
6932 cl.verify_counts(&_old_set, &_humongous_set, &_free_list);
6933 }
6935 // Optimized nmethod scanning
6937 class RegisterNMethodOopClosure: public OopClosure {
6938 G1CollectedHeap* _g1h;
6939 nmethod* _nm;
6941 template <class T> void do_oop_work(T* p) {
6942 T heap_oop = oopDesc::load_heap_oop(p);
6943 if (!oopDesc::is_null(heap_oop)) {
6944 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6945 HeapRegion* hr = _g1h->heap_region_containing(obj);
6946 assert(!hr->continuesHumongous(),
6947 err_msg("trying to add code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6948 " starting at "HR_FORMAT,
6949 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6951 // HeapRegion::add_strong_code_root() avoids adding duplicate
6952 // entries but having duplicates is OK since we "mark" nmethods
6953 // as visited when we scan the strong code root lists during the GC.
6954 hr->add_strong_code_root(_nm);
6955 assert(hr->rem_set()->strong_code_roots_list_contains(_nm),
6956 err_msg("failed to add code root "PTR_FORMAT" to remembered set of region "HR_FORMAT,
6957 _nm, HR_FORMAT_PARAMS(hr)));
6958 }
6959 }
6961 public:
6962 RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6963 _g1h(g1h), _nm(nm) {}
6965 void do_oop(oop* p) { do_oop_work(p); }
6966 void do_oop(narrowOop* p) { do_oop_work(p); }
6967 };
6969 class UnregisterNMethodOopClosure: public OopClosure {
6970 G1CollectedHeap* _g1h;
6971 nmethod* _nm;
6973 template <class T> void do_oop_work(T* p) {
6974 T heap_oop = oopDesc::load_heap_oop(p);
6975 if (!oopDesc::is_null(heap_oop)) {
6976 oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6977 HeapRegion* hr = _g1h->heap_region_containing(obj);
6978 assert(!hr->continuesHumongous(),
6979 err_msg("trying to remove code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6980 " starting at "HR_FORMAT,
6981 _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6983 hr->remove_strong_code_root(_nm);
6984 assert(!hr->rem_set()->strong_code_roots_list_contains(_nm),
6985 err_msg("failed to remove code root "PTR_FORMAT" of region "HR_FORMAT,
6986 _nm, HR_FORMAT_PARAMS(hr)));
6987 }
6988 }
6990 public:
6991 UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6992 _g1h(g1h), _nm(nm) {}
6994 void do_oop(oop* p) { do_oop_work(p); }
6995 void do_oop(narrowOop* p) { do_oop_work(p); }
6996 };
6998 void G1CollectedHeap::register_nmethod(nmethod* nm) {
6999 CollectedHeap::register_nmethod(nm);
7001 guarantee(nm != NULL, "sanity");
7002 RegisterNMethodOopClosure reg_cl(this, nm);
7003 nm->oops_do(®_cl);
7004 }
7006 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
7007 CollectedHeap::unregister_nmethod(nm);
7009 guarantee(nm != NULL, "sanity");
7010 UnregisterNMethodOopClosure reg_cl(this, nm);
7011 nm->oops_do(®_cl, true);
7012 }
7014 class MigrateCodeRootsHeapRegionClosure: public HeapRegionClosure {
7015 public:
7016 bool doHeapRegion(HeapRegion *hr) {
7017 assert(!hr->isHumongous(),
7018 err_msg("humongous region "HR_FORMAT" should not have been added to collection set",
7019 HR_FORMAT_PARAMS(hr)));
7020 hr->migrate_strong_code_roots();
7021 return false;
7022 }
7023 };
7025 void G1CollectedHeap::migrate_strong_code_roots() {
7026 MigrateCodeRootsHeapRegionClosure cl;
7027 double migrate_start = os::elapsedTime();
7028 collection_set_iterate(&cl);
7029 double migration_time_ms = (os::elapsedTime() - migrate_start) * 1000.0;
7030 g1_policy()->phase_times()->record_strong_code_root_migration_time(migration_time_ms);
7031 }
7033 void G1CollectedHeap::purge_code_root_memory() {
7034 double purge_start = os::elapsedTime();
7035 G1CodeRootSet::purge_chunks(G1CodeRootsChunkCacheKeepPercent);
7036 double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
7037 g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
7038 }
7040 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
7041 G1CollectedHeap* _g1h;
7043 public:
7044 RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
7045 _g1h(g1h) {}
7047 void do_code_blob(CodeBlob* cb) {
7048 nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
7049 if (nm == NULL) {
7050 return;
7051 }
7053 if (ScavengeRootsInCode) {
7054 _g1h->register_nmethod(nm);
7055 }
7056 }
7057 };
7059 void G1CollectedHeap::rebuild_strong_code_roots() {
7060 RebuildStrongCodeRootClosure blob_cl(this);
7061 CodeCache::blobs_do(&blob_cl);
7062 }