1 /*
   2  * Copyright (c) 2001, 2014, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #if !defined(__clang_major__) && defined(__GNUC__)
  26 // FIXME, formats have issues.  Disable this macro definition, compile, and study warnings for more information.
  27 #define ATTRIBUTE_PRINTF(x,y)
  28 #endif
  29 
  30 #include "precompiled.hpp"
  31 #include "classfile/metadataOnStackMark.hpp"
  32 #include "classfile/stringTable.hpp"
  33 #include "code/codeCache.hpp"
  34 #include "code/icBuffer.hpp"
  35 #include "gc_implementation/g1/bufferingOopClosure.hpp"
  36 #include "gc_implementation/g1/concurrentG1Refine.hpp"
  37 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
  38 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
  39 #include "gc_implementation/g1/g1AllocRegion.inline.hpp"
  40 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
  41 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
  42 #include "gc_implementation/g1/g1ErgoVerbose.hpp"
  43 #include "gc_implementation/g1/g1EvacFailure.hpp"
  44 #include "gc_implementation/g1/g1GCPhaseTimes.hpp"
  45 #include "gc_implementation/g1/g1Log.hpp"
  46 #include "gc_implementation/g1/g1MarkSweep.hpp"
  47 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
  48 #include "gc_implementation/g1/g1ParScanThreadState.inline.hpp"
  49 #include "gc_implementation/g1/g1RegionToSpaceMapper.hpp"
  50 #include "gc_implementation/g1/g1RemSet.inline.hpp"
  51 #include "gc_implementation/g1/g1StringDedup.hpp"
  52 #include "gc_implementation/g1/g1YCTypes.hpp"
  53 #include "gc_implementation/g1/heapRegion.inline.hpp"
  54 #include "gc_implementation/g1/heapRegionRemSet.hpp"
  55 #include "gc_implementation/g1/heapRegionSet.inline.hpp"
  56 #include "gc_implementation/g1/vm_operations_g1.hpp"
  57 #include "gc_implementation/shared/gcHeapSummary.hpp"
  58 #include "gc_implementation/shared/gcTimer.hpp"
  59 #include "gc_implementation/shared/gcTrace.hpp"
  60 #include "gc_implementation/shared/gcTraceTime.hpp"
  61 #include "gc_implementation/shared/isGCActiveMark.hpp"
  62 #include "memory/allocation.hpp"
  63 #include "memory/gcLocker.inline.hpp"
  64 #include "memory/generationSpec.hpp"
  65 #include "memory/iterator.hpp"
  66 #include "memory/referenceProcessor.hpp"
  67 #include "oops/oop.inline.hpp"
  68 #include "oops/oop.pcgc.inline.hpp"
  69 #include "runtime/atomic.inline.hpp"
  70 #include "runtime/orderAccess.inline.hpp"
  71 #include "runtime/vmThread.hpp"
  72 #include "utilities/globalDefinitions.hpp"
  73 
  74 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
  75 
  76 // turn it on so that the contents of the young list (scan-only /
  77 // to-be-collected) are printed at "strategic" points before / during
  78 // / after the collection --- this is useful for debugging
  79 #define YOUNG_LIST_VERBOSE 0
  80 // CURRENT STATUS
  81 // This file is under construction.  Search for "FIXME".
  82 
  83 // INVARIANTS/NOTES
  84 //
  85 // All allocation activity covered by the G1CollectedHeap interface is
  86 // serialized by acquiring the HeapLock.  This happens in mem_allocate
  87 // and allocate_new_tlab, which are the "entry" points to the
  88 // allocation code from the rest of the JVM.  (Note that this does not
  89 // apply to TLAB allocation, which is not part of this interface: it
  90 // is done by clients of this interface.)
  91 
  92 // Notes on implementation of parallelism in different tasks.
  93 //
  94 // G1ParVerifyTask uses heap_region_par_iterate() for parallelism.
  95 // The number of GC workers is passed to heap_region_par_iterate().
  96 // It does use run_task() which sets _n_workers in the task.
  97 // G1ParTask executes g1_process_roots() ->
  98 // SharedHeap::process_roots() which calls eventually to
  99 // CardTableModRefBS::par_non_clean_card_iterate_work() which uses
 100 // SequentialSubTasksDone.  SharedHeap::process_roots() also
 101 // directly uses SubTasksDone (_process_strong_tasks field in SharedHeap).
 102 //
 103 
 104 // Local to this file.
 105 
 106 class RefineCardTableEntryClosure: public CardTableEntryClosure {
 107   bool _concurrent;
 108 public:
 109   RefineCardTableEntryClosure() : _concurrent(true) { }
 110 
 111   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
 112     bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, false);
 113     // This path is executed by the concurrent refine or mutator threads,
 114     // concurrently, and so we do not care if card_ptr contains references
 115     // that point into the collection set.
 116     assert(!oops_into_cset, "should be");
 117 
 118     if (_concurrent && SuspendibleThreadSet::should_yield()) {
 119       // Caller will actually yield.
 120       return false;
 121     }
 122     // Otherwise, we finished successfully; return true.
 123     return true;
 124   }
 125 
 126   void set_concurrent(bool b) { _concurrent = b; }
 127 };
 128 
 129 
 130 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
 131  private:
 132   size_t _num_processed;
 133 
 134  public:
 135   RedirtyLoggedCardTableEntryClosure() : CardTableEntryClosure(), _num_processed(0) { }
 136 
 137   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
 138     *card_ptr = CardTableModRefBS::dirty_card_val();
 139     _num_processed++;
 140     return true;
 141   }
 142 
 143   size_t num_processed() const { return _num_processed; }
 144 };
 145 
 146 YoungList::YoungList(G1CollectedHeap* g1h) :
 147     _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0),
 148     _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) {
 149   guarantee(check_list_empty(false), "just making sure...");
 150 }
 151 
 152 void YoungList::push_region(HeapRegion *hr) {
 153   assert(!hr->is_young(), "should not already be young");
 154   assert(hr->get_next_young_region() == NULL, "cause it should!");
 155 
 156   hr->set_next_young_region(_head);
 157   _head = hr;
 158 
 159   _g1h->g1_policy()->set_region_eden(hr, (int) _length);
 160   ++_length;
 161 }
 162 
 163 void YoungList::add_survivor_region(HeapRegion* hr) {
 164   assert(hr->is_survivor(), "should be flagged as survivor region");
 165   assert(hr->get_next_young_region() == NULL, "cause it should!");
 166 
 167   hr->set_next_young_region(_survivor_head);
 168   if (_survivor_head == NULL) {
 169     _survivor_tail = hr;
 170   }
 171   _survivor_head = hr;
 172   ++_survivor_length;
 173 }
 174 
 175 void YoungList::empty_list(HeapRegion* list) {
 176   while (list != NULL) {
 177     HeapRegion* next = list->get_next_young_region();
 178     list->set_next_young_region(NULL);
 179     list->uninstall_surv_rate_group();
 180     // This is called before a Full GC and all the non-empty /
 181     // non-humongous regions at the end of the Full GC will end up as
 182     // old anyway.
 183     list->set_old();
 184     list = next;
 185   }
 186 }
 187 
 188 void YoungList::empty_list() {
 189   assert(check_list_well_formed(), "young list should be well formed");
 190 
 191   empty_list(_head);
 192   _head = NULL;
 193   _length = 0;
 194 
 195   empty_list(_survivor_head);
 196   _survivor_head = NULL;
 197   _survivor_tail = NULL;
 198   _survivor_length = 0;
 199 
 200   _last_sampled_rs_lengths = 0;
 201 
 202   assert(check_list_empty(false), "just making sure...");
 203 }
 204 
 205 bool YoungList::check_list_well_formed() {
 206   bool ret = true;
 207 
 208   uint length = 0;
 209   HeapRegion* curr = _head;
 210   HeapRegion* last = NULL;
 211   while (curr != NULL) {
 212     if (!curr->is_young()) {
 213       gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
 214                              "incorrectly tagged (y: %d, surv: %d)",
 215                              curr->bottom(), curr->end(),
 216                              curr->is_young(), curr->is_survivor());
 217       ret = false;
 218     }
 219     ++length;
 220     last = curr;
 221     curr = curr->get_next_young_region();
 222   }
 223   ret = ret && (length == _length);
 224 
 225   if (!ret) {
 226     gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
 227     gclog_or_tty->print_cr("###   list has %u entries, _length is %u",
 228                            length, _length);
 229   }
 230 
 231   return ret;
 232 }
 233 
 234 bool YoungList::check_list_empty(bool check_sample) {
 235   bool ret = true;
 236 
 237   if (_length != 0) {
 238     gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u",
 239                   _length);
 240     ret = false;
 241   }
 242   if (check_sample && _last_sampled_rs_lengths != 0) {
 243     gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
 244     ret = false;
 245   }
 246   if (_head != NULL) {
 247     gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
 248     ret = false;
 249   }
 250   if (!ret) {
 251     gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
 252   }
 253 
 254   return ret;
 255 }
 256 
 257 void
 258 YoungList::rs_length_sampling_init() {
 259   _sampled_rs_lengths = 0;
 260   _curr               = _head;
 261 }
 262 
 263 bool
 264 YoungList::rs_length_sampling_more() {
 265   return _curr != NULL;
 266 }
 267 
 268 void
 269 YoungList::rs_length_sampling_next() {
 270   assert( _curr != NULL, "invariant" );
 271   size_t rs_length = _curr->rem_set()->occupied();
 272 
 273   _sampled_rs_lengths += rs_length;
 274 
 275   // The current region may not yet have been added to the
 276   // incremental collection set (it gets added when it is
 277   // retired as the current allocation region).
 278   if (_curr->in_collection_set()) {
 279     // Update the collection set policy information for this region
 280     _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
 281   }
 282 
 283   _curr = _curr->get_next_young_region();
 284   if (_curr == NULL) {
 285     _last_sampled_rs_lengths = _sampled_rs_lengths;
 286     // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
 287   }
 288 }
 289 
 290 void
 291 YoungList::reset_auxilary_lists() {
 292   guarantee( is_empty(), "young list should be empty" );
 293   assert(check_list_well_formed(), "young list should be well formed");
 294 
 295   // Add survivor regions to SurvRateGroup.
 296   _g1h->g1_policy()->note_start_adding_survivor_regions();
 297   _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
 298 
 299   int young_index_in_cset = 0;
 300   for (HeapRegion* curr = _survivor_head;
 301        curr != NULL;
 302        curr = curr->get_next_young_region()) {
 303     _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
 304 
 305     // The region is a non-empty survivor so let's add it to
 306     // the incremental collection set for the next evacuation
 307     // pause.
 308     _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
 309     young_index_in_cset += 1;
 310   }
 311   assert((uint) young_index_in_cset == _survivor_length, "post-condition");
 312   _g1h->g1_policy()->note_stop_adding_survivor_regions();
 313 
 314   _head   = _survivor_head;
 315   _length = _survivor_length;
 316   if (_survivor_head != NULL) {
 317     assert(_survivor_tail != NULL, "cause it shouldn't be");
 318     assert(_survivor_length > 0, "invariant");
 319     _survivor_tail->set_next_young_region(NULL);
 320   }
 321 
 322   // Don't clear the survivor list handles until the start of
 323   // the next evacuation pause - we need it in order to re-tag
 324   // the survivor regions from this evacuation pause as 'young'
 325   // at the start of the next.
 326 
 327   _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
 328 
 329   assert(check_list_well_formed(), "young list should be well formed");
 330 }
 331 
 332 void YoungList::print() {
 333   HeapRegion* lists[] = {_head,   _survivor_head};
 334   const char* names[] = {"YOUNG", "SURVIVOR"};
 335 
 336   for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) {
 337     gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
 338     HeapRegion *curr = lists[list];
 339     if (curr == NULL)
 340       gclog_or_tty->print_cr("  empty");
 341     while (curr != NULL) {
 342       gclog_or_tty->print_cr("  "HR_FORMAT", P: "PTR_FORMAT ", N: "PTR_FORMAT", age: %4d",
 343                              HR_FORMAT_PARAMS(curr),
 344                              curr->prev_top_at_mark_start(),
 345                              curr->next_top_at_mark_start(),
 346                              curr->age_in_surv_rate_group_cond());
 347       curr = curr->get_next_young_region();
 348     }
 349   }
 350 
 351   gclog_or_tty->cr();
 352 }
 353 
 354 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
 355   HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
 356 }
 357 
 358 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
 359   // The from card cache is not the memory that is actually committed. So we cannot
 360   // take advantage of the zero_filled parameter.
 361   reset_from_card_cache(start_idx, num_regions);
 362 }
 363 
 364 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
 365 {
 366   // Claim the right to put the region on the dirty cards region list
 367   // by installing a self pointer.
 368   HeapRegion* next = hr->get_next_dirty_cards_region();
 369   if (next == NULL) {
 370     HeapRegion* res = (HeapRegion*)
 371       Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
 372                           NULL);
 373     if (res == NULL) {
 374       HeapRegion* head;
 375       do {
 376         // Put the region to the dirty cards region list.
 377         head = _dirty_cards_region_list;
 378         next = (HeapRegion*)
 379           Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
 380         if (next == head) {
 381           assert(hr->get_next_dirty_cards_region() == hr,
 382                  "hr->get_next_dirty_cards_region() != hr");
 383           if (next == NULL) {
 384             // The last region in the list points to itself.
 385             hr->set_next_dirty_cards_region(hr);
 386           } else {
 387             hr->set_next_dirty_cards_region(next);
 388           }
 389         }
 390       } while (next != head);
 391     }
 392   }
 393 }
 394 
 395 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
 396 {
 397   HeapRegion* head;
 398   HeapRegion* hr;
 399   do {
 400     head = _dirty_cards_region_list;
 401     if (head == NULL) {
 402       return NULL;
 403     }
 404     HeapRegion* new_head = head->get_next_dirty_cards_region();
 405     if (head == new_head) {
 406       // The last region.
 407       new_head = NULL;
 408     }
 409     hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
 410                                           head);
 411   } while (hr != head);
 412   assert(hr != NULL, "invariant");
 413   hr->set_next_dirty_cards_region(NULL);
 414   return hr;
 415 }
 416 
 417 #ifdef ASSERT
 418 // A region is added to the collection set as it is retired
 419 // so an address p can point to a region which will be in the
 420 // collection set but has not yet been retired.  This method
 421 // therefore is only accurate during a GC pause after all
 422 // regions have been retired.  It is used for debugging
 423 // to check if an nmethod has references to objects that can
 424 // be move during a partial collection.  Though it can be
 425 // inaccurate, it is sufficient for G1 because the conservative
 426 // implementation of is_scavengable() for G1 will indicate that
 427 // all nmethods must be scanned during a partial collection.
 428 bool G1CollectedHeap::is_in_partial_collection(const void* p) {
 429   if (p == NULL) {
 430     return false;
 431   }
 432   return heap_region_containing(p)->in_collection_set();
 433 }
 434 #endif
 435 
 436 // Returns true if the reference points to an object that
 437 // can move in an incremental collection.
 438 bool G1CollectedHeap::is_scavengable(const void* p) {
 439   HeapRegion* hr = heap_region_containing(p);
 440   return !hr->is_humongous();
 441 }
 442 
 443 // Private class members.
 444 
 445 G1CollectedHeap* G1CollectedHeap::_g1h;
 446 
 447 // Private methods.
 448 
 449 HeapRegion*
 450 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
 451   MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
 452   while (!_secondary_free_list.is_empty() || free_regions_coming()) {
 453     if (!_secondary_free_list.is_empty()) {
 454       if (G1ConcRegionFreeingVerbose) {
 455         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 456                                "secondary_free_list has %u entries",
 457                                _secondary_free_list.length());
 458       }
 459       // It looks as if there are free regions available on the
 460       // secondary_free_list. Let's move them to the free_list and try
 461       // again to allocate from it.
 462       append_secondary_free_list();
 463 
 464       assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not "
 465              "empty we should have moved at least one entry to the free_list");
 466       HeapRegion* res = _hrm.allocate_free_region(is_old);
 467       if (G1ConcRegionFreeingVerbose) {
 468         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 469                                "allocated "HR_FORMAT" from secondary_free_list",
 470                                HR_FORMAT_PARAMS(res));
 471       }
 472       return res;
 473     }
 474 
 475     // Wait here until we get notified either when (a) there are no
 476     // more free regions coming or (b) some regions have been moved on
 477     // the secondary_free_list.
 478     SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
 479   }
 480 
 481   if (G1ConcRegionFreeingVerbose) {
 482     gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 483                            "could not allocate from secondary_free_list");
 484   }
 485   return NULL;
 486 }
 487 
 488 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
 489   assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
 490          "the only time we use this to allocate a humongous region is "
 491          "when we are allocating a single humongous region");
 492 
 493   HeapRegion* res;
 494   if (G1StressConcRegionFreeing) {
 495     if (!_secondary_free_list.is_empty()) {
 496       if (G1ConcRegionFreeingVerbose) {
 497         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 498                                "forced to look at the secondary_free_list");
 499       }
 500       res = new_region_try_secondary_free_list(is_old);
 501       if (res != NULL) {
 502         return res;
 503       }
 504     }
 505   }
 506 
 507   res = _hrm.allocate_free_region(is_old);
 508 
 509   if (res == NULL) {
 510     if (G1ConcRegionFreeingVerbose) {
 511       gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 512                              "res == NULL, trying the secondary_free_list");
 513     }
 514     res = new_region_try_secondary_free_list(is_old);
 515   }
 516   if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
 517     // Currently, only attempts to allocate GC alloc regions set
 518     // do_expand to true. So, we should only reach here during a
 519     // safepoint. If this assumption changes we might have to
 520     // reconsider the use of _expand_heap_after_alloc_failure.
 521     assert(SafepointSynchronize::is_at_safepoint(), "invariant");
 522 
 523     ergo_verbose1(ErgoHeapSizing,
 524                   "attempt heap expansion",
 525                   ergo_format_reason("region allocation request failed")
 526                   ergo_format_byte("allocation request"),
 527                   word_size * HeapWordSize);
 528     if (expand(word_size * HeapWordSize)) {
 529       // Given that expand() succeeded in expanding the heap, and we
 530       // always expand the heap by an amount aligned to the heap
 531       // region size, the free list should in theory not be empty.
 532       // In either case allocate_free_region() will check for NULL.
 533       res = _hrm.allocate_free_region(is_old);
 534     } else {
 535       _expand_heap_after_alloc_failure = false;
 536     }
 537   }
 538   return res;
 539 }
 540 
 541 HeapWord*
 542 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
 543                                                            uint num_regions,
 544                                                            size_t word_size,
 545                                                            AllocationContext_t context) {
 546   assert(first != G1_NO_HRM_INDEX, "pre-condition");
 547   assert(is_humongous(word_size), "word_size should be humongous");
 548   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 549 
 550   // Index of last region in the series + 1.
 551   uint last = first + num_regions;
 552 
 553   // We need to initialize the region(s) we just discovered. This is
 554   // a bit tricky given that it can happen concurrently with
 555   // refinement threads refining cards on these regions and
 556   // potentially wanting to refine the BOT as they are scanning
 557   // those cards (this can happen shortly after a cleanup; see CR
 558   // 6991377). So we have to set up the region(s) carefully and in
 559   // a specific order.
 560 
 561   // The word size sum of all the regions we will allocate.
 562   size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
 563   assert(word_size <= word_size_sum, "sanity");
 564 
 565   // This will be the "starts humongous" region.
 566   HeapRegion* first_hr = region_at(first);
 567   // The header of the new object will be placed at the bottom of
 568   // the first region.
 569   HeapWord* new_obj = first_hr->bottom();
 570   // This will be the new end of the first region in the series that
 571   // should also match the end of the last region in the series.
 572   HeapWord* new_end = new_obj + word_size_sum;
 573   // This will be the new top of the first region that will reflect
 574   // this allocation.
 575   HeapWord* new_top = new_obj + word_size;
 576 
 577   // First, we need to zero the header of the space that we will be
 578   // allocating. When we update top further down, some refinement
 579   // threads might try to scan the region. By zeroing the header we
 580   // ensure that any thread that will try to scan the region will
 581   // come across the zero klass word and bail out.
 582   //
 583   // NOTE: It would not have been correct to have used
 584   // CollectedHeap::fill_with_object() and make the space look like
 585   // an int array. The thread that is doing the allocation will
 586   // later update the object header to a potentially different array
 587   // type and, for a very short period of time, the klass and length
 588   // fields will be inconsistent. This could cause a refinement
 589   // thread to calculate the object size incorrectly.
 590   Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
 591 
 592   // We will set up the first region as "starts humongous". This
 593   // will also update the BOT covering all the regions to reflect
 594   // that there is a single object that starts at the bottom of the
 595   // first region.
 596   first_hr->set_starts_humongous(new_top, new_end);
 597   first_hr->set_allocation_context(context);
 598   // Then, if there are any, we will set up the "continues
 599   // humongous" regions.
 600   HeapRegion* hr = NULL;
 601   for (uint i = first + 1; i < last; ++i) {
 602     hr = region_at(i);
 603     hr->set_continues_humongous(first_hr);
 604     hr->set_allocation_context(context);
 605   }
 606   // If we have "continues humongous" regions (hr != NULL), then the
 607   // end of the last one should match new_end.
 608   assert(hr == NULL || hr->end() == new_end, "sanity");
 609 
 610   // Up to this point no concurrent thread would have been able to
 611   // do any scanning on any region in this series. All the top
 612   // fields still point to bottom, so the intersection between
 613   // [bottom,top] and [card_start,card_end] will be empty. Before we
 614   // update the top fields, we'll do a storestore to make sure that
 615   // no thread sees the update to top before the zeroing of the
 616   // object header and the BOT initialization.
 617   OrderAccess::storestore();
 618 
 619   // Now that the BOT and the object header have been initialized,
 620   // we can update top of the "starts humongous" region.
 621   assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
 622          "new_top should be in this region");
 623   first_hr->set_top(new_top);
 624   if (_hr_printer.is_active()) {
 625     HeapWord* bottom = first_hr->bottom();
 626     HeapWord* end = first_hr->orig_end();
 627     if ((first + 1) == last) {
 628       // the series has a single humongous region
 629       _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
 630     } else {
 631       // the series has more than one humongous regions
 632       _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
 633     }
 634   }
 635 
 636   // Now, we will update the top fields of the "continues humongous"
 637   // regions. The reason we need to do this is that, otherwise,
 638   // these regions would look empty and this will confuse parts of
 639   // G1. For example, the code that looks for a consecutive number
 640   // of empty regions will consider them empty and try to
 641   // re-allocate them. We can extend is_empty() to also include
 642   // !is_continues_humongous(), but it is easier to just update the top
 643   // fields here. The way we set top for all regions (i.e., top ==
 644   // end for all regions but the last one, top == new_top for the
 645   // last one) is actually used when we will free up the humongous
 646   // region in free_humongous_region().
 647   hr = NULL;
 648   for (uint i = first + 1; i < last; ++i) {
 649     hr = region_at(i);
 650     if ((i + 1) == last) {
 651       // last continues humongous region
 652       assert(hr->bottom() < new_top && new_top <= hr->end(),
 653              "new_top should fall on this region");
 654       hr->set_top(new_top);
 655       _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
 656     } else {
 657       // not last one
 658       assert(new_top > hr->end(), "new_top should be above this region");
 659       hr->set_top(hr->end());
 660       _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
 661     }
 662   }
 663   // If we have continues humongous regions (hr != NULL), then the
 664   // end of the last one should match new_end and its top should
 665   // match new_top.
 666   assert(hr == NULL ||
 667          (hr->end() == new_end && hr->top() == new_top), "sanity");
 668   check_bitmaps("Humongous Region Allocation", first_hr);
 669 
 670   assert(first_hr->used() == word_size * HeapWordSize, "invariant");
 671   _allocator->increase_used(first_hr->used());
 672   _humongous_set.add(first_hr);
 673 
 674   return new_obj;
 675 }
 676 
 677 // If could fit into free regions w/o expansion, try.
 678 // Otherwise, if can expand, do so.
 679 // Otherwise, if using ex regions might help, try with ex given back.
 680 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) {
 681   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 682 
 683   verify_region_sets_optional();
 684 
 685   uint first = G1_NO_HRM_INDEX;
 686   uint obj_regions = (uint)(align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords);
 687 
 688   if (obj_regions == 1) {
 689     // Only one region to allocate, try to use a fast path by directly allocating
 690     // from the free lists. Do not try to expand here, we will potentially do that
 691     // later.
 692     HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
 693     if (hr != NULL) {
 694       first = hr->hrm_index();
 695     }
 696   } else {
 697     // We can't allocate humongous regions spanning more than one region while
 698     // cleanupComplete() is running, since some of the regions we find to be
 699     // empty might not yet be added to the free list. It is not straightforward
 700     // to know in which list they are on so that we can remove them. We only
 701     // need to do this if we need to allocate more than one region to satisfy the
 702     // current humongous allocation request. If we are only allocating one region
 703     // we use the one-region region allocation code (see above), that already
 704     // potentially waits for regions from the secondary free list.
 705     wait_while_free_regions_coming();
 706     append_secondary_free_list_if_not_empty_with_lock();
 707 
 708     // Policy: Try only empty regions (i.e. already committed first). Maybe we
 709     // are lucky enough to find some.
 710     first = _hrm.find_contiguous_only_empty(obj_regions);
 711     if (first != G1_NO_HRM_INDEX) {
 712       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 713     }
 714   }
 715 
 716   if (first == G1_NO_HRM_INDEX) {
 717     // Policy: We could not find enough regions for the humongous object in the
 718     // free list. Look through the heap to find a mix of free and uncommitted regions.
 719     // If so, try expansion.
 720     first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
 721     if (first != G1_NO_HRM_INDEX) {
 722       // We found something. Make sure these regions are committed, i.e. expand
 723       // the heap. Alternatively we could do a defragmentation GC.
 724       ergo_verbose1(ErgoHeapSizing,
 725                     "attempt heap expansion",
 726                     ergo_format_reason("humongous allocation request failed")
 727                     ergo_format_byte("allocation request"),
 728                     word_size * HeapWordSize);
 729 
 730       _hrm.expand_at(first, obj_regions);
 731       g1_policy()->record_new_heap_size(num_regions());
 732 
 733 #ifdef ASSERT
 734       for (uint i = first; i < first + obj_regions; ++i) {
 735         HeapRegion* hr = region_at(i);
 736         assert(hr->is_free(), "sanity");
 737         assert(hr->is_empty(), "sanity");
 738         assert(is_on_master_free_list(hr), "sanity");
 739       }
 740 #endif
 741       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 742     } else {
 743       // Policy: Potentially trigger a defragmentation GC.
 744     }
 745   }
 746 
 747   HeapWord* result = NULL;
 748   if (first != G1_NO_HRM_INDEX) {
 749     result = humongous_obj_allocate_initialize_regions(first, obj_regions,
 750                                                        word_size, context);
 751     assert(result != NULL, "it should always return a valid result");
 752 
 753     // A successful humongous object allocation changes the used space
 754     // information of the old generation so we need to recalculate the
 755     // sizes and update the jstat counters here.
 756     g1mm()->update_sizes();
 757   }
 758 
 759   verify_region_sets_optional();
 760 
 761   return result;
 762 }
 763 
 764 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
 765   assert_heap_not_locked_and_not_at_safepoint();
 766   assert(!is_humongous(word_size), "we do not allow humongous TLABs");
 767 
 768   unsigned int dummy_gc_count_before;
 769   int dummy_gclocker_retry_count = 0;
 770   return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
 771 }
 772 
 773 HeapWord*
 774 G1CollectedHeap::mem_allocate(size_t word_size,
 775                               bool*  gc_overhead_limit_was_exceeded) {
 776   assert_heap_not_locked_and_not_at_safepoint();
 777 
 778   // Loop until the allocation is satisfied, or unsatisfied after GC.
 779   for (int try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 780     unsigned int gc_count_before;
 781 
 782     HeapWord* result = NULL;
 783     if (!is_humongous(word_size)) {
 784       result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
 785     } else {
 786       result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
 787     }
 788     if (result != NULL) {
 789       return result;
 790     }
 791 
 792     // Create the garbage collection operation...
 793     VM_G1CollectForAllocation op(gc_count_before, word_size);
 794     op.set_allocation_context(AllocationContext::current());
 795 
 796     // ...and get the VM thread to execute it.
 797     VMThread::execute(&op);
 798 
 799     if (op.prologue_succeeded() && op.pause_succeeded()) {
 800       // If the operation was successful we'll return the result even
 801       // if it is NULL. If the allocation attempt failed immediately
 802       // after a Full GC, it's unlikely we'll be able to allocate now.
 803       HeapWord* result = op.result();
 804       if (result != NULL && !is_humongous(word_size)) {
 805         // Allocations that take place on VM operations do not do any
 806         // card dirtying and we have to do it here. We only have to do
 807         // this for non-humongous allocations, though.
 808         dirty_young_block(result, word_size);
 809       }
 810       return result;
 811     } else {
 812       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 813         return NULL;
 814       }
 815       assert(op.result() == NULL,
 816              "the result should be NULL if the VM op did not succeed");
 817     }
 818 
 819     // Give a warning if we seem to be looping forever.
 820     if ((QueuedAllocationWarningCount > 0) &&
 821         (try_count % QueuedAllocationWarningCount == 0)) {
 822       warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
 823     }
 824   }
 825 
 826   ShouldNotReachHere();
 827   return NULL;
 828 }
 829 
 830 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
 831                                                    AllocationContext_t context,
 832                                                    unsigned int *gc_count_before_ret,
 833                                                    int* gclocker_retry_count_ret) {
 834   // Make sure you read the note in attempt_allocation_humongous().
 835 
 836   assert_heap_not_locked_and_not_at_safepoint();
 837   assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
 838          "be called for humongous allocation requests");
 839 
 840   // We should only get here after the first-level allocation attempt
 841   // (attempt_allocation()) failed to allocate.
 842 
 843   // We will loop until a) we manage to successfully perform the
 844   // allocation or b) we successfully schedule a collection which
 845   // fails to perform the allocation. b) is the only case when we'll
 846   // return NULL.
 847   HeapWord* result = NULL;
 848   for (int try_count = 1; /* we'll return */; try_count += 1) {
 849     bool should_try_gc;
 850     unsigned int gc_count_before;
 851 
 852     {
 853       MutexLockerEx x(Heap_lock);
 854       result = _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size,
 855                                                                                     false /* bot_updates */);
 856       if (result != NULL) {
 857         return result;
 858       }
 859 
 860       // If we reach here, attempt_allocation_locked() above failed to
 861       // allocate a new region. So the mutator alloc region should be NULL.
 862       assert(_allocator->mutator_alloc_region(context)->get() == NULL, "only way to get here");
 863 
 864       if (GC_locker::is_active_and_needs_gc()) {
 865         if (g1_policy()->can_expand_young_list()) {
 866           // No need for an ergo verbose message here,
 867           // can_expand_young_list() does this when it returns true.
 868           result = _allocator->mutator_alloc_region(context)->attempt_allocation_force(word_size,
 869                                                                                        false /* bot_updates */);
 870           if (result != NULL) {
 871             return result;
 872           }
 873         }
 874         should_try_gc = false;
 875       } else {
 876         // The GCLocker may not be active but the GCLocker initiated
 877         // GC may not yet have been performed (GCLocker::needs_gc()
 878         // returns true). In this case we do not try this GC and
 879         // wait until the GCLocker initiated GC is performed, and
 880         // then retry the allocation.
 881         if (GC_locker::needs_gc()) {
 882           should_try_gc = false;
 883         } else {
 884           // Read the GC count while still holding the Heap_lock.
 885           gc_count_before = total_collections();
 886           should_try_gc = true;
 887         }
 888       }
 889     }
 890 
 891     if (should_try_gc) {
 892       bool succeeded;
 893       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 894           GCCause::_g1_inc_collection_pause);
 895       if (result != NULL) {
 896         assert(succeeded, "only way to get back a non-NULL result");
 897         return result;
 898       }
 899 
 900       if (succeeded) {
 901         // If we get here we successfully scheduled a collection which
 902         // failed to allocate. No point in trying to allocate
 903         // further. We'll just return NULL.
 904         MutexLockerEx x(Heap_lock);
 905         *gc_count_before_ret = total_collections();
 906         return NULL;
 907       }
 908     } else {
 909       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
 910         MutexLockerEx x(Heap_lock);
 911         *gc_count_before_ret = total_collections();
 912         return NULL;
 913       }
 914       // The GCLocker is either active or the GCLocker initiated
 915       // GC has not yet been performed. Stall until it is and
 916       // then retry the allocation.
 917       GC_locker::stall_until_clear();
 918       (*gclocker_retry_count_ret) += 1;
 919     }
 920 
 921     // We can reach here if we were unsuccessful in scheduling a
 922     // collection (because another thread beat us to it) or if we were
 923     // stalled due to the GC locker. In either can we should retry the
 924     // allocation attempt in case another thread successfully
 925     // performed a collection and reclaimed enough space. We do the
 926     // first attempt (without holding the Heap_lock) here and the
 927     // follow-on attempt will be at the start of the next loop
 928     // iteration (after taking the Heap_lock).
 929     result = _allocator->mutator_alloc_region(context)->attempt_allocation(word_size,
 930                                                                            false /* bot_updates */);
 931     if (result != NULL) {
 932       return result;
 933     }
 934 
 935     // Give a warning if we seem to be looping forever.
 936     if ((QueuedAllocationWarningCount > 0) &&
 937         (try_count % QueuedAllocationWarningCount == 0)) {
 938       warning("G1CollectedHeap::attempt_allocation_slow() "
 939               "retries %d times", try_count);
 940     }
 941   }
 942 
 943   ShouldNotReachHere();
 944   return NULL;
 945 }
 946 
 947 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
 948                                                         unsigned int * gc_count_before_ret,
 949                                                         int* gclocker_retry_count_ret) {
 950   // The structure of this method has a lot of similarities to
 951   // attempt_allocation_slow(). The reason these two were not merged
 952   // into a single one is that such a method would require several "if
 953   // allocation is not humongous do this, otherwise do that"
 954   // conditional paths which would obscure its flow. In fact, an early
 955   // version of this code did use a unified method which was harder to
 956   // follow and, as a result, it had subtle bugs that were hard to
 957   // track down. So keeping these two methods separate allows each to
 958   // be more readable. It will be good to keep these two in sync as
 959   // much as possible.
 960 
 961   assert_heap_not_locked_and_not_at_safepoint();
 962   assert(is_humongous(word_size), "attempt_allocation_humongous() "
 963          "should only be called for humongous allocations");
 964 
 965   // Humongous objects can exhaust the heap quickly, so we should check if we
 966   // need to start a marking cycle at each humongous object allocation. We do
 967   // the check before we do the actual allocation. The reason for doing it
 968   // before the allocation is that we avoid having to keep track of the newly
 969   // allocated memory while we do a GC.
 970   if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
 971                                            word_size)) {
 972     collect(GCCause::_g1_humongous_allocation);
 973   }
 974 
 975   // We will loop until a) we manage to successfully perform the
 976   // allocation or b) we successfully schedule a collection which
 977   // fails to perform the allocation. b) is the only case when we'll
 978   // return NULL.
 979   HeapWord* result = NULL;
 980   for (int try_count = 1; /* we'll return */; try_count += 1) {
 981     bool should_try_gc;
 982     unsigned int gc_count_before;
 983 
 984     {
 985       MutexLockerEx x(Heap_lock);
 986 
 987       // Given that humongous objects are not allocated in young
 988       // regions, we'll first try to do the allocation without doing a
 989       // collection hoping that there's enough space in the heap.
 990       result = humongous_obj_allocate(word_size, AllocationContext::current());
 991       if (result != NULL) {
 992         return result;
 993       }
 994 
 995       if (GC_locker::is_active_and_needs_gc()) {
 996         should_try_gc = false;
 997       } else {
 998          // The GCLocker may not be active but the GCLocker initiated
 999         // GC may not yet have been performed (GCLocker::needs_gc()
1000         // returns true). In this case we do not try this GC and
1001         // wait until the GCLocker initiated GC is performed, and
1002         // then retry the allocation.
1003         if (GC_locker::needs_gc()) {
1004           should_try_gc = false;
1005         } else {
1006           // Read the GC count while still holding the Heap_lock.
1007           gc_count_before = total_collections();
1008           should_try_gc = true;
1009         }
1010       }
1011     }
1012 
1013     if (should_try_gc) {
1014       // If we failed to allocate the humongous object, we should try to
1015       // do a collection pause (if we're allowed) in case it reclaims
1016       // enough space for the allocation to succeed after the pause.
1017 
1018       bool succeeded;
1019       result = do_collection_pause(word_size, gc_count_before, &succeeded,
1020           GCCause::_g1_humongous_allocation);
1021       if (result != NULL) {
1022         assert(succeeded, "only way to get back a non-NULL result");
1023         return result;
1024       }
1025 
1026       if (succeeded) {
1027         // If we get here we successfully scheduled a collection which
1028         // failed to allocate. No point in trying to allocate
1029         // further. We'll just return NULL.
1030         MutexLockerEx x(Heap_lock);
1031         *gc_count_before_ret = total_collections();
1032         return NULL;
1033       }
1034     } else {
1035       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1036         MutexLockerEx x(Heap_lock);
1037         *gc_count_before_ret = total_collections();
1038         return NULL;
1039       }
1040       // The GCLocker is either active or the GCLocker initiated
1041       // GC has not yet been performed. Stall until it is and
1042       // then retry the allocation.
1043       GC_locker::stall_until_clear();
1044       (*gclocker_retry_count_ret) += 1;
1045     }
1046 
1047     // We can reach here if we were unsuccessful in scheduling a
1048     // collection (because another thread beat us to it) or if we were
1049     // stalled due to the GC locker. In either can we should retry the
1050     // allocation attempt in case another thread successfully
1051     // performed a collection and reclaimed enough space.  Give a
1052     // warning if we seem to be looping forever.
1053 
1054     if ((QueuedAllocationWarningCount > 0) &&
1055         (try_count % QueuedAllocationWarningCount == 0)) {
1056       warning("G1CollectedHeap::attempt_allocation_humongous() "
1057               "retries %d times", try_count);
1058     }
1059   }
1060 
1061   ShouldNotReachHere();
1062   return NULL;
1063 }
1064 
1065 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1066                                                            AllocationContext_t context,
1067                                                            bool expect_null_mutator_alloc_region) {
1068   assert_at_safepoint(true /* should_be_vm_thread */);
1069   assert(_allocator->mutator_alloc_region(context)->get() == NULL ||
1070                                              !expect_null_mutator_alloc_region,
1071          "the current alloc region was unexpectedly found to be non-NULL");
1072 
1073   if (!is_humongous(word_size)) {
1074     return _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size,
1075                                                       false /* bot_updates */);
1076   } else {
1077     HeapWord* result = humongous_obj_allocate(word_size, context);
1078     if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1079       g1_policy()->set_initiate_conc_mark_if_possible();
1080     }
1081     return result;
1082   }
1083 
1084   ShouldNotReachHere();
1085 }
1086 
1087 class PostMCRemSetClearClosure: public HeapRegionClosure {
1088   G1CollectedHeap* _g1h;
1089   ModRefBarrierSet* _mr_bs;
1090 public:
1091   PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1092     _g1h(g1h), _mr_bs(mr_bs) {}
1093 
1094   bool doHeapRegion(HeapRegion* r) {
1095     HeapRegionRemSet* hrrs = r->rem_set();
1096 
1097     if (r->is_continues_humongous()) {
1098       // We'll assert that the strong code root list and RSet is empty
1099       assert(hrrs->strong_code_roots_list_length() == 0, "sanity");
1100       assert(hrrs->occupied() == 0, "RSet should be empty");
1101       return false;
1102     }
1103 
1104     _g1h->reset_gc_time_stamps(r);
1105     hrrs->clear();
1106     // You might think here that we could clear just the cards
1107     // corresponding to the used region.  But no: if we leave a dirty card
1108     // in a region we might allocate into, then it would prevent that card
1109     // from being enqueued, and cause it to be missed.
1110     // Re: the performance cost: we shouldn't be doing full GC anyway!
1111     _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1112 
1113     return false;
1114   }
1115 };
1116 
1117 void G1CollectedHeap::clear_rsets_post_compaction() {
1118   PostMCRemSetClearClosure rs_clear(this, g1_barrier_set());
1119   heap_region_iterate(&rs_clear);
1120 }
1121 
1122 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1123   G1CollectedHeap*   _g1h;
1124   UpdateRSOopClosure _cl;
1125   int                _worker_i;
1126 public:
1127   RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1128     _cl(g1->g1_rem_set(), worker_i),
1129     _worker_i(worker_i),
1130     _g1h(g1)
1131   { }
1132 
1133   bool doHeapRegion(HeapRegion* r) {
1134     if (!r->is_continues_humongous()) {
1135       _cl.set_from(r);
1136       r->oop_iterate(&_cl);
1137     }
1138     return false;
1139   }
1140 };
1141 
1142 class ParRebuildRSTask: public AbstractGangTask {
1143   G1CollectedHeap* _g1;
1144   HeapRegionClaimer _hrclaimer;
1145 
1146 public:
1147   ParRebuildRSTask(G1CollectedHeap* g1) :
1148       AbstractGangTask("ParRebuildRSTask"), _g1(g1), _hrclaimer(g1->workers()->active_workers()) {}
1149 
1150   void work(uint worker_id) {
1151     RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1152     _g1->heap_region_par_iterate(&rebuild_rs, worker_id, &_hrclaimer);
1153   }
1154 };
1155 
1156 class PostCompactionPrinterClosure: public HeapRegionClosure {
1157 private:
1158   G1HRPrinter* _hr_printer;
1159 public:
1160   bool doHeapRegion(HeapRegion* hr) {
1161     assert(!hr->is_young(), "not expecting to find young regions");
1162     if (hr->is_free()) {
1163       // We only generate output for non-empty regions.
1164     } else if (hr->is_starts_humongous()) {
1165       if (hr->region_num() == 1) {
1166         // single humongous region
1167         _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
1168       } else {
1169         _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
1170       }
1171     } else if (hr->is_continues_humongous()) {
1172       _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1173     } else if (hr->is_old()) {
1174       _hr_printer->post_compaction(hr, G1HRPrinter::Old);
1175     } else {
1176       ShouldNotReachHere();
1177     }
1178     return false;
1179   }
1180 
1181   PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1182     : _hr_printer(hr_printer) { }
1183 };
1184 
1185 void G1CollectedHeap::print_hrm_post_compaction() {
1186   PostCompactionPrinterClosure cl(hr_printer());
1187   heap_region_iterate(&cl);
1188 }
1189 
1190 bool G1CollectedHeap::do_collection(bool explicit_gc,
1191                                     bool clear_all_soft_refs,
1192                                     size_t word_size) {
1193   assert_at_safepoint(true /* should_be_vm_thread */);
1194 
1195   if (GC_locker::check_active_before_gc()) {
1196     return false;
1197   }
1198 
1199   STWGCTimer* gc_timer = G1MarkSweep::gc_timer();
1200   gc_timer->register_gc_start();
1201 
1202   SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer();
1203   gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start());
1204 
1205   SvcGCMarker sgcm(SvcGCMarker::FULL);
1206   ResourceMark rm;
1207 
1208   print_heap_before_gc();
1209   trace_heap_before_gc(gc_tracer);
1210 
1211   size_t metadata_prev_used = MetaspaceAux::used_bytes();
1212 
1213   verify_region_sets_optional();
1214 
1215   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1216                            collector_policy()->should_clear_all_soft_refs();
1217 
1218   ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1219 
1220   {
1221     IsGCActiveMark x;
1222 
1223     // Timing
1224     assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant");
1225     TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
1226 
1227     {
1228       GCTraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, NULL, gc_tracer->gc_id());
1229       TraceCollectorStats tcs(g1mm()->full_collection_counters());
1230       TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1231 
1232       double start = os::elapsedTime();
1233       g1_policy()->record_full_collection_start();
1234 
1235       // Note: When we have a more flexible GC logging framework that
1236       // allows us to add optional attributes to a GC log record we
1237       // could consider timing and reporting how long we wait in the
1238       // following two methods.
1239       wait_while_free_regions_coming();
1240       // If we start the compaction before the CM threads finish
1241       // scanning the root regions we might trip them over as we'll
1242       // be moving objects / updating references. So let's wait until
1243       // they are done. By telling them to abort, they should complete
1244       // early.
1245       _cm->root_regions()->abort();
1246       _cm->root_regions()->wait_until_scan_finished();
1247       append_secondary_free_list_if_not_empty_with_lock();
1248 
1249       gc_prologue(true);
1250       increment_total_collections(true /* full gc */);
1251       increment_old_marking_cycles_started();
1252 
1253       assert(used() == recalculate_used(), "Should be equal");
1254 
1255       verify_before_gc();
1256 
1257       check_bitmaps("Full GC Start");
1258       pre_full_gc_dump(gc_timer);
1259 
1260       COMPILER2_PRESENT(DerivedPointerTable::clear());
1261 
1262       // Disable discovery and empty the discovered lists
1263       // for the CM ref processor.
1264       ref_processor_cm()->disable_discovery();
1265       ref_processor_cm()->abandon_partial_discovery();
1266       ref_processor_cm()->verify_no_references_recorded();
1267 
1268       // Abandon current iterations of concurrent marking and concurrent
1269       // refinement, if any are in progress. We have to do this before
1270       // wait_until_scan_finished() below.
1271       concurrent_mark()->abort();
1272 
1273       // Make sure we'll choose a new allocation region afterwards.
1274       _allocator->release_mutator_alloc_region();
1275       _allocator->abandon_gc_alloc_regions();
1276       g1_rem_set()->cleanupHRRS();
1277 
1278       // We should call this after we retire any currently active alloc
1279       // regions so that all the ALLOC / RETIRE events are generated
1280       // before the start GC event.
1281       _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1282 
1283       // We may have added regions to the current incremental collection
1284       // set between the last GC or pause and now. We need to clear the
1285       // incremental collection set and then start rebuilding it afresh
1286       // after this full GC.
1287       abandon_collection_set(g1_policy()->inc_cset_head());
1288       g1_policy()->clear_incremental_cset();
1289       g1_policy()->stop_incremental_cset_building();
1290 
1291       tear_down_region_sets(false /* free_list_only */);
1292       g1_policy()->set_gcs_are_young(true);
1293 
1294       // See the comments in g1CollectedHeap.hpp and
1295       // G1CollectedHeap::ref_processing_init() about
1296       // how reference processing currently works in G1.
1297 
1298       // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1299       ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1300 
1301       // Temporarily clear the STW ref processor's _is_alive_non_header field.
1302       ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1303 
1304       ref_processor_stw()->enable_discovery();
1305       ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1306 
1307       // Do collection work
1308       {
1309         HandleMark hm;  // Discard invalid handles created during gc
1310         G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1311       }
1312 
1313       assert(num_free_regions() == 0, "we should not have added any free regions");
1314       rebuild_region_sets(false /* free_list_only */);
1315 
1316       // Enqueue any discovered reference objects that have
1317       // not been removed from the discovered lists.
1318       ref_processor_stw()->enqueue_discovered_references();
1319 
1320       COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1321 
1322       MemoryService::track_memory_usage();
1323 
1324       assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1325       ref_processor_stw()->verify_no_references_recorded();
1326 
1327       // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1328       ClassLoaderDataGraph::purge();
1329       MetaspaceAux::verify_metrics();
1330 
1331       // Note: since we've just done a full GC, concurrent
1332       // marking is no longer active. Therefore we need not
1333       // re-enable reference discovery for the CM ref processor.
1334       // That will be done at the start of the next marking cycle.
1335       assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1336       ref_processor_cm()->verify_no_references_recorded();
1337 
1338       reset_gc_time_stamp();
1339       // Since everything potentially moved, we will clear all remembered
1340       // sets, and clear all cards.  Later we will rebuild remembered
1341       // sets. We will also reset the GC time stamps of the regions.
1342       clear_rsets_post_compaction();
1343       check_gc_time_stamps();
1344 
1345       // Resize the heap if necessary.
1346       resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1347 
1348       if (_hr_printer.is_active()) {
1349         // We should do this after we potentially resize the heap so
1350         // that all the COMMIT / UNCOMMIT events are generated before
1351         // the end GC event.
1352 
1353         print_hrm_post_compaction();
1354         _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1355       }
1356 
1357       G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
1358       if (hot_card_cache->use_cache()) {
1359         hot_card_cache->reset_card_counts();
1360         hot_card_cache->reset_hot_cache();
1361       }
1362 
1363       // Rebuild remembered sets of all regions.
1364       uint n_workers =
1365         AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1366                                                 workers()->active_workers(),
1367                                                 Threads::number_of_non_daemon_threads());
1368       assert(UseDynamicNumberOfGCThreads ||
1369              n_workers == workers()->total_workers(),
1370              "If not dynamic should be using all the  workers");
1371       workers()->set_active_workers(n_workers);
1372       // Set parallel threads in the heap (_n_par_threads) only
1373       // before a parallel phase and always reset it to 0 after
1374       // the phase so that the number of parallel threads does
1375       // no get carried forward to a serial phase where there
1376       // may be code that is "possibly_parallel".
1377       set_par_threads(n_workers);
1378 
1379       ParRebuildRSTask rebuild_rs_task(this);
1380       assert(UseDynamicNumberOfGCThreads ||
1381              workers()->active_workers() == workers()->total_workers(),
1382              "Unless dynamic should use total workers");
1383       // Use the most recent number of  active workers
1384       assert(workers()->active_workers() > 0,
1385              "Active workers not properly set");
1386       set_par_threads(workers()->active_workers());
1387       workers()->run_task(&rebuild_rs_task);
1388       set_par_threads(0);
1389 
1390       // Rebuild the strong code root lists for each region
1391       rebuild_strong_code_roots();
1392 
1393       if (true) { // FIXME
1394         MetaspaceGC::compute_new_size();
1395       }
1396 
1397 #ifdef TRACESPINNING
1398       ParallelTaskTerminator::print_termination_counts();
1399 #endif
1400 
1401       // Discard all rset updates
1402       JavaThread::dirty_card_queue_set().abandon_logs();
1403       assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1404 
1405       _young_list->reset_sampled_info();
1406       // At this point there should be no regions in the
1407       // entire heap tagged as young.
1408       assert(check_young_list_empty(true /* check_heap */),
1409              "young list should be empty at this point");
1410 
1411       // Update the number of full collections that have been completed.
1412       increment_old_marking_cycles_completed(false /* concurrent */);
1413 
1414       _hrm.verify_optional();
1415       verify_region_sets_optional();
1416 
1417       verify_after_gc();
1418 
1419       // Clear the previous marking bitmap, if needed for bitmap verification.
1420       // Note we cannot do this when we clear the next marking bitmap in
1421       // ConcurrentMark::abort() above since VerifyDuringGC verifies the
1422       // objects marked during a full GC against the previous bitmap.
1423       // But we need to clear it before calling check_bitmaps below since
1424       // the full GC has compacted objects and updated TAMS but not updated
1425       // the prev bitmap.
1426       if (G1VerifyBitmaps) {
1427         ((CMBitMap*) concurrent_mark()->prevMarkBitMap())->clearAll();
1428       }
1429       check_bitmaps("Full GC End");
1430 
1431       // Start a new incremental collection set for the next pause
1432       assert(g1_policy()->collection_set() == NULL, "must be");
1433       g1_policy()->start_incremental_cset_building();
1434 
1435       clear_cset_fast_test();
1436 
1437       _allocator->init_mutator_alloc_region();
1438 
1439       double end = os::elapsedTime();
1440       g1_policy()->record_full_collection_end();
1441 
1442       if (G1Log::fine()) {
1443         g1_policy()->print_heap_transition();
1444       }
1445 
1446       // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1447       // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1448       // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1449       // before any GC notifications are raised.
1450       g1mm()->update_sizes();
1451 
1452       gc_epilogue(true);
1453     }
1454 
1455     if (G1Log::finer()) {
1456       g1_policy()->print_detailed_heap_transition(true /* full */);
1457     }
1458 
1459     print_heap_after_gc();
1460     trace_heap_after_gc(gc_tracer);
1461 
1462     post_full_gc_dump(gc_timer);
1463 
1464     gc_timer->register_gc_end();
1465     gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
1466   }
1467 
1468   return true;
1469 }
1470 
1471 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1472   // do_collection() will return whether it succeeded in performing
1473   // the GC. Currently, there is no facility on the
1474   // do_full_collection() API to notify the caller than the collection
1475   // did not succeed (e.g., because it was locked out by the GC
1476   // locker). So, right now, we'll ignore the return value.
1477   bool dummy = do_collection(true,                /* explicit_gc */
1478                              clear_all_soft_refs,
1479                              0                    /* word_size */);
1480 }
1481 
1482 // This code is mostly copied from TenuredGeneration.
1483 void
1484 G1CollectedHeap::
1485 resize_if_necessary_after_full_collection(size_t word_size) {
1486   // Include the current allocation, if any, and bytes that will be
1487   // pre-allocated to support collections, as "used".
1488   const size_t used_after_gc = used();
1489   const size_t capacity_after_gc = capacity();
1490   const size_t free_after_gc = capacity_after_gc - used_after_gc;
1491 
1492   // This is enforced in arguments.cpp.
1493   assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1494          "otherwise the code below doesn't make sense");
1495 
1496   // We don't have floating point command-line arguments
1497   const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1498   const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1499   const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1500   const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1501 
1502   const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1503   const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1504 
1505   // We have to be careful here as these two calculations can overflow
1506   // 32-bit size_t's.
1507   double used_after_gc_d = (double) used_after_gc;
1508   double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1509   double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1510 
1511   // Let's make sure that they are both under the max heap size, which
1512   // by default will make them fit into a size_t.
1513   double desired_capacity_upper_bound = (double) max_heap_size;
1514   minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1515                                     desired_capacity_upper_bound);
1516   maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1517                                     desired_capacity_upper_bound);
1518 
1519   // We can now safely turn them into size_t's.
1520   size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1521   size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1522 
1523   // This assert only makes sense here, before we adjust them
1524   // with respect to the min and max heap size.
1525   assert(minimum_desired_capacity <= maximum_desired_capacity,
1526          err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1527                  "maximum_desired_capacity = "SIZE_FORMAT,
1528                  minimum_desired_capacity, maximum_desired_capacity));
1529 
1530   // Should not be greater than the heap max size. No need to adjust
1531   // it with respect to the heap min size as it's a lower bound (i.e.,
1532   // we'll try to make the capacity larger than it, not smaller).
1533   minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1534   // Should not be less than the heap min size. No need to adjust it
1535   // with respect to the heap max size as it's an upper bound (i.e.,
1536   // we'll try to make the capacity smaller than it, not greater).
1537   maximum_desired_capacity =  MAX2(maximum_desired_capacity, min_heap_size);
1538 
1539   if (capacity_after_gc < minimum_desired_capacity) {
1540     // Don't expand unless it's significant
1541     size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1542     ergo_verbose4(ErgoHeapSizing,
1543                   "attempt heap expansion",
1544                   ergo_format_reason("capacity lower than "
1545                                      "min desired capacity after Full GC")
1546                   ergo_format_byte("capacity")
1547                   ergo_format_byte("occupancy")
1548                   ergo_format_byte_perc("min desired capacity"),
1549                   capacity_after_gc, used_after_gc,
1550                   minimum_desired_capacity, (double) MinHeapFreeRatio);
1551     expand(expand_bytes);
1552 
1553     // No expansion, now see if we want to shrink
1554   } else if (capacity_after_gc > maximum_desired_capacity) {
1555     // Capacity too large, compute shrinking size
1556     size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1557     ergo_verbose4(ErgoHeapSizing,
1558                   "attempt heap shrinking",
1559                   ergo_format_reason("capacity higher than "
1560                                      "max desired capacity after Full GC")
1561                   ergo_format_byte("capacity")
1562                   ergo_format_byte("occupancy")
1563                   ergo_format_byte_perc("max desired capacity"),
1564                   capacity_after_gc, used_after_gc,
1565                   maximum_desired_capacity, (double) MaxHeapFreeRatio);
1566     shrink(shrink_bytes);
1567   }
1568 }
1569 
1570 
1571 HeapWord*
1572 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1573                                            AllocationContext_t context,
1574                                            bool* succeeded) {
1575   assert_at_safepoint(true /* should_be_vm_thread */);
1576 
1577   *succeeded = true;
1578   // Let's attempt the allocation first.
1579   HeapWord* result =
1580     attempt_allocation_at_safepoint(word_size,
1581                                     context,
1582                                     false /* expect_null_mutator_alloc_region */);
1583   if (result != NULL) {
1584     assert(*succeeded, "sanity");
1585     return result;
1586   }
1587 
1588   // In a G1 heap, we're supposed to keep allocation from failing by
1589   // incremental pauses.  Therefore, at least for now, we'll favor
1590   // expansion over collection.  (This might change in the future if we can
1591   // do something smarter than full collection to satisfy a failed alloc.)
1592   result = expand_and_allocate(word_size, context);
1593   if (result != NULL) {
1594     assert(*succeeded, "sanity");
1595     return result;
1596   }
1597 
1598   // Expansion didn't work, we'll try to do a Full GC.
1599   bool gc_succeeded = do_collection(false, /* explicit_gc */
1600                                     false, /* clear_all_soft_refs */
1601                                     word_size);
1602   if (!gc_succeeded) {
1603     *succeeded = false;
1604     return NULL;
1605   }
1606 
1607   // Retry the allocation
1608   result = attempt_allocation_at_safepoint(word_size,
1609                                            context,
1610                                            true /* expect_null_mutator_alloc_region */);
1611   if (result != NULL) {
1612     assert(*succeeded, "sanity");
1613     return result;
1614   }
1615 
1616   // Then, try a Full GC that will collect all soft references.
1617   gc_succeeded = do_collection(false, /* explicit_gc */
1618                                true,  /* clear_all_soft_refs */
1619                                word_size);
1620   if (!gc_succeeded) {
1621     *succeeded = false;
1622     return NULL;
1623   }
1624 
1625   // Retry the allocation once more
1626   result = attempt_allocation_at_safepoint(word_size,
1627                                            context,
1628                                            true /* expect_null_mutator_alloc_region */);
1629   if (result != NULL) {
1630     assert(*succeeded, "sanity");
1631     return result;
1632   }
1633 
1634   assert(!collector_policy()->should_clear_all_soft_refs(),
1635          "Flag should have been handled and cleared prior to this point");
1636 
1637   // What else?  We might try synchronous finalization later.  If the total
1638   // space available is large enough for the allocation, then a more
1639   // complete compaction phase than we've tried so far might be
1640   // appropriate.
1641   assert(*succeeded, "sanity");
1642   return NULL;
1643 }
1644 
1645 // Attempting to expand the heap sufficiently
1646 // to support an allocation of the given "word_size".  If
1647 // successful, perform the allocation and return the address of the
1648 // allocated block, or else "NULL".
1649 
1650 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) {
1651   assert_at_safepoint(true /* should_be_vm_thread */);
1652 
1653   verify_region_sets_optional();
1654 
1655   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1656   ergo_verbose1(ErgoHeapSizing,
1657                 "attempt heap expansion",
1658                 ergo_format_reason("allocation request failed")
1659                 ergo_format_byte("allocation request"),
1660                 word_size * HeapWordSize);
1661   if (expand(expand_bytes)) {
1662     _hrm.verify_optional();
1663     verify_region_sets_optional();
1664     return attempt_allocation_at_safepoint(word_size,
1665                                            context,
1666                                            false /* expect_null_mutator_alloc_region */);
1667   }
1668   return NULL;
1669 }
1670 
1671 bool G1CollectedHeap::expand(size_t expand_bytes) {
1672   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1673   aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1674                                        HeapRegion::GrainBytes);
1675   ergo_verbose2(ErgoHeapSizing,
1676                 "expand the heap",
1677                 ergo_format_byte("requested expansion amount")
1678                 ergo_format_byte("attempted expansion amount"),
1679                 expand_bytes, aligned_expand_bytes);
1680 
1681   if (is_maximal_no_gc()) {
1682     ergo_verbose0(ErgoHeapSizing,
1683                       "did not expand the heap",
1684                       ergo_format_reason("heap already fully expanded"));
1685     return false;
1686   }
1687 
1688   uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1689   assert(regions_to_expand > 0, "Must expand by at least one region");
1690 
1691   uint expanded_by = _hrm.expand_by(regions_to_expand);
1692 
1693   if (expanded_by > 0) {
1694     size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1695     assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1696     g1_policy()->record_new_heap_size(num_regions());
1697   } else {
1698     ergo_verbose0(ErgoHeapSizing,
1699                   "did not expand the heap",
1700                   ergo_format_reason("heap expansion operation failed"));
1701     // The expansion of the virtual storage space was unsuccessful.
1702     // Let's see if it was because we ran out of swap.
1703     if (G1ExitOnExpansionFailure &&
1704         _hrm.available() >= regions_to_expand) {
1705       // We had head room...
1706       vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1707     }
1708   }
1709   return regions_to_expand > 0;
1710 }
1711 
1712 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1713   size_t aligned_shrink_bytes =
1714     ReservedSpace::page_align_size_down(shrink_bytes);
1715   aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1716                                          HeapRegion::GrainBytes);
1717   uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1718 
1719   uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1720   size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1721 
1722   ergo_verbose3(ErgoHeapSizing,
1723                 "shrink the heap",
1724                 ergo_format_byte("requested shrinking amount")
1725                 ergo_format_byte("aligned shrinking amount")
1726                 ergo_format_byte("attempted shrinking amount"),
1727                 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1728   if (num_regions_removed > 0) {
1729     g1_policy()->record_new_heap_size(num_regions());
1730   } else {
1731     ergo_verbose0(ErgoHeapSizing,
1732                   "did not shrink the heap",
1733                   ergo_format_reason("heap shrinking operation failed"));
1734   }
1735 }
1736 
1737 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1738   verify_region_sets_optional();
1739 
1740   // We should only reach here at the end of a Full GC which means we
1741   // should not not be holding to any GC alloc regions. The method
1742   // below will make sure of that and do any remaining clean up.
1743   _allocator->abandon_gc_alloc_regions();
1744 
1745   // Instead of tearing down / rebuilding the free lists here, we
1746   // could instead use the remove_all_pending() method on free_list to
1747   // remove only the ones that we need to remove.
1748   tear_down_region_sets(true /* free_list_only */);
1749   shrink_helper(shrink_bytes);
1750   rebuild_region_sets(true /* free_list_only */);
1751 
1752   _hrm.verify_optional();
1753   verify_region_sets_optional();
1754 }
1755 
1756 // Public methods.
1757 
1758 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1759 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1760 #endif // _MSC_VER
1761 
1762 
1763 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1764   SharedHeap(policy_),
1765   _g1_policy(policy_),
1766   _dirty_card_queue_set(false),
1767   _into_cset_dirty_card_queue_set(false),
1768   _is_alive_closure_cm(this),
1769   _is_alive_closure_stw(this),
1770   _ref_processor_cm(NULL),
1771   _ref_processor_stw(NULL),
1772   _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
1773   _bot_shared(NULL),
1774   _evac_failure_scan_stack(NULL),
1775   _mark_in_progress(false),
1776   _cg1r(NULL),
1777   _g1mm(NULL),
1778   _refine_cte_cl(NULL),
1779   _full_collection(false),
1780   _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1781   _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1782   _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1783   _humongous_is_live(),
1784   _has_humongous_reclaim_candidates(false),
1785   _free_regions_coming(false),
1786   _young_list(new YoungList(this)),
1787   _gc_time_stamp(0),
1788   _survivor_plab_stats(YoungPLABSize, PLABWeight),
1789   _old_plab_stats(OldPLABSize, PLABWeight),
1790   _expand_heap_after_alloc_failure(true),
1791   _surviving_young_words(NULL),
1792   _old_marking_cycles_started(0),
1793   _old_marking_cycles_completed(0),
1794   _concurrent_cycle_started(false),
1795   _heap_summary_sent(false),
1796   _in_cset_fast_test(),
1797   _dirty_cards_region_list(NULL),
1798   _worker_cset_start_region(NULL),
1799   _worker_cset_start_region_time_stamp(NULL),
1800   _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1801   _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
1802   _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1803   _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) {
1804 
1805   _g1h = this;
1806   if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
1807     vm_exit_during_initialization("Failed necessary allocation.");
1808   }
1809 
1810   _allocator = G1Allocator::create_allocator(_g1h);
1811   _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1812 
1813   int n_queues = MAX2((int)ParallelGCThreads, 1);
1814   _task_queues = new RefToScanQueueSet(n_queues);
1815 
1816   uint n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1817   assert(n_rem_sets > 0, "Invariant.");
1818 
1819   _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1820   _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC);
1821   _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1822 
1823   for (int i = 0; i < n_queues; i++) {
1824     RefToScanQueue* q = new RefToScanQueue();
1825     q->initialize();
1826     _task_queues->register_queue(i, q);
1827     ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1828   }
1829   clear_cset_start_regions();
1830 
1831   // Initialize the G1EvacuationFailureALot counters and flags.
1832   NOT_PRODUCT(reset_evacuation_should_fail();)
1833 
1834   guarantee(_task_queues != NULL, "task_queues allocation failure.");
1835 }
1836 
1837 jint G1CollectedHeap::initialize() {
1838   CollectedHeap::pre_initialize();
1839   os::enable_vtime();
1840 
1841   G1Log::init();
1842 
1843   // Necessary to satisfy locking discipline assertions.
1844 
1845   MutexLocker x(Heap_lock);
1846 
1847   // We have to initialize the printer before committing the heap, as
1848   // it will be used then.
1849   _hr_printer.set_active(G1PrintHeapRegions);
1850 
1851   // While there are no constraints in the GC code that HeapWordSize
1852   // be any particular value, there are multiple other areas in the
1853   // system which believe this to be true (e.g. oop->object_size in some
1854   // cases incorrectly returns the size in wordSize units rather than
1855   // HeapWordSize).
1856   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1857 
1858   size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1859   size_t max_byte_size = collector_policy()->max_heap_byte_size();
1860   size_t heap_alignment = collector_policy()->heap_alignment();
1861 
1862   // Ensure that the sizes are properly aligned.
1863   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1864   Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1865   Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1866 
1867   _refine_cte_cl = new RefineCardTableEntryClosure();
1868 
1869   _cg1r = new ConcurrentG1Refine(this, _refine_cte_cl);
1870 
1871   // Reserve the maximum.
1872 
1873   // When compressed oops are enabled, the preferred heap base
1874   // is calculated by subtracting the requested size from the
1875   // 32Gb boundary and using the result as the base address for
1876   // heap reservation. If the requested size is not aligned to
1877   // HeapRegion::GrainBytes (i.e. the alignment that is passed
1878   // into the ReservedHeapSpace constructor) then the actual
1879   // base of the reserved heap may end up differing from the
1880   // address that was requested (i.e. the preferred heap base).
1881   // If this happens then we could end up using a non-optimal
1882   // compressed oops mode.
1883 
1884   ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1885                                                  heap_alignment);
1886 
1887   initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
1888 
1889   // Create the barrier set for the entire reserved region.
1890   G1SATBCardTableLoggingModRefBS* bs
1891     = new G1SATBCardTableLoggingModRefBS(reserved_region());
1892   bs->initialize();
1893   assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity");
1894   set_barrier_set(bs);
1895 
1896   // Also create a G1 rem set.
1897   _g1_rem_set = new G1RemSet(this, g1_barrier_set());
1898 
1899   // Carve out the G1 part of the heap.
1900 
1901   ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1902   G1RegionToSpaceMapper* heap_storage =
1903     G1RegionToSpaceMapper::create_mapper(g1_rs,
1904                                          UseLargePages ? os::large_page_size() : os::vm_page_size(),
1905                                          HeapRegion::GrainBytes,
1906                                          1,
1907                                          mtJavaHeap);
1908   heap_storage->set_mapping_changed_listener(&_listener);
1909 
1910   // Reserve space for the block offset table. We do not support automatic uncommit
1911   // for the card table at this time. BOT only.
1912   ReservedSpace bot_rs(G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize));
1913   G1RegionToSpaceMapper* bot_storage =
1914     G1RegionToSpaceMapper::create_mapper(bot_rs,
1915                                          os::vm_page_size(),
1916                                          HeapRegion::GrainBytes,
1917                                          G1BlockOffsetSharedArray::N_bytes,
1918                                          mtGC);
1919 
1920   ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize));
1921   G1RegionToSpaceMapper* cardtable_storage =
1922     G1RegionToSpaceMapper::create_mapper(cardtable_rs,
1923                                          os::vm_page_size(),
1924                                          HeapRegion::GrainBytes,
1925                                          G1BlockOffsetSharedArray::N_bytes,
1926                                          mtGC);
1927 
1928   // Reserve space for the card counts table.
1929   ReservedSpace card_counts_rs(G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize));
1930   G1RegionToSpaceMapper* card_counts_storage =
1931     G1RegionToSpaceMapper::create_mapper(card_counts_rs,
1932                                          os::vm_page_size(),
1933                                          HeapRegion::GrainBytes,
1934                                          G1BlockOffsetSharedArray::N_bytes,
1935                                          mtGC);
1936 
1937   // Reserve space for prev and next bitmap.
1938   size_t bitmap_size = CMBitMap::compute_size(g1_rs.size());
1939 
1940   ReservedSpace prev_bitmap_rs(ReservedSpace::allocation_align_size_up(bitmap_size));
1941   G1RegionToSpaceMapper* prev_bitmap_storage =
1942     G1RegionToSpaceMapper::create_mapper(prev_bitmap_rs,
1943                                          os::vm_page_size(),
1944                                          HeapRegion::GrainBytes,
1945                                          CMBitMap::mark_distance(),
1946                                          mtGC);
1947 
1948   ReservedSpace next_bitmap_rs(ReservedSpace::allocation_align_size_up(bitmap_size));
1949   G1RegionToSpaceMapper* next_bitmap_storage =
1950     G1RegionToSpaceMapper::create_mapper(next_bitmap_rs,
1951                                          os::vm_page_size(),
1952                                          HeapRegion::GrainBytes,
1953                                          CMBitMap::mark_distance(),
1954                                          mtGC);
1955 
1956   _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1957   g1_barrier_set()->initialize(cardtable_storage);
1958    // Do later initialization work for concurrent refinement.
1959   _cg1r->init(card_counts_storage);
1960 
1961   // 6843694 - ensure that the maximum region index can fit
1962   // in the remembered set structures.
1963   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1964   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1965 
1966   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1967   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1968   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1969             "too many cards per region");
1970 
1971   FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
1972 
1973   _bot_shared = new G1BlockOffsetSharedArray(reserved_region(), bot_storage);
1974 
1975   _g1h = this;
1976 
1977   _in_cset_fast_test.initialize(_hrm.reserved().start(), _hrm.reserved().end(), HeapRegion::GrainBytes);
1978   _humongous_is_live.initialize(_hrm.reserved().start(), _hrm.reserved().end(), HeapRegion::GrainBytes);
1979 
1980   // Create the ConcurrentMark data structure and thread.
1981   // (Must do this late, so that "max_regions" is defined.)
1982   _cm = new ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1983   if (_cm == NULL || !_cm->completed_initialization()) {
1984     vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark");
1985     return JNI_ENOMEM;
1986   }
1987   _cmThread = _cm->cmThread();
1988 
1989   // Initialize the from_card cache structure of HeapRegionRemSet.
1990   HeapRegionRemSet::init_heap(max_regions());
1991 
1992   // Now expand into the initial heap size.
1993   if (!expand(init_byte_size)) {
1994     vm_shutdown_during_initialization("Failed to allocate initial heap.");
1995     return JNI_ENOMEM;
1996   }
1997 
1998   // Perform any initialization actions delegated to the policy.
1999   g1_policy()->init();
2000 
2001   JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
2002                                                SATB_Q_FL_lock,
2003                                                G1SATBProcessCompletedThreshold,
2004                                                Shared_SATB_Q_lock);
2005 
2006   JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl,
2007                                                 DirtyCardQ_CBL_mon,
2008                                                 DirtyCardQ_FL_lock,
2009                                                 concurrent_g1_refine()->yellow_zone(),
2010                                                 concurrent_g1_refine()->red_zone(),
2011                                                 Shared_DirtyCardQ_lock);
2012 
2013   dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code
2014                                     DirtyCardQ_CBL_mon,
2015                                     DirtyCardQ_FL_lock,
2016                                     -1, // never trigger processing
2017                                     -1, // no limit on length
2018                                     Shared_DirtyCardQ_lock,
2019                                     &JavaThread::dirty_card_queue_set());
2020 
2021   // Initialize the card queue set used to hold cards containing
2022   // references into the collection set.
2023   _into_cset_dirty_card_queue_set.initialize(NULL, // Should never be called by the Java code
2024                                              DirtyCardQ_CBL_mon,
2025                                              DirtyCardQ_FL_lock,
2026                                              -1, // never trigger processing
2027                                              -1, // no limit on length
2028                                              Shared_DirtyCardQ_lock,
2029                                              &JavaThread::dirty_card_queue_set());
2030 
2031   // In case we're keeping closure specialization stats, initialize those
2032   // counts and that mechanism.
2033   SpecializationStats::clear();
2034 
2035   // Here we allocate the dummy HeapRegion that is required by the
2036   // G1AllocRegion class.
2037   HeapRegion* dummy_region = _hrm.get_dummy_region();
2038 
2039   // We'll re-use the same region whether the alloc region will
2040   // require BOT updates or not and, if it doesn't, then a non-young
2041   // region will complain that it cannot support allocations without
2042   // BOT updates. So we'll tag the dummy region as eden to avoid that.
2043   dummy_region->set_eden();
2044   // Make sure it's full.
2045   dummy_region->set_top(dummy_region->end());
2046   G1AllocRegion::setup(this, dummy_region);
2047 
2048   _allocator->init_mutator_alloc_region();
2049 
2050   // Do create of the monitoring and management support so that
2051   // values in the heap have been properly initialized.
2052   _g1mm = new G1MonitoringSupport(this);
2053 
2054   G1StringDedup::initialize();
2055 
2056   return JNI_OK;
2057 }
2058 
2059 void G1CollectedHeap::stop() {
2060   // Stop all concurrent threads. We do this to make sure these threads
2061   // do not continue to execute and access resources (e.g. gclog_or_tty)
2062   // that are destroyed during shutdown.
2063   _cg1r->stop();
2064   _cmThread->stop();
2065   if (G1StringDedup::is_enabled()) {
2066     G1StringDedup::stop();
2067   }
2068 }
2069 
2070 void G1CollectedHeap::clear_humongous_is_live_table() {
2071   guarantee(G1EagerReclaimHumongousObjects, "Should only be called if true");
2072   _humongous_is_live.clear();
2073 }
2074 
2075 size_t G1CollectedHeap::conservative_max_heap_alignment() {
2076   return HeapRegion::max_region_size();
2077 }
2078 
2079 void G1CollectedHeap::ref_processing_init() {
2080   // Reference processing in G1 currently works as follows:
2081   //
2082   // * There are two reference processor instances. One is
2083   //   used to record and process discovered references
2084   //   during concurrent marking; the other is used to
2085   //   record and process references during STW pauses
2086   //   (both full and incremental).
2087   // * Both ref processors need to 'span' the entire heap as
2088   //   the regions in the collection set may be dotted around.
2089   //
2090   // * For the concurrent marking ref processor:
2091   //   * Reference discovery is enabled at initial marking.
2092   //   * Reference discovery is disabled and the discovered
2093   //     references processed etc during remarking.
2094   //   * Reference discovery is MT (see below).
2095   //   * Reference discovery requires a barrier (see below).
2096   //   * Reference processing may or may not be MT
2097   //     (depending on the value of ParallelRefProcEnabled
2098   //     and ParallelGCThreads).
2099   //   * A full GC disables reference discovery by the CM
2100   //     ref processor and abandons any entries on it's
2101   //     discovered lists.
2102   //
2103   // * For the STW processor:
2104   //   * Non MT discovery is enabled at the start of a full GC.
2105   //   * Processing and enqueueing during a full GC is non-MT.
2106   //   * During a full GC, references are processed after marking.
2107   //
2108   //   * Discovery (may or may not be MT) is enabled at the start
2109   //     of an incremental evacuation pause.
2110   //   * References are processed near the end of a STW evacuation pause.
2111   //   * For both types of GC:
2112   //     * Discovery is atomic - i.e. not concurrent.
2113   //     * Reference discovery will not need a barrier.
2114 
2115   SharedHeap::ref_processing_init();
2116   MemRegion mr = reserved_region();
2117 
2118   // Concurrent Mark ref processor
2119   _ref_processor_cm =
2120     new ReferenceProcessor(mr,    // span
2121                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2122                                 // mt processing
2123                            (int) ParallelGCThreads,
2124                                 // degree of mt processing
2125                            (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2126                                 // mt discovery
2127                            (int) MAX2(ParallelGCThreads, ConcGCThreads),
2128                                 // degree of mt discovery
2129                            false,
2130                                 // Reference discovery is not atomic
2131                            &_is_alive_closure_cm);
2132                                 // is alive closure
2133                                 // (for efficiency/performance)
2134 
2135   // STW ref processor
2136   _ref_processor_stw =
2137     new ReferenceProcessor(mr,    // span
2138                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2139                                 // mt processing
2140                            MAX2((int)ParallelGCThreads, 1),
2141                                 // degree of mt processing
2142                            (ParallelGCThreads > 1),
2143                                 // mt discovery
2144                            MAX2((int)ParallelGCThreads, 1),
2145                                 // degree of mt discovery
2146                            true,
2147                                 // Reference discovery is atomic
2148                            &_is_alive_closure_stw);
2149                                 // is alive closure
2150                                 // (for efficiency/performance)
2151 }
2152 
2153 size_t G1CollectedHeap::capacity() const {
2154   return _hrm.length() * HeapRegion::GrainBytes;
2155 }
2156 
2157 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2158   assert(!hr->is_continues_humongous(), "pre-condition");
2159   hr->reset_gc_time_stamp();
2160   if (hr->is_starts_humongous()) {
2161     uint first_index = hr->hrm_index() + 1;
2162     uint last_index = hr->last_hc_index();
2163     for (uint i = first_index; i < last_index; i += 1) {
2164       HeapRegion* chr = region_at(i);
2165       assert(chr->is_continues_humongous(), "sanity");
2166       chr->reset_gc_time_stamp();
2167     }
2168   }
2169 }
2170 
2171 #ifndef PRODUCT
2172 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2173 private:
2174   unsigned _gc_time_stamp;
2175   bool _failures;
2176 
2177 public:
2178   CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2179     _gc_time_stamp(gc_time_stamp), _failures(false) { }
2180 
2181   virtual bool doHeapRegion(HeapRegion* hr) {
2182     unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2183     if (_gc_time_stamp != region_gc_time_stamp) {
2184       gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, "
2185                              "expected %d", HR_FORMAT_PARAMS(hr),
2186                              region_gc_time_stamp, _gc_time_stamp);
2187       _failures = true;
2188     }
2189     return false;
2190   }
2191 
2192   bool failures() { return _failures; }
2193 };
2194 
2195 void G1CollectedHeap::check_gc_time_stamps() {
2196   CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2197   heap_region_iterate(&cl);
2198   guarantee(!cl.failures(), "all GC time stamps should have been reset");
2199 }
2200 #endif // PRODUCT
2201 
2202 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2203                                                  DirtyCardQueue* into_cset_dcq,
2204                                                  bool concurrent,
2205                                                  uint worker_i) {
2206   // Clean cards in the hot card cache
2207   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
2208   hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq);
2209 
2210   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2211   int n_completed_buffers = 0;
2212   while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2213     n_completed_buffers++;
2214   }
2215   g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers);
2216   dcqs.clear_n_completed_buffers();
2217   assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2218 }
2219 
2220 
2221 // Computes the sum of the storage used by the various regions.
2222 size_t G1CollectedHeap::used() const {
2223   return _allocator->used();
2224 }
2225 
2226 size_t G1CollectedHeap::used_unlocked() const {
2227   return _allocator->used_unlocked();
2228 }
2229 
2230 class SumUsedClosure: public HeapRegionClosure {
2231   size_t _used;
2232 public:
2233   SumUsedClosure() : _used(0) {}
2234   bool doHeapRegion(HeapRegion* r) {
2235     if (!r->is_continues_humongous()) {
2236       _used += r->used();
2237     }
2238     return false;
2239   }
2240   size_t result() { return _used; }
2241 };
2242 
2243 size_t G1CollectedHeap::recalculate_used() const {
2244   double recalculate_used_start = os::elapsedTime();
2245 
2246   SumUsedClosure blk;
2247   heap_region_iterate(&blk);
2248 
2249   g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2250   return blk.result();
2251 }
2252 
2253 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2254   switch (cause) {
2255     case GCCause::_gc_locker:               return GCLockerInvokesConcurrent;
2256     case GCCause::_java_lang_system_gc:     return ExplicitGCInvokesConcurrent;
2257     case GCCause::_g1_humongous_allocation: return true;
2258     case GCCause::_update_allocation_context_stats_inc: return true;
2259     case GCCause::_wb_conc_mark:            return true;
2260     default:                                return false;
2261   }
2262 }
2263 
2264 #ifndef PRODUCT
2265 void G1CollectedHeap::allocate_dummy_regions() {
2266   // Let's fill up most of the region
2267   size_t word_size = HeapRegion::GrainWords - 1024;
2268   // And as a result the region we'll allocate will be humongous.
2269   guarantee(is_humongous(word_size), "sanity");
2270 
2271   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2272     // Let's use the existing mechanism for the allocation
2273     HeapWord* dummy_obj = humongous_obj_allocate(word_size,
2274                                                  AllocationContext::system());
2275     if (dummy_obj != NULL) {
2276       MemRegion mr(dummy_obj, word_size);
2277       CollectedHeap::fill_with_object(mr);
2278     } else {
2279       // If we can't allocate once, we probably cannot allocate
2280       // again. Let's get out of the loop.
2281       break;
2282     }
2283   }
2284 }
2285 #endif // !PRODUCT
2286 
2287 void G1CollectedHeap::increment_old_marking_cycles_started() {
2288   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2289     _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2290     err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2291     _old_marking_cycles_started, _old_marking_cycles_completed));
2292 
2293   _old_marking_cycles_started++;
2294 }
2295 
2296 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2297   MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2298 
2299   // We assume that if concurrent == true, then the caller is a
2300   // concurrent thread that was joined the Suspendible Thread
2301   // Set. If there's ever a cheap way to check this, we should add an
2302   // assert here.
2303 
2304   // Given that this method is called at the end of a Full GC or of a
2305   // concurrent cycle, and those can be nested (i.e., a Full GC can
2306   // interrupt a concurrent cycle), the number of full collections
2307   // completed should be either one (in the case where there was no
2308   // nesting) or two (when a Full GC interrupted a concurrent cycle)
2309   // behind the number of full collections started.
2310 
2311   // This is the case for the inner caller, i.e. a Full GC.
2312   assert(concurrent ||
2313          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2314          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2315          err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
2316                  "is inconsistent with _old_marking_cycles_completed = %u",
2317                  _old_marking_cycles_started, _old_marking_cycles_completed));
2318 
2319   // This is the case for the outer caller, i.e. the concurrent cycle.
2320   assert(!concurrent ||
2321          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2322          err_msg("for outer caller (concurrent cycle): "
2323                  "_old_marking_cycles_started = %u "
2324                  "is inconsistent with _old_marking_cycles_completed = %u",
2325                  _old_marking_cycles_started, _old_marking_cycles_completed));
2326 
2327   _old_marking_cycles_completed += 1;
2328 
2329   // We need to clear the "in_progress" flag in the CM thread before
2330   // we wake up any waiters (especially when ExplicitInvokesConcurrent
2331   // is set) so that if a waiter requests another System.gc() it doesn't
2332   // incorrectly see that a marking cycle is still in progress.
2333   if (concurrent) {
2334     _cmThread->clear_in_progress();
2335   }
2336 
2337   // This notify_all() will ensure that a thread that called
2338   // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2339   // and it's waiting for a full GC to finish will be woken up. It is
2340   // waiting in VM_G1IncCollectionPause::doit_epilogue().
2341   FullGCCount_lock->notify_all();
2342 }
2343 
2344 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) {
2345   _concurrent_cycle_started = true;
2346   _gc_timer_cm->register_gc_start(start_time);
2347 
2348   _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start());
2349   trace_heap_before_gc(_gc_tracer_cm);
2350 }
2351 
2352 void G1CollectedHeap::register_concurrent_cycle_end() {
2353   if (_concurrent_cycle_started) {
2354     if (_cm->has_aborted()) {
2355       _gc_tracer_cm->report_concurrent_mode_failure();
2356     }
2357 
2358     _gc_timer_cm->register_gc_end();
2359     _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
2360 
2361     // Clear state variables to prepare for the next concurrent cycle.
2362     _concurrent_cycle_started = false;
2363     _heap_summary_sent = false;
2364   }
2365 }
2366 
2367 void G1CollectedHeap::trace_heap_after_concurrent_cycle() {
2368   if (_concurrent_cycle_started) {
2369     // This function can be called when:
2370     //  the cleanup pause is run
2371     //  the concurrent cycle is aborted before the cleanup pause.
2372     //  the concurrent cycle is aborted after the cleanup pause,
2373     //   but before the concurrent cycle end has been registered.
2374     // Make sure that we only send the heap information once.
2375     if (!_heap_summary_sent) {
2376       trace_heap_after_gc(_gc_tracer_cm);
2377       _heap_summary_sent = true;
2378     }
2379   }
2380 }
2381 
2382 G1YCType G1CollectedHeap::yc_type() {
2383   bool is_young = g1_policy()->gcs_are_young();
2384   bool is_initial_mark = g1_policy()->during_initial_mark_pause();
2385   bool is_during_mark = mark_in_progress();
2386 
2387   if (is_initial_mark) {
2388     return InitialMark;
2389   } else if (is_during_mark) {
2390     return DuringMark;
2391   } else if (is_young) {
2392     return Normal;
2393   } else {
2394     return Mixed;
2395   }
2396 }
2397 
2398 void G1CollectedHeap::collect(GCCause::Cause cause) {
2399   assert_heap_not_locked();
2400 
2401   unsigned int gc_count_before;
2402   unsigned int old_marking_count_before;
2403   unsigned int full_gc_count_before;
2404   bool retry_gc;
2405 
2406   do {
2407     retry_gc = false;
2408 
2409     {
2410       MutexLocker ml(Heap_lock);
2411 
2412       // Read the GC count while holding the Heap_lock
2413       gc_count_before = total_collections();
2414       full_gc_count_before = total_full_collections();
2415       old_marking_count_before = _old_marking_cycles_started;
2416     }
2417 
2418     if (should_do_concurrent_full_gc(cause)) {
2419       // Schedule an initial-mark evacuation pause that will start a
2420       // concurrent cycle. We're setting word_size to 0 which means that
2421       // we are not requesting a post-GC allocation.
2422       VM_G1IncCollectionPause op(gc_count_before,
2423                                  0,     /* word_size */
2424                                  true,  /* should_initiate_conc_mark */
2425                                  g1_policy()->max_pause_time_ms(),
2426                                  cause);
2427       op.set_allocation_context(AllocationContext::current());
2428 
2429       VMThread::execute(&op);
2430       if (!op.pause_succeeded()) {
2431         if (old_marking_count_before == _old_marking_cycles_started) {
2432           retry_gc = op.should_retry_gc();
2433         } else {
2434           // A Full GC happened while we were trying to schedule the
2435           // initial-mark GC. No point in starting a new cycle given
2436           // that the whole heap was collected anyway.
2437         }
2438 
2439         if (retry_gc) {
2440           if (GC_locker::is_active_and_needs_gc()) {
2441             GC_locker::stall_until_clear();
2442           }
2443         }
2444       }
2445     } else {
2446       if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2447           DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2448 
2449         // Schedule a standard evacuation pause. We're setting word_size
2450         // to 0 which means that we are not requesting a post-GC allocation.
2451         VM_G1IncCollectionPause op(gc_count_before,
2452                                    0,     /* word_size */
2453                                    false, /* should_initiate_conc_mark */
2454                                    g1_policy()->max_pause_time_ms(),
2455                                    cause);
2456         VMThread::execute(&op);
2457       } else {
2458         // Schedule a Full GC.
2459         VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2460         VMThread::execute(&op);
2461       }
2462     }
2463   } while (retry_gc);
2464 }
2465 
2466 bool G1CollectedHeap::is_in(const void* p) const {
2467   if (_hrm.reserved().contains(p)) {
2468     // Given that we know that p is in the reserved space,
2469     // heap_region_containing_raw() should successfully
2470     // return the containing region.
2471     HeapRegion* hr = heap_region_containing_raw(p);
2472     return hr->is_in(p);
2473   } else {
2474     return false;
2475   }
2476 }
2477 
2478 #ifdef ASSERT
2479 bool G1CollectedHeap::is_in_exact(const void* p) const {
2480   bool contains = reserved_region().contains(p);
2481   bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2482   if (contains && available) {
2483     return true;
2484   } else {
2485     return false;
2486   }
2487 }
2488 #endif
2489 
2490 // Iteration functions.
2491 
2492 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion.
2493 
2494 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2495   ExtendedOopClosure* _cl;
2496 public:
2497   IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {}
2498   bool doHeapRegion(HeapRegion* r) {
2499     if (!r->is_continues_humongous()) {
2500       r->oop_iterate(_cl);
2501     }
2502     return false;
2503   }
2504 };
2505 
2506 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) {
2507   IterateOopClosureRegionClosure blk(cl);
2508   heap_region_iterate(&blk);
2509 }
2510 
2511 // Iterates an ObjectClosure over all objects within a HeapRegion.
2512 
2513 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2514   ObjectClosure* _cl;
2515 public:
2516   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2517   bool doHeapRegion(HeapRegion* r) {
2518     if (!r->is_continues_humongous()) {
2519       r->object_iterate(_cl);
2520     }
2521     return false;
2522   }
2523 };
2524 
2525 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2526   IterateObjectClosureRegionClosure blk(cl);
2527   heap_region_iterate(&blk);
2528 }
2529 
2530 // Calls a SpaceClosure on a HeapRegion.
2531 
2532 class SpaceClosureRegionClosure: public HeapRegionClosure {
2533   SpaceClosure* _cl;
2534 public:
2535   SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2536   bool doHeapRegion(HeapRegion* r) {
2537     _cl->do_space(r);
2538     return false;
2539   }
2540 };
2541 
2542 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2543   SpaceClosureRegionClosure blk(cl);
2544   heap_region_iterate(&blk);
2545 }
2546 
2547 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2548   _hrm.iterate(cl);
2549 }
2550 
2551 void
2552 G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl,
2553                                          uint worker_id,
2554                                          HeapRegionClaimer *hrclaimer,
2555                                          bool concurrent) const {
2556   _hrm.par_iterate(cl, worker_id, hrclaimer, concurrent);
2557 }
2558 
2559 // Clear the cached CSet starting regions and (more importantly)
2560 // the time stamps. Called when we reset the GC time stamp.
2561 void G1CollectedHeap::clear_cset_start_regions() {
2562   assert(_worker_cset_start_region != NULL, "sanity");
2563   assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2564 
2565   int n_queues = MAX2((int)ParallelGCThreads, 1);
2566   for (int i = 0; i < n_queues; i++) {
2567     _worker_cset_start_region[i] = NULL;
2568     _worker_cset_start_region_time_stamp[i] = 0;
2569   }
2570 }
2571 
2572 // Given the id of a worker, obtain or calculate a suitable
2573 // starting region for iterating over the current collection set.
2574 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) {
2575   assert(get_gc_time_stamp() > 0, "should have been updated by now");
2576 
2577   HeapRegion* result = NULL;
2578   unsigned gc_time_stamp = get_gc_time_stamp();
2579 
2580   if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2581     // Cached starting region for current worker was set
2582     // during the current pause - so it's valid.
2583     // Note: the cached starting heap region may be NULL
2584     // (when the collection set is empty).
2585     result = _worker_cset_start_region[worker_i];
2586     assert(result == NULL || result->in_collection_set(), "sanity");
2587     return result;
2588   }
2589 
2590   // The cached entry was not valid so let's calculate
2591   // a suitable starting heap region for this worker.
2592 
2593   // We want the parallel threads to start their collection
2594   // set iteration at different collection set regions to
2595   // avoid contention.
2596   // If we have:
2597   //          n collection set regions
2598   //          p threads
2599   // Then thread t will start at region floor ((t * n) / p)
2600 
2601   result = g1_policy()->collection_set();
2602   uint cs_size = g1_policy()->cset_region_length();
2603   uint active_workers = workers()->active_workers();
2604   assert(UseDynamicNumberOfGCThreads ||
2605            active_workers == workers()->total_workers(),
2606            "Unless dynamic should use total workers");
2607 
2608   uint end_ind   = (cs_size * worker_i) / active_workers;
2609   uint start_ind = 0;
2610 
2611   if (worker_i > 0 &&
2612       _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2613     // Previous workers starting region is valid
2614     // so let's iterate from there
2615     start_ind = (cs_size * (worker_i - 1)) / active_workers;
2616     result = _worker_cset_start_region[worker_i - 1];
2617   }
2618 
2619   for (uint i = start_ind; i < end_ind; i++) {
2620     result = result->next_in_collection_set();
2621   }
2622 
2623   // Note: the calculated starting heap region may be NULL
2624   // (when the collection set is empty).
2625   assert(result == NULL || result->in_collection_set(), "sanity");
2626   assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2627          "should be updated only once per pause");
2628   _worker_cset_start_region[worker_i] = result;
2629   OrderAccess::storestore();
2630   _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2631   return result;
2632 }
2633 
2634 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2635   HeapRegion* r = g1_policy()->collection_set();
2636   while (r != NULL) {
2637     HeapRegion* next = r->next_in_collection_set();
2638     if (cl->doHeapRegion(r)) {
2639       cl->incomplete();
2640       return;
2641     }
2642     r = next;
2643   }
2644 }
2645 
2646 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2647                                                   HeapRegionClosure *cl) {
2648   if (r == NULL) {
2649     // The CSet is empty so there's nothing to do.
2650     return;
2651   }
2652 
2653   assert(r->in_collection_set(),
2654          "Start region must be a member of the collection set.");
2655   HeapRegion* cur = r;
2656   while (cur != NULL) {
2657     HeapRegion* next = cur->next_in_collection_set();
2658     if (cl->doHeapRegion(cur) && false) {
2659       cl->incomplete();
2660       return;
2661     }
2662     cur = next;
2663   }
2664   cur = g1_policy()->collection_set();
2665   while (cur != r) {
2666     HeapRegion* next = cur->next_in_collection_set();
2667     if (cl->doHeapRegion(cur) && false) {
2668       cl->incomplete();
2669       return;
2670     }
2671     cur = next;
2672   }
2673 }
2674 
2675 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const {
2676   HeapRegion* result = _hrm.next_region_in_heap(from);
2677   while (result != NULL && result->is_humongous()) {
2678     result = _hrm.next_region_in_heap(result);
2679   }
2680   return result;
2681 }
2682 
2683 Space* G1CollectedHeap::space_containing(const void* addr) const {
2684   return heap_region_containing(addr);
2685 }
2686 
2687 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2688   Space* sp = space_containing(addr);
2689   return sp->block_start(addr);
2690 }
2691 
2692 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2693   Space* sp = space_containing(addr);
2694   return sp->block_size(addr);
2695 }
2696 
2697 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2698   Space* sp = space_containing(addr);
2699   return sp->block_is_obj(addr);
2700 }
2701 
2702 bool G1CollectedHeap::supports_tlab_allocation() const {
2703   return true;
2704 }
2705 
2706 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2707   return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes;
2708 }
2709 
2710 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2711   return young_list()->eden_used_bytes();
2712 }
2713 
2714 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2715 // must be smaller than the humongous object limit.
2716 size_t G1CollectedHeap::max_tlab_size() const {
2717   return align_size_down(_humongous_object_threshold_in_words - 1, MinObjAlignment);
2718 }
2719 
2720 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2721   // Return the remaining space in the cur alloc region, but not less than
2722   // the min TLAB size.
2723 
2724   // Also, this value can be at most the humongous object threshold,
2725   // since we can't allow tlabs to grow big enough to accommodate
2726   // humongous objects.
2727 
2728   HeapRegion* hr = _allocator->mutator_alloc_region(AllocationContext::current())->get();
2729   size_t max_tlab = max_tlab_size() * wordSize;
2730   if (hr == NULL) {
2731     return max_tlab;
2732   } else {
2733     return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab);
2734   }
2735 }
2736 
2737 size_t G1CollectedHeap::max_capacity() const {
2738   return _hrm.reserved().byte_size();
2739 }
2740 
2741 jlong G1CollectedHeap::millis_since_last_gc() {
2742   // assert(false, "NYI");
2743   return 0;
2744 }
2745 
2746 void G1CollectedHeap::prepare_for_verify() {
2747   if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
2748     ensure_parsability(false);
2749   }
2750   g1_rem_set()->prepare_for_verify();
2751 }
2752 
2753 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr,
2754                                               VerifyOption vo) {
2755   switch (vo) {
2756   case VerifyOption_G1UsePrevMarking:
2757     return hr->obj_allocated_since_prev_marking(obj);
2758   case VerifyOption_G1UseNextMarking:
2759     return hr->obj_allocated_since_next_marking(obj);
2760   case VerifyOption_G1UseMarkWord:
2761     return false;
2762   default:
2763     ShouldNotReachHere();
2764   }
2765   return false; // keep some compilers happy
2766 }
2767 
2768 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) {
2769   switch (vo) {
2770   case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start();
2771   case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start();
2772   case VerifyOption_G1UseMarkWord:    return NULL;
2773   default:                            ShouldNotReachHere();
2774   }
2775   return NULL; // keep some compilers happy
2776 }
2777 
2778 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) {
2779   switch (vo) {
2780   case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj);
2781   case VerifyOption_G1UseNextMarking: return isMarkedNext(obj);
2782   case VerifyOption_G1UseMarkWord:    return obj->is_gc_marked();
2783   default:                            ShouldNotReachHere();
2784   }
2785   return false; // keep some compilers happy
2786 }
2787 
2788 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) {
2789   switch (vo) {
2790   case VerifyOption_G1UsePrevMarking: return "PTAMS";
2791   case VerifyOption_G1UseNextMarking: return "NTAMS";
2792   case VerifyOption_G1UseMarkWord:    return "NONE";
2793   default:                            ShouldNotReachHere();
2794   }
2795   return NULL; // keep some compilers happy
2796 }
2797 
2798 class VerifyRootsClosure: public OopClosure {
2799 private:
2800   G1CollectedHeap* _g1h;
2801   VerifyOption     _vo;
2802   bool             _failures;
2803 public:
2804   // _vo == UsePrevMarking -> use "prev" marking information,
2805   // _vo == UseNextMarking -> use "next" marking information,
2806   // _vo == UseMarkWord    -> use mark word from object header.
2807   VerifyRootsClosure(VerifyOption vo) :
2808     _g1h(G1CollectedHeap::heap()),
2809     _vo(vo),
2810     _failures(false) { }
2811 
2812   bool failures() { return _failures; }
2813 
2814   template <class T> void do_oop_nv(T* p) {
2815     T heap_oop = oopDesc::load_heap_oop(p);
2816     if (!oopDesc::is_null(heap_oop)) {
2817       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2818       if (_g1h->is_obj_dead_cond(obj, _vo)) {
2819         gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
2820                               "points to dead obj "PTR_FORMAT, p, (void*) obj);
2821         if (_vo == VerifyOption_G1UseMarkWord) {
2822           gclog_or_tty->print_cr("  Mark word: "PTR_FORMAT, (void*)(obj->mark()));
2823         }
2824         obj->print_on(gclog_or_tty);
2825         _failures = true;
2826       }
2827     }
2828   }
2829 
2830   void do_oop(oop* p)       { do_oop_nv(p); }
2831   void do_oop(narrowOop* p) { do_oop_nv(p); }
2832 };
2833 
2834 class G1VerifyCodeRootOopClosure: public OopClosure {
2835   G1CollectedHeap* _g1h;
2836   OopClosure* _root_cl;
2837   nmethod* _nm;
2838   VerifyOption _vo;
2839   bool _failures;
2840 
2841   template <class T> void do_oop_work(T* p) {
2842     // First verify that this root is live
2843     _root_cl->do_oop(p);
2844 
2845     if (!G1VerifyHeapRegionCodeRoots) {
2846       // We're not verifying the code roots attached to heap region.
2847       return;
2848     }
2849 
2850     // Don't check the code roots during marking verification in a full GC
2851     if (_vo == VerifyOption_G1UseMarkWord) {
2852       return;
2853     }
2854 
2855     // Now verify that the current nmethod (which contains p) is
2856     // in the code root list of the heap region containing the
2857     // object referenced by p.
2858 
2859     T heap_oop = oopDesc::load_heap_oop(p);
2860     if (!oopDesc::is_null(heap_oop)) {
2861       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2862 
2863       // Now fetch the region containing the object
2864       HeapRegion* hr = _g1h->heap_region_containing(obj);
2865       HeapRegionRemSet* hrrs = hr->rem_set();
2866       // Verify that the strong code root list for this region
2867       // contains the nmethod
2868       if (!hrrs->strong_code_roots_list_contains(_nm)) {
2869         gclog_or_tty->print_cr("Code root location "PTR_FORMAT" "
2870                               "from nmethod "PTR_FORMAT" not in strong "
2871                               "code roots for region ["PTR_FORMAT","PTR_FORMAT")",
2872                               p, _nm, hr->bottom(), hr->end());
2873         _failures = true;
2874       }
2875     }
2876   }
2877 
2878 public:
2879   G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo):
2880     _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {}
2881 
2882   void do_oop(oop* p) { do_oop_work(p); }
2883   void do_oop(narrowOop* p) { do_oop_work(p); }
2884 
2885   void set_nmethod(nmethod* nm) { _nm = nm; }
2886   bool failures() { return _failures; }
2887 };
2888 
2889 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure {
2890   G1VerifyCodeRootOopClosure* _oop_cl;
2891 
2892 public:
2893   G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl):
2894     _oop_cl(oop_cl) {}
2895 
2896   void do_code_blob(CodeBlob* cb) {
2897     nmethod* nm = cb->as_nmethod_or_null();
2898     if (nm != NULL) {
2899       _oop_cl->set_nmethod(nm);
2900       nm->oops_do(_oop_cl);
2901     }
2902   }
2903 };
2904 
2905 class YoungRefCounterClosure : public OopClosure {
2906   G1CollectedHeap* _g1h;
2907   int              _count;
2908  public:
2909   YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {}
2910   void do_oop(oop* p)       { if (_g1h->is_in_young(*p)) { _count++; } }
2911   void do_oop(narrowOop* p) { ShouldNotReachHere(); }
2912 
2913   int count() { return _count; }
2914   void reset_count() { _count = 0; };
2915 };
2916 
2917 class VerifyKlassClosure: public KlassClosure {
2918   YoungRefCounterClosure _young_ref_counter_closure;
2919   OopClosure *_oop_closure;
2920  public:
2921   VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {}
2922   void do_klass(Klass* k) {
2923     k->oops_do(_oop_closure);
2924 
2925     _young_ref_counter_closure.reset_count();
2926     k->oops_do(&_young_ref_counter_closure);
2927     if (_young_ref_counter_closure.count() > 0) {
2928       guarantee(k->has_modified_oops(), err_msg("Klass " PTR_FORMAT ", has young refs but is not dirty.", k));
2929     }
2930   }
2931 };
2932 
2933 class VerifyLivenessOopClosure: public OopClosure {
2934   G1CollectedHeap* _g1h;
2935   VerifyOption _vo;
2936 public:
2937   VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
2938     _g1h(g1h), _vo(vo)
2939   { }
2940   void do_oop(narrowOop *p) { do_oop_work(p); }
2941   void do_oop(      oop *p) { do_oop_work(p); }
2942 
2943   template <class T> void do_oop_work(T *p) {
2944     oop obj = oopDesc::load_decode_heap_oop(p);
2945     guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
2946               "Dead object referenced by a not dead object");
2947   }
2948 };
2949 
2950 class VerifyObjsInRegionClosure: public ObjectClosure {
2951 private:
2952   G1CollectedHeap* _g1h;
2953   size_t _live_bytes;
2954   HeapRegion *_hr;
2955   VerifyOption _vo;
2956 public:
2957   // _vo == UsePrevMarking -> use "prev" marking information,
2958   // _vo == UseNextMarking -> use "next" marking information,
2959   // _vo == UseMarkWord    -> use mark word from object header.
2960   VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
2961     : _live_bytes(0), _hr(hr), _vo(vo) {
2962     _g1h = G1CollectedHeap::heap();
2963   }
2964   void do_object(oop o) {
2965     VerifyLivenessOopClosure isLive(_g1h, _vo);
2966     assert(o != NULL, "Huh?");
2967     if (!_g1h->is_obj_dead_cond(o, _vo)) {
2968       // If the object is alive according to the mark word,
2969       // then verify that the marking information agrees.
2970       // Note we can't verify the contra-positive of the
2971       // above: if the object is dead (according to the mark
2972       // word), it may not be marked, or may have been marked
2973       // but has since became dead, or may have been allocated
2974       // since the last marking.
2975       if (_vo == VerifyOption_G1UseMarkWord) {
2976         guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
2977       }
2978 
2979       o->oop_iterate_no_header(&isLive);
2980       if (!_hr->obj_allocated_since_prev_marking(o)) {
2981         size_t obj_size = o->size();    // Make sure we don't overflow
2982         _live_bytes += (obj_size * HeapWordSize);
2983       }
2984     }
2985   }
2986   size_t live_bytes() { return _live_bytes; }
2987 };
2988 
2989 class PrintObjsInRegionClosure : public ObjectClosure {
2990   HeapRegion *_hr;
2991   G1CollectedHeap *_g1;
2992 public:
2993   PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
2994     _g1 = G1CollectedHeap::heap();
2995   };
2996 
2997   void do_object(oop o) {
2998     if (o != NULL) {
2999       HeapWord *start = (HeapWord *) o;
3000       size_t word_sz = o->size();
3001       gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
3002                           " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
3003                           (void*) o, word_sz,
3004                           _g1->isMarkedPrev(o),
3005                           _g1->isMarkedNext(o),
3006                           _hr->obj_allocated_since_prev_marking(o));
3007       HeapWord *end = start + word_sz;
3008       HeapWord *cur;
3009       int *val;
3010       for (cur = start; cur < end; cur++) {
3011         val = (int *) cur;
3012         gclog_or_tty->print("\t "PTR_FORMAT":%d\n", val, *val);
3013       }
3014     }
3015   }
3016 };
3017 
3018 class VerifyRegionClosure: public HeapRegionClosure {
3019 private:
3020   bool             _par;
3021   VerifyOption     _vo;
3022   bool             _failures;
3023 public:
3024   // _vo == UsePrevMarking -> use "prev" marking information,
3025   // _vo == UseNextMarking -> use "next" marking information,
3026   // _vo == UseMarkWord    -> use mark word from object header.
3027   VerifyRegionClosure(bool par, VerifyOption vo)
3028     : _par(par),
3029       _vo(vo),
3030       _failures(false) {}
3031 
3032   bool failures() {
3033     return _failures;
3034   }
3035 
3036   bool doHeapRegion(HeapRegion* r) {
3037     if (!r->is_continues_humongous()) {
3038       bool failures = false;
3039       r->verify(_vo, &failures);
3040       if (failures) {
3041         _failures = true;
3042       } else {
3043         VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
3044         r->object_iterate(&not_dead_yet_cl);
3045         if (_vo != VerifyOption_G1UseNextMarking) {
3046           if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
3047             gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
3048                                    "max_live_bytes "SIZE_FORMAT" "
3049                                    "< calculated "SIZE_FORMAT,
3050                                    r->bottom(), r->end(),
3051                                    r->max_live_bytes(),
3052                                  not_dead_yet_cl.live_bytes());
3053             _failures = true;
3054           }
3055         } else {
3056           // When vo == UseNextMarking we cannot currently do a sanity
3057           // check on the live bytes as the calculation has not been
3058           // finalized yet.
3059         }
3060       }
3061     }
3062     return false; // stop the region iteration if we hit a failure
3063   }
3064 };
3065 
3066 // This is the task used for parallel verification of the heap regions
3067 
3068 class G1ParVerifyTask: public AbstractGangTask {
3069 private:
3070   G1CollectedHeap*  _g1h;
3071   VerifyOption      _vo;
3072   bool              _failures;
3073   HeapRegionClaimer _hrclaimer;
3074 
3075 public:
3076   // _vo == UsePrevMarking -> use "prev" marking information,
3077   // _vo == UseNextMarking -> use "next" marking information,
3078   // _vo == UseMarkWord    -> use mark word from object header.
3079   G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
3080       AbstractGangTask("Parallel verify task"),
3081       _g1h(g1h),
3082       _vo(vo),
3083       _failures(false),
3084       _hrclaimer(g1h->workers()->active_workers()) {}
3085 
3086   bool failures() {
3087     return _failures;
3088   }
3089 
3090   void work(uint worker_id) {
3091     HandleMark hm;
3092     VerifyRegionClosure blk(true, _vo);
3093     _g1h->heap_region_par_iterate(&blk, worker_id, &_hrclaimer);
3094     if (blk.failures()) {
3095       _failures = true;
3096     }
3097   }
3098 };
3099 
3100 void G1CollectedHeap::verify(bool silent, VerifyOption vo) {
3101   if (SafepointSynchronize::is_at_safepoint()) {
3102     assert(Thread::current()->is_VM_thread(),
3103            "Expected to be executed serially by the VM thread at this point");
3104 
3105     if (!silent) { gclog_or_tty->print("Roots "); }
3106     VerifyRootsClosure rootsCl(vo);
3107     VerifyKlassClosure klassCl(this, &rootsCl);
3108     CLDToKlassAndOopClosure cldCl(&klassCl, &rootsCl, false);
3109 
3110     // We apply the relevant closures to all the oops in the
3111     // system dictionary, class loader data graph, the string table
3112     // and the nmethods in the code cache.
3113     G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo);
3114     G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl);
3115 
3116     process_all_roots(true,            // activate StrongRootsScope
3117                       SO_AllCodeCache, // roots scanning options
3118                       &rootsCl,
3119                       &cldCl,
3120                       &blobsCl);
3121 
3122     bool failures = rootsCl.failures() || codeRootsCl.failures();
3123 
3124     if (vo != VerifyOption_G1UseMarkWord) {
3125       // If we're verifying during a full GC then the region sets
3126       // will have been torn down at the start of the GC. Therefore
3127       // verifying the region sets will fail. So we only verify
3128       // the region sets when not in a full GC.
3129       if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3130       verify_region_sets();
3131     }
3132 
3133     if (!silent) { gclog_or_tty->print("HeapRegions "); }
3134     if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3135 
3136       G1ParVerifyTask task(this, vo);
3137       assert(UseDynamicNumberOfGCThreads ||
3138         workers()->active_workers() == workers()->total_workers(),
3139         "If not dynamic should be using all the workers");
3140       int n_workers = workers()->active_workers();
3141       set_par_threads(n_workers);
3142       workers()->run_task(&task);
3143       set_par_threads(0);
3144       if (task.failures()) {
3145         failures = true;
3146       }
3147 
3148     } else {
3149       VerifyRegionClosure blk(false, vo);
3150       heap_region_iterate(&blk);
3151       if (blk.failures()) {
3152         failures = true;
3153       }
3154     }
3155 
3156     if (G1StringDedup::is_enabled()) {
3157       if (!silent) gclog_or_tty->print("StrDedup ");
3158       G1StringDedup::verify();
3159     }
3160 
3161     if (failures) {
3162       gclog_or_tty->print_cr("Heap:");
3163       // It helps to have the per-region information in the output to
3164       // help us track down what went wrong. This is why we call
3165       // print_extended_on() instead of print_on().
3166       print_extended_on(gclog_or_tty);
3167       gclog_or_tty->cr();
3168 #ifndef PRODUCT
3169       if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3170         concurrent_mark()->print_reachable("at-verification-failure",
3171                                            vo, false /* all */);
3172       }
3173 #endif
3174       gclog_or_tty->flush();
3175     }
3176     guarantee(!failures, "there should not have been any failures");
3177   } else {
3178     if (!silent) {
3179       gclog_or_tty->print("(SKIPPING Roots, HeapRegionSets, HeapRegions, RemSet");
3180       if (G1StringDedup::is_enabled()) {
3181         gclog_or_tty->print(", StrDedup");
3182       }
3183       gclog_or_tty->print(") ");
3184     }
3185   }
3186 }
3187 
3188 void G1CollectedHeap::verify(bool silent) {
3189   verify(silent, VerifyOption_G1UsePrevMarking);
3190 }
3191 
3192 double G1CollectedHeap::verify(bool guard, const char* msg) {
3193   double verify_time_ms = 0.0;
3194 
3195   if (guard && total_collections() >= VerifyGCStartAt) {
3196     double verify_start = os::elapsedTime();
3197     HandleMark hm;  // Discard invalid handles created during verification
3198     prepare_for_verify();
3199     Universe::verify(VerifyOption_G1UsePrevMarking, msg);
3200     verify_time_ms = (os::elapsedTime() - verify_start) * 1000;
3201   }
3202 
3203   return verify_time_ms;
3204 }
3205 
3206 void G1CollectedHeap::verify_before_gc() {
3207   double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:");
3208   g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms);
3209 }
3210 
3211 void G1CollectedHeap::verify_after_gc() {
3212   double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:");
3213   g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms);
3214 }
3215 
3216 class PrintRegionClosure: public HeapRegionClosure {
3217   outputStream* _st;
3218 public:
3219   PrintRegionClosure(outputStream* st) : _st(st) {}
3220   bool doHeapRegion(HeapRegion* r) {
3221     r->print_on(_st);
3222     return false;
3223   }
3224 };
3225 
3226 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3227                                        const HeapRegion* hr,
3228                                        const VerifyOption vo) const {
3229   switch (vo) {
3230   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
3231   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
3232   case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked();
3233   default:                            ShouldNotReachHere();
3234   }
3235   return false; // keep some compilers happy
3236 }
3237 
3238 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3239                                        const VerifyOption vo) const {
3240   switch (vo) {
3241   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
3242   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
3243   case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked();
3244   default:                            ShouldNotReachHere();
3245   }
3246   return false; // keep some compilers happy
3247 }
3248 
3249 void G1CollectedHeap::print_on(outputStream* st) const {
3250   st->print(" %-20s", "garbage-first heap");
3251   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3252             capacity()/K, used_unlocked()/K);
3253   st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3254             _hrm.reserved().start(),
3255             _hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords,
3256             _hrm.reserved().end());
3257   st->cr();
3258   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3259   uint young_regions = _young_list->length();
3260   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3261             (size_t) young_regions * HeapRegion::GrainBytes / K);
3262   uint survivor_regions = g1_policy()->recorded_survivor_regions();
3263   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3264             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3265   st->cr();
3266   MetaspaceAux::print_on(st);
3267 }
3268 
3269 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3270   print_on(st);
3271 
3272   // Print the per-region information.
3273   st->cr();
3274   st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3275                "HS=humongous(starts), HC=humongous(continues), "
3276                "CS=collection set, F=free, TS=gc time stamp, "
3277                "PTAMS=previous top-at-mark-start, "
3278                "NTAMS=next top-at-mark-start)");
3279   PrintRegionClosure blk(st);
3280   heap_region_iterate(&blk);
3281 }
3282 
3283 void G1CollectedHeap::print_on_error(outputStream* st) const {
3284   this->CollectedHeap::print_on_error(st);
3285 
3286   if (_cm != NULL) {
3287     st->cr();
3288     _cm->print_on_error(st);
3289   }
3290 }
3291 
3292 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3293   workers()->print_worker_threads_on(st);
3294   _cmThread->print_on(st);
3295   st->cr();
3296   _cm->print_worker_threads_on(st);
3297   _cg1r->print_worker_threads_on(st);
3298   if (G1StringDedup::is_enabled()) {
3299     G1StringDedup::print_worker_threads_on(st);
3300   }
3301 }
3302 
3303 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3304   workers()->threads_do(tc);
3305   tc->do_thread(_cmThread);
3306   _cg1r->threads_do(tc);
3307   if (G1StringDedup::is_enabled()) {
3308     G1StringDedup::threads_do(tc);
3309   }
3310 }
3311 
3312 void G1CollectedHeap::print_tracing_info() const {
3313   // We'll overload this to mean "trace GC pause statistics."
3314   if (TraceYoungGenTime || TraceOldGenTime) {
3315     // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3316     // to that.
3317     g1_policy()->print_tracing_info();
3318   }
3319   if (G1SummarizeRSetStats) {
3320     g1_rem_set()->print_summary_info();
3321   }
3322   if (G1SummarizeConcMark) {
3323     concurrent_mark()->print_summary_info();
3324   }
3325   g1_policy()->print_yg_surv_rate_info();
3326   SpecializationStats::print();
3327 }
3328 
3329 #ifndef PRODUCT
3330 // Helpful for debugging RSet issues.
3331 
3332 class PrintRSetsClosure : public HeapRegionClosure {
3333 private:
3334   const char* _msg;
3335   size_t _occupied_sum;
3336 
3337 public:
3338   bool doHeapRegion(HeapRegion* r) {
3339     HeapRegionRemSet* hrrs = r->rem_set();
3340     size_t occupied = hrrs->occupied();
3341     _occupied_sum += occupied;
3342 
3343     gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3344                            HR_FORMAT_PARAMS(r));
3345     if (occupied == 0) {
3346       gclog_or_tty->print_cr("  RSet is empty");
3347     } else {
3348       hrrs->print();
3349     }
3350     gclog_or_tty->print_cr("----------");
3351     return false;
3352   }
3353 
3354   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3355     gclog_or_tty->cr();
3356     gclog_or_tty->print_cr("========================================");
3357     gclog_or_tty->print_cr("%s", msg);
3358     gclog_or_tty->cr();
3359   }
3360 
3361   ~PrintRSetsClosure() {
3362     gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3363     gclog_or_tty->print_cr("========================================");
3364     gclog_or_tty->cr();
3365   }
3366 };
3367 
3368 void G1CollectedHeap::print_cset_rsets() {
3369   PrintRSetsClosure cl("Printing CSet RSets");
3370   collection_set_iterate(&cl);
3371 }
3372 
3373 void G1CollectedHeap::print_all_rsets() {
3374   PrintRSetsClosure cl("Printing All RSets");;
3375   heap_region_iterate(&cl);
3376 }
3377 #endif // PRODUCT
3378 
3379 G1CollectedHeap* G1CollectedHeap::heap() {
3380   assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3381          "not a garbage-first heap");
3382   return _g1h;
3383 }
3384 
3385 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3386   // always_do_update_barrier = false;
3387   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3388   // Fill TLAB's and such
3389   accumulate_statistics_all_tlabs();
3390   ensure_parsability(true);
3391 
3392   if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) &&
3393       (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3394     g1_rem_set()->print_periodic_summary_info("Before GC RS summary");
3395   }
3396 }
3397 
3398 void G1CollectedHeap::gc_epilogue(bool full) {
3399 
3400   if (G1SummarizeRSetStats &&
3401       (G1SummarizeRSetStatsPeriod > 0) &&
3402       // we are at the end of the GC. Total collections has already been increased.
3403       ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) {
3404     g1_rem_set()->print_periodic_summary_info("After GC RS summary");
3405   }
3406 
3407   // FIXME: what is this about?
3408   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3409   // is set.
3410   COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3411                         "derived pointer present"));
3412   // always_do_update_barrier = true;
3413 
3414   resize_all_tlabs();
3415   allocation_context_stats().update(full);
3416 
3417   // We have just completed a GC. Update the soft reference
3418   // policy with the new heap occupancy
3419   Universe::update_heap_info_at_gc();
3420 }
3421 
3422 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3423                                                unsigned int gc_count_before,
3424                                                bool* succeeded,
3425                                                GCCause::Cause gc_cause) {
3426   assert_heap_not_locked_and_not_at_safepoint();
3427   g1_policy()->record_stop_world_start();
3428   VM_G1IncCollectionPause op(gc_count_before,
3429                              word_size,
3430                              false, /* should_initiate_conc_mark */
3431                              g1_policy()->max_pause_time_ms(),
3432                              gc_cause);
3433 
3434   op.set_allocation_context(AllocationContext::current());
3435   VMThread::execute(&op);
3436 
3437   HeapWord* result = op.result();
3438   bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3439   assert(result == NULL || ret_succeeded,
3440          "the result should be NULL if the VM did not succeed");
3441   *succeeded = ret_succeeded;
3442 
3443   assert_heap_not_locked();
3444   return result;
3445 }
3446 
3447 void
3448 G1CollectedHeap::doConcurrentMark() {
3449   MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3450   if (!_cmThread->in_progress()) {
3451     _cmThread->set_started();
3452     CGC_lock->notify();
3453   }
3454 }
3455 
3456 size_t G1CollectedHeap::pending_card_num() {
3457   size_t extra_cards = 0;
3458   JavaThread *curr = Threads::first();
3459   while (curr != NULL) {
3460     DirtyCardQueue& dcq = curr->dirty_card_queue();
3461     extra_cards += dcq.size();
3462     curr = curr->next();
3463   }
3464   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3465   size_t buffer_size = dcqs.buffer_size();
3466   size_t buffer_num = dcqs.completed_buffers_num();
3467 
3468   // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
3469   // in bytes - not the number of 'entries'. We need to convert
3470   // into a number of cards.
3471   return (buffer_size * buffer_num + extra_cards) / oopSize;
3472 }
3473 
3474 size_t G1CollectedHeap::cards_scanned() {
3475   return g1_rem_set()->cardsScanned();
3476 }
3477 
3478 bool G1CollectedHeap::humongous_region_is_always_live(uint index) {
3479   HeapRegion* region = region_at(index);
3480   assert(region->is_starts_humongous(), "Must start a humongous object");
3481   return oop(region->bottom())->is_objArray() || !region->rem_set()->is_empty();
3482 }
3483 
3484 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
3485  private:
3486   size_t _total_humongous;
3487   size_t _candidate_humongous;
3488 
3489   DirtyCardQueue _dcq;
3490 
3491   bool humongous_region_is_candidate(uint index) {
3492     HeapRegion* region = G1CollectedHeap::heap()->region_at(index);
3493     assert(region->is_starts_humongous(), "Must start a humongous object");
3494     HeapRegionRemSet* const rset = region->rem_set();
3495     bool const allow_stale_refs = G1EagerReclaimHumongousObjectsWithStaleRefs;
3496     return !oop(region->bottom())->is_objArray() &&
3497            ((allow_stale_refs && rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries)) ||
3498             (!allow_stale_refs && rset->is_empty()));
3499   }
3500 
3501  public:
3502   RegisterHumongousWithInCSetFastTestClosure()
3503   : _total_humongous(0),
3504     _candidate_humongous(0),
3505     _dcq(&JavaThread::dirty_card_queue_set()) {
3506   }
3507 
3508   virtual bool doHeapRegion(HeapRegion* r) {
3509     if (!r->is_starts_humongous()) {
3510       return false;
3511     }
3512     G1CollectedHeap* g1h = G1CollectedHeap::heap();
3513 
3514     uint region_idx = r->hrm_index();
3515     bool is_candidate = humongous_region_is_candidate(region_idx);
3516     // Is_candidate already filters out humongous object with large remembered sets.
3517     // If we have a humongous object with a few remembered sets, we simply flush these
3518     // remembered set entries into the DCQS. That will result in automatic
3519     // re-evaluation of their remembered set entries during the following evacuation
3520     // phase.
3521     if (is_candidate) {
3522       if (!r->rem_set()->is_empty()) {
3523         guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
3524                   "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
3525         G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set();
3526         HeapRegionRemSetIterator hrrs(r->rem_set());
3527         size_t card_index;
3528         while (hrrs.has_next(card_index)) {
3529           jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index);
3530           if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
3531             *card_ptr = CardTableModRefBS::dirty_card_val();
3532             _dcq.enqueue(card_ptr);
3533           }
3534         }
3535         r->rem_set()->clear_locked();
3536       }
3537       assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
3538       g1h->register_humongous_region_with_in_cset_fast_test(region_idx);
3539       _candidate_humongous++;
3540     }
3541     _total_humongous++;
3542 
3543     return false;
3544   }
3545 
3546   size_t total_humongous() const { return _total_humongous; }
3547   size_t candidate_humongous() const { return _candidate_humongous; }
3548 
3549   void flush_rem_set_entries() { _dcq.flush(); }
3550 };
3551 
3552 void G1CollectedHeap::register_humongous_regions_with_in_cset_fast_test() {
3553   if (!G1EagerReclaimHumongousObjects) {
3554     g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
3555     return;
3556   }
3557   double time = os::elapsed_counter();
3558 
3559   RegisterHumongousWithInCSetFastTestClosure cl;
3560   heap_region_iterate(&cl);
3561 
3562   time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
3563   g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
3564                                                                   cl.total_humongous(),
3565                                                                   cl.candidate_humongous());
3566   _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
3567 
3568   if (_has_humongous_reclaim_candidates || G1TraceEagerReclaimHumongousObjects) {
3569     clear_humongous_is_live_table();
3570   }
3571 
3572   // Finally flush all remembered set entries to re-check into the global DCQS.
3573   cl.flush_rem_set_entries();
3574 }
3575 
3576 void
3577 G1CollectedHeap::setup_surviving_young_words() {
3578   assert(_surviving_young_words == NULL, "pre-condition");
3579   uint array_length = g1_policy()->young_cset_region_length();
3580   _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3581   if (_surviving_young_words == NULL) {
3582     vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR,
3583                           "Not enough space for young surv words summary.");
3584   }
3585   memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3586 #ifdef ASSERT
3587   for (uint i = 0;  i < array_length; ++i) {
3588     assert( _surviving_young_words[i] == 0, "memset above" );
3589   }
3590 #endif // !ASSERT
3591 }
3592 
3593 void
3594 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3595   MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3596   uint array_length = g1_policy()->young_cset_region_length();
3597   for (uint i = 0; i < array_length; ++i) {
3598     _surviving_young_words[i] += surv_young_words[i];
3599   }
3600 }
3601 
3602 void
3603 G1CollectedHeap::cleanup_surviving_young_words() {
3604   guarantee( _surviving_young_words != NULL, "pre-condition" );
3605   FREE_C_HEAP_ARRAY(size_t, _surviving_young_words);
3606   _surviving_young_words = NULL;
3607 }
3608 
3609 #ifdef ASSERT
3610 class VerifyCSetClosure: public HeapRegionClosure {
3611 public:
3612   bool doHeapRegion(HeapRegion* hr) {
3613     // Here we check that the CSet region's RSet is ready for parallel
3614     // iteration. The fields that we'll verify are only manipulated
3615     // when the region is part of a CSet and is collected. Afterwards,
3616     // we reset these fields when we clear the region's RSet (when the
3617     // region is freed) so they are ready when the region is
3618     // re-allocated. The only exception to this is if there's an
3619     // evacuation failure and instead of freeing the region we leave
3620     // it in the heap. In that case, we reset these fields during
3621     // evacuation failure handling.
3622     guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3623 
3624     // Here's a good place to add any other checks we'd like to
3625     // perform on CSet regions.
3626     return false;
3627   }
3628 };
3629 #endif // ASSERT
3630 
3631 #if TASKQUEUE_STATS
3632 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3633   st->print_raw_cr("GC Task Stats");
3634   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3635   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3636 }
3637 
3638 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3639   print_taskqueue_stats_hdr(st);
3640 
3641   TaskQueueStats totals;
3642   const int n = workers()->total_workers();
3643   for (int i = 0; i < n; ++i) {
3644     st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3645     totals += task_queue(i)->stats;
3646   }
3647   st->print_raw("tot "); totals.print(st); st->cr();
3648 
3649   DEBUG_ONLY(totals.verify());
3650 }
3651 
3652 void G1CollectedHeap::reset_taskqueue_stats() {
3653   const int n = workers()->total_workers();
3654   for (int i = 0; i < n; ++i) {
3655     task_queue(i)->stats.reset();
3656   }
3657 }
3658 #endif // TASKQUEUE_STATS
3659 
3660 void G1CollectedHeap::log_gc_header() {
3661   if (!G1Log::fine()) {
3662     return;
3663   }
3664 
3665   gclog_or_tty->gclog_stamp(_gc_tracer_stw->gc_id());
3666 
3667   GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
3668     .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)")
3669     .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : "");
3670 
3671   gclog_or_tty->print("[%s", (const char*)gc_cause_str);
3672 }
3673 
3674 void G1CollectedHeap::log_gc_footer(double pause_time_sec) {
3675   if (!G1Log::fine()) {
3676     return;
3677   }
3678 
3679   if (G1Log::finer()) {
3680     if (evacuation_failed()) {
3681       gclog_or_tty->print(" (to-space exhausted)");
3682     }
3683     gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3684     g1_policy()->phase_times()->note_gc_end();
3685     g1_policy()->phase_times()->print(pause_time_sec);
3686     g1_policy()->print_detailed_heap_transition();
3687   } else {
3688     if (evacuation_failed()) {
3689       gclog_or_tty->print("--");
3690     }
3691     g1_policy()->print_heap_transition();
3692     gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3693   }
3694   gclog_or_tty->flush();
3695 }
3696 
3697 bool
3698 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3699   assert_at_safepoint(true /* should_be_vm_thread */);
3700   guarantee(!is_gc_active(), "collection is not reentrant");
3701 
3702   if (GC_locker::check_active_before_gc()) {
3703     return false;
3704   }
3705 
3706   _gc_timer_stw->register_gc_start();
3707 
3708   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3709 
3710   SvcGCMarker sgcm(SvcGCMarker::MINOR);
3711   ResourceMark rm;
3712 
3713   print_heap_before_gc();
3714   trace_heap_before_gc(_gc_tracer_stw);
3715 
3716   verify_region_sets_optional();
3717   verify_dirty_young_regions();
3718 
3719   // This call will decide whether this pause is an initial-mark
3720   // pause. If it is, during_initial_mark_pause() will return true
3721   // for the duration of this pause.
3722   g1_policy()->decide_on_conc_mark_initiation();
3723 
3724   // We do not allow initial-mark to be piggy-backed on a mixed GC.
3725   assert(!g1_policy()->during_initial_mark_pause() ||
3726           g1_policy()->gcs_are_young(), "sanity");
3727 
3728   // We also do not allow mixed GCs during marking.
3729   assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3730 
3731   // Record whether this pause is an initial mark. When the current
3732   // thread has completed its logging output and it's safe to signal
3733   // the CM thread, the flag's value in the policy has been reset.
3734   bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3735 
3736   // Inner scope for scope based logging, timers, and stats collection
3737   {
3738     EvacuationInfo evacuation_info;
3739 
3740     if (g1_policy()->during_initial_mark_pause()) {
3741       // We are about to start a marking cycle, so we increment the
3742       // full collection counter.
3743       increment_old_marking_cycles_started();
3744       register_concurrent_cycle_start(_gc_timer_stw->gc_start());
3745     }
3746 
3747     _gc_tracer_stw->report_yc_type(yc_type());
3748 
3749     TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3750 
3751     int active_workers = workers()->active_workers();
3752     double pause_start_sec = os::elapsedTime();
3753     g1_policy()->phase_times()->note_gc_start(active_workers);
3754     log_gc_header();
3755 
3756     TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3757     TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3758 
3759     // If the secondary_free_list is not empty, append it to the
3760     // free_list. No need to wait for the cleanup operation to finish;
3761     // the region allocation code will check the secondary_free_list
3762     // and wait if necessary. If the G1StressConcRegionFreeing flag is
3763     // set, skip this step so that the region allocation code has to
3764     // get entries from the secondary_free_list.
3765     if (!G1StressConcRegionFreeing) {
3766       append_secondary_free_list_if_not_empty_with_lock();
3767     }
3768 
3769     assert(check_young_list_well_formed(), "young list should be well formed");
3770 
3771     // Don't dynamically change the number of GC threads this early.  A value of
3772     // 0 is used to indicate serial work.  When parallel work is done,
3773     // it will be set.
3774 
3775     { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3776       IsGCActiveMark x;
3777 
3778       gc_prologue(false);
3779       increment_total_collections(false /* full gc */);
3780       increment_gc_time_stamp();
3781 
3782       verify_before_gc();
3783 
3784       check_bitmaps("GC Start");
3785 
3786       COMPILER2_PRESENT(DerivedPointerTable::clear());
3787 
3788       // Please see comment in g1CollectedHeap.hpp and
3789       // G1CollectedHeap::ref_processing_init() to see how
3790       // reference processing currently works in G1.
3791 
3792       // Enable discovery in the STW reference processor
3793       ref_processor_stw()->enable_discovery();
3794 
3795       {
3796         // We want to temporarily turn off discovery by the
3797         // CM ref processor, if necessary, and turn it back on
3798         // on again later if we do. Using a scoped
3799         // NoRefDiscovery object will do this.
3800         NoRefDiscovery no_cm_discovery(ref_processor_cm());
3801 
3802         // Forget the current alloc region (we might even choose it to be part
3803         // of the collection set!).
3804         _allocator->release_mutator_alloc_region();
3805 
3806         // We should call this after we retire the mutator alloc
3807         // region(s) so that all the ALLOC / RETIRE events are generated
3808         // before the start GC event.
3809         _hr_printer.start_gc(false /* full */, (size_t) total_collections());
3810 
3811         // This timing is only used by the ergonomics to handle our pause target.
3812         // It is unclear why this should not include the full pause. We will
3813         // investigate this in CR 7178365.
3814         //
3815         // Preserving the old comment here if that helps the investigation:
3816         //
3817         // The elapsed time induced by the start time below deliberately elides
3818         // the possible verification above.
3819         double sample_start_time_sec = os::elapsedTime();
3820 
3821 #if YOUNG_LIST_VERBOSE
3822         gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
3823         _young_list->print();
3824         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3825 #endif // YOUNG_LIST_VERBOSE
3826 
3827         g1_policy()->record_collection_pause_start(sample_start_time_sec);
3828 
3829         double scan_wait_start = os::elapsedTime();
3830         // We have to wait until the CM threads finish scanning the
3831         // root regions as it's the only way to ensure that all the
3832         // objects on them have been correctly scanned before we start
3833         // moving them during the GC.
3834         bool waited = _cm->root_regions()->wait_until_scan_finished();
3835         double wait_time_ms = 0.0;
3836         if (waited) {
3837           double scan_wait_end = os::elapsedTime();
3838           wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
3839         }
3840         g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
3841 
3842 #if YOUNG_LIST_VERBOSE
3843         gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
3844         _young_list->print();
3845 #endif // YOUNG_LIST_VERBOSE
3846 
3847         if (g1_policy()->during_initial_mark_pause()) {
3848           concurrent_mark()->checkpointRootsInitialPre();
3849         }
3850 
3851 #if YOUNG_LIST_VERBOSE
3852         gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
3853         _young_list->print();
3854         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3855 #endif // YOUNG_LIST_VERBOSE
3856 
3857         g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info);
3858 
3859         register_humongous_regions_with_in_cset_fast_test();
3860 
3861         assert(check_cset_fast_test(), "Inconsistency in the InCSetState table.");
3862 
3863         _cm->note_start_of_gc();
3864         // We should not verify the per-thread SATB buffers given that
3865         // we have not filtered them yet (we'll do so during the
3866         // GC). We also call this after finalize_cset() to
3867         // ensure that the CSet has been finalized.
3868         _cm->verify_no_cset_oops(true  /* verify_stacks */,
3869                                  true  /* verify_enqueued_buffers */,
3870                                  false /* verify_thread_buffers */,
3871                                  true  /* verify_fingers */);
3872 
3873         if (_hr_printer.is_active()) {
3874           HeapRegion* hr = g1_policy()->collection_set();
3875           while (hr != NULL) {
3876             _hr_printer.cset(hr);
3877             hr = hr->next_in_collection_set();
3878           }
3879         }
3880 
3881 #ifdef ASSERT
3882         VerifyCSetClosure cl;
3883         collection_set_iterate(&cl);
3884 #endif // ASSERT
3885 
3886         setup_surviving_young_words();
3887 
3888         // Initialize the GC alloc regions.
3889         _allocator->init_gc_alloc_regions(evacuation_info);
3890 
3891         // Actually do the work...
3892         evacuate_collection_set(evacuation_info);
3893 
3894         // We do this to mainly verify the per-thread SATB buffers
3895         // (which have been filtered by now) since we didn't verify
3896         // them earlier. No point in re-checking the stacks / enqueued
3897         // buffers given that the CSet has not changed since last time
3898         // we checked.
3899         _cm->verify_no_cset_oops(false /* verify_stacks */,
3900                                  false /* verify_enqueued_buffers */,
3901                                  true  /* verify_thread_buffers */,
3902                                  true  /* verify_fingers */);
3903 
3904         free_collection_set(g1_policy()->collection_set(), evacuation_info);
3905 
3906         eagerly_reclaim_humongous_regions();
3907 
3908         g1_policy()->clear_collection_set();
3909 
3910         cleanup_surviving_young_words();
3911 
3912         // Start a new incremental collection set for the next pause.
3913         g1_policy()->start_incremental_cset_building();
3914 
3915         clear_cset_fast_test();
3916 
3917         _young_list->reset_sampled_info();
3918 
3919         // Don't check the whole heap at this point as the
3920         // GC alloc regions from this pause have been tagged
3921         // as survivors and moved on to the survivor list.
3922         // Survivor regions will fail the !is_young() check.
3923         assert(check_young_list_empty(false /* check_heap */),
3924           "young list should be empty");
3925 
3926 #if YOUNG_LIST_VERBOSE
3927         gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
3928         _young_list->print();
3929 #endif // YOUNG_LIST_VERBOSE
3930 
3931         g1_policy()->record_survivor_regions(_young_list->survivor_length(),
3932                                              _young_list->first_survivor_region(),
3933                                              _young_list->last_survivor_region());
3934 
3935         _young_list->reset_auxilary_lists();
3936 
3937         if (evacuation_failed()) {
3938           _allocator->set_used(recalculate_used());
3939           uint n_queues = MAX2((int)ParallelGCThreads, 1);
3940           for (uint i = 0; i < n_queues; i++) {
3941             if (_evacuation_failed_info_array[i].has_failed()) {
3942               _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
3943             }
3944           }
3945         } else {
3946           // The "used" of the the collection set have already been subtracted
3947           // when they were freed.  Add in the bytes evacuated.
3948           _allocator->increase_used(g1_policy()->bytes_copied_during_gc());
3949         }
3950 
3951         if (g1_policy()->during_initial_mark_pause()) {
3952           // We have to do this before we notify the CM threads that
3953           // they can start working to make sure that all the
3954           // appropriate initialization is done on the CM object.
3955           concurrent_mark()->checkpointRootsInitialPost();
3956           set_marking_started();
3957           // Note that we don't actually trigger the CM thread at
3958           // this point. We do that later when we're sure that
3959           // the current thread has completed its logging output.
3960         }
3961 
3962         allocate_dummy_regions();
3963 
3964 #if YOUNG_LIST_VERBOSE
3965         gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
3966         _young_list->print();
3967         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3968 #endif // YOUNG_LIST_VERBOSE
3969 
3970         _allocator->init_mutator_alloc_region();
3971 
3972         {
3973           size_t expand_bytes = g1_policy()->expansion_amount();
3974           if (expand_bytes > 0) {
3975             size_t bytes_before = capacity();
3976             // No need for an ergo verbose message here,
3977             // expansion_amount() does this when it returns a value > 0.
3978             if (!expand(expand_bytes)) {
3979               // We failed to expand the heap. Cannot do anything about it.
3980             }
3981           }
3982         }
3983 
3984         // We redo the verification but now wrt to the new CSet which
3985         // has just got initialized after the previous CSet was freed.
3986         _cm->verify_no_cset_oops(true  /* verify_stacks */,
3987                                  true  /* verify_enqueued_buffers */,
3988                                  true  /* verify_thread_buffers */,
3989                                  true  /* verify_fingers */);
3990         _cm->note_end_of_gc();
3991 
3992         // This timing is only used by the ergonomics to handle our pause target.
3993         // It is unclear why this should not include the full pause. We will
3994         // investigate this in CR 7178365.
3995         double sample_end_time_sec = os::elapsedTime();
3996         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3997         g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info);
3998 
3999         MemoryService::track_memory_usage();
4000 
4001         // In prepare_for_verify() below we'll need to scan the deferred
4002         // update buffers to bring the RSets up-to-date if
4003         // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
4004         // the update buffers we'll probably need to scan cards on the
4005         // regions we just allocated to (i.e., the GC alloc
4006         // regions). However, during the last GC we called
4007         // set_saved_mark() on all the GC alloc regions, so card
4008         // scanning might skip the [saved_mark_word()...top()] area of
4009         // those regions (i.e., the area we allocated objects into
4010         // during the last GC). But it shouldn't. Given that
4011         // saved_mark_word() is conditional on whether the GC time stamp
4012         // on the region is current or not, by incrementing the GC time
4013         // stamp here we invalidate all the GC time stamps on all the
4014         // regions and saved_mark_word() will simply return top() for
4015         // all the regions. This is a nicer way of ensuring this rather
4016         // than iterating over the regions and fixing them. In fact, the
4017         // GC time stamp increment here also ensures that
4018         // saved_mark_word() will return top() between pauses, i.e.,
4019         // during concurrent refinement. So we don't need the
4020         // is_gc_active() check to decided which top to use when
4021         // scanning cards (see CR 7039627).
4022         increment_gc_time_stamp();
4023 
4024         verify_after_gc();
4025         check_bitmaps("GC End");
4026 
4027         assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
4028         ref_processor_stw()->verify_no_references_recorded();
4029 
4030         // CM reference discovery will be re-enabled if necessary.
4031       }
4032 
4033       // We should do this after we potentially expand the heap so
4034       // that all the COMMIT events are generated before the end GC
4035       // event, and after we retire the GC alloc regions so that all
4036       // RETIRE events are generated before the end GC event.
4037       _hr_printer.end_gc(false /* full */, (size_t) total_collections());
4038 
4039 #ifdef TRACESPINNING
4040       ParallelTaskTerminator::print_termination_counts();
4041 #endif
4042 
4043       gc_epilogue(false);
4044     }
4045 
4046     // Print the remainder of the GC log output.
4047     log_gc_footer(os::elapsedTime() - pause_start_sec);
4048 
4049     // It is not yet to safe to tell the concurrent mark to
4050     // start as we have some optional output below. We don't want the
4051     // output from the concurrent mark thread interfering with this
4052     // logging output either.
4053 
4054     _hrm.verify_optional();
4055     verify_region_sets_optional();
4056 
4057     TASKQUEUE_STATS_ONLY(if (PrintTaskqueue) print_taskqueue_stats());
4058     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
4059 
4060     print_heap_after_gc();
4061     trace_heap_after_gc(_gc_tracer_stw);
4062 
4063     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
4064     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
4065     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
4066     // before any GC notifications are raised.
4067     g1mm()->update_sizes();
4068 
4069     _gc_tracer_stw->report_evacuation_info(&evacuation_info);
4070     _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
4071     _gc_timer_stw->register_gc_end();
4072     _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
4073   }
4074   // It should now be safe to tell the concurrent mark thread to start
4075   // without its logging output interfering with the logging output
4076   // that came from the pause.
4077 
4078   if (should_start_conc_mark) {
4079     // CAUTION: after the doConcurrentMark() call below,
4080     // the concurrent marking thread(s) could be running
4081     // concurrently with us. Make sure that anything after
4082     // this point does not assume that we are the only GC thread
4083     // running. Note: of course, the actual marking work will
4084     // not start until the safepoint itself is released in
4085     // SuspendibleThreadSet::desynchronize().
4086     doConcurrentMark();
4087   }
4088 
4089   return true;
4090 }
4091 
4092 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4093   _drain_in_progress = false;
4094   set_evac_failure_closure(cl);
4095   _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4096 }
4097 
4098 void G1CollectedHeap::finalize_for_evac_failure() {
4099   assert(_evac_failure_scan_stack != NULL &&
4100          _evac_failure_scan_stack->length() == 0,
4101          "Postcondition");
4102   assert(!_drain_in_progress, "Postcondition");
4103   delete _evac_failure_scan_stack;
4104   _evac_failure_scan_stack = NULL;
4105 }
4106 
4107 void G1CollectedHeap::remove_self_forwarding_pointers() {
4108   double remove_self_forwards_start = os::elapsedTime();
4109 
4110   set_par_threads();
4111   G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4112   workers()->run_task(&rsfp_task);
4113   set_par_threads(0);
4114 
4115   // Now restore saved marks, if any.
4116   assert(_objs_with_preserved_marks.size() ==
4117             _preserved_marks_of_objs.size(), "Both or none.");
4118   while (!_objs_with_preserved_marks.is_empty()) {
4119     oop obj = _objs_with_preserved_marks.pop();
4120     markOop m = _preserved_marks_of_objs.pop();
4121     obj->set_mark(m);
4122   }
4123   _objs_with_preserved_marks.clear(true);
4124   _preserved_marks_of_objs.clear(true);
4125 
4126   g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
4127 }
4128 
4129 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4130   _evac_failure_scan_stack->push(obj);
4131 }
4132 
4133 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4134   assert(_evac_failure_scan_stack != NULL, "precondition");
4135 
4136   while (_evac_failure_scan_stack->length() > 0) {
4137      oop obj = _evac_failure_scan_stack->pop();
4138      _evac_failure_closure->set_region(heap_region_containing(obj));
4139      obj->oop_iterate_backwards(_evac_failure_closure);
4140   }
4141 }
4142 
4143 oop
4144 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state,
4145                                                oop old) {
4146   assert(obj_in_cs(old),
4147          err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4148                  (HeapWord*) old));
4149   markOop m = old->mark();
4150   oop forward_ptr = old->forward_to_atomic(old);
4151   if (forward_ptr == NULL) {
4152     // Forward-to-self succeeded.
4153     assert(_par_scan_state != NULL, "par scan state");
4154     OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4155     uint queue_num = _par_scan_state->queue_num();
4156 
4157     _evacuation_failed = true;
4158     _evacuation_failed_info_array[queue_num].register_copy_failure(old->size());
4159     if (_evac_failure_closure != cl) {
4160       MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4161       assert(!_drain_in_progress,
4162              "Should only be true while someone holds the lock.");
4163       // Set the global evac-failure closure to the current thread's.
4164       assert(_evac_failure_closure == NULL, "Or locking has failed.");
4165       set_evac_failure_closure(cl);
4166       // Now do the common part.
4167       handle_evacuation_failure_common(old, m);
4168       // Reset to NULL.
4169       set_evac_failure_closure(NULL);
4170     } else {
4171       // The lock is already held, and this is recursive.
4172       assert(_drain_in_progress, "This should only be the recursive case.");
4173       handle_evacuation_failure_common(old, m);
4174     }
4175     return old;
4176   } else {
4177     // Forward-to-self failed. Either someone else managed to allocate
4178     // space for this object (old != forward_ptr) or they beat us in
4179     // self-forwarding it (old == forward_ptr).
4180     assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4181            err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4182                    "should not be in the CSet",
4183                    (HeapWord*) old, (HeapWord*) forward_ptr));
4184     return forward_ptr;
4185   }
4186 }
4187 
4188 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4189   preserve_mark_if_necessary(old, m);
4190 
4191   HeapRegion* r = heap_region_containing(old);
4192   if (!r->evacuation_failed()) {
4193     r->set_evacuation_failed(true);
4194     _hr_printer.evac_failure(r);
4195   }
4196 
4197   push_on_evac_failure_scan_stack(old);
4198 
4199   if (!_drain_in_progress) {
4200     // prevent recursion in copy_to_survivor_space()
4201     _drain_in_progress = true;
4202     drain_evac_failure_scan_stack();
4203     _drain_in_progress = false;
4204   }
4205 }
4206 
4207 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4208   assert(evacuation_failed(), "Oversaving!");
4209   // We want to call the "for_promotion_failure" version only in the
4210   // case of a promotion failure.
4211   if (m->must_be_preserved_for_promotion_failure(obj)) {
4212     _objs_with_preserved_marks.push(obj);
4213     _preserved_marks_of_objs.push(m);
4214   }
4215 }
4216 
4217 void G1ParCopyHelper::mark_object(oop obj) {
4218   assert(!_g1->heap_region_containing(obj)->in_collection_set(), "should not mark objects in the CSet");
4219 
4220   // We know that the object is not moving so it's safe to read its size.
4221   _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4222 }
4223 
4224 void G1ParCopyHelper::mark_forwarded_object(oop from_obj, oop to_obj) {
4225   assert(from_obj->is_forwarded(), "from obj should be forwarded");
4226   assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4227   assert(from_obj != to_obj, "should not be self-forwarded");
4228 
4229   assert(_g1->heap_region_containing(from_obj)->in_collection_set(), "from obj should be in the CSet");
4230   assert(!_g1->heap_region_containing(to_obj)->in_collection_set(), "should not mark objects in the CSet");
4231 
4232   // The object might be in the process of being copied by another
4233   // worker so we cannot trust that its to-space image is
4234   // well-formed. So we have to read its size from its from-space
4235   // image which we know should not be changing.
4236   _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4237 }
4238 
4239 template <class T>
4240 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) {
4241   if (_g1->heap_region_containing_raw(new_obj)->is_young()) {
4242     _scanned_klass->record_modified_oops();
4243   }
4244 }
4245 
4246 template <G1Barrier barrier, G1Mark do_mark_object>
4247 template <class T>
4248 void G1ParCopyClosure<barrier, do_mark_object>::do_oop_work(T* p) {
4249   T heap_oop = oopDesc::load_heap_oop(p);
4250 
4251   if (oopDesc::is_null(heap_oop)) {
4252     return;
4253   }
4254 
4255   oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
4256 
4257   assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4258 
4259   const InCSetState state = _g1->in_cset_state(obj);
4260   if (state.is_in_cset()) {
4261     oop forwardee;
4262     markOop m = obj->mark();
4263     if (m->is_marked()) {
4264       forwardee = (oop) m->decode_pointer();
4265     } else {
4266       forwardee = _par_scan_state->copy_to_survivor_space(state, obj, m);
4267     }
4268     assert(forwardee != NULL, "forwardee should not be NULL");
4269     oopDesc::encode_store_heap_oop(p, forwardee);
4270     if (do_mark_object != G1MarkNone && forwardee != obj) {
4271       // If the object is self-forwarded we don't need to explicitly
4272       // mark it, the evacuation failure protocol will do so.
4273       mark_forwarded_object(obj, forwardee);
4274     }
4275 
4276     if (barrier == G1BarrierKlass) {
4277       do_klass_barrier(p, forwardee);
4278     }
4279   } else {
4280     if (state.is_humongous()) {
4281       _g1->set_humongous_is_live(obj);
4282     }
4283     // The object is not in collection set. If we're a root scanning
4284     // closure during an initial mark pause then attempt to mark the object.
4285     if (do_mark_object == G1MarkFromRoot) {
4286       mark_object(obj);
4287     }
4288   }
4289 
4290   if (barrier == G1BarrierEvac) {
4291     _par_scan_state->update_rs(_from, p, _worker_id);
4292   }
4293 }
4294 
4295 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(oop* p);
4296 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(narrowOop* p);
4297 
4298 class G1ParEvacuateFollowersClosure : public VoidClosure {
4299 protected:
4300   G1CollectedHeap*              _g1h;
4301   G1ParScanThreadState*         _par_scan_state;
4302   RefToScanQueueSet*            _queues;
4303   ParallelTaskTerminator*       _terminator;
4304 
4305   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
4306   RefToScanQueueSet*      queues()         { return _queues; }
4307   ParallelTaskTerminator* terminator()     { return _terminator; }
4308 
4309 public:
4310   G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4311                                 G1ParScanThreadState* par_scan_state,
4312                                 RefToScanQueueSet* queues,
4313                                 ParallelTaskTerminator* terminator)
4314     : _g1h(g1h), _par_scan_state(par_scan_state),
4315       _queues(queues), _terminator(terminator) {}
4316 
4317   void do_void();
4318 
4319 private:
4320   inline bool offer_termination();
4321 };
4322 
4323 bool G1ParEvacuateFollowersClosure::offer_termination() {
4324   G1ParScanThreadState* const pss = par_scan_state();
4325   pss->start_term_time();
4326   const bool res = terminator()->offer_termination();
4327   pss->end_term_time();
4328   return res;
4329 }
4330 
4331 void G1ParEvacuateFollowersClosure::do_void() {
4332   G1ParScanThreadState* const pss = par_scan_state();
4333   pss->trim_queue();
4334   do {
4335     pss->steal_and_trim_queue(queues());
4336   } while (!offer_termination());
4337 }
4338 
4339 class G1KlassScanClosure : public KlassClosure {
4340  G1ParCopyHelper* _closure;
4341  bool             _process_only_dirty;
4342  int              _count;
4343  public:
4344   G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty)
4345       : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {}
4346   void do_klass(Klass* klass) {
4347     // If the klass has not been dirtied we know that there's
4348     // no references into  the young gen and we can skip it.
4349    if (!_process_only_dirty || klass->has_modified_oops()) {
4350       // Clean the klass since we're going to scavenge all the metadata.
4351       klass->clear_modified_oops();
4352 
4353       // Tell the closure that this klass is the Klass to scavenge
4354       // and is the one to dirty if oops are left pointing into the young gen.
4355       _closure->set_scanned_klass(klass);
4356 
4357       klass->oops_do(_closure);
4358 
4359       _closure->set_scanned_klass(NULL);
4360     }
4361     _count++;
4362   }
4363 };
4364 
4365 class G1CodeBlobClosure : public CodeBlobClosure {
4366   class HeapRegionGatheringOopClosure : public OopClosure {
4367     G1CollectedHeap* _g1h;
4368     OopClosure* _work;
4369     nmethod* _nm;
4370 
4371     template <typename T>
4372     void do_oop_work(T* p) {
4373       _work->do_oop(p);
4374       T oop_or_narrowoop = oopDesc::load_heap_oop(p);
4375       if (!oopDesc::is_null(oop_or_narrowoop)) {
4376         oop o = oopDesc::decode_heap_oop_not_null(oop_or_narrowoop);
4377         HeapRegion* hr = _g1h->heap_region_containing_raw(o);
4378         assert(!_g1h->obj_in_cs(o) || hr->rem_set()->strong_code_roots_list_contains(_nm), "if o still in CS then evacuation failed and nm must already be in the remset");
4379         hr->add_strong_code_root(_nm);
4380       }
4381     }
4382 
4383   public:
4384     HeapRegionGatheringOopClosure(OopClosure* oc) : _g1h(G1CollectedHeap::heap()), _work(oc), _nm(NULL) {}
4385 
4386     void do_oop(oop* o) {
4387       do_oop_work(o);
4388     }
4389 
4390     void do_oop(narrowOop* o) {
4391       do_oop_work(o);
4392     }
4393 
4394     void set_nm(nmethod* nm) {
4395       _nm = nm;
4396     }
4397   };
4398 
4399   HeapRegionGatheringOopClosure _oc;
4400 public:
4401   G1CodeBlobClosure(OopClosure* oc) : _oc(oc) {}
4402 
4403   void do_code_blob(CodeBlob* cb) {
4404     nmethod* nm = cb->as_nmethod_or_null();
4405     if (nm != NULL) {
4406       if (!nm->test_set_oops_do_mark()) {
4407         _oc.set_nm(nm);
4408         nm->oops_do(&_oc);
4409         nm->fix_oop_relocations();
4410       }
4411     }
4412   }
4413 };
4414 
4415 class G1ParTask : public AbstractGangTask {
4416 protected:
4417   G1CollectedHeap*       _g1h;
4418   RefToScanQueueSet      *_queues;
4419   ParallelTaskTerminator _terminator;
4420   uint _n_workers;
4421 
4422   Mutex _stats_lock;
4423   Mutex* stats_lock() { return &_stats_lock; }
4424 
4425 public:
4426   G1ParTask(G1CollectedHeap* g1h, RefToScanQueueSet *task_queues)
4427     : AbstractGangTask("G1 collection"),
4428       _g1h(g1h),
4429       _queues(task_queues),
4430       _terminator(0, _queues),
4431       _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4432   {}
4433 
4434   RefToScanQueueSet* queues() { return _queues; }
4435 
4436   RefToScanQueue *work_queue(int i) {
4437     return queues()->queue(i);
4438   }
4439 
4440   ParallelTaskTerminator* terminator() { return &_terminator; }
4441 
4442   virtual void set_for_termination(int active_workers) {
4443     // This task calls set_n_termination() in par_non_clean_card_iterate_work()
4444     // in the young space (_par_seq_tasks) in the G1 heap
4445     // for SequentialSubTasksDone.
4446     // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap
4447     // both of which need setting by set_n_termination().
4448     _g1h->SharedHeap::set_n_termination(active_workers);
4449     _g1h->set_n_termination(active_workers);
4450     terminator()->reset_for_reuse(active_workers);
4451     _n_workers = active_workers;
4452   }
4453 
4454   // Helps out with CLD processing.
4455   //
4456   // During InitialMark we need to:
4457   // 1) Scavenge all CLDs for the young GC.
4458   // 2) Mark all objects directly reachable from strong CLDs.
4459   template <G1Mark do_mark_object>
4460   class G1CLDClosure : public CLDClosure {
4461     G1ParCopyClosure<G1BarrierNone,  do_mark_object>* _oop_closure;
4462     G1ParCopyClosure<G1BarrierKlass, do_mark_object>  _oop_in_klass_closure;
4463     G1KlassScanClosure                                _klass_in_cld_closure;
4464     bool                                              _claim;
4465 
4466    public:
4467     G1CLDClosure(G1ParCopyClosure<G1BarrierNone, do_mark_object>* oop_closure,
4468                  bool only_young, bool claim)
4469         : _oop_closure(oop_closure),
4470           _oop_in_klass_closure(oop_closure->g1(),
4471                                 oop_closure->pss(),
4472                                 oop_closure->rp()),
4473           _klass_in_cld_closure(&_oop_in_klass_closure, only_young),
4474           _claim(claim) {
4475 
4476     }
4477 
4478     void do_cld(ClassLoaderData* cld) {
4479       cld->oops_do(_oop_closure, &_klass_in_cld_closure, _claim);
4480     }
4481   };
4482 
4483   void work(uint worker_id) {
4484     if (worker_id >= _n_workers) return;  // no work needed this round
4485 
4486     double start_time_ms = os::elapsedTime() * 1000.0;
4487     _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms);
4488 
4489     {
4490       ResourceMark rm;
4491       HandleMark   hm;
4492 
4493       ReferenceProcessor*             rp = _g1h->ref_processor_stw();
4494 
4495       G1ParScanThreadState            pss(_g1h, worker_id, rp);
4496       G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
4497 
4498       pss.set_evac_failure_closure(&evac_failure_cl);
4499 
4500       bool only_young = _g1h->g1_policy()->gcs_are_young();
4501 
4502       // Non-IM young GC.
4503       G1ParCopyClosure<G1BarrierNone, G1MarkNone>             scan_only_root_cl(_g1h, &pss, rp);
4504       G1CLDClosure<G1MarkNone>                                scan_only_cld_cl(&scan_only_root_cl,
4505                                                                                only_young, // Only process dirty klasses.
4506                                                                                false);     // No need to claim CLDs.
4507       // IM young GC.
4508       //    Strong roots closures.
4509       G1ParCopyClosure<G1BarrierNone, G1MarkFromRoot>         scan_mark_root_cl(_g1h, &pss, rp);
4510       G1CLDClosure<G1MarkFromRoot>                            scan_mark_cld_cl(&scan_mark_root_cl,
4511                                                                                false, // Process all klasses.
4512                                                                                true); // Need to claim CLDs.
4513       //    Weak roots closures.
4514       G1ParCopyClosure<G1BarrierNone, G1MarkPromotedFromRoot> scan_mark_weak_root_cl(_g1h, &pss, rp);
4515       G1CLDClosure<G1MarkPromotedFromRoot>                    scan_mark_weak_cld_cl(&scan_mark_weak_root_cl,
4516                                                                                     false, // Process all klasses.
4517                                                                                     true); // Need to claim CLDs.
4518 
4519       G1CodeBlobClosure scan_only_code_cl(&scan_only_root_cl);
4520       G1CodeBlobClosure scan_mark_code_cl(&scan_mark_root_cl);
4521       // IM Weak code roots are handled later.
4522 
4523       OopClosure* strong_root_cl;
4524       OopClosure* weak_root_cl;
4525       CLDClosure* strong_cld_cl;
4526       CLDClosure* weak_cld_cl;
4527       CodeBlobClosure* strong_code_cl;
4528 
4529       if (_g1h->g1_policy()->during_initial_mark_pause()) {
4530         // We also need to mark copied objects.
4531         strong_root_cl = &scan_mark_root_cl;
4532         strong_cld_cl  = &scan_mark_cld_cl;
4533         strong_code_cl = &scan_mark_code_cl;
4534         if (ClassUnloadingWithConcurrentMark) {
4535           weak_root_cl = &scan_mark_weak_root_cl;
4536           weak_cld_cl  = &scan_mark_weak_cld_cl;
4537         } else {
4538           weak_root_cl = &scan_mark_root_cl;
4539           weak_cld_cl  = &scan_mark_cld_cl;
4540         }
4541       } else {
4542         strong_root_cl = &scan_only_root_cl;
4543         weak_root_cl   = &scan_only_root_cl;
4544         strong_cld_cl  = &scan_only_cld_cl;
4545         weak_cld_cl    = &scan_only_cld_cl;
4546         strong_code_cl = &scan_only_code_cl;
4547       }
4548 
4549 
4550       G1ParPushHeapRSClosure  push_heap_rs_cl(_g1h, &pss);
4551 
4552       pss.start_strong_roots();
4553       _g1h->g1_process_roots(strong_root_cl,
4554                              weak_root_cl,
4555                              &push_heap_rs_cl,
4556                              strong_cld_cl,
4557                              weak_cld_cl,
4558                              strong_code_cl,
4559                              worker_id);
4560 
4561       pss.end_strong_roots();
4562 
4563       {
4564         double start = os::elapsedTime();
4565         G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4566         evac.do_void();
4567         double elapsed_ms = (os::elapsedTime()-start)*1000.0;
4568         double term_ms = pss.term_time()*1000.0;
4569         _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms);
4570         _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts());
4571       }
4572       _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4573       _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4574 
4575       if (PrintTerminationStats) {
4576         MutexLocker x(stats_lock());
4577         pss.print_termination_stats(worker_id);
4578       }
4579 
4580       assert(pss.queue_is_empty(), "should be empty");
4581 
4582       // Close the inner scope so that the ResourceMark and HandleMark
4583       // destructors are executed here and are included as part of the
4584       // "GC Worker Time".
4585     }
4586 
4587     double end_time_ms = os::elapsedTime() * 1000.0;
4588     _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms);
4589   }
4590 };
4591 
4592 // *** Common G1 Evacuation Stuff
4593 
4594 // This method is run in a GC worker.
4595 
4596 void
4597 G1CollectedHeap::
4598 g1_process_roots(OopClosure* scan_non_heap_roots,
4599                  OopClosure* scan_non_heap_weak_roots,
4600                  G1ParPushHeapRSClosure* scan_rs,
4601                  CLDClosure* scan_strong_clds,
4602                  CLDClosure* scan_weak_clds,
4603                  CodeBlobClosure* scan_strong_code,
4604                  uint worker_i) {
4605 
4606   // First scan the shared roots.
4607   double ext_roots_start = os::elapsedTime();
4608   double closure_app_time_sec = 0.0;
4609 
4610   bool during_im = _g1h->g1_policy()->during_initial_mark_pause();
4611   bool trace_metadata = during_im && ClassUnloadingWithConcurrentMark;
4612 
4613   BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
4614   BufferingOopClosure buf_scan_non_heap_weak_roots(scan_non_heap_weak_roots);
4615 
4616   process_roots(false, // no scoping; this is parallel code
4617                 SharedHeap::SO_None,
4618                 &buf_scan_non_heap_roots,
4619                 &buf_scan_non_heap_weak_roots,
4620                 scan_strong_clds,
4621                 // Unloading Initial Marks handle the weak CLDs separately.
4622                 (trace_metadata ? NULL : scan_weak_clds),
4623                 scan_strong_code);
4624 
4625   // Now the CM ref_processor roots.
4626   if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
4627     // We need to treat the discovered reference lists of the
4628     // concurrent mark ref processor as roots and keep entries
4629     // (which are added by the marking threads) on them live
4630     // until they can be processed at the end of marking.
4631     ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
4632   }
4633 
4634   if (trace_metadata) {
4635     // Barrier to make sure all workers passed
4636     // the strong CLD and strong nmethods phases.
4637     active_strong_roots_scope()->wait_until_all_workers_done_with_threads(n_par_threads());
4638 
4639     // Now take the complement of the strong CLDs.
4640     ClassLoaderDataGraph::roots_cld_do(NULL, scan_weak_clds);
4641   }
4642 
4643   // Finish up any enqueued closure apps (attributed as object copy time).
4644   buf_scan_non_heap_roots.done();
4645   buf_scan_non_heap_weak_roots.done();
4646 
4647   double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds()
4648       + buf_scan_non_heap_weak_roots.closure_app_seconds();
4649 
4650   g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
4651 
4652   double ext_root_time_ms =
4653     ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0;
4654 
4655   g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
4656 
4657   // During conc marking we have to filter the per-thread SATB buffers
4658   // to make sure we remove any oops into the CSet (which will show up
4659   // as implicitly live).
4660   double satb_filtering_ms = 0.0;
4661   if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) {
4662     if (mark_in_progress()) {
4663       double satb_filter_start = os::elapsedTime();
4664 
4665       JavaThread::satb_mark_queue_set().filter_thread_buffers();
4666 
4667       satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0;
4668     }
4669   }
4670   g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms);
4671 
4672   // Now scan the complement of the collection set.
4673   G1CodeBlobClosure scavenge_cs_nmethods(scan_non_heap_weak_roots);
4674 
4675   g1_rem_set()->oops_into_collection_set_do(scan_rs, &scavenge_cs_nmethods, worker_i);
4676 
4677   _process_strong_tasks->all_tasks_completed();
4678 }
4679 
4680 class G1StringSymbolTableUnlinkTask : public AbstractGangTask {
4681 private:
4682   BoolObjectClosure* _is_alive;
4683   int _initial_string_table_size;
4684   int _initial_symbol_table_size;
4685 
4686   bool  _process_strings;
4687   int _strings_processed;
4688   int _strings_removed;
4689 
4690   bool  _process_symbols;
4691   int _symbols_processed;
4692   int _symbols_removed;
4693 
4694 public:
4695   G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) :
4696     AbstractGangTask("String/Symbol Unlinking"),
4697     _is_alive(is_alive),
4698     _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
4699     _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) {
4700 
4701     _initial_string_table_size = StringTable::the_table()->table_size();
4702     _initial_symbol_table_size = SymbolTable::the_table()->table_size();
4703     if (process_strings) {
4704       StringTable::clear_parallel_claimed_index();
4705     }
4706     if (process_symbols) {
4707       SymbolTable::clear_parallel_claimed_index();
4708     }
4709   }
4710 
4711   ~G1StringSymbolTableUnlinkTask() {
4712     guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size,
4713               err_msg("claim value %d after unlink less than initial string table size %d",
4714                       StringTable::parallel_claimed_index(), _initial_string_table_size));
4715     guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
4716               err_msg("claim value %d after unlink less than initial symbol table size %d",
4717                       SymbolTable::parallel_claimed_index(), _initial_symbol_table_size));
4718 
4719     if (G1TraceStringSymbolTableScrubbing) {
4720       gclog_or_tty->print_cr("Cleaned string and symbol table, "
4721                              "strings: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed, "
4722                              "symbols: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed",
4723                              strings_processed(), strings_removed(),
4724                              symbols_processed(), symbols_removed());
4725     }
4726   }
4727 
4728   void work(uint worker_id) {
4729     int strings_processed = 0;
4730     int strings_removed = 0;
4731     int symbols_processed = 0;
4732     int symbols_removed = 0;
4733     if (_process_strings) {
4734       StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
4735       Atomic::add(strings_processed, &_strings_processed);
4736       Atomic::add(strings_removed, &_strings_removed);
4737     }
4738     if (_process_symbols) {
4739       SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
4740       Atomic::add(symbols_processed, &_symbols_processed);
4741       Atomic::add(symbols_removed, &_symbols_removed);
4742     }
4743   }
4744 
4745   size_t strings_processed() const { return (size_t)_strings_processed; }
4746   size_t strings_removed()   const { return (size_t)_strings_removed; }
4747 
4748   size_t symbols_processed() const { return (size_t)_symbols_processed; }
4749   size_t symbols_removed()   const { return (size_t)_symbols_removed; }
4750 };
4751 
4752 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
4753 private:
4754   static Monitor* _lock;
4755 
4756   BoolObjectClosure* const _is_alive;
4757   const bool               _unloading_occurred;
4758   const uint               _num_workers;
4759 
4760   // Variables used to claim nmethods.
4761   nmethod* _first_nmethod;
4762   volatile nmethod* _claimed_nmethod;
4763 
4764   // The list of nmethods that need to be processed by the second pass.
4765   volatile nmethod* _postponed_list;
4766   volatile uint     _num_entered_barrier;
4767 
4768  public:
4769   G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
4770       _is_alive(is_alive),
4771       _unloading_occurred(unloading_occurred),
4772       _num_workers(num_workers),
4773       _first_nmethod(NULL),
4774       _claimed_nmethod(NULL),
4775       _postponed_list(NULL),
4776       _num_entered_barrier(0)
4777   {
4778     nmethod::increase_unloading_clock();
4779     // Get first alive nmethod
4780     NMethodIterator iter = NMethodIterator();
4781     if(iter.next_alive()) {
4782       _first_nmethod = iter.method();
4783     }
4784     _claimed_nmethod = (volatile nmethod*)_first_nmethod;
4785   }
4786 
4787   ~G1CodeCacheUnloadingTask() {
4788     CodeCache::verify_clean_inline_caches();
4789 
4790     CodeCache::set_needs_cache_clean(false);
4791     guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
4792 
4793     CodeCache::verify_icholder_relocations();
4794   }
4795 
4796  private:
4797   void add_to_postponed_list(nmethod* nm) {
4798       nmethod* old;
4799       do {
4800         old = (nmethod*)_postponed_list;
4801         nm->set_unloading_next(old);
4802       } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old);
4803   }
4804 
4805   void clean_nmethod(nmethod* nm) {
4806     bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
4807 
4808     if (postponed) {
4809       // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
4810       add_to_postponed_list(nm);
4811     }
4812 
4813     // Mark that this thread has been cleaned/unloaded.
4814     // After this call, it will be safe to ask if this nmethod was unloaded or not.
4815     nm->set_unloading_clock(nmethod::global_unloading_clock());
4816   }
4817 
4818   void clean_nmethod_postponed(nmethod* nm) {
4819     nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
4820   }
4821 
4822   static const int MaxClaimNmethods = 16;
4823 
4824   void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) {
4825     nmethod* first;
4826     NMethodIterator last;
4827 
4828     do {
4829       *num_claimed_nmethods = 0;
4830 
4831       first = (nmethod*)_claimed_nmethod;
4832       last = NMethodIterator(first);
4833 
4834       if (first != NULL) {
4835 
4836         for (int i = 0; i < MaxClaimNmethods; i++) {
4837           if (!last.next_alive()) {
4838             break;
4839           }
4840           claimed_nmethods[i] = last.method();
4841           (*num_claimed_nmethods)++;
4842         }
4843       }
4844 
4845     } while ((nmethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first);
4846   }
4847 
4848   nmethod* claim_postponed_nmethod() {
4849     nmethod* claim;
4850     nmethod* next;
4851 
4852     do {
4853       claim = (nmethod*)_postponed_list;
4854       if (claim == NULL) {
4855         return NULL;
4856       }
4857 
4858       next = claim->unloading_next();
4859 
4860     } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim);
4861 
4862     return claim;
4863   }
4864 
4865  public:
4866   // Mark that we're done with the first pass of nmethod cleaning.
4867   void barrier_mark(uint worker_id) {
4868     MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
4869     _num_entered_barrier++;
4870     if (_num_entered_barrier == _num_workers) {
4871       ml.notify_all();
4872     }
4873   }
4874 
4875   // See if we have to wait for the other workers to
4876   // finish their first-pass nmethod cleaning work.
4877   void barrier_wait(uint worker_id) {
4878     if (_num_entered_barrier < _num_workers) {
4879       MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
4880       while (_num_entered_barrier < _num_workers) {
4881           ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
4882       }
4883     }
4884   }
4885 
4886   // Cleaning and unloading of nmethods. Some work has to be postponed
4887   // to the second pass, when we know which nmethods survive.
4888   void work_first_pass(uint worker_id) {
4889     // The first nmethods is claimed by the first worker.
4890     if (worker_id == 0 && _first_nmethod != NULL) {
4891       clean_nmethod(_first_nmethod);
4892       _first_nmethod = NULL;
4893     }
4894 
4895     int num_claimed_nmethods;
4896     nmethod* claimed_nmethods[MaxClaimNmethods];
4897 
4898     while (true) {
4899       claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
4900 
4901       if (num_claimed_nmethods == 0) {
4902         break;
4903       }
4904 
4905       for (int i = 0; i < num_claimed_nmethods; i++) {
4906         clean_nmethod(claimed_nmethods[i]);
4907       }
4908     }
4909 
4910     // The nmethod cleaning helps out and does the CodeCache part of MetadataOnStackMark.
4911     // Need to retire the buffers now that this thread has stopped cleaning nmethods.
4912     MetadataOnStackMark::retire_buffer_for_thread(Thread::current());
4913   }
4914 
4915   void work_second_pass(uint worker_id) {
4916     nmethod* nm;
4917     // Take care of postponed nmethods.
4918     while ((nm = claim_postponed_nmethod()) != NULL) {
4919       clean_nmethod_postponed(nm);
4920     }
4921   }
4922 };
4923 
4924 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never);
4925 
4926 class G1KlassCleaningTask : public StackObj {
4927   BoolObjectClosure*                      _is_alive;
4928   volatile jint                           _clean_klass_tree_claimed;
4929   ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
4930 
4931  public:
4932   G1KlassCleaningTask(BoolObjectClosure* is_alive) :
4933       _is_alive(is_alive),
4934       _clean_klass_tree_claimed(0),
4935       _klass_iterator() {
4936   }
4937 
4938  private:
4939   bool claim_clean_klass_tree_task() {
4940     if (_clean_klass_tree_claimed) {
4941       return false;
4942     }
4943 
4944     return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0;
4945   }
4946 
4947   InstanceKlass* claim_next_klass() {
4948     Klass* klass;
4949     do {
4950       klass =_klass_iterator.next_klass();
4951     } while (klass != NULL && !klass->oop_is_instance());
4952 
4953     return (InstanceKlass*)klass;
4954   }
4955 
4956 public:
4957 
4958   void clean_klass(InstanceKlass* ik) {
4959     ik->clean_implementors_list(_is_alive);
4960     ik->clean_method_data(_is_alive);
4961 
4962     // G1 specific cleanup work that has
4963     // been moved here to be done in parallel.
4964     ik->clean_dependent_nmethods();
4965     if (JvmtiExport::has_redefined_a_class()) {
4966       InstanceKlass::purge_previous_versions(ik);
4967     }
4968   }
4969 
4970   void work() {
4971     ResourceMark rm;
4972 
4973     // One worker will clean the subklass/sibling klass tree.
4974     if (claim_clean_klass_tree_task()) {
4975       Klass::clean_subklass_tree(_is_alive);
4976     }
4977 
4978     // All workers will help cleaning the classes,
4979     InstanceKlass* klass;
4980     while ((klass = claim_next_klass()) != NULL) {
4981       clean_klass(klass);
4982     }
4983   }
4984 };
4985 
4986 // To minimize the remark pause times, the tasks below are done in parallel.
4987 class G1ParallelCleaningTask : public AbstractGangTask {
4988 private:
4989   G1StringSymbolTableUnlinkTask _string_symbol_task;
4990   G1CodeCacheUnloadingTask      _code_cache_task;
4991   G1KlassCleaningTask           _klass_cleaning_task;
4992 
4993 public:
4994   // The constructor is run in the VMThread.
4995   G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) :
4996       AbstractGangTask("Parallel Cleaning"),
4997       _string_symbol_task(is_alive, process_strings, process_symbols),
4998       _code_cache_task(num_workers, is_alive, unloading_occurred),
4999       _klass_cleaning_task(is_alive) {
5000   }
5001 
5002   void pre_work_verification() {
5003     assert(!MetadataOnStackMark::has_buffer_for_thread(Thread::current()), "Should be empty");
5004   }
5005 
5006   void post_work_verification() {
5007     assert(!MetadataOnStackMark::has_buffer_for_thread(Thread::current()), "Should be empty");
5008   }
5009 
5010   // The parallel work done by all worker threads.
5011   void work(uint worker_id) {
5012     pre_work_verification();
5013 
5014     // Do first pass of code cache cleaning.
5015     _code_cache_task.work_first_pass(worker_id);
5016 
5017     // Let the threads mark that the first pass is done.
5018     _code_cache_task.barrier_mark(worker_id);
5019 
5020     // Clean the Strings and Symbols.
5021     _string_symbol_task.work(worker_id);
5022 
5023     // Wait for all workers to finish the first code cache cleaning pass.
5024     _code_cache_task.barrier_wait(worker_id);
5025 
5026     // Do the second code cache cleaning work, which realize on
5027     // the liveness information gathered during the first pass.
5028     _code_cache_task.work_second_pass(worker_id);
5029 
5030     // Clean all klasses that were not unloaded.
5031     _klass_cleaning_task.work();
5032 
5033     post_work_verification();
5034   }
5035 };
5036 
5037 
5038 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive,
5039                                         bool process_strings,
5040                                         bool process_symbols,
5041                                         bool class_unloading_occurred) {
5042   uint n_workers = workers()->active_workers();
5043 
5044   G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols,
5045                                         n_workers, class_unloading_occurred);
5046   set_par_threads(n_workers);
5047   workers()->run_task(&g1_unlink_task);
5048   set_par_threads(0);
5049 }
5050 
5051 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive,
5052                                                      bool process_strings, bool process_symbols) {
5053   {
5054     uint n_workers = _g1h->workers()->active_workers();
5055     G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols);
5056     set_par_threads(n_workers);
5057     workers()->run_task(&g1_unlink_task);
5058     set_par_threads(0);
5059   }
5060 
5061   if (G1StringDedup::is_enabled()) {
5062     G1StringDedup::unlink(is_alive);
5063   }
5064 }
5065 
5066 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
5067  private:
5068   DirtyCardQueueSet* _queue;
5069  public:
5070   G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue) : AbstractGangTask("Redirty Cards"), _queue(queue) { }
5071 
5072   virtual void work(uint worker_id) {
5073     double start_time = os::elapsedTime();
5074 
5075     RedirtyLoggedCardTableEntryClosure cl;
5076     _queue->par_apply_closure_to_all_completed_buffers(&cl);
5077 
5078     G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
5079     timer->record_redirty_logged_cards_time_ms(worker_id, (os::elapsedTime() - start_time) * 1000.0);
5080     timer->record_redirty_logged_cards_processed_cards(worker_id, cl.num_processed());
5081   }
5082 };
5083 
5084 void G1CollectedHeap::redirty_logged_cards() {
5085   double redirty_logged_cards_start = os::elapsedTime();
5086 
5087   uint n_workers = _g1h->workers()->active_workers();
5088 
5089   G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set());
5090   dirty_card_queue_set().reset_for_par_iteration();
5091   set_par_threads(n_workers);
5092   workers()->run_task(&redirty_task);
5093   set_par_threads(0);
5094 
5095   DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5096   dcq.merge_bufferlists(&dirty_card_queue_set());
5097   assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5098 
5099   g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
5100 }
5101 
5102 // Weak Reference Processing support
5103 
5104 // An always "is_alive" closure that is used to preserve referents.
5105 // If the object is non-null then it's alive.  Used in the preservation
5106 // of referent objects that are pointed to by reference objects
5107 // discovered by the CM ref processor.
5108 class G1AlwaysAliveClosure: public BoolObjectClosure {
5109   G1CollectedHeap* _g1;
5110 public:
5111   G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5112   bool do_object_b(oop p) {
5113     if (p != NULL) {
5114       return true;
5115     }
5116     return false;
5117   }
5118 };
5119 
5120 bool G1STWIsAliveClosure::do_object_b(oop p) {
5121   // An object is reachable if it is outside the collection set,
5122   // or is inside and copied.
5123   return !_g1->obj_in_cs(p) || p->is_forwarded();
5124 }
5125 
5126 // Non Copying Keep Alive closure
5127 class G1KeepAliveClosure: public OopClosure {
5128   G1CollectedHeap* _g1;
5129 public:
5130   G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5131   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
5132   void do_oop(oop* p) {
5133     oop obj = *p;
5134     assert(obj != NULL, "the caller should have filtered out NULL values");
5135 
5136     const InCSetState cset_state = _g1->in_cset_state(obj);
5137     if (!cset_state.is_in_cset_or_humongous()) {
5138       return;
5139     }
5140     if (cset_state.is_in_cset()) {
5141       assert( obj->is_forwarded(), "invariant" );
5142       *p = obj->forwardee();
5143     } else {
5144       assert(!obj->is_forwarded(), "invariant" );
5145       assert(cset_state.is_humongous(),
5146              err_msg("Only allowed InCSet state is IsHumongous, but is %d", cset_state.value()));
5147       _g1->set_humongous_is_live(obj);
5148     }
5149   }
5150 };
5151 
5152 // Copying Keep Alive closure - can be called from both
5153 // serial and parallel code as long as different worker
5154 // threads utilize different G1ParScanThreadState instances
5155 // and different queues.
5156 
5157 class G1CopyingKeepAliveClosure: public OopClosure {
5158   G1CollectedHeap*         _g1h;
5159   OopClosure*              _copy_non_heap_obj_cl;
5160   G1ParScanThreadState*    _par_scan_state;
5161 
5162 public:
5163   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
5164                             OopClosure* non_heap_obj_cl,
5165                             G1ParScanThreadState* pss):
5166     _g1h(g1h),
5167     _copy_non_heap_obj_cl(non_heap_obj_cl),
5168     _par_scan_state(pss)
5169   {}
5170 
5171   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
5172   virtual void do_oop(      oop* p) { do_oop_work(p); }
5173 
5174   template <class T> void do_oop_work(T* p) {
5175     oop obj = oopDesc::load_decode_heap_oop(p);
5176 
5177     if (_g1h->is_in_cset_or_humongous(obj)) {
5178       // If the referent object has been forwarded (either copied
5179       // to a new location or to itself in the event of an
5180       // evacuation failure) then we need to update the reference
5181       // field and, if both reference and referent are in the G1
5182       // heap, update the RSet for the referent.
5183       //
5184       // If the referent has not been forwarded then we have to keep
5185       // it alive by policy. Therefore we have copy the referent.
5186       //
5187       // If the reference field is in the G1 heap then we can push
5188       // on the PSS queue. When the queue is drained (after each
5189       // phase of reference processing) the object and it's followers
5190       // will be copied, the reference field set to point to the
5191       // new location, and the RSet updated. Otherwise we need to
5192       // use the the non-heap or metadata closures directly to copy
5193       // the referent object and update the pointer, while avoiding
5194       // updating the RSet.
5195 
5196       if (_g1h->is_in_g1_reserved(p)) {
5197         _par_scan_state->push_on_queue(p);
5198       } else {
5199         assert(!Metaspace::contains((const void*)p),
5200                err_msg("Unexpectedly found a pointer from metadata: "
5201                               PTR_FORMAT, p));
5202         _copy_non_heap_obj_cl->do_oop(p);
5203       }
5204     }
5205   }
5206 };
5207 
5208 // Serial drain queue closure. Called as the 'complete_gc'
5209 // closure for each discovered list in some of the
5210 // reference processing phases.
5211 
5212 class G1STWDrainQueueClosure: public VoidClosure {
5213 protected:
5214   G1CollectedHeap* _g1h;
5215   G1ParScanThreadState* _par_scan_state;
5216 
5217   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
5218 
5219 public:
5220   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
5221     _g1h(g1h),
5222     _par_scan_state(pss)
5223   { }
5224 
5225   void do_void() {
5226     G1ParScanThreadState* const pss = par_scan_state();
5227     pss->trim_queue();
5228   }
5229 };
5230 
5231 // Parallel Reference Processing closures
5232 
5233 // Implementation of AbstractRefProcTaskExecutor for parallel reference
5234 // processing during G1 evacuation pauses.
5235 
5236 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5237 private:
5238   G1CollectedHeap*   _g1h;
5239   RefToScanQueueSet* _queues;
5240   FlexibleWorkGang*  _workers;
5241   int                _active_workers;
5242 
5243 public:
5244   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5245                         FlexibleWorkGang* workers,
5246                         RefToScanQueueSet *task_queues,
5247                         int n_workers) :
5248     _g1h(g1h),
5249     _queues(task_queues),
5250     _workers(workers),
5251     _active_workers(n_workers)
5252   {
5253     assert(n_workers > 0, "shouldn't call this otherwise");
5254   }
5255 
5256   // Executes the given task using concurrent marking worker threads.
5257   virtual void execute(ProcessTask& task);
5258   virtual void execute(EnqueueTask& task);
5259 };
5260 
5261 // Gang task for possibly parallel reference processing
5262 
5263 class G1STWRefProcTaskProxy: public AbstractGangTask {
5264   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5265   ProcessTask&     _proc_task;
5266   G1CollectedHeap* _g1h;
5267   RefToScanQueueSet *_task_queues;
5268   ParallelTaskTerminator* _terminator;
5269 
5270 public:
5271   G1STWRefProcTaskProxy(ProcessTask& proc_task,
5272                      G1CollectedHeap* g1h,
5273                      RefToScanQueueSet *task_queues,
5274                      ParallelTaskTerminator* terminator) :
5275     AbstractGangTask("Process reference objects in parallel"),
5276     _proc_task(proc_task),
5277     _g1h(g1h),
5278     _task_queues(task_queues),
5279     _terminator(terminator)
5280   {}
5281 
5282   virtual void work(uint worker_id) {
5283     // The reference processing task executed by a single worker.
5284     ResourceMark rm;
5285     HandleMark   hm;
5286 
5287     G1STWIsAliveClosure is_alive(_g1h);
5288 
5289     G1ParScanThreadState            pss(_g1h, worker_id, NULL);
5290     G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5291 
5292     pss.set_evac_failure_closure(&evac_failure_cl);
5293 
5294     G1ParScanExtRootClosure        only_copy_non_heap_cl(_g1h, &pss, NULL);
5295 
5296     G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5297 
5298     OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5299 
5300     if (_g1h->g1_policy()->during_initial_mark_pause()) {
5301       // We also need to mark copied objects.
5302       copy_non_heap_cl = &copy_mark_non_heap_cl;
5303     }
5304 
5305     // Keep alive closure.
5306     G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5307 
5308     // Complete GC closure
5309     G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5310 
5311     // Call the reference processing task's work routine.
5312     _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5313 
5314     // Note we cannot assert that the refs array is empty here as not all
5315     // of the processing tasks (specifically phase2 - pp2_work) execute
5316     // the complete_gc closure (which ordinarily would drain the queue) so
5317     // the queue may not be empty.
5318   }
5319 };
5320 
5321 // Driver routine for parallel reference processing.
5322 // Creates an instance of the ref processing gang
5323 // task and has the worker threads execute it.
5324 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5325   assert(_workers != NULL, "Need parallel worker threads.");
5326 
5327   ParallelTaskTerminator terminator(_active_workers, _queues);
5328   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5329 
5330   _g1h->set_par_threads(_active_workers);
5331   _workers->run_task(&proc_task_proxy);
5332   _g1h->set_par_threads(0);
5333 }
5334 
5335 // Gang task for parallel reference enqueueing.
5336 
5337 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5338   typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5339   EnqueueTask& _enq_task;
5340 
5341 public:
5342   G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5343     AbstractGangTask("Enqueue reference objects in parallel"),
5344     _enq_task(enq_task)
5345   { }
5346 
5347   virtual void work(uint worker_id) {
5348     _enq_task.work(worker_id);
5349   }
5350 };
5351 
5352 // Driver routine for parallel reference enqueueing.
5353 // Creates an instance of the ref enqueueing gang
5354 // task and has the worker threads execute it.
5355 
5356 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5357   assert(_workers != NULL, "Need parallel worker threads.");
5358 
5359   G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5360 
5361   _g1h->set_par_threads(_active_workers);
5362   _workers->run_task(&enq_task_proxy);
5363   _g1h->set_par_threads(0);
5364 }
5365 
5366 // End of weak reference support closures
5367 
5368 // Abstract task used to preserve (i.e. copy) any referent objects
5369 // that are in the collection set and are pointed to by reference
5370 // objects discovered by the CM ref processor.
5371 
5372 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5373 protected:
5374   G1CollectedHeap* _g1h;
5375   RefToScanQueueSet      *_queues;
5376   ParallelTaskTerminator _terminator;
5377   uint _n_workers;
5378 
5379 public:
5380   G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
5381     AbstractGangTask("ParPreserveCMReferents"),
5382     _g1h(g1h),
5383     _queues(task_queues),
5384     _terminator(workers, _queues),
5385     _n_workers(workers)
5386   { }
5387 
5388   void work(uint worker_id) {
5389     ResourceMark rm;
5390     HandleMark   hm;
5391 
5392     G1ParScanThreadState            pss(_g1h, worker_id, NULL);
5393     G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5394 
5395     pss.set_evac_failure_closure(&evac_failure_cl);
5396 
5397     assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5398 
5399     G1ParScanExtRootClosure        only_copy_non_heap_cl(_g1h, &pss, NULL);
5400 
5401     G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5402 
5403     OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5404 
5405     if (_g1h->g1_policy()->during_initial_mark_pause()) {
5406       // We also need to mark copied objects.
5407       copy_non_heap_cl = &copy_mark_non_heap_cl;
5408     }
5409 
5410     // Is alive closure
5411     G1AlwaysAliveClosure always_alive(_g1h);
5412 
5413     // Copying keep alive closure. Applied to referent objects that need
5414     // to be copied.
5415     G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5416 
5417     ReferenceProcessor* rp = _g1h->ref_processor_cm();
5418 
5419     uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5420     uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5421 
5422     // limit is set using max_num_q() - which was set using ParallelGCThreads.
5423     // So this must be true - but assert just in case someone decides to
5424     // change the worker ids.
5425     assert(0 <= worker_id && worker_id < limit, "sanity");
5426     assert(!rp->discovery_is_atomic(), "check this code");
5427 
5428     // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5429     for (uint idx = worker_id; idx < limit; idx += stride) {
5430       DiscoveredList& ref_list = rp->discovered_refs()[idx];
5431 
5432       DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5433       while (iter.has_next()) {
5434         // Since discovery is not atomic for the CM ref processor, we
5435         // can see some null referent objects.
5436         iter.load_ptrs(DEBUG_ONLY(true));
5437         oop ref = iter.obj();
5438 
5439         // This will filter nulls.
5440         if (iter.is_referent_alive()) {
5441           iter.make_referent_alive();
5442         }
5443         iter.move_to_next();
5444       }
5445     }
5446 
5447     // Drain the queue - which may cause stealing
5448     G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5449     drain_queue.do_void();
5450     // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5451     assert(pss.queue_is_empty(), "should be");
5452   }
5453 };
5454 
5455 // Weak Reference processing during an evacuation pause (part 1).
5456 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) {
5457   double ref_proc_start = os::elapsedTime();
5458 
5459   ReferenceProcessor* rp = _ref_processor_stw;
5460   assert(rp->discovery_enabled(), "should have been enabled");
5461 
5462   // Any reference objects, in the collection set, that were 'discovered'
5463   // by the CM ref processor should have already been copied (either by
5464   // applying the external root copy closure to the discovered lists, or
5465   // by following an RSet entry).
5466   //
5467   // But some of the referents, that are in the collection set, that these
5468   // reference objects point to may not have been copied: the STW ref
5469   // processor would have seen that the reference object had already
5470   // been 'discovered' and would have skipped discovering the reference,
5471   // but would not have treated the reference object as a regular oop.
5472   // As a result the copy closure would not have been applied to the
5473   // referent object.
5474   //
5475   // We need to explicitly copy these referent objects - the references
5476   // will be processed at the end of remarking.
5477   //
5478   // We also need to do this copying before we process the reference
5479   // objects discovered by the STW ref processor in case one of these
5480   // referents points to another object which is also referenced by an
5481   // object discovered by the STW ref processor.
5482 
5483   assert(no_of_gc_workers == workers()->active_workers(), "Need to reset active GC workers");
5484 
5485   set_par_threads(no_of_gc_workers);
5486   G1ParPreserveCMReferentsTask keep_cm_referents(this,
5487                                                  no_of_gc_workers,
5488                                                  _task_queues);
5489 
5490   workers()->run_task(&keep_cm_referents);
5491 
5492   set_par_threads(0);
5493 
5494   // Closure to test whether a referent is alive.
5495   G1STWIsAliveClosure is_alive(this);
5496 
5497   // Even when parallel reference processing is enabled, the processing
5498   // of JNI refs is serial and performed serially by the current thread
5499   // rather than by a worker. The following PSS will be used for processing
5500   // JNI refs.
5501 
5502   // Use only a single queue for this PSS.
5503   G1ParScanThreadState            pss(this, 0, NULL);
5504 
5505   // We do not embed a reference processor in the copying/scanning
5506   // closures while we're actually processing the discovered
5507   // reference objects.
5508   G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5509 
5510   pss.set_evac_failure_closure(&evac_failure_cl);
5511 
5512   assert(pss.queue_is_empty(), "pre-condition");
5513 
5514   G1ParScanExtRootClosure        only_copy_non_heap_cl(this, &pss, NULL);
5515 
5516   G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5517 
5518   OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5519 
5520   if (_g1h->g1_policy()->during_initial_mark_pause()) {
5521     // We also need to mark copied objects.
5522     copy_non_heap_cl = &copy_mark_non_heap_cl;
5523   }
5524 
5525   // Keep alive closure.
5526   G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, &pss);
5527 
5528   // Serial Complete GC closure
5529   G1STWDrainQueueClosure drain_queue(this, &pss);
5530 
5531   // Setup the soft refs policy...
5532   rp->setup_policy(false);
5533 
5534   ReferenceProcessorStats stats;
5535   if (!rp->processing_is_mt()) {
5536     // Serial reference processing...
5537     stats = rp->process_discovered_references(&is_alive,
5538                                               &keep_alive,
5539                                               &drain_queue,
5540                                               NULL,
5541                                               _gc_timer_stw,
5542                                               _gc_tracer_stw->gc_id());
5543   } else {
5544     // Parallel reference processing
5545     assert(rp->num_q() == no_of_gc_workers, "sanity");
5546     assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5547 
5548     G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5549     stats = rp->process_discovered_references(&is_alive,
5550                                               &keep_alive,
5551                                               &drain_queue,
5552                                               &par_task_executor,
5553                                               _gc_timer_stw,
5554                                               _gc_tracer_stw->gc_id());
5555   }
5556 
5557   _gc_tracer_stw->report_gc_reference_stats(stats);
5558 
5559   // We have completed copying any necessary live referent objects.
5560   assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5561 
5562   double ref_proc_time = os::elapsedTime() - ref_proc_start;
5563   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5564 }
5565 
5566 // Weak Reference processing during an evacuation pause (part 2).
5567 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) {
5568   double ref_enq_start = os::elapsedTime();
5569 
5570   ReferenceProcessor* rp = _ref_processor_stw;
5571   assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5572 
5573   // Now enqueue any remaining on the discovered lists on to
5574   // the pending list.
5575   if (!rp->processing_is_mt()) {
5576     // Serial reference processing...
5577     rp->enqueue_discovered_references();
5578   } else {
5579     // Parallel reference enqueueing
5580 
5581     assert(no_of_gc_workers == workers()->active_workers(),
5582            "Need to reset active workers");
5583     assert(rp->num_q() == no_of_gc_workers, "sanity");
5584     assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5585 
5586     G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5587     rp->enqueue_discovered_references(&par_task_executor);
5588   }
5589 
5590   rp->verify_no_references_recorded();
5591   assert(!rp->discovery_enabled(), "should have been disabled");
5592 
5593   // FIXME
5594   // CM's reference processing also cleans up the string and symbol tables.
5595   // Should we do that here also? We could, but it is a serial operation
5596   // and could significantly increase the pause time.
5597 
5598   double ref_enq_time = os::elapsedTime() - ref_enq_start;
5599   g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5600 }
5601 
5602 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) {
5603   _expand_heap_after_alloc_failure = true;
5604   _evacuation_failed = false;
5605 
5606   // Should G1EvacuationFailureALot be in effect for this GC?
5607   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
5608 
5609   g1_rem_set()->prepare_for_oops_into_collection_set_do();
5610 
5611   // Disable the hot card cache.
5612   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
5613   hot_card_cache->reset_hot_cache_claimed_index();
5614   hot_card_cache->set_use_cache(false);
5615 
5616   uint n_workers;
5617   n_workers =
5618     AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
5619                                    workers()->active_workers(),
5620                                    Threads::number_of_non_daemon_threads());
5621   assert(UseDynamicNumberOfGCThreads ||
5622          n_workers == workers()->total_workers(),
5623          "If not dynamic should be using all the  workers");
5624   workers()->set_active_workers(n_workers);
5625   set_par_threads(n_workers);
5626 
5627   G1ParTask g1_par_task(this, _task_queues);
5628 
5629   init_for_evac_failure(NULL);
5630 
5631   assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5632   double start_par_time_sec = os::elapsedTime();
5633   double end_par_time_sec;
5634 
5635   {
5636     StrongRootsScope srs(this);
5637     // InitialMark needs claim bits to keep track of the marked-through CLDs.
5638     if (g1_policy()->during_initial_mark_pause()) {
5639       ClassLoaderDataGraph::clear_claimed_marks();
5640     }
5641 
5642      // The individual threads will set their evac-failure closures.
5643      if (PrintTerminationStats) G1ParScanThreadState::print_termination_stats_hdr();
5644      // These tasks use ShareHeap::_process_strong_tasks
5645      assert(UseDynamicNumberOfGCThreads ||
5646             workers()->active_workers() == workers()->total_workers(),
5647             "If not dynamic should be using all the  workers");
5648     workers()->run_task(&g1_par_task);
5649     end_par_time_sec = os::elapsedTime();
5650 
5651     // Closing the inner scope will execute the destructor
5652     // for the StrongRootsScope object. We record the current
5653     // elapsed time before closing the scope so that time
5654     // taken for the SRS destructor is NOT included in the
5655     // reported parallel time.
5656   }
5657 
5658   double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5659   g1_policy()->phase_times()->record_par_time(par_time_ms);
5660 
5661   double code_root_fixup_time_ms =
5662         (os::elapsedTime() - end_par_time_sec) * 1000.0;
5663   g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms);
5664 
5665   set_par_threads(0);
5666 
5667   // Process any discovered reference objects - we have
5668   // to do this _before_ we retire the GC alloc regions
5669   // as we may have to copy some 'reachable' referent
5670   // objects (and their reachable sub-graphs) that were
5671   // not copied during the pause.
5672   process_discovered_references(n_workers);
5673 
5674   if (G1StringDedup::is_enabled()) {
5675     G1STWIsAliveClosure is_alive(this);
5676     G1KeepAliveClosure keep_alive(this);
5677     G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive);
5678   }
5679 
5680   _allocator->release_gc_alloc_regions(n_workers, evacuation_info);
5681   g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5682 
5683   // Reset and re-enable the hot card cache.
5684   // Note the counts for the cards in the regions in the
5685   // collection set are reset when the collection set is freed.
5686   hot_card_cache->reset_hot_cache();
5687   hot_card_cache->set_use_cache(true);
5688 
5689   purge_code_root_memory();
5690 
5691   finalize_for_evac_failure();
5692 
5693   if (evacuation_failed()) {
5694     remove_self_forwarding_pointers();
5695 
5696     // Reset the G1EvacuationFailureALot counters and flags
5697     // Note: the values are reset only when an actual
5698     // evacuation failure occurs.
5699     NOT_PRODUCT(reset_evacuation_should_fail();)
5700   }
5701 
5702   // Enqueue any remaining references remaining on the STW
5703   // reference processor's discovered lists. We need to do
5704   // this after the card table is cleaned (and verified) as
5705   // the act of enqueueing entries on to the pending list
5706   // will log these updates (and dirty their associated
5707   // cards). We need these updates logged to update any
5708   // RSets.
5709   enqueue_discovered_references(n_workers);
5710 
5711   redirty_logged_cards();
5712   COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5713 }
5714 
5715 void G1CollectedHeap::free_region(HeapRegion* hr,
5716                                   FreeRegionList* free_list,
5717                                   bool par,
5718                                   bool locked) {
5719   assert(!hr->is_free(), "the region should not be free");
5720   assert(!hr->is_empty(), "the region should not be empty");
5721   assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
5722   assert(free_list != NULL, "pre-condition");
5723 
5724   if (G1VerifyBitmaps) {
5725     MemRegion mr(hr->bottom(), hr->end());
5726     concurrent_mark()->clearRangePrevBitmap(mr);
5727   }
5728 
5729   // Clear the card counts for this region.
5730   // Note: we only need to do this if the region is not young
5731   // (since we don't refine cards in young regions).
5732   if (!hr->is_young()) {
5733     _cg1r->hot_card_cache()->reset_card_counts(hr);
5734   }
5735   hr->hr_clear(par, true /* clear_space */, locked /* locked */);
5736   free_list->add_ordered(hr);
5737 }
5738 
5739 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
5740                                      FreeRegionList* free_list,
5741                                      bool par) {
5742   assert(hr->is_starts_humongous(), "this is only for starts humongous regions");
5743   assert(free_list != NULL, "pre-condition");
5744 
5745   size_t hr_capacity = hr->capacity();
5746   // We need to read this before we make the region non-humongous,
5747   // otherwise the information will be gone.
5748   uint last_index = hr->last_hc_index();
5749   hr->clear_humongous();
5750   free_region(hr, free_list, par);
5751 
5752   uint i = hr->hrm_index() + 1;
5753   while (i < last_index) {
5754     HeapRegion* curr_hr = region_at(i);
5755     assert(curr_hr->is_continues_humongous(), "invariant");
5756     curr_hr->clear_humongous();
5757     free_region(curr_hr, free_list, par);
5758     i += 1;
5759   }
5760 }
5761 
5762 void G1CollectedHeap::remove_from_old_sets(const HeapRegionSetCount& old_regions_removed,
5763                                        const HeapRegionSetCount& humongous_regions_removed) {
5764   if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 0) {
5765     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5766     _old_set.bulk_remove(old_regions_removed);
5767     _humongous_set.bulk_remove(humongous_regions_removed);
5768   }
5769 
5770 }
5771 
5772 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
5773   assert(list != NULL, "list can't be null");
5774   if (!list->is_empty()) {
5775     MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
5776     _hrm.insert_list_into_free_list(list);
5777   }
5778 }
5779 
5780 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
5781   _allocator->decrease_used(bytes);
5782 }
5783 
5784 class G1ParCleanupCTTask : public AbstractGangTask {
5785   G1SATBCardTableModRefBS* _ct_bs;
5786   G1CollectedHeap* _g1h;
5787   HeapRegion* volatile _su_head;
5788 public:
5789   G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs,
5790                      G1CollectedHeap* g1h) :
5791     AbstractGangTask("G1 Par Cleanup CT Task"),
5792     _ct_bs(ct_bs), _g1h(g1h) { }
5793 
5794   void work(uint worker_id) {
5795     HeapRegion* r;
5796     while (r = _g1h->pop_dirty_cards_region()) {
5797       clear_cards(r);
5798     }
5799   }
5800 
5801   void clear_cards(HeapRegion* r) {
5802     // Cards of the survivors should have already been dirtied.
5803     if (!r->is_survivor()) {
5804       _ct_bs->clear(MemRegion(r->bottom(), r->end()));
5805     }
5806   }
5807 };
5808 
5809 #ifndef PRODUCT
5810 class G1VerifyCardTableCleanup: public HeapRegionClosure {
5811   G1CollectedHeap* _g1h;
5812   G1SATBCardTableModRefBS* _ct_bs;
5813 public:
5814   G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs)
5815     : _g1h(g1h), _ct_bs(ct_bs) { }
5816   virtual bool doHeapRegion(HeapRegion* r) {
5817     if (r->is_survivor()) {
5818       _g1h->verify_dirty_region(r);
5819     } else {
5820       _g1h->verify_not_dirty_region(r);
5821     }
5822     return false;
5823   }
5824 };
5825 
5826 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
5827   // All of the region should be clean.
5828   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5829   MemRegion mr(hr->bottom(), hr->end());
5830   ct_bs->verify_not_dirty_region(mr);
5831 }
5832 
5833 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
5834   // We cannot guarantee that [bottom(),end()] is dirty.  Threads
5835   // dirty allocated blocks as they allocate them. The thread that
5836   // retires each region and replaces it with a new one will do a
5837   // maximal allocation to fill in [pre_dummy_top(),end()] but will
5838   // not dirty that area (one less thing to have to do while holding
5839   // a lock). So we can only verify that [bottom(),pre_dummy_top()]
5840   // is dirty.
5841   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5842   MemRegion mr(hr->bottom(), hr->pre_dummy_top());
5843   if (hr->is_young()) {
5844     ct_bs->verify_g1_young_region(mr);
5845   } else {
5846     ct_bs->verify_dirty_region(mr);
5847   }
5848 }
5849 
5850 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
5851   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5852   for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
5853     verify_dirty_region(hr);
5854   }
5855 }
5856 
5857 void G1CollectedHeap::verify_dirty_young_regions() {
5858   verify_dirty_young_list(_young_list->first_region());
5859 }
5860 
5861 bool G1CollectedHeap::verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
5862                                                HeapWord* tams, HeapWord* end) {
5863   guarantee(tams <= end,
5864             err_msg("tams: "PTR_FORMAT" end: "PTR_FORMAT, tams, end));
5865   HeapWord* result = bitmap->getNextMarkedWordAddress(tams, end);
5866   if (result < end) {
5867     gclog_or_tty->cr();
5868     gclog_or_tty->print_cr("## wrong marked address on %s bitmap: "PTR_FORMAT,
5869                            bitmap_name, result);
5870     gclog_or_tty->print_cr("## %s tams: "PTR_FORMAT" end: "PTR_FORMAT,
5871                            bitmap_name, tams, end);
5872     return false;
5873   }
5874   return true;
5875 }
5876 
5877 bool G1CollectedHeap::verify_bitmaps(const char* caller, HeapRegion* hr) {
5878   CMBitMapRO* prev_bitmap = concurrent_mark()->prevMarkBitMap();
5879   CMBitMapRO* next_bitmap = (CMBitMapRO*) concurrent_mark()->nextMarkBitMap();
5880 
5881   HeapWord* bottom = hr->bottom();
5882   HeapWord* ptams  = hr->prev_top_at_mark_start();
5883   HeapWord* ntams  = hr->next_top_at_mark_start();
5884   HeapWord* end    = hr->end();
5885 
5886   bool res_p = verify_no_bits_over_tams("prev", prev_bitmap, ptams, end);
5887 
5888   bool res_n = true;
5889   // We reset mark_in_progress() before we reset _cmThread->in_progress() and in this window
5890   // we do the clearing of the next bitmap concurrently. Thus, we can not verify the bitmap
5891   // if we happen to be in that state.
5892   if (mark_in_progress() || !_cmThread->in_progress()) {
5893     res_n = verify_no_bits_over_tams("next", next_bitmap, ntams, end);
5894   }
5895   if (!res_p || !res_n) {
5896     gclog_or_tty->print_cr("#### Bitmap verification failed for "HR_FORMAT,
5897                            HR_FORMAT_PARAMS(hr));
5898     gclog_or_tty->print_cr("#### Caller: %s", caller);
5899     return false;
5900   }
5901   return true;
5902 }
5903 
5904 void G1CollectedHeap::check_bitmaps(const char* caller, HeapRegion* hr) {
5905   if (!G1VerifyBitmaps) return;
5906 
5907   guarantee(verify_bitmaps(caller, hr), "bitmap verification");
5908 }
5909 
5910 class G1VerifyBitmapClosure : public HeapRegionClosure {
5911 private:
5912   const char* _caller;
5913   G1CollectedHeap* _g1h;
5914   bool _failures;
5915 
5916 public:
5917   G1VerifyBitmapClosure(const char* caller, G1CollectedHeap* g1h) :
5918     _caller(caller), _g1h(g1h), _failures(false) { }
5919 
5920   bool failures() { return _failures; }
5921 
5922   virtual bool doHeapRegion(HeapRegion* hr) {
5923     if (hr->is_continues_humongous()) return false;
5924 
5925     bool result = _g1h->verify_bitmaps(_caller, hr);
5926     if (!result) {
5927       _failures = true;
5928     }
5929     return false;
5930   }
5931 };
5932 
5933 void G1CollectedHeap::check_bitmaps(const char* caller) {
5934   if (!G1VerifyBitmaps) return;
5935 
5936   G1VerifyBitmapClosure cl(caller, this);
5937   heap_region_iterate(&cl);
5938   guarantee(!cl.failures(), "bitmap verification");
5939 }
5940 
5941 class G1CheckCSetFastTableClosure : public HeapRegionClosure {
5942  private:
5943   bool _failures;
5944  public:
5945   G1CheckCSetFastTableClosure() : HeapRegionClosure(), _failures(false) { }
5946 
5947   virtual bool doHeapRegion(HeapRegion* hr) {
5948     uint i = hr->hrm_index();
5949     InCSetState cset_state = (InCSetState) G1CollectedHeap::heap()->_in_cset_fast_test.get_by_index(i);
5950     if (hr->is_humongous()) {
5951       if (hr->in_collection_set()) {
5952         gclog_or_tty->print_cr("\n## humongous region %u in CSet", i);
5953         _failures = true;
5954         return true;
5955       }
5956       if (cset_state.is_in_cset()) {
5957         gclog_or_tty->print_cr("\n## inconsistent cset state %d for humongous region %u", cset_state.value(), i);
5958         _failures = true;
5959         return true;
5960       }
5961       if (hr->is_continues_humongous() && cset_state.is_humongous()) {
5962         gclog_or_tty->print_cr("\n## inconsistent cset state %d for continues humongous region %u", cset_state.value(), i);
5963         _failures = true;
5964         return true;
5965       }
5966     } else {
5967       if (cset_state.is_humongous()) {
5968         gclog_or_tty->print_cr("\n## inconsistent cset state %d for non-humongous region %u", cset_state.value(), i);
5969         _failures = true;
5970         return true;
5971       }
5972       if (hr->in_collection_set() != cset_state.is_in_cset()) {
5973         gclog_or_tty->print_cr("\n## in CSet %d / cset state %d inconsistency for region %u",
5974                                hr->in_collection_set(), cset_state.value(), i);
5975         _failures = true;
5976         return true;
5977       }
5978       if (cset_state.is_in_cset()) {
5979         if (hr->is_young() != (cset_state.is_young())) {
5980           gclog_or_tty->print_cr("\n## is_young %d / cset state %d inconsistency for region %u",
5981                                  hr->is_young(), cset_state.value(), i);
5982           _failures = true;
5983           return true;
5984         }
5985         if (hr->is_old() != (cset_state.is_old())) {
5986           gclog_or_tty->print_cr("\n## is_old %d / cset state %d inconsistency for region %u",
5987                                  hr->is_old(), cset_state.value(), i);
5988           _failures = true;
5989           return true;
5990         }
5991       }
5992     }
5993     return false;
5994   }
5995 
5996   bool failures() const { return _failures; }
5997 };
5998 
5999 bool G1CollectedHeap::check_cset_fast_test() {
6000   G1CheckCSetFastTableClosure cl;
6001   _hrm.iterate(&cl);
6002   return !cl.failures();
6003 }
6004 #endif // PRODUCT
6005 
6006 void G1CollectedHeap::cleanUpCardTable() {
6007   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6008   double start = os::elapsedTime();
6009 
6010   {
6011     // Iterate over the dirty cards region list.
6012     G1ParCleanupCTTask cleanup_task(ct_bs, this);
6013 
6014     set_par_threads();
6015     workers()->run_task(&cleanup_task);
6016     set_par_threads(0);
6017 #ifndef PRODUCT
6018     if (G1VerifyCTCleanup || VerifyAfterGC) {
6019       G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
6020       heap_region_iterate(&cleanup_verifier);
6021     }
6022 #endif
6023   }
6024 
6025   double elapsed = os::elapsedTime() - start;
6026   g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
6027 }
6028 
6029 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) {
6030   size_t pre_used = 0;
6031   FreeRegionList local_free_list("Local List for CSet Freeing");
6032 
6033   double young_time_ms     = 0.0;
6034   double non_young_time_ms = 0.0;
6035 
6036   // Since the collection set is a superset of the the young list,
6037   // all we need to do to clear the young list is clear its
6038   // head and length, and unlink any young regions in the code below
6039   _young_list->clear();
6040 
6041   G1CollectorPolicy* policy = g1_policy();
6042 
6043   double start_sec = os::elapsedTime();
6044   bool non_young = true;
6045 
6046   HeapRegion* cur = cs_head;
6047   int age_bound = -1;
6048   size_t rs_lengths = 0;
6049 
6050   while (cur != NULL) {
6051     assert(!is_on_master_free_list(cur), "sanity");
6052     if (non_young) {
6053       if (cur->is_young()) {
6054         double end_sec = os::elapsedTime();
6055         double elapsed_ms = (end_sec - start_sec) * 1000.0;
6056         non_young_time_ms += elapsed_ms;
6057 
6058         start_sec = os::elapsedTime();
6059         non_young = false;
6060       }
6061     } else {
6062       if (!cur->is_young()) {
6063         double end_sec = os::elapsedTime();
6064         double elapsed_ms = (end_sec - start_sec) * 1000.0;
6065         young_time_ms += elapsed_ms;
6066 
6067         start_sec = os::elapsedTime();
6068         non_young = true;
6069       }
6070     }
6071 
6072     rs_lengths += cur->rem_set()->occupied_locked();
6073 
6074     HeapRegion* next = cur->next_in_collection_set();
6075     assert(cur->in_collection_set(), "bad CS");
6076     cur->set_next_in_collection_set(NULL);
6077     cur->set_in_collection_set(false);
6078 
6079     if (cur->is_young()) {
6080       int index = cur->young_index_in_cset();
6081       assert(index != -1, "invariant");
6082       assert((uint) index < policy->young_cset_region_length(), "invariant");
6083       size_t words_survived = _surviving_young_words[index];
6084       cur->record_surv_words_in_group(words_survived);
6085 
6086       // At this point the we have 'popped' cur from the collection set
6087       // (linked via next_in_collection_set()) but it is still in the
6088       // young list (linked via next_young_region()). Clear the
6089       // _next_young_region field.
6090       cur->set_next_young_region(NULL);
6091     } else {
6092       int index = cur->young_index_in_cset();
6093       assert(index == -1, "invariant");
6094     }
6095 
6096     assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
6097             (!cur->is_young() && cur->young_index_in_cset() == -1),
6098             "invariant" );
6099 
6100     if (!cur->evacuation_failed()) {
6101       MemRegion used_mr = cur->used_region();
6102 
6103       // And the region is empty.
6104       assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
6105       pre_used += cur->used();
6106       free_region(cur, &local_free_list, false /* par */, true /* locked */);
6107     } else {
6108       cur->uninstall_surv_rate_group();
6109       if (cur->is_young()) {
6110         cur->set_young_index_in_cset(-1);
6111       }
6112       cur->set_evacuation_failed(false);
6113       // The region is now considered to be old.
6114       cur->set_old();
6115       _old_set.add(cur);
6116       evacuation_info.increment_collectionset_used_after(cur->used());
6117     }
6118     cur = next;
6119   }
6120 
6121   evacuation_info.set_regions_freed(local_free_list.length());
6122   policy->record_max_rs_lengths(rs_lengths);
6123   policy->cset_regions_freed();
6124 
6125   double end_sec = os::elapsedTime();
6126   double elapsed_ms = (end_sec - start_sec) * 1000.0;
6127 
6128   if (non_young) {
6129     non_young_time_ms += elapsed_ms;
6130   } else {
6131     young_time_ms += elapsed_ms;
6132   }
6133 
6134   prepend_to_freelist(&local_free_list);
6135   decrement_summary_bytes(pre_used);
6136   policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
6137   policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
6138 }
6139 
6140 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
6141  private:
6142   FreeRegionList* _free_region_list;
6143   HeapRegionSet* _proxy_set;
6144   HeapRegionSetCount _humongous_regions_removed;
6145   size_t _freed_bytes;
6146  public:
6147 
6148   G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
6149     _free_region_list(free_region_list), _humongous_regions_removed(), _freed_bytes(0) {
6150   }
6151 
6152   virtual bool doHeapRegion(HeapRegion* r) {
6153     if (!r->is_starts_humongous()) {
6154       return false;
6155     }
6156 
6157     G1CollectedHeap* g1h = G1CollectedHeap::heap();
6158 
6159     oop obj = (oop)r->bottom();
6160     CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap();
6161 
6162     // The following checks whether the humongous object is live are sufficient.
6163     // The main additional check (in addition to having a reference from the roots
6164     // or the young gen) is whether the humongous object has a remembered set entry.
6165     //
6166     // A humongous object cannot be live if there is no remembered set for it
6167     // because:
6168     // - there can be no references from within humongous starts regions referencing
6169     // the object because we never allocate other objects into them.
6170     // (I.e. there are no intra-region references that may be missed by the
6171     // remembered set)
6172     // - as soon there is a remembered set entry to the humongous starts region
6173     // (i.e. it has "escaped" to an old object) this remembered set entry will stay
6174     // until the end of a concurrent mark.
6175     //
6176     // It is not required to check whether the object has been found dead by marking
6177     // or not, in fact it would prevent reclamation within a concurrent cycle, as
6178     // all objects allocated during that time are considered live.
6179     // SATB marking is even more conservative than the remembered set.
6180     // So if at this point in the collection there is no remembered set entry,
6181     // nobody has a reference to it.
6182     // At the start of collection we flush all refinement logs, and remembered sets
6183     // are completely up-to-date wrt to references to the humongous object.
6184     //
6185     // Other implementation considerations:
6186     // - never consider object arrays at this time because they would pose
6187     // considerable effort for cleaning up the the remembered sets. This is
6188     // required because stale remembered sets might reference locations that
6189     // are currently allocated into.
6190     uint region_idx = r->hrm_index();
6191     if (g1h->humongous_is_live(region_idx) ||
6192         g1h->humongous_region_is_always_live(region_idx)) {
6193 
6194       if (G1TraceEagerReclaimHumongousObjects) {
6195         gclog_or_tty->print_cr("Live humongous region %u size "SIZE_FORMAT" start "PTR_FORMAT" length "UINT32_FORMAT" with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is marked %d live-other %d obj array %d",
6196                                region_idx,
6197                                obj->size()*HeapWordSize,
6198                                r->bottom(),
6199                                r->region_num(),
6200                                r->rem_set()->occupied(),
6201                                r->rem_set()->strong_code_roots_list_length(),
6202                                next_bitmap->isMarked(r->bottom()),
6203                                g1h->humongous_is_live(region_idx),
6204                                obj->is_objArray()
6205                               );
6206       }
6207 
6208       return false;
6209     }
6210 
6211     guarantee(!obj->is_objArray(),
6212               err_msg("Eagerly reclaiming object arrays is not supported, but the object "PTR_FORMAT" is.",
6213                       r->bottom()));
6214 
6215     if (G1TraceEagerReclaimHumongousObjects) {
6216       gclog_or_tty->print_cr("Dead humongous region %u size "SIZE_FORMAT" start "PTR_FORMAT" length "UINT32_FORMAT" with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is marked %d live-other %d obj array %d",
6217                              region_idx,
6218                              obj->size()*HeapWordSize,
6219                              r->bottom(),
6220                              r->region_num(),
6221                              r->rem_set()->occupied(),
6222                              r->rem_set()->strong_code_roots_list_length(),
6223                              next_bitmap->isMarked(r->bottom()),
6224                              g1h->humongous_is_live(region_idx),
6225                              obj->is_objArray()
6226                             );
6227     }
6228     // Need to clear mark bit of the humongous object if already set.
6229     if (next_bitmap->isMarked(r->bottom())) {
6230       next_bitmap->clear(r->bottom());
6231     }
6232     _freed_bytes += r->used();
6233     r->set_containing_set(NULL);
6234     _humongous_regions_removed.increment(1u, r->capacity());
6235     g1h->free_humongous_region(r, _free_region_list, false);
6236 
6237     return false;
6238   }
6239 
6240   HeapRegionSetCount& humongous_free_count() {
6241     return _humongous_regions_removed;
6242   }
6243 
6244   size_t bytes_freed() const {
6245     return _freed_bytes;
6246   }
6247 
6248   size_t humongous_reclaimed() const {
6249     return _humongous_regions_removed.length();
6250   }
6251 };
6252 
6253 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
6254   assert_at_safepoint(true);
6255 
6256   if (!G1EagerReclaimHumongousObjects ||
6257       (!_has_humongous_reclaim_candidates && !G1TraceEagerReclaimHumongousObjects)) {
6258     g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
6259     return;
6260   }
6261 
6262   double start_time = os::elapsedTime();
6263 
6264   FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
6265 
6266   G1FreeHumongousRegionClosure cl(&local_cleanup_list);
6267   heap_region_iterate(&cl);
6268 
6269   HeapRegionSetCount empty_set;
6270   remove_from_old_sets(empty_set, cl.humongous_free_count());
6271 
6272   G1HRPrinter* hr_printer = _g1h->hr_printer();
6273   if (hr_printer->is_active()) {
6274     FreeRegionListIterator iter(&local_cleanup_list);
6275     while (iter.more_available()) {
6276       HeapRegion* hr = iter.get_next();
6277       hr_printer->cleanup(hr);
6278     }
6279   }
6280 
6281   prepend_to_freelist(&local_cleanup_list);
6282   decrement_summary_bytes(cl.bytes_freed());
6283 
6284   g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
6285                                                                     cl.humongous_reclaimed());
6286 }
6287 
6288 // This routine is similar to the above but does not record
6289 // any policy statistics or update free lists; we are abandoning
6290 // the current incremental collection set in preparation of a
6291 // full collection. After the full GC we will start to build up
6292 // the incremental collection set again.
6293 // This is only called when we're doing a full collection
6294 // and is immediately followed by the tearing down of the young list.
6295 
6296 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
6297   HeapRegion* cur = cs_head;
6298 
6299   while (cur != NULL) {
6300     HeapRegion* next = cur->next_in_collection_set();
6301     assert(cur->in_collection_set(), "bad CS");
6302     cur->set_next_in_collection_set(NULL);
6303     cur->set_in_collection_set(false);
6304     cur->set_young_index_in_cset(-1);
6305     cur = next;
6306   }
6307 }
6308 
6309 void G1CollectedHeap::set_free_regions_coming() {
6310   if (G1ConcRegionFreeingVerbose) {
6311     gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6312                            "setting free regions coming");
6313   }
6314 
6315   assert(!free_regions_coming(), "pre-condition");
6316   _free_regions_coming = true;
6317 }
6318 
6319 void G1CollectedHeap::reset_free_regions_coming() {
6320   assert(free_regions_coming(), "pre-condition");
6321 
6322   {
6323     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6324     _free_regions_coming = false;
6325     SecondaryFreeList_lock->notify_all();
6326   }
6327 
6328   if (G1ConcRegionFreeingVerbose) {
6329     gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6330                            "reset free regions coming");
6331   }
6332 }
6333 
6334 void G1CollectedHeap::wait_while_free_regions_coming() {
6335   // Most of the time we won't have to wait, so let's do a quick test
6336   // first before we take the lock.
6337   if (!free_regions_coming()) {
6338     return;
6339   }
6340 
6341   if (G1ConcRegionFreeingVerbose) {
6342     gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6343                            "waiting for free regions");
6344   }
6345 
6346   {
6347     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6348     while (free_regions_coming()) {
6349       SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
6350     }
6351   }
6352 
6353   if (G1ConcRegionFreeingVerbose) {
6354     gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6355                            "done waiting for free regions");
6356   }
6357 }
6358 
6359 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
6360   assert(heap_lock_held_for_gc(),
6361               "the heap lock should already be held by or for this thread");
6362   _young_list->push_region(hr);
6363 }
6364 
6365 class NoYoungRegionsClosure: public HeapRegionClosure {
6366 private:
6367   bool _success;
6368 public:
6369   NoYoungRegionsClosure() : _success(true) { }
6370   bool doHeapRegion(HeapRegion* r) {
6371     if (r->is_young()) {
6372       gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
6373                              r->bottom(), r->end());
6374       _success = false;
6375     }
6376     return false;
6377   }
6378   bool success() { return _success; }
6379 };
6380 
6381 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
6382   bool ret = _young_list->check_list_empty(check_sample);
6383 
6384   if (check_heap) {
6385     NoYoungRegionsClosure closure;
6386     heap_region_iterate(&closure);
6387     ret = ret && closure.success();
6388   }
6389 
6390   return ret;
6391 }
6392 
6393 class TearDownRegionSetsClosure : public HeapRegionClosure {
6394 private:
6395   HeapRegionSet *_old_set;
6396 
6397 public:
6398   TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
6399 
6400   bool doHeapRegion(HeapRegion* r) {
6401     if (r->is_old()) {
6402       _old_set->remove(r);
6403     } else {
6404       // We ignore free regions, we'll empty the free list afterwards.
6405       // We ignore young regions, we'll empty the young list afterwards.
6406       // We ignore humongous regions, we're not tearing down the
6407       // humongous regions set.
6408       assert(r->is_free() || r->is_young() || r->is_humongous(),
6409              "it cannot be another type");
6410     }
6411     return false;
6412   }
6413 
6414   ~TearDownRegionSetsClosure() {
6415     assert(_old_set->is_empty(), "post-condition");
6416   }
6417 };
6418 
6419 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6420   assert_at_safepoint(true /* should_be_vm_thread */);
6421 
6422   if (!free_list_only) {
6423     TearDownRegionSetsClosure cl(&_old_set);
6424     heap_region_iterate(&cl);
6425 
6426     // Note that emptying the _young_list is postponed and instead done as
6427     // the first step when rebuilding the regions sets again. The reason for
6428     // this is that during a full GC string deduplication needs to know if
6429     // a collected region was young or old when the full GC was initiated.
6430   }
6431   _hrm.remove_all_free_regions();
6432 }
6433 
6434 class RebuildRegionSetsClosure : public HeapRegionClosure {
6435 private:
6436   bool            _free_list_only;
6437   HeapRegionSet*   _old_set;
6438   HeapRegionManager*   _hrm;
6439   size_t          _total_used;
6440 
6441 public:
6442   RebuildRegionSetsClosure(bool free_list_only,
6443                            HeapRegionSet* old_set, HeapRegionManager* hrm) :
6444     _free_list_only(free_list_only),
6445     _old_set(old_set), _hrm(hrm), _total_used(0) {
6446     assert(_hrm->num_free_regions() == 0, "pre-condition");
6447     if (!free_list_only) {
6448       assert(_old_set->is_empty(), "pre-condition");
6449     }
6450   }
6451 
6452   bool doHeapRegion(HeapRegion* r) {
6453     if (r->is_continues_humongous()) {
6454       return false;
6455     }
6456 
6457     if (r->is_empty()) {
6458       // Add free regions to the free list
6459       r->set_free();
6460       r->set_allocation_context(AllocationContext::system());
6461       _hrm->insert_into_free_list(r);
6462     } else if (!_free_list_only) {
6463       assert(!r->is_young(), "we should not come across young regions");
6464 
6465       if (r->is_humongous()) {
6466         // We ignore humongous regions, we left the humongous set unchanged
6467       } else {
6468         // Objects that were compacted would have ended up on regions
6469         // that were previously old or free.
6470         assert(r->is_free() || r->is_old(), "invariant");
6471         // We now consider them old, so register as such.
6472         r->set_old();
6473         _old_set->add(r);
6474       }
6475       _total_used += r->used();
6476     }
6477 
6478     return false;
6479   }
6480 
6481   size_t total_used() {
6482     return _total_used;
6483   }
6484 };
6485 
6486 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6487   assert_at_safepoint(true /* should_be_vm_thread */);
6488 
6489   if (!free_list_only) {
6490     _young_list->empty_list();
6491   }
6492 
6493   RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
6494   heap_region_iterate(&cl);
6495 
6496   if (!free_list_only) {
6497     _allocator->set_used(cl.total_used());
6498   }
6499   assert(_allocator->used_unlocked() == recalculate_used(),
6500          err_msg("inconsistent _allocator->used_unlocked(), "
6501                  "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6502                  _allocator->used_unlocked(), recalculate_used()));
6503 }
6504 
6505 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6506   _refine_cte_cl->set_concurrent(concurrent);
6507 }
6508 
6509 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6510   HeapRegion* hr = heap_region_containing(p);
6511   return hr->is_in(p);
6512 }
6513 
6514 // Methods for the mutator alloc region
6515 
6516 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6517                                                       bool force) {
6518   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6519   assert(!force || g1_policy()->can_expand_young_list(),
6520          "if force is true we should be able to expand the young list");
6521   bool young_list_full = g1_policy()->is_young_list_full();
6522   if (force || !young_list_full) {
6523     HeapRegion* new_alloc_region = new_region(word_size,
6524                                               false /* is_old */,
6525                                               false /* do_expand */);
6526     if (new_alloc_region != NULL) {
6527       set_region_short_lived_locked(new_alloc_region);
6528       _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6529       check_bitmaps("Mutator Region Allocation", new_alloc_region);
6530       return new_alloc_region;
6531     }
6532   }
6533   return NULL;
6534 }
6535 
6536 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6537                                                   size_t allocated_bytes) {
6538   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6539   assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
6540 
6541   g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6542   _allocator->increase_used(allocated_bytes);
6543   _hr_printer.retire(alloc_region);
6544   // We update the eden sizes here, when the region is retired,
6545   // instead of when it's allocated, since this is the point that its
6546   // used space has been recored in _summary_bytes_used.
6547   g1mm()->update_eden_size();
6548 }
6549 
6550 void G1CollectedHeap::set_par_threads() {
6551   // Don't change the number of workers.  Use the value previously set
6552   // in the workgroup.
6553   uint n_workers = workers()->active_workers();
6554   assert(UseDynamicNumberOfGCThreads ||
6555            n_workers == workers()->total_workers(),
6556       "Otherwise should be using the total number of workers");
6557   if (n_workers == 0) {
6558     assert(false, "Should have been set in prior evacuation pause.");
6559     n_workers = ParallelGCThreads;
6560     workers()->set_active_workers(n_workers);
6561   }
6562   set_par_threads(n_workers);
6563 }
6564 
6565 // Methods for the GC alloc regions
6566 
6567 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6568                                                  uint count,
6569                                                  InCSetState dest) {
6570   assert(FreeList_lock->owned_by_self(), "pre-condition");
6571 
6572   if (count < g1_policy()->max_regions(dest)) {
6573     const bool is_survivor = (dest.is_young());
6574     HeapRegion* new_alloc_region = new_region(word_size,
6575                                               !is_survivor,
6576                                               true /* do_expand */);
6577     if (new_alloc_region != NULL) {
6578       // We really only need to do this for old regions given that we
6579       // should never scan survivors. But it doesn't hurt to do it
6580       // for survivors too.
6581       new_alloc_region->record_timestamp();
6582       if (is_survivor) {
6583         new_alloc_region->set_survivor();
6584         _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6585         check_bitmaps("Survivor Region Allocation", new_alloc_region);
6586       } else {
6587         new_alloc_region->set_old();
6588         _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6589         check_bitmaps("Old Region Allocation", new_alloc_region);
6590       }
6591       bool during_im = g1_policy()->during_initial_mark_pause();
6592       new_alloc_region->note_start_of_copying(during_im);
6593       return new_alloc_region;
6594     }
6595   }
6596   return NULL;
6597 }
6598 
6599 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6600                                              size_t allocated_bytes,
6601                                              InCSetState dest) {
6602   bool during_im = g1_policy()->during_initial_mark_pause();
6603   alloc_region->note_end_of_copying(during_im);
6604   g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6605   if (dest.is_young()) {
6606     young_list()->add_survivor_region(alloc_region);
6607   } else {
6608     _old_set.add(alloc_region);
6609   }
6610   _hr_printer.retire(alloc_region);
6611 }
6612 
6613 // Heap region set verification
6614 
6615 class VerifyRegionListsClosure : public HeapRegionClosure {
6616 private:
6617   HeapRegionSet*   _old_set;
6618   HeapRegionSet*   _humongous_set;
6619   HeapRegionManager*   _hrm;
6620 
6621 public:
6622   HeapRegionSetCount _old_count;
6623   HeapRegionSetCount _humongous_count;
6624   HeapRegionSetCount _free_count;
6625 
6626   VerifyRegionListsClosure(HeapRegionSet* old_set,
6627                            HeapRegionSet* humongous_set,
6628                            HeapRegionManager* hrm) :
6629     _old_set(old_set), _humongous_set(humongous_set), _hrm(hrm),
6630     _old_count(), _humongous_count(), _free_count(){ }
6631 
6632   bool doHeapRegion(HeapRegion* hr) {
6633     if (hr->is_continues_humongous()) {
6634       return false;
6635     }
6636 
6637     if (hr->is_young()) {
6638       // TODO
6639     } else if (hr->is_starts_humongous()) {
6640       assert(hr->containing_set() == _humongous_set, err_msg("Heap region %u is starts humongous but not in humongous set.", hr->hrm_index()));
6641       _humongous_count.increment(1u, hr->capacity());
6642     } else if (hr->is_empty()) {
6643       assert(_hrm->is_free(hr), err_msg("Heap region %u is empty but not on the free list.", hr->hrm_index()));
6644       _free_count.increment(1u, hr->capacity());
6645     } else if (hr->is_old()) {
6646       assert(hr->containing_set() == _old_set, err_msg("Heap region %u is old but not in the old set.", hr->hrm_index()));
6647       _old_count.increment(1u, hr->capacity());
6648     } else {
6649       ShouldNotReachHere();
6650     }
6651     return false;
6652   }
6653 
6654   void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, HeapRegionManager* free_list) {
6655     guarantee(old_set->length() == _old_count.length(), err_msg("Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length()));
6656     guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), err_msg("Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6657         old_set->total_capacity_bytes(), _old_count.capacity()));
6658 
6659     guarantee(humongous_set->length() == _humongous_count.length(), err_msg("Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length()));
6660     guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), err_msg("Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6661         humongous_set->total_capacity_bytes(), _humongous_count.capacity()));
6662 
6663     guarantee(free_list->num_free_regions() == _free_count.length(), err_msg("Free list count mismatch. Expected %u, actual %u.", free_list->num_free_regions(), _free_count.length()));
6664     guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), err_msg("Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6665         free_list->total_capacity_bytes(), _free_count.capacity()));
6666   }
6667 };
6668 
6669 void G1CollectedHeap::verify_region_sets() {
6670   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6671 
6672   // First, check the explicit lists.
6673   _hrm.verify();
6674   {
6675     // Given that a concurrent operation might be adding regions to
6676     // the secondary free list we have to take the lock before
6677     // verifying it.
6678     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6679     _secondary_free_list.verify_list();
6680   }
6681 
6682   // If a concurrent region freeing operation is in progress it will
6683   // be difficult to correctly attributed any free regions we come
6684   // across to the correct free list given that they might belong to
6685   // one of several (free_list, secondary_free_list, any local lists,
6686   // etc.). So, if that's the case we will skip the rest of the
6687   // verification operation. Alternatively, waiting for the concurrent
6688   // operation to complete will have a non-trivial effect on the GC's
6689   // operation (no concurrent operation will last longer than the
6690   // interval between two calls to verification) and it might hide
6691   // any issues that we would like to catch during testing.
6692   if (free_regions_coming()) {
6693     return;
6694   }
6695 
6696   // Make sure we append the secondary_free_list on the free_list so
6697   // that all free regions we will come across can be safely
6698   // attributed to the free_list.
6699   append_secondary_free_list_if_not_empty_with_lock();
6700 
6701   // Finally, make sure that the region accounting in the lists is
6702   // consistent with what we see in the heap.
6703 
6704   VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_hrm);
6705   heap_region_iterate(&cl);
6706   cl.verify_counts(&_old_set, &_humongous_set, &_hrm);
6707 }
6708 
6709 // Optimized nmethod scanning
6710 
6711 class RegisterNMethodOopClosure: public OopClosure {
6712   G1CollectedHeap* _g1h;
6713   nmethod* _nm;
6714 
6715   template <class T> void do_oop_work(T* p) {
6716     T heap_oop = oopDesc::load_heap_oop(p);
6717     if (!oopDesc::is_null(heap_oop)) {
6718       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6719       HeapRegion* hr = _g1h->heap_region_containing(obj);
6720       assert(!hr->is_continues_humongous(),
6721              err_msg("trying to add code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6722                      " starting at "HR_FORMAT,
6723                      _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6724 
6725       // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
6726       hr->add_strong_code_root_locked(_nm);
6727     }
6728   }
6729 
6730 public:
6731   RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6732     _g1h(g1h), _nm(nm) {}
6733 
6734   void do_oop(oop* p)       { do_oop_work(p); }
6735   void do_oop(narrowOop* p) { do_oop_work(p); }
6736 };
6737 
6738 class UnregisterNMethodOopClosure: public OopClosure {
6739   G1CollectedHeap* _g1h;
6740   nmethod* _nm;
6741 
6742   template <class T> void do_oop_work(T* p) {
6743     T heap_oop = oopDesc::load_heap_oop(p);
6744     if (!oopDesc::is_null(heap_oop)) {
6745       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6746       HeapRegion* hr = _g1h->heap_region_containing(obj);
6747       assert(!hr->is_continues_humongous(),
6748              err_msg("trying to remove code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6749                      " starting at "HR_FORMAT,
6750                      _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6751 
6752       hr->remove_strong_code_root(_nm);
6753     }
6754   }
6755 
6756 public:
6757   UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6758     _g1h(g1h), _nm(nm) {}
6759 
6760   void do_oop(oop* p)       { do_oop_work(p); }
6761   void do_oop(narrowOop* p) { do_oop_work(p); }
6762 };
6763 
6764 void G1CollectedHeap::register_nmethod(nmethod* nm) {
6765   CollectedHeap::register_nmethod(nm);
6766 
6767   guarantee(nm != NULL, "sanity");
6768   RegisterNMethodOopClosure reg_cl(this, nm);
6769   nm->oops_do(&reg_cl);
6770 }
6771 
6772 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
6773   CollectedHeap::unregister_nmethod(nm);
6774 
6775   guarantee(nm != NULL, "sanity");
6776   UnregisterNMethodOopClosure reg_cl(this, nm);
6777   nm->oops_do(&reg_cl, true);
6778 }
6779 
6780 void G1CollectedHeap::purge_code_root_memory() {
6781   double purge_start = os::elapsedTime();
6782   G1CodeRootSet::purge();
6783   double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
6784   g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
6785 }
6786 
6787 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
6788   G1CollectedHeap* _g1h;
6789 
6790 public:
6791   RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
6792     _g1h(g1h) {}
6793 
6794   void do_code_blob(CodeBlob* cb) {
6795     nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
6796     if (nm == NULL) {
6797       return;
6798     }
6799 
6800     if (ScavengeRootsInCode) {
6801       _g1h->register_nmethod(nm);
6802     }
6803   }
6804 };
6805 
6806 void G1CollectedHeap::rebuild_strong_code_roots() {
6807   RebuildStrongCodeRootClosure blob_cl(this);
6808   CodeCache::blobs_do(&blob_cl);
6809 }