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(true /*verify_disabled*/, true /*verify_no_refs*/);
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 gen rem set (and barrier set) for the entire reserved region.
1890   _rem_set = collector_policy()->create_rem_set(reserved_region());
1891   set_barrier_set(rem_set()->bs());
1892   if (!barrier_set()->is_a(BarrierSet::G1SATBCTLogging)) {
1893     vm_exit_during_initialization("G1 requires a G1SATBLoggingCardTableModRefBS");
1894     return JNI_ENOMEM;
1895   }
1896 
1897   // Also create a G1 rem set.
1898   _g1_rem_set = new G1RemSet(this, g1_barrier_set());
1899 
1900   // Carve out the G1 part of the heap.
1901 
1902   ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1903   G1RegionToSpaceMapper* heap_storage =
1904     G1RegionToSpaceMapper::create_mapper(g1_rs,
1905                                          UseLargePages ? os::large_page_size() : os::vm_page_size(),
1906                                          HeapRegion::GrainBytes,
1907                                          1,
1908                                          mtJavaHeap);
1909   heap_storage->set_mapping_changed_listener(&_listener);
1910 
1911   // Reserve space for the block offset table. We do not support automatic uncommit
1912   // for the card table at this time. BOT only.
1913   ReservedSpace bot_rs(G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize));
1914   G1RegionToSpaceMapper* bot_storage =
1915     G1RegionToSpaceMapper::create_mapper(bot_rs,
1916                                          os::vm_page_size(),
1917                                          HeapRegion::GrainBytes,
1918                                          G1BlockOffsetSharedArray::N_bytes,
1919                                          mtGC);
1920 
1921   ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize));
1922   G1RegionToSpaceMapper* cardtable_storage =
1923     G1RegionToSpaceMapper::create_mapper(cardtable_rs,
1924                                          os::vm_page_size(),
1925                                          HeapRegion::GrainBytes,
1926                                          G1BlockOffsetSharedArray::N_bytes,
1927                                          mtGC);
1928 
1929   // Reserve space for the card counts table.
1930   ReservedSpace card_counts_rs(G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize));
1931   G1RegionToSpaceMapper* card_counts_storage =
1932     G1RegionToSpaceMapper::create_mapper(card_counts_rs,
1933                                          os::vm_page_size(),
1934                                          HeapRegion::GrainBytes,
1935                                          G1BlockOffsetSharedArray::N_bytes,
1936                                          mtGC);
1937 
1938   // Reserve space for prev and next bitmap.
1939   size_t bitmap_size = CMBitMap::compute_size(g1_rs.size());
1940 
1941   ReservedSpace prev_bitmap_rs(ReservedSpace::allocation_align_size_up(bitmap_size));
1942   G1RegionToSpaceMapper* prev_bitmap_storage =
1943     G1RegionToSpaceMapper::create_mapper(prev_bitmap_rs,
1944                                          os::vm_page_size(),
1945                                          HeapRegion::GrainBytes,
1946                                          CMBitMap::mark_distance(),
1947                                          mtGC);
1948 
1949   ReservedSpace next_bitmap_rs(ReservedSpace::allocation_align_size_up(bitmap_size));
1950   G1RegionToSpaceMapper* next_bitmap_storage =
1951     G1RegionToSpaceMapper::create_mapper(next_bitmap_rs,
1952                                          os::vm_page_size(),
1953                                          HeapRegion::GrainBytes,
1954                                          CMBitMap::mark_distance(),
1955                                          mtGC);
1956 
1957   _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1958   g1_barrier_set()->initialize(cardtable_storage);
1959    // Do later initialization work for concurrent refinement.
1960   _cg1r->init(card_counts_storage);
1961 
1962   // 6843694 - ensure that the maximum region index can fit
1963   // in the remembered set structures.
1964   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1965   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1966 
1967   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1968   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1969   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1970             "too many cards per region");
1971 
1972   FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
1973 
1974   _bot_shared = new G1BlockOffsetSharedArray(reserved_region(), bot_storage);
1975 
1976   _g1h = this;
1977 
1978   _in_cset_fast_test.initialize(_hrm.reserved().start(), _hrm.reserved().end(), HeapRegion::GrainBytes);
1979   _humongous_is_live.initialize(_hrm.reserved().start(), _hrm.reserved().end(), HeapRegion::GrainBytes);
1980 
1981   // Create the ConcurrentMark data structure and thread.
1982   // (Must do this late, so that "max_regions" is defined.)
1983   _cm = new ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1984   if (_cm == NULL || !_cm->completed_initialization()) {
1985     vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark");
1986     return JNI_ENOMEM;
1987   }
1988   _cmThread = _cm->cmThread();
1989 
1990   // Initialize the from_card cache structure of HeapRegionRemSet.
1991   HeapRegionRemSet::init_heap(max_regions());
1992 
1993   // Now expand into the initial heap size.
1994   if (!expand(init_byte_size)) {
1995     vm_shutdown_during_initialization("Failed to allocate initial heap.");
1996     return JNI_ENOMEM;
1997   }
1998 
1999   // Perform any initialization actions delegated to the policy.
2000   g1_policy()->init();
2001 
2002   JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
2003                                                SATB_Q_FL_lock,
2004                                                G1SATBProcessCompletedThreshold,
2005                                                Shared_SATB_Q_lock);
2006 
2007   JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl,
2008                                                 DirtyCardQ_CBL_mon,
2009                                                 DirtyCardQ_FL_lock,
2010                                                 concurrent_g1_refine()->yellow_zone(),
2011                                                 concurrent_g1_refine()->red_zone(),
2012                                                 Shared_DirtyCardQ_lock);
2013 
2014   dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code
2015                                     DirtyCardQ_CBL_mon,
2016                                     DirtyCardQ_FL_lock,
2017                                     -1, // never trigger processing
2018                                     -1, // no limit on length
2019                                     Shared_DirtyCardQ_lock,
2020                                     &JavaThread::dirty_card_queue_set());
2021 
2022   // Initialize the card queue set used to hold cards containing
2023   // references into the collection set.
2024   _into_cset_dirty_card_queue_set.initialize(NULL, // Should never be called by the Java code
2025                                              DirtyCardQ_CBL_mon,
2026                                              DirtyCardQ_FL_lock,
2027                                              -1, // never trigger processing
2028                                              -1, // no limit on length
2029                                              Shared_DirtyCardQ_lock,
2030                                              &JavaThread::dirty_card_queue_set());
2031 
2032   // In case we're keeping closure specialization stats, initialize those
2033   // counts and that mechanism.
2034   SpecializationStats::clear();
2035 
2036   // Here we allocate the dummy HeapRegion that is required by the
2037   // G1AllocRegion class.
2038   HeapRegion* dummy_region = _hrm.get_dummy_region();
2039 
2040   // We'll re-use the same region whether the alloc region will
2041   // require BOT updates or not and, if it doesn't, then a non-young
2042   // region will complain that it cannot support allocations without
2043   // BOT updates. So we'll tag the dummy region as eden to avoid that.
2044   dummy_region->set_eden();
2045   // Make sure it's full.
2046   dummy_region->set_top(dummy_region->end());
2047   G1AllocRegion::setup(this, dummy_region);
2048 
2049   _allocator->init_mutator_alloc_region();
2050 
2051   // Do create of the monitoring and management support so that
2052   // values in the heap have been properly initialized.
2053   _g1mm = new G1MonitoringSupport(this);
2054 
2055   G1StringDedup::initialize();
2056 
2057   return JNI_OK;
2058 }
2059 
2060 void G1CollectedHeap::stop() {
2061   // Stop all concurrent threads. We do this to make sure these threads
2062   // do not continue to execute and access resources (e.g. gclog_or_tty)
2063   // that are destroyed during shutdown.
2064   _cg1r->stop();
2065   _cmThread->stop();
2066   if (G1StringDedup::is_enabled()) {
2067     G1StringDedup::stop();
2068   }
2069 }
2070 
2071 void G1CollectedHeap::clear_humongous_is_live_table() {
2072   guarantee(G1ReclaimDeadHumongousObjectsAtYoungGC, "Should only be called if true");
2073   _humongous_is_live.clear();
2074 }
2075 
2076 size_t G1CollectedHeap::conservative_max_heap_alignment() {
2077   return HeapRegion::max_region_size();
2078 }
2079 
2080 void G1CollectedHeap::ref_processing_init() {
2081   // Reference processing in G1 currently works as follows:
2082   //
2083   // * There are two reference processor instances. One is
2084   //   used to record and process discovered references
2085   //   during concurrent marking; the other is used to
2086   //   record and process references during STW pauses
2087   //   (both full and incremental).
2088   // * Both ref processors need to 'span' the entire heap as
2089   //   the regions in the collection set may be dotted around.
2090   //
2091   // * For the concurrent marking ref processor:
2092   //   * Reference discovery is enabled at initial marking.
2093   //   * Reference discovery is disabled and the discovered
2094   //     references processed etc during remarking.
2095   //   * Reference discovery is MT (see below).
2096   //   * Reference discovery requires a barrier (see below).
2097   //   * Reference processing may or may not be MT
2098   //     (depending on the value of ParallelRefProcEnabled
2099   //     and ParallelGCThreads).
2100   //   * A full GC disables reference discovery by the CM
2101   //     ref processor and abandons any entries on it's
2102   //     discovered lists.
2103   //
2104   // * For the STW processor:
2105   //   * Non MT discovery is enabled at the start of a full GC.
2106   //   * Processing and enqueueing during a full GC is non-MT.
2107   //   * During a full GC, references are processed after marking.
2108   //
2109   //   * Discovery (may or may not be MT) is enabled at the start
2110   //     of an incremental evacuation pause.
2111   //   * References are processed near the end of a STW evacuation pause.
2112   //   * For both types of GC:
2113   //     * Discovery is atomic - i.e. not concurrent.
2114   //     * Reference discovery will not need a barrier.
2115 
2116   SharedHeap::ref_processing_init();
2117   MemRegion mr = reserved_region();
2118 
2119   // Concurrent Mark ref processor
2120   _ref_processor_cm =
2121     new ReferenceProcessor(mr,    // span
2122                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2123                                 // mt processing
2124                            (int) ParallelGCThreads,
2125                                 // degree of mt processing
2126                            (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2127                                 // mt discovery
2128                            (int) MAX2(ParallelGCThreads, ConcGCThreads),
2129                                 // degree of mt discovery
2130                            false,
2131                                 // Reference discovery is not atomic
2132                            &_is_alive_closure_cm);
2133                                 // is alive closure
2134                                 // (for efficiency/performance)
2135 
2136   // STW ref processor
2137   _ref_processor_stw =
2138     new ReferenceProcessor(mr,    // span
2139                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2140                                 // mt processing
2141                            MAX2((int)ParallelGCThreads, 1),
2142                                 // degree of mt processing
2143                            (ParallelGCThreads > 1),
2144                                 // mt discovery
2145                            MAX2((int)ParallelGCThreads, 1),
2146                                 // degree of mt discovery
2147                            true,
2148                                 // Reference discovery is atomic
2149                            &_is_alive_closure_stw);
2150                                 // is alive closure
2151                                 // (for efficiency/performance)
2152 }
2153 
2154 size_t G1CollectedHeap::capacity() const {
2155   return _hrm.length() * HeapRegion::GrainBytes;
2156 }
2157 
2158 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2159   assert(!hr->is_continues_humongous(), "pre-condition");
2160   hr->reset_gc_time_stamp();
2161   if (hr->is_starts_humongous()) {
2162     uint first_index = hr->hrm_index() + 1;
2163     uint last_index = hr->last_hc_index();
2164     for (uint i = first_index; i < last_index; i += 1) {
2165       HeapRegion* chr = region_at(i);
2166       assert(chr->is_continues_humongous(), "sanity");
2167       chr->reset_gc_time_stamp();
2168     }
2169   }
2170 }
2171 
2172 #ifndef PRODUCT
2173 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2174 private:
2175   unsigned _gc_time_stamp;
2176   bool _failures;
2177 
2178 public:
2179   CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2180     _gc_time_stamp(gc_time_stamp), _failures(false) { }
2181 
2182   virtual bool doHeapRegion(HeapRegion* hr) {
2183     unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2184     if (_gc_time_stamp != region_gc_time_stamp) {
2185       gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, "
2186                              "expected %d", HR_FORMAT_PARAMS(hr),
2187                              region_gc_time_stamp, _gc_time_stamp);
2188       _failures = true;
2189     }
2190     return false;
2191   }
2192 
2193   bool failures() { return _failures; }
2194 };
2195 
2196 void G1CollectedHeap::check_gc_time_stamps() {
2197   CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2198   heap_region_iterate(&cl);
2199   guarantee(!cl.failures(), "all GC time stamps should have been reset");
2200 }
2201 #endif // PRODUCT
2202 
2203 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2204                                                  DirtyCardQueue* into_cset_dcq,
2205                                                  bool concurrent,
2206                                                  uint worker_i) {
2207   // Clean cards in the hot card cache
2208   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
2209   hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq);
2210 
2211   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2212   int n_completed_buffers = 0;
2213   while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2214     n_completed_buffers++;
2215   }
2216   g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers);
2217   dcqs.clear_n_completed_buffers();
2218   assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2219 }
2220 
2221 
2222 // Computes the sum of the storage used by the various regions.
2223 size_t G1CollectedHeap::used() const {
2224   return _allocator->used();
2225 }
2226 
2227 size_t G1CollectedHeap::used_unlocked() const {
2228   return _allocator->used_unlocked();
2229 }
2230 
2231 class SumUsedClosure: public HeapRegionClosure {
2232   size_t _used;
2233 public:
2234   SumUsedClosure() : _used(0) {}
2235   bool doHeapRegion(HeapRegion* r) {
2236     if (!r->is_continues_humongous()) {
2237       _used += r->used();
2238     }
2239     return false;
2240   }
2241   size_t result() { return _used; }
2242 };
2243 
2244 size_t G1CollectedHeap::recalculate_used() const {
2245   double recalculate_used_start = os::elapsedTime();
2246 
2247   SumUsedClosure blk;
2248   heap_region_iterate(&blk);
2249 
2250   g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2251   return blk.result();
2252 }
2253 
2254 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2255   switch (cause) {
2256     case GCCause::_gc_locker:               return GCLockerInvokesConcurrent;
2257     case GCCause::_java_lang_system_gc:     return ExplicitGCInvokesConcurrent;
2258     case GCCause::_g1_humongous_allocation: return true;
2259     case GCCause::_update_allocation_context_stats_inc: return true;
2260     case GCCause::_wb_conc_mark:            return true;
2261     default:                                return false;
2262   }
2263 }
2264 
2265 #ifndef PRODUCT
2266 void G1CollectedHeap::allocate_dummy_regions() {
2267   // Let's fill up most of the region
2268   size_t word_size = HeapRegion::GrainWords - 1024;
2269   // And as a result the region we'll allocate will be humongous.
2270   guarantee(is_humongous(word_size), "sanity");
2271 
2272   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2273     // Let's use the existing mechanism for the allocation
2274     HeapWord* dummy_obj = humongous_obj_allocate(word_size,
2275                                                  AllocationContext::system());
2276     if (dummy_obj != NULL) {
2277       MemRegion mr(dummy_obj, word_size);
2278       CollectedHeap::fill_with_object(mr);
2279     } else {
2280       // If we can't allocate once, we probably cannot allocate
2281       // again. Let's get out of the loop.
2282       break;
2283     }
2284   }
2285 }
2286 #endif // !PRODUCT
2287 
2288 void G1CollectedHeap::increment_old_marking_cycles_started() {
2289   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2290     _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2291     err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2292     _old_marking_cycles_started, _old_marking_cycles_completed));
2293 
2294   _old_marking_cycles_started++;
2295 }
2296 
2297 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2298   MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2299 
2300   // We assume that if concurrent == true, then the caller is a
2301   // concurrent thread that was joined the Suspendible Thread
2302   // Set. If there's ever a cheap way to check this, we should add an
2303   // assert here.
2304 
2305   // Given that this method is called at the end of a Full GC or of a
2306   // concurrent cycle, and those can be nested (i.e., a Full GC can
2307   // interrupt a concurrent cycle), the number of full collections
2308   // completed should be either one (in the case where there was no
2309   // nesting) or two (when a Full GC interrupted a concurrent cycle)
2310   // behind the number of full collections started.
2311 
2312   // This is the case for the inner caller, i.e. a Full GC.
2313   assert(concurrent ||
2314          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2315          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2316          err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
2317                  "is inconsistent with _old_marking_cycles_completed = %u",
2318                  _old_marking_cycles_started, _old_marking_cycles_completed));
2319 
2320   // This is the case for the outer caller, i.e. the concurrent cycle.
2321   assert(!concurrent ||
2322          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2323          err_msg("for outer caller (concurrent cycle): "
2324                  "_old_marking_cycles_started = %u "
2325                  "is inconsistent with _old_marking_cycles_completed = %u",
2326                  _old_marking_cycles_started, _old_marking_cycles_completed));
2327 
2328   _old_marking_cycles_completed += 1;
2329 
2330   // We need to clear the "in_progress" flag in the CM thread before
2331   // we wake up any waiters (especially when ExplicitInvokesConcurrent
2332   // is set) so that if a waiter requests another System.gc() it doesn't
2333   // incorrectly see that a marking cycle is still in progress.
2334   if (concurrent) {
2335     _cmThread->clear_in_progress();
2336   }
2337 
2338   // This notify_all() will ensure that a thread that called
2339   // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2340   // and it's waiting for a full GC to finish will be woken up. It is
2341   // waiting in VM_G1IncCollectionPause::doit_epilogue().
2342   FullGCCount_lock->notify_all();
2343 }
2344 
2345 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) {
2346   _concurrent_cycle_started = true;
2347   _gc_timer_cm->register_gc_start(start_time);
2348 
2349   _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start());
2350   trace_heap_before_gc(_gc_tracer_cm);
2351 }
2352 
2353 void G1CollectedHeap::register_concurrent_cycle_end() {
2354   if (_concurrent_cycle_started) {
2355     if (_cm->has_aborted()) {
2356       _gc_tracer_cm->report_concurrent_mode_failure();
2357     }
2358 
2359     _gc_timer_cm->register_gc_end();
2360     _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
2361 
2362     // Clear state variables to prepare for the next concurrent cycle.
2363     _concurrent_cycle_started = false;
2364     _heap_summary_sent = false;
2365   }
2366 }
2367 
2368 void G1CollectedHeap::trace_heap_after_concurrent_cycle() {
2369   if (_concurrent_cycle_started) {
2370     // This function can be called when:
2371     //  the cleanup pause is run
2372     //  the concurrent cycle is aborted before the cleanup pause.
2373     //  the concurrent cycle is aborted after the cleanup pause,
2374     //   but before the concurrent cycle end has been registered.
2375     // Make sure that we only send the heap information once.
2376     if (!_heap_summary_sent) {
2377       trace_heap_after_gc(_gc_tracer_cm);
2378       _heap_summary_sent = true;
2379     }
2380   }
2381 }
2382 
2383 G1YCType G1CollectedHeap::yc_type() {
2384   bool is_young = g1_policy()->gcs_are_young();
2385   bool is_initial_mark = g1_policy()->during_initial_mark_pause();
2386   bool is_during_mark = mark_in_progress();
2387 
2388   if (is_initial_mark) {
2389     return InitialMark;
2390   } else if (is_during_mark) {
2391     return DuringMark;
2392   } else if (is_young) {
2393     return Normal;
2394   } else {
2395     return Mixed;
2396   }
2397 }
2398 
2399 void G1CollectedHeap::collect(GCCause::Cause cause) {
2400   assert_heap_not_locked();
2401 
2402   unsigned int gc_count_before;
2403   unsigned int old_marking_count_before;
2404   unsigned int full_gc_count_before;
2405   bool retry_gc;
2406 
2407   do {
2408     retry_gc = false;
2409 
2410     {
2411       MutexLocker ml(Heap_lock);
2412 
2413       // Read the GC count while holding the Heap_lock
2414       gc_count_before = total_collections();
2415       full_gc_count_before = total_full_collections();
2416       old_marking_count_before = _old_marking_cycles_started;
2417     }
2418 
2419     if (should_do_concurrent_full_gc(cause)) {
2420       // Schedule an initial-mark evacuation pause that will start a
2421       // concurrent cycle. We're setting word_size to 0 which means that
2422       // we are not requesting a post-GC allocation.
2423       VM_G1IncCollectionPause op(gc_count_before,
2424                                  0,     /* word_size */
2425                                  true,  /* should_initiate_conc_mark */
2426                                  g1_policy()->max_pause_time_ms(),
2427                                  cause);
2428       op.set_allocation_context(AllocationContext::current());
2429 
2430       VMThread::execute(&op);
2431       if (!op.pause_succeeded()) {
2432         if (old_marking_count_before == _old_marking_cycles_started) {
2433           retry_gc = op.should_retry_gc();
2434         } else {
2435           // A Full GC happened while we were trying to schedule the
2436           // initial-mark GC. No point in starting a new cycle given
2437           // that the whole heap was collected anyway.
2438         }
2439 
2440         if (retry_gc) {
2441           if (GC_locker::is_active_and_needs_gc()) {
2442             GC_locker::stall_until_clear();
2443           }
2444         }
2445       }
2446     } else {
2447       if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2448           DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2449 
2450         // Schedule a standard evacuation pause. We're setting word_size
2451         // to 0 which means that we are not requesting a post-GC allocation.
2452         VM_G1IncCollectionPause op(gc_count_before,
2453                                    0,     /* word_size */
2454                                    false, /* should_initiate_conc_mark */
2455                                    g1_policy()->max_pause_time_ms(),
2456                                    cause);
2457         VMThread::execute(&op);
2458       } else {
2459         // Schedule a Full GC.
2460         VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2461         VMThread::execute(&op);
2462       }
2463     }
2464   } while (retry_gc);
2465 }
2466 
2467 bool G1CollectedHeap::is_in(const void* p) const {
2468   if (_hrm.reserved().contains(p)) {
2469     // Given that we know that p is in the reserved space,
2470     // heap_region_containing_raw() should successfully
2471     // return the containing region.
2472     HeapRegion* hr = heap_region_containing_raw(p);
2473     return hr->is_in(p);
2474   } else {
2475     return false;
2476   }
2477 }
2478 
2479 #ifdef ASSERT
2480 bool G1CollectedHeap::is_in_exact(const void* p) const {
2481   bool contains = reserved_region().contains(p);
2482   bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2483   if (contains && available) {
2484     return true;
2485   } else {
2486     return false;
2487   }
2488 }
2489 #endif
2490 
2491 // Iteration functions.
2492 
2493 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion.
2494 
2495 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2496   ExtendedOopClosure* _cl;
2497 public:
2498   IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {}
2499   bool doHeapRegion(HeapRegion* r) {
2500     if (!r->is_continues_humongous()) {
2501       r->oop_iterate(_cl);
2502     }
2503     return false;
2504   }
2505 };
2506 
2507 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) {
2508   IterateOopClosureRegionClosure blk(cl);
2509   heap_region_iterate(&blk);
2510 }
2511 
2512 // Iterates an ObjectClosure over all objects within a HeapRegion.
2513 
2514 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2515   ObjectClosure* _cl;
2516 public:
2517   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2518   bool doHeapRegion(HeapRegion* r) {
2519     if (!r->is_continues_humongous()) {
2520       r->object_iterate(_cl);
2521     }
2522     return false;
2523   }
2524 };
2525 
2526 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2527   IterateObjectClosureRegionClosure blk(cl);
2528   heap_region_iterate(&blk);
2529 }
2530 
2531 // Calls a SpaceClosure on a HeapRegion.
2532 
2533 class SpaceClosureRegionClosure: public HeapRegionClosure {
2534   SpaceClosure* _cl;
2535 public:
2536   SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2537   bool doHeapRegion(HeapRegion* r) {
2538     _cl->do_space(r);
2539     return false;
2540   }
2541 };
2542 
2543 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2544   SpaceClosureRegionClosure blk(cl);
2545   heap_region_iterate(&blk);
2546 }
2547 
2548 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2549   _hrm.iterate(cl);
2550 }
2551 
2552 void
2553 G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl,
2554                                          uint worker_id,
2555                                          HeapRegionClaimer *hrclaimer,
2556                                          bool concurrent) const {
2557   _hrm.par_iterate(cl, worker_id, hrclaimer, concurrent);
2558 }
2559 
2560 // Clear the cached CSet starting regions and (more importantly)
2561 // the time stamps. Called when we reset the GC time stamp.
2562 void G1CollectedHeap::clear_cset_start_regions() {
2563   assert(_worker_cset_start_region != NULL, "sanity");
2564   assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2565 
2566   int n_queues = MAX2((int)ParallelGCThreads, 1);
2567   for (int i = 0; i < n_queues; i++) {
2568     _worker_cset_start_region[i] = NULL;
2569     _worker_cset_start_region_time_stamp[i] = 0;
2570   }
2571 }
2572 
2573 // Given the id of a worker, obtain or calculate a suitable
2574 // starting region for iterating over the current collection set.
2575 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) {
2576   assert(get_gc_time_stamp() > 0, "should have been updated by now");
2577 
2578   HeapRegion* result = NULL;
2579   unsigned gc_time_stamp = get_gc_time_stamp();
2580 
2581   if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2582     // Cached starting region for current worker was set
2583     // during the current pause - so it's valid.
2584     // Note: the cached starting heap region may be NULL
2585     // (when the collection set is empty).
2586     result = _worker_cset_start_region[worker_i];
2587     assert(result == NULL || result->in_collection_set(), "sanity");
2588     return result;
2589   }
2590 
2591   // The cached entry was not valid so let's calculate
2592   // a suitable starting heap region for this worker.
2593 
2594   // We want the parallel threads to start their collection
2595   // set iteration at different collection set regions to
2596   // avoid contention.
2597   // If we have:
2598   //          n collection set regions
2599   //          p threads
2600   // Then thread t will start at region floor ((t * n) / p)
2601 
2602   result = g1_policy()->collection_set();
2603   uint cs_size = g1_policy()->cset_region_length();
2604   uint active_workers = workers()->active_workers();
2605   assert(UseDynamicNumberOfGCThreads ||
2606            active_workers == workers()->total_workers(),
2607            "Unless dynamic should use total workers");
2608 
2609   uint end_ind   = (cs_size * worker_i) / active_workers;
2610   uint start_ind = 0;
2611 
2612   if (worker_i > 0 &&
2613       _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2614     // Previous workers starting region is valid
2615     // so let's iterate from there
2616     start_ind = (cs_size * (worker_i - 1)) / active_workers;
2617     result = _worker_cset_start_region[worker_i - 1];
2618   }
2619 
2620   for (uint i = start_ind; i < end_ind; i++) {
2621     result = result->next_in_collection_set();
2622   }
2623 
2624   // Note: the calculated starting heap region may be NULL
2625   // (when the collection set is empty).
2626   assert(result == NULL || result->in_collection_set(), "sanity");
2627   assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2628          "should be updated only once per pause");
2629   _worker_cset_start_region[worker_i] = result;
2630   OrderAccess::storestore();
2631   _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2632   return result;
2633 }
2634 
2635 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2636   HeapRegion* r = g1_policy()->collection_set();
2637   while (r != NULL) {
2638     HeapRegion* next = r->next_in_collection_set();
2639     if (cl->doHeapRegion(r)) {
2640       cl->incomplete();
2641       return;
2642     }
2643     r = next;
2644   }
2645 }
2646 
2647 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2648                                                   HeapRegionClosure *cl) {
2649   if (r == NULL) {
2650     // The CSet is empty so there's nothing to do.
2651     return;
2652   }
2653 
2654   assert(r->in_collection_set(),
2655          "Start region must be a member of the collection set.");
2656   HeapRegion* cur = r;
2657   while (cur != NULL) {
2658     HeapRegion* next = cur->next_in_collection_set();
2659     if (cl->doHeapRegion(cur) && false) {
2660       cl->incomplete();
2661       return;
2662     }
2663     cur = next;
2664   }
2665   cur = g1_policy()->collection_set();
2666   while (cur != r) {
2667     HeapRegion* next = cur->next_in_collection_set();
2668     if (cl->doHeapRegion(cur) && false) {
2669       cl->incomplete();
2670       return;
2671     }
2672     cur = next;
2673   }
2674 }
2675 
2676 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const {
2677   HeapRegion* result = _hrm.next_region_in_heap(from);
2678   while (result != NULL && result->is_humongous()) {
2679     result = _hrm.next_region_in_heap(result);
2680   }
2681   return result;
2682 }
2683 
2684 Space* G1CollectedHeap::space_containing(const void* addr) const {
2685   return heap_region_containing(addr);
2686 }
2687 
2688 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2689   Space* sp = space_containing(addr);
2690   return sp->block_start(addr);
2691 }
2692 
2693 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2694   Space* sp = space_containing(addr);
2695   return sp->block_size(addr);
2696 }
2697 
2698 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2699   Space* sp = space_containing(addr);
2700   return sp->block_is_obj(addr);
2701 }
2702 
2703 bool G1CollectedHeap::supports_tlab_allocation() const {
2704   return true;
2705 }
2706 
2707 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2708   return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes;
2709 }
2710 
2711 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2712   return young_list()->eden_used_bytes();
2713 }
2714 
2715 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2716 // must be smaller than the humongous object limit.
2717 size_t G1CollectedHeap::max_tlab_size() const {
2718   return align_size_down(_humongous_object_threshold_in_words - 1, MinObjAlignment);
2719 }
2720 
2721 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2722   // Return the remaining space in the cur alloc region, but not less than
2723   // the min TLAB size.
2724 
2725   // Also, this value can be at most the humongous object threshold,
2726   // since we can't allow tlabs to grow big enough to accommodate
2727   // humongous objects.
2728 
2729   HeapRegion* hr = _allocator->mutator_alloc_region(AllocationContext::current())->get();
2730   size_t max_tlab = max_tlab_size() * wordSize;
2731   if (hr == NULL) {
2732     return max_tlab;
2733   } else {
2734     return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab);
2735   }
2736 }
2737 
2738 size_t G1CollectedHeap::max_capacity() const {
2739   return _hrm.reserved().byte_size();
2740 }
2741 
2742 jlong G1CollectedHeap::millis_since_last_gc() {
2743   // assert(false, "NYI");
2744   return 0;
2745 }
2746 
2747 void G1CollectedHeap::prepare_for_verify() {
2748   if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
2749     ensure_parsability(false);
2750   }
2751   g1_rem_set()->prepare_for_verify();
2752 }
2753 
2754 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr,
2755                                               VerifyOption vo) {
2756   switch (vo) {
2757   case VerifyOption_G1UsePrevMarking:
2758     return hr->obj_allocated_since_prev_marking(obj);
2759   case VerifyOption_G1UseNextMarking:
2760     return hr->obj_allocated_since_next_marking(obj);
2761   case VerifyOption_G1UseMarkWord:
2762     return false;
2763   default:
2764     ShouldNotReachHere();
2765   }
2766   return false; // keep some compilers happy
2767 }
2768 
2769 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) {
2770   switch (vo) {
2771   case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start();
2772   case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start();
2773   case VerifyOption_G1UseMarkWord:    return NULL;
2774   default:                            ShouldNotReachHere();
2775   }
2776   return NULL; // keep some compilers happy
2777 }
2778 
2779 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) {
2780   switch (vo) {
2781   case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj);
2782   case VerifyOption_G1UseNextMarking: return isMarkedNext(obj);
2783   case VerifyOption_G1UseMarkWord:    return obj->is_gc_marked();
2784   default:                            ShouldNotReachHere();
2785   }
2786   return false; // keep some compilers happy
2787 }
2788 
2789 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) {
2790   switch (vo) {
2791   case VerifyOption_G1UsePrevMarking: return "PTAMS";
2792   case VerifyOption_G1UseNextMarking: return "NTAMS";
2793   case VerifyOption_G1UseMarkWord:    return "NONE";
2794   default:                            ShouldNotReachHere();
2795   }
2796   return NULL; // keep some compilers happy
2797 }
2798 
2799 class VerifyRootsClosure: public OopClosure {
2800 private:
2801   G1CollectedHeap* _g1h;
2802   VerifyOption     _vo;
2803   bool             _failures;
2804 public:
2805   // _vo == UsePrevMarking -> use "prev" marking information,
2806   // _vo == UseNextMarking -> use "next" marking information,
2807   // _vo == UseMarkWord    -> use mark word from object header.
2808   VerifyRootsClosure(VerifyOption vo) :
2809     _g1h(G1CollectedHeap::heap()),
2810     _vo(vo),
2811     _failures(false) { }
2812 
2813   bool failures() { return _failures; }
2814 
2815   template <class T> void do_oop_nv(T* p) {
2816     T heap_oop = oopDesc::load_heap_oop(p);
2817     if (!oopDesc::is_null(heap_oop)) {
2818       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2819       if (_g1h->is_obj_dead_cond(obj, _vo)) {
2820         gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
2821                               "points to dead obj "PTR_FORMAT, p, (void*) obj);
2822         if (_vo == VerifyOption_G1UseMarkWord) {
2823           gclog_or_tty->print_cr("  Mark word: "PTR_FORMAT, (void*)(obj->mark()));
2824         }
2825         obj->print_on(gclog_or_tty);
2826         _failures = true;
2827       }
2828     }
2829   }
2830 
2831   void do_oop(oop* p)       { do_oop_nv(p); }
2832   void do_oop(narrowOop* p) { do_oop_nv(p); }
2833 };
2834 
2835 class G1VerifyCodeRootOopClosure: public OopClosure {
2836   G1CollectedHeap* _g1h;
2837   OopClosure* _root_cl;
2838   nmethod* _nm;
2839   VerifyOption _vo;
2840   bool _failures;
2841 
2842   template <class T> void do_oop_work(T* p) {
2843     // First verify that this root is live
2844     _root_cl->do_oop(p);
2845 
2846     if (!G1VerifyHeapRegionCodeRoots) {
2847       // We're not verifying the code roots attached to heap region.
2848       return;
2849     }
2850 
2851     // Don't check the code roots during marking verification in a full GC
2852     if (_vo == VerifyOption_G1UseMarkWord) {
2853       return;
2854     }
2855 
2856     // Now verify that the current nmethod (which contains p) is
2857     // in the code root list of the heap region containing the
2858     // object referenced by p.
2859 
2860     T heap_oop = oopDesc::load_heap_oop(p);
2861     if (!oopDesc::is_null(heap_oop)) {
2862       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2863 
2864       // Now fetch the region containing the object
2865       HeapRegion* hr = _g1h->heap_region_containing(obj);
2866       HeapRegionRemSet* hrrs = hr->rem_set();
2867       // Verify that the strong code root list for this region
2868       // contains the nmethod
2869       if (!hrrs->strong_code_roots_list_contains(_nm)) {
2870         gclog_or_tty->print_cr("Code root location "PTR_FORMAT" "
2871                               "from nmethod "PTR_FORMAT" not in strong "
2872                               "code roots for region ["PTR_FORMAT","PTR_FORMAT")",
2873                               p, _nm, hr->bottom(), hr->end());
2874         _failures = true;
2875       }
2876     }
2877   }
2878 
2879 public:
2880   G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo):
2881     _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {}
2882 
2883   void do_oop(oop* p) { do_oop_work(p); }
2884   void do_oop(narrowOop* p) { do_oop_work(p); }
2885 
2886   void set_nmethod(nmethod* nm) { _nm = nm; }
2887   bool failures() { return _failures; }
2888 };
2889 
2890 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure {
2891   G1VerifyCodeRootOopClosure* _oop_cl;
2892 
2893 public:
2894   G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl):
2895     _oop_cl(oop_cl) {}
2896 
2897   void do_code_blob(CodeBlob* cb) {
2898     nmethod* nm = cb->as_nmethod_or_null();
2899     if (nm != NULL) {
2900       _oop_cl->set_nmethod(nm);
2901       nm->oops_do(_oop_cl);
2902     }
2903   }
2904 };
2905 
2906 class YoungRefCounterClosure : public OopClosure {
2907   G1CollectedHeap* _g1h;
2908   int              _count;
2909  public:
2910   YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {}
2911   void do_oop(oop* p)       { if (_g1h->is_in_young(*p)) { _count++; } }
2912   void do_oop(narrowOop* p) { ShouldNotReachHere(); }
2913 
2914   int count() { return _count; }
2915   void reset_count() { _count = 0; };
2916 };
2917 
2918 class VerifyKlassClosure: public KlassClosure {
2919   YoungRefCounterClosure _young_ref_counter_closure;
2920   OopClosure *_oop_closure;
2921  public:
2922   VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {}
2923   void do_klass(Klass* k) {
2924     k->oops_do(_oop_closure);
2925 
2926     _young_ref_counter_closure.reset_count();
2927     k->oops_do(&_young_ref_counter_closure);
2928     if (_young_ref_counter_closure.count() > 0) {
2929       guarantee(k->has_modified_oops(), err_msg("Klass " PTR_FORMAT ", has young refs but is not dirty.", k));
2930     }
2931   }
2932 };
2933 
2934 class VerifyLivenessOopClosure: public OopClosure {
2935   G1CollectedHeap* _g1h;
2936   VerifyOption _vo;
2937 public:
2938   VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
2939     _g1h(g1h), _vo(vo)
2940   { }
2941   void do_oop(narrowOop *p) { do_oop_work(p); }
2942   void do_oop(      oop *p) { do_oop_work(p); }
2943 
2944   template <class T> void do_oop_work(T *p) {
2945     oop obj = oopDesc::load_decode_heap_oop(p);
2946     guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
2947               "Dead object referenced by a not dead object");
2948   }
2949 };
2950 
2951 class VerifyObjsInRegionClosure: public ObjectClosure {
2952 private:
2953   G1CollectedHeap* _g1h;
2954   size_t _live_bytes;
2955   HeapRegion *_hr;
2956   VerifyOption _vo;
2957 public:
2958   // _vo == UsePrevMarking -> use "prev" marking information,
2959   // _vo == UseNextMarking -> use "next" marking information,
2960   // _vo == UseMarkWord    -> use mark word from object header.
2961   VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
2962     : _live_bytes(0), _hr(hr), _vo(vo) {
2963     _g1h = G1CollectedHeap::heap();
2964   }
2965   void do_object(oop o) {
2966     VerifyLivenessOopClosure isLive(_g1h, _vo);
2967     assert(o != NULL, "Huh?");
2968     if (!_g1h->is_obj_dead_cond(o, _vo)) {
2969       // If the object is alive according to the mark word,
2970       // then verify that the marking information agrees.
2971       // Note we can't verify the contra-positive of the
2972       // above: if the object is dead (according to the mark
2973       // word), it may not be marked, or may have been marked
2974       // but has since became dead, or may have been allocated
2975       // since the last marking.
2976       if (_vo == VerifyOption_G1UseMarkWord) {
2977         guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
2978       }
2979 
2980       o->oop_iterate_no_header(&isLive);
2981       if (!_hr->obj_allocated_since_prev_marking(o)) {
2982         size_t obj_size = o->size();    // Make sure we don't overflow
2983         _live_bytes += (obj_size * HeapWordSize);
2984       }
2985     }
2986   }
2987   size_t live_bytes() { return _live_bytes; }
2988 };
2989 
2990 class PrintObjsInRegionClosure : public ObjectClosure {
2991   HeapRegion *_hr;
2992   G1CollectedHeap *_g1;
2993 public:
2994   PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
2995     _g1 = G1CollectedHeap::heap();
2996   };
2997 
2998   void do_object(oop o) {
2999     if (o != NULL) {
3000       HeapWord *start = (HeapWord *) o;
3001       size_t word_sz = o->size();
3002       gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
3003                           " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
3004                           (void*) o, word_sz,
3005                           _g1->isMarkedPrev(o),
3006                           _g1->isMarkedNext(o),
3007                           _hr->obj_allocated_since_prev_marking(o));
3008       HeapWord *end = start + word_sz;
3009       HeapWord *cur;
3010       int *val;
3011       for (cur = start; cur < end; cur++) {
3012         val = (int *) cur;
3013         gclog_or_tty->print("\t "PTR_FORMAT":%d\n", val, *val);
3014       }
3015     }
3016   }
3017 };
3018 
3019 class VerifyRegionClosure: public HeapRegionClosure {
3020 private:
3021   bool             _par;
3022   VerifyOption     _vo;
3023   bool             _failures;
3024 public:
3025   // _vo == UsePrevMarking -> use "prev" marking information,
3026   // _vo == UseNextMarking -> use "next" marking information,
3027   // _vo == UseMarkWord    -> use mark word from object header.
3028   VerifyRegionClosure(bool par, VerifyOption vo)
3029     : _par(par),
3030       _vo(vo),
3031       _failures(false) {}
3032 
3033   bool failures() {
3034     return _failures;
3035   }
3036 
3037   bool doHeapRegion(HeapRegion* r) {
3038     if (!r->is_continues_humongous()) {
3039       bool failures = false;
3040       r->verify(_vo, &failures);
3041       if (failures) {
3042         _failures = true;
3043       } else {
3044         VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
3045         r->object_iterate(&not_dead_yet_cl);
3046         if (_vo != VerifyOption_G1UseNextMarking) {
3047           if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
3048             gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
3049                                    "max_live_bytes "SIZE_FORMAT" "
3050                                    "< calculated "SIZE_FORMAT,
3051                                    r->bottom(), r->end(),
3052                                    r->max_live_bytes(),
3053                                  not_dead_yet_cl.live_bytes());
3054             _failures = true;
3055           }
3056         } else {
3057           // When vo == UseNextMarking we cannot currently do a sanity
3058           // check on the live bytes as the calculation has not been
3059           // finalized yet.
3060         }
3061       }
3062     }
3063     return false; // stop the region iteration if we hit a failure
3064   }
3065 };
3066 
3067 // This is the task used for parallel verification of the heap regions
3068 
3069 class G1ParVerifyTask: public AbstractGangTask {
3070 private:
3071   G1CollectedHeap*  _g1h;
3072   VerifyOption      _vo;
3073   bool              _failures;
3074   HeapRegionClaimer _hrclaimer;
3075 
3076 public:
3077   // _vo == UsePrevMarking -> use "prev" marking information,
3078   // _vo == UseNextMarking -> use "next" marking information,
3079   // _vo == UseMarkWord    -> use mark word from object header.
3080   G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
3081       AbstractGangTask("Parallel verify task"),
3082       _g1h(g1h),
3083       _vo(vo),
3084       _failures(false),
3085       _hrclaimer(g1h->workers()->active_workers()) {}
3086 
3087   bool failures() {
3088     return _failures;
3089   }
3090 
3091   void work(uint worker_id) {
3092     HandleMark hm;
3093     VerifyRegionClosure blk(true, _vo);
3094     _g1h->heap_region_par_iterate(&blk, worker_id, &_hrclaimer);
3095     if (blk.failures()) {
3096       _failures = true;
3097     }
3098   }
3099 };
3100 
3101 void G1CollectedHeap::verify(bool silent, VerifyOption vo) {
3102   if (SafepointSynchronize::is_at_safepoint()) {
3103     assert(Thread::current()->is_VM_thread(),
3104            "Expected to be executed serially by the VM thread at this point");
3105 
3106     if (!silent) { gclog_or_tty->print("Roots "); }
3107     VerifyRootsClosure rootsCl(vo);
3108     VerifyKlassClosure klassCl(this, &rootsCl);
3109     CLDToKlassAndOopClosure cldCl(&klassCl, &rootsCl, false);
3110 
3111     // We apply the relevant closures to all the oops in the
3112     // system dictionary, class loader data graph, the string table
3113     // and the nmethods in the code cache.
3114     G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo);
3115     G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl);
3116 
3117     process_all_roots(true,            // activate StrongRootsScope
3118                       SO_AllCodeCache, // roots scanning options
3119                       &rootsCl,
3120                       &cldCl,
3121                       &blobsCl);
3122 
3123     bool failures = rootsCl.failures() || codeRootsCl.failures();
3124 
3125     if (vo != VerifyOption_G1UseMarkWord) {
3126       // If we're verifying during a full GC then the region sets
3127       // will have been torn down at the start of the GC. Therefore
3128       // verifying the region sets will fail. So we only verify
3129       // the region sets when not in a full GC.
3130       if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3131       verify_region_sets();
3132     }
3133 
3134     if (!silent) { gclog_or_tty->print("HeapRegions "); }
3135     if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3136 
3137       G1ParVerifyTask task(this, vo);
3138       assert(UseDynamicNumberOfGCThreads ||
3139         workers()->active_workers() == workers()->total_workers(),
3140         "If not dynamic should be using all the workers");
3141       int n_workers = workers()->active_workers();
3142       set_par_threads(n_workers);
3143       workers()->run_task(&task);
3144       set_par_threads(0);
3145       if (task.failures()) {
3146         failures = true;
3147       }
3148 
3149     } else {
3150       VerifyRegionClosure blk(false, vo);
3151       heap_region_iterate(&blk);
3152       if (blk.failures()) {
3153         failures = true;
3154       }
3155     }
3156     if (!silent) gclog_or_tty->print("RemSet ");
3157     rem_set()->verify();
3158 
3159     if (G1StringDedup::is_enabled()) {
3160       if (!silent) gclog_or_tty->print("StrDedup ");
3161       G1StringDedup::verify();
3162     }
3163 
3164     if (failures) {
3165       gclog_or_tty->print_cr("Heap:");
3166       // It helps to have the per-region information in the output to
3167       // help us track down what went wrong. This is why we call
3168       // print_extended_on() instead of print_on().
3169       print_extended_on(gclog_or_tty);
3170       gclog_or_tty->cr();
3171 #ifndef PRODUCT
3172       if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3173         concurrent_mark()->print_reachable("at-verification-failure",
3174                                            vo, false /* all */);
3175       }
3176 #endif
3177       gclog_or_tty->flush();
3178     }
3179     guarantee(!failures, "there should not have been any failures");
3180   } else {
3181     if (!silent) {
3182       gclog_or_tty->print("(SKIPPING Roots, HeapRegionSets, HeapRegions, RemSet");
3183       if (G1StringDedup::is_enabled()) {
3184         gclog_or_tty->print(", StrDedup");
3185       }
3186       gclog_or_tty->print(") ");
3187     }
3188   }
3189 }
3190 
3191 void G1CollectedHeap::verify(bool silent) {
3192   verify(silent, VerifyOption_G1UsePrevMarking);
3193 }
3194 
3195 double G1CollectedHeap::verify(bool guard, const char* msg) {
3196   double verify_time_ms = 0.0;
3197 
3198   if (guard && total_collections() >= VerifyGCStartAt) {
3199     double verify_start = os::elapsedTime();
3200     HandleMark hm;  // Discard invalid handles created during verification
3201     prepare_for_verify();
3202     Universe::verify(VerifyOption_G1UsePrevMarking, msg);
3203     verify_time_ms = (os::elapsedTime() - verify_start) * 1000;
3204   }
3205 
3206   return verify_time_ms;
3207 }
3208 
3209 void G1CollectedHeap::verify_before_gc() {
3210   double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:");
3211   g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms);
3212 }
3213 
3214 void G1CollectedHeap::verify_after_gc() {
3215   double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:");
3216   g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms);
3217 }
3218 
3219 class PrintRegionClosure: public HeapRegionClosure {
3220   outputStream* _st;
3221 public:
3222   PrintRegionClosure(outputStream* st) : _st(st) {}
3223   bool doHeapRegion(HeapRegion* r) {
3224     r->print_on(_st);
3225     return false;
3226   }
3227 };
3228 
3229 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3230                                        const HeapRegion* hr,
3231                                        const VerifyOption vo) const {
3232   switch (vo) {
3233   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
3234   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
3235   case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked();
3236   default:                            ShouldNotReachHere();
3237   }
3238   return false; // keep some compilers happy
3239 }
3240 
3241 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3242                                        const VerifyOption vo) const {
3243   switch (vo) {
3244   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
3245   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
3246   case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked();
3247   default:                            ShouldNotReachHere();
3248   }
3249   return false; // keep some compilers happy
3250 }
3251 
3252 void G1CollectedHeap::print_on(outputStream* st) const {
3253   st->print(" %-20s", "garbage-first heap");
3254   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3255             capacity()/K, used_unlocked()/K);
3256   st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3257             _hrm.reserved().start(),
3258             _hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords,
3259             _hrm.reserved().end());
3260   st->cr();
3261   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3262   uint young_regions = _young_list->length();
3263   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3264             (size_t) young_regions * HeapRegion::GrainBytes / K);
3265   uint survivor_regions = g1_policy()->recorded_survivor_regions();
3266   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3267             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3268   st->cr();
3269   MetaspaceAux::print_on(st);
3270 }
3271 
3272 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3273   print_on(st);
3274 
3275   // Print the per-region information.
3276   st->cr();
3277   st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3278                "HS=humongous(starts), HC=humongous(continues), "
3279                "CS=collection set, F=free, TS=gc time stamp, "
3280                "PTAMS=previous top-at-mark-start, "
3281                "NTAMS=next top-at-mark-start)");
3282   PrintRegionClosure blk(st);
3283   heap_region_iterate(&blk);
3284 }
3285 
3286 void G1CollectedHeap::print_on_error(outputStream* st) const {
3287   this->CollectedHeap::print_on_error(st);
3288 
3289   if (_cm != NULL) {
3290     st->cr();
3291     _cm->print_on_error(st);
3292   }
3293 }
3294 
3295 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3296   workers()->print_worker_threads_on(st);
3297   _cmThread->print_on(st);
3298   st->cr();
3299   _cm->print_worker_threads_on(st);
3300   _cg1r->print_worker_threads_on(st);
3301   if (G1StringDedup::is_enabled()) {
3302     G1StringDedup::print_worker_threads_on(st);
3303   }
3304 }
3305 
3306 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3307   workers()->threads_do(tc);
3308   tc->do_thread(_cmThread);
3309   _cg1r->threads_do(tc);
3310   if (G1StringDedup::is_enabled()) {
3311     G1StringDedup::threads_do(tc);
3312   }
3313 }
3314 
3315 void G1CollectedHeap::print_tracing_info() const {
3316   // We'll overload this to mean "trace GC pause statistics."
3317   if (TraceYoungGenTime || TraceOldGenTime) {
3318     // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3319     // to that.
3320     g1_policy()->print_tracing_info();
3321   }
3322   if (G1SummarizeRSetStats) {
3323     g1_rem_set()->print_summary_info();
3324   }
3325   if (G1SummarizeConcMark) {
3326     concurrent_mark()->print_summary_info();
3327   }
3328   g1_policy()->print_yg_surv_rate_info();
3329   SpecializationStats::print();
3330 }
3331 
3332 #ifndef PRODUCT
3333 // Helpful for debugging RSet issues.
3334 
3335 class PrintRSetsClosure : public HeapRegionClosure {
3336 private:
3337   const char* _msg;
3338   size_t _occupied_sum;
3339 
3340 public:
3341   bool doHeapRegion(HeapRegion* r) {
3342     HeapRegionRemSet* hrrs = r->rem_set();
3343     size_t occupied = hrrs->occupied();
3344     _occupied_sum += occupied;
3345 
3346     gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3347                            HR_FORMAT_PARAMS(r));
3348     if (occupied == 0) {
3349       gclog_or_tty->print_cr("  RSet is empty");
3350     } else {
3351       hrrs->print();
3352     }
3353     gclog_or_tty->print_cr("----------");
3354     return false;
3355   }
3356 
3357   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3358     gclog_or_tty->cr();
3359     gclog_or_tty->print_cr("========================================");
3360     gclog_or_tty->print_cr("%s", msg);
3361     gclog_or_tty->cr();
3362   }
3363 
3364   ~PrintRSetsClosure() {
3365     gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3366     gclog_or_tty->print_cr("========================================");
3367     gclog_or_tty->cr();
3368   }
3369 };
3370 
3371 void G1CollectedHeap::print_cset_rsets() {
3372   PrintRSetsClosure cl("Printing CSet RSets");
3373   collection_set_iterate(&cl);
3374 }
3375 
3376 void G1CollectedHeap::print_all_rsets() {
3377   PrintRSetsClosure cl("Printing All RSets");;
3378   heap_region_iterate(&cl);
3379 }
3380 #endif // PRODUCT
3381 
3382 G1CollectedHeap* G1CollectedHeap::heap() {
3383   assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3384          "not a garbage-first heap");
3385   return _g1h;
3386 }
3387 
3388 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3389   // always_do_update_barrier = false;
3390   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3391   // Fill TLAB's and such
3392   accumulate_statistics_all_tlabs();
3393   ensure_parsability(true);
3394 
3395   if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) &&
3396       (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3397     g1_rem_set()->print_periodic_summary_info("Before GC RS summary");
3398   }
3399 }
3400 
3401 void G1CollectedHeap::gc_epilogue(bool full) {
3402 
3403   if (G1SummarizeRSetStats &&
3404       (G1SummarizeRSetStatsPeriod > 0) &&
3405       // we are at the end of the GC. Total collections has already been increased.
3406       ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) {
3407     g1_rem_set()->print_periodic_summary_info("After GC RS summary");
3408   }
3409 
3410   // FIXME: what is this about?
3411   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3412   // is set.
3413   COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3414                         "derived pointer present"));
3415   // always_do_update_barrier = true;
3416 
3417   resize_all_tlabs();
3418   allocation_context_stats().update(full);
3419 
3420   // We have just completed a GC. Update the soft reference
3421   // policy with the new heap occupancy
3422   Universe::update_heap_info_at_gc();
3423 }
3424 
3425 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3426                                                unsigned int gc_count_before,
3427                                                bool* succeeded,
3428                                                GCCause::Cause gc_cause) {
3429   assert_heap_not_locked_and_not_at_safepoint();
3430   g1_policy()->record_stop_world_start();
3431   VM_G1IncCollectionPause op(gc_count_before,
3432                              word_size,
3433                              false, /* should_initiate_conc_mark */
3434                              g1_policy()->max_pause_time_ms(),
3435                              gc_cause);
3436 
3437   op.set_allocation_context(AllocationContext::current());
3438   VMThread::execute(&op);
3439 
3440   HeapWord* result = op.result();
3441   bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3442   assert(result == NULL || ret_succeeded,
3443          "the result should be NULL if the VM did not succeed");
3444   *succeeded = ret_succeeded;
3445 
3446   assert_heap_not_locked();
3447   return result;
3448 }
3449 
3450 void
3451 G1CollectedHeap::doConcurrentMark() {
3452   MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3453   if (!_cmThread->in_progress()) {
3454     _cmThread->set_started();
3455     CGC_lock->notify();
3456   }
3457 }
3458 
3459 size_t G1CollectedHeap::pending_card_num() {
3460   size_t extra_cards = 0;
3461   JavaThread *curr = Threads::first();
3462   while (curr != NULL) {
3463     DirtyCardQueue& dcq = curr->dirty_card_queue();
3464     extra_cards += dcq.size();
3465     curr = curr->next();
3466   }
3467   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3468   size_t buffer_size = dcqs.buffer_size();
3469   size_t buffer_num = dcqs.completed_buffers_num();
3470 
3471   // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
3472   // in bytes - not the number of 'entries'. We need to convert
3473   // into a number of cards.
3474   return (buffer_size * buffer_num + extra_cards) / oopSize;
3475 }
3476 
3477 size_t G1CollectedHeap::cards_scanned() {
3478   return g1_rem_set()->cardsScanned();
3479 }
3480 
3481 bool G1CollectedHeap::humongous_region_is_always_live(uint index) {
3482   HeapRegion* region = region_at(index);
3483   assert(region->is_starts_humongous(), "Must start a humongous object");
3484   return oop(region->bottom())->is_objArray() || !region->rem_set()->is_empty();
3485 }
3486 
3487 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
3488  private:
3489   size_t _total_humongous;
3490   size_t _candidate_humongous;
3491  public:
3492   RegisterHumongousWithInCSetFastTestClosure() : _total_humongous(0), _candidate_humongous(0) {
3493   }
3494 
3495   virtual bool doHeapRegion(HeapRegion* r) {
3496     if (!r->is_starts_humongous()) {
3497       return false;
3498     }
3499     G1CollectedHeap* g1h = G1CollectedHeap::heap();
3500 
3501     uint region_idx = r->hrm_index();
3502     bool is_candidate = !g1h->humongous_region_is_always_live(region_idx);
3503     // Is_candidate already filters out humongous regions with some remembered set.
3504     // This will not lead to humongous object that we mistakenly keep alive because
3505     // during young collection the remembered sets will only be added to.
3506     if (is_candidate) {
3507       g1h->register_humongous_region_with_in_cset_fast_test(region_idx);
3508       _candidate_humongous++;
3509     }
3510     _total_humongous++;
3511 
3512     return false;
3513   }
3514 
3515   size_t total_humongous() const { return _total_humongous; }
3516   size_t candidate_humongous() const { return _candidate_humongous; }
3517 };
3518 
3519 void G1CollectedHeap::register_humongous_regions_with_in_cset_fast_test() {
3520   if (!G1ReclaimDeadHumongousObjectsAtYoungGC) {
3521     g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0, 0);
3522     return;
3523   }
3524 
3525   RegisterHumongousWithInCSetFastTestClosure cl;
3526   heap_region_iterate(&cl);
3527   g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(cl.total_humongous(),
3528                                                                   cl.candidate_humongous());
3529   _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
3530 
3531   if (_has_humongous_reclaim_candidates || G1TraceReclaimDeadHumongousObjectsAtYoungGC) {
3532     clear_humongous_is_live_table();
3533   }
3534 }
3535 
3536 void
3537 G1CollectedHeap::setup_surviving_young_words() {
3538   assert(_surviving_young_words == NULL, "pre-condition");
3539   uint array_length = g1_policy()->young_cset_region_length();
3540   _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3541   if (_surviving_young_words == NULL) {
3542     vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR,
3543                           "Not enough space for young surv words summary.");
3544   }
3545   memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3546 #ifdef ASSERT
3547   for (uint i = 0;  i < array_length; ++i) {
3548     assert( _surviving_young_words[i] == 0, "memset above" );
3549   }
3550 #endif // !ASSERT
3551 }
3552 
3553 void
3554 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3555   MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3556   uint array_length = g1_policy()->young_cset_region_length();
3557   for (uint i = 0; i < array_length; ++i) {
3558     _surviving_young_words[i] += surv_young_words[i];
3559   }
3560 }
3561 
3562 void
3563 G1CollectedHeap::cleanup_surviving_young_words() {
3564   guarantee( _surviving_young_words != NULL, "pre-condition" );
3565   FREE_C_HEAP_ARRAY(size_t, _surviving_young_words);
3566   _surviving_young_words = NULL;
3567 }
3568 
3569 #ifdef ASSERT
3570 class VerifyCSetClosure: public HeapRegionClosure {
3571 public:
3572   bool doHeapRegion(HeapRegion* hr) {
3573     // Here we check that the CSet region's RSet is ready for parallel
3574     // iteration. The fields that we'll verify are only manipulated
3575     // when the region is part of a CSet and is collected. Afterwards,
3576     // we reset these fields when we clear the region's RSet (when the
3577     // region is freed) so they are ready when the region is
3578     // re-allocated. The only exception to this is if there's an
3579     // evacuation failure and instead of freeing the region we leave
3580     // it in the heap. In that case, we reset these fields during
3581     // evacuation failure handling.
3582     guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3583 
3584     // Here's a good place to add any other checks we'd like to
3585     // perform on CSet regions.
3586     return false;
3587   }
3588 };
3589 #endif // ASSERT
3590 
3591 #if TASKQUEUE_STATS
3592 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3593   st->print_raw_cr("GC Task Stats");
3594   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3595   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3596 }
3597 
3598 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3599   print_taskqueue_stats_hdr(st);
3600 
3601   TaskQueueStats totals;
3602   const int n = workers()->total_workers();
3603   for (int i = 0; i < n; ++i) {
3604     st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3605     totals += task_queue(i)->stats;
3606   }
3607   st->print_raw("tot "); totals.print(st); st->cr();
3608 
3609   DEBUG_ONLY(totals.verify());
3610 }
3611 
3612 void G1CollectedHeap::reset_taskqueue_stats() {
3613   const int n = workers()->total_workers();
3614   for (int i = 0; i < n; ++i) {
3615     task_queue(i)->stats.reset();
3616   }
3617 }
3618 #endif // TASKQUEUE_STATS
3619 
3620 void G1CollectedHeap::log_gc_header() {
3621   if (!G1Log::fine()) {
3622     return;
3623   }
3624 
3625   gclog_or_tty->gclog_stamp(_gc_tracer_stw->gc_id());
3626 
3627   GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
3628     .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)")
3629     .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : "");
3630 
3631   gclog_or_tty->print("[%s", (const char*)gc_cause_str);
3632 }
3633 
3634 void G1CollectedHeap::log_gc_footer(double pause_time_sec) {
3635   if (!G1Log::fine()) {
3636     return;
3637   }
3638 
3639   if (G1Log::finer()) {
3640     if (evacuation_failed()) {
3641       gclog_or_tty->print(" (to-space exhausted)");
3642     }
3643     gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3644     g1_policy()->phase_times()->note_gc_end();
3645     g1_policy()->phase_times()->print(pause_time_sec);
3646     g1_policy()->print_detailed_heap_transition();
3647   } else {
3648     if (evacuation_failed()) {
3649       gclog_or_tty->print("--");
3650     }
3651     g1_policy()->print_heap_transition();
3652     gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3653   }
3654   gclog_or_tty->flush();
3655 }
3656 
3657 bool
3658 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3659   assert_at_safepoint(true /* should_be_vm_thread */);
3660   guarantee(!is_gc_active(), "collection is not reentrant");
3661 
3662   if (GC_locker::check_active_before_gc()) {
3663     return false;
3664   }
3665 
3666   _gc_timer_stw->register_gc_start();
3667 
3668   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3669 
3670   SvcGCMarker sgcm(SvcGCMarker::MINOR);
3671   ResourceMark rm;
3672 
3673   print_heap_before_gc();
3674   trace_heap_before_gc(_gc_tracer_stw);
3675 
3676   verify_region_sets_optional();
3677   verify_dirty_young_regions();
3678 
3679   // This call will decide whether this pause is an initial-mark
3680   // pause. If it is, during_initial_mark_pause() will return true
3681   // for the duration of this pause.
3682   g1_policy()->decide_on_conc_mark_initiation();
3683 
3684   // We do not allow initial-mark to be piggy-backed on a mixed GC.
3685   assert(!g1_policy()->during_initial_mark_pause() ||
3686           g1_policy()->gcs_are_young(), "sanity");
3687 
3688   // We also do not allow mixed GCs during marking.
3689   assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3690 
3691   // Record whether this pause is an initial mark. When the current
3692   // thread has completed its logging output and it's safe to signal
3693   // the CM thread, the flag's value in the policy has been reset.
3694   bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3695 
3696   // Inner scope for scope based logging, timers, and stats collection
3697   {
3698     EvacuationInfo evacuation_info;
3699 
3700     if (g1_policy()->during_initial_mark_pause()) {
3701       // We are about to start a marking cycle, so we increment the
3702       // full collection counter.
3703       increment_old_marking_cycles_started();
3704       register_concurrent_cycle_start(_gc_timer_stw->gc_start());
3705     }
3706 
3707     _gc_tracer_stw->report_yc_type(yc_type());
3708 
3709     TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3710 
3711     int active_workers = workers()->active_workers();
3712     double pause_start_sec = os::elapsedTime();
3713     g1_policy()->phase_times()->note_gc_start(active_workers);
3714     log_gc_header();
3715 
3716     TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3717     TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3718 
3719     // If the secondary_free_list is not empty, append it to the
3720     // free_list. No need to wait for the cleanup operation to finish;
3721     // the region allocation code will check the secondary_free_list
3722     // and wait if necessary. If the G1StressConcRegionFreeing flag is
3723     // set, skip this step so that the region allocation code has to
3724     // get entries from the secondary_free_list.
3725     if (!G1StressConcRegionFreeing) {
3726       append_secondary_free_list_if_not_empty_with_lock();
3727     }
3728 
3729     assert(check_young_list_well_formed(), "young list should be well formed");
3730 
3731     // Don't dynamically change the number of GC threads this early.  A value of
3732     // 0 is used to indicate serial work.  When parallel work is done,
3733     // it will be set.
3734 
3735     { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3736       IsGCActiveMark x;
3737 
3738       gc_prologue(false);
3739       increment_total_collections(false /* full gc */);
3740       increment_gc_time_stamp();
3741 
3742       verify_before_gc();
3743 
3744       check_bitmaps("GC Start");
3745 
3746       COMPILER2_PRESENT(DerivedPointerTable::clear());
3747 
3748       // Please see comment in g1CollectedHeap.hpp and
3749       // G1CollectedHeap::ref_processing_init() to see how
3750       // reference processing currently works in G1.
3751 
3752       // Enable discovery in the STW reference processor
3753       ref_processor_stw()->enable_discovery(true /*verify_disabled*/,
3754                                             true /*verify_no_refs*/);
3755 
3756       {
3757         // We want to temporarily turn off discovery by the
3758         // CM ref processor, if necessary, and turn it back on
3759         // on again later if we do. Using a scoped
3760         // NoRefDiscovery object will do this.
3761         NoRefDiscovery no_cm_discovery(ref_processor_cm());
3762 
3763         // Forget the current alloc region (we might even choose it to be part
3764         // of the collection set!).
3765         _allocator->release_mutator_alloc_region();
3766 
3767         // We should call this after we retire the mutator alloc
3768         // region(s) so that all the ALLOC / RETIRE events are generated
3769         // before the start GC event.
3770         _hr_printer.start_gc(false /* full */, (size_t) total_collections());
3771 
3772         // This timing is only used by the ergonomics to handle our pause target.
3773         // It is unclear why this should not include the full pause. We will
3774         // investigate this in CR 7178365.
3775         //
3776         // Preserving the old comment here if that helps the investigation:
3777         //
3778         // The elapsed time induced by the start time below deliberately elides
3779         // the possible verification above.
3780         double sample_start_time_sec = os::elapsedTime();
3781 
3782 #if YOUNG_LIST_VERBOSE
3783         gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
3784         _young_list->print();
3785         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3786 #endif // YOUNG_LIST_VERBOSE
3787 
3788         g1_policy()->record_collection_pause_start(sample_start_time_sec);
3789 
3790         double scan_wait_start = os::elapsedTime();
3791         // We have to wait until the CM threads finish scanning the
3792         // root regions as it's the only way to ensure that all the
3793         // objects on them have been correctly scanned before we start
3794         // moving them during the GC.
3795         bool waited = _cm->root_regions()->wait_until_scan_finished();
3796         double wait_time_ms = 0.0;
3797         if (waited) {
3798           double scan_wait_end = os::elapsedTime();
3799           wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
3800         }
3801         g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
3802 
3803 #if YOUNG_LIST_VERBOSE
3804         gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
3805         _young_list->print();
3806 #endif // YOUNG_LIST_VERBOSE
3807 
3808         if (g1_policy()->during_initial_mark_pause()) {
3809           concurrent_mark()->checkpointRootsInitialPre();
3810         }
3811 
3812 #if YOUNG_LIST_VERBOSE
3813         gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
3814         _young_list->print();
3815         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3816 #endif // YOUNG_LIST_VERBOSE
3817 
3818         g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info);
3819 
3820         register_humongous_regions_with_in_cset_fast_test();
3821 
3822         _cm->note_start_of_gc();
3823         // We should not verify the per-thread SATB buffers given that
3824         // we have not filtered them yet (we'll do so during the
3825         // GC). We also call this after finalize_cset() to
3826         // ensure that the CSet has been finalized.
3827         _cm->verify_no_cset_oops(true  /* verify_stacks */,
3828                                  true  /* verify_enqueued_buffers */,
3829                                  false /* verify_thread_buffers */,
3830                                  true  /* verify_fingers */);
3831 
3832         if (_hr_printer.is_active()) {
3833           HeapRegion* hr = g1_policy()->collection_set();
3834           while (hr != NULL) {
3835             _hr_printer.cset(hr);
3836             hr = hr->next_in_collection_set();
3837           }
3838         }
3839 
3840 #ifdef ASSERT
3841         VerifyCSetClosure cl;
3842         collection_set_iterate(&cl);
3843 #endif // ASSERT
3844 
3845         setup_surviving_young_words();
3846 
3847         // Initialize the GC alloc regions.
3848         _allocator->init_gc_alloc_regions(evacuation_info);
3849 
3850         // Actually do the work...
3851         evacuate_collection_set(evacuation_info);
3852 
3853         // We do this to mainly verify the per-thread SATB buffers
3854         // (which have been filtered by now) since we didn't verify
3855         // them earlier. No point in re-checking the stacks / enqueued
3856         // buffers given that the CSet has not changed since last time
3857         // we checked.
3858         _cm->verify_no_cset_oops(false /* verify_stacks */,
3859                                  false /* verify_enqueued_buffers */,
3860                                  true  /* verify_thread_buffers */,
3861                                  true  /* verify_fingers */);
3862 
3863         free_collection_set(g1_policy()->collection_set(), evacuation_info);
3864 
3865         eagerly_reclaim_humongous_regions();
3866 
3867         g1_policy()->clear_collection_set();
3868 
3869         cleanup_surviving_young_words();
3870 
3871         // Start a new incremental collection set for the next pause.
3872         g1_policy()->start_incremental_cset_building();
3873 
3874         clear_cset_fast_test();
3875 
3876         _young_list->reset_sampled_info();
3877 
3878         // Don't check the whole heap at this point as the
3879         // GC alloc regions from this pause have been tagged
3880         // as survivors and moved on to the survivor list.
3881         // Survivor regions will fail the !is_young() check.
3882         assert(check_young_list_empty(false /* check_heap */),
3883           "young list should be empty");
3884 
3885 #if YOUNG_LIST_VERBOSE
3886         gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
3887         _young_list->print();
3888 #endif // YOUNG_LIST_VERBOSE
3889 
3890         g1_policy()->record_survivor_regions(_young_list->survivor_length(),
3891                                              _young_list->first_survivor_region(),
3892                                              _young_list->last_survivor_region());
3893 
3894         _young_list->reset_auxilary_lists();
3895 
3896         if (evacuation_failed()) {
3897           _allocator->set_used(recalculate_used());
3898           uint n_queues = MAX2((int)ParallelGCThreads, 1);
3899           for (uint i = 0; i < n_queues; i++) {
3900             if (_evacuation_failed_info_array[i].has_failed()) {
3901               _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
3902             }
3903           }
3904         } else {
3905           // The "used" of the the collection set have already been subtracted
3906           // when they were freed.  Add in the bytes evacuated.
3907           _allocator->increase_used(g1_policy()->bytes_copied_during_gc());
3908         }
3909 
3910         if (g1_policy()->during_initial_mark_pause()) {
3911           // We have to do this before we notify the CM threads that
3912           // they can start working to make sure that all the
3913           // appropriate initialization is done on the CM object.
3914           concurrent_mark()->checkpointRootsInitialPost();
3915           set_marking_started();
3916           // Note that we don't actually trigger the CM thread at
3917           // this point. We do that later when we're sure that
3918           // the current thread has completed its logging output.
3919         }
3920 
3921         allocate_dummy_regions();
3922 
3923 #if YOUNG_LIST_VERBOSE
3924         gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
3925         _young_list->print();
3926         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3927 #endif // YOUNG_LIST_VERBOSE
3928 
3929         _allocator->init_mutator_alloc_region();
3930 
3931         {
3932           size_t expand_bytes = g1_policy()->expansion_amount();
3933           if (expand_bytes > 0) {
3934             size_t bytes_before = capacity();
3935             // No need for an ergo verbose message here,
3936             // expansion_amount() does this when it returns a value > 0.
3937             if (!expand(expand_bytes)) {
3938               // We failed to expand the heap. Cannot do anything about it.
3939             }
3940           }
3941         }
3942 
3943         // We redo the verification but now wrt to the new CSet which
3944         // has just got initialized after the previous CSet was freed.
3945         _cm->verify_no_cset_oops(true  /* verify_stacks */,
3946                                  true  /* verify_enqueued_buffers */,
3947                                  true  /* verify_thread_buffers */,
3948                                  true  /* verify_fingers */);
3949         _cm->note_end_of_gc();
3950 
3951         // This timing is only used by the ergonomics to handle our pause target.
3952         // It is unclear why this should not include the full pause. We will
3953         // investigate this in CR 7178365.
3954         double sample_end_time_sec = os::elapsedTime();
3955         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3956         g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info);
3957 
3958         MemoryService::track_memory_usage();
3959 
3960         // In prepare_for_verify() below we'll need to scan the deferred
3961         // update buffers to bring the RSets up-to-date if
3962         // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
3963         // the update buffers we'll probably need to scan cards on the
3964         // regions we just allocated to (i.e., the GC alloc
3965         // regions). However, during the last GC we called
3966         // set_saved_mark() on all the GC alloc regions, so card
3967         // scanning might skip the [saved_mark_word()...top()] area of
3968         // those regions (i.e., the area we allocated objects into
3969         // during the last GC). But it shouldn't. Given that
3970         // saved_mark_word() is conditional on whether the GC time stamp
3971         // on the region is current or not, by incrementing the GC time
3972         // stamp here we invalidate all the GC time stamps on all the
3973         // regions and saved_mark_word() will simply return top() for
3974         // all the regions. This is a nicer way of ensuring this rather
3975         // than iterating over the regions and fixing them. In fact, the
3976         // GC time stamp increment here also ensures that
3977         // saved_mark_word() will return top() between pauses, i.e.,
3978         // during concurrent refinement. So we don't need the
3979         // is_gc_active() check to decided which top to use when
3980         // scanning cards (see CR 7039627).
3981         increment_gc_time_stamp();
3982 
3983         verify_after_gc();
3984         check_bitmaps("GC End");
3985 
3986         assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
3987         ref_processor_stw()->verify_no_references_recorded();
3988 
3989         // CM reference discovery will be re-enabled if necessary.
3990       }
3991 
3992       // We should do this after we potentially expand the heap so
3993       // that all the COMMIT events are generated before the end GC
3994       // event, and after we retire the GC alloc regions so that all
3995       // RETIRE events are generated before the end GC event.
3996       _hr_printer.end_gc(false /* full */, (size_t) total_collections());
3997 
3998 #ifdef TRACESPINNING
3999       ParallelTaskTerminator::print_termination_counts();
4000 #endif
4001 
4002       gc_epilogue(false);
4003     }
4004 
4005     // Print the remainder of the GC log output.
4006     log_gc_footer(os::elapsedTime() - pause_start_sec);
4007 
4008     // It is not yet to safe to tell the concurrent mark to
4009     // start as we have some optional output below. We don't want the
4010     // output from the concurrent mark thread interfering with this
4011     // logging output either.
4012 
4013     _hrm.verify_optional();
4014     verify_region_sets_optional();
4015 
4016     TASKQUEUE_STATS_ONLY(if (PrintTaskqueue) print_taskqueue_stats());
4017     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
4018 
4019     print_heap_after_gc();
4020     trace_heap_after_gc(_gc_tracer_stw);
4021 
4022     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
4023     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
4024     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
4025     // before any GC notifications are raised.
4026     g1mm()->update_sizes();
4027 
4028     _gc_tracer_stw->report_evacuation_info(&evacuation_info);
4029     _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
4030     _gc_timer_stw->register_gc_end();
4031     _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
4032   }
4033   // It should now be safe to tell the concurrent mark thread to start
4034   // without its logging output interfering with the logging output
4035   // that came from the pause.
4036 
4037   if (should_start_conc_mark) {
4038     // CAUTION: after the doConcurrentMark() call below,
4039     // the concurrent marking thread(s) could be running
4040     // concurrently with us. Make sure that anything after
4041     // this point does not assume that we are the only GC thread
4042     // running. Note: of course, the actual marking work will
4043     // not start until the safepoint itself is released in
4044     // SuspendibleThreadSet::desynchronize().
4045     doConcurrentMark();
4046   }
4047 
4048   return true;
4049 }
4050 
4051 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
4052 {
4053   size_t gclab_word_size;
4054   switch (purpose) {
4055     case GCAllocForSurvived:
4056       gclab_word_size = _survivor_plab_stats.desired_plab_sz();
4057       break;
4058     case GCAllocForTenured:
4059       gclab_word_size = _old_plab_stats.desired_plab_sz();
4060       break;
4061     default:
4062       assert(false, "unknown GCAllocPurpose");
4063       gclab_word_size = _old_plab_stats.desired_plab_sz();
4064       break;
4065   }
4066 
4067   // Prevent humongous PLAB sizes for two reasons:
4068   // * PLABs are allocated using a similar paths as oops, but should
4069   //   never be in a humongous region
4070   // * Allowing humongous PLABs needlessly churns the region free lists
4071   return MIN2(_humongous_object_threshold_in_words, gclab_word_size);
4072 }
4073 
4074 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4075   _drain_in_progress = false;
4076   set_evac_failure_closure(cl);
4077   _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4078 }
4079 
4080 void G1CollectedHeap::finalize_for_evac_failure() {
4081   assert(_evac_failure_scan_stack != NULL &&
4082          _evac_failure_scan_stack->length() == 0,
4083          "Postcondition");
4084   assert(!_drain_in_progress, "Postcondition");
4085   delete _evac_failure_scan_stack;
4086   _evac_failure_scan_stack = NULL;
4087 }
4088 
4089 void G1CollectedHeap::remove_self_forwarding_pointers() {
4090   double remove_self_forwards_start = os::elapsedTime();
4091 
4092   set_par_threads();
4093   G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4094   workers()->run_task(&rsfp_task);
4095   set_par_threads(0);
4096 
4097   // Now restore saved marks, if any.
4098   assert(_objs_with_preserved_marks.size() ==
4099             _preserved_marks_of_objs.size(), "Both or none.");
4100   while (!_objs_with_preserved_marks.is_empty()) {
4101     oop obj = _objs_with_preserved_marks.pop();
4102     markOop m = _preserved_marks_of_objs.pop();
4103     obj->set_mark(m);
4104   }
4105   _objs_with_preserved_marks.clear(true);
4106   _preserved_marks_of_objs.clear(true);
4107 
4108   g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
4109 }
4110 
4111 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4112   _evac_failure_scan_stack->push(obj);
4113 }
4114 
4115 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4116   assert(_evac_failure_scan_stack != NULL, "precondition");
4117 
4118   while (_evac_failure_scan_stack->length() > 0) {
4119      oop obj = _evac_failure_scan_stack->pop();
4120      _evac_failure_closure->set_region(heap_region_containing(obj));
4121      obj->oop_iterate_backwards(_evac_failure_closure);
4122   }
4123 }
4124 
4125 oop
4126 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state,
4127                                                oop old) {
4128   assert(obj_in_cs(old),
4129          err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4130                  (HeapWord*) old));
4131   markOop m = old->mark();
4132   oop forward_ptr = old->forward_to_atomic(old);
4133   if (forward_ptr == NULL) {
4134     // Forward-to-self succeeded.
4135     assert(_par_scan_state != NULL, "par scan state");
4136     OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4137     uint queue_num = _par_scan_state->queue_num();
4138 
4139     _evacuation_failed = true;
4140     _evacuation_failed_info_array[queue_num].register_copy_failure(old->size());
4141     if (_evac_failure_closure != cl) {
4142       MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4143       assert(!_drain_in_progress,
4144              "Should only be true while someone holds the lock.");
4145       // Set the global evac-failure closure to the current thread's.
4146       assert(_evac_failure_closure == NULL, "Or locking has failed.");
4147       set_evac_failure_closure(cl);
4148       // Now do the common part.
4149       handle_evacuation_failure_common(old, m);
4150       // Reset to NULL.
4151       set_evac_failure_closure(NULL);
4152     } else {
4153       // The lock is already held, and this is recursive.
4154       assert(_drain_in_progress, "This should only be the recursive case.");
4155       handle_evacuation_failure_common(old, m);
4156     }
4157     return old;
4158   } else {
4159     // Forward-to-self failed. Either someone else managed to allocate
4160     // space for this object (old != forward_ptr) or they beat us in
4161     // self-forwarding it (old == forward_ptr).
4162     assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4163            err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4164                    "should not be in the CSet",
4165                    (HeapWord*) old, (HeapWord*) forward_ptr));
4166     return forward_ptr;
4167   }
4168 }
4169 
4170 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4171   preserve_mark_if_necessary(old, m);
4172 
4173   HeapRegion* r = heap_region_containing(old);
4174   if (!r->evacuation_failed()) {
4175     r->set_evacuation_failed(true);
4176     _hr_printer.evac_failure(r);
4177   }
4178 
4179   push_on_evac_failure_scan_stack(old);
4180 
4181   if (!_drain_in_progress) {
4182     // prevent recursion in copy_to_survivor_space()
4183     _drain_in_progress = true;
4184     drain_evac_failure_scan_stack();
4185     _drain_in_progress = false;
4186   }
4187 }
4188 
4189 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4190   assert(evacuation_failed(), "Oversaving!");
4191   // We want to call the "for_promotion_failure" version only in the
4192   // case of a promotion failure.
4193   if (m->must_be_preserved_for_promotion_failure(obj)) {
4194     _objs_with_preserved_marks.push(obj);
4195     _preserved_marks_of_objs.push(m);
4196   }
4197 }
4198 
4199 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
4200                                                   size_t word_size,
4201                                                   AllocationContext_t context) {
4202   if (purpose == GCAllocForSurvived) {
4203     HeapWord* result = survivor_attempt_allocation(word_size, context);
4204     if (result != NULL) {
4205       return result;
4206     } else {
4207       // Let's try to allocate in the old gen in case we can fit the
4208       // object there.
4209       return old_attempt_allocation(word_size, context);
4210     }
4211   } else {
4212     assert(purpose ==  GCAllocForTenured, "sanity");
4213     HeapWord* result = old_attempt_allocation(word_size, context);
4214     if (result != NULL) {
4215       return result;
4216     } else {
4217       // Let's try to allocate in the survivors in case we can fit the
4218       // object there.
4219       return survivor_attempt_allocation(word_size, context);
4220     }
4221   }
4222 
4223   ShouldNotReachHere();
4224   // Trying to keep some compilers happy.
4225   return NULL;
4226 }
4227 
4228 void G1ParCopyHelper::mark_object(oop obj) {
4229   assert(!_g1->heap_region_containing(obj)->in_collection_set(), "should not mark objects in the CSet");
4230 
4231   // We know that the object is not moving so it's safe to read its size.
4232   _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4233 }
4234 
4235 void G1ParCopyHelper::mark_forwarded_object(oop from_obj, oop to_obj) {
4236   assert(from_obj->is_forwarded(), "from obj should be forwarded");
4237   assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4238   assert(from_obj != to_obj, "should not be self-forwarded");
4239 
4240   assert(_g1->heap_region_containing(from_obj)->in_collection_set(), "from obj should be in the CSet");
4241   assert(!_g1->heap_region_containing(to_obj)->in_collection_set(), "should not mark objects in the CSet");
4242 
4243   // The object might be in the process of being copied by another
4244   // worker so we cannot trust that its to-space image is
4245   // well-formed. So we have to read its size from its from-space
4246   // image which we know should not be changing.
4247   _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4248 }
4249 
4250 template <class T>
4251 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) {
4252   if (_g1->heap_region_containing_raw(new_obj)->is_young()) {
4253     _scanned_klass->record_modified_oops();
4254   }
4255 }
4256 
4257 template <G1Barrier barrier, G1Mark do_mark_object>
4258 template <class T>
4259 void G1ParCopyClosure<barrier, do_mark_object>::do_oop_work(T* p) {
4260   T heap_oop = oopDesc::load_heap_oop(p);
4261 
4262   if (oopDesc::is_null(heap_oop)) {
4263     return;
4264   }
4265 
4266   oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
4267 
4268   assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4269 
4270   G1CollectedHeap::in_cset_state_t state = _g1->in_cset_state(obj);
4271 
4272   if (state == G1CollectedHeap::InCSet) {
4273     oop forwardee;
4274     markOop m = obj->mark();
4275     if (m->is_marked()) {
4276       forwardee = (oop) m->decode_pointer();
4277     } else {
4278       forwardee = _par_scan_state->copy_to_survivor_space(obj, m);
4279     }
4280     assert(forwardee != NULL, "forwardee should not be NULL");
4281     oopDesc::encode_store_heap_oop(p, forwardee);
4282     if (do_mark_object != G1MarkNone && forwardee != obj) {
4283       // If the object is self-forwarded we don't need to explicitly
4284       // mark it, the evacuation failure protocol will do so.
4285       mark_forwarded_object(obj, forwardee);
4286     }
4287 
4288     if (barrier == G1BarrierKlass) {
4289       do_klass_barrier(p, forwardee);
4290     }
4291   } else {
4292     if (state == G1CollectedHeap::IsHumongous) {
4293       _g1->set_humongous_is_live(obj);
4294     }
4295     // The object is not in collection set. If we're a root scanning
4296     // closure during an initial mark pause then attempt to mark the object.
4297     if (do_mark_object == G1MarkFromRoot) {
4298       mark_object(obj);
4299     }
4300   }
4301 
4302   if (barrier == G1BarrierEvac) {
4303     _par_scan_state->update_rs(_from, p, _worker_id);
4304   }
4305 }
4306 
4307 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(oop* p);
4308 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(narrowOop* p);
4309 
4310 class G1ParEvacuateFollowersClosure : public VoidClosure {
4311 protected:
4312   G1CollectedHeap*              _g1h;
4313   G1ParScanThreadState*         _par_scan_state;
4314   RefToScanQueueSet*            _queues;
4315   ParallelTaskTerminator*       _terminator;
4316 
4317   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
4318   RefToScanQueueSet*      queues()         { return _queues; }
4319   ParallelTaskTerminator* terminator()     { return _terminator; }
4320 
4321 public:
4322   G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4323                                 G1ParScanThreadState* par_scan_state,
4324                                 RefToScanQueueSet* queues,
4325                                 ParallelTaskTerminator* terminator)
4326     : _g1h(g1h), _par_scan_state(par_scan_state),
4327       _queues(queues), _terminator(terminator) {}
4328 
4329   void do_void();
4330 
4331 private:
4332   inline bool offer_termination();
4333 };
4334 
4335 bool G1ParEvacuateFollowersClosure::offer_termination() {
4336   G1ParScanThreadState* const pss = par_scan_state();
4337   pss->start_term_time();
4338   const bool res = terminator()->offer_termination();
4339   pss->end_term_time();
4340   return res;
4341 }
4342 
4343 void G1ParEvacuateFollowersClosure::do_void() {
4344   G1ParScanThreadState* const pss = par_scan_state();
4345   pss->trim_queue();
4346   do {
4347     pss->steal_and_trim_queue(queues());
4348   } while (!offer_termination());
4349 }
4350 
4351 class G1KlassScanClosure : public KlassClosure {
4352  G1ParCopyHelper* _closure;
4353  bool             _process_only_dirty;
4354  int              _count;
4355  public:
4356   G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty)
4357       : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {}
4358   void do_klass(Klass* klass) {
4359     // If the klass has not been dirtied we know that there's
4360     // no references into  the young gen and we can skip it.
4361    if (!_process_only_dirty || klass->has_modified_oops()) {
4362       // Clean the klass since we're going to scavenge all the metadata.
4363       klass->clear_modified_oops();
4364 
4365       // Tell the closure that this klass is the Klass to scavenge
4366       // and is the one to dirty if oops are left pointing into the young gen.
4367       _closure->set_scanned_klass(klass);
4368 
4369       klass->oops_do(_closure);
4370 
4371       _closure->set_scanned_klass(NULL);
4372     }
4373     _count++;
4374   }
4375 };
4376 
4377 class G1CodeBlobClosure : public CodeBlobClosure {
4378   class HeapRegionGatheringOopClosure : public OopClosure {
4379     G1CollectedHeap* _g1h;
4380     OopClosure* _work;
4381     nmethod* _nm;
4382 
4383     template <typename T>
4384     void do_oop_work(T* p) {
4385       _work->do_oop(p);
4386       T oop_or_narrowoop = oopDesc::load_heap_oop(p);
4387       if (!oopDesc::is_null(oop_or_narrowoop)) {
4388         oop o = oopDesc::decode_heap_oop_not_null(oop_or_narrowoop);
4389         HeapRegion* hr = _g1h->heap_region_containing_raw(o);
4390         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");
4391         hr->add_strong_code_root(_nm);
4392       }
4393     }
4394 
4395   public:
4396     HeapRegionGatheringOopClosure(OopClosure* oc) : _g1h(G1CollectedHeap::heap()), _work(oc), _nm(NULL) {}
4397 
4398     void do_oop(oop* o) {
4399       do_oop_work(o);
4400     }
4401 
4402     void do_oop(narrowOop* o) {
4403       do_oop_work(o);
4404     }
4405 
4406     void set_nm(nmethod* nm) {
4407       _nm = nm;
4408     }
4409   };
4410 
4411   HeapRegionGatheringOopClosure _oc;
4412 public:
4413   G1CodeBlobClosure(OopClosure* oc) : _oc(oc) {}
4414 
4415   void do_code_blob(CodeBlob* cb) {
4416     nmethod* nm = cb->as_nmethod_or_null();
4417     if (nm != NULL) {
4418       if (!nm->test_set_oops_do_mark()) {
4419         _oc.set_nm(nm);
4420         nm->oops_do(&_oc);
4421         nm->fix_oop_relocations();
4422       }
4423     }
4424   }
4425 };
4426 
4427 class G1ParTask : public AbstractGangTask {
4428 protected:
4429   G1CollectedHeap*       _g1h;
4430   RefToScanQueueSet      *_queues;
4431   ParallelTaskTerminator _terminator;
4432   uint _n_workers;
4433 
4434   Mutex _stats_lock;
4435   Mutex* stats_lock() { return &_stats_lock; }
4436 
4437 public:
4438   G1ParTask(G1CollectedHeap* g1h, RefToScanQueueSet *task_queues)
4439     : AbstractGangTask("G1 collection"),
4440       _g1h(g1h),
4441       _queues(task_queues),
4442       _terminator(0, _queues),
4443       _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4444   {}
4445 
4446   RefToScanQueueSet* queues() { return _queues; }
4447 
4448   RefToScanQueue *work_queue(int i) {
4449     return queues()->queue(i);
4450   }
4451 
4452   ParallelTaskTerminator* terminator() { return &_terminator; }
4453 
4454   virtual void set_for_termination(int active_workers) {
4455     // This task calls set_n_termination() in par_non_clean_card_iterate_work()
4456     // in the young space (_par_seq_tasks) in the G1 heap
4457     // for SequentialSubTasksDone.
4458     // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap
4459     // both of which need setting by set_n_termination().
4460     _g1h->SharedHeap::set_n_termination(active_workers);
4461     _g1h->set_n_termination(active_workers);
4462     terminator()->reset_for_reuse(active_workers);
4463     _n_workers = active_workers;
4464   }
4465 
4466   // Helps out with CLD processing.
4467   //
4468   // During InitialMark we need to:
4469   // 1) Scavenge all CLDs for the young GC.
4470   // 2) Mark all objects directly reachable from strong CLDs.
4471   template <G1Mark do_mark_object>
4472   class G1CLDClosure : public CLDClosure {
4473     G1ParCopyClosure<G1BarrierNone,  do_mark_object>* _oop_closure;
4474     G1ParCopyClosure<G1BarrierKlass, do_mark_object>  _oop_in_klass_closure;
4475     G1KlassScanClosure                                _klass_in_cld_closure;
4476     bool                                              _claim;
4477 
4478    public:
4479     G1CLDClosure(G1ParCopyClosure<G1BarrierNone, do_mark_object>* oop_closure,
4480                  bool only_young, bool claim)
4481         : _oop_closure(oop_closure),
4482           _oop_in_klass_closure(oop_closure->g1(),
4483                                 oop_closure->pss(),
4484                                 oop_closure->rp()),
4485           _klass_in_cld_closure(&_oop_in_klass_closure, only_young),
4486           _claim(claim) {
4487 
4488     }
4489 
4490     void do_cld(ClassLoaderData* cld) {
4491       cld->oops_do(_oop_closure, &_klass_in_cld_closure, _claim);
4492     }
4493   };
4494 
4495   void work(uint worker_id) {
4496     if (worker_id >= _n_workers) return;  // no work needed this round
4497 
4498     double start_time_ms = os::elapsedTime() * 1000.0;
4499     _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms);
4500 
4501     {
4502       ResourceMark rm;
4503       HandleMark   hm;
4504 
4505       ReferenceProcessor*             rp = _g1h->ref_processor_stw();
4506 
4507       G1ParScanThreadState            pss(_g1h, worker_id, rp);
4508       G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
4509 
4510       pss.set_evac_failure_closure(&evac_failure_cl);
4511 
4512       bool only_young = _g1h->g1_policy()->gcs_are_young();
4513 
4514       // Non-IM young GC.
4515       G1ParCopyClosure<G1BarrierNone, G1MarkNone>             scan_only_root_cl(_g1h, &pss, rp);
4516       G1CLDClosure<G1MarkNone>                                scan_only_cld_cl(&scan_only_root_cl,
4517                                                                                only_young, // Only process dirty klasses.
4518                                                                                false);     // No need to claim CLDs.
4519       // IM young GC.
4520       //    Strong roots closures.
4521       G1ParCopyClosure<G1BarrierNone, G1MarkFromRoot>         scan_mark_root_cl(_g1h, &pss, rp);
4522       G1CLDClosure<G1MarkFromRoot>                            scan_mark_cld_cl(&scan_mark_root_cl,
4523                                                                                false, // Process all klasses.
4524                                                                                true); // Need to claim CLDs.
4525       //    Weak roots closures.
4526       G1ParCopyClosure<G1BarrierNone, G1MarkPromotedFromRoot> scan_mark_weak_root_cl(_g1h, &pss, rp);
4527       G1CLDClosure<G1MarkPromotedFromRoot>                    scan_mark_weak_cld_cl(&scan_mark_weak_root_cl,
4528                                                                                     false, // Process all klasses.
4529                                                                                     true); // Need to claim CLDs.
4530 
4531       G1CodeBlobClosure scan_only_code_cl(&scan_only_root_cl);
4532       G1CodeBlobClosure scan_mark_code_cl(&scan_mark_root_cl);
4533       // IM Weak code roots are handled later.
4534 
4535       OopClosure* strong_root_cl;
4536       OopClosure* weak_root_cl;
4537       CLDClosure* strong_cld_cl;
4538       CLDClosure* weak_cld_cl;
4539       CodeBlobClosure* strong_code_cl;
4540 
4541       if (_g1h->g1_policy()->during_initial_mark_pause()) {
4542         // We also need to mark copied objects.
4543         strong_root_cl = &scan_mark_root_cl;
4544         strong_cld_cl  = &scan_mark_cld_cl;
4545         strong_code_cl = &scan_mark_code_cl;
4546         if (ClassUnloadingWithConcurrentMark) {
4547           weak_root_cl = &scan_mark_weak_root_cl;
4548           weak_cld_cl  = &scan_mark_weak_cld_cl;
4549         } else {
4550           weak_root_cl = &scan_mark_root_cl;
4551           weak_cld_cl  = &scan_mark_cld_cl;
4552         }
4553       } else {
4554         strong_root_cl = &scan_only_root_cl;
4555         weak_root_cl   = &scan_only_root_cl;
4556         strong_cld_cl  = &scan_only_cld_cl;
4557         weak_cld_cl    = &scan_only_cld_cl;
4558         strong_code_cl = &scan_only_code_cl;
4559       }
4560 
4561 
4562       G1ParPushHeapRSClosure  push_heap_rs_cl(_g1h, &pss);
4563 
4564       pss.start_strong_roots();
4565       _g1h->g1_process_roots(strong_root_cl,
4566                              weak_root_cl,
4567                              &push_heap_rs_cl,
4568                              strong_cld_cl,
4569                              weak_cld_cl,
4570                              strong_code_cl,
4571                              worker_id);
4572 
4573       pss.end_strong_roots();
4574 
4575       {
4576         double start = os::elapsedTime();
4577         G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4578         evac.do_void();
4579         double elapsed_ms = (os::elapsedTime()-start)*1000.0;
4580         double term_ms = pss.term_time()*1000.0;
4581         _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms);
4582         _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts());
4583       }
4584       _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4585       _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4586 
4587       if (PrintTerminationStats) {
4588         MutexLocker x(stats_lock());
4589         pss.print_termination_stats(worker_id);
4590       }
4591 
4592       assert(pss.queue_is_empty(), "should be empty");
4593 
4594       // Close the inner scope so that the ResourceMark and HandleMark
4595       // destructors are executed here and are included as part of the
4596       // "GC Worker Time".
4597     }
4598 
4599     double end_time_ms = os::elapsedTime() * 1000.0;
4600     _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms);
4601   }
4602 };
4603 
4604 // *** Common G1 Evacuation Stuff
4605 
4606 // This method is run in a GC worker.
4607 
4608 void
4609 G1CollectedHeap::
4610 g1_process_roots(OopClosure* scan_non_heap_roots,
4611                  OopClosure* scan_non_heap_weak_roots,
4612                  G1ParPushHeapRSClosure* scan_rs,
4613                  CLDClosure* scan_strong_clds,
4614                  CLDClosure* scan_weak_clds,
4615                  CodeBlobClosure* scan_strong_code,
4616                  uint worker_i) {
4617 
4618   // First scan the shared roots.
4619   double ext_roots_start = os::elapsedTime();
4620   double closure_app_time_sec = 0.0;
4621 
4622   bool during_im = _g1h->g1_policy()->during_initial_mark_pause();
4623   bool trace_metadata = during_im && ClassUnloadingWithConcurrentMark;
4624 
4625   BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
4626   BufferingOopClosure buf_scan_non_heap_weak_roots(scan_non_heap_weak_roots);
4627 
4628   process_roots(false, // no scoping; this is parallel code
4629                 SharedHeap::SO_None,
4630                 &buf_scan_non_heap_roots,
4631                 &buf_scan_non_heap_weak_roots,
4632                 scan_strong_clds,
4633                 // Unloading Initial Marks handle the weak CLDs separately.
4634                 (trace_metadata ? NULL : scan_weak_clds),
4635                 scan_strong_code);
4636 
4637   // Now the CM ref_processor roots.
4638   if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
4639     // We need to treat the discovered reference lists of the
4640     // concurrent mark ref processor as roots and keep entries
4641     // (which are added by the marking threads) on them live
4642     // until they can be processed at the end of marking.
4643     ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
4644   }
4645 
4646   if (trace_metadata) {
4647     // Barrier to make sure all workers passed
4648     // the strong CLD and strong nmethods phases.
4649     active_strong_roots_scope()->wait_until_all_workers_done_with_threads(n_par_threads());
4650 
4651     // Now take the complement of the strong CLDs.
4652     ClassLoaderDataGraph::roots_cld_do(NULL, scan_weak_clds);
4653   }
4654 
4655   // Finish up any enqueued closure apps (attributed as object copy time).
4656   buf_scan_non_heap_roots.done();
4657   buf_scan_non_heap_weak_roots.done();
4658 
4659   double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds()
4660       + buf_scan_non_heap_weak_roots.closure_app_seconds();
4661 
4662   g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
4663 
4664   double ext_root_time_ms =
4665     ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0;
4666 
4667   g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
4668 
4669   // During conc marking we have to filter the per-thread SATB buffers
4670   // to make sure we remove any oops into the CSet (which will show up
4671   // as implicitly live).
4672   double satb_filtering_ms = 0.0;
4673   if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) {
4674     if (mark_in_progress()) {
4675       double satb_filter_start = os::elapsedTime();
4676 
4677       JavaThread::satb_mark_queue_set().filter_thread_buffers();
4678 
4679       satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0;
4680     }
4681   }
4682   g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms);
4683 
4684   // Now scan the complement of the collection set.
4685   G1CodeBlobClosure scavenge_cs_nmethods(scan_non_heap_weak_roots);
4686 
4687   g1_rem_set()->oops_into_collection_set_do(scan_rs, &scavenge_cs_nmethods, worker_i);
4688 
4689   _process_strong_tasks->all_tasks_completed();
4690 }
4691 
4692 class G1StringSymbolTableUnlinkTask : public AbstractGangTask {
4693 private:
4694   BoolObjectClosure* _is_alive;
4695   int _initial_string_table_size;
4696   int _initial_symbol_table_size;
4697 
4698   bool  _process_strings;
4699   int _strings_processed;
4700   int _strings_removed;
4701 
4702   bool  _process_symbols;
4703   int _symbols_processed;
4704   int _symbols_removed;
4705 
4706 public:
4707   G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) :
4708     AbstractGangTask("String/Symbol Unlinking"),
4709     _is_alive(is_alive),
4710     _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
4711     _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) {
4712 
4713     _initial_string_table_size = StringTable::the_table()->table_size();
4714     _initial_symbol_table_size = SymbolTable::the_table()->table_size();
4715     if (process_strings) {
4716       StringTable::clear_parallel_claimed_index();
4717     }
4718     if (process_symbols) {
4719       SymbolTable::clear_parallel_claimed_index();
4720     }
4721   }
4722 
4723   ~G1StringSymbolTableUnlinkTask() {
4724     guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size,
4725               err_msg("claim value %d after unlink less than initial string table size %d",
4726                       StringTable::parallel_claimed_index(), _initial_string_table_size));
4727     guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
4728               err_msg("claim value %d after unlink less than initial symbol table size %d",
4729                       SymbolTable::parallel_claimed_index(), _initial_symbol_table_size));
4730 
4731     if (G1TraceStringSymbolTableScrubbing) {
4732       gclog_or_tty->print_cr("Cleaned string and symbol table, "
4733                              "strings: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed, "
4734                              "symbols: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed",
4735                              strings_processed(), strings_removed(),
4736                              symbols_processed(), symbols_removed());
4737     }
4738   }
4739 
4740   void work(uint worker_id) {
4741     int strings_processed = 0;
4742     int strings_removed = 0;
4743     int symbols_processed = 0;
4744     int symbols_removed = 0;
4745     if (_process_strings) {
4746       StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
4747       Atomic::add(strings_processed, &_strings_processed);
4748       Atomic::add(strings_removed, &_strings_removed);
4749     }
4750     if (_process_symbols) {
4751       SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
4752       Atomic::add(symbols_processed, &_symbols_processed);
4753       Atomic::add(symbols_removed, &_symbols_removed);
4754     }
4755   }
4756 
4757   size_t strings_processed() const { return (size_t)_strings_processed; }
4758   size_t strings_removed()   const { return (size_t)_strings_removed; }
4759 
4760   size_t symbols_processed() const { return (size_t)_symbols_processed; }
4761   size_t symbols_removed()   const { return (size_t)_symbols_removed; }
4762 };
4763 
4764 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
4765 private:
4766   static Monitor* _lock;
4767 
4768   BoolObjectClosure* const _is_alive;
4769   const bool               _unloading_occurred;
4770   const uint               _num_workers;
4771 
4772   // Variables used to claim nmethods.
4773   nmethod* _first_nmethod;
4774   volatile nmethod* _claimed_nmethod;
4775 
4776   // The list of nmethods that need to be processed by the second pass.
4777   volatile nmethod* _postponed_list;
4778   volatile uint     _num_entered_barrier;
4779 
4780  public:
4781   G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
4782       _is_alive(is_alive),
4783       _unloading_occurred(unloading_occurred),
4784       _num_workers(num_workers),
4785       _first_nmethod(NULL),
4786       _claimed_nmethod(NULL),
4787       _postponed_list(NULL),
4788       _num_entered_barrier(0)
4789   {
4790     nmethod::increase_unloading_clock();
4791     // Get first alive nmethod
4792     NMethodIterator iter = NMethodIterator();
4793     if(iter.next_alive()) {
4794       _first_nmethod = iter.method();
4795     }
4796     _claimed_nmethod = (volatile nmethod*)_first_nmethod;
4797   }
4798 
4799   ~G1CodeCacheUnloadingTask() {
4800     CodeCache::verify_clean_inline_caches();
4801 
4802     CodeCache::set_needs_cache_clean(false);
4803     guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
4804 
4805     CodeCache::verify_icholder_relocations();
4806   }
4807 
4808  private:
4809   void add_to_postponed_list(nmethod* nm) {
4810       nmethod* old;
4811       do {
4812         old = (nmethod*)_postponed_list;
4813         nm->set_unloading_next(old);
4814       } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old);
4815   }
4816 
4817   void clean_nmethod(nmethod* nm) {
4818     bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
4819 
4820     if (postponed) {
4821       // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
4822       add_to_postponed_list(nm);
4823     }
4824 
4825     // Mark that this thread has been cleaned/unloaded.
4826     // After this call, it will be safe to ask if this nmethod was unloaded or not.
4827     nm->set_unloading_clock(nmethod::global_unloading_clock());
4828   }
4829 
4830   void clean_nmethod_postponed(nmethod* nm) {
4831     nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
4832   }
4833 
4834   static const int MaxClaimNmethods = 16;
4835 
4836   void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) {
4837     nmethod* first;
4838     NMethodIterator last;
4839 
4840     do {
4841       *num_claimed_nmethods = 0;
4842 
4843       first = (nmethod*)_claimed_nmethod;
4844       last = NMethodIterator(first);
4845 
4846       if (first != NULL) {
4847 
4848         for (int i = 0; i < MaxClaimNmethods; i++) {
4849           if (!last.next_alive()) {
4850             break;
4851           }
4852           claimed_nmethods[i] = last.method();
4853           (*num_claimed_nmethods)++;
4854         }
4855       }
4856 
4857     } while ((nmethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first);
4858   }
4859 
4860   nmethod* claim_postponed_nmethod() {
4861     nmethod* claim;
4862     nmethod* next;
4863 
4864     do {
4865       claim = (nmethod*)_postponed_list;
4866       if (claim == NULL) {
4867         return NULL;
4868       }
4869 
4870       next = claim->unloading_next();
4871 
4872     } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim);
4873 
4874     return claim;
4875   }
4876 
4877  public:
4878   // Mark that we're done with the first pass of nmethod cleaning.
4879   void barrier_mark(uint worker_id) {
4880     MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
4881     _num_entered_barrier++;
4882     if (_num_entered_barrier == _num_workers) {
4883       ml.notify_all();
4884     }
4885   }
4886 
4887   // See if we have to wait for the other workers to
4888   // finish their first-pass nmethod cleaning work.
4889   void barrier_wait(uint worker_id) {
4890     if (_num_entered_barrier < _num_workers) {
4891       MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
4892       while (_num_entered_barrier < _num_workers) {
4893           ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
4894       }
4895     }
4896   }
4897 
4898   // Cleaning and unloading of nmethods. Some work has to be postponed
4899   // to the second pass, when we know which nmethods survive.
4900   void work_first_pass(uint worker_id) {
4901     // The first nmethods is claimed by the first worker.
4902     if (worker_id == 0 && _first_nmethod != NULL) {
4903       clean_nmethod(_first_nmethod);
4904       _first_nmethod = NULL;
4905     }
4906 
4907     int num_claimed_nmethods;
4908     nmethod* claimed_nmethods[MaxClaimNmethods];
4909 
4910     while (true) {
4911       claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
4912 
4913       if (num_claimed_nmethods == 0) {
4914         break;
4915       }
4916 
4917       for (int i = 0; i < num_claimed_nmethods; i++) {
4918         clean_nmethod(claimed_nmethods[i]);
4919       }
4920     }
4921 
4922     // The nmethod cleaning helps out and does the CodeCache part of MetadataOnStackMark.
4923     // Need to retire the buffers now that this thread has stopped cleaning nmethods.
4924     MetadataOnStackMark::retire_buffer_for_thread(Thread::current());
4925   }
4926 
4927   void work_second_pass(uint worker_id) {
4928     nmethod* nm;
4929     // Take care of postponed nmethods.
4930     while ((nm = claim_postponed_nmethod()) != NULL) {
4931       clean_nmethod_postponed(nm);
4932     }
4933   }
4934 };
4935 
4936 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock");
4937 
4938 class G1KlassCleaningTask : public StackObj {
4939   BoolObjectClosure*                      _is_alive;
4940   volatile jint                           _clean_klass_tree_claimed;
4941   ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
4942 
4943  public:
4944   G1KlassCleaningTask(BoolObjectClosure* is_alive) :
4945       _is_alive(is_alive),
4946       _clean_klass_tree_claimed(0),
4947       _klass_iterator() {
4948   }
4949 
4950  private:
4951   bool claim_clean_klass_tree_task() {
4952     if (_clean_klass_tree_claimed) {
4953       return false;
4954     }
4955 
4956     return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0;
4957   }
4958 
4959   InstanceKlass* claim_next_klass() {
4960     Klass* klass;
4961     do {
4962       klass =_klass_iterator.next_klass();
4963     } while (klass != NULL && !klass->oop_is_instance());
4964 
4965     return (InstanceKlass*)klass;
4966   }
4967 
4968 public:
4969 
4970   void clean_klass(InstanceKlass* ik) {
4971     ik->clean_implementors_list(_is_alive);
4972     ik->clean_method_data(_is_alive);
4973 
4974     // G1 specific cleanup work that has
4975     // been moved here to be done in parallel.
4976     ik->clean_dependent_nmethods();
4977     if (JvmtiExport::has_redefined_a_class()) {
4978       InstanceKlass::purge_previous_versions(ik);
4979     }
4980   }
4981 
4982   void work() {
4983     ResourceMark rm;
4984 
4985     // One worker will clean the subklass/sibling klass tree.
4986     if (claim_clean_klass_tree_task()) {
4987       Klass::clean_subklass_tree(_is_alive);
4988     }
4989 
4990     // All workers will help cleaning the classes,
4991     InstanceKlass* klass;
4992     while ((klass = claim_next_klass()) != NULL) {
4993       clean_klass(klass);
4994     }
4995   }
4996 };
4997 
4998 // To minimize the remark pause times, the tasks below are done in parallel.
4999 class G1ParallelCleaningTask : public AbstractGangTask {
5000 private:
5001   G1StringSymbolTableUnlinkTask _string_symbol_task;
5002   G1CodeCacheUnloadingTask      _code_cache_task;
5003   G1KlassCleaningTask           _klass_cleaning_task;
5004 
5005 public:
5006   // The constructor is run in the VMThread.
5007   G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) :
5008       AbstractGangTask("Parallel Cleaning"),
5009       _string_symbol_task(is_alive, process_strings, process_symbols),
5010       _code_cache_task(num_workers, is_alive, unloading_occurred),
5011       _klass_cleaning_task(is_alive) {
5012   }
5013 
5014   void pre_work_verification() {
5015     assert(!MetadataOnStackMark::has_buffer_for_thread(Thread::current()), "Should be empty");
5016   }
5017 
5018   void post_work_verification() {
5019     assert(!MetadataOnStackMark::has_buffer_for_thread(Thread::current()), "Should be empty");
5020   }
5021 
5022   // The parallel work done by all worker threads.
5023   void work(uint worker_id) {
5024     pre_work_verification();
5025 
5026     // Do first pass of code cache cleaning.
5027     _code_cache_task.work_first_pass(worker_id);
5028 
5029     // Let the threads mark that the first pass is done.
5030     _code_cache_task.barrier_mark(worker_id);
5031 
5032     // Clean the Strings and Symbols.
5033     _string_symbol_task.work(worker_id);
5034 
5035     // Wait for all workers to finish the first code cache cleaning pass.
5036     _code_cache_task.barrier_wait(worker_id);
5037 
5038     // Do the second code cache cleaning work, which realize on
5039     // the liveness information gathered during the first pass.
5040     _code_cache_task.work_second_pass(worker_id);
5041 
5042     // Clean all klasses that were not unloaded.
5043     _klass_cleaning_task.work();
5044 
5045     post_work_verification();
5046   }
5047 };
5048 
5049 
5050 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive,
5051                                         bool process_strings,
5052                                         bool process_symbols,
5053                                         bool class_unloading_occurred) {
5054   uint n_workers = workers()->active_workers();
5055 
5056   G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols,
5057                                         n_workers, class_unloading_occurred);
5058   set_par_threads(n_workers);
5059   workers()->run_task(&g1_unlink_task);
5060   set_par_threads(0);
5061 }
5062 
5063 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive,
5064                                                      bool process_strings, bool process_symbols) {
5065   {
5066     uint n_workers = _g1h->workers()->active_workers();
5067     G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols);
5068     set_par_threads(n_workers);
5069     workers()->run_task(&g1_unlink_task);
5070     set_par_threads(0);
5071   }
5072 
5073   if (G1StringDedup::is_enabled()) {
5074     G1StringDedup::unlink(is_alive);
5075   }
5076 }
5077 
5078 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
5079  private:
5080   DirtyCardQueueSet* _queue;
5081  public:
5082   G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue) : AbstractGangTask("Redirty Cards"), _queue(queue) { }
5083 
5084   virtual void work(uint worker_id) {
5085     double start_time = os::elapsedTime();
5086 
5087     RedirtyLoggedCardTableEntryClosure cl;
5088     _queue->par_apply_closure_to_all_completed_buffers(&cl);
5089 
5090     G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
5091     timer->record_redirty_logged_cards_time_ms(worker_id, (os::elapsedTime() - start_time) * 1000.0);
5092     timer->record_redirty_logged_cards_processed_cards(worker_id, cl.num_processed());
5093   }
5094 };
5095 
5096 void G1CollectedHeap::redirty_logged_cards() {
5097   double redirty_logged_cards_start = os::elapsedTime();
5098 
5099   uint n_workers = _g1h->workers()->active_workers();
5100 
5101   G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set());
5102   dirty_card_queue_set().reset_for_par_iteration();
5103   set_par_threads(n_workers);
5104   workers()->run_task(&redirty_task);
5105   set_par_threads(0);
5106 
5107   DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5108   dcq.merge_bufferlists(&dirty_card_queue_set());
5109   assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5110 
5111   g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
5112 }
5113 
5114 // Weak Reference Processing support
5115 
5116 // An always "is_alive" closure that is used to preserve referents.
5117 // If the object is non-null then it's alive.  Used in the preservation
5118 // of referent objects that are pointed to by reference objects
5119 // discovered by the CM ref processor.
5120 class G1AlwaysAliveClosure: public BoolObjectClosure {
5121   G1CollectedHeap* _g1;
5122 public:
5123   G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5124   bool do_object_b(oop p) {
5125     if (p != NULL) {
5126       return true;
5127     }
5128     return false;
5129   }
5130 };
5131 
5132 bool G1STWIsAliveClosure::do_object_b(oop p) {
5133   // An object is reachable if it is outside the collection set,
5134   // or is inside and copied.
5135   return !_g1->obj_in_cs(p) || p->is_forwarded();
5136 }
5137 
5138 // Non Copying Keep Alive closure
5139 class G1KeepAliveClosure: public OopClosure {
5140   G1CollectedHeap* _g1;
5141 public:
5142   G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5143   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
5144   void do_oop(oop* p) {
5145     oop obj = *p;
5146     assert(obj != NULL, "the caller should have filtered out NULL values");
5147 
5148     G1CollectedHeap::in_cset_state_t cset_state = _g1->in_cset_state(obj);
5149     if (cset_state == G1CollectedHeap::InNeither) {
5150       return;
5151     }
5152     if (cset_state == G1CollectedHeap::InCSet) {
5153       assert( obj->is_forwarded(), "invariant" );
5154       *p = obj->forwardee();
5155     } else {
5156       assert(!obj->is_forwarded(), "invariant" );
5157       assert(cset_state == G1CollectedHeap::IsHumongous,
5158              err_msg("Only allowed InCSet state is IsHumongous, but is %d", cset_state));
5159       _g1->set_humongous_is_live(obj);
5160     }
5161   }
5162 };
5163 
5164 // Copying Keep Alive closure - can be called from both
5165 // serial and parallel code as long as different worker
5166 // threads utilize different G1ParScanThreadState instances
5167 // and different queues.
5168 
5169 class G1CopyingKeepAliveClosure: public OopClosure {
5170   G1CollectedHeap*         _g1h;
5171   OopClosure*              _copy_non_heap_obj_cl;
5172   G1ParScanThreadState*    _par_scan_state;
5173 
5174 public:
5175   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
5176                             OopClosure* non_heap_obj_cl,
5177                             G1ParScanThreadState* pss):
5178     _g1h(g1h),
5179     _copy_non_heap_obj_cl(non_heap_obj_cl),
5180     _par_scan_state(pss)
5181   {}
5182 
5183   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
5184   virtual void do_oop(      oop* p) { do_oop_work(p); }
5185 
5186   template <class T> void do_oop_work(T* p) {
5187     oop obj = oopDesc::load_decode_heap_oop(p);
5188 
5189     if (_g1h->is_in_cset_or_humongous(obj)) {
5190       // If the referent object has been forwarded (either copied
5191       // to a new location or to itself in the event of an
5192       // evacuation failure) then we need to update the reference
5193       // field and, if both reference and referent are in the G1
5194       // heap, update the RSet for the referent.
5195       //
5196       // If the referent has not been forwarded then we have to keep
5197       // it alive by policy. Therefore we have copy the referent.
5198       //
5199       // If the reference field is in the G1 heap then we can push
5200       // on the PSS queue. When the queue is drained (after each
5201       // phase of reference processing) the object and it's followers
5202       // will be copied, the reference field set to point to the
5203       // new location, and the RSet updated. Otherwise we need to
5204       // use the the non-heap or metadata closures directly to copy
5205       // the referent object and update the pointer, while avoiding
5206       // updating the RSet.
5207 
5208       if (_g1h->is_in_g1_reserved(p)) {
5209         _par_scan_state->push_on_queue(p);
5210       } else {
5211         assert(!Metaspace::contains((const void*)p),
5212                err_msg("Unexpectedly found a pointer from metadata: "
5213                               PTR_FORMAT, p));
5214         _copy_non_heap_obj_cl->do_oop(p);
5215       }
5216     }
5217   }
5218 };
5219 
5220 // Serial drain queue closure. Called as the 'complete_gc'
5221 // closure for each discovered list in some of the
5222 // reference processing phases.
5223 
5224 class G1STWDrainQueueClosure: public VoidClosure {
5225 protected:
5226   G1CollectedHeap* _g1h;
5227   G1ParScanThreadState* _par_scan_state;
5228 
5229   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
5230 
5231 public:
5232   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
5233     _g1h(g1h),
5234     _par_scan_state(pss)
5235   { }
5236 
5237   void do_void() {
5238     G1ParScanThreadState* const pss = par_scan_state();
5239     pss->trim_queue();
5240   }
5241 };
5242 
5243 // Parallel Reference Processing closures
5244 
5245 // Implementation of AbstractRefProcTaskExecutor for parallel reference
5246 // processing during G1 evacuation pauses.
5247 
5248 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5249 private:
5250   G1CollectedHeap*   _g1h;
5251   RefToScanQueueSet* _queues;
5252   FlexibleWorkGang*  _workers;
5253   int                _active_workers;
5254 
5255 public:
5256   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5257                         FlexibleWorkGang* workers,
5258                         RefToScanQueueSet *task_queues,
5259                         int n_workers) :
5260     _g1h(g1h),
5261     _queues(task_queues),
5262     _workers(workers),
5263     _active_workers(n_workers)
5264   {
5265     assert(n_workers > 0, "shouldn't call this otherwise");
5266   }
5267 
5268   // Executes the given task using concurrent marking worker threads.
5269   virtual void execute(ProcessTask& task);
5270   virtual void execute(EnqueueTask& task);
5271 };
5272 
5273 // Gang task for possibly parallel reference processing
5274 
5275 class G1STWRefProcTaskProxy: public AbstractGangTask {
5276   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5277   ProcessTask&     _proc_task;
5278   G1CollectedHeap* _g1h;
5279   RefToScanQueueSet *_task_queues;
5280   ParallelTaskTerminator* _terminator;
5281 
5282 public:
5283   G1STWRefProcTaskProxy(ProcessTask& proc_task,
5284                      G1CollectedHeap* g1h,
5285                      RefToScanQueueSet *task_queues,
5286                      ParallelTaskTerminator* terminator) :
5287     AbstractGangTask("Process reference objects in parallel"),
5288     _proc_task(proc_task),
5289     _g1h(g1h),
5290     _task_queues(task_queues),
5291     _terminator(terminator)
5292   {}
5293 
5294   virtual void work(uint worker_id) {
5295     // The reference processing task executed by a single worker.
5296     ResourceMark rm;
5297     HandleMark   hm;
5298 
5299     G1STWIsAliveClosure is_alive(_g1h);
5300 
5301     G1ParScanThreadState            pss(_g1h, worker_id, NULL);
5302     G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5303 
5304     pss.set_evac_failure_closure(&evac_failure_cl);
5305 
5306     G1ParScanExtRootClosure        only_copy_non_heap_cl(_g1h, &pss, NULL);
5307 
5308     G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5309 
5310     OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5311 
5312     if (_g1h->g1_policy()->during_initial_mark_pause()) {
5313       // We also need to mark copied objects.
5314       copy_non_heap_cl = &copy_mark_non_heap_cl;
5315     }
5316 
5317     // Keep alive closure.
5318     G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5319 
5320     // Complete GC closure
5321     G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5322 
5323     // Call the reference processing task's work routine.
5324     _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5325 
5326     // Note we cannot assert that the refs array is empty here as not all
5327     // of the processing tasks (specifically phase2 - pp2_work) execute
5328     // the complete_gc closure (which ordinarily would drain the queue) so
5329     // the queue may not be empty.
5330   }
5331 };
5332 
5333 // Driver routine for parallel reference processing.
5334 // Creates an instance of the ref processing gang
5335 // task and has the worker threads execute it.
5336 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5337   assert(_workers != NULL, "Need parallel worker threads.");
5338 
5339   ParallelTaskTerminator terminator(_active_workers, _queues);
5340   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5341 
5342   _g1h->set_par_threads(_active_workers);
5343   _workers->run_task(&proc_task_proxy);
5344   _g1h->set_par_threads(0);
5345 }
5346 
5347 // Gang task for parallel reference enqueueing.
5348 
5349 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5350   typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5351   EnqueueTask& _enq_task;
5352 
5353 public:
5354   G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5355     AbstractGangTask("Enqueue reference objects in parallel"),
5356     _enq_task(enq_task)
5357   { }
5358 
5359   virtual void work(uint worker_id) {
5360     _enq_task.work(worker_id);
5361   }
5362 };
5363 
5364 // Driver routine for parallel reference enqueueing.
5365 // Creates an instance of the ref enqueueing gang
5366 // task and has the worker threads execute it.
5367 
5368 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5369   assert(_workers != NULL, "Need parallel worker threads.");
5370 
5371   G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5372 
5373   _g1h->set_par_threads(_active_workers);
5374   _workers->run_task(&enq_task_proxy);
5375   _g1h->set_par_threads(0);
5376 }
5377 
5378 // End of weak reference support closures
5379 
5380 // Abstract task used to preserve (i.e. copy) any referent objects
5381 // that are in the collection set and are pointed to by reference
5382 // objects discovered by the CM ref processor.
5383 
5384 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5385 protected:
5386   G1CollectedHeap* _g1h;
5387   RefToScanQueueSet      *_queues;
5388   ParallelTaskTerminator _terminator;
5389   uint _n_workers;
5390 
5391 public:
5392   G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
5393     AbstractGangTask("ParPreserveCMReferents"),
5394     _g1h(g1h),
5395     _queues(task_queues),
5396     _terminator(workers, _queues),
5397     _n_workers(workers)
5398   { }
5399 
5400   void work(uint worker_id) {
5401     ResourceMark rm;
5402     HandleMark   hm;
5403 
5404     G1ParScanThreadState            pss(_g1h, worker_id, NULL);
5405     G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5406 
5407     pss.set_evac_failure_closure(&evac_failure_cl);
5408 
5409     assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5410 
5411     G1ParScanExtRootClosure        only_copy_non_heap_cl(_g1h, &pss, NULL);
5412 
5413     G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5414 
5415     OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5416 
5417     if (_g1h->g1_policy()->during_initial_mark_pause()) {
5418       // We also need to mark copied objects.
5419       copy_non_heap_cl = &copy_mark_non_heap_cl;
5420     }
5421 
5422     // Is alive closure
5423     G1AlwaysAliveClosure always_alive(_g1h);
5424 
5425     // Copying keep alive closure. Applied to referent objects that need
5426     // to be copied.
5427     G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5428 
5429     ReferenceProcessor* rp = _g1h->ref_processor_cm();
5430 
5431     uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5432     uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5433 
5434     // limit is set using max_num_q() - which was set using ParallelGCThreads.
5435     // So this must be true - but assert just in case someone decides to
5436     // change the worker ids.
5437     assert(0 <= worker_id && worker_id < limit, "sanity");
5438     assert(!rp->discovery_is_atomic(), "check this code");
5439 
5440     // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5441     for (uint idx = worker_id; idx < limit; idx += stride) {
5442       DiscoveredList& ref_list = rp->discovered_refs()[idx];
5443 
5444       DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5445       while (iter.has_next()) {
5446         // Since discovery is not atomic for the CM ref processor, we
5447         // can see some null referent objects.
5448         iter.load_ptrs(DEBUG_ONLY(true));
5449         oop ref = iter.obj();
5450 
5451         // This will filter nulls.
5452         if (iter.is_referent_alive()) {
5453           iter.make_referent_alive();
5454         }
5455         iter.move_to_next();
5456       }
5457     }
5458 
5459     // Drain the queue - which may cause stealing
5460     G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5461     drain_queue.do_void();
5462     // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5463     assert(pss.queue_is_empty(), "should be");
5464   }
5465 };
5466 
5467 // Weak Reference processing during an evacuation pause (part 1).
5468 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) {
5469   double ref_proc_start = os::elapsedTime();
5470 
5471   ReferenceProcessor* rp = _ref_processor_stw;
5472   assert(rp->discovery_enabled(), "should have been enabled");
5473 
5474   // Any reference objects, in the collection set, that were 'discovered'
5475   // by the CM ref processor should have already been copied (either by
5476   // applying the external root copy closure to the discovered lists, or
5477   // by following an RSet entry).
5478   //
5479   // But some of the referents, that are in the collection set, that these
5480   // reference objects point to may not have been copied: the STW ref
5481   // processor would have seen that the reference object had already
5482   // been 'discovered' and would have skipped discovering the reference,
5483   // but would not have treated the reference object as a regular oop.
5484   // As a result the copy closure would not have been applied to the
5485   // referent object.
5486   //
5487   // We need to explicitly copy these referent objects - the references
5488   // will be processed at the end of remarking.
5489   //
5490   // We also need to do this copying before we process the reference
5491   // objects discovered by the STW ref processor in case one of these
5492   // referents points to another object which is also referenced by an
5493   // object discovered by the STW ref processor.
5494 
5495   assert(no_of_gc_workers == workers()->active_workers(), "Need to reset active GC workers");
5496 
5497   set_par_threads(no_of_gc_workers);
5498   G1ParPreserveCMReferentsTask keep_cm_referents(this,
5499                                                  no_of_gc_workers,
5500                                                  _task_queues);
5501 
5502   workers()->run_task(&keep_cm_referents);
5503 
5504   set_par_threads(0);
5505 
5506   // Closure to test whether a referent is alive.
5507   G1STWIsAliveClosure is_alive(this);
5508 
5509   // Even when parallel reference processing is enabled, the processing
5510   // of JNI refs is serial and performed serially by the current thread
5511   // rather than by a worker. The following PSS will be used for processing
5512   // JNI refs.
5513 
5514   // Use only a single queue for this PSS.
5515   G1ParScanThreadState            pss(this, 0, NULL);
5516 
5517   // We do not embed a reference processor in the copying/scanning
5518   // closures while we're actually processing the discovered
5519   // reference objects.
5520   G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5521 
5522   pss.set_evac_failure_closure(&evac_failure_cl);
5523 
5524   assert(pss.queue_is_empty(), "pre-condition");
5525 
5526   G1ParScanExtRootClosure        only_copy_non_heap_cl(this, &pss, NULL);
5527 
5528   G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5529 
5530   OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5531 
5532   if (_g1h->g1_policy()->during_initial_mark_pause()) {
5533     // We also need to mark copied objects.
5534     copy_non_heap_cl = &copy_mark_non_heap_cl;
5535   }
5536 
5537   // Keep alive closure.
5538   G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, &pss);
5539 
5540   // Serial Complete GC closure
5541   G1STWDrainQueueClosure drain_queue(this, &pss);
5542 
5543   // Setup the soft refs policy...
5544   rp->setup_policy(false);
5545 
5546   ReferenceProcessorStats stats;
5547   if (!rp->processing_is_mt()) {
5548     // Serial reference processing...
5549     stats = rp->process_discovered_references(&is_alive,
5550                                               &keep_alive,
5551                                               &drain_queue,
5552                                               NULL,
5553                                               _gc_timer_stw,
5554                                               _gc_tracer_stw->gc_id());
5555   } else {
5556     // Parallel reference processing
5557     assert(rp->num_q() == no_of_gc_workers, "sanity");
5558     assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5559 
5560     G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5561     stats = rp->process_discovered_references(&is_alive,
5562                                               &keep_alive,
5563                                               &drain_queue,
5564                                               &par_task_executor,
5565                                               _gc_timer_stw,
5566                                               _gc_tracer_stw->gc_id());
5567   }
5568 
5569   _gc_tracer_stw->report_gc_reference_stats(stats);
5570 
5571   // We have completed copying any necessary live referent objects.
5572   assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5573 
5574   double ref_proc_time = os::elapsedTime() - ref_proc_start;
5575   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5576 }
5577 
5578 // Weak Reference processing during an evacuation pause (part 2).
5579 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) {
5580   double ref_enq_start = os::elapsedTime();
5581 
5582   ReferenceProcessor* rp = _ref_processor_stw;
5583   assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5584 
5585   // Now enqueue any remaining on the discovered lists on to
5586   // the pending list.
5587   if (!rp->processing_is_mt()) {
5588     // Serial reference processing...
5589     rp->enqueue_discovered_references();
5590   } else {
5591     // Parallel reference enqueueing
5592 
5593     assert(no_of_gc_workers == workers()->active_workers(),
5594            "Need to reset active workers");
5595     assert(rp->num_q() == no_of_gc_workers, "sanity");
5596     assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5597 
5598     G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5599     rp->enqueue_discovered_references(&par_task_executor);
5600   }
5601 
5602   rp->verify_no_references_recorded();
5603   assert(!rp->discovery_enabled(), "should have been disabled");
5604 
5605   // FIXME
5606   // CM's reference processing also cleans up the string and symbol tables.
5607   // Should we do that here also? We could, but it is a serial operation
5608   // and could significantly increase the pause time.
5609 
5610   double ref_enq_time = os::elapsedTime() - ref_enq_start;
5611   g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5612 }
5613 
5614 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) {
5615   _expand_heap_after_alloc_failure = true;
5616   _evacuation_failed = false;
5617 
5618   // Should G1EvacuationFailureALot be in effect for this GC?
5619   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
5620 
5621   g1_rem_set()->prepare_for_oops_into_collection_set_do();
5622 
5623   // Disable the hot card cache.
5624   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
5625   hot_card_cache->reset_hot_cache_claimed_index();
5626   hot_card_cache->set_use_cache(false);
5627 
5628   uint n_workers;
5629   n_workers =
5630     AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
5631                                    workers()->active_workers(),
5632                                    Threads::number_of_non_daemon_threads());
5633   assert(UseDynamicNumberOfGCThreads ||
5634          n_workers == workers()->total_workers(),
5635          "If not dynamic should be using all the  workers");
5636   workers()->set_active_workers(n_workers);
5637   set_par_threads(n_workers);
5638 
5639   G1ParTask g1_par_task(this, _task_queues);
5640 
5641   init_for_evac_failure(NULL);
5642 
5643   rem_set()->prepare_for_younger_refs_iterate(true);
5644 
5645   assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5646   double start_par_time_sec = os::elapsedTime();
5647   double end_par_time_sec;
5648 
5649   {
5650     StrongRootsScope srs(this);
5651     // InitialMark needs claim bits to keep track of the marked-through CLDs.
5652     if (g1_policy()->during_initial_mark_pause()) {
5653       ClassLoaderDataGraph::clear_claimed_marks();
5654     }
5655 
5656      // The individual threads will set their evac-failure closures.
5657      if (PrintTerminationStats) G1ParScanThreadState::print_termination_stats_hdr();
5658      // These tasks use ShareHeap::_process_strong_tasks
5659      assert(UseDynamicNumberOfGCThreads ||
5660             workers()->active_workers() == workers()->total_workers(),
5661             "If not dynamic should be using all the  workers");
5662     workers()->run_task(&g1_par_task);
5663     end_par_time_sec = os::elapsedTime();
5664 
5665     // Closing the inner scope will execute the destructor
5666     // for the StrongRootsScope object. We record the current
5667     // elapsed time before closing the scope so that time
5668     // taken for the SRS destructor is NOT included in the
5669     // reported parallel time.
5670   }
5671 
5672   double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5673   g1_policy()->phase_times()->record_par_time(par_time_ms);
5674 
5675   double code_root_fixup_time_ms =
5676         (os::elapsedTime() - end_par_time_sec) * 1000.0;
5677   g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms);
5678 
5679   set_par_threads(0);
5680 
5681   // Process any discovered reference objects - we have
5682   // to do this _before_ we retire the GC alloc regions
5683   // as we may have to copy some 'reachable' referent
5684   // objects (and their reachable sub-graphs) that were
5685   // not copied during the pause.
5686   process_discovered_references(n_workers);
5687 
5688   if (G1StringDedup::is_enabled()) {
5689     G1STWIsAliveClosure is_alive(this);
5690     G1KeepAliveClosure keep_alive(this);
5691     G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive);
5692   }
5693 
5694   _allocator->release_gc_alloc_regions(n_workers, evacuation_info);
5695   g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5696 
5697   // Reset and re-enable the hot card cache.
5698   // Note the counts for the cards in the regions in the
5699   // collection set are reset when the collection set is freed.
5700   hot_card_cache->reset_hot_cache();
5701   hot_card_cache->set_use_cache(true);
5702 
5703   purge_code_root_memory();
5704 
5705   finalize_for_evac_failure();
5706 
5707   if (evacuation_failed()) {
5708     remove_self_forwarding_pointers();
5709 
5710     // Reset the G1EvacuationFailureALot counters and flags
5711     // Note: the values are reset only when an actual
5712     // evacuation failure occurs.
5713     NOT_PRODUCT(reset_evacuation_should_fail();)
5714   }
5715 
5716   // Enqueue any remaining references remaining on the STW
5717   // reference processor's discovered lists. We need to do
5718   // this after the card table is cleaned (and verified) as
5719   // the act of enqueueing entries on to the pending list
5720   // will log these updates (and dirty their associated
5721   // cards). We need these updates logged to update any
5722   // RSets.
5723   enqueue_discovered_references(n_workers);
5724 
5725   redirty_logged_cards();
5726   COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5727 }
5728 
5729 void G1CollectedHeap::free_region(HeapRegion* hr,
5730                                   FreeRegionList* free_list,
5731                                   bool par,
5732                                   bool locked) {
5733   assert(!hr->is_free(), "the region should not be free");
5734   assert(!hr->is_empty(), "the region should not be empty");
5735   assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
5736   assert(free_list != NULL, "pre-condition");
5737 
5738   if (G1VerifyBitmaps) {
5739     MemRegion mr(hr->bottom(), hr->end());
5740     concurrent_mark()->clearRangePrevBitmap(mr);
5741   }
5742 
5743   // Clear the card counts for this region.
5744   // Note: we only need to do this if the region is not young
5745   // (since we don't refine cards in young regions).
5746   if (!hr->is_young()) {
5747     _cg1r->hot_card_cache()->reset_card_counts(hr);
5748   }
5749   hr->hr_clear(par, true /* clear_space */, locked /* locked */);
5750   free_list->add_ordered(hr);
5751 }
5752 
5753 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
5754                                      FreeRegionList* free_list,
5755                                      bool par) {
5756   assert(hr->is_starts_humongous(), "this is only for starts humongous regions");
5757   assert(free_list != NULL, "pre-condition");
5758 
5759   size_t hr_capacity = hr->capacity();
5760   // We need to read this before we make the region non-humongous,
5761   // otherwise the information will be gone.
5762   uint last_index = hr->last_hc_index();
5763   hr->clear_humongous();
5764   free_region(hr, free_list, par);
5765 
5766   uint i = hr->hrm_index() + 1;
5767   while (i < last_index) {
5768     HeapRegion* curr_hr = region_at(i);
5769     assert(curr_hr->is_continues_humongous(), "invariant");
5770     curr_hr->clear_humongous();
5771     free_region(curr_hr, free_list, par);
5772     i += 1;
5773   }
5774 }
5775 
5776 void G1CollectedHeap::remove_from_old_sets(const HeapRegionSetCount& old_regions_removed,
5777                                        const HeapRegionSetCount& humongous_regions_removed) {
5778   if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 0) {
5779     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5780     _old_set.bulk_remove(old_regions_removed);
5781     _humongous_set.bulk_remove(humongous_regions_removed);
5782   }
5783 
5784 }
5785 
5786 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
5787   assert(list != NULL, "list can't be null");
5788   if (!list->is_empty()) {
5789     MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
5790     _hrm.insert_list_into_free_list(list);
5791   }
5792 }
5793 
5794 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
5795   _allocator->decrease_used(bytes);
5796 }
5797 
5798 class G1ParCleanupCTTask : public AbstractGangTask {
5799   G1SATBCardTableModRefBS* _ct_bs;
5800   G1CollectedHeap* _g1h;
5801   HeapRegion* volatile _su_head;
5802 public:
5803   G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs,
5804                      G1CollectedHeap* g1h) :
5805     AbstractGangTask("G1 Par Cleanup CT Task"),
5806     _ct_bs(ct_bs), _g1h(g1h) { }
5807 
5808   void work(uint worker_id) {
5809     HeapRegion* r;
5810     while (r = _g1h->pop_dirty_cards_region()) {
5811       clear_cards(r);
5812     }
5813   }
5814 
5815   void clear_cards(HeapRegion* r) {
5816     // Cards of the survivors should have already been dirtied.
5817     if (!r->is_survivor()) {
5818       _ct_bs->clear(MemRegion(r->bottom(), r->end()));
5819     }
5820   }
5821 };
5822 
5823 #ifndef PRODUCT
5824 class G1VerifyCardTableCleanup: public HeapRegionClosure {
5825   G1CollectedHeap* _g1h;
5826   G1SATBCardTableModRefBS* _ct_bs;
5827 public:
5828   G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs)
5829     : _g1h(g1h), _ct_bs(ct_bs) { }
5830   virtual bool doHeapRegion(HeapRegion* r) {
5831     if (r->is_survivor()) {
5832       _g1h->verify_dirty_region(r);
5833     } else {
5834       _g1h->verify_not_dirty_region(r);
5835     }
5836     return false;
5837   }
5838 };
5839 
5840 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
5841   // All of the region should be clean.
5842   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5843   MemRegion mr(hr->bottom(), hr->end());
5844   ct_bs->verify_not_dirty_region(mr);
5845 }
5846 
5847 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
5848   // We cannot guarantee that [bottom(),end()] is dirty.  Threads
5849   // dirty allocated blocks as they allocate them. The thread that
5850   // retires each region and replaces it with a new one will do a
5851   // maximal allocation to fill in [pre_dummy_top(),end()] but will
5852   // not dirty that area (one less thing to have to do while holding
5853   // a lock). So we can only verify that [bottom(),pre_dummy_top()]
5854   // is dirty.
5855   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5856   MemRegion mr(hr->bottom(), hr->pre_dummy_top());
5857   if (hr->is_young()) {
5858     ct_bs->verify_g1_young_region(mr);
5859   } else {
5860     ct_bs->verify_dirty_region(mr);
5861   }
5862 }
5863 
5864 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
5865   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5866   for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
5867     verify_dirty_region(hr);
5868   }
5869 }
5870 
5871 void G1CollectedHeap::verify_dirty_young_regions() {
5872   verify_dirty_young_list(_young_list->first_region());
5873 }
5874 
5875 bool G1CollectedHeap::verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
5876                                                HeapWord* tams, HeapWord* end) {
5877   guarantee(tams <= end,
5878             err_msg("tams: "PTR_FORMAT" end: "PTR_FORMAT, tams, end));
5879   HeapWord* result = bitmap->getNextMarkedWordAddress(tams, end);
5880   if (result < end) {
5881     gclog_or_tty->cr();
5882     gclog_or_tty->print_cr("## wrong marked address on %s bitmap: "PTR_FORMAT,
5883                            bitmap_name, result);
5884     gclog_or_tty->print_cr("## %s tams: "PTR_FORMAT" end: "PTR_FORMAT,
5885                            bitmap_name, tams, end);
5886     return false;
5887   }
5888   return true;
5889 }
5890 
5891 bool G1CollectedHeap::verify_bitmaps(const char* caller, HeapRegion* hr) {
5892   CMBitMapRO* prev_bitmap = concurrent_mark()->prevMarkBitMap();
5893   CMBitMapRO* next_bitmap = (CMBitMapRO*) concurrent_mark()->nextMarkBitMap();
5894 
5895   HeapWord* bottom = hr->bottom();
5896   HeapWord* ptams  = hr->prev_top_at_mark_start();
5897   HeapWord* ntams  = hr->next_top_at_mark_start();
5898   HeapWord* end    = hr->end();
5899 
5900   bool res_p = verify_no_bits_over_tams("prev", prev_bitmap, ptams, end);
5901 
5902   bool res_n = true;
5903   // We reset mark_in_progress() before we reset _cmThread->in_progress() and in this window
5904   // we do the clearing of the next bitmap concurrently. Thus, we can not verify the bitmap
5905   // if we happen to be in that state.
5906   if (mark_in_progress() || !_cmThread->in_progress()) {
5907     res_n = verify_no_bits_over_tams("next", next_bitmap, ntams, end);
5908   }
5909   if (!res_p || !res_n) {
5910     gclog_or_tty->print_cr("#### Bitmap verification failed for "HR_FORMAT,
5911                            HR_FORMAT_PARAMS(hr));
5912     gclog_or_tty->print_cr("#### Caller: %s", caller);
5913     return false;
5914   }
5915   return true;
5916 }
5917 
5918 void G1CollectedHeap::check_bitmaps(const char* caller, HeapRegion* hr) {
5919   if (!G1VerifyBitmaps) return;
5920 
5921   guarantee(verify_bitmaps(caller, hr), "bitmap verification");
5922 }
5923 
5924 class G1VerifyBitmapClosure : public HeapRegionClosure {
5925 private:
5926   const char* _caller;
5927   G1CollectedHeap* _g1h;
5928   bool _failures;
5929 
5930 public:
5931   G1VerifyBitmapClosure(const char* caller, G1CollectedHeap* g1h) :
5932     _caller(caller), _g1h(g1h), _failures(false) { }
5933 
5934   bool failures() { return _failures; }
5935 
5936   virtual bool doHeapRegion(HeapRegion* hr) {
5937     if (hr->is_continues_humongous()) return false;
5938 
5939     bool result = _g1h->verify_bitmaps(_caller, hr);
5940     if (!result) {
5941       _failures = true;
5942     }
5943     return false;
5944   }
5945 };
5946 
5947 void G1CollectedHeap::check_bitmaps(const char* caller) {
5948   if (!G1VerifyBitmaps) return;
5949 
5950   G1VerifyBitmapClosure cl(caller, this);
5951   heap_region_iterate(&cl);
5952   guarantee(!cl.failures(), "bitmap verification");
5953 }
5954 #endif // PRODUCT
5955 
5956 void G1CollectedHeap::cleanUpCardTable() {
5957   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5958   double start = os::elapsedTime();
5959 
5960   {
5961     // Iterate over the dirty cards region list.
5962     G1ParCleanupCTTask cleanup_task(ct_bs, this);
5963 
5964     set_par_threads();
5965     workers()->run_task(&cleanup_task);
5966     set_par_threads(0);
5967 #ifndef PRODUCT
5968     if (G1VerifyCTCleanup || VerifyAfterGC) {
5969       G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
5970       heap_region_iterate(&cleanup_verifier);
5971     }
5972 #endif
5973   }
5974 
5975   double elapsed = os::elapsedTime() - start;
5976   g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
5977 }
5978 
5979 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) {
5980   size_t pre_used = 0;
5981   FreeRegionList local_free_list("Local List for CSet Freeing");
5982 
5983   double young_time_ms     = 0.0;
5984   double non_young_time_ms = 0.0;
5985 
5986   // Since the collection set is a superset of the the young list,
5987   // all we need to do to clear the young list is clear its
5988   // head and length, and unlink any young regions in the code below
5989   _young_list->clear();
5990 
5991   G1CollectorPolicy* policy = g1_policy();
5992 
5993   double start_sec = os::elapsedTime();
5994   bool non_young = true;
5995 
5996   HeapRegion* cur = cs_head;
5997   int age_bound = -1;
5998   size_t rs_lengths = 0;
5999 
6000   while (cur != NULL) {
6001     assert(!is_on_master_free_list(cur), "sanity");
6002     if (non_young) {
6003       if (cur->is_young()) {
6004         double end_sec = os::elapsedTime();
6005         double elapsed_ms = (end_sec - start_sec) * 1000.0;
6006         non_young_time_ms += elapsed_ms;
6007 
6008         start_sec = os::elapsedTime();
6009         non_young = false;
6010       }
6011     } else {
6012       if (!cur->is_young()) {
6013         double end_sec = os::elapsedTime();
6014         double elapsed_ms = (end_sec - start_sec) * 1000.0;
6015         young_time_ms += elapsed_ms;
6016 
6017         start_sec = os::elapsedTime();
6018         non_young = true;
6019       }
6020     }
6021 
6022     rs_lengths += cur->rem_set()->occupied_locked();
6023 
6024     HeapRegion* next = cur->next_in_collection_set();
6025     assert(cur->in_collection_set(), "bad CS");
6026     cur->set_next_in_collection_set(NULL);
6027     cur->set_in_collection_set(false);
6028 
6029     if (cur->is_young()) {
6030       int index = cur->young_index_in_cset();
6031       assert(index != -1, "invariant");
6032       assert((uint) index < policy->young_cset_region_length(), "invariant");
6033       size_t words_survived = _surviving_young_words[index];
6034       cur->record_surv_words_in_group(words_survived);
6035 
6036       // At this point the we have 'popped' cur from the collection set
6037       // (linked via next_in_collection_set()) but it is still in the
6038       // young list (linked via next_young_region()). Clear the
6039       // _next_young_region field.
6040       cur->set_next_young_region(NULL);
6041     } else {
6042       int index = cur->young_index_in_cset();
6043       assert(index == -1, "invariant");
6044     }
6045 
6046     assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
6047             (!cur->is_young() && cur->young_index_in_cset() == -1),
6048             "invariant" );
6049 
6050     if (!cur->evacuation_failed()) {
6051       MemRegion used_mr = cur->used_region();
6052 
6053       // And the region is empty.
6054       assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
6055       pre_used += cur->used();
6056       free_region(cur, &local_free_list, false /* par */, true /* locked */);
6057     } else {
6058       cur->uninstall_surv_rate_group();
6059       if (cur->is_young()) {
6060         cur->set_young_index_in_cset(-1);
6061       }
6062       cur->set_evacuation_failed(false);
6063       // The region is now considered to be old.
6064       cur->set_old();
6065       _old_set.add(cur);
6066       evacuation_info.increment_collectionset_used_after(cur->used());
6067     }
6068     cur = next;
6069   }
6070 
6071   evacuation_info.set_regions_freed(local_free_list.length());
6072   policy->record_max_rs_lengths(rs_lengths);
6073   policy->cset_regions_freed();
6074 
6075   double end_sec = os::elapsedTime();
6076   double elapsed_ms = (end_sec - start_sec) * 1000.0;
6077 
6078   if (non_young) {
6079     non_young_time_ms += elapsed_ms;
6080   } else {
6081     young_time_ms += elapsed_ms;
6082   }
6083 
6084   prepend_to_freelist(&local_free_list);
6085   decrement_summary_bytes(pre_used);
6086   policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
6087   policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
6088 }
6089 
6090 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
6091  private:
6092   FreeRegionList* _free_region_list;
6093   HeapRegionSet* _proxy_set;
6094   HeapRegionSetCount _humongous_regions_removed;
6095   size_t _freed_bytes;
6096  public:
6097 
6098   G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
6099     _free_region_list(free_region_list), _humongous_regions_removed(), _freed_bytes(0) {
6100   }
6101 
6102   virtual bool doHeapRegion(HeapRegion* r) {
6103     if (!r->is_starts_humongous()) {
6104       return false;
6105     }
6106 
6107     G1CollectedHeap* g1h = G1CollectedHeap::heap();
6108 
6109     oop obj = (oop)r->bottom();
6110     CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap();
6111 
6112     // The following checks whether the humongous object is live are sufficient.
6113     // The main additional check (in addition to having a reference from the roots
6114     // or the young gen) is whether the humongous object has a remembered set entry.
6115     //
6116     // A humongous object cannot be live if there is no remembered set for it
6117     // because:
6118     // - there can be no references from within humongous starts regions referencing
6119     // the object because we never allocate other objects into them.
6120     // (I.e. there are no intra-region references that may be missed by the
6121     // remembered set)
6122     // - as soon there is a remembered set entry to the humongous starts region
6123     // (i.e. it has "escaped" to an old object) this remembered set entry will stay
6124     // until the end of a concurrent mark.
6125     //
6126     // It is not required to check whether the object has been found dead by marking
6127     // or not, in fact it would prevent reclamation within a concurrent cycle, as
6128     // all objects allocated during that time are considered live.
6129     // SATB marking is even more conservative than the remembered set.
6130     // So if at this point in the collection there is no remembered set entry,
6131     // nobody has a reference to it.
6132     // At the start of collection we flush all refinement logs, and remembered sets
6133     // are completely up-to-date wrt to references to the humongous object.
6134     //
6135     // Other implementation considerations:
6136     // - never consider object arrays: while they are a valid target, they have not
6137     // been observed to be used as temporary objects.
6138     // - they would also pose considerable effort for cleaning up the the remembered
6139     // sets.
6140     // While this cleanup is not strictly necessary to be done (or done instantly),
6141     // given that their occurrence is very low, this saves us this additional
6142     // complexity.
6143     uint region_idx = r->hrm_index();
6144     if (g1h->humongous_is_live(region_idx) ||
6145         g1h->humongous_region_is_always_live(region_idx)) {
6146 
6147       if (G1TraceReclaimDeadHumongousObjectsAtYoungGC) {
6148         gclog_or_tty->print_cr("Live humongous %d region %d size "SIZE_FORMAT" with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is marked %d live-other %d obj array %d",
6149                                r->is_humongous(),
6150                                region_idx,
6151                                obj->size()*HeapWordSize,
6152                                r->rem_set()->occupied(),
6153                                r->rem_set()->strong_code_roots_list_length(),
6154                                next_bitmap->isMarked(r->bottom()),
6155                                g1h->humongous_is_live(region_idx),
6156                                obj->is_objArray()
6157                               );
6158       }
6159 
6160       return false;
6161     }
6162 
6163     guarantee(!obj->is_objArray(),
6164               err_msg("Eagerly reclaiming object arrays is not supported, but the object "PTR_FORMAT" is.",
6165                       r->bottom()));
6166 
6167     if (G1TraceReclaimDeadHumongousObjectsAtYoungGC) {
6168       gclog_or_tty->print_cr("Reclaim humongous region %d size "SIZE_FORMAT" start "PTR_FORMAT" region %d length "UINT32_FORMAT" with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is marked %d live-other %d obj array %d",
6169                              r->is_humongous(),
6170                              obj->size()*HeapWordSize,
6171                              r->bottom(),
6172                              region_idx,
6173                              r->region_num(),
6174                              r->rem_set()->occupied(),
6175                              r->rem_set()->strong_code_roots_list_length(),
6176                              next_bitmap->isMarked(r->bottom()),
6177                              g1h->humongous_is_live(region_idx),
6178                              obj->is_objArray()
6179                             );
6180     }
6181     // Need to clear mark bit of the humongous object if already set.
6182     if (next_bitmap->isMarked(r->bottom())) {
6183       next_bitmap->clear(r->bottom());
6184     }
6185     _freed_bytes += r->used();
6186     r->set_containing_set(NULL);
6187     _humongous_regions_removed.increment(1u, r->capacity());
6188     g1h->free_humongous_region(r, _free_region_list, false);
6189 
6190     return false;
6191   }
6192 
6193   HeapRegionSetCount& humongous_free_count() {
6194     return _humongous_regions_removed;
6195   }
6196 
6197   size_t bytes_freed() const {
6198     return _freed_bytes;
6199   }
6200 
6201   size_t humongous_reclaimed() const {
6202     return _humongous_regions_removed.length();
6203   }
6204 };
6205 
6206 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
6207   assert_at_safepoint(true);
6208 
6209   if (!G1ReclaimDeadHumongousObjectsAtYoungGC ||
6210       (!_has_humongous_reclaim_candidates && !G1TraceReclaimDeadHumongousObjectsAtYoungGC)) {
6211     g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
6212     return;
6213   }
6214 
6215   double start_time = os::elapsedTime();
6216 
6217   FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
6218 
6219   G1FreeHumongousRegionClosure cl(&local_cleanup_list);
6220   heap_region_iterate(&cl);
6221 
6222   HeapRegionSetCount empty_set;
6223   remove_from_old_sets(empty_set, cl.humongous_free_count());
6224 
6225   G1HRPrinter* hr_printer = _g1h->hr_printer();
6226   if (hr_printer->is_active()) {
6227     FreeRegionListIterator iter(&local_cleanup_list);
6228     while (iter.more_available()) {
6229       HeapRegion* hr = iter.get_next();
6230       hr_printer->cleanup(hr);
6231     }
6232   }
6233 
6234   prepend_to_freelist(&local_cleanup_list);
6235   decrement_summary_bytes(cl.bytes_freed());
6236 
6237   g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
6238                                                                     cl.humongous_reclaimed());
6239 }
6240 
6241 // This routine is similar to the above but does not record
6242 // any policy statistics or update free lists; we are abandoning
6243 // the current incremental collection set in preparation of a
6244 // full collection. After the full GC we will start to build up
6245 // the incremental collection set again.
6246 // This is only called when we're doing a full collection
6247 // and is immediately followed by the tearing down of the young list.
6248 
6249 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
6250   HeapRegion* cur = cs_head;
6251 
6252   while (cur != NULL) {
6253     HeapRegion* next = cur->next_in_collection_set();
6254     assert(cur->in_collection_set(), "bad CS");
6255     cur->set_next_in_collection_set(NULL);
6256     cur->set_in_collection_set(false);
6257     cur->set_young_index_in_cset(-1);
6258     cur = next;
6259   }
6260 }
6261 
6262 void G1CollectedHeap::set_free_regions_coming() {
6263   if (G1ConcRegionFreeingVerbose) {
6264     gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6265                            "setting free regions coming");
6266   }
6267 
6268   assert(!free_regions_coming(), "pre-condition");
6269   _free_regions_coming = true;
6270 }
6271 
6272 void G1CollectedHeap::reset_free_regions_coming() {
6273   assert(free_regions_coming(), "pre-condition");
6274 
6275   {
6276     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6277     _free_regions_coming = false;
6278     SecondaryFreeList_lock->notify_all();
6279   }
6280 
6281   if (G1ConcRegionFreeingVerbose) {
6282     gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6283                            "reset free regions coming");
6284   }
6285 }
6286 
6287 void G1CollectedHeap::wait_while_free_regions_coming() {
6288   // Most of the time we won't have to wait, so let's do a quick test
6289   // first before we take the lock.
6290   if (!free_regions_coming()) {
6291     return;
6292   }
6293 
6294   if (G1ConcRegionFreeingVerbose) {
6295     gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6296                            "waiting for free regions");
6297   }
6298 
6299   {
6300     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6301     while (free_regions_coming()) {
6302       SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
6303     }
6304   }
6305 
6306   if (G1ConcRegionFreeingVerbose) {
6307     gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6308                            "done waiting for free regions");
6309   }
6310 }
6311 
6312 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
6313   assert(heap_lock_held_for_gc(),
6314               "the heap lock should already be held by or for this thread");
6315   _young_list->push_region(hr);
6316 }
6317 
6318 class NoYoungRegionsClosure: public HeapRegionClosure {
6319 private:
6320   bool _success;
6321 public:
6322   NoYoungRegionsClosure() : _success(true) { }
6323   bool doHeapRegion(HeapRegion* r) {
6324     if (r->is_young()) {
6325       gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
6326                              r->bottom(), r->end());
6327       _success = false;
6328     }
6329     return false;
6330   }
6331   bool success() { return _success; }
6332 };
6333 
6334 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
6335   bool ret = _young_list->check_list_empty(check_sample);
6336 
6337   if (check_heap) {
6338     NoYoungRegionsClosure closure;
6339     heap_region_iterate(&closure);
6340     ret = ret && closure.success();
6341   }
6342 
6343   return ret;
6344 }
6345 
6346 class TearDownRegionSetsClosure : public HeapRegionClosure {
6347 private:
6348   HeapRegionSet *_old_set;
6349 
6350 public:
6351   TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
6352 
6353   bool doHeapRegion(HeapRegion* r) {
6354     if (r->is_old()) {
6355       _old_set->remove(r);
6356     } else {
6357       // We ignore free regions, we'll empty the free list afterwards.
6358       // We ignore young regions, we'll empty the young list afterwards.
6359       // We ignore humongous regions, we're not tearing down the
6360       // humongous regions set.
6361       assert(r->is_free() || r->is_young() || r->is_humongous(),
6362              "it cannot be another type");
6363     }
6364     return false;
6365   }
6366 
6367   ~TearDownRegionSetsClosure() {
6368     assert(_old_set->is_empty(), "post-condition");
6369   }
6370 };
6371 
6372 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6373   assert_at_safepoint(true /* should_be_vm_thread */);
6374 
6375   if (!free_list_only) {
6376     TearDownRegionSetsClosure cl(&_old_set);
6377     heap_region_iterate(&cl);
6378 
6379     // Note that emptying the _young_list is postponed and instead done as
6380     // the first step when rebuilding the regions sets again. The reason for
6381     // this is that during a full GC string deduplication needs to know if
6382     // a collected region was young or old when the full GC was initiated.
6383   }
6384   _hrm.remove_all_free_regions();
6385 }
6386 
6387 class RebuildRegionSetsClosure : public HeapRegionClosure {
6388 private:
6389   bool            _free_list_only;
6390   HeapRegionSet*   _old_set;
6391   HeapRegionManager*   _hrm;
6392   size_t          _total_used;
6393 
6394 public:
6395   RebuildRegionSetsClosure(bool free_list_only,
6396                            HeapRegionSet* old_set, HeapRegionManager* hrm) :
6397     _free_list_only(free_list_only),
6398     _old_set(old_set), _hrm(hrm), _total_used(0) {
6399     assert(_hrm->num_free_regions() == 0, "pre-condition");
6400     if (!free_list_only) {
6401       assert(_old_set->is_empty(), "pre-condition");
6402     }
6403   }
6404 
6405   bool doHeapRegion(HeapRegion* r) {
6406     if (r->is_continues_humongous()) {
6407       return false;
6408     }
6409 
6410     if (r->is_empty()) {
6411       // Add free regions to the free list
6412       r->set_free();
6413       r->set_allocation_context(AllocationContext::system());
6414       _hrm->insert_into_free_list(r);
6415     } else if (!_free_list_only) {
6416       assert(!r->is_young(), "we should not come across young regions");
6417 
6418       if (r->is_humongous()) {
6419         // We ignore humongous regions, we left the humongous set unchanged
6420       } else {
6421         // Objects that were compacted would have ended up on regions
6422         // that were previously old or free.
6423         assert(r->is_free() || r->is_old(), "invariant");
6424         // We now consider them old, so register as such.
6425         r->set_old();
6426         _old_set->add(r);
6427       }
6428       _total_used += r->used();
6429     }
6430 
6431     return false;
6432   }
6433 
6434   size_t total_used() {
6435     return _total_used;
6436   }
6437 };
6438 
6439 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6440   assert_at_safepoint(true /* should_be_vm_thread */);
6441 
6442   if (!free_list_only) {
6443     _young_list->empty_list();
6444   }
6445 
6446   RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
6447   heap_region_iterate(&cl);
6448 
6449   if (!free_list_only) {
6450     _allocator->set_used(cl.total_used());
6451   }
6452   assert(_allocator->used_unlocked() == recalculate_used(),
6453          err_msg("inconsistent _allocator->used_unlocked(), "
6454                  "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6455                  _allocator->used_unlocked(), recalculate_used()));
6456 }
6457 
6458 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6459   _refine_cte_cl->set_concurrent(concurrent);
6460 }
6461 
6462 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6463   HeapRegion* hr = heap_region_containing(p);
6464   return hr->is_in(p);
6465 }
6466 
6467 // Methods for the mutator alloc region
6468 
6469 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6470                                                       bool force) {
6471   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6472   assert(!force || g1_policy()->can_expand_young_list(),
6473          "if force is true we should be able to expand the young list");
6474   bool young_list_full = g1_policy()->is_young_list_full();
6475   if (force || !young_list_full) {
6476     HeapRegion* new_alloc_region = new_region(word_size,
6477                                               false /* is_old */,
6478                                               false /* do_expand */);
6479     if (new_alloc_region != NULL) {
6480       set_region_short_lived_locked(new_alloc_region);
6481       _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6482       check_bitmaps("Mutator Region Allocation", new_alloc_region);
6483       return new_alloc_region;
6484     }
6485   }
6486   return NULL;
6487 }
6488 
6489 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6490                                                   size_t allocated_bytes) {
6491   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6492   assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
6493 
6494   g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6495   _allocator->increase_used(allocated_bytes);
6496   _hr_printer.retire(alloc_region);
6497   // We update the eden sizes here, when the region is retired,
6498   // instead of when it's allocated, since this is the point that its
6499   // used space has been recored in _summary_bytes_used.
6500   g1mm()->update_eden_size();
6501 }
6502 
6503 void G1CollectedHeap::set_par_threads() {
6504   // Don't change the number of workers.  Use the value previously set
6505   // in the workgroup.
6506   uint n_workers = workers()->active_workers();
6507   assert(UseDynamicNumberOfGCThreads ||
6508            n_workers == workers()->total_workers(),
6509       "Otherwise should be using the total number of workers");
6510   if (n_workers == 0) {
6511     assert(false, "Should have been set in prior evacuation pause.");
6512     n_workers = ParallelGCThreads;
6513     workers()->set_active_workers(n_workers);
6514   }
6515   set_par_threads(n_workers);
6516 }
6517 
6518 // Methods for the GC alloc regions
6519 
6520 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6521                                                  uint count,
6522                                                  GCAllocPurpose ap) {
6523   assert(FreeList_lock->owned_by_self(), "pre-condition");
6524 
6525   if (count < g1_policy()->max_regions(ap)) {
6526     bool survivor = (ap == GCAllocForSurvived);
6527     HeapRegion* new_alloc_region = new_region(word_size,
6528                                               !survivor,
6529                                               true /* do_expand */);
6530     if (new_alloc_region != NULL) {
6531       // We really only need to do this for old regions given that we
6532       // should never scan survivors. But it doesn't hurt to do it
6533       // for survivors too.
6534       new_alloc_region->record_timestamp();
6535       if (survivor) {
6536         new_alloc_region->set_survivor();
6537         _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6538         check_bitmaps("Survivor Region Allocation", new_alloc_region);
6539       } else {
6540         new_alloc_region->set_old();
6541         _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6542         check_bitmaps("Old Region Allocation", new_alloc_region);
6543       }
6544       bool during_im = g1_policy()->during_initial_mark_pause();
6545       new_alloc_region->note_start_of_copying(during_im);
6546       return new_alloc_region;
6547     } else {
6548       g1_policy()->note_alloc_region_limit_reached(ap);
6549     }
6550   }
6551   return NULL;
6552 }
6553 
6554 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6555                                              size_t allocated_bytes,
6556                                              GCAllocPurpose ap) {
6557   bool during_im = g1_policy()->during_initial_mark_pause();
6558   alloc_region->note_end_of_copying(during_im);
6559   g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6560   if (ap == GCAllocForSurvived) {
6561     young_list()->add_survivor_region(alloc_region);
6562   } else {
6563     _old_set.add(alloc_region);
6564   }
6565   _hr_printer.retire(alloc_region);
6566 }
6567 
6568 // Heap region set verification
6569 
6570 class VerifyRegionListsClosure : public HeapRegionClosure {
6571 private:
6572   HeapRegionSet*   _old_set;
6573   HeapRegionSet*   _humongous_set;
6574   HeapRegionManager*   _hrm;
6575 
6576 public:
6577   HeapRegionSetCount _old_count;
6578   HeapRegionSetCount _humongous_count;
6579   HeapRegionSetCount _free_count;
6580 
6581   VerifyRegionListsClosure(HeapRegionSet* old_set,
6582                            HeapRegionSet* humongous_set,
6583                            HeapRegionManager* hrm) :
6584     _old_set(old_set), _humongous_set(humongous_set), _hrm(hrm),
6585     _old_count(), _humongous_count(), _free_count(){ }
6586 
6587   bool doHeapRegion(HeapRegion* hr) {
6588     if (hr->is_continues_humongous()) {
6589       return false;
6590     }
6591 
6592     if (hr->is_young()) {
6593       // TODO
6594     } else if (hr->is_starts_humongous()) {
6595       assert(hr->containing_set() == _humongous_set, err_msg("Heap region %u is starts humongous but not in humongous set.", hr->hrm_index()));
6596       _humongous_count.increment(1u, hr->capacity());
6597     } else if (hr->is_empty()) {
6598       assert(_hrm->is_free(hr), err_msg("Heap region %u is empty but not on the free list.", hr->hrm_index()));
6599       _free_count.increment(1u, hr->capacity());
6600     } else if (hr->is_old()) {
6601       assert(hr->containing_set() == _old_set, err_msg("Heap region %u is old but not in the old set.", hr->hrm_index()));
6602       _old_count.increment(1u, hr->capacity());
6603     } else {
6604       ShouldNotReachHere();
6605     }
6606     return false;
6607   }
6608 
6609   void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, HeapRegionManager* free_list) {
6610     guarantee(old_set->length() == _old_count.length(), err_msg("Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length()));
6611     guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), err_msg("Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6612         old_set->total_capacity_bytes(), _old_count.capacity()));
6613 
6614     guarantee(humongous_set->length() == _humongous_count.length(), err_msg("Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length()));
6615     guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), err_msg("Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6616         humongous_set->total_capacity_bytes(), _humongous_count.capacity()));
6617 
6618     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()));
6619     guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), err_msg("Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6620         free_list->total_capacity_bytes(), _free_count.capacity()));
6621   }
6622 };
6623 
6624 void G1CollectedHeap::verify_region_sets() {
6625   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6626 
6627   // First, check the explicit lists.
6628   _hrm.verify();
6629   {
6630     // Given that a concurrent operation might be adding regions to
6631     // the secondary free list we have to take the lock before
6632     // verifying it.
6633     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6634     _secondary_free_list.verify_list();
6635   }
6636 
6637   // If a concurrent region freeing operation is in progress it will
6638   // be difficult to correctly attributed any free regions we come
6639   // across to the correct free list given that they might belong to
6640   // one of several (free_list, secondary_free_list, any local lists,
6641   // etc.). So, if that's the case we will skip the rest of the
6642   // verification operation. Alternatively, waiting for the concurrent
6643   // operation to complete will have a non-trivial effect on the GC's
6644   // operation (no concurrent operation will last longer than the
6645   // interval between two calls to verification) and it might hide
6646   // any issues that we would like to catch during testing.
6647   if (free_regions_coming()) {
6648     return;
6649   }
6650 
6651   // Make sure we append the secondary_free_list on the free_list so
6652   // that all free regions we will come across can be safely
6653   // attributed to the free_list.
6654   append_secondary_free_list_if_not_empty_with_lock();
6655 
6656   // Finally, make sure that the region accounting in the lists is
6657   // consistent with what we see in the heap.
6658 
6659   VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_hrm);
6660   heap_region_iterate(&cl);
6661   cl.verify_counts(&_old_set, &_humongous_set, &_hrm);
6662 }
6663 
6664 // Optimized nmethod scanning
6665 
6666 class RegisterNMethodOopClosure: public OopClosure {
6667   G1CollectedHeap* _g1h;
6668   nmethod* _nm;
6669 
6670   template <class T> void do_oop_work(T* p) {
6671     T heap_oop = oopDesc::load_heap_oop(p);
6672     if (!oopDesc::is_null(heap_oop)) {
6673       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6674       HeapRegion* hr = _g1h->heap_region_containing(obj);
6675       assert(!hr->is_continues_humongous(),
6676              err_msg("trying to add code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6677                      " starting at "HR_FORMAT,
6678                      _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6679 
6680       // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
6681       hr->add_strong_code_root_locked(_nm);
6682     }
6683   }
6684 
6685 public:
6686   RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6687     _g1h(g1h), _nm(nm) {}
6688 
6689   void do_oop(oop* p)       { do_oop_work(p); }
6690   void do_oop(narrowOop* p) { do_oop_work(p); }
6691 };
6692 
6693 class UnregisterNMethodOopClosure: public OopClosure {
6694   G1CollectedHeap* _g1h;
6695   nmethod* _nm;
6696 
6697   template <class T> void do_oop_work(T* p) {
6698     T heap_oop = oopDesc::load_heap_oop(p);
6699     if (!oopDesc::is_null(heap_oop)) {
6700       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6701       HeapRegion* hr = _g1h->heap_region_containing(obj);
6702       assert(!hr->is_continues_humongous(),
6703              err_msg("trying to remove code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6704                      " starting at "HR_FORMAT,
6705                      _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6706 
6707       hr->remove_strong_code_root(_nm);
6708     }
6709   }
6710 
6711 public:
6712   UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6713     _g1h(g1h), _nm(nm) {}
6714 
6715   void do_oop(oop* p)       { do_oop_work(p); }
6716   void do_oop(narrowOop* p) { do_oop_work(p); }
6717 };
6718 
6719 void G1CollectedHeap::register_nmethod(nmethod* nm) {
6720   CollectedHeap::register_nmethod(nm);
6721 
6722   guarantee(nm != NULL, "sanity");
6723   RegisterNMethodOopClosure reg_cl(this, nm);
6724   nm->oops_do(&reg_cl);
6725 }
6726 
6727 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
6728   CollectedHeap::unregister_nmethod(nm);
6729 
6730   guarantee(nm != NULL, "sanity");
6731   UnregisterNMethodOopClosure reg_cl(this, nm);
6732   nm->oops_do(&reg_cl, true);
6733 }
6734 
6735 void G1CollectedHeap::purge_code_root_memory() {
6736   double purge_start = os::elapsedTime();
6737   G1CodeRootSet::purge();
6738   double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
6739   g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
6740 }
6741 
6742 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
6743   G1CollectedHeap* _g1h;
6744 
6745 public:
6746   RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
6747     _g1h(g1h) {}
6748 
6749   void do_code_blob(CodeBlob* cb) {
6750     nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
6751     if (nm == NULL) {
6752       return;
6753     }
6754 
6755     if (ScavengeRootsInCode) {
6756       _g1h->register_nmethod(nm);
6757     }
6758   }
6759 };
6760 
6761 void G1CollectedHeap::rebuild_strong_code_roots() {
6762   RebuildStrongCodeRootClosure blob_cl(this);
6763   CodeCache::blobs_do(&blob_cl);
6764 }