1 /*
   2  * Copyright (c) 2001, 2014, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #if !defined(__clang_major__) && defined(__GNUC__)
  26 // FIXME, formats have issues.  Disable this macro definition, compile, and study warnings for more information.
  27 #define ATTRIBUTE_PRINTF(x,y)
  28 #endif
  29 
  30 #include "precompiled.hpp"
  31 #include "classfile/metadataOnStackMark.hpp"
  32 #include "classfile/stringTable.hpp"
  33 #include "code/codeCache.hpp"
  34 #include "code/icBuffer.hpp"
  35 #include "gc_implementation/g1/bufferingOopClosure.hpp"
  36 #include "gc_implementation/g1/concurrentG1Refine.hpp"
  37 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
  38 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
  39 #include "gc_implementation/g1/g1AllocRegion.inline.hpp"
  40 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
  41 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
  42 #include "gc_implementation/g1/g1ErgoVerbose.hpp"
  43 #include "gc_implementation/g1/g1EvacFailure.hpp"
  44 #include "gc_implementation/g1/g1GCPhaseTimes.hpp"
  45 #include "gc_implementation/g1/g1Log.hpp"
  46 #include "gc_implementation/g1/g1MarkSweep.hpp"
  47 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
  48 #include "gc_implementation/g1/g1ParScanThreadState.inline.hpp"
  49 #include "gc_implementation/g1/g1RegionToSpaceMapper.hpp"
  50 #include "gc_implementation/g1/g1RemSet.inline.hpp"
  51 #include "gc_implementation/g1/g1StringDedup.hpp"
  52 #include "gc_implementation/g1/g1YCTypes.hpp"
  53 #include "gc_implementation/g1/heapRegion.inline.hpp"
  54 #include "gc_implementation/g1/heapRegionRemSet.hpp"
  55 #include "gc_implementation/g1/heapRegionSet.inline.hpp"
  56 #include "gc_implementation/g1/vm_operations_g1.hpp"
  57 #include "gc_implementation/shared/gcHeapSummary.hpp"
  58 #include "gc_implementation/shared/gcTimer.hpp"
  59 #include "gc_implementation/shared/gcTrace.hpp"
  60 #include "gc_implementation/shared/gcTraceTime.hpp"
  61 #include "gc_implementation/shared/isGCActiveMark.hpp"
  62 #include "memory/allocation.hpp"
  63 #include "memory/gcLocker.inline.hpp"
  64 #include "memory/generationSpec.hpp"
  65 #include "memory/iterator.hpp"
  66 #include "memory/referenceProcessor.hpp"
  67 #include "oops/oop.inline.hpp"
  68 #include "oops/oop.pcgc.inline.hpp"
  69 #include "runtime/atomic.inline.hpp"
  70 #include "runtime/orderAccess.inline.hpp"
  71 #include "runtime/vmThread.hpp"
  72 #include "utilities/globalDefinitions.hpp"
  73 
  74 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
  75 
  76 // turn it on so that the contents of the young list (scan-only /
  77 // to-be-collected) are printed at "strategic" points before / during
  78 // / after the collection --- this is useful for debugging
  79 #define YOUNG_LIST_VERBOSE 0
  80 // CURRENT STATUS
  81 // This file is under construction.  Search for "FIXME".
  82 
  83 // INVARIANTS/NOTES
  84 //
  85 // All allocation activity covered by the G1CollectedHeap interface is
  86 // serialized by acquiring the HeapLock.  This happens in mem_allocate
  87 // and allocate_new_tlab, which are the "entry" points to the
  88 // allocation code from the rest of the JVM.  (Note that this does not
  89 // apply to TLAB allocation, which is not part of this interface: it
  90 // is done by clients of this interface.)
  91 
  92 // Notes on implementation of parallelism in different tasks.
  93 //
  94 // G1ParVerifyTask uses heap_region_par_iterate() for parallelism.
  95 // The number of GC workers is passed to heap_region_par_iterate().
  96 // It does use run_task() which sets _n_workers in the task.
  97 // G1ParTask executes g1_process_roots() ->
  98 // SharedHeap::process_roots() which calls eventually to
  99 // CardTableModRefBS::par_non_clean_card_iterate_work() which uses
 100 // SequentialSubTasksDone.  SharedHeap::process_roots() also
 101 // directly uses SubTasksDone (_process_strong_tasks field in SharedHeap).
 102 //
 103 
 104 // Local to this file.
 105 
 106 class RefineCardTableEntryClosure: public CardTableEntryClosure {
 107   bool _concurrent;
 108 public:
 109   RefineCardTableEntryClosure() : _concurrent(true) { }
 110 
 111   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
 112     bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, false);
 113     // This path is executed by the concurrent refine or mutator threads,
 114     // concurrently, and so we do not care if card_ptr contains references
 115     // that point into the collection set.
 116     assert(!oops_into_cset, "should be");
 117 
 118     if (_concurrent && SuspendibleThreadSet::should_yield()) {
 119       // Caller will actually yield.
 120       return false;
 121     }
 122     // Otherwise, we finished successfully; return true.
 123     return true;
 124   }
 125 
 126   void set_concurrent(bool b) { _concurrent = b; }
 127 };
 128 
 129 
 130 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
 131  private:
 132   size_t _num_processed;
 133 
 134  public:
 135   RedirtyLoggedCardTableEntryClosure() : CardTableEntryClosure(), _num_processed(0) { }
 136 
 137   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
 138     *card_ptr = CardTableModRefBS::dirty_card_val();
 139     _num_processed++;
 140     return true;
 141   }
 142 
 143   size_t num_processed() const { return _num_processed; }
 144 };
 145 
 146 YoungList::YoungList(G1CollectedHeap* g1h) :
 147     _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0),
 148     _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) {
 149   guarantee(check_list_empty(false), "just making sure...");
 150 }
 151 
 152 void YoungList::push_region(HeapRegion *hr) {
 153   assert(!hr->is_young(), "should not already be young");
 154   assert(hr->get_next_young_region() == NULL, "cause it should!");
 155 
 156   hr->set_next_young_region(_head);
 157   _head = hr;
 158 
 159   _g1h->g1_policy()->set_region_eden(hr, (int) _length);
 160   ++_length;
 161 }
 162 
 163 void YoungList::add_survivor_region(HeapRegion* hr) {
 164   assert(hr->is_survivor(), "should be flagged as survivor region");
 165   assert(hr->get_next_young_region() == NULL, "cause it should!");
 166 
 167   hr->set_next_young_region(_survivor_head);
 168   if (_survivor_head == NULL) {
 169     _survivor_tail = hr;
 170   }
 171   _survivor_head = hr;
 172   ++_survivor_length;
 173 }
 174 
 175 void YoungList::empty_list(HeapRegion* list) {
 176   while (list != NULL) {
 177     HeapRegion* next = list->get_next_young_region();
 178     list->set_next_young_region(NULL);
 179     list->uninstall_surv_rate_group();
 180     // This is called before a Full GC and all the non-empty /
 181     // non-humongous regions at the end of the Full GC will end up as
 182     // old anyway.
 183     list->set_old();
 184     list = next;
 185   }
 186 }
 187 
 188 void YoungList::empty_list() {
 189   assert(check_list_well_formed(), "young list should be well formed");
 190 
 191   empty_list(_head);
 192   _head = NULL;
 193   _length = 0;
 194 
 195   empty_list(_survivor_head);
 196   _survivor_head = NULL;
 197   _survivor_tail = NULL;
 198   _survivor_length = 0;
 199 
 200   _last_sampled_rs_lengths = 0;
 201 
 202   assert(check_list_empty(false), "just making sure...");
 203 }
 204 
 205 bool YoungList::check_list_well_formed() {
 206   bool ret = true;
 207 
 208   uint length = 0;
 209   HeapRegion* curr = _head;
 210   HeapRegion* last = NULL;
 211   while (curr != NULL) {
 212     if (!curr->is_young()) {
 213       gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
 214                              "incorrectly tagged (y: %d, surv: %d)",
 215                              curr->bottom(), curr->end(),
 216                              curr->is_young(), curr->is_survivor());
 217       ret = false;
 218     }
 219     ++length;
 220     last = curr;
 221     curr = curr->get_next_young_region();
 222   }
 223   ret = ret && (length == _length);
 224 
 225   if (!ret) {
 226     gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
 227     gclog_or_tty->print_cr("###   list has %u entries, _length is %u",
 228                            length, _length);
 229   }
 230 
 231   return ret;
 232 }
 233 
 234 bool YoungList::check_list_empty(bool check_sample) {
 235   bool ret = true;
 236 
 237   if (_length != 0) {
 238     gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u",
 239                   _length);
 240     ret = false;
 241   }
 242   if (check_sample && _last_sampled_rs_lengths != 0) {
 243     gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
 244     ret = false;
 245   }
 246   if (_head != NULL) {
 247     gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
 248     ret = false;
 249   }
 250   if (!ret) {
 251     gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
 252   }
 253 
 254   return ret;
 255 }
 256 
 257 void
 258 YoungList::rs_length_sampling_init() {
 259   _sampled_rs_lengths = 0;
 260   _curr               = _head;
 261 }
 262 
 263 bool
 264 YoungList::rs_length_sampling_more() {
 265   return _curr != NULL;
 266 }
 267 
 268 void
 269 YoungList::rs_length_sampling_next() {
 270   assert( _curr != NULL, "invariant" );
 271   size_t rs_length = _curr->rem_set()->occupied();
 272 
 273   _sampled_rs_lengths += rs_length;
 274 
 275   // The current region may not yet have been added to the
 276   // incremental collection set (it gets added when it is
 277   // retired as the current allocation region).
 278   if (_curr->in_collection_set()) {
 279     // Update the collection set policy information for this region
 280     _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
 281   }
 282 
 283   _curr = _curr->get_next_young_region();
 284   if (_curr == NULL) {
 285     _last_sampled_rs_lengths = _sampled_rs_lengths;
 286     // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
 287   }
 288 }
 289 
 290 void
 291 YoungList::reset_auxilary_lists() {
 292   guarantee( is_empty(), "young list should be empty" );
 293   assert(check_list_well_formed(), "young list should be well formed");
 294 
 295   // Add survivor regions to SurvRateGroup.
 296   _g1h->g1_policy()->note_start_adding_survivor_regions();
 297   _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
 298 
 299   int young_index_in_cset = 0;
 300   for (HeapRegion* curr = _survivor_head;
 301        curr != NULL;
 302        curr = curr->get_next_young_region()) {
 303     _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
 304 
 305     // The region is a non-empty survivor so let's add it to
 306     // the incremental collection set for the next evacuation
 307     // pause.
 308     _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
 309     young_index_in_cset += 1;
 310   }
 311   assert((uint) young_index_in_cset == _survivor_length, "post-condition");
 312   _g1h->g1_policy()->note_stop_adding_survivor_regions();
 313 
 314   _head   = _survivor_head;
 315   _length = _survivor_length;
 316   if (_survivor_head != NULL) {
 317     assert(_survivor_tail != NULL, "cause it shouldn't be");
 318     assert(_survivor_length > 0, "invariant");
 319     _survivor_tail->set_next_young_region(NULL);
 320   }
 321 
 322   // Don't clear the survivor list handles until the start of
 323   // the next evacuation pause - we need it in order to re-tag
 324   // the survivor regions from this evacuation pause as 'young'
 325   // at the start of the next.
 326 
 327   _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
 328 
 329   assert(check_list_well_formed(), "young list should be well formed");
 330 }
 331 
 332 void YoungList::print() {
 333   HeapRegion* lists[] = {_head,   _survivor_head};
 334   const char* names[] = {"YOUNG", "SURVIVOR"};
 335 
 336   for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) {
 337     gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
 338     HeapRegion *curr = lists[list];
 339     if (curr == NULL)
 340       gclog_or_tty->print_cr("  empty");
 341     while (curr != NULL) {
 342       gclog_or_tty->print_cr("  "HR_FORMAT", P: "PTR_FORMAT ", N: "PTR_FORMAT", age: %4d",
 343                              HR_FORMAT_PARAMS(curr),
 344                              curr->prev_top_at_mark_start(),
 345                              curr->next_top_at_mark_start(),
 346                              curr->age_in_surv_rate_group_cond());
 347       curr = curr->get_next_young_region();
 348     }
 349   }
 350 
 351   gclog_or_tty->cr();
 352 }
 353 
 354 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
 355   HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
 356 }
 357 
 358 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
 359   // The from card cache is not the memory that is actually committed. So we cannot
 360   // take advantage of the zero_filled parameter.
 361   reset_from_card_cache(start_idx, num_regions);
 362 }
 363 
 364 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
 365 {
 366   // Claim the right to put the region on the dirty cards region list
 367   // by installing a self pointer.
 368   HeapRegion* next = hr->get_next_dirty_cards_region();
 369   if (next == NULL) {
 370     HeapRegion* res = (HeapRegion*)
 371       Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
 372                           NULL);
 373     if (res == NULL) {
 374       HeapRegion* head;
 375       do {
 376         // Put the region to the dirty cards region list.
 377         head = _dirty_cards_region_list;
 378         next = (HeapRegion*)
 379           Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
 380         if (next == head) {
 381           assert(hr->get_next_dirty_cards_region() == hr,
 382                  "hr->get_next_dirty_cards_region() != hr");
 383           if (next == NULL) {
 384             // The last region in the list points to itself.
 385             hr->set_next_dirty_cards_region(hr);
 386           } else {
 387             hr->set_next_dirty_cards_region(next);
 388           }
 389         }
 390       } while (next != head);
 391     }
 392   }
 393 }
 394 
 395 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
 396 {
 397   HeapRegion* head;
 398   HeapRegion* hr;
 399   do {
 400     head = _dirty_cards_region_list;
 401     if (head == NULL) {
 402       return NULL;
 403     }
 404     HeapRegion* new_head = head->get_next_dirty_cards_region();
 405     if (head == new_head) {
 406       // The last region.
 407       new_head = NULL;
 408     }
 409     hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
 410                                           head);
 411   } while (hr != head);
 412   assert(hr != NULL, "invariant");
 413   hr->set_next_dirty_cards_region(NULL);
 414   return hr;
 415 }
 416 
 417 #ifdef ASSERT
 418 // A region is added to the collection set as it is retired
 419 // so an address p can point to a region which will be in the
 420 // collection set but has not yet been retired.  This method
 421 // therefore is only accurate during a GC pause after all
 422 // regions have been retired.  It is used for debugging
 423 // to check if an nmethod has references to objects that can
 424 // be move during a partial collection.  Though it can be
 425 // inaccurate, it is sufficient for G1 because the conservative
 426 // implementation of is_scavengable() for G1 will indicate that
 427 // all nmethods must be scanned during a partial collection.
 428 bool G1CollectedHeap::is_in_partial_collection(const void* p) {
 429   if (p == NULL) {
 430     return false;
 431   }
 432   return heap_region_containing(p)->in_collection_set();
 433 }
 434 #endif
 435 
 436 // Returns true if the reference points to an object that
 437 // can move in an incremental collection.
 438 bool G1CollectedHeap::is_scavengable(const void* p) {
 439   HeapRegion* hr = heap_region_containing(p);
 440   return !hr->is_humongous();
 441 }
 442 
 443 // Private class members.
 444 
 445 G1CollectedHeap* G1CollectedHeap::_g1h;
 446 
 447 // Private methods.
 448 
 449 HeapRegion*
 450 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
 451   MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
 452   while (!_secondary_free_list.is_empty() || free_regions_coming()) {
 453     if (!_secondary_free_list.is_empty()) {
 454       if (G1ConcRegionFreeingVerbose) {
 455         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 456                                "secondary_free_list has %u entries",
 457                                _secondary_free_list.length());
 458       }
 459       // It looks as if there are free regions available on the
 460       // secondary_free_list. Let's move them to the free_list and try
 461       // again to allocate from it.
 462       append_secondary_free_list();
 463 
 464       assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not "
 465              "empty we should have moved at least one entry to the free_list");
 466       HeapRegion* res = _hrm.allocate_free_region(is_old);
 467       if (G1ConcRegionFreeingVerbose) {
 468         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 469                                "allocated "HR_FORMAT" from secondary_free_list",
 470                                HR_FORMAT_PARAMS(res));
 471       }
 472       return res;
 473     }
 474 
 475     // Wait here until we get notified either when (a) there are no
 476     // more free regions coming or (b) some regions have been moved on
 477     // the secondary_free_list.
 478     SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
 479   }
 480 
 481   if (G1ConcRegionFreeingVerbose) {
 482     gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 483                            "could not allocate from secondary_free_list");
 484   }
 485   return NULL;
 486 }
 487 
 488 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
 489   assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
 490          "the only time we use this to allocate a humongous region is "
 491          "when we are allocating a single humongous region");
 492 
 493   HeapRegion* res;
 494   if (G1StressConcRegionFreeing) {
 495     if (!_secondary_free_list.is_empty()) {
 496       if (G1ConcRegionFreeingVerbose) {
 497         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 498                                "forced to look at the secondary_free_list");
 499       }
 500       res = new_region_try_secondary_free_list(is_old);
 501       if (res != NULL) {
 502         return res;
 503       }
 504     }
 505   }
 506 
 507   res = _hrm.allocate_free_region(is_old);
 508 
 509   if (res == NULL) {
 510     if (G1ConcRegionFreeingVerbose) {
 511       gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 512                              "res == NULL, trying the secondary_free_list");
 513     }
 514     res = new_region_try_secondary_free_list(is_old);
 515   }
 516   if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
 517     // Currently, only attempts to allocate GC alloc regions set
 518     // do_expand to true. So, we should only reach here during a
 519     // safepoint. If this assumption changes we might have to
 520     // reconsider the use of _expand_heap_after_alloc_failure.
 521     assert(SafepointSynchronize::is_at_safepoint(), "invariant");
 522 
 523     ergo_verbose1(ErgoHeapSizing,
 524                   "attempt heap expansion",
 525                   ergo_format_reason("region allocation request failed")
 526                   ergo_format_byte("allocation request"),
 527                   word_size * HeapWordSize);
 528     if (expand(word_size * HeapWordSize)) {
 529       // Given that expand() succeeded in expanding the heap, and we
 530       // always expand the heap by an amount aligned to the heap
 531       // region size, the free list should in theory not be empty.
 532       // In either case allocate_free_region() will check for NULL.
 533       res = _hrm.allocate_free_region(is_old);
 534     } else {
 535       _expand_heap_after_alloc_failure = false;
 536     }
 537   }
 538   return res;
 539 }
 540 
 541 HeapWord*
 542 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
 543                                                            uint num_regions,
 544                                                            size_t word_size,
 545                                                            AllocationContext_t context) {
 546   assert(first != G1_NO_HRM_INDEX, "pre-condition");
 547   assert(is_humongous(word_size), "word_size should be humongous");
 548   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 549 
 550   // Index of last region in the series + 1.
 551   uint last = first + num_regions;
 552 
 553   // We need to initialize the region(s) we just discovered. This is
 554   // a bit tricky given that it can happen concurrently with
 555   // refinement threads refining cards on these regions and
 556   // potentially wanting to refine the BOT as they are scanning
 557   // those cards (this can happen shortly after a cleanup; see CR
 558   // 6991377). So we have to set up the region(s) carefully and in
 559   // a specific order.
 560 
 561   // The word size sum of all the regions we will allocate.
 562   size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
 563   assert(word_size <= word_size_sum, "sanity");
 564 
 565   // This will be the "starts humongous" region.
 566   HeapRegion* first_hr = region_at(first);
 567   // The header of the new object will be placed at the bottom of
 568   // the first region.
 569   HeapWord* new_obj = first_hr->bottom();
 570   // This will be the new end of the first region in the series that
 571   // should also match the end of the last region in the series.
 572   HeapWord* new_end = new_obj + word_size_sum;
 573   // This will be the new top of the first region that will reflect
 574   // this allocation.
 575   HeapWord* new_top = new_obj + word_size;
 576 
 577   // First, we need to zero the header of the space that we will be
 578   // allocating. When we update top further down, some refinement
 579   // threads might try to scan the region. By zeroing the header we
 580   // ensure that any thread that will try to scan the region will
 581   // come across the zero klass word and bail out.
 582   //
 583   // NOTE: It would not have been correct to have used
 584   // CollectedHeap::fill_with_object() and make the space look like
 585   // an int array. The thread that is doing the allocation will
 586   // later update the object header to a potentially different array
 587   // type and, for a very short period of time, the klass and length
 588   // fields will be inconsistent. This could cause a refinement
 589   // thread to calculate the object size incorrectly.
 590   Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
 591 
 592   // We will set up the first region as "starts humongous". This
 593   // will also update the BOT covering all the regions to reflect
 594   // that there is a single object that starts at the bottom of the
 595   // first region.
 596   first_hr->set_starts_humongous(new_top, new_end);
 597   first_hr->set_allocation_context(context);
 598   // Then, if there are any, we will set up the "continues
 599   // humongous" regions.
 600   HeapRegion* hr = NULL;
 601   for (uint i = first + 1; i < last; ++i) {
 602     hr = region_at(i);
 603     hr->set_continues_humongous(first_hr);
 604     hr->set_allocation_context(context);
 605   }
 606   // If we have "continues humongous" regions (hr != NULL), then the
 607   // end of the last one should match new_end.
 608   assert(hr == NULL || hr->end() == new_end, "sanity");
 609 
 610   // Up to this point no concurrent thread would have been able to
 611   // do any scanning on any region in this series. All the top
 612   // fields still point to bottom, so the intersection between
 613   // [bottom,top] and [card_start,card_end] will be empty. Before we
 614   // update the top fields, we'll do a storestore to make sure that
 615   // no thread sees the update to top before the zeroing of the
 616   // object header and the BOT initialization.
 617   OrderAccess::storestore();
 618 
 619   // Now that the BOT and the object header have been initialized,
 620   // we can update top of the "starts humongous" region.
 621   assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
 622          "new_top should be in this region");
 623   first_hr->set_top(new_top);
 624   if (_hr_printer.is_active()) {
 625     HeapWord* bottom = first_hr->bottom();
 626     HeapWord* end = first_hr->orig_end();
 627     if ((first + 1) == last) {
 628       // the series has a single humongous region
 629       _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
 630     } else {
 631       // the series has more than one humongous regions
 632       _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
 633     }
 634   }
 635 
 636   // Now, we will update the top fields of the "continues humongous"
 637   // regions. The reason we need to do this is that, otherwise,
 638   // these regions would look empty and this will confuse parts of
 639   // G1. For example, the code that looks for a consecutive number
 640   // of empty regions will consider them empty and try to
 641   // re-allocate them. We can extend is_empty() to also include
 642   // !is_continues_humongous(), but it is easier to just update the top
 643   // fields here. The way we set top for all regions (i.e., top ==
 644   // end for all regions but the last one, top == new_top for the
 645   // last one) is actually used when we will free up the humongous
 646   // region in free_humongous_region().
 647   hr = NULL;
 648   for (uint i = first + 1; i < last; ++i) {
 649     hr = region_at(i);
 650     if ((i + 1) == last) {
 651       // last continues humongous region
 652       assert(hr->bottom() < new_top && new_top <= hr->end(),
 653              "new_top should fall on this region");
 654       hr->set_top(new_top);
 655       _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
 656     } else {
 657       // not last one
 658       assert(new_top > hr->end(), "new_top should be above this region");
 659       hr->set_top(hr->end());
 660       _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
 661     }
 662   }
 663   // If we have continues humongous regions (hr != NULL), then the
 664   // end of the last one should match new_end and its top should
 665   // match new_top.
 666   assert(hr == NULL ||
 667          (hr->end() == new_end && hr->top() == new_top), "sanity");
 668   check_bitmaps("Humongous Region Allocation", first_hr);
 669 
 670   assert(first_hr->used() == word_size * HeapWordSize, "invariant");
 671   _allocator->increase_used(first_hr->used());
 672   _humongous_set.add(first_hr);
 673 
 674   return new_obj;
 675 }
 676 
 677 // If could fit into free regions w/o expansion, try.
 678 // Otherwise, if can expand, do so.
 679 // Otherwise, if using ex regions might help, try with ex given back.
 680 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) {
 681   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 682 
 683   verify_region_sets_optional();
 684 
 685   uint first = G1_NO_HRM_INDEX;
 686   uint obj_regions = (uint)(align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords);
 687 
 688   if (obj_regions == 1) {
 689     // Only one region to allocate, try to use a fast path by directly allocating
 690     // from the free lists. Do not try to expand here, we will potentially do that
 691     // later.
 692     HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
 693     if (hr != NULL) {
 694       first = hr->hrm_index();
 695     }
 696   } else {
 697     // We can't allocate humongous regions spanning more than one region while
 698     // cleanupComplete() is running, since some of the regions we find to be
 699     // empty might not yet be added to the free list. It is not straightforward
 700     // to know in which list they are on so that we can remove them. We only
 701     // need to do this if we need to allocate more than one region to satisfy the
 702     // current humongous allocation request. If we are only allocating one region
 703     // we use the one-region region allocation code (see above), that already
 704     // potentially waits for regions from the secondary free list.
 705     wait_while_free_regions_coming();
 706     append_secondary_free_list_if_not_empty_with_lock();
 707 
 708     // Policy: Try only empty regions (i.e. already committed first). Maybe we
 709     // are lucky enough to find some.
 710     first = _hrm.find_contiguous_only_empty(obj_regions);
 711     if (first != G1_NO_HRM_INDEX) {
 712       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 713     }
 714   }
 715 
 716   if (first == G1_NO_HRM_INDEX) {
 717     // Policy: We could not find enough regions for the humongous object in the
 718     // free list. Look through the heap to find a mix of free and uncommitted regions.
 719     // If so, try expansion.
 720     first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
 721     if (first != G1_NO_HRM_INDEX) {
 722       // We found something. Make sure these regions are committed, i.e. expand
 723       // the heap. Alternatively we could do a defragmentation GC.
 724       ergo_verbose1(ErgoHeapSizing,
 725                     "attempt heap expansion",
 726                     ergo_format_reason("humongous allocation request failed")
 727                     ergo_format_byte("allocation request"),
 728                     word_size * HeapWordSize);
 729 
 730       _hrm.expand_at(first, obj_regions);
 731       g1_policy()->record_new_heap_size(num_regions());
 732 
 733 #ifdef ASSERT
 734       for (uint i = first; i < first + obj_regions; ++i) {
 735         HeapRegion* hr = region_at(i);
 736         assert(hr->is_free(), "sanity");
 737         assert(hr->is_empty(), "sanity");
 738         assert(is_on_master_free_list(hr), "sanity");
 739       }
 740 #endif
 741       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 742     } else {
 743       // Policy: Potentially trigger a defragmentation GC.
 744     }
 745   }
 746 
 747   HeapWord* result = NULL;
 748   if (first != G1_NO_HRM_INDEX) {
 749     result = humongous_obj_allocate_initialize_regions(first, obj_regions,
 750                                                        word_size, context);
 751     assert(result != NULL, "it should always return a valid result");
 752 
 753     // A successful humongous object allocation changes the used space
 754     // information of the old generation so we need to recalculate the
 755     // sizes and update the jstat counters here.
 756     g1mm()->update_sizes();
 757   }
 758 
 759   verify_region_sets_optional();
 760 
 761   return result;
 762 }
 763 
 764 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
 765   assert_heap_not_locked_and_not_at_safepoint();
 766   assert(!is_humongous(word_size), "we do not allow humongous TLABs");
 767 
 768   unsigned int dummy_gc_count_before;
 769   int dummy_gclocker_retry_count = 0;
 770   return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
 771 }
 772 
 773 HeapWord*
 774 G1CollectedHeap::mem_allocate(size_t word_size,
 775                               bool*  gc_overhead_limit_was_exceeded) {
 776   assert_heap_not_locked_and_not_at_safepoint();
 777 
 778   // Loop until the allocation is satisfied, or unsatisfied after GC.
 779   for (int try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 780     unsigned int gc_count_before;
 781 
 782     HeapWord* result = NULL;
 783     if (!is_humongous(word_size)) {
 784       result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
 785     } else {
 786       result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
 787     }
 788     if (result != NULL) {
 789       return result;
 790     }
 791 
 792     // Create the garbage collection operation...
 793     VM_G1CollectForAllocation op(gc_count_before, word_size);
 794     op.set_allocation_context(AllocationContext::current());
 795 
 796     // ...and get the VM thread to execute it.
 797     VMThread::execute(&op);
 798 
 799     if (op.prologue_succeeded() && op.pause_succeeded()) {
 800       // If the operation was successful we'll return the result even
 801       // if it is NULL. If the allocation attempt failed immediately
 802       // after a Full GC, it's unlikely we'll be able to allocate now.
 803       HeapWord* result = op.result();
 804       if (result != NULL && !is_humongous(word_size)) {
 805         // Allocations that take place on VM operations do not do any
 806         // card dirtying and we have to do it here. We only have to do
 807         // this for non-humongous allocations, though.
 808         dirty_young_block(result, word_size);
 809       }
 810       return result;
 811     } else {
 812       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 813         return NULL;
 814       }
 815       assert(op.result() == NULL,
 816              "the result should be NULL if the VM op did not succeed");
 817     }
 818 
 819     // Give a warning if we seem to be looping forever.
 820     if ((QueuedAllocationWarningCount > 0) &&
 821         (try_count % QueuedAllocationWarningCount == 0)) {
 822       warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
 823     }
 824   }
 825 
 826   ShouldNotReachHere();
 827   return NULL;
 828 }
 829 
 830 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
 831                                                    AllocationContext_t context,
 832                                                    unsigned int *gc_count_before_ret,
 833                                                    int* gclocker_retry_count_ret) {
 834   // Make sure you read the note in attempt_allocation_humongous().
 835 
 836   assert_heap_not_locked_and_not_at_safepoint();
 837   assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
 838          "be called for humongous allocation requests");
 839 
 840   // We should only get here after the first-level allocation attempt
 841   // (attempt_allocation()) failed to allocate.
 842 
 843   // We will loop until a) we manage to successfully perform the
 844   // allocation or b) we successfully schedule a collection which
 845   // fails to perform the allocation. b) is the only case when we'll
 846   // return NULL.
 847   HeapWord* result = NULL;
 848   for (int try_count = 1; /* we'll return */; try_count += 1) {
 849     bool should_try_gc;
 850     unsigned int gc_count_before;
 851 
 852     {
 853       MutexLockerEx x(Heap_lock);
 854       result = _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size,
 855                                                                                     false /* bot_updates */);
 856       if (result != NULL) {
 857         return result;
 858       }
 859 
 860       // If we reach here, attempt_allocation_locked() above failed to
 861       // allocate a new region. So the mutator alloc region should be NULL.
 862       assert(_allocator->mutator_alloc_region(context)->get() == NULL, "only way to get here");
 863 
 864       if (GC_locker::is_active_and_needs_gc()) {
 865         if (g1_policy()->can_expand_young_list()) {
 866           // No need for an ergo verbose message here,
 867           // can_expand_young_list() does this when it returns true.
 868           result = _allocator->mutator_alloc_region(context)->attempt_allocation_force(word_size,
 869                                                                                        false /* bot_updates */);
 870           if (result != NULL) {
 871             return result;
 872           }
 873         }
 874         should_try_gc = false;
 875       } else {
 876         // The GCLocker may not be active but the GCLocker initiated
 877         // GC may not yet have been performed (GCLocker::needs_gc()
 878         // returns true). In this case we do not try this GC and
 879         // wait until the GCLocker initiated GC is performed, and
 880         // then retry the allocation.
 881         if (GC_locker::needs_gc()) {
 882           should_try_gc = false;
 883         } else {
 884           // Read the GC count while still holding the Heap_lock.
 885           gc_count_before = total_collections();
 886           should_try_gc = true;
 887         }
 888       }
 889     }
 890 
 891     if (should_try_gc) {
 892       bool succeeded;
 893       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 894           GCCause::_g1_inc_collection_pause);
 895       if (result != NULL) {
 896         assert(succeeded, "only way to get back a non-NULL result");
 897         return result;
 898       }
 899 
 900       if (succeeded) {
 901         // If we get here we successfully scheduled a collection which
 902         // failed to allocate. No point in trying to allocate
 903         // further. We'll just return NULL.
 904         MutexLockerEx x(Heap_lock);
 905         *gc_count_before_ret = total_collections();
 906         return NULL;
 907       }
 908     } else {
 909       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
 910         MutexLockerEx x(Heap_lock);
 911         *gc_count_before_ret = total_collections();
 912         return NULL;
 913       }
 914       // The GCLocker is either active or the GCLocker initiated
 915       // GC has not yet been performed. Stall until it is and
 916       // then retry the allocation.
 917       GC_locker::stall_until_clear();
 918       (*gclocker_retry_count_ret) += 1;
 919     }
 920 
 921     // We can reach here if we were unsuccessful in scheduling a
 922     // collection (because another thread beat us to it) or if we were
 923     // stalled due to the GC locker. In either can we should retry the
 924     // allocation attempt in case another thread successfully
 925     // performed a collection and reclaimed enough space. We do the
 926     // first attempt (without holding the Heap_lock) here and the
 927     // follow-on attempt will be at the start of the next loop
 928     // iteration (after taking the Heap_lock).
 929     result = _allocator->mutator_alloc_region(context)->attempt_allocation(word_size,
 930                                                                            false /* bot_updates */);
 931     if (result != NULL) {
 932       return result;
 933     }
 934 
 935     // Give a warning if we seem to be looping forever.
 936     if ((QueuedAllocationWarningCount > 0) &&
 937         (try_count % QueuedAllocationWarningCount == 0)) {
 938       warning("G1CollectedHeap::attempt_allocation_slow() "
 939               "retries %d times", try_count);
 940     }
 941   }
 942 
 943   ShouldNotReachHere();
 944   return NULL;
 945 }
 946 
 947 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
 948                                                         unsigned int * gc_count_before_ret,
 949                                                         int* gclocker_retry_count_ret) {
 950   // The structure of this method has a lot of similarities to
 951   // attempt_allocation_slow(). The reason these two were not merged
 952   // into a single one is that such a method would require several "if
 953   // allocation is not humongous do this, otherwise do that"
 954   // conditional paths which would obscure its flow. In fact, an early
 955   // version of this code did use a unified method which was harder to
 956   // follow and, as a result, it had subtle bugs that were hard to
 957   // track down. So keeping these two methods separate allows each to
 958   // be more readable. It will be good to keep these two in sync as
 959   // much as possible.
 960 
 961   assert_heap_not_locked_and_not_at_safepoint();
 962   assert(is_humongous(word_size), "attempt_allocation_humongous() "
 963          "should only be called for humongous allocations");
 964 
 965   // Humongous objects can exhaust the heap quickly, so we should check if we
 966   // need to start a marking cycle at each humongous object allocation. We do
 967   // the check before we do the actual allocation. The reason for doing it
 968   // before the allocation is that we avoid having to keep track of the newly
 969   // allocated memory while we do a GC.
 970   if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
 971                                            word_size)) {
 972     collect(GCCause::_g1_humongous_allocation);
 973   }
 974 
 975   // We will loop until a) we manage to successfully perform the
 976   // allocation or b) we successfully schedule a collection which
 977   // fails to perform the allocation. b) is the only case when we'll
 978   // return NULL.
 979   HeapWord* result = NULL;
 980   for (int try_count = 1; /* we'll return */; try_count += 1) {
 981     bool should_try_gc;
 982     unsigned int gc_count_before;
 983 
 984     {
 985       MutexLockerEx x(Heap_lock);
 986 
 987       // Given that humongous objects are not allocated in young
 988       // regions, we'll first try to do the allocation without doing a
 989       // collection hoping that there's enough space in the heap.
 990       result = humongous_obj_allocate(word_size, AllocationContext::current());
 991       if (result != NULL) {
 992         return result;
 993       }
 994 
 995       if (GC_locker::is_active_and_needs_gc()) {
 996         should_try_gc = false;
 997       } else {
 998          // The GCLocker may not be active but the GCLocker initiated
 999         // GC may not yet have been performed (GCLocker::needs_gc()
1000         // returns true). In this case we do not try this GC and
1001         // wait until the GCLocker initiated GC is performed, and
1002         // then retry the allocation.
1003         if (GC_locker::needs_gc()) {
1004           should_try_gc = false;
1005         } else {
1006           // Read the GC count while still holding the Heap_lock.
1007           gc_count_before = total_collections();
1008           should_try_gc = true;
1009         }
1010       }
1011     }
1012 
1013     if (should_try_gc) {
1014       // If we failed to allocate the humongous object, we should try to
1015       // do a collection pause (if we're allowed) in case it reclaims
1016       // enough space for the allocation to succeed after the pause.
1017 
1018       bool succeeded;
1019       result = do_collection_pause(word_size, gc_count_before, &succeeded,
1020           GCCause::_g1_humongous_allocation);
1021       if (result != NULL) {
1022         assert(succeeded, "only way to get back a non-NULL result");
1023         return result;
1024       }
1025 
1026       if (succeeded) {
1027         // If we get here we successfully scheduled a collection which
1028         // failed to allocate. No point in trying to allocate
1029         // further. We'll just return NULL.
1030         MutexLockerEx x(Heap_lock);
1031         *gc_count_before_ret = total_collections();
1032         return NULL;
1033       }
1034     } else {
1035       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1036         MutexLockerEx x(Heap_lock);
1037         *gc_count_before_ret = total_collections();
1038         return NULL;
1039       }
1040       // The GCLocker is either active or the GCLocker initiated
1041       // GC has not yet been performed. Stall until it is and
1042       // then retry the allocation.
1043       GC_locker::stall_until_clear();
1044       (*gclocker_retry_count_ret) += 1;
1045     }
1046 
1047     // We can reach here if we were unsuccessful in scheduling a
1048     // collection (because another thread beat us to it) or if we were
1049     // stalled due to the GC locker. In either can we should retry the
1050     // allocation attempt in case another thread successfully
1051     // performed a collection and reclaimed enough space.  Give a
1052     // warning if we seem to be looping forever.
1053 
1054     if ((QueuedAllocationWarningCount > 0) &&
1055         (try_count % QueuedAllocationWarningCount == 0)) {
1056       warning("G1CollectedHeap::attempt_allocation_humongous() "
1057               "retries %d times", try_count);
1058     }
1059   }
1060 
1061   ShouldNotReachHere();
1062   return NULL;
1063 }
1064 
1065 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1066                                                            AllocationContext_t context,
1067                                                            bool expect_null_mutator_alloc_region) {
1068   assert_at_safepoint(true /* should_be_vm_thread */);
1069   assert(_allocator->mutator_alloc_region(context)->get() == NULL ||
1070                                              !expect_null_mutator_alloc_region,
1071          "the current alloc region was unexpectedly found to be non-NULL");
1072 
1073   if (!is_humongous(word_size)) {
1074     return _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size,
1075                                                       false /* bot_updates */);
1076   } else {
1077     HeapWord* result = humongous_obj_allocate(word_size, context);
1078     if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1079       g1_policy()->set_initiate_conc_mark_if_possible();
1080     }
1081     return result;
1082   }
1083 
1084   ShouldNotReachHere();
1085 }
1086 
1087 class PostMCRemSetClearClosure: public HeapRegionClosure {
1088   G1CollectedHeap* _g1h;
1089   ModRefBarrierSet* _mr_bs;
1090 public:
1091   PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1092     _g1h(g1h), _mr_bs(mr_bs) {}
1093 
1094   bool doHeapRegion(HeapRegion* r) {
1095     HeapRegionRemSet* hrrs = r->rem_set();
1096 
1097     if (r->is_continues_humongous()) {
1098       // We'll assert that the strong code root list and RSet is empty
1099       assert(hrrs->strong_code_roots_list_length() == 0, "sanity");
1100       assert(hrrs->occupied() == 0, "RSet should be empty");
1101       return false;
1102     }
1103 
1104     _g1h->reset_gc_time_stamps(r);
1105     hrrs->clear();
1106     // You might think here that we could clear just the cards
1107     // corresponding to the used region.  But no: if we leave a dirty card
1108     // in a region we might allocate into, then it would prevent that card
1109     // from being enqueued, and cause it to be missed.
1110     // Re: the performance cost: we shouldn't be doing full GC anyway!
1111     _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1112 
1113     return false;
1114   }
1115 };
1116 
1117 void G1CollectedHeap::clear_rsets_post_compaction() {
1118   PostMCRemSetClearClosure rs_clear(this, g1_barrier_set());
1119   heap_region_iterate(&rs_clear);
1120 }
1121 
1122 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1123   G1CollectedHeap*   _g1h;
1124   UpdateRSOopClosure _cl;
1125   int                _worker_i;
1126 public:
1127   RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1128     _cl(g1->g1_rem_set(), worker_i),
1129     _worker_i(worker_i),
1130     _g1h(g1)
1131   { }
1132 
1133   bool doHeapRegion(HeapRegion* r) {
1134     if (!r->is_continues_humongous()) {
1135       _cl.set_from(r);
1136       r->oop_iterate(&_cl);
1137     }
1138     return false;
1139   }
1140 };
1141 
1142 class ParRebuildRSTask: public AbstractGangTask {
1143   G1CollectedHeap* _g1;
1144   HeapRegionClaimer _hrclaimer;
1145 
1146 public:
1147   ParRebuildRSTask(G1CollectedHeap* g1) :
1148       AbstractGangTask("ParRebuildRSTask"), _g1(g1), _hrclaimer(g1->workers()->active_workers()) {}
1149 
1150   void work(uint worker_id) {
1151     RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1152     _g1->heap_region_par_iterate(&rebuild_rs, worker_id, &_hrclaimer);
1153   }
1154 };
1155 
1156 class PostCompactionPrinterClosure: public HeapRegionClosure {
1157 private:
1158   G1HRPrinter* _hr_printer;
1159 public:
1160   bool doHeapRegion(HeapRegion* hr) {
1161     assert(!hr->is_young(), "not expecting to find young regions");
1162     if (hr->is_free()) {
1163       // We only generate output for non-empty regions.
1164     } else if (hr->is_starts_humongous()) {
1165       if (hr->region_num() == 1) {
1166         // single humongous region
1167         _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
1168       } else {
1169         _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
1170       }
1171     } else if (hr->is_continues_humongous()) {
1172       _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1173     } else if (hr->is_old()) {
1174       _hr_printer->post_compaction(hr, G1HRPrinter::Old);
1175     } else {
1176       ShouldNotReachHere();
1177     }
1178     return false;
1179   }
1180 
1181   PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1182     : _hr_printer(hr_printer) { }
1183 };
1184 
1185 void G1CollectedHeap::print_hrm_post_compaction() {
1186   PostCompactionPrinterClosure cl(hr_printer());
1187   heap_region_iterate(&cl);
1188 }
1189 
1190 bool G1CollectedHeap::do_collection(bool explicit_gc,
1191                                     bool clear_all_soft_refs,
1192                                     size_t word_size) {
1193   assert_at_safepoint(true /* should_be_vm_thread */);
1194 
1195   if (GC_locker::check_active_before_gc()) {
1196     return false;
1197   }
1198 
1199   STWGCTimer* gc_timer = G1MarkSweep::gc_timer();
1200   gc_timer->register_gc_start();
1201 
1202   SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer();
1203   gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start());
1204 
1205   SvcGCMarker sgcm(SvcGCMarker::FULL);
1206   ResourceMark rm;
1207 
1208   print_heap_before_gc();
1209   trace_heap_before_gc(gc_tracer);
1210 
1211   size_t metadata_prev_used = MetaspaceAux::used_bytes();
1212 
1213   verify_region_sets_optional();
1214 
1215   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1216                            collector_policy()->should_clear_all_soft_refs();
1217 
1218   ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1219 
1220   {
1221     IsGCActiveMark x;
1222 
1223     // Timing
1224     assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant");
1225     TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
1226 
1227     {
1228       GCTraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, NULL, gc_tracer->gc_id());
1229       TraceCollectorStats tcs(g1mm()->full_collection_counters());
1230       TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1231 
1232       g1_policy()->record_full_collection_start();
1233 
1234       // Note: When we have a more flexible GC logging framework that
1235       // allows us to add optional attributes to a GC log record we
1236       // could consider timing and reporting how long we wait in the
1237       // following two methods.
1238       wait_while_free_regions_coming();
1239       // If we start the compaction before the CM threads finish
1240       // scanning the root regions we might trip them over as we'll
1241       // be moving objects / updating references. So let's wait until
1242       // they are done. By telling them to abort, they should complete
1243       // early.
1244       _cm->root_regions()->abort();
1245       _cm->root_regions()->wait_until_scan_finished();
1246       append_secondary_free_list_if_not_empty_with_lock();
1247 
1248       gc_prologue(true);
1249       increment_total_collections(true /* full gc */);
1250       increment_old_marking_cycles_started();
1251 
1252       assert(used() == recalculate_used(), "Should be equal");
1253 
1254       verify_before_gc();
1255 
1256       check_bitmaps("Full GC Start");
1257       pre_full_gc_dump(gc_timer);
1258 
1259       COMPILER2_PRESENT(DerivedPointerTable::clear());
1260 
1261       // Disable discovery and empty the discovered lists
1262       // for the CM ref processor.
1263       ref_processor_cm()->disable_discovery();
1264       ref_processor_cm()->abandon_partial_discovery();
1265       ref_processor_cm()->verify_no_references_recorded();
1266 
1267       // Abandon current iterations of concurrent marking and concurrent
1268       // refinement, if any are in progress. We have to do this before
1269       // wait_until_scan_finished() below.
1270       concurrent_mark()->abort();
1271 
1272       // Make sure we'll choose a new allocation region afterwards.
1273       _allocator->release_mutator_alloc_region();
1274       _allocator->abandon_gc_alloc_regions();
1275       g1_rem_set()->cleanupHRRS();
1276 
1277       // We should call this after we retire any currently active alloc
1278       // regions so that all the ALLOC / RETIRE events are generated
1279       // before the start GC event.
1280       _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1281 
1282       // We may have added regions to the current incremental collection
1283       // set between the last GC or pause and now. We need to clear the
1284       // incremental collection set and then start rebuilding it afresh
1285       // after this full GC.
1286       abandon_collection_set(g1_policy()->inc_cset_head());
1287       g1_policy()->clear_incremental_cset();
1288       g1_policy()->stop_incremental_cset_building();
1289 
1290       tear_down_region_sets(false /* free_list_only */);
1291       g1_policy()->set_gcs_are_young(true);
1292 
1293       // See the comments in g1CollectedHeap.hpp and
1294       // G1CollectedHeap::ref_processing_init() about
1295       // how reference processing currently works in G1.
1296 
1297       // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1298       ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1299 
1300       // Temporarily clear the STW ref processor's _is_alive_non_header field.
1301       ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1302 
1303       ref_processor_stw()->enable_discovery();
1304       ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1305 
1306       // Do collection work
1307       {
1308         HandleMark hm;  // Discard invalid handles created during gc
1309         G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1310       }
1311 
1312       assert(num_free_regions() == 0, "we should not have added any free regions");
1313       rebuild_region_sets(false /* free_list_only */);
1314 
1315       // Enqueue any discovered reference objects that have
1316       // not been removed from the discovered lists.
1317       ref_processor_stw()->enqueue_discovered_references();
1318 
1319       COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1320 
1321       MemoryService::track_memory_usage();
1322 
1323       assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1324       ref_processor_stw()->verify_no_references_recorded();
1325 
1326       // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1327       ClassLoaderDataGraph::purge();
1328       MetaspaceAux::verify_metrics();
1329 
1330       // Note: since we've just done a full GC, concurrent
1331       // marking is no longer active. Therefore we need not
1332       // re-enable reference discovery for the CM ref processor.
1333       // That will be done at the start of the next marking cycle.
1334       assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1335       ref_processor_cm()->verify_no_references_recorded();
1336 
1337       reset_gc_time_stamp();
1338       // Since everything potentially moved, we will clear all remembered
1339       // sets, and clear all cards.  Later we will rebuild remembered
1340       // sets. We will also reset the GC time stamps of the regions.
1341       clear_rsets_post_compaction();
1342       check_gc_time_stamps();
1343 
1344       // Resize the heap if necessary.
1345       resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1346 
1347       if (_hr_printer.is_active()) {
1348         // We should do this after we potentially resize the heap so
1349         // that all the COMMIT / UNCOMMIT events are generated before
1350         // the end GC event.
1351 
1352         print_hrm_post_compaction();
1353         _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1354       }
1355 
1356       G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
1357       if (hot_card_cache->use_cache()) {
1358         hot_card_cache->reset_card_counts();
1359         hot_card_cache->reset_hot_cache();
1360       }
1361 
1362       // Rebuild remembered sets of all regions.
1363       uint n_workers =
1364         AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1365                                                 workers()->active_workers(),
1366                                                 Threads::number_of_non_daemon_threads());
1367       assert(UseDynamicNumberOfGCThreads ||
1368              n_workers == workers()->total_workers(),
1369              "If not dynamic should be using all the  workers");
1370       workers()->set_active_workers(n_workers);
1371       // Set parallel threads in the heap (_n_par_threads) only
1372       // before a parallel phase and always reset it to 0 after
1373       // the phase so that the number of parallel threads does
1374       // no get carried forward to a serial phase where there
1375       // may be code that is "possibly_parallel".
1376       set_par_threads(n_workers);
1377 
1378       ParRebuildRSTask rebuild_rs_task(this);
1379       assert(UseDynamicNumberOfGCThreads ||
1380              workers()->active_workers() == workers()->total_workers(),
1381              "Unless dynamic should use total workers");
1382       // Use the most recent number of  active workers
1383       assert(workers()->active_workers() > 0,
1384              "Active workers not properly set");
1385       set_par_threads(workers()->active_workers());
1386       workers()->run_task(&rebuild_rs_task);
1387       set_par_threads(0);
1388 
1389       // Rebuild the strong code root lists for each region
1390       rebuild_strong_code_roots();
1391 
1392       if (true) { // FIXME
1393         MetaspaceGC::compute_new_size();
1394       }
1395 
1396 #ifdef TRACESPINNING
1397       ParallelTaskTerminator::print_termination_counts();
1398 #endif
1399 
1400       // Discard all rset updates
1401       JavaThread::dirty_card_queue_set().abandon_logs();
1402       assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1403 
1404       _young_list->reset_sampled_info();
1405       // At this point there should be no regions in the
1406       // entire heap tagged as young.
1407       assert(check_young_list_empty(true /* check_heap */),
1408              "young list should be empty at this point");
1409 
1410       // Update the number of full collections that have been completed.
1411       increment_old_marking_cycles_completed(false /* concurrent */);
1412 
1413       _hrm.verify_optional();
1414       verify_region_sets_optional();
1415 
1416       verify_after_gc();
1417 
1418       // Clear the previous marking bitmap, if needed for bitmap verification.
1419       // Note we cannot do this when we clear the next marking bitmap in
1420       // ConcurrentMark::abort() above since VerifyDuringGC verifies the
1421       // objects marked during a full GC against the previous bitmap.
1422       // But we need to clear it before calling check_bitmaps below since
1423       // the full GC has compacted objects and updated TAMS but not updated
1424       // the prev bitmap.
1425       if (G1VerifyBitmaps) {
1426         ((CMBitMap*) concurrent_mark()->prevMarkBitMap())->clearAll();
1427       }
1428       check_bitmaps("Full GC End");
1429 
1430       // Start a new incremental collection set for the next pause
1431       assert(g1_policy()->collection_set() == NULL, "must be");
1432       g1_policy()->start_incremental_cset_building();
1433 
1434       clear_cset_fast_test();
1435 
1436       _allocator->init_mutator_alloc_region();
1437 
1438       g1_policy()->record_full_collection_end();
1439 
1440       if (G1Log::fine()) {
1441         g1_policy()->print_heap_transition();
1442       }
1443 
1444       // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1445       // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1446       // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1447       // before any GC notifications are raised.
1448       g1mm()->update_sizes();
1449 
1450       gc_epilogue(true);
1451     }
1452 
1453     if (G1Log::finer()) {
1454       g1_policy()->print_detailed_heap_transition(true /* full */);
1455     }
1456 
1457     print_heap_after_gc();
1458     trace_heap_after_gc(gc_tracer);
1459 
1460     post_full_gc_dump(gc_timer);
1461 
1462     gc_timer->register_gc_end();
1463     gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
1464   }
1465 
1466   return true;
1467 }
1468 
1469 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1470   // do_collection() will return whether it succeeded in performing
1471   // the GC. Currently, there is no facility on the
1472   // do_full_collection() API to notify the caller than the collection
1473   // did not succeed (e.g., because it was locked out by the GC
1474   // locker). So, right now, we'll ignore the return value.
1475   bool dummy = do_collection(true,                /* explicit_gc */
1476                              clear_all_soft_refs,
1477                              0                    /* word_size */);
1478 }
1479 
1480 // This code is mostly copied from TenuredGeneration.
1481 void
1482 G1CollectedHeap::
1483 resize_if_necessary_after_full_collection(size_t word_size) {
1484   // Include the current allocation, if any, and bytes that will be
1485   // pre-allocated to support collections, as "used".
1486   const size_t used_after_gc = used();
1487   const size_t capacity_after_gc = capacity();
1488   const size_t free_after_gc = capacity_after_gc - used_after_gc;
1489 
1490   // This is enforced in arguments.cpp.
1491   assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1492          "otherwise the code below doesn't make sense");
1493 
1494   // We don't have floating point command-line arguments
1495   const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1496   const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1497   const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1498   const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1499 
1500   const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1501   const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1502 
1503   // We have to be careful here as these two calculations can overflow
1504   // 32-bit size_t's.
1505   double used_after_gc_d = (double) used_after_gc;
1506   double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1507   double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1508 
1509   // Let's make sure that they are both under the max heap size, which
1510   // by default will make them fit into a size_t.
1511   double desired_capacity_upper_bound = (double) max_heap_size;
1512   minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1513                                     desired_capacity_upper_bound);
1514   maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1515                                     desired_capacity_upper_bound);
1516 
1517   // We can now safely turn them into size_t's.
1518   size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1519   size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1520 
1521   // This assert only makes sense here, before we adjust them
1522   // with respect to the min and max heap size.
1523   assert(minimum_desired_capacity <= maximum_desired_capacity,
1524          err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1525                  "maximum_desired_capacity = "SIZE_FORMAT,
1526                  minimum_desired_capacity, maximum_desired_capacity));
1527 
1528   // Should not be greater than the heap max size. No need to adjust
1529   // it with respect to the heap min size as it's a lower bound (i.e.,
1530   // we'll try to make the capacity larger than it, not smaller).
1531   minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1532   // Should not be less than the heap min size. No need to adjust it
1533   // with respect to the heap max size as it's an upper bound (i.e.,
1534   // we'll try to make the capacity smaller than it, not greater).
1535   maximum_desired_capacity =  MAX2(maximum_desired_capacity, min_heap_size);
1536 
1537   if (capacity_after_gc < minimum_desired_capacity) {
1538     // Don't expand unless it's significant
1539     size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1540     ergo_verbose4(ErgoHeapSizing,
1541                   "attempt heap expansion",
1542                   ergo_format_reason("capacity lower than "
1543                                      "min desired capacity after Full GC")
1544                   ergo_format_byte("capacity")
1545                   ergo_format_byte("occupancy")
1546                   ergo_format_byte_perc("min desired capacity"),
1547                   capacity_after_gc, used_after_gc,
1548                   minimum_desired_capacity, (double) MinHeapFreeRatio);
1549     expand(expand_bytes);
1550 
1551     // No expansion, now see if we want to shrink
1552   } else if (capacity_after_gc > maximum_desired_capacity) {
1553     // Capacity too large, compute shrinking size
1554     size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1555     ergo_verbose4(ErgoHeapSizing,
1556                   "attempt heap shrinking",
1557                   ergo_format_reason("capacity higher than "
1558                                      "max desired capacity after Full GC")
1559                   ergo_format_byte("capacity")
1560                   ergo_format_byte("occupancy")
1561                   ergo_format_byte_perc("max desired capacity"),
1562                   capacity_after_gc, used_after_gc,
1563                   maximum_desired_capacity, (double) MaxHeapFreeRatio);
1564     shrink(shrink_bytes);
1565   }
1566 }
1567 
1568 
1569 HeapWord*
1570 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1571                                            AllocationContext_t context,
1572                                            bool* succeeded) {
1573   assert_at_safepoint(true /* should_be_vm_thread */);
1574 
1575   *succeeded = true;
1576   // Let's attempt the allocation first.
1577   HeapWord* result =
1578     attempt_allocation_at_safepoint(word_size,
1579                                     context,
1580                                     false /* expect_null_mutator_alloc_region */);
1581   if (result != NULL) {
1582     assert(*succeeded, "sanity");
1583     return result;
1584   }
1585 
1586   // In a G1 heap, we're supposed to keep allocation from failing by
1587   // incremental pauses.  Therefore, at least for now, we'll favor
1588   // expansion over collection.  (This might change in the future if we can
1589   // do something smarter than full collection to satisfy a failed alloc.)
1590   result = expand_and_allocate(word_size, context);
1591   if (result != NULL) {
1592     assert(*succeeded, "sanity");
1593     return result;
1594   }
1595 
1596   // Expansion didn't work, we'll try to do a Full GC.
1597   bool gc_succeeded = do_collection(false, /* explicit_gc */
1598                                     false, /* clear_all_soft_refs */
1599                                     word_size);
1600   if (!gc_succeeded) {
1601     *succeeded = false;
1602     return NULL;
1603   }
1604 
1605   // Retry the allocation
1606   result = attempt_allocation_at_safepoint(word_size,
1607                                            context,
1608                                            true /* expect_null_mutator_alloc_region */);
1609   if (result != NULL) {
1610     assert(*succeeded, "sanity");
1611     return result;
1612   }
1613 
1614   // Then, try a Full GC that will collect all soft references.
1615   gc_succeeded = do_collection(false, /* explicit_gc */
1616                                true,  /* clear_all_soft_refs */
1617                                word_size);
1618   if (!gc_succeeded) {
1619     *succeeded = false;
1620     return NULL;
1621   }
1622 
1623   // Retry the allocation once more
1624   result = attempt_allocation_at_safepoint(word_size,
1625                                            context,
1626                                            true /* expect_null_mutator_alloc_region */);
1627   if (result != NULL) {
1628     assert(*succeeded, "sanity");
1629     return result;
1630   }
1631 
1632   assert(!collector_policy()->should_clear_all_soft_refs(),
1633          "Flag should have been handled and cleared prior to this point");
1634 
1635   // What else?  We might try synchronous finalization later.  If the total
1636   // space available is large enough for the allocation, then a more
1637   // complete compaction phase than we've tried so far might be
1638   // appropriate.
1639   assert(*succeeded, "sanity");
1640   return NULL;
1641 }
1642 
1643 // Attempting to expand the heap sufficiently
1644 // to support an allocation of the given "word_size".  If
1645 // successful, perform the allocation and return the address of the
1646 // allocated block, or else "NULL".
1647 
1648 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) {
1649   assert_at_safepoint(true /* should_be_vm_thread */);
1650 
1651   verify_region_sets_optional();
1652 
1653   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1654   ergo_verbose1(ErgoHeapSizing,
1655                 "attempt heap expansion",
1656                 ergo_format_reason("allocation request failed")
1657                 ergo_format_byte("allocation request"),
1658                 word_size * HeapWordSize);
1659   if (expand(expand_bytes)) {
1660     _hrm.verify_optional();
1661     verify_region_sets_optional();
1662     return attempt_allocation_at_safepoint(word_size,
1663                                            context,
1664                                            false /* expect_null_mutator_alloc_region */);
1665   }
1666   return NULL;
1667 }
1668 
1669 bool G1CollectedHeap::expand(size_t expand_bytes) {
1670   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1671   aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1672                                        HeapRegion::GrainBytes);
1673   ergo_verbose2(ErgoHeapSizing,
1674                 "expand the heap",
1675                 ergo_format_byte("requested expansion amount")
1676                 ergo_format_byte("attempted expansion amount"),
1677                 expand_bytes, aligned_expand_bytes);
1678 
1679   if (is_maximal_no_gc()) {
1680     ergo_verbose0(ErgoHeapSizing,
1681                       "did not expand the heap",
1682                       ergo_format_reason("heap already fully expanded"));
1683     return false;
1684   }
1685 
1686   uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1687   assert(regions_to_expand > 0, "Must expand by at least one region");
1688 
1689   uint expanded_by = _hrm.expand_by(regions_to_expand);
1690 
1691   if (expanded_by > 0) {
1692     size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1693     assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1694     g1_policy()->record_new_heap_size(num_regions());
1695   } else {
1696     ergo_verbose0(ErgoHeapSizing,
1697                   "did not expand the heap",
1698                   ergo_format_reason("heap expansion operation failed"));
1699     // The expansion of the virtual storage space was unsuccessful.
1700     // Let's see if it was because we ran out of swap.
1701     if (G1ExitOnExpansionFailure &&
1702         _hrm.available() >= regions_to_expand) {
1703       // We had head room...
1704       vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1705     }
1706   }
1707   return regions_to_expand > 0;
1708 }
1709 
1710 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1711   size_t aligned_shrink_bytes =
1712     ReservedSpace::page_align_size_down(shrink_bytes);
1713   aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1714                                          HeapRegion::GrainBytes);
1715   uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1716 
1717   uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1718   size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1719 
1720   ergo_verbose3(ErgoHeapSizing,
1721                 "shrink the heap",
1722                 ergo_format_byte("requested shrinking amount")
1723                 ergo_format_byte("aligned shrinking amount")
1724                 ergo_format_byte("attempted shrinking amount"),
1725                 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1726   if (num_regions_removed > 0) {
1727     g1_policy()->record_new_heap_size(num_regions());
1728   } else {
1729     ergo_verbose0(ErgoHeapSizing,
1730                   "did not shrink the heap",
1731                   ergo_format_reason("heap shrinking operation failed"));
1732   }
1733 }
1734 
1735 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1736   verify_region_sets_optional();
1737 
1738   // We should only reach here at the end of a Full GC which means we
1739   // should not not be holding to any GC alloc regions. The method
1740   // below will make sure of that and do any remaining clean up.
1741   _allocator->abandon_gc_alloc_regions();
1742 
1743   // Instead of tearing down / rebuilding the free lists here, we
1744   // could instead use the remove_all_pending() method on free_list to
1745   // remove only the ones that we need to remove.
1746   tear_down_region_sets(true /* free_list_only */);
1747   shrink_helper(shrink_bytes);
1748   rebuild_region_sets(true /* free_list_only */);
1749 
1750   _hrm.verify_optional();
1751   verify_region_sets_optional();
1752 }
1753 
1754 // Public methods.
1755 
1756 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1757   SharedHeap(policy_),
1758   _g1_policy(policy_),
1759   _dirty_card_queue_set(false),
1760   _into_cset_dirty_card_queue_set(false),
1761   _ref_processor_cm(NULL),
1762   _ref_processor_stw(NULL),
1763   _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
1764   _bot_shared(NULL),
1765   _evac_failure_scan_stack(NULL),
1766   _mark_in_progress(false),
1767   _cg1r(NULL),
1768   _g1mm(NULL),
1769   _refine_cte_cl(NULL),
1770   _full_collection(false),
1771   _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1772   _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1773   _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1774   _humongous_is_live(),
1775   _has_humongous_reclaim_candidates(false),
1776   _free_regions_coming(false),
1777   _gc_time_stamp(0),
1778   _survivor_plab_stats(YoungPLABSize, PLABWeight),
1779   _old_plab_stats(OldPLABSize, PLABWeight),
1780   _expand_heap_after_alloc_failure(true),
1781   _surviving_young_words(NULL),
1782   _old_marking_cycles_started(0),
1783   _old_marking_cycles_completed(0),
1784   _concurrent_cycle_started(false),
1785   _heap_summary_sent(false),
1786   _in_cset_fast_test(),
1787   _dirty_cards_region_list(NULL),
1788   _worker_cset_start_region(NULL),
1789   _worker_cset_start_region_time_stamp(NULL),
1790   _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1791   _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
1792   _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1793   _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) {
1794 
1795   _is_alive_closure_cm = G1CMIsAliveClosure(this);
1796   _is_alive_closure_stw = G1STWIsAliveClosure(this);
1797   _young_list = new YoungList(this);
1798   _g1h = this;
1799 
1800   if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
1801     vm_exit_during_initialization("Failed necessary allocation.");
1802   }
1803 
1804   _allocator = G1Allocator::create_allocator(_g1h);
1805   _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1806 
1807   int n_queues = MAX2((int)ParallelGCThreads, 1);
1808   _task_queues = new RefToScanQueueSet(n_queues);
1809 
1810   uint n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1811   assert(n_rem_sets > 0, "Invariant.");
1812 
1813   _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1814   _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC);
1815   _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1816 
1817   for (int i = 0; i < n_queues; i++) {
1818     RefToScanQueue* q = new RefToScanQueue();
1819     q->initialize();
1820     _task_queues->register_queue(i, q);
1821     ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1822   }
1823   clear_cset_start_regions();
1824 
1825   // Initialize the G1EvacuationFailureALot counters and flags.
1826   NOT_PRODUCT(reset_evacuation_should_fail();)
1827 
1828   guarantee(_task_queues != NULL, "task_queues allocation failure.");
1829 }
1830 
1831 jint G1CollectedHeap::initialize() {
1832   CollectedHeap::pre_initialize();
1833   os::enable_vtime();
1834 
1835   G1Log::init();
1836 
1837   // Necessary to satisfy locking discipline assertions.
1838 
1839   MutexLocker x(Heap_lock);
1840 
1841   // We have to initialize the printer before committing the heap, as
1842   // it will be used then.
1843   _hr_printer.set_active(G1PrintHeapRegions);
1844 
1845   // While there are no constraints in the GC code that HeapWordSize
1846   // be any particular value, there are multiple other areas in the
1847   // system which believe this to be true (e.g. oop->object_size in some
1848   // cases incorrectly returns the size in wordSize units rather than
1849   // HeapWordSize).
1850   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1851 
1852   size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1853   size_t max_byte_size = collector_policy()->max_heap_byte_size();
1854   size_t heap_alignment = collector_policy()->heap_alignment();
1855 
1856   // Ensure that the sizes are properly aligned.
1857   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1858   Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1859   Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1860 
1861   _refine_cte_cl = new RefineCardTableEntryClosure();
1862 
1863   _cg1r = new ConcurrentG1Refine(this, _refine_cte_cl);
1864 
1865   // Reserve the maximum.
1866 
1867   // When compressed oops are enabled, the preferred heap base
1868   // is calculated by subtracting the requested size from the
1869   // 32Gb boundary and using the result as the base address for
1870   // heap reservation. If the requested size is not aligned to
1871   // HeapRegion::GrainBytes (i.e. the alignment that is passed
1872   // into the ReservedHeapSpace constructor) then the actual
1873   // base of the reserved heap may end up differing from the
1874   // address that was requested (i.e. the preferred heap base).
1875   // If this happens then we could end up using a non-optimal
1876   // compressed oops mode.
1877 
1878   ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1879                                                  heap_alignment);
1880 
1881   initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
1882 
1883   // Create the barrier set for the entire reserved region.
1884   G1SATBCardTableLoggingModRefBS* bs
1885     = new G1SATBCardTableLoggingModRefBS(reserved_region());
1886   bs->initialize();
1887   assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity");
1888   set_barrier_set(bs);
1889 
1890   // Also create a G1 rem set.
1891   _g1_rem_set = new G1RemSet(this, g1_barrier_set());
1892 
1893   // Carve out the G1 part of the heap.
1894 
1895   ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1896   G1RegionToSpaceMapper* heap_storage =
1897     G1RegionToSpaceMapper::create_mapper(g1_rs,
1898                                          UseLargePages ? os::large_page_size() : os::vm_page_size(),
1899                                          HeapRegion::GrainBytes,
1900                                          1,
1901                                          mtJavaHeap);
1902   heap_storage->set_mapping_changed_listener(&_listener);
1903 
1904   // Reserve space for the block offset table. We do not support automatic uncommit
1905   // for the card table at this time. BOT only.
1906   ReservedSpace bot_rs(G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize));
1907   G1RegionToSpaceMapper* bot_storage =
1908     G1RegionToSpaceMapper::create_mapper(bot_rs,
1909                                          os::vm_page_size(),
1910                                          HeapRegion::GrainBytes,
1911                                          G1BlockOffsetSharedArray::N_bytes,
1912                                          mtGC);
1913 
1914   ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize));
1915   G1RegionToSpaceMapper* cardtable_storage =
1916     G1RegionToSpaceMapper::create_mapper(cardtable_rs,
1917                                          os::vm_page_size(),
1918                                          HeapRegion::GrainBytes,
1919                                          G1BlockOffsetSharedArray::N_bytes,
1920                                          mtGC);
1921 
1922   // Reserve space for the card counts table.
1923   ReservedSpace card_counts_rs(G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize));
1924   G1RegionToSpaceMapper* card_counts_storage =
1925     G1RegionToSpaceMapper::create_mapper(card_counts_rs,
1926                                          os::vm_page_size(),
1927                                          HeapRegion::GrainBytes,
1928                                          G1BlockOffsetSharedArray::N_bytes,
1929                                          mtGC);
1930 
1931   // Reserve space for prev and next bitmap.
1932   size_t bitmap_size = CMBitMap::compute_size(g1_rs.size());
1933 
1934   ReservedSpace prev_bitmap_rs(ReservedSpace::allocation_align_size_up(bitmap_size));
1935   G1RegionToSpaceMapper* prev_bitmap_storage =
1936     G1RegionToSpaceMapper::create_mapper(prev_bitmap_rs,
1937                                          os::vm_page_size(),
1938                                          HeapRegion::GrainBytes,
1939                                          CMBitMap::mark_distance(),
1940                                          mtGC);
1941 
1942   ReservedSpace next_bitmap_rs(ReservedSpace::allocation_align_size_up(bitmap_size));
1943   G1RegionToSpaceMapper* next_bitmap_storage =
1944     G1RegionToSpaceMapper::create_mapper(next_bitmap_rs,
1945                                          os::vm_page_size(),
1946                                          HeapRegion::GrainBytes,
1947                                          CMBitMap::mark_distance(),
1948                                          mtGC);
1949 
1950   _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1951   g1_barrier_set()->initialize(cardtable_storage);
1952    // Do later initialization work for concurrent refinement.
1953   _cg1r->init(card_counts_storage);
1954 
1955   // 6843694 - ensure that the maximum region index can fit
1956   // in the remembered set structures.
1957   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1958   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1959 
1960   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1961   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1962   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1963             "too many cards per region");
1964 
1965   FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
1966 
1967   _bot_shared = new G1BlockOffsetSharedArray(reserved_region(), bot_storage);
1968 
1969   _g1h = this;
1970 
1971   _in_cset_fast_test.initialize(_hrm.reserved().start(), _hrm.reserved().end(), HeapRegion::GrainBytes);
1972   _humongous_is_live.initialize(_hrm.reserved().start(), _hrm.reserved().end(), HeapRegion::GrainBytes);
1973 
1974   // Create the ConcurrentMark data structure and thread.
1975   // (Must do this late, so that "max_regions" is defined.)
1976   _cm = new ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1977   if (_cm == NULL || !_cm->completed_initialization()) {
1978     vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark");
1979     return JNI_ENOMEM;
1980   }
1981   _cmThread = _cm->cmThread();
1982 
1983   // Initialize the from_card cache structure of HeapRegionRemSet.
1984   HeapRegionRemSet::init_heap(max_regions());
1985 
1986   // Now expand into the initial heap size.
1987   if (!expand(init_byte_size)) {
1988     vm_shutdown_during_initialization("Failed to allocate initial heap.");
1989     return JNI_ENOMEM;
1990   }
1991 
1992   // Perform any initialization actions delegated to the policy.
1993   g1_policy()->init();
1994 
1995   JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
1996                                                SATB_Q_FL_lock,
1997                                                G1SATBProcessCompletedThreshold,
1998                                                Shared_SATB_Q_lock);
1999 
2000   JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl,
2001                                                 DirtyCardQ_CBL_mon,
2002                                                 DirtyCardQ_FL_lock,
2003                                                 concurrent_g1_refine()->yellow_zone(),
2004                                                 concurrent_g1_refine()->red_zone(),
2005                                                 Shared_DirtyCardQ_lock);
2006 
2007   dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code
2008                                     DirtyCardQ_CBL_mon,
2009                                     DirtyCardQ_FL_lock,
2010                                     -1, // never trigger processing
2011                                     -1, // no limit on length
2012                                     Shared_DirtyCardQ_lock,
2013                                     &JavaThread::dirty_card_queue_set());
2014 
2015   // Initialize the card queue set used to hold cards containing
2016   // references into the collection set.
2017   _into_cset_dirty_card_queue_set.initialize(NULL, // Should never be called by the Java code
2018                                              DirtyCardQ_CBL_mon,
2019                                              DirtyCardQ_FL_lock,
2020                                              -1, // never trigger processing
2021                                              -1, // no limit on length
2022                                              Shared_DirtyCardQ_lock,
2023                                              &JavaThread::dirty_card_queue_set());
2024 
2025   // In case we're keeping closure specialization stats, initialize those
2026   // counts and that mechanism.
2027   SpecializationStats::clear();
2028 
2029   // Here we allocate the dummy HeapRegion that is required by the
2030   // G1AllocRegion class.
2031   HeapRegion* dummy_region = _hrm.get_dummy_region();
2032 
2033   // We'll re-use the same region whether the alloc region will
2034   // require BOT updates or not and, if it doesn't, then a non-young
2035   // region will complain that it cannot support allocations without
2036   // BOT updates. So we'll tag the dummy region as eden to avoid that.
2037   dummy_region->set_eden();
2038   // Make sure it's full.
2039   dummy_region->set_top(dummy_region->end());
2040   G1AllocRegion::setup(this, dummy_region);
2041 
2042   _allocator->init_mutator_alloc_region();
2043 
2044   // Do create of the monitoring and management support so that
2045   // values in the heap have been properly initialized.
2046   _g1mm = new G1MonitoringSupport(this);
2047 
2048   G1StringDedup::initialize();
2049 
2050   return JNI_OK;
2051 }
2052 
2053 void G1CollectedHeap::stop() {
2054   // Stop all concurrent threads. We do this to make sure these threads
2055   // do not continue to execute and access resources (e.g. gclog_or_tty)
2056   // that are destroyed during shutdown.
2057   _cg1r->stop();
2058   _cmThread->stop();
2059   if (G1StringDedup::is_enabled()) {
2060     G1StringDedup::stop();
2061   }
2062 }
2063 
2064 void G1CollectedHeap::clear_humongous_is_live_table() {
2065   guarantee(G1EagerReclaimHumongousObjects, "Should only be called if true");
2066   _humongous_is_live.clear();
2067 }
2068 
2069 size_t G1CollectedHeap::conservative_max_heap_alignment() {
2070   return HeapRegion::max_region_size();
2071 }
2072 
2073 void G1CollectedHeap::ref_processing_init() {
2074   // Reference processing in G1 currently works as follows:
2075   //
2076   // * There are two reference processor instances. One is
2077   //   used to record and process discovered references
2078   //   during concurrent marking; the other is used to
2079   //   record and process references during STW pauses
2080   //   (both full and incremental).
2081   // * Both ref processors need to 'span' the entire heap as
2082   //   the regions in the collection set may be dotted around.
2083   //
2084   // * For the concurrent marking ref processor:
2085   //   * Reference discovery is enabled at initial marking.
2086   //   * Reference discovery is disabled and the discovered
2087   //     references processed etc during remarking.
2088   //   * Reference discovery is MT (see below).
2089   //   * Reference discovery requires a barrier (see below).
2090   //   * Reference processing may or may not be MT
2091   //     (depending on the value of ParallelRefProcEnabled
2092   //     and ParallelGCThreads).
2093   //   * A full GC disables reference discovery by the CM
2094   //     ref processor and abandons any entries on it's
2095   //     discovered lists.
2096   //
2097   // * For the STW processor:
2098   //   * Non MT discovery is enabled at the start of a full GC.
2099   //   * Processing and enqueueing during a full GC is non-MT.
2100   //   * During a full GC, references are processed after marking.
2101   //
2102   //   * Discovery (may or may not be MT) is enabled at the start
2103   //     of an incremental evacuation pause.
2104   //   * References are processed near the end of a STW evacuation pause.
2105   //   * For both types of GC:
2106   //     * Discovery is atomic - i.e. not concurrent.
2107   //     * Reference discovery will not need a barrier.
2108 
2109   SharedHeap::ref_processing_init();
2110   MemRegion mr = reserved_region();
2111 
2112   // Concurrent Mark ref processor
2113   _ref_processor_cm =
2114     new ReferenceProcessor(mr,    // span
2115                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2116                                 // mt processing
2117                            (int) ParallelGCThreads,
2118                                 // degree of mt processing
2119                            (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2120                                 // mt discovery
2121                            (int) MAX2(ParallelGCThreads, ConcGCThreads),
2122                                 // degree of mt discovery
2123                            false,
2124                                 // Reference discovery is not atomic
2125                            &_is_alive_closure_cm);
2126                                 // is alive closure
2127                                 // (for efficiency/performance)
2128 
2129   // STW ref processor
2130   _ref_processor_stw =
2131     new ReferenceProcessor(mr,    // span
2132                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2133                                 // mt processing
2134                            MAX2((int)ParallelGCThreads, 1),
2135                                 // degree of mt processing
2136                            (ParallelGCThreads > 1),
2137                                 // mt discovery
2138                            MAX2((int)ParallelGCThreads, 1),
2139                                 // degree of mt discovery
2140                            true,
2141                                 // Reference discovery is atomic
2142                            &_is_alive_closure_stw);
2143                                 // is alive closure
2144                                 // (for efficiency/performance)
2145 }
2146 
2147 size_t G1CollectedHeap::capacity() const {
2148   return _hrm.length() * HeapRegion::GrainBytes;
2149 }
2150 
2151 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2152   assert(!hr->is_continues_humongous(), "pre-condition");
2153   hr->reset_gc_time_stamp();
2154   if (hr->is_starts_humongous()) {
2155     uint first_index = hr->hrm_index() + 1;
2156     uint last_index = hr->last_hc_index();
2157     for (uint i = first_index; i < last_index; i += 1) {
2158       HeapRegion* chr = region_at(i);
2159       assert(chr->is_continues_humongous(), "sanity");
2160       chr->reset_gc_time_stamp();
2161     }
2162   }
2163 }
2164 
2165 #ifndef PRODUCT
2166 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2167 private:
2168   unsigned _gc_time_stamp;
2169   bool _failures;
2170 
2171 public:
2172   CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2173     _gc_time_stamp(gc_time_stamp), _failures(false) { }
2174 
2175   virtual bool doHeapRegion(HeapRegion* hr) {
2176     unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2177     if (_gc_time_stamp != region_gc_time_stamp) {
2178       gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, "
2179                              "expected %d", HR_FORMAT_PARAMS(hr),
2180                              region_gc_time_stamp, _gc_time_stamp);
2181       _failures = true;
2182     }
2183     return false;
2184   }
2185 
2186   bool failures() { return _failures; }
2187 };
2188 
2189 void G1CollectedHeap::check_gc_time_stamps() {
2190   CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2191   heap_region_iterate(&cl);
2192   guarantee(!cl.failures(), "all GC time stamps should have been reset");
2193 }
2194 #endif // PRODUCT
2195 
2196 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2197                                                  DirtyCardQueue* into_cset_dcq,
2198                                                  bool concurrent,
2199                                                  uint worker_i) {
2200   // Clean cards in the hot card cache
2201   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
2202   hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq);
2203 
2204   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2205   int n_completed_buffers = 0;
2206   while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2207     n_completed_buffers++;
2208   }
2209   g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers);
2210   dcqs.clear_n_completed_buffers();
2211   assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2212 }
2213 
2214 
2215 // Computes the sum of the storage used by the various regions.
2216 size_t G1CollectedHeap::used() const {
2217   return _allocator->used();
2218 }
2219 
2220 size_t G1CollectedHeap::used_unlocked() const {
2221   return _allocator->used_unlocked();
2222 }
2223 
2224 class SumUsedClosure: public HeapRegionClosure {
2225   size_t _used;
2226 public:
2227   SumUsedClosure() : _used(0) {}
2228   bool doHeapRegion(HeapRegion* r) {
2229     if (!r->is_continues_humongous()) {
2230       _used += r->used();
2231     }
2232     return false;
2233   }
2234   size_t result() { return _used; }
2235 };
2236 
2237 size_t G1CollectedHeap::recalculate_used() const {
2238   double recalculate_used_start = os::elapsedTime();
2239 
2240   SumUsedClosure blk;
2241   heap_region_iterate(&blk);
2242 
2243   g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2244   return blk.result();
2245 }
2246 
2247 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2248   switch (cause) {
2249     case GCCause::_gc_locker:               return GCLockerInvokesConcurrent;
2250     case GCCause::_java_lang_system_gc:     return ExplicitGCInvokesConcurrent;
2251     case GCCause::_g1_humongous_allocation: return true;
2252     case GCCause::_update_allocation_context_stats_inc: return true;
2253     case GCCause::_wb_conc_mark:            return true;
2254     default:                                return false;
2255   }
2256 }
2257 
2258 #ifndef PRODUCT
2259 void G1CollectedHeap::allocate_dummy_regions() {
2260   // Let's fill up most of the region
2261   size_t word_size = HeapRegion::GrainWords - 1024;
2262   // And as a result the region we'll allocate will be humongous.
2263   guarantee(is_humongous(word_size), "sanity");
2264 
2265   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2266     // Let's use the existing mechanism for the allocation
2267     HeapWord* dummy_obj = humongous_obj_allocate(word_size,
2268                                                  AllocationContext::system());
2269     if (dummy_obj != NULL) {
2270       MemRegion mr(dummy_obj, word_size);
2271       CollectedHeap::fill_with_object(mr);
2272     } else {
2273       // If we can't allocate once, we probably cannot allocate
2274       // again. Let's get out of the loop.
2275       break;
2276     }
2277   }
2278 }
2279 #endif // !PRODUCT
2280 
2281 void G1CollectedHeap::increment_old_marking_cycles_started() {
2282   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2283     _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2284     err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2285     _old_marking_cycles_started, _old_marking_cycles_completed));
2286 
2287   _old_marking_cycles_started++;
2288 }
2289 
2290 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2291   MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2292 
2293   // We assume that if concurrent == true, then the caller is a
2294   // concurrent thread that was joined the Suspendible Thread
2295   // Set. If there's ever a cheap way to check this, we should add an
2296   // assert here.
2297 
2298   // Given that this method is called at the end of a Full GC or of a
2299   // concurrent cycle, and those can be nested (i.e., a Full GC can
2300   // interrupt a concurrent cycle), the number of full collections
2301   // completed should be either one (in the case where there was no
2302   // nesting) or two (when a Full GC interrupted a concurrent cycle)
2303   // behind the number of full collections started.
2304 
2305   // This is the case for the inner caller, i.e. a Full GC.
2306   assert(concurrent ||
2307          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2308          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2309          err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
2310                  "is inconsistent with _old_marking_cycles_completed = %u",
2311                  _old_marking_cycles_started, _old_marking_cycles_completed));
2312 
2313   // This is the case for the outer caller, i.e. the concurrent cycle.
2314   assert(!concurrent ||
2315          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2316          err_msg("for outer caller (concurrent cycle): "
2317                  "_old_marking_cycles_started = %u "
2318                  "is inconsistent with _old_marking_cycles_completed = %u",
2319                  _old_marking_cycles_started, _old_marking_cycles_completed));
2320 
2321   _old_marking_cycles_completed += 1;
2322 
2323   // We need to clear the "in_progress" flag in the CM thread before
2324   // we wake up any waiters (especially when ExplicitInvokesConcurrent
2325   // is set) so that if a waiter requests another System.gc() it doesn't
2326   // incorrectly see that a marking cycle is still in progress.
2327   if (concurrent) {
2328     _cmThread->clear_in_progress();
2329   }
2330 
2331   // This notify_all() will ensure that a thread that called
2332   // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2333   // and it's waiting for a full GC to finish will be woken up. It is
2334   // waiting in VM_G1IncCollectionPause::doit_epilogue().
2335   FullGCCount_lock->notify_all();
2336 }
2337 
2338 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) {
2339   _concurrent_cycle_started = true;
2340   _gc_timer_cm->register_gc_start(start_time);
2341 
2342   _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start());
2343   trace_heap_before_gc(_gc_tracer_cm);
2344 }
2345 
2346 void G1CollectedHeap::register_concurrent_cycle_end() {
2347   if (_concurrent_cycle_started) {
2348     if (_cm->has_aborted()) {
2349       _gc_tracer_cm->report_concurrent_mode_failure();
2350     }
2351 
2352     _gc_timer_cm->register_gc_end();
2353     _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
2354 
2355     // Clear state variables to prepare for the next concurrent cycle.
2356     _concurrent_cycle_started = false;
2357     _heap_summary_sent = false;
2358   }
2359 }
2360 
2361 void G1CollectedHeap::trace_heap_after_concurrent_cycle() {
2362   if (_concurrent_cycle_started) {
2363     // This function can be called when:
2364     //  the cleanup pause is run
2365     //  the concurrent cycle is aborted before the cleanup pause.
2366     //  the concurrent cycle is aborted after the cleanup pause,
2367     //   but before the concurrent cycle end has been registered.
2368     // Make sure that we only send the heap information once.
2369     if (!_heap_summary_sent) {
2370       trace_heap_after_gc(_gc_tracer_cm);
2371       _heap_summary_sent = true;
2372     }
2373   }
2374 }
2375 
2376 G1YCType G1CollectedHeap::yc_type() {
2377   bool is_young = g1_policy()->gcs_are_young();
2378   bool is_initial_mark = g1_policy()->during_initial_mark_pause();
2379   bool is_during_mark = mark_in_progress();
2380 
2381   if (is_initial_mark) {
2382     return InitialMark;
2383   } else if (is_during_mark) {
2384     return DuringMark;
2385   } else if (is_young) {
2386     return Normal;
2387   } else {
2388     return Mixed;
2389   }
2390 }
2391 
2392 void G1CollectedHeap::collect(GCCause::Cause cause) {
2393   assert_heap_not_locked();
2394 
2395   unsigned int gc_count_before;
2396   unsigned int old_marking_count_before;
2397   unsigned int full_gc_count_before;
2398   bool retry_gc;
2399 
2400   do {
2401     retry_gc = false;
2402 
2403     {
2404       MutexLocker ml(Heap_lock);
2405 
2406       // Read the GC count while holding the Heap_lock
2407       gc_count_before = total_collections();
2408       full_gc_count_before = total_full_collections();
2409       old_marking_count_before = _old_marking_cycles_started;
2410     }
2411 
2412     if (should_do_concurrent_full_gc(cause)) {
2413       // Schedule an initial-mark evacuation pause that will start a
2414       // concurrent cycle. We're setting word_size to 0 which means that
2415       // we are not requesting a post-GC allocation.
2416       VM_G1IncCollectionPause op(gc_count_before,
2417                                  0,     /* word_size */
2418                                  true,  /* should_initiate_conc_mark */
2419                                  g1_policy()->max_pause_time_ms(),
2420                                  cause);
2421       op.set_allocation_context(AllocationContext::current());
2422 
2423       VMThread::execute(&op);
2424       if (!op.pause_succeeded()) {
2425         if (old_marking_count_before == _old_marking_cycles_started) {
2426           retry_gc = op.should_retry_gc();
2427         } else {
2428           // A Full GC happened while we were trying to schedule the
2429           // initial-mark GC. No point in starting a new cycle given
2430           // that the whole heap was collected anyway.
2431         }
2432 
2433         if (retry_gc) {
2434           if (GC_locker::is_active_and_needs_gc()) {
2435             GC_locker::stall_until_clear();
2436           }
2437         }
2438       }
2439     } else {
2440       if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2441           DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2442 
2443         // Schedule a standard evacuation pause. We're setting word_size
2444         // to 0 which means that we are not requesting a post-GC allocation.
2445         VM_G1IncCollectionPause op(gc_count_before,
2446                                    0,     /* word_size */
2447                                    false, /* should_initiate_conc_mark */
2448                                    g1_policy()->max_pause_time_ms(),
2449                                    cause);
2450         VMThread::execute(&op);
2451       } else {
2452         // Schedule a Full GC.
2453         VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2454         VMThread::execute(&op);
2455       }
2456     }
2457   } while (retry_gc);
2458 }
2459 
2460 bool G1CollectedHeap::is_in(const void* p) const {
2461   if (_hrm.reserved().contains(p)) {
2462     // Given that we know that p is in the reserved space,
2463     // heap_region_containing_raw() should successfully
2464     // return the containing region.
2465     HeapRegion* hr = heap_region_containing_raw(p);
2466     return hr->is_in(p);
2467   } else {
2468     return false;
2469   }
2470 }
2471 
2472 #ifdef ASSERT
2473 bool G1CollectedHeap::is_in_exact(const void* p) const {
2474   bool contains = reserved_region().contains(p);
2475   bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2476   if (contains && available) {
2477     return true;
2478   } else {
2479     return false;
2480   }
2481 }
2482 #endif
2483 
2484 // Iteration functions.
2485 
2486 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion.
2487 
2488 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2489   ExtendedOopClosure* _cl;
2490 public:
2491   IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {}
2492   bool doHeapRegion(HeapRegion* r) {
2493     if (!r->is_continues_humongous()) {
2494       r->oop_iterate(_cl);
2495     }
2496     return false;
2497   }
2498 };
2499 
2500 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) {
2501   IterateOopClosureRegionClosure blk(cl);
2502   heap_region_iterate(&blk);
2503 }
2504 
2505 // Iterates an ObjectClosure over all objects within a HeapRegion.
2506 
2507 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2508   ObjectClosure* _cl;
2509 public:
2510   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2511   bool doHeapRegion(HeapRegion* r) {
2512     if (!r->is_continues_humongous()) {
2513       r->object_iterate(_cl);
2514     }
2515     return false;
2516   }
2517 };
2518 
2519 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2520   IterateObjectClosureRegionClosure blk(cl);
2521   heap_region_iterate(&blk);
2522 }
2523 
2524 // Calls a SpaceClosure on a HeapRegion.
2525 
2526 class SpaceClosureRegionClosure: public HeapRegionClosure {
2527   SpaceClosure* _cl;
2528 public:
2529   SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2530   bool doHeapRegion(HeapRegion* r) {
2531     _cl->do_space(r);
2532     return false;
2533   }
2534 };
2535 
2536 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2537   SpaceClosureRegionClosure blk(cl);
2538   heap_region_iterate(&blk);
2539 }
2540 
2541 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2542   _hrm.iterate(cl);
2543 }
2544 
2545 void
2546 G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl,
2547                                          uint worker_id,
2548                                          HeapRegionClaimer *hrclaimer,
2549                                          bool concurrent) const {
2550   _hrm.par_iterate(cl, worker_id, hrclaimer, concurrent);
2551 }
2552 
2553 // Clear the cached CSet starting regions and (more importantly)
2554 // the time stamps. Called when we reset the GC time stamp.
2555 void G1CollectedHeap::clear_cset_start_regions() {
2556   assert(_worker_cset_start_region != NULL, "sanity");
2557   assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2558 
2559   int n_queues = MAX2((int)ParallelGCThreads, 1);
2560   for (int i = 0; i < n_queues; i++) {
2561     _worker_cset_start_region[i] = NULL;
2562     _worker_cset_start_region_time_stamp[i] = 0;
2563   }
2564 }
2565 
2566 // Given the id of a worker, obtain or calculate a suitable
2567 // starting region for iterating over the current collection set.
2568 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) {
2569   assert(get_gc_time_stamp() > 0, "should have been updated by now");
2570 
2571   HeapRegion* result = NULL;
2572   unsigned gc_time_stamp = get_gc_time_stamp();
2573 
2574   if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2575     // Cached starting region for current worker was set
2576     // during the current pause - so it's valid.
2577     // Note: the cached starting heap region may be NULL
2578     // (when the collection set is empty).
2579     result = _worker_cset_start_region[worker_i];
2580     assert(result == NULL || result->in_collection_set(), "sanity");
2581     return result;
2582   }
2583 
2584   // The cached entry was not valid so let's calculate
2585   // a suitable starting heap region for this worker.
2586 
2587   // We want the parallel threads to start their collection
2588   // set iteration at different collection set regions to
2589   // avoid contention.
2590   // If we have:
2591   //          n collection set regions
2592   //          p threads
2593   // Then thread t will start at region floor ((t * n) / p)
2594 
2595   result = g1_policy()->collection_set();
2596   uint cs_size = g1_policy()->cset_region_length();
2597   uint active_workers = workers()->active_workers();
2598   assert(UseDynamicNumberOfGCThreads ||
2599            active_workers == workers()->total_workers(),
2600            "Unless dynamic should use total workers");
2601 
2602   uint end_ind   = (cs_size * worker_i) / active_workers;
2603   uint start_ind = 0;
2604 
2605   if (worker_i > 0 &&
2606       _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2607     // Previous workers starting region is valid
2608     // so let's iterate from there
2609     start_ind = (cs_size * (worker_i - 1)) / active_workers;
2610     result = _worker_cset_start_region[worker_i - 1];
2611   }
2612 
2613   for (uint i = start_ind; i < end_ind; i++) {
2614     result = result->next_in_collection_set();
2615   }
2616 
2617   // Note: the calculated starting heap region may be NULL
2618   // (when the collection set is empty).
2619   assert(result == NULL || result->in_collection_set(), "sanity");
2620   assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2621          "should be updated only once per pause");
2622   _worker_cset_start_region[worker_i] = result;
2623   OrderAccess::storestore();
2624   _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2625   return result;
2626 }
2627 
2628 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2629   HeapRegion* r = g1_policy()->collection_set();
2630   while (r != NULL) {
2631     HeapRegion* next = r->next_in_collection_set();
2632     if (cl->doHeapRegion(r)) {
2633       cl->incomplete();
2634       return;
2635     }
2636     r = next;
2637   }
2638 }
2639 
2640 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2641                                                   HeapRegionClosure *cl) {
2642   if (r == NULL) {
2643     // The CSet is empty so there's nothing to do.
2644     return;
2645   }
2646 
2647   assert(r->in_collection_set(),
2648          "Start region must be a member of the collection set.");
2649   HeapRegion* cur = r;
2650   while (cur != NULL) {
2651     HeapRegion* next = cur->next_in_collection_set();
2652     if (cl->doHeapRegion(cur) && false) {
2653       cl->incomplete();
2654       return;
2655     }
2656     cur = next;
2657   }
2658   cur = g1_policy()->collection_set();
2659   while (cur != r) {
2660     HeapRegion* next = cur->next_in_collection_set();
2661     if (cl->doHeapRegion(cur) && false) {
2662       cl->incomplete();
2663       return;
2664     }
2665     cur = next;
2666   }
2667 }
2668 
2669 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const {
2670   HeapRegion* result = _hrm.next_region_in_heap(from);
2671   while (result != NULL && result->is_humongous()) {
2672     result = _hrm.next_region_in_heap(result);
2673   }
2674   return result;
2675 }
2676 
2677 Space* G1CollectedHeap::space_containing(const void* addr) const {
2678   return heap_region_containing(addr);
2679 }
2680 
2681 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2682   Space* sp = space_containing(addr);
2683   return sp->block_start(addr);
2684 }
2685 
2686 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2687   Space* sp = space_containing(addr);
2688   return sp->block_size(addr);
2689 }
2690 
2691 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2692   Space* sp = space_containing(addr);
2693   return sp->block_is_obj(addr);
2694 }
2695 
2696 bool G1CollectedHeap::supports_tlab_allocation() const {
2697   return true;
2698 }
2699 
2700 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2701   return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes;
2702 }
2703 
2704 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2705   return young_list()->eden_used_bytes();
2706 }
2707 
2708 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2709 // must be smaller than the humongous object limit.
2710 size_t G1CollectedHeap::max_tlab_size() const {
2711   return align_size_down(_humongous_object_threshold_in_words - 1, MinObjAlignment);
2712 }
2713 
2714 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2715   // Return the remaining space in the cur alloc region, but not less than
2716   // the min TLAB size.
2717 
2718   // Also, this value can be at most the humongous object threshold,
2719   // since we can't allow tlabs to grow big enough to accommodate
2720   // humongous objects.
2721 
2722   HeapRegion* hr = _allocator->mutator_alloc_region(AllocationContext::current())->get();
2723   size_t max_tlab = max_tlab_size() * wordSize;
2724   if (hr == NULL) {
2725     return max_tlab;
2726   } else {
2727     return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab);
2728   }
2729 }
2730 
2731 size_t G1CollectedHeap::max_capacity() const {
2732   return _hrm.reserved().byte_size();
2733 }
2734 
2735 jlong G1CollectedHeap::millis_since_last_gc() {
2736   // assert(false, "NYI");
2737   return 0;
2738 }
2739 
2740 void G1CollectedHeap::prepare_for_verify() {
2741   if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
2742     ensure_parsability(false);
2743   }
2744   g1_rem_set()->prepare_for_verify();
2745 }
2746 
2747 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr,
2748                                               VerifyOption vo) {
2749   switch (vo) {
2750   case VerifyOption_G1UsePrevMarking:
2751     return hr->obj_allocated_since_prev_marking(obj);
2752   case VerifyOption_G1UseNextMarking:
2753     return hr->obj_allocated_since_next_marking(obj);
2754   case VerifyOption_G1UseMarkWord:
2755     return false;
2756   default:
2757     ShouldNotReachHere();
2758   }
2759   return false; // keep some compilers happy
2760 }
2761 
2762 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) {
2763   switch (vo) {
2764   case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start();
2765   case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start();
2766   case VerifyOption_G1UseMarkWord:    return NULL;
2767   default:                            ShouldNotReachHere();
2768   }
2769   return NULL; // keep some compilers happy
2770 }
2771 
2772 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) {
2773   switch (vo) {
2774   case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj);
2775   case VerifyOption_G1UseNextMarking: return isMarkedNext(obj);
2776   case VerifyOption_G1UseMarkWord:    return obj->is_gc_marked();
2777   default:                            ShouldNotReachHere();
2778   }
2779   return false; // keep some compilers happy
2780 }
2781 
2782 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) {
2783   switch (vo) {
2784   case VerifyOption_G1UsePrevMarking: return "PTAMS";
2785   case VerifyOption_G1UseNextMarking: return "NTAMS";
2786   case VerifyOption_G1UseMarkWord:    return "NONE";
2787   default:                            ShouldNotReachHere();
2788   }
2789   return NULL; // keep some compilers happy
2790 }
2791 
2792 class VerifyRootsClosure: public OopClosure {
2793 private:
2794   G1CollectedHeap* _g1h;
2795   VerifyOption     _vo;
2796   bool             _failures;
2797 public:
2798   // _vo == UsePrevMarking -> use "prev" marking information,
2799   // _vo == UseNextMarking -> use "next" marking information,
2800   // _vo == UseMarkWord    -> use mark word from object header.
2801   VerifyRootsClosure(VerifyOption vo) :
2802     _g1h(G1CollectedHeap::heap()),
2803     _vo(vo),
2804     _failures(false) { }
2805 
2806   bool failures() { return _failures; }
2807 
2808   template <class T> void do_oop_nv(T* p) {
2809     T heap_oop = oopDesc::load_heap_oop(p);
2810     if (!oopDesc::is_null(heap_oop)) {
2811       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2812       if (_g1h->is_obj_dead_cond(obj, _vo)) {
2813         gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
2814                               "points to dead obj "PTR_FORMAT, p, (void*) obj);
2815         if (_vo == VerifyOption_G1UseMarkWord) {
2816           gclog_or_tty->print_cr("  Mark word: "PTR_FORMAT, (void*)(obj->mark()));
2817         }
2818         obj->print_on(gclog_or_tty);
2819         _failures = true;
2820       }
2821     }
2822   }
2823 
2824   void do_oop(oop* p)       { do_oop_nv(p); }
2825   void do_oop(narrowOop* p) { do_oop_nv(p); }
2826 };
2827 
2828 class G1VerifyCodeRootOopClosure: public OopClosure {
2829   G1CollectedHeap* _g1h;
2830   OopClosure* _root_cl;
2831   nmethod* _nm;
2832   VerifyOption _vo;
2833   bool _failures;
2834 
2835   template <class T> void do_oop_work(T* p) {
2836     // First verify that this root is live
2837     _root_cl->do_oop(p);
2838 
2839     if (!G1VerifyHeapRegionCodeRoots) {
2840       // We're not verifying the code roots attached to heap region.
2841       return;
2842     }
2843 
2844     // Don't check the code roots during marking verification in a full GC
2845     if (_vo == VerifyOption_G1UseMarkWord) {
2846       return;
2847     }
2848 
2849     // Now verify that the current nmethod (which contains p) is
2850     // in the code root list of the heap region containing the
2851     // object referenced by p.
2852 
2853     T heap_oop = oopDesc::load_heap_oop(p);
2854     if (!oopDesc::is_null(heap_oop)) {
2855       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2856 
2857       // Now fetch the region containing the object
2858       HeapRegion* hr = _g1h->heap_region_containing(obj);
2859       HeapRegionRemSet* hrrs = hr->rem_set();
2860       // Verify that the strong code root list for this region
2861       // contains the nmethod
2862       if (!hrrs->strong_code_roots_list_contains(_nm)) {
2863         gclog_or_tty->print_cr("Code root location "PTR_FORMAT" "
2864                               "from nmethod "PTR_FORMAT" not in strong "
2865                               "code roots for region ["PTR_FORMAT","PTR_FORMAT")",
2866                               p, _nm, hr->bottom(), hr->end());
2867         _failures = true;
2868       }
2869     }
2870   }
2871 
2872 public:
2873   G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo):
2874     _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {}
2875 
2876   void do_oop(oop* p) { do_oop_work(p); }
2877   void do_oop(narrowOop* p) { do_oop_work(p); }
2878 
2879   void set_nmethod(nmethod* nm) { _nm = nm; }
2880   bool failures() { return _failures; }
2881 };
2882 
2883 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure {
2884   G1VerifyCodeRootOopClosure* _oop_cl;
2885 
2886 public:
2887   G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl):
2888     _oop_cl(oop_cl) {}
2889 
2890   void do_code_blob(CodeBlob* cb) {
2891     nmethod* nm = cb->as_nmethod_or_null();
2892     if (nm != NULL) {
2893       _oop_cl->set_nmethod(nm);
2894       nm->oops_do(_oop_cl);
2895     }
2896   }
2897 };
2898 
2899 class YoungRefCounterClosure : public OopClosure {
2900   G1CollectedHeap* _g1h;
2901   int              _count;
2902  public:
2903   YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {}
2904   void do_oop(oop* p)       { if (_g1h->is_in_young(*p)) { _count++; } }
2905   void do_oop(narrowOop* p) { ShouldNotReachHere(); }
2906 
2907   int count() { return _count; }
2908   void reset_count() { _count = 0; };
2909 };
2910 
2911 class VerifyKlassClosure: public KlassClosure {
2912   YoungRefCounterClosure _young_ref_counter_closure;
2913   OopClosure *_oop_closure;
2914  public:
2915   VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {}
2916   void do_klass(Klass* k) {
2917     k->oops_do(_oop_closure);
2918 
2919     _young_ref_counter_closure.reset_count();
2920     k->oops_do(&_young_ref_counter_closure);
2921     if (_young_ref_counter_closure.count() > 0) {
2922       guarantee(k->has_modified_oops(), err_msg("Klass " PTR_FORMAT ", has young refs but is not dirty.", k));
2923     }
2924   }
2925 };
2926 
2927 class VerifyLivenessOopClosure: public OopClosure {
2928   G1CollectedHeap* _g1h;
2929   VerifyOption _vo;
2930 public:
2931   VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
2932     _g1h(g1h), _vo(vo)
2933   { }
2934   void do_oop(narrowOop *p) { do_oop_work(p); }
2935   void do_oop(      oop *p) { do_oop_work(p); }
2936 
2937   template <class T> void do_oop_work(T *p) {
2938     oop obj = oopDesc::load_decode_heap_oop(p);
2939     guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
2940               "Dead object referenced by a not dead object");
2941   }
2942 };
2943 
2944 class VerifyObjsInRegionClosure: public ObjectClosure {
2945 private:
2946   G1CollectedHeap* _g1h;
2947   size_t _live_bytes;
2948   HeapRegion *_hr;
2949   VerifyOption _vo;
2950 public:
2951   // _vo == UsePrevMarking -> use "prev" marking information,
2952   // _vo == UseNextMarking -> use "next" marking information,
2953   // _vo == UseMarkWord    -> use mark word from object header.
2954   VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
2955     : _live_bytes(0), _hr(hr), _vo(vo) {
2956     _g1h = G1CollectedHeap::heap();
2957   }
2958   void do_object(oop o) {
2959     VerifyLivenessOopClosure isLive(_g1h, _vo);
2960     assert(o != NULL, "Huh?");
2961     if (!_g1h->is_obj_dead_cond(o, _vo)) {
2962       // If the object is alive according to the mark word,
2963       // then verify that the marking information agrees.
2964       // Note we can't verify the contra-positive of the
2965       // above: if the object is dead (according to the mark
2966       // word), it may not be marked, or may have been marked
2967       // but has since became dead, or may have been allocated
2968       // since the last marking.
2969       if (_vo == VerifyOption_G1UseMarkWord) {
2970         guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
2971       }
2972 
2973       o->oop_iterate_no_header(&isLive);
2974       if (!_hr->obj_allocated_since_prev_marking(o)) {
2975         size_t obj_size = o->size();    // Make sure we don't overflow
2976         _live_bytes += (obj_size * HeapWordSize);
2977       }
2978     }
2979   }
2980   size_t live_bytes() { return _live_bytes; }
2981 };
2982 
2983 class PrintObjsInRegionClosure : public ObjectClosure {
2984   HeapRegion *_hr;
2985   G1CollectedHeap *_g1;
2986 public:
2987   PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
2988     _g1 = G1CollectedHeap::heap();
2989   };
2990 
2991   void do_object(oop o) {
2992     if (o != NULL) {
2993       HeapWord *start = (HeapWord *) o;
2994       size_t word_sz = o->size();
2995       gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
2996                           " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
2997                           (void*) o, word_sz,
2998                           _g1->isMarkedPrev(o),
2999                           _g1->isMarkedNext(o),
3000                           _hr->obj_allocated_since_prev_marking(o));
3001       HeapWord *end = start + word_sz;
3002       HeapWord *cur;
3003       int *val;
3004       for (cur = start; cur < end; cur++) {
3005         val = (int *) cur;
3006         gclog_or_tty->print("\t "PTR_FORMAT":%d\n", val, *val);
3007       }
3008     }
3009   }
3010 };
3011 
3012 class VerifyRegionClosure: public HeapRegionClosure {
3013 private:
3014   bool             _par;
3015   VerifyOption     _vo;
3016   bool             _failures;
3017 public:
3018   // _vo == UsePrevMarking -> use "prev" marking information,
3019   // _vo == UseNextMarking -> use "next" marking information,
3020   // _vo == UseMarkWord    -> use mark word from object header.
3021   VerifyRegionClosure(bool par, VerifyOption vo)
3022     : _par(par),
3023       _vo(vo),
3024       _failures(false) {}
3025 
3026   bool failures() {
3027     return _failures;
3028   }
3029 
3030   bool doHeapRegion(HeapRegion* r) {
3031     if (!r->is_continues_humongous()) {
3032       bool failures = false;
3033       r->verify(_vo, &failures);
3034       if (failures) {
3035         _failures = true;
3036       } else {
3037         VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
3038         r->object_iterate(&not_dead_yet_cl);
3039         if (_vo != VerifyOption_G1UseNextMarking) {
3040           if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
3041             gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
3042                                    "max_live_bytes "SIZE_FORMAT" "
3043                                    "< calculated "SIZE_FORMAT,
3044                                    r->bottom(), r->end(),
3045                                    r->max_live_bytes(),
3046                                  not_dead_yet_cl.live_bytes());
3047             _failures = true;
3048           }
3049         } else {
3050           // When vo == UseNextMarking we cannot currently do a sanity
3051           // check on the live bytes as the calculation has not been
3052           // finalized yet.
3053         }
3054       }
3055     }
3056     return false; // stop the region iteration if we hit a failure
3057   }
3058 };
3059 
3060 // This is the task used for parallel verification of the heap regions
3061 
3062 class G1ParVerifyTask: public AbstractGangTask {
3063 private:
3064   G1CollectedHeap*  _g1h;
3065   VerifyOption      _vo;
3066   bool              _failures;
3067   HeapRegionClaimer _hrclaimer;
3068 
3069 public:
3070   // _vo == UsePrevMarking -> use "prev" marking information,
3071   // _vo == UseNextMarking -> use "next" marking information,
3072   // _vo == UseMarkWord    -> use mark word from object header.
3073   G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
3074       AbstractGangTask("Parallel verify task"),
3075       _g1h(g1h),
3076       _vo(vo),
3077       _failures(false),
3078       _hrclaimer(g1h->workers()->active_workers()) {}
3079 
3080   bool failures() {
3081     return _failures;
3082   }
3083 
3084   void work(uint worker_id) {
3085     HandleMark hm;
3086     VerifyRegionClosure blk(true, _vo);
3087     _g1h->heap_region_par_iterate(&blk, worker_id, &_hrclaimer);
3088     if (blk.failures()) {
3089       _failures = true;
3090     }
3091   }
3092 };
3093 
3094 void G1CollectedHeap::verify(bool silent, VerifyOption vo) {
3095   if (SafepointSynchronize::is_at_safepoint()) {
3096     assert(Thread::current()->is_VM_thread(),
3097            "Expected to be executed serially by the VM thread at this point");
3098 
3099     if (!silent) { gclog_or_tty->print("Roots "); }
3100     VerifyRootsClosure rootsCl(vo);
3101     VerifyKlassClosure klassCl(this, &rootsCl);
3102     CLDToKlassAndOopClosure cldCl(&klassCl, &rootsCl, false);
3103 
3104     // We apply the relevant closures to all the oops in the
3105     // system dictionary, class loader data graph, the string table
3106     // and the nmethods in the code cache.
3107     G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo);
3108     G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl);
3109 
3110     process_all_roots(true,            // activate StrongRootsScope
3111                       SO_AllCodeCache, // roots scanning options
3112                       &rootsCl,
3113                       &cldCl,
3114                       &blobsCl);
3115 
3116     bool failures = rootsCl.failures() || codeRootsCl.failures();
3117 
3118     if (vo != VerifyOption_G1UseMarkWord) {
3119       // If we're verifying during a full GC then the region sets
3120       // will have been torn down at the start of the GC. Therefore
3121       // verifying the region sets will fail. So we only verify
3122       // the region sets when not in a full GC.
3123       if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3124       verify_region_sets();
3125     }
3126 
3127     if (!silent) { gclog_or_tty->print("HeapRegions "); }
3128     if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3129 
3130       G1ParVerifyTask task(this, vo);
3131       assert(UseDynamicNumberOfGCThreads ||
3132         workers()->active_workers() == workers()->total_workers(),
3133         "If not dynamic should be using all the workers");
3134       int n_workers = workers()->active_workers();
3135       set_par_threads(n_workers);
3136       workers()->run_task(&task);
3137       set_par_threads(0);
3138       if (task.failures()) {
3139         failures = true;
3140       }
3141 
3142     } else {
3143       VerifyRegionClosure blk(false, vo);
3144       heap_region_iterate(&blk);
3145       if (blk.failures()) {
3146         failures = true;
3147       }
3148     }
3149 
3150     if (G1StringDedup::is_enabled()) {
3151       if (!silent) gclog_or_tty->print("StrDedup ");
3152       G1StringDedup::verify();
3153     }
3154 
3155     if (failures) {
3156       gclog_or_tty->print_cr("Heap:");
3157       // It helps to have the per-region information in the output to
3158       // help us track down what went wrong. This is why we call
3159       // print_extended_on() instead of print_on().
3160       print_extended_on(gclog_or_tty);
3161       gclog_or_tty->cr();
3162 #ifndef PRODUCT
3163       if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3164         concurrent_mark()->print_reachable("at-verification-failure",
3165                                            vo, false /* all */);
3166       }
3167 #endif
3168       gclog_or_tty->flush();
3169     }
3170     guarantee(!failures, "there should not have been any failures");
3171   } else {
3172     if (!silent) {
3173       gclog_or_tty->print("(SKIPPING Roots, HeapRegionSets, HeapRegions, RemSet");
3174       if (G1StringDedup::is_enabled()) {
3175         gclog_or_tty->print(", StrDedup");
3176       }
3177       gclog_or_tty->print(") ");
3178     }
3179   }
3180 }
3181 
3182 void G1CollectedHeap::verify(bool silent) {
3183   verify(silent, VerifyOption_G1UsePrevMarking);
3184 }
3185 
3186 double G1CollectedHeap::verify(bool guard, const char* msg) {
3187   double verify_time_ms = 0.0;
3188 
3189   if (guard && total_collections() >= VerifyGCStartAt) {
3190     double verify_start = os::elapsedTime();
3191     HandleMark hm;  // Discard invalid handles created during verification
3192     prepare_for_verify();
3193     Universe::verify(VerifyOption_G1UsePrevMarking, msg);
3194     verify_time_ms = (os::elapsedTime() - verify_start) * 1000;
3195   }
3196 
3197   return verify_time_ms;
3198 }
3199 
3200 void G1CollectedHeap::verify_before_gc() {
3201   double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:");
3202   g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms);
3203 }
3204 
3205 void G1CollectedHeap::verify_after_gc() {
3206   double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:");
3207   g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms);
3208 }
3209 
3210 class PrintRegionClosure: public HeapRegionClosure {
3211   outputStream* _st;
3212 public:
3213   PrintRegionClosure(outputStream* st) : _st(st) {}
3214   bool doHeapRegion(HeapRegion* r) {
3215     r->print_on(_st);
3216     return false;
3217   }
3218 };
3219 
3220 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3221                                        const HeapRegion* hr,
3222                                        const VerifyOption vo) const {
3223   switch (vo) {
3224   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
3225   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
3226   case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked();
3227   default:                            ShouldNotReachHere();
3228   }
3229   return false; // keep some compilers happy
3230 }
3231 
3232 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3233                                        const VerifyOption vo) const {
3234   switch (vo) {
3235   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
3236   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
3237   case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked();
3238   default:                            ShouldNotReachHere();
3239   }
3240   return false; // keep some compilers happy
3241 }
3242 
3243 void G1CollectedHeap::print_on(outputStream* st) const {
3244   st->print(" %-20s", "garbage-first heap");
3245   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3246             capacity()/K, used_unlocked()/K);
3247   st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3248             _hrm.reserved().start(),
3249             _hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords,
3250             _hrm.reserved().end());
3251   st->cr();
3252   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3253   uint young_regions = _young_list->length();
3254   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3255             (size_t) young_regions * HeapRegion::GrainBytes / K);
3256   uint survivor_regions = g1_policy()->recorded_survivor_regions();
3257   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3258             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3259   st->cr();
3260   MetaspaceAux::print_on(st);
3261 }
3262 
3263 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3264   print_on(st);
3265 
3266   // Print the per-region information.
3267   st->cr();
3268   st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3269                "HS=humongous(starts), HC=humongous(continues), "
3270                "CS=collection set, F=free, TS=gc time stamp, "
3271                "PTAMS=previous top-at-mark-start, "
3272                "NTAMS=next top-at-mark-start)");
3273   PrintRegionClosure blk(st);
3274   heap_region_iterate(&blk);
3275 }
3276 
3277 void G1CollectedHeap::print_on_error(outputStream* st) const {
3278   this->CollectedHeap::print_on_error(st);
3279 
3280   if (_cm != NULL) {
3281     st->cr();
3282     _cm->print_on_error(st);
3283   }
3284 }
3285 
3286 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3287   workers()->print_worker_threads_on(st);
3288   _cmThread->print_on(st);
3289   st->cr();
3290   _cm->print_worker_threads_on(st);
3291   _cg1r->print_worker_threads_on(st);
3292   if (G1StringDedup::is_enabled()) {
3293     G1StringDedup::print_worker_threads_on(st);
3294   }
3295 }
3296 
3297 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3298   workers()->threads_do(tc);
3299   tc->do_thread(_cmThread);
3300   _cg1r->threads_do(tc);
3301   if (G1StringDedup::is_enabled()) {
3302     G1StringDedup::threads_do(tc);
3303   }
3304 }
3305 
3306 void G1CollectedHeap::print_tracing_info() const {
3307   // We'll overload this to mean "trace GC pause statistics."
3308   if (TraceYoungGenTime || TraceOldGenTime) {
3309     // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3310     // to that.
3311     g1_policy()->print_tracing_info();
3312   }
3313   if (G1SummarizeRSetStats) {
3314     g1_rem_set()->print_summary_info();
3315   }
3316   if (G1SummarizeConcMark) {
3317     concurrent_mark()->print_summary_info();
3318   }
3319   g1_policy()->print_yg_surv_rate_info();
3320   SpecializationStats::print();
3321 }
3322 
3323 #ifndef PRODUCT
3324 // Helpful for debugging RSet issues.
3325 
3326 class PrintRSetsClosure : public HeapRegionClosure {
3327 private:
3328   const char* _msg;
3329   size_t _occupied_sum;
3330 
3331 public:
3332   bool doHeapRegion(HeapRegion* r) {
3333     HeapRegionRemSet* hrrs = r->rem_set();
3334     size_t occupied = hrrs->occupied();
3335     _occupied_sum += occupied;
3336 
3337     gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3338                            HR_FORMAT_PARAMS(r));
3339     if (occupied == 0) {
3340       gclog_or_tty->print_cr("  RSet is empty");
3341     } else {
3342       hrrs->print();
3343     }
3344     gclog_or_tty->print_cr("----------");
3345     return false;
3346   }
3347 
3348   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3349     gclog_or_tty->cr();
3350     gclog_or_tty->print_cr("========================================");
3351     gclog_or_tty->print_cr("%s", msg);
3352     gclog_or_tty->cr();
3353   }
3354 
3355   ~PrintRSetsClosure() {
3356     gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3357     gclog_or_tty->print_cr("========================================");
3358     gclog_or_tty->cr();
3359   }
3360 };
3361 
3362 void G1CollectedHeap::print_cset_rsets() {
3363   PrintRSetsClosure cl("Printing CSet RSets");
3364   collection_set_iterate(&cl);
3365 }
3366 
3367 void G1CollectedHeap::print_all_rsets() {
3368   PrintRSetsClosure cl("Printing All RSets");;
3369   heap_region_iterate(&cl);
3370 }
3371 #endif // PRODUCT
3372 
3373 G1CollectedHeap* G1CollectedHeap::heap() {
3374   assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3375          "not a garbage-first heap");
3376   return _g1h;
3377 }
3378 
3379 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3380   // always_do_update_barrier = false;
3381   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3382   // Fill TLAB's and such
3383   accumulate_statistics_all_tlabs();
3384   ensure_parsability(true);
3385 
3386   if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) &&
3387       (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3388     g1_rem_set()->print_periodic_summary_info("Before GC RS summary");
3389   }
3390 }
3391 
3392 void G1CollectedHeap::gc_epilogue(bool full) {
3393 
3394   if (G1SummarizeRSetStats &&
3395       (G1SummarizeRSetStatsPeriod > 0) &&
3396       // we are at the end of the GC. Total collections has already been increased.
3397       ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) {
3398     g1_rem_set()->print_periodic_summary_info("After GC RS summary");
3399   }
3400 
3401   // FIXME: what is this about?
3402   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3403   // is set.
3404   COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3405                         "derived pointer present"));
3406   // always_do_update_barrier = true;
3407 
3408   resize_all_tlabs();
3409   allocation_context_stats().update(full);
3410 
3411   // We have just completed a GC. Update the soft reference
3412   // policy with the new heap occupancy
3413   Universe::update_heap_info_at_gc();
3414 }
3415 
3416 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3417                                                unsigned int gc_count_before,
3418                                                bool* succeeded,
3419                                                GCCause::Cause gc_cause) {
3420   assert_heap_not_locked_and_not_at_safepoint();
3421   g1_policy()->record_stop_world_start();
3422   VM_G1IncCollectionPause op(gc_count_before,
3423                              word_size,
3424                              false, /* should_initiate_conc_mark */
3425                              g1_policy()->max_pause_time_ms(),
3426                              gc_cause);
3427 
3428   op.set_allocation_context(AllocationContext::current());
3429   VMThread::execute(&op);
3430 
3431   HeapWord* result = op.result();
3432   bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3433   assert(result == NULL || ret_succeeded,
3434          "the result should be NULL if the VM did not succeed");
3435   *succeeded = ret_succeeded;
3436 
3437   assert_heap_not_locked();
3438   return result;
3439 }
3440 
3441 void
3442 G1CollectedHeap::doConcurrentMark() {
3443   MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3444   if (!_cmThread->in_progress()) {
3445     _cmThread->set_started();
3446     CGC_lock->notify();
3447   }
3448 }
3449 
3450 size_t G1CollectedHeap::pending_card_num() {
3451   size_t extra_cards = 0;
3452   JavaThread *curr = Threads::first();
3453   while (curr != NULL) {
3454     DirtyCardQueue& dcq = curr->dirty_card_queue();
3455     extra_cards += dcq.size();
3456     curr = curr->next();
3457   }
3458   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3459   size_t buffer_size = dcqs.buffer_size();
3460   size_t buffer_num = dcqs.completed_buffers_num();
3461 
3462   // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
3463   // in bytes - not the number of 'entries'. We need to convert
3464   // into a number of cards.
3465   return (buffer_size * buffer_num + extra_cards) / oopSize;
3466 }
3467 
3468 size_t G1CollectedHeap::cards_scanned() {
3469   return g1_rem_set()->cardsScanned();
3470 }
3471 
3472 bool G1CollectedHeap::humongous_region_is_always_live(uint index) {
3473   HeapRegion* region = region_at(index);
3474   assert(region->is_starts_humongous(), "Must start a humongous object");
3475   return oop(region->bottom())->is_objArray() || !region->rem_set()->is_empty();
3476 }
3477 
3478 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
3479  private:
3480   size_t _total_humongous;
3481   size_t _candidate_humongous;
3482 
3483   DirtyCardQueue _dcq;
3484 
3485   bool humongous_region_is_candidate(uint index) {
3486     HeapRegion* region = G1CollectedHeap::heap()->region_at(index);
3487     assert(region->is_starts_humongous(), "Must start a humongous object");
3488     HeapRegionRemSet* const rset = region->rem_set();
3489     bool const allow_stale_refs = G1EagerReclaimHumongousObjectsWithStaleRefs;
3490     return !oop(region->bottom())->is_objArray() &&
3491            ((allow_stale_refs && rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries)) ||
3492             (!allow_stale_refs && rset->is_empty()));
3493   }
3494 
3495  public:
3496   RegisterHumongousWithInCSetFastTestClosure()
3497   : _total_humongous(0),
3498     _candidate_humongous(0),
3499     _dcq(&JavaThread::dirty_card_queue_set()) {
3500   }
3501 
3502   virtual bool doHeapRegion(HeapRegion* r) {
3503     if (!r->is_starts_humongous()) {
3504       return false;
3505     }
3506     G1CollectedHeap* g1h = G1CollectedHeap::heap();
3507 
3508     uint region_idx = r->hrm_index();
3509     bool is_candidate = humongous_region_is_candidate(region_idx);
3510     // Is_candidate already filters out humongous object with large remembered sets.
3511     // If we have a humongous object with a few remembered sets, we simply flush these
3512     // remembered set entries into the DCQS. That will result in automatic
3513     // re-evaluation of their remembered set entries during the following evacuation
3514     // phase.
3515     if (is_candidate) {
3516       if (!r->rem_set()->is_empty()) {
3517         guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
3518                   "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
3519         G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set();
3520         HeapRegionRemSetIterator hrrs(r->rem_set());
3521         size_t card_index;
3522         while (hrrs.has_next(card_index)) {
3523           jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index);
3524           if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
3525             *card_ptr = CardTableModRefBS::dirty_card_val();
3526             _dcq.enqueue(card_ptr);
3527           }
3528         }
3529         r->rem_set()->clear_locked();
3530       }
3531       assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
3532       g1h->register_humongous_region_with_in_cset_fast_test(region_idx);
3533       _candidate_humongous++;
3534     }
3535     _total_humongous++;
3536 
3537     return false;
3538   }
3539 
3540   size_t total_humongous() const { return _total_humongous; }
3541   size_t candidate_humongous() const { return _candidate_humongous; }
3542 
3543   void flush_rem_set_entries() { _dcq.flush(); }
3544 };
3545 
3546 void G1CollectedHeap::register_humongous_regions_with_in_cset_fast_test() {
3547   if (!G1EagerReclaimHumongousObjects) {
3548     g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
3549     return;
3550   }
3551   double time = os::elapsed_counter();
3552 
3553   RegisterHumongousWithInCSetFastTestClosure cl;
3554   heap_region_iterate(&cl);
3555 
3556   time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
3557   g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
3558                                                                   cl.total_humongous(),
3559                                                                   cl.candidate_humongous());
3560   _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
3561 
3562   if (_has_humongous_reclaim_candidates || G1TraceEagerReclaimHumongousObjects) {
3563     clear_humongous_is_live_table();
3564   }
3565 
3566   // Finally flush all remembered set entries to re-check into the global DCQS.
3567   cl.flush_rem_set_entries();
3568 }
3569 
3570 void
3571 G1CollectedHeap::setup_surviving_young_words() {
3572   assert(_surviving_young_words == NULL, "pre-condition");
3573   uint array_length = g1_policy()->young_cset_region_length();
3574   _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3575   if (_surviving_young_words == NULL) {
3576     vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR,
3577                           "Not enough space for young surv words summary.");
3578   }
3579   memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3580 #ifdef ASSERT
3581   for (uint i = 0;  i < array_length; ++i) {
3582     assert( _surviving_young_words[i] == 0, "memset above" );
3583   }
3584 #endif // !ASSERT
3585 }
3586 
3587 void
3588 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3589   MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3590   uint array_length = g1_policy()->young_cset_region_length();
3591   for (uint i = 0; i < array_length; ++i) {
3592     _surviving_young_words[i] += surv_young_words[i];
3593   }
3594 }
3595 
3596 void
3597 G1CollectedHeap::cleanup_surviving_young_words() {
3598   guarantee( _surviving_young_words != NULL, "pre-condition" );
3599   FREE_C_HEAP_ARRAY(size_t, _surviving_young_words);
3600   _surviving_young_words = NULL;
3601 }
3602 
3603 #ifdef ASSERT
3604 class VerifyCSetClosure: public HeapRegionClosure {
3605 public:
3606   bool doHeapRegion(HeapRegion* hr) {
3607     // Here we check that the CSet region's RSet is ready for parallel
3608     // iteration. The fields that we'll verify are only manipulated
3609     // when the region is part of a CSet and is collected. Afterwards,
3610     // we reset these fields when we clear the region's RSet (when the
3611     // region is freed) so they are ready when the region is
3612     // re-allocated. The only exception to this is if there's an
3613     // evacuation failure and instead of freeing the region we leave
3614     // it in the heap. In that case, we reset these fields during
3615     // evacuation failure handling.
3616     guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3617 
3618     // Here's a good place to add any other checks we'd like to
3619     // perform on CSet regions.
3620     return false;
3621   }
3622 };
3623 #endif // ASSERT
3624 
3625 #if TASKQUEUE_STATS
3626 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3627   st->print_raw_cr("GC Task Stats");
3628   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3629   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3630 }
3631 
3632 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3633   print_taskqueue_stats_hdr(st);
3634 
3635   TaskQueueStats totals;
3636   const int n = workers()->total_workers();
3637   for (int i = 0; i < n; ++i) {
3638     st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3639     totals += task_queue(i)->stats;
3640   }
3641   st->print_raw("tot "); totals.print(st); st->cr();
3642 
3643   DEBUG_ONLY(totals.verify());
3644 }
3645 
3646 void G1CollectedHeap::reset_taskqueue_stats() {
3647   const int n = workers()->total_workers();
3648   for (int i = 0; i < n; ++i) {
3649     task_queue(i)->stats.reset();
3650   }
3651 }
3652 #endif // TASKQUEUE_STATS
3653 
3654 void G1CollectedHeap::log_gc_header() {
3655   if (!G1Log::fine()) {
3656     return;
3657   }
3658 
3659   gclog_or_tty->gclog_stamp(_gc_tracer_stw->gc_id());
3660 
3661   GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
3662     .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)")
3663     .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : "");
3664 
3665   gclog_or_tty->print("[%s", (const char*)gc_cause_str);
3666 }
3667 
3668 void G1CollectedHeap::log_gc_footer(double pause_time_sec) {
3669   if (!G1Log::fine()) {
3670     return;
3671   }
3672 
3673   if (G1Log::finer()) {
3674     if (evacuation_failed()) {
3675       gclog_or_tty->print(" (to-space exhausted)");
3676     }
3677     gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3678     g1_policy()->phase_times()->note_gc_end();
3679     g1_policy()->phase_times()->print(pause_time_sec);
3680     g1_policy()->print_detailed_heap_transition();
3681   } else {
3682     if (evacuation_failed()) {
3683       gclog_or_tty->print("--");
3684     }
3685     g1_policy()->print_heap_transition();
3686     gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3687   }
3688   gclog_or_tty->flush();
3689 }
3690 
3691 bool
3692 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3693   assert_at_safepoint(true /* should_be_vm_thread */);
3694   guarantee(!is_gc_active(), "collection is not reentrant");
3695 
3696   if (GC_locker::check_active_before_gc()) {
3697     return false;
3698   }
3699 
3700   _gc_timer_stw->register_gc_start();
3701 
3702   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3703 
3704   SvcGCMarker sgcm(SvcGCMarker::MINOR);
3705   ResourceMark rm;
3706 
3707   print_heap_before_gc();
3708   trace_heap_before_gc(_gc_tracer_stw);
3709 
3710   verify_region_sets_optional();
3711   verify_dirty_young_regions();
3712 
3713   // This call will decide whether this pause is an initial-mark
3714   // pause. If it is, during_initial_mark_pause() will return true
3715   // for the duration of this pause.
3716   g1_policy()->decide_on_conc_mark_initiation();
3717 
3718   // We do not allow initial-mark to be piggy-backed on a mixed GC.
3719   assert(!g1_policy()->during_initial_mark_pause() ||
3720           g1_policy()->gcs_are_young(), "sanity");
3721 
3722   // We also do not allow mixed GCs during marking.
3723   assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3724 
3725   // Record whether this pause is an initial mark. When the current
3726   // thread has completed its logging output and it's safe to signal
3727   // the CM thread, the flag's value in the policy has been reset.
3728   bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3729 
3730   // Inner scope for scope based logging, timers, and stats collection
3731   {
3732     EvacuationInfo evacuation_info;
3733 
3734     if (g1_policy()->during_initial_mark_pause()) {
3735       // We are about to start a marking cycle, so we increment the
3736       // full collection counter.
3737       increment_old_marking_cycles_started();
3738       register_concurrent_cycle_start(_gc_timer_stw->gc_start());
3739     }
3740 
3741     _gc_tracer_stw->report_yc_type(yc_type());
3742 
3743     TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3744 
3745     int active_workers = workers()->active_workers();
3746     double pause_start_sec = os::elapsedTime();
3747     g1_policy()->phase_times()->note_gc_start(active_workers);
3748     log_gc_header();
3749 
3750     TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3751     TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3752 
3753     // If the secondary_free_list is not empty, append it to the
3754     // free_list. No need to wait for the cleanup operation to finish;
3755     // the region allocation code will check the secondary_free_list
3756     // and wait if necessary. If the G1StressConcRegionFreeing flag is
3757     // set, skip this step so that the region allocation code has to
3758     // get entries from the secondary_free_list.
3759     if (!G1StressConcRegionFreeing) {
3760       append_secondary_free_list_if_not_empty_with_lock();
3761     }
3762 
3763     assert(check_young_list_well_formed(), "young list should be well formed");
3764 
3765     // Don't dynamically change the number of GC threads this early.  A value of
3766     // 0 is used to indicate serial work.  When parallel work is done,
3767     // it will be set.
3768 
3769     { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3770       IsGCActiveMark x;
3771 
3772       gc_prologue(false);
3773       increment_total_collections(false /* full gc */);
3774       increment_gc_time_stamp();
3775 
3776       verify_before_gc();
3777 
3778       check_bitmaps("GC Start");
3779 
3780       COMPILER2_PRESENT(DerivedPointerTable::clear());
3781 
3782       // Please see comment in g1CollectedHeap.hpp and
3783       // G1CollectedHeap::ref_processing_init() to see how
3784       // reference processing currently works in G1.
3785 
3786       // Enable discovery in the STW reference processor
3787       ref_processor_stw()->enable_discovery();
3788 
3789       {
3790         // We want to temporarily turn off discovery by the
3791         // CM ref processor, if necessary, and turn it back on
3792         // on again later if we do. Using a scoped
3793         // NoRefDiscovery object will do this.
3794         NoRefDiscovery no_cm_discovery(ref_processor_cm());
3795 
3796         // Forget the current alloc region (we might even choose it to be part
3797         // of the collection set!).
3798         _allocator->release_mutator_alloc_region();
3799 
3800         // We should call this after we retire the mutator alloc
3801         // region(s) so that all the ALLOC / RETIRE events are generated
3802         // before the start GC event.
3803         _hr_printer.start_gc(false /* full */, (size_t) total_collections());
3804 
3805         // This timing is only used by the ergonomics to handle our pause target.
3806         // It is unclear why this should not include the full pause. We will
3807         // investigate this in CR 7178365.
3808         //
3809         // Preserving the old comment here if that helps the investigation:
3810         //
3811         // The elapsed time induced by the start time below deliberately elides
3812         // the possible verification above.
3813         double sample_start_time_sec = os::elapsedTime();
3814 
3815 #if YOUNG_LIST_VERBOSE
3816         gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
3817         _young_list->print();
3818         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3819 #endif // YOUNG_LIST_VERBOSE
3820 
3821         g1_policy()->record_collection_pause_start(sample_start_time_sec);
3822 
3823         double scan_wait_start = os::elapsedTime();
3824         // We have to wait until the CM threads finish scanning the
3825         // root regions as it's the only way to ensure that all the
3826         // objects on them have been correctly scanned before we start
3827         // moving them during the GC.
3828         bool waited = _cm->root_regions()->wait_until_scan_finished();
3829         double wait_time_ms = 0.0;
3830         if (waited) {
3831           double scan_wait_end = os::elapsedTime();
3832           wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
3833         }
3834         g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
3835 
3836 #if YOUNG_LIST_VERBOSE
3837         gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
3838         _young_list->print();
3839 #endif // YOUNG_LIST_VERBOSE
3840 
3841         if (g1_policy()->during_initial_mark_pause()) {
3842           concurrent_mark()->checkpointRootsInitialPre();
3843         }
3844 
3845 #if YOUNG_LIST_VERBOSE
3846         gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
3847         _young_list->print();
3848         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3849 #endif // YOUNG_LIST_VERBOSE
3850 
3851         g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info);
3852 
3853         register_humongous_regions_with_in_cset_fast_test();
3854 
3855         assert(check_cset_fast_test(), "Inconsistency in the InCSetState table.");
3856 
3857         _cm->note_start_of_gc();
3858         // We should not verify the per-thread SATB buffers given that
3859         // we have not filtered them yet (we'll do so during the
3860         // GC). We also call this after finalize_cset() to
3861         // ensure that the CSet has been finalized.
3862         _cm->verify_no_cset_oops(true  /* verify_stacks */,
3863                                  true  /* verify_enqueued_buffers */,
3864                                  false /* verify_thread_buffers */,
3865                                  true  /* verify_fingers */);
3866 
3867         if (_hr_printer.is_active()) {
3868           HeapRegion* hr = g1_policy()->collection_set();
3869           while (hr != NULL) {
3870             _hr_printer.cset(hr);
3871             hr = hr->next_in_collection_set();
3872           }
3873         }
3874 
3875 #ifdef ASSERT
3876         VerifyCSetClosure cl;
3877         collection_set_iterate(&cl);
3878 #endif // ASSERT
3879 
3880         setup_surviving_young_words();
3881 
3882         // Initialize the GC alloc regions.
3883         _allocator->init_gc_alloc_regions(evacuation_info);
3884 
3885         // Actually do the work...
3886         evacuate_collection_set(evacuation_info);
3887 
3888         // We do this to mainly verify the per-thread SATB buffers
3889         // (which have been filtered by now) since we didn't verify
3890         // them earlier. No point in re-checking the stacks / enqueued
3891         // buffers given that the CSet has not changed since last time
3892         // we checked.
3893         _cm->verify_no_cset_oops(false /* verify_stacks */,
3894                                  false /* verify_enqueued_buffers */,
3895                                  true  /* verify_thread_buffers */,
3896                                  true  /* verify_fingers */);
3897 
3898         free_collection_set(g1_policy()->collection_set(), evacuation_info);
3899 
3900         eagerly_reclaim_humongous_regions();
3901 
3902         g1_policy()->clear_collection_set();
3903 
3904         cleanup_surviving_young_words();
3905 
3906         // Start a new incremental collection set for the next pause.
3907         g1_policy()->start_incremental_cset_building();
3908 
3909         clear_cset_fast_test();
3910 
3911         _young_list->reset_sampled_info();
3912 
3913         // Don't check the whole heap at this point as the
3914         // GC alloc regions from this pause have been tagged
3915         // as survivors and moved on to the survivor list.
3916         // Survivor regions will fail the !is_young() check.
3917         assert(check_young_list_empty(false /* check_heap */),
3918           "young list should be empty");
3919 
3920 #if YOUNG_LIST_VERBOSE
3921         gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
3922         _young_list->print();
3923 #endif // YOUNG_LIST_VERBOSE
3924 
3925         g1_policy()->record_survivor_regions(_young_list->survivor_length(),
3926                                              _young_list->first_survivor_region(),
3927                                              _young_list->last_survivor_region());
3928 
3929         _young_list->reset_auxilary_lists();
3930 
3931         if (evacuation_failed()) {
3932           _allocator->set_used(recalculate_used());
3933           uint n_queues = MAX2((int)ParallelGCThreads, 1);
3934           for (uint i = 0; i < n_queues; i++) {
3935             if (_evacuation_failed_info_array[i].has_failed()) {
3936               _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
3937             }
3938           }
3939         } else {
3940           // The "used" of the the collection set have already been subtracted
3941           // when they were freed.  Add in the bytes evacuated.
3942           _allocator->increase_used(g1_policy()->bytes_copied_during_gc());
3943         }
3944 
3945         if (g1_policy()->during_initial_mark_pause()) {
3946           // We have to do this before we notify the CM threads that
3947           // they can start working to make sure that all the
3948           // appropriate initialization is done on the CM object.
3949           concurrent_mark()->checkpointRootsInitialPost();
3950           set_marking_started();
3951           // Note that we don't actually trigger the CM thread at
3952           // this point. We do that later when we're sure that
3953           // the current thread has completed its logging output.
3954         }
3955 
3956         allocate_dummy_regions();
3957 
3958 #if YOUNG_LIST_VERBOSE
3959         gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
3960         _young_list->print();
3961         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3962 #endif // YOUNG_LIST_VERBOSE
3963 
3964         _allocator->init_mutator_alloc_region();
3965 
3966         {
3967           size_t expand_bytes = g1_policy()->expansion_amount();
3968           if (expand_bytes > 0) {
3969             size_t bytes_before = capacity();
3970             // No need for an ergo verbose message here,
3971             // expansion_amount() does this when it returns a value > 0.
3972             if (!expand(expand_bytes)) {
3973               // We failed to expand the heap. Cannot do anything about it.
3974             }
3975           }
3976         }
3977 
3978         // We redo the verification but now wrt to the new CSet which
3979         // has just got initialized after the previous CSet was freed.
3980         _cm->verify_no_cset_oops(true  /* verify_stacks */,
3981                                  true  /* verify_enqueued_buffers */,
3982                                  true  /* verify_thread_buffers */,
3983                                  true  /* verify_fingers */);
3984         _cm->note_end_of_gc();
3985 
3986         // This timing is only used by the ergonomics to handle our pause target.
3987         // It is unclear why this should not include the full pause. We will
3988         // investigate this in CR 7178365.
3989         double sample_end_time_sec = os::elapsedTime();
3990         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3991         g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info);
3992 
3993         MemoryService::track_memory_usage();
3994 
3995         // In prepare_for_verify() below we'll need to scan the deferred
3996         // update buffers to bring the RSets up-to-date if
3997         // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
3998         // the update buffers we'll probably need to scan cards on the
3999         // regions we just allocated to (i.e., the GC alloc
4000         // regions). However, during the last GC we called
4001         // set_saved_mark() on all the GC alloc regions, so card
4002         // scanning might skip the [saved_mark_word()...top()] area of
4003         // those regions (i.e., the area we allocated objects into
4004         // during the last GC). But it shouldn't. Given that
4005         // saved_mark_word() is conditional on whether the GC time stamp
4006         // on the region is current or not, by incrementing the GC time
4007         // stamp here we invalidate all the GC time stamps on all the
4008         // regions and saved_mark_word() will simply return top() for
4009         // all the regions. This is a nicer way of ensuring this rather
4010         // than iterating over the regions and fixing them. In fact, the
4011         // GC time stamp increment here also ensures that
4012         // saved_mark_word() will return top() between pauses, i.e.,
4013         // during concurrent refinement. So we don't need the
4014         // is_gc_active() check to decided which top to use when
4015         // scanning cards (see CR 7039627).
4016         increment_gc_time_stamp();
4017 
4018         verify_after_gc();
4019         check_bitmaps("GC End");
4020 
4021         assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
4022         ref_processor_stw()->verify_no_references_recorded();
4023 
4024         // CM reference discovery will be re-enabled if necessary.
4025       }
4026 
4027       // We should do this after we potentially expand the heap so
4028       // that all the COMMIT events are generated before the end GC
4029       // event, and after we retire the GC alloc regions so that all
4030       // RETIRE events are generated before the end GC event.
4031       _hr_printer.end_gc(false /* full */, (size_t) total_collections());
4032 
4033 #ifdef TRACESPINNING
4034       ParallelTaskTerminator::print_termination_counts();
4035 #endif
4036 
4037       gc_epilogue(false);
4038     }
4039 
4040     // Print the remainder of the GC log output.
4041     log_gc_footer(os::elapsedTime() - pause_start_sec);
4042 
4043     // It is not yet to safe to tell the concurrent mark to
4044     // start as we have some optional output below. We don't want the
4045     // output from the concurrent mark thread interfering with this
4046     // logging output either.
4047 
4048     _hrm.verify_optional();
4049     verify_region_sets_optional();
4050 
4051     TASKQUEUE_STATS_ONLY(if (PrintTaskqueue) print_taskqueue_stats());
4052     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
4053 
4054     print_heap_after_gc();
4055     trace_heap_after_gc(_gc_tracer_stw);
4056 
4057     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
4058     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
4059     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
4060     // before any GC notifications are raised.
4061     g1mm()->update_sizes();
4062 
4063     _gc_tracer_stw->report_evacuation_info(&evacuation_info);
4064     _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
4065     _gc_timer_stw->register_gc_end();
4066     _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
4067   }
4068   // It should now be safe to tell the concurrent mark thread to start
4069   // without its logging output interfering with the logging output
4070   // that came from the pause.
4071 
4072   if (should_start_conc_mark) {
4073     // CAUTION: after the doConcurrentMark() call below,
4074     // the concurrent marking thread(s) could be running
4075     // concurrently with us. Make sure that anything after
4076     // this point does not assume that we are the only GC thread
4077     // running. Note: of course, the actual marking work will
4078     // not start until the safepoint itself is released in
4079     // SuspendibleThreadSet::desynchronize().
4080     doConcurrentMark();
4081   }
4082 
4083   return true;
4084 }
4085 
4086 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4087   _drain_in_progress = false;
4088   set_evac_failure_closure(cl);
4089   _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4090 }
4091 
4092 void G1CollectedHeap::finalize_for_evac_failure() {
4093   assert(_evac_failure_scan_stack != NULL &&
4094          _evac_failure_scan_stack->length() == 0,
4095          "Postcondition");
4096   assert(!_drain_in_progress, "Postcondition");
4097   delete _evac_failure_scan_stack;
4098   _evac_failure_scan_stack = NULL;
4099 }
4100 
4101 void G1CollectedHeap::remove_self_forwarding_pointers() {
4102   double remove_self_forwards_start = os::elapsedTime();
4103 
4104   set_par_threads();
4105   G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4106   workers()->run_task(&rsfp_task);
4107   set_par_threads(0);
4108 
4109   // Now restore saved marks, if any.
4110   assert(_objs_with_preserved_marks.size() ==
4111             _preserved_marks_of_objs.size(), "Both or none.");
4112   while (!_objs_with_preserved_marks.is_empty()) {
4113     oop obj = _objs_with_preserved_marks.pop();
4114     markOop m = _preserved_marks_of_objs.pop();
4115     obj->set_mark(m);
4116   }
4117   _objs_with_preserved_marks.clear(true);
4118   _preserved_marks_of_objs.clear(true);
4119 
4120   g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
4121 }
4122 
4123 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4124   _evac_failure_scan_stack->push(obj);
4125 }
4126 
4127 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4128   assert(_evac_failure_scan_stack != NULL, "precondition");
4129 
4130   while (_evac_failure_scan_stack->length() > 0) {
4131      oop obj = _evac_failure_scan_stack->pop();
4132      _evac_failure_closure->set_region(heap_region_containing(obj));
4133      obj->oop_iterate_backwards(_evac_failure_closure);
4134   }
4135 }
4136 
4137 oop
4138 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state,
4139                                                oop old) {
4140   assert(obj_in_cs(old),
4141          err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4142                  (HeapWord*) old));
4143   markOop m = old->mark();
4144   oop forward_ptr = old->forward_to_atomic(old);
4145   if (forward_ptr == NULL) {
4146     // Forward-to-self succeeded.
4147     assert(_par_scan_state != NULL, "par scan state");
4148     OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4149     uint queue_num = _par_scan_state->queue_num();
4150 
4151     _evacuation_failed = true;
4152     _evacuation_failed_info_array[queue_num].register_copy_failure(old->size());
4153     if (_evac_failure_closure != cl) {
4154       MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4155       assert(!_drain_in_progress,
4156              "Should only be true while someone holds the lock.");
4157       // Set the global evac-failure closure to the current thread's.
4158       assert(_evac_failure_closure == NULL, "Or locking has failed.");
4159       set_evac_failure_closure(cl);
4160       // Now do the common part.
4161       handle_evacuation_failure_common(old, m);
4162       // Reset to NULL.
4163       set_evac_failure_closure(NULL);
4164     } else {
4165       // The lock is already held, and this is recursive.
4166       assert(_drain_in_progress, "This should only be the recursive case.");
4167       handle_evacuation_failure_common(old, m);
4168     }
4169     return old;
4170   } else {
4171     // Forward-to-self failed. Either someone else managed to allocate
4172     // space for this object (old != forward_ptr) or they beat us in
4173     // self-forwarding it (old == forward_ptr).
4174     assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4175            err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4176                    "should not be in the CSet",
4177                    (HeapWord*) old, (HeapWord*) forward_ptr));
4178     return forward_ptr;
4179   }
4180 }
4181 
4182 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4183   preserve_mark_if_necessary(old, m);
4184 
4185   HeapRegion* r = heap_region_containing(old);
4186   if (!r->evacuation_failed()) {
4187     r->set_evacuation_failed(true);
4188     _hr_printer.evac_failure(r);
4189   }
4190 
4191   push_on_evac_failure_scan_stack(old);
4192 
4193   if (!_drain_in_progress) {
4194     // prevent recursion in copy_to_survivor_space()
4195     _drain_in_progress = true;
4196     drain_evac_failure_scan_stack();
4197     _drain_in_progress = false;
4198   }
4199 }
4200 
4201 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4202   assert(evacuation_failed(), "Oversaving!");
4203   // We want to call the "for_promotion_failure" version only in the
4204   // case of a promotion failure.
4205   if (m->must_be_preserved_for_promotion_failure(obj)) {
4206     _objs_with_preserved_marks.push(obj);
4207     _preserved_marks_of_objs.push(m);
4208   }
4209 }
4210 
4211 void G1ParCopyHelper::mark_object(oop obj) {
4212   assert(!_g1->heap_region_containing(obj)->in_collection_set(), "should not mark objects in the CSet");
4213 
4214   // We know that the object is not moving so it's safe to read its size.
4215   _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4216 }
4217 
4218 void G1ParCopyHelper::mark_forwarded_object(oop from_obj, oop to_obj) {
4219   assert(from_obj->is_forwarded(), "from obj should be forwarded");
4220   assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4221   assert(from_obj != to_obj, "should not be self-forwarded");
4222 
4223   assert(_g1->heap_region_containing(from_obj)->in_collection_set(), "from obj should be in the CSet");
4224   assert(!_g1->heap_region_containing(to_obj)->in_collection_set(), "should not mark objects in the CSet");
4225 
4226   // The object might be in the process of being copied by another
4227   // worker so we cannot trust that its to-space image is
4228   // well-formed. So we have to read its size from its from-space
4229   // image which we know should not be changing.
4230   _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4231 }
4232 
4233 template <class T>
4234 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) {
4235   if (_g1->heap_region_containing_raw(new_obj)->is_young()) {
4236     _scanned_klass->record_modified_oops();
4237   }
4238 }
4239 
4240 template <G1Barrier barrier, G1Mark do_mark_object>
4241 template <class T>
4242 void G1ParCopyClosure<barrier, do_mark_object>::do_oop_work(T* p) {
4243   T heap_oop = oopDesc::load_heap_oop(p);
4244 
4245   if (oopDesc::is_null(heap_oop)) {
4246     return;
4247   }
4248 
4249   oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
4250 
4251   assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4252 
4253   const InCSetState state = _g1->in_cset_state(obj);
4254   if (state.is_in_cset()) {
4255     oop forwardee;
4256     markOop m = obj->mark();
4257     if (m->is_marked()) {
4258       forwardee = (oop) m->decode_pointer();
4259     } else {
4260       forwardee = _par_scan_state->copy_to_survivor_space(state, obj, m);
4261     }
4262     assert(forwardee != NULL, "forwardee should not be NULL");
4263     oopDesc::encode_store_heap_oop(p, forwardee);
4264     if (do_mark_object != G1MarkNone && forwardee != obj) {
4265       // If the object is self-forwarded we don't need to explicitly
4266       // mark it, the evacuation failure protocol will do so.
4267       mark_forwarded_object(obj, forwardee);
4268     }
4269 
4270     if (barrier == G1BarrierKlass) {
4271       do_klass_barrier(p, forwardee);
4272     }
4273   } else {
4274     if (state.is_humongous()) {
4275       _g1->set_humongous_is_live(obj);
4276     }
4277     // The object is not in collection set. If we're a root scanning
4278     // closure during an initial mark pause then attempt to mark the object.
4279     if (do_mark_object == G1MarkFromRoot) {
4280       mark_object(obj);
4281     }
4282   }
4283 
4284   if (barrier == G1BarrierEvac) {
4285     _par_scan_state->update_rs(_from, p, _worker_id);
4286   }
4287 }
4288 
4289 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(oop* p);
4290 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(narrowOop* p);
4291 
4292 class G1ParEvacuateFollowersClosure : public VoidClosure {
4293 protected:
4294   G1CollectedHeap*              _g1h;
4295   G1ParScanThreadState*         _par_scan_state;
4296   RefToScanQueueSet*            _queues;
4297   ParallelTaskTerminator*       _terminator;
4298 
4299   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
4300   RefToScanQueueSet*      queues()         { return _queues; }
4301   ParallelTaskTerminator* terminator()     { return _terminator; }
4302 
4303 public:
4304   G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4305                                 G1ParScanThreadState* par_scan_state,
4306                                 RefToScanQueueSet* queues,
4307                                 ParallelTaskTerminator* terminator)
4308     : _g1h(g1h), _par_scan_state(par_scan_state),
4309       _queues(queues), _terminator(terminator) {}
4310 
4311   void do_void();
4312 
4313 private:
4314   inline bool offer_termination();
4315 };
4316 
4317 bool G1ParEvacuateFollowersClosure::offer_termination() {
4318   G1ParScanThreadState* const pss = par_scan_state();
4319   pss->start_term_time();
4320   const bool res = terminator()->offer_termination();
4321   pss->end_term_time();
4322   return res;
4323 }
4324 
4325 void G1ParEvacuateFollowersClosure::do_void() {
4326   G1ParScanThreadState* const pss = par_scan_state();
4327   pss->trim_queue();
4328   do {
4329     pss->steal_and_trim_queue(queues());
4330   } while (!offer_termination());
4331 }
4332 
4333 class G1KlassScanClosure : public KlassClosure {
4334  G1ParCopyHelper* _closure;
4335  bool             _process_only_dirty;
4336  int              _count;
4337  public:
4338   G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty)
4339       : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {}
4340   void do_klass(Klass* klass) {
4341     // If the klass has not been dirtied we know that there's
4342     // no references into  the young gen and we can skip it.
4343    if (!_process_only_dirty || klass->has_modified_oops()) {
4344       // Clean the klass since we're going to scavenge all the metadata.
4345       klass->clear_modified_oops();
4346 
4347       // Tell the closure that this klass is the Klass to scavenge
4348       // and is the one to dirty if oops are left pointing into the young gen.
4349       _closure->set_scanned_klass(klass);
4350 
4351       klass->oops_do(_closure);
4352 
4353       _closure->set_scanned_klass(NULL);
4354     }
4355     _count++;
4356   }
4357 };
4358 
4359 class G1CodeBlobClosure : public CodeBlobClosure {
4360   class HeapRegionGatheringOopClosure : public OopClosure {
4361     G1CollectedHeap* _g1h;
4362     OopClosure* _work;
4363     nmethod* _nm;
4364 
4365     template <typename T>
4366     void do_oop_work(T* p) {
4367       _work->do_oop(p);
4368       T oop_or_narrowoop = oopDesc::load_heap_oop(p);
4369       if (!oopDesc::is_null(oop_or_narrowoop)) {
4370         oop o = oopDesc::decode_heap_oop_not_null(oop_or_narrowoop);
4371         HeapRegion* hr = _g1h->heap_region_containing_raw(o);
4372         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");
4373         hr->add_strong_code_root(_nm);
4374       }
4375     }
4376 
4377   public:
4378     HeapRegionGatheringOopClosure(OopClosure* oc) : _g1h(G1CollectedHeap::heap()), _work(oc), _nm(NULL) {}
4379 
4380     void do_oop(oop* o) {
4381       do_oop_work(o);
4382     }
4383 
4384     void do_oop(narrowOop* o) {
4385       do_oop_work(o);
4386     }
4387 
4388     void set_nm(nmethod* nm) {
4389       _nm = nm;
4390     }
4391   };
4392 
4393   HeapRegionGatheringOopClosure _oc;
4394 public:
4395   G1CodeBlobClosure(OopClosure* oc) : _oc(oc) {}
4396 
4397   void do_code_blob(CodeBlob* cb) {
4398     nmethod* nm = cb->as_nmethod_or_null();
4399     if (nm != NULL) {
4400       if (!nm->test_set_oops_do_mark()) {
4401         _oc.set_nm(nm);
4402         nm->oops_do(&_oc);
4403         nm->fix_oop_relocations();
4404       }
4405     }
4406   }
4407 };
4408 
4409 class G1ParTask : public AbstractGangTask {
4410 protected:
4411   G1CollectedHeap*       _g1h;
4412   RefToScanQueueSet      *_queues;
4413   ParallelTaskTerminator _terminator;
4414   uint _n_workers;
4415 
4416   Mutex _stats_lock;
4417   Mutex* stats_lock() { return &_stats_lock; }
4418 
4419 public:
4420   G1ParTask(G1CollectedHeap* g1h, RefToScanQueueSet *task_queues)
4421     : AbstractGangTask("G1 collection"),
4422       _g1h(g1h),
4423       _queues(task_queues),
4424       _terminator(0, _queues),
4425       _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4426   {}
4427 
4428   RefToScanQueueSet* queues() { return _queues; }
4429 
4430   RefToScanQueue *work_queue(int i) {
4431     return queues()->queue(i);
4432   }
4433 
4434   ParallelTaskTerminator* terminator() { return &_terminator; }
4435 
4436   virtual void set_for_termination(int active_workers) {
4437     // This task calls set_n_termination() in par_non_clean_card_iterate_work()
4438     // in the young space (_par_seq_tasks) in the G1 heap
4439     // for SequentialSubTasksDone.
4440     // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap
4441     // both of which need setting by set_n_termination().
4442     _g1h->SharedHeap::set_n_termination(active_workers);
4443     _g1h->set_n_termination(active_workers);
4444     terminator()->reset_for_reuse(active_workers);
4445     _n_workers = active_workers;
4446   }
4447 
4448   // Helps out with CLD processing.
4449   //
4450   // During InitialMark we need to:
4451   // 1) Scavenge all CLDs for the young GC.
4452   // 2) Mark all objects directly reachable from strong CLDs.
4453   template <G1Mark do_mark_object>
4454   class G1CLDClosure : public CLDClosure {
4455     G1ParCopyClosure<G1BarrierNone,  do_mark_object>* _oop_closure;
4456     G1ParCopyClosure<G1BarrierKlass, do_mark_object>  _oop_in_klass_closure;
4457     G1KlassScanClosure                                _klass_in_cld_closure;
4458     bool                                              _claim;
4459 
4460    public:
4461     G1CLDClosure(G1ParCopyClosure<G1BarrierNone, do_mark_object>* oop_closure,
4462                  bool only_young, bool claim)
4463         : _oop_closure(oop_closure),
4464           _oop_in_klass_closure(oop_closure->g1(),
4465                                 oop_closure->pss(),
4466                                 oop_closure->rp()),
4467           _klass_in_cld_closure(&_oop_in_klass_closure, only_young),
4468           _claim(claim) {
4469 
4470     }
4471 
4472     void do_cld(ClassLoaderData* cld) {
4473       cld->oops_do(_oop_closure, &_klass_in_cld_closure, _claim);
4474     }
4475   };
4476 
4477   void work(uint worker_id) {
4478     if (worker_id >= _n_workers) return;  // no work needed this round
4479 
4480     double start_time_ms = os::elapsedTime() * 1000.0;
4481     _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms);
4482 
4483     {
4484       ResourceMark rm;
4485       HandleMark   hm;
4486 
4487       ReferenceProcessor*             rp = _g1h->ref_processor_stw();
4488 
4489       G1ParScanThreadState            pss(_g1h, worker_id, rp);
4490       G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
4491 
4492       pss.set_evac_failure_closure(&evac_failure_cl);
4493 
4494       bool only_young = _g1h->g1_policy()->gcs_are_young();
4495 
4496       // Non-IM young GC.
4497       G1ParCopyClosure<G1BarrierNone, G1MarkNone>             scan_only_root_cl(_g1h, &pss, rp);
4498       G1CLDClosure<G1MarkNone>                                scan_only_cld_cl(&scan_only_root_cl,
4499                                                                                only_young, // Only process dirty klasses.
4500                                                                                false);     // No need to claim CLDs.
4501       // IM young GC.
4502       //    Strong roots closures.
4503       G1ParCopyClosure<G1BarrierNone, G1MarkFromRoot>         scan_mark_root_cl(_g1h, &pss, rp);
4504       G1CLDClosure<G1MarkFromRoot>                            scan_mark_cld_cl(&scan_mark_root_cl,
4505                                                                                false, // Process all klasses.
4506                                                                                true); // Need to claim CLDs.
4507       //    Weak roots closures.
4508       G1ParCopyClosure<G1BarrierNone, G1MarkPromotedFromRoot> scan_mark_weak_root_cl(_g1h, &pss, rp);
4509       G1CLDClosure<G1MarkPromotedFromRoot>                    scan_mark_weak_cld_cl(&scan_mark_weak_root_cl,
4510                                                                                     false, // Process all klasses.
4511                                                                                     true); // Need to claim CLDs.
4512 
4513       G1CodeBlobClosure scan_only_code_cl(&scan_only_root_cl);
4514       G1CodeBlobClosure scan_mark_code_cl(&scan_mark_root_cl);
4515       // IM Weak code roots are handled later.
4516 
4517       OopClosure* strong_root_cl;
4518       OopClosure* weak_root_cl;
4519       CLDClosure* strong_cld_cl;
4520       CLDClosure* weak_cld_cl;
4521       CodeBlobClosure* strong_code_cl;
4522 
4523       if (_g1h->g1_policy()->during_initial_mark_pause()) {
4524         // We also need to mark copied objects.
4525         strong_root_cl = &scan_mark_root_cl;
4526         strong_cld_cl  = &scan_mark_cld_cl;
4527         strong_code_cl = &scan_mark_code_cl;
4528         if (ClassUnloadingWithConcurrentMark) {
4529           weak_root_cl = &scan_mark_weak_root_cl;
4530           weak_cld_cl  = &scan_mark_weak_cld_cl;
4531         } else {
4532           weak_root_cl = &scan_mark_root_cl;
4533           weak_cld_cl  = &scan_mark_cld_cl;
4534         }
4535       } else {
4536         strong_root_cl = &scan_only_root_cl;
4537         weak_root_cl   = &scan_only_root_cl;
4538         strong_cld_cl  = &scan_only_cld_cl;
4539         weak_cld_cl    = &scan_only_cld_cl;
4540         strong_code_cl = &scan_only_code_cl;
4541       }
4542 
4543 
4544       G1ParPushHeapRSClosure  push_heap_rs_cl(_g1h, &pss);
4545 
4546       pss.start_strong_roots();
4547       _g1h->g1_process_roots(strong_root_cl,
4548                              weak_root_cl,
4549                              &push_heap_rs_cl,
4550                              strong_cld_cl,
4551                              weak_cld_cl,
4552                              strong_code_cl,
4553                              worker_id);
4554 
4555       pss.end_strong_roots();
4556 
4557       {
4558         double start = os::elapsedTime();
4559         G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4560         evac.do_void();
4561         double elapsed_ms = (os::elapsedTime()-start)*1000.0;
4562         double term_ms = pss.term_time()*1000.0;
4563         _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms);
4564         _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts());
4565       }
4566       _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4567       _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4568 
4569       if (PrintTerminationStats) {
4570         MutexLocker x(stats_lock());
4571         pss.print_termination_stats(worker_id);
4572       }
4573 
4574       assert(pss.queue_is_empty(), "should be empty");
4575 
4576       // Close the inner scope so that the ResourceMark and HandleMark
4577       // destructors are executed here and are included as part of the
4578       // "GC Worker Time".
4579     }
4580 
4581     double end_time_ms = os::elapsedTime() * 1000.0;
4582     _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms);
4583   }
4584 };
4585 
4586 // *** Common G1 Evacuation Stuff
4587 
4588 // This method is run in a GC worker.
4589 
4590 void
4591 G1CollectedHeap::
4592 g1_process_roots(OopClosure* scan_non_heap_roots,
4593                  OopClosure* scan_non_heap_weak_roots,
4594                  G1ParPushHeapRSClosure* scan_rs,
4595                  CLDClosure* scan_strong_clds,
4596                  CLDClosure* scan_weak_clds,
4597                  CodeBlobClosure* scan_strong_code,
4598                  uint worker_i) {
4599 
4600   // First scan the shared roots.
4601   double ext_roots_start = os::elapsedTime();
4602   double closure_app_time_sec = 0.0;
4603 
4604   bool during_im = _g1h->g1_policy()->during_initial_mark_pause();
4605   bool trace_metadata = during_im && ClassUnloadingWithConcurrentMark;
4606 
4607   BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
4608   BufferingOopClosure buf_scan_non_heap_weak_roots(scan_non_heap_weak_roots);
4609 
4610   process_roots(false, // no scoping; this is parallel code
4611                 SharedHeap::SO_None,
4612                 &buf_scan_non_heap_roots,
4613                 &buf_scan_non_heap_weak_roots,
4614                 scan_strong_clds,
4615                 // Unloading Initial Marks handle the weak CLDs separately.
4616                 (trace_metadata ? NULL : scan_weak_clds),
4617                 scan_strong_code);
4618 
4619   // Now the CM ref_processor roots.
4620   if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
4621     // We need to treat the discovered reference lists of the
4622     // concurrent mark ref processor as roots and keep entries
4623     // (which are added by the marking threads) on them live
4624     // until they can be processed at the end of marking.
4625     ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
4626   }
4627 
4628   if (trace_metadata) {
4629     // Barrier to make sure all workers passed
4630     // the strong CLD and strong nmethods phases.
4631     active_strong_roots_scope()->wait_until_all_workers_done_with_threads(n_par_threads());
4632 
4633     // Now take the complement of the strong CLDs.
4634     ClassLoaderDataGraph::roots_cld_do(NULL, scan_weak_clds);
4635   }
4636 
4637   // Finish up any enqueued closure apps (attributed as object copy time).
4638   buf_scan_non_heap_roots.done();
4639   buf_scan_non_heap_weak_roots.done();
4640 
4641   double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds()
4642       + buf_scan_non_heap_weak_roots.closure_app_seconds();
4643 
4644   g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
4645 
4646   double ext_root_time_ms =
4647     ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0;
4648 
4649   g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
4650 
4651   // During conc marking we have to filter the per-thread SATB buffers
4652   // to make sure we remove any oops into the CSet (which will show up
4653   // as implicitly live).
4654   double satb_filtering_ms = 0.0;
4655   if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) {
4656     if (mark_in_progress()) {
4657       double satb_filter_start = os::elapsedTime();
4658 
4659       JavaThread::satb_mark_queue_set().filter_thread_buffers();
4660 
4661       satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0;
4662     }
4663   }
4664   g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms);
4665 
4666   // Now scan the complement of the collection set.
4667   G1CodeBlobClosure scavenge_cs_nmethods(scan_non_heap_weak_roots);
4668 
4669   g1_rem_set()->oops_into_collection_set_do(scan_rs, &scavenge_cs_nmethods, worker_i);
4670 
4671   _process_strong_tasks->all_tasks_completed();
4672 }
4673 
4674 class G1StringSymbolTableUnlinkTask : public AbstractGangTask {
4675 private:
4676   BoolObjectClosure* _is_alive;
4677   int _initial_string_table_size;
4678   int _initial_symbol_table_size;
4679 
4680   bool  _process_strings;
4681   int _strings_processed;
4682   int _strings_removed;
4683 
4684   bool  _process_symbols;
4685   int _symbols_processed;
4686   int _symbols_removed;
4687 
4688 public:
4689   G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) :
4690     AbstractGangTask("String/Symbol Unlinking"),
4691     _is_alive(is_alive),
4692     _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
4693     _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) {
4694 
4695     _initial_string_table_size = StringTable::the_table()->table_size();
4696     _initial_symbol_table_size = SymbolTable::the_table()->table_size();
4697     if (process_strings) {
4698       StringTable::clear_parallel_claimed_index();
4699     }
4700     if (process_symbols) {
4701       SymbolTable::clear_parallel_claimed_index();
4702     }
4703   }
4704 
4705   ~G1StringSymbolTableUnlinkTask() {
4706     guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size,
4707               err_msg("claim value %d after unlink less than initial string table size %d",
4708                       StringTable::parallel_claimed_index(), _initial_string_table_size));
4709     guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
4710               err_msg("claim value %d after unlink less than initial symbol table size %d",
4711                       SymbolTable::parallel_claimed_index(), _initial_symbol_table_size));
4712 
4713     if (G1TraceStringSymbolTableScrubbing) {
4714       gclog_or_tty->print_cr("Cleaned string and symbol table, "
4715                              "strings: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed, "
4716                              "symbols: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed",
4717                              strings_processed(), strings_removed(),
4718                              symbols_processed(), symbols_removed());
4719     }
4720   }
4721 
4722   void work(uint worker_id) {
4723     int strings_processed = 0;
4724     int strings_removed = 0;
4725     int symbols_processed = 0;
4726     int symbols_removed = 0;
4727     if (_process_strings) {
4728       StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
4729       Atomic::add(strings_processed, &_strings_processed);
4730       Atomic::add(strings_removed, &_strings_removed);
4731     }
4732     if (_process_symbols) {
4733       SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
4734       Atomic::add(symbols_processed, &_symbols_processed);
4735       Atomic::add(symbols_removed, &_symbols_removed);
4736     }
4737   }
4738 
4739   size_t strings_processed() const { return (size_t)_strings_processed; }
4740   size_t strings_removed()   const { return (size_t)_strings_removed; }
4741 
4742   size_t symbols_processed() const { return (size_t)_symbols_processed; }
4743   size_t symbols_removed()   const { return (size_t)_symbols_removed; }
4744 };
4745 
4746 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
4747 private:
4748   static Monitor* _lock;
4749 
4750   BoolObjectClosure* const _is_alive;
4751   const bool               _unloading_occurred;
4752   const uint               _num_workers;
4753 
4754   // Variables used to claim nmethods.
4755   nmethod* _first_nmethod;
4756   volatile nmethod* _claimed_nmethod;
4757 
4758   // The list of nmethods that need to be processed by the second pass.
4759   volatile nmethod* _postponed_list;
4760   volatile uint     _num_entered_barrier;
4761 
4762  public:
4763   G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
4764       _is_alive(is_alive),
4765       _unloading_occurred(unloading_occurred),
4766       _num_workers(num_workers),
4767       _first_nmethod(NULL),
4768       _claimed_nmethod(NULL),
4769       _postponed_list(NULL),
4770       _num_entered_barrier(0)
4771   {
4772     nmethod::increase_unloading_clock();
4773     // Get first alive nmethod
4774     NMethodIterator iter = NMethodIterator();
4775     if(iter.next_alive()) {
4776       _first_nmethod = iter.method();
4777     }
4778     _claimed_nmethod = (volatile nmethod*)_first_nmethod;
4779   }
4780 
4781   ~G1CodeCacheUnloadingTask() {
4782     CodeCache::verify_clean_inline_caches();
4783 
4784     CodeCache::set_needs_cache_clean(false);
4785     guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
4786 
4787     CodeCache::verify_icholder_relocations();
4788   }
4789 
4790  private:
4791   void add_to_postponed_list(nmethod* nm) {
4792       nmethod* old;
4793       do {
4794         old = (nmethod*)_postponed_list;
4795         nm->set_unloading_next(old);
4796       } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old);
4797   }
4798 
4799   void clean_nmethod(nmethod* nm) {
4800     bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
4801 
4802     if (postponed) {
4803       // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
4804       add_to_postponed_list(nm);
4805     }
4806 
4807     // Mark that this thread has been cleaned/unloaded.
4808     // After this call, it will be safe to ask if this nmethod was unloaded or not.
4809     nm->set_unloading_clock(nmethod::global_unloading_clock());
4810   }
4811 
4812   void clean_nmethod_postponed(nmethod* nm) {
4813     nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
4814   }
4815 
4816   static const int MaxClaimNmethods = 16;
4817 
4818   void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) {
4819     nmethod* first;
4820     NMethodIterator last;
4821 
4822     do {
4823       *num_claimed_nmethods = 0;
4824 
4825       first = (nmethod*)_claimed_nmethod;
4826       last = NMethodIterator(first);
4827 
4828       if (first != NULL) {
4829 
4830         for (int i = 0; i < MaxClaimNmethods; i++) {
4831           if (!last.next_alive()) {
4832             break;
4833           }
4834           claimed_nmethods[i] = last.method();
4835           (*num_claimed_nmethods)++;
4836         }
4837       }
4838 
4839     } while ((nmethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first);
4840   }
4841 
4842   nmethod* claim_postponed_nmethod() {
4843     nmethod* claim;
4844     nmethod* next;
4845 
4846     do {
4847       claim = (nmethod*)_postponed_list;
4848       if (claim == NULL) {
4849         return NULL;
4850       }
4851 
4852       next = claim->unloading_next();
4853 
4854     } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim);
4855 
4856     return claim;
4857   }
4858 
4859  public:
4860   // Mark that we're done with the first pass of nmethod cleaning.
4861   void barrier_mark(uint worker_id) {
4862     MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
4863     _num_entered_barrier++;
4864     if (_num_entered_barrier == _num_workers) {
4865       ml.notify_all();
4866     }
4867   }
4868 
4869   // See if we have to wait for the other workers to
4870   // finish their first-pass nmethod cleaning work.
4871   void barrier_wait(uint worker_id) {
4872     if (_num_entered_barrier < _num_workers) {
4873       MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
4874       while (_num_entered_barrier < _num_workers) {
4875           ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
4876       }
4877     }
4878   }
4879 
4880   // Cleaning and unloading of nmethods. Some work has to be postponed
4881   // to the second pass, when we know which nmethods survive.
4882   void work_first_pass(uint worker_id) {
4883     // The first nmethods is claimed by the first worker.
4884     if (worker_id == 0 && _first_nmethod != NULL) {
4885       clean_nmethod(_first_nmethod);
4886       _first_nmethod = NULL;
4887     }
4888 
4889     int num_claimed_nmethods;
4890     nmethod* claimed_nmethods[MaxClaimNmethods];
4891 
4892     while (true) {
4893       claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
4894 
4895       if (num_claimed_nmethods == 0) {
4896         break;
4897       }
4898 
4899       for (int i = 0; i < num_claimed_nmethods; i++) {
4900         clean_nmethod(claimed_nmethods[i]);
4901       }
4902     }
4903 
4904     // The nmethod cleaning helps out and does the CodeCache part of MetadataOnStackMark.
4905     // Need to retire the buffers now that this thread has stopped cleaning nmethods.
4906     MetadataOnStackMark::retire_buffer_for_thread(Thread::current());
4907   }
4908 
4909   void work_second_pass(uint worker_id) {
4910     nmethod* nm;
4911     // Take care of postponed nmethods.
4912     while ((nm = claim_postponed_nmethod()) != NULL) {
4913       clean_nmethod_postponed(nm);
4914     }
4915   }
4916 };
4917 
4918 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never);
4919 
4920 class G1KlassCleaningTask : public StackObj {
4921   BoolObjectClosure*                      _is_alive;
4922   volatile jint                           _clean_klass_tree_claimed;
4923   ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
4924 
4925  public:
4926   G1KlassCleaningTask(BoolObjectClosure* is_alive) :
4927       _is_alive(is_alive),
4928       _clean_klass_tree_claimed(0),
4929       _klass_iterator() {
4930   }
4931 
4932  private:
4933   bool claim_clean_klass_tree_task() {
4934     if (_clean_klass_tree_claimed) {
4935       return false;
4936     }
4937 
4938     return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0;
4939   }
4940 
4941   InstanceKlass* claim_next_klass() {
4942     Klass* klass;
4943     do {
4944       klass =_klass_iterator.next_klass();
4945     } while (klass != NULL && !klass->oop_is_instance());
4946 
4947     return (InstanceKlass*)klass;
4948   }
4949 
4950 public:
4951 
4952   void clean_klass(InstanceKlass* ik) {
4953     ik->clean_implementors_list(_is_alive);
4954     ik->clean_method_data(_is_alive);
4955 
4956     // G1 specific cleanup work that has
4957     // been moved here to be done in parallel.
4958     ik->clean_dependent_nmethods();
4959     if (JvmtiExport::has_redefined_a_class()) {
4960       InstanceKlass::purge_previous_versions(ik);
4961     }
4962   }
4963 
4964   void work() {
4965     ResourceMark rm;
4966 
4967     // One worker will clean the subklass/sibling klass tree.
4968     if (claim_clean_klass_tree_task()) {
4969       Klass::clean_subklass_tree(_is_alive);
4970     }
4971 
4972     // All workers will help cleaning the classes,
4973     InstanceKlass* klass;
4974     while ((klass = claim_next_klass()) != NULL) {
4975       clean_klass(klass);
4976     }
4977   }
4978 };
4979 
4980 // To minimize the remark pause times, the tasks below are done in parallel.
4981 class G1ParallelCleaningTask : public AbstractGangTask {
4982 private:
4983   G1StringSymbolTableUnlinkTask _string_symbol_task;
4984   G1CodeCacheUnloadingTask      _code_cache_task;
4985   G1KlassCleaningTask           _klass_cleaning_task;
4986 
4987 public:
4988   // The constructor is run in the VMThread.
4989   G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) :
4990       AbstractGangTask("Parallel Cleaning"),
4991       _string_symbol_task(is_alive, process_strings, process_symbols),
4992       _code_cache_task(num_workers, is_alive, unloading_occurred),
4993       _klass_cleaning_task(is_alive) {
4994   }
4995 
4996   void pre_work_verification() {
4997     assert(!MetadataOnStackMark::has_buffer_for_thread(Thread::current()), "Should be empty");
4998   }
4999 
5000   void post_work_verification() {
5001     assert(!MetadataOnStackMark::has_buffer_for_thread(Thread::current()), "Should be empty");
5002   }
5003 
5004   // The parallel work done by all worker threads.
5005   void work(uint worker_id) {
5006     pre_work_verification();
5007 
5008     // Do first pass of code cache cleaning.
5009     _code_cache_task.work_first_pass(worker_id);
5010 
5011     // Let the threads mark that the first pass is done.
5012     _code_cache_task.barrier_mark(worker_id);
5013 
5014     // Clean the Strings and Symbols.
5015     _string_symbol_task.work(worker_id);
5016 
5017     // Wait for all workers to finish the first code cache cleaning pass.
5018     _code_cache_task.barrier_wait(worker_id);
5019 
5020     // Do the second code cache cleaning work, which realize on
5021     // the liveness information gathered during the first pass.
5022     _code_cache_task.work_second_pass(worker_id);
5023 
5024     // Clean all klasses that were not unloaded.
5025     _klass_cleaning_task.work();
5026 
5027     post_work_verification();
5028   }
5029 };
5030 
5031 
5032 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive,
5033                                         bool process_strings,
5034                                         bool process_symbols,
5035                                         bool class_unloading_occurred) {
5036   uint n_workers = workers()->active_workers();
5037 
5038   G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols,
5039                                         n_workers, class_unloading_occurred);
5040   set_par_threads(n_workers);
5041   workers()->run_task(&g1_unlink_task);
5042   set_par_threads(0);
5043 }
5044 
5045 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive,
5046                                                      bool process_strings, bool process_symbols) {
5047   {
5048     uint n_workers = _g1h->workers()->active_workers();
5049     G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols);
5050     set_par_threads(n_workers);
5051     workers()->run_task(&g1_unlink_task);
5052     set_par_threads(0);
5053   }
5054 
5055   if (G1StringDedup::is_enabled()) {
5056     G1StringDedup::unlink(is_alive);
5057   }
5058 }
5059 
5060 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
5061  private:
5062   DirtyCardQueueSet* _queue;
5063  public:
5064   G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue) : AbstractGangTask("Redirty Cards"), _queue(queue) { }
5065 
5066   virtual void work(uint worker_id) {
5067     double start_time = os::elapsedTime();
5068 
5069     RedirtyLoggedCardTableEntryClosure cl;
5070     _queue->par_apply_closure_to_all_completed_buffers(&cl);
5071 
5072     G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
5073     timer->record_redirty_logged_cards_time_ms(worker_id, (os::elapsedTime() - start_time) * 1000.0);
5074     timer->record_redirty_logged_cards_processed_cards(worker_id, cl.num_processed());
5075   }
5076 };
5077 
5078 void G1CollectedHeap::redirty_logged_cards() {
5079   double redirty_logged_cards_start = os::elapsedTime();
5080 
5081   uint n_workers = _g1h->workers()->active_workers();
5082 
5083   G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set());
5084   dirty_card_queue_set().reset_for_par_iteration();
5085   set_par_threads(n_workers);
5086   workers()->run_task(&redirty_task);
5087   set_par_threads(0);
5088 
5089   DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5090   dcq.merge_bufferlists(&dirty_card_queue_set());
5091   assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5092 
5093   g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
5094 }
5095 
5096 // Weak Reference Processing support
5097 
5098 // An always "is_alive" closure that is used to preserve referents.
5099 // If the object is non-null then it's alive.  Used in the preservation
5100 // of referent objects that are pointed to by reference objects
5101 // discovered by the CM ref processor.
5102 class G1AlwaysAliveClosure: public BoolObjectClosure {
5103   G1CollectedHeap* _g1;
5104 public:
5105   G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5106   bool do_object_b(oop p) {
5107     if (p != NULL) {
5108       return true;
5109     }
5110     return false;
5111   }
5112 };
5113 
5114 bool G1STWIsAliveClosure::do_object_b(oop p) {
5115   // An object is reachable if it is outside the collection set,
5116   // or is inside and copied.
5117   return !_g1->obj_in_cs(p) || p->is_forwarded();
5118 }
5119 
5120 // Non Copying Keep Alive closure
5121 class G1KeepAliveClosure: public OopClosure {
5122   G1CollectedHeap* _g1;
5123 public:
5124   G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5125   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
5126   void do_oop(oop* p) {
5127     oop obj = *p;
5128     assert(obj != NULL, "the caller should have filtered out NULL values");
5129 
5130     const InCSetState cset_state = _g1->in_cset_state(obj);
5131     if (!cset_state.is_in_cset_or_humongous()) {
5132       return;
5133     }
5134     if (cset_state.is_in_cset()) {
5135       assert( obj->is_forwarded(), "invariant" );
5136       *p = obj->forwardee();
5137     } else {
5138       assert(!obj->is_forwarded(), "invariant" );
5139       assert(cset_state.is_humongous(),
5140              err_msg("Only allowed InCSet state is IsHumongous, but is %d", cset_state.value()));
5141       _g1->set_humongous_is_live(obj);
5142     }
5143   }
5144 };
5145 
5146 // Copying Keep Alive closure - can be called from both
5147 // serial and parallel code as long as different worker
5148 // threads utilize different G1ParScanThreadState instances
5149 // and different queues.
5150 
5151 class G1CopyingKeepAliveClosure: public OopClosure {
5152   G1CollectedHeap*         _g1h;
5153   OopClosure*              _copy_non_heap_obj_cl;
5154   G1ParScanThreadState*    _par_scan_state;
5155 
5156 public:
5157   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
5158                             OopClosure* non_heap_obj_cl,
5159                             G1ParScanThreadState* pss):
5160     _g1h(g1h),
5161     _copy_non_heap_obj_cl(non_heap_obj_cl),
5162     _par_scan_state(pss)
5163   {}
5164 
5165   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
5166   virtual void do_oop(      oop* p) { do_oop_work(p); }
5167 
5168   template <class T> void do_oop_work(T* p) {
5169     oop obj = oopDesc::load_decode_heap_oop(p);
5170 
5171     if (_g1h->is_in_cset_or_humongous(obj)) {
5172       // If the referent object has been forwarded (either copied
5173       // to a new location or to itself in the event of an
5174       // evacuation failure) then we need to update the reference
5175       // field and, if both reference and referent are in the G1
5176       // heap, update the RSet for the referent.
5177       //
5178       // If the referent has not been forwarded then we have to keep
5179       // it alive by policy. Therefore we have copy the referent.
5180       //
5181       // If the reference field is in the G1 heap then we can push
5182       // on the PSS queue. When the queue is drained (after each
5183       // phase of reference processing) the object and it's followers
5184       // will be copied, the reference field set to point to the
5185       // new location, and the RSet updated. Otherwise we need to
5186       // use the the non-heap or metadata closures directly to copy
5187       // the referent object and update the pointer, while avoiding
5188       // updating the RSet.
5189 
5190       if (_g1h->is_in_g1_reserved(p)) {
5191         _par_scan_state->push_on_queue(p);
5192       } else {
5193         assert(!Metaspace::contains((const void*)p),
5194                err_msg("Unexpectedly found a pointer from metadata: "
5195                               PTR_FORMAT, p));
5196         _copy_non_heap_obj_cl->do_oop(p);
5197       }
5198     }
5199   }
5200 };
5201 
5202 // Serial drain queue closure. Called as the 'complete_gc'
5203 // closure for each discovered list in some of the
5204 // reference processing phases.
5205 
5206 class G1STWDrainQueueClosure: public VoidClosure {
5207 protected:
5208   G1CollectedHeap* _g1h;
5209   G1ParScanThreadState* _par_scan_state;
5210 
5211   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
5212 
5213 public:
5214   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
5215     _g1h(g1h),
5216     _par_scan_state(pss)
5217   { }
5218 
5219   void do_void() {
5220     G1ParScanThreadState* const pss = par_scan_state();
5221     pss->trim_queue();
5222   }
5223 };
5224 
5225 // Parallel Reference Processing closures
5226 
5227 // Implementation of AbstractRefProcTaskExecutor for parallel reference
5228 // processing during G1 evacuation pauses.
5229 
5230 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5231 private:
5232   G1CollectedHeap*   _g1h;
5233   RefToScanQueueSet* _queues;
5234   FlexibleWorkGang*  _workers;
5235   int                _active_workers;
5236 
5237 public:
5238   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5239                         FlexibleWorkGang* workers,
5240                         RefToScanQueueSet *task_queues,
5241                         int n_workers) :
5242     _g1h(g1h),
5243     _queues(task_queues),
5244     _workers(workers),
5245     _active_workers(n_workers)
5246   {
5247     assert(n_workers > 0, "shouldn't call this otherwise");
5248   }
5249 
5250   // Executes the given task using concurrent marking worker threads.
5251   virtual void execute(ProcessTask& task);
5252   virtual void execute(EnqueueTask& task);
5253 };
5254 
5255 // Gang task for possibly parallel reference processing
5256 
5257 class G1STWRefProcTaskProxy: public AbstractGangTask {
5258   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5259   ProcessTask&     _proc_task;
5260   G1CollectedHeap* _g1h;
5261   RefToScanQueueSet *_task_queues;
5262   ParallelTaskTerminator* _terminator;
5263 
5264 public:
5265   G1STWRefProcTaskProxy(ProcessTask& proc_task,
5266                      G1CollectedHeap* g1h,
5267                      RefToScanQueueSet *task_queues,
5268                      ParallelTaskTerminator* terminator) :
5269     AbstractGangTask("Process reference objects in parallel"),
5270     _proc_task(proc_task),
5271     _g1h(g1h),
5272     _task_queues(task_queues),
5273     _terminator(terminator)
5274   {}
5275 
5276   virtual void work(uint worker_id) {
5277     // The reference processing task executed by a single worker.
5278     ResourceMark rm;
5279     HandleMark   hm;
5280 
5281     G1STWIsAliveClosure is_alive(_g1h);
5282 
5283     G1ParScanThreadState            pss(_g1h, worker_id, NULL);
5284     G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5285 
5286     pss.set_evac_failure_closure(&evac_failure_cl);
5287 
5288     G1ParScanExtRootClosure        only_copy_non_heap_cl(_g1h, &pss, NULL);
5289 
5290     G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5291 
5292     OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5293 
5294     if (_g1h->g1_policy()->during_initial_mark_pause()) {
5295       // We also need to mark copied objects.
5296       copy_non_heap_cl = &copy_mark_non_heap_cl;
5297     }
5298 
5299     // Keep alive closure.
5300     G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5301 
5302     // Complete GC closure
5303     G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5304 
5305     // Call the reference processing task's work routine.
5306     _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5307 
5308     // Note we cannot assert that the refs array is empty here as not all
5309     // of the processing tasks (specifically phase2 - pp2_work) execute
5310     // the complete_gc closure (which ordinarily would drain the queue) so
5311     // the queue may not be empty.
5312   }
5313 };
5314 
5315 // Driver routine for parallel reference processing.
5316 // Creates an instance of the ref processing gang
5317 // task and has the worker threads execute it.
5318 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5319   assert(_workers != NULL, "Need parallel worker threads.");
5320 
5321   ParallelTaskTerminator terminator(_active_workers, _queues);
5322   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5323 
5324   _g1h->set_par_threads(_active_workers);
5325   _workers->run_task(&proc_task_proxy);
5326   _g1h->set_par_threads(0);
5327 }
5328 
5329 // Gang task for parallel reference enqueueing.
5330 
5331 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5332   typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5333   EnqueueTask& _enq_task;
5334 
5335 public:
5336   G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5337     AbstractGangTask("Enqueue reference objects in parallel"),
5338     _enq_task(enq_task)
5339   { }
5340 
5341   virtual void work(uint worker_id) {
5342     _enq_task.work(worker_id);
5343   }
5344 };
5345 
5346 // Driver routine for parallel reference enqueueing.
5347 // Creates an instance of the ref enqueueing gang
5348 // task and has the worker threads execute it.
5349 
5350 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5351   assert(_workers != NULL, "Need parallel worker threads.");
5352 
5353   G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5354 
5355   _g1h->set_par_threads(_active_workers);
5356   _workers->run_task(&enq_task_proxy);
5357   _g1h->set_par_threads(0);
5358 }
5359 
5360 // End of weak reference support closures
5361 
5362 // Abstract task used to preserve (i.e. copy) any referent objects
5363 // that are in the collection set and are pointed to by reference
5364 // objects discovered by the CM ref processor.
5365 
5366 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5367 protected:
5368   G1CollectedHeap* _g1h;
5369   RefToScanQueueSet      *_queues;
5370   ParallelTaskTerminator _terminator;
5371   uint _n_workers;
5372 
5373 public:
5374   G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
5375     AbstractGangTask("ParPreserveCMReferents"),
5376     _g1h(g1h),
5377     _queues(task_queues),
5378     _terminator(workers, _queues),
5379     _n_workers(workers)
5380   { }
5381 
5382   void work(uint worker_id) {
5383     ResourceMark rm;
5384     HandleMark   hm;
5385 
5386     G1ParScanThreadState            pss(_g1h, worker_id, NULL);
5387     G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5388 
5389     pss.set_evac_failure_closure(&evac_failure_cl);
5390 
5391     assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5392 
5393     G1ParScanExtRootClosure        only_copy_non_heap_cl(_g1h, &pss, NULL);
5394 
5395     G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5396 
5397     OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5398 
5399     if (_g1h->g1_policy()->during_initial_mark_pause()) {
5400       // We also need to mark copied objects.
5401       copy_non_heap_cl = &copy_mark_non_heap_cl;
5402     }
5403 
5404     // Is alive closure
5405     G1AlwaysAliveClosure always_alive(_g1h);
5406 
5407     // Copying keep alive closure. Applied to referent objects that need
5408     // to be copied.
5409     G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5410 
5411     ReferenceProcessor* rp = _g1h->ref_processor_cm();
5412 
5413     uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5414     uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5415 
5416     // limit is set using max_num_q() - which was set using ParallelGCThreads.
5417     // So this must be true - but assert just in case someone decides to
5418     // change the worker ids.
5419     assert(0 <= worker_id && worker_id < limit, "sanity");
5420     assert(!rp->discovery_is_atomic(), "check this code");
5421 
5422     // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5423     for (uint idx = worker_id; idx < limit; idx += stride) {
5424       DiscoveredList& ref_list = rp->discovered_refs()[idx];
5425 
5426       DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5427       while (iter.has_next()) {
5428         // Since discovery is not atomic for the CM ref processor, we
5429         // can see some null referent objects.
5430         iter.load_ptrs(DEBUG_ONLY(true));
5431         oop ref = iter.obj();
5432 
5433         // This will filter nulls.
5434         if (iter.is_referent_alive()) {
5435           iter.make_referent_alive();
5436         }
5437         iter.move_to_next();
5438       }
5439     }
5440 
5441     // Drain the queue - which may cause stealing
5442     G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5443     drain_queue.do_void();
5444     // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5445     assert(pss.queue_is_empty(), "should be");
5446   }
5447 };
5448 
5449 // Weak Reference processing during an evacuation pause (part 1).
5450 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) {
5451   double ref_proc_start = os::elapsedTime();
5452 
5453   ReferenceProcessor* rp = _ref_processor_stw;
5454   assert(rp->discovery_enabled(), "should have been enabled");
5455 
5456   // Any reference objects, in the collection set, that were 'discovered'
5457   // by the CM ref processor should have already been copied (either by
5458   // applying the external root copy closure to the discovered lists, or
5459   // by following an RSet entry).
5460   //
5461   // But some of the referents, that are in the collection set, that these
5462   // reference objects point to may not have been copied: the STW ref
5463   // processor would have seen that the reference object had already
5464   // been 'discovered' and would have skipped discovering the reference,
5465   // but would not have treated the reference object as a regular oop.
5466   // As a result the copy closure would not have been applied to the
5467   // referent object.
5468   //
5469   // We need to explicitly copy these referent objects - the references
5470   // will be processed at the end of remarking.
5471   //
5472   // We also need to do this copying before we process the reference
5473   // objects discovered by the STW ref processor in case one of these
5474   // referents points to another object which is also referenced by an
5475   // object discovered by the STW ref processor.
5476 
5477   assert(no_of_gc_workers == workers()->active_workers(), "Need to reset active GC workers");
5478 
5479   set_par_threads(no_of_gc_workers);
5480   G1ParPreserveCMReferentsTask keep_cm_referents(this,
5481                                                  no_of_gc_workers,
5482                                                  _task_queues);
5483 
5484   workers()->run_task(&keep_cm_referents);
5485 
5486   set_par_threads(0);
5487 
5488   // Closure to test whether a referent is alive.
5489   G1STWIsAliveClosure is_alive(this);
5490 
5491   // Even when parallel reference processing is enabled, the processing
5492   // of JNI refs is serial and performed serially by the current thread
5493   // rather than by a worker. The following PSS will be used for processing
5494   // JNI refs.
5495 
5496   // Use only a single queue for this PSS.
5497   G1ParScanThreadState            pss(this, 0, NULL);
5498 
5499   // We do not embed a reference processor in the copying/scanning
5500   // closures while we're actually processing the discovered
5501   // reference objects.
5502   G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5503 
5504   pss.set_evac_failure_closure(&evac_failure_cl);
5505 
5506   assert(pss.queue_is_empty(), "pre-condition");
5507 
5508   G1ParScanExtRootClosure        only_copy_non_heap_cl(this, &pss, NULL);
5509 
5510   G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5511 
5512   OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5513 
5514   if (_g1h->g1_policy()->during_initial_mark_pause()) {
5515     // We also need to mark copied objects.
5516     copy_non_heap_cl = &copy_mark_non_heap_cl;
5517   }
5518 
5519   // Keep alive closure.
5520   G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, &pss);
5521 
5522   // Serial Complete GC closure
5523   G1STWDrainQueueClosure drain_queue(this, &pss);
5524 
5525   // Setup the soft refs policy...
5526   rp->setup_policy(false);
5527 
5528   ReferenceProcessorStats stats;
5529   if (!rp->processing_is_mt()) {
5530     // Serial reference processing...
5531     stats = rp->process_discovered_references(&is_alive,
5532                                               &keep_alive,
5533                                               &drain_queue,
5534                                               NULL,
5535                                               _gc_timer_stw,
5536                                               _gc_tracer_stw->gc_id());
5537   } else {
5538     // Parallel reference processing
5539     assert(rp->num_q() == no_of_gc_workers, "sanity");
5540     assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5541 
5542     G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5543     stats = rp->process_discovered_references(&is_alive,
5544                                               &keep_alive,
5545                                               &drain_queue,
5546                                               &par_task_executor,
5547                                               _gc_timer_stw,
5548                                               _gc_tracer_stw->gc_id());
5549   }
5550 
5551   _gc_tracer_stw->report_gc_reference_stats(stats);
5552 
5553   // We have completed copying any necessary live referent objects.
5554   assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5555 
5556   double ref_proc_time = os::elapsedTime() - ref_proc_start;
5557   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5558 }
5559 
5560 // Weak Reference processing during an evacuation pause (part 2).
5561 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) {
5562   double ref_enq_start = os::elapsedTime();
5563 
5564   ReferenceProcessor* rp = _ref_processor_stw;
5565   assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5566 
5567   // Now enqueue any remaining on the discovered lists on to
5568   // the pending list.
5569   if (!rp->processing_is_mt()) {
5570     // Serial reference processing...
5571     rp->enqueue_discovered_references();
5572   } else {
5573     // Parallel reference enqueueing
5574 
5575     assert(no_of_gc_workers == workers()->active_workers(),
5576            "Need to reset active workers");
5577     assert(rp->num_q() == no_of_gc_workers, "sanity");
5578     assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5579 
5580     G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5581     rp->enqueue_discovered_references(&par_task_executor);
5582   }
5583 
5584   rp->verify_no_references_recorded();
5585   assert(!rp->discovery_enabled(), "should have been disabled");
5586 
5587   // FIXME
5588   // CM's reference processing also cleans up the string and symbol tables.
5589   // Should we do that here also? We could, but it is a serial operation
5590   // and could significantly increase the pause time.
5591 
5592   double ref_enq_time = os::elapsedTime() - ref_enq_start;
5593   g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5594 }
5595 
5596 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) {
5597   _expand_heap_after_alloc_failure = true;
5598   _evacuation_failed = false;
5599 
5600   // Should G1EvacuationFailureALot be in effect for this GC?
5601   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
5602 
5603   g1_rem_set()->prepare_for_oops_into_collection_set_do();
5604 
5605   // Disable the hot card cache.
5606   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
5607   hot_card_cache->reset_hot_cache_claimed_index();
5608   hot_card_cache->set_use_cache(false);
5609 
5610   uint n_workers;
5611   n_workers =
5612     AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
5613                                    workers()->active_workers(),
5614                                    Threads::number_of_non_daemon_threads());
5615   assert(UseDynamicNumberOfGCThreads ||
5616          n_workers == workers()->total_workers(),
5617          "If not dynamic should be using all the  workers");
5618   workers()->set_active_workers(n_workers);
5619   set_par_threads(n_workers);
5620 
5621   G1ParTask g1_par_task(this, _task_queues);
5622 
5623   init_for_evac_failure(NULL);
5624 
5625   assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5626   double start_par_time_sec = os::elapsedTime();
5627   double end_par_time_sec;
5628 
5629   {
5630     StrongRootsScope srs(this);
5631     // InitialMark needs claim bits to keep track of the marked-through CLDs.
5632     if (g1_policy()->during_initial_mark_pause()) {
5633       ClassLoaderDataGraph::clear_claimed_marks();
5634     }
5635 
5636      // The individual threads will set their evac-failure closures.
5637      if (PrintTerminationStats) G1ParScanThreadState::print_termination_stats_hdr();
5638      // These tasks use ShareHeap::_process_strong_tasks
5639      assert(UseDynamicNumberOfGCThreads ||
5640             workers()->active_workers() == workers()->total_workers(),
5641             "If not dynamic should be using all the  workers");
5642     workers()->run_task(&g1_par_task);
5643     end_par_time_sec = os::elapsedTime();
5644 
5645     // Closing the inner scope will execute the destructor
5646     // for the StrongRootsScope object. We record the current
5647     // elapsed time before closing the scope so that time
5648     // taken for the SRS destructor is NOT included in the
5649     // reported parallel time.
5650   }
5651 
5652   double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5653   g1_policy()->phase_times()->record_par_time(par_time_ms);
5654 
5655   double code_root_fixup_time_ms =
5656         (os::elapsedTime() - end_par_time_sec) * 1000.0;
5657   g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms);
5658 
5659   set_par_threads(0);
5660 
5661   // Process any discovered reference objects - we have
5662   // to do this _before_ we retire the GC alloc regions
5663   // as we may have to copy some 'reachable' referent
5664   // objects (and their reachable sub-graphs) that were
5665   // not copied during the pause.
5666   process_discovered_references(n_workers);
5667 
5668   if (G1StringDedup::is_enabled()) {
5669     G1STWIsAliveClosure is_alive(this);
5670     G1KeepAliveClosure keep_alive(this);
5671     G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive);
5672   }
5673 
5674   _allocator->release_gc_alloc_regions(n_workers, evacuation_info);
5675   g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5676 
5677   // Reset and re-enable the hot card cache.
5678   // Note the counts for the cards in the regions in the
5679   // collection set are reset when the collection set is freed.
5680   hot_card_cache->reset_hot_cache();
5681   hot_card_cache->set_use_cache(true);
5682 
5683   purge_code_root_memory();
5684 
5685   finalize_for_evac_failure();
5686 
5687   if (evacuation_failed()) {
5688     remove_self_forwarding_pointers();
5689 
5690     // Reset the G1EvacuationFailureALot counters and flags
5691     // Note: the values are reset only when an actual
5692     // evacuation failure occurs.
5693     NOT_PRODUCT(reset_evacuation_should_fail();)
5694   }
5695 
5696   // Enqueue any remaining references remaining on the STW
5697   // reference processor's discovered lists. We need to do
5698   // this after the card table is cleaned (and verified) as
5699   // the act of enqueueing entries on to the pending list
5700   // will log these updates (and dirty their associated
5701   // cards). We need these updates logged to update any
5702   // RSets.
5703   enqueue_discovered_references(n_workers);
5704 
5705   redirty_logged_cards();
5706   COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5707 }
5708 
5709 void G1CollectedHeap::free_region(HeapRegion* hr,
5710                                   FreeRegionList* free_list,
5711                                   bool par,
5712                                   bool locked) {
5713   assert(!hr->is_free(), "the region should not be free");
5714   assert(!hr->is_empty(), "the region should not be empty");
5715   assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
5716   assert(free_list != NULL, "pre-condition");
5717 
5718   if (G1VerifyBitmaps) {
5719     MemRegion mr(hr->bottom(), hr->end());
5720     concurrent_mark()->clearRangePrevBitmap(mr);
5721   }
5722 
5723   // Clear the card counts for this region.
5724   // Note: we only need to do this if the region is not young
5725   // (since we don't refine cards in young regions).
5726   if (!hr->is_young()) {
5727     _cg1r->hot_card_cache()->reset_card_counts(hr);
5728   }
5729   hr->hr_clear(par, true /* clear_space */, locked /* locked */);
5730   free_list->add_ordered(hr);
5731 }
5732 
5733 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
5734                                      FreeRegionList* free_list,
5735                                      bool par) {
5736   assert(hr->is_starts_humongous(), "this is only for starts humongous regions");
5737   assert(free_list != NULL, "pre-condition");
5738 
5739   size_t hr_capacity = hr->capacity();
5740   // We need to read this before we make the region non-humongous,
5741   // otherwise the information will be gone.
5742   uint last_index = hr->last_hc_index();
5743   hr->clear_humongous();
5744   free_region(hr, free_list, par);
5745 
5746   uint i = hr->hrm_index() + 1;
5747   while (i < last_index) {
5748     HeapRegion* curr_hr = region_at(i);
5749     assert(curr_hr->is_continues_humongous(), "invariant");
5750     curr_hr->clear_humongous();
5751     free_region(curr_hr, free_list, par);
5752     i += 1;
5753   }
5754 }
5755 
5756 void G1CollectedHeap::remove_from_old_sets(const HeapRegionSetCount& old_regions_removed,
5757                                        const HeapRegionSetCount& humongous_regions_removed) {
5758   if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 0) {
5759     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5760     _old_set.bulk_remove(old_regions_removed);
5761     _humongous_set.bulk_remove(humongous_regions_removed);
5762   }
5763 
5764 }
5765 
5766 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
5767   assert(list != NULL, "list can't be null");
5768   if (!list->is_empty()) {
5769     MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
5770     _hrm.insert_list_into_free_list(list);
5771   }
5772 }
5773 
5774 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
5775   _allocator->decrease_used(bytes);
5776 }
5777 
5778 class G1ParCleanupCTTask : public AbstractGangTask {
5779   G1SATBCardTableModRefBS* _ct_bs;
5780   G1CollectedHeap* _g1h;
5781   HeapRegion* volatile _su_head;
5782 public:
5783   G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs,
5784                      G1CollectedHeap* g1h) :
5785     AbstractGangTask("G1 Par Cleanup CT Task"),
5786     _ct_bs(ct_bs), _g1h(g1h) { }
5787 
5788   void work(uint worker_id) {
5789     HeapRegion* r;
5790     while (r = _g1h->pop_dirty_cards_region()) {
5791       clear_cards(r);
5792     }
5793   }
5794 
5795   void clear_cards(HeapRegion* r) {
5796     // Cards of the survivors should have already been dirtied.
5797     if (!r->is_survivor()) {
5798       _ct_bs->clear(MemRegion(r->bottom(), r->end()));
5799     }
5800   }
5801 };
5802 
5803 #ifndef PRODUCT
5804 class G1VerifyCardTableCleanup: public HeapRegionClosure {
5805   G1CollectedHeap* _g1h;
5806   G1SATBCardTableModRefBS* _ct_bs;
5807 public:
5808   G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs)
5809     : _g1h(g1h), _ct_bs(ct_bs) { }
5810   virtual bool doHeapRegion(HeapRegion* r) {
5811     if (r->is_survivor()) {
5812       _g1h->verify_dirty_region(r);
5813     } else {
5814       _g1h->verify_not_dirty_region(r);
5815     }
5816     return false;
5817   }
5818 };
5819 
5820 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
5821   // All of the region should be clean.
5822   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5823   MemRegion mr(hr->bottom(), hr->end());
5824   ct_bs->verify_not_dirty_region(mr);
5825 }
5826 
5827 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
5828   // We cannot guarantee that [bottom(),end()] is dirty.  Threads
5829   // dirty allocated blocks as they allocate them. The thread that
5830   // retires each region and replaces it with a new one will do a
5831   // maximal allocation to fill in [pre_dummy_top(),end()] but will
5832   // not dirty that area (one less thing to have to do while holding
5833   // a lock). So we can only verify that [bottom(),pre_dummy_top()]
5834   // is dirty.
5835   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5836   MemRegion mr(hr->bottom(), hr->pre_dummy_top());
5837   if (hr->is_young()) {
5838     ct_bs->verify_g1_young_region(mr);
5839   } else {
5840     ct_bs->verify_dirty_region(mr);
5841   }
5842 }
5843 
5844 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
5845   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5846   for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
5847     verify_dirty_region(hr);
5848   }
5849 }
5850 
5851 void G1CollectedHeap::verify_dirty_young_regions() {
5852   verify_dirty_young_list(_young_list->first_region());
5853 }
5854 
5855 bool G1CollectedHeap::verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
5856                                                HeapWord* tams, HeapWord* end) {
5857   guarantee(tams <= end,
5858             err_msg("tams: "PTR_FORMAT" end: "PTR_FORMAT, tams, end));
5859   HeapWord* result = bitmap->getNextMarkedWordAddress(tams, end);
5860   if (result < end) {
5861     gclog_or_tty->cr();
5862     gclog_or_tty->print_cr("## wrong marked address on %s bitmap: "PTR_FORMAT,
5863                            bitmap_name, result);
5864     gclog_or_tty->print_cr("## %s tams: "PTR_FORMAT" end: "PTR_FORMAT,
5865                            bitmap_name, tams, end);
5866     return false;
5867   }
5868   return true;
5869 }
5870 
5871 bool G1CollectedHeap::verify_bitmaps(const char* caller, HeapRegion* hr) {
5872   CMBitMapRO* prev_bitmap = concurrent_mark()->prevMarkBitMap();
5873   CMBitMapRO* next_bitmap = (CMBitMapRO*) concurrent_mark()->nextMarkBitMap();
5874 
5875   HeapWord* bottom = hr->bottom();
5876   HeapWord* ptams  = hr->prev_top_at_mark_start();
5877   HeapWord* ntams  = hr->next_top_at_mark_start();
5878   HeapWord* end    = hr->end();
5879 
5880   bool res_p = verify_no_bits_over_tams("prev", prev_bitmap, ptams, end);
5881 
5882   bool res_n = true;
5883   // We reset mark_in_progress() before we reset _cmThread->in_progress() and in this window
5884   // we do the clearing of the next bitmap concurrently. Thus, we can not verify the bitmap
5885   // if we happen to be in that state.
5886   if (mark_in_progress() || !_cmThread->in_progress()) {
5887     res_n = verify_no_bits_over_tams("next", next_bitmap, ntams, end);
5888   }
5889   if (!res_p || !res_n) {
5890     gclog_or_tty->print_cr("#### Bitmap verification failed for "HR_FORMAT,
5891                            HR_FORMAT_PARAMS(hr));
5892     gclog_or_tty->print_cr("#### Caller: %s", caller);
5893     return false;
5894   }
5895   return true;
5896 }
5897 
5898 void G1CollectedHeap::check_bitmaps(const char* caller, HeapRegion* hr) {
5899   if (!G1VerifyBitmaps) return;
5900 
5901   guarantee(verify_bitmaps(caller, hr), "bitmap verification");
5902 }
5903 
5904 class G1VerifyBitmapClosure : public HeapRegionClosure {
5905 private:
5906   const char* _caller;
5907   G1CollectedHeap* _g1h;
5908   bool _failures;
5909 
5910 public:
5911   G1VerifyBitmapClosure(const char* caller, G1CollectedHeap* g1h) :
5912     _caller(caller), _g1h(g1h), _failures(false) { }
5913 
5914   bool failures() { return _failures; }
5915 
5916   virtual bool doHeapRegion(HeapRegion* hr) {
5917     if (hr->is_continues_humongous()) return false;
5918 
5919     bool result = _g1h->verify_bitmaps(_caller, hr);
5920     if (!result) {
5921       _failures = true;
5922     }
5923     return false;
5924   }
5925 };
5926 
5927 void G1CollectedHeap::check_bitmaps(const char* caller) {
5928   if (!G1VerifyBitmaps) return;
5929 
5930   G1VerifyBitmapClosure cl(caller, this);
5931   heap_region_iterate(&cl);
5932   guarantee(!cl.failures(), "bitmap verification");
5933 }
5934 
5935 class G1CheckCSetFastTableClosure : public HeapRegionClosure {
5936  private:
5937   bool _failures;
5938  public:
5939   G1CheckCSetFastTableClosure() : HeapRegionClosure(), _failures(false) { }
5940 
5941   virtual bool doHeapRegion(HeapRegion* hr) {
5942     uint i = hr->hrm_index();
5943     InCSetState cset_state = (InCSetState) G1CollectedHeap::heap()->_in_cset_fast_test.get_by_index(i);
5944     if (hr->is_humongous()) {
5945       if (hr->in_collection_set()) {
5946         gclog_or_tty->print_cr("\n## humongous region %u in CSet", i);
5947         _failures = true;
5948         return true;
5949       }
5950       if (cset_state.is_in_cset()) {
5951         gclog_or_tty->print_cr("\n## inconsistent cset state %d for humongous region %u", cset_state.value(), i);
5952         _failures = true;
5953         return true;
5954       }
5955       if (hr->is_continues_humongous() && cset_state.is_humongous()) {
5956         gclog_or_tty->print_cr("\n## inconsistent cset state %d for continues humongous region %u", cset_state.value(), i);
5957         _failures = true;
5958         return true;
5959       }
5960     } else {
5961       if (cset_state.is_humongous()) {
5962         gclog_or_tty->print_cr("\n## inconsistent cset state %d for non-humongous region %u", cset_state.value(), i);
5963         _failures = true;
5964         return true;
5965       }
5966       if (hr->in_collection_set() != cset_state.is_in_cset()) {
5967         gclog_or_tty->print_cr("\n## in CSet %d / cset state %d inconsistency for region %u",
5968                                hr->in_collection_set(), cset_state.value(), i);
5969         _failures = true;
5970         return true;
5971       }
5972       if (cset_state.is_in_cset()) {
5973         if (hr->is_young() != (cset_state.is_young())) {
5974           gclog_or_tty->print_cr("\n## is_young %d / cset state %d inconsistency for region %u",
5975                                  hr->is_young(), cset_state.value(), i);
5976           _failures = true;
5977           return true;
5978         }
5979         if (hr->is_old() != (cset_state.is_old())) {
5980           gclog_or_tty->print_cr("\n## is_old %d / cset state %d inconsistency for region %u",
5981                                  hr->is_old(), cset_state.value(), i);
5982           _failures = true;
5983           return true;
5984         }
5985       }
5986     }
5987     return false;
5988   }
5989 
5990   bool failures() const { return _failures; }
5991 };
5992 
5993 bool G1CollectedHeap::check_cset_fast_test() {
5994   G1CheckCSetFastTableClosure cl;
5995   _hrm.iterate(&cl);
5996   return !cl.failures();
5997 }
5998 #endif // PRODUCT
5999 
6000 void G1CollectedHeap::cleanUpCardTable() {
6001   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6002   double start = os::elapsedTime();
6003 
6004   {
6005     // Iterate over the dirty cards region list.
6006     G1ParCleanupCTTask cleanup_task(ct_bs, this);
6007 
6008     set_par_threads();
6009     workers()->run_task(&cleanup_task);
6010     set_par_threads(0);
6011 #ifndef PRODUCT
6012     if (G1VerifyCTCleanup || VerifyAfterGC) {
6013       G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
6014       heap_region_iterate(&cleanup_verifier);
6015     }
6016 #endif
6017   }
6018 
6019   double elapsed = os::elapsedTime() - start;
6020   g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
6021 }
6022 
6023 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) {
6024   size_t pre_used = 0;
6025   FreeRegionList local_free_list("Local List for CSet Freeing");
6026 
6027   double young_time_ms     = 0.0;
6028   double non_young_time_ms = 0.0;
6029 
6030   // Since the collection set is a superset of the the young list,
6031   // all we need to do to clear the young list is clear its
6032   // head and length, and unlink any young regions in the code below
6033   _young_list->clear();
6034 
6035   G1CollectorPolicy* policy = g1_policy();
6036 
6037   double start_sec = os::elapsedTime();
6038   bool non_young = true;
6039 
6040   HeapRegion* cur = cs_head;
6041   int age_bound = -1;
6042   size_t rs_lengths = 0;
6043 
6044   while (cur != NULL) {
6045     assert(!is_on_master_free_list(cur), "sanity");
6046     if (non_young) {
6047       if (cur->is_young()) {
6048         double end_sec = os::elapsedTime();
6049         double elapsed_ms = (end_sec - start_sec) * 1000.0;
6050         non_young_time_ms += elapsed_ms;
6051 
6052         start_sec = os::elapsedTime();
6053         non_young = false;
6054       }
6055     } else {
6056       if (!cur->is_young()) {
6057         double end_sec = os::elapsedTime();
6058         double elapsed_ms = (end_sec - start_sec) * 1000.0;
6059         young_time_ms += elapsed_ms;
6060 
6061         start_sec = os::elapsedTime();
6062         non_young = true;
6063       }
6064     }
6065 
6066     rs_lengths += cur->rem_set()->occupied_locked();
6067 
6068     HeapRegion* next = cur->next_in_collection_set();
6069     assert(cur->in_collection_set(), "bad CS");
6070     cur->set_next_in_collection_set(NULL);
6071     cur->set_in_collection_set(false);
6072 
6073     if (cur->is_young()) {
6074       int index = cur->young_index_in_cset();
6075       assert(index != -1, "invariant");
6076       assert((uint) index < policy->young_cset_region_length(), "invariant");
6077       size_t words_survived = _surviving_young_words[index];
6078       cur->record_surv_words_in_group(words_survived);
6079 
6080       // At this point the we have 'popped' cur from the collection set
6081       // (linked via next_in_collection_set()) but it is still in the
6082       // young list (linked via next_young_region()). Clear the
6083       // _next_young_region field.
6084       cur->set_next_young_region(NULL);
6085     } else {
6086       int index = cur->young_index_in_cset();
6087       assert(index == -1, "invariant");
6088     }
6089 
6090     assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
6091             (!cur->is_young() && cur->young_index_in_cset() == -1),
6092             "invariant" );
6093 
6094     if (!cur->evacuation_failed()) {
6095       MemRegion used_mr = cur->used_region();
6096 
6097       // And the region is empty.
6098       assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
6099       pre_used += cur->used();
6100       free_region(cur, &local_free_list, false /* par */, true /* locked */);
6101     } else {
6102       cur->uninstall_surv_rate_group();
6103       if (cur->is_young()) {
6104         cur->set_young_index_in_cset(-1);
6105       }
6106       cur->set_evacuation_failed(false);
6107       // The region is now considered to be old.
6108       cur->set_old();
6109       _old_set.add(cur);
6110       evacuation_info.increment_collectionset_used_after(cur->used());
6111     }
6112     cur = next;
6113   }
6114 
6115   evacuation_info.set_regions_freed(local_free_list.length());
6116   policy->record_max_rs_lengths(rs_lengths);
6117   policy->cset_regions_freed();
6118 
6119   double end_sec = os::elapsedTime();
6120   double elapsed_ms = (end_sec - start_sec) * 1000.0;
6121 
6122   if (non_young) {
6123     non_young_time_ms += elapsed_ms;
6124   } else {
6125     young_time_ms += elapsed_ms;
6126   }
6127 
6128   prepend_to_freelist(&local_free_list);
6129   decrement_summary_bytes(pre_used);
6130   policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
6131   policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
6132 }
6133 
6134 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
6135  private:
6136   FreeRegionList* _free_region_list;
6137   HeapRegionSet* _proxy_set;
6138   HeapRegionSetCount _humongous_regions_removed;
6139   size_t _freed_bytes;
6140  public:
6141 
6142   G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
6143     _free_region_list(free_region_list), _humongous_regions_removed(), _freed_bytes(0) {
6144   }
6145 
6146   virtual bool doHeapRegion(HeapRegion* r) {
6147     if (!r->is_starts_humongous()) {
6148       return false;
6149     }
6150 
6151     G1CollectedHeap* g1h = G1CollectedHeap::heap();
6152 
6153     oop obj = (oop)r->bottom();
6154     CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap();
6155 
6156     // The following checks whether the humongous object is live are sufficient.
6157     // The main additional check (in addition to having a reference from the roots
6158     // or the young gen) is whether the humongous object has a remembered set entry.
6159     //
6160     // A humongous object cannot be live if there is no remembered set for it
6161     // because:
6162     // - there can be no references from within humongous starts regions referencing
6163     // the object because we never allocate other objects into them.
6164     // (I.e. there are no intra-region references that may be missed by the
6165     // remembered set)
6166     // - as soon there is a remembered set entry to the humongous starts region
6167     // (i.e. it has "escaped" to an old object) this remembered set entry will stay
6168     // until the end of a concurrent mark.
6169     //
6170     // It is not required to check whether the object has been found dead by marking
6171     // or not, in fact it would prevent reclamation within a concurrent cycle, as
6172     // all objects allocated during that time are considered live.
6173     // SATB marking is even more conservative than the remembered set.
6174     // So if at this point in the collection there is no remembered set entry,
6175     // nobody has a reference to it.
6176     // At the start of collection we flush all refinement logs, and remembered sets
6177     // are completely up-to-date wrt to references to the humongous object.
6178     //
6179     // Other implementation considerations:
6180     // - never consider object arrays at this time because they would pose
6181     // considerable effort for cleaning up the the remembered sets. This is
6182     // required because stale remembered sets might reference locations that
6183     // are currently allocated into.
6184     uint region_idx = r->hrm_index();
6185     if (g1h->humongous_is_live(region_idx) ||
6186         g1h->humongous_region_is_always_live(region_idx)) {
6187 
6188       if (G1TraceEagerReclaimHumongousObjects) {
6189         gclog_or_tty->print_cr("Live humongous region %u size "SIZE_FORMAT" start "PTR_FORMAT" length "UINT32_FORMAT" with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is marked %d live-other %d obj array %d",
6190                                region_idx,
6191                                obj->size()*HeapWordSize,
6192                                r->bottom(),
6193                                r->region_num(),
6194                                r->rem_set()->occupied(),
6195                                r->rem_set()->strong_code_roots_list_length(),
6196                                next_bitmap->isMarked(r->bottom()),
6197                                g1h->humongous_is_live(region_idx),
6198                                obj->is_objArray()
6199                               );
6200       }
6201 
6202       return false;
6203     }
6204 
6205     guarantee(!obj->is_objArray(),
6206               err_msg("Eagerly reclaiming object arrays is not supported, but the object "PTR_FORMAT" is.",
6207                       r->bottom()));
6208 
6209     if (G1TraceEagerReclaimHumongousObjects) {
6210       gclog_or_tty->print_cr("Dead humongous region %u size "SIZE_FORMAT" start "PTR_FORMAT" length "UINT32_FORMAT" with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is marked %d live-other %d obj array %d",
6211                              region_idx,
6212                              obj->size()*HeapWordSize,
6213                              r->bottom(),
6214                              r->region_num(),
6215                              r->rem_set()->occupied(),
6216                              r->rem_set()->strong_code_roots_list_length(),
6217                              next_bitmap->isMarked(r->bottom()),
6218                              g1h->humongous_is_live(region_idx),
6219                              obj->is_objArray()
6220                             );
6221     }
6222     // Need to clear mark bit of the humongous object if already set.
6223     if (next_bitmap->isMarked(r->bottom())) {
6224       next_bitmap->clear(r->bottom());
6225     }
6226     _freed_bytes += r->used();
6227     r->set_containing_set(NULL);
6228     _humongous_regions_removed.increment(1u, r->capacity());
6229     g1h->free_humongous_region(r, _free_region_list, false);
6230 
6231     return false;
6232   }
6233 
6234   HeapRegionSetCount& humongous_free_count() {
6235     return _humongous_regions_removed;
6236   }
6237 
6238   size_t bytes_freed() const {
6239     return _freed_bytes;
6240   }
6241 
6242   size_t humongous_reclaimed() const {
6243     return _humongous_regions_removed.length();
6244   }
6245 };
6246 
6247 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
6248   assert_at_safepoint(true);
6249 
6250   if (!G1EagerReclaimHumongousObjects ||
6251       (!_has_humongous_reclaim_candidates && !G1TraceEagerReclaimHumongousObjects)) {
6252     g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
6253     return;
6254   }
6255 
6256   double start_time = os::elapsedTime();
6257 
6258   FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
6259 
6260   G1FreeHumongousRegionClosure cl(&local_cleanup_list);
6261   heap_region_iterate(&cl);
6262 
6263   HeapRegionSetCount empty_set;
6264   remove_from_old_sets(empty_set, cl.humongous_free_count());
6265 
6266   G1HRPrinter* hr_printer = _g1h->hr_printer();
6267   if (hr_printer->is_active()) {
6268     FreeRegionListIterator iter(&local_cleanup_list);
6269     while (iter.more_available()) {
6270       HeapRegion* hr = iter.get_next();
6271       hr_printer->cleanup(hr);
6272     }
6273   }
6274 
6275   prepend_to_freelist(&local_cleanup_list);
6276   decrement_summary_bytes(cl.bytes_freed());
6277 
6278   g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
6279                                                                     cl.humongous_reclaimed());
6280 }
6281 
6282 // This routine is similar to the above but does not record
6283 // any policy statistics or update free lists; we are abandoning
6284 // the current incremental collection set in preparation of a
6285 // full collection. After the full GC we will start to build up
6286 // the incremental collection set again.
6287 // This is only called when we're doing a full collection
6288 // and is immediately followed by the tearing down of the young list.
6289 
6290 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
6291   HeapRegion* cur = cs_head;
6292 
6293   while (cur != NULL) {
6294     HeapRegion* next = cur->next_in_collection_set();
6295     assert(cur->in_collection_set(), "bad CS");
6296     cur->set_next_in_collection_set(NULL);
6297     cur->set_in_collection_set(false);
6298     cur->set_young_index_in_cset(-1);
6299     cur = next;
6300   }
6301 }
6302 
6303 void G1CollectedHeap::set_free_regions_coming() {
6304   if (G1ConcRegionFreeingVerbose) {
6305     gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6306                            "setting free regions coming");
6307   }
6308 
6309   assert(!free_regions_coming(), "pre-condition");
6310   _free_regions_coming = true;
6311 }
6312 
6313 void G1CollectedHeap::reset_free_regions_coming() {
6314   assert(free_regions_coming(), "pre-condition");
6315 
6316   {
6317     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6318     _free_regions_coming = false;
6319     SecondaryFreeList_lock->notify_all();
6320   }
6321 
6322   if (G1ConcRegionFreeingVerbose) {
6323     gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6324                            "reset free regions coming");
6325   }
6326 }
6327 
6328 void G1CollectedHeap::wait_while_free_regions_coming() {
6329   // Most of the time we won't have to wait, so let's do a quick test
6330   // first before we take the lock.
6331   if (!free_regions_coming()) {
6332     return;
6333   }
6334 
6335   if (G1ConcRegionFreeingVerbose) {
6336     gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6337                            "waiting for free regions");
6338   }
6339 
6340   {
6341     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6342     while (free_regions_coming()) {
6343       SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
6344     }
6345   }
6346 
6347   if (G1ConcRegionFreeingVerbose) {
6348     gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6349                            "done waiting for free regions");
6350   }
6351 }
6352 
6353 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
6354   assert(heap_lock_held_for_gc(),
6355               "the heap lock should already be held by or for this thread");
6356   _young_list->push_region(hr);
6357 }
6358 
6359 class NoYoungRegionsClosure: public HeapRegionClosure {
6360 private:
6361   bool _success;
6362 public:
6363   NoYoungRegionsClosure() : _success(true) { }
6364   bool doHeapRegion(HeapRegion* r) {
6365     if (r->is_young()) {
6366       gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
6367                              r->bottom(), r->end());
6368       _success = false;
6369     }
6370     return false;
6371   }
6372   bool success() { return _success; }
6373 };
6374 
6375 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
6376   bool ret = _young_list->check_list_empty(check_sample);
6377 
6378   if (check_heap) {
6379     NoYoungRegionsClosure closure;
6380     heap_region_iterate(&closure);
6381     ret = ret && closure.success();
6382   }
6383 
6384   return ret;
6385 }
6386 
6387 class TearDownRegionSetsClosure : public HeapRegionClosure {
6388 private:
6389   HeapRegionSet *_old_set;
6390 
6391 public:
6392   TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
6393 
6394   bool doHeapRegion(HeapRegion* r) {
6395     if (r->is_old()) {
6396       _old_set->remove(r);
6397     } else {
6398       // We ignore free regions, we'll empty the free list afterwards.
6399       // We ignore young regions, we'll empty the young list afterwards.
6400       // We ignore humongous regions, we're not tearing down the
6401       // humongous regions set.
6402       assert(r->is_free() || r->is_young() || r->is_humongous(),
6403              "it cannot be another type");
6404     }
6405     return false;
6406   }
6407 
6408   ~TearDownRegionSetsClosure() {
6409     assert(_old_set->is_empty(), "post-condition");
6410   }
6411 };
6412 
6413 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6414   assert_at_safepoint(true /* should_be_vm_thread */);
6415 
6416   if (!free_list_only) {
6417     TearDownRegionSetsClosure cl(&_old_set);
6418     heap_region_iterate(&cl);
6419 
6420     // Note that emptying the _young_list is postponed and instead done as
6421     // the first step when rebuilding the regions sets again. The reason for
6422     // this is that during a full GC string deduplication needs to know if
6423     // a collected region was young or old when the full GC was initiated.
6424   }
6425   _hrm.remove_all_free_regions();
6426 }
6427 
6428 class RebuildRegionSetsClosure : public HeapRegionClosure {
6429 private:
6430   bool            _free_list_only;
6431   HeapRegionSet*   _old_set;
6432   HeapRegionManager*   _hrm;
6433   size_t          _total_used;
6434 
6435 public:
6436   RebuildRegionSetsClosure(bool free_list_only,
6437                            HeapRegionSet* old_set, HeapRegionManager* hrm) :
6438     _free_list_only(free_list_only),
6439     _old_set(old_set), _hrm(hrm), _total_used(0) {
6440     assert(_hrm->num_free_regions() == 0, "pre-condition");
6441     if (!free_list_only) {
6442       assert(_old_set->is_empty(), "pre-condition");
6443     }
6444   }
6445 
6446   bool doHeapRegion(HeapRegion* r) {
6447     if (r->is_continues_humongous()) {
6448       return false;
6449     }
6450 
6451     if (r->is_empty()) {
6452       // Add free regions to the free list
6453       r->set_free();
6454       r->set_allocation_context(AllocationContext::system());
6455       _hrm->insert_into_free_list(r);
6456     } else if (!_free_list_only) {
6457       assert(!r->is_young(), "we should not come across young regions");
6458 
6459       if (r->is_humongous()) {
6460         // We ignore humongous regions, we left the humongous set unchanged
6461       } else {
6462         // Objects that were compacted would have ended up on regions
6463         // that were previously old or free.
6464         assert(r->is_free() || r->is_old(), "invariant");
6465         // We now consider them old, so register as such.
6466         r->set_old();
6467         _old_set->add(r);
6468       }
6469       _total_used += r->used();
6470     }
6471 
6472     return false;
6473   }
6474 
6475   size_t total_used() {
6476     return _total_used;
6477   }
6478 };
6479 
6480 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6481   assert_at_safepoint(true /* should_be_vm_thread */);
6482 
6483   if (!free_list_only) {
6484     _young_list->empty_list();
6485   }
6486 
6487   RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
6488   heap_region_iterate(&cl);
6489 
6490   if (!free_list_only) {
6491     _allocator->set_used(cl.total_used());
6492   }
6493   assert(_allocator->used_unlocked() == recalculate_used(),
6494          err_msg("inconsistent _allocator->used_unlocked(), "
6495                  "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6496                  _allocator->used_unlocked(), recalculate_used()));
6497 }
6498 
6499 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6500   _refine_cte_cl->set_concurrent(concurrent);
6501 }
6502 
6503 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6504   HeapRegion* hr = heap_region_containing(p);
6505   return hr->is_in(p);
6506 }
6507 
6508 // Methods for the mutator alloc region
6509 
6510 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6511                                                       bool force) {
6512   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6513   assert(!force || g1_policy()->can_expand_young_list(),
6514          "if force is true we should be able to expand the young list");
6515   bool young_list_full = g1_policy()->is_young_list_full();
6516   if (force || !young_list_full) {
6517     HeapRegion* new_alloc_region = new_region(word_size,
6518                                               false /* is_old */,
6519                                               false /* do_expand */);
6520     if (new_alloc_region != NULL) {
6521       set_region_short_lived_locked(new_alloc_region);
6522       _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6523       check_bitmaps("Mutator Region Allocation", new_alloc_region);
6524       return new_alloc_region;
6525     }
6526   }
6527   return NULL;
6528 }
6529 
6530 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6531                                                   size_t allocated_bytes) {
6532   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6533   assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
6534 
6535   g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6536   _allocator->increase_used(allocated_bytes);
6537   _hr_printer.retire(alloc_region);
6538   // We update the eden sizes here, when the region is retired,
6539   // instead of when it's allocated, since this is the point that its
6540   // used space has been recored in _summary_bytes_used.
6541   g1mm()->update_eden_size();
6542 }
6543 
6544 void G1CollectedHeap::set_par_threads() {
6545   // Don't change the number of workers.  Use the value previously set
6546   // in the workgroup.
6547   uint n_workers = workers()->active_workers();
6548   assert(UseDynamicNumberOfGCThreads ||
6549            n_workers == workers()->total_workers(),
6550       "Otherwise should be using the total number of workers");
6551   if (n_workers == 0) {
6552     assert(false, "Should have been set in prior evacuation pause.");
6553     n_workers = ParallelGCThreads;
6554     workers()->set_active_workers(n_workers);
6555   }
6556   set_par_threads(n_workers);
6557 }
6558 
6559 // Methods for the GC alloc regions
6560 
6561 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6562                                                  uint count,
6563                                                  InCSetState dest) {
6564   assert(FreeList_lock->owned_by_self(), "pre-condition");
6565 
6566   if (count < g1_policy()->max_regions(dest)) {
6567     const bool is_survivor = (dest.is_young());
6568     HeapRegion* new_alloc_region = new_region(word_size,
6569                                               !is_survivor,
6570                                               true /* do_expand */);
6571     if (new_alloc_region != NULL) {
6572       // We really only need to do this for old regions given that we
6573       // should never scan survivors. But it doesn't hurt to do it
6574       // for survivors too.
6575       new_alloc_region->record_timestamp();
6576       if (is_survivor) {
6577         new_alloc_region->set_survivor();
6578         _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6579         check_bitmaps("Survivor Region Allocation", new_alloc_region);
6580       } else {
6581         new_alloc_region->set_old();
6582         _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6583         check_bitmaps("Old Region Allocation", new_alloc_region);
6584       }
6585       bool during_im = g1_policy()->during_initial_mark_pause();
6586       new_alloc_region->note_start_of_copying(during_im);
6587       return new_alloc_region;
6588     }
6589   }
6590   return NULL;
6591 }
6592 
6593 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6594                                              size_t allocated_bytes,
6595                                              InCSetState dest) {
6596   bool during_im = g1_policy()->during_initial_mark_pause();
6597   alloc_region->note_end_of_copying(during_im);
6598   g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6599   if (dest.is_young()) {
6600     young_list()->add_survivor_region(alloc_region);
6601   } else {
6602     _old_set.add(alloc_region);
6603   }
6604   _hr_printer.retire(alloc_region);
6605 }
6606 
6607 // Heap region set verification
6608 
6609 class VerifyRegionListsClosure : public HeapRegionClosure {
6610 private:
6611   HeapRegionSet*   _old_set;
6612   HeapRegionSet*   _humongous_set;
6613   HeapRegionManager*   _hrm;
6614 
6615 public:
6616   HeapRegionSetCount _old_count;
6617   HeapRegionSetCount _humongous_count;
6618   HeapRegionSetCount _free_count;
6619 
6620   VerifyRegionListsClosure(HeapRegionSet* old_set,
6621                            HeapRegionSet* humongous_set,
6622                            HeapRegionManager* hrm) :
6623     _old_set(old_set), _humongous_set(humongous_set), _hrm(hrm),
6624     _old_count(), _humongous_count(), _free_count(){ }
6625 
6626   bool doHeapRegion(HeapRegion* hr) {
6627     if (hr->is_continues_humongous()) {
6628       return false;
6629     }
6630 
6631     if (hr->is_young()) {
6632       // TODO
6633     } else if (hr->is_starts_humongous()) {
6634       assert(hr->containing_set() == _humongous_set, err_msg("Heap region %u is starts humongous but not in humongous set.", hr->hrm_index()));
6635       _humongous_count.increment(1u, hr->capacity());
6636     } else if (hr->is_empty()) {
6637       assert(_hrm->is_free(hr), err_msg("Heap region %u is empty but not on the free list.", hr->hrm_index()));
6638       _free_count.increment(1u, hr->capacity());
6639     } else if (hr->is_old()) {
6640       assert(hr->containing_set() == _old_set, err_msg("Heap region %u is old but not in the old set.", hr->hrm_index()));
6641       _old_count.increment(1u, hr->capacity());
6642     } else {
6643       ShouldNotReachHere();
6644     }
6645     return false;
6646   }
6647 
6648   void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, HeapRegionManager* free_list) {
6649     guarantee(old_set->length() == _old_count.length(), err_msg("Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length()));
6650     guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), err_msg("Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6651         old_set->total_capacity_bytes(), _old_count.capacity()));
6652 
6653     guarantee(humongous_set->length() == _humongous_count.length(), err_msg("Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length()));
6654     guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), err_msg("Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6655         humongous_set->total_capacity_bytes(), _humongous_count.capacity()));
6656 
6657     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()));
6658     guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), err_msg("Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6659         free_list->total_capacity_bytes(), _free_count.capacity()));
6660   }
6661 };
6662 
6663 void G1CollectedHeap::verify_region_sets() {
6664   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6665 
6666   // First, check the explicit lists.
6667   _hrm.verify();
6668   {
6669     // Given that a concurrent operation might be adding regions to
6670     // the secondary free list we have to take the lock before
6671     // verifying it.
6672     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6673     _secondary_free_list.verify_list();
6674   }
6675 
6676   // If a concurrent region freeing operation is in progress it will
6677   // be difficult to correctly attributed any free regions we come
6678   // across to the correct free list given that they might belong to
6679   // one of several (free_list, secondary_free_list, any local lists,
6680   // etc.). So, if that's the case we will skip the rest of the
6681   // verification operation. Alternatively, waiting for the concurrent
6682   // operation to complete will have a non-trivial effect on the GC's
6683   // operation (no concurrent operation will last longer than the
6684   // interval between two calls to verification) and it might hide
6685   // any issues that we would like to catch during testing.
6686   if (free_regions_coming()) {
6687     return;
6688   }
6689 
6690   // Make sure we append the secondary_free_list on the free_list so
6691   // that all free regions we will come across can be safely
6692   // attributed to the free_list.
6693   append_secondary_free_list_if_not_empty_with_lock();
6694 
6695   // Finally, make sure that the region accounting in the lists is
6696   // consistent with what we see in the heap.
6697 
6698   VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_hrm);
6699   heap_region_iterate(&cl);
6700   cl.verify_counts(&_old_set, &_humongous_set, &_hrm);
6701 }
6702 
6703 // Optimized nmethod scanning
6704 
6705 class RegisterNMethodOopClosure: public OopClosure {
6706   G1CollectedHeap* _g1h;
6707   nmethod* _nm;
6708 
6709   template <class T> void do_oop_work(T* p) {
6710     T heap_oop = oopDesc::load_heap_oop(p);
6711     if (!oopDesc::is_null(heap_oop)) {
6712       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6713       HeapRegion* hr = _g1h->heap_region_containing(obj);
6714       assert(!hr->is_continues_humongous(),
6715              err_msg("trying to add code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6716                      " starting at "HR_FORMAT,
6717                      _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6718 
6719       // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
6720       hr->add_strong_code_root_locked(_nm);
6721     }
6722   }
6723 
6724 public:
6725   RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6726     _g1h(g1h), _nm(nm) {}
6727 
6728   void do_oop(oop* p)       { do_oop_work(p); }
6729   void do_oop(narrowOop* p) { do_oop_work(p); }
6730 };
6731 
6732 class UnregisterNMethodOopClosure: public OopClosure {
6733   G1CollectedHeap* _g1h;
6734   nmethod* _nm;
6735 
6736   template <class T> void do_oop_work(T* p) {
6737     T heap_oop = oopDesc::load_heap_oop(p);
6738     if (!oopDesc::is_null(heap_oop)) {
6739       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6740       HeapRegion* hr = _g1h->heap_region_containing(obj);
6741       assert(!hr->is_continues_humongous(),
6742              err_msg("trying to remove code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6743                      " starting at "HR_FORMAT,
6744                      _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6745 
6746       hr->remove_strong_code_root(_nm);
6747     }
6748   }
6749 
6750 public:
6751   UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6752     _g1h(g1h), _nm(nm) {}
6753 
6754   void do_oop(oop* p)       { do_oop_work(p); }
6755   void do_oop(narrowOop* p) { do_oop_work(p); }
6756 };
6757 
6758 void G1CollectedHeap::register_nmethod(nmethod* nm) {
6759   CollectedHeap::register_nmethod(nm);
6760 
6761   guarantee(nm != NULL, "sanity");
6762   RegisterNMethodOopClosure reg_cl(this, nm);
6763   nm->oops_do(&reg_cl);
6764 }
6765 
6766 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
6767   CollectedHeap::unregister_nmethod(nm);
6768 
6769   guarantee(nm != NULL, "sanity");
6770   UnregisterNMethodOopClosure reg_cl(this, nm);
6771   nm->oops_do(&reg_cl, true);
6772 }
6773 
6774 void G1CollectedHeap::purge_code_root_memory() {
6775   double purge_start = os::elapsedTime();
6776   G1CodeRootSet::purge();
6777   double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
6778   g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
6779 }
6780 
6781 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
6782   G1CollectedHeap* _g1h;
6783 
6784 public:
6785   RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
6786     _g1h(g1h) {}
6787 
6788   void do_code_blob(CodeBlob* cb) {
6789     nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
6790     if (nm == NULL) {
6791       return;
6792     }
6793 
6794     if (ScavengeRootsInCode) {
6795       _g1h->register_nmethod(nm);
6796     }
6797   }
6798 };
6799 
6800 void G1CollectedHeap::rebuild_strong_code_roots() {
6801   RebuildStrongCodeRootClosure blob_cl(this);
6802   CodeCache::blobs_do(&blob_cl);
6803 }