1 /*
   2  * Copyright (c) 2001, 2015, 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 #include "precompiled.hpp"
  26 #include "classfile/metadataOnStackMark.hpp"
  27 #include "classfile/stringTable.hpp"
  28 #include "code/codeCache.hpp"
  29 #include "code/icBuffer.hpp"
  30 #include "gc_implementation/g1/bufferingOopClosure.hpp"
  31 #include "gc_implementation/g1/concurrentG1Refine.hpp"
  32 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
  33 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
  34 #include "gc_implementation/g1/g1AllocRegion.inline.hpp"
  35 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
  36 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
  37 #include "gc_implementation/g1/g1ErgoVerbose.hpp"
  38 #include "gc_implementation/g1/g1EvacFailure.hpp"
  39 #include "gc_implementation/g1/g1GCPhaseTimes.hpp"
  40 #include "gc_implementation/g1/g1Log.hpp"
  41 #include "gc_implementation/g1/g1MarkSweep.hpp"
  42 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
  43 #include "gc_implementation/g1/g1ParScanThreadState.inline.hpp"
  44 #include "gc_implementation/g1/g1RegionToSpaceMapper.hpp"
  45 #include "gc_implementation/g1/g1RemSet.inline.hpp"
  46 #include "gc_implementation/g1/g1RootProcessor.hpp"
  47 #include "gc_implementation/g1/g1StringDedup.hpp"
  48 #include "gc_implementation/g1/g1YCTypes.hpp"
  49 #include "gc_implementation/g1/heapRegion.inline.hpp"
  50 #include "gc_implementation/g1/heapRegionRemSet.hpp"
  51 #include "gc_implementation/g1/heapRegionSet.inline.hpp"
  52 #include "gc_implementation/g1/vm_operations_g1.hpp"
  53 #include "gc_implementation/shared/gcHeapSummary.hpp"
  54 #include "gc_implementation/shared/gcTimer.hpp"
  55 #include "gc_implementation/shared/gcTrace.hpp"
  56 #include "gc_implementation/shared/gcTraceTime.hpp"
  57 #include "gc_implementation/shared/isGCActiveMark.hpp"
  58 #include "memory/allocation.hpp"
  59 #include "memory/gcLocker.inline.hpp"
  60 #include "memory/generationSpec.hpp"
  61 #include "memory/iterator.hpp"
  62 #include "memory/referenceProcessor.hpp"
  63 #include "oops/oop.inline.hpp"
  64 #include "runtime/atomic.inline.hpp"
  65 #include "runtime/orderAccess.inline.hpp"
  66 #include "runtime/vmThread.hpp"
  67 #include "utilities/globalDefinitions.hpp"
  68 #include "utilities/stack.inline.hpp"
  69 #include "utilities/taskqueue.inline.hpp"
  70 
  71 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
  72 
  73 // turn it on so that the contents of the young list (scan-only /
  74 // to-be-collected) are printed at "strategic" points before / during
  75 // / after the collection --- this is useful for debugging
  76 #define YOUNG_LIST_VERBOSE 0
  77 // CURRENT STATUS
  78 // This file is under construction.  Search for "FIXME".
  79 
  80 // INVARIANTS/NOTES
  81 //
  82 // All allocation activity covered by the G1CollectedHeap interface is
  83 // serialized by acquiring the HeapLock.  This happens in mem_allocate
  84 // and allocate_new_tlab, which are the "entry" points to the
  85 // allocation code from the rest of the JVM.  (Note that this does not
  86 // apply to TLAB allocation, which is not part of this interface: it
  87 // is done by clients of this interface.)
  88 
  89 // Local to this file.
  90 
  91 class RefineCardTableEntryClosure: public CardTableEntryClosure {
  92   bool _concurrent;
  93 public:
  94   RefineCardTableEntryClosure() : _concurrent(true) { }
  95 
  96   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
  97     bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, false);
  98     // This path is executed by the concurrent refine or mutator threads,
  99     // concurrently, and so we do not care if card_ptr contains references
 100     // that point into the collection set.
 101     assert(!oops_into_cset, "should be");
 102 
 103     if (_concurrent && SuspendibleThreadSet::should_yield()) {
 104       // Caller will actually yield.
 105       return false;
 106     }
 107     // Otherwise, we finished successfully; return true.
 108     return true;
 109   }
 110 
 111   void set_concurrent(bool b) { _concurrent = b; }
 112 };
 113 
 114 
 115 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
 116  private:
 117   size_t _num_processed;
 118 
 119  public:
 120   RedirtyLoggedCardTableEntryClosure() : CardTableEntryClosure(), _num_processed(0) { }
 121 
 122   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
 123     *card_ptr = CardTableModRefBS::dirty_card_val();
 124     _num_processed++;
 125     return true;
 126   }
 127 
 128   size_t num_processed() const { return _num_processed; }
 129 };
 130 
 131 YoungList::YoungList(G1CollectedHeap* g1h) :
 132     _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0),
 133     _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) {
 134   guarantee(check_list_empty(false), "just making sure...");
 135 }
 136 
 137 void YoungList::push_region(HeapRegion *hr) {
 138   assert(!hr->is_young(), "should not already be young");
 139   assert(hr->get_next_young_region() == NULL, "cause it should!");
 140 
 141   hr->set_next_young_region(_head);
 142   _head = hr;
 143 
 144   _g1h->g1_policy()->set_region_eden(hr, (int) _length);
 145   ++_length;
 146 }
 147 
 148 void YoungList::add_survivor_region(HeapRegion* hr) {
 149   assert(hr->is_survivor(), "should be flagged as survivor region");
 150   assert(hr->get_next_young_region() == NULL, "cause it should!");
 151 
 152   hr->set_next_young_region(_survivor_head);
 153   if (_survivor_head == NULL) {
 154     _survivor_tail = hr;
 155   }
 156   _survivor_head = hr;
 157   ++_survivor_length;
 158 }
 159 
 160 void YoungList::empty_list(HeapRegion* list) {
 161   while (list != NULL) {
 162     HeapRegion* next = list->get_next_young_region();
 163     list->set_next_young_region(NULL);
 164     list->uninstall_surv_rate_group();
 165     // This is called before a Full GC and all the non-empty /
 166     // non-humongous regions at the end of the Full GC will end up as
 167     // old anyway.
 168     list->set_old();
 169     list = next;
 170   }
 171 }
 172 
 173 void YoungList::empty_list() {
 174   assert(check_list_well_formed(), "young list should be well formed");
 175 
 176   empty_list(_head);
 177   _head = NULL;
 178   _length = 0;
 179 
 180   empty_list(_survivor_head);
 181   _survivor_head = NULL;
 182   _survivor_tail = NULL;
 183   _survivor_length = 0;
 184 
 185   _last_sampled_rs_lengths = 0;
 186 
 187   assert(check_list_empty(false), "just making sure...");
 188 }
 189 
 190 bool YoungList::check_list_well_formed() {
 191   bool ret = true;
 192 
 193   uint length = 0;
 194   HeapRegion* curr = _head;
 195   HeapRegion* last = NULL;
 196   while (curr != NULL) {
 197     if (!curr->is_young()) {
 198       gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
 199                              "incorrectly tagged (y: %d, surv: %d)",
 200                              p2i(curr->bottom()), p2i(curr->end()),
 201                              curr->is_young(), curr->is_survivor());
 202       ret = false;
 203     }
 204     ++length;
 205     last = curr;
 206     curr = curr->get_next_young_region();
 207   }
 208   ret = ret && (length == _length);
 209 
 210   if (!ret) {
 211     gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
 212     gclog_or_tty->print_cr("###   list has %u entries, _length is %u",
 213                            length, _length);
 214   }
 215 
 216   return ret;
 217 }
 218 
 219 bool YoungList::check_list_empty(bool check_sample) {
 220   bool ret = true;
 221 
 222   if (_length != 0) {
 223     gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u",
 224                   _length);
 225     ret = false;
 226   }
 227   if (check_sample && _last_sampled_rs_lengths != 0) {
 228     gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
 229     ret = false;
 230   }
 231   if (_head != NULL) {
 232     gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
 233     ret = false;
 234   }
 235   if (!ret) {
 236     gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
 237   }
 238 
 239   return ret;
 240 }
 241 
 242 void
 243 YoungList::rs_length_sampling_init() {
 244   _sampled_rs_lengths = 0;
 245   _curr               = _head;
 246 }
 247 
 248 bool
 249 YoungList::rs_length_sampling_more() {
 250   return _curr != NULL;
 251 }
 252 
 253 void
 254 YoungList::rs_length_sampling_next() {
 255   assert( _curr != NULL, "invariant" );
 256   size_t rs_length = _curr->rem_set()->occupied();
 257 
 258   _sampled_rs_lengths += rs_length;
 259 
 260   // The current region may not yet have been added to the
 261   // incremental collection set (it gets added when it is
 262   // retired as the current allocation region).
 263   if (_curr->in_collection_set()) {
 264     // Update the collection set policy information for this region
 265     _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
 266   }
 267 
 268   _curr = _curr->get_next_young_region();
 269   if (_curr == NULL) {
 270     _last_sampled_rs_lengths = _sampled_rs_lengths;
 271     // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
 272   }
 273 }
 274 
 275 void
 276 YoungList::reset_auxilary_lists() {
 277   guarantee( is_empty(), "young list should be empty" );
 278   assert(check_list_well_formed(), "young list should be well formed");
 279 
 280   // Add survivor regions to SurvRateGroup.
 281   _g1h->g1_policy()->note_start_adding_survivor_regions();
 282   _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
 283 
 284   int young_index_in_cset = 0;
 285   for (HeapRegion* curr = _survivor_head;
 286        curr != NULL;
 287        curr = curr->get_next_young_region()) {
 288     _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
 289 
 290     // The region is a non-empty survivor so let's add it to
 291     // the incremental collection set for the next evacuation
 292     // pause.
 293     _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
 294     young_index_in_cset += 1;
 295   }
 296   assert((uint) young_index_in_cset == _survivor_length, "post-condition");
 297   _g1h->g1_policy()->note_stop_adding_survivor_regions();
 298 
 299   _head   = _survivor_head;
 300   _length = _survivor_length;
 301   if (_survivor_head != NULL) {
 302     assert(_survivor_tail != NULL, "cause it shouldn't be");
 303     assert(_survivor_length > 0, "invariant");
 304     _survivor_tail->set_next_young_region(NULL);
 305   }
 306 
 307   // Don't clear the survivor list handles until the start of
 308   // the next evacuation pause - we need it in order to re-tag
 309   // the survivor regions from this evacuation pause as 'young'
 310   // at the start of the next.
 311 
 312   _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
 313 
 314   assert(check_list_well_formed(), "young list should be well formed");
 315 }
 316 
 317 void YoungList::print() {
 318   HeapRegion* lists[] = {_head,   _survivor_head};
 319   const char* names[] = {"YOUNG", "SURVIVOR"};
 320 
 321   for (uint list = 0; list < ARRAY_SIZE(lists); ++list) {
 322     gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
 323     HeapRegion *curr = lists[list];
 324     if (curr == NULL)
 325       gclog_or_tty->print_cr("  empty");
 326     while (curr != NULL) {
 327       gclog_or_tty->print_cr("  "HR_FORMAT", P: "PTR_FORMAT ", N: "PTR_FORMAT", age: %4d",
 328                              HR_FORMAT_PARAMS(curr),
 329                              p2i(curr->prev_top_at_mark_start()),
 330                              p2i(curr->next_top_at_mark_start()),
 331                              curr->age_in_surv_rate_group_cond());
 332       curr = curr->get_next_young_region();
 333     }
 334   }
 335 
 336   gclog_or_tty->cr();
 337 }
 338 
 339 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
 340   HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
 341 }
 342 
 343 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
 344   // The from card cache is not the memory that is actually committed. So we cannot
 345   // take advantage of the zero_filled parameter.
 346   reset_from_card_cache(start_idx, num_regions);
 347 }
 348 
 349 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
 350 {
 351   // Claim the right to put the region on the dirty cards region list
 352   // by installing a self pointer.
 353   HeapRegion* next = hr->get_next_dirty_cards_region();
 354   if (next == NULL) {
 355     HeapRegion* res = (HeapRegion*)
 356       Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
 357                           NULL);
 358     if (res == NULL) {
 359       HeapRegion* head;
 360       do {
 361         // Put the region to the dirty cards region list.
 362         head = _dirty_cards_region_list;
 363         next = (HeapRegion*)
 364           Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
 365         if (next == head) {
 366           assert(hr->get_next_dirty_cards_region() == hr,
 367                  "hr->get_next_dirty_cards_region() != hr");
 368           if (next == NULL) {
 369             // The last region in the list points to itself.
 370             hr->set_next_dirty_cards_region(hr);
 371           } else {
 372             hr->set_next_dirty_cards_region(next);
 373           }
 374         }
 375       } while (next != head);
 376     }
 377   }
 378 }
 379 
 380 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
 381 {
 382   HeapRegion* head;
 383   HeapRegion* hr;
 384   do {
 385     head = _dirty_cards_region_list;
 386     if (head == NULL) {
 387       return NULL;
 388     }
 389     HeapRegion* new_head = head->get_next_dirty_cards_region();
 390     if (head == new_head) {
 391       // The last region.
 392       new_head = NULL;
 393     }
 394     hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
 395                                           head);
 396   } while (hr != head);
 397   assert(hr != NULL, "invariant");
 398   hr->set_next_dirty_cards_region(NULL);
 399   return hr;
 400 }
 401 
 402 // Returns true if the reference points to an object that
 403 // can move in an incremental collection.
 404 bool G1CollectedHeap::is_scavengable(const void* p) {
 405   HeapRegion* hr = heap_region_containing(p);
 406   return !hr->is_humongous();
 407 }
 408 
 409 // Private methods.
 410 
 411 HeapRegion*
 412 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
 413   MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
 414   while (!_secondary_free_list.is_empty() || free_regions_coming()) {
 415     if (!_secondary_free_list.is_empty()) {
 416       if (G1ConcRegionFreeingVerbose) {
 417         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 418                                "secondary_free_list has %u entries",
 419                                _secondary_free_list.length());
 420       }
 421       // It looks as if there are free regions available on the
 422       // secondary_free_list. Let's move them to the free_list and try
 423       // again to allocate from it.
 424       append_secondary_free_list();
 425 
 426       assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not "
 427              "empty we should have moved at least one entry to the free_list");
 428       HeapRegion* res = _hrm.allocate_free_region(is_old);
 429       if (G1ConcRegionFreeingVerbose) {
 430         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 431                                "allocated "HR_FORMAT" from secondary_free_list",
 432                                HR_FORMAT_PARAMS(res));
 433       }
 434       return res;
 435     }
 436 
 437     // Wait here until we get notified either when (a) there are no
 438     // more free regions coming or (b) some regions have been moved on
 439     // the secondary_free_list.
 440     SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
 441   }
 442 
 443   if (G1ConcRegionFreeingVerbose) {
 444     gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 445                            "could not allocate from secondary_free_list");
 446   }
 447   return NULL;
 448 }
 449 
 450 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
 451   assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
 452          "the only time we use this to allocate a humongous region is "
 453          "when we are allocating a single humongous region");
 454 
 455   HeapRegion* res;
 456   if (G1StressConcRegionFreeing) {
 457     if (!_secondary_free_list.is_empty()) {
 458       if (G1ConcRegionFreeingVerbose) {
 459         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 460                                "forced to look at the secondary_free_list");
 461       }
 462       res = new_region_try_secondary_free_list(is_old);
 463       if (res != NULL) {
 464         return res;
 465       }
 466     }
 467   }
 468 
 469   res = _hrm.allocate_free_region(is_old);
 470 
 471   if (res == NULL) {
 472     if (G1ConcRegionFreeingVerbose) {
 473       gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 474                              "res == NULL, trying the secondary_free_list");
 475     }
 476     res = new_region_try_secondary_free_list(is_old);
 477   }
 478   if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
 479     // Currently, only attempts to allocate GC alloc regions set
 480     // do_expand to true. So, we should only reach here during a
 481     // safepoint. If this assumption changes we might have to
 482     // reconsider the use of _expand_heap_after_alloc_failure.
 483     assert(SafepointSynchronize::is_at_safepoint(), "invariant");
 484 
 485     ergo_verbose1(ErgoHeapSizing,
 486                   "attempt heap expansion",
 487                   ergo_format_reason("region allocation request failed")
 488                   ergo_format_byte("allocation request"),
 489                   word_size * HeapWordSize);
 490     if (expand(word_size * HeapWordSize)) {
 491       // Given that expand() succeeded in expanding the heap, and we
 492       // always expand the heap by an amount aligned to the heap
 493       // region size, the free list should in theory not be empty.
 494       // In either case allocate_free_region() will check for NULL.
 495       res = _hrm.allocate_free_region(is_old);
 496     } else {
 497       _expand_heap_after_alloc_failure = false;
 498     }
 499   }
 500   return res;
 501 }
 502 
 503 HeapWord*
 504 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
 505                                                            uint num_regions,
 506                                                            size_t word_size,
 507                                                            AllocationContext_t context) {
 508   assert(first != G1_NO_HRM_INDEX, "pre-condition");
 509   assert(is_humongous(word_size), "word_size should be humongous");
 510   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 511 
 512   // Index of last region in the series + 1.
 513   uint last = first + num_regions;
 514 
 515   // We need to initialize the region(s) we just discovered. This is
 516   // a bit tricky given that it can happen concurrently with
 517   // refinement threads refining cards on these regions and
 518   // potentially wanting to refine the BOT as they are scanning
 519   // those cards (this can happen shortly after a cleanup; see CR
 520   // 6991377). So we have to set up the region(s) carefully and in
 521   // a specific order.
 522 
 523   // The word size sum of all the regions we will allocate.
 524   size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
 525   assert(word_size <= word_size_sum, "sanity");
 526 
 527   // This will be the "starts humongous" region.
 528   HeapRegion* first_hr = region_at(first);
 529   // The header of the new object will be placed at the bottom of
 530   // the first region.
 531   HeapWord* new_obj = first_hr->bottom();
 532   // This will be the new end of the first region in the series that
 533   // should also match the end of the last region in the series.
 534   HeapWord* new_end = new_obj + word_size_sum;
 535   // This will be the new top of the first region that will reflect
 536   // this allocation.
 537   HeapWord* new_top = new_obj + word_size;
 538 
 539   // First, we need to zero the header of the space that we will be
 540   // allocating. When we update top further down, some refinement
 541   // threads might try to scan the region. By zeroing the header we
 542   // ensure that any thread that will try to scan the region will
 543   // come across the zero klass word and bail out.
 544   //
 545   // NOTE: It would not have been correct to have used
 546   // CollectedHeap::fill_with_object() and make the space look like
 547   // an int array. The thread that is doing the allocation will
 548   // later update the object header to a potentially different array
 549   // type and, for a very short period of time, the klass and length
 550   // fields will be inconsistent. This could cause a refinement
 551   // thread to calculate the object size incorrectly.
 552   Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
 553 
 554   // We will set up the first region as "starts humongous". This
 555   // will also update the BOT covering all the regions to reflect
 556   // that there is a single object that starts at the bottom of the
 557   // first region.
 558   first_hr->set_starts_humongous(new_top, new_end);
 559   first_hr->set_allocation_context(context);
 560   // Then, if there are any, we will set up the "continues
 561   // humongous" regions.
 562   HeapRegion* hr = NULL;
 563   for (uint i = first + 1; i < last; ++i) {
 564     hr = region_at(i);
 565     hr->set_continues_humongous(first_hr);
 566     hr->set_allocation_context(context);
 567   }
 568   // If we have "continues humongous" regions (hr != NULL), then the
 569   // end of the last one should match new_end.
 570   assert(hr == NULL || hr->end() == new_end, "sanity");
 571 
 572   // Up to this point no concurrent thread would have been able to
 573   // do any scanning on any region in this series. All the top
 574   // fields still point to bottom, so the intersection between
 575   // [bottom,top] and [card_start,card_end] will be empty. Before we
 576   // update the top fields, we'll do a storestore to make sure that
 577   // no thread sees the update to top before the zeroing of the
 578   // object header and the BOT initialization.
 579   OrderAccess::storestore();
 580 
 581   // Now that the BOT and the object header have been initialized,
 582   // we can update top of the "starts humongous" region.
 583   assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
 584          "new_top should be in this region");
 585   first_hr->set_top(new_top);
 586   if (_hr_printer.is_active()) {
 587     HeapWord* bottom = first_hr->bottom();
 588     HeapWord* end = first_hr->orig_end();
 589     if ((first + 1) == last) {
 590       // the series has a single humongous region
 591       _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
 592     } else {
 593       // the series has more than one humongous regions
 594       _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
 595     }
 596   }
 597 
 598   // Now, we will update the top fields of the "continues humongous"
 599   // regions. The reason we need to do this is that, otherwise,
 600   // these regions would look empty and this will confuse parts of
 601   // G1. For example, the code that looks for a consecutive number
 602   // of empty regions will consider them empty and try to
 603   // re-allocate them. We can extend is_empty() to also include
 604   // !is_continues_humongous(), but it is easier to just update the top
 605   // fields here. The way we set top for all regions (i.e., top ==
 606   // end for all regions but the last one, top == new_top for the
 607   // last one) is actually used when we will free up the humongous
 608   // region in free_humongous_region().
 609   hr = NULL;
 610   for (uint i = first + 1; i < last; ++i) {
 611     hr = region_at(i);
 612     if ((i + 1) == last) {
 613       // last continues humongous region
 614       assert(hr->bottom() < new_top && new_top <= hr->end(),
 615              "new_top should fall on this region");
 616       hr->set_top(new_top);
 617       _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
 618     } else {
 619       // not last one
 620       assert(new_top > hr->end(), "new_top should be above this region");
 621       hr->set_top(hr->end());
 622       _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
 623     }
 624   }
 625   // If we have continues humongous regions (hr != NULL), then the
 626   // end of the last one should match new_end and its top should
 627   // match new_top.
 628   assert(hr == NULL ||
 629          (hr->end() == new_end && hr->top() == new_top), "sanity");
 630   check_bitmaps("Humongous Region Allocation", first_hr);
 631 
 632   assert(first_hr->used() == word_size * HeapWordSize, "invariant");
 633   _allocator->increase_used(first_hr->used());
 634   _humongous_set.add(first_hr);
 635 
 636   return new_obj;
 637 }
 638 
 639 // If could fit into free regions w/o expansion, try.
 640 // Otherwise, if can expand, do so.
 641 // Otherwise, if using ex regions might help, try with ex given back.
 642 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) {
 643   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 644 
 645   verify_region_sets_optional();
 646 
 647   uint first = G1_NO_HRM_INDEX;
 648   uint obj_regions = (uint)(align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords);
 649 
 650   if (obj_regions == 1) {
 651     // Only one region to allocate, try to use a fast path by directly allocating
 652     // from the free lists. Do not try to expand here, we will potentially do that
 653     // later.
 654     HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
 655     if (hr != NULL) {
 656       first = hr->hrm_index();
 657     }
 658   } else {
 659     // We can't allocate humongous regions spanning more than one region while
 660     // cleanupComplete() is running, since some of the regions we find to be
 661     // empty might not yet be added to the free list. It is not straightforward
 662     // to know in which list they are on so that we can remove them. We only
 663     // need to do this if we need to allocate more than one region to satisfy the
 664     // current humongous allocation request. If we are only allocating one region
 665     // we use the one-region region allocation code (see above), that already
 666     // potentially waits for regions from the secondary free list.
 667     wait_while_free_regions_coming();
 668     append_secondary_free_list_if_not_empty_with_lock();
 669 
 670     // Policy: Try only empty regions (i.e. already committed first). Maybe we
 671     // are lucky enough to find some.
 672     first = _hrm.find_contiguous_only_empty(obj_regions);
 673     if (first != G1_NO_HRM_INDEX) {
 674       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 675     }
 676   }
 677 
 678   if (first == G1_NO_HRM_INDEX) {
 679     // Policy: We could not find enough regions for the humongous object in the
 680     // free list. Look through the heap to find a mix of free and uncommitted regions.
 681     // If so, try expansion.
 682     first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
 683     if (first != G1_NO_HRM_INDEX) {
 684       // We found something. Make sure these regions are committed, i.e. expand
 685       // the heap. Alternatively we could do a defragmentation GC.
 686       ergo_verbose1(ErgoHeapSizing,
 687                     "attempt heap expansion",
 688                     ergo_format_reason("humongous allocation request failed")
 689                     ergo_format_byte("allocation request"),
 690                     word_size * HeapWordSize);
 691 
 692       _hrm.expand_at(first, obj_regions);
 693       g1_policy()->record_new_heap_size(num_regions());
 694 
 695 #ifdef ASSERT
 696       for (uint i = first; i < first + obj_regions; ++i) {
 697         HeapRegion* hr = region_at(i);
 698         assert(hr->is_free(), "sanity");
 699         assert(hr->is_empty(), "sanity");
 700         assert(is_on_master_free_list(hr), "sanity");
 701       }
 702 #endif
 703       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 704     } else {
 705       // Policy: Potentially trigger a defragmentation GC.
 706     }
 707   }
 708 
 709   HeapWord* result = NULL;
 710   if (first != G1_NO_HRM_INDEX) {
 711     result = humongous_obj_allocate_initialize_regions(first, obj_regions,
 712                                                        word_size, context);
 713     assert(result != NULL, "it should always return a valid result");
 714 
 715     // A successful humongous object allocation changes the used space
 716     // information of the old generation so we need to recalculate the
 717     // sizes and update the jstat counters here.
 718     g1mm()->update_sizes();
 719   }
 720 
 721   verify_region_sets_optional();
 722 
 723   return result;
 724 }
 725 
 726 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
 727   assert_heap_not_locked_and_not_at_safepoint();
 728   assert(!is_humongous(word_size), "we do not allow humongous TLABs");
 729 
 730   uint dummy_gc_count_before;
 731   uint dummy_gclocker_retry_count = 0;
 732   return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
 733 }
 734 
 735 HeapWord*
 736 G1CollectedHeap::mem_allocate(size_t word_size,
 737                               bool*  gc_overhead_limit_was_exceeded) {
 738   assert_heap_not_locked_and_not_at_safepoint();
 739 
 740   // Loop until the allocation is satisfied, or unsatisfied after GC.
 741   for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 742     uint gc_count_before;
 743 
 744     HeapWord* result = NULL;
 745     if (!is_humongous(word_size)) {
 746       result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
 747     } else {
 748       result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
 749     }
 750     if (result != NULL) {
 751       return result;
 752     }
 753 
 754     // Create the garbage collection operation...
 755     VM_G1CollectForAllocation op(gc_count_before, word_size);
 756     op.set_allocation_context(AllocationContext::current());
 757 
 758     // ...and get the VM thread to execute it.
 759     VMThread::execute(&op);
 760 
 761     if (op.prologue_succeeded() && op.pause_succeeded()) {
 762       // If the operation was successful we'll return the result even
 763       // if it is NULL. If the allocation attempt failed immediately
 764       // after a Full GC, it's unlikely we'll be able to allocate now.
 765       HeapWord* result = op.result();
 766       if (result != NULL && !is_humongous(word_size)) {
 767         // Allocations that take place on VM operations do not do any
 768         // card dirtying and we have to do it here. We only have to do
 769         // this for non-humongous allocations, though.
 770         dirty_young_block(result, word_size);
 771       }
 772       return result;
 773     } else {
 774       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 775         return NULL;
 776       }
 777       assert(op.result() == NULL,
 778              "the result should be NULL if the VM op did not succeed");
 779     }
 780 
 781     // Give a warning if we seem to be looping forever.
 782     if ((QueuedAllocationWarningCount > 0) &&
 783         (try_count % QueuedAllocationWarningCount == 0)) {
 784       warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
 785     }
 786   }
 787 
 788   ShouldNotReachHere();
 789   return NULL;
 790 }
 791 
 792 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
 793                                                    AllocationContext_t context,
 794                                                    uint* gc_count_before_ret,
 795                                                    uint* gclocker_retry_count_ret) {
 796   // Make sure you read the note in attempt_allocation_humongous().
 797 
 798   assert_heap_not_locked_and_not_at_safepoint();
 799   assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
 800          "be called for humongous allocation requests");
 801 
 802   // We should only get here after the first-level allocation attempt
 803   // (attempt_allocation()) failed to allocate.
 804 
 805   // We will loop until a) we manage to successfully perform the
 806   // allocation or b) we successfully schedule a collection which
 807   // fails to perform the allocation. b) is the only case when we'll
 808   // return NULL.
 809   HeapWord* result = NULL;
 810   for (int try_count = 1; /* we'll return */; try_count += 1) {
 811     bool should_try_gc;
 812     uint gc_count_before;
 813 
 814     {
 815       MutexLockerEx x(Heap_lock);
 816       result = _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size,
 817                                                                                     false /* bot_updates */);
 818       if (result != NULL) {
 819         return result;
 820       }
 821 
 822       // If we reach here, attempt_allocation_locked() above failed to
 823       // allocate a new region. So the mutator alloc region should be NULL.
 824       assert(_allocator->mutator_alloc_region(context)->get() == NULL, "only way to get here");
 825 
 826       if (GC_locker::is_active_and_needs_gc()) {
 827         if (g1_policy()->can_expand_young_list()) {
 828           // No need for an ergo verbose message here,
 829           // can_expand_young_list() does this when it returns true.
 830           result = _allocator->mutator_alloc_region(context)->attempt_allocation_force(word_size,
 831                                                                                        false /* bot_updates */);
 832           if (result != NULL) {
 833             return result;
 834           }
 835         }
 836         should_try_gc = false;
 837       } else {
 838         // The GCLocker may not be active but the GCLocker initiated
 839         // GC may not yet have been performed (GCLocker::needs_gc()
 840         // returns true). In this case we do not try this GC and
 841         // wait until the GCLocker initiated GC is performed, and
 842         // then retry the allocation.
 843         if (GC_locker::needs_gc()) {
 844           should_try_gc = false;
 845         } else {
 846           // Read the GC count while still holding the Heap_lock.
 847           gc_count_before = total_collections();
 848           should_try_gc = true;
 849         }
 850       }
 851     }
 852 
 853     if (should_try_gc) {
 854       bool succeeded;
 855       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 856                                    GCCause::_g1_inc_collection_pause);
 857       if (result != NULL) {
 858         assert(succeeded, "only way to get back a non-NULL result");
 859         return result;
 860       }
 861 
 862       if (succeeded) {
 863         // If we get here we successfully scheduled a collection which
 864         // failed to allocate. No point in trying to allocate
 865         // further. We'll just return NULL.
 866         MutexLockerEx x(Heap_lock);
 867         *gc_count_before_ret = total_collections();
 868         return NULL;
 869       }
 870     } else {
 871       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
 872         MutexLockerEx x(Heap_lock);
 873         *gc_count_before_ret = total_collections();
 874         return NULL;
 875       }
 876       // The GCLocker is either active or the GCLocker initiated
 877       // GC has not yet been performed. Stall until it is and
 878       // then retry the allocation.
 879       GC_locker::stall_until_clear();
 880       (*gclocker_retry_count_ret) += 1;
 881     }
 882 
 883     // We can reach here if we were unsuccessful in scheduling a
 884     // collection (because another thread beat us to it) or if we were
 885     // stalled due to the GC locker. In either can we should retry the
 886     // allocation attempt in case another thread successfully
 887     // performed a collection and reclaimed enough space. We do the
 888     // first attempt (without holding the Heap_lock) here and the
 889     // follow-on attempt will be at the start of the next loop
 890     // iteration (after taking the Heap_lock).
 891     result = _allocator->mutator_alloc_region(context)->attempt_allocation(word_size,
 892                                                                            false /* bot_updates */);
 893     if (result != NULL) {
 894       return result;
 895     }
 896 
 897     // Give a warning if we seem to be looping forever.
 898     if ((QueuedAllocationWarningCount > 0) &&
 899         (try_count % QueuedAllocationWarningCount == 0)) {
 900       warning("G1CollectedHeap::attempt_allocation_slow() "
 901               "retries %d times", try_count);
 902     }
 903   }
 904 
 905   ShouldNotReachHere();
 906   return NULL;
 907 }
 908 
 909 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
 910                                                         uint* gc_count_before_ret,
 911                                                         uint* gclocker_retry_count_ret) {
 912   // The structure of this method has a lot of similarities to
 913   // attempt_allocation_slow(). The reason these two were not merged
 914   // into a single one is that such a method would require several "if
 915   // allocation is not humongous do this, otherwise do that"
 916   // conditional paths which would obscure its flow. In fact, an early
 917   // version of this code did use a unified method which was harder to
 918   // follow and, as a result, it had subtle bugs that were hard to
 919   // track down. So keeping these two methods separate allows each to
 920   // be more readable. It will be good to keep these two in sync as
 921   // much as possible.
 922 
 923   assert_heap_not_locked_and_not_at_safepoint();
 924   assert(is_humongous(word_size), "attempt_allocation_humongous() "
 925          "should only be called for humongous allocations");
 926 
 927   // Humongous objects can exhaust the heap quickly, so we should check if we
 928   // need to start a marking cycle at each humongous object allocation. We do
 929   // the check before we do the actual allocation. The reason for doing it
 930   // before the allocation is that we avoid having to keep track of the newly
 931   // allocated memory while we do a GC.
 932   if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
 933                                            word_size)) {
 934     collect(GCCause::_g1_humongous_allocation);
 935   }
 936 
 937   // We will loop until a) we manage to successfully perform the
 938   // allocation or b) we successfully schedule a collection which
 939   // fails to perform the allocation. b) is the only case when we'll
 940   // return NULL.
 941   HeapWord* result = NULL;
 942   for (int try_count = 1; /* we'll return */; try_count += 1) {
 943     bool should_try_gc;
 944     uint gc_count_before;
 945 
 946     {
 947       MutexLockerEx x(Heap_lock);
 948 
 949       // Given that humongous objects are not allocated in young
 950       // regions, we'll first try to do the allocation without doing a
 951       // collection hoping that there's enough space in the heap.
 952       result = humongous_obj_allocate(word_size, AllocationContext::current());
 953       if (result != NULL) {
 954         return result;
 955       }
 956 
 957       if (GC_locker::is_active_and_needs_gc()) {
 958         should_try_gc = false;
 959       } else {
 960          // The GCLocker may not be active but the GCLocker initiated
 961         // GC may not yet have been performed (GCLocker::needs_gc()
 962         // returns true). In this case we do not try this GC and
 963         // wait until the GCLocker initiated GC is performed, and
 964         // then retry the allocation.
 965         if (GC_locker::needs_gc()) {
 966           should_try_gc = false;
 967         } else {
 968           // Read the GC count while still holding the Heap_lock.
 969           gc_count_before = total_collections();
 970           should_try_gc = true;
 971         }
 972       }
 973     }
 974 
 975     if (should_try_gc) {
 976       // If we failed to allocate the humongous object, we should try to
 977       // do a collection pause (if we're allowed) in case it reclaims
 978       // enough space for the allocation to succeed after the pause.
 979 
 980       bool succeeded;
 981       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 982                                    GCCause::_g1_humongous_allocation);
 983       if (result != NULL) {
 984         assert(succeeded, "only way to get back a non-NULL result");
 985         return result;
 986       }
 987 
 988       if (succeeded) {
 989         // If we get here we successfully scheduled a collection which
 990         // failed to allocate. No point in trying to allocate
 991         // further. We'll just return NULL.
 992         MutexLockerEx x(Heap_lock);
 993         *gc_count_before_ret = total_collections();
 994         return NULL;
 995       }
 996     } else {
 997       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
 998         MutexLockerEx x(Heap_lock);
 999         *gc_count_before_ret = total_collections();
1000         return NULL;
1001       }
1002       // The GCLocker is either active or the GCLocker initiated
1003       // GC has not yet been performed. Stall until it is and
1004       // then retry the allocation.
1005       GC_locker::stall_until_clear();
1006       (*gclocker_retry_count_ret) += 1;
1007     }
1008 
1009     // We can reach here if we were unsuccessful in scheduling a
1010     // collection (because another thread beat us to it) or if we were
1011     // stalled due to the GC locker. In either can we should retry the
1012     // allocation attempt in case another thread successfully
1013     // performed a collection and reclaimed enough space.  Give a
1014     // warning if we seem to be looping forever.
1015 
1016     if ((QueuedAllocationWarningCount > 0) &&
1017         (try_count % QueuedAllocationWarningCount == 0)) {
1018       warning("G1CollectedHeap::attempt_allocation_humongous() "
1019               "retries %d times", try_count);
1020     }
1021   }
1022 
1023   ShouldNotReachHere();
1024   return NULL;
1025 }
1026 
1027 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1028                                                            AllocationContext_t context,
1029                                                            bool expect_null_mutator_alloc_region) {
1030   assert_at_safepoint(true /* should_be_vm_thread */);
1031   assert(_allocator->mutator_alloc_region(context)->get() == NULL ||
1032                                              !expect_null_mutator_alloc_region,
1033          "the current alloc region was unexpectedly found to be non-NULL");
1034 
1035   if (!is_humongous(word_size)) {
1036     return _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size,
1037                                                       false /* bot_updates */);
1038   } else {
1039     HeapWord* result = humongous_obj_allocate(word_size, context);
1040     if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1041       g1_policy()->set_initiate_conc_mark_if_possible();
1042     }
1043     return result;
1044   }
1045 
1046   ShouldNotReachHere();
1047 }
1048 
1049 class PostMCRemSetClearClosure: public HeapRegionClosure {
1050   G1CollectedHeap* _g1h;
1051   ModRefBarrierSet* _mr_bs;
1052 public:
1053   PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1054     _g1h(g1h), _mr_bs(mr_bs) {}
1055 
1056   bool doHeapRegion(HeapRegion* r) {
1057     HeapRegionRemSet* hrrs = r->rem_set();
1058 
1059     if (r->is_continues_humongous()) {
1060       // We'll assert that the strong code root list and RSet is empty
1061       assert(hrrs->strong_code_roots_list_length() == 0, "sanity");
1062       assert(hrrs->occupied() == 0, "RSet should be empty");
1063       return false;
1064     }
1065 
1066     _g1h->reset_gc_time_stamps(r);
1067     hrrs->clear();
1068     // You might think here that we could clear just the cards
1069     // corresponding to the used region.  But no: if we leave a dirty card
1070     // in a region we might allocate into, then it would prevent that card
1071     // from being enqueued, and cause it to be missed.
1072     // Re: the performance cost: we shouldn't be doing full GC anyway!
1073     _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1074 
1075     return false;
1076   }
1077 };
1078 
1079 void G1CollectedHeap::clear_rsets_post_compaction() {
1080   PostMCRemSetClearClosure rs_clear(this, g1_barrier_set());
1081   heap_region_iterate(&rs_clear);
1082 }
1083 
1084 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1085   G1CollectedHeap*   _g1h;
1086   UpdateRSOopClosure _cl;
1087 public:
1088   RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, uint worker_i = 0) :
1089     _cl(g1->g1_rem_set(), worker_i),
1090     _g1h(g1)
1091   { }
1092 
1093   bool doHeapRegion(HeapRegion* r) {
1094     if (!r->is_continues_humongous()) {
1095       _cl.set_from(r);
1096       r->oop_iterate(&_cl);
1097     }
1098     return false;
1099   }
1100 };
1101 
1102 class ParRebuildRSTask: public AbstractGangTask {
1103   G1CollectedHeap* _g1;
1104   HeapRegionClaimer _hrclaimer;
1105 
1106 public:
1107   ParRebuildRSTask(G1CollectedHeap* g1) :
1108       AbstractGangTask("ParRebuildRSTask"), _g1(g1), _hrclaimer(g1->workers()->active_workers()) {}
1109 
1110   void work(uint worker_id) {
1111     RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1112     _g1->heap_region_par_iterate(&rebuild_rs, worker_id, &_hrclaimer);
1113   }
1114 };
1115 
1116 class PostCompactionPrinterClosure: public HeapRegionClosure {
1117 private:
1118   G1HRPrinter* _hr_printer;
1119 public:
1120   bool doHeapRegion(HeapRegion* hr) {
1121     assert(!hr->is_young(), "not expecting to find young regions");
1122     if (hr->is_free()) {
1123       // We only generate output for non-empty regions.
1124     } else if (hr->is_starts_humongous()) {
1125       if (hr->region_num() == 1) {
1126         // single humongous region
1127         _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
1128       } else {
1129         _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
1130       }
1131     } else if (hr->is_continues_humongous()) {
1132       _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1133     } else if (hr->is_old()) {
1134       _hr_printer->post_compaction(hr, G1HRPrinter::Old);
1135     } else {
1136       ShouldNotReachHere();
1137     }
1138     return false;
1139   }
1140 
1141   PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1142     : _hr_printer(hr_printer) { }
1143 };
1144 
1145 void G1CollectedHeap::print_hrm_post_compaction() {
1146   PostCompactionPrinterClosure cl(hr_printer());
1147   heap_region_iterate(&cl);
1148 }
1149 
1150 bool G1CollectedHeap::do_collection(bool explicit_gc,
1151                                     bool clear_all_soft_refs,
1152                                     size_t word_size) {
1153   assert_at_safepoint(true /* should_be_vm_thread */);
1154 
1155   if (GC_locker::check_active_before_gc()) {
1156     return false;
1157   }
1158 
1159   STWGCTimer* gc_timer = G1MarkSweep::gc_timer();
1160   gc_timer->register_gc_start();
1161 
1162   SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer();
1163   gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start());
1164 
1165   SvcGCMarker sgcm(SvcGCMarker::FULL);
1166   ResourceMark rm;
1167 
1168   G1Log::update_level();
1169   print_heap_before_gc();
1170   trace_heap_before_gc(gc_tracer);
1171 
1172   size_t metadata_prev_used = MetaspaceAux::used_bytes();
1173 
1174   verify_region_sets_optional();
1175 
1176   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1177                            collector_policy()->should_clear_all_soft_refs();
1178 
1179   ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1180 
1181   {
1182     IsGCActiveMark x;
1183 
1184     // Timing
1185     assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant");
1186     TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
1187 
1188     {
1189       GCTraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, NULL, gc_tracer->gc_id());
1190       TraceCollectorStats tcs(g1mm()->full_collection_counters());
1191       TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1192 
1193       g1_policy()->record_full_collection_start();
1194 
1195       // Note: When we have a more flexible GC logging framework that
1196       // allows us to add optional attributes to a GC log record we
1197       // could consider timing and reporting how long we wait in the
1198       // following two methods.
1199       wait_while_free_regions_coming();
1200       // If we start the compaction before the CM threads finish
1201       // scanning the root regions we might trip them over as we'll
1202       // be moving objects / updating references. So let's wait until
1203       // they are done. By telling them to abort, they should complete
1204       // early.
1205       _cm->root_regions()->abort();
1206       _cm->root_regions()->wait_until_scan_finished();
1207       append_secondary_free_list_if_not_empty_with_lock();
1208 
1209       gc_prologue(true);
1210       increment_total_collections(true /* full gc */);
1211       increment_old_marking_cycles_started();
1212 
1213       assert(used() == recalculate_used(), "Should be equal");
1214 
1215       verify_before_gc();
1216 
1217       check_bitmaps("Full GC Start");
1218       pre_full_gc_dump(gc_timer);
1219 
1220       COMPILER2_PRESENT(DerivedPointerTable::clear());
1221 
1222       // Disable discovery and empty the discovered lists
1223       // for the CM ref processor.
1224       ref_processor_cm()->disable_discovery();
1225       ref_processor_cm()->abandon_partial_discovery();
1226       ref_processor_cm()->verify_no_references_recorded();
1227 
1228       // Abandon current iterations of concurrent marking and concurrent
1229       // refinement, if any are in progress. We have to do this before
1230       // wait_until_scan_finished() below.
1231       concurrent_mark()->abort();
1232 
1233       // Make sure we'll choose a new allocation region afterwards.
1234       _allocator->release_mutator_alloc_region();
1235       _allocator->abandon_gc_alloc_regions();
1236       g1_rem_set()->cleanupHRRS();
1237 
1238       // We should call this after we retire any currently active alloc
1239       // regions so that all the ALLOC / RETIRE events are generated
1240       // before the start GC event.
1241       _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1242 
1243       // We may have added regions to the current incremental collection
1244       // set between the last GC or pause and now. We need to clear the
1245       // incremental collection set and then start rebuilding it afresh
1246       // after this full GC.
1247       abandon_collection_set(g1_policy()->inc_cset_head());
1248       g1_policy()->clear_incremental_cset();
1249       g1_policy()->stop_incremental_cset_building();
1250 
1251       tear_down_region_sets(false /* free_list_only */);
1252       g1_policy()->set_gcs_are_young(true);
1253 
1254       // See the comments in g1CollectedHeap.hpp and
1255       // G1CollectedHeap::ref_processing_init() about
1256       // how reference processing currently works in G1.
1257 
1258       // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1259       ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1260 
1261       // Temporarily clear the STW ref processor's _is_alive_non_header field.
1262       ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1263 
1264       ref_processor_stw()->enable_discovery();
1265       ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1266 
1267       // Do collection work
1268       {
1269         HandleMark hm;  // Discard invalid handles created during gc
1270         G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1271       }
1272 
1273       assert(num_free_regions() == 0, "we should not have added any free regions");
1274       rebuild_region_sets(false /* free_list_only */);
1275 
1276       // Enqueue any discovered reference objects that have
1277       // not been removed from the discovered lists.
1278       ref_processor_stw()->enqueue_discovered_references();
1279 
1280       COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1281 
1282       MemoryService::track_memory_usage();
1283 
1284       assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1285       ref_processor_stw()->verify_no_references_recorded();
1286 
1287       // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1288       ClassLoaderDataGraph::purge();
1289       MetaspaceAux::verify_metrics();
1290 
1291       // Note: since we've just done a full GC, concurrent
1292       // marking is no longer active. Therefore we need not
1293       // re-enable reference discovery for the CM ref processor.
1294       // That will be done at the start of the next marking cycle.
1295       assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1296       ref_processor_cm()->verify_no_references_recorded();
1297 
1298       reset_gc_time_stamp();
1299       // Since everything potentially moved, we will clear all remembered
1300       // sets, and clear all cards.  Later we will rebuild remembered
1301       // sets. We will also reset the GC time stamps of the regions.
1302       clear_rsets_post_compaction();
1303       check_gc_time_stamps();
1304 
1305       // Resize the heap if necessary.
1306       resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1307 
1308       if (_hr_printer.is_active()) {
1309         // We should do this after we potentially resize the heap so
1310         // that all the COMMIT / UNCOMMIT events are generated before
1311         // the end GC event.
1312 
1313         print_hrm_post_compaction();
1314         _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1315       }
1316 
1317       G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
1318       if (hot_card_cache->use_cache()) {
1319         hot_card_cache->reset_card_counts();
1320         hot_card_cache->reset_hot_cache();
1321       }
1322 
1323       // Rebuild remembered sets of all regions.
1324       uint n_workers =
1325         AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1326                                                 workers()->active_workers(),
1327                                                 Threads::number_of_non_daemon_threads());
1328       assert(UseDynamicNumberOfGCThreads ||
1329              n_workers == workers()->total_workers(),
1330              "If not dynamic should be using all the  workers");
1331       workers()->set_active_workers(n_workers);
1332       // Set parallel threads in the heap (_n_par_threads) only
1333       // before a parallel phase and always reset it to 0 after
1334       // the phase so that the number of parallel threads does
1335       // no get carried forward to a serial phase where there
1336       // may be code that is "possibly_parallel".
1337       set_par_threads(n_workers);
1338 
1339       ParRebuildRSTask rebuild_rs_task(this);
1340       assert(UseDynamicNumberOfGCThreads ||
1341              workers()->active_workers() == workers()->total_workers(),
1342              "Unless dynamic should use total workers");
1343       // Use the most recent number of  active workers
1344       assert(workers()->active_workers() > 0,
1345              "Active workers not properly set");
1346       set_par_threads(workers()->active_workers());
1347       workers()->run_task(&rebuild_rs_task);
1348       set_par_threads(0);
1349 
1350       // Rebuild the strong code root lists for each region
1351       rebuild_strong_code_roots();
1352 
1353       if (true) { // FIXME
1354         MetaspaceGC::compute_new_size();
1355       }
1356 
1357 #ifdef TRACESPINNING
1358       ParallelTaskTerminator::print_termination_counts();
1359 #endif
1360 
1361       // Discard all rset updates
1362       JavaThread::dirty_card_queue_set().abandon_logs();
1363       assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1364 
1365       _young_list->reset_sampled_info();
1366       // At this point there should be no regions in the
1367       // entire heap tagged as young.
1368       assert(check_young_list_empty(true /* check_heap */),
1369              "young list should be empty at this point");
1370 
1371       // Update the number of full collections that have been completed.
1372       increment_old_marking_cycles_completed(false /* concurrent */);
1373 
1374       _hrm.verify_optional();
1375       verify_region_sets_optional();
1376 
1377       verify_after_gc();
1378 
1379       // Clear the previous marking bitmap, if needed for bitmap verification.
1380       // Note we cannot do this when we clear the next marking bitmap in
1381       // ConcurrentMark::abort() above since VerifyDuringGC verifies the
1382       // objects marked during a full GC against the previous bitmap.
1383       // But we need to clear it before calling check_bitmaps below since
1384       // the full GC has compacted objects and updated TAMS but not updated
1385       // the prev bitmap.
1386       if (G1VerifyBitmaps) {
1387         ((CMBitMap*) concurrent_mark()->prevMarkBitMap())->clearAll();
1388       }
1389       check_bitmaps("Full GC End");
1390 
1391       // Start a new incremental collection set for the next pause
1392       assert(g1_policy()->collection_set() == NULL, "must be");
1393       g1_policy()->start_incremental_cset_building();
1394 
1395       clear_cset_fast_test();
1396 
1397       _allocator->init_mutator_alloc_region();
1398 
1399       g1_policy()->record_full_collection_end();
1400 
1401       if (G1Log::fine()) {
1402         g1_policy()->print_heap_transition();
1403       }
1404 
1405       // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1406       // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1407       // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1408       // before any GC notifications are raised.
1409       g1mm()->update_sizes();
1410 
1411       gc_epilogue(true);
1412     }
1413 
1414     if (G1Log::finer()) {
1415       g1_policy()->print_detailed_heap_transition(true /* full */);
1416     }
1417 
1418     print_heap_after_gc();
1419     trace_heap_after_gc(gc_tracer);
1420 
1421     post_full_gc_dump(gc_timer);
1422 
1423     gc_timer->register_gc_end();
1424     gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
1425   }
1426 
1427   return true;
1428 }
1429 
1430 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1431   // do_collection() will return whether it succeeded in performing
1432   // the GC. Currently, there is no facility on the
1433   // do_full_collection() API to notify the caller than the collection
1434   // did not succeed (e.g., because it was locked out by the GC
1435   // locker). So, right now, we'll ignore the return value.
1436   bool dummy = do_collection(true,                /* explicit_gc */
1437                              clear_all_soft_refs,
1438                              0                    /* word_size */);
1439 }
1440 
1441 // This code is mostly copied from TenuredGeneration.
1442 void
1443 G1CollectedHeap::
1444 resize_if_necessary_after_full_collection(size_t word_size) {
1445   // Include the current allocation, if any, and bytes that will be
1446   // pre-allocated to support collections, as "used".
1447   const size_t used_after_gc = used();
1448   const size_t capacity_after_gc = capacity();
1449   const size_t free_after_gc = capacity_after_gc - used_after_gc;
1450 
1451   // This is enforced in arguments.cpp.
1452   assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1453          "otherwise the code below doesn't make sense");
1454 
1455   // We don't have floating point command-line arguments
1456   const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1457   const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1458   const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1459   const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1460 
1461   const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1462   const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1463 
1464   // We have to be careful here as these two calculations can overflow
1465   // 32-bit size_t's.
1466   double used_after_gc_d = (double) used_after_gc;
1467   double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1468   double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1469 
1470   // Let's make sure that they are both under the max heap size, which
1471   // by default will make them fit into a size_t.
1472   double desired_capacity_upper_bound = (double) max_heap_size;
1473   minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1474                                     desired_capacity_upper_bound);
1475   maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1476                                     desired_capacity_upper_bound);
1477 
1478   // We can now safely turn them into size_t's.
1479   size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1480   size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1481 
1482   // This assert only makes sense here, before we adjust them
1483   // with respect to the min and max heap size.
1484   assert(minimum_desired_capacity <= maximum_desired_capacity,
1485          err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1486                  "maximum_desired_capacity = "SIZE_FORMAT,
1487                  minimum_desired_capacity, maximum_desired_capacity));
1488 
1489   // Should not be greater than the heap max size. No need to adjust
1490   // it with respect to the heap min size as it's a lower bound (i.e.,
1491   // we'll try to make the capacity larger than it, not smaller).
1492   minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1493   // Should not be less than the heap min size. No need to adjust it
1494   // with respect to the heap max size as it's an upper bound (i.e.,
1495   // we'll try to make the capacity smaller than it, not greater).
1496   maximum_desired_capacity =  MAX2(maximum_desired_capacity, min_heap_size);
1497 
1498   if (capacity_after_gc < minimum_desired_capacity) {
1499     // Don't expand unless it's significant
1500     size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1501     ergo_verbose4(ErgoHeapSizing,
1502                   "attempt heap expansion",
1503                   ergo_format_reason("capacity lower than "
1504                                      "min desired capacity after Full GC")
1505                   ergo_format_byte("capacity")
1506                   ergo_format_byte("occupancy")
1507                   ergo_format_byte_perc("min desired capacity"),
1508                   capacity_after_gc, used_after_gc,
1509                   minimum_desired_capacity, (double) MinHeapFreeRatio);
1510     expand(expand_bytes);
1511 
1512     // No expansion, now see if we want to shrink
1513   } else if (capacity_after_gc > maximum_desired_capacity) {
1514     // Capacity too large, compute shrinking size
1515     size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1516     ergo_verbose4(ErgoHeapSizing,
1517                   "attempt heap shrinking",
1518                   ergo_format_reason("capacity higher than "
1519                                      "max desired capacity after Full GC")
1520                   ergo_format_byte("capacity")
1521                   ergo_format_byte("occupancy")
1522                   ergo_format_byte_perc("max desired capacity"),
1523                   capacity_after_gc, used_after_gc,
1524                   maximum_desired_capacity, (double) MaxHeapFreeRatio);
1525     shrink(shrink_bytes);
1526   }
1527 }
1528 
1529 
1530 HeapWord*
1531 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1532                                            AllocationContext_t context,
1533                                            bool* succeeded) {
1534   assert_at_safepoint(true /* should_be_vm_thread */);
1535 
1536   *succeeded = true;
1537   // Let's attempt the allocation first.
1538   HeapWord* result =
1539     attempt_allocation_at_safepoint(word_size,
1540                                     context,
1541                                     false /* expect_null_mutator_alloc_region */);
1542   if (result != NULL) {
1543     assert(*succeeded, "sanity");
1544     return result;
1545   }
1546 
1547   // In a G1 heap, we're supposed to keep allocation from failing by
1548   // incremental pauses.  Therefore, at least for now, we'll favor
1549   // expansion over collection.  (This might change in the future if we can
1550   // do something smarter than full collection to satisfy a failed alloc.)
1551   result = expand_and_allocate(word_size, context);
1552   if (result != NULL) {
1553     assert(*succeeded, "sanity");
1554     return result;
1555   }
1556 
1557   // Expansion didn't work, we'll try to do a Full GC.
1558   bool gc_succeeded = do_collection(false, /* explicit_gc */
1559                                     false, /* clear_all_soft_refs */
1560                                     word_size);
1561   if (!gc_succeeded) {
1562     *succeeded = false;
1563     return NULL;
1564   }
1565 
1566   // Retry the allocation
1567   result = attempt_allocation_at_safepoint(word_size,
1568                                            context,
1569                                            true /* expect_null_mutator_alloc_region */);
1570   if (result != NULL) {
1571     assert(*succeeded, "sanity");
1572     return result;
1573   }
1574 
1575   // Then, try a Full GC that will collect all soft references.
1576   gc_succeeded = do_collection(false, /* explicit_gc */
1577                                true,  /* clear_all_soft_refs */
1578                                word_size);
1579   if (!gc_succeeded) {
1580     *succeeded = false;
1581     return NULL;
1582   }
1583 
1584   // Retry the allocation once more
1585   result = attempt_allocation_at_safepoint(word_size,
1586                                            context,
1587                                            true /* expect_null_mutator_alloc_region */);
1588   if (result != NULL) {
1589     assert(*succeeded, "sanity");
1590     return result;
1591   }
1592 
1593   assert(!collector_policy()->should_clear_all_soft_refs(),
1594          "Flag should have been handled and cleared prior to this point");
1595 
1596   // What else?  We might try synchronous finalization later.  If the total
1597   // space available is large enough for the allocation, then a more
1598   // complete compaction phase than we've tried so far might be
1599   // appropriate.
1600   assert(*succeeded, "sanity");
1601   return NULL;
1602 }
1603 
1604 // Attempting to expand the heap sufficiently
1605 // to support an allocation of the given "word_size".  If
1606 // successful, perform the allocation and return the address of the
1607 // allocated block, or else "NULL".
1608 
1609 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) {
1610   assert_at_safepoint(true /* should_be_vm_thread */);
1611 
1612   verify_region_sets_optional();
1613 
1614   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1615   ergo_verbose1(ErgoHeapSizing,
1616                 "attempt heap expansion",
1617                 ergo_format_reason("allocation request failed")
1618                 ergo_format_byte("allocation request"),
1619                 word_size * HeapWordSize);
1620   if (expand(expand_bytes)) {
1621     _hrm.verify_optional();
1622     verify_region_sets_optional();
1623     return attempt_allocation_at_safepoint(word_size,
1624                                            context,
1625                                            false /* expect_null_mutator_alloc_region */);
1626   }
1627   return NULL;
1628 }
1629 
1630 bool G1CollectedHeap::expand(size_t expand_bytes) {
1631   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1632   aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1633                                        HeapRegion::GrainBytes);
1634   ergo_verbose2(ErgoHeapSizing,
1635                 "expand the heap",
1636                 ergo_format_byte("requested expansion amount")
1637                 ergo_format_byte("attempted expansion amount"),
1638                 expand_bytes, aligned_expand_bytes);
1639 
1640   if (is_maximal_no_gc()) {
1641     ergo_verbose0(ErgoHeapSizing,
1642                       "did not expand the heap",
1643                       ergo_format_reason("heap already fully expanded"));
1644     return false;
1645   }
1646 
1647   uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1648   assert(regions_to_expand > 0, "Must expand by at least one region");
1649 
1650   uint expanded_by = _hrm.expand_by(regions_to_expand);
1651 
1652   if (expanded_by > 0) {
1653     size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1654     assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1655     g1_policy()->record_new_heap_size(num_regions());
1656   } else {
1657     ergo_verbose0(ErgoHeapSizing,
1658                   "did not expand the heap",
1659                   ergo_format_reason("heap expansion operation failed"));
1660     // The expansion of the virtual storage space was unsuccessful.
1661     // Let's see if it was because we ran out of swap.
1662     if (G1ExitOnExpansionFailure &&
1663         _hrm.available() >= regions_to_expand) {
1664       // We had head room...
1665       vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1666     }
1667   }
1668   return regions_to_expand > 0;
1669 }
1670 
1671 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1672   size_t aligned_shrink_bytes =
1673     ReservedSpace::page_align_size_down(shrink_bytes);
1674   aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1675                                          HeapRegion::GrainBytes);
1676   uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1677 
1678   uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1679   size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1680 
1681   ergo_verbose3(ErgoHeapSizing,
1682                 "shrink the heap",
1683                 ergo_format_byte("requested shrinking amount")
1684                 ergo_format_byte("aligned shrinking amount")
1685                 ergo_format_byte("attempted shrinking amount"),
1686                 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1687   if (num_regions_removed > 0) {
1688     g1_policy()->record_new_heap_size(num_regions());
1689   } else {
1690     ergo_verbose0(ErgoHeapSizing,
1691                   "did not shrink the heap",
1692                   ergo_format_reason("heap shrinking operation failed"));
1693   }
1694 }
1695 
1696 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1697   verify_region_sets_optional();
1698 
1699   // We should only reach here at the end of a Full GC which means we
1700   // should not not be holding to any GC alloc regions. The method
1701   // below will make sure of that and do any remaining clean up.
1702   _allocator->abandon_gc_alloc_regions();
1703 
1704   // Instead of tearing down / rebuilding the free lists here, we
1705   // could instead use the remove_all_pending() method on free_list to
1706   // remove only the ones that we need to remove.
1707   tear_down_region_sets(true /* free_list_only */);
1708   shrink_helper(shrink_bytes);
1709   rebuild_region_sets(true /* free_list_only */);
1710 
1711   _hrm.verify_optional();
1712   verify_region_sets_optional();
1713 }
1714 
1715 // Public methods.
1716 
1717 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1718 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1719 #endif // _MSC_VER
1720 
1721 
1722 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1723   CollectedHeap(),
1724   _g1_policy(policy_),
1725   _dirty_card_queue_set(false),
1726   _into_cset_dirty_card_queue_set(false),
1727   _is_alive_closure_cm(this),
1728   _is_alive_closure_stw(this),
1729   _ref_processor_cm(NULL),
1730   _ref_processor_stw(NULL),
1731   _bot_shared(NULL),
1732   _evac_failure_scan_stack(NULL),
1733   _mark_in_progress(false),
1734   _cg1r(NULL),
1735   _g1mm(NULL),
1736   _refine_cte_cl(NULL),
1737   _full_collection(false),
1738   _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1739   _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1740   _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1741   _humongous_reclaim_candidates(),
1742   _has_humongous_reclaim_candidates(false),
1743   _free_regions_coming(false),
1744   _young_list(new YoungList(this)),
1745   _gc_time_stamp(0),
1746   _survivor_plab_stats(YoungPLABSize, PLABWeight),
1747   _old_plab_stats(OldPLABSize, PLABWeight),
1748   _expand_heap_after_alloc_failure(true),
1749   _surviving_young_words(NULL),
1750   _old_marking_cycles_started(0),
1751   _old_marking_cycles_completed(0),
1752   _concurrent_cycle_started(false),
1753   _heap_summary_sent(false),
1754   _in_cset_fast_test(),
1755   _dirty_cards_region_list(NULL),
1756   _worker_cset_start_region(NULL),
1757   _worker_cset_start_region_time_stamp(NULL),
1758   _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1759   _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
1760   _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1761   _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) {
1762 
1763   _workers = new FlexibleWorkGang("GC Thread", ParallelGCThreads,
1764                           /* are_GC_task_threads */true,
1765                           /* are_ConcurrentGC_threads */false);
1766   _workers->initialize_workers();
1767 
1768   _allocator = G1Allocator::create_allocator(this);
1769   _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1770 
1771   int n_queues = MAX2((int)ParallelGCThreads, 1);
1772   _task_queues = new RefToScanQueueSet(n_queues);
1773 
1774   uint n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1775   assert(n_rem_sets > 0, "Invariant.");
1776 
1777   _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1778   _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(uint, n_queues, mtGC);
1779   _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1780 
1781   for (int i = 0; i < n_queues; i++) {
1782     RefToScanQueue* q = new RefToScanQueue();
1783     q->initialize();
1784     _task_queues->register_queue(i, q);
1785     ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1786   }
1787   clear_cset_start_regions();
1788 
1789   // Initialize the G1EvacuationFailureALot counters and flags.
1790   NOT_PRODUCT(reset_evacuation_should_fail();)
1791 
1792   guarantee(_task_queues != NULL, "task_queues allocation failure.");
1793 }
1794 
1795 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1796                                                                  size_t size,
1797                                                                  size_t translation_factor) {
1798   size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1799   // Allocate a new reserved space, preferring to use large pages.
1800   ReservedSpace rs(size, preferred_page_size);
1801   G1RegionToSpaceMapper* result  =
1802     G1RegionToSpaceMapper::create_mapper(rs,
1803                                          size,
1804                                          rs.alignment(),
1805                                          HeapRegion::GrainBytes,
1806                                          translation_factor,
1807                                          mtGC);
1808   if (TracePageSizes) {
1809     gclog_or_tty->print_cr("G1 '%s': pg_sz=" SIZE_FORMAT " base=" PTR_FORMAT " size=" SIZE_FORMAT " alignment=" SIZE_FORMAT " reqsize=" SIZE_FORMAT,
1810                            description, preferred_page_size, p2i(rs.base()), rs.size(), rs.alignment(), size);
1811   }
1812   return result;
1813 }
1814 
1815 jint G1CollectedHeap::initialize() {
1816   CollectedHeap::pre_initialize();
1817   os::enable_vtime();
1818 
1819   G1Log::init();
1820 
1821   // Necessary to satisfy locking discipline assertions.
1822 
1823   MutexLocker x(Heap_lock);
1824 
1825   // We have to initialize the printer before committing the heap, as
1826   // it will be used then.
1827   _hr_printer.set_active(G1PrintHeapRegions);
1828 
1829   // While there are no constraints in the GC code that HeapWordSize
1830   // be any particular value, there are multiple other areas in the
1831   // system which believe this to be true (e.g. oop->object_size in some
1832   // cases incorrectly returns the size in wordSize units rather than
1833   // HeapWordSize).
1834   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1835 
1836   size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1837   size_t max_byte_size = collector_policy()->max_heap_byte_size();
1838   size_t heap_alignment = collector_policy()->heap_alignment();
1839 
1840   // Ensure that the sizes are properly aligned.
1841   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1842   Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1843   Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1844 
1845   _refine_cte_cl = new RefineCardTableEntryClosure();
1846 
1847   _cg1r = new ConcurrentG1Refine(this, _refine_cte_cl);
1848 
1849   // Reserve the maximum.
1850 
1851   // When compressed oops are enabled, the preferred heap base
1852   // is calculated by subtracting the requested size from the
1853   // 32Gb boundary and using the result as the base address for
1854   // heap reservation. If the requested size is not aligned to
1855   // HeapRegion::GrainBytes (i.e. the alignment that is passed
1856   // into the ReservedHeapSpace constructor) then the actual
1857   // base of the reserved heap may end up differing from the
1858   // address that was requested (i.e. the preferred heap base).
1859   // If this happens then we could end up using a non-optimal
1860   // compressed oops mode.
1861 
1862   ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1863                                                  heap_alignment);
1864 
1865   initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
1866 
1867   // Create the barrier set for the entire reserved region.
1868   G1SATBCardTableLoggingModRefBS* bs
1869     = new G1SATBCardTableLoggingModRefBS(reserved_region());
1870   bs->initialize();
1871   assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity");
1872   set_barrier_set(bs);
1873 
1874   // Also create a G1 rem set.
1875   _g1_rem_set = new G1RemSet(this, g1_barrier_set());
1876 
1877   // Carve out the G1 part of the heap.
1878 
1879   ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1880   G1RegionToSpaceMapper* heap_storage =
1881     G1RegionToSpaceMapper::create_mapper(g1_rs,
1882                                          g1_rs.size(),
1883                                          UseLargePages ? os::large_page_size() : os::vm_page_size(),
1884                                          HeapRegion::GrainBytes,
1885                                          1,
1886                                          mtJavaHeap);
1887   heap_storage->set_mapping_changed_listener(&_listener);
1888 
1889   // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1890   G1RegionToSpaceMapper* bot_storage =
1891     create_aux_memory_mapper("Block offset table",
1892                              G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize),
1893                              G1BlockOffsetSharedArray::heap_map_factor());
1894 
1895   ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize));
1896   G1RegionToSpaceMapper* cardtable_storage =
1897     create_aux_memory_mapper("Card table",
1898                              G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize),
1899                              G1SATBCardTableLoggingModRefBS::heap_map_factor());
1900 
1901   G1RegionToSpaceMapper* card_counts_storage =
1902     create_aux_memory_mapper("Card counts table",
1903                              G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1904                              G1CardCounts::heap_map_factor());
1905 
1906   size_t bitmap_size = CMBitMap::compute_size(g1_rs.size());
1907   G1RegionToSpaceMapper* prev_bitmap_storage =
1908     create_aux_memory_mapper("Prev Bitmap", bitmap_size, CMBitMap::heap_map_factor());
1909   G1RegionToSpaceMapper* next_bitmap_storage =
1910     create_aux_memory_mapper("Next Bitmap", bitmap_size, CMBitMap::heap_map_factor());
1911 
1912   _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1913   g1_barrier_set()->initialize(cardtable_storage);
1914    // Do later initialization work for concurrent refinement.
1915   _cg1r->init(card_counts_storage);
1916 
1917   // 6843694 - ensure that the maximum region index can fit
1918   // in the remembered set structures.
1919   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1920   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1921 
1922   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1923   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1924   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1925             "too many cards per region");
1926 
1927   FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
1928 
1929   _bot_shared = new G1BlockOffsetSharedArray(reserved_region(), bot_storage);
1930 
1931   {
1932     HeapWord* start = _hrm.reserved().start();
1933     HeapWord* end = _hrm.reserved().end();
1934     size_t granularity = HeapRegion::GrainBytes;
1935 
1936     _in_cset_fast_test.initialize(start, end, granularity);
1937     _humongous_reclaim_candidates.initialize(start, end, granularity);
1938   }
1939 
1940   // Create the ConcurrentMark data structure and thread.
1941   // (Must do this late, so that "max_regions" is defined.)
1942   _cm = new ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1943   if (_cm == NULL || !_cm->completed_initialization()) {
1944     vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark");
1945     return JNI_ENOMEM;
1946   }
1947   _cmThread = _cm->cmThread();
1948 
1949   // Initialize the from_card cache structure of HeapRegionRemSet.
1950   HeapRegionRemSet::init_heap(max_regions());
1951 
1952   // Now expand into the initial heap size.
1953   if (!expand(init_byte_size)) {
1954     vm_shutdown_during_initialization("Failed to allocate initial heap.");
1955     return JNI_ENOMEM;
1956   }
1957 
1958   // Perform any initialization actions delegated to the policy.
1959   g1_policy()->init();
1960 
1961   JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
1962                                                SATB_Q_FL_lock,
1963                                                G1SATBProcessCompletedThreshold,
1964                                                Shared_SATB_Q_lock);
1965 
1966   JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl,
1967                                                 DirtyCardQ_CBL_mon,
1968                                                 DirtyCardQ_FL_lock,
1969                                                 concurrent_g1_refine()->yellow_zone(),
1970                                                 concurrent_g1_refine()->red_zone(),
1971                                                 Shared_DirtyCardQ_lock);
1972 
1973   dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code
1974                                     DirtyCardQ_CBL_mon,
1975                                     DirtyCardQ_FL_lock,
1976                                     -1, // never trigger processing
1977                                     -1, // no limit on length
1978                                     Shared_DirtyCardQ_lock,
1979                                     &JavaThread::dirty_card_queue_set());
1980 
1981   // Initialize the card queue set used to hold cards containing
1982   // references into the collection set.
1983   _into_cset_dirty_card_queue_set.initialize(NULL, // Should never be called by the Java code
1984                                              DirtyCardQ_CBL_mon,
1985                                              DirtyCardQ_FL_lock,
1986                                              -1, // never trigger processing
1987                                              -1, // no limit on length
1988                                              Shared_DirtyCardQ_lock,
1989                                              &JavaThread::dirty_card_queue_set());
1990 
1991   // Here we allocate the dummy HeapRegion that is required by the
1992   // G1AllocRegion class.
1993   HeapRegion* dummy_region = _hrm.get_dummy_region();
1994 
1995   // We'll re-use the same region whether the alloc region will
1996   // require BOT updates or not and, if it doesn't, then a non-young
1997   // region will complain that it cannot support allocations without
1998   // BOT updates. So we'll tag the dummy region as eden to avoid that.
1999   dummy_region->set_eden();
2000   // Make sure it's full.
2001   dummy_region->set_top(dummy_region->end());
2002   G1AllocRegion::setup(this, dummy_region);
2003 
2004   _allocator->init_mutator_alloc_region();
2005 
2006   // Do create of the monitoring and management support so that
2007   // values in the heap have been properly initialized.
2008   _g1mm = new G1MonitoringSupport(this);
2009 
2010   G1StringDedup::initialize();
2011 
2012   return JNI_OK;
2013 }
2014 
2015 void G1CollectedHeap::stop() {
2016   // Stop all concurrent threads. We do this to make sure these threads
2017   // do not continue to execute and access resources (e.g. gclog_or_tty)
2018   // that are destroyed during shutdown.
2019   _cg1r->stop();
2020   _cmThread->stop();
2021   if (G1StringDedup::is_enabled()) {
2022     G1StringDedup::stop();
2023   }
2024 }
2025 
2026 size_t G1CollectedHeap::conservative_max_heap_alignment() {
2027   return HeapRegion::max_region_size();
2028 }
2029 
2030 void G1CollectedHeap::post_initialize() {
2031   CollectedHeap::post_initialize();
2032   ref_processing_init();
2033 }
2034 
2035 void G1CollectedHeap::ref_processing_init() {
2036   // Reference processing in G1 currently works as follows:
2037   //
2038   // * There are two reference processor instances. One is
2039   //   used to record and process discovered references
2040   //   during concurrent marking; the other is used to
2041   //   record and process references during STW pauses
2042   //   (both full and incremental).
2043   // * Both ref processors need to 'span' the entire heap as
2044   //   the regions in the collection set may be dotted around.
2045   //
2046   // * For the concurrent marking ref processor:
2047   //   * Reference discovery is enabled at initial marking.
2048   //   * Reference discovery is disabled and the discovered
2049   //     references processed etc during remarking.
2050   //   * Reference discovery is MT (see below).
2051   //   * Reference discovery requires a barrier (see below).
2052   //   * Reference processing may or may not be MT
2053   //     (depending on the value of ParallelRefProcEnabled
2054   //     and ParallelGCThreads).
2055   //   * A full GC disables reference discovery by the CM
2056   //     ref processor and abandons any entries on it's
2057   //     discovered lists.
2058   //
2059   // * For the STW processor:
2060   //   * Non MT discovery is enabled at the start of a full GC.
2061   //   * Processing and enqueueing during a full GC is non-MT.
2062   //   * During a full GC, references are processed after marking.
2063   //
2064   //   * Discovery (may or may not be MT) is enabled at the start
2065   //     of an incremental evacuation pause.
2066   //   * References are processed near the end of a STW evacuation pause.
2067   //   * For both types of GC:
2068   //     * Discovery is atomic - i.e. not concurrent.
2069   //     * Reference discovery will not need a barrier.
2070 
2071   MemRegion mr = reserved_region();
2072 
2073   // Concurrent Mark ref processor
2074   _ref_processor_cm =
2075     new ReferenceProcessor(mr,    // span
2076                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2077                                 // mt processing
2078                            (int) ParallelGCThreads,
2079                                 // degree of mt processing
2080                            (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2081                                 // mt discovery
2082                            (int) MAX2(ParallelGCThreads, ConcGCThreads),
2083                                 // degree of mt discovery
2084                            false,
2085                                 // Reference discovery is not atomic
2086                            &_is_alive_closure_cm);
2087                                 // is alive closure
2088                                 // (for efficiency/performance)
2089 
2090   // STW ref processor
2091   _ref_processor_stw =
2092     new ReferenceProcessor(mr,    // span
2093                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2094                                 // mt processing
2095                            MAX2((int)ParallelGCThreads, 1),
2096                                 // degree of mt processing
2097                            (ParallelGCThreads > 1),
2098                                 // mt discovery
2099                            MAX2((int)ParallelGCThreads, 1),
2100                                 // degree of mt discovery
2101                            true,
2102                                 // Reference discovery is atomic
2103                            &_is_alive_closure_stw);
2104                                 // is alive closure
2105                                 // (for efficiency/performance)
2106 }
2107 
2108 size_t G1CollectedHeap::capacity() const {
2109   return _hrm.length() * HeapRegion::GrainBytes;
2110 }
2111 
2112 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2113   assert(!hr->is_continues_humongous(), "pre-condition");
2114   hr->reset_gc_time_stamp();
2115   if (hr->is_starts_humongous()) {
2116     uint first_index = hr->hrm_index() + 1;
2117     uint last_index = hr->last_hc_index();
2118     for (uint i = first_index; i < last_index; i += 1) {
2119       HeapRegion* chr = region_at(i);
2120       assert(chr->is_continues_humongous(), "sanity");
2121       chr->reset_gc_time_stamp();
2122     }
2123   }
2124 }
2125 
2126 #ifndef PRODUCT
2127 
2128 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2129 private:
2130   unsigned _gc_time_stamp;
2131   bool _failures;
2132 
2133 public:
2134   CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2135     _gc_time_stamp(gc_time_stamp), _failures(false) { }
2136 
2137   virtual bool doHeapRegion(HeapRegion* hr) {
2138     unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2139     if (_gc_time_stamp != region_gc_time_stamp) {
2140       gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, "
2141                              "expected %d", HR_FORMAT_PARAMS(hr),
2142                              region_gc_time_stamp, _gc_time_stamp);
2143       _failures = true;
2144     }
2145     return false;
2146   }
2147 
2148   bool failures() { return _failures; }
2149 };
2150 
2151 void G1CollectedHeap::check_gc_time_stamps() {
2152   CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2153   heap_region_iterate(&cl);
2154   guarantee(!cl.failures(), "all GC time stamps should have been reset");
2155 }
2156 #endif // PRODUCT
2157 
2158 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2159                                                  DirtyCardQueue* into_cset_dcq,
2160                                                  bool concurrent,
2161                                                  uint worker_i) {
2162   // Clean cards in the hot card cache
2163   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
2164   hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq);
2165 
2166   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2167   size_t n_completed_buffers = 0;
2168   while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2169     n_completed_buffers++;
2170   }
2171   g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers);
2172   dcqs.clear_n_completed_buffers();
2173   assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2174 }
2175 
2176 
2177 // Computes the sum of the storage used by the various regions.
2178 size_t G1CollectedHeap::used() const {
2179   return _allocator->used();
2180 }
2181 
2182 size_t G1CollectedHeap::used_unlocked() const {
2183   return _allocator->used_unlocked();
2184 }
2185 
2186 class SumUsedClosure: public HeapRegionClosure {
2187   size_t _used;
2188 public:
2189   SumUsedClosure() : _used(0) {}
2190   bool doHeapRegion(HeapRegion* r) {
2191     if (!r->is_continues_humongous()) {
2192       _used += r->used();
2193     }
2194     return false;
2195   }
2196   size_t result() { return _used; }
2197 };
2198 
2199 size_t G1CollectedHeap::recalculate_used() const {
2200   double recalculate_used_start = os::elapsedTime();
2201 
2202   SumUsedClosure blk;
2203   heap_region_iterate(&blk);
2204 
2205   g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2206   return blk.result();
2207 }
2208 
2209 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2210   switch (cause) {
2211     case GCCause::_gc_locker:               return GCLockerInvokesConcurrent;
2212     case GCCause::_java_lang_system_gc:     return ExplicitGCInvokesConcurrent;
2213     case GCCause::_g1_humongous_allocation: return true;
2214     case GCCause::_update_allocation_context_stats_inc: return true;
2215     case GCCause::_wb_conc_mark:            return true;
2216     default:                                return false;
2217   }
2218 }
2219 
2220 #ifndef PRODUCT
2221 void G1CollectedHeap::allocate_dummy_regions() {
2222   // Let's fill up most of the region
2223   size_t word_size = HeapRegion::GrainWords - 1024;
2224   // And as a result the region we'll allocate will be humongous.
2225   guarantee(is_humongous(word_size), "sanity");
2226 
2227   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2228     // Let's use the existing mechanism for the allocation
2229     HeapWord* dummy_obj = humongous_obj_allocate(word_size,
2230                                                  AllocationContext::system());
2231     if (dummy_obj != NULL) {
2232       MemRegion mr(dummy_obj, word_size);
2233       CollectedHeap::fill_with_object(mr);
2234     } else {
2235       // If we can't allocate once, we probably cannot allocate
2236       // again. Let's get out of the loop.
2237       break;
2238     }
2239   }
2240 }
2241 #endif // !PRODUCT
2242 
2243 void G1CollectedHeap::increment_old_marking_cycles_started() {
2244   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2245     _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2246     err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2247     _old_marking_cycles_started, _old_marking_cycles_completed));
2248 
2249   _old_marking_cycles_started++;
2250 }
2251 
2252 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2253   MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2254 
2255   // We assume that if concurrent == true, then the caller is a
2256   // concurrent thread that was joined the Suspendible Thread
2257   // Set. If there's ever a cheap way to check this, we should add an
2258   // assert here.
2259 
2260   // Given that this method is called at the end of a Full GC or of a
2261   // concurrent cycle, and those can be nested (i.e., a Full GC can
2262   // interrupt a concurrent cycle), the number of full collections
2263   // completed should be either one (in the case where there was no
2264   // nesting) or two (when a Full GC interrupted a concurrent cycle)
2265   // behind the number of full collections started.
2266 
2267   // This is the case for the inner caller, i.e. a Full GC.
2268   assert(concurrent ||
2269          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2270          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2271          err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
2272                  "is inconsistent with _old_marking_cycles_completed = %u",
2273                  _old_marking_cycles_started, _old_marking_cycles_completed));
2274 
2275   // This is the case for the outer caller, i.e. the concurrent cycle.
2276   assert(!concurrent ||
2277          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2278          err_msg("for outer caller (concurrent cycle): "
2279                  "_old_marking_cycles_started = %u "
2280                  "is inconsistent with _old_marking_cycles_completed = %u",
2281                  _old_marking_cycles_started, _old_marking_cycles_completed));
2282 
2283   _old_marking_cycles_completed += 1;
2284 
2285   // We need to clear the "in_progress" flag in the CM thread before
2286   // we wake up any waiters (especially when ExplicitInvokesConcurrent
2287   // is set) so that if a waiter requests another System.gc() it doesn't
2288   // incorrectly see that a marking cycle is still in progress.
2289   if (concurrent) {
2290     _cmThread->clear_in_progress();
2291   }
2292 
2293   // This notify_all() will ensure that a thread that called
2294   // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2295   // and it's waiting for a full GC to finish will be woken up. It is
2296   // waiting in VM_G1IncCollectionPause::doit_epilogue().
2297   FullGCCount_lock->notify_all();
2298 }
2299 
2300 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) {
2301   _concurrent_cycle_started = true;
2302   _gc_timer_cm->register_gc_start(start_time);
2303 
2304   _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start());
2305   trace_heap_before_gc(_gc_tracer_cm);
2306 }
2307 
2308 void G1CollectedHeap::register_concurrent_cycle_end() {
2309   if (_concurrent_cycle_started) {
2310     if (_cm->has_aborted()) {
2311       _gc_tracer_cm->report_concurrent_mode_failure();
2312     }
2313 
2314     _gc_timer_cm->register_gc_end();
2315     _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
2316 
2317     // Clear state variables to prepare for the next concurrent cycle.
2318     _concurrent_cycle_started = false;
2319     _heap_summary_sent = false;
2320   }
2321 }
2322 
2323 void G1CollectedHeap::trace_heap_after_concurrent_cycle() {
2324   if (_concurrent_cycle_started) {
2325     // This function can be called when:
2326     //  the cleanup pause is run
2327     //  the concurrent cycle is aborted before the cleanup pause.
2328     //  the concurrent cycle is aborted after the cleanup pause,
2329     //   but before the concurrent cycle end has been registered.
2330     // Make sure that we only send the heap information once.
2331     if (!_heap_summary_sent) {
2332       trace_heap_after_gc(_gc_tracer_cm);
2333       _heap_summary_sent = true;
2334     }
2335   }
2336 }
2337 
2338 G1YCType G1CollectedHeap::yc_type() {
2339   bool is_young = g1_policy()->gcs_are_young();
2340   bool is_initial_mark = g1_policy()->during_initial_mark_pause();
2341   bool is_during_mark = mark_in_progress();
2342 
2343   if (is_initial_mark) {
2344     return InitialMark;
2345   } else if (is_during_mark) {
2346     return DuringMark;
2347   } else if (is_young) {
2348     return Normal;
2349   } else {
2350     return Mixed;
2351   }
2352 }
2353 
2354 void G1CollectedHeap::collect(GCCause::Cause cause) {
2355   assert_heap_not_locked();
2356 
2357   uint gc_count_before;
2358   uint old_marking_count_before;
2359   uint full_gc_count_before;
2360   bool retry_gc;
2361 
2362   do {
2363     retry_gc = false;
2364 
2365     {
2366       MutexLocker ml(Heap_lock);
2367 
2368       // Read the GC count while holding the Heap_lock
2369       gc_count_before = total_collections();
2370       full_gc_count_before = total_full_collections();
2371       old_marking_count_before = _old_marking_cycles_started;
2372     }
2373 
2374     if (should_do_concurrent_full_gc(cause)) {
2375       // Schedule an initial-mark evacuation pause that will start a
2376       // concurrent cycle. We're setting word_size to 0 which means that
2377       // we are not requesting a post-GC allocation.
2378       VM_G1IncCollectionPause op(gc_count_before,
2379                                  0,     /* word_size */
2380                                  true,  /* should_initiate_conc_mark */
2381                                  g1_policy()->max_pause_time_ms(),
2382                                  cause);
2383       op.set_allocation_context(AllocationContext::current());
2384 
2385       VMThread::execute(&op);
2386       if (!op.pause_succeeded()) {
2387         if (old_marking_count_before == _old_marking_cycles_started) {
2388           retry_gc = op.should_retry_gc();
2389         } else {
2390           // A Full GC happened while we were trying to schedule the
2391           // initial-mark GC. No point in starting a new cycle given
2392           // that the whole heap was collected anyway.
2393         }
2394 
2395         if (retry_gc) {
2396           if (GC_locker::is_active_and_needs_gc()) {
2397             GC_locker::stall_until_clear();
2398           }
2399         }
2400       }
2401     } else {
2402       if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2403           DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2404 
2405         // Schedule a standard evacuation pause. We're setting word_size
2406         // to 0 which means that we are not requesting a post-GC allocation.
2407         VM_G1IncCollectionPause op(gc_count_before,
2408                                    0,     /* word_size */
2409                                    false, /* should_initiate_conc_mark */
2410                                    g1_policy()->max_pause_time_ms(),
2411                                    cause);
2412         VMThread::execute(&op);
2413       } else {
2414         // Schedule a Full GC.
2415         VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2416         VMThread::execute(&op);
2417       }
2418     }
2419   } while (retry_gc);
2420 }
2421 
2422 bool G1CollectedHeap::is_in(const void* p) const {
2423   if (_hrm.reserved().contains(p)) {
2424     // Given that we know that p is in the reserved space,
2425     // heap_region_containing_raw() should successfully
2426     // return the containing region.
2427     HeapRegion* hr = heap_region_containing_raw(p);
2428     return hr->is_in(p);
2429   } else {
2430     return false;
2431   }
2432 }
2433 
2434 #ifdef ASSERT
2435 bool G1CollectedHeap::is_in_exact(const void* p) const {
2436   bool contains = reserved_region().contains(p);
2437   bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2438   if (contains && available) {
2439     return true;
2440   } else {
2441     return false;
2442   }
2443 }
2444 #endif
2445 
2446 // Iteration functions.
2447 
2448 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion.
2449 
2450 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2451   ExtendedOopClosure* _cl;
2452 public:
2453   IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {}
2454   bool doHeapRegion(HeapRegion* r) {
2455     if (!r->is_continues_humongous()) {
2456       r->oop_iterate(_cl);
2457     }
2458     return false;
2459   }
2460 };
2461 
2462 // Iterates an ObjectClosure over all objects within a HeapRegion.
2463 
2464 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2465   ObjectClosure* _cl;
2466 public:
2467   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2468   bool doHeapRegion(HeapRegion* r) {
2469     if (!r->is_continues_humongous()) {
2470       r->object_iterate(_cl);
2471     }
2472     return false;
2473   }
2474 };
2475 
2476 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2477   IterateObjectClosureRegionClosure blk(cl);
2478   heap_region_iterate(&blk);
2479 }
2480 
2481 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2482   _hrm.iterate(cl);
2483 }
2484 
2485 void
2486 G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl,
2487                                          uint worker_id,
2488                                          HeapRegionClaimer *hrclaimer,
2489                                          bool concurrent) const {
2490   _hrm.par_iterate(cl, worker_id, hrclaimer, concurrent);
2491 }
2492 
2493 // Clear the cached CSet starting regions and (more importantly)
2494 // the time stamps. Called when we reset the GC time stamp.
2495 void G1CollectedHeap::clear_cset_start_regions() {
2496   assert(_worker_cset_start_region != NULL, "sanity");
2497   assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2498 
2499   int n_queues = MAX2((int)ParallelGCThreads, 1);
2500   for (int i = 0; i < n_queues; i++) {
2501     _worker_cset_start_region[i] = NULL;
2502     _worker_cset_start_region_time_stamp[i] = 0;
2503   }
2504 }
2505 
2506 // Given the id of a worker, obtain or calculate a suitable
2507 // starting region for iterating over the current collection set.
2508 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) {
2509   assert(get_gc_time_stamp() > 0, "should have been updated by now");
2510 
2511   HeapRegion* result = NULL;
2512   unsigned gc_time_stamp = get_gc_time_stamp();
2513 
2514   if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2515     // Cached starting region for current worker was set
2516     // during the current pause - so it's valid.
2517     // Note: the cached starting heap region may be NULL
2518     // (when the collection set is empty).
2519     result = _worker_cset_start_region[worker_i];
2520     assert(result == NULL || result->in_collection_set(), "sanity");
2521     return result;
2522   }
2523 
2524   // The cached entry was not valid so let's calculate
2525   // a suitable starting heap region for this worker.
2526 
2527   // We want the parallel threads to start their collection
2528   // set iteration at different collection set regions to
2529   // avoid contention.
2530   // If we have:
2531   //          n collection set regions
2532   //          p threads
2533   // Then thread t will start at region floor ((t * n) / p)
2534 
2535   result = g1_policy()->collection_set();
2536   uint cs_size = g1_policy()->cset_region_length();
2537   uint active_workers = workers()->active_workers();
2538   assert(UseDynamicNumberOfGCThreads ||
2539            active_workers == workers()->total_workers(),
2540            "Unless dynamic should use total workers");
2541 
2542   uint end_ind   = (cs_size * worker_i) / active_workers;
2543   uint start_ind = 0;
2544 
2545   if (worker_i > 0 &&
2546       _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2547     // Previous workers starting region is valid
2548     // so let's iterate from there
2549     start_ind = (cs_size * (worker_i - 1)) / active_workers;
2550     result = _worker_cset_start_region[worker_i - 1];
2551   }
2552 
2553   for (uint i = start_ind; i < end_ind; i++) {
2554     result = result->next_in_collection_set();
2555   }
2556 
2557   // Note: the calculated starting heap region may be NULL
2558   // (when the collection set is empty).
2559   assert(result == NULL || result->in_collection_set(), "sanity");
2560   assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2561          "should be updated only once per pause");
2562   _worker_cset_start_region[worker_i] = result;
2563   OrderAccess::storestore();
2564   _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2565   return result;
2566 }
2567 
2568 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2569   HeapRegion* r = g1_policy()->collection_set();
2570   while (r != NULL) {
2571     HeapRegion* next = r->next_in_collection_set();
2572     if (cl->doHeapRegion(r)) {
2573       cl->incomplete();
2574       return;
2575     }
2576     r = next;
2577   }
2578 }
2579 
2580 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2581                                                   HeapRegionClosure *cl) {
2582   if (r == NULL) {
2583     // The CSet is empty so there's nothing to do.
2584     return;
2585   }
2586 
2587   assert(r->in_collection_set(),
2588          "Start region must be a member of the collection set.");
2589   HeapRegion* cur = r;
2590   while (cur != NULL) {
2591     HeapRegion* next = cur->next_in_collection_set();
2592     if (cl->doHeapRegion(cur) && false) {
2593       cl->incomplete();
2594       return;
2595     }
2596     cur = next;
2597   }
2598   cur = g1_policy()->collection_set();
2599   while (cur != r) {
2600     HeapRegion* next = cur->next_in_collection_set();
2601     if (cl->doHeapRegion(cur) && false) {
2602       cl->incomplete();
2603       return;
2604     }
2605     cur = next;
2606   }
2607 }
2608 
2609 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const {
2610   HeapRegion* result = _hrm.next_region_in_heap(from);
2611   while (result != NULL && result->is_humongous()) {
2612     result = _hrm.next_region_in_heap(result);
2613   }
2614   return result;
2615 }
2616 
2617 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2618   HeapRegion* hr = heap_region_containing(addr);
2619   return hr->block_start(addr);
2620 }
2621 
2622 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2623   HeapRegion* hr = heap_region_containing(addr);
2624   return hr->block_size(addr);
2625 }
2626 
2627 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2628   HeapRegion* hr = heap_region_containing(addr);
2629   return hr->block_is_obj(addr);
2630 }
2631 
2632 bool G1CollectedHeap::supports_tlab_allocation() const {
2633   return true;
2634 }
2635 
2636 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2637   return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes;
2638 }
2639 
2640 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2641   return young_list()->eden_used_bytes();
2642 }
2643 
2644 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2645 // must be smaller than the humongous object limit.
2646 size_t G1CollectedHeap::max_tlab_size() const {
2647   return align_size_down(_humongous_object_threshold_in_words - 1, MinObjAlignment);
2648 }
2649 
2650 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2651   // Return the remaining space in the cur alloc region, but not less than
2652   // the min TLAB size.
2653 
2654   // Also, this value can be at most the humongous object threshold,
2655   // since we can't allow tlabs to grow big enough to accommodate
2656   // humongous objects.
2657 
2658   HeapRegion* hr = _allocator->mutator_alloc_region(AllocationContext::current())->get();
2659   size_t max_tlab = max_tlab_size() * wordSize;
2660   if (hr == NULL) {
2661     return max_tlab;
2662   } else {
2663     return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab);
2664   }
2665 }
2666 
2667 size_t G1CollectedHeap::max_capacity() const {
2668   return _hrm.reserved().byte_size();
2669 }
2670 
2671 jlong G1CollectedHeap::millis_since_last_gc() {
2672   // assert(false, "NYI");
2673   return 0;
2674 }
2675 
2676 void G1CollectedHeap::prepare_for_verify() {
2677   if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
2678     ensure_parsability(false);
2679   }
2680   g1_rem_set()->prepare_for_verify();
2681 }
2682 
2683 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr,
2684                                               VerifyOption vo) {
2685   switch (vo) {
2686   case VerifyOption_G1UsePrevMarking:
2687     return hr->obj_allocated_since_prev_marking(obj);
2688   case VerifyOption_G1UseNextMarking:
2689     return hr->obj_allocated_since_next_marking(obj);
2690   case VerifyOption_G1UseMarkWord:
2691     return false;
2692   default:
2693     ShouldNotReachHere();
2694   }
2695   return false; // keep some compilers happy
2696 }
2697 
2698 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) {
2699   switch (vo) {
2700   case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start();
2701   case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start();
2702   case VerifyOption_G1UseMarkWord:    return NULL;
2703   default:                            ShouldNotReachHere();
2704   }
2705   return NULL; // keep some compilers happy
2706 }
2707 
2708 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) {
2709   switch (vo) {
2710   case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj);
2711   case VerifyOption_G1UseNextMarking: return isMarkedNext(obj);
2712   case VerifyOption_G1UseMarkWord:    return obj->is_gc_marked();
2713   default:                            ShouldNotReachHere();
2714   }
2715   return false; // keep some compilers happy
2716 }
2717 
2718 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) {
2719   switch (vo) {
2720   case VerifyOption_G1UsePrevMarking: return "PTAMS";
2721   case VerifyOption_G1UseNextMarking: return "NTAMS";
2722   case VerifyOption_G1UseMarkWord:    return "NONE";
2723   default:                            ShouldNotReachHere();
2724   }
2725   return NULL; // keep some compilers happy
2726 }
2727 
2728 class VerifyRootsClosure: public OopClosure {
2729 private:
2730   G1CollectedHeap* _g1h;
2731   VerifyOption     _vo;
2732   bool             _failures;
2733 public:
2734   // _vo == UsePrevMarking -> use "prev" marking information,
2735   // _vo == UseNextMarking -> use "next" marking information,
2736   // _vo == UseMarkWord    -> use mark word from object header.
2737   VerifyRootsClosure(VerifyOption vo) :
2738     _g1h(G1CollectedHeap::heap()),
2739     _vo(vo),
2740     _failures(false) { }
2741 
2742   bool failures() { return _failures; }
2743 
2744   template <class T> void do_oop_nv(T* p) {
2745     T heap_oop = oopDesc::load_heap_oop(p);
2746     if (!oopDesc::is_null(heap_oop)) {
2747       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2748       if (_g1h->is_obj_dead_cond(obj, _vo)) {
2749         gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
2750                                "points to dead obj "PTR_FORMAT, p2i(p), p2i(obj));
2751         if (_vo == VerifyOption_G1UseMarkWord) {
2752           gclog_or_tty->print_cr("  Mark word: "INTPTR_FORMAT, (intptr_t)obj->mark());
2753         }
2754         obj->print_on(gclog_or_tty);
2755         _failures = true;
2756       }
2757     }
2758   }
2759 
2760   void do_oop(oop* p)       { do_oop_nv(p); }
2761   void do_oop(narrowOop* p) { do_oop_nv(p); }
2762 };
2763 
2764 class G1VerifyCodeRootOopClosure: public OopClosure {
2765   G1CollectedHeap* _g1h;
2766   OopClosure* _root_cl;
2767   nmethod* _nm;
2768   VerifyOption _vo;
2769   bool _failures;
2770 
2771   template <class T> void do_oop_work(T* p) {
2772     // First verify that this root is live
2773     _root_cl->do_oop(p);
2774 
2775     if (!G1VerifyHeapRegionCodeRoots) {
2776       // We're not verifying the code roots attached to heap region.
2777       return;
2778     }
2779 
2780     // Don't check the code roots during marking verification in a full GC
2781     if (_vo == VerifyOption_G1UseMarkWord) {
2782       return;
2783     }
2784 
2785     // Now verify that the current nmethod (which contains p) is
2786     // in the code root list of the heap region containing the
2787     // object referenced by p.
2788 
2789     T heap_oop = oopDesc::load_heap_oop(p);
2790     if (!oopDesc::is_null(heap_oop)) {
2791       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2792 
2793       // Now fetch the region containing the object
2794       HeapRegion* hr = _g1h->heap_region_containing(obj);
2795       HeapRegionRemSet* hrrs = hr->rem_set();
2796       // Verify that the strong code root list for this region
2797       // contains the nmethod
2798       if (!hrrs->strong_code_roots_list_contains(_nm)) {
2799         gclog_or_tty->print_cr("Code root location "PTR_FORMAT" "
2800                                "from nmethod "PTR_FORMAT" not in strong "
2801                                "code roots for region ["PTR_FORMAT","PTR_FORMAT")",
2802                                p2i(p), p2i(_nm), p2i(hr->bottom()), p2i(hr->end()));
2803         _failures = true;
2804       }
2805     }
2806   }
2807 
2808 public:
2809   G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo):
2810     _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {}
2811 
2812   void do_oop(oop* p) { do_oop_work(p); }
2813   void do_oop(narrowOop* p) { do_oop_work(p); }
2814 
2815   void set_nmethod(nmethod* nm) { _nm = nm; }
2816   bool failures() { return _failures; }
2817 };
2818 
2819 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure {
2820   G1VerifyCodeRootOopClosure* _oop_cl;
2821 
2822 public:
2823   G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl):
2824     _oop_cl(oop_cl) {}
2825 
2826   void do_code_blob(CodeBlob* cb) {
2827     nmethod* nm = cb->as_nmethod_or_null();
2828     if (nm != NULL) {
2829       _oop_cl->set_nmethod(nm);
2830       nm->oops_do(_oop_cl);
2831     }
2832   }
2833 };
2834 
2835 class YoungRefCounterClosure : public OopClosure {
2836   G1CollectedHeap* _g1h;
2837   int              _count;
2838  public:
2839   YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {}
2840   void do_oop(oop* p)       { if (_g1h->is_in_young(*p)) { _count++; } }
2841   void do_oop(narrowOop* p) { ShouldNotReachHere(); }
2842 
2843   int count() { return _count; }
2844   void reset_count() { _count = 0; };
2845 };
2846 
2847 class VerifyKlassClosure: public KlassClosure {
2848   YoungRefCounterClosure _young_ref_counter_closure;
2849   OopClosure *_oop_closure;
2850  public:
2851   VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {}
2852   void do_klass(Klass* k) {
2853     k->oops_do(_oop_closure);
2854 
2855     _young_ref_counter_closure.reset_count();
2856     k->oops_do(&_young_ref_counter_closure);
2857     if (_young_ref_counter_closure.count() > 0) {
2858       guarantee(k->has_modified_oops(), err_msg("Klass " PTR_FORMAT ", has young refs but is not dirty.", p2i(k)));
2859     }
2860   }
2861 };
2862 
2863 class VerifyLivenessOopClosure: public OopClosure {
2864   G1CollectedHeap* _g1h;
2865   VerifyOption _vo;
2866 public:
2867   VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
2868     _g1h(g1h), _vo(vo)
2869   { }
2870   void do_oop(narrowOop *p) { do_oop_work(p); }
2871   void do_oop(      oop *p) { do_oop_work(p); }
2872 
2873   template <class T> void do_oop_work(T *p) {
2874     oop obj = oopDesc::load_decode_heap_oop(p);
2875     guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
2876               "Dead object referenced by a not dead object");
2877   }
2878 };
2879 
2880 class VerifyObjsInRegionClosure: public ObjectClosure {
2881 private:
2882   G1CollectedHeap* _g1h;
2883   size_t _live_bytes;
2884   HeapRegion *_hr;
2885   VerifyOption _vo;
2886 public:
2887   // _vo == UsePrevMarking -> use "prev" marking information,
2888   // _vo == UseNextMarking -> use "next" marking information,
2889   // _vo == UseMarkWord    -> use mark word from object header.
2890   VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
2891     : _live_bytes(0), _hr(hr), _vo(vo) {
2892     _g1h = G1CollectedHeap::heap();
2893   }
2894   void do_object(oop o) {
2895     VerifyLivenessOopClosure isLive(_g1h, _vo);
2896     assert(o != NULL, "Huh?");
2897     if (!_g1h->is_obj_dead_cond(o, _vo)) {
2898       // If the object is alive according to the mark word,
2899       // then verify that the marking information agrees.
2900       // Note we can't verify the contra-positive of the
2901       // above: if the object is dead (according to the mark
2902       // word), it may not be marked, or may have been marked
2903       // but has since became dead, or may have been allocated
2904       // since the last marking.
2905       if (_vo == VerifyOption_G1UseMarkWord) {
2906         guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
2907       }
2908 
2909       o->oop_iterate_no_header(&isLive);
2910       if (!_hr->obj_allocated_since_prev_marking(o)) {
2911         size_t obj_size = o->size();    // Make sure we don't overflow
2912         _live_bytes += (obj_size * HeapWordSize);
2913       }
2914     }
2915   }
2916   size_t live_bytes() { return _live_bytes; }
2917 };
2918 
2919 class VerifyRegionClosure: public HeapRegionClosure {
2920 private:
2921   bool             _par;
2922   VerifyOption     _vo;
2923   bool             _failures;
2924 public:
2925   // _vo == UsePrevMarking -> use "prev" marking information,
2926   // _vo == UseNextMarking -> use "next" marking information,
2927   // _vo == UseMarkWord    -> use mark word from object header.
2928   VerifyRegionClosure(bool par, VerifyOption vo)
2929     : _par(par),
2930       _vo(vo),
2931       _failures(false) {}
2932 
2933   bool failures() {
2934     return _failures;
2935   }
2936 
2937   bool doHeapRegion(HeapRegion* r) {
2938     if (!r->is_continues_humongous()) {
2939       bool failures = false;
2940       r->verify(_vo, &failures);
2941       if (failures) {
2942         _failures = true;
2943       } else {
2944         VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
2945         r->object_iterate(&not_dead_yet_cl);
2946         if (_vo != VerifyOption_G1UseNextMarking) {
2947           if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
2948             gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
2949                                    "max_live_bytes "SIZE_FORMAT" "
2950                                    "< calculated "SIZE_FORMAT,
2951                                    p2i(r->bottom()), p2i(r->end()),
2952                                    r->max_live_bytes(),
2953                                  not_dead_yet_cl.live_bytes());
2954             _failures = true;
2955           }
2956         } else {
2957           // When vo == UseNextMarking we cannot currently do a sanity
2958           // check on the live bytes as the calculation has not been
2959           // finalized yet.
2960         }
2961       }
2962     }
2963     return false; // stop the region iteration if we hit a failure
2964   }
2965 };
2966 
2967 // This is the task used for parallel verification of the heap regions
2968 
2969 class G1ParVerifyTask: public AbstractGangTask {
2970 private:
2971   G1CollectedHeap*  _g1h;
2972   VerifyOption      _vo;
2973   bool              _failures;
2974   HeapRegionClaimer _hrclaimer;
2975 
2976 public:
2977   // _vo == UsePrevMarking -> use "prev" marking information,
2978   // _vo == UseNextMarking -> use "next" marking information,
2979   // _vo == UseMarkWord    -> use mark word from object header.
2980   G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
2981       AbstractGangTask("Parallel verify task"),
2982       _g1h(g1h),
2983       _vo(vo),
2984       _failures(false),
2985       _hrclaimer(g1h->workers()->active_workers()) {}
2986 
2987   bool failures() {
2988     return _failures;
2989   }
2990 
2991   void work(uint worker_id) {
2992     HandleMark hm;
2993     VerifyRegionClosure blk(true, _vo);
2994     _g1h->heap_region_par_iterate(&blk, worker_id, &_hrclaimer);
2995     if (blk.failures()) {
2996       _failures = true;
2997     }
2998   }
2999 };
3000 
3001 void G1CollectedHeap::verify(bool silent, VerifyOption vo) {
3002   if (SafepointSynchronize::is_at_safepoint()) {
3003     assert(Thread::current()->is_VM_thread(),
3004            "Expected to be executed serially by the VM thread at this point");
3005 
3006     if (!silent) { gclog_or_tty->print("Roots "); }
3007     VerifyRootsClosure rootsCl(vo);
3008     VerifyKlassClosure klassCl(this, &rootsCl);
3009     CLDToKlassAndOopClosure cldCl(&klassCl, &rootsCl, false);
3010 
3011     // We apply the relevant closures to all the oops in the
3012     // system dictionary, class loader data graph, the string table
3013     // and the nmethods in the code cache.
3014     G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo);
3015     G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl);
3016 
3017     {
3018       G1RootProcessor root_processor(this);
3019       root_processor.process_all_roots(&rootsCl,
3020                                        &cldCl,
3021                                        &blobsCl);
3022     }
3023 
3024     bool failures = rootsCl.failures() || codeRootsCl.failures();
3025 
3026     if (vo != VerifyOption_G1UseMarkWord) {
3027       // If we're verifying during a full GC then the region sets
3028       // will have been torn down at the start of the GC. Therefore
3029       // verifying the region sets will fail. So we only verify
3030       // the region sets when not in a full GC.
3031       if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3032       verify_region_sets();
3033     }
3034 
3035     if (!silent) { gclog_or_tty->print("HeapRegions "); }
3036     if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3037 
3038       G1ParVerifyTask task(this, vo);
3039       assert(UseDynamicNumberOfGCThreads ||
3040         workers()->active_workers() == workers()->total_workers(),
3041         "If not dynamic should be using all the workers");
3042       uint n_workers = workers()->active_workers();
3043       set_par_threads(n_workers);
3044       workers()->run_task(&task);
3045       set_par_threads(0);
3046       if (task.failures()) {
3047         failures = true;
3048       }
3049 
3050     } else {
3051       VerifyRegionClosure blk(false, vo);
3052       heap_region_iterate(&blk);
3053       if (blk.failures()) {
3054         failures = true;
3055       }
3056     }
3057 
3058     if (G1StringDedup::is_enabled()) {
3059       if (!silent) gclog_or_tty->print("StrDedup ");
3060       G1StringDedup::verify();
3061     }
3062 
3063     if (failures) {
3064       gclog_or_tty->print_cr("Heap:");
3065       // It helps to have the per-region information in the output to
3066       // help us track down what went wrong. This is why we call
3067       // print_extended_on() instead of print_on().
3068       print_extended_on(gclog_or_tty);
3069       gclog_or_tty->cr();
3070       gclog_or_tty->flush();
3071     }
3072     guarantee(!failures, "there should not have been any failures");
3073   } else {
3074     if (!silent) {
3075       gclog_or_tty->print("(SKIPPING Roots, HeapRegionSets, HeapRegions, RemSet");
3076       if (G1StringDedup::is_enabled()) {
3077         gclog_or_tty->print(", StrDedup");
3078       }
3079       gclog_or_tty->print(") ");
3080     }
3081   }
3082 }
3083 
3084 void G1CollectedHeap::verify(bool silent) {
3085   verify(silent, VerifyOption_G1UsePrevMarking);
3086 }
3087 
3088 double G1CollectedHeap::verify(bool guard, const char* msg) {
3089   double verify_time_ms = 0.0;
3090 
3091   if (guard && total_collections() >= VerifyGCStartAt) {
3092     double verify_start = os::elapsedTime();
3093     HandleMark hm;  // Discard invalid handles created during verification
3094     prepare_for_verify();
3095     Universe::verify(VerifyOption_G1UsePrevMarking, msg);
3096     verify_time_ms = (os::elapsedTime() - verify_start) * 1000;
3097   }
3098 
3099   return verify_time_ms;
3100 }
3101 
3102 void G1CollectedHeap::verify_before_gc() {
3103   double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:");
3104   g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms);
3105 }
3106 
3107 void G1CollectedHeap::verify_after_gc() {
3108   double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:");
3109   g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms);
3110 }
3111 
3112 class PrintRegionClosure: public HeapRegionClosure {
3113   outputStream* _st;
3114 public:
3115   PrintRegionClosure(outputStream* st) : _st(st) {}
3116   bool doHeapRegion(HeapRegion* r) {
3117     r->print_on(_st);
3118     return false;
3119   }
3120 };
3121 
3122 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3123                                        const HeapRegion* hr,
3124                                        const VerifyOption vo) const {
3125   switch (vo) {
3126   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
3127   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
3128   case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked();
3129   default:                            ShouldNotReachHere();
3130   }
3131   return false; // keep some compilers happy
3132 }
3133 
3134 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3135                                        const VerifyOption vo) const {
3136   switch (vo) {
3137   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
3138   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
3139   case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked();
3140   default:                            ShouldNotReachHere();
3141   }
3142   return false; // keep some compilers happy
3143 }
3144 
3145 void G1CollectedHeap::print_on(outputStream* st) const {
3146   st->print(" %-20s", "garbage-first heap");
3147   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3148             capacity()/K, used_unlocked()/K);
3149   st->print(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")",
3150             p2i(_hrm.reserved().start()),
3151             p2i(_hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords),
3152             p2i(_hrm.reserved().end()));
3153   st->cr();
3154   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3155   uint young_regions = _young_list->length();
3156   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3157             (size_t) young_regions * HeapRegion::GrainBytes / K);
3158   uint survivor_regions = g1_policy()->recorded_survivor_regions();
3159   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3160             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3161   st->cr();
3162   MetaspaceAux::print_on(st);
3163 }
3164 
3165 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3166   print_on(st);
3167 
3168   // Print the per-region information.
3169   st->cr();
3170   st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3171                "HS=humongous(starts), HC=humongous(continues), "
3172                "CS=collection set, F=free, TS=gc time stamp, "
3173                "PTAMS=previous top-at-mark-start, "
3174                "NTAMS=next top-at-mark-start)");
3175   PrintRegionClosure blk(st);
3176   heap_region_iterate(&blk);
3177 }
3178 
3179 void G1CollectedHeap::print_on_error(outputStream* st) const {
3180   this->CollectedHeap::print_on_error(st);
3181 
3182   if (_cm != NULL) {
3183     st->cr();
3184     _cm->print_on_error(st);
3185   }
3186 }
3187 
3188 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3189   workers()->print_worker_threads_on(st);
3190   _cmThread->print_on(st);
3191   st->cr();
3192   _cm->print_worker_threads_on(st);
3193   _cg1r->print_worker_threads_on(st);
3194   if (G1StringDedup::is_enabled()) {
3195     G1StringDedup::print_worker_threads_on(st);
3196   }
3197 }
3198 
3199 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3200   workers()->threads_do(tc);
3201   tc->do_thread(_cmThread);
3202   _cg1r->threads_do(tc);
3203   if (G1StringDedup::is_enabled()) {
3204     G1StringDedup::threads_do(tc);
3205   }
3206 }
3207 
3208 void G1CollectedHeap::print_tracing_info() const {
3209   // We'll overload this to mean "trace GC pause statistics."
3210   if (TraceYoungGenTime || TraceOldGenTime) {
3211     // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3212     // to that.
3213     g1_policy()->print_tracing_info();
3214   }
3215   if (G1SummarizeRSetStats) {
3216     g1_rem_set()->print_summary_info();
3217   }
3218   if (G1SummarizeConcMark) {
3219     concurrent_mark()->print_summary_info();
3220   }
3221   g1_policy()->print_yg_surv_rate_info();
3222 }
3223 
3224 #ifndef PRODUCT
3225 // Helpful for debugging RSet issues.
3226 
3227 class PrintRSetsClosure : public HeapRegionClosure {
3228 private:
3229   const char* _msg;
3230   size_t _occupied_sum;
3231 
3232 public:
3233   bool doHeapRegion(HeapRegion* r) {
3234     HeapRegionRemSet* hrrs = r->rem_set();
3235     size_t occupied = hrrs->occupied();
3236     _occupied_sum += occupied;
3237 
3238     gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3239                            HR_FORMAT_PARAMS(r));
3240     if (occupied == 0) {
3241       gclog_or_tty->print_cr("  RSet is empty");
3242     } else {
3243       hrrs->print();
3244     }
3245     gclog_or_tty->print_cr("----------");
3246     return false;
3247   }
3248 
3249   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3250     gclog_or_tty->cr();
3251     gclog_or_tty->print_cr("========================================");
3252     gclog_or_tty->print_cr("%s", msg);
3253     gclog_or_tty->cr();
3254   }
3255 
3256   ~PrintRSetsClosure() {
3257     gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3258     gclog_or_tty->print_cr("========================================");
3259     gclog_or_tty->cr();
3260   }
3261 };
3262 
3263 void G1CollectedHeap::print_cset_rsets() {
3264   PrintRSetsClosure cl("Printing CSet RSets");
3265   collection_set_iterate(&cl);
3266 }
3267 
3268 void G1CollectedHeap::print_all_rsets() {
3269   PrintRSetsClosure cl("Printing All RSets");;
3270   heap_region_iterate(&cl);
3271 }
3272 #endif // PRODUCT
3273 
3274 G1CollectedHeap* G1CollectedHeap::heap() {
3275   CollectedHeap* heap = Universe::heap();
3276   assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
3277   assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap");
3278   return (G1CollectedHeap*)heap;
3279 }
3280 
3281 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3282   // always_do_update_barrier = false;
3283   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3284   // Fill TLAB's and such
3285   accumulate_statistics_all_tlabs();
3286   ensure_parsability(true);
3287 
3288   if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) &&
3289       (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3290     g1_rem_set()->print_periodic_summary_info("Before GC RS summary");
3291   }
3292 }
3293 
3294 void G1CollectedHeap::gc_epilogue(bool full) {
3295 
3296   if (G1SummarizeRSetStats &&
3297       (G1SummarizeRSetStatsPeriod > 0) &&
3298       // we are at the end of the GC. Total collections has already been increased.
3299       ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) {
3300     g1_rem_set()->print_periodic_summary_info("After GC RS summary");
3301   }
3302 
3303   // FIXME: what is this about?
3304   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3305   // is set.
3306   COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3307                         "derived pointer present"));
3308   // always_do_update_barrier = true;
3309 
3310   resize_all_tlabs();
3311   allocation_context_stats().update(full);
3312 
3313   // We have just completed a GC. Update the soft reference
3314   // policy with the new heap occupancy
3315   Universe::update_heap_info_at_gc();
3316 }
3317 
3318 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3319                                                uint gc_count_before,
3320                                                bool* succeeded,
3321                                                GCCause::Cause gc_cause) {
3322   assert_heap_not_locked_and_not_at_safepoint();
3323   g1_policy()->record_stop_world_start();
3324   VM_G1IncCollectionPause op(gc_count_before,
3325                              word_size,
3326                              false, /* should_initiate_conc_mark */
3327                              g1_policy()->max_pause_time_ms(),
3328                              gc_cause);
3329 
3330   op.set_allocation_context(AllocationContext::current());
3331   VMThread::execute(&op);
3332 
3333   HeapWord* result = op.result();
3334   bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3335   assert(result == NULL || ret_succeeded,
3336          "the result should be NULL if the VM did not succeed");
3337   *succeeded = ret_succeeded;
3338 
3339   assert_heap_not_locked();
3340   return result;
3341 }
3342 
3343 void
3344 G1CollectedHeap::doConcurrentMark() {
3345   MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3346   if (!_cmThread->in_progress()) {
3347     _cmThread->set_started();
3348     CGC_lock->notify();
3349   }
3350 }
3351 
3352 size_t G1CollectedHeap::pending_card_num() {
3353   size_t extra_cards = 0;
3354   JavaThread *curr = Threads::first();
3355   while (curr != NULL) {
3356     DirtyCardQueue& dcq = curr->dirty_card_queue();
3357     extra_cards += dcq.size();
3358     curr = curr->next();
3359   }
3360   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3361   size_t buffer_size = dcqs.buffer_size();
3362   size_t buffer_num = dcqs.completed_buffers_num();
3363 
3364   // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
3365   // in bytes - not the number of 'entries'. We need to convert
3366   // into a number of cards.
3367   return (buffer_size * buffer_num + extra_cards) / oopSize;
3368 }
3369 
3370 size_t G1CollectedHeap::cards_scanned() {
3371   return g1_rem_set()->cardsScanned();
3372 }
3373 
3374 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
3375  private:
3376   size_t _total_humongous;
3377   size_t _candidate_humongous;
3378 
3379   DirtyCardQueue _dcq;
3380 
3381   // We don't nominate objects with many remembered set entries, on
3382   // the assumption that such objects are likely still live.
3383   bool is_remset_small(HeapRegion* region) const {
3384     HeapRegionRemSet* const rset = region->rem_set();
3385     return G1EagerReclaimHumongousObjectsWithStaleRefs
3386       ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries)
3387       : rset->is_empty();
3388   }
3389 
3390   bool is_typeArray_region(HeapRegion* region) const {
3391     return oop(region->bottom())->is_typeArray();
3392   }
3393 
3394   bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const {
3395     assert(region->is_starts_humongous(), "Must start a humongous object");
3396 
3397     // Candidate selection must satisfy the following constraints
3398     // while concurrent marking is in progress:
3399     //
3400     // * In order to maintain SATB invariants, an object must not be
3401     // reclaimed if it was allocated before the start of marking and
3402     // has not had its references scanned.  Such an object must have
3403     // its references (including type metadata) scanned to ensure no
3404     // live objects are missed by the marking process.  Objects
3405     // allocated after the start of concurrent marking don't need to
3406     // be scanned.
3407     //
3408     // * An object must not be reclaimed if it is on the concurrent
3409     // mark stack.  Objects allocated after the start of concurrent
3410     // marking are never pushed on the mark stack.
3411     //
3412     // Nominating only objects allocated after the start of concurrent
3413     // marking is sufficient to meet both constraints.  This may miss
3414     // some objects that satisfy the constraints, but the marking data
3415     // structures don't support efficiently performing the needed
3416     // additional tests or scrubbing of the mark stack.
3417     //
3418     // However, we presently only nominate is_typeArray() objects.
3419     // A humongous object containing references induces remembered
3420     // set entries on other regions.  In order to reclaim such an
3421     // object, those remembered sets would need to be cleaned up.
3422     //
3423     // We also treat is_typeArray() objects specially, allowing them
3424     // to be reclaimed even if allocated before the start of
3425     // concurrent mark.  For this we rely on mark stack insertion to
3426     // exclude is_typeArray() objects, preventing reclaiming an object
3427     // that is in the mark stack.  We also rely on the metadata for
3428     // such objects to be built-in and so ensured to be kept live.
3429     // Frequent allocation and drop of large binary blobs is an
3430     // important use case for eager reclaim, and this special handling
3431     // may reduce needed headroom.
3432 
3433     return is_typeArray_region(region) && is_remset_small(region);
3434   }
3435 
3436  public:
3437   RegisterHumongousWithInCSetFastTestClosure()
3438   : _total_humongous(0),
3439     _candidate_humongous(0),
3440     _dcq(&JavaThread::dirty_card_queue_set()) {
3441   }
3442 
3443   virtual bool doHeapRegion(HeapRegion* r) {
3444     if (!r->is_starts_humongous()) {
3445       return false;
3446     }
3447     G1CollectedHeap* g1h = G1CollectedHeap::heap();
3448 
3449     bool is_candidate = humongous_region_is_candidate(g1h, r);
3450     uint rindex = r->hrm_index();
3451     g1h->set_humongous_reclaim_candidate(rindex, is_candidate);
3452     if (is_candidate) {
3453       _candidate_humongous++;
3454       g1h->register_humongous_region_with_cset(rindex);
3455       // Is_candidate already filters out humongous object with large remembered sets.
3456       // If we have a humongous object with a few remembered sets, we simply flush these
3457       // remembered set entries into the DCQS. That will result in automatic
3458       // re-evaluation of their remembered set entries during the following evacuation
3459       // phase.
3460       if (!r->rem_set()->is_empty()) {
3461         guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
3462                   "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
3463         G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set();
3464         HeapRegionRemSetIterator hrrs(r->rem_set());
3465         size_t card_index;
3466         while (hrrs.has_next(card_index)) {
3467           jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index);
3468           // The remembered set might contain references to already freed
3469           // regions. Filter out such entries to avoid failing card table
3470           // verification.
3471           if (!g1h->heap_region_containing(bs->addr_for(card_ptr))->is_free()) {
3472             if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
3473               *card_ptr = CardTableModRefBS::dirty_card_val();
3474               _dcq.enqueue(card_ptr);
3475             }
3476           }
3477         }
3478         r->rem_set()->clear_locked();
3479       }
3480       assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
3481     }
3482     _total_humongous++;
3483 
3484     return false;
3485   }
3486 
3487   size_t total_humongous() const { return _total_humongous; }
3488   size_t candidate_humongous() const { return _candidate_humongous; }
3489 
3490   void flush_rem_set_entries() { _dcq.flush(); }
3491 };
3492 
3493 void G1CollectedHeap::register_humongous_regions_with_cset() {
3494   if (!G1EagerReclaimHumongousObjects) {
3495     g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
3496     return;
3497   }
3498   double time = os::elapsed_counter();
3499 
3500   // Collect reclaim candidate information and register candidates with cset.
3501   RegisterHumongousWithInCSetFastTestClosure cl;
3502   heap_region_iterate(&cl);
3503 
3504   time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
3505   g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
3506                                                                   cl.total_humongous(),
3507                                                                   cl.candidate_humongous());
3508   _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
3509 
3510   // Finally flush all remembered set entries to re-check into the global DCQS.
3511   cl.flush_rem_set_entries();
3512 }
3513 
3514 void
3515 G1CollectedHeap::setup_surviving_young_words() {
3516   assert(_surviving_young_words == NULL, "pre-condition");
3517   uint array_length = g1_policy()->young_cset_region_length();
3518   _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3519   if (_surviving_young_words == NULL) {
3520     vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR,
3521                           "Not enough space for young surv words summary.");
3522   }
3523   memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3524 #ifdef ASSERT
3525   for (uint i = 0;  i < array_length; ++i) {
3526     assert( _surviving_young_words[i] == 0, "memset above" );
3527   }
3528 #endif // !ASSERT
3529 }
3530 
3531 void
3532 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3533   MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3534   uint array_length = g1_policy()->young_cset_region_length();
3535   for (uint i = 0; i < array_length; ++i) {
3536     _surviving_young_words[i] += surv_young_words[i];
3537   }
3538 }
3539 
3540 void
3541 G1CollectedHeap::cleanup_surviving_young_words() {
3542   guarantee( _surviving_young_words != NULL, "pre-condition" );
3543   FREE_C_HEAP_ARRAY(size_t, _surviving_young_words);
3544   _surviving_young_words = NULL;
3545 }
3546 
3547 #ifdef ASSERT
3548 class VerifyCSetClosure: public HeapRegionClosure {
3549 public:
3550   bool doHeapRegion(HeapRegion* hr) {
3551     // Here we check that the CSet region's RSet is ready for parallel
3552     // iteration. The fields that we'll verify are only manipulated
3553     // when the region is part of a CSet and is collected. Afterwards,
3554     // we reset these fields when we clear the region's RSet (when the
3555     // region is freed) so they are ready when the region is
3556     // re-allocated. The only exception to this is if there's an
3557     // evacuation failure and instead of freeing the region we leave
3558     // it in the heap. In that case, we reset these fields during
3559     // evacuation failure handling.
3560     guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3561 
3562     // Here's a good place to add any other checks we'd like to
3563     // perform on CSet regions.
3564     return false;
3565   }
3566 };
3567 #endif // ASSERT
3568 
3569 #if TASKQUEUE_STATS
3570 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3571   st->print_raw_cr("GC Task Stats");
3572   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3573   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3574 }
3575 
3576 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3577   print_taskqueue_stats_hdr(st);
3578 
3579   TaskQueueStats totals;
3580   const uint n = workers()->total_workers();
3581   for (uint i = 0; i < n; ++i) {
3582     st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
3583     totals += task_queue(i)->stats;
3584   }
3585   st->print_raw("tot "); totals.print(st); st->cr();
3586 
3587   DEBUG_ONLY(totals.verify());
3588 }
3589 
3590 void G1CollectedHeap::reset_taskqueue_stats() {
3591   const uint n = workers()->total_workers();
3592   for (uint i = 0; i < n; ++i) {
3593     task_queue(i)->stats.reset();
3594   }
3595 }
3596 #endif // TASKQUEUE_STATS
3597 
3598 void G1CollectedHeap::log_gc_header() {
3599   if (!G1Log::fine()) {
3600     return;
3601   }
3602 
3603   gclog_or_tty->gclog_stamp(_gc_tracer_stw->gc_id());
3604 
3605   GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
3606     .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)")
3607     .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : "");
3608 
3609   gclog_or_tty->print("[%s", (const char*)gc_cause_str);
3610 }
3611 
3612 void G1CollectedHeap::log_gc_footer(double pause_time_sec) {
3613   if (!G1Log::fine()) {
3614     return;
3615   }
3616 
3617   if (G1Log::finer()) {
3618     if (evacuation_failed()) {
3619       gclog_or_tty->print(" (to-space exhausted)");
3620     }
3621     gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3622     g1_policy()->phase_times()->note_gc_end();
3623     g1_policy()->phase_times()->print(pause_time_sec);
3624     g1_policy()->print_detailed_heap_transition();
3625   } else {
3626     if (evacuation_failed()) {
3627       gclog_or_tty->print("--");
3628     }
3629     g1_policy()->print_heap_transition();
3630     gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3631   }
3632   gclog_or_tty->flush();
3633 }
3634 
3635 bool
3636 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3637   assert_at_safepoint(true /* should_be_vm_thread */);
3638   guarantee(!is_gc_active(), "collection is not reentrant");
3639 
3640   if (GC_locker::check_active_before_gc()) {
3641     return false;
3642   }
3643 
3644   _gc_timer_stw->register_gc_start();
3645 
3646   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3647 
3648   SvcGCMarker sgcm(SvcGCMarker::MINOR);
3649   ResourceMark rm;
3650 
3651   G1Log::update_level();
3652   print_heap_before_gc();
3653   trace_heap_before_gc(_gc_tracer_stw);
3654 
3655   verify_region_sets_optional();
3656   verify_dirty_young_regions();
3657 
3658   // This call will decide whether this pause is an initial-mark
3659   // pause. If it is, during_initial_mark_pause() will return true
3660   // for the duration of this pause.
3661   g1_policy()->decide_on_conc_mark_initiation();
3662 
3663   // We do not allow initial-mark to be piggy-backed on a mixed GC.
3664   assert(!g1_policy()->during_initial_mark_pause() ||
3665           g1_policy()->gcs_are_young(), "sanity");
3666 
3667   // We also do not allow mixed GCs during marking.
3668   assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3669 
3670   // Record whether this pause is an initial mark. When the current
3671   // thread has completed its logging output and it's safe to signal
3672   // the CM thread, the flag's value in the policy has been reset.
3673   bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3674 
3675   // Inner scope for scope based logging, timers, and stats collection
3676   {
3677     EvacuationInfo evacuation_info;
3678 
3679     if (g1_policy()->during_initial_mark_pause()) {
3680       // We are about to start a marking cycle, so we increment the
3681       // full collection counter.
3682       increment_old_marking_cycles_started();
3683       register_concurrent_cycle_start(_gc_timer_stw->gc_start());
3684     }
3685 
3686     _gc_tracer_stw->report_yc_type(yc_type());
3687 
3688     TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3689 
3690     uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
3691                                                                   workers()->active_workers(),
3692                                                                   Threads::number_of_non_daemon_threads());
3693     assert(UseDynamicNumberOfGCThreads ||
3694            active_workers == workers()->total_workers(),
3695            "If not dynamic should be using all the  workers");
3696     workers()->set_active_workers(active_workers);
3697 
3698     double pause_start_sec = os::elapsedTime();
3699     g1_policy()->phase_times()->note_gc_start(active_workers, mark_in_progress());
3700     log_gc_header();
3701 
3702     TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3703     TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3704 
3705     // If the secondary_free_list is not empty, append it to the
3706     // free_list. No need to wait for the cleanup operation to finish;
3707     // the region allocation code will check the secondary_free_list
3708     // and wait if necessary. If the G1StressConcRegionFreeing flag is
3709     // set, skip this step so that the region allocation code has to
3710     // get entries from the secondary_free_list.
3711     if (!G1StressConcRegionFreeing) {
3712       append_secondary_free_list_if_not_empty_with_lock();
3713     }
3714 
3715     assert(check_young_list_well_formed(), "young list should be well formed");
3716 
3717     // Don't dynamically change the number of GC threads this early.  A value of
3718     // 0 is used to indicate serial work.  When parallel work is done,
3719     // it will be set.
3720 
3721     { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3722       IsGCActiveMark x;
3723 
3724       gc_prologue(false);
3725       increment_total_collections(false /* full gc */);
3726       increment_gc_time_stamp();
3727 
3728       verify_before_gc();
3729 
3730       check_bitmaps("GC Start");
3731 
3732       COMPILER2_PRESENT(DerivedPointerTable::clear());
3733 
3734       // Please see comment in g1CollectedHeap.hpp and
3735       // G1CollectedHeap::ref_processing_init() to see how
3736       // reference processing currently works in G1.
3737 
3738       // Enable discovery in the STW reference processor
3739       ref_processor_stw()->enable_discovery();
3740 
3741       {
3742         // We want to temporarily turn off discovery by the
3743         // CM ref processor, if necessary, and turn it back on
3744         // on again later if we do. Using a scoped
3745         // NoRefDiscovery object will do this.
3746         NoRefDiscovery no_cm_discovery(ref_processor_cm());
3747 
3748         // Forget the current alloc region (we might even choose it to be part
3749         // of the collection set!).
3750         _allocator->release_mutator_alloc_region();
3751 
3752         // We should call this after we retire the mutator alloc
3753         // region(s) so that all the ALLOC / RETIRE events are generated
3754         // before the start GC event.
3755         _hr_printer.start_gc(false /* full */, (size_t) total_collections());
3756 
3757         // This timing is only used by the ergonomics to handle our pause target.
3758         // It is unclear why this should not include the full pause. We will
3759         // investigate this in CR 7178365.
3760         //
3761         // Preserving the old comment here if that helps the investigation:
3762         //
3763         // The elapsed time induced by the start time below deliberately elides
3764         // the possible verification above.
3765         double sample_start_time_sec = os::elapsedTime();
3766 
3767 #if YOUNG_LIST_VERBOSE
3768         gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
3769         _young_list->print();
3770         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3771 #endif // YOUNG_LIST_VERBOSE
3772 
3773         g1_policy()->record_collection_pause_start(sample_start_time_sec);
3774 
3775         double scan_wait_start = os::elapsedTime();
3776         // We have to wait until the CM threads finish scanning the
3777         // root regions as it's the only way to ensure that all the
3778         // objects on them have been correctly scanned before we start
3779         // moving them during the GC.
3780         bool waited = _cm->root_regions()->wait_until_scan_finished();
3781         double wait_time_ms = 0.0;
3782         if (waited) {
3783           double scan_wait_end = os::elapsedTime();
3784           wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
3785         }
3786         g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
3787 
3788 #if YOUNG_LIST_VERBOSE
3789         gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
3790         _young_list->print();
3791 #endif // YOUNG_LIST_VERBOSE
3792 
3793         if (g1_policy()->during_initial_mark_pause()) {
3794           concurrent_mark()->checkpointRootsInitialPre();
3795         }
3796 
3797 #if YOUNG_LIST_VERBOSE
3798         gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
3799         _young_list->print();
3800         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3801 #endif // YOUNG_LIST_VERBOSE
3802 
3803         g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info);
3804 
3805         register_humongous_regions_with_cset();
3806 
3807         assert(check_cset_fast_test(), "Inconsistency in the InCSetState table.");
3808 
3809         _cm->note_start_of_gc();
3810         // We call this after finalize_cset() to
3811         // ensure that the CSet has been finalized.
3812         _cm->verify_no_cset_oops();
3813 
3814         if (_hr_printer.is_active()) {
3815           HeapRegion* hr = g1_policy()->collection_set();
3816           while (hr != NULL) {
3817             _hr_printer.cset(hr);
3818             hr = hr->next_in_collection_set();
3819           }
3820         }
3821 
3822 #ifdef ASSERT
3823         VerifyCSetClosure cl;
3824         collection_set_iterate(&cl);
3825 #endif // ASSERT
3826 
3827         setup_surviving_young_words();
3828 
3829         // Initialize the GC alloc regions.
3830         _allocator->init_gc_alloc_regions(evacuation_info);
3831 
3832         // Actually do the work...
3833         evacuate_collection_set(evacuation_info);
3834 
3835         free_collection_set(g1_policy()->collection_set(), evacuation_info);
3836 
3837         eagerly_reclaim_humongous_regions();
3838 
3839         g1_policy()->clear_collection_set();
3840 
3841         cleanup_surviving_young_words();
3842 
3843         // Start a new incremental collection set for the next pause.
3844         g1_policy()->start_incremental_cset_building();
3845 
3846         clear_cset_fast_test();
3847 
3848         _young_list->reset_sampled_info();
3849 
3850         // Don't check the whole heap at this point as the
3851         // GC alloc regions from this pause have been tagged
3852         // as survivors and moved on to the survivor list.
3853         // Survivor regions will fail the !is_young() check.
3854         assert(check_young_list_empty(false /* check_heap */),
3855           "young list should be empty");
3856 
3857 #if YOUNG_LIST_VERBOSE
3858         gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
3859         _young_list->print();
3860 #endif // YOUNG_LIST_VERBOSE
3861 
3862         g1_policy()->record_survivor_regions(_young_list->survivor_length(),
3863                                              _young_list->first_survivor_region(),
3864                                              _young_list->last_survivor_region());
3865 
3866         _young_list->reset_auxilary_lists();
3867 
3868         if (evacuation_failed()) {
3869           _allocator->set_used(recalculate_used());
3870           uint n_queues = MAX2((int)ParallelGCThreads, 1);
3871           for (uint i = 0; i < n_queues; i++) {
3872             if (_evacuation_failed_info_array[i].has_failed()) {
3873               _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
3874             }
3875           }
3876         } else {
3877           // The "used" of the the collection set have already been subtracted
3878           // when they were freed.  Add in the bytes evacuated.
3879           _allocator->increase_used(g1_policy()->bytes_copied_during_gc());
3880         }
3881 
3882         if (g1_policy()->during_initial_mark_pause()) {
3883           // We have to do this before we notify the CM threads that
3884           // they can start working to make sure that all the
3885           // appropriate initialization is done on the CM object.
3886           concurrent_mark()->checkpointRootsInitialPost();
3887           set_marking_started();
3888           // Note that we don't actually trigger the CM thread at
3889           // this point. We do that later when we're sure that
3890           // the current thread has completed its logging output.
3891         }
3892 
3893         allocate_dummy_regions();
3894 
3895 #if YOUNG_LIST_VERBOSE
3896         gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
3897         _young_list->print();
3898         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3899 #endif // YOUNG_LIST_VERBOSE
3900 
3901         _allocator->init_mutator_alloc_region();
3902 
3903         {
3904           size_t expand_bytes = g1_policy()->expansion_amount();
3905           if (expand_bytes > 0) {
3906             size_t bytes_before = capacity();
3907             // No need for an ergo verbose message here,
3908             // expansion_amount() does this when it returns a value > 0.
3909             if (!expand(expand_bytes)) {
3910               // We failed to expand the heap. Cannot do anything about it.
3911             }
3912           }
3913         }
3914 
3915         // We redo the verification but now wrt to the new CSet which
3916         // has just got initialized after the previous CSet was freed.
3917         _cm->verify_no_cset_oops();
3918         _cm->note_end_of_gc();
3919 
3920         // This timing is only used by the ergonomics to handle our pause target.
3921         // It is unclear why this should not include the full pause. We will
3922         // investigate this in CR 7178365.
3923         double sample_end_time_sec = os::elapsedTime();
3924         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3925         g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info);
3926 
3927         MemoryService::track_memory_usage();
3928 
3929         // In prepare_for_verify() below we'll need to scan the deferred
3930         // update buffers to bring the RSets up-to-date if
3931         // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
3932         // the update buffers we'll probably need to scan cards on the
3933         // regions we just allocated to (i.e., the GC alloc
3934         // regions). However, during the last GC we called
3935         // set_saved_mark() on all the GC alloc regions, so card
3936         // scanning might skip the [saved_mark_word()...top()] area of
3937         // those regions (i.e., the area we allocated objects into
3938         // during the last GC). But it shouldn't. Given that
3939         // saved_mark_word() is conditional on whether the GC time stamp
3940         // on the region is current or not, by incrementing the GC time
3941         // stamp here we invalidate all the GC time stamps on all the
3942         // regions and saved_mark_word() will simply return top() for
3943         // all the regions. This is a nicer way of ensuring this rather
3944         // than iterating over the regions and fixing them. In fact, the
3945         // GC time stamp increment here also ensures that
3946         // saved_mark_word() will return top() between pauses, i.e.,
3947         // during concurrent refinement. So we don't need the
3948         // is_gc_active() check to decided which top to use when
3949         // scanning cards (see CR 7039627).
3950         increment_gc_time_stamp();
3951 
3952         verify_after_gc();
3953         check_bitmaps("GC End");
3954 
3955         assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
3956         ref_processor_stw()->verify_no_references_recorded();
3957 
3958         // CM reference discovery will be re-enabled if necessary.
3959       }
3960 
3961       // We should do this after we potentially expand the heap so
3962       // that all the COMMIT events are generated before the end GC
3963       // event, and after we retire the GC alloc regions so that all
3964       // RETIRE events are generated before the end GC event.
3965       _hr_printer.end_gc(false /* full */, (size_t) total_collections());
3966 
3967 #ifdef TRACESPINNING
3968       ParallelTaskTerminator::print_termination_counts();
3969 #endif
3970 
3971       gc_epilogue(false);
3972     }
3973 
3974     // Print the remainder of the GC log output.
3975     log_gc_footer(os::elapsedTime() - pause_start_sec);
3976 
3977     // It is not yet to safe to tell the concurrent mark to
3978     // start as we have some optional output below. We don't want the
3979     // output from the concurrent mark thread interfering with this
3980     // logging output either.
3981 
3982     _hrm.verify_optional();
3983     verify_region_sets_optional();
3984 
3985     TASKQUEUE_STATS_ONLY(if (PrintTaskqueue) print_taskqueue_stats());
3986     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3987 
3988     print_heap_after_gc();
3989     trace_heap_after_gc(_gc_tracer_stw);
3990 
3991     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3992     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3993     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3994     // before any GC notifications are raised.
3995     g1mm()->update_sizes();
3996 
3997     _gc_tracer_stw->report_evacuation_info(&evacuation_info);
3998     _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
3999     _gc_timer_stw->register_gc_end();
4000     _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
4001   }
4002   // It should now be safe to tell the concurrent mark thread to start
4003   // without its logging output interfering with the logging output
4004   // that came from the pause.
4005 
4006   if (should_start_conc_mark) {
4007     // CAUTION: after the doConcurrentMark() call below,
4008     // the concurrent marking thread(s) could be running
4009     // concurrently with us. Make sure that anything after
4010     // this point does not assume that we are the only GC thread
4011     // running. Note: of course, the actual marking work will
4012     // not start until the safepoint itself is released in
4013     // SuspendibleThreadSet::desynchronize().
4014     doConcurrentMark();
4015   }
4016 
4017   return true;
4018 }
4019 
4020 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4021   _drain_in_progress = false;
4022   set_evac_failure_closure(cl);
4023   _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4024 }
4025 
4026 void G1CollectedHeap::finalize_for_evac_failure() {
4027   assert(_evac_failure_scan_stack != NULL &&
4028          _evac_failure_scan_stack->length() == 0,
4029          "Postcondition");
4030   assert(!_drain_in_progress, "Postcondition");
4031   delete _evac_failure_scan_stack;
4032   _evac_failure_scan_stack = NULL;
4033 }
4034 
4035 void G1CollectedHeap::remove_self_forwarding_pointers() {
4036   double remove_self_forwards_start = os::elapsedTime();
4037 
4038   set_par_threads();
4039   G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4040   workers()->run_task(&rsfp_task);
4041   set_par_threads(0);
4042 
4043   // Now restore saved marks, if any.
4044   assert(_objs_with_preserved_marks.size() ==
4045             _preserved_marks_of_objs.size(), "Both or none.");
4046   while (!_objs_with_preserved_marks.is_empty()) {
4047     oop obj = _objs_with_preserved_marks.pop();
4048     markOop m = _preserved_marks_of_objs.pop();
4049     obj->set_mark(m);
4050   }
4051   _objs_with_preserved_marks.clear(true);
4052   _preserved_marks_of_objs.clear(true);
4053 
4054   g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
4055 }
4056 
4057 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4058   _evac_failure_scan_stack->push(obj);
4059 }
4060 
4061 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4062   assert(_evac_failure_scan_stack != NULL, "precondition");
4063 
4064   while (_evac_failure_scan_stack->length() > 0) {
4065      oop obj = _evac_failure_scan_stack->pop();
4066      _evac_failure_closure->set_region(heap_region_containing(obj));
4067      obj->oop_iterate_backwards(_evac_failure_closure);
4068   }
4069 }
4070 
4071 oop
4072 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state,
4073                                                oop old) {
4074   assert(obj_in_cs(old),
4075          err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4076                  p2i(old)));
4077   markOop m = old->mark();
4078   oop forward_ptr = old->forward_to_atomic(old);
4079   if (forward_ptr == NULL) {
4080     // Forward-to-self succeeded.
4081     assert(_par_scan_state != NULL, "par scan state");
4082     OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4083     uint queue_num = _par_scan_state->queue_num();
4084 
4085     _evacuation_failed = true;
4086     _evacuation_failed_info_array[queue_num].register_copy_failure(old->size());
4087     if (_evac_failure_closure != cl) {
4088       MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4089       assert(!_drain_in_progress,
4090              "Should only be true while someone holds the lock.");
4091       // Set the global evac-failure closure to the current thread's.
4092       assert(_evac_failure_closure == NULL, "Or locking has failed.");
4093       set_evac_failure_closure(cl);
4094       // Now do the common part.
4095       handle_evacuation_failure_common(old, m);
4096       // Reset to NULL.
4097       set_evac_failure_closure(NULL);
4098     } else {
4099       // The lock is already held, and this is recursive.
4100       assert(_drain_in_progress, "This should only be the recursive case.");
4101       handle_evacuation_failure_common(old, m);
4102     }
4103     return old;
4104   } else {
4105     // Forward-to-self failed. Either someone else managed to allocate
4106     // space for this object (old != forward_ptr) or they beat us in
4107     // self-forwarding it (old == forward_ptr).
4108     assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4109            err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4110                    "should not be in the CSet",
4111                    p2i(old), p2i(forward_ptr)));
4112     return forward_ptr;
4113   }
4114 }
4115 
4116 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4117   preserve_mark_if_necessary(old, m);
4118 
4119   HeapRegion* r = heap_region_containing(old);
4120   if (!r->evacuation_failed()) {
4121     r->set_evacuation_failed(true);
4122     _hr_printer.evac_failure(r);
4123   }
4124 
4125   push_on_evac_failure_scan_stack(old);
4126 
4127   if (!_drain_in_progress) {
4128     // prevent recursion in copy_to_survivor_space()
4129     _drain_in_progress = true;
4130     drain_evac_failure_scan_stack();
4131     _drain_in_progress = false;
4132   }
4133 }
4134 
4135 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4136   assert(evacuation_failed(), "Oversaving!");
4137   // We want to call the "for_promotion_failure" version only in the
4138   // case of a promotion failure.
4139   if (m->must_be_preserved_for_promotion_failure(obj)) {
4140     _objs_with_preserved_marks.push(obj);
4141     _preserved_marks_of_objs.push(m);
4142   }
4143 }
4144 
4145 void G1ParCopyHelper::mark_object(oop obj) {
4146   assert(!_g1->heap_region_containing(obj)->in_collection_set(), "should not mark objects in the CSet");
4147 
4148   // We know that the object is not moving so it's safe to read its size.
4149   _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4150 }
4151 
4152 void G1ParCopyHelper::mark_forwarded_object(oop from_obj, oop to_obj) {
4153   assert(from_obj->is_forwarded(), "from obj should be forwarded");
4154   assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4155   assert(from_obj != to_obj, "should not be self-forwarded");
4156 
4157   assert(_g1->heap_region_containing(from_obj)->in_collection_set(), "from obj should be in the CSet");
4158   assert(!_g1->heap_region_containing(to_obj)->in_collection_set(), "should not mark objects in the CSet");
4159 
4160   // The object might be in the process of being copied by another
4161   // worker so we cannot trust that its to-space image is
4162   // well-formed. So we have to read its size from its from-space
4163   // image which we know should not be changing.
4164   _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4165 }
4166 
4167 template <class T>
4168 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) {
4169   if (_g1->heap_region_containing_raw(new_obj)->is_young()) {
4170     _scanned_klass->record_modified_oops();
4171   }
4172 }
4173 
4174 template <G1Barrier barrier, G1Mark do_mark_object>
4175 template <class T>
4176 void G1ParCopyClosure<barrier, do_mark_object>::do_oop_work(T* p) {
4177   T heap_oop = oopDesc::load_heap_oop(p);
4178 
4179   if (oopDesc::is_null(heap_oop)) {
4180     return;
4181   }
4182 
4183   oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
4184 
4185   assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4186 
4187   const InCSetState state = _g1->in_cset_state(obj);
4188   if (state.is_in_cset()) {
4189     oop forwardee;
4190     markOop m = obj->mark();
4191     if (m->is_marked()) {
4192       forwardee = (oop) m->decode_pointer();
4193     } else {
4194       forwardee = _par_scan_state->copy_to_survivor_space(state, obj, m);
4195     }
4196     assert(forwardee != NULL, "forwardee should not be NULL");
4197     oopDesc::encode_store_heap_oop(p, forwardee);
4198     if (do_mark_object != G1MarkNone && forwardee != obj) {
4199       // If the object is self-forwarded we don't need to explicitly
4200       // mark it, the evacuation failure protocol will do so.
4201       mark_forwarded_object(obj, forwardee);
4202     }
4203 
4204     if (barrier == G1BarrierKlass) {
4205       do_klass_barrier(p, forwardee);
4206     }
4207   } else {
4208     if (state.is_humongous()) {
4209       _g1->set_humongous_is_live(obj);
4210     }
4211     // The object is not in collection set. If we're a root scanning
4212     // closure during an initial mark pause then attempt to mark the object.
4213     if (do_mark_object == G1MarkFromRoot) {
4214       mark_object(obj);
4215     }
4216   }
4217 
4218   if (barrier == G1BarrierEvac) {
4219     _par_scan_state->update_rs(_from, p, _worker_id);
4220   }
4221 }
4222 
4223 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(oop* p);
4224 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(narrowOop* p);
4225 
4226 class G1ParEvacuateFollowersClosure : public VoidClosure {
4227 protected:
4228   G1CollectedHeap*              _g1h;
4229   G1ParScanThreadState*         _par_scan_state;
4230   RefToScanQueueSet*            _queues;
4231   ParallelTaskTerminator*       _terminator;
4232 
4233   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
4234   RefToScanQueueSet*      queues()         { return _queues; }
4235   ParallelTaskTerminator* terminator()     { return _terminator; }
4236 
4237 public:
4238   G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4239                                 G1ParScanThreadState* par_scan_state,
4240                                 RefToScanQueueSet* queues,
4241                                 ParallelTaskTerminator* terminator)
4242     : _g1h(g1h), _par_scan_state(par_scan_state),
4243       _queues(queues), _terminator(terminator) {}
4244 
4245   void do_void();
4246 
4247 private:
4248   inline bool offer_termination();
4249 };
4250 
4251 bool G1ParEvacuateFollowersClosure::offer_termination() {
4252   G1ParScanThreadState* const pss = par_scan_state();
4253   pss->start_term_time();
4254   const bool res = terminator()->offer_termination();
4255   pss->end_term_time();
4256   return res;
4257 }
4258 
4259 void G1ParEvacuateFollowersClosure::do_void() {
4260   G1ParScanThreadState* const pss = par_scan_state();
4261   pss->trim_queue();
4262   do {
4263     pss->steal_and_trim_queue(queues());
4264   } while (!offer_termination());
4265 }
4266 
4267 class G1KlassScanClosure : public KlassClosure {
4268  G1ParCopyHelper* _closure;
4269  bool             _process_only_dirty;
4270  int              _count;
4271  public:
4272   G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty)
4273       : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {}
4274   void do_klass(Klass* klass) {
4275     // If the klass has not been dirtied we know that there's
4276     // no references into  the young gen and we can skip it.
4277    if (!_process_only_dirty || klass->has_modified_oops()) {
4278       // Clean the klass since we're going to scavenge all the metadata.
4279       klass->clear_modified_oops();
4280 
4281       // Tell the closure that this klass is the Klass to scavenge
4282       // and is the one to dirty if oops are left pointing into the young gen.
4283       _closure->set_scanned_klass(klass);
4284 
4285       klass->oops_do(_closure);
4286 
4287       _closure->set_scanned_klass(NULL);
4288     }
4289     _count++;
4290   }
4291 };
4292 
4293 class G1ParTask : public AbstractGangTask {
4294 protected:
4295   G1CollectedHeap*       _g1h;
4296   RefToScanQueueSet      *_queues;
4297   G1RootProcessor*       _root_processor;
4298   ParallelTaskTerminator _terminator;
4299   uint _n_workers;
4300 
4301   Mutex _stats_lock;
4302   Mutex* stats_lock() { return &_stats_lock; }
4303 
4304 public:
4305   G1ParTask(G1CollectedHeap* g1h, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor)
4306     : AbstractGangTask("G1 collection"),
4307       _g1h(g1h),
4308       _queues(task_queues),
4309       _root_processor(root_processor),
4310       _terminator(0, _queues),
4311       _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4312   {}
4313 
4314   RefToScanQueueSet* queues() { return _queues; }
4315 
4316   RefToScanQueue *work_queue(int i) {
4317     return queues()->queue(i);
4318   }
4319 
4320   ParallelTaskTerminator* terminator() { return &_terminator; }
4321 
4322   virtual void set_for_termination(uint active_workers) {
4323     _root_processor->set_num_workers(active_workers);
4324     terminator()->reset_for_reuse(active_workers);
4325     _n_workers = active_workers;
4326   }
4327 
4328   // Helps out with CLD processing.
4329   //
4330   // During InitialMark we need to:
4331   // 1) Scavenge all CLDs for the young GC.
4332   // 2) Mark all objects directly reachable from strong CLDs.
4333   template <G1Mark do_mark_object>
4334   class G1CLDClosure : public CLDClosure {
4335     G1ParCopyClosure<G1BarrierNone,  do_mark_object>* _oop_closure;
4336     G1ParCopyClosure<G1BarrierKlass, do_mark_object>  _oop_in_klass_closure;
4337     G1KlassScanClosure                                _klass_in_cld_closure;
4338     bool                                              _claim;
4339 
4340    public:
4341     G1CLDClosure(G1ParCopyClosure<G1BarrierNone, do_mark_object>* oop_closure,
4342                  bool only_young, bool claim)
4343         : _oop_closure(oop_closure),
4344           _oop_in_klass_closure(oop_closure->g1(),
4345                                 oop_closure->pss(),
4346                                 oop_closure->rp()),
4347           _klass_in_cld_closure(&_oop_in_klass_closure, only_young),
4348           _claim(claim) {
4349 
4350     }
4351 
4352     void do_cld(ClassLoaderData* cld) {
4353       cld->oops_do(_oop_closure, &_klass_in_cld_closure, _claim);
4354     }
4355   };
4356 
4357   void work(uint worker_id) {
4358     if (worker_id >= _n_workers) return;  // no work needed this round
4359 
4360     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, os::elapsedTime());
4361 
4362     {
4363       ResourceMark rm;
4364       HandleMark   hm;
4365 
4366       ReferenceProcessor*             rp = _g1h->ref_processor_stw();
4367 
4368       G1ParScanThreadState            pss(_g1h, worker_id, rp);
4369       G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
4370 
4371       pss.set_evac_failure_closure(&evac_failure_cl);
4372 
4373       bool only_young = _g1h->g1_policy()->gcs_are_young();
4374 
4375       // Non-IM young GC.
4376       G1ParCopyClosure<G1BarrierNone, G1MarkNone>             scan_only_root_cl(_g1h, &pss, rp);
4377       G1CLDClosure<G1MarkNone>                                scan_only_cld_cl(&scan_only_root_cl,
4378                                                                                only_young, // Only process dirty klasses.
4379                                                                                false);     // No need to claim CLDs.
4380       // IM young GC.
4381       //    Strong roots closures.
4382       G1ParCopyClosure<G1BarrierNone, G1MarkFromRoot>         scan_mark_root_cl(_g1h, &pss, rp);
4383       G1CLDClosure<G1MarkFromRoot>                            scan_mark_cld_cl(&scan_mark_root_cl,
4384                                                                                false, // Process all klasses.
4385                                                                                true); // Need to claim CLDs.
4386       //    Weak roots closures.
4387       G1ParCopyClosure<G1BarrierNone, G1MarkPromotedFromRoot> scan_mark_weak_root_cl(_g1h, &pss, rp);
4388       G1CLDClosure<G1MarkPromotedFromRoot>                    scan_mark_weak_cld_cl(&scan_mark_weak_root_cl,
4389                                                                                     false, // Process all klasses.
4390                                                                                     true); // Need to claim CLDs.
4391 
4392       OopClosure* strong_root_cl;
4393       OopClosure* weak_root_cl;
4394       CLDClosure* strong_cld_cl;
4395       CLDClosure* weak_cld_cl;
4396 
4397       bool trace_metadata = false;
4398 
4399       if (_g1h->g1_policy()->during_initial_mark_pause()) {
4400         // We also need to mark copied objects.
4401         strong_root_cl = &scan_mark_root_cl;
4402         strong_cld_cl  = &scan_mark_cld_cl;
4403         if (ClassUnloadingWithConcurrentMark) {
4404           weak_root_cl = &scan_mark_weak_root_cl;
4405           weak_cld_cl  = &scan_mark_weak_cld_cl;
4406           trace_metadata = true;
4407         } else {
4408           weak_root_cl = &scan_mark_root_cl;
4409           weak_cld_cl  = &scan_mark_cld_cl;
4410         }
4411       } else {
4412         strong_root_cl = &scan_only_root_cl;
4413         weak_root_cl   = &scan_only_root_cl;
4414         strong_cld_cl  = &scan_only_cld_cl;
4415         weak_cld_cl    = &scan_only_cld_cl;
4416       }
4417 
4418       pss.start_strong_roots();
4419 
4420       _root_processor->evacuate_roots(strong_root_cl,
4421                                       weak_root_cl,
4422                                       strong_cld_cl,
4423                                       weak_cld_cl,
4424                                       trace_metadata,
4425                                       worker_id);
4426 
4427       G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss);
4428       _root_processor->scan_remembered_sets(&push_heap_rs_cl,
4429                                             weak_root_cl,
4430                                             worker_id);
4431       pss.end_strong_roots();
4432 
4433       {
4434         double start = os::elapsedTime();
4435         G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4436         evac.do_void();
4437         double elapsed_sec = os::elapsedTime() - start;
4438         double term_sec = pss.term_time();
4439         _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec);
4440         _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec);
4441         _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, pss.term_attempts());
4442       }
4443       _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4444       _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4445 
4446       if (PrintTerminationStats) {
4447         MutexLocker x(stats_lock());
4448         pss.print_termination_stats(worker_id);
4449       }
4450 
4451       assert(pss.queue_is_empty(), "should be empty");
4452 
4453       // Close the inner scope so that the ResourceMark and HandleMark
4454       // destructors are executed here and are included as part of the
4455       // "GC Worker Time".
4456     }
4457     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime());
4458   }
4459 };
4460 
4461 class G1StringSymbolTableUnlinkTask : public AbstractGangTask {
4462 private:
4463   BoolObjectClosure* _is_alive;
4464   int _initial_string_table_size;
4465   int _initial_symbol_table_size;
4466 
4467   bool  _process_strings;
4468   int _strings_processed;
4469   int _strings_removed;
4470 
4471   bool  _process_symbols;
4472   int _symbols_processed;
4473   int _symbols_removed;
4474 
4475 public:
4476   G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) :
4477     AbstractGangTask("String/Symbol Unlinking"),
4478     _is_alive(is_alive),
4479     _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
4480     _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) {
4481 
4482     _initial_string_table_size = StringTable::the_table()->table_size();
4483     _initial_symbol_table_size = SymbolTable::the_table()->table_size();
4484     if (process_strings) {
4485       StringTable::clear_parallel_claimed_index();
4486     }
4487     if (process_symbols) {
4488       SymbolTable::clear_parallel_claimed_index();
4489     }
4490   }
4491 
4492   ~G1StringSymbolTableUnlinkTask() {
4493     guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size,
4494               err_msg("claim value %d after unlink less than initial string table size %d",
4495                       StringTable::parallel_claimed_index(), _initial_string_table_size));
4496     guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
4497               err_msg("claim value %d after unlink less than initial symbol table size %d",
4498                       SymbolTable::parallel_claimed_index(), _initial_symbol_table_size));
4499 
4500     if (G1TraceStringSymbolTableScrubbing) {
4501       gclog_or_tty->print_cr("Cleaned string and symbol table, "
4502                              "strings: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed, "
4503                              "symbols: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed",
4504                              strings_processed(), strings_removed(),
4505                              symbols_processed(), symbols_removed());
4506     }
4507   }
4508 
4509   void work(uint worker_id) {
4510     int strings_processed = 0;
4511     int strings_removed = 0;
4512     int symbols_processed = 0;
4513     int symbols_removed = 0;
4514     if (_process_strings) {
4515       StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
4516       Atomic::add(strings_processed, &_strings_processed);
4517       Atomic::add(strings_removed, &_strings_removed);
4518     }
4519     if (_process_symbols) {
4520       SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
4521       Atomic::add(symbols_processed, &_symbols_processed);
4522       Atomic::add(symbols_removed, &_symbols_removed);
4523     }
4524   }
4525 
4526   size_t strings_processed() const { return (size_t)_strings_processed; }
4527   size_t strings_removed()   const { return (size_t)_strings_removed; }
4528 
4529   size_t symbols_processed() const { return (size_t)_symbols_processed; }
4530   size_t symbols_removed()   const { return (size_t)_symbols_removed; }
4531 };
4532 
4533 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
4534 private:
4535   static Monitor* _lock;
4536 
4537   BoolObjectClosure* const _is_alive;
4538   const bool               _unloading_occurred;
4539   const uint               _num_workers;
4540 
4541   // Variables used to claim nmethods.
4542   nmethod* _first_nmethod;
4543   volatile nmethod* _claimed_nmethod;
4544 
4545   // The list of nmethods that need to be processed by the second pass.
4546   volatile nmethod* _postponed_list;
4547   volatile uint     _num_entered_barrier;
4548 
4549  public:
4550   G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
4551       _is_alive(is_alive),
4552       _unloading_occurred(unloading_occurred),
4553       _num_workers(num_workers),
4554       _first_nmethod(NULL),
4555       _claimed_nmethod(NULL),
4556       _postponed_list(NULL),
4557       _num_entered_barrier(0)
4558   {
4559     nmethod::increase_unloading_clock();
4560     // Get first alive nmethod
4561     NMethodIterator iter = NMethodIterator();
4562     if(iter.next_alive()) {
4563       _first_nmethod = iter.method();
4564     }
4565     _claimed_nmethod = (volatile nmethod*)_first_nmethod;
4566   }
4567 
4568   ~G1CodeCacheUnloadingTask() {
4569     CodeCache::verify_clean_inline_caches();
4570 
4571     CodeCache::set_needs_cache_clean(false);
4572     guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
4573 
4574     CodeCache::verify_icholder_relocations();
4575   }
4576 
4577  private:
4578   void add_to_postponed_list(nmethod* nm) {
4579       nmethod* old;
4580       do {
4581         old = (nmethod*)_postponed_list;
4582         nm->set_unloading_next(old);
4583       } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old);
4584   }
4585 
4586   void clean_nmethod(nmethod* nm) {
4587     bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
4588 
4589     if (postponed) {
4590       // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
4591       add_to_postponed_list(nm);
4592     }
4593 
4594     // Mark that this thread has been cleaned/unloaded.
4595     // After this call, it will be safe to ask if this nmethod was unloaded or not.
4596     nm->set_unloading_clock(nmethod::global_unloading_clock());
4597   }
4598 
4599   void clean_nmethod_postponed(nmethod* nm) {
4600     nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
4601   }
4602 
4603   static const int MaxClaimNmethods = 16;
4604 
4605   void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) {
4606     nmethod* first;
4607     NMethodIterator last;
4608 
4609     do {
4610       *num_claimed_nmethods = 0;
4611 
4612       first = (nmethod*)_claimed_nmethod;
4613       last = NMethodIterator(first);
4614 
4615       if (first != NULL) {
4616 
4617         for (int i = 0; i < MaxClaimNmethods; i++) {
4618           if (!last.next_alive()) {
4619             break;
4620           }
4621           claimed_nmethods[i] = last.method();
4622           (*num_claimed_nmethods)++;
4623         }
4624       }
4625 
4626     } while ((nmethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first);
4627   }
4628 
4629   nmethod* claim_postponed_nmethod() {
4630     nmethod* claim;
4631     nmethod* next;
4632 
4633     do {
4634       claim = (nmethod*)_postponed_list;
4635       if (claim == NULL) {
4636         return NULL;
4637       }
4638 
4639       next = claim->unloading_next();
4640 
4641     } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim);
4642 
4643     return claim;
4644   }
4645 
4646  public:
4647   // Mark that we're done with the first pass of nmethod cleaning.
4648   void barrier_mark(uint worker_id) {
4649     MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
4650     _num_entered_barrier++;
4651     if (_num_entered_barrier == _num_workers) {
4652       ml.notify_all();
4653     }
4654   }
4655 
4656   // See if we have to wait for the other workers to
4657   // finish their first-pass nmethod cleaning work.
4658   void barrier_wait(uint worker_id) {
4659     if (_num_entered_barrier < _num_workers) {
4660       MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
4661       while (_num_entered_barrier < _num_workers) {
4662           ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
4663       }
4664     }
4665   }
4666 
4667   // Cleaning and unloading of nmethods. Some work has to be postponed
4668   // to the second pass, when we know which nmethods survive.
4669   void work_first_pass(uint worker_id) {
4670     // The first nmethods is claimed by the first worker.
4671     if (worker_id == 0 && _first_nmethod != NULL) {
4672       clean_nmethod(_first_nmethod);
4673       _first_nmethod = NULL;
4674     }
4675 
4676     int num_claimed_nmethods;
4677     nmethod* claimed_nmethods[MaxClaimNmethods];
4678 
4679     while (true) {
4680       claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
4681 
4682       if (num_claimed_nmethods == 0) {
4683         break;
4684       }
4685 
4686       for (int i = 0; i < num_claimed_nmethods; i++) {
4687         clean_nmethod(claimed_nmethods[i]);
4688       }
4689     }
4690   }
4691 
4692   void work_second_pass(uint worker_id) {
4693     nmethod* nm;
4694     // Take care of postponed nmethods.
4695     while ((nm = claim_postponed_nmethod()) != NULL) {
4696       clean_nmethod_postponed(nm);
4697     }
4698   }
4699 };
4700 
4701 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never);
4702 
4703 class G1KlassCleaningTask : public StackObj {
4704   BoolObjectClosure*                      _is_alive;
4705   volatile jint                           _clean_klass_tree_claimed;
4706   ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
4707 
4708  public:
4709   G1KlassCleaningTask(BoolObjectClosure* is_alive) :
4710       _is_alive(is_alive),
4711       _clean_klass_tree_claimed(0),
4712       _klass_iterator() {
4713   }
4714 
4715  private:
4716   bool claim_clean_klass_tree_task() {
4717     if (_clean_klass_tree_claimed) {
4718       return false;
4719     }
4720 
4721     return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0;
4722   }
4723 
4724   InstanceKlass* claim_next_klass() {
4725     Klass* klass;
4726     do {
4727       klass =_klass_iterator.next_klass();
4728     } while (klass != NULL && !klass->oop_is_instance());
4729 
4730     return (InstanceKlass*)klass;
4731   }
4732 
4733 public:
4734 
4735   void clean_klass(InstanceKlass* ik) {
4736     ik->clean_implementors_list(_is_alive);
4737     ik->clean_method_data(_is_alive);
4738 
4739     // G1 specific cleanup work that has
4740     // been moved here to be done in parallel.
4741     ik->clean_dependent_nmethods();
4742   }
4743 
4744   void work() {
4745     ResourceMark rm;
4746 
4747     // One worker will clean the subklass/sibling klass tree.
4748     if (claim_clean_klass_tree_task()) {
4749       Klass::clean_subklass_tree(_is_alive);
4750     }
4751 
4752     // All workers will help cleaning the classes,
4753     InstanceKlass* klass;
4754     while ((klass = claim_next_klass()) != NULL) {
4755       clean_klass(klass);
4756     }
4757   }
4758 };
4759 
4760 // To minimize the remark pause times, the tasks below are done in parallel.
4761 class G1ParallelCleaningTask : public AbstractGangTask {
4762 private:
4763   G1StringSymbolTableUnlinkTask _string_symbol_task;
4764   G1CodeCacheUnloadingTask      _code_cache_task;
4765   G1KlassCleaningTask           _klass_cleaning_task;
4766 
4767 public:
4768   // The constructor is run in the VMThread.
4769   G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) :
4770       AbstractGangTask("Parallel Cleaning"),
4771       _string_symbol_task(is_alive, process_strings, process_symbols),
4772       _code_cache_task(num_workers, is_alive, unloading_occurred),
4773       _klass_cleaning_task(is_alive) {
4774   }
4775 
4776   // The parallel work done by all worker threads.
4777   void work(uint worker_id) {
4778     // Do first pass of code cache cleaning.
4779     _code_cache_task.work_first_pass(worker_id);
4780 
4781     // Let the threads mark that the first pass is done.
4782     _code_cache_task.barrier_mark(worker_id);
4783 
4784     // Clean the Strings and Symbols.
4785     _string_symbol_task.work(worker_id);
4786 
4787     // Wait for all workers to finish the first code cache cleaning pass.
4788     _code_cache_task.barrier_wait(worker_id);
4789 
4790     // Do the second code cache cleaning work, which realize on
4791     // the liveness information gathered during the first pass.
4792     _code_cache_task.work_second_pass(worker_id);
4793 
4794     // Clean all klasses that were not unloaded.
4795     _klass_cleaning_task.work();
4796   }
4797 };
4798 
4799 
4800 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive,
4801                                         bool process_strings,
4802                                         bool process_symbols,
4803                                         bool class_unloading_occurred) {
4804   uint n_workers = workers()->active_workers();
4805 
4806   G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols,
4807                                         n_workers, class_unloading_occurred);
4808   set_par_threads(n_workers);
4809   workers()->run_task(&g1_unlink_task);
4810   set_par_threads(0);
4811 }
4812 
4813 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive,
4814                                                      bool process_strings, bool process_symbols) {
4815   {
4816     uint n_workers = workers()->active_workers();
4817     G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols);
4818     set_par_threads(n_workers);
4819     workers()->run_task(&g1_unlink_task);
4820     set_par_threads(0);
4821   }
4822 
4823   if (G1StringDedup::is_enabled()) {
4824     G1StringDedup::unlink(is_alive);
4825   }
4826 }
4827 
4828 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
4829  private:
4830   DirtyCardQueueSet* _queue;
4831  public:
4832   G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue) : AbstractGangTask("Redirty Cards"), _queue(queue) { }
4833 
4834   virtual void work(uint worker_id) {
4835     G1GCPhaseTimes* phase_times = G1CollectedHeap::heap()->g1_policy()->phase_times();
4836     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id);
4837 
4838     RedirtyLoggedCardTableEntryClosure cl;
4839     _queue->par_apply_closure_to_all_completed_buffers(&cl);
4840 
4841     phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_processed());
4842   }
4843 };
4844 
4845 void G1CollectedHeap::redirty_logged_cards() {
4846   double redirty_logged_cards_start = os::elapsedTime();
4847 
4848   uint n_workers = workers()->active_workers();
4849 
4850   G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set());
4851   dirty_card_queue_set().reset_for_par_iteration();
4852   set_par_threads(n_workers);
4853   workers()->run_task(&redirty_task);
4854   set_par_threads(0);
4855 
4856   DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
4857   dcq.merge_bufferlists(&dirty_card_queue_set());
4858   assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
4859 
4860   g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
4861 }
4862 
4863 // Weak Reference Processing support
4864 
4865 // An always "is_alive" closure that is used to preserve referents.
4866 // If the object is non-null then it's alive.  Used in the preservation
4867 // of referent objects that are pointed to by reference objects
4868 // discovered by the CM ref processor.
4869 class G1AlwaysAliveClosure: public BoolObjectClosure {
4870   G1CollectedHeap* _g1;
4871 public:
4872   G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
4873   bool do_object_b(oop p) {
4874     if (p != NULL) {
4875       return true;
4876     }
4877     return false;
4878   }
4879 };
4880 
4881 bool G1STWIsAliveClosure::do_object_b(oop p) {
4882   // An object is reachable if it is outside the collection set,
4883   // or is inside and copied.
4884   return !_g1->obj_in_cs(p) || p->is_forwarded();
4885 }
4886 
4887 // Non Copying Keep Alive closure
4888 class G1KeepAliveClosure: public OopClosure {
4889   G1CollectedHeap* _g1;
4890 public:
4891   G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
4892   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
4893   void do_oop(oop* p) {
4894     oop obj = *p;
4895     assert(obj != NULL, "the caller should have filtered out NULL values");
4896 
4897     const InCSetState cset_state = _g1->in_cset_state(obj);
4898     if (!cset_state.is_in_cset_or_humongous()) {
4899       return;
4900     }
4901     if (cset_state.is_in_cset()) {
4902       assert( obj->is_forwarded(), "invariant" );
4903       *p = obj->forwardee();
4904     } else {
4905       assert(!obj->is_forwarded(), "invariant" );
4906       assert(cset_state.is_humongous(),
4907              err_msg("Only allowed InCSet state is IsHumongous, but is %d", cset_state.value()));
4908       _g1->set_humongous_is_live(obj);
4909     }
4910   }
4911 };
4912 
4913 // Copying Keep Alive closure - can be called from both
4914 // serial and parallel code as long as different worker
4915 // threads utilize different G1ParScanThreadState instances
4916 // and different queues.
4917 
4918 class G1CopyingKeepAliveClosure: public OopClosure {
4919   G1CollectedHeap*         _g1h;
4920   OopClosure*              _copy_non_heap_obj_cl;
4921   G1ParScanThreadState*    _par_scan_state;
4922 
4923 public:
4924   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
4925                             OopClosure* non_heap_obj_cl,
4926                             G1ParScanThreadState* pss):
4927     _g1h(g1h),
4928     _copy_non_heap_obj_cl(non_heap_obj_cl),
4929     _par_scan_state(pss)
4930   {}
4931 
4932   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
4933   virtual void do_oop(      oop* p) { do_oop_work(p); }
4934 
4935   template <class T> void do_oop_work(T* p) {
4936     oop obj = oopDesc::load_decode_heap_oop(p);
4937 
4938     if (_g1h->is_in_cset_or_humongous(obj)) {
4939       // If the referent object has been forwarded (either copied
4940       // to a new location or to itself in the event of an
4941       // evacuation failure) then we need to update the reference
4942       // field and, if both reference and referent are in the G1
4943       // heap, update the RSet for the referent.
4944       //
4945       // If the referent has not been forwarded then we have to keep
4946       // it alive by policy. Therefore we have copy the referent.
4947       //
4948       // If the reference field is in the G1 heap then we can push
4949       // on the PSS queue. When the queue is drained (after each
4950       // phase of reference processing) the object and it's followers
4951       // will be copied, the reference field set to point to the
4952       // new location, and the RSet updated. Otherwise we need to
4953       // use the the non-heap or metadata closures directly to copy
4954       // the referent object and update the pointer, while avoiding
4955       // updating the RSet.
4956 
4957       if (_g1h->is_in_g1_reserved(p)) {
4958         _par_scan_state->push_on_queue(p);
4959       } else {
4960         assert(!Metaspace::contains((const void*)p),
4961                err_msg("Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p)));
4962         _copy_non_heap_obj_cl->do_oop(p);
4963       }
4964     }
4965   }
4966 };
4967 
4968 // Serial drain queue closure. Called as the 'complete_gc'
4969 // closure for each discovered list in some of the
4970 // reference processing phases.
4971 
4972 class G1STWDrainQueueClosure: public VoidClosure {
4973 protected:
4974   G1CollectedHeap* _g1h;
4975   G1ParScanThreadState* _par_scan_state;
4976 
4977   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
4978 
4979 public:
4980   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
4981     _g1h(g1h),
4982     _par_scan_state(pss)
4983   { }
4984 
4985   void do_void() {
4986     G1ParScanThreadState* const pss = par_scan_state();
4987     pss->trim_queue();
4988   }
4989 };
4990 
4991 // Parallel Reference Processing closures
4992 
4993 // Implementation of AbstractRefProcTaskExecutor for parallel reference
4994 // processing during G1 evacuation pauses.
4995 
4996 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
4997 private:
4998   G1CollectedHeap*   _g1h;
4999   RefToScanQueueSet* _queues;
5000   FlexibleWorkGang*  _workers;
5001   uint               _active_workers;
5002 
5003 public:
5004   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5005                            FlexibleWorkGang* workers,
5006                            RefToScanQueueSet *task_queues,
5007                            uint n_workers) :
5008     _g1h(g1h),
5009     _queues(task_queues),
5010     _workers(workers),
5011     _active_workers(n_workers)
5012   {
5013     assert(n_workers > 0, "shouldn't call this otherwise");
5014   }
5015 
5016   // Executes the given task using concurrent marking worker threads.
5017   virtual void execute(ProcessTask& task);
5018   virtual void execute(EnqueueTask& task);
5019 };
5020 
5021 // Gang task for possibly parallel reference processing
5022 
5023 class G1STWRefProcTaskProxy: public AbstractGangTask {
5024   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5025   ProcessTask&     _proc_task;
5026   G1CollectedHeap* _g1h;
5027   RefToScanQueueSet *_task_queues;
5028   ParallelTaskTerminator* _terminator;
5029 
5030 public:
5031   G1STWRefProcTaskProxy(ProcessTask& proc_task,
5032                      G1CollectedHeap* g1h,
5033                      RefToScanQueueSet *task_queues,
5034                      ParallelTaskTerminator* terminator) :
5035     AbstractGangTask("Process reference objects in parallel"),
5036     _proc_task(proc_task),
5037     _g1h(g1h),
5038     _task_queues(task_queues),
5039     _terminator(terminator)
5040   {}
5041 
5042   virtual void work(uint worker_id) {
5043     // The reference processing task executed by a single worker.
5044     ResourceMark rm;
5045     HandleMark   hm;
5046 
5047     G1STWIsAliveClosure is_alive(_g1h);
5048 
5049     G1ParScanThreadState            pss(_g1h, worker_id, NULL);
5050     G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5051 
5052     pss.set_evac_failure_closure(&evac_failure_cl);
5053 
5054     G1ParScanExtRootClosure        only_copy_non_heap_cl(_g1h, &pss, NULL);
5055 
5056     G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5057 
5058     OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5059 
5060     if (_g1h->g1_policy()->during_initial_mark_pause()) {
5061       // We also need to mark copied objects.
5062       copy_non_heap_cl = &copy_mark_non_heap_cl;
5063     }
5064 
5065     // Keep alive closure.
5066     G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5067 
5068     // Complete GC closure
5069     G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5070 
5071     // Call the reference processing task's work routine.
5072     _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5073 
5074     // Note we cannot assert that the refs array is empty here as not all
5075     // of the processing tasks (specifically phase2 - pp2_work) execute
5076     // the complete_gc closure (which ordinarily would drain the queue) so
5077     // the queue may not be empty.
5078   }
5079 };
5080 
5081 // Driver routine for parallel reference processing.
5082 // Creates an instance of the ref processing gang
5083 // task and has the worker threads execute it.
5084 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5085   assert(_workers != NULL, "Need parallel worker threads.");
5086 
5087   ParallelTaskTerminator terminator(_active_workers, _queues);
5088   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5089 
5090   _g1h->set_par_threads(_active_workers);
5091   _workers->run_task(&proc_task_proxy);
5092   _g1h->set_par_threads(0);
5093 }
5094 
5095 // Gang task for parallel reference enqueueing.
5096 
5097 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5098   typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5099   EnqueueTask& _enq_task;
5100 
5101 public:
5102   G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5103     AbstractGangTask("Enqueue reference objects in parallel"),
5104     _enq_task(enq_task)
5105   { }
5106 
5107   virtual void work(uint worker_id) {
5108     _enq_task.work(worker_id);
5109   }
5110 };
5111 
5112 // Driver routine for parallel reference enqueueing.
5113 // Creates an instance of the ref enqueueing gang
5114 // task and has the worker threads execute it.
5115 
5116 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5117   assert(_workers != NULL, "Need parallel worker threads.");
5118 
5119   G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5120 
5121   _g1h->set_par_threads(_active_workers);
5122   _workers->run_task(&enq_task_proxy);
5123   _g1h->set_par_threads(0);
5124 }
5125 
5126 // End of weak reference support closures
5127 
5128 // Abstract task used to preserve (i.e. copy) any referent objects
5129 // that are in the collection set and are pointed to by reference
5130 // objects discovered by the CM ref processor.
5131 
5132 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5133 protected:
5134   G1CollectedHeap* _g1h;
5135   RefToScanQueueSet      *_queues;
5136   ParallelTaskTerminator _terminator;
5137   uint _n_workers;
5138 
5139 public:
5140   G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, uint workers, RefToScanQueueSet *task_queues) :
5141     AbstractGangTask("ParPreserveCMReferents"),
5142     _g1h(g1h),
5143     _queues(task_queues),
5144     _terminator(workers, _queues),
5145     _n_workers(workers)
5146   { }
5147 
5148   void work(uint worker_id) {
5149     ResourceMark rm;
5150     HandleMark   hm;
5151 
5152     G1ParScanThreadState            pss(_g1h, worker_id, NULL);
5153     G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5154 
5155     pss.set_evac_failure_closure(&evac_failure_cl);
5156 
5157     assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5158 
5159     G1ParScanExtRootClosure        only_copy_non_heap_cl(_g1h, &pss, NULL);
5160 
5161     G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5162 
5163     OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5164 
5165     if (_g1h->g1_policy()->during_initial_mark_pause()) {
5166       // We also need to mark copied objects.
5167       copy_non_heap_cl = &copy_mark_non_heap_cl;
5168     }
5169 
5170     // Is alive closure
5171     G1AlwaysAliveClosure always_alive(_g1h);
5172 
5173     // Copying keep alive closure. Applied to referent objects that need
5174     // to be copied.
5175     G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5176 
5177     ReferenceProcessor* rp = _g1h->ref_processor_cm();
5178 
5179     uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5180     uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5181 
5182     // limit is set using max_num_q() - which was set using ParallelGCThreads.
5183     // So this must be true - but assert just in case someone decides to
5184     // change the worker ids.
5185     assert(worker_id < limit, "sanity");
5186     assert(!rp->discovery_is_atomic(), "check this code");
5187 
5188     // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5189     for (uint idx = worker_id; idx < limit; idx += stride) {
5190       DiscoveredList& ref_list = rp->discovered_refs()[idx];
5191 
5192       DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5193       while (iter.has_next()) {
5194         // Since discovery is not atomic for the CM ref processor, we
5195         // can see some null referent objects.
5196         iter.load_ptrs(DEBUG_ONLY(true));
5197         oop ref = iter.obj();
5198 
5199         // This will filter nulls.
5200         if (iter.is_referent_alive()) {
5201           iter.make_referent_alive();
5202         }
5203         iter.move_to_next();
5204       }
5205     }
5206 
5207     // Drain the queue - which may cause stealing
5208     G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5209     drain_queue.do_void();
5210     // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5211     assert(pss.queue_is_empty(), "should be");
5212   }
5213 };
5214 
5215 // Weak Reference processing during an evacuation pause (part 1).
5216 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) {
5217   double ref_proc_start = os::elapsedTime();
5218 
5219   ReferenceProcessor* rp = _ref_processor_stw;
5220   assert(rp->discovery_enabled(), "should have been enabled");
5221 
5222   // Any reference objects, in the collection set, that were 'discovered'
5223   // by the CM ref processor should have already been copied (either by
5224   // applying the external root copy closure to the discovered lists, or
5225   // by following an RSet entry).
5226   //
5227   // But some of the referents, that are in the collection set, that these
5228   // reference objects point to may not have been copied: the STW ref
5229   // processor would have seen that the reference object had already
5230   // been 'discovered' and would have skipped discovering the reference,
5231   // but would not have treated the reference object as a regular oop.
5232   // As a result the copy closure would not have been applied to the
5233   // referent object.
5234   //
5235   // We need to explicitly copy these referent objects - the references
5236   // will be processed at the end of remarking.
5237   //
5238   // We also need to do this copying before we process the reference
5239   // objects discovered by the STW ref processor in case one of these
5240   // referents points to another object which is also referenced by an
5241   // object discovered by the STW ref processor.
5242 
5243   assert(no_of_gc_workers == workers()->active_workers(), "Need to reset active GC workers");
5244 
5245   set_par_threads(no_of_gc_workers);
5246   G1ParPreserveCMReferentsTask keep_cm_referents(this,
5247                                                  no_of_gc_workers,
5248                                                  _task_queues);
5249 
5250   workers()->run_task(&keep_cm_referents);
5251 
5252   set_par_threads(0);
5253 
5254   // Closure to test whether a referent is alive.
5255   G1STWIsAliveClosure is_alive(this);
5256 
5257   // Even when parallel reference processing is enabled, the processing
5258   // of JNI refs is serial and performed serially by the current thread
5259   // rather than by a worker. The following PSS will be used for processing
5260   // JNI refs.
5261 
5262   // Use only a single queue for this PSS.
5263   G1ParScanThreadState            pss(this, 0, NULL);
5264 
5265   // We do not embed a reference processor in the copying/scanning
5266   // closures while we're actually processing the discovered
5267   // reference objects.
5268   G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5269 
5270   pss.set_evac_failure_closure(&evac_failure_cl);
5271 
5272   assert(pss.queue_is_empty(), "pre-condition");
5273 
5274   G1ParScanExtRootClosure        only_copy_non_heap_cl(this, &pss, NULL);
5275 
5276   G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5277 
5278   OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5279 
5280   if (g1_policy()->during_initial_mark_pause()) {
5281     // We also need to mark copied objects.
5282     copy_non_heap_cl = &copy_mark_non_heap_cl;
5283   }
5284 
5285   // Keep alive closure.
5286   G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, &pss);
5287 
5288   // Serial Complete GC closure
5289   G1STWDrainQueueClosure drain_queue(this, &pss);
5290 
5291   // Setup the soft refs policy...
5292   rp->setup_policy(false);
5293 
5294   ReferenceProcessorStats stats;
5295   if (!rp->processing_is_mt()) {
5296     // Serial reference processing...
5297     stats = rp->process_discovered_references(&is_alive,
5298                                               &keep_alive,
5299                                               &drain_queue,
5300                                               NULL,
5301                                               _gc_timer_stw,
5302                                               _gc_tracer_stw->gc_id());
5303   } else {
5304     // Parallel reference processing
5305     assert(rp->num_q() == no_of_gc_workers, "sanity");
5306     assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5307 
5308     G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5309     stats = rp->process_discovered_references(&is_alive,
5310                                               &keep_alive,
5311                                               &drain_queue,
5312                                               &par_task_executor,
5313                                               _gc_timer_stw,
5314                                               _gc_tracer_stw->gc_id());
5315   }
5316 
5317   _gc_tracer_stw->report_gc_reference_stats(stats);
5318 
5319   // We have completed copying any necessary live referent objects.
5320   assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5321 
5322   double ref_proc_time = os::elapsedTime() - ref_proc_start;
5323   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5324 }
5325 
5326 // Weak Reference processing during an evacuation pause (part 2).
5327 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) {
5328   double ref_enq_start = os::elapsedTime();
5329 
5330   ReferenceProcessor* rp = _ref_processor_stw;
5331   assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5332 
5333   // Now enqueue any remaining on the discovered lists on to
5334   // the pending list.
5335   if (!rp->processing_is_mt()) {
5336     // Serial reference processing...
5337     rp->enqueue_discovered_references();
5338   } else {
5339     // Parallel reference enqueueing
5340 
5341     assert(no_of_gc_workers == workers()->active_workers(),
5342            "Need to reset active workers");
5343     assert(rp->num_q() == no_of_gc_workers, "sanity");
5344     assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5345 
5346     G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5347     rp->enqueue_discovered_references(&par_task_executor);
5348   }
5349 
5350   rp->verify_no_references_recorded();
5351   assert(!rp->discovery_enabled(), "should have been disabled");
5352 
5353   // FIXME
5354   // CM's reference processing also cleans up the string and symbol tables.
5355   // Should we do that here also? We could, but it is a serial operation
5356   // and could significantly increase the pause time.
5357 
5358   double ref_enq_time = os::elapsedTime() - ref_enq_start;
5359   g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5360 }
5361 
5362 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) {
5363   _expand_heap_after_alloc_failure = true;
5364   _evacuation_failed = false;
5365 
5366   // Should G1EvacuationFailureALot be in effect for this GC?
5367   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
5368 
5369   g1_rem_set()->prepare_for_oops_into_collection_set_do();
5370 
5371   // Disable the hot card cache.
5372   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
5373   hot_card_cache->reset_hot_cache_claimed_index();
5374   hot_card_cache->set_use_cache(false);
5375 
5376   const uint n_workers = workers()->active_workers();
5377   assert(UseDynamicNumberOfGCThreads ||
5378          n_workers == workers()->total_workers(),
5379          "If not dynamic should be using all the  workers");
5380   set_par_threads(n_workers);
5381 
5382 
5383   init_for_evac_failure(NULL);
5384 
5385   assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5386   double start_par_time_sec = os::elapsedTime();
5387   double end_par_time_sec;
5388 
5389   {
5390     G1RootProcessor root_processor(this);
5391     G1ParTask g1_par_task(this, _task_queues, &root_processor);
5392     // InitialMark needs claim bits to keep track of the marked-through CLDs.
5393     if (g1_policy()->during_initial_mark_pause()) {
5394       ClassLoaderDataGraph::clear_claimed_marks();
5395     }
5396 
5397      // The individual threads will set their evac-failure closures.
5398      if (PrintTerminationStats) G1ParScanThreadState::print_termination_stats_hdr();
5399      // These tasks use ShareHeap::_process_strong_tasks
5400      assert(UseDynamicNumberOfGCThreads ||
5401             workers()->active_workers() == workers()->total_workers(),
5402             "If not dynamic should be using all the  workers");
5403     workers()->run_task(&g1_par_task);
5404     end_par_time_sec = os::elapsedTime();
5405 
5406     // Closing the inner scope will execute the destructor
5407     // for the G1RootProcessor object. We record the current
5408     // elapsed time before closing the scope so that time
5409     // taken for the destructor is NOT included in the
5410     // reported parallel time.
5411   }
5412 
5413   G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
5414 
5415   double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5416   phase_times->record_par_time(par_time_ms);
5417 
5418   double code_root_fixup_time_ms =
5419         (os::elapsedTime() - end_par_time_sec) * 1000.0;
5420   phase_times->record_code_root_fixup_time(code_root_fixup_time_ms);
5421 
5422   set_par_threads(0);
5423 
5424   // Process any discovered reference objects - we have
5425   // to do this _before_ we retire the GC alloc regions
5426   // as we may have to copy some 'reachable' referent
5427   // objects (and their reachable sub-graphs) that were
5428   // not copied during the pause.
5429   process_discovered_references(n_workers);
5430 
5431   if (G1StringDedup::is_enabled()) {
5432     double fixup_start = os::elapsedTime();
5433 
5434     G1STWIsAliveClosure is_alive(this);
5435     G1KeepAliveClosure keep_alive(this);
5436     G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, phase_times);
5437 
5438     double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
5439     phase_times->record_string_dedup_fixup_time(fixup_time_ms);
5440   }
5441 
5442   _allocator->release_gc_alloc_regions(n_workers, evacuation_info);
5443   g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5444 
5445   // Reset and re-enable the hot card cache.
5446   // Note the counts for the cards in the regions in the
5447   // collection set are reset when the collection set is freed.
5448   hot_card_cache->reset_hot_cache();
5449   hot_card_cache->set_use_cache(true);
5450 
5451   purge_code_root_memory();
5452 
5453   finalize_for_evac_failure();
5454 
5455   if (evacuation_failed()) {
5456     remove_self_forwarding_pointers();
5457 
5458     // Reset the G1EvacuationFailureALot counters and flags
5459     // Note: the values are reset only when an actual
5460     // evacuation failure occurs.
5461     NOT_PRODUCT(reset_evacuation_should_fail();)
5462   }
5463 
5464   // Enqueue any remaining references remaining on the STW
5465   // reference processor's discovered lists. We need to do
5466   // this after the card table is cleaned (and verified) as
5467   // the act of enqueueing entries on to the pending list
5468   // will log these updates (and dirty their associated
5469   // cards). We need these updates logged to update any
5470   // RSets.
5471   enqueue_discovered_references(n_workers);
5472 
5473   redirty_logged_cards();
5474   COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5475 }
5476 
5477 void G1CollectedHeap::free_region(HeapRegion* hr,
5478                                   FreeRegionList* free_list,
5479                                   bool par,
5480                                   bool locked) {
5481   assert(!hr->is_free(), "the region should not be free");
5482   assert(!hr->is_empty(), "the region should not be empty");
5483   assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
5484   assert(free_list != NULL, "pre-condition");
5485 
5486   if (G1VerifyBitmaps) {
5487     MemRegion mr(hr->bottom(), hr->end());
5488     concurrent_mark()->clearRangePrevBitmap(mr);
5489   }
5490 
5491   // Clear the card counts for this region.
5492   // Note: we only need to do this if the region is not young
5493   // (since we don't refine cards in young regions).
5494   if (!hr->is_young()) {
5495     _cg1r->hot_card_cache()->reset_card_counts(hr);
5496   }
5497   hr->hr_clear(par, true /* clear_space */, locked /* locked */);
5498   free_list->add_ordered(hr);
5499 }
5500 
5501 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
5502                                      FreeRegionList* free_list,
5503                                      bool par) {
5504   assert(hr->is_starts_humongous(), "this is only for starts humongous regions");
5505   assert(free_list != NULL, "pre-condition");
5506 
5507   size_t hr_capacity = hr->capacity();
5508   // We need to read this before we make the region non-humongous,
5509   // otherwise the information will be gone.
5510   uint last_index = hr->last_hc_index();
5511   hr->clear_humongous();
5512   free_region(hr, free_list, par);
5513 
5514   uint i = hr->hrm_index() + 1;
5515   while (i < last_index) {
5516     HeapRegion* curr_hr = region_at(i);
5517     assert(curr_hr->is_continues_humongous(), "invariant");
5518     curr_hr->clear_humongous();
5519     free_region(curr_hr, free_list, par);
5520     i += 1;
5521   }
5522 }
5523 
5524 void G1CollectedHeap::remove_from_old_sets(const HeapRegionSetCount& old_regions_removed,
5525                                        const HeapRegionSetCount& humongous_regions_removed) {
5526   if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 0) {
5527     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5528     _old_set.bulk_remove(old_regions_removed);
5529     _humongous_set.bulk_remove(humongous_regions_removed);
5530   }
5531 
5532 }
5533 
5534 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
5535   assert(list != NULL, "list can't be null");
5536   if (!list->is_empty()) {
5537     MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
5538     _hrm.insert_list_into_free_list(list);
5539   }
5540 }
5541 
5542 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
5543   _allocator->decrease_used(bytes);
5544 }
5545 
5546 class G1ParCleanupCTTask : public AbstractGangTask {
5547   G1SATBCardTableModRefBS* _ct_bs;
5548   G1CollectedHeap* _g1h;
5549   HeapRegion* volatile _su_head;
5550 public:
5551   G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs,
5552                      G1CollectedHeap* g1h) :
5553     AbstractGangTask("G1 Par Cleanup CT Task"),
5554     _ct_bs(ct_bs), _g1h(g1h) { }
5555 
5556   void work(uint worker_id) {
5557     HeapRegion* r;
5558     while (r = _g1h->pop_dirty_cards_region()) {
5559       clear_cards(r);
5560     }
5561   }
5562 
5563   void clear_cards(HeapRegion* r) {
5564     // Cards of the survivors should have already been dirtied.
5565     if (!r->is_survivor()) {
5566       _ct_bs->clear(MemRegion(r->bottom(), r->end()));
5567     }
5568   }
5569 };
5570 
5571 #ifndef PRODUCT
5572 class G1VerifyCardTableCleanup: public HeapRegionClosure {
5573   G1CollectedHeap* _g1h;
5574   G1SATBCardTableModRefBS* _ct_bs;
5575 public:
5576   G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs)
5577     : _g1h(g1h), _ct_bs(ct_bs) { }
5578   virtual bool doHeapRegion(HeapRegion* r) {
5579     if (r->is_survivor()) {
5580       _g1h->verify_dirty_region(r);
5581     } else {
5582       _g1h->verify_not_dirty_region(r);
5583     }
5584     return false;
5585   }
5586 };
5587 
5588 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
5589   // All of the region should be clean.
5590   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5591   MemRegion mr(hr->bottom(), hr->end());
5592   ct_bs->verify_not_dirty_region(mr);
5593 }
5594 
5595 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
5596   // We cannot guarantee that [bottom(),end()] is dirty.  Threads
5597   // dirty allocated blocks as they allocate them. The thread that
5598   // retires each region and replaces it with a new one will do a
5599   // maximal allocation to fill in [pre_dummy_top(),end()] but will
5600   // not dirty that area (one less thing to have to do while holding
5601   // a lock). So we can only verify that [bottom(),pre_dummy_top()]
5602   // is dirty.
5603   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5604   MemRegion mr(hr->bottom(), hr->pre_dummy_top());
5605   if (hr->is_young()) {
5606     ct_bs->verify_g1_young_region(mr);
5607   } else {
5608     ct_bs->verify_dirty_region(mr);
5609   }
5610 }
5611 
5612 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
5613   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5614   for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
5615     verify_dirty_region(hr);
5616   }
5617 }
5618 
5619 void G1CollectedHeap::verify_dirty_young_regions() {
5620   verify_dirty_young_list(_young_list->first_region());
5621 }
5622 
5623 bool G1CollectedHeap::verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
5624                                                HeapWord* tams, HeapWord* end) {
5625   guarantee(tams <= end,
5626             err_msg("tams: "PTR_FORMAT" end: "PTR_FORMAT, p2i(tams), p2i(end)));
5627   HeapWord* result = bitmap->getNextMarkedWordAddress(tams, end);
5628   if (result < end) {
5629     gclog_or_tty->cr();
5630     gclog_or_tty->print_cr("## wrong marked address on %s bitmap: "PTR_FORMAT,
5631                            bitmap_name, p2i(result));
5632     gclog_or_tty->print_cr("## %s tams: "PTR_FORMAT" end: "PTR_FORMAT,
5633                            bitmap_name, p2i(tams), p2i(end));
5634     return false;
5635   }
5636   return true;
5637 }
5638 
5639 bool G1CollectedHeap::verify_bitmaps(const char* caller, HeapRegion* hr) {
5640   CMBitMapRO* prev_bitmap = concurrent_mark()->prevMarkBitMap();
5641   CMBitMapRO* next_bitmap = (CMBitMapRO*) concurrent_mark()->nextMarkBitMap();
5642 
5643   HeapWord* bottom = hr->bottom();
5644   HeapWord* ptams  = hr->prev_top_at_mark_start();
5645   HeapWord* ntams  = hr->next_top_at_mark_start();
5646   HeapWord* end    = hr->end();
5647 
5648   bool res_p = verify_no_bits_over_tams("prev", prev_bitmap, ptams, end);
5649 
5650   bool res_n = true;
5651   // We reset mark_in_progress() before we reset _cmThread->in_progress() and in this window
5652   // we do the clearing of the next bitmap concurrently. Thus, we can not verify the bitmap
5653   // if we happen to be in that state.
5654   if (mark_in_progress() || !_cmThread->in_progress()) {
5655     res_n = verify_no_bits_over_tams("next", next_bitmap, ntams, end);
5656   }
5657   if (!res_p || !res_n) {
5658     gclog_or_tty->print_cr("#### Bitmap verification failed for "HR_FORMAT,
5659                            HR_FORMAT_PARAMS(hr));
5660     gclog_or_tty->print_cr("#### Caller: %s", caller);
5661     return false;
5662   }
5663   return true;
5664 }
5665 
5666 void G1CollectedHeap::check_bitmaps(const char* caller, HeapRegion* hr) {
5667   if (!G1VerifyBitmaps) return;
5668 
5669   guarantee(verify_bitmaps(caller, hr), "bitmap verification");
5670 }
5671 
5672 class G1VerifyBitmapClosure : public HeapRegionClosure {
5673 private:
5674   const char* _caller;
5675   G1CollectedHeap* _g1h;
5676   bool _failures;
5677 
5678 public:
5679   G1VerifyBitmapClosure(const char* caller, G1CollectedHeap* g1h) :
5680     _caller(caller), _g1h(g1h), _failures(false) { }
5681 
5682   bool failures() { return _failures; }
5683 
5684   virtual bool doHeapRegion(HeapRegion* hr) {
5685     if (hr->is_continues_humongous()) return false;
5686 
5687     bool result = _g1h->verify_bitmaps(_caller, hr);
5688     if (!result) {
5689       _failures = true;
5690     }
5691     return false;
5692   }
5693 };
5694 
5695 void G1CollectedHeap::check_bitmaps(const char* caller) {
5696   if (!G1VerifyBitmaps) return;
5697 
5698   G1VerifyBitmapClosure cl(caller, this);
5699   heap_region_iterate(&cl);
5700   guarantee(!cl.failures(), "bitmap verification");
5701 }
5702 
5703 class G1CheckCSetFastTableClosure : public HeapRegionClosure {
5704  private:
5705   bool _failures;
5706  public:
5707   G1CheckCSetFastTableClosure() : HeapRegionClosure(), _failures(false) { }
5708 
5709   virtual bool doHeapRegion(HeapRegion* hr) {
5710     uint i = hr->hrm_index();
5711     InCSetState cset_state = (InCSetState) G1CollectedHeap::heap()->_in_cset_fast_test.get_by_index(i);
5712     if (hr->is_humongous()) {
5713       if (hr->in_collection_set()) {
5714         gclog_or_tty->print_cr("\n## humongous region %u in CSet", i);
5715         _failures = true;
5716         return true;
5717       }
5718       if (cset_state.is_in_cset()) {
5719         gclog_or_tty->print_cr("\n## inconsistent cset state %d for humongous region %u", cset_state.value(), i);
5720         _failures = true;
5721         return true;
5722       }
5723       if (hr->is_continues_humongous() && cset_state.is_humongous()) {
5724         gclog_or_tty->print_cr("\n## inconsistent cset state %d for continues humongous region %u", cset_state.value(), i);
5725         _failures = true;
5726         return true;
5727       }
5728     } else {
5729       if (cset_state.is_humongous()) {
5730         gclog_or_tty->print_cr("\n## inconsistent cset state %d for non-humongous region %u", cset_state.value(), i);
5731         _failures = true;
5732         return true;
5733       }
5734       if (hr->in_collection_set() != cset_state.is_in_cset()) {
5735         gclog_or_tty->print_cr("\n## in CSet %d / cset state %d inconsistency for region %u",
5736                                hr->in_collection_set(), cset_state.value(), i);
5737         _failures = true;
5738         return true;
5739       }
5740       if (cset_state.is_in_cset()) {
5741         if (hr->is_young() != (cset_state.is_young())) {
5742           gclog_or_tty->print_cr("\n## is_young %d / cset state %d inconsistency for region %u",
5743                                  hr->is_young(), cset_state.value(), i);
5744           _failures = true;
5745           return true;
5746         }
5747         if (hr->is_old() != (cset_state.is_old())) {
5748           gclog_or_tty->print_cr("\n## is_old %d / cset state %d inconsistency for region %u",
5749                                  hr->is_old(), cset_state.value(), i);
5750           _failures = true;
5751           return true;
5752         }
5753       }
5754     }
5755     return false;
5756   }
5757 
5758   bool failures() const { return _failures; }
5759 };
5760 
5761 bool G1CollectedHeap::check_cset_fast_test() {
5762   G1CheckCSetFastTableClosure cl;
5763   _hrm.iterate(&cl);
5764   return !cl.failures();
5765 }
5766 #endif // PRODUCT
5767 
5768 void G1CollectedHeap::cleanUpCardTable() {
5769   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5770   double start = os::elapsedTime();
5771 
5772   {
5773     // Iterate over the dirty cards region list.
5774     G1ParCleanupCTTask cleanup_task(ct_bs, this);
5775 
5776     set_par_threads();
5777     workers()->run_task(&cleanup_task);
5778     set_par_threads(0);
5779 #ifndef PRODUCT
5780     if (G1VerifyCTCleanup || VerifyAfterGC) {
5781       G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
5782       heap_region_iterate(&cleanup_verifier);
5783     }
5784 #endif
5785   }
5786 
5787   double elapsed = os::elapsedTime() - start;
5788   g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
5789 }
5790 
5791 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) {
5792   size_t pre_used = 0;
5793   FreeRegionList local_free_list("Local List for CSet Freeing");
5794 
5795   double young_time_ms     = 0.0;
5796   double non_young_time_ms = 0.0;
5797 
5798   // Since the collection set is a superset of the the young list,
5799   // all we need to do to clear the young list is clear its
5800   // head and length, and unlink any young regions in the code below
5801   _young_list->clear();
5802 
5803   G1CollectorPolicy* policy = g1_policy();
5804 
5805   double start_sec = os::elapsedTime();
5806   bool non_young = true;
5807 
5808   HeapRegion* cur = cs_head;
5809   int age_bound = -1;
5810   size_t rs_lengths = 0;
5811 
5812   while (cur != NULL) {
5813     assert(!is_on_master_free_list(cur), "sanity");
5814     if (non_young) {
5815       if (cur->is_young()) {
5816         double end_sec = os::elapsedTime();
5817         double elapsed_ms = (end_sec - start_sec) * 1000.0;
5818         non_young_time_ms += elapsed_ms;
5819 
5820         start_sec = os::elapsedTime();
5821         non_young = false;
5822       }
5823     } else {
5824       if (!cur->is_young()) {
5825         double end_sec = os::elapsedTime();
5826         double elapsed_ms = (end_sec - start_sec) * 1000.0;
5827         young_time_ms += elapsed_ms;
5828 
5829         start_sec = os::elapsedTime();
5830         non_young = true;
5831       }
5832     }
5833 
5834     rs_lengths += cur->rem_set()->occupied_locked();
5835 
5836     HeapRegion* next = cur->next_in_collection_set();
5837     assert(cur->in_collection_set(), "bad CS");
5838     cur->set_next_in_collection_set(NULL);
5839     clear_in_cset(cur);
5840 
5841     if (cur->is_young()) {
5842       int index = cur->young_index_in_cset();
5843       assert(index != -1, "invariant");
5844       assert((uint) index < policy->young_cset_region_length(), "invariant");
5845       size_t words_survived = _surviving_young_words[index];
5846       cur->record_surv_words_in_group(words_survived);
5847 
5848       // At this point the we have 'popped' cur from the collection set
5849       // (linked via next_in_collection_set()) but it is still in the
5850       // young list (linked via next_young_region()). Clear the
5851       // _next_young_region field.
5852       cur->set_next_young_region(NULL);
5853     } else {
5854       int index = cur->young_index_in_cset();
5855       assert(index == -1, "invariant");
5856     }
5857 
5858     assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
5859             (!cur->is_young() && cur->young_index_in_cset() == -1),
5860             "invariant" );
5861 
5862     if (!cur->evacuation_failed()) {
5863       MemRegion used_mr = cur->used_region();
5864 
5865       // And the region is empty.
5866       assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
5867       pre_used += cur->used();
5868       free_region(cur, &local_free_list, false /* par */, true /* locked */);
5869     } else {
5870       cur->uninstall_surv_rate_group();
5871       if (cur->is_young()) {
5872         cur->set_young_index_in_cset(-1);
5873       }
5874       cur->set_evacuation_failed(false);
5875       // The region is now considered to be old.
5876       cur->set_old();
5877       _old_set.add(cur);
5878       evacuation_info.increment_collectionset_used_after(cur->used());
5879     }
5880     cur = next;
5881   }
5882 
5883   evacuation_info.set_regions_freed(local_free_list.length());
5884   policy->record_max_rs_lengths(rs_lengths);
5885   policy->cset_regions_freed();
5886 
5887   double end_sec = os::elapsedTime();
5888   double elapsed_ms = (end_sec - start_sec) * 1000.0;
5889 
5890   if (non_young) {
5891     non_young_time_ms += elapsed_ms;
5892   } else {
5893     young_time_ms += elapsed_ms;
5894   }
5895 
5896   prepend_to_freelist(&local_free_list);
5897   decrement_summary_bytes(pre_used);
5898   policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
5899   policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
5900 }
5901 
5902 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
5903  private:
5904   FreeRegionList* _free_region_list;
5905   HeapRegionSet* _proxy_set;
5906   HeapRegionSetCount _humongous_regions_removed;
5907   size_t _freed_bytes;
5908  public:
5909 
5910   G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
5911     _free_region_list(free_region_list), _humongous_regions_removed(), _freed_bytes(0) {
5912   }
5913 
5914   virtual bool doHeapRegion(HeapRegion* r) {
5915     if (!r->is_starts_humongous()) {
5916       return false;
5917     }
5918 
5919     G1CollectedHeap* g1h = G1CollectedHeap::heap();
5920 
5921     oop obj = (oop)r->bottom();
5922     CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap();
5923 
5924     // The following checks whether the humongous object is live are sufficient.
5925     // The main additional check (in addition to having a reference from the roots
5926     // or the young gen) is whether the humongous object has a remembered set entry.
5927     //
5928     // A humongous object cannot be live if there is no remembered set for it
5929     // because:
5930     // - there can be no references from within humongous starts regions referencing
5931     // the object because we never allocate other objects into them.
5932     // (I.e. there are no intra-region references that may be missed by the
5933     // remembered set)
5934     // - as soon there is a remembered set entry to the humongous starts region
5935     // (i.e. it has "escaped" to an old object) this remembered set entry will stay
5936     // until the end of a concurrent mark.
5937     //
5938     // It is not required to check whether the object has been found dead by marking
5939     // or not, in fact it would prevent reclamation within a concurrent cycle, as
5940     // all objects allocated during that time are considered live.
5941     // SATB marking is even more conservative than the remembered set.
5942     // So if at this point in the collection there is no remembered set entry,
5943     // nobody has a reference to it.
5944     // At the start of collection we flush all refinement logs, and remembered sets
5945     // are completely up-to-date wrt to references to the humongous object.
5946     //
5947     // Other implementation considerations:
5948     // - never consider object arrays at this time because they would pose
5949     // considerable effort for cleaning up the the remembered sets. This is
5950     // required because stale remembered sets might reference locations that
5951     // are currently allocated into.
5952     uint region_idx = r->hrm_index();
5953     if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
5954         !r->rem_set()->is_empty()) {
5955 
5956       if (G1TraceEagerReclaimHumongousObjects) {
5957         gclog_or_tty->print_cr("Live humongous region %u size "SIZE_FORMAT" start "PTR_FORMAT" length %u with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is marked %d reclaim candidate %d type array %d",
5958                                region_idx,
5959                                (size_t)obj->size() * HeapWordSize,
5960                                p2i(r->bottom()),
5961                                r->region_num(),
5962                                r->rem_set()->occupied(),
5963                                r->rem_set()->strong_code_roots_list_length(),
5964                                next_bitmap->isMarked(r->bottom()),
5965                                g1h->is_humongous_reclaim_candidate(region_idx),
5966                                obj->is_typeArray()
5967                               );
5968       }
5969 
5970       return false;
5971     }
5972 
5973     guarantee(obj->is_typeArray(),
5974               err_msg("Only eagerly reclaiming type arrays is supported, but the object "
5975                       PTR_FORMAT " is not.",
5976                       p2i(r->bottom())));
5977 
5978     if (G1TraceEagerReclaimHumongousObjects) {
5979       gclog_or_tty->print_cr("Dead humongous region %u size "SIZE_FORMAT" start "PTR_FORMAT" length %u with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is marked %d reclaim candidate %d type array %d",
5980                              region_idx,
5981                              (size_t)obj->size() * HeapWordSize,
5982                              p2i(r->bottom()),
5983                              r->region_num(),
5984                              r->rem_set()->occupied(),
5985                              r->rem_set()->strong_code_roots_list_length(),
5986                              next_bitmap->isMarked(r->bottom()),
5987                              g1h->is_humongous_reclaim_candidate(region_idx),
5988                              obj->is_typeArray()
5989                             );
5990     }
5991     // Need to clear mark bit of the humongous object if already set.
5992     if (next_bitmap->isMarked(r->bottom())) {
5993       next_bitmap->clear(r->bottom());
5994     }
5995     _freed_bytes += r->used();
5996     r->set_containing_set(NULL);
5997     _humongous_regions_removed.increment(1u, r->capacity());
5998     g1h->free_humongous_region(r, _free_region_list, false);
5999 
6000     return false;
6001   }
6002 
6003   HeapRegionSetCount& humongous_free_count() {
6004     return _humongous_regions_removed;
6005   }
6006 
6007   size_t bytes_freed() const {
6008     return _freed_bytes;
6009   }
6010 
6011   size_t humongous_reclaimed() const {
6012     return _humongous_regions_removed.length();
6013   }
6014 };
6015 
6016 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
6017   assert_at_safepoint(true);
6018 
6019   if (!G1EagerReclaimHumongousObjects ||
6020       (!_has_humongous_reclaim_candidates && !G1TraceEagerReclaimHumongousObjects)) {
6021     g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
6022     return;
6023   }
6024 
6025   double start_time = os::elapsedTime();
6026 
6027   FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
6028 
6029   G1FreeHumongousRegionClosure cl(&local_cleanup_list);
6030   heap_region_iterate(&cl);
6031 
6032   HeapRegionSetCount empty_set;
6033   remove_from_old_sets(empty_set, cl.humongous_free_count());
6034 
6035   G1HRPrinter* hrp = hr_printer();
6036   if (hrp->is_active()) {
6037     FreeRegionListIterator iter(&local_cleanup_list);
6038     while (iter.more_available()) {
6039       HeapRegion* hr = iter.get_next();
6040       hrp->cleanup(hr);
6041     }
6042   }
6043 
6044   prepend_to_freelist(&local_cleanup_list);
6045   decrement_summary_bytes(cl.bytes_freed());
6046 
6047   g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
6048                                                                     cl.humongous_reclaimed());
6049 }
6050 
6051 // This routine is similar to the above but does not record
6052 // any policy statistics or update free lists; we are abandoning
6053 // the current incremental collection set in preparation of a
6054 // full collection. After the full GC we will start to build up
6055 // the incremental collection set again.
6056 // This is only called when we're doing a full collection
6057 // and is immediately followed by the tearing down of the young list.
6058 
6059 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
6060   HeapRegion* cur = cs_head;
6061 
6062   while (cur != NULL) {
6063     HeapRegion* next = cur->next_in_collection_set();
6064     assert(cur->in_collection_set(), "bad CS");
6065     cur->set_next_in_collection_set(NULL);
6066     clear_in_cset(cur);
6067     cur->set_young_index_in_cset(-1);
6068     cur = next;
6069   }
6070 }
6071 
6072 void G1CollectedHeap::set_free_regions_coming() {
6073   if (G1ConcRegionFreeingVerbose) {
6074     gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6075                            "setting free regions coming");
6076   }
6077 
6078   assert(!free_regions_coming(), "pre-condition");
6079   _free_regions_coming = true;
6080 }
6081 
6082 void G1CollectedHeap::reset_free_regions_coming() {
6083   assert(free_regions_coming(), "pre-condition");
6084 
6085   {
6086     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6087     _free_regions_coming = false;
6088     SecondaryFreeList_lock->notify_all();
6089   }
6090 
6091   if (G1ConcRegionFreeingVerbose) {
6092     gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6093                            "reset free regions coming");
6094   }
6095 }
6096 
6097 void G1CollectedHeap::wait_while_free_regions_coming() {
6098   // Most of the time we won't have to wait, so let's do a quick test
6099   // first before we take the lock.
6100   if (!free_regions_coming()) {
6101     return;
6102   }
6103 
6104   if (G1ConcRegionFreeingVerbose) {
6105     gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6106                            "waiting for free regions");
6107   }
6108 
6109   {
6110     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6111     while (free_regions_coming()) {
6112       SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
6113     }
6114   }
6115 
6116   if (G1ConcRegionFreeingVerbose) {
6117     gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6118                            "done waiting for free regions");
6119   }
6120 }
6121 
6122 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
6123   _young_list->push_region(hr);
6124 }
6125 
6126 class NoYoungRegionsClosure: public HeapRegionClosure {
6127 private:
6128   bool _success;
6129 public:
6130   NoYoungRegionsClosure() : _success(true) { }
6131   bool doHeapRegion(HeapRegion* r) {
6132     if (r->is_young()) {
6133       gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
6134                              p2i(r->bottom()), p2i(r->end()));
6135       _success = false;
6136     }
6137     return false;
6138   }
6139   bool success() { return _success; }
6140 };
6141 
6142 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
6143   bool ret = _young_list->check_list_empty(check_sample);
6144 
6145   if (check_heap) {
6146     NoYoungRegionsClosure closure;
6147     heap_region_iterate(&closure);
6148     ret = ret && closure.success();
6149   }
6150 
6151   return ret;
6152 }
6153 
6154 class TearDownRegionSetsClosure : public HeapRegionClosure {
6155 private:
6156   HeapRegionSet *_old_set;
6157 
6158 public:
6159   TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
6160 
6161   bool doHeapRegion(HeapRegion* r) {
6162     if (r->is_old()) {
6163       _old_set->remove(r);
6164     } else {
6165       // We ignore free regions, we'll empty the free list afterwards.
6166       // We ignore young regions, we'll empty the young list afterwards.
6167       // We ignore humongous regions, we're not tearing down the
6168       // humongous regions set.
6169       assert(r->is_free() || r->is_young() || r->is_humongous(),
6170              "it cannot be another type");
6171     }
6172     return false;
6173   }
6174 
6175   ~TearDownRegionSetsClosure() {
6176     assert(_old_set->is_empty(), "post-condition");
6177   }
6178 };
6179 
6180 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6181   assert_at_safepoint(true /* should_be_vm_thread */);
6182 
6183   if (!free_list_only) {
6184     TearDownRegionSetsClosure cl(&_old_set);
6185     heap_region_iterate(&cl);
6186 
6187     // Note that emptying the _young_list is postponed and instead done as
6188     // the first step when rebuilding the regions sets again. The reason for
6189     // this is that during a full GC string deduplication needs to know if
6190     // a collected region was young or old when the full GC was initiated.
6191   }
6192   _hrm.remove_all_free_regions();
6193 }
6194 
6195 class RebuildRegionSetsClosure : public HeapRegionClosure {
6196 private:
6197   bool            _free_list_only;
6198   HeapRegionSet*   _old_set;
6199   HeapRegionManager*   _hrm;
6200   size_t          _total_used;
6201 
6202 public:
6203   RebuildRegionSetsClosure(bool free_list_only,
6204                            HeapRegionSet* old_set, HeapRegionManager* hrm) :
6205     _free_list_only(free_list_only),
6206     _old_set(old_set), _hrm(hrm), _total_used(0) {
6207     assert(_hrm->num_free_regions() == 0, "pre-condition");
6208     if (!free_list_only) {
6209       assert(_old_set->is_empty(), "pre-condition");
6210     }
6211   }
6212 
6213   bool doHeapRegion(HeapRegion* r) {
6214     if (r->is_continues_humongous()) {
6215       return false;
6216     }
6217 
6218     if (r->is_empty()) {
6219       // Add free regions to the free list
6220       r->set_free();
6221       r->set_allocation_context(AllocationContext::system());
6222       _hrm->insert_into_free_list(r);
6223     } else if (!_free_list_only) {
6224       assert(!r->is_young(), "we should not come across young regions");
6225 
6226       if (r->is_humongous()) {
6227         // We ignore humongous regions, we left the humongous set unchanged
6228       } else {
6229         // Objects that were compacted would have ended up on regions
6230         // that were previously old or free.
6231         assert(r->is_free() || r->is_old(), "invariant");
6232         // We now consider them old, so register as such.
6233         r->set_old();
6234         _old_set->add(r);
6235       }
6236       _total_used += r->used();
6237     }
6238 
6239     return false;
6240   }
6241 
6242   size_t total_used() {
6243     return _total_used;
6244   }
6245 };
6246 
6247 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6248   assert_at_safepoint(true /* should_be_vm_thread */);
6249 
6250   if (!free_list_only) {
6251     _young_list->empty_list();
6252   }
6253 
6254   RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
6255   heap_region_iterate(&cl);
6256 
6257   if (!free_list_only) {
6258     _allocator->set_used(cl.total_used());
6259   }
6260   assert(_allocator->used_unlocked() == recalculate_used(),
6261          err_msg("inconsistent _allocator->used_unlocked(), "
6262                  "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6263                  _allocator->used_unlocked(), recalculate_used()));
6264 }
6265 
6266 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6267   _refine_cte_cl->set_concurrent(concurrent);
6268 }
6269 
6270 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6271   HeapRegion* hr = heap_region_containing(p);
6272   return hr->is_in(p);
6273 }
6274 
6275 // Methods for the mutator alloc region
6276 
6277 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6278                                                       bool force) {
6279   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6280   assert(!force || g1_policy()->can_expand_young_list(),
6281          "if force is true we should be able to expand the young list");
6282   bool young_list_full = g1_policy()->is_young_list_full();
6283   if (force || !young_list_full) {
6284     HeapRegion* new_alloc_region = new_region(word_size,
6285                                               false /* is_old */,
6286                                               false /* do_expand */);
6287     if (new_alloc_region != NULL) {
6288       set_region_short_lived_locked(new_alloc_region);
6289       _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6290       check_bitmaps("Mutator Region Allocation", new_alloc_region);
6291       return new_alloc_region;
6292     }
6293   }
6294   return NULL;
6295 }
6296 
6297 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6298                                                   size_t allocated_bytes) {
6299   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6300   assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
6301 
6302   g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6303   _allocator->increase_used(allocated_bytes);
6304   _hr_printer.retire(alloc_region);
6305   // We update the eden sizes here, when the region is retired,
6306   // instead of when it's allocated, since this is the point that its
6307   // used space has been recored in _summary_bytes_used.
6308   g1mm()->update_eden_size();
6309 }
6310 
6311 void G1CollectedHeap::set_par_threads() {
6312   // Don't change the number of workers.  Use the value previously set
6313   // in the workgroup.
6314   uint n_workers = workers()->active_workers();
6315   assert(UseDynamicNumberOfGCThreads ||
6316            n_workers == workers()->total_workers(),
6317       "Otherwise should be using the total number of workers");
6318   if (n_workers == 0) {
6319     assert(false, "Should have been set in prior evacuation pause.");
6320     n_workers = ParallelGCThreads;
6321     workers()->set_active_workers(n_workers);
6322   }
6323   set_par_threads(n_workers);
6324 }
6325 
6326 // Methods for the GC alloc regions
6327 
6328 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6329                                                  uint count,
6330                                                  InCSetState dest) {
6331   assert(FreeList_lock->owned_by_self(), "pre-condition");
6332 
6333   if (count < g1_policy()->max_regions(dest)) {
6334     const bool is_survivor = (dest.is_young());
6335     HeapRegion* new_alloc_region = new_region(word_size,
6336                                               !is_survivor,
6337                                               true /* do_expand */);
6338     if (new_alloc_region != NULL) {
6339       // We really only need to do this for old regions given that we
6340       // should never scan survivors. But it doesn't hurt to do it
6341       // for survivors too.
6342       new_alloc_region->record_timestamp();
6343       if (is_survivor) {
6344         new_alloc_region->set_survivor();
6345         _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6346         check_bitmaps("Survivor Region Allocation", new_alloc_region);
6347       } else {
6348         new_alloc_region->set_old();
6349         _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6350         check_bitmaps("Old Region Allocation", new_alloc_region);
6351       }
6352       bool during_im = g1_policy()->during_initial_mark_pause();
6353       new_alloc_region->note_start_of_copying(during_im);
6354       return new_alloc_region;
6355     }
6356   }
6357   return NULL;
6358 }
6359 
6360 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6361                                              size_t allocated_bytes,
6362                                              InCSetState dest) {
6363   bool during_im = g1_policy()->during_initial_mark_pause();
6364   alloc_region->note_end_of_copying(during_im);
6365   g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6366   if (dest.is_young()) {
6367     young_list()->add_survivor_region(alloc_region);
6368   } else {
6369     _old_set.add(alloc_region);
6370   }
6371   _hr_printer.retire(alloc_region);
6372 }
6373 
6374 // Heap region set verification
6375 
6376 class VerifyRegionListsClosure : public HeapRegionClosure {
6377 private:
6378   HeapRegionSet*   _old_set;
6379   HeapRegionSet*   _humongous_set;
6380   HeapRegionManager*   _hrm;
6381 
6382 public:
6383   HeapRegionSetCount _old_count;
6384   HeapRegionSetCount _humongous_count;
6385   HeapRegionSetCount _free_count;
6386 
6387   VerifyRegionListsClosure(HeapRegionSet* old_set,
6388                            HeapRegionSet* humongous_set,
6389                            HeapRegionManager* hrm) :
6390     _old_set(old_set), _humongous_set(humongous_set), _hrm(hrm),
6391     _old_count(), _humongous_count(), _free_count(){ }
6392 
6393   bool doHeapRegion(HeapRegion* hr) {
6394     if (hr->is_continues_humongous()) {
6395       return false;
6396     }
6397 
6398     if (hr->is_young()) {
6399       // TODO
6400     } else if (hr->is_starts_humongous()) {
6401       assert(hr->containing_set() == _humongous_set, err_msg("Heap region %u is starts humongous but not in humongous set.", hr->hrm_index()));
6402       _humongous_count.increment(1u, hr->capacity());
6403     } else if (hr->is_empty()) {
6404       assert(_hrm->is_free(hr), err_msg("Heap region %u is empty but not on the free list.", hr->hrm_index()));
6405       _free_count.increment(1u, hr->capacity());
6406     } else if (hr->is_old()) {
6407       assert(hr->containing_set() == _old_set, err_msg("Heap region %u is old but not in the old set.", hr->hrm_index()));
6408       _old_count.increment(1u, hr->capacity());
6409     } else {
6410       ShouldNotReachHere();
6411     }
6412     return false;
6413   }
6414 
6415   void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, HeapRegionManager* free_list) {
6416     guarantee(old_set->length() == _old_count.length(), err_msg("Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length()));
6417     guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), err_msg("Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6418         old_set->total_capacity_bytes(), _old_count.capacity()));
6419 
6420     guarantee(humongous_set->length() == _humongous_count.length(), err_msg("Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length()));
6421     guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), err_msg("Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6422         humongous_set->total_capacity_bytes(), _humongous_count.capacity()));
6423 
6424     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()));
6425     guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), err_msg("Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6426         free_list->total_capacity_bytes(), _free_count.capacity()));
6427   }
6428 };
6429 
6430 void G1CollectedHeap::verify_region_sets() {
6431   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6432 
6433   // First, check the explicit lists.
6434   _hrm.verify();
6435   {
6436     // Given that a concurrent operation might be adding regions to
6437     // the secondary free list we have to take the lock before
6438     // verifying it.
6439     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6440     _secondary_free_list.verify_list();
6441   }
6442 
6443   // If a concurrent region freeing operation is in progress it will
6444   // be difficult to correctly attributed any free regions we come
6445   // across to the correct free list given that they might belong to
6446   // one of several (free_list, secondary_free_list, any local lists,
6447   // etc.). So, if that's the case we will skip the rest of the
6448   // verification operation. Alternatively, waiting for the concurrent
6449   // operation to complete will have a non-trivial effect on the GC's
6450   // operation (no concurrent operation will last longer than the
6451   // interval between two calls to verification) and it might hide
6452   // any issues that we would like to catch during testing.
6453   if (free_regions_coming()) {
6454     return;
6455   }
6456 
6457   // Make sure we append the secondary_free_list on the free_list so
6458   // that all free regions we will come across can be safely
6459   // attributed to the free_list.
6460   append_secondary_free_list_if_not_empty_with_lock();
6461 
6462   // Finally, make sure that the region accounting in the lists is
6463   // consistent with what we see in the heap.
6464 
6465   VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_hrm);
6466   heap_region_iterate(&cl);
6467   cl.verify_counts(&_old_set, &_humongous_set, &_hrm);
6468 }
6469 
6470 // Optimized nmethod scanning
6471 
6472 class RegisterNMethodOopClosure: public OopClosure {
6473   G1CollectedHeap* _g1h;
6474   nmethod* _nm;
6475 
6476   template <class T> void do_oop_work(T* p) {
6477     T heap_oop = oopDesc::load_heap_oop(p);
6478     if (!oopDesc::is_null(heap_oop)) {
6479       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6480       HeapRegion* hr = _g1h->heap_region_containing(obj);
6481       assert(!hr->is_continues_humongous(),
6482              err_msg("trying to add code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6483                      " starting at "HR_FORMAT,
6484                      p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6485 
6486       // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
6487       hr->add_strong_code_root_locked(_nm);
6488     }
6489   }
6490 
6491 public:
6492   RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6493     _g1h(g1h), _nm(nm) {}
6494 
6495   void do_oop(oop* p)       { do_oop_work(p); }
6496   void do_oop(narrowOop* p) { do_oop_work(p); }
6497 };
6498 
6499 class UnregisterNMethodOopClosure: public OopClosure {
6500   G1CollectedHeap* _g1h;
6501   nmethod* _nm;
6502 
6503   template <class T> void do_oop_work(T* p) {
6504     T heap_oop = oopDesc::load_heap_oop(p);
6505     if (!oopDesc::is_null(heap_oop)) {
6506       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6507       HeapRegion* hr = _g1h->heap_region_containing(obj);
6508       assert(!hr->is_continues_humongous(),
6509              err_msg("trying to remove code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6510                      " starting at "HR_FORMAT,
6511                      p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6512 
6513       hr->remove_strong_code_root(_nm);
6514     }
6515   }
6516 
6517 public:
6518   UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6519     _g1h(g1h), _nm(nm) {}
6520 
6521   void do_oop(oop* p)       { do_oop_work(p); }
6522   void do_oop(narrowOop* p) { do_oop_work(p); }
6523 };
6524 
6525 void G1CollectedHeap::register_nmethod(nmethod* nm) {
6526   CollectedHeap::register_nmethod(nm);
6527 
6528   guarantee(nm != NULL, "sanity");
6529   RegisterNMethodOopClosure reg_cl(this, nm);
6530   nm->oops_do(&reg_cl);
6531 }
6532 
6533 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
6534   CollectedHeap::unregister_nmethod(nm);
6535 
6536   guarantee(nm != NULL, "sanity");
6537   UnregisterNMethodOopClosure reg_cl(this, nm);
6538   nm->oops_do(&reg_cl, true);
6539 }
6540 
6541 void G1CollectedHeap::purge_code_root_memory() {
6542   double purge_start = os::elapsedTime();
6543   G1CodeRootSet::purge();
6544   double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
6545   g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
6546 }
6547 
6548 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
6549   G1CollectedHeap* _g1h;
6550 
6551 public:
6552   RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
6553     _g1h(g1h) {}
6554 
6555   void do_code_blob(CodeBlob* cb) {
6556     nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
6557     if (nm == NULL) {
6558       return;
6559     }
6560 
6561     if (ScavengeRootsInCode) {
6562       _g1h->register_nmethod(nm);
6563     }
6564   }
6565 };
6566 
6567 void G1CollectedHeap::rebuild_strong_code_roots() {
6568   RebuildStrongCodeRootClosure blob_cl(this);
6569   CodeCache::blobs_do(&blob_cl);
6570 }