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   size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
1881   G1RegionToSpaceMapper* heap_storage =
1882     G1RegionToSpaceMapper::create_mapper(g1_rs,
1883                                          g1_rs.size(),
1884                                          page_size,
1885                                          HeapRegion::GrainBytes,
1886                                          1,
1887                                          mtJavaHeap);
1888   os::trace_page_sizes("G1 Heap", collector_policy()->min_heap_byte_size(),
1889                        max_byte_size, page_size,
1890                        heap_rs.base(),
1891                        heap_rs.size());
1892   heap_storage->set_mapping_changed_listener(&_listener);
1893 
1894   // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1895   G1RegionToSpaceMapper* bot_storage =
1896     create_aux_memory_mapper("Block offset table",
1897                              G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize),
1898                              G1BlockOffsetSharedArray::heap_map_factor());
1899 
1900   ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize));
1901   G1RegionToSpaceMapper* cardtable_storage =
1902     create_aux_memory_mapper("Card table",
1903                              G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize),
1904                              G1SATBCardTableLoggingModRefBS::heap_map_factor());
1905 
1906   G1RegionToSpaceMapper* card_counts_storage =
1907     create_aux_memory_mapper("Card counts table",
1908                              G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1909                              G1CardCounts::heap_map_factor());
1910 
1911   size_t bitmap_size = CMBitMap::compute_size(g1_rs.size());
1912   G1RegionToSpaceMapper* prev_bitmap_storage =
1913     create_aux_memory_mapper("Prev Bitmap", bitmap_size, CMBitMap::heap_map_factor());
1914   G1RegionToSpaceMapper* next_bitmap_storage =
1915     create_aux_memory_mapper("Next Bitmap", bitmap_size, CMBitMap::heap_map_factor());
1916 
1917   _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1918   g1_barrier_set()->initialize(cardtable_storage);
1919    // Do later initialization work for concurrent refinement.
1920   _cg1r->init(card_counts_storage);
1921 
1922   // 6843694 - ensure that the maximum region index can fit
1923   // in the remembered set structures.
1924   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1925   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1926 
1927   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1928   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1929   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1930             "too many cards per region");
1931 
1932   FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
1933 
1934   _bot_shared = new G1BlockOffsetSharedArray(reserved_region(), bot_storage);
1935 
1936   {
1937     HeapWord* start = _hrm.reserved().start();
1938     HeapWord* end = _hrm.reserved().end();
1939     size_t granularity = HeapRegion::GrainBytes;
1940 
1941     _in_cset_fast_test.initialize(start, end, granularity);
1942     _humongous_reclaim_candidates.initialize(start, end, granularity);
1943   }
1944 
1945   // Create the ConcurrentMark data structure and thread.
1946   // (Must do this late, so that "max_regions" is defined.)
1947   _cm = new ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1948   if (_cm == NULL || !_cm->completed_initialization()) {
1949     vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark");
1950     return JNI_ENOMEM;
1951   }
1952   _cmThread = _cm->cmThread();
1953 
1954   // Initialize the from_card cache structure of HeapRegionRemSet.
1955   HeapRegionRemSet::init_heap(max_regions());
1956 
1957   // Now expand into the initial heap size.
1958   if (!expand(init_byte_size)) {
1959     vm_shutdown_during_initialization("Failed to allocate initial heap.");
1960     return JNI_ENOMEM;
1961   }
1962 
1963   // Perform any initialization actions delegated to the policy.
1964   g1_policy()->init();
1965 
1966   JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
1967                                                SATB_Q_FL_lock,
1968                                                G1SATBProcessCompletedThreshold,
1969                                                Shared_SATB_Q_lock);
1970 
1971   JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl,
1972                                                 DirtyCardQ_CBL_mon,
1973                                                 DirtyCardQ_FL_lock,
1974                                                 concurrent_g1_refine()->yellow_zone(),
1975                                                 concurrent_g1_refine()->red_zone(),
1976                                                 Shared_DirtyCardQ_lock);
1977 
1978   dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code
1979                                     DirtyCardQ_CBL_mon,
1980                                     DirtyCardQ_FL_lock,
1981                                     -1, // never trigger processing
1982                                     -1, // no limit on length
1983                                     Shared_DirtyCardQ_lock,
1984                                     &JavaThread::dirty_card_queue_set());
1985 
1986   // Initialize the card queue set used to hold cards containing
1987   // references into the collection set.
1988   _into_cset_dirty_card_queue_set.initialize(NULL, // Should never be called by the Java code
1989                                              DirtyCardQ_CBL_mon,
1990                                              DirtyCardQ_FL_lock,
1991                                              -1, // never trigger processing
1992                                              -1, // no limit on length
1993                                              Shared_DirtyCardQ_lock,
1994                                              &JavaThread::dirty_card_queue_set());
1995 
1996   // Here we allocate the dummy HeapRegion that is required by the
1997   // G1AllocRegion class.
1998   HeapRegion* dummy_region = _hrm.get_dummy_region();
1999 
2000   // We'll re-use the same region whether the alloc region will
2001   // require BOT updates or not and, if it doesn't, then a non-young
2002   // region will complain that it cannot support allocations without
2003   // BOT updates. So we'll tag the dummy region as eden to avoid that.
2004   dummy_region->set_eden();
2005   // Make sure it's full.
2006   dummy_region->set_top(dummy_region->end());
2007   G1AllocRegion::setup(this, dummy_region);
2008 
2009   _allocator->init_mutator_alloc_region();
2010 
2011   // Do create of the monitoring and management support so that
2012   // values in the heap have been properly initialized.
2013   _g1mm = new G1MonitoringSupport(this);
2014 
2015   G1StringDedup::initialize();
2016 
2017   return JNI_OK;
2018 }
2019 
2020 void G1CollectedHeap::stop() {
2021   // Stop all concurrent threads. We do this to make sure these threads
2022   // do not continue to execute and access resources (e.g. gclog_or_tty)
2023   // that are destroyed during shutdown.
2024   _cg1r->stop();
2025   _cmThread->stop();
2026   if (G1StringDedup::is_enabled()) {
2027     G1StringDedup::stop();
2028   }
2029 }
2030 
2031 size_t G1CollectedHeap::conservative_max_heap_alignment() {
2032   return HeapRegion::max_region_size();
2033 }
2034 
2035 void G1CollectedHeap::post_initialize() {
2036   CollectedHeap::post_initialize();
2037   ref_processing_init();
2038 }
2039 
2040 void G1CollectedHeap::ref_processing_init() {
2041   // Reference processing in G1 currently works as follows:
2042   //
2043   // * There are two reference processor instances. One is
2044   //   used to record and process discovered references
2045   //   during concurrent marking; the other is used to
2046   //   record and process references during STW pauses
2047   //   (both full and incremental).
2048   // * Both ref processors need to 'span' the entire heap as
2049   //   the regions in the collection set may be dotted around.
2050   //
2051   // * For the concurrent marking ref processor:
2052   //   * Reference discovery is enabled at initial marking.
2053   //   * Reference discovery is disabled and the discovered
2054   //     references processed etc during remarking.
2055   //   * Reference discovery is MT (see below).
2056   //   * Reference discovery requires a barrier (see below).
2057   //   * Reference processing may or may not be MT
2058   //     (depending on the value of ParallelRefProcEnabled
2059   //     and ParallelGCThreads).
2060   //   * A full GC disables reference discovery by the CM
2061   //     ref processor and abandons any entries on it's
2062   //     discovered lists.
2063   //
2064   // * For the STW processor:
2065   //   * Non MT discovery is enabled at the start of a full GC.
2066   //   * Processing and enqueueing during a full GC is non-MT.
2067   //   * During a full GC, references are processed after marking.
2068   //
2069   //   * Discovery (may or may not be MT) is enabled at the start
2070   //     of an incremental evacuation pause.
2071   //   * References are processed near the end of a STW evacuation pause.
2072   //   * For both types of GC:
2073   //     * Discovery is atomic - i.e. not concurrent.
2074   //     * Reference discovery will not need a barrier.
2075 
2076   MemRegion mr = reserved_region();
2077 
2078   // Concurrent Mark ref processor
2079   _ref_processor_cm =
2080     new ReferenceProcessor(mr,    // span
2081                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2082                                 // mt processing
2083                            (int) ParallelGCThreads,
2084                                 // degree of mt processing
2085                            (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2086                                 // mt discovery
2087                            (int) MAX2(ParallelGCThreads, ConcGCThreads),
2088                                 // degree of mt discovery
2089                            false,
2090                                 // Reference discovery is not atomic
2091                            &_is_alive_closure_cm);
2092                                 // is alive closure
2093                                 // (for efficiency/performance)
2094 
2095   // STW ref processor
2096   _ref_processor_stw =
2097     new ReferenceProcessor(mr,    // span
2098                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2099                                 // mt processing
2100                            MAX2((int)ParallelGCThreads, 1),
2101                                 // degree of mt processing
2102                            (ParallelGCThreads > 1),
2103                                 // mt discovery
2104                            MAX2((int)ParallelGCThreads, 1),
2105                                 // degree of mt discovery
2106                            true,
2107                                 // Reference discovery is atomic
2108                            &_is_alive_closure_stw);
2109                                 // is alive closure
2110                                 // (for efficiency/performance)
2111 }
2112 
2113 size_t G1CollectedHeap::capacity() const {
2114   return _hrm.length() * HeapRegion::GrainBytes;
2115 }
2116 
2117 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2118   assert(!hr->is_continues_humongous(), "pre-condition");
2119   hr->reset_gc_time_stamp();
2120   if (hr->is_starts_humongous()) {
2121     uint first_index = hr->hrm_index() + 1;
2122     uint last_index = hr->last_hc_index();
2123     for (uint i = first_index; i < last_index; i += 1) {
2124       HeapRegion* chr = region_at(i);
2125       assert(chr->is_continues_humongous(), "sanity");
2126       chr->reset_gc_time_stamp();
2127     }
2128   }
2129 }
2130 
2131 #ifndef PRODUCT
2132 
2133 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2134 private:
2135   unsigned _gc_time_stamp;
2136   bool _failures;
2137 
2138 public:
2139   CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2140     _gc_time_stamp(gc_time_stamp), _failures(false) { }
2141 
2142   virtual bool doHeapRegion(HeapRegion* hr) {
2143     unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2144     if (_gc_time_stamp != region_gc_time_stamp) {
2145       gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, "
2146                              "expected %d", HR_FORMAT_PARAMS(hr),
2147                              region_gc_time_stamp, _gc_time_stamp);
2148       _failures = true;
2149     }
2150     return false;
2151   }
2152 
2153   bool failures() { return _failures; }
2154 };
2155 
2156 void G1CollectedHeap::check_gc_time_stamps() {
2157   CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2158   heap_region_iterate(&cl);
2159   guarantee(!cl.failures(), "all GC time stamps should have been reset");
2160 }
2161 #endif // PRODUCT
2162 
2163 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2164                                                  DirtyCardQueue* into_cset_dcq,
2165                                                  bool concurrent,
2166                                                  uint worker_i) {
2167   // Clean cards in the hot card cache
2168   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
2169   hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq);
2170 
2171   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2172   size_t n_completed_buffers = 0;
2173   while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2174     n_completed_buffers++;
2175   }
2176   g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers);
2177   dcqs.clear_n_completed_buffers();
2178   assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2179 }
2180 
2181 
2182 // Computes the sum of the storage used by the various regions.
2183 size_t G1CollectedHeap::used() const {
2184   return _allocator->used();
2185 }
2186 
2187 size_t G1CollectedHeap::used_unlocked() const {
2188   return _allocator->used_unlocked();
2189 }
2190 
2191 class SumUsedClosure: public HeapRegionClosure {
2192   size_t _used;
2193 public:
2194   SumUsedClosure() : _used(0) {}
2195   bool doHeapRegion(HeapRegion* r) {
2196     if (!r->is_continues_humongous()) {
2197       _used += r->used();
2198     }
2199     return false;
2200   }
2201   size_t result() { return _used; }
2202 };
2203 
2204 size_t G1CollectedHeap::recalculate_used() const {
2205   double recalculate_used_start = os::elapsedTime();
2206 
2207   SumUsedClosure blk;
2208   heap_region_iterate(&blk);
2209 
2210   g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2211   return blk.result();
2212 }
2213 
2214 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2215   switch (cause) {
2216     case GCCause::_gc_locker:               return GCLockerInvokesConcurrent;
2217     case GCCause::_java_lang_system_gc:     return ExplicitGCInvokesConcurrent;
2218     case GCCause::_g1_humongous_allocation: return true;
2219     case GCCause::_update_allocation_context_stats_inc: return true;
2220     case GCCause::_wb_conc_mark:            return true;
2221     default:                                return false;
2222   }
2223 }
2224 
2225 #ifndef PRODUCT
2226 void G1CollectedHeap::allocate_dummy_regions() {
2227   // Let's fill up most of the region
2228   size_t word_size = HeapRegion::GrainWords - 1024;
2229   // And as a result the region we'll allocate will be humongous.
2230   guarantee(is_humongous(word_size), "sanity");
2231 
2232   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2233     // Let's use the existing mechanism for the allocation
2234     HeapWord* dummy_obj = humongous_obj_allocate(word_size,
2235                                                  AllocationContext::system());
2236     if (dummy_obj != NULL) {
2237       MemRegion mr(dummy_obj, word_size);
2238       CollectedHeap::fill_with_object(mr);
2239     } else {
2240       // If we can't allocate once, we probably cannot allocate
2241       // again. Let's get out of the loop.
2242       break;
2243     }
2244   }
2245 }
2246 #endif // !PRODUCT
2247 
2248 void G1CollectedHeap::increment_old_marking_cycles_started() {
2249   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2250     _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2251     err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2252     _old_marking_cycles_started, _old_marking_cycles_completed));
2253 
2254   _old_marking_cycles_started++;
2255 }
2256 
2257 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2258   MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2259 
2260   // We assume that if concurrent == true, then the caller is a
2261   // concurrent thread that was joined the Suspendible Thread
2262   // Set. If there's ever a cheap way to check this, we should add an
2263   // assert here.
2264 
2265   // Given that this method is called at the end of a Full GC or of a
2266   // concurrent cycle, and those can be nested (i.e., a Full GC can
2267   // interrupt a concurrent cycle), the number of full collections
2268   // completed should be either one (in the case where there was no
2269   // nesting) or two (when a Full GC interrupted a concurrent cycle)
2270   // behind the number of full collections started.
2271 
2272   // This is the case for the inner caller, i.e. a Full GC.
2273   assert(concurrent ||
2274          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2275          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2276          err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
2277                  "is inconsistent with _old_marking_cycles_completed = %u",
2278                  _old_marking_cycles_started, _old_marking_cycles_completed));
2279 
2280   // This is the case for the outer caller, i.e. the concurrent cycle.
2281   assert(!concurrent ||
2282          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2283          err_msg("for outer caller (concurrent cycle): "
2284                  "_old_marking_cycles_started = %u "
2285                  "is inconsistent with _old_marking_cycles_completed = %u",
2286                  _old_marking_cycles_started, _old_marking_cycles_completed));
2287 
2288   _old_marking_cycles_completed += 1;
2289 
2290   // We need to clear the "in_progress" flag in the CM thread before
2291   // we wake up any waiters (especially when ExplicitInvokesConcurrent
2292   // is set) so that if a waiter requests another System.gc() it doesn't
2293   // incorrectly see that a marking cycle is still in progress.
2294   if (concurrent) {
2295     _cmThread->clear_in_progress();
2296   }
2297 
2298   // This notify_all() will ensure that a thread that called
2299   // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2300   // and it's waiting for a full GC to finish will be woken up. It is
2301   // waiting in VM_G1IncCollectionPause::doit_epilogue().
2302   FullGCCount_lock->notify_all();
2303 }
2304 
2305 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) {
2306   _concurrent_cycle_started = true;
2307   _gc_timer_cm->register_gc_start(start_time);
2308 
2309   _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start());
2310   trace_heap_before_gc(_gc_tracer_cm);
2311 }
2312 
2313 void G1CollectedHeap::register_concurrent_cycle_end() {
2314   if (_concurrent_cycle_started) {
2315     if (_cm->has_aborted()) {
2316       _gc_tracer_cm->report_concurrent_mode_failure();
2317     }
2318 
2319     _gc_timer_cm->register_gc_end();
2320     _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
2321 
2322     // Clear state variables to prepare for the next concurrent cycle.
2323     _concurrent_cycle_started = false;
2324     _heap_summary_sent = false;
2325   }
2326 }
2327 
2328 void G1CollectedHeap::trace_heap_after_concurrent_cycle() {
2329   if (_concurrent_cycle_started) {
2330     // This function can be called when:
2331     //  the cleanup pause is run
2332     //  the concurrent cycle is aborted before the cleanup pause.
2333     //  the concurrent cycle is aborted after the cleanup pause,
2334     //   but before the concurrent cycle end has been registered.
2335     // Make sure that we only send the heap information once.
2336     if (!_heap_summary_sent) {
2337       trace_heap_after_gc(_gc_tracer_cm);
2338       _heap_summary_sent = true;
2339     }
2340   }
2341 }
2342 
2343 G1YCType G1CollectedHeap::yc_type() {
2344   bool is_young = g1_policy()->gcs_are_young();
2345   bool is_initial_mark = g1_policy()->during_initial_mark_pause();
2346   bool is_during_mark = mark_in_progress();
2347 
2348   if (is_initial_mark) {
2349     return InitialMark;
2350   } else if (is_during_mark) {
2351     return DuringMark;
2352   } else if (is_young) {
2353     return Normal;
2354   } else {
2355     return Mixed;
2356   }
2357 }
2358 
2359 void G1CollectedHeap::collect(GCCause::Cause cause) {
2360   assert_heap_not_locked();
2361 
2362   uint gc_count_before;
2363   uint old_marking_count_before;
2364   uint full_gc_count_before;
2365   bool retry_gc;
2366 
2367   do {
2368     retry_gc = false;
2369 
2370     {
2371       MutexLocker ml(Heap_lock);
2372 
2373       // Read the GC count while holding the Heap_lock
2374       gc_count_before = total_collections();
2375       full_gc_count_before = total_full_collections();
2376       old_marking_count_before = _old_marking_cycles_started;
2377     }
2378 
2379     if (should_do_concurrent_full_gc(cause)) {
2380       // Schedule an initial-mark evacuation pause that will start a
2381       // concurrent cycle. We're setting word_size to 0 which means that
2382       // we are not requesting a post-GC allocation.
2383       VM_G1IncCollectionPause op(gc_count_before,
2384                                  0,     /* word_size */
2385                                  true,  /* should_initiate_conc_mark */
2386                                  g1_policy()->max_pause_time_ms(),
2387                                  cause);
2388       op.set_allocation_context(AllocationContext::current());
2389 
2390       VMThread::execute(&op);
2391       if (!op.pause_succeeded()) {
2392         if (old_marking_count_before == _old_marking_cycles_started) {
2393           retry_gc = op.should_retry_gc();
2394         } else {
2395           // A Full GC happened while we were trying to schedule the
2396           // initial-mark GC. No point in starting a new cycle given
2397           // that the whole heap was collected anyway.
2398         }
2399 
2400         if (retry_gc) {
2401           if (GC_locker::is_active_and_needs_gc()) {
2402             GC_locker::stall_until_clear();
2403           }
2404         }
2405       }
2406     } else {
2407       if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2408           DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2409 
2410         // Schedule a standard evacuation pause. We're setting word_size
2411         // to 0 which means that we are not requesting a post-GC allocation.
2412         VM_G1IncCollectionPause op(gc_count_before,
2413                                    0,     /* word_size */
2414                                    false, /* should_initiate_conc_mark */
2415                                    g1_policy()->max_pause_time_ms(),
2416                                    cause);
2417         VMThread::execute(&op);
2418       } else {
2419         // Schedule a Full GC.
2420         VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2421         VMThread::execute(&op);
2422       }
2423     }
2424   } while (retry_gc);
2425 }
2426 
2427 bool G1CollectedHeap::is_in(const void* p) const {
2428   if (_hrm.reserved().contains(p)) {
2429     // Given that we know that p is in the reserved space,
2430     // heap_region_containing_raw() should successfully
2431     // return the containing region.
2432     HeapRegion* hr = heap_region_containing_raw(p);
2433     return hr->is_in(p);
2434   } else {
2435     return false;
2436   }
2437 }
2438 
2439 #ifdef ASSERT
2440 bool G1CollectedHeap::is_in_exact(const void* p) const {
2441   bool contains = reserved_region().contains(p);
2442   bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2443   if (contains && available) {
2444     return true;
2445   } else {
2446     return false;
2447   }
2448 }
2449 #endif
2450 
2451 // Iteration functions.
2452 
2453 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion.
2454 
2455 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2456   ExtendedOopClosure* _cl;
2457 public:
2458   IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {}
2459   bool doHeapRegion(HeapRegion* r) {
2460     if (!r->is_continues_humongous()) {
2461       r->oop_iterate(_cl);
2462     }
2463     return false;
2464   }
2465 };
2466 
2467 // Iterates an ObjectClosure over all objects within a HeapRegion.
2468 
2469 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2470   ObjectClosure* _cl;
2471 public:
2472   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2473   bool doHeapRegion(HeapRegion* r) {
2474     if (!r->is_continues_humongous()) {
2475       r->object_iterate(_cl);
2476     }
2477     return false;
2478   }
2479 };
2480 
2481 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2482   IterateObjectClosureRegionClosure blk(cl);
2483   heap_region_iterate(&blk);
2484 }
2485 
2486 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2487   _hrm.iterate(cl);
2488 }
2489 
2490 void
2491 G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl,
2492                                          uint worker_id,
2493                                          HeapRegionClaimer *hrclaimer,
2494                                          bool concurrent) const {
2495   _hrm.par_iterate(cl, worker_id, hrclaimer, concurrent);
2496 }
2497 
2498 // Clear the cached CSet starting regions and (more importantly)
2499 // the time stamps. Called when we reset the GC time stamp.
2500 void G1CollectedHeap::clear_cset_start_regions() {
2501   assert(_worker_cset_start_region != NULL, "sanity");
2502   assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2503 
2504   int n_queues = MAX2((int)ParallelGCThreads, 1);
2505   for (int i = 0; i < n_queues; i++) {
2506     _worker_cset_start_region[i] = NULL;
2507     _worker_cset_start_region_time_stamp[i] = 0;
2508   }
2509 }
2510 
2511 // Given the id of a worker, obtain or calculate a suitable
2512 // starting region for iterating over the current collection set.
2513 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) {
2514   assert(get_gc_time_stamp() > 0, "should have been updated by now");
2515 
2516   HeapRegion* result = NULL;
2517   unsigned gc_time_stamp = get_gc_time_stamp();
2518 
2519   if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2520     // Cached starting region for current worker was set
2521     // during the current pause - so it's valid.
2522     // Note: the cached starting heap region may be NULL
2523     // (when the collection set is empty).
2524     result = _worker_cset_start_region[worker_i];
2525     assert(result == NULL || result->in_collection_set(), "sanity");
2526     return result;
2527   }
2528 
2529   // The cached entry was not valid so let's calculate
2530   // a suitable starting heap region for this worker.
2531 
2532   // We want the parallel threads to start their collection
2533   // set iteration at different collection set regions to
2534   // avoid contention.
2535   // If we have:
2536   //          n collection set regions
2537   //          p threads
2538   // Then thread t will start at region floor ((t * n) / p)
2539 
2540   result = g1_policy()->collection_set();
2541   uint cs_size = g1_policy()->cset_region_length();
2542   uint active_workers = workers()->active_workers();
2543   assert(UseDynamicNumberOfGCThreads ||
2544            active_workers == workers()->total_workers(),
2545            "Unless dynamic should use total workers");
2546 
2547   uint end_ind   = (cs_size * worker_i) / active_workers;
2548   uint start_ind = 0;
2549 
2550   if (worker_i > 0 &&
2551       _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2552     // Previous workers starting region is valid
2553     // so let's iterate from there
2554     start_ind = (cs_size * (worker_i - 1)) / active_workers;
2555     result = _worker_cset_start_region[worker_i - 1];
2556   }
2557 
2558   for (uint i = start_ind; i < end_ind; i++) {
2559     result = result->next_in_collection_set();
2560   }
2561 
2562   // Note: the calculated starting heap region may be NULL
2563   // (when the collection set is empty).
2564   assert(result == NULL || result->in_collection_set(), "sanity");
2565   assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2566          "should be updated only once per pause");
2567   _worker_cset_start_region[worker_i] = result;
2568   OrderAccess::storestore();
2569   _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2570   return result;
2571 }
2572 
2573 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2574   HeapRegion* r = g1_policy()->collection_set();
2575   while (r != NULL) {
2576     HeapRegion* next = r->next_in_collection_set();
2577     if (cl->doHeapRegion(r)) {
2578       cl->incomplete();
2579       return;
2580     }
2581     r = next;
2582   }
2583 }
2584 
2585 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2586                                                   HeapRegionClosure *cl) {
2587   if (r == NULL) {
2588     // The CSet is empty so there's nothing to do.
2589     return;
2590   }
2591 
2592   assert(r->in_collection_set(),
2593          "Start region must be a member of the collection set.");
2594   HeapRegion* cur = r;
2595   while (cur != NULL) {
2596     HeapRegion* next = cur->next_in_collection_set();
2597     if (cl->doHeapRegion(cur) && false) {
2598       cl->incomplete();
2599       return;
2600     }
2601     cur = next;
2602   }
2603   cur = g1_policy()->collection_set();
2604   while (cur != r) {
2605     HeapRegion* next = cur->next_in_collection_set();
2606     if (cl->doHeapRegion(cur) && false) {
2607       cl->incomplete();
2608       return;
2609     }
2610     cur = next;
2611   }
2612 }
2613 
2614 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const {
2615   HeapRegion* result = _hrm.next_region_in_heap(from);
2616   while (result != NULL && result->is_humongous()) {
2617     result = _hrm.next_region_in_heap(result);
2618   }
2619   return result;
2620 }
2621 
2622 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2623   HeapRegion* hr = heap_region_containing(addr);
2624   return hr->block_start(addr);
2625 }
2626 
2627 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2628   HeapRegion* hr = heap_region_containing(addr);
2629   return hr->block_size(addr);
2630 }
2631 
2632 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2633   HeapRegion* hr = heap_region_containing(addr);
2634   return hr->block_is_obj(addr);
2635 }
2636 
2637 bool G1CollectedHeap::supports_tlab_allocation() const {
2638   return true;
2639 }
2640 
2641 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2642   return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes;
2643 }
2644 
2645 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2646   return young_list()->eden_used_bytes();
2647 }
2648 
2649 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2650 // must be smaller than the humongous object limit.
2651 size_t G1CollectedHeap::max_tlab_size() const {
2652   return align_size_down(_humongous_object_threshold_in_words - 1, MinObjAlignment);
2653 }
2654 
2655 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2656   // Return the remaining space in the cur alloc region, but not less than
2657   // the min TLAB size.
2658 
2659   // Also, this value can be at most the humongous object threshold,
2660   // since we can't allow tlabs to grow big enough to accommodate
2661   // humongous objects.
2662 
2663   HeapRegion* hr = _allocator->mutator_alloc_region(AllocationContext::current())->get();
2664   size_t max_tlab = max_tlab_size() * wordSize;
2665   if (hr == NULL) {
2666     return max_tlab;
2667   } else {
2668     return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab);
2669   }
2670 }
2671 
2672 size_t G1CollectedHeap::max_capacity() const {
2673   return _hrm.reserved().byte_size();
2674 }
2675 
2676 jlong G1CollectedHeap::millis_since_last_gc() {
2677   // assert(false, "NYI");
2678   return 0;
2679 }
2680 
2681 void G1CollectedHeap::prepare_for_verify() {
2682   if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
2683     ensure_parsability(false);
2684   }
2685   g1_rem_set()->prepare_for_verify();
2686 }
2687 
2688 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr,
2689                                               VerifyOption vo) {
2690   switch (vo) {
2691   case VerifyOption_G1UsePrevMarking:
2692     return hr->obj_allocated_since_prev_marking(obj);
2693   case VerifyOption_G1UseNextMarking:
2694     return hr->obj_allocated_since_next_marking(obj);
2695   case VerifyOption_G1UseMarkWord:
2696     return false;
2697   default:
2698     ShouldNotReachHere();
2699   }
2700   return false; // keep some compilers happy
2701 }
2702 
2703 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) {
2704   switch (vo) {
2705   case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start();
2706   case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start();
2707   case VerifyOption_G1UseMarkWord:    return NULL;
2708   default:                            ShouldNotReachHere();
2709   }
2710   return NULL; // keep some compilers happy
2711 }
2712 
2713 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) {
2714   switch (vo) {
2715   case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj);
2716   case VerifyOption_G1UseNextMarking: return isMarkedNext(obj);
2717   case VerifyOption_G1UseMarkWord:    return obj->is_gc_marked();
2718   default:                            ShouldNotReachHere();
2719   }
2720   return false; // keep some compilers happy
2721 }
2722 
2723 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) {
2724   switch (vo) {
2725   case VerifyOption_G1UsePrevMarking: return "PTAMS";
2726   case VerifyOption_G1UseNextMarking: return "NTAMS";
2727   case VerifyOption_G1UseMarkWord:    return "NONE";
2728   default:                            ShouldNotReachHere();
2729   }
2730   return NULL; // keep some compilers happy
2731 }
2732 
2733 class VerifyRootsClosure: public OopClosure {
2734 private:
2735   G1CollectedHeap* _g1h;
2736   VerifyOption     _vo;
2737   bool             _failures;
2738 public:
2739   // _vo == UsePrevMarking -> use "prev" marking information,
2740   // _vo == UseNextMarking -> use "next" marking information,
2741   // _vo == UseMarkWord    -> use mark word from object header.
2742   VerifyRootsClosure(VerifyOption vo) :
2743     _g1h(G1CollectedHeap::heap()),
2744     _vo(vo),
2745     _failures(false) { }
2746 
2747   bool failures() { return _failures; }
2748 
2749   template <class T> void do_oop_nv(T* p) {
2750     T heap_oop = oopDesc::load_heap_oop(p);
2751     if (!oopDesc::is_null(heap_oop)) {
2752       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2753       if (_g1h->is_obj_dead_cond(obj, _vo)) {
2754         gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
2755                                "points to dead obj "PTR_FORMAT, p2i(p), p2i(obj));
2756         if (_vo == VerifyOption_G1UseMarkWord) {
2757           gclog_or_tty->print_cr("  Mark word: "INTPTR_FORMAT, (intptr_t)obj->mark());
2758         }
2759         obj->print_on(gclog_or_tty);
2760         _failures = true;
2761       }
2762     }
2763   }
2764 
2765   void do_oop(oop* p)       { do_oop_nv(p); }
2766   void do_oop(narrowOop* p) { do_oop_nv(p); }
2767 };
2768 
2769 class G1VerifyCodeRootOopClosure: public OopClosure {
2770   G1CollectedHeap* _g1h;
2771   OopClosure* _root_cl;
2772   nmethod* _nm;
2773   VerifyOption _vo;
2774   bool _failures;
2775 
2776   template <class T> void do_oop_work(T* p) {
2777     // First verify that this root is live
2778     _root_cl->do_oop(p);
2779 
2780     if (!G1VerifyHeapRegionCodeRoots) {
2781       // We're not verifying the code roots attached to heap region.
2782       return;
2783     }
2784 
2785     // Don't check the code roots during marking verification in a full GC
2786     if (_vo == VerifyOption_G1UseMarkWord) {
2787       return;
2788     }
2789 
2790     // Now verify that the current nmethod (which contains p) is
2791     // in the code root list of the heap region containing the
2792     // object referenced by p.
2793 
2794     T heap_oop = oopDesc::load_heap_oop(p);
2795     if (!oopDesc::is_null(heap_oop)) {
2796       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2797 
2798       // Now fetch the region containing the object
2799       HeapRegion* hr = _g1h->heap_region_containing(obj);
2800       HeapRegionRemSet* hrrs = hr->rem_set();
2801       // Verify that the strong code root list for this region
2802       // contains the nmethod
2803       if (!hrrs->strong_code_roots_list_contains(_nm)) {
2804         gclog_or_tty->print_cr("Code root location "PTR_FORMAT" "
2805                                "from nmethod "PTR_FORMAT" not in strong "
2806                                "code roots for region ["PTR_FORMAT","PTR_FORMAT")",
2807                                p2i(p), p2i(_nm), p2i(hr->bottom()), p2i(hr->end()));
2808         _failures = true;
2809       }
2810     }
2811   }
2812 
2813 public:
2814   G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo):
2815     _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {}
2816 
2817   void do_oop(oop* p) { do_oop_work(p); }
2818   void do_oop(narrowOop* p) { do_oop_work(p); }
2819 
2820   void set_nmethod(nmethod* nm) { _nm = nm; }
2821   bool failures() { return _failures; }
2822 };
2823 
2824 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure {
2825   G1VerifyCodeRootOopClosure* _oop_cl;
2826 
2827 public:
2828   G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl):
2829     _oop_cl(oop_cl) {}
2830 
2831   void do_code_blob(CodeBlob* cb) {
2832     nmethod* nm = cb->as_nmethod_or_null();
2833     if (nm != NULL) {
2834       _oop_cl->set_nmethod(nm);
2835       nm->oops_do(_oop_cl);
2836     }
2837   }
2838 };
2839 
2840 class YoungRefCounterClosure : public OopClosure {
2841   G1CollectedHeap* _g1h;
2842   int              _count;
2843  public:
2844   YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {}
2845   void do_oop(oop* p)       { if (_g1h->is_in_young(*p)) { _count++; } }
2846   void do_oop(narrowOop* p) { ShouldNotReachHere(); }
2847 
2848   int count() { return _count; }
2849   void reset_count() { _count = 0; };
2850 };
2851 
2852 class VerifyKlassClosure: public KlassClosure {
2853   YoungRefCounterClosure _young_ref_counter_closure;
2854   OopClosure *_oop_closure;
2855  public:
2856   VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {}
2857   void do_klass(Klass* k) {
2858     k->oops_do(_oop_closure);
2859 
2860     _young_ref_counter_closure.reset_count();
2861     k->oops_do(&_young_ref_counter_closure);
2862     if (_young_ref_counter_closure.count() > 0) {
2863       guarantee(k->has_modified_oops(), err_msg("Klass " PTR_FORMAT ", has young refs but is not dirty.", p2i(k)));
2864     }
2865   }
2866 };
2867 
2868 class VerifyLivenessOopClosure: public OopClosure {
2869   G1CollectedHeap* _g1h;
2870   VerifyOption _vo;
2871 public:
2872   VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
2873     _g1h(g1h), _vo(vo)
2874   { }
2875   void do_oop(narrowOop *p) { do_oop_work(p); }
2876   void do_oop(      oop *p) { do_oop_work(p); }
2877 
2878   template <class T> void do_oop_work(T *p) {
2879     oop obj = oopDesc::load_decode_heap_oop(p);
2880     guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
2881               "Dead object referenced by a not dead object");
2882   }
2883 };
2884 
2885 class VerifyObjsInRegionClosure: public ObjectClosure {
2886 private:
2887   G1CollectedHeap* _g1h;
2888   size_t _live_bytes;
2889   HeapRegion *_hr;
2890   VerifyOption _vo;
2891 public:
2892   // _vo == UsePrevMarking -> use "prev" marking information,
2893   // _vo == UseNextMarking -> use "next" marking information,
2894   // _vo == UseMarkWord    -> use mark word from object header.
2895   VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
2896     : _live_bytes(0), _hr(hr), _vo(vo) {
2897     _g1h = G1CollectedHeap::heap();
2898   }
2899   void do_object(oop o) {
2900     VerifyLivenessOopClosure isLive(_g1h, _vo);
2901     assert(o != NULL, "Huh?");
2902     if (!_g1h->is_obj_dead_cond(o, _vo)) {
2903       // If the object is alive according to the mark word,
2904       // then verify that the marking information agrees.
2905       // Note we can't verify the contra-positive of the
2906       // above: if the object is dead (according to the mark
2907       // word), it may not be marked, or may have been marked
2908       // but has since became dead, or may have been allocated
2909       // since the last marking.
2910       if (_vo == VerifyOption_G1UseMarkWord) {
2911         guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
2912       }
2913 
2914       o->oop_iterate_no_header(&isLive);
2915       if (!_hr->obj_allocated_since_prev_marking(o)) {
2916         size_t obj_size = o->size();    // Make sure we don't overflow
2917         _live_bytes += (obj_size * HeapWordSize);
2918       }
2919     }
2920   }
2921   size_t live_bytes() { return _live_bytes; }
2922 };
2923 
2924 class VerifyRegionClosure: public HeapRegionClosure {
2925 private:
2926   bool             _par;
2927   VerifyOption     _vo;
2928   bool             _failures;
2929 public:
2930   // _vo == UsePrevMarking -> use "prev" marking information,
2931   // _vo == UseNextMarking -> use "next" marking information,
2932   // _vo == UseMarkWord    -> use mark word from object header.
2933   VerifyRegionClosure(bool par, VerifyOption vo)
2934     : _par(par),
2935       _vo(vo),
2936       _failures(false) {}
2937 
2938   bool failures() {
2939     return _failures;
2940   }
2941 
2942   bool doHeapRegion(HeapRegion* r) {
2943     if (!r->is_continues_humongous()) {
2944       bool failures = false;
2945       r->verify(_vo, &failures);
2946       if (failures) {
2947         _failures = true;
2948       } else {
2949         VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
2950         r->object_iterate(&not_dead_yet_cl);
2951         if (_vo != VerifyOption_G1UseNextMarking) {
2952           if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
2953             gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
2954                                    "max_live_bytes "SIZE_FORMAT" "
2955                                    "< calculated "SIZE_FORMAT,
2956                                    p2i(r->bottom()), p2i(r->end()),
2957                                    r->max_live_bytes(),
2958                                  not_dead_yet_cl.live_bytes());
2959             _failures = true;
2960           }
2961         } else {
2962           // When vo == UseNextMarking we cannot currently do a sanity
2963           // check on the live bytes as the calculation has not been
2964           // finalized yet.
2965         }
2966       }
2967     }
2968     return false; // stop the region iteration if we hit a failure
2969   }
2970 };
2971 
2972 // This is the task used for parallel verification of the heap regions
2973 
2974 class G1ParVerifyTask: public AbstractGangTask {
2975 private:
2976   G1CollectedHeap*  _g1h;
2977   VerifyOption      _vo;
2978   bool              _failures;
2979   HeapRegionClaimer _hrclaimer;
2980 
2981 public:
2982   // _vo == UsePrevMarking -> use "prev" marking information,
2983   // _vo == UseNextMarking -> use "next" marking information,
2984   // _vo == UseMarkWord    -> use mark word from object header.
2985   G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
2986       AbstractGangTask("Parallel verify task"),
2987       _g1h(g1h),
2988       _vo(vo),
2989       _failures(false),
2990       _hrclaimer(g1h->workers()->active_workers()) {}
2991 
2992   bool failures() {
2993     return _failures;
2994   }
2995 
2996   void work(uint worker_id) {
2997     HandleMark hm;
2998     VerifyRegionClosure blk(true, _vo);
2999     _g1h->heap_region_par_iterate(&blk, worker_id, &_hrclaimer);
3000     if (blk.failures()) {
3001       _failures = true;
3002     }
3003   }
3004 };
3005 
3006 void G1CollectedHeap::verify(bool silent, VerifyOption vo) {
3007   if (SafepointSynchronize::is_at_safepoint()) {
3008     assert(Thread::current()->is_VM_thread(),
3009            "Expected to be executed serially by the VM thread at this point");
3010 
3011     if (!silent) { gclog_or_tty->print("Roots "); }
3012     VerifyRootsClosure rootsCl(vo);
3013     VerifyKlassClosure klassCl(this, &rootsCl);
3014     CLDToKlassAndOopClosure cldCl(&klassCl, &rootsCl, false);
3015 
3016     // We apply the relevant closures to all the oops in the
3017     // system dictionary, class loader data graph, the string table
3018     // and the nmethods in the code cache.
3019     G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo);
3020     G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl);
3021 
3022     {
3023       G1RootProcessor root_processor(this);
3024       root_processor.process_all_roots(&rootsCl,
3025                                        &cldCl,
3026                                        &blobsCl);
3027     }
3028 
3029     bool failures = rootsCl.failures() || codeRootsCl.failures();
3030 
3031     if (vo != VerifyOption_G1UseMarkWord) {
3032       // If we're verifying during a full GC then the region sets
3033       // will have been torn down at the start of the GC. Therefore
3034       // verifying the region sets will fail. So we only verify
3035       // the region sets when not in a full GC.
3036       if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3037       verify_region_sets();
3038     }
3039 
3040     if (!silent) { gclog_or_tty->print("HeapRegions "); }
3041     if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3042 
3043       G1ParVerifyTask task(this, vo);
3044       assert(UseDynamicNumberOfGCThreads ||
3045         workers()->active_workers() == workers()->total_workers(),
3046         "If not dynamic should be using all the workers");
3047       uint n_workers = workers()->active_workers();
3048       set_par_threads(n_workers);
3049       workers()->run_task(&task);
3050       set_par_threads(0);
3051       if (task.failures()) {
3052         failures = true;
3053       }
3054 
3055     } else {
3056       VerifyRegionClosure blk(false, vo);
3057       heap_region_iterate(&blk);
3058       if (blk.failures()) {
3059         failures = true;
3060       }
3061     }
3062 
3063     if (G1StringDedup::is_enabled()) {
3064       if (!silent) gclog_or_tty->print("StrDedup ");
3065       G1StringDedup::verify();
3066     }
3067 
3068     if (failures) {
3069       gclog_or_tty->print_cr("Heap:");
3070       // It helps to have the per-region information in the output to
3071       // help us track down what went wrong. This is why we call
3072       // print_extended_on() instead of print_on().
3073       print_extended_on(gclog_or_tty);
3074       gclog_or_tty->cr();
3075       gclog_or_tty->flush();
3076     }
3077     guarantee(!failures, "there should not have been any failures");
3078   } else {
3079     if (!silent) {
3080       gclog_or_tty->print("(SKIPPING Roots, HeapRegionSets, HeapRegions, RemSet");
3081       if (G1StringDedup::is_enabled()) {
3082         gclog_or_tty->print(", StrDedup");
3083       }
3084       gclog_or_tty->print(") ");
3085     }
3086   }
3087 }
3088 
3089 void G1CollectedHeap::verify(bool silent) {
3090   verify(silent, VerifyOption_G1UsePrevMarking);
3091 }
3092 
3093 double G1CollectedHeap::verify(bool guard, const char* msg) {
3094   double verify_time_ms = 0.0;
3095 
3096   if (guard && total_collections() >= VerifyGCStartAt) {
3097     double verify_start = os::elapsedTime();
3098     HandleMark hm;  // Discard invalid handles created during verification
3099     prepare_for_verify();
3100     Universe::verify(VerifyOption_G1UsePrevMarking, msg);
3101     verify_time_ms = (os::elapsedTime() - verify_start) * 1000;
3102   }
3103 
3104   return verify_time_ms;
3105 }
3106 
3107 void G1CollectedHeap::verify_before_gc() {
3108   double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:");
3109   g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms);
3110 }
3111 
3112 void G1CollectedHeap::verify_after_gc() {
3113   double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:");
3114   g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms);
3115 }
3116 
3117 class PrintRegionClosure: public HeapRegionClosure {
3118   outputStream* _st;
3119 public:
3120   PrintRegionClosure(outputStream* st) : _st(st) {}
3121   bool doHeapRegion(HeapRegion* r) {
3122     r->print_on(_st);
3123     return false;
3124   }
3125 };
3126 
3127 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3128                                        const HeapRegion* hr,
3129                                        const VerifyOption vo) const {
3130   switch (vo) {
3131   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
3132   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
3133   case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked();
3134   default:                            ShouldNotReachHere();
3135   }
3136   return false; // keep some compilers happy
3137 }
3138 
3139 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3140                                        const VerifyOption vo) const {
3141   switch (vo) {
3142   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
3143   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
3144   case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked();
3145   default:                            ShouldNotReachHere();
3146   }
3147   return false; // keep some compilers happy
3148 }
3149 
3150 void G1CollectedHeap::print_on(outputStream* st) const {
3151   st->print(" %-20s", "garbage-first heap");
3152   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3153             capacity()/K, used_unlocked()/K);
3154   st->print(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")",
3155             p2i(_hrm.reserved().start()),
3156             p2i(_hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords),
3157             p2i(_hrm.reserved().end()));
3158   st->cr();
3159   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3160   uint young_regions = _young_list->length();
3161   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3162             (size_t) young_regions * HeapRegion::GrainBytes / K);
3163   uint survivor_regions = g1_policy()->recorded_survivor_regions();
3164   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3165             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3166   st->cr();
3167   MetaspaceAux::print_on(st);
3168 }
3169 
3170 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3171   print_on(st);
3172 
3173   // Print the per-region information.
3174   st->cr();
3175   st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3176                "HS=humongous(starts), HC=humongous(continues), "
3177                "CS=collection set, F=free, TS=gc time stamp, "
3178                "PTAMS=previous top-at-mark-start, "
3179                "NTAMS=next top-at-mark-start)");
3180   PrintRegionClosure blk(st);
3181   heap_region_iterate(&blk);
3182 }
3183 
3184 void G1CollectedHeap::print_on_error(outputStream* st) const {
3185   this->CollectedHeap::print_on_error(st);
3186 
3187   if (_cm != NULL) {
3188     st->cr();
3189     _cm->print_on_error(st);
3190   }
3191 }
3192 
3193 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3194   workers()->print_worker_threads_on(st);
3195   _cmThread->print_on(st);
3196   st->cr();
3197   _cm->print_worker_threads_on(st);
3198   _cg1r->print_worker_threads_on(st);
3199   if (G1StringDedup::is_enabled()) {
3200     G1StringDedup::print_worker_threads_on(st);
3201   }
3202 }
3203 
3204 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3205   workers()->threads_do(tc);
3206   tc->do_thread(_cmThread);
3207   _cg1r->threads_do(tc);
3208   if (G1StringDedup::is_enabled()) {
3209     G1StringDedup::threads_do(tc);
3210   }
3211 }
3212 
3213 void G1CollectedHeap::print_tracing_info() const {
3214   // We'll overload this to mean "trace GC pause statistics."
3215   if (TraceYoungGenTime || TraceOldGenTime) {
3216     // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3217     // to that.
3218     g1_policy()->print_tracing_info();
3219   }
3220   if (G1SummarizeRSetStats) {
3221     g1_rem_set()->print_summary_info();
3222   }
3223   if (G1SummarizeConcMark) {
3224     concurrent_mark()->print_summary_info();
3225   }
3226   g1_policy()->print_yg_surv_rate_info();
3227 }
3228 
3229 #ifndef PRODUCT
3230 // Helpful for debugging RSet issues.
3231 
3232 class PrintRSetsClosure : public HeapRegionClosure {
3233 private:
3234   const char* _msg;
3235   size_t _occupied_sum;
3236 
3237 public:
3238   bool doHeapRegion(HeapRegion* r) {
3239     HeapRegionRemSet* hrrs = r->rem_set();
3240     size_t occupied = hrrs->occupied();
3241     _occupied_sum += occupied;
3242 
3243     gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3244                            HR_FORMAT_PARAMS(r));
3245     if (occupied == 0) {
3246       gclog_or_tty->print_cr("  RSet is empty");
3247     } else {
3248       hrrs->print();
3249     }
3250     gclog_or_tty->print_cr("----------");
3251     return false;
3252   }
3253 
3254   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3255     gclog_or_tty->cr();
3256     gclog_or_tty->print_cr("========================================");
3257     gclog_or_tty->print_cr("%s", msg);
3258     gclog_or_tty->cr();
3259   }
3260 
3261   ~PrintRSetsClosure() {
3262     gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3263     gclog_or_tty->print_cr("========================================");
3264     gclog_or_tty->cr();
3265   }
3266 };
3267 
3268 void G1CollectedHeap::print_cset_rsets() {
3269   PrintRSetsClosure cl("Printing CSet RSets");
3270   collection_set_iterate(&cl);
3271 }
3272 
3273 void G1CollectedHeap::print_all_rsets() {
3274   PrintRSetsClosure cl("Printing All RSets");;
3275   heap_region_iterate(&cl);
3276 }
3277 #endif // PRODUCT
3278 
3279 G1CollectedHeap* G1CollectedHeap::heap() {
3280   CollectedHeap* heap = Universe::heap();
3281   assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
3282   assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap");
3283   return (G1CollectedHeap*)heap;
3284 }
3285 
3286 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3287   // always_do_update_barrier = false;
3288   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3289   // Fill TLAB's and such
3290   accumulate_statistics_all_tlabs();
3291   ensure_parsability(true);
3292 
3293   if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) &&
3294       (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3295     g1_rem_set()->print_periodic_summary_info("Before GC RS summary");
3296   }
3297 }
3298 
3299 void G1CollectedHeap::gc_epilogue(bool full) {
3300 
3301   if (G1SummarizeRSetStats &&
3302       (G1SummarizeRSetStatsPeriod > 0) &&
3303       // we are at the end of the GC. Total collections has already been increased.
3304       ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) {
3305     g1_rem_set()->print_periodic_summary_info("After GC RS summary");
3306   }
3307 
3308   // FIXME: what is this about?
3309   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3310   // is set.
3311   COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3312                         "derived pointer present"));
3313   // always_do_update_barrier = true;
3314 
3315   resize_all_tlabs();
3316   allocation_context_stats().update(full);
3317 
3318   // We have just completed a GC. Update the soft reference
3319   // policy with the new heap occupancy
3320   Universe::update_heap_info_at_gc();
3321 }
3322 
3323 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3324                                                uint gc_count_before,
3325                                                bool* succeeded,
3326                                                GCCause::Cause gc_cause) {
3327   assert_heap_not_locked_and_not_at_safepoint();
3328   g1_policy()->record_stop_world_start();
3329   VM_G1IncCollectionPause op(gc_count_before,
3330                              word_size,
3331                              false, /* should_initiate_conc_mark */
3332                              g1_policy()->max_pause_time_ms(),
3333                              gc_cause);
3334 
3335   op.set_allocation_context(AllocationContext::current());
3336   VMThread::execute(&op);
3337 
3338   HeapWord* result = op.result();
3339   bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3340   assert(result == NULL || ret_succeeded,
3341          "the result should be NULL if the VM did not succeed");
3342   *succeeded = ret_succeeded;
3343 
3344   assert_heap_not_locked();
3345   return result;
3346 }
3347 
3348 void
3349 G1CollectedHeap::doConcurrentMark() {
3350   MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3351   if (!_cmThread->in_progress()) {
3352     _cmThread->set_started();
3353     CGC_lock->notify();
3354   }
3355 }
3356 
3357 size_t G1CollectedHeap::pending_card_num() {
3358   size_t extra_cards = 0;
3359   JavaThread *curr = Threads::first();
3360   while (curr != NULL) {
3361     DirtyCardQueue& dcq = curr->dirty_card_queue();
3362     extra_cards += dcq.size();
3363     curr = curr->next();
3364   }
3365   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3366   size_t buffer_size = dcqs.buffer_size();
3367   size_t buffer_num = dcqs.completed_buffers_num();
3368 
3369   // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
3370   // in bytes - not the number of 'entries'. We need to convert
3371   // into a number of cards.
3372   return (buffer_size * buffer_num + extra_cards) / oopSize;
3373 }
3374 
3375 size_t G1CollectedHeap::cards_scanned() {
3376   return g1_rem_set()->cardsScanned();
3377 }
3378 
3379 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
3380  private:
3381   size_t _total_humongous;
3382   size_t _candidate_humongous;
3383 
3384   DirtyCardQueue _dcq;
3385 
3386   // We don't nominate objects with many remembered set entries, on
3387   // the assumption that such objects are likely still live.
3388   bool is_remset_small(HeapRegion* region) const {
3389     HeapRegionRemSet* const rset = region->rem_set();
3390     return G1EagerReclaimHumongousObjectsWithStaleRefs
3391       ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries)
3392       : rset->is_empty();
3393   }
3394 
3395   bool is_typeArray_region(HeapRegion* region) const {
3396     return oop(region->bottom())->is_typeArray();
3397   }
3398 
3399   bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const {
3400     assert(region->is_starts_humongous(), "Must start a humongous object");
3401 
3402     // Candidate selection must satisfy the following constraints
3403     // while concurrent marking is in progress:
3404     //
3405     // * In order to maintain SATB invariants, an object must not be
3406     // reclaimed if it was allocated before the start of marking and
3407     // has not had its references scanned.  Such an object must have
3408     // its references (including type metadata) scanned to ensure no
3409     // live objects are missed by the marking process.  Objects
3410     // allocated after the start of concurrent marking don't need to
3411     // be scanned.
3412     //
3413     // * An object must not be reclaimed if it is on the concurrent
3414     // mark stack.  Objects allocated after the start of concurrent
3415     // marking are never pushed on the mark stack.
3416     //
3417     // Nominating only objects allocated after the start of concurrent
3418     // marking is sufficient to meet both constraints.  This may miss
3419     // some objects that satisfy the constraints, but the marking data
3420     // structures don't support efficiently performing the needed
3421     // additional tests or scrubbing of the mark stack.
3422     //
3423     // However, we presently only nominate is_typeArray() objects.
3424     // A humongous object containing references induces remembered
3425     // set entries on other regions.  In order to reclaim such an
3426     // object, those remembered sets would need to be cleaned up.
3427     //
3428     // We also treat is_typeArray() objects specially, allowing them
3429     // to be reclaimed even if allocated before the start of
3430     // concurrent mark.  For this we rely on mark stack insertion to
3431     // exclude is_typeArray() objects, preventing reclaiming an object
3432     // that is in the mark stack.  We also rely on the metadata for
3433     // such objects to be built-in and so ensured to be kept live.
3434     // Frequent allocation and drop of large binary blobs is an
3435     // important use case for eager reclaim, and this special handling
3436     // may reduce needed headroom.
3437 
3438     return is_typeArray_region(region) && is_remset_small(region);
3439   }
3440 
3441  public:
3442   RegisterHumongousWithInCSetFastTestClosure()
3443   : _total_humongous(0),
3444     _candidate_humongous(0),
3445     _dcq(&JavaThread::dirty_card_queue_set()) {
3446   }
3447 
3448   virtual bool doHeapRegion(HeapRegion* r) {
3449     if (!r->is_starts_humongous()) {
3450       return false;
3451     }
3452     G1CollectedHeap* g1h = G1CollectedHeap::heap();
3453 
3454     bool is_candidate = humongous_region_is_candidate(g1h, r);
3455     uint rindex = r->hrm_index();
3456     g1h->set_humongous_reclaim_candidate(rindex, is_candidate);
3457     if (is_candidate) {
3458       _candidate_humongous++;
3459       g1h->register_humongous_region_with_cset(rindex);
3460       // Is_candidate already filters out humongous object with large remembered sets.
3461       // If we have a humongous object with a few remembered sets, we simply flush these
3462       // remembered set entries into the DCQS. That will result in automatic
3463       // re-evaluation of their remembered set entries during the following evacuation
3464       // phase.
3465       if (!r->rem_set()->is_empty()) {
3466         guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
3467                   "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
3468         G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set();
3469         HeapRegionRemSetIterator hrrs(r->rem_set());
3470         size_t card_index;
3471         while (hrrs.has_next(card_index)) {
3472           jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index);
3473           // The remembered set might contain references to already freed
3474           // regions. Filter out such entries to avoid failing card table
3475           // verification.
3476           if (!g1h->heap_region_containing(bs->addr_for(card_ptr))->is_free()) {
3477             if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
3478               *card_ptr = CardTableModRefBS::dirty_card_val();
3479               _dcq.enqueue(card_ptr);
3480             }
3481           }
3482         }
3483         r->rem_set()->clear_locked();
3484       }
3485       assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
3486     }
3487     _total_humongous++;
3488 
3489     return false;
3490   }
3491 
3492   size_t total_humongous() const { return _total_humongous; }
3493   size_t candidate_humongous() const { return _candidate_humongous; }
3494 
3495   void flush_rem_set_entries() { _dcq.flush(); }
3496 };
3497 
3498 void G1CollectedHeap::register_humongous_regions_with_cset() {
3499   if (!G1EagerReclaimHumongousObjects) {
3500     g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
3501     return;
3502   }
3503   double time = os::elapsed_counter();
3504 
3505   // Collect reclaim candidate information and register candidates with cset.
3506   RegisterHumongousWithInCSetFastTestClosure cl;
3507   heap_region_iterate(&cl);
3508 
3509   time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
3510   g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
3511                                                                   cl.total_humongous(),
3512                                                                   cl.candidate_humongous());
3513   _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
3514 
3515   // Finally flush all remembered set entries to re-check into the global DCQS.
3516   cl.flush_rem_set_entries();
3517 }
3518 
3519 void
3520 G1CollectedHeap::setup_surviving_young_words() {
3521   assert(_surviving_young_words == NULL, "pre-condition");
3522   uint array_length = g1_policy()->young_cset_region_length();
3523   _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3524   if (_surviving_young_words == NULL) {
3525     vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR,
3526                           "Not enough space for young surv words summary.");
3527   }
3528   memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3529 #ifdef ASSERT
3530   for (uint i = 0;  i < array_length; ++i) {
3531     assert( _surviving_young_words[i] == 0, "memset above" );
3532   }
3533 #endif // !ASSERT
3534 }
3535 
3536 void
3537 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3538   MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3539   uint array_length = g1_policy()->young_cset_region_length();
3540   for (uint i = 0; i < array_length; ++i) {
3541     _surviving_young_words[i] += surv_young_words[i];
3542   }
3543 }
3544 
3545 void
3546 G1CollectedHeap::cleanup_surviving_young_words() {
3547   guarantee( _surviving_young_words != NULL, "pre-condition" );
3548   FREE_C_HEAP_ARRAY(size_t, _surviving_young_words);
3549   _surviving_young_words = NULL;
3550 }
3551 
3552 #ifdef ASSERT
3553 class VerifyCSetClosure: public HeapRegionClosure {
3554 public:
3555   bool doHeapRegion(HeapRegion* hr) {
3556     // Here we check that the CSet region's RSet is ready for parallel
3557     // iteration. The fields that we'll verify are only manipulated
3558     // when the region is part of a CSet and is collected. Afterwards,
3559     // we reset these fields when we clear the region's RSet (when the
3560     // region is freed) so they are ready when the region is
3561     // re-allocated. The only exception to this is if there's an
3562     // evacuation failure and instead of freeing the region we leave
3563     // it in the heap. In that case, we reset these fields during
3564     // evacuation failure handling.
3565     guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3566 
3567     // Here's a good place to add any other checks we'd like to
3568     // perform on CSet regions.
3569     return false;
3570   }
3571 };
3572 #endif // ASSERT
3573 
3574 #if TASKQUEUE_STATS
3575 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3576   st->print_raw_cr("GC Task Stats");
3577   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3578   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3579 }
3580 
3581 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3582   print_taskqueue_stats_hdr(st);
3583 
3584   TaskQueueStats totals;
3585   const uint n = workers()->total_workers();
3586   for (uint i = 0; i < n; ++i) {
3587     st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
3588     totals += task_queue(i)->stats;
3589   }
3590   st->print_raw("tot "); totals.print(st); st->cr();
3591 
3592   DEBUG_ONLY(totals.verify());
3593 }
3594 
3595 void G1CollectedHeap::reset_taskqueue_stats() {
3596   const uint n = workers()->total_workers();
3597   for (uint i = 0; i < n; ++i) {
3598     task_queue(i)->stats.reset();
3599   }
3600 }
3601 #endif // TASKQUEUE_STATS
3602 
3603 void G1CollectedHeap::log_gc_header() {
3604   if (!G1Log::fine()) {
3605     return;
3606   }
3607 
3608   gclog_or_tty->gclog_stamp(_gc_tracer_stw->gc_id());
3609 
3610   GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
3611     .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)")
3612     .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : "");
3613 
3614   gclog_or_tty->print("[%s", (const char*)gc_cause_str);
3615 }
3616 
3617 void G1CollectedHeap::log_gc_footer(double pause_time_sec) {
3618   if (!G1Log::fine()) {
3619     return;
3620   }
3621 
3622   if (G1Log::finer()) {
3623     if (evacuation_failed()) {
3624       gclog_or_tty->print(" (to-space exhausted)");
3625     }
3626     gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3627     g1_policy()->phase_times()->note_gc_end();
3628     g1_policy()->phase_times()->print(pause_time_sec);
3629     g1_policy()->print_detailed_heap_transition();
3630   } else {
3631     if (evacuation_failed()) {
3632       gclog_or_tty->print("--");
3633     }
3634     g1_policy()->print_heap_transition();
3635     gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3636   }
3637   gclog_or_tty->flush();
3638 }
3639 
3640 bool
3641 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3642   assert_at_safepoint(true /* should_be_vm_thread */);
3643   guarantee(!is_gc_active(), "collection is not reentrant");
3644 
3645   if (GC_locker::check_active_before_gc()) {
3646     return false;
3647   }
3648 
3649   _gc_timer_stw->register_gc_start();
3650 
3651   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3652 
3653   SvcGCMarker sgcm(SvcGCMarker::MINOR);
3654   ResourceMark rm;
3655 
3656   G1Log::update_level();
3657   print_heap_before_gc();
3658   trace_heap_before_gc(_gc_tracer_stw);
3659 
3660   verify_region_sets_optional();
3661   verify_dirty_young_regions();
3662 
3663   // This call will decide whether this pause is an initial-mark
3664   // pause. If it is, during_initial_mark_pause() will return true
3665   // for the duration of this pause.
3666   g1_policy()->decide_on_conc_mark_initiation();
3667 
3668   // We do not allow initial-mark to be piggy-backed on a mixed GC.
3669   assert(!g1_policy()->during_initial_mark_pause() ||
3670           g1_policy()->gcs_are_young(), "sanity");
3671 
3672   // We also do not allow mixed GCs during marking.
3673   assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3674 
3675   // Record whether this pause is an initial mark. When the current
3676   // thread has completed its logging output and it's safe to signal
3677   // the CM thread, the flag's value in the policy has been reset.
3678   bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3679 
3680   // Inner scope for scope based logging, timers, and stats collection
3681   {
3682     EvacuationInfo evacuation_info;
3683 
3684     if (g1_policy()->during_initial_mark_pause()) {
3685       // We are about to start a marking cycle, so we increment the
3686       // full collection counter.
3687       increment_old_marking_cycles_started();
3688       register_concurrent_cycle_start(_gc_timer_stw->gc_start());
3689     }
3690 
3691     _gc_tracer_stw->report_yc_type(yc_type());
3692 
3693     TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3694 
3695     uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
3696                                                                   workers()->active_workers(),
3697                                                                   Threads::number_of_non_daemon_threads());
3698     assert(UseDynamicNumberOfGCThreads ||
3699            active_workers == workers()->total_workers(),
3700            "If not dynamic should be using all the  workers");
3701     workers()->set_active_workers(active_workers);
3702 
3703     double pause_start_sec = os::elapsedTime();
3704     g1_policy()->phase_times()->note_gc_start(active_workers, mark_in_progress());
3705     log_gc_header();
3706 
3707     TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3708     TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3709 
3710     // If the secondary_free_list is not empty, append it to the
3711     // free_list. No need to wait for the cleanup operation to finish;
3712     // the region allocation code will check the secondary_free_list
3713     // and wait if necessary. If the G1StressConcRegionFreeing flag is
3714     // set, skip this step so that the region allocation code has to
3715     // get entries from the secondary_free_list.
3716     if (!G1StressConcRegionFreeing) {
3717       append_secondary_free_list_if_not_empty_with_lock();
3718     }
3719 
3720     assert(check_young_list_well_formed(), "young list should be well formed");
3721 
3722     // Don't dynamically change the number of GC threads this early.  A value of
3723     // 0 is used to indicate serial work.  When parallel work is done,
3724     // it will be set.
3725 
3726     { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3727       IsGCActiveMark x;
3728 
3729       gc_prologue(false);
3730       increment_total_collections(false /* full gc */);
3731       increment_gc_time_stamp();
3732 
3733       verify_before_gc();
3734 
3735       check_bitmaps("GC Start");
3736 
3737       COMPILER2_PRESENT(DerivedPointerTable::clear());
3738 
3739       // Please see comment in g1CollectedHeap.hpp and
3740       // G1CollectedHeap::ref_processing_init() to see how
3741       // reference processing currently works in G1.
3742 
3743       // Enable discovery in the STW reference processor
3744       ref_processor_stw()->enable_discovery();
3745 
3746       {
3747         // We want to temporarily turn off discovery by the
3748         // CM ref processor, if necessary, and turn it back on
3749         // on again later if we do. Using a scoped
3750         // NoRefDiscovery object will do this.
3751         NoRefDiscovery no_cm_discovery(ref_processor_cm());
3752 
3753         // Forget the current alloc region (we might even choose it to be part
3754         // of the collection set!).
3755         _allocator->release_mutator_alloc_region();
3756 
3757         // We should call this after we retire the mutator alloc
3758         // region(s) so that all the ALLOC / RETIRE events are generated
3759         // before the start GC event.
3760         _hr_printer.start_gc(false /* full */, (size_t) total_collections());
3761 
3762         // This timing is only used by the ergonomics to handle our pause target.
3763         // It is unclear why this should not include the full pause. We will
3764         // investigate this in CR 7178365.
3765         //
3766         // Preserving the old comment here if that helps the investigation:
3767         //
3768         // The elapsed time induced by the start time below deliberately elides
3769         // the possible verification above.
3770         double sample_start_time_sec = os::elapsedTime();
3771 
3772 #if YOUNG_LIST_VERBOSE
3773         gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
3774         _young_list->print();
3775         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3776 #endif // YOUNG_LIST_VERBOSE
3777 
3778         g1_policy()->record_collection_pause_start(sample_start_time_sec);
3779 
3780         double scan_wait_start = os::elapsedTime();
3781         // We have to wait until the CM threads finish scanning the
3782         // root regions as it's the only way to ensure that all the
3783         // objects on them have been correctly scanned before we start
3784         // moving them during the GC.
3785         bool waited = _cm->root_regions()->wait_until_scan_finished();
3786         double wait_time_ms = 0.0;
3787         if (waited) {
3788           double scan_wait_end = os::elapsedTime();
3789           wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
3790         }
3791         g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
3792 
3793 #if YOUNG_LIST_VERBOSE
3794         gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
3795         _young_list->print();
3796 #endif // YOUNG_LIST_VERBOSE
3797 
3798         if (g1_policy()->during_initial_mark_pause()) {
3799           concurrent_mark()->checkpointRootsInitialPre();
3800         }
3801 
3802 #if YOUNG_LIST_VERBOSE
3803         gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
3804         _young_list->print();
3805         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3806 #endif // YOUNG_LIST_VERBOSE
3807 
3808         g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info);
3809 
3810         register_humongous_regions_with_cset();
3811 
3812         assert(check_cset_fast_test(), "Inconsistency in the InCSetState table.");
3813 
3814         _cm->note_start_of_gc();
3815         // We call this after finalize_cset() to
3816         // ensure that the CSet has been finalized.
3817         _cm->verify_no_cset_oops();
3818 
3819         if (_hr_printer.is_active()) {
3820           HeapRegion* hr = g1_policy()->collection_set();
3821           while (hr != NULL) {
3822             _hr_printer.cset(hr);
3823             hr = hr->next_in_collection_set();
3824           }
3825         }
3826 
3827 #ifdef ASSERT
3828         VerifyCSetClosure cl;
3829         collection_set_iterate(&cl);
3830 #endif // ASSERT
3831 
3832         setup_surviving_young_words();
3833 
3834         // Initialize the GC alloc regions.
3835         _allocator->init_gc_alloc_regions(evacuation_info);
3836 
3837         // Actually do the work...
3838         evacuate_collection_set(evacuation_info);
3839 
3840         free_collection_set(g1_policy()->collection_set(), evacuation_info);
3841 
3842         eagerly_reclaim_humongous_regions();
3843 
3844         g1_policy()->clear_collection_set();
3845 
3846         cleanup_surviving_young_words();
3847 
3848         // Start a new incremental collection set for the next pause.
3849         g1_policy()->start_incremental_cset_building();
3850 
3851         clear_cset_fast_test();
3852 
3853         _young_list->reset_sampled_info();
3854 
3855         // Don't check the whole heap at this point as the
3856         // GC alloc regions from this pause have been tagged
3857         // as survivors and moved on to the survivor list.
3858         // Survivor regions will fail the !is_young() check.
3859         assert(check_young_list_empty(false /* check_heap */),
3860           "young list should be empty");
3861 
3862 #if YOUNG_LIST_VERBOSE
3863         gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
3864         _young_list->print();
3865 #endif // YOUNG_LIST_VERBOSE
3866 
3867         g1_policy()->record_survivor_regions(_young_list->survivor_length(),
3868                                              _young_list->first_survivor_region(),
3869                                              _young_list->last_survivor_region());
3870 
3871         _young_list->reset_auxilary_lists();
3872 
3873         if (evacuation_failed()) {
3874           _allocator->set_used(recalculate_used());
3875           uint n_queues = MAX2((int)ParallelGCThreads, 1);
3876           for (uint i = 0; i < n_queues; i++) {
3877             if (_evacuation_failed_info_array[i].has_failed()) {
3878               _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
3879             }
3880           }
3881         } else {
3882           // The "used" of the the collection set have already been subtracted
3883           // when they were freed.  Add in the bytes evacuated.
3884           _allocator->increase_used(g1_policy()->bytes_copied_during_gc());
3885         }
3886 
3887         if (g1_policy()->during_initial_mark_pause()) {
3888           // We have to do this before we notify the CM threads that
3889           // they can start working to make sure that all the
3890           // appropriate initialization is done on the CM object.
3891           concurrent_mark()->checkpointRootsInitialPost();
3892           set_marking_started();
3893           // Note that we don't actually trigger the CM thread at
3894           // this point. We do that later when we're sure that
3895           // the current thread has completed its logging output.
3896         }
3897 
3898         allocate_dummy_regions();
3899 
3900 #if YOUNG_LIST_VERBOSE
3901         gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
3902         _young_list->print();
3903         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3904 #endif // YOUNG_LIST_VERBOSE
3905 
3906         _allocator->init_mutator_alloc_region();
3907 
3908         {
3909           size_t expand_bytes = g1_policy()->expansion_amount();
3910           if (expand_bytes > 0) {
3911             size_t bytes_before = capacity();
3912             // No need for an ergo verbose message here,
3913             // expansion_amount() does this when it returns a value > 0.
3914             if (!expand(expand_bytes)) {
3915               // We failed to expand the heap. Cannot do anything about it.
3916             }
3917           }
3918         }
3919 
3920         // We redo the verification but now wrt to the new CSet which
3921         // has just got initialized after the previous CSet was freed.
3922         _cm->verify_no_cset_oops();
3923         _cm->note_end_of_gc();
3924 
3925         // This timing is only used by the ergonomics to handle our pause target.
3926         // It is unclear why this should not include the full pause. We will
3927         // investigate this in CR 7178365.
3928         double sample_end_time_sec = os::elapsedTime();
3929         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3930         g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info);
3931 
3932         MemoryService::track_memory_usage();
3933 
3934         // In prepare_for_verify() below we'll need to scan the deferred
3935         // update buffers to bring the RSets up-to-date if
3936         // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
3937         // the update buffers we'll probably need to scan cards on the
3938         // regions we just allocated to (i.e., the GC alloc
3939         // regions). However, during the last GC we called
3940         // set_saved_mark() on all the GC alloc regions, so card
3941         // scanning might skip the [saved_mark_word()...top()] area of
3942         // those regions (i.e., the area we allocated objects into
3943         // during the last GC). But it shouldn't. Given that
3944         // saved_mark_word() is conditional on whether the GC time stamp
3945         // on the region is current or not, by incrementing the GC time
3946         // stamp here we invalidate all the GC time stamps on all the
3947         // regions and saved_mark_word() will simply return top() for
3948         // all the regions. This is a nicer way of ensuring this rather
3949         // than iterating over the regions and fixing them. In fact, the
3950         // GC time stamp increment here also ensures that
3951         // saved_mark_word() will return top() between pauses, i.e.,
3952         // during concurrent refinement. So we don't need the
3953         // is_gc_active() check to decided which top to use when
3954         // scanning cards (see CR 7039627).
3955         increment_gc_time_stamp();
3956 
3957         verify_after_gc();
3958         check_bitmaps("GC End");
3959 
3960         assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
3961         ref_processor_stw()->verify_no_references_recorded();
3962 
3963         // CM reference discovery will be re-enabled if necessary.
3964       }
3965 
3966       // We should do this after we potentially expand the heap so
3967       // that all the COMMIT events are generated before the end GC
3968       // event, and after we retire the GC alloc regions so that all
3969       // RETIRE events are generated before the end GC event.
3970       _hr_printer.end_gc(false /* full */, (size_t) total_collections());
3971 
3972 #ifdef TRACESPINNING
3973       ParallelTaskTerminator::print_termination_counts();
3974 #endif
3975 
3976       gc_epilogue(false);
3977     }
3978 
3979     // Print the remainder of the GC log output.
3980     log_gc_footer(os::elapsedTime() - pause_start_sec);
3981 
3982     // It is not yet to safe to tell the concurrent mark to
3983     // start as we have some optional output below. We don't want the
3984     // output from the concurrent mark thread interfering with this
3985     // logging output either.
3986 
3987     _hrm.verify_optional();
3988     verify_region_sets_optional();
3989 
3990     TASKQUEUE_STATS_ONLY(if (PrintTaskqueue) print_taskqueue_stats());
3991     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3992 
3993     print_heap_after_gc();
3994     trace_heap_after_gc(_gc_tracer_stw);
3995 
3996     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3997     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3998     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3999     // before any GC notifications are raised.
4000     g1mm()->update_sizes();
4001 
4002     _gc_tracer_stw->report_evacuation_info(&evacuation_info);
4003     _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
4004     _gc_timer_stw->register_gc_end();
4005     _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
4006   }
4007   // It should now be safe to tell the concurrent mark thread to start
4008   // without its logging output interfering with the logging output
4009   // that came from the pause.
4010 
4011   if (should_start_conc_mark) {
4012     // CAUTION: after the doConcurrentMark() call below,
4013     // the concurrent marking thread(s) could be running
4014     // concurrently with us. Make sure that anything after
4015     // this point does not assume that we are the only GC thread
4016     // running. Note: of course, the actual marking work will
4017     // not start until the safepoint itself is released in
4018     // SuspendibleThreadSet::desynchronize().
4019     doConcurrentMark();
4020   }
4021 
4022   return true;
4023 }
4024 
4025 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4026   _drain_in_progress = false;
4027   set_evac_failure_closure(cl);
4028   _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4029 }
4030 
4031 void G1CollectedHeap::finalize_for_evac_failure() {
4032   assert(_evac_failure_scan_stack != NULL &&
4033          _evac_failure_scan_stack->length() == 0,
4034          "Postcondition");
4035   assert(!_drain_in_progress, "Postcondition");
4036   delete _evac_failure_scan_stack;
4037   _evac_failure_scan_stack = NULL;
4038 }
4039 
4040 void G1CollectedHeap::remove_self_forwarding_pointers() {
4041   double remove_self_forwards_start = os::elapsedTime();
4042 
4043   set_par_threads();
4044   G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4045   workers()->run_task(&rsfp_task);
4046   set_par_threads(0);
4047 
4048   // Now restore saved marks, if any.
4049   assert(_objs_with_preserved_marks.size() ==
4050             _preserved_marks_of_objs.size(), "Both or none.");
4051   while (!_objs_with_preserved_marks.is_empty()) {
4052     oop obj = _objs_with_preserved_marks.pop();
4053     markOop m = _preserved_marks_of_objs.pop();
4054     obj->set_mark(m);
4055   }
4056   _objs_with_preserved_marks.clear(true);
4057   _preserved_marks_of_objs.clear(true);
4058 
4059   g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
4060 }
4061 
4062 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4063   _evac_failure_scan_stack->push(obj);
4064 }
4065 
4066 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4067   assert(_evac_failure_scan_stack != NULL, "precondition");
4068 
4069   while (_evac_failure_scan_stack->length() > 0) {
4070      oop obj = _evac_failure_scan_stack->pop();
4071      _evac_failure_closure->set_region(heap_region_containing(obj));
4072      obj->oop_iterate_backwards(_evac_failure_closure);
4073   }
4074 }
4075 
4076 oop
4077 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state,
4078                                                oop old) {
4079   assert(obj_in_cs(old),
4080          err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4081                  p2i(old)));
4082   markOop m = old->mark();
4083   oop forward_ptr = old->forward_to_atomic(old);
4084   if (forward_ptr == NULL) {
4085     // Forward-to-self succeeded.
4086     assert(_par_scan_state != NULL, "par scan state");
4087     OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4088     uint queue_num = _par_scan_state->queue_num();
4089 
4090     _evacuation_failed = true;
4091     _evacuation_failed_info_array[queue_num].register_copy_failure(old->size());
4092     if (_evac_failure_closure != cl) {
4093       MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4094       assert(!_drain_in_progress,
4095              "Should only be true while someone holds the lock.");
4096       // Set the global evac-failure closure to the current thread's.
4097       assert(_evac_failure_closure == NULL, "Or locking has failed.");
4098       set_evac_failure_closure(cl);
4099       // Now do the common part.
4100       handle_evacuation_failure_common(old, m);
4101       // Reset to NULL.
4102       set_evac_failure_closure(NULL);
4103     } else {
4104       // The lock is already held, and this is recursive.
4105       assert(_drain_in_progress, "This should only be the recursive case.");
4106       handle_evacuation_failure_common(old, m);
4107     }
4108     return old;
4109   } else {
4110     // Forward-to-self failed. Either someone else managed to allocate
4111     // space for this object (old != forward_ptr) or they beat us in
4112     // self-forwarding it (old == forward_ptr).
4113     assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4114            err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4115                    "should not be in the CSet",
4116                    p2i(old), p2i(forward_ptr)));
4117     return forward_ptr;
4118   }
4119 }
4120 
4121 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4122   preserve_mark_if_necessary(old, m);
4123 
4124   HeapRegion* r = heap_region_containing(old);
4125   if (!r->evacuation_failed()) {
4126     r->set_evacuation_failed(true);
4127     _hr_printer.evac_failure(r);
4128   }
4129 
4130   push_on_evac_failure_scan_stack(old);
4131 
4132   if (!_drain_in_progress) {
4133     // prevent recursion in copy_to_survivor_space()
4134     _drain_in_progress = true;
4135     drain_evac_failure_scan_stack();
4136     _drain_in_progress = false;
4137   }
4138 }
4139 
4140 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4141   assert(evacuation_failed(), "Oversaving!");
4142   // We want to call the "for_promotion_failure" version only in the
4143   // case of a promotion failure.
4144   if (m->must_be_preserved_for_promotion_failure(obj)) {
4145     _objs_with_preserved_marks.push(obj);
4146     _preserved_marks_of_objs.push(m);
4147   }
4148 }
4149 
4150 void G1ParCopyHelper::mark_object(oop obj) {
4151   assert(!_g1->heap_region_containing(obj)->in_collection_set(), "should not mark objects in the CSet");
4152 
4153   // We know that the object is not moving so it's safe to read its size.
4154   _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4155 }
4156 
4157 void G1ParCopyHelper::mark_forwarded_object(oop from_obj, oop to_obj) {
4158   assert(from_obj->is_forwarded(), "from obj should be forwarded");
4159   assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4160   assert(from_obj != to_obj, "should not be self-forwarded");
4161 
4162   assert(_g1->heap_region_containing(from_obj)->in_collection_set(), "from obj should be in the CSet");
4163   assert(!_g1->heap_region_containing(to_obj)->in_collection_set(), "should not mark objects in the CSet");
4164 
4165   // The object might be in the process of being copied by another
4166   // worker so we cannot trust that its to-space image is
4167   // well-formed. So we have to read its size from its from-space
4168   // image which we know should not be changing.
4169   _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4170 }
4171 
4172 template <class T>
4173 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) {
4174   if (_g1->heap_region_containing_raw(new_obj)->is_young()) {
4175     _scanned_klass->record_modified_oops();
4176   }
4177 }
4178 
4179 template <G1Barrier barrier, G1Mark do_mark_object>
4180 template <class T>
4181 void G1ParCopyClosure<barrier, do_mark_object>::do_oop_work(T* p) {
4182   T heap_oop = oopDesc::load_heap_oop(p);
4183 
4184   if (oopDesc::is_null(heap_oop)) {
4185     return;
4186   }
4187 
4188   oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
4189 
4190   assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4191 
4192   const InCSetState state = _g1->in_cset_state(obj);
4193   if (state.is_in_cset()) {
4194     oop forwardee;
4195     markOop m = obj->mark();
4196     if (m->is_marked()) {
4197       forwardee = (oop) m->decode_pointer();
4198     } else {
4199       forwardee = _par_scan_state->copy_to_survivor_space(state, obj, m);
4200     }
4201     assert(forwardee != NULL, "forwardee should not be NULL");
4202     oopDesc::encode_store_heap_oop(p, forwardee);
4203     if (do_mark_object != G1MarkNone && forwardee != obj) {
4204       // If the object is self-forwarded we don't need to explicitly
4205       // mark it, the evacuation failure protocol will do so.
4206       mark_forwarded_object(obj, forwardee);
4207     }
4208 
4209     if (barrier == G1BarrierKlass) {
4210       do_klass_barrier(p, forwardee);
4211     }
4212   } else {
4213     if (state.is_humongous()) {
4214       _g1->set_humongous_is_live(obj);
4215     }
4216     // The object is not in collection set. If we're a root scanning
4217     // closure during an initial mark pause then attempt to mark the object.
4218     if (do_mark_object == G1MarkFromRoot) {
4219       mark_object(obj);
4220     }
4221   }
4222 
4223   if (barrier == G1BarrierEvac) {
4224     _par_scan_state->update_rs(_from, p, _worker_id);
4225   }
4226 }
4227 
4228 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(oop* p);
4229 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(narrowOop* p);
4230 
4231 class G1ParEvacuateFollowersClosure : public VoidClosure {
4232 protected:
4233   G1CollectedHeap*              _g1h;
4234   G1ParScanThreadState*         _par_scan_state;
4235   RefToScanQueueSet*            _queues;
4236   ParallelTaskTerminator*       _terminator;
4237 
4238   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
4239   RefToScanQueueSet*      queues()         { return _queues; }
4240   ParallelTaskTerminator* terminator()     { return _terminator; }
4241 
4242 public:
4243   G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4244                                 G1ParScanThreadState* par_scan_state,
4245                                 RefToScanQueueSet* queues,
4246                                 ParallelTaskTerminator* terminator)
4247     : _g1h(g1h), _par_scan_state(par_scan_state),
4248       _queues(queues), _terminator(terminator) {}
4249 
4250   void do_void();
4251 
4252 private:
4253   inline bool offer_termination();
4254 };
4255 
4256 bool G1ParEvacuateFollowersClosure::offer_termination() {
4257   G1ParScanThreadState* const pss = par_scan_state();
4258   pss->start_term_time();
4259   const bool res = terminator()->offer_termination();
4260   pss->end_term_time();
4261   return res;
4262 }
4263 
4264 void G1ParEvacuateFollowersClosure::do_void() {
4265   G1ParScanThreadState* const pss = par_scan_state();
4266   pss->trim_queue();
4267   do {
4268     pss->steal_and_trim_queue(queues());
4269   } while (!offer_termination());
4270 }
4271 
4272 class G1KlassScanClosure : public KlassClosure {
4273  G1ParCopyHelper* _closure;
4274  bool             _process_only_dirty;
4275  int              _count;
4276  public:
4277   G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty)
4278       : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {}
4279   void do_klass(Klass* klass) {
4280     // If the klass has not been dirtied we know that there's
4281     // no references into  the young gen and we can skip it.
4282    if (!_process_only_dirty || klass->has_modified_oops()) {
4283       // Clean the klass since we're going to scavenge all the metadata.
4284       klass->clear_modified_oops();
4285 
4286       // Tell the closure that this klass is the Klass to scavenge
4287       // and is the one to dirty if oops are left pointing into the young gen.
4288       _closure->set_scanned_klass(klass);
4289 
4290       klass->oops_do(_closure);
4291 
4292       _closure->set_scanned_klass(NULL);
4293     }
4294     _count++;
4295   }
4296 };
4297 
4298 class G1ParTask : public AbstractGangTask {
4299 protected:
4300   G1CollectedHeap*       _g1h;
4301   RefToScanQueueSet      *_queues;
4302   G1RootProcessor*       _root_processor;
4303   ParallelTaskTerminator _terminator;
4304   uint _n_workers;
4305 
4306   Mutex _stats_lock;
4307   Mutex* stats_lock() { return &_stats_lock; }
4308 
4309 public:
4310   G1ParTask(G1CollectedHeap* g1h, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor)
4311     : AbstractGangTask("G1 collection"),
4312       _g1h(g1h),
4313       _queues(task_queues),
4314       _root_processor(root_processor),
4315       _terminator(0, _queues),
4316       _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4317   {}
4318 
4319   RefToScanQueueSet* queues() { return _queues; }
4320 
4321   RefToScanQueue *work_queue(int i) {
4322     return queues()->queue(i);
4323   }
4324 
4325   ParallelTaskTerminator* terminator() { return &_terminator; }
4326 
4327   virtual void set_for_termination(uint active_workers) {
4328     _root_processor->set_num_workers(active_workers);
4329     terminator()->reset_for_reuse(active_workers);
4330     _n_workers = active_workers;
4331   }
4332 
4333   // Helps out with CLD processing.
4334   //
4335   // During InitialMark we need to:
4336   // 1) Scavenge all CLDs for the young GC.
4337   // 2) Mark all objects directly reachable from strong CLDs.
4338   template <G1Mark do_mark_object>
4339   class G1CLDClosure : public CLDClosure {
4340     G1ParCopyClosure<G1BarrierNone,  do_mark_object>* _oop_closure;
4341     G1ParCopyClosure<G1BarrierKlass, do_mark_object>  _oop_in_klass_closure;
4342     G1KlassScanClosure                                _klass_in_cld_closure;
4343     bool                                              _claim;
4344 
4345    public:
4346     G1CLDClosure(G1ParCopyClosure<G1BarrierNone, do_mark_object>* oop_closure,
4347                  bool only_young, bool claim)
4348         : _oop_closure(oop_closure),
4349           _oop_in_klass_closure(oop_closure->g1(),
4350                                 oop_closure->pss(),
4351                                 oop_closure->rp()),
4352           _klass_in_cld_closure(&_oop_in_klass_closure, only_young),
4353           _claim(claim) {
4354 
4355     }
4356 
4357     void do_cld(ClassLoaderData* cld) {
4358       cld->oops_do(_oop_closure, &_klass_in_cld_closure, _claim);
4359     }
4360   };
4361 
4362   void work(uint worker_id) {
4363     if (worker_id >= _n_workers) return;  // no work needed this round
4364 
4365     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, os::elapsedTime());
4366 
4367     {
4368       ResourceMark rm;
4369       HandleMark   hm;
4370 
4371       ReferenceProcessor*             rp = _g1h->ref_processor_stw();
4372 
4373       G1ParScanThreadState            pss(_g1h, worker_id, rp);
4374       G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
4375 
4376       pss.set_evac_failure_closure(&evac_failure_cl);
4377 
4378       bool only_young = _g1h->g1_policy()->gcs_are_young();
4379 
4380       // Non-IM young GC.
4381       G1ParCopyClosure<G1BarrierNone, G1MarkNone>             scan_only_root_cl(_g1h, &pss, rp);
4382       G1CLDClosure<G1MarkNone>                                scan_only_cld_cl(&scan_only_root_cl,
4383                                                                                only_young, // Only process dirty klasses.
4384                                                                                false);     // No need to claim CLDs.
4385       // IM young GC.
4386       //    Strong roots closures.
4387       G1ParCopyClosure<G1BarrierNone, G1MarkFromRoot>         scan_mark_root_cl(_g1h, &pss, rp);
4388       G1CLDClosure<G1MarkFromRoot>                            scan_mark_cld_cl(&scan_mark_root_cl,
4389                                                                                false, // Process all klasses.
4390                                                                                true); // Need to claim CLDs.
4391       //    Weak roots closures.
4392       G1ParCopyClosure<G1BarrierNone, G1MarkPromotedFromRoot> scan_mark_weak_root_cl(_g1h, &pss, rp);
4393       G1CLDClosure<G1MarkPromotedFromRoot>                    scan_mark_weak_cld_cl(&scan_mark_weak_root_cl,
4394                                                                                     false, // Process all klasses.
4395                                                                                     true); // Need to claim CLDs.
4396 
4397       OopClosure* strong_root_cl;
4398       OopClosure* weak_root_cl;
4399       CLDClosure* strong_cld_cl;
4400       CLDClosure* weak_cld_cl;
4401 
4402       bool trace_metadata = false;
4403 
4404       if (_g1h->g1_policy()->during_initial_mark_pause()) {
4405         // We also need to mark copied objects.
4406         strong_root_cl = &scan_mark_root_cl;
4407         strong_cld_cl  = &scan_mark_cld_cl;
4408         if (ClassUnloadingWithConcurrentMark) {
4409           weak_root_cl = &scan_mark_weak_root_cl;
4410           weak_cld_cl  = &scan_mark_weak_cld_cl;
4411           trace_metadata = true;
4412         } else {
4413           weak_root_cl = &scan_mark_root_cl;
4414           weak_cld_cl  = &scan_mark_cld_cl;
4415         }
4416       } else {
4417         strong_root_cl = &scan_only_root_cl;
4418         weak_root_cl   = &scan_only_root_cl;
4419         strong_cld_cl  = &scan_only_cld_cl;
4420         weak_cld_cl    = &scan_only_cld_cl;
4421       }
4422 
4423       pss.start_strong_roots();
4424 
4425       _root_processor->evacuate_roots(strong_root_cl,
4426                                       weak_root_cl,
4427                                       strong_cld_cl,
4428                                       weak_cld_cl,
4429                                       trace_metadata,
4430                                       worker_id);
4431 
4432       G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss);
4433       _root_processor->scan_remembered_sets(&push_heap_rs_cl,
4434                                             weak_root_cl,
4435                                             worker_id);
4436       pss.end_strong_roots();
4437 
4438       {
4439         double start = os::elapsedTime();
4440         G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4441         evac.do_void();
4442         double elapsed_sec = os::elapsedTime() - start;
4443         double term_sec = pss.term_time();
4444         _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec);
4445         _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec);
4446         _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, pss.term_attempts());
4447       }
4448       _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4449       _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4450 
4451       if (PrintTerminationStats) {
4452         MutexLocker x(stats_lock());
4453         pss.print_termination_stats(worker_id);
4454       }
4455 
4456       assert(pss.queue_is_empty(), "should be empty");
4457 
4458       // Close the inner scope so that the ResourceMark and HandleMark
4459       // destructors are executed here and are included as part of the
4460       // "GC Worker Time".
4461     }
4462     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime());
4463   }
4464 };
4465 
4466 class G1StringSymbolTableUnlinkTask : public AbstractGangTask {
4467 private:
4468   BoolObjectClosure* _is_alive;
4469   int _initial_string_table_size;
4470   int _initial_symbol_table_size;
4471 
4472   bool  _process_strings;
4473   int _strings_processed;
4474   int _strings_removed;
4475 
4476   bool  _process_symbols;
4477   int _symbols_processed;
4478   int _symbols_removed;
4479 
4480 public:
4481   G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) :
4482     AbstractGangTask("String/Symbol Unlinking"),
4483     _is_alive(is_alive),
4484     _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
4485     _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) {
4486 
4487     _initial_string_table_size = StringTable::the_table()->table_size();
4488     _initial_symbol_table_size = SymbolTable::the_table()->table_size();
4489     if (process_strings) {
4490       StringTable::clear_parallel_claimed_index();
4491     }
4492     if (process_symbols) {
4493       SymbolTable::clear_parallel_claimed_index();
4494     }
4495   }
4496 
4497   ~G1StringSymbolTableUnlinkTask() {
4498     guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size,
4499               err_msg("claim value %d after unlink less than initial string table size %d",
4500                       StringTable::parallel_claimed_index(), _initial_string_table_size));
4501     guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
4502               err_msg("claim value %d after unlink less than initial symbol table size %d",
4503                       SymbolTable::parallel_claimed_index(), _initial_symbol_table_size));
4504 
4505     if (G1TraceStringSymbolTableScrubbing) {
4506       gclog_or_tty->print_cr("Cleaned string and symbol table, "
4507                              "strings: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed, "
4508                              "symbols: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed",
4509                              strings_processed(), strings_removed(),
4510                              symbols_processed(), symbols_removed());
4511     }
4512   }
4513 
4514   void work(uint worker_id) {
4515     int strings_processed = 0;
4516     int strings_removed = 0;
4517     int symbols_processed = 0;
4518     int symbols_removed = 0;
4519     if (_process_strings) {
4520       StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
4521       Atomic::add(strings_processed, &_strings_processed);
4522       Atomic::add(strings_removed, &_strings_removed);
4523     }
4524     if (_process_symbols) {
4525       SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
4526       Atomic::add(symbols_processed, &_symbols_processed);
4527       Atomic::add(symbols_removed, &_symbols_removed);
4528     }
4529   }
4530 
4531   size_t strings_processed() const { return (size_t)_strings_processed; }
4532   size_t strings_removed()   const { return (size_t)_strings_removed; }
4533 
4534   size_t symbols_processed() const { return (size_t)_symbols_processed; }
4535   size_t symbols_removed()   const { return (size_t)_symbols_removed; }
4536 };
4537 
4538 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
4539 private:
4540   static Monitor* _lock;
4541 
4542   BoolObjectClosure* const _is_alive;
4543   const bool               _unloading_occurred;
4544   const uint               _num_workers;
4545 
4546   // Variables used to claim nmethods.
4547   nmethod* _first_nmethod;
4548   volatile nmethod* _claimed_nmethod;
4549 
4550   // The list of nmethods that need to be processed by the second pass.
4551   volatile nmethod* _postponed_list;
4552   volatile uint     _num_entered_barrier;
4553 
4554  public:
4555   G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
4556       _is_alive(is_alive),
4557       _unloading_occurred(unloading_occurred),
4558       _num_workers(num_workers),
4559       _first_nmethod(NULL),
4560       _claimed_nmethod(NULL),
4561       _postponed_list(NULL),
4562       _num_entered_barrier(0)
4563   {
4564     nmethod::increase_unloading_clock();
4565     // Get first alive nmethod
4566     NMethodIterator iter = NMethodIterator();
4567     if(iter.next_alive()) {
4568       _first_nmethod = iter.method();
4569     }
4570     _claimed_nmethod = (volatile nmethod*)_first_nmethod;
4571   }
4572 
4573   ~G1CodeCacheUnloadingTask() {
4574     CodeCache::verify_clean_inline_caches();
4575 
4576     CodeCache::set_needs_cache_clean(false);
4577     guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
4578 
4579     CodeCache::verify_icholder_relocations();
4580   }
4581 
4582  private:
4583   void add_to_postponed_list(nmethod* nm) {
4584       nmethod* old;
4585       do {
4586         old = (nmethod*)_postponed_list;
4587         nm->set_unloading_next(old);
4588       } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old);
4589   }
4590 
4591   void clean_nmethod(nmethod* nm) {
4592     bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
4593 
4594     if (postponed) {
4595       // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
4596       add_to_postponed_list(nm);
4597     }
4598 
4599     // Mark that this thread has been cleaned/unloaded.
4600     // After this call, it will be safe to ask if this nmethod was unloaded or not.
4601     nm->set_unloading_clock(nmethod::global_unloading_clock());
4602   }
4603 
4604   void clean_nmethod_postponed(nmethod* nm) {
4605     nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
4606   }
4607 
4608   static const int MaxClaimNmethods = 16;
4609 
4610   void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) {
4611     nmethod* first;
4612     NMethodIterator last;
4613 
4614     do {
4615       *num_claimed_nmethods = 0;
4616 
4617       first = (nmethod*)_claimed_nmethod;
4618       last = NMethodIterator(first);
4619 
4620       if (first != NULL) {
4621 
4622         for (int i = 0; i < MaxClaimNmethods; i++) {
4623           if (!last.next_alive()) {
4624             break;
4625           }
4626           claimed_nmethods[i] = last.method();
4627           (*num_claimed_nmethods)++;
4628         }
4629       }
4630 
4631     } while ((nmethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first);
4632   }
4633 
4634   nmethod* claim_postponed_nmethod() {
4635     nmethod* claim;
4636     nmethod* next;
4637 
4638     do {
4639       claim = (nmethod*)_postponed_list;
4640       if (claim == NULL) {
4641         return NULL;
4642       }
4643 
4644       next = claim->unloading_next();
4645 
4646     } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim);
4647 
4648     return claim;
4649   }
4650 
4651  public:
4652   // Mark that we're done with the first pass of nmethod cleaning.
4653   void barrier_mark(uint worker_id) {
4654     MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
4655     _num_entered_barrier++;
4656     if (_num_entered_barrier == _num_workers) {
4657       ml.notify_all();
4658     }
4659   }
4660 
4661   // See if we have to wait for the other workers to
4662   // finish their first-pass nmethod cleaning work.
4663   void barrier_wait(uint worker_id) {
4664     if (_num_entered_barrier < _num_workers) {
4665       MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
4666       while (_num_entered_barrier < _num_workers) {
4667           ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
4668       }
4669     }
4670   }
4671 
4672   // Cleaning and unloading of nmethods. Some work has to be postponed
4673   // to the second pass, when we know which nmethods survive.
4674   void work_first_pass(uint worker_id) {
4675     // The first nmethods is claimed by the first worker.
4676     if (worker_id == 0 && _first_nmethod != NULL) {
4677       clean_nmethod(_first_nmethod);
4678       _first_nmethod = NULL;
4679     }
4680 
4681     int num_claimed_nmethods;
4682     nmethod* claimed_nmethods[MaxClaimNmethods];
4683 
4684     while (true) {
4685       claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
4686 
4687       if (num_claimed_nmethods == 0) {
4688         break;
4689       }
4690 
4691       for (int i = 0; i < num_claimed_nmethods; i++) {
4692         clean_nmethod(claimed_nmethods[i]);
4693       }
4694     }
4695   }
4696 
4697   void work_second_pass(uint worker_id) {
4698     nmethod* nm;
4699     // Take care of postponed nmethods.
4700     while ((nm = claim_postponed_nmethod()) != NULL) {
4701       clean_nmethod_postponed(nm);
4702     }
4703   }
4704 };
4705 
4706 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never);
4707 
4708 class G1KlassCleaningTask : public StackObj {
4709   BoolObjectClosure*                      _is_alive;
4710   volatile jint                           _clean_klass_tree_claimed;
4711   ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
4712 
4713  public:
4714   G1KlassCleaningTask(BoolObjectClosure* is_alive) :
4715       _is_alive(is_alive),
4716       _clean_klass_tree_claimed(0),
4717       _klass_iterator() {
4718   }
4719 
4720  private:
4721   bool claim_clean_klass_tree_task() {
4722     if (_clean_klass_tree_claimed) {
4723       return false;
4724     }
4725 
4726     return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0;
4727   }
4728 
4729   InstanceKlass* claim_next_klass() {
4730     Klass* klass;
4731     do {
4732       klass =_klass_iterator.next_klass();
4733     } while (klass != NULL && !klass->oop_is_instance());
4734 
4735     return (InstanceKlass*)klass;
4736   }
4737 
4738 public:
4739 
4740   void clean_klass(InstanceKlass* ik) {
4741     ik->clean_implementors_list(_is_alive);
4742     ik->clean_method_data(_is_alive);
4743 
4744     // G1 specific cleanup work that has
4745     // been moved here to be done in parallel.
4746     ik->clean_dependent_nmethods();
4747   }
4748 
4749   void work() {
4750     ResourceMark rm;
4751 
4752     // One worker will clean the subklass/sibling klass tree.
4753     if (claim_clean_klass_tree_task()) {
4754       Klass::clean_subklass_tree(_is_alive);
4755     }
4756 
4757     // All workers will help cleaning the classes,
4758     InstanceKlass* klass;
4759     while ((klass = claim_next_klass()) != NULL) {
4760       clean_klass(klass);
4761     }
4762   }
4763 };
4764 
4765 // To minimize the remark pause times, the tasks below are done in parallel.
4766 class G1ParallelCleaningTask : public AbstractGangTask {
4767 private:
4768   G1StringSymbolTableUnlinkTask _string_symbol_task;
4769   G1CodeCacheUnloadingTask      _code_cache_task;
4770   G1KlassCleaningTask           _klass_cleaning_task;
4771 
4772 public:
4773   // The constructor is run in the VMThread.
4774   G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) :
4775       AbstractGangTask("Parallel Cleaning"),
4776       _string_symbol_task(is_alive, process_strings, process_symbols),
4777       _code_cache_task(num_workers, is_alive, unloading_occurred),
4778       _klass_cleaning_task(is_alive) {
4779   }
4780 
4781   // The parallel work done by all worker threads.
4782   void work(uint worker_id) {
4783     // Do first pass of code cache cleaning.
4784     _code_cache_task.work_first_pass(worker_id);
4785 
4786     // Let the threads mark that the first pass is done.
4787     _code_cache_task.barrier_mark(worker_id);
4788 
4789     // Clean the Strings and Symbols.
4790     _string_symbol_task.work(worker_id);
4791 
4792     // Wait for all workers to finish the first code cache cleaning pass.
4793     _code_cache_task.barrier_wait(worker_id);
4794 
4795     // Do the second code cache cleaning work, which realize on
4796     // the liveness information gathered during the first pass.
4797     _code_cache_task.work_second_pass(worker_id);
4798 
4799     // Clean all klasses that were not unloaded.
4800     _klass_cleaning_task.work();
4801   }
4802 };
4803 
4804 
4805 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive,
4806                                         bool process_strings,
4807                                         bool process_symbols,
4808                                         bool class_unloading_occurred) {
4809   uint n_workers = workers()->active_workers();
4810 
4811   G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols,
4812                                         n_workers, class_unloading_occurred);
4813   set_par_threads(n_workers);
4814   workers()->run_task(&g1_unlink_task);
4815   set_par_threads(0);
4816 }
4817 
4818 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive,
4819                                                      bool process_strings, bool process_symbols) {
4820   {
4821     uint n_workers = workers()->active_workers();
4822     G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols);
4823     set_par_threads(n_workers);
4824     workers()->run_task(&g1_unlink_task);
4825     set_par_threads(0);
4826   }
4827 
4828   if (G1StringDedup::is_enabled()) {
4829     G1StringDedup::unlink(is_alive);
4830   }
4831 }
4832 
4833 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
4834  private:
4835   DirtyCardQueueSet* _queue;
4836  public:
4837   G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue) : AbstractGangTask("Redirty Cards"), _queue(queue) { }
4838 
4839   virtual void work(uint worker_id) {
4840     G1GCPhaseTimes* phase_times = G1CollectedHeap::heap()->g1_policy()->phase_times();
4841     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id);
4842 
4843     RedirtyLoggedCardTableEntryClosure cl;
4844     _queue->par_apply_closure_to_all_completed_buffers(&cl);
4845 
4846     phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_processed());
4847   }
4848 };
4849 
4850 void G1CollectedHeap::redirty_logged_cards() {
4851   double redirty_logged_cards_start = os::elapsedTime();
4852 
4853   uint n_workers = workers()->active_workers();
4854 
4855   G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set());
4856   dirty_card_queue_set().reset_for_par_iteration();
4857   set_par_threads(n_workers);
4858   workers()->run_task(&redirty_task);
4859   set_par_threads(0);
4860 
4861   DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
4862   dcq.merge_bufferlists(&dirty_card_queue_set());
4863   assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
4864 
4865   g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
4866 }
4867 
4868 // Weak Reference Processing support
4869 
4870 // An always "is_alive" closure that is used to preserve referents.
4871 // If the object is non-null then it's alive.  Used in the preservation
4872 // of referent objects that are pointed to by reference objects
4873 // discovered by the CM ref processor.
4874 class G1AlwaysAliveClosure: public BoolObjectClosure {
4875   G1CollectedHeap* _g1;
4876 public:
4877   G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
4878   bool do_object_b(oop p) {
4879     if (p != NULL) {
4880       return true;
4881     }
4882     return false;
4883   }
4884 };
4885 
4886 bool G1STWIsAliveClosure::do_object_b(oop p) {
4887   // An object is reachable if it is outside the collection set,
4888   // or is inside and copied.
4889   return !_g1->obj_in_cs(p) || p->is_forwarded();
4890 }
4891 
4892 // Non Copying Keep Alive closure
4893 class G1KeepAliveClosure: public OopClosure {
4894   G1CollectedHeap* _g1;
4895 public:
4896   G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
4897   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
4898   void do_oop(oop* p) {
4899     oop obj = *p;
4900     assert(obj != NULL, "the caller should have filtered out NULL values");
4901 
4902     const InCSetState cset_state = _g1->in_cset_state(obj);
4903     if (!cset_state.is_in_cset_or_humongous()) {
4904       return;
4905     }
4906     if (cset_state.is_in_cset()) {
4907       assert( obj->is_forwarded(), "invariant" );
4908       *p = obj->forwardee();
4909     } else {
4910       assert(!obj->is_forwarded(), "invariant" );
4911       assert(cset_state.is_humongous(),
4912              err_msg("Only allowed InCSet state is IsHumongous, but is %d", cset_state.value()));
4913       _g1->set_humongous_is_live(obj);
4914     }
4915   }
4916 };
4917 
4918 // Copying Keep Alive closure - can be called from both
4919 // serial and parallel code as long as different worker
4920 // threads utilize different G1ParScanThreadState instances
4921 // and different queues.
4922 
4923 class G1CopyingKeepAliveClosure: public OopClosure {
4924   G1CollectedHeap*         _g1h;
4925   OopClosure*              _copy_non_heap_obj_cl;
4926   G1ParScanThreadState*    _par_scan_state;
4927 
4928 public:
4929   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
4930                             OopClosure* non_heap_obj_cl,
4931                             G1ParScanThreadState* pss):
4932     _g1h(g1h),
4933     _copy_non_heap_obj_cl(non_heap_obj_cl),
4934     _par_scan_state(pss)
4935   {}
4936 
4937   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
4938   virtual void do_oop(      oop* p) { do_oop_work(p); }
4939 
4940   template <class T> void do_oop_work(T* p) {
4941     oop obj = oopDesc::load_decode_heap_oop(p);
4942 
4943     if (_g1h->is_in_cset_or_humongous(obj)) {
4944       // If the referent object has been forwarded (either copied
4945       // to a new location or to itself in the event of an
4946       // evacuation failure) then we need to update the reference
4947       // field and, if both reference and referent are in the G1
4948       // heap, update the RSet for the referent.
4949       //
4950       // If the referent has not been forwarded then we have to keep
4951       // it alive by policy. Therefore we have copy the referent.
4952       //
4953       // If the reference field is in the G1 heap then we can push
4954       // on the PSS queue. When the queue is drained (after each
4955       // phase of reference processing) the object and it's followers
4956       // will be copied, the reference field set to point to the
4957       // new location, and the RSet updated. Otherwise we need to
4958       // use the the non-heap or metadata closures directly to copy
4959       // the referent object and update the pointer, while avoiding
4960       // updating the RSet.
4961 
4962       if (_g1h->is_in_g1_reserved(p)) {
4963         _par_scan_state->push_on_queue(p);
4964       } else {
4965         assert(!Metaspace::contains((const void*)p),
4966                err_msg("Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p)));
4967         _copy_non_heap_obj_cl->do_oop(p);
4968       }
4969     }
4970   }
4971 };
4972 
4973 // Serial drain queue closure. Called as the 'complete_gc'
4974 // closure for each discovered list in some of the
4975 // reference processing phases.
4976 
4977 class G1STWDrainQueueClosure: public VoidClosure {
4978 protected:
4979   G1CollectedHeap* _g1h;
4980   G1ParScanThreadState* _par_scan_state;
4981 
4982   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
4983 
4984 public:
4985   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
4986     _g1h(g1h),
4987     _par_scan_state(pss)
4988   { }
4989 
4990   void do_void() {
4991     G1ParScanThreadState* const pss = par_scan_state();
4992     pss->trim_queue();
4993   }
4994 };
4995 
4996 // Parallel Reference Processing closures
4997 
4998 // Implementation of AbstractRefProcTaskExecutor for parallel reference
4999 // processing during G1 evacuation pauses.
5000 
5001 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5002 private:
5003   G1CollectedHeap*   _g1h;
5004   RefToScanQueueSet* _queues;
5005   FlexibleWorkGang*  _workers;
5006   uint               _active_workers;
5007 
5008 public:
5009   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5010                            FlexibleWorkGang* workers,
5011                            RefToScanQueueSet *task_queues,
5012                            uint n_workers) :
5013     _g1h(g1h),
5014     _queues(task_queues),
5015     _workers(workers),
5016     _active_workers(n_workers)
5017   {
5018     assert(n_workers > 0, "shouldn't call this otherwise");
5019   }
5020 
5021   // Executes the given task using concurrent marking worker threads.
5022   virtual void execute(ProcessTask& task);
5023   virtual void execute(EnqueueTask& task);
5024 };
5025 
5026 // Gang task for possibly parallel reference processing
5027 
5028 class G1STWRefProcTaskProxy: public AbstractGangTask {
5029   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5030   ProcessTask&     _proc_task;
5031   G1CollectedHeap* _g1h;
5032   RefToScanQueueSet *_task_queues;
5033   ParallelTaskTerminator* _terminator;
5034 
5035 public:
5036   G1STWRefProcTaskProxy(ProcessTask& proc_task,
5037                      G1CollectedHeap* g1h,
5038                      RefToScanQueueSet *task_queues,
5039                      ParallelTaskTerminator* terminator) :
5040     AbstractGangTask("Process reference objects in parallel"),
5041     _proc_task(proc_task),
5042     _g1h(g1h),
5043     _task_queues(task_queues),
5044     _terminator(terminator)
5045   {}
5046 
5047   virtual void work(uint worker_id) {
5048     // The reference processing task executed by a single worker.
5049     ResourceMark rm;
5050     HandleMark   hm;
5051 
5052     G1STWIsAliveClosure is_alive(_g1h);
5053 
5054     G1ParScanThreadState            pss(_g1h, worker_id, NULL);
5055     G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5056 
5057     pss.set_evac_failure_closure(&evac_failure_cl);
5058 
5059     G1ParScanExtRootClosure        only_copy_non_heap_cl(_g1h, &pss, NULL);
5060 
5061     G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5062 
5063     OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5064 
5065     if (_g1h->g1_policy()->during_initial_mark_pause()) {
5066       // We also need to mark copied objects.
5067       copy_non_heap_cl = &copy_mark_non_heap_cl;
5068     }
5069 
5070     // Keep alive closure.
5071     G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5072 
5073     // Complete GC closure
5074     G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5075 
5076     // Call the reference processing task's work routine.
5077     _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5078 
5079     // Note we cannot assert that the refs array is empty here as not all
5080     // of the processing tasks (specifically phase2 - pp2_work) execute
5081     // the complete_gc closure (which ordinarily would drain the queue) so
5082     // the queue may not be empty.
5083   }
5084 };
5085 
5086 // Driver routine for parallel reference processing.
5087 // Creates an instance of the ref processing gang
5088 // task and has the worker threads execute it.
5089 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5090   assert(_workers != NULL, "Need parallel worker threads.");
5091 
5092   ParallelTaskTerminator terminator(_active_workers, _queues);
5093   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5094 
5095   _g1h->set_par_threads(_active_workers);
5096   _workers->run_task(&proc_task_proxy);
5097   _g1h->set_par_threads(0);
5098 }
5099 
5100 // Gang task for parallel reference enqueueing.
5101 
5102 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5103   typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5104   EnqueueTask& _enq_task;
5105 
5106 public:
5107   G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5108     AbstractGangTask("Enqueue reference objects in parallel"),
5109     _enq_task(enq_task)
5110   { }
5111 
5112   virtual void work(uint worker_id) {
5113     _enq_task.work(worker_id);
5114   }
5115 };
5116 
5117 // Driver routine for parallel reference enqueueing.
5118 // Creates an instance of the ref enqueueing gang
5119 // task and has the worker threads execute it.
5120 
5121 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5122   assert(_workers != NULL, "Need parallel worker threads.");
5123 
5124   G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5125 
5126   _g1h->set_par_threads(_active_workers);
5127   _workers->run_task(&enq_task_proxy);
5128   _g1h->set_par_threads(0);
5129 }
5130 
5131 // End of weak reference support closures
5132 
5133 // Abstract task used to preserve (i.e. copy) any referent objects
5134 // that are in the collection set and are pointed to by reference
5135 // objects discovered by the CM ref processor.
5136 
5137 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5138 protected:
5139   G1CollectedHeap* _g1h;
5140   RefToScanQueueSet      *_queues;
5141   ParallelTaskTerminator _terminator;
5142   uint _n_workers;
5143 
5144 public:
5145   G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, uint workers, RefToScanQueueSet *task_queues) :
5146     AbstractGangTask("ParPreserveCMReferents"),
5147     _g1h(g1h),
5148     _queues(task_queues),
5149     _terminator(workers, _queues),
5150     _n_workers(workers)
5151   { }
5152 
5153   void work(uint worker_id) {
5154     ResourceMark rm;
5155     HandleMark   hm;
5156 
5157     G1ParScanThreadState            pss(_g1h, worker_id, NULL);
5158     G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5159 
5160     pss.set_evac_failure_closure(&evac_failure_cl);
5161 
5162     assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5163 
5164     G1ParScanExtRootClosure        only_copy_non_heap_cl(_g1h, &pss, NULL);
5165 
5166     G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5167 
5168     OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5169 
5170     if (_g1h->g1_policy()->during_initial_mark_pause()) {
5171       // We also need to mark copied objects.
5172       copy_non_heap_cl = &copy_mark_non_heap_cl;
5173     }
5174 
5175     // Is alive closure
5176     G1AlwaysAliveClosure always_alive(_g1h);
5177 
5178     // Copying keep alive closure. Applied to referent objects that need
5179     // to be copied.
5180     G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5181 
5182     ReferenceProcessor* rp = _g1h->ref_processor_cm();
5183 
5184     uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5185     uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5186 
5187     // limit is set using max_num_q() - which was set using ParallelGCThreads.
5188     // So this must be true - but assert just in case someone decides to
5189     // change the worker ids.
5190     assert(worker_id < limit, "sanity");
5191     assert(!rp->discovery_is_atomic(), "check this code");
5192 
5193     // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5194     for (uint idx = worker_id; idx < limit; idx += stride) {
5195       DiscoveredList& ref_list = rp->discovered_refs()[idx];
5196 
5197       DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5198       while (iter.has_next()) {
5199         // Since discovery is not atomic for the CM ref processor, we
5200         // can see some null referent objects.
5201         iter.load_ptrs(DEBUG_ONLY(true));
5202         oop ref = iter.obj();
5203 
5204         // This will filter nulls.
5205         if (iter.is_referent_alive()) {
5206           iter.make_referent_alive();
5207         }
5208         iter.move_to_next();
5209       }
5210     }
5211 
5212     // Drain the queue - which may cause stealing
5213     G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5214     drain_queue.do_void();
5215     // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5216     assert(pss.queue_is_empty(), "should be");
5217   }
5218 };
5219 
5220 // Weak Reference processing during an evacuation pause (part 1).
5221 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) {
5222   double ref_proc_start = os::elapsedTime();
5223 
5224   ReferenceProcessor* rp = _ref_processor_stw;
5225   assert(rp->discovery_enabled(), "should have been enabled");
5226 
5227   // Any reference objects, in the collection set, that were 'discovered'
5228   // by the CM ref processor should have already been copied (either by
5229   // applying the external root copy closure to the discovered lists, or
5230   // by following an RSet entry).
5231   //
5232   // But some of the referents, that are in the collection set, that these
5233   // reference objects point to may not have been copied: the STW ref
5234   // processor would have seen that the reference object had already
5235   // been 'discovered' and would have skipped discovering the reference,
5236   // but would not have treated the reference object as a regular oop.
5237   // As a result the copy closure would not have been applied to the
5238   // referent object.
5239   //
5240   // We need to explicitly copy these referent objects - the references
5241   // will be processed at the end of remarking.
5242   //
5243   // We also need to do this copying before we process the reference
5244   // objects discovered by the STW ref processor in case one of these
5245   // referents points to another object which is also referenced by an
5246   // object discovered by the STW ref processor.
5247 
5248   assert(no_of_gc_workers == workers()->active_workers(), "Need to reset active GC workers");
5249 
5250   set_par_threads(no_of_gc_workers);
5251   G1ParPreserveCMReferentsTask keep_cm_referents(this,
5252                                                  no_of_gc_workers,
5253                                                  _task_queues);
5254 
5255   workers()->run_task(&keep_cm_referents);
5256 
5257   set_par_threads(0);
5258 
5259   // Closure to test whether a referent is alive.
5260   G1STWIsAliveClosure is_alive(this);
5261 
5262   // Even when parallel reference processing is enabled, the processing
5263   // of JNI refs is serial and performed serially by the current thread
5264   // rather than by a worker. The following PSS will be used for processing
5265   // JNI refs.
5266 
5267   // Use only a single queue for this PSS.
5268   G1ParScanThreadState            pss(this, 0, NULL);
5269 
5270   // We do not embed a reference processor in the copying/scanning
5271   // closures while we're actually processing the discovered
5272   // reference objects.
5273   G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5274 
5275   pss.set_evac_failure_closure(&evac_failure_cl);
5276 
5277   assert(pss.queue_is_empty(), "pre-condition");
5278 
5279   G1ParScanExtRootClosure        only_copy_non_heap_cl(this, &pss, NULL);
5280 
5281   G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5282 
5283   OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5284 
5285   if (g1_policy()->during_initial_mark_pause()) {
5286     // We also need to mark copied objects.
5287     copy_non_heap_cl = &copy_mark_non_heap_cl;
5288   }
5289 
5290   // Keep alive closure.
5291   G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, &pss);
5292 
5293   // Serial Complete GC closure
5294   G1STWDrainQueueClosure drain_queue(this, &pss);
5295 
5296   // Setup the soft refs policy...
5297   rp->setup_policy(false);
5298 
5299   ReferenceProcessorStats stats;
5300   if (!rp->processing_is_mt()) {
5301     // Serial reference processing...
5302     stats = rp->process_discovered_references(&is_alive,
5303                                               &keep_alive,
5304                                               &drain_queue,
5305                                               NULL,
5306                                               _gc_timer_stw,
5307                                               _gc_tracer_stw->gc_id());
5308   } else {
5309     // Parallel reference processing
5310     assert(rp->num_q() == no_of_gc_workers, "sanity");
5311     assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5312 
5313     G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5314     stats = rp->process_discovered_references(&is_alive,
5315                                               &keep_alive,
5316                                               &drain_queue,
5317                                               &par_task_executor,
5318                                               _gc_timer_stw,
5319                                               _gc_tracer_stw->gc_id());
5320   }
5321 
5322   _gc_tracer_stw->report_gc_reference_stats(stats);
5323 
5324   // We have completed copying any necessary live referent objects.
5325   assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5326 
5327   double ref_proc_time = os::elapsedTime() - ref_proc_start;
5328   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5329 }
5330 
5331 // Weak Reference processing during an evacuation pause (part 2).
5332 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) {
5333   double ref_enq_start = os::elapsedTime();
5334 
5335   ReferenceProcessor* rp = _ref_processor_stw;
5336   assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5337 
5338   // Now enqueue any remaining on the discovered lists on to
5339   // the pending list.
5340   if (!rp->processing_is_mt()) {
5341     // Serial reference processing...
5342     rp->enqueue_discovered_references();
5343   } else {
5344     // Parallel reference enqueueing
5345 
5346     assert(no_of_gc_workers == workers()->active_workers(),
5347            "Need to reset active workers");
5348     assert(rp->num_q() == no_of_gc_workers, "sanity");
5349     assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5350 
5351     G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5352     rp->enqueue_discovered_references(&par_task_executor);
5353   }
5354 
5355   rp->verify_no_references_recorded();
5356   assert(!rp->discovery_enabled(), "should have been disabled");
5357 
5358   // FIXME
5359   // CM's reference processing also cleans up the string and symbol tables.
5360   // Should we do that here also? We could, but it is a serial operation
5361   // and could significantly increase the pause time.
5362 
5363   double ref_enq_time = os::elapsedTime() - ref_enq_start;
5364   g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5365 }
5366 
5367 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) {
5368   _expand_heap_after_alloc_failure = true;
5369   _evacuation_failed = false;
5370 
5371   // Should G1EvacuationFailureALot be in effect for this GC?
5372   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
5373 
5374   g1_rem_set()->prepare_for_oops_into_collection_set_do();
5375 
5376   // Disable the hot card cache.
5377   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
5378   hot_card_cache->reset_hot_cache_claimed_index();
5379   hot_card_cache->set_use_cache(false);
5380 
5381   const uint n_workers = workers()->active_workers();
5382   assert(UseDynamicNumberOfGCThreads ||
5383          n_workers == workers()->total_workers(),
5384          "If not dynamic should be using all the  workers");
5385   set_par_threads(n_workers);
5386 
5387 
5388   init_for_evac_failure(NULL);
5389 
5390   assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5391   double start_par_time_sec = os::elapsedTime();
5392   double end_par_time_sec;
5393 
5394   {
5395     G1RootProcessor root_processor(this);
5396     G1ParTask g1_par_task(this, _task_queues, &root_processor);
5397     // InitialMark needs claim bits to keep track of the marked-through CLDs.
5398     if (g1_policy()->during_initial_mark_pause()) {
5399       ClassLoaderDataGraph::clear_claimed_marks();
5400     }
5401 
5402      // The individual threads will set their evac-failure closures.
5403      if (PrintTerminationStats) G1ParScanThreadState::print_termination_stats_hdr();
5404      // These tasks use ShareHeap::_process_strong_tasks
5405      assert(UseDynamicNumberOfGCThreads ||
5406             workers()->active_workers() == workers()->total_workers(),
5407             "If not dynamic should be using all the  workers");
5408     workers()->run_task(&g1_par_task);
5409     end_par_time_sec = os::elapsedTime();
5410 
5411     // Closing the inner scope will execute the destructor
5412     // for the G1RootProcessor object. We record the current
5413     // elapsed time before closing the scope so that time
5414     // taken for the destructor is NOT included in the
5415     // reported parallel time.
5416   }
5417 
5418   G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
5419 
5420   double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5421   phase_times->record_par_time(par_time_ms);
5422 
5423   double code_root_fixup_time_ms =
5424         (os::elapsedTime() - end_par_time_sec) * 1000.0;
5425   phase_times->record_code_root_fixup_time(code_root_fixup_time_ms);
5426 
5427   set_par_threads(0);
5428 
5429   // Process any discovered reference objects - we have
5430   // to do this _before_ we retire the GC alloc regions
5431   // as we may have to copy some 'reachable' referent
5432   // objects (and their reachable sub-graphs) that were
5433   // not copied during the pause.
5434   process_discovered_references(n_workers);
5435 
5436   if (G1StringDedup::is_enabled()) {
5437     double fixup_start = os::elapsedTime();
5438 
5439     G1STWIsAliveClosure is_alive(this);
5440     G1KeepAliveClosure keep_alive(this);
5441     G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, phase_times);
5442 
5443     double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
5444     phase_times->record_string_dedup_fixup_time(fixup_time_ms);
5445   }
5446 
5447   _allocator->release_gc_alloc_regions(n_workers, evacuation_info);
5448   g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5449 
5450   // Reset and re-enable the hot card cache.
5451   // Note the counts for the cards in the regions in the
5452   // collection set are reset when the collection set is freed.
5453   hot_card_cache->reset_hot_cache();
5454   hot_card_cache->set_use_cache(true);
5455 
5456   purge_code_root_memory();
5457 
5458   finalize_for_evac_failure();
5459 
5460   if (evacuation_failed()) {
5461     remove_self_forwarding_pointers();
5462 
5463     // Reset the G1EvacuationFailureALot counters and flags
5464     // Note: the values are reset only when an actual
5465     // evacuation failure occurs.
5466     NOT_PRODUCT(reset_evacuation_should_fail();)
5467   }
5468 
5469   // Enqueue any remaining references remaining on the STW
5470   // reference processor's discovered lists. We need to do
5471   // this after the card table is cleaned (and verified) as
5472   // the act of enqueueing entries on to the pending list
5473   // will log these updates (and dirty their associated
5474   // cards). We need these updates logged to update any
5475   // RSets.
5476   enqueue_discovered_references(n_workers);
5477 
5478   redirty_logged_cards();
5479   COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5480 }
5481 
5482 void G1CollectedHeap::free_region(HeapRegion* hr,
5483                                   FreeRegionList* free_list,
5484                                   bool par,
5485                                   bool locked) {
5486   assert(!hr->is_free(), "the region should not be free");
5487   assert(!hr->is_empty(), "the region should not be empty");
5488   assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
5489   assert(free_list != NULL, "pre-condition");
5490 
5491   if (G1VerifyBitmaps) {
5492     MemRegion mr(hr->bottom(), hr->end());
5493     concurrent_mark()->clearRangePrevBitmap(mr);
5494   }
5495 
5496   // Clear the card counts for this region.
5497   // Note: we only need to do this if the region is not young
5498   // (since we don't refine cards in young regions).
5499   if (!hr->is_young()) {
5500     _cg1r->hot_card_cache()->reset_card_counts(hr);
5501   }
5502   hr->hr_clear(par, true /* clear_space */, locked /* locked */);
5503   free_list->add_ordered(hr);
5504 }
5505 
5506 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
5507                                      FreeRegionList* free_list,
5508                                      bool par) {
5509   assert(hr->is_starts_humongous(), "this is only for starts humongous regions");
5510   assert(free_list != NULL, "pre-condition");
5511 
5512   size_t hr_capacity = hr->capacity();
5513   // We need to read this before we make the region non-humongous,
5514   // otherwise the information will be gone.
5515   uint last_index = hr->last_hc_index();
5516   hr->clear_humongous();
5517   free_region(hr, free_list, par);
5518 
5519   uint i = hr->hrm_index() + 1;
5520   while (i < last_index) {
5521     HeapRegion* curr_hr = region_at(i);
5522     assert(curr_hr->is_continues_humongous(), "invariant");
5523     curr_hr->clear_humongous();
5524     free_region(curr_hr, free_list, par);
5525     i += 1;
5526   }
5527 }
5528 
5529 void G1CollectedHeap::remove_from_old_sets(const HeapRegionSetCount& old_regions_removed,
5530                                        const HeapRegionSetCount& humongous_regions_removed) {
5531   if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 0) {
5532     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5533     _old_set.bulk_remove(old_regions_removed);
5534     _humongous_set.bulk_remove(humongous_regions_removed);
5535   }
5536 
5537 }
5538 
5539 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
5540   assert(list != NULL, "list can't be null");
5541   if (!list->is_empty()) {
5542     MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
5543     _hrm.insert_list_into_free_list(list);
5544   }
5545 }
5546 
5547 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
5548   _allocator->decrease_used(bytes);
5549 }
5550 
5551 class G1ParCleanupCTTask : public AbstractGangTask {
5552   G1SATBCardTableModRefBS* _ct_bs;
5553   G1CollectedHeap* _g1h;
5554   HeapRegion* volatile _su_head;
5555 public:
5556   G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs,
5557                      G1CollectedHeap* g1h) :
5558     AbstractGangTask("G1 Par Cleanup CT Task"),
5559     _ct_bs(ct_bs), _g1h(g1h) { }
5560 
5561   void work(uint worker_id) {
5562     HeapRegion* r;
5563     while (r = _g1h->pop_dirty_cards_region()) {
5564       clear_cards(r);
5565     }
5566   }
5567 
5568   void clear_cards(HeapRegion* r) {
5569     // Cards of the survivors should have already been dirtied.
5570     if (!r->is_survivor()) {
5571       _ct_bs->clear(MemRegion(r->bottom(), r->end()));
5572     }
5573   }
5574 };
5575 
5576 #ifndef PRODUCT
5577 class G1VerifyCardTableCleanup: public HeapRegionClosure {
5578   G1CollectedHeap* _g1h;
5579   G1SATBCardTableModRefBS* _ct_bs;
5580 public:
5581   G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs)
5582     : _g1h(g1h), _ct_bs(ct_bs) { }
5583   virtual bool doHeapRegion(HeapRegion* r) {
5584     if (r->is_survivor()) {
5585       _g1h->verify_dirty_region(r);
5586     } else {
5587       _g1h->verify_not_dirty_region(r);
5588     }
5589     return false;
5590   }
5591 };
5592 
5593 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
5594   // All of the region should be clean.
5595   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5596   MemRegion mr(hr->bottom(), hr->end());
5597   ct_bs->verify_not_dirty_region(mr);
5598 }
5599 
5600 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
5601   // We cannot guarantee that [bottom(),end()] is dirty.  Threads
5602   // dirty allocated blocks as they allocate them. The thread that
5603   // retires each region and replaces it with a new one will do a
5604   // maximal allocation to fill in [pre_dummy_top(),end()] but will
5605   // not dirty that area (one less thing to have to do while holding
5606   // a lock). So we can only verify that [bottom(),pre_dummy_top()]
5607   // is dirty.
5608   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5609   MemRegion mr(hr->bottom(), hr->pre_dummy_top());
5610   if (hr->is_young()) {
5611     ct_bs->verify_g1_young_region(mr);
5612   } else {
5613     ct_bs->verify_dirty_region(mr);
5614   }
5615 }
5616 
5617 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
5618   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5619   for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
5620     verify_dirty_region(hr);
5621   }
5622 }
5623 
5624 void G1CollectedHeap::verify_dirty_young_regions() {
5625   verify_dirty_young_list(_young_list->first_region());
5626 }
5627 
5628 bool G1CollectedHeap::verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
5629                                                HeapWord* tams, HeapWord* end) {
5630   guarantee(tams <= end,
5631             err_msg("tams: "PTR_FORMAT" end: "PTR_FORMAT, p2i(tams), p2i(end)));
5632   HeapWord* result = bitmap->getNextMarkedWordAddress(tams, end);
5633   if (result < end) {
5634     gclog_or_tty->cr();
5635     gclog_or_tty->print_cr("## wrong marked address on %s bitmap: "PTR_FORMAT,
5636                            bitmap_name, p2i(result));
5637     gclog_or_tty->print_cr("## %s tams: "PTR_FORMAT" end: "PTR_FORMAT,
5638                            bitmap_name, p2i(tams), p2i(end));
5639     return false;
5640   }
5641   return true;
5642 }
5643 
5644 bool G1CollectedHeap::verify_bitmaps(const char* caller, HeapRegion* hr) {
5645   CMBitMapRO* prev_bitmap = concurrent_mark()->prevMarkBitMap();
5646   CMBitMapRO* next_bitmap = (CMBitMapRO*) concurrent_mark()->nextMarkBitMap();
5647 
5648   HeapWord* bottom = hr->bottom();
5649   HeapWord* ptams  = hr->prev_top_at_mark_start();
5650   HeapWord* ntams  = hr->next_top_at_mark_start();
5651   HeapWord* end    = hr->end();
5652 
5653   bool res_p = verify_no_bits_over_tams("prev", prev_bitmap, ptams, end);
5654 
5655   bool res_n = true;
5656   // We reset mark_in_progress() before we reset _cmThread->in_progress() and in this window
5657   // we do the clearing of the next bitmap concurrently. Thus, we can not verify the bitmap
5658   // if we happen to be in that state.
5659   if (mark_in_progress() || !_cmThread->in_progress()) {
5660     res_n = verify_no_bits_over_tams("next", next_bitmap, ntams, end);
5661   }
5662   if (!res_p || !res_n) {
5663     gclog_or_tty->print_cr("#### Bitmap verification failed for "HR_FORMAT,
5664                            HR_FORMAT_PARAMS(hr));
5665     gclog_or_tty->print_cr("#### Caller: %s", caller);
5666     return false;
5667   }
5668   return true;
5669 }
5670 
5671 void G1CollectedHeap::check_bitmaps(const char* caller, HeapRegion* hr) {
5672   if (!G1VerifyBitmaps) return;
5673 
5674   guarantee(verify_bitmaps(caller, hr), "bitmap verification");
5675 }
5676 
5677 class G1VerifyBitmapClosure : public HeapRegionClosure {
5678 private:
5679   const char* _caller;
5680   G1CollectedHeap* _g1h;
5681   bool _failures;
5682 
5683 public:
5684   G1VerifyBitmapClosure(const char* caller, G1CollectedHeap* g1h) :
5685     _caller(caller), _g1h(g1h), _failures(false) { }
5686 
5687   bool failures() { return _failures; }
5688 
5689   virtual bool doHeapRegion(HeapRegion* hr) {
5690     if (hr->is_continues_humongous()) return false;
5691 
5692     bool result = _g1h->verify_bitmaps(_caller, hr);
5693     if (!result) {
5694       _failures = true;
5695     }
5696     return false;
5697   }
5698 };
5699 
5700 void G1CollectedHeap::check_bitmaps(const char* caller) {
5701   if (!G1VerifyBitmaps) return;
5702 
5703   G1VerifyBitmapClosure cl(caller, this);
5704   heap_region_iterate(&cl);
5705   guarantee(!cl.failures(), "bitmap verification");
5706 }
5707 
5708 class G1CheckCSetFastTableClosure : public HeapRegionClosure {
5709  private:
5710   bool _failures;
5711  public:
5712   G1CheckCSetFastTableClosure() : HeapRegionClosure(), _failures(false) { }
5713 
5714   virtual bool doHeapRegion(HeapRegion* hr) {
5715     uint i = hr->hrm_index();
5716     InCSetState cset_state = (InCSetState) G1CollectedHeap::heap()->_in_cset_fast_test.get_by_index(i);
5717     if (hr->is_humongous()) {
5718       if (hr->in_collection_set()) {
5719         gclog_or_tty->print_cr("\n## humongous region %u in CSet", i);
5720         _failures = true;
5721         return true;
5722       }
5723       if (cset_state.is_in_cset()) {
5724         gclog_or_tty->print_cr("\n## inconsistent cset state %d for humongous region %u", cset_state.value(), i);
5725         _failures = true;
5726         return true;
5727       }
5728       if (hr->is_continues_humongous() && cset_state.is_humongous()) {
5729         gclog_or_tty->print_cr("\n## inconsistent cset state %d for continues humongous region %u", cset_state.value(), i);
5730         _failures = true;
5731         return true;
5732       }
5733     } else {
5734       if (cset_state.is_humongous()) {
5735         gclog_or_tty->print_cr("\n## inconsistent cset state %d for non-humongous region %u", cset_state.value(), i);
5736         _failures = true;
5737         return true;
5738       }
5739       if (hr->in_collection_set() != cset_state.is_in_cset()) {
5740         gclog_or_tty->print_cr("\n## in CSet %d / cset state %d inconsistency for region %u",
5741                                hr->in_collection_set(), cset_state.value(), i);
5742         _failures = true;
5743         return true;
5744       }
5745       if (cset_state.is_in_cset()) {
5746         if (hr->is_young() != (cset_state.is_young())) {
5747           gclog_or_tty->print_cr("\n## is_young %d / cset state %d inconsistency for region %u",
5748                                  hr->is_young(), cset_state.value(), i);
5749           _failures = true;
5750           return true;
5751         }
5752         if (hr->is_old() != (cset_state.is_old())) {
5753           gclog_or_tty->print_cr("\n## is_old %d / cset state %d inconsistency for region %u",
5754                                  hr->is_old(), cset_state.value(), i);
5755           _failures = true;
5756           return true;
5757         }
5758       }
5759     }
5760     return false;
5761   }
5762 
5763   bool failures() const { return _failures; }
5764 };
5765 
5766 bool G1CollectedHeap::check_cset_fast_test() {
5767   G1CheckCSetFastTableClosure cl;
5768   _hrm.iterate(&cl);
5769   return !cl.failures();
5770 }
5771 #endif // PRODUCT
5772 
5773 void G1CollectedHeap::cleanUpCardTable() {
5774   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5775   double start = os::elapsedTime();
5776 
5777   {
5778     // Iterate over the dirty cards region list.
5779     G1ParCleanupCTTask cleanup_task(ct_bs, this);
5780 
5781     set_par_threads();
5782     workers()->run_task(&cleanup_task);
5783     set_par_threads(0);
5784 #ifndef PRODUCT
5785     if (G1VerifyCTCleanup || VerifyAfterGC) {
5786       G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
5787       heap_region_iterate(&cleanup_verifier);
5788     }
5789 #endif
5790   }
5791 
5792   double elapsed = os::elapsedTime() - start;
5793   g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
5794 }
5795 
5796 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) {
5797   size_t pre_used = 0;
5798   FreeRegionList local_free_list("Local List for CSet Freeing");
5799 
5800   double young_time_ms     = 0.0;
5801   double non_young_time_ms = 0.0;
5802 
5803   // Since the collection set is a superset of the the young list,
5804   // all we need to do to clear the young list is clear its
5805   // head and length, and unlink any young regions in the code below
5806   _young_list->clear();
5807 
5808   G1CollectorPolicy* policy = g1_policy();
5809 
5810   double start_sec = os::elapsedTime();
5811   bool non_young = true;
5812 
5813   HeapRegion* cur = cs_head;
5814   int age_bound = -1;
5815   size_t rs_lengths = 0;
5816 
5817   while (cur != NULL) {
5818     assert(!is_on_master_free_list(cur), "sanity");
5819     if (non_young) {
5820       if (cur->is_young()) {
5821         double end_sec = os::elapsedTime();
5822         double elapsed_ms = (end_sec - start_sec) * 1000.0;
5823         non_young_time_ms += elapsed_ms;
5824 
5825         start_sec = os::elapsedTime();
5826         non_young = false;
5827       }
5828     } else {
5829       if (!cur->is_young()) {
5830         double end_sec = os::elapsedTime();
5831         double elapsed_ms = (end_sec - start_sec) * 1000.0;
5832         young_time_ms += elapsed_ms;
5833 
5834         start_sec = os::elapsedTime();
5835         non_young = true;
5836       }
5837     }
5838 
5839     rs_lengths += cur->rem_set()->occupied_locked();
5840 
5841     HeapRegion* next = cur->next_in_collection_set();
5842     assert(cur->in_collection_set(), "bad CS");
5843     cur->set_next_in_collection_set(NULL);
5844     clear_in_cset(cur);
5845 
5846     if (cur->is_young()) {
5847       int index = cur->young_index_in_cset();
5848       assert(index != -1, "invariant");
5849       assert((uint) index < policy->young_cset_region_length(), "invariant");
5850       size_t words_survived = _surviving_young_words[index];
5851       cur->record_surv_words_in_group(words_survived);
5852 
5853       // At this point the we have 'popped' cur from the collection set
5854       // (linked via next_in_collection_set()) but it is still in the
5855       // young list (linked via next_young_region()). Clear the
5856       // _next_young_region field.
5857       cur->set_next_young_region(NULL);
5858     } else {
5859       int index = cur->young_index_in_cset();
5860       assert(index == -1, "invariant");
5861     }
5862 
5863     assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
5864             (!cur->is_young() && cur->young_index_in_cset() == -1),
5865             "invariant" );
5866 
5867     if (!cur->evacuation_failed()) {
5868       MemRegion used_mr = cur->used_region();
5869 
5870       // And the region is empty.
5871       assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
5872       pre_used += cur->used();
5873       free_region(cur, &local_free_list, false /* par */, true /* locked */);
5874     } else {
5875       cur->uninstall_surv_rate_group();
5876       if (cur->is_young()) {
5877         cur->set_young_index_in_cset(-1);
5878       }
5879       cur->set_evacuation_failed(false);
5880       // The region is now considered to be old.
5881       cur->set_old();
5882       _old_set.add(cur);
5883       evacuation_info.increment_collectionset_used_after(cur->used());
5884     }
5885     cur = next;
5886   }
5887 
5888   evacuation_info.set_regions_freed(local_free_list.length());
5889   policy->record_max_rs_lengths(rs_lengths);
5890   policy->cset_regions_freed();
5891 
5892   double end_sec = os::elapsedTime();
5893   double elapsed_ms = (end_sec - start_sec) * 1000.0;
5894 
5895   if (non_young) {
5896     non_young_time_ms += elapsed_ms;
5897   } else {
5898     young_time_ms += elapsed_ms;
5899   }
5900 
5901   prepend_to_freelist(&local_free_list);
5902   decrement_summary_bytes(pre_used);
5903   policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
5904   policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
5905 }
5906 
5907 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
5908  private:
5909   FreeRegionList* _free_region_list;
5910   HeapRegionSet* _proxy_set;
5911   HeapRegionSetCount _humongous_regions_removed;
5912   size_t _freed_bytes;
5913  public:
5914 
5915   G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
5916     _free_region_list(free_region_list), _humongous_regions_removed(), _freed_bytes(0) {
5917   }
5918 
5919   virtual bool doHeapRegion(HeapRegion* r) {
5920     if (!r->is_starts_humongous()) {
5921       return false;
5922     }
5923 
5924     G1CollectedHeap* g1h = G1CollectedHeap::heap();
5925 
5926     oop obj = (oop)r->bottom();
5927     CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap();
5928 
5929     // The following checks whether the humongous object is live are sufficient.
5930     // The main additional check (in addition to having a reference from the roots
5931     // or the young gen) is whether the humongous object has a remembered set entry.
5932     //
5933     // A humongous object cannot be live if there is no remembered set for it
5934     // because:
5935     // - there can be no references from within humongous starts regions referencing
5936     // the object because we never allocate other objects into them.
5937     // (I.e. there are no intra-region references that may be missed by the
5938     // remembered set)
5939     // - as soon there is a remembered set entry to the humongous starts region
5940     // (i.e. it has "escaped" to an old object) this remembered set entry will stay
5941     // until the end of a concurrent mark.
5942     //
5943     // It is not required to check whether the object has been found dead by marking
5944     // or not, in fact it would prevent reclamation within a concurrent cycle, as
5945     // all objects allocated during that time are considered live.
5946     // SATB marking is even more conservative than the remembered set.
5947     // So if at this point in the collection there is no remembered set entry,
5948     // nobody has a reference to it.
5949     // At the start of collection we flush all refinement logs, and remembered sets
5950     // are completely up-to-date wrt to references to the humongous object.
5951     //
5952     // Other implementation considerations:
5953     // - never consider object arrays at this time because they would pose
5954     // considerable effort for cleaning up the the remembered sets. This is
5955     // required because stale remembered sets might reference locations that
5956     // are currently allocated into.
5957     uint region_idx = r->hrm_index();
5958     if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
5959         !r->rem_set()->is_empty()) {
5960 
5961       if (G1TraceEagerReclaimHumongousObjects) {
5962         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",
5963                                region_idx,
5964                                (size_t)obj->size() * HeapWordSize,
5965                                p2i(r->bottom()),
5966                                r->region_num(),
5967                                r->rem_set()->occupied(),
5968                                r->rem_set()->strong_code_roots_list_length(),
5969                                next_bitmap->isMarked(r->bottom()),
5970                                g1h->is_humongous_reclaim_candidate(region_idx),
5971                                obj->is_typeArray()
5972                               );
5973       }
5974 
5975       return false;
5976     }
5977 
5978     guarantee(obj->is_typeArray(),
5979               err_msg("Only eagerly reclaiming type arrays is supported, but the object "
5980                       PTR_FORMAT " is not.",
5981                       p2i(r->bottom())));
5982 
5983     if (G1TraceEagerReclaimHumongousObjects) {
5984       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",
5985                              region_idx,
5986                              (size_t)obj->size() * HeapWordSize,
5987                              p2i(r->bottom()),
5988                              r->region_num(),
5989                              r->rem_set()->occupied(),
5990                              r->rem_set()->strong_code_roots_list_length(),
5991                              next_bitmap->isMarked(r->bottom()),
5992                              g1h->is_humongous_reclaim_candidate(region_idx),
5993                              obj->is_typeArray()
5994                             );
5995     }
5996     // Need to clear mark bit of the humongous object if already set.
5997     if (next_bitmap->isMarked(r->bottom())) {
5998       next_bitmap->clear(r->bottom());
5999     }
6000     _freed_bytes += r->used();
6001     r->set_containing_set(NULL);
6002     _humongous_regions_removed.increment(1u, r->capacity());
6003     g1h->free_humongous_region(r, _free_region_list, false);
6004 
6005     return false;
6006   }
6007 
6008   HeapRegionSetCount& humongous_free_count() {
6009     return _humongous_regions_removed;
6010   }
6011 
6012   size_t bytes_freed() const {
6013     return _freed_bytes;
6014   }
6015 
6016   size_t humongous_reclaimed() const {
6017     return _humongous_regions_removed.length();
6018   }
6019 };
6020 
6021 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
6022   assert_at_safepoint(true);
6023 
6024   if (!G1EagerReclaimHumongousObjects ||
6025       (!_has_humongous_reclaim_candidates && !G1TraceEagerReclaimHumongousObjects)) {
6026     g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
6027     return;
6028   }
6029 
6030   double start_time = os::elapsedTime();
6031 
6032   FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
6033 
6034   G1FreeHumongousRegionClosure cl(&local_cleanup_list);
6035   heap_region_iterate(&cl);
6036 
6037   HeapRegionSetCount empty_set;
6038   remove_from_old_sets(empty_set, cl.humongous_free_count());
6039 
6040   G1HRPrinter* hrp = hr_printer();
6041   if (hrp->is_active()) {
6042     FreeRegionListIterator iter(&local_cleanup_list);
6043     while (iter.more_available()) {
6044       HeapRegion* hr = iter.get_next();
6045       hrp->cleanup(hr);
6046     }
6047   }
6048 
6049   prepend_to_freelist(&local_cleanup_list);
6050   decrement_summary_bytes(cl.bytes_freed());
6051 
6052   g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
6053                                                                     cl.humongous_reclaimed());
6054 }
6055 
6056 // This routine is similar to the above but does not record
6057 // any policy statistics or update free lists; we are abandoning
6058 // the current incremental collection set in preparation of a
6059 // full collection. After the full GC we will start to build up
6060 // the incremental collection set again.
6061 // This is only called when we're doing a full collection
6062 // and is immediately followed by the tearing down of the young list.
6063 
6064 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
6065   HeapRegion* cur = cs_head;
6066 
6067   while (cur != NULL) {
6068     HeapRegion* next = cur->next_in_collection_set();
6069     assert(cur->in_collection_set(), "bad CS");
6070     cur->set_next_in_collection_set(NULL);
6071     clear_in_cset(cur);
6072     cur->set_young_index_in_cset(-1);
6073     cur = next;
6074   }
6075 }
6076 
6077 void G1CollectedHeap::set_free_regions_coming() {
6078   if (G1ConcRegionFreeingVerbose) {
6079     gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6080                            "setting free regions coming");
6081   }
6082 
6083   assert(!free_regions_coming(), "pre-condition");
6084   _free_regions_coming = true;
6085 }
6086 
6087 void G1CollectedHeap::reset_free_regions_coming() {
6088   assert(free_regions_coming(), "pre-condition");
6089 
6090   {
6091     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6092     _free_regions_coming = false;
6093     SecondaryFreeList_lock->notify_all();
6094   }
6095 
6096   if (G1ConcRegionFreeingVerbose) {
6097     gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6098                            "reset free regions coming");
6099   }
6100 }
6101 
6102 void G1CollectedHeap::wait_while_free_regions_coming() {
6103   // Most of the time we won't have to wait, so let's do a quick test
6104   // first before we take the lock.
6105   if (!free_regions_coming()) {
6106     return;
6107   }
6108 
6109   if (G1ConcRegionFreeingVerbose) {
6110     gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6111                            "waiting for free regions");
6112   }
6113 
6114   {
6115     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6116     while (free_regions_coming()) {
6117       SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
6118     }
6119   }
6120 
6121   if (G1ConcRegionFreeingVerbose) {
6122     gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6123                            "done waiting for free regions");
6124   }
6125 }
6126 
6127 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
6128   _young_list->push_region(hr);
6129 }
6130 
6131 class NoYoungRegionsClosure: public HeapRegionClosure {
6132 private:
6133   bool _success;
6134 public:
6135   NoYoungRegionsClosure() : _success(true) { }
6136   bool doHeapRegion(HeapRegion* r) {
6137     if (r->is_young()) {
6138       gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
6139                              p2i(r->bottom()), p2i(r->end()));
6140       _success = false;
6141     }
6142     return false;
6143   }
6144   bool success() { return _success; }
6145 };
6146 
6147 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
6148   bool ret = _young_list->check_list_empty(check_sample);
6149 
6150   if (check_heap) {
6151     NoYoungRegionsClosure closure;
6152     heap_region_iterate(&closure);
6153     ret = ret && closure.success();
6154   }
6155 
6156   return ret;
6157 }
6158 
6159 class TearDownRegionSetsClosure : public HeapRegionClosure {
6160 private:
6161   HeapRegionSet *_old_set;
6162 
6163 public:
6164   TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
6165 
6166   bool doHeapRegion(HeapRegion* r) {
6167     if (r->is_old()) {
6168       _old_set->remove(r);
6169     } else {
6170       // We ignore free regions, we'll empty the free list afterwards.
6171       // We ignore young regions, we'll empty the young list afterwards.
6172       // We ignore humongous regions, we're not tearing down the
6173       // humongous regions set.
6174       assert(r->is_free() || r->is_young() || r->is_humongous(),
6175              "it cannot be another type");
6176     }
6177     return false;
6178   }
6179 
6180   ~TearDownRegionSetsClosure() {
6181     assert(_old_set->is_empty(), "post-condition");
6182   }
6183 };
6184 
6185 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6186   assert_at_safepoint(true /* should_be_vm_thread */);
6187 
6188   if (!free_list_only) {
6189     TearDownRegionSetsClosure cl(&_old_set);
6190     heap_region_iterate(&cl);
6191 
6192     // Note that emptying the _young_list is postponed and instead done as
6193     // the first step when rebuilding the regions sets again. The reason for
6194     // this is that during a full GC string deduplication needs to know if
6195     // a collected region was young or old when the full GC was initiated.
6196   }
6197   _hrm.remove_all_free_regions();
6198 }
6199 
6200 class RebuildRegionSetsClosure : public HeapRegionClosure {
6201 private:
6202   bool            _free_list_only;
6203   HeapRegionSet*   _old_set;
6204   HeapRegionManager*   _hrm;
6205   size_t          _total_used;
6206 
6207 public:
6208   RebuildRegionSetsClosure(bool free_list_only,
6209                            HeapRegionSet* old_set, HeapRegionManager* hrm) :
6210     _free_list_only(free_list_only),
6211     _old_set(old_set), _hrm(hrm), _total_used(0) {
6212     assert(_hrm->num_free_regions() == 0, "pre-condition");
6213     if (!free_list_only) {
6214       assert(_old_set->is_empty(), "pre-condition");
6215     }
6216   }
6217 
6218   bool doHeapRegion(HeapRegion* r) {
6219     if (r->is_continues_humongous()) {
6220       return false;
6221     }
6222 
6223     if (r->is_empty()) {
6224       // Add free regions to the free list
6225       r->set_free();
6226       r->set_allocation_context(AllocationContext::system());
6227       _hrm->insert_into_free_list(r);
6228     } else if (!_free_list_only) {
6229       assert(!r->is_young(), "we should not come across young regions");
6230 
6231       if (r->is_humongous()) {
6232         // We ignore humongous regions, we left the humongous set unchanged
6233       } else {
6234         // Objects that were compacted would have ended up on regions
6235         // that were previously old or free.
6236         assert(r->is_free() || r->is_old(), "invariant");
6237         // We now consider them old, so register as such.
6238         r->set_old();
6239         _old_set->add(r);
6240       }
6241       _total_used += r->used();
6242     }
6243 
6244     return false;
6245   }
6246 
6247   size_t total_used() {
6248     return _total_used;
6249   }
6250 };
6251 
6252 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6253   assert_at_safepoint(true /* should_be_vm_thread */);
6254 
6255   if (!free_list_only) {
6256     _young_list->empty_list();
6257   }
6258 
6259   RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
6260   heap_region_iterate(&cl);
6261 
6262   if (!free_list_only) {
6263     _allocator->set_used(cl.total_used());
6264   }
6265   assert(_allocator->used_unlocked() == recalculate_used(),
6266          err_msg("inconsistent _allocator->used_unlocked(), "
6267                  "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6268                  _allocator->used_unlocked(), recalculate_used()));
6269 }
6270 
6271 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6272   _refine_cte_cl->set_concurrent(concurrent);
6273 }
6274 
6275 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6276   HeapRegion* hr = heap_region_containing(p);
6277   return hr->is_in(p);
6278 }
6279 
6280 // Methods for the mutator alloc region
6281 
6282 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6283                                                       bool force) {
6284   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6285   assert(!force || g1_policy()->can_expand_young_list(),
6286          "if force is true we should be able to expand the young list");
6287   bool young_list_full = g1_policy()->is_young_list_full();
6288   if (force || !young_list_full) {
6289     HeapRegion* new_alloc_region = new_region(word_size,
6290                                               false /* is_old */,
6291                                               false /* do_expand */);
6292     if (new_alloc_region != NULL) {
6293       set_region_short_lived_locked(new_alloc_region);
6294       _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6295       check_bitmaps("Mutator Region Allocation", new_alloc_region);
6296       return new_alloc_region;
6297     }
6298   }
6299   return NULL;
6300 }
6301 
6302 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6303                                                   size_t allocated_bytes) {
6304   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6305   assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
6306 
6307   g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6308   _allocator->increase_used(allocated_bytes);
6309   _hr_printer.retire(alloc_region);
6310   // We update the eden sizes here, when the region is retired,
6311   // instead of when it's allocated, since this is the point that its
6312   // used space has been recored in _summary_bytes_used.
6313   g1mm()->update_eden_size();
6314 }
6315 
6316 void G1CollectedHeap::set_par_threads() {
6317   // Don't change the number of workers.  Use the value previously set
6318   // in the workgroup.
6319   uint n_workers = workers()->active_workers();
6320   assert(UseDynamicNumberOfGCThreads ||
6321            n_workers == workers()->total_workers(),
6322       "Otherwise should be using the total number of workers");
6323   if (n_workers == 0) {
6324     assert(false, "Should have been set in prior evacuation pause.");
6325     n_workers = ParallelGCThreads;
6326     workers()->set_active_workers(n_workers);
6327   }
6328   set_par_threads(n_workers);
6329 }
6330 
6331 // Methods for the GC alloc regions
6332 
6333 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6334                                                  uint count,
6335                                                  InCSetState dest) {
6336   assert(FreeList_lock->owned_by_self(), "pre-condition");
6337 
6338   if (count < g1_policy()->max_regions(dest)) {
6339     const bool is_survivor = (dest.is_young());
6340     HeapRegion* new_alloc_region = new_region(word_size,
6341                                               !is_survivor,
6342                                               true /* do_expand */);
6343     if (new_alloc_region != NULL) {
6344       // We really only need to do this for old regions given that we
6345       // should never scan survivors. But it doesn't hurt to do it
6346       // for survivors too.
6347       new_alloc_region->record_timestamp();
6348       if (is_survivor) {
6349         new_alloc_region->set_survivor();
6350         _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6351         check_bitmaps("Survivor Region Allocation", new_alloc_region);
6352       } else {
6353         new_alloc_region->set_old();
6354         _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6355         check_bitmaps("Old Region Allocation", new_alloc_region);
6356       }
6357       bool during_im = g1_policy()->during_initial_mark_pause();
6358       new_alloc_region->note_start_of_copying(during_im);
6359       return new_alloc_region;
6360     }
6361   }
6362   return NULL;
6363 }
6364 
6365 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6366                                              size_t allocated_bytes,
6367                                              InCSetState dest) {
6368   bool during_im = g1_policy()->during_initial_mark_pause();
6369   alloc_region->note_end_of_copying(during_im);
6370   g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6371   if (dest.is_young()) {
6372     young_list()->add_survivor_region(alloc_region);
6373   } else {
6374     _old_set.add(alloc_region);
6375   }
6376   _hr_printer.retire(alloc_region);
6377 }
6378 
6379 // Heap region set verification
6380 
6381 class VerifyRegionListsClosure : public HeapRegionClosure {
6382 private:
6383   HeapRegionSet*   _old_set;
6384   HeapRegionSet*   _humongous_set;
6385   HeapRegionManager*   _hrm;
6386 
6387 public:
6388   HeapRegionSetCount _old_count;
6389   HeapRegionSetCount _humongous_count;
6390   HeapRegionSetCount _free_count;
6391 
6392   VerifyRegionListsClosure(HeapRegionSet* old_set,
6393                            HeapRegionSet* humongous_set,
6394                            HeapRegionManager* hrm) :
6395     _old_set(old_set), _humongous_set(humongous_set), _hrm(hrm),
6396     _old_count(), _humongous_count(), _free_count(){ }
6397 
6398   bool doHeapRegion(HeapRegion* hr) {
6399     if (hr->is_continues_humongous()) {
6400       return false;
6401     }
6402 
6403     if (hr->is_young()) {
6404       // TODO
6405     } else if (hr->is_starts_humongous()) {
6406       assert(hr->containing_set() == _humongous_set, err_msg("Heap region %u is starts humongous but not in humongous set.", hr->hrm_index()));
6407       _humongous_count.increment(1u, hr->capacity());
6408     } else if (hr->is_empty()) {
6409       assert(_hrm->is_free(hr), err_msg("Heap region %u is empty but not on the free list.", hr->hrm_index()));
6410       _free_count.increment(1u, hr->capacity());
6411     } else if (hr->is_old()) {
6412       assert(hr->containing_set() == _old_set, err_msg("Heap region %u is old but not in the old set.", hr->hrm_index()));
6413       _old_count.increment(1u, hr->capacity());
6414     } else {
6415       ShouldNotReachHere();
6416     }
6417     return false;
6418   }
6419 
6420   void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, HeapRegionManager* free_list) {
6421     guarantee(old_set->length() == _old_count.length(), err_msg("Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length()));
6422     guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), err_msg("Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6423         old_set->total_capacity_bytes(), _old_count.capacity()));
6424 
6425     guarantee(humongous_set->length() == _humongous_count.length(), err_msg("Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length()));
6426     guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), err_msg("Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6427         humongous_set->total_capacity_bytes(), _humongous_count.capacity()));
6428 
6429     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()));
6430     guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), err_msg("Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6431         free_list->total_capacity_bytes(), _free_count.capacity()));
6432   }
6433 };
6434 
6435 void G1CollectedHeap::verify_region_sets() {
6436   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6437 
6438   // First, check the explicit lists.
6439   _hrm.verify();
6440   {
6441     // Given that a concurrent operation might be adding regions to
6442     // the secondary free list we have to take the lock before
6443     // verifying it.
6444     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6445     _secondary_free_list.verify_list();
6446   }
6447 
6448   // If a concurrent region freeing operation is in progress it will
6449   // be difficult to correctly attributed any free regions we come
6450   // across to the correct free list given that they might belong to
6451   // one of several (free_list, secondary_free_list, any local lists,
6452   // etc.). So, if that's the case we will skip the rest of the
6453   // verification operation. Alternatively, waiting for the concurrent
6454   // operation to complete will have a non-trivial effect on the GC's
6455   // operation (no concurrent operation will last longer than the
6456   // interval between two calls to verification) and it might hide
6457   // any issues that we would like to catch during testing.
6458   if (free_regions_coming()) {
6459     return;
6460   }
6461 
6462   // Make sure we append the secondary_free_list on the free_list so
6463   // that all free regions we will come across can be safely
6464   // attributed to the free_list.
6465   append_secondary_free_list_if_not_empty_with_lock();
6466 
6467   // Finally, make sure that the region accounting in the lists is
6468   // consistent with what we see in the heap.
6469 
6470   VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_hrm);
6471   heap_region_iterate(&cl);
6472   cl.verify_counts(&_old_set, &_humongous_set, &_hrm);
6473 }
6474 
6475 // Optimized nmethod scanning
6476 
6477 class RegisterNMethodOopClosure: public OopClosure {
6478   G1CollectedHeap* _g1h;
6479   nmethod* _nm;
6480 
6481   template <class T> void do_oop_work(T* p) {
6482     T heap_oop = oopDesc::load_heap_oop(p);
6483     if (!oopDesc::is_null(heap_oop)) {
6484       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6485       HeapRegion* hr = _g1h->heap_region_containing(obj);
6486       assert(!hr->is_continues_humongous(),
6487              err_msg("trying to add code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6488                      " starting at "HR_FORMAT,
6489                      p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6490 
6491       // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
6492       hr->add_strong_code_root_locked(_nm);
6493     }
6494   }
6495 
6496 public:
6497   RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6498     _g1h(g1h), _nm(nm) {}
6499 
6500   void do_oop(oop* p)       { do_oop_work(p); }
6501   void do_oop(narrowOop* p) { do_oop_work(p); }
6502 };
6503 
6504 class UnregisterNMethodOopClosure: public OopClosure {
6505   G1CollectedHeap* _g1h;
6506   nmethod* _nm;
6507 
6508   template <class T> void do_oop_work(T* p) {
6509     T heap_oop = oopDesc::load_heap_oop(p);
6510     if (!oopDesc::is_null(heap_oop)) {
6511       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6512       HeapRegion* hr = _g1h->heap_region_containing(obj);
6513       assert(!hr->is_continues_humongous(),
6514              err_msg("trying to remove code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6515                      " starting at "HR_FORMAT,
6516                      p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6517 
6518       hr->remove_strong_code_root(_nm);
6519     }
6520   }
6521 
6522 public:
6523   UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6524     _g1h(g1h), _nm(nm) {}
6525 
6526   void do_oop(oop* p)       { do_oop_work(p); }
6527   void do_oop(narrowOop* p) { do_oop_work(p); }
6528 };
6529 
6530 void G1CollectedHeap::register_nmethod(nmethod* nm) {
6531   CollectedHeap::register_nmethod(nm);
6532 
6533   guarantee(nm != NULL, "sanity");
6534   RegisterNMethodOopClosure reg_cl(this, nm);
6535   nm->oops_do(&reg_cl);
6536 }
6537 
6538 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
6539   CollectedHeap::unregister_nmethod(nm);
6540 
6541   guarantee(nm != NULL, "sanity");
6542   UnregisterNMethodOopClosure reg_cl(this, nm);
6543   nm->oops_do(&reg_cl, true);
6544 }
6545 
6546 void G1CollectedHeap::purge_code_root_memory() {
6547   double purge_start = os::elapsedTime();
6548   G1CodeRootSet::purge();
6549   double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
6550   g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
6551 }
6552 
6553 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
6554   G1CollectedHeap* _g1h;
6555 
6556 public:
6557   RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
6558     _g1h(g1h) {}
6559 
6560   void do_code_blob(CodeBlob* cb) {
6561     nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
6562     if (nm == NULL) {
6563       return;
6564     }
6565 
6566     if (ScavengeRootsInCode) {
6567       _g1h->register_nmethod(nm);
6568     }
6569   }
6570 };
6571 
6572 void G1CollectedHeap::rebuild_strong_code_roots() {
6573   RebuildStrongCodeRootClosure blob_cl(this);
6574   CodeCache::blobs_do(&blob_cl);
6575 }