1 /*
   2  * Copyright (c) 2001, 2014, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #if !defined(__clang_major__) && defined(__GNUC__)
  26 // FIXME, formats have issues.  Disable this macro definition, compile, and study warnings for more information.
  27 #define ATTRIBUTE_PRINTF(x,y)
  28 #endif
  29 
  30 #include "precompiled.hpp"
  31 #include "classfile/stringTable.hpp"
  32 #include "code/codeCache.hpp"
  33 #include "code/icBuffer.hpp"
  34 #include "gc_implementation/g1/bufferingOopClosure.hpp"
  35 #include "gc_implementation/g1/concurrentG1Refine.hpp"
  36 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
  37 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
  38 #include "gc_implementation/g1/g1AllocRegion.inline.hpp"
  39 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
  40 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
  41 #include "gc_implementation/g1/g1ErgoVerbose.hpp"
  42 #include "gc_implementation/g1/g1EvacFailure.hpp"
  43 #include "gc_implementation/g1/g1GCPhaseTimes.hpp"
  44 #include "gc_implementation/g1/g1Log.hpp"
  45 #include "gc_implementation/g1/g1MarkSweep.hpp"
  46 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
  47 #include "gc_implementation/g1/g1ParScanThreadState.inline.hpp"
  48 #include "gc_implementation/g1/g1RemSet.inline.hpp"
  49 #include "gc_implementation/g1/g1StringDedup.hpp"
  50 #include "gc_implementation/g1/g1YCTypes.hpp"
  51 #include "gc_implementation/g1/heapRegion.inline.hpp"
  52 #include "gc_implementation/g1/heapRegionRemSet.hpp"
  53 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
  54 #include "gc_implementation/g1/vm_operations_g1.hpp"
  55 #include "gc_implementation/shared/gcHeapSummary.hpp"
  56 #include "gc_implementation/shared/gcTimer.hpp"
  57 #include "gc_implementation/shared/gcTrace.hpp"
  58 #include "gc_implementation/shared/gcTraceTime.hpp"
  59 #include "gc_implementation/shared/isGCActiveMark.hpp"
  60 #include "memory/allocation.hpp"
  61 #include "memory/gcLocker.inline.hpp"
  62 #include "memory/generationSpec.hpp"
  63 #include "memory/iterator.hpp"
  64 #include "memory/referenceProcessor.hpp"
  65 #include "oops/oop.inline.hpp"
  66 #include "oops/oop.pcgc.inline.hpp"
  67 #include "runtime/atomic.inline.hpp"
  68 #include "runtime/orderAccess.inline.hpp"
  69 #include "runtime/vmThread.hpp"
  70 #include "utilities/globalDefinitions.hpp"
  71 
  72 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
  73 
  74 // turn it on so that the contents of the young list (scan-only /
  75 // to-be-collected) are printed at "strategic" points before / during
  76 // / after the collection --- this is useful for debugging
  77 #define YOUNG_LIST_VERBOSE 0
  78 // CURRENT STATUS
  79 // This file is under construction.  Search for "FIXME".
  80 
  81 // INVARIANTS/NOTES
  82 //
  83 // All allocation activity covered by the G1CollectedHeap interface is
  84 // serialized by acquiring the HeapLock.  This happens in mem_allocate
  85 // and allocate_new_tlab, which are the "entry" points to the
  86 // allocation code from the rest of the JVM.  (Note that this does not
  87 // apply to TLAB allocation, which is not part of this interface: it
  88 // is done by clients of this interface.)
  89 
  90 // Notes on implementation of parallelism in different tasks.
  91 //
  92 // G1ParVerifyTask uses heap_region_par_iterate_chunked() for parallelism.
  93 // The number of GC workers is passed to heap_region_par_iterate_chunked().
  94 // It does use run_task() which sets _n_workers in the task.
  95 // G1ParTask executes g1_process_roots() ->
  96 // SharedHeap::process_roots() which calls eventually to
  97 // CardTableModRefBS::par_non_clean_card_iterate_work() which uses
  98 // SequentialSubTasksDone.  SharedHeap::process_roots() also
  99 // directly uses SubTasksDone (_process_strong_tasks field in SharedHeap).
 100 //
 101 
 102 // Local to this file.
 103 
 104 class RefineCardTableEntryClosure: public CardTableEntryClosure {
 105   bool _concurrent;
 106 public:
 107   RefineCardTableEntryClosure() : _concurrent(true) { }
 108 
 109   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
 110     bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, false);
 111     // This path is executed by the concurrent refine or mutator threads,
 112     // concurrently, and so we do not care if card_ptr contains references
 113     // that point into the collection set.
 114     assert(!oops_into_cset, "should be");
 115 
 116     if (_concurrent && SuspendibleThreadSet::should_yield()) {
 117       // Caller will actually yield.
 118       return false;
 119     }
 120     // Otherwise, we finished successfully; return true.
 121     return true;
 122   }
 123 
 124   void set_concurrent(bool b) { _concurrent = b; }
 125 };
 126 
 127 
 128 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure {
 129   size_t _num_processed;
 130   CardTableModRefBS* _ctbs;
 131   int _histo[256];
 132 
 133  public:
 134   ClearLoggedCardTableEntryClosure() :
 135     _num_processed(0), _ctbs(G1CollectedHeap::heap()->g1_barrier_set())
 136   {
 137     for (int i = 0; i < 256; i++) _histo[i] = 0;
 138   }
 139 
 140   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
 141     unsigned char* ujb = (unsigned char*)card_ptr;
 142     int ind = (int)(*ujb);
 143     _histo[ind]++;
 144 
 145     *card_ptr = (jbyte)CardTableModRefBS::clean_card_val();
 146     _num_processed++;
 147 
 148     return true;
 149   }
 150 
 151   size_t num_processed() { return _num_processed; }
 152 
 153   void print_histo() {
 154     gclog_or_tty->print_cr("Card table value histogram:");
 155     for (int i = 0; i < 256; i++) {
 156       if (_histo[i] != 0) {
 157         gclog_or_tty->print_cr("  %d: %d", i, _histo[i]);
 158       }
 159     }
 160   }
 161 };
 162 
 163 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
 164  private:
 165   size_t _num_processed;
 166 
 167  public:
 168   RedirtyLoggedCardTableEntryClosure() : CardTableEntryClosure(), _num_processed(0) { }
 169 
 170   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
 171     *card_ptr = CardTableModRefBS::dirty_card_val();
 172     _num_processed++;
 173     return true;
 174   }
 175 
 176   size_t num_processed() const { return _num_processed; }
 177 };
 178 
 179 YoungList::YoungList(G1CollectedHeap* g1h) :
 180     _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0),
 181     _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) {
 182   guarantee(check_list_empty(false), "just making sure...");
 183 }
 184 
 185 void YoungList::push_region(HeapRegion *hr) {
 186   assert(!hr->is_young(), "should not already be young");
 187   assert(hr->get_next_young_region() == NULL, "cause it should!");
 188 
 189   hr->set_next_young_region(_head);
 190   _head = hr;
 191 
 192   _g1h->g1_policy()->set_region_eden(hr, (int) _length);
 193   ++_length;
 194 }
 195 
 196 void YoungList::add_survivor_region(HeapRegion* hr) {
 197   assert(hr->is_survivor(), "should be flagged as survivor region");
 198   assert(hr->get_next_young_region() == NULL, "cause it should!");
 199 
 200   hr->set_next_young_region(_survivor_head);
 201   if (_survivor_head == NULL) {
 202     _survivor_tail = hr;
 203   }
 204   _survivor_head = hr;
 205   ++_survivor_length;
 206 }
 207 
 208 void YoungList::empty_list(HeapRegion* list) {
 209   while (list != NULL) {
 210     HeapRegion* next = list->get_next_young_region();
 211     list->set_next_young_region(NULL);
 212     list->uninstall_surv_rate_group();
 213     list->set_not_young();
 214     list = next;
 215   }
 216 }
 217 
 218 void YoungList::empty_list() {
 219   assert(check_list_well_formed(), "young list should be well formed");
 220 
 221   empty_list(_head);
 222   _head = NULL;
 223   _length = 0;
 224 
 225   empty_list(_survivor_head);
 226   _survivor_head = NULL;
 227   _survivor_tail = NULL;
 228   _survivor_length = 0;
 229 
 230   _last_sampled_rs_lengths = 0;
 231 
 232   assert(check_list_empty(false), "just making sure...");
 233 }
 234 
 235 bool YoungList::check_list_well_formed() {
 236   bool ret = true;
 237 
 238   uint length = 0;
 239   HeapRegion* curr = _head;
 240   HeapRegion* last = NULL;
 241   while (curr != NULL) {
 242     if (!curr->is_young()) {
 243       gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
 244                              "incorrectly tagged (y: %d, surv: %d)",
 245                              curr->bottom(), curr->end(),
 246                              curr->is_young(), curr->is_survivor());
 247       ret = false;
 248     }
 249     ++length;
 250     last = curr;
 251     curr = curr->get_next_young_region();
 252   }
 253   ret = ret && (length == _length);
 254 
 255   if (!ret) {
 256     gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
 257     gclog_or_tty->print_cr("###   list has %u entries, _length is %u",
 258                            length, _length);
 259   }
 260 
 261   return ret;
 262 }
 263 
 264 bool YoungList::check_list_empty(bool check_sample) {
 265   bool ret = true;
 266 
 267   if (_length != 0) {
 268     gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u",
 269                   _length);
 270     ret = false;
 271   }
 272   if (check_sample && _last_sampled_rs_lengths != 0) {
 273     gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
 274     ret = false;
 275   }
 276   if (_head != NULL) {
 277     gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
 278     ret = false;
 279   }
 280   if (!ret) {
 281     gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
 282   }
 283 
 284   return ret;
 285 }
 286 
 287 void
 288 YoungList::rs_length_sampling_init() {
 289   _sampled_rs_lengths = 0;
 290   _curr               = _head;
 291 }
 292 
 293 bool
 294 YoungList::rs_length_sampling_more() {
 295   return _curr != NULL;
 296 }
 297 
 298 void
 299 YoungList::rs_length_sampling_next() {
 300   assert( _curr != NULL, "invariant" );
 301   size_t rs_length = _curr->rem_set()->occupied();
 302 
 303   _sampled_rs_lengths += rs_length;
 304 
 305   // The current region may not yet have been added to the
 306   // incremental collection set (it gets added when it is
 307   // retired as the current allocation region).
 308   if (_curr->in_collection_set()) {
 309     // Update the collection set policy information for this region
 310     _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
 311   }
 312 
 313   _curr = _curr->get_next_young_region();
 314   if (_curr == NULL) {
 315     _last_sampled_rs_lengths = _sampled_rs_lengths;
 316     // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
 317   }
 318 }
 319 
 320 void
 321 YoungList::reset_auxilary_lists() {
 322   guarantee( is_empty(), "young list should be empty" );
 323   assert(check_list_well_formed(), "young list should be well formed");
 324 
 325   // Add survivor regions to SurvRateGroup.
 326   _g1h->g1_policy()->note_start_adding_survivor_regions();
 327   _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
 328 
 329   int young_index_in_cset = 0;
 330   for (HeapRegion* curr = _survivor_head;
 331        curr != NULL;
 332        curr = curr->get_next_young_region()) {
 333     _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
 334 
 335     // The region is a non-empty survivor so let's add it to
 336     // the incremental collection set for the next evacuation
 337     // pause.
 338     _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
 339     young_index_in_cset += 1;
 340   }
 341   assert((uint) young_index_in_cset == _survivor_length, "post-condition");
 342   _g1h->g1_policy()->note_stop_adding_survivor_regions();
 343 
 344   _head   = _survivor_head;
 345   _length = _survivor_length;
 346   if (_survivor_head != NULL) {
 347     assert(_survivor_tail != NULL, "cause it shouldn't be");
 348     assert(_survivor_length > 0, "invariant");
 349     _survivor_tail->set_next_young_region(NULL);
 350   }
 351 
 352   // Don't clear the survivor list handles until the start of
 353   // the next evacuation pause - we need it in order to re-tag
 354   // the survivor regions from this evacuation pause as 'young'
 355   // at the start of the next.
 356 
 357   _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
 358 
 359   assert(check_list_well_formed(), "young list should be well formed");
 360 }
 361 
 362 void YoungList::print() {
 363   HeapRegion* lists[] = {_head,   _survivor_head};
 364   const char* names[] = {"YOUNG", "SURVIVOR"};
 365 
 366   for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) {
 367     gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
 368     HeapRegion *curr = lists[list];
 369     if (curr == NULL)
 370       gclog_or_tty->print_cr("  empty");
 371     while (curr != NULL) {
 372       gclog_or_tty->print_cr("  "HR_FORMAT", P: "PTR_FORMAT "N: "PTR_FORMAT", age: %4d",
 373                              HR_FORMAT_PARAMS(curr),
 374                              curr->prev_top_at_mark_start(),
 375                              curr->next_top_at_mark_start(),
 376                              curr->age_in_surv_rate_group_cond());
 377       curr = curr->get_next_young_region();
 378     }
 379   }
 380 
 381   gclog_or_tty->cr();
 382 }
 383 
 384 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
 385 {
 386   // Claim the right to put the region on the dirty cards region list
 387   // by installing a self pointer.
 388   HeapRegion* next = hr->get_next_dirty_cards_region();
 389   if (next == NULL) {
 390     HeapRegion* res = (HeapRegion*)
 391       Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
 392                           NULL);
 393     if (res == NULL) {
 394       HeapRegion* head;
 395       do {
 396         // Put the region to the dirty cards region list.
 397         head = _dirty_cards_region_list;
 398         next = (HeapRegion*)
 399           Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
 400         if (next == head) {
 401           assert(hr->get_next_dirty_cards_region() == hr,
 402                  "hr->get_next_dirty_cards_region() != hr");
 403           if (next == NULL) {
 404             // The last region in the list points to itself.
 405             hr->set_next_dirty_cards_region(hr);
 406           } else {
 407             hr->set_next_dirty_cards_region(next);
 408           }
 409         }
 410       } while (next != head);
 411     }
 412   }
 413 }
 414 
 415 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
 416 {
 417   HeapRegion* head;
 418   HeapRegion* hr;
 419   do {
 420     head = _dirty_cards_region_list;
 421     if (head == NULL) {
 422       return NULL;
 423     }
 424     HeapRegion* new_head = head->get_next_dirty_cards_region();
 425     if (head == new_head) {
 426       // The last region.
 427       new_head = NULL;
 428     }
 429     hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
 430                                           head);
 431   } while (hr != head);
 432   assert(hr != NULL, "invariant");
 433   hr->set_next_dirty_cards_region(NULL);
 434   return hr;
 435 }
 436 
 437 #ifdef ASSERT
 438 // A region is added to the collection set as it is retired
 439 // so an address p can point to a region which will be in the
 440 // collection set but has not yet been retired.  This method
 441 // therefore is only accurate during a GC pause after all
 442 // regions have been retired.  It is used for debugging
 443 // to check if an nmethod has references to objects that can
 444 // be move during a partial collection.  Though it can be
 445 // inaccurate, it is sufficient for G1 because the conservative
 446 // implementation of is_scavengable() for G1 will indicate that
 447 // all nmethods must be scanned during a partial collection.
 448 bool G1CollectedHeap::is_in_partial_collection(const void* p) {
 449   if (p == NULL) {
 450     return false;
 451   }
 452   return heap_region_containing(p)->in_collection_set();
 453 }
 454 #endif
 455 
 456 // Returns true if the reference points to an object that
 457 // can move in an incremental collection.
 458 bool G1CollectedHeap::is_scavengable(const void* p) {
 459   HeapRegion* hr = heap_region_containing(p);
 460   return !hr->isHumongous();
 461 }
 462 
 463 void G1CollectedHeap::check_ct_logs_at_safepoint() {
 464   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
 465   CardTableModRefBS* ct_bs = g1_barrier_set();
 466 
 467   // Count the dirty cards at the start.
 468   CountNonCleanMemRegionClosure count1(this);
 469   ct_bs->mod_card_iterate(&count1);
 470   int orig_count = count1.n();
 471 
 472   // First clear the logged cards.
 473   ClearLoggedCardTableEntryClosure clear;
 474   dcqs.apply_closure_to_all_completed_buffers(&clear);
 475   dcqs.iterate_closure_all_threads(&clear, false);
 476   clear.print_histo();
 477 
 478   // Now ensure that there's no dirty cards.
 479   CountNonCleanMemRegionClosure count2(this);
 480   ct_bs->mod_card_iterate(&count2);
 481   if (count2.n() != 0) {
 482     gclog_or_tty->print_cr("Card table has %d entries; %d originally",
 483                            count2.n(), orig_count);
 484   }
 485   guarantee(count2.n() == 0, "Card table should be clean.");
 486 
 487   RedirtyLoggedCardTableEntryClosure redirty;
 488   dcqs.apply_closure_to_all_completed_buffers(&redirty);
 489   dcqs.iterate_closure_all_threads(&redirty, false);
 490   gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
 491                          clear.num_processed(), orig_count);
 492   guarantee(redirty.num_processed() == clear.num_processed(),
 493             err_msg("Redirtied "SIZE_FORMAT" cards, bug cleared "SIZE_FORMAT,
 494                     redirty.num_processed(), clear.num_processed()));
 495 
 496   CountNonCleanMemRegionClosure count3(this);
 497   ct_bs->mod_card_iterate(&count3);
 498   if (count3.n() != orig_count) {
 499     gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
 500                            orig_count, count3.n());
 501     guarantee(count3.n() >= orig_count, "Should have restored them all.");
 502   }
 503 }
 504 
 505 // Private class members.
 506 
 507 G1CollectedHeap* G1CollectedHeap::_g1h;
 508 
 509 // Private methods.
 510 
 511 HeapRegion*
 512 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
 513   MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
 514   while (!_secondary_free_list.is_empty() || free_regions_coming()) {
 515     if (!_secondary_free_list.is_empty()) {
 516       if (G1ConcRegionFreeingVerbose) {
 517         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 518                                "secondary_free_list has %u entries",
 519                                _secondary_free_list.length());
 520       }
 521       // It looks as if there are free regions available on the
 522       // secondary_free_list. Let's move them to the free_list and try
 523       // again to allocate from it.
 524       append_secondary_free_list();
 525 
 526       assert(!_free_list.is_empty(), "if the secondary_free_list was not "
 527              "empty we should have moved at least one entry to the free_list");
 528       HeapRegion* res = _free_list.remove_region(is_old);
 529       if (G1ConcRegionFreeingVerbose) {
 530         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 531                                "allocated "HR_FORMAT" from secondary_free_list",
 532                                HR_FORMAT_PARAMS(res));
 533       }
 534       return res;
 535     }
 536 
 537     // Wait here until we get notified either when (a) there are no
 538     // more free regions coming or (b) some regions have been moved on
 539     // the secondary_free_list.
 540     SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
 541   }
 542 
 543   if (G1ConcRegionFreeingVerbose) {
 544     gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 545                            "could not allocate from secondary_free_list");
 546   }
 547   return NULL;
 548 }
 549 
 550 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
 551   assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords,
 552          "the only time we use this to allocate a humongous region is "
 553          "when we are allocating a single humongous region");
 554 
 555   HeapRegion* res;
 556   if (G1StressConcRegionFreeing) {
 557     if (!_secondary_free_list.is_empty()) {
 558       if (G1ConcRegionFreeingVerbose) {
 559         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 560                                "forced to look at the secondary_free_list");
 561       }
 562       res = new_region_try_secondary_free_list(is_old);
 563       if (res != NULL) {
 564         return res;
 565       }
 566     }
 567   }
 568 
 569   res = _free_list.remove_region(is_old);
 570 
 571   if (res == NULL) {
 572     if (G1ConcRegionFreeingVerbose) {
 573       gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 574                              "res == NULL, trying the secondary_free_list");
 575     }
 576     res = new_region_try_secondary_free_list(is_old);
 577   }
 578   if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
 579     // Currently, only attempts to allocate GC alloc regions set
 580     // do_expand to true. So, we should only reach here during a
 581     // safepoint. If this assumption changes we might have to
 582     // reconsider the use of _expand_heap_after_alloc_failure.
 583     assert(SafepointSynchronize::is_at_safepoint(), "invariant");
 584 
 585     ergo_verbose1(ErgoHeapSizing,
 586                   "attempt heap expansion",
 587                   ergo_format_reason("region allocation request failed")
 588                   ergo_format_byte("allocation request"),
 589                   word_size * HeapWordSize);
 590     if (expand(word_size * HeapWordSize)) {
 591       // Given that expand() succeeded in expanding the heap, and we
 592       // always expand the heap by an amount aligned to the heap
 593       // region size, the free list should in theory not be empty.
 594       // In either case remove_region() will check for NULL.
 595       res = _free_list.remove_region(is_old);
 596     } else {
 597       _expand_heap_after_alloc_failure = false;
 598     }
 599   }
 600   return res;
 601 }
 602 
 603 uint G1CollectedHeap::humongous_obj_allocate_find_first(uint num_regions,
 604                                                         size_t word_size) {
 605   assert(isHumongous(word_size), "word_size should be humongous");
 606   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 607 
 608   uint first = G1_NULL_HRS_INDEX;
 609   if (num_regions == 1) {
 610     // Only one region to allocate, no need to go through the slower
 611     // path. The caller will attempt the expansion if this fails, so
 612     // let's not try to expand here too.
 613     HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
 614     if (hr != NULL) {
 615       first = hr->hrs_index();
 616     } else {
 617       first = G1_NULL_HRS_INDEX;
 618     }
 619   } else {
 620     // We can't allocate humongous regions while cleanupComplete() is
 621     // running, since some of the regions we find to be empty might not
 622     // yet be added to the free list and it is not straightforward to
 623     // know which list they are on so that we can remove them. Note
 624     // that we only need to do this if we need to allocate more than
 625     // one region to satisfy the current humongous allocation
 626     // request. If we are only allocating one region we use the common
 627     // region allocation code (see above).
 628     wait_while_free_regions_coming();
 629     append_secondary_free_list_if_not_empty_with_lock();
 630 
 631     if (free_regions() >= num_regions) {
 632       first = _hrs.find_contiguous(num_regions);
 633       if (first != G1_NULL_HRS_INDEX) {
 634         for (uint i = first; i < first + num_regions; ++i) {
 635           HeapRegion* hr = region_at(i);
 636           assert(hr->is_empty(), "sanity");
 637           assert(is_on_master_free_list(hr), "sanity");
 638           hr->set_pending_removal(true);
 639         }
 640         _free_list.remove_all_pending(num_regions);
 641       }
 642     }
 643   }
 644   return first;
 645 }
 646 
 647 HeapWord*
 648 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
 649                                                            uint num_regions,
 650                                                            size_t word_size) {
 651   assert(first != G1_NULL_HRS_INDEX, "pre-condition");
 652   assert(isHumongous(word_size), "word_size should be humongous");
 653   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 654 
 655   // Index of last region in the series + 1.
 656   uint last = first + num_regions;
 657 
 658   // We need to initialize the region(s) we just discovered. This is
 659   // a bit tricky given that it can happen concurrently with
 660   // refinement threads refining cards on these regions and
 661   // potentially wanting to refine the BOT as they are scanning
 662   // those cards (this can happen shortly after a cleanup; see CR
 663   // 6991377). So we have to set up the region(s) carefully and in
 664   // a specific order.
 665 
 666   // The word size sum of all the regions we will allocate.
 667   size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
 668   assert(word_size <= word_size_sum, "sanity");
 669 
 670   // This will be the "starts humongous" region.
 671   HeapRegion* first_hr = region_at(first);
 672   // The header of the new object will be placed at the bottom of
 673   // the first region.
 674   HeapWord* new_obj = first_hr->bottom();
 675   // This will be the new end of the first region in the series that
 676   // should also match the end of the last region in the series.
 677   HeapWord* new_end = new_obj + word_size_sum;
 678   // This will be the new top of the first region that will reflect
 679   // this allocation.
 680   HeapWord* new_top = new_obj + word_size;
 681 
 682   // First, we need to zero the header of the space that we will be
 683   // allocating. When we update top further down, some refinement
 684   // threads might try to scan the region. By zeroing the header we
 685   // ensure that any thread that will try to scan the region will
 686   // come across the zero klass word and bail out.
 687   //
 688   // NOTE: It would not have been correct to have used
 689   // CollectedHeap::fill_with_object() and make the space look like
 690   // an int array. The thread that is doing the allocation will
 691   // later update the object header to a potentially different array
 692   // type and, for a very short period of time, the klass and length
 693   // fields will be inconsistent. This could cause a refinement
 694   // thread to calculate the object size incorrectly.
 695   Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
 696 
 697   // We will set up the first region as "starts humongous". This
 698   // will also update the BOT covering all the regions to reflect
 699   // that there is a single object that starts at the bottom of the
 700   // first region.
 701   first_hr->set_startsHumongous(new_top, new_end);
 702 
 703   // Then, if there are any, we will set up the "continues
 704   // humongous" regions.
 705   HeapRegion* hr = NULL;
 706   for (uint i = first + 1; i < last; ++i) {
 707     hr = region_at(i);
 708     hr->set_continuesHumongous(first_hr);
 709   }
 710   // If we have "continues humongous" regions (hr != NULL), then the
 711   // end of the last one should match new_end.
 712   assert(hr == NULL || hr->end() == new_end, "sanity");
 713 
 714   // Up to this point no concurrent thread would have been able to
 715   // do any scanning on any region in this series. All the top
 716   // fields still point to bottom, so the intersection between
 717   // [bottom,top] and [card_start,card_end] will be empty. Before we
 718   // update the top fields, we'll do a storestore to make sure that
 719   // no thread sees the update to top before the zeroing of the
 720   // object header and the BOT initialization.
 721   OrderAccess::storestore();
 722 
 723   // Now that the BOT and the object header have been initialized,
 724   // we can update top of the "starts humongous" region.
 725   assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
 726          "new_top should be in this region");
 727   first_hr->set_top(new_top);
 728   if (_hr_printer.is_active()) {
 729     HeapWord* bottom = first_hr->bottom();
 730     HeapWord* end = first_hr->orig_end();
 731     if ((first + 1) == last) {
 732       // the series has a single humongous region
 733       _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
 734     } else {
 735       // the series has more than one humongous regions
 736       _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
 737     }
 738   }
 739 
 740   // Now, we will update the top fields of the "continues humongous"
 741   // regions. The reason we need to do this is that, otherwise,
 742   // these regions would look empty and this will confuse parts of
 743   // G1. For example, the code that looks for a consecutive number
 744   // of empty regions will consider them empty and try to
 745   // re-allocate them. We can extend is_empty() to also include
 746   // !continuesHumongous(), but it is easier to just update the top
 747   // fields here. The way we set top for all regions (i.e., top ==
 748   // end for all regions but the last one, top == new_top for the
 749   // last one) is actually used when we will free up the humongous
 750   // region in free_humongous_region().
 751   hr = NULL;
 752   for (uint i = first + 1; i < last; ++i) {
 753     hr = region_at(i);
 754     if ((i + 1) == last) {
 755       // last continues humongous region
 756       assert(hr->bottom() < new_top && new_top <= hr->end(),
 757              "new_top should fall on this region");
 758       hr->set_top(new_top);
 759       _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
 760     } else {
 761       // not last one
 762       assert(new_top > hr->end(), "new_top should be above this region");
 763       hr->set_top(hr->end());
 764       _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
 765     }
 766   }
 767   // If we have continues humongous regions (hr != NULL), then the
 768   // end of the last one should match new_end and its top should
 769   // match new_top.
 770   assert(hr == NULL ||
 771          (hr->end() == new_end && hr->top() == new_top), "sanity");
 772   check_bitmaps("Humongous Region Allocation", first_hr);
 773 
 774   assert(first_hr->used() == word_size * HeapWordSize, "invariant");
 775   _summary_bytes_used += first_hr->used();
 776   _humongous_set.add(first_hr);
 777 
 778   return new_obj;
 779 }
 780 
 781 // If could fit into free regions w/o expansion, try.
 782 // Otherwise, if can expand, do so.
 783 // Otherwise, if using ex regions might help, try with ex given back.
 784 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
 785   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 786 
 787   verify_region_sets_optional();
 788 
 789   size_t word_size_rounded = round_to(word_size, HeapRegion::GrainWords);
 790   uint num_regions = (uint) (word_size_rounded / HeapRegion::GrainWords);
 791   uint x_num = expansion_regions();
 792   uint fs = _hrs.free_suffix();
 793   uint first = humongous_obj_allocate_find_first(num_regions, word_size);
 794   if (first == G1_NULL_HRS_INDEX) {
 795     // The only thing we can do now is attempt expansion.
 796     if (fs + x_num >= num_regions) {
 797       // If the number of regions we're trying to allocate for this
 798       // object is at most the number of regions in the free suffix,
 799       // then the call to humongous_obj_allocate_find_first() above
 800       // should have succeeded and we wouldn't be here.
 801       //
 802       // We should only be trying to expand when the free suffix is
 803       // not sufficient for the object _and_ we have some expansion
 804       // room available.
 805       assert(num_regions > fs, "earlier allocation should have succeeded");
 806 
 807       ergo_verbose1(ErgoHeapSizing,
 808                     "attempt heap expansion",
 809                     ergo_format_reason("humongous allocation request failed")
 810                     ergo_format_byte("allocation request"),
 811                     word_size * HeapWordSize);
 812       if (expand((num_regions - fs) * HeapRegion::GrainBytes)) {
 813         // Even though the heap was expanded, it might not have
 814         // reached the desired size. So, we cannot assume that the
 815         // allocation will succeed.
 816         first = humongous_obj_allocate_find_first(num_regions, word_size);
 817       }
 818     }
 819   }
 820 
 821   HeapWord* result = NULL;
 822   if (first != G1_NULL_HRS_INDEX) {
 823     result =
 824       humongous_obj_allocate_initialize_regions(first, num_regions, word_size);
 825     assert(result != NULL, "it should always return a valid result");
 826 
 827     // A successful humongous object allocation changes the used space
 828     // information of the old generation so we need to recalculate the
 829     // sizes and update the jstat counters here.
 830     g1mm()->update_sizes();
 831   }
 832 
 833   verify_region_sets_optional();
 834 
 835   return result;
 836 }
 837 
 838 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
 839   assert_heap_not_locked_and_not_at_safepoint();
 840   assert(!isHumongous(word_size), "we do not allow humongous TLABs");
 841 
 842   unsigned int dummy_gc_count_before;
 843   int dummy_gclocker_retry_count = 0;
 844   return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
 845 }
 846 
 847 HeapWord*
 848 G1CollectedHeap::mem_allocate(size_t word_size,
 849                               bool*  gc_overhead_limit_was_exceeded) {
 850   assert_heap_not_locked_and_not_at_safepoint();
 851 
 852   // Loop until the allocation is satisfied, or unsatisfied after GC.
 853   for (int try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 854     unsigned int gc_count_before;
 855 
 856     HeapWord* result = NULL;
 857     if (!isHumongous(word_size)) {
 858       result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
 859     } else {
 860       result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
 861     }
 862     if (result != NULL) {
 863       return result;
 864     }
 865 
 866     // Create the garbage collection operation...
 867     VM_G1CollectForAllocation op(gc_count_before, word_size);
 868     // ...and get the VM thread to execute it.
 869     VMThread::execute(&op);
 870 
 871     if (op.prologue_succeeded() && op.pause_succeeded()) {
 872       // If the operation was successful we'll return the result even
 873       // if it is NULL. If the allocation attempt failed immediately
 874       // after a Full GC, it's unlikely we'll be able to allocate now.
 875       HeapWord* result = op.result();
 876       if (result != NULL && !isHumongous(word_size)) {
 877         // Allocations that take place on VM operations do not do any
 878         // card dirtying and we have to do it here. We only have to do
 879         // this for non-humongous allocations, though.
 880         dirty_young_block(result, word_size);
 881       }
 882       return result;
 883     } else {
 884       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 885         return NULL;
 886       }
 887       assert(op.result() == NULL,
 888              "the result should be NULL if the VM op did not succeed");
 889     }
 890 
 891     // Give a warning if we seem to be looping forever.
 892     if ((QueuedAllocationWarningCount > 0) &&
 893         (try_count % QueuedAllocationWarningCount == 0)) {
 894       warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
 895     }
 896   }
 897 
 898   ShouldNotReachHere();
 899   return NULL;
 900 }
 901 
 902 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
 903                                            unsigned int *gc_count_before_ret,
 904                                            int* gclocker_retry_count_ret) {
 905   // Make sure you read the note in attempt_allocation_humongous().
 906 
 907   assert_heap_not_locked_and_not_at_safepoint();
 908   assert(!isHumongous(word_size), "attempt_allocation_slow() should not "
 909          "be called for humongous allocation requests");
 910 
 911   // We should only get here after the first-level allocation attempt
 912   // (attempt_allocation()) failed to allocate.
 913 
 914   // We will loop until a) we manage to successfully perform the
 915   // allocation or b) we successfully schedule a collection which
 916   // fails to perform the allocation. b) is the only case when we'll
 917   // return NULL.
 918   HeapWord* result = NULL;
 919   for (int try_count = 1; /* we'll return */; try_count += 1) {
 920     bool should_try_gc;
 921     unsigned int gc_count_before;
 922 
 923     {
 924       MutexLockerEx x(Heap_lock);
 925 
 926       result = _mutator_alloc_region.attempt_allocation_locked(word_size,
 927                                                       false /* bot_updates */);
 928       if (result != NULL) {
 929         return result;
 930       }
 931 
 932       // If we reach here, attempt_allocation_locked() above failed to
 933       // allocate a new region. So the mutator alloc region should be NULL.
 934       assert(_mutator_alloc_region.get() == NULL, "only way to get here");
 935 
 936       if (GC_locker::is_active_and_needs_gc()) {
 937         if (g1_policy()->can_expand_young_list()) {
 938           // No need for an ergo verbose message here,
 939           // can_expand_young_list() does this when it returns true.
 940           result = _mutator_alloc_region.attempt_allocation_force(word_size,
 941                                                       false /* bot_updates */);
 942           if (result != NULL) {
 943             return result;
 944           }
 945         }
 946         should_try_gc = false;
 947       } else {
 948         // The GCLocker may not be active but the GCLocker initiated
 949         // GC may not yet have been performed (GCLocker::needs_gc()
 950         // returns true). In this case we do not try this GC and
 951         // wait until the GCLocker initiated GC is performed, and
 952         // then retry the allocation.
 953         if (GC_locker::needs_gc()) {
 954           should_try_gc = false;
 955         } else {
 956           // Read the GC count while still holding the Heap_lock.
 957           gc_count_before = total_collections();
 958           should_try_gc = true;
 959         }
 960       }
 961     }
 962 
 963     if (should_try_gc) {
 964       bool succeeded;
 965       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 966           GCCause::_g1_inc_collection_pause);
 967       if (result != NULL) {
 968         assert(succeeded, "only way to get back a non-NULL result");
 969         return result;
 970       }
 971 
 972       if (succeeded) {
 973         // If we get here we successfully scheduled a collection which
 974         // failed to allocate. No point in trying to allocate
 975         // further. We'll just return NULL.
 976         MutexLockerEx x(Heap_lock);
 977         *gc_count_before_ret = total_collections();
 978         return NULL;
 979       }
 980     } else {
 981       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
 982         MutexLockerEx x(Heap_lock);
 983         *gc_count_before_ret = total_collections();
 984         return NULL;
 985       }
 986       // The GCLocker is either active or the GCLocker initiated
 987       // GC has not yet been performed. Stall until it is and
 988       // then retry the allocation.
 989       GC_locker::stall_until_clear();
 990       (*gclocker_retry_count_ret) += 1;
 991     }
 992 
 993     // We can reach here if we were unsuccessful in scheduling a
 994     // collection (because another thread beat us to it) or if we were
 995     // stalled due to the GC locker. In either can we should retry the
 996     // allocation attempt in case another thread successfully
 997     // performed a collection and reclaimed enough space. We do the
 998     // first attempt (without holding the Heap_lock) here and the
 999     // follow-on attempt will be at the start of the next loop
1000     // iteration (after taking the Heap_lock).
1001     result = _mutator_alloc_region.attempt_allocation(word_size,
1002                                                       false /* bot_updates */);
1003     if (result != NULL) {
1004       return result;
1005     }
1006 
1007     // Give a warning if we seem to be looping forever.
1008     if ((QueuedAllocationWarningCount > 0) &&
1009         (try_count % QueuedAllocationWarningCount == 0)) {
1010       warning("G1CollectedHeap::attempt_allocation_slow() "
1011               "retries %d times", try_count);
1012     }
1013   }
1014 
1015   ShouldNotReachHere();
1016   return NULL;
1017 }
1018 
1019 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
1020                                           unsigned int * gc_count_before_ret,
1021                                           int* gclocker_retry_count_ret) {
1022   // The structure of this method has a lot of similarities to
1023   // attempt_allocation_slow(). The reason these two were not merged
1024   // into a single one is that such a method would require several "if
1025   // allocation is not humongous do this, otherwise do that"
1026   // conditional paths which would obscure its flow. In fact, an early
1027   // version of this code did use a unified method which was harder to
1028   // follow and, as a result, it had subtle bugs that were hard to
1029   // track down. So keeping these two methods separate allows each to
1030   // be more readable. It will be good to keep these two in sync as
1031   // much as possible.
1032 
1033   assert_heap_not_locked_and_not_at_safepoint();
1034   assert(isHumongous(word_size), "attempt_allocation_humongous() "
1035          "should only be called for humongous allocations");
1036 
1037   // Humongous objects can exhaust the heap quickly, so we should check if we
1038   // need to start a marking cycle at each humongous object allocation. We do
1039   // the check before we do the actual allocation. The reason for doing it
1040   // before the allocation is that we avoid having to keep track of the newly
1041   // allocated memory while we do a GC.
1042   if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
1043                                            word_size)) {
1044     collect(GCCause::_g1_humongous_allocation);
1045   }
1046 
1047   // We will loop until a) we manage to successfully perform the
1048   // allocation or b) we successfully schedule a collection which
1049   // fails to perform the allocation. b) is the only case when we'll
1050   // return NULL.
1051   HeapWord* result = NULL;
1052   for (int try_count = 1; /* we'll return */; try_count += 1) {
1053     bool should_try_gc;
1054     unsigned int gc_count_before;
1055 
1056     {
1057       MutexLockerEx x(Heap_lock);
1058 
1059       // Given that humongous objects are not allocated in young
1060       // regions, we'll first try to do the allocation without doing a
1061       // collection hoping that there's enough space in the heap.
1062       result = humongous_obj_allocate(word_size);
1063       if (result != NULL) {
1064         return result;
1065       }
1066 
1067       if (GC_locker::is_active_and_needs_gc()) {
1068         should_try_gc = false;
1069       } else {
1070          // The GCLocker may not be active but the GCLocker initiated
1071         // GC may not yet have been performed (GCLocker::needs_gc()
1072         // returns true). In this case we do not try this GC and
1073         // wait until the GCLocker initiated GC is performed, and
1074         // then retry the allocation.
1075         if (GC_locker::needs_gc()) {
1076           should_try_gc = false;
1077         } else {
1078           // Read the GC count while still holding the Heap_lock.
1079           gc_count_before = total_collections();
1080           should_try_gc = true;
1081         }
1082       }
1083     }
1084 
1085     if (should_try_gc) {
1086       // If we failed to allocate the humongous object, we should try to
1087       // do a collection pause (if we're allowed) in case it reclaims
1088       // enough space for the allocation to succeed after the pause.
1089 
1090       bool succeeded;
1091       result = do_collection_pause(word_size, gc_count_before, &succeeded,
1092           GCCause::_g1_humongous_allocation);
1093       if (result != NULL) {
1094         assert(succeeded, "only way to get back a non-NULL result");
1095         return result;
1096       }
1097 
1098       if (succeeded) {
1099         // If we get here we successfully scheduled a collection which
1100         // failed to allocate. No point in trying to allocate
1101         // further. We'll just return NULL.
1102         MutexLockerEx x(Heap_lock);
1103         *gc_count_before_ret = total_collections();
1104         return NULL;
1105       }
1106     } else {
1107       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1108         MutexLockerEx x(Heap_lock);
1109         *gc_count_before_ret = total_collections();
1110         return NULL;
1111       }
1112       // The GCLocker is either active or the GCLocker initiated
1113       // GC has not yet been performed. Stall until it is and
1114       // then retry the allocation.
1115       GC_locker::stall_until_clear();
1116       (*gclocker_retry_count_ret) += 1;
1117     }
1118 
1119     // We can reach here if we were unsuccessful in scheduling a
1120     // collection (because another thread beat us to it) or if we were
1121     // stalled due to the GC locker. In either can we should retry the
1122     // allocation attempt in case another thread successfully
1123     // performed a collection and reclaimed enough space.  Give a
1124     // warning if we seem to be looping forever.
1125 
1126     if ((QueuedAllocationWarningCount > 0) &&
1127         (try_count % QueuedAllocationWarningCount == 0)) {
1128       warning("G1CollectedHeap::attempt_allocation_humongous() "
1129               "retries %d times", try_count);
1130     }
1131   }
1132 
1133   ShouldNotReachHere();
1134   return NULL;
1135 }
1136 
1137 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1138                                        bool expect_null_mutator_alloc_region) {
1139   assert_at_safepoint(true /* should_be_vm_thread */);
1140   assert(_mutator_alloc_region.get() == NULL ||
1141                                              !expect_null_mutator_alloc_region,
1142          "the current alloc region was unexpectedly found to be non-NULL");
1143 
1144   if (!isHumongous(word_size)) {
1145     return _mutator_alloc_region.attempt_allocation_locked(word_size,
1146                                                       false /* bot_updates */);
1147   } else {
1148     HeapWord* result = humongous_obj_allocate(word_size);
1149     if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1150       g1_policy()->set_initiate_conc_mark_if_possible();
1151     }
1152     return result;
1153   }
1154 
1155   ShouldNotReachHere();
1156 }
1157 
1158 class PostMCRemSetClearClosure: public HeapRegionClosure {
1159   G1CollectedHeap* _g1h;
1160   ModRefBarrierSet* _mr_bs;
1161 public:
1162   PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1163     _g1h(g1h), _mr_bs(mr_bs) {}
1164 
1165   bool doHeapRegion(HeapRegion* r) {
1166     HeapRegionRemSet* hrrs = r->rem_set();
1167 
1168     if (r->continuesHumongous()) {
1169       // We'll assert that the strong code root list and RSet is empty
1170       assert(hrrs->strong_code_roots_list_length() == 0, "sanity");
1171       assert(hrrs->occupied() == 0, "RSet should be empty");
1172       return false;
1173     }
1174 
1175     _g1h->reset_gc_time_stamps(r);
1176     hrrs->clear();
1177     // You might think here that we could clear just the cards
1178     // corresponding to the used region.  But no: if we leave a dirty card
1179     // in a region we might allocate into, then it would prevent that card
1180     // from being enqueued, and cause it to be missed.
1181     // Re: the performance cost: we shouldn't be doing full GC anyway!
1182     _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1183 
1184     return false;
1185   }
1186 };
1187 
1188 void G1CollectedHeap::clear_rsets_post_compaction() {
1189   PostMCRemSetClearClosure rs_clear(this, g1_barrier_set());
1190   heap_region_iterate(&rs_clear);
1191 }
1192 
1193 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1194   G1CollectedHeap*   _g1h;
1195   UpdateRSOopClosure _cl;
1196   int                _worker_i;
1197 public:
1198   RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1199     _cl(g1->g1_rem_set(), worker_i),
1200     _worker_i(worker_i),
1201     _g1h(g1)
1202   { }
1203 
1204   bool doHeapRegion(HeapRegion* r) {
1205     if (!r->continuesHumongous()) {
1206       _cl.set_from(r);
1207       r->oop_iterate(&_cl);
1208     }
1209     return false;
1210   }
1211 };
1212 
1213 class ParRebuildRSTask: public AbstractGangTask {
1214   G1CollectedHeap* _g1;
1215 public:
1216   ParRebuildRSTask(G1CollectedHeap* g1)
1217     : AbstractGangTask("ParRebuildRSTask"),
1218       _g1(g1)
1219   { }
1220 
1221   void work(uint worker_id) {
1222     RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1223     _g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id,
1224                                           _g1->workers()->active_workers(),
1225                                          HeapRegion::RebuildRSClaimValue);
1226   }
1227 };
1228 
1229 class PostCompactionPrinterClosure: public HeapRegionClosure {
1230 private:
1231   G1HRPrinter* _hr_printer;
1232 public:
1233   bool doHeapRegion(HeapRegion* hr) {
1234     assert(!hr->is_young(), "not expecting to find young regions");
1235     // We only generate output for non-empty regions.
1236     if (!hr->is_empty()) {
1237       if (!hr->isHumongous()) {
1238         _hr_printer->post_compaction(hr, G1HRPrinter::Old);
1239       } else if (hr->startsHumongous()) {
1240         if (hr->region_num() == 1) {
1241           // single humongous region
1242           _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
1243         } else {
1244           _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
1245         }
1246       } else {
1247         assert(hr->continuesHumongous(), "only way to get here");
1248         _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1249       }
1250     }
1251     return false;
1252   }
1253 
1254   PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1255     : _hr_printer(hr_printer) { }
1256 };
1257 
1258 void G1CollectedHeap::print_hrs_post_compaction() {
1259   PostCompactionPrinterClosure cl(hr_printer());
1260   heap_region_iterate(&cl);
1261 }
1262 
1263 bool G1CollectedHeap::do_collection(bool explicit_gc,
1264                                     bool clear_all_soft_refs,
1265                                     size_t word_size) {
1266   assert_at_safepoint(true /* should_be_vm_thread */);
1267 
1268   if (GC_locker::check_active_before_gc()) {
1269     return false;
1270   }
1271 
1272   STWGCTimer* gc_timer = G1MarkSweep::gc_timer();
1273   gc_timer->register_gc_start();
1274 
1275   SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer();
1276   gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start());
1277 
1278   SvcGCMarker sgcm(SvcGCMarker::FULL);
1279   ResourceMark rm;
1280 
1281   print_heap_before_gc();
1282   trace_heap_before_gc(gc_tracer);
1283 
1284   size_t metadata_prev_used = MetaspaceAux::used_bytes();
1285 
1286   verify_region_sets_optional();
1287 
1288   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1289                            collector_policy()->should_clear_all_soft_refs();
1290 
1291   ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1292 
1293   {
1294     IsGCActiveMark x;
1295 
1296     // Timing
1297     assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant");
1298     gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps);
1299     TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
1300 
1301     {
1302       GCTraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, NULL, gc_tracer->gc_id());
1303       TraceCollectorStats tcs(g1mm()->full_collection_counters());
1304       TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1305 
1306       double start = os::elapsedTime();
1307       g1_policy()->record_full_collection_start();
1308 
1309       // Note: When we have a more flexible GC logging framework that
1310       // allows us to add optional attributes to a GC log record we
1311       // could consider timing and reporting how long we wait in the
1312       // following two methods.
1313       wait_while_free_regions_coming();
1314       // If we start the compaction before the CM threads finish
1315       // scanning the root regions we might trip them over as we'll
1316       // be moving objects / updating references. So let's wait until
1317       // they are done. By telling them to abort, they should complete
1318       // early.
1319       _cm->root_regions()->abort();
1320       _cm->root_regions()->wait_until_scan_finished();
1321       append_secondary_free_list_if_not_empty_with_lock();
1322 
1323       gc_prologue(true);
1324       increment_total_collections(true /* full gc */);
1325       increment_old_marking_cycles_started();
1326 
1327       assert(used() == recalculate_used(), "Should be equal");
1328 
1329       verify_before_gc();
1330 
1331       check_bitmaps("Full GC Start");
1332       pre_full_gc_dump(gc_timer);
1333 
1334       COMPILER2_PRESENT(DerivedPointerTable::clear());
1335 
1336       // Disable discovery and empty the discovered lists
1337       // for the CM ref processor.
1338       ref_processor_cm()->disable_discovery();
1339       ref_processor_cm()->abandon_partial_discovery();
1340       ref_processor_cm()->verify_no_references_recorded();
1341 
1342       // Abandon current iterations of concurrent marking and concurrent
1343       // refinement, if any are in progress. We have to do this before
1344       // wait_until_scan_finished() below.
1345       concurrent_mark()->abort();
1346 
1347       // Make sure we'll choose a new allocation region afterwards.
1348       release_mutator_alloc_region();
1349       abandon_gc_alloc_regions();
1350       g1_rem_set()->cleanupHRRS();
1351 
1352       // We should call this after we retire any currently active alloc
1353       // regions so that all the ALLOC / RETIRE events are generated
1354       // before the start GC event.
1355       _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1356 
1357       // We may have added regions to the current incremental collection
1358       // set between the last GC or pause and now. We need to clear the
1359       // incremental collection set and then start rebuilding it afresh
1360       // after this full GC.
1361       abandon_collection_set(g1_policy()->inc_cset_head());
1362       g1_policy()->clear_incremental_cset();
1363       g1_policy()->stop_incremental_cset_building();
1364 
1365       tear_down_region_sets(false /* free_list_only */);
1366       g1_policy()->set_gcs_are_young(true);
1367 
1368       // See the comments in g1CollectedHeap.hpp and
1369       // G1CollectedHeap::ref_processing_init() about
1370       // how reference processing currently works in G1.
1371 
1372       // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1373       ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1374 
1375       // Temporarily clear the STW ref processor's _is_alive_non_header field.
1376       ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1377 
1378       ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
1379       ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1380 
1381       // Do collection work
1382       {
1383         HandleMark hm;  // Discard invalid handles created during gc
1384         G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1385       }
1386 
1387       assert(free_regions() == 0, "we should not have added any free regions");
1388       rebuild_region_sets(false /* free_list_only */);
1389 
1390       // Enqueue any discovered reference objects that have
1391       // not been removed from the discovered lists.
1392       ref_processor_stw()->enqueue_discovered_references();
1393 
1394       COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1395 
1396       MemoryService::track_memory_usage();
1397 
1398       assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1399       ref_processor_stw()->verify_no_references_recorded();
1400 
1401       // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1402       ClassLoaderDataGraph::purge();
1403       MetaspaceAux::verify_metrics();
1404 
1405       // Note: since we've just done a full GC, concurrent
1406       // marking is no longer active. Therefore we need not
1407       // re-enable reference discovery for the CM ref processor.
1408       // That will be done at the start of the next marking cycle.
1409       assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1410       ref_processor_cm()->verify_no_references_recorded();
1411 
1412       reset_gc_time_stamp();
1413       // Since everything potentially moved, we will clear all remembered
1414       // sets, and clear all cards.  Later we will rebuild remembered
1415       // sets. We will also reset the GC time stamps of the regions.
1416       clear_rsets_post_compaction();
1417       check_gc_time_stamps();
1418 
1419       // Resize the heap if necessary.
1420       resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1421 
1422       if (_hr_printer.is_active()) {
1423         // We should do this after we potentially resize the heap so
1424         // that all the COMMIT / UNCOMMIT events are generated before
1425         // the end GC event.
1426 
1427         print_hrs_post_compaction();
1428         _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1429       }
1430 
1431       G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
1432       if (hot_card_cache->use_cache()) {
1433         hot_card_cache->reset_card_counts();
1434         hot_card_cache->reset_hot_cache();
1435       }
1436 
1437       // Rebuild remembered sets of all regions.
1438       if (G1CollectedHeap::use_parallel_gc_threads()) {
1439         uint n_workers =
1440           AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1441                                                   workers()->active_workers(),
1442                                                   Threads::number_of_non_daemon_threads());
1443         assert(UseDynamicNumberOfGCThreads ||
1444                n_workers == workers()->total_workers(),
1445                "If not dynamic should be using all the  workers");
1446         workers()->set_active_workers(n_workers);
1447         // Set parallel threads in the heap (_n_par_threads) only
1448         // before a parallel phase and always reset it to 0 after
1449         // the phase so that the number of parallel threads does
1450         // no get carried forward to a serial phase where there
1451         // may be code that is "possibly_parallel".
1452         set_par_threads(n_workers);
1453 
1454         ParRebuildRSTask rebuild_rs_task(this);
1455         assert(check_heap_region_claim_values(
1456                HeapRegion::InitialClaimValue), "sanity check");
1457         assert(UseDynamicNumberOfGCThreads ||
1458                workers()->active_workers() == workers()->total_workers(),
1459                "Unless dynamic should use total workers");
1460         // Use the most recent number of  active workers
1461         assert(workers()->active_workers() > 0,
1462                "Active workers not properly set");
1463         set_par_threads(workers()->active_workers());
1464         workers()->run_task(&rebuild_rs_task);
1465         set_par_threads(0);
1466         assert(check_heap_region_claim_values(
1467                HeapRegion::RebuildRSClaimValue), "sanity check");
1468         reset_heap_region_claim_values();
1469       } else {
1470         RebuildRSOutOfRegionClosure rebuild_rs(this);
1471         heap_region_iterate(&rebuild_rs);
1472       }
1473 
1474       // Rebuild the strong code root lists for each region
1475       rebuild_strong_code_roots();
1476 
1477       if (true) { // FIXME
1478         MetaspaceGC::compute_new_size();
1479       }
1480 
1481 #ifdef TRACESPINNING
1482       ParallelTaskTerminator::print_termination_counts();
1483 #endif
1484 
1485       // Discard all rset updates
1486       JavaThread::dirty_card_queue_set().abandon_logs();
1487       assert(!G1DeferredRSUpdate
1488              || (G1DeferredRSUpdate &&
1489                 (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any");
1490 
1491       _young_list->reset_sampled_info();
1492       // At this point there should be no regions in the
1493       // entire heap tagged as young.
1494       assert(check_young_list_empty(true /* check_heap */),
1495              "young list should be empty at this point");
1496 
1497       // Update the number of full collections that have been completed.
1498       increment_old_marking_cycles_completed(false /* concurrent */);
1499 
1500       _hrs.verify_optional();
1501       verify_region_sets_optional();
1502 
1503       verify_after_gc();
1504 
1505       // Clear the previous marking bitmap, if needed for bitmap verification.
1506       // Note we cannot do this when we clear the next marking bitmap in
1507       // ConcurrentMark::abort() above since VerifyDuringGC verifies the
1508       // objects marked during a full GC against the previous bitmap.
1509       // But we need to clear it before calling check_bitmaps below since
1510       // the full GC has compacted objects and updated TAMS but not updated
1511       // the prev bitmap.
1512       if (G1VerifyBitmaps) {
1513         ((CMBitMap*) concurrent_mark()->prevMarkBitMap())->clearAll();
1514       }
1515       check_bitmaps("Full GC End");
1516 
1517       // Start a new incremental collection set for the next pause
1518       assert(g1_policy()->collection_set() == NULL, "must be");
1519       g1_policy()->start_incremental_cset_building();
1520 
1521       clear_cset_fast_test();
1522 
1523       init_mutator_alloc_region();
1524 
1525       double end = os::elapsedTime();
1526       g1_policy()->record_full_collection_end();
1527 
1528       if (G1Log::fine()) {
1529         g1_policy()->print_heap_transition();
1530       }
1531 
1532       // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1533       // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1534       // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1535       // before any GC notifications are raised.
1536       g1mm()->update_sizes();
1537 
1538       gc_epilogue(true);
1539     }
1540 
1541     if (G1Log::finer()) {
1542       g1_policy()->print_detailed_heap_transition(true /* full */);
1543     }
1544 
1545     print_heap_after_gc();
1546     trace_heap_after_gc(gc_tracer);
1547 
1548     post_full_gc_dump(gc_timer);
1549 
1550     gc_timer->register_gc_end();
1551     gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
1552   }
1553 
1554   return true;
1555 }
1556 
1557 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1558   // do_collection() will return whether it succeeded in performing
1559   // the GC. Currently, there is no facility on the
1560   // do_full_collection() API to notify the caller than the collection
1561   // did not succeed (e.g., because it was locked out by the GC
1562   // locker). So, right now, we'll ignore the return value.
1563   bool dummy = do_collection(true,                /* explicit_gc */
1564                              clear_all_soft_refs,
1565                              0                    /* word_size */);
1566 }
1567 
1568 // This code is mostly copied from TenuredGeneration.
1569 void
1570 G1CollectedHeap::
1571 resize_if_necessary_after_full_collection(size_t word_size) {
1572   // Include the current allocation, if any, and bytes that will be
1573   // pre-allocated to support collections, as "used".
1574   const size_t used_after_gc = used();
1575   const size_t capacity_after_gc = capacity();
1576   const size_t free_after_gc = capacity_after_gc - used_after_gc;
1577 
1578   // This is enforced in arguments.cpp.
1579   assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1580          "otherwise the code below doesn't make sense");
1581 
1582   // We don't have floating point command-line arguments
1583   const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1584   const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1585   const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1586   const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1587 
1588   const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1589   const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1590 
1591   // We have to be careful here as these two calculations can overflow
1592   // 32-bit size_t's.
1593   double used_after_gc_d = (double) used_after_gc;
1594   double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1595   double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1596 
1597   // Let's make sure that they are both under the max heap size, which
1598   // by default will make them fit into a size_t.
1599   double desired_capacity_upper_bound = (double) max_heap_size;
1600   minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1601                                     desired_capacity_upper_bound);
1602   maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1603                                     desired_capacity_upper_bound);
1604 
1605   // We can now safely turn them into size_t's.
1606   size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1607   size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1608 
1609   // This assert only makes sense here, before we adjust them
1610   // with respect to the min and max heap size.
1611   assert(minimum_desired_capacity <= maximum_desired_capacity,
1612          err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1613                  "maximum_desired_capacity = "SIZE_FORMAT,
1614                  minimum_desired_capacity, maximum_desired_capacity));
1615 
1616   // Should not be greater than the heap max size. No need to adjust
1617   // it with respect to the heap min size as it's a lower bound (i.e.,
1618   // we'll try to make the capacity larger than it, not smaller).
1619   minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1620   // Should not be less than the heap min size. No need to adjust it
1621   // with respect to the heap max size as it's an upper bound (i.e.,
1622   // we'll try to make the capacity smaller than it, not greater).
1623   maximum_desired_capacity =  MAX2(maximum_desired_capacity, min_heap_size);
1624 
1625   if (capacity_after_gc < minimum_desired_capacity) {
1626     // Don't expand unless it's significant
1627     size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1628     ergo_verbose4(ErgoHeapSizing,
1629                   "attempt heap expansion",
1630                   ergo_format_reason("capacity lower than "
1631                                      "min desired capacity after Full GC")
1632                   ergo_format_byte("capacity")
1633                   ergo_format_byte("occupancy")
1634                   ergo_format_byte_perc("min desired capacity"),
1635                   capacity_after_gc, used_after_gc,
1636                   minimum_desired_capacity, (double) MinHeapFreeRatio);
1637     expand(expand_bytes);
1638 
1639     // No expansion, now see if we want to shrink
1640   } else if (capacity_after_gc > maximum_desired_capacity) {
1641     // Capacity too large, compute shrinking size
1642     size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1643     ergo_verbose4(ErgoHeapSizing,
1644                   "attempt heap shrinking",
1645                   ergo_format_reason("capacity higher than "
1646                                      "max desired capacity after Full GC")
1647                   ergo_format_byte("capacity")
1648                   ergo_format_byte("occupancy")
1649                   ergo_format_byte_perc("max desired capacity"),
1650                   capacity_after_gc, used_after_gc,
1651                   maximum_desired_capacity, (double) MaxHeapFreeRatio);
1652     shrink(shrink_bytes);
1653   }
1654 }
1655 
1656 
1657 HeapWord*
1658 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1659                                            bool* succeeded) {
1660   assert_at_safepoint(true /* should_be_vm_thread */);
1661 
1662   *succeeded = true;
1663   // Let's attempt the allocation first.
1664   HeapWord* result =
1665     attempt_allocation_at_safepoint(word_size,
1666                                  false /* expect_null_mutator_alloc_region */);
1667   if (result != NULL) {
1668     assert(*succeeded, "sanity");
1669     return result;
1670   }
1671 
1672   // In a G1 heap, we're supposed to keep allocation from failing by
1673   // incremental pauses.  Therefore, at least for now, we'll favor
1674   // expansion over collection.  (This might change in the future if we can
1675   // do something smarter than full collection to satisfy a failed alloc.)
1676   result = expand_and_allocate(word_size);
1677   if (result != NULL) {
1678     assert(*succeeded, "sanity");
1679     return result;
1680   }
1681 
1682   // Expansion didn't work, we'll try to do a Full GC.
1683   bool gc_succeeded = do_collection(false, /* explicit_gc */
1684                                     false, /* clear_all_soft_refs */
1685                                     word_size);
1686   if (!gc_succeeded) {
1687     *succeeded = false;
1688     return NULL;
1689   }
1690 
1691   // Retry the allocation
1692   result = attempt_allocation_at_safepoint(word_size,
1693                                   true /* expect_null_mutator_alloc_region */);
1694   if (result != NULL) {
1695     assert(*succeeded, "sanity");
1696     return result;
1697   }
1698 
1699   // Then, try a Full GC that will collect all soft references.
1700   gc_succeeded = do_collection(false, /* explicit_gc */
1701                                true,  /* clear_all_soft_refs */
1702                                word_size);
1703   if (!gc_succeeded) {
1704     *succeeded = false;
1705     return NULL;
1706   }
1707 
1708   // Retry the allocation once more
1709   result = attempt_allocation_at_safepoint(word_size,
1710                                   true /* expect_null_mutator_alloc_region */);
1711   if (result != NULL) {
1712     assert(*succeeded, "sanity");
1713     return result;
1714   }
1715 
1716   assert(!collector_policy()->should_clear_all_soft_refs(),
1717          "Flag should have been handled and cleared prior to this point");
1718 
1719   // What else?  We might try synchronous finalization later.  If the total
1720   // space available is large enough for the allocation, then a more
1721   // complete compaction phase than we've tried so far might be
1722   // appropriate.
1723   assert(*succeeded, "sanity");
1724   return NULL;
1725 }
1726 
1727 // Attempting to expand the heap sufficiently
1728 // to support an allocation of the given "word_size".  If
1729 // successful, perform the allocation and return the address of the
1730 // allocated block, or else "NULL".
1731 
1732 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1733   assert_at_safepoint(true /* should_be_vm_thread */);
1734 
1735   verify_region_sets_optional();
1736 
1737   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1738   ergo_verbose1(ErgoHeapSizing,
1739                 "attempt heap expansion",
1740                 ergo_format_reason("allocation request failed")
1741                 ergo_format_byte("allocation request"),
1742                 word_size * HeapWordSize);
1743   if (expand(expand_bytes)) {
1744     _hrs.verify_optional();
1745     verify_region_sets_optional();
1746     return attempt_allocation_at_safepoint(word_size,
1747                                  false /* expect_null_mutator_alloc_region */);
1748   }
1749   return NULL;
1750 }
1751 
1752 void G1CollectedHeap::update_committed_space(HeapWord* old_end,
1753                                              HeapWord* new_end) {
1754   assert(old_end != new_end, "don't call this otherwise");
1755   assert((HeapWord*) _g1_storage.high() == new_end, "invariant");
1756 
1757   // Update the committed mem region.
1758   _g1_committed.set_end(new_end);
1759   // Tell the card table about the update.
1760   Universe::heap()->barrier_set()->resize_covered_region(_g1_committed);
1761   // Tell the BOT about the update.
1762   _bot_shared->resize(_g1_committed.word_size());
1763   // Tell the hot card cache about the update
1764   _cg1r->hot_card_cache()->resize_card_counts(capacity());
1765 }
1766 
1767 bool G1CollectedHeap::expand(size_t expand_bytes) {
1768   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1769   aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1770                                        HeapRegion::GrainBytes);
1771   ergo_verbose2(ErgoHeapSizing,
1772                 "expand the heap",
1773                 ergo_format_byte("requested expansion amount")
1774                 ergo_format_byte("attempted expansion amount"),
1775                 expand_bytes, aligned_expand_bytes);
1776 
1777   if (_g1_storage.uncommitted_size() == 0) {
1778     ergo_verbose0(ErgoHeapSizing,
1779                       "did not expand the heap",
1780                       ergo_format_reason("heap already fully expanded"));
1781     return false;
1782   }
1783 
1784   // First commit the memory.
1785   HeapWord* old_end = (HeapWord*) _g1_storage.high();
1786   bool successful = _g1_storage.expand_by(aligned_expand_bytes);
1787   if (successful) {
1788     // Then propagate this update to the necessary data structures.
1789     HeapWord* new_end = (HeapWord*) _g1_storage.high();
1790     update_committed_space(old_end, new_end);
1791 
1792     FreeRegionList expansion_list("Local Expansion List");
1793     MemRegion mr = _hrs.expand_by(old_end, new_end, &expansion_list);
1794     assert(mr.start() == old_end, "post-condition");
1795     // mr might be a smaller region than what was requested if
1796     // expand_by() was unable to allocate the HeapRegion instances
1797     assert(mr.end() <= new_end, "post-condition");
1798 
1799     size_t actual_expand_bytes = mr.byte_size();
1800     assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1801     assert(actual_expand_bytes == expansion_list.total_capacity_bytes(),
1802            "post-condition");
1803     if (actual_expand_bytes < aligned_expand_bytes) {
1804       // We could not expand _hrs to the desired size. In this case we
1805       // need to shrink the committed space accordingly.
1806       assert(mr.end() < new_end, "invariant");
1807 
1808       size_t diff_bytes = aligned_expand_bytes - actual_expand_bytes;
1809       // First uncommit the memory.
1810       _g1_storage.shrink_by(diff_bytes);
1811       // Then propagate this update to the necessary data structures.
1812       update_committed_space(new_end, mr.end());
1813     }
1814     _free_list.add_as_tail(&expansion_list);
1815 
1816     if (_hr_printer.is_active()) {
1817       HeapWord* curr = mr.start();
1818       while (curr < mr.end()) {
1819         HeapWord* curr_end = curr + HeapRegion::GrainWords;
1820         _hr_printer.commit(curr, curr_end);
1821         curr = curr_end;
1822       }
1823       assert(curr == mr.end(), "post-condition");
1824     }
1825     g1_policy()->record_new_heap_size(n_regions());
1826   } else {
1827     ergo_verbose0(ErgoHeapSizing,
1828                   "did not expand the heap",
1829                   ergo_format_reason("heap expansion operation failed"));
1830     // The expansion of the virtual storage space was unsuccessful.
1831     // Let's see if it was because we ran out of swap.
1832     if (G1ExitOnExpansionFailure &&
1833         _g1_storage.uncommitted_size() >= aligned_expand_bytes) {
1834       // We had head room...
1835       vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1836     }
1837   }
1838   return successful;
1839 }
1840 
1841 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1842   size_t aligned_shrink_bytes =
1843     ReservedSpace::page_align_size_down(shrink_bytes);
1844   aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1845                                          HeapRegion::GrainBytes);
1846   uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1847 
1848   uint num_regions_removed = _hrs.shrink_by(num_regions_to_remove);
1849   HeapWord* old_end = (HeapWord*) _g1_storage.high();
1850   size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1851 
1852   ergo_verbose3(ErgoHeapSizing,
1853                 "shrink the heap",
1854                 ergo_format_byte("requested shrinking amount")
1855                 ergo_format_byte("aligned shrinking amount")
1856                 ergo_format_byte("attempted shrinking amount"),
1857                 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1858   if (num_regions_removed > 0) {
1859     _g1_storage.shrink_by(shrunk_bytes);
1860     HeapWord* new_end = (HeapWord*) _g1_storage.high();
1861 
1862     if (_hr_printer.is_active()) {
1863       HeapWord* curr = old_end;
1864       while (curr > new_end) {
1865         HeapWord* curr_end = curr;
1866         curr -= HeapRegion::GrainWords;
1867         _hr_printer.uncommit(curr, curr_end);
1868       }
1869     }
1870 
1871     _expansion_regions += num_regions_removed;
1872     update_committed_space(old_end, new_end);
1873     HeapRegionRemSet::shrink_heap(n_regions());
1874     g1_policy()->record_new_heap_size(n_regions());
1875   } else {
1876     ergo_verbose0(ErgoHeapSizing,
1877                   "did not shrink the heap",
1878                   ergo_format_reason("heap shrinking operation failed"));
1879   }
1880 }
1881 
1882 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1883   verify_region_sets_optional();
1884 
1885   // We should only reach here at the end of a Full GC which means we
1886   // should not not be holding to any GC alloc regions. The method
1887   // below will make sure of that and do any remaining clean up.
1888   abandon_gc_alloc_regions();
1889 
1890   // Instead of tearing down / rebuilding the free lists here, we
1891   // could instead use the remove_all_pending() method on free_list to
1892   // remove only the ones that we need to remove.
1893   tear_down_region_sets(true /* free_list_only */);
1894   shrink_helper(shrink_bytes);
1895   rebuild_region_sets(true /* free_list_only */);
1896 
1897   _hrs.verify_optional();
1898   verify_region_sets_optional();
1899 }
1900 
1901 // Public methods.
1902 
1903 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1904 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1905 #endif // _MSC_VER
1906 
1907 
1908 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1909   SharedHeap(policy_),
1910   _g1_policy(policy_),
1911   _dirty_card_queue_set(false),
1912   _into_cset_dirty_card_queue_set(false),
1913   _is_alive_closure_cm(this),
1914   _is_alive_closure_stw(this),
1915   _ref_processor_cm(NULL),
1916   _ref_processor_stw(NULL),
1917   _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
1918   _bot_shared(NULL),
1919   _evac_failure_scan_stack(NULL),
1920   _mark_in_progress(false),
1921   _cg1r(NULL), _summary_bytes_used(0),
1922   _g1mm(NULL),
1923   _refine_cte_cl(NULL),
1924   _full_collection(false),
1925   _free_list("Master Free List", new MasterFreeRegionListMtSafeChecker()),
1926   _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1927   _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1928   _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1929   _humongous_is_live(),
1930   _has_humongous_reclaim_candidates(false),
1931   _free_regions_coming(false),
1932   _young_list(new YoungList(this)),
1933   _gc_time_stamp(0),
1934   _retained_old_gc_alloc_region(NULL),
1935   _survivor_plab_stats(YoungPLABSize, PLABWeight),
1936   _old_plab_stats(OldPLABSize, PLABWeight),
1937   _expand_heap_after_alloc_failure(true),
1938   _surviving_young_words(NULL),
1939   _old_marking_cycles_started(0),
1940   _old_marking_cycles_completed(0),
1941   _concurrent_cycle_started(false),
1942   _in_cset_fast_test(),
1943   _dirty_cards_region_list(NULL),
1944   _worker_cset_start_region(NULL),
1945   _worker_cset_start_region_time_stamp(NULL),
1946   _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1947   _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
1948   _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1949   _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) {
1950 
1951   _g1h = this;
1952   if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
1953     vm_exit_during_initialization("Failed necessary allocation.");
1954   }
1955 
1956   _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1957 
1958   int n_queues = MAX2((int)ParallelGCThreads, 1);
1959   _task_queues = new RefToScanQueueSet(n_queues);
1960 
1961   uint n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1962   assert(n_rem_sets > 0, "Invariant.");
1963 
1964   _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1965   _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC);
1966   _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1967 
1968   for (int i = 0; i < n_queues; i++) {
1969     RefToScanQueue* q = new RefToScanQueue();
1970     q->initialize();
1971     _task_queues->register_queue(i, q);
1972     ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1973   }
1974   clear_cset_start_regions();
1975 
1976   // Initialize the G1EvacuationFailureALot counters and flags.
1977   NOT_PRODUCT(reset_evacuation_should_fail();)
1978 
1979   guarantee(_task_queues != NULL, "task_queues allocation failure.");
1980 }
1981 
1982 jint G1CollectedHeap::initialize() {
1983   CollectedHeap::pre_initialize();
1984   os::enable_vtime();
1985 
1986   G1Log::init();
1987 
1988   // Necessary to satisfy locking discipline assertions.
1989 
1990   MutexLocker x(Heap_lock);
1991 
1992   // We have to initialize the printer before committing the heap, as
1993   // it will be used then.
1994   _hr_printer.set_active(G1PrintHeapRegions);
1995 
1996   // While there are no constraints in the GC code that HeapWordSize
1997   // be any particular value, there are multiple other areas in the
1998   // system which believe this to be true (e.g. oop->object_size in some
1999   // cases incorrectly returns the size in wordSize units rather than
2000   // HeapWordSize).
2001   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
2002 
2003   size_t init_byte_size = collector_policy()->initial_heap_byte_size();
2004   size_t max_byte_size = collector_policy()->max_heap_byte_size();
2005   size_t heap_alignment = collector_policy()->heap_alignment();
2006 
2007   // Ensure that the sizes are properly aligned.
2008   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
2009   Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
2010   Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
2011 
2012   _refine_cte_cl = new RefineCardTableEntryClosure();
2013 
2014   _cg1r = new ConcurrentG1Refine(this, _refine_cte_cl);
2015 
2016   // Reserve the maximum.
2017 
2018   // When compressed oops are enabled, the preferred heap base
2019   // is calculated by subtracting the requested size from the
2020   // 32Gb boundary and using the result as the base address for
2021   // heap reservation. If the requested size is not aligned to
2022   // HeapRegion::GrainBytes (i.e. the alignment that is passed
2023   // into the ReservedHeapSpace constructor) then the actual
2024   // base of the reserved heap may end up differing from the
2025   // address that was requested (i.e. the preferred heap base).
2026   // If this happens then we could end up using a non-optimal
2027   // compressed oops mode.
2028 
2029   ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
2030                                                  heap_alignment);
2031 
2032   // It is important to do this in a way such that concurrent readers can't
2033   // temporarily think something is in the heap.  (I've actually seen this
2034   // happen in asserts: DLD.)
2035   _reserved.set_word_size(0);
2036   _reserved.set_start((HeapWord*)heap_rs.base());
2037   _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size()));
2038 
2039   _expansion_regions = (uint) (max_byte_size / HeapRegion::GrainBytes);
2040 
2041   // Create the gen rem set (and barrier set) for the entire reserved region.
2042   _rem_set = collector_policy()->create_rem_set(_reserved, 2);
2043   set_barrier_set(rem_set()->bs());
2044   if (!barrier_set()->is_a(BarrierSet::G1SATBCTLogging)) {
2045     vm_exit_during_initialization("G1 requires a G1SATBLoggingCardTableModRefBS");
2046     return JNI_ENOMEM;
2047   }
2048 
2049   // Also create a G1 rem set.
2050   _g1_rem_set = new G1RemSet(this, g1_barrier_set());
2051 
2052   // Carve out the G1 part of the heap.
2053 
2054   ReservedSpace g1_rs   = heap_rs.first_part(max_byte_size);
2055   _g1_reserved = MemRegion((HeapWord*)g1_rs.base(),
2056                            g1_rs.size()/HeapWordSize);
2057 
2058   _g1_storage.initialize(g1_rs, 0);
2059   _g1_committed = MemRegion((HeapWord*)_g1_storage.low(), (size_t) 0);
2060   _hrs.initialize((HeapWord*) _g1_reserved.start(),
2061                   (HeapWord*) _g1_reserved.end());
2062   assert(_hrs.max_length() == _expansion_regions,
2063          err_msg("max length: %u expansion regions: %u",
2064                  _hrs.max_length(), _expansion_regions));
2065 
2066   // Do later initialization work for concurrent refinement.
2067   _cg1r->init();
2068 
2069   // 6843694 - ensure that the maximum region index can fit
2070   // in the remembered set structures.
2071   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
2072   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
2073 
2074   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
2075   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
2076   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
2077             "too many cards per region");
2078 
2079   FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
2080 
2081   _bot_shared = new G1BlockOffsetSharedArray(_reserved,
2082                                              heap_word_size(init_byte_size));
2083 
2084   _g1h = this;
2085 
2086   _in_cset_fast_test.initialize(_g1_reserved.start(), _g1_reserved.end(), HeapRegion::GrainBytes);
2087   _humongous_is_live.initialize(_g1_reserved.start(), _g1_reserved.end(), HeapRegion::GrainBytes);
2088 
2089   // Create the ConcurrentMark data structure and thread.
2090   // (Must do this late, so that "max_regions" is defined.)
2091   _cm = new ConcurrentMark(this, heap_rs);
2092   if (_cm == NULL || !_cm->completed_initialization()) {
2093     vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark");
2094     return JNI_ENOMEM;
2095   }
2096   _cmThread = _cm->cmThread();
2097 
2098   // Initialize the from_card cache structure of HeapRegionRemSet.
2099   HeapRegionRemSet::init_heap(max_regions());
2100 
2101   // Now expand into the initial heap size.
2102   if (!expand(init_byte_size)) {
2103     vm_shutdown_during_initialization("Failed to allocate initial heap.");
2104     return JNI_ENOMEM;
2105   }
2106 
2107   // Perform any initialization actions delegated to the policy.
2108   g1_policy()->init();
2109 
2110   JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
2111                                                SATB_Q_FL_lock,
2112                                                G1SATBProcessCompletedThreshold,
2113                                                Shared_SATB_Q_lock);
2114 
2115   JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl,
2116                                                 DirtyCardQ_CBL_mon,
2117                                                 DirtyCardQ_FL_lock,
2118                                                 concurrent_g1_refine()->yellow_zone(),
2119                                                 concurrent_g1_refine()->red_zone(),
2120                                                 Shared_DirtyCardQ_lock);
2121 
2122   if (G1DeferredRSUpdate) {
2123     dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code
2124                                       DirtyCardQ_CBL_mon,
2125                                       DirtyCardQ_FL_lock,
2126                                       -1, // never trigger processing
2127                                       -1, // no limit on length
2128                                       Shared_DirtyCardQ_lock,
2129                                       &JavaThread::dirty_card_queue_set());
2130   }
2131 
2132   // Initialize the card queue set used to hold cards containing
2133   // references into the collection set.
2134   _into_cset_dirty_card_queue_set.initialize(NULL, // Should never be called by the Java code
2135                                              DirtyCardQ_CBL_mon,
2136                                              DirtyCardQ_FL_lock,
2137                                              -1, // never trigger processing
2138                                              -1, // no limit on length
2139                                              Shared_DirtyCardQ_lock,
2140                                              &JavaThread::dirty_card_queue_set());
2141 
2142   // In case we're keeping closure specialization stats, initialize those
2143   // counts and that mechanism.
2144   SpecializationStats::clear();
2145 
2146   // Here we allocate the dummy full region that is required by the
2147   // G1AllocRegion class. If we don't pass an address in the reserved
2148   // space here, lots of asserts fire.
2149 
2150   HeapRegion* dummy_region = new_heap_region(0 /* index of bottom region */,
2151                                              _g1_reserved.start());
2152   // We'll re-use the same region whether the alloc region will
2153   // require BOT updates or not and, if it doesn't, then a non-young
2154   // region will complain that it cannot support allocations without
2155   // BOT updates. So we'll tag the dummy region as young to avoid that.
2156   dummy_region->set_young();
2157   // Make sure it's full.
2158   dummy_region->set_top(dummy_region->end());
2159   G1AllocRegion::setup(this, dummy_region);
2160 
2161   init_mutator_alloc_region();
2162 
2163   // Do create of the monitoring and management support so that
2164   // values in the heap have been properly initialized.
2165   _g1mm = new G1MonitoringSupport(this);
2166 
2167   G1StringDedup::initialize();
2168 
2169   return JNI_OK;
2170 }
2171 
2172 void G1CollectedHeap::stop() {
2173   // Stop all concurrent threads. We do this to make sure these threads
2174   // do not continue to execute and access resources (e.g. gclog_or_tty)
2175   // that are destroyed during shutdown.
2176   _cg1r->stop();
2177   _cmThread->stop();
2178   if (G1StringDedup::is_enabled()) {
2179     G1StringDedup::stop();
2180   }
2181 }
2182 
2183 void G1CollectedHeap::clear_humongous_is_live_table() {
2184   guarantee(G1ReclaimDeadHumongousObjectsAtYoungGC, "Should only be called if true");
2185   _humongous_is_live.clear();
2186 }
2187 
2188 size_t G1CollectedHeap::conservative_max_heap_alignment() {
2189   return HeapRegion::max_region_size();
2190 }
2191 
2192 void G1CollectedHeap::ref_processing_init() {
2193   // Reference processing in G1 currently works as follows:
2194   //
2195   // * There are two reference processor instances. One is
2196   //   used to record and process discovered references
2197   //   during concurrent marking; the other is used to
2198   //   record and process references during STW pauses
2199   //   (both full and incremental).
2200   // * Both ref processors need to 'span' the entire heap as
2201   //   the regions in the collection set may be dotted around.
2202   //
2203   // * For the concurrent marking ref processor:
2204   //   * Reference discovery is enabled at initial marking.
2205   //   * Reference discovery is disabled and the discovered
2206   //     references processed etc during remarking.
2207   //   * Reference discovery is MT (see below).
2208   //   * Reference discovery requires a barrier (see below).
2209   //   * Reference processing may or may not be MT
2210   //     (depending on the value of ParallelRefProcEnabled
2211   //     and ParallelGCThreads).
2212   //   * A full GC disables reference discovery by the CM
2213   //     ref processor and abandons any entries on it's
2214   //     discovered lists.
2215   //
2216   // * For the STW processor:
2217   //   * Non MT discovery is enabled at the start of a full GC.
2218   //   * Processing and enqueueing during a full GC is non-MT.
2219   //   * During a full GC, references are processed after marking.
2220   //
2221   //   * Discovery (may or may not be MT) is enabled at the start
2222   //     of an incremental evacuation pause.
2223   //   * References are processed near the end of a STW evacuation pause.
2224   //   * For both types of GC:
2225   //     * Discovery is atomic - i.e. not concurrent.
2226   //     * Reference discovery will not need a barrier.
2227 
2228   SharedHeap::ref_processing_init();
2229   MemRegion mr = reserved_region();
2230 
2231   // Concurrent Mark ref processor
2232   _ref_processor_cm =
2233     new ReferenceProcessor(mr,    // span
2234                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2235                                 // mt processing
2236                            (int) ParallelGCThreads,
2237                                 // degree of mt processing
2238                            (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2239                                 // mt discovery
2240                            (int) MAX2(ParallelGCThreads, ConcGCThreads),
2241                                 // degree of mt discovery
2242                            false,
2243                                 // Reference discovery is not atomic
2244                            &_is_alive_closure_cm);
2245                                 // is alive closure
2246                                 // (for efficiency/performance)
2247 
2248   // STW ref processor
2249   _ref_processor_stw =
2250     new ReferenceProcessor(mr,    // span
2251                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2252                                 // mt processing
2253                            MAX2((int)ParallelGCThreads, 1),
2254                                 // degree of mt processing
2255                            (ParallelGCThreads > 1),
2256                                 // mt discovery
2257                            MAX2((int)ParallelGCThreads, 1),
2258                                 // degree of mt discovery
2259                            true,
2260                                 // Reference discovery is atomic
2261                            &_is_alive_closure_stw);
2262                                 // is alive closure
2263                                 // (for efficiency/performance)
2264 }
2265 
2266 size_t G1CollectedHeap::capacity() const {
2267   return _g1_committed.byte_size();
2268 }
2269 
2270 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2271   assert(!hr->continuesHumongous(), "pre-condition");
2272   hr->reset_gc_time_stamp();
2273   if (hr->startsHumongous()) {
2274     uint first_index = hr->hrs_index() + 1;
2275     uint last_index = hr->last_hc_index();
2276     for (uint i = first_index; i < last_index; i += 1) {
2277       HeapRegion* chr = region_at(i);
2278       assert(chr->continuesHumongous(), "sanity");
2279       chr->reset_gc_time_stamp();
2280     }
2281   }
2282 }
2283 
2284 #ifndef PRODUCT
2285 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2286 private:
2287   unsigned _gc_time_stamp;
2288   bool _failures;
2289 
2290 public:
2291   CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2292     _gc_time_stamp(gc_time_stamp), _failures(false) { }
2293 
2294   virtual bool doHeapRegion(HeapRegion* hr) {
2295     unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2296     if (_gc_time_stamp != region_gc_time_stamp) {
2297       gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, "
2298                              "expected %d", HR_FORMAT_PARAMS(hr),
2299                              region_gc_time_stamp, _gc_time_stamp);
2300       _failures = true;
2301     }
2302     return false;
2303   }
2304 
2305   bool failures() { return _failures; }
2306 };
2307 
2308 void G1CollectedHeap::check_gc_time_stamps() {
2309   CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2310   heap_region_iterate(&cl);
2311   guarantee(!cl.failures(), "all GC time stamps should have been reset");
2312 }
2313 #endif // PRODUCT
2314 
2315 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2316                                                  DirtyCardQueue* into_cset_dcq,
2317                                                  bool concurrent,
2318                                                  uint worker_i) {
2319   // Clean cards in the hot card cache
2320   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
2321   hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq);
2322 
2323   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2324   int n_completed_buffers = 0;
2325   while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2326     n_completed_buffers++;
2327   }
2328   g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers);
2329   dcqs.clear_n_completed_buffers();
2330   assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2331 }
2332 
2333 
2334 // Computes the sum of the storage used by the various regions.
2335 
2336 size_t G1CollectedHeap::used() const {
2337   assert(Heap_lock->owner() != NULL,
2338          "Should be owned on this thread's behalf.");
2339   size_t result = _summary_bytes_used;
2340   // Read only once in case it is set to NULL concurrently
2341   HeapRegion* hr = _mutator_alloc_region.get();
2342   if (hr != NULL)
2343     result += hr->used();
2344   return result;
2345 }
2346 
2347 size_t G1CollectedHeap::used_unlocked() const {
2348   size_t result = _summary_bytes_used;
2349   return result;
2350 }
2351 
2352 class SumUsedClosure: public HeapRegionClosure {
2353   size_t _used;
2354 public:
2355   SumUsedClosure() : _used(0) {}
2356   bool doHeapRegion(HeapRegion* r) {
2357     if (!r->continuesHumongous()) {
2358       _used += r->used();
2359     }
2360     return false;
2361   }
2362   size_t result() { return _used; }
2363 };
2364 
2365 size_t G1CollectedHeap::recalculate_used() const {
2366   double recalculate_used_start = os::elapsedTime();
2367 
2368   SumUsedClosure blk;
2369   heap_region_iterate(&blk);
2370 
2371   g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2372   return blk.result();
2373 }
2374 
2375 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2376   switch (cause) {
2377     case GCCause::_gc_locker:               return GCLockerInvokesConcurrent;
2378     case GCCause::_java_lang_system_gc:     return ExplicitGCInvokesConcurrent;
2379     case GCCause::_g1_humongous_allocation: return true;
2380     default:                                return false;
2381   }
2382 }
2383 
2384 #ifndef PRODUCT
2385 void G1CollectedHeap::allocate_dummy_regions() {
2386   // Let's fill up most of the region
2387   size_t word_size = HeapRegion::GrainWords - 1024;
2388   // And as a result the region we'll allocate will be humongous.
2389   guarantee(isHumongous(word_size), "sanity");
2390 
2391   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2392     // Let's use the existing mechanism for the allocation
2393     HeapWord* dummy_obj = humongous_obj_allocate(word_size);
2394     if (dummy_obj != NULL) {
2395       MemRegion mr(dummy_obj, word_size);
2396       CollectedHeap::fill_with_object(mr);
2397     } else {
2398       // If we can't allocate once, we probably cannot allocate
2399       // again. Let's get out of the loop.
2400       break;
2401     }
2402   }
2403 }
2404 #endif // !PRODUCT
2405 
2406 void G1CollectedHeap::increment_old_marking_cycles_started() {
2407   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2408     _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2409     err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2410     _old_marking_cycles_started, _old_marking_cycles_completed));
2411 
2412   _old_marking_cycles_started++;
2413 }
2414 
2415 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2416   MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2417 
2418   // We assume that if concurrent == true, then the caller is a
2419   // concurrent thread that was joined the Suspendible Thread
2420   // Set. If there's ever a cheap way to check this, we should add an
2421   // assert here.
2422 
2423   // Given that this method is called at the end of a Full GC or of a
2424   // concurrent cycle, and those can be nested (i.e., a Full GC can
2425   // interrupt a concurrent cycle), the number of full collections
2426   // completed should be either one (in the case where there was no
2427   // nesting) or two (when a Full GC interrupted a concurrent cycle)
2428   // behind the number of full collections started.
2429 
2430   // This is the case for the inner caller, i.e. a Full GC.
2431   assert(concurrent ||
2432          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2433          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2434          err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
2435                  "is inconsistent with _old_marking_cycles_completed = %u",
2436                  _old_marking_cycles_started, _old_marking_cycles_completed));
2437 
2438   // This is the case for the outer caller, i.e. the concurrent cycle.
2439   assert(!concurrent ||
2440          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2441          err_msg("for outer caller (concurrent cycle): "
2442                  "_old_marking_cycles_started = %u "
2443                  "is inconsistent with _old_marking_cycles_completed = %u",
2444                  _old_marking_cycles_started, _old_marking_cycles_completed));
2445 
2446   _old_marking_cycles_completed += 1;
2447 
2448   // We need to clear the "in_progress" flag in the CM thread before
2449   // we wake up any waiters (especially when ExplicitInvokesConcurrent
2450   // is set) so that if a waiter requests another System.gc() it doesn't
2451   // incorrectly see that a marking cycle is still in progress.
2452   if (concurrent) {
2453     _cmThread->clear_in_progress();
2454   }
2455 
2456   // This notify_all() will ensure that a thread that called
2457   // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2458   // and it's waiting for a full GC to finish will be woken up. It is
2459   // waiting in VM_G1IncCollectionPause::doit_epilogue().
2460   FullGCCount_lock->notify_all();
2461 }
2462 
2463 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) {
2464   _concurrent_cycle_started = true;
2465   _gc_timer_cm->register_gc_start(start_time);
2466 
2467   _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start());
2468   trace_heap_before_gc(_gc_tracer_cm);
2469 }
2470 
2471 void G1CollectedHeap::register_concurrent_cycle_end() {
2472   if (_concurrent_cycle_started) {
2473     if (_cm->has_aborted()) {
2474       _gc_tracer_cm->report_concurrent_mode_failure();
2475     }
2476 
2477     _gc_timer_cm->register_gc_end();
2478     _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
2479 
2480     _concurrent_cycle_started = false;
2481   }
2482 }
2483 
2484 void G1CollectedHeap::trace_heap_after_concurrent_cycle() {
2485   if (_concurrent_cycle_started) {
2486     trace_heap_after_gc(_gc_tracer_cm);
2487   }
2488 }
2489 
2490 G1YCType G1CollectedHeap::yc_type() {
2491   bool is_young = g1_policy()->gcs_are_young();
2492   bool is_initial_mark = g1_policy()->during_initial_mark_pause();
2493   bool is_during_mark = mark_in_progress();
2494 
2495   if (is_initial_mark) {
2496     return InitialMark;
2497   } else if (is_during_mark) {
2498     return DuringMark;
2499   } else if (is_young) {
2500     return Normal;
2501   } else {
2502     return Mixed;
2503   }
2504 }
2505 
2506 void G1CollectedHeap::collect(GCCause::Cause cause) {
2507   assert_heap_not_locked();
2508 
2509   unsigned int gc_count_before;
2510   unsigned int old_marking_count_before;
2511   bool retry_gc;
2512 
2513   do {
2514     retry_gc = false;
2515 
2516     {
2517       MutexLocker ml(Heap_lock);
2518 
2519       // Read the GC count while holding the Heap_lock
2520       gc_count_before = total_collections();
2521       old_marking_count_before = _old_marking_cycles_started;
2522     }
2523 
2524     if (should_do_concurrent_full_gc(cause)) {
2525       // Schedule an initial-mark evacuation pause that will start a
2526       // concurrent cycle. We're setting word_size to 0 which means that
2527       // we are not requesting a post-GC allocation.
2528       VM_G1IncCollectionPause op(gc_count_before,
2529                                  0,     /* word_size */
2530                                  true,  /* should_initiate_conc_mark */
2531                                  g1_policy()->max_pause_time_ms(),
2532                                  cause);
2533 
2534       VMThread::execute(&op);
2535       if (!op.pause_succeeded()) {
2536         if (old_marking_count_before == _old_marking_cycles_started) {
2537           retry_gc = op.should_retry_gc();
2538         } else {
2539           // A Full GC happened while we were trying to schedule the
2540           // initial-mark GC. No point in starting a new cycle given
2541           // that the whole heap was collected anyway.
2542         }
2543 
2544         if (retry_gc) {
2545           if (GC_locker::is_active_and_needs_gc()) {
2546             GC_locker::stall_until_clear();
2547           }
2548         }
2549       }
2550     } else {
2551       if (cause == GCCause::_gc_locker
2552           DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2553 
2554         // Schedule a standard evacuation pause. We're setting word_size
2555         // to 0 which means that we are not requesting a post-GC allocation.
2556         VM_G1IncCollectionPause op(gc_count_before,
2557                                    0,     /* word_size */
2558                                    false, /* should_initiate_conc_mark */
2559                                    g1_policy()->max_pause_time_ms(),
2560                                    cause);
2561         VMThread::execute(&op);
2562       } else {
2563         // Schedule a Full GC.
2564         VM_G1CollectFull op(gc_count_before, old_marking_count_before, cause);
2565         VMThread::execute(&op);
2566       }
2567     }
2568   } while (retry_gc);
2569 }
2570 
2571 bool G1CollectedHeap::is_in(const void* p) const {
2572   if (_g1_committed.contains(p)) {
2573     // Given that we know that p is in the committed space,
2574     // heap_region_containing_raw() should successfully
2575     // return the containing region.
2576     HeapRegion* hr = heap_region_containing_raw(p);
2577     return hr->is_in(p);
2578   } else {
2579     return false;
2580   }
2581 }
2582 
2583 // Iteration functions.
2584 
2585 // Iterates an OopClosure over all ref-containing fields of objects
2586 // within a HeapRegion.
2587 
2588 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2589   MemRegion _mr;
2590   ExtendedOopClosure* _cl;
2591 public:
2592   IterateOopClosureRegionClosure(MemRegion mr, ExtendedOopClosure* cl)
2593     : _mr(mr), _cl(cl) {}
2594   bool doHeapRegion(HeapRegion* r) {
2595     if (!r->continuesHumongous()) {
2596       r->oop_iterate(_cl);
2597     }
2598     return false;
2599   }
2600 };
2601 
2602 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) {
2603   IterateOopClosureRegionClosure blk(_g1_committed, cl);
2604   heap_region_iterate(&blk);
2605 }
2606 
2607 void G1CollectedHeap::oop_iterate(MemRegion mr, ExtendedOopClosure* cl) {
2608   IterateOopClosureRegionClosure blk(mr, cl);
2609   heap_region_iterate(&blk);
2610 }
2611 
2612 // Iterates an ObjectClosure over all objects within a HeapRegion.
2613 
2614 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2615   ObjectClosure* _cl;
2616 public:
2617   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2618   bool doHeapRegion(HeapRegion* r) {
2619     if (! r->continuesHumongous()) {
2620       r->object_iterate(_cl);
2621     }
2622     return false;
2623   }
2624 };
2625 
2626 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2627   IterateObjectClosureRegionClosure blk(cl);
2628   heap_region_iterate(&blk);
2629 }
2630 
2631 // Calls a SpaceClosure on a HeapRegion.
2632 
2633 class SpaceClosureRegionClosure: public HeapRegionClosure {
2634   SpaceClosure* _cl;
2635 public:
2636   SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2637   bool doHeapRegion(HeapRegion* r) {
2638     _cl->do_space(r);
2639     return false;
2640   }
2641 };
2642 
2643 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2644   SpaceClosureRegionClosure blk(cl);
2645   heap_region_iterate(&blk);
2646 }
2647 
2648 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2649   _hrs.iterate(cl);
2650 }
2651 
2652 void
2653 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
2654                                                  uint worker_id,
2655                                                  uint no_of_par_workers,
2656                                                  jint claim_value) {
2657   const uint regions = n_regions();
2658   const uint max_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
2659                              no_of_par_workers :
2660                              1);
2661   assert(UseDynamicNumberOfGCThreads ||
2662          no_of_par_workers == workers()->total_workers(),
2663          "Non dynamic should use fixed number of workers");
2664   // try to spread out the starting points of the workers
2665   const HeapRegion* start_hr =
2666                         start_region_for_worker(worker_id, no_of_par_workers);
2667   const uint start_index = start_hr->hrs_index();
2668 
2669   // each worker will actually look at all regions
2670   for (uint count = 0; count < regions; ++count) {
2671     const uint index = (start_index + count) % regions;
2672     assert(0 <= index && index < regions, "sanity");
2673     HeapRegion* r = region_at(index);
2674     // we'll ignore "continues humongous" regions (we'll process them
2675     // when we come across their corresponding "start humongous"
2676     // region) and regions already claimed
2677     if (r->claim_value() == claim_value || r->continuesHumongous()) {
2678       continue;
2679     }
2680     // OK, try to claim it
2681     if (r->claimHeapRegion(claim_value)) {
2682       // success!
2683       assert(!r->continuesHumongous(), "sanity");
2684       if (r->startsHumongous()) {
2685         // If the region is "starts humongous" we'll iterate over its
2686         // "continues humongous" first; in fact we'll do them
2687         // first. The order is important. In on case, calling the
2688         // closure on the "starts humongous" region might de-allocate
2689         // and clear all its "continues humongous" regions and, as a
2690         // result, we might end up processing them twice. So, we'll do
2691         // them first (notice: most closures will ignore them anyway) and
2692         // then we'll do the "starts humongous" region.
2693         for (uint ch_index = index + 1; ch_index < regions; ++ch_index) {
2694           HeapRegion* chr = region_at(ch_index);
2695 
2696           // if the region has already been claimed or it's not
2697           // "continues humongous" we're done
2698           if (chr->claim_value() == claim_value ||
2699               !chr->continuesHumongous()) {
2700             break;
2701           }
2702 
2703           // No one should have claimed it directly. We can given
2704           // that we claimed its "starts humongous" region.
2705           assert(chr->claim_value() != claim_value, "sanity");
2706           assert(chr->humongous_start_region() == r, "sanity");
2707 
2708           if (chr->claimHeapRegion(claim_value)) {
2709             // we should always be able to claim it; no one else should
2710             // be trying to claim this region
2711 
2712             bool res2 = cl->doHeapRegion(chr);
2713             assert(!res2, "Should not abort");
2714 
2715             // Right now, this holds (i.e., no closure that actually
2716             // does something with "continues humongous" regions
2717             // clears them). We might have to weaken it in the future,
2718             // but let's leave these two asserts here for extra safety.
2719             assert(chr->continuesHumongous(), "should still be the case");
2720             assert(chr->humongous_start_region() == r, "sanity");
2721           } else {
2722             guarantee(false, "we should not reach here");
2723           }
2724         }
2725       }
2726 
2727       assert(!r->continuesHumongous(), "sanity");
2728       bool res = cl->doHeapRegion(r);
2729       assert(!res, "Should not abort");
2730     }
2731   }
2732 }
2733 
2734 class ResetClaimValuesClosure: public HeapRegionClosure {
2735 public:
2736   bool doHeapRegion(HeapRegion* r) {
2737     r->set_claim_value(HeapRegion::InitialClaimValue);
2738     return false;
2739   }
2740 };
2741 
2742 void G1CollectedHeap::reset_heap_region_claim_values() {
2743   ResetClaimValuesClosure blk;
2744   heap_region_iterate(&blk);
2745 }
2746 
2747 void G1CollectedHeap::reset_cset_heap_region_claim_values() {
2748   ResetClaimValuesClosure blk;
2749   collection_set_iterate(&blk);
2750 }
2751 
2752 #ifdef ASSERT
2753 // This checks whether all regions in the heap have the correct claim
2754 // value. I also piggy-backed on this a check to ensure that the
2755 // humongous_start_region() information on "continues humongous"
2756 // regions is correct.
2757 
2758 class CheckClaimValuesClosure : public HeapRegionClosure {
2759 private:
2760   jint _claim_value;
2761   uint _failures;
2762   HeapRegion* _sh_region;
2763 
2764 public:
2765   CheckClaimValuesClosure(jint claim_value) :
2766     _claim_value(claim_value), _failures(0), _sh_region(NULL) { }
2767   bool doHeapRegion(HeapRegion* r) {
2768     if (r->claim_value() != _claim_value) {
2769       gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2770                              "claim value = %d, should be %d",
2771                              HR_FORMAT_PARAMS(r),
2772                              r->claim_value(), _claim_value);
2773       ++_failures;
2774     }
2775     if (!r->isHumongous()) {
2776       _sh_region = NULL;
2777     } else if (r->startsHumongous()) {
2778       _sh_region = r;
2779     } else if (r->continuesHumongous()) {
2780       if (r->humongous_start_region() != _sh_region) {
2781         gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2782                                "HS = "PTR_FORMAT", should be "PTR_FORMAT,
2783                                HR_FORMAT_PARAMS(r),
2784                                r->humongous_start_region(),
2785                                _sh_region);
2786         ++_failures;
2787       }
2788     }
2789     return false;
2790   }
2791   uint failures() { return _failures; }
2792 };
2793 
2794 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
2795   CheckClaimValuesClosure cl(claim_value);
2796   heap_region_iterate(&cl);
2797   return cl.failures() == 0;
2798 }
2799 
2800 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure {
2801 private:
2802   jint _claim_value;
2803   uint _failures;
2804 
2805 public:
2806   CheckClaimValuesInCSetHRClosure(jint claim_value) :
2807     _claim_value(claim_value), _failures(0) { }
2808 
2809   uint failures() { return _failures; }
2810 
2811   bool doHeapRegion(HeapRegion* hr) {
2812     assert(hr->in_collection_set(), "how?");
2813     assert(!hr->isHumongous(), "H-region in CSet");
2814     if (hr->claim_value() != _claim_value) {
2815       gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", "
2816                              "claim value = %d, should be %d",
2817                              HR_FORMAT_PARAMS(hr),
2818                              hr->claim_value(), _claim_value);
2819       _failures += 1;
2820     }
2821     return false;
2822   }
2823 };
2824 
2825 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) {
2826   CheckClaimValuesInCSetHRClosure cl(claim_value);
2827   collection_set_iterate(&cl);
2828   return cl.failures() == 0;
2829 }
2830 #endif // ASSERT
2831 
2832 // Clear the cached CSet starting regions and (more importantly)
2833 // the time stamps. Called when we reset the GC time stamp.
2834 void G1CollectedHeap::clear_cset_start_regions() {
2835   assert(_worker_cset_start_region != NULL, "sanity");
2836   assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2837 
2838   int n_queues = MAX2((int)ParallelGCThreads, 1);
2839   for (int i = 0; i < n_queues; i++) {
2840     _worker_cset_start_region[i] = NULL;
2841     _worker_cset_start_region_time_stamp[i] = 0;
2842   }
2843 }
2844 
2845 // Given the id of a worker, obtain or calculate a suitable
2846 // starting region for iterating over the current collection set.
2847 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) {
2848   assert(get_gc_time_stamp() > 0, "should have been updated by now");
2849 
2850   HeapRegion* result = NULL;
2851   unsigned gc_time_stamp = get_gc_time_stamp();
2852 
2853   if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2854     // Cached starting region for current worker was set
2855     // during the current pause - so it's valid.
2856     // Note: the cached starting heap region may be NULL
2857     // (when the collection set is empty).
2858     result = _worker_cset_start_region[worker_i];
2859     assert(result == NULL || result->in_collection_set(), "sanity");
2860     return result;
2861   }
2862 
2863   // The cached entry was not valid so let's calculate
2864   // a suitable starting heap region for this worker.
2865 
2866   // We want the parallel threads to start their collection
2867   // set iteration at different collection set regions to
2868   // avoid contention.
2869   // If we have:
2870   //          n collection set regions
2871   //          p threads
2872   // Then thread t will start at region floor ((t * n) / p)
2873 
2874   result = g1_policy()->collection_set();
2875   if (G1CollectedHeap::use_parallel_gc_threads()) {
2876     uint cs_size = g1_policy()->cset_region_length();
2877     uint active_workers = workers()->active_workers();
2878     assert(UseDynamicNumberOfGCThreads ||
2879              active_workers == workers()->total_workers(),
2880              "Unless dynamic should use total workers");
2881 
2882     uint end_ind   = (cs_size * worker_i) / active_workers;
2883     uint start_ind = 0;
2884 
2885     if (worker_i > 0 &&
2886         _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2887       // Previous workers starting region is valid
2888       // so let's iterate from there
2889       start_ind = (cs_size * (worker_i - 1)) / active_workers;
2890       result = _worker_cset_start_region[worker_i - 1];
2891     }
2892 
2893     for (uint i = start_ind; i < end_ind; i++) {
2894       result = result->next_in_collection_set();
2895     }
2896   }
2897 
2898   // Note: the calculated starting heap region may be NULL
2899   // (when the collection set is empty).
2900   assert(result == NULL || result->in_collection_set(), "sanity");
2901   assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2902          "should be updated only once per pause");
2903   _worker_cset_start_region[worker_i] = result;
2904   OrderAccess::storestore();
2905   _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2906   return result;
2907 }
2908 
2909 HeapRegion* G1CollectedHeap::start_region_for_worker(uint worker_i,
2910                                                      uint no_of_par_workers) {
2911   uint worker_num =
2912            G1CollectedHeap::use_parallel_gc_threads() ? no_of_par_workers : 1U;
2913   assert(UseDynamicNumberOfGCThreads ||
2914          no_of_par_workers == workers()->total_workers(),
2915          "Non dynamic should use fixed number of workers");
2916   const uint start_index = n_regions() * worker_i / worker_num;
2917   return region_at(start_index);
2918 }
2919 
2920 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2921   HeapRegion* r = g1_policy()->collection_set();
2922   while (r != NULL) {
2923     HeapRegion* next = r->next_in_collection_set();
2924     if (cl->doHeapRegion(r)) {
2925       cl->incomplete();
2926       return;
2927     }
2928     r = next;
2929   }
2930 }
2931 
2932 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2933                                                   HeapRegionClosure *cl) {
2934   if (r == NULL) {
2935     // The CSet is empty so there's nothing to do.
2936     return;
2937   }
2938 
2939   assert(r->in_collection_set(),
2940          "Start region must be a member of the collection set.");
2941   HeapRegion* cur = r;
2942   while (cur != NULL) {
2943     HeapRegion* next = cur->next_in_collection_set();
2944     if (cl->doHeapRegion(cur) && false) {
2945       cl->incomplete();
2946       return;
2947     }
2948     cur = next;
2949   }
2950   cur = g1_policy()->collection_set();
2951   while (cur != r) {
2952     HeapRegion* next = cur->next_in_collection_set();
2953     if (cl->doHeapRegion(cur) && false) {
2954       cl->incomplete();
2955       return;
2956     }
2957     cur = next;
2958   }
2959 }
2960 
2961 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const {
2962   // We're not using an iterator given that it will wrap around when
2963   // it reaches the last region and this is not what we want here.
2964   for (uint index = from->hrs_index() + 1; index < n_regions(); index++) {
2965     HeapRegion* hr = region_at(index);
2966     if (!hr->isHumongous()) {
2967       return hr;
2968     }
2969   }
2970   return NULL;
2971 }
2972 
2973 Space* G1CollectedHeap::space_containing(const void* addr) const {
2974   return heap_region_containing(addr);
2975 }
2976 
2977 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2978   Space* sp = space_containing(addr);
2979   return sp->block_start(addr);
2980 }
2981 
2982 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2983   Space* sp = space_containing(addr);
2984   return sp->block_size(addr);
2985 }
2986 
2987 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2988   Space* sp = space_containing(addr);
2989   return sp->block_is_obj(addr);
2990 }
2991 
2992 bool G1CollectedHeap::supports_tlab_allocation() const {
2993   return true;
2994 }
2995 
2996 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2997   return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes;
2998 }
2999 
3000 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
3001   return young_list()->eden_used_bytes();
3002 }
3003 
3004 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
3005 // must be smaller than the humongous object limit.
3006 size_t G1CollectedHeap::max_tlab_size() const {
3007   return align_size_down(_humongous_object_threshold_in_words - 1, MinObjAlignment);
3008 }
3009 
3010 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
3011   // Return the remaining space in the cur alloc region, but not less than
3012   // the min TLAB size.
3013 
3014   // Also, this value can be at most the humongous object threshold,
3015   // since we can't allow tlabs to grow big enough to accommodate
3016   // humongous objects.
3017 
3018   HeapRegion* hr = _mutator_alloc_region.get();
3019   size_t max_tlab = max_tlab_size() * wordSize;
3020   if (hr == NULL) {
3021     return max_tlab;
3022   } else {
3023     return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab);
3024   }
3025 }
3026 
3027 size_t G1CollectedHeap::max_capacity() const {
3028   return _g1_reserved.byte_size();
3029 }
3030 
3031 jlong G1CollectedHeap::millis_since_last_gc() {
3032   // assert(false, "NYI");
3033   return 0;
3034 }
3035 
3036 void G1CollectedHeap::prepare_for_verify() {
3037   if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
3038     ensure_parsability(false);
3039   }
3040   g1_rem_set()->prepare_for_verify();
3041 }
3042 
3043 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr,
3044                                               VerifyOption vo) {
3045   switch (vo) {
3046   case VerifyOption_G1UsePrevMarking:
3047     return hr->obj_allocated_since_prev_marking(obj);
3048   case VerifyOption_G1UseNextMarking:
3049     return hr->obj_allocated_since_next_marking(obj);
3050   case VerifyOption_G1UseMarkWord:
3051     return false;
3052   default:
3053     ShouldNotReachHere();
3054   }
3055   return false; // keep some compilers happy
3056 }
3057 
3058 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) {
3059   switch (vo) {
3060   case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start();
3061   case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start();
3062   case VerifyOption_G1UseMarkWord:    return NULL;
3063   default:                            ShouldNotReachHere();
3064   }
3065   return NULL; // keep some compilers happy
3066 }
3067 
3068 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) {
3069   switch (vo) {
3070   case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj);
3071   case VerifyOption_G1UseNextMarking: return isMarkedNext(obj);
3072   case VerifyOption_G1UseMarkWord:    return obj->is_gc_marked();
3073   default:                            ShouldNotReachHere();
3074   }
3075   return false; // keep some compilers happy
3076 }
3077 
3078 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) {
3079   switch (vo) {
3080   case VerifyOption_G1UsePrevMarking: return "PTAMS";
3081   case VerifyOption_G1UseNextMarking: return "NTAMS";
3082   case VerifyOption_G1UseMarkWord:    return "NONE";
3083   default:                            ShouldNotReachHere();
3084   }
3085   return NULL; // keep some compilers happy
3086 }
3087 
3088 class VerifyRootsClosure: public OopClosure {
3089 private:
3090   G1CollectedHeap* _g1h;
3091   VerifyOption     _vo;
3092   bool             _failures;
3093 public:
3094   // _vo == UsePrevMarking -> use "prev" marking information,
3095   // _vo == UseNextMarking -> use "next" marking information,
3096   // _vo == UseMarkWord    -> use mark word from object header.
3097   VerifyRootsClosure(VerifyOption vo) :
3098     _g1h(G1CollectedHeap::heap()),
3099     _vo(vo),
3100     _failures(false) { }
3101 
3102   bool failures() { return _failures; }
3103 
3104   template <class T> void do_oop_nv(T* p) {
3105     T heap_oop = oopDesc::load_heap_oop(p);
3106     if (!oopDesc::is_null(heap_oop)) {
3107       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3108       if (_g1h->is_obj_dead_cond(obj, _vo)) {
3109         gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
3110                               "points to dead obj "PTR_FORMAT, p, (void*) obj);
3111         if (_vo == VerifyOption_G1UseMarkWord) {
3112           gclog_or_tty->print_cr("  Mark word: "PTR_FORMAT, (void*)(obj->mark()));
3113         }
3114         obj->print_on(gclog_or_tty);
3115         _failures = true;
3116       }
3117     }
3118   }
3119 
3120   void do_oop(oop* p)       { do_oop_nv(p); }
3121   void do_oop(narrowOop* p) { do_oop_nv(p); }
3122 };
3123 
3124 class G1VerifyCodeRootOopClosure: public OopClosure {
3125   G1CollectedHeap* _g1h;
3126   OopClosure* _root_cl;
3127   nmethod* _nm;
3128   VerifyOption _vo;
3129   bool _failures;
3130 
3131   template <class T> void do_oop_work(T* p) {
3132     // First verify that this root is live
3133     _root_cl->do_oop(p);
3134 
3135     if (!G1VerifyHeapRegionCodeRoots) {
3136       // We're not verifying the code roots attached to heap region.
3137       return;
3138     }
3139 
3140     // Don't check the code roots during marking verification in a full GC
3141     if (_vo == VerifyOption_G1UseMarkWord) {
3142       return;
3143     }
3144 
3145     // Now verify that the current nmethod (which contains p) is
3146     // in the code root list of the heap region containing the
3147     // object referenced by p.
3148 
3149     T heap_oop = oopDesc::load_heap_oop(p);
3150     if (!oopDesc::is_null(heap_oop)) {
3151       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3152 
3153       // Now fetch the region containing the object
3154       HeapRegion* hr = _g1h->heap_region_containing(obj);
3155       HeapRegionRemSet* hrrs = hr->rem_set();
3156       // Verify that the strong code root list for this region
3157       // contains the nmethod
3158       if (!hrrs->strong_code_roots_list_contains(_nm)) {
3159         gclog_or_tty->print_cr("Code root location "PTR_FORMAT" "
3160                               "from nmethod "PTR_FORMAT" not in strong "
3161                               "code roots for region ["PTR_FORMAT","PTR_FORMAT")",
3162                               p, _nm, hr->bottom(), hr->end());
3163         _failures = true;
3164       }
3165     }
3166   }
3167 
3168 public:
3169   G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo):
3170     _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {}
3171 
3172   void do_oop(oop* p) { do_oop_work(p); }
3173   void do_oop(narrowOop* p) { do_oop_work(p); }
3174 
3175   void set_nmethod(nmethod* nm) { _nm = nm; }
3176   bool failures() { return _failures; }
3177 };
3178 
3179 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure {
3180   G1VerifyCodeRootOopClosure* _oop_cl;
3181 
3182 public:
3183   G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl):
3184     _oop_cl(oop_cl) {}
3185 
3186   void do_code_blob(CodeBlob* cb) {
3187     nmethod* nm = cb->as_nmethod_or_null();
3188     if (nm != NULL) {
3189       _oop_cl->set_nmethod(nm);
3190       nm->oops_do(_oop_cl);
3191     }
3192   }
3193 };
3194 
3195 class YoungRefCounterClosure : public OopClosure {
3196   G1CollectedHeap* _g1h;
3197   int              _count;
3198  public:
3199   YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {}
3200   void do_oop(oop* p)       { if (_g1h->is_in_young(*p)) { _count++; } }
3201   void do_oop(narrowOop* p) { ShouldNotReachHere(); }
3202 
3203   int count() { return _count; }
3204   void reset_count() { _count = 0; };
3205 };
3206 
3207 class VerifyKlassClosure: public KlassClosure {
3208   YoungRefCounterClosure _young_ref_counter_closure;
3209   OopClosure *_oop_closure;
3210  public:
3211   VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {}
3212   void do_klass(Klass* k) {
3213     k->oops_do(_oop_closure);
3214 
3215     _young_ref_counter_closure.reset_count();
3216     k->oops_do(&_young_ref_counter_closure);
3217     if (_young_ref_counter_closure.count() > 0) {
3218       guarantee(k->has_modified_oops(), err_msg("Klass " PTR_FORMAT ", has young refs but is not dirty.", k));
3219     }
3220   }
3221 };
3222 
3223 class VerifyLivenessOopClosure: public OopClosure {
3224   G1CollectedHeap* _g1h;
3225   VerifyOption _vo;
3226 public:
3227   VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
3228     _g1h(g1h), _vo(vo)
3229   { }
3230   void do_oop(narrowOop *p) { do_oop_work(p); }
3231   void do_oop(      oop *p) { do_oop_work(p); }
3232 
3233   template <class T> void do_oop_work(T *p) {
3234     oop obj = oopDesc::load_decode_heap_oop(p);
3235     guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
3236               "Dead object referenced by a not dead object");
3237   }
3238 };
3239 
3240 class VerifyObjsInRegionClosure: public ObjectClosure {
3241 private:
3242   G1CollectedHeap* _g1h;
3243   size_t _live_bytes;
3244   HeapRegion *_hr;
3245   VerifyOption _vo;
3246 public:
3247   // _vo == UsePrevMarking -> use "prev" marking information,
3248   // _vo == UseNextMarking -> use "next" marking information,
3249   // _vo == UseMarkWord    -> use mark word from object header.
3250   VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
3251     : _live_bytes(0), _hr(hr), _vo(vo) {
3252     _g1h = G1CollectedHeap::heap();
3253   }
3254   void do_object(oop o) {
3255     VerifyLivenessOopClosure isLive(_g1h, _vo);
3256     assert(o != NULL, "Huh?");
3257     if (!_g1h->is_obj_dead_cond(o, _vo)) {
3258       // If the object is alive according to the mark word,
3259       // then verify that the marking information agrees.
3260       // Note we can't verify the contra-positive of the
3261       // above: if the object is dead (according to the mark
3262       // word), it may not be marked, or may have been marked
3263       // but has since became dead, or may have been allocated
3264       // since the last marking.
3265       if (_vo == VerifyOption_G1UseMarkWord) {
3266         guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
3267       }
3268 
3269       o->oop_iterate_no_header(&isLive);
3270       if (!_hr->obj_allocated_since_prev_marking(o)) {
3271         size_t obj_size = o->size();    // Make sure we don't overflow
3272         _live_bytes += (obj_size * HeapWordSize);
3273       }
3274     }
3275   }
3276   size_t live_bytes() { return _live_bytes; }
3277 };
3278 
3279 class PrintObjsInRegionClosure : public ObjectClosure {
3280   HeapRegion *_hr;
3281   G1CollectedHeap *_g1;
3282 public:
3283   PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
3284     _g1 = G1CollectedHeap::heap();
3285   };
3286 
3287   void do_object(oop o) {
3288     if (o != NULL) {
3289       HeapWord *start = (HeapWord *) o;
3290       size_t word_sz = o->size();
3291       gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
3292                           " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
3293                           (void*) o, word_sz,
3294                           _g1->isMarkedPrev(o),
3295                           _g1->isMarkedNext(o),
3296                           _hr->obj_allocated_since_prev_marking(o));
3297       HeapWord *end = start + word_sz;
3298       HeapWord *cur;
3299       int *val;
3300       for (cur = start; cur < end; cur++) {
3301         val = (int *) cur;
3302         gclog_or_tty->print("\t "PTR_FORMAT":%d\n", val, *val);
3303       }
3304     }
3305   }
3306 };
3307 
3308 class VerifyRegionClosure: public HeapRegionClosure {
3309 private:
3310   bool             _par;
3311   VerifyOption     _vo;
3312   bool             _failures;
3313 public:
3314   // _vo == UsePrevMarking -> use "prev" marking information,
3315   // _vo == UseNextMarking -> use "next" marking information,
3316   // _vo == UseMarkWord    -> use mark word from object header.
3317   VerifyRegionClosure(bool par, VerifyOption vo)
3318     : _par(par),
3319       _vo(vo),
3320       _failures(false) {}
3321 
3322   bool failures() {
3323     return _failures;
3324   }
3325 
3326   bool doHeapRegion(HeapRegion* r) {
3327     if (!r->continuesHumongous()) {
3328       bool failures = false;
3329       r->verify(_vo, &failures);
3330       if (failures) {
3331         _failures = true;
3332       } else {
3333         VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
3334         r->object_iterate(&not_dead_yet_cl);
3335         if (_vo != VerifyOption_G1UseNextMarking) {
3336           if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
3337             gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
3338                                    "max_live_bytes "SIZE_FORMAT" "
3339                                    "< calculated "SIZE_FORMAT,
3340                                    r->bottom(), r->end(),
3341                                    r->max_live_bytes(),
3342                                  not_dead_yet_cl.live_bytes());
3343             _failures = true;
3344           }
3345         } else {
3346           // When vo == UseNextMarking we cannot currently do a sanity
3347           // check on the live bytes as the calculation has not been
3348           // finalized yet.
3349         }
3350       }
3351     }
3352     return false; // stop the region iteration if we hit a failure
3353   }
3354 };
3355 
3356 // This is the task used for parallel verification of the heap regions
3357 
3358 class G1ParVerifyTask: public AbstractGangTask {
3359 private:
3360   G1CollectedHeap* _g1h;
3361   VerifyOption     _vo;
3362   bool             _failures;
3363 
3364 public:
3365   // _vo == UsePrevMarking -> use "prev" marking information,
3366   // _vo == UseNextMarking -> use "next" marking information,
3367   // _vo == UseMarkWord    -> use mark word from object header.
3368   G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
3369     AbstractGangTask("Parallel verify task"),
3370     _g1h(g1h),
3371     _vo(vo),
3372     _failures(false) { }
3373 
3374   bool failures() {
3375     return _failures;
3376   }
3377 
3378   void work(uint worker_id) {
3379     HandleMark hm;
3380     VerifyRegionClosure blk(true, _vo);
3381     _g1h->heap_region_par_iterate_chunked(&blk, worker_id,
3382                                           _g1h->workers()->active_workers(),
3383                                           HeapRegion::ParVerifyClaimValue);
3384     if (blk.failures()) {
3385       _failures = true;
3386     }
3387   }
3388 };
3389 
3390 void G1CollectedHeap::verify(bool silent, VerifyOption vo) {
3391   if (SafepointSynchronize::is_at_safepoint()) {
3392     assert(Thread::current()->is_VM_thread(),
3393            "Expected to be executed serially by the VM thread at this point");
3394 
3395     if (!silent) { gclog_or_tty->print("Roots "); }
3396     VerifyRootsClosure rootsCl(vo);
3397     VerifyKlassClosure klassCl(this, &rootsCl);
3398     CLDToKlassAndOopClosure cldCl(&klassCl, &rootsCl, false);
3399 
3400     // We apply the relevant closures to all the oops in the
3401     // system dictionary, class loader data graph, the string table
3402     // and the nmethods in the code cache.
3403     G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo);
3404     G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl);
3405 
3406     process_all_roots(true,            // activate StrongRootsScope
3407                       SO_AllCodeCache, // roots scanning options
3408                       &rootsCl,
3409                       &cldCl,
3410                       &blobsCl);
3411 
3412     bool failures = rootsCl.failures() || codeRootsCl.failures();
3413 
3414     if (vo != VerifyOption_G1UseMarkWord) {
3415       // If we're verifying during a full GC then the region sets
3416       // will have been torn down at the start of the GC. Therefore
3417       // verifying the region sets will fail. So we only verify
3418       // the region sets when not in a full GC.
3419       if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3420       verify_region_sets();
3421     }
3422 
3423     if (!silent) { gclog_or_tty->print("HeapRegions "); }
3424     if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3425       assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3426              "sanity check");
3427 
3428       G1ParVerifyTask task(this, vo);
3429       assert(UseDynamicNumberOfGCThreads ||
3430         workers()->active_workers() == workers()->total_workers(),
3431         "If not dynamic should be using all the workers");
3432       int n_workers = workers()->active_workers();
3433       set_par_threads(n_workers);
3434       workers()->run_task(&task);
3435       set_par_threads(0);
3436       if (task.failures()) {
3437         failures = true;
3438       }
3439 
3440       // Checks that the expected amount of parallel work was done.
3441       // The implication is that n_workers is > 0.
3442       assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
3443              "sanity check");
3444 
3445       reset_heap_region_claim_values();
3446 
3447       assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3448              "sanity check");
3449     } else {
3450       VerifyRegionClosure blk(false, vo);
3451       heap_region_iterate(&blk);
3452       if (blk.failures()) {
3453         failures = true;
3454       }
3455     }
3456     if (!silent) gclog_or_tty->print("RemSet ");
3457     rem_set()->verify();
3458 
3459     if (G1StringDedup::is_enabled()) {
3460       if (!silent) gclog_or_tty->print("StrDedup ");
3461       G1StringDedup::verify();
3462     }
3463 
3464     if (failures) {
3465       gclog_or_tty->print_cr("Heap:");
3466       // It helps to have the per-region information in the output to
3467       // help us track down what went wrong. This is why we call
3468       // print_extended_on() instead of print_on().
3469       print_extended_on(gclog_or_tty);
3470       gclog_or_tty->cr();
3471 #ifndef PRODUCT
3472       if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3473         concurrent_mark()->print_reachable("at-verification-failure",
3474                                            vo, false /* all */);
3475       }
3476 #endif
3477       gclog_or_tty->flush();
3478     }
3479     guarantee(!failures, "there should not have been any failures");
3480   } else {
3481     if (!silent) {
3482       gclog_or_tty->print("(SKIPPING Roots, HeapRegionSets, HeapRegions, RemSet");
3483       if (G1StringDedup::is_enabled()) {
3484         gclog_or_tty->print(", StrDedup");
3485       }
3486       gclog_or_tty->print(") ");
3487     }
3488   }
3489 }
3490 
3491 void G1CollectedHeap::verify(bool silent) {
3492   verify(silent, VerifyOption_G1UsePrevMarking);
3493 }
3494 
3495 double G1CollectedHeap::verify(bool guard, const char* msg) {
3496   double verify_time_ms = 0.0;
3497 
3498   if (guard && total_collections() >= VerifyGCStartAt) {
3499     double verify_start = os::elapsedTime();
3500     HandleMark hm;  // Discard invalid handles created during verification
3501     prepare_for_verify();
3502     Universe::verify(VerifyOption_G1UsePrevMarking, msg);
3503     verify_time_ms = (os::elapsedTime() - verify_start) * 1000;
3504   }
3505 
3506   return verify_time_ms;
3507 }
3508 
3509 void G1CollectedHeap::verify_before_gc() {
3510   double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:");
3511   g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms);
3512 }
3513 
3514 void G1CollectedHeap::verify_after_gc() {
3515   double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:");
3516   g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms);
3517 }
3518 
3519 class PrintRegionClosure: public HeapRegionClosure {
3520   outputStream* _st;
3521 public:
3522   PrintRegionClosure(outputStream* st) : _st(st) {}
3523   bool doHeapRegion(HeapRegion* r) {
3524     r->print_on(_st);
3525     return false;
3526   }
3527 };
3528 
3529 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3530                                        const HeapRegion* hr,
3531                                        const VerifyOption vo) const {
3532   switch (vo) {
3533   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
3534   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
3535   case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked();
3536   default:                            ShouldNotReachHere();
3537   }
3538   return false; // keep some compilers happy
3539 }
3540 
3541 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3542                                        const VerifyOption vo) const {
3543   switch (vo) {
3544   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
3545   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
3546   case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked();
3547   default:                            ShouldNotReachHere();
3548   }
3549   return false; // keep some compilers happy
3550 }
3551 
3552 void G1CollectedHeap::print_on(outputStream* st) const {
3553   st->print(" %-20s", "garbage-first heap");
3554   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3555             capacity()/K, used_unlocked()/K);
3556   st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3557             _g1_storage.low_boundary(),
3558             _g1_storage.high(),
3559             _g1_storage.high_boundary());
3560   st->cr();
3561   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3562   uint young_regions = _young_list->length();
3563   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3564             (size_t) young_regions * HeapRegion::GrainBytes / K);
3565   uint survivor_regions = g1_policy()->recorded_survivor_regions();
3566   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3567             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3568   st->cr();
3569   MetaspaceAux::print_on(st);
3570 }
3571 
3572 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3573   print_on(st);
3574 
3575   // Print the per-region information.
3576   st->cr();
3577   st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3578                "HS=humongous(starts), HC=humongous(continues), "
3579                "CS=collection set, F=free, TS=gc time stamp, "
3580                "PTAMS=previous top-at-mark-start, "
3581                "NTAMS=next top-at-mark-start)");
3582   PrintRegionClosure blk(st);
3583   heap_region_iterate(&blk);
3584 }
3585 
3586 void G1CollectedHeap::print_on_error(outputStream* st) const {
3587   this->CollectedHeap::print_on_error(st);
3588 
3589   if (_cm != NULL) {
3590     st->cr();
3591     _cm->print_on_error(st);
3592   }
3593 }
3594 
3595 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3596   if (G1CollectedHeap::use_parallel_gc_threads()) {
3597     workers()->print_worker_threads_on(st);
3598   }
3599   _cmThread->print_on(st);
3600   st->cr();
3601   _cm->print_worker_threads_on(st);
3602   _cg1r->print_worker_threads_on(st);
3603   if (G1StringDedup::is_enabled()) {
3604     G1StringDedup::print_worker_threads_on(st);
3605   }
3606 }
3607 
3608 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3609   if (G1CollectedHeap::use_parallel_gc_threads()) {
3610     workers()->threads_do(tc);
3611   }
3612   tc->do_thread(_cmThread);
3613   _cg1r->threads_do(tc);
3614   if (G1StringDedup::is_enabled()) {
3615     G1StringDedup::threads_do(tc);
3616   }
3617 }
3618 
3619 void G1CollectedHeap::print_tracing_info() const {
3620   // We'll overload this to mean "trace GC pause statistics."
3621   if (TraceYoungGenTime || TraceOldGenTime) {
3622     // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3623     // to that.
3624     g1_policy()->print_tracing_info();
3625   }
3626   if (G1SummarizeRSetStats) {
3627     g1_rem_set()->print_summary_info();
3628   }
3629   if (G1SummarizeConcMark) {
3630     concurrent_mark()->print_summary_info();
3631   }
3632   g1_policy()->print_yg_surv_rate_info();
3633   SpecializationStats::print();
3634 }
3635 
3636 #ifndef PRODUCT
3637 // Helpful for debugging RSet issues.
3638 
3639 class PrintRSetsClosure : public HeapRegionClosure {
3640 private:
3641   const char* _msg;
3642   size_t _occupied_sum;
3643 
3644 public:
3645   bool doHeapRegion(HeapRegion* r) {
3646     HeapRegionRemSet* hrrs = r->rem_set();
3647     size_t occupied = hrrs->occupied();
3648     _occupied_sum += occupied;
3649 
3650     gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3651                            HR_FORMAT_PARAMS(r));
3652     if (occupied == 0) {
3653       gclog_or_tty->print_cr("  RSet is empty");
3654     } else {
3655       hrrs->print();
3656     }
3657     gclog_or_tty->print_cr("----------");
3658     return false;
3659   }
3660 
3661   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3662     gclog_or_tty->cr();
3663     gclog_or_tty->print_cr("========================================");
3664     gclog_or_tty->print_cr("%s", msg);
3665     gclog_or_tty->cr();
3666   }
3667 
3668   ~PrintRSetsClosure() {
3669     gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3670     gclog_or_tty->print_cr("========================================");
3671     gclog_or_tty->cr();
3672   }
3673 };
3674 
3675 void G1CollectedHeap::print_cset_rsets() {
3676   PrintRSetsClosure cl("Printing CSet RSets");
3677   collection_set_iterate(&cl);
3678 }
3679 
3680 void G1CollectedHeap::print_all_rsets() {
3681   PrintRSetsClosure cl("Printing All RSets");;
3682   heap_region_iterate(&cl);
3683 }
3684 #endif // PRODUCT
3685 
3686 G1CollectedHeap* G1CollectedHeap::heap() {
3687   assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3688          "not a garbage-first heap");
3689   return _g1h;
3690 }
3691 
3692 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3693   // always_do_update_barrier = false;
3694   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3695   // Fill TLAB's and such
3696   accumulate_statistics_all_tlabs();
3697   ensure_parsability(true);
3698 
3699   if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) &&
3700       (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3701     g1_rem_set()->print_periodic_summary_info("Before GC RS summary");
3702   }
3703 }
3704 
3705 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) {
3706 
3707   if (G1SummarizeRSetStats &&
3708       (G1SummarizeRSetStatsPeriod > 0) &&
3709       // we are at the end of the GC. Total collections has already been increased.
3710       ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) {
3711     g1_rem_set()->print_periodic_summary_info("After GC RS summary");
3712   }
3713 
3714   // FIXME: what is this about?
3715   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3716   // is set.
3717   COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3718                         "derived pointer present"));
3719   // always_do_update_barrier = true;
3720 
3721   resize_all_tlabs();
3722 
3723   // We have just completed a GC. Update the soft reference
3724   // policy with the new heap occupancy
3725   Universe::update_heap_info_at_gc();
3726 }
3727 
3728 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3729                                                unsigned int gc_count_before,
3730                                                bool* succeeded,
3731                                                GCCause::Cause gc_cause) {
3732   assert_heap_not_locked_and_not_at_safepoint();
3733   g1_policy()->record_stop_world_start();
3734   VM_G1IncCollectionPause op(gc_count_before,
3735                              word_size,
3736                              false, /* should_initiate_conc_mark */
3737                              g1_policy()->max_pause_time_ms(),
3738                              gc_cause);
3739   VMThread::execute(&op);
3740 
3741   HeapWord* result = op.result();
3742   bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3743   assert(result == NULL || ret_succeeded,
3744          "the result should be NULL if the VM did not succeed");
3745   *succeeded = ret_succeeded;
3746 
3747   assert_heap_not_locked();
3748   return result;
3749 }
3750 
3751 void
3752 G1CollectedHeap::doConcurrentMark() {
3753   MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3754   if (!_cmThread->in_progress()) {
3755     _cmThread->set_started();
3756     CGC_lock->notify();
3757   }
3758 }
3759 
3760 size_t G1CollectedHeap::pending_card_num() {
3761   size_t extra_cards = 0;
3762   JavaThread *curr = Threads::first();
3763   while (curr != NULL) {
3764     DirtyCardQueue& dcq = curr->dirty_card_queue();
3765     extra_cards += dcq.size();
3766     curr = curr->next();
3767   }
3768   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3769   size_t buffer_size = dcqs.buffer_size();
3770   size_t buffer_num = dcqs.completed_buffers_num();
3771 
3772   // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
3773   // in bytes - not the number of 'entries'. We need to convert
3774   // into a number of cards.
3775   return (buffer_size * buffer_num + extra_cards) / oopSize;
3776 }
3777 
3778 size_t G1CollectedHeap::cards_scanned() {
3779   return g1_rem_set()->cardsScanned();
3780 }
3781 
3782 bool G1CollectedHeap::humongous_region_is_always_live(uint index) {
3783   HeapRegion* region = region_at(index);
3784   assert(region->startsHumongous(), "Must start a humongous object");
3785   return oop(region->bottom())->is_objArray() || !region->rem_set()->is_empty();
3786 }
3787 
3788 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
3789  private:
3790   size_t _total_humongous;
3791   size_t _candidate_humongous;
3792  public:
3793   RegisterHumongousWithInCSetFastTestClosure() : _total_humongous(0), _candidate_humongous(0) {
3794   }
3795 
3796   virtual bool doHeapRegion(HeapRegion* r) {
3797     if (!r->startsHumongous()) {
3798       return false;
3799     }
3800     G1CollectedHeap* g1h = G1CollectedHeap::heap();
3801 
3802     uint region_idx = r->hrs_index();
3803     bool is_candidate = !g1h->humongous_region_is_always_live(region_idx);
3804     // Is_candidate already filters out humongous regions with some remembered set.
3805     // This will not lead to humongous object that we mistakenly keep alive because
3806     // during young collection the remembered sets will only be added to.
3807     if (is_candidate) {
3808       g1h->register_humongous_region_with_in_cset_fast_test(region_idx);
3809       _candidate_humongous++;
3810     }
3811     _total_humongous++;
3812 
3813     return false;
3814   }
3815 
3816   size_t total_humongous() const { return _total_humongous; }
3817   size_t candidate_humongous() const { return _candidate_humongous; }
3818 };
3819 
3820 void G1CollectedHeap::register_humongous_regions_with_in_cset_fast_test() {
3821   if (!G1ReclaimDeadHumongousObjectsAtYoungGC) {
3822     g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0, 0);
3823     return;
3824   }
3825 
3826   RegisterHumongousWithInCSetFastTestClosure cl;
3827   heap_region_iterate(&cl);
3828   g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(cl.total_humongous(),
3829                                                                   cl.candidate_humongous());
3830   _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
3831 
3832   if (_has_humongous_reclaim_candidates) {
3833     clear_humongous_is_live_table();
3834   }
3835 }
3836 
3837 void
3838 G1CollectedHeap::setup_surviving_young_words() {
3839   assert(_surviving_young_words == NULL, "pre-condition");
3840   uint array_length = g1_policy()->young_cset_region_length();
3841   _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3842   if (_surviving_young_words == NULL) {
3843     vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR,
3844                           "Not enough space for young surv words summary.");
3845   }
3846   memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3847 #ifdef ASSERT
3848   for (uint i = 0;  i < array_length; ++i) {
3849     assert( _surviving_young_words[i] == 0, "memset above" );
3850   }
3851 #endif // !ASSERT
3852 }
3853 
3854 void
3855 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3856   MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3857   uint array_length = g1_policy()->young_cset_region_length();
3858   for (uint i = 0; i < array_length; ++i) {
3859     _surviving_young_words[i] += surv_young_words[i];
3860   }
3861 }
3862 
3863 void
3864 G1CollectedHeap::cleanup_surviving_young_words() {
3865   guarantee( _surviving_young_words != NULL, "pre-condition" );
3866   FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC);
3867   _surviving_young_words = NULL;
3868 }
3869 
3870 #ifdef ASSERT
3871 class VerifyCSetClosure: public HeapRegionClosure {
3872 public:
3873   bool doHeapRegion(HeapRegion* hr) {
3874     // Here we check that the CSet region's RSet is ready for parallel
3875     // iteration. The fields that we'll verify are only manipulated
3876     // when the region is part of a CSet and is collected. Afterwards,
3877     // we reset these fields when we clear the region's RSet (when the
3878     // region is freed) so they are ready when the region is
3879     // re-allocated. The only exception to this is if there's an
3880     // evacuation failure and instead of freeing the region we leave
3881     // it in the heap. In that case, we reset these fields during
3882     // evacuation failure handling.
3883     guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3884 
3885     // Here's a good place to add any other checks we'd like to
3886     // perform on CSet regions.
3887     return false;
3888   }
3889 };
3890 #endif // ASSERT
3891 
3892 #if TASKQUEUE_STATS
3893 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3894   st->print_raw_cr("GC Task Stats");
3895   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3896   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3897 }
3898 
3899 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3900   print_taskqueue_stats_hdr(st);
3901 
3902   TaskQueueStats totals;
3903   const int n = workers() != NULL ? workers()->total_workers() : 1;
3904   for (int i = 0; i < n; ++i) {
3905     st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3906     totals += task_queue(i)->stats;
3907   }
3908   st->print_raw("tot "); totals.print(st); st->cr();
3909 
3910   DEBUG_ONLY(totals.verify());
3911 }
3912 
3913 void G1CollectedHeap::reset_taskqueue_stats() {
3914   const int n = workers() != NULL ? workers()->total_workers() : 1;
3915   for (int i = 0; i < n; ++i) {
3916     task_queue(i)->stats.reset();
3917   }
3918 }
3919 #endif // TASKQUEUE_STATS
3920 
3921 void G1CollectedHeap::log_gc_header() {
3922   if (!G1Log::fine()) {
3923     return;
3924   }
3925 
3926   gclog_or_tty->gclog_stamp(_gc_tracer_stw->gc_id());
3927 
3928   GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
3929     .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)")
3930     .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : "");
3931 
3932   gclog_or_tty->print("[%s", (const char*)gc_cause_str);
3933 }
3934 
3935 void G1CollectedHeap::log_gc_footer(double pause_time_sec) {
3936   if (!G1Log::fine()) {
3937     return;
3938   }
3939 
3940   if (G1Log::finer()) {
3941     if (evacuation_failed()) {
3942       gclog_or_tty->print(" (to-space exhausted)");
3943     }
3944     gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3945     g1_policy()->phase_times()->note_gc_end();
3946     g1_policy()->phase_times()->print(pause_time_sec);
3947     g1_policy()->print_detailed_heap_transition();
3948   } else {
3949     if (evacuation_failed()) {
3950       gclog_or_tty->print("--");
3951     }
3952     g1_policy()->print_heap_transition();
3953     gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3954   }
3955   gclog_or_tty->flush();
3956 }
3957 
3958 bool
3959 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3960   assert_at_safepoint(true /* should_be_vm_thread */);
3961   guarantee(!is_gc_active(), "collection is not reentrant");
3962 
3963   if (GC_locker::check_active_before_gc()) {
3964     return false;
3965   }
3966 
3967   _gc_timer_stw->register_gc_start();
3968 
3969   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3970 
3971   SvcGCMarker sgcm(SvcGCMarker::MINOR);
3972   ResourceMark rm;
3973 
3974   print_heap_before_gc();
3975   trace_heap_before_gc(_gc_tracer_stw);
3976 
3977   verify_region_sets_optional();
3978   verify_dirty_young_regions();
3979 
3980   // This call will decide whether this pause is an initial-mark
3981   // pause. If it is, during_initial_mark_pause() will return true
3982   // for the duration of this pause.
3983   g1_policy()->decide_on_conc_mark_initiation();
3984 
3985   // We do not allow initial-mark to be piggy-backed on a mixed GC.
3986   assert(!g1_policy()->during_initial_mark_pause() ||
3987           g1_policy()->gcs_are_young(), "sanity");
3988 
3989   // We also do not allow mixed GCs during marking.
3990   assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3991 
3992   // Record whether this pause is an initial mark. When the current
3993   // thread has completed its logging output and it's safe to signal
3994   // the CM thread, the flag's value in the policy has been reset.
3995   bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3996 
3997   // Inner scope for scope based logging, timers, and stats collection
3998   {
3999     EvacuationInfo evacuation_info;
4000 
4001     if (g1_policy()->during_initial_mark_pause()) {
4002       // We are about to start a marking cycle, so we increment the
4003       // full collection counter.
4004       increment_old_marking_cycles_started();
4005       register_concurrent_cycle_start(_gc_timer_stw->gc_start());
4006     }
4007 
4008     _gc_tracer_stw->report_yc_type(yc_type());
4009 
4010     TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
4011 
4012     int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
4013                                 workers()->active_workers() : 1);
4014     double pause_start_sec = os::elapsedTime();
4015     g1_policy()->phase_times()->note_gc_start(active_workers);
4016     log_gc_header();
4017 
4018     TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
4019     TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
4020 
4021     // If the secondary_free_list is not empty, append it to the
4022     // free_list. No need to wait for the cleanup operation to finish;
4023     // the region allocation code will check the secondary_free_list
4024     // and wait if necessary. If the G1StressConcRegionFreeing flag is
4025     // set, skip this step so that the region allocation code has to
4026     // get entries from the secondary_free_list.
4027     if (!G1StressConcRegionFreeing) {
4028       append_secondary_free_list_if_not_empty_with_lock();
4029     }
4030 
4031     assert(check_young_list_well_formed(), "young list should be well formed");
4032     assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
4033            "sanity check");
4034 
4035     // Don't dynamically change the number of GC threads this early.  A value of
4036     // 0 is used to indicate serial work.  When parallel work is done,
4037     // it will be set.
4038 
4039     { // Call to jvmpi::post_class_unload_events must occur outside of active GC
4040       IsGCActiveMark x;
4041 
4042       gc_prologue(false);
4043       increment_total_collections(false /* full gc */);
4044       increment_gc_time_stamp();
4045 
4046       verify_before_gc();
4047 
4048       check_bitmaps("GC Start");
4049 
4050       COMPILER2_PRESENT(DerivedPointerTable::clear());
4051 
4052       // Please see comment in g1CollectedHeap.hpp and
4053       // G1CollectedHeap::ref_processing_init() to see how
4054       // reference processing currently works in G1.
4055 
4056       // Enable discovery in the STW reference processor
4057       ref_processor_stw()->enable_discovery(true /*verify_disabled*/,
4058                                             true /*verify_no_refs*/);
4059 
4060       {
4061         // We want to temporarily turn off discovery by the
4062         // CM ref processor, if necessary, and turn it back on
4063         // on again later if we do. Using a scoped
4064         // NoRefDiscovery object will do this.
4065         NoRefDiscovery no_cm_discovery(ref_processor_cm());
4066 
4067         // Forget the current alloc region (we might even choose it to be part
4068         // of the collection set!).
4069         release_mutator_alloc_region();
4070 
4071         // We should call this after we retire the mutator alloc
4072         // region(s) so that all the ALLOC / RETIRE events are generated
4073         // before the start GC event.
4074         _hr_printer.start_gc(false /* full */, (size_t) total_collections());
4075 
4076         // This timing is only used by the ergonomics to handle our pause target.
4077         // It is unclear why this should not include the full pause. We will
4078         // investigate this in CR 7178365.
4079         //
4080         // Preserving the old comment here if that helps the investigation:
4081         //
4082         // The elapsed time induced by the start time below deliberately elides
4083         // the possible verification above.
4084         double sample_start_time_sec = os::elapsedTime();
4085 
4086 #if YOUNG_LIST_VERBOSE
4087         gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
4088         _young_list->print();
4089         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4090 #endif // YOUNG_LIST_VERBOSE
4091 
4092         g1_policy()->record_collection_pause_start(sample_start_time_sec);
4093 
4094         double scan_wait_start = os::elapsedTime();
4095         // We have to wait until the CM threads finish scanning the
4096         // root regions as it's the only way to ensure that all the
4097         // objects on them have been correctly scanned before we start
4098         // moving them during the GC.
4099         bool waited = _cm->root_regions()->wait_until_scan_finished();
4100         double wait_time_ms = 0.0;
4101         if (waited) {
4102           double scan_wait_end = os::elapsedTime();
4103           wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
4104         }
4105         g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
4106 
4107 #if YOUNG_LIST_VERBOSE
4108         gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
4109         _young_list->print();
4110 #endif // YOUNG_LIST_VERBOSE
4111 
4112         if (g1_policy()->during_initial_mark_pause()) {
4113           concurrent_mark()->checkpointRootsInitialPre();
4114         }
4115 
4116 #if YOUNG_LIST_VERBOSE
4117         gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
4118         _young_list->print();
4119         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4120 #endif // YOUNG_LIST_VERBOSE
4121 
4122         g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info);
4123 
4124         register_humongous_regions_with_in_cset_fast_test();
4125 
4126         _cm->note_start_of_gc();
4127         // We should not verify the per-thread SATB buffers given that
4128         // we have not filtered them yet (we'll do so during the
4129         // GC). We also call this after finalize_cset() to
4130         // ensure that the CSet has been finalized.
4131         _cm->verify_no_cset_oops(true  /* verify_stacks */,
4132                                  true  /* verify_enqueued_buffers */,
4133                                  false /* verify_thread_buffers */,
4134                                  true  /* verify_fingers */);
4135 
4136         if (_hr_printer.is_active()) {
4137           HeapRegion* hr = g1_policy()->collection_set();
4138           while (hr != NULL) {
4139             G1HRPrinter::RegionType type;
4140             if (!hr->is_young()) {
4141               type = G1HRPrinter::Old;
4142             } else if (hr->is_survivor()) {
4143               type = G1HRPrinter::Survivor;
4144             } else {
4145               type = G1HRPrinter::Eden;
4146             }
4147             _hr_printer.cset(hr);
4148             hr = hr->next_in_collection_set();
4149           }
4150         }
4151 
4152 #ifdef ASSERT
4153         VerifyCSetClosure cl;
4154         collection_set_iterate(&cl);
4155 #endif // ASSERT
4156 
4157         setup_surviving_young_words();
4158 
4159         // Initialize the GC alloc regions.
4160         init_gc_alloc_regions(evacuation_info);
4161 
4162         // Actually do the work...
4163         evacuate_collection_set(evacuation_info);
4164 
4165         // We do this to mainly verify the per-thread SATB buffers
4166         // (which have been filtered by now) since we didn't verify
4167         // them earlier. No point in re-checking the stacks / enqueued
4168         // buffers given that the CSet has not changed since last time
4169         // we checked.
4170         _cm->verify_no_cset_oops(false /* verify_stacks */,
4171                                  false /* verify_enqueued_buffers */,
4172                                  true  /* verify_thread_buffers */,
4173                                  true  /* verify_fingers */);
4174 
4175         free_collection_set(g1_policy()->collection_set(), evacuation_info);
4176 
4177         eagerly_reclaim_humongous_regions();
4178 
4179         g1_policy()->clear_collection_set();
4180 
4181         cleanup_surviving_young_words();
4182 
4183         // Start a new incremental collection set for the next pause.
4184         g1_policy()->start_incremental_cset_building();
4185 
4186         clear_cset_fast_test();
4187 
4188         _young_list->reset_sampled_info();
4189 
4190         // Don't check the whole heap at this point as the
4191         // GC alloc regions from this pause have been tagged
4192         // as survivors and moved on to the survivor list.
4193         // Survivor regions will fail the !is_young() check.
4194         assert(check_young_list_empty(false /* check_heap */),
4195           "young list should be empty");
4196 
4197 #if YOUNG_LIST_VERBOSE
4198         gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
4199         _young_list->print();
4200 #endif // YOUNG_LIST_VERBOSE
4201 
4202         g1_policy()->record_survivor_regions(_young_list->survivor_length(),
4203                                              _young_list->first_survivor_region(),
4204                                              _young_list->last_survivor_region());
4205 
4206         _young_list->reset_auxilary_lists();
4207 
4208         if (evacuation_failed()) {
4209           _summary_bytes_used = recalculate_used();
4210           uint n_queues = MAX2((int)ParallelGCThreads, 1);
4211           for (uint i = 0; i < n_queues; i++) {
4212             if (_evacuation_failed_info_array[i].has_failed()) {
4213               _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
4214             }
4215           }
4216         } else {
4217           // The "used" of the the collection set have already been subtracted
4218           // when they were freed.  Add in the bytes evacuated.
4219           _summary_bytes_used += g1_policy()->bytes_copied_during_gc();
4220         }
4221 
4222         if (g1_policy()->during_initial_mark_pause()) {
4223           // We have to do this before we notify the CM threads that
4224           // they can start working to make sure that all the
4225           // appropriate initialization is done on the CM object.
4226           concurrent_mark()->checkpointRootsInitialPost();
4227           set_marking_started();
4228           // Note that we don't actually trigger the CM thread at
4229           // this point. We do that later when we're sure that
4230           // the current thread has completed its logging output.
4231         }
4232 
4233         allocate_dummy_regions();
4234 
4235 #if YOUNG_LIST_VERBOSE
4236         gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
4237         _young_list->print();
4238         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4239 #endif // YOUNG_LIST_VERBOSE
4240 
4241         init_mutator_alloc_region();
4242 
4243         {
4244           size_t expand_bytes = g1_policy()->expansion_amount();
4245           if (expand_bytes > 0) {
4246             size_t bytes_before = capacity();
4247             // No need for an ergo verbose message here,
4248             // expansion_amount() does this when it returns a value > 0.
4249             if (!expand(expand_bytes)) {
4250               // We failed to expand the heap so let's verify that
4251               // committed/uncommitted amount match the backing store
4252               assert(capacity() == _g1_storage.committed_size(), "committed size mismatch");
4253               assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch");
4254             }
4255           }
4256         }
4257 
4258         // We redo the verification but now wrt to the new CSet which
4259         // has just got initialized after the previous CSet was freed.
4260         _cm->verify_no_cset_oops(true  /* verify_stacks */,
4261                                  true  /* verify_enqueued_buffers */,
4262                                  true  /* verify_thread_buffers */,
4263                                  true  /* verify_fingers */);
4264         _cm->note_end_of_gc();
4265 
4266         // This timing is only used by the ergonomics to handle our pause target.
4267         // It is unclear why this should not include the full pause. We will
4268         // investigate this in CR 7178365.
4269         double sample_end_time_sec = os::elapsedTime();
4270         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
4271         g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info);
4272 
4273         MemoryService::track_memory_usage();
4274 
4275         // In prepare_for_verify() below we'll need to scan the deferred
4276         // update buffers to bring the RSets up-to-date if
4277         // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
4278         // the update buffers we'll probably need to scan cards on the
4279         // regions we just allocated to (i.e., the GC alloc
4280         // regions). However, during the last GC we called
4281         // set_saved_mark() on all the GC alloc regions, so card
4282         // scanning might skip the [saved_mark_word()...top()] area of
4283         // those regions (i.e., the area we allocated objects into
4284         // during the last GC). But it shouldn't. Given that
4285         // saved_mark_word() is conditional on whether the GC time stamp
4286         // on the region is current or not, by incrementing the GC time
4287         // stamp here we invalidate all the GC time stamps on all the
4288         // regions and saved_mark_word() will simply return top() for
4289         // all the regions. This is a nicer way of ensuring this rather
4290         // than iterating over the regions and fixing them. In fact, the
4291         // GC time stamp increment here also ensures that
4292         // saved_mark_word() will return top() between pauses, i.e.,
4293         // during concurrent refinement. So we don't need the
4294         // is_gc_active() check to decided which top to use when
4295         // scanning cards (see CR 7039627).
4296         increment_gc_time_stamp();
4297 
4298         verify_after_gc();
4299         check_bitmaps("GC End");
4300 
4301         assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
4302         ref_processor_stw()->verify_no_references_recorded();
4303 
4304         // CM reference discovery will be re-enabled if necessary.
4305       }
4306 
4307       // We should do this after we potentially expand the heap so
4308       // that all the COMMIT events are generated before the end GC
4309       // event, and after we retire the GC alloc regions so that all
4310       // RETIRE events are generated before the end GC event.
4311       _hr_printer.end_gc(false /* full */, (size_t) total_collections());
4312 
4313       if (mark_in_progress()) {
4314         concurrent_mark()->update_g1_committed();
4315       }
4316 
4317 #ifdef TRACESPINNING
4318       ParallelTaskTerminator::print_termination_counts();
4319 #endif
4320 
4321       gc_epilogue(false);
4322     }
4323 
4324     // Print the remainder of the GC log output.
4325     log_gc_footer(os::elapsedTime() - pause_start_sec);
4326 
4327     // It is not yet to safe to tell the concurrent mark to
4328     // start as we have some optional output below. We don't want the
4329     // output from the concurrent mark thread interfering with this
4330     // logging output either.
4331 
4332     _hrs.verify_optional();
4333     verify_region_sets_optional();
4334 
4335     TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
4336     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
4337 
4338     print_heap_after_gc();
4339     trace_heap_after_gc(_gc_tracer_stw);
4340 
4341     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
4342     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
4343     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
4344     // before any GC notifications are raised.
4345     g1mm()->update_sizes();
4346 
4347     _gc_tracer_stw->report_evacuation_info(&evacuation_info);
4348     _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
4349     _gc_timer_stw->register_gc_end();
4350     _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
4351   }
4352   // It should now be safe to tell the concurrent mark thread to start
4353   // without its logging output interfering with the logging output
4354   // that came from the pause.
4355 
4356   if (should_start_conc_mark) {
4357     // CAUTION: after the doConcurrentMark() call below,
4358     // the concurrent marking thread(s) could be running
4359     // concurrently with us. Make sure that anything after
4360     // this point does not assume that we are the only GC thread
4361     // running. Note: of course, the actual marking work will
4362     // not start until the safepoint itself is released in
4363     // SuspendibleThreadSet::desynchronize().
4364     doConcurrentMark();
4365   }
4366 
4367   return true;
4368 }
4369 
4370 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
4371 {
4372   size_t gclab_word_size;
4373   switch (purpose) {
4374     case GCAllocForSurvived:
4375       gclab_word_size = _survivor_plab_stats.desired_plab_sz();
4376       break;
4377     case GCAllocForTenured:
4378       gclab_word_size = _old_plab_stats.desired_plab_sz();
4379       break;
4380     default:
4381       assert(false, "unknown GCAllocPurpose");
4382       gclab_word_size = _old_plab_stats.desired_plab_sz();
4383       break;
4384   }
4385 
4386   // Prevent humongous PLAB sizes for two reasons:
4387   // * PLABs are allocated using a similar paths as oops, but should
4388   //   never be in a humongous region
4389   // * Allowing humongous PLABs needlessly churns the region free lists
4390   return MIN2(_humongous_object_threshold_in_words, gclab_word_size);
4391 }
4392 
4393 void G1CollectedHeap::init_mutator_alloc_region() {
4394   assert(_mutator_alloc_region.get() == NULL, "pre-condition");
4395   _mutator_alloc_region.init();
4396 }
4397 
4398 void G1CollectedHeap::release_mutator_alloc_region() {
4399   _mutator_alloc_region.release();
4400   assert(_mutator_alloc_region.get() == NULL, "post-condition");
4401 }
4402 
4403 void G1CollectedHeap::use_retained_old_gc_alloc_region(EvacuationInfo& evacuation_info) {
4404   HeapRegion* retained_region = _retained_old_gc_alloc_region;
4405   _retained_old_gc_alloc_region = NULL;
4406 
4407   // We will discard the current GC alloc region if:
4408   // a) it's in the collection set (it can happen!),
4409   // b) it's already full (no point in using it),
4410   // c) it's empty (this means that it was emptied during
4411   // a cleanup and it should be on the free list now), or
4412   // d) it's humongous (this means that it was emptied
4413   // during a cleanup and was added to the free list, but
4414   // has been subsequently used to allocate a humongous
4415   // object that may be less than the region size).
4416   if (retained_region != NULL &&
4417       !retained_region->in_collection_set() &&
4418       !(retained_region->top() == retained_region->end()) &&
4419       !retained_region->is_empty() &&
4420       !retained_region->isHumongous()) {
4421     retained_region->record_top_and_timestamp();
4422     // The retained region was added to the old region set when it was
4423     // retired. We have to remove it now, since we don't allow regions
4424     // we allocate to in the region sets. We'll re-add it later, when
4425     // it's retired again.
4426     _old_set.remove(retained_region);
4427     bool during_im = g1_policy()->during_initial_mark_pause();
4428     retained_region->note_start_of_copying(during_im);
4429     _old_gc_alloc_region.set(retained_region);
4430     _hr_printer.reuse(retained_region);
4431     evacuation_info.set_alloc_regions_used_before(retained_region->used());
4432   }
4433 }
4434 
4435 void G1CollectedHeap::init_gc_alloc_regions(EvacuationInfo& evacuation_info) {
4436   assert_at_safepoint(true /* should_be_vm_thread */);
4437 
4438   _survivor_gc_alloc_region.init();
4439   _old_gc_alloc_region.init();
4440 
4441   use_retained_old_gc_alloc_region(evacuation_info);
4442 }
4443 
4444 void G1CollectedHeap::release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info) {
4445   evacuation_info.set_allocation_regions(_survivor_gc_alloc_region.count() +
4446                                          _old_gc_alloc_region.count());
4447   _survivor_gc_alloc_region.release();
4448   // If we have an old GC alloc region to release, we'll save it in
4449   // _retained_old_gc_alloc_region. If we don't
4450   // _retained_old_gc_alloc_region will become NULL. This is what we
4451   // want either way so no reason to check explicitly for either
4452   // condition.
4453   _retained_old_gc_alloc_region = _old_gc_alloc_region.release();
4454 
4455   if (ResizePLAB) {
4456     _survivor_plab_stats.adjust_desired_plab_sz(no_of_gc_workers);
4457     _old_plab_stats.adjust_desired_plab_sz(no_of_gc_workers);
4458   }
4459 }
4460 
4461 void G1CollectedHeap::abandon_gc_alloc_regions() {
4462   assert(_survivor_gc_alloc_region.get() == NULL, "pre-condition");
4463   assert(_old_gc_alloc_region.get() == NULL, "pre-condition");
4464   _retained_old_gc_alloc_region = NULL;
4465 }
4466 
4467 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4468   _drain_in_progress = false;
4469   set_evac_failure_closure(cl);
4470   _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4471 }
4472 
4473 void G1CollectedHeap::finalize_for_evac_failure() {
4474   assert(_evac_failure_scan_stack != NULL &&
4475          _evac_failure_scan_stack->length() == 0,
4476          "Postcondition");
4477   assert(!_drain_in_progress, "Postcondition");
4478   delete _evac_failure_scan_stack;
4479   _evac_failure_scan_stack = NULL;
4480 }
4481 
4482 void G1CollectedHeap::remove_self_forwarding_pointers() {
4483   assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4484 
4485   double remove_self_forwards_start = os::elapsedTime();
4486 
4487   G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4488 
4489   if (G1CollectedHeap::use_parallel_gc_threads()) {
4490     set_par_threads();
4491     workers()->run_task(&rsfp_task);
4492     set_par_threads(0);
4493   } else {
4494     rsfp_task.work(0);
4495   }
4496 
4497   assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity");
4498 
4499   // Reset the claim values in the regions in the collection set.
4500   reset_cset_heap_region_claim_values();
4501 
4502   assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4503 
4504   // Now restore saved marks, if any.
4505   assert(_objs_with_preserved_marks.size() ==
4506             _preserved_marks_of_objs.size(), "Both or none.");
4507   while (!_objs_with_preserved_marks.is_empty()) {
4508     oop obj = _objs_with_preserved_marks.pop();
4509     markOop m = _preserved_marks_of_objs.pop();
4510     obj->set_mark(m);
4511   }
4512   _objs_with_preserved_marks.clear(true);
4513   _preserved_marks_of_objs.clear(true);
4514 
4515   g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
4516 }
4517 
4518 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4519   _evac_failure_scan_stack->push(obj);
4520 }
4521 
4522 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4523   assert(_evac_failure_scan_stack != NULL, "precondition");
4524 
4525   while (_evac_failure_scan_stack->length() > 0) {
4526      oop obj = _evac_failure_scan_stack->pop();
4527      _evac_failure_closure->set_region(heap_region_containing(obj));
4528      obj->oop_iterate_backwards(_evac_failure_closure);
4529   }
4530 }
4531 
4532 oop
4533 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state,
4534                                                oop old) {
4535   assert(obj_in_cs(old),
4536          err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4537                  (HeapWord*) old));
4538   markOop m = old->mark();
4539   oop forward_ptr = old->forward_to_atomic(old);
4540   if (forward_ptr == NULL) {
4541     // Forward-to-self succeeded.
4542     assert(_par_scan_state != NULL, "par scan state");
4543     OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4544     uint queue_num = _par_scan_state->queue_num();
4545 
4546     _evacuation_failed = true;
4547     _evacuation_failed_info_array[queue_num].register_copy_failure(old->size());
4548     if (_evac_failure_closure != cl) {
4549       MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4550       assert(!_drain_in_progress,
4551              "Should only be true while someone holds the lock.");
4552       // Set the global evac-failure closure to the current thread's.
4553       assert(_evac_failure_closure == NULL, "Or locking has failed.");
4554       set_evac_failure_closure(cl);
4555       // Now do the common part.
4556       handle_evacuation_failure_common(old, m);
4557       // Reset to NULL.
4558       set_evac_failure_closure(NULL);
4559     } else {
4560       // The lock is already held, and this is recursive.
4561       assert(_drain_in_progress, "This should only be the recursive case.");
4562       handle_evacuation_failure_common(old, m);
4563     }
4564     return old;
4565   } else {
4566     // Forward-to-self failed. Either someone else managed to allocate
4567     // space for this object (old != forward_ptr) or they beat us in
4568     // self-forwarding it (old == forward_ptr).
4569     assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4570            err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4571                    "should not be in the CSet",
4572                    (HeapWord*) old, (HeapWord*) forward_ptr));
4573     return forward_ptr;
4574   }
4575 }
4576 
4577 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4578   preserve_mark_if_necessary(old, m);
4579 
4580   HeapRegion* r = heap_region_containing(old);
4581   if (!r->evacuation_failed()) {
4582     r->set_evacuation_failed(true);
4583     _hr_printer.evac_failure(r);
4584   }
4585 
4586   push_on_evac_failure_scan_stack(old);
4587 
4588   if (!_drain_in_progress) {
4589     // prevent recursion in copy_to_survivor_space()
4590     _drain_in_progress = true;
4591     drain_evac_failure_scan_stack();
4592     _drain_in_progress = false;
4593   }
4594 }
4595 
4596 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4597   assert(evacuation_failed(), "Oversaving!");
4598   // We want to call the "for_promotion_failure" version only in the
4599   // case of a promotion failure.
4600   if (m->must_be_preserved_for_promotion_failure(obj)) {
4601     _objs_with_preserved_marks.push(obj);
4602     _preserved_marks_of_objs.push(m);
4603   }
4604 }
4605 
4606 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
4607                                                   size_t word_size) {
4608   if (purpose == GCAllocForSurvived) {
4609     HeapWord* result = survivor_attempt_allocation(word_size);
4610     if (result != NULL) {
4611       return result;
4612     } else {
4613       // Let's try to allocate in the old gen in case we can fit the
4614       // object there.
4615       return old_attempt_allocation(word_size);
4616     }
4617   } else {
4618     assert(purpose ==  GCAllocForTenured, "sanity");
4619     HeapWord* result = old_attempt_allocation(word_size);
4620     if (result != NULL) {
4621       return result;
4622     } else {
4623       // Let's try to allocate in the survivors in case we can fit the
4624       // object there.
4625       return survivor_attempt_allocation(word_size);
4626     }
4627   }
4628 
4629   ShouldNotReachHere();
4630   // Trying to keep some compilers happy.
4631   return NULL;
4632 }
4633 
4634 G1ParGCAllocBuffer::G1ParGCAllocBuffer(size_t gclab_word_size) :
4635   ParGCAllocBuffer(gclab_word_size), _retired(true) { }
4636 
4637 void G1ParCopyHelper::mark_object(oop obj) {
4638   assert(!_g1->heap_region_containing(obj)->in_collection_set(), "should not mark objects in the CSet");
4639 
4640   // We know that the object is not moving so it's safe to read its size.
4641   _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4642 }
4643 
4644 void G1ParCopyHelper::mark_forwarded_object(oop from_obj, oop to_obj) {
4645   assert(from_obj->is_forwarded(), "from obj should be forwarded");
4646   assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4647   assert(from_obj != to_obj, "should not be self-forwarded");
4648 
4649   assert(_g1->heap_region_containing(from_obj)->in_collection_set(), "from obj should be in the CSet");
4650   assert(!_g1->heap_region_containing(to_obj)->in_collection_set(), "should not mark objects in the CSet");
4651 
4652   // The object might be in the process of being copied by another
4653   // worker so we cannot trust that its to-space image is
4654   // well-formed. So we have to read its size from its from-space
4655   // image which we know should not be changing.
4656   _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4657 }
4658 
4659 template <class T>
4660 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) {
4661   if (_g1->heap_region_containing_raw(new_obj)->is_young()) {
4662     _scanned_klass->record_modified_oops();
4663   }
4664 }
4665 
4666 template <G1Barrier barrier, G1Mark do_mark_object>
4667 template <class T>
4668 void G1ParCopyClosure<barrier, do_mark_object>::do_oop_work(T* p) {
4669   T heap_oop = oopDesc::load_heap_oop(p);
4670 
4671   if (oopDesc::is_null(heap_oop)) {
4672     return;
4673   }
4674 
4675   oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
4676 
4677   assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4678 
4679   G1CollectedHeap::in_cset_state_t state = _g1->in_cset_state(obj);
4680 
4681   if (state == G1CollectedHeap::InCSet) {
4682     oop forwardee;
4683     if (obj->is_forwarded()) {
4684       forwardee = obj->forwardee();
4685     } else {
4686       forwardee = _par_scan_state->copy_to_survivor_space(obj);
4687     }
4688     assert(forwardee != NULL, "forwardee should not be NULL");
4689     oopDesc::encode_store_heap_oop(p, forwardee);
4690     if (do_mark_object != G1MarkNone && forwardee != obj) {
4691       // If the object is self-forwarded we don't need to explicitly
4692       // mark it, the evacuation failure protocol will do so.
4693       mark_forwarded_object(obj, forwardee);
4694     }
4695 
4696     if (barrier == G1BarrierKlass) {
4697       do_klass_barrier(p, forwardee);
4698     }
4699   } else {
4700     if (state == G1CollectedHeap::IsHumongous) {
4701       _g1->set_humongous_is_live(obj);
4702     }
4703     // The object is not in collection set. If we're a root scanning
4704     // closure during an initial mark pause then attempt to mark the object.
4705     if (do_mark_object == G1MarkFromRoot) {
4706       mark_object(obj);
4707     }
4708   }
4709 
4710   if (barrier == G1BarrierEvac) {
4711     _par_scan_state->update_rs(_from, p, _worker_id);
4712   }
4713 }
4714 
4715 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(oop* p);
4716 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(narrowOop* p);
4717 
4718 class G1ParEvacuateFollowersClosure : public VoidClosure {
4719 protected:
4720   G1CollectedHeap*              _g1h;
4721   G1ParScanThreadState*         _par_scan_state;
4722   RefToScanQueueSet*            _queues;
4723   ParallelTaskTerminator*       _terminator;
4724 
4725   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
4726   RefToScanQueueSet*      queues()         { return _queues; }
4727   ParallelTaskTerminator* terminator()     { return _terminator; }
4728 
4729 public:
4730   G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4731                                 G1ParScanThreadState* par_scan_state,
4732                                 RefToScanQueueSet* queues,
4733                                 ParallelTaskTerminator* terminator)
4734     : _g1h(g1h), _par_scan_state(par_scan_state),
4735       _queues(queues), _terminator(terminator) {}
4736 
4737   void do_void();
4738 
4739 private:
4740   inline bool offer_termination();
4741 };
4742 
4743 bool G1ParEvacuateFollowersClosure::offer_termination() {
4744   G1ParScanThreadState* const pss = par_scan_state();
4745   pss->start_term_time();
4746   const bool res = terminator()->offer_termination();
4747   pss->end_term_time();
4748   return res;
4749 }
4750 
4751 void G1ParEvacuateFollowersClosure::do_void() {
4752   G1ParScanThreadState* const pss = par_scan_state();
4753   pss->trim_queue();
4754   do {
4755     pss->steal_and_trim_queue(queues());
4756   } while (!offer_termination());
4757 }
4758 
4759 class G1KlassScanClosure : public KlassClosure {
4760  G1ParCopyHelper* _closure;
4761  bool             _process_only_dirty;
4762  int              _count;
4763  public:
4764   G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty)
4765       : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {}
4766   void do_klass(Klass* klass) {
4767     // If the klass has not been dirtied we know that there's
4768     // no references into  the young gen and we can skip it.
4769    if (!_process_only_dirty || klass->has_modified_oops()) {
4770       // Clean the klass since we're going to scavenge all the metadata.
4771       klass->clear_modified_oops();
4772 
4773       // Tell the closure that this klass is the Klass to scavenge
4774       // and is the one to dirty if oops are left pointing into the young gen.
4775       _closure->set_scanned_klass(klass);
4776 
4777       klass->oops_do(_closure);
4778 
4779       _closure->set_scanned_klass(NULL);
4780     }
4781     _count++;
4782   }
4783 };
4784 
4785 class G1ParTask : public AbstractGangTask {
4786 protected:
4787   G1CollectedHeap*       _g1h;
4788   RefToScanQueueSet      *_queues;
4789   ParallelTaskTerminator _terminator;
4790   uint _n_workers;
4791 
4792   Mutex _stats_lock;
4793   Mutex* stats_lock() { return &_stats_lock; }
4794 
4795   size_t getNCards() {
4796     return (_g1h->capacity() + G1BlockOffsetSharedArray::N_bytes - 1)
4797       / G1BlockOffsetSharedArray::N_bytes;
4798   }
4799 
4800 public:
4801   G1ParTask(G1CollectedHeap* g1h, RefToScanQueueSet *task_queues)
4802     : AbstractGangTask("G1 collection"),
4803       _g1h(g1h),
4804       _queues(task_queues),
4805       _terminator(0, _queues),
4806       _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4807   {}
4808 
4809   RefToScanQueueSet* queues() { return _queues; }
4810 
4811   RefToScanQueue *work_queue(int i) {
4812     return queues()->queue(i);
4813   }
4814 
4815   ParallelTaskTerminator* terminator() { return &_terminator; }
4816 
4817   virtual void set_for_termination(int active_workers) {
4818     // This task calls set_n_termination() in par_non_clean_card_iterate_work()
4819     // in the young space (_par_seq_tasks) in the G1 heap
4820     // for SequentialSubTasksDone.
4821     // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap
4822     // both of which need setting by set_n_termination().
4823     _g1h->SharedHeap::set_n_termination(active_workers);
4824     _g1h->set_n_termination(active_workers);
4825     terminator()->reset_for_reuse(active_workers);
4826     _n_workers = active_workers;
4827   }
4828 
4829   // Helps out with CLD processing.
4830   //
4831   // During InitialMark we need to:
4832   // 1) Scavenge all CLDs for the young GC.
4833   // 2) Mark all objects directly reachable from strong CLDs.
4834   template <G1Mark do_mark_object>
4835   class G1CLDClosure : public CLDClosure {
4836     G1ParCopyClosure<G1BarrierNone,  do_mark_object>* _oop_closure;
4837     G1ParCopyClosure<G1BarrierKlass, do_mark_object>  _oop_in_klass_closure;
4838     G1KlassScanClosure                                _klass_in_cld_closure;
4839     bool                                              _claim;
4840 
4841    public:
4842     G1CLDClosure(G1ParCopyClosure<G1BarrierNone, do_mark_object>* oop_closure,
4843                  bool only_young, bool claim)
4844         : _oop_closure(oop_closure),
4845           _oop_in_klass_closure(oop_closure->g1(),
4846                                 oop_closure->pss(),
4847                                 oop_closure->rp()),
4848           _klass_in_cld_closure(&_oop_in_klass_closure, only_young),
4849           _claim(claim) {
4850 
4851     }
4852 
4853     void do_cld(ClassLoaderData* cld) {
4854       cld->oops_do(_oop_closure, &_klass_in_cld_closure, _claim);
4855     }
4856   };
4857 
4858   class G1CodeBlobClosure: public CodeBlobClosure {
4859     OopClosure* _f;
4860 
4861    public:
4862     G1CodeBlobClosure(OopClosure* f) : _f(f) {}
4863     void do_code_blob(CodeBlob* blob) {
4864       nmethod* that = blob->as_nmethod_or_null();
4865       if (that != NULL) {
4866         if (!that->test_set_oops_do_mark()) {
4867           that->oops_do(_f);
4868           that->fix_oop_relocations();
4869         }
4870       }
4871     }
4872   };
4873 
4874   void work(uint worker_id) {
4875     if (worker_id >= _n_workers) return;  // no work needed this round
4876 
4877     double start_time_ms = os::elapsedTime() * 1000.0;
4878     _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms);
4879 
4880     {
4881       ResourceMark rm;
4882       HandleMark   hm;
4883 
4884       ReferenceProcessor*             rp = _g1h->ref_processor_stw();
4885 
4886       G1ParScanThreadState            pss(_g1h, worker_id, rp);
4887       G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
4888 
4889       pss.set_evac_failure_closure(&evac_failure_cl);
4890 
4891       bool only_young = _g1h->g1_policy()->gcs_are_young();
4892 
4893       // Non-IM young GC.
4894       G1ParCopyClosure<G1BarrierNone, G1MarkNone>             scan_only_root_cl(_g1h, &pss, rp);
4895       G1CLDClosure<G1MarkNone>                                scan_only_cld_cl(&scan_only_root_cl,
4896                                                                                only_young, // Only process dirty klasses.
4897                                                                                false);     // No need to claim CLDs.
4898       // IM young GC.
4899       //    Strong roots closures.
4900       G1ParCopyClosure<G1BarrierNone, G1MarkFromRoot>         scan_mark_root_cl(_g1h, &pss, rp);
4901       G1CLDClosure<G1MarkFromRoot>                            scan_mark_cld_cl(&scan_mark_root_cl,
4902                                                                                false, // Process all klasses.
4903                                                                                true); // Need to claim CLDs.
4904       //    Weak roots closures.
4905       G1ParCopyClosure<G1BarrierNone, G1MarkPromotedFromRoot> scan_mark_weak_root_cl(_g1h, &pss, rp);
4906       G1CLDClosure<G1MarkPromotedFromRoot>                    scan_mark_weak_cld_cl(&scan_mark_weak_root_cl,
4907                                                                                     false, // Process all klasses.
4908                                                                                     true); // Need to claim CLDs.
4909 
4910       G1CodeBlobClosure scan_only_code_cl(&scan_only_root_cl);
4911       G1CodeBlobClosure scan_mark_code_cl(&scan_mark_root_cl);
4912       // IM Weak code roots are handled later.
4913 
4914       OopClosure* strong_root_cl;
4915       OopClosure* weak_root_cl;
4916       CLDClosure* strong_cld_cl;
4917       CLDClosure* weak_cld_cl;
4918       CodeBlobClosure* strong_code_cl;
4919 
4920       if (_g1h->g1_policy()->during_initial_mark_pause()) {
4921         // We also need to mark copied objects.
4922         strong_root_cl = &scan_mark_root_cl;
4923         weak_root_cl   = &scan_mark_weak_root_cl;
4924         strong_cld_cl  = &scan_mark_cld_cl;
4925         weak_cld_cl    = &scan_mark_weak_cld_cl;
4926         strong_code_cl = &scan_mark_code_cl;
4927       } else {
4928         strong_root_cl = &scan_only_root_cl;
4929         weak_root_cl   = &scan_only_root_cl;
4930         strong_cld_cl  = &scan_only_cld_cl;
4931         weak_cld_cl    = &scan_only_cld_cl;
4932         strong_code_cl = &scan_only_code_cl;
4933       }
4934 
4935 
4936       G1ParPushHeapRSClosure  push_heap_rs_cl(_g1h, &pss);
4937 
4938       pss.start_strong_roots();
4939       _g1h->g1_process_roots(strong_root_cl,
4940                              weak_root_cl,
4941                              &push_heap_rs_cl,
4942                              strong_cld_cl,
4943                              weak_cld_cl,
4944                              strong_code_cl,
4945                              worker_id);
4946 
4947       pss.end_strong_roots();
4948 
4949       {
4950         double start = os::elapsedTime();
4951         G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4952         evac.do_void();
4953         double elapsed_ms = (os::elapsedTime()-start)*1000.0;
4954         double term_ms = pss.term_time()*1000.0;
4955         _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms);
4956         _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts());
4957       }
4958       _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4959       _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4960 
4961       if (ParallelGCVerbose) {
4962         MutexLocker x(stats_lock());
4963         pss.print_termination_stats(worker_id);
4964       }
4965 
4966       assert(pss.queue_is_empty(), "should be empty");
4967 
4968       // Close the inner scope so that the ResourceMark and HandleMark
4969       // destructors are executed here and are included as part of the
4970       // "GC Worker Time".
4971     }
4972 
4973     double end_time_ms = os::elapsedTime() * 1000.0;
4974     _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms);
4975   }
4976 };
4977 
4978 // *** Common G1 Evacuation Stuff
4979 
4980 // This method is run in a GC worker.
4981 
4982 void
4983 G1CollectedHeap::
4984 g1_process_roots(OopClosure* scan_non_heap_roots,
4985                  OopClosure* scan_non_heap_weak_roots,
4986                  OopsInHeapRegionClosure* scan_rs,
4987                  CLDClosure* scan_strong_clds,
4988                  CLDClosure* scan_weak_clds,
4989                  CodeBlobClosure* scan_strong_code,
4990                  uint worker_i) {
4991 
4992   // First scan the shared roots.
4993   double ext_roots_start = os::elapsedTime();
4994   double closure_app_time_sec = 0.0;
4995 
4996   bool during_im = _g1h->g1_policy()->during_initial_mark_pause();
4997 
4998   BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
4999   BufferingOopClosure buf_scan_non_heap_weak_roots(scan_non_heap_weak_roots);
5000 
5001   process_roots(false, // no scoping; this is parallel code
5002                 SharedHeap::SO_None,
5003                 &buf_scan_non_heap_roots,
5004                 &buf_scan_non_heap_weak_roots,
5005                 scan_strong_clds,
5006                 // Initial Mark handles the weak CLDs separately.
5007                 (during_im ? NULL : scan_weak_clds),
5008                 scan_strong_code);
5009 
5010   // Now the CM ref_processor roots.
5011   if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
5012     // We need to treat the discovered reference lists of the
5013     // concurrent mark ref processor as roots and keep entries
5014     // (which are added by the marking threads) on them live
5015     // until they can be processed at the end of marking.
5016     ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
5017   }
5018 
5019   if (during_im) {
5020     // Barrier to make sure all workers passed
5021     // the strong CLD and strong nmethods phases.
5022     active_strong_roots_scope()->wait_until_all_workers_done_with_threads(n_par_threads());
5023 
5024     // Now take the complement of the strong CLDs.
5025     ClassLoaderDataGraph::roots_cld_do(NULL, scan_weak_clds);
5026   }
5027 
5028   // Finish up any enqueued closure apps (attributed as object copy time).
5029   buf_scan_non_heap_roots.done();
5030   buf_scan_non_heap_weak_roots.done();
5031 
5032   double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds()
5033       + buf_scan_non_heap_weak_roots.closure_app_seconds();
5034 
5035   g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
5036 
5037   double ext_root_time_ms =
5038     ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0;
5039 
5040   g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
5041 
5042   // During conc marking we have to filter the per-thread SATB buffers
5043   // to make sure we remove any oops into the CSet (which will show up
5044   // as implicitly live).
5045   double satb_filtering_ms = 0.0;
5046   if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) {
5047     if (mark_in_progress()) {
5048       double satb_filter_start = os::elapsedTime();
5049 
5050       JavaThread::satb_mark_queue_set().filter_thread_buffers();
5051 
5052       satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0;
5053     }
5054   }
5055   g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms);
5056 
5057   // Now scan the complement of the collection set.
5058   MarkingCodeBlobClosure scavenge_cs_nmethods(scan_non_heap_weak_roots, CodeBlobToOopClosure::FixRelocations);
5059 
5060   g1_rem_set()->oops_into_collection_set_do(scan_rs, &scavenge_cs_nmethods, worker_i);
5061 
5062   _process_strong_tasks->all_tasks_completed();
5063 }
5064 
5065 class G1StringSymbolTableUnlinkTask : public AbstractGangTask {
5066 private:
5067   BoolObjectClosure* _is_alive;
5068   int _initial_string_table_size;
5069   int _initial_symbol_table_size;
5070 
5071   bool  _process_strings;
5072   int _strings_processed;
5073   int _strings_removed;
5074 
5075   bool  _process_symbols;
5076   int _symbols_processed;
5077   int _symbols_removed;
5078 
5079   bool _do_in_parallel;
5080 public:
5081   G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) :
5082     AbstractGangTask("String/Symbol Unlinking"),
5083     _is_alive(is_alive),
5084     _do_in_parallel(G1CollectedHeap::use_parallel_gc_threads()),
5085     _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
5086     _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) {
5087 
5088     _initial_string_table_size = StringTable::the_table()->table_size();
5089     _initial_symbol_table_size = SymbolTable::the_table()->table_size();
5090     if (process_strings) {
5091       StringTable::clear_parallel_claimed_index();
5092     }
5093     if (process_symbols) {
5094       SymbolTable::clear_parallel_claimed_index();
5095     }
5096   }
5097 
5098   ~G1StringSymbolTableUnlinkTask() {
5099     guarantee(!_process_strings || !_do_in_parallel || StringTable::parallel_claimed_index() >= _initial_string_table_size,
5100               err_msg("claim value %d after unlink less than initial string table size %d",
5101                       StringTable::parallel_claimed_index(), _initial_string_table_size));
5102     guarantee(!_process_symbols || !_do_in_parallel || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
5103               err_msg("claim value %d after unlink less than initial symbol table size %d",
5104                       SymbolTable::parallel_claimed_index(), _initial_symbol_table_size));
5105 
5106     if (G1TraceStringSymbolTableScrubbing) {
5107       gclog_or_tty->print_cr("Cleaned string and symbol table, "
5108                              "strings: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed, "
5109                              "symbols: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed",
5110                              strings_processed(), strings_removed(),
5111                              symbols_processed(), symbols_removed());
5112     }
5113   }
5114 
5115   void work(uint worker_id) {
5116     if (_do_in_parallel) {
5117       int strings_processed = 0;
5118       int strings_removed = 0;
5119       int symbols_processed = 0;
5120       int symbols_removed = 0;
5121       if (_process_strings) {
5122         StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
5123         Atomic::add(strings_processed, &_strings_processed);
5124         Atomic::add(strings_removed, &_strings_removed);
5125       }
5126       if (_process_symbols) {
5127         SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
5128         Atomic::add(symbols_processed, &_symbols_processed);
5129         Atomic::add(symbols_removed, &_symbols_removed);
5130       }
5131     } else {
5132       if (_process_strings) {
5133         StringTable::unlink(_is_alive, &_strings_processed, &_strings_removed);
5134       }
5135       if (_process_symbols) {
5136         SymbolTable::unlink(&_symbols_processed, &_symbols_removed);
5137       }
5138     }
5139   }
5140 
5141   size_t strings_processed() const { return (size_t)_strings_processed; }
5142   size_t strings_removed()   const { return (size_t)_strings_removed; }
5143 
5144   size_t symbols_processed() const { return (size_t)_symbols_processed; }
5145   size_t symbols_removed()   const { return (size_t)_symbols_removed; }
5146 };
5147 
5148 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
5149 private:
5150   static Monitor* _lock;
5151 
5152   BoolObjectClosure* const _is_alive;
5153   const bool               _unloading_occurred;
5154   const uint               _num_workers;
5155 
5156   // Variables used to claim nmethods.
5157   nmethod* _first_nmethod;
5158   volatile nmethod* _claimed_nmethod;
5159 
5160   // The list of nmethods that need to be processed by the second pass.
5161   volatile nmethod* _postponed_list;
5162   volatile uint     _num_entered_barrier;
5163 
5164  public:
5165   G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
5166       _is_alive(is_alive),
5167       _unloading_occurred(unloading_occurred),
5168       _num_workers(num_workers),
5169       _first_nmethod(NULL),
5170       _claimed_nmethod(NULL),
5171       _postponed_list(NULL),
5172       _num_entered_barrier(0)
5173   {
5174     nmethod::increase_unloading_clock();
5175     _first_nmethod = CodeCache::alive_nmethod(CodeCache::first());
5176     _claimed_nmethod = (volatile nmethod*)_first_nmethod;
5177   }
5178 
5179   ~G1CodeCacheUnloadingTask() {
5180     CodeCache::verify_clean_inline_caches();
5181 
5182     CodeCache::set_needs_cache_clean(false);
5183     guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
5184 
5185     CodeCache::verify_icholder_relocations();
5186   }
5187 
5188  private:
5189   void add_to_postponed_list(nmethod* nm) {
5190       nmethod* old;
5191       do {
5192         old = (nmethod*)_postponed_list;
5193         nm->set_unloading_next(old);
5194       } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old);
5195   }
5196 
5197   void clean_nmethod(nmethod* nm) {
5198     bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
5199 
5200     if (postponed) {
5201       // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
5202       add_to_postponed_list(nm);
5203     }
5204 
5205     // Mark that this thread has been cleaned/unloaded.
5206     // After this call, it will be safe to ask if this nmethod was unloaded or not.
5207     nm->set_unloading_clock(nmethod::global_unloading_clock());
5208   }
5209 
5210   void clean_nmethod_postponed(nmethod* nm) {
5211     nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
5212   }
5213 
5214   static const int MaxClaimNmethods = 16;
5215 
5216   void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) {
5217     nmethod* first;
5218     nmethod* last;
5219 
5220     do {
5221       *num_claimed_nmethods = 0;
5222 
5223       first = last = (nmethod*)_claimed_nmethod;
5224 
5225       if (first != NULL) {
5226         for (int i = 0; i < MaxClaimNmethods; i++) {
5227           last = CodeCache::alive_nmethod(CodeCache::next(last));
5228 
5229           if (last == NULL) {
5230             break;
5231           }
5232 
5233           claimed_nmethods[i] = last;
5234           (*num_claimed_nmethods)++;
5235         }
5236       }
5237 
5238     } while ((nmethod*)Atomic::cmpxchg_ptr(last, &_claimed_nmethod, first) != first);
5239   }
5240 
5241   nmethod* claim_postponed_nmethod() {
5242     nmethod* claim;
5243     nmethod* next;
5244 
5245     do {
5246       claim = (nmethod*)_postponed_list;
5247       if (claim == NULL) {
5248         return NULL;
5249       }
5250 
5251       next = claim->unloading_next();
5252 
5253     } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim);
5254 
5255     return claim;
5256   }
5257 
5258  public:
5259   // Mark that we're done with the first pass of nmethod cleaning.
5260   void barrier_mark(uint worker_id) {
5261     MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
5262     _num_entered_barrier++;
5263     if (_num_entered_barrier == _num_workers) {
5264       ml.notify_all();
5265     }
5266   }
5267 
5268   // See if we have to wait for the other workers to
5269   // finish their first-pass nmethod cleaning work.
5270   void barrier_wait(uint worker_id) {
5271     if (_num_entered_barrier < _num_workers) {
5272       MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
5273       while (_num_entered_barrier < _num_workers) {
5274           ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
5275       }
5276     }
5277   }
5278 
5279   // Cleaning and unloading of nmethods. Some work has to be postponed
5280   // to the second pass, when we know which nmethods survive.
5281   void work_first_pass(uint worker_id) {
5282     // The first nmethods is claimed by the first worker.
5283     if (worker_id == 0 && _first_nmethod != NULL) {
5284       clean_nmethod(_first_nmethod);
5285       _first_nmethod = NULL;
5286     }
5287 
5288     int num_claimed_nmethods;
5289     nmethod* claimed_nmethods[MaxClaimNmethods];
5290 
5291     while (true) {
5292       claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
5293 
5294       if (num_claimed_nmethods == 0) {
5295         break;
5296       }
5297 
5298       for (int i = 0; i < num_claimed_nmethods; i++) {
5299         clean_nmethod(claimed_nmethods[i]);
5300       }
5301     }
5302   }
5303 
5304   void work_second_pass(uint worker_id) {
5305     nmethod* nm;
5306     // Take care of postponed nmethods.
5307     while ((nm = claim_postponed_nmethod()) != NULL) {
5308       clean_nmethod_postponed(nm);
5309     }
5310   }
5311 };
5312 
5313 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock");
5314 
5315 class G1KlassCleaningTask : public StackObj {
5316   BoolObjectClosure*                      _is_alive;
5317   volatile jint                           _clean_klass_tree_claimed;
5318   ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
5319 
5320  public:
5321   G1KlassCleaningTask(BoolObjectClosure* is_alive) :
5322       _is_alive(is_alive),
5323       _clean_klass_tree_claimed(0),
5324       _klass_iterator() {
5325   }
5326 
5327  private:
5328   bool claim_clean_klass_tree_task() {
5329     if (_clean_klass_tree_claimed) {
5330       return false;
5331     }
5332 
5333     return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0;
5334   }
5335 
5336   InstanceKlass* claim_next_klass() {
5337     Klass* klass;
5338     do {
5339       klass =_klass_iterator.next_klass();
5340     } while (klass != NULL && !klass->oop_is_instance());
5341 
5342     return (InstanceKlass*)klass;
5343   }
5344 
5345 public:
5346 
5347   void clean_klass(InstanceKlass* ik) {
5348     ik->clean_implementors_list(_is_alive);
5349     ik->clean_method_data(_is_alive);
5350 
5351     // G1 specific cleanup work that has
5352     // been moved here to be done in parallel.
5353     ik->clean_dependent_nmethods();
5354   }
5355 
5356   void work() {
5357     ResourceMark rm;
5358 
5359     // One worker will clean the subklass/sibling klass tree.
5360     if (claim_clean_klass_tree_task()) {
5361       Klass::clean_subklass_tree(_is_alive);
5362     }
5363 
5364     // All workers will help cleaning the classes,
5365     InstanceKlass* klass;
5366     while ((klass = claim_next_klass()) != NULL) {
5367       clean_klass(klass);
5368     }
5369   }
5370 };
5371 
5372 // To minimize the remark pause times, the tasks below are done in parallel.
5373 class G1ParallelCleaningTask : public AbstractGangTask {
5374 private:
5375   G1StringSymbolTableUnlinkTask _string_symbol_task;
5376   G1CodeCacheUnloadingTask      _code_cache_task;
5377   G1KlassCleaningTask           _klass_cleaning_task;
5378 
5379 public:
5380   // The constructor is run in the VMThread.
5381   G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) :
5382       AbstractGangTask("Parallel Cleaning"),
5383       _string_symbol_task(is_alive, process_strings, process_symbols),
5384       _code_cache_task(num_workers, is_alive, unloading_occurred),
5385       _klass_cleaning_task(is_alive) {
5386   }
5387 
5388   // The parallel work done by all worker threads.
5389   void work(uint worker_id) {
5390     // Do first pass of code cache cleaning.
5391     _code_cache_task.work_first_pass(worker_id);
5392 
5393     // Let the threads mark that the first pass is done.
5394     _code_cache_task.barrier_mark(worker_id);
5395 
5396     // Clean the Strings and Symbols.
5397     _string_symbol_task.work(worker_id);
5398 
5399     // Wait for all workers to finish the first code cache cleaning pass.
5400     _code_cache_task.barrier_wait(worker_id);
5401 
5402     // Do the second code cache cleaning work, which realize on
5403     // the liveness information gathered during the first pass.
5404     _code_cache_task.work_second_pass(worker_id);
5405 
5406     // Clean all klasses that were not unloaded.
5407     _klass_cleaning_task.work();
5408   }
5409 };
5410 
5411 
5412 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive,
5413                                         bool process_strings,
5414                                         bool process_symbols,
5415                                         bool class_unloading_occurred) {
5416   uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5417                     workers()->active_workers() : 1);
5418 
5419   G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols,
5420                                         n_workers, class_unloading_occurred);
5421   if (G1CollectedHeap::use_parallel_gc_threads()) {
5422     set_par_threads(n_workers);
5423     workers()->run_task(&g1_unlink_task);
5424     set_par_threads(0);
5425   } else {
5426     g1_unlink_task.work(0);
5427   }
5428 }
5429 
5430 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive,
5431                                                      bool process_strings, bool process_symbols) {
5432   {
5433     uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5434                      _g1h->workers()->active_workers() : 1);
5435     G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols);
5436     if (G1CollectedHeap::use_parallel_gc_threads()) {
5437       set_par_threads(n_workers);
5438       workers()->run_task(&g1_unlink_task);
5439       set_par_threads(0);
5440     } else {
5441       g1_unlink_task.work(0);
5442     }
5443   }
5444 
5445   if (G1StringDedup::is_enabled()) {
5446     G1StringDedup::unlink(is_alive);
5447   }
5448 }
5449 
5450 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
5451  private:
5452   DirtyCardQueueSet* _queue;
5453  public:
5454   G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue) : AbstractGangTask("Redirty Cards"), _queue(queue) { }
5455 
5456   virtual void work(uint worker_id) {
5457     double start_time = os::elapsedTime();
5458 
5459     RedirtyLoggedCardTableEntryClosure cl;
5460     if (G1CollectedHeap::heap()->use_parallel_gc_threads()) {
5461       _queue->par_apply_closure_to_all_completed_buffers(&cl);
5462     } else {
5463       _queue->apply_closure_to_all_completed_buffers(&cl);
5464     }
5465 
5466     G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
5467     timer->record_redirty_logged_cards_time_ms(worker_id, (os::elapsedTime() - start_time) * 1000.0);
5468     timer->record_redirty_logged_cards_processed_cards(worker_id, cl.num_processed());
5469   }
5470 };
5471 
5472 void G1CollectedHeap::redirty_logged_cards() {
5473   guarantee(G1DeferredRSUpdate, "Must only be called when using deferred RS updates.");
5474   double redirty_logged_cards_start = os::elapsedTime();
5475 
5476   uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5477                    _g1h->workers()->active_workers() : 1);
5478 
5479   G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set());
5480   dirty_card_queue_set().reset_for_par_iteration();
5481   if (use_parallel_gc_threads()) {
5482     set_par_threads(n_workers);
5483     workers()->run_task(&redirty_task);
5484     set_par_threads(0);
5485   } else {
5486     redirty_task.work(0);
5487   }
5488 
5489   DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5490   dcq.merge_bufferlists(&dirty_card_queue_set());
5491   assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5492 
5493   g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
5494 }
5495 
5496 // Weak Reference Processing support
5497 
5498 // An always "is_alive" closure that is used to preserve referents.
5499 // If the object is non-null then it's alive.  Used in the preservation
5500 // of referent objects that are pointed to by reference objects
5501 // discovered by the CM ref processor.
5502 class G1AlwaysAliveClosure: public BoolObjectClosure {
5503   G1CollectedHeap* _g1;
5504 public:
5505   G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5506   bool do_object_b(oop p) {
5507     if (p != NULL) {
5508       return true;
5509     }
5510     return false;
5511   }
5512 };
5513 
5514 bool G1STWIsAliveClosure::do_object_b(oop p) {
5515   // An object is reachable if it is outside the collection set,
5516   // or is inside and copied.
5517   return !_g1->obj_in_cs(p) || p->is_forwarded();
5518 }
5519 
5520 // Non Copying Keep Alive closure
5521 class G1KeepAliveClosure: public OopClosure {
5522   G1CollectedHeap* _g1;
5523 public:
5524   G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5525   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
5526   void do_oop(oop* p) {
5527     oop obj = *p;
5528 
5529     G1CollectedHeap::in_cset_state_t cset_state = _g1->in_cset_state(obj);
5530     if (obj == NULL || cset_state == G1CollectedHeap::InNeither) {
5531       return;
5532     }
5533     if (cset_state == G1CollectedHeap::InCSet) {
5534       assert( obj->is_forwarded(), "invariant" );
5535       *p = obj->forwardee();
5536     } else {
5537       assert(!obj->is_forwarded(), "invariant" );
5538       assert(cset_state == G1CollectedHeap::IsHumongous,
5539              err_msg("Only allowed InCSet state is IsHumongous, but is %d", cset_state));
5540       _g1->set_humongous_is_live(obj);
5541     }
5542   }
5543 };
5544 
5545 // Copying Keep Alive closure - can be called from both
5546 // serial and parallel code as long as different worker
5547 // threads utilize different G1ParScanThreadState instances
5548 // and different queues.
5549 
5550 class G1CopyingKeepAliveClosure: public OopClosure {
5551   G1CollectedHeap*         _g1h;
5552   OopClosure*              _copy_non_heap_obj_cl;
5553   G1ParScanThreadState*    _par_scan_state;
5554 
5555 public:
5556   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
5557                             OopClosure* non_heap_obj_cl,
5558                             G1ParScanThreadState* pss):
5559     _g1h(g1h),
5560     _copy_non_heap_obj_cl(non_heap_obj_cl),
5561     _par_scan_state(pss)
5562   {}
5563 
5564   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
5565   virtual void do_oop(      oop* p) { do_oop_work(p); }
5566 
5567   template <class T> void do_oop_work(T* p) {
5568     oop obj = oopDesc::load_decode_heap_oop(p);
5569 
5570     if (_g1h->is_in_cset_or_humongous(obj)) {
5571       // If the referent object has been forwarded (either copied
5572       // to a new location or to itself in the event of an
5573       // evacuation failure) then we need to update the reference
5574       // field and, if both reference and referent are in the G1
5575       // heap, update the RSet for the referent.
5576       //
5577       // If the referent has not been forwarded then we have to keep
5578       // it alive by policy. Therefore we have copy the referent.
5579       //
5580       // If the reference field is in the G1 heap then we can push
5581       // on the PSS queue. When the queue is drained (after each
5582       // phase of reference processing) the object and it's followers
5583       // will be copied, the reference field set to point to the
5584       // new location, and the RSet updated. Otherwise we need to
5585       // use the the non-heap or metadata closures directly to copy
5586       // the referent object and update the pointer, while avoiding
5587       // updating the RSet.
5588 
5589       if (_g1h->is_in_g1_reserved(p)) {
5590         _par_scan_state->push_on_queue(p);
5591       } else {
5592         assert(!Metaspace::contains((const void*)p),
5593                err_msg("Unexpectedly found a pointer from metadata: "
5594                               PTR_FORMAT, p));
5595         _copy_non_heap_obj_cl->do_oop(p);
5596       }
5597     }
5598   }
5599 };
5600 
5601 // Serial drain queue closure. Called as the 'complete_gc'
5602 // closure for each discovered list in some of the
5603 // reference processing phases.
5604 
5605 class G1STWDrainQueueClosure: public VoidClosure {
5606 protected:
5607   G1CollectedHeap* _g1h;
5608   G1ParScanThreadState* _par_scan_state;
5609 
5610   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
5611 
5612 public:
5613   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
5614     _g1h(g1h),
5615     _par_scan_state(pss)
5616   { }
5617 
5618   void do_void() {
5619     G1ParScanThreadState* const pss = par_scan_state();
5620     pss->trim_queue();
5621   }
5622 };
5623 
5624 // Parallel Reference Processing closures
5625 
5626 // Implementation of AbstractRefProcTaskExecutor for parallel reference
5627 // processing during G1 evacuation pauses.
5628 
5629 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5630 private:
5631   G1CollectedHeap*   _g1h;
5632   RefToScanQueueSet* _queues;
5633   FlexibleWorkGang*  _workers;
5634   int                _active_workers;
5635 
5636 public:
5637   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5638                         FlexibleWorkGang* workers,
5639                         RefToScanQueueSet *task_queues,
5640                         int n_workers) :
5641     _g1h(g1h),
5642     _queues(task_queues),
5643     _workers(workers),
5644     _active_workers(n_workers)
5645   {
5646     assert(n_workers > 0, "shouldn't call this otherwise");
5647   }
5648 
5649   // Executes the given task using concurrent marking worker threads.
5650   virtual void execute(ProcessTask& task);
5651   virtual void execute(EnqueueTask& task);
5652 };
5653 
5654 // Gang task for possibly parallel reference processing
5655 
5656 class G1STWRefProcTaskProxy: public AbstractGangTask {
5657   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5658   ProcessTask&     _proc_task;
5659   G1CollectedHeap* _g1h;
5660   RefToScanQueueSet *_task_queues;
5661   ParallelTaskTerminator* _terminator;
5662 
5663 public:
5664   G1STWRefProcTaskProxy(ProcessTask& proc_task,
5665                      G1CollectedHeap* g1h,
5666                      RefToScanQueueSet *task_queues,
5667                      ParallelTaskTerminator* terminator) :
5668     AbstractGangTask("Process reference objects in parallel"),
5669     _proc_task(proc_task),
5670     _g1h(g1h),
5671     _task_queues(task_queues),
5672     _terminator(terminator)
5673   {}
5674 
5675   virtual void work(uint worker_id) {
5676     // The reference processing task executed by a single worker.
5677     ResourceMark rm;
5678     HandleMark   hm;
5679 
5680     G1STWIsAliveClosure is_alive(_g1h);
5681 
5682     G1ParScanThreadState            pss(_g1h, worker_id, NULL);
5683     G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5684 
5685     pss.set_evac_failure_closure(&evac_failure_cl);
5686 
5687     G1ParScanExtRootClosure        only_copy_non_heap_cl(_g1h, &pss, NULL);
5688 
5689     G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5690 
5691     OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5692 
5693     if (_g1h->g1_policy()->during_initial_mark_pause()) {
5694       // We also need to mark copied objects.
5695       copy_non_heap_cl = &copy_mark_non_heap_cl;
5696     }
5697 
5698     // Keep alive closure.
5699     G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5700 
5701     // Complete GC closure
5702     G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5703 
5704     // Call the reference processing task's work routine.
5705     _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5706 
5707     // Note we cannot assert that the refs array is empty here as not all
5708     // of the processing tasks (specifically phase2 - pp2_work) execute
5709     // the complete_gc closure (which ordinarily would drain the queue) so
5710     // the queue may not be empty.
5711   }
5712 };
5713 
5714 // Driver routine for parallel reference processing.
5715 // Creates an instance of the ref processing gang
5716 // task and has the worker threads execute it.
5717 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5718   assert(_workers != NULL, "Need parallel worker threads.");
5719 
5720   ParallelTaskTerminator terminator(_active_workers, _queues);
5721   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5722 
5723   _g1h->set_par_threads(_active_workers);
5724   _workers->run_task(&proc_task_proxy);
5725   _g1h->set_par_threads(0);
5726 }
5727 
5728 // Gang task for parallel reference enqueueing.
5729 
5730 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5731   typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5732   EnqueueTask& _enq_task;
5733 
5734 public:
5735   G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5736     AbstractGangTask("Enqueue reference objects in parallel"),
5737     _enq_task(enq_task)
5738   { }
5739 
5740   virtual void work(uint worker_id) {
5741     _enq_task.work(worker_id);
5742   }
5743 };
5744 
5745 // Driver routine for parallel reference enqueueing.
5746 // Creates an instance of the ref enqueueing gang
5747 // task and has the worker threads execute it.
5748 
5749 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5750   assert(_workers != NULL, "Need parallel worker threads.");
5751 
5752   G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5753 
5754   _g1h->set_par_threads(_active_workers);
5755   _workers->run_task(&enq_task_proxy);
5756   _g1h->set_par_threads(0);
5757 }
5758 
5759 // End of weak reference support closures
5760 
5761 // Abstract task used to preserve (i.e. copy) any referent objects
5762 // that are in the collection set and are pointed to by reference
5763 // objects discovered by the CM ref processor.
5764 
5765 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5766 protected:
5767   G1CollectedHeap* _g1h;
5768   RefToScanQueueSet      *_queues;
5769   ParallelTaskTerminator _terminator;
5770   uint _n_workers;
5771 
5772 public:
5773   G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
5774     AbstractGangTask("ParPreserveCMReferents"),
5775     _g1h(g1h),
5776     _queues(task_queues),
5777     _terminator(workers, _queues),
5778     _n_workers(workers)
5779   { }
5780 
5781   void work(uint worker_id) {
5782     ResourceMark rm;
5783     HandleMark   hm;
5784 
5785     G1ParScanThreadState            pss(_g1h, worker_id, NULL);
5786     G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5787 
5788     pss.set_evac_failure_closure(&evac_failure_cl);
5789 
5790     assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5791 
5792     G1ParScanExtRootClosure        only_copy_non_heap_cl(_g1h, &pss, NULL);
5793 
5794     G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5795 
5796     OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5797 
5798     if (_g1h->g1_policy()->during_initial_mark_pause()) {
5799       // We also need to mark copied objects.
5800       copy_non_heap_cl = &copy_mark_non_heap_cl;
5801     }
5802 
5803     // Is alive closure
5804     G1AlwaysAliveClosure always_alive(_g1h);
5805 
5806     // Copying keep alive closure. Applied to referent objects that need
5807     // to be copied.
5808     G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5809 
5810     ReferenceProcessor* rp = _g1h->ref_processor_cm();
5811 
5812     uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5813     uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5814 
5815     // limit is set using max_num_q() - which was set using ParallelGCThreads.
5816     // So this must be true - but assert just in case someone decides to
5817     // change the worker ids.
5818     assert(0 <= worker_id && worker_id < limit, "sanity");
5819     assert(!rp->discovery_is_atomic(), "check this code");
5820 
5821     // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5822     for (uint idx = worker_id; idx < limit; idx += stride) {
5823       DiscoveredList& ref_list = rp->discovered_refs()[idx];
5824 
5825       DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5826       while (iter.has_next()) {
5827         // Since discovery is not atomic for the CM ref processor, we
5828         // can see some null referent objects.
5829         iter.load_ptrs(DEBUG_ONLY(true));
5830         oop ref = iter.obj();
5831 
5832         // This will filter nulls.
5833         if (iter.is_referent_alive()) {
5834           iter.make_referent_alive();
5835         }
5836         iter.move_to_next();
5837       }
5838     }
5839 
5840     // Drain the queue - which may cause stealing
5841     G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5842     drain_queue.do_void();
5843     // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5844     assert(pss.queue_is_empty(), "should be");
5845   }
5846 };
5847 
5848 // Weak Reference processing during an evacuation pause (part 1).
5849 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) {
5850   double ref_proc_start = os::elapsedTime();
5851 
5852   ReferenceProcessor* rp = _ref_processor_stw;
5853   assert(rp->discovery_enabled(), "should have been enabled");
5854 
5855   // Any reference objects, in the collection set, that were 'discovered'
5856   // by the CM ref processor should have already been copied (either by
5857   // applying the external root copy closure to the discovered lists, or
5858   // by following an RSet entry).
5859   //
5860   // But some of the referents, that are in the collection set, that these
5861   // reference objects point to may not have been copied: the STW ref
5862   // processor would have seen that the reference object had already
5863   // been 'discovered' and would have skipped discovering the reference,
5864   // but would not have treated the reference object as a regular oop.
5865   // As a result the copy closure would not have been applied to the
5866   // referent object.
5867   //
5868   // We need to explicitly copy these referent objects - the references
5869   // will be processed at the end of remarking.
5870   //
5871   // We also need to do this copying before we process the reference
5872   // objects discovered by the STW ref processor in case one of these
5873   // referents points to another object which is also referenced by an
5874   // object discovered by the STW ref processor.
5875 
5876   assert(!G1CollectedHeap::use_parallel_gc_threads() ||
5877            no_of_gc_workers == workers()->active_workers(),
5878            "Need to reset active GC workers");
5879 
5880   set_par_threads(no_of_gc_workers);
5881   G1ParPreserveCMReferentsTask keep_cm_referents(this,
5882                                                  no_of_gc_workers,
5883                                                  _task_queues);
5884 
5885   if (G1CollectedHeap::use_parallel_gc_threads()) {
5886     workers()->run_task(&keep_cm_referents);
5887   } else {
5888     keep_cm_referents.work(0);
5889   }
5890 
5891   set_par_threads(0);
5892 
5893   // Closure to test whether a referent is alive.
5894   G1STWIsAliveClosure is_alive(this);
5895 
5896   // Even when parallel reference processing is enabled, the processing
5897   // of JNI refs is serial and performed serially by the current thread
5898   // rather than by a worker. The following PSS will be used for processing
5899   // JNI refs.
5900 
5901   // Use only a single queue for this PSS.
5902   G1ParScanThreadState            pss(this, 0, NULL);
5903 
5904   // We do not embed a reference processor in the copying/scanning
5905   // closures while we're actually processing the discovered
5906   // reference objects.
5907   G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5908 
5909   pss.set_evac_failure_closure(&evac_failure_cl);
5910 
5911   assert(pss.queue_is_empty(), "pre-condition");
5912 
5913   G1ParScanExtRootClosure        only_copy_non_heap_cl(this, &pss, NULL);
5914 
5915   G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5916 
5917   OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5918 
5919   if (_g1h->g1_policy()->during_initial_mark_pause()) {
5920     // We also need to mark copied objects.
5921     copy_non_heap_cl = &copy_mark_non_heap_cl;
5922   }
5923 
5924   // Keep alive closure.
5925   G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, &pss);
5926 
5927   // Serial Complete GC closure
5928   G1STWDrainQueueClosure drain_queue(this, &pss);
5929 
5930   // Setup the soft refs policy...
5931   rp->setup_policy(false);
5932 
5933   ReferenceProcessorStats stats;
5934   if (!rp->processing_is_mt()) {
5935     // Serial reference processing...
5936     stats = rp->process_discovered_references(&is_alive,
5937                                               &keep_alive,
5938                                               &drain_queue,
5939                                               NULL,
5940                                               _gc_timer_stw,
5941                                               _gc_tracer_stw->gc_id());
5942   } else {
5943     // Parallel reference processing
5944     assert(rp->num_q() == no_of_gc_workers, "sanity");
5945     assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5946 
5947     G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5948     stats = rp->process_discovered_references(&is_alive,
5949                                               &keep_alive,
5950                                               &drain_queue,
5951                                               &par_task_executor,
5952                                               _gc_timer_stw,
5953                                               _gc_tracer_stw->gc_id());
5954   }
5955 
5956   _gc_tracer_stw->report_gc_reference_stats(stats);
5957 
5958   // We have completed copying any necessary live referent objects.
5959   assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5960 
5961   double ref_proc_time = os::elapsedTime() - ref_proc_start;
5962   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5963 }
5964 
5965 // Weak Reference processing during an evacuation pause (part 2).
5966 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) {
5967   double ref_enq_start = os::elapsedTime();
5968 
5969   ReferenceProcessor* rp = _ref_processor_stw;
5970   assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5971 
5972   // Now enqueue any remaining on the discovered lists on to
5973   // the pending list.
5974   if (!rp->processing_is_mt()) {
5975     // Serial reference processing...
5976     rp->enqueue_discovered_references();
5977   } else {
5978     // Parallel reference enqueueing
5979 
5980     assert(no_of_gc_workers == workers()->active_workers(),
5981            "Need to reset active workers");
5982     assert(rp->num_q() == no_of_gc_workers, "sanity");
5983     assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5984 
5985     G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5986     rp->enqueue_discovered_references(&par_task_executor);
5987   }
5988 
5989   rp->verify_no_references_recorded();
5990   assert(!rp->discovery_enabled(), "should have been disabled");
5991 
5992   // FIXME
5993   // CM's reference processing also cleans up the string and symbol tables.
5994   // Should we do that here also? We could, but it is a serial operation
5995   // and could significantly increase the pause time.
5996 
5997   double ref_enq_time = os::elapsedTime() - ref_enq_start;
5998   g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5999 }
6000 
6001 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) {
6002   _expand_heap_after_alloc_failure = true;
6003   _evacuation_failed = false;
6004 
6005   // Should G1EvacuationFailureALot be in effect for this GC?
6006   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
6007 
6008   g1_rem_set()->prepare_for_oops_into_collection_set_do();
6009 
6010   // Disable the hot card cache.
6011   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
6012   hot_card_cache->reset_hot_cache_claimed_index();
6013   hot_card_cache->set_use_cache(false);
6014 
6015   uint n_workers;
6016   if (G1CollectedHeap::use_parallel_gc_threads()) {
6017     n_workers =
6018       AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
6019                                      workers()->active_workers(),
6020                                      Threads::number_of_non_daemon_threads());
6021     assert(UseDynamicNumberOfGCThreads ||
6022            n_workers == workers()->total_workers(),
6023            "If not dynamic should be using all the  workers");
6024     workers()->set_active_workers(n_workers);
6025     set_par_threads(n_workers);
6026   } else {
6027     assert(n_par_threads() == 0,
6028            "Should be the original non-parallel value");
6029     n_workers = 1;
6030   }
6031 
6032   G1ParTask g1_par_task(this, _task_queues);
6033 
6034   init_for_evac_failure(NULL);
6035 
6036   rem_set()->prepare_for_younger_refs_iterate(true);
6037 
6038   assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
6039   double start_par_time_sec = os::elapsedTime();
6040   double end_par_time_sec;
6041 
6042   {
6043     StrongRootsScope srs(this);
6044     // InitialMark needs claim bits to keep track of the marked-through CLDs.
6045     if (g1_policy()->during_initial_mark_pause()) {
6046       ClassLoaderDataGraph::clear_claimed_marks();
6047     }
6048 
6049     if (G1CollectedHeap::use_parallel_gc_threads()) {
6050       // The individual threads will set their evac-failure closures.
6051       if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
6052       // These tasks use ShareHeap::_process_strong_tasks
6053       assert(UseDynamicNumberOfGCThreads ||
6054              workers()->active_workers() == workers()->total_workers(),
6055              "If not dynamic should be using all the  workers");
6056       workers()->run_task(&g1_par_task);
6057     } else {
6058       g1_par_task.set_for_termination(n_workers);
6059       g1_par_task.work(0);
6060     }
6061     end_par_time_sec = os::elapsedTime();
6062 
6063     // Closing the inner scope will execute the destructor
6064     // for the StrongRootsScope object. We record the current
6065     // elapsed time before closing the scope so that time
6066     // taken for the SRS destructor is NOT included in the
6067     // reported parallel time.
6068   }
6069 
6070   double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
6071   g1_policy()->phase_times()->record_par_time(par_time_ms);
6072 
6073   double code_root_fixup_time_ms =
6074         (os::elapsedTime() - end_par_time_sec) * 1000.0;
6075   g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms);
6076 
6077   set_par_threads(0);
6078 
6079   // Process any discovered reference objects - we have
6080   // to do this _before_ we retire the GC alloc regions
6081   // as we may have to copy some 'reachable' referent
6082   // objects (and their reachable sub-graphs) that were
6083   // not copied during the pause.
6084   process_discovered_references(n_workers);
6085 
6086   // Weak root processing.
6087   {
6088     G1STWIsAliveClosure is_alive(this);
6089     G1KeepAliveClosure keep_alive(this);
6090     JNIHandles::weak_oops_do(&is_alive, &keep_alive);
6091     if (G1StringDedup::is_enabled()) {
6092       G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive);
6093     }
6094   }
6095 
6096   release_gc_alloc_regions(n_workers, evacuation_info);
6097   g1_rem_set()->cleanup_after_oops_into_collection_set_do();
6098 
6099   // Reset and re-enable the hot card cache.
6100   // Note the counts for the cards in the regions in the
6101   // collection set are reset when the collection set is freed.
6102   hot_card_cache->reset_hot_cache();
6103   hot_card_cache->set_use_cache(true);
6104 
6105   // Migrate the strong code roots attached to each region in
6106   // the collection set. Ideally we would like to do this
6107   // after we have finished the scanning/evacuation of the
6108   // strong code roots for a particular heap region.
6109   migrate_strong_code_roots();
6110 
6111   purge_code_root_memory();
6112 
6113   if (g1_policy()->during_initial_mark_pause()) {
6114     // Reset the claim values set during marking the strong code roots
6115     reset_heap_region_claim_values();
6116   }
6117 
6118   finalize_for_evac_failure();
6119 
6120   if (evacuation_failed()) {
6121     remove_self_forwarding_pointers();
6122 
6123     // Reset the G1EvacuationFailureALot counters and flags
6124     // Note: the values are reset only when an actual
6125     // evacuation failure occurs.
6126     NOT_PRODUCT(reset_evacuation_should_fail();)
6127   }
6128 
6129   // Enqueue any remaining references remaining on the STW
6130   // reference processor's discovered lists. We need to do
6131   // this after the card table is cleaned (and verified) as
6132   // the act of enqueueing entries on to the pending list
6133   // will log these updates (and dirty their associated
6134   // cards). We need these updates logged to update any
6135   // RSets.
6136   enqueue_discovered_references(n_workers);
6137 
6138   if (G1DeferredRSUpdate) {
6139     redirty_logged_cards();
6140   }
6141   COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
6142 }
6143 
6144 void G1CollectedHeap::free_region(HeapRegion* hr,
6145                                   FreeRegionList* free_list,
6146                                   bool par,
6147                                   bool locked) {
6148   assert(!hr->isHumongous(), "this is only for non-humongous regions");
6149   assert(!hr->is_empty(), "the region should not be empty");
6150   assert(free_list != NULL, "pre-condition");
6151 
6152   if (G1VerifyBitmaps) {
6153     MemRegion mr(hr->bottom(), hr->end());
6154     concurrent_mark()->clearRangePrevBitmap(mr);
6155   }
6156 
6157   // Clear the card counts for this region.
6158   // Note: we only need to do this if the region is not young
6159   // (since we don't refine cards in young regions).
6160   if (!hr->is_young()) {
6161     _cg1r->hot_card_cache()->reset_card_counts(hr);
6162   }
6163   hr->hr_clear(par, true /* clear_space */, locked /* locked */);
6164   free_list->add_ordered(hr);
6165 }
6166 
6167 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
6168                                      FreeRegionList* free_list,
6169                                      bool par) {
6170   assert(hr->startsHumongous(), "this is only for starts humongous regions");
6171   assert(free_list != NULL, "pre-condition");
6172 
6173   size_t hr_capacity = hr->capacity();
6174   // We need to read this before we make the region non-humongous,
6175   // otherwise the information will be gone.
6176   uint last_index = hr->last_hc_index();
6177   hr->set_notHumongous();
6178   free_region(hr, free_list, par);
6179 
6180   uint i = hr->hrs_index() + 1;
6181   while (i < last_index) {
6182     HeapRegion* curr_hr = region_at(i);
6183     assert(curr_hr->continuesHumongous(), "invariant");
6184     curr_hr->set_notHumongous();
6185     free_region(curr_hr, free_list, par);
6186     i += 1;
6187   }
6188 }
6189 
6190 void G1CollectedHeap::remove_from_old_sets(const HeapRegionSetCount& old_regions_removed,
6191                                        const HeapRegionSetCount& humongous_regions_removed) {
6192   if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 0) {
6193     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
6194     _old_set.bulk_remove(old_regions_removed);
6195     _humongous_set.bulk_remove(humongous_regions_removed);
6196   }
6197 
6198 }
6199 
6200 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
6201   assert(list != NULL, "list can't be null");
6202   if (!list->is_empty()) {
6203     MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
6204     _free_list.add_ordered(list);
6205   }
6206 }
6207 
6208 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
6209   assert(_summary_bytes_used >= bytes,
6210          err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" should be >= bytes: "SIZE_FORMAT,
6211                   _summary_bytes_used, bytes));
6212   _summary_bytes_used -= bytes;
6213 }
6214 
6215 class G1ParCleanupCTTask : public AbstractGangTask {
6216   G1SATBCardTableModRefBS* _ct_bs;
6217   G1CollectedHeap* _g1h;
6218   HeapRegion* volatile _su_head;
6219 public:
6220   G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs,
6221                      G1CollectedHeap* g1h) :
6222     AbstractGangTask("G1 Par Cleanup CT Task"),
6223     _ct_bs(ct_bs), _g1h(g1h) { }
6224 
6225   void work(uint worker_id) {
6226     HeapRegion* r;
6227     while (r = _g1h->pop_dirty_cards_region()) {
6228       clear_cards(r);
6229     }
6230   }
6231 
6232   void clear_cards(HeapRegion* r) {
6233     // Cards of the survivors should have already been dirtied.
6234     if (!r->is_survivor()) {
6235       _ct_bs->clear(MemRegion(r->bottom(), r->end()));
6236     }
6237   }
6238 };
6239 
6240 #ifndef PRODUCT
6241 class G1VerifyCardTableCleanup: public HeapRegionClosure {
6242   G1CollectedHeap* _g1h;
6243   G1SATBCardTableModRefBS* _ct_bs;
6244 public:
6245   G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs)
6246     : _g1h(g1h), _ct_bs(ct_bs) { }
6247   virtual bool doHeapRegion(HeapRegion* r) {
6248     if (r->is_survivor()) {
6249       _g1h->verify_dirty_region(r);
6250     } else {
6251       _g1h->verify_not_dirty_region(r);
6252     }
6253     return false;
6254   }
6255 };
6256 
6257 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
6258   // All of the region should be clean.
6259   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6260   MemRegion mr(hr->bottom(), hr->end());
6261   ct_bs->verify_not_dirty_region(mr);
6262 }
6263 
6264 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
6265   // We cannot guarantee that [bottom(),end()] is dirty.  Threads
6266   // dirty allocated blocks as they allocate them. The thread that
6267   // retires each region and replaces it with a new one will do a
6268   // maximal allocation to fill in [pre_dummy_top(),end()] but will
6269   // not dirty that area (one less thing to have to do while holding
6270   // a lock). So we can only verify that [bottom(),pre_dummy_top()]
6271   // is dirty.
6272   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6273   MemRegion mr(hr->bottom(), hr->pre_dummy_top());
6274   if (hr->is_young()) {
6275     ct_bs->verify_g1_young_region(mr);
6276   } else {
6277     ct_bs->verify_dirty_region(mr);
6278   }
6279 }
6280 
6281 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
6282   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6283   for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
6284     verify_dirty_region(hr);
6285   }
6286 }
6287 
6288 void G1CollectedHeap::verify_dirty_young_regions() {
6289   verify_dirty_young_list(_young_list->first_region());
6290 }
6291 
6292 bool G1CollectedHeap::verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
6293                                                HeapWord* tams, HeapWord* end) {
6294   guarantee(tams <= end,
6295             err_msg("tams: "PTR_FORMAT" end: "PTR_FORMAT, tams, end));
6296   HeapWord* result = bitmap->getNextMarkedWordAddress(tams, end);
6297   if (result < end) {
6298     gclog_or_tty->cr();
6299     gclog_or_tty->print_cr("## wrong marked address on %s bitmap: "PTR_FORMAT,
6300                            bitmap_name, result);
6301     gclog_or_tty->print_cr("## %s tams: "PTR_FORMAT" end: "PTR_FORMAT,
6302                            bitmap_name, tams, end);
6303     return false;
6304   }
6305   return true;
6306 }
6307 
6308 bool G1CollectedHeap::verify_bitmaps(const char* caller, HeapRegion* hr) {
6309   CMBitMapRO* prev_bitmap = concurrent_mark()->prevMarkBitMap();
6310   CMBitMapRO* next_bitmap = (CMBitMapRO*) concurrent_mark()->nextMarkBitMap();
6311 
6312   HeapWord* bottom = hr->bottom();
6313   HeapWord* ptams  = hr->prev_top_at_mark_start();
6314   HeapWord* ntams  = hr->next_top_at_mark_start();
6315   HeapWord* end    = hr->end();
6316 
6317   bool res_p = verify_no_bits_over_tams("prev", prev_bitmap, ptams, end);
6318 
6319   bool res_n = true;
6320   // We reset mark_in_progress() before we reset _cmThread->in_progress() and in this window
6321   // we do the clearing of the next bitmap concurrently. Thus, we can not verify the bitmap
6322   // if we happen to be in that state.
6323   if (mark_in_progress() || !_cmThread->in_progress()) {
6324     res_n = verify_no_bits_over_tams("next", next_bitmap, ntams, end);
6325   }
6326   if (!res_p || !res_n) {
6327     gclog_or_tty->print_cr("#### Bitmap verification failed for "HR_FORMAT,
6328                            HR_FORMAT_PARAMS(hr));
6329     gclog_or_tty->print_cr("#### Caller: %s", caller);
6330     return false;
6331   }
6332   return true;
6333 }
6334 
6335 void G1CollectedHeap::check_bitmaps(const char* caller, HeapRegion* hr) {
6336   if (!G1VerifyBitmaps) return;
6337 
6338   guarantee(verify_bitmaps(caller, hr), "bitmap verification");
6339 }
6340 
6341 class G1VerifyBitmapClosure : public HeapRegionClosure {
6342 private:
6343   const char* _caller;
6344   G1CollectedHeap* _g1h;
6345   bool _failures;
6346 
6347 public:
6348   G1VerifyBitmapClosure(const char* caller, G1CollectedHeap* g1h) :
6349     _caller(caller), _g1h(g1h), _failures(false) { }
6350 
6351   bool failures() { return _failures; }
6352 
6353   virtual bool doHeapRegion(HeapRegion* hr) {
6354     if (hr->continuesHumongous()) return false;
6355 
6356     bool result = _g1h->verify_bitmaps(_caller, hr);
6357     if (!result) {
6358       _failures = true;
6359     }
6360     return false;
6361   }
6362 };
6363 
6364 void G1CollectedHeap::check_bitmaps(const char* caller) {
6365   if (!G1VerifyBitmaps) return;
6366 
6367   G1VerifyBitmapClosure cl(caller, this);
6368   heap_region_iterate(&cl);
6369   guarantee(!cl.failures(), "bitmap verification");
6370 }
6371 #endif // PRODUCT
6372 
6373 void G1CollectedHeap::cleanUpCardTable() {
6374   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6375   double start = os::elapsedTime();
6376 
6377   {
6378     // Iterate over the dirty cards region list.
6379     G1ParCleanupCTTask cleanup_task(ct_bs, this);
6380 
6381     if (G1CollectedHeap::use_parallel_gc_threads()) {
6382       set_par_threads();
6383       workers()->run_task(&cleanup_task);
6384       set_par_threads(0);
6385     } else {
6386       while (_dirty_cards_region_list) {
6387         HeapRegion* r = _dirty_cards_region_list;
6388         cleanup_task.clear_cards(r);
6389         _dirty_cards_region_list = r->get_next_dirty_cards_region();
6390         if (_dirty_cards_region_list == r) {
6391           // The last region.
6392           _dirty_cards_region_list = NULL;
6393         }
6394         r->set_next_dirty_cards_region(NULL);
6395       }
6396     }
6397 #ifndef PRODUCT
6398     if (G1VerifyCTCleanup || VerifyAfterGC) {
6399       G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
6400       heap_region_iterate(&cleanup_verifier);
6401     }
6402 #endif
6403   }
6404 
6405   double elapsed = os::elapsedTime() - start;
6406   g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
6407 }
6408 
6409 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) {
6410   size_t pre_used = 0;
6411   FreeRegionList local_free_list("Local List for CSet Freeing");
6412 
6413   double young_time_ms     = 0.0;
6414   double non_young_time_ms = 0.0;
6415 
6416   // Since the collection set is a superset of the the young list,
6417   // all we need to do to clear the young list is clear its
6418   // head and length, and unlink any young regions in the code below
6419   _young_list->clear();
6420 
6421   G1CollectorPolicy* policy = g1_policy();
6422 
6423   double start_sec = os::elapsedTime();
6424   bool non_young = true;
6425 
6426   HeapRegion* cur = cs_head;
6427   int age_bound = -1;
6428   size_t rs_lengths = 0;
6429 
6430   while (cur != NULL) {
6431     assert(!is_on_master_free_list(cur), "sanity");
6432     if (non_young) {
6433       if (cur->is_young()) {
6434         double end_sec = os::elapsedTime();
6435         double elapsed_ms = (end_sec - start_sec) * 1000.0;
6436         non_young_time_ms += elapsed_ms;
6437 
6438         start_sec = os::elapsedTime();
6439         non_young = false;
6440       }
6441     } else {
6442       if (!cur->is_young()) {
6443         double end_sec = os::elapsedTime();
6444         double elapsed_ms = (end_sec - start_sec) * 1000.0;
6445         young_time_ms += elapsed_ms;
6446 
6447         start_sec = os::elapsedTime();
6448         non_young = true;
6449       }
6450     }
6451 
6452     rs_lengths += cur->rem_set()->occupied_locked();
6453 
6454     HeapRegion* next = cur->next_in_collection_set();
6455     assert(cur->in_collection_set(), "bad CS");
6456     cur->set_next_in_collection_set(NULL);
6457     cur->set_in_collection_set(false);
6458 
6459     if (cur->is_young()) {
6460       int index = cur->young_index_in_cset();
6461       assert(index != -1, "invariant");
6462       assert((uint) index < policy->young_cset_region_length(), "invariant");
6463       size_t words_survived = _surviving_young_words[index];
6464       cur->record_surv_words_in_group(words_survived);
6465 
6466       // At this point the we have 'popped' cur from the collection set
6467       // (linked via next_in_collection_set()) but it is still in the
6468       // young list (linked via next_young_region()). Clear the
6469       // _next_young_region field.
6470       cur->set_next_young_region(NULL);
6471     } else {
6472       int index = cur->young_index_in_cset();
6473       assert(index == -1, "invariant");
6474     }
6475 
6476     assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
6477             (!cur->is_young() && cur->young_index_in_cset() == -1),
6478             "invariant" );
6479 
6480     if (!cur->evacuation_failed()) {
6481       MemRegion used_mr = cur->used_region();
6482 
6483       // And the region is empty.
6484       assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
6485       pre_used += cur->used();
6486       free_region(cur, &local_free_list, false /* par */, true /* locked */);
6487     } else {
6488       cur->uninstall_surv_rate_group();
6489       if (cur->is_young()) {
6490         cur->set_young_index_in_cset(-1);
6491       }
6492       cur->set_not_young();
6493       cur->set_evacuation_failed(false);
6494       // The region is now considered to be old.
6495       _old_set.add(cur);
6496       evacuation_info.increment_collectionset_used_after(cur->used());
6497     }
6498     cur = next;
6499   }
6500 
6501   evacuation_info.set_regions_freed(local_free_list.length());
6502   policy->record_max_rs_lengths(rs_lengths);
6503   policy->cset_regions_freed();
6504 
6505   double end_sec = os::elapsedTime();
6506   double elapsed_ms = (end_sec - start_sec) * 1000.0;
6507 
6508   if (non_young) {
6509     non_young_time_ms += elapsed_ms;
6510   } else {
6511     young_time_ms += elapsed_ms;
6512   }
6513 
6514   prepend_to_freelist(&local_free_list);
6515   decrement_summary_bytes(pre_used);
6516   policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
6517   policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
6518 }
6519 
6520 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
6521  private:
6522   FreeRegionList* _free_region_list;
6523   HeapRegionSet* _proxy_set;
6524   HeapRegionSetCount _humongous_regions_removed;
6525   size_t _freed_bytes;
6526  public:
6527 
6528   G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
6529     _free_region_list(free_region_list), _humongous_regions_removed(), _freed_bytes(0) {
6530   }
6531 
6532   virtual bool doHeapRegion(HeapRegion* r) {
6533     if (!r->startsHumongous()) {
6534       return false;
6535     }
6536 
6537     G1CollectedHeap* g1h = G1CollectedHeap::heap();
6538 
6539     // The following checks whether the humongous object is live are sufficient.
6540     // The main additional check (in addition to having a reference from the roots
6541     // or the young gen) is whether the humongous object has a remembered set entry.
6542     //
6543     // A humongous object cannot be live if there is no remembered set for it
6544     // because:
6545     // - there can be no references from within humongous starts regions referencing
6546     // the object because we never allocate other objects into them.
6547     // (I.e. there are no intra-region references that may be missed by the
6548     // remembered set)
6549     // - as soon there is a remembered set entry to the humongous starts region
6550     // (i.e. it has "escaped" to an old object) this remembered set entry will stay
6551     // until the end of a concurrent mark.
6552     //
6553     // It is not required to check whether the object has been found dead by marking
6554     // or not, in fact it would prevent reclamation within a concurrent cycle, as
6555     // all objects allocated during that time are considered live.
6556     // SATB marking is even more conservative than the remembered set.
6557     // So if at this point in the collection there is no remembered set entry,
6558     // nobody has a reference to it.
6559     // At the start of collection we flush all refinement logs, and remembered sets
6560     // are completely up-to-date wrt to references to the humongous object.
6561     //
6562     // Other implementation considerations:
6563     // - never consider object arrays: while they are a valid target, they have not
6564     // been observed to be used as temporary objects.
6565     // - they would also pose considerable effort for cleaning up the the remembered
6566     // sets.
6567     // While this cleanup is not strictly necessary to be done (or done instantly),
6568     // given that their occurrence is very low, this saves us this additional
6569     // complexity.
6570     uint region_idx = r->hrs_index();
6571     if (g1h->humongous_is_live(region_idx) ||
6572         g1h->humongous_region_is_always_live(region_idx)) {
6573 
6574       if (G1TraceReclaimDeadHumongousObjectsAtYoungGC) {
6575         gclog_or_tty->print_cr("Live humongous %d region %d with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is dead-bitmap %d live-other %d obj array %d",
6576                                r->isHumongous(),
6577                                region_idx,
6578                                r->rem_set()->occupied(),
6579                                r->rem_set()->strong_code_roots_list_length(),
6580                                g1h->mark_in_progress() && !g1h->g1_policy()->during_initial_mark_pause(),
6581                                g1h->humongous_is_live(region_idx),
6582                                oop(r->bottom())->is_objArray()
6583                               );
6584       }
6585 
6586       return false;
6587     }
6588 
6589     guarantee(!((oop)(r->bottom()))->is_objArray(),
6590               err_msg("Eagerly reclaiming object arrays is not supported, but the object "PTR_FORMAT" is.",
6591                       r->bottom()));
6592 
6593     if (G1TraceReclaimDeadHumongousObjectsAtYoungGC) {
6594       gclog_or_tty->print_cr("Reclaim humongous region %d start "PTR_FORMAT" region %d length "UINT32_FORMAT" with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is dead-bitmap %d live-other %d obj array %d",
6595                              r->isHumongous(),
6596                              r->bottom(),
6597                              region_idx,
6598                              r->region_num(),
6599                              r->rem_set()->occupied(),
6600                              r->rem_set()->strong_code_roots_list_length(),
6601                              g1h->mark_in_progress() && !g1h->g1_policy()->during_initial_mark_pause(),
6602                              g1h->humongous_is_live(region_idx),
6603                              oop(r->bottom())->is_objArray()
6604                             );
6605     }
6606     _freed_bytes += r->used();
6607     r->set_containing_set(NULL);
6608     _humongous_regions_removed.increment(1u, r->capacity());
6609     g1h->free_humongous_region(r, _free_region_list, false);
6610 
6611     return false;
6612   }
6613 
6614   HeapRegionSetCount& humongous_free_count() {
6615     return _humongous_regions_removed;
6616   }
6617 
6618   size_t bytes_freed() const {
6619     return _freed_bytes;
6620   }
6621 
6622   size_t humongous_reclaimed() const {
6623     return _humongous_regions_removed.length();
6624   }
6625 };
6626 
6627 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
6628   assert_at_safepoint(true);
6629 
6630   if (!G1ReclaimDeadHumongousObjectsAtYoungGC || !_has_humongous_reclaim_candidates) {
6631     g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
6632     return;
6633   }
6634 
6635   double start_time = os::elapsedTime();
6636 
6637   FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
6638 
6639   G1FreeHumongousRegionClosure cl(&local_cleanup_list);
6640   heap_region_iterate(&cl);
6641 
6642   HeapRegionSetCount empty_set;
6643   remove_from_old_sets(empty_set, cl.humongous_free_count());
6644 
6645   G1HRPrinter* hr_printer = _g1h->hr_printer();
6646   if (hr_printer->is_active()) {
6647     FreeRegionListIterator iter(&local_cleanup_list);
6648     while (iter.more_available()) {
6649       HeapRegion* hr = iter.get_next();
6650       hr_printer->cleanup(hr);
6651     }
6652   }
6653 
6654   prepend_to_freelist(&local_cleanup_list);
6655   decrement_summary_bytes(cl.bytes_freed());
6656 
6657   g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
6658                                                                     cl.humongous_reclaimed());
6659 }
6660 
6661 // This routine is similar to the above but does not record
6662 // any policy statistics or update free lists; we are abandoning
6663 // the current incremental collection set in preparation of a
6664 // full collection. After the full GC we will start to build up
6665 // the incremental collection set again.
6666 // This is only called when we're doing a full collection
6667 // and is immediately followed by the tearing down of the young list.
6668 
6669 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
6670   HeapRegion* cur = cs_head;
6671 
6672   while (cur != NULL) {
6673     HeapRegion* next = cur->next_in_collection_set();
6674     assert(cur->in_collection_set(), "bad CS");
6675     cur->set_next_in_collection_set(NULL);
6676     cur->set_in_collection_set(false);
6677     cur->set_young_index_in_cset(-1);
6678     cur = next;
6679   }
6680 }
6681 
6682 void G1CollectedHeap::set_free_regions_coming() {
6683   if (G1ConcRegionFreeingVerbose) {
6684     gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6685                            "setting free regions coming");
6686   }
6687 
6688   assert(!free_regions_coming(), "pre-condition");
6689   _free_regions_coming = true;
6690 }
6691 
6692 void G1CollectedHeap::reset_free_regions_coming() {
6693   assert(free_regions_coming(), "pre-condition");
6694 
6695   {
6696     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6697     _free_regions_coming = false;
6698     SecondaryFreeList_lock->notify_all();
6699   }
6700 
6701   if (G1ConcRegionFreeingVerbose) {
6702     gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6703                            "reset free regions coming");
6704   }
6705 }
6706 
6707 void G1CollectedHeap::wait_while_free_regions_coming() {
6708   // Most of the time we won't have to wait, so let's do a quick test
6709   // first before we take the lock.
6710   if (!free_regions_coming()) {
6711     return;
6712   }
6713 
6714   if (G1ConcRegionFreeingVerbose) {
6715     gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6716                            "waiting for free regions");
6717   }
6718 
6719   {
6720     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6721     while (free_regions_coming()) {
6722       SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
6723     }
6724   }
6725 
6726   if (G1ConcRegionFreeingVerbose) {
6727     gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6728                            "done waiting for free regions");
6729   }
6730 }
6731 
6732 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
6733   assert(heap_lock_held_for_gc(),
6734               "the heap lock should already be held by or for this thread");
6735   _young_list->push_region(hr);
6736 }
6737 
6738 class NoYoungRegionsClosure: public HeapRegionClosure {
6739 private:
6740   bool _success;
6741 public:
6742   NoYoungRegionsClosure() : _success(true) { }
6743   bool doHeapRegion(HeapRegion* r) {
6744     if (r->is_young()) {
6745       gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
6746                              r->bottom(), r->end());
6747       _success = false;
6748     }
6749     return false;
6750   }
6751   bool success() { return _success; }
6752 };
6753 
6754 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
6755   bool ret = _young_list->check_list_empty(check_sample);
6756 
6757   if (check_heap) {
6758     NoYoungRegionsClosure closure;
6759     heap_region_iterate(&closure);
6760     ret = ret && closure.success();
6761   }
6762 
6763   return ret;
6764 }
6765 
6766 class TearDownRegionSetsClosure : public HeapRegionClosure {
6767 private:
6768   HeapRegionSet *_old_set;
6769 
6770 public:
6771   TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
6772 
6773   bool doHeapRegion(HeapRegion* r) {
6774     if (r->is_empty()) {
6775       // We ignore empty regions, we'll empty the free list afterwards
6776     } else if (r->is_young()) {
6777       // We ignore young regions, we'll empty the young list afterwards
6778     } else if (r->isHumongous()) {
6779       // We ignore humongous regions, we're not tearing down the
6780       // humongous region set
6781     } else {
6782       // The rest should be old
6783       _old_set->remove(r);
6784     }
6785     return false;
6786   }
6787 
6788   ~TearDownRegionSetsClosure() {
6789     assert(_old_set->is_empty(), "post-condition");
6790   }
6791 };
6792 
6793 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6794   assert_at_safepoint(true /* should_be_vm_thread */);
6795 
6796   if (!free_list_only) {
6797     TearDownRegionSetsClosure cl(&_old_set);
6798     heap_region_iterate(&cl);
6799 
6800     // Note that emptying the _young_list is postponed and instead done as
6801     // the first step when rebuilding the regions sets again. The reason for
6802     // this is that during a full GC string deduplication needs to know if
6803     // a collected region was young or old when the full GC was initiated.
6804   }
6805   _free_list.remove_all();
6806 }
6807 
6808 class RebuildRegionSetsClosure : public HeapRegionClosure {
6809 private:
6810   bool            _free_list_only;
6811   HeapRegionSet*   _old_set;
6812   FreeRegionList* _free_list;
6813   size_t          _total_used;
6814 
6815 public:
6816   RebuildRegionSetsClosure(bool free_list_only,
6817                            HeapRegionSet* old_set, FreeRegionList* free_list) :
6818     _free_list_only(free_list_only),
6819     _old_set(old_set), _free_list(free_list), _total_used(0) {
6820     assert(_free_list->is_empty(), "pre-condition");
6821     if (!free_list_only) {
6822       assert(_old_set->is_empty(), "pre-condition");
6823     }
6824   }
6825 
6826   bool doHeapRegion(HeapRegion* r) {
6827     if (r->continuesHumongous()) {
6828       return false;
6829     }
6830 
6831     if (r->is_empty()) {
6832       // Add free regions to the free list
6833       _free_list->add_as_tail(r);
6834     } else if (!_free_list_only) {
6835       assert(!r->is_young(), "we should not come across young regions");
6836 
6837       if (r->isHumongous()) {
6838         // We ignore humongous regions, we left the humongous set unchanged
6839       } else {
6840         // The rest should be old, add them to the old set
6841         _old_set->add(r);
6842       }
6843       _total_used += r->used();
6844     }
6845 
6846     return false;
6847   }
6848 
6849   size_t total_used() {
6850     return _total_used;
6851   }
6852 };
6853 
6854 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6855   assert_at_safepoint(true /* should_be_vm_thread */);
6856 
6857   if (!free_list_only) {
6858     _young_list->empty_list();
6859   }
6860 
6861   RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_free_list);
6862   heap_region_iterate(&cl);
6863 
6864   if (!free_list_only) {
6865     _summary_bytes_used = cl.total_used();
6866   }
6867   assert(_summary_bytes_used == recalculate_used(),
6868          err_msg("inconsistent _summary_bytes_used, "
6869                  "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6870                  _summary_bytes_used, recalculate_used()));
6871 }
6872 
6873 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6874   _refine_cte_cl->set_concurrent(concurrent);
6875 }
6876 
6877 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6878   HeapRegion* hr = heap_region_containing(p);
6879   return hr->is_in(p);
6880 }
6881 
6882 // Methods for the mutator alloc region
6883 
6884 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6885                                                       bool force) {
6886   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6887   assert(!force || g1_policy()->can_expand_young_list(),
6888          "if force is true we should be able to expand the young list");
6889   bool young_list_full = g1_policy()->is_young_list_full();
6890   if (force || !young_list_full) {
6891     HeapRegion* new_alloc_region = new_region(word_size,
6892                                               false /* is_old */,
6893                                               false /* do_expand */);
6894     if (new_alloc_region != NULL) {
6895       set_region_short_lived_locked(new_alloc_region);
6896       _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6897       check_bitmaps("Mutator Region Allocation", new_alloc_region);
6898       return new_alloc_region;
6899     }
6900   }
6901   return NULL;
6902 }
6903 
6904 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6905                                                   size_t allocated_bytes) {
6906   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6907   assert(alloc_region->is_young(), "all mutator alloc regions should be young");
6908 
6909   g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6910   _summary_bytes_used += allocated_bytes;
6911   _hr_printer.retire(alloc_region);
6912   // We update the eden sizes here, when the region is retired,
6913   // instead of when it's allocated, since this is the point that its
6914   // used space has been recored in _summary_bytes_used.
6915   g1mm()->update_eden_size();
6916 }
6917 
6918 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
6919                                                     bool force) {
6920   return _g1h->new_mutator_alloc_region(word_size, force);
6921 }
6922 
6923 void G1CollectedHeap::set_par_threads() {
6924   // Don't change the number of workers.  Use the value previously set
6925   // in the workgroup.
6926   assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise");
6927   uint n_workers = workers()->active_workers();
6928   assert(UseDynamicNumberOfGCThreads ||
6929            n_workers == workers()->total_workers(),
6930       "Otherwise should be using the total number of workers");
6931   if (n_workers == 0) {
6932     assert(false, "Should have been set in prior evacuation pause.");
6933     n_workers = ParallelGCThreads;
6934     workers()->set_active_workers(n_workers);
6935   }
6936   set_par_threads(n_workers);
6937 }
6938 
6939 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
6940                                        size_t allocated_bytes) {
6941   _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
6942 }
6943 
6944 // Methods for the GC alloc regions
6945 
6946 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6947                                                  uint count,
6948                                                  GCAllocPurpose ap) {
6949   assert(FreeList_lock->owned_by_self(), "pre-condition");
6950 
6951   if (count < g1_policy()->max_regions(ap)) {
6952     bool survivor = (ap == GCAllocForSurvived);
6953     HeapRegion* new_alloc_region = new_region(word_size,
6954                                               !survivor,
6955                                               true /* do_expand */);
6956     if (new_alloc_region != NULL) {
6957       // We really only need to do this for old regions given that we
6958       // should never scan survivors. But it doesn't hurt to do it
6959       // for survivors too.
6960       new_alloc_region->record_top_and_timestamp();
6961       if (survivor) {
6962         new_alloc_region->set_survivor();
6963         _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6964         check_bitmaps("Survivor Region Allocation", new_alloc_region);
6965       } else {
6966         _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6967         check_bitmaps("Old Region Allocation", new_alloc_region);
6968       }
6969       bool during_im = g1_policy()->during_initial_mark_pause();
6970       new_alloc_region->note_start_of_copying(during_im);
6971       return new_alloc_region;
6972     } else {
6973       g1_policy()->note_alloc_region_limit_reached(ap);
6974     }
6975   }
6976   return NULL;
6977 }
6978 
6979 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6980                                              size_t allocated_bytes,
6981                                              GCAllocPurpose ap) {
6982   bool during_im = g1_policy()->during_initial_mark_pause();
6983   alloc_region->note_end_of_copying(during_im);
6984   g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6985   if (ap == GCAllocForSurvived) {
6986     young_list()->add_survivor_region(alloc_region);
6987   } else {
6988     _old_set.add(alloc_region);
6989   }
6990   _hr_printer.retire(alloc_region);
6991 }
6992 
6993 HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size,
6994                                                        bool force) {
6995   assert(!force, "not supported for GC alloc regions");
6996   return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForSurvived);
6997 }
6998 
6999 void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region,
7000                                           size_t allocated_bytes) {
7001   _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
7002                                GCAllocForSurvived);
7003 }
7004 
7005 HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size,
7006                                                   bool force) {
7007   assert(!force, "not supported for GC alloc regions");
7008   return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForTenured);
7009 }
7010 
7011 void OldGCAllocRegion::retire_region(HeapRegion* alloc_region,
7012                                      size_t allocated_bytes) {
7013   _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
7014                                GCAllocForTenured);
7015 }
7016 // Heap region set verification
7017 
7018 class VerifyRegionListsClosure : public HeapRegionClosure {
7019 private:
7020   HeapRegionSet*   _old_set;
7021   HeapRegionSet*   _humongous_set;
7022   FreeRegionList*  _free_list;
7023 
7024 public:
7025   HeapRegionSetCount _old_count;
7026   HeapRegionSetCount _humongous_count;
7027   HeapRegionSetCount _free_count;
7028 
7029   VerifyRegionListsClosure(HeapRegionSet* old_set,
7030                            HeapRegionSet* humongous_set,
7031                            FreeRegionList* free_list) :
7032     _old_set(old_set), _humongous_set(humongous_set), _free_list(free_list),
7033     _old_count(), _humongous_count(), _free_count(){ }
7034 
7035   bool doHeapRegion(HeapRegion* hr) {
7036     if (hr->continuesHumongous()) {
7037       return false;
7038     }
7039 
7040     if (hr->is_young()) {
7041       // TODO
7042     } else if (hr->startsHumongous()) {
7043       assert(hr->containing_set() == _humongous_set, err_msg("Heap region %u is starts humongous but not in humongous set.", hr->hrs_index()));
7044       _humongous_count.increment(1u, hr->capacity());
7045     } else if (hr->is_empty()) {
7046       assert(hr->containing_set() == _free_list, err_msg("Heap region %u is empty but not on the free list.", hr->hrs_index()));
7047       _free_count.increment(1u, hr->capacity());
7048     } else {
7049       assert(hr->containing_set() == _old_set, err_msg("Heap region %u is old but not in the old set.", hr->hrs_index()));
7050       _old_count.increment(1u, hr->capacity());
7051     }
7052     return false;
7053   }
7054 
7055   void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, FreeRegionList* free_list) {
7056     guarantee(old_set->length() == _old_count.length(), err_msg("Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length()));
7057     guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), err_msg("Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
7058         old_set->total_capacity_bytes(), _old_count.capacity()));
7059 
7060     guarantee(humongous_set->length() == _humongous_count.length(), err_msg("Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length()));
7061     guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), err_msg("Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
7062         humongous_set->total_capacity_bytes(), _humongous_count.capacity()));
7063 
7064     guarantee(free_list->length() == _free_count.length(), err_msg("Free list count mismatch. Expected %u, actual %u.", free_list->length(), _free_count.length()));
7065     guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), err_msg("Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
7066         free_list->total_capacity_bytes(), _free_count.capacity()));
7067   }
7068 };
7069 
7070 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
7071                                              HeapWord* bottom) {
7072   HeapWord* end = bottom + HeapRegion::GrainWords;
7073   MemRegion mr(bottom, end);
7074   assert(_g1_reserved.contains(mr), "invariant");
7075   // This might return NULL if the allocation fails
7076   return new HeapRegion(hrs_index, _bot_shared, mr);
7077 }
7078 
7079 void G1CollectedHeap::verify_region_sets() {
7080   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
7081 
7082   // First, check the explicit lists.
7083   _free_list.verify_list();
7084   {
7085     // Given that a concurrent operation might be adding regions to
7086     // the secondary free list we have to take the lock before
7087     // verifying it.
7088     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
7089     _secondary_free_list.verify_list();
7090   }
7091 
7092   // If a concurrent region freeing operation is in progress it will
7093   // be difficult to correctly attributed any free regions we come
7094   // across to the correct free list given that they might belong to
7095   // one of several (free_list, secondary_free_list, any local lists,
7096   // etc.). So, if that's the case we will skip the rest of the
7097   // verification operation. Alternatively, waiting for the concurrent
7098   // operation to complete will have a non-trivial effect on the GC's
7099   // operation (no concurrent operation will last longer than the
7100   // interval between two calls to verification) and it might hide
7101   // any issues that we would like to catch during testing.
7102   if (free_regions_coming()) {
7103     return;
7104   }
7105 
7106   // Make sure we append the secondary_free_list on the free_list so
7107   // that all free regions we will come across can be safely
7108   // attributed to the free_list.
7109   append_secondary_free_list_if_not_empty_with_lock();
7110 
7111   // Finally, make sure that the region accounting in the lists is
7112   // consistent with what we see in the heap.
7113 
7114   VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_free_list);
7115   heap_region_iterate(&cl);
7116   cl.verify_counts(&_old_set, &_humongous_set, &_free_list);
7117 }
7118 
7119 // Optimized nmethod scanning
7120 
7121 class RegisterNMethodOopClosure: public OopClosure {
7122   G1CollectedHeap* _g1h;
7123   nmethod* _nm;
7124 
7125   template <class T> void do_oop_work(T* p) {
7126     T heap_oop = oopDesc::load_heap_oop(p);
7127     if (!oopDesc::is_null(heap_oop)) {
7128       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
7129       HeapRegion* hr = _g1h->heap_region_containing(obj);
7130       assert(!hr->continuesHumongous(),
7131              err_msg("trying to add code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
7132                      " starting at "HR_FORMAT,
7133                      _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
7134 
7135       // HeapRegion::add_strong_code_root() avoids adding duplicate
7136       // entries but having duplicates is  OK since we "mark" nmethods
7137       // as visited when we scan the strong code root lists during the GC.
7138       hr->add_strong_code_root(_nm);
7139       assert(hr->rem_set()->strong_code_roots_list_contains(_nm),
7140              err_msg("failed to add code root "PTR_FORMAT" to remembered set of region "HR_FORMAT,
7141                      _nm, HR_FORMAT_PARAMS(hr)));
7142     }
7143   }
7144 
7145 public:
7146   RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
7147     _g1h(g1h), _nm(nm) {}
7148 
7149   void do_oop(oop* p)       { do_oop_work(p); }
7150   void do_oop(narrowOop* p) { do_oop_work(p); }
7151 };
7152 
7153 class UnregisterNMethodOopClosure: public OopClosure {
7154   G1CollectedHeap* _g1h;
7155   nmethod* _nm;
7156 
7157   template <class T> void do_oop_work(T* p) {
7158     T heap_oop = oopDesc::load_heap_oop(p);
7159     if (!oopDesc::is_null(heap_oop)) {
7160       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
7161       HeapRegion* hr = _g1h->heap_region_containing(obj);
7162       assert(!hr->continuesHumongous(),
7163              err_msg("trying to remove code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
7164                      " starting at "HR_FORMAT,
7165                      _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
7166 
7167       hr->remove_strong_code_root(_nm);
7168       assert(!hr->rem_set()->strong_code_roots_list_contains(_nm),
7169              err_msg("failed to remove code root "PTR_FORMAT" of region "HR_FORMAT,
7170                      _nm, HR_FORMAT_PARAMS(hr)));
7171     }
7172   }
7173 
7174 public:
7175   UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
7176     _g1h(g1h), _nm(nm) {}
7177 
7178   void do_oop(oop* p)       { do_oop_work(p); }
7179   void do_oop(narrowOop* p) { do_oop_work(p); }
7180 };
7181 
7182 void G1CollectedHeap::register_nmethod(nmethod* nm) {
7183   CollectedHeap::register_nmethod(nm);
7184 
7185   guarantee(nm != NULL, "sanity");
7186   RegisterNMethodOopClosure reg_cl(this, nm);
7187   nm->oops_do(&reg_cl);
7188 }
7189 
7190 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
7191   CollectedHeap::unregister_nmethod(nm);
7192 
7193   guarantee(nm != NULL, "sanity");
7194   UnregisterNMethodOopClosure reg_cl(this, nm);
7195   nm->oops_do(&reg_cl, true);
7196 }
7197 
7198 class MigrateCodeRootsHeapRegionClosure: public HeapRegionClosure {
7199 public:
7200   bool doHeapRegion(HeapRegion *hr) {
7201     assert(!hr->isHumongous(),
7202            err_msg("humongous region "HR_FORMAT" should not have been added to collection set",
7203                    HR_FORMAT_PARAMS(hr)));
7204     hr->migrate_strong_code_roots();
7205     return false;
7206   }
7207 };
7208 
7209 void G1CollectedHeap::migrate_strong_code_roots() {
7210   MigrateCodeRootsHeapRegionClosure cl;
7211   double migrate_start = os::elapsedTime();
7212   collection_set_iterate(&cl);
7213   double migration_time_ms = (os::elapsedTime() - migrate_start) * 1000.0;
7214   g1_policy()->phase_times()->record_strong_code_root_migration_time(migration_time_ms);
7215 }
7216 
7217 void G1CollectedHeap::purge_code_root_memory() {
7218   double purge_start = os::elapsedTime();
7219   G1CodeRootSet::purge_chunks(G1CodeRootsChunkCacheKeepPercent);
7220   double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
7221   g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
7222 }
7223 
7224 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
7225   G1CollectedHeap* _g1h;
7226 
7227 public:
7228   RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
7229     _g1h(g1h) {}
7230 
7231   void do_code_blob(CodeBlob* cb) {
7232     nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
7233     if (nm == NULL) {
7234       return;
7235     }
7236 
7237     if (ScavengeRootsInCode) {
7238       _g1h->register_nmethod(nm);
7239     }
7240   }
7241 };
7242 
7243 void G1CollectedHeap::rebuild_strong_code_roots() {
7244   RebuildStrongCodeRootClosure blob_cl(this);
7245   CodeCache::blobs_do(&blob_cl);
7246 }