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   _humongous_is_live.clear();
2185 }
2186 
2187 size_t G1CollectedHeap::conservative_max_heap_alignment() {
2188   return HeapRegion::max_region_size();
2189 }
2190 
2191 void G1CollectedHeap::ref_processing_init() {
2192   // Reference processing in G1 currently works as follows:
2193   //
2194   // * There are two reference processor instances. One is
2195   //   used to record and process discovered references
2196   //   during concurrent marking; the other is used to
2197   //   record and process references during STW pauses
2198   //   (both full and incremental).
2199   // * Both ref processors need to 'span' the entire heap as
2200   //   the regions in the collection set may be dotted around.
2201   //
2202   // * For the concurrent marking ref processor:
2203   //   * Reference discovery is enabled at initial marking.
2204   //   * Reference discovery is disabled and the discovered
2205   //     references processed etc during remarking.
2206   //   * Reference discovery is MT (see below).
2207   //   * Reference discovery requires a barrier (see below).
2208   //   * Reference processing may or may not be MT
2209   //     (depending on the value of ParallelRefProcEnabled
2210   //     and ParallelGCThreads).
2211   //   * A full GC disables reference discovery by the CM
2212   //     ref processor and abandons any entries on it's
2213   //     discovered lists.
2214   //
2215   // * For the STW processor:
2216   //   * Non MT discovery is enabled at the start of a full GC.
2217   //   * Processing and enqueueing during a full GC is non-MT.
2218   //   * During a full GC, references are processed after marking.
2219   //
2220   //   * Discovery (may or may not be MT) is enabled at the start
2221   //     of an incremental evacuation pause.
2222   //   * References are processed near the end of a STW evacuation pause.
2223   //   * For both types of GC:
2224   //     * Discovery is atomic - i.e. not concurrent.
2225   //     * Reference discovery will not need a barrier.
2226 
2227   SharedHeap::ref_processing_init();
2228   MemRegion mr = reserved_region();
2229 
2230   // Concurrent Mark ref processor
2231   _ref_processor_cm =
2232     new ReferenceProcessor(mr,    // span
2233                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2234                                 // mt processing
2235                            (int) ParallelGCThreads,
2236                                 // degree of mt processing
2237                            (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2238                                 // mt discovery
2239                            (int) MAX2(ParallelGCThreads, ConcGCThreads),
2240                                 // degree of mt discovery
2241                            false,
2242                                 // Reference discovery is not atomic
2243                            &_is_alive_closure_cm);
2244                                 // is alive closure
2245                                 // (for efficiency/performance)
2246 
2247   // STW ref processor
2248   _ref_processor_stw =
2249     new ReferenceProcessor(mr,    // span
2250                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2251                                 // mt processing
2252                            MAX2((int)ParallelGCThreads, 1),
2253                                 // degree of mt processing
2254                            (ParallelGCThreads > 1),
2255                                 // mt discovery
2256                            MAX2((int)ParallelGCThreads, 1),
2257                                 // degree of mt discovery
2258                            true,
2259                                 // Reference discovery is atomic
2260                            &_is_alive_closure_stw);
2261                                 // is alive closure
2262                                 // (for efficiency/performance)
2263 }
2264 
2265 size_t G1CollectedHeap::capacity() const {
2266   return _g1_committed.byte_size();
2267 }
2268 
2269 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2270   assert(!hr->continuesHumongous(), "pre-condition");
2271   hr->reset_gc_time_stamp();
2272   if (hr->startsHumongous()) {
2273     uint first_index = hr->hrs_index() + 1;
2274     uint last_index = hr->last_hc_index();
2275     for (uint i = first_index; i < last_index; i += 1) {
2276       HeapRegion* chr = region_at(i);
2277       assert(chr->continuesHumongous(), "sanity");
2278       chr->reset_gc_time_stamp();
2279     }
2280   }
2281 }
2282 
2283 #ifndef PRODUCT
2284 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2285 private:
2286   unsigned _gc_time_stamp;
2287   bool _failures;
2288 
2289 public:
2290   CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2291     _gc_time_stamp(gc_time_stamp), _failures(false) { }
2292 
2293   virtual bool doHeapRegion(HeapRegion* hr) {
2294     unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2295     if (_gc_time_stamp != region_gc_time_stamp) {
2296       gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, "
2297                              "expected %d", HR_FORMAT_PARAMS(hr),
2298                              region_gc_time_stamp, _gc_time_stamp);
2299       _failures = true;
2300     }
2301     return false;
2302   }
2303 
2304   bool failures() { return _failures; }
2305 };
2306 
2307 void G1CollectedHeap::check_gc_time_stamps() {
2308   CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2309   heap_region_iterate(&cl);
2310   guarantee(!cl.failures(), "all GC time stamps should have been reset");
2311 }
2312 #endif // PRODUCT
2313 
2314 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2315                                                  DirtyCardQueue* into_cset_dcq,
2316                                                  bool concurrent,
2317                                                  uint worker_i) {
2318   // Clean cards in the hot card cache
2319   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
2320   hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq);
2321 
2322   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2323   int n_completed_buffers = 0;
2324   while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2325     n_completed_buffers++;
2326   }
2327   g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers);
2328   dcqs.clear_n_completed_buffers();
2329   assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2330 }
2331 
2332 
2333 // Computes the sum of the storage used by the various regions.
2334 
2335 size_t G1CollectedHeap::used() const {
2336   assert(Heap_lock->owner() != NULL,
2337          "Should be owned on this thread's behalf.");
2338   size_t result = _summary_bytes_used;
2339   // Read only once in case it is set to NULL concurrently
2340   HeapRegion* hr = _mutator_alloc_region.get();
2341   if (hr != NULL)
2342     result += hr->used();
2343   return result;
2344 }
2345 
2346 size_t G1CollectedHeap::used_unlocked() const {
2347   size_t result = _summary_bytes_used;
2348   return result;
2349 }
2350 
2351 class SumUsedClosure: public HeapRegionClosure {
2352   size_t _used;
2353 public:
2354   SumUsedClosure() : _used(0) {}
2355   bool doHeapRegion(HeapRegion* r) {
2356     if (!r->continuesHumongous()) {
2357       _used += r->used();
2358     }
2359     return false;
2360   }
2361   size_t result() { return _used; }
2362 };
2363 
2364 size_t G1CollectedHeap::recalculate_used() const {
2365   double recalculate_used_start = os::elapsedTime();
2366 
2367   SumUsedClosure blk;
2368   heap_region_iterate(&blk);
2369 
2370   g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2371   return blk.result();
2372 }
2373 
2374 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2375   switch (cause) {
2376     case GCCause::_gc_locker:               return GCLockerInvokesConcurrent;
2377     case GCCause::_java_lang_system_gc:     return ExplicitGCInvokesConcurrent;
2378     case GCCause::_g1_humongous_allocation: return true;
2379     default:                                return false;
2380   }
2381 }
2382 
2383 #ifndef PRODUCT
2384 void G1CollectedHeap::allocate_dummy_regions() {
2385   // Let's fill up most of the region
2386   size_t word_size = HeapRegion::GrainWords - 1024;
2387   // And as a result the region we'll allocate will be humongous.
2388   guarantee(isHumongous(word_size), "sanity");
2389 
2390   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2391     // Let's use the existing mechanism for the allocation
2392     HeapWord* dummy_obj = humongous_obj_allocate(word_size);
2393     if (dummy_obj != NULL) {
2394       MemRegion mr(dummy_obj, word_size);
2395       CollectedHeap::fill_with_object(mr);
2396     } else {
2397       // If we can't allocate once, we probably cannot allocate
2398       // again. Let's get out of the loop.
2399       break;
2400     }
2401   }
2402 }
2403 #endif // !PRODUCT
2404 
2405 void G1CollectedHeap::increment_old_marking_cycles_started() {
2406   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2407     _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2408     err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2409     _old_marking_cycles_started, _old_marking_cycles_completed));
2410 
2411   _old_marking_cycles_started++;
2412 }
2413 
2414 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2415   MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2416 
2417   // We assume that if concurrent == true, then the caller is a
2418   // concurrent thread that was joined the Suspendible Thread
2419   // Set. If there's ever a cheap way to check this, we should add an
2420   // assert here.
2421 
2422   // Given that this method is called at the end of a Full GC or of a
2423   // concurrent cycle, and those can be nested (i.e., a Full GC can
2424   // interrupt a concurrent cycle), the number of full collections
2425   // completed should be either one (in the case where there was no
2426   // nesting) or two (when a Full GC interrupted a concurrent cycle)
2427   // behind the number of full collections started.
2428 
2429   // This is the case for the inner caller, i.e. a Full GC.
2430   assert(concurrent ||
2431          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2432          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2433          err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
2434                  "is inconsistent with _old_marking_cycles_completed = %u",
2435                  _old_marking_cycles_started, _old_marking_cycles_completed));
2436 
2437   // This is the case for the outer caller, i.e. the concurrent cycle.
2438   assert(!concurrent ||
2439          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2440          err_msg("for outer caller (concurrent cycle): "
2441                  "_old_marking_cycles_started = %u "
2442                  "is inconsistent with _old_marking_cycles_completed = %u",
2443                  _old_marking_cycles_started, _old_marking_cycles_completed));
2444 
2445   _old_marking_cycles_completed += 1;
2446 
2447   // We need to clear the "in_progress" flag in the CM thread before
2448   // we wake up any waiters (especially when ExplicitInvokesConcurrent
2449   // is set) so that if a waiter requests another System.gc() it doesn't
2450   // incorrectly see that a marking cycle is still in progress.
2451   if (concurrent) {
2452     _cmThread->clear_in_progress();
2453   }
2454 
2455   // This notify_all() will ensure that a thread that called
2456   // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2457   // and it's waiting for a full GC to finish will be woken up. It is
2458   // waiting in VM_G1IncCollectionPause::doit_epilogue().
2459   FullGCCount_lock->notify_all();
2460 }
2461 
2462 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) {
2463   _concurrent_cycle_started = true;
2464   _gc_timer_cm->register_gc_start(start_time);
2465 
2466   _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start());
2467   trace_heap_before_gc(_gc_tracer_cm);
2468 }
2469 
2470 void G1CollectedHeap::register_concurrent_cycle_end() {
2471   if (_concurrent_cycle_started) {
2472     if (_cm->has_aborted()) {
2473       _gc_tracer_cm->report_concurrent_mode_failure();
2474     }
2475 
2476     _gc_timer_cm->register_gc_end();
2477     _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
2478 
2479     _concurrent_cycle_started = false;
2480   }
2481 }
2482 
2483 void G1CollectedHeap::trace_heap_after_concurrent_cycle() {
2484   if (_concurrent_cycle_started) {
2485     trace_heap_after_gc(_gc_tracer_cm);
2486   }
2487 }
2488 
2489 G1YCType G1CollectedHeap::yc_type() {
2490   bool is_young = g1_policy()->gcs_are_young();
2491   bool is_initial_mark = g1_policy()->during_initial_mark_pause();
2492   bool is_during_mark = mark_in_progress();
2493 
2494   if (is_initial_mark) {
2495     return InitialMark;
2496   } else if (is_during_mark) {
2497     return DuringMark;
2498   } else if (is_young) {
2499     return Normal;
2500   } else {
2501     return Mixed;
2502   }
2503 }
2504 
2505 void G1CollectedHeap::collect(GCCause::Cause cause) {
2506   assert_heap_not_locked();
2507 
2508   unsigned int gc_count_before;
2509   unsigned int old_marking_count_before;
2510   bool retry_gc;
2511 
2512   do {
2513     retry_gc = false;
2514 
2515     {
2516       MutexLocker ml(Heap_lock);
2517 
2518       // Read the GC count while holding the Heap_lock
2519       gc_count_before = total_collections();
2520       old_marking_count_before = _old_marking_cycles_started;
2521     }
2522 
2523     if (should_do_concurrent_full_gc(cause)) {
2524       // Schedule an initial-mark evacuation pause that will start a
2525       // concurrent cycle. We're setting word_size to 0 which means that
2526       // we are not requesting a post-GC allocation.
2527       VM_G1IncCollectionPause op(gc_count_before,
2528                                  0,     /* word_size */
2529                                  true,  /* should_initiate_conc_mark */
2530                                  g1_policy()->max_pause_time_ms(),
2531                                  cause);
2532 
2533       VMThread::execute(&op);
2534       if (!op.pause_succeeded()) {
2535         if (old_marking_count_before == _old_marking_cycles_started) {
2536           retry_gc = op.should_retry_gc();
2537         } else {
2538           // A Full GC happened while we were trying to schedule the
2539           // initial-mark GC. No point in starting a new cycle given
2540           // that the whole heap was collected anyway.
2541         }
2542 
2543         if (retry_gc) {
2544           if (GC_locker::is_active_and_needs_gc()) {
2545             GC_locker::stall_until_clear();
2546           }
2547         }
2548       }
2549     } else {
2550       if (cause == GCCause::_gc_locker
2551           DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2552 
2553         // Schedule a standard evacuation pause. We're setting word_size
2554         // to 0 which means that we are not requesting a post-GC allocation.
2555         VM_G1IncCollectionPause op(gc_count_before,
2556                                    0,     /* word_size */
2557                                    false, /* should_initiate_conc_mark */
2558                                    g1_policy()->max_pause_time_ms(),
2559                                    cause);
2560         VMThread::execute(&op);
2561       } else {
2562         // Schedule a Full GC.
2563         VM_G1CollectFull op(gc_count_before, old_marking_count_before, cause);
2564         VMThread::execute(&op);
2565       }
2566     }
2567   } while (retry_gc);
2568 }
2569 
2570 bool G1CollectedHeap::is_in(const void* p) const {
2571   if (_g1_committed.contains(p)) {
2572     // Given that we know that p is in the committed space,
2573     // heap_region_containing_raw() should successfully
2574     // return the containing region.
2575     HeapRegion* hr = heap_region_containing_raw(p);
2576     return hr->is_in(p);
2577   } else {
2578     return false;
2579   }
2580 }
2581 
2582 // Iteration functions.
2583 
2584 // Iterates an OopClosure over all ref-containing fields of objects
2585 // within a HeapRegion.
2586 
2587 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2588   MemRegion _mr;
2589   ExtendedOopClosure* _cl;
2590 public:
2591   IterateOopClosureRegionClosure(MemRegion mr, ExtendedOopClosure* cl)
2592     : _mr(mr), _cl(cl) {}
2593   bool doHeapRegion(HeapRegion* r) {
2594     if (!r->continuesHumongous()) {
2595       r->oop_iterate(_cl);
2596     }
2597     return false;
2598   }
2599 };
2600 
2601 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) {
2602   IterateOopClosureRegionClosure blk(_g1_committed, cl);
2603   heap_region_iterate(&blk);
2604 }
2605 
2606 void G1CollectedHeap::oop_iterate(MemRegion mr, ExtendedOopClosure* cl) {
2607   IterateOopClosureRegionClosure blk(mr, cl);
2608   heap_region_iterate(&blk);
2609 }
2610 
2611 // Iterates an ObjectClosure over all objects within a HeapRegion.
2612 
2613 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2614   ObjectClosure* _cl;
2615 public:
2616   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2617   bool doHeapRegion(HeapRegion* r) {
2618     if (! r->continuesHumongous()) {
2619       r->object_iterate(_cl);
2620     }
2621     return false;
2622   }
2623 };
2624 
2625 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2626   IterateObjectClosureRegionClosure blk(cl);
2627   heap_region_iterate(&blk);
2628 }
2629 
2630 // Calls a SpaceClosure on a HeapRegion.
2631 
2632 class SpaceClosureRegionClosure: public HeapRegionClosure {
2633   SpaceClosure* _cl;
2634 public:
2635   SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2636   bool doHeapRegion(HeapRegion* r) {
2637     _cl->do_space(r);
2638     return false;
2639   }
2640 };
2641 
2642 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2643   SpaceClosureRegionClosure blk(cl);
2644   heap_region_iterate(&blk);
2645 }
2646 
2647 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2648   _hrs.iterate(cl);
2649 }
2650 
2651 void
2652 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
2653                                                  uint worker_id,
2654                                                  uint no_of_par_workers,
2655                                                  jint claim_value) {
2656   const uint regions = n_regions();
2657   const uint max_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
2658                              no_of_par_workers :
2659                              1);
2660   assert(UseDynamicNumberOfGCThreads ||
2661          no_of_par_workers == workers()->total_workers(),
2662          "Non dynamic should use fixed number of workers");
2663   // try to spread out the starting points of the workers
2664   const HeapRegion* start_hr =
2665                         start_region_for_worker(worker_id, no_of_par_workers);
2666   const uint start_index = start_hr->hrs_index();
2667 
2668   // each worker will actually look at all regions
2669   for (uint count = 0; count < regions; ++count) {
2670     const uint index = (start_index + count) % regions;
2671     assert(0 <= index && index < regions, "sanity");
2672     HeapRegion* r = region_at(index);
2673     // we'll ignore "continues humongous" regions (we'll process them
2674     // when we come across their corresponding "start humongous"
2675     // region) and regions already claimed
2676     if (r->claim_value() == claim_value || r->continuesHumongous()) {
2677       continue;
2678     }
2679     // OK, try to claim it
2680     if (r->claimHeapRegion(claim_value)) {
2681       // success!
2682       assert(!r->continuesHumongous(), "sanity");
2683       if (r->startsHumongous()) {
2684         // If the region is "starts humongous" we'll iterate over its
2685         // "continues humongous" first; in fact we'll do them
2686         // first. The order is important. In on case, calling the
2687         // closure on the "starts humongous" region might de-allocate
2688         // and clear all its "continues humongous" regions and, as a
2689         // result, we might end up processing them twice. So, we'll do
2690         // them first (notice: most closures will ignore them anyway) and
2691         // then we'll do the "starts humongous" region.
2692         for (uint ch_index = index + 1; ch_index < regions; ++ch_index) {
2693           HeapRegion* chr = region_at(ch_index);
2694 
2695           // if the region has already been claimed or it's not
2696           // "continues humongous" we're done
2697           if (chr->claim_value() == claim_value ||
2698               !chr->continuesHumongous()) {
2699             break;
2700           }
2701 
2702           // No one should have claimed it directly. We can given
2703           // that we claimed its "starts humongous" region.
2704           assert(chr->claim_value() != claim_value, "sanity");
2705           assert(chr->humongous_start_region() == r, "sanity");
2706 
2707           if (chr->claimHeapRegion(claim_value)) {
2708             // we should always be able to claim it; no one else should
2709             // be trying to claim this region
2710 
2711             bool res2 = cl->doHeapRegion(chr);
2712             assert(!res2, "Should not abort");
2713 
2714             // Right now, this holds (i.e., no closure that actually
2715             // does something with "continues humongous" regions
2716             // clears them). We might have to weaken it in the future,
2717             // but let's leave these two asserts here for extra safety.
2718             assert(chr->continuesHumongous(), "should still be the case");
2719             assert(chr->humongous_start_region() == r, "sanity");
2720           } else {
2721             guarantee(false, "we should not reach here");
2722           }
2723         }
2724       }
2725 
2726       assert(!r->continuesHumongous(), "sanity");
2727       bool res = cl->doHeapRegion(r);
2728       assert(!res, "Should not abort");
2729     }
2730   }
2731 }
2732 
2733 class ResetClaimValuesClosure: public HeapRegionClosure {
2734 public:
2735   bool doHeapRegion(HeapRegion* r) {
2736     r->set_claim_value(HeapRegion::InitialClaimValue);
2737     return false;
2738   }
2739 };
2740 
2741 void G1CollectedHeap::reset_heap_region_claim_values() {
2742   ResetClaimValuesClosure blk;
2743   heap_region_iterate(&blk);
2744 }
2745 
2746 void G1CollectedHeap::reset_cset_heap_region_claim_values() {
2747   ResetClaimValuesClosure blk;
2748   collection_set_iterate(&blk);
2749 }
2750 
2751 #ifdef ASSERT
2752 // This checks whether all regions in the heap have the correct claim
2753 // value. I also piggy-backed on this a check to ensure that the
2754 // humongous_start_region() information on "continues humongous"
2755 // regions is correct.
2756 
2757 class CheckClaimValuesClosure : public HeapRegionClosure {
2758 private:
2759   jint _claim_value;
2760   uint _failures;
2761   HeapRegion* _sh_region;
2762 
2763 public:
2764   CheckClaimValuesClosure(jint claim_value) :
2765     _claim_value(claim_value), _failures(0), _sh_region(NULL) { }
2766   bool doHeapRegion(HeapRegion* r) {
2767     if (r->claim_value() != _claim_value) {
2768       gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2769                              "claim value = %d, should be %d",
2770                              HR_FORMAT_PARAMS(r),
2771                              r->claim_value(), _claim_value);
2772       ++_failures;
2773     }
2774     if (!r->isHumongous()) {
2775       _sh_region = NULL;
2776     } else if (r->startsHumongous()) {
2777       _sh_region = r;
2778     } else if (r->continuesHumongous()) {
2779       if (r->humongous_start_region() != _sh_region) {
2780         gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2781                                "HS = "PTR_FORMAT", should be "PTR_FORMAT,
2782                                HR_FORMAT_PARAMS(r),
2783                                r->humongous_start_region(),
2784                                _sh_region);
2785         ++_failures;
2786       }
2787     }
2788     return false;
2789   }
2790   uint failures() { return _failures; }
2791 };
2792 
2793 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
2794   CheckClaimValuesClosure cl(claim_value);
2795   heap_region_iterate(&cl);
2796   return cl.failures() == 0;
2797 }
2798 
2799 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure {
2800 private:
2801   jint _claim_value;
2802   uint _failures;
2803 
2804 public:
2805   CheckClaimValuesInCSetHRClosure(jint claim_value) :
2806     _claim_value(claim_value), _failures(0) { }
2807 
2808   uint failures() { return _failures; }
2809 
2810   bool doHeapRegion(HeapRegion* hr) {
2811     assert(hr->in_collection_set(), "how?");
2812     assert(!hr->isHumongous(), "H-region in CSet");
2813     if (hr->claim_value() != _claim_value) {
2814       gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", "
2815                              "claim value = %d, should be %d",
2816                              HR_FORMAT_PARAMS(hr),
2817                              hr->claim_value(), _claim_value);
2818       _failures += 1;
2819     }
2820     return false;
2821   }
2822 };
2823 
2824 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) {
2825   CheckClaimValuesInCSetHRClosure cl(claim_value);
2826   collection_set_iterate(&cl);
2827   return cl.failures() == 0;
2828 }
2829 #endif // ASSERT
2830 
2831 // Clear the cached CSet starting regions and (more importantly)
2832 // the time stamps. Called when we reset the GC time stamp.
2833 void G1CollectedHeap::clear_cset_start_regions() {
2834   assert(_worker_cset_start_region != NULL, "sanity");
2835   assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2836 
2837   int n_queues = MAX2((int)ParallelGCThreads, 1);
2838   for (int i = 0; i < n_queues; i++) {
2839     _worker_cset_start_region[i] = NULL;
2840     _worker_cset_start_region_time_stamp[i] = 0;
2841   }
2842 }
2843 
2844 // Given the id of a worker, obtain or calculate a suitable
2845 // starting region for iterating over the current collection set.
2846 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) {
2847   assert(get_gc_time_stamp() > 0, "should have been updated by now");
2848 
2849   HeapRegion* result = NULL;
2850   unsigned gc_time_stamp = get_gc_time_stamp();
2851 
2852   if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2853     // Cached starting region for current worker was set
2854     // during the current pause - so it's valid.
2855     // Note: the cached starting heap region may be NULL
2856     // (when the collection set is empty).
2857     result = _worker_cset_start_region[worker_i];
2858     assert(result == NULL || result->in_collection_set(), "sanity");
2859     return result;
2860   }
2861 
2862   // The cached entry was not valid so let's calculate
2863   // a suitable starting heap region for this worker.
2864 
2865   // We want the parallel threads to start their collection
2866   // set iteration at different collection set regions to
2867   // avoid contention.
2868   // If we have:
2869   //          n collection set regions
2870   //          p threads
2871   // Then thread t will start at region floor ((t * n) / p)
2872 
2873   result = g1_policy()->collection_set();
2874   if (G1CollectedHeap::use_parallel_gc_threads()) {
2875     uint cs_size = g1_policy()->cset_region_length();
2876     uint active_workers = workers()->active_workers();
2877     assert(UseDynamicNumberOfGCThreads ||
2878              active_workers == workers()->total_workers(),
2879              "Unless dynamic should use total workers");
2880 
2881     uint end_ind   = (cs_size * worker_i) / active_workers;
2882     uint start_ind = 0;
2883 
2884     if (worker_i > 0 &&
2885         _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2886       // Previous workers starting region is valid
2887       // so let's iterate from there
2888       start_ind = (cs_size * (worker_i - 1)) / active_workers;
2889       result = _worker_cset_start_region[worker_i - 1];
2890     }
2891 
2892     for (uint i = start_ind; i < end_ind; i++) {
2893       result = result->next_in_collection_set();
2894     }
2895   }
2896 
2897   // Note: the calculated starting heap region may be NULL
2898   // (when the collection set is empty).
2899   assert(result == NULL || result->in_collection_set(), "sanity");
2900   assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2901          "should be updated only once per pause");
2902   _worker_cset_start_region[worker_i] = result;
2903   OrderAccess::storestore();
2904   _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2905   return result;
2906 }
2907 
2908 HeapRegion* G1CollectedHeap::start_region_for_worker(uint worker_i,
2909                                                      uint no_of_par_workers) {
2910   uint worker_num =
2911            G1CollectedHeap::use_parallel_gc_threads() ? no_of_par_workers : 1U;
2912   assert(UseDynamicNumberOfGCThreads ||
2913          no_of_par_workers == workers()->total_workers(),
2914          "Non dynamic should use fixed number of workers");
2915   const uint start_index = n_regions() * worker_i / worker_num;
2916   return region_at(start_index);
2917 }
2918 
2919 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2920   HeapRegion* r = g1_policy()->collection_set();
2921   while (r != NULL) {
2922     HeapRegion* next = r->next_in_collection_set();
2923     if (cl->doHeapRegion(r)) {
2924       cl->incomplete();
2925       return;
2926     }
2927     r = next;
2928   }
2929 }
2930 
2931 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2932                                                   HeapRegionClosure *cl) {
2933   if (r == NULL) {
2934     // The CSet is empty so there's nothing to do.
2935     return;
2936   }
2937 
2938   assert(r->in_collection_set(),
2939          "Start region must be a member of the collection set.");
2940   HeapRegion* cur = r;
2941   while (cur != NULL) {
2942     HeapRegion* next = cur->next_in_collection_set();
2943     if (cl->doHeapRegion(cur) && false) {
2944       cl->incomplete();
2945       return;
2946     }
2947     cur = next;
2948   }
2949   cur = g1_policy()->collection_set();
2950   while (cur != r) {
2951     HeapRegion* next = cur->next_in_collection_set();
2952     if (cl->doHeapRegion(cur) && false) {
2953       cl->incomplete();
2954       return;
2955     }
2956     cur = next;
2957   }
2958 }
2959 
2960 CompactibleSpace* G1CollectedHeap::first_compactible_space() {
2961   return n_regions() > 0 ? region_at(0) : NULL;
2962 }
2963 
2964 
2965 Space* G1CollectedHeap::space_containing(const void* addr) const {
2966   return heap_region_containing(addr);
2967 }
2968 
2969 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2970   Space* sp = space_containing(addr);
2971   return sp->block_start(addr);
2972 }
2973 
2974 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2975   Space* sp = space_containing(addr);
2976   return sp->block_size(addr);
2977 }
2978 
2979 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2980   Space* sp = space_containing(addr);
2981   return sp->block_is_obj(addr);
2982 }
2983 
2984 bool G1CollectedHeap::supports_tlab_allocation() const {
2985   return true;
2986 }
2987 
2988 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2989   return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes;
2990 }
2991 
2992 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2993   return young_list()->eden_used_bytes();
2994 }
2995 
2996 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2997 // must be smaller than the humongous object limit.
2998 size_t G1CollectedHeap::max_tlab_size() const {
2999   return align_size_down(_humongous_object_threshold_in_words - 1, MinObjAlignment);
3000 }
3001 
3002 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
3003   // Return the remaining space in the cur alloc region, but not less than
3004   // the min TLAB size.
3005 
3006   // Also, this value can be at most the humongous object threshold,
3007   // since we can't allow tlabs to grow big enough to accommodate
3008   // humongous objects.
3009 
3010   HeapRegion* hr = _mutator_alloc_region.get();
3011   size_t max_tlab = max_tlab_size() * wordSize;
3012   if (hr == NULL) {
3013     return max_tlab;
3014   } else {
3015     return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab);
3016   }
3017 }
3018 
3019 size_t G1CollectedHeap::max_capacity() const {
3020   return _g1_reserved.byte_size();
3021 }
3022 
3023 jlong G1CollectedHeap::millis_since_last_gc() {
3024   // assert(false, "NYI");
3025   return 0;
3026 }
3027 
3028 void G1CollectedHeap::prepare_for_verify() {
3029   if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
3030     ensure_parsability(false);
3031   }
3032   g1_rem_set()->prepare_for_verify();
3033 }
3034 
3035 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr,
3036                                               VerifyOption vo) {
3037   switch (vo) {
3038   case VerifyOption_G1UsePrevMarking:
3039     return hr->obj_allocated_since_prev_marking(obj);
3040   case VerifyOption_G1UseNextMarking:
3041     return hr->obj_allocated_since_next_marking(obj);
3042   case VerifyOption_G1UseMarkWord:
3043     return false;
3044   default:
3045     ShouldNotReachHere();
3046   }
3047   return false; // keep some compilers happy
3048 }
3049 
3050 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) {
3051   switch (vo) {
3052   case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start();
3053   case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start();
3054   case VerifyOption_G1UseMarkWord:    return NULL;
3055   default:                            ShouldNotReachHere();
3056   }
3057   return NULL; // keep some compilers happy
3058 }
3059 
3060 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) {
3061   switch (vo) {
3062   case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj);
3063   case VerifyOption_G1UseNextMarking: return isMarkedNext(obj);
3064   case VerifyOption_G1UseMarkWord:    return obj->is_gc_marked();
3065   default:                            ShouldNotReachHere();
3066   }
3067   return false; // keep some compilers happy
3068 }
3069 
3070 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) {
3071   switch (vo) {
3072   case VerifyOption_G1UsePrevMarking: return "PTAMS";
3073   case VerifyOption_G1UseNextMarking: return "NTAMS";
3074   case VerifyOption_G1UseMarkWord:    return "NONE";
3075   default:                            ShouldNotReachHere();
3076   }
3077   return NULL; // keep some compilers happy
3078 }
3079 
3080 class VerifyRootsClosure: public OopClosure {
3081 private:
3082   G1CollectedHeap* _g1h;
3083   VerifyOption     _vo;
3084   bool             _failures;
3085 public:
3086   // _vo == UsePrevMarking -> use "prev" marking information,
3087   // _vo == UseNextMarking -> use "next" marking information,
3088   // _vo == UseMarkWord    -> use mark word from object header.
3089   VerifyRootsClosure(VerifyOption vo) :
3090     _g1h(G1CollectedHeap::heap()),
3091     _vo(vo),
3092     _failures(false) { }
3093 
3094   bool failures() { return _failures; }
3095 
3096   template <class T> void do_oop_nv(T* p) {
3097     T heap_oop = oopDesc::load_heap_oop(p);
3098     if (!oopDesc::is_null(heap_oop)) {
3099       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3100       if (_g1h->is_obj_dead_cond(obj, _vo)) {
3101         gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
3102                               "points to dead obj "PTR_FORMAT, p, (void*) obj);
3103         if (_vo == VerifyOption_G1UseMarkWord) {
3104           gclog_or_tty->print_cr("  Mark word: "PTR_FORMAT, (void*)(obj->mark()));
3105         }
3106         obj->print_on(gclog_or_tty);
3107         _failures = true;
3108       }
3109     }
3110   }
3111 
3112   void do_oop(oop* p)       { do_oop_nv(p); }
3113   void do_oop(narrowOop* p) { do_oop_nv(p); }
3114 };
3115 
3116 class G1VerifyCodeRootOopClosure: public OopClosure {
3117   G1CollectedHeap* _g1h;
3118   OopClosure* _root_cl;
3119   nmethod* _nm;
3120   VerifyOption _vo;
3121   bool _failures;
3122 
3123   template <class T> void do_oop_work(T* p) {
3124     // First verify that this root is live
3125     _root_cl->do_oop(p);
3126 
3127     if (!G1VerifyHeapRegionCodeRoots) {
3128       // We're not verifying the code roots attached to heap region.
3129       return;
3130     }
3131 
3132     // Don't check the code roots during marking verification in a full GC
3133     if (_vo == VerifyOption_G1UseMarkWord) {
3134       return;
3135     }
3136 
3137     // Now verify that the current nmethod (which contains p) is
3138     // in the code root list of the heap region containing the
3139     // object referenced by p.
3140 
3141     T heap_oop = oopDesc::load_heap_oop(p);
3142     if (!oopDesc::is_null(heap_oop)) {
3143       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3144 
3145       // Now fetch the region containing the object
3146       HeapRegion* hr = _g1h->heap_region_containing(obj);
3147       HeapRegionRemSet* hrrs = hr->rem_set();
3148       // Verify that the strong code root list for this region
3149       // contains the nmethod
3150       if (!hrrs->strong_code_roots_list_contains(_nm)) {
3151         gclog_or_tty->print_cr("Code root location "PTR_FORMAT" "
3152                               "from nmethod "PTR_FORMAT" not in strong "
3153                               "code roots for region ["PTR_FORMAT","PTR_FORMAT")",
3154                               p, _nm, hr->bottom(), hr->end());
3155         _failures = true;
3156       }
3157     }
3158   }
3159 
3160 public:
3161   G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo):
3162     _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {}
3163 
3164   void do_oop(oop* p) { do_oop_work(p); }
3165   void do_oop(narrowOop* p) { do_oop_work(p); }
3166 
3167   void set_nmethod(nmethod* nm) { _nm = nm; }
3168   bool failures() { return _failures; }
3169 };
3170 
3171 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure {
3172   G1VerifyCodeRootOopClosure* _oop_cl;
3173 
3174 public:
3175   G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl):
3176     _oop_cl(oop_cl) {}
3177 
3178   void do_code_blob(CodeBlob* cb) {
3179     nmethod* nm = cb->as_nmethod_or_null();
3180     if (nm != NULL) {
3181       _oop_cl->set_nmethod(nm);
3182       nm->oops_do(_oop_cl);
3183     }
3184   }
3185 };
3186 
3187 class YoungRefCounterClosure : public OopClosure {
3188   G1CollectedHeap* _g1h;
3189   int              _count;
3190  public:
3191   YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {}
3192   void do_oop(oop* p)       { if (_g1h->is_in_young(*p)) { _count++; } }
3193   void do_oop(narrowOop* p) { ShouldNotReachHere(); }
3194 
3195   int count() { return _count; }
3196   void reset_count() { _count = 0; };
3197 };
3198 
3199 class VerifyKlassClosure: public KlassClosure {
3200   YoungRefCounterClosure _young_ref_counter_closure;
3201   OopClosure *_oop_closure;
3202  public:
3203   VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {}
3204   void do_klass(Klass* k) {
3205     k->oops_do(_oop_closure);
3206 
3207     _young_ref_counter_closure.reset_count();
3208     k->oops_do(&_young_ref_counter_closure);
3209     if (_young_ref_counter_closure.count() > 0) {
3210       guarantee(k->has_modified_oops(), err_msg("Klass " PTR_FORMAT ", has young refs but is not dirty.", k));
3211     }
3212   }
3213 };
3214 
3215 class VerifyLivenessOopClosure: public OopClosure {
3216   G1CollectedHeap* _g1h;
3217   VerifyOption _vo;
3218 public:
3219   VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
3220     _g1h(g1h), _vo(vo)
3221   { }
3222   void do_oop(narrowOop *p) { do_oop_work(p); }
3223   void do_oop(      oop *p) { do_oop_work(p); }
3224 
3225   template <class T> void do_oop_work(T *p) {
3226     oop obj = oopDesc::load_decode_heap_oop(p);
3227     guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
3228               "Dead object referenced by a not dead object");
3229   }
3230 };
3231 
3232 class VerifyObjsInRegionClosure: public ObjectClosure {
3233 private:
3234   G1CollectedHeap* _g1h;
3235   size_t _live_bytes;
3236   HeapRegion *_hr;
3237   VerifyOption _vo;
3238 public:
3239   // _vo == UsePrevMarking -> use "prev" marking information,
3240   // _vo == UseNextMarking -> use "next" marking information,
3241   // _vo == UseMarkWord    -> use mark word from object header.
3242   VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
3243     : _live_bytes(0), _hr(hr), _vo(vo) {
3244     _g1h = G1CollectedHeap::heap();
3245   }
3246   void do_object(oop o) {
3247     VerifyLivenessOopClosure isLive(_g1h, _vo);
3248     assert(o != NULL, "Huh?");
3249     if (!_g1h->is_obj_dead_cond(o, _vo)) {
3250       // If the object is alive according to the mark word,
3251       // then verify that the marking information agrees.
3252       // Note we can't verify the contra-positive of the
3253       // above: if the object is dead (according to the mark
3254       // word), it may not be marked, or may have been marked
3255       // but has since became dead, or may have been allocated
3256       // since the last marking.
3257       if (_vo == VerifyOption_G1UseMarkWord) {
3258         guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
3259       }
3260 
3261       o->oop_iterate_no_header(&isLive);
3262       if (!_hr->obj_allocated_since_prev_marking(o)) {
3263         size_t obj_size = o->size();    // Make sure we don't overflow
3264         _live_bytes += (obj_size * HeapWordSize);
3265       }
3266     }
3267   }
3268   size_t live_bytes() { return _live_bytes; }
3269 };
3270 
3271 class PrintObjsInRegionClosure : public ObjectClosure {
3272   HeapRegion *_hr;
3273   G1CollectedHeap *_g1;
3274 public:
3275   PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
3276     _g1 = G1CollectedHeap::heap();
3277   };
3278 
3279   void do_object(oop o) {
3280     if (o != NULL) {
3281       HeapWord *start = (HeapWord *) o;
3282       size_t word_sz = o->size();
3283       gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
3284                           " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
3285                           (void*) o, word_sz,
3286                           _g1->isMarkedPrev(o),
3287                           _g1->isMarkedNext(o),
3288                           _hr->obj_allocated_since_prev_marking(o));
3289       HeapWord *end = start + word_sz;
3290       HeapWord *cur;
3291       int *val;
3292       for (cur = start; cur < end; cur++) {
3293         val = (int *) cur;
3294         gclog_or_tty->print("\t "PTR_FORMAT":%d\n", val, *val);
3295       }
3296     }
3297   }
3298 };
3299 
3300 class VerifyRegionClosure: public HeapRegionClosure {
3301 private:
3302   bool             _par;
3303   VerifyOption     _vo;
3304   bool             _failures;
3305 public:
3306   // _vo == UsePrevMarking -> use "prev" marking information,
3307   // _vo == UseNextMarking -> use "next" marking information,
3308   // _vo == UseMarkWord    -> use mark word from object header.
3309   VerifyRegionClosure(bool par, VerifyOption vo)
3310     : _par(par),
3311       _vo(vo),
3312       _failures(false) {}
3313 
3314   bool failures() {
3315     return _failures;
3316   }
3317 
3318   bool doHeapRegion(HeapRegion* r) {
3319     if (!r->continuesHumongous()) {
3320       bool failures = false;
3321       r->verify(_vo, &failures);
3322       if (failures) {
3323         _failures = true;
3324       } else {
3325         VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
3326         r->object_iterate(&not_dead_yet_cl);
3327         if (_vo != VerifyOption_G1UseNextMarking) {
3328           if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
3329             gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
3330                                    "max_live_bytes "SIZE_FORMAT" "
3331                                    "< calculated "SIZE_FORMAT,
3332                                    r->bottom(), r->end(),
3333                                    r->max_live_bytes(),
3334                                  not_dead_yet_cl.live_bytes());
3335             _failures = true;
3336           }
3337         } else {
3338           // When vo == UseNextMarking we cannot currently do a sanity
3339           // check on the live bytes as the calculation has not been
3340           // finalized yet.
3341         }
3342       }
3343     }
3344     return false; // stop the region iteration if we hit a failure
3345   }
3346 };
3347 
3348 // This is the task used for parallel verification of the heap regions
3349 
3350 class G1ParVerifyTask: public AbstractGangTask {
3351 private:
3352   G1CollectedHeap* _g1h;
3353   VerifyOption     _vo;
3354   bool             _failures;
3355 
3356 public:
3357   // _vo == UsePrevMarking -> use "prev" marking information,
3358   // _vo == UseNextMarking -> use "next" marking information,
3359   // _vo == UseMarkWord    -> use mark word from object header.
3360   G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
3361     AbstractGangTask("Parallel verify task"),
3362     _g1h(g1h),
3363     _vo(vo),
3364     _failures(false) { }
3365 
3366   bool failures() {
3367     return _failures;
3368   }
3369 
3370   void work(uint worker_id) {
3371     HandleMark hm;
3372     VerifyRegionClosure blk(true, _vo);
3373     _g1h->heap_region_par_iterate_chunked(&blk, worker_id,
3374                                           _g1h->workers()->active_workers(),
3375                                           HeapRegion::ParVerifyClaimValue);
3376     if (blk.failures()) {
3377       _failures = true;
3378     }
3379   }
3380 };
3381 
3382 void G1CollectedHeap::verify(bool silent, VerifyOption vo) {
3383   if (SafepointSynchronize::is_at_safepoint()) {
3384     assert(Thread::current()->is_VM_thread(),
3385            "Expected to be executed serially by the VM thread at this point");
3386 
3387     if (!silent) { gclog_or_tty->print("Roots "); }
3388     VerifyRootsClosure rootsCl(vo);
3389     VerifyKlassClosure klassCl(this, &rootsCl);
3390     CLDToKlassAndOopClosure cldCl(&klassCl, &rootsCl, false);
3391 
3392     // We apply the relevant closures to all the oops in the
3393     // system dictionary, class loader data graph, the string table
3394     // and the nmethods in the code cache.
3395     G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo);
3396     G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl);
3397 
3398     process_all_roots(true,            // activate StrongRootsScope
3399                       SO_AllCodeCache, // roots scanning options
3400                       &rootsCl,
3401                       &cldCl,
3402                       &blobsCl);
3403 
3404     bool failures = rootsCl.failures() || codeRootsCl.failures();
3405 
3406     if (vo != VerifyOption_G1UseMarkWord) {
3407       // If we're verifying during a full GC then the region sets
3408       // will have been torn down at the start of the GC. Therefore
3409       // verifying the region sets will fail. So we only verify
3410       // the region sets when not in a full GC.
3411       if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3412       verify_region_sets();
3413     }
3414 
3415     if (!silent) { gclog_or_tty->print("HeapRegions "); }
3416     if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3417       assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3418              "sanity check");
3419 
3420       G1ParVerifyTask task(this, vo);
3421       assert(UseDynamicNumberOfGCThreads ||
3422         workers()->active_workers() == workers()->total_workers(),
3423         "If not dynamic should be using all the workers");
3424       int n_workers = workers()->active_workers();
3425       set_par_threads(n_workers);
3426       workers()->run_task(&task);
3427       set_par_threads(0);
3428       if (task.failures()) {
3429         failures = true;
3430       }
3431 
3432       // Checks that the expected amount of parallel work was done.
3433       // The implication is that n_workers is > 0.
3434       assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
3435              "sanity check");
3436 
3437       reset_heap_region_claim_values();
3438 
3439       assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3440              "sanity check");
3441     } else {
3442       VerifyRegionClosure blk(false, vo);
3443       heap_region_iterate(&blk);
3444       if (blk.failures()) {
3445         failures = true;
3446       }
3447     }
3448     if (!silent) gclog_or_tty->print("RemSet ");
3449     rem_set()->verify();
3450 
3451     if (G1StringDedup::is_enabled()) {
3452       if (!silent) gclog_or_tty->print("StrDedup ");
3453       G1StringDedup::verify();
3454     }
3455 
3456     if (failures) {
3457       gclog_or_tty->print_cr("Heap:");
3458       // It helps to have the per-region information in the output to
3459       // help us track down what went wrong. This is why we call
3460       // print_extended_on() instead of print_on().
3461       print_extended_on(gclog_or_tty);
3462       gclog_or_tty->cr();
3463 #ifndef PRODUCT
3464       if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3465         concurrent_mark()->print_reachable("at-verification-failure",
3466                                            vo, false /* all */);
3467       }
3468 #endif
3469       gclog_or_tty->flush();
3470     }
3471     guarantee(!failures, "there should not have been any failures");
3472   } else {
3473     if (!silent) {
3474       gclog_or_tty->print("(SKIPPING Roots, HeapRegionSets, HeapRegions, RemSet");
3475       if (G1StringDedup::is_enabled()) {
3476         gclog_or_tty->print(", StrDedup");
3477       }
3478       gclog_or_tty->print(") ");
3479     }
3480   }
3481 }
3482 
3483 void G1CollectedHeap::verify(bool silent) {
3484   verify(silent, VerifyOption_G1UsePrevMarking);
3485 }
3486 
3487 double G1CollectedHeap::verify(bool guard, const char* msg) {
3488   double verify_time_ms = 0.0;
3489 
3490   if (guard && total_collections() >= VerifyGCStartAt) {
3491     double verify_start = os::elapsedTime();
3492     HandleMark hm;  // Discard invalid handles created during verification
3493     prepare_for_verify();
3494     Universe::verify(VerifyOption_G1UsePrevMarking, msg);
3495     verify_time_ms = (os::elapsedTime() - verify_start) * 1000;
3496   }
3497 
3498   return verify_time_ms;
3499 }
3500 
3501 void G1CollectedHeap::verify_before_gc() {
3502   double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:");
3503   g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms);
3504 }
3505 
3506 void G1CollectedHeap::verify_after_gc() {
3507   double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:");
3508   g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms);
3509 }
3510 
3511 class PrintRegionClosure: public HeapRegionClosure {
3512   outputStream* _st;
3513 public:
3514   PrintRegionClosure(outputStream* st) : _st(st) {}
3515   bool doHeapRegion(HeapRegion* r) {
3516     r->print_on(_st);
3517     return false;
3518   }
3519 };
3520 
3521 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3522                                        const HeapRegion* hr,
3523                                        const VerifyOption vo) const {
3524   switch (vo) {
3525   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
3526   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
3527   case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked();
3528   default:                            ShouldNotReachHere();
3529   }
3530   return false; // keep some compilers happy
3531 }
3532 
3533 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3534                                        const VerifyOption vo) const {
3535   switch (vo) {
3536   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
3537   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
3538   case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked();
3539   default:                            ShouldNotReachHere();
3540   }
3541   return false; // keep some compilers happy
3542 }
3543 
3544 void G1CollectedHeap::print_on(outputStream* st) const {
3545   st->print(" %-20s", "garbage-first heap");
3546   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3547             capacity()/K, used_unlocked()/K);
3548   st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3549             _g1_storage.low_boundary(),
3550             _g1_storage.high(),
3551             _g1_storage.high_boundary());
3552   st->cr();
3553   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3554   uint young_regions = _young_list->length();
3555   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3556             (size_t) young_regions * HeapRegion::GrainBytes / K);
3557   uint survivor_regions = g1_policy()->recorded_survivor_regions();
3558   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3559             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3560   st->cr();
3561   MetaspaceAux::print_on(st);
3562 }
3563 
3564 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3565   print_on(st);
3566 
3567   // Print the per-region information.
3568   st->cr();
3569   st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3570                "HS=humongous(starts), HC=humongous(continues), "
3571                "CS=collection set, F=free, TS=gc time stamp, "
3572                "PTAMS=previous top-at-mark-start, "
3573                "NTAMS=next top-at-mark-start)");
3574   PrintRegionClosure blk(st);
3575   heap_region_iterate(&blk);
3576 }
3577 
3578 void G1CollectedHeap::print_on_error(outputStream* st) const {
3579   this->CollectedHeap::print_on_error(st);
3580 
3581   if (_cm != NULL) {
3582     st->cr();
3583     _cm->print_on_error(st);
3584   }
3585 }
3586 
3587 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3588   if (G1CollectedHeap::use_parallel_gc_threads()) {
3589     workers()->print_worker_threads_on(st);
3590   }
3591   _cmThread->print_on(st);
3592   st->cr();
3593   _cm->print_worker_threads_on(st);
3594   _cg1r->print_worker_threads_on(st);
3595   if (G1StringDedup::is_enabled()) {
3596     G1StringDedup::print_worker_threads_on(st);
3597   }
3598 }
3599 
3600 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3601   if (G1CollectedHeap::use_parallel_gc_threads()) {
3602     workers()->threads_do(tc);
3603   }
3604   tc->do_thread(_cmThread);
3605   _cg1r->threads_do(tc);
3606   if (G1StringDedup::is_enabled()) {
3607     G1StringDedup::threads_do(tc);
3608   }
3609 }
3610 
3611 void G1CollectedHeap::print_tracing_info() const {
3612   // We'll overload this to mean "trace GC pause statistics."
3613   if (TraceYoungGenTime || TraceOldGenTime) {
3614     // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3615     // to that.
3616     g1_policy()->print_tracing_info();
3617   }
3618   if (G1SummarizeRSetStats) {
3619     g1_rem_set()->print_summary_info();
3620   }
3621   if (G1SummarizeConcMark) {
3622     concurrent_mark()->print_summary_info();
3623   }
3624   g1_policy()->print_yg_surv_rate_info();
3625   SpecializationStats::print();
3626 }
3627 
3628 #ifndef PRODUCT
3629 // Helpful for debugging RSet issues.
3630 
3631 class PrintRSetsClosure : public HeapRegionClosure {
3632 private:
3633   const char* _msg;
3634   size_t _occupied_sum;
3635 
3636 public:
3637   bool doHeapRegion(HeapRegion* r) {
3638     HeapRegionRemSet* hrrs = r->rem_set();
3639     size_t occupied = hrrs->occupied();
3640     _occupied_sum += occupied;
3641 
3642     gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3643                            HR_FORMAT_PARAMS(r));
3644     if (occupied == 0) {
3645       gclog_or_tty->print_cr("  RSet is empty");
3646     } else {
3647       hrrs->print();
3648     }
3649     gclog_or_tty->print_cr("----------");
3650     return false;
3651   }
3652 
3653   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3654     gclog_or_tty->cr();
3655     gclog_or_tty->print_cr("========================================");
3656     gclog_or_tty->print_cr("%s", msg);
3657     gclog_or_tty->cr();
3658   }
3659 
3660   ~PrintRSetsClosure() {
3661     gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3662     gclog_or_tty->print_cr("========================================");
3663     gclog_or_tty->cr();
3664   }
3665 };
3666 
3667 void G1CollectedHeap::print_cset_rsets() {
3668   PrintRSetsClosure cl("Printing CSet RSets");
3669   collection_set_iterate(&cl);
3670 }
3671 
3672 void G1CollectedHeap::print_all_rsets() {
3673   PrintRSetsClosure cl("Printing All RSets");;
3674   heap_region_iterate(&cl);
3675 }
3676 #endif // PRODUCT
3677 
3678 G1CollectedHeap* G1CollectedHeap::heap() {
3679   assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3680          "not a garbage-first heap");
3681   return _g1h;
3682 }
3683 
3684 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3685   // always_do_update_barrier = false;
3686   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3687   // Fill TLAB's and such
3688   accumulate_statistics_all_tlabs();
3689   ensure_parsability(true);
3690 
3691   if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) &&
3692       (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3693     g1_rem_set()->print_periodic_summary_info("Before GC RS summary");
3694   }
3695 
3696   if (G1ReclaimDeadHumongousObjectsAtYoungGC) {
3697     clear_humongous_is_live_table();
3698   }
3699 }
3700 
3701 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) {
3702 
3703   if (G1SummarizeRSetStats &&
3704       (G1SummarizeRSetStatsPeriod > 0) &&
3705       // we are at the end of the GC. Total collections has already been increased.
3706       ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) {
3707     g1_rem_set()->print_periodic_summary_info("After GC RS summary");
3708   }
3709 
3710   // FIXME: what is this about?
3711   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3712   // is set.
3713   COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3714                         "derived pointer present"));
3715   // always_do_update_barrier = true;
3716 
3717   resize_all_tlabs();
3718 
3719   // We have just completed a GC. Update the soft reference
3720   // policy with the new heap occupancy
3721   Universe::update_heap_info_at_gc();
3722 }
3723 
3724 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3725                                                unsigned int gc_count_before,
3726                                                bool* succeeded,
3727                                                GCCause::Cause gc_cause) {
3728   assert_heap_not_locked_and_not_at_safepoint();
3729   g1_policy()->record_stop_world_start();
3730   VM_G1IncCollectionPause op(gc_count_before,
3731                              word_size,
3732                              false, /* should_initiate_conc_mark */
3733                              g1_policy()->max_pause_time_ms(),
3734                              gc_cause);
3735   VMThread::execute(&op);
3736 
3737   HeapWord* result = op.result();
3738   bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3739   assert(result == NULL || ret_succeeded,
3740          "the result should be NULL if the VM did not succeed");
3741   *succeeded = ret_succeeded;
3742 
3743   assert_heap_not_locked();
3744   return result;
3745 }
3746 
3747 void
3748 G1CollectedHeap::doConcurrentMark() {
3749   MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3750   if (!_cmThread->in_progress()) {
3751     _cmThread->set_started();
3752     CGC_lock->notify();
3753   }
3754 }
3755 
3756 size_t G1CollectedHeap::pending_card_num() {
3757   size_t extra_cards = 0;
3758   JavaThread *curr = Threads::first();
3759   while (curr != NULL) {
3760     DirtyCardQueue& dcq = curr->dirty_card_queue();
3761     extra_cards += dcq.size();
3762     curr = curr->next();
3763   }
3764   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3765   size_t buffer_size = dcqs.buffer_size();
3766   size_t buffer_num = dcqs.completed_buffers_num();
3767 
3768   // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
3769   // in bytes - not the number of 'entries'. We need to convert
3770   // into a number of cards.
3771   return (buffer_size * buffer_num + extra_cards) / oopSize;
3772 }
3773 
3774 size_t G1CollectedHeap::cards_scanned() {
3775   return g1_rem_set()->cardsScanned();
3776 }
3777 
3778 bool G1CollectedHeap::humongous_region_is_always_live(HeapRegion* region) {
3779   assert(region->startsHumongous(), "Must start a humongous object");
3780   return oop(region->bottom())->is_objArray() || !region->rem_set()->is_empty();
3781 }
3782 
3783 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
3784  private:
3785   size_t _total_humongous;
3786   size_t _candidate_humongous;
3787  public:
3788   RegisterHumongousWithInCSetFastTestClosure() : _total_humongous(0), _candidate_humongous(0) {
3789   }
3790 
3791   virtual bool doHeapRegion(HeapRegion* r) {
3792     if (!r->startsHumongous()) {
3793       return false;
3794     }
3795     G1CollectedHeap* g1h = G1CollectedHeap::heap();
3796 
3797     bool is_candidate = !g1h->humongous_region_is_always_live(r);
3798     if (is_candidate) {
3799       // Do not even try to reclaim a humongous object that we already know will
3800       // not be treated as live later. A young collection will not decrease the
3801       // amount of remembered set entries for that region.
3802       g1h->register_humongous_region_with_in_cset_fast_test(r->hrs_index());
3803       _candidate_humongous++;
3804     }
3805     _total_humongous++;
3806     
3807     return false;
3808   }
3809 
3810   size_t total_humongous() const { return _total_humongous; }
3811   size_t candidate_humongous() const { return _candidate_humongous; }
3812 };
3813 
3814 void G1CollectedHeap::register_humongous_regions_with_in_cset_fast_test() {
3815   RegisterHumongousWithInCSetFastTestClosure cl;
3816   heap_region_iterate(&cl);
3817   g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(cl.total_humongous(),
3818                                                                   cl.candidate_humongous());
3819   _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
3820 }
3821 
3822 void
3823 G1CollectedHeap::setup_surviving_young_words() {
3824   assert(_surviving_young_words == NULL, "pre-condition");
3825   uint array_length = g1_policy()->young_cset_region_length();
3826   _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3827   if (_surviving_young_words == NULL) {
3828     vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR,
3829                           "Not enough space for young surv words summary.");
3830   }
3831   memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3832 #ifdef ASSERT
3833   for (uint i = 0;  i < array_length; ++i) {
3834     assert( _surviving_young_words[i] == 0, "memset above" );
3835   }
3836 #endif // !ASSERT
3837 }
3838 
3839 void
3840 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3841   MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3842   uint array_length = g1_policy()->young_cset_region_length();
3843   for (uint i = 0; i < array_length; ++i) {
3844     _surviving_young_words[i] += surv_young_words[i];
3845   }
3846 }
3847 
3848 void
3849 G1CollectedHeap::cleanup_surviving_young_words() {
3850   guarantee( _surviving_young_words != NULL, "pre-condition" );
3851   FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC);
3852   _surviving_young_words = NULL;
3853 }
3854 
3855 #ifdef ASSERT
3856 class VerifyCSetClosure: public HeapRegionClosure {
3857 public:
3858   bool doHeapRegion(HeapRegion* hr) {
3859     // Here we check that the CSet region's RSet is ready for parallel
3860     // iteration. The fields that we'll verify are only manipulated
3861     // when the region is part of a CSet and is collected. Afterwards,
3862     // we reset these fields when we clear the region's RSet (when the
3863     // region is freed) so they are ready when the region is
3864     // re-allocated. The only exception to this is if there's an
3865     // evacuation failure and instead of freeing the region we leave
3866     // it in the heap. In that case, we reset these fields during
3867     // evacuation failure handling.
3868     guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3869 
3870     // Here's a good place to add any other checks we'd like to
3871     // perform on CSet regions.
3872     return false;
3873   }
3874 };
3875 #endif // ASSERT
3876 
3877 #if TASKQUEUE_STATS
3878 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3879   st->print_raw_cr("GC Task Stats");
3880   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3881   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3882 }
3883 
3884 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3885   print_taskqueue_stats_hdr(st);
3886 
3887   TaskQueueStats totals;
3888   const int n = workers() != NULL ? workers()->total_workers() : 1;
3889   for (int i = 0; i < n; ++i) {
3890     st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3891     totals += task_queue(i)->stats;
3892   }
3893   st->print_raw("tot "); totals.print(st); st->cr();
3894 
3895   DEBUG_ONLY(totals.verify());
3896 }
3897 
3898 void G1CollectedHeap::reset_taskqueue_stats() {
3899   const int n = workers() != NULL ? workers()->total_workers() : 1;
3900   for (int i = 0; i < n; ++i) {
3901     task_queue(i)->stats.reset();
3902   }
3903 }
3904 #endif // TASKQUEUE_STATS
3905 
3906 void G1CollectedHeap::log_gc_header() {
3907   if (!G1Log::fine()) {
3908     return;
3909   }
3910 
3911   gclog_or_tty->gclog_stamp(_gc_tracer_stw->gc_id());
3912 
3913   GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
3914     .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)")
3915     .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : "");
3916 
3917   gclog_or_tty->print("[%s", (const char*)gc_cause_str);
3918 }
3919 
3920 void G1CollectedHeap::log_gc_footer(double pause_time_sec) {
3921   if (!G1Log::fine()) {
3922     return;
3923   }
3924 
3925   if (G1Log::finer()) {
3926     if (evacuation_failed()) {
3927       gclog_or_tty->print(" (to-space exhausted)");
3928     }
3929     gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3930     g1_policy()->phase_times()->note_gc_end();
3931     g1_policy()->phase_times()->print(pause_time_sec);
3932     g1_policy()->print_detailed_heap_transition();
3933   } else {
3934     if (evacuation_failed()) {
3935       gclog_or_tty->print("--");
3936     }
3937     g1_policy()->print_heap_transition();
3938     gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3939   }
3940   gclog_or_tty->flush();
3941 }
3942 
3943 bool
3944 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3945   assert_at_safepoint(true /* should_be_vm_thread */);
3946   guarantee(!is_gc_active(), "collection is not reentrant");
3947 
3948   if (GC_locker::check_active_before_gc()) {
3949     return false;
3950   }
3951 
3952   _gc_timer_stw->register_gc_start();
3953 
3954   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3955 
3956   SvcGCMarker sgcm(SvcGCMarker::MINOR);
3957   ResourceMark rm;
3958 
3959   print_heap_before_gc();
3960   trace_heap_before_gc(_gc_tracer_stw);
3961 
3962   verify_region_sets_optional();
3963   verify_dirty_young_regions();
3964 
3965   // This call will decide whether this pause is an initial-mark
3966   // pause. If it is, during_initial_mark_pause() will return true
3967   // for the duration of this pause.
3968   g1_policy()->decide_on_conc_mark_initiation();
3969 
3970   // We do not allow initial-mark to be piggy-backed on a mixed GC.
3971   assert(!g1_policy()->during_initial_mark_pause() ||
3972           g1_policy()->gcs_are_young(), "sanity");
3973 
3974   // We also do not allow mixed GCs during marking.
3975   assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3976 
3977   // Record whether this pause is an initial mark. When the current
3978   // thread has completed its logging output and it's safe to signal
3979   // the CM thread, the flag's value in the policy has been reset.
3980   bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3981 
3982   // Inner scope for scope based logging, timers, and stats collection
3983   {
3984     EvacuationInfo evacuation_info;
3985 
3986     if (g1_policy()->during_initial_mark_pause()) {
3987       // We are about to start a marking cycle, so we increment the
3988       // full collection counter.
3989       increment_old_marking_cycles_started();
3990       register_concurrent_cycle_start(_gc_timer_stw->gc_start());
3991     }
3992 
3993     _gc_tracer_stw->report_yc_type(yc_type());
3994 
3995     TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3996 
3997     int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
3998                                 workers()->active_workers() : 1);
3999     double pause_start_sec = os::elapsedTime();
4000     g1_policy()->phase_times()->note_gc_start(active_workers);
4001     log_gc_header();
4002 
4003     TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
4004     TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
4005 
4006     // If the secondary_free_list is not empty, append it to the
4007     // free_list. No need to wait for the cleanup operation to finish;
4008     // the region allocation code will check the secondary_free_list
4009     // and wait if necessary. If the G1StressConcRegionFreeing flag is
4010     // set, skip this step so that the region allocation code has to
4011     // get entries from the secondary_free_list.
4012     if (!G1StressConcRegionFreeing) {
4013       append_secondary_free_list_if_not_empty_with_lock();
4014     }
4015 
4016     assert(check_young_list_well_formed(), "young list should be well formed");
4017     assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
4018            "sanity check");
4019 
4020     // Don't dynamically change the number of GC threads this early.  A value of
4021     // 0 is used to indicate serial work.  When parallel work is done,
4022     // it will be set.
4023 
4024     { // Call to jvmpi::post_class_unload_events must occur outside of active GC
4025       IsGCActiveMark x;
4026 
4027       gc_prologue(false);
4028       increment_total_collections(false /* full gc */);
4029       increment_gc_time_stamp();
4030 
4031       verify_before_gc();
4032 
4033       check_bitmaps("GC Start");
4034 
4035       COMPILER2_PRESENT(DerivedPointerTable::clear());
4036 
4037       // Please see comment in g1CollectedHeap.hpp and
4038       // G1CollectedHeap::ref_processing_init() to see how
4039       // reference processing currently works in G1.
4040 
4041       // Enable discovery in the STW reference processor
4042       ref_processor_stw()->enable_discovery(true /*verify_disabled*/,
4043                                             true /*verify_no_refs*/);
4044 
4045       {
4046         // We want to temporarily turn off discovery by the
4047         // CM ref processor, if necessary, and turn it back on
4048         // on again later if we do. Using a scoped
4049         // NoRefDiscovery object will do this.
4050         NoRefDiscovery no_cm_discovery(ref_processor_cm());
4051 
4052         // Forget the current alloc region (we might even choose it to be part
4053         // of the collection set!).
4054         release_mutator_alloc_region();
4055 
4056         // We should call this after we retire the mutator alloc
4057         // region(s) so that all the ALLOC / RETIRE events are generated
4058         // before the start GC event.
4059         _hr_printer.start_gc(false /* full */, (size_t) total_collections());
4060 
4061         // This timing is only used by the ergonomics to handle our pause target.
4062         // It is unclear why this should not include the full pause. We will
4063         // investigate this in CR 7178365.
4064         //
4065         // Preserving the old comment here if that helps the investigation:
4066         //
4067         // The elapsed time induced by the start time below deliberately elides
4068         // the possible verification above.
4069         double sample_start_time_sec = os::elapsedTime();
4070 
4071 #if YOUNG_LIST_VERBOSE
4072         gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
4073         _young_list->print();
4074         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4075 #endif // YOUNG_LIST_VERBOSE
4076 
4077         g1_policy()->record_collection_pause_start(sample_start_time_sec);
4078 
4079         double scan_wait_start = os::elapsedTime();
4080         // We have to wait until the CM threads finish scanning the
4081         // root regions as it's the only way to ensure that all the
4082         // objects on them have been correctly scanned before we start
4083         // moving them during the GC.
4084         bool waited = _cm->root_regions()->wait_until_scan_finished();
4085         double wait_time_ms = 0.0;
4086         if (waited) {
4087           double scan_wait_end = os::elapsedTime();
4088           wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
4089         }
4090         g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
4091 
4092 #if YOUNG_LIST_VERBOSE
4093         gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
4094         _young_list->print();
4095 #endif // YOUNG_LIST_VERBOSE
4096 
4097         if (g1_policy()->during_initial_mark_pause()) {
4098           concurrent_mark()->checkpointRootsInitialPre();
4099         }
4100 
4101 #if YOUNG_LIST_VERBOSE
4102         gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
4103         _young_list->print();
4104         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4105 #endif // YOUNG_LIST_VERBOSE
4106 
4107         g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info);
4108 
4109         if (G1ReclaimDeadHumongousObjectsAtYoungGC) {
4110           register_humongous_regions_with_in_cset_fast_test();
4111         }
4112 
4113         _cm->note_start_of_gc();
4114         // We should not verify the per-thread SATB buffers given that
4115         // we have not filtered them yet (we'll do so during the
4116         // GC). We also call this after finalize_cset() to
4117         // ensure that the CSet has been finalized.
4118         _cm->verify_no_cset_oops(true  /* verify_stacks */,
4119                                  true  /* verify_enqueued_buffers */,
4120                                  false /* verify_thread_buffers */,
4121                                  true  /* verify_fingers */);
4122 
4123         if (_hr_printer.is_active()) {
4124           HeapRegion* hr = g1_policy()->collection_set();
4125           while (hr != NULL) {
4126             G1HRPrinter::RegionType type;
4127             if (!hr->is_young()) {
4128               type = G1HRPrinter::Old;
4129             } else if (hr->is_survivor()) {
4130               type = G1HRPrinter::Survivor;
4131             } else {
4132               type = G1HRPrinter::Eden;
4133             }
4134             _hr_printer.cset(hr);
4135             hr = hr->next_in_collection_set();
4136           }
4137         }
4138 
4139 #ifdef ASSERT
4140         VerifyCSetClosure cl;
4141         collection_set_iterate(&cl);
4142 #endif // ASSERT
4143 
4144         setup_surviving_young_words();
4145 
4146         // Initialize the GC alloc regions.
4147         init_gc_alloc_regions(evacuation_info);
4148 
4149         // Actually do the work...
4150         evacuate_collection_set(evacuation_info);
4151 
4152         // We do this to mainly verify the per-thread SATB buffers
4153         // (which have been filtered by now) since we didn't verify
4154         // them earlier. No point in re-checking the stacks / enqueued
4155         // buffers given that the CSet has not changed since last time
4156         // we checked.
4157         _cm->verify_no_cset_oops(false /* verify_stacks */,
4158                                  false /* verify_enqueued_buffers */,
4159                                  true  /* verify_thread_buffers */,
4160                                  true  /* verify_fingers */);
4161 
4162         free_collection_set(g1_policy()->collection_set(), evacuation_info);
4163         if (G1ReclaimDeadHumongousObjectsAtYoungGC && _has_humongous_reclaim_candidates) {
4164           eagerly_reclaim_humongous_regions();
4165         }
4166         g1_policy()->clear_collection_set();
4167 
4168         cleanup_surviving_young_words();
4169 
4170         // Start a new incremental collection set for the next pause.
4171         g1_policy()->start_incremental_cset_building();
4172 
4173         clear_cset_fast_test();
4174 
4175         _young_list->reset_sampled_info();
4176 
4177         // Don't check the whole heap at this point as the
4178         // GC alloc regions from this pause have been tagged
4179         // as survivors and moved on to the survivor list.
4180         // Survivor regions will fail the !is_young() check.
4181         assert(check_young_list_empty(false /* check_heap */),
4182           "young list should be empty");
4183 
4184 #if YOUNG_LIST_VERBOSE
4185         gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
4186         _young_list->print();
4187 #endif // YOUNG_LIST_VERBOSE
4188 
4189         g1_policy()->record_survivor_regions(_young_list->survivor_length(),
4190                                              _young_list->first_survivor_region(),
4191                                              _young_list->last_survivor_region());
4192 
4193         _young_list->reset_auxilary_lists();
4194 
4195         if (evacuation_failed()) {
4196           _summary_bytes_used = recalculate_used();
4197           uint n_queues = MAX2((int)ParallelGCThreads, 1);
4198           for (uint i = 0; i < n_queues; i++) {
4199             if (_evacuation_failed_info_array[i].has_failed()) {
4200               _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
4201             }
4202           }
4203         } else {
4204           // The "used" of the the collection set have already been subtracted
4205           // when they were freed.  Add in the bytes evacuated.
4206           _summary_bytes_used += g1_policy()->bytes_copied_during_gc();
4207         }
4208 
4209         if (g1_policy()->during_initial_mark_pause()) {
4210           // We have to do this before we notify the CM threads that
4211           // they can start working to make sure that all the
4212           // appropriate initialization is done on the CM object.
4213           concurrent_mark()->checkpointRootsInitialPost();
4214           set_marking_started();
4215           // Note that we don't actually trigger the CM thread at
4216           // this point. We do that later when we're sure that
4217           // the current thread has completed its logging output.
4218         }
4219 
4220         allocate_dummy_regions();
4221 
4222 #if YOUNG_LIST_VERBOSE
4223         gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
4224         _young_list->print();
4225         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4226 #endif // YOUNG_LIST_VERBOSE
4227 
4228         init_mutator_alloc_region();
4229 
4230         {
4231           size_t expand_bytes = g1_policy()->expansion_amount();
4232           if (expand_bytes > 0) {
4233             size_t bytes_before = capacity();
4234             // No need for an ergo verbose message here,
4235             // expansion_amount() does this when it returns a value > 0.
4236             if (!expand(expand_bytes)) {
4237               // We failed to expand the heap so let's verify that
4238               // committed/uncommitted amount match the backing store
4239               assert(capacity() == _g1_storage.committed_size(), "committed size mismatch");
4240               assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch");
4241             }
4242           }
4243         }
4244 
4245         // We redo the verification but now wrt to the new CSet which
4246         // has just got initialized after the previous CSet was freed.
4247         _cm->verify_no_cset_oops(true  /* verify_stacks */,
4248                                  true  /* verify_enqueued_buffers */,
4249                                  true  /* verify_thread_buffers */,
4250                                  true  /* verify_fingers */);
4251         _cm->note_end_of_gc();
4252 
4253         // This timing is only used by the ergonomics to handle our pause target.
4254         // It is unclear why this should not include the full pause. We will
4255         // investigate this in CR 7178365.
4256         double sample_end_time_sec = os::elapsedTime();
4257         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
4258         g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info);
4259 
4260         MemoryService::track_memory_usage();
4261 
4262         // In prepare_for_verify() below we'll need to scan the deferred
4263         // update buffers to bring the RSets up-to-date if
4264         // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
4265         // the update buffers we'll probably need to scan cards on the
4266         // regions we just allocated to (i.e., the GC alloc
4267         // regions). However, during the last GC we called
4268         // set_saved_mark() on all the GC alloc regions, so card
4269         // scanning might skip the [saved_mark_word()...top()] area of
4270         // those regions (i.e., the area we allocated objects into
4271         // during the last GC). But it shouldn't. Given that
4272         // saved_mark_word() is conditional on whether the GC time stamp
4273         // on the region is current or not, by incrementing the GC time
4274         // stamp here we invalidate all the GC time stamps on all the
4275         // regions and saved_mark_word() will simply return top() for
4276         // all the regions. This is a nicer way of ensuring this rather
4277         // than iterating over the regions and fixing them. In fact, the
4278         // GC time stamp increment here also ensures that
4279         // saved_mark_word() will return top() between pauses, i.e.,
4280         // during concurrent refinement. So we don't need the
4281         // is_gc_active() check to decided which top to use when
4282         // scanning cards (see CR 7039627).
4283         increment_gc_time_stamp();
4284 
4285         verify_after_gc();
4286         check_bitmaps("GC End");
4287 
4288         assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
4289         ref_processor_stw()->verify_no_references_recorded();
4290 
4291         // CM reference discovery will be re-enabled if necessary.
4292       }
4293 
4294       // We should do this after we potentially expand the heap so
4295       // that all the COMMIT events are generated before the end GC
4296       // event, and after we retire the GC alloc regions so that all
4297       // RETIRE events are generated before the end GC event.
4298       _hr_printer.end_gc(false /* full */, (size_t) total_collections());
4299 
4300       if (mark_in_progress()) {
4301         concurrent_mark()->update_g1_committed();
4302       }
4303 
4304 #ifdef TRACESPINNING
4305       ParallelTaskTerminator::print_termination_counts();
4306 #endif
4307 
4308       gc_epilogue(false);
4309     }
4310 
4311     // Print the remainder of the GC log output.
4312     log_gc_footer(os::elapsedTime() - pause_start_sec);
4313 
4314     // It is not yet to safe to tell the concurrent mark to
4315     // start as we have some optional output below. We don't want the
4316     // output from the concurrent mark thread interfering with this
4317     // logging output either.
4318 
4319     _hrs.verify_optional();
4320     verify_region_sets_optional();
4321 
4322     TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
4323     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
4324 
4325     print_heap_after_gc();
4326     trace_heap_after_gc(_gc_tracer_stw);
4327 
4328     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
4329     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
4330     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
4331     // before any GC notifications are raised.
4332     g1mm()->update_sizes();
4333 
4334     _gc_tracer_stw->report_evacuation_info(&evacuation_info);
4335     _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
4336     _gc_timer_stw->register_gc_end();
4337     _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
4338   }
4339   // It should now be safe to tell the concurrent mark thread to start
4340   // without its logging output interfering with the logging output
4341   // that came from the pause.
4342 
4343   if (should_start_conc_mark) {
4344     // CAUTION: after the doConcurrentMark() call below,
4345     // the concurrent marking thread(s) could be running
4346     // concurrently with us. Make sure that anything after
4347     // this point does not assume that we are the only GC thread
4348     // running. Note: of course, the actual marking work will
4349     // not start until the safepoint itself is released in
4350     // SuspendibleThreadSet::desynchronize().
4351     doConcurrentMark();
4352   }
4353 
4354   return true;
4355 }
4356 
4357 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
4358 {
4359   size_t gclab_word_size;
4360   switch (purpose) {
4361     case GCAllocForSurvived:
4362       gclab_word_size = _survivor_plab_stats.desired_plab_sz();
4363       break;
4364     case GCAllocForTenured:
4365       gclab_word_size = _old_plab_stats.desired_plab_sz();
4366       break;
4367     default:
4368       assert(false, "unknown GCAllocPurpose");
4369       gclab_word_size = _old_plab_stats.desired_plab_sz();
4370       break;
4371   }
4372 
4373   // Prevent humongous PLAB sizes for two reasons:
4374   // * PLABs are allocated using a similar paths as oops, but should
4375   //   never be in a humongous region
4376   // * Allowing humongous PLABs needlessly churns the region free lists
4377   return MIN2(_humongous_object_threshold_in_words, gclab_word_size);
4378 }
4379 
4380 void G1CollectedHeap::init_mutator_alloc_region() {
4381   assert(_mutator_alloc_region.get() == NULL, "pre-condition");
4382   _mutator_alloc_region.init();
4383 }
4384 
4385 void G1CollectedHeap::release_mutator_alloc_region() {
4386   _mutator_alloc_region.release();
4387   assert(_mutator_alloc_region.get() == NULL, "post-condition");
4388 }
4389 
4390 void G1CollectedHeap::use_retained_old_gc_alloc_region(EvacuationInfo& evacuation_info) {
4391   HeapRegion* retained_region = _retained_old_gc_alloc_region;
4392   _retained_old_gc_alloc_region = NULL;
4393 
4394   // We will discard the current GC alloc region if:
4395   // a) it's in the collection set (it can happen!),
4396   // b) it's already full (no point in using it),
4397   // c) it's empty (this means that it was emptied during
4398   // a cleanup and it should be on the free list now), or
4399   // d) it's humongous (this means that it was emptied
4400   // during a cleanup and was added to the free list, but
4401   // has been subsequently used to allocate a humongous
4402   // object that may be less than the region size).
4403   if (retained_region != NULL &&
4404       !retained_region->in_collection_set() &&
4405       !(retained_region->top() == retained_region->end()) &&
4406       !retained_region->is_empty() &&
4407       !retained_region->isHumongous()) {
4408     retained_region->record_top_and_timestamp();
4409     // The retained region was added to the old region set when it was
4410     // retired. We have to remove it now, since we don't allow regions
4411     // we allocate to in the region sets. We'll re-add it later, when
4412     // it's retired again.
4413     _old_set.remove(retained_region);
4414     bool during_im = g1_policy()->during_initial_mark_pause();
4415     retained_region->note_start_of_copying(during_im);
4416     _old_gc_alloc_region.set(retained_region);
4417     _hr_printer.reuse(retained_region);
4418     evacuation_info.set_alloc_regions_used_before(retained_region->used());
4419   }
4420 }
4421 
4422 void G1CollectedHeap::init_gc_alloc_regions(EvacuationInfo& evacuation_info) {
4423   assert_at_safepoint(true /* should_be_vm_thread */);
4424 
4425   _survivor_gc_alloc_region.init();
4426   _old_gc_alloc_region.init();
4427 
4428   use_retained_old_gc_alloc_region(evacuation_info);
4429 }
4430 
4431 void G1CollectedHeap::release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info) {
4432   evacuation_info.set_allocation_regions(_survivor_gc_alloc_region.count() +
4433                                          _old_gc_alloc_region.count());
4434   _survivor_gc_alloc_region.release();
4435   // If we have an old GC alloc region to release, we'll save it in
4436   // _retained_old_gc_alloc_region. If we don't
4437   // _retained_old_gc_alloc_region will become NULL. This is what we
4438   // want either way so no reason to check explicitly for either
4439   // condition.
4440   _retained_old_gc_alloc_region = _old_gc_alloc_region.release();
4441 
4442   if (ResizePLAB) {
4443     _survivor_plab_stats.adjust_desired_plab_sz(no_of_gc_workers);
4444     _old_plab_stats.adjust_desired_plab_sz(no_of_gc_workers);
4445   }
4446 }
4447 
4448 void G1CollectedHeap::abandon_gc_alloc_regions() {
4449   assert(_survivor_gc_alloc_region.get() == NULL, "pre-condition");
4450   assert(_old_gc_alloc_region.get() == NULL, "pre-condition");
4451   _retained_old_gc_alloc_region = NULL;
4452 }
4453 
4454 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4455   _drain_in_progress = false;
4456   set_evac_failure_closure(cl);
4457   _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4458 }
4459 
4460 void G1CollectedHeap::finalize_for_evac_failure() {
4461   assert(_evac_failure_scan_stack != NULL &&
4462          _evac_failure_scan_stack->length() == 0,
4463          "Postcondition");
4464   assert(!_drain_in_progress, "Postcondition");
4465   delete _evac_failure_scan_stack;
4466   _evac_failure_scan_stack = NULL;
4467 }
4468 
4469 void G1CollectedHeap::remove_self_forwarding_pointers() {
4470   assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4471 
4472   double remove_self_forwards_start = os::elapsedTime();
4473 
4474   G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4475 
4476   if (G1CollectedHeap::use_parallel_gc_threads()) {
4477     set_par_threads();
4478     workers()->run_task(&rsfp_task);
4479     set_par_threads(0);
4480   } else {
4481     rsfp_task.work(0);
4482   }
4483 
4484   assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity");
4485 
4486   // Reset the claim values in the regions in the collection set.
4487   reset_cset_heap_region_claim_values();
4488 
4489   assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4490 
4491   // Now restore saved marks, if any.
4492   assert(_objs_with_preserved_marks.size() ==
4493             _preserved_marks_of_objs.size(), "Both or none.");
4494   while (!_objs_with_preserved_marks.is_empty()) {
4495     oop obj = _objs_with_preserved_marks.pop();
4496     markOop m = _preserved_marks_of_objs.pop();
4497     obj->set_mark(m);
4498   }
4499   _objs_with_preserved_marks.clear(true);
4500   _preserved_marks_of_objs.clear(true);
4501 
4502   g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
4503 }
4504 
4505 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4506   _evac_failure_scan_stack->push(obj);
4507 }
4508 
4509 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4510   assert(_evac_failure_scan_stack != NULL, "precondition");
4511 
4512   while (_evac_failure_scan_stack->length() > 0) {
4513      oop obj = _evac_failure_scan_stack->pop();
4514      _evac_failure_closure->set_region(heap_region_containing(obj));
4515      obj->oop_iterate_backwards(_evac_failure_closure);
4516   }
4517 }
4518 
4519 oop
4520 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state,
4521                                                oop old) {
4522   assert(obj_in_cs(old),
4523          err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4524                  (HeapWord*) old));
4525   markOop m = old->mark();
4526   oop forward_ptr = old->forward_to_atomic(old);
4527   if (forward_ptr == NULL) {
4528     // Forward-to-self succeeded.
4529     assert(_par_scan_state != NULL, "par scan state");
4530     OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4531     uint queue_num = _par_scan_state->queue_num();
4532 
4533     _evacuation_failed = true;
4534     _evacuation_failed_info_array[queue_num].register_copy_failure(old->size());
4535     if (_evac_failure_closure != cl) {
4536       MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4537       assert(!_drain_in_progress,
4538              "Should only be true while someone holds the lock.");
4539       // Set the global evac-failure closure to the current thread's.
4540       assert(_evac_failure_closure == NULL, "Or locking has failed.");
4541       set_evac_failure_closure(cl);
4542       // Now do the common part.
4543       handle_evacuation_failure_common(old, m);
4544       // Reset to NULL.
4545       set_evac_failure_closure(NULL);
4546     } else {
4547       // The lock is already held, and this is recursive.
4548       assert(_drain_in_progress, "This should only be the recursive case.");
4549       handle_evacuation_failure_common(old, m);
4550     }
4551     return old;
4552   } else {
4553     // Forward-to-self failed. Either someone else managed to allocate
4554     // space for this object (old != forward_ptr) or they beat us in
4555     // self-forwarding it (old == forward_ptr).
4556     assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4557            err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4558                    "should not be in the CSet",
4559                    (HeapWord*) old, (HeapWord*) forward_ptr));
4560     return forward_ptr;
4561   }
4562 }
4563 
4564 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4565   preserve_mark_if_necessary(old, m);
4566 
4567   HeapRegion* r = heap_region_containing(old);
4568   if (!r->evacuation_failed()) {
4569     r->set_evacuation_failed(true);
4570     _hr_printer.evac_failure(r);
4571   }
4572 
4573   push_on_evac_failure_scan_stack(old);
4574 
4575   if (!_drain_in_progress) {
4576     // prevent recursion in copy_to_survivor_space()
4577     _drain_in_progress = true;
4578     drain_evac_failure_scan_stack();
4579     _drain_in_progress = false;
4580   }
4581 }
4582 
4583 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4584   assert(evacuation_failed(), "Oversaving!");
4585   // We want to call the "for_promotion_failure" version only in the
4586   // case of a promotion failure.
4587   if (m->must_be_preserved_for_promotion_failure(obj)) {
4588     _objs_with_preserved_marks.push(obj);
4589     _preserved_marks_of_objs.push(m);
4590   }
4591 }
4592 
4593 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
4594                                                   size_t word_size) {
4595   if (purpose == GCAllocForSurvived) {
4596     HeapWord* result = survivor_attempt_allocation(word_size);
4597     if (result != NULL) {
4598       return result;
4599     } else {
4600       // Let's try to allocate in the old gen in case we can fit the
4601       // object there.
4602       return old_attempt_allocation(word_size);
4603     }
4604   } else {
4605     assert(purpose ==  GCAllocForTenured, "sanity");
4606     HeapWord* result = old_attempt_allocation(word_size);
4607     if (result != NULL) {
4608       return result;
4609     } else {
4610       // Let's try to allocate in the survivors in case we can fit the
4611       // object there.
4612       return survivor_attempt_allocation(word_size);
4613     }
4614   }
4615 
4616   ShouldNotReachHere();
4617   // Trying to keep some compilers happy.
4618   return NULL;
4619 }
4620 
4621 G1ParGCAllocBuffer::G1ParGCAllocBuffer(size_t gclab_word_size) :
4622   ParGCAllocBuffer(gclab_word_size), _retired(true) { }
4623 
4624 void G1ParCopyHelper::mark_object(oop obj) {
4625   assert(!_g1->heap_region_containing(obj)->in_collection_set(), "should not mark objects in the CSet");
4626 
4627   // We know that the object is not moving so it's safe to read its size.
4628   _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4629 }
4630 
4631 void G1ParCopyHelper::mark_forwarded_object(oop from_obj, oop to_obj) {
4632   assert(from_obj->is_forwarded(), "from obj should be forwarded");
4633   assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4634   assert(from_obj != to_obj, "should not be self-forwarded");
4635 
4636   assert(_g1->heap_region_containing(from_obj)->in_collection_set(), "from obj should be in the CSet");
4637   assert(!_g1->heap_region_containing(to_obj)->in_collection_set(), "should not mark objects in the CSet");
4638 
4639   // The object might be in the process of being copied by another
4640   // worker so we cannot trust that its to-space image is
4641   // well-formed. So we have to read its size from its from-space
4642   // image which we know should not be changing.
4643   _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4644 }
4645 
4646 template <class T>
4647 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) {
4648   if (_g1->heap_region_containing_raw(new_obj)->is_young()) {
4649     _scanned_klass->record_modified_oops();
4650   }
4651 }
4652 
4653 template <G1Barrier barrier, G1Mark do_mark_object>
4654 template <class T>
4655 void G1ParCopyClosure<barrier, do_mark_object>::do_oop_work(T* p) {
4656   T heap_oop = oopDesc::load_heap_oop(p);
4657 
4658   if (oopDesc::is_null(heap_oop)) {
4659     return;
4660   }
4661 
4662   oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
4663 
4664   assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4665   bool needs_marking = true;
4666 
4667   if (_g1->is_in_cset_or_humongous(obj)) {
4668     oop forwardee;
4669     if (obj->is_forwarded()) {
4670       forwardee = obj->forwardee();
4671     } else {
4672       forwardee = _par_scan_state->copy_to_survivor_space(obj);
4673     }
4674     if (forwardee != NULL) {
4675       oopDesc::encode_store_heap_oop(p, forwardee);
4676       if (do_mark_object != G1MarkNone && forwardee != obj) {
4677         // If the object is self-forwarded we don't need to explicitly
4678         // mark it, the evacuation failure protocol will do so.
4679         mark_forwarded_object(obj, forwardee);
4680       }
4681 
4682       if (barrier == G1BarrierKlass) {
4683         do_klass_barrier(p, forwardee);
4684       }
4685       needs_marking = false;
4686     }
4687   }
4688   if (needs_marking) {
4689     // The object is not in collection set. If we're a root scanning
4690     // closure during an initial mark pause then attempt to mark the object.
4691     if (do_mark_object == G1MarkFromRoot) {
4692       mark_object(obj);
4693     }
4694   }
4695 
4696   if (barrier == G1BarrierEvac) {
4697     _par_scan_state->update_rs(_from, p, _worker_id);
4698   }
4699 }
4700 
4701 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(oop* p);
4702 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(narrowOop* p);
4703 
4704 class G1ParEvacuateFollowersClosure : public VoidClosure {
4705 protected:
4706   G1CollectedHeap*              _g1h;
4707   G1ParScanThreadState*         _par_scan_state;
4708   RefToScanQueueSet*            _queues;
4709   ParallelTaskTerminator*       _terminator;
4710 
4711   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
4712   RefToScanQueueSet*      queues()         { return _queues; }
4713   ParallelTaskTerminator* terminator()     { return _terminator; }
4714 
4715 public:
4716   G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4717                                 G1ParScanThreadState* par_scan_state,
4718                                 RefToScanQueueSet* queues,
4719                                 ParallelTaskTerminator* terminator)
4720     : _g1h(g1h), _par_scan_state(par_scan_state),
4721       _queues(queues), _terminator(terminator) {}
4722 
4723   void do_void();
4724 
4725 private:
4726   inline bool offer_termination();
4727 };
4728 
4729 bool G1ParEvacuateFollowersClosure::offer_termination() {
4730   G1ParScanThreadState* const pss = par_scan_state();
4731   pss->start_term_time();
4732   const bool res = terminator()->offer_termination();
4733   pss->end_term_time();
4734   return res;
4735 }
4736 
4737 void G1ParEvacuateFollowersClosure::do_void() {
4738   G1ParScanThreadState* const pss = par_scan_state();
4739   pss->trim_queue();
4740   do {
4741     pss->steal_and_trim_queue(queues());
4742   } while (!offer_termination());
4743 }
4744 
4745 class G1KlassScanClosure : public KlassClosure {
4746  G1ParCopyHelper* _closure;
4747  bool             _process_only_dirty;
4748  int              _count;
4749  public:
4750   G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty)
4751       : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {}
4752   void do_klass(Klass* klass) {
4753     // If the klass has not been dirtied we know that there's
4754     // no references into  the young gen and we can skip it.
4755    if (!_process_only_dirty || klass->has_modified_oops()) {
4756       // Clean the klass since we're going to scavenge all the metadata.
4757       klass->clear_modified_oops();
4758 
4759       // Tell the closure that this klass is the Klass to scavenge
4760       // and is the one to dirty if oops are left pointing into the young gen.
4761       _closure->set_scanned_klass(klass);
4762 
4763       klass->oops_do(_closure);
4764 
4765       _closure->set_scanned_klass(NULL);
4766     }
4767     _count++;
4768   }
4769 };
4770 
4771 class G1ParTask : public AbstractGangTask {
4772 protected:
4773   G1CollectedHeap*       _g1h;
4774   RefToScanQueueSet      *_queues;
4775   ParallelTaskTerminator _terminator;
4776   uint _n_workers;
4777 
4778   Mutex _stats_lock;
4779   Mutex* stats_lock() { return &_stats_lock; }
4780 
4781   size_t getNCards() {
4782     return (_g1h->capacity() + G1BlockOffsetSharedArray::N_bytes - 1)
4783       / G1BlockOffsetSharedArray::N_bytes;
4784   }
4785 
4786 public:
4787   G1ParTask(G1CollectedHeap* g1h, RefToScanQueueSet *task_queues)
4788     : AbstractGangTask("G1 collection"),
4789       _g1h(g1h),
4790       _queues(task_queues),
4791       _terminator(0, _queues),
4792       _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4793   {}
4794 
4795   RefToScanQueueSet* queues() { return _queues; }
4796 
4797   RefToScanQueue *work_queue(int i) {
4798     return queues()->queue(i);
4799   }
4800 
4801   ParallelTaskTerminator* terminator() { return &_terminator; }
4802 
4803   virtual void set_for_termination(int active_workers) {
4804     // This task calls set_n_termination() in par_non_clean_card_iterate_work()
4805     // in the young space (_par_seq_tasks) in the G1 heap
4806     // for SequentialSubTasksDone.
4807     // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap
4808     // both of which need setting by set_n_termination().
4809     _g1h->SharedHeap::set_n_termination(active_workers);
4810     _g1h->set_n_termination(active_workers);
4811     terminator()->reset_for_reuse(active_workers);
4812     _n_workers = active_workers;
4813   }
4814 
4815   // Helps out with CLD processing.
4816   //
4817   // During InitialMark we need to:
4818   // 1) Scavenge all CLDs for the young GC.
4819   // 2) Mark all objects directly reachable from strong CLDs.
4820   template <G1Mark do_mark_object>
4821   class G1CLDClosure : public CLDClosure {
4822     G1ParCopyClosure<G1BarrierNone,  do_mark_object>* _oop_closure;
4823     G1ParCopyClosure<G1BarrierKlass, do_mark_object>  _oop_in_klass_closure;
4824     G1KlassScanClosure                                _klass_in_cld_closure;
4825     bool                                              _claim;
4826 
4827    public:
4828     G1CLDClosure(G1ParCopyClosure<G1BarrierNone, do_mark_object>* oop_closure,
4829                  bool only_young, bool claim)
4830         : _oop_closure(oop_closure),
4831           _oop_in_klass_closure(oop_closure->g1(),
4832                                 oop_closure->pss(),
4833                                 oop_closure->rp()),
4834           _klass_in_cld_closure(&_oop_in_klass_closure, only_young),
4835           _claim(claim) {
4836 
4837     }
4838 
4839     void do_cld(ClassLoaderData* cld) {
4840       cld->oops_do(_oop_closure, &_klass_in_cld_closure, _claim);
4841     }
4842   };
4843 
4844   class G1CodeBlobClosure: public CodeBlobClosure {
4845     OopClosure* _f;
4846 
4847    public:
4848     G1CodeBlobClosure(OopClosure* f) : _f(f) {}
4849     void do_code_blob(CodeBlob* blob) {
4850       nmethod* that = blob->as_nmethod_or_null();
4851       if (that != NULL) {
4852         if (!that->test_set_oops_do_mark()) {
4853           that->oops_do(_f);
4854           that->fix_oop_relocations();
4855         }
4856       }
4857     }
4858   };
4859 
4860   void work(uint worker_id) {
4861     if (worker_id >= _n_workers) return;  // no work needed this round
4862 
4863     double start_time_ms = os::elapsedTime() * 1000.0;
4864     _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms);
4865 
4866     {
4867       ResourceMark rm;
4868       HandleMark   hm;
4869 
4870       ReferenceProcessor*             rp = _g1h->ref_processor_stw();
4871 
4872       G1ParScanThreadState            pss(_g1h, worker_id, rp);
4873       G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
4874 
4875       pss.set_evac_failure_closure(&evac_failure_cl);
4876 
4877       bool only_young = _g1h->g1_policy()->gcs_are_young();
4878 
4879       // Non-IM young GC.
4880       G1ParCopyClosure<G1BarrierNone, G1MarkNone>             scan_only_root_cl(_g1h, &pss, rp);
4881       G1CLDClosure<G1MarkNone>                                scan_only_cld_cl(&scan_only_root_cl,
4882                                                                                only_young, // Only process dirty klasses.
4883                                                                                false);     // No need to claim CLDs.
4884       // IM young GC.
4885       //    Strong roots closures.
4886       G1ParCopyClosure<G1BarrierNone, G1MarkFromRoot>         scan_mark_root_cl(_g1h, &pss, rp);
4887       G1CLDClosure<G1MarkFromRoot>                            scan_mark_cld_cl(&scan_mark_root_cl,
4888                                                                                false, // Process all klasses.
4889                                                                                true); // Need to claim CLDs.
4890       //    Weak roots closures.
4891       G1ParCopyClosure<G1BarrierNone, G1MarkPromotedFromRoot> scan_mark_weak_root_cl(_g1h, &pss, rp);
4892       G1CLDClosure<G1MarkPromotedFromRoot>                    scan_mark_weak_cld_cl(&scan_mark_weak_root_cl,
4893                                                                                     false, // Process all klasses.
4894                                                                                     true); // Need to claim CLDs.
4895 
4896       G1CodeBlobClosure scan_only_code_cl(&scan_only_root_cl);
4897       G1CodeBlobClosure scan_mark_code_cl(&scan_mark_root_cl);
4898       // IM Weak code roots are handled later.
4899 
4900       OopClosure* strong_root_cl;
4901       OopClosure* weak_root_cl;
4902       CLDClosure* strong_cld_cl;
4903       CLDClosure* weak_cld_cl;
4904       CodeBlobClosure* strong_code_cl;
4905 
4906       if (_g1h->g1_policy()->during_initial_mark_pause()) {
4907         // We also need to mark copied objects.
4908         strong_root_cl = &scan_mark_root_cl;
4909         weak_root_cl   = &scan_mark_weak_root_cl;
4910         strong_cld_cl  = &scan_mark_cld_cl;
4911         weak_cld_cl    = &scan_mark_weak_cld_cl;
4912         strong_code_cl = &scan_mark_code_cl;
4913       } else {
4914         strong_root_cl = &scan_only_root_cl;
4915         weak_root_cl   = &scan_only_root_cl;
4916         strong_cld_cl  = &scan_only_cld_cl;
4917         weak_cld_cl    = &scan_only_cld_cl;
4918         strong_code_cl = &scan_only_code_cl;
4919       }
4920 
4921 
4922       G1ParPushHeapRSClosure  push_heap_rs_cl(_g1h, &pss);
4923 
4924       pss.start_strong_roots();
4925       _g1h->g1_process_roots(strong_root_cl,
4926                              weak_root_cl,
4927                              &push_heap_rs_cl,
4928                              strong_cld_cl,
4929                              weak_cld_cl,
4930                              strong_code_cl,
4931                              worker_id);
4932 
4933       pss.end_strong_roots();
4934 
4935       {
4936         double start = os::elapsedTime();
4937         G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4938         evac.do_void();
4939         double elapsed_ms = (os::elapsedTime()-start)*1000.0;
4940         double term_ms = pss.term_time()*1000.0;
4941         _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms);
4942         _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts());
4943       }
4944       _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4945       _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4946 
4947       if (ParallelGCVerbose) {
4948         MutexLocker x(stats_lock());
4949         pss.print_termination_stats(worker_id);
4950       }
4951 
4952       assert(pss.queue_is_empty(), "should be empty");
4953 
4954       // Close the inner scope so that the ResourceMark and HandleMark
4955       // destructors are executed here and are included as part of the
4956       // "GC Worker Time".
4957     }
4958 
4959     double end_time_ms = os::elapsedTime() * 1000.0;
4960     _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms);
4961   }
4962 };
4963 
4964 // *** Common G1 Evacuation Stuff
4965 
4966 // This method is run in a GC worker.
4967 
4968 void
4969 G1CollectedHeap::
4970 g1_process_roots(OopClosure* scan_non_heap_roots,
4971                  OopClosure* scan_non_heap_weak_roots,
4972                  OopsInHeapRegionClosure* scan_rs,
4973                  CLDClosure* scan_strong_clds,
4974                  CLDClosure* scan_weak_clds,
4975                  CodeBlobClosure* scan_strong_code,
4976                  uint worker_i) {
4977 
4978   // First scan the shared roots.
4979   double ext_roots_start = os::elapsedTime();
4980   double closure_app_time_sec = 0.0;
4981 
4982   bool during_im = _g1h->g1_policy()->during_initial_mark_pause();
4983 
4984   BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
4985   BufferingOopClosure buf_scan_non_heap_weak_roots(scan_non_heap_weak_roots);
4986 
4987   process_roots(false, // no scoping; this is parallel code
4988                 SharedHeap::SO_None,
4989                 &buf_scan_non_heap_roots,
4990                 &buf_scan_non_heap_weak_roots,
4991                 scan_strong_clds,
4992                 // Initial Mark handles the weak CLDs separately.
4993                 (during_im ? NULL : scan_weak_clds),
4994                 scan_strong_code);
4995 
4996   // Now the CM ref_processor roots.
4997   if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
4998     // We need to treat the discovered reference lists of the
4999     // concurrent mark ref processor as roots and keep entries
5000     // (which are added by the marking threads) on them live
5001     // until they can be processed at the end of marking.
5002     ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
5003   }
5004 
5005   if (during_im) {
5006     // Barrier to make sure all workers passed
5007     // the strong CLD and strong nmethods phases.
5008     active_strong_roots_scope()->wait_until_all_workers_done_with_threads(n_par_threads());
5009 
5010     // Now take the complement of the strong CLDs.
5011     ClassLoaderDataGraph::roots_cld_do(NULL, scan_weak_clds);
5012   }
5013 
5014   // Finish up any enqueued closure apps (attributed as object copy time).
5015   buf_scan_non_heap_roots.done();
5016   buf_scan_non_heap_weak_roots.done();
5017 
5018   double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds()
5019       + buf_scan_non_heap_weak_roots.closure_app_seconds();
5020 
5021   g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
5022 
5023   double ext_root_time_ms =
5024     ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0;
5025 
5026   g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
5027 
5028   // During conc marking we have to filter the per-thread SATB buffers
5029   // to make sure we remove any oops into the CSet (which will show up
5030   // as implicitly live).
5031   double satb_filtering_ms = 0.0;
5032   if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) {
5033     if (mark_in_progress()) {
5034       double satb_filter_start = os::elapsedTime();
5035 
5036       JavaThread::satb_mark_queue_set().filter_thread_buffers();
5037 
5038       satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0;
5039     }
5040   }
5041   g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms);
5042 
5043   // Now scan the complement of the collection set.
5044   MarkingCodeBlobClosure scavenge_cs_nmethods(scan_non_heap_weak_roots, CodeBlobToOopClosure::FixRelocations);
5045 
5046   g1_rem_set()->oops_into_collection_set_do(scan_rs, &scavenge_cs_nmethods, worker_i);
5047 
5048   _process_strong_tasks->all_tasks_completed();
5049 }
5050 
5051 class G1StringSymbolTableUnlinkTask : public AbstractGangTask {
5052 private:
5053   BoolObjectClosure* _is_alive;
5054   int _initial_string_table_size;
5055   int _initial_symbol_table_size;
5056 
5057   bool  _process_strings;
5058   int _strings_processed;
5059   int _strings_removed;
5060 
5061   bool  _process_symbols;
5062   int _symbols_processed;
5063   int _symbols_removed;
5064 
5065   bool _do_in_parallel;
5066 public:
5067   G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) :
5068     AbstractGangTask("String/Symbol Unlinking"),
5069     _is_alive(is_alive),
5070     _do_in_parallel(G1CollectedHeap::use_parallel_gc_threads()),
5071     _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
5072     _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) {
5073 
5074     _initial_string_table_size = StringTable::the_table()->table_size();
5075     _initial_symbol_table_size = SymbolTable::the_table()->table_size();
5076     if (process_strings) {
5077       StringTable::clear_parallel_claimed_index();
5078     }
5079     if (process_symbols) {
5080       SymbolTable::clear_parallel_claimed_index();
5081     }
5082   }
5083 
5084   ~G1StringSymbolTableUnlinkTask() {
5085     guarantee(!_process_strings || !_do_in_parallel || StringTable::parallel_claimed_index() >= _initial_string_table_size,
5086               err_msg("claim value %d after unlink less than initial string table size %d",
5087                       StringTable::parallel_claimed_index(), _initial_string_table_size));
5088     guarantee(!_process_symbols || !_do_in_parallel || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
5089               err_msg("claim value %d after unlink less than initial symbol table size %d",
5090                       SymbolTable::parallel_claimed_index(), _initial_symbol_table_size));
5091 
5092     if (G1TraceStringSymbolTableScrubbing) {
5093       gclog_or_tty->print_cr("Cleaned string and symbol table, "
5094                              "strings: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed, "
5095                              "symbols: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed",
5096                              strings_processed(), strings_removed(),
5097                              symbols_processed(), symbols_removed());
5098     }
5099   }
5100 
5101   void work(uint worker_id) {
5102     if (_do_in_parallel) {
5103       int strings_processed = 0;
5104       int strings_removed = 0;
5105       int symbols_processed = 0;
5106       int symbols_removed = 0;
5107       if (_process_strings) {
5108         StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
5109         Atomic::add(strings_processed, &_strings_processed);
5110         Atomic::add(strings_removed, &_strings_removed);
5111       }
5112       if (_process_symbols) {
5113         SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
5114         Atomic::add(symbols_processed, &_symbols_processed);
5115         Atomic::add(symbols_removed, &_symbols_removed);
5116       }
5117     } else {
5118       if (_process_strings) {
5119         StringTable::unlink(_is_alive, &_strings_processed, &_strings_removed);
5120       }
5121       if (_process_symbols) {
5122         SymbolTable::unlink(&_symbols_processed, &_symbols_removed);
5123       }
5124     }
5125   }
5126 
5127   size_t strings_processed() const { return (size_t)_strings_processed; }
5128   size_t strings_removed()   const { return (size_t)_strings_removed; }
5129 
5130   size_t symbols_processed() const { return (size_t)_symbols_processed; }
5131   size_t symbols_removed()   const { return (size_t)_symbols_removed; }
5132 };
5133 
5134 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
5135 private:
5136   static Monitor* _lock;
5137 
5138   BoolObjectClosure* const _is_alive;
5139   const bool               _unloading_occurred;
5140   const uint               _num_workers;
5141 
5142   // Variables used to claim nmethods.
5143   nmethod* _first_nmethod;
5144   volatile nmethod* _claimed_nmethod;
5145 
5146   // The list of nmethods that need to be processed by the second pass.
5147   volatile nmethod* _postponed_list;
5148   volatile uint     _num_entered_barrier;
5149 
5150  public:
5151   G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
5152       _is_alive(is_alive),
5153       _unloading_occurred(unloading_occurred),
5154       _num_workers(num_workers),
5155       _first_nmethod(NULL),
5156       _claimed_nmethod(NULL),
5157       _postponed_list(NULL),
5158       _num_entered_barrier(0)
5159   {
5160     nmethod::increase_unloading_clock();
5161     _first_nmethod = CodeCache::alive_nmethod(CodeCache::first());
5162     _claimed_nmethod = (volatile nmethod*)_first_nmethod;
5163   }
5164 
5165   ~G1CodeCacheUnloadingTask() {
5166     CodeCache::verify_clean_inline_caches();
5167 
5168     CodeCache::set_needs_cache_clean(false);
5169     guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
5170 
5171     CodeCache::verify_icholder_relocations();
5172   }
5173 
5174  private:
5175   void add_to_postponed_list(nmethod* nm) {
5176       nmethod* old;
5177       do {
5178         old = (nmethod*)_postponed_list;
5179         nm->set_unloading_next(old);
5180       } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old);
5181   }
5182 
5183   void clean_nmethod(nmethod* nm) {
5184     bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
5185 
5186     if (postponed) {
5187       // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
5188       add_to_postponed_list(nm);
5189     }
5190 
5191     // Mark that this thread has been cleaned/unloaded.
5192     // After this call, it will be safe to ask if this nmethod was unloaded or not.
5193     nm->set_unloading_clock(nmethod::global_unloading_clock());
5194   }
5195 
5196   void clean_nmethod_postponed(nmethod* nm) {
5197     nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
5198   }
5199 
5200   static const int MaxClaimNmethods = 16;
5201 
5202   void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) {
5203     nmethod* first;
5204     nmethod* last;
5205 
5206     do {
5207       *num_claimed_nmethods = 0;
5208 
5209       first = last = (nmethod*)_claimed_nmethod;
5210 
5211       if (first != NULL) {
5212         for (int i = 0; i < MaxClaimNmethods; i++) {
5213           last = CodeCache::alive_nmethod(CodeCache::next(last));
5214 
5215           if (last == NULL) {
5216             break;
5217           }
5218 
5219           claimed_nmethods[i] = last;
5220           (*num_claimed_nmethods)++;
5221         }
5222       }
5223 
5224     } while ((nmethod*)Atomic::cmpxchg_ptr(last, &_claimed_nmethod, first) != first);
5225   }
5226 
5227   nmethod* claim_postponed_nmethod() {
5228     nmethod* claim;
5229     nmethod* next;
5230 
5231     do {
5232       claim = (nmethod*)_postponed_list;
5233       if (claim == NULL) {
5234         return NULL;
5235       }
5236 
5237       next = claim->unloading_next();
5238 
5239     } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim);
5240 
5241     return claim;
5242   }
5243 
5244  public:
5245   // Mark that we're done with the first pass of nmethod cleaning.
5246   void barrier_mark(uint worker_id) {
5247     MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
5248     _num_entered_barrier++;
5249     if (_num_entered_barrier == _num_workers) {
5250       ml.notify_all();
5251     }
5252   }
5253 
5254   // See if we have to wait for the other workers to
5255   // finish their first-pass nmethod cleaning work.
5256   void barrier_wait(uint worker_id) {
5257     if (_num_entered_barrier < _num_workers) {
5258       MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
5259       while (_num_entered_barrier < _num_workers) {
5260           ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
5261       }
5262     }
5263   }
5264 
5265   // Cleaning and unloading of nmethods. Some work has to be postponed
5266   // to the second pass, when we know which nmethods survive.
5267   void work_first_pass(uint worker_id) {
5268     // The first nmethods is claimed by the first worker.
5269     if (worker_id == 0 && _first_nmethod != NULL) {
5270       clean_nmethod(_first_nmethod);
5271       _first_nmethod = NULL;
5272     }
5273 
5274     int num_claimed_nmethods;
5275     nmethod* claimed_nmethods[MaxClaimNmethods];
5276 
5277     while (true) {
5278       claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
5279 
5280       if (num_claimed_nmethods == 0) {
5281         break;
5282       }
5283 
5284       for (int i = 0; i < num_claimed_nmethods; i++) {
5285         clean_nmethod(claimed_nmethods[i]);
5286       }
5287     }
5288   }
5289 
5290   void work_second_pass(uint worker_id) {
5291     nmethod* nm;
5292     // Take care of postponed nmethods.
5293     while ((nm = claim_postponed_nmethod()) != NULL) {
5294       clean_nmethod_postponed(nm);
5295     }
5296   }
5297 };
5298 
5299 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock");
5300 
5301 class G1KlassCleaningTask : public StackObj {
5302   BoolObjectClosure*                      _is_alive;
5303   volatile jint                           _clean_klass_tree_claimed;
5304   ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
5305 
5306  public:
5307   G1KlassCleaningTask(BoolObjectClosure* is_alive) :
5308       _is_alive(is_alive),
5309       _clean_klass_tree_claimed(0),
5310       _klass_iterator() {
5311   }
5312 
5313  private:
5314   bool claim_clean_klass_tree_task() {
5315     if (_clean_klass_tree_claimed) {
5316       return false;
5317     }
5318 
5319     return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0;
5320   }
5321 
5322   InstanceKlass* claim_next_klass() {
5323     Klass* klass;
5324     do {
5325       klass =_klass_iterator.next_klass();
5326     } while (klass != NULL && !klass->oop_is_instance());
5327 
5328     return (InstanceKlass*)klass;
5329   }
5330 
5331 public:
5332 
5333   void clean_klass(InstanceKlass* ik) {
5334     ik->clean_implementors_list(_is_alive);
5335     ik->clean_method_data(_is_alive);
5336 
5337     // G1 specific cleanup work that has
5338     // been moved here to be done in parallel.
5339     ik->clean_dependent_nmethods();
5340   }
5341 
5342   void work() {
5343     ResourceMark rm;
5344 
5345     // One worker will clean the subklass/sibling klass tree.
5346     if (claim_clean_klass_tree_task()) {
5347       Klass::clean_subklass_tree(_is_alive);
5348     }
5349 
5350     // All workers will help cleaning the classes,
5351     InstanceKlass* klass;
5352     while ((klass = claim_next_klass()) != NULL) {
5353       clean_klass(klass);
5354     }
5355   }
5356 };
5357 
5358 // To minimize the remark pause times, the tasks below are done in parallel.
5359 class G1ParallelCleaningTask : public AbstractGangTask {
5360 private:
5361   G1StringSymbolTableUnlinkTask _string_symbol_task;
5362   G1CodeCacheUnloadingTask      _code_cache_task;
5363   G1KlassCleaningTask           _klass_cleaning_task;
5364 
5365 public:
5366   // The constructor is run in the VMThread.
5367   G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) :
5368       AbstractGangTask("Parallel Cleaning"),
5369       _string_symbol_task(is_alive, process_strings, process_symbols),
5370       _code_cache_task(num_workers, is_alive, unloading_occurred),
5371       _klass_cleaning_task(is_alive) {
5372   }
5373 
5374   // The parallel work done by all worker threads.
5375   void work(uint worker_id) {
5376     // Do first pass of code cache cleaning.
5377     _code_cache_task.work_first_pass(worker_id);
5378 
5379     // Let the threads, mark that the first pass is done.
5380     _code_cache_task.barrier_mark(worker_id);
5381 
5382     // Clean the Strings and Symbols.
5383     _string_symbol_task.work(worker_id);
5384 
5385     // Wait for all workers to finish the first code cache cleaning pass.
5386     _code_cache_task.barrier_wait(worker_id);
5387 
5388     // Do the second code cache cleaning work, which realize on
5389     // the liveness information gathered during the first pass.
5390     _code_cache_task.work_second_pass(worker_id);
5391 
5392     // Clean all klasses that were not unloaded.
5393     _klass_cleaning_task.work();
5394   }
5395 };
5396 
5397 
5398 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive,
5399                                         bool process_strings,
5400                                         bool process_symbols,
5401                                         bool class_unloading_occurred) {
5402   uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5403                     workers()->active_workers() : 1);
5404 
5405   G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols,
5406                                         n_workers, class_unloading_occurred);
5407   if (G1CollectedHeap::use_parallel_gc_threads()) {
5408     set_par_threads(n_workers);
5409     workers()->run_task(&g1_unlink_task);
5410     set_par_threads(0);
5411   } else {
5412     g1_unlink_task.work(0);
5413   }
5414 }
5415 
5416 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive,
5417                                                      bool process_strings, bool process_symbols) {
5418   {
5419     uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5420                      _g1h->workers()->active_workers() : 1);
5421     G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols);
5422     if (G1CollectedHeap::use_parallel_gc_threads()) {
5423       set_par_threads(n_workers);
5424       workers()->run_task(&g1_unlink_task);
5425       set_par_threads(0);
5426     } else {
5427       g1_unlink_task.work(0);
5428     }
5429   }
5430 
5431   if (G1StringDedup::is_enabled()) {
5432     G1StringDedup::unlink(is_alive);
5433   }
5434 }
5435 
5436 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
5437  private:
5438   DirtyCardQueueSet* _queue;
5439  public:
5440   G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue) : AbstractGangTask("Redirty Cards"), _queue(queue) { }
5441 
5442   virtual void work(uint worker_id) {
5443     double start_time = os::elapsedTime();
5444 
5445     RedirtyLoggedCardTableEntryClosure cl;
5446     if (G1CollectedHeap::heap()->use_parallel_gc_threads()) {
5447       _queue->par_apply_closure_to_all_completed_buffers(&cl);
5448     } else {
5449       _queue->apply_closure_to_all_completed_buffers(&cl);
5450     }
5451 
5452     G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
5453     timer->record_redirty_logged_cards_time_ms(worker_id, (os::elapsedTime() - start_time) * 1000.0);
5454     timer->record_redirty_logged_cards_processed_cards(worker_id, cl.num_processed());
5455   }
5456 };
5457 
5458 void G1CollectedHeap::redirty_logged_cards() {
5459   guarantee(G1DeferredRSUpdate, "Must only be called when using deferred RS updates.");
5460   double redirty_logged_cards_start = os::elapsedTime();
5461 
5462   uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5463                    _g1h->workers()->active_workers() : 1);
5464 
5465   G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set());
5466   dirty_card_queue_set().reset_for_par_iteration();
5467   if (use_parallel_gc_threads()) {
5468     set_par_threads(n_workers);
5469     workers()->run_task(&redirty_task);
5470     set_par_threads(0);
5471   } else {
5472     redirty_task.work(0);
5473   }
5474 
5475   DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5476   dcq.merge_bufferlists(&dirty_card_queue_set());
5477   assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5478 
5479   g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
5480 }
5481 
5482 // Weak Reference Processing support
5483 
5484 // An always "is_alive" closure that is used to preserve referents.
5485 // If the object is non-null then it's alive.  Used in the preservation
5486 // of referent objects that are pointed to by reference objects
5487 // discovered by the CM ref processor.
5488 class G1AlwaysAliveClosure: public BoolObjectClosure {
5489   G1CollectedHeap* _g1;
5490 public:
5491   G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5492   bool do_object_b(oop p) {
5493     if (p != NULL) {
5494       return true;
5495     }
5496     return false;
5497   }
5498 };
5499 
5500 bool G1STWIsAliveClosure::do_object_b(oop p) {
5501   // An object is reachable if it is outside the collection set,
5502   // or is inside and copied.
5503   return !_g1->obj_in_cs(p) || p->is_forwarded();
5504 }
5505 
5506 // Non Copying Keep Alive closure
5507 class G1KeepAliveClosure: public OopClosure {
5508   G1CollectedHeap* _g1;
5509 public:
5510   G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5511   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
5512   void do_oop(oop* p) {
5513     oop obj = *p;
5514 
5515     if (obj == NULL || !_g1->is_in_cset_or_humongous(obj)) {
5516       return;
5517     }
5518     if (_g1->is_in_cset(obj)) {
5519       assert( obj->is_forwarded(), "invariant" );
5520       *p = obj->forwardee();        
5521     } else {
5522       assert(!obj->is_forwarded(), "invariant" );
5523       _g1->set_humongous_is_live(obj);
5524     }
5525   }
5526 };
5527 
5528 // Copying Keep Alive closure - can be called from both
5529 // serial and parallel code as long as different worker
5530 // threads utilize different G1ParScanThreadState instances
5531 // and different queues.
5532 
5533 class G1CopyingKeepAliveClosure: public OopClosure {
5534   G1CollectedHeap*         _g1h;
5535   OopClosure*              _copy_non_heap_obj_cl;
5536   G1ParScanThreadState*    _par_scan_state;
5537 
5538 public:
5539   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
5540                             OopClosure* non_heap_obj_cl,
5541                             G1ParScanThreadState* pss):
5542     _g1h(g1h),
5543     _copy_non_heap_obj_cl(non_heap_obj_cl),
5544     _par_scan_state(pss)
5545   {}
5546 
5547   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
5548   virtual void do_oop(      oop* p) { do_oop_work(p); }
5549 
5550   template <class T> void do_oop_work(T* p) {
5551     oop obj = oopDesc::load_decode_heap_oop(p);
5552 
5553     if (_g1h->is_in_cset_or_humongous(obj)) {
5554       // If the referent object has been forwarded (either copied
5555       // to a new location or to itself in the event of an
5556       // evacuation failure) then we need to update the reference
5557       // field and, if both reference and referent are in the G1
5558       // heap, update the RSet for the referent.
5559       //
5560       // If the referent has not been forwarded then we have to keep
5561       // it alive by policy. Therefore we have copy the referent.
5562       //
5563       // If the reference field is in the G1 heap then we can push
5564       // on the PSS queue. When the queue is drained (after each
5565       // phase of reference processing) the object and it's followers
5566       // will be copied, the reference field set to point to the
5567       // new location, and the RSet updated. Otherwise we need to
5568       // use the the non-heap or metadata closures directly to copy
5569       // the referent object and update the pointer, while avoiding
5570       // updating the RSet.
5571 
5572       if (_g1h->is_in_g1_reserved(p)) {
5573         _par_scan_state->push_on_queue(p);
5574       } else {
5575         assert(!Metaspace::contains((const void*)p),
5576                err_msg("Unexpectedly found a pointer from metadata: "
5577                               PTR_FORMAT, p));
5578           _copy_non_heap_obj_cl->do_oop(p);
5579         }
5580       }
5581     }
5582 };
5583 
5584 // Serial drain queue closure. Called as the 'complete_gc'
5585 // closure for each discovered list in some of the
5586 // reference processing phases.
5587 
5588 class G1STWDrainQueueClosure: public VoidClosure {
5589 protected:
5590   G1CollectedHeap* _g1h;
5591   G1ParScanThreadState* _par_scan_state;
5592 
5593   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
5594 
5595 public:
5596   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
5597     _g1h(g1h),
5598     _par_scan_state(pss)
5599   { }
5600 
5601   void do_void() {
5602     G1ParScanThreadState* const pss = par_scan_state();
5603     pss->trim_queue();
5604   }
5605 };
5606 
5607 // Parallel Reference Processing closures
5608 
5609 // Implementation of AbstractRefProcTaskExecutor for parallel reference
5610 // processing during G1 evacuation pauses.
5611 
5612 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5613 private:
5614   G1CollectedHeap*   _g1h;
5615   RefToScanQueueSet* _queues;
5616   FlexibleWorkGang*  _workers;
5617   int                _active_workers;
5618 
5619 public:
5620   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5621                         FlexibleWorkGang* workers,
5622                         RefToScanQueueSet *task_queues,
5623                         int n_workers) :
5624     _g1h(g1h),
5625     _queues(task_queues),
5626     _workers(workers),
5627     _active_workers(n_workers)
5628   {
5629     assert(n_workers > 0, "shouldn't call this otherwise");
5630   }
5631 
5632   // Executes the given task using concurrent marking worker threads.
5633   virtual void execute(ProcessTask& task);
5634   virtual void execute(EnqueueTask& task);
5635 };
5636 
5637 // Gang task for possibly parallel reference processing
5638 
5639 class G1STWRefProcTaskProxy: public AbstractGangTask {
5640   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5641   ProcessTask&     _proc_task;
5642   G1CollectedHeap* _g1h;
5643   RefToScanQueueSet *_task_queues;
5644   ParallelTaskTerminator* _terminator;
5645 
5646 public:
5647   G1STWRefProcTaskProxy(ProcessTask& proc_task,
5648                      G1CollectedHeap* g1h,
5649                      RefToScanQueueSet *task_queues,
5650                      ParallelTaskTerminator* terminator) :
5651     AbstractGangTask("Process reference objects in parallel"),
5652     _proc_task(proc_task),
5653     _g1h(g1h),
5654     _task_queues(task_queues),
5655     _terminator(terminator)
5656   {}
5657 
5658   virtual void work(uint worker_id) {
5659     // The reference processing task executed by a single worker.
5660     ResourceMark rm;
5661     HandleMark   hm;
5662 
5663     G1STWIsAliveClosure is_alive(_g1h);
5664 
5665     G1ParScanThreadState            pss(_g1h, worker_id, NULL);
5666     G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5667 
5668     pss.set_evac_failure_closure(&evac_failure_cl);
5669 
5670     G1ParScanExtRootClosure        only_copy_non_heap_cl(_g1h, &pss, NULL);
5671 
5672     G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5673 
5674     OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5675 
5676     if (_g1h->g1_policy()->during_initial_mark_pause()) {
5677       // We also need to mark copied objects.
5678       copy_non_heap_cl = &copy_mark_non_heap_cl;
5679     }
5680 
5681     // Keep alive closure.
5682     G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5683 
5684     // Complete GC closure
5685     G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5686 
5687     // Call the reference processing task's work routine.
5688     _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5689 
5690     // Note we cannot assert that the refs array is empty here as not all
5691     // of the processing tasks (specifically phase2 - pp2_work) execute
5692     // the complete_gc closure (which ordinarily would drain the queue) so
5693     // the queue may not be empty.
5694   }
5695 };
5696 
5697 // Driver routine for parallel reference processing.
5698 // Creates an instance of the ref processing gang
5699 // task and has the worker threads execute it.
5700 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5701   assert(_workers != NULL, "Need parallel worker threads.");
5702 
5703   ParallelTaskTerminator terminator(_active_workers, _queues);
5704   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5705 
5706   _g1h->set_par_threads(_active_workers);
5707   _workers->run_task(&proc_task_proxy);
5708   _g1h->set_par_threads(0);
5709 }
5710 
5711 // Gang task for parallel reference enqueueing.
5712 
5713 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5714   typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5715   EnqueueTask& _enq_task;
5716 
5717 public:
5718   G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5719     AbstractGangTask("Enqueue reference objects in parallel"),
5720     _enq_task(enq_task)
5721   { }
5722 
5723   virtual void work(uint worker_id) {
5724     _enq_task.work(worker_id);
5725   }
5726 };
5727 
5728 // Driver routine for parallel reference enqueueing.
5729 // Creates an instance of the ref enqueueing gang
5730 // task and has the worker threads execute it.
5731 
5732 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5733   assert(_workers != NULL, "Need parallel worker threads.");
5734 
5735   G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5736 
5737   _g1h->set_par_threads(_active_workers);
5738   _workers->run_task(&enq_task_proxy);
5739   _g1h->set_par_threads(0);
5740 }
5741 
5742 // End of weak reference support closures
5743 
5744 // Abstract task used to preserve (i.e. copy) any referent objects
5745 // that are in the collection set and are pointed to by reference
5746 // objects discovered by the CM ref processor.
5747 
5748 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5749 protected:
5750   G1CollectedHeap* _g1h;
5751   RefToScanQueueSet      *_queues;
5752   ParallelTaskTerminator _terminator;
5753   uint _n_workers;
5754 
5755 public:
5756   G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
5757     AbstractGangTask("ParPreserveCMReferents"),
5758     _g1h(g1h),
5759     _queues(task_queues),
5760     _terminator(workers, _queues),
5761     _n_workers(workers)
5762   { }
5763 
5764   void work(uint worker_id) {
5765     ResourceMark rm;
5766     HandleMark   hm;
5767 
5768     G1ParScanThreadState            pss(_g1h, worker_id, NULL);
5769     G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5770 
5771     pss.set_evac_failure_closure(&evac_failure_cl);
5772 
5773     assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5774 
5775     G1ParScanExtRootClosure        only_copy_non_heap_cl(_g1h, &pss, NULL);
5776 
5777     G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5778 
5779     OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5780 
5781     if (_g1h->g1_policy()->during_initial_mark_pause()) {
5782       // We also need to mark copied objects.
5783       copy_non_heap_cl = &copy_mark_non_heap_cl;
5784     }
5785 
5786     // Is alive closure
5787     G1AlwaysAliveClosure always_alive(_g1h);
5788 
5789     // Copying keep alive closure. Applied to referent objects that need
5790     // to be copied.
5791     G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5792 
5793     ReferenceProcessor* rp = _g1h->ref_processor_cm();
5794 
5795     uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5796     uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5797 
5798     // limit is set using max_num_q() - which was set using ParallelGCThreads.
5799     // So this must be true - but assert just in case someone decides to
5800     // change the worker ids.
5801     assert(0 <= worker_id && worker_id < limit, "sanity");
5802     assert(!rp->discovery_is_atomic(), "check this code");
5803 
5804     // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5805     for (uint idx = worker_id; idx < limit; idx += stride) {
5806       DiscoveredList& ref_list = rp->discovered_refs()[idx];
5807 
5808       DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5809       while (iter.has_next()) {
5810         // Since discovery is not atomic for the CM ref processor, we
5811         // can see some null referent objects.
5812         iter.load_ptrs(DEBUG_ONLY(true));
5813         oop ref = iter.obj();
5814 
5815         // This will filter nulls.
5816         if (iter.is_referent_alive()) {
5817           iter.make_referent_alive();
5818         }
5819         iter.move_to_next();
5820       }
5821     }
5822 
5823     // Drain the queue - which may cause stealing
5824     G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5825     drain_queue.do_void();
5826     // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5827     assert(pss.queue_is_empty(), "should be");
5828   }
5829 };
5830 
5831 // Weak Reference processing during an evacuation pause (part 1).
5832 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) {
5833   double ref_proc_start = os::elapsedTime();
5834 
5835   ReferenceProcessor* rp = _ref_processor_stw;
5836   assert(rp->discovery_enabled(), "should have been enabled");
5837 
5838   // Any reference objects, in the collection set, that were 'discovered'
5839   // by the CM ref processor should have already been copied (either by
5840   // applying the external root copy closure to the discovered lists, or
5841   // by following an RSet entry).
5842   //
5843   // But some of the referents, that are in the collection set, that these
5844   // reference objects point to may not have been copied: the STW ref
5845   // processor would have seen that the reference object had already
5846   // been 'discovered' and would have skipped discovering the reference,
5847   // but would not have treated the reference object as a regular oop.
5848   // As a result the copy closure would not have been applied to the
5849   // referent object.
5850   //
5851   // We need to explicitly copy these referent objects - the references
5852   // will be processed at the end of remarking.
5853   //
5854   // We also need to do this copying before we process the reference
5855   // objects discovered by the STW ref processor in case one of these
5856   // referents points to another object which is also referenced by an
5857   // object discovered by the STW ref processor.
5858 
5859   assert(!G1CollectedHeap::use_parallel_gc_threads() ||
5860            no_of_gc_workers == workers()->active_workers(),
5861            "Need to reset active GC workers");
5862 
5863   set_par_threads(no_of_gc_workers);
5864   G1ParPreserveCMReferentsTask keep_cm_referents(this,
5865                                                  no_of_gc_workers,
5866                                                  _task_queues);
5867 
5868   if (G1CollectedHeap::use_parallel_gc_threads()) {
5869     workers()->run_task(&keep_cm_referents);
5870   } else {
5871     keep_cm_referents.work(0);
5872   }
5873 
5874   set_par_threads(0);
5875 
5876   // Closure to test whether a referent is alive.
5877   G1STWIsAliveClosure is_alive(this);
5878 
5879   // Even when parallel reference processing is enabled, the processing
5880   // of JNI refs is serial and performed serially by the current thread
5881   // rather than by a worker. The following PSS will be used for processing
5882   // JNI refs.
5883 
5884   // Use only a single queue for this PSS.
5885   G1ParScanThreadState            pss(this, 0, NULL);
5886 
5887   // We do not embed a reference processor in the copying/scanning
5888   // closures while we're actually processing the discovered
5889   // reference objects.
5890   G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5891 
5892   pss.set_evac_failure_closure(&evac_failure_cl);
5893 
5894   assert(pss.queue_is_empty(), "pre-condition");
5895 
5896   G1ParScanExtRootClosure        only_copy_non_heap_cl(this, &pss, NULL);
5897 
5898   G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5899 
5900   OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5901 
5902   if (_g1h->g1_policy()->during_initial_mark_pause()) {
5903     // We also need to mark copied objects.
5904     copy_non_heap_cl = &copy_mark_non_heap_cl;
5905   }
5906 
5907   // Keep alive closure.
5908   G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, &pss);
5909 
5910   // Serial Complete GC closure
5911   G1STWDrainQueueClosure drain_queue(this, &pss);
5912 
5913   // Setup the soft refs policy...
5914   rp->setup_policy(false);
5915 
5916   ReferenceProcessorStats stats;
5917   if (!rp->processing_is_mt()) {
5918     // Serial reference processing...
5919     stats = rp->process_discovered_references(&is_alive,
5920                                               &keep_alive,
5921                                               &drain_queue,
5922                                               NULL,
5923                                               _gc_timer_stw,
5924                                               _gc_tracer_stw->gc_id());
5925   } else {
5926     // Parallel reference processing
5927     assert(rp->num_q() == no_of_gc_workers, "sanity");
5928     assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5929 
5930     G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5931     stats = rp->process_discovered_references(&is_alive,
5932                                               &keep_alive,
5933                                               &drain_queue,
5934                                               &par_task_executor,
5935                                               _gc_timer_stw,
5936                                               _gc_tracer_stw->gc_id());
5937   }
5938 
5939   _gc_tracer_stw->report_gc_reference_stats(stats);
5940 
5941   // We have completed copying any necessary live referent objects.
5942   assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5943 
5944   double ref_proc_time = os::elapsedTime() - ref_proc_start;
5945   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5946 }
5947 
5948 // Weak Reference processing during an evacuation pause (part 2).
5949 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) {
5950   double ref_enq_start = os::elapsedTime();
5951 
5952   ReferenceProcessor* rp = _ref_processor_stw;
5953   assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5954 
5955   // Now enqueue any remaining on the discovered lists on to
5956   // the pending list.
5957   if (!rp->processing_is_mt()) {
5958     // Serial reference processing...
5959     rp->enqueue_discovered_references();
5960   } else {
5961     // Parallel reference enqueueing
5962 
5963     assert(no_of_gc_workers == workers()->active_workers(),
5964            "Need to reset active workers");
5965     assert(rp->num_q() == no_of_gc_workers, "sanity");
5966     assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5967 
5968     G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5969     rp->enqueue_discovered_references(&par_task_executor);
5970   }
5971 
5972   rp->verify_no_references_recorded();
5973   assert(!rp->discovery_enabled(), "should have been disabled");
5974 
5975   // FIXME
5976   // CM's reference processing also cleans up the string and symbol tables.
5977   // Should we do that here also? We could, but it is a serial operation
5978   // and could significantly increase the pause time.
5979 
5980   double ref_enq_time = os::elapsedTime() - ref_enq_start;
5981   g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5982 }
5983 
5984 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) {
5985   _expand_heap_after_alloc_failure = true;
5986   _evacuation_failed = false;
5987 
5988   // Should G1EvacuationFailureALot be in effect for this GC?
5989   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
5990 
5991   g1_rem_set()->prepare_for_oops_into_collection_set_do();
5992 
5993   // Disable the hot card cache.
5994   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
5995   hot_card_cache->reset_hot_cache_claimed_index();
5996   hot_card_cache->set_use_cache(false);
5997 
5998   uint n_workers;
5999   if (G1CollectedHeap::use_parallel_gc_threads()) {
6000     n_workers =
6001       AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
6002                                      workers()->active_workers(),
6003                                      Threads::number_of_non_daemon_threads());
6004     assert(UseDynamicNumberOfGCThreads ||
6005            n_workers == workers()->total_workers(),
6006            "If not dynamic should be using all the  workers");
6007     workers()->set_active_workers(n_workers);
6008     set_par_threads(n_workers);
6009   } else {
6010     assert(n_par_threads() == 0,
6011            "Should be the original non-parallel value");
6012     n_workers = 1;
6013   }
6014 
6015   G1ParTask g1_par_task(this, _task_queues);
6016 
6017   init_for_evac_failure(NULL);
6018 
6019   rem_set()->prepare_for_younger_refs_iterate(true);
6020 
6021   assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
6022   double start_par_time_sec = os::elapsedTime();
6023   double end_par_time_sec;
6024 
6025   {
6026     StrongRootsScope srs(this);
6027     // InitialMark needs claim bits to keep track of the marked-through CLDs.
6028     if (g1_policy()->during_initial_mark_pause()) {
6029       ClassLoaderDataGraph::clear_claimed_marks();
6030     }
6031 
6032     if (G1CollectedHeap::use_parallel_gc_threads()) {
6033       // The individual threads will set their evac-failure closures.
6034       if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
6035       // These tasks use ShareHeap::_process_strong_tasks
6036       assert(UseDynamicNumberOfGCThreads ||
6037              workers()->active_workers() == workers()->total_workers(),
6038              "If not dynamic should be using all the  workers");
6039       workers()->run_task(&g1_par_task);
6040     } else {
6041       g1_par_task.set_for_termination(n_workers);
6042       g1_par_task.work(0);
6043     }
6044     end_par_time_sec = os::elapsedTime();
6045 
6046     // Closing the inner scope will execute the destructor
6047     // for the StrongRootsScope object. We record the current
6048     // elapsed time before closing the scope so that time
6049     // taken for the SRS destructor is NOT included in the
6050     // reported parallel time.
6051   }
6052 
6053   double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
6054   g1_policy()->phase_times()->record_par_time(par_time_ms);
6055 
6056   double code_root_fixup_time_ms =
6057         (os::elapsedTime() - end_par_time_sec) * 1000.0;
6058   g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms);
6059 
6060   set_par_threads(0);
6061 
6062   // Process any discovered reference objects - we have
6063   // to do this _before_ we retire the GC alloc regions
6064   // as we may have to copy some 'reachable' referent
6065   // objects (and their reachable sub-graphs) that were
6066   // not copied during the pause.
6067   process_discovered_references(n_workers);
6068 
6069   // Weak root processing.
6070   {
6071     G1STWIsAliveClosure is_alive(this);
6072     G1KeepAliveClosure keep_alive(this);
6073     JNIHandles::weak_oops_do(&is_alive, &keep_alive);
6074     if (G1StringDedup::is_enabled()) {
6075       G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive);
6076     }
6077   }
6078 
6079   release_gc_alloc_regions(n_workers, evacuation_info);
6080   g1_rem_set()->cleanup_after_oops_into_collection_set_do();
6081 
6082   // Reset and re-enable the hot card cache.
6083   // Note the counts for the cards in the regions in the
6084   // collection set are reset when the collection set is freed.
6085   hot_card_cache->reset_hot_cache();
6086   hot_card_cache->set_use_cache(true);
6087 
6088   // Migrate the strong code roots attached to each region in
6089   // the collection set. Ideally we would like to do this
6090   // after we have finished the scanning/evacuation of the
6091   // strong code roots for a particular heap region.
6092   migrate_strong_code_roots();
6093 
6094   purge_code_root_memory();
6095 
6096   if (g1_policy()->during_initial_mark_pause()) {
6097     // Reset the claim values set during marking the strong code roots
6098     reset_heap_region_claim_values();
6099   }
6100 
6101   finalize_for_evac_failure();
6102 
6103   if (evacuation_failed()) {
6104     remove_self_forwarding_pointers();
6105 
6106     // Reset the G1EvacuationFailureALot counters and flags
6107     // Note: the values are reset only when an actual
6108     // evacuation failure occurs.
6109     NOT_PRODUCT(reset_evacuation_should_fail();)
6110   }
6111 
6112   // Enqueue any remaining references remaining on the STW
6113   // reference processor's discovered lists. We need to do
6114   // this after the card table is cleaned (and verified) as
6115   // the act of enqueueing entries on to the pending list
6116   // will log these updates (and dirty their associated
6117   // cards). We need these updates logged to update any
6118   // RSets.
6119   enqueue_discovered_references(n_workers);
6120 
6121   if (G1DeferredRSUpdate) {
6122     redirty_logged_cards();
6123   }
6124   COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
6125 }
6126 
6127 void G1CollectedHeap::free_region(HeapRegion* hr,
6128                                   FreeRegionList* free_list,
6129                                   bool par,
6130                                   bool locked) {
6131   assert(!hr->isHumongous(), "this is only for non-humongous regions");
6132   assert(!hr->is_empty(), "the region should not be empty");
6133   assert(free_list != NULL, "pre-condition");
6134 
6135   if (G1VerifyBitmaps) {
6136     MemRegion mr(hr->bottom(), hr->end());
6137     concurrent_mark()->clearRangePrevBitmap(mr);
6138   }
6139 
6140   // Clear the card counts for this region.
6141   // Note: we only need to do this if the region is not young
6142   // (since we don't refine cards in young regions).
6143   if (!hr->is_young()) {
6144     _cg1r->hot_card_cache()->reset_card_counts(hr);
6145   }
6146   hr->hr_clear(par, true /* clear_space */, locked /* locked */);
6147   free_list->add_ordered(hr);
6148 }
6149 
6150 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
6151                                      FreeRegionList* free_list,
6152                                      bool par) {
6153   assert(hr->startsHumongous(), "this is only for starts humongous regions");
6154   assert(free_list != NULL, "pre-condition");
6155 
6156   size_t hr_capacity = hr->capacity();
6157   // We need to read this before we make the region non-humongous,
6158   // otherwise the information will be gone.
6159   uint last_index = hr->last_hc_index();
6160   hr->set_notHumongous();
6161   free_region(hr, free_list, par);
6162 
6163   uint i = hr->hrs_index() + 1;
6164   while (i < last_index) {
6165     HeapRegion* curr_hr = region_at(i);
6166     assert(curr_hr->continuesHumongous(), "invariant");
6167     curr_hr->set_notHumongous();
6168     free_region(curr_hr, free_list, par);
6169     i += 1;
6170   }
6171 }
6172 
6173 void G1CollectedHeap::remove_from_old_sets(const HeapRegionSetCount& old_regions_removed,
6174                                        const HeapRegionSetCount& humongous_regions_removed) {
6175   if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 0) {
6176     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
6177     _old_set.bulk_remove(old_regions_removed);
6178     _humongous_set.bulk_remove(humongous_regions_removed);
6179   }
6180 
6181 }
6182 
6183 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
6184   assert(list != NULL, "list can't be null");
6185   if (!list->is_empty()) {
6186     MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
6187     _free_list.add_ordered(list);
6188   }
6189 }
6190 
6191 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
6192   assert(_summary_bytes_used >= bytes,
6193          err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" should be >= bytes: "SIZE_FORMAT,
6194                   _summary_bytes_used, bytes));
6195   _summary_bytes_used -= bytes;
6196 }
6197 
6198 class G1ParCleanupCTTask : public AbstractGangTask {
6199   G1SATBCardTableModRefBS* _ct_bs;
6200   G1CollectedHeap* _g1h;
6201   HeapRegion* volatile _su_head;
6202 public:
6203   G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs,
6204                      G1CollectedHeap* g1h) :
6205     AbstractGangTask("G1 Par Cleanup CT Task"),
6206     _ct_bs(ct_bs), _g1h(g1h) { }
6207 
6208   void work(uint worker_id) {
6209     HeapRegion* r;
6210     while (r = _g1h->pop_dirty_cards_region()) {
6211       clear_cards(r);
6212     }
6213   }
6214 
6215   void clear_cards(HeapRegion* r) {
6216     // Cards of the survivors should have already been dirtied.
6217     if (!r->is_survivor()) {
6218       _ct_bs->clear(MemRegion(r->bottom(), r->end()));
6219     }
6220   }
6221 };
6222 
6223 #ifndef PRODUCT
6224 class G1VerifyCardTableCleanup: public HeapRegionClosure {
6225   G1CollectedHeap* _g1h;
6226   G1SATBCardTableModRefBS* _ct_bs;
6227 public:
6228   G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs)
6229     : _g1h(g1h), _ct_bs(ct_bs) { }
6230   virtual bool doHeapRegion(HeapRegion* r) {
6231     if (r->is_survivor()) {
6232       _g1h->verify_dirty_region(r);
6233     } else {
6234       _g1h->verify_not_dirty_region(r);
6235     }
6236     return false;
6237   }
6238 };
6239 
6240 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
6241   // All of the region should be clean.
6242   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6243   MemRegion mr(hr->bottom(), hr->end());
6244   ct_bs->verify_not_dirty_region(mr);
6245 }
6246 
6247 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
6248   // We cannot guarantee that [bottom(),end()] is dirty.  Threads
6249   // dirty allocated blocks as they allocate them. The thread that
6250   // retires each region and replaces it with a new one will do a
6251   // maximal allocation to fill in [pre_dummy_top(),end()] but will
6252   // not dirty that area (one less thing to have to do while holding
6253   // a lock). So we can only verify that [bottom(),pre_dummy_top()]
6254   // is dirty.
6255   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6256   MemRegion mr(hr->bottom(), hr->pre_dummy_top());
6257   if (hr->is_young()) {
6258     ct_bs->verify_g1_young_region(mr);
6259   } else {
6260     ct_bs->verify_dirty_region(mr);
6261   }
6262 }
6263 
6264 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
6265   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6266   for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
6267     verify_dirty_region(hr);
6268   }
6269 }
6270 
6271 void G1CollectedHeap::verify_dirty_young_regions() {
6272   verify_dirty_young_list(_young_list->first_region());
6273 }
6274 
6275 bool G1CollectedHeap::verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
6276                                                HeapWord* tams, HeapWord* end) {
6277   guarantee(tams <= end,
6278             err_msg("tams: "PTR_FORMAT" end: "PTR_FORMAT, tams, end));
6279   HeapWord* result = bitmap->getNextMarkedWordAddress(tams, end);
6280   if (result < end) {
6281     gclog_or_tty->cr();
6282     gclog_or_tty->print_cr("## wrong marked address on %s bitmap: "PTR_FORMAT,
6283                            bitmap_name, result);
6284     gclog_or_tty->print_cr("## %s tams: "PTR_FORMAT" end: "PTR_FORMAT,
6285                            bitmap_name, tams, end);
6286     return false;
6287   }
6288   return true;
6289 }
6290 
6291 bool G1CollectedHeap::verify_bitmaps(const char* caller, HeapRegion* hr) {
6292   CMBitMapRO* prev_bitmap = concurrent_mark()->prevMarkBitMap();
6293   CMBitMapRO* next_bitmap = (CMBitMapRO*) concurrent_mark()->nextMarkBitMap();
6294 
6295   HeapWord* bottom = hr->bottom();
6296   HeapWord* ptams  = hr->prev_top_at_mark_start();
6297   HeapWord* ntams  = hr->next_top_at_mark_start();
6298   HeapWord* end    = hr->end();
6299 
6300   bool res_p = verify_no_bits_over_tams("prev", prev_bitmap, ptams, end);
6301 
6302   bool res_n = true;
6303   // We reset mark_in_progress() before we reset _cmThread->in_progress() and in this window
6304   // we do the clearing of the next bitmap concurrently. Thus, we can not verify the bitmap
6305   // if we happen to be in that state.
6306   if (mark_in_progress() || !_cmThread->in_progress()) {
6307     res_n = verify_no_bits_over_tams("next", next_bitmap, ntams, end);
6308   }
6309   if (!res_p || !res_n) {
6310     gclog_or_tty->print_cr("#### Bitmap verification failed for "HR_FORMAT,
6311                            HR_FORMAT_PARAMS(hr));
6312     gclog_or_tty->print_cr("#### Caller: %s", caller);
6313     return false;
6314   }
6315   return true;
6316 }
6317 
6318 void G1CollectedHeap::check_bitmaps(const char* caller, HeapRegion* hr) {
6319   if (!G1VerifyBitmaps) return;
6320 
6321   guarantee(verify_bitmaps(caller, hr), "bitmap verification");
6322 }
6323 
6324 class G1VerifyBitmapClosure : public HeapRegionClosure {
6325 private:
6326   const char* _caller;
6327   G1CollectedHeap* _g1h;
6328   bool _failures;
6329 
6330 public:
6331   G1VerifyBitmapClosure(const char* caller, G1CollectedHeap* g1h) :
6332     _caller(caller), _g1h(g1h), _failures(false) { }
6333 
6334   bool failures() { return _failures; }
6335 
6336   virtual bool doHeapRegion(HeapRegion* hr) {
6337     if (hr->continuesHumongous()) return false;
6338 
6339     bool result = _g1h->verify_bitmaps(_caller, hr);
6340     if (!result) {
6341       _failures = true;
6342     }
6343     return false;
6344   }
6345 };
6346 
6347 void G1CollectedHeap::check_bitmaps(const char* caller) {
6348   if (!G1VerifyBitmaps) return;
6349 
6350   G1VerifyBitmapClosure cl(caller, this);
6351   heap_region_iterate(&cl);
6352   guarantee(!cl.failures(), "bitmap verification");
6353 }
6354 #endif // PRODUCT
6355 
6356 void G1CollectedHeap::cleanUpCardTable() {
6357   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6358   double start = os::elapsedTime();
6359 
6360   {
6361     // Iterate over the dirty cards region list.
6362     G1ParCleanupCTTask cleanup_task(ct_bs, this);
6363 
6364     if (G1CollectedHeap::use_parallel_gc_threads()) {
6365       set_par_threads();
6366       workers()->run_task(&cleanup_task);
6367       set_par_threads(0);
6368     } else {
6369       while (_dirty_cards_region_list) {
6370         HeapRegion* r = _dirty_cards_region_list;
6371         cleanup_task.clear_cards(r);
6372         _dirty_cards_region_list = r->get_next_dirty_cards_region();
6373         if (_dirty_cards_region_list == r) {
6374           // The last region.
6375           _dirty_cards_region_list = NULL;
6376         }
6377         r->set_next_dirty_cards_region(NULL);
6378       }
6379     }
6380 #ifndef PRODUCT
6381     if (G1VerifyCTCleanup || VerifyAfterGC) {
6382       G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
6383       heap_region_iterate(&cleanup_verifier);
6384     }
6385 #endif
6386   }
6387 
6388   double elapsed = os::elapsedTime() - start;
6389   g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
6390 }
6391 
6392 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) {
6393   size_t pre_used = 0;
6394   FreeRegionList local_free_list("Local List for CSet Freeing");
6395 
6396   double young_time_ms     = 0.0;
6397   double non_young_time_ms = 0.0;
6398 
6399   // Since the collection set is a superset of the the young list,
6400   // all we need to do to clear the young list is clear its
6401   // head and length, and unlink any young regions in the code below
6402   _young_list->clear();
6403 
6404   G1CollectorPolicy* policy = g1_policy();
6405 
6406   double start_sec = os::elapsedTime();
6407   bool non_young = true;
6408 
6409   HeapRegion* cur = cs_head;
6410   int age_bound = -1;
6411   size_t rs_lengths = 0;
6412 
6413   while (cur != NULL) {
6414     assert(!is_on_master_free_list(cur), "sanity");
6415     if (non_young) {
6416       if (cur->is_young()) {
6417         double end_sec = os::elapsedTime();
6418         double elapsed_ms = (end_sec - start_sec) * 1000.0;
6419         non_young_time_ms += elapsed_ms;
6420 
6421         start_sec = os::elapsedTime();
6422         non_young = false;
6423       }
6424     } else {
6425       if (!cur->is_young()) {
6426         double end_sec = os::elapsedTime();
6427         double elapsed_ms = (end_sec - start_sec) * 1000.0;
6428         young_time_ms += elapsed_ms;
6429 
6430         start_sec = os::elapsedTime();
6431         non_young = true;
6432       }
6433     }
6434 
6435     rs_lengths += cur->rem_set()->occupied_locked();
6436 
6437     HeapRegion* next = cur->next_in_collection_set();
6438     assert(cur->in_collection_set(), "bad CS");
6439     cur->set_next_in_collection_set(NULL);
6440     cur->set_in_collection_set(false);
6441 
6442     if (cur->is_young()) {
6443       int index = cur->young_index_in_cset();
6444       assert(index != -1, "invariant");
6445       assert((uint) index < policy->young_cset_region_length(), "invariant");
6446       size_t words_survived = _surviving_young_words[index];
6447       cur->record_surv_words_in_group(words_survived);
6448 
6449       // At this point the we have 'popped' cur from the collection set
6450       // (linked via next_in_collection_set()) but it is still in the
6451       // young list (linked via next_young_region()). Clear the
6452       // _next_young_region field.
6453       cur->set_next_young_region(NULL);
6454     } else {
6455       int index = cur->young_index_in_cset();
6456       assert(index == -1, "invariant");
6457     }
6458 
6459     assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
6460             (!cur->is_young() && cur->young_index_in_cset() == -1),
6461             "invariant" );
6462 
6463     if (!cur->evacuation_failed()) {
6464       MemRegion used_mr = cur->used_region();
6465 
6466       // And the region is empty.
6467       assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
6468       pre_used += cur->used();
6469       free_region(cur, &local_free_list, false /* par */, true /* locked */);
6470     } else {
6471       cur->uninstall_surv_rate_group();
6472       if (cur->is_young()) {
6473         cur->set_young_index_in_cset(-1);
6474       }
6475       cur->set_not_young();
6476       cur->set_evacuation_failed(false);
6477       // The region is now considered to be old.
6478       _old_set.add(cur);
6479       evacuation_info.increment_collectionset_used_after(cur->used());
6480     }
6481     cur = next;
6482   }
6483 
6484   evacuation_info.set_regions_freed(local_free_list.length());
6485   policy->record_max_rs_lengths(rs_lengths);
6486   policy->cset_regions_freed();
6487 
6488   double end_sec = os::elapsedTime();
6489   double elapsed_ms = (end_sec - start_sec) * 1000.0;
6490 
6491   if (non_young) {
6492     non_young_time_ms += elapsed_ms;
6493   } else {
6494     young_time_ms += elapsed_ms;
6495   }
6496 
6497   prepend_to_freelist(&local_free_list);
6498   decrement_summary_bytes(pre_used);
6499   policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
6500   policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
6501 }
6502 
6503 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
6504  private:
6505   FreeRegionList* _free_region_list;
6506   HeapRegionSet* _proxy_set;
6507   HeapRegionSetCount _humongous_regions_removed;
6508   size_t _freed_bytes;
6509  public:
6510 
6511   G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
6512     _free_region_list(free_region_list), _humongous_regions_removed(), _freed_bytes(0) {
6513   }
6514 
6515   virtual bool doHeapRegion(HeapRegion* r) {
6516     if (!r->startsHumongous()) {
6517       return false;
6518     }
6519 
6520     G1CollectedHeap* g1h = G1CollectedHeap::heap();
6521 
6522     // The following checks whether the humongous object is live are sufficient.
6523     // The main additional check (in addition to having a reference from the roots
6524     // or the young gen) is whether the humongous object has a remembered set entry.
6525     //
6526     // A humongous object cannot be live if there is no remembered set for it
6527     // because:
6528     // - there can be no references from within humongous starts regions referencing
6529     // the object because we never allocate other objects into them.
6530     // (I.e. there are no intra-region references that may be missed by the
6531     // remembered set)
6532     // - as soon there is a remembered set entry to the humongous starts region
6533     // (i.e. it has "escaped" to an old object) this remembered set entry will stay
6534     // until the end of a concurrent mark.
6535     //
6536     // It is not required to check whether the object has been found dead by marking
6537     // or not, in fact it would prevent reclamation within a concurrent cycle, as
6538     // all objects allocated during that time are considered live.
6539     // SATB marking is even more conservative than the remembered set.
6540     // So if at this point in the collection there is no remembered set entry,
6541     // nobody has a reference to it.
6542     // At the start of collection we flush all refinement logs, and remembered sets
6543     // are completely up-to-date wrt to references to the humongous object.
6544     //
6545     // Other implementation considerations:
6546     // - never consider object arrays: while they are a valid target, they have not
6547     // been observed to be used as temporary objects.
6548     // - they would also pose considerable effort for cleaning up the the remembered
6549     // sets.
6550     // While this cleanup is not strictly necessary to be done (or done instantly),
6551     // given that their occurrence is very low, this saves us this additional
6552     // complexity.
6553     if (g1h->humongous_is_live(r->hrs_index()) ||
6554         g1h->humongous_region_is_always_live(r)) {
6555 
6556       if (G1TraceReclaimDeadHumongousObjectsAtYoungGC) {
6557         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",
6558                                r->isHumongous(),
6559                                r->hrs_index(),
6560                                r->rem_set()->occupied(),
6561                                r->rem_set()->strong_code_roots_list_length(),
6562                                g1h->mark_in_progress() && !g1h->g1_policy()->during_initial_mark_pause(),
6563                                g1h->humongous_is_live(r->hrs_index()),
6564                                oop(r->bottom())->is_objArray()
6565                               );
6566       }
6567 
6568       return false;
6569     }
6570 
6571     guarantee(!((oop)(r->bottom()))->is_objArray(), 
6572               err_msg("Eagerly reclaiming object arrays is not supported, but the object "PTR_FORMAT" is.",
6573                       r->bottom()));
6574 
6575     if (G1TraceReclaimDeadHumongousObjectsAtYoungGC) {
6576       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",
6577                              r->isHumongous(),
6578                              r->bottom(),
6579                              r->hrs_index(),
6580                              r->region_num(),
6581                              r->rem_set()->occupied(),
6582                              r->rem_set()->strong_code_roots_list_length(),
6583                              g1h->mark_in_progress() && !g1h->g1_policy()->during_initial_mark_pause(),
6584                              g1h->humongous_is_live(r->hrs_index()),
6585                              oop(r->bottom())->is_objArray()
6586                             );
6587     }
6588     _freed_bytes += r->used();
6589     r->set_containing_set(NULL);
6590     _humongous_regions_removed.increment(1u, r->capacity());
6591     g1h->free_humongous_region(r, _free_region_list, false);
6592 
6593     return false;
6594   }
6595 
6596   HeapRegionSetCount& humongous_free_count() {
6597     return _humongous_regions_removed;
6598   }
6599 
6600   size_t bytes_freed() const {
6601     return _freed_bytes;
6602   }
6603 
6604   size_t humongous_reclaimed() const {
6605     return _humongous_regions_removed.length();
6606   }
6607 };
6608 
6609 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
6610   assert_at_safepoint(true);
6611   guarantee(G1ReclaimDeadHumongousObjectsAtYoungGC, "Feature must be enabled");
6612   guarantee(_has_humongous_reclaim_candidates, "Should not reach here if no candidates for eager reclaim were found.");
6613 
6614   double start_time = os::elapsedTime();
6615 
6616   FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
6617 
6618   G1FreeHumongousRegionClosure cl(&local_cleanup_list);
6619   heap_region_iterate(&cl);
6620 
6621   HeapRegionSetCount empty_set;
6622   remove_from_old_sets(empty_set, cl.humongous_free_count());
6623 
6624   G1HRPrinter* hr_printer = _g1h->hr_printer();
6625   if (hr_printer->is_active()) {
6626     FreeRegionListIterator iter(&local_cleanup_list);
6627     while (iter.more_available()) {
6628       HeapRegion* hr = iter.get_next();
6629       hr_printer->cleanup(hr);
6630     }
6631   }
6632 
6633   prepend_to_freelist(&local_cleanup_list);
6634   decrement_summary_bytes(cl.bytes_freed());
6635 
6636   g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
6637                                                                     cl.humongous_reclaimed());
6638 }
6639 
6640 // This routine is similar to the above but does not record
6641 // any policy statistics or update free lists; we are abandoning
6642 // the current incremental collection set in preparation of a
6643 // full collection. After the full GC we will start to build up
6644 // the incremental collection set again.
6645 // This is only called when we're doing a full collection
6646 // and is immediately followed by the tearing down of the young list.
6647 
6648 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
6649   HeapRegion* cur = cs_head;
6650 
6651   while (cur != NULL) {
6652     HeapRegion* next = cur->next_in_collection_set();
6653     assert(cur->in_collection_set(), "bad CS");
6654     cur->set_next_in_collection_set(NULL);
6655     cur->set_in_collection_set(false);
6656     cur->set_young_index_in_cset(-1);
6657     cur = next;
6658   }
6659 }
6660 
6661 void G1CollectedHeap::set_free_regions_coming() {
6662   if (G1ConcRegionFreeingVerbose) {
6663     gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6664                            "setting free regions coming");
6665   }
6666 
6667   assert(!free_regions_coming(), "pre-condition");
6668   _free_regions_coming = true;
6669 }
6670 
6671 void G1CollectedHeap::reset_free_regions_coming() {
6672   assert(free_regions_coming(), "pre-condition");
6673 
6674   {
6675     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6676     _free_regions_coming = false;
6677     SecondaryFreeList_lock->notify_all();
6678   }
6679 
6680   if (G1ConcRegionFreeingVerbose) {
6681     gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6682                            "reset free regions coming");
6683   }
6684 }
6685 
6686 void G1CollectedHeap::wait_while_free_regions_coming() {
6687   // Most of the time we won't have to wait, so let's do a quick test
6688   // first before we take the lock.
6689   if (!free_regions_coming()) {
6690     return;
6691   }
6692 
6693   if (G1ConcRegionFreeingVerbose) {
6694     gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6695                            "waiting for free regions");
6696   }
6697 
6698   {
6699     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6700     while (free_regions_coming()) {
6701       SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
6702     }
6703   }
6704 
6705   if (G1ConcRegionFreeingVerbose) {
6706     gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6707                            "done waiting for free regions");
6708   }
6709 }
6710 
6711 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
6712   assert(heap_lock_held_for_gc(),
6713               "the heap lock should already be held by or for this thread");
6714   _young_list->push_region(hr);
6715 }
6716 
6717 class NoYoungRegionsClosure: public HeapRegionClosure {
6718 private:
6719   bool _success;
6720 public:
6721   NoYoungRegionsClosure() : _success(true) { }
6722   bool doHeapRegion(HeapRegion* r) {
6723     if (r->is_young()) {
6724       gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
6725                              r->bottom(), r->end());
6726       _success = false;
6727     }
6728     return false;
6729   }
6730   bool success() { return _success; }
6731 };
6732 
6733 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
6734   bool ret = _young_list->check_list_empty(check_sample);
6735 
6736   if (check_heap) {
6737     NoYoungRegionsClosure closure;
6738     heap_region_iterate(&closure);
6739     ret = ret && closure.success();
6740   }
6741 
6742   return ret;
6743 }
6744 
6745 class TearDownRegionSetsClosure : public HeapRegionClosure {
6746 private:
6747   HeapRegionSet *_old_set;
6748 
6749 public:
6750   TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
6751 
6752   bool doHeapRegion(HeapRegion* r) {
6753     if (r->is_empty()) {
6754       // We ignore empty regions, we'll empty the free list afterwards
6755     } else if (r->is_young()) {
6756       // We ignore young regions, we'll empty the young list afterwards
6757     } else if (r->isHumongous()) {
6758       // We ignore humongous regions, we're not tearing down the
6759       // humongous region set
6760     } else {
6761       // The rest should be old
6762       _old_set->remove(r);
6763     }
6764     return false;
6765   }
6766 
6767   ~TearDownRegionSetsClosure() {
6768     assert(_old_set->is_empty(), "post-condition");
6769   }
6770 };
6771 
6772 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6773   assert_at_safepoint(true /* should_be_vm_thread */);
6774 
6775   if (!free_list_only) {
6776     TearDownRegionSetsClosure cl(&_old_set);
6777     heap_region_iterate(&cl);
6778 
6779     // Note that emptying the _young_list is postponed and instead done as
6780     // the first step when rebuilding the regions sets again. The reason for
6781     // this is that during a full GC string deduplication needs to know if
6782     // a collected region was young or old when the full GC was initiated.
6783   }
6784   _free_list.remove_all();
6785 }
6786 
6787 class RebuildRegionSetsClosure : public HeapRegionClosure {
6788 private:
6789   bool            _free_list_only;
6790   HeapRegionSet*   _old_set;
6791   FreeRegionList* _free_list;
6792   size_t          _total_used;
6793 
6794 public:
6795   RebuildRegionSetsClosure(bool free_list_only,
6796                            HeapRegionSet* old_set, FreeRegionList* free_list) :
6797     _free_list_only(free_list_only),
6798     _old_set(old_set), _free_list(free_list), _total_used(0) {
6799     assert(_free_list->is_empty(), "pre-condition");
6800     if (!free_list_only) {
6801       assert(_old_set->is_empty(), "pre-condition");
6802     }
6803   }
6804 
6805   bool doHeapRegion(HeapRegion* r) {
6806     if (r->continuesHumongous()) {
6807       return false;
6808     }
6809 
6810     if (r->is_empty()) {
6811       // Add free regions to the free list
6812       _free_list->add_as_tail(r);
6813     } else if (!_free_list_only) {
6814       assert(!r->is_young(), "we should not come across young regions");
6815 
6816       if (r->isHumongous()) {
6817         // We ignore humongous regions, we left the humongous set unchanged
6818       } else {
6819         // The rest should be old, add them to the old set
6820         _old_set->add(r);
6821       }
6822       _total_used += r->used();
6823     }
6824 
6825     return false;
6826   }
6827 
6828   size_t total_used() {
6829     return _total_used;
6830   }
6831 };
6832 
6833 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6834   assert_at_safepoint(true /* should_be_vm_thread */);
6835 
6836   if (!free_list_only) {
6837     _young_list->empty_list();
6838   }
6839 
6840   RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_free_list);
6841   heap_region_iterate(&cl);
6842 
6843   if (!free_list_only) {
6844     _summary_bytes_used = cl.total_used();
6845   }
6846   assert(_summary_bytes_used == recalculate_used(),
6847          err_msg("inconsistent _summary_bytes_used, "
6848                  "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6849                  _summary_bytes_used, recalculate_used()));
6850 }
6851 
6852 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6853   _refine_cte_cl->set_concurrent(concurrent);
6854 }
6855 
6856 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6857   HeapRegion* hr = heap_region_containing(p);
6858   return hr->is_in(p);
6859 }
6860 
6861 // Methods for the mutator alloc region
6862 
6863 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6864                                                       bool force) {
6865   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6866   assert(!force || g1_policy()->can_expand_young_list(),
6867          "if force is true we should be able to expand the young list");
6868   bool young_list_full = g1_policy()->is_young_list_full();
6869   if (force || !young_list_full) {
6870     HeapRegion* new_alloc_region = new_region(word_size,
6871                                               false /* is_old */,
6872                                               false /* do_expand */);
6873     if (new_alloc_region != NULL) {
6874       set_region_short_lived_locked(new_alloc_region);
6875       _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6876       check_bitmaps("Mutator Region Allocation", new_alloc_region);
6877       return new_alloc_region;
6878     }
6879   }
6880   return NULL;
6881 }
6882 
6883 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6884                                                   size_t allocated_bytes) {
6885   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6886   assert(alloc_region->is_young(), "all mutator alloc regions should be young");
6887 
6888   g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6889   _summary_bytes_used += allocated_bytes;
6890   _hr_printer.retire(alloc_region);
6891   // We update the eden sizes here, when the region is retired,
6892   // instead of when it's allocated, since this is the point that its
6893   // used space has been recored in _summary_bytes_used.
6894   g1mm()->update_eden_size();
6895 }
6896 
6897 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
6898                                                     bool force) {
6899   return _g1h->new_mutator_alloc_region(word_size, force);
6900 }
6901 
6902 void G1CollectedHeap::set_par_threads() {
6903   // Don't change the number of workers.  Use the value previously set
6904   // in the workgroup.
6905   assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise");
6906   uint n_workers = workers()->active_workers();
6907   assert(UseDynamicNumberOfGCThreads ||
6908            n_workers == workers()->total_workers(),
6909       "Otherwise should be using the total number of workers");
6910   if (n_workers == 0) {
6911     assert(false, "Should have been set in prior evacuation pause.");
6912     n_workers = ParallelGCThreads;
6913     workers()->set_active_workers(n_workers);
6914   }
6915   set_par_threads(n_workers);
6916 }
6917 
6918 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
6919                                        size_t allocated_bytes) {
6920   _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
6921 }
6922 
6923 // Methods for the GC alloc regions
6924 
6925 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6926                                                  uint count,
6927                                                  GCAllocPurpose ap) {
6928   assert(FreeList_lock->owned_by_self(), "pre-condition");
6929 
6930   if (count < g1_policy()->max_regions(ap)) {
6931     bool survivor = (ap == GCAllocForSurvived);
6932     HeapRegion* new_alloc_region = new_region(word_size,
6933                                               !survivor,
6934                                               true /* do_expand */);
6935     if (new_alloc_region != NULL) {
6936       // We really only need to do this for old regions given that we
6937       // should never scan survivors. But it doesn't hurt to do it
6938       // for survivors too.
6939       new_alloc_region->record_top_and_timestamp();
6940       if (survivor) {
6941         new_alloc_region->set_survivor();
6942         _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6943         check_bitmaps("Survivor Region Allocation", new_alloc_region);
6944       } else {
6945         _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6946         check_bitmaps("Old Region Allocation", new_alloc_region);
6947       }
6948       bool during_im = g1_policy()->during_initial_mark_pause();
6949       new_alloc_region->note_start_of_copying(during_im);
6950       return new_alloc_region;
6951     } else {
6952       g1_policy()->note_alloc_region_limit_reached(ap);
6953     }
6954   }
6955   return NULL;
6956 }
6957 
6958 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6959                                              size_t allocated_bytes,
6960                                              GCAllocPurpose ap) {
6961   bool during_im = g1_policy()->during_initial_mark_pause();
6962   alloc_region->note_end_of_copying(during_im);
6963   g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6964   if (ap == GCAllocForSurvived) {
6965     young_list()->add_survivor_region(alloc_region);
6966   } else {
6967     _old_set.add(alloc_region);
6968   }
6969   _hr_printer.retire(alloc_region);
6970 }
6971 
6972 HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size,
6973                                                        bool force) {
6974   assert(!force, "not supported for GC alloc regions");
6975   return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForSurvived);
6976 }
6977 
6978 void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region,
6979                                           size_t allocated_bytes) {
6980   _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6981                                GCAllocForSurvived);
6982 }
6983 
6984 HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size,
6985                                                   bool force) {
6986   assert(!force, "not supported for GC alloc regions");
6987   return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForTenured);
6988 }
6989 
6990 void OldGCAllocRegion::retire_region(HeapRegion* alloc_region,
6991                                      size_t allocated_bytes) {
6992   _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6993                                GCAllocForTenured);
6994 }
6995 // Heap region set verification
6996 
6997 class VerifyRegionListsClosure : public HeapRegionClosure {
6998 private:
6999   HeapRegionSet*   _old_set;
7000   HeapRegionSet*   _humongous_set;
7001   FreeRegionList*  _free_list;
7002 
7003 public:
7004   HeapRegionSetCount _old_count;
7005   HeapRegionSetCount _humongous_count;
7006   HeapRegionSetCount _free_count;
7007 
7008   VerifyRegionListsClosure(HeapRegionSet* old_set,
7009                            HeapRegionSet* humongous_set,
7010                            FreeRegionList* free_list) :
7011     _old_set(old_set), _humongous_set(humongous_set), _free_list(free_list),
7012     _old_count(), _humongous_count(), _free_count(){ }
7013 
7014   bool doHeapRegion(HeapRegion* hr) {
7015     if (hr->continuesHumongous()) {
7016       return false;
7017     }
7018 
7019     if (hr->is_young()) {
7020       // TODO
7021     } else if (hr->startsHumongous()) {
7022       assert(hr->containing_set() == _humongous_set, err_msg("Heap region %u is starts humongous but not in humongous set.", hr->hrs_index()));
7023       _humongous_count.increment(1u, hr->capacity());
7024     } else if (hr->is_empty()) {
7025       assert(hr->containing_set() == _free_list, err_msg("Heap region %u is empty but not on the free list.", hr->hrs_index()));
7026       _free_count.increment(1u, hr->capacity());
7027     } else {
7028       assert(hr->containing_set() == _old_set, err_msg("Heap region %u is old but not in the old set.", hr->hrs_index()));
7029       _old_count.increment(1u, hr->capacity());
7030     }
7031     return false;
7032   }
7033 
7034   void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, FreeRegionList* free_list) {
7035     guarantee(old_set->length() == _old_count.length(), err_msg("Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length()));
7036     guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), err_msg("Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
7037         old_set->total_capacity_bytes(), _old_count.capacity()));
7038 
7039     guarantee(humongous_set->length() == _humongous_count.length(), err_msg("Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length()));
7040     guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), err_msg("Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
7041         humongous_set->total_capacity_bytes(), _humongous_count.capacity()));
7042 
7043     guarantee(free_list->length() == _free_count.length(), err_msg("Free list count mismatch. Expected %u, actual %u.", free_list->length(), _free_count.length()));
7044     guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), err_msg("Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
7045         free_list->total_capacity_bytes(), _free_count.capacity()));
7046   }
7047 };
7048 
7049 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
7050                                              HeapWord* bottom) {
7051   HeapWord* end = bottom + HeapRegion::GrainWords;
7052   MemRegion mr(bottom, end);
7053   assert(_g1_reserved.contains(mr), "invariant");
7054   // This might return NULL if the allocation fails
7055   return new HeapRegion(hrs_index, _bot_shared, mr);
7056 }
7057 
7058 void G1CollectedHeap::verify_region_sets() {
7059   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
7060 
7061   // First, check the explicit lists.
7062   _free_list.verify_list();
7063   {
7064     // Given that a concurrent operation might be adding regions to
7065     // the secondary free list we have to take the lock before
7066     // verifying it.
7067     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
7068     _secondary_free_list.verify_list();
7069   }
7070 
7071   // If a concurrent region freeing operation is in progress it will
7072   // be difficult to correctly attributed any free regions we come
7073   // across to the correct free list given that they might belong to
7074   // one of several (free_list, secondary_free_list, any local lists,
7075   // etc.). So, if that's the case we will skip the rest of the
7076   // verification operation. Alternatively, waiting for the concurrent
7077   // operation to complete will have a non-trivial effect on the GC's
7078   // operation (no concurrent operation will last longer than the
7079   // interval between two calls to verification) and it might hide
7080   // any issues that we would like to catch during testing.
7081   if (free_regions_coming()) {
7082     return;
7083   }
7084 
7085   // Make sure we append the secondary_free_list on the free_list so
7086   // that all free regions we will come across can be safely
7087   // attributed to the free_list.
7088   append_secondary_free_list_if_not_empty_with_lock();
7089 
7090   // Finally, make sure that the region accounting in the lists is
7091   // consistent with what we see in the heap.
7092 
7093   VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_free_list);
7094   heap_region_iterate(&cl);
7095   cl.verify_counts(&_old_set, &_humongous_set, &_free_list);
7096 }
7097 
7098 // Optimized nmethod scanning
7099 
7100 class RegisterNMethodOopClosure: public OopClosure {
7101   G1CollectedHeap* _g1h;
7102   nmethod* _nm;
7103 
7104   template <class T> void do_oop_work(T* p) {
7105     T heap_oop = oopDesc::load_heap_oop(p);
7106     if (!oopDesc::is_null(heap_oop)) {
7107       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
7108       HeapRegion* hr = _g1h->heap_region_containing(obj);
7109       assert(!hr->continuesHumongous(),
7110              err_msg("trying to add code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
7111                      " starting at "HR_FORMAT,
7112                      _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
7113 
7114       // HeapRegion::add_strong_code_root() avoids adding duplicate
7115       // entries but having duplicates is  OK since we "mark" nmethods
7116       // as visited when we scan the strong code root lists during the GC.
7117       hr->add_strong_code_root(_nm);
7118       assert(hr->rem_set()->strong_code_roots_list_contains(_nm),
7119              err_msg("failed to add code root "PTR_FORMAT" to remembered set of region "HR_FORMAT,
7120                      _nm, HR_FORMAT_PARAMS(hr)));
7121     }
7122   }
7123 
7124 public:
7125   RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
7126     _g1h(g1h), _nm(nm) {}
7127 
7128   void do_oop(oop* p)       { do_oop_work(p); }
7129   void do_oop(narrowOop* p) { do_oop_work(p); }
7130 };
7131 
7132 class UnregisterNMethodOopClosure: public OopClosure {
7133   G1CollectedHeap* _g1h;
7134   nmethod* _nm;
7135 
7136   template <class T> void do_oop_work(T* p) {
7137     T heap_oop = oopDesc::load_heap_oop(p);
7138     if (!oopDesc::is_null(heap_oop)) {
7139       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
7140       HeapRegion* hr = _g1h->heap_region_containing(obj);
7141       assert(!hr->continuesHumongous(),
7142              err_msg("trying to remove code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
7143                      " starting at "HR_FORMAT,
7144                      _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
7145 
7146       hr->remove_strong_code_root(_nm);
7147       assert(!hr->rem_set()->strong_code_roots_list_contains(_nm),
7148              err_msg("failed to remove code root "PTR_FORMAT" of region "HR_FORMAT,
7149                      _nm, HR_FORMAT_PARAMS(hr)));
7150     }
7151   }
7152 
7153 public:
7154   UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
7155     _g1h(g1h), _nm(nm) {}
7156 
7157   void do_oop(oop* p)       { do_oop_work(p); }
7158   void do_oop(narrowOop* p) { do_oop_work(p); }
7159 };
7160 
7161 void G1CollectedHeap::register_nmethod(nmethod* nm) {
7162   CollectedHeap::register_nmethod(nm);
7163 
7164   guarantee(nm != NULL, "sanity");
7165   RegisterNMethodOopClosure reg_cl(this, nm);
7166   nm->oops_do(&reg_cl);
7167 }
7168 
7169 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
7170   CollectedHeap::unregister_nmethod(nm);
7171 
7172   guarantee(nm != NULL, "sanity");
7173   UnregisterNMethodOopClosure reg_cl(this, nm);
7174   nm->oops_do(&reg_cl, true);
7175 }
7176 
7177 class MigrateCodeRootsHeapRegionClosure: public HeapRegionClosure {
7178 public:
7179   bool doHeapRegion(HeapRegion *hr) {
7180     assert(!hr->isHumongous(),
7181            err_msg("humongous region "HR_FORMAT" should not have been added to collection set",
7182                    HR_FORMAT_PARAMS(hr)));
7183     hr->migrate_strong_code_roots();
7184     return false;
7185   }
7186 };
7187 
7188 void G1CollectedHeap::migrate_strong_code_roots() {
7189   MigrateCodeRootsHeapRegionClosure cl;
7190   double migrate_start = os::elapsedTime();
7191   collection_set_iterate(&cl);
7192   double migration_time_ms = (os::elapsedTime() - migrate_start) * 1000.0;
7193   g1_policy()->phase_times()->record_strong_code_root_migration_time(migration_time_ms);
7194 }
7195 
7196 void G1CollectedHeap::purge_code_root_memory() {
7197   double purge_start = os::elapsedTime();
7198   G1CodeRootSet::purge_chunks(G1CodeRootsChunkCacheKeepPercent);
7199   double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
7200   g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
7201 }
7202 
7203 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
7204   G1CollectedHeap* _g1h;
7205 
7206 public:
7207   RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
7208     _g1h(g1h) {}
7209 
7210   void do_code_blob(CodeBlob* cb) {
7211     nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
7212     if (nm == NULL) {
7213       return;
7214     }
7215 
7216     if (ScavengeRootsInCode) {
7217       _g1h->register_nmethod(nm);
7218     }
7219   }
7220 };
7221 
7222 void G1CollectedHeap::rebuild_strong_code_roots() {
7223   RebuildStrongCodeRootClosure blob_cl(this);
7224   CodeCache::blobs_do(&blob_cl);
7225 }