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 #include "precompiled.hpp"
  26 #include "code/codeCache.hpp"
  27 #include "code/icBuffer.hpp"
  28 #include "gc_implementation/g1/bufferingOopClosure.hpp"
  29 #include "gc_implementation/g1/concurrentG1Refine.hpp"
  30 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
  31 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
  32 #include "gc_implementation/g1/g1AllocRegion.inline.hpp"
  33 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
  34 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
  35 #include "gc_implementation/g1/g1ErgoVerbose.hpp"
  36 #include "gc_implementation/g1/g1EvacFailure.hpp"
  37 #include "gc_implementation/g1/g1GCPhaseTimes.hpp"
  38 #include "gc_implementation/g1/g1Log.hpp"
  39 #include "gc_implementation/g1/g1MarkSweep.hpp"
  40 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
  41 #include "gc_implementation/g1/g1RemSet.inline.hpp"
  42 #include "gc_implementation/g1/g1YCTypes.hpp"
  43 #include "gc_implementation/g1/heapRegion.inline.hpp"
  44 #include "gc_implementation/g1/heapRegionRemSet.hpp"
  45 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
  46 #include "gc_implementation/g1/vm_operations_g1.hpp"
  47 #include "gc_implementation/shared/gcHeapSummary.hpp"
  48 #include "gc_implementation/shared/gcTimer.hpp"
  49 #include "gc_implementation/shared/gcTrace.hpp"
  50 #include "gc_implementation/shared/gcTraceTime.hpp"
  51 #include "gc_implementation/shared/isGCActiveMark.hpp"
  52 #include "memory/gcLocker.inline.hpp"
  53 #include "memory/generationSpec.hpp"
  54 #include "memory/iterator.hpp"
  55 #include "memory/referenceProcessor.hpp"
  56 #include "oops/oop.inline.hpp"
  57 #include "oops/oop.pcgc.inline.hpp"
  58 #include "runtime/vmThread.hpp"
  59 #include "utilities/ticks.hpp"
  60 
  61 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
  62 
  63 // turn it on so that the contents of the young list (scan-only /
  64 // to-be-collected) are printed at "strategic" points before / during
  65 // / after the collection --- this is useful for debugging
  66 #define YOUNG_LIST_VERBOSE 0
  67 // CURRENT STATUS
  68 // This file is under construction.  Search for "FIXME".
  69 
  70 // INVARIANTS/NOTES
  71 //
  72 // All allocation activity covered by the G1CollectedHeap interface is
  73 // serialized by acquiring the HeapLock.  This happens in mem_allocate
  74 // and allocate_new_tlab, which are the "entry" points to the
  75 // allocation code from the rest of the JVM.  (Note that this does not
  76 // apply to TLAB allocation, which is not part of this interface: it
  77 // is done by clients of this interface.)
  78 
  79 // Notes on implementation of parallelism in different tasks.
  80 //
  81 // G1ParVerifyTask uses heap_region_par_iterate_chunked() for parallelism.
  82 // The number of GC workers is passed to heap_region_par_iterate_chunked().
  83 // It does use run_task() which sets _n_workers in the task.
  84 // G1ParTask executes g1_process_strong_roots() ->
  85 // SharedHeap::process_strong_roots() which calls eventually to
  86 // CardTableModRefBS::par_non_clean_card_iterate_work() which uses
  87 // SequentialSubTasksDone.  SharedHeap::process_strong_roots() also
  88 // directly uses SubTasksDone (_process_strong_tasks field in SharedHeap).
  89 //
  90 
  91 // Local to this file.
  92 
  93 class RefineCardTableEntryClosure: public CardTableEntryClosure {
  94   SuspendibleThreadSet* _sts;
  95   G1RemSet* _g1rs;
  96   ConcurrentG1Refine* _cg1r;
  97   bool _concurrent;
  98 public:
  99   RefineCardTableEntryClosure(SuspendibleThreadSet* sts,
 100                               G1RemSet* g1rs,
 101                               ConcurrentG1Refine* cg1r) :
 102     _sts(sts), _g1rs(g1rs), _cg1r(cg1r), _concurrent(true)
 103   {}
 104   bool do_card_ptr(jbyte* card_ptr, int worker_i) {
 105     bool oops_into_cset = _g1rs->refine_card(card_ptr, worker_i, false);
 106     // This path is executed by the concurrent refine or mutator threads,
 107     // concurrently, and so we do not care if card_ptr contains references
 108     // that point into the collection set.
 109     assert(!oops_into_cset, "should be");
 110 
 111     if (_concurrent && _sts->should_yield()) {
 112       // Caller will actually yield.
 113       return false;
 114     }
 115     // Otherwise, we finished successfully; return true.
 116     return true;
 117   }
 118   void set_concurrent(bool b) { _concurrent = b; }
 119 };
 120 
 121 
 122 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure {
 123   int _calls;
 124   G1CollectedHeap* _g1h;
 125   CardTableModRefBS* _ctbs;
 126   int _histo[256];
 127 public:
 128   ClearLoggedCardTableEntryClosure() :
 129     _calls(0), _g1h(G1CollectedHeap::heap()), _ctbs(_g1h->g1_barrier_set())
 130   {
 131     for (int i = 0; i < 256; i++) _histo[i] = 0;
 132   }
 133   bool do_card_ptr(jbyte* card_ptr, int worker_i) {
 134     if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
 135       _calls++;
 136       unsigned char* ujb = (unsigned char*)card_ptr;
 137       int ind = (int)(*ujb);
 138       _histo[ind]++;
 139       *card_ptr = -1;
 140     }
 141     return true;
 142   }
 143   int calls() { return _calls; }
 144   void print_histo() {
 145     gclog_or_tty->print_cr("Card table value histogram:");
 146     for (int i = 0; i < 256; i++) {
 147       if (_histo[i] != 0) {
 148         gclog_or_tty->print_cr("  %d: %d", i, _histo[i]);
 149       }
 150     }
 151   }
 152 };
 153 
 154 class RedirtyLoggedCardTableEntryClosure: public CardTableEntryClosure {
 155   int _calls;
 156   G1CollectedHeap* _g1h;
 157   CardTableModRefBS* _ctbs;
 158 public:
 159   RedirtyLoggedCardTableEntryClosure() :
 160     _calls(0), _g1h(G1CollectedHeap::heap()), _ctbs(_g1h->g1_barrier_set()) {}
 161 
 162   bool do_card_ptr(jbyte* card_ptr, int worker_i) {
 163     if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
 164       _calls++;
 165       *card_ptr = 0;
 166     }
 167     return true;
 168   }
 169   int calls() { return _calls; }
 170 };
 171 
 172 class RedirtyLoggedCardTableEntryFastClosure : public CardTableEntryClosure {
 173 public:
 174   bool do_card_ptr(jbyte* card_ptr, int worker_i) {
 175     *card_ptr = CardTableModRefBS::dirty_card_val();
 176     return true;
 177   }
 178 };
 179 
 180 YoungList::YoungList(G1CollectedHeap* g1h) :
 181     _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0),
 182     _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) {
 183   guarantee(check_list_empty(false), "just making sure...");
 184 }
 185 
 186 void YoungList::push_region(HeapRegion *hr) {
 187   assert(!hr->is_young(), "should not already be young");
 188   assert(hr->get_next_young_region() == NULL, "cause it should!");
 189 
 190   hr->set_next_young_region(_head);
 191   _head = hr;
 192 
 193   _g1h->g1_policy()->set_region_eden(hr, (int) _length);
 194   ++_length;
 195 }
 196 
 197 void YoungList::add_survivor_region(HeapRegion* hr) {
 198   assert(hr->is_survivor(), "should be flagged as survivor region");
 199   assert(hr->get_next_young_region() == NULL, "cause it should!");
 200 
 201   hr->set_next_young_region(_survivor_head);
 202   if (_survivor_head == NULL) {
 203     _survivor_tail = hr;
 204   }
 205   _survivor_head = hr;
 206   ++_survivor_length;
 207 }
 208 
 209 void YoungList::empty_list(HeapRegion* list) {
 210   while (list != NULL) {
 211     HeapRegion* next = list->get_next_young_region();
 212     list->set_next_young_region(NULL);
 213     list->uninstall_surv_rate_group();
 214     list->set_not_young();
 215     list = next;
 216   }
 217 }
 218 
 219 void YoungList::empty_list() {
 220   assert(check_list_well_formed(), "young list should be well formed");
 221 
 222   empty_list(_head);
 223   _head = NULL;
 224   _length = 0;
 225 
 226   empty_list(_survivor_head);
 227   _survivor_head = NULL;
 228   _survivor_tail = NULL;
 229   _survivor_length = 0;
 230 
 231   _last_sampled_rs_lengths = 0;
 232 
 233   assert(check_list_empty(false), "just making sure...");
 234 }
 235 
 236 bool YoungList::check_list_well_formed() {
 237   bool ret = true;
 238 
 239   uint length = 0;
 240   HeapRegion* curr = _head;
 241   HeapRegion* last = NULL;
 242   while (curr != NULL) {
 243     if (!curr->is_young()) {
 244       gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
 245                              "incorrectly tagged (y: %d, surv: %d)",
 246                              curr->bottom(), curr->end(),
 247                              curr->is_young(), curr->is_survivor());
 248       ret = false;
 249     }
 250     ++length;
 251     last = curr;
 252     curr = curr->get_next_young_region();
 253   }
 254   ret = ret && (length == _length);
 255 
 256   if (!ret) {
 257     gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
 258     gclog_or_tty->print_cr("###   list has %u entries, _length is %u",
 259                            length, _length);
 260   }
 261 
 262   return ret;
 263 }
 264 
 265 bool YoungList::check_list_empty(bool check_sample) {
 266   bool ret = true;
 267 
 268   if (_length != 0) {
 269     gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u",
 270                   _length);
 271     ret = false;
 272   }
 273   if (check_sample && _last_sampled_rs_lengths != 0) {
 274     gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
 275     ret = false;
 276   }
 277   if (_head != NULL) {
 278     gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
 279     ret = false;
 280   }
 281   if (!ret) {
 282     gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
 283   }
 284 
 285   return ret;
 286 }
 287 
 288 void
 289 YoungList::rs_length_sampling_init() {
 290   _sampled_rs_lengths = 0;
 291   _curr               = _head;
 292 }
 293 
 294 bool
 295 YoungList::rs_length_sampling_more() {
 296   return _curr != NULL;
 297 }
 298 
 299 void
 300 YoungList::rs_length_sampling_next() {
 301   assert( _curr != NULL, "invariant" );
 302   size_t rs_length = _curr->rem_set()->occupied();
 303 
 304   _sampled_rs_lengths += rs_length;
 305 
 306   // The current region may not yet have been added to the
 307   // incremental collection set (it gets added when it is
 308   // retired as the current allocation region).
 309   if (_curr->in_collection_set()) {
 310     // Update the collection set policy information for this region
 311     _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
 312   }
 313 
 314   _curr = _curr->get_next_young_region();
 315   if (_curr == NULL) {
 316     _last_sampled_rs_lengths = _sampled_rs_lengths;
 317     // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
 318   }
 319 }
 320 
 321 void
 322 YoungList::reset_auxilary_lists() {
 323   guarantee( is_empty(), "young list should be empty" );
 324   assert(check_list_well_formed(), "young list should be well formed");
 325 
 326   // Add survivor regions to SurvRateGroup.
 327   _g1h->g1_policy()->note_start_adding_survivor_regions();
 328   _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
 329 
 330   int young_index_in_cset = 0;
 331   for (HeapRegion* curr = _survivor_head;
 332        curr != NULL;
 333        curr = curr->get_next_young_region()) {
 334     _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
 335 
 336     // The region is a non-empty survivor so let's add it to
 337     // the incremental collection set for the next evacuation
 338     // pause.
 339     _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
 340     young_index_in_cset += 1;
 341   }
 342   assert((uint) young_index_in_cset == _survivor_length, "post-condition");
 343   _g1h->g1_policy()->note_stop_adding_survivor_regions();
 344 
 345   _head   = _survivor_head;
 346   _length = _survivor_length;
 347   if (_survivor_head != NULL) {
 348     assert(_survivor_tail != NULL, "cause it shouldn't be");
 349     assert(_survivor_length > 0, "invariant");
 350     _survivor_tail->set_next_young_region(NULL);
 351   }
 352 
 353   // Don't clear the survivor list handles until the start of
 354   // the next evacuation pause - we need it in order to re-tag
 355   // the survivor regions from this evacuation pause as 'young'
 356   // at the start of the next.
 357 
 358   _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
 359 
 360   assert(check_list_well_formed(), "young list should be well formed");
 361 }
 362 
 363 void YoungList::print() {
 364   HeapRegion* lists[] = {_head,   _survivor_head};
 365   const char* names[] = {"YOUNG", "SURVIVOR"};
 366 
 367   for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) {
 368     gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
 369     HeapRegion *curr = lists[list];
 370     if (curr == NULL)
 371       gclog_or_tty->print_cr("  empty");
 372     while (curr != NULL) {
 373       gclog_or_tty->print_cr("  "HR_FORMAT", P: "PTR_FORMAT "N: "PTR_FORMAT", age: %4d",
 374                              HR_FORMAT_PARAMS(curr),
 375                              curr->prev_top_at_mark_start(),
 376                              curr->next_top_at_mark_start(),
 377                              curr->age_in_surv_rate_group_cond());
 378       curr = curr->get_next_young_region();
 379     }
 380   }
 381 
 382   gclog_or_tty->print_cr("");
 383 }
 384 
 385 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
 386 {
 387   // Claim the right to put the region on the dirty cards region list
 388   // by installing a self pointer.
 389   HeapRegion* next = hr->get_next_dirty_cards_region();
 390   if (next == NULL) {
 391     HeapRegion* res = (HeapRegion*)
 392       Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
 393                           NULL);
 394     if (res == NULL) {
 395       HeapRegion* head;
 396       do {
 397         // Put the region to the dirty cards region list.
 398         head = _dirty_cards_region_list;
 399         next = (HeapRegion*)
 400           Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
 401         if (next == head) {
 402           assert(hr->get_next_dirty_cards_region() == hr,
 403                  "hr->get_next_dirty_cards_region() != hr");
 404           if (next == NULL) {
 405             // The last region in the list points to itself.
 406             hr->set_next_dirty_cards_region(hr);
 407           } else {
 408             hr->set_next_dirty_cards_region(next);
 409           }
 410         }
 411       } while (next != head);
 412     }
 413   }
 414 }
 415 
 416 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
 417 {
 418   HeapRegion* head;
 419   HeapRegion* hr;
 420   do {
 421     head = _dirty_cards_region_list;
 422     if (head == NULL) {
 423       return NULL;
 424     }
 425     HeapRegion* new_head = head->get_next_dirty_cards_region();
 426     if (head == new_head) {
 427       // The last region.
 428       new_head = NULL;
 429     }
 430     hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
 431                                           head);
 432   } while (hr != head);
 433   assert(hr != NULL, "invariant");
 434   hr->set_next_dirty_cards_region(NULL);
 435   return hr;
 436 }
 437 
 438 void G1CollectedHeap::stop_conc_gc_threads() {
 439   _cg1r->stop();
 440   _cmThread->stop();
 441 }
 442 
 443 #ifdef ASSERT
 444 // A region is added to the collection set as it is retired
 445 // so an address p can point to a region which will be in the
 446 // collection set but has not yet been retired.  This method
 447 // therefore is only accurate during a GC pause after all
 448 // regions have been retired.  It is used for debugging
 449 // to check if an nmethod has references to objects that can
 450 // be move during a partial collection.  Though it can be
 451 // inaccurate, it is sufficient for G1 because the conservative
 452 // implementation of is_scavengable() for G1 will indicate that
 453 // all nmethods must be scanned during a partial collection.
 454 bool G1CollectedHeap::is_in_partial_collection(const void* p) {
 455   HeapRegion* hr = heap_region_containing(p);
 456   return hr != NULL && hr->in_collection_set();
 457 }
 458 #endif
 459 
 460 // Returns true if the reference points to an object that
 461 // can move in an incremental collection.
 462 bool G1CollectedHeap::is_scavengable(const void* p) {
 463   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 464   G1CollectorPolicy* g1p = g1h->g1_policy();
 465   HeapRegion* hr = heap_region_containing(p);
 466   if (hr == NULL) {
 467      // null
 468      assert(p == NULL, err_msg("Not NULL " PTR_FORMAT ,p));
 469      return false;
 470   } else {
 471     return !hr->isHumongous();
 472   }
 473 }
 474 
 475 void G1CollectedHeap::check_ct_logs_at_safepoint() {
 476   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
 477   CardTableModRefBS* ct_bs = g1_barrier_set();
 478 
 479   // Count the dirty cards at the start.
 480   CountNonCleanMemRegionClosure count1(this);
 481   ct_bs->mod_card_iterate(&count1);
 482   int orig_count = count1.n();
 483 
 484   // First clear the logged cards.
 485   ClearLoggedCardTableEntryClosure clear;
 486   dcqs.set_closure(&clear);
 487   dcqs.apply_closure_to_all_completed_buffers();
 488   dcqs.iterate_closure_all_threads(false);
 489   clear.print_histo();
 490 
 491   // Now ensure that there's no dirty cards.
 492   CountNonCleanMemRegionClosure count2(this);
 493   ct_bs->mod_card_iterate(&count2);
 494   if (count2.n() != 0) {
 495     gclog_or_tty->print_cr("Card table has %d entries; %d originally",
 496                            count2.n(), orig_count);
 497   }
 498   guarantee(count2.n() == 0, "Card table should be clean.");
 499 
 500   RedirtyLoggedCardTableEntryClosure redirty;
 501   JavaThread::dirty_card_queue_set().set_closure(&redirty);
 502   dcqs.apply_closure_to_all_completed_buffers();
 503   dcqs.iterate_closure_all_threads(false);
 504   gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
 505                          clear.calls(), orig_count);
 506   guarantee(redirty.calls() == clear.calls(),
 507             "Or else mechanism is broken.");
 508 
 509   CountNonCleanMemRegionClosure count3(this);
 510   ct_bs->mod_card_iterate(&count3);
 511   if (count3.n() != orig_count) {
 512     gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
 513                            orig_count, count3.n());
 514     guarantee(count3.n() >= orig_count, "Should have restored them all.");
 515   }
 516 
 517   JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
 518 }
 519 
 520 // Private class members.
 521 
 522 G1CollectedHeap* G1CollectedHeap::_g1h;
 523 
 524 // Private methods.
 525 
 526 HeapRegion*
 527 G1CollectedHeap::new_region_try_secondary_free_list() {
 528   MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
 529   while (!_secondary_free_list.is_empty() || free_regions_coming()) {
 530     if (!_secondary_free_list.is_empty()) {
 531       if (G1ConcRegionFreeingVerbose) {
 532         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 533                                "secondary_free_list has %u entries",
 534                                _secondary_free_list.length());
 535       }
 536       // It looks as if there are free regions available on the
 537       // secondary_free_list. Let's move them to the free_list and try
 538       // again to allocate from it.
 539       append_secondary_free_list();
 540 
 541       assert(!_free_list.is_empty(), "if the secondary_free_list was not "
 542              "empty we should have moved at least one entry to the free_list");
 543       HeapRegion* res = _free_list.remove_head();
 544       if (G1ConcRegionFreeingVerbose) {
 545         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 546                                "allocated "HR_FORMAT" from secondary_free_list",
 547                                HR_FORMAT_PARAMS(res));
 548       }
 549       return res;
 550     }
 551 
 552     // Wait here until we get notified either when (a) there are no
 553     // more free regions coming or (b) some regions have been moved on
 554     // the secondary_free_list.
 555     SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
 556   }
 557 
 558   if (G1ConcRegionFreeingVerbose) {
 559     gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 560                            "could not allocate from secondary_free_list");
 561   }
 562   return NULL;
 563 }
 564 
 565 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool do_expand) {
 566   assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords,
 567          "the only time we use this to allocate a humongous region is "
 568          "when we are allocating a single humongous region");
 569 
 570   HeapRegion* res;
 571   if (G1StressConcRegionFreeing) {
 572     if (!_secondary_free_list.is_empty()) {
 573       if (G1ConcRegionFreeingVerbose) {
 574         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 575                                "forced to look at the secondary_free_list");
 576       }
 577       res = new_region_try_secondary_free_list();
 578       if (res != NULL) {
 579         return res;
 580       }
 581     }
 582   }
 583   res = _free_list.remove_head_or_null();
 584   if (res == NULL) {
 585     if (G1ConcRegionFreeingVerbose) {
 586       gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 587                              "res == NULL, trying the secondary_free_list");
 588     }
 589     res = new_region_try_secondary_free_list();
 590   }
 591   if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
 592     // Currently, only attempts to allocate GC alloc regions set
 593     // do_expand to true. So, we should only reach here during a
 594     // safepoint. If this assumption changes we might have to
 595     // reconsider the use of _expand_heap_after_alloc_failure.
 596     assert(SafepointSynchronize::is_at_safepoint(), "invariant");
 597 
 598     ergo_verbose1(ErgoHeapSizing,
 599                   "attempt heap expansion",
 600                   ergo_format_reason("region allocation request failed")
 601                   ergo_format_byte("allocation request"),
 602                   word_size * HeapWordSize);
 603     if (expand(word_size * HeapWordSize)) {
 604       // Given that expand() succeeded in expanding the heap, and we
 605       // always expand the heap by an amount aligned to the heap
 606       // region size, the free list should in theory not be empty. So
 607       // it would probably be OK to use remove_head(). But the extra
 608       // check for NULL is unlikely to be a performance issue here (we
 609       // just expanded the heap!) so let's just be conservative and
 610       // use remove_head_or_null().
 611       res = _free_list.remove_head_or_null();
 612     } else {
 613       _expand_heap_after_alloc_failure = false;
 614     }
 615   }
 616   return res;
 617 }
 618 
 619 uint G1CollectedHeap::humongous_obj_allocate_find_first(uint num_regions,
 620                                                         size_t word_size) {
 621   assert(isHumongous(word_size), "word_size should be humongous");
 622   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 623 
 624   uint first = G1_NULL_HRS_INDEX;
 625   if (num_regions == 1) {
 626     // Only one region to allocate, no need to go through the slower
 627     // path. The caller will attempt the expansion if this fails, so
 628     // let's not try to expand here too.
 629     HeapRegion* hr = new_region(word_size, false /* do_expand */);
 630     if (hr != NULL) {
 631       first = hr->hrs_index();
 632     } else {
 633       first = G1_NULL_HRS_INDEX;
 634     }
 635   } else {
 636     // We can't allocate humongous regions while cleanupComplete() is
 637     // running, since some of the regions we find to be empty might not
 638     // yet be added to the free list and it is not straightforward to
 639     // know which list they are on so that we can remove them. Note
 640     // that we only need to do this if we need to allocate more than
 641     // one region to satisfy the current humongous allocation
 642     // request. If we are only allocating one region we use the common
 643     // region allocation code (see above).
 644     wait_while_free_regions_coming();
 645     append_secondary_free_list_if_not_empty_with_lock();
 646 
 647     if (free_regions() >= num_regions) {
 648       first = _hrs.find_contiguous(num_regions);
 649       if (first != G1_NULL_HRS_INDEX) {
 650         for (uint i = first; i < first + num_regions; ++i) {
 651           HeapRegion* hr = region_at(i);
 652           assert(hr->is_empty(), "sanity");
 653           assert(is_on_master_free_list(hr), "sanity");
 654           hr->set_pending_removal(true);
 655         }
 656         _free_list.remove_all_pending(num_regions);
 657       }
 658     }
 659   }
 660   return first;
 661 }
 662 
 663 HeapWord*
 664 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
 665                                                            uint num_regions,
 666                                                            size_t word_size) {
 667   assert(first != G1_NULL_HRS_INDEX, "pre-condition");
 668   assert(isHumongous(word_size), "word_size should be humongous");
 669   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 670 
 671   // Index of last region in the series + 1.
 672   uint last = first + num_regions;
 673 
 674   // We need to initialize the region(s) we just discovered. This is
 675   // a bit tricky given that it can happen concurrently with
 676   // refinement threads refining cards on these regions and
 677   // potentially wanting to refine the BOT as they are scanning
 678   // those cards (this can happen shortly after a cleanup; see CR
 679   // 6991377). So we have to set up the region(s) carefully and in
 680   // a specific order.
 681 
 682   // The word size sum of all the regions we will allocate.
 683   size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
 684   assert(word_size <= word_size_sum, "sanity");
 685 
 686   // This will be the "starts humongous" region.
 687   HeapRegion* first_hr = region_at(first);
 688   // The header of the new object will be placed at the bottom of
 689   // the first region.
 690   HeapWord* new_obj = first_hr->bottom();
 691   // This will be the new end of the first region in the series that
 692   // should also match the end of the last region in the series.
 693   HeapWord* new_end = new_obj + word_size_sum;
 694   // This will be the new top of the first region that will reflect
 695   // this allocation.
 696   HeapWord* new_top = new_obj + word_size;
 697 
 698   // First, we need to zero the header of the space that we will be
 699   // allocating. When we update top further down, some refinement
 700   // threads might try to scan the region. By zeroing the header we
 701   // ensure that any thread that will try to scan the region will
 702   // come across the zero klass word and bail out.
 703   //
 704   // NOTE: It would not have been correct to have used
 705   // CollectedHeap::fill_with_object() and make the space look like
 706   // an int array. The thread that is doing the allocation will
 707   // later update the object header to a potentially different array
 708   // type and, for a very short period of time, the klass and length
 709   // fields will be inconsistent. This could cause a refinement
 710   // thread to calculate the object size incorrectly.
 711   Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
 712 
 713   // We will set up the first region as "starts humongous". This
 714   // will also update the BOT covering all the regions to reflect
 715   // that there is a single object that starts at the bottom of the
 716   // first region.
 717   first_hr->set_startsHumongous(new_top, new_end);
 718 
 719   // Then, if there are any, we will set up the "continues
 720   // humongous" regions.
 721   HeapRegion* hr = NULL;
 722   for (uint i = first + 1; i < last; ++i) {
 723     hr = region_at(i);
 724     hr->set_continuesHumongous(first_hr);
 725   }
 726   // If we have "continues humongous" regions (hr != NULL), then the
 727   // end of the last one should match new_end.
 728   assert(hr == NULL || hr->end() == new_end, "sanity");
 729 
 730   // Up to this point no concurrent thread would have been able to
 731   // do any scanning on any region in this series. All the top
 732   // fields still point to bottom, so the intersection between
 733   // [bottom,top] and [card_start,card_end] will be empty. Before we
 734   // update the top fields, we'll do a storestore to make sure that
 735   // no thread sees the update to top before the zeroing of the
 736   // object header and the BOT initialization.
 737   OrderAccess::storestore();
 738 
 739   // Now that the BOT and the object header have been initialized,
 740   // we can update top of the "starts humongous" region.
 741   assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
 742          "new_top should be in this region");
 743   first_hr->set_top(new_top);
 744   if (_hr_printer.is_active()) {
 745     HeapWord* bottom = first_hr->bottom();
 746     HeapWord* end = first_hr->orig_end();
 747     if ((first + 1) == last) {
 748       // the series has a single humongous region
 749       _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
 750     } else {
 751       // the series has more than one humongous regions
 752       _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
 753     }
 754   }
 755 
 756   // Now, we will update the top fields of the "continues humongous"
 757   // regions. The reason we need to do this is that, otherwise,
 758   // these regions would look empty and this will confuse parts of
 759   // G1. For example, the code that looks for a consecutive number
 760   // of empty regions will consider them empty and try to
 761   // re-allocate them. We can extend is_empty() to also include
 762   // !continuesHumongous(), but it is easier to just update the top
 763   // fields here. The way we set top for all regions (i.e., top ==
 764   // end for all regions but the last one, top == new_top for the
 765   // last one) is actually used when we will free up the humongous
 766   // region in free_humongous_region().
 767   hr = NULL;
 768   for (uint i = first + 1; i < last; ++i) {
 769     hr = region_at(i);
 770     if ((i + 1) == last) {
 771       // last continues humongous region
 772       assert(hr->bottom() < new_top && new_top <= hr->end(),
 773              "new_top should fall on this region");
 774       hr->set_top(new_top);
 775       _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
 776     } else {
 777       // not last one
 778       assert(new_top > hr->end(), "new_top should be above this region");
 779       hr->set_top(hr->end());
 780       _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
 781     }
 782   }
 783   // If we have continues humongous regions (hr != NULL), then the
 784   // end of the last one should match new_end and its top should
 785   // match new_top.
 786   assert(hr == NULL ||
 787          (hr->end() == new_end && hr->top() == new_top), "sanity");
 788 
 789   assert(first_hr->used() == word_size * HeapWordSize, "invariant");
 790   _summary_bytes_used += first_hr->used();
 791   _humongous_set.add(first_hr);
 792 
 793   return new_obj;
 794 }
 795 
 796 // If could fit into free regions w/o expansion, try.
 797 // Otherwise, if can expand, do so.
 798 // Otherwise, if using ex regions might help, try with ex given back.
 799 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
 800   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 801 
 802   verify_region_sets_optional();
 803 
 804   size_t word_size_rounded = round_to(word_size, HeapRegion::GrainWords);
 805   uint num_regions = (uint) (word_size_rounded / HeapRegion::GrainWords);
 806   uint x_num = expansion_regions();
 807   uint fs = _hrs.free_suffix();
 808   uint first = humongous_obj_allocate_find_first(num_regions, word_size);
 809   if (first == G1_NULL_HRS_INDEX) {
 810     // The only thing we can do now is attempt expansion.
 811     if (fs + x_num >= num_regions) {
 812       // If the number of regions we're trying to allocate for this
 813       // object is at most the number of regions in the free suffix,
 814       // then the call to humongous_obj_allocate_find_first() above
 815       // should have succeeded and we wouldn't be here.
 816       //
 817       // We should only be trying to expand when the free suffix is
 818       // not sufficient for the object _and_ we have some expansion
 819       // room available.
 820       assert(num_regions > fs, "earlier allocation should have succeeded");
 821 
 822       ergo_verbose1(ErgoHeapSizing,
 823                     "attempt heap expansion",
 824                     ergo_format_reason("humongous allocation request failed")
 825                     ergo_format_byte("allocation request"),
 826                     word_size * HeapWordSize);
 827       if (expand((num_regions - fs) * HeapRegion::GrainBytes)) {
 828         // Even though the heap was expanded, it might not have
 829         // reached the desired size. So, we cannot assume that the
 830         // allocation will succeed.
 831         first = humongous_obj_allocate_find_first(num_regions, word_size);
 832       }
 833     }
 834   }
 835 
 836   HeapWord* result = NULL;
 837   if (first != G1_NULL_HRS_INDEX) {
 838     result =
 839       humongous_obj_allocate_initialize_regions(first, num_regions, word_size);
 840     assert(result != NULL, "it should always return a valid result");
 841 
 842     // A successful humongous object allocation changes the used space
 843     // information of the old generation so we need to recalculate the
 844     // sizes and update the jstat counters here.
 845     g1mm()->update_sizes();
 846   }
 847 
 848   verify_region_sets_optional();
 849 
 850   return result;
 851 }
 852 
 853 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
 854   assert_heap_not_locked_and_not_at_safepoint();
 855   assert(!isHumongous(word_size), "we do not allow humongous TLABs");
 856 
 857   unsigned int dummy_gc_count_before;
 858   int dummy_gclocker_retry_count = 0;
 859   return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
 860 }
 861 
 862 HeapWord*
 863 G1CollectedHeap::mem_allocate(size_t word_size,
 864                               bool*  gc_overhead_limit_was_exceeded) {
 865   assert_heap_not_locked_and_not_at_safepoint();
 866 
 867   // Loop until the allocation is satisfied, or unsatisfied after GC.
 868   for (int try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 869     unsigned int gc_count_before;
 870 
 871     HeapWord* result = NULL;
 872     if (!isHumongous(word_size)) {
 873       result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
 874     } else {
 875       result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
 876     }
 877     if (result != NULL) {
 878       return result;
 879     }
 880 
 881     // Create the garbage collection operation...
 882     VM_G1CollectForAllocation op(gc_count_before, word_size);
 883     // ...and get the VM thread to execute it.
 884     VMThread::execute(&op);
 885 
 886     if (op.prologue_succeeded() && op.pause_succeeded()) {
 887       // If the operation was successful we'll return the result even
 888       // if it is NULL. If the allocation attempt failed immediately
 889       // after a Full GC, it's unlikely we'll be able to allocate now.
 890       HeapWord* result = op.result();
 891       if (result != NULL && !isHumongous(word_size)) {
 892         // Allocations that take place on VM operations do not do any
 893         // card dirtying and we have to do it here. We only have to do
 894         // this for non-humongous allocations, though.
 895         dirty_young_block(result, word_size);
 896       }
 897       return result;
 898     } else {
 899       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 900         return NULL;
 901       }
 902       assert(op.result() == NULL,
 903              "the result should be NULL if the VM op did not succeed");
 904     }
 905 
 906     // Give a warning if we seem to be looping forever.
 907     if ((QueuedAllocationWarningCount > 0) &&
 908         (try_count % QueuedAllocationWarningCount == 0)) {
 909       warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
 910     }
 911   }
 912 
 913   ShouldNotReachHere();
 914   return NULL;
 915 }
 916 
 917 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
 918                                            unsigned int *gc_count_before_ret,
 919                                            int* gclocker_retry_count_ret) {
 920   // Make sure you read the note in attempt_allocation_humongous().
 921 
 922   assert_heap_not_locked_and_not_at_safepoint();
 923   assert(!isHumongous(word_size), "attempt_allocation_slow() should not "
 924          "be called for humongous allocation requests");
 925 
 926   // We should only get here after the first-level allocation attempt
 927   // (attempt_allocation()) failed to allocate.
 928 
 929   // We will loop until a) we manage to successfully perform the
 930   // allocation or b) we successfully schedule a collection which
 931   // fails to perform the allocation. b) is the only case when we'll
 932   // return NULL.
 933   HeapWord* result = NULL;
 934   for (int try_count = 1; /* we'll return */; try_count += 1) {
 935     bool should_try_gc;
 936     unsigned int gc_count_before;
 937 
 938     {
 939       MutexLockerEx x(Heap_lock);
 940 
 941       result = _mutator_alloc_region.attempt_allocation_locked(word_size,
 942                                                       false /* bot_updates */);
 943       if (result != NULL) {
 944         return result;
 945       }
 946 
 947       // If we reach here, attempt_allocation_locked() above failed to
 948       // allocate a new region. So the mutator alloc region should be NULL.
 949       assert(_mutator_alloc_region.get() == NULL, "only way to get here");
 950 
 951       if (GC_locker::is_active_and_needs_gc()) {
 952         if (g1_policy()->can_expand_young_list()) {
 953           // No need for an ergo verbose message here,
 954           // can_expand_young_list() does this when it returns true.
 955           result = _mutator_alloc_region.attempt_allocation_force(word_size,
 956                                                       false /* bot_updates */);
 957           if (result != NULL) {
 958             return result;
 959           }
 960         }
 961         should_try_gc = false;
 962       } else {
 963         // The GCLocker may not be active but the GCLocker initiated
 964         // GC may not yet have been performed (GCLocker::needs_gc()
 965         // returns true). In this case we do not try this GC and
 966         // wait until the GCLocker initiated GC is performed, and
 967         // then retry the allocation.
 968         if (GC_locker::needs_gc()) {
 969           should_try_gc = false;
 970         } else {
 971           // Read the GC count while still holding the Heap_lock.
 972           gc_count_before = total_collections();
 973           should_try_gc = true;
 974         }
 975       }
 976     }
 977 
 978     if (should_try_gc) {
 979       bool succeeded;
 980       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 981           GCCause::_g1_inc_collection_pause);
 982       if (result != NULL) {
 983         assert(succeeded, "only way to get back a non-NULL result");
 984         return result;
 985       }
 986 
 987       if (succeeded) {
 988         // If we get here we successfully scheduled a collection which
 989         // failed to allocate. No point in trying to allocate
 990         // further. We'll just return NULL.
 991         MutexLockerEx x(Heap_lock);
 992         *gc_count_before_ret = total_collections();
 993         return NULL;
 994       }
 995     } else {
 996       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
 997         MutexLockerEx x(Heap_lock);
 998         *gc_count_before_ret = total_collections();
 999         return NULL;
1000       }
1001       // The GCLocker is either active or the GCLocker initiated
1002       // GC has not yet been performed. Stall until it is and
1003       // then retry the allocation.
1004       GC_locker::stall_until_clear();
1005       (*gclocker_retry_count_ret) += 1;
1006     }
1007 
1008     // We can reach here if we were unsuccessful in scheduling a
1009     // collection (because another thread beat us to it) or if we were
1010     // stalled due to the GC locker. In either can we should retry the
1011     // allocation attempt in case another thread successfully
1012     // performed a collection and reclaimed enough space. We do the
1013     // first attempt (without holding the Heap_lock) here and the
1014     // follow-on attempt will be at the start of the next loop
1015     // iteration (after taking the Heap_lock).
1016     result = _mutator_alloc_region.attempt_allocation(word_size,
1017                                                       false /* bot_updates */);
1018     if (result != NULL) {
1019       return result;
1020     }
1021 
1022     // Give a warning if we seem to be looping forever.
1023     if ((QueuedAllocationWarningCount > 0) &&
1024         (try_count % QueuedAllocationWarningCount == 0)) {
1025       warning("G1CollectedHeap::attempt_allocation_slow() "
1026               "retries %d times", try_count);
1027     }
1028   }
1029 
1030   ShouldNotReachHere();
1031   return NULL;
1032 }
1033 
1034 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
1035                                           unsigned int * gc_count_before_ret,
1036                                           int* gclocker_retry_count_ret) {
1037   // The structure of this method has a lot of similarities to
1038   // attempt_allocation_slow(). The reason these two were not merged
1039   // into a single one is that such a method would require several "if
1040   // allocation is not humongous do this, otherwise do that"
1041   // conditional paths which would obscure its flow. In fact, an early
1042   // version of this code did use a unified method which was harder to
1043   // follow and, as a result, it had subtle bugs that were hard to
1044   // track down. So keeping these two methods separate allows each to
1045   // be more readable. It will be good to keep these two in sync as
1046   // much as possible.
1047 
1048   assert_heap_not_locked_and_not_at_safepoint();
1049   assert(isHumongous(word_size), "attempt_allocation_humongous() "
1050          "should only be called for humongous allocations");
1051 
1052   // Humongous objects can exhaust the heap quickly, so we should check if we
1053   // need to start a marking cycle at each humongous object allocation. We do
1054   // the check before we do the actual allocation. The reason for doing it
1055   // before the allocation is that we avoid having to keep track of the newly
1056   // allocated memory while we do a GC.
1057   if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
1058                                            word_size)) {
1059     collect(GCCause::_g1_humongous_allocation);
1060   }
1061 
1062   // We will loop until a) we manage to successfully perform the
1063   // allocation or b) we successfully schedule a collection which
1064   // fails to perform the allocation. b) is the only case when we'll
1065   // return NULL.
1066   HeapWord* result = NULL;
1067   for (int try_count = 1; /* we'll return */; try_count += 1) {
1068     bool should_try_gc;
1069     unsigned int gc_count_before;
1070 
1071     {
1072       MutexLockerEx x(Heap_lock);
1073 
1074       // Given that humongous objects are not allocated in young
1075       // regions, we'll first try to do the allocation without doing a
1076       // collection hoping that there's enough space in the heap.
1077       result = humongous_obj_allocate(word_size);
1078       if (result != NULL) {
1079         return result;
1080       }
1081 
1082       if (GC_locker::is_active_and_needs_gc()) {
1083         should_try_gc = false;
1084       } else {
1085          // The GCLocker may not be active but the GCLocker initiated
1086         // GC may not yet have been performed (GCLocker::needs_gc()
1087         // returns true). In this case we do not try this GC and
1088         // wait until the GCLocker initiated GC is performed, and
1089         // then retry the allocation.
1090         if (GC_locker::needs_gc()) {
1091           should_try_gc = false;
1092         } else {
1093           // Read the GC count while still holding the Heap_lock.
1094           gc_count_before = total_collections();
1095           should_try_gc = true;
1096         }
1097       }
1098     }
1099 
1100     if (should_try_gc) {
1101       // If we failed to allocate the humongous object, we should try to
1102       // do a collection pause (if we're allowed) in case it reclaims
1103       // enough space for the allocation to succeed after the pause.
1104 
1105       bool succeeded;
1106       result = do_collection_pause(word_size, gc_count_before, &succeeded,
1107           GCCause::_g1_humongous_allocation);
1108       if (result != NULL) {
1109         assert(succeeded, "only way to get back a non-NULL result");
1110         return result;
1111       }
1112 
1113       if (succeeded) {
1114         // If we get here we successfully scheduled a collection which
1115         // failed to allocate. No point in trying to allocate
1116         // further. We'll just return NULL.
1117         MutexLockerEx x(Heap_lock);
1118         *gc_count_before_ret = total_collections();
1119         return NULL;
1120       }
1121     } else {
1122       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1123         MutexLockerEx x(Heap_lock);
1124         *gc_count_before_ret = total_collections();
1125         return NULL;
1126       }
1127       // The GCLocker is either active or the GCLocker initiated
1128       // GC has not yet been performed. Stall until it is and
1129       // then retry the allocation.
1130       GC_locker::stall_until_clear();
1131       (*gclocker_retry_count_ret) += 1;
1132     }
1133 
1134     // We can reach here if we were unsuccessful in scheduling a
1135     // collection (because another thread beat us to it) or if we were
1136     // stalled due to the GC locker. In either can we should retry the
1137     // allocation attempt in case another thread successfully
1138     // performed a collection and reclaimed enough space.  Give a
1139     // warning if we seem to be looping forever.
1140 
1141     if ((QueuedAllocationWarningCount > 0) &&
1142         (try_count % QueuedAllocationWarningCount == 0)) {
1143       warning("G1CollectedHeap::attempt_allocation_humongous() "
1144               "retries %d times", try_count);
1145     }
1146   }
1147 
1148   ShouldNotReachHere();
1149   return NULL;
1150 }
1151 
1152 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1153                                        bool expect_null_mutator_alloc_region) {
1154   assert_at_safepoint(true /* should_be_vm_thread */);
1155   assert(_mutator_alloc_region.get() == NULL ||
1156                                              !expect_null_mutator_alloc_region,
1157          "the current alloc region was unexpectedly found to be non-NULL");
1158 
1159   if (!isHumongous(word_size)) {
1160     return _mutator_alloc_region.attempt_allocation_locked(word_size,
1161                                                       false /* bot_updates */);
1162   } else {
1163     HeapWord* result = humongous_obj_allocate(word_size);
1164     if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1165       g1_policy()->set_initiate_conc_mark_if_possible();
1166     }
1167     return result;
1168   }
1169 
1170   ShouldNotReachHere();
1171 }
1172 
1173 class PostMCRemSetClearClosure: public HeapRegionClosure {
1174   G1CollectedHeap* _g1h;
1175   ModRefBarrierSet* _mr_bs;
1176 public:
1177   PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1178     _g1h(g1h), _mr_bs(mr_bs) {}
1179 
1180   bool doHeapRegion(HeapRegion* r) {
1181     HeapRegionRemSet* hrrs = r->rem_set();
1182 
1183     if (r->continuesHumongous()) {
1184       // We'll assert that the strong code root list and RSet is empty
1185       assert(hrrs->strong_code_roots_list_length() == 0, "sanity");
1186       assert(hrrs->occupied() == 0, "RSet should be empty");
1187       return false;
1188     }
1189 
1190     _g1h->reset_gc_time_stamps(r);
1191     hrrs->clear();
1192     // You might think here that we could clear just the cards
1193     // corresponding to the used region.  But no: if we leave a dirty card
1194     // in a region we might allocate into, then it would prevent that card
1195     // from being enqueued, and cause it to be missed.
1196     // Re: the performance cost: we shouldn't be doing full GC anyway!
1197     _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1198 
1199     return false;
1200   }
1201 };
1202 
1203 void G1CollectedHeap::clear_rsets_post_compaction() {
1204   PostMCRemSetClearClosure rs_clear(this, g1_barrier_set());
1205   heap_region_iterate(&rs_clear);
1206 }
1207 
1208 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1209   G1CollectedHeap*   _g1h;
1210   UpdateRSOopClosure _cl;
1211   int                _worker_i;
1212 public:
1213   RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1214     _cl(g1->g1_rem_set(), worker_i),
1215     _worker_i(worker_i),
1216     _g1h(g1)
1217   { }
1218 
1219   bool doHeapRegion(HeapRegion* r) {
1220     if (!r->continuesHumongous()) {
1221       _cl.set_from(r);
1222       r->oop_iterate(&_cl);
1223     }
1224     return false;
1225   }
1226 };
1227 
1228 class ParRebuildRSTask: public AbstractGangTask {
1229   G1CollectedHeap* _g1;
1230 public:
1231   ParRebuildRSTask(G1CollectedHeap* g1)
1232     : AbstractGangTask("ParRebuildRSTask"),
1233       _g1(g1)
1234   { }
1235 
1236   void work(uint worker_id) {
1237     RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1238     _g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id,
1239                                           _g1->workers()->active_workers(),
1240                                          HeapRegion::RebuildRSClaimValue);
1241   }
1242 };
1243 
1244 class PostCompactionPrinterClosure: public HeapRegionClosure {
1245 private:
1246   G1HRPrinter* _hr_printer;
1247 public:
1248   bool doHeapRegion(HeapRegion* hr) {
1249     assert(!hr->is_young(), "not expecting to find young regions");
1250     // We only generate output for non-empty regions.
1251     if (!hr->is_empty()) {
1252       if (!hr->isHumongous()) {
1253         _hr_printer->post_compaction(hr, G1HRPrinter::Old);
1254       } else if (hr->startsHumongous()) {
1255         if (hr->region_num() == 1) {
1256           // single humongous region
1257           _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
1258         } else {
1259           _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
1260         }
1261       } else {
1262         assert(hr->continuesHumongous(), "only way to get here");
1263         _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1264       }
1265     }
1266     return false;
1267   }
1268 
1269   PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1270     : _hr_printer(hr_printer) { }
1271 };
1272 
1273 void G1CollectedHeap::print_hrs_post_compaction() {
1274   PostCompactionPrinterClosure cl(hr_printer());
1275   heap_region_iterate(&cl);
1276 }
1277 
1278 bool G1CollectedHeap::do_collection(bool explicit_gc,
1279                                     bool clear_all_soft_refs,
1280                                     size_t word_size) {
1281   assert_at_safepoint(true /* should_be_vm_thread */);
1282 
1283   if (GC_locker::check_active_before_gc()) {
1284     return false;
1285   }
1286 
1287   STWGCTimer* gc_timer = G1MarkSweep::gc_timer();
1288   gc_timer->register_gc_start();
1289 
1290   SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer();
1291   gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start());
1292 
1293   SvcGCMarker sgcm(SvcGCMarker::FULL);
1294   ResourceMark rm;
1295 
1296   print_heap_before_gc();
1297   trace_heap_before_gc(gc_tracer);
1298 
1299   size_t metadata_prev_used = MetaspaceAux::allocated_used_bytes();
1300 
1301   HRSPhaseSetter x(HRSPhaseFullGC);
1302   verify_region_sets_optional();
1303 
1304   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1305                            collector_policy()->should_clear_all_soft_refs();
1306 
1307   ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1308 
1309   {
1310     IsGCActiveMark x;
1311 
1312     // Timing
1313     assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant");
1314     gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps);
1315     TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
1316 
1317     {
1318       GCTraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, NULL);
1319       TraceCollectorStats tcs(g1mm()->full_collection_counters());
1320       TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1321 
1322       double start = os::elapsedTime();
1323       g1_policy()->record_full_collection_start();
1324 
1325       // Note: When we have a more flexible GC logging framework that
1326       // allows us to add optional attributes to a GC log record we
1327       // could consider timing and reporting how long we wait in the
1328       // following two methods.
1329       wait_while_free_regions_coming();
1330       // If we start the compaction before the CM threads finish
1331       // scanning the root regions we might trip them over as we'll
1332       // be moving objects / updating references. So let's wait until
1333       // they are done. By telling them to abort, they should complete
1334       // early.
1335       _cm->root_regions()->abort();
1336       _cm->root_regions()->wait_until_scan_finished();
1337       append_secondary_free_list_if_not_empty_with_lock();
1338 
1339       gc_prologue(true);
1340       increment_total_collections(true /* full gc */);
1341       increment_old_marking_cycles_started();
1342 
1343       assert(used() == recalculate_used(), "Should be equal");
1344 
1345       verify_before_gc();
1346 
1347       pre_full_gc_dump(gc_timer);
1348 
1349       COMPILER2_PRESENT(DerivedPointerTable::clear());
1350 
1351       // Disable discovery and empty the discovered lists
1352       // for the CM ref processor.
1353       ref_processor_cm()->disable_discovery();
1354       ref_processor_cm()->abandon_partial_discovery();
1355       ref_processor_cm()->verify_no_references_recorded();
1356 
1357       // Abandon current iterations of concurrent marking and concurrent
1358       // refinement, if any are in progress. We have to do this before
1359       // wait_until_scan_finished() below.
1360       concurrent_mark()->abort();
1361 
1362       // Make sure we'll choose a new allocation region afterwards.
1363       release_mutator_alloc_region();
1364       abandon_gc_alloc_regions();
1365       g1_rem_set()->cleanupHRRS();
1366 
1367       // We should call this after we retire any currently active alloc
1368       // regions so that all the ALLOC / RETIRE events are generated
1369       // before the start GC event.
1370       _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1371 
1372       // We may have added regions to the current incremental collection
1373       // set between the last GC or pause and now. We need to clear the
1374       // incremental collection set and then start rebuilding it afresh
1375       // after this full GC.
1376       abandon_collection_set(g1_policy()->inc_cset_head());
1377       g1_policy()->clear_incremental_cset();
1378       g1_policy()->stop_incremental_cset_building();
1379 
1380       tear_down_region_sets(false /* free_list_only */);
1381       g1_policy()->set_gcs_are_young(true);
1382 
1383       // See the comments in g1CollectedHeap.hpp and
1384       // G1CollectedHeap::ref_processing_init() about
1385       // how reference processing currently works in G1.
1386 
1387       // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1388       ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1389 
1390       // Temporarily clear the STW ref processor's _is_alive_non_header field.
1391       ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1392 
1393       ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
1394       ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1395 
1396       // Do collection work
1397       {
1398         HandleMark hm;  // Discard invalid handles created during gc
1399         G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1400       }
1401 
1402       assert(free_regions() == 0, "we should not have added any free regions");
1403       rebuild_region_sets(false /* free_list_only */);
1404 
1405       // Enqueue any discovered reference objects that have
1406       // not been removed from the discovered lists.
1407       ref_processor_stw()->enqueue_discovered_references();
1408 
1409       COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1410 
1411       MemoryService::track_memory_usage();
1412 
1413       assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1414       ref_processor_stw()->verify_no_references_recorded();
1415 
1416       // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1417       ClassLoaderDataGraph::purge();
1418       MetaspaceAux::verify_metrics();
1419 
1420       // Note: since we've just done a full GC, concurrent
1421       // marking is no longer active. Therefore we need not
1422       // re-enable reference discovery for the CM ref processor.
1423       // That will be done at the start of the next marking cycle.
1424       assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1425       ref_processor_cm()->verify_no_references_recorded();
1426 
1427       reset_gc_time_stamp();
1428       // Since everything potentially moved, we will clear all remembered
1429       // sets, and clear all cards.  Later we will rebuild remembered
1430       // sets. We will also reset the GC time stamps of the regions.
1431       clear_rsets_post_compaction();
1432       check_gc_time_stamps();
1433 
1434       // Resize the heap if necessary.
1435       resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1436 
1437       if (_hr_printer.is_active()) {
1438         // We should do this after we potentially resize the heap so
1439         // that all the COMMIT / UNCOMMIT events are generated before
1440         // the end GC event.
1441 
1442         print_hrs_post_compaction();
1443         _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1444       }
1445 
1446       G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
1447       if (hot_card_cache->use_cache()) {
1448         hot_card_cache->reset_card_counts();
1449         hot_card_cache->reset_hot_cache();
1450       }
1451 
1452       // Rebuild remembered sets of all regions.
1453       if (G1CollectedHeap::use_parallel_gc_threads()) {
1454         uint n_workers =
1455           AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1456                                                   workers()->active_workers(),
1457                                                   Threads::number_of_non_daemon_threads());
1458         assert(UseDynamicNumberOfGCThreads ||
1459                n_workers == workers()->total_workers(),
1460                "If not dynamic should be using all the  workers");
1461         workers()->set_active_workers(n_workers);
1462         // Set parallel threads in the heap (_n_par_threads) only
1463         // before a parallel phase and always reset it to 0 after
1464         // the phase so that the number of parallel threads does
1465         // no get carried forward to a serial phase where there
1466         // may be code that is "possibly_parallel".
1467         set_par_threads(n_workers);
1468 
1469         ParRebuildRSTask rebuild_rs_task(this);
1470         assert(check_heap_region_claim_values(
1471                HeapRegion::InitialClaimValue), "sanity check");
1472         assert(UseDynamicNumberOfGCThreads ||
1473                workers()->active_workers() == workers()->total_workers(),
1474                "Unless dynamic should use total workers");
1475         // Use the most recent number of  active workers
1476         assert(workers()->active_workers() > 0,
1477                "Active workers not properly set");
1478         set_par_threads(workers()->active_workers());
1479         workers()->run_task(&rebuild_rs_task);
1480         set_par_threads(0);
1481         assert(check_heap_region_claim_values(
1482                HeapRegion::RebuildRSClaimValue), "sanity check");
1483         reset_heap_region_claim_values();
1484       } else {
1485         RebuildRSOutOfRegionClosure rebuild_rs(this);
1486         heap_region_iterate(&rebuild_rs);
1487       }
1488 
1489       // Rebuild the strong code root lists for each region
1490       rebuild_strong_code_roots();
1491 
1492       if (true) { // FIXME
1493         MetaspaceGC::compute_new_size();
1494       }
1495 
1496 #ifdef TRACESPINNING
1497       ParallelTaskTerminator::print_termination_counts();
1498 #endif
1499 
1500       // Discard all rset updates
1501       JavaThread::dirty_card_queue_set().abandon_logs();
1502       assert(!G1DeferredRSUpdate
1503              || (G1DeferredRSUpdate &&
1504                 (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any");
1505 
1506       _young_list->reset_sampled_info();
1507       // At this point there should be no regions in the
1508       // entire heap tagged as young.
1509       assert(check_young_list_empty(true /* check_heap */),
1510              "young list should be empty at this point");
1511 
1512       // Update the number of full collections that have been completed.
1513       increment_old_marking_cycles_completed(false /* concurrent */);
1514 
1515       _hrs.verify_optional();
1516       verify_region_sets_optional();
1517 
1518       verify_after_gc();
1519 
1520       // Start a new incremental collection set for the next pause
1521       assert(g1_policy()->collection_set() == NULL, "must be");
1522       g1_policy()->start_incremental_cset_building();
1523 
1524       // Clear the _cset_fast_test bitmap in anticipation of adding
1525       // regions to the incremental collection set for the next
1526       // evacuation pause.
1527       clear_cset_fast_test();
1528 
1529       init_mutator_alloc_region();
1530 
1531       double end = os::elapsedTime();
1532       g1_policy()->record_full_collection_end();
1533 
1534       if (G1Log::fine()) {
1535         g1_policy()->print_heap_transition();
1536       }
1537 
1538       // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1539       // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1540       // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1541       // before any GC notifications are raised.
1542       g1mm()->update_sizes();
1543 
1544       gc_epilogue(true);
1545     }
1546 
1547     if (G1Log::finer()) {
1548       g1_policy()->print_detailed_heap_transition(true /* full */);
1549     }
1550 
1551     print_heap_after_gc();
1552     trace_heap_after_gc(gc_tracer);
1553 
1554     post_full_gc_dump(gc_timer);
1555 
1556     gc_timer->register_gc_end();
1557     gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
1558   }
1559 
1560   return true;
1561 }
1562 
1563 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1564   // do_collection() will return whether it succeeded in performing
1565   // the GC. Currently, there is no facility on the
1566   // do_full_collection() API to notify the caller than the collection
1567   // did not succeed (e.g., because it was locked out by the GC
1568   // locker). So, right now, we'll ignore the return value.
1569   bool dummy = do_collection(true,                /* explicit_gc */
1570                              clear_all_soft_refs,
1571                              0                    /* word_size */);
1572 }
1573 
1574 // This code is mostly copied from TenuredGeneration.
1575 void
1576 G1CollectedHeap::
1577 resize_if_necessary_after_full_collection(size_t word_size) {
1578   // Include the current allocation, if any, and bytes that will be
1579   // pre-allocated to support collections, as "used".
1580   const size_t used_after_gc = used();
1581   const size_t capacity_after_gc = capacity();
1582   const size_t free_after_gc = capacity_after_gc - used_after_gc;
1583 
1584   // This is enforced in arguments.cpp.
1585   assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1586          "otherwise the code below doesn't make sense");
1587 
1588   // We don't have floating point command-line arguments
1589   const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1590   const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1591   const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1592   const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1593 
1594   const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1595   const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1596 
1597   // We have to be careful here as these two calculations can overflow
1598   // 32-bit size_t's.
1599   double used_after_gc_d = (double) used_after_gc;
1600   double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1601   double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1602 
1603   // Let's make sure that they are both under the max heap size, which
1604   // by default will make them fit into a size_t.
1605   double desired_capacity_upper_bound = (double) max_heap_size;
1606   minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1607                                     desired_capacity_upper_bound);
1608   maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1609                                     desired_capacity_upper_bound);
1610 
1611   // We can now safely turn them into size_t's.
1612   size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1613   size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1614 
1615   // This assert only makes sense here, before we adjust them
1616   // with respect to the min and max heap size.
1617   assert(minimum_desired_capacity <= maximum_desired_capacity,
1618          err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1619                  "maximum_desired_capacity = "SIZE_FORMAT,
1620                  minimum_desired_capacity, maximum_desired_capacity));
1621 
1622   // Should not be greater than the heap max size. No need to adjust
1623   // it with respect to the heap min size as it's a lower bound (i.e.,
1624   // we'll try to make the capacity larger than it, not smaller).
1625   minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1626   // Should not be less than the heap min size. No need to adjust it
1627   // with respect to the heap max size as it's an upper bound (i.e.,
1628   // we'll try to make the capacity smaller than it, not greater).
1629   maximum_desired_capacity =  MAX2(maximum_desired_capacity, min_heap_size);
1630 
1631   if (capacity_after_gc < minimum_desired_capacity) {
1632     // Don't expand unless it's significant
1633     size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1634     ergo_verbose4(ErgoHeapSizing,
1635                   "attempt heap expansion",
1636                   ergo_format_reason("capacity lower than "
1637                                      "min desired capacity after Full GC")
1638                   ergo_format_byte("capacity")
1639                   ergo_format_byte("occupancy")
1640                   ergo_format_byte_perc("min desired capacity"),
1641                   capacity_after_gc, used_after_gc,
1642                   minimum_desired_capacity, (double) MinHeapFreeRatio);
1643     expand(expand_bytes);
1644 
1645     // No expansion, now see if we want to shrink
1646   } else if (capacity_after_gc > maximum_desired_capacity) {
1647     // Capacity too large, compute shrinking size
1648     size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1649     ergo_verbose4(ErgoHeapSizing,
1650                   "attempt heap shrinking",
1651                   ergo_format_reason("capacity higher than "
1652                                      "max desired capacity after Full GC")
1653                   ergo_format_byte("capacity")
1654                   ergo_format_byte("occupancy")
1655                   ergo_format_byte_perc("max desired capacity"),
1656                   capacity_after_gc, used_after_gc,
1657                   maximum_desired_capacity, (double) MaxHeapFreeRatio);
1658     shrink(shrink_bytes);
1659   }
1660 }
1661 
1662 
1663 HeapWord*
1664 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1665                                            bool* succeeded) {
1666   assert_at_safepoint(true /* should_be_vm_thread */);
1667 
1668   *succeeded = true;
1669   // Let's attempt the allocation first.
1670   HeapWord* result =
1671     attempt_allocation_at_safepoint(word_size,
1672                                  false /* expect_null_mutator_alloc_region */);
1673   if (result != NULL) {
1674     assert(*succeeded, "sanity");
1675     return result;
1676   }
1677 
1678   // In a G1 heap, we're supposed to keep allocation from failing by
1679   // incremental pauses.  Therefore, at least for now, we'll favor
1680   // expansion over collection.  (This might change in the future if we can
1681   // do something smarter than full collection to satisfy a failed alloc.)
1682   result = expand_and_allocate(word_size);
1683   if (result != NULL) {
1684     assert(*succeeded, "sanity");
1685     return result;
1686   }
1687 
1688   // Expansion didn't work, we'll try to do a Full GC.
1689   bool gc_succeeded = do_collection(false, /* explicit_gc */
1690                                     false, /* clear_all_soft_refs */
1691                                     word_size);
1692   if (!gc_succeeded) {
1693     *succeeded = false;
1694     return NULL;
1695   }
1696 
1697   // Retry the allocation
1698   result = attempt_allocation_at_safepoint(word_size,
1699                                   true /* expect_null_mutator_alloc_region */);
1700   if (result != NULL) {
1701     assert(*succeeded, "sanity");
1702     return result;
1703   }
1704 
1705   // Then, try a Full GC that will collect all soft references.
1706   gc_succeeded = do_collection(false, /* explicit_gc */
1707                                true,  /* clear_all_soft_refs */
1708                                word_size);
1709   if (!gc_succeeded) {
1710     *succeeded = false;
1711     return NULL;
1712   }
1713 
1714   // Retry the allocation once more
1715   result = attempt_allocation_at_safepoint(word_size,
1716                                   true /* expect_null_mutator_alloc_region */);
1717   if (result != NULL) {
1718     assert(*succeeded, "sanity");
1719     return result;
1720   }
1721 
1722   assert(!collector_policy()->should_clear_all_soft_refs(),
1723          "Flag should have been handled and cleared prior to this point");
1724 
1725   // What else?  We might try synchronous finalization later.  If the total
1726   // space available is large enough for the allocation, then a more
1727   // complete compaction phase than we've tried so far might be
1728   // appropriate.
1729   assert(*succeeded, "sanity");
1730   return NULL;
1731 }
1732 
1733 // Attempting to expand the heap sufficiently
1734 // to support an allocation of the given "word_size".  If
1735 // successful, perform the allocation and return the address of the
1736 // allocated block, or else "NULL".
1737 
1738 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1739   assert_at_safepoint(true /* should_be_vm_thread */);
1740 
1741   verify_region_sets_optional();
1742 
1743   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1744   ergo_verbose1(ErgoHeapSizing,
1745                 "attempt heap expansion",
1746                 ergo_format_reason("allocation request failed")
1747                 ergo_format_byte("allocation request"),
1748                 word_size * HeapWordSize);
1749   if (expand(expand_bytes)) {
1750     _hrs.verify_optional();
1751     verify_region_sets_optional();
1752     return attempt_allocation_at_safepoint(word_size,
1753                                  false /* expect_null_mutator_alloc_region */);
1754   }
1755   return NULL;
1756 }
1757 
1758 void G1CollectedHeap::update_committed_space(HeapWord* old_end,
1759                                              HeapWord* new_end) {
1760   assert(old_end != new_end, "don't call this otherwise");
1761   assert((HeapWord*) _g1_storage.high() == new_end, "invariant");
1762 
1763   // Update the committed mem region.
1764   _g1_committed.set_end(new_end);
1765   // Tell the card table about the update.
1766   Universe::heap()->barrier_set()->resize_covered_region(_g1_committed);
1767   // Tell the BOT about the update.
1768   _bot_shared->resize(_g1_committed.word_size());
1769   // Tell the hot card cache about the update
1770   _cg1r->hot_card_cache()->resize_card_counts(capacity());
1771 }
1772 
1773 bool G1CollectedHeap::expand(size_t expand_bytes) {
1774   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1775   aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1776                                        HeapRegion::GrainBytes);
1777   ergo_verbose2(ErgoHeapSizing,
1778                 "expand the heap",
1779                 ergo_format_byte("requested expansion amount")
1780                 ergo_format_byte("attempted expansion amount"),
1781                 expand_bytes, aligned_expand_bytes);
1782 
1783   if (_g1_storage.uncommitted_size() == 0) {
1784     ergo_verbose0(ErgoHeapSizing,
1785                       "did not expand the heap",
1786                       ergo_format_reason("heap already fully expanded"));
1787     return false;
1788   }
1789 
1790   // First commit the memory.
1791   HeapWord* old_end = (HeapWord*) _g1_storage.high();
1792   bool successful = _g1_storage.expand_by(aligned_expand_bytes);
1793   if (successful) {
1794     // Then propagate this update to the necessary data structures.
1795     HeapWord* new_end = (HeapWord*) _g1_storage.high();
1796     update_committed_space(old_end, new_end);
1797 
1798     FreeRegionList expansion_list("Local Expansion List");
1799     MemRegion mr = _hrs.expand_by(old_end, new_end, &expansion_list);
1800     assert(mr.start() == old_end, "post-condition");
1801     // mr might be a smaller region than what was requested if
1802     // expand_by() was unable to allocate the HeapRegion instances
1803     assert(mr.end() <= new_end, "post-condition");
1804 
1805     size_t actual_expand_bytes = mr.byte_size();
1806     assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1807     assert(actual_expand_bytes == expansion_list.total_capacity_bytes(),
1808            "post-condition");
1809     if (actual_expand_bytes < aligned_expand_bytes) {
1810       // We could not expand _hrs to the desired size. In this case we
1811       // need to shrink the committed space accordingly.
1812       assert(mr.end() < new_end, "invariant");
1813 
1814       size_t diff_bytes = aligned_expand_bytes - actual_expand_bytes;
1815       // First uncommit the memory.
1816       _g1_storage.shrink_by(diff_bytes);
1817       // Then propagate this update to the necessary data structures.
1818       update_committed_space(new_end, mr.end());
1819     }
1820     _free_list.add_as_tail(&expansion_list);
1821 
1822     if (_hr_printer.is_active()) {
1823       HeapWord* curr = mr.start();
1824       while (curr < mr.end()) {
1825         HeapWord* curr_end = curr + HeapRegion::GrainWords;
1826         _hr_printer.commit(curr, curr_end);
1827         curr = curr_end;
1828       }
1829       assert(curr == mr.end(), "post-condition");
1830     }
1831     g1_policy()->record_new_heap_size(n_regions());
1832   } else {
1833     ergo_verbose0(ErgoHeapSizing,
1834                   "did not expand the heap",
1835                   ergo_format_reason("heap expansion operation failed"));
1836     // The expansion of the virtual storage space was unsuccessful.
1837     // Let's see if it was because we ran out of swap.
1838     if (G1ExitOnExpansionFailure &&
1839         _g1_storage.uncommitted_size() >= aligned_expand_bytes) {
1840       // We had head room...
1841       vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1842     }
1843   }
1844   return successful;
1845 }
1846 
1847 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1848   size_t aligned_shrink_bytes =
1849     ReservedSpace::page_align_size_down(shrink_bytes);
1850   aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1851                                          HeapRegion::GrainBytes);
1852   uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1853 
1854   uint num_regions_removed = _hrs.shrink_by(num_regions_to_remove);
1855   HeapWord* old_end = (HeapWord*) _g1_storage.high();
1856   size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1857 
1858   ergo_verbose3(ErgoHeapSizing,
1859                 "shrink the heap",
1860                 ergo_format_byte("requested shrinking amount")
1861                 ergo_format_byte("aligned shrinking amount")
1862                 ergo_format_byte("attempted shrinking amount"),
1863                 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1864   if (num_regions_removed > 0) {
1865     _g1_storage.shrink_by(shrunk_bytes);
1866     HeapWord* new_end = (HeapWord*) _g1_storage.high();
1867 
1868     if (_hr_printer.is_active()) {
1869       HeapWord* curr = old_end;
1870       while (curr > new_end) {
1871         HeapWord* curr_end = curr;
1872         curr -= HeapRegion::GrainWords;
1873         _hr_printer.uncommit(curr, curr_end);
1874       }
1875     }
1876 
1877     _expansion_regions += num_regions_removed;
1878     update_committed_space(old_end, new_end);
1879     HeapRegionRemSet::shrink_heap(n_regions());
1880     g1_policy()->record_new_heap_size(n_regions());
1881   } else {
1882     ergo_verbose0(ErgoHeapSizing,
1883                   "did not shrink the heap",
1884                   ergo_format_reason("heap shrinking operation failed"));
1885   }
1886 }
1887 
1888 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1889   verify_region_sets_optional();
1890 
1891   // We should only reach here at the end of a Full GC which means we
1892   // should not not be holding to any GC alloc regions. The method
1893   // below will make sure of that and do any remaining clean up.
1894   abandon_gc_alloc_regions();
1895 
1896   // Instead of tearing down / rebuilding the free lists here, we
1897   // could instead use the remove_all_pending() method on free_list to
1898   // remove only the ones that we need to remove.
1899   tear_down_region_sets(true /* free_list_only */);
1900   shrink_helper(shrink_bytes);
1901   rebuild_region_sets(true /* free_list_only */);
1902 
1903   _hrs.verify_optional();
1904   verify_region_sets_optional();
1905 }
1906 
1907 // Public methods.
1908 
1909 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1910 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1911 #endif // _MSC_VER
1912 
1913 
1914 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1915   SharedHeap(policy_),
1916   _g1_policy(policy_),
1917   _dirty_card_queue_set(false),
1918   _into_cset_dirty_card_queue_set(false),
1919   _is_alive_closure_cm(this),
1920   _is_alive_closure_stw(this),
1921   _ref_processor_cm(NULL),
1922   _ref_processor_stw(NULL),
1923   _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
1924   _bot_shared(NULL),
1925   _evac_failure_scan_stack(NULL),
1926   _mark_in_progress(false),
1927   _cg1r(NULL), _summary_bytes_used(0),
1928   _g1mm(NULL),
1929   _refine_cte_cl(NULL),
1930   _full_collection(false),
1931   _free_list("Master Free List"),
1932   _secondary_free_list("Secondary Free List"),
1933   _old_set("Old Set"),
1934   _humongous_set("Master Humongous Set"),
1935   _free_regions_coming(false),
1936   _young_list(new YoungList(this)),
1937   _gc_time_stamp(0),
1938   _retained_old_gc_alloc_region(NULL),
1939   _survivor_plab_stats(YoungPLABSize, PLABWeight),
1940   _old_plab_stats(OldPLABSize, PLABWeight),
1941   _expand_heap_after_alloc_failure(true),
1942   _surviving_young_words(NULL),
1943   _old_marking_cycles_started(0),
1944   _old_marking_cycles_completed(0),
1945   _concurrent_cycle_started(false),
1946   _in_cset_fast_test(NULL),
1947   _in_cset_fast_test_base(NULL),
1948   _dirty_cards_region_list(NULL),
1949   _worker_cset_start_region(NULL),
1950   _worker_cset_start_region_time_stamp(NULL),
1951   _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1952   _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
1953   _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1954   _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) {
1955 
1956   _g1h = this;
1957   if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
1958     vm_exit_during_initialization("Failed necessary allocation.");
1959   }
1960 
1961   _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1962 
1963   int n_queues = MAX2((int)ParallelGCThreads, 1);
1964   _task_queues = new RefToScanQueueSet(n_queues);
1965 
1966   int n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1967   assert(n_rem_sets > 0, "Invariant.");
1968 
1969   _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1970   _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC);
1971   _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1972 
1973   for (int i = 0; i < n_queues; i++) {
1974     RefToScanQueue* q = new RefToScanQueue();
1975     q->initialize();
1976     _task_queues->register_queue(i, q);
1977     ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1978   }
1979   clear_cset_start_regions();
1980 
1981   // Initialize the G1EvacuationFailureALot counters and flags.
1982   NOT_PRODUCT(reset_evacuation_should_fail();)
1983 
1984   guarantee(_task_queues != NULL, "task_queues allocation failure.");
1985 }
1986 
1987 jint G1CollectedHeap::initialize() {
1988   CollectedHeap::pre_initialize();
1989   os::enable_vtime();
1990 
1991   G1Log::init();
1992 
1993   // Necessary to satisfy locking discipline assertions.
1994 
1995   MutexLocker x(Heap_lock);
1996 
1997   // We have to initialize the printer before committing the heap, as
1998   // it will be used then.
1999   _hr_printer.set_active(G1PrintHeapRegions);
2000 
2001   // While there are no constraints in the GC code that HeapWordSize
2002   // be any particular value, there are multiple other areas in the
2003   // system which believe this to be true (e.g. oop->object_size in some
2004   // cases incorrectly returns the size in wordSize units rather than
2005   // HeapWordSize).
2006   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
2007 
2008   size_t init_byte_size = collector_policy()->initial_heap_byte_size();
2009   size_t max_byte_size = collector_policy()->max_heap_byte_size();
2010   size_t heap_alignment = collector_policy()->heap_alignment();
2011 
2012   // Ensure that the sizes are properly aligned.
2013   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
2014   Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
2015   Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
2016 
2017   _cg1r = new ConcurrentG1Refine(this);
2018 
2019   // Reserve the maximum.
2020 
2021   // When compressed oops are enabled, the preferred heap base
2022   // is calculated by subtracting the requested size from the
2023   // 32Gb boundary and using the result as the base address for
2024   // heap reservation. If the requested size is not aligned to
2025   // HeapRegion::GrainBytes (i.e. the alignment that is passed
2026   // into the ReservedHeapSpace constructor) then the actual
2027   // base of the reserved heap may end up differing from the
2028   // address that was requested (i.e. the preferred heap base).
2029   // If this happens then we could end up using a non-optimal
2030   // compressed oops mode.
2031 
2032   ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
2033                                                  heap_alignment);
2034 
2035   // It is important to do this in a way such that concurrent readers can't
2036   // temporarily think something is in the heap.  (I've actually seen this
2037   // happen in asserts: DLD.)
2038   _reserved.set_word_size(0);
2039   _reserved.set_start((HeapWord*)heap_rs.base());
2040   _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size()));
2041 
2042   _expansion_regions = (uint) (max_byte_size / HeapRegion::GrainBytes);
2043 
2044   // Create the gen rem set (and barrier set) for the entire reserved region.
2045   _rem_set = collector_policy()->create_rem_set(_reserved, 2);
2046   set_barrier_set(rem_set()->bs());
2047   if (!barrier_set()->is_a(BarrierSet::G1SATBCTLogging)) {
2048     vm_exit_during_initialization("G1 requires a G1SATBLoggingCardTableModRefBS");
2049     return JNI_ENOMEM;
2050   }
2051 
2052   // Also create a G1 rem set.
2053   _g1_rem_set = new G1RemSet(this, g1_barrier_set());
2054 
2055   // Carve out the G1 part of the heap.
2056 
2057   ReservedSpace g1_rs   = heap_rs.first_part(max_byte_size);
2058   _g1_reserved = MemRegion((HeapWord*)g1_rs.base(),
2059                            g1_rs.size()/HeapWordSize);
2060 
2061   _g1_storage.initialize(g1_rs, 0);
2062   _g1_committed = MemRegion((HeapWord*)_g1_storage.low(), (size_t) 0);
2063   _hrs.initialize((HeapWord*) _g1_reserved.start(),
2064                   (HeapWord*) _g1_reserved.end());
2065   assert(_hrs.max_length() == _expansion_regions,
2066          err_msg("max length: %u expansion regions: %u",
2067                  _hrs.max_length(), _expansion_regions));
2068 
2069   // Do later initialization work for concurrent refinement.
2070   _cg1r->init();
2071 
2072   // 6843694 - ensure that the maximum region index can fit
2073   // in the remembered set structures.
2074   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
2075   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
2076 
2077   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
2078   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
2079   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
2080             "too many cards per region");
2081 
2082   HeapRegionSet::set_unrealistically_long_length(max_regions() + 1);
2083 
2084   _bot_shared = new G1BlockOffsetSharedArray(_reserved,
2085                                              heap_word_size(init_byte_size));
2086 
2087   _g1h = this;
2088 
2089   _in_cset_fast_test_length = max_regions();
2090   _in_cset_fast_test_base =
2091                    NEW_C_HEAP_ARRAY(bool, (size_t) _in_cset_fast_test_length, mtGC);
2092 
2093   // We're biasing _in_cset_fast_test to avoid subtracting the
2094   // beginning of the heap every time we want to index; basically
2095   // it's the same with what we do with the card table.
2096   _in_cset_fast_test = _in_cset_fast_test_base -
2097                ((uintx) _g1_reserved.start() >> HeapRegion::LogOfHRGrainBytes);
2098 
2099   // Clear the _cset_fast_test bitmap in anticipation of adding
2100   // regions to the incremental collection set for the first
2101   // evacuation pause.
2102   clear_cset_fast_test();
2103 
2104   // Create the ConcurrentMark data structure and thread.
2105   // (Must do this late, so that "max_regions" is defined.)
2106   _cm = new ConcurrentMark(this, heap_rs);
2107   if (_cm == NULL || !_cm->completed_initialization()) {
2108     vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark");
2109     return JNI_ENOMEM;
2110   }
2111   _cmThread = _cm->cmThread();
2112 
2113   // Initialize the from_card cache structure of HeapRegionRemSet.
2114   HeapRegionRemSet::init_heap(max_regions());
2115 
2116   // Now expand into the initial heap size.
2117   if (!expand(init_byte_size)) {
2118     vm_shutdown_during_initialization("Failed to allocate initial heap.");
2119     return JNI_ENOMEM;
2120   }
2121 
2122   // Perform any initialization actions delegated to the policy.
2123   g1_policy()->init();
2124 
2125   _refine_cte_cl =
2126     new RefineCardTableEntryClosure(ConcurrentG1RefineThread::sts(),
2127                                     g1_rem_set(),
2128                                     concurrent_g1_refine());
2129   JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
2130 
2131   JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
2132                                                SATB_Q_FL_lock,
2133                                                G1SATBProcessCompletedThreshold,
2134                                                Shared_SATB_Q_lock);
2135 
2136   JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
2137                                                 DirtyCardQ_FL_lock,
2138                                                 concurrent_g1_refine()->yellow_zone(),
2139                                                 concurrent_g1_refine()->red_zone(),
2140                                                 Shared_DirtyCardQ_lock);
2141 
2142   if (G1DeferredRSUpdate) {
2143     dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
2144                                       DirtyCardQ_FL_lock,
2145                                       -1, // never trigger processing
2146                                       -1, // no limit on length
2147                                       Shared_DirtyCardQ_lock,
2148                                       &JavaThread::dirty_card_queue_set());
2149   }
2150 
2151   // Initialize the card queue set used to hold cards containing
2152   // references into the collection set.
2153   _into_cset_dirty_card_queue_set.initialize(DirtyCardQ_CBL_mon,
2154                                              DirtyCardQ_FL_lock,
2155                                              -1, // never trigger processing
2156                                              -1, // no limit on length
2157                                              Shared_DirtyCardQ_lock,
2158                                              &JavaThread::dirty_card_queue_set());
2159 
2160   // In case we're keeping closure specialization stats, initialize those
2161   // counts and that mechanism.
2162   SpecializationStats::clear();
2163 
2164   // Here we allocate the dummy full region that is required by the
2165   // G1AllocRegion class. If we don't pass an address in the reserved
2166   // space here, lots of asserts fire.
2167 
2168   HeapRegion* dummy_region = new_heap_region(0 /* index of bottom region */,
2169                                              _g1_reserved.start());
2170   // We'll re-use the same region whether the alloc region will
2171   // require BOT updates or not and, if it doesn't, then a non-young
2172   // region will complain that it cannot support allocations without
2173   // BOT updates. So we'll tag the dummy region as young to avoid that.
2174   dummy_region->set_young();
2175   // Make sure it's full.
2176   dummy_region->set_top(dummy_region->end());
2177   G1AllocRegion::setup(this, dummy_region);
2178 
2179   init_mutator_alloc_region();
2180 
2181   // Do create of the monitoring and management support so that
2182   // values in the heap have been properly initialized.
2183   _g1mm = new G1MonitoringSupport(this);
2184 
2185   return JNI_OK;
2186 }
2187 
2188 size_t G1CollectedHeap::conservative_max_heap_alignment() {
2189   return HeapRegion::max_region_size();
2190 }
2191 
2192 void G1CollectedHeap::ref_processing_init() {
2193   // Reference processing in G1 currently works as follows:
2194   //
2195   // * There are two reference processor instances. One is
2196   //   used to record and process discovered references
2197   //   during concurrent marking; the other is used to
2198   //   record and process references during STW pauses
2199   //   (both full and incremental).
2200   // * Both ref processors need to 'span' the entire heap as
2201   //   the regions in the collection set may be dotted around.
2202   //
2203   // * For the concurrent marking ref processor:
2204   //   * Reference discovery is enabled at initial marking.
2205   //   * Reference discovery is disabled and the discovered
2206   //     references processed etc during remarking.
2207   //   * Reference discovery is MT (see below).
2208   //   * Reference discovery requires a barrier (see below).
2209   //   * Reference processing may or may not be MT
2210   //     (depending on the value of ParallelRefProcEnabled
2211   //     and ParallelGCThreads).
2212   //   * A full GC disables reference discovery by the CM
2213   //     ref processor and abandons any entries on it's
2214   //     discovered lists.
2215   //
2216   // * For the STW processor:
2217   //   * Non MT discovery is enabled at the start of a full GC.
2218   //   * Processing and enqueueing during a full GC is non-MT.
2219   //   * During a full GC, references are processed after marking.
2220   //
2221   //   * Discovery (may or may not be MT) is enabled at the start
2222   //     of an incremental evacuation pause.
2223   //   * References are processed near the end of a STW evacuation pause.
2224   //   * For both types of GC:
2225   //     * Discovery is atomic - i.e. not concurrent.
2226   //     * Reference discovery will not need a barrier.
2227 
2228   SharedHeap::ref_processing_init();
2229   MemRegion mr = reserved_region();
2230 
2231   // Concurrent Mark ref processor
2232   _ref_processor_cm =
2233     new ReferenceProcessor(mr,    // span
2234                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2235                                 // mt processing
2236                            (int) ParallelGCThreads,
2237                                 // degree of mt processing
2238                            (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2239                                 // mt discovery
2240                            (int) MAX2(ParallelGCThreads, ConcGCThreads),
2241                                 // degree of mt discovery
2242                            false,
2243                                 // Reference discovery is not atomic
2244                            &_is_alive_closure_cm,
2245                                 // is alive closure
2246                                 // (for efficiency/performance)
2247                            true);
2248                                 // Setting next fields of discovered
2249                                 // lists requires a barrier.
2250 
2251   // STW ref processor
2252   _ref_processor_stw =
2253     new ReferenceProcessor(mr,    // span
2254                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2255                                 // mt processing
2256                            MAX2((int)ParallelGCThreads, 1),
2257                                 // degree of mt processing
2258                            (ParallelGCThreads > 1),
2259                                 // mt discovery
2260                            MAX2((int)ParallelGCThreads, 1),
2261                                 // degree of mt discovery
2262                            true,
2263                                 // Reference discovery is atomic
2264                            &_is_alive_closure_stw,
2265                                 // is alive closure
2266                                 // (for efficiency/performance)
2267                            false);
2268                                 // Setting next fields of discovered
2269                                 // lists does not require a barrier.
2270 }
2271 
2272 size_t G1CollectedHeap::capacity() const {
2273   return _g1_committed.byte_size();
2274 }
2275 
2276 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2277   assert(!hr->continuesHumongous(), "pre-condition");
2278   hr->reset_gc_time_stamp();
2279   if (hr->startsHumongous()) {
2280     uint first_index = hr->hrs_index() + 1;
2281     uint last_index = hr->last_hc_index();
2282     for (uint i = first_index; i < last_index; i += 1) {
2283       HeapRegion* chr = region_at(i);
2284       assert(chr->continuesHumongous(), "sanity");
2285       chr->reset_gc_time_stamp();
2286     }
2287   }
2288 }
2289 
2290 #ifndef PRODUCT
2291 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2292 private:
2293   unsigned _gc_time_stamp;
2294   bool _failures;
2295 
2296 public:
2297   CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2298     _gc_time_stamp(gc_time_stamp), _failures(false) { }
2299 
2300   virtual bool doHeapRegion(HeapRegion* hr) {
2301     unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2302     if (_gc_time_stamp != region_gc_time_stamp) {
2303       gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, "
2304                              "expected %d", HR_FORMAT_PARAMS(hr),
2305                              region_gc_time_stamp, _gc_time_stamp);
2306       _failures = true;
2307     }
2308     return false;
2309   }
2310 
2311   bool failures() { return _failures; }
2312 };
2313 
2314 void G1CollectedHeap::check_gc_time_stamps() {
2315   CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2316   heap_region_iterate(&cl);
2317   guarantee(!cl.failures(), "all GC time stamps should have been reset");
2318 }
2319 #endif // PRODUCT
2320 
2321 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2322                                                  DirtyCardQueue* into_cset_dcq,
2323                                                  bool concurrent,
2324                                                  int worker_i) {
2325   // Clean cards in the hot card cache
2326   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
2327   hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq);
2328 
2329   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2330   int n_completed_buffers = 0;
2331   while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2332     n_completed_buffers++;
2333   }
2334   g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers);
2335   dcqs.clear_n_completed_buffers();
2336   assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2337 }
2338 
2339 
2340 // Computes the sum of the storage used by the various regions.
2341 
2342 size_t G1CollectedHeap::used() const {
2343   assert(Heap_lock->owner() != NULL,
2344          "Should be owned on this thread's behalf.");
2345   size_t result = _summary_bytes_used;
2346   // Read only once in case it is set to NULL concurrently
2347   HeapRegion* hr = _mutator_alloc_region.get();
2348   if (hr != NULL)
2349     result += hr->used();
2350   return result;
2351 }
2352 
2353 size_t G1CollectedHeap::used_unlocked() const {
2354   size_t result = _summary_bytes_used;
2355   return result;
2356 }
2357 
2358 class SumUsedClosure: public HeapRegionClosure {
2359   size_t _used;
2360 public:
2361   SumUsedClosure() : _used(0) {}
2362   bool doHeapRegion(HeapRegion* r) {
2363     if (!r->continuesHumongous()) {
2364       _used += r->used();
2365     }
2366     return false;
2367   }
2368   size_t result() { return _used; }
2369 };
2370 
2371 size_t G1CollectedHeap::recalculate_used() const {
2372   SumUsedClosure blk;
2373   heap_region_iterate(&blk);
2374   return blk.result();
2375 }
2376 
2377 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2378   switch (cause) {
2379     case GCCause::_gc_locker:               return GCLockerInvokesConcurrent;
2380     case GCCause::_java_lang_system_gc:     return ExplicitGCInvokesConcurrent;
2381     case GCCause::_g1_humongous_allocation: return true;
2382     default:                                return false;
2383   }
2384 }
2385 
2386 #ifndef PRODUCT
2387 void G1CollectedHeap::allocate_dummy_regions() {
2388   // Let's fill up most of the region
2389   size_t word_size = HeapRegion::GrainWords - 1024;
2390   // And as a result the region we'll allocate will be humongous.
2391   guarantee(isHumongous(word_size), "sanity");
2392 
2393   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2394     // Let's use the existing mechanism for the allocation
2395     HeapWord* dummy_obj = humongous_obj_allocate(word_size);
2396     if (dummy_obj != NULL) {
2397       MemRegion mr(dummy_obj, word_size);
2398       CollectedHeap::fill_with_object(mr);
2399     } else {
2400       // If we can't allocate once, we probably cannot allocate
2401       // again. Let's get out of the loop.
2402       break;
2403     }
2404   }
2405 }
2406 #endif // !PRODUCT
2407 
2408 void G1CollectedHeap::increment_old_marking_cycles_started() {
2409   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2410     _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2411     err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2412     _old_marking_cycles_started, _old_marking_cycles_completed));
2413 
2414   _old_marking_cycles_started++;
2415 }
2416 
2417 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2418   MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2419 
2420   // We assume that if concurrent == true, then the caller is a
2421   // concurrent thread that was joined the Suspendible Thread
2422   // Set. If there's ever a cheap way to check this, we should add an
2423   // assert here.
2424 
2425   // Given that this method is called at the end of a Full GC or of a
2426   // concurrent cycle, and those can be nested (i.e., a Full GC can
2427   // interrupt a concurrent cycle), the number of full collections
2428   // completed should be either one (in the case where there was no
2429   // nesting) or two (when a Full GC interrupted a concurrent cycle)
2430   // behind the number of full collections started.
2431 
2432   // This is the case for the inner caller, i.e. a Full GC.
2433   assert(concurrent ||
2434          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2435          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2436          err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
2437                  "is inconsistent with _old_marking_cycles_completed = %u",
2438                  _old_marking_cycles_started, _old_marking_cycles_completed));
2439 
2440   // This is the case for the outer caller, i.e. the concurrent cycle.
2441   assert(!concurrent ||
2442          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2443          err_msg("for outer caller (concurrent cycle): "
2444                  "_old_marking_cycles_started = %u "
2445                  "is inconsistent with _old_marking_cycles_completed = %u",
2446                  _old_marking_cycles_started, _old_marking_cycles_completed));
2447 
2448   _old_marking_cycles_completed += 1;
2449 
2450   // We need to clear the "in_progress" flag in the CM thread before
2451   // we wake up any waiters (especially when ExplicitInvokesConcurrent
2452   // is set) so that if a waiter requests another System.gc() it doesn't
2453   // incorrectly see that a marking cycle is still in progress.
2454   if (concurrent) {
2455     _cmThread->clear_in_progress();
2456   }
2457 
2458   // This notify_all() will ensure that a thread that called
2459   // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2460   // and it's waiting for a full GC to finish will be woken up. It is
2461   // waiting in VM_G1IncCollectionPause::doit_epilogue().
2462   FullGCCount_lock->notify_all();
2463 }
2464 
2465 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) {
2466   _concurrent_cycle_started = true;
2467   _gc_timer_cm->register_gc_start(start_time);
2468 
2469   _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start());
2470   trace_heap_before_gc(_gc_tracer_cm);
2471 }
2472 
2473 void G1CollectedHeap::register_concurrent_cycle_end() {
2474   if (_concurrent_cycle_started) {
2475     if (_cm->has_aborted()) {
2476       _gc_tracer_cm->report_concurrent_mode_failure();
2477     }
2478 
2479     _gc_timer_cm->register_gc_end();
2480     _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
2481 
2482     _concurrent_cycle_started = false;
2483   }
2484 }
2485 
2486 void G1CollectedHeap::trace_heap_after_concurrent_cycle() {
2487   if (_concurrent_cycle_started) {
2488     trace_heap_after_gc(_gc_tracer_cm);
2489   }
2490 }
2491 
2492 G1YCType G1CollectedHeap::yc_type() {
2493   bool is_young = g1_policy()->gcs_are_young();
2494   bool is_initial_mark = g1_policy()->during_initial_mark_pause();
2495   bool is_during_mark = mark_in_progress();
2496 
2497   if (is_initial_mark) {
2498     return InitialMark;
2499   } else if (is_during_mark) {
2500     return DuringMark;
2501   } else if (is_young) {
2502     return Normal;
2503   } else {
2504     return Mixed;
2505   }
2506 }
2507 
2508 void G1CollectedHeap::collect(GCCause::Cause cause) {
2509   assert_heap_not_locked();
2510 
2511   unsigned int gc_count_before;
2512   unsigned int old_marking_count_before;
2513   bool retry_gc;
2514 
2515   do {
2516     retry_gc = false;
2517 
2518     {
2519       MutexLocker ml(Heap_lock);
2520 
2521       // Read the GC count while holding the Heap_lock
2522       gc_count_before = total_collections();
2523       old_marking_count_before = _old_marking_cycles_started;
2524     }
2525 
2526     if (should_do_concurrent_full_gc(cause)) {
2527       // Schedule an initial-mark evacuation pause that will start a
2528       // concurrent cycle. We're setting word_size to 0 which means that
2529       // we are not requesting a post-GC allocation.
2530       VM_G1IncCollectionPause op(gc_count_before,
2531                                  0,     /* word_size */
2532                                  true,  /* should_initiate_conc_mark */
2533                                  g1_policy()->max_pause_time_ms(),
2534                                  cause);
2535 
2536       VMThread::execute(&op);
2537       if (!op.pause_succeeded()) {
2538         if (old_marking_count_before == _old_marking_cycles_started) {
2539           retry_gc = op.should_retry_gc();
2540         } else {
2541           // A Full GC happened while we were trying to schedule the
2542           // initial-mark GC. No point in starting a new cycle given
2543           // that the whole heap was collected anyway.
2544         }
2545 
2546         if (retry_gc) {
2547           if (GC_locker::is_active_and_needs_gc()) {
2548             GC_locker::stall_until_clear();
2549           }
2550         }
2551       }
2552     } else {
2553       if (cause == GCCause::_gc_locker
2554           DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2555 
2556         // Schedule a standard evacuation pause. We're setting word_size
2557         // to 0 which means that we are not requesting a post-GC allocation.
2558         VM_G1IncCollectionPause op(gc_count_before,
2559                                    0,     /* word_size */
2560                                    false, /* should_initiate_conc_mark */
2561                                    g1_policy()->max_pause_time_ms(),
2562                                    cause);
2563         VMThread::execute(&op);
2564       } else {
2565         // Schedule a Full GC.
2566         VM_G1CollectFull op(gc_count_before, old_marking_count_before, cause);
2567         VMThread::execute(&op);
2568       }
2569     }
2570   } while (retry_gc);
2571 }
2572 
2573 bool G1CollectedHeap::is_in(const void* p) const {
2574   if (_g1_committed.contains(p)) {
2575     // Given that we know that p is in the committed space,
2576     // heap_region_containing_raw() should successfully
2577     // return the containing region.
2578     HeapRegion* hr = heap_region_containing_raw(p);
2579     return hr->is_in(p);
2580   } else {
2581     return false;
2582   }
2583 }
2584 
2585 // Iteration functions.
2586 
2587 // Iterates an OopClosure over all ref-containing fields of objects
2588 // within a HeapRegion.
2589 
2590 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2591   MemRegion _mr;
2592   ExtendedOopClosure* _cl;
2593 public:
2594   IterateOopClosureRegionClosure(MemRegion mr, ExtendedOopClosure* cl)
2595     : _mr(mr), _cl(cl) {}
2596   bool doHeapRegion(HeapRegion* r) {
2597     if (!r->continuesHumongous()) {
2598       r->oop_iterate(_cl);
2599     }
2600     return false;
2601   }
2602 };
2603 
2604 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) {
2605   IterateOopClosureRegionClosure blk(_g1_committed, cl);
2606   heap_region_iterate(&blk);
2607 }
2608 
2609 void G1CollectedHeap::oop_iterate(MemRegion mr, ExtendedOopClosure* cl) {
2610   IterateOopClosureRegionClosure blk(mr, cl);
2611   heap_region_iterate(&blk);
2612 }
2613 
2614 // Iterates an ObjectClosure over all objects within a HeapRegion.
2615 
2616 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2617   ObjectClosure* _cl;
2618 public:
2619   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2620   bool doHeapRegion(HeapRegion* r) {
2621     if (! r->continuesHumongous()) {
2622       r->object_iterate(_cl);
2623     }
2624     return false;
2625   }
2626 };
2627 
2628 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2629   IterateObjectClosureRegionClosure blk(cl);
2630   heap_region_iterate(&blk);
2631 }
2632 
2633 // Calls a SpaceClosure on a HeapRegion.
2634 
2635 class SpaceClosureRegionClosure: public HeapRegionClosure {
2636   SpaceClosure* _cl;
2637 public:
2638   SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2639   bool doHeapRegion(HeapRegion* r) {
2640     _cl->do_space(r);
2641     return false;
2642   }
2643 };
2644 
2645 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2646   SpaceClosureRegionClosure blk(cl);
2647   heap_region_iterate(&blk);
2648 }
2649 
2650 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2651   _hrs.iterate(cl);
2652 }
2653 
2654 void
2655 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
2656                                                  uint worker_id,
2657                                                  uint no_of_par_workers,
2658                                                  jint claim_value) {
2659   const uint regions = n_regions();
2660   const uint max_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
2661                              no_of_par_workers :
2662                              1);
2663   assert(UseDynamicNumberOfGCThreads ||
2664          no_of_par_workers == workers()->total_workers(),
2665          "Non dynamic should use fixed number of workers");
2666   // try to spread out the starting points of the workers
2667   const HeapRegion* start_hr =
2668                         start_region_for_worker(worker_id, no_of_par_workers);
2669   const uint start_index = start_hr->hrs_index();
2670 
2671   // each worker will actually look at all regions
2672   for (uint count = 0; count < regions; ++count) {
2673     const uint index = (start_index + count) % regions;
2674     assert(0 <= index && index < regions, "sanity");
2675     HeapRegion* r = region_at(index);
2676     // we'll ignore "continues humongous" regions (we'll process them
2677     // when we come across their corresponding "start humongous"
2678     // region) and regions already claimed
2679     if (r->claim_value() == claim_value || r->continuesHumongous()) {
2680       continue;
2681     }
2682     // OK, try to claim it
2683     if (r->claimHeapRegion(claim_value)) {
2684       // success!
2685       assert(!r->continuesHumongous(), "sanity");
2686       if (r->startsHumongous()) {
2687         // If the region is "starts humongous" we'll iterate over its
2688         // "continues humongous" first; in fact we'll do them
2689         // first. The order is important. In on case, calling the
2690         // closure on the "starts humongous" region might de-allocate
2691         // and clear all its "continues humongous" regions and, as a
2692         // result, we might end up processing them twice. So, we'll do
2693         // them first (notice: most closures will ignore them anyway) and
2694         // then we'll do the "starts humongous" region.
2695         for (uint ch_index = index + 1; ch_index < regions; ++ch_index) {
2696           HeapRegion* chr = region_at(ch_index);
2697 
2698           // if the region has already been claimed or it's not
2699           // "continues humongous" we're done
2700           if (chr->claim_value() == claim_value ||
2701               !chr->continuesHumongous()) {
2702             break;
2703           }
2704 
2705           // No one should have claimed it directly. We can given
2706           // that we claimed its "starts humongous" region.
2707           assert(chr->claim_value() != claim_value, "sanity");
2708           assert(chr->humongous_start_region() == r, "sanity");
2709 
2710           if (chr->claimHeapRegion(claim_value)) {
2711             // we should always be able to claim it; no one else should
2712             // be trying to claim this region
2713 
2714             bool res2 = cl->doHeapRegion(chr);
2715             assert(!res2, "Should not abort");
2716 
2717             // Right now, this holds (i.e., no closure that actually
2718             // does something with "continues humongous" regions
2719             // clears them). We might have to weaken it in the future,
2720             // but let's leave these two asserts here for extra safety.
2721             assert(chr->continuesHumongous(), "should still be the case");
2722             assert(chr->humongous_start_region() == r, "sanity");
2723           } else {
2724             guarantee(false, "we should not reach here");
2725           }
2726         }
2727       }
2728 
2729       assert(!r->continuesHumongous(), "sanity");
2730       bool res = cl->doHeapRegion(r);
2731       assert(!res, "Should not abort");
2732     }
2733   }
2734 }
2735 
2736 class ResetClaimValuesClosure: public HeapRegionClosure {
2737 public:
2738   bool doHeapRegion(HeapRegion* r) {
2739     r->set_claim_value(HeapRegion::InitialClaimValue);
2740     return false;
2741   }
2742 };
2743 
2744 void G1CollectedHeap::reset_heap_region_claim_values() {
2745   ResetClaimValuesClosure blk;
2746   heap_region_iterate(&blk);
2747 }
2748 
2749 void G1CollectedHeap::reset_cset_heap_region_claim_values() {
2750   ResetClaimValuesClosure blk;
2751   collection_set_iterate(&blk);
2752 }
2753 
2754 #ifdef ASSERT
2755 // This checks whether all regions in the heap have the correct claim
2756 // value. I also piggy-backed on this a check to ensure that the
2757 // humongous_start_region() information on "continues humongous"
2758 // regions is correct.
2759 
2760 class CheckClaimValuesClosure : public HeapRegionClosure {
2761 private:
2762   jint _claim_value;
2763   uint _failures;
2764   HeapRegion* _sh_region;
2765 
2766 public:
2767   CheckClaimValuesClosure(jint claim_value) :
2768     _claim_value(claim_value), _failures(0), _sh_region(NULL) { }
2769   bool doHeapRegion(HeapRegion* r) {
2770     if (r->claim_value() != _claim_value) {
2771       gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2772                              "claim value = %d, should be %d",
2773                              HR_FORMAT_PARAMS(r),
2774                              r->claim_value(), _claim_value);
2775       ++_failures;
2776     }
2777     if (!r->isHumongous()) {
2778       _sh_region = NULL;
2779     } else if (r->startsHumongous()) {
2780       _sh_region = r;
2781     } else if (r->continuesHumongous()) {
2782       if (r->humongous_start_region() != _sh_region) {
2783         gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2784                                "HS = "PTR_FORMAT", should be "PTR_FORMAT,
2785                                HR_FORMAT_PARAMS(r),
2786                                r->humongous_start_region(),
2787                                _sh_region);
2788         ++_failures;
2789       }
2790     }
2791     return false;
2792   }
2793   uint failures() { return _failures; }
2794 };
2795 
2796 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
2797   CheckClaimValuesClosure cl(claim_value);
2798   heap_region_iterate(&cl);
2799   return cl.failures() == 0;
2800 }
2801 
2802 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure {
2803 private:
2804   jint _claim_value;
2805   uint _failures;
2806 
2807 public:
2808   CheckClaimValuesInCSetHRClosure(jint claim_value) :
2809     _claim_value(claim_value), _failures(0) { }
2810 
2811   uint failures() { return _failures; }
2812 
2813   bool doHeapRegion(HeapRegion* hr) {
2814     assert(hr->in_collection_set(), "how?");
2815     assert(!hr->isHumongous(), "H-region in CSet");
2816     if (hr->claim_value() != _claim_value) {
2817       gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", "
2818                              "claim value = %d, should be %d",
2819                              HR_FORMAT_PARAMS(hr),
2820                              hr->claim_value(), _claim_value);
2821       _failures += 1;
2822     }
2823     return false;
2824   }
2825 };
2826 
2827 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) {
2828   CheckClaimValuesInCSetHRClosure cl(claim_value);
2829   collection_set_iterate(&cl);
2830   return cl.failures() == 0;
2831 }
2832 #endif // ASSERT
2833 
2834 // Clear the cached CSet starting regions and (more importantly)
2835 // the time stamps. Called when we reset the GC time stamp.
2836 void G1CollectedHeap::clear_cset_start_regions() {
2837   assert(_worker_cset_start_region != NULL, "sanity");
2838   assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2839 
2840   int n_queues = MAX2((int)ParallelGCThreads, 1);
2841   for (int i = 0; i < n_queues; i++) {
2842     _worker_cset_start_region[i] = NULL;
2843     _worker_cset_start_region_time_stamp[i] = 0;
2844   }
2845 }
2846 
2847 // Given the id of a worker, obtain or calculate a suitable
2848 // starting region for iterating over the current collection set.
2849 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(int worker_i) {
2850   assert(get_gc_time_stamp() > 0, "should have been updated by now");
2851 
2852   HeapRegion* result = NULL;
2853   unsigned gc_time_stamp = get_gc_time_stamp();
2854 
2855   if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2856     // Cached starting region for current worker was set
2857     // during the current pause - so it's valid.
2858     // Note: the cached starting heap region may be NULL
2859     // (when the collection set is empty).
2860     result = _worker_cset_start_region[worker_i];
2861     assert(result == NULL || result->in_collection_set(), "sanity");
2862     return result;
2863   }
2864 
2865   // The cached entry was not valid so let's calculate
2866   // a suitable starting heap region for this worker.
2867 
2868   // We want the parallel threads to start their collection
2869   // set iteration at different collection set regions to
2870   // avoid contention.
2871   // If we have:
2872   //          n collection set regions
2873   //          p threads
2874   // Then thread t will start at region floor ((t * n) / p)
2875 
2876   result = g1_policy()->collection_set();
2877   if (G1CollectedHeap::use_parallel_gc_threads()) {
2878     uint cs_size = g1_policy()->cset_region_length();
2879     uint active_workers = workers()->active_workers();
2880     assert(UseDynamicNumberOfGCThreads ||
2881              active_workers == workers()->total_workers(),
2882              "Unless dynamic should use total workers");
2883 
2884     uint end_ind   = (cs_size * worker_i) / active_workers;
2885     uint start_ind = 0;
2886 
2887     if (worker_i > 0 &&
2888         _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2889       // Previous workers starting region is valid
2890       // so let's iterate from there
2891       start_ind = (cs_size * (worker_i - 1)) / active_workers;
2892       result = _worker_cset_start_region[worker_i - 1];
2893     }
2894 
2895     for (uint i = start_ind; i < end_ind; i++) {
2896       result = result->next_in_collection_set();
2897     }
2898   }
2899 
2900   // Note: the calculated starting heap region may be NULL
2901   // (when the collection set is empty).
2902   assert(result == NULL || result->in_collection_set(), "sanity");
2903   assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2904          "should be updated only once per pause");
2905   _worker_cset_start_region[worker_i] = result;
2906   OrderAccess::storestore();
2907   _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2908   return result;
2909 }
2910 
2911 HeapRegion* G1CollectedHeap::start_region_for_worker(uint worker_i,
2912                                                      uint no_of_par_workers) {
2913   uint worker_num =
2914            G1CollectedHeap::use_parallel_gc_threads() ? no_of_par_workers : 1U;
2915   assert(UseDynamicNumberOfGCThreads ||
2916          no_of_par_workers == workers()->total_workers(),
2917          "Non dynamic should use fixed number of workers");
2918   const uint start_index = n_regions() * worker_i / worker_num;
2919   return region_at(start_index);
2920 }
2921 
2922 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2923   HeapRegion* r = g1_policy()->collection_set();
2924   while (r != NULL) {
2925     HeapRegion* next = r->next_in_collection_set();
2926     if (cl->doHeapRegion(r)) {
2927       cl->incomplete();
2928       return;
2929     }
2930     r = next;
2931   }
2932 }
2933 
2934 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2935                                                   HeapRegionClosure *cl) {
2936   if (r == NULL) {
2937     // The CSet is empty so there's nothing to do.
2938     return;
2939   }
2940 
2941   assert(r->in_collection_set(),
2942          "Start region must be a member of the collection set.");
2943   HeapRegion* cur = r;
2944   while (cur != NULL) {
2945     HeapRegion* next = cur->next_in_collection_set();
2946     if (cl->doHeapRegion(cur) && false) {
2947       cl->incomplete();
2948       return;
2949     }
2950     cur = next;
2951   }
2952   cur = g1_policy()->collection_set();
2953   while (cur != r) {
2954     HeapRegion* next = cur->next_in_collection_set();
2955     if (cl->doHeapRegion(cur) && false) {
2956       cl->incomplete();
2957       return;
2958     }
2959     cur = next;
2960   }
2961 }
2962 
2963 CompactibleSpace* G1CollectedHeap::first_compactible_space() {
2964   return n_regions() > 0 ? region_at(0) : NULL;
2965 }
2966 
2967 
2968 Space* G1CollectedHeap::space_containing(const void* addr) const {
2969   Space* res = heap_region_containing(addr);
2970   return res;
2971 }
2972 
2973 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2974   Space* sp = space_containing(addr);
2975   if (sp != NULL) {
2976     return sp->block_start(addr);
2977   }
2978   return NULL;
2979 }
2980 
2981 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2982   Space* sp = space_containing(addr);
2983   assert(sp != NULL, "block_size of address outside of heap");
2984   return sp->block_size(addr);
2985 }
2986 
2987 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2988   Space* sp = space_containing(addr);
2989   return sp->block_is_obj(addr);
2990 }
2991 
2992 bool G1CollectedHeap::supports_tlab_allocation() const {
2993   return true;
2994 }
2995 
2996 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2997   return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes;
2998 }
2999 
3000 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
3001   return young_list()->eden_used_bytes();
3002 }
3003 
3004 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
3005 // must be smaller than the humongous object limit.
3006 size_t G1CollectedHeap::max_tlab_size() const {
3007   return align_size_down(_humongous_object_threshold_in_words - 1, MinObjAlignment);
3008 }
3009 
3010 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
3011   // Return the remaining space in the cur alloc region, but not less than
3012   // the min TLAB size.
3013 
3014   // Also, this value can be at most the humongous object threshold,
3015   // since we can't allow tlabs to grow big enough to accommodate
3016   // humongous objects.
3017 
3018   HeapRegion* hr = _mutator_alloc_region.get();
3019   size_t max_tlab = max_tlab_size() * wordSize;
3020   if (hr == NULL) {
3021     return max_tlab;
3022   } else {
3023     return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab);
3024   }
3025 }
3026 
3027 size_t G1CollectedHeap::max_capacity() const {
3028   return _g1_reserved.byte_size();
3029 }
3030 
3031 jlong G1CollectedHeap::millis_since_last_gc() {
3032   // assert(false, "NYI");
3033   return 0;
3034 }
3035 
3036 void G1CollectedHeap::prepare_for_verify() {
3037   if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
3038     ensure_parsability(false);
3039   }
3040   g1_rem_set()->prepare_for_verify();
3041 }
3042 
3043 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr,
3044                                               VerifyOption vo) {
3045   switch (vo) {
3046   case VerifyOption_G1UsePrevMarking:
3047     return hr->obj_allocated_since_prev_marking(obj);
3048   case VerifyOption_G1UseNextMarking:
3049     return hr->obj_allocated_since_next_marking(obj);
3050   case VerifyOption_G1UseMarkWord:
3051     return false;
3052   default:
3053     ShouldNotReachHere();
3054   }
3055   return false; // keep some compilers happy
3056 }
3057 
3058 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) {
3059   switch (vo) {
3060   case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start();
3061   case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start();
3062   case VerifyOption_G1UseMarkWord:    return NULL;
3063   default:                            ShouldNotReachHere();
3064   }
3065   return NULL; // keep some compilers happy
3066 }
3067 
3068 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) {
3069   switch (vo) {
3070   case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj);
3071   case VerifyOption_G1UseNextMarking: return isMarkedNext(obj);
3072   case VerifyOption_G1UseMarkWord:    return obj->is_gc_marked();
3073   default:                            ShouldNotReachHere();
3074   }
3075   return false; // keep some compilers happy
3076 }
3077 
3078 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) {
3079   switch (vo) {
3080   case VerifyOption_G1UsePrevMarking: return "PTAMS";
3081   case VerifyOption_G1UseNextMarking: return "NTAMS";
3082   case VerifyOption_G1UseMarkWord:    return "NONE";
3083   default:                            ShouldNotReachHere();
3084   }
3085   return NULL; // keep some compilers happy
3086 }
3087 
3088 class VerifyRootsClosure: public OopClosure {
3089 private:
3090   G1CollectedHeap* _g1h;
3091   VerifyOption     _vo;
3092   bool             _failures;
3093 public:
3094   // _vo == UsePrevMarking -> use "prev" marking information,
3095   // _vo == UseNextMarking -> use "next" marking information,
3096   // _vo == UseMarkWord    -> use mark word from object header.
3097   VerifyRootsClosure(VerifyOption vo) :
3098     _g1h(G1CollectedHeap::heap()),
3099     _vo(vo),
3100     _failures(false) { }
3101 
3102   bool failures() { return _failures; }
3103 
3104   template <class T> void do_oop_nv(T* p) {
3105     T heap_oop = oopDesc::load_heap_oop(p);
3106     if (!oopDesc::is_null(heap_oop)) {
3107       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3108       if (_g1h->is_obj_dead_cond(obj, _vo)) {
3109         gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
3110                               "points to dead obj "PTR_FORMAT, p, (void*) obj);
3111         if (_vo == VerifyOption_G1UseMarkWord) {
3112           gclog_or_tty->print_cr("  Mark word: "PTR_FORMAT, (void*)(obj->mark()));
3113         }
3114         obj->print_on(gclog_or_tty);
3115         _failures = true;
3116       }
3117     }
3118   }
3119 
3120   void do_oop(oop* p)       { do_oop_nv(p); }
3121   void do_oop(narrowOop* p) { do_oop_nv(p); }
3122 };
3123 
3124 class G1VerifyCodeRootOopClosure: public OopClosure {
3125   G1CollectedHeap* _g1h;
3126   OopClosure* _root_cl;
3127   nmethod* _nm;
3128   VerifyOption _vo;
3129   bool _failures;
3130 
3131   template <class T> void do_oop_work(T* p) {
3132     // First verify that this root is live
3133     _root_cl->do_oop(p);
3134 
3135     if (!G1VerifyHeapRegionCodeRoots) {
3136       // We're not verifying the code roots attached to heap region.
3137       return;
3138     }
3139 
3140     // Don't check the code roots during marking verification in a full GC
3141     if (_vo == VerifyOption_G1UseMarkWord) {
3142       return;
3143     }
3144 
3145     // Now verify that the current nmethod (which contains p) is
3146     // in the code root list of the heap region containing the
3147     // object referenced by p.
3148 
3149     T heap_oop = oopDesc::load_heap_oop(p);
3150     if (!oopDesc::is_null(heap_oop)) {
3151       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3152 
3153       // Now fetch the region containing the object
3154       HeapRegion* hr = _g1h->heap_region_containing(obj);
3155       HeapRegionRemSet* hrrs = hr->rem_set();
3156       // Verify that the strong code root list for this region
3157       // contains the nmethod
3158       if (!hrrs->strong_code_roots_list_contains(_nm)) {
3159         gclog_or_tty->print_cr("Code root location "PTR_FORMAT" "
3160                               "from nmethod "PTR_FORMAT" not in strong "
3161                               "code roots for region ["PTR_FORMAT","PTR_FORMAT")",
3162                               p, _nm, hr->bottom(), hr->end());
3163         _failures = true;
3164       }
3165     }
3166   }
3167 
3168 public:
3169   G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo):
3170     _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {}
3171 
3172   void do_oop(oop* p) { do_oop_work(p); }
3173   void do_oop(narrowOop* p) { do_oop_work(p); }
3174 
3175   void set_nmethod(nmethod* nm) { _nm = nm; }
3176   bool failures() { return _failures; }
3177 };
3178 
3179 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure {
3180   G1VerifyCodeRootOopClosure* _oop_cl;
3181 
3182 public:
3183   G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl):
3184     _oop_cl(oop_cl) {}
3185 
3186   void do_code_blob(CodeBlob* cb) {
3187     nmethod* nm = cb->as_nmethod_or_null();
3188     if (nm != NULL) {
3189       _oop_cl->set_nmethod(nm);
3190       nm->oops_do(_oop_cl);
3191     }
3192   }
3193 };
3194 
3195 class YoungRefCounterClosure : public OopClosure {
3196   G1CollectedHeap* _g1h;
3197   int              _count;
3198  public:
3199   YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {}
3200   void do_oop(oop* p)       { if (_g1h->is_in_young(*p)) { _count++; } }
3201   void do_oop(narrowOop* p) { ShouldNotReachHere(); }
3202 
3203   int count() { return _count; }
3204   void reset_count() { _count = 0; };
3205 };
3206 
3207 class VerifyKlassClosure: public KlassClosure {
3208   YoungRefCounterClosure _young_ref_counter_closure;
3209   OopClosure *_oop_closure;
3210  public:
3211   VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {}
3212   void do_klass(Klass* k) {
3213     k->oops_do(_oop_closure);
3214 
3215     _young_ref_counter_closure.reset_count();
3216     k->oops_do(&_young_ref_counter_closure);
3217     if (_young_ref_counter_closure.count() > 0) {
3218       guarantee(k->has_modified_oops(), err_msg("Klass %p, has young refs but is not dirty.", k));
3219     }
3220   }
3221 };
3222 
3223 class VerifyLivenessOopClosure: public OopClosure {
3224   G1CollectedHeap* _g1h;
3225   VerifyOption _vo;
3226 public:
3227   VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
3228     _g1h(g1h), _vo(vo)
3229   { }
3230   void do_oop(narrowOop *p) { do_oop_work(p); }
3231   void do_oop(      oop *p) { do_oop_work(p); }
3232 
3233   template <class T> void do_oop_work(T *p) {
3234     oop obj = oopDesc::load_decode_heap_oop(p);
3235     guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
3236               "Dead object referenced by a not dead object");
3237   }
3238 };
3239 
3240 class VerifyObjsInRegionClosure: public ObjectClosure {
3241 private:
3242   G1CollectedHeap* _g1h;
3243   size_t _live_bytes;
3244   HeapRegion *_hr;
3245   VerifyOption _vo;
3246 public:
3247   // _vo == UsePrevMarking -> use "prev" marking information,
3248   // _vo == UseNextMarking -> use "next" marking information,
3249   // _vo == UseMarkWord    -> use mark word from object header.
3250   VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
3251     : _live_bytes(0), _hr(hr), _vo(vo) {
3252     _g1h = G1CollectedHeap::heap();
3253   }
3254   void do_object(oop o) {
3255     VerifyLivenessOopClosure isLive(_g1h, _vo);
3256     assert(o != NULL, "Huh?");
3257     if (!_g1h->is_obj_dead_cond(o, _vo)) {
3258       // If the object is alive according to the mark word,
3259       // then verify that the marking information agrees.
3260       // Note we can't verify the contra-positive of the
3261       // above: if the object is dead (according to the mark
3262       // word), it may not be marked, or may have been marked
3263       // but has since became dead, or may have been allocated
3264       // since the last marking.
3265       if (_vo == VerifyOption_G1UseMarkWord) {
3266         guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
3267       }
3268 
3269       o->oop_iterate_no_header(&isLive);
3270       if (!_hr->obj_allocated_since_prev_marking(o)) {
3271         size_t obj_size = o->size();    // Make sure we don't overflow
3272         _live_bytes += (obj_size * HeapWordSize);
3273       }
3274     }
3275   }
3276   size_t live_bytes() { return _live_bytes; }
3277 };
3278 
3279 class PrintObjsInRegionClosure : public ObjectClosure {
3280   HeapRegion *_hr;
3281   G1CollectedHeap *_g1;
3282 public:
3283   PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
3284     _g1 = G1CollectedHeap::heap();
3285   };
3286 
3287   void do_object(oop o) {
3288     if (o != NULL) {
3289       HeapWord *start = (HeapWord *) o;
3290       size_t word_sz = o->size();
3291       gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
3292                           " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
3293                           (void*) o, word_sz,
3294                           _g1->isMarkedPrev(o),
3295                           _g1->isMarkedNext(o),
3296                           _hr->obj_allocated_since_prev_marking(o));
3297       HeapWord *end = start + word_sz;
3298       HeapWord *cur;
3299       int *val;
3300       for (cur = start; cur < end; cur++) {
3301         val = (int *) cur;
3302         gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val);
3303       }
3304     }
3305   }
3306 };
3307 
3308 class VerifyRegionClosure: public HeapRegionClosure {
3309 private:
3310   bool             _par;
3311   VerifyOption     _vo;
3312   bool             _failures;
3313 public:
3314   // _vo == UsePrevMarking -> use "prev" marking information,
3315   // _vo == UseNextMarking -> use "next" marking information,
3316   // _vo == UseMarkWord    -> use mark word from object header.
3317   VerifyRegionClosure(bool par, VerifyOption vo)
3318     : _par(par),
3319       _vo(vo),
3320       _failures(false) {}
3321 
3322   bool failures() {
3323     return _failures;
3324   }
3325 
3326   bool doHeapRegion(HeapRegion* r) {
3327     if (!r->continuesHumongous()) {
3328       bool failures = false;
3329       r->verify(_vo, &failures);
3330       if (failures) {
3331         _failures = true;
3332       } else {
3333         VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
3334         r->object_iterate(&not_dead_yet_cl);
3335         if (_vo != VerifyOption_G1UseNextMarking) {
3336           if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
3337             gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
3338                                    "max_live_bytes "SIZE_FORMAT" "
3339                                    "< calculated "SIZE_FORMAT,
3340                                    r->bottom(), r->end(),
3341                                    r->max_live_bytes(),
3342                                  not_dead_yet_cl.live_bytes());
3343             _failures = true;
3344           }
3345         } else {
3346           // When vo == UseNextMarking we cannot currently do a sanity
3347           // check on the live bytes as the calculation has not been
3348           // finalized yet.
3349         }
3350       }
3351     }
3352     return false; // stop the region iteration if we hit a failure
3353   }
3354 };
3355 
3356 // This is the task used for parallel verification of the heap regions
3357 
3358 class G1ParVerifyTask: public AbstractGangTask {
3359 private:
3360   G1CollectedHeap* _g1h;
3361   VerifyOption     _vo;
3362   bool             _failures;
3363 
3364 public:
3365   // _vo == UsePrevMarking -> use "prev" marking information,
3366   // _vo == UseNextMarking -> use "next" marking information,
3367   // _vo == UseMarkWord    -> use mark word from object header.
3368   G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
3369     AbstractGangTask("Parallel verify task"),
3370     _g1h(g1h),
3371     _vo(vo),
3372     _failures(false) { }
3373 
3374   bool failures() {
3375     return _failures;
3376   }
3377 
3378   void work(uint worker_id) {
3379     HandleMark hm;
3380     VerifyRegionClosure blk(true, _vo);
3381     _g1h->heap_region_par_iterate_chunked(&blk, worker_id,
3382                                           _g1h->workers()->active_workers(),
3383                                           HeapRegion::ParVerifyClaimValue);
3384     if (blk.failures()) {
3385       _failures = true;
3386     }
3387   }
3388 };
3389 
3390 void G1CollectedHeap::verify(bool silent, VerifyOption vo) {
3391   if (SafepointSynchronize::is_at_safepoint()) {
3392     assert(Thread::current()->is_VM_thread(),
3393            "Expected to be executed serially by the VM thread at this point");
3394 
3395     if (!silent) { gclog_or_tty->print("Roots "); }
3396     VerifyRootsClosure rootsCl(vo);
3397     VerifyKlassClosure klassCl(this, &rootsCl);
3398 
3399     // We apply the relevant closures to all the oops in the
3400     // system dictionary, class loader data graph and the string table.
3401     // Don't verify the code cache here, since it's verified below.
3402     const int so = SO_AllClasses | SO_Strings;
3403 
3404     // Need cleared claim bits for the strong roots processing
3405     ClassLoaderDataGraph::clear_claimed_marks();
3406 
3407     process_strong_roots(true,      // activate StrongRootsScope
3408                          ScanningOption(so),  // roots scanning options
3409                          &rootsCl,
3410                          &klassCl
3411                          );
3412 
3413     // Verify the nmethods in the code cache.
3414     G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo);
3415     G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl);
3416     CodeCache::blobs_do(&blobsCl);
3417 
3418     bool failures = rootsCl.failures() || codeRootsCl.failures();
3419 
3420     if (vo != VerifyOption_G1UseMarkWord) {
3421       // If we're verifying during a full GC then the region sets
3422       // will have been torn down at the start of the GC. Therefore
3423       // verifying the region sets will fail. So we only verify
3424       // the region sets when not in a full GC.
3425       if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3426       verify_region_sets();
3427     }
3428 
3429     if (!silent) { gclog_or_tty->print("HeapRegions "); }
3430     if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3431       assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3432              "sanity check");
3433 
3434       G1ParVerifyTask task(this, vo);
3435       assert(UseDynamicNumberOfGCThreads ||
3436         workers()->active_workers() == workers()->total_workers(),
3437         "If not dynamic should be using all the workers");
3438       int n_workers = workers()->active_workers();
3439       set_par_threads(n_workers);
3440       workers()->run_task(&task);
3441       set_par_threads(0);
3442       if (task.failures()) {
3443         failures = true;
3444       }
3445 
3446       // Checks that the expected amount of parallel work was done.
3447       // The implication is that n_workers is > 0.
3448       assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
3449              "sanity check");
3450 
3451       reset_heap_region_claim_values();
3452 
3453       assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3454              "sanity check");
3455     } else {
3456       VerifyRegionClosure blk(false, vo);
3457       heap_region_iterate(&blk);
3458       if (blk.failures()) {
3459         failures = true;
3460       }
3461     }
3462     if (!silent) gclog_or_tty->print("RemSet ");
3463     rem_set()->verify();
3464 
3465     if (failures) {
3466       gclog_or_tty->print_cr("Heap:");
3467       // It helps to have the per-region information in the output to
3468       // help us track down what went wrong. This is why we call
3469       // print_extended_on() instead of print_on().
3470       print_extended_on(gclog_or_tty);
3471       gclog_or_tty->print_cr("");
3472 #ifndef PRODUCT
3473       if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3474         concurrent_mark()->print_reachable("at-verification-failure",
3475                                            vo, false /* all */);
3476       }
3477 #endif
3478       gclog_or_tty->flush();
3479     }
3480     guarantee(!failures, "there should not have been any failures");
3481   } else {
3482     if (!silent)
3483       gclog_or_tty->print("(SKIPPING roots, heapRegionSets, heapRegions, remset) ");
3484   }
3485 }
3486 
3487 void G1CollectedHeap::verify(bool silent) {
3488   verify(silent, VerifyOption_G1UsePrevMarking);
3489 }
3490 
3491 double G1CollectedHeap::verify(bool guard, const char* msg) {
3492   double verify_time_ms = 0.0;
3493 
3494   if (guard && total_collections() >= VerifyGCStartAt) {
3495     double verify_start = os::elapsedTime();
3496     HandleMark hm;  // Discard invalid handles created during verification
3497     prepare_for_verify();
3498     Universe::verify(VerifyOption_G1UsePrevMarking, msg);
3499     verify_time_ms = (os::elapsedTime() - verify_start) * 1000;
3500   }
3501 
3502   return verify_time_ms;
3503 }
3504 
3505 void G1CollectedHeap::verify_before_gc() {
3506   double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:");
3507   g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms);
3508 }
3509 
3510 void G1CollectedHeap::verify_after_gc() {
3511   double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:");
3512   g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms);
3513 }
3514 
3515 class PrintRegionClosure: public HeapRegionClosure {
3516   outputStream* _st;
3517 public:
3518   PrintRegionClosure(outputStream* st) : _st(st) {}
3519   bool doHeapRegion(HeapRegion* r) {
3520     r->print_on(_st);
3521     return false;
3522   }
3523 };
3524 
3525 void G1CollectedHeap::print_on(outputStream* st) const {
3526   st->print(" %-20s", "garbage-first heap");
3527   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3528             capacity()/K, used_unlocked()/K);
3529   st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3530             _g1_storage.low_boundary(),
3531             _g1_storage.high(),
3532             _g1_storage.high_boundary());
3533   st->cr();
3534   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3535   uint young_regions = _young_list->length();
3536   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3537             (size_t) young_regions * HeapRegion::GrainBytes / K);
3538   uint survivor_regions = g1_policy()->recorded_survivor_regions();
3539   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3540             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3541   st->cr();
3542   MetaspaceAux::print_on(st);
3543 }
3544 
3545 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3546   print_on(st);
3547 
3548   // Print the per-region information.
3549   st->cr();
3550   st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3551                "HS=humongous(starts), HC=humongous(continues), "
3552                "CS=collection set, F=free, TS=gc time stamp, "
3553                "PTAMS=previous top-at-mark-start, "
3554                "NTAMS=next top-at-mark-start)");
3555   PrintRegionClosure blk(st);
3556   heap_region_iterate(&blk);
3557 }
3558 
3559 void G1CollectedHeap::print_on_error(outputStream* st) const {
3560   this->CollectedHeap::print_on_error(st);
3561 
3562   if (_cm != NULL) {
3563     st->cr();
3564     _cm->print_on_error(st);
3565   }
3566 }
3567 
3568 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3569   if (G1CollectedHeap::use_parallel_gc_threads()) {
3570     workers()->print_worker_threads_on(st);
3571   }
3572   _cmThread->print_on(st);
3573   st->cr();
3574   _cm->print_worker_threads_on(st);
3575   _cg1r->print_worker_threads_on(st);
3576 }
3577 
3578 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3579   if (G1CollectedHeap::use_parallel_gc_threads()) {
3580     workers()->threads_do(tc);
3581   }
3582   tc->do_thread(_cmThread);
3583   _cg1r->threads_do(tc);
3584 }
3585 
3586 void G1CollectedHeap::print_tracing_info() const {
3587   // We'll overload this to mean "trace GC pause statistics."
3588   if (TraceGen0Time || TraceGen1Time) {
3589     // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3590     // to that.
3591     g1_policy()->print_tracing_info();
3592   }
3593   if (G1SummarizeRSetStats) {
3594     g1_rem_set()->print_summary_info();
3595   }
3596   if (G1SummarizeConcMark) {
3597     concurrent_mark()->print_summary_info();
3598   }
3599   g1_policy()->print_yg_surv_rate_info();
3600   SpecializationStats::print();
3601 }
3602 
3603 #ifndef PRODUCT
3604 // Helpful for debugging RSet issues.
3605 
3606 class PrintRSetsClosure : public HeapRegionClosure {
3607 private:
3608   const char* _msg;
3609   size_t _occupied_sum;
3610 
3611 public:
3612   bool doHeapRegion(HeapRegion* r) {
3613     HeapRegionRemSet* hrrs = r->rem_set();
3614     size_t occupied = hrrs->occupied();
3615     _occupied_sum += occupied;
3616 
3617     gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3618                            HR_FORMAT_PARAMS(r));
3619     if (occupied == 0) {
3620       gclog_or_tty->print_cr("  RSet is empty");
3621     } else {
3622       hrrs->print();
3623     }
3624     gclog_or_tty->print_cr("----------");
3625     return false;
3626   }
3627 
3628   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3629     gclog_or_tty->cr();
3630     gclog_or_tty->print_cr("========================================");
3631     gclog_or_tty->print_cr(msg);
3632     gclog_or_tty->cr();
3633   }
3634 
3635   ~PrintRSetsClosure() {
3636     gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3637     gclog_or_tty->print_cr("========================================");
3638     gclog_or_tty->cr();
3639   }
3640 };
3641 
3642 void G1CollectedHeap::print_cset_rsets() {
3643   PrintRSetsClosure cl("Printing CSet RSets");
3644   collection_set_iterate(&cl);
3645 }
3646 
3647 void G1CollectedHeap::print_all_rsets() {
3648   PrintRSetsClosure cl("Printing All RSets");;
3649   heap_region_iterate(&cl);
3650 }
3651 #endif // PRODUCT
3652 
3653 G1CollectedHeap* G1CollectedHeap::heap() {
3654   assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3655          "not a garbage-first heap");
3656   return _g1h;
3657 }
3658 
3659 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3660   // always_do_update_barrier = false;
3661   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3662   // Fill TLAB's and such
3663   accumulate_statistics_all_tlabs();
3664   ensure_parsability(true);
3665 
3666   if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) &&
3667       (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3668     g1_rem_set()->print_periodic_summary_info("Before GC RS summary");
3669   }
3670 }
3671 
3672 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) {
3673 
3674   if (G1SummarizeRSetStats &&
3675       (G1SummarizeRSetStatsPeriod > 0) &&
3676       // we are at the end of the GC. Total collections has already been increased.
3677       ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) {
3678     g1_rem_set()->print_periodic_summary_info("After GC RS summary");
3679   }
3680 
3681   // FIXME: what is this about?
3682   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3683   // is set.
3684   COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3685                         "derived pointer present"));
3686   // always_do_update_barrier = true;
3687 
3688   resize_all_tlabs();
3689 
3690   // We have just completed a GC. Update the soft reference
3691   // policy with the new heap occupancy
3692   Universe::update_heap_info_at_gc();
3693 }
3694 
3695 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3696                                                unsigned int gc_count_before,
3697                                                bool* succeeded,
3698                                                GCCause::Cause gc_cause) {
3699   assert_heap_not_locked_and_not_at_safepoint();
3700   g1_policy()->record_stop_world_start();
3701   VM_G1IncCollectionPause op(gc_count_before,
3702                              word_size,
3703                              false, /* should_initiate_conc_mark */
3704                              g1_policy()->max_pause_time_ms(),
3705                              gc_cause);
3706   VMThread::execute(&op);
3707 
3708   HeapWord* result = op.result();
3709   bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3710   assert(result == NULL || ret_succeeded,
3711          "the result should be NULL if the VM did not succeed");
3712   *succeeded = ret_succeeded;
3713 
3714   assert_heap_not_locked();
3715   return result;
3716 }
3717 
3718 void
3719 G1CollectedHeap::doConcurrentMark() {
3720   MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3721   if (!_cmThread->in_progress()) {
3722     _cmThread->set_started();
3723     CGC_lock->notify();
3724   }
3725 }
3726 
3727 size_t G1CollectedHeap::pending_card_num() {
3728   size_t extra_cards = 0;
3729   JavaThread *curr = Threads::first();
3730   while (curr != NULL) {
3731     DirtyCardQueue& dcq = curr->dirty_card_queue();
3732     extra_cards += dcq.size();
3733     curr = curr->next();
3734   }
3735   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3736   size_t buffer_size = dcqs.buffer_size();
3737   size_t buffer_num = dcqs.completed_buffers_num();
3738 
3739   // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
3740   // in bytes - not the number of 'entries'. We need to convert
3741   // into a number of cards.
3742   return (buffer_size * buffer_num + extra_cards) / oopSize;
3743 }
3744 
3745 size_t G1CollectedHeap::cards_scanned() {
3746   return g1_rem_set()->cardsScanned();
3747 }
3748 
3749 void
3750 G1CollectedHeap::setup_surviving_young_words() {
3751   assert(_surviving_young_words == NULL, "pre-condition");
3752   uint array_length = g1_policy()->young_cset_region_length();
3753   _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3754   if (_surviving_young_words == NULL) {
3755     vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR,
3756                           "Not enough space for young surv words summary.");
3757   }
3758   memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3759 #ifdef ASSERT
3760   for (uint i = 0;  i < array_length; ++i) {
3761     assert( _surviving_young_words[i] == 0, "memset above" );
3762   }
3763 #endif // !ASSERT
3764 }
3765 
3766 void
3767 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3768   MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3769   uint array_length = g1_policy()->young_cset_region_length();
3770   for (uint i = 0; i < array_length; ++i) {
3771     _surviving_young_words[i] += surv_young_words[i];
3772   }
3773 }
3774 
3775 void
3776 G1CollectedHeap::cleanup_surviving_young_words() {
3777   guarantee( _surviving_young_words != NULL, "pre-condition" );
3778   FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC);
3779   _surviving_young_words = NULL;
3780 }
3781 
3782 #ifdef ASSERT
3783 class VerifyCSetClosure: public HeapRegionClosure {
3784 public:
3785   bool doHeapRegion(HeapRegion* hr) {
3786     // Here we check that the CSet region's RSet is ready for parallel
3787     // iteration. The fields that we'll verify are only manipulated
3788     // when the region is part of a CSet and is collected. Afterwards,
3789     // we reset these fields when we clear the region's RSet (when the
3790     // region is freed) so they are ready when the region is
3791     // re-allocated. The only exception to this is if there's an
3792     // evacuation failure and instead of freeing the region we leave
3793     // it in the heap. In that case, we reset these fields during
3794     // evacuation failure handling.
3795     guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3796 
3797     // Here's a good place to add any other checks we'd like to
3798     // perform on CSet regions.
3799     return false;
3800   }
3801 };
3802 #endif // ASSERT
3803 
3804 #if TASKQUEUE_STATS
3805 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3806   st->print_raw_cr("GC Task Stats");
3807   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3808   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3809 }
3810 
3811 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3812   print_taskqueue_stats_hdr(st);
3813 
3814   TaskQueueStats totals;
3815   const int n = workers() != NULL ? workers()->total_workers() : 1;
3816   for (int i = 0; i < n; ++i) {
3817     st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3818     totals += task_queue(i)->stats;
3819   }
3820   st->print_raw("tot "); totals.print(st); st->cr();
3821 
3822   DEBUG_ONLY(totals.verify());
3823 }
3824 
3825 void G1CollectedHeap::reset_taskqueue_stats() {
3826   const int n = workers() != NULL ? workers()->total_workers() : 1;
3827   for (int i = 0; i < n; ++i) {
3828     task_queue(i)->stats.reset();
3829   }
3830 }
3831 #endif // TASKQUEUE_STATS
3832 
3833 void G1CollectedHeap::log_gc_header() {
3834   if (!G1Log::fine()) {
3835     return;
3836   }
3837 
3838   gclog_or_tty->date_stamp(PrintGCDateStamps);
3839   gclog_or_tty->stamp(PrintGCTimeStamps);
3840 
3841   GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
3842     .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)")
3843     .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : "");
3844 
3845   gclog_or_tty->print("[%s", (const char*)gc_cause_str);
3846 }
3847 
3848 void G1CollectedHeap::log_gc_footer(double pause_time_sec) {
3849   if (!G1Log::fine()) {
3850     return;
3851   }
3852 
3853   if (G1Log::finer()) {
3854     if (evacuation_failed()) {
3855       gclog_or_tty->print(" (to-space exhausted)");
3856     }
3857     gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3858     g1_policy()->phase_times()->note_gc_end();
3859     g1_policy()->phase_times()->print(pause_time_sec);
3860     g1_policy()->print_detailed_heap_transition();
3861   } else {
3862     if (evacuation_failed()) {
3863       gclog_or_tty->print("--");
3864     }
3865     g1_policy()->print_heap_transition();
3866     gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3867   }
3868   gclog_or_tty->flush();
3869 }
3870 
3871 bool
3872 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3873   assert_at_safepoint(true /* should_be_vm_thread */);
3874   guarantee(!is_gc_active(), "collection is not reentrant");
3875 
3876   if (GC_locker::check_active_before_gc()) {
3877     return false;
3878   }
3879 
3880   _gc_timer_stw->register_gc_start();
3881 
3882   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3883 
3884   SvcGCMarker sgcm(SvcGCMarker::MINOR);
3885   ResourceMark rm;
3886 
3887   print_heap_before_gc();
3888   trace_heap_before_gc(_gc_tracer_stw);
3889 
3890   HRSPhaseSetter x(HRSPhaseEvacuation);
3891   verify_region_sets_optional();
3892   verify_dirty_young_regions();
3893 
3894   // This call will decide whether this pause is an initial-mark
3895   // pause. If it is, during_initial_mark_pause() will return true
3896   // for the duration of this pause.
3897   g1_policy()->decide_on_conc_mark_initiation();
3898 
3899   // We do not allow initial-mark to be piggy-backed on a mixed GC.
3900   assert(!g1_policy()->during_initial_mark_pause() ||
3901           g1_policy()->gcs_are_young(), "sanity");
3902 
3903   // We also do not allow mixed GCs during marking.
3904   assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3905 
3906   // Record whether this pause is an initial mark. When the current
3907   // thread has completed its logging output and it's safe to signal
3908   // the CM thread, the flag's value in the policy has been reset.
3909   bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3910 
3911   // Inner scope for scope based logging, timers, and stats collection
3912   {
3913     EvacuationInfo evacuation_info;
3914 
3915     if (g1_policy()->during_initial_mark_pause()) {
3916       // We are about to start a marking cycle, so we increment the
3917       // full collection counter.
3918       increment_old_marking_cycles_started();
3919       register_concurrent_cycle_start(_gc_timer_stw->gc_start());
3920     }
3921 
3922     _gc_tracer_stw->report_yc_type(yc_type());
3923 
3924     TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3925 
3926     int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
3927                                 workers()->active_workers() : 1);
3928     double pause_start_sec = os::elapsedTime();
3929     g1_policy()->phase_times()->note_gc_start(active_workers);
3930     log_gc_header();
3931 
3932     TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3933     TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3934 
3935     // If the secondary_free_list is not empty, append it to the
3936     // free_list. No need to wait for the cleanup operation to finish;
3937     // the region allocation code will check the secondary_free_list
3938     // and wait if necessary. If the G1StressConcRegionFreeing flag is
3939     // set, skip this step so that the region allocation code has to
3940     // get entries from the secondary_free_list.
3941     if (!G1StressConcRegionFreeing) {
3942       append_secondary_free_list_if_not_empty_with_lock();
3943     }
3944 
3945     assert(check_young_list_well_formed(), "young list should be well formed");
3946     assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3947            "sanity check");
3948 
3949     // Don't dynamically change the number of GC threads this early.  A value of
3950     // 0 is used to indicate serial work.  When parallel work is done,
3951     // it will be set.
3952 
3953     { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3954       IsGCActiveMark x;
3955 
3956       gc_prologue(false);
3957       increment_total_collections(false /* full gc */);
3958       increment_gc_time_stamp();
3959 
3960       verify_before_gc();
3961 
3962       COMPILER2_PRESENT(DerivedPointerTable::clear());
3963 
3964       // Please see comment in g1CollectedHeap.hpp and
3965       // G1CollectedHeap::ref_processing_init() to see how
3966       // reference processing currently works in G1.
3967 
3968       // Enable discovery in the STW reference processor
3969       ref_processor_stw()->enable_discovery(true /*verify_disabled*/,
3970                                             true /*verify_no_refs*/);
3971 
3972       {
3973         // We want to temporarily turn off discovery by the
3974         // CM ref processor, if necessary, and turn it back on
3975         // on again later if we do. Using a scoped
3976         // NoRefDiscovery object will do this.
3977         NoRefDiscovery no_cm_discovery(ref_processor_cm());
3978 
3979         // Forget the current alloc region (we might even choose it to be part
3980         // of the collection set!).
3981         release_mutator_alloc_region();
3982 
3983         // We should call this after we retire the mutator alloc
3984         // region(s) so that all the ALLOC / RETIRE events are generated
3985         // before the start GC event.
3986         _hr_printer.start_gc(false /* full */, (size_t) total_collections());
3987 
3988         // This timing is only used by the ergonomics to handle our pause target.
3989         // It is unclear why this should not include the full pause. We will
3990         // investigate this in CR 7178365.
3991         //
3992         // Preserving the old comment here if that helps the investigation:
3993         //
3994         // The elapsed time induced by the start time below deliberately elides
3995         // the possible verification above.
3996         double sample_start_time_sec = os::elapsedTime();
3997 
3998 #if YOUNG_LIST_VERBOSE
3999         gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
4000         _young_list->print();
4001         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4002 #endif // YOUNG_LIST_VERBOSE
4003 
4004         g1_policy()->record_collection_pause_start(sample_start_time_sec);
4005 
4006         double scan_wait_start = os::elapsedTime();
4007         // We have to wait until the CM threads finish scanning the
4008         // root regions as it's the only way to ensure that all the
4009         // objects on them have been correctly scanned before we start
4010         // moving them during the GC.
4011         bool waited = _cm->root_regions()->wait_until_scan_finished();
4012         double wait_time_ms = 0.0;
4013         if (waited) {
4014           double scan_wait_end = os::elapsedTime();
4015           wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
4016         }
4017         g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
4018 
4019 #if YOUNG_LIST_VERBOSE
4020         gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
4021         _young_list->print();
4022 #endif // YOUNG_LIST_VERBOSE
4023 
4024         if (g1_policy()->during_initial_mark_pause()) {
4025           concurrent_mark()->checkpointRootsInitialPre();
4026         }
4027 
4028 #if YOUNG_LIST_VERBOSE
4029         gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
4030         _young_list->print();
4031         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4032 #endif // YOUNG_LIST_VERBOSE
4033 
4034         g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info);
4035 
4036         _cm->note_start_of_gc();
4037         // We should not verify the per-thread SATB buffers given that
4038         // we have not filtered them yet (we'll do so during the
4039         // GC). We also call this after finalize_cset() to
4040         // ensure that the CSet has been finalized.
4041         _cm->verify_no_cset_oops(true  /* verify_stacks */,
4042                                  true  /* verify_enqueued_buffers */,
4043                                  false /* verify_thread_buffers */,
4044                                  true  /* verify_fingers */);
4045 
4046         if (_hr_printer.is_active()) {
4047           HeapRegion* hr = g1_policy()->collection_set();
4048           while (hr != NULL) {
4049             G1HRPrinter::RegionType type;
4050             if (!hr->is_young()) {
4051               type = G1HRPrinter::Old;
4052             } else if (hr->is_survivor()) {
4053               type = G1HRPrinter::Survivor;
4054             } else {
4055               type = G1HRPrinter::Eden;
4056             }
4057             _hr_printer.cset(hr);
4058             hr = hr->next_in_collection_set();
4059           }
4060         }
4061 
4062 #ifdef ASSERT
4063         VerifyCSetClosure cl;
4064         collection_set_iterate(&cl);
4065 #endif // ASSERT
4066 
4067         setup_surviving_young_words();
4068 
4069         // Initialize the GC alloc regions.
4070         init_gc_alloc_regions(evacuation_info);
4071 
4072         // Actually do the work...
4073         evacuate_collection_set(evacuation_info);
4074 
4075         // We do this to mainly verify the per-thread SATB buffers
4076         // (which have been filtered by now) since we didn't verify
4077         // them earlier. No point in re-checking the stacks / enqueued
4078         // buffers given that the CSet has not changed since last time
4079         // we checked.
4080         _cm->verify_no_cset_oops(false /* verify_stacks */,
4081                                  false /* verify_enqueued_buffers */,
4082                                  true  /* verify_thread_buffers */,
4083                                  true  /* verify_fingers */);
4084 
4085         free_collection_set(g1_policy()->collection_set(), evacuation_info);
4086         g1_policy()->clear_collection_set();
4087 
4088         cleanup_surviving_young_words();
4089 
4090         // Start a new incremental collection set for the next pause.
4091         g1_policy()->start_incremental_cset_building();
4092 
4093         // Clear the _cset_fast_test bitmap in anticipation of adding
4094         // regions to the incremental collection set for the next
4095         // evacuation pause.
4096         clear_cset_fast_test();
4097 
4098         _young_list->reset_sampled_info();
4099 
4100         // Don't check the whole heap at this point as the
4101         // GC alloc regions from this pause have been tagged
4102         // as survivors and moved on to the survivor list.
4103         // Survivor regions will fail the !is_young() check.
4104         assert(check_young_list_empty(false /* check_heap */),
4105           "young list should be empty");
4106 
4107 #if YOUNG_LIST_VERBOSE
4108         gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
4109         _young_list->print();
4110 #endif // YOUNG_LIST_VERBOSE
4111 
4112         g1_policy()->record_survivor_regions(_young_list->survivor_length(),
4113                                              _young_list->first_survivor_region(),
4114                                              _young_list->last_survivor_region());
4115 
4116         _young_list->reset_auxilary_lists();
4117 
4118         if (evacuation_failed()) {
4119           _summary_bytes_used = recalculate_used();
4120           uint n_queues = MAX2((int)ParallelGCThreads, 1);
4121           for (uint i = 0; i < n_queues; i++) {
4122             if (_evacuation_failed_info_array[i].has_failed()) {
4123               _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
4124             }
4125           }
4126         } else {
4127           // The "used" of the the collection set have already been subtracted
4128           // when they were freed.  Add in the bytes evacuated.
4129           _summary_bytes_used += g1_policy()->bytes_copied_during_gc();
4130         }
4131 
4132         if (g1_policy()->during_initial_mark_pause()) {
4133           // We have to do this before we notify the CM threads that
4134           // they can start working to make sure that all the
4135           // appropriate initialization is done on the CM object.
4136           concurrent_mark()->checkpointRootsInitialPost();
4137           set_marking_started();
4138           // Note that we don't actually trigger the CM thread at
4139           // this point. We do that later when we're sure that
4140           // the current thread has completed its logging output.
4141         }
4142 
4143         allocate_dummy_regions();
4144 
4145 #if YOUNG_LIST_VERBOSE
4146         gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
4147         _young_list->print();
4148         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4149 #endif // YOUNG_LIST_VERBOSE
4150 
4151         init_mutator_alloc_region();
4152 
4153         {
4154           size_t expand_bytes = g1_policy()->expansion_amount();
4155           if (expand_bytes > 0) {
4156             size_t bytes_before = capacity();
4157             // No need for an ergo verbose message here,
4158             // expansion_amount() does this when it returns a value > 0.
4159             if (!expand(expand_bytes)) {
4160               // We failed to expand the heap so let's verify that
4161               // committed/uncommitted amount match the backing store
4162               assert(capacity() == _g1_storage.committed_size(), "committed size mismatch");
4163               assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch");
4164             }
4165           }
4166         }
4167 
4168         // We redo the verification but now wrt to the new CSet which
4169         // has just got initialized after the previous CSet was freed.
4170         _cm->verify_no_cset_oops(true  /* verify_stacks */,
4171                                  true  /* verify_enqueued_buffers */,
4172                                  true  /* verify_thread_buffers */,
4173                                  true  /* verify_fingers */);
4174         _cm->note_end_of_gc();
4175 
4176         // This timing is only used by the ergonomics to handle our pause target.
4177         // It is unclear why this should not include the full pause. We will
4178         // investigate this in CR 7178365.
4179         double sample_end_time_sec = os::elapsedTime();
4180         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
4181         g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info);
4182 
4183         MemoryService::track_memory_usage();
4184 
4185         // In prepare_for_verify() below we'll need to scan the deferred
4186         // update buffers to bring the RSets up-to-date if
4187         // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
4188         // the update buffers we'll probably need to scan cards on the
4189         // regions we just allocated to (i.e., the GC alloc
4190         // regions). However, during the last GC we called
4191         // set_saved_mark() on all the GC alloc regions, so card
4192         // scanning might skip the [saved_mark_word()...top()] area of
4193         // those regions (i.e., the area we allocated objects into
4194         // during the last GC). But it shouldn't. Given that
4195         // saved_mark_word() is conditional on whether the GC time stamp
4196         // on the region is current or not, by incrementing the GC time
4197         // stamp here we invalidate all the GC time stamps on all the
4198         // regions and saved_mark_word() will simply return top() for
4199         // all the regions. This is a nicer way of ensuring this rather
4200         // than iterating over the regions and fixing them. In fact, the
4201         // GC time stamp increment here also ensures that
4202         // saved_mark_word() will return top() between pauses, i.e.,
4203         // during concurrent refinement. So we don't need the
4204         // is_gc_active() check to decided which top to use when
4205         // scanning cards (see CR 7039627).
4206         increment_gc_time_stamp();
4207 
4208         verify_after_gc();
4209 
4210         assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
4211         ref_processor_stw()->verify_no_references_recorded();
4212 
4213         // CM reference discovery will be re-enabled if necessary.
4214       }
4215 
4216       // We should do this after we potentially expand the heap so
4217       // that all the COMMIT events are generated before the end GC
4218       // event, and after we retire the GC alloc regions so that all
4219       // RETIRE events are generated before the end GC event.
4220       _hr_printer.end_gc(false /* full */, (size_t) total_collections());
4221 
4222       if (mark_in_progress()) {
4223         concurrent_mark()->update_g1_committed();
4224       }
4225 
4226 #ifdef TRACESPINNING
4227       ParallelTaskTerminator::print_termination_counts();
4228 #endif
4229 
4230       gc_epilogue(false);
4231     }
4232 
4233     // Print the remainder of the GC log output.
4234     log_gc_footer(os::elapsedTime() - pause_start_sec);
4235 
4236     // It is not yet to safe to tell the concurrent mark to
4237     // start as we have some optional output below. We don't want the
4238     // output from the concurrent mark thread interfering with this
4239     // logging output either.
4240 
4241     _hrs.verify_optional();
4242     verify_region_sets_optional();
4243 
4244     TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
4245     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
4246 
4247     print_heap_after_gc();
4248     trace_heap_after_gc(_gc_tracer_stw);
4249 
4250     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
4251     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
4252     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
4253     // before any GC notifications are raised.
4254     g1mm()->update_sizes();
4255 
4256     _gc_tracer_stw->report_evacuation_info(&evacuation_info);
4257     _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
4258     _gc_timer_stw->register_gc_end();
4259     _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
4260   }
4261   // It should now be safe to tell the concurrent mark thread to start
4262   // without its logging output interfering with the logging output
4263   // that came from the pause.
4264 
4265   if (should_start_conc_mark) {
4266     // CAUTION: after the doConcurrentMark() call below,
4267     // the concurrent marking thread(s) could be running
4268     // concurrently with us. Make sure that anything after
4269     // this point does not assume that we are the only GC thread
4270     // running. Note: of course, the actual marking work will
4271     // not start until the safepoint itself is released in
4272     // ConcurrentGCThread::safepoint_desynchronize().
4273     doConcurrentMark();
4274   }
4275 
4276   return true;
4277 }
4278 
4279 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
4280 {
4281   size_t gclab_word_size;
4282   switch (purpose) {
4283     case GCAllocForSurvived:
4284       gclab_word_size = _survivor_plab_stats.desired_plab_sz();
4285       break;
4286     case GCAllocForTenured:
4287       gclab_word_size = _old_plab_stats.desired_plab_sz();
4288       break;
4289     default:
4290       assert(false, "unknown GCAllocPurpose");
4291       gclab_word_size = _old_plab_stats.desired_plab_sz();
4292       break;
4293   }
4294 
4295   // Prevent humongous PLAB sizes for two reasons:
4296   // * PLABs are allocated using a similar paths as oops, but should
4297   //   never be in a humongous region
4298   // * Allowing humongous PLABs needlessly churns the region free lists
4299   return MIN2(_humongous_object_threshold_in_words, gclab_word_size);
4300 }
4301 
4302 void G1CollectedHeap::init_mutator_alloc_region() {
4303   assert(_mutator_alloc_region.get() == NULL, "pre-condition");
4304   _mutator_alloc_region.init();
4305 }
4306 
4307 void G1CollectedHeap::release_mutator_alloc_region() {
4308   _mutator_alloc_region.release();
4309   assert(_mutator_alloc_region.get() == NULL, "post-condition");
4310 }
4311 
4312 void G1CollectedHeap::init_gc_alloc_regions(EvacuationInfo& evacuation_info) {
4313   assert_at_safepoint(true /* should_be_vm_thread */);
4314 
4315   _survivor_gc_alloc_region.init();
4316   _old_gc_alloc_region.init();
4317   HeapRegion* retained_region = _retained_old_gc_alloc_region;
4318   _retained_old_gc_alloc_region = NULL;
4319 
4320   // We will discard the current GC alloc region if:
4321   // a) it's in the collection set (it can happen!),
4322   // b) it's already full (no point in using it),
4323   // c) it's empty (this means that it was emptied during
4324   // a cleanup and it should be on the free list now), or
4325   // d) it's humongous (this means that it was emptied
4326   // during a cleanup and was added to the free list, but
4327   // has been subsequently used to allocate a humongous
4328   // object that may be less than the region size).
4329   if (retained_region != NULL &&
4330       !retained_region->in_collection_set() &&
4331       !(retained_region->top() == retained_region->end()) &&
4332       !retained_region->is_empty() &&
4333       !retained_region->isHumongous()) {
4334     retained_region->set_saved_mark();
4335     // The retained region was added to the old region set when it was
4336     // retired. We have to remove it now, since we don't allow regions
4337     // we allocate to in the region sets. We'll re-add it later, when
4338     // it's retired again.
4339     _old_set.remove(retained_region);
4340     bool during_im = g1_policy()->during_initial_mark_pause();
4341     retained_region->note_start_of_copying(during_im);
4342     _old_gc_alloc_region.set(retained_region);
4343     _hr_printer.reuse(retained_region);
4344     evacuation_info.set_alloc_regions_used_before(retained_region->used());
4345   }
4346 }
4347 
4348 void G1CollectedHeap::release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info) {
4349   evacuation_info.set_allocation_regions(_survivor_gc_alloc_region.count() +
4350                                          _old_gc_alloc_region.count());
4351   _survivor_gc_alloc_region.release();
4352   // If we have an old GC alloc region to release, we'll save it in
4353   // _retained_old_gc_alloc_region. If we don't
4354   // _retained_old_gc_alloc_region will become NULL. This is what we
4355   // want either way so no reason to check explicitly for either
4356   // condition.
4357   _retained_old_gc_alloc_region = _old_gc_alloc_region.release();
4358 
4359   if (ResizePLAB) {
4360     _survivor_plab_stats.adjust_desired_plab_sz(no_of_gc_workers);
4361     _old_plab_stats.adjust_desired_plab_sz(no_of_gc_workers);
4362   }
4363 }
4364 
4365 void G1CollectedHeap::abandon_gc_alloc_regions() {
4366   assert(_survivor_gc_alloc_region.get() == NULL, "pre-condition");
4367   assert(_old_gc_alloc_region.get() == NULL, "pre-condition");
4368   _retained_old_gc_alloc_region = NULL;
4369 }
4370 
4371 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4372   _drain_in_progress = false;
4373   set_evac_failure_closure(cl);
4374   _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4375 }
4376 
4377 void G1CollectedHeap::finalize_for_evac_failure() {
4378   assert(_evac_failure_scan_stack != NULL &&
4379          _evac_failure_scan_stack->length() == 0,
4380          "Postcondition");
4381   assert(!_drain_in_progress, "Postcondition");
4382   delete _evac_failure_scan_stack;
4383   _evac_failure_scan_stack = NULL;
4384 }
4385 
4386 void G1CollectedHeap::remove_self_forwarding_pointers() {
4387   assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4388 
4389   G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4390 
4391   if (G1CollectedHeap::use_parallel_gc_threads()) {
4392     set_par_threads();
4393     workers()->run_task(&rsfp_task);
4394     set_par_threads(0);
4395   } else {
4396     rsfp_task.work(0);
4397   }
4398 
4399   assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity");
4400 
4401   // Reset the claim values in the regions in the collection set.
4402   reset_cset_heap_region_claim_values();
4403 
4404   assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4405 
4406   // Now restore saved marks, if any.
4407   assert(_objs_with_preserved_marks.size() ==
4408             _preserved_marks_of_objs.size(), "Both or none.");
4409   while (!_objs_with_preserved_marks.is_empty()) {
4410     oop obj = _objs_with_preserved_marks.pop();
4411     markOop m = _preserved_marks_of_objs.pop();
4412     obj->set_mark(m);
4413   }
4414   _objs_with_preserved_marks.clear(true);
4415   _preserved_marks_of_objs.clear(true);
4416 }
4417 
4418 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4419   _evac_failure_scan_stack->push(obj);
4420 }
4421 
4422 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4423   assert(_evac_failure_scan_stack != NULL, "precondition");
4424 
4425   while (_evac_failure_scan_stack->length() > 0) {
4426      oop obj = _evac_failure_scan_stack->pop();
4427      _evac_failure_closure->set_region(heap_region_containing(obj));
4428      obj->oop_iterate_backwards(_evac_failure_closure);
4429   }
4430 }
4431 
4432 oop
4433 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state,
4434                                                oop old) {
4435   assert(obj_in_cs(old),
4436          err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4437                  (HeapWord*) old));
4438   markOop m = old->mark();
4439   oop forward_ptr = old->forward_to_atomic(old);
4440   if (forward_ptr == NULL) {
4441     // Forward-to-self succeeded.
4442     assert(_par_scan_state != NULL, "par scan state");
4443     OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4444     uint queue_num = _par_scan_state->queue_num();
4445 
4446     _evacuation_failed = true;
4447     _evacuation_failed_info_array[queue_num].register_copy_failure(old->size());
4448     if (_evac_failure_closure != cl) {
4449       MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4450       assert(!_drain_in_progress,
4451              "Should only be true while someone holds the lock.");
4452       // Set the global evac-failure closure to the current thread's.
4453       assert(_evac_failure_closure == NULL, "Or locking has failed.");
4454       set_evac_failure_closure(cl);
4455       // Now do the common part.
4456       handle_evacuation_failure_common(old, m);
4457       // Reset to NULL.
4458       set_evac_failure_closure(NULL);
4459     } else {
4460       // The lock is already held, and this is recursive.
4461       assert(_drain_in_progress, "This should only be the recursive case.");
4462       handle_evacuation_failure_common(old, m);
4463     }
4464     return old;
4465   } else {
4466     // Forward-to-self failed. Either someone else managed to allocate
4467     // space for this object (old != forward_ptr) or they beat us in
4468     // self-forwarding it (old == forward_ptr).
4469     assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4470            err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4471                    "should not be in the CSet",
4472                    (HeapWord*) old, (HeapWord*) forward_ptr));
4473     return forward_ptr;
4474   }
4475 }
4476 
4477 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4478   preserve_mark_if_necessary(old, m);
4479 
4480   HeapRegion* r = heap_region_containing(old);
4481   if (!r->evacuation_failed()) {
4482     r->set_evacuation_failed(true);
4483     _hr_printer.evac_failure(r);
4484   }
4485 
4486   push_on_evac_failure_scan_stack(old);
4487 
4488   if (!_drain_in_progress) {
4489     // prevent recursion in copy_to_survivor_space()
4490     _drain_in_progress = true;
4491     drain_evac_failure_scan_stack();
4492     _drain_in_progress = false;
4493   }
4494 }
4495 
4496 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4497   assert(evacuation_failed(), "Oversaving!");
4498   // We want to call the "for_promotion_failure" version only in the
4499   // case of a promotion failure.
4500   if (m->must_be_preserved_for_promotion_failure(obj)) {
4501     _objs_with_preserved_marks.push(obj);
4502     _preserved_marks_of_objs.push(m);
4503   }
4504 }
4505 
4506 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
4507                                                   size_t word_size) {
4508   if (purpose == GCAllocForSurvived) {
4509     HeapWord* result = survivor_attempt_allocation(word_size);
4510     if (result != NULL) {
4511       return result;
4512     } else {
4513       // Let's try to allocate in the old gen in case we can fit the
4514       // object there.
4515       return old_attempt_allocation(word_size);
4516     }
4517   } else {
4518     assert(purpose ==  GCAllocForTenured, "sanity");
4519     HeapWord* result = old_attempt_allocation(word_size);
4520     if (result != NULL) {
4521       return result;
4522     } else {
4523       // Let's try to allocate in the survivors in case we can fit the
4524       // object there.
4525       return survivor_attempt_allocation(word_size);
4526     }
4527   }
4528 
4529   ShouldNotReachHere();
4530   // Trying to keep some compilers happy.
4531   return NULL;
4532 }
4533 
4534 G1ParGCAllocBuffer::G1ParGCAllocBuffer(size_t gclab_word_size) :
4535   ParGCAllocBuffer(gclab_word_size), _retired(false) { }
4536 
4537 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, uint queue_num)
4538   : _g1h(g1h),
4539     _refs(g1h->task_queue(queue_num)),
4540     _dcq(&g1h->dirty_card_queue_set()),
4541     _ct_bs(g1h->g1_barrier_set()),
4542     _g1_rem(g1h->g1_rem_set()),
4543     _hash_seed(17), _queue_num(queue_num),
4544     _term_attempts(0),
4545     _surviving_alloc_buffer(g1h->desired_plab_sz(GCAllocForSurvived)),
4546     _tenured_alloc_buffer(g1h->desired_plab_sz(GCAllocForTenured)),
4547     _age_table(false),
4548     _strong_roots_time(0), _term_time(0),
4549     _alloc_buffer_waste(0), _undo_waste(0) {
4550   // we allocate G1YoungSurvRateNumRegions plus one entries, since
4551   // we "sacrifice" entry 0 to keep track of surviving bytes for
4552   // non-young regions (where the age is -1)
4553   // We also add a few elements at the beginning and at the end in
4554   // an attempt to eliminate cache contention
4555   uint real_length = 1 + _g1h->g1_policy()->young_cset_region_length();
4556   uint array_length = PADDING_ELEM_NUM +
4557                       real_length +
4558                       PADDING_ELEM_NUM;
4559   _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length, mtGC);
4560   if (_surviving_young_words_base == NULL)
4561     vm_exit_out_of_memory(array_length * sizeof(size_t), OOM_MALLOC_ERROR,
4562                           "Not enough space for young surv histo.");
4563   _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM;
4564   memset(_surviving_young_words, 0, (size_t) real_length * sizeof(size_t));
4565 
4566   _alloc_buffers[GCAllocForSurvived] = &_surviving_alloc_buffer;
4567   _alloc_buffers[GCAllocForTenured]  = &_tenured_alloc_buffer;
4568 
4569   _start = os::elapsedTime();
4570 }
4571 
4572 void
4573 G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st)
4574 {
4575   st->print_raw_cr("GC Termination Stats");
4576   st->print_raw_cr("     elapsed  --strong roots-- -------termination-------"
4577                    " ------waste (KiB)------");
4578   st->print_raw_cr("thr     ms        ms      %        ms      %    attempts"
4579                    "  total   alloc    undo");
4580   st->print_raw_cr("--- --------- --------- ------ --------- ------ --------"
4581                    " ------- ------- -------");
4582 }
4583 
4584 void
4585 G1ParScanThreadState::print_termination_stats(int i,
4586                                               outputStream* const st) const
4587 {
4588   const double elapsed_ms = elapsed_time() * 1000.0;
4589   const double s_roots_ms = strong_roots_time() * 1000.0;
4590   const double term_ms    = term_time() * 1000.0;
4591   st->print_cr("%3d %9.2f %9.2f %6.2f "
4592                "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
4593                SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
4594                i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms,
4595                term_ms, term_ms * 100 / elapsed_ms, term_attempts(),
4596                (alloc_buffer_waste() + undo_waste()) * HeapWordSize / K,
4597                alloc_buffer_waste() * HeapWordSize / K,
4598                undo_waste() * HeapWordSize / K);
4599 }
4600 
4601 #ifdef ASSERT
4602 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const {
4603   assert(ref != NULL, "invariant");
4604   assert(UseCompressedOops, "sanity");
4605   assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, ref));
4606   oop p = oopDesc::load_decode_heap_oop(ref);
4607   assert(_g1h->is_in_g1_reserved(p),
4608          err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, (void *)p));
4609   return true;
4610 }
4611 
4612 bool G1ParScanThreadState::verify_ref(oop* ref) const {
4613   assert(ref != NULL, "invariant");
4614   if (has_partial_array_mask(ref)) {
4615     // Must be in the collection set--it's already been copied.
4616     oop p = clear_partial_array_mask(ref);
4617     assert(_g1h->obj_in_cs(p),
4618            err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, (void *)p));
4619   } else {
4620     oop p = oopDesc::load_decode_heap_oop(ref);
4621     assert(_g1h->is_in_g1_reserved(p),
4622            err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, (void *)p));
4623   }
4624   return true;
4625 }
4626 
4627 bool G1ParScanThreadState::verify_task(StarTask ref) const {
4628   if (ref.is_narrow()) {
4629     return verify_ref((narrowOop*) ref);
4630   } else {
4631     return verify_ref((oop*) ref);
4632   }
4633 }
4634 #endif // ASSERT
4635 
4636 void G1ParScanThreadState::trim_queue() {
4637   assert(_evac_cl != NULL, "not set");
4638   assert(_evac_failure_cl != NULL, "not set");
4639   assert(_partial_scan_cl != NULL, "not set");
4640 
4641   StarTask ref;
4642   do {
4643     // Drain the overflow stack first, so other threads can steal.
4644     while (refs()->pop_overflow(ref)) {
4645       deal_with_reference(ref);
4646     }
4647 
4648     while (refs()->pop_local(ref)) {
4649       deal_with_reference(ref);
4650     }
4651   } while (!refs()->is_empty());
4652 }
4653 
4654 G1ParClosureSuper::G1ParClosureSuper(G1CollectedHeap* g1,
4655                                      G1ParScanThreadState* par_scan_state) :
4656   _g1(g1), _par_scan_state(par_scan_state),
4657   _worker_id(par_scan_state->queue_num()) { }
4658 
4659 void G1ParCopyHelper::mark_object(oop obj) {
4660 #ifdef ASSERT
4661   HeapRegion* hr = _g1->heap_region_containing(obj);
4662   assert(hr != NULL, "sanity");
4663   assert(!hr->in_collection_set(), "should not mark objects in the CSet");
4664 #endif // ASSERT
4665 
4666   // We know that the object is not moving so it's safe to read its size.
4667   _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4668 }
4669 
4670 void G1ParCopyHelper::mark_forwarded_object(oop from_obj, oop to_obj) {
4671 #ifdef ASSERT
4672   assert(from_obj->is_forwarded(), "from obj should be forwarded");
4673   assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4674   assert(from_obj != to_obj, "should not be self-forwarded");
4675 
4676   HeapRegion* from_hr = _g1->heap_region_containing(from_obj);
4677   assert(from_hr != NULL, "sanity");
4678   assert(from_hr->in_collection_set(), "from obj should be in the CSet");
4679 
4680   HeapRegion* to_hr = _g1->heap_region_containing(to_obj);
4681   assert(to_hr != NULL, "sanity");
4682   assert(!to_hr->in_collection_set(), "should not mark objects in the CSet");
4683 #endif // ASSERT
4684 
4685   // The object might be in the process of being copied by another
4686   // worker so we cannot trust that its to-space image is
4687   // well-formed. So we have to read its size from its from-space
4688   // image which we know should not be changing.
4689   _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4690 }
4691 
4692 template <G1Barrier barrier, bool do_mark_object>
4693 oop G1ParCopyClosure<barrier, do_mark_object>
4694   ::copy_to_survivor_space(oop old) {
4695   size_t word_sz = old->size();
4696   HeapRegion* from_region = _g1->heap_region_containing_raw(old);
4697   // +1 to make the -1 indexes valid...
4698   int       young_index = from_region->young_index_in_cset()+1;
4699   assert( (from_region->is_young() && young_index >  0) ||
4700          (!from_region->is_young() && young_index == 0), "invariant" );
4701   G1CollectorPolicy* g1p = _g1->g1_policy();
4702   markOop m = old->mark();
4703   int age = m->has_displaced_mark_helper() ? m->displaced_mark_helper()->age()
4704                                            : m->age();
4705   GCAllocPurpose alloc_purpose = g1p->evacuation_destination(from_region, age,
4706                                                              word_sz);
4707   HeapWord* obj_ptr = _par_scan_state->allocate(alloc_purpose, word_sz);
4708 #ifndef PRODUCT
4709   // Should this evacuation fail?
4710   if (_g1->evacuation_should_fail()) {
4711     if (obj_ptr != NULL) {
4712       _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz);
4713       obj_ptr = NULL;
4714     }
4715   }
4716 #endif // !PRODUCT
4717 
4718   if (obj_ptr == NULL) {
4719     // This will either forward-to-self, or detect that someone else has
4720     // installed a forwarding pointer.
4721     return _g1->handle_evacuation_failure_par(_par_scan_state, old);
4722   }
4723 
4724   oop obj = oop(obj_ptr);
4725 
4726   // We're going to allocate linearly, so might as well prefetch ahead.
4727   Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
4728 
4729   oop forward_ptr = old->forward_to_atomic(obj);
4730   if (forward_ptr == NULL) {
4731     Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
4732     if (g1p->track_object_age(alloc_purpose)) {
4733       // We could simply do obj->incr_age(). However, this causes a
4734       // performance issue. obj->incr_age() will first check whether
4735       // the object has a displaced mark by checking its mark word;
4736       // getting the mark word from the new location of the object
4737       // stalls. So, given that we already have the mark word and we
4738       // are about to install it anyway, it's better to increase the
4739       // age on the mark word, when the object does not have a
4740       // displaced mark word. We're not expecting many objects to have
4741       // a displaced marked word, so that case is not optimized
4742       // further (it could be...) and we simply call obj->incr_age().
4743 
4744       if (m->has_displaced_mark_helper()) {
4745         // in this case, we have to install the mark word first,
4746         // otherwise obj looks to be forwarded (the old mark word,
4747         // which contains the forward pointer, was copied)
4748         obj->set_mark(m);
4749         obj->incr_age();
4750       } else {
4751         m = m->incr_age();
4752         obj->set_mark(m);
4753       }
4754       _par_scan_state->age_table()->add(obj, word_sz);
4755     } else {
4756       obj->set_mark(m);
4757     }
4758 
4759     size_t* surv_young_words = _par_scan_state->surviving_young_words();
4760     surv_young_words[young_index] += word_sz;
4761 
4762     if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
4763       // We keep track of the next start index in the length field of
4764       // the to-space object. The actual length can be found in the
4765       // length field of the from-space object.
4766       arrayOop(obj)->set_length(0);
4767       oop* old_p = set_partial_array_mask(old);
4768       _par_scan_state->push_on_queue(old_p);
4769     } else {
4770       // No point in using the slower heap_region_containing() method,
4771       // given that we know obj is in the heap.
4772       _scanner.set_region(_g1->heap_region_containing_raw(obj));
4773       obj->oop_iterate_backwards(&_scanner);
4774     }
4775   } else {
4776     _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz);
4777     obj = forward_ptr;
4778   }
4779   return obj;
4780 }
4781 
4782 template <class T>
4783 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) {
4784   if (_g1->heap_region_containing_raw(new_obj)->is_young()) {
4785     _scanned_klass->record_modified_oops();
4786   }
4787 }
4788 
4789 template <G1Barrier barrier, bool do_mark_object>
4790 template <class T>
4791 void G1ParCopyClosure<barrier, do_mark_object>::do_oop_work(T* p) {
4792   oop obj = oopDesc::load_decode_heap_oop(p);






4793 
4794   assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4795 
4796   // here the null check is implicit in the cset_fast_test() test
4797   if (_g1->in_cset_fast_test(obj)) {
4798     oop forwardee;
4799     if (obj->is_forwarded()) {
4800       forwardee = obj->forwardee();
4801     } else {
4802       forwardee = copy_to_survivor_space(obj);
4803     }
4804     assert(forwardee != NULL, "forwardee should not be NULL");
4805     oopDesc::encode_store_heap_oop(p, forwardee);
4806     if (do_mark_object && forwardee != obj) {
4807       // If the object is self-forwarded we don't need to explicitly
4808       // mark it, the evacuation failure protocol will do so.
4809       mark_forwarded_object(obj, forwardee);
4810     }
4811 
4812     if (barrier == G1BarrierKlass) {
4813       do_klass_barrier(p, forwardee);
4814     }
4815   } else {
4816     // The object is not in collection set. If we're a root scanning
4817     // closure during an initial mark pause (i.e. do_mark_object will
4818     // be true) then attempt to mark the object.
4819     if (do_mark_object && _g1->is_in_g1_reserved(obj)) {
4820       mark_object(obj);
4821     }
4822   }
4823 
4824   if (barrier == G1BarrierEvac && obj != NULL) {
4825     _par_scan_state->update_rs(_from, p, _worker_id);
4826   }
4827 }
4828 
4829 template void G1ParCopyClosure<G1BarrierEvac, false>::do_oop_work(oop* p);
4830 template void G1ParCopyClosure<G1BarrierEvac, false>::do_oop_work(narrowOop* p);
4831 
4832 template <class T> void G1ParScanPartialArrayClosure::do_oop_nv(T* p) {
4833   assert(has_partial_array_mask(p), "invariant");
4834   oop from_obj = clear_partial_array_mask(p);
4835 
4836   assert(Universe::heap()->is_in_reserved(from_obj), "must be in heap.");
4837   assert(from_obj->is_objArray(), "must be obj array");
4838   objArrayOop from_obj_array = objArrayOop(from_obj);
4839   // The from-space object contains the real length.
4840   int length                 = from_obj_array->length();
4841 
4842   assert(from_obj->is_forwarded(), "must be forwarded");
4843   oop to_obj                 = from_obj->forwardee();
4844   assert(from_obj != to_obj, "should not be chunking self-forwarded objects");
4845   objArrayOop to_obj_array   = objArrayOop(to_obj);
4846   // We keep track of the next start index in the length field of the
4847   // to-space object.
4848   int next_index             = to_obj_array->length();
4849   assert(0 <= next_index && next_index < length,
4850          err_msg("invariant, next index: %d, length: %d", next_index, length));
4851 
4852   int start                  = next_index;
4853   int end                    = length;
4854   int remainder              = end - start;
4855   // We'll try not to push a range that's smaller than ParGCArrayScanChunk.
4856   if (remainder > 2 * ParGCArrayScanChunk) {
4857     end = start + ParGCArrayScanChunk;
4858     to_obj_array->set_length(end);
4859     // Push the remainder before we process the range in case another
4860     // worker has run out of things to do and can steal it.
4861     oop* from_obj_p = set_partial_array_mask(from_obj);
4862     _par_scan_state->push_on_queue(from_obj_p);
4863   } else {
4864     assert(length == end, "sanity");
4865     // We'll process the final range for this object. Restore the length
4866     // so that the heap remains parsable in case of evacuation failure.
4867     to_obj_array->set_length(end);
4868   }
4869   _scanner.set_region(_g1->heap_region_containing_raw(to_obj));
4870   // Process indexes [start,end). It will also process the header
4871   // along with the first chunk (i.e., the chunk with start == 0).
4872   // Note that at this point the length field of to_obj_array is not
4873   // correct given that we are using it to keep track of the next
4874   // start index. oop_iterate_range() (thankfully!) ignores the length
4875   // field and only relies on the start / end parameters.  It does
4876   // however return the size of the object which will be incorrect. So
4877   // we have to ignore it even if we wanted to use it.
4878   to_obj_array->oop_iterate_range(&_scanner, start, end);
4879 }
4880 
4881 class G1ParEvacuateFollowersClosure : public VoidClosure {
4882 protected:
4883   G1CollectedHeap*              _g1h;
4884   G1ParScanThreadState*         _par_scan_state;
4885   RefToScanQueueSet*            _queues;
4886   ParallelTaskTerminator*       _terminator;
4887 
4888   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
4889   RefToScanQueueSet*      queues()         { return _queues; }
4890   ParallelTaskTerminator* terminator()     { return _terminator; }
4891 
4892 public:
4893   G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4894                                 G1ParScanThreadState* par_scan_state,
4895                                 RefToScanQueueSet* queues,
4896                                 ParallelTaskTerminator* terminator)
4897     : _g1h(g1h), _par_scan_state(par_scan_state),
4898       _queues(queues), _terminator(terminator) {}
4899 
4900   void do_void();
4901 
4902 private:
4903   inline bool offer_termination();
4904 };
4905 
4906 bool G1ParEvacuateFollowersClosure::offer_termination() {
4907   G1ParScanThreadState* const pss = par_scan_state();
4908   pss->start_term_time();
4909   const bool res = terminator()->offer_termination();
4910   pss->end_term_time();
4911   return res;
4912 }
4913 
4914 void G1ParEvacuateFollowersClosure::do_void() {
4915   StarTask stolen_task;
4916   G1ParScanThreadState* const pss = par_scan_state();
4917   pss->trim_queue();
4918 
4919   do {
4920     while (queues()->steal(pss->queue_num(), pss->hash_seed(), stolen_task)) {
4921       assert(pss->verify_task(stolen_task), "sanity");
4922       if (stolen_task.is_narrow()) {
4923         pss->deal_with_reference((narrowOop*) stolen_task);
4924       } else {
4925         pss->deal_with_reference((oop*) stolen_task);
4926       }
4927 
4928       // We've just processed a reference and we might have made
4929       // available new entries on the queues. So we have to make sure
4930       // we drain the queues as necessary.
4931       pss->trim_queue();
4932     }
4933   } while (!offer_termination());
4934 
4935   pss->retire_alloc_buffers();
4936 }
4937 
4938 class G1KlassScanClosure : public KlassClosure {
4939  G1ParCopyHelper* _closure;
4940  bool             _process_only_dirty;
4941  int              _count;
4942  public:
4943   G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty)
4944       : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {}
4945   void do_klass(Klass* klass) {
4946     // If the klass has not been dirtied we know that there's
4947     // no references into  the young gen and we can skip it.
4948    if (!_process_only_dirty || klass->has_modified_oops()) {
4949       // Clean the klass since we're going to scavenge all the metadata.
4950       klass->clear_modified_oops();
4951 
4952       // Tell the closure that this klass is the Klass to scavenge
4953       // and is the one to dirty if oops are left pointing into the young gen.
4954       _closure->set_scanned_klass(klass);
4955 
4956       klass->oops_do(_closure);
4957 
4958       _closure->set_scanned_klass(NULL);
4959     }
4960     _count++;
4961   }
4962 };
4963 
4964 class G1ParTask : public AbstractGangTask {
4965 protected:
4966   G1CollectedHeap*       _g1h;
4967   RefToScanQueueSet      *_queues;
4968   ParallelTaskTerminator _terminator;
4969   uint _n_workers;
4970 
4971   Mutex _stats_lock;
4972   Mutex* stats_lock() { return &_stats_lock; }
4973 
4974   size_t getNCards() {
4975     return (_g1h->capacity() + G1BlockOffsetSharedArray::N_bytes - 1)
4976       / G1BlockOffsetSharedArray::N_bytes;
4977   }
4978 
4979 public:
4980   G1ParTask(G1CollectedHeap* g1h,
4981             RefToScanQueueSet *task_queues)
4982     : AbstractGangTask("G1 collection"),
4983       _g1h(g1h),
4984       _queues(task_queues),
4985       _terminator(0, _queues),
4986       _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4987   {}
4988 
4989   RefToScanQueueSet* queues() { return _queues; }
4990 
4991   RefToScanQueue *work_queue(int i) {
4992     return queues()->queue(i);
4993   }
4994 
4995   ParallelTaskTerminator* terminator() { return &_terminator; }
4996 
4997   virtual void set_for_termination(int active_workers) {
4998     // This task calls set_n_termination() in par_non_clean_card_iterate_work()
4999     // in the young space (_par_seq_tasks) in the G1 heap
5000     // for SequentialSubTasksDone.
5001     // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap
5002     // both of which need setting by set_n_termination().
5003     _g1h->SharedHeap::set_n_termination(active_workers);
5004     _g1h->set_n_termination(active_workers);
5005     terminator()->reset_for_reuse(active_workers);
5006     _n_workers = active_workers;
5007   }
5008 
5009   void work(uint worker_id) {
5010     if (worker_id >= _n_workers) return;  // no work needed this round
5011 
5012     double start_time_ms = os::elapsedTime() * 1000.0;
5013     _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms);
5014 
5015     {
5016       ResourceMark rm;
5017       HandleMark   hm;
5018 
5019       ReferenceProcessor*             rp = _g1h->ref_processor_stw();
5020 
5021       G1ParScanThreadState            pss(_g1h, worker_id);
5022       G1ParScanHeapEvacClosure        scan_evac_cl(_g1h, &pss, rp);
5023       G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
5024       G1ParScanPartialArrayClosure    partial_scan_cl(_g1h, &pss, rp);
5025 
5026       pss.set_evac_closure(&scan_evac_cl);
5027       pss.set_evac_failure_closure(&evac_failure_cl);
5028       pss.set_partial_scan_closure(&partial_scan_cl);
5029 
5030       G1ParScanExtRootClosure        only_scan_root_cl(_g1h, &pss, rp);
5031       G1ParScanMetadataClosure       only_scan_metadata_cl(_g1h, &pss, rp);
5032 
5033       G1ParScanAndMarkExtRootClosure scan_mark_root_cl(_g1h, &pss, rp);
5034       G1ParScanAndMarkMetadataClosure scan_mark_metadata_cl(_g1h, &pss, rp);
5035 
5036       bool only_young                 = _g1h->g1_policy()->gcs_are_young();
5037       G1KlassScanClosure              scan_mark_klasses_cl_s(&scan_mark_metadata_cl, false);
5038       G1KlassScanClosure              only_scan_klasses_cl_s(&only_scan_metadata_cl, only_young);
5039 
5040       OopClosure*                    scan_root_cl = &only_scan_root_cl;
5041       G1KlassScanClosure*            scan_klasses_cl = &only_scan_klasses_cl_s;
5042 
5043       if (_g1h->g1_policy()->during_initial_mark_pause()) {
5044         // We also need to mark copied objects.
5045         scan_root_cl = &scan_mark_root_cl;
5046         scan_klasses_cl = &scan_mark_klasses_cl_s;
5047       }
5048 
5049       G1ParPushHeapRSClosure          push_heap_rs_cl(_g1h, &pss);
5050 
5051       // Don't scan the scavengable methods in the code cache as part
5052       // of strong root scanning. The code roots that point into a
5053       // region in the collection set are scanned when we scan the
5054       // region's RSet.
5055       int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings;
5056 
5057       pss.start_strong_roots();
5058       _g1h->g1_process_strong_roots(/* is scavenging */ true,
5059                                     SharedHeap::ScanningOption(so),
5060                                     scan_root_cl,
5061                                     &push_heap_rs_cl,
5062                                     scan_klasses_cl,
5063                                     worker_id);
5064       pss.end_strong_roots();
5065 
5066       {
5067         double start = os::elapsedTime();
5068         G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
5069         evac.do_void();
5070         double elapsed_ms = (os::elapsedTime()-start)*1000.0;
5071         double term_ms = pss.term_time()*1000.0;
5072         _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms);
5073         _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts());
5074       }
5075       _g1h->g1_policy()->record_thread_age_table(pss.age_table());
5076       _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
5077 
5078       if (ParallelGCVerbose) {
5079         MutexLocker x(stats_lock());
5080         pss.print_termination_stats(worker_id);
5081       }
5082 
5083       assert(pss.refs()->is_empty(), "should be empty");
5084 
5085       // Close the inner scope so that the ResourceMark and HandleMark
5086       // destructors are executed here and are included as part of the
5087       // "GC Worker Time".
5088     }
5089 
5090     double end_time_ms = os::elapsedTime() * 1000.0;
5091     _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms);
5092   }
5093 };
5094 
5095 // *** Common G1 Evacuation Stuff
5096 
5097 // This method is run in a GC worker.
5098 
5099 void
5100 G1CollectedHeap::
5101 g1_process_strong_roots(bool is_scavenging,
5102                         ScanningOption so,
5103                         OopClosure* scan_non_heap_roots,
5104                         OopsInHeapRegionClosure* scan_rs,
5105                         G1KlassScanClosure* scan_klasses,
5106                         int worker_i) {
5107 
5108   // First scan the strong roots
5109   double ext_roots_start = os::elapsedTime();
5110   double closure_app_time_sec = 0.0;
5111 
5112   BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
5113 
5114   process_strong_roots(false, // no scoping; this is parallel code
5115                        so,
5116                        &buf_scan_non_heap_roots,
5117                        scan_klasses
5118                        );
5119 
5120   // Now the CM ref_processor roots.
5121   if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
5122     // We need to treat the discovered reference lists of the
5123     // concurrent mark ref processor as roots and keep entries
5124     // (which are added by the marking threads) on them live
5125     // until they can be processed at the end of marking.
5126     ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
5127   }
5128 
5129   // Finish up any enqueued closure apps (attributed as object copy time).
5130   buf_scan_non_heap_roots.done();
5131 
5132   double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds();
5133 
5134   g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
5135 
5136   double ext_root_time_ms =
5137     ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0;
5138 
5139   g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
5140 
5141   // During conc marking we have to filter the per-thread SATB buffers
5142   // to make sure we remove any oops into the CSet (which will show up
5143   // as implicitly live).
5144   double satb_filtering_ms = 0.0;
5145   if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) {
5146     if (mark_in_progress()) {
5147       double satb_filter_start = os::elapsedTime();
5148 
5149       JavaThread::satb_mark_queue_set().filter_thread_buffers();
5150 
5151       satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0;
5152     }
5153   }
5154   g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms);
5155 
5156   // If this is an initial mark pause, and we're not scanning
5157   // the entire code cache, we need to mark the oops in the
5158   // strong code root lists for the regions that are not in
5159   // the collection set.
5160   // Note all threads participate in this set of root tasks.
5161   double mark_strong_code_roots_ms = 0.0;
5162   if (g1_policy()->during_initial_mark_pause() && !(so & SO_AllCodeCache)) {
5163     double mark_strong_roots_start = os::elapsedTime();
5164     mark_strong_code_roots(worker_i);
5165     mark_strong_code_roots_ms = (os::elapsedTime() - mark_strong_roots_start) * 1000.0;
5166   }
5167   g1_policy()->phase_times()->record_strong_code_root_mark_time(worker_i, mark_strong_code_roots_ms);
5168 
5169   // Now scan the complement of the collection set.
5170   CodeBlobToOopClosure eager_scan_code_roots(scan_non_heap_roots, true /* do_marking */);
5171   g1_rem_set()->oops_into_collection_set_do(scan_rs, &eager_scan_code_roots, worker_i);
5172 
5173   _process_strong_tasks->all_tasks_completed();
5174 }
5175 
5176 class G1StringSymbolTableUnlinkTask : public AbstractGangTask {
5177 private:
5178   BoolObjectClosure* _is_alive;
5179   int _initial_string_table_size;
5180   int _initial_symbol_table_size;
5181 
5182   bool  _process_strings;
5183   int _strings_processed;
5184   int _strings_removed;
5185 
5186   bool  _process_symbols;
5187   int _symbols_processed;
5188   int _symbols_removed;
5189 
5190   bool _do_in_parallel;
5191 public:
5192   G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) :
5193     AbstractGangTask("Par String/Symbol table unlink"), _is_alive(is_alive),
5194     _do_in_parallel(G1CollectedHeap::use_parallel_gc_threads()),
5195     _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
5196     _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) {
5197 
5198     _initial_string_table_size = StringTable::the_table()->table_size();
5199     _initial_symbol_table_size = SymbolTable::the_table()->table_size();
5200     if (process_strings) {
5201       StringTable::clear_parallel_claimed_index();
5202     }
5203     if (process_symbols) {
5204       SymbolTable::clear_parallel_claimed_index();
5205     }
5206   }
5207 
5208   ~G1StringSymbolTableUnlinkTask() {
5209     guarantee(!_process_strings || !_do_in_parallel || StringTable::parallel_claimed_index() >= _initial_string_table_size,
5210               err_msg("claim value "INT32_FORMAT" after unlink less than initial string table size "INT32_FORMAT,
5211                       StringTable::parallel_claimed_index(), _initial_string_table_size));
5212     guarantee(!_process_symbols || !_do_in_parallel || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
5213               err_msg("claim value "INT32_FORMAT" after unlink less than initial symbol table size "INT32_FORMAT,
5214                       SymbolTable::parallel_claimed_index(), _initial_symbol_table_size));
5215   }
5216 
5217   void work(uint worker_id) {
5218     if (_do_in_parallel) {
5219       int strings_processed = 0;
5220       int strings_removed = 0;
5221       int symbols_processed = 0;
5222       int symbols_removed = 0;
5223       if (_process_strings) {
5224         StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
5225         Atomic::add(strings_processed, &_strings_processed);
5226         Atomic::add(strings_removed, &_strings_removed);
5227       }
5228       if (_process_symbols) {
5229         SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
5230         Atomic::add(symbols_processed, &_symbols_processed);
5231         Atomic::add(symbols_removed, &_symbols_removed);
5232       }
5233     } else {
5234       if (_process_strings) {
5235         StringTable::unlink(_is_alive, &_strings_processed, &_strings_removed);
5236       }
5237       if (_process_symbols) {
5238         SymbolTable::unlink(&_symbols_processed, &_symbols_removed);
5239       }
5240     }
5241   }
5242 
5243   size_t strings_processed() const { return (size_t)_strings_processed; }
5244   size_t strings_removed()   const { return (size_t)_strings_removed; }
5245 
5246   size_t symbols_processed() const { return (size_t)_symbols_processed; }
5247   size_t symbols_removed()   const { return (size_t)_symbols_removed; }
5248 };
5249 
5250 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive,
5251                                                      bool process_strings, bool process_symbols) {
5252   uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5253                    _g1h->workers()->active_workers() : 1);
5254 
5255   G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols);
5256   if (G1CollectedHeap::use_parallel_gc_threads()) {
5257     set_par_threads(n_workers);
5258     workers()->run_task(&g1_unlink_task);
5259     set_par_threads(0);
5260   } else {
5261     g1_unlink_task.work(0);
5262   }
5263   if (G1TraceStringSymbolTableScrubbing) {
5264     gclog_or_tty->print_cr("Cleaned string and symbol table, "
5265                            "strings: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed, "
5266                            "symbols: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed",
5267                            g1_unlink_task.strings_processed(), g1_unlink_task.strings_removed(),
5268                            g1_unlink_task.symbols_processed(), g1_unlink_task.symbols_removed());
5269   }
5270 }
5271 
5272 // Weak Reference Processing support
5273 
5274 // An always "is_alive" closure that is used to preserve referents.
5275 // If the object is non-null then it's alive.  Used in the preservation
5276 // of referent objects that are pointed to by reference objects
5277 // discovered by the CM ref processor.
5278 class G1AlwaysAliveClosure: public BoolObjectClosure {
5279   G1CollectedHeap* _g1;
5280 public:
5281   G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5282   bool do_object_b(oop p) {
5283     if (p != NULL) {
5284       return true;
5285     }
5286     return false;
5287   }
5288 };
5289 
5290 bool G1STWIsAliveClosure::do_object_b(oop p) {
5291   // An object is reachable if it is outside the collection set,
5292   // or is inside and copied.
5293   return !_g1->obj_in_cs(p) || p->is_forwarded();
5294 }
5295 
5296 // Non Copying Keep Alive closure
5297 class G1KeepAliveClosure: public OopClosure {
5298   G1CollectedHeap* _g1;
5299 public:
5300   G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5301   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
5302   void do_oop(      oop* p) {
5303     oop obj = *p;
5304 
5305     if (_g1->obj_in_cs(obj)) {
5306       assert( obj->is_forwarded(), "invariant" );
5307       *p = obj->forwardee();
5308     }
5309   }
5310 };
5311 
5312 // Copying Keep Alive closure - can be called from both
5313 // serial and parallel code as long as different worker
5314 // threads utilize different G1ParScanThreadState instances
5315 // and different queues.
5316 
5317 class G1CopyingKeepAliveClosure: public OopClosure {
5318   G1CollectedHeap*         _g1h;
5319   OopClosure*              _copy_non_heap_obj_cl;
5320   OopsInHeapRegionClosure* _copy_metadata_obj_cl;
5321   G1ParScanThreadState*    _par_scan_state;
5322 
5323 public:
5324   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
5325                             OopClosure* non_heap_obj_cl,
5326                             OopsInHeapRegionClosure* metadata_obj_cl,
5327                             G1ParScanThreadState* pss):
5328     _g1h(g1h),
5329     _copy_non_heap_obj_cl(non_heap_obj_cl),
5330     _copy_metadata_obj_cl(metadata_obj_cl),
5331     _par_scan_state(pss)
5332   {}
5333 
5334   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
5335   virtual void do_oop(      oop* p) { do_oop_work(p); }
5336 
5337   template <class T> void do_oop_work(T* p) {
5338     oop obj = oopDesc::load_decode_heap_oop(p);
5339 
5340     if (_g1h->obj_in_cs(obj)) {
5341       // If the referent object has been forwarded (either copied
5342       // to a new location or to itself in the event of an
5343       // evacuation failure) then we need to update the reference
5344       // field and, if both reference and referent are in the G1
5345       // heap, update the RSet for the referent.
5346       //
5347       // If the referent has not been forwarded then we have to keep
5348       // it alive by policy. Therefore we have copy the referent.
5349       //
5350       // If the reference field is in the G1 heap then we can push
5351       // on the PSS queue. When the queue is drained (after each
5352       // phase of reference processing) the object and it's followers
5353       // will be copied, the reference field set to point to the
5354       // new location, and the RSet updated. Otherwise we need to
5355       // use the the non-heap or metadata closures directly to copy
5356       // the referent object and update the pointer, while avoiding
5357       // updating the RSet.
5358 
5359       if (_g1h->is_in_g1_reserved(p)) {
5360         _par_scan_state->push_on_queue(p);
5361       } else {
5362         assert(!ClassLoaderDataGraph::contains((address)p),
5363                err_msg("Otherwise need to call _copy_metadata_obj_cl->do_oop(p) "
5364                               PTR_FORMAT, p));
5365           _copy_non_heap_obj_cl->do_oop(p);
5366         }
5367       }
5368     }
5369 };
5370 
5371 // Serial drain queue closure. Called as the 'complete_gc'
5372 // closure for each discovered list in some of the
5373 // reference processing phases.
5374 
5375 class G1STWDrainQueueClosure: public VoidClosure {
5376 protected:
5377   G1CollectedHeap* _g1h;
5378   G1ParScanThreadState* _par_scan_state;
5379 
5380   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
5381 
5382 public:
5383   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
5384     _g1h(g1h),
5385     _par_scan_state(pss)
5386   { }
5387 
5388   void do_void() {
5389     G1ParScanThreadState* const pss = par_scan_state();
5390     pss->trim_queue();
5391   }
5392 };
5393 
5394 // Parallel Reference Processing closures
5395 
5396 // Implementation of AbstractRefProcTaskExecutor for parallel reference
5397 // processing during G1 evacuation pauses.
5398 
5399 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5400 private:
5401   G1CollectedHeap*   _g1h;
5402   RefToScanQueueSet* _queues;
5403   FlexibleWorkGang*  _workers;
5404   int                _active_workers;
5405 
5406 public:
5407   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5408                         FlexibleWorkGang* workers,
5409                         RefToScanQueueSet *task_queues,
5410                         int n_workers) :
5411     _g1h(g1h),
5412     _queues(task_queues),
5413     _workers(workers),
5414     _active_workers(n_workers)
5415   {
5416     assert(n_workers > 0, "shouldn't call this otherwise");
5417   }
5418 
5419   // Executes the given task using concurrent marking worker threads.
5420   virtual void execute(ProcessTask& task);
5421   virtual void execute(EnqueueTask& task);
5422 };
5423 
5424 // Gang task for possibly parallel reference processing
5425 
5426 class G1STWRefProcTaskProxy: public AbstractGangTask {
5427   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5428   ProcessTask&     _proc_task;
5429   G1CollectedHeap* _g1h;
5430   RefToScanQueueSet *_task_queues;
5431   ParallelTaskTerminator* _terminator;
5432 
5433 public:
5434   G1STWRefProcTaskProxy(ProcessTask& proc_task,
5435                      G1CollectedHeap* g1h,
5436                      RefToScanQueueSet *task_queues,
5437                      ParallelTaskTerminator* terminator) :
5438     AbstractGangTask("Process reference objects in parallel"),
5439     _proc_task(proc_task),
5440     _g1h(g1h),
5441     _task_queues(task_queues),
5442     _terminator(terminator)
5443   {}
5444 
5445   virtual void work(uint worker_id) {
5446     // The reference processing task executed by a single worker.
5447     ResourceMark rm;
5448     HandleMark   hm;
5449 
5450     G1STWIsAliveClosure is_alive(_g1h);
5451 
5452     G1ParScanThreadState pss(_g1h, worker_id);
5453 
5454     G1ParScanHeapEvacClosure        scan_evac_cl(_g1h, &pss, NULL);
5455     G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5456     G1ParScanPartialArrayClosure    partial_scan_cl(_g1h, &pss, NULL);
5457 
5458     pss.set_evac_closure(&scan_evac_cl);
5459     pss.set_evac_failure_closure(&evac_failure_cl);
5460     pss.set_partial_scan_closure(&partial_scan_cl);
5461 
5462     G1ParScanExtRootClosure        only_copy_non_heap_cl(_g1h, &pss, NULL);
5463     G1ParScanMetadataClosure       only_copy_metadata_cl(_g1h, &pss, NULL);
5464 
5465     G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5466     G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(_g1h, &pss, NULL);
5467 
5468     OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5469     OopsInHeapRegionClosure*       copy_metadata_cl = &only_copy_metadata_cl;
5470 
5471     if (_g1h->g1_policy()->during_initial_mark_pause()) {
5472       // We also need to mark copied objects.
5473       copy_non_heap_cl = &copy_mark_non_heap_cl;
5474       copy_metadata_cl = &copy_mark_metadata_cl;
5475     }
5476 
5477     // Keep alive closure.
5478     G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_metadata_cl, &pss);
5479 
5480     // Complete GC closure
5481     G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5482 
5483     // Call the reference processing task's work routine.
5484     _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5485 
5486     // Note we cannot assert that the refs array is empty here as not all
5487     // of the processing tasks (specifically phase2 - pp2_work) execute
5488     // the complete_gc closure (which ordinarily would drain the queue) so
5489     // the queue may not be empty.
5490   }
5491 };
5492 
5493 // Driver routine for parallel reference processing.
5494 // Creates an instance of the ref processing gang
5495 // task and has the worker threads execute it.
5496 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5497   assert(_workers != NULL, "Need parallel worker threads.");
5498 
5499   ParallelTaskTerminator terminator(_active_workers, _queues);
5500   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5501 
5502   _g1h->set_par_threads(_active_workers);
5503   _workers->run_task(&proc_task_proxy);
5504   _g1h->set_par_threads(0);
5505 }
5506 
5507 // Gang task for parallel reference enqueueing.
5508 
5509 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5510   typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5511   EnqueueTask& _enq_task;
5512 
5513 public:
5514   G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5515     AbstractGangTask("Enqueue reference objects in parallel"),
5516     _enq_task(enq_task)
5517   { }
5518 
5519   virtual void work(uint worker_id) {
5520     _enq_task.work(worker_id);
5521   }
5522 };
5523 
5524 // Driver routine for parallel reference enqueueing.
5525 // Creates an instance of the ref enqueueing gang
5526 // task and has the worker threads execute it.
5527 
5528 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5529   assert(_workers != NULL, "Need parallel worker threads.");
5530 
5531   G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5532 
5533   _g1h->set_par_threads(_active_workers);
5534   _workers->run_task(&enq_task_proxy);
5535   _g1h->set_par_threads(0);
5536 }
5537 
5538 // End of weak reference support closures
5539 
5540 // Abstract task used to preserve (i.e. copy) any referent objects
5541 // that are in the collection set and are pointed to by reference
5542 // objects discovered by the CM ref processor.
5543 
5544 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5545 protected:
5546   G1CollectedHeap* _g1h;
5547   RefToScanQueueSet      *_queues;
5548   ParallelTaskTerminator _terminator;
5549   uint _n_workers;
5550 
5551 public:
5552   G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
5553     AbstractGangTask("ParPreserveCMReferents"),
5554     _g1h(g1h),
5555     _queues(task_queues),
5556     _terminator(workers, _queues),
5557     _n_workers(workers)
5558   { }
5559 
5560   void work(uint worker_id) {
5561     ResourceMark rm;
5562     HandleMark   hm;
5563 
5564     G1ParScanThreadState            pss(_g1h, worker_id);
5565     G1ParScanHeapEvacClosure        scan_evac_cl(_g1h, &pss, NULL);
5566     G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5567     G1ParScanPartialArrayClosure    partial_scan_cl(_g1h, &pss, NULL);
5568 
5569     pss.set_evac_closure(&scan_evac_cl);
5570     pss.set_evac_failure_closure(&evac_failure_cl);
5571     pss.set_partial_scan_closure(&partial_scan_cl);
5572 
5573     assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5574 
5575 
5576     G1ParScanExtRootClosure        only_copy_non_heap_cl(_g1h, &pss, NULL);
5577     G1ParScanMetadataClosure       only_copy_metadata_cl(_g1h, &pss, NULL);
5578 
5579     G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5580     G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(_g1h, &pss, NULL);
5581 
5582     OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5583     OopsInHeapRegionClosure*       copy_metadata_cl = &only_copy_metadata_cl;
5584 
5585     if (_g1h->g1_policy()->during_initial_mark_pause()) {
5586       // We also need to mark copied objects.
5587       copy_non_heap_cl = &copy_mark_non_heap_cl;
5588       copy_metadata_cl = &copy_mark_metadata_cl;
5589     }
5590 
5591     // Is alive closure
5592     G1AlwaysAliveClosure always_alive(_g1h);
5593 
5594     // Copying keep alive closure. Applied to referent objects that need
5595     // to be copied.
5596     G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_metadata_cl, &pss);
5597 
5598     ReferenceProcessor* rp = _g1h->ref_processor_cm();
5599 
5600     uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5601     uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5602 
5603     // limit is set using max_num_q() - which was set using ParallelGCThreads.
5604     // So this must be true - but assert just in case someone decides to
5605     // change the worker ids.
5606     assert(0 <= worker_id && worker_id < limit, "sanity");
5607     assert(!rp->discovery_is_atomic(), "check this code");
5608 
5609     // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5610     for (uint idx = worker_id; idx < limit; idx += stride) {
5611       DiscoveredList& ref_list = rp->discovered_refs()[idx];
5612 
5613       DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5614       while (iter.has_next()) {
5615         // Since discovery is not atomic for the CM ref processor, we
5616         // can see some null referent objects.
5617         iter.load_ptrs(DEBUG_ONLY(true));
5618         oop ref = iter.obj();
5619 
5620         // This will filter nulls.
5621         if (iter.is_referent_alive()) {
5622           iter.make_referent_alive();
5623         }
5624         iter.move_to_next();
5625       }
5626     }
5627 
5628     // Drain the queue - which may cause stealing
5629     G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5630     drain_queue.do_void();
5631     // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5632     assert(pss.refs()->is_empty(), "should be");
5633   }
5634 };
5635 
5636 // Weak Reference processing during an evacuation pause (part 1).
5637 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) {
5638   double ref_proc_start = os::elapsedTime();
5639 
5640   ReferenceProcessor* rp = _ref_processor_stw;
5641   assert(rp->discovery_enabled(), "should have been enabled");
5642 
5643   // Any reference objects, in the collection set, that were 'discovered'
5644   // by the CM ref processor should have already been copied (either by
5645   // applying the external root copy closure to the discovered lists, or
5646   // by following an RSet entry).
5647   //
5648   // But some of the referents, that are in the collection set, that these
5649   // reference objects point to may not have been copied: the STW ref
5650   // processor would have seen that the reference object had already
5651   // been 'discovered' and would have skipped discovering the reference,
5652   // but would not have treated the reference object as a regular oop.
5653   // As a result the copy closure would not have been applied to the
5654   // referent object.
5655   //
5656   // We need to explicitly copy these referent objects - the references
5657   // will be processed at the end of remarking.
5658   //
5659   // We also need to do this copying before we process the reference
5660   // objects discovered by the STW ref processor in case one of these
5661   // referents points to another object which is also referenced by an
5662   // object discovered by the STW ref processor.
5663 
5664   assert(!G1CollectedHeap::use_parallel_gc_threads() ||
5665            no_of_gc_workers == workers()->active_workers(),
5666            "Need to reset active GC workers");
5667 
5668   set_par_threads(no_of_gc_workers);
5669   G1ParPreserveCMReferentsTask keep_cm_referents(this,
5670                                                  no_of_gc_workers,
5671                                                  _task_queues);
5672 
5673   if (G1CollectedHeap::use_parallel_gc_threads()) {
5674     workers()->run_task(&keep_cm_referents);
5675   } else {
5676     keep_cm_referents.work(0);
5677   }
5678 
5679   set_par_threads(0);
5680 
5681   // Closure to test whether a referent is alive.
5682   G1STWIsAliveClosure is_alive(this);
5683 
5684   // Even when parallel reference processing is enabled, the processing
5685   // of JNI refs is serial and performed serially by the current thread
5686   // rather than by a worker. The following PSS will be used for processing
5687   // JNI refs.
5688 
5689   // Use only a single queue for this PSS.
5690   G1ParScanThreadState pss(this, 0);
5691 
5692   // We do not embed a reference processor in the copying/scanning
5693   // closures while we're actually processing the discovered
5694   // reference objects.
5695   G1ParScanHeapEvacClosure        scan_evac_cl(this, &pss, NULL);
5696   G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5697   G1ParScanPartialArrayClosure    partial_scan_cl(this, &pss, NULL);
5698 
5699   pss.set_evac_closure(&scan_evac_cl);
5700   pss.set_evac_failure_closure(&evac_failure_cl);
5701   pss.set_partial_scan_closure(&partial_scan_cl);
5702 
5703   assert(pss.refs()->is_empty(), "pre-condition");
5704 
5705   G1ParScanExtRootClosure        only_copy_non_heap_cl(this, &pss, NULL);
5706   G1ParScanMetadataClosure       only_copy_metadata_cl(this, &pss, NULL);
5707 
5708   G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5709   G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(this, &pss, NULL);
5710 
5711   OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5712   OopsInHeapRegionClosure*       copy_metadata_cl = &only_copy_metadata_cl;
5713 
5714   if (_g1h->g1_policy()->during_initial_mark_pause()) {
5715     // We also need to mark copied objects.
5716     copy_non_heap_cl = &copy_mark_non_heap_cl;
5717     copy_metadata_cl = &copy_mark_metadata_cl;
5718   }
5719 
5720   // Keep alive closure.
5721   G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, copy_metadata_cl, &pss);
5722 
5723   // Serial Complete GC closure
5724   G1STWDrainQueueClosure drain_queue(this, &pss);
5725 
5726   // Setup the soft refs policy...
5727   rp->setup_policy(false);
5728 
5729   ReferenceProcessorStats stats;
5730   if (!rp->processing_is_mt()) {
5731     // Serial reference processing...
5732     stats = rp->process_discovered_references(&is_alive,
5733                                               &keep_alive,
5734                                               &drain_queue,
5735                                               NULL,
5736                                               _gc_timer_stw);
5737   } else {
5738     // Parallel reference processing
5739     assert(rp->num_q() == no_of_gc_workers, "sanity");
5740     assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5741 
5742     G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5743     stats = rp->process_discovered_references(&is_alive,
5744                                               &keep_alive,
5745                                               &drain_queue,
5746                                               &par_task_executor,
5747                                               _gc_timer_stw);
5748   }
5749 
5750   _gc_tracer_stw->report_gc_reference_stats(stats);
5751   // We have completed copying any necessary live referent objects
5752   // (that were not copied during the actual pause) so we can
5753   // retire any active alloc buffers
5754   pss.retire_alloc_buffers();
5755   assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5756 
5757   double ref_proc_time = os::elapsedTime() - ref_proc_start;
5758   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5759 }
5760 
5761 // Weak Reference processing during an evacuation pause (part 2).
5762 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) {
5763   double ref_enq_start = os::elapsedTime();
5764 
5765   ReferenceProcessor* rp = _ref_processor_stw;
5766   assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5767 
5768   // Now enqueue any remaining on the discovered lists on to
5769   // the pending list.
5770   if (!rp->processing_is_mt()) {
5771     // Serial reference processing...
5772     rp->enqueue_discovered_references();
5773   } else {
5774     // Parallel reference enqueueing
5775 
5776     assert(no_of_gc_workers == workers()->active_workers(),
5777            "Need to reset active workers");
5778     assert(rp->num_q() == no_of_gc_workers, "sanity");
5779     assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5780 
5781     G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5782     rp->enqueue_discovered_references(&par_task_executor);
5783   }
5784 
5785   rp->verify_no_references_recorded();
5786   assert(!rp->discovery_enabled(), "should have been disabled");
5787 
5788   // FIXME
5789   // CM's reference processing also cleans up the string and symbol tables.
5790   // Should we do that here also? We could, but it is a serial operation
5791   // and could significantly increase the pause time.
5792 
5793   double ref_enq_time = os::elapsedTime() - ref_enq_start;
5794   g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5795 }
5796 
5797 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) {
5798   _expand_heap_after_alloc_failure = true;
5799   _evacuation_failed = false;
5800 
5801   // Should G1EvacuationFailureALot be in effect for this GC?
5802   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
5803 
5804   g1_rem_set()->prepare_for_oops_into_collection_set_do();
5805 
5806   // Disable the hot card cache.
5807   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
5808   hot_card_cache->reset_hot_cache_claimed_index();
5809   hot_card_cache->set_use_cache(false);
5810 
5811   uint n_workers;
5812   if (G1CollectedHeap::use_parallel_gc_threads()) {
5813     n_workers =
5814       AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
5815                                      workers()->active_workers(),
5816                                      Threads::number_of_non_daemon_threads());
5817     assert(UseDynamicNumberOfGCThreads ||
5818            n_workers == workers()->total_workers(),
5819            "If not dynamic should be using all the  workers");
5820     workers()->set_active_workers(n_workers);
5821     set_par_threads(n_workers);
5822   } else {
5823     assert(n_par_threads() == 0,
5824            "Should be the original non-parallel value");
5825     n_workers = 1;
5826   }
5827 
5828   G1ParTask g1_par_task(this, _task_queues);
5829 
5830   init_for_evac_failure(NULL);
5831 
5832   rem_set()->prepare_for_younger_refs_iterate(true);
5833 
5834   assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5835   double start_par_time_sec = os::elapsedTime();
5836   double end_par_time_sec;
5837 
5838   {
5839     StrongRootsScope srs(this);
5840 
5841     if (G1CollectedHeap::use_parallel_gc_threads()) {
5842       // The individual threads will set their evac-failure closures.
5843       if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
5844       // These tasks use ShareHeap::_process_strong_tasks
5845       assert(UseDynamicNumberOfGCThreads ||
5846              workers()->active_workers() == workers()->total_workers(),
5847              "If not dynamic should be using all the  workers");
5848       workers()->run_task(&g1_par_task);
5849     } else {
5850       g1_par_task.set_for_termination(n_workers);
5851       g1_par_task.work(0);
5852     }
5853     end_par_time_sec = os::elapsedTime();
5854 
5855     // Closing the inner scope will execute the destructor
5856     // for the StrongRootsScope object. We record the current
5857     // elapsed time before closing the scope so that time
5858     // taken for the SRS destructor is NOT included in the
5859     // reported parallel time.
5860   }
5861 
5862   double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5863   g1_policy()->phase_times()->record_par_time(par_time_ms);
5864 
5865   double code_root_fixup_time_ms =
5866         (os::elapsedTime() - end_par_time_sec) * 1000.0;
5867   g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms);
5868 
5869   set_par_threads(0);
5870 
5871   // Process any discovered reference objects - we have
5872   // to do this _before_ we retire the GC alloc regions
5873   // as we may have to copy some 'reachable' referent
5874   // objects (and their reachable sub-graphs) that were
5875   // not copied during the pause.
5876   process_discovered_references(n_workers);
5877 
5878   // Weak root processing.
5879   {
5880     G1STWIsAliveClosure is_alive(this);
5881     G1KeepAliveClosure keep_alive(this);
5882     JNIHandles::weak_oops_do(&is_alive, &keep_alive);
5883   }
5884 
5885   release_gc_alloc_regions(n_workers, evacuation_info);
5886   g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5887 
5888   // Reset and re-enable the hot card cache.
5889   // Note the counts for the cards in the regions in the
5890   // collection set are reset when the collection set is freed.
5891   hot_card_cache->reset_hot_cache();
5892   hot_card_cache->set_use_cache(true);
5893 
5894   // Migrate the strong code roots attached to each region in
5895   // the collection set. Ideally we would like to do this
5896   // after we have finished the scanning/evacuation of the
5897   // strong code roots for a particular heap region.
5898   migrate_strong_code_roots();
5899 
5900   if (g1_policy()->during_initial_mark_pause()) {
5901     // Reset the claim values set during marking the strong code roots
5902     reset_heap_region_claim_values();
5903   }
5904 
5905   finalize_for_evac_failure();
5906 
5907   if (evacuation_failed()) {
5908     remove_self_forwarding_pointers();
5909 
5910     // Reset the G1EvacuationFailureALot counters and flags
5911     // Note: the values are reset only when an actual
5912     // evacuation failure occurs.
5913     NOT_PRODUCT(reset_evacuation_should_fail();)
5914   }
5915 
5916   // Enqueue any remaining references remaining on the STW
5917   // reference processor's discovered lists. We need to do
5918   // this after the card table is cleaned (and verified) as
5919   // the act of enqueueing entries on to the pending list
5920   // will log these updates (and dirty their associated
5921   // cards). We need these updates logged to update any
5922   // RSets.
5923   enqueue_discovered_references(n_workers);
5924 
5925   if (G1DeferredRSUpdate) {
5926     RedirtyLoggedCardTableEntryFastClosure redirty;
5927     dirty_card_queue_set().set_closure(&redirty);
5928     dirty_card_queue_set().apply_closure_to_all_completed_buffers();
5929 
5930     DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5931     dcq.merge_bufferlists(&dirty_card_queue_set());
5932     assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5933   }
5934   COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5935 }
5936 
5937 void G1CollectedHeap::free_region_if_empty(HeapRegion* hr,
5938                                      size_t* pre_used,
5939                                      FreeRegionList* free_list,
5940                                      OldRegionSet* old_proxy_set,
5941                                      HumongousRegionSet* humongous_proxy_set,
5942                                      HRRSCleanupTask* hrrs_cleanup_task,
5943                                      bool par) {
5944   if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) {
5945     if (hr->isHumongous()) {
5946       assert(hr->startsHumongous(), "we should only see starts humongous");
5947       free_humongous_region(hr, pre_used, free_list, humongous_proxy_set, par);
5948     } else {
5949       _old_set.remove_with_proxy(hr, old_proxy_set);
5950       free_region(hr, pre_used, free_list, par);
5951     }
5952   } else {
5953     hr->rem_set()->do_cleanup_work(hrrs_cleanup_task);
5954   }
5955 }
5956 
5957 void G1CollectedHeap::free_region(HeapRegion* hr,
5958                                   size_t* pre_used,
5959                                   FreeRegionList* free_list,
5960                                   bool par) {
5961   assert(!hr->isHumongous(), "this is only for non-humongous regions");
5962   assert(!hr->is_empty(), "the region should not be empty");
5963   assert(free_list != NULL, "pre-condition");
5964 
5965   // Clear the card counts for this region.
5966   // Note: we only need to do this if the region is not young
5967   // (since we don't refine cards in young regions).
5968   if (!hr->is_young()) {
5969     _cg1r->hot_card_cache()->reset_card_counts(hr);
5970   }
5971   *pre_used += hr->used();
5972   hr->hr_clear(par, true /* clear_space */);
5973   free_list->add_as_head(hr);
5974 }
5975 
5976 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
5977                                      size_t* pre_used,
5978                                      FreeRegionList* free_list,
5979                                      HumongousRegionSet* humongous_proxy_set,
5980                                      bool par) {
5981   assert(hr->startsHumongous(), "this is only for starts humongous regions");
5982   assert(free_list != NULL, "pre-condition");
5983   assert(humongous_proxy_set != NULL, "pre-condition");
5984 
5985   size_t hr_used = hr->used();
5986   size_t hr_capacity = hr->capacity();
5987   size_t hr_pre_used = 0;
5988   _humongous_set.remove_with_proxy(hr, humongous_proxy_set);
5989   // We need to read this before we make the region non-humongous,
5990   // otherwise the information will be gone.
5991   uint last_index = hr->last_hc_index();
5992   hr->set_notHumongous();
5993   free_region(hr, &hr_pre_used, free_list, par);
5994 
5995   uint i = hr->hrs_index() + 1;
5996   while (i < last_index) {
5997     HeapRegion* curr_hr = region_at(i);
5998     assert(curr_hr->continuesHumongous(), "invariant");
5999     curr_hr->set_notHumongous();
6000     free_region(curr_hr, &hr_pre_used, free_list, par);
6001     i += 1;
6002   }
6003   assert(hr_pre_used == hr_used,
6004          err_msg("hr_pre_used: "SIZE_FORMAT" and hr_used: "SIZE_FORMAT" "
6005                  "should be the same", hr_pre_used, hr_used));
6006   *pre_used += hr_pre_used;
6007 }
6008 
6009 void G1CollectedHeap::update_sets_after_freeing_regions(size_t pre_used,
6010                                        FreeRegionList* free_list,
6011                                        OldRegionSet* old_proxy_set,
6012                                        HumongousRegionSet* humongous_proxy_set,
6013                                        bool par) {
6014   if (pre_used > 0) {
6015     Mutex* lock = (par) ? ParGCRareEvent_lock : NULL;
6016     MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag);
6017     assert(_summary_bytes_used >= pre_used,
6018            err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" "
6019                    "should be >= pre_used: "SIZE_FORMAT,
6020                    _summary_bytes_used, pre_used));
6021     _summary_bytes_used -= pre_used;
6022   }
6023   if (free_list != NULL && !free_list->is_empty()) {
6024     MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
6025     _free_list.add_as_head(free_list);
6026   }
6027   if (old_proxy_set != NULL && !old_proxy_set->is_empty()) {
6028     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
6029     _old_set.update_from_proxy(old_proxy_set);
6030   }
6031   if (humongous_proxy_set != NULL && !humongous_proxy_set->is_empty()) {
6032     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
6033     _humongous_set.update_from_proxy(humongous_proxy_set);
6034   }
6035 }
6036 
6037 class G1ParCleanupCTTask : public AbstractGangTask {
6038   G1SATBCardTableModRefBS* _ct_bs;
6039   G1CollectedHeap* _g1h;
6040   HeapRegion* volatile _su_head;
6041 public:
6042   G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs,
6043                      G1CollectedHeap* g1h) :
6044     AbstractGangTask("G1 Par Cleanup CT Task"),
6045     _ct_bs(ct_bs), _g1h(g1h) { }
6046 
6047   void work(uint worker_id) {
6048     HeapRegion* r;
6049     while (r = _g1h->pop_dirty_cards_region()) {
6050       clear_cards(r);
6051     }
6052   }
6053 
6054   void clear_cards(HeapRegion* r) {
6055     // Cards of the survivors should have already been dirtied.
6056     if (!r->is_survivor()) {
6057       _ct_bs->clear(MemRegion(r->bottom(), r->end()));
6058     }
6059   }
6060 };
6061 
6062 #ifndef PRODUCT
6063 class G1VerifyCardTableCleanup: public HeapRegionClosure {
6064   G1CollectedHeap* _g1h;
6065   G1SATBCardTableModRefBS* _ct_bs;
6066 public:
6067   G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs)
6068     : _g1h(g1h), _ct_bs(ct_bs) { }
6069   virtual bool doHeapRegion(HeapRegion* r) {
6070     if (r->is_survivor()) {
6071       _g1h->verify_dirty_region(r);
6072     } else {
6073       _g1h->verify_not_dirty_region(r);
6074     }
6075     return false;
6076   }
6077 };
6078 
6079 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
6080   // All of the region should be clean.
6081   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6082   MemRegion mr(hr->bottom(), hr->end());
6083   ct_bs->verify_not_dirty_region(mr);
6084 }
6085 
6086 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
6087   // We cannot guarantee that [bottom(),end()] is dirty.  Threads
6088   // dirty allocated blocks as they allocate them. The thread that
6089   // retires each region and replaces it with a new one will do a
6090   // maximal allocation to fill in [pre_dummy_top(),end()] but will
6091   // not dirty that area (one less thing to have to do while holding
6092   // a lock). So we can only verify that [bottom(),pre_dummy_top()]
6093   // is dirty.
6094   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6095   MemRegion mr(hr->bottom(), hr->pre_dummy_top());
6096   if (hr->is_young()) {
6097     ct_bs->verify_g1_young_region(mr);
6098   } else {
6099     ct_bs->verify_dirty_region(mr);
6100   }
6101 }
6102 
6103 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
6104   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6105   for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
6106     verify_dirty_region(hr);
6107   }
6108 }
6109 
6110 void G1CollectedHeap::verify_dirty_young_regions() {
6111   verify_dirty_young_list(_young_list->first_region());
6112 }
6113 #endif
6114 
6115 void G1CollectedHeap::cleanUpCardTable() {
6116   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6117   double start = os::elapsedTime();
6118 
6119   {
6120     // Iterate over the dirty cards region list.
6121     G1ParCleanupCTTask cleanup_task(ct_bs, this);
6122 
6123     if (G1CollectedHeap::use_parallel_gc_threads()) {
6124       set_par_threads();
6125       workers()->run_task(&cleanup_task);
6126       set_par_threads(0);
6127     } else {
6128       while (_dirty_cards_region_list) {
6129         HeapRegion* r = _dirty_cards_region_list;
6130         cleanup_task.clear_cards(r);
6131         _dirty_cards_region_list = r->get_next_dirty_cards_region();
6132         if (_dirty_cards_region_list == r) {
6133           // The last region.
6134           _dirty_cards_region_list = NULL;
6135         }
6136         r->set_next_dirty_cards_region(NULL);
6137       }
6138     }
6139 #ifndef PRODUCT
6140     if (G1VerifyCTCleanup || VerifyAfterGC) {
6141       G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
6142       heap_region_iterate(&cleanup_verifier);
6143     }
6144 #endif
6145   }
6146 
6147   double elapsed = os::elapsedTime() - start;
6148   g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
6149 }
6150 
6151 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) {
6152   size_t pre_used = 0;
6153   FreeRegionList local_free_list("Local List for CSet Freeing");
6154 
6155   double young_time_ms     = 0.0;
6156   double non_young_time_ms = 0.0;
6157 
6158   // Since the collection set is a superset of the the young list,
6159   // all we need to do to clear the young list is clear its
6160   // head and length, and unlink any young regions in the code below
6161   _young_list->clear();
6162 
6163   G1CollectorPolicy* policy = g1_policy();
6164 
6165   double start_sec = os::elapsedTime();
6166   bool non_young = true;
6167 
6168   HeapRegion* cur = cs_head;
6169   int age_bound = -1;
6170   size_t rs_lengths = 0;
6171 
6172   while (cur != NULL) {
6173     assert(!is_on_master_free_list(cur), "sanity");
6174     if (non_young) {
6175       if (cur->is_young()) {
6176         double end_sec = os::elapsedTime();
6177         double elapsed_ms = (end_sec - start_sec) * 1000.0;
6178         non_young_time_ms += elapsed_ms;
6179 
6180         start_sec = os::elapsedTime();
6181         non_young = false;
6182       }
6183     } else {
6184       if (!cur->is_young()) {
6185         double end_sec = os::elapsedTime();
6186         double elapsed_ms = (end_sec - start_sec) * 1000.0;
6187         young_time_ms += elapsed_ms;
6188 
6189         start_sec = os::elapsedTime();
6190         non_young = true;
6191       }
6192     }
6193 
6194     rs_lengths += cur->rem_set()->occupied();
6195 
6196     HeapRegion* next = cur->next_in_collection_set();
6197     assert(cur->in_collection_set(), "bad CS");
6198     cur->set_next_in_collection_set(NULL);
6199     cur->set_in_collection_set(false);
6200 
6201     if (cur->is_young()) {
6202       int index = cur->young_index_in_cset();
6203       assert(index != -1, "invariant");
6204       assert((uint) index < policy->young_cset_region_length(), "invariant");
6205       size_t words_survived = _surviving_young_words[index];
6206       cur->record_surv_words_in_group(words_survived);
6207 
6208       // At this point the we have 'popped' cur from the collection set
6209       // (linked via next_in_collection_set()) but it is still in the
6210       // young list (linked via next_young_region()). Clear the
6211       // _next_young_region field.
6212       cur->set_next_young_region(NULL);
6213     } else {
6214       int index = cur->young_index_in_cset();
6215       assert(index == -1, "invariant");
6216     }
6217 
6218     assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
6219             (!cur->is_young() && cur->young_index_in_cset() == -1),
6220             "invariant" );
6221 
6222     if (!cur->evacuation_failed()) {
6223       MemRegion used_mr = cur->used_region();
6224 
6225       // And the region is empty.
6226       assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
6227       free_region(cur, &pre_used, &local_free_list, false /* par */);
6228     } else {
6229       cur->uninstall_surv_rate_group();
6230       if (cur->is_young()) {
6231         cur->set_young_index_in_cset(-1);
6232       }
6233       cur->set_not_young();
6234       cur->set_evacuation_failed(false);
6235       // The region is now considered to be old.
6236       _old_set.add(cur);
6237       evacuation_info.increment_collectionset_used_after(cur->used());
6238     }
6239     cur = next;
6240   }
6241 
6242   evacuation_info.set_regions_freed(local_free_list.length());
6243   policy->record_max_rs_lengths(rs_lengths);
6244   policy->cset_regions_freed();
6245 
6246   double end_sec = os::elapsedTime();
6247   double elapsed_ms = (end_sec - start_sec) * 1000.0;
6248 
6249   if (non_young) {
6250     non_young_time_ms += elapsed_ms;
6251   } else {
6252     young_time_ms += elapsed_ms;
6253   }
6254 
6255   update_sets_after_freeing_regions(pre_used, &local_free_list,
6256                                     NULL /* old_proxy_set */,
6257                                     NULL /* humongous_proxy_set */,
6258                                     false /* par */);
6259   policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
6260   policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
6261 }
6262 
6263 // This routine is similar to the above but does not record
6264 // any policy statistics or update free lists; we are abandoning
6265 // the current incremental collection set in preparation of a
6266 // full collection. After the full GC we will start to build up
6267 // the incremental collection set again.
6268 // This is only called when we're doing a full collection
6269 // and is immediately followed by the tearing down of the young list.
6270 
6271 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
6272   HeapRegion* cur = cs_head;
6273 
6274   while (cur != NULL) {
6275     HeapRegion* next = cur->next_in_collection_set();
6276     assert(cur->in_collection_set(), "bad CS");
6277     cur->set_next_in_collection_set(NULL);
6278     cur->set_in_collection_set(false);
6279     cur->set_young_index_in_cset(-1);
6280     cur = next;
6281   }
6282 }
6283 
6284 void G1CollectedHeap::set_free_regions_coming() {
6285   if (G1ConcRegionFreeingVerbose) {
6286     gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6287                            "setting free regions coming");
6288   }
6289 
6290   assert(!free_regions_coming(), "pre-condition");
6291   _free_regions_coming = true;
6292 }
6293 
6294 void G1CollectedHeap::reset_free_regions_coming() {
6295   assert(free_regions_coming(), "pre-condition");
6296 
6297   {
6298     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6299     _free_regions_coming = false;
6300     SecondaryFreeList_lock->notify_all();
6301   }
6302 
6303   if (G1ConcRegionFreeingVerbose) {
6304     gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6305                            "reset free regions coming");
6306   }
6307 }
6308 
6309 void G1CollectedHeap::wait_while_free_regions_coming() {
6310   // Most of the time we won't have to wait, so let's do a quick test
6311   // first before we take the lock.
6312   if (!free_regions_coming()) {
6313     return;
6314   }
6315 
6316   if (G1ConcRegionFreeingVerbose) {
6317     gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6318                            "waiting for free regions");
6319   }
6320 
6321   {
6322     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6323     while (free_regions_coming()) {
6324       SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
6325     }
6326   }
6327 
6328   if (G1ConcRegionFreeingVerbose) {
6329     gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6330                            "done waiting for free regions");
6331   }
6332 }
6333 
6334 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
6335   assert(heap_lock_held_for_gc(),
6336               "the heap lock should already be held by or for this thread");
6337   _young_list->push_region(hr);
6338 }
6339 
6340 class NoYoungRegionsClosure: public HeapRegionClosure {
6341 private:
6342   bool _success;
6343 public:
6344   NoYoungRegionsClosure() : _success(true) { }
6345   bool doHeapRegion(HeapRegion* r) {
6346     if (r->is_young()) {
6347       gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
6348                              r->bottom(), r->end());
6349       _success = false;
6350     }
6351     return false;
6352   }
6353   bool success() { return _success; }
6354 };
6355 
6356 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
6357   bool ret = _young_list->check_list_empty(check_sample);
6358 
6359   if (check_heap) {
6360     NoYoungRegionsClosure closure;
6361     heap_region_iterate(&closure);
6362     ret = ret && closure.success();
6363   }
6364 
6365   return ret;
6366 }
6367 
6368 class TearDownRegionSetsClosure : public HeapRegionClosure {
6369 private:
6370   OldRegionSet *_old_set;
6371 
6372 public:
6373   TearDownRegionSetsClosure(OldRegionSet* old_set) : _old_set(old_set) { }
6374 
6375   bool doHeapRegion(HeapRegion* r) {
6376     if (r->is_empty()) {
6377       // We ignore empty regions, we'll empty the free list afterwards
6378     } else if (r->is_young()) {
6379       // We ignore young regions, we'll empty the young list afterwards
6380     } else if (r->isHumongous()) {
6381       // We ignore humongous regions, we're not tearing down the
6382       // humongous region set
6383     } else {
6384       // The rest should be old
6385       _old_set->remove(r);
6386     }
6387     return false;
6388   }
6389 
6390   ~TearDownRegionSetsClosure() {
6391     assert(_old_set->is_empty(), "post-condition");
6392   }
6393 };
6394 
6395 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6396   assert_at_safepoint(true /* should_be_vm_thread */);
6397 
6398   if (!free_list_only) {
6399     TearDownRegionSetsClosure cl(&_old_set);
6400     heap_region_iterate(&cl);
6401 
6402     // Need to do this after the heap iteration to be able to
6403     // recognize the young regions and ignore them during the iteration.
6404     _young_list->empty_list();
6405   }
6406   _free_list.remove_all();
6407 }
6408 
6409 class RebuildRegionSetsClosure : public HeapRegionClosure {
6410 private:
6411   bool            _free_list_only;
6412   OldRegionSet*   _old_set;
6413   FreeRegionList* _free_list;
6414   size_t          _total_used;
6415 
6416 public:
6417   RebuildRegionSetsClosure(bool free_list_only,
6418                            OldRegionSet* old_set, FreeRegionList* free_list) :
6419     _free_list_only(free_list_only),
6420     _old_set(old_set), _free_list(free_list), _total_used(0) {
6421     assert(_free_list->is_empty(), "pre-condition");
6422     if (!free_list_only) {
6423       assert(_old_set->is_empty(), "pre-condition");
6424     }
6425   }
6426 
6427   bool doHeapRegion(HeapRegion* r) {
6428     if (r->continuesHumongous()) {
6429       return false;
6430     }
6431 
6432     if (r->is_empty()) {
6433       // Add free regions to the free list
6434       _free_list->add_as_tail(r);
6435     } else if (!_free_list_only) {
6436       assert(!r->is_young(), "we should not come across young regions");
6437 
6438       if (r->isHumongous()) {
6439         // We ignore humongous regions, we left the humongous set unchanged
6440       } else {
6441         // The rest should be old, add them to the old set
6442         _old_set->add(r);
6443       }
6444       _total_used += r->used();
6445     }
6446 
6447     return false;
6448   }
6449 
6450   size_t total_used() {
6451     return _total_used;
6452   }
6453 };
6454 
6455 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6456   assert_at_safepoint(true /* should_be_vm_thread */);
6457 
6458   RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_free_list);
6459   heap_region_iterate(&cl);
6460 
6461   if (!free_list_only) {
6462     _summary_bytes_used = cl.total_used();
6463   }
6464   assert(_summary_bytes_used == recalculate_used(),
6465          err_msg("inconsistent _summary_bytes_used, "
6466                  "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6467                  _summary_bytes_used, recalculate_used()));
6468 }
6469 
6470 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6471   _refine_cte_cl->set_concurrent(concurrent);
6472 }
6473 
6474 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6475   HeapRegion* hr = heap_region_containing(p);
6476   if (hr == NULL) {
6477     return false;
6478   } else {
6479     return hr->is_in(p);
6480   }
6481 }
6482 
6483 // Methods for the mutator alloc region
6484 
6485 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6486                                                       bool force) {
6487   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6488   assert(!force || g1_policy()->can_expand_young_list(),
6489          "if force is true we should be able to expand the young list");
6490   bool young_list_full = g1_policy()->is_young_list_full();
6491   if (force || !young_list_full) {
6492     HeapRegion* new_alloc_region = new_region(word_size,
6493                                               false /* do_expand */);
6494     if (new_alloc_region != NULL) {
6495       set_region_short_lived_locked(new_alloc_region);
6496       _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6497       return new_alloc_region;
6498     }
6499   }
6500   return NULL;
6501 }
6502 
6503 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6504                                                   size_t allocated_bytes) {
6505   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6506   assert(alloc_region->is_young(), "all mutator alloc regions should be young");
6507 
6508   g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6509   _summary_bytes_used += allocated_bytes;
6510   _hr_printer.retire(alloc_region);
6511   // We update the eden sizes here, when the region is retired,
6512   // instead of when it's allocated, since this is the point that its
6513   // used space has been recored in _summary_bytes_used.
6514   g1mm()->update_eden_size();
6515 }
6516 
6517 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
6518                                                     bool force) {
6519   return _g1h->new_mutator_alloc_region(word_size, force);
6520 }
6521 
6522 void G1CollectedHeap::set_par_threads() {
6523   // Don't change the number of workers.  Use the value previously set
6524   // in the workgroup.
6525   assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise");
6526   uint n_workers = workers()->active_workers();
6527   assert(UseDynamicNumberOfGCThreads ||
6528            n_workers == workers()->total_workers(),
6529       "Otherwise should be using the total number of workers");
6530   if (n_workers == 0) {
6531     assert(false, "Should have been set in prior evacuation pause.");
6532     n_workers = ParallelGCThreads;
6533     workers()->set_active_workers(n_workers);
6534   }
6535   set_par_threads(n_workers);
6536 }
6537 
6538 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
6539                                        size_t allocated_bytes) {
6540   _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
6541 }
6542 
6543 // Methods for the GC alloc regions
6544 
6545 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6546                                                  uint count,
6547                                                  GCAllocPurpose ap) {
6548   assert(FreeList_lock->owned_by_self(), "pre-condition");
6549 
6550   if (count < g1_policy()->max_regions(ap)) {
6551     HeapRegion* new_alloc_region = new_region(word_size,
6552                                               true /* do_expand */);
6553     if (new_alloc_region != NULL) {
6554       // We really only need to do this for old regions given that we
6555       // should never scan survivors. But it doesn't hurt to do it
6556       // for survivors too.
6557       new_alloc_region->set_saved_mark();
6558       if (ap == GCAllocForSurvived) {
6559         new_alloc_region->set_survivor();
6560         _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6561       } else {
6562         _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6563       }
6564       bool during_im = g1_policy()->during_initial_mark_pause();
6565       new_alloc_region->note_start_of_copying(during_im);
6566       return new_alloc_region;
6567     } else {
6568       g1_policy()->note_alloc_region_limit_reached(ap);
6569     }
6570   }
6571   return NULL;
6572 }
6573 
6574 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6575                                              size_t allocated_bytes,
6576                                              GCAllocPurpose ap) {
6577   bool during_im = g1_policy()->during_initial_mark_pause();
6578   alloc_region->note_end_of_copying(during_im);
6579   g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6580   if (ap == GCAllocForSurvived) {
6581     young_list()->add_survivor_region(alloc_region);
6582   } else {
6583     _old_set.add(alloc_region);
6584   }
6585   _hr_printer.retire(alloc_region);
6586 }
6587 
6588 HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size,
6589                                                        bool force) {
6590   assert(!force, "not supported for GC alloc regions");
6591   return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForSurvived);
6592 }
6593 
6594 void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region,
6595                                           size_t allocated_bytes) {
6596   _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6597                                GCAllocForSurvived);
6598 }
6599 
6600 HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size,
6601                                                   bool force) {
6602   assert(!force, "not supported for GC alloc regions");
6603   return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForTenured);
6604 }
6605 
6606 void OldGCAllocRegion::retire_region(HeapRegion* alloc_region,
6607                                      size_t allocated_bytes) {
6608   _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6609                                GCAllocForTenured);
6610 }
6611 // Heap region set verification
6612 
6613 class VerifyRegionListsClosure : public HeapRegionClosure {
6614 private:
6615   FreeRegionList*     _free_list;
6616   OldRegionSet*       _old_set;
6617   HumongousRegionSet* _humongous_set;
6618   uint                _region_count;
6619 
6620 public:
6621   VerifyRegionListsClosure(OldRegionSet* old_set,
6622                            HumongousRegionSet* humongous_set,
6623                            FreeRegionList* free_list) :
6624     _old_set(old_set), _humongous_set(humongous_set),
6625     _free_list(free_list), _region_count(0) { }
6626 
6627   uint region_count() { return _region_count; }
6628 
6629   bool doHeapRegion(HeapRegion* hr) {
6630     _region_count += 1;
6631 
6632     if (hr->continuesHumongous()) {
6633       return false;
6634     }
6635 
6636     if (hr->is_young()) {
6637       // TODO
6638     } else if (hr->startsHumongous()) {
6639       _humongous_set->verify_next_region(hr);
6640     } else if (hr->is_empty()) {
6641       _free_list->verify_next_region(hr);
6642     } else {
6643       _old_set->verify_next_region(hr);
6644     }
6645     return false;
6646   }
6647 };
6648 
6649 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
6650                                              HeapWord* bottom) {
6651   HeapWord* end = bottom + HeapRegion::GrainWords;
6652   MemRegion mr(bottom, end);
6653   assert(_g1_reserved.contains(mr), "invariant");
6654   // This might return NULL if the allocation fails
6655   return new HeapRegion(hrs_index, _bot_shared, mr);
6656 }
6657 
6658 void G1CollectedHeap::verify_region_sets() {
6659   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6660 
6661   // First, check the explicit lists.
6662   _free_list.verify();
6663   {
6664     // Given that a concurrent operation might be adding regions to
6665     // the secondary free list we have to take the lock before
6666     // verifying it.
6667     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6668     _secondary_free_list.verify();
6669   }
6670   _old_set.verify();
6671   _humongous_set.verify();
6672 
6673   // If a concurrent region freeing operation is in progress it will
6674   // be difficult to correctly attributed any free regions we come
6675   // across to the correct free list given that they might belong to
6676   // one of several (free_list, secondary_free_list, any local lists,
6677   // etc.). So, if that's the case we will skip the rest of the
6678   // verification operation. Alternatively, waiting for the concurrent
6679   // operation to complete will have a non-trivial effect on the GC's
6680   // operation (no concurrent operation will last longer than the
6681   // interval between two calls to verification) and it might hide
6682   // any issues that we would like to catch during testing.
6683   if (free_regions_coming()) {
6684     return;
6685   }
6686 
6687   // Make sure we append the secondary_free_list on the free_list so
6688   // that all free regions we will come across can be safely
6689   // attributed to the free_list.
6690   append_secondary_free_list_if_not_empty_with_lock();
6691 
6692   // Finally, make sure that the region accounting in the lists is
6693   // consistent with what we see in the heap.
6694   _old_set.verify_start();
6695   _humongous_set.verify_start();
6696   _free_list.verify_start();
6697 
6698   VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_free_list);
6699   heap_region_iterate(&cl);
6700 
6701   _old_set.verify_end();
6702   _humongous_set.verify_end();
6703   _free_list.verify_end();
6704 }
6705 
6706 // Optimized nmethod scanning
6707 
6708 class RegisterNMethodOopClosure: public OopClosure {
6709   G1CollectedHeap* _g1h;
6710   nmethod* _nm;
6711 
6712   template <class T> void do_oop_work(T* p) {
6713     T heap_oop = oopDesc::load_heap_oop(p);
6714     if (!oopDesc::is_null(heap_oop)) {
6715       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6716       HeapRegion* hr = _g1h->heap_region_containing(obj);
6717       assert(!hr->continuesHumongous(),
6718              err_msg("trying to add code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6719                      " starting at "HR_FORMAT,
6720                      _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6721 
6722       // HeapRegion::add_strong_code_root() avoids adding duplicate
6723       // entries but having duplicates is  OK since we "mark" nmethods
6724       // as visited when we scan the strong code root lists during the GC.
6725       hr->add_strong_code_root(_nm);
6726       assert(hr->rem_set()->strong_code_roots_list_contains(_nm),
6727              err_msg("failed to add code root "PTR_FORMAT" to remembered set of region "HR_FORMAT,
6728                      _nm, HR_FORMAT_PARAMS(hr)));
6729     }
6730   }
6731 
6732 public:
6733   RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6734     _g1h(g1h), _nm(nm) {}
6735 
6736   void do_oop(oop* p)       { do_oop_work(p); }
6737   void do_oop(narrowOop* p) { do_oop_work(p); }
6738 };
6739 
6740 class UnregisterNMethodOopClosure: public OopClosure {
6741   G1CollectedHeap* _g1h;
6742   nmethod* _nm;
6743 
6744   template <class T> void do_oop_work(T* p) {
6745     T heap_oop = oopDesc::load_heap_oop(p);
6746     if (!oopDesc::is_null(heap_oop)) {
6747       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6748       HeapRegion* hr = _g1h->heap_region_containing(obj);
6749       assert(!hr->continuesHumongous(),
6750              err_msg("trying to remove code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6751                      " starting at "HR_FORMAT,
6752                      _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6753 
6754       hr->remove_strong_code_root(_nm);
6755       assert(!hr->rem_set()->strong_code_roots_list_contains(_nm),
6756              err_msg("failed to remove code root "PTR_FORMAT" of region "HR_FORMAT,
6757                      _nm, HR_FORMAT_PARAMS(hr)));
6758     }
6759   }
6760 
6761 public:
6762   UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6763     _g1h(g1h), _nm(nm) {}
6764 
6765   void do_oop(oop* p)       { do_oop_work(p); }
6766   void do_oop(narrowOop* p) { do_oop_work(p); }
6767 };
6768 
6769 void G1CollectedHeap::register_nmethod(nmethod* nm) {
6770   CollectedHeap::register_nmethod(nm);
6771 
6772   guarantee(nm != NULL, "sanity");
6773   RegisterNMethodOopClosure reg_cl(this, nm);
6774   nm->oops_do(&reg_cl);
6775 }
6776 
6777 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
6778   CollectedHeap::unregister_nmethod(nm);
6779 
6780   guarantee(nm != NULL, "sanity");
6781   UnregisterNMethodOopClosure reg_cl(this, nm);
6782   nm->oops_do(&reg_cl, true);
6783 }
6784 
6785 class MigrateCodeRootsHeapRegionClosure: public HeapRegionClosure {
6786 public:
6787   bool doHeapRegion(HeapRegion *hr) {
6788     assert(!hr->isHumongous(),
6789            err_msg("humongous region "HR_FORMAT" should not have been added to collection set",
6790                    HR_FORMAT_PARAMS(hr)));
6791     hr->migrate_strong_code_roots();
6792     return false;
6793   }
6794 };
6795 
6796 void G1CollectedHeap::migrate_strong_code_roots() {
6797   MigrateCodeRootsHeapRegionClosure cl;
6798   double migrate_start = os::elapsedTime();
6799   collection_set_iterate(&cl);
6800   double migration_time_ms = (os::elapsedTime() - migrate_start) * 1000.0;
6801   g1_policy()->phase_times()->record_strong_code_root_migration_time(migration_time_ms);
6802 }
6803 
6804 // Mark all the code roots that point into regions *not* in the
6805 // collection set.
6806 //
6807 // Note we do not want to use a "marking" CodeBlobToOopClosure while
6808 // walking the the code roots lists of regions not in the collection
6809 // set. Suppose we have an nmethod (M) that points to objects in two
6810 // separate regions - one in the collection set (R1) and one not (R2).
6811 // Using a "marking" CodeBlobToOopClosure here would result in "marking"
6812 // nmethod M when walking the code roots for R1. When we come to scan
6813 // the code roots for R2, we would see that M is already marked and it
6814 // would be skipped and the objects in R2 that are referenced from M
6815 // would not be evacuated.
6816 
6817 class MarkStrongCodeRootCodeBlobClosure: public CodeBlobClosure {
6818 
6819   class MarkStrongCodeRootOopClosure: public OopClosure {
6820     ConcurrentMark* _cm;
6821     HeapRegion* _hr;
6822     uint _worker_id;
6823 
6824     template <class T> void do_oop_work(T* p) {
6825       T heap_oop = oopDesc::load_heap_oop(p);
6826       if (!oopDesc::is_null(heap_oop)) {
6827         oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6828         // Only mark objects in the region (which is assumed
6829         // to be not in the collection set).
6830         if (_hr->is_in(obj)) {
6831           _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
6832         }
6833       }
6834     }
6835 
6836   public:
6837     MarkStrongCodeRootOopClosure(ConcurrentMark* cm, HeapRegion* hr, uint worker_id) :
6838       _cm(cm), _hr(hr), _worker_id(worker_id) {
6839       assert(!_hr->in_collection_set(), "sanity");
6840     }
6841 
6842     void do_oop(narrowOop* p) { do_oop_work(p); }
6843     void do_oop(oop* p)       { do_oop_work(p); }
6844   };
6845 
6846   MarkStrongCodeRootOopClosure _oop_cl;
6847 
6848 public:
6849   MarkStrongCodeRootCodeBlobClosure(ConcurrentMark* cm, HeapRegion* hr, uint worker_id):
6850     _oop_cl(cm, hr, worker_id) {}
6851 
6852   void do_code_blob(CodeBlob* cb) {
6853     nmethod* nm = (cb == NULL) ? NULL : cb->as_nmethod_or_null();
6854     if (nm != NULL) {
6855       nm->oops_do(&_oop_cl);
6856     }
6857   }
6858 };
6859 
6860 class MarkStrongCodeRootsHRClosure: public HeapRegionClosure {
6861   G1CollectedHeap* _g1h;
6862   uint _worker_id;
6863 
6864 public:
6865   MarkStrongCodeRootsHRClosure(G1CollectedHeap* g1h, uint worker_id) :
6866     _g1h(g1h), _worker_id(worker_id) {}
6867 
6868   bool doHeapRegion(HeapRegion *hr) {
6869     HeapRegionRemSet* hrrs = hr->rem_set();
6870     if (hr->continuesHumongous()) {
6871       // Code roots should never be attached to a continuation of a humongous region
6872       assert(hrrs->strong_code_roots_list_length() == 0,
6873              err_msg("code roots should never be attached to continuations of humongous region "HR_FORMAT
6874                      " starting at "HR_FORMAT", but has "INT32_FORMAT,
6875                      HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()),
6876                      hrrs->strong_code_roots_list_length()));
6877       return false;
6878     }
6879 
6880     if (hr->in_collection_set()) {
6881       // Don't mark code roots into regions in the collection set here.
6882       // They will be marked when we scan them.
6883       return false;
6884     }
6885 
6886     MarkStrongCodeRootCodeBlobClosure cb_cl(_g1h->concurrent_mark(), hr, _worker_id);
6887     hr->strong_code_roots_do(&cb_cl);
6888     return false;
6889   }
6890 };
6891 
6892 void G1CollectedHeap::mark_strong_code_roots(uint worker_id) {
6893   MarkStrongCodeRootsHRClosure cl(this, worker_id);
6894   if (G1CollectedHeap::use_parallel_gc_threads()) {
6895     heap_region_par_iterate_chunked(&cl,
6896                                     worker_id,
6897                                     workers()->active_workers(),
6898                                     HeapRegion::ParMarkRootClaimValue);
6899   } else {
6900     heap_region_iterate(&cl);
6901   }
6902 }
6903 
6904 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
6905   G1CollectedHeap* _g1h;
6906 
6907 public:
6908   RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
6909     _g1h(g1h) {}
6910 
6911   void do_code_blob(CodeBlob* cb) {
6912     nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
6913     if (nm == NULL) {
6914       return;
6915     }
6916 
6917     if (ScavengeRootsInCode && nm->detect_scavenge_root_oops()) {
6918       _g1h->register_nmethod(nm);
6919     }
6920   }
6921 };
6922 
6923 void G1CollectedHeap::rebuild_strong_code_roots() {
6924   RebuildStrongCodeRootClosure blob_cl(this);
6925   CodeCache::blobs_do(&blob_cl);
6926 }
--- EOF ---