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/g1StringDedup.hpp"
  43 #include "gc_implementation/g1/g1YCTypes.hpp"
  44 #include "gc_implementation/g1/heapRegion.inline.hpp"
  45 #include "gc_implementation/g1/heapRegionRemSet.hpp"
  46 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
  47 #include "gc_implementation/g1/vm_operations_g1.hpp"
  48 #include "gc_implementation/shared/gcHeapSummary.hpp"
  49 #include "gc_implementation/shared/gcTimer.hpp"
  50 #include "gc_implementation/shared/gcTrace.hpp"
  51 #include "gc_implementation/shared/gcTraceTime.hpp"
  52 #include "gc_implementation/shared/isGCActiveMark.hpp"
  53 #include "memory/gcLocker.inline.hpp"
  54 #include "memory/generationSpec.hpp"
  55 #include "memory/iterator.hpp"
  56 #include "memory/referenceProcessor.hpp"
  57 #include "oops/oop.inline.hpp"
  58 #include "oops/oop.pcgc.inline.hpp"
  59 #include "runtime/vmThread.hpp"
  60 #include "utilities/ticks.hpp"
  61 
  62 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
  63 
  64 // turn it on so that the contents of the young list (scan-only /
  65 // to-be-collected) are printed at "strategic" points before / during
  66 // / after the collection --- this is useful for debugging
  67 #define YOUNG_LIST_VERBOSE 0
  68 // CURRENT STATUS
  69 // This file is under construction.  Search for "FIXME".
  70 
  71 // INVARIANTS/NOTES
  72 //
  73 // All allocation activity covered by the G1CollectedHeap interface is
  74 // serialized by acquiring the HeapLock.  This happens in mem_allocate
  75 // and allocate_new_tlab, which are the "entry" points to the
  76 // allocation code from the rest of the JVM.  (Note that this does not
  77 // apply to TLAB allocation, which is not part of this interface: it
  78 // is done by clients of this interface.)
  79 
  80 // Notes on implementation of parallelism in different tasks.
  81 //
  82 // G1ParVerifyTask uses heap_region_par_iterate_chunked() for parallelism.
  83 // The number of GC workers is passed to heap_region_par_iterate_chunked().
  84 // It does use run_task() which sets _n_workers in the task.
  85 // G1ParTask executes g1_process_strong_roots() ->
  86 // SharedHeap::process_strong_roots() which calls eventually to
  87 // CardTableModRefBS::par_non_clean_card_iterate_work() which uses
  88 // SequentialSubTasksDone.  SharedHeap::process_strong_roots() also
  89 // directly uses SubTasksDone (_process_strong_tasks field in SharedHeap).
  90 //
  91 
  92 // Local to this file.
  93 
  94 class RefineCardTableEntryClosure: public CardTableEntryClosure {
  95   SuspendibleThreadSet* _sts;
  96   G1RemSet* _g1rs;
  97   ConcurrentG1Refine* _cg1r;
  98   bool _concurrent;
  99 public:
 100   RefineCardTableEntryClosure(SuspendibleThreadSet* sts,
 101                               G1RemSet* g1rs,
 102                               ConcurrentG1Refine* cg1r) :
 103     _sts(sts), _g1rs(g1rs), _cg1r(cg1r), _concurrent(true)
 104   {}
 105   bool do_card_ptr(jbyte* card_ptr, int worker_i) {
 106     bool oops_into_cset = _g1rs->refine_card(card_ptr, worker_i, false);
 107     // This path is executed by the concurrent refine or mutator threads,
 108     // concurrently, and so we do not care if card_ptr contains references
 109     // that point into the collection set.
 110     assert(!oops_into_cset, "should be");
 111 
 112     if (_concurrent && _sts->should_yield()) {
 113       // Caller will actually yield.
 114       return false;
 115     }
 116     // Otherwise, we finished successfully; return true.
 117     return true;
 118   }
 119   void set_concurrent(bool b) { _concurrent = b; }
 120 };
 121 
 122 
 123 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure {
 124   int _calls;
 125   G1CollectedHeap* _g1h;
 126   CardTableModRefBS* _ctbs;
 127   int _histo[256];
 128 public:
 129   ClearLoggedCardTableEntryClosure() :
 130     _calls(0), _g1h(G1CollectedHeap::heap()), _ctbs(_g1h->g1_barrier_set())
 131   {
 132     for (int i = 0; i < 256; i++) _histo[i] = 0;
 133   }
 134   bool do_card_ptr(jbyte* card_ptr, int worker_i) {
 135     if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
 136       _calls++;
 137       unsigned char* ujb = (unsigned char*)card_ptr;
 138       int ind = (int)(*ujb);
 139       _histo[ind]++;
 140       *card_ptr = -1;
 141     }
 142     return true;
 143   }
 144   int calls() { return _calls; }
 145   void print_histo() {
 146     gclog_or_tty->print_cr("Card table value histogram:");
 147     for (int i = 0; i < 256; i++) {
 148       if (_histo[i] != 0) {
 149         gclog_or_tty->print_cr("  %d: %d", i, _histo[i]);
 150       }
 151     }
 152   }
 153 };
 154 
 155 class RedirtyLoggedCardTableEntryClosure: public CardTableEntryClosure {
 156   int _calls;
 157   G1CollectedHeap* _g1h;
 158   CardTableModRefBS* _ctbs;
 159 public:
 160   RedirtyLoggedCardTableEntryClosure() :
 161     _calls(0), _g1h(G1CollectedHeap::heap()), _ctbs(_g1h->g1_barrier_set()) {}
 162 
 163   bool do_card_ptr(jbyte* card_ptr, int worker_i) {
 164     if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
 165       _calls++;
 166       *card_ptr = 0;
 167     }
 168     return true;
 169   }
 170   int calls() { return _calls; }
 171 };
 172 
 173 YoungList::YoungList(G1CollectedHeap* g1h) :
 174     _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0),
 175     _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) {
 176   guarantee(check_list_empty(false), "just making sure...");
 177 }
 178 
 179 void YoungList::push_region(HeapRegion *hr) {
 180   assert(!hr->is_young(), "should not already be young");
 181   assert(hr->get_next_young_region() == NULL, "cause it should!");
 182 
 183   hr->set_next_young_region(_head);
 184   _head = hr;
 185 
 186   _g1h->g1_policy()->set_region_eden(hr, (int) _length);
 187   ++_length;
 188 }
 189 
 190 void YoungList::add_survivor_region(HeapRegion* hr) {
 191   assert(hr->is_survivor(), "should be flagged as survivor region");
 192   assert(hr->get_next_young_region() == NULL, "cause it should!");
 193 
 194   hr->set_next_young_region(_survivor_head);
 195   if (_survivor_head == NULL) {
 196     _survivor_tail = hr;
 197   }
 198   _survivor_head = hr;
 199   ++_survivor_length;
 200 }
 201 
 202 void YoungList::empty_list(HeapRegion* list) {
 203   while (list != NULL) {
 204     HeapRegion* next = list->get_next_young_region();
 205     list->set_next_young_region(NULL);
 206     list->uninstall_surv_rate_group();
 207     list->set_not_young();
 208     list = next;
 209   }
 210 }
 211 
 212 void YoungList::empty_list() {
 213   assert(check_list_well_formed(), "young list should be well formed");
 214 
 215   empty_list(_head);
 216   _head = NULL;
 217   _length = 0;
 218 
 219   empty_list(_survivor_head);
 220   _survivor_head = NULL;
 221   _survivor_tail = NULL;
 222   _survivor_length = 0;
 223 
 224   _last_sampled_rs_lengths = 0;
 225 
 226   assert(check_list_empty(false), "just making sure...");
 227 }
 228 
 229 bool YoungList::check_list_well_formed() {
 230   bool ret = true;
 231 
 232   uint length = 0;
 233   HeapRegion* curr = _head;
 234   HeapRegion* last = NULL;
 235   while (curr != NULL) {
 236     if (!curr->is_young()) {
 237       gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
 238                              "incorrectly tagged (y: %d, surv: %d)",
 239                              curr->bottom(), curr->end(),
 240                              curr->is_young(), curr->is_survivor());
 241       ret = false;
 242     }
 243     ++length;
 244     last = curr;
 245     curr = curr->get_next_young_region();
 246   }
 247   ret = ret && (length == _length);
 248 
 249   if (!ret) {
 250     gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
 251     gclog_or_tty->print_cr("###   list has %u entries, _length is %u",
 252                            length, _length);
 253   }
 254 
 255   return ret;
 256 }
 257 
 258 bool YoungList::check_list_empty(bool check_sample) {
 259   bool ret = true;
 260 
 261   if (_length != 0) {
 262     gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u",
 263                   _length);
 264     ret = false;
 265   }
 266   if (check_sample && _last_sampled_rs_lengths != 0) {
 267     gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
 268     ret = false;
 269   }
 270   if (_head != NULL) {
 271     gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
 272     ret = false;
 273   }
 274   if (!ret) {
 275     gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
 276   }
 277 
 278   return ret;
 279 }
 280 
 281 void
 282 YoungList::rs_length_sampling_init() {
 283   _sampled_rs_lengths = 0;
 284   _curr               = _head;
 285 }
 286 
 287 bool
 288 YoungList::rs_length_sampling_more() {
 289   return _curr != NULL;
 290 }
 291 
 292 void
 293 YoungList::rs_length_sampling_next() {
 294   assert( _curr != NULL, "invariant" );
 295   size_t rs_length = _curr->rem_set()->occupied();
 296 
 297   _sampled_rs_lengths += rs_length;
 298 
 299   // The current region may not yet have been added to the
 300   // incremental collection set (it gets added when it is
 301   // retired as the current allocation region).
 302   if (_curr->in_collection_set()) {
 303     // Update the collection set policy information for this region
 304     _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
 305   }
 306 
 307   _curr = _curr->get_next_young_region();
 308   if (_curr == NULL) {
 309     _last_sampled_rs_lengths = _sampled_rs_lengths;
 310     // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
 311   }
 312 }
 313 
 314 void
 315 YoungList::reset_auxilary_lists() {
 316   guarantee( is_empty(), "young list should be empty" );
 317   assert(check_list_well_formed(), "young list should be well formed");
 318 
 319   // Add survivor regions to SurvRateGroup.
 320   _g1h->g1_policy()->note_start_adding_survivor_regions();
 321   _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
 322 
 323   int young_index_in_cset = 0;
 324   for (HeapRegion* curr = _survivor_head;
 325        curr != NULL;
 326        curr = curr->get_next_young_region()) {
 327     _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
 328 
 329     // The region is a non-empty survivor so let's add it to
 330     // the incremental collection set for the next evacuation
 331     // pause.
 332     _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
 333     young_index_in_cset += 1;
 334   }
 335   assert((uint) young_index_in_cset == _survivor_length, "post-condition");
 336   _g1h->g1_policy()->note_stop_adding_survivor_regions();
 337 
 338   _head   = _survivor_head;
 339   _length = _survivor_length;
 340   if (_survivor_head != NULL) {
 341     assert(_survivor_tail != NULL, "cause it shouldn't be");
 342     assert(_survivor_length > 0, "invariant");
 343     _survivor_tail->set_next_young_region(NULL);
 344   }
 345 
 346   // Don't clear the survivor list handles until the start of
 347   // the next evacuation pause - we need it in order to re-tag
 348   // the survivor regions from this evacuation pause as 'young'
 349   // at the start of the next.
 350 
 351   _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
 352 
 353   assert(check_list_well_formed(), "young list should be well formed");
 354 }
 355 
 356 void YoungList::print() {
 357   HeapRegion* lists[] = {_head,   _survivor_head};
 358   const char* names[] = {"YOUNG", "SURVIVOR"};
 359 
 360   for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) {
 361     gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
 362     HeapRegion *curr = lists[list];
 363     if (curr == NULL)
 364       gclog_or_tty->print_cr("  empty");
 365     while (curr != NULL) {
 366       gclog_or_tty->print_cr("  "HR_FORMAT", P: "PTR_FORMAT "N: "PTR_FORMAT", age: %4d",
 367                              HR_FORMAT_PARAMS(curr),
 368                              curr->prev_top_at_mark_start(),
 369                              curr->next_top_at_mark_start(),
 370                              curr->age_in_surv_rate_group_cond());
 371       curr = curr->get_next_young_region();
 372     }
 373   }
 374 
 375   gclog_or_tty->print_cr("");
 376 }
 377 
 378 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
 379 {
 380   // Claim the right to put the region on the dirty cards region list
 381   // by installing a self pointer.
 382   HeapRegion* next = hr->get_next_dirty_cards_region();
 383   if (next == NULL) {
 384     HeapRegion* res = (HeapRegion*)
 385       Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
 386                           NULL);
 387     if (res == NULL) {
 388       HeapRegion* head;
 389       do {
 390         // Put the region to the dirty cards region list.
 391         head = _dirty_cards_region_list;
 392         next = (HeapRegion*)
 393           Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
 394         if (next == head) {
 395           assert(hr->get_next_dirty_cards_region() == hr,
 396                  "hr->get_next_dirty_cards_region() != hr");
 397           if (next == NULL) {
 398             // The last region in the list points to itself.
 399             hr->set_next_dirty_cards_region(hr);
 400           } else {
 401             hr->set_next_dirty_cards_region(next);
 402           }
 403         }
 404       } while (next != head);
 405     }
 406   }
 407 }
 408 
 409 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
 410 {
 411   HeapRegion* head;
 412   HeapRegion* hr;
 413   do {
 414     head = _dirty_cards_region_list;
 415     if (head == NULL) {
 416       return NULL;
 417     }
 418     HeapRegion* new_head = head->get_next_dirty_cards_region();
 419     if (head == new_head) {
 420       // The last region.
 421       new_head = NULL;
 422     }
 423     hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
 424                                           head);
 425   } while (hr != head);
 426   assert(hr != NULL, "invariant");
 427   hr->set_next_dirty_cards_region(NULL);
 428   return hr;
 429 }
 430 
 431 void G1CollectedHeap::stop_conc_gc_threads() {
 432   _cg1r->stop();
 433   _cmThread->stop();
 434 }
 435 
 436 #ifdef ASSERT
 437 // A region is added to the collection set as it is retired
 438 // so an address p can point to a region which will be in the
 439 // collection set but has not yet been retired.  This method
 440 // therefore is only accurate during a GC pause after all
 441 // regions have been retired.  It is used for debugging
 442 // to check if an nmethod has references to objects that can
 443 // be move during a partial collection.  Though it can be
 444 // inaccurate, it is sufficient for G1 because the conservative
 445 // implementation of is_scavengable() for G1 will indicate that
 446 // all nmethods must be scanned during a partial collection.
 447 bool G1CollectedHeap::is_in_partial_collection(const void* p) {
 448   HeapRegion* hr = heap_region_containing(p);
 449   return hr != NULL && hr->in_collection_set();
 450 }
 451 #endif
 452 
 453 // Returns true if the reference points to an object that
 454 // can move in an incremental collection.
 455 bool G1CollectedHeap::is_scavengable(const void* p) {
 456   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 457   G1CollectorPolicy* g1p = g1h->g1_policy();
 458   HeapRegion* hr = heap_region_containing(p);
 459   if (hr == NULL) {
 460      // null
 461      assert(p == NULL, err_msg("Not NULL " PTR_FORMAT ,p));
 462      return false;
 463   } else {
 464     return !hr->isHumongous();
 465   }
 466 }
 467 
 468 void G1CollectedHeap::check_ct_logs_at_safepoint() {
 469   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
 470   CardTableModRefBS* ct_bs = g1_barrier_set();
 471 
 472   // Count the dirty cards at the start.
 473   CountNonCleanMemRegionClosure count1(this);
 474   ct_bs->mod_card_iterate(&count1);
 475   int orig_count = count1.n();
 476 
 477   // First clear the logged cards.
 478   ClearLoggedCardTableEntryClosure clear;
 479   dcqs.set_closure(&clear);
 480   dcqs.apply_closure_to_all_completed_buffers();
 481   dcqs.iterate_closure_all_threads(false);
 482   clear.print_histo();
 483 
 484   // Now ensure that there's no dirty cards.
 485   CountNonCleanMemRegionClosure count2(this);
 486   ct_bs->mod_card_iterate(&count2);
 487   if (count2.n() != 0) {
 488     gclog_or_tty->print_cr("Card table has %d entries; %d originally",
 489                            count2.n(), orig_count);
 490   }
 491   guarantee(count2.n() == 0, "Card table should be clean.");
 492 
 493   RedirtyLoggedCardTableEntryClosure redirty;
 494   JavaThread::dirty_card_queue_set().set_closure(&redirty);
 495   dcqs.apply_closure_to_all_completed_buffers();
 496   dcqs.iterate_closure_all_threads(false);
 497   gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
 498                          clear.calls(), orig_count);
 499   guarantee(redirty.calls() == clear.calls(),
 500             "Or else mechanism is broken.");
 501 
 502   CountNonCleanMemRegionClosure count3(this);
 503   ct_bs->mod_card_iterate(&count3);
 504   if (count3.n() != orig_count) {
 505     gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
 506                            orig_count, count3.n());
 507     guarantee(count3.n() >= orig_count, "Should have restored them all.");
 508   }
 509 
 510   JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
 511 }
 512 
 513 // Private class members.
 514 
 515 G1CollectedHeap* G1CollectedHeap::_g1h;
 516 
 517 // Private methods.
 518 
 519 HeapRegion*
 520 G1CollectedHeap::new_region_try_secondary_free_list() {
 521   MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
 522   while (!_secondary_free_list.is_empty() || free_regions_coming()) {
 523     if (!_secondary_free_list.is_empty()) {
 524       if (G1ConcRegionFreeingVerbose) {
 525         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 526                                "secondary_free_list has %u entries",
 527                                _secondary_free_list.length());
 528       }
 529       // It looks as if there are free regions available on the
 530       // secondary_free_list. Let's move them to the free_list and try
 531       // again to allocate from it.
 532       append_secondary_free_list();
 533 
 534       assert(!_free_list.is_empty(), "if the secondary_free_list was not "
 535              "empty we should have moved at least one entry to the free_list");
 536       HeapRegion* res = _free_list.remove_head();
 537       if (G1ConcRegionFreeingVerbose) {
 538         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 539                                "allocated "HR_FORMAT" from secondary_free_list",
 540                                HR_FORMAT_PARAMS(res));
 541       }
 542       return res;
 543     }
 544 
 545     // Wait here until we get notified either when (a) there are no
 546     // more free regions coming or (b) some regions have been moved on
 547     // the secondary_free_list.
 548     SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
 549   }
 550 
 551   if (G1ConcRegionFreeingVerbose) {
 552     gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 553                            "could not allocate from secondary_free_list");
 554   }
 555   return NULL;
 556 }
 557 
 558 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool do_expand) {
 559   assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords,
 560          "the only time we use this to allocate a humongous region is "
 561          "when we are allocating a single humongous region");
 562 
 563   HeapRegion* res;
 564   if (G1StressConcRegionFreeing) {
 565     if (!_secondary_free_list.is_empty()) {
 566       if (G1ConcRegionFreeingVerbose) {
 567         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 568                                "forced to look at the secondary_free_list");
 569       }
 570       res = new_region_try_secondary_free_list();
 571       if (res != NULL) {
 572         return res;
 573       }
 574     }
 575   }
 576   res = _free_list.remove_head_or_null();
 577   if (res == NULL) {
 578     if (G1ConcRegionFreeingVerbose) {
 579       gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 580                              "res == NULL, trying the secondary_free_list");
 581     }
 582     res = new_region_try_secondary_free_list();
 583   }
 584   if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
 585     // Currently, only attempts to allocate GC alloc regions set
 586     // do_expand to true. So, we should only reach here during a
 587     // safepoint. If this assumption changes we might have to
 588     // reconsider the use of _expand_heap_after_alloc_failure.
 589     assert(SafepointSynchronize::is_at_safepoint(), "invariant");
 590 
 591     ergo_verbose1(ErgoHeapSizing,
 592                   "attempt heap expansion",
 593                   ergo_format_reason("region allocation request failed")
 594                   ergo_format_byte("allocation request"),
 595                   word_size * HeapWordSize);
 596     if (expand(word_size * HeapWordSize)) {
 597       // Given that expand() succeeded in expanding the heap, and we
 598       // always expand the heap by an amount aligned to the heap
 599       // region size, the free list should in theory not be empty. So
 600       // it would probably be OK to use remove_head(). But the extra
 601       // check for NULL is unlikely to be a performance issue here (we
 602       // just expanded the heap!) so let's just be conservative and
 603       // use remove_head_or_null().
 604       res = _free_list.remove_head_or_null();
 605     } else {
 606       _expand_heap_after_alloc_failure = false;
 607     }
 608   }
 609   return res;
 610 }
 611 
 612 uint G1CollectedHeap::humongous_obj_allocate_find_first(uint num_regions,
 613                                                         size_t word_size) {
 614   assert(isHumongous(word_size), "word_size should be humongous");
 615   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 616 
 617   uint first = G1_NULL_HRS_INDEX;
 618   if (num_regions == 1) {
 619     // Only one region to allocate, no need to go through the slower
 620     // path. The caller will attempt the expansion if this fails, so
 621     // let's not try to expand here too.
 622     HeapRegion* hr = new_region(word_size, false /* do_expand */);
 623     if (hr != NULL) {
 624       first = hr->hrs_index();
 625     } else {
 626       first = G1_NULL_HRS_INDEX;
 627     }
 628   } else {
 629     // We can't allocate humongous regions while cleanupComplete() is
 630     // running, since some of the regions we find to be empty might not
 631     // yet be added to the free list and it is not straightforward to
 632     // know which list they are on so that we can remove them. Note
 633     // that we only need to do this if we need to allocate more than
 634     // one region to satisfy the current humongous allocation
 635     // request. If we are only allocating one region we use the common
 636     // region allocation code (see above).
 637     wait_while_free_regions_coming();
 638     append_secondary_free_list_if_not_empty_with_lock();
 639 
 640     if (free_regions() >= num_regions) {
 641       first = _hrs.find_contiguous(num_regions);
 642       if (first != G1_NULL_HRS_INDEX) {
 643         for (uint i = first; i < first + num_regions; ++i) {
 644           HeapRegion* hr = region_at(i);
 645           assert(hr->is_empty(), "sanity");
 646           assert(is_on_master_free_list(hr), "sanity");
 647           hr->set_pending_removal(true);
 648         }
 649         _free_list.remove_all_pending(num_regions);
 650       }
 651     }
 652   }
 653   return first;
 654 }
 655 
 656 HeapWord*
 657 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
 658                                                            uint num_regions,
 659                                                            size_t word_size) {
 660   assert(first != G1_NULL_HRS_INDEX, "pre-condition");
 661   assert(isHumongous(word_size), "word_size should be humongous");
 662   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 663 
 664   // Index of last region in the series + 1.
 665   uint last = first + num_regions;
 666 
 667   // We need to initialize the region(s) we just discovered. This is
 668   // a bit tricky given that it can happen concurrently with
 669   // refinement threads refining cards on these regions and
 670   // potentially wanting to refine the BOT as they are scanning
 671   // those cards (this can happen shortly after a cleanup; see CR
 672   // 6991377). So we have to set up the region(s) carefully and in
 673   // a specific order.
 674 
 675   // The word size sum of all the regions we will allocate.
 676   size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
 677   assert(word_size <= word_size_sum, "sanity");
 678 
 679   // This will be the "starts humongous" region.
 680   HeapRegion* first_hr = region_at(first);
 681   // The header of the new object will be placed at the bottom of
 682   // the first region.
 683   HeapWord* new_obj = first_hr->bottom();
 684   // This will be the new end of the first region in the series that
 685   // should also match the end of the last region in the series.
 686   HeapWord* new_end = new_obj + word_size_sum;
 687   // This will be the new top of the first region that will reflect
 688   // this allocation.
 689   HeapWord* new_top = new_obj + word_size;
 690 
 691   // First, we need to zero the header of the space that we will be
 692   // allocating. When we update top further down, some refinement
 693   // threads might try to scan the region. By zeroing the header we
 694   // ensure that any thread that will try to scan the region will
 695   // come across the zero klass word and bail out.
 696   //
 697   // NOTE: It would not have been correct to have used
 698   // CollectedHeap::fill_with_object() and make the space look like
 699   // an int array. The thread that is doing the allocation will
 700   // later update the object header to a potentially different array
 701   // type and, for a very short period of time, the klass and length
 702   // fields will be inconsistent. This could cause a refinement
 703   // thread to calculate the object size incorrectly.
 704   Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
 705 
 706   // We will set up the first region as "starts humongous". This
 707   // will also update the BOT covering all the regions to reflect
 708   // that there is a single object that starts at the bottom of the
 709   // first region.
 710   first_hr->set_startsHumongous(new_top, new_end);
 711 
 712   // Then, if there are any, we will set up the "continues
 713   // humongous" regions.
 714   HeapRegion* hr = NULL;
 715   for (uint i = first + 1; i < last; ++i) {
 716     hr = region_at(i);
 717     hr->set_continuesHumongous(first_hr);
 718   }
 719   // If we have "continues humongous" regions (hr != NULL), then the
 720   // end of the last one should match new_end.
 721   assert(hr == NULL || hr->end() == new_end, "sanity");
 722 
 723   // Up to this point no concurrent thread would have been able to
 724   // do any scanning on any region in this series. All the top
 725   // fields still point to bottom, so the intersection between
 726   // [bottom,top] and [card_start,card_end] will be empty. Before we
 727   // update the top fields, we'll do a storestore to make sure that
 728   // no thread sees the update to top before the zeroing of the
 729   // object header and the BOT initialization.
 730   OrderAccess::storestore();
 731 
 732   // Now that the BOT and the object header have been initialized,
 733   // we can update top of the "starts humongous" region.
 734   assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
 735          "new_top should be in this region");
 736   first_hr->set_top(new_top);
 737   if (_hr_printer.is_active()) {
 738     HeapWord* bottom = first_hr->bottom();
 739     HeapWord* end = first_hr->orig_end();
 740     if ((first + 1) == last) {
 741       // the series has a single humongous region
 742       _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
 743     } else {
 744       // the series has more than one humongous regions
 745       _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
 746     }
 747   }
 748 
 749   // Now, we will update the top fields of the "continues humongous"
 750   // regions. The reason we need to do this is that, otherwise,
 751   // these regions would look empty and this will confuse parts of
 752   // G1. For example, the code that looks for a consecutive number
 753   // of empty regions will consider them empty and try to
 754   // re-allocate them. We can extend is_empty() to also include
 755   // !continuesHumongous(), but it is easier to just update the top
 756   // fields here. The way we set top for all regions (i.e., top ==
 757   // end for all regions but the last one, top == new_top for the
 758   // last one) is actually used when we will free up the humongous
 759   // region in free_humongous_region().
 760   hr = NULL;
 761   for (uint i = first + 1; i < last; ++i) {
 762     hr = region_at(i);
 763     if ((i + 1) == last) {
 764       // last continues humongous region
 765       assert(hr->bottom() < new_top && new_top <= hr->end(),
 766              "new_top should fall on this region");
 767       hr->set_top(new_top);
 768       _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
 769     } else {
 770       // not last one
 771       assert(new_top > hr->end(), "new_top should be above this region");
 772       hr->set_top(hr->end());
 773       _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
 774     }
 775   }
 776   // If we have continues humongous regions (hr != NULL), then the
 777   // end of the last one should match new_end and its top should
 778   // match new_top.
 779   assert(hr == NULL ||
 780          (hr->end() == new_end && hr->top() == new_top), "sanity");
 781 
 782   assert(first_hr->used() == word_size * HeapWordSize, "invariant");
 783   _summary_bytes_used += first_hr->used();
 784   _humongous_set.add(first_hr);
 785 
 786   return new_obj;
 787 }
 788 
 789 // If could fit into free regions w/o expansion, try.
 790 // Otherwise, if can expand, do so.
 791 // Otherwise, if using ex regions might help, try with ex given back.
 792 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
 793   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 794 
 795   verify_region_sets_optional();
 796 
 797   size_t word_size_rounded = round_to(word_size, HeapRegion::GrainWords);
 798   uint num_regions = (uint) (word_size_rounded / HeapRegion::GrainWords);
 799   uint x_num = expansion_regions();
 800   uint fs = _hrs.free_suffix();
 801   uint first = humongous_obj_allocate_find_first(num_regions, word_size);
 802   if (first == G1_NULL_HRS_INDEX) {
 803     // The only thing we can do now is attempt expansion.
 804     if (fs + x_num >= num_regions) {
 805       // If the number of regions we're trying to allocate for this
 806       // object is at most the number of regions in the free suffix,
 807       // then the call to humongous_obj_allocate_find_first() above
 808       // should have succeeded and we wouldn't be here.
 809       //
 810       // We should only be trying to expand when the free suffix is
 811       // not sufficient for the object _and_ we have some expansion
 812       // room available.
 813       assert(num_regions > fs, "earlier allocation should have succeeded");
 814 
 815       ergo_verbose1(ErgoHeapSizing,
 816                     "attempt heap expansion",
 817                     ergo_format_reason("humongous allocation request failed")
 818                     ergo_format_byte("allocation request"),
 819                     word_size * HeapWordSize);
 820       if (expand((num_regions - fs) * HeapRegion::GrainBytes)) {
 821         // Even though the heap was expanded, it might not have
 822         // reached the desired size. So, we cannot assume that the
 823         // allocation will succeed.
 824         first = humongous_obj_allocate_find_first(num_regions, word_size);
 825       }
 826     }
 827   }
 828 
 829   HeapWord* result = NULL;
 830   if (first != G1_NULL_HRS_INDEX) {
 831     result =
 832       humongous_obj_allocate_initialize_regions(first, num_regions, word_size);
 833     assert(result != NULL, "it should always return a valid result");
 834 
 835     // A successful humongous object allocation changes the used space
 836     // information of the old generation so we need to recalculate the
 837     // sizes and update the jstat counters here.
 838     g1mm()->update_sizes();
 839   }
 840 
 841   verify_region_sets_optional();
 842 
 843   return result;
 844 }
 845 
 846 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
 847   assert_heap_not_locked_and_not_at_safepoint();
 848   assert(!isHumongous(word_size), "we do not allow humongous TLABs");
 849 
 850   unsigned int dummy_gc_count_before;
 851   int dummy_gclocker_retry_count = 0;
 852   return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
 853 }
 854 
 855 HeapWord*
 856 G1CollectedHeap::mem_allocate(size_t word_size,
 857                               bool*  gc_overhead_limit_was_exceeded) {
 858   assert_heap_not_locked_and_not_at_safepoint();
 859 
 860   // Loop until the allocation is satisfied, or unsatisfied after GC.
 861   for (int try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 862     unsigned int gc_count_before;
 863 
 864     HeapWord* result = NULL;
 865     if (!isHumongous(word_size)) {
 866       result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
 867     } else {
 868       result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
 869     }
 870     if (result != NULL) {
 871       return result;
 872     }
 873 
 874     // Create the garbage collection operation...
 875     VM_G1CollectForAllocation op(gc_count_before, word_size);
 876     // ...and get the VM thread to execute it.
 877     VMThread::execute(&op);
 878 
 879     if (op.prologue_succeeded() && op.pause_succeeded()) {
 880       // If the operation was successful we'll return the result even
 881       // if it is NULL. If the allocation attempt failed immediately
 882       // after a Full GC, it's unlikely we'll be able to allocate now.
 883       HeapWord* result = op.result();
 884       if (result != NULL && !isHumongous(word_size)) {
 885         // Allocations that take place on VM operations do not do any
 886         // card dirtying and we have to do it here. We only have to do
 887         // this for non-humongous allocations, though.
 888         dirty_young_block(result, word_size);
 889       }
 890       return result;
 891     } else {
 892       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 893         return NULL;
 894       }
 895       assert(op.result() == NULL,
 896              "the result should be NULL if the VM op did not succeed");
 897     }
 898 
 899     // Give a warning if we seem to be looping forever.
 900     if ((QueuedAllocationWarningCount > 0) &&
 901         (try_count % QueuedAllocationWarningCount == 0)) {
 902       warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
 903     }
 904   }
 905 
 906   ShouldNotReachHere();
 907   return NULL;
 908 }
 909 
 910 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
 911                                            unsigned int *gc_count_before_ret,
 912                                            int* gclocker_retry_count_ret) {
 913   // Make sure you read the note in attempt_allocation_humongous().
 914 
 915   assert_heap_not_locked_and_not_at_safepoint();
 916   assert(!isHumongous(word_size), "attempt_allocation_slow() should not "
 917          "be called for humongous allocation requests");
 918 
 919   // We should only get here after the first-level allocation attempt
 920   // (attempt_allocation()) failed to allocate.
 921 
 922   // We will loop until a) we manage to successfully perform the
 923   // allocation or b) we successfully schedule a collection which
 924   // fails to perform the allocation. b) is the only case when we'll
 925   // return NULL.
 926   HeapWord* result = NULL;
 927   for (int try_count = 1; /* we'll return */; try_count += 1) {
 928     bool should_try_gc;
 929     unsigned int gc_count_before;
 930 
 931     {
 932       MutexLockerEx x(Heap_lock);
 933 
 934       result = _mutator_alloc_region.attempt_allocation_locked(word_size,
 935                                                       false /* bot_updates */);
 936       if (result != NULL) {
 937         return result;
 938       }
 939 
 940       // If we reach here, attempt_allocation_locked() above failed to
 941       // allocate a new region. So the mutator alloc region should be NULL.
 942       assert(_mutator_alloc_region.get() == NULL, "only way to get here");
 943 
 944       if (GC_locker::is_active_and_needs_gc()) {
 945         if (g1_policy()->can_expand_young_list()) {
 946           // No need for an ergo verbose message here,
 947           // can_expand_young_list() does this when it returns true.
 948           result = _mutator_alloc_region.attempt_allocation_force(word_size,
 949                                                       false /* bot_updates */);
 950           if (result != NULL) {
 951             return result;
 952           }
 953         }
 954         should_try_gc = false;
 955       } else {
 956         // The GCLocker may not be active but the GCLocker initiated
 957         // GC may not yet have been performed (GCLocker::needs_gc()
 958         // returns true). In this case we do not try this GC and
 959         // wait until the GCLocker initiated GC is performed, and
 960         // then retry the allocation.
 961         if (GC_locker::needs_gc()) {
 962           should_try_gc = false;
 963         } else {
 964           // Read the GC count while still holding the Heap_lock.
 965           gc_count_before = total_collections();
 966           should_try_gc = true;
 967         }
 968       }
 969     }
 970 
 971     if (should_try_gc) {
 972       bool succeeded;
 973       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 974           GCCause::_g1_inc_collection_pause);
 975       if (result != NULL) {
 976         assert(succeeded, "only way to get back a non-NULL result");
 977         return result;
 978       }
 979 
 980       if (succeeded) {
 981         // If we get here we successfully scheduled a collection which
 982         // failed to allocate. No point in trying to allocate
 983         // further. We'll just return NULL.
 984         MutexLockerEx x(Heap_lock);
 985         *gc_count_before_ret = total_collections();
 986         return NULL;
 987       }
 988     } else {
 989       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
 990         MutexLockerEx x(Heap_lock);
 991         *gc_count_before_ret = total_collections();
 992         return NULL;
 993       }
 994       // The GCLocker is either active or the GCLocker initiated
 995       // GC has not yet been performed. Stall until it is and
 996       // then retry the allocation.
 997       GC_locker::stall_until_clear();
 998       (*gclocker_retry_count_ret) += 1;
 999     }
1000 
1001     // We can reach here if we were unsuccessful in scheduling a
1002     // collection (because another thread beat us to it) or if we were
1003     // stalled due to the GC locker. In either can we should retry the
1004     // allocation attempt in case another thread successfully
1005     // performed a collection and reclaimed enough space. We do the
1006     // first attempt (without holding the Heap_lock) here and the
1007     // follow-on attempt will be at the start of the next loop
1008     // iteration (after taking the Heap_lock).
1009     result = _mutator_alloc_region.attempt_allocation(word_size,
1010                                                       false /* bot_updates */);
1011     if (result != NULL) {
1012       return result;
1013     }
1014 
1015     // Give a warning if we seem to be looping forever.
1016     if ((QueuedAllocationWarningCount > 0) &&
1017         (try_count % QueuedAllocationWarningCount == 0)) {
1018       warning("G1CollectedHeap::attempt_allocation_slow() "
1019               "retries %d times", try_count);
1020     }
1021   }
1022 
1023   ShouldNotReachHere();
1024   return NULL;
1025 }
1026 
1027 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
1028                                           unsigned int * gc_count_before_ret,
1029                                           int* gclocker_retry_count_ret) {
1030   // The structure of this method has a lot of similarities to
1031   // attempt_allocation_slow(). The reason these two were not merged
1032   // into a single one is that such a method would require several "if
1033   // allocation is not humongous do this, otherwise do that"
1034   // conditional paths which would obscure its flow. In fact, an early
1035   // version of this code did use a unified method which was harder to
1036   // follow and, as a result, it had subtle bugs that were hard to
1037   // track down. So keeping these two methods separate allows each to
1038   // be more readable. It will be good to keep these two in sync as
1039   // much as possible.
1040 
1041   assert_heap_not_locked_and_not_at_safepoint();
1042   assert(isHumongous(word_size), "attempt_allocation_humongous() "
1043          "should only be called for humongous allocations");
1044 
1045   // Humongous objects can exhaust the heap quickly, so we should check if we
1046   // need to start a marking cycle at each humongous object allocation. We do
1047   // the check before we do the actual allocation. The reason for doing it
1048   // before the allocation is that we avoid having to keep track of the newly
1049   // allocated memory while we do a GC.
1050   if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
1051                                            word_size)) {
1052     collect(GCCause::_g1_humongous_allocation);
1053   }
1054 
1055   // We will loop until a) we manage to successfully perform the
1056   // allocation or b) we successfully schedule a collection which
1057   // fails to perform the allocation. b) is the only case when we'll
1058   // return NULL.
1059   HeapWord* result = NULL;
1060   for (int try_count = 1; /* we'll return */; try_count += 1) {
1061     bool should_try_gc;
1062     unsigned int gc_count_before;
1063 
1064     {
1065       MutexLockerEx x(Heap_lock);
1066 
1067       // Given that humongous objects are not allocated in young
1068       // regions, we'll first try to do the allocation without doing a
1069       // collection hoping that there's enough space in the heap.
1070       result = humongous_obj_allocate(word_size);
1071       if (result != NULL) {
1072         return result;
1073       }
1074 
1075       if (GC_locker::is_active_and_needs_gc()) {
1076         should_try_gc = false;
1077       } else {
1078          // The GCLocker may not be active but the GCLocker initiated
1079         // GC may not yet have been performed (GCLocker::needs_gc()
1080         // returns true). In this case we do not try this GC and
1081         // wait until the GCLocker initiated GC is performed, and
1082         // then retry the allocation.
1083         if (GC_locker::needs_gc()) {
1084           should_try_gc = false;
1085         } else {
1086           // Read the GC count while still holding the Heap_lock.
1087           gc_count_before = total_collections();
1088           should_try_gc = true;
1089         }
1090       }
1091     }
1092 
1093     if (should_try_gc) {
1094       // If we failed to allocate the humongous object, we should try to
1095       // do a collection pause (if we're allowed) in case it reclaims
1096       // enough space for the allocation to succeed after the pause.
1097 
1098       bool succeeded;
1099       result = do_collection_pause(word_size, gc_count_before, &succeeded,
1100           GCCause::_g1_humongous_allocation);
1101       if (result != NULL) {
1102         assert(succeeded, "only way to get back a non-NULL result");
1103         return result;
1104       }
1105 
1106       if (succeeded) {
1107         // If we get here we successfully scheduled a collection which
1108         // failed to allocate. No point in trying to allocate
1109         // further. We'll just return NULL.
1110         MutexLockerEx x(Heap_lock);
1111         *gc_count_before_ret = total_collections();
1112         return NULL;
1113       }
1114     } else {
1115       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1116         MutexLockerEx x(Heap_lock);
1117         *gc_count_before_ret = total_collections();
1118         return NULL;
1119       }
1120       // The GCLocker is either active or the GCLocker initiated
1121       // GC has not yet been performed. Stall until it is and
1122       // then retry the allocation.
1123       GC_locker::stall_until_clear();
1124       (*gclocker_retry_count_ret) += 1;
1125     }
1126 
1127     // We can reach here if we were unsuccessful in scheduling a
1128     // collection (because another thread beat us to it) or if we were
1129     // stalled due to the GC locker. In either can we should retry the
1130     // allocation attempt in case another thread successfully
1131     // performed a collection and reclaimed enough space.  Give a
1132     // warning if we seem to be looping forever.
1133 
1134     if ((QueuedAllocationWarningCount > 0) &&
1135         (try_count % QueuedAllocationWarningCount == 0)) {
1136       warning("G1CollectedHeap::attempt_allocation_humongous() "
1137               "retries %d times", try_count);
1138     }
1139   }
1140 
1141   ShouldNotReachHere();
1142   return NULL;
1143 }
1144 
1145 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1146                                        bool expect_null_mutator_alloc_region) {
1147   assert_at_safepoint(true /* should_be_vm_thread */);
1148   assert(_mutator_alloc_region.get() == NULL ||
1149                                              !expect_null_mutator_alloc_region,
1150          "the current alloc region was unexpectedly found to be non-NULL");
1151 
1152   if (!isHumongous(word_size)) {
1153     return _mutator_alloc_region.attempt_allocation_locked(word_size,
1154                                                       false /* bot_updates */);
1155   } else {
1156     HeapWord* result = humongous_obj_allocate(word_size);
1157     if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1158       g1_policy()->set_initiate_conc_mark_if_possible();
1159     }
1160     return result;
1161   }
1162 
1163   ShouldNotReachHere();
1164 }
1165 
1166 class PostMCRemSetClearClosure: public HeapRegionClosure {
1167   G1CollectedHeap* _g1h;
1168   ModRefBarrierSet* _mr_bs;
1169 public:
1170   PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1171     _g1h(g1h), _mr_bs(mr_bs) {}
1172 
1173   bool doHeapRegion(HeapRegion* r) {
1174     HeapRegionRemSet* hrrs = r->rem_set();
1175 
1176     if (r->continuesHumongous()) {
1177       // We'll assert that the strong code root list and RSet is empty
1178       assert(hrrs->strong_code_roots_list_length() == 0, "sanity");
1179       assert(hrrs->occupied() == 0, "RSet should be empty");
1180       return false;
1181     }
1182 
1183     _g1h->reset_gc_time_stamps(r);
1184     hrrs->clear();
1185     // You might think here that we could clear just the cards
1186     // corresponding to the used region.  But no: if we leave a dirty card
1187     // in a region we might allocate into, then it would prevent that card
1188     // from being enqueued, and cause it to be missed.
1189     // Re: the performance cost: we shouldn't be doing full GC anyway!
1190     _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1191 
1192     return false;
1193   }
1194 };
1195 
1196 void G1CollectedHeap::clear_rsets_post_compaction() {
1197   PostMCRemSetClearClosure rs_clear(this, g1_barrier_set());
1198   heap_region_iterate(&rs_clear);
1199 }
1200 
1201 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1202   G1CollectedHeap*   _g1h;
1203   UpdateRSOopClosure _cl;
1204   int                _worker_i;
1205 public:
1206   RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1207     _cl(g1->g1_rem_set(), worker_i),
1208     _worker_i(worker_i),
1209     _g1h(g1)
1210   { }
1211 
1212   bool doHeapRegion(HeapRegion* r) {
1213     if (!r->continuesHumongous()) {
1214       _cl.set_from(r);
1215       r->oop_iterate(&_cl);
1216     }
1217     return false;
1218   }
1219 };
1220 
1221 class ParRebuildRSTask: public AbstractGangTask {
1222   G1CollectedHeap* _g1;
1223 public:
1224   ParRebuildRSTask(G1CollectedHeap* g1)
1225     : AbstractGangTask("ParRebuildRSTask"),
1226       _g1(g1)
1227   { }
1228 
1229   void work(uint worker_id) {
1230     RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1231     _g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id,
1232                                           _g1->workers()->active_workers(),
1233                                          HeapRegion::RebuildRSClaimValue);
1234   }
1235 };
1236 
1237 class PostCompactionPrinterClosure: public HeapRegionClosure {
1238 private:
1239   G1HRPrinter* _hr_printer;
1240 public:
1241   bool doHeapRegion(HeapRegion* hr) {
1242     assert(!hr->is_young(), "not expecting to find young regions");
1243     // We only generate output for non-empty regions.
1244     if (!hr->is_empty()) {
1245       if (!hr->isHumongous()) {
1246         _hr_printer->post_compaction(hr, G1HRPrinter::Old);
1247       } else if (hr->startsHumongous()) {
1248         if (hr->region_num() == 1) {
1249           // single humongous region
1250           _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
1251         } else {
1252           _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
1253         }
1254       } else {
1255         assert(hr->continuesHumongous(), "only way to get here");
1256         _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1257       }
1258     }
1259     return false;
1260   }
1261 
1262   PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1263     : _hr_printer(hr_printer) { }
1264 };
1265 
1266 void G1CollectedHeap::print_hrs_post_compaction() {
1267   PostCompactionPrinterClosure cl(hr_printer());
1268   heap_region_iterate(&cl);
1269 }
1270 
1271 bool G1CollectedHeap::do_collection(bool explicit_gc,
1272                                     bool clear_all_soft_refs,
1273                                     size_t word_size) {
1274   assert_at_safepoint(true /* should_be_vm_thread */);
1275 
1276   if (GC_locker::check_active_before_gc()) {
1277     return false;
1278   }
1279 
1280   STWGCTimer* gc_timer = G1MarkSweep::gc_timer();
1281   gc_timer->register_gc_start();
1282 
1283   SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer();
1284   gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start());
1285 
1286   SvcGCMarker sgcm(SvcGCMarker::FULL);
1287   ResourceMark rm;
1288 
1289   print_heap_before_gc();
1290   trace_heap_before_gc(gc_tracer);
1291 
1292   size_t metadata_prev_used = MetaspaceAux::allocated_used_bytes();
1293 
1294   verify_region_sets_optional();
1295 
1296   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1297                            collector_policy()->should_clear_all_soft_refs();
1298 
1299   ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1300 
1301   {
1302     IsGCActiveMark x;
1303 
1304     // Timing
1305     assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant");
1306     gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps);
1307     TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
1308 
1309     {
1310       GCTraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, NULL);
1311       TraceCollectorStats tcs(g1mm()->full_collection_counters());
1312       TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1313 
1314       double start = os::elapsedTime();
1315       g1_policy()->record_full_collection_start();
1316 
1317       // Note: When we have a more flexible GC logging framework that
1318       // allows us to add optional attributes to a GC log record we
1319       // could consider timing and reporting how long we wait in the
1320       // following two methods.
1321       wait_while_free_regions_coming();
1322       // If we start the compaction before the CM threads finish
1323       // scanning the root regions we might trip them over as we'll
1324       // be moving objects / updating references. So let's wait until
1325       // they are done. By telling them to abort, they should complete
1326       // early.
1327       _cm->root_regions()->abort();
1328       _cm->root_regions()->wait_until_scan_finished();
1329       append_secondary_free_list_if_not_empty_with_lock();
1330 
1331       gc_prologue(true);
1332       increment_total_collections(true /* full gc */);
1333       increment_old_marking_cycles_started();
1334 
1335       assert(used() == recalculate_used(), "Should be equal");
1336 
1337       verify_before_gc();
1338 
1339       pre_full_gc_dump(gc_timer);
1340 
1341       COMPILER2_PRESENT(DerivedPointerTable::clear());
1342 
1343       // Disable discovery and empty the discovered lists
1344       // for the CM ref processor.
1345       ref_processor_cm()->disable_discovery();
1346       ref_processor_cm()->abandon_partial_discovery();
1347       ref_processor_cm()->verify_no_references_recorded();
1348 
1349       // Abandon current iterations of concurrent marking and concurrent
1350       // refinement, if any are in progress. We have to do this before
1351       // wait_until_scan_finished() below.
1352       concurrent_mark()->abort();
1353 
1354       // Make sure we'll choose a new allocation region afterwards.
1355       release_mutator_alloc_region();
1356       abandon_gc_alloc_regions();
1357       g1_rem_set()->cleanupHRRS();
1358 
1359       // We should call this after we retire any currently active alloc
1360       // regions so that all the ALLOC / RETIRE events are generated
1361       // before the start GC event.
1362       _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1363 
1364       // We may have added regions to the current incremental collection
1365       // set between the last GC or pause and now. We need to clear the
1366       // incremental collection set and then start rebuilding it afresh
1367       // after this full GC.
1368       abandon_collection_set(g1_policy()->inc_cset_head());
1369       g1_policy()->clear_incremental_cset();
1370       g1_policy()->stop_incremental_cset_building();
1371 
1372       tear_down_region_sets(false /* free_list_only */);
1373       g1_policy()->set_gcs_are_young(true);
1374 
1375       // See the comments in g1CollectedHeap.hpp and
1376       // G1CollectedHeap::ref_processing_init() about
1377       // how reference processing currently works in G1.
1378 
1379       // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1380       ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1381 
1382       // Temporarily clear the STW ref processor's _is_alive_non_header field.
1383       ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1384 
1385       ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
1386       ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1387 
1388       // Do collection work
1389       {
1390         HandleMark hm;  // Discard invalid handles created during gc
1391         G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1392       }
1393 
1394       assert(free_regions() == 0, "we should not have added any free regions");
1395       rebuild_region_sets(false /* free_list_only */);
1396 
1397       // Enqueue any discovered reference objects that have
1398       // not been removed from the discovered lists.
1399       ref_processor_stw()->enqueue_discovered_references();
1400 
1401       COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1402 
1403       MemoryService::track_memory_usage();
1404 
1405       assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1406       ref_processor_stw()->verify_no_references_recorded();
1407 
1408       // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1409       ClassLoaderDataGraph::purge();
1410       MetaspaceAux::verify_metrics();
1411 
1412       // Note: since we've just done a full GC, concurrent
1413       // marking is no longer active. Therefore we need not
1414       // re-enable reference discovery for the CM ref processor.
1415       // That will be done at the start of the next marking cycle.
1416       assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1417       ref_processor_cm()->verify_no_references_recorded();
1418 
1419       reset_gc_time_stamp();
1420       // Since everything potentially moved, we will clear all remembered
1421       // sets, and clear all cards.  Later we will rebuild remembered
1422       // sets. We will also reset the GC time stamps of the regions.
1423       clear_rsets_post_compaction();
1424       check_gc_time_stamps();
1425 
1426       // Resize the heap if necessary.
1427       resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1428 
1429       if (_hr_printer.is_active()) {
1430         // We should do this after we potentially resize the heap so
1431         // that all the COMMIT / UNCOMMIT events are generated before
1432         // the end GC event.
1433 
1434         print_hrs_post_compaction();
1435         _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1436       }
1437 
1438       G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
1439       if (hot_card_cache->use_cache()) {
1440         hot_card_cache->reset_card_counts();
1441         hot_card_cache->reset_hot_cache();
1442       }
1443 
1444       // Rebuild remembered sets of all regions.
1445       if (G1CollectedHeap::use_parallel_gc_threads()) {
1446         uint n_workers =
1447           AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1448                                                   workers()->active_workers(),
1449                                                   Threads::number_of_non_daemon_threads());
1450         assert(UseDynamicNumberOfGCThreads ||
1451                n_workers == workers()->total_workers(),
1452                "If not dynamic should be using all the  workers");
1453         workers()->set_active_workers(n_workers);
1454         // Set parallel threads in the heap (_n_par_threads) only
1455         // before a parallel phase and always reset it to 0 after
1456         // the phase so that the number of parallel threads does
1457         // no get carried forward to a serial phase where there
1458         // may be code that is "possibly_parallel".
1459         set_par_threads(n_workers);
1460 
1461         ParRebuildRSTask rebuild_rs_task(this);
1462         assert(check_heap_region_claim_values(
1463                HeapRegion::InitialClaimValue), "sanity check");
1464         assert(UseDynamicNumberOfGCThreads ||
1465                workers()->active_workers() == workers()->total_workers(),
1466                "Unless dynamic should use total workers");
1467         // Use the most recent number of  active workers
1468         assert(workers()->active_workers() > 0,
1469                "Active workers not properly set");
1470         set_par_threads(workers()->active_workers());
1471         workers()->run_task(&rebuild_rs_task);
1472         set_par_threads(0);
1473         assert(check_heap_region_claim_values(
1474                HeapRegion::RebuildRSClaimValue), "sanity check");
1475         reset_heap_region_claim_values();
1476       } else {
1477         RebuildRSOutOfRegionClosure rebuild_rs(this);
1478         heap_region_iterate(&rebuild_rs);
1479       }
1480 
1481       // Rebuild the strong code root lists for each region
1482       rebuild_strong_code_roots();
1483 
1484       if (true) { // FIXME
1485         MetaspaceGC::compute_new_size();
1486       }
1487 
1488 #ifdef TRACESPINNING
1489       ParallelTaskTerminator::print_termination_counts();
1490 #endif
1491 
1492       // Discard all rset updates
1493       JavaThread::dirty_card_queue_set().abandon_logs();
1494       assert(!G1DeferredRSUpdate
1495              || (G1DeferredRSUpdate &&
1496                 (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any");
1497 
1498       _young_list->reset_sampled_info();
1499       // At this point there should be no regions in the
1500       // entire heap tagged as young.
1501       assert(check_young_list_empty(true /* check_heap */),
1502              "young list should be empty at this point");
1503 
1504       // Update the number of full collections that have been completed.
1505       increment_old_marking_cycles_completed(false /* concurrent */);
1506 
1507       _hrs.verify_optional();
1508       verify_region_sets_optional();
1509 
1510       verify_after_gc();
1511 
1512       // Start a new incremental collection set for the next pause
1513       assert(g1_policy()->collection_set() == NULL, "must be");
1514       g1_policy()->start_incremental_cset_building();
1515 
1516       // Clear the _cset_fast_test bitmap in anticipation of adding
1517       // regions to the incremental collection set for the next
1518       // evacuation pause.
1519       clear_cset_fast_test();
1520 
1521       init_mutator_alloc_region();
1522 
1523       double end = os::elapsedTime();
1524       g1_policy()->record_full_collection_end();
1525 
1526       if (G1Log::fine()) {
1527         g1_policy()->print_heap_transition();
1528       }
1529 
1530       // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1531       // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1532       // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1533       // before any GC notifications are raised.
1534       g1mm()->update_sizes();
1535 
1536       gc_epilogue(true);
1537     }
1538 
1539     if (G1Log::finer()) {
1540       g1_policy()->print_detailed_heap_transition(true /* full */);
1541     }
1542 
1543     print_heap_after_gc();
1544     trace_heap_after_gc(gc_tracer);
1545 
1546     post_full_gc_dump(gc_timer);
1547 
1548     gc_timer->register_gc_end();
1549     gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
1550   }
1551 
1552   return true;
1553 }
1554 
1555 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1556   // do_collection() will return whether it succeeded in performing
1557   // the GC. Currently, there is no facility on the
1558   // do_full_collection() API to notify the caller than the collection
1559   // did not succeed (e.g., because it was locked out by the GC
1560   // locker). So, right now, we'll ignore the return value.
1561   bool dummy = do_collection(true,                /* explicit_gc */
1562                              clear_all_soft_refs,
1563                              0                    /* word_size */);
1564 }
1565 
1566 // This code is mostly copied from TenuredGeneration.
1567 void
1568 G1CollectedHeap::
1569 resize_if_necessary_after_full_collection(size_t word_size) {
1570   // Include the current allocation, if any, and bytes that will be
1571   // pre-allocated to support collections, as "used".
1572   const size_t used_after_gc = used();
1573   const size_t capacity_after_gc = capacity();
1574   const size_t free_after_gc = capacity_after_gc - used_after_gc;
1575 
1576   // This is enforced in arguments.cpp.
1577   assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1578          "otherwise the code below doesn't make sense");
1579 
1580   // We don't have floating point command-line arguments
1581   const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1582   const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1583   const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1584   const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1585 
1586   const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1587   const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1588 
1589   // We have to be careful here as these two calculations can overflow
1590   // 32-bit size_t's.
1591   double used_after_gc_d = (double) used_after_gc;
1592   double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1593   double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1594 
1595   // Let's make sure that they are both under the max heap size, which
1596   // by default will make them fit into a size_t.
1597   double desired_capacity_upper_bound = (double) max_heap_size;
1598   minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1599                                     desired_capacity_upper_bound);
1600   maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1601                                     desired_capacity_upper_bound);
1602 
1603   // We can now safely turn them into size_t's.
1604   size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1605   size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1606 
1607   // This assert only makes sense here, before we adjust them
1608   // with respect to the min and max heap size.
1609   assert(minimum_desired_capacity <= maximum_desired_capacity,
1610          err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1611                  "maximum_desired_capacity = "SIZE_FORMAT,
1612                  minimum_desired_capacity, maximum_desired_capacity));
1613 
1614   // Should not be greater than the heap max size. No need to adjust
1615   // it with respect to the heap min size as it's a lower bound (i.e.,
1616   // we'll try to make the capacity larger than it, not smaller).
1617   minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1618   // Should not be less than the heap min size. No need to adjust it
1619   // with respect to the heap max size as it's an upper bound (i.e.,
1620   // we'll try to make the capacity smaller than it, not greater).
1621   maximum_desired_capacity =  MAX2(maximum_desired_capacity, min_heap_size);
1622 
1623   if (capacity_after_gc < minimum_desired_capacity) {
1624     // Don't expand unless it's significant
1625     size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1626     ergo_verbose4(ErgoHeapSizing,
1627                   "attempt heap expansion",
1628                   ergo_format_reason("capacity lower than "
1629                                      "min desired capacity after Full GC")
1630                   ergo_format_byte("capacity")
1631                   ergo_format_byte("occupancy")
1632                   ergo_format_byte_perc("min desired capacity"),
1633                   capacity_after_gc, used_after_gc,
1634                   minimum_desired_capacity, (double) MinHeapFreeRatio);
1635     expand(expand_bytes);
1636 
1637     // No expansion, now see if we want to shrink
1638   } else if (capacity_after_gc > maximum_desired_capacity) {
1639     // Capacity too large, compute shrinking size
1640     size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1641     ergo_verbose4(ErgoHeapSizing,
1642                   "attempt heap shrinking",
1643                   ergo_format_reason("capacity higher than "
1644                                      "max desired capacity after Full GC")
1645                   ergo_format_byte("capacity")
1646                   ergo_format_byte("occupancy")
1647                   ergo_format_byte_perc("max desired capacity"),
1648                   capacity_after_gc, used_after_gc,
1649                   maximum_desired_capacity, (double) MaxHeapFreeRatio);
1650     shrink(shrink_bytes);
1651   }
1652 }
1653 
1654 
1655 HeapWord*
1656 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1657                                            bool* succeeded) {
1658   assert_at_safepoint(true /* should_be_vm_thread */);
1659 
1660   *succeeded = true;
1661   // Let's attempt the allocation first.
1662   HeapWord* result =
1663     attempt_allocation_at_safepoint(word_size,
1664                                  false /* expect_null_mutator_alloc_region */);
1665   if (result != NULL) {
1666     assert(*succeeded, "sanity");
1667     return result;
1668   }
1669 
1670   // In a G1 heap, we're supposed to keep allocation from failing by
1671   // incremental pauses.  Therefore, at least for now, we'll favor
1672   // expansion over collection.  (This might change in the future if we can
1673   // do something smarter than full collection to satisfy a failed alloc.)
1674   result = expand_and_allocate(word_size);
1675   if (result != NULL) {
1676     assert(*succeeded, "sanity");
1677     return result;
1678   }
1679 
1680   // Expansion didn't work, we'll try to do a Full GC.
1681   bool gc_succeeded = do_collection(false, /* explicit_gc */
1682                                     false, /* clear_all_soft_refs */
1683                                     word_size);
1684   if (!gc_succeeded) {
1685     *succeeded = false;
1686     return NULL;
1687   }
1688 
1689   // Retry the allocation
1690   result = attempt_allocation_at_safepoint(word_size,
1691                                   true /* expect_null_mutator_alloc_region */);
1692   if (result != NULL) {
1693     assert(*succeeded, "sanity");
1694     return result;
1695   }
1696 
1697   // Then, try a Full GC that will collect all soft references.
1698   gc_succeeded = do_collection(false, /* explicit_gc */
1699                                true,  /* clear_all_soft_refs */
1700                                word_size);
1701   if (!gc_succeeded) {
1702     *succeeded = false;
1703     return NULL;
1704   }
1705 
1706   // Retry the allocation once more
1707   result = attempt_allocation_at_safepoint(word_size,
1708                                   true /* expect_null_mutator_alloc_region */);
1709   if (result != NULL) {
1710     assert(*succeeded, "sanity");
1711     return result;
1712   }
1713 
1714   assert(!collector_policy()->should_clear_all_soft_refs(),
1715          "Flag should have been handled and cleared prior to this point");
1716 
1717   // What else?  We might try synchronous finalization later.  If the total
1718   // space available is large enough for the allocation, then a more
1719   // complete compaction phase than we've tried so far might be
1720   // appropriate.
1721   assert(*succeeded, "sanity");
1722   return NULL;
1723 }
1724 
1725 // Attempting to expand the heap sufficiently
1726 // to support an allocation of the given "word_size".  If
1727 // successful, perform the allocation and return the address of the
1728 // allocated block, or else "NULL".
1729 
1730 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1731   assert_at_safepoint(true /* should_be_vm_thread */);
1732 
1733   verify_region_sets_optional();
1734 
1735   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1736   ergo_verbose1(ErgoHeapSizing,
1737                 "attempt heap expansion",
1738                 ergo_format_reason("allocation request failed")
1739                 ergo_format_byte("allocation request"),
1740                 word_size * HeapWordSize);
1741   if (expand(expand_bytes)) {
1742     _hrs.verify_optional();
1743     verify_region_sets_optional();
1744     return attempt_allocation_at_safepoint(word_size,
1745                                  false /* expect_null_mutator_alloc_region */);
1746   }
1747   return NULL;
1748 }
1749 
1750 void G1CollectedHeap::update_committed_space(HeapWord* old_end,
1751                                              HeapWord* new_end) {
1752   assert(old_end != new_end, "don't call this otherwise");
1753   assert((HeapWord*) _g1_storage.high() == new_end, "invariant");
1754 
1755   // Update the committed mem region.
1756   _g1_committed.set_end(new_end);
1757   // Tell the card table about the update.
1758   Universe::heap()->barrier_set()->resize_covered_region(_g1_committed);
1759   // Tell the BOT about the update.
1760   _bot_shared->resize(_g1_committed.word_size());
1761   // Tell the hot card cache about the update
1762   _cg1r->hot_card_cache()->resize_card_counts(capacity());
1763 }
1764 
1765 bool G1CollectedHeap::expand(size_t expand_bytes) {
1766   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1767   aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1768                                        HeapRegion::GrainBytes);
1769   ergo_verbose2(ErgoHeapSizing,
1770                 "expand the heap",
1771                 ergo_format_byte("requested expansion amount")
1772                 ergo_format_byte("attempted expansion amount"),
1773                 expand_bytes, aligned_expand_bytes);
1774 
1775   if (_g1_storage.uncommitted_size() == 0) {
1776     ergo_verbose0(ErgoHeapSizing,
1777                       "did not expand the heap",
1778                       ergo_format_reason("heap already fully expanded"));
1779     return false;
1780   }
1781 
1782   // First commit the memory.
1783   HeapWord* old_end = (HeapWord*) _g1_storage.high();
1784   bool successful = _g1_storage.expand_by(aligned_expand_bytes);
1785   if (successful) {
1786     // Then propagate this update to the necessary data structures.
1787     HeapWord* new_end = (HeapWord*) _g1_storage.high();
1788     update_committed_space(old_end, new_end);
1789 
1790     FreeRegionList expansion_list("Local Expansion List");
1791     MemRegion mr = _hrs.expand_by(old_end, new_end, &expansion_list);
1792     assert(mr.start() == old_end, "post-condition");
1793     // mr might be a smaller region than what was requested if
1794     // expand_by() was unable to allocate the HeapRegion instances
1795     assert(mr.end() <= new_end, "post-condition");
1796 
1797     size_t actual_expand_bytes = mr.byte_size();
1798     assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1799     assert(actual_expand_bytes == expansion_list.total_capacity_bytes(),
1800            "post-condition");
1801     if (actual_expand_bytes < aligned_expand_bytes) {
1802       // We could not expand _hrs to the desired size. In this case we
1803       // need to shrink the committed space accordingly.
1804       assert(mr.end() < new_end, "invariant");
1805 
1806       size_t diff_bytes = aligned_expand_bytes - actual_expand_bytes;
1807       // First uncommit the memory.
1808       _g1_storage.shrink_by(diff_bytes);
1809       // Then propagate this update to the necessary data structures.
1810       update_committed_space(new_end, mr.end());
1811     }
1812     _free_list.add_as_tail(&expansion_list);
1813 
1814     if (_hr_printer.is_active()) {
1815       HeapWord* curr = mr.start();
1816       while (curr < mr.end()) {
1817         HeapWord* curr_end = curr + HeapRegion::GrainWords;
1818         _hr_printer.commit(curr, curr_end);
1819         curr = curr_end;
1820       }
1821       assert(curr == mr.end(), "post-condition");
1822     }
1823     g1_policy()->record_new_heap_size(n_regions());
1824   } else {
1825     ergo_verbose0(ErgoHeapSizing,
1826                   "did not expand the heap",
1827                   ergo_format_reason("heap expansion operation failed"));
1828     // The expansion of the virtual storage space was unsuccessful.
1829     // Let's see if it was because we ran out of swap.
1830     if (G1ExitOnExpansionFailure &&
1831         _g1_storage.uncommitted_size() >= aligned_expand_bytes) {
1832       // We had head room...
1833       vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1834     }
1835   }
1836   return successful;
1837 }
1838 
1839 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1840   size_t aligned_shrink_bytes =
1841     ReservedSpace::page_align_size_down(shrink_bytes);
1842   aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1843                                          HeapRegion::GrainBytes);
1844   uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1845 
1846   uint num_regions_removed = _hrs.shrink_by(num_regions_to_remove);
1847   HeapWord* old_end = (HeapWord*) _g1_storage.high();
1848   size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1849 
1850   ergo_verbose3(ErgoHeapSizing,
1851                 "shrink the heap",
1852                 ergo_format_byte("requested shrinking amount")
1853                 ergo_format_byte("aligned shrinking amount")
1854                 ergo_format_byte("attempted shrinking amount"),
1855                 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1856   if (num_regions_removed > 0) {
1857     _g1_storage.shrink_by(shrunk_bytes);
1858     HeapWord* new_end = (HeapWord*) _g1_storage.high();
1859 
1860     if (_hr_printer.is_active()) {
1861       HeapWord* curr = old_end;
1862       while (curr > new_end) {
1863         HeapWord* curr_end = curr;
1864         curr -= HeapRegion::GrainWords;
1865         _hr_printer.uncommit(curr, curr_end);
1866       }
1867     }
1868 
1869     _expansion_regions += num_regions_removed;
1870     update_committed_space(old_end, new_end);
1871     HeapRegionRemSet::shrink_heap(n_regions());
1872     g1_policy()->record_new_heap_size(n_regions());
1873   } else {
1874     ergo_verbose0(ErgoHeapSizing,
1875                   "did not shrink the heap",
1876                   ergo_format_reason("heap shrinking operation failed"));
1877   }
1878 }
1879 
1880 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1881   verify_region_sets_optional();
1882 
1883   // We should only reach here at the end of a Full GC which means we
1884   // should not not be holding to any GC alloc regions. The method
1885   // below will make sure of that and do any remaining clean up.
1886   abandon_gc_alloc_regions();
1887 
1888   // Instead of tearing down / rebuilding the free lists here, we
1889   // could instead use the remove_all_pending() method on free_list to
1890   // remove only the ones that we need to remove.
1891   tear_down_region_sets(true /* free_list_only */);
1892   shrink_helper(shrink_bytes);
1893   rebuild_region_sets(true /* free_list_only */);
1894 
1895   _hrs.verify_optional();
1896   verify_region_sets_optional();
1897 }
1898 
1899 // Public methods.
1900 
1901 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1902 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1903 #endif // _MSC_VER
1904 
1905 
1906 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1907   SharedHeap(policy_),
1908   _g1_policy(policy_),
1909   _dirty_card_queue_set(false),
1910   _into_cset_dirty_card_queue_set(false),
1911   _is_alive_closure_cm(this),
1912   _is_alive_closure_stw(this),
1913   _ref_processor_cm(NULL),
1914   _ref_processor_stw(NULL),
1915   _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
1916   _bot_shared(NULL),
1917   _evac_failure_scan_stack(NULL),
1918   _mark_in_progress(false),
1919   _cg1r(NULL), _summary_bytes_used(0),
1920   _g1mm(NULL),
1921   _refine_cte_cl(NULL),
1922   _full_collection(false),
1923   _free_list("Master Free List", new MasterFreeRegionListMtSafeChecker()),
1924   _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1925   _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1926   _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1927   _free_regions_coming(false),
1928   _young_list(new YoungList(this)),
1929   _gc_time_stamp(0),
1930   _retained_old_gc_alloc_region(NULL),
1931   _survivor_plab_stats(YoungPLABSize, PLABWeight),
1932   _old_plab_stats(OldPLABSize, PLABWeight),
1933   _expand_heap_after_alloc_failure(true),
1934   _surviving_young_words(NULL),
1935   _old_marking_cycles_started(0),
1936   _old_marking_cycles_completed(0),
1937   _concurrent_cycle_started(false),
1938   _in_cset_fast_test(NULL),
1939   _in_cset_fast_test_base(NULL),
1940   _dirty_cards_region_list(NULL),
1941   _worker_cset_start_region(NULL),
1942   _worker_cset_start_region_time_stamp(NULL),
1943   _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1944   _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
1945   _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1946   _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) {
1947 
1948   _g1h = this;
1949   if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
1950     vm_exit_during_initialization("Failed necessary allocation.");
1951   }
1952 
1953   _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1954 
1955   int n_queues = MAX2((int)ParallelGCThreads, 1);
1956   _task_queues = new RefToScanQueueSet(n_queues);
1957 
1958   uint n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1959   assert(n_rem_sets > 0, "Invariant.");
1960 
1961   _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1962   _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC);
1963   _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1964 
1965   for (int i = 0; i < n_queues; i++) {
1966     RefToScanQueue* q = new RefToScanQueue();
1967     q->initialize();
1968     _task_queues->register_queue(i, q);
1969     ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1970   }
1971   clear_cset_start_regions();
1972 
1973   // Initialize the G1EvacuationFailureALot counters and flags.
1974   NOT_PRODUCT(reset_evacuation_should_fail();)
1975 
1976   guarantee(_task_queues != NULL, "task_queues allocation failure.");
1977 }
1978 
1979 jint G1CollectedHeap::initialize() {
1980   CollectedHeap::pre_initialize();
1981   os::enable_vtime();
1982 
1983   G1Log::init();
1984 
1985   // Necessary to satisfy locking discipline assertions.
1986 
1987   MutexLocker x(Heap_lock);
1988 
1989   // We have to initialize the printer before committing the heap, as
1990   // it will be used then.
1991   _hr_printer.set_active(G1PrintHeapRegions);
1992 
1993   // While there are no constraints in the GC code that HeapWordSize
1994   // be any particular value, there are multiple other areas in the
1995   // system which believe this to be true (e.g. oop->object_size in some
1996   // cases incorrectly returns the size in wordSize units rather than
1997   // HeapWordSize).
1998   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1999 
2000   size_t init_byte_size = collector_policy()->initial_heap_byte_size();
2001   size_t max_byte_size = collector_policy()->max_heap_byte_size();
2002   size_t heap_alignment = collector_policy()->heap_alignment();
2003 
2004   // Ensure that the sizes are properly aligned.
2005   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
2006   Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
2007   Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
2008 
2009   _cg1r = new ConcurrentG1Refine(this);
2010 
2011   // Reserve the maximum.
2012 
2013   // When compressed oops are enabled, the preferred heap base
2014   // is calculated by subtracting the requested size from the
2015   // 32Gb boundary and using the result as the base address for
2016   // heap reservation. If the requested size is not aligned to
2017   // HeapRegion::GrainBytes (i.e. the alignment that is passed
2018   // into the ReservedHeapSpace constructor) then the actual
2019   // base of the reserved heap may end up differing from the
2020   // address that was requested (i.e. the preferred heap base).
2021   // If this happens then we could end up using a non-optimal
2022   // compressed oops mode.
2023 
2024   ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
2025                                                  heap_alignment);
2026 
2027   // It is important to do this in a way such that concurrent readers can't
2028   // temporarily think something is in the heap.  (I've actually seen this
2029   // happen in asserts: DLD.)
2030   _reserved.set_word_size(0);
2031   _reserved.set_start((HeapWord*)heap_rs.base());
2032   _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size()));
2033 
2034   _expansion_regions = (uint) (max_byte_size / HeapRegion::GrainBytes);
2035 
2036   // Create the gen rem set (and barrier set) for the entire reserved region.
2037   _rem_set = collector_policy()->create_rem_set(_reserved, 2);
2038   set_barrier_set(rem_set()->bs());
2039   if (!barrier_set()->is_a(BarrierSet::G1SATBCTLogging)) {
2040     vm_exit_during_initialization("G1 requires a G1SATBLoggingCardTableModRefBS");
2041     return JNI_ENOMEM;
2042   }
2043 
2044   // Also create a G1 rem set.
2045   _g1_rem_set = new G1RemSet(this, g1_barrier_set());
2046 
2047   // Carve out the G1 part of the heap.
2048 
2049   ReservedSpace g1_rs   = heap_rs.first_part(max_byte_size);
2050   _g1_reserved = MemRegion((HeapWord*)g1_rs.base(),
2051                            g1_rs.size()/HeapWordSize);
2052 
2053   _g1_storage.initialize(g1_rs, 0);
2054   _g1_committed = MemRegion((HeapWord*)_g1_storage.low(), (size_t) 0);
2055   _hrs.initialize((HeapWord*) _g1_reserved.start(),
2056                   (HeapWord*) _g1_reserved.end());
2057   assert(_hrs.max_length() == _expansion_regions,
2058          err_msg("max length: %u expansion regions: %u",
2059                  _hrs.max_length(), _expansion_regions));
2060 
2061   // Do later initialization work for concurrent refinement.
2062   _cg1r->init();
2063 
2064   // 6843694 - ensure that the maximum region index can fit
2065   // in the remembered set structures.
2066   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
2067   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
2068 
2069   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
2070   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
2071   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
2072             "too many cards per region");
2073 
2074   FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
2075 
2076   _bot_shared = new G1BlockOffsetSharedArray(_reserved,
2077                                              heap_word_size(init_byte_size));
2078 
2079   _g1h = this;
2080 
2081   _in_cset_fast_test_length = max_regions();
2082   _in_cset_fast_test_base =
2083                    NEW_C_HEAP_ARRAY(bool, (size_t) _in_cset_fast_test_length, mtGC);
2084 
2085   // We're biasing _in_cset_fast_test to avoid subtracting the
2086   // beginning of the heap every time we want to index; basically
2087   // it's the same with what we do with the card table.
2088   _in_cset_fast_test = _in_cset_fast_test_base -
2089                ((uintx) _g1_reserved.start() >> HeapRegion::LogOfHRGrainBytes);
2090 
2091   // Clear the _cset_fast_test bitmap in anticipation of adding
2092   // regions to the incremental collection set for the first
2093   // evacuation pause.
2094   clear_cset_fast_test();
2095 
2096   // Create the ConcurrentMark data structure and thread.
2097   // (Must do this late, so that "max_regions" is defined.)
2098   _cm = new ConcurrentMark(this, heap_rs);
2099   if (_cm == NULL || !_cm->completed_initialization()) {
2100     vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark");
2101     return JNI_ENOMEM;
2102   }
2103   _cmThread = _cm->cmThread();
2104 
2105   // Initialize the from_card cache structure of HeapRegionRemSet.
2106   HeapRegionRemSet::init_heap(max_regions());
2107 
2108   // Now expand into the initial heap size.
2109   if (!expand(init_byte_size)) {
2110     vm_shutdown_during_initialization("Failed to allocate initial heap.");
2111     return JNI_ENOMEM;
2112   }
2113 
2114   // Perform any initialization actions delegated to the policy.
2115   g1_policy()->init();
2116 
2117   _refine_cte_cl =
2118     new RefineCardTableEntryClosure(ConcurrentG1RefineThread::sts(),
2119                                     g1_rem_set(),
2120                                     concurrent_g1_refine());
2121   JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
2122 
2123   JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
2124                                                SATB_Q_FL_lock,
2125                                                G1SATBProcessCompletedThreshold,
2126                                                Shared_SATB_Q_lock);
2127 
2128   JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
2129                                                 DirtyCardQ_FL_lock,
2130                                                 concurrent_g1_refine()->yellow_zone(),
2131                                                 concurrent_g1_refine()->red_zone(),
2132                                                 Shared_DirtyCardQ_lock);
2133 
2134   if (G1DeferredRSUpdate) {
2135     dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
2136                                       DirtyCardQ_FL_lock,
2137                                       -1, // never trigger processing
2138                                       -1, // no limit on length
2139                                       Shared_DirtyCardQ_lock,
2140                                       &JavaThread::dirty_card_queue_set());
2141   }
2142 
2143   // Initialize the card queue set used to hold cards containing
2144   // references into the collection set.
2145   _into_cset_dirty_card_queue_set.initialize(DirtyCardQ_CBL_mon,
2146                                              DirtyCardQ_FL_lock,
2147                                              -1, // never trigger processing
2148                                              -1, // no limit on length
2149                                              Shared_DirtyCardQ_lock,
2150                                              &JavaThread::dirty_card_queue_set());
2151 
2152   // In case we're keeping closure specialization stats, initialize those
2153   // counts and that mechanism.
2154   SpecializationStats::clear();
2155 
2156   // Here we allocate the dummy full region that is required by the
2157   // G1AllocRegion class. If we don't pass an address in the reserved
2158   // space here, lots of asserts fire.
2159 
2160   HeapRegion* dummy_region = new_heap_region(0 /* index of bottom region */,
2161                                              _g1_reserved.start());
2162   // We'll re-use the same region whether the alloc region will
2163   // require BOT updates or not and, if it doesn't, then a non-young
2164   // region will complain that it cannot support allocations without
2165   // BOT updates. So we'll tag the dummy region as young to avoid that.
2166   dummy_region->set_young();
2167   // Make sure it's full.
2168   dummy_region->set_top(dummy_region->end());
2169   G1AllocRegion::setup(this, dummy_region);
2170 
2171   init_mutator_alloc_region();
2172 
2173   // Do create of the monitoring and management support so that
2174   // values in the heap have been properly initialized.
2175   _g1mm = new G1MonitoringSupport(this);
2176 
2177   G1StringDedup::initialize();
2178 
2179   return JNI_OK;
2180 }
2181 
2182 size_t G1CollectedHeap::conservative_max_heap_alignment() {
2183   return HeapRegion::max_region_size();
2184 }
2185 
2186 void G1CollectedHeap::ref_processing_init() {
2187   // Reference processing in G1 currently works as follows:
2188   //
2189   // * There are two reference processor instances. One is
2190   //   used to record and process discovered references
2191   //   during concurrent marking; the other is used to
2192   //   record and process references during STW pauses
2193   //   (both full and incremental).
2194   // * Both ref processors need to 'span' the entire heap as
2195   //   the regions in the collection set may be dotted around.
2196   //
2197   // * For the concurrent marking ref processor:
2198   //   * Reference discovery is enabled at initial marking.
2199   //   * Reference discovery is disabled and the discovered
2200   //     references processed etc during remarking.
2201   //   * Reference discovery is MT (see below).
2202   //   * Reference discovery requires a barrier (see below).
2203   //   * Reference processing may or may not be MT
2204   //     (depending on the value of ParallelRefProcEnabled
2205   //     and ParallelGCThreads).
2206   //   * A full GC disables reference discovery by the CM
2207   //     ref processor and abandons any entries on it's
2208   //     discovered lists.
2209   //
2210   // * For the STW processor:
2211   //   * Non MT discovery is enabled at the start of a full GC.
2212   //   * Processing and enqueueing during a full GC is non-MT.
2213   //   * During a full GC, references are processed after marking.
2214   //
2215   //   * Discovery (may or may not be MT) is enabled at the start
2216   //     of an incremental evacuation pause.
2217   //   * References are processed near the end of a STW evacuation pause.
2218   //   * For both types of GC:
2219   //     * Discovery is atomic - i.e. not concurrent.
2220   //     * Reference discovery will not need a barrier.
2221 
2222   SharedHeap::ref_processing_init();
2223   MemRegion mr = reserved_region();
2224 
2225   // Concurrent Mark ref processor
2226   _ref_processor_cm =
2227     new ReferenceProcessor(mr,    // span
2228                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2229                                 // mt processing
2230                            (int) ParallelGCThreads,
2231                                 // degree of mt processing
2232                            (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2233                                 // mt discovery
2234                            (int) MAX2(ParallelGCThreads, ConcGCThreads),
2235                                 // degree of mt discovery
2236                            false,
2237                                 // Reference discovery is not atomic
2238                            &_is_alive_closure_cm,
2239                                 // is alive closure
2240                                 // (for efficiency/performance)
2241                            true);
2242                                 // Setting next fields of discovered
2243                                 // lists requires a barrier.
2244 
2245   // STW ref processor
2246   _ref_processor_stw =
2247     new ReferenceProcessor(mr,    // span
2248                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2249                                 // mt processing
2250                            MAX2((int)ParallelGCThreads, 1),
2251                                 // degree of mt processing
2252                            (ParallelGCThreads > 1),
2253                                 // mt discovery
2254                            MAX2((int)ParallelGCThreads, 1),
2255                                 // degree of mt discovery
2256                            true,
2257                                 // Reference discovery is atomic
2258                            &_is_alive_closure_stw,
2259                                 // is alive closure
2260                                 // (for efficiency/performance)
2261                            false);
2262                                 // Setting next fields of discovered
2263                                 // lists does not require a barrier.
2264 }
2265 
2266 size_t G1CollectedHeap::capacity() const {
2267   return _g1_committed.byte_size();
2268 }
2269 
2270 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2271   assert(!hr->continuesHumongous(), "pre-condition");
2272   hr->reset_gc_time_stamp();
2273   if (hr->startsHumongous()) {
2274     uint first_index = hr->hrs_index() + 1;
2275     uint last_index = hr->last_hc_index();
2276     for (uint i = first_index; i < last_index; i += 1) {
2277       HeapRegion* chr = region_at(i);
2278       assert(chr->continuesHumongous(), "sanity");
2279       chr->reset_gc_time_stamp();
2280     }
2281   }
2282 }
2283 
2284 #ifndef PRODUCT
2285 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2286 private:
2287   unsigned _gc_time_stamp;
2288   bool _failures;
2289 
2290 public:
2291   CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2292     _gc_time_stamp(gc_time_stamp), _failures(false) { }
2293 
2294   virtual bool doHeapRegion(HeapRegion* hr) {
2295     unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2296     if (_gc_time_stamp != region_gc_time_stamp) {
2297       gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, "
2298                              "expected %d", HR_FORMAT_PARAMS(hr),
2299                              region_gc_time_stamp, _gc_time_stamp);
2300       _failures = true;
2301     }
2302     return false;
2303   }
2304 
2305   bool failures() { return _failures; }
2306 };
2307 
2308 void G1CollectedHeap::check_gc_time_stamps() {
2309   CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2310   heap_region_iterate(&cl);
2311   guarantee(!cl.failures(), "all GC time stamps should have been reset");
2312 }
2313 #endif // PRODUCT
2314 
2315 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2316                                                  DirtyCardQueue* into_cset_dcq,
2317                                                  bool concurrent,
2318                                                  int worker_i) {
2319   // Clean cards in the hot card cache
2320   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
2321   hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq);
2322 
2323   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2324   int n_completed_buffers = 0;
2325   while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2326     n_completed_buffers++;
2327   }
2328   g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers);
2329   dcqs.clear_n_completed_buffers();
2330   assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2331 }
2332 
2333 
2334 // Computes the sum of the storage used by the various regions.
2335 
2336 size_t G1CollectedHeap::used() const {
2337   assert(Heap_lock->owner() != NULL,
2338          "Should be owned on this thread's behalf.");
2339   size_t result = _summary_bytes_used;
2340   // Read only once in case it is set to NULL concurrently
2341   HeapRegion* hr = _mutator_alloc_region.get();
2342   if (hr != NULL)
2343     result += hr->used();
2344   return result;
2345 }
2346 
2347 size_t G1CollectedHeap::used_unlocked() const {
2348   size_t result = _summary_bytes_used;
2349   return result;
2350 }
2351 
2352 class SumUsedClosure: public HeapRegionClosure {
2353   size_t _used;
2354 public:
2355   SumUsedClosure() : _used(0) {}
2356   bool doHeapRegion(HeapRegion* r) {
2357     if (!r->continuesHumongous()) {
2358       _used += r->used();
2359     }
2360     return false;
2361   }
2362   size_t result() { return _used; }
2363 };
2364 
2365 size_t G1CollectedHeap::recalculate_used() const {
2366   double recalculate_used_start = os::elapsedTime();
2367 
2368   SumUsedClosure blk;
2369   heap_region_iterate(&blk);
2370 
2371   g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2372   return blk.result();
2373 }
2374 
2375 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2376   switch (cause) {
2377     case GCCause::_gc_locker:               return GCLockerInvokesConcurrent;
2378     case GCCause::_java_lang_system_gc:     return ExplicitGCInvokesConcurrent;
2379     case GCCause::_g1_humongous_allocation: return true;
2380     default:                                return false;
2381   }
2382 }
2383 
2384 #ifndef PRODUCT
2385 void G1CollectedHeap::allocate_dummy_regions() {
2386   // Let's fill up most of the region
2387   size_t word_size = HeapRegion::GrainWords - 1024;
2388   // And as a result the region we'll allocate will be humongous.
2389   guarantee(isHumongous(word_size), "sanity");
2390 
2391   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2392     // Let's use the existing mechanism for the allocation
2393     HeapWord* dummy_obj = humongous_obj_allocate(word_size);
2394     if (dummy_obj != NULL) {
2395       MemRegion mr(dummy_obj, word_size);
2396       CollectedHeap::fill_with_object(mr);
2397     } else {
2398       // If we can't allocate once, we probably cannot allocate
2399       // again. Let's get out of the loop.
2400       break;
2401     }
2402   }
2403 }
2404 #endif // !PRODUCT
2405 
2406 void G1CollectedHeap::increment_old_marking_cycles_started() {
2407   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2408     _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2409     err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2410     _old_marking_cycles_started, _old_marking_cycles_completed));
2411 
2412   _old_marking_cycles_started++;
2413 }
2414 
2415 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2416   MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2417 
2418   // We assume that if concurrent == true, then the caller is a
2419   // concurrent thread that was joined the Suspendible Thread
2420   // Set. If there's ever a cheap way to check this, we should add an
2421   // assert here.
2422 
2423   // Given that this method is called at the end of a Full GC or of a
2424   // concurrent cycle, and those can be nested (i.e., a Full GC can
2425   // interrupt a concurrent cycle), the number of full collections
2426   // completed should be either one (in the case where there was no
2427   // nesting) or two (when a Full GC interrupted a concurrent cycle)
2428   // behind the number of full collections started.
2429 
2430   // This is the case for the inner caller, i.e. a Full GC.
2431   assert(concurrent ||
2432          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2433          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2434          err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
2435                  "is inconsistent with _old_marking_cycles_completed = %u",
2436                  _old_marking_cycles_started, _old_marking_cycles_completed));
2437 
2438   // This is the case for the outer caller, i.e. the concurrent cycle.
2439   assert(!concurrent ||
2440          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2441          err_msg("for outer caller (concurrent cycle): "
2442                  "_old_marking_cycles_started = %u "
2443                  "is inconsistent with _old_marking_cycles_completed = %u",
2444                  _old_marking_cycles_started, _old_marking_cycles_completed));
2445 
2446   _old_marking_cycles_completed += 1;
2447 
2448   // We need to clear the "in_progress" flag in the CM thread before
2449   // we wake up any waiters (especially when ExplicitInvokesConcurrent
2450   // is set) so that if a waiter requests another System.gc() it doesn't
2451   // incorrectly see that a marking cycle is still in progress.
2452   if (concurrent) {
2453     _cmThread->clear_in_progress();
2454   }
2455 
2456   // This notify_all() will ensure that a thread that called
2457   // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2458   // and it's waiting for a full GC to finish will be woken up. It is
2459   // waiting in VM_G1IncCollectionPause::doit_epilogue().
2460   FullGCCount_lock->notify_all();
2461 }
2462 
2463 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) {
2464   _concurrent_cycle_started = true;
2465   _gc_timer_cm->register_gc_start(start_time);
2466 
2467   _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start());
2468   trace_heap_before_gc(_gc_tracer_cm);
2469 }
2470 
2471 void G1CollectedHeap::register_concurrent_cycle_end() {
2472   if (_concurrent_cycle_started) {
2473     if (_cm->has_aborted()) {
2474       _gc_tracer_cm->report_concurrent_mode_failure();
2475     }
2476 
2477     _gc_timer_cm->register_gc_end();
2478     _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
2479 
2480     _concurrent_cycle_started = false;
2481   }
2482 }
2483 
2484 void G1CollectedHeap::trace_heap_after_concurrent_cycle() {
2485   if (_concurrent_cycle_started) {
2486     trace_heap_after_gc(_gc_tracer_cm);
2487   }
2488 }
2489 
2490 G1YCType G1CollectedHeap::yc_type() {
2491   bool is_young = g1_policy()->gcs_are_young();
2492   bool is_initial_mark = g1_policy()->during_initial_mark_pause();
2493   bool is_during_mark = mark_in_progress();
2494 
2495   if (is_initial_mark) {
2496     return InitialMark;
2497   } else if (is_during_mark) {
2498     return DuringMark;
2499   } else if (is_young) {
2500     return Normal;
2501   } else {
2502     return Mixed;
2503   }
2504 }
2505 
2506 void G1CollectedHeap::collect(GCCause::Cause cause) {
2507   assert_heap_not_locked();
2508 
2509   unsigned int gc_count_before;
2510   unsigned int old_marking_count_before;
2511   bool retry_gc;
2512 
2513   do {
2514     retry_gc = false;
2515 
2516     {
2517       MutexLocker ml(Heap_lock);
2518 
2519       // Read the GC count while holding the Heap_lock
2520       gc_count_before = total_collections();
2521       old_marking_count_before = _old_marking_cycles_started;
2522     }
2523 
2524     if (should_do_concurrent_full_gc(cause)) {
2525       // Schedule an initial-mark evacuation pause that will start a
2526       // concurrent cycle. We're setting word_size to 0 which means that
2527       // we are not requesting a post-GC allocation.
2528       VM_G1IncCollectionPause op(gc_count_before,
2529                                  0,     /* word_size */
2530                                  true,  /* should_initiate_conc_mark */
2531                                  g1_policy()->max_pause_time_ms(),
2532                                  cause);
2533 
2534       VMThread::execute(&op);
2535       if (!op.pause_succeeded()) {
2536         if (old_marking_count_before == _old_marking_cycles_started) {
2537           retry_gc = op.should_retry_gc();
2538         } else {
2539           // A Full GC happened while we were trying to schedule the
2540           // initial-mark GC. No point in starting a new cycle given
2541           // that the whole heap was collected anyway.
2542         }
2543 
2544         if (retry_gc) {
2545           if (GC_locker::is_active_and_needs_gc()) {
2546             GC_locker::stall_until_clear();
2547           }
2548         }
2549       }
2550     } else {
2551       if (cause == GCCause::_gc_locker
2552           DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2553 
2554         // Schedule a standard evacuation pause. We're setting word_size
2555         // to 0 which means that we are not requesting a post-GC allocation.
2556         VM_G1IncCollectionPause op(gc_count_before,
2557                                    0,     /* word_size */
2558                                    false, /* should_initiate_conc_mark */
2559                                    g1_policy()->max_pause_time_ms(),
2560                                    cause);
2561         VMThread::execute(&op);
2562       } else {
2563         // Schedule a Full GC.
2564         VM_G1CollectFull op(gc_count_before, old_marking_count_before, cause);
2565         VMThread::execute(&op);
2566       }
2567     }
2568   } while (retry_gc);
2569 }
2570 
2571 bool G1CollectedHeap::is_in(const void* p) const {
2572   if (_g1_committed.contains(p)) {
2573     // Given that we know that p is in the committed space,
2574     // heap_region_containing_raw() should successfully
2575     // return the containing region.
2576     HeapRegion* hr = heap_region_containing_raw(p);
2577     return hr->is_in(p);
2578   } else {
2579     return false;
2580   }
2581 }
2582 
2583 // Iteration functions.
2584 
2585 // Iterates an OopClosure over all ref-containing fields of objects
2586 // within a HeapRegion.
2587 
2588 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2589   MemRegion _mr;
2590   ExtendedOopClosure* _cl;
2591 public:
2592   IterateOopClosureRegionClosure(MemRegion mr, ExtendedOopClosure* cl)
2593     : _mr(mr), _cl(cl) {}
2594   bool doHeapRegion(HeapRegion* r) {
2595     if (!r->continuesHumongous()) {
2596       r->oop_iterate(_cl);
2597     }
2598     return false;
2599   }
2600 };
2601 
2602 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) {
2603   IterateOopClosureRegionClosure blk(_g1_committed, cl);
2604   heap_region_iterate(&blk);
2605 }
2606 
2607 void G1CollectedHeap::oop_iterate(MemRegion mr, ExtendedOopClosure* cl) {
2608   IterateOopClosureRegionClosure blk(mr, cl);
2609   heap_region_iterate(&blk);
2610 }
2611 
2612 // Iterates an ObjectClosure over all objects within a HeapRegion.
2613 
2614 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2615   ObjectClosure* _cl;
2616 public:
2617   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2618   bool doHeapRegion(HeapRegion* r) {
2619     if (! r->continuesHumongous()) {
2620       r->object_iterate(_cl);
2621     }
2622     return false;
2623   }
2624 };
2625 
2626 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2627   IterateObjectClosureRegionClosure blk(cl);
2628   heap_region_iterate(&blk);
2629 }
2630 
2631 // Calls a SpaceClosure on a HeapRegion.
2632 
2633 class SpaceClosureRegionClosure: public HeapRegionClosure {
2634   SpaceClosure* _cl;
2635 public:
2636   SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2637   bool doHeapRegion(HeapRegion* r) {
2638     _cl->do_space(r);
2639     return false;
2640   }
2641 };
2642 
2643 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2644   SpaceClosureRegionClosure blk(cl);
2645   heap_region_iterate(&blk);
2646 }
2647 
2648 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2649   _hrs.iterate(cl);
2650 }
2651 
2652 void
2653 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
2654                                                  uint worker_id,
2655                                                  uint no_of_par_workers,
2656                                                  jint claim_value) {
2657   const uint regions = n_regions();
2658   const uint max_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
2659                              no_of_par_workers :
2660                              1);
2661   assert(UseDynamicNumberOfGCThreads ||
2662          no_of_par_workers == workers()->total_workers(),
2663          "Non dynamic should use fixed number of workers");
2664   // try to spread out the starting points of the workers
2665   const HeapRegion* start_hr =
2666                         start_region_for_worker(worker_id, no_of_par_workers);
2667   const uint start_index = start_hr->hrs_index();
2668 
2669   // each worker will actually look at all regions
2670   for (uint count = 0; count < regions; ++count) {
2671     const uint index = (start_index + count) % regions;
2672     assert(0 <= index && index < regions, "sanity");
2673     HeapRegion* r = region_at(index);
2674     // we'll ignore "continues humongous" regions (we'll process them
2675     // when we come across their corresponding "start humongous"
2676     // region) and regions already claimed
2677     if (r->claim_value() == claim_value || r->continuesHumongous()) {
2678       continue;
2679     }
2680     // OK, try to claim it
2681     if (r->claimHeapRegion(claim_value)) {
2682       // success!
2683       assert(!r->continuesHumongous(), "sanity");
2684       if (r->startsHumongous()) {
2685         // If the region is "starts humongous" we'll iterate over its
2686         // "continues humongous" first; in fact we'll do them
2687         // first. The order is important. In on case, calling the
2688         // closure on the "starts humongous" region might de-allocate
2689         // and clear all its "continues humongous" regions and, as a
2690         // result, we might end up processing them twice. So, we'll do
2691         // them first (notice: most closures will ignore them anyway) and
2692         // then we'll do the "starts humongous" region.
2693         for (uint ch_index = index + 1; ch_index < regions; ++ch_index) {
2694           HeapRegion* chr = region_at(ch_index);
2695 
2696           // if the region has already been claimed or it's not
2697           // "continues humongous" we're done
2698           if (chr->claim_value() == claim_value ||
2699               !chr->continuesHumongous()) {
2700             break;
2701           }
2702 
2703           // No one should have claimed it directly. We can given
2704           // that we claimed its "starts humongous" region.
2705           assert(chr->claim_value() != claim_value, "sanity");
2706           assert(chr->humongous_start_region() == r, "sanity");
2707 
2708           if (chr->claimHeapRegion(claim_value)) {
2709             // we should always be able to claim it; no one else should
2710             // be trying to claim this region
2711 
2712             bool res2 = cl->doHeapRegion(chr);
2713             assert(!res2, "Should not abort");
2714 
2715             // Right now, this holds (i.e., no closure that actually
2716             // does something with "continues humongous" regions
2717             // clears them). We might have to weaken it in the future,
2718             // but let's leave these two asserts here for extra safety.
2719             assert(chr->continuesHumongous(), "should still be the case");
2720             assert(chr->humongous_start_region() == r, "sanity");
2721           } else {
2722             guarantee(false, "we should not reach here");
2723           }
2724         }
2725       }
2726 
2727       assert(!r->continuesHumongous(), "sanity");
2728       bool res = cl->doHeapRegion(r);
2729       assert(!res, "Should not abort");
2730     }
2731   }
2732 }
2733 
2734 class ResetClaimValuesClosure: public HeapRegionClosure {
2735 public:
2736   bool doHeapRegion(HeapRegion* r) {
2737     r->set_claim_value(HeapRegion::InitialClaimValue);
2738     return false;
2739   }
2740 };
2741 
2742 void G1CollectedHeap::reset_heap_region_claim_values() {
2743   ResetClaimValuesClosure blk;
2744   heap_region_iterate(&blk);
2745 }
2746 
2747 void G1CollectedHeap::reset_cset_heap_region_claim_values() {
2748   ResetClaimValuesClosure blk;
2749   collection_set_iterate(&blk);
2750 }
2751 
2752 #ifdef ASSERT
2753 // This checks whether all regions in the heap have the correct claim
2754 // value. I also piggy-backed on this a check to ensure that the
2755 // humongous_start_region() information on "continues humongous"
2756 // regions is correct.
2757 
2758 class CheckClaimValuesClosure : public HeapRegionClosure {
2759 private:
2760   jint _claim_value;
2761   uint _failures;
2762   HeapRegion* _sh_region;
2763 
2764 public:
2765   CheckClaimValuesClosure(jint claim_value) :
2766     _claim_value(claim_value), _failures(0), _sh_region(NULL) { }
2767   bool doHeapRegion(HeapRegion* r) {
2768     if (r->claim_value() != _claim_value) {
2769       gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2770                              "claim value = %d, should be %d",
2771                              HR_FORMAT_PARAMS(r),
2772                              r->claim_value(), _claim_value);
2773       ++_failures;
2774     }
2775     if (!r->isHumongous()) {
2776       _sh_region = NULL;
2777     } else if (r->startsHumongous()) {
2778       _sh_region = r;
2779     } else if (r->continuesHumongous()) {
2780       if (r->humongous_start_region() != _sh_region) {
2781         gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2782                                "HS = "PTR_FORMAT", should be "PTR_FORMAT,
2783                                HR_FORMAT_PARAMS(r),
2784                                r->humongous_start_region(),
2785                                _sh_region);
2786         ++_failures;
2787       }
2788     }
2789     return false;
2790   }
2791   uint failures() { return _failures; }
2792 };
2793 
2794 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
2795   CheckClaimValuesClosure cl(claim_value);
2796   heap_region_iterate(&cl);
2797   return cl.failures() == 0;
2798 }
2799 
2800 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure {
2801 private:
2802   jint _claim_value;
2803   uint _failures;
2804 
2805 public:
2806   CheckClaimValuesInCSetHRClosure(jint claim_value) :
2807     _claim_value(claim_value), _failures(0) { }
2808 
2809   uint failures() { return _failures; }
2810 
2811   bool doHeapRegion(HeapRegion* hr) {
2812     assert(hr->in_collection_set(), "how?");
2813     assert(!hr->isHumongous(), "H-region in CSet");
2814     if (hr->claim_value() != _claim_value) {
2815       gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", "
2816                              "claim value = %d, should be %d",
2817                              HR_FORMAT_PARAMS(hr),
2818                              hr->claim_value(), _claim_value);
2819       _failures += 1;
2820     }
2821     return false;
2822   }
2823 };
2824 
2825 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) {
2826   CheckClaimValuesInCSetHRClosure cl(claim_value);
2827   collection_set_iterate(&cl);
2828   return cl.failures() == 0;
2829 }
2830 #endif // ASSERT
2831 
2832 // Clear the cached CSet starting regions and (more importantly)
2833 // the time stamps. Called when we reset the GC time stamp.
2834 void G1CollectedHeap::clear_cset_start_regions() {
2835   assert(_worker_cset_start_region != NULL, "sanity");
2836   assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2837 
2838   int n_queues = MAX2((int)ParallelGCThreads, 1);
2839   for (int i = 0; i < n_queues; i++) {
2840     _worker_cset_start_region[i] = NULL;
2841     _worker_cset_start_region_time_stamp[i] = 0;
2842   }
2843 }
2844 
2845 // Given the id of a worker, obtain or calculate a suitable
2846 // starting region for iterating over the current collection set.
2847 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(int worker_i) {
2848   assert(get_gc_time_stamp() > 0, "should have been updated by now");
2849 
2850   HeapRegion* result = NULL;
2851   unsigned gc_time_stamp = get_gc_time_stamp();
2852 
2853   if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2854     // Cached starting region for current worker was set
2855     // during the current pause - so it's valid.
2856     // Note: the cached starting heap region may be NULL
2857     // (when the collection set is empty).
2858     result = _worker_cset_start_region[worker_i];
2859     assert(result == NULL || result->in_collection_set(), "sanity");
2860     return result;
2861   }
2862 
2863   // The cached entry was not valid so let's calculate
2864   // a suitable starting heap region for this worker.
2865 
2866   // We want the parallel threads to start their collection
2867   // set iteration at different collection set regions to
2868   // avoid contention.
2869   // If we have:
2870   //          n collection set regions
2871   //          p threads
2872   // Then thread t will start at region floor ((t * n) / p)
2873 
2874   result = g1_policy()->collection_set();
2875   if (G1CollectedHeap::use_parallel_gc_threads()) {
2876     uint cs_size = g1_policy()->cset_region_length();
2877     uint active_workers = workers()->active_workers();
2878     assert(UseDynamicNumberOfGCThreads ||
2879              active_workers == workers()->total_workers(),
2880              "Unless dynamic should use total workers");
2881 
2882     uint end_ind   = (cs_size * worker_i) / active_workers;
2883     uint start_ind = 0;
2884 
2885     if (worker_i > 0 &&
2886         _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2887       // Previous workers starting region is valid
2888       // so let's iterate from there
2889       start_ind = (cs_size * (worker_i - 1)) / active_workers;
2890       result = _worker_cset_start_region[worker_i - 1];
2891     }
2892 
2893     for (uint i = start_ind; i < end_ind; i++) {
2894       result = result->next_in_collection_set();
2895     }
2896   }
2897 
2898   // Note: the calculated starting heap region may be NULL
2899   // (when the collection set is empty).
2900   assert(result == NULL || result->in_collection_set(), "sanity");
2901   assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2902          "should be updated only once per pause");
2903   _worker_cset_start_region[worker_i] = result;
2904   OrderAccess::storestore();
2905   _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2906   return result;
2907 }
2908 
2909 HeapRegion* G1CollectedHeap::start_region_for_worker(uint worker_i,
2910                                                      uint no_of_par_workers) {
2911   uint worker_num =
2912            G1CollectedHeap::use_parallel_gc_threads() ? no_of_par_workers : 1U;
2913   assert(UseDynamicNumberOfGCThreads ||
2914          no_of_par_workers == workers()->total_workers(),
2915          "Non dynamic should use fixed number of workers");
2916   const uint start_index = n_regions() * worker_i / worker_num;
2917   return region_at(start_index);
2918 }
2919 
2920 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2921   HeapRegion* r = g1_policy()->collection_set();
2922   while (r != NULL) {
2923     HeapRegion* next = r->next_in_collection_set();
2924     if (cl->doHeapRegion(r)) {
2925       cl->incomplete();
2926       return;
2927     }
2928     r = next;
2929   }
2930 }
2931 
2932 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2933                                                   HeapRegionClosure *cl) {
2934   if (r == NULL) {
2935     // The CSet is empty so there's nothing to do.
2936     return;
2937   }
2938 
2939   assert(r->in_collection_set(),
2940          "Start region must be a member of the collection set.");
2941   HeapRegion* cur = r;
2942   while (cur != NULL) {
2943     HeapRegion* next = cur->next_in_collection_set();
2944     if (cl->doHeapRegion(cur) && false) {
2945       cl->incomplete();
2946       return;
2947     }
2948     cur = next;
2949   }
2950   cur = g1_policy()->collection_set();
2951   while (cur != r) {
2952     HeapRegion* next = cur->next_in_collection_set();
2953     if (cl->doHeapRegion(cur) && false) {
2954       cl->incomplete();
2955       return;
2956     }
2957     cur = next;
2958   }
2959 }
2960 
2961 CompactibleSpace* G1CollectedHeap::first_compactible_space() {
2962   return n_regions() > 0 ? region_at(0) : NULL;
2963 }
2964 
2965 
2966 Space* G1CollectedHeap::space_containing(const void* addr) const {
2967   Space* res = heap_region_containing(addr);
2968   return res;
2969 }
2970 
2971 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2972   Space* sp = space_containing(addr);
2973   if (sp != NULL) {
2974     return sp->block_start(addr);
2975   }
2976   return NULL;
2977 }
2978 
2979 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2980   Space* sp = space_containing(addr);
2981   assert(sp != NULL, "block_size of address outside of heap");
2982   return sp->block_size(addr);
2983 }
2984 
2985 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2986   Space* sp = space_containing(addr);
2987   return sp->block_is_obj(addr);
2988 }
2989 
2990 bool G1CollectedHeap::supports_tlab_allocation() const {
2991   return true;
2992 }
2993 
2994 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2995   return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes;
2996 }
2997 
2998 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2999   return young_list()->eden_used_bytes();
3000 }
3001 
3002 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
3003 // must be smaller than the humongous object limit.
3004 size_t G1CollectedHeap::max_tlab_size() const {
3005   return align_size_down(_humongous_object_threshold_in_words - 1, MinObjAlignment);
3006 }
3007 
3008 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
3009   // Return the remaining space in the cur alloc region, but not less than
3010   // the min TLAB size.
3011 
3012   // Also, this value can be at most the humongous object threshold,
3013   // since we can't allow tlabs to grow big enough to accommodate
3014   // humongous objects.
3015 
3016   HeapRegion* hr = _mutator_alloc_region.get();
3017   size_t max_tlab = max_tlab_size() * wordSize;
3018   if (hr == NULL) {
3019     return max_tlab;
3020   } else {
3021     return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab);
3022   }
3023 }
3024 
3025 size_t G1CollectedHeap::max_capacity() const {
3026   return _g1_reserved.byte_size();
3027 }
3028 
3029 jlong G1CollectedHeap::millis_since_last_gc() {
3030   // assert(false, "NYI");
3031   return 0;
3032 }
3033 
3034 void G1CollectedHeap::prepare_for_verify() {
3035   if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
3036     ensure_parsability(false);
3037   }
3038   g1_rem_set()->prepare_for_verify();
3039 }
3040 
3041 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr,
3042                                               VerifyOption vo) {
3043   switch (vo) {
3044   case VerifyOption_G1UsePrevMarking:
3045     return hr->obj_allocated_since_prev_marking(obj);
3046   case VerifyOption_G1UseNextMarking:
3047     return hr->obj_allocated_since_next_marking(obj);
3048   case VerifyOption_G1UseMarkWord:
3049     return false;
3050   default:
3051     ShouldNotReachHere();
3052   }
3053   return false; // keep some compilers happy
3054 }
3055 
3056 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) {
3057   switch (vo) {
3058   case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start();
3059   case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start();
3060   case VerifyOption_G1UseMarkWord:    return NULL;
3061   default:                            ShouldNotReachHere();
3062   }
3063   return NULL; // keep some compilers happy
3064 }
3065 
3066 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) {
3067   switch (vo) {
3068   case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj);
3069   case VerifyOption_G1UseNextMarking: return isMarkedNext(obj);
3070   case VerifyOption_G1UseMarkWord:    return obj->is_gc_marked();
3071   default:                            ShouldNotReachHere();
3072   }
3073   return false; // keep some compilers happy
3074 }
3075 
3076 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) {
3077   switch (vo) {
3078   case VerifyOption_G1UsePrevMarking: return "PTAMS";
3079   case VerifyOption_G1UseNextMarking: return "NTAMS";
3080   case VerifyOption_G1UseMarkWord:    return "NONE";
3081   default:                            ShouldNotReachHere();
3082   }
3083   return NULL; // keep some compilers happy
3084 }
3085 
3086 class VerifyRootsClosure: public OopClosure {
3087 private:
3088   G1CollectedHeap* _g1h;
3089   VerifyOption     _vo;
3090   bool             _failures;
3091 public:
3092   // _vo == UsePrevMarking -> use "prev" marking information,
3093   // _vo == UseNextMarking -> use "next" marking information,
3094   // _vo == UseMarkWord    -> use mark word from object header.
3095   VerifyRootsClosure(VerifyOption vo) :
3096     _g1h(G1CollectedHeap::heap()),
3097     _vo(vo),
3098     _failures(false) { }
3099 
3100   bool failures() { return _failures; }
3101 
3102   template <class T> void do_oop_nv(T* p) {
3103     T heap_oop = oopDesc::load_heap_oop(p);
3104     if (!oopDesc::is_null(heap_oop)) {
3105       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3106       if (_g1h->is_obj_dead_cond(obj, _vo)) {
3107         gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
3108                               "points to dead obj "PTR_FORMAT, p, (void*) obj);
3109         if (_vo == VerifyOption_G1UseMarkWord) {
3110           gclog_or_tty->print_cr("  Mark word: "PTR_FORMAT, (void*)(obj->mark()));
3111         }
3112         obj->print_on(gclog_or_tty);
3113         _failures = true;
3114       }
3115     }
3116   }
3117 
3118   void do_oop(oop* p)       { do_oop_nv(p); }
3119   void do_oop(narrowOop* p) { do_oop_nv(p); }
3120 };
3121 
3122 class G1VerifyCodeRootOopClosure: public OopClosure {
3123   G1CollectedHeap* _g1h;
3124   OopClosure* _root_cl;
3125   nmethod* _nm;
3126   VerifyOption _vo;
3127   bool _failures;
3128 
3129   template <class T> void do_oop_work(T* p) {
3130     // First verify that this root is live
3131     _root_cl->do_oop(p);
3132 
3133     if (!G1VerifyHeapRegionCodeRoots) {
3134       // We're not verifying the code roots attached to heap region.
3135       return;
3136     }
3137 
3138     // Don't check the code roots during marking verification in a full GC
3139     if (_vo == VerifyOption_G1UseMarkWord) {
3140       return;
3141     }
3142 
3143     // Now verify that the current nmethod (which contains p) is
3144     // in the code root list of the heap region containing the
3145     // object referenced by p.
3146 
3147     T heap_oop = oopDesc::load_heap_oop(p);
3148     if (!oopDesc::is_null(heap_oop)) {
3149       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3150 
3151       // Now fetch the region containing the object
3152       HeapRegion* hr = _g1h->heap_region_containing(obj);
3153       HeapRegionRemSet* hrrs = hr->rem_set();
3154       // Verify that the strong code root list for this region
3155       // contains the nmethod
3156       if (!hrrs->strong_code_roots_list_contains(_nm)) {
3157         gclog_or_tty->print_cr("Code root location "PTR_FORMAT" "
3158                               "from nmethod "PTR_FORMAT" not in strong "
3159                               "code roots for region ["PTR_FORMAT","PTR_FORMAT")",
3160                               p, _nm, hr->bottom(), hr->end());
3161         _failures = true;
3162       }
3163     }
3164   }
3165 
3166 public:
3167   G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo):
3168     _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {}
3169 
3170   void do_oop(oop* p) { do_oop_work(p); }
3171   void do_oop(narrowOop* p) { do_oop_work(p); }
3172 
3173   void set_nmethod(nmethod* nm) { _nm = nm; }
3174   bool failures() { return _failures; }
3175 };
3176 
3177 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure {
3178   G1VerifyCodeRootOopClosure* _oop_cl;
3179 
3180 public:
3181   G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl):
3182     _oop_cl(oop_cl) {}
3183 
3184   void do_code_blob(CodeBlob* cb) {
3185     nmethod* nm = cb->as_nmethod_or_null();
3186     if (nm != NULL) {
3187       _oop_cl->set_nmethod(nm);
3188       nm->oops_do(_oop_cl);
3189     }
3190   }
3191 };
3192 
3193 class YoungRefCounterClosure : public OopClosure {
3194   G1CollectedHeap* _g1h;
3195   int              _count;
3196  public:
3197   YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {}
3198   void do_oop(oop* p)       { if (_g1h->is_in_young(*p)) { _count++; } }
3199   void do_oop(narrowOop* p) { ShouldNotReachHere(); }
3200 
3201   int count() { return _count; }
3202   void reset_count() { _count = 0; };
3203 };
3204 
3205 class VerifyKlassClosure: public KlassClosure {
3206   YoungRefCounterClosure _young_ref_counter_closure;
3207   OopClosure *_oop_closure;
3208  public:
3209   VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {}
3210   void do_klass(Klass* k) {
3211     k->oops_do(_oop_closure);
3212 
3213     _young_ref_counter_closure.reset_count();
3214     k->oops_do(&_young_ref_counter_closure);
3215     if (_young_ref_counter_closure.count() > 0) {
3216       guarantee(k->has_modified_oops(), err_msg("Klass %p, has young refs but is not dirty.", k));
3217     }
3218   }
3219 };
3220 
3221 class VerifyLivenessOopClosure: public OopClosure {
3222   G1CollectedHeap* _g1h;
3223   VerifyOption _vo;
3224 public:
3225   VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
3226     _g1h(g1h), _vo(vo)
3227   { }
3228   void do_oop(narrowOop *p) { do_oop_work(p); }
3229   void do_oop(      oop *p) { do_oop_work(p); }
3230 
3231   template <class T> void do_oop_work(T *p) {
3232     oop obj = oopDesc::load_decode_heap_oop(p);
3233     guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
3234               "Dead object referenced by a not dead object");
3235   }
3236 };
3237 
3238 class VerifyObjsInRegionClosure: public ObjectClosure {
3239 private:
3240   G1CollectedHeap* _g1h;
3241   size_t _live_bytes;
3242   HeapRegion *_hr;
3243   VerifyOption _vo;
3244 public:
3245   // _vo == UsePrevMarking -> use "prev" marking information,
3246   // _vo == UseNextMarking -> use "next" marking information,
3247   // _vo == UseMarkWord    -> use mark word from object header.
3248   VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
3249     : _live_bytes(0), _hr(hr), _vo(vo) {
3250     _g1h = G1CollectedHeap::heap();
3251   }
3252   void do_object(oop o) {
3253     VerifyLivenessOopClosure isLive(_g1h, _vo);
3254     assert(o != NULL, "Huh?");
3255     if (!_g1h->is_obj_dead_cond(o, _vo)) {
3256       // If the object is alive according to the mark word,
3257       // then verify that the marking information agrees.
3258       // Note we can't verify the contra-positive of the
3259       // above: if the object is dead (according to the mark
3260       // word), it may not be marked, or may have been marked
3261       // but has since became dead, or may have been allocated
3262       // since the last marking.
3263       if (_vo == VerifyOption_G1UseMarkWord) {
3264         guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
3265       }
3266 
3267       o->oop_iterate_no_header(&isLive);
3268       if (!_hr->obj_allocated_since_prev_marking(o)) {
3269         size_t obj_size = o->size();    // Make sure we don't overflow
3270         _live_bytes += (obj_size * HeapWordSize);
3271       }
3272     }
3273   }
3274   size_t live_bytes() { return _live_bytes; }
3275 };
3276 
3277 class PrintObjsInRegionClosure : public ObjectClosure {
3278   HeapRegion *_hr;
3279   G1CollectedHeap *_g1;
3280 public:
3281   PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
3282     _g1 = G1CollectedHeap::heap();
3283   };
3284 
3285   void do_object(oop o) {
3286     if (o != NULL) {
3287       HeapWord *start = (HeapWord *) o;
3288       size_t word_sz = o->size();
3289       gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
3290                           " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
3291                           (void*) o, word_sz,
3292                           _g1->isMarkedPrev(o),
3293                           _g1->isMarkedNext(o),
3294                           _hr->obj_allocated_since_prev_marking(o));
3295       HeapWord *end = start + word_sz;
3296       HeapWord *cur;
3297       int *val;
3298       for (cur = start; cur < end; cur++) {
3299         val = (int *) cur;
3300         gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val);
3301       }
3302     }
3303   }
3304 };
3305 
3306 class VerifyRegionClosure: public HeapRegionClosure {
3307 private:
3308   bool             _par;
3309   VerifyOption     _vo;
3310   bool             _failures;
3311 public:
3312   // _vo == UsePrevMarking -> use "prev" marking information,
3313   // _vo == UseNextMarking -> use "next" marking information,
3314   // _vo == UseMarkWord    -> use mark word from object header.
3315   VerifyRegionClosure(bool par, VerifyOption vo)
3316     : _par(par),
3317       _vo(vo),
3318       _failures(false) {}
3319 
3320   bool failures() {
3321     return _failures;
3322   }
3323 
3324   bool doHeapRegion(HeapRegion* r) {
3325     if (!r->continuesHumongous()) {
3326       bool failures = false;
3327       r->verify(_vo, &failures);
3328       if (failures) {
3329         _failures = true;
3330       } else {
3331         VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
3332         r->object_iterate(&not_dead_yet_cl);
3333         if (_vo != VerifyOption_G1UseNextMarking) {
3334           if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
3335             gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
3336                                    "max_live_bytes "SIZE_FORMAT" "
3337                                    "< calculated "SIZE_FORMAT,
3338                                    r->bottom(), r->end(),
3339                                    r->max_live_bytes(),
3340                                  not_dead_yet_cl.live_bytes());
3341             _failures = true;
3342           }
3343         } else {
3344           // When vo == UseNextMarking we cannot currently do a sanity
3345           // check on the live bytes as the calculation has not been
3346           // finalized yet.
3347         }
3348       }
3349     }
3350     return false; // stop the region iteration if we hit a failure
3351   }
3352 };
3353 
3354 // This is the task used for parallel verification of the heap regions
3355 
3356 class G1ParVerifyTask: public AbstractGangTask {
3357 private:
3358   G1CollectedHeap* _g1h;
3359   VerifyOption     _vo;
3360   bool             _failures;
3361 
3362 public:
3363   // _vo == UsePrevMarking -> use "prev" marking information,
3364   // _vo == UseNextMarking -> use "next" marking information,
3365   // _vo == UseMarkWord    -> use mark word from object header.
3366   G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
3367     AbstractGangTask("Parallel verify task"),
3368     _g1h(g1h),
3369     _vo(vo),
3370     _failures(false) { }
3371 
3372   bool failures() {
3373     return _failures;
3374   }
3375 
3376   void work(uint worker_id) {
3377     HandleMark hm;
3378     VerifyRegionClosure blk(true, _vo);
3379     _g1h->heap_region_par_iterate_chunked(&blk, worker_id,
3380                                           _g1h->workers()->active_workers(),
3381                                           HeapRegion::ParVerifyClaimValue);
3382     if (blk.failures()) {
3383       _failures = true;
3384     }
3385   }
3386 };
3387 
3388 void G1CollectedHeap::verify(bool silent, VerifyOption vo) {
3389   if (SafepointSynchronize::is_at_safepoint()) {
3390     assert(Thread::current()->is_VM_thread(),
3391            "Expected to be executed serially by the VM thread at this point");
3392 
3393     if (!silent) { gclog_or_tty->print("Roots "); }
3394     VerifyRootsClosure rootsCl(vo);
3395     VerifyKlassClosure klassCl(this, &rootsCl);
3396 
3397     // We apply the relevant closures to all the oops in the
3398     // system dictionary, class loader data graph and the string table.
3399     // Don't verify the code cache here, since it's verified below.
3400     const int so = SO_AllClasses | SO_Strings;
3401 
3402     // Need cleared claim bits for the strong roots processing
3403     ClassLoaderDataGraph::clear_claimed_marks();
3404 
3405     process_strong_roots(true,      // activate StrongRootsScope
3406                          ScanningOption(so),  // roots scanning options
3407                          &rootsCl,
3408                          &klassCl
3409                          );
3410 
3411     // Verify the nmethods in the code cache.
3412     G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo);
3413     G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl);
3414     CodeCache::blobs_do(&blobsCl);
3415 
3416     bool failures = rootsCl.failures() || codeRootsCl.failures();
3417 
3418     if (vo != VerifyOption_G1UseMarkWord) {
3419       // If we're verifying during a full GC then the region sets
3420       // will have been torn down at the start of the GC. Therefore
3421       // verifying the region sets will fail. So we only verify
3422       // the region sets when not in a full GC.
3423       if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3424       verify_region_sets();
3425     }
3426 
3427     if (!silent) { gclog_or_tty->print("HeapRegions "); }
3428     if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3429       assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3430              "sanity check");
3431 
3432       G1ParVerifyTask task(this, vo);
3433       assert(UseDynamicNumberOfGCThreads ||
3434         workers()->active_workers() == workers()->total_workers(),
3435         "If not dynamic should be using all the workers");
3436       int n_workers = workers()->active_workers();
3437       set_par_threads(n_workers);
3438       workers()->run_task(&task);
3439       set_par_threads(0);
3440       if (task.failures()) {
3441         failures = true;
3442       }
3443 
3444       // Checks that the expected amount of parallel work was done.
3445       // The implication is that n_workers is > 0.
3446       assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
3447              "sanity check");
3448 
3449       reset_heap_region_claim_values();
3450 
3451       assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3452              "sanity check");
3453     } else {
3454       VerifyRegionClosure blk(false, vo);
3455       heap_region_iterate(&blk);
3456       if (blk.failures()) {
3457         failures = true;
3458       }
3459     }
3460     if (!silent) gclog_or_tty->print("RemSet ");
3461     rem_set()->verify();
3462 
3463     if (G1StringDedup::is_enabled()) {
3464       if (!silent) gclog_or_tty->print("StrDedup ");
3465       G1StringDedup::verify();
3466     }
3467 
3468     if (failures) {
3469       gclog_or_tty->print_cr("Heap:");
3470       // It helps to have the per-region information in the output to
3471       // help us track down what went wrong. This is why we call
3472       // print_extended_on() instead of print_on().
3473       print_extended_on(gclog_or_tty);
3474       gclog_or_tty->print_cr("");
3475 #ifndef PRODUCT
3476       if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3477         concurrent_mark()->print_reachable("at-verification-failure",
3478                                            vo, false /* all */);
3479       }
3480 #endif
3481       gclog_or_tty->flush();
3482     }
3483     guarantee(!failures, "there should not have been any failures");
3484   } else {
3485     if (!silent) {
3486       gclog_or_tty->print("(SKIPPING Roots, HeapRegionSets, HeapRegions, RemSet");
3487       if (G1StringDedup::is_enabled()) {
3488         gclog_or_tty->print(", StrDedup");
3489       }
3490       gclog_or_tty->print(") ");
3491     }
3492   }
3493 }
3494 
3495 void G1CollectedHeap::verify(bool silent) {
3496   verify(silent, VerifyOption_G1UsePrevMarking);
3497 }
3498 
3499 double G1CollectedHeap::verify(bool guard, const char* msg) {
3500   double verify_time_ms = 0.0;
3501 
3502   if (guard && total_collections() >= VerifyGCStartAt) {
3503     double verify_start = os::elapsedTime();
3504     HandleMark hm;  // Discard invalid handles created during verification
3505     prepare_for_verify();
3506     Universe::verify(VerifyOption_G1UsePrevMarking, msg);
3507     verify_time_ms = (os::elapsedTime() - verify_start) * 1000;
3508   }
3509 
3510   return verify_time_ms;
3511 }
3512 
3513 void G1CollectedHeap::verify_before_gc() {
3514   double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:");
3515   g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms);
3516 }
3517 
3518 void G1CollectedHeap::verify_after_gc() {
3519   double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:");
3520   g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms);
3521 }
3522 
3523 class PrintRegionClosure: public HeapRegionClosure {
3524   outputStream* _st;
3525 public:
3526   PrintRegionClosure(outputStream* st) : _st(st) {}
3527   bool doHeapRegion(HeapRegion* r) {
3528     r->print_on(_st);
3529     return false;
3530   }
3531 };
3532 
3533 void G1CollectedHeap::print_on(outputStream* st) const {
3534   st->print(" %-20s", "garbage-first heap");
3535   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3536             capacity()/K, used_unlocked()/K);
3537   st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3538             _g1_storage.low_boundary(),
3539             _g1_storage.high(),
3540             _g1_storage.high_boundary());
3541   st->cr();
3542   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3543   uint young_regions = _young_list->length();
3544   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3545             (size_t) young_regions * HeapRegion::GrainBytes / K);
3546   uint survivor_regions = g1_policy()->recorded_survivor_regions();
3547   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3548             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3549   st->cr();
3550   MetaspaceAux::print_on(st);
3551 }
3552 
3553 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3554   print_on(st);
3555 
3556   // Print the per-region information.
3557   st->cr();
3558   st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3559                "HS=humongous(starts), HC=humongous(continues), "
3560                "CS=collection set, F=free, TS=gc time stamp, "
3561                "PTAMS=previous top-at-mark-start, "
3562                "NTAMS=next top-at-mark-start)");
3563   PrintRegionClosure blk(st);
3564   heap_region_iterate(&blk);
3565 }
3566 
3567 void G1CollectedHeap::print_on_error(outputStream* st) const {
3568   this->CollectedHeap::print_on_error(st);
3569 
3570   if (_cm != NULL) {
3571     st->cr();
3572     _cm->print_on_error(st);
3573   }
3574 }
3575 
3576 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3577   if (G1CollectedHeap::use_parallel_gc_threads()) {
3578     workers()->print_worker_threads_on(st);
3579   }
3580   _cmThread->print_on(st);
3581   st->cr();
3582   _cm->print_worker_threads_on(st);
3583   _cg1r->print_worker_threads_on(st);
3584   if (G1StringDedup::is_enabled()) {
3585     G1StringDedup::print_worker_threads_on(st);
3586   }
3587 }
3588 
3589 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3590   if (G1CollectedHeap::use_parallel_gc_threads()) {
3591     workers()->threads_do(tc);
3592   }
3593   tc->do_thread(_cmThread);
3594   _cg1r->threads_do(tc);
3595   if (G1StringDedup::is_enabled()) {
3596     G1StringDedup::threads_do(tc);
3597   }
3598 }
3599 
3600 void G1CollectedHeap::print_tracing_info() const {
3601   // We'll overload this to mean "trace GC pause statistics."
3602   if (TraceGen0Time || TraceGen1Time) {
3603     // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3604     // to that.
3605     g1_policy()->print_tracing_info();
3606   }
3607   if (G1SummarizeRSetStats) {
3608     g1_rem_set()->print_summary_info();
3609   }
3610   if (G1SummarizeConcMark) {
3611     concurrent_mark()->print_summary_info();
3612   }
3613   g1_policy()->print_yg_surv_rate_info();
3614   SpecializationStats::print();
3615 }
3616 
3617 #ifndef PRODUCT
3618 // Helpful for debugging RSet issues.
3619 
3620 class PrintRSetsClosure : public HeapRegionClosure {
3621 private:
3622   const char* _msg;
3623   size_t _occupied_sum;
3624 
3625 public:
3626   bool doHeapRegion(HeapRegion* r) {
3627     HeapRegionRemSet* hrrs = r->rem_set();
3628     size_t occupied = hrrs->occupied();
3629     _occupied_sum += occupied;
3630 
3631     gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3632                            HR_FORMAT_PARAMS(r));
3633     if (occupied == 0) {
3634       gclog_or_tty->print_cr("  RSet is empty");
3635     } else {
3636       hrrs->print();
3637     }
3638     gclog_or_tty->print_cr("----------");
3639     return false;
3640   }
3641 
3642   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3643     gclog_or_tty->cr();
3644     gclog_or_tty->print_cr("========================================");
3645     gclog_or_tty->print_cr(msg);
3646     gclog_or_tty->cr();
3647   }
3648 
3649   ~PrintRSetsClosure() {
3650     gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3651     gclog_or_tty->print_cr("========================================");
3652     gclog_or_tty->cr();
3653   }
3654 };
3655 
3656 void G1CollectedHeap::print_cset_rsets() {
3657   PrintRSetsClosure cl("Printing CSet RSets");
3658   collection_set_iterate(&cl);
3659 }
3660 
3661 void G1CollectedHeap::print_all_rsets() {
3662   PrintRSetsClosure cl("Printing All RSets");;
3663   heap_region_iterate(&cl);
3664 }
3665 #endif // PRODUCT
3666 
3667 G1CollectedHeap* G1CollectedHeap::heap() {
3668   assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3669          "not a garbage-first heap");
3670   return _g1h;
3671 }
3672 
3673 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3674   // always_do_update_barrier = false;
3675   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3676   // Fill TLAB's and such
3677   accumulate_statistics_all_tlabs();
3678   ensure_parsability(true);
3679 
3680   if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) &&
3681       (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3682     g1_rem_set()->print_periodic_summary_info("Before GC RS summary");
3683   }
3684 }
3685 
3686 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) {
3687 
3688   if (G1SummarizeRSetStats &&
3689       (G1SummarizeRSetStatsPeriod > 0) &&
3690       // we are at the end of the GC. Total collections has already been increased.
3691       ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) {
3692     g1_rem_set()->print_periodic_summary_info("After GC RS summary");
3693   }
3694 
3695   // FIXME: what is this about?
3696   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3697   // is set.
3698   COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3699                         "derived pointer present"));
3700   // always_do_update_barrier = true;
3701 
3702   resize_all_tlabs();
3703 
3704   // We have just completed a GC. Update the soft reference
3705   // policy with the new heap occupancy
3706   Universe::update_heap_info_at_gc();
3707 }
3708 
3709 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3710                                                unsigned int gc_count_before,
3711                                                bool* succeeded,
3712                                                GCCause::Cause gc_cause) {
3713   assert_heap_not_locked_and_not_at_safepoint();
3714   g1_policy()->record_stop_world_start();
3715   VM_G1IncCollectionPause op(gc_count_before,
3716                              word_size,
3717                              false, /* should_initiate_conc_mark */
3718                              g1_policy()->max_pause_time_ms(),
3719                              gc_cause);
3720   VMThread::execute(&op);
3721 
3722   HeapWord* result = op.result();
3723   bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3724   assert(result == NULL || ret_succeeded,
3725          "the result should be NULL if the VM did not succeed");
3726   *succeeded = ret_succeeded;
3727 
3728   assert_heap_not_locked();
3729   return result;
3730 }
3731 
3732 void
3733 G1CollectedHeap::doConcurrentMark() {
3734   MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3735   if (!_cmThread->in_progress()) {
3736     _cmThread->set_started();
3737     CGC_lock->notify();
3738   }
3739 }
3740 
3741 size_t G1CollectedHeap::pending_card_num() {
3742   size_t extra_cards = 0;
3743   JavaThread *curr = Threads::first();
3744   while (curr != NULL) {
3745     DirtyCardQueue& dcq = curr->dirty_card_queue();
3746     extra_cards += dcq.size();
3747     curr = curr->next();
3748   }
3749   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3750   size_t buffer_size = dcqs.buffer_size();
3751   size_t buffer_num = dcqs.completed_buffers_num();
3752 
3753   // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
3754   // in bytes - not the number of 'entries'. We need to convert
3755   // into a number of cards.
3756   return (buffer_size * buffer_num + extra_cards) / oopSize;
3757 }
3758 
3759 size_t G1CollectedHeap::cards_scanned() {
3760   return g1_rem_set()->cardsScanned();
3761 }
3762 
3763 void
3764 G1CollectedHeap::setup_surviving_young_words() {
3765   assert(_surviving_young_words == NULL, "pre-condition");
3766   uint array_length = g1_policy()->young_cset_region_length();
3767   _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3768   if (_surviving_young_words == NULL) {
3769     vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR,
3770                           "Not enough space for young surv words summary.");
3771   }
3772   memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3773 #ifdef ASSERT
3774   for (uint i = 0;  i < array_length; ++i) {
3775     assert( _surviving_young_words[i] == 0, "memset above" );
3776   }
3777 #endif // !ASSERT
3778 }
3779 
3780 void
3781 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3782   MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3783   uint array_length = g1_policy()->young_cset_region_length();
3784   for (uint i = 0; i < array_length; ++i) {
3785     _surviving_young_words[i] += surv_young_words[i];
3786   }
3787 }
3788 
3789 void
3790 G1CollectedHeap::cleanup_surviving_young_words() {
3791   guarantee( _surviving_young_words != NULL, "pre-condition" );
3792   FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC);
3793   _surviving_young_words = NULL;
3794 }
3795 
3796 #ifdef ASSERT
3797 class VerifyCSetClosure: public HeapRegionClosure {
3798 public:
3799   bool doHeapRegion(HeapRegion* hr) {
3800     // Here we check that the CSet region's RSet is ready for parallel
3801     // iteration. The fields that we'll verify are only manipulated
3802     // when the region is part of a CSet and is collected. Afterwards,
3803     // we reset these fields when we clear the region's RSet (when the
3804     // region is freed) so they are ready when the region is
3805     // re-allocated. The only exception to this is if there's an
3806     // evacuation failure and instead of freeing the region we leave
3807     // it in the heap. In that case, we reset these fields during
3808     // evacuation failure handling.
3809     guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3810 
3811     // Here's a good place to add any other checks we'd like to
3812     // perform on CSet regions.
3813     return false;
3814   }
3815 };
3816 #endif // ASSERT
3817 
3818 #if TASKQUEUE_STATS
3819 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3820   st->print_raw_cr("GC Task Stats");
3821   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3822   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3823 }
3824 
3825 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3826   print_taskqueue_stats_hdr(st);
3827 
3828   TaskQueueStats totals;
3829   const int n = workers() != NULL ? workers()->total_workers() : 1;
3830   for (int i = 0; i < n; ++i) {
3831     st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3832     totals += task_queue(i)->stats;
3833   }
3834   st->print_raw("tot "); totals.print(st); st->cr();
3835 
3836   DEBUG_ONLY(totals.verify());
3837 }
3838 
3839 void G1CollectedHeap::reset_taskqueue_stats() {
3840   const int n = workers() != NULL ? workers()->total_workers() : 1;
3841   for (int i = 0; i < n; ++i) {
3842     task_queue(i)->stats.reset();
3843   }
3844 }
3845 #endif // TASKQUEUE_STATS
3846 
3847 void G1CollectedHeap::log_gc_header() {
3848   if (!G1Log::fine()) {
3849     return;
3850   }
3851 
3852   gclog_or_tty->date_stamp(PrintGCDateStamps);
3853   gclog_or_tty->stamp(PrintGCTimeStamps);
3854 
3855   GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
3856     .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)")
3857     .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : "");
3858 
3859   gclog_or_tty->print("[%s", (const char*)gc_cause_str);
3860 }
3861 
3862 void G1CollectedHeap::log_gc_footer(double pause_time_sec) {
3863   if (!G1Log::fine()) {
3864     return;
3865   }
3866 
3867   if (G1Log::finer()) {
3868     if (evacuation_failed()) {
3869       gclog_or_tty->print(" (to-space exhausted)");
3870     }
3871     gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3872     g1_policy()->phase_times()->note_gc_end();
3873     g1_policy()->phase_times()->print(pause_time_sec);
3874     g1_policy()->print_detailed_heap_transition();
3875   } else {
3876     if (evacuation_failed()) {
3877       gclog_or_tty->print("--");
3878     }
3879     g1_policy()->print_heap_transition();
3880     gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3881   }
3882   gclog_or_tty->flush();
3883 }
3884 
3885 bool
3886 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3887   assert_at_safepoint(true /* should_be_vm_thread */);
3888   guarantee(!is_gc_active(), "collection is not reentrant");
3889 
3890   if (GC_locker::check_active_before_gc()) {
3891     return false;
3892   }
3893 
3894   _gc_timer_stw->register_gc_start();
3895 
3896   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3897 
3898   SvcGCMarker sgcm(SvcGCMarker::MINOR);
3899   ResourceMark rm;
3900 
3901   print_heap_before_gc();
3902   trace_heap_before_gc(_gc_tracer_stw);
3903 
3904   verify_region_sets_optional();
3905   verify_dirty_young_regions();
3906 
3907   // This call will decide whether this pause is an initial-mark
3908   // pause. If it is, during_initial_mark_pause() will return true
3909   // for the duration of this pause.
3910   g1_policy()->decide_on_conc_mark_initiation();
3911 
3912   // We do not allow initial-mark to be piggy-backed on a mixed GC.
3913   assert(!g1_policy()->during_initial_mark_pause() ||
3914           g1_policy()->gcs_are_young(), "sanity");
3915 
3916   // We also do not allow mixed GCs during marking.
3917   assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3918 
3919   // Record whether this pause is an initial mark. When the current
3920   // thread has completed its logging output and it's safe to signal
3921   // the CM thread, the flag's value in the policy has been reset.
3922   bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3923 
3924   // Inner scope for scope based logging, timers, and stats collection
3925   {
3926     EvacuationInfo evacuation_info;
3927 
3928     if (g1_policy()->during_initial_mark_pause()) {
3929       // We are about to start a marking cycle, so we increment the
3930       // full collection counter.
3931       increment_old_marking_cycles_started();
3932       register_concurrent_cycle_start(_gc_timer_stw->gc_start());
3933     }
3934 
3935     _gc_tracer_stw->report_yc_type(yc_type());
3936 
3937     TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3938 
3939     int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
3940                                 workers()->active_workers() : 1);
3941     double pause_start_sec = os::elapsedTime();
3942     g1_policy()->phase_times()->note_gc_start(active_workers);
3943     log_gc_header();
3944 
3945     TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3946     TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3947 
3948     // If the secondary_free_list is not empty, append it to the
3949     // free_list. No need to wait for the cleanup operation to finish;
3950     // the region allocation code will check the secondary_free_list
3951     // and wait if necessary. If the G1StressConcRegionFreeing flag is
3952     // set, skip this step so that the region allocation code has to
3953     // get entries from the secondary_free_list.
3954     if (!G1StressConcRegionFreeing) {
3955       append_secondary_free_list_if_not_empty_with_lock();
3956     }
3957 
3958     assert(check_young_list_well_formed(), "young list should be well formed");
3959     assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3960            "sanity check");
3961 
3962     // Don't dynamically change the number of GC threads this early.  A value of
3963     // 0 is used to indicate serial work.  When parallel work is done,
3964     // it will be set.
3965 
3966     { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3967       IsGCActiveMark x;
3968 
3969       gc_prologue(false);
3970       increment_total_collections(false /* full gc */);
3971       increment_gc_time_stamp();
3972 
3973       verify_before_gc();
3974 
3975       COMPILER2_PRESENT(DerivedPointerTable::clear());
3976 
3977       // Please see comment in g1CollectedHeap.hpp and
3978       // G1CollectedHeap::ref_processing_init() to see how
3979       // reference processing currently works in G1.
3980 
3981       // Enable discovery in the STW reference processor
3982       ref_processor_stw()->enable_discovery(true /*verify_disabled*/,
3983                                             true /*verify_no_refs*/);
3984 
3985       {
3986         // We want to temporarily turn off discovery by the
3987         // CM ref processor, if necessary, and turn it back on
3988         // on again later if we do. Using a scoped
3989         // NoRefDiscovery object will do this.
3990         NoRefDiscovery no_cm_discovery(ref_processor_cm());
3991 
3992         // Forget the current alloc region (we might even choose it to be part
3993         // of the collection set!).
3994         release_mutator_alloc_region();
3995 
3996         // We should call this after we retire the mutator alloc
3997         // region(s) so that all the ALLOC / RETIRE events are generated
3998         // before the start GC event.
3999         _hr_printer.start_gc(false /* full */, (size_t) total_collections());
4000 
4001         // This timing is only used by the ergonomics to handle our pause target.
4002         // It is unclear why this should not include the full pause. We will
4003         // investigate this in CR 7178365.
4004         //
4005         // Preserving the old comment here if that helps the investigation:
4006         //
4007         // The elapsed time induced by the start time below deliberately elides
4008         // the possible verification above.
4009         double sample_start_time_sec = os::elapsedTime();
4010 
4011 #if YOUNG_LIST_VERBOSE
4012         gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
4013         _young_list->print();
4014         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4015 #endif // YOUNG_LIST_VERBOSE
4016 
4017         g1_policy()->record_collection_pause_start(sample_start_time_sec);
4018 
4019         double scan_wait_start = os::elapsedTime();
4020         // We have to wait until the CM threads finish scanning the
4021         // root regions as it's the only way to ensure that all the
4022         // objects on them have been correctly scanned before we start
4023         // moving them during the GC.
4024         bool waited = _cm->root_regions()->wait_until_scan_finished();
4025         double wait_time_ms = 0.0;
4026         if (waited) {
4027           double scan_wait_end = os::elapsedTime();
4028           wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
4029         }
4030         g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
4031 
4032 #if YOUNG_LIST_VERBOSE
4033         gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
4034         _young_list->print();
4035 #endif // YOUNG_LIST_VERBOSE
4036 
4037         if (g1_policy()->during_initial_mark_pause()) {
4038           concurrent_mark()->checkpointRootsInitialPre();
4039         }
4040 
4041 #if YOUNG_LIST_VERBOSE
4042         gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
4043         _young_list->print();
4044         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4045 #endif // YOUNG_LIST_VERBOSE
4046 
4047         g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info);
4048 
4049         _cm->note_start_of_gc();
4050         // We should not verify the per-thread SATB buffers given that
4051         // we have not filtered them yet (we'll do so during the
4052         // GC). We also call this after finalize_cset() to
4053         // ensure that the CSet has been finalized.
4054         _cm->verify_no_cset_oops(true  /* verify_stacks */,
4055                                  true  /* verify_enqueued_buffers */,
4056                                  false /* verify_thread_buffers */,
4057                                  true  /* verify_fingers */);
4058 
4059         if (_hr_printer.is_active()) {
4060           HeapRegion* hr = g1_policy()->collection_set();
4061           while (hr != NULL) {
4062             G1HRPrinter::RegionType type;
4063             if (!hr->is_young()) {
4064               type = G1HRPrinter::Old;
4065             } else if (hr->is_survivor()) {
4066               type = G1HRPrinter::Survivor;
4067             } else {
4068               type = G1HRPrinter::Eden;
4069             }
4070             _hr_printer.cset(hr);
4071             hr = hr->next_in_collection_set();
4072           }
4073         }
4074 
4075 #ifdef ASSERT
4076         VerifyCSetClosure cl;
4077         collection_set_iterate(&cl);
4078 #endif // ASSERT
4079 
4080         setup_surviving_young_words();
4081 
4082         // Initialize the GC alloc regions.
4083         init_gc_alloc_regions(evacuation_info);
4084 
4085         // Actually do the work...
4086         evacuate_collection_set(evacuation_info);
4087 
4088         // We do this to mainly verify the per-thread SATB buffers
4089         // (which have been filtered by now) since we didn't verify
4090         // them earlier. No point in re-checking the stacks / enqueued
4091         // buffers given that the CSet has not changed since last time
4092         // we checked.
4093         _cm->verify_no_cset_oops(false /* verify_stacks */,
4094                                  false /* verify_enqueued_buffers */,
4095                                  true  /* verify_thread_buffers */,
4096                                  true  /* verify_fingers */);
4097 
4098         free_collection_set(g1_policy()->collection_set(), evacuation_info);
4099         g1_policy()->clear_collection_set();
4100 
4101         cleanup_surviving_young_words();
4102 
4103         // Start a new incremental collection set for the next pause.
4104         g1_policy()->start_incremental_cset_building();
4105 
4106         // Clear the _cset_fast_test bitmap in anticipation of adding
4107         // regions to the incremental collection set for the next
4108         // evacuation pause.
4109         clear_cset_fast_test();
4110 
4111         _young_list->reset_sampled_info();
4112 
4113         // Don't check the whole heap at this point as the
4114         // GC alloc regions from this pause have been tagged
4115         // as survivors and moved on to the survivor list.
4116         // Survivor regions will fail the !is_young() check.
4117         assert(check_young_list_empty(false /* check_heap */),
4118           "young list should be empty");
4119 
4120 #if YOUNG_LIST_VERBOSE
4121         gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
4122         _young_list->print();
4123 #endif // YOUNG_LIST_VERBOSE
4124 
4125         g1_policy()->record_survivor_regions(_young_list->survivor_length(),
4126                                              _young_list->first_survivor_region(),
4127                                              _young_list->last_survivor_region());
4128 
4129         _young_list->reset_auxilary_lists();
4130 
4131         if (evacuation_failed()) {
4132           _summary_bytes_used = recalculate_used();
4133           uint n_queues = MAX2((int)ParallelGCThreads, 1);
4134           for (uint i = 0; i < n_queues; i++) {
4135             if (_evacuation_failed_info_array[i].has_failed()) {
4136               _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
4137             }
4138           }
4139         } else {
4140           // The "used" of the the collection set have already been subtracted
4141           // when they were freed.  Add in the bytes evacuated.
4142           _summary_bytes_used += g1_policy()->bytes_copied_during_gc();
4143         }
4144 
4145         if (g1_policy()->during_initial_mark_pause()) {
4146           // We have to do this before we notify the CM threads that
4147           // they can start working to make sure that all the
4148           // appropriate initialization is done on the CM object.
4149           concurrent_mark()->checkpointRootsInitialPost();
4150           set_marking_started();
4151           // Note that we don't actually trigger the CM thread at
4152           // this point. We do that later when we're sure that
4153           // the current thread has completed its logging output.
4154         }
4155 
4156         allocate_dummy_regions();
4157 
4158 #if YOUNG_LIST_VERBOSE
4159         gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
4160         _young_list->print();
4161         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4162 #endif // YOUNG_LIST_VERBOSE
4163 
4164         init_mutator_alloc_region();
4165 
4166         {
4167           size_t expand_bytes = g1_policy()->expansion_amount();
4168           if (expand_bytes > 0) {
4169             size_t bytes_before = capacity();
4170             // No need for an ergo verbose message here,
4171             // expansion_amount() does this when it returns a value > 0.
4172             if (!expand(expand_bytes)) {
4173               // We failed to expand the heap so let's verify that
4174               // committed/uncommitted amount match the backing store
4175               assert(capacity() == _g1_storage.committed_size(), "committed size mismatch");
4176               assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch");
4177             }
4178           }
4179         }
4180 
4181         // We redo the verification but now wrt to the new CSet which
4182         // has just got initialized after the previous CSet was freed.
4183         _cm->verify_no_cset_oops(true  /* verify_stacks */,
4184                                  true  /* verify_enqueued_buffers */,
4185                                  true  /* verify_thread_buffers */,
4186                                  true  /* verify_fingers */);
4187         _cm->note_end_of_gc();
4188 
4189         // This timing is only used by the ergonomics to handle our pause target.
4190         // It is unclear why this should not include the full pause. We will
4191         // investigate this in CR 7178365.
4192         double sample_end_time_sec = os::elapsedTime();
4193         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
4194         g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info);
4195 
4196         MemoryService::track_memory_usage();
4197 
4198         // In prepare_for_verify() below we'll need to scan the deferred
4199         // update buffers to bring the RSets up-to-date if
4200         // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
4201         // the update buffers we'll probably need to scan cards on the
4202         // regions we just allocated to (i.e., the GC alloc
4203         // regions). However, during the last GC we called
4204         // set_saved_mark() on all the GC alloc regions, so card
4205         // scanning might skip the [saved_mark_word()...top()] area of
4206         // those regions (i.e., the area we allocated objects into
4207         // during the last GC). But it shouldn't. Given that
4208         // saved_mark_word() is conditional on whether the GC time stamp
4209         // on the region is current or not, by incrementing the GC time
4210         // stamp here we invalidate all the GC time stamps on all the
4211         // regions and saved_mark_word() will simply return top() for
4212         // all the regions. This is a nicer way of ensuring this rather
4213         // than iterating over the regions and fixing them. In fact, the
4214         // GC time stamp increment here also ensures that
4215         // saved_mark_word() will return top() between pauses, i.e.,
4216         // during concurrent refinement. So we don't need the
4217         // is_gc_active() check to decided which top to use when
4218         // scanning cards (see CR 7039627).
4219         increment_gc_time_stamp();
4220 
4221         verify_after_gc();
4222 
4223         assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
4224         ref_processor_stw()->verify_no_references_recorded();
4225 
4226         // CM reference discovery will be re-enabled if necessary.
4227       }
4228 
4229       // We should do this after we potentially expand the heap so
4230       // that all the COMMIT events are generated before the end GC
4231       // event, and after we retire the GC alloc regions so that all
4232       // RETIRE events are generated before the end GC event.
4233       _hr_printer.end_gc(false /* full */, (size_t) total_collections());
4234 
4235       if (mark_in_progress()) {
4236         concurrent_mark()->update_g1_committed();
4237       }
4238 
4239 #ifdef TRACESPINNING
4240       ParallelTaskTerminator::print_termination_counts();
4241 #endif
4242 
4243       gc_epilogue(false);
4244     }
4245 
4246     // Print the remainder of the GC log output.
4247     log_gc_footer(os::elapsedTime() - pause_start_sec);
4248 
4249     // It is not yet to safe to tell the concurrent mark to
4250     // start as we have some optional output below. We don't want the
4251     // output from the concurrent mark thread interfering with this
4252     // logging output either.
4253 
4254     _hrs.verify_optional();
4255     verify_region_sets_optional();
4256 
4257     TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
4258     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
4259 
4260     print_heap_after_gc();
4261     trace_heap_after_gc(_gc_tracer_stw);
4262 
4263     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
4264     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
4265     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
4266     // before any GC notifications are raised.
4267     g1mm()->update_sizes();
4268 
4269     _gc_tracer_stw->report_evacuation_info(&evacuation_info);
4270     _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
4271     _gc_timer_stw->register_gc_end();
4272     _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
4273   }
4274   // It should now be safe to tell the concurrent mark thread to start
4275   // without its logging output interfering with the logging output
4276   // that came from the pause.
4277 
4278   if (should_start_conc_mark) {
4279     // CAUTION: after the doConcurrentMark() call below,
4280     // the concurrent marking thread(s) could be running
4281     // concurrently with us. Make sure that anything after
4282     // this point does not assume that we are the only GC thread
4283     // running. Note: of course, the actual marking work will
4284     // not start until the safepoint itself is released in
4285     // ConcurrentGCThread::safepoint_desynchronize().
4286     doConcurrentMark();
4287   }
4288 
4289   return true;
4290 }
4291 
4292 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
4293 {
4294   size_t gclab_word_size;
4295   switch (purpose) {
4296     case GCAllocForSurvived:
4297       gclab_word_size = _survivor_plab_stats.desired_plab_sz();
4298       break;
4299     case GCAllocForTenured:
4300       gclab_word_size = _old_plab_stats.desired_plab_sz();
4301       break;
4302     default:
4303       assert(false, "unknown GCAllocPurpose");
4304       gclab_word_size = _old_plab_stats.desired_plab_sz();
4305       break;
4306   }
4307 
4308   // Prevent humongous PLAB sizes for two reasons:
4309   // * PLABs are allocated using a similar paths as oops, but should
4310   //   never be in a humongous region
4311   // * Allowing humongous PLABs needlessly churns the region free lists
4312   return MIN2(_humongous_object_threshold_in_words, gclab_word_size);
4313 }
4314 
4315 void G1CollectedHeap::init_mutator_alloc_region() {
4316   assert(_mutator_alloc_region.get() == NULL, "pre-condition");
4317   _mutator_alloc_region.init();
4318 }
4319 
4320 void G1CollectedHeap::release_mutator_alloc_region() {
4321   _mutator_alloc_region.release();
4322   assert(_mutator_alloc_region.get() == NULL, "post-condition");
4323 }
4324 
4325 void G1CollectedHeap::init_gc_alloc_regions(EvacuationInfo& evacuation_info) {
4326   assert_at_safepoint(true /* should_be_vm_thread */);
4327 
4328   _survivor_gc_alloc_region.init();
4329   _old_gc_alloc_region.init();
4330   HeapRegion* retained_region = _retained_old_gc_alloc_region;
4331   _retained_old_gc_alloc_region = NULL;
4332 
4333   // We will discard the current GC alloc region if:
4334   // a) it's in the collection set (it can happen!),
4335   // b) it's already full (no point in using it),
4336   // c) it's empty (this means that it was emptied during
4337   // a cleanup and it should be on the free list now), or
4338   // d) it's humongous (this means that it was emptied
4339   // during a cleanup and was added to the free list, but
4340   // has been subsequently used to allocate a humongous
4341   // object that may be less than the region size).
4342   if (retained_region != NULL &&
4343       !retained_region->in_collection_set() &&
4344       !(retained_region->top() == retained_region->end()) &&
4345       !retained_region->is_empty() &&
4346       !retained_region->isHumongous()) {
4347     retained_region->set_saved_mark();
4348     // The retained region was added to the old region set when it was
4349     // retired. We have to remove it now, since we don't allow regions
4350     // we allocate to in the region sets. We'll re-add it later, when
4351     // it's retired again.
4352     _old_set.remove(retained_region);
4353     bool during_im = g1_policy()->during_initial_mark_pause();
4354     retained_region->note_start_of_copying(during_im);
4355     _old_gc_alloc_region.set(retained_region);
4356     _hr_printer.reuse(retained_region);
4357     evacuation_info.set_alloc_regions_used_before(retained_region->used());
4358   }
4359 }
4360 
4361 void G1CollectedHeap::release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info) {
4362   evacuation_info.set_allocation_regions(_survivor_gc_alloc_region.count() +
4363                                          _old_gc_alloc_region.count());
4364   _survivor_gc_alloc_region.release();
4365   // If we have an old GC alloc region to release, we'll save it in
4366   // _retained_old_gc_alloc_region. If we don't
4367   // _retained_old_gc_alloc_region will become NULL. This is what we
4368   // want either way so no reason to check explicitly for either
4369   // condition.
4370   _retained_old_gc_alloc_region = _old_gc_alloc_region.release();
4371 
4372   if (ResizePLAB) {
4373     _survivor_plab_stats.adjust_desired_plab_sz(no_of_gc_workers);
4374     _old_plab_stats.adjust_desired_plab_sz(no_of_gc_workers);
4375   }
4376 }
4377 
4378 void G1CollectedHeap::abandon_gc_alloc_regions() {
4379   assert(_survivor_gc_alloc_region.get() == NULL, "pre-condition");
4380   assert(_old_gc_alloc_region.get() == NULL, "pre-condition");
4381   _retained_old_gc_alloc_region = NULL;
4382 }
4383 
4384 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4385   _drain_in_progress = false;
4386   set_evac_failure_closure(cl);
4387   _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4388 }
4389 
4390 void G1CollectedHeap::finalize_for_evac_failure() {
4391   assert(_evac_failure_scan_stack != NULL &&
4392          _evac_failure_scan_stack->length() == 0,
4393          "Postcondition");
4394   assert(!_drain_in_progress, "Postcondition");
4395   delete _evac_failure_scan_stack;
4396   _evac_failure_scan_stack = NULL;
4397 }
4398 
4399 void G1CollectedHeap::remove_self_forwarding_pointers() {
4400   assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4401 
4402   double remove_self_forwards_start = os::elapsedTime();
4403 
4404   G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4405 
4406   if (G1CollectedHeap::use_parallel_gc_threads()) {
4407     set_par_threads();
4408     workers()->run_task(&rsfp_task);
4409     set_par_threads(0);
4410   } else {
4411     rsfp_task.work(0);
4412   }
4413 
4414   assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity");
4415 
4416   // Reset the claim values in the regions in the collection set.
4417   reset_cset_heap_region_claim_values();
4418 
4419   assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4420 
4421   // Now restore saved marks, if any.
4422   assert(_objs_with_preserved_marks.size() ==
4423             _preserved_marks_of_objs.size(), "Both or none.");
4424   while (!_objs_with_preserved_marks.is_empty()) {
4425     oop obj = _objs_with_preserved_marks.pop();
4426     markOop m = _preserved_marks_of_objs.pop();
4427     obj->set_mark(m);
4428   }
4429   _objs_with_preserved_marks.clear(true);
4430   _preserved_marks_of_objs.clear(true);
4431 
4432   g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
4433 }
4434 
4435 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4436   _evac_failure_scan_stack->push(obj);
4437 }
4438 
4439 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4440   assert(_evac_failure_scan_stack != NULL, "precondition");
4441 
4442   while (_evac_failure_scan_stack->length() > 0) {
4443      oop obj = _evac_failure_scan_stack->pop();
4444      _evac_failure_closure->set_region(heap_region_containing(obj));
4445      obj->oop_iterate_backwards(_evac_failure_closure);
4446   }
4447 }
4448 
4449 oop
4450 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state,
4451                                                oop old) {
4452   assert(obj_in_cs(old),
4453          err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4454                  (HeapWord*) old));
4455   markOop m = old->mark();
4456   oop forward_ptr = old->forward_to_atomic(old);
4457   if (forward_ptr == NULL) {
4458     // Forward-to-self succeeded.
4459     assert(_par_scan_state != NULL, "par scan state");
4460     OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4461     uint queue_num = _par_scan_state->queue_num();
4462 
4463     _evacuation_failed = true;
4464     _evacuation_failed_info_array[queue_num].register_copy_failure(old->size());
4465     if (_evac_failure_closure != cl) {
4466       MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4467       assert(!_drain_in_progress,
4468              "Should only be true while someone holds the lock.");
4469       // Set the global evac-failure closure to the current thread's.
4470       assert(_evac_failure_closure == NULL, "Or locking has failed.");
4471       set_evac_failure_closure(cl);
4472       // Now do the common part.
4473       handle_evacuation_failure_common(old, m);
4474       // Reset to NULL.
4475       set_evac_failure_closure(NULL);
4476     } else {
4477       // The lock is already held, and this is recursive.
4478       assert(_drain_in_progress, "This should only be the recursive case.");
4479       handle_evacuation_failure_common(old, m);
4480     }
4481     return old;
4482   } else {
4483     // Forward-to-self failed. Either someone else managed to allocate
4484     // space for this object (old != forward_ptr) or they beat us in
4485     // self-forwarding it (old == forward_ptr).
4486     assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4487            err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4488                    "should not be in the CSet",
4489                    (HeapWord*) old, (HeapWord*) forward_ptr));
4490     return forward_ptr;
4491   }
4492 }
4493 
4494 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4495   preserve_mark_if_necessary(old, m);
4496 
4497   HeapRegion* r = heap_region_containing(old);
4498   if (!r->evacuation_failed()) {
4499     r->set_evacuation_failed(true);
4500     _hr_printer.evac_failure(r);
4501   }
4502 
4503   push_on_evac_failure_scan_stack(old);
4504 
4505   if (!_drain_in_progress) {
4506     // prevent recursion in copy_to_survivor_space()
4507     _drain_in_progress = true;
4508     drain_evac_failure_scan_stack();
4509     _drain_in_progress = false;
4510   }
4511 }
4512 
4513 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4514   assert(evacuation_failed(), "Oversaving!");
4515   // We want to call the "for_promotion_failure" version only in the
4516   // case of a promotion failure.
4517   if (m->must_be_preserved_for_promotion_failure(obj)) {
4518     _objs_with_preserved_marks.push(obj);
4519     _preserved_marks_of_objs.push(m);
4520   }
4521 }
4522 
4523 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
4524                                                   size_t word_size) {
4525   if (purpose == GCAllocForSurvived) {
4526     HeapWord* result = survivor_attempt_allocation(word_size);
4527     if (result != NULL) {
4528       return result;
4529     } else {
4530       // Let's try to allocate in the old gen in case we can fit the
4531       // object there.
4532       return old_attempt_allocation(word_size);
4533     }
4534   } else {
4535     assert(purpose ==  GCAllocForTenured, "sanity");
4536     HeapWord* result = old_attempt_allocation(word_size);
4537     if (result != NULL) {
4538       return result;
4539     } else {
4540       // Let's try to allocate in the survivors in case we can fit the
4541       // object there.
4542       return survivor_attempt_allocation(word_size);
4543     }
4544   }
4545 
4546   ShouldNotReachHere();
4547   // Trying to keep some compilers happy.
4548   return NULL;
4549 }
4550 
4551 G1ParGCAllocBuffer::G1ParGCAllocBuffer(size_t gclab_word_size) :
4552   ParGCAllocBuffer(gclab_word_size), _retired(false) { }
4553 
4554 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, uint queue_num, ReferenceProcessor* rp)
4555   : _g1h(g1h),
4556     _refs(g1h->task_queue(queue_num)),
4557     _dcq(&g1h->dirty_card_queue_set()),
4558     _ct_bs(g1h->g1_barrier_set()),
4559     _g1_rem(g1h->g1_rem_set()),
4560     _hash_seed(17), _queue_num(queue_num),
4561     _term_attempts(0),
4562     _surviving_alloc_buffer(g1h->desired_plab_sz(GCAllocForSurvived)),
4563     _tenured_alloc_buffer(g1h->desired_plab_sz(GCAllocForTenured)),
4564     _age_table(false), _scanner(g1h, this, rp),
4565     _strong_roots_time(0), _term_time(0),
4566     _alloc_buffer_waste(0), _undo_waste(0) {
4567   // we allocate G1YoungSurvRateNumRegions plus one entries, since
4568   // we "sacrifice" entry 0 to keep track of surviving bytes for
4569   // non-young regions (where the age is -1)
4570   // We also add a few elements at the beginning and at the end in
4571   // an attempt to eliminate cache contention
4572   uint real_length = 1 + _g1h->g1_policy()->young_cset_region_length();
4573   uint array_length = PADDING_ELEM_NUM +
4574                       real_length +
4575                       PADDING_ELEM_NUM;
4576   _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length, mtGC);
4577   if (_surviving_young_words_base == NULL)
4578     vm_exit_out_of_memory(array_length * sizeof(size_t), OOM_MALLOC_ERROR,
4579                           "Not enough space for young surv histo.");
4580   _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM;
4581   memset(_surviving_young_words, 0, (size_t) real_length * sizeof(size_t));
4582 
4583   _alloc_buffers[GCAllocForSurvived] = &_surviving_alloc_buffer;
4584   _alloc_buffers[GCAllocForTenured]  = &_tenured_alloc_buffer;
4585 
4586   _start = os::elapsedTime();
4587 }
4588 
4589 void
4590 G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st)
4591 {
4592   st->print_raw_cr("GC Termination Stats");
4593   st->print_raw_cr("     elapsed  --strong roots-- -------termination-------"
4594                    " ------waste (KiB)------");
4595   st->print_raw_cr("thr     ms        ms      %        ms      %    attempts"
4596                    "  total   alloc    undo");
4597   st->print_raw_cr("--- --------- --------- ------ --------- ------ --------"
4598                    " ------- ------- -------");
4599 }
4600 
4601 void
4602 G1ParScanThreadState::print_termination_stats(int i,
4603                                               outputStream* const st) const
4604 {
4605   const double elapsed_ms = elapsed_time() * 1000.0;
4606   const double s_roots_ms = strong_roots_time() * 1000.0;
4607   const double term_ms    = term_time() * 1000.0;
4608   st->print_cr("%3d %9.2f %9.2f %6.2f "
4609                "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
4610                SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
4611                i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms,
4612                term_ms, term_ms * 100 / elapsed_ms, term_attempts(),
4613                (alloc_buffer_waste() + undo_waste()) * HeapWordSize / K,
4614                alloc_buffer_waste() * HeapWordSize / K,
4615                undo_waste() * HeapWordSize / K);
4616 }
4617 
4618 #ifdef ASSERT
4619 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const {
4620   assert(ref != NULL, "invariant");
4621   assert(UseCompressedOops, "sanity");
4622   assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, ref));
4623   oop p = oopDesc::load_decode_heap_oop(ref);
4624   assert(_g1h->is_in_g1_reserved(p),
4625          err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, (void *)p));
4626   return true;
4627 }
4628 
4629 bool G1ParScanThreadState::verify_ref(oop* ref) const {
4630   assert(ref != NULL, "invariant");
4631   if (has_partial_array_mask(ref)) {
4632     // Must be in the collection set--it's already been copied.
4633     oop p = clear_partial_array_mask(ref);
4634     assert(_g1h->obj_in_cs(p),
4635            err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, (void *)p));
4636   } else {
4637     oop p = oopDesc::load_decode_heap_oop(ref);
4638     assert(_g1h->is_in_g1_reserved(p),
4639            err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, (void *)p));
4640   }
4641   return true;
4642 }
4643 
4644 bool G1ParScanThreadState::verify_task(StarTask ref) const {
4645   if (ref.is_narrow()) {
4646     return verify_ref((narrowOop*) ref);
4647   } else {
4648     return verify_ref((oop*) ref);
4649   }
4650 }
4651 #endif // ASSERT
4652 
4653 void G1ParScanThreadState::trim_queue() {
4654   assert(_evac_failure_cl != NULL, "not set");
4655 
4656   StarTask ref;
4657   do {
4658     // Drain the overflow stack first, so other threads can steal.
4659     while (refs()->pop_overflow(ref)) {
4660       deal_with_reference(ref);
4661     }
4662 
4663     while (refs()->pop_local(ref)) {
4664       deal_with_reference(ref);
4665     }
4666   } while (!refs()->is_empty());
4667 }
4668 
4669 G1ParClosureSuper::G1ParClosureSuper(G1CollectedHeap* g1,
4670                                      G1ParScanThreadState* par_scan_state) :
4671   _g1(g1), _par_scan_state(par_scan_state),
4672   _worker_id(par_scan_state->queue_num()) { }
4673 
4674 void G1ParCopyHelper::mark_object(oop obj) {
4675 #ifdef ASSERT
4676   HeapRegion* hr = _g1->heap_region_containing(obj);
4677   assert(hr != NULL, "sanity");
4678   assert(!hr->in_collection_set(), "should not mark objects in the CSet");
4679 #endif // ASSERT
4680 
4681   // We know that the object is not moving so it's safe to read its size.
4682   _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4683 }
4684 
4685 void G1ParCopyHelper::mark_forwarded_object(oop from_obj, oop to_obj) {
4686 #ifdef ASSERT
4687   assert(from_obj->is_forwarded(), "from obj should be forwarded");
4688   assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4689   assert(from_obj != to_obj, "should not be self-forwarded");
4690 
4691   HeapRegion* from_hr = _g1->heap_region_containing(from_obj);
4692   assert(from_hr != NULL, "sanity");
4693   assert(from_hr->in_collection_set(), "from obj should be in the CSet");
4694 
4695   HeapRegion* to_hr = _g1->heap_region_containing(to_obj);
4696   assert(to_hr != NULL, "sanity");
4697   assert(!to_hr->in_collection_set(), "should not mark objects in the CSet");
4698 #endif // ASSERT
4699 
4700   // The object might be in the process of being copied by another
4701   // worker so we cannot trust that its to-space image is
4702   // well-formed. So we have to read its size from its from-space
4703   // image which we know should not be changing.
4704   _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4705 }
4706 
4707 oop G1ParScanThreadState::copy_to_survivor_space(oop const old) {
4708   size_t word_sz = old->size();
4709   HeapRegion* from_region = _g1h->heap_region_containing_raw(old);
4710   // +1 to make the -1 indexes valid...
4711   int       young_index = from_region->young_index_in_cset()+1;
4712   assert( (from_region->is_young() && young_index >  0) ||
4713          (!from_region->is_young() && young_index == 0), "invariant" );
4714   G1CollectorPolicy* g1p = _g1h->g1_policy();
4715   markOop m = old->mark();
4716   int age = m->has_displaced_mark_helper() ? m->displaced_mark_helper()->age()
4717                                            : m->age();
4718   GCAllocPurpose alloc_purpose = g1p->evacuation_destination(from_region, age,
4719                                                              word_sz);
4720   HeapWord* obj_ptr = allocate(alloc_purpose, word_sz);
4721 #ifndef PRODUCT
4722   // Should this evacuation fail?
4723   if (_g1h->evacuation_should_fail()) {
4724     if (obj_ptr != NULL) {
4725       undo_allocation(alloc_purpose, obj_ptr, word_sz);
4726       obj_ptr = NULL;
4727     }
4728   }
4729 #endif // !PRODUCT
4730 
4731   if (obj_ptr == NULL) {
4732     // This will either forward-to-self, or detect that someone else has
4733     // installed a forwarding pointer.
4734     return _g1h->handle_evacuation_failure_par(this, old);
4735   }
4736 
4737   oop obj = oop(obj_ptr);
4738 
4739   // We're going to allocate linearly, so might as well prefetch ahead.
4740   Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
4741 
4742   oop forward_ptr = old->forward_to_atomic(obj);
4743   if (forward_ptr == NULL) {
4744     Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
4745 
4746     // alloc_purpose is just a hint to allocate() above, recheck the type of region
4747     // we actually allocated from and update alloc_purpose accordingly
4748     HeapRegion* to_region = _g1h->heap_region_containing_raw(obj_ptr);
4749     alloc_purpose = to_region->is_young() ? GCAllocForSurvived : GCAllocForTenured;
4750 
4751     if (g1p->track_object_age(alloc_purpose)) {
4752       // We could simply do obj->incr_age(). However, this causes a
4753       // performance issue. obj->incr_age() will first check whether
4754       // the object has a displaced mark by checking its mark word;
4755       // getting the mark word from the new location of the object
4756       // stalls. So, given that we already have the mark word and we
4757       // are about to install it anyway, it's better to increase the
4758       // age on the mark word, when the object does not have a
4759       // displaced mark word. We're not expecting many objects to have
4760       // a displaced marked word, so that case is not optimized
4761       // further (it could be...) and we simply call obj->incr_age().
4762 
4763       if (m->has_displaced_mark_helper()) {
4764         // in this case, we have to install the mark word first,
4765         // otherwise obj looks to be forwarded (the old mark word,
4766         // which contains the forward pointer, was copied)
4767         obj->set_mark(m);
4768         obj->incr_age();
4769       } else {
4770         m = m->incr_age();
4771         obj->set_mark(m);
4772       }
4773       age_table()->add(obj, word_sz);
4774     } else {
4775       obj->set_mark(m);
4776     }
4777 
4778     if (G1StringDedup::is_enabled()) {
4779       G1StringDedup::enqueue_from_evacuation(from_region->is_young(),
4780                                              to_region->is_young(),
4781                                              queue_num(),
4782                                              obj);
4783     }
4784 
4785     size_t* surv_young_words = surviving_young_words();
4786     surv_young_words[young_index] += word_sz;
4787 
4788     if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
4789       // We keep track of the next start index in the length field of
4790       // the to-space object. The actual length can be found in the
4791       // length field of the from-space object.
4792       arrayOop(obj)->set_length(0);
4793       oop* old_p = set_partial_array_mask(old);
4794       push_on_queue(old_p);
4795     } else {
4796       // No point in using the slower heap_region_containing() method,
4797       // given that we know obj is in the heap.
4798       _scanner.set_region(_g1h->heap_region_containing_raw(obj));
4799       obj->oop_iterate_backwards(&_scanner);
4800     }
4801   } else {
4802     undo_allocation(alloc_purpose, obj_ptr, word_sz);
4803     obj = forward_ptr;
4804   }
4805   return obj;
4806 }
4807 
4808 template <class T>
4809 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) {
4810   if (_g1->heap_region_containing_raw(new_obj)->is_young()) {
4811     _scanned_klass->record_modified_oops();
4812   }
4813 }
4814 
4815 template <G1Barrier barrier, bool do_mark_object>
4816 template <class T>
4817 void G1ParCopyClosure<barrier, do_mark_object>::do_oop_work(T* p) {
4818   T heap_oop = oopDesc::load_heap_oop(p);
4819 
4820   if (oopDesc::is_null(heap_oop)) {
4821     return;
4822   }
4823 
4824   oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
4825 
4826   assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4827 
4828   if (_g1->in_cset_fast_test(obj)) {
4829     oop forwardee;
4830     if (obj->is_forwarded()) {
4831       forwardee = obj->forwardee();
4832     } else {
4833       forwardee = _par_scan_state->copy_to_survivor_space(obj);
4834     }
4835     assert(forwardee != NULL, "forwardee should not be NULL");
4836     oopDesc::encode_store_heap_oop(p, forwardee);
4837     if (do_mark_object && forwardee != obj) {
4838       // If the object is self-forwarded we don't need to explicitly
4839       // mark it, the evacuation failure protocol will do so.
4840       mark_forwarded_object(obj, forwardee);
4841     }
4842 
4843     if (barrier == G1BarrierKlass) {
4844       do_klass_barrier(p, forwardee);
4845     }
4846   } else {
4847     // The object is not in collection set. If we're a root scanning
4848     // closure during an initial mark pause (i.e. do_mark_object will
4849     // be true) then attempt to mark the object.
4850     if (do_mark_object) {
4851       mark_object(obj);
4852     }
4853   }
4854 
4855   if (barrier == G1BarrierEvac) {
4856     _par_scan_state->update_rs(_from, p, _worker_id);
4857   }
4858 }
4859 
4860 template void G1ParCopyClosure<G1BarrierEvac, false>::do_oop_work(oop* p);
4861 template void G1ParCopyClosure<G1BarrierEvac, false>::do_oop_work(narrowOop* p);
4862 
4863 class G1ParEvacuateFollowersClosure : public VoidClosure {
4864 protected:
4865   G1CollectedHeap*              _g1h;
4866   G1ParScanThreadState*         _par_scan_state;
4867   RefToScanQueueSet*            _queues;
4868   ParallelTaskTerminator*       _terminator;
4869 
4870   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
4871   RefToScanQueueSet*      queues()         { return _queues; }
4872   ParallelTaskTerminator* terminator()     { return _terminator; }
4873 
4874 public:
4875   G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4876                                 G1ParScanThreadState* par_scan_state,
4877                                 RefToScanQueueSet* queues,
4878                                 ParallelTaskTerminator* terminator)
4879     : _g1h(g1h), _par_scan_state(par_scan_state),
4880       _queues(queues), _terminator(terminator) {}
4881 
4882   void do_void();
4883 
4884 private:
4885   inline bool offer_termination();
4886 };
4887 
4888 bool G1ParEvacuateFollowersClosure::offer_termination() {
4889   G1ParScanThreadState* const pss = par_scan_state();
4890   pss->start_term_time();
4891   const bool res = terminator()->offer_termination();
4892   pss->end_term_time();
4893   return res;
4894 }
4895 
4896 void G1ParEvacuateFollowersClosure::do_void() {
4897   StarTask stolen_task;
4898   G1ParScanThreadState* const pss = par_scan_state();
4899   pss->trim_queue();
4900 
4901   do {
4902     while (queues()->steal(pss->queue_num(), pss->hash_seed(), stolen_task)) {
4903       assert(pss->verify_task(stolen_task), "sanity");
4904       if (stolen_task.is_narrow()) {
4905         pss->deal_with_reference((narrowOop*) stolen_task);
4906       } else {
4907         pss->deal_with_reference((oop*) stolen_task);
4908       }
4909 
4910       // We've just processed a reference and we might have made
4911       // available new entries on the queues. So we have to make sure
4912       // we drain the queues as necessary.
4913       pss->trim_queue();
4914     }
4915   } while (!offer_termination());
4916 
4917   pss->retire_alloc_buffers();
4918 }
4919 
4920 class G1KlassScanClosure : public KlassClosure {
4921  G1ParCopyHelper* _closure;
4922  bool             _process_only_dirty;
4923  int              _count;
4924  public:
4925   G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty)
4926       : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {}
4927   void do_klass(Klass* klass) {
4928     // If the klass has not been dirtied we know that there's
4929     // no references into  the young gen and we can skip it.
4930    if (!_process_only_dirty || klass->has_modified_oops()) {
4931       // Clean the klass since we're going to scavenge all the metadata.
4932       klass->clear_modified_oops();
4933 
4934       // Tell the closure that this klass is the Klass to scavenge
4935       // and is the one to dirty if oops are left pointing into the young gen.
4936       _closure->set_scanned_klass(klass);
4937 
4938       klass->oops_do(_closure);
4939 
4940       _closure->set_scanned_klass(NULL);
4941     }
4942     _count++;
4943   }
4944 };
4945 
4946 class G1ParTask : public AbstractGangTask {
4947 protected:
4948   G1CollectedHeap*       _g1h;
4949   RefToScanQueueSet      *_queues;
4950   ParallelTaskTerminator _terminator;
4951   uint _n_workers;
4952 
4953   Mutex _stats_lock;
4954   Mutex* stats_lock() { return &_stats_lock; }
4955 
4956   size_t getNCards() {
4957     return (_g1h->capacity() + G1BlockOffsetSharedArray::N_bytes - 1)
4958       / G1BlockOffsetSharedArray::N_bytes;
4959   }
4960 
4961 public:
4962   G1ParTask(G1CollectedHeap* g1h,
4963             RefToScanQueueSet *task_queues)
4964     : AbstractGangTask("G1 collection"),
4965       _g1h(g1h),
4966       _queues(task_queues),
4967       _terminator(0, _queues),
4968       _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4969   {}
4970 
4971   RefToScanQueueSet* queues() { return _queues; }
4972 
4973   RefToScanQueue *work_queue(int i) {
4974     return queues()->queue(i);
4975   }
4976 
4977   ParallelTaskTerminator* terminator() { return &_terminator; }
4978 
4979   virtual void set_for_termination(int active_workers) {
4980     // This task calls set_n_termination() in par_non_clean_card_iterate_work()
4981     // in the young space (_par_seq_tasks) in the G1 heap
4982     // for SequentialSubTasksDone.
4983     // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap
4984     // both of which need setting by set_n_termination().
4985     _g1h->SharedHeap::set_n_termination(active_workers);
4986     _g1h->set_n_termination(active_workers);
4987     terminator()->reset_for_reuse(active_workers);
4988     _n_workers = active_workers;
4989   }
4990 
4991   void work(uint worker_id) {
4992     if (worker_id >= _n_workers) return;  // no work needed this round
4993 
4994     double start_time_ms = os::elapsedTime() * 1000.0;
4995     _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms);
4996 
4997     {
4998       ResourceMark rm;
4999       HandleMark   hm;
5000 
5001       ReferenceProcessor*             rp = _g1h->ref_processor_stw();
5002 
5003       G1ParScanThreadState            pss(_g1h, worker_id, rp);
5004       G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
5005 
5006       pss.set_evac_failure_closure(&evac_failure_cl);
5007 
5008       G1ParScanExtRootClosure        only_scan_root_cl(_g1h, &pss, rp);
5009       G1ParScanMetadataClosure       only_scan_metadata_cl(_g1h, &pss, rp);
5010 
5011       G1ParScanAndMarkExtRootClosure scan_mark_root_cl(_g1h, &pss, rp);
5012       G1ParScanAndMarkMetadataClosure scan_mark_metadata_cl(_g1h, &pss, rp);
5013 
5014       bool only_young                 = _g1h->g1_policy()->gcs_are_young();
5015       G1KlassScanClosure              scan_mark_klasses_cl_s(&scan_mark_metadata_cl, false);
5016       G1KlassScanClosure              only_scan_klasses_cl_s(&only_scan_metadata_cl, only_young);
5017 
5018       OopClosure*                    scan_root_cl = &only_scan_root_cl;
5019       G1KlassScanClosure*            scan_klasses_cl = &only_scan_klasses_cl_s;
5020 
5021       if (_g1h->g1_policy()->during_initial_mark_pause()) {
5022         // We also need to mark copied objects.
5023         scan_root_cl = &scan_mark_root_cl;
5024         scan_klasses_cl = &scan_mark_klasses_cl_s;
5025       }
5026 
5027       G1ParPushHeapRSClosure          push_heap_rs_cl(_g1h, &pss);
5028 
5029       // Don't scan the scavengable methods in the code cache as part
5030       // of strong root scanning. The code roots that point into a
5031       // region in the collection set are scanned when we scan the
5032       // region's RSet.
5033       int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings;
5034 
5035       pss.start_strong_roots();
5036       _g1h->g1_process_strong_roots(/* is scavenging */ true,
5037                                     SharedHeap::ScanningOption(so),
5038                                     scan_root_cl,
5039                                     &push_heap_rs_cl,
5040                                     scan_klasses_cl,
5041                                     worker_id);
5042       pss.end_strong_roots();
5043 
5044       {
5045         double start = os::elapsedTime();
5046         G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
5047         evac.do_void();
5048         double elapsed_ms = (os::elapsedTime()-start)*1000.0;
5049         double term_ms = pss.term_time()*1000.0;
5050         _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms);
5051         _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts());
5052       }
5053       _g1h->g1_policy()->record_thread_age_table(pss.age_table());
5054       _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
5055 
5056       if (ParallelGCVerbose) {
5057         MutexLocker x(stats_lock());
5058         pss.print_termination_stats(worker_id);
5059       }
5060 
5061       assert(pss.refs()->is_empty(), "should be empty");
5062 
5063       // Close the inner scope so that the ResourceMark and HandleMark
5064       // destructors are executed here and are included as part of the
5065       // "GC Worker Time".
5066     }
5067 
5068     double end_time_ms = os::elapsedTime() * 1000.0;
5069     _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms);
5070   }
5071 };
5072 
5073 // *** Common G1 Evacuation Stuff
5074 
5075 // This method is run in a GC worker.
5076 
5077 void
5078 G1CollectedHeap::
5079 g1_process_strong_roots(bool is_scavenging,
5080                         ScanningOption so,
5081                         OopClosure* scan_non_heap_roots,
5082                         OopsInHeapRegionClosure* scan_rs,
5083                         G1KlassScanClosure* scan_klasses,
5084                         int worker_i) {
5085 
5086   // First scan the strong roots
5087   double ext_roots_start = os::elapsedTime();
5088   double closure_app_time_sec = 0.0;
5089 
5090   BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
5091 
5092   process_strong_roots(false, // no scoping; this is parallel code
5093                        so,
5094                        &buf_scan_non_heap_roots,
5095                        scan_klasses
5096                        );
5097 
5098   // Now the CM ref_processor roots.
5099   if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
5100     // We need to treat the discovered reference lists of the
5101     // concurrent mark ref processor as roots and keep entries
5102     // (which are added by the marking threads) on them live
5103     // until they can be processed at the end of marking.
5104     ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
5105   }
5106 
5107   // Finish up any enqueued closure apps (attributed as object copy time).
5108   buf_scan_non_heap_roots.done();
5109 
5110   double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds();
5111 
5112   g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
5113 
5114   double ext_root_time_ms =
5115     ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0;
5116 
5117   g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
5118 
5119   // During conc marking we have to filter the per-thread SATB buffers
5120   // to make sure we remove any oops into the CSet (which will show up
5121   // as implicitly live).
5122   double satb_filtering_ms = 0.0;
5123   if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) {
5124     if (mark_in_progress()) {
5125       double satb_filter_start = os::elapsedTime();
5126 
5127       JavaThread::satb_mark_queue_set().filter_thread_buffers();
5128 
5129       satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0;
5130     }
5131   }
5132   g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms);
5133 
5134   // If this is an initial mark pause, and we're not scanning
5135   // the entire code cache, we need to mark the oops in the
5136   // strong code root lists for the regions that are not in
5137   // the collection set.
5138   // Note all threads participate in this set of root tasks.
5139   double mark_strong_code_roots_ms = 0.0;
5140   if (g1_policy()->during_initial_mark_pause() && !(so & SO_AllCodeCache)) {
5141     double mark_strong_roots_start = os::elapsedTime();
5142     mark_strong_code_roots(worker_i);
5143     mark_strong_code_roots_ms = (os::elapsedTime() - mark_strong_roots_start) * 1000.0;
5144   }
5145   g1_policy()->phase_times()->record_strong_code_root_mark_time(worker_i, mark_strong_code_roots_ms);
5146 
5147   // Now scan the complement of the collection set.
5148   CodeBlobToOopClosure eager_scan_code_roots(scan_non_heap_roots, true /* do_marking */);
5149   g1_rem_set()->oops_into_collection_set_do(scan_rs, &eager_scan_code_roots, worker_i);
5150 
5151   _process_strong_tasks->all_tasks_completed();
5152 }
5153 
5154 class G1StringSymbolTableUnlinkTask : public AbstractGangTask {
5155 private:
5156   BoolObjectClosure* _is_alive;
5157   int _initial_string_table_size;
5158   int _initial_symbol_table_size;
5159 
5160   bool  _process_strings;
5161   int _strings_processed;
5162   int _strings_removed;
5163 
5164   bool  _process_symbols;
5165   int _symbols_processed;
5166   int _symbols_removed;
5167 
5168   bool _do_in_parallel;
5169 public:
5170   G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) :
5171     AbstractGangTask("Par String/Symbol table unlink"), _is_alive(is_alive),
5172     _do_in_parallel(G1CollectedHeap::use_parallel_gc_threads()),
5173     _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
5174     _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) {
5175 
5176     _initial_string_table_size = StringTable::the_table()->table_size();
5177     _initial_symbol_table_size = SymbolTable::the_table()->table_size();
5178     if (process_strings) {
5179       StringTable::clear_parallel_claimed_index();
5180     }
5181     if (process_symbols) {
5182       SymbolTable::clear_parallel_claimed_index();
5183     }
5184   }
5185 
5186   ~G1StringSymbolTableUnlinkTask() {
5187     guarantee(!_process_strings || !_do_in_parallel || StringTable::parallel_claimed_index() >= _initial_string_table_size,
5188               err_msg("claim value "INT32_FORMAT" after unlink less than initial string table size "INT32_FORMAT,
5189                       StringTable::parallel_claimed_index(), _initial_string_table_size));
5190     guarantee(!_process_symbols || !_do_in_parallel || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
5191               err_msg("claim value "INT32_FORMAT" after unlink less than initial symbol table size "INT32_FORMAT,
5192                       SymbolTable::parallel_claimed_index(), _initial_symbol_table_size));
5193   }
5194 
5195   void work(uint worker_id) {
5196     if (_do_in_parallel) {
5197       int strings_processed = 0;
5198       int strings_removed = 0;
5199       int symbols_processed = 0;
5200       int symbols_removed = 0;
5201       if (_process_strings) {
5202         StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
5203         Atomic::add(strings_processed, &_strings_processed);
5204         Atomic::add(strings_removed, &_strings_removed);
5205       }
5206       if (_process_symbols) {
5207         SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
5208         Atomic::add(symbols_processed, &_symbols_processed);
5209         Atomic::add(symbols_removed, &_symbols_removed);
5210       }
5211     } else {
5212       if (_process_strings) {
5213         StringTable::unlink(_is_alive, &_strings_processed, &_strings_removed);
5214       }
5215       if (_process_symbols) {
5216         SymbolTable::unlink(&_symbols_processed, &_symbols_removed);
5217       }
5218     }
5219   }
5220 
5221   size_t strings_processed() const { return (size_t)_strings_processed; }
5222   size_t strings_removed()   const { return (size_t)_strings_removed; }
5223 
5224   size_t symbols_processed() const { return (size_t)_symbols_processed; }
5225   size_t symbols_removed()   const { return (size_t)_symbols_removed; }
5226 };
5227 
5228 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive,
5229                                                      bool process_strings, bool process_symbols) {
5230   uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5231                    _g1h->workers()->active_workers() : 1);
5232 
5233   G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols);
5234   if (G1CollectedHeap::use_parallel_gc_threads()) {
5235     set_par_threads(n_workers);
5236     workers()->run_task(&g1_unlink_task);
5237     set_par_threads(0);
5238   } else {
5239     g1_unlink_task.work(0);
5240   }
5241   if (G1TraceStringSymbolTableScrubbing) {
5242     gclog_or_tty->print_cr("Cleaned string and symbol table, "
5243                            "strings: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed, "
5244                            "symbols: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed",
5245                            g1_unlink_task.strings_processed(), g1_unlink_task.strings_removed(),
5246                            g1_unlink_task.symbols_processed(), g1_unlink_task.symbols_removed());
5247   }
5248 
5249   if (G1StringDedup::is_enabled()) {
5250     G1StringDedup::unlink(is_alive);
5251   }
5252 }
5253 
5254 class RedirtyLoggedCardTableEntryFastClosure : public CardTableEntryClosure {
5255 public:
5256   bool do_card_ptr(jbyte* card_ptr, int worker_i) {
5257     *card_ptr = CardTableModRefBS::dirty_card_val();
5258     return true;
5259   }
5260 };
5261 
5262 void G1CollectedHeap::redirty_logged_cards() {
5263   guarantee(G1DeferredRSUpdate, "Must only be called when using deferred RS updates.");
5264   double redirty_logged_cards_start = os::elapsedTime();
5265 
5266   RedirtyLoggedCardTableEntryFastClosure redirty;
5267   dirty_card_queue_set().set_closure(&redirty);
5268   dirty_card_queue_set().apply_closure_to_all_completed_buffers();
5269 
5270   DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5271   dcq.merge_bufferlists(&dirty_card_queue_set());
5272   assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5273 
5274   g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
5275 }
5276 
5277 // Weak Reference Processing support
5278 
5279 // An always "is_alive" closure that is used to preserve referents.
5280 // If the object is non-null then it's alive.  Used in the preservation
5281 // of referent objects that are pointed to by reference objects
5282 // discovered by the CM ref processor.
5283 class G1AlwaysAliveClosure: public BoolObjectClosure {
5284   G1CollectedHeap* _g1;
5285 public:
5286   G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5287   bool do_object_b(oop p) {
5288     if (p != NULL) {
5289       return true;
5290     }
5291     return false;
5292   }
5293 };
5294 
5295 bool G1STWIsAliveClosure::do_object_b(oop p) {
5296   // An object is reachable if it is outside the collection set,
5297   // or is inside and copied.
5298   return !_g1->obj_in_cs(p) || p->is_forwarded();
5299 }
5300 
5301 // Non Copying Keep Alive closure
5302 class G1KeepAliveClosure: public OopClosure {
5303   G1CollectedHeap* _g1;
5304 public:
5305   G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5306   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
5307   void do_oop(      oop* p) {
5308     oop obj = *p;
5309 
5310     if (_g1->obj_in_cs(obj)) {
5311       assert( obj->is_forwarded(), "invariant" );
5312       *p = obj->forwardee();
5313     }
5314   }
5315 };
5316 
5317 // Copying Keep Alive closure - can be called from both
5318 // serial and parallel code as long as different worker
5319 // threads utilize different G1ParScanThreadState instances
5320 // and different queues.
5321 
5322 class G1CopyingKeepAliveClosure: public OopClosure {
5323   G1CollectedHeap*         _g1h;
5324   OopClosure*              _copy_non_heap_obj_cl;
5325   OopsInHeapRegionClosure* _copy_metadata_obj_cl;
5326   G1ParScanThreadState*    _par_scan_state;
5327 
5328 public:
5329   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
5330                             OopClosure* non_heap_obj_cl,
5331                             OopsInHeapRegionClosure* metadata_obj_cl,
5332                             G1ParScanThreadState* pss):
5333     _g1h(g1h),
5334     _copy_non_heap_obj_cl(non_heap_obj_cl),
5335     _copy_metadata_obj_cl(metadata_obj_cl),
5336     _par_scan_state(pss)
5337   {}
5338 
5339   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
5340   virtual void do_oop(      oop* p) { do_oop_work(p); }
5341 
5342   template <class T> void do_oop_work(T* p) {
5343     oop obj = oopDesc::load_decode_heap_oop(p);
5344 
5345     if (_g1h->obj_in_cs(obj)) {
5346       // If the referent object has been forwarded (either copied
5347       // to a new location or to itself in the event of an
5348       // evacuation failure) then we need to update the reference
5349       // field and, if both reference and referent are in the G1
5350       // heap, update the RSet for the referent.
5351       //
5352       // If the referent has not been forwarded then we have to keep
5353       // it alive by policy. Therefore we have copy the referent.
5354       //
5355       // If the reference field is in the G1 heap then we can push
5356       // on the PSS queue. When the queue is drained (after each
5357       // phase of reference processing) the object and it's followers
5358       // will be copied, the reference field set to point to the
5359       // new location, and the RSet updated. Otherwise we need to
5360       // use the the non-heap or metadata closures directly to copy
5361       // the referent object and update the pointer, while avoiding
5362       // updating the RSet.
5363 
5364       if (_g1h->is_in_g1_reserved(p)) {
5365         _par_scan_state->push_on_queue(p);
5366       } else {
5367         assert(!ClassLoaderDataGraph::contains((address)p),
5368                err_msg("Otherwise need to call _copy_metadata_obj_cl->do_oop(p) "
5369                               PTR_FORMAT, p));
5370           _copy_non_heap_obj_cl->do_oop(p);
5371         }
5372       }
5373     }
5374 };
5375 
5376 // Serial drain queue closure. Called as the 'complete_gc'
5377 // closure for each discovered list in some of the
5378 // reference processing phases.
5379 
5380 class G1STWDrainQueueClosure: public VoidClosure {
5381 protected:
5382   G1CollectedHeap* _g1h;
5383   G1ParScanThreadState* _par_scan_state;
5384 
5385   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
5386 
5387 public:
5388   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
5389     _g1h(g1h),
5390     _par_scan_state(pss)
5391   { }
5392 
5393   void do_void() {
5394     G1ParScanThreadState* const pss = par_scan_state();
5395     pss->trim_queue();
5396   }
5397 };
5398 
5399 // Parallel Reference Processing closures
5400 
5401 // Implementation of AbstractRefProcTaskExecutor for parallel reference
5402 // processing during G1 evacuation pauses.
5403 
5404 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5405 private:
5406   G1CollectedHeap*   _g1h;
5407   RefToScanQueueSet* _queues;
5408   FlexibleWorkGang*  _workers;
5409   int                _active_workers;
5410 
5411 public:
5412   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5413                         FlexibleWorkGang* workers,
5414                         RefToScanQueueSet *task_queues,
5415                         int n_workers) :
5416     _g1h(g1h),
5417     _queues(task_queues),
5418     _workers(workers),
5419     _active_workers(n_workers)
5420   {
5421     assert(n_workers > 0, "shouldn't call this otherwise");
5422   }
5423 
5424   // Executes the given task using concurrent marking worker threads.
5425   virtual void execute(ProcessTask& task);
5426   virtual void execute(EnqueueTask& task);
5427 };
5428 
5429 // Gang task for possibly parallel reference processing
5430 
5431 class G1STWRefProcTaskProxy: public AbstractGangTask {
5432   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5433   ProcessTask&     _proc_task;
5434   G1CollectedHeap* _g1h;
5435   RefToScanQueueSet *_task_queues;
5436   ParallelTaskTerminator* _terminator;
5437 
5438 public:
5439   G1STWRefProcTaskProxy(ProcessTask& proc_task,
5440                      G1CollectedHeap* g1h,
5441                      RefToScanQueueSet *task_queues,
5442                      ParallelTaskTerminator* terminator) :
5443     AbstractGangTask("Process reference objects in parallel"),
5444     _proc_task(proc_task),
5445     _g1h(g1h),
5446     _task_queues(task_queues),
5447     _terminator(terminator)
5448   {}
5449 
5450   virtual void work(uint worker_id) {
5451     // The reference processing task executed by a single worker.
5452     ResourceMark rm;
5453     HandleMark   hm;
5454 
5455     G1STWIsAliveClosure is_alive(_g1h);
5456 
5457     G1ParScanThreadState            pss(_g1h, worker_id, NULL);
5458     G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5459 
5460     pss.set_evac_failure_closure(&evac_failure_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, NULL);
5565     G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5566 
5567     pss.set_evac_failure_closure(&evac_failure_cl);
5568 
5569     assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5570 
5571 
5572     G1ParScanExtRootClosure        only_copy_non_heap_cl(_g1h, &pss, NULL);
5573     G1ParScanMetadataClosure       only_copy_metadata_cl(_g1h, &pss, NULL);
5574 
5575     G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5576     G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(_g1h, &pss, NULL);
5577 
5578     OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5579     OopsInHeapRegionClosure*       copy_metadata_cl = &only_copy_metadata_cl;
5580 
5581     if (_g1h->g1_policy()->during_initial_mark_pause()) {
5582       // We also need to mark copied objects.
5583       copy_non_heap_cl = &copy_mark_non_heap_cl;
5584       copy_metadata_cl = &copy_mark_metadata_cl;
5585     }
5586 
5587     // Is alive closure
5588     G1AlwaysAliveClosure always_alive(_g1h);
5589 
5590     // Copying keep alive closure. Applied to referent objects that need
5591     // to be copied.
5592     G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_metadata_cl, &pss);
5593 
5594     ReferenceProcessor* rp = _g1h->ref_processor_cm();
5595 
5596     uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5597     uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5598 
5599     // limit is set using max_num_q() - which was set using ParallelGCThreads.
5600     // So this must be true - but assert just in case someone decides to
5601     // change the worker ids.
5602     assert(0 <= worker_id && worker_id < limit, "sanity");
5603     assert(!rp->discovery_is_atomic(), "check this code");
5604 
5605     // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5606     for (uint idx = worker_id; idx < limit; idx += stride) {
5607       DiscoveredList& ref_list = rp->discovered_refs()[idx];
5608 
5609       DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5610       while (iter.has_next()) {
5611         // Since discovery is not atomic for the CM ref processor, we
5612         // can see some null referent objects.
5613         iter.load_ptrs(DEBUG_ONLY(true));
5614         oop ref = iter.obj();
5615 
5616         // This will filter nulls.
5617         if (iter.is_referent_alive()) {
5618           iter.make_referent_alive();
5619         }
5620         iter.move_to_next();
5621       }
5622     }
5623 
5624     // Drain the queue - which may cause stealing
5625     G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5626     drain_queue.do_void();
5627     // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5628     assert(pss.refs()->is_empty(), "should be");
5629   }
5630 };
5631 
5632 // Weak Reference processing during an evacuation pause (part 1).
5633 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) {
5634   double ref_proc_start = os::elapsedTime();
5635 
5636   ReferenceProcessor* rp = _ref_processor_stw;
5637   assert(rp->discovery_enabled(), "should have been enabled");
5638 
5639   // Any reference objects, in the collection set, that were 'discovered'
5640   // by the CM ref processor should have already been copied (either by
5641   // applying the external root copy closure to the discovered lists, or
5642   // by following an RSet entry).
5643   //
5644   // But some of the referents, that are in the collection set, that these
5645   // reference objects point to may not have been copied: the STW ref
5646   // processor would have seen that the reference object had already
5647   // been 'discovered' and would have skipped discovering the reference,
5648   // but would not have treated the reference object as a regular oop.
5649   // As a result the copy closure would not have been applied to the
5650   // referent object.
5651   //
5652   // We need to explicitly copy these referent objects - the references
5653   // will be processed at the end of remarking.
5654   //
5655   // We also need to do this copying before we process the reference
5656   // objects discovered by the STW ref processor in case one of these
5657   // referents points to another object which is also referenced by an
5658   // object discovered by the STW ref processor.
5659 
5660   assert(!G1CollectedHeap::use_parallel_gc_threads() ||
5661            no_of_gc_workers == workers()->active_workers(),
5662            "Need to reset active GC workers");
5663 
5664   set_par_threads(no_of_gc_workers);
5665   G1ParPreserveCMReferentsTask keep_cm_referents(this,
5666                                                  no_of_gc_workers,
5667                                                  _task_queues);
5668 
5669   if (G1CollectedHeap::use_parallel_gc_threads()) {
5670     workers()->run_task(&keep_cm_referents);
5671   } else {
5672     keep_cm_referents.work(0);
5673   }
5674 
5675   set_par_threads(0);
5676 
5677   // Closure to test whether a referent is alive.
5678   G1STWIsAliveClosure is_alive(this);
5679 
5680   // Even when parallel reference processing is enabled, the processing
5681   // of JNI refs is serial and performed serially by the current thread
5682   // rather than by a worker. The following PSS will be used for processing
5683   // JNI refs.
5684 
5685   // Use only a single queue for this PSS.
5686   G1ParScanThreadState            pss(this, 0, NULL);
5687 
5688   // We do not embed a reference processor in the copying/scanning
5689   // closures while we're actually processing the discovered
5690   // reference objects.
5691   G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5692 
5693   pss.set_evac_failure_closure(&evac_failure_cl);
5694 
5695   assert(pss.refs()->is_empty(), "pre-condition");
5696 
5697   G1ParScanExtRootClosure        only_copy_non_heap_cl(this, &pss, NULL);
5698   G1ParScanMetadataClosure       only_copy_metadata_cl(this, &pss, NULL);
5699 
5700   G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5701   G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(this, &pss, NULL);
5702 
5703   OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5704   OopsInHeapRegionClosure*       copy_metadata_cl = &only_copy_metadata_cl;
5705 
5706   if (_g1h->g1_policy()->during_initial_mark_pause()) {
5707     // We also need to mark copied objects.
5708     copy_non_heap_cl = &copy_mark_non_heap_cl;
5709     copy_metadata_cl = &copy_mark_metadata_cl;
5710   }
5711 
5712   // Keep alive closure.
5713   G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, copy_metadata_cl, &pss);
5714 
5715   // Serial Complete GC closure
5716   G1STWDrainQueueClosure drain_queue(this, &pss);
5717 
5718   // Setup the soft refs policy...
5719   rp->setup_policy(false);
5720 
5721   ReferenceProcessorStats stats;
5722   if (!rp->processing_is_mt()) {
5723     // Serial reference processing...
5724     stats = rp->process_discovered_references(&is_alive,
5725                                               &keep_alive,
5726                                               &drain_queue,
5727                                               NULL,
5728                                               _gc_timer_stw);
5729   } else {
5730     // Parallel reference processing
5731     assert(rp->num_q() == no_of_gc_workers, "sanity");
5732     assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5733 
5734     G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5735     stats = rp->process_discovered_references(&is_alive,
5736                                               &keep_alive,
5737                                               &drain_queue,
5738                                               &par_task_executor,
5739                                               _gc_timer_stw);
5740   }
5741 
5742   _gc_tracer_stw->report_gc_reference_stats(stats);
5743   // We have completed copying any necessary live referent objects
5744   // (that were not copied during the actual pause) so we can
5745   // retire any active alloc buffers
5746   pss.retire_alloc_buffers();
5747   assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5748 
5749   double ref_proc_time = os::elapsedTime() - ref_proc_start;
5750   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5751 }
5752 
5753 // Weak Reference processing during an evacuation pause (part 2).
5754 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) {
5755   double ref_enq_start = os::elapsedTime();
5756 
5757   ReferenceProcessor* rp = _ref_processor_stw;
5758   assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5759 
5760   // Now enqueue any remaining on the discovered lists on to
5761   // the pending list.
5762   if (!rp->processing_is_mt()) {
5763     // Serial reference processing...
5764     rp->enqueue_discovered_references();
5765   } else {
5766     // Parallel reference enqueueing
5767 
5768     assert(no_of_gc_workers == workers()->active_workers(),
5769            "Need to reset active workers");
5770     assert(rp->num_q() == no_of_gc_workers, "sanity");
5771     assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5772 
5773     G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5774     rp->enqueue_discovered_references(&par_task_executor);
5775   }
5776 
5777   rp->verify_no_references_recorded();
5778   assert(!rp->discovery_enabled(), "should have been disabled");
5779 
5780   // FIXME
5781   // CM's reference processing also cleans up the string and symbol tables.
5782   // Should we do that here also? We could, but it is a serial operation
5783   // and could significantly increase the pause time.
5784 
5785   double ref_enq_time = os::elapsedTime() - ref_enq_start;
5786   g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5787 }
5788 
5789 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) {
5790   _expand_heap_after_alloc_failure = true;
5791   _evacuation_failed = false;
5792 
5793   // Should G1EvacuationFailureALot be in effect for this GC?
5794   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
5795 
5796   g1_rem_set()->prepare_for_oops_into_collection_set_do();
5797 
5798   // Disable the hot card cache.
5799   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
5800   hot_card_cache->reset_hot_cache_claimed_index();
5801   hot_card_cache->set_use_cache(false);
5802 
5803   uint n_workers;
5804   if (G1CollectedHeap::use_parallel_gc_threads()) {
5805     n_workers =
5806       AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
5807                                      workers()->active_workers(),
5808                                      Threads::number_of_non_daemon_threads());
5809     assert(UseDynamicNumberOfGCThreads ||
5810            n_workers == workers()->total_workers(),
5811            "If not dynamic should be using all the  workers");
5812     workers()->set_active_workers(n_workers);
5813     set_par_threads(n_workers);
5814   } else {
5815     assert(n_par_threads() == 0,
5816            "Should be the original non-parallel value");
5817     n_workers = 1;
5818   }
5819 
5820   G1ParTask g1_par_task(this, _task_queues);
5821 
5822   init_for_evac_failure(NULL);
5823 
5824   rem_set()->prepare_for_younger_refs_iterate(true);
5825 
5826   assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5827   double start_par_time_sec = os::elapsedTime();
5828   double end_par_time_sec;
5829 
5830   {
5831     StrongRootsScope srs(this);
5832 
5833     if (G1CollectedHeap::use_parallel_gc_threads()) {
5834       // The individual threads will set their evac-failure closures.
5835       if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
5836       // These tasks use ShareHeap::_process_strong_tasks
5837       assert(UseDynamicNumberOfGCThreads ||
5838              workers()->active_workers() == workers()->total_workers(),
5839              "If not dynamic should be using all the  workers");
5840       workers()->run_task(&g1_par_task);
5841     } else {
5842       g1_par_task.set_for_termination(n_workers);
5843       g1_par_task.work(0);
5844     }
5845     end_par_time_sec = os::elapsedTime();
5846 
5847     // Closing the inner scope will execute the destructor
5848     // for the StrongRootsScope object. We record the current
5849     // elapsed time before closing the scope so that time
5850     // taken for the SRS destructor is NOT included in the
5851     // reported parallel time.
5852   }
5853 
5854   double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5855   g1_policy()->phase_times()->record_par_time(par_time_ms);
5856 
5857   double code_root_fixup_time_ms =
5858         (os::elapsedTime() - end_par_time_sec) * 1000.0;
5859   g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms);
5860 
5861   set_par_threads(0);
5862 
5863   // Process any discovered reference objects - we have
5864   // to do this _before_ we retire the GC alloc regions
5865   // as we may have to copy some 'reachable' referent
5866   // objects (and their reachable sub-graphs) that were
5867   // not copied during the pause.
5868   process_discovered_references(n_workers);
5869 
5870   // Weak root processing.
5871   {
5872     G1STWIsAliveClosure is_alive(this);
5873     G1KeepAliveClosure keep_alive(this);
5874     JNIHandles::weak_oops_do(&is_alive, &keep_alive);
5875     if (G1StringDedup::is_enabled()) {
5876       G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive);
5877     }
5878   }
5879 
5880   release_gc_alloc_regions(n_workers, evacuation_info);
5881   g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5882 
5883   // Reset and re-enable the hot card cache.
5884   // Note the counts for the cards in the regions in the
5885   // collection set are reset when the collection set is freed.
5886   hot_card_cache->reset_hot_cache();
5887   hot_card_cache->set_use_cache(true);
5888 
5889   // Migrate the strong code roots attached to each region in
5890   // the collection set. Ideally we would like to do this
5891   // after we have finished the scanning/evacuation of the
5892   // strong code roots for a particular heap region.
5893   migrate_strong_code_roots();
5894 
5895   purge_code_root_memory();
5896 
5897   if (g1_policy()->during_initial_mark_pause()) {
5898     // Reset the claim values set during marking the strong code roots
5899     reset_heap_region_claim_values();
5900   }
5901 
5902   finalize_for_evac_failure();
5903 
5904   if (evacuation_failed()) {
5905     remove_self_forwarding_pointers();
5906 
5907     // Reset the G1EvacuationFailureALot counters and flags
5908     // Note: the values are reset only when an actual
5909     // evacuation failure occurs.
5910     NOT_PRODUCT(reset_evacuation_should_fail();)
5911   }
5912 
5913   // Enqueue any remaining references remaining on the STW
5914   // reference processor's discovered lists. We need to do
5915   // this after the card table is cleaned (and verified) as
5916   // the act of enqueueing entries on to the pending list
5917   // will log these updates (and dirty their associated
5918   // cards). We need these updates logged to update any
5919   // RSets.
5920   enqueue_discovered_references(n_workers);
5921 
5922   if (G1DeferredRSUpdate) {
5923     redirty_logged_cards();
5924   }
5925   COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5926 }
5927 
5928 void G1CollectedHeap::free_region(HeapRegion* hr,
5929                                   FreeRegionList* free_list,
5930                                   bool par,
5931                                   bool locked) {
5932   assert(!hr->isHumongous(), "this is only for non-humongous regions");
5933   assert(!hr->is_empty(), "the region should not be empty");
5934   assert(free_list != NULL, "pre-condition");
5935 
5936   // Clear the card counts for this region.
5937   // Note: we only need to do this if the region is not young
5938   // (since we don't refine cards in young regions).
5939   if (!hr->is_young()) {
5940     _cg1r->hot_card_cache()->reset_card_counts(hr);
5941   }
5942   hr->hr_clear(par, true /* clear_space */, locked /* locked */);
5943   free_list->add_as_head(hr);
5944 }
5945 
5946 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
5947                                      FreeRegionList* free_list,
5948                                      bool par) {
5949   assert(hr->startsHumongous(), "this is only for starts humongous regions");
5950   assert(free_list != NULL, "pre-condition");
5951 
5952   size_t hr_capacity = hr->capacity();
5953   // We need to read this before we make the region non-humongous,
5954   // otherwise the information will be gone.
5955   uint last_index = hr->last_hc_index();
5956   hr->set_notHumongous();
5957   free_region(hr, free_list, par);
5958 
5959   uint i = hr->hrs_index() + 1;
5960   while (i < last_index) {
5961     HeapRegion* curr_hr = region_at(i);
5962     assert(curr_hr->continuesHumongous(), "invariant");
5963     curr_hr->set_notHumongous();
5964     free_region(curr_hr, free_list, par);
5965     i += 1;
5966   }
5967 }
5968 
5969 void G1CollectedHeap::remove_from_old_sets(const HeapRegionSetCount& old_regions_removed,
5970                                        const HeapRegionSetCount& humongous_regions_removed) {
5971   if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 0) {
5972     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5973     _old_set.bulk_remove(old_regions_removed);
5974     _humongous_set.bulk_remove(humongous_regions_removed);
5975   }
5976 
5977 }
5978 
5979 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
5980   assert(list != NULL, "list can't be null");
5981   if (!list->is_empty()) {
5982     MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
5983     _free_list.add_as_head(list);
5984   }
5985 }
5986 
5987 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
5988   assert(_summary_bytes_used >= bytes,
5989          err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" should be >= bytes: "SIZE_FORMAT,
5990                   _summary_bytes_used, bytes));
5991   _summary_bytes_used -= bytes;
5992 }
5993 
5994 class G1ParCleanupCTTask : public AbstractGangTask {
5995   G1SATBCardTableModRefBS* _ct_bs;
5996   G1CollectedHeap* _g1h;
5997   HeapRegion* volatile _su_head;
5998 public:
5999   G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs,
6000                      G1CollectedHeap* g1h) :
6001     AbstractGangTask("G1 Par Cleanup CT Task"),
6002     _ct_bs(ct_bs), _g1h(g1h) { }
6003 
6004   void work(uint worker_id) {
6005     HeapRegion* r;
6006     while (r = _g1h->pop_dirty_cards_region()) {
6007       clear_cards(r);
6008     }
6009   }
6010 
6011   void clear_cards(HeapRegion* r) {
6012     // Cards of the survivors should have already been dirtied.
6013     if (!r->is_survivor()) {
6014       _ct_bs->clear(MemRegion(r->bottom(), r->end()));
6015     }
6016   }
6017 };
6018 
6019 #ifndef PRODUCT
6020 class G1VerifyCardTableCleanup: public HeapRegionClosure {
6021   G1CollectedHeap* _g1h;
6022   G1SATBCardTableModRefBS* _ct_bs;
6023 public:
6024   G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs)
6025     : _g1h(g1h), _ct_bs(ct_bs) { }
6026   virtual bool doHeapRegion(HeapRegion* r) {
6027     if (r->is_survivor()) {
6028       _g1h->verify_dirty_region(r);
6029     } else {
6030       _g1h->verify_not_dirty_region(r);
6031     }
6032     return false;
6033   }
6034 };
6035 
6036 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
6037   // All of the region should be clean.
6038   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6039   MemRegion mr(hr->bottom(), hr->end());
6040   ct_bs->verify_not_dirty_region(mr);
6041 }
6042 
6043 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
6044   // We cannot guarantee that [bottom(),end()] is dirty.  Threads
6045   // dirty allocated blocks as they allocate them. The thread that
6046   // retires each region and replaces it with a new one will do a
6047   // maximal allocation to fill in [pre_dummy_top(),end()] but will
6048   // not dirty that area (one less thing to have to do while holding
6049   // a lock). So we can only verify that [bottom(),pre_dummy_top()]
6050   // is dirty.
6051   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6052   MemRegion mr(hr->bottom(), hr->pre_dummy_top());
6053   if (hr->is_young()) {
6054     ct_bs->verify_g1_young_region(mr);
6055   } else {
6056     ct_bs->verify_dirty_region(mr);
6057   }
6058 }
6059 
6060 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
6061   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6062   for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
6063     verify_dirty_region(hr);
6064   }
6065 }
6066 
6067 void G1CollectedHeap::verify_dirty_young_regions() {
6068   verify_dirty_young_list(_young_list->first_region());
6069 }
6070 #endif
6071 
6072 void G1CollectedHeap::cleanUpCardTable() {
6073   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6074   double start = os::elapsedTime();
6075 
6076   {
6077     // Iterate over the dirty cards region list.
6078     G1ParCleanupCTTask cleanup_task(ct_bs, this);
6079 
6080     if (G1CollectedHeap::use_parallel_gc_threads()) {
6081       set_par_threads();
6082       workers()->run_task(&cleanup_task);
6083       set_par_threads(0);
6084     } else {
6085       while (_dirty_cards_region_list) {
6086         HeapRegion* r = _dirty_cards_region_list;
6087         cleanup_task.clear_cards(r);
6088         _dirty_cards_region_list = r->get_next_dirty_cards_region();
6089         if (_dirty_cards_region_list == r) {
6090           // The last region.
6091           _dirty_cards_region_list = NULL;
6092         }
6093         r->set_next_dirty_cards_region(NULL);
6094       }
6095     }
6096 #ifndef PRODUCT
6097     if (G1VerifyCTCleanup || VerifyAfterGC) {
6098       G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
6099       heap_region_iterate(&cleanup_verifier);
6100     }
6101 #endif
6102   }
6103 
6104   double elapsed = os::elapsedTime() - start;
6105   g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
6106 }
6107 
6108 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) {
6109   size_t pre_used = 0;
6110   FreeRegionList local_free_list("Local List for CSet Freeing");
6111 
6112   double young_time_ms     = 0.0;
6113   double non_young_time_ms = 0.0;
6114 
6115   // Since the collection set is a superset of the the young list,
6116   // all we need to do to clear the young list is clear its
6117   // head and length, and unlink any young regions in the code below
6118   _young_list->clear();
6119 
6120   G1CollectorPolicy* policy = g1_policy();
6121 
6122   double start_sec = os::elapsedTime();
6123   bool non_young = true;
6124 
6125   HeapRegion* cur = cs_head;
6126   int age_bound = -1;
6127   size_t rs_lengths = 0;
6128 
6129   while (cur != NULL) {
6130     assert(!is_on_master_free_list(cur), "sanity");
6131     if (non_young) {
6132       if (cur->is_young()) {
6133         double end_sec = os::elapsedTime();
6134         double elapsed_ms = (end_sec - start_sec) * 1000.0;
6135         non_young_time_ms += elapsed_ms;
6136 
6137         start_sec = os::elapsedTime();
6138         non_young = false;
6139       }
6140     } else {
6141       if (!cur->is_young()) {
6142         double end_sec = os::elapsedTime();
6143         double elapsed_ms = (end_sec - start_sec) * 1000.0;
6144         young_time_ms += elapsed_ms;
6145 
6146         start_sec = os::elapsedTime();
6147         non_young = true;
6148       }
6149     }
6150 
6151     rs_lengths += cur->rem_set()->occupied_locked();
6152 
6153     HeapRegion* next = cur->next_in_collection_set();
6154     assert(cur->in_collection_set(), "bad CS");
6155     cur->set_next_in_collection_set(NULL);
6156     cur->set_in_collection_set(false);
6157 
6158     if (cur->is_young()) {
6159       int index = cur->young_index_in_cset();
6160       assert(index != -1, "invariant");
6161       assert((uint) index < policy->young_cset_region_length(), "invariant");
6162       size_t words_survived = _surviving_young_words[index];
6163       cur->record_surv_words_in_group(words_survived);
6164 
6165       // At this point the we have 'popped' cur from the collection set
6166       // (linked via next_in_collection_set()) but it is still in the
6167       // young list (linked via next_young_region()). Clear the
6168       // _next_young_region field.
6169       cur->set_next_young_region(NULL);
6170     } else {
6171       int index = cur->young_index_in_cset();
6172       assert(index == -1, "invariant");
6173     }
6174 
6175     assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
6176             (!cur->is_young() && cur->young_index_in_cset() == -1),
6177             "invariant" );
6178 
6179     if (!cur->evacuation_failed()) {
6180       MemRegion used_mr = cur->used_region();
6181 
6182       // And the region is empty.
6183       assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
6184       pre_used += cur->used();
6185       free_region(cur, &local_free_list, false /* par */, true /* locked */);
6186     } else {
6187       cur->uninstall_surv_rate_group();
6188       if (cur->is_young()) {
6189         cur->set_young_index_in_cset(-1);
6190       }
6191       cur->set_not_young();
6192       cur->set_evacuation_failed(false);
6193       // The region is now considered to be old.
6194       _old_set.add(cur);
6195       evacuation_info.increment_collectionset_used_after(cur->used());
6196     }
6197     cur = next;
6198   }
6199 
6200   evacuation_info.set_regions_freed(local_free_list.length());
6201   policy->record_max_rs_lengths(rs_lengths);
6202   policy->cset_regions_freed();
6203 
6204   double end_sec = os::elapsedTime();
6205   double elapsed_ms = (end_sec - start_sec) * 1000.0;
6206 
6207   if (non_young) {
6208     non_young_time_ms += elapsed_ms;
6209   } else {
6210     young_time_ms += elapsed_ms;
6211   }
6212 
6213   prepend_to_freelist(&local_free_list);
6214   decrement_summary_bytes(pre_used);
6215   policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
6216   policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
6217 }
6218 
6219 // This routine is similar to the above but does not record
6220 // any policy statistics or update free lists; we are abandoning
6221 // the current incremental collection set in preparation of a
6222 // full collection. After the full GC we will start to build up
6223 // the incremental collection set again.
6224 // This is only called when we're doing a full collection
6225 // and is immediately followed by the tearing down of the young list.
6226 
6227 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
6228   HeapRegion* cur = cs_head;
6229 
6230   while (cur != NULL) {
6231     HeapRegion* next = cur->next_in_collection_set();
6232     assert(cur->in_collection_set(), "bad CS");
6233     cur->set_next_in_collection_set(NULL);
6234     cur->set_in_collection_set(false);
6235     cur->set_young_index_in_cset(-1);
6236     cur = next;
6237   }
6238 }
6239 
6240 void G1CollectedHeap::set_free_regions_coming() {
6241   if (G1ConcRegionFreeingVerbose) {
6242     gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6243                            "setting free regions coming");
6244   }
6245 
6246   assert(!free_regions_coming(), "pre-condition");
6247   _free_regions_coming = true;
6248 }
6249 
6250 void G1CollectedHeap::reset_free_regions_coming() {
6251   assert(free_regions_coming(), "pre-condition");
6252 
6253   {
6254     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6255     _free_regions_coming = false;
6256     SecondaryFreeList_lock->notify_all();
6257   }
6258 
6259   if (G1ConcRegionFreeingVerbose) {
6260     gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6261                            "reset free regions coming");
6262   }
6263 }
6264 
6265 void G1CollectedHeap::wait_while_free_regions_coming() {
6266   // Most of the time we won't have to wait, so let's do a quick test
6267   // first before we take the lock.
6268   if (!free_regions_coming()) {
6269     return;
6270   }
6271 
6272   if (G1ConcRegionFreeingVerbose) {
6273     gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6274                            "waiting for free regions");
6275   }
6276 
6277   {
6278     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6279     while (free_regions_coming()) {
6280       SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
6281     }
6282   }
6283 
6284   if (G1ConcRegionFreeingVerbose) {
6285     gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6286                            "done waiting for free regions");
6287   }
6288 }
6289 
6290 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
6291   assert(heap_lock_held_for_gc(),
6292               "the heap lock should already be held by or for this thread");
6293   _young_list->push_region(hr);
6294 }
6295 
6296 class NoYoungRegionsClosure: public HeapRegionClosure {
6297 private:
6298   bool _success;
6299 public:
6300   NoYoungRegionsClosure() : _success(true) { }
6301   bool doHeapRegion(HeapRegion* r) {
6302     if (r->is_young()) {
6303       gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
6304                              r->bottom(), r->end());
6305       _success = false;
6306     }
6307     return false;
6308   }
6309   bool success() { return _success; }
6310 };
6311 
6312 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
6313   bool ret = _young_list->check_list_empty(check_sample);
6314 
6315   if (check_heap) {
6316     NoYoungRegionsClosure closure;
6317     heap_region_iterate(&closure);
6318     ret = ret && closure.success();
6319   }
6320 
6321   return ret;
6322 }
6323 
6324 class TearDownRegionSetsClosure : public HeapRegionClosure {
6325 private:
6326   HeapRegionSet *_old_set;
6327 
6328 public:
6329   TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
6330 
6331   bool doHeapRegion(HeapRegion* r) {
6332     if (r->is_empty()) {
6333       // We ignore empty regions, we'll empty the free list afterwards
6334     } else if (r->is_young()) {
6335       // We ignore young regions, we'll empty the young list afterwards
6336     } else if (r->isHumongous()) {
6337       // We ignore humongous regions, we're not tearing down the
6338       // humongous region set
6339     } else {
6340       // The rest should be old
6341       _old_set->remove(r);
6342     }
6343     return false;
6344   }
6345 
6346   ~TearDownRegionSetsClosure() {
6347     assert(_old_set->is_empty(), "post-condition");
6348   }
6349 };
6350 
6351 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6352   assert_at_safepoint(true /* should_be_vm_thread */);
6353 
6354   if (!free_list_only) {
6355     TearDownRegionSetsClosure cl(&_old_set);
6356     heap_region_iterate(&cl);
6357 
6358     // Note that emptying the _young_list is postponed and instead done as
6359     // the first step when rebuilding the regions sets again. The reason for
6360     // this is that during a full GC string deduplication needs to know if
6361     // a collected region was young or old when the full GC was initiated.
6362   }
6363   _free_list.remove_all();
6364 }
6365 
6366 class RebuildRegionSetsClosure : public HeapRegionClosure {
6367 private:
6368   bool            _free_list_only;
6369   HeapRegionSet*   _old_set;
6370   FreeRegionList* _free_list;
6371   size_t          _total_used;
6372 
6373 public:
6374   RebuildRegionSetsClosure(bool free_list_only,
6375                            HeapRegionSet* old_set, FreeRegionList* free_list) :
6376     _free_list_only(free_list_only),
6377     _old_set(old_set), _free_list(free_list), _total_used(0) {
6378     assert(_free_list->is_empty(), "pre-condition");
6379     if (!free_list_only) {
6380       assert(_old_set->is_empty(), "pre-condition");
6381     }
6382   }
6383 
6384   bool doHeapRegion(HeapRegion* r) {
6385     if (r->continuesHumongous()) {
6386       return false;
6387     }
6388 
6389     if (r->is_empty()) {
6390       // Add free regions to the free list
6391       _free_list->add_as_tail(r);
6392     } else if (!_free_list_only) {
6393       assert(!r->is_young(), "we should not come across young regions");
6394 
6395       if (r->isHumongous()) {
6396         // We ignore humongous regions, we left the humongous set unchanged
6397       } else {
6398         // The rest should be old, add them to the old set
6399         _old_set->add(r);
6400       }
6401       _total_used += r->used();
6402     }
6403 
6404     return false;
6405   }
6406 
6407   size_t total_used() {
6408     return _total_used;
6409   }
6410 };
6411 
6412 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6413   assert_at_safepoint(true /* should_be_vm_thread */);
6414 
6415   if (!free_list_only) {
6416     _young_list->empty_list();
6417   }
6418 
6419   RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_free_list);
6420   heap_region_iterate(&cl);
6421 
6422   if (!free_list_only) {
6423     _summary_bytes_used = cl.total_used();
6424   }
6425   assert(_summary_bytes_used == recalculate_used(),
6426          err_msg("inconsistent _summary_bytes_used, "
6427                  "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6428                  _summary_bytes_used, recalculate_used()));
6429 }
6430 
6431 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6432   _refine_cte_cl->set_concurrent(concurrent);
6433 }
6434 
6435 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6436   HeapRegion* hr = heap_region_containing(p);
6437   if (hr == NULL) {
6438     return false;
6439   } else {
6440     return hr->is_in(p);
6441   }
6442 }
6443 
6444 // Methods for the mutator alloc region
6445 
6446 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6447                                                       bool force) {
6448   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6449   assert(!force || g1_policy()->can_expand_young_list(),
6450          "if force is true we should be able to expand the young list");
6451   bool young_list_full = g1_policy()->is_young_list_full();
6452   if (force || !young_list_full) {
6453     HeapRegion* new_alloc_region = new_region(word_size,
6454                                               false /* do_expand */);
6455     if (new_alloc_region != NULL) {
6456       set_region_short_lived_locked(new_alloc_region);
6457       _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6458       return new_alloc_region;
6459     }
6460   }
6461   return NULL;
6462 }
6463 
6464 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6465                                                   size_t allocated_bytes) {
6466   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6467   assert(alloc_region->is_young(), "all mutator alloc regions should be young");
6468 
6469   g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6470   _summary_bytes_used += allocated_bytes;
6471   _hr_printer.retire(alloc_region);
6472   // We update the eden sizes here, when the region is retired,
6473   // instead of when it's allocated, since this is the point that its
6474   // used space has been recored in _summary_bytes_used.
6475   g1mm()->update_eden_size();
6476 }
6477 
6478 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
6479                                                     bool force) {
6480   return _g1h->new_mutator_alloc_region(word_size, force);
6481 }
6482 
6483 void G1CollectedHeap::set_par_threads() {
6484   // Don't change the number of workers.  Use the value previously set
6485   // in the workgroup.
6486   assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise");
6487   uint n_workers = workers()->active_workers();
6488   assert(UseDynamicNumberOfGCThreads ||
6489            n_workers == workers()->total_workers(),
6490       "Otherwise should be using the total number of workers");
6491   if (n_workers == 0) {
6492     assert(false, "Should have been set in prior evacuation pause.");
6493     n_workers = ParallelGCThreads;
6494     workers()->set_active_workers(n_workers);
6495   }
6496   set_par_threads(n_workers);
6497 }
6498 
6499 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
6500                                        size_t allocated_bytes) {
6501   _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
6502 }
6503 
6504 // Methods for the GC alloc regions
6505 
6506 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6507                                                  uint count,
6508                                                  GCAllocPurpose ap) {
6509   assert(FreeList_lock->owned_by_self(), "pre-condition");
6510 
6511   if (count < g1_policy()->max_regions(ap)) {
6512     HeapRegion* new_alloc_region = new_region(word_size,
6513                                               true /* do_expand */);
6514     if (new_alloc_region != NULL) {
6515       // We really only need to do this for old regions given that we
6516       // should never scan survivors. But it doesn't hurt to do it
6517       // for survivors too.
6518       new_alloc_region->set_saved_mark();
6519       if (ap == GCAllocForSurvived) {
6520         new_alloc_region->set_survivor();
6521         _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6522       } else {
6523         _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6524       }
6525       bool during_im = g1_policy()->during_initial_mark_pause();
6526       new_alloc_region->note_start_of_copying(during_im);
6527       return new_alloc_region;
6528     } else {
6529       g1_policy()->note_alloc_region_limit_reached(ap);
6530     }
6531   }
6532   return NULL;
6533 }
6534 
6535 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6536                                              size_t allocated_bytes,
6537                                              GCAllocPurpose ap) {
6538   bool during_im = g1_policy()->during_initial_mark_pause();
6539   alloc_region->note_end_of_copying(during_im);
6540   g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6541   if (ap == GCAllocForSurvived) {
6542     young_list()->add_survivor_region(alloc_region);
6543   } else {
6544     _old_set.add(alloc_region);
6545   }
6546   _hr_printer.retire(alloc_region);
6547 }
6548 
6549 HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size,
6550                                                        bool force) {
6551   assert(!force, "not supported for GC alloc regions");
6552   return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForSurvived);
6553 }
6554 
6555 void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region,
6556                                           size_t allocated_bytes) {
6557   _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6558                                GCAllocForSurvived);
6559 }
6560 
6561 HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size,
6562                                                   bool force) {
6563   assert(!force, "not supported for GC alloc regions");
6564   return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForTenured);
6565 }
6566 
6567 void OldGCAllocRegion::retire_region(HeapRegion* alloc_region,
6568                                      size_t allocated_bytes) {
6569   _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6570                                GCAllocForTenured);
6571 }
6572 // Heap region set verification
6573 
6574 class VerifyRegionListsClosure : public HeapRegionClosure {
6575 private:
6576   HeapRegionSet*   _old_set;
6577   HeapRegionSet*   _humongous_set;
6578   FreeRegionList*  _free_list;
6579 
6580 public:
6581   HeapRegionSetCount _old_count;
6582   HeapRegionSetCount _humongous_count;
6583   HeapRegionSetCount _free_count;
6584 
6585   VerifyRegionListsClosure(HeapRegionSet* old_set,
6586                            HeapRegionSet* humongous_set,
6587                            FreeRegionList* free_list) :
6588     _old_set(old_set), _humongous_set(humongous_set), _free_list(free_list),
6589     _old_count(), _humongous_count(), _free_count(){ }
6590 
6591   bool doHeapRegion(HeapRegion* hr) {
6592     if (hr->continuesHumongous()) {
6593       return false;
6594     }
6595 
6596     if (hr->is_young()) {
6597       // TODO
6598     } else if (hr->startsHumongous()) {
6599       assert(hr->containing_set() == _humongous_set, err_msg("Heap region %u is starts humongous but not in humongous set.", hr->region_num()));
6600       _humongous_count.increment(1u, hr->capacity());
6601     } else if (hr->is_empty()) {
6602       assert(hr->containing_set() == _free_list, err_msg("Heap region %u is empty but not on the free list.", hr->region_num()));
6603       _free_count.increment(1u, hr->capacity());
6604     } else {
6605       assert(hr->containing_set() == _old_set, err_msg("Heap region %u is old but not in the old set.", hr->region_num()));
6606       _old_count.increment(1u, hr->capacity());
6607     }
6608     return false;
6609   }
6610 
6611   void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, FreeRegionList* free_list) {
6612     guarantee(old_set->length() == _old_count.length(), err_msg("Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length()));
6613     guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), err_msg("Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6614         old_set->total_capacity_bytes(), _old_count.capacity()));
6615 
6616     guarantee(humongous_set->length() == _humongous_count.length(), err_msg("Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length()));
6617     guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), err_msg("Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6618         humongous_set->total_capacity_bytes(), _humongous_count.capacity()));
6619 
6620     guarantee(free_list->length() == _free_count.length(), err_msg("Free list count mismatch. Expected %u, actual %u.", free_list->length(), _free_count.length()));
6621     guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), err_msg("Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6622         free_list->total_capacity_bytes(), _free_count.capacity()));
6623   }
6624 };
6625 
6626 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
6627                                              HeapWord* bottom) {
6628   HeapWord* end = bottom + HeapRegion::GrainWords;
6629   MemRegion mr(bottom, end);
6630   assert(_g1_reserved.contains(mr), "invariant");
6631   // This might return NULL if the allocation fails
6632   return new HeapRegion(hrs_index, _bot_shared, mr);
6633 }
6634 
6635 void G1CollectedHeap::verify_region_sets() {
6636   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6637 
6638   // First, check the explicit lists.
6639   _free_list.verify_list();
6640   {
6641     // Given that a concurrent operation might be adding regions to
6642     // the secondary free list we have to take the lock before
6643     // verifying it.
6644     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6645     _secondary_free_list.verify_list();
6646   }
6647 
6648   // If a concurrent region freeing operation is in progress it will
6649   // be difficult to correctly attributed any free regions we come
6650   // across to the correct free list given that they might belong to
6651   // one of several (free_list, secondary_free_list, any local lists,
6652   // etc.). So, if that's the case we will skip the rest of the
6653   // verification operation. Alternatively, waiting for the concurrent
6654   // operation to complete will have a non-trivial effect on the GC's
6655   // operation (no concurrent operation will last longer than the
6656   // interval between two calls to verification) and it might hide
6657   // any issues that we would like to catch during testing.
6658   if (free_regions_coming()) {
6659     return;
6660   }
6661 
6662   // Make sure we append the secondary_free_list on the free_list so
6663   // that all free regions we will come across can be safely
6664   // attributed to the free_list.
6665   append_secondary_free_list_if_not_empty_with_lock();
6666 
6667   // Finally, make sure that the region accounting in the lists is
6668   // consistent with what we see in the heap.
6669 
6670   VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_free_list);
6671   heap_region_iterate(&cl);
6672   cl.verify_counts(&_old_set, &_humongous_set, &_free_list);
6673 }
6674 
6675 // Optimized nmethod scanning
6676 
6677 class RegisterNMethodOopClosure: public OopClosure {
6678   G1CollectedHeap* _g1h;
6679   nmethod* _nm;
6680 
6681   template <class T> void do_oop_work(T* p) {
6682     T heap_oop = oopDesc::load_heap_oop(p);
6683     if (!oopDesc::is_null(heap_oop)) {
6684       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6685       HeapRegion* hr = _g1h->heap_region_containing(obj);
6686       assert(!hr->continuesHumongous(),
6687              err_msg("trying to add code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6688                      " starting at "HR_FORMAT,
6689                      _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6690 
6691       // HeapRegion::add_strong_code_root() avoids adding duplicate
6692       // entries but having duplicates is  OK since we "mark" nmethods
6693       // as visited when we scan the strong code root lists during the GC.
6694       hr->add_strong_code_root(_nm);
6695       assert(hr->rem_set()->strong_code_roots_list_contains(_nm),
6696              err_msg("failed to add code root "PTR_FORMAT" to remembered set of region "HR_FORMAT,
6697                      _nm, HR_FORMAT_PARAMS(hr)));
6698     }
6699   }
6700 
6701 public:
6702   RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6703     _g1h(g1h), _nm(nm) {}
6704 
6705   void do_oop(oop* p)       { do_oop_work(p); }
6706   void do_oop(narrowOop* p) { do_oop_work(p); }
6707 };
6708 
6709 class UnregisterNMethodOopClosure: public OopClosure {
6710   G1CollectedHeap* _g1h;
6711   nmethod* _nm;
6712 
6713   template <class T> void do_oop_work(T* p) {
6714     T heap_oop = oopDesc::load_heap_oop(p);
6715     if (!oopDesc::is_null(heap_oop)) {
6716       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6717       HeapRegion* hr = _g1h->heap_region_containing(obj);
6718       assert(!hr->continuesHumongous(),
6719              err_msg("trying to remove code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6720                      " starting at "HR_FORMAT,
6721                      _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6722 
6723       hr->remove_strong_code_root(_nm);
6724       assert(!hr->rem_set()->strong_code_roots_list_contains(_nm),
6725              err_msg("failed to remove code root "PTR_FORMAT" of region "HR_FORMAT,
6726                      _nm, HR_FORMAT_PARAMS(hr)));
6727     }
6728   }
6729 
6730 public:
6731   UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6732     _g1h(g1h), _nm(nm) {}
6733 
6734   void do_oop(oop* p)       { do_oop_work(p); }
6735   void do_oop(narrowOop* p) { do_oop_work(p); }
6736 };
6737 
6738 void G1CollectedHeap::register_nmethod(nmethod* nm) {
6739   CollectedHeap::register_nmethod(nm);
6740 
6741   guarantee(nm != NULL, "sanity");
6742   RegisterNMethodOopClosure reg_cl(this, nm);
6743   nm->oops_do(&reg_cl);
6744 }
6745 
6746 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
6747   CollectedHeap::unregister_nmethod(nm);
6748 
6749   guarantee(nm != NULL, "sanity");
6750   UnregisterNMethodOopClosure reg_cl(this, nm);
6751   nm->oops_do(&reg_cl, true);
6752 }
6753 
6754 class MigrateCodeRootsHeapRegionClosure: public HeapRegionClosure {
6755 public:
6756   bool doHeapRegion(HeapRegion *hr) {
6757     assert(!hr->isHumongous(),
6758            err_msg("humongous region "HR_FORMAT" should not have been added to collection set",
6759                    HR_FORMAT_PARAMS(hr)));
6760     hr->migrate_strong_code_roots();
6761     return false;
6762   }
6763 };
6764 
6765 void G1CollectedHeap::migrate_strong_code_roots() {
6766   MigrateCodeRootsHeapRegionClosure cl;
6767   double migrate_start = os::elapsedTime();
6768   collection_set_iterate(&cl);
6769   double migration_time_ms = (os::elapsedTime() - migrate_start) * 1000.0;
6770   g1_policy()->phase_times()->record_strong_code_root_migration_time(migration_time_ms);
6771 }
6772 
6773 void G1CollectedHeap::purge_code_root_memory() {
6774   double purge_start = os::elapsedTime();
6775   G1CodeRootSet::purge_chunks(G1CodeRootsChunkCacheKeepPercent);
6776   double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
6777   g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
6778 }
6779 
6780 // Mark all the code roots that point into regions *not* in the
6781 // collection set.
6782 //
6783 // Note we do not want to use a "marking" CodeBlobToOopClosure while
6784 // walking the the code roots lists of regions not in the collection
6785 // set. Suppose we have an nmethod (M) that points to objects in two
6786 // separate regions - one in the collection set (R1) and one not (R2).
6787 // Using a "marking" CodeBlobToOopClosure here would result in "marking"
6788 // nmethod M when walking the code roots for R1. When we come to scan
6789 // the code roots for R2, we would see that M is already marked and it
6790 // would be skipped and the objects in R2 that are referenced from M
6791 // would not be evacuated.
6792 
6793 class MarkStrongCodeRootCodeBlobClosure: public CodeBlobClosure {
6794 
6795   class MarkStrongCodeRootOopClosure: public OopClosure {
6796     ConcurrentMark* _cm;
6797     HeapRegion* _hr;
6798     uint _worker_id;
6799 
6800     template <class T> void do_oop_work(T* p) {
6801       T heap_oop = oopDesc::load_heap_oop(p);
6802       if (!oopDesc::is_null(heap_oop)) {
6803         oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6804         // Only mark objects in the region (which is assumed
6805         // to be not in the collection set).
6806         if (_hr->is_in(obj)) {
6807           _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
6808         }
6809       }
6810     }
6811 
6812   public:
6813     MarkStrongCodeRootOopClosure(ConcurrentMark* cm, HeapRegion* hr, uint worker_id) :
6814       _cm(cm), _hr(hr), _worker_id(worker_id) {
6815       assert(!_hr->in_collection_set(), "sanity");
6816     }
6817 
6818     void do_oop(narrowOop* p) { do_oop_work(p); }
6819     void do_oop(oop* p)       { do_oop_work(p); }
6820   };
6821 
6822   MarkStrongCodeRootOopClosure _oop_cl;
6823 
6824 public:
6825   MarkStrongCodeRootCodeBlobClosure(ConcurrentMark* cm, HeapRegion* hr, uint worker_id):
6826     _oop_cl(cm, hr, worker_id) {}
6827 
6828   void do_code_blob(CodeBlob* cb) {
6829     nmethod* nm = (cb == NULL) ? NULL : cb->as_nmethod_or_null();
6830     if (nm != NULL) {
6831       nm->oops_do(&_oop_cl);
6832     }
6833   }
6834 };
6835 
6836 class MarkStrongCodeRootsHRClosure: public HeapRegionClosure {
6837   G1CollectedHeap* _g1h;
6838   uint _worker_id;
6839 
6840 public:
6841   MarkStrongCodeRootsHRClosure(G1CollectedHeap* g1h, uint worker_id) :
6842     _g1h(g1h), _worker_id(worker_id) {}
6843 
6844   bool doHeapRegion(HeapRegion *hr) {
6845     HeapRegionRemSet* hrrs = hr->rem_set();
6846     if (hr->continuesHumongous()) {
6847       // Code roots should never be attached to a continuation of a humongous region
6848       assert(hrrs->strong_code_roots_list_length() == 0,
6849              err_msg("code roots should never be attached to continuations of humongous region "HR_FORMAT
6850                      " starting at "HR_FORMAT", but has "SIZE_FORMAT,
6851                      HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()),
6852                      hrrs->strong_code_roots_list_length()));
6853       return false;
6854     }
6855 
6856     if (hr->in_collection_set()) {
6857       // Don't mark code roots into regions in the collection set here.
6858       // They will be marked when we scan them.
6859       return false;
6860     }
6861 
6862     MarkStrongCodeRootCodeBlobClosure cb_cl(_g1h->concurrent_mark(), hr, _worker_id);
6863     hr->strong_code_roots_do(&cb_cl);
6864     return false;
6865   }
6866 };
6867 
6868 void G1CollectedHeap::mark_strong_code_roots(uint worker_id) {
6869   MarkStrongCodeRootsHRClosure cl(this, worker_id);
6870   if (G1CollectedHeap::use_parallel_gc_threads()) {
6871     heap_region_par_iterate_chunked(&cl,
6872                                     worker_id,
6873                                     workers()->active_workers(),
6874                                     HeapRegion::ParMarkRootClaimValue);
6875   } else {
6876     heap_region_iterate(&cl);
6877   }
6878 }
6879 
6880 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
6881   G1CollectedHeap* _g1h;
6882 
6883 public:
6884   RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
6885     _g1h(g1h) {}
6886 
6887   void do_code_blob(CodeBlob* cb) {
6888     nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
6889     if (nm == NULL) {
6890       return;
6891     }
6892 
6893     if (ScavengeRootsInCode && nm->detect_scavenge_root_oops()) {
6894       _g1h->register_nmethod(nm);
6895     }
6896   }
6897 };
6898 
6899 void G1CollectedHeap::rebuild_strong_code_roots() {
6900   RebuildStrongCodeRootClosure blob_cl(this);
6901   CodeCache::blobs_do(&blob_cl);
6902 }