1 /*
   2  * Copyright (c) 2001, 2013, 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/icBuffer.hpp"
  27 #include "gc_implementation/g1/bufferingOopClosure.hpp"
  28 #include "gc_implementation/g1/concurrentG1Refine.hpp"
  29 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
  30 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
  31 #include "gc_implementation/g1/g1AllocRegion.inline.hpp"
  32 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
  33 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
  34 #include "gc_implementation/g1/g1ErgoVerbose.hpp"
  35 #include "gc_implementation/g1/g1EvacFailure.hpp"
  36 #include "gc_implementation/g1/g1GCPhaseTimes.hpp"
  37 #include "gc_implementation/g1/g1Log.hpp"
  38 #include "gc_implementation/g1/g1MarkSweep.hpp"
  39 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
  40 #include "gc_implementation/g1/g1RemSet.inline.hpp"
  41 #include "gc_implementation/g1/g1YCTypes.hpp"
  42 #include "gc_implementation/g1/heapRegion.inline.hpp"
  43 #include "gc_implementation/g1/heapRegionRemSet.hpp"
  44 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
  45 #include "gc_implementation/g1/vm_operations_g1.hpp"
  46 #include "gc_implementation/shared/gcHeapSummary.hpp"
  47 #include "gc_implementation/shared/gcTimer.hpp"
  48 #include "gc_implementation/shared/gcTrace.hpp"
  49 #include "gc_implementation/shared/gcTraceTime.hpp"
  50 #include "gc_implementation/shared/isGCActiveMark.hpp"
  51 #include "memory/gcLocker.inline.hpp"
  52 #include "memory/genOopClosures.inline.hpp"
  53 #include "memory/generationSpec.hpp"
  54 #include "memory/referenceProcessor.hpp"
  55 #include "oops/oop.inline.hpp"
  56 #include "oops/oop.pcgc.inline.hpp"
  57 #include "runtime/vmThread.hpp"
  58 
  59 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
  60 
  61 // turn it on so that the contents of the young list (scan-only /
  62 // to-be-collected) are printed at "strategic" points before / during
  63 // / after the collection --- this is useful for debugging
  64 #define YOUNG_LIST_VERBOSE 0
  65 // CURRENT STATUS
  66 // This file is under construction.  Search for "FIXME".
  67 
  68 // INVARIANTS/NOTES
  69 //
  70 // All allocation activity covered by the G1CollectedHeap interface is
  71 // serialized by acquiring the HeapLock.  This happens in mem_allocate
  72 // and allocate_new_tlab, which are the "entry" points to the
  73 // allocation code from the rest of the JVM.  (Note that this does not
  74 // apply to TLAB allocation, which is not part of this interface: it
  75 // is done by clients of this interface.)
  76 
  77 // Notes on implementation of parallelism in different tasks.
  78 //
  79 // G1ParVerifyTask uses heap_region_par_iterate_chunked() for parallelism.
  80 // The number of GC workers is passed to heap_region_par_iterate_chunked().
  81 // It does use run_task() which sets _n_workers in the task.
  82 // G1ParTask executes g1_process_strong_roots() ->
  83 // SharedHeap::process_strong_roots() which calls eventually to
  84 // CardTableModRefBS::par_non_clean_card_iterate_work() which uses
  85 // SequentialSubTasksDone.  SharedHeap::process_strong_roots() also
  86 // directly uses SubTasksDone (_process_strong_tasks field in SharedHeap).
  87 //
  88 
  89 // Local to this file.
  90 
  91 class RefineCardTableEntryClosure: public CardTableEntryClosure {
  92   SuspendibleThreadSet* _sts;
  93   G1RemSet* _g1rs;
  94   ConcurrentG1Refine* _cg1r;
  95   bool _concurrent;
  96 public:
  97   RefineCardTableEntryClosure(SuspendibleThreadSet* sts,
  98                               G1RemSet* g1rs,
  99                               ConcurrentG1Refine* cg1r) :
 100     _sts(sts), _g1rs(g1rs), _cg1r(cg1r), _concurrent(true)
 101   {}
 102   bool do_card_ptr(jbyte* card_ptr, int worker_i) {
 103     bool oops_into_cset = _g1rs->refine_card(card_ptr, worker_i, false);
 104     // This path is executed by the concurrent refine or mutator threads,
 105     // concurrently, and so we do not care if card_ptr contains references
 106     // that point into the collection set.
 107     assert(!oops_into_cset, "should be");
 108 
 109     if (_concurrent && _sts->should_yield()) {
 110       // Caller will actually yield.
 111       return false;
 112     }
 113     // Otherwise, we finished successfully; return true.
 114     return true;
 115   }
 116   void set_concurrent(bool b) { _concurrent = b; }
 117 };
 118 
 119 
 120 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure {
 121   int _calls;
 122   G1CollectedHeap* _g1h;
 123   CardTableModRefBS* _ctbs;
 124   int _histo[256];
 125 public:
 126   ClearLoggedCardTableEntryClosure() :
 127     _calls(0)
 128   {
 129     _g1h = G1CollectedHeap::heap();
 130     _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
 131     for (int i = 0; i < 256; i++) _histo[i] = 0;
 132   }
 133   bool do_card_ptr(jbyte* card_ptr, int worker_i) {
 134     if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
 135       _calls++;
 136       unsigned char* ujb = (unsigned char*)card_ptr;
 137       int ind = (int)(*ujb);
 138       _histo[ind]++;
 139       *card_ptr = -1;
 140     }
 141     return true;
 142   }
 143   int calls() { return _calls; }
 144   void print_histo() {
 145     gclog_or_tty->print_cr("Card table value histogram:");
 146     for (int i = 0; i < 256; i++) {
 147       if (_histo[i] != 0) {
 148         gclog_or_tty->print_cr("  %d: %d", i, _histo[i]);
 149       }
 150     }
 151   }
 152 };
 153 
 154 class RedirtyLoggedCardTableEntryClosure: public CardTableEntryClosure {
 155   int _calls;
 156   G1CollectedHeap* _g1h;
 157   CardTableModRefBS* _ctbs;
 158 public:
 159   RedirtyLoggedCardTableEntryClosure() :
 160     _calls(0)
 161   {
 162     _g1h = G1CollectedHeap::heap();
 163     _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
 164   }
 165   bool do_card_ptr(jbyte* card_ptr, int worker_i) {
 166     if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
 167       _calls++;
 168       *card_ptr = 0;
 169     }
 170     return true;
 171   }
 172   int calls() { return _calls; }
 173 };
 174 
 175 class RedirtyLoggedCardTableEntryFastClosure : public CardTableEntryClosure {
 176 public:
 177   bool do_card_ptr(jbyte* card_ptr, int worker_i) {
 178     *card_ptr = CardTableModRefBS::dirty_card_val();
 179     return true;
 180   }
 181 };
 182 
 183 YoungList::YoungList(G1CollectedHeap* g1h) :
 184     _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0),
 185     _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) {
 186   guarantee(check_list_empty(false), "just making sure...");
 187 }
 188 
 189 void YoungList::push_region(HeapRegion *hr) {
 190   assert(!hr->is_young(), "should not already be young");
 191   assert(hr->get_next_young_region() == NULL, "cause it should!");
 192 
 193   hr->set_next_young_region(_head);
 194   _head = hr;
 195 
 196   _g1h->g1_policy()->set_region_eden(hr, (int) _length);
 197   ++_length;
 198 }
 199 
 200 void YoungList::add_survivor_region(HeapRegion* hr) {
 201   assert(hr->is_survivor(), "should be flagged as survivor region");
 202   assert(hr->get_next_young_region() == NULL, "cause it should!");
 203 
 204   hr->set_next_young_region(_survivor_head);
 205   if (_survivor_head == NULL) {
 206     _survivor_tail = hr;
 207   }
 208   _survivor_head = hr;
 209   ++_survivor_length;
 210 }
 211 
 212 void YoungList::empty_list(HeapRegion* list) {
 213   while (list != NULL) {
 214     HeapRegion* next = list->get_next_young_region();
 215     list->set_next_young_region(NULL);
 216     list->uninstall_surv_rate_group();
 217     list->set_not_young();
 218     list = next;
 219   }
 220 }
 221 
 222 void YoungList::empty_list() {
 223   assert(check_list_well_formed(), "young list should be well formed");
 224 
 225   empty_list(_head);
 226   _head = NULL;
 227   _length = 0;
 228 
 229   empty_list(_survivor_head);
 230   _survivor_head = NULL;
 231   _survivor_tail = NULL;
 232   _survivor_length = 0;
 233 
 234   _last_sampled_rs_lengths = 0;
 235 
 236   assert(check_list_empty(false), "just making sure...");
 237 }
 238 
 239 bool YoungList::check_list_well_formed() {
 240   bool ret = true;
 241 
 242   uint length = 0;
 243   HeapRegion* curr = _head;
 244   HeapRegion* last = NULL;
 245   while (curr != NULL) {
 246     if (!curr->is_young()) {
 247       gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
 248                              "incorrectly tagged (y: %d, surv: %d)",
 249                              curr->bottom(), curr->end(),
 250                              curr->is_young(), curr->is_survivor());
 251       ret = false;
 252     }
 253     ++length;
 254     last = curr;
 255     curr = curr->get_next_young_region();
 256   }
 257   ret = ret && (length == _length);
 258 
 259   if (!ret) {
 260     gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
 261     gclog_or_tty->print_cr("###   list has %u entries, _length is %u",
 262                            length, _length);
 263   }
 264 
 265   return ret;
 266 }
 267 
 268 bool YoungList::check_list_empty(bool check_sample) {
 269   bool ret = true;
 270 
 271   if (_length != 0) {
 272     gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u",
 273                   _length);
 274     ret = false;
 275   }
 276   if (check_sample && _last_sampled_rs_lengths != 0) {
 277     gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
 278     ret = false;
 279   }
 280   if (_head != NULL) {
 281     gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
 282     ret = false;
 283   }
 284   if (!ret) {
 285     gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
 286   }
 287 
 288   return ret;
 289 }
 290 
 291 void
 292 YoungList::rs_length_sampling_init() {
 293   _sampled_rs_lengths = 0;
 294   _curr               = _head;
 295 }
 296 
 297 bool
 298 YoungList::rs_length_sampling_more() {
 299   return _curr != NULL;
 300 }
 301 
 302 void
 303 YoungList::rs_length_sampling_next() {
 304   assert( _curr != NULL, "invariant" );
 305   size_t rs_length = _curr->rem_set()->occupied();
 306 
 307   _sampled_rs_lengths += rs_length;
 308 
 309   // The current region may not yet have been added to the
 310   // incremental collection set (it gets added when it is
 311   // retired as the current allocation region).
 312   if (_curr->in_collection_set()) {
 313     // Update the collection set policy information for this region
 314     _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
 315   }
 316 
 317   _curr = _curr->get_next_young_region();
 318   if (_curr == NULL) {
 319     _last_sampled_rs_lengths = _sampled_rs_lengths;
 320     // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
 321   }
 322 }
 323 
 324 void
 325 YoungList::reset_auxilary_lists() {
 326   guarantee( is_empty(), "young list should be empty" );
 327   assert(check_list_well_formed(), "young list should be well formed");
 328 
 329   // Add survivor regions to SurvRateGroup.
 330   _g1h->g1_policy()->note_start_adding_survivor_regions();
 331   _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
 332 
 333   int young_index_in_cset = 0;
 334   for (HeapRegion* curr = _survivor_head;
 335        curr != NULL;
 336        curr = curr->get_next_young_region()) {
 337     _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
 338 
 339     // The region is a non-empty survivor so let's add it to
 340     // the incremental collection set for the next evacuation
 341     // pause.
 342     _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
 343     young_index_in_cset += 1;
 344   }
 345   assert((uint) young_index_in_cset == _survivor_length, "post-condition");
 346   _g1h->g1_policy()->note_stop_adding_survivor_regions();
 347 
 348   _head   = _survivor_head;
 349   _length = _survivor_length;
 350   if (_survivor_head != NULL) {
 351     assert(_survivor_tail != NULL, "cause it shouldn't be");
 352     assert(_survivor_length > 0, "invariant");
 353     _survivor_tail->set_next_young_region(NULL);
 354   }
 355 
 356   // Don't clear the survivor list handles until the start of
 357   // the next evacuation pause - we need it in order to re-tag
 358   // the survivor regions from this evacuation pause as 'young'
 359   // at the start of the next.
 360 
 361   _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
 362 
 363   assert(check_list_well_formed(), "young list should be well formed");
 364 }
 365 
 366 void YoungList::print() {
 367   HeapRegion* lists[] = {_head,   _survivor_head};
 368   const char* names[] = {"YOUNG", "SURVIVOR"};
 369 
 370   for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) {
 371     gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
 372     HeapRegion *curr = lists[list];
 373     if (curr == NULL)
 374       gclog_or_tty->print_cr("  empty");
 375     while (curr != NULL) {
 376       gclog_or_tty->print_cr("  "HR_FORMAT", P: "PTR_FORMAT "N: "PTR_FORMAT", age: %4d",
 377                              HR_FORMAT_PARAMS(curr),
 378                              curr->prev_top_at_mark_start(),
 379                              curr->next_top_at_mark_start(),
 380                              curr->age_in_surv_rate_group_cond());
 381       curr = curr->get_next_young_region();
 382     }
 383   }
 384 
 385   gclog_or_tty->print_cr("");
 386 }
 387 
 388 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
 389 {
 390   // Claim the right to put the region on the dirty cards region list
 391   // by installing a self pointer.
 392   HeapRegion* next = hr->get_next_dirty_cards_region();
 393   if (next == NULL) {
 394     HeapRegion* res = (HeapRegion*)
 395       Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
 396                           NULL);
 397     if (res == NULL) {
 398       HeapRegion* head;
 399       do {
 400         // Put the region to the dirty cards region list.
 401         head = _dirty_cards_region_list;
 402         next = (HeapRegion*)
 403           Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
 404         if (next == head) {
 405           assert(hr->get_next_dirty_cards_region() == hr,
 406                  "hr->get_next_dirty_cards_region() != hr");
 407           if (next == NULL) {
 408             // The last region in the list points to itself.
 409             hr->set_next_dirty_cards_region(hr);
 410           } else {
 411             hr->set_next_dirty_cards_region(next);
 412           }
 413         }
 414       } while (next != head);
 415     }
 416   }
 417 }
 418 
 419 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
 420 {
 421   HeapRegion* head;
 422   HeapRegion* hr;
 423   do {
 424     head = _dirty_cards_region_list;
 425     if (head == NULL) {
 426       return NULL;
 427     }
 428     HeapRegion* new_head = head->get_next_dirty_cards_region();
 429     if (head == new_head) {
 430       // The last region.
 431       new_head = NULL;
 432     }
 433     hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
 434                                           head);
 435   } while (hr != head);
 436   assert(hr != NULL, "invariant");
 437   hr->set_next_dirty_cards_region(NULL);
 438   return hr;
 439 }
 440 
 441 void G1CollectedHeap::stop_conc_gc_threads() {
 442   _cg1r->stop();
 443   _cmThread->stop();
 444 }
 445 
 446 #ifdef ASSERT
 447 // A region is added to the collection set as it is retired
 448 // so an address p can point to a region which will be in the
 449 // collection set but has not yet been retired.  This method
 450 // therefore is only accurate during a GC pause after all
 451 // regions have been retired.  It is used for debugging
 452 // to check if an nmethod has references to objects that can
 453 // be move during a partial collection.  Though it can be
 454 // inaccurate, it is sufficient for G1 because the conservative
 455 // implementation of is_scavengable() for G1 will indicate that
 456 // all nmethods must be scanned during a partial collection.
 457 bool G1CollectedHeap::is_in_partial_collection(const void* p) {
 458   HeapRegion* hr = heap_region_containing(p);
 459   return hr != NULL && hr->in_collection_set();
 460 }
 461 #endif
 462 
 463 // Returns true if the reference points to an object that
 464 // can move in an incremental collection.
 465 bool G1CollectedHeap::is_scavengable(const void* p) {
 466   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 467   G1CollectorPolicy* g1p = g1h->g1_policy();
 468   HeapRegion* hr = heap_region_containing(p);
 469   if (hr == NULL) {
 470      // null
 471      assert(p == NULL, err_msg("Not NULL " PTR_FORMAT ,p));
 472      return false;
 473   } else {
 474     return !hr->isHumongous();
 475   }
 476 }
 477 
 478 void G1CollectedHeap::check_ct_logs_at_safepoint() {
 479   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
 480   CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
 481 
 482   // Count the dirty cards at the start.
 483   CountNonCleanMemRegionClosure count1(this);
 484   ct_bs->mod_card_iterate(&count1);
 485   int orig_count = count1.n();
 486 
 487   // First clear the logged cards.
 488   ClearLoggedCardTableEntryClosure clear;
 489   dcqs.set_closure(&clear);
 490   dcqs.apply_closure_to_all_completed_buffers();
 491   dcqs.iterate_closure_all_threads(false);
 492   clear.print_histo();
 493 
 494   // Now ensure that there's no dirty cards.
 495   CountNonCleanMemRegionClosure count2(this);
 496   ct_bs->mod_card_iterate(&count2);
 497   if (count2.n() != 0) {
 498     gclog_or_tty->print_cr("Card table has %d entries; %d originally",
 499                            count2.n(), orig_count);
 500   }
 501   guarantee(count2.n() == 0, "Card table should be clean.");
 502 
 503   RedirtyLoggedCardTableEntryClosure redirty;
 504   JavaThread::dirty_card_queue_set().set_closure(&redirty);
 505   dcqs.apply_closure_to_all_completed_buffers();
 506   dcqs.iterate_closure_all_threads(false);
 507   gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
 508                          clear.calls(), orig_count);
 509   guarantee(redirty.calls() == clear.calls(),
 510             "Or else mechanism is broken.");
 511 
 512   CountNonCleanMemRegionClosure count3(this);
 513   ct_bs->mod_card_iterate(&count3);
 514   if (count3.n() != orig_count) {
 515     gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
 516                            orig_count, count3.n());
 517     guarantee(count3.n() >= orig_count, "Should have restored them all.");
 518   }
 519 
 520   JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
 521 }
 522 
 523 // Private class members.
 524 
 525 G1CollectedHeap* G1CollectedHeap::_g1h;
 526 
 527 // Private methods.
 528 
 529 HeapRegion*
 530 G1CollectedHeap::new_region_try_secondary_free_list() {
 531   MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
 532   while (!_secondary_free_list.is_empty() || free_regions_coming()) {
 533     if (!_secondary_free_list.is_empty()) {
 534       if (G1ConcRegionFreeingVerbose) {
 535         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 536                                "secondary_free_list has %u entries",
 537                                _secondary_free_list.length());
 538       }
 539       // It looks as if there are free regions available on the
 540       // secondary_free_list. Let's move them to the free_list and try
 541       // again to allocate from it.
 542       append_secondary_free_list();
 543 
 544       assert(!_free_list.is_empty(), "if the secondary_free_list was not "
 545              "empty we should have moved at least one entry to the free_list");
 546       HeapRegion* res = _free_list.remove_head();
 547       if (G1ConcRegionFreeingVerbose) {
 548         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 549                                "allocated "HR_FORMAT" from secondary_free_list",
 550                                HR_FORMAT_PARAMS(res));
 551       }
 552       return res;
 553     }
 554 
 555     // Wait here until we get notified either when (a) there are no
 556     // more free regions coming or (b) some regions have been moved on
 557     // the secondary_free_list.
 558     SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
 559   }
 560 
 561   if (G1ConcRegionFreeingVerbose) {
 562     gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 563                            "could not allocate from secondary_free_list");
 564   }
 565   return NULL;
 566 }
 567 
 568 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool do_expand) {
 569   assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords,
 570          "the only time we use this to allocate a humongous region is "
 571          "when we are allocating a single humongous region");
 572 
 573   HeapRegion* res;
 574   if (G1StressConcRegionFreeing) {
 575     if (!_secondary_free_list.is_empty()) {
 576       if (G1ConcRegionFreeingVerbose) {
 577         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 578                                "forced to look at the secondary_free_list");
 579       }
 580       res = new_region_try_secondary_free_list();
 581       if (res != NULL) {
 582         return res;
 583       }
 584     }
 585   }
 586   res = _free_list.remove_head_or_null();
 587   if (res == NULL) {
 588     if (G1ConcRegionFreeingVerbose) {
 589       gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 590                              "res == NULL, trying the secondary_free_list");
 591     }
 592     res = new_region_try_secondary_free_list();
 593   }
 594   if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
 595     // Currently, only attempts to allocate GC alloc regions set
 596     // do_expand to true. So, we should only reach here during a
 597     // safepoint. If this assumption changes we might have to
 598     // reconsider the use of _expand_heap_after_alloc_failure.
 599     assert(SafepointSynchronize::is_at_safepoint(), "invariant");
 600 
 601     ergo_verbose1(ErgoHeapSizing,
 602                   "attempt heap expansion",
 603                   ergo_format_reason("region allocation request failed")
 604                   ergo_format_byte("allocation request"),
 605                   word_size * HeapWordSize);
 606     if (expand(word_size * HeapWordSize)) {
 607       // Given that expand() succeeded in expanding the heap, and we
 608       // always expand the heap by an amount aligned to the heap
 609       // region size, the free list should in theory not be empty. So
 610       // it would probably be OK to use remove_head(). But the extra
 611       // check for NULL is unlikely to be a performance issue here (we
 612       // just expanded the heap!) so let's just be conservative and
 613       // use remove_head_or_null().
 614       res = _free_list.remove_head_or_null();
 615     } else {
 616       _expand_heap_after_alloc_failure = false;
 617     }
 618   }
 619   return res;
 620 }
 621 
 622 uint G1CollectedHeap::humongous_obj_allocate_find_first(uint num_regions,
 623                                                         size_t word_size) {
 624   assert(isHumongous(word_size), "word_size should be humongous");
 625   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 626 
 627   uint first = G1_NULL_HRS_INDEX;
 628   if (num_regions == 1) {
 629     // Only one region to allocate, no need to go through the slower
 630     // path. The caller will attempt the expansion if this fails, so
 631     // let's not try to expand here too.
 632     HeapRegion* hr = new_region(word_size, false /* do_expand */);
 633     if (hr != NULL) {
 634       first = hr->hrs_index();
 635     } else {
 636       first = G1_NULL_HRS_INDEX;
 637     }
 638   } else {
 639     // We can't allocate humongous regions while cleanupComplete() is
 640     // running, since some of the regions we find to be empty might not
 641     // yet be added to the free list and it is not straightforward to
 642     // know which list they are on so that we can remove them. Note
 643     // that we only need to do this if we need to allocate more than
 644     // one region to satisfy the current humongous allocation
 645     // request. If we are only allocating one region we use the common
 646     // region allocation code (see above).
 647     wait_while_free_regions_coming();
 648     append_secondary_free_list_if_not_empty_with_lock();
 649 
 650     if (free_regions() >= num_regions) {
 651       first = _hrs.find_contiguous(num_regions);
 652       if (first != G1_NULL_HRS_INDEX) {
 653         for (uint i = first; i < first + num_regions; ++i) {
 654           HeapRegion* hr = region_at(i);
 655           assert(hr->is_empty(), "sanity");
 656           assert(is_on_master_free_list(hr), "sanity");
 657           hr->set_pending_removal(true);
 658         }
 659         _free_list.remove_all_pending(num_regions);
 660       }
 661     }
 662   }
 663   return first;
 664 }
 665 
 666 HeapWord*
 667 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
 668                                                            uint num_regions,
 669                                                            size_t word_size) {
 670   assert(first != G1_NULL_HRS_INDEX, "pre-condition");
 671   assert(isHumongous(word_size), "word_size should be humongous");
 672   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 673 
 674   // Index of last region in the series + 1.
 675   uint last = first + num_regions;
 676 
 677   // We need to initialize the region(s) we just discovered. This is
 678   // a bit tricky given that it can happen concurrently with
 679   // refinement threads refining cards on these regions and
 680   // potentially wanting to refine the BOT as they are scanning
 681   // those cards (this can happen shortly after a cleanup; see CR
 682   // 6991377). So we have to set up the region(s) carefully and in
 683   // a specific order.
 684 
 685   // The word size sum of all the regions we will allocate.
 686   size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
 687   assert(word_size <= word_size_sum, "sanity");
 688 
 689   // This will be the "starts humongous" region.
 690   HeapRegion* first_hr = region_at(first);
 691   // The header of the new object will be placed at the bottom of
 692   // the first region.
 693   HeapWord* new_obj = first_hr->bottom();
 694   // This will be the new end of the first region in the series that
 695   // should also match the end of the last region in the series.
 696   HeapWord* new_end = new_obj + word_size_sum;
 697   // This will be the new top of the first region that will reflect
 698   // this allocation.
 699   HeapWord* new_top = new_obj + word_size;
 700 
 701   // First, we need to zero the header of the space that we will be
 702   // allocating. When we update top further down, some refinement
 703   // threads might try to scan the region. By zeroing the header we
 704   // ensure that any thread that will try to scan the region will
 705   // come across the zero klass word and bail out.
 706   //
 707   // NOTE: It would not have been correct to have used
 708   // CollectedHeap::fill_with_object() and make the space look like
 709   // an int array. The thread that is doing the allocation will
 710   // later update the object header to a potentially different array
 711   // type and, for a very short period of time, the klass and length
 712   // fields will be inconsistent. This could cause a refinement
 713   // thread to calculate the object size incorrectly.
 714   Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
 715 
 716   // We will set up the first region as "starts humongous". This
 717   // will also update the BOT covering all the regions to reflect
 718   // that there is a single object that starts at the bottom of the
 719   // first region.
 720   first_hr->set_startsHumongous(new_top, new_end);
 721 
 722   // Then, if there are any, we will set up the "continues
 723   // humongous" regions.
 724   HeapRegion* hr = NULL;
 725   for (uint i = first + 1; i < last; ++i) {
 726     hr = region_at(i);
 727     hr->set_continuesHumongous(first_hr);
 728   }
 729   // If we have "continues humongous" regions (hr != NULL), then the
 730   // end of the last one should match new_end.
 731   assert(hr == NULL || hr->end() == new_end, "sanity");
 732 
 733   // Up to this point no concurrent thread would have been able to
 734   // do any scanning on any region in this series. All the top
 735   // fields still point to bottom, so the intersection between
 736   // [bottom,top] and [card_start,card_end] will be empty. Before we
 737   // update the top fields, we'll do a storestore to make sure that
 738   // no thread sees the update to top before the zeroing of the
 739   // object header and the BOT initialization.
 740   OrderAccess::storestore();
 741 
 742   // Now that the BOT and the object header have been initialized,
 743   // we can update top of the "starts humongous" region.
 744   assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
 745          "new_top should be in this region");
 746   first_hr->set_top(new_top);
 747   if (_hr_printer.is_active()) {
 748     HeapWord* bottom = first_hr->bottom();
 749     HeapWord* end = first_hr->orig_end();
 750     if ((first + 1) == last) {
 751       // the series has a single humongous region
 752       _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
 753     } else {
 754       // the series has more than one humongous regions
 755       _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
 756     }
 757   }
 758 
 759   // Now, we will update the top fields of the "continues humongous"
 760   // regions. The reason we need to do this is that, otherwise,
 761   // these regions would look empty and this will confuse parts of
 762   // G1. For example, the code that looks for a consecutive number
 763   // of empty regions will consider them empty and try to
 764   // re-allocate them. We can extend is_empty() to also include
 765   // !continuesHumongous(), but it is easier to just update the top
 766   // fields here. The way we set top for all regions (i.e., top ==
 767   // end for all regions but the last one, top == new_top for the
 768   // last one) is actually used when we will free up the humongous
 769   // region in free_humongous_region().
 770   hr = NULL;
 771   for (uint i = first + 1; i < last; ++i) {
 772     hr = region_at(i);
 773     if ((i + 1) == last) {
 774       // last continues humongous region
 775       assert(hr->bottom() < new_top && new_top <= hr->end(),
 776              "new_top should fall on this region");
 777       hr->set_top(new_top);
 778       _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
 779     } else {
 780       // not last one
 781       assert(new_top > hr->end(), "new_top should be above this region");
 782       hr->set_top(hr->end());
 783       _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
 784     }
 785   }
 786   // If we have continues humongous regions (hr != NULL), then the
 787   // end of the last one should match new_end and its top should
 788   // match new_top.
 789   assert(hr == NULL ||
 790          (hr->end() == new_end && hr->top() == new_top), "sanity");
 791 
 792   assert(first_hr->used() == word_size * HeapWordSize, "invariant");
 793   _summary_bytes_used += first_hr->used();
 794   _humongous_set.add(first_hr);
 795 
 796   return new_obj;
 797 }
 798 
 799 // If could fit into free regions w/o expansion, try.
 800 // Otherwise, if can expand, do so.
 801 // Otherwise, if using ex regions might help, try with ex given back.
 802 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
 803   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 804 
 805   verify_region_sets_optional();
 806 
 807   size_t word_size_rounded = round_to(word_size, HeapRegion::GrainWords);
 808   uint num_regions = (uint) (word_size_rounded / HeapRegion::GrainWords);
 809   uint x_num = expansion_regions();
 810   uint fs = _hrs.free_suffix();
 811   uint first = humongous_obj_allocate_find_first(num_regions, word_size);
 812   if (first == G1_NULL_HRS_INDEX) {
 813     // The only thing we can do now is attempt expansion.
 814     if (fs + x_num >= num_regions) {
 815       // If the number of regions we're trying to allocate for this
 816       // object is at most the number of regions in the free suffix,
 817       // then the call to humongous_obj_allocate_find_first() above
 818       // should have succeeded and we wouldn't be here.
 819       //
 820       // We should only be trying to expand when the free suffix is
 821       // not sufficient for the object _and_ we have some expansion
 822       // room available.
 823       assert(num_regions > fs, "earlier allocation should have succeeded");
 824 
 825       ergo_verbose1(ErgoHeapSizing,
 826                     "attempt heap expansion",
 827                     ergo_format_reason("humongous allocation request failed")
 828                     ergo_format_byte("allocation request"),
 829                     word_size * HeapWordSize);
 830       if (expand((num_regions - fs) * HeapRegion::GrainBytes)) {
 831         // Even though the heap was expanded, it might not have
 832         // reached the desired size. So, we cannot assume that the
 833         // allocation will succeed.
 834         first = humongous_obj_allocate_find_first(num_regions, word_size);
 835       }
 836     }
 837   }
 838 
 839   HeapWord* result = NULL;
 840   if (first != G1_NULL_HRS_INDEX) {
 841     result =
 842       humongous_obj_allocate_initialize_regions(first, num_regions, word_size);
 843     assert(result != NULL, "it should always return a valid result");
 844 
 845     // A successful humongous object allocation changes the used space
 846     // information of the old generation so we need to recalculate the
 847     // sizes and update the jstat counters here.
 848     g1mm()->update_sizes();
 849   }
 850 
 851   verify_region_sets_optional();
 852 
 853   return result;
 854 }
 855 
 856 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
 857   assert_heap_not_locked_and_not_at_safepoint();
 858   assert(!isHumongous(word_size), "we do not allow humongous TLABs");
 859 
 860   unsigned int dummy_gc_count_before;
 861   int dummy_gclocker_retry_count = 0;
 862   return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
 863 }
 864 
 865 HeapWord*
 866 G1CollectedHeap::mem_allocate(size_t word_size,
 867                               bool*  gc_overhead_limit_was_exceeded) {
 868   assert_heap_not_locked_and_not_at_safepoint();
 869 
 870   // Loop until the allocation is satisfied, or unsatisfied after GC.
 871   for (int try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 872     unsigned int gc_count_before;
 873 
 874     HeapWord* result = NULL;
 875     if (!isHumongous(word_size)) {
 876       result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
 877     } else {
 878       result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
 879     }
 880     if (result != NULL) {
 881       return result;
 882     }
 883 
 884     // Create the garbage collection operation...
 885     VM_G1CollectForAllocation op(gc_count_before, word_size);
 886     // ...and get the VM thread to execute it.
 887     VMThread::execute(&op);
 888 
 889     if (op.prologue_succeeded() && op.pause_succeeded()) {
 890       // If the operation was successful we'll return the result even
 891       // if it is NULL. If the allocation attempt failed immediately
 892       // after a Full GC, it's unlikely we'll be able to allocate now.
 893       HeapWord* result = op.result();
 894       if (result != NULL && !isHumongous(word_size)) {
 895         // Allocations that take place on VM operations do not do any
 896         // card dirtying and we have to do it here. We only have to do
 897         // this for non-humongous allocations, though.
 898         dirty_young_block(result, word_size);
 899       }
 900       return result;
 901     } else {
 902       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 903         return NULL;
 904       }
 905       assert(op.result() == NULL,
 906              "the result should be NULL if the VM op did not succeed");
 907     }
 908 
 909     // Give a warning if we seem to be looping forever.
 910     if ((QueuedAllocationWarningCount > 0) &&
 911         (try_count % QueuedAllocationWarningCount == 0)) {
 912       warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
 913     }
 914   }
 915 
 916   ShouldNotReachHere();
 917   return NULL;
 918 }
 919 
 920 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
 921                                            unsigned int *gc_count_before_ret,
 922                                            int* gclocker_retry_count_ret) {
 923   // Make sure you read the note in attempt_allocation_humongous().
 924 
 925   assert_heap_not_locked_and_not_at_safepoint();
 926   assert(!isHumongous(word_size), "attempt_allocation_slow() should not "
 927          "be called for humongous allocation requests");
 928 
 929   // We should only get here after the first-level allocation attempt
 930   // (attempt_allocation()) failed to allocate.
 931 
 932   // We will loop until a) we manage to successfully perform the
 933   // allocation or b) we successfully schedule a collection which
 934   // fails to perform the allocation. b) is the only case when we'll
 935   // return NULL.
 936   HeapWord* result = NULL;
 937   for (int try_count = 1; /* we'll return */; try_count += 1) {
 938     bool should_try_gc;
 939     unsigned int gc_count_before;
 940 
 941     {
 942       MutexLockerEx x(Heap_lock);
 943 
 944       result = _mutator_alloc_region.attempt_allocation_locked(word_size,
 945                                                       false /* bot_updates */);
 946       if (result != NULL) {
 947         return result;
 948       }
 949 
 950       // If we reach here, attempt_allocation_locked() above failed to
 951       // allocate a new region. So the mutator alloc region should be NULL.
 952       assert(_mutator_alloc_region.get() == NULL, "only way to get here");
 953 
 954       if (GC_locker::is_active_and_needs_gc()) {
 955         if (g1_policy()->can_expand_young_list()) {
 956           // No need for an ergo verbose message here,
 957           // can_expand_young_list() does this when it returns true.
 958           result = _mutator_alloc_region.attempt_allocation_force(word_size,
 959                                                       false /* bot_updates */);
 960           if (result != NULL) {
 961             return result;
 962           }
 963         }
 964         should_try_gc = false;
 965       } else {
 966         // The GCLocker may not be active but the GCLocker initiated
 967         // GC may not yet have been performed (GCLocker::needs_gc()
 968         // returns true). In this case we do not try this GC and
 969         // wait until the GCLocker initiated GC is performed, and
 970         // then retry the allocation.
 971         if (GC_locker::needs_gc()) {
 972           should_try_gc = false;
 973         } else {
 974           // Read the GC count while still holding the Heap_lock.
 975           gc_count_before = total_collections();
 976           should_try_gc = true;
 977         }
 978       }
 979     }
 980 
 981     if (should_try_gc) {
 982       bool succeeded;
 983       result = do_collection_pause(word_size, gc_count_before, &succeeded);
 984       if (result != NULL) {
 985         assert(succeeded, "only way to get back a non-NULL result");
 986         return result;
 987       }
 988 
 989       if (succeeded) {
 990         // If we get here we successfully scheduled a collection which
 991         // failed to allocate. No point in trying to allocate
 992         // further. We'll just return NULL.
 993         MutexLockerEx x(Heap_lock);
 994         *gc_count_before_ret = total_collections();
 995         return NULL;
 996       }
 997     } else {
 998       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
 999         MutexLockerEx x(Heap_lock);
1000         *gc_count_before_ret = total_collections();
1001         return NULL;
1002       }
1003       // The GCLocker is either active or the GCLocker initiated
1004       // GC has not yet been performed. Stall until it is and
1005       // then retry the allocation.
1006       GC_locker::stall_until_clear();
1007       (*gclocker_retry_count_ret) += 1;
1008     }
1009 
1010     // We can reach here if we were unsuccessful in scheduling a
1011     // collection (because another thread beat us to it) or if we were
1012     // stalled due to the GC locker. In either can we should retry the
1013     // allocation attempt in case another thread successfully
1014     // performed a collection and reclaimed enough space. We do the
1015     // first attempt (without holding the Heap_lock) here and the
1016     // follow-on attempt will be at the start of the next loop
1017     // iteration (after taking the Heap_lock).
1018     result = _mutator_alloc_region.attempt_allocation(word_size,
1019                                                       false /* bot_updates */);
1020     if (result != NULL) {
1021       return result;
1022     }
1023 
1024     // Give a warning if we seem to be looping forever.
1025     if ((QueuedAllocationWarningCount > 0) &&
1026         (try_count % QueuedAllocationWarningCount == 0)) {
1027       warning("G1CollectedHeap::attempt_allocation_slow() "
1028               "retries %d times", try_count);
1029     }
1030   }
1031 
1032   ShouldNotReachHere();
1033   return NULL;
1034 }
1035 
1036 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
1037                                           unsigned int * gc_count_before_ret,
1038                                           int* gclocker_retry_count_ret) {
1039   // The structure of this method has a lot of similarities to
1040   // attempt_allocation_slow(). The reason these two were not merged
1041   // into a single one is that such a method would require several "if
1042   // allocation is not humongous do this, otherwise do that"
1043   // conditional paths which would obscure its flow. In fact, an early
1044   // version of this code did use a unified method which was harder to
1045   // follow and, as a result, it had subtle bugs that were hard to
1046   // track down. So keeping these two methods separate allows each to
1047   // be more readable. It will be good to keep these two in sync as
1048   // much as possible.
1049 
1050   assert_heap_not_locked_and_not_at_safepoint();
1051   assert(isHumongous(word_size), "attempt_allocation_humongous() "
1052          "should only be called for humongous allocations");
1053 
1054   // Humongous objects can exhaust the heap quickly, so we should check if we
1055   // need to start a marking cycle at each humongous object allocation. We do
1056   // the check before we do the actual allocation. The reason for doing it
1057   // before the allocation is that we avoid having to keep track of the newly
1058   // allocated memory while we do a GC.
1059   if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
1060                                            word_size)) {
1061     collect(GCCause::_g1_humongous_allocation);
1062   }
1063 
1064   // We will loop until a) we manage to successfully perform the
1065   // allocation or b) we successfully schedule a collection which
1066   // fails to perform the allocation. b) is the only case when we'll
1067   // return NULL.
1068   HeapWord* result = NULL;
1069   for (int try_count = 1; /* we'll return */; try_count += 1) {
1070     bool should_try_gc;
1071     unsigned int gc_count_before;
1072 
1073     {
1074       MutexLockerEx x(Heap_lock);
1075 
1076       // Given that humongous objects are not allocated in young
1077       // regions, we'll first try to do the allocation without doing a
1078       // collection hoping that there's enough space in the heap.
1079       result = humongous_obj_allocate(word_size);
1080       if (result != NULL) {
1081         return result;
1082       }
1083 
1084       if (GC_locker::is_active_and_needs_gc()) {
1085         should_try_gc = false;
1086       } else {
1087          // The GCLocker may not be active but the GCLocker initiated
1088         // GC may not yet have been performed (GCLocker::needs_gc()
1089         // returns true). In this case we do not try this GC and
1090         // wait until the GCLocker initiated GC is performed, and
1091         // then retry the allocation.
1092         if (GC_locker::needs_gc()) {
1093           should_try_gc = false;
1094         } else {
1095           // Read the GC count while still holding the Heap_lock.
1096           gc_count_before = total_collections();
1097           should_try_gc = true;
1098         }
1099       }
1100     }
1101 
1102     if (should_try_gc) {
1103       // If we failed to allocate the humongous object, we should try to
1104       // do a collection pause (if we're allowed) in case it reclaims
1105       // enough space for the allocation to succeed after the pause.
1106 
1107       bool succeeded;
1108       result = do_collection_pause(word_size, gc_count_before, &succeeded);
1109       if (result != NULL) {
1110         assert(succeeded, "only way to get back a non-NULL result");
1111         return result;
1112       }
1113 
1114       if (succeeded) {
1115         // If we get here we successfully scheduled a collection which
1116         // failed to allocate. No point in trying to allocate
1117         // further. We'll just return NULL.
1118         MutexLockerEx x(Heap_lock);
1119         *gc_count_before_ret = total_collections();
1120         return NULL;
1121       }
1122     } else {
1123       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1124         MutexLockerEx x(Heap_lock);
1125         *gc_count_before_ret = total_collections();
1126         return NULL;
1127       }
1128       // The GCLocker is either active or the GCLocker initiated
1129       // GC has not yet been performed. Stall until it is and
1130       // then retry the allocation.
1131       GC_locker::stall_until_clear();
1132       (*gclocker_retry_count_ret) += 1;
1133     }
1134 
1135     // We can reach here if we were unsuccessful in scheduling a
1136     // collection (because another thread beat us to it) or if we were
1137     // stalled due to the GC locker. In either can we should retry the
1138     // allocation attempt in case another thread successfully
1139     // performed a collection and reclaimed enough space.  Give a
1140     // warning if we seem to be looping forever.
1141 
1142     if ((QueuedAllocationWarningCount > 0) &&
1143         (try_count % QueuedAllocationWarningCount == 0)) {
1144       warning("G1CollectedHeap::attempt_allocation_humongous() "
1145               "retries %d times", try_count);
1146     }
1147   }
1148 
1149   ShouldNotReachHere();
1150   return NULL;
1151 }
1152 
1153 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1154                                        bool expect_null_mutator_alloc_region) {
1155   assert_at_safepoint(true /* should_be_vm_thread */);
1156   assert(_mutator_alloc_region.get() == NULL ||
1157                                              !expect_null_mutator_alloc_region,
1158          "the current alloc region was unexpectedly found to be non-NULL");
1159 
1160   if (!isHumongous(word_size)) {
1161     return _mutator_alloc_region.attempt_allocation_locked(word_size,
1162                                                       false /* bot_updates */);
1163   } else {
1164     HeapWord* result = humongous_obj_allocate(word_size);
1165     if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1166       g1_policy()->set_initiate_conc_mark_if_possible();
1167     }
1168     return result;
1169   }
1170 
1171   ShouldNotReachHere();
1172 }
1173 
1174 class PostMCRemSetClearClosure: public HeapRegionClosure {
1175   G1CollectedHeap* _g1h;
1176   ModRefBarrierSet* _mr_bs;
1177 public:
1178   PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1179     _g1h(g1h), _mr_bs(mr_bs) { }
1180   bool doHeapRegion(HeapRegion* r) {
1181     if (r->continuesHumongous()) {
1182       return false;
1183     }
1184     _g1h->reset_gc_time_stamps(r);
1185     HeapRegionRemSet* hrrs = r->rem_set();
1186     if (hrrs != NULL) hrrs->clear();
1187     // You might think here that we could clear just the cards
1188     // corresponding to the used region.  But no: if we leave a dirty card
1189     // in a region we might allocate into, then it would prevent that card
1190     // from being enqueued, and cause it to be missed.
1191     // Re: the performance cost: we shouldn't be doing full GC anyway!
1192     _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1193     return false;
1194   }
1195 };
1196 
1197 void G1CollectedHeap::clear_rsets_post_compaction() {
1198   PostMCRemSetClearClosure rs_clear(this, mr_bs());
1199   heap_region_iterate(&rs_clear);
1200 }
1201 
1202 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1203   G1CollectedHeap*   _g1h;
1204   UpdateRSOopClosure _cl;
1205   int                _worker_i;
1206 public:
1207   RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1208     _cl(g1->g1_rem_set(), worker_i),
1209     _worker_i(worker_i),
1210     _g1h(g1)
1211   { }
1212 
1213   bool doHeapRegion(HeapRegion* r) {
1214     if (!r->continuesHumongous()) {
1215       _cl.set_from(r);
1216       r->oop_iterate(&_cl);
1217     }
1218     return false;
1219   }
1220 };
1221 
1222 class ParRebuildRSTask: public AbstractGangTask {
1223   G1CollectedHeap* _g1;
1224 public:
1225   ParRebuildRSTask(G1CollectedHeap* g1)
1226     : AbstractGangTask("ParRebuildRSTask"),
1227       _g1(g1)
1228   { }
1229 
1230   void work(uint worker_id) {
1231     RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1232     _g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id,
1233                                           _g1->workers()->active_workers(),
1234                                          HeapRegion::RebuildRSClaimValue);
1235   }
1236 };
1237 
1238 class PostCompactionPrinterClosure: public HeapRegionClosure {
1239 private:
1240   G1HRPrinter* _hr_printer;
1241 public:
1242   bool doHeapRegion(HeapRegion* hr) {
1243     assert(!hr->is_young(), "not expecting to find young regions");
1244     // We only generate output for non-empty regions.
1245     if (!hr->is_empty()) {
1246       if (!hr->isHumongous()) {
1247         _hr_printer->post_compaction(hr, G1HRPrinter::Old);
1248       } else if (hr->startsHumongous()) {
1249         if (hr->region_num() == 1) {
1250           // single humongous region
1251           _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
1252         } else {
1253           _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
1254         }
1255       } else {
1256         assert(hr->continuesHumongous(), "only way to get here");
1257         _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1258       }
1259     }
1260     return false;
1261   }
1262 
1263   PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1264     : _hr_printer(hr_printer) { }
1265 };
1266 
1267 void G1CollectedHeap::print_hrs_post_compaction() {
1268   PostCompactionPrinterClosure cl(hr_printer());
1269   heap_region_iterate(&cl);
1270 }
1271 
1272 double G1CollectedHeap::verify(bool guard, const char* msg) {
1273   double verify_time_ms = 0.0;
1274 
1275   if (guard && total_collections() >= VerifyGCStartAt) {
1276     double verify_start = os::elapsedTime();
1277     HandleMark hm;  // Discard invalid handles created during verification
1278     prepare_for_verify();
1279     Universe::verify(VerifyOption_G1UsePrevMarking, msg);
1280     verify_time_ms = (os::elapsedTime() - verify_start) * 1000;
1281   }
1282 
1283   return verify_time_ms;
1284 }
1285 
1286 void G1CollectedHeap::verify_before_gc() {
1287   double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:");
1288   g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms);
1289 }
1290 
1291 void G1CollectedHeap::verify_after_gc() {
1292   double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:");
1293   g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms);
1294 }
1295 
1296 bool G1CollectedHeap::do_collection(bool explicit_gc,
1297                                     bool clear_all_soft_refs,
1298                                     size_t word_size) {
1299   assert_at_safepoint(true /* should_be_vm_thread */);
1300 
1301   if (GC_locker::check_active_before_gc()) {
1302     return false;
1303   }
1304 
1305   STWGCTimer* gc_timer = G1MarkSweep::gc_timer();
1306   gc_timer->register_gc_start(os::elapsed_counter());
1307 
1308   SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer();
1309   gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start());
1310 
1311   SvcGCMarker sgcm(SvcGCMarker::FULL);
1312   ResourceMark rm;
1313 
1314   print_heap_before_gc();
1315   trace_heap_before_gc(gc_tracer);
1316 
1317   size_t metadata_prev_used = MetaspaceAux::allocated_used_bytes();
1318 
1319   HRSPhaseSetter x(HRSPhaseFullGC);
1320   verify_region_sets_optional();
1321 
1322   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1323                            collector_policy()->should_clear_all_soft_refs();
1324 
1325   ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1326 
1327   {
1328     IsGCActiveMark x;
1329 
1330     // Timing
1331     assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant");
1332     gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps);
1333     TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
1334 
1335     {
1336       GCTraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, NULL);
1337       TraceCollectorStats tcs(g1mm()->full_collection_counters());
1338       TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1339 
1340       double start = os::elapsedTime();
1341       g1_policy()->record_full_collection_start();
1342 
1343       // Note: When we have a more flexible GC logging framework that
1344       // allows us to add optional attributes to a GC log record we
1345       // could consider timing and reporting how long we wait in the
1346       // following two methods.
1347       wait_while_free_regions_coming();
1348       // If we start the compaction before the CM threads finish
1349       // scanning the root regions we might trip them over as we'll
1350       // be moving objects / updating references. So let's wait until
1351       // they are done. By telling them to abort, they should complete
1352       // early.
1353       _cm->root_regions()->abort();
1354       _cm->root_regions()->wait_until_scan_finished();
1355       append_secondary_free_list_if_not_empty_with_lock();
1356 
1357       gc_prologue(true);
1358       increment_total_collections(true /* full gc */);
1359       increment_old_marking_cycles_started();
1360 
1361       assert(used() == recalculate_used(), "Should be equal");
1362 
1363       verify_before_gc();
1364 
1365       pre_full_gc_dump(gc_timer);
1366 
1367       COMPILER2_PRESENT(DerivedPointerTable::clear());
1368 
1369       // Disable discovery and empty the discovered lists
1370       // for the CM ref processor.
1371       ref_processor_cm()->disable_discovery();
1372       ref_processor_cm()->abandon_partial_discovery();
1373       ref_processor_cm()->verify_no_references_recorded();
1374 
1375       // Abandon current iterations of concurrent marking and concurrent
1376       // refinement, if any are in progress. We have to do this before
1377       // wait_until_scan_finished() below.
1378       concurrent_mark()->abort();
1379 
1380       // Make sure we'll choose a new allocation region afterwards.
1381       release_mutator_alloc_region();
1382       abandon_gc_alloc_regions();
1383       g1_rem_set()->cleanupHRRS();
1384 
1385       // We should call this after we retire any currently active alloc
1386       // regions so that all the ALLOC / RETIRE events are generated
1387       // before the start GC event.
1388       _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1389 
1390       // We may have added regions to the current incremental collection
1391       // set between the last GC or pause and now. We need to clear the
1392       // incremental collection set and then start rebuilding it afresh
1393       // after this full GC.
1394       abandon_collection_set(g1_policy()->inc_cset_head());
1395       g1_policy()->clear_incremental_cset();
1396       g1_policy()->stop_incremental_cset_building();
1397 
1398       tear_down_region_sets(false /* free_list_only */);
1399       g1_policy()->set_gcs_are_young(true);
1400 
1401       // See the comments in g1CollectedHeap.hpp and
1402       // G1CollectedHeap::ref_processing_init() about
1403       // how reference processing currently works in G1.
1404 
1405       // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1406       ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1407 
1408       // Temporarily clear the STW ref processor's _is_alive_non_header field.
1409       ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1410 
1411       ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
1412       ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1413 
1414       // Do collection work
1415       {
1416         HandleMark hm;  // Discard invalid handles created during gc
1417         G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1418       }
1419 
1420       assert(free_regions() == 0, "we should not have added any free regions");
1421       rebuild_region_sets(false /* free_list_only */);
1422 
1423       // Enqueue any discovered reference objects that have
1424       // not been removed from the discovered lists.
1425       ref_processor_stw()->enqueue_discovered_references();
1426 
1427       COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1428 
1429       MemoryService::track_memory_usage();
1430 
1431       assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1432       ref_processor_stw()->verify_no_references_recorded();
1433 
1434       // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1435       ClassLoaderDataGraph::purge();
1436     MetaspaceAux::verify_metrics();
1437 
1438       // Note: since we've just done a full GC, concurrent
1439       // marking is no longer active. Therefore we need not
1440       // re-enable reference discovery for the CM ref processor.
1441       // That will be done at the start of the next marking cycle.
1442       assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1443       ref_processor_cm()->verify_no_references_recorded();
1444 
1445       reset_gc_time_stamp();
1446       // Since everything potentially moved, we will clear all remembered
1447       // sets, and clear all cards.  Later we will rebuild remembered
1448       // sets. We will also reset the GC time stamps of the regions.
1449       clear_rsets_post_compaction();
1450       check_gc_time_stamps();
1451 
1452       // Resize the heap if necessary.
1453       resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1454 
1455       if (_hr_printer.is_active()) {
1456         // We should do this after we potentially resize the heap so
1457         // that all the COMMIT / UNCOMMIT events are generated before
1458         // the end GC event.
1459 
1460         print_hrs_post_compaction();
1461         _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1462       }
1463 
1464       G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
1465       if (hot_card_cache->use_cache()) {
1466         hot_card_cache->reset_card_counts();
1467         hot_card_cache->reset_hot_cache();
1468       }
1469 
1470       // Rebuild remembered sets of all regions.
1471       if (G1CollectedHeap::use_parallel_gc_threads()) {
1472         uint n_workers =
1473           AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1474                                                   workers()->active_workers(),
1475                                                   Threads::number_of_non_daemon_threads());
1476         assert(UseDynamicNumberOfGCThreads ||
1477                n_workers == workers()->total_workers(),
1478                "If not dynamic should be using all the  workers");
1479         workers()->set_active_workers(n_workers);
1480         // Set parallel threads in the heap (_n_par_threads) only
1481         // before a parallel phase and always reset it to 0 after
1482         // the phase so that the number of parallel threads does
1483         // no get carried forward to a serial phase where there
1484         // may be code that is "possibly_parallel".
1485         set_par_threads(n_workers);
1486 
1487         ParRebuildRSTask rebuild_rs_task(this);
1488         assert(check_heap_region_claim_values(
1489                HeapRegion::InitialClaimValue), "sanity check");
1490         assert(UseDynamicNumberOfGCThreads ||
1491                workers()->active_workers() == workers()->total_workers(),
1492                "Unless dynamic should use total workers");
1493         // Use the most recent number of  active workers
1494         assert(workers()->active_workers() > 0,
1495                "Active workers not properly set");
1496         set_par_threads(workers()->active_workers());
1497         workers()->run_task(&rebuild_rs_task);
1498         set_par_threads(0);
1499         assert(check_heap_region_claim_values(
1500                HeapRegion::RebuildRSClaimValue), "sanity check");
1501         reset_heap_region_claim_values();
1502       } else {
1503         RebuildRSOutOfRegionClosure rebuild_rs(this);
1504         heap_region_iterate(&rebuild_rs);
1505       }
1506 
1507       if (true) { // FIXME
1508         MetaspaceGC::compute_new_size();
1509       }
1510 
1511 #ifdef TRACESPINNING
1512       ParallelTaskTerminator::print_termination_counts();
1513 #endif
1514 
1515       // Discard all rset updates
1516       JavaThread::dirty_card_queue_set().abandon_logs();
1517       assert(!G1DeferredRSUpdate
1518              || (G1DeferredRSUpdate &&
1519                 (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any");
1520 
1521       _young_list->reset_sampled_info();
1522       // At this point there should be no regions in the
1523       // entire heap tagged as young.
1524       assert(check_young_list_empty(true /* check_heap */),
1525              "young list should be empty at this point");
1526 
1527       // Update the number of full collections that have been completed.
1528       increment_old_marking_cycles_completed(false /* concurrent */);
1529 
1530       _hrs.verify_optional();
1531       verify_region_sets_optional();
1532 
1533       verify_after_gc();
1534 
1535       // Start a new incremental collection set for the next pause
1536       assert(g1_policy()->collection_set() == NULL, "must be");
1537       g1_policy()->start_incremental_cset_building();
1538 
1539       // Clear the _cset_fast_test bitmap in anticipation of adding
1540       // regions to the incremental collection set for the next
1541       // evacuation pause.
1542       clear_cset_fast_test();
1543 
1544       init_mutator_alloc_region();
1545 
1546       double end = os::elapsedTime();
1547       g1_policy()->record_full_collection_end();
1548 
1549       if (G1Log::fine()) {
1550         g1_policy()->print_heap_transition();
1551       }
1552 
1553       // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1554       // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1555       // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1556       // before any GC notifications are raised.
1557       g1mm()->update_sizes();
1558 
1559       gc_epilogue(true);
1560     }
1561 
1562     if (G1Log::finer()) {
1563       g1_policy()->print_detailed_heap_transition(true /* full */);
1564     }
1565 
1566     print_heap_after_gc();
1567     trace_heap_after_gc(gc_tracer);
1568 
1569     post_full_gc_dump(gc_timer);
1570 
1571     gc_timer->register_gc_end(os::elapsed_counter());
1572     gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
1573   }
1574 
1575   return true;
1576 }
1577 
1578 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1579   // do_collection() will return whether it succeeded in performing
1580   // the GC. Currently, there is no facility on the
1581   // do_full_collection() API to notify the caller than the collection
1582   // did not succeed (e.g., because it was locked out by the GC
1583   // locker). So, right now, we'll ignore the return value.
1584   bool dummy = do_collection(true,                /* explicit_gc */
1585                              clear_all_soft_refs,
1586                              0                    /* word_size */);
1587 }
1588 
1589 // This code is mostly copied from TenuredGeneration.
1590 void
1591 G1CollectedHeap::
1592 resize_if_necessary_after_full_collection(size_t word_size) {
1593   assert(MinHeapFreeRatio <= MaxHeapFreeRatio, "sanity check");
1594 
1595   // Include the current allocation, if any, and bytes that will be
1596   // pre-allocated to support collections, as "used".
1597   const size_t used_after_gc = used();
1598   const size_t capacity_after_gc = capacity();
1599   const size_t free_after_gc = capacity_after_gc - used_after_gc;
1600 
1601   // This is enforced in arguments.cpp.
1602   assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1603          "otherwise the code below doesn't make sense");
1604 
1605   // We don't have floating point command-line arguments
1606   const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1607   const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1608   const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1609   const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1610 
1611   const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1612   const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1613 
1614   // We have to be careful here as these two calculations can overflow
1615   // 32-bit size_t's.
1616   double used_after_gc_d = (double) used_after_gc;
1617   double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1618   double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1619 
1620   // Let's make sure that they are both under the max heap size, which
1621   // by default will make them fit into a size_t.
1622   double desired_capacity_upper_bound = (double) max_heap_size;
1623   minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1624                                     desired_capacity_upper_bound);
1625   maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1626                                     desired_capacity_upper_bound);
1627 
1628   // We can now safely turn them into size_t's.
1629   size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1630   size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1631 
1632   // This assert only makes sense here, before we adjust them
1633   // with respect to the min and max heap size.
1634   assert(minimum_desired_capacity <= maximum_desired_capacity,
1635          err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1636                  "maximum_desired_capacity = "SIZE_FORMAT,
1637                  minimum_desired_capacity, maximum_desired_capacity));
1638 
1639   // Should not be greater than the heap max size. No need to adjust
1640   // it with respect to the heap min size as it's a lower bound (i.e.,
1641   // we'll try to make the capacity larger than it, not smaller).
1642   minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1643   // Should not be less than the heap min size. No need to adjust it
1644   // with respect to the heap max size as it's an upper bound (i.e.,
1645   // we'll try to make the capacity smaller than it, not greater).
1646   maximum_desired_capacity =  MAX2(maximum_desired_capacity, min_heap_size);
1647 
1648   if (capacity_after_gc < minimum_desired_capacity) {
1649     // Don't expand unless it's significant
1650     size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1651     ergo_verbose4(ErgoHeapSizing,
1652                   "attempt heap expansion",
1653                   ergo_format_reason("capacity lower than "
1654                                      "min desired capacity after Full GC")
1655                   ergo_format_byte("capacity")
1656                   ergo_format_byte("occupancy")
1657                   ergo_format_byte_perc("min desired capacity"),
1658                   capacity_after_gc, used_after_gc,
1659                   minimum_desired_capacity, (double) MinHeapFreeRatio);
1660     expand(expand_bytes);
1661 
1662     // No expansion, now see if we want to shrink
1663   } else if (capacity_after_gc > maximum_desired_capacity) {
1664     // Capacity too large, compute shrinking size
1665     size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1666     ergo_verbose4(ErgoHeapSizing,
1667                   "attempt heap shrinking",
1668                   ergo_format_reason("capacity higher than "
1669                                      "max desired capacity after Full GC")
1670                   ergo_format_byte("capacity")
1671                   ergo_format_byte("occupancy")
1672                   ergo_format_byte_perc("max desired capacity"),
1673                   capacity_after_gc, used_after_gc,
1674                   maximum_desired_capacity, (double) MaxHeapFreeRatio);
1675     shrink(shrink_bytes);
1676   }
1677 }
1678 
1679 
1680 HeapWord*
1681 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1682                                            bool* succeeded) {
1683   assert_at_safepoint(true /* should_be_vm_thread */);
1684 
1685   *succeeded = true;
1686   // Let's attempt the allocation first.
1687   HeapWord* result =
1688     attempt_allocation_at_safepoint(word_size,
1689                                  false /* expect_null_mutator_alloc_region */);
1690   if (result != NULL) {
1691     assert(*succeeded, "sanity");
1692     return result;
1693   }
1694 
1695   // In a G1 heap, we're supposed to keep allocation from failing by
1696   // incremental pauses.  Therefore, at least for now, we'll favor
1697   // expansion over collection.  (This might change in the future if we can
1698   // do something smarter than full collection to satisfy a failed alloc.)
1699   result = expand_and_allocate(word_size);
1700   if (result != NULL) {
1701     assert(*succeeded, "sanity");
1702     return result;
1703   }
1704 
1705   // Expansion didn't work, we'll try to do a Full GC.
1706   bool gc_succeeded = do_collection(false, /* explicit_gc */
1707                                     false, /* clear_all_soft_refs */
1708                                     word_size);
1709   if (!gc_succeeded) {
1710     *succeeded = false;
1711     return NULL;
1712   }
1713 
1714   // Retry the allocation
1715   result = attempt_allocation_at_safepoint(word_size,
1716                                   true /* expect_null_mutator_alloc_region */);
1717   if (result != NULL) {
1718     assert(*succeeded, "sanity");
1719     return result;
1720   }
1721 
1722   // Then, try a Full GC that will collect all soft references.
1723   gc_succeeded = do_collection(false, /* explicit_gc */
1724                                true,  /* clear_all_soft_refs */
1725                                word_size);
1726   if (!gc_succeeded) {
1727     *succeeded = false;
1728     return NULL;
1729   }
1730 
1731   // Retry the allocation once more
1732   result = attempt_allocation_at_safepoint(word_size,
1733                                   true /* expect_null_mutator_alloc_region */);
1734   if (result != NULL) {
1735     assert(*succeeded, "sanity");
1736     return result;
1737   }
1738 
1739   assert(!collector_policy()->should_clear_all_soft_refs(),
1740          "Flag should have been handled and cleared prior to this point");
1741 
1742   // What else?  We might try synchronous finalization later.  If the total
1743   // space available is large enough for the allocation, then a more
1744   // complete compaction phase than we've tried so far might be
1745   // appropriate.
1746   assert(*succeeded, "sanity");
1747   return NULL;
1748 }
1749 
1750 // Attempting to expand the heap sufficiently
1751 // to support an allocation of the given "word_size".  If
1752 // successful, perform the allocation and return the address of the
1753 // allocated block, or else "NULL".
1754 
1755 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1756   assert_at_safepoint(true /* should_be_vm_thread */);
1757 
1758   verify_region_sets_optional();
1759 
1760   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1761   ergo_verbose1(ErgoHeapSizing,
1762                 "attempt heap expansion",
1763                 ergo_format_reason("allocation request failed")
1764                 ergo_format_byte("allocation request"),
1765                 word_size * HeapWordSize);
1766   if (expand(expand_bytes)) {
1767     _hrs.verify_optional();
1768     verify_region_sets_optional();
1769     return attempt_allocation_at_safepoint(word_size,
1770                                  false /* expect_null_mutator_alloc_region */);
1771   }
1772   return NULL;
1773 }
1774 
1775 void G1CollectedHeap::update_committed_space(HeapWord* old_end,
1776                                              HeapWord* new_end) {
1777   assert(old_end != new_end, "don't call this otherwise");
1778   assert((HeapWord*) _g1_storage.high() == new_end, "invariant");
1779 
1780   // Update the committed mem region.
1781   _g1_committed.set_end(new_end);
1782   // Tell the card table about the update.
1783   Universe::heap()->barrier_set()->resize_covered_region(_g1_committed);
1784   // Tell the BOT about the update.
1785   _bot_shared->resize(_g1_committed.word_size());
1786   // Tell the hot card cache about the update
1787   _cg1r->hot_card_cache()->resize_card_counts(capacity());
1788 }
1789 
1790 bool G1CollectedHeap::expand(size_t expand_bytes) {
1791   size_t old_mem_size = _g1_storage.committed_size();
1792   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1793   aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1794                                        HeapRegion::GrainBytes);
1795   ergo_verbose2(ErgoHeapSizing,
1796                 "expand the heap",
1797                 ergo_format_byte("requested expansion amount")
1798                 ergo_format_byte("attempted expansion amount"),
1799                 expand_bytes, aligned_expand_bytes);
1800 
1801   // First commit the memory.
1802   HeapWord* old_end = (HeapWord*) _g1_storage.high();
1803   bool successful = _g1_storage.expand_by(aligned_expand_bytes);
1804   if (successful) {
1805     // Then propagate this update to the necessary data structures.
1806     HeapWord* new_end = (HeapWord*) _g1_storage.high();
1807     update_committed_space(old_end, new_end);
1808 
1809     FreeRegionList expansion_list("Local Expansion List");
1810     MemRegion mr = _hrs.expand_by(old_end, new_end, &expansion_list);
1811     assert(mr.start() == old_end, "post-condition");
1812     // mr might be a smaller region than what was requested if
1813     // expand_by() was unable to allocate the HeapRegion instances
1814     assert(mr.end() <= new_end, "post-condition");
1815 
1816     size_t actual_expand_bytes = mr.byte_size();
1817     assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1818     assert(actual_expand_bytes == expansion_list.total_capacity_bytes(),
1819            "post-condition");
1820     if (actual_expand_bytes < aligned_expand_bytes) {
1821       // We could not expand _hrs to the desired size. In this case we
1822       // need to shrink the committed space accordingly.
1823       assert(mr.end() < new_end, "invariant");
1824 
1825       size_t diff_bytes = aligned_expand_bytes - actual_expand_bytes;
1826       // First uncommit the memory.
1827       _g1_storage.shrink_by(diff_bytes);
1828       // Then propagate this update to the necessary data structures.
1829       update_committed_space(new_end, mr.end());
1830     }
1831     _free_list.add_as_tail(&expansion_list);
1832 
1833     if (_hr_printer.is_active()) {
1834       HeapWord* curr = mr.start();
1835       while (curr < mr.end()) {
1836         HeapWord* curr_end = curr + HeapRegion::GrainWords;
1837         _hr_printer.commit(curr, curr_end);
1838         curr = curr_end;
1839       }
1840       assert(curr == mr.end(), "post-condition");
1841     }
1842     g1_policy()->record_new_heap_size(n_regions());
1843   } else {
1844     ergo_verbose0(ErgoHeapSizing,
1845                   "did not expand the heap",
1846                   ergo_format_reason("heap expansion operation failed"));
1847     // The expansion of the virtual storage space was unsuccessful.
1848     // Let's see if it was because we ran out of swap.
1849     if (G1ExitOnExpansionFailure &&
1850         _g1_storage.uncommitted_size() >= aligned_expand_bytes) {
1851       // We had head room...
1852       vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1853     }
1854   }
1855   return successful;
1856 }
1857 
1858 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1859   size_t old_mem_size = _g1_storage.committed_size();
1860   size_t aligned_shrink_bytes =
1861     ReservedSpace::page_align_size_down(shrink_bytes);
1862   aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1863                                          HeapRegion::GrainBytes);
1864   uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1865 
1866   uint num_regions_removed = _hrs.shrink_by(num_regions_to_remove);
1867   HeapWord* old_end = (HeapWord*) _g1_storage.high();
1868   size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1869 
1870   ergo_verbose3(ErgoHeapSizing,
1871                 "shrink the heap",
1872                 ergo_format_byte("requested shrinking amount")
1873                 ergo_format_byte("aligned shrinking amount")
1874                 ergo_format_byte("attempted shrinking amount"),
1875                 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1876   if (num_regions_removed > 0) {
1877     _g1_storage.shrink_by(shrunk_bytes);
1878     HeapWord* new_end = (HeapWord*) _g1_storage.high();
1879 
1880     if (_hr_printer.is_active()) {
1881       HeapWord* curr = old_end;
1882       while (curr > new_end) {
1883         HeapWord* curr_end = curr;
1884         curr -= HeapRegion::GrainWords;
1885         _hr_printer.uncommit(curr, curr_end);
1886       }
1887     }
1888 
1889     _expansion_regions += num_regions_removed;
1890     update_committed_space(old_end, new_end);
1891     HeapRegionRemSet::shrink_heap(n_regions());
1892     g1_policy()->record_new_heap_size(n_regions());
1893   } else {
1894     ergo_verbose0(ErgoHeapSizing,
1895                   "did not shrink the heap",
1896                   ergo_format_reason("heap shrinking operation failed"));
1897   }
1898 }
1899 
1900 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1901   verify_region_sets_optional();
1902 
1903   // We should only reach here at the end of a Full GC which means we
1904   // should not not be holding to any GC alloc regions. The method
1905   // below will make sure of that and do any remaining clean up.
1906   abandon_gc_alloc_regions();
1907 
1908   // Instead of tearing down / rebuilding the free lists here, we
1909   // could instead use the remove_all_pending() method on free_list to
1910   // remove only the ones that we need to remove.
1911   tear_down_region_sets(true /* free_list_only */);
1912   shrink_helper(shrink_bytes);
1913   rebuild_region_sets(true /* free_list_only */);
1914 
1915   _hrs.verify_optional();
1916   verify_region_sets_optional();
1917 }
1918 
1919 // Public methods.
1920 
1921 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1922 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1923 #endif // _MSC_VER
1924 
1925 
1926 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1927   SharedHeap(policy_),
1928   _g1_policy(policy_),
1929   _dirty_card_queue_set(false),
1930   _into_cset_dirty_card_queue_set(false),
1931   _is_alive_closure_cm(this),
1932   _is_alive_closure_stw(this),
1933   _ref_processor_cm(NULL),
1934   _ref_processor_stw(NULL),
1935   _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
1936   _bot_shared(NULL),
1937   _evac_failure_scan_stack(NULL),
1938   _mark_in_progress(false),
1939   _cg1r(NULL), _summary_bytes_used(0),
1940   _g1mm(NULL),
1941   _refine_cte_cl(NULL),
1942   _full_collection(false),
1943   _free_list("Master Free List"),
1944   _secondary_free_list("Secondary Free List"),
1945   _old_set("Old Set"),
1946   _humongous_set("Master Humongous Set"),
1947   _free_regions_coming(false),
1948   _young_list(new YoungList(this)),
1949   _gc_time_stamp(0),
1950   _retained_old_gc_alloc_region(NULL),
1951   _survivor_plab_stats(YoungPLABSize, PLABWeight),
1952   _old_plab_stats(OldPLABSize, PLABWeight),
1953   _expand_heap_after_alloc_failure(true),
1954   _surviving_young_words(NULL),
1955   _old_marking_cycles_started(0),
1956   _old_marking_cycles_completed(0),
1957   _concurrent_cycle_started(false),
1958   _in_cset_fast_test(NULL),
1959   _in_cset_fast_test_base(NULL),
1960   _dirty_cards_region_list(NULL),
1961   _worker_cset_start_region(NULL),
1962   _worker_cset_start_region_time_stamp(NULL),
1963   _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1964   _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
1965   _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1966   _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) {
1967 
1968   _g1h = this;
1969   if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
1970     vm_exit_during_initialization("Failed necessary allocation.");
1971   }
1972 
1973   _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1974 
1975   int n_queues = MAX2((int)ParallelGCThreads, 1);
1976   _task_queues = new RefToScanQueueSet(n_queues);
1977 
1978   int n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1979   assert(n_rem_sets > 0, "Invariant.");
1980 
1981   _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1982   _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC);
1983   _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1984 
1985   for (int i = 0; i < n_queues; i++) {
1986     RefToScanQueue* q = new RefToScanQueue();
1987     q->initialize();
1988     _task_queues->register_queue(i, q);
1989     ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1990   }
1991   clear_cset_start_regions();
1992 
1993   // Initialize the G1EvacuationFailureALot counters and flags.
1994   NOT_PRODUCT(reset_evacuation_should_fail();)
1995 
1996   guarantee(_task_queues != NULL, "task_queues allocation failure.");
1997 }
1998 
1999 jint G1CollectedHeap::initialize() {
2000   CollectedHeap::pre_initialize();
2001   os::enable_vtime();
2002 
2003   G1Log::init();
2004 
2005   // Necessary to satisfy locking discipline assertions.
2006 
2007   MutexLocker x(Heap_lock);
2008 
2009   // We have to initialize the printer before committing the heap, as
2010   // it will be used then.
2011   _hr_printer.set_active(G1PrintHeapRegions);
2012 
2013   // While there are no constraints in the GC code that HeapWordSize
2014   // be any particular value, there are multiple other areas in the
2015   // system which believe this to be true (e.g. oop->object_size in some
2016   // cases incorrectly returns the size in wordSize units rather than
2017   // HeapWordSize).
2018   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
2019 
2020   size_t init_byte_size = collector_policy()->initial_heap_byte_size();
2021   size_t max_byte_size = collector_policy()->max_heap_byte_size();

2022 
2023   // Ensure that the sizes are properly aligned.
2024   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
2025   Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");

2026 
2027   _cg1r = new ConcurrentG1Refine(this);
2028 
2029   // Reserve the maximum.
2030 
2031   // When compressed oops are enabled, the preferred heap base
2032   // is calculated by subtracting the requested size from the
2033   // 32Gb boundary and using the result as the base address for
2034   // heap reservation. If the requested size is not aligned to
2035   // HeapRegion::GrainBytes (i.e. the alignment that is passed
2036   // into the ReservedHeapSpace constructor) then the actual
2037   // base of the reserved heap may end up differing from the
2038   // address that was requested (i.e. the preferred heap base).
2039   // If this happens then we could end up using a non-optimal
2040   // compressed oops mode.
2041 
2042   // Since max_byte_size is aligned to the size of a heap region (checked
2043   // above).
2044   Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
2045 
2046   ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
2047                                                  HeapRegion::GrainBytes);
2048 
2049   // It is important to do this in a way such that concurrent readers can't
2050   // temporarily think something is in the heap.  (I've actually seen this
2051   // happen in asserts: DLD.)
2052   _reserved.set_word_size(0);
2053   _reserved.set_start((HeapWord*)heap_rs.base());
2054   _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size()));
2055 
2056   _expansion_regions = (uint) (max_byte_size / HeapRegion::GrainBytes);
2057 
2058   // Create the gen rem set (and barrier set) for the entire reserved region.
2059   _rem_set = collector_policy()->create_rem_set(_reserved, 2);
2060   set_barrier_set(rem_set()->bs());
2061   if (barrier_set()->is_a(BarrierSet::ModRef)) {
2062     _mr_bs = (ModRefBarrierSet*)_barrier_set;
2063   } else {
2064     vm_exit_during_initialization("G1 requires a mod ref bs.");
2065     return JNI_ENOMEM;
2066   }
2067 
2068   // Also create a G1 rem set.
2069   if (mr_bs()->is_a(BarrierSet::CardTableModRef)) {
2070     _g1_rem_set = new G1RemSet(this, (CardTableModRefBS*)mr_bs());
2071   } else {
2072     vm_exit_during_initialization("G1 requires a cardtable mod ref bs.");
2073     return JNI_ENOMEM;
2074   }
2075 
2076   // Carve out the G1 part of the heap.
2077 
2078   ReservedSpace g1_rs   = heap_rs.first_part(max_byte_size);
2079   _g1_reserved = MemRegion((HeapWord*)g1_rs.base(),
2080                            g1_rs.size()/HeapWordSize);
2081 
2082   _g1_storage.initialize(g1_rs, 0);
2083   _g1_committed = MemRegion((HeapWord*)_g1_storage.low(), (size_t) 0);
2084   _hrs.initialize((HeapWord*) _g1_reserved.start(),
2085                   (HeapWord*) _g1_reserved.end(),
2086                   _expansion_regions);
2087 
2088   // Do later initialization work for concurrent refinement.
2089   _cg1r->init();
2090 
2091   // 6843694 - ensure that the maximum region index can fit
2092   // in the remembered set structures.
2093   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
2094   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
2095 
2096   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
2097   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
2098   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
2099             "too many cards per region");
2100 
2101   HeapRegionSet::set_unrealistically_long_length(max_regions() + 1);
2102 
2103   _bot_shared = new G1BlockOffsetSharedArray(_reserved,
2104                                              heap_word_size(init_byte_size));
2105 
2106   _g1h = this;
2107 
2108   _in_cset_fast_test_length = max_regions();
2109   _in_cset_fast_test_base =
2110                    NEW_C_HEAP_ARRAY(bool, (size_t) _in_cset_fast_test_length, mtGC);
2111 
2112   // We're biasing _in_cset_fast_test to avoid subtracting the
2113   // beginning of the heap every time we want to index; basically
2114   // it's the same with what we do with the card table.
2115   _in_cset_fast_test = _in_cset_fast_test_base -
2116                ((uintx) _g1_reserved.start() >> HeapRegion::LogOfHRGrainBytes);
2117 
2118   // Clear the _cset_fast_test bitmap in anticipation of adding
2119   // regions to the incremental collection set for the first
2120   // evacuation pause.
2121   clear_cset_fast_test();
2122 
2123   // Create the ConcurrentMark data structure and thread.
2124   // (Must do this late, so that "max_regions" is defined.)
2125   _cm = new ConcurrentMark(this, heap_rs);
2126   if (_cm == NULL || !_cm->completed_initialization()) {
2127     vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark");
2128     return JNI_ENOMEM;
2129   }
2130   _cmThread = _cm->cmThread();
2131 
2132   // Initialize the from_card cache structure of HeapRegionRemSet.
2133   HeapRegionRemSet::init_heap(max_regions());
2134 
2135   // Now expand into the initial heap size.
2136   if (!expand(init_byte_size)) {
2137     vm_shutdown_during_initialization("Failed to allocate initial heap.");
2138     return JNI_ENOMEM;
2139   }
2140 
2141   // Perform any initialization actions delegated to the policy.
2142   g1_policy()->init();
2143 
2144   _refine_cte_cl =
2145     new RefineCardTableEntryClosure(ConcurrentG1RefineThread::sts(),
2146                                     g1_rem_set(),
2147                                     concurrent_g1_refine());
2148   JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
2149 
2150   JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
2151                                                SATB_Q_FL_lock,
2152                                                G1SATBProcessCompletedThreshold,
2153                                                Shared_SATB_Q_lock);
2154 
2155   JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
2156                                                 DirtyCardQ_FL_lock,
2157                                                 concurrent_g1_refine()->yellow_zone(),
2158                                                 concurrent_g1_refine()->red_zone(),
2159                                                 Shared_DirtyCardQ_lock);
2160 
2161   if (G1DeferredRSUpdate) {
2162     dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
2163                                       DirtyCardQ_FL_lock,
2164                                       -1, // never trigger processing
2165                                       -1, // no limit on length
2166                                       Shared_DirtyCardQ_lock,
2167                                       &JavaThread::dirty_card_queue_set());
2168   }
2169 
2170   // Initialize the card queue set used to hold cards containing
2171   // references into the collection set.
2172   _into_cset_dirty_card_queue_set.initialize(DirtyCardQ_CBL_mon,
2173                                              DirtyCardQ_FL_lock,
2174                                              -1, // never trigger processing
2175                                              -1, // no limit on length
2176                                              Shared_DirtyCardQ_lock,
2177                                              &JavaThread::dirty_card_queue_set());
2178 
2179   // In case we're keeping closure specialization stats, initialize those
2180   // counts and that mechanism.
2181   SpecializationStats::clear();
2182 
2183   // Here we allocate the dummy full region that is required by the
2184   // G1AllocRegion class. If we don't pass an address in the reserved
2185   // space here, lots of asserts fire.
2186 
2187   HeapRegion* dummy_region = new_heap_region(0 /* index of bottom region */,
2188                                              _g1_reserved.start());
2189   // We'll re-use the same region whether the alloc region will
2190   // require BOT updates or not and, if it doesn't, then a non-young
2191   // region will complain that it cannot support allocations without
2192   // BOT updates. So we'll tag the dummy region as young to avoid that.
2193   dummy_region->set_young();
2194   // Make sure it's full.
2195   dummy_region->set_top(dummy_region->end());
2196   G1AllocRegion::setup(this, dummy_region);
2197 
2198   init_mutator_alloc_region();
2199 
2200   // Do create of the monitoring and management support so that
2201   // values in the heap have been properly initialized.
2202   _g1mm = new G1MonitoringSupport(this);
2203 
2204   return JNI_OK;
2205 }
2206 
2207 void G1CollectedHeap::ref_processing_init() {
2208   // Reference processing in G1 currently works as follows:
2209   //
2210   // * There are two reference processor instances. One is
2211   //   used to record and process discovered references
2212   //   during concurrent marking; the other is used to
2213   //   record and process references during STW pauses
2214   //   (both full and incremental).
2215   // * Both ref processors need to 'span' the entire heap as
2216   //   the regions in the collection set may be dotted around.
2217   //
2218   // * For the concurrent marking ref processor:
2219   //   * Reference discovery is enabled at initial marking.
2220   //   * Reference discovery is disabled and the discovered
2221   //     references processed etc during remarking.
2222   //   * Reference discovery is MT (see below).
2223   //   * Reference discovery requires a barrier (see below).
2224   //   * Reference processing may or may not be MT
2225   //     (depending on the value of ParallelRefProcEnabled
2226   //     and ParallelGCThreads).
2227   //   * A full GC disables reference discovery by the CM
2228   //     ref processor and abandons any entries on it's
2229   //     discovered lists.
2230   //
2231   // * For the STW processor:
2232   //   * Non MT discovery is enabled at the start of a full GC.
2233   //   * Processing and enqueueing during a full GC is non-MT.
2234   //   * During a full GC, references are processed after marking.
2235   //
2236   //   * Discovery (may or may not be MT) is enabled at the start
2237   //     of an incremental evacuation pause.
2238   //   * References are processed near the end of a STW evacuation pause.
2239   //   * For both types of GC:
2240   //     * Discovery is atomic - i.e. not concurrent.
2241   //     * Reference discovery will not need a barrier.
2242 
2243   SharedHeap::ref_processing_init();
2244   MemRegion mr = reserved_region();
2245 
2246   // Concurrent Mark ref processor
2247   _ref_processor_cm =
2248     new ReferenceProcessor(mr,    // span
2249                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2250                                 // mt processing
2251                            (int) ParallelGCThreads,
2252                                 // degree of mt processing
2253                            (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2254                                 // mt discovery
2255                            (int) MAX2(ParallelGCThreads, ConcGCThreads),
2256                                 // degree of mt discovery
2257                            false,
2258                                 // Reference discovery is not atomic
2259                            &_is_alive_closure_cm,
2260                                 // is alive closure
2261                                 // (for efficiency/performance)
2262                            true);
2263                                 // Setting next fields of discovered
2264                                 // lists requires a barrier.
2265 
2266   // STW ref processor
2267   _ref_processor_stw =
2268     new ReferenceProcessor(mr,    // span
2269                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2270                                 // mt processing
2271                            MAX2((int)ParallelGCThreads, 1),
2272                                 // degree of mt processing
2273                            (ParallelGCThreads > 1),
2274                                 // mt discovery
2275                            MAX2((int)ParallelGCThreads, 1),
2276                                 // degree of mt discovery
2277                            true,
2278                                 // Reference discovery is atomic
2279                            &_is_alive_closure_stw,
2280                                 // is alive closure
2281                                 // (for efficiency/performance)
2282                            false);
2283                                 // Setting next fields of discovered
2284                                 // lists requires a barrier.
2285 }
2286 
2287 size_t G1CollectedHeap::capacity() const {
2288   return _g1_committed.byte_size();
2289 }
2290 
2291 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2292   assert(!hr->continuesHumongous(), "pre-condition");
2293   hr->reset_gc_time_stamp();
2294   if (hr->startsHumongous()) {
2295     uint first_index = hr->hrs_index() + 1;
2296     uint last_index = hr->last_hc_index();
2297     for (uint i = first_index; i < last_index; i += 1) {
2298       HeapRegion* chr = region_at(i);
2299       assert(chr->continuesHumongous(), "sanity");
2300       chr->reset_gc_time_stamp();
2301     }
2302   }
2303 }
2304 
2305 #ifndef PRODUCT
2306 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2307 private:
2308   unsigned _gc_time_stamp;
2309   bool _failures;
2310 
2311 public:
2312   CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2313     _gc_time_stamp(gc_time_stamp), _failures(false) { }
2314 
2315   virtual bool doHeapRegion(HeapRegion* hr) {
2316     unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2317     if (_gc_time_stamp != region_gc_time_stamp) {
2318       gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, "
2319                              "expected %d", HR_FORMAT_PARAMS(hr),
2320                              region_gc_time_stamp, _gc_time_stamp);
2321       _failures = true;
2322     }
2323     return false;
2324   }
2325 
2326   bool failures() { return _failures; }
2327 };
2328 
2329 void G1CollectedHeap::check_gc_time_stamps() {
2330   CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2331   heap_region_iterate(&cl);
2332   guarantee(!cl.failures(), "all GC time stamps should have been reset");
2333 }
2334 #endif // PRODUCT
2335 
2336 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2337                                                  DirtyCardQueue* into_cset_dcq,
2338                                                  bool concurrent,
2339                                                  int worker_i) {
2340   // Clean cards in the hot card cache
2341   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
2342   hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq);
2343 
2344   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2345   int n_completed_buffers = 0;
2346   while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2347     n_completed_buffers++;
2348   }
2349   g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers);
2350   dcqs.clear_n_completed_buffers();
2351   assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2352 }
2353 
2354 
2355 // Computes the sum of the storage used by the various regions.
2356 
2357 size_t G1CollectedHeap::used() const {
2358   assert(Heap_lock->owner() != NULL,
2359          "Should be owned on this thread's behalf.");
2360   size_t result = _summary_bytes_used;
2361   // Read only once in case it is set to NULL concurrently
2362   HeapRegion* hr = _mutator_alloc_region.get();
2363   if (hr != NULL)
2364     result += hr->used();
2365   return result;
2366 }
2367 
2368 size_t G1CollectedHeap::used_unlocked() const {
2369   size_t result = _summary_bytes_used;
2370   return result;
2371 }
2372 
2373 class SumUsedClosure: public HeapRegionClosure {
2374   size_t _used;
2375 public:
2376   SumUsedClosure() : _used(0) {}
2377   bool doHeapRegion(HeapRegion* r) {
2378     if (!r->continuesHumongous()) {
2379       _used += r->used();
2380     }
2381     return false;
2382   }
2383   size_t result() { return _used; }
2384 };
2385 
2386 size_t G1CollectedHeap::recalculate_used() const {
2387   SumUsedClosure blk;
2388   heap_region_iterate(&blk);
2389   return blk.result();
2390 }
2391 
2392 size_t G1CollectedHeap::unsafe_max_alloc() {
2393   if (free_regions() > 0) return HeapRegion::GrainBytes;
2394   // otherwise, is there space in the current allocation region?
2395 
2396   // We need to store the current allocation region in a local variable
2397   // here. The problem is that this method doesn't take any locks and
2398   // there may be other threads which overwrite the current allocation
2399   // region field. attempt_allocation(), for example, sets it to NULL
2400   // and this can happen *after* the NULL check here but before the call
2401   // to free(), resulting in a SIGSEGV. Note that this doesn't appear
2402   // to be a problem in the optimized build, since the two loads of the
2403   // current allocation region field are optimized away.
2404   HeapRegion* hr = _mutator_alloc_region.get();
2405   if (hr == NULL) {
2406     return 0;
2407   }
2408   return hr->free();
2409 }
2410 
2411 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2412   switch (cause) {
2413     case GCCause::_gc_locker:               return GCLockerInvokesConcurrent;
2414     case GCCause::_java_lang_system_gc:     return ExplicitGCInvokesConcurrent;
2415     case GCCause::_g1_humongous_allocation: return true;
2416     default:                                return false;
2417   }
2418 }
2419 
2420 #ifndef PRODUCT
2421 void G1CollectedHeap::allocate_dummy_regions() {
2422   // Let's fill up most of the region
2423   size_t word_size = HeapRegion::GrainWords - 1024;
2424   // And as a result the region we'll allocate will be humongous.
2425   guarantee(isHumongous(word_size), "sanity");
2426 
2427   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2428     // Let's use the existing mechanism for the allocation
2429     HeapWord* dummy_obj = humongous_obj_allocate(word_size);
2430     if (dummy_obj != NULL) {
2431       MemRegion mr(dummy_obj, word_size);
2432       CollectedHeap::fill_with_object(mr);
2433     } else {
2434       // If we can't allocate once, we probably cannot allocate
2435       // again. Let's get out of the loop.
2436       break;
2437     }
2438   }
2439 }
2440 #endif // !PRODUCT
2441 
2442 void G1CollectedHeap::increment_old_marking_cycles_started() {
2443   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2444     _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2445     err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2446     _old_marking_cycles_started, _old_marking_cycles_completed));
2447 
2448   _old_marking_cycles_started++;
2449 }
2450 
2451 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2452   MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2453 
2454   // We assume that if concurrent == true, then the caller is a
2455   // concurrent thread that was joined the Suspendible Thread
2456   // Set. If there's ever a cheap way to check this, we should add an
2457   // assert here.
2458 
2459   // Given that this method is called at the end of a Full GC or of a
2460   // concurrent cycle, and those can be nested (i.e., a Full GC can
2461   // interrupt a concurrent cycle), the number of full collections
2462   // completed should be either one (in the case where there was no
2463   // nesting) or two (when a Full GC interrupted a concurrent cycle)
2464   // behind the number of full collections started.
2465 
2466   // This is the case for the inner caller, i.e. a Full GC.
2467   assert(concurrent ||
2468          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2469          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2470          err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
2471                  "is inconsistent with _old_marking_cycles_completed = %u",
2472                  _old_marking_cycles_started, _old_marking_cycles_completed));
2473 
2474   // This is the case for the outer caller, i.e. the concurrent cycle.
2475   assert(!concurrent ||
2476          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2477          err_msg("for outer caller (concurrent cycle): "
2478                  "_old_marking_cycles_started = %u "
2479                  "is inconsistent with _old_marking_cycles_completed = %u",
2480                  _old_marking_cycles_started, _old_marking_cycles_completed));
2481 
2482   _old_marking_cycles_completed += 1;
2483 
2484   // We need to clear the "in_progress" flag in the CM thread before
2485   // we wake up any waiters (especially when ExplicitInvokesConcurrent
2486   // is set) so that if a waiter requests another System.gc() it doesn't
2487   // incorrectly see that a marking cycle is still in progress.
2488   if (concurrent) {
2489     _cmThread->clear_in_progress();
2490   }
2491 
2492   // This notify_all() will ensure that a thread that called
2493   // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2494   // and it's waiting for a full GC to finish will be woken up. It is
2495   // waiting in VM_G1IncCollectionPause::doit_epilogue().
2496   FullGCCount_lock->notify_all();
2497 }
2498 
2499 void G1CollectedHeap::register_concurrent_cycle_start(jlong start_time) {
2500   _concurrent_cycle_started = true;
2501   _gc_timer_cm->register_gc_start(start_time);
2502 
2503   _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start());
2504   trace_heap_before_gc(_gc_tracer_cm);
2505 }
2506 
2507 void G1CollectedHeap::register_concurrent_cycle_end() {
2508   if (_concurrent_cycle_started) {
2509     _gc_timer_cm->register_gc_end(os::elapsed_counter());
2510 
2511     if (_cm->has_aborted()) {
2512       _gc_tracer_cm->report_concurrent_mode_failure();
2513     }
2514     _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
2515 
2516     _concurrent_cycle_started = false;
2517   }
2518 }
2519 
2520 void G1CollectedHeap::trace_heap_after_concurrent_cycle() {
2521   if (_concurrent_cycle_started) {
2522     trace_heap_after_gc(_gc_tracer_cm);
2523   }
2524 }
2525 
2526 G1YCType G1CollectedHeap::yc_type() {
2527   bool is_young = g1_policy()->gcs_are_young();
2528   bool is_initial_mark = g1_policy()->during_initial_mark_pause();
2529   bool is_during_mark = mark_in_progress();
2530 
2531   if (is_initial_mark) {
2532     return InitialMark;
2533   } else if (is_during_mark) {
2534     return DuringMark;
2535   } else if (is_young) {
2536     return Normal;
2537   } else {
2538     return Mixed;
2539   }
2540 }
2541 
2542 void G1CollectedHeap::collect(GCCause::Cause cause) {
2543   assert_heap_not_locked();
2544 
2545   unsigned int gc_count_before;
2546   unsigned int old_marking_count_before;
2547   bool retry_gc;
2548 
2549   do {
2550     retry_gc = false;
2551 
2552     {
2553       MutexLocker ml(Heap_lock);
2554 
2555       // Read the GC count while holding the Heap_lock
2556       gc_count_before = total_collections();
2557       old_marking_count_before = _old_marking_cycles_started;
2558     }
2559 
2560     if (should_do_concurrent_full_gc(cause)) {
2561       // Schedule an initial-mark evacuation pause that will start a
2562       // concurrent cycle. We're setting word_size to 0 which means that
2563       // we are not requesting a post-GC allocation.
2564       VM_G1IncCollectionPause op(gc_count_before,
2565                                  0,     /* word_size */
2566                                  true,  /* should_initiate_conc_mark */
2567                                  g1_policy()->max_pause_time_ms(),
2568                                  cause);
2569 
2570       VMThread::execute(&op);
2571       if (!op.pause_succeeded()) {
2572         if (old_marking_count_before == _old_marking_cycles_started) {
2573           retry_gc = op.should_retry_gc();
2574         } else {
2575           // A Full GC happened while we were trying to schedule the
2576           // initial-mark GC. No point in starting a new cycle given
2577           // that the whole heap was collected anyway.
2578         }
2579 
2580         if (retry_gc) {
2581           if (GC_locker::is_active_and_needs_gc()) {
2582             GC_locker::stall_until_clear();
2583           }
2584         }
2585       }
2586     } else {
2587       if (cause == GCCause::_gc_locker
2588           DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2589 
2590         // Schedule a standard evacuation pause. We're setting word_size
2591         // to 0 which means that we are not requesting a post-GC allocation.
2592         VM_G1IncCollectionPause op(gc_count_before,
2593                                    0,     /* word_size */
2594                                    false, /* should_initiate_conc_mark */
2595                                    g1_policy()->max_pause_time_ms(),
2596                                    cause);
2597         VMThread::execute(&op);
2598       } else {
2599         // Schedule a Full GC.
2600         VM_G1CollectFull op(gc_count_before, old_marking_count_before, cause);
2601         VMThread::execute(&op);
2602       }
2603     }
2604   } while (retry_gc);
2605 }
2606 
2607 bool G1CollectedHeap::is_in(const void* p) const {
2608   if (_g1_committed.contains(p)) {
2609     // Given that we know that p is in the committed space,
2610     // heap_region_containing_raw() should successfully
2611     // return the containing region.
2612     HeapRegion* hr = heap_region_containing_raw(p);
2613     return hr->is_in(p);
2614   } else {
2615     return false;
2616   }
2617 }
2618 
2619 // Iteration functions.
2620 
2621 // Iterates an OopClosure over all ref-containing fields of objects
2622 // within a HeapRegion.
2623 
2624 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2625   MemRegion _mr;
2626   ExtendedOopClosure* _cl;
2627 public:
2628   IterateOopClosureRegionClosure(MemRegion mr, ExtendedOopClosure* cl)
2629     : _mr(mr), _cl(cl) {}
2630   bool doHeapRegion(HeapRegion* r) {
2631     if (!r->continuesHumongous()) {
2632       r->oop_iterate(_cl);
2633     }
2634     return false;
2635   }
2636 };
2637 
2638 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) {
2639   IterateOopClosureRegionClosure blk(_g1_committed, cl);
2640   heap_region_iterate(&blk);
2641 }
2642 
2643 void G1CollectedHeap::oop_iterate(MemRegion mr, ExtendedOopClosure* cl) {
2644   IterateOopClosureRegionClosure blk(mr, cl);
2645   heap_region_iterate(&blk);
2646 }
2647 
2648 // Iterates an ObjectClosure over all objects within a HeapRegion.
2649 
2650 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2651   ObjectClosure* _cl;
2652 public:
2653   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2654   bool doHeapRegion(HeapRegion* r) {
2655     if (! r->continuesHumongous()) {
2656       r->object_iterate(_cl);
2657     }
2658     return false;
2659   }
2660 };
2661 
2662 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2663   IterateObjectClosureRegionClosure blk(cl);
2664   heap_region_iterate(&blk);
2665 }
2666 
2667 // Calls a SpaceClosure on a HeapRegion.
2668 
2669 class SpaceClosureRegionClosure: public HeapRegionClosure {
2670   SpaceClosure* _cl;
2671 public:
2672   SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2673   bool doHeapRegion(HeapRegion* r) {
2674     _cl->do_space(r);
2675     return false;
2676   }
2677 };
2678 
2679 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2680   SpaceClosureRegionClosure blk(cl);
2681   heap_region_iterate(&blk);
2682 }
2683 
2684 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2685   _hrs.iterate(cl);
2686 }
2687 
2688 void
2689 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
2690                                                  uint worker_id,
2691                                                  uint no_of_par_workers,
2692                                                  jint claim_value) {
2693   const uint regions = n_regions();
2694   const uint max_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
2695                              no_of_par_workers :
2696                              1);
2697   assert(UseDynamicNumberOfGCThreads ||
2698          no_of_par_workers == workers()->total_workers(),
2699          "Non dynamic should use fixed number of workers");
2700   // try to spread out the starting points of the workers
2701   const HeapRegion* start_hr =
2702                         start_region_for_worker(worker_id, no_of_par_workers);
2703   const uint start_index = start_hr->hrs_index();
2704 
2705   // each worker will actually look at all regions
2706   for (uint count = 0; count < regions; ++count) {
2707     const uint index = (start_index + count) % regions;
2708     assert(0 <= index && index < regions, "sanity");
2709     HeapRegion* r = region_at(index);
2710     // we'll ignore "continues humongous" regions (we'll process them
2711     // when we come across their corresponding "start humongous"
2712     // region) and regions already claimed
2713     if (r->claim_value() == claim_value || r->continuesHumongous()) {
2714       continue;
2715     }
2716     // OK, try to claim it
2717     if (r->claimHeapRegion(claim_value)) {
2718       // success!
2719       assert(!r->continuesHumongous(), "sanity");
2720       if (r->startsHumongous()) {
2721         // If the region is "starts humongous" we'll iterate over its
2722         // "continues humongous" first; in fact we'll do them
2723         // first. The order is important. In on case, calling the
2724         // closure on the "starts humongous" region might de-allocate
2725         // and clear all its "continues humongous" regions and, as a
2726         // result, we might end up processing them twice. So, we'll do
2727         // them first (notice: most closures will ignore them anyway) and
2728         // then we'll do the "starts humongous" region.
2729         for (uint ch_index = index + 1; ch_index < regions; ++ch_index) {
2730           HeapRegion* chr = region_at(ch_index);
2731 
2732           // if the region has already been claimed or it's not
2733           // "continues humongous" we're done
2734           if (chr->claim_value() == claim_value ||
2735               !chr->continuesHumongous()) {
2736             break;
2737           }
2738 
2739           // No one should have claimed it directly. We can given
2740           // that we claimed its "starts humongous" region.
2741           assert(chr->claim_value() != claim_value, "sanity");
2742           assert(chr->humongous_start_region() == r, "sanity");
2743 
2744           if (chr->claimHeapRegion(claim_value)) {
2745             // we should always be able to claim it; no one else should
2746             // be trying to claim this region
2747 
2748             bool res2 = cl->doHeapRegion(chr);
2749             assert(!res2, "Should not abort");
2750 
2751             // Right now, this holds (i.e., no closure that actually
2752             // does something with "continues humongous" regions
2753             // clears them). We might have to weaken it in the future,
2754             // but let's leave these two asserts here for extra safety.
2755             assert(chr->continuesHumongous(), "should still be the case");
2756             assert(chr->humongous_start_region() == r, "sanity");
2757           } else {
2758             guarantee(false, "we should not reach here");
2759           }
2760         }
2761       }
2762 
2763       assert(!r->continuesHumongous(), "sanity");
2764       bool res = cl->doHeapRegion(r);
2765       assert(!res, "Should not abort");
2766     }
2767   }
2768 }
2769 
2770 class ResetClaimValuesClosure: public HeapRegionClosure {
2771 public:
2772   bool doHeapRegion(HeapRegion* r) {
2773     r->set_claim_value(HeapRegion::InitialClaimValue);
2774     return false;
2775   }
2776 };
2777 
2778 void G1CollectedHeap::reset_heap_region_claim_values() {
2779   ResetClaimValuesClosure blk;
2780   heap_region_iterate(&blk);
2781 }
2782 
2783 void G1CollectedHeap::reset_cset_heap_region_claim_values() {
2784   ResetClaimValuesClosure blk;
2785   collection_set_iterate(&blk);
2786 }
2787 
2788 #ifdef ASSERT
2789 // This checks whether all regions in the heap have the correct claim
2790 // value. I also piggy-backed on this a check to ensure that the
2791 // humongous_start_region() information on "continues humongous"
2792 // regions is correct.
2793 
2794 class CheckClaimValuesClosure : public HeapRegionClosure {
2795 private:
2796   jint _claim_value;
2797   uint _failures;
2798   HeapRegion* _sh_region;
2799 
2800 public:
2801   CheckClaimValuesClosure(jint claim_value) :
2802     _claim_value(claim_value), _failures(0), _sh_region(NULL) { }
2803   bool doHeapRegion(HeapRegion* r) {
2804     if (r->claim_value() != _claim_value) {
2805       gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2806                              "claim value = %d, should be %d",
2807                              HR_FORMAT_PARAMS(r),
2808                              r->claim_value(), _claim_value);
2809       ++_failures;
2810     }
2811     if (!r->isHumongous()) {
2812       _sh_region = NULL;
2813     } else if (r->startsHumongous()) {
2814       _sh_region = r;
2815     } else if (r->continuesHumongous()) {
2816       if (r->humongous_start_region() != _sh_region) {
2817         gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2818                                "HS = "PTR_FORMAT", should be "PTR_FORMAT,
2819                                HR_FORMAT_PARAMS(r),
2820                                r->humongous_start_region(),
2821                                _sh_region);
2822         ++_failures;
2823       }
2824     }
2825     return false;
2826   }
2827   uint failures() { return _failures; }
2828 };
2829 
2830 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
2831   CheckClaimValuesClosure cl(claim_value);
2832   heap_region_iterate(&cl);
2833   return cl.failures() == 0;
2834 }
2835 
2836 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure {
2837 private:
2838   jint _claim_value;
2839   uint _failures;
2840 
2841 public:
2842   CheckClaimValuesInCSetHRClosure(jint claim_value) :
2843     _claim_value(claim_value), _failures(0) { }
2844 
2845   uint failures() { return _failures; }
2846 
2847   bool doHeapRegion(HeapRegion* hr) {
2848     assert(hr->in_collection_set(), "how?");
2849     assert(!hr->isHumongous(), "H-region in CSet");
2850     if (hr->claim_value() != _claim_value) {
2851       gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", "
2852                              "claim value = %d, should be %d",
2853                              HR_FORMAT_PARAMS(hr),
2854                              hr->claim_value(), _claim_value);
2855       _failures += 1;
2856     }
2857     return false;
2858   }
2859 };
2860 
2861 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) {
2862   CheckClaimValuesInCSetHRClosure cl(claim_value);
2863   collection_set_iterate(&cl);
2864   return cl.failures() == 0;
2865 }
2866 #endif // ASSERT
2867 
2868 // Clear the cached CSet starting regions and (more importantly)
2869 // the time stamps. Called when we reset the GC time stamp.
2870 void G1CollectedHeap::clear_cset_start_regions() {
2871   assert(_worker_cset_start_region != NULL, "sanity");
2872   assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2873 
2874   int n_queues = MAX2((int)ParallelGCThreads, 1);
2875   for (int i = 0; i < n_queues; i++) {
2876     _worker_cset_start_region[i] = NULL;
2877     _worker_cset_start_region_time_stamp[i] = 0;
2878   }
2879 }
2880 
2881 // Given the id of a worker, obtain or calculate a suitable
2882 // starting region for iterating over the current collection set.
2883 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(int worker_i) {
2884   assert(get_gc_time_stamp() > 0, "should have been updated by now");
2885 
2886   HeapRegion* result = NULL;
2887   unsigned gc_time_stamp = get_gc_time_stamp();
2888 
2889   if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2890     // Cached starting region for current worker was set
2891     // during the current pause - so it's valid.
2892     // Note: the cached starting heap region may be NULL
2893     // (when the collection set is empty).
2894     result = _worker_cset_start_region[worker_i];
2895     assert(result == NULL || result->in_collection_set(), "sanity");
2896     return result;
2897   }
2898 
2899   // The cached entry was not valid so let's calculate
2900   // a suitable starting heap region for this worker.
2901 
2902   // We want the parallel threads to start their collection
2903   // set iteration at different collection set regions to
2904   // avoid contention.
2905   // If we have:
2906   //          n collection set regions
2907   //          p threads
2908   // Then thread t will start at region floor ((t * n) / p)
2909 
2910   result = g1_policy()->collection_set();
2911   if (G1CollectedHeap::use_parallel_gc_threads()) {
2912     uint cs_size = g1_policy()->cset_region_length();
2913     uint active_workers = workers()->active_workers();
2914     assert(UseDynamicNumberOfGCThreads ||
2915              active_workers == workers()->total_workers(),
2916              "Unless dynamic should use total workers");
2917 
2918     uint end_ind   = (cs_size * worker_i) / active_workers;
2919     uint start_ind = 0;
2920 
2921     if (worker_i > 0 &&
2922         _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2923       // Previous workers starting region is valid
2924       // so let's iterate from there
2925       start_ind = (cs_size * (worker_i - 1)) / active_workers;
2926       result = _worker_cset_start_region[worker_i - 1];
2927     }
2928 
2929     for (uint i = start_ind; i < end_ind; i++) {
2930       result = result->next_in_collection_set();
2931     }
2932   }
2933 
2934   // Note: the calculated starting heap region may be NULL
2935   // (when the collection set is empty).
2936   assert(result == NULL || result->in_collection_set(), "sanity");
2937   assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2938          "should be updated only once per pause");
2939   _worker_cset_start_region[worker_i] = result;
2940   OrderAccess::storestore();
2941   _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2942   return result;
2943 }
2944 
2945 HeapRegion* G1CollectedHeap::start_region_for_worker(uint worker_i,
2946                                                      uint no_of_par_workers) {
2947   uint worker_num =
2948            G1CollectedHeap::use_parallel_gc_threads() ? no_of_par_workers : 1U;
2949   assert(UseDynamicNumberOfGCThreads ||
2950          no_of_par_workers == workers()->total_workers(),
2951          "Non dynamic should use fixed number of workers");
2952   const uint start_index = n_regions() * worker_i / worker_num;
2953   return region_at(start_index);
2954 }
2955 
2956 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2957   HeapRegion* r = g1_policy()->collection_set();
2958   while (r != NULL) {
2959     HeapRegion* next = r->next_in_collection_set();
2960     if (cl->doHeapRegion(r)) {
2961       cl->incomplete();
2962       return;
2963     }
2964     r = next;
2965   }
2966 }
2967 
2968 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2969                                                   HeapRegionClosure *cl) {
2970   if (r == NULL) {
2971     // The CSet is empty so there's nothing to do.
2972     return;
2973   }
2974 
2975   assert(r->in_collection_set(),
2976          "Start region must be a member of the collection set.");
2977   HeapRegion* cur = r;
2978   while (cur != NULL) {
2979     HeapRegion* next = cur->next_in_collection_set();
2980     if (cl->doHeapRegion(cur) && false) {
2981       cl->incomplete();
2982       return;
2983     }
2984     cur = next;
2985   }
2986   cur = g1_policy()->collection_set();
2987   while (cur != r) {
2988     HeapRegion* next = cur->next_in_collection_set();
2989     if (cl->doHeapRegion(cur) && false) {
2990       cl->incomplete();
2991       return;
2992     }
2993     cur = next;
2994   }
2995 }
2996 
2997 CompactibleSpace* G1CollectedHeap::first_compactible_space() {
2998   return n_regions() > 0 ? region_at(0) : NULL;
2999 }
3000 
3001 
3002 Space* G1CollectedHeap::space_containing(const void* addr) const {
3003   Space* res = heap_region_containing(addr);
3004   return res;
3005 }
3006 
3007 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
3008   Space* sp = space_containing(addr);
3009   if (sp != NULL) {
3010     return sp->block_start(addr);
3011   }
3012   return NULL;
3013 }
3014 
3015 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
3016   Space* sp = space_containing(addr);
3017   assert(sp != NULL, "block_size of address outside of heap");
3018   return sp->block_size(addr);
3019 }
3020 
3021 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
3022   Space* sp = space_containing(addr);
3023   return sp->block_is_obj(addr);
3024 }
3025 
3026 bool G1CollectedHeap::supports_tlab_allocation() const {
3027   return true;
3028 }
3029 
3030 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
3031   return HeapRegion::GrainBytes;
3032 }
3033 
3034 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
3035   // Return the remaining space in the cur alloc region, but not less than
3036   // the min TLAB size.
3037 
3038   // Also, this value can be at most the humongous object threshold,
3039   // since we can't allow tlabs to grow big enough to accommodate
3040   // humongous objects.
3041 
3042   HeapRegion* hr = _mutator_alloc_region.get();
3043   size_t max_tlab_size = _humongous_object_threshold_in_words * wordSize;
3044   if (hr == NULL) {
3045     return max_tlab_size;
3046   } else {
3047     return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab_size);
3048   }
3049 }
3050 
3051 size_t G1CollectedHeap::max_capacity() const {
3052   return _g1_reserved.byte_size();
3053 }
3054 
3055 jlong G1CollectedHeap::millis_since_last_gc() {
3056   // assert(false, "NYI");
3057   return 0;
3058 }
3059 
3060 void G1CollectedHeap::prepare_for_verify() {
3061   if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
3062     ensure_parsability(false);
3063   }
3064   g1_rem_set()->prepare_for_verify();
3065 }
3066 
3067 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr,
3068                                               VerifyOption vo) {
3069   switch (vo) {
3070   case VerifyOption_G1UsePrevMarking:
3071     return hr->obj_allocated_since_prev_marking(obj);
3072   case VerifyOption_G1UseNextMarking:
3073     return hr->obj_allocated_since_next_marking(obj);
3074   case VerifyOption_G1UseMarkWord:
3075     return false;
3076   default:
3077     ShouldNotReachHere();
3078   }
3079   return false; // keep some compilers happy
3080 }
3081 
3082 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) {
3083   switch (vo) {
3084   case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start();
3085   case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start();
3086   case VerifyOption_G1UseMarkWord:    return NULL;
3087   default:                            ShouldNotReachHere();
3088   }
3089   return NULL; // keep some compilers happy
3090 }
3091 
3092 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) {
3093   switch (vo) {
3094   case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj);
3095   case VerifyOption_G1UseNextMarking: return isMarkedNext(obj);
3096   case VerifyOption_G1UseMarkWord:    return obj->is_gc_marked();
3097   default:                            ShouldNotReachHere();
3098   }
3099   return false; // keep some compilers happy
3100 }
3101 
3102 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) {
3103   switch (vo) {
3104   case VerifyOption_G1UsePrevMarking: return "PTAMS";
3105   case VerifyOption_G1UseNextMarking: return "NTAMS";
3106   case VerifyOption_G1UseMarkWord:    return "NONE";
3107   default:                            ShouldNotReachHere();
3108   }
3109   return NULL; // keep some compilers happy
3110 }
3111 
3112 class VerifyLivenessOopClosure: public OopClosure {
3113   G1CollectedHeap* _g1h;
3114   VerifyOption _vo;
3115 public:
3116   VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
3117     _g1h(g1h), _vo(vo)
3118   { }
3119   void do_oop(narrowOop *p) { do_oop_work(p); }
3120   void do_oop(      oop *p) { do_oop_work(p); }
3121 
3122   template <class T> void do_oop_work(T *p) {
3123     oop obj = oopDesc::load_decode_heap_oop(p);
3124     guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
3125               "Dead object referenced by a not dead object");
3126   }
3127 };
3128 
3129 class VerifyObjsInRegionClosure: public ObjectClosure {
3130 private:
3131   G1CollectedHeap* _g1h;
3132   size_t _live_bytes;
3133   HeapRegion *_hr;
3134   VerifyOption _vo;
3135 public:
3136   // _vo == UsePrevMarking -> use "prev" marking information,
3137   // _vo == UseNextMarking -> use "next" marking information,
3138   // _vo == UseMarkWord    -> use mark word from object header.
3139   VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
3140     : _live_bytes(0), _hr(hr), _vo(vo) {
3141     _g1h = G1CollectedHeap::heap();
3142   }
3143   void do_object(oop o) {
3144     VerifyLivenessOopClosure isLive(_g1h, _vo);
3145     assert(o != NULL, "Huh?");
3146     if (!_g1h->is_obj_dead_cond(o, _vo)) {
3147       // If the object is alive according to the mark word,
3148       // then verify that the marking information agrees.
3149       // Note we can't verify the contra-positive of the
3150       // above: if the object is dead (according to the mark
3151       // word), it may not be marked, or may have been marked
3152       // but has since became dead, or may have been allocated
3153       // since the last marking.
3154       if (_vo == VerifyOption_G1UseMarkWord) {
3155         guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
3156       }
3157 
3158       o->oop_iterate_no_header(&isLive);
3159       if (!_hr->obj_allocated_since_prev_marking(o)) {
3160         size_t obj_size = o->size();    // Make sure we don't overflow
3161         _live_bytes += (obj_size * HeapWordSize);
3162       }
3163     }
3164   }
3165   size_t live_bytes() { return _live_bytes; }
3166 };
3167 
3168 class PrintObjsInRegionClosure : public ObjectClosure {
3169   HeapRegion *_hr;
3170   G1CollectedHeap *_g1;
3171 public:
3172   PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
3173     _g1 = G1CollectedHeap::heap();
3174   };
3175 
3176   void do_object(oop o) {
3177     if (o != NULL) {
3178       HeapWord *start = (HeapWord *) o;
3179       size_t word_sz = o->size();
3180       gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
3181                           " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
3182                           (void*) o, word_sz,
3183                           _g1->isMarkedPrev(o),
3184                           _g1->isMarkedNext(o),
3185                           _hr->obj_allocated_since_prev_marking(o));
3186       HeapWord *end = start + word_sz;
3187       HeapWord *cur;
3188       int *val;
3189       for (cur = start; cur < end; cur++) {
3190         val = (int *) cur;
3191         gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val);
3192       }
3193     }
3194   }
3195 };
3196 
3197 class VerifyRegionClosure: public HeapRegionClosure {
3198 private:
3199   bool             _par;
3200   VerifyOption     _vo;
3201   bool             _failures;
3202 public:
3203   // _vo == UsePrevMarking -> use "prev" marking information,
3204   // _vo == UseNextMarking -> use "next" marking information,
3205   // _vo == UseMarkWord    -> use mark word from object header.
3206   VerifyRegionClosure(bool par, VerifyOption vo)
3207     : _par(par),
3208       _vo(vo),
3209       _failures(false) {}
3210 
3211   bool failures() {
3212     return _failures;
3213   }
3214 
3215   bool doHeapRegion(HeapRegion* r) {
3216     if (!r->continuesHumongous()) {
3217       bool failures = false;
3218       r->verify(_vo, &failures);
3219       if (failures) {
3220         _failures = true;
3221       } else {
3222         VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
3223         r->object_iterate(&not_dead_yet_cl);
3224         if (_vo != VerifyOption_G1UseNextMarking) {
3225           if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
3226             gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
3227                                    "max_live_bytes "SIZE_FORMAT" "
3228                                    "< calculated "SIZE_FORMAT,
3229                                    r->bottom(), r->end(),
3230                                    r->max_live_bytes(),
3231                                  not_dead_yet_cl.live_bytes());
3232             _failures = true;
3233           }
3234         } else {
3235           // When vo == UseNextMarking we cannot currently do a sanity
3236           // check on the live bytes as the calculation has not been
3237           // finalized yet.
3238         }
3239       }
3240     }
3241     return false; // stop the region iteration if we hit a failure
3242   }
3243 };
3244 
3245 class YoungRefCounterClosure : public OopClosure {
3246   G1CollectedHeap* _g1h;
3247   int              _count;
3248  public:
3249   YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {}
3250   void do_oop(oop* p)       { if (_g1h->is_in_young(*p)) { _count++; } }
3251   void do_oop(narrowOop* p) { ShouldNotReachHere(); }
3252 
3253   int count() { return _count; }
3254   void reset_count() { _count = 0; };
3255 };
3256 
3257 class VerifyKlassClosure: public KlassClosure {
3258   YoungRefCounterClosure _young_ref_counter_closure;
3259   OopClosure *_oop_closure;
3260  public:
3261   VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {}
3262   void do_klass(Klass* k) {
3263     k->oops_do(_oop_closure);
3264 
3265     _young_ref_counter_closure.reset_count();
3266     k->oops_do(&_young_ref_counter_closure);
3267     if (_young_ref_counter_closure.count() > 0) {
3268       guarantee(k->has_modified_oops(), err_msg("Klass %p, has young refs but is not dirty.", k));
3269     }
3270   }
3271 };
3272 
3273 // TODO: VerifyRootsClosure extends OopsInGenClosure so that we can
3274 //       pass it as the perm_blk to SharedHeap::process_strong_roots.
3275 //       When process_strong_roots stop calling perm_blk->younger_refs_iterate
3276 //       we can change this closure to extend the simpler OopClosure.
3277 class VerifyRootsClosure: public OopsInGenClosure {
3278 private:
3279   G1CollectedHeap* _g1h;
3280   VerifyOption     _vo;
3281   bool             _failures;
3282 public:
3283   // _vo == UsePrevMarking -> use "prev" marking information,
3284   // _vo == UseNextMarking -> use "next" marking information,
3285   // _vo == UseMarkWord    -> use mark word from object header.
3286   VerifyRootsClosure(VerifyOption vo) :
3287     _g1h(G1CollectedHeap::heap()),
3288     _vo(vo),
3289     _failures(false) { }
3290 
3291   bool failures() { return _failures; }
3292 
3293   template <class T> void do_oop_nv(T* p) {
3294     T heap_oop = oopDesc::load_heap_oop(p);
3295     if (!oopDesc::is_null(heap_oop)) {
3296       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3297       if (_g1h->is_obj_dead_cond(obj, _vo)) {
3298         gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
3299                               "points to dead obj "PTR_FORMAT, p, (void*) obj);
3300         if (_vo == VerifyOption_G1UseMarkWord) {
3301           gclog_or_tty->print_cr("  Mark word: "PTR_FORMAT, (void*)(obj->mark()));
3302         }
3303         obj->print_on(gclog_or_tty);
3304         _failures = true;
3305       }
3306     }
3307   }
3308 
3309   void do_oop(oop* p)       { do_oop_nv(p); }
3310   void do_oop(narrowOop* p) { do_oop_nv(p); }
3311 };
3312 
3313 // This is the task used for parallel heap verification.
3314 
3315 class G1ParVerifyTask: public AbstractGangTask {
3316 private:
3317   G1CollectedHeap* _g1h;
3318   VerifyOption     _vo;
3319   bool             _failures;
3320 
3321 public:
3322   // _vo == UsePrevMarking -> use "prev" marking information,
3323   // _vo == UseNextMarking -> use "next" marking information,
3324   // _vo == UseMarkWord    -> use mark word from object header.
3325   G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
3326     AbstractGangTask("Parallel verify task"),
3327     _g1h(g1h),
3328     _vo(vo),
3329     _failures(false) { }
3330 
3331   bool failures() {
3332     return _failures;
3333   }
3334 
3335   void work(uint worker_id) {
3336     HandleMark hm;
3337     VerifyRegionClosure blk(true, _vo);
3338     _g1h->heap_region_par_iterate_chunked(&blk, worker_id,
3339                                           _g1h->workers()->active_workers(),
3340                                           HeapRegion::ParVerifyClaimValue);
3341     if (blk.failures()) {
3342       _failures = true;
3343     }
3344   }
3345 };
3346 
3347 void G1CollectedHeap::verify(bool silent) {
3348   verify(silent, VerifyOption_G1UsePrevMarking);
3349 }
3350 
3351 void G1CollectedHeap::verify(bool silent,
3352                              VerifyOption vo) {
3353   if (SafepointSynchronize::is_at_safepoint()) {
3354     if (!silent) { gclog_or_tty->print("Roots "); }
3355     VerifyRootsClosure rootsCl(vo);
3356 
3357     assert(Thread::current()->is_VM_thread(),
3358            "Expected to be executed serially by the VM thread at this point");
3359 
3360     CodeBlobToOopClosure blobsCl(&rootsCl, /*do_marking=*/ false);
3361     VerifyKlassClosure klassCl(this, &rootsCl);
3362 
3363     // We apply the relevant closures to all the oops in the
3364     // system dictionary, the string table and the code cache.
3365     const int so = SO_AllClasses | SO_Strings | SO_CodeCache;
3366 
3367     // Need cleared claim bits for the strong roots processing
3368     ClassLoaderDataGraph::clear_claimed_marks();
3369 
3370     process_strong_roots(true,      // activate StrongRootsScope
3371                          false,     // we set "is scavenging" to false,
3372                                     // so we don't reset the dirty cards.
3373                          ScanningOption(so),  // roots scanning options
3374                          &rootsCl,
3375                          &blobsCl,
3376                          &klassCl
3377                          );
3378 
3379     bool failures = rootsCl.failures();
3380 
3381     if (vo != VerifyOption_G1UseMarkWord) {
3382       // If we're verifying during a full GC then the region sets
3383       // will have been torn down at the start of the GC. Therefore
3384       // verifying the region sets will fail. So we only verify
3385       // the region sets when not in a full GC.
3386       if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3387       verify_region_sets();
3388     }
3389 
3390     if (!silent) { gclog_or_tty->print("HeapRegions "); }
3391     if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3392       assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3393              "sanity check");
3394 
3395       G1ParVerifyTask task(this, vo);
3396       assert(UseDynamicNumberOfGCThreads ||
3397         workers()->active_workers() == workers()->total_workers(),
3398         "If not dynamic should be using all the workers");
3399       int n_workers = workers()->active_workers();
3400       set_par_threads(n_workers);
3401       workers()->run_task(&task);
3402       set_par_threads(0);
3403       if (task.failures()) {
3404         failures = true;
3405       }
3406 
3407       // Checks that the expected amount of parallel work was done.
3408       // The implication is that n_workers is > 0.
3409       assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
3410              "sanity check");
3411 
3412       reset_heap_region_claim_values();
3413 
3414       assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3415              "sanity check");
3416     } else {
3417       VerifyRegionClosure blk(false, vo);
3418       heap_region_iterate(&blk);
3419       if (blk.failures()) {
3420         failures = true;
3421       }
3422     }
3423     if (!silent) gclog_or_tty->print("RemSet ");
3424     rem_set()->verify();
3425 
3426     if (failures) {
3427       gclog_or_tty->print_cr("Heap:");
3428       // It helps to have the per-region information in the output to
3429       // help us track down what went wrong. This is why we call
3430       // print_extended_on() instead of print_on().
3431       print_extended_on(gclog_or_tty);
3432       gclog_or_tty->print_cr("");
3433 #ifndef PRODUCT
3434       if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3435         concurrent_mark()->print_reachable("at-verification-failure",
3436                                            vo, false /* all */);
3437       }
3438 #endif
3439       gclog_or_tty->flush();
3440     }
3441     guarantee(!failures, "there should not have been any failures");
3442   } else {
3443     if (!silent)
3444       gclog_or_tty->print("(SKIPPING roots, heapRegionSets, heapRegions, remset) ");
3445   }
3446 }
3447 
3448 class PrintRegionClosure: public HeapRegionClosure {
3449   outputStream* _st;
3450 public:
3451   PrintRegionClosure(outputStream* st) : _st(st) {}
3452   bool doHeapRegion(HeapRegion* r) {
3453     r->print_on(_st);
3454     return false;
3455   }
3456 };
3457 
3458 void G1CollectedHeap::print_on(outputStream* st) const {
3459   st->print(" %-20s", "garbage-first heap");
3460   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3461             capacity()/K, used_unlocked()/K);
3462   st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3463             _g1_storage.low_boundary(),
3464             _g1_storage.high(),
3465             _g1_storage.high_boundary());
3466   st->cr();
3467   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3468   uint young_regions = _young_list->length();
3469   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3470             (size_t) young_regions * HeapRegion::GrainBytes / K);
3471   uint survivor_regions = g1_policy()->recorded_survivor_regions();
3472   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3473             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3474   st->cr();
3475   MetaspaceAux::print_on(st);
3476 }
3477 
3478 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3479   print_on(st);
3480 
3481   // Print the per-region information.
3482   st->cr();
3483   st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3484                "HS=humongous(starts), HC=humongous(continues), "
3485                "CS=collection set, F=free, TS=gc time stamp, "
3486                "PTAMS=previous top-at-mark-start, "
3487                "NTAMS=next top-at-mark-start)");
3488   PrintRegionClosure blk(st);
3489   heap_region_iterate(&blk);
3490 }
3491 
3492 void G1CollectedHeap::print_on_error(outputStream* st) const {
3493   this->CollectedHeap::print_on_error(st);
3494 
3495   if (_cm != NULL) {
3496     st->cr();
3497     _cm->print_on_error(st);
3498   }
3499 }
3500 
3501 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3502   if (G1CollectedHeap::use_parallel_gc_threads()) {
3503     workers()->print_worker_threads_on(st);
3504   }
3505   _cmThread->print_on(st);
3506   st->cr();
3507   _cm->print_worker_threads_on(st);
3508   _cg1r->print_worker_threads_on(st);
3509 }
3510 
3511 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3512   if (G1CollectedHeap::use_parallel_gc_threads()) {
3513     workers()->threads_do(tc);
3514   }
3515   tc->do_thread(_cmThread);
3516   _cg1r->threads_do(tc);
3517 }
3518 
3519 void G1CollectedHeap::print_tracing_info() const {
3520   // We'll overload this to mean "trace GC pause statistics."
3521   if (TraceGen0Time || TraceGen1Time) {
3522     // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3523     // to that.
3524     g1_policy()->print_tracing_info();
3525   }
3526   if (G1SummarizeRSetStats) {
3527     g1_rem_set()->print_summary_info();
3528   }
3529   if (G1SummarizeConcMark) {
3530     concurrent_mark()->print_summary_info();
3531   }
3532   g1_policy()->print_yg_surv_rate_info();
3533   SpecializationStats::print();
3534 }
3535 
3536 #ifndef PRODUCT
3537 // Helpful for debugging RSet issues.
3538 
3539 class PrintRSetsClosure : public HeapRegionClosure {
3540 private:
3541   const char* _msg;
3542   size_t _occupied_sum;
3543 
3544 public:
3545   bool doHeapRegion(HeapRegion* r) {
3546     HeapRegionRemSet* hrrs = r->rem_set();
3547     size_t occupied = hrrs->occupied();
3548     _occupied_sum += occupied;
3549 
3550     gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3551                            HR_FORMAT_PARAMS(r));
3552     if (occupied == 0) {
3553       gclog_or_tty->print_cr("  RSet is empty");
3554     } else {
3555       hrrs->print();
3556     }
3557     gclog_or_tty->print_cr("----------");
3558     return false;
3559   }
3560 
3561   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3562     gclog_or_tty->cr();
3563     gclog_or_tty->print_cr("========================================");
3564     gclog_or_tty->print_cr(msg);
3565     gclog_or_tty->cr();
3566   }
3567 
3568   ~PrintRSetsClosure() {
3569     gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3570     gclog_or_tty->print_cr("========================================");
3571     gclog_or_tty->cr();
3572   }
3573 };
3574 
3575 void G1CollectedHeap::print_cset_rsets() {
3576   PrintRSetsClosure cl("Printing CSet RSets");
3577   collection_set_iterate(&cl);
3578 }
3579 
3580 void G1CollectedHeap::print_all_rsets() {
3581   PrintRSetsClosure cl("Printing All RSets");;
3582   heap_region_iterate(&cl);
3583 }
3584 #endif // PRODUCT
3585 
3586 G1CollectedHeap* G1CollectedHeap::heap() {
3587   assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3588          "not a garbage-first heap");
3589   return _g1h;
3590 }
3591 
3592 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3593   // always_do_update_barrier = false;
3594   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3595   // Fill TLAB's and such
3596   ensure_parsability(true);
3597 }
3598 
3599 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) {
3600 
3601   if (G1SummarizeRSetStats &&
3602       (G1SummarizeRSetStatsPeriod > 0) &&
3603       // we are at the end of the GC. Total collections has already been increased.
3604       ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) {
3605     g1_rem_set()->print_periodic_summary_info();
3606   }
3607 
3608   // FIXME: what is this about?
3609   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3610   // is set.
3611   COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3612                         "derived pointer present"));
3613   // always_do_update_barrier = true;
3614 
3615   // We have just completed a GC. Update the soft reference
3616   // policy with the new heap occupancy
3617   Universe::update_heap_info_at_gc();
3618 }
3619 
3620 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3621                                                unsigned int gc_count_before,
3622                                                bool* succeeded) {
3623   assert_heap_not_locked_and_not_at_safepoint();
3624   g1_policy()->record_stop_world_start();
3625   VM_G1IncCollectionPause op(gc_count_before,
3626                              word_size,
3627                              false, /* should_initiate_conc_mark */
3628                              g1_policy()->max_pause_time_ms(),
3629                              GCCause::_g1_inc_collection_pause);
3630   VMThread::execute(&op);
3631 
3632   HeapWord* result = op.result();
3633   bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3634   assert(result == NULL || ret_succeeded,
3635          "the result should be NULL if the VM did not succeed");
3636   *succeeded = ret_succeeded;
3637 
3638   assert_heap_not_locked();
3639   return result;
3640 }
3641 
3642 void
3643 G1CollectedHeap::doConcurrentMark() {
3644   MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3645   if (!_cmThread->in_progress()) {
3646     _cmThread->set_started();
3647     CGC_lock->notify();
3648   }
3649 }
3650 
3651 size_t G1CollectedHeap::pending_card_num() {
3652   size_t extra_cards = 0;
3653   JavaThread *curr = Threads::first();
3654   while (curr != NULL) {
3655     DirtyCardQueue& dcq = curr->dirty_card_queue();
3656     extra_cards += dcq.size();
3657     curr = curr->next();
3658   }
3659   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3660   size_t buffer_size = dcqs.buffer_size();
3661   size_t buffer_num = dcqs.completed_buffers_num();
3662 
3663   // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
3664   // in bytes - not the number of 'entries'. We need to convert
3665   // into a number of cards.
3666   return (buffer_size * buffer_num + extra_cards) / oopSize;
3667 }
3668 
3669 size_t G1CollectedHeap::cards_scanned() {
3670   return g1_rem_set()->cardsScanned();
3671 }
3672 
3673 void
3674 G1CollectedHeap::setup_surviving_young_words() {
3675   assert(_surviving_young_words == NULL, "pre-condition");
3676   uint array_length = g1_policy()->young_cset_region_length();
3677   _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3678   if (_surviving_young_words == NULL) {
3679     vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR,
3680                           "Not enough space for young surv words summary.");
3681   }
3682   memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3683 #ifdef ASSERT
3684   for (uint i = 0;  i < array_length; ++i) {
3685     assert( _surviving_young_words[i] == 0, "memset above" );
3686   }
3687 #endif // !ASSERT
3688 }
3689 
3690 void
3691 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3692   MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3693   uint array_length = g1_policy()->young_cset_region_length();
3694   for (uint i = 0; i < array_length; ++i) {
3695     _surviving_young_words[i] += surv_young_words[i];
3696   }
3697 }
3698 
3699 void
3700 G1CollectedHeap::cleanup_surviving_young_words() {
3701   guarantee( _surviving_young_words != NULL, "pre-condition" );
3702   FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC);
3703   _surviving_young_words = NULL;
3704 }
3705 
3706 #ifdef ASSERT
3707 class VerifyCSetClosure: public HeapRegionClosure {
3708 public:
3709   bool doHeapRegion(HeapRegion* hr) {
3710     // Here we check that the CSet region's RSet is ready for parallel
3711     // iteration. The fields that we'll verify are only manipulated
3712     // when the region is part of a CSet and is collected. Afterwards,
3713     // we reset these fields when we clear the region's RSet (when the
3714     // region is freed) so they are ready when the region is
3715     // re-allocated. The only exception to this is if there's an
3716     // evacuation failure and instead of freeing the region we leave
3717     // it in the heap. In that case, we reset these fields during
3718     // evacuation failure handling.
3719     guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3720 
3721     // Here's a good place to add any other checks we'd like to
3722     // perform on CSet regions.
3723     return false;
3724   }
3725 };
3726 #endif // ASSERT
3727 
3728 #if TASKQUEUE_STATS
3729 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3730   st->print_raw_cr("GC Task Stats");
3731   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3732   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3733 }
3734 
3735 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3736   print_taskqueue_stats_hdr(st);
3737 
3738   TaskQueueStats totals;
3739   const int n = workers() != NULL ? workers()->total_workers() : 1;
3740   for (int i = 0; i < n; ++i) {
3741     st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3742     totals += task_queue(i)->stats;
3743   }
3744   st->print_raw("tot "); totals.print(st); st->cr();
3745 
3746   DEBUG_ONLY(totals.verify());
3747 }
3748 
3749 void G1CollectedHeap::reset_taskqueue_stats() {
3750   const int n = workers() != NULL ? workers()->total_workers() : 1;
3751   for (int i = 0; i < n; ++i) {
3752     task_queue(i)->stats.reset();
3753   }
3754 }
3755 #endif // TASKQUEUE_STATS
3756 
3757 void G1CollectedHeap::log_gc_header() {
3758   if (!G1Log::fine()) {
3759     return;
3760   }
3761 
3762   gclog_or_tty->date_stamp(PrintGCDateStamps);
3763   gclog_or_tty->stamp(PrintGCTimeStamps);
3764 
3765   GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
3766     .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)")
3767     .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : "");
3768 
3769   gclog_or_tty->print("[%s", (const char*)gc_cause_str);
3770 }
3771 
3772 void G1CollectedHeap::log_gc_footer(double pause_time_sec) {
3773   if (!G1Log::fine()) {
3774     return;
3775   }
3776 
3777   if (G1Log::finer()) {
3778     if (evacuation_failed()) {
3779       gclog_or_tty->print(" (to-space exhausted)");
3780     }
3781     gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3782     g1_policy()->phase_times()->note_gc_end();
3783     g1_policy()->phase_times()->print(pause_time_sec);
3784     g1_policy()->print_detailed_heap_transition();
3785   } else {
3786     if (evacuation_failed()) {
3787       gclog_or_tty->print("--");
3788     }
3789     g1_policy()->print_heap_transition();
3790     gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3791   }
3792   gclog_or_tty->flush();
3793 }
3794 
3795 bool
3796 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3797   assert_at_safepoint(true /* should_be_vm_thread */);
3798   guarantee(!is_gc_active(), "collection is not reentrant");
3799 
3800   if (GC_locker::check_active_before_gc()) {
3801     return false;
3802   }
3803 
3804   _gc_timer_stw->register_gc_start(os::elapsed_counter());
3805 
3806   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3807 
3808   SvcGCMarker sgcm(SvcGCMarker::MINOR);
3809   ResourceMark rm;
3810 
3811   print_heap_before_gc();
3812   trace_heap_before_gc(_gc_tracer_stw);
3813 
3814   HRSPhaseSetter x(HRSPhaseEvacuation);
3815   verify_region_sets_optional();
3816   verify_dirty_young_regions();
3817 
3818   // This call will decide whether this pause is an initial-mark
3819   // pause. If it is, during_initial_mark_pause() will return true
3820   // for the duration of this pause.
3821   g1_policy()->decide_on_conc_mark_initiation();
3822 
3823   // We do not allow initial-mark to be piggy-backed on a mixed GC.
3824   assert(!g1_policy()->during_initial_mark_pause() ||
3825           g1_policy()->gcs_are_young(), "sanity");
3826 
3827   // We also do not allow mixed GCs during marking.
3828   assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3829 
3830   // Record whether this pause is an initial mark. When the current
3831   // thread has completed its logging output and it's safe to signal
3832   // the CM thread, the flag's value in the policy has been reset.
3833   bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3834 
3835   // Inner scope for scope based logging, timers, and stats collection
3836   {
3837     EvacuationInfo evacuation_info;
3838 
3839     if (g1_policy()->during_initial_mark_pause()) {
3840       // We are about to start a marking cycle, so we increment the
3841       // full collection counter.
3842       increment_old_marking_cycles_started();
3843       register_concurrent_cycle_start(_gc_timer_stw->gc_start());
3844     }
3845 
3846     _gc_tracer_stw->report_yc_type(yc_type());
3847 
3848     TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3849 
3850     int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
3851                                 workers()->active_workers() : 1);
3852     double pause_start_sec = os::elapsedTime();
3853     g1_policy()->phase_times()->note_gc_start(active_workers);
3854     log_gc_header();
3855 
3856     TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3857     TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3858 
3859     // If the secondary_free_list is not empty, append it to the
3860     // free_list. No need to wait for the cleanup operation to finish;
3861     // the region allocation code will check the secondary_free_list
3862     // and wait if necessary. If the G1StressConcRegionFreeing flag is
3863     // set, skip this step so that the region allocation code has to
3864     // get entries from the secondary_free_list.
3865     if (!G1StressConcRegionFreeing) {
3866       append_secondary_free_list_if_not_empty_with_lock();
3867     }
3868 
3869     assert(check_young_list_well_formed(),
3870       "young list should be well formed");
3871 
3872     // Don't dynamically change the number of GC threads this early.  A value of
3873     // 0 is used to indicate serial work.  When parallel work is done,
3874     // it will be set.
3875 
3876     { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3877       IsGCActiveMark x;
3878 
3879       gc_prologue(false);
3880       increment_total_collections(false /* full gc */);
3881       increment_gc_time_stamp();
3882 
3883       verify_before_gc();
3884 
3885       COMPILER2_PRESENT(DerivedPointerTable::clear());
3886 
3887       // Please see comment in g1CollectedHeap.hpp and
3888       // G1CollectedHeap::ref_processing_init() to see how
3889       // reference processing currently works in G1.
3890 
3891       // Enable discovery in the STW reference processor
3892       ref_processor_stw()->enable_discovery(true /*verify_disabled*/,
3893                                             true /*verify_no_refs*/);
3894 
3895       {
3896         // We want to temporarily turn off discovery by the
3897         // CM ref processor, if necessary, and turn it back on
3898         // on again later if we do. Using a scoped
3899         // NoRefDiscovery object will do this.
3900         NoRefDiscovery no_cm_discovery(ref_processor_cm());
3901 
3902         // Forget the current alloc region (we might even choose it to be part
3903         // of the collection set!).
3904         release_mutator_alloc_region();
3905 
3906         // We should call this after we retire the mutator alloc
3907         // region(s) so that all the ALLOC / RETIRE events are generated
3908         // before the start GC event.
3909         _hr_printer.start_gc(false /* full */, (size_t) total_collections());
3910 
3911         // This timing is only used by the ergonomics to handle our pause target.
3912         // It is unclear why this should not include the full pause. We will
3913         // investigate this in CR 7178365.
3914         //
3915         // Preserving the old comment here if that helps the investigation:
3916         //
3917         // The elapsed time induced by the start time below deliberately elides
3918         // the possible verification above.
3919         double sample_start_time_sec = os::elapsedTime();
3920 
3921 #if YOUNG_LIST_VERBOSE
3922         gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
3923         _young_list->print();
3924         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3925 #endif // YOUNG_LIST_VERBOSE
3926 
3927         g1_policy()->record_collection_pause_start(sample_start_time_sec);
3928 
3929         double scan_wait_start = os::elapsedTime();
3930         // We have to wait until the CM threads finish scanning the
3931         // root regions as it's the only way to ensure that all the
3932         // objects on them have been correctly scanned before we start
3933         // moving them during the GC.
3934         bool waited = _cm->root_regions()->wait_until_scan_finished();
3935         double wait_time_ms = 0.0;
3936         if (waited) {
3937           double scan_wait_end = os::elapsedTime();
3938           wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
3939         }
3940         g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
3941 
3942 #if YOUNG_LIST_VERBOSE
3943         gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
3944         _young_list->print();
3945 #endif // YOUNG_LIST_VERBOSE
3946 
3947         if (g1_policy()->during_initial_mark_pause()) {
3948           concurrent_mark()->checkpointRootsInitialPre();
3949         }
3950 
3951 #if YOUNG_LIST_VERBOSE
3952         gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
3953         _young_list->print();
3954         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3955 #endif // YOUNG_LIST_VERBOSE
3956 
3957         g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info);
3958 
3959         _cm->note_start_of_gc();
3960         // We should not verify the per-thread SATB buffers given that
3961         // we have not filtered them yet (we'll do so during the
3962         // GC). We also call this after finalize_cset() to
3963         // ensure that the CSet has been finalized.
3964         _cm->verify_no_cset_oops(true  /* verify_stacks */,
3965                                  true  /* verify_enqueued_buffers */,
3966                                  false /* verify_thread_buffers */,
3967                                  true  /* verify_fingers */);
3968 
3969         if (_hr_printer.is_active()) {
3970           HeapRegion* hr = g1_policy()->collection_set();
3971           while (hr != NULL) {
3972             G1HRPrinter::RegionType type;
3973             if (!hr->is_young()) {
3974               type = G1HRPrinter::Old;
3975             } else if (hr->is_survivor()) {
3976               type = G1HRPrinter::Survivor;
3977             } else {
3978               type = G1HRPrinter::Eden;
3979             }
3980             _hr_printer.cset(hr);
3981             hr = hr->next_in_collection_set();
3982           }
3983         }
3984 
3985 #ifdef ASSERT
3986         VerifyCSetClosure cl;
3987         collection_set_iterate(&cl);
3988 #endif // ASSERT
3989 
3990         setup_surviving_young_words();
3991 
3992         // Initialize the GC alloc regions.
3993         init_gc_alloc_regions(evacuation_info);
3994 
3995         // Actually do the work...
3996         evacuate_collection_set(evacuation_info);
3997 
3998         // We do this to mainly verify the per-thread SATB buffers
3999         // (which have been filtered by now) since we didn't verify
4000         // them earlier. No point in re-checking the stacks / enqueued
4001         // buffers given that the CSet has not changed since last time
4002         // we checked.
4003         _cm->verify_no_cset_oops(false /* verify_stacks */,
4004                                  false /* verify_enqueued_buffers */,
4005                                  true  /* verify_thread_buffers */,
4006                                  true  /* verify_fingers */);
4007 
4008         free_collection_set(g1_policy()->collection_set(), evacuation_info);
4009         g1_policy()->clear_collection_set();
4010 
4011         cleanup_surviving_young_words();
4012 
4013         // Start a new incremental collection set for the next pause.
4014         g1_policy()->start_incremental_cset_building();
4015 
4016         // Clear the _cset_fast_test bitmap in anticipation of adding
4017         // regions to the incremental collection set for the next
4018         // evacuation pause.
4019         clear_cset_fast_test();
4020 
4021         _young_list->reset_sampled_info();
4022 
4023         // Don't check the whole heap at this point as the
4024         // GC alloc regions from this pause have been tagged
4025         // as survivors and moved on to the survivor list.
4026         // Survivor regions will fail the !is_young() check.
4027         assert(check_young_list_empty(false /* check_heap */),
4028           "young list should be empty");
4029 
4030 #if YOUNG_LIST_VERBOSE
4031         gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
4032         _young_list->print();
4033 #endif // YOUNG_LIST_VERBOSE
4034 
4035         g1_policy()->record_survivor_regions(_young_list->survivor_length(),
4036                                              _young_list->first_survivor_region(),
4037                                              _young_list->last_survivor_region());
4038 
4039         _young_list->reset_auxilary_lists();
4040 
4041         if (evacuation_failed()) {
4042           _summary_bytes_used = recalculate_used();
4043           uint n_queues = MAX2((int)ParallelGCThreads, 1);
4044           for (uint i = 0; i < n_queues; i++) {
4045             if (_evacuation_failed_info_array[i].has_failed()) {
4046               _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
4047             }
4048           }
4049         } else {
4050           // The "used" of the the collection set have already been subtracted
4051           // when they were freed.  Add in the bytes evacuated.
4052           _summary_bytes_used += g1_policy()->bytes_copied_during_gc();
4053         }
4054 
4055         if (g1_policy()->during_initial_mark_pause()) {
4056           // We have to do this before we notify the CM threads that
4057           // they can start working to make sure that all the
4058           // appropriate initialization is done on the CM object.
4059           concurrent_mark()->checkpointRootsInitialPost();
4060           set_marking_started();
4061           // Note that we don't actually trigger the CM thread at
4062           // this point. We do that later when we're sure that
4063           // the current thread has completed its logging output.
4064         }
4065 
4066         allocate_dummy_regions();
4067 
4068 #if YOUNG_LIST_VERBOSE
4069         gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
4070         _young_list->print();
4071         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4072 #endif // YOUNG_LIST_VERBOSE
4073 
4074         init_mutator_alloc_region();
4075 
4076         {
4077           size_t expand_bytes = g1_policy()->expansion_amount();
4078           if (expand_bytes > 0) {
4079             size_t bytes_before = capacity();
4080             // No need for an ergo verbose message here,
4081             // expansion_amount() does this when it returns a value > 0.
4082             if (!expand(expand_bytes)) {
4083               // We failed to expand the heap so let's verify that
4084               // committed/uncommitted amount match the backing store
4085               assert(capacity() == _g1_storage.committed_size(), "committed size mismatch");
4086               assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch");
4087             }
4088           }
4089         }
4090 
4091         // We redo the verification but now wrt to the new CSet which
4092         // has just got initialized after the previous CSet was freed.
4093         _cm->verify_no_cset_oops(true  /* verify_stacks */,
4094                                  true  /* verify_enqueued_buffers */,
4095                                  true  /* verify_thread_buffers */,
4096                                  true  /* verify_fingers */);
4097         _cm->note_end_of_gc();
4098 
4099         // This timing is only used by the ergonomics to handle our pause target.
4100         // It is unclear why this should not include the full pause. We will
4101         // investigate this in CR 7178365.
4102         double sample_end_time_sec = os::elapsedTime();
4103         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
4104         g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info);
4105 
4106         MemoryService::track_memory_usage();
4107 
4108         // In prepare_for_verify() below we'll need to scan the deferred
4109         // update buffers to bring the RSets up-to-date if
4110         // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
4111         // the update buffers we'll probably need to scan cards on the
4112         // regions we just allocated to (i.e., the GC alloc
4113         // regions). However, during the last GC we called
4114         // set_saved_mark() on all the GC alloc regions, so card
4115         // scanning might skip the [saved_mark_word()...top()] area of
4116         // those regions (i.e., the area we allocated objects into
4117         // during the last GC). But it shouldn't. Given that
4118         // saved_mark_word() is conditional on whether the GC time stamp
4119         // on the region is current or not, by incrementing the GC time
4120         // stamp here we invalidate all the GC time stamps on all the
4121         // regions and saved_mark_word() will simply return top() for
4122         // all the regions. This is a nicer way of ensuring this rather
4123         // than iterating over the regions and fixing them. In fact, the
4124         // GC time stamp increment here also ensures that
4125         // saved_mark_word() will return top() between pauses, i.e.,
4126         // during concurrent refinement. So we don't need the
4127         // is_gc_active() check to decided which top to use when
4128         // scanning cards (see CR 7039627).
4129         increment_gc_time_stamp();
4130 
4131         verify_after_gc();
4132 
4133         assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
4134         ref_processor_stw()->verify_no_references_recorded();
4135 
4136         // CM reference discovery will be re-enabled if necessary.
4137       }
4138 
4139       // We should do this after we potentially expand the heap so
4140       // that all the COMMIT events are generated before the end GC
4141       // event, and after we retire the GC alloc regions so that all
4142       // RETIRE events are generated before the end GC event.
4143       _hr_printer.end_gc(false /* full */, (size_t) total_collections());
4144 
4145       if (mark_in_progress()) {
4146         concurrent_mark()->update_g1_committed();
4147       }
4148 
4149 #ifdef TRACESPINNING
4150       ParallelTaskTerminator::print_termination_counts();
4151 #endif
4152 
4153       gc_epilogue(false);
4154     }
4155 
4156     // Print the remainder of the GC log output.
4157     log_gc_footer(os::elapsedTime() - pause_start_sec);
4158 
4159     // It is not yet to safe to tell the concurrent mark to
4160     // start as we have some optional output below. We don't want the
4161     // output from the concurrent mark thread interfering with this
4162     // logging output either.
4163 
4164     _hrs.verify_optional();
4165     verify_region_sets_optional();
4166 
4167     TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
4168     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
4169 
4170     print_heap_after_gc();
4171     trace_heap_after_gc(_gc_tracer_stw);
4172 
4173     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
4174     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
4175     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
4176     // before any GC notifications are raised.
4177     g1mm()->update_sizes();
4178 
4179     _gc_tracer_stw->report_evacuation_info(&evacuation_info);
4180     _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
4181     _gc_timer_stw->register_gc_end(os::elapsed_counter());
4182     _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
4183   }
4184   // It should now be safe to tell the concurrent mark thread to start
4185   // without its logging output interfering with the logging output
4186   // that came from the pause.
4187 
4188   if (should_start_conc_mark) {
4189     // CAUTION: after the doConcurrentMark() call below,
4190     // the concurrent marking thread(s) could be running
4191     // concurrently with us. Make sure that anything after
4192     // this point does not assume that we are the only GC thread
4193     // running. Note: of course, the actual marking work will
4194     // not start until the safepoint itself is released in
4195     // ConcurrentGCThread::safepoint_desynchronize().
4196     doConcurrentMark();
4197   }
4198 
4199   return true;
4200 }
4201 
4202 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
4203 {
4204   size_t gclab_word_size;
4205   switch (purpose) {
4206     case GCAllocForSurvived:
4207       gclab_word_size = _survivor_plab_stats.desired_plab_sz();
4208       break;
4209     case GCAllocForTenured:
4210       gclab_word_size = _old_plab_stats.desired_plab_sz();
4211       break;
4212     default:
4213       assert(false, "unknown GCAllocPurpose");
4214       gclab_word_size = _old_plab_stats.desired_plab_sz();
4215       break;
4216   }
4217 
4218   // Prevent humongous PLAB sizes for two reasons:
4219   // * PLABs are allocated using a similar paths as oops, but should
4220   //   never be in a humongous region
4221   // * Allowing humongous PLABs needlessly churns the region free lists
4222   return MIN2(_humongous_object_threshold_in_words, gclab_word_size);
4223 }
4224 
4225 void G1CollectedHeap::init_mutator_alloc_region() {
4226   assert(_mutator_alloc_region.get() == NULL, "pre-condition");
4227   _mutator_alloc_region.init();
4228 }
4229 
4230 void G1CollectedHeap::release_mutator_alloc_region() {
4231   _mutator_alloc_region.release();
4232   assert(_mutator_alloc_region.get() == NULL, "post-condition");
4233 }
4234 
4235 void G1CollectedHeap::init_gc_alloc_regions(EvacuationInfo& evacuation_info) {
4236   assert_at_safepoint(true /* should_be_vm_thread */);
4237 
4238   _survivor_gc_alloc_region.init();
4239   _old_gc_alloc_region.init();
4240   HeapRegion* retained_region = _retained_old_gc_alloc_region;
4241   _retained_old_gc_alloc_region = NULL;
4242 
4243   // We will discard the current GC alloc region if:
4244   // a) it's in the collection set (it can happen!),
4245   // b) it's already full (no point in using it),
4246   // c) it's empty (this means that it was emptied during
4247   // a cleanup and it should be on the free list now), or
4248   // d) it's humongous (this means that it was emptied
4249   // during a cleanup and was added to the free list, but
4250   // has been subsequently used to allocate a humongous
4251   // object that may be less than the region size).
4252   if (retained_region != NULL &&
4253       !retained_region->in_collection_set() &&
4254       !(retained_region->top() == retained_region->end()) &&
4255       !retained_region->is_empty() &&
4256       !retained_region->isHumongous()) {
4257     retained_region->set_saved_mark();
4258     // The retained region was added to the old region set when it was
4259     // retired. We have to remove it now, since we don't allow regions
4260     // we allocate to in the region sets. We'll re-add it later, when
4261     // it's retired again.
4262     _old_set.remove(retained_region);
4263     bool during_im = g1_policy()->during_initial_mark_pause();
4264     retained_region->note_start_of_copying(during_im);
4265     _old_gc_alloc_region.set(retained_region);
4266     _hr_printer.reuse(retained_region);
4267     evacuation_info.set_alloc_regions_used_before(retained_region->used());
4268   }
4269 }
4270 
4271 void G1CollectedHeap::release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info) {
4272   evacuation_info.set_allocation_regions(_survivor_gc_alloc_region.count() +
4273                                          _old_gc_alloc_region.count());
4274   _survivor_gc_alloc_region.release();
4275   // If we have an old GC alloc region to release, we'll save it in
4276   // _retained_old_gc_alloc_region. If we don't
4277   // _retained_old_gc_alloc_region will become NULL. This is what we
4278   // want either way so no reason to check explicitly for either
4279   // condition.
4280   _retained_old_gc_alloc_region = _old_gc_alloc_region.release();
4281 
4282   if (ResizePLAB) {
4283     _survivor_plab_stats.adjust_desired_plab_sz(no_of_gc_workers);
4284     _old_plab_stats.adjust_desired_plab_sz(no_of_gc_workers);
4285   }
4286 }
4287 
4288 void G1CollectedHeap::abandon_gc_alloc_regions() {
4289   assert(_survivor_gc_alloc_region.get() == NULL, "pre-condition");
4290   assert(_old_gc_alloc_region.get() == NULL, "pre-condition");
4291   _retained_old_gc_alloc_region = NULL;
4292 }
4293 
4294 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4295   _drain_in_progress = false;
4296   set_evac_failure_closure(cl);
4297   _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4298 }
4299 
4300 void G1CollectedHeap::finalize_for_evac_failure() {
4301   assert(_evac_failure_scan_stack != NULL &&
4302          _evac_failure_scan_stack->length() == 0,
4303          "Postcondition");
4304   assert(!_drain_in_progress, "Postcondition");
4305   delete _evac_failure_scan_stack;
4306   _evac_failure_scan_stack = NULL;
4307 }
4308 
4309 void G1CollectedHeap::remove_self_forwarding_pointers() {
4310   assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4311 
4312   G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4313 
4314   if (G1CollectedHeap::use_parallel_gc_threads()) {
4315     set_par_threads();
4316     workers()->run_task(&rsfp_task);
4317     set_par_threads(0);
4318   } else {
4319     rsfp_task.work(0);
4320   }
4321 
4322   assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity");
4323 
4324   // Reset the claim values in the regions in the collection set.
4325   reset_cset_heap_region_claim_values();
4326 
4327   assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4328 
4329   // Now restore saved marks, if any.
4330   assert(_objs_with_preserved_marks.size() ==
4331             _preserved_marks_of_objs.size(), "Both or none.");
4332   while (!_objs_with_preserved_marks.is_empty()) {
4333     oop obj = _objs_with_preserved_marks.pop();
4334     markOop m = _preserved_marks_of_objs.pop();
4335     obj->set_mark(m);
4336   }
4337   _objs_with_preserved_marks.clear(true);
4338   _preserved_marks_of_objs.clear(true);
4339 }
4340 
4341 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4342   _evac_failure_scan_stack->push(obj);
4343 }
4344 
4345 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4346   assert(_evac_failure_scan_stack != NULL, "precondition");
4347 
4348   while (_evac_failure_scan_stack->length() > 0) {
4349      oop obj = _evac_failure_scan_stack->pop();
4350      _evac_failure_closure->set_region(heap_region_containing(obj));
4351      obj->oop_iterate_backwards(_evac_failure_closure);
4352   }
4353 }
4354 
4355 oop
4356 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state,
4357                                                oop old) {
4358   assert(obj_in_cs(old),
4359          err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4360                  (HeapWord*) old));
4361   markOop m = old->mark();
4362   oop forward_ptr = old->forward_to_atomic(old);
4363   if (forward_ptr == NULL) {
4364     // Forward-to-self succeeded.
4365     assert(_par_scan_state != NULL, "par scan state");
4366     OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4367     uint queue_num = _par_scan_state->queue_num();
4368 
4369     _evacuation_failed = true;
4370     _evacuation_failed_info_array[queue_num].register_copy_failure(old->size());
4371     if (_evac_failure_closure != cl) {
4372       MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4373       assert(!_drain_in_progress,
4374              "Should only be true while someone holds the lock.");
4375       // Set the global evac-failure closure to the current thread's.
4376       assert(_evac_failure_closure == NULL, "Or locking has failed.");
4377       set_evac_failure_closure(cl);
4378       // Now do the common part.
4379       handle_evacuation_failure_common(old, m);
4380       // Reset to NULL.
4381       set_evac_failure_closure(NULL);
4382     } else {
4383       // The lock is already held, and this is recursive.
4384       assert(_drain_in_progress, "This should only be the recursive case.");
4385       handle_evacuation_failure_common(old, m);
4386     }
4387     return old;
4388   } else {
4389     // Forward-to-self failed. Either someone else managed to allocate
4390     // space for this object (old != forward_ptr) or they beat us in
4391     // self-forwarding it (old == forward_ptr).
4392     assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4393            err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4394                    "should not be in the CSet",
4395                    (HeapWord*) old, (HeapWord*) forward_ptr));
4396     return forward_ptr;
4397   }
4398 }
4399 
4400 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4401   preserve_mark_if_necessary(old, m);
4402 
4403   HeapRegion* r = heap_region_containing(old);
4404   if (!r->evacuation_failed()) {
4405     r->set_evacuation_failed(true);
4406     _hr_printer.evac_failure(r);
4407   }
4408 
4409   push_on_evac_failure_scan_stack(old);
4410 
4411   if (!_drain_in_progress) {
4412     // prevent recursion in copy_to_survivor_space()
4413     _drain_in_progress = true;
4414     drain_evac_failure_scan_stack();
4415     _drain_in_progress = false;
4416   }
4417 }
4418 
4419 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4420   assert(evacuation_failed(), "Oversaving!");
4421   // We want to call the "for_promotion_failure" version only in the
4422   // case of a promotion failure.
4423   if (m->must_be_preserved_for_promotion_failure(obj)) {
4424     _objs_with_preserved_marks.push(obj);
4425     _preserved_marks_of_objs.push(m);
4426   }
4427 }
4428 
4429 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
4430                                                   size_t word_size) {
4431   if (purpose == GCAllocForSurvived) {
4432     HeapWord* result = survivor_attempt_allocation(word_size);
4433     if (result != NULL) {
4434       return result;
4435     } else {
4436       // Let's try to allocate in the old gen in case we can fit the
4437       // object there.
4438       return old_attempt_allocation(word_size);
4439     }
4440   } else {
4441     assert(purpose ==  GCAllocForTenured, "sanity");
4442     HeapWord* result = old_attempt_allocation(word_size);
4443     if (result != NULL) {
4444       return result;
4445     } else {
4446       // Let's try to allocate in the survivors in case we can fit the
4447       // object there.
4448       return survivor_attempt_allocation(word_size);
4449     }
4450   }
4451 
4452   ShouldNotReachHere();
4453   // Trying to keep some compilers happy.
4454   return NULL;
4455 }
4456 
4457 G1ParGCAllocBuffer::G1ParGCAllocBuffer(size_t gclab_word_size) :
4458   ParGCAllocBuffer(gclab_word_size), _retired(false) { }
4459 
4460 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, uint queue_num)
4461   : _g1h(g1h),
4462     _refs(g1h->task_queue(queue_num)),
4463     _dcq(&g1h->dirty_card_queue_set()),
4464     _ct_bs((CardTableModRefBS*)_g1h->barrier_set()),
4465     _g1_rem(g1h->g1_rem_set()),
4466     _hash_seed(17), _queue_num(queue_num),
4467     _term_attempts(0),
4468     _surviving_alloc_buffer(g1h->desired_plab_sz(GCAllocForSurvived)),
4469     _tenured_alloc_buffer(g1h->desired_plab_sz(GCAllocForTenured)),
4470     _age_table(false),
4471     _strong_roots_time(0), _term_time(0),
4472     _alloc_buffer_waste(0), _undo_waste(0) {
4473   // we allocate G1YoungSurvRateNumRegions plus one entries, since
4474   // we "sacrifice" entry 0 to keep track of surviving bytes for
4475   // non-young regions (where the age is -1)
4476   // We also add a few elements at the beginning and at the end in
4477   // an attempt to eliminate cache contention
4478   uint real_length = 1 + _g1h->g1_policy()->young_cset_region_length();
4479   uint array_length = PADDING_ELEM_NUM +
4480                       real_length +
4481                       PADDING_ELEM_NUM;
4482   _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length, mtGC);
4483   if (_surviving_young_words_base == NULL)
4484     vm_exit_out_of_memory(array_length * sizeof(size_t), OOM_MALLOC_ERROR,
4485                           "Not enough space for young surv histo.");
4486   _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM;
4487   memset(_surviving_young_words, 0, (size_t) real_length * sizeof(size_t));
4488 
4489   _alloc_buffers[GCAllocForSurvived] = &_surviving_alloc_buffer;
4490   _alloc_buffers[GCAllocForTenured]  = &_tenured_alloc_buffer;
4491 
4492   _start = os::elapsedTime();
4493 }
4494 
4495 void
4496 G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st)
4497 {
4498   st->print_raw_cr("GC Termination Stats");
4499   st->print_raw_cr("     elapsed  --strong roots-- -------termination-------"
4500                    " ------waste (KiB)------");
4501   st->print_raw_cr("thr     ms        ms      %        ms      %    attempts"
4502                    "  total   alloc    undo");
4503   st->print_raw_cr("--- --------- --------- ------ --------- ------ --------"
4504                    " ------- ------- -------");
4505 }
4506 
4507 void
4508 G1ParScanThreadState::print_termination_stats(int i,
4509                                               outputStream* const st) const
4510 {
4511   const double elapsed_ms = elapsed_time() * 1000.0;
4512   const double s_roots_ms = strong_roots_time() * 1000.0;
4513   const double term_ms    = term_time() * 1000.0;
4514   st->print_cr("%3d %9.2f %9.2f %6.2f "
4515                "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
4516                SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
4517                i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms,
4518                term_ms, term_ms * 100 / elapsed_ms, term_attempts(),
4519                (alloc_buffer_waste() + undo_waste()) * HeapWordSize / K,
4520                alloc_buffer_waste() * HeapWordSize / K,
4521                undo_waste() * HeapWordSize / K);
4522 }
4523 
4524 #ifdef ASSERT
4525 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const {
4526   assert(ref != NULL, "invariant");
4527   assert(UseCompressedOops, "sanity");
4528   assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, ref));
4529   oop p = oopDesc::load_decode_heap_oop(ref);
4530   assert(_g1h->is_in_g1_reserved(p),
4531          err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4532   return true;
4533 }
4534 
4535 bool G1ParScanThreadState::verify_ref(oop* ref) const {
4536   assert(ref != NULL, "invariant");
4537   if (has_partial_array_mask(ref)) {
4538     // Must be in the collection set--it's already been copied.
4539     oop p = clear_partial_array_mask(ref);
4540     assert(_g1h->obj_in_cs(p),
4541            err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4542   } else {
4543     oop p = oopDesc::load_decode_heap_oop(ref);
4544     assert(_g1h->is_in_g1_reserved(p),
4545            err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4546   }
4547   return true;
4548 }
4549 
4550 bool G1ParScanThreadState::verify_task(StarTask ref) const {
4551   if (ref.is_narrow()) {
4552     return verify_ref((narrowOop*) ref);
4553   } else {
4554     return verify_ref((oop*) ref);
4555   }
4556 }
4557 #endif // ASSERT
4558 
4559 void G1ParScanThreadState::trim_queue() {
4560   assert(_evac_cl != NULL, "not set");
4561   assert(_evac_failure_cl != NULL, "not set");
4562   assert(_partial_scan_cl != NULL, "not set");
4563 
4564   StarTask ref;
4565   do {
4566     // Drain the overflow stack first, so other threads can steal.
4567     while (refs()->pop_overflow(ref)) {
4568       deal_with_reference(ref);
4569     }
4570 
4571     while (refs()->pop_local(ref)) {
4572       deal_with_reference(ref);
4573     }
4574   } while (!refs()->is_empty());
4575 }
4576 
4577 G1ParClosureSuper::G1ParClosureSuper(G1CollectedHeap* g1,
4578                                      G1ParScanThreadState* par_scan_state) :
4579   _g1(g1), _g1_rem(_g1->g1_rem_set()), _cm(_g1->concurrent_mark()),
4580   _par_scan_state(par_scan_state),
4581   _worker_id(par_scan_state->queue_num()),
4582   _during_initial_mark(_g1->g1_policy()->during_initial_mark_pause()),
4583   _mark_in_progress(_g1->mark_in_progress()) { }
4584 
4585 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4586 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>::mark_object(oop obj) {
4587 #ifdef ASSERT
4588   HeapRegion* hr = _g1->heap_region_containing(obj);
4589   assert(hr != NULL, "sanity");
4590   assert(!hr->in_collection_set(), "should not mark objects in the CSet");
4591 #endif // ASSERT
4592 
4593   // We know that the object is not moving so it's safe to read its size.
4594   _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4595 }
4596 
4597 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4598 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4599   ::mark_forwarded_object(oop from_obj, oop to_obj) {
4600 #ifdef ASSERT
4601   assert(from_obj->is_forwarded(), "from obj should be forwarded");
4602   assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4603   assert(from_obj != to_obj, "should not be self-forwarded");
4604 
4605   HeapRegion* from_hr = _g1->heap_region_containing(from_obj);
4606   assert(from_hr != NULL, "sanity");
4607   assert(from_hr->in_collection_set(), "from obj should be in the CSet");
4608 
4609   HeapRegion* to_hr = _g1->heap_region_containing(to_obj);
4610   assert(to_hr != NULL, "sanity");
4611   assert(!to_hr->in_collection_set(), "should not mark objects in the CSet");
4612 #endif // ASSERT
4613 
4614   // The object might be in the process of being copied by another
4615   // worker so we cannot trust that its to-space image is
4616   // well-formed. So we have to read its size from its from-space
4617   // image which we know should not be changing.
4618   _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4619 }
4620 
4621 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4622 oop G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4623   ::copy_to_survivor_space(oop old) {
4624   size_t word_sz = old->size();
4625   HeapRegion* from_region = _g1->heap_region_containing_raw(old);
4626   // +1 to make the -1 indexes valid...
4627   int       young_index = from_region->young_index_in_cset()+1;
4628   assert( (from_region->is_young() && young_index >  0) ||
4629          (!from_region->is_young() && young_index == 0), "invariant" );
4630   G1CollectorPolicy* g1p = _g1->g1_policy();
4631   markOop m = old->mark();
4632   int age = m->has_displaced_mark_helper() ? m->displaced_mark_helper()->age()
4633                                            : m->age();
4634   GCAllocPurpose alloc_purpose = g1p->evacuation_destination(from_region, age,
4635                                                              word_sz);
4636   HeapWord* obj_ptr = _par_scan_state->allocate(alloc_purpose, word_sz);
4637 #ifndef PRODUCT
4638   // Should this evacuation fail?
4639   if (_g1->evacuation_should_fail()) {
4640     if (obj_ptr != NULL) {
4641       _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz);
4642       obj_ptr = NULL;
4643     }
4644   }
4645 #endif // !PRODUCT
4646 
4647   if (obj_ptr == NULL) {
4648     // This will either forward-to-self, or detect that someone else has
4649     // installed a forwarding pointer.
4650     return _g1->handle_evacuation_failure_par(_par_scan_state, old);
4651   }
4652 
4653   oop obj = oop(obj_ptr);
4654 
4655   // We're going to allocate linearly, so might as well prefetch ahead.
4656   Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
4657 
4658   oop forward_ptr = old->forward_to_atomic(obj);
4659   if (forward_ptr == NULL) {
4660     Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
4661     if (g1p->track_object_age(alloc_purpose)) {
4662       // We could simply do obj->incr_age(). However, this causes a
4663       // performance issue. obj->incr_age() will first check whether
4664       // the object has a displaced mark by checking its mark word;
4665       // getting the mark word from the new location of the object
4666       // stalls. So, given that we already have the mark word and we
4667       // are about to install it anyway, it's better to increase the
4668       // age on the mark word, when the object does not have a
4669       // displaced mark word. We're not expecting many objects to have
4670       // a displaced marked word, so that case is not optimized
4671       // further (it could be...) and we simply call obj->incr_age().
4672 
4673       if (m->has_displaced_mark_helper()) {
4674         // in this case, we have to install the mark word first,
4675         // otherwise obj looks to be forwarded (the old mark word,
4676         // which contains the forward pointer, was copied)
4677         obj->set_mark(m);
4678         obj->incr_age();
4679       } else {
4680         m = m->incr_age();
4681         obj->set_mark(m);
4682       }
4683       _par_scan_state->age_table()->add(obj, word_sz);
4684     } else {
4685       obj->set_mark(m);
4686     }
4687 
4688     size_t* surv_young_words = _par_scan_state->surviving_young_words();
4689     surv_young_words[young_index] += word_sz;
4690 
4691     if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
4692       // We keep track of the next start index in the length field of
4693       // the to-space object. The actual length can be found in the
4694       // length field of the from-space object.
4695       arrayOop(obj)->set_length(0);
4696       oop* old_p = set_partial_array_mask(old);
4697       _par_scan_state->push_on_queue(old_p);
4698     } else {
4699       // No point in using the slower heap_region_containing() method,
4700       // given that we know obj is in the heap.
4701       _scanner.set_region(_g1->heap_region_containing_raw(obj));
4702       obj->oop_iterate_backwards(&_scanner);
4703     }
4704   } else {
4705     _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz);
4706     obj = forward_ptr;
4707   }
4708   return obj;
4709 }
4710 
4711 template <class T>
4712 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) {
4713   if (_g1->heap_region_containing_raw(new_obj)->is_young()) {
4714     _scanned_klass->record_modified_oops();
4715   }
4716 }
4717 
4718 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4719 template <class T>
4720 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4721 ::do_oop_work(T* p) {
4722   oop obj = oopDesc::load_decode_heap_oop(p);
4723   assert(barrier != G1BarrierRS || obj != NULL,
4724          "Precondition: G1BarrierRS implies obj is non-NULL");
4725 
4726   assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4727 
4728   // here the null check is implicit in the cset_fast_test() test
4729   if (_g1->in_cset_fast_test(obj)) {
4730     oop forwardee;
4731     if (obj->is_forwarded()) {
4732       forwardee = obj->forwardee();
4733     } else {
4734       forwardee = copy_to_survivor_space(obj);
4735     }
4736     assert(forwardee != NULL, "forwardee should not be NULL");
4737     oopDesc::encode_store_heap_oop(p, forwardee);
4738     if (do_mark_object && forwardee != obj) {
4739       // If the object is self-forwarded we don't need to explicitly
4740       // mark it, the evacuation failure protocol will do so.
4741       mark_forwarded_object(obj, forwardee);
4742     }
4743 
4744     // When scanning the RS, we only care about objs in CS.
4745     if (barrier == G1BarrierRS) {
4746       _par_scan_state->update_rs(_from, p, _worker_id);
4747     } else if (barrier == G1BarrierKlass) {
4748       do_klass_barrier(p, forwardee);
4749     }
4750   } else {
4751     // The object is not in collection set. If we're a root scanning
4752     // closure during an initial mark pause (i.e. do_mark_object will
4753     // be true) then attempt to mark the object.
4754     if (do_mark_object && _g1->is_in_g1_reserved(obj)) {
4755       mark_object(obj);
4756     }
4757   }
4758 
4759   if (barrier == G1BarrierEvac && obj != NULL) {
4760     _par_scan_state->update_rs(_from, p, _worker_id);
4761   }
4762 
4763   if (do_gen_barrier && obj != NULL) {
4764     par_do_barrier(p);
4765   }
4766 }
4767 
4768 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(oop* p);
4769 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(narrowOop* p);
4770 
4771 template <class T> void G1ParScanPartialArrayClosure::do_oop_nv(T* p) {
4772   assert(has_partial_array_mask(p), "invariant");
4773   oop from_obj = clear_partial_array_mask(p);
4774 
4775   assert(Universe::heap()->is_in_reserved(from_obj), "must be in heap.");
4776   assert(from_obj->is_objArray(), "must be obj array");
4777   objArrayOop from_obj_array = objArrayOop(from_obj);
4778   // The from-space object contains the real length.
4779   int length                 = from_obj_array->length();
4780 
4781   assert(from_obj->is_forwarded(), "must be forwarded");
4782   oop to_obj                 = from_obj->forwardee();
4783   assert(from_obj != to_obj, "should not be chunking self-forwarded objects");
4784   objArrayOop to_obj_array   = objArrayOop(to_obj);
4785   // We keep track of the next start index in the length field of the
4786   // to-space object.
4787   int next_index             = to_obj_array->length();
4788   assert(0 <= next_index && next_index < length,
4789          err_msg("invariant, next index: %d, length: %d", next_index, length));
4790 
4791   int start                  = next_index;
4792   int end                    = length;
4793   int remainder              = end - start;
4794   // We'll try not to push a range that's smaller than ParGCArrayScanChunk.
4795   if (remainder > 2 * ParGCArrayScanChunk) {
4796     end = start + ParGCArrayScanChunk;
4797     to_obj_array->set_length(end);
4798     // Push the remainder before we process the range in case another
4799     // worker has run out of things to do and can steal it.
4800     oop* from_obj_p = set_partial_array_mask(from_obj);
4801     _par_scan_state->push_on_queue(from_obj_p);
4802   } else {
4803     assert(length == end, "sanity");
4804     // We'll process the final range for this object. Restore the length
4805     // so that the heap remains parsable in case of evacuation failure.
4806     to_obj_array->set_length(end);
4807   }
4808   _scanner.set_region(_g1->heap_region_containing_raw(to_obj));
4809   // Process indexes [start,end). It will also process the header
4810   // along with the first chunk (i.e., the chunk with start == 0).
4811   // Note that at this point the length field of to_obj_array is not
4812   // correct given that we are using it to keep track of the next
4813   // start index. oop_iterate_range() (thankfully!) ignores the length
4814   // field and only relies on the start / end parameters.  It does
4815   // however return the size of the object which will be incorrect. So
4816   // we have to ignore it even if we wanted to use it.
4817   to_obj_array->oop_iterate_range(&_scanner, start, end);
4818 }
4819 
4820 class G1ParEvacuateFollowersClosure : public VoidClosure {
4821 protected:
4822   G1CollectedHeap*              _g1h;
4823   G1ParScanThreadState*         _par_scan_state;
4824   RefToScanQueueSet*            _queues;
4825   ParallelTaskTerminator*       _terminator;
4826 
4827   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
4828   RefToScanQueueSet*      queues()         { return _queues; }
4829   ParallelTaskTerminator* terminator()     { return _terminator; }
4830 
4831 public:
4832   G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4833                                 G1ParScanThreadState* par_scan_state,
4834                                 RefToScanQueueSet* queues,
4835                                 ParallelTaskTerminator* terminator)
4836     : _g1h(g1h), _par_scan_state(par_scan_state),
4837       _queues(queues), _terminator(terminator) {}
4838 
4839   void do_void();
4840 
4841 private:
4842   inline bool offer_termination();
4843 };
4844 
4845 bool G1ParEvacuateFollowersClosure::offer_termination() {
4846   G1ParScanThreadState* const pss = par_scan_state();
4847   pss->start_term_time();
4848   const bool res = terminator()->offer_termination();
4849   pss->end_term_time();
4850   return res;
4851 }
4852 
4853 void G1ParEvacuateFollowersClosure::do_void() {
4854   StarTask stolen_task;
4855   G1ParScanThreadState* const pss = par_scan_state();
4856   pss->trim_queue();
4857 
4858   do {
4859     while (queues()->steal(pss->queue_num(), pss->hash_seed(), stolen_task)) {
4860       assert(pss->verify_task(stolen_task), "sanity");
4861       if (stolen_task.is_narrow()) {
4862         pss->deal_with_reference((narrowOop*) stolen_task);
4863       } else {
4864         pss->deal_with_reference((oop*) stolen_task);
4865       }
4866 
4867       // We've just processed a reference and we might have made
4868       // available new entries on the queues. So we have to make sure
4869       // we drain the queues as necessary.
4870       pss->trim_queue();
4871     }
4872   } while (!offer_termination());
4873 
4874   pss->retire_alloc_buffers();
4875 }
4876 
4877 class G1KlassScanClosure : public KlassClosure {
4878  G1ParCopyHelper* _closure;
4879  bool             _process_only_dirty;
4880  int              _count;
4881  public:
4882   G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty)
4883       : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {}
4884   void do_klass(Klass* klass) {
4885     // If the klass has not been dirtied we know that there's
4886     // no references into  the young gen and we can skip it.
4887    if (!_process_only_dirty || klass->has_modified_oops()) {
4888       // Clean the klass since we're going to scavenge all the metadata.
4889       klass->clear_modified_oops();
4890 
4891       // Tell the closure that this klass is the Klass to scavenge
4892       // and is the one to dirty if oops are left pointing into the young gen.
4893       _closure->set_scanned_klass(klass);
4894 
4895       klass->oops_do(_closure);
4896 
4897       _closure->set_scanned_klass(NULL);
4898     }
4899     _count++;
4900   }
4901 };
4902 
4903 class G1ParTask : public AbstractGangTask {
4904 protected:
4905   G1CollectedHeap*       _g1h;
4906   RefToScanQueueSet      *_queues;
4907   ParallelTaskTerminator _terminator;
4908   uint _n_workers;
4909 
4910   Mutex _stats_lock;
4911   Mutex* stats_lock() { return &_stats_lock; }
4912 
4913   size_t getNCards() {
4914     return (_g1h->capacity() + G1BlockOffsetSharedArray::N_bytes - 1)
4915       / G1BlockOffsetSharedArray::N_bytes;
4916   }
4917 
4918 public:
4919   G1ParTask(G1CollectedHeap* g1h,
4920             RefToScanQueueSet *task_queues)
4921     : AbstractGangTask("G1 collection"),
4922       _g1h(g1h),
4923       _queues(task_queues),
4924       _terminator(0, _queues),
4925       _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4926   {}
4927 
4928   RefToScanQueueSet* queues() { return _queues; }
4929 
4930   RefToScanQueue *work_queue(int i) {
4931     return queues()->queue(i);
4932   }
4933 
4934   ParallelTaskTerminator* terminator() { return &_terminator; }
4935 
4936   virtual void set_for_termination(int active_workers) {
4937     // This task calls set_n_termination() in par_non_clean_card_iterate_work()
4938     // in the young space (_par_seq_tasks) in the G1 heap
4939     // for SequentialSubTasksDone.
4940     // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap
4941     // both of which need setting by set_n_termination().
4942     _g1h->SharedHeap::set_n_termination(active_workers);
4943     _g1h->set_n_termination(active_workers);
4944     terminator()->reset_for_reuse(active_workers);
4945     _n_workers = active_workers;
4946   }
4947 
4948   void work(uint worker_id) {
4949     if (worker_id >= _n_workers) return;  // no work needed this round
4950 
4951     double start_time_ms = os::elapsedTime() * 1000.0;
4952     _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms);
4953 
4954     {
4955       ResourceMark rm;
4956       HandleMark   hm;
4957 
4958       ReferenceProcessor*             rp = _g1h->ref_processor_stw();
4959 
4960       G1ParScanThreadState            pss(_g1h, worker_id);
4961       G1ParScanHeapEvacClosure        scan_evac_cl(_g1h, &pss, rp);
4962       G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
4963       G1ParScanPartialArrayClosure    partial_scan_cl(_g1h, &pss, rp);
4964 
4965       pss.set_evac_closure(&scan_evac_cl);
4966       pss.set_evac_failure_closure(&evac_failure_cl);
4967       pss.set_partial_scan_closure(&partial_scan_cl);
4968 
4969       G1ParScanExtRootClosure        only_scan_root_cl(_g1h, &pss, rp);
4970       G1ParScanMetadataClosure       only_scan_metadata_cl(_g1h, &pss, rp);
4971 
4972       G1ParScanAndMarkExtRootClosure scan_mark_root_cl(_g1h, &pss, rp);
4973       G1ParScanAndMarkMetadataClosure scan_mark_metadata_cl(_g1h, &pss, rp);
4974 
4975       bool only_young                 = _g1h->g1_policy()->gcs_are_young();
4976       G1KlassScanClosure              scan_mark_klasses_cl_s(&scan_mark_metadata_cl, false);
4977       G1KlassScanClosure              only_scan_klasses_cl_s(&only_scan_metadata_cl, only_young);
4978 
4979       OopClosure*                    scan_root_cl = &only_scan_root_cl;
4980       G1KlassScanClosure*            scan_klasses_cl = &only_scan_klasses_cl_s;
4981 
4982       if (_g1h->g1_policy()->during_initial_mark_pause()) {
4983         // We also need to mark copied objects.
4984         scan_root_cl = &scan_mark_root_cl;
4985         scan_klasses_cl = &scan_mark_klasses_cl_s;
4986       }
4987 
4988       G1ParPushHeapRSClosure          push_heap_rs_cl(_g1h, &pss);
4989 
4990       int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings | SharedHeap::SO_CodeCache;
4991 
4992       pss.start_strong_roots();
4993       _g1h->g1_process_strong_roots(/* is scavenging */ true,
4994                                     SharedHeap::ScanningOption(so),
4995                                     scan_root_cl,
4996                                     &push_heap_rs_cl,
4997                                     scan_klasses_cl,
4998                                     worker_id);
4999       pss.end_strong_roots();
5000 
5001       {
5002         double start = os::elapsedTime();
5003         G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
5004         evac.do_void();
5005         double elapsed_ms = (os::elapsedTime()-start)*1000.0;
5006         double term_ms = pss.term_time()*1000.0;
5007         _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms);
5008         _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts());
5009       }
5010       _g1h->g1_policy()->record_thread_age_table(pss.age_table());
5011       _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
5012 
5013       if (ParallelGCVerbose) {
5014         MutexLocker x(stats_lock());
5015         pss.print_termination_stats(worker_id);
5016       }
5017 
5018       assert(pss.refs()->is_empty(), "should be empty");
5019 
5020       // Close the inner scope so that the ResourceMark and HandleMark
5021       // destructors are executed here and are included as part of the
5022       // "GC Worker Time".
5023     }
5024 
5025     double end_time_ms = os::elapsedTime() * 1000.0;
5026     _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms);
5027   }
5028 };
5029 
5030 // *** Common G1 Evacuation Stuff
5031 
5032 // Closures that support the filtering of CodeBlobs scanned during
5033 // external root scanning.
5034 
5035 // Closure applied to reference fields in code blobs (specifically nmethods)
5036 // to determine whether an nmethod contains references that point into
5037 // the collection set. Used as a predicate when walking code roots so
5038 // that only nmethods that point into the collection set are added to the
5039 // 'marked' list.
5040 
5041 class G1FilteredCodeBlobToOopClosure : public CodeBlobToOopClosure {
5042 
5043   class G1PointsIntoCSOopClosure : public OopClosure {
5044     G1CollectedHeap* _g1;
5045     bool _points_into_cs;
5046   public:
5047     G1PointsIntoCSOopClosure(G1CollectedHeap* g1) :
5048       _g1(g1), _points_into_cs(false) { }
5049 
5050     bool points_into_cs() const { return _points_into_cs; }
5051 
5052     template <class T>
5053     void do_oop_nv(T* p) {
5054       if (!_points_into_cs) {
5055         T heap_oop = oopDesc::load_heap_oop(p);
5056         if (!oopDesc::is_null(heap_oop) &&
5057             _g1->in_cset_fast_test(oopDesc::decode_heap_oop_not_null(heap_oop))) {
5058           _points_into_cs = true;
5059         }
5060       }
5061     }
5062 
5063     virtual void do_oop(oop* p)        { do_oop_nv(p); }
5064     virtual void do_oop(narrowOop* p)  { do_oop_nv(p); }
5065   };
5066 
5067   G1CollectedHeap* _g1;
5068 
5069 public:
5070   G1FilteredCodeBlobToOopClosure(G1CollectedHeap* g1, OopClosure* cl) :
5071     CodeBlobToOopClosure(cl, true), _g1(g1) { }
5072 
5073   virtual void do_code_blob(CodeBlob* cb) {
5074     nmethod* nm = cb->as_nmethod_or_null();
5075     if (nm != NULL && !(nm->test_oops_do_mark())) {
5076       G1PointsIntoCSOopClosure predicate_cl(_g1);
5077       nm->oops_do(&predicate_cl);
5078 
5079       if (predicate_cl.points_into_cs()) {
5080         // At least one of the reference fields or the oop relocations
5081         // in the nmethod points into the collection set. We have to
5082         // 'mark' this nmethod.
5083         // Note: Revisit the following if CodeBlobToOopClosure::do_code_blob()
5084         // or MarkingCodeBlobClosure::do_code_blob() change.
5085         if (!nm->test_set_oops_do_mark()) {
5086           do_newly_marked_nmethod(nm);
5087         }
5088       }
5089     }
5090   }
5091 };
5092 
5093 // This method is run in a GC worker.
5094 
5095 void
5096 G1CollectedHeap::
5097 g1_process_strong_roots(bool is_scavenging,
5098                         ScanningOption so,
5099                         OopClosure* scan_non_heap_roots,
5100                         OopsInHeapRegionClosure* scan_rs,
5101                         G1KlassScanClosure* scan_klasses,
5102                         int worker_i) {
5103 
5104   // First scan the strong roots
5105   double ext_roots_start = os::elapsedTime();
5106   double closure_app_time_sec = 0.0;
5107 
5108   BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
5109 
5110   // Walk the code cache w/o buffering, because StarTask cannot handle
5111   // unaligned oop locations.
5112   G1FilteredCodeBlobToOopClosure eager_scan_code_roots(this, scan_non_heap_roots);
5113 
5114   process_strong_roots(false, // no scoping; this is parallel code
5115                        is_scavenging, so,
5116                        &buf_scan_non_heap_roots,
5117                        &eager_scan_code_roots,
5118                        scan_klasses
5119                        );
5120 
5121   // Now the CM ref_processor roots.
5122   if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
5123     // We need to treat the discovered reference lists of the
5124     // concurrent mark ref processor as roots and keep entries
5125     // (which are added by the marking threads) on them live
5126     // until they can be processed at the end of marking.
5127     ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
5128   }
5129 
5130   // Finish up any enqueued closure apps (attributed as object copy time).
5131   buf_scan_non_heap_roots.done();
5132 
5133   double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds();
5134 
5135   g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
5136 
5137   double ext_root_time_ms =
5138     ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0;
5139 
5140   g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
5141 
5142   // During conc marking we have to filter the per-thread SATB buffers
5143   // to make sure we remove any oops into the CSet (which will show up
5144   // as implicitly live).
5145   double satb_filtering_ms = 0.0;
5146   if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) {
5147     if (mark_in_progress()) {
5148       double satb_filter_start = os::elapsedTime();
5149 
5150       JavaThread::satb_mark_queue_set().filter_thread_buffers();
5151 
5152       satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0;
5153     }
5154   }
5155   g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms);
5156 
5157   // Now scan the complement of the collection set.
5158   if (scan_rs != NULL) {
5159     g1_rem_set()->oops_into_collection_set_do(scan_rs, worker_i);
5160   }
5161   _process_strong_tasks->all_tasks_completed();
5162 }
5163 
5164 void
5165 G1CollectedHeap::g1_process_weak_roots(OopClosure* root_closure) {
5166   CodeBlobToOopClosure roots_in_blobs(root_closure, /*do_marking=*/ false);
5167   SharedHeap::process_weak_roots(root_closure, &roots_in_blobs);
5168 }
5169 
5170 // Weak Reference Processing support
5171 
5172 // An always "is_alive" closure that is used to preserve referents.
5173 // If the object is non-null then it's alive.  Used in the preservation
5174 // of referent objects that are pointed to by reference objects
5175 // discovered by the CM ref processor.
5176 class G1AlwaysAliveClosure: public BoolObjectClosure {
5177   G1CollectedHeap* _g1;
5178 public:
5179   G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5180   bool do_object_b(oop p) {
5181     if (p != NULL) {
5182       return true;
5183     }
5184     return false;
5185   }
5186 };
5187 
5188 bool G1STWIsAliveClosure::do_object_b(oop p) {
5189   // An object is reachable if it is outside the collection set,
5190   // or is inside and copied.
5191   return !_g1->obj_in_cs(p) || p->is_forwarded();
5192 }
5193 
5194 // Non Copying Keep Alive closure
5195 class G1KeepAliveClosure: public OopClosure {
5196   G1CollectedHeap* _g1;
5197 public:
5198   G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5199   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
5200   void do_oop(      oop* p) {
5201     oop obj = *p;
5202 
5203     if (_g1->obj_in_cs(obj)) {
5204       assert( obj->is_forwarded(), "invariant" );
5205       *p = obj->forwardee();
5206     }
5207   }
5208 };
5209 
5210 // Copying Keep Alive closure - can be called from both
5211 // serial and parallel code as long as different worker
5212 // threads utilize different G1ParScanThreadState instances
5213 // and different queues.
5214 
5215 class G1CopyingKeepAliveClosure: public OopClosure {
5216   G1CollectedHeap*         _g1h;
5217   OopClosure*              _copy_non_heap_obj_cl;
5218   OopsInHeapRegionClosure* _copy_metadata_obj_cl;
5219   G1ParScanThreadState*    _par_scan_state;
5220 
5221 public:
5222   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
5223                             OopClosure* non_heap_obj_cl,
5224                             OopsInHeapRegionClosure* metadata_obj_cl,
5225                             G1ParScanThreadState* pss):
5226     _g1h(g1h),
5227     _copy_non_heap_obj_cl(non_heap_obj_cl),
5228     _copy_metadata_obj_cl(metadata_obj_cl),
5229     _par_scan_state(pss)
5230   {}
5231 
5232   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
5233   virtual void do_oop(      oop* p) { do_oop_work(p); }
5234 
5235   template <class T> void do_oop_work(T* p) {
5236     oop obj = oopDesc::load_decode_heap_oop(p);
5237 
5238     if (_g1h->obj_in_cs(obj)) {
5239       // If the referent object has been forwarded (either copied
5240       // to a new location or to itself in the event of an
5241       // evacuation failure) then we need to update the reference
5242       // field and, if both reference and referent are in the G1
5243       // heap, update the RSet for the referent.
5244       //
5245       // If the referent has not been forwarded then we have to keep
5246       // it alive by policy. Therefore we have copy the referent.
5247       //
5248       // If the reference field is in the G1 heap then we can push
5249       // on the PSS queue. When the queue is drained (after each
5250       // phase of reference processing) the object and it's followers
5251       // will be copied, the reference field set to point to the
5252       // new location, and the RSet updated. Otherwise we need to
5253       // use the the non-heap or metadata closures directly to copy
5254       // the referent object and update the pointer, while avoiding
5255       // updating the RSet.
5256 
5257       if (_g1h->is_in_g1_reserved(p)) {
5258         _par_scan_state->push_on_queue(p);
5259       } else {
5260         assert(!ClassLoaderDataGraph::contains((address)p),
5261                err_msg("Otherwise need to call _copy_metadata_obj_cl->do_oop(p) "
5262                               PTR_FORMAT, p));
5263           _copy_non_heap_obj_cl->do_oop(p);
5264         }
5265       }
5266     }
5267 };
5268 
5269 // Serial drain queue closure. Called as the 'complete_gc'
5270 // closure for each discovered list in some of the
5271 // reference processing phases.
5272 
5273 class G1STWDrainQueueClosure: public VoidClosure {
5274 protected:
5275   G1CollectedHeap* _g1h;
5276   G1ParScanThreadState* _par_scan_state;
5277 
5278   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
5279 
5280 public:
5281   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
5282     _g1h(g1h),
5283     _par_scan_state(pss)
5284   { }
5285 
5286   void do_void() {
5287     G1ParScanThreadState* const pss = par_scan_state();
5288     pss->trim_queue();
5289   }
5290 };
5291 
5292 // Parallel Reference Processing closures
5293 
5294 // Implementation of AbstractRefProcTaskExecutor for parallel reference
5295 // processing during G1 evacuation pauses.
5296 
5297 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5298 private:
5299   G1CollectedHeap*   _g1h;
5300   RefToScanQueueSet* _queues;
5301   FlexibleWorkGang*  _workers;
5302   int                _active_workers;
5303 
5304 public:
5305   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5306                         FlexibleWorkGang* workers,
5307                         RefToScanQueueSet *task_queues,
5308                         int n_workers) :
5309     _g1h(g1h),
5310     _queues(task_queues),
5311     _workers(workers),
5312     _active_workers(n_workers)
5313   {
5314     assert(n_workers > 0, "shouldn't call this otherwise");
5315   }
5316 
5317   // Executes the given task using concurrent marking worker threads.
5318   virtual void execute(ProcessTask& task);
5319   virtual void execute(EnqueueTask& task);
5320 };
5321 
5322 // Gang task for possibly parallel reference processing
5323 
5324 class G1STWRefProcTaskProxy: public AbstractGangTask {
5325   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5326   ProcessTask&     _proc_task;
5327   G1CollectedHeap* _g1h;
5328   RefToScanQueueSet *_task_queues;
5329   ParallelTaskTerminator* _terminator;
5330 
5331 public:
5332   G1STWRefProcTaskProxy(ProcessTask& proc_task,
5333                      G1CollectedHeap* g1h,
5334                      RefToScanQueueSet *task_queues,
5335                      ParallelTaskTerminator* terminator) :
5336     AbstractGangTask("Process reference objects in parallel"),
5337     _proc_task(proc_task),
5338     _g1h(g1h),
5339     _task_queues(task_queues),
5340     _terminator(terminator)
5341   {}
5342 
5343   virtual void work(uint worker_id) {
5344     // The reference processing task executed by a single worker.
5345     ResourceMark rm;
5346     HandleMark   hm;
5347 
5348     G1STWIsAliveClosure is_alive(_g1h);
5349 
5350     G1ParScanThreadState pss(_g1h, worker_id);
5351 
5352     G1ParScanHeapEvacClosure        scan_evac_cl(_g1h, &pss, NULL);
5353     G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5354     G1ParScanPartialArrayClosure    partial_scan_cl(_g1h, &pss, NULL);
5355 
5356     pss.set_evac_closure(&scan_evac_cl);
5357     pss.set_evac_failure_closure(&evac_failure_cl);
5358     pss.set_partial_scan_closure(&partial_scan_cl);
5359 
5360     G1ParScanExtRootClosure        only_copy_non_heap_cl(_g1h, &pss, NULL);
5361     G1ParScanMetadataClosure       only_copy_metadata_cl(_g1h, &pss, NULL);
5362 
5363     G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5364     G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(_g1h, &pss, NULL);
5365 
5366     OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5367     OopsInHeapRegionClosure*       copy_metadata_cl = &only_copy_metadata_cl;
5368 
5369     if (_g1h->g1_policy()->during_initial_mark_pause()) {
5370       // We also need to mark copied objects.
5371       copy_non_heap_cl = &copy_mark_non_heap_cl;
5372       copy_metadata_cl = &copy_mark_metadata_cl;
5373     }
5374 
5375     // Keep alive closure.
5376     G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_metadata_cl, &pss);
5377 
5378     // Complete GC closure
5379     G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5380 
5381     // Call the reference processing task's work routine.
5382     _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5383 
5384     // Note we cannot assert that the refs array is empty here as not all
5385     // of the processing tasks (specifically phase2 - pp2_work) execute
5386     // the complete_gc closure (which ordinarily would drain the queue) so
5387     // the queue may not be empty.
5388   }
5389 };
5390 
5391 // Driver routine for parallel reference processing.
5392 // Creates an instance of the ref processing gang
5393 // task and has the worker threads execute it.
5394 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5395   assert(_workers != NULL, "Need parallel worker threads.");
5396 
5397   ParallelTaskTerminator terminator(_active_workers, _queues);
5398   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5399 
5400   _g1h->set_par_threads(_active_workers);
5401   _workers->run_task(&proc_task_proxy);
5402   _g1h->set_par_threads(0);
5403 }
5404 
5405 // Gang task for parallel reference enqueueing.
5406 
5407 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5408   typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5409   EnqueueTask& _enq_task;
5410 
5411 public:
5412   G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5413     AbstractGangTask("Enqueue reference objects in parallel"),
5414     _enq_task(enq_task)
5415   { }
5416 
5417   virtual void work(uint worker_id) {
5418     _enq_task.work(worker_id);
5419   }
5420 };
5421 
5422 // Driver routine for parallel reference enqueueing.
5423 // Creates an instance of the ref enqueueing gang
5424 // task and has the worker threads execute it.
5425 
5426 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5427   assert(_workers != NULL, "Need parallel worker threads.");
5428 
5429   G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5430 
5431   _g1h->set_par_threads(_active_workers);
5432   _workers->run_task(&enq_task_proxy);
5433   _g1h->set_par_threads(0);
5434 }
5435 
5436 // End of weak reference support closures
5437 
5438 // Abstract task used to preserve (i.e. copy) any referent objects
5439 // that are in the collection set and are pointed to by reference
5440 // objects discovered by the CM ref processor.
5441 
5442 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5443 protected:
5444   G1CollectedHeap* _g1h;
5445   RefToScanQueueSet      *_queues;
5446   ParallelTaskTerminator _terminator;
5447   uint _n_workers;
5448 
5449 public:
5450   G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
5451     AbstractGangTask("ParPreserveCMReferents"),
5452     _g1h(g1h),
5453     _queues(task_queues),
5454     _terminator(workers, _queues),
5455     _n_workers(workers)
5456   { }
5457 
5458   void work(uint worker_id) {
5459     ResourceMark rm;
5460     HandleMark   hm;
5461 
5462     G1ParScanThreadState            pss(_g1h, worker_id);
5463     G1ParScanHeapEvacClosure        scan_evac_cl(_g1h, &pss, NULL);
5464     G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5465     G1ParScanPartialArrayClosure    partial_scan_cl(_g1h, &pss, NULL);
5466 
5467     pss.set_evac_closure(&scan_evac_cl);
5468     pss.set_evac_failure_closure(&evac_failure_cl);
5469     pss.set_partial_scan_closure(&partial_scan_cl);
5470 
5471     assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5472 
5473 
5474     G1ParScanExtRootClosure        only_copy_non_heap_cl(_g1h, &pss, NULL);
5475     G1ParScanMetadataClosure       only_copy_metadata_cl(_g1h, &pss, NULL);
5476 
5477     G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5478     G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(_g1h, &pss, NULL);
5479 
5480     OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5481     OopsInHeapRegionClosure*       copy_metadata_cl = &only_copy_metadata_cl;
5482 
5483     if (_g1h->g1_policy()->during_initial_mark_pause()) {
5484       // We also need to mark copied objects.
5485       copy_non_heap_cl = &copy_mark_non_heap_cl;
5486       copy_metadata_cl = &copy_mark_metadata_cl;
5487     }
5488 
5489     // Is alive closure
5490     G1AlwaysAliveClosure always_alive(_g1h);
5491 
5492     // Copying keep alive closure. Applied to referent objects that need
5493     // to be copied.
5494     G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_metadata_cl, &pss);
5495 
5496     ReferenceProcessor* rp = _g1h->ref_processor_cm();
5497 
5498     uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5499     uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5500 
5501     // limit is set using max_num_q() - which was set using ParallelGCThreads.
5502     // So this must be true - but assert just in case someone decides to
5503     // change the worker ids.
5504     assert(0 <= worker_id && worker_id < limit, "sanity");
5505     assert(!rp->discovery_is_atomic(), "check this code");
5506 
5507     // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5508     for (uint idx = worker_id; idx < limit; idx += stride) {
5509       DiscoveredList& ref_list = rp->discovered_refs()[idx];
5510 
5511       DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5512       while (iter.has_next()) {
5513         // Since discovery is not atomic for the CM ref processor, we
5514         // can see some null referent objects.
5515         iter.load_ptrs(DEBUG_ONLY(true));
5516         oop ref = iter.obj();
5517 
5518         // This will filter nulls.
5519         if (iter.is_referent_alive()) {
5520           iter.make_referent_alive();
5521         }
5522         iter.move_to_next();
5523       }
5524     }
5525 
5526     // Drain the queue - which may cause stealing
5527     G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5528     drain_queue.do_void();
5529     // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5530     assert(pss.refs()->is_empty(), "should be");
5531   }
5532 };
5533 
5534 // Weak Reference processing during an evacuation pause (part 1).
5535 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) {
5536   double ref_proc_start = os::elapsedTime();
5537 
5538   ReferenceProcessor* rp = _ref_processor_stw;
5539   assert(rp->discovery_enabled(), "should have been enabled");
5540 
5541   // Any reference objects, in the collection set, that were 'discovered'
5542   // by the CM ref processor should have already been copied (either by
5543   // applying the external root copy closure to the discovered lists, or
5544   // by following an RSet entry).
5545   //
5546   // But some of the referents, that are in the collection set, that these
5547   // reference objects point to may not have been copied: the STW ref
5548   // processor would have seen that the reference object had already
5549   // been 'discovered' and would have skipped discovering the reference,
5550   // but would not have treated the reference object as a regular oop.
5551   // As a result the copy closure would not have been applied to the
5552   // referent object.
5553   //
5554   // We need to explicitly copy these referent objects - the references
5555   // will be processed at the end of remarking.
5556   //
5557   // We also need to do this copying before we process the reference
5558   // objects discovered by the STW ref processor in case one of these
5559   // referents points to another object which is also referenced by an
5560   // object discovered by the STW ref processor.
5561 
5562   assert(!G1CollectedHeap::use_parallel_gc_threads() ||
5563            no_of_gc_workers == workers()->active_workers(),
5564            "Need to reset active GC workers");
5565 
5566   set_par_threads(no_of_gc_workers);
5567   G1ParPreserveCMReferentsTask keep_cm_referents(this,
5568                                                  no_of_gc_workers,
5569                                                  _task_queues);
5570 
5571   if (G1CollectedHeap::use_parallel_gc_threads()) {
5572     workers()->run_task(&keep_cm_referents);
5573   } else {
5574     keep_cm_referents.work(0);
5575   }
5576 
5577   set_par_threads(0);
5578 
5579   // Closure to test whether a referent is alive.
5580   G1STWIsAliveClosure is_alive(this);
5581 
5582   // Even when parallel reference processing is enabled, the processing
5583   // of JNI refs is serial and performed serially by the current thread
5584   // rather than by a worker. The following PSS will be used for processing
5585   // JNI refs.
5586 
5587   // Use only a single queue for this PSS.
5588   G1ParScanThreadState pss(this, 0);
5589 
5590   // We do not embed a reference processor in the copying/scanning
5591   // closures while we're actually processing the discovered
5592   // reference objects.
5593   G1ParScanHeapEvacClosure        scan_evac_cl(this, &pss, NULL);
5594   G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5595   G1ParScanPartialArrayClosure    partial_scan_cl(this, &pss, NULL);
5596 
5597   pss.set_evac_closure(&scan_evac_cl);
5598   pss.set_evac_failure_closure(&evac_failure_cl);
5599   pss.set_partial_scan_closure(&partial_scan_cl);
5600 
5601   assert(pss.refs()->is_empty(), "pre-condition");
5602 
5603   G1ParScanExtRootClosure        only_copy_non_heap_cl(this, &pss, NULL);
5604   G1ParScanMetadataClosure       only_copy_metadata_cl(this, &pss, NULL);
5605 
5606   G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5607   G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(this, &pss, NULL);
5608 
5609   OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5610   OopsInHeapRegionClosure*       copy_metadata_cl = &only_copy_metadata_cl;
5611 
5612   if (_g1h->g1_policy()->during_initial_mark_pause()) {
5613     // We also need to mark copied objects.
5614     copy_non_heap_cl = &copy_mark_non_heap_cl;
5615     copy_metadata_cl = &copy_mark_metadata_cl;
5616   }
5617 
5618   // Keep alive closure.
5619   G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, copy_metadata_cl, &pss);
5620 
5621   // Serial Complete GC closure
5622   G1STWDrainQueueClosure drain_queue(this, &pss);
5623 
5624   // Setup the soft refs policy...
5625   rp->setup_policy(false);
5626 
5627   ReferenceProcessorStats stats;
5628   if (!rp->processing_is_mt()) {
5629     // Serial reference processing...
5630     stats = rp->process_discovered_references(&is_alive,
5631                                               &keep_alive,
5632                                               &drain_queue,
5633                                               NULL,
5634                                               _gc_timer_stw);
5635   } else {
5636     // Parallel reference processing
5637     assert(rp->num_q() == no_of_gc_workers, "sanity");
5638     assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5639 
5640     G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5641     stats = rp->process_discovered_references(&is_alive,
5642                                               &keep_alive,
5643                                               &drain_queue,
5644                                               &par_task_executor,
5645                                               _gc_timer_stw);
5646   }
5647 
5648   _gc_tracer_stw->report_gc_reference_stats(stats);
5649   // We have completed copying any necessary live referent objects
5650   // (that were not copied during the actual pause) so we can
5651   // retire any active alloc buffers
5652   pss.retire_alloc_buffers();
5653   assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5654 
5655   double ref_proc_time = os::elapsedTime() - ref_proc_start;
5656   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5657 }
5658 
5659 // Weak Reference processing during an evacuation pause (part 2).
5660 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) {
5661   double ref_enq_start = os::elapsedTime();
5662 
5663   ReferenceProcessor* rp = _ref_processor_stw;
5664   assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5665 
5666   // Now enqueue any remaining on the discovered lists on to
5667   // the pending list.
5668   if (!rp->processing_is_mt()) {
5669     // Serial reference processing...
5670     rp->enqueue_discovered_references();
5671   } else {
5672     // Parallel reference enqueueing
5673 
5674     assert(no_of_gc_workers == workers()->active_workers(),
5675            "Need to reset active workers");
5676     assert(rp->num_q() == no_of_gc_workers, "sanity");
5677     assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5678 
5679     G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5680     rp->enqueue_discovered_references(&par_task_executor);
5681   }
5682 
5683   rp->verify_no_references_recorded();
5684   assert(!rp->discovery_enabled(), "should have been disabled");
5685 
5686   // FIXME
5687   // CM's reference processing also cleans up the string and symbol tables.
5688   // Should we do that here also? We could, but it is a serial operation
5689   // and could significantly increase the pause time.
5690 
5691   double ref_enq_time = os::elapsedTime() - ref_enq_start;
5692   g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5693 }
5694 
5695 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) {
5696   _expand_heap_after_alloc_failure = true;
5697   _evacuation_failed = false;
5698 
5699   // Should G1EvacuationFailureALot be in effect for this GC?
5700   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
5701 
5702   g1_rem_set()->prepare_for_oops_into_collection_set_do();
5703 
5704   // Disable the hot card cache.
5705   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
5706   hot_card_cache->reset_hot_cache_claimed_index();
5707   hot_card_cache->set_use_cache(false);
5708 
5709   uint n_workers;
5710   if (G1CollectedHeap::use_parallel_gc_threads()) {
5711     n_workers =
5712       AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
5713                                      workers()->active_workers(),
5714                                      Threads::number_of_non_daemon_threads());
5715     assert(UseDynamicNumberOfGCThreads ||
5716            n_workers == workers()->total_workers(),
5717            "If not dynamic should be using all the  workers");
5718     workers()->set_active_workers(n_workers);
5719     set_par_threads(n_workers);
5720   } else {
5721     assert(n_par_threads() == 0,
5722            "Should be the original non-parallel value");
5723     n_workers = 1;
5724   }
5725 
5726   G1ParTask g1_par_task(this, _task_queues);
5727 
5728   init_for_evac_failure(NULL);
5729 
5730   rem_set()->prepare_for_younger_refs_iterate(true);
5731 
5732   assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5733   double start_par_time_sec = os::elapsedTime();
5734   double end_par_time_sec;
5735 
5736   {
5737     StrongRootsScope srs(this);
5738 
5739     if (G1CollectedHeap::use_parallel_gc_threads()) {
5740       // The individual threads will set their evac-failure closures.
5741       if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
5742       // These tasks use ShareHeap::_process_strong_tasks
5743       assert(UseDynamicNumberOfGCThreads ||
5744              workers()->active_workers() == workers()->total_workers(),
5745              "If not dynamic should be using all the  workers");
5746       workers()->run_task(&g1_par_task);
5747     } else {
5748       g1_par_task.set_for_termination(n_workers);
5749       g1_par_task.work(0);
5750     }
5751     end_par_time_sec = os::elapsedTime();
5752 
5753     // Closing the inner scope will execute the destructor
5754     // for the StrongRootsScope object. We record the current
5755     // elapsed time before closing the scope so that time
5756     // taken for the SRS destructor is NOT included in the
5757     // reported parallel time.
5758   }
5759 
5760   double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5761   g1_policy()->phase_times()->record_par_time(par_time_ms);
5762 
5763   double code_root_fixup_time_ms =
5764         (os::elapsedTime() - end_par_time_sec) * 1000.0;
5765   g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms);
5766 
5767   set_par_threads(0);
5768 
5769   // Process any discovered reference objects - we have
5770   // to do this _before_ we retire the GC alloc regions
5771   // as we may have to copy some 'reachable' referent
5772   // objects (and their reachable sub-graphs) that were
5773   // not copied during the pause.
5774   process_discovered_references(n_workers);
5775 
5776   // Weak root processing.
5777   // Note: when JSR 292 is enabled and code blobs can contain
5778   // non-perm oops then we will need to process the code blobs
5779   // here too.
5780   {
5781     G1STWIsAliveClosure is_alive(this);
5782     G1KeepAliveClosure keep_alive(this);
5783     JNIHandles::weak_oops_do(&is_alive, &keep_alive);
5784   }
5785 
5786   release_gc_alloc_regions(n_workers, evacuation_info);
5787   g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5788 
5789   // Reset and re-enable the hot card cache.
5790   // Note the counts for the cards in the regions in the
5791   // collection set are reset when the collection set is freed.
5792   hot_card_cache->reset_hot_cache();
5793   hot_card_cache->set_use_cache(true);
5794 
5795   finalize_for_evac_failure();
5796 
5797   if (evacuation_failed()) {
5798     remove_self_forwarding_pointers();
5799 
5800     // Reset the G1EvacuationFailureALot counters and flags
5801     // Note: the values are reset only when an actual
5802     // evacuation failure occurs.
5803     NOT_PRODUCT(reset_evacuation_should_fail();)
5804   }
5805 
5806   // Enqueue any remaining references remaining on the STW
5807   // reference processor's discovered lists. We need to do
5808   // this after the card table is cleaned (and verified) as
5809   // the act of enqueueing entries on to the pending list
5810   // will log these updates (and dirty their associated
5811   // cards). We need these updates logged to update any
5812   // RSets.
5813   enqueue_discovered_references(n_workers);
5814 
5815   if (G1DeferredRSUpdate) {
5816     RedirtyLoggedCardTableEntryFastClosure redirty;
5817     dirty_card_queue_set().set_closure(&redirty);
5818     dirty_card_queue_set().apply_closure_to_all_completed_buffers();
5819 
5820     DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5821     dcq.merge_bufferlists(&dirty_card_queue_set());
5822     assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5823   }
5824   COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5825 }
5826 
5827 void G1CollectedHeap::free_region_if_empty(HeapRegion* hr,
5828                                      size_t* pre_used,
5829                                      FreeRegionList* free_list,
5830                                      OldRegionSet* old_proxy_set,
5831                                      HumongousRegionSet* humongous_proxy_set,
5832                                      HRRSCleanupTask* hrrs_cleanup_task,
5833                                      bool par) {
5834   if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) {
5835     if (hr->isHumongous()) {
5836       assert(hr->startsHumongous(), "we should only see starts humongous");
5837       free_humongous_region(hr, pre_used, free_list, humongous_proxy_set, par);
5838     } else {
5839       _old_set.remove_with_proxy(hr, old_proxy_set);
5840       free_region(hr, pre_used, free_list, par);
5841     }
5842   } else {
5843     hr->rem_set()->do_cleanup_work(hrrs_cleanup_task);
5844   }
5845 }
5846 
5847 void G1CollectedHeap::free_region(HeapRegion* hr,
5848                                   size_t* pre_used,
5849                                   FreeRegionList* free_list,
5850                                   bool par) {
5851   assert(!hr->isHumongous(), "this is only for non-humongous regions");
5852   assert(!hr->is_empty(), "the region should not be empty");
5853   assert(free_list != NULL, "pre-condition");
5854 
5855   // Clear the card counts for this region.
5856   // Note: we only need to do this if the region is not young
5857   // (since we don't refine cards in young regions).
5858   if (!hr->is_young()) {
5859     _cg1r->hot_card_cache()->reset_card_counts(hr);
5860   }
5861   *pre_used += hr->used();
5862   hr->hr_clear(par, true /* clear_space */);
5863   free_list->add_as_head(hr);
5864 }
5865 
5866 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
5867                                      size_t* pre_used,
5868                                      FreeRegionList* free_list,
5869                                      HumongousRegionSet* humongous_proxy_set,
5870                                      bool par) {
5871   assert(hr->startsHumongous(), "this is only for starts humongous regions");
5872   assert(free_list != NULL, "pre-condition");
5873   assert(humongous_proxy_set != NULL, "pre-condition");
5874 
5875   size_t hr_used = hr->used();
5876   size_t hr_capacity = hr->capacity();
5877   size_t hr_pre_used = 0;
5878   _humongous_set.remove_with_proxy(hr, humongous_proxy_set);
5879   // We need to read this before we make the region non-humongous,
5880   // otherwise the information will be gone.
5881   uint last_index = hr->last_hc_index();
5882   hr->set_notHumongous();
5883   free_region(hr, &hr_pre_used, free_list, par);
5884 
5885   uint i = hr->hrs_index() + 1;
5886   while (i < last_index) {
5887     HeapRegion* curr_hr = region_at(i);
5888     assert(curr_hr->continuesHumongous(), "invariant");
5889     curr_hr->set_notHumongous();
5890     free_region(curr_hr, &hr_pre_used, free_list, par);
5891     i += 1;
5892   }
5893   assert(hr_pre_used == hr_used,
5894          err_msg("hr_pre_used: "SIZE_FORMAT" and hr_used: "SIZE_FORMAT" "
5895                  "should be the same", hr_pre_used, hr_used));
5896   *pre_used += hr_pre_used;
5897 }
5898 
5899 void G1CollectedHeap::update_sets_after_freeing_regions(size_t pre_used,
5900                                        FreeRegionList* free_list,
5901                                        OldRegionSet* old_proxy_set,
5902                                        HumongousRegionSet* humongous_proxy_set,
5903                                        bool par) {
5904   if (pre_used > 0) {
5905     Mutex* lock = (par) ? ParGCRareEvent_lock : NULL;
5906     MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag);
5907     assert(_summary_bytes_used >= pre_used,
5908            err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" "
5909                    "should be >= pre_used: "SIZE_FORMAT,
5910                    _summary_bytes_used, pre_used));
5911     _summary_bytes_used -= pre_used;
5912   }
5913   if (free_list != NULL && !free_list->is_empty()) {
5914     MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
5915     _free_list.add_as_head(free_list);
5916   }
5917   if (old_proxy_set != NULL && !old_proxy_set->is_empty()) {
5918     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5919     _old_set.update_from_proxy(old_proxy_set);
5920   }
5921   if (humongous_proxy_set != NULL && !humongous_proxy_set->is_empty()) {
5922     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5923     _humongous_set.update_from_proxy(humongous_proxy_set);
5924   }
5925 }
5926 
5927 class G1ParCleanupCTTask : public AbstractGangTask {
5928   CardTableModRefBS* _ct_bs;
5929   G1CollectedHeap* _g1h;
5930   HeapRegion* volatile _su_head;
5931 public:
5932   G1ParCleanupCTTask(CardTableModRefBS* ct_bs,
5933                      G1CollectedHeap* g1h) :
5934     AbstractGangTask("G1 Par Cleanup CT Task"),
5935     _ct_bs(ct_bs), _g1h(g1h) { }
5936 
5937   void work(uint worker_id) {
5938     HeapRegion* r;
5939     while (r = _g1h->pop_dirty_cards_region()) {
5940       clear_cards(r);
5941     }
5942   }
5943 
5944   void clear_cards(HeapRegion* r) {
5945     // Cards of the survivors should have already been dirtied.
5946     if (!r->is_survivor()) {
5947       _ct_bs->clear(MemRegion(r->bottom(), r->end()));
5948     }
5949   }
5950 };
5951 
5952 #ifndef PRODUCT
5953 class G1VerifyCardTableCleanup: public HeapRegionClosure {
5954   G1CollectedHeap* _g1h;
5955   CardTableModRefBS* _ct_bs;
5956 public:
5957   G1VerifyCardTableCleanup(G1CollectedHeap* g1h, CardTableModRefBS* ct_bs)
5958     : _g1h(g1h), _ct_bs(ct_bs) { }
5959   virtual bool doHeapRegion(HeapRegion* r) {
5960     if (r->is_survivor()) {
5961       _g1h->verify_dirty_region(r);
5962     } else {
5963       _g1h->verify_not_dirty_region(r);
5964     }
5965     return false;
5966   }
5967 };
5968 
5969 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
5970   // All of the region should be clean.
5971   CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
5972   MemRegion mr(hr->bottom(), hr->end());
5973   ct_bs->verify_not_dirty_region(mr);
5974 }
5975 
5976 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
5977   // We cannot guarantee that [bottom(),end()] is dirty.  Threads
5978   // dirty allocated blocks as they allocate them. The thread that
5979   // retires each region and replaces it with a new one will do a
5980   // maximal allocation to fill in [pre_dummy_top(),end()] but will
5981   // not dirty that area (one less thing to have to do while holding
5982   // a lock). So we can only verify that [bottom(),pre_dummy_top()]
5983   // is dirty.
5984   CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set();
5985   MemRegion mr(hr->bottom(), hr->pre_dummy_top());
5986   ct_bs->verify_dirty_region(mr);
5987 }
5988 
5989 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
5990   CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set();
5991   for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
5992     verify_dirty_region(hr);
5993   }
5994 }
5995 
5996 void G1CollectedHeap::verify_dirty_young_regions() {
5997   verify_dirty_young_list(_young_list->first_region());
5998 }
5999 #endif
6000 
6001 void G1CollectedHeap::cleanUpCardTable() {
6002   CardTableModRefBS* ct_bs = (CardTableModRefBS*) (barrier_set());
6003   double start = os::elapsedTime();
6004 
6005   {
6006     // Iterate over the dirty cards region list.
6007     G1ParCleanupCTTask cleanup_task(ct_bs, this);
6008 
6009     if (G1CollectedHeap::use_parallel_gc_threads()) {
6010       set_par_threads();
6011       workers()->run_task(&cleanup_task);
6012       set_par_threads(0);
6013     } else {
6014       while (_dirty_cards_region_list) {
6015         HeapRegion* r = _dirty_cards_region_list;
6016         cleanup_task.clear_cards(r);
6017         _dirty_cards_region_list = r->get_next_dirty_cards_region();
6018         if (_dirty_cards_region_list == r) {
6019           // The last region.
6020           _dirty_cards_region_list = NULL;
6021         }
6022         r->set_next_dirty_cards_region(NULL);
6023       }
6024     }
6025 #ifndef PRODUCT
6026     if (G1VerifyCTCleanup || VerifyAfterGC) {
6027       G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
6028       heap_region_iterate(&cleanup_verifier);
6029     }
6030 #endif
6031   }
6032 
6033   double elapsed = os::elapsedTime() - start;
6034   g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
6035 }
6036 
6037 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) {
6038   size_t pre_used = 0;
6039   FreeRegionList local_free_list("Local List for CSet Freeing");
6040 
6041   double young_time_ms     = 0.0;
6042   double non_young_time_ms = 0.0;
6043 
6044   // Since the collection set is a superset of the the young list,
6045   // all we need to do to clear the young list is clear its
6046   // head and length, and unlink any young regions in the code below
6047   _young_list->clear();
6048 
6049   G1CollectorPolicy* policy = g1_policy();
6050 
6051   double start_sec = os::elapsedTime();
6052   bool non_young = true;
6053 
6054   HeapRegion* cur = cs_head;
6055   int age_bound = -1;
6056   size_t rs_lengths = 0;
6057 
6058   while (cur != NULL) {
6059     assert(!is_on_master_free_list(cur), "sanity");
6060     if (non_young) {
6061       if (cur->is_young()) {
6062         double end_sec = os::elapsedTime();
6063         double elapsed_ms = (end_sec - start_sec) * 1000.0;
6064         non_young_time_ms += elapsed_ms;
6065 
6066         start_sec = os::elapsedTime();
6067         non_young = false;
6068       }
6069     } else {
6070       if (!cur->is_young()) {
6071         double end_sec = os::elapsedTime();
6072         double elapsed_ms = (end_sec - start_sec) * 1000.0;
6073         young_time_ms += elapsed_ms;
6074 
6075         start_sec = os::elapsedTime();
6076         non_young = true;
6077       }
6078     }
6079 
6080     rs_lengths += cur->rem_set()->occupied();
6081 
6082     HeapRegion* next = cur->next_in_collection_set();
6083     assert(cur->in_collection_set(), "bad CS");
6084     cur->set_next_in_collection_set(NULL);
6085     cur->set_in_collection_set(false);
6086 
6087     if (cur->is_young()) {
6088       int index = cur->young_index_in_cset();
6089       assert(index != -1, "invariant");
6090       assert((uint) index < policy->young_cset_region_length(), "invariant");
6091       size_t words_survived = _surviving_young_words[index];
6092       cur->record_surv_words_in_group(words_survived);
6093 
6094       // At this point the we have 'popped' cur from the collection set
6095       // (linked via next_in_collection_set()) but it is still in the
6096       // young list (linked via next_young_region()). Clear the
6097       // _next_young_region field.
6098       cur->set_next_young_region(NULL);
6099     } else {
6100       int index = cur->young_index_in_cset();
6101       assert(index == -1, "invariant");
6102     }
6103 
6104     assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
6105             (!cur->is_young() && cur->young_index_in_cset() == -1),
6106             "invariant" );
6107 
6108     if (!cur->evacuation_failed()) {
6109       MemRegion used_mr = cur->used_region();
6110 
6111       // And the region is empty.
6112       assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
6113       free_region(cur, &pre_used, &local_free_list, false /* par */);
6114     } else {
6115       cur->uninstall_surv_rate_group();
6116       if (cur->is_young()) {
6117         cur->set_young_index_in_cset(-1);
6118       }
6119       cur->set_not_young();
6120       cur->set_evacuation_failed(false);
6121       // The region is now considered to be old.
6122       _old_set.add(cur);
6123       evacuation_info.increment_collectionset_used_after(cur->used());
6124     }
6125     cur = next;
6126   }
6127 
6128   evacuation_info.set_regions_freed(local_free_list.length());
6129   policy->record_max_rs_lengths(rs_lengths);
6130   policy->cset_regions_freed();
6131 
6132   double end_sec = os::elapsedTime();
6133   double elapsed_ms = (end_sec - start_sec) * 1000.0;
6134 
6135   if (non_young) {
6136     non_young_time_ms += elapsed_ms;
6137   } else {
6138     young_time_ms += elapsed_ms;
6139   }
6140 
6141   update_sets_after_freeing_regions(pre_used, &local_free_list,
6142                                     NULL /* old_proxy_set */,
6143                                     NULL /* humongous_proxy_set */,
6144                                     false /* par */);
6145   policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
6146   policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
6147 }
6148 
6149 // This routine is similar to the above but does not record
6150 // any policy statistics or update free lists; we are abandoning
6151 // the current incremental collection set in preparation of a
6152 // full collection. After the full GC we will start to build up
6153 // the incremental collection set again.
6154 // This is only called when we're doing a full collection
6155 // and is immediately followed by the tearing down of the young list.
6156 
6157 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
6158   HeapRegion* cur = cs_head;
6159 
6160   while (cur != NULL) {
6161     HeapRegion* next = cur->next_in_collection_set();
6162     assert(cur->in_collection_set(), "bad CS");
6163     cur->set_next_in_collection_set(NULL);
6164     cur->set_in_collection_set(false);
6165     cur->set_young_index_in_cset(-1);
6166     cur = next;
6167   }
6168 }
6169 
6170 void G1CollectedHeap::set_free_regions_coming() {
6171   if (G1ConcRegionFreeingVerbose) {
6172     gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6173                            "setting free regions coming");
6174   }
6175 
6176   assert(!free_regions_coming(), "pre-condition");
6177   _free_regions_coming = true;
6178 }
6179 
6180 void G1CollectedHeap::reset_free_regions_coming() {
6181   assert(free_regions_coming(), "pre-condition");
6182 
6183   {
6184     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6185     _free_regions_coming = false;
6186     SecondaryFreeList_lock->notify_all();
6187   }
6188 
6189   if (G1ConcRegionFreeingVerbose) {
6190     gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6191                            "reset free regions coming");
6192   }
6193 }
6194 
6195 void G1CollectedHeap::wait_while_free_regions_coming() {
6196   // Most of the time we won't have to wait, so let's do a quick test
6197   // first before we take the lock.
6198   if (!free_regions_coming()) {
6199     return;
6200   }
6201 
6202   if (G1ConcRegionFreeingVerbose) {
6203     gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6204                            "waiting for free regions");
6205   }
6206 
6207   {
6208     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6209     while (free_regions_coming()) {
6210       SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
6211     }
6212   }
6213 
6214   if (G1ConcRegionFreeingVerbose) {
6215     gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6216                            "done waiting for free regions");
6217   }
6218 }
6219 
6220 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
6221   assert(heap_lock_held_for_gc(),
6222               "the heap lock should already be held by or for this thread");
6223   _young_list->push_region(hr);
6224 }
6225 
6226 class NoYoungRegionsClosure: public HeapRegionClosure {
6227 private:
6228   bool _success;
6229 public:
6230   NoYoungRegionsClosure() : _success(true) { }
6231   bool doHeapRegion(HeapRegion* r) {
6232     if (r->is_young()) {
6233       gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
6234                              r->bottom(), r->end());
6235       _success = false;
6236     }
6237     return false;
6238   }
6239   bool success() { return _success; }
6240 };
6241 
6242 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
6243   bool ret = _young_list->check_list_empty(check_sample);
6244 
6245   if (check_heap) {
6246     NoYoungRegionsClosure closure;
6247     heap_region_iterate(&closure);
6248     ret = ret && closure.success();
6249   }
6250 
6251   return ret;
6252 }
6253 
6254 class TearDownRegionSetsClosure : public HeapRegionClosure {
6255 private:
6256   OldRegionSet *_old_set;
6257 
6258 public:
6259   TearDownRegionSetsClosure(OldRegionSet* old_set) : _old_set(old_set) { }
6260 
6261   bool doHeapRegion(HeapRegion* r) {
6262     if (r->is_empty()) {
6263       // We ignore empty regions, we'll empty the free list afterwards
6264     } else if (r->is_young()) {
6265       // We ignore young regions, we'll empty the young list afterwards
6266     } else if (r->isHumongous()) {
6267       // We ignore humongous regions, we're not tearing down the
6268       // humongous region set
6269     } else {
6270       // The rest should be old
6271       _old_set->remove(r);
6272     }
6273     return false;
6274   }
6275 
6276   ~TearDownRegionSetsClosure() {
6277     assert(_old_set->is_empty(), "post-condition");
6278   }
6279 };
6280 
6281 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6282   assert_at_safepoint(true /* should_be_vm_thread */);
6283 
6284   if (!free_list_only) {
6285     TearDownRegionSetsClosure cl(&_old_set);
6286     heap_region_iterate(&cl);
6287 
6288     // Need to do this after the heap iteration to be able to
6289     // recognize the young regions and ignore them during the iteration.
6290     _young_list->empty_list();
6291   }
6292   _free_list.remove_all();
6293 }
6294 
6295 class RebuildRegionSetsClosure : public HeapRegionClosure {
6296 private:
6297   bool            _free_list_only;
6298   OldRegionSet*   _old_set;
6299   FreeRegionList* _free_list;
6300   size_t          _total_used;
6301 
6302 public:
6303   RebuildRegionSetsClosure(bool free_list_only,
6304                            OldRegionSet* old_set, FreeRegionList* free_list) :
6305     _free_list_only(free_list_only),
6306     _old_set(old_set), _free_list(free_list), _total_used(0) {
6307     assert(_free_list->is_empty(), "pre-condition");
6308     if (!free_list_only) {
6309       assert(_old_set->is_empty(), "pre-condition");
6310     }
6311   }
6312 
6313   bool doHeapRegion(HeapRegion* r) {
6314     if (r->continuesHumongous()) {
6315       return false;
6316     }
6317 
6318     if (r->is_empty()) {
6319       // Add free regions to the free list
6320       _free_list->add_as_tail(r);
6321     } else if (!_free_list_only) {
6322       assert(!r->is_young(), "we should not come across young regions");
6323 
6324       if (r->isHumongous()) {
6325         // We ignore humongous regions, we left the humongous set unchanged
6326       } else {
6327         // The rest should be old, add them to the old set
6328         _old_set->add(r);
6329       }
6330       _total_used += r->used();
6331     }
6332 
6333     return false;
6334   }
6335 
6336   size_t total_used() {
6337     return _total_used;
6338   }
6339 };
6340 
6341 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6342   assert_at_safepoint(true /* should_be_vm_thread */);
6343 
6344   RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_free_list);
6345   heap_region_iterate(&cl);
6346 
6347   if (!free_list_only) {
6348     _summary_bytes_used = cl.total_used();
6349   }
6350   assert(_summary_bytes_used == recalculate_used(),
6351          err_msg("inconsistent _summary_bytes_used, "
6352                  "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6353                  _summary_bytes_used, recalculate_used()));
6354 }
6355 
6356 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6357   _refine_cte_cl->set_concurrent(concurrent);
6358 }
6359 
6360 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6361   HeapRegion* hr = heap_region_containing(p);
6362   if (hr == NULL) {
6363     return false;
6364   } else {
6365     return hr->is_in(p);
6366   }
6367 }
6368 
6369 // Methods for the mutator alloc region
6370 
6371 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6372                                                       bool force) {
6373   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6374   assert(!force || g1_policy()->can_expand_young_list(),
6375          "if force is true we should be able to expand the young list");
6376   bool young_list_full = g1_policy()->is_young_list_full();
6377   if (force || !young_list_full) {
6378     HeapRegion* new_alloc_region = new_region(word_size,
6379                                               false /* do_expand */);
6380     if (new_alloc_region != NULL) {
6381       set_region_short_lived_locked(new_alloc_region);
6382       _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6383       return new_alloc_region;
6384     }
6385   }
6386   return NULL;
6387 }
6388 
6389 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6390                                                   size_t allocated_bytes) {
6391   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6392   assert(alloc_region->is_young(), "all mutator alloc regions should be young");
6393 
6394   g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6395   _summary_bytes_used += allocated_bytes;
6396   _hr_printer.retire(alloc_region);
6397   // We update the eden sizes here, when the region is retired,
6398   // instead of when it's allocated, since this is the point that its
6399   // used space has been recored in _summary_bytes_used.
6400   g1mm()->update_eden_size();
6401 }
6402 
6403 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
6404                                                     bool force) {
6405   return _g1h->new_mutator_alloc_region(word_size, force);
6406 }
6407 
6408 void G1CollectedHeap::set_par_threads() {
6409   // Don't change the number of workers.  Use the value previously set
6410   // in the workgroup.
6411   assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise");
6412   uint n_workers = workers()->active_workers();
6413   assert(UseDynamicNumberOfGCThreads ||
6414            n_workers == workers()->total_workers(),
6415       "Otherwise should be using the total number of workers");
6416   if (n_workers == 0) {
6417     assert(false, "Should have been set in prior evacuation pause.");
6418     n_workers = ParallelGCThreads;
6419     workers()->set_active_workers(n_workers);
6420   }
6421   set_par_threads(n_workers);
6422 }
6423 
6424 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
6425                                        size_t allocated_bytes) {
6426   _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
6427 }
6428 
6429 // Methods for the GC alloc regions
6430 
6431 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6432                                                  uint count,
6433                                                  GCAllocPurpose ap) {
6434   assert(FreeList_lock->owned_by_self(), "pre-condition");
6435 
6436   if (count < g1_policy()->max_regions(ap)) {
6437     HeapRegion* new_alloc_region = new_region(word_size,
6438                                               true /* do_expand */);
6439     if (new_alloc_region != NULL) {
6440       // We really only need to do this for old regions given that we
6441       // should never scan survivors. But it doesn't hurt to do it
6442       // for survivors too.
6443       new_alloc_region->set_saved_mark();
6444       if (ap == GCAllocForSurvived) {
6445         new_alloc_region->set_survivor();
6446         _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6447       } else {
6448         _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6449       }
6450       bool during_im = g1_policy()->during_initial_mark_pause();
6451       new_alloc_region->note_start_of_copying(during_im);
6452       return new_alloc_region;
6453     } else {
6454       g1_policy()->note_alloc_region_limit_reached(ap);
6455     }
6456   }
6457   return NULL;
6458 }
6459 
6460 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6461                                              size_t allocated_bytes,
6462                                              GCAllocPurpose ap) {
6463   bool during_im = g1_policy()->during_initial_mark_pause();
6464   alloc_region->note_end_of_copying(during_im);
6465   g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6466   if (ap == GCAllocForSurvived) {
6467     young_list()->add_survivor_region(alloc_region);
6468   } else {
6469     _old_set.add(alloc_region);
6470   }
6471   _hr_printer.retire(alloc_region);
6472 }
6473 
6474 HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size,
6475                                                        bool force) {
6476   assert(!force, "not supported for GC alloc regions");
6477   return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForSurvived);
6478 }
6479 
6480 void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region,
6481                                           size_t allocated_bytes) {
6482   _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6483                                GCAllocForSurvived);
6484 }
6485 
6486 HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size,
6487                                                   bool force) {
6488   assert(!force, "not supported for GC alloc regions");
6489   return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForTenured);
6490 }
6491 
6492 void OldGCAllocRegion::retire_region(HeapRegion* alloc_region,
6493                                      size_t allocated_bytes) {
6494   _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6495                                GCAllocForTenured);
6496 }
6497 // Heap region set verification
6498 
6499 class VerifyRegionListsClosure : public HeapRegionClosure {
6500 private:
6501   FreeRegionList*     _free_list;
6502   OldRegionSet*       _old_set;
6503   HumongousRegionSet* _humongous_set;
6504   uint                _region_count;
6505 
6506 public:
6507   VerifyRegionListsClosure(OldRegionSet* old_set,
6508                            HumongousRegionSet* humongous_set,
6509                            FreeRegionList* free_list) :
6510     _old_set(old_set), _humongous_set(humongous_set),
6511     _free_list(free_list), _region_count(0) { }
6512 
6513   uint region_count() { return _region_count; }
6514 
6515   bool doHeapRegion(HeapRegion* hr) {
6516     _region_count += 1;
6517 
6518     if (hr->continuesHumongous()) {
6519       return false;
6520     }
6521 
6522     if (hr->is_young()) {
6523       // TODO
6524     } else if (hr->startsHumongous()) {
6525       _humongous_set->verify_next_region(hr);
6526     } else if (hr->is_empty()) {
6527       _free_list->verify_next_region(hr);
6528     } else {
6529       _old_set->verify_next_region(hr);
6530     }
6531     return false;
6532   }
6533 };
6534 
6535 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
6536                                              HeapWord* bottom) {
6537   HeapWord* end = bottom + HeapRegion::GrainWords;
6538   MemRegion mr(bottom, end);
6539   assert(_g1_reserved.contains(mr), "invariant");
6540   // This might return NULL if the allocation fails
6541   return new HeapRegion(hrs_index, _bot_shared, mr);
6542 }
6543 
6544 void G1CollectedHeap::verify_region_sets() {
6545   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6546 
6547   // First, check the explicit lists.
6548   _free_list.verify();
6549   {
6550     // Given that a concurrent operation might be adding regions to
6551     // the secondary free list we have to take the lock before
6552     // verifying it.
6553     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6554     _secondary_free_list.verify();
6555   }
6556   _old_set.verify();
6557   _humongous_set.verify();
6558 
6559   // If a concurrent region freeing operation is in progress it will
6560   // be difficult to correctly attributed any free regions we come
6561   // across to the correct free list given that they might belong to
6562   // one of several (free_list, secondary_free_list, any local lists,
6563   // etc.). So, if that's the case we will skip the rest of the
6564   // verification operation. Alternatively, waiting for the concurrent
6565   // operation to complete will have a non-trivial effect on the GC's
6566   // operation (no concurrent operation will last longer than the
6567   // interval between two calls to verification) and it might hide
6568   // any issues that we would like to catch during testing.
6569   if (free_regions_coming()) {
6570     return;
6571   }
6572 
6573   // Make sure we append the secondary_free_list on the free_list so
6574   // that all free regions we will come across can be safely
6575   // attributed to the free_list.
6576   append_secondary_free_list_if_not_empty_with_lock();
6577 
6578   // Finally, make sure that the region accounting in the lists is
6579   // consistent with what we see in the heap.
6580   _old_set.verify_start();
6581   _humongous_set.verify_start();
6582   _free_list.verify_start();
6583 
6584   VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_free_list);
6585   heap_region_iterate(&cl);
6586 
6587   _old_set.verify_end();
6588   _humongous_set.verify_end();
6589   _free_list.verify_end();
6590 }
--- EOF ---