1 /*
   2  * Copyright (c) 2001, 2018, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #if !defined(__clang_major__) && defined(__GNUC__)
  26 #define ATTRIBUTE_PRINTF(x,y) // FIXME, formats are a mess.
  27 #endif
  28 
  29 #include "precompiled.hpp"
  30 #include "classfile/metadataOnStackMark.hpp"
  31 #include "code/codeCache.hpp"
  32 #include "code/icBuffer.hpp"
  33 #include "gc_implementation/g1/bufferingOopClosure.hpp"
  34 #include "gc_implementation/g1/concurrentG1Refine.hpp"
  35 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
  36 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
  37 #include "gc_implementation/g1/g1AllocRegion.inline.hpp"
  38 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
  39 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
  40 #include "gc_implementation/g1/g1ErgoVerbose.hpp"
  41 #include "gc_implementation/g1/g1EvacFailure.hpp"
  42 #include "gc_implementation/g1/g1GCPhaseTimes.hpp"
  43 #include "gc_implementation/g1/g1Log.hpp"
  44 #include "gc_implementation/g1/g1MarkSweep.hpp"
  45 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
  46 #include "gc_implementation/g1/g1ParScanThreadState.inline.hpp"
  47 #include "gc_implementation/g1/g1RegionToSpaceMapper.hpp"
  48 #include "gc_implementation/g1/g1RemSet.inline.hpp"
  49 #include "gc_implementation/g1/g1RootProcessor.hpp"
  50 #include "gc_implementation/g1/g1StringDedup.hpp"
  51 #include "gc_implementation/g1/g1YCTypes.hpp"
  52 #include "gc_implementation/g1/heapRegion.inline.hpp"
  53 #include "gc_implementation/g1/heapRegionRemSet.hpp"
  54 #include "gc_implementation/g1/heapRegionSet.inline.hpp"
  55 #include "gc_implementation/g1/vm_operations_g1.hpp"
  56 #include "gc_implementation/shared/gcHeapSummary.hpp"
  57 #include "gc_implementation/shared/gcTimer.hpp"
  58 #include "gc_implementation/shared/gcTrace.hpp"
  59 #include "gc_implementation/shared/gcTraceTime.hpp"
  60 #include "gc_implementation/shared/isGCActiveMark.hpp"
  61 #include "memory/allocation.hpp"
  62 #include "memory/gcLocker.inline.hpp"
  63 #include "memory/generationSpec.hpp"
  64 #include "memory/iterator.hpp"
  65 #include "memory/referenceProcessor.hpp"
  66 #include "oops/oop.inline.hpp"
  67 #include "oops/oop.pcgc.inline.hpp"
  68 #include "runtime/orderAccess.inline.hpp"
  69 #include "runtime/vmThread.hpp"
  70 
  71 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
  72 
  73 // turn it on so that the contents of the young list (scan-only /
  74 // to-be-collected) are printed at "strategic" points before / during
  75 // / after the collection --- this is useful for debugging
  76 #define YOUNG_LIST_VERBOSE 0
  77 // CURRENT STATUS
  78 // This file is under construction.  Search for "FIXME".
  79 
  80 // INVARIANTS/NOTES
  81 //
  82 // All allocation activity covered by the G1CollectedHeap interface is
  83 // serialized by acquiring the HeapLock.  This happens in mem_allocate
  84 // and allocate_new_tlab, which are the "entry" points to the
  85 // allocation code from the rest of the JVM.  (Note that this does not
  86 // apply to TLAB allocation, which is not part of this interface: it
  87 // is done by clients of this interface.)
  88 
  89 // Local to this file.
  90 
  91 class RefineCardTableEntryClosure: public CardTableEntryClosure {
  92   bool _concurrent;
  93 public:
  94   RefineCardTableEntryClosure() : _concurrent(true) { }
  95 
  96   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
  97     bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, false);
  98     // This path is executed by the concurrent refine or mutator threads,
  99     // concurrently, and so we do not care if card_ptr contains references
 100     // that point into the collection set.
 101     assert(!oops_into_cset, "should be");
 102 
 103     if (_concurrent && SuspendibleThreadSet::should_yield()) {
 104       // Caller will actually yield.
 105       return false;
 106     }
 107     // Otherwise, we finished successfully; return true.
 108     return true;
 109   }
 110 
 111   void set_concurrent(bool b) { _concurrent = b; }
 112 };
 113 
 114 
 115 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure {
 116   size_t _num_processed;
 117   CardTableModRefBS* _ctbs;
 118   int _histo[256];
 119 
 120  public:
 121   ClearLoggedCardTableEntryClosure() :
 122     _num_processed(0), _ctbs(G1CollectedHeap::heap()->g1_barrier_set())
 123   {
 124     for (int i = 0; i < 256; i++) _histo[i] = 0;
 125   }
 126 
 127   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
 128     unsigned char* ujb = (unsigned char*)card_ptr;
 129     int ind = (int)(*ujb);
 130     _histo[ind]++;
 131 
 132     *card_ptr = (jbyte)CardTableModRefBS::clean_card_val();
 133     _num_processed++;
 134 
 135     return true;
 136   }
 137 
 138   size_t num_processed() { return _num_processed; }
 139 
 140   void print_histo() {
 141     gclog_or_tty->print_cr("Card table value histogram:");
 142     for (int i = 0; i < 256; i++) {
 143       if (_histo[i] != 0) {
 144         gclog_or_tty->print_cr("  %d: %d", i, _histo[i]);
 145       }
 146     }
 147   }
 148 };
 149 
 150 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
 151  private:
 152   size_t _num_processed;
 153 
 154  public:
 155   RedirtyLoggedCardTableEntryClosure() : CardTableEntryClosure(), _num_processed(0) { }
 156 
 157   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
 158     *card_ptr = CardTableModRefBS::dirty_card_val();
 159     _num_processed++;
 160     return true;
 161   }
 162 
 163   size_t num_processed() const { return _num_processed; }
 164 };
 165 
 166 YoungList::YoungList(G1CollectedHeap* g1h) :
 167     _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0),
 168     _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) {
 169   guarantee(check_list_empty(false), "just making sure...");
 170 }
 171 
 172 void YoungList::push_region(HeapRegion *hr) {
 173   assert(!hr->is_young(), "should not already be young");
 174   assert(hr->get_next_young_region() == NULL, "cause it should!");
 175 
 176   hr->set_next_young_region(_head);
 177   _head = hr;
 178 
 179   _g1h->g1_policy()->set_region_eden(hr, (int) _length);
 180   ++_length;
 181 }
 182 
 183 void YoungList::add_survivor_region(HeapRegion* hr) {
 184   assert(hr->is_survivor(), "should be flagged as survivor region");
 185   assert(hr->get_next_young_region() == NULL, "cause it should!");
 186 
 187   hr->set_next_young_region(_survivor_head);
 188   if (_survivor_head == NULL) {
 189     _survivor_tail = hr;
 190   }
 191   _survivor_head = hr;
 192   ++_survivor_length;
 193 }
 194 
 195 void YoungList::empty_list(HeapRegion* list) {
 196   while (list != NULL) {
 197     HeapRegion* next = list->get_next_young_region();
 198     list->set_next_young_region(NULL);
 199     list->uninstall_surv_rate_group();
 200     // This is called before a Full GC and all the non-empty /
 201     // non-humongous regions at the end of the Full GC will end up as
 202     // old anyway.
 203     list->set_old();
 204     list = next;
 205   }
 206 }
 207 
 208 void YoungList::empty_list() {
 209   assert(check_list_well_formed(), "young list should be well formed");
 210 
 211   empty_list(_head);
 212   _head = NULL;
 213   _length = 0;
 214 
 215   empty_list(_survivor_head);
 216   _survivor_head = NULL;
 217   _survivor_tail = NULL;
 218   _survivor_length = 0;
 219 
 220   _last_sampled_rs_lengths = 0;
 221 
 222   assert(check_list_empty(false), "just making sure...");
 223 }
 224 
 225 bool YoungList::check_list_well_formed() {
 226   bool ret = true;
 227 
 228   uint length = 0;
 229   HeapRegion* curr = _head;
 230   HeapRegion* last = NULL;
 231   while (curr != NULL) {
 232     if (!curr->is_young()) {
 233       gclog_or_tty->print_cr("### YOUNG REGION " PTR_FORMAT "-" PTR_FORMAT " "
 234                              "incorrectly tagged (y: %d, surv: %d)",
 235                              curr->bottom(), curr->end(),
 236                              curr->is_young(), curr->is_survivor());
 237       ret = false;
 238     }
 239     ++length;
 240     last = curr;
 241     curr = curr->get_next_young_region();
 242   }
 243   ret = ret && (length == _length);
 244 
 245   if (!ret) {
 246     gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
 247     gclog_or_tty->print_cr("###   list has %u entries, _length is %u",
 248                            length, _length);
 249   }
 250 
 251   return ret;
 252 }
 253 
 254 bool YoungList::check_list_empty(bool check_sample) {
 255   bool ret = true;
 256 
 257   if (_length != 0) {
 258     gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u",
 259                   _length);
 260     ret = false;
 261   }
 262   if (check_sample && _last_sampled_rs_lengths != 0) {
 263     gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
 264     ret = false;
 265   }
 266   if (_head != NULL) {
 267     gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
 268     ret = false;
 269   }
 270   if (!ret) {
 271     gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
 272   }
 273 
 274   return ret;
 275 }
 276 
 277 void
 278 YoungList::rs_length_sampling_init() {
 279   _sampled_rs_lengths = 0;
 280   _curr               = _head;
 281 }
 282 
 283 bool
 284 YoungList::rs_length_sampling_more() {
 285   return _curr != NULL;
 286 }
 287 
 288 void
 289 YoungList::rs_length_sampling_next() {
 290   assert( _curr != NULL, "invariant" );
 291   size_t rs_length = _curr->rem_set()->occupied();
 292 
 293   _sampled_rs_lengths += rs_length;
 294 
 295   // The current region may not yet have been added to the
 296   // incremental collection set (it gets added when it is
 297   // retired as the current allocation region).
 298   if (_curr->in_collection_set()) {
 299     // Update the collection set policy information for this region
 300     _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
 301   }
 302 
 303   _curr = _curr->get_next_young_region();
 304   if (_curr == NULL) {
 305     _last_sampled_rs_lengths = _sampled_rs_lengths;
 306     // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
 307   }
 308 }
 309 
 310 void
 311 YoungList::reset_auxilary_lists() {
 312   guarantee( is_empty(), "young list should be empty" );
 313   assert(check_list_well_formed(), "young list should be well formed");
 314 
 315   // Add survivor regions to SurvRateGroup.
 316   _g1h->g1_policy()->note_start_adding_survivor_regions();
 317   _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
 318 
 319   int young_index_in_cset = 0;
 320   for (HeapRegion* curr = _survivor_head;
 321        curr != NULL;
 322        curr = curr->get_next_young_region()) {
 323     _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
 324 
 325     // The region is a non-empty survivor so let's add it to
 326     // the incremental collection set for the next evacuation
 327     // pause.
 328     _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
 329     young_index_in_cset += 1;
 330   }
 331   assert((uint) young_index_in_cset == _survivor_length, "post-condition");
 332   _g1h->g1_policy()->note_stop_adding_survivor_regions();
 333 
 334   _head   = _survivor_head;
 335   _length = _survivor_length;
 336   if (_survivor_head != NULL) {
 337     assert(_survivor_tail != NULL, "cause it shouldn't be");
 338     assert(_survivor_length > 0, "invariant");
 339     _survivor_tail->set_next_young_region(NULL);
 340   }
 341 
 342   // Don't clear the survivor list handles until the start of
 343   // the next evacuation pause - we need it in order to re-tag
 344   // the survivor regions from this evacuation pause as 'young'
 345   // at the start of the next.
 346 
 347   _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
 348 
 349   assert(check_list_well_formed(), "young list should be well formed");
 350 }
 351 
 352 void YoungList::print() {
 353   HeapRegion* lists[] = {_head,   _survivor_head};
 354   const char* names[] = {"YOUNG", "SURVIVOR"};
 355 
 356   for (uint list = 0; list < ARRAY_SIZE(lists); ++list) {
 357     gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
 358     HeapRegion *curr = lists[list];
 359     if (curr == NULL)
 360       gclog_or_tty->print_cr("  empty");
 361     while (curr != NULL) {
 362       gclog_or_tty->print_cr("  " HR_FORMAT ", P: " PTR_FORMAT ", N: " PTR_FORMAT ", age: %4d",
 363                              HR_FORMAT_PARAMS(curr),
 364                              curr->prev_top_at_mark_start(),
 365                              curr->next_top_at_mark_start(),
 366                              curr->age_in_surv_rate_group_cond());
 367       curr = curr->get_next_young_region();
 368     }
 369   }
 370 
 371   gclog_or_tty->cr();
 372 }
 373 
 374 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
 375   OtherRegionsTable::invalidate(start_idx, num_regions);
 376 }
 377 
 378 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
 379   // The from card cache is not the memory that is actually committed. So we cannot
 380   // take advantage of the zero_filled parameter.
 381   reset_from_card_cache(start_idx, num_regions);
 382 }
 383 
 384 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
 385 {
 386   // Claim the right to put the region on the dirty cards region list
 387   // by installing a self pointer.
 388   HeapRegion* next = hr->get_next_dirty_cards_region();
 389   if (next == NULL) {
 390     HeapRegion* res = (HeapRegion*)
 391       Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
 392                           NULL);
 393     if (res == NULL) {
 394       HeapRegion* head;
 395       do {
 396         // Put the region to the dirty cards region list.
 397         head = _dirty_cards_region_list;
 398         next = (HeapRegion*)
 399           Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
 400         if (next == head) {
 401           assert(hr->get_next_dirty_cards_region() == hr,
 402                  "hr->get_next_dirty_cards_region() != hr");
 403           if (next == NULL) {
 404             // The last region in the list points to itself.
 405             hr->set_next_dirty_cards_region(hr);
 406           } else {
 407             hr->set_next_dirty_cards_region(next);
 408           }
 409         }
 410       } while (next != head);
 411     }
 412   }
 413 }
 414 
 415 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
 416 {
 417   HeapRegion* head;
 418   HeapRegion* hr;
 419   do {
 420     head = _dirty_cards_region_list;
 421     if (head == NULL) {
 422       return NULL;
 423     }
 424     HeapRegion* new_head = head->get_next_dirty_cards_region();
 425     if (head == new_head) {
 426       // The last region.
 427       new_head = NULL;
 428     }
 429     hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
 430                                           head);
 431   } while (hr != head);
 432   assert(hr != NULL, "invariant");
 433   hr->set_next_dirty_cards_region(NULL);
 434   return hr;
 435 }
 436 
 437 #ifdef ASSERT
 438 // A region is added to the collection set as it is retired
 439 // so an address p can point to a region which will be in the
 440 // collection set but has not yet been retired.  This method
 441 // therefore is only accurate during a GC pause after all
 442 // regions have been retired.  It is used for debugging
 443 // to check if an nmethod has references to objects that can
 444 // be move during a partial collection.  Though it can be
 445 // inaccurate, it is sufficient for G1 because the conservative
 446 // implementation of is_scavengable() for G1 will indicate that
 447 // all nmethods must be scanned during a partial collection.
 448 bool G1CollectedHeap::is_in_partial_collection(const void* p) {
 449   if (p == NULL) {
 450     return false;
 451   }
 452   return heap_region_containing(p)->in_collection_set();
 453 }
 454 #endif
 455 
 456 // Returns true if the reference points to an object that
 457 // can move in an incremental collection.
 458 bool G1CollectedHeap::is_scavengable(const void* p) {
 459   HeapRegion* hr = heap_region_containing(p);
 460   return !hr->isHumongous();
 461 }
 462 
 463 void G1CollectedHeap::check_ct_logs_at_safepoint() {
 464   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
 465   CardTableModRefBS* ct_bs = g1_barrier_set();
 466 
 467   // Count the dirty cards at the start.
 468   CountNonCleanMemRegionClosure count1(this);
 469   ct_bs->mod_card_iterate(&count1);
 470   int orig_count = count1.n();
 471 
 472   // First clear the logged cards.
 473   ClearLoggedCardTableEntryClosure clear;
 474   dcqs.apply_closure_to_all_completed_buffers(&clear);
 475   dcqs.iterate_closure_all_threads(&clear, false);
 476   clear.print_histo();
 477 
 478   // Now ensure that there's no dirty cards.
 479   CountNonCleanMemRegionClosure count2(this);
 480   ct_bs->mod_card_iterate(&count2);
 481   if (count2.n() != 0) {
 482     gclog_or_tty->print_cr("Card table has %d entries; %d originally",
 483                            count2.n(), orig_count);
 484   }
 485   guarantee(count2.n() == 0, "Card table should be clean.");
 486 
 487   RedirtyLoggedCardTableEntryClosure redirty;
 488   dcqs.apply_closure_to_all_completed_buffers(&redirty);
 489   dcqs.iterate_closure_all_threads(&redirty, false);
 490   gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
 491                          clear.num_processed(), orig_count);
 492   guarantee(redirty.num_processed() == clear.num_processed(),
 493             err_msg("Redirtied " SIZE_FORMAT " cards, bug cleared " SIZE_FORMAT,
 494                     redirty.num_processed(), clear.num_processed()));
 495 
 496   CountNonCleanMemRegionClosure count3(this);
 497   ct_bs->mod_card_iterate(&count3);
 498   if (count3.n() != orig_count) {
 499     gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
 500                            orig_count, count3.n());
 501     guarantee(count3.n() >= orig_count, "Should have restored them all.");
 502   }
 503 }
 504 
 505 // Private class members.
 506 
 507 G1CollectedHeap* G1CollectedHeap::_g1h;
 508 
 509 // Private methods.
 510 
 511 HeapRegion*
 512 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
 513   MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
 514   while (!_secondary_free_list.is_empty() || free_regions_coming()) {
 515     if (!_secondary_free_list.is_empty()) {
 516       if (G1ConcRegionFreeingVerbose) {
 517         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 518                                "secondary_free_list has %u entries",
 519                                _secondary_free_list.length());
 520       }
 521       // It looks as if there are free regions available on the
 522       // secondary_free_list. Let's move them to the free_list and try
 523       // again to allocate from it.
 524       append_secondary_free_list();
 525 
 526       assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not "
 527              "empty we should have moved at least one entry to the free_list");
 528       HeapRegion* res = _hrm.allocate_free_region(is_old);
 529       if (G1ConcRegionFreeingVerbose) {
 530         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 531                                "allocated " HR_FORMAT " from secondary_free_list",
 532                                HR_FORMAT_PARAMS(res));
 533       }
 534       return res;
 535     }
 536 
 537     // Wait here until we get notified either when (a) there are no
 538     // more free regions coming or (b) some regions have been moved on
 539     // the secondary_free_list.
 540     SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
 541   }
 542 
 543   if (G1ConcRegionFreeingVerbose) {
 544     gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 545                            "could not allocate from secondary_free_list");
 546   }
 547   return NULL;
 548 }
 549 
 550 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
 551   assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords,
 552          "the only time we use this to allocate a humongous region is "
 553          "when we are allocating a single humongous region");
 554 
 555   HeapRegion* res;
 556   if (G1StressConcRegionFreeing) {
 557     if (!_secondary_free_list.is_empty()) {
 558       if (G1ConcRegionFreeingVerbose) {
 559         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 560                                "forced to look at the secondary_free_list");
 561       }
 562       res = new_region_try_secondary_free_list(is_old);
 563       if (res != NULL) {
 564         return res;
 565       }
 566     }
 567   }
 568 
 569   res = _hrm.allocate_free_region(is_old);
 570 
 571   if (res == NULL) {
 572     if (G1ConcRegionFreeingVerbose) {
 573       gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 574                              "res == NULL, trying the secondary_free_list");
 575     }
 576     res = new_region_try_secondary_free_list(is_old);
 577   }
 578   if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
 579     // Currently, only attempts to allocate GC alloc regions set
 580     // do_expand to true. So, we should only reach here during a
 581     // safepoint. If this assumption changes we might have to
 582     // reconsider the use of _expand_heap_after_alloc_failure.
 583     assert(SafepointSynchronize::is_at_safepoint(), "invariant");
 584 
 585     ergo_verbose1(ErgoHeapSizing,
 586                   "attempt heap expansion",
 587                   ergo_format_reason("region allocation request failed")
 588                   ergo_format_byte("allocation request"),
 589                   word_size * HeapWordSize);
 590     if (expand(word_size * HeapWordSize)) {
 591       // Given that expand() succeeded in expanding the heap, and we
 592       // always expand the heap by an amount aligned to the heap
 593       // region size, the free list should in theory not be empty.
 594       // In either case allocate_free_region() will check for NULL.
 595       res = _hrm.allocate_free_region(is_old);
 596     } else {
 597       _expand_heap_after_alloc_failure = false;
 598     }
 599   }
 600   return res;
 601 }
 602 
 603 HeapWord*
 604 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
 605                                                            uint num_regions,
 606                                                            size_t word_size,
 607                                                            AllocationContext_t context) {
 608   assert(first != G1_NO_HRM_INDEX, "pre-condition");
 609   assert(isHumongous(word_size), "word_size should be humongous");
 610   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 611 
 612   // Index of last region in the series + 1.
 613   uint last = first + num_regions;
 614 
 615   // We need to initialize the region(s) we just discovered. This is
 616   // a bit tricky given that it can happen concurrently with
 617   // refinement threads refining cards on these regions and
 618   // potentially wanting to refine the BOT as they are scanning
 619   // those cards (this can happen shortly after a cleanup; see CR
 620   // 6991377). So we have to set up the region(s) carefully and in
 621   // a specific order.
 622 
 623   // The word size sum of all the regions we will allocate.
 624   size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
 625   assert(word_size <= word_size_sum, "sanity");
 626 
 627   // This will be the "starts humongous" region.
 628   HeapRegion* first_hr = region_at(first);
 629   // The header of the new object will be placed at the bottom of
 630   // the first region.
 631   HeapWord* new_obj = first_hr->bottom();
 632   // This will be the new end of the first region in the series that
 633   // should also match the end of the last region in the series.
 634   HeapWord* new_end = new_obj + word_size_sum;
 635   // This will be the new top of the first region that will reflect
 636   // this allocation.
 637   HeapWord* new_top = new_obj + word_size;
 638 
 639   // First, we need to zero the header of the space that we will be
 640   // allocating. When we update top further down, some refinement
 641   // threads might try to scan the region. By zeroing the header we
 642   // ensure that any thread that will try to scan the region will
 643   // come across the zero klass word and bail out.
 644   //
 645   // NOTE: It would not have been correct to have used
 646   // CollectedHeap::fill_with_object() and make the space look like
 647   // an int array. The thread that is doing the allocation will
 648   // later update the object header to a potentially different array
 649   // type and, for a very short period of time, the klass and length
 650   // fields will be inconsistent. This could cause a refinement
 651   // thread to calculate the object size incorrectly.
 652   Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
 653 
 654   // We will set up the first region as "starts humongous". This
 655   // will also update the BOT covering all the regions to reflect
 656   // that there is a single object that starts at the bottom of the
 657   // first region.
 658   first_hr->set_startsHumongous(new_top, new_end);
 659   first_hr->set_allocation_context(context);
 660   // Then, if there are any, we will set up the "continues
 661   // humongous" regions.
 662   HeapRegion* hr = NULL;
 663   for (uint i = first + 1; i < last; ++i) {
 664     hr = region_at(i);
 665     hr->set_continuesHumongous(first_hr);
 666     hr->set_allocation_context(context);
 667   }
 668   // If we have "continues humongous" regions (hr != NULL), then the
 669   // end of the last one should match new_end.
 670   assert(hr == NULL || hr->end() == new_end, "sanity");
 671 
 672   // Up to this point no concurrent thread would have been able to
 673   // do any scanning on any region in this series. All the top
 674   // fields still point to bottom, so the intersection between
 675   // [bottom,top] and [card_start,card_end] will be empty. Before we
 676   // update the top fields, we'll do a storestore to make sure that
 677   // no thread sees the update to top before the zeroing of the
 678   // object header and the BOT initialization.
 679   OrderAccess::storestore();
 680 
 681   // Now that the BOT and the object header have been initialized,
 682   // we can update top of the "starts humongous" region.
 683   assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
 684          "new_top should be in this region");
 685   first_hr->set_top(new_top);
 686   if (_hr_printer.is_active()) {
 687     HeapWord* bottom = first_hr->bottom();
 688     HeapWord* end = first_hr->orig_end();
 689     if ((first + 1) == last) {
 690       // the series has a single humongous region
 691       _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
 692     } else {
 693       // the series has more than one humongous regions
 694       _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
 695     }
 696   }
 697 
 698   // Now, we will update the top fields of the "continues humongous"
 699   // regions. The reason we need to do this is that, otherwise,
 700   // these regions would look empty and this will confuse parts of
 701   // G1. For example, the code that looks for a consecutive number
 702   // of empty regions will consider them empty and try to
 703   // re-allocate them. We can extend is_empty() to also include
 704   // !continuesHumongous(), but it is easier to just update the top
 705   // fields here. The way we set top for all regions (i.e., top ==
 706   // end for all regions but the last one, top == new_top for the
 707   // last one) is actually used when we will free up the humongous
 708   // region in free_humongous_region().
 709   hr = NULL;
 710   for (uint i = first + 1; i < last; ++i) {
 711     hr = region_at(i);
 712     if ((i + 1) == last) {
 713       // last continues humongous region
 714       assert(hr->bottom() < new_top && new_top <= hr->end(),
 715              "new_top should fall on this region");
 716       hr->set_top(new_top);
 717       _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
 718     } else {
 719       // not last one
 720       assert(new_top > hr->end(), "new_top should be above this region");
 721       hr->set_top(hr->end());
 722       _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
 723     }
 724   }
 725   // If we have continues humongous regions (hr != NULL), then the
 726   // end of the last one should match new_end and its top should
 727   // match new_top.
 728   assert(hr == NULL ||
 729          (hr->end() == new_end && hr->top() == new_top), "sanity");
 730   check_bitmaps("Humongous Region Allocation", first_hr);
 731 
 732   assert(first_hr->used() == word_size * HeapWordSize, "invariant");
 733   _allocator->increase_used(first_hr->used());
 734   _humongous_set.add(first_hr);
 735 
 736   return new_obj;
 737 }
 738 
 739 // If could fit into free regions w/o expansion, try.
 740 // Otherwise, if can expand, do so.
 741 // Otherwise, if using ex regions might help, try with ex given back.
 742 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) {
 743   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 744 
 745   verify_region_sets_optional();
 746 
 747   uint first = G1_NO_HRM_INDEX;
 748   uint obj_regions = (uint)(align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords);
 749 
 750   if (obj_regions == 1) {
 751     // Only one region to allocate, try to use a fast path by directly allocating
 752     // from the free lists. Do not try to expand here, we will potentially do that
 753     // later.
 754     HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
 755     if (hr != NULL) {
 756       first = hr->hrm_index();
 757     }
 758   } else {
 759     // We can't allocate humongous regions spanning more than one region while
 760     // cleanupComplete() is running, since some of the regions we find to be
 761     // empty might not yet be added to the free list. It is not straightforward
 762     // to know in which list they are on so that we can remove them. We only
 763     // need to do this if we need to allocate more than one region to satisfy the
 764     // current humongous allocation request. If we are only allocating one region
 765     // we use the one-region region allocation code (see above), that already
 766     // potentially waits for regions from the secondary free list.
 767     wait_while_free_regions_coming();
 768     append_secondary_free_list_if_not_empty_with_lock();
 769 
 770     // Policy: Try only empty regions (i.e. already committed first). Maybe we
 771     // are lucky enough to find some.
 772     first = _hrm.find_contiguous_only_empty(obj_regions);
 773     if (first != G1_NO_HRM_INDEX) {
 774       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 775     }
 776   }
 777 
 778   if (first == G1_NO_HRM_INDEX) {
 779     // Policy: We could not find enough regions for the humongous object in the
 780     // free list. Look through the heap to find a mix of free and uncommitted regions.
 781     // If so, try expansion.
 782     first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
 783     if (first != G1_NO_HRM_INDEX) {
 784       // We found something. Make sure these regions are committed, i.e. expand
 785       // the heap. Alternatively we could do a defragmentation GC.
 786       ergo_verbose1(ErgoHeapSizing,
 787                     "attempt heap expansion",
 788                     ergo_format_reason("humongous allocation request failed")
 789                     ergo_format_byte("allocation request"),
 790                     word_size * HeapWordSize);
 791 
 792       _hrm.expand_at(first, obj_regions);
 793       g1_policy()->record_new_heap_size(num_regions());
 794 
 795 #ifdef ASSERT
 796       for (uint i = first; i < first + obj_regions; ++i) {
 797         HeapRegion* hr = region_at(i);
 798         assert(hr->is_free(), "sanity");
 799         assert(hr->is_empty(), "sanity");
 800         assert(is_on_master_free_list(hr), "sanity");
 801       }
 802 #endif
 803       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 804     } else {
 805       // Policy: Potentially trigger a defragmentation GC.
 806     }
 807   }
 808 
 809   HeapWord* result = NULL;
 810   if (first != G1_NO_HRM_INDEX) {
 811     result = humongous_obj_allocate_initialize_regions(first, obj_regions,
 812                                                        word_size, context);
 813     assert(result != NULL, "it should always return a valid result");
 814 
 815     // A successful humongous object allocation changes the used space
 816     // information of the old generation so we need to recalculate the
 817     // sizes and update the jstat counters here.
 818     g1mm()->update_sizes();
 819   }
 820 
 821   verify_region_sets_optional();
 822 
 823   return result;
 824 }
 825 
 826 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
 827   assert_heap_not_locked_and_not_at_safepoint();
 828   assert(!isHumongous(word_size), "we do not allow humongous TLABs");
 829 
 830   uint dummy_gc_count_before;
 831   uint dummy_gclocker_retry_count = 0;
 832   return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
 833 }
 834 
 835 HeapWord*
 836 G1CollectedHeap::mem_allocate(size_t word_size,
 837                               bool*  gc_overhead_limit_was_exceeded) {
 838   assert_heap_not_locked_and_not_at_safepoint();
 839 
 840   // Loop until the allocation is satisfied, or unsatisfied after GC.
 841   for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 842     uint gc_count_before;
 843 
 844     HeapWord* result = NULL;
 845     if (!isHumongous(word_size)) {
 846       result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
 847     } else {
 848       result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
 849     }
 850     if (result != NULL) {
 851       return result;
 852     }
 853 
 854     // Create the garbage collection operation...
 855     VM_G1CollectForAllocation op(gc_count_before, word_size);
 856     op.set_allocation_context(AllocationContext::current());
 857 
 858     // ...and get the VM thread to execute it.
 859     VMThread::execute(&op);
 860 
 861     if (op.prologue_succeeded() && op.pause_succeeded()) {
 862       // If the operation was successful we'll return the result even
 863       // if it is NULL. If the allocation attempt failed immediately
 864       // after a Full GC, it's unlikely we'll be able to allocate now.
 865       HeapWord* result = op.result();
 866       if (result != NULL && !isHumongous(word_size)) {
 867         // Allocations that take place on VM operations do not do any
 868         // card dirtying and we have to do it here. We only have to do
 869         // this for non-humongous allocations, though.
 870         dirty_young_block(result, word_size);
 871       }
 872       return result;
 873     } else {
 874       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 875         return NULL;
 876       }
 877       assert(op.result() == NULL,
 878              "the result should be NULL if the VM op did not succeed");
 879     }
 880 
 881     // Give a warning if we seem to be looping forever.
 882     if ((QueuedAllocationWarningCount > 0) &&
 883         (try_count % QueuedAllocationWarningCount == 0)) {
 884       warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
 885     }
 886   }
 887 
 888   ShouldNotReachHere();
 889   return NULL;
 890 }
 891 
 892 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
 893                                                    AllocationContext_t context,
 894                                                    uint* gc_count_before_ret,
 895                                                    uint* gclocker_retry_count_ret) {
 896   // Make sure you read the note in attempt_allocation_humongous().
 897 
 898   assert_heap_not_locked_and_not_at_safepoint();
 899   assert(!isHumongous(word_size), "attempt_allocation_slow() should not "
 900          "be called for humongous allocation requests");
 901 
 902   // We should only get here after the first-level allocation attempt
 903   // (attempt_allocation()) failed to allocate.
 904 
 905   // We will loop until a) we manage to successfully perform the
 906   // allocation or b) we successfully schedule a collection which
 907   // fails to perform the allocation. b) is the only case when we'll
 908   // return NULL.
 909   HeapWord* result = NULL;
 910   for (int try_count = 1; /* we'll return */; try_count += 1) {
 911     bool should_try_gc;
 912     uint gc_count_before;
 913 
 914     {
 915       MutexLockerEx x(Heap_lock);
 916       result = _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size,
 917                                                                                     false /* bot_updates */);
 918       if (result != NULL) {
 919         return result;
 920       }
 921 
 922       // If we reach here, attempt_allocation_locked() above failed to
 923       // allocate a new region. So the mutator alloc region should be NULL.
 924       assert(_allocator->mutator_alloc_region(context)->get() == NULL, "only way to get here");
 925 
 926       if (GC_locker::is_active_and_needs_gc()) {
 927         if (g1_policy()->can_expand_young_list()) {
 928           // No need for an ergo verbose message here,
 929           // can_expand_young_list() does this when it returns true.
 930           result = _allocator->mutator_alloc_region(context)->attempt_allocation_force(word_size,
 931                                                                                        false /* bot_updates */);
 932           if (result != NULL) {
 933             return result;
 934           }
 935         }
 936         should_try_gc = false;
 937       } else {
 938         // The GCLocker may not be active but the GCLocker initiated
 939         // GC may not yet have been performed (GCLocker::needs_gc()
 940         // returns true). In this case we do not try this GC and
 941         // wait until the GCLocker initiated GC is performed, and
 942         // then retry the allocation.
 943         if (GC_locker::needs_gc()) {
 944           should_try_gc = false;
 945         } else {
 946           // Read the GC count while still holding the Heap_lock.
 947           gc_count_before = total_collections();
 948           should_try_gc = true;
 949         }
 950       }
 951     }
 952 
 953     if (should_try_gc) {
 954       bool succeeded;
 955       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 956                                    GCCause::_g1_inc_collection_pause);
 957       if (result != NULL) {
 958         assert(succeeded, "only way to get back a non-NULL result");
 959         return result;
 960       }
 961 
 962       if (succeeded) {
 963         // If we get here we successfully scheduled a collection which
 964         // failed to allocate. No point in trying to allocate
 965         // further. We'll just return NULL.
 966         MutexLockerEx x(Heap_lock);
 967         *gc_count_before_ret = total_collections();
 968         return NULL;
 969       }
 970     } else {
 971       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
 972         MutexLockerEx x(Heap_lock);
 973         *gc_count_before_ret = total_collections();
 974         return NULL;
 975       }
 976       // The GCLocker is either active or the GCLocker initiated
 977       // GC has not yet been performed. Stall until it is and
 978       // then retry the allocation.
 979       GC_locker::stall_until_clear();
 980       (*gclocker_retry_count_ret) += 1;
 981     }
 982 
 983     // We can reach here if we were unsuccessful in scheduling a
 984     // collection (because another thread beat us to it) or if we were
 985     // stalled due to the GC locker. In either can we should retry the
 986     // allocation attempt in case another thread successfully
 987     // performed a collection and reclaimed enough space. We do the
 988     // first attempt (without holding the Heap_lock) here and the
 989     // follow-on attempt will be at the start of the next loop
 990     // iteration (after taking the Heap_lock).
 991     result = _allocator->mutator_alloc_region(context)->attempt_allocation(word_size,
 992                                                                            false /* bot_updates */);
 993     if (result != NULL) {
 994       return result;
 995     }
 996 
 997     // Give a warning if we seem to be looping forever.
 998     if ((QueuedAllocationWarningCount > 0) &&
 999         (try_count % QueuedAllocationWarningCount == 0)) {
1000       warning("G1CollectedHeap::attempt_allocation_slow() "
1001               "retries %d times", try_count);
1002     }
1003   }
1004 
1005   ShouldNotReachHere();
1006   return NULL;
1007 }
1008 
1009 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
1010                                                         uint* gc_count_before_ret,
1011                                                         uint* gclocker_retry_count_ret) {
1012   // The structure of this method has a lot of similarities to
1013   // attempt_allocation_slow(). The reason these two were not merged
1014   // into a single one is that such a method would require several "if
1015   // allocation is not humongous do this, otherwise do that"
1016   // conditional paths which would obscure its flow. In fact, an early
1017   // version of this code did use a unified method which was harder to
1018   // follow and, as a result, it had subtle bugs that were hard to
1019   // track down. So keeping these two methods separate allows each to
1020   // be more readable. It will be good to keep these two in sync as
1021   // much as possible.
1022 
1023   assert_heap_not_locked_and_not_at_safepoint();
1024   assert(isHumongous(word_size), "attempt_allocation_humongous() "
1025          "should only be called for humongous allocations");
1026 
1027   // Humongous objects can exhaust the heap quickly, so we should check if we
1028   // need to start a marking cycle at each humongous object allocation. We do
1029   // the check before we do the actual allocation. The reason for doing it
1030   // before the allocation is that we avoid having to keep track of the newly
1031   // allocated memory while we do a GC.
1032   if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
1033                                            word_size)) {
1034     collect(GCCause::_g1_humongous_allocation);
1035   }
1036 
1037   // We will loop until a) we manage to successfully perform the
1038   // allocation or b) we successfully schedule a collection which
1039   // fails to perform the allocation. b) is the only case when we'll
1040   // return NULL.
1041   HeapWord* result = NULL;
1042   for (int try_count = 1; /* we'll return */; try_count += 1) {
1043     bool should_try_gc;
1044     uint gc_count_before;
1045 
1046     {
1047       MutexLockerEx x(Heap_lock);
1048 
1049       // Given that humongous objects are not allocated in young
1050       // regions, we'll first try to do the allocation without doing a
1051       // collection hoping that there's enough space in the heap.
1052       result = humongous_obj_allocate(word_size, AllocationContext::current());
1053       if (result != NULL) {
1054         return result;
1055       }
1056 
1057       if (GC_locker::is_active_and_needs_gc()) {
1058         should_try_gc = false;
1059       } else {
1060          // The GCLocker may not be active but the GCLocker initiated
1061         // GC may not yet have been performed (GCLocker::needs_gc()
1062         // returns true). In this case we do not try this GC and
1063         // wait until the GCLocker initiated GC is performed, and
1064         // then retry the allocation.
1065         if (GC_locker::needs_gc()) {
1066           should_try_gc = false;
1067         } else {
1068           // Read the GC count while still holding the Heap_lock.
1069           gc_count_before = total_collections();
1070           should_try_gc = true;
1071         }
1072       }
1073     }
1074 
1075     if (should_try_gc) {
1076       // If we failed to allocate the humongous object, we should try to
1077       // do a collection pause (if we're allowed) in case it reclaims
1078       // enough space for the allocation to succeed after the pause.
1079 
1080       bool succeeded;
1081       result = do_collection_pause(word_size, gc_count_before, &succeeded,
1082                                    GCCause::_g1_humongous_allocation);
1083       if (result != NULL) {
1084         assert(succeeded, "only way to get back a non-NULL result");
1085         return result;
1086       }
1087 
1088       if (succeeded) {
1089         // If we get here we successfully scheduled a collection which
1090         // failed to allocate. No point in trying to allocate
1091         // further. We'll just return NULL.
1092         MutexLockerEx x(Heap_lock);
1093         *gc_count_before_ret = total_collections();
1094         return NULL;
1095       }
1096     } else {
1097       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1098         MutexLockerEx x(Heap_lock);
1099         *gc_count_before_ret = total_collections();
1100         return NULL;
1101       }
1102       // The GCLocker is either active or the GCLocker initiated
1103       // GC has not yet been performed. Stall until it is and
1104       // then retry the allocation.
1105       GC_locker::stall_until_clear();
1106       (*gclocker_retry_count_ret) += 1;
1107     }
1108 
1109     // We can reach here if we were unsuccessful in scheduling a
1110     // collection (because another thread beat us to it) or if we were
1111     // stalled due to the GC locker. In either can we should retry the
1112     // allocation attempt in case another thread successfully
1113     // performed a collection and reclaimed enough space.  Give a
1114     // warning if we seem to be looping forever.
1115 
1116     if ((QueuedAllocationWarningCount > 0) &&
1117         (try_count % QueuedAllocationWarningCount == 0)) {
1118       warning("G1CollectedHeap::attempt_allocation_humongous() "
1119               "retries %d times", try_count);
1120     }
1121   }
1122 
1123   ShouldNotReachHere();
1124   return NULL;
1125 }
1126 
1127 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1128                                                            AllocationContext_t context,
1129                                                            bool expect_null_mutator_alloc_region) {
1130   assert_at_safepoint(true /* should_be_vm_thread */);
1131   assert(_allocator->mutator_alloc_region(context)->get() == NULL ||
1132                                              !expect_null_mutator_alloc_region,
1133          "the current alloc region was unexpectedly found to be non-NULL");
1134 
1135   if (!isHumongous(word_size)) {
1136     return _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size,
1137                                                       false /* bot_updates */);
1138   } else {
1139     HeapWord* result = humongous_obj_allocate(word_size, context);
1140     if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1141       g1_policy()->set_initiate_conc_mark_if_possible();
1142     }
1143     return result;
1144   }
1145 
1146   ShouldNotReachHere();
1147 }
1148 
1149 class PostMCRemSetClearClosure: public HeapRegionClosure {
1150   G1CollectedHeap* _g1h;
1151   ModRefBarrierSet* _mr_bs;
1152 public:
1153   PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1154     _g1h(g1h), _mr_bs(mr_bs) {}
1155 
1156   bool doHeapRegion(HeapRegion* r) {
1157     HeapRegionRemSet* hrrs = r->rem_set();
1158 
1159     if (r->continuesHumongous()) {
1160       // We'll assert that the strong code root list and RSet is empty
1161       assert(hrrs->strong_code_roots_list_length() == 0, "sanity");
1162       assert(hrrs->occupied() == 0, "RSet should be empty");
1163       return false;
1164     }
1165 
1166     _g1h->reset_gc_time_stamps(r);
1167     hrrs->clear();
1168     // You might think here that we could clear just the cards
1169     // corresponding to the used region.  But no: if we leave a dirty card
1170     // in a region we might allocate into, then it would prevent that card
1171     // from being enqueued, and cause it to be missed.
1172     // Re: the performance cost: we shouldn't be doing full GC anyway!
1173     _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1174 
1175     return false;
1176   }
1177 };
1178 
1179 void G1CollectedHeap::clear_rsets_post_compaction() {
1180   PostMCRemSetClearClosure rs_clear(this, g1_barrier_set());
1181   heap_region_iterate(&rs_clear);
1182 }
1183 
1184 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1185   G1CollectedHeap*   _g1h;
1186   UpdateRSOopClosure _cl;
1187   int                _worker_i;
1188 public:
1189   RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1190     _cl(g1->g1_rem_set(), worker_i),
1191     _worker_i(worker_i),
1192     _g1h(g1)
1193   { }
1194 
1195   bool doHeapRegion(HeapRegion* r) {
1196     if (!r->continuesHumongous()) {
1197       _cl.set_from(r);
1198       r->oop_iterate(&_cl);
1199     }
1200     return false;
1201   }
1202 };
1203 
1204 class ParRebuildRSTask: public AbstractGangTask {
1205   G1CollectedHeap* _g1;
1206 public:
1207   ParRebuildRSTask(G1CollectedHeap* g1)
1208     : AbstractGangTask("ParRebuildRSTask"),
1209       _g1(g1)
1210   { }
1211 
1212   void work(uint worker_id) {
1213     RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1214     _g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id,
1215                                           _g1->workers()->active_workers(),
1216                                          HeapRegion::RebuildRSClaimValue);
1217   }
1218 };
1219 
1220 class PostCompactionPrinterClosure: public HeapRegionClosure {
1221 private:
1222   G1HRPrinter* _hr_printer;
1223 public:
1224   bool doHeapRegion(HeapRegion* hr) {
1225     assert(!hr->is_young(), "not expecting to find young regions");
1226     if (hr->is_free()) {
1227       // We only generate output for non-empty regions.
1228     } else if (hr->startsHumongous()) {
1229       if (hr->region_num() == 1) {
1230         // single humongous region
1231         _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
1232       } else {
1233         _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
1234       }
1235     } else if (hr->continuesHumongous()) {
1236       _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1237     } else if (hr->is_old()) {
1238       _hr_printer->post_compaction(hr, G1HRPrinter::Old);
1239     } else {
1240       ShouldNotReachHere();
1241     }
1242     return false;
1243   }
1244 
1245   PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1246     : _hr_printer(hr_printer) { }
1247 };
1248 
1249 void G1CollectedHeap::print_hrm_post_compaction() {
1250   PostCompactionPrinterClosure cl(hr_printer());
1251   heap_region_iterate(&cl);
1252 }
1253 
1254 bool G1CollectedHeap::do_collection(bool explicit_gc,
1255                                     bool clear_all_soft_refs,
1256                                     size_t word_size) {
1257   assert_at_safepoint(true /* should_be_vm_thread */);
1258 
1259   if (GC_locker::check_active_before_gc()) {
1260     return false;
1261   }
1262 
1263   STWGCTimer* gc_timer = G1MarkSweep::gc_timer();
1264   gc_timer->register_gc_start();
1265 
1266   SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer();
1267   gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start());
1268 
1269   SvcGCMarker sgcm(SvcGCMarker::FULL);
1270   ResourceMark rm;
1271 
1272   print_heap_before_gc();
1273   trace_heap_before_gc(gc_tracer);
1274 
1275   size_t metadata_prev_used = MetaspaceAux::used_bytes();
1276 
1277   verify_region_sets_optional();
1278 
1279   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1280                            collector_policy()->should_clear_all_soft_refs();
1281 
1282   ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1283 
1284   {
1285     IsGCActiveMark x;
1286 
1287     // Timing
1288     assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant");
1289     TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
1290 
1291     {
1292       GCTraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, NULL, gc_tracer->gc_id());
1293       TraceCollectorStats tcs(g1mm()->full_collection_counters());
1294       TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1295 
1296       double start = os::elapsedTime();
1297       g1_policy()->record_full_collection_start();
1298 
1299       // Note: When we have a more flexible GC logging framework that
1300       // allows us to add optional attributes to a GC log record we
1301       // could consider timing and reporting how long we wait in the
1302       // following two methods.
1303       wait_while_free_regions_coming();
1304       // If we start the compaction before the CM threads finish
1305       // scanning the root regions we might trip them over as we'll
1306       // be moving objects / updating references. So let's wait until
1307       // they are done. By telling them to abort, they should complete
1308       // early.
1309       _cm->root_regions()->abort();
1310       _cm->root_regions()->wait_until_scan_finished();
1311       append_secondary_free_list_if_not_empty_with_lock();
1312 
1313       gc_prologue(true);
1314       increment_total_collections(true /* full gc */);
1315       increment_old_marking_cycles_started();
1316 
1317       assert(used() == recalculate_used(), "Should be equal");
1318 
1319       verify_before_gc();
1320 
1321       check_bitmaps("Full GC Start");
1322       pre_full_gc_dump(gc_timer);
1323 
1324       COMPILER2_PRESENT(DerivedPointerTable::clear());
1325 
1326       // Disable discovery and empty the discovered lists
1327       // for the CM ref processor.
1328       ref_processor_cm()->disable_discovery();
1329       ref_processor_cm()->abandon_partial_discovery();
1330       ref_processor_cm()->verify_no_references_recorded();
1331 
1332       // Abandon current iterations of concurrent marking and concurrent
1333       // refinement, if any are in progress. We have to do this before
1334       // wait_until_scan_finished() below.
1335       concurrent_mark()->abort();
1336 
1337       // Make sure we'll choose a new allocation region afterwards.
1338       _allocator->release_mutator_alloc_region();
1339       _allocator->abandon_gc_alloc_regions();
1340       g1_rem_set()->cleanupHRRS();
1341 
1342       // We should call this after we retire any currently active alloc
1343       // regions so that all the ALLOC / RETIRE events are generated
1344       // before the start GC event.
1345       _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1346 
1347       // We may have added regions to the current incremental collection
1348       // set between the last GC or pause and now. We need to clear the
1349       // incremental collection set and then start rebuilding it afresh
1350       // after this full GC.
1351       abandon_collection_set(g1_policy()->inc_cset_head());
1352       g1_policy()->clear_incremental_cset();
1353       g1_policy()->stop_incremental_cset_building();
1354 
1355       tear_down_region_sets(false /* free_list_only */);
1356       g1_policy()->set_gcs_are_young(true);
1357 
1358       // See the comments in g1CollectedHeap.hpp and
1359       // G1CollectedHeap::ref_processing_init() about
1360       // how reference processing currently works in G1.
1361 
1362       // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1363       ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1364 
1365       // Temporarily clear the STW ref processor's _is_alive_non_header field.
1366       ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1367 
1368       ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
1369       ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1370 
1371       // Do collection work
1372       {
1373         HandleMark hm;  // Discard invalid handles created during gc
1374         G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1375       }
1376 
1377       assert(num_free_regions() == 0, "we should not have added any free regions");
1378       rebuild_region_sets(false /* free_list_only */);
1379 
1380       // Enqueue any discovered reference objects that have
1381       // not been removed from the discovered lists.
1382       ref_processor_stw()->enqueue_discovered_references();
1383 
1384       COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1385 
1386       MemoryService::track_memory_usage();
1387 
1388       assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1389       ref_processor_stw()->verify_no_references_recorded();
1390 
1391       // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1392       ClassLoaderDataGraph::purge();
1393       MetaspaceAux::verify_metrics();
1394 
1395       // Note: since we've just done a full GC, concurrent
1396       // marking is no longer active. Therefore we need not
1397       // re-enable reference discovery for the CM ref processor.
1398       // That will be done at the start of the next marking cycle.
1399       assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1400       ref_processor_cm()->verify_no_references_recorded();
1401 
1402       reset_gc_time_stamp();
1403       // Since everything potentially moved, we will clear all remembered
1404       // sets, and clear all cards.  Later we will rebuild remembered
1405       // sets. We will also reset the GC time stamps of the regions.
1406       clear_rsets_post_compaction();
1407       check_gc_time_stamps();
1408 
1409       // Resize the heap if necessary.
1410       resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1411 
1412       if (_hr_printer.is_active()) {
1413         // We should do this after we potentially resize the heap so
1414         // that all the COMMIT / UNCOMMIT events are generated before
1415         // the end GC event.
1416 
1417         print_hrm_post_compaction();
1418         _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1419       }
1420 
1421       G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
1422       if (hot_card_cache->use_cache()) {
1423         hot_card_cache->reset_card_counts();
1424         hot_card_cache->reset_hot_cache();
1425       }
1426 
1427       // Rebuild remembered sets of all regions.
1428       if (G1CollectedHeap::use_parallel_gc_threads()) {
1429         uint n_workers =
1430           AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1431                                                   workers()->active_workers(),
1432                                                   Threads::number_of_non_daemon_threads());
1433         assert(UseDynamicNumberOfGCThreads ||
1434                n_workers == workers()->total_workers(),
1435                "If not dynamic should be using all the  workers");
1436         workers()->set_active_workers(n_workers);
1437         // Set parallel threads in the heap (_n_par_threads) only
1438         // before a parallel phase and always reset it to 0 after
1439         // the phase so that the number of parallel threads does
1440         // no get carried forward to a serial phase where there
1441         // may be code that is "possibly_parallel".
1442         set_par_threads(n_workers);
1443 
1444         ParRebuildRSTask rebuild_rs_task(this);
1445         assert(check_heap_region_claim_values(
1446                HeapRegion::InitialClaimValue), "sanity check");
1447         assert(UseDynamicNumberOfGCThreads ||
1448                workers()->active_workers() == workers()->total_workers(),
1449                "Unless dynamic should use total workers");
1450         // Use the most recent number of  active workers
1451         assert(workers()->active_workers() > 0,
1452                "Active workers not properly set");
1453         set_par_threads(workers()->active_workers());
1454         workers()->run_task(&rebuild_rs_task);
1455         set_par_threads(0);
1456         assert(check_heap_region_claim_values(
1457                HeapRegion::RebuildRSClaimValue), "sanity check");
1458         reset_heap_region_claim_values();
1459       } else {
1460         RebuildRSOutOfRegionClosure rebuild_rs(this);
1461         heap_region_iterate(&rebuild_rs);
1462       }
1463 
1464       // Rebuild the strong code root lists for each region
1465       rebuild_strong_code_roots();
1466 
1467       // Purge code root memory
1468       purge_code_root_memory();
1469 
1470       if (true) { // FIXME
1471         MetaspaceGC::compute_new_size();
1472       }
1473 
1474 #ifdef TRACESPINNING
1475       ParallelTaskTerminator::print_termination_counts();
1476 #endif
1477 
1478       // Discard all rset updates
1479       JavaThread::dirty_card_queue_set().abandon_logs();
1480       assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1481 
1482       _young_list->reset_sampled_info();
1483       // At this point there should be no regions in the
1484       // entire heap tagged as young.
1485       assert(check_young_list_empty(true /* check_heap */),
1486              "young list should be empty at this point");
1487 
1488       // Update the number of full collections that have been completed.
1489       increment_old_marking_cycles_completed(false /* concurrent */);
1490 
1491       _hrm.verify_optional();
1492       verify_region_sets_optional();
1493 
1494       verify_after_gc();
1495 
1496       // Clear the previous marking bitmap, if needed for bitmap verification.
1497       // Note we cannot do this when we clear the next marking bitmap in
1498       // ConcurrentMark::abort() above since VerifyDuringGC verifies the
1499       // objects marked during a full GC against the previous bitmap.
1500       // But we need to clear it before calling check_bitmaps below since
1501       // the full GC has compacted objects and updated TAMS but not updated
1502       // the prev bitmap.
1503       if (G1VerifyBitmaps) {
1504         ((CMBitMap*) concurrent_mark()->prevMarkBitMap())->clearAll();
1505       }
1506       check_bitmaps("Full GC End");
1507 
1508       // Start a new incremental collection set for the next pause
1509       assert(g1_policy()->collection_set() == NULL, "must be");
1510       g1_policy()->start_incremental_cset_building();
1511 
1512       clear_cset_fast_test();
1513 
1514       _allocator->init_mutator_alloc_region();
1515 
1516       double end = os::elapsedTime();
1517       g1_policy()->record_full_collection_end();
1518 
1519       if (G1Log::fine()) {
1520         g1_policy()->print_heap_transition();
1521       }
1522 
1523       // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1524       // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1525       // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1526       // before any GC notifications are raised.
1527       g1mm()->update_sizes();
1528 
1529       gc_epilogue(true);
1530     }
1531 
1532     if (G1Log::finer()) {
1533       g1_policy()->print_detailed_heap_transition(true /* full */);
1534     }
1535 
1536     print_heap_after_gc();
1537     trace_heap_after_gc(gc_tracer);
1538 
1539     post_full_gc_dump(gc_timer);
1540 
1541     gc_timer->register_gc_end();
1542     gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
1543   }
1544 
1545   return true;
1546 }
1547 
1548 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1549   // do_collection() will return whether it succeeded in performing
1550   // the GC. Currently, there is no facility on the
1551   // do_full_collection() API to notify the caller than the collection
1552   // did not succeed (e.g., because it was locked out by the GC
1553   // locker). So, right now, we'll ignore the return value.
1554   bool dummy = do_collection(true,                /* explicit_gc */
1555                              clear_all_soft_refs,
1556                              0                    /* word_size */);
1557 }
1558 
1559 // This code is mostly copied from TenuredGeneration.
1560 void
1561 G1CollectedHeap::
1562 resize_if_necessary_after_full_collection(size_t word_size) {
1563   // Include the current allocation, if any, and bytes that will be
1564   // pre-allocated to support collections, as "used".
1565   const size_t used_after_gc = used();
1566   const size_t capacity_after_gc = capacity();
1567   const size_t free_after_gc = capacity_after_gc - used_after_gc;
1568 
1569   // This is enforced in arguments.cpp.
1570   assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1571          "otherwise the code below doesn't make sense");
1572 
1573   // We don't have floating point command-line arguments
1574   const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1575   const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1576   const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1577   const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1578 
1579   const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1580   const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1581 
1582   // We have to be careful here as these two calculations can overflow
1583   // 32-bit size_t's.
1584   double used_after_gc_d = (double) used_after_gc;
1585   double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1586   double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1587 
1588   // Let's make sure that they are both under the max heap size, which
1589   // by default will make them fit into a size_t.
1590   double desired_capacity_upper_bound = (double) max_heap_size;
1591   minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1592                                     desired_capacity_upper_bound);
1593   maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1594                                     desired_capacity_upper_bound);
1595 
1596   // We can now safely turn them into size_t's.
1597   size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1598   size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1599 
1600   // This assert only makes sense here, before we adjust them
1601   // with respect to the min and max heap size.
1602   assert(minimum_desired_capacity <= maximum_desired_capacity,
1603          err_msg("minimum_desired_capacity = " SIZE_FORMAT ", "
1604                  "maximum_desired_capacity = " SIZE_FORMAT,
1605                  minimum_desired_capacity, maximum_desired_capacity));
1606 
1607   // Should not be greater than the heap max size. No need to adjust
1608   // it with respect to the heap min size as it's a lower bound (i.e.,
1609   // we'll try to make the capacity larger than it, not smaller).
1610   minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1611   // Should not be less than the heap min size. No need to adjust it
1612   // with respect to the heap max size as it's an upper bound (i.e.,
1613   // we'll try to make the capacity smaller than it, not greater).
1614   maximum_desired_capacity =  MAX2(maximum_desired_capacity, min_heap_size);
1615 
1616   if (capacity_after_gc < minimum_desired_capacity) {
1617     // Don't expand unless it's significant
1618     size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1619     ergo_verbose4(ErgoHeapSizing,
1620                   "attempt heap expansion",
1621                   ergo_format_reason("capacity lower than "
1622                                      "min desired capacity after Full GC")
1623                   ergo_format_byte("capacity")
1624                   ergo_format_byte("occupancy")
1625                   ergo_format_byte_perc("min desired capacity"),
1626                   capacity_after_gc, used_after_gc,
1627                   minimum_desired_capacity, (double) MinHeapFreeRatio);
1628     expand(expand_bytes);
1629 
1630     // No expansion, now see if we want to shrink
1631   } else if (capacity_after_gc > maximum_desired_capacity) {
1632     // Capacity too large, compute shrinking size
1633     size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1634     ergo_verbose4(ErgoHeapSizing,
1635                   "attempt heap shrinking",
1636                   ergo_format_reason("capacity higher than "
1637                                      "max desired capacity after Full GC")
1638                   ergo_format_byte("capacity")
1639                   ergo_format_byte("occupancy")
1640                   ergo_format_byte_perc("max desired capacity"),
1641                   capacity_after_gc, used_after_gc,
1642                   maximum_desired_capacity, (double) MaxHeapFreeRatio);
1643     shrink(shrink_bytes);
1644   }
1645 }
1646 
1647 
1648 HeapWord*
1649 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1650                                            AllocationContext_t context,
1651                                            bool* succeeded) {
1652   assert_at_safepoint(true /* should_be_vm_thread */);
1653 
1654   *succeeded = true;
1655   // Let's attempt the allocation first.
1656   HeapWord* result =
1657     attempt_allocation_at_safepoint(word_size,
1658                                     context,
1659                                     false /* expect_null_mutator_alloc_region */);
1660   if (result != NULL) {
1661     assert(*succeeded, "sanity");
1662     return result;
1663   }
1664 
1665   // In a G1 heap, we're supposed to keep allocation from failing by
1666   // incremental pauses.  Therefore, at least for now, we'll favor
1667   // expansion over collection.  (This might change in the future if we can
1668   // do something smarter than full collection to satisfy a failed alloc.)
1669   result = expand_and_allocate(word_size, context);
1670   if (result != NULL) {
1671     assert(*succeeded, "sanity");
1672     return result;
1673   }
1674 
1675   // Expansion didn't work, we'll try to do a Full GC.
1676   bool gc_succeeded = do_collection(false, /* explicit_gc */
1677                                     false, /* clear_all_soft_refs */
1678                                     word_size);
1679   if (!gc_succeeded) {
1680     *succeeded = false;
1681     return NULL;
1682   }
1683 
1684   // Retry the allocation
1685   result = attempt_allocation_at_safepoint(word_size,
1686                                            context,
1687                                            true /* expect_null_mutator_alloc_region */);
1688   if (result != NULL) {
1689     assert(*succeeded, "sanity");
1690     return result;
1691   }
1692 
1693   // Then, try a Full GC that will collect all soft references.
1694   gc_succeeded = do_collection(false, /* explicit_gc */
1695                                true,  /* clear_all_soft_refs */
1696                                word_size);
1697   if (!gc_succeeded) {
1698     *succeeded = false;
1699     return NULL;
1700   }
1701 
1702   // Retry the allocation once more
1703   result = attempt_allocation_at_safepoint(word_size,
1704                                            context,
1705                                            true /* expect_null_mutator_alloc_region */);
1706   if (result != NULL) {
1707     assert(*succeeded, "sanity");
1708     return result;
1709   }
1710 
1711   assert(!collector_policy()->should_clear_all_soft_refs(),
1712          "Flag should have been handled and cleared prior to this point");
1713 
1714   // What else?  We might try synchronous finalization later.  If the total
1715   // space available is large enough for the allocation, then a more
1716   // complete compaction phase than we've tried so far might be
1717   // appropriate.
1718   assert(*succeeded, "sanity");
1719   return NULL;
1720 }
1721 
1722 // Attempting to expand the heap sufficiently
1723 // to support an allocation of the given "word_size".  If
1724 // successful, perform the allocation and return the address of the
1725 // allocated block, or else "NULL".
1726 
1727 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) {
1728   assert_at_safepoint(true /* should_be_vm_thread */);
1729 
1730   verify_region_sets_optional();
1731 
1732   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1733   ergo_verbose1(ErgoHeapSizing,
1734                 "attempt heap expansion",
1735                 ergo_format_reason("allocation request failed")
1736                 ergo_format_byte("allocation request"),
1737                 word_size * HeapWordSize);
1738   if (expand(expand_bytes)) {
1739     _hrm.verify_optional();
1740     verify_region_sets_optional();
1741     return attempt_allocation_at_safepoint(word_size,
1742                                            context,
1743                                            false /* expect_null_mutator_alloc_region */);
1744   }
1745   return NULL;
1746 }
1747 
1748 bool G1CollectedHeap::expand(size_t expand_bytes) {
1749   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1750   aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1751                                        HeapRegion::GrainBytes);
1752   ergo_verbose2(ErgoHeapSizing,
1753                 "expand the heap",
1754                 ergo_format_byte("requested expansion amount")
1755                 ergo_format_byte("attempted expansion amount"),
1756                 expand_bytes, aligned_expand_bytes);
1757 
1758   if (is_maximal_no_gc()) {
1759     ergo_verbose0(ErgoHeapSizing,
1760                       "did not expand the heap",
1761                       ergo_format_reason("heap already fully expanded"));
1762     return false;
1763   }
1764 
1765   uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1766   assert(regions_to_expand > 0, "Must expand by at least one region");
1767 
1768   uint expanded_by = _hrm.expand_by(regions_to_expand);
1769 
1770   if (expanded_by > 0) {
1771     size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1772     assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1773     g1_policy()->record_new_heap_size(num_regions());
1774   } else {
1775     ergo_verbose0(ErgoHeapSizing,
1776                   "did not expand the heap",
1777                   ergo_format_reason("heap expansion operation failed"));
1778     // The expansion of the virtual storage space was unsuccessful.
1779     // Let's see if it was because we ran out of swap.
1780     if (G1ExitOnExpansionFailure &&
1781         _hrm.available() >= regions_to_expand) {
1782       // We had head room...
1783       vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1784     }
1785   }
1786   return regions_to_expand > 0;
1787 }
1788 
1789 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1790   size_t aligned_shrink_bytes =
1791     ReservedSpace::page_align_size_down(shrink_bytes);
1792   aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1793                                          HeapRegion::GrainBytes);
1794   uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1795 
1796   uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1797   size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1798 
1799   ergo_verbose3(ErgoHeapSizing,
1800                 "shrink the heap",
1801                 ergo_format_byte("requested shrinking amount")
1802                 ergo_format_byte("aligned shrinking amount")
1803                 ergo_format_byte("attempted shrinking amount"),
1804                 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1805   if (num_regions_removed > 0) {
1806     g1_policy()->record_new_heap_size(num_regions());
1807   } else {
1808     ergo_verbose0(ErgoHeapSizing,
1809                   "did not shrink the heap",
1810                   ergo_format_reason("heap shrinking operation failed"));
1811   }
1812 }
1813 
1814 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1815   verify_region_sets_optional();
1816 
1817   // We should only reach here at the end of a Full GC which means we
1818   // should not not be holding to any GC alloc regions. The method
1819   // below will make sure of that and do any remaining clean up.
1820   _allocator->abandon_gc_alloc_regions();
1821 
1822   // Instead of tearing down / rebuilding the free lists here, we
1823   // could instead use the remove_all_pending() method on free_list to
1824   // remove only the ones that we need to remove.
1825   tear_down_region_sets(true /* free_list_only */);
1826   shrink_helper(shrink_bytes);
1827   rebuild_region_sets(true /* free_list_only */);
1828 
1829   _hrm.verify_optional();
1830   verify_region_sets_optional();
1831 }
1832 
1833 // Public methods.
1834 
1835 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1836 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1837 #endif // _MSC_VER
1838 
1839 
1840 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1841   SharedHeap(policy_),
1842   _g1_policy(policy_),
1843   _dirty_card_queue_set(false),
1844   _into_cset_dirty_card_queue_set(false),
1845   _is_alive_closure_cm(this),
1846   _is_alive_closure_stw(this),
1847   _ref_processor_cm(NULL),
1848   _ref_processor_stw(NULL),
1849   _bot_shared(NULL),
1850   _evac_failure_scan_stack(NULL),
1851   _mark_in_progress(false),
1852   _cg1r(NULL),
1853   _g1mm(NULL),
1854   _refine_cte_cl(NULL),
1855   _full_collection(false),
1856   _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1857   _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1858   _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1859   _humongous_reclaim_candidates(),
1860   _has_humongous_reclaim_candidates(false),
1861   _free_regions_coming(false),
1862   _young_list(new YoungList(this)),
1863   _gc_time_stamp(0),
1864   _survivor_plab_stats(YoungPLABSize, PLABWeight),
1865   _old_plab_stats(OldPLABSize, PLABWeight),
1866   _expand_heap_after_alloc_failure(true),
1867   _surviving_young_words(NULL),
1868   _old_marking_cycles_started(0),
1869   _old_marking_cycles_completed(0),
1870   _concurrent_cycle_started(false),
1871   _heap_summary_sent(false),
1872   _in_cset_fast_test(),
1873   _dirty_cards_region_list(NULL),
1874   _worker_cset_start_region(NULL),
1875   _worker_cset_start_region_time_stamp(NULL),
1876   _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1877   _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
1878   _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1879   _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) {
1880 
1881   _g1h = this;
1882 
1883   _allocator = G1Allocator::create_allocator(_g1h);
1884   _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1885 
1886   int n_queues = MAX2((int)ParallelGCThreads, 1);
1887   _task_queues = new RefToScanQueueSet(n_queues);
1888 
1889   uint n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1890   assert(n_rem_sets > 0, "Invariant.");
1891 
1892   _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1893   _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(uint, n_queues, mtGC);
1894   _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1895 
1896   for (int i = 0; i < n_queues; i++) {
1897     RefToScanQueue* q = new RefToScanQueue();
1898     q->initialize();
1899     _task_queues->register_queue(i, q);
1900     ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1901   }
1902   clear_cset_start_regions();
1903 
1904   // Initialize the G1EvacuationFailureALot counters and flags.
1905   NOT_PRODUCT(reset_evacuation_should_fail();)
1906 
1907   guarantee(_task_queues != NULL, "task_queues allocation failure.");
1908 }
1909 
1910 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1911                                                                  size_t size,
1912                                                                  size_t translation_factor) {
1913   size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1914   // Allocate a new reserved space, preferring to use large pages.
1915   ReservedSpace rs(size, preferred_page_size);
1916   G1RegionToSpaceMapper* result  =
1917     G1RegionToSpaceMapper::create_mapper(rs,
1918                                          size,
1919                                          rs.alignment(),
1920                                          HeapRegion::GrainBytes,
1921                                          translation_factor,
1922                                          mtGC);
1923   if (TracePageSizes) {
1924     gclog_or_tty->print_cr("G1 '%s': pg_sz=" SIZE_FORMAT " base=" PTR_FORMAT " size=" SIZE_FORMAT " alignment=" SIZE_FORMAT " reqsize=" SIZE_FORMAT,
1925                            description, preferred_page_size, p2i(rs.base()), rs.size(), rs.alignment(), size);
1926   }
1927   return result;
1928 }
1929 
1930 jint G1CollectedHeap::initialize() {
1931   CollectedHeap::pre_initialize();
1932   os::enable_vtime();
1933 
1934   G1Log::init();
1935 
1936   // Necessary to satisfy locking discipline assertions.
1937 
1938   MutexLocker x(Heap_lock);
1939 
1940   // We have to initialize the printer before committing the heap, as
1941   // it will be used then.
1942   _hr_printer.set_active(G1PrintHeapRegions);
1943 
1944   // While there are no constraints in the GC code that HeapWordSize
1945   // be any particular value, there are multiple other areas in the
1946   // system which believe this to be true (e.g. oop->object_size in some
1947   // cases incorrectly returns the size in wordSize units rather than
1948   // HeapWordSize).
1949   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1950 
1951   size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1952   size_t max_byte_size = collector_policy()->max_heap_byte_size();
1953   size_t heap_alignment = collector_policy()->heap_alignment();
1954 
1955   // Ensure that the sizes are properly aligned.
1956   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1957   Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1958   Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1959 
1960   _refine_cte_cl = new RefineCardTableEntryClosure();
1961 
1962   _cg1r = new ConcurrentG1Refine(this, _refine_cte_cl);
1963 
1964   // Reserve the maximum.
1965 
1966   // When compressed oops are enabled, the preferred heap base
1967   // is calculated by subtracting the requested size from the
1968   // 32Gb boundary and using the result as the base address for
1969   // heap reservation. If the requested size is not aligned to
1970   // HeapRegion::GrainBytes (i.e. the alignment that is passed
1971   // into the ReservedHeapSpace constructor) then the actual
1972   // base of the reserved heap may end up differing from the
1973   // address that was requested (i.e. the preferred heap base).
1974   // If this happens then we could end up using a non-optimal
1975   // compressed oops mode.
1976 
1977   ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1978                                                  heap_alignment);
1979 
1980   // It is important to do this in a way such that concurrent readers can't
1981   // temporarily think something is in the heap.  (I've actually seen this
1982   // happen in asserts: DLD.)
1983   _reserved.set_word_size(0);
1984   _reserved.set_start((HeapWord*)heap_rs.base());
1985   _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size()));
1986 
1987   // Create the gen rem set (and barrier set) for the entire reserved region.
1988   _rem_set = collector_policy()->create_rem_set(_reserved, 2);
1989   set_barrier_set(rem_set()->bs());
1990   if (!barrier_set()->is_a(BarrierSet::G1SATBCTLogging)) {
1991     vm_exit_during_initialization("G1 requires a G1SATBLoggingCardTableModRefBS");
1992     return JNI_ENOMEM;
1993   }
1994 
1995   // Also create a G1 rem set.
1996   _g1_rem_set = new G1RemSet(this, g1_barrier_set());
1997 
1998   // Carve out the G1 part of the heap.
1999 
2000   ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
2001   G1RegionToSpaceMapper* heap_storage =
2002     G1RegionToSpaceMapper::create_mapper(g1_rs,
2003                                          g1_rs.size(),
2004                                          UseLargePages ? os::large_page_size() : os::vm_page_size(),
2005                                          HeapRegion::GrainBytes,
2006                                          1,
2007                                          mtJavaHeap);
2008   heap_storage->set_mapping_changed_listener(&_listener);
2009 
2010   // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
2011   G1RegionToSpaceMapper* bot_storage =
2012     create_aux_memory_mapper("Block offset table",
2013                              G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize),
2014                              G1BlockOffsetSharedArray::N_bytes);
2015 
2016   ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize));
2017   G1RegionToSpaceMapper* cardtable_storage =
2018     create_aux_memory_mapper("Card table",
2019                              G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize),
2020                              G1BlockOffsetSharedArray::N_bytes);
2021 
2022   G1RegionToSpaceMapper* card_counts_storage =
2023     create_aux_memory_mapper("Card counts table",
2024                              G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize),
2025                              G1BlockOffsetSharedArray::N_bytes);
2026 
2027   size_t bitmap_size = CMBitMap::compute_size(g1_rs.size());
2028   G1RegionToSpaceMapper* prev_bitmap_storage =
2029     create_aux_memory_mapper("Prev Bitmap", bitmap_size, CMBitMap::mark_distance());
2030   G1RegionToSpaceMapper* next_bitmap_storage =
2031     create_aux_memory_mapper("Next Bitmap", bitmap_size, CMBitMap::mark_distance());
2032 
2033   _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
2034   g1_barrier_set()->initialize(cardtable_storage);
2035    // Do later initialization work for concurrent refinement.
2036   _cg1r->init(card_counts_storage);
2037 
2038   // 6843694 - ensure that the maximum region index can fit
2039   // in the remembered set structures.
2040   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
2041   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
2042 
2043   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
2044   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
2045   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
2046             "too many cards per region");
2047 
2048   FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
2049 
2050   _bot_shared = new G1BlockOffsetSharedArray(_reserved, bot_storage);
2051 
2052   _g1h = this;
2053 
2054   {
2055     HeapWord* start = _hrm.reserved().start();
2056     HeapWord* end = _hrm.reserved().end();
2057     size_t granularity = HeapRegion::GrainBytes;
2058 
2059     _in_cset_fast_test.initialize(start, end, granularity);
2060     _humongous_reclaim_candidates.initialize(start, end, granularity);
2061   }
2062 
2063   // Create the ConcurrentMark data structure and thread.
2064   // (Must do this late, so that "max_regions" is defined.)
2065   _cm = new ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
2066   if (_cm == NULL || !_cm->completed_initialization()) {
2067     vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark");
2068     return JNI_ENOMEM;
2069   }
2070   _cmThread = _cm->cmThread();
2071 
2072   // Initialize the from_card cache structure of HeapRegionRemSet.
2073   HeapRegionRemSet::init_heap(max_regions());
2074 
2075   // Now expand into the initial heap size.
2076   if (!expand(init_byte_size)) {
2077     vm_shutdown_during_initialization("Failed to allocate initial heap.");
2078     return JNI_ENOMEM;
2079   }
2080 
2081   // Perform any initialization actions delegated to the policy.
2082   g1_policy()->init();
2083 
2084   JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
2085                                                SATB_Q_FL_lock,
2086                                                G1SATBProcessCompletedThreshold,
2087                                                Shared_SATB_Q_lock);
2088 
2089   JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl,
2090                                                 DirtyCardQ_CBL_mon,
2091                                                 DirtyCardQ_FL_lock,
2092                                                 concurrent_g1_refine()->yellow_zone(),
2093                                                 concurrent_g1_refine()->red_zone(),
2094                                                 Shared_DirtyCardQ_lock);
2095 
2096   dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code
2097                                     DirtyCardQ_CBL_mon,
2098                                     DirtyCardQ_FL_lock,
2099                                     -1, // never trigger processing
2100                                     -1, // no limit on length
2101                                     Shared_DirtyCardQ_lock,
2102                                     &JavaThread::dirty_card_queue_set());
2103 
2104   // Initialize the card queue set used to hold cards containing
2105   // references into the collection set.
2106   _into_cset_dirty_card_queue_set.initialize(NULL, // Should never be called by the Java code
2107                                              DirtyCardQ_CBL_mon,
2108                                              DirtyCardQ_FL_lock,
2109                                              -1, // never trigger processing
2110                                              -1, // no limit on length
2111                                              Shared_DirtyCardQ_lock,
2112                                              &JavaThread::dirty_card_queue_set());
2113 
2114   // In case we're keeping closure specialization stats, initialize those
2115   // counts and that mechanism.
2116   SpecializationStats::clear();
2117 
2118   // Here we allocate the dummy HeapRegion that is required by the
2119   // G1AllocRegion class.
2120   HeapRegion* dummy_region = _hrm.get_dummy_region();
2121 
2122   // We'll re-use the same region whether the alloc region will
2123   // require BOT updates or not and, if it doesn't, then a non-young
2124   // region will complain that it cannot support allocations without
2125   // BOT updates. So we'll tag the dummy region as eden to avoid that.
2126   dummy_region->set_eden();
2127   // Make sure it's full.
2128   dummy_region->set_top(dummy_region->end());
2129   G1AllocRegion::setup(this, dummy_region);
2130 
2131   _allocator->init_mutator_alloc_region();
2132 
2133   // Do create of the monitoring and management support so that
2134   // values in the heap have been properly initialized.
2135   _g1mm = new G1MonitoringSupport(this);
2136 
2137   G1StringDedup::initialize();
2138 
2139   return JNI_OK;
2140 }
2141 
2142 void G1CollectedHeap::stop() {
2143   // Stop all concurrent threads. We do this to make sure these threads
2144   // do not continue to execute and access resources (e.g. gclog_or_tty)
2145   // that are destroyed during shutdown.
2146   _cg1r->stop();
2147   _cmThread->stop();
2148   if (G1StringDedup::is_enabled()) {
2149     G1StringDedup::stop();
2150   }
2151 }
2152 
2153 size_t G1CollectedHeap::conservative_max_heap_alignment() {
2154   return HeapRegion::max_region_size();
2155 }
2156 
2157 void G1CollectedHeap::ref_processing_init() {
2158   // Reference processing in G1 currently works as follows:
2159   //
2160   // * There are two reference processor instances. One is
2161   //   used to record and process discovered references
2162   //   during concurrent marking; the other is used to
2163   //   record and process references during STW pauses
2164   //   (both full and incremental).
2165   // * Both ref processors need to 'span' the entire heap as
2166   //   the regions in the collection set may be dotted around.
2167   //
2168   // * For the concurrent marking ref processor:
2169   //   * Reference discovery is enabled at initial marking.
2170   //   * Reference discovery is disabled and the discovered
2171   //     references processed etc during remarking.
2172   //   * Reference discovery is MT (see below).
2173   //   * Reference discovery requires a barrier (see below).
2174   //   * Reference processing may or may not be MT
2175   //     (depending on the value of ParallelRefProcEnabled
2176   //     and ParallelGCThreads).
2177   //   * A full GC disables reference discovery by the CM
2178   //     ref processor and abandons any entries on it's
2179   //     discovered lists.
2180   //
2181   // * For the STW processor:
2182   //   * Non MT discovery is enabled at the start of a full GC.
2183   //   * Processing and enqueueing during a full GC is non-MT.
2184   //   * During a full GC, references are processed after marking.
2185   //
2186   //   * Discovery (may or may not be MT) is enabled at the start
2187   //     of an incremental evacuation pause.
2188   //   * References are processed near the end of a STW evacuation pause.
2189   //   * For both types of GC:
2190   //     * Discovery is atomic - i.e. not concurrent.
2191   //     * Reference discovery will not need a barrier.
2192 
2193   SharedHeap::ref_processing_init();
2194   MemRegion mr = reserved_region();
2195 
2196   // Concurrent Mark ref processor
2197   _ref_processor_cm =
2198     new ReferenceProcessor(mr,    // span
2199                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2200                                 // mt processing
2201                            (int) ParallelGCThreads,
2202                                 // degree of mt processing
2203                            (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2204                                 // mt discovery
2205                            (int) MAX2(ParallelGCThreads, ConcGCThreads),
2206                                 // degree of mt discovery
2207                            false,
2208                                 // Reference discovery is not atomic
2209                            &_is_alive_closure_cm);
2210                                 // is alive closure
2211                                 // (for efficiency/performance)
2212 
2213   // STW ref processor
2214   _ref_processor_stw =
2215     new ReferenceProcessor(mr,    // span
2216                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2217                                 // mt processing
2218                            MAX2((int)ParallelGCThreads, 1),
2219                                 // degree of mt processing
2220                            (ParallelGCThreads > 1),
2221                                 // mt discovery
2222                            MAX2((int)ParallelGCThreads, 1),
2223                                 // degree of mt discovery
2224                            true,
2225                                 // Reference discovery is atomic
2226                            &_is_alive_closure_stw);
2227                                 // is alive closure
2228                                 // (for efficiency/performance)
2229 }
2230 
2231 size_t G1CollectedHeap::capacity() const {
2232   return _hrm.length() * HeapRegion::GrainBytes;
2233 }
2234 
2235 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2236   assert(!hr->continuesHumongous(), "pre-condition");
2237   hr->reset_gc_time_stamp();
2238   if (hr->startsHumongous()) {
2239     uint first_index = hr->hrm_index() + 1;
2240     uint last_index = hr->last_hc_index();
2241     for (uint i = first_index; i < last_index; i += 1) {
2242       HeapRegion* chr = region_at(i);
2243       assert(chr->continuesHumongous(), "sanity");
2244       chr->reset_gc_time_stamp();
2245     }
2246   }
2247 }
2248 
2249 #ifndef PRODUCT
2250 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2251 private:
2252   unsigned _gc_time_stamp;
2253   bool _failures;
2254 
2255 public:
2256   CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2257     _gc_time_stamp(gc_time_stamp), _failures(false) { }
2258 
2259   virtual bool doHeapRegion(HeapRegion* hr) {
2260     unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2261     if (_gc_time_stamp != region_gc_time_stamp) {
2262       gclog_or_tty->print_cr("Region " HR_FORMAT " has GC time stamp = %d, "
2263                              "expected %d", HR_FORMAT_PARAMS(hr),
2264                              region_gc_time_stamp, _gc_time_stamp);
2265       _failures = true;
2266     }
2267     return false;
2268   }
2269 
2270   bool failures() { return _failures; }
2271 };
2272 
2273 void G1CollectedHeap::check_gc_time_stamps() {
2274   CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2275   heap_region_iterate(&cl);
2276   guarantee(!cl.failures(), "all GC time stamps should have been reset");
2277 }
2278 #endif // PRODUCT
2279 
2280 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2281                                                  DirtyCardQueue* into_cset_dcq,
2282                                                  bool concurrent,
2283                                                  uint worker_i) {
2284   // Clean cards in the hot card cache
2285   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
2286   hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq);
2287 
2288   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2289   size_t n_completed_buffers = 0;
2290   while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2291     n_completed_buffers++;
2292   }
2293   g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers);
2294   dcqs.clear_n_completed_buffers();
2295   assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2296 }
2297 
2298 
2299 // Computes the sum of the storage used by the various regions.
2300 size_t G1CollectedHeap::used() const {
2301   return _allocator->used();
2302 }
2303 
2304 size_t G1CollectedHeap::used_unlocked() const {
2305   return _allocator->used_unlocked();
2306 }
2307 
2308 class SumUsedClosure: public HeapRegionClosure {
2309   size_t _used;
2310 public:
2311   SumUsedClosure() : _used(0) {}
2312   bool doHeapRegion(HeapRegion* r) {
2313     if (!r->continuesHumongous()) {
2314       _used += r->used();
2315     }
2316     return false;
2317   }
2318   size_t result() { return _used; }
2319 };
2320 
2321 size_t G1CollectedHeap::recalculate_used() const {
2322   double recalculate_used_start = os::elapsedTime();
2323 
2324   SumUsedClosure blk;
2325   heap_region_iterate(&blk);
2326 
2327   g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2328   return blk.result();
2329 }
2330 
2331 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2332   switch (cause) {
2333     case GCCause::_gc_locker:               return GCLockerInvokesConcurrent;
2334     case GCCause::_java_lang_system_gc:     return ExplicitGCInvokesConcurrent;
2335     case GCCause::_g1_humongous_allocation: return true;
2336     case GCCause::_update_allocation_context_stats_inc: return true;
2337     case GCCause::_wb_conc_mark:            return true;
2338     default:                                return false;
2339   }
2340 }
2341 
2342 #ifndef PRODUCT
2343 void G1CollectedHeap::allocate_dummy_regions() {
2344   // Let's fill up most of the region
2345   size_t word_size = HeapRegion::GrainWords - 1024;
2346   // And as a result the region we'll allocate will be humongous.
2347   guarantee(isHumongous(word_size), "sanity");
2348 
2349   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2350     // Let's use the existing mechanism for the allocation
2351     HeapWord* dummy_obj = humongous_obj_allocate(word_size,
2352                                                  AllocationContext::system());
2353     if (dummy_obj != NULL) {
2354       MemRegion mr(dummy_obj, word_size);
2355       CollectedHeap::fill_with_object(mr);
2356     } else {
2357       // If we can't allocate once, we probably cannot allocate
2358       // again. Let's get out of the loop.
2359       break;
2360     }
2361   }
2362 }
2363 #endif // !PRODUCT
2364 
2365 void G1CollectedHeap::increment_old_marking_cycles_started() {
2366   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2367     _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2368     err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2369     _old_marking_cycles_started, _old_marking_cycles_completed));
2370 
2371   _old_marking_cycles_started++;
2372 }
2373 
2374 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2375   MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2376 
2377   // We assume that if concurrent == true, then the caller is a
2378   // concurrent thread that was joined the Suspendible Thread
2379   // Set. If there's ever a cheap way to check this, we should add an
2380   // assert here.
2381 
2382   // Given that this method is called at the end of a Full GC or of a
2383   // concurrent cycle, and those can be nested (i.e., a Full GC can
2384   // interrupt a concurrent cycle), the number of full collections
2385   // completed should be either one (in the case where there was no
2386   // nesting) or two (when a Full GC interrupted a concurrent cycle)
2387   // behind the number of full collections started.
2388 
2389   // This is the case for the inner caller, i.e. a Full GC.
2390   assert(concurrent ||
2391          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2392          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2393          err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
2394                  "is inconsistent with _old_marking_cycles_completed = %u",
2395                  _old_marking_cycles_started, _old_marking_cycles_completed));
2396 
2397   // This is the case for the outer caller, i.e. the concurrent cycle.
2398   assert(!concurrent ||
2399          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2400          err_msg("for outer caller (concurrent cycle): "
2401                  "_old_marking_cycles_started = %u "
2402                  "is inconsistent with _old_marking_cycles_completed = %u",
2403                  _old_marking_cycles_started, _old_marking_cycles_completed));
2404 
2405   _old_marking_cycles_completed += 1;
2406 
2407   // We need to clear the "in_progress" flag in the CM thread before
2408   // we wake up any waiters (especially when ExplicitInvokesConcurrent
2409   // is set) so that if a waiter requests another System.gc() it doesn't
2410   // incorrectly see that a marking cycle is still in progress.
2411   if (concurrent) {
2412     _cmThread->clear_in_progress();
2413   }
2414 
2415   // This notify_all() will ensure that a thread that called
2416   // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2417   // and it's waiting for a full GC to finish will be woken up. It is
2418   // waiting in VM_G1IncCollectionPause::doit_epilogue().
2419   FullGCCount_lock->notify_all();
2420 }
2421 
2422 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) {
2423   _concurrent_cycle_started = true;
2424   _gc_timer_cm->register_gc_start(start_time);
2425 
2426   _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start());
2427   trace_heap_before_gc(_gc_tracer_cm);
2428 }
2429 
2430 void G1CollectedHeap::register_concurrent_cycle_end() {
2431   if (_concurrent_cycle_started) {
2432     if (_cm->has_aborted()) {
2433       _gc_tracer_cm->report_concurrent_mode_failure();
2434     }
2435 
2436     _gc_timer_cm->register_gc_end();
2437     _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
2438 
2439     // Clear state variables to prepare for the next concurrent cycle.
2440     _concurrent_cycle_started = false;
2441     _heap_summary_sent = false;
2442   }
2443 }
2444 
2445 void G1CollectedHeap::trace_heap_after_concurrent_cycle() {
2446   if (_concurrent_cycle_started) {
2447     // This function can be called when:
2448     //  the cleanup pause is run
2449     //  the concurrent cycle is aborted before the cleanup pause.
2450     //  the concurrent cycle is aborted after the cleanup pause,
2451     //   but before the concurrent cycle end has been registered.
2452     // Make sure that we only send the heap information once.
2453     if (!_heap_summary_sent) {
2454       trace_heap_after_gc(_gc_tracer_cm);
2455       _heap_summary_sent = true;
2456     }
2457   }
2458 }
2459 
2460 G1YCType G1CollectedHeap::yc_type() {
2461   bool is_young = g1_policy()->gcs_are_young();
2462   bool is_initial_mark = g1_policy()->during_initial_mark_pause();
2463   bool is_during_mark = mark_in_progress();
2464 
2465   if (is_initial_mark) {
2466     return InitialMark;
2467   } else if (is_during_mark) {
2468     return DuringMark;
2469   } else if (is_young) {
2470     return Normal;
2471   } else {
2472     return Mixed;
2473   }
2474 }
2475 
2476 void G1CollectedHeap::collect(GCCause::Cause cause) {
2477   assert_heap_not_locked();
2478 
2479   uint gc_count_before;
2480   uint old_marking_count_before;
2481   uint full_gc_count_before;
2482   bool retry_gc;
2483 
2484   do {
2485     retry_gc = false;
2486 
2487     {
2488       MutexLocker ml(Heap_lock);
2489 
2490       // Read the GC count while holding the Heap_lock
2491       gc_count_before = total_collections();
2492       full_gc_count_before = total_full_collections();
2493       old_marking_count_before = _old_marking_cycles_started;
2494     }
2495 
2496     if (should_do_concurrent_full_gc(cause)) {
2497       // Schedule an initial-mark evacuation pause that will start a
2498       // concurrent cycle. We're setting word_size to 0 which means that
2499       // we are not requesting a post-GC allocation.
2500       VM_G1IncCollectionPause op(gc_count_before,
2501                                  0,     /* word_size */
2502                                  true,  /* should_initiate_conc_mark */
2503                                  g1_policy()->max_pause_time_ms(),
2504                                  cause);
2505       op.set_allocation_context(AllocationContext::current());
2506 
2507       VMThread::execute(&op);
2508       if (!op.pause_succeeded()) {
2509         if (old_marking_count_before == _old_marking_cycles_started) {
2510           retry_gc = op.should_retry_gc();
2511         } else {
2512           // A Full GC happened while we were trying to schedule the
2513           // initial-mark GC. No point in starting a new cycle given
2514           // that the whole heap was collected anyway.
2515         }
2516 
2517         if (retry_gc) {
2518           if (GC_locker::is_active_and_needs_gc()) {
2519             GC_locker::stall_until_clear();
2520           }
2521         }
2522       }
2523     } else {
2524       if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2525           DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2526 
2527         // Schedule a standard evacuation pause. We're setting word_size
2528         // to 0 which means that we are not requesting a post-GC allocation.
2529         VM_G1IncCollectionPause op(gc_count_before,
2530                                    0,     /* word_size */
2531                                    false, /* should_initiate_conc_mark */
2532                                    g1_policy()->max_pause_time_ms(),
2533                                    cause);
2534         VMThread::execute(&op);
2535       } else {
2536         // Schedule a Full GC.
2537         VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2538         VMThread::execute(&op);
2539       }
2540     }
2541   } while (retry_gc);
2542 }
2543 
2544 bool G1CollectedHeap::is_in(const void* p) const {
2545   if (_hrm.reserved().contains(p)) {
2546     // Given that we know that p is in the reserved space,
2547     // heap_region_containing_raw() should successfully
2548     // return the containing region.
2549     HeapRegion* hr = heap_region_containing_raw(p);
2550     return hr->is_in(p);
2551   } else {
2552     return false;
2553   }
2554 }
2555 
2556 #ifdef ASSERT
2557 bool G1CollectedHeap::is_in_exact(const void* p) const {
2558   bool contains = reserved_region().contains(p);
2559   bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2560   if (contains && available) {
2561     return true;
2562   } else {
2563     return false;
2564   }
2565 }
2566 #endif
2567 
2568 // Iteration functions.
2569 
2570 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion.
2571 
2572 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2573   ExtendedOopClosure* _cl;
2574 public:
2575   IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {}
2576   bool doHeapRegion(HeapRegion* r) {
2577     if (!r->continuesHumongous()) {
2578       r->oop_iterate(_cl);
2579     }
2580     return false;
2581   }
2582 };
2583 
2584 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) {
2585   IterateOopClosureRegionClosure blk(cl);
2586   heap_region_iterate(&blk);
2587 }
2588 
2589 // Iterates an ObjectClosure over all objects within a HeapRegion.
2590 
2591 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2592   ObjectClosure* _cl;
2593 public:
2594   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2595   bool doHeapRegion(HeapRegion* r) {
2596     if (! r->continuesHumongous()) {
2597       r->object_iterate(_cl);
2598     }
2599     return false;
2600   }
2601 };
2602 
2603 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2604   IterateObjectClosureRegionClosure blk(cl);
2605   heap_region_iterate(&blk);
2606 }
2607 
2608 // Calls a SpaceClosure on a HeapRegion.
2609 
2610 class SpaceClosureRegionClosure: public HeapRegionClosure {
2611   SpaceClosure* _cl;
2612 public:
2613   SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2614   bool doHeapRegion(HeapRegion* r) {
2615     _cl->do_space(r);
2616     return false;
2617   }
2618 };
2619 
2620 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2621   SpaceClosureRegionClosure blk(cl);
2622   heap_region_iterate(&blk);
2623 }
2624 
2625 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2626   _hrm.iterate(cl);
2627 }
2628 
2629 void
2630 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
2631                                                  uint worker_id,
2632                                                  uint num_workers,
2633                                                  jint claim_value) const {
2634   _hrm.par_iterate(cl, worker_id, num_workers, claim_value);
2635 }
2636 
2637 class ResetClaimValuesClosure: public HeapRegionClosure {
2638 public:
2639   bool doHeapRegion(HeapRegion* r) {
2640     r->set_claim_value(HeapRegion::InitialClaimValue);
2641     return false;
2642   }
2643 };
2644 
2645 void G1CollectedHeap::reset_heap_region_claim_values() {
2646   ResetClaimValuesClosure blk;
2647   heap_region_iterate(&blk);
2648 }
2649 
2650 void G1CollectedHeap::reset_cset_heap_region_claim_values() {
2651   ResetClaimValuesClosure blk;
2652   collection_set_iterate(&blk);
2653 }
2654 
2655 #ifdef ASSERT
2656 // This checks whether all regions in the heap have the correct claim
2657 // value. I also piggy-backed on this a check to ensure that the
2658 // humongous_start_region() information on "continues humongous"
2659 // regions is correct.
2660 
2661 class CheckClaimValuesClosure : public HeapRegionClosure {
2662 private:
2663   jint _claim_value;
2664   uint _failures;
2665   HeapRegion* _sh_region;
2666 
2667 public:
2668   CheckClaimValuesClosure(jint claim_value) :
2669     _claim_value(claim_value), _failures(0), _sh_region(NULL) { }
2670   bool doHeapRegion(HeapRegion* r) {
2671     if (r->claim_value() != _claim_value) {
2672       gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2673                              "claim value = %d, should be %d",
2674                              HR_FORMAT_PARAMS(r),
2675                              r->claim_value(), _claim_value);
2676       ++_failures;
2677     }
2678     if (!r->isHumongous()) {
2679       _sh_region = NULL;
2680     } else if (r->startsHumongous()) {
2681       _sh_region = r;
2682     } else if (r->continuesHumongous()) {
2683       if (r->humongous_start_region() != _sh_region) {
2684         gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2685                                "HS = " PTR_FORMAT ", should be " PTR_FORMAT,
2686                                HR_FORMAT_PARAMS(r),
2687                                r->humongous_start_region(),
2688                                _sh_region);
2689         ++_failures;
2690       }
2691     }
2692     return false;
2693   }
2694   uint failures() { return _failures; }
2695 };
2696 
2697 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
2698   CheckClaimValuesClosure cl(claim_value);
2699   heap_region_iterate(&cl);
2700   return cl.failures() == 0;
2701 }
2702 
2703 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure {
2704 private:
2705   jint _claim_value;
2706   uint _failures;
2707 
2708 public:
2709   CheckClaimValuesInCSetHRClosure(jint claim_value) :
2710     _claim_value(claim_value), _failures(0) { }
2711 
2712   uint failures() { return _failures; }
2713 
2714   bool doHeapRegion(HeapRegion* hr) {
2715     assert(hr->in_collection_set(), "how?");
2716     assert(!hr->isHumongous(), "H-region in CSet");
2717     if (hr->claim_value() != _claim_value) {
2718       gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", "
2719                              "claim value = %d, should be %d",
2720                              HR_FORMAT_PARAMS(hr),
2721                              hr->claim_value(), _claim_value);
2722       _failures += 1;
2723     }
2724     return false;
2725   }
2726 };
2727 
2728 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) {
2729   CheckClaimValuesInCSetHRClosure cl(claim_value);
2730   collection_set_iterate(&cl);
2731   return cl.failures() == 0;
2732 }
2733 #endif // ASSERT
2734 
2735 // Clear the cached CSet starting regions and (more importantly)
2736 // the time stamps. Called when we reset the GC time stamp.
2737 void G1CollectedHeap::clear_cset_start_regions() {
2738   assert(_worker_cset_start_region != NULL, "sanity");
2739   assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2740 
2741   int n_queues = MAX2((int)ParallelGCThreads, 1);
2742   for (int i = 0; i < n_queues; i++) {
2743     _worker_cset_start_region[i] = NULL;
2744     _worker_cset_start_region_time_stamp[i] = 0;
2745   }
2746 }
2747 
2748 // Given the id of a worker, obtain or calculate a suitable
2749 // starting region for iterating over the current collection set.
2750 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) {
2751   assert(get_gc_time_stamp() > 0, "should have been updated by now");
2752 
2753   HeapRegion* result = NULL;
2754   unsigned gc_time_stamp = get_gc_time_stamp();
2755 
2756   if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2757     // Cached starting region for current worker was set
2758     // during the current pause - so it's valid.
2759     // Note: the cached starting heap region may be NULL
2760     // (when the collection set is empty).
2761     result = _worker_cset_start_region[worker_i];
2762     assert(result == NULL || result->in_collection_set(), "sanity");
2763     return result;
2764   }
2765 
2766   // The cached entry was not valid so let's calculate
2767   // a suitable starting heap region for this worker.
2768 
2769   // We want the parallel threads to start their collection
2770   // set iteration at different collection set regions to
2771   // avoid contention.
2772   // If we have:
2773   //          n collection set regions
2774   //          p threads
2775   // Then thread t will start at region floor ((t * n) / p)
2776 
2777   result = g1_policy()->collection_set();
2778   if (G1CollectedHeap::use_parallel_gc_threads()) {
2779     uint cs_size = g1_policy()->cset_region_length();
2780     uint active_workers = workers()->active_workers();
2781     assert(UseDynamicNumberOfGCThreads ||
2782              active_workers == workers()->total_workers(),
2783              "Unless dynamic should use total workers");
2784 
2785     uint end_ind   = (cs_size * worker_i) / active_workers;
2786     uint start_ind = 0;
2787 
2788     if (worker_i > 0 &&
2789         _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2790       // Previous workers starting region is valid
2791       // so let's iterate from there
2792       start_ind = (cs_size * (worker_i - 1)) / active_workers;
2793       result = _worker_cset_start_region[worker_i - 1];
2794     }
2795 
2796     for (uint i = start_ind; i < end_ind; i++) {
2797       result = result->next_in_collection_set();
2798     }
2799   }
2800 
2801   // Note: the calculated starting heap region may be NULL
2802   // (when the collection set is empty).
2803   assert(result == NULL || result->in_collection_set(), "sanity");
2804   assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2805          "should be updated only once per pause");
2806   _worker_cset_start_region[worker_i] = result;
2807   OrderAccess::storestore();
2808   _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2809   return result;
2810 }
2811 
2812 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2813   HeapRegion* r = g1_policy()->collection_set();
2814   while (r != NULL) {
2815     HeapRegion* next = r->next_in_collection_set();
2816     if (cl->doHeapRegion(r)) {
2817       cl->incomplete();
2818       return;
2819     }
2820     r = next;
2821   }
2822 }
2823 
2824 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2825                                                   HeapRegionClosure *cl) {
2826   if (r == NULL) {
2827     // The CSet is empty so there's nothing to do.
2828     return;
2829   }
2830 
2831   assert(r->in_collection_set(),
2832          "Start region must be a member of the collection set.");
2833   HeapRegion* cur = r;
2834   while (cur != NULL) {
2835     HeapRegion* next = cur->next_in_collection_set();
2836     if (cl->doHeapRegion(cur) && false) {
2837       cl->incomplete();
2838       return;
2839     }
2840     cur = next;
2841   }
2842   cur = g1_policy()->collection_set();
2843   while (cur != r) {
2844     HeapRegion* next = cur->next_in_collection_set();
2845     if (cl->doHeapRegion(cur) && false) {
2846       cl->incomplete();
2847       return;
2848     }
2849     cur = next;
2850   }
2851 }
2852 
2853 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const {
2854   HeapRegion* result = _hrm.next_region_in_heap(from);
2855   while (result != NULL && result->isHumongous()) {
2856     result = _hrm.next_region_in_heap(result);
2857   }
2858   return result;
2859 }
2860 
2861 Space* G1CollectedHeap::space_containing(const void* addr) const {
2862   return heap_region_containing(addr);
2863 }
2864 
2865 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2866   Space* sp = space_containing(addr);
2867   return sp->block_start(addr);
2868 }
2869 
2870 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2871   Space* sp = space_containing(addr);
2872   return sp->block_size(addr);
2873 }
2874 
2875 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2876   Space* sp = space_containing(addr);
2877   return sp->block_is_obj(addr);
2878 }
2879 
2880 bool G1CollectedHeap::supports_tlab_allocation() const {
2881   return true;
2882 }
2883 
2884 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2885   return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes;
2886 }
2887 
2888 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2889   return young_list()->eden_used_bytes();
2890 }
2891 
2892 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2893 // must be smaller than the humongous object limit.
2894 size_t G1CollectedHeap::max_tlab_size() const {
2895   return align_size_down(_humongous_object_threshold_in_words - 1, MinObjAlignment);
2896 }
2897 
2898 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2899   // Return the remaining space in the cur alloc region, but not less than
2900   // the min TLAB size.
2901 
2902   // Also, this value can be at most the humongous object threshold,
2903   // since we can't allow tlabs to grow big enough to accommodate
2904   // humongous objects.
2905 
2906   HeapRegion* hr = _allocator->mutator_alloc_region(AllocationContext::current())->get();
2907   size_t max_tlab = max_tlab_size() * wordSize;
2908   if (hr == NULL) {
2909     return max_tlab;
2910   } else {
2911     return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab);
2912   }
2913 }
2914 
2915 size_t G1CollectedHeap::max_capacity() const {
2916   return _hrm.reserved().byte_size();
2917 }
2918 
2919 jlong G1CollectedHeap::millis_since_last_gc() {
2920   // assert(false, "NYI");
2921   return 0;
2922 }
2923 
2924 void G1CollectedHeap::prepare_for_verify() {
2925   if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
2926     ensure_parsability(false);
2927   }
2928   g1_rem_set()->prepare_for_verify();
2929 }
2930 
2931 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr,
2932                                               VerifyOption vo) {
2933   switch (vo) {
2934   case VerifyOption_G1UsePrevMarking:
2935     return hr->obj_allocated_since_prev_marking(obj);
2936   case VerifyOption_G1UseNextMarking:
2937     return hr->obj_allocated_since_next_marking(obj);
2938   case VerifyOption_G1UseMarkWord:
2939     return false;
2940   default:
2941     ShouldNotReachHere();
2942   }
2943   return false; // keep some compilers happy
2944 }
2945 
2946 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) {
2947   switch (vo) {
2948   case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start();
2949   case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start();
2950   case VerifyOption_G1UseMarkWord:    return NULL;
2951   default:                            ShouldNotReachHere();
2952   }
2953   return NULL; // keep some compilers happy
2954 }
2955 
2956 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) {
2957   switch (vo) {
2958   case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj);
2959   case VerifyOption_G1UseNextMarking: return isMarkedNext(obj);
2960   case VerifyOption_G1UseMarkWord:    return obj->is_gc_marked();
2961   default:                            ShouldNotReachHere();
2962   }
2963   return false; // keep some compilers happy
2964 }
2965 
2966 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) {
2967   switch (vo) {
2968   case VerifyOption_G1UsePrevMarking: return "PTAMS";
2969   case VerifyOption_G1UseNextMarking: return "NTAMS";
2970   case VerifyOption_G1UseMarkWord:    return "NONE";
2971   default:                            ShouldNotReachHere();
2972   }
2973   return NULL; // keep some compilers happy
2974 }
2975 
2976 class VerifyRootsClosure: public OopClosure {
2977 private:
2978   G1CollectedHeap* _g1h;
2979   VerifyOption     _vo;
2980   bool             _failures;
2981 public:
2982   // _vo == UsePrevMarking -> use "prev" marking information,
2983   // _vo == UseNextMarking -> use "next" marking information,
2984   // _vo == UseMarkWord    -> use mark word from object header.
2985   VerifyRootsClosure(VerifyOption vo) :
2986     _g1h(G1CollectedHeap::heap()),
2987     _vo(vo),
2988     _failures(false) { }
2989 
2990   bool failures() { return _failures; }
2991 
2992   template <class T> void do_oop_nv(T* p) {
2993     T heap_oop = oopDesc::load_heap_oop(p);
2994     if (!oopDesc::is_null(heap_oop)) {
2995       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2996       if (_g1h->is_obj_dead_cond(obj, _vo)) {
2997         gclog_or_tty->print_cr("Root location " PTR_FORMAT " "
2998                               "points to dead obj " PTR_FORMAT, p, (void*) obj);
2999         if (_vo == VerifyOption_G1UseMarkWord) {
3000           gclog_or_tty->print_cr("  Mark word: " PTR_FORMAT, (void*)(obj->mark()));
3001         }
3002         obj->print_on(gclog_or_tty);
3003         _failures = true;
3004       }
3005     }
3006   }
3007 
3008   void do_oop(oop* p)       { do_oop_nv(p); }
3009   void do_oop(narrowOop* p) { do_oop_nv(p); }
3010 };
3011 
3012 class G1VerifyCodeRootOopClosure: public OopClosure {
3013   G1CollectedHeap* _g1h;
3014   OopClosure* _root_cl;
3015   nmethod* _nm;
3016   VerifyOption _vo;
3017   bool _failures;
3018 
3019   template <class T> void do_oop_work(T* p) {
3020     // First verify that this root is live
3021     _root_cl->do_oop(p);
3022 
3023     if (!G1VerifyHeapRegionCodeRoots) {
3024       // We're not verifying the code roots attached to heap region.
3025       return;
3026     }
3027 
3028     // Don't check the code roots during marking verification in a full GC
3029     if (_vo == VerifyOption_G1UseMarkWord) {
3030       return;
3031     }
3032 
3033     // Now verify that the current nmethod (which contains p) is
3034     // in the code root list of the heap region containing the
3035     // object referenced by p.
3036 
3037     T heap_oop = oopDesc::load_heap_oop(p);
3038     if (!oopDesc::is_null(heap_oop)) {
3039       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3040 
3041       // Now fetch the region containing the object
3042       HeapRegion* hr = _g1h->heap_region_containing(obj);
3043       HeapRegionRemSet* hrrs = hr->rem_set();
3044       // Verify that the strong code root list for this region
3045       // contains the nmethod
3046       if (!hrrs->strong_code_roots_list_contains(_nm)) {
3047         gclog_or_tty->print_cr("Code root location " PTR_FORMAT " "
3048                               "from nmethod " PTR_FORMAT " not in strong "
3049                               "code roots for region [" PTR_FORMAT "," PTR_FORMAT ")",
3050                               p, _nm, hr->bottom(), hr->end());
3051         _failures = true;
3052       }
3053     }
3054   }
3055 
3056 public:
3057   G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo):
3058     _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {}
3059 
3060   void do_oop(oop* p) { do_oop_work(p); }
3061   void do_oop(narrowOop* p) { do_oop_work(p); }
3062 
3063   void set_nmethod(nmethod* nm) { _nm = nm; }
3064   bool failures() { return _failures; }
3065 };
3066 
3067 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure {
3068   G1VerifyCodeRootOopClosure* _oop_cl;
3069 
3070 public:
3071   G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl):
3072     _oop_cl(oop_cl) {}
3073 
3074   void do_code_blob(CodeBlob* cb) {
3075     nmethod* nm = cb->as_nmethod_or_null();
3076     if (nm != NULL) {
3077       _oop_cl->set_nmethod(nm);
3078       nm->oops_do(_oop_cl);
3079     }
3080   }
3081 };
3082 
3083 class YoungRefCounterClosure : public OopClosure {
3084   G1CollectedHeap* _g1h;
3085   int              _count;
3086  public:
3087   YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {}
3088   void do_oop(oop* p)       { if (_g1h->is_in_young(*p)) { _count++; } }
3089   void do_oop(narrowOop* p) { ShouldNotReachHere(); }
3090 
3091   int count() { return _count; }
3092   void reset_count() { _count = 0; };
3093 };
3094 
3095 class VerifyKlassClosure: public KlassClosure {
3096   YoungRefCounterClosure _young_ref_counter_closure;
3097   OopClosure *_oop_closure;
3098  public:
3099   VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {}
3100   void do_klass(Klass* k) {
3101     k->oops_do(_oop_closure);
3102 
3103     _young_ref_counter_closure.reset_count();
3104     k->oops_do(&_young_ref_counter_closure);
3105     if (_young_ref_counter_closure.count() > 0) {
3106       guarantee(k->has_modified_oops(), err_msg("Klass %p, has young refs but is not dirty.", k));
3107     }
3108   }
3109 };
3110 
3111 class VerifyLivenessOopClosure: public OopClosure {
3112   G1CollectedHeap* _g1h;
3113   VerifyOption _vo;
3114 public:
3115   VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
3116     _g1h(g1h), _vo(vo)
3117   { }
3118   void do_oop(narrowOop *p) { do_oop_work(p); }
3119   void do_oop(      oop *p) { do_oop_work(p); }
3120 
3121   template <class T> void do_oop_work(T *p) {
3122     oop obj = oopDesc::load_decode_heap_oop(p);
3123     guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
3124               "Dead object referenced by a not dead object");
3125   }
3126 };
3127 
3128 class VerifyObjsInRegionClosure: public ObjectClosure {
3129 private:
3130   G1CollectedHeap* _g1h;
3131   size_t _live_bytes;
3132   HeapRegion *_hr;
3133   VerifyOption _vo;
3134 public:
3135   // _vo == UsePrevMarking -> use "prev" marking information,
3136   // _vo == UseNextMarking -> use "next" marking information,
3137   // _vo == UseMarkWord    -> use mark word from object header.
3138   VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
3139     : _live_bytes(0), _hr(hr), _vo(vo) {
3140     _g1h = G1CollectedHeap::heap();
3141   }
3142   void do_object(oop o) {
3143     VerifyLivenessOopClosure isLive(_g1h, _vo);
3144     assert(o != NULL, "Huh?");
3145     if (!_g1h->is_obj_dead_cond(o, _vo)) {
3146       // If the object is alive according to the mark word,
3147       // then verify that the marking information agrees.
3148       // Note we can't verify the contra-positive of the
3149       // above: if the object is dead (according to the mark
3150       // word), it may not be marked, or may have been marked
3151       // but has since became dead, or may have been allocated
3152       // since the last marking.
3153       if (_vo == VerifyOption_G1UseMarkWord) {
3154         guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
3155       }
3156 
3157       o->oop_iterate_no_header(&isLive);
3158       if (!_hr->obj_allocated_since_prev_marking(o)) {
3159         size_t obj_size = o->size();    // Make sure we don't overflow
3160         _live_bytes += (obj_size * HeapWordSize);
3161       }
3162     }
3163   }
3164   size_t live_bytes() { return _live_bytes; }
3165 };
3166 
3167 class PrintObjsInRegionClosure : public ObjectClosure {
3168   HeapRegion *_hr;
3169   G1CollectedHeap *_g1;
3170 public:
3171   PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
3172     _g1 = G1CollectedHeap::heap();
3173   };
3174 
3175   void do_object(oop o) {
3176     if (o != NULL) {
3177       HeapWord *start = (HeapWord *) o;
3178       size_t word_sz = o->size();
3179       gclog_or_tty->print("\nPrinting obj " PTR_FORMAT " of size " SIZE_FORMAT
3180                           " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
3181                           (void*) o, word_sz,
3182                           _g1->isMarkedPrev(o),
3183                           _g1->isMarkedNext(o),
3184                           _hr->obj_allocated_since_prev_marking(o));
3185       HeapWord *end = start + word_sz;
3186       HeapWord *cur;
3187       int *val;
3188       for (cur = start; cur < end; cur++) {
3189         val = (int *) cur;
3190         gclog_or_tty->print("\t " PTR_FORMAT ":" PTR_FORMAT "\n", val, *val);
3191       }
3192     }
3193   }
3194 };
3195 
3196 class VerifyRegionClosure: public HeapRegionClosure {
3197 private:
3198   bool             _par;
3199   VerifyOption     _vo;
3200   bool             _failures;
3201 public:
3202   // _vo == UsePrevMarking -> use "prev" marking information,
3203   // _vo == UseNextMarking -> use "next" marking information,
3204   // _vo == UseMarkWord    -> use mark word from object header.
3205   VerifyRegionClosure(bool par, VerifyOption vo)
3206     : _par(par),
3207       _vo(vo),
3208       _failures(false) {}
3209 
3210   bool failures() {
3211     return _failures;
3212   }
3213 
3214   bool doHeapRegion(HeapRegion* r) {
3215     if (!r->continuesHumongous()) {
3216       bool failures = false;
3217       r->verify(_vo, &failures);
3218       if (failures) {
3219         _failures = true;
3220       } else {
3221         VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
3222         r->object_iterate(&not_dead_yet_cl);
3223         if (_vo != VerifyOption_G1UseNextMarking) {
3224           if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
3225             gclog_or_tty->print_cr("[" PTR_FORMAT "," PTR_FORMAT "] "
3226                                    "max_live_bytes " SIZE_FORMAT " "
3227                                    "< calculated " SIZE_FORMAT,
3228                                    r->bottom(), r->end(),
3229                                    r->max_live_bytes(),
3230                                  not_dead_yet_cl.live_bytes());
3231             _failures = true;
3232           }
3233         } else {
3234           // When vo == UseNextMarking we cannot currently do a sanity
3235           // check on the live bytes as the calculation has not been
3236           // finalized yet.
3237         }
3238       }
3239     }
3240     return false; // stop the region iteration if we hit a failure
3241   }
3242 };
3243 
3244 // This is the task used for parallel verification of the heap regions
3245 
3246 class G1ParVerifyTask: public AbstractGangTask {
3247 private:
3248   G1CollectedHeap* _g1h;
3249   VerifyOption     _vo;
3250   bool             _failures;
3251 
3252 public:
3253   // _vo == UsePrevMarking -> use "prev" marking information,
3254   // _vo == UseNextMarking -> use "next" marking information,
3255   // _vo == UseMarkWord    -> use mark word from object header.
3256   G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
3257     AbstractGangTask("Parallel verify task"),
3258     _g1h(g1h),
3259     _vo(vo),
3260     _failures(false) { }
3261 
3262   bool failures() {
3263     return _failures;
3264   }
3265 
3266   void work(uint worker_id) {
3267     HandleMark hm;
3268     VerifyRegionClosure blk(true, _vo);
3269     _g1h->heap_region_par_iterate_chunked(&blk, worker_id,
3270                                           _g1h->workers()->active_workers(),
3271                                           HeapRegion::ParVerifyClaimValue);
3272     if (blk.failures()) {
3273       _failures = true;
3274     }
3275   }
3276 };
3277 
3278 void G1CollectedHeap::verify(bool silent, VerifyOption vo) {
3279   if (SafepointSynchronize::is_at_safepoint()) {
3280     assert(Thread::current()->is_VM_thread(),
3281            "Expected to be executed serially by the VM thread at this point");
3282 
3283     if (!silent) { gclog_or_tty->print("Roots "); }
3284     VerifyRootsClosure rootsCl(vo);
3285     VerifyKlassClosure klassCl(this, &rootsCl);
3286     CLDToKlassAndOopClosure cldCl(&klassCl, &rootsCl, false);
3287 
3288     // We apply the relevant closures to all the oops in the
3289     // system dictionary, class loader data graph, the string table
3290     // and the nmethods in the code cache.
3291     G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo);
3292     G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl);
3293 
3294     {
3295       G1RootProcessor root_processor(this);
3296       root_processor.process_all_roots(&rootsCl,
3297                                        &cldCl,
3298                                        &blobsCl);
3299     }
3300 
3301     bool failures = rootsCl.failures() || codeRootsCl.failures();
3302 
3303     if (vo != VerifyOption_G1UseMarkWord) {
3304       // If we're verifying during a full GC then the region sets
3305       // will have been torn down at the start of the GC. Therefore
3306       // verifying the region sets will fail. So we only verify
3307       // the region sets when not in a full GC.
3308       if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3309       verify_region_sets();
3310     }
3311 
3312     if (!silent) { gclog_or_tty->print("HeapRegions "); }
3313     if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3314       assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3315              "sanity check");
3316 
3317       G1ParVerifyTask task(this, vo);
3318       assert(UseDynamicNumberOfGCThreads ||
3319         workers()->active_workers() == workers()->total_workers(),
3320         "If not dynamic should be using all the workers");
3321       int n_workers = workers()->active_workers();
3322       set_par_threads(n_workers);
3323       workers()->run_task(&task);
3324       set_par_threads(0);
3325       if (task.failures()) {
3326         failures = true;
3327       }
3328 
3329       // Checks that the expected amount of parallel work was done.
3330       // The implication is that n_workers is > 0.
3331       assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
3332              "sanity check");
3333 
3334       reset_heap_region_claim_values();
3335 
3336       assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3337              "sanity check");
3338     } else {
3339       VerifyRegionClosure blk(false, vo);
3340       heap_region_iterate(&blk);
3341       if (blk.failures()) {
3342         failures = true;
3343       }
3344     }
3345     if (!silent) gclog_or_tty->print("RemSet ");
3346     rem_set()->verify();
3347 
3348     if (G1StringDedup::is_enabled()) {
3349       if (!silent) gclog_or_tty->print("StrDedup ");
3350       G1StringDedup::verify();
3351     }
3352 
3353     if (failures) {
3354       gclog_or_tty->print_cr("Heap:");
3355       // It helps to have the per-region information in the output to
3356       // help us track down what went wrong. This is why we call
3357       // print_extended_on() instead of print_on().
3358       print_extended_on(gclog_or_tty);
3359       gclog_or_tty->cr();
3360 #ifndef PRODUCT
3361       if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3362         concurrent_mark()->print_reachable("at-verification-failure",
3363                                            vo, false /* all */);
3364       }
3365 #endif
3366       gclog_or_tty->flush();
3367     }
3368     guarantee(!failures, "there should not have been any failures");
3369   } else {
3370     if (!silent) {
3371       gclog_or_tty->print("(SKIPPING Roots, HeapRegionSets, HeapRegions, RemSet");
3372       if (G1StringDedup::is_enabled()) {
3373         gclog_or_tty->print(", StrDedup");
3374       }
3375       gclog_or_tty->print(") ");
3376     }
3377   }
3378 }
3379 
3380 void G1CollectedHeap::verify(bool silent) {
3381   verify(silent, VerifyOption_G1UsePrevMarking);
3382 }
3383 
3384 double G1CollectedHeap::verify(bool guard, const char* msg) {
3385   double verify_time_ms = 0.0;
3386 
3387   if (guard && total_collections() >= VerifyGCStartAt) {
3388     double verify_start = os::elapsedTime();
3389     HandleMark hm;  // Discard invalid handles created during verification
3390     prepare_for_verify();
3391     Universe::verify(VerifyOption_G1UsePrevMarking, msg);
3392     verify_time_ms = (os::elapsedTime() - verify_start) * 1000;
3393   }
3394 
3395   return verify_time_ms;
3396 }
3397 
3398 void G1CollectedHeap::verify_before_gc() {
3399   double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:");
3400   g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms);
3401 }
3402 
3403 void G1CollectedHeap::verify_after_gc() {
3404   double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:");
3405   g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms);
3406 }
3407 
3408 class PrintRegionClosure: public HeapRegionClosure {
3409   outputStream* _st;
3410 public:
3411   PrintRegionClosure(outputStream* st) : _st(st) {}
3412   bool doHeapRegion(HeapRegion* r) {
3413     r->print_on(_st);
3414     return false;
3415   }
3416 };
3417 
3418 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3419                                        const HeapRegion* hr,
3420                                        const VerifyOption vo) const {
3421   switch (vo) {
3422   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
3423   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
3424   case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked();
3425   default:                            ShouldNotReachHere();
3426   }
3427   return false; // keep some compilers happy
3428 }
3429 
3430 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3431                                        const VerifyOption vo) const {
3432   switch (vo) {
3433   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
3434   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
3435   case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked();
3436   default:                            ShouldNotReachHere();
3437   }
3438   return false; // keep some compilers happy
3439 }
3440 
3441 void G1CollectedHeap::print_on(outputStream* st) const {
3442   st->print(" %-20s", "garbage-first heap");
3443   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3444             capacity()/K, used_unlocked()/K);
3445   st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3446             _hrm.reserved().start(),
3447             _hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords,
3448             _hrm.reserved().end());
3449   st->cr();
3450   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3451   uint young_regions = _young_list->length();
3452   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3453             (size_t) young_regions * HeapRegion::GrainBytes / K);
3454   uint survivor_regions = g1_policy()->recorded_survivor_regions();
3455   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3456             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3457   st->cr();
3458   MetaspaceAux::print_on(st);
3459 }
3460 
3461 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3462   print_on(st);
3463 
3464   // Print the per-region information.
3465   st->cr();
3466   st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3467                "HS=humongous(starts), HC=humongous(continues), "
3468                "CS=collection set, F=free, TS=gc time stamp, "
3469                "PTAMS=previous top-at-mark-start, "
3470                "NTAMS=next top-at-mark-start)");
3471   PrintRegionClosure blk(st);
3472   heap_region_iterate(&blk);
3473 }
3474 
3475 void G1CollectedHeap::print_on_error(outputStream* st) const {
3476   this->CollectedHeap::print_on_error(st);
3477 
3478   if (_cm != NULL) {
3479     st->cr();
3480     _cm->print_on_error(st);
3481   }
3482 }
3483 
3484 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3485   if (G1CollectedHeap::use_parallel_gc_threads()) {
3486     workers()->print_worker_threads_on(st);
3487   }
3488   _cmThread->print_on(st);
3489   st->cr();
3490   _cm->print_worker_threads_on(st);
3491   _cg1r->print_worker_threads_on(st);
3492   if (G1StringDedup::is_enabled()) {
3493     G1StringDedup::print_worker_threads_on(st);
3494   }
3495 }
3496 
3497 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3498   if (G1CollectedHeap::use_parallel_gc_threads()) {
3499     workers()->threads_do(tc);
3500   }
3501   tc->do_thread(_cmThread);
3502   _cg1r->threads_do(tc);
3503   if (G1StringDedup::is_enabled()) {
3504     G1StringDedup::threads_do(tc);
3505   }
3506 }
3507 
3508 void G1CollectedHeap::print_tracing_info() const {
3509   // We'll overload this to mean "trace GC pause statistics."
3510   if (TraceGen0Time || TraceGen1Time) {
3511     // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3512     // to that.
3513     g1_policy()->print_tracing_info();
3514   }
3515   if (G1SummarizeRSetStats) {
3516     g1_rem_set()->print_summary_info();
3517   }
3518   if (G1SummarizeConcMark) {
3519     concurrent_mark()->print_summary_info();
3520   }
3521   g1_policy()->print_yg_surv_rate_info();
3522   SpecializationStats::print();
3523 }
3524 
3525 #ifndef PRODUCT
3526 // Helpful for debugging RSet issues.
3527 
3528 class PrintRSetsClosure : public HeapRegionClosure {
3529 private:
3530   const char* _msg;
3531   size_t _occupied_sum;
3532 
3533 public:
3534   bool doHeapRegion(HeapRegion* r) {
3535     HeapRegionRemSet* hrrs = r->rem_set();
3536     size_t occupied = hrrs->occupied();
3537     _occupied_sum += occupied;
3538 
3539     gclog_or_tty->print_cr("Printing RSet for region " HR_FORMAT,
3540                            HR_FORMAT_PARAMS(r));
3541     if (occupied == 0) {
3542       gclog_or_tty->print_cr("  RSet is empty");
3543     } else {
3544       hrrs->print();
3545     }
3546     gclog_or_tty->print_cr("----------");
3547     return false;
3548   }
3549 
3550   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3551     gclog_or_tty->cr();
3552     gclog_or_tty->print_cr("========================================");
3553     gclog_or_tty->print_cr("%s", msg);
3554     gclog_or_tty->cr();
3555   }
3556 
3557   ~PrintRSetsClosure() {
3558     gclog_or_tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
3559     gclog_or_tty->print_cr("========================================");
3560     gclog_or_tty->cr();
3561   }
3562 };
3563 
3564 void G1CollectedHeap::print_cset_rsets() {
3565   PrintRSetsClosure cl("Printing CSet RSets");
3566   collection_set_iterate(&cl);
3567 }
3568 
3569 void G1CollectedHeap::print_all_rsets() {
3570   PrintRSetsClosure cl("Printing All RSets");;
3571   heap_region_iterate(&cl);
3572 }
3573 #endif // PRODUCT
3574 
3575 G1CollectedHeap* G1CollectedHeap::heap() {
3576   assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3577          "not a garbage-first heap");
3578   return _g1h;
3579 }
3580 
3581 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3582   // always_do_update_barrier = false;
3583   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3584   // Fill TLAB's and such
3585   accumulate_statistics_all_tlabs();
3586   ensure_parsability(true);
3587 
3588   if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) &&
3589       (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3590     g1_rem_set()->print_periodic_summary_info("Before GC RS summary");
3591   }
3592 }
3593 
3594 void G1CollectedHeap::gc_epilogue(bool full) {
3595 
3596   if (G1SummarizeRSetStats &&
3597       (G1SummarizeRSetStatsPeriod > 0) &&
3598       // we are at the end of the GC. Total collections has already been increased.
3599       ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) {
3600     g1_rem_set()->print_periodic_summary_info("After GC RS summary");
3601   }
3602 
3603   // FIXME: what is this about?
3604   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3605   // is set.
3606   COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3607                         "derived pointer present"));
3608   // always_do_update_barrier = true;
3609 
3610   resize_all_tlabs();
3611   allocation_context_stats().update(full);
3612 
3613   // We have just completed a GC. Update the soft reference
3614   // policy with the new heap occupancy
3615   Universe::update_heap_info_at_gc();
3616 }
3617 
3618 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3619                                                uint gc_count_before,
3620                                                bool* succeeded,
3621                                                GCCause::Cause gc_cause) {
3622   assert_heap_not_locked_and_not_at_safepoint();
3623   g1_policy()->record_stop_world_start();
3624   VM_G1IncCollectionPause op(gc_count_before,
3625                              word_size,
3626                              false, /* should_initiate_conc_mark */
3627                              g1_policy()->max_pause_time_ms(),
3628                              gc_cause);
3629 
3630   op.set_allocation_context(AllocationContext::current());
3631   VMThread::execute(&op);
3632 
3633   HeapWord* result = op.result();
3634   bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3635   assert(result == NULL || ret_succeeded,
3636          "the result should be NULL if the VM did not succeed");
3637   *succeeded = ret_succeeded;
3638 
3639   assert_heap_not_locked();
3640   return result;
3641 }
3642 
3643 void
3644 G1CollectedHeap::doConcurrentMark() {
3645   MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3646   if (!_cmThread->in_progress()) {
3647     _cmThread->set_started();
3648     CGC_lock->notify();
3649   }
3650 }
3651 
3652 size_t G1CollectedHeap::pending_card_num() {
3653   size_t extra_cards = 0;
3654   JavaThread *curr = Threads::first();
3655   while (curr != NULL) {
3656     DirtyCardQueue& dcq = curr->dirty_card_queue();
3657     extra_cards += dcq.size();
3658     curr = curr->next();
3659   }
3660   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3661   size_t buffer_size = dcqs.buffer_size();
3662   size_t buffer_num = dcqs.completed_buffers_num();
3663 
3664   // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
3665   // in bytes - not the number of 'entries'. We need to convert
3666   // into a number of cards.
3667   return (buffer_size * buffer_num + extra_cards) / oopSize;
3668 }
3669 
3670 size_t G1CollectedHeap::cards_scanned() {
3671   return g1_rem_set()->cardsScanned();
3672 }
3673 
3674 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
3675  private:
3676   size_t _total_humongous;
3677   size_t _candidate_humongous;
3678 
3679   DirtyCardQueue _dcq;
3680 
3681   // We don't nominate objects with many remembered set entries, on
3682   // the assumption that such objects are likely still live.
3683   bool is_remset_small(HeapRegion* region) const {
3684     HeapRegionRemSet* const rset = region->rem_set();
3685     return G1EagerReclaimHumongousObjectsWithStaleRefs
3686       ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries)
3687       : rset->is_empty();
3688   }
3689 
3690   bool is_typeArray_region(HeapRegion* region) const {
3691     return oop(region->bottom())->is_typeArray();
3692   }
3693 
3694   bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const {
3695     assert(region->startsHumongous(), "Must start a humongous object");
3696 
3697     // Candidate selection must satisfy the following constraints
3698     // while concurrent marking is in progress:
3699     //
3700     // * In order to maintain SATB invariants, an object must not be
3701     // reclaimed if it was allocated before the start of marking and
3702     // has not had its references scanned.  Such an object must have
3703     // its references (including type metadata) scanned to ensure no
3704     // live objects are missed by the marking process.  Objects
3705     // allocated after the start of concurrent marking don't need to
3706     // be scanned.
3707     //
3708     // * An object must not be reclaimed if it is on the concurrent
3709     // mark stack.  Objects allocated after the start of concurrent
3710     // marking are never pushed on the mark stack.
3711     //
3712     // Nominating only objects allocated after the start of concurrent
3713     // marking is sufficient to meet both constraints.  This may miss
3714     // some objects that satisfy the constraints, but the marking data
3715     // structures don't support efficiently performing the needed
3716     // additional tests or scrubbing of the mark stack.
3717     //
3718     // However, we presently only nominate is_typeArray() objects.
3719     // A humongous object containing references induces remembered
3720     // set entries on other regions.  In order to reclaim such an
3721     // object, those remembered sets would need to be cleaned up.
3722     //
3723     // We also treat is_typeArray() objects specially, allowing them
3724     // to be reclaimed even if allocated before the start of
3725     // concurrent mark.  For this we rely on mark stack insertion to
3726     // exclude is_typeArray() objects, preventing reclaiming an object
3727     // that is in the mark stack.  We also rely on the metadata for
3728     // such objects to be built-in and so ensured to be kept live.
3729     // Frequent allocation and drop of large binary blobs is an
3730     // important use case for eager reclaim, and this special handling
3731     // may reduce needed headroom.
3732 
3733     return is_typeArray_region(region) && is_remset_small(region);
3734   }
3735 
3736  public:
3737   RegisterHumongousWithInCSetFastTestClosure()
3738   : _total_humongous(0),
3739     _candidate_humongous(0),
3740     _dcq(&JavaThread::dirty_card_queue_set()) {
3741   }
3742 
3743   virtual bool doHeapRegion(HeapRegion* r) {
3744     if (!r->startsHumongous()) {
3745       return false;
3746     }
3747     G1CollectedHeap* g1h = G1CollectedHeap::heap();
3748 
3749     bool is_candidate = humongous_region_is_candidate(g1h, r);
3750     uint rindex = r->hrm_index();
3751     g1h->set_humongous_reclaim_candidate(rindex, is_candidate);
3752     if (is_candidate) {
3753       _candidate_humongous++;
3754       g1h->register_humongous_region_with_in_cset_fast_test(rindex);
3755       // Is_candidate already filters out humongous object with large remembered sets.
3756       // If we have a humongous object with a few remembered sets, we simply flush these
3757       // remembered set entries into the DCQS. That will result in automatic
3758       // re-evaluation of their remembered set entries during the following evacuation
3759       // phase.
3760       if (!r->rem_set()->is_empty()) {
3761         guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
3762                   "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
3763         G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set();
3764         HeapRegionRemSetIterator hrrs(r->rem_set());
3765         size_t card_index;
3766         while (hrrs.has_next(card_index)) {
3767           jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index);
3768           if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
3769             *card_ptr = CardTableModRefBS::dirty_card_val();
3770             _dcq.enqueue(card_ptr);
3771           }
3772         }
3773         assert(hrrs.n_yielded() == r->rem_set()->occupied(),
3774                err_msg("Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries",
3775                hrrs.n_yielded(), r->rem_set()->occupied()));
3776         r->rem_set()->clear_locked();
3777       }
3778       assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
3779     }
3780     _total_humongous++;
3781 
3782     return false;
3783   }
3784 
3785   size_t total_humongous() const { return _total_humongous; }
3786   size_t candidate_humongous() const { return _candidate_humongous; }
3787 
3788   void flush_rem_set_entries() { _dcq.flush(); }
3789 };
3790 
3791 void G1CollectedHeap::register_humongous_regions_with_in_cset_fast_test() {
3792   if (!G1EagerReclaimHumongousObjects) {
3793     g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
3794     return;
3795   }
3796   double time = os::elapsed_counter();
3797 
3798   // Collect reclaim candidate information and register candidates with cset.
3799   RegisterHumongousWithInCSetFastTestClosure cl;
3800   heap_region_iterate(&cl);
3801 
3802   time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
3803   g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
3804                                                                   cl.total_humongous(),
3805                                                                   cl.candidate_humongous());
3806   _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
3807 
3808   // Finally flush all remembered set entries to re-check into the global DCQS.
3809   cl.flush_rem_set_entries();
3810 }
3811 
3812 void
3813 G1CollectedHeap::setup_surviving_young_words() {
3814   assert(_surviving_young_words == NULL, "pre-condition");
3815   uint array_length = g1_policy()->young_cset_region_length();
3816   _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3817   if (_surviving_young_words == NULL) {
3818     vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR,
3819                           "Not enough space for young surv words summary.");
3820   }
3821   memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3822 #ifdef ASSERT
3823   for (uint i = 0;  i < array_length; ++i) {
3824     assert( _surviving_young_words[i] == 0, "memset above" );
3825   }
3826 #endif // !ASSERT
3827 }
3828 
3829 void
3830 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3831   MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3832   uint array_length = g1_policy()->young_cset_region_length();
3833   for (uint i = 0; i < array_length; ++i) {
3834     _surviving_young_words[i] += surv_young_words[i];
3835   }
3836 }
3837 
3838 void
3839 G1CollectedHeap::cleanup_surviving_young_words() {
3840   guarantee( _surviving_young_words != NULL, "pre-condition" );
3841   FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC);
3842   _surviving_young_words = NULL;
3843 }
3844 
3845 class VerifyRegionRemSetClosure : public HeapRegionClosure {
3846   public:
3847     bool doHeapRegion(HeapRegion* hr) {
3848       if (!hr->continuesHumongous()) {
3849         hr->verify_rem_set();
3850       }
3851       return false;
3852     }
3853 };
3854 
3855 #ifdef ASSERT
3856 class VerifyCSetClosure: public HeapRegionClosure {
3857 public:
3858   bool doHeapRegion(HeapRegion* hr) {
3859     // Here we check that the CSet region's RSet is ready for parallel
3860     // iteration. The fields that we'll verify are only manipulated
3861     // when the region is part of a CSet and is collected. Afterwards,
3862     // we reset these fields when we clear the region's RSet (when the
3863     // region is freed) so they are ready when the region is
3864     // re-allocated. The only exception to this is if there's an
3865     // evacuation failure and instead of freeing the region we leave
3866     // it in the heap. In that case, we reset these fields during
3867     // evacuation failure handling.
3868     guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3869 
3870     // Here's a good place to add any other checks we'd like to
3871     // perform on CSet regions.
3872     return false;
3873   }
3874 };
3875 #endif // ASSERT
3876 
3877 #if TASKQUEUE_STATS
3878 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3879   st->print_raw_cr("GC Task Stats");
3880   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3881   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3882 }
3883 
3884 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3885   print_taskqueue_stats_hdr(st);
3886 
3887   TaskQueueStats totals;
3888   const int n = workers() != NULL ? workers()->total_workers() : 1;
3889   for (int i = 0; i < n; ++i) {
3890     st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3891     totals += task_queue(i)->stats;
3892   }
3893   st->print_raw("tot "); totals.print(st); st->cr();
3894 
3895   DEBUG_ONLY(totals.verify());
3896 }
3897 
3898 void G1CollectedHeap::reset_taskqueue_stats() {
3899   const int n = workers() != NULL ? workers()->total_workers() : 1;
3900   for (int i = 0; i < n; ++i) {
3901     task_queue(i)->stats.reset();
3902   }
3903 }
3904 #endif // TASKQUEUE_STATS
3905 
3906 void G1CollectedHeap::log_gc_header() {
3907   if (!G1Log::fine()) {
3908     return;
3909   }
3910 
3911   gclog_or_tty->gclog_stamp(_gc_tracer_stw->gc_id());
3912 
3913   GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
3914     .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)")
3915     .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : "");
3916 
3917   gclog_or_tty->print("[%s", (const char*)gc_cause_str);
3918 }
3919 
3920 void G1CollectedHeap::log_gc_footer(double pause_time_sec) {
3921   if (!G1Log::fine()) {
3922     return;
3923   }
3924 
3925   if (G1Log::finer()) {
3926     if (evacuation_failed()) {
3927       gclog_or_tty->print(" (to-space exhausted)");
3928     }
3929     gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3930     g1_policy()->phase_times()->note_gc_end();
3931     g1_policy()->phase_times()->print(pause_time_sec);
3932     g1_policy()->print_detailed_heap_transition();
3933   } else {
3934     if (evacuation_failed()) {
3935       gclog_or_tty->print("--");
3936     }
3937     g1_policy()->print_heap_transition();
3938     gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3939   }
3940   gclog_or_tty->flush();
3941 }
3942 
3943 bool
3944 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3945   assert_at_safepoint(true /* should_be_vm_thread */);
3946   guarantee(!is_gc_active(), "collection is not reentrant");
3947 
3948   if (GC_locker::check_active_before_gc()) {
3949     return false;
3950   }
3951 
3952   _gc_timer_stw->register_gc_start();
3953 
3954   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3955 
3956   SvcGCMarker sgcm(SvcGCMarker::MINOR);
3957   ResourceMark rm;
3958 
3959   print_heap_before_gc();
3960   trace_heap_before_gc(_gc_tracer_stw);
3961 
3962   verify_region_sets_optional();
3963   verify_dirty_young_regions();
3964 
3965   // This call will decide whether this pause is an initial-mark
3966   // pause. If it is, during_initial_mark_pause() will return true
3967   // for the duration of this pause.
3968   g1_policy()->decide_on_conc_mark_initiation();
3969 
3970   // We do not allow initial-mark to be piggy-backed on a mixed GC.
3971   assert(!g1_policy()->during_initial_mark_pause() ||
3972           g1_policy()->gcs_are_young(), "sanity");
3973 
3974   // We also do not allow mixed GCs during marking.
3975   assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3976 
3977   // Record whether this pause is an initial mark. When the current
3978   // thread has completed its logging output and it's safe to signal
3979   // the CM thread, the flag's value in the policy has been reset.
3980   bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3981 
3982   // Inner scope for scope based logging, timers, and stats collection
3983   {
3984     EvacuationInfo evacuation_info;
3985 
3986     if (g1_policy()->during_initial_mark_pause()) {
3987       // We are about to start a marking cycle, so we increment the
3988       // full collection counter.
3989       increment_old_marking_cycles_started();
3990       register_concurrent_cycle_start(_gc_timer_stw->gc_start());
3991     }
3992 
3993     _gc_tracer_stw->report_yc_type(yc_type());
3994 
3995     TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3996 
3997     uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
3998                                                                   workers()->active_workers(),
3999                                                                   Threads::number_of_non_daemon_threads());
4000     assert(UseDynamicNumberOfGCThreads ||
4001            active_workers == workers()->total_workers(),
4002            "If not dynamic should be using all the  workers");
4003     workers()->set_active_workers(active_workers);
4004 
4005 
4006     double pause_start_sec = os::elapsedTime();
4007     g1_policy()->phase_times()->note_gc_start(active_workers, mark_in_progress());
4008     log_gc_header();
4009 
4010     TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
4011     TraceMemoryManagerStats tms(false /* fullGC */, gc_cause(),
4012                                 yc_type() == Mixed /* allMemoryPoolsAffected */);
4013 
4014     // If the secondary_free_list is not empty, append it to the
4015     // free_list. No need to wait for the cleanup operation to finish;
4016     // the region allocation code will check the secondary_free_list
4017     // and wait if necessary. If the G1StressConcRegionFreeing flag is
4018     // set, skip this step so that the region allocation code has to
4019     // get entries from the secondary_free_list.
4020     if (!G1StressConcRegionFreeing) {
4021       append_secondary_free_list_if_not_empty_with_lock();
4022     }
4023 
4024     assert(check_young_list_well_formed(), "young list should be well formed");
4025     assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
4026            "sanity check");
4027 
4028     // Don't dynamically change the number of GC threads this early.  A value of
4029     // 0 is used to indicate serial work.  When parallel work is done,
4030     // it will be set.
4031 
4032     { // Call to jvmpi::post_class_unload_events must occur outside of active GC
4033       IsGCActiveMark x;
4034 
4035       gc_prologue(false);
4036       increment_total_collections(false /* full gc */);
4037       increment_gc_time_stamp();
4038 
4039       if (VerifyRememberedSets) {
4040         if (!VerifySilently) {
4041           gclog_or_tty->print_cr("[Verifying RemSets before GC]");
4042         }
4043         VerifyRegionRemSetClosure v_cl;
4044         heap_region_iterate(&v_cl);
4045       }
4046 
4047       verify_before_gc();
4048       check_bitmaps("GC Start");
4049 
4050       COMPILER2_PRESENT(DerivedPointerTable::clear());
4051 
4052       // Please see comment in g1CollectedHeap.hpp and
4053       // G1CollectedHeap::ref_processing_init() to see how
4054       // reference processing currently works in G1.
4055 
4056       // Enable discovery in the STW reference processor
4057       ref_processor_stw()->enable_discovery(true /*verify_disabled*/,
4058                                             true /*verify_no_refs*/);
4059 
4060       {
4061         // We want to temporarily turn off discovery by the
4062         // CM ref processor, if necessary, and turn it back on
4063         // on again later if we do. Using a scoped
4064         // NoRefDiscovery object will do this.
4065         NoRefDiscovery no_cm_discovery(ref_processor_cm());
4066 
4067         // Forget the current alloc region (we might even choose it to be part
4068         // of the collection set!).
4069         _allocator->release_mutator_alloc_region();
4070 
4071         // We should call this after we retire the mutator alloc
4072         // region(s) so that all the ALLOC / RETIRE events are generated
4073         // before the start GC event.
4074         _hr_printer.start_gc(false /* full */, (size_t) total_collections());
4075 
4076         // This timing is only used by the ergonomics to handle our pause target.
4077         // It is unclear why this should not include the full pause. We will
4078         // investigate this in CR 7178365.
4079         //
4080         // Preserving the old comment here if that helps the investigation:
4081         //
4082         // The elapsed time induced by the start time below deliberately elides
4083         // the possible verification above.
4084         double sample_start_time_sec = os::elapsedTime();
4085 
4086 #if YOUNG_LIST_VERBOSE
4087         gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
4088         _young_list->print();
4089         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4090 #endif // YOUNG_LIST_VERBOSE
4091 
4092         g1_policy()->record_collection_pause_start(sample_start_time_sec);
4093 
4094         double scan_wait_start = os::elapsedTime();
4095         // We have to wait until the CM threads finish scanning the
4096         // root regions as it's the only way to ensure that all the
4097         // objects on them have been correctly scanned before we start
4098         // moving them during the GC.
4099         bool waited = _cm->root_regions()->wait_until_scan_finished();
4100         double wait_time_ms = 0.0;
4101         if (waited) {
4102           double scan_wait_end = os::elapsedTime();
4103           wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
4104         }
4105         g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
4106 
4107 #if YOUNG_LIST_VERBOSE
4108         gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
4109         _young_list->print();
4110 #endif // YOUNG_LIST_VERBOSE
4111 
4112         if (g1_policy()->during_initial_mark_pause()) {
4113           concurrent_mark()->checkpointRootsInitialPre();
4114         }
4115 
4116 #if YOUNG_LIST_VERBOSE
4117         gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
4118         _young_list->print();
4119         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4120 #endif // YOUNG_LIST_VERBOSE
4121 
4122         g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info);
4123 
4124         // Make sure the remembered sets are up to date. This needs to be
4125         // done before register_humongous_regions_with_cset(), because the
4126         // remembered sets are used there to choose eager reclaim candidates.
4127         // If the remembered sets are not up to date we might miss some
4128         // entries that need to be handled.
4129         g1_rem_set()->cleanupHRRS();
4130 
4131         register_humongous_regions_with_in_cset_fast_test();
4132 
4133         assert(check_cset_fast_test(), "Inconsistency in the InCSetState table.");
4134 
4135         _cm->note_start_of_gc();
4136         // We call this after finalize_cset() to
4137         // ensure that the CSet has been finalized.
4138         _cm->verify_no_cset_oops();
4139 
4140         if (_hr_printer.is_active()) {
4141           HeapRegion* hr = g1_policy()->collection_set();
4142           while (hr != NULL) {
4143             _hr_printer.cset(hr);
4144             hr = hr->next_in_collection_set();
4145           }
4146         }
4147 
4148 #ifdef ASSERT
4149         VerifyCSetClosure cl;
4150         collection_set_iterate(&cl);
4151 #endif // ASSERT
4152 
4153         setup_surviving_young_words();
4154 
4155         // Initialize the GC alloc regions.
4156         _allocator->init_gc_alloc_regions(evacuation_info);
4157 
4158         // Actually do the work...
4159         evacuate_collection_set(evacuation_info);
4160 
4161         free_collection_set(g1_policy()->collection_set(), evacuation_info);
4162 
4163         eagerly_reclaim_humongous_regions();
4164 
4165         g1_policy()->clear_collection_set();
4166 
4167         cleanup_surviving_young_words();
4168 
4169         // Start a new incremental collection set for the next pause.
4170         g1_policy()->start_incremental_cset_building();
4171 
4172         clear_cset_fast_test();
4173 
4174         _young_list->reset_sampled_info();
4175 
4176         // Don't check the whole heap at this point as the
4177         // GC alloc regions from this pause have been tagged
4178         // as survivors and moved on to the survivor list.
4179         // Survivor regions will fail the !is_young() check.
4180         assert(check_young_list_empty(false /* check_heap */),
4181           "young list should be empty");
4182 
4183 #if YOUNG_LIST_VERBOSE
4184         gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
4185         _young_list->print();
4186 #endif // YOUNG_LIST_VERBOSE
4187 
4188         g1_policy()->record_survivor_regions(_young_list->survivor_length(),
4189                                              _young_list->first_survivor_region(),
4190                                              _young_list->last_survivor_region());
4191 
4192         _young_list->reset_auxilary_lists();
4193 
4194         if (evacuation_failed()) {
4195           _allocator->set_used(recalculate_used());
4196           uint n_queues = MAX2((int)ParallelGCThreads, 1);
4197           for (uint i = 0; i < n_queues; i++) {
4198             if (_evacuation_failed_info_array[i].has_failed()) {
4199               _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
4200             }
4201           }
4202         } else {
4203           // The "used" of the the collection set have already been subtracted
4204           // when they were freed.  Add in the bytes evacuated.
4205           _allocator->increase_used(g1_policy()->bytes_copied_during_gc());
4206         }
4207 
4208         if (g1_policy()->during_initial_mark_pause()) {
4209           // We have to do this before we notify the CM threads that
4210           // they can start working to make sure that all the
4211           // appropriate initialization is done on the CM object.
4212           concurrent_mark()->checkpointRootsInitialPost();
4213           set_marking_started();
4214           // Note that we don't actually trigger the CM thread at
4215           // this point. We do that later when we're sure that
4216           // the current thread has completed its logging output.
4217         }
4218 
4219         allocate_dummy_regions();
4220 
4221 #if YOUNG_LIST_VERBOSE
4222         gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
4223         _young_list->print();
4224         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4225 #endif // YOUNG_LIST_VERBOSE
4226 
4227         _allocator->init_mutator_alloc_region();
4228 
4229         {
4230           size_t expand_bytes = g1_policy()->expansion_amount();
4231           if (expand_bytes > 0) {
4232             size_t bytes_before = capacity();
4233             // No need for an ergo verbose message here,
4234             // expansion_amount() does this when it returns a value > 0.
4235             if (!expand(expand_bytes)) {
4236               // We failed to expand the heap. Cannot do anything about it.
4237             }
4238           }
4239         }
4240 
4241         // We redo the verification but now wrt to the new CSet which
4242         // has just got initialized after the previous CSet was freed.
4243         _cm->verify_no_cset_oops();
4244         _cm->note_end_of_gc();
4245 
4246         // This timing is only used by the ergonomics to handle our pause target.
4247         // It is unclear why this should not include the full pause. We will
4248         // investigate this in CR 7178365.
4249         double sample_end_time_sec = os::elapsedTime();
4250         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
4251         g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info);
4252 
4253         MemoryService::track_memory_usage();
4254 
4255         // In prepare_for_verify() below we'll need to scan the deferred
4256         // update buffers to bring the RSets up-to-date if
4257         // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
4258         // the update buffers we'll probably need to scan cards on the
4259         // regions we just allocated to (i.e., the GC alloc
4260         // regions). However, during the last GC we called
4261         // set_saved_mark() on all the GC alloc regions, so card
4262         // scanning might skip the [saved_mark_word()...top()] area of
4263         // those regions (i.e., the area we allocated objects into
4264         // during the last GC). But it shouldn't. Given that
4265         // saved_mark_word() is conditional on whether the GC time stamp
4266         // on the region is current or not, by incrementing the GC time
4267         // stamp here we invalidate all the GC time stamps on all the
4268         // regions and saved_mark_word() will simply return top() for
4269         // all the regions. This is a nicer way of ensuring this rather
4270         // than iterating over the regions and fixing them. In fact, the
4271         // GC time stamp increment here also ensures that
4272         // saved_mark_word() will return top() between pauses, i.e.,
4273         // during concurrent refinement. So we don't need the
4274         // is_gc_active() check to decided which top to use when
4275         // scanning cards (see CR 7039627).
4276         increment_gc_time_stamp();
4277 
4278         if (VerifyRememberedSets) {
4279           if (!VerifySilently) {
4280             gclog_or_tty->print_cr("[Verifying RemSets after GC]");
4281           }
4282           VerifyRegionRemSetClosure v_cl;
4283           heap_region_iterate(&v_cl);
4284         }
4285 
4286         verify_after_gc();
4287         check_bitmaps("GC End");
4288 
4289         assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
4290         ref_processor_stw()->verify_no_references_recorded();
4291 
4292         // CM reference discovery will be re-enabled if necessary.
4293       }
4294 
4295       // We should do this after we potentially expand the heap so
4296       // that all the COMMIT events are generated before the end GC
4297       // event, and after we retire the GC alloc regions so that all
4298       // RETIRE events are generated before the end GC event.
4299       _hr_printer.end_gc(false /* full */, (size_t) total_collections());
4300 
4301 #ifdef TRACESPINNING
4302       ParallelTaskTerminator::print_termination_counts();
4303 #endif
4304 
4305       gc_epilogue(false);
4306     }
4307 
4308     // Print the remainder of the GC log output.
4309     log_gc_footer(os::elapsedTime() - pause_start_sec);
4310 
4311     // It is not yet to safe to tell the concurrent mark to
4312     // start as we have some optional output below. We don't want the
4313     // output from the concurrent mark thread interfering with this
4314     // logging output either.
4315 
4316     _hrm.verify_optional();
4317     verify_region_sets_optional();
4318 
4319     TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
4320     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
4321 
4322     print_heap_after_gc();
4323     trace_heap_after_gc(_gc_tracer_stw);
4324 
4325     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
4326     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
4327     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
4328     // before any GC notifications are raised.
4329     g1mm()->update_sizes();
4330 
4331     _gc_tracer_stw->report_evacuation_info(&evacuation_info);
4332     _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
4333     _gc_timer_stw->register_gc_end();
4334     _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
4335   }
4336   // It should now be safe to tell the concurrent mark thread to start
4337   // without its logging output interfering with the logging output
4338   // that came from the pause.
4339 
4340   if (should_start_conc_mark) {
4341     // CAUTION: after the doConcurrentMark() call below,
4342     // the concurrent marking thread(s) could be running
4343     // concurrently with us. Make sure that anything after
4344     // this point does not assume that we are the only GC thread
4345     // running. Note: of course, the actual marking work will
4346     // not start until the safepoint itself is released in
4347     // SuspendibleThreadSet::desynchronize().
4348     doConcurrentMark();
4349   }
4350 
4351   return true;
4352 }
4353 
4354 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4355   _drain_in_progress = false;
4356   set_evac_failure_closure(cl);
4357   _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4358 }
4359 
4360 void G1CollectedHeap::finalize_for_evac_failure() {
4361   assert(_evac_failure_scan_stack != NULL &&
4362          _evac_failure_scan_stack->length() == 0,
4363          "Postcondition");
4364   assert(!_drain_in_progress, "Postcondition");
4365   delete _evac_failure_scan_stack;
4366   _evac_failure_scan_stack = NULL;
4367 }
4368 
4369 void G1CollectedHeap::remove_self_forwarding_pointers() {
4370   assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4371 
4372   double remove_self_forwards_start = os::elapsedTime();
4373 
4374   G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4375 
4376   if (G1CollectedHeap::use_parallel_gc_threads()) {
4377     set_par_threads();
4378     workers()->run_task(&rsfp_task);
4379     set_par_threads(0);
4380   } else {
4381     rsfp_task.work(0);
4382   }
4383 
4384   assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity");
4385 
4386   // Reset the claim values in the regions in the collection set.
4387   reset_cset_heap_region_claim_values();
4388 
4389   assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4390 
4391   // Now restore saved marks, if any.
4392   assert(_objs_with_preserved_marks.size() ==
4393             _preserved_marks_of_objs.size(), "Both or none.");
4394   while (!_objs_with_preserved_marks.is_empty()) {
4395     oop obj = _objs_with_preserved_marks.pop();
4396     markOop m = _preserved_marks_of_objs.pop();
4397     obj->set_mark(m);
4398   }
4399   _objs_with_preserved_marks.clear(true);
4400   _preserved_marks_of_objs.clear(true);
4401 
4402   g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
4403 }
4404 
4405 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4406   _evac_failure_scan_stack->push(obj);
4407 }
4408 
4409 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4410   assert(_evac_failure_scan_stack != NULL, "precondition");
4411 
4412   while (_evac_failure_scan_stack->length() > 0) {
4413      oop obj = _evac_failure_scan_stack->pop();
4414      _evac_failure_closure->set_region(heap_region_containing(obj));
4415      obj->oop_iterate_backwards(_evac_failure_closure);
4416   }
4417 }
4418 
4419 oop
4420 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state,
4421                                                oop old) {
4422   assert(obj_in_cs(old),
4423          err_msg("obj: " PTR_FORMAT " should still be in the CSet",
4424                  (HeapWord*) old));
4425   markOop m = old->mark();
4426   oop forward_ptr = old->forward_to_atomic(old);
4427   if (forward_ptr == NULL) {
4428     // Forward-to-self succeeded.
4429     assert(_par_scan_state != NULL, "par scan state");
4430     OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4431     uint queue_num = _par_scan_state->queue_num();
4432 
4433     _evacuation_failed = true;
4434     _evacuation_failed_info_array[queue_num].register_copy_failure(old->size());
4435     if (_evac_failure_closure != cl) {
4436       MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4437       assert(!_drain_in_progress,
4438              "Should only be true while someone holds the lock.");
4439       // Set the global evac-failure closure to the current thread's.
4440       assert(_evac_failure_closure == NULL, "Or locking has failed.");
4441       set_evac_failure_closure(cl);
4442       // Now do the common part.
4443       handle_evacuation_failure_common(old, m);
4444       // Reset to NULL.
4445       set_evac_failure_closure(NULL);
4446     } else {
4447       // The lock is already held, and this is recursive.
4448       assert(_drain_in_progress, "This should only be the recursive case.");
4449       handle_evacuation_failure_common(old, m);
4450     }
4451     return old;
4452   } else {
4453     // Forward-to-self failed. Either someone else managed to allocate
4454     // space for this object (old != forward_ptr) or they beat us in
4455     // self-forwarding it (old == forward_ptr).
4456     assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4457            err_msg("obj: " PTR_FORMAT " forwarded to: " PTR_FORMAT " "
4458                    "should not be in the CSet",
4459                    (HeapWord*) old, (HeapWord*) forward_ptr));
4460     return forward_ptr;
4461   }
4462 }
4463 
4464 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4465   preserve_mark_if_necessary(old, m);
4466 
4467   HeapRegion* r = heap_region_containing(old);
4468   if (!r->evacuation_failed()) {
4469     r->set_evacuation_failed(true);
4470     _hr_printer.evac_failure(r);
4471   }
4472 
4473   push_on_evac_failure_scan_stack(old);
4474 
4475   if (!_drain_in_progress) {
4476     // prevent recursion in copy_to_survivor_space()
4477     _drain_in_progress = true;
4478     drain_evac_failure_scan_stack();
4479     _drain_in_progress = false;
4480   }
4481 }
4482 
4483 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4484   assert(evacuation_failed(), "Oversaving!");
4485   // We want to call the "for_promotion_failure" version only in the
4486   // case of a promotion failure.
4487   if (m->must_be_preserved_for_promotion_failure(obj)) {
4488     _objs_with_preserved_marks.push(obj);
4489     _preserved_marks_of_objs.push(m);
4490   }
4491 }
4492 
4493 void G1ParCopyHelper::mark_object(oop obj) {
4494   assert(!_g1->heap_region_containing(obj)->in_collection_set(), "should not mark objects in the CSet");
4495 
4496   // We know that the object is not moving so it's safe to read its size.
4497   _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4498 }
4499 
4500 void G1ParCopyHelper::mark_forwarded_object(oop from_obj, oop to_obj) {
4501   assert(from_obj->is_forwarded(), "from obj should be forwarded");
4502   assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4503   assert(from_obj != to_obj, "should not be self-forwarded");
4504 
4505   assert(_g1->heap_region_containing(from_obj)->in_collection_set(), "from obj should be in the CSet");
4506   assert(!_g1->heap_region_containing(to_obj)->in_collection_set(), "should not mark objects in the CSet");
4507 
4508   // The object might be in the process of being copied by another
4509   // worker so we cannot trust that its to-space image is
4510   // well-formed. So we have to read its size from its from-space
4511   // image which we know should not be changing.
4512   _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4513 }
4514 
4515 template <class T>
4516 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) {
4517   if (_g1->heap_region_containing_raw(new_obj)->is_young()) {
4518     _scanned_klass->record_modified_oops();
4519   }
4520 }
4521 
4522 template <G1Barrier barrier, G1Mark do_mark_object>
4523 template <class T>
4524 void G1ParCopyClosure<barrier, do_mark_object>::do_oop_work(T* p) {
4525   T heap_oop = oopDesc::load_heap_oop(p);
4526 
4527   if (oopDesc::is_null(heap_oop)) {
4528     return;
4529   }
4530 
4531   oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
4532 
4533   assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4534 
4535   const InCSetState state = _g1->in_cset_state(obj);
4536   if (state.is_in_cset()) {
4537     oop forwardee;
4538     markOop m = obj->mark();
4539     if (m->is_marked()) {
4540       forwardee = (oop) m->decode_pointer();
4541     } else {
4542       forwardee = _par_scan_state->copy_to_survivor_space(state, obj, m);
4543     }
4544     assert(forwardee != NULL, "forwardee should not be NULL");
4545     oopDesc::encode_store_heap_oop(p, forwardee);
4546     if (do_mark_object != G1MarkNone && forwardee != obj) {
4547       // If the object is self-forwarded we don't need to explicitly
4548       // mark it, the evacuation failure protocol will do so.
4549       mark_forwarded_object(obj, forwardee);
4550     }
4551 
4552     if (barrier == G1BarrierKlass) {
4553       do_klass_barrier(p, forwardee);
4554     }
4555   } else {
4556     if (state.is_humongous()) {
4557       _g1->set_humongous_is_live(obj);
4558     }
4559     // The object is not in collection set. If we're a root scanning
4560     // closure during an initial mark pause then attempt to mark the object.
4561     if (do_mark_object == G1MarkFromRoot) {
4562       mark_object(obj);
4563     }
4564   }
4565 
4566   if (barrier == G1BarrierEvac) {
4567     _par_scan_state->update_rs(_from, p, _worker_id);
4568   }
4569 }
4570 
4571 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(oop* p);
4572 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(narrowOop* p);
4573 
4574 class G1ParEvacuateFollowersClosure : public VoidClosure {
4575 protected:
4576   G1CollectedHeap*              _g1h;
4577   G1ParScanThreadState*         _par_scan_state;
4578   RefToScanQueueSet*            _queues;
4579   ParallelTaskTerminator*       _terminator;
4580 
4581   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
4582   RefToScanQueueSet*      queues()         { return _queues; }
4583   ParallelTaskTerminator* terminator()     { return _terminator; }
4584 
4585 public:
4586   G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4587                                 G1ParScanThreadState* par_scan_state,
4588                                 RefToScanQueueSet* queues,
4589                                 ParallelTaskTerminator* terminator)
4590     : _g1h(g1h), _par_scan_state(par_scan_state),
4591       _queues(queues), _terminator(terminator) {}
4592 
4593   void do_void();
4594 
4595 private:
4596   inline bool offer_termination();
4597 };
4598 
4599 bool G1ParEvacuateFollowersClosure::offer_termination() {
4600   G1ParScanThreadState* const pss = par_scan_state();
4601   pss->start_term_time();
4602   const bool res = terminator()->offer_termination();
4603   pss->end_term_time();
4604   return res;
4605 }
4606 
4607 void G1ParEvacuateFollowersClosure::do_void() {
4608   G1ParScanThreadState* const pss = par_scan_state();
4609   pss->trim_queue();
4610   do {
4611     pss->steal_and_trim_queue(queues());
4612   } while (!offer_termination());
4613 }
4614 
4615 class G1KlassScanClosure : public KlassClosure {
4616  G1ParCopyHelper* _closure;
4617  bool             _process_only_dirty;
4618  int              _count;
4619  public:
4620   G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty)
4621       : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {}
4622   void do_klass(Klass* klass) {
4623     // If the klass has not been dirtied we know that there's
4624     // no references into  the young gen and we can skip it.
4625    if (!_process_only_dirty || klass->has_modified_oops()) {
4626       // Clean the klass since we're going to scavenge all the metadata.
4627       klass->clear_modified_oops();
4628 
4629       // Tell the closure that this klass is the Klass to scavenge
4630       // and is the one to dirty if oops are left pointing into the young gen.
4631       _closure->set_scanned_klass(klass);
4632 
4633       klass->oops_do(_closure);
4634 
4635       _closure->set_scanned_klass(NULL);
4636     }
4637     _count++;
4638   }
4639 };
4640 
4641 class G1ParTask : public AbstractGangTask {
4642 protected:
4643   G1CollectedHeap*       _g1h;
4644   RefToScanQueueSet      *_queues;
4645   G1RootProcessor*       _root_processor;
4646   ParallelTaskTerminator _terminator;
4647   uint _n_workers;
4648 
4649   Mutex _stats_lock;
4650   Mutex* stats_lock() { return &_stats_lock; }
4651 
4652 public:
4653   G1ParTask(G1CollectedHeap* g1h, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor)
4654     : AbstractGangTask("G1 collection"),
4655       _g1h(g1h),
4656       _queues(task_queues),
4657       _root_processor(root_processor),
4658       _terminator(0, _queues),
4659       _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4660   {}
4661 
4662   RefToScanQueueSet* queues() { return _queues; }
4663 
4664   RefToScanQueue *work_queue(int i) {
4665     return queues()->queue(i);
4666   }
4667 
4668   ParallelTaskTerminator* terminator() { return &_terminator; }
4669 
4670   virtual void set_for_termination(int active_workers) {
4671     _root_processor->set_num_workers(active_workers);
4672     terminator()->reset_for_reuse(active_workers);
4673     _n_workers = active_workers;
4674   }
4675 
4676   // Helps out with CLD processing.
4677   //
4678   // During InitialMark we need to:
4679   // 1) Scavenge all CLDs for the young GC.
4680   // 2) Mark all objects directly reachable from strong CLDs.
4681   template <G1Mark do_mark_object>
4682   class G1CLDClosure : public CLDClosure {
4683     G1ParCopyClosure<G1BarrierNone,  do_mark_object>* _oop_closure;
4684     G1ParCopyClosure<G1BarrierKlass, do_mark_object>  _oop_in_klass_closure;
4685     G1KlassScanClosure                                _klass_in_cld_closure;
4686     bool                                              _claim;
4687 
4688    public:
4689     G1CLDClosure(G1ParCopyClosure<G1BarrierNone, do_mark_object>* oop_closure,
4690                  bool only_young, bool claim)
4691         : _oop_closure(oop_closure),
4692           _oop_in_klass_closure(oop_closure->g1(),
4693                                 oop_closure->pss(),
4694                                 oop_closure->rp()),
4695           _klass_in_cld_closure(&_oop_in_klass_closure, only_young),
4696           _claim(claim) {
4697 
4698     }
4699 
4700     void do_cld(ClassLoaderData* cld) {
4701       cld->oops_do(_oop_closure, &_klass_in_cld_closure, _claim);
4702     }
4703   };
4704 
4705   void work(uint worker_id) {
4706     if (worker_id >= _n_workers) return;  // no work needed this round
4707 
4708     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, os::elapsedTime());
4709 
4710     {
4711       ResourceMark rm;
4712       HandleMark   hm;
4713 
4714       ReferenceProcessor*             rp = _g1h->ref_processor_stw();
4715 
4716       G1ParScanThreadState            pss(_g1h, worker_id, rp);
4717       G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
4718 
4719       pss.set_evac_failure_closure(&evac_failure_cl);
4720 
4721       bool only_young = _g1h->g1_policy()->gcs_are_young();
4722 
4723       // Non-IM young GC.
4724       G1ParCopyClosure<G1BarrierNone, G1MarkNone>             scan_only_root_cl(_g1h, &pss, rp);
4725       G1CLDClosure<G1MarkNone>                                scan_only_cld_cl(&scan_only_root_cl,
4726                                                                                only_young, // Only process dirty klasses.
4727                                                                                false);     // No need to claim CLDs.
4728       // IM young GC.
4729       //    Strong roots closures.
4730       G1ParCopyClosure<G1BarrierNone, G1MarkFromRoot>         scan_mark_root_cl(_g1h, &pss, rp);
4731       G1CLDClosure<G1MarkFromRoot>                            scan_mark_cld_cl(&scan_mark_root_cl,
4732                                                                                false, // Process all klasses.
4733                                                                                true); // Need to claim CLDs.
4734       //    Weak roots closures.
4735       G1ParCopyClosure<G1BarrierNone, G1MarkPromotedFromRoot> scan_mark_weak_root_cl(_g1h, &pss, rp);
4736       G1CLDClosure<G1MarkPromotedFromRoot>                    scan_mark_weak_cld_cl(&scan_mark_weak_root_cl,
4737                                                                                     false, // Process all klasses.
4738                                                                                     true); // Need to claim CLDs.
4739 
4740       OopClosure* strong_root_cl;
4741       OopClosure* weak_root_cl;
4742       CLDClosure* strong_cld_cl;
4743       CLDClosure* weak_cld_cl;
4744 
4745       bool trace_metadata = false;
4746 
4747       if (_g1h->g1_policy()->during_initial_mark_pause()) {
4748         // We also need to mark copied objects.
4749         strong_root_cl = &scan_mark_root_cl;
4750         strong_cld_cl  = &scan_mark_cld_cl;
4751         if (ClassUnloadingWithConcurrentMark) {
4752           weak_root_cl = &scan_mark_weak_root_cl;
4753           weak_cld_cl  = &scan_mark_weak_cld_cl;
4754           trace_metadata = true;
4755         } else {
4756           weak_root_cl = &scan_mark_root_cl;
4757           weak_cld_cl  = &scan_mark_cld_cl;
4758         }
4759       } else {
4760         strong_root_cl = &scan_only_root_cl;
4761         weak_root_cl   = &scan_only_root_cl;
4762         strong_cld_cl  = &scan_only_cld_cl;
4763         weak_cld_cl    = &scan_only_cld_cl;
4764       }
4765 
4766       pss.start_strong_roots();
4767 
4768       _root_processor->evacuate_roots(strong_root_cl,
4769                                       weak_root_cl,
4770                                       strong_cld_cl,
4771                                       weak_cld_cl,
4772                                       trace_metadata,
4773                                       worker_id);
4774 
4775       G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss);
4776       _root_processor->scan_remembered_sets(&push_heap_rs_cl,
4777                                             weak_root_cl,
4778                                             worker_id);
4779       pss.end_strong_roots();
4780 
4781       {
4782         double start = os::elapsedTime();
4783         G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4784         evac.do_void();
4785         double elapsed_sec = os::elapsedTime() - start;
4786         double term_sec = pss.term_time();
4787         _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec);
4788         _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec);
4789         _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, pss.term_attempts());
4790       }
4791       _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4792       _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4793 
4794       if (ParallelGCVerbose) {
4795         MutexLocker x(stats_lock());
4796         pss.print_termination_stats(worker_id);
4797       }
4798 
4799       assert(pss.queue_is_empty(), "should be empty");
4800 
4801       // Close the inner scope so that the ResourceMark and HandleMark
4802       // destructors are executed here and are included as part of the
4803       // "GC Worker Time".
4804     }
4805     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime());
4806   }
4807 };
4808 
4809 class G1StringSymbolTableUnlinkTask : public AbstractGangTask {
4810 private:
4811   BoolObjectClosure* _is_alive;
4812   int _initial_string_table_size;
4813   int _initial_symbol_table_size;
4814 
4815   bool  _process_strings;
4816   int _strings_processed;
4817   int _strings_removed;
4818 
4819   bool  _process_symbols;
4820   int _symbols_processed;
4821   int _symbols_removed;
4822 
4823   bool _do_in_parallel;
4824 public:
4825   G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) :
4826     AbstractGangTask("String/Symbol Unlinking"),
4827     _is_alive(is_alive),
4828     _do_in_parallel(G1CollectedHeap::use_parallel_gc_threads()),
4829     _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
4830     _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) {
4831 
4832     _initial_string_table_size = StringTable::the_table()->table_size();
4833     _initial_symbol_table_size = SymbolTable::the_table()->table_size();
4834     if (process_strings) {
4835       StringTable::clear_parallel_claimed_index();
4836     }
4837     if (process_symbols) {
4838       SymbolTable::clear_parallel_claimed_index();
4839     }
4840   }
4841 
4842   ~G1StringSymbolTableUnlinkTask() {
4843     guarantee(!_process_strings || !_do_in_parallel || StringTable::parallel_claimed_index() >= _initial_string_table_size,
4844               err_msg("claim value " INT32_FORMAT " after unlink less than initial string table size " INT32_FORMAT,
4845                       StringTable::parallel_claimed_index(), _initial_string_table_size));
4846     guarantee(!_process_symbols || !_do_in_parallel || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
4847               err_msg("claim value " INT32_FORMAT " after unlink less than initial symbol table size " INT32_FORMAT,
4848                       SymbolTable::parallel_claimed_index(), _initial_symbol_table_size));
4849 
4850     if (G1TraceStringSymbolTableScrubbing) {
4851       gclog_or_tty->print_cr("Cleaned string and symbol table, "
4852                              "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, "
4853                              "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed",
4854                              strings_processed(), strings_removed(),
4855                              symbols_processed(), symbols_removed());
4856     }
4857   }
4858 
4859   void work(uint worker_id) {
4860     if (_do_in_parallel) {
4861       int strings_processed = 0;
4862       int strings_removed = 0;
4863       int symbols_processed = 0;
4864       int symbols_removed = 0;
4865       if (_process_strings) {
4866         StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
4867         Atomic::add(strings_processed, &_strings_processed);
4868         Atomic::add(strings_removed, &_strings_removed);
4869       }
4870       if (_process_symbols) {
4871         SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
4872         Atomic::add(symbols_processed, &_symbols_processed);
4873         Atomic::add(symbols_removed, &_symbols_removed);
4874       }
4875     } else {
4876       if (_process_strings) {
4877         StringTable::unlink(_is_alive, &_strings_processed, &_strings_removed);
4878       }
4879       if (_process_symbols) {
4880         SymbolTable::unlink(&_symbols_processed, &_symbols_removed);
4881       }
4882     }
4883   }
4884 
4885   size_t strings_processed() const { return (size_t)_strings_processed; }
4886   size_t strings_removed()   const { return (size_t)_strings_removed; }
4887 
4888   size_t symbols_processed() const { return (size_t)_symbols_processed; }
4889   size_t symbols_removed()   const { return (size_t)_symbols_removed; }
4890 };
4891 
4892 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
4893 private:
4894   static Monitor* _lock;
4895 
4896   BoolObjectClosure* const _is_alive;
4897   const bool               _unloading_occurred;
4898   const uint               _num_workers;
4899 
4900   // Variables used to claim nmethods.
4901   nmethod* _first_nmethod;
4902   volatile nmethod* _claimed_nmethod;
4903 
4904   // The list of nmethods that need to be processed by the second pass.
4905   volatile nmethod* _postponed_list;
4906   volatile uint     _num_entered_barrier;
4907 
4908  public:
4909   G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
4910       _is_alive(is_alive),
4911       _unloading_occurred(unloading_occurred),
4912       _num_workers(num_workers),
4913       _first_nmethod(NULL),
4914       _claimed_nmethod(NULL),
4915       _postponed_list(NULL),
4916       _num_entered_barrier(0)
4917   {
4918     nmethod::increase_unloading_clock();
4919     _first_nmethod = CodeCache::alive_nmethod(CodeCache::first());
4920     _claimed_nmethod = (volatile nmethod*)_first_nmethod;
4921   }
4922 
4923   ~G1CodeCacheUnloadingTask() {
4924     CodeCache::verify_clean_inline_caches();
4925 
4926     CodeCache::set_needs_cache_clean(false);
4927     guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
4928 
4929     CodeCache::verify_icholder_relocations();
4930   }
4931 
4932  private:
4933   void add_to_postponed_list(nmethod* nm) {
4934       nmethod* old;
4935       do {
4936         old = (nmethod*)_postponed_list;
4937         nm->set_unloading_next(old);
4938       } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old);
4939   }
4940 
4941   void clean_nmethod(nmethod* nm) {
4942     bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
4943 
4944     if (postponed) {
4945       // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
4946       add_to_postponed_list(nm);
4947     }
4948 
4949     // Mark that this thread has been cleaned/unloaded.
4950     // After this call, it will be safe to ask if this nmethod was unloaded or not.
4951     nm->set_unloading_clock(nmethod::global_unloading_clock());
4952   }
4953 
4954   void clean_nmethod_postponed(nmethod* nm) {
4955     nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
4956   }
4957 
4958   static const int MaxClaimNmethods = 16;
4959 
4960   void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) {
4961     nmethod* first;
4962     nmethod* last;
4963 
4964     do {
4965       *num_claimed_nmethods = 0;
4966 
4967       first = last = (nmethod*)_claimed_nmethod;
4968 
4969       if (first != NULL) {
4970         for (int i = 0; i < MaxClaimNmethods; i++) {
4971           last = CodeCache::alive_nmethod(CodeCache::next(last));
4972 
4973           if (last == NULL) {
4974             break;
4975           }
4976 
4977           claimed_nmethods[i] = last;
4978           (*num_claimed_nmethods)++;
4979         }
4980       }
4981 
4982     } while ((nmethod*)Atomic::cmpxchg_ptr(last, &_claimed_nmethod, first) != first);
4983   }
4984 
4985   nmethod* claim_postponed_nmethod() {
4986     nmethod* claim;
4987     nmethod* next;
4988 
4989     do {
4990       claim = (nmethod*)_postponed_list;
4991       if (claim == NULL) {
4992         return NULL;
4993       }
4994 
4995       next = claim->unloading_next();
4996 
4997     } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim);
4998 
4999     return claim;
5000   }
5001 
5002  public:
5003   // Mark that we're done with the first pass of nmethod cleaning.
5004   void barrier_mark(uint worker_id) {
5005     MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
5006     _num_entered_barrier++;
5007     if (_num_entered_barrier == _num_workers) {
5008       ml.notify_all();
5009     }
5010   }
5011 
5012   // See if we have to wait for the other workers to
5013   // finish their first-pass nmethod cleaning work.
5014   void barrier_wait(uint worker_id) {
5015     if (_num_entered_barrier < _num_workers) {
5016       MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
5017       while (_num_entered_barrier < _num_workers) {
5018           ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
5019       }
5020     }
5021   }
5022 
5023   // Cleaning and unloading of nmethods. Some work has to be postponed
5024   // to the second pass, when we know which nmethods survive.
5025   void work_first_pass(uint worker_id) {
5026     // The first nmethods is claimed by the first worker.
5027     if (worker_id == 0 && _first_nmethod != NULL) {
5028       clean_nmethod(_first_nmethod);
5029       _first_nmethod = NULL;
5030     }
5031 
5032     int num_claimed_nmethods;
5033     nmethod* claimed_nmethods[MaxClaimNmethods];
5034 
5035     while (true) {
5036       claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
5037 
5038       if (num_claimed_nmethods == 0) {
5039         break;
5040       }
5041 
5042       for (int i = 0; i < num_claimed_nmethods; i++) {
5043         clean_nmethod(claimed_nmethods[i]);
5044       }
5045     }
5046 
5047     // The nmethod cleaning helps out and does the CodeCache part of MetadataOnStackMark.
5048     // Need to retire the buffers now that this thread has stopped cleaning nmethods.
5049     MetadataOnStackMark::retire_buffer_for_thread(Thread::current());
5050   }
5051 
5052   void work_second_pass(uint worker_id) {
5053     nmethod* nm;
5054     // Take care of postponed nmethods.
5055     while ((nm = claim_postponed_nmethod()) != NULL) {
5056       clean_nmethod_postponed(nm);
5057     }
5058   }
5059 };
5060 
5061 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock");
5062 
5063 class G1KlassCleaningTask : public StackObj {
5064   BoolObjectClosure*                      _is_alive;
5065   volatile jint                           _clean_klass_tree_claimed;
5066   ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
5067 
5068  public:
5069   G1KlassCleaningTask(BoolObjectClosure* is_alive) :
5070       _is_alive(is_alive),
5071       _clean_klass_tree_claimed(0),
5072       _klass_iterator() {
5073   }
5074 
5075  private:
5076   bool claim_clean_klass_tree_task() {
5077     if (_clean_klass_tree_claimed) {
5078       return false;
5079     }
5080 
5081     return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0;
5082   }
5083 
5084   InstanceKlass* claim_next_klass() {
5085     Klass* klass;
5086     do {
5087       klass =_klass_iterator.next_klass();
5088     } while (klass != NULL && !klass->oop_is_instance());
5089 
5090     return (InstanceKlass*)klass;
5091   }
5092 
5093 public:
5094 
5095   void clean_klass(InstanceKlass* ik) {
5096     ik->clean_weak_instanceklass_links(_is_alive);
5097 
5098     if (JvmtiExport::has_redefined_a_class()) {
5099       InstanceKlass::purge_previous_versions(ik);
5100     }
5101   }
5102 
5103   void work() {
5104     ResourceMark rm;
5105 
5106     // One worker will clean the subklass/sibling klass tree.
5107     if (claim_clean_klass_tree_task()) {
5108       Klass::clean_subklass_tree(_is_alive);
5109     }
5110 
5111     // All workers will help cleaning the classes,
5112     InstanceKlass* klass;
5113     while ((klass = claim_next_klass()) != NULL) {
5114       clean_klass(klass);
5115     }
5116   }
5117 };
5118 
5119 // To minimize the remark pause times, the tasks below are done in parallel.
5120 class G1ParallelCleaningTask : public AbstractGangTask {
5121 private:
5122   G1StringSymbolTableUnlinkTask _string_symbol_task;
5123   G1CodeCacheUnloadingTask      _code_cache_task;
5124   G1KlassCleaningTask           _klass_cleaning_task;
5125 
5126 public:
5127   // The constructor is run in the VMThread.
5128   G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) :
5129       AbstractGangTask("Parallel Cleaning"),
5130       _string_symbol_task(is_alive, process_strings, process_symbols),
5131       _code_cache_task(num_workers, is_alive, unloading_occurred),
5132       _klass_cleaning_task(is_alive) {
5133   }
5134 
5135   void pre_work_verification() {
5136     // The VM Thread will have registered Metadata during the single-threaded phase of MetadataStackOnMark.
5137     assert(Thread::current()->is_VM_thread()
5138            || !MetadataOnStackMark::has_buffer_for_thread(Thread::current()), "Should be empty");
5139   }
5140 
5141   void post_work_verification() {
5142     assert(!MetadataOnStackMark::has_buffer_for_thread(Thread::current()), "Should be empty");
5143   }
5144 
5145   // The parallel work done by all worker threads.
5146   void work(uint worker_id) {
5147     pre_work_verification();
5148 
5149     // Do first pass of code cache cleaning.
5150     _code_cache_task.work_first_pass(worker_id);
5151 
5152     // Let the threads mark that the first pass is done.
5153     _code_cache_task.barrier_mark(worker_id);
5154 
5155     // Clean the Strings and Symbols.
5156     _string_symbol_task.work(worker_id);
5157 
5158     // Wait for all workers to finish the first code cache cleaning pass.
5159     _code_cache_task.barrier_wait(worker_id);
5160 
5161     // Do the second code cache cleaning work, which realize on
5162     // the liveness information gathered during the first pass.
5163     _code_cache_task.work_second_pass(worker_id);
5164 
5165     // Clean all klasses that were not unloaded.
5166     _klass_cleaning_task.work();
5167 
5168     post_work_verification();
5169   }
5170 };
5171 
5172 
5173 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive,
5174                                         bool process_strings,
5175                                         bool process_symbols,
5176                                         bool class_unloading_occurred) {
5177   uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5178                     workers()->active_workers() : 1);
5179 
5180   G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols,
5181                                         n_workers, class_unloading_occurred);
5182   if (G1CollectedHeap::use_parallel_gc_threads()) {
5183     set_par_threads(n_workers);
5184     workers()->run_task(&g1_unlink_task);
5185     set_par_threads(0);
5186   } else {
5187     g1_unlink_task.work(0);
5188   }
5189 }
5190 
5191 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive,
5192                                                      bool process_strings, bool process_symbols) {
5193   {
5194     uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5195                      _g1h->workers()->active_workers() : 1);
5196     G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols);
5197     if (G1CollectedHeap::use_parallel_gc_threads()) {
5198       set_par_threads(n_workers);
5199       workers()->run_task(&g1_unlink_task);
5200       set_par_threads(0);
5201     } else {
5202       g1_unlink_task.work(0);
5203     }
5204   }
5205 
5206   if (G1StringDedup::is_enabled()) {
5207     G1StringDedup::unlink(is_alive);
5208   }
5209 }
5210 
5211 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
5212  private:
5213   DirtyCardQueueSet* _queue;
5214  public:
5215   G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue) : AbstractGangTask("Redirty Cards"), _queue(queue) { }
5216 
5217   virtual void work(uint worker_id) {
5218     G1GCPhaseTimes* phase_times = G1CollectedHeap::heap()->g1_policy()->phase_times();
5219     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id);
5220 
5221     RedirtyLoggedCardTableEntryClosure cl;
5222     if (G1CollectedHeap::heap()->use_parallel_gc_threads()) {
5223       _queue->par_apply_closure_to_all_completed_buffers(&cl);
5224     } else {
5225       _queue->apply_closure_to_all_completed_buffers(&cl);
5226     }
5227 
5228     phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_processed());
5229   }
5230 };
5231 
5232 void G1CollectedHeap::redirty_logged_cards() {
5233   double redirty_logged_cards_start = os::elapsedTime();
5234 
5235   uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5236                    _g1h->workers()->active_workers() : 1);
5237 
5238   G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set());
5239   dirty_card_queue_set().reset_for_par_iteration();
5240   if (use_parallel_gc_threads()) {
5241     set_par_threads(n_workers);
5242     workers()->run_task(&redirty_task);
5243     set_par_threads(0);
5244   } else {
5245     redirty_task.work(0);
5246   }
5247 
5248   DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5249   dcq.merge_bufferlists(&dirty_card_queue_set());
5250   assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5251 
5252   g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
5253 }
5254 
5255 // Weak Reference Processing support
5256 
5257 // An always "is_alive" closure that is used to preserve referents.
5258 // If the object is non-null then it's alive.  Used in the preservation
5259 // of referent objects that are pointed to by reference objects
5260 // discovered by the CM ref processor.
5261 class G1AlwaysAliveClosure: public BoolObjectClosure {
5262   G1CollectedHeap* _g1;
5263 public:
5264   G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5265   bool do_object_b(oop p) {
5266     if (p != NULL) {
5267       return true;
5268     }
5269     return false;
5270   }
5271 };
5272 
5273 bool G1STWIsAliveClosure::do_object_b(oop p) {
5274   // An object is reachable if it is outside the collection set,
5275   // or is inside and copied.
5276   return !_g1->obj_in_cs(p) || p->is_forwarded();
5277 }
5278 
5279 // Non Copying Keep Alive closure
5280 class G1KeepAliveClosure: public OopClosure {
5281   G1CollectedHeap* _g1;
5282 public:
5283   G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5284   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
5285   void do_oop(oop* p) {
5286     oop obj = *p;
5287     assert(obj != NULL, "the caller should have filtered out NULL values");
5288 
5289     const InCSetState cset_state = _g1->in_cset_state(obj);
5290     if (!cset_state.is_in_cset_or_humongous()) {
5291       return;
5292     }
5293     if (cset_state.is_in_cset()) {
5294       assert( obj->is_forwarded(), "invariant" );
5295       *p = obj->forwardee();
5296     } else {
5297       assert(!obj->is_forwarded(), "invariant" );
5298       assert(cset_state.is_humongous(),
5299              err_msg("Only allowed InCSet state is IsHumongous, but is %d", cset_state.value()));
5300       _g1->set_humongous_is_live(obj);
5301     }
5302   }
5303 };
5304 
5305 // Copying Keep Alive closure - can be called from both
5306 // serial and parallel code as long as different worker
5307 // threads utilize different G1ParScanThreadState instances
5308 // and different queues.
5309 
5310 class G1CopyingKeepAliveClosure: public OopClosure {
5311   G1CollectedHeap*         _g1h;
5312   OopClosure*              _copy_non_heap_obj_cl;
5313   G1ParScanThreadState*    _par_scan_state;
5314 
5315 public:
5316   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
5317                             OopClosure* non_heap_obj_cl,
5318                             G1ParScanThreadState* pss):
5319     _g1h(g1h),
5320     _copy_non_heap_obj_cl(non_heap_obj_cl),
5321     _par_scan_state(pss)
5322   {}
5323 
5324   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
5325   virtual void do_oop(      oop* p) { do_oop_work(p); }
5326 
5327   template <class T> void do_oop_work(T* p) {
5328     oop obj = oopDesc::load_decode_heap_oop(p);
5329 
5330     if (_g1h->is_in_cset_or_humongous(obj)) {
5331       // If the referent object has been forwarded (either copied
5332       // to a new location or to itself in the event of an
5333       // evacuation failure) then we need to update the reference
5334       // field and, if both reference and referent are in the G1
5335       // heap, update the RSet for the referent.
5336       //
5337       // If the referent has not been forwarded then we have to keep
5338       // it alive by policy. Therefore we have copy the referent.
5339       //
5340       // If the reference field is in the G1 heap then we can push
5341       // on the PSS queue. When the queue is drained (after each
5342       // phase of reference processing) the object and it's followers
5343       // will be copied, the reference field set to point to the
5344       // new location, and the RSet updated. Otherwise we need to
5345       // use the the non-heap or metadata closures directly to copy
5346       // the referent object and update the pointer, while avoiding
5347       // updating the RSet.
5348 
5349       if (_g1h->is_in_g1_reserved(p)) {
5350         _par_scan_state->push_on_queue(p);
5351       } else {
5352         assert(!Metaspace::contains((const void*)p),
5353                err_msg("Unexpectedly found a pointer from metadata: "
5354                               PTR_FORMAT, p));
5355         _copy_non_heap_obj_cl->do_oop(p);
5356       }
5357     }
5358   }
5359 };
5360 
5361 // Serial drain queue closure. Called as the 'complete_gc'
5362 // closure for each discovered list in some of the
5363 // reference processing phases.
5364 
5365 class G1STWDrainQueueClosure: public VoidClosure {
5366 protected:
5367   G1CollectedHeap* _g1h;
5368   G1ParScanThreadState* _par_scan_state;
5369 
5370   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
5371 
5372 public:
5373   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
5374     _g1h(g1h),
5375     _par_scan_state(pss)
5376   { }
5377 
5378   void do_void() {
5379     G1ParScanThreadState* const pss = par_scan_state();
5380     pss->trim_queue();
5381   }
5382 };
5383 
5384 // Parallel Reference Processing closures
5385 
5386 // Implementation of AbstractRefProcTaskExecutor for parallel reference
5387 // processing during G1 evacuation pauses.
5388 
5389 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5390 private:
5391   G1CollectedHeap*   _g1h;
5392   RefToScanQueueSet* _queues;
5393   FlexibleWorkGang*  _workers;
5394   int                _active_workers;
5395 
5396 public:
5397   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5398                         FlexibleWorkGang* workers,
5399                         RefToScanQueueSet *task_queues,
5400                         int n_workers) :
5401     _g1h(g1h),
5402     _queues(task_queues),
5403     _workers(workers),
5404     _active_workers(n_workers)
5405   {
5406     assert(n_workers > 0, "shouldn't call this otherwise");
5407   }
5408 
5409   // Executes the given task using concurrent marking worker threads.
5410   virtual void execute(ProcessTask& task);
5411   virtual void execute(EnqueueTask& task);
5412 };
5413 
5414 // Gang task for possibly parallel reference processing
5415 
5416 class G1STWRefProcTaskProxy: public AbstractGangTask {
5417   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5418   ProcessTask&     _proc_task;
5419   G1CollectedHeap* _g1h;
5420   RefToScanQueueSet *_task_queues;
5421   ParallelTaskTerminator* _terminator;
5422 
5423 public:
5424   G1STWRefProcTaskProxy(ProcessTask& proc_task,
5425                      G1CollectedHeap* g1h,
5426                      RefToScanQueueSet *task_queues,
5427                      ParallelTaskTerminator* terminator) :
5428     AbstractGangTask("Process reference objects in parallel"),
5429     _proc_task(proc_task),
5430     _g1h(g1h),
5431     _task_queues(task_queues),
5432     _terminator(terminator)
5433   {}
5434 
5435   virtual void work(uint worker_id) {
5436     // The reference processing task executed by a single worker.
5437     ResourceMark rm;
5438     HandleMark   hm;
5439 
5440     G1STWIsAliveClosure is_alive(_g1h);
5441 
5442     G1ParScanThreadState            pss(_g1h, worker_id, NULL);
5443     G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5444 
5445     pss.set_evac_failure_closure(&evac_failure_cl);
5446 
5447     G1ParScanExtRootClosure        only_copy_non_heap_cl(_g1h, &pss, NULL);
5448 
5449     G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5450 
5451     OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5452 
5453     if (_g1h->g1_policy()->during_initial_mark_pause()) {
5454       // We also need to mark copied objects.
5455       copy_non_heap_cl = &copy_mark_non_heap_cl;
5456     }
5457 
5458     // Keep alive closure.
5459     G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5460 
5461     // Complete GC closure
5462     G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5463 
5464     // Call the reference processing task's work routine.
5465     _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5466 
5467     // Note we cannot assert that the refs array is empty here as not all
5468     // of the processing tasks (specifically phase2 - pp2_work) execute
5469     // the complete_gc closure (which ordinarily would drain the queue) so
5470     // the queue may not be empty.
5471   }
5472 };
5473 
5474 // Driver routine for parallel reference processing.
5475 // Creates an instance of the ref processing gang
5476 // task and has the worker threads execute it.
5477 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5478   assert(_workers != NULL, "Need parallel worker threads.");
5479 
5480   ParallelTaskTerminator terminator(_active_workers, _queues);
5481   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5482 
5483   _g1h->set_par_threads(_active_workers);
5484   _workers->run_task(&proc_task_proxy);
5485   _g1h->set_par_threads(0);
5486 }
5487 
5488 // Gang task for parallel reference enqueueing.
5489 
5490 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5491   typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5492   EnqueueTask& _enq_task;
5493 
5494 public:
5495   G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5496     AbstractGangTask("Enqueue reference objects in parallel"),
5497     _enq_task(enq_task)
5498   { }
5499 
5500   virtual void work(uint worker_id) {
5501     _enq_task.work(worker_id);
5502   }
5503 };
5504 
5505 // Driver routine for parallel reference enqueueing.
5506 // Creates an instance of the ref enqueueing gang
5507 // task and has the worker threads execute it.
5508 
5509 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5510   assert(_workers != NULL, "Need parallel worker threads.");
5511 
5512   G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5513 
5514   _g1h->set_par_threads(_active_workers);
5515   _workers->run_task(&enq_task_proxy);
5516   _g1h->set_par_threads(0);
5517 }
5518 
5519 // End of weak reference support closures
5520 
5521 // Abstract task used to preserve (i.e. copy) any referent objects
5522 // that are in the collection set and are pointed to by reference
5523 // objects discovered by the CM ref processor.
5524 
5525 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5526 protected:
5527   G1CollectedHeap* _g1h;
5528   RefToScanQueueSet      *_queues;
5529   ParallelTaskTerminator _terminator;
5530   uint _n_workers;
5531 
5532 public:
5533   G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
5534     AbstractGangTask("ParPreserveCMReferents"),
5535     _g1h(g1h),
5536     _queues(task_queues),
5537     _terminator(workers, _queues),
5538     _n_workers(workers)
5539   { }
5540 
5541   void work(uint worker_id) {
5542     ResourceMark rm;
5543     HandleMark   hm;
5544 
5545     G1ParScanThreadState            pss(_g1h, worker_id, NULL);
5546     G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5547 
5548     pss.set_evac_failure_closure(&evac_failure_cl);
5549 
5550     assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5551 
5552     G1ParScanExtRootClosure        only_copy_non_heap_cl(_g1h, &pss, NULL);
5553 
5554     G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5555 
5556     OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5557 
5558     if (_g1h->g1_policy()->during_initial_mark_pause()) {
5559       // We also need to mark copied objects.
5560       copy_non_heap_cl = &copy_mark_non_heap_cl;
5561     }
5562 
5563     // Is alive closure
5564     G1AlwaysAliveClosure always_alive(_g1h);
5565 
5566     // Copying keep alive closure. Applied to referent objects that need
5567     // to be copied.
5568     G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5569 
5570     ReferenceProcessor* rp = _g1h->ref_processor_cm();
5571 
5572     uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5573     uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5574 
5575     // limit is set using max_num_q() - which was set using ParallelGCThreads.
5576     // So this must be true - but assert just in case someone decides to
5577     // change the worker ids.
5578     assert(0 <= worker_id && worker_id < limit, "sanity");
5579     assert(!rp->discovery_is_atomic(), "check this code");
5580 
5581     // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5582     for (uint idx = worker_id; idx < limit; idx += stride) {
5583       DiscoveredList& ref_list = rp->discovered_refs()[idx];
5584 
5585       DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5586       while (iter.has_next()) {
5587         // Since discovery is not atomic for the CM ref processor, we
5588         // can see some null referent objects.
5589         iter.load_ptrs(DEBUG_ONLY(true));
5590         oop ref = iter.obj();
5591 
5592         // This will filter nulls.
5593         if (iter.is_referent_alive()) {
5594           iter.make_referent_alive();
5595         }
5596         iter.move_to_next();
5597       }
5598     }
5599 
5600     // Drain the queue - which may cause stealing
5601     G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5602     drain_queue.do_void();
5603     // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5604     assert(pss.queue_is_empty(), "should be");
5605   }
5606 };
5607 
5608 // Weak Reference processing during an evacuation pause (part 1).
5609 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) {
5610   double ref_proc_start = os::elapsedTime();
5611 
5612   ReferenceProcessor* rp = _ref_processor_stw;
5613   assert(rp->discovery_enabled(), "should have been enabled");
5614 
5615   // Any reference objects, in the collection set, that were 'discovered'
5616   // by the CM ref processor should have already been copied (either by
5617   // applying the external root copy closure to the discovered lists, or
5618   // by following an RSet entry).
5619   //
5620   // But some of the referents, that are in the collection set, that these
5621   // reference objects point to may not have been copied: the STW ref
5622   // processor would have seen that the reference object had already
5623   // been 'discovered' and would have skipped discovering the reference,
5624   // but would not have treated the reference object as a regular oop.
5625   // As a result the copy closure would not have been applied to the
5626   // referent object.
5627   //
5628   // We need to explicitly copy these referent objects - the references
5629   // will be processed at the end of remarking.
5630   //
5631   // We also need to do this copying before we process the reference
5632   // objects discovered by the STW ref processor in case one of these
5633   // referents points to another object which is also referenced by an
5634   // object discovered by the STW ref processor.
5635 
5636   assert(!G1CollectedHeap::use_parallel_gc_threads() ||
5637            no_of_gc_workers == workers()->active_workers(),
5638            "Need to reset active GC workers");
5639 
5640   set_par_threads(no_of_gc_workers);
5641   G1ParPreserveCMReferentsTask keep_cm_referents(this,
5642                                                  no_of_gc_workers,
5643                                                  _task_queues);
5644 
5645   if (G1CollectedHeap::use_parallel_gc_threads()) {
5646     workers()->run_task(&keep_cm_referents);
5647   } else {
5648     keep_cm_referents.work(0);
5649   }
5650 
5651   set_par_threads(0);
5652 
5653   // Closure to test whether a referent is alive.
5654   G1STWIsAliveClosure is_alive(this);
5655 
5656   // Even when parallel reference processing is enabled, the processing
5657   // of JNI refs is serial and performed serially by the current thread
5658   // rather than by a worker. The following PSS will be used for processing
5659   // JNI refs.
5660 
5661   // Use only a single queue for this PSS.
5662   G1ParScanThreadState            pss(this, 0, NULL);
5663 
5664   // We do not embed a reference processor in the copying/scanning
5665   // closures while we're actually processing the discovered
5666   // reference objects.
5667   G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5668 
5669   pss.set_evac_failure_closure(&evac_failure_cl);
5670 
5671   assert(pss.queue_is_empty(), "pre-condition");
5672 
5673   G1ParScanExtRootClosure        only_copy_non_heap_cl(this, &pss, NULL);
5674 
5675   G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5676 
5677   OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5678 
5679   if (_g1h->g1_policy()->during_initial_mark_pause()) {
5680     // We also need to mark copied objects.
5681     copy_non_heap_cl = &copy_mark_non_heap_cl;
5682   }
5683 
5684   // Keep alive closure.
5685   G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, &pss);
5686 
5687   // Serial Complete GC closure
5688   G1STWDrainQueueClosure drain_queue(this, &pss);
5689 
5690   // Setup the soft refs policy...
5691   rp->setup_policy(false);
5692 
5693   ReferenceProcessorStats stats;
5694   if (!rp->processing_is_mt()) {
5695     // Serial reference processing...
5696     stats = rp->process_discovered_references(&is_alive,
5697                                               &keep_alive,
5698                                               &drain_queue,
5699                                               NULL,
5700                                               _gc_timer_stw,
5701                                               _gc_tracer_stw->gc_id());
5702   } else {
5703     // Parallel reference processing
5704     assert(rp->num_q() == no_of_gc_workers, "sanity");
5705     assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5706 
5707     G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5708     stats = rp->process_discovered_references(&is_alive,
5709                                               &keep_alive,
5710                                               &drain_queue,
5711                                               &par_task_executor,
5712                                               _gc_timer_stw,
5713                                               _gc_tracer_stw->gc_id());
5714   }
5715 
5716   _gc_tracer_stw->report_gc_reference_stats(stats);
5717 
5718   // We have completed copying any necessary live referent objects.
5719   assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5720 
5721   double ref_proc_time = os::elapsedTime() - ref_proc_start;
5722   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5723 }
5724 
5725 // Weak Reference processing during an evacuation pause (part 2).
5726 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) {
5727   double ref_enq_start = os::elapsedTime();
5728 
5729   ReferenceProcessor* rp = _ref_processor_stw;
5730   assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5731 
5732   // Now enqueue any remaining on the discovered lists on to
5733   // the pending list.
5734   if (!rp->processing_is_mt()) {
5735     // Serial reference processing...
5736     rp->enqueue_discovered_references();
5737   } else {
5738     // Parallel reference enqueueing
5739 
5740     assert(no_of_gc_workers == workers()->active_workers(),
5741            "Need to reset active workers");
5742     assert(rp->num_q() == no_of_gc_workers, "sanity");
5743     assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5744 
5745     G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5746     rp->enqueue_discovered_references(&par_task_executor);
5747   }
5748 
5749   rp->verify_no_references_recorded();
5750   assert(!rp->discovery_enabled(), "should have been disabled");
5751 
5752   // FIXME
5753   // CM's reference processing also cleans up the string and symbol tables.
5754   // Should we do that here also? We could, but it is a serial operation
5755   // and could significantly increase the pause time.
5756 
5757   double ref_enq_time = os::elapsedTime() - ref_enq_start;
5758   g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5759 }
5760 
5761 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) {
5762   _expand_heap_after_alloc_failure = true;
5763   _evacuation_failed = false;
5764 
5765   // Should G1EvacuationFailureALot be in effect for this GC?
5766   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
5767 
5768   g1_rem_set()->prepare_for_oops_into_collection_set_do();
5769 
5770   // Disable the hot card cache.
5771   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
5772   hot_card_cache->reset_hot_cache_claimed_index();
5773   hot_card_cache->set_use_cache(false);
5774 
5775   const uint n_workers = workers()->active_workers();
5776     assert(UseDynamicNumberOfGCThreads ||
5777            n_workers == workers()->total_workers(),
5778            "If not dynamic should be using all the  workers");
5779     set_par_threads(n_workers);
5780 
5781   init_for_evac_failure(NULL);
5782 
5783   rem_set()->prepare_for_younger_refs_iterate(true);
5784 
5785   assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5786   double start_par_time_sec = os::elapsedTime();
5787   double end_par_time_sec;
5788 
5789   {
5790     G1RootProcessor root_processor(this);
5791     G1ParTask g1_par_task(this, _task_queues, &root_processor);
5792     // InitialMark needs claim bits to keep track of the marked-through CLDs.
5793     if (g1_policy()->during_initial_mark_pause()) {
5794       ClassLoaderDataGraph::clear_claimed_marks();
5795     }
5796 
5797     if (G1CollectedHeap::use_parallel_gc_threads()) {
5798       // The individual threads will set their evac-failure closures.
5799       if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
5800       // These tasks use ShareHeap::_process_strong_tasks
5801       assert(UseDynamicNumberOfGCThreads ||
5802              workers()->active_workers() == workers()->total_workers(),
5803              "If not dynamic should be using all the  workers");
5804       workers()->run_task(&g1_par_task);
5805     } else {
5806       g1_par_task.set_for_termination(n_workers);
5807       g1_par_task.work(0);
5808     }
5809     end_par_time_sec = os::elapsedTime();
5810 
5811     // Closing the inner scope will execute the destructor
5812     // for the G1RootProcessor object. We record the current
5813     // elapsed time before closing the scope so that time
5814     // taken for the destructor is NOT included in the
5815     // reported parallel time.
5816   }
5817 
5818   G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
5819 
5820   double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5821   phase_times->record_par_time(par_time_ms);
5822 
5823   double code_root_fixup_time_ms =
5824         (os::elapsedTime() - end_par_time_sec) * 1000.0;
5825   phase_times->record_code_root_fixup_time(code_root_fixup_time_ms);
5826 
5827   set_par_threads(0);
5828 
5829   // Process any discovered reference objects - we have
5830   // to do this _before_ we retire the GC alloc regions
5831   // as we may have to copy some 'reachable' referent
5832   // objects (and their reachable sub-graphs) that were
5833   // not copied during the pause.
5834   process_discovered_references(n_workers);
5835 
5836   if (G1StringDedup::is_enabled()) {
5837     double fixup_start = os::elapsedTime();
5838 
5839     G1STWIsAliveClosure is_alive(this);
5840     G1KeepAliveClosure keep_alive(this);
5841     G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, phase_times);
5842 
5843     double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
5844     phase_times->record_string_dedup_fixup_time(fixup_time_ms);
5845   }
5846 
5847   _allocator->release_gc_alloc_regions(n_workers, evacuation_info);
5848   g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5849 
5850   // Reset and re-enable the hot card cache.
5851   // Note the counts for the cards in the regions in the
5852   // collection set are reset when the collection set is freed.
5853   hot_card_cache->reset_hot_cache();
5854   hot_card_cache->set_use_cache(true);
5855 
5856   purge_code_root_memory();
5857 
5858   if (g1_policy()->during_initial_mark_pause()) {
5859     // Reset the claim values set during marking the strong code roots
5860     reset_heap_region_claim_values();
5861   }
5862 
5863   finalize_for_evac_failure();
5864 
5865   if (evacuation_failed()) {
5866     remove_self_forwarding_pointers();
5867 
5868     // Reset the G1EvacuationFailureALot counters and flags
5869     // Note: the values are reset only when an actual
5870     // evacuation failure occurs.
5871     NOT_PRODUCT(reset_evacuation_should_fail();)
5872   }
5873 
5874   // Enqueue any remaining references remaining on the STW
5875   // reference processor's discovered lists. We need to do
5876   // this after the card table is cleaned (and verified) as
5877   // the act of enqueueing entries on to the pending list
5878   // will log these updates (and dirty their associated
5879   // cards). We need these updates logged to update any
5880   // RSets.
5881   enqueue_discovered_references(n_workers);
5882 
5883   redirty_logged_cards();
5884   COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5885 }
5886 
5887 void G1CollectedHeap::free_region(HeapRegion* hr,
5888                                   FreeRegionList* free_list,
5889                                   bool par,
5890                                   bool locked) {
5891   assert(!hr->is_free(), "the region should not be free");
5892   assert(!hr->is_empty(), "the region should not be empty");
5893   assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
5894   assert(free_list != NULL, "pre-condition");
5895 
5896   if (G1VerifyBitmaps) {
5897     MemRegion mr(hr->bottom(), hr->end());
5898     concurrent_mark()->clearRangePrevBitmap(mr);
5899   }
5900 
5901   // Clear the card counts for this region.
5902   // Note: we only need to do this if the region is not young
5903   // (since we don't refine cards in young regions).
5904   if (!hr->is_young()) {
5905     _cg1r->hot_card_cache()->reset_card_counts(hr);
5906   }
5907   hr->hr_clear(par, true /* clear_space */, locked /* locked */);
5908   free_list->add_ordered(hr);
5909 }
5910 
5911 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
5912                                      FreeRegionList* free_list,
5913                                      bool par) {
5914   assert(hr->startsHumongous(), "this is only for starts humongous regions");
5915   assert(free_list != NULL, "pre-condition");
5916 
5917   size_t hr_capacity = hr->capacity();
5918   // We need to read this before we make the region non-humongous,
5919   // otherwise the information will be gone.
5920   uint last_index = hr->last_hc_index();
5921   hr->clear_humongous();
5922   free_region(hr, free_list, par);
5923 
5924   uint i = hr->hrm_index() + 1;
5925   while (i < last_index) {
5926     HeapRegion* curr_hr = region_at(i);
5927     assert(curr_hr->continuesHumongous(), "invariant");
5928     curr_hr->clear_humongous();
5929     free_region(curr_hr, free_list, par);
5930     i += 1;
5931   }
5932 }
5933 
5934 void G1CollectedHeap::remove_from_old_sets(const HeapRegionSetCount& old_regions_removed,
5935                                        const HeapRegionSetCount& humongous_regions_removed) {
5936   if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 0) {
5937     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5938     _old_set.bulk_remove(old_regions_removed);
5939     _humongous_set.bulk_remove(humongous_regions_removed);
5940   }
5941 
5942 }
5943 
5944 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
5945   assert(list != NULL, "list can't be null");
5946   if (!list->is_empty()) {
5947     MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
5948     _hrm.insert_list_into_free_list(list);
5949   }
5950 }
5951 
5952 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
5953   _allocator->decrease_used(bytes);
5954 }
5955 
5956 class G1ParCleanupCTTask : public AbstractGangTask {
5957   G1SATBCardTableModRefBS* _ct_bs;
5958   G1CollectedHeap* _g1h;
5959   HeapRegion* volatile _su_head;
5960 public:
5961   G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs,
5962                      G1CollectedHeap* g1h) :
5963     AbstractGangTask("G1 Par Cleanup CT Task"),
5964     _ct_bs(ct_bs), _g1h(g1h) { }
5965 
5966   void work(uint worker_id) {
5967     HeapRegion* r;
5968     while (r = _g1h->pop_dirty_cards_region()) {
5969       clear_cards(r);
5970     }
5971   }
5972 
5973   void clear_cards(HeapRegion* r) {
5974     // Cards of the survivors should have already been dirtied.
5975     if (!r->is_survivor()) {
5976       _ct_bs->clear(MemRegion(r->bottom(), r->end()));
5977     }
5978   }
5979 };
5980 
5981 #ifndef PRODUCT
5982 class G1VerifyCardTableCleanup: public HeapRegionClosure {
5983   G1CollectedHeap* _g1h;
5984   G1SATBCardTableModRefBS* _ct_bs;
5985 public:
5986   G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs)
5987     : _g1h(g1h), _ct_bs(ct_bs) { }
5988   virtual bool doHeapRegion(HeapRegion* r) {
5989     if (r->is_survivor()) {
5990       _g1h->verify_dirty_region(r);
5991     } else {
5992       _g1h->verify_not_dirty_region(r);
5993     }
5994     return false;
5995   }
5996 };
5997 
5998 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
5999   // All of the region should be clean.
6000   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6001   MemRegion mr(hr->bottom(), hr->end());
6002   ct_bs->verify_not_dirty_region(mr);
6003 }
6004 
6005 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
6006   // We cannot guarantee that [bottom(),end()] is dirty.  Threads
6007   // dirty allocated blocks as they allocate them. The thread that
6008   // retires each region and replaces it with a new one will do a
6009   // maximal allocation to fill in [pre_dummy_top(),end()] but will
6010   // not dirty that area (one less thing to have to do while holding
6011   // a lock). So we can only verify that [bottom(),pre_dummy_top()]
6012   // is dirty.
6013   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6014   MemRegion mr(hr->bottom(), hr->pre_dummy_top());
6015   if (hr->is_young()) {
6016     ct_bs->verify_g1_young_region(mr);
6017   } else {
6018     ct_bs->verify_dirty_region(mr);
6019   }
6020 }
6021 
6022 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
6023   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6024   for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
6025     verify_dirty_region(hr);
6026   }
6027 }
6028 
6029 void G1CollectedHeap::verify_dirty_young_regions() {
6030   verify_dirty_young_list(_young_list->first_region());
6031 }
6032 
6033 bool G1CollectedHeap::verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
6034                                                HeapWord* tams, HeapWord* end) {
6035   guarantee(tams <= end,
6036             err_msg("tams: " PTR_FORMAT " end: " PTR_FORMAT, tams, end));
6037   HeapWord* result = bitmap->getNextMarkedWordAddress(tams, end);
6038   if (result < end) {
6039     gclog_or_tty->cr();
6040     gclog_or_tty->print_cr("## wrong marked address on %s bitmap: " PTR_FORMAT,
6041                            bitmap_name, result);
6042     gclog_or_tty->print_cr("## %s tams: " PTR_FORMAT " end: " PTR_FORMAT,
6043                            bitmap_name, tams, end);
6044     return false;
6045   }
6046   return true;
6047 }
6048 
6049 bool G1CollectedHeap::verify_bitmaps(const char* caller, HeapRegion* hr) {
6050   CMBitMapRO* prev_bitmap = concurrent_mark()->prevMarkBitMap();
6051   CMBitMapRO* next_bitmap = (CMBitMapRO*) concurrent_mark()->nextMarkBitMap();
6052 
6053   HeapWord* bottom = hr->bottom();
6054   HeapWord* ptams  = hr->prev_top_at_mark_start();
6055   HeapWord* ntams  = hr->next_top_at_mark_start();
6056   HeapWord* end    = hr->end();
6057 
6058   bool res_p = verify_no_bits_over_tams("prev", prev_bitmap, ptams, end);
6059 
6060   bool res_n = true;
6061   // We reset mark_in_progress() before we reset _cmThread->in_progress() and in this window
6062   // we do the clearing of the next bitmap concurrently. Thus, we can not verify the bitmap
6063   // if we happen to be in that state.
6064   if (mark_in_progress() || !_cmThread->in_progress()) {
6065     res_n = verify_no_bits_over_tams("next", next_bitmap, ntams, end);
6066   }
6067   if (!res_p || !res_n) {
6068     gclog_or_tty->print_cr("#### Bitmap verification failed for " HR_FORMAT,
6069                            HR_FORMAT_PARAMS(hr));
6070     gclog_or_tty->print_cr("#### Caller: %s", caller);
6071     return false;
6072   }
6073   return true;
6074 }
6075 
6076 void G1CollectedHeap::check_bitmaps(const char* caller, HeapRegion* hr) {
6077   if (!G1VerifyBitmaps) return;
6078 
6079   guarantee(verify_bitmaps(caller, hr), "bitmap verification");
6080 }
6081 
6082 class G1VerifyBitmapClosure : public HeapRegionClosure {
6083 private:
6084   const char* _caller;
6085   G1CollectedHeap* _g1h;
6086   bool _failures;
6087 
6088 public:
6089   G1VerifyBitmapClosure(const char* caller, G1CollectedHeap* g1h) :
6090     _caller(caller), _g1h(g1h), _failures(false) { }
6091 
6092   bool failures() { return _failures; }
6093 
6094   virtual bool doHeapRegion(HeapRegion* hr) {
6095     if (hr->continuesHumongous()) return false;
6096 
6097     bool result = _g1h->verify_bitmaps(_caller, hr);
6098     if (!result) {
6099       _failures = true;
6100     }
6101     return false;
6102   }
6103 };
6104 
6105 void G1CollectedHeap::check_bitmaps(const char* caller) {
6106   if (!G1VerifyBitmaps) return;
6107 
6108   G1VerifyBitmapClosure cl(caller, this);
6109   heap_region_iterate(&cl);
6110   guarantee(!cl.failures(), "bitmap verification");
6111 }
6112 
6113 class G1CheckCSetFastTableClosure : public HeapRegionClosure {
6114  private:
6115   bool _failures;
6116  public:
6117   G1CheckCSetFastTableClosure() : HeapRegionClosure(), _failures(false) { }
6118 
6119   virtual bool doHeapRegion(HeapRegion* hr) {
6120     uint i = hr->hrm_index();
6121     InCSetState cset_state = (InCSetState) G1CollectedHeap::heap()->_in_cset_fast_test.get_by_index(i);
6122     if (hr->isHumongous()) {
6123       if (hr->in_collection_set()) {
6124         gclog_or_tty->print_cr("\n## humongous region %u in CSet", i);
6125         _failures = true;
6126         return true;
6127       }
6128       if (cset_state.is_in_cset()) {
6129         gclog_or_tty->print_cr("\n## inconsistent cset state %d for humongous region %u", cset_state.value(), i);
6130         _failures = true;
6131         return true;
6132       }
6133       if (hr->continuesHumongous() && cset_state.is_humongous()) {
6134         gclog_or_tty->print_cr("\n## inconsistent cset state %d for continues humongous region %u", cset_state.value(), i);
6135         _failures = true;
6136         return true;
6137       }
6138     } else {
6139       if (cset_state.is_humongous()) {
6140         gclog_or_tty->print_cr("\n## inconsistent cset state %d for non-humongous region %u", cset_state.value(), i);
6141         _failures = true;
6142         return true;
6143       }
6144       if (hr->in_collection_set() != cset_state.is_in_cset()) {
6145         gclog_or_tty->print_cr("\n## in CSet %d / cset state %d inconsistency for region %u",
6146                                hr->in_collection_set(), cset_state.value(), i);
6147        _failures = true;
6148        return true;
6149       }
6150       if (cset_state.is_in_cset()) {
6151         if (hr->is_young() != (cset_state.is_young())) {
6152           gclog_or_tty->print_cr("\n## is_young %d / cset state %d inconsistency for region %u",
6153                                  hr->is_young(), cset_state.value(), i);
6154           _failures = true;
6155           return true;
6156         }
6157         if (hr->is_old() != (cset_state.is_old())) {
6158           gclog_or_tty->print_cr("\n## is_old %d / cset state %d inconsistency for region %u",
6159                                  hr->is_old(), cset_state.value(), i);
6160           _failures = true;
6161           return true;
6162         }
6163       }
6164     }
6165     return false;
6166   }
6167 
6168   bool failures() const { return _failures; }
6169 };
6170 
6171 bool G1CollectedHeap::check_cset_fast_test() {
6172   G1CheckCSetFastTableClosure cl;
6173   _hrm.iterate(&cl);
6174   return !cl.failures();
6175 }
6176 #endif // PRODUCT
6177 
6178 void G1CollectedHeap::cleanUpCardTable() {
6179   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6180   double start = os::elapsedTime();
6181 
6182   {
6183     // Iterate over the dirty cards region list.
6184     G1ParCleanupCTTask cleanup_task(ct_bs, this);
6185 
6186     if (G1CollectedHeap::use_parallel_gc_threads()) {
6187       set_par_threads();
6188       workers()->run_task(&cleanup_task);
6189       set_par_threads(0);
6190     } else {
6191       while (_dirty_cards_region_list) {
6192         HeapRegion* r = _dirty_cards_region_list;
6193         cleanup_task.clear_cards(r);
6194         _dirty_cards_region_list = r->get_next_dirty_cards_region();
6195         if (_dirty_cards_region_list == r) {
6196           // The last region.
6197           _dirty_cards_region_list = NULL;
6198         }
6199         r->set_next_dirty_cards_region(NULL);
6200       }
6201     }
6202 #ifndef PRODUCT
6203     if (G1VerifyCTCleanup || VerifyAfterGC) {
6204       G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
6205       heap_region_iterate(&cleanup_verifier);
6206     }
6207 #endif
6208   }
6209 
6210   double elapsed = os::elapsedTime() - start;
6211   g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
6212 }
6213 
6214 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) {
6215   size_t pre_used = 0;
6216   FreeRegionList local_free_list("Local List for CSet Freeing");
6217 
6218   double young_time_ms     = 0.0;
6219   double non_young_time_ms = 0.0;
6220 
6221   // Since the collection set is a superset of the the young list,
6222   // all we need to do to clear the young list is clear its
6223   // head and length, and unlink any young regions in the code below
6224   _young_list->clear();
6225 
6226   G1CollectorPolicy* policy = g1_policy();
6227 
6228   double start_sec = os::elapsedTime();
6229   bool non_young = true;
6230 
6231   HeapRegion* cur = cs_head;
6232   int age_bound = -1;
6233   size_t rs_lengths = 0;
6234 
6235   while (cur != NULL) {
6236     assert(!is_on_master_free_list(cur), "sanity");
6237     if (non_young) {
6238       if (cur->is_young()) {
6239         double end_sec = os::elapsedTime();
6240         double elapsed_ms = (end_sec - start_sec) * 1000.0;
6241         non_young_time_ms += elapsed_ms;
6242 
6243         start_sec = os::elapsedTime();
6244         non_young = false;
6245       }
6246     } else {
6247       if (!cur->is_young()) {
6248         double end_sec = os::elapsedTime();
6249         double elapsed_ms = (end_sec - start_sec) * 1000.0;
6250         young_time_ms += elapsed_ms;
6251 
6252         start_sec = os::elapsedTime();
6253         non_young = true;
6254       }
6255     }
6256 
6257     rs_lengths += cur->rem_set()->occupied_locked();
6258 
6259     HeapRegion* next = cur->next_in_collection_set();
6260     assert(cur->in_collection_set(), "bad CS");
6261     cur->set_next_in_collection_set(NULL);
6262     cur->set_in_collection_set(false);
6263 
6264     if (cur->is_young()) {
6265       int index = cur->young_index_in_cset();
6266       assert(index != -1, "invariant");
6267       assert((uint) index < policy->young_cset_region_length(), "invariant");
6268       size_t words_survived = _surviving_young_words[index];
6269       cur->record_surv_words_in_group(words_survived);
6270 
6271       // At this point the we have 'popped' cur from the collection set
6272       // (linked via next_in_collection_set()) but it is still in the
6273       // young list (linked via next_young_region()). Clear the
6274       // _next_young_region field.
6275       cur->set_next_young_region(NULL);
6276     } else {
6277       int index = cur->young_index_in_cset();
6278       assert(index == -1, "invariant");
6279     }
6280 
6281     assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
6282             (!cur->is_young() && cur->young_index_in_cset() == -1),
6283             "invariant" );
6284 
6285     if (!cur->evacuation_failed()) {
6286       MemRegion used_mr = cur->used_region();
6287 
6288       // And the region is empty.
6289       assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
6290       pre_used += cur->used();
6291       free_region(cur, &local_free_list, false /* par */, true /* locked */);
6292     } else {
6293       cur->uninstall_surv_rate_group();
6294       if (cur->is_young()) {
6295         cur->set_young_index_in_cset(-1);
6296       }
6297       cur->set_evacuation_failed(false);
6298       // The region is now considered to be old.
6299       cur->set_old();
6300       _old_set.add(cur);
6301       evacuation_info.increment_collectionset_used_after(cur->used());
6302     }
6303     cur = next;
6304   }
6305 
6306   evacuation_info.set_regions_freed(local_free_list.length());
6307   policy->record_max_rs_lengths(rs_lengths);
6308   policy->cset_regions_freed();
6309 
6310   double end_sec = os::elapsedTime();
6311   double elapsed_ms = (end_sec - start_sec) * 1000.0;
6312 
6313   if (non_young) {
6314     non_young_time_ms += elapsed_ms;
6315   } else {
6316     young_time_ms += elapsed_ms;
6317   }
6318 
6319   prepend_to_freelist(&local_free_list);
6320   decrement_summary_bytes(pre_used);
6321   policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
6322   policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
6323 }
6324 
6325 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
6326  private:
6327   FreeRegionList* _free_region_list;
6328   HeapRegionSet* _proxy_set;
6329   HeapRegionSetCount _humongous_regions_removed;
6330   size_t _freed_bytes;
6331  public:
6332 
6333   G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
6334     _free_region_list(free_region_list), _humongous_regions_removed(), _freed_bytes(0) {
6335   }
6336 
6337   virtual bool doHeapRegion(HeapRegion* r) {
6338     if (!r->startsHumongous()) {
6339       return false;
6340     }
6341 
6342     G1CollectedHeap* g1h = G1CollectedHeap::heap();
6343 
6344     oop obj = (oop)r->bottom();
6345     CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap();
6346 
6347     // The following checks whether the humongous object is live are sufficient.
6348     // The main additional check (in addition to having a reference from the roots
6349     // or the young gen) is whether the humongous object has a remembered set entry.
6350     //
6351     // A humongous object cannot be live if there is no remembered set for it
6352     // because:
6353     // - there can be no references from within humongous starts regions referencing
6354     // the object because we never allocate other objects into them.
6355     // (I.e. there are no intra-region references that may be missed by the
6356     // remembered set)
6357     // - as soon there is a remembered set entry to the humongous starts region
6358     // (i.e. it has "escaped" to an old object) this remembered set entry will stay
6359     // until the end of a concurrent mark.
6360     //
6361     // It is not required to check whether the object has been found dead by marking
6362     // or not, in fact it would prevent reclamation within a concurrent cycle, as
6363     // all objects allocated during that time are considered live.
6364     // SATB marking is even more conservative than the remembered set.
6365     // So if at this point in the collection there is no remembered set entry,
6366     // nobody has a reference to it.
6367     // At the start of collection we flush all refinement logs, and remembered sets
6368     // are completely up-to-date wrt to references to the humongous object.
6369     //
6370     // Other implementation considerations:
6371     // - never consider object arrays at this time because they would pose
6372     // considerable effort for cleaning up the the remembered sets. This is
6373     // required because stale remembered sets might reference locations that
6374     // are currently allocated into.
6375     uint region_idx = r->hrm_index();
6376     if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
6377         !r->rem_set()->is_empty()) {
6378 
6379       if (G1TraceEagerReclaimHumongousObjects) {
6380         gclog_or_tty->print_cr("Live humongous region %u size " SIZE_FORMAT " start " PTR_FORMAT " length " UINT32_FORMAT " with remset " SIZE_FORMAT " code roots " SIZE_FORMAT " is marked %d reclaim candidate %d type array %d",
6381                                region_idx,
6382                                obj->size()*HeapWordSize,
6383                                r->bottom(),
6384                                r->region_num(),
6385                                r->rem_set()->occupied(),
6386                                r->rem_set()->strong_code_roots_list_length(),
6387                                next_bitmap->isMarked(r->bottom()),
6388                                g1h->is_humongous_reclaim_candidate(region_idx),
6389                                obj->is_typeArray()
6390                               );
6391       }
6392 
6393       return false;
6394     }
6395 
6396     guarantee(obj->is_typeArray(),
6397               err_msg("Only eagerly reclaiming type arrays is supported, but the object "
6398                       PTR_FORMAT " is not.",
6399                       r->bottom()));
6400 
6401     if (G1TraceEagerReclaimHumongousObjects) {
6402       gclog_or_tty->print_cr("Dead humongous region %u size " SIZE_FORMAT " start " PTR_FORMAT " length " UINT32_FORMAT " with remset " SIZE_FORMAT " code roots " SIZE_FORMAT " is marked %d reclaim candidate %d type array %d",
6403                              region_idx,
6404                              obj->size()*HeapWordSize,
6405                              r->bottom(),
6406                              r->region_num(),
6407                              r->rem_set()->occupied(),
6408                              r->rem_set()->strong_code_roots_list_length(),
6409                              next_bitmap->isMarked(r->bottom()),
6410                              g1h->is_humongous_reclaim_candidate(region_idx),
6411                              obj->is_typeArray()
6412                             );
6413     }
6414     // Need to clear mark bit of the humongous object if already set.
6415     if (next_bitmap->isMarked(r->bottom())) {
6416       next_bitmap->clear(r->bottom());
6417     }
6418     _freed_bytes += r->used();
6419     r->set_containing_set(NULL);
6420     _humongous_regions_removed.increment(1u, r->capacity());
6421     g1h->free_humongous_region(r, _free_region_list, false);
6422 
6423     return false;
6424   }
6425 
6426   HeapRegionSetCount& humongous_free_count() {
6427     return _humongous_regions_removed;
6428   }
6429 
6430   size_t bytes_freed() const {
6431     return _freed_bytes;
6432   }
6433 
6434   size_t humongous_reclaimed() const {
6435     return _humongous_regions_removed.length();
6436   }
6437 };
6438 
6439 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
6440   assert_at_safepoint(true);
6441 
6442   if (!G1EagerReclaimHumongousObjects ||
6443       (!_has_humongous_reclaim_candidates && !G1TraceEagerReclaimHumongousObjects)) {
6444     g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
6445     return;
6446   }
6447 
6448   double start_time = os::elapsedTime();
6449 
6450   FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
6451 
6452   G1FreeHumongousRegionClosure cl(&local_cleanup_list);
6453   heap_region_iterate(&cl);
6454 
6455   HeapRegionSetCount empty_set;
6456   remove_from_old_sets(empty_set, cl.humongous_free_count());
6457 
6458   G1HRPrinter* hr_printer = _g1h->hr_printer();
6459   if (hr_printer->is_active()) {
6460     FreeRegionListIterator iter(&local_cleanup_list);
6461     while (iter.more_available()) {
6462       HeapRegion* hr = iter.get_next();
6463       hr_printer->cleanup(hr);
6464     }
6465   }
6466 
6467   prepend_to_freelist(&local_cleanup_list);
6468   decrement_summary_bytes(cl.bytes_freed());
6469 
6470   g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
6471                                                                     cl.humongous_reclaimed());
6472 }
6473 
6474 // This routine is similar to the above but does not record
6475 // any policy statistics or update free lists; we are abandoning
6476 // the current incremental collection set in preparation of a
6477 // full collection. After the full GC we will start to build up
6478 // the incremental collection set again.
6479 // This is only called when we're doing a full collection
6480 // and is immediately followed by the tearing down of the young list.
6481 
6482 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
6483   HeapRegion* cur = cs_head;
6484 
6485   while (cur != NULL) {
6486     HeapRegion* next = cur->next_in_collection_set();
6487     assert(cur->in_collection_set(), "bad CS");
6488     cur->set_next_in_collection_set(NULL);
6489     cur->set_in_collection_set(false);
6490     cur->set_young_index_in_cset(-1);
6491     cur = next;
6492   }
6493 }
6494 
6495 void G1CollectedHeap::set_free_regions_coming() {
6496   if (G1ConcRegionFreeingVerbose) {
6497     gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6498                            "setting free regions coming");
6499   }
6500 
6501   assert(!free_regions_coming(), "pre-condition");
6502   _free_regions_coming = true;
6503 }
6504 
6505 void G1CollectedHeap::reset_free_regions_coming() {
6506   assert(free_regions_coming(), "pre-condition");
6507 
6508   {
6509     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6510     _free_regions_coming = false;
6511     SecondaryFreeList_lock->notify_all();
6512   }
6513 
6514   if (G1ConcRegionFreeingVerbose) {
6515     gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6516                            "reset free regions coming");
6517   }
6518 }
6519 
6520 void G1CollectedHeap::wait_while_free_regions_coming() {
6521   // Most of the time we won't have to wait, so let's do a quick test
6522   // first before we take the lock.
6523   if (!free_regions_coming()) {
6524     return;
6525   }
6526 
6527   if (G1ConcRegionFreeingVerbose) {
6528     gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6529                            "waiting for free regions");
6530   }
6531 
6532   {
6533     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6534     while (free_regions_coming()) {
6535       SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
6536     }
6537   }
6538 
6539   if (G1ConcRegionFreeingVerbose) {
6540     gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6541                            "done waiting for free regions");
6542   }
6543 }
6544 
6545 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
6546   assert(heap_lock_held_for_gc(),
6547               "the heap lock should already be held by or for this thread");
6548   _young_list->push_region(hr);
6549 }
6550 
6551 class NoYoungRegionsClosure: public HeapRegionClosure {
6552 private:
6553   bool _success;
6554 public:
6555   NoYoungRegionsClosure() : _success(true) { }
6556   bool doHeapRegion(HeapRegion* r) {
6557     if (r->is_young()) {
6558       gclog_or_tty->print_cr("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
6559                              r->bottom(), r->end());
6560       _success = false;
6561     }
6562     return false;
6563   }
6564   bool success() { return _success; }
6565 };
6566 
6567 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
6568   bool ret = _young_list->check_list_empty(check_sample);
6569 
6570   if (check_heap) {
6571     NoYoungRegionsClosure closure;
6572     heap_region_iterate(&closure);
6573     ret = ret && closure.success();
6574   }
6575 
6576   return ret;
6577 }
6578 
6579 class TearDownRegionSetsClosure : public HeapRegionClosure {
6580 private:
6581   HeapRegionSet *_old_set;
6582 
6583 public:
6584   TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
6585 
6586   bool doHeapRegion(HeapRegion* r) {
6587     if (r->is_old()) {
6588       _old_set->remove(r);
6589     } else {
6590       // We ignore free regions, we'll empty the free list afterwards.
6591       // We ignore young regions, we'll empty the young list afterwards.
6592       // We ignore humongous regions, we're not tearing down the
6593       // humongous regions set.
6594       assert(r->is_free() || r->is_young() || r->isHumongous(),
6595              "it cannot be another type");
6596     }
6597     return false;
6598   }
6599 
6600   ~TearDownRegionSetsClosure() {
6601     assert(_old_set->is_empty(), "post-condition");
6602   }
6603 };
6604 
6605 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6606   assert_at_safepoint(true /* should_be_vm_thread */);
6607 
6608   if (!free_list_only) {
6609     TearDownRegionSetsClosure cl(&_old_set);
6610     heap_region_iterate(&cl);
6611 
6612     // Note that emptying the _young_list is postponed and instead done as
6613     // the first step when rebuilding the regions sets again. The reason for
6614     // this is that during a full GC string deduplication needs to know if
6615     // a collected region was young or old when the full GC was initiated.
6616   }
6617   _hrm.remove_all_free_regions();
6618 }
6619 
6620 class RebuildRegionSetsClosure : public HeapRegionClosure {
6621 private:
6622   bool            _free_list_only;
6623   HeapRegionSet*   _old_set;
6624   HeapRegionManager*   _hrm;
6625   size_t          _total_used;
6626 
6627 public:
6628   RebuildRegionSetsClosure(bool free_list_only,
6629                            HeapRegionSet* old_set, HeapRegionManager* hrm) :
6630     _free_list_only(free_list_only),
6631     _old_set(old_set), _hrm(hrm), _total_used(0) {
6632     assert(_hrm->num_free_regions() == 0, "pre-condition");
6633     if (!free_list_only) {
6634       assert(_old_set->is_empty(), "pre-condition");
6635     }
6636   }
6637 
6638   bool doHeapRegion(HeapRegion* r) {
6639     if (r->continuesHumongous()) {
6640       return false;
6641     }
6642 
6643     if (r->is_empty()) {
6644       // Add free regions to the free list
6645       r->set_free();
6646       r->set_allocation_context(AllocationContext::system());
6647       _hrm->insert_into_free_list(r);
6648     } else if (!_free_list_only) {
6649       assert(!r->is_young(), "we should not come across young regions");
6650 
6651       if (r->isHumongous()) {
6652         // We ignore humongous regions, we left the humongous set unchanged
6653       } else {
6654         // Objects that were compacted would have ended up on regions
6655         // that were previously old or free.
6656         assert(r->is_free() || r->is_old(), "invariant");
6657         // We now consider them old, so register as such.
6658         r->set_old();
6659         _old_set->add(r);
6660       }
6661       _total_used += r->used();
6662     }
6663 
6664     return false;
6665   }
6666 
6667   size_t total_used() {
6668     return _total_used;
6669   }
6670 };
6671 
6672 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6673   assert_at_safepoint(true /* should_be_vm_thread */);
6674 
6675   if (!free_list_only) {
6676     _young_list->empty_list();
6677   }
6678 
6679   RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
6680   heap_region_iterate(&cl);
6681 
6682   if (!free_list_only) {
6683     _allocator->set_used(cl.total_used());
6684   }
6685   assert(_allocator->used_unlocked() == recalculate_used(),
6686          err_msg("inconsistent _allocator->used_unlocked(), "
6687                  "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT,
6688                  _allocator->used_unlocked(), recalculate_used()));
6689 }
6690 
6691 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6692   _refine_cte_cl->set_concurrent(concurrent);
6693 }
6694 
6695 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6696   HeapRegion* hr = heap_region_containing(p);
6697   return hr->is_in(p);
6698 }
6699 
6700 // Methods for the mutator alloc region
6701 
6702 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6703                                                       bool force) {
6704   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6705   assert(!force || g1_policy()->can_expand_young_list(),
6706          "if force is true we should be able to expand the young list");
6707   bool young_list_full = g1_policy()->is_young_list_full();
6708   if (force || !young_list_full) {
6709     HeapRegion* new_alloc_region = new_region(word_size,
6710                                               false /* is_old */,
6711                                               false /* do_expand */);
6712     if (new_alloc_region != NULL) {
6713       set_region_short_lived_locked(new_alloc_region);
6714       _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6715       check_bitmaps("Mutator Region Allocation", new_alloc_region);
6716       return new_alloc_region;
6717     }
6718   }
6719   return NULL;
6720 }
6721 
6722 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6723                                                   size_t allocated_bytes) {
6724   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6725   assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
6726 
6727   g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6728   _allocator->increase_used(allocated_bytes);
6729   _hr_printer.retire(alloc_region);
6730   // We update the eden sizes here, when the region is retired,
6731   // instead of when it's allocated, since this is the point that its
6732   // used space has been recored in _summary_bytes_used.
6733   g1mm()->update_eden_size();
6734 }
6735 
6736 void G1CollectedHeap::set_par_threads() {
6737   // Don't change the number of workers.  Use the value previously set
6738   // in the workgroup.
6739   assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise");
6740   uint n_workers = workers()->active_workers();
6741   assert(UseDynamicNumberOfGCThreads ||
6742            n_workers == workers()->total_workers(),
6743       "Otherwise should be using the total number of workers");
6744   if (n_workers == 0) {
6745     assert(false, "Should have been set in prior evacuation pause.");
6746     n_workers = ParallelGCThreads;
6747     workers()->set_active_workers(n_workers);
6748   }
6749   set_par_threads(n_workers);
6750 }
6751 
6752 // Methods for the GC alloc regions
6753 
6754 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6755                                                  uint count,
6756                                                  InCSetState dest) {
6757   assert(FreeList_lock->owned_by_self(), "pre-condition");
6758 
6759   if (count < g1_policy()->max_regions(dest)) {
6760     const bool is_survivor = (dest.is_young());
6761     HeapRegion* new_alloc_region = new_region(word_size,
6762                                               !is_survivor,
6763                                               true /* do_expand */);
6764     if (new_alloc_region != NULL) {
6765       // We really only need to do this for old regions given that we
6766       // should never scan survivors. But it doesn't hurt to do it
6767       // for survivors too.
6768       new_alloc_region->record_timestamp();
6769       if (is_survivor) {
6770         new_alloc_region->set_survivor();
6771         _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6772         check_bitmaps("Survivor Region Allocation", new_alloc_region);
6773       } else {
6774         new_alloc_region->set_old();
6775         _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6776         check_bitmaps("Old Region Allocation", new_alloc_region);
6777       }
6778       bool during_im = g1_policy()->during_initial_mark_pause();
6779       new_alloc_region->note_start_of_copying(during_im);
6780       return new_alloc_region;
6781     }
6782   }
6783   return NULL;
6784 }
6785 
6786 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6787                                              size_t allocated_bytes,
6788                                              InCSetState dest) {
6789   bool during_im = g1_policy()->during_initial_mark_pause();
6790   alloc_region->note_end_of_copying(during_im);
6791   g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6792   if (dest.is_young()) {
6793     young_list()->add_survivor_region(alloc_region);
6794   } else {
6795     _old_set.add(alloc_region);
6796   }
6797   _hr_printer.retire(alloc_region);
6798 }
6799 
6800 // Heap region set verification
6801 
6802 class VerifyRegionListsClosure : public HeapRegionClosure {
6803 private:
6804   HeapRegionSet*   _old_set;
6805   HeapRegionSet*   _humongous_set;
6806   HeapRegionManager*   _hrm;
6807 
6808 public:
6809   HeapRegionSetCount _old_count;
6810   HeapRegionSetCount _humongous_count;
6811   HeapRegionSetCount _free_count;
6812 
6813   VerifyRegionListsClosure(HeapRegionSet* old_set,
6814                            HeapRegionSet* humongous_set,
6815                            HeapRegionManager* hrm) :
6816     _old_set(old_set), _humongous_set(humongous_set), _hrm(hrm),
6817     _old_count(), _humongous_count(), _free_count(){ }
6818 
6819   bool doHeapRegion(HeapRegion* hr) {
6820     if (hr->continuesHumongous()) {
6821       return false;
6822     }
6823 
6824     if (hr->is_young()) {
6825       // TODO
6826     } else if (hr->startsHumongous()) {
6827       assert(hr->containing_set() == _humongous_set, err_msg("Heap region %u is starts humongous but not in humongous set.", hr->hrm_index()));
6828       _humongous_count.increment(1u, hr->capacity());
6829     } else if (hr->is_empty()) {
6830       assert(_hrm->is_free(hr), err_msg("Heap region %u is empty but not on the free list.", hr->hrm_index()));
6831       _free_count.increment(1u, hr->capacity());
6832     } else if (hr->is_old()) {
6833       assert(hr->containing_set() == _old_set, err_msg("Heap region %u is old but not in the old set.", hr->hrm_index()));
6834       _old_count.increment(1u, hr->capacity());
6835     } else {
6836       ShouldNotReachHere();
6837     }
6838     return false;
6839   }
6840 
6841   void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, HeapRegionManager* free_list) {
6842     guarantee(old_set->length() == _old_count.length(), err_msg("Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length()));
6843     guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), err_msg("Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6844         old_set->total_capacity_bytes(), _old_count.capacity()));
6845 
6846     guarantee(humongous_set->length() == _humongous_count.length(), err_msg("Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length()));
6847     guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), err_msg("Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6848         humongous_set->total_capacity_bytes(), _humongous_count.capacity()));
6849 
6850     guarantee(free_list->num_free_regions() == _free_count.length(), err_msg("Free list count mismatch. Expected %u, actual %u.", free_list->num_free_regions(), _free_count.length()));
6851     guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), err_msg("Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6852         free_list->total_capacity_bytes(), _free_count.capacity()));
6853   }
6854 };
6855 
6856 void G1CollectedHeap::verify_region_sets() {
6857   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6858 
6859   // First, check the explicit lists.
6860   _hrm.verify();
6861   {
6862     // Given that a concurrent operation might be adding regions to
6863     // the secondary free list we have to take the lock before
6864     // verifying it.
6865     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6866     _secondary_free_list.verify_list();
6867   }
6868 
6869   // If a concurrent region freeing operation is in progress it will
6870   // be difficult to correctly attributed any free regions we come
6871   // across to the correct free list given that they might belong to
6872   // one of several (free_list, secondary_free_list, any local lists,
6873   // etc.). So, if that's the case we will skip the rest of the
6874   // verification operation. Alternatively, waiting for the concurrent
6875   // operation to complete will have a non-trivial effect on the GC's
6876   // operation (no concurrent operation will last longer than the
6877   // interval between two calls to verification) and it might hide
6878   // any issues that we would like to catch during testing.
6879   if (free_regions_coming()) {
6880     return;
6881   }
6882 
6883   // Make sure we append the secondary_free_list on the free_list so
6884   // that all free regions we will come across can be safely
6885   // attributed to the free_list.
6886   append_secondary_free_list_if_not_empty_with_lock();
6887 
6888   // Finally, make sure that the region accounting in the lists is
6889   // consistent with what we see in the heap.
6890 
6891   VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_hrm);
6892   heap_region_iterate(&cl);
6893   cl.verify_counts(&_old_set, &_humongous_set, &_hrm);
6894 }
6895 
6896 // Optimized nmethod scanning
6897 
6898 class RegisterNMethodOopClosure: public OopClosure {
6899   G1CollectedHeap* _g1h;
6900   nmethod* _nm;
6901 
6902   template <class T> void do_oop_work(T* p) {
6903     T heap_oop = oopDesc::load_heap_oop(p);
6904     if (!oopDesc::is_null(heap_oop)) {
6905       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6906       HeapRegion* hr = _g1h->heap_region_containing(obj);
6907       assert(!hr->continuesHumongous(),
6908              err_msg("trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
6909                      " starting at " HR_FORMAT,
6910                      _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6911 
6912       // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
6913       hr->add_strong_code_root_locked(_nm);
6914     }
6915   }
6916 
6917 public:
6918   RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6919     _g1h(g1h), _nm(nm) {}
6920 
6921   void do_oop(oop* p)       { do_oop_work(p); }
6922   void do_oop(narrowOop* p) { do_oop_work(p); }
6923 };
6924 
6925 class UnregisterNMethodOopClosure: public OopClosure {
6926   G1CollectedHeap* _g1h;
6927   nmethod* _nm;
6928 
6929   template <class T> void do_oop_work(T* p) {
6930     T heap_oop = oopDesc::load_heap_oop(p);
6931     if (!oopDesc::is_null(heap_oop)) {
6932       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6933       HeapRegion* hr = _g1h->heap_region_containing(obj);
6934       assert(!hr->continuesHumongous(),
6935              err_msg("trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
6936                      " starting at " HR_FORMAT,
6937                      _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6938 
6939       hr->remove_strong_code_root(_nm);
6940     }
6941   }
6942 
6943 public:
6944   UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6945     _g1h(g1h), _nm(nm) {}
6946 
6947   void do_oop(oop* p)       { do_oop_work(p); }
6948   void do_oop(narrowOop* p) { do_oop_work(p); }
6949 };
6950 
6951 void G1CollectedHeap::register_nmethod(nmethod* nm) {
6952   CollectedHeap::register_nmethod(nm);
6953 
6954   guarantee(nm != NULL, "sanity");
6955   RegisterNMethodOopClosure reg_cl(this, nm);
6956   nm->oops_do(&reg_cl);
6957 }
6958 
6959 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
6960   CollectedHeap::unregister_nmethod(nm);
6961 
6962   guarantee(nm != NULL, "sanity");
6963   UnregisterNMethodOopClosure reg_cl(this, nm);
6964   nm->oops_do(&reg_cl, true);
6965 }
6966 
6967 void G1CollectedHeap::purge_code_root_memory() {
6968   double purge_start = os::elapsedTime();
6969   G1CodeRootSet::purge();
6970   double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
6971   g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
6972 }
6973 
6974 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
6975   G1CollectedHeap* _g1h;
6976 
6977 public:
6978   RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
6979     _g1h(g1h) {}
6980 
6981   void do_code_blob(CodeBlob* cb) {
6982     nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
6983     if (nm == NULL) {
6984       return;
6985     }
6986 
6987     if (ScavengeRootsInCode) {
6988       _g1h->register_nmethod(nm);
6989     }
6990   }
6991 };
6992 
6993 void G1CollectedHeap::rebuild_strong_code_roots() {
6994   RebuildStrongCodeRootClosure blob_cl(this);
6995   CodeCache::blobs_do(&blob_cl);
6996 }
--- EOF ---