1 /*
   2  * Copyright (c) 2001, 2014, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #if !defined(__clang_major__) && defined(__GNUC__)
  26 // FIXME, formats have issues.  Disable this macro definition, compile, and study warnings for more information.
  27 #define ATTRIBUTE_PRINTF(x,y)
  28 #endif
  29 
  30 #include "precompiled.hpp"
  31 #include "classfile/stringTable.hpp"
  32 #include "code/codeCache.hpp"
  33 #include "code/icBuffer.hpp"
  34 #include "gc_implementation/g1/bufferingOopClosure.hpp"
  35 #include "gc_implementation/g1/concurrentG1Refine.hpp"
  36 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
  37 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
  38 #include "gc_implementation/g1/g1AllocRegion.inline.hpp"
  39 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
  40 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
  41 #include "gc_implementation/g1/g1ErgoVerbose.hpp"
  42 #include "gc_implementation/g1/g1EvacFailure.hpp"
  43 #include "gc_implementation/g1/g1GCPhaseTimes.hpp"
  44 #include "gc_implementation/g1/g1Log.hpp"
  45 #include "gc_implementation/g1/g1MarkSweep.hpp"
  46 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
  47 #include "gc_implementation/g1/g1ParScanThreadState.inline.hpp"
  48 #include "gc_implementation/g1/g1RegionToSpaceMapper.hpp"
  49 #include "gc_implementation/g1/g1RemSet.inline.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/atomic.inline.hpp"
  69 #include "runtime/orderAccess.inline.hpp"
  70 #include "runtime/vmThread.hpp"
  71 #include "utilities/globalDefinitions.hpp"
  72 
  73 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
  74 
  75 // turn it on so that the contents of the young list (scan-only /
  76 // to-be-collected) are printed at "strategic" points before / during
  77 // / after the collection --- this is useful for debugging
  78 #define YOUNG_LIST_VERBOSE 0
  79 // CURRENT STATUS
  80 // This file is under construction.  Search for "FIXME".
  81 
  82 // INVARIANTS/NOTES
  83 //
  84 // All allocation activity covered by the G1CollectedHeap interface is
  85 // serialized by acquiring the HeapLock.  This happens in mem_allocate
  86 // and allocate_new_tlab, which are the "entry" points to the
  87 // allocation code from the rest of the JVM.  (Note that this does not
  88 // apply to TLAB allocation, which is not part of this interface: it
  89 // is done by clients of this interface.)
  90 
  91 // Notes on implementation of parallelism in different tasks.
  92 //
  93 // G1ParVerifyTask uses heap_region_par_iterate_chunked() for parallelism.
  94 // The number of GC workers is passed to heap_region_par_iterate_chunked().
  95 // It does use run_task() which sets _n_workers in the task.
  96 // G1ParTask executes g1_process_roots() ->
  97 // SharedHeap::process_roots() which calls eventually to
  98 // CardTableModRefBS::par_non_clean_card_iterate_work() which uses
  99 // SequentialSubTasksDone.  SharedHeap::process_roots() also
 100 // directly uses SubTasksDone (_process_strong_tasks field in SharedHeap).
 101 //
 102 
 103 // Local to this file.
 104 
 105 class RefineCardTableEntryClosure: public CardTableEntryClosure {
 106   bool _concurrent;
 107 public:
 108   RefineCardTableEntryClosure() : _concurrent(true) { }
 109 
 110   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
 111     bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, false);
 112     // This path is executed by the concurrent refine or mutator threads,
 113     // concurrently, and so we do not care if card_ptr contains references
 114     // that point into the collection set.
 115     assert(!oops_into_cset, "should be");
 116 
 117     if (_concurrent && SuspendibleThreadSet::should_yield()) {
 118       // Caller will actually yield.
 119       return false;
 120     }
 121     // Otherwise, we finished successfully; return true.
 122     return true;
 123   }
 124 
 125   void set_concurrent(bool b) { _concurrent = b; }
 126 };
 127 
 128 
 129 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure {
 130   size_t _num_processed;
 131   CardTableModRefBS* _ctbs;
 132   int _histo[256];
 133 
 134  public:
 135   ClearLoggedCardTableEntryClosure() :
 136     _num_processed(0), _ctbs(G1CollectedHeap::heap()->g1_barrier_set())
 137   {
 138     for (int i = 0; i < 256; i++) _histo[i] = 0;
 139   }
 140 
 141   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
 142     unsigned char* ujb = (unsigned char*)card_ptr;
 143     int ind = (int)(*ujb);
 144     _histo[ind]++;
 145 
 146     *card_ptr = (jbyte)CardTableModRefBS::clean_card_val();
 147     _num_processed++;
 148 
 149     return true;
 150   }
 151 
 152   size_t num_processed() { return _num_processed; }
 153 
 154   void print_histo() {
 155     gclog_or_tty->print_cr("Card table value histogram:");
 156     for (int i = 0; i < 256; i++) {
 157       if (_histo[i] != 0) {
 158         gclog_or_tty->print_cr("  %d: %d", i, _histo[i]);
 159       }
 160     }
 161   }
 162 };
 163 
 164 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
 165  private:
 166   size_t _num_processed;
 167 
 168  public:
 169   RedirtyLoggedCardTableEntryClosure() : CardTableEntryClosure(), _num_processed(0) { }
 170 
 171   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
 172     *card_ptr = CardTableModRefBS::dirty_card_val();
 173     _num_processed++;
 174     return true;
 175   }
 176 
 177   size_t num_processed() const { return _num_processed; }
 178 };
 179 
 180 YoungList::YoungList(G1CollectedHeap* g1h) :
 181     _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0),
 182     _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) {
 183   guarantee(check_list_empty(false), "just making sure...");
 184 }
 185 
 186 void YoungList::push_region(HeapRegion *hr) {
 187   assert(!hr->is_young(), "should not already be young");
 188   assert(hr->get_next_young_region() == NULL, "cause it should!");
 189 
 190   hr->set_next_young_region(_head);
 191   _head = hr;
 192 
 193   _g1h->g1_policy()->set_region_eden(hr, (int) _length);
 194   ++_length;
 195 }
 196 
 197 void YoungList::add_survivor_region(HeapRegion* hr) {
 198   assert(hr->is_survivor(), "should be flagged as survivor region");
 199   assert(hr->get_next_young_region() == NULL, "cause it should!");
 200 
 201   hr->set_next_young_region(_survivor_head);
 202   if (_survivor_head == NULL) {
 203     _survivor_tail = hr;
 204   }
 205   _survivor_head = hr;
 206   ++_survivor_length;
 207 }
 208 
 209 void YoungList::empty_list(HeapRegion* list) {
 210   while (list != NULL) {
 211     HeapRegion* next = list->get_next_young_region();
 212     list->set_next_young_region(NULL);
 213     list->uninstall_surv_rate_group();
 214     // This is called before a Full GC and all the non-empty /
 215     // non-humongous regions at the end of the Full GC will end up as
 216     // old anyway.
 217     list->set_old();
 218     list = next;
 219   }
 220 }
 221 
 222 void YoungList::empty_list() {
 223   assert(check_list_well_formed(), "young list should be well formed");
 224 
 225   empty_list(_head);
 226   _head = NULL;
 227   _length = 0;
 228 
 229   empty_list(_survivor_head);
 230   _survivor_head = NULL;
 231   _survivor_tail = NULL;
 232   _survivor_length = 0;
 233 
 234   _last_sampled_rs_lengths = 0;
 235 
 236   assert(check_list_empty(false), "just making sure...");
 237 }
 238 
 239 bool YoungList::check_list_well_formed() {
 240   bool ret = true;
 241 
 242   uint length = 0;
 243   HeapRegion* curr = _head;
 244   HeapRegion* last = NULL;
 245   while (curr != NULL) {
 246     if (!curr->is_young()) {
 247       gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
 248                              "incorrectly tagged (y: %d, surv: %d)",
 249                              curr->bottom(), curr->end(),
 250                              curr->is_young(), curr->is_survivor());
 251       ret = false;
 252     }
 253     ++length;
 254     last = curr;
 255     curr = curr->get_next_young_region();
 256   }
 257   ret = ret && (length == _length);
 258 
 259   if (!ret) {
 260     gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
 261     gclog_or_tty->print_cr("###   list has %u entries, _length is %u",
 262                            length, _length);
 263   }
 264 
 265   return ret;
 266 }
 267 
 268 bool YoungList::check_list_empty(bool check_sample) {
 269   bool ret = true;
 270 
 271   if (_length != 0) {
 272     gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u",
 273                   _length);
 274     ret = false;
 275   }
 276   if (check_sample && _last_sampled_rs_lengths != 0) {
 277     gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
 278     ret = false;
 279   }
 280   if (_head != NULL) {
 281     gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
 282     ret = false;
 283   }
 284   if (!ret) {
 285     gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
 286   }
 287 
 288   return ret;
 289 }
 290 
 291 void
 292 YoungList::rs_length_sampling_init() {
 293   _sampled_rs_lengths = 0;
 294   _curr               = _head;
 295 }
 296 
 297 bool
 298 YoungList::rs_length_sampling_more() {
 299   return _curr != NULL;
 300 }
 301 
 302 void
 303 YoungList::rs_length_sampling_next() {
 304   assert( _curr != NULL, "invariant" );
 305   size_t rs_length = _curr->rem_set()->occupied();
 306 
 307   _sampled_rs_lengths += rs_length;
 308 
 309   // The current region may not yet have been added to the
 310   // incremental collection set (it gets added when it is
 311   // retired as the current allocation region).
 312   if (_curr->in_collection_set()) {
 313     // Update the collection set policy information for this region
 314     _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
 315   }
 316 
 317   _curr = _curr->get_next_young_region();
 318   if (_curr == NULL) {
 319     _last_sampled_rs_lengths = _sampled_rs_lengths;
 320     // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
 321   }
 322 }
 323 
 324 void
 325 YoungList::reset_auxilary_lists() {
 326   guarantee( is_empty(), "young list should be empty" );
 327   assert(check_list_well_formed(), "young list should be well formed");
 328 
 329   // Add survivor regions to SurvRateGroup.
 330   _g1h->g1_policy()->note_start_adding_survivor_regions();
 331   _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
 332 
 333   int young_index_in_cset = 0;
 334   for (HeapRegion* curr = _survivor_head;
 335        curr != NULL;
 336        curr = curr->get_next_young_region()) {
 337     _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
 338 
 339     // The region is a non-empty survivor so let's add it to
 340     // the incremental collection set for the next evacuation
 341     // pause.
 342     _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
 343     young_index_in_cset += 1;
 344   }
 345   assert((uint) young_index_in_cset == _survivor_length, "post-condition");
 346   _g1h->g1_policy()->note_stop_adding_survivor_regions();
 347 
 348   _head   = _survivor_head;
 349   _length = _survivor_length;
 350   if (_survivor_head != NULL) {
 351     assert(_survivor_tail != NULL, "cause it shouldn't be");
 352     assert(_survivor_length > 0, "invariant");
 353     _survivor_tail->set_next_young_region(NULL);
 354   }
 355 
 356   // Don't clear the survivor list handles until the start of
 357   // the next evacuation pause - we need it in order to re-tag
 358   // the survivor regions from this evacuation pause as 'young'
 359   // at the start of the next.
 360 
 361   _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
 362 
 363   assert(check_list_well_formed(), "young list should be well formed");
 364 }
 365 
 366 void YoungList::print() {
 367   HeapRegion* lists[] = {_head,   _survivor_head};
 368   const char* names[] = {"YOUNG", "SURVIVOR"};
 369 
 370   for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) {
 371     gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
 372     HeapRegion *curr = lists[list];
 373     if (curr == NULL)
 374       gclog_or_tty->print_cr("  empty");
 375     while (curr != NULL) {
 376       gclog_or_tty->print_cr("  "HR_FORMAT", P: "PTR_FORMAT ", N: "PTR_FORMAT", age: %4d",
 377                              HR_FORMAT_PARAMS(curr),
 378                              curr->prev_top_at_mark_start(),
 379                              curr->next_top_at_mark_start(),
 380                              curr->age_in_surv_rate_group_cond());
 381       curr = curr->get_next_young_region();
 382     }
 383   }
 384 
 385   gclog_or_tty->cr();
 386 }
 387 
 388 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
 389   OtherRegionsTable::invalidate(start_idx, num_regions);
 390 }
 391 
 392 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions) {
 393   reset_from_card_cache(start_idx, num_regions);
 394 }
 395 
 396 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
 397 {
 398   // Claim the right to put the region on the dirty cards region list
 399   // by installing a self pointer.
 400   HeapRegion* next = hr->get_next_dirty_cards_region();
 401   if (next == NULL) {
 402     HeapRegion* res = (HeapRegion*)
 403       Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
 404                           NULL);
 405     if (res == NULL) {
 406       HeapRegion* head;
 407       do {
 408         // Put the region to the dirty cards region list.
 409         head = _dirty_cards_region_list;
 410         next = (HeapRegion*)
 411           Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
 412         if (next == head) {
 413           assert(hr->get_next_dirty_cards_region() == hr,
 414                  "hr->get_next_dirty_cards_region() != hr");
 415           if (next == NULL) {
 416             // The last region in the list points to itself.
 417             hr->set_next_dirty_cards_region(hr);
 418           } else {
 419             hr->set_next_dirty_cards_region(next);
 420           }
 421         }
 422       } while (next != head);
 423     }
 424   }
 425 }
 426 
 427 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
 428 {
 429   HeapRegion* head;
 430   HeapRegion* hr;
 431   do {
 432     head = _dirty_cards_region_list;
 433     if (head == NULL) {
 434       return NULL;
 435     }
 436     HeapRegion* new_head = head->get_next_dirty_cards_region();
 437     if (head == new_head) {
 438       // The last region.
 439       new_head = NULL;
 440     }
 441     hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
 442                                           head);
 443   } while (hr != head);
 444   assert(hr != NULL, "invariant");
 445   hr->set_next_dirty_cards_region(NULL);
 446   return hr;
 447 }
 448 
 449 #ifdef ASSERT
 450 // A region is added to the collection set as it is retired
 451 // so an address p can point to a region which will be in the
 452 // collection set but has not yet been retired.  This method
 453 // therefore is only accurate during a GC pause after all
 454 // regions have been retired.  It is used for debugging
 455 // to check if an nmethod has references to objects that can
 456 // be move during a partial collection.  Though it can be
 457 // inaccurate, it is sufficient for G1 because the conservative
 458 // implementation of is_scavengable() for G1 will indicate that
 459 // all nmethods must be scanned during a partial collection.
 460 bool G1CollectedHeap::is_in_partial_collection(const void* p) {
 461   if (p == NULL) {
 462     return false;
 463   }
 464   return heap_region_containing(p)->in_collection_set();
 465 }
 466 #endif
 467 
 468 // Returns true if the reference points to an object that
 469 // can move in an incremental collection.
 470 bool G1CollectedHeap::is_scavengable(const void* p) {
 471   HeapRegion* hr = heap_region_containing(p);
 472   return !hr->is_humongous();
 473 }
 474 
 475 void G1CollectedHeap::check_ct_logs_at_safepoint() {
 476   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
 477   CardTableModRefBS* ct_bs = g1_barrier_set();
 478 
 479   // Count the dirty cards at the start.
 480   CountNonCleanMemRegionClosure count1(this);
 481   ct_bs->mod_card_iterate(&count1);
 482   int orig_count = count1.n();
 483 
 484   // First clear the logged cards.
 485   ClearLoggedCardTableEntryClosure clear;
 486   dcqs.apply_closure_to_all_completed_buffers(&clear);
 487   dcqs.iterate_closure_all_threads(&clear, false);
 488   clear.print_histo();
 489 
 490   // Now ensure that there's no dirty cards.
 491   CountNonCleanMemRegionClosure count2(this);
 492   ct_bs->mod_card_iterate(&count2);
 493   if (count2.n() != 0) {
 494     gclog_or_tty->print_cr("Card table has %d entries; %d originally",
 495                            count2.n(), orig_count);
 496   }
 497   guarantee(count2.n() == 0, "Card table should be clean.");
 498 
 499   RedirtyLoggedCardTableEntryClosure redirty;
 500   dcqs.apply_closure_to_all_completed_buffers(&redirty);
 501   dcqs.iterate_closure_all_threads(&redirty, false);
 502   gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
 503                          clear.num_processed(), orig_count);
 504   guarantee(redirty.num_processed() == clear.num_processed(),
 505             err_msg("Redirtied "SIZE_FORMAT" cards, bug cleared "SIZE_FORMAT,
 506                     redirty.num_processed(), clear.num_processed()));
 507 
 508   CountNonCleanMemRegionClosure count3(this);
 509   ct_bs->mod_card_iterate(&count3);
 510   if (count3.n() != orig_count) {
 511     gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
 512                            orig_count, count3.n());
 513     guarantee(count3.n() >= orig_count, "Should have restored them all.");
 514   }
 515 }
 516 
 517 // Private class members.
 518 
 519 G1CollectedHeap* G1CollectedHeap::_g1h;
 520 
 521 // Private methods.
 522 
 523 HeapRegion*
 524 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
 525   MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
 526   while (!_secondary_free_list.is_empty() || free_regions_coming()) {
 527     if (!_secondary_free_list.is_empty()) {
 528       if (G1ConcRegionFreeingVerbose) {
 529         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 530                                "secondary_free_list has %u entries",
 531                                _secondary_free_list.length());
 532       }
 533       // It looks as if there are free regions available on the
 534       // secondary_free_list. Let's move them to the free_list and try
 535       // again to allocate from it.
 536       append_secondary_free_list();
 537 
 538       assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not "
 539              "empty we should have moved at least one entry to the free_list");
 540       HeapRegion* res = _hrm.allocate_free_region(is_old);
 541       if (G1ConcRegionFreeingVerbose) {
 542         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 543                                "allocated "HR_FORMAT" from secondary_free_list",
 544                                HR_FORMAT_PARAMS(res));
 545       }
 546       return res;
 547     }
 548 
 549     // Wait here until we get notified either when (a) there are no
 550     // more free regions coming or (b) some regions have been moved on
 551     // the secondary_free_list.
 552     SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
 553   }
 554 
 555   if (G1ConcRegionFreeingVerbose) {
 556     gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 557                            "could not allocate from secondary_free_list");
 558   }
 559   return NULL;
 560 }
 561 
 562 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
 563   assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
 564          "the only time we use this to allocate a humongous region is "
 565          "when we are allocating a single humongous region");
 566 
 567   HeapRegion* res;
 568   if (G1StressConcRegionFreeing) {
 569     if (!_secondary_free_list.is_empty()) {
 570       if (G1ConcRegionFreeingVerbose) {
 571         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 572                                "forced to look at the secondary_free_list");
 573       }
 574       res = new_region_try_secondary_free_list(is_old);
 575       if (res != NULL) {
 576         return res;
 577       }
 578     }
 579   }
 580 
 581   res = _hrm.allocate_free_region(is_old);
 582 
 583   if (res == NULL) {
 584     if (G1ConcRegionFreeingVerbose) {
 585       gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 586                              "res == NULL, trying the secondary_free_list");
 587     }
 588     res = new_region_try_secondary_free_list(is_old);
 589   }
 590   if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
 591     // Currently, only attempts to allocate GC alloc regions set
 592     // do_expand to true. So, we should only reach here during a
 593     // safepoint. If this assumption changes we might have to
 594     // reconsider the use of _expand_heap_after_alloc_failure.
 595     assert(SafepointSynchronize::is_at_safepoint(), "invariant");
 596 
 597     ergo_verbose1(ErgoHeapSizing,
 598                   "attempt heap expansion",
 599                   ergo_format_reason("region allocation request failed")
 600                   ergo_format_byte("allocation request"),
 601                   word_size * HeapWordSize);
 602     if (expand(word_size * HeapWordSize)) {
 603       // Given that expand() succeeded in expanding the heap, and we
 604       // always expand the heap by an amount aligned to the heap
 605       // region size, the free list should in theory not be empty.
 606       // In either case allocate_free_region() will check for NULL.
 607       res = _hrm.allocate_free_region(is_old);
 608     } else {
 609       _expand_heap_after_alloc_failure = false;
 610     }
 611   }
 612   return res;
 613 }
 614 
 615 HeapWord*
 616 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
 617                                                            uint num_regions,
 618                                                            size_t word_size,
 619                                                            AllocationContext_t context) {
 620   assert(first != G1_NO_HRM_INDEX, "pre-condition");
 621   assert(is_humongous(word_size), "word_size should be humongous");
 622   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 623 
 624   // Index of last region in the series + 1.
 625   uint last = first + num_regions;
 626 
 627   // We need to initialize the region(s) we just discovered. This is
 628   // a bit tricky given that it can happen concurrently with
 629   // refinement threads refining cards on these regions and
 630   // potentially wanting to refine the BOT as they are scanning
 631   // those cards (this can happen shortly after a cleanup; see CR
 632   // 6991377). So we have to set up the region(s) carefully and in
 633   // a specific order.
 634 
 635   // The word size sum of all the regions we will allocate.
 636   size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
 637   assert(word_size <= word_size_sum, "sanity");
 638 
 639   // This will be the "starts humongous" region.
 640   HeapRegion* first_hr = region_at(first);
 641   // The header of the new object will be placed at the bottom of
 642   // the first region.
 643   HeapWord* new_obj = first_hr->bottom();
 644   // This will be the new end of the first region in the series that
 645   // should also match the end of the last region in the series.
 646   HeapWord* new_end = new_obj + word_size_sum;
 647   // This will be the new top of the first region that will reflect
 648   // this allocation.
 649   HeapWord* new_top = new_obj + word_size;
 650 
 651   // First, we need to zero the header of the space that we will be
 652   // allocating. When we update top further down, some refinement
 653   // threads might try to scan the region. By zeroing the header we
 654   // ensure that any thread that will try to scan the region will
 655   // come across the zero klass word and bail out.
 656   //
 657   // NOTE: It would not have been correct to have used
 658   // CollectedHeap::fill_with_object() and make the space look like
 659   // an int array. The thread that is doing the allocation will
 660   // later update the object header to a potentially different array
 661   // type and, for a very short period of time, the klass and length
 662   // fields will be inconsistent. This could cause a refinement
 663   // thread to calculate the object size incorrectly.
 664   Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
 665 
 666   // We will set up the first region as "starts humongous". This
 667   // will also update the BOT covering all the regions to reflect
 668   // that there is a single object that starts at the bottom of the
 669   // first region.
 670   first_hr->set_starts_humongous(new_top, new_end);
 671   first_hr->set_allocation_context(context);
 672   // Then, if there are any, we will set up the "continues
 673   // humongous" regions.
 674   HeapRegion* hr = NULL;
 675   for (uint i = first + 1; i < last; ++i) {
 676     hr = region_at(i);
 677     hr->set_continues_humongous(first_hr);
 678     hr->set_allocation_context(context);
 679   }
 680   // If we have "continues humongous" regions (hr != NULL), then the
 681   // end of the last one should match new_end.
 682   assert(hr == NULL || hr->end() == new_end, "sanity");
 683 
 684   // Up to this point no concurrent thread would have been able to
 685   // do any scanning on any region in this series. All the top
 686   // fields still point to bottom, so the intersection between
 687   // [bottom,top] and [card_start,card_end] will be empty. Before we
 688   // update the top fields, we'll do a storestore to make sure that
 689   // no thread sees the update to top before the zeroing of the
 690   // object header and the BOT initialization.
 691   OrderAccess::storestore();
 692 
 693   // Now that the BOT and the object header have been initialized,
 694   // we can update top of the "starts humongous" region.
 695   assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
 696          "new_top should be in this region");
 697   first_hr->set_top(new_top);
 698   if (_hr_printer.is_active()) {
 699     HeapWord* bottom = first_hr->bottom();
 700     HeapWord* end = first_hr->orig_end();
 701     if ((first + 1) == last) {
 702       // the series has a single humongous region
 703       _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
 704     } else {
 705       // the series has more than one humongous regions
 706       _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
 707     }
 708   }
 709 
 710   // Now, we will update the top fields of the "continues humongous"
 711   // regions. The reason we need to do this is that, otherwise,
 712   // these regions would look empty and this will confuse parts of
 713   // G1. For example, the code that looks for a consecutive number
 714   // of empty regions will consider them empty and try to
 715   // re-allocate them. We can extend is_empty() to also include
 716   // !is_continues_humongous(), but it is easier to just update the top
 717   // fields here. The way we set top for all regions (i.e., top ==
 718   // end for all regions but the last one, top == new_top for the
 719   // last one) is actually used when we will free up the humongous
 720   // region in free_humongous_region().
 721   hr = NULL;
 722   for (uint i = first + 1; i < last; ++i) {
 723     hr = region_at(i);
 724     if ((i + 1) == last) {
 725       // last continues humongous region
 726       assert(hr->bottom() < new_top && new_top <= hr->end(),
 727              "new_top should fall on this region");
 728       hr->set_top(new_top);
 729       _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
 730     } else {
 731       // not last one
 732       assert(new_top > hr->end(), "new_top should be above this region");
 733       hr->set_top(hr->end());
 734       _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
 735     }
 736   }
 737   // If we have continues humongous regions (hr != NULL), then the
 738   // end of the last one should match new_end and its top should
 739   // match new_top.
 740   assert(hr == NULL ||
 741          (hr->end() == new_end && hr->top() == new_top), "sanity");
 742   check_bitmaps("Humongous Region Allocation", first_hr);
 743 
 744   assert(first_hr->used() == word_size * HeapWordSize, "invariant");
 745   _allocator->increase_used(first_hr->used());
 746   _humongous_set.add(first_hr);
 747 
 748   return new_obj;
 749 }
 750 
 751 // If could fit into free regions w/o expansion, try.
 752 // Otherwise, if can expand, do so.
 753 // Otherwise, if using ex regions might help, try with ex given back.
 754 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) {
 755   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 756 
 757   verify_region_sets_optional();
 758 
 759   uint first = G1_NO_HRM_INDEX;
 760   uint obj_regions = (uint)(align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords);
 761 
 762   if (obj_regions == 1) {
 763     // Only one region to allocate, try to use a fast path by directly allocating
 764     // from the free lists. Do not try to expand here, we will potentially do that
 765     // later.
 766     HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
 767     if (hr != NULL) {
 768       first = hr->hrm_index();
 769     }
 770   } else {
 771     // We can't allocate humongous regions spanning more than one region while
 772     // cleanupComplete() is running, since some of the regions we find to be
 773     // empty might not yet be added to the free list. It is not straightforward
 774     // to know in which list they are on so that we can remove them. We only
 775     // need to do this if we need to allocate more than one region to satisfy the
 776     // current humongous allocation request. If we are only allocating one region
 777     // we use the one-region region allocation code (see above), that already
 778     // potentially waits for regions from the secondary free list.
 779     wait_while_free_regions_coming();
 780     append_secondary_free_list_if_not_empty_with_lock();
 781 
 782     // Policy: Try only empty regions (i.e. already committed first). Maybe we
 783     // are lucky enough to find some.
 784     first = _hrm.find_contiguous_only_empty(obj_regions);
 785     if (first != G1_NO_HRM_INDEX) {
 786       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 787     }
 788   }
 789 
 790   if (first == G1_NO_HRM_INDEX) {
 791     // Policy: We could not find enough regions for the humongous object in the
 792     // free list. Look through the heap to find a mix of free and uncommitted regions.
 793     // If so, try expansion.
 794     first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
 795     if (first != G1_NO_HRM_INDEX) {
 796       // We found something. Make sure these regions are committed, i.e. expand
 797       // the heap. Alternatively we could do a defragmentation GC.
 798       ergo_verbose1(ErgoHeapSizing,
 799                     "attempt heap expansion",
 800                     ergo_format_reason("humongous allocation request failed")
 801                     ergo_format_byte("allocation request"),
 802                     word_size * HeapWordSize);
 803 
 804       _hrm.expand_at(first, obj_regions);
 805       g1_policy()->record_new_heap_size(num_regions());
 806 
 807 #ifdef ASSERT
 808       for (uint i = first; i < first + obj_regions; ++i) {
 809         HeapRegion* hr = region_at(i);
 810         assert(hr->is_free(), "sanity");
 811         assert(hr->is_empty(), "sanity");
 812         assert(is_on_master_free_list(hr), "sanity");
 813       }
 814 #endif
 815       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 816     } else {
 817       // Policy: Potentially trigger a defragmentation GC.
 818     }
 819   }
 820 
 821   HeapWord* result = NULL;
 822   if (first != G1_NO_HRM_INDEX) {
 823     result = humongous_obj_allocate_initialize_regions(first, obj_regions,
 824                                                        word_size, context);
 825     assert(result != NULL, "it should always return a valid result");
 826 
 827     // A successful humongous object allocation changes the used space
 828     // information of the old generation so we need to recalculate the
 829     // sizes and update the jstat counters here.
 830     g1mm()->update_sizes();
 831   }
 832 
 833   verify_region_sets_optional();
 834 
 835   return result;
 836 }
 837 
 838 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
 839   assert_heap_not_locked_and_not_at_safepoint();
 840   assert(!is_humongous(word_size), "we do not allow humongous TLABs");
 841 
 842   unsigned int dummy_gc_count_before;
 843   int dummy_gclocker_retry_count = 0;
 844   return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
 845 }
 846 
 847 HeapWord*
 848 G1CollectedHeap::mem_allocate(size_t word_size,
 849                               bool*  gc_overhead_limit_was_exceeded) {
 850   assert_heap_not_locked_and_not_at_safepoint();
 851 
 852   // Loop until the allocation is satisfied, or unsatisfied after GC.
 853   for (int try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 854     unsigned int gc_count_before;
 855 
 856     HeapWord* result = NULL;
 857     if (!is_humongous(word_size)) {
 858       result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
 859     } else {
 860       result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
 861     }
 862     if (result != NULL) {
 863       return result;
 864     }
 865 
 866     // Create the garbage collection operation...
 867     VM_G1CollectForAllocation op(gc_count_before, word_size);
 868     op.set_allocation_context(AllocationContext::current());
 869 
 870     // ...and get the VM thread to execute it.
 871     VMThread::execute(&op);
 872 
 873     if (op.prologue_succeeded() && op.pause_succeeded()) {
 874       // If the operation was successful we'll return the result even
 875       // if it is NULL. If the allocation attempt failed immediately
 876       // after a Full GC, it's unlikely we'll be able to allocate now.
 877       HeapWord* result = op.result();
 878       if (result != NULL && !is_humongous(word_size)) {
 879         // Allocations that take place on VM operations do not do any
 880         // card dirtying and we have to do it here. We only have to do
 881         // this for non-humongous allocations, though.
 882         dirty_young_block(result, word_size);
 883       }
 884       return result;
 885     } else {
 886       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 887         return NULL;
 888       }
 889       assert(op.result() == NULL,
 890              "the result should be NULL if the VM op did not succeed");
 891     }
 892 
 893     // Give a warning if we seem to be looping forever.
 894     if ((QueuedAllocationWarningCount > 0) &&
 895         (try_count % QueuedAllocationWarningCount == 0)) {
 896       warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
 897     }
 898   }
 899 
 900   ShouldNotReachHere();
 901   return NULL;
 902 }
 903 
 904 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
 905                                                    AllocationContext_t context,
 906                                                    unsigned int *gc_count_before_ret,
 907                                                    int* gclocker_retry_count_ret) {
 908   // Make sure you read the note in attempt_allocation_humongous().
 909 
 910   assert_heap_not_locked_and_not_at_safepoint();
 911   assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
 912          "be called for humongous allocation requests");
 913 
 914   // We should only get here after the first-level allocation attempt
 915   // (attempt_allocation()) failed to allocate.
 916 
 917   // We will loop until a) we manage to successfully perform the
 918   // allocation or b) we successfully schedule a collection which
 919   // fails to perform the allocation. b) is the only case when we'll
 920   // return NULL.
 921   HeapWord* result = NULL;
 922   for (int try_count = 1; /* we'll return */; try_count += 1) {
 923     bool should_try_gc;
 924     unsigned int gc_count_before;
 925 
 926     {
 927       MutexLockerEx x(Heap_lock);
 928       result = _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size,
 929                                                                                     false /* bot_updates */);
 930       if (result != NULL) {
 931         return result;
 932       }
 933 
 934       // If we reach here, attempt_allocation_locked() above failed to
 935       // allocate a new region. So the mutator alloc region should be NULL.
 936       assert(_allocator->mutator_alloc_region(context)->get() == NULL, "only way to get here");
 937 
 938       if (GC_locker::is_active_and_needs_gc()) {
 939         if (g1_policy()->can_expand_young_list()) {
 940           // No need for an ergo verbose message here,
 941           // can_expand_young_list() does this when it returns true.
 942           result = _allocator->mutator_alloc_region(context)->attempt_allocation_force(word_size,
 943                                                                                        false /* bot_updates */);
 944           if (result != NULL) {
 945             return result;
 946           }
 947         }
 948         should_try_gc = false;
 949       } else {
 950         // The GCLocker may not be active but the GCLocker initiated
 951         // GC may not yet have been performed (GCLocker::needs_gc()
 952         // returns true). In this case we do not try this GC and
 953         // wait until the GCLocker initiated GC is performed, and
 954         // then retry the allocation.
 955         if (GC_locker::needs_gc()) {
 956           should_try_gc = false;
 957         } else {
 958           // Read the GC count while still holding the Heap_lock.
 959           gc_count_before = total_collections();
 960           should_try_gc = true;
 961         }
 962       }
 963     }
 964 
 965     if (should_try_gc) {
 966       bool succeeded;
 967       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 968           GCCause::_g1_inc_collection_pause);
 969       if (result != NULL) {
 970         assert(succeeded, "only way to get back a non-NULL result");
 971         return result;
 972       }
 973 
 974       if (succeeded) {
 975         // If we get here we successfully scheduled a collection which
 976         // failed to allocate. No point in trying to allocate
 977         // further. We'll just return NULL.
 978         MutexLockerEx x(Heap_lock);
 979         *gc_count_before_ret = total_collections();
 980         return NULL;
 981       }
 982     } else {
 983       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
 984         MutexLockerEx x(Heap_lock);
 985         *gc_count_before_ret = total_collections();
 986         return NULL;
 987       }
 988       // The GCLocker is either active or the GCLocker initiated
 989       // GC has not yet been performed. Stall until it is and
 990       // then retry the allocation.
 991       GC_locker::stall_until_clear();
 992       (*gclocker_retry_count_ret) += 1;
 993     }
 994 
 995     // We can reach here if we were unsuccessful in scheduling a
 996     // collection (because another thread beat us to it) or if we were
 997     // stalled due to the GC locker. In either can we should retry the
 998     // allocation attempt in case another thread successfully
 999     // performed a collection and reclaimed enough space. We do the
1000     // first attempt (without holding the Heap_lock) here and the
1001     // follow-on attempt will be at the start of the next loop
1002     // iteration (after taking the Heap_lock).
1003     result = _allocator->mutator_alloc_region(context)->attempt_allocation(word_size,
1004                                                                            false /* bot_updates */);
1005     if (result != NULL) {
1006       return result;
1007     }
1008 
1009     // Give a warning if we seem to be looping forever.
1010     if ((QueuedAllocationWarningCount > 0) &&
1011         (try_count % QueuedAllocationWarningCount == 0)) {
1012       warning("G1CollectedHeap::attempt_allocation_slow() "
1013               "retries %d times", try_count);
1014     }
1015   }
1016 
1017   ShouldNotReachHere();
1018   return NULL;
1019 }
1020 
1021 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
1022                                                         unsigned int * gc_count_before_ret,
1023                                                         int* gclocker_retry_count_ret) {
1024   // The structure of this method has a lot of similarities to
1025   // attempt_allocation_slow(). The reason these two were not merged
1026   // into a single one is that such a method would require several "if
1027   // allocation is not humongous do this, otherwise do that"
1028   // conditional paths which would obscure its flow. In fact, an early
1029   // version of this code did use a unified method which was harder to
1030   // follow and, as a result, it had subtle bugs that were hard to
1031   // track down. So keeping these two methods separate allows each to
1032   // be more readable. It will be good to keep these two in sync as
1033   // much as possible.
1034 
1035   assert_heap_not_locked_and_not_at_safepoint();
1036   assert(is_humongous(word_size), "attempt_allocation_humongous() "
1037          "should only be called for humongous allocations");
1038 
1039   // Humongous objects can exhaust the heap quickly, so we should check if we
1040   // need to start a marking cycle at each humongous object allocation. We do
1041   // the check before we do the actual allocation. The reason for doing it
1042   // before the allocation is that we avoid having to keep track of the newly
1043   // allocated memory while we do a GC.
1044   if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
1045                                            word_size)) {
1046     collect(GCCause::_g1_humongous_allocation);
1047   }
1048 
1049   // We will loop until a) we manage to successfully perform the
1050   // allocation or b) we successfully schedule a collection which
1051   // fails to perform the allocation. b) is the only case when we'll
1052   // return NULL.
1053   HeapWord* result = NULL;
1054   for (int try_count = 1; /* we'll return */; try_count += 1) {
1055     bool should_try_gc;
1056     unsigned int gc_count_before;
1057 
1058     {
1059       MutexLockerEx x(Heap_lock);
1060 
1061       // Given that humongous objects are not allocated in young
1062       // regions, we'll first try to do the allocation without doing a
1063       // collection hoping that there's enough space in the heap.
1064       result = humongous_obj_allocate(word_size, AllocationContext::current());
1065       if (result != NULL) {
1066         return result;
1067       }
1068 
1069       if (GC_locker::is_active_and_needs_gc()) {
1070         should_try_gc = false;
1071       } else {
1072          // The GCLocker may not be active but the GCLocker initiated
1073         // GC may not yet have been performed (GCLocker::needs_gc()
1074         // returns true). In this case we do not try this GC and
1075         // wait until the GCLocker initiated GC is performed, and
1076         // then retry the allocation.
1077         if (GC_locker::needs_gc()) {
1078           should_try_gc = false;
1079         } else {
1080           // Read the GC count while still holding the Heap_lock.
1081           gc_count_before = total_collections();
1082           should_try_gc = true;
1083         }
1084       }
1085     }
1086 
1087     if (should_try_gc) {
1088       // If we failed to allocate the humongous object, we should try to
1089       // do a collection pause (if we're allowed) in case it reclaims
1090       // enough space for the allocation to succeed after the pause.
1091 
1092       bool succeeded;
1093       result = do_collection_pause(word_size, gc_count_before, &succeeded,
1094           GCCause::_g1_humongous_allocation);
1095       if (result != NULL) {
1096         assert(succeeded, "only way to get back a non-NULL result");
1097         return result;
1098       }
1099 
1100       if (succeeded) {
1101         // If we get here we successfully scheduled a collection which
1102         // failed to allocate. No point in trying to allocate
1103         // further. We'll just return NULL.
1104         MutexLockerEx x(Heap_lock);
1105         *gc_count_before_ret = total_collections();
1106         return NULL;
1107       }
1108     } else {
1109       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1110         MutexLockerEx x(Heap_lock);
1111         *gc_count_before_ret = total_collections();
1112         return NULL;
1113       }
1114       // The GCLocker is either active or the GCLocker initiated
1115       // GC has not yet been performed. Stall until it is and
1116       // then retry the allocation.
1117       GC_locker::stall_until_clear();
1118       (*gclocker_retry_count_ret) += 1;
1119     }
1120 
1121     // We can reach here if we were unsuccessful in scheduling a
1122     // collection (because another thread beat us to it) or if we were
1123     // stalled due to the GC locker. In either can we should retry the
1124     // allocation attempt in case another thread successfully
1125     // performed a collection and reclaimed enough space.  Give a
1126     // warning if we seem to be looping forever.
1127 
1128     if ((QueuedAllocationWarningCount > 0) &&
1129         (try_count % QueuedAllocationWarningCount == 0)) {
1130       warning("G1CollectedHeap::attempt_allocation_humongous() "
1131               "retries %d times", try_count);
1132     }
1133   }
1134 
1135   ShouldNotReachHere();
1136   return NULL;
1137 }
1138 
1139 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1140                                                            AllocationContext_t context,
1141                                                            bool expect_null_mutator_alloc_region) {
1142   assert_at_safepoint(true /* should_be_vm_thread */);
1143   assert(_allocator->mutator_alloc_region(context)->get() == NULL ||
1144                                              !expect_null_mutator_alloc_region,
1145          "the current alloc region was unexpectedly found to be non-NULL");
1146 
1147   if (!is_humongous(word_size)) {
1148     return _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size,
1149                                                       false /* bot_updates */);
1150   } else {
1151     HeapWord* result = humongous_obj_allocate(word_size, context);
1152     if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1153       g1_policy()->set_initiate_conc_mark_if_possible();
1154     }
1155     return result;
1156   }
1157 
1158   ShouldNotReachHere();
1159 }
1160 
1161 class PostMCRemSetClearClosure: public HeapRegionClosure {
1162   G1CollectedHeap* _g1h;
1163   ModRefBarrierSet* _mr_bs;
1164 public:
1165   PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1166     _g1h(g1h), _mr_bs(mr_bs) {}
1167 
1168   bool doHeapRegion(HeapRegion* r) {
1169     HeapRegionRemSet* hrrs = r->rem_set();
1170 
1171     if (r->is_continues_humongous()) {
1172       // We'll assert that the strong code root list and RSet is empty
1173       assert(hrrs->strong_code_roots_list_length() == 0, "sanity");
1174       assert(hrrs->occupied() == 0, "RSet should be empty");
1175       return false;
1176     }
1177 
1178     _g1h->reset_gc_time_stamps(r);
1179     hrrs->clear();
1180     // You might think here that we could clear just the cards
1181     // corresponding to the used region.  But no: if we leave a dirty card
1182     // in a region we might allocate into, then it would prevent that card
1183     // from being enqueued, and cause it to be missed.
1184     // Re: the performance cost: we shouldn't be doing full GC anyway!
1185     _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1186 
1187     return false;
1188   }
1189 };
1190 
1191 void G1CollectedHeap::clear_rsets_post_compaction() {
1192   PostMCRemSetClearClosure rs_clear(this, g1_barrier_set());
1193   heap_region_iterate(&rs_clear);
1194 }
1195 
1196 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1197   G1CollectedHeap*   _g1h;
1198   UpdateRSOopClosure _cl;
1199   int                _worker_i;
1200 public:
1201   RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1202     _cl(g1->g1_rem_set(), worker_i),
1203     _worker_i(worker_i),
1204     _g1h(g1)
1205   { }
1206 
1207   bool doHeapRegion(HeapRegion* r) {
1208     if (!r->is_continues_humongous()) {
1209       _cl.set_from(r);
1210       r->oop_iterate(&_cl);
1211     }
1212     return false;
1213   }
1214 };
1215 
1216 class ParRebuildRSTask: public AbstractGangTask {
1217   G1CollectedHeap* _g1;
1218 public:
1219   ParRebuildRSTask(G1CollectedHeap* g1)
1220     : AbstractGangTask("ParRebuildRSTask"),
1221       _g1(g1)
1222   { }
1223 
1224   void work(uint worker_id) {
1225     RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1226     _g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id,
1227                                           _g1->workers()->active_workers(),
1228                                          HeapRegion::RebuildRSClaimValue);
1229   }
1230 };
1231 
1232 class PostCompactionPrinterClosure: public HeapRegionClosure {
1233 private:
1234   G1HRPrinter* _hr_printer;
1235 public:
1236   bool doHeapRegion(HeapRegion* hr) {
1237     assert(!hr->is_young(), "not expecting to find young regions");
1238     if (hr->is_free()) {
1239       // We only generate output for non-empty regions.
1240     } else if (hr->is_starts_humongous()) {
1241       if (hr->region_num() == 1) {
1242         // single humongous region
1243         _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
1244       } else {
1245         _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
1246       }
1247     } else if (hr->is_continues_humongous()) {
1248       _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1249     } else if (hr->is_old()) {
1250       _hr_printer->post_compaction(hr, G1HRPrinter::Old);
1251     } else {
1252       ShouldNotReachHere();
1253     }
1254     return false;
1255   }
1256 
1257   PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1258     : _hr_printer(hr_printer) { }
1259 };
1260 
1261 void G1CollectedHeap::print_hrm_post_compaction() {
1262   PostCompactionPrinterClosure cl(hr_printer());
1263   heap_region_iterate(&cl);
1264 }
1265 
1266 bool G1CollectedHeap::do_collection(bool explicit_gc,
1267                                     bool clear_all_soft_refs,
1268                                     size_t word_size) {
1269   assert_at_safepoint(true /* should_be_vm_thread */);
1270 
1271   if (GC_locker::check_active_before_gc()) {
1272     return false;
1273   }
1274 
1275   STWGCTimer* gc_timer = G1MarkSweep::gc_timer();
1276   gc_timer->register_gc_start();
1277 
1278   SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer();
1279   gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start());
1280 
1281   SvcGCMarker sgcm(SvcGCMarker::FULL);
1282   ResourceMark rm;
1283 
1284   print_heap_before_gc();
1285   trace_heap_before_gc(gc_tracer);
1286 
1287   size_t metadata_prev_used = MetaspaceAux::used_bytes();
1288 
1289   verify_region_sets_optional();
1290 
1291   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1292                            collector_policy()->should_clear_all_soft_refs();
1293 
1294   ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1295 
1296   {
1297     IsGCActiveMark x;
1298 
1299     // Timing
1300     assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant");
1301     gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps);
1302     TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
1303 
1304     {
1305       GCTraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, NULL, gc_tracer->gc_id());
1306       TraceCollectorStats tcs(g1mm()->full_collection_counters());
1307       TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1308 
1309       double start = os::elapsedTime();
1310       g1_policy()->record_full_collection_start();
1311 
1312       // Note: When we have a more flexible GC logging framework that
1313       // allows us to add optional attributes to a GC log record we
1314       // could consider timing and reporting how long we wait in the
1315       // following two methods.
1316       wait_while_free_regions_coming();
1317       // If we start the compaction before the CM threads finish
1318       // scanning the root regions we might trip them over as we'll
1319       // be moving objects / updating references. So let's wait until
1320       // they are done. By telling them to abort, they should complete
1321       // early.
1322       _cm->root_regions()->abort();
1323       _cm->root_regions()->wait_until_scan_finished();
1324       append_secondary_free_list_if_not_empty_with_lock();
1325 
1326       gc_prologue(true);
1327       increment_total_collections(true /* full gc */);
1328       increment_old_marking_cycles_started();
1329 
1330       assert(used() == recalculate_used(), "Should be equal");
1331 
1332       verify_before_gc();
1333 
1334       check_bitmaps("Full GC Start");
1335       pre_full_gc_dump(gc_timer);
1336 
1337       COMPILER2_PRESENT(DerivedPointerTable::clear());
1338 
1339       // Disable discovery and empty the discovered lists
1340       // for the CM ref processor.
1341       ref_processor_cm()->disable_discovery();
1342       ref_processor_cm()->abandon_partial_discovery();
1343       ref_processor_cm()->verify_no_references_recorded();
1344 
1345       // Abandon current iterations of concurrent marking and concurrent
1346       // refinement, if any are in progress. We have to do this before
1347       // wait_until_scan_finished() below.
1348       concurrent_mark()->abort();
1349 
1350       // Make sure we'll choose a new allocation region afterwards.
1351       _allocator->release_mutator_alloc_region();
1352       _allocator->abandon_gc_alloc_regions();
1353       g1_rem_set()->cleanupHRRS();
1354 
1355       // We should call this after we retire any currently active alloc
1356       // regions so that all the ALLOC / RETIRE events are generated
1357       // before the start GC event.
1358       _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1359 
1360       // We may have added regions to the current incremental collection
1361       // set between the last GC or pause and now. We need to clear the
1362       // incremental collection set and then start rebuilding it afresh
1363       // after this full GC.
1364       abandon_collection_set(g1_policy()->inc_cset_head());
1365       g1_policy()->clear_incremental_cset();
1366       g1_policy()->stop_incremental_cset_building();
1367 
1368       tear_down_region_sets(false /* free_list_only */);
1369       g1_policy()->set_gcs_are_young(true);
1370 
1371       // See the comments in g1CollectedHeap.hpp and
1372       // G1CollectedHeap::ref_processing_init() about
1373       // how reference processing currently works in G1.
1374 
1375       // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1376       ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1377 
1378       // Temporarily clear the STW ref processor's _is_alive_non_header field.
1379       ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1380 
1381       ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
1382       ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1383 
1384       // Do collection work
1385       {
1386         HandleMark hm;  // Discard invalid handles created during gc
1387         G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1388       }
1389 
1390       assert(num_free_regions() == 0, "we should not have added any free regions");
1391       rebuild_region_sets(false /* free_list_only */);
1392 
1393       // Enqueue any discovered reference objects that have
1394       // not been removed from the discovered lists.
1395       ref_processor_stw()->enqueue_discovered_references();
1396 
1397       COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1398 
1399       MemoryService::track_memory_usage();
1400 
1401       assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1402       ref_processor_stw()->verify_no_references_recorded();
1403 
1404       // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1405       ClassLoaderDataGraph::purge();
1406       MetaspaceAux::verify_metrics();
1407 
1408       // Note: since we've just done a full GC, concurrent
1409       // marking is no longer active. Therefore we need not
1410       // re-enable reference discovery for the CM ref processor.
1411       // That will be done at the start of the next marking cycle.
1412       assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1413       ref_processor_cm()->verify_no_references_recorded();
1414 
1415       reset_gc_time_stamp();
1416       // Since everything potentially moved, we will clear all remembered
1417       // sets, and clear all cards.  Later we will rebuild remembered
1418       // sets. We will also reset the GC time stamps of the regions.
1419       clear_rsets_post_compaction();
1420       check_gc_time_stamps();
1421 
1422       // Resize the heap if necessary.
1423       resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1424 
1425       if (_hr_printer.is_active()) {
1426         // We should do this after we potentially resize the heap so
1427         // that all the COMMIT / UNCOMMIT events are generated before
1428         // the end GC event.
1429 
1430         print_hrm_post_compaction();
1431         _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1432       }
1433 
1434       G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
1435       if (hot_card_cache->use_cache()) {
1436         hot_card_cache->reset_card_counts();
1437         hot_card_cache->reset_hot_cache();
1438       }
1439 
1440       // Rebuild remembered sets of all regions.
1441       if (G1CollectedHeap::use_parallel_gc_threads()) {
1442         uint n_workers =
1443           AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1444                                                   workers()->active_workers(),
1445                                                   Threads::number_of_non_daemon_threads());
1446         assert(UseDynamicNumberOfGCThreads ||
1447                n_workers == workers()->total_workers(),
1448                "If not dynamic should be using all the  workers");
1449         workers()->set_active_workers(n_workers);
1450         // Set parallel threads in the heap (_n_par_threads) only
1451         // before a parallel phase and always reset it to 0 after
1452         // the phase so that the number of parallel threads does
1453         // no get carried forward to a serial phase where there
1454         // may be code that is "possibly_parallel".
1455         set_par_threads(n_workers);
1456 
1457         ParRebuildRSTask rebuild_rs_task(this);
1458         assert(check_heap_region_claim_values(
1459                HeapRegion::InitialClaimValue), "sanity check");
1460         assert(UseDynamicNumberOfGCThreads ||
1461                workers()->active_workers() == workers()->total_workers(),
1462                "Unless dynamic should use total workers");
1463         // Use the most recent number of  active workers
1464         assert(workers()->active_workers() > 0,
1465                "Active workers not properly set");
1466         set_par_threads(workers()->active_workers());
1467         workers()->run_task(&rebuild_rs_task);
1468         set_par_threads(0);
1469         assert(check_heap_region_claim_values(
1470                HeapRegion::RebuildRSClaimValue), "sanity check");
1471         reset_heap_region_claim_values();
1472       } else {
1473         RebuildRSOutOfRegionClosure rebuild_rs(this);
1474         heap_region_iterate(&rebuild_rs);
1475       }
1476 
1477       // Rebuild the strong code root lists for each region
1478       rebuild_strong_code_roots();
1479 
1480       if (true) { // FIXME
1481         MetaspaceGC::compute_new_size();
1482       }
1483 
1484 #ifdef TRACESPINNING
1485       ParallelTaskTerminator::print_termination_counts();
1486 #endif
1487 
1488       // Discard all rset updates
1489       JavaThread::dirty_card_queue_set().abandon_logs();
1490       assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1491 
1492       _young_list->reset_sampled_info();
1493       // At this point there should be no regions in the
1494       // entire heap tagged as young.
1495       assert(check_young_list_empty(true /* check_heap */),
1496              "young list should be empty at this point");
1497 
1498       // Update the number of full collections that have been completed.
1499       increment_old_marking_cycles_completed(false /* concurrent */);
1500 
1501       _hrm.verify_optional();
1502       verify_region_sets_optional();
1503 
1504       verify_after_gc();
1505 
1506       // Clear the previous marking bitmap, if needed for bitmap verification.
1507       // Note we cannot do this when we clear the next marking bitmap in
1508       // ConcurrentMark::abort() above since VerifyDuringGC verifies the
1509       // objects marked during a full GC against the previous bitmap.
1510       // But we need to clear it before calling check_bitmaps below since
1511       // the full GC has compacted objects and updated TAMS but not updated
1512       // the prev bitmap.
1513       if (G1VerifyBitmaps) {
1514         ((CMBitMap*) concurrent_mark()->prevMarkBitMap())->clearAll();
1515       }
1516       check_bitmaps("Full GC End");
1517 
1518       // Start a new incremental collection set for the next pause
1519       assert(g1_policy()->collection_set() == NULL, "must be");
1520       g1_policy()->start_incremental_cset_building();
1521 
1522       clear_cset_fast_test();
1523 
1524       _allocator->init_mutator_alloc_region();
1525 
1526       double end = os::elapsedTime();
1527       g1_policy()->record_full_collection_end();
1528 
1529       if (G1Log::fine()) {
1530         g1_policy()->print_heap_transition();
1531       }
1532 
1533       // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1534       // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1535       // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1536       // before any GC notifications are raised.
1537       g1mm()->update_sizes();
1538 
1539       gc_epilogue(true);
1540     }
1541 
1542     if (G1Log::finer()) {
1543       g1_policy()->print_detailed_heap_transition(true /* full */);
1544     }
1545 
1546     print_heap_after_gc();
1547     trace_heap_after_gc(gc_tracer);
1548 
1549     post_full_gc_dump(gc_timer);
1550 
1551     gc_timer->register_gc_end();
1552     gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
1553   }
1554 
1555   return true;
1556 }
1557 
1558 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1559   // do_collection() will return whether it succeeded in performing
1560   // the GC. Currently, there is no facility on the
1561   // do_full_collection() API to notify the caller than the collection
1562   // did not succeed (e.g., because it was locked out by the GC
1563   // locker). So, right now, we'll ignore the return value.
1564   bool dummy = do_collection(true,                /* explicit_gc */
1565                              clear_all_soft_refs,
1566                              0                    /* word_size */);
1567 }
1568 
1569 // This code is mostly copied from TenuredGeneration.
1570 void
1571 G1CollectedHeap::
1572 resize_if_necessary_after_full_collection(size_t word_size) {
1573   // Include the current allocation, if any, and bytes that will be
1574   // pre-allocated to support collections, as "used".
1575   const size_t used_after_gc = used();
1576   const size_t capacity_after_gc = capacity();
1577   const size_t free_after_gc = capacity_after_gc - used_after_gc;
1578 
1579   // This is enforced in arguments.cpp.
1580   assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1581          "otherwise the code below doesn't make sense");
1582 
1583   // We don't have floating point command-line arguments
1584   const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1585   const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1586   const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1587   const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1588 
1589   const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1590   const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1591 
1592   // We have to be careful here as these two calculations can overflow
1593   // 32-bit size_t's.
1594   double used_after_gc_d = (double) used_after_gc;
1595   double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1596   double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1597 
1598   // Let's make sure that they are both under the max heap size, which
1599   // by default will make them fit into a size_t.
1600   double desired_capacity_upper_bound = (double) max_heap_size;
1601   minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1602                                     desired_capacity_upper_bound);
1603   maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1604                                     desired_capacity_upper_bound);
1605 
1606   // We can now safely turn them into size_t's.
1607   size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1608   size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1609 
1610   // This assert only makes sense here, before we adjust them
1611   // with respect to the min and max heap size.
1612   assert(minimum_desired_capacity <= maximum_desired_capacity,
1613          err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1614                  "maximum_desired_capacity = "SIZE_FORMAT,
1615                  minimum_desired_capacity, maximum_desired_capacity));
1616 
1617   // Should not be greater than the heap max size. No need to adjust
1618   // it with respect to the heap min size as it's a lower bound (i.e.,
1619   // we'll try to make the capacity larger than it, not smaller).
1620   minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1621   // Should not be less than the heap min size. No need to adjust it
1622   // with respect to the heap max size as it's an upper bound (i.e.,
1623   // we'll try to make the capacity smaller than it, not greater).
1624   maximum_desired_capacity =  MAX2(maximum_desired_capacity, min_heap_size);
1625 
1626   if (capacity_after_gc < minimum_desired_capacity) {
1627     // Don't expand unless it's significant
1628     size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1629     ergo_verbose4(ErgoHeapSizing,
1630                   "attempt heap expansion",
1631                   ergo_format_reason("capacity lower than "
1632                                      "min desired capacity after Full GC")
1633                   ergo_format_byte("capacity")
1634                   ergo_format_byte("occupancy")
1635                   ergo_format_byte_perc("min desired capacity"),
1636                   capacity_after_gc, used_after_gc,
1637                   minimum_desired_capacity, (double) MinHeapFreeRatio);
1638     expand(expand_bytes);
1639 
1640     // No expansion, now see if we want to shrink
1641   } else if (capacity_after_gc > maximum_desired_capacity) {
1642     // Capacity too large, compute shrinking size
1643     size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1644     ergo_verbose4(ErgoHeapSizing,
1645                   "attempt heap shrinking",
1646                   ergo_format_reason("capacity higher than "
1647                                      "max desired capacity after Full GC")
1648                   ergo_format_byte("capacity")
1649                   ergo_format_byte("occupancy")
1650                   ergo_format_byte_perc("max desired capacity"),
1651                   capacity_after_gc, used_after_gc,
1652                   maximum_desired_capacity, (double) MaxHeapFreeRatio);
1653     shrink(shrink_bytes);
1654   }
1655 }
1656 
1657 
1658 HeapWord*
1659 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1660                                            AllocationContext_t context,
1661                                            bool* succeeded) {
1662   assert_at_safepoint(true /* should_be_vm_thread */);
1663 
1664   *succeeded = true;
1665   // Let's attempt the allocation first.
1666   HeapWord* result =
1667     attempt_allocation_at_safepoint(word_size,
1668                                     context,
1669                                     false /* expect_null_mutator_alloc_region */);
1670   if (result != NULL) {
1671     assert(*succeeded, "sanity");
1672     return result;
1673   }
1674 
1675   // In a G1 heap, we're supposed to keep allocation from failing by
1676   // incremental pauses.  Therefore, at least for now, we'll favor
1677   // expansion over collection.  (This might change in the future if we can
1678   // do something smarter than full collection to satisfy a failed alloc.)
1679   result = expand_and_allocate(word_size, context);
1680   if (result != NULL) {
1681     assert(*succeeded, "sanity");
1682     return result;
1683   }
1684 
1685   // Expansion didn't work, we'll try to do a Full GC.
1686   bool gc_succeeded = do_collection(false, /* explicit_gc */
1687                                     false, /* clear_all_soft_refs */
1688                                     word_size);
1689   if (!gc_succeeded) {
1690     *succeeded = false;
1691     return NULL;
1692   }
1693 
1694   // Retry the allocation
1695   result = attempt_allocation_at_safepoint(word_size,
1696                                            context,
1697                                            true /* expect_null_mutator_alloc_region */);
1698   if (result != NULL) {
1699     assert(*succeeded, "sanity");
1700     return result;
1701   }
1702 
1703   // Then, try a Full GC that will collect all soft references.
1704   gc_succeeded = do_collection(false, /* explicit_gc */
1705                                true,  /* clear_all_soft_refs */
1706                                word_size);
1707   if (!gc_succeeded) {
1708     *succeeded = false;
1709     return NULL;
1710   }
1711 
1712   // Retry the allocation once more
1713   result = attempt_allocation_at_safepoint(word_size,
1714                                            context,
1715                                            true /* expect_null_mutator_alloc_region */);
1716   if (result != NULL) {
1717     assert(*succeeded, "sanity");
1718     return result;
1719   }
1720 
1721   assert(!collector_policy()->should_clear_all_soft_refs(),
1722          "Flag should have been handled and cleared prior to this point");
1723 
1724   // What else?  We might try synchronous finalization later.  If the total
1725   // space available is large enough for the allocation, then a more
1726   // complete compaction phase than we've tried so far might be
1727   // appropriate.
1728   assert(*succeeded, "sanity");
1729   return NULL;
1730 }
1731 
1732 // Attempting to expand the heap sufficiently
1733 // to support an allocation of the given "word_size".  If
1734 // successful, perform the allocation and return the address of the
1735 // allocated block, or else "NULL".
1736 
1737 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) {
1738   assert_at_safepoint(true /* should_be_vm_thread */);
1739 
1740   verify_region_sets_optional();
1741 
1742   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1743   ergo_verbose1(ErgoHeapSizing,
1744                 "attempt heap expansion",
1745                 ergo_format_reason("allocation request failed")
1746                 ergo_format_byte("allocation request"),
1747                 word_size * HeapWordSize);
1748   if (expand(expand_bytes)) {
1749     _hrm.verify_optional();
1750     verify_region_sets_optional();
1751     return attempt_allocation_at_safepoint(word_size,
1752                                            context,
1753                                            false /* expect_null_mutator_alloc_region */);
1754   }
1755   return NULL;
1756 }
1757 
1758 bool G1CollectedHeap::expand(size_t expand_bytes) {
1759   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1760   aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1761                                        HeapRegion::GrainBytes);
1762   ergo_verbose2(ErgoHeapSizing,
1763                 "expand the heap",
1764                 ergo_format_byte("requested expansion amount")
1765                 ergo_format_byte("attempted expansion amount"),
1766                 expand_bytes, aligned_expand_bytes);
1767 
1768   if (is_maximal_no_gc()) {
1769     ergo_verbose0(ErgoHeapSizing,
1770                       "did not expand the heap",
1771                       ergo_format_reason("heap already fully expanded"));
1772     return false;
1773   }
1774 
1775   uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1776   assert(regions_to_expand > 0, "Must expand by at least one region");
1777 
1778   uint expanded_by = _hrm.expand_by(regions_to_expand);
1779 
1780   if (expanded_by > 0) {
1781     size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1782     assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1783     g1_policy()->record_new_heap_size(num_regions());
1784   } else {
1785     ergo_verbose0(ErgoHeapSizing,
1786                   "did not expand the heap",
1787                   ergo_format_reason("heap expansion operation failed"));
1788     // The expansion of the virtual storage space was unsuccessful.
1789     // Let's see if it was because we ran out of swap.
1790     if (G1ExitOnExpansionFailure &&
1791         _hrm.available() >= regions_to_expand) {
1792       // We had head room...
1793       vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1794     }
1795   }
1796   return regions_to_expand > 0;
1797 }
1798 
1799 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1800   size_t aligned_shrink_bytes =
1801     ReservedSpace::page_align_size_down(shrink_bytes);
1802   aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1803                                          HeapRegion::GrainBytes);
1804   uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1805 
1806   uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1807   size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1808 
1809   ergo_verbose3(ErgoHeapSizing,
1810                 "shrink the heap",
1811                 ergo_format_byte("requested shrinking amount")
1812                 ergo_format_byte("aligned shrinking amount")
1813                 ergo_format_byte("attempted shrinking amount"),
1814                 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1815   if (num_regions_removed > 0) {
1816     g1_policy()->record_new_heap_size(num_regions());
1817   } else {
1818     ergo_verbose0(ErgoHeapSizing,
1819                   "did not shrink the heap",
1820                   ergo_format_reason("heap shrinking operation failed"));
1821   }
1822 }
1823 
1824 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1825   verify_region_sets_optional();
1826 
1827   // We should only reach here at the end of a Full GC which means we
1828   // should not not be holding to any GC alloc regions. The method
1829   // below will make sure of that and do any remaining clean up.
1830   _allocator->abandon_gc_alloc_regions();
1831 
1832   // Instead of tearing down / rebuilding the free lists here, we
1833   // could instead use the remove_all_pending() method on free_list to
1834   // remove only the ones that we need to remove.
1835   tear_down_region_sets(true /* free_list_only */);
1836   shrink_helper(shrink_bytes);
1837   rebuild_region_sets(true /* free_list_only */);
1838 
1839   _hrm.verify_optional();
1840   verify_region_sets_optional();
1841 }
1842 
1843 // Public methods.
1844 
1845 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1846 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1847 #endif // _MSC_VER
1848 
1849 
1850 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1851   SharedHeap(policy_),
1852   _g1_policy(policy_),
1853   _dirty_card_queue_set(false),
1854   _into_cset_dirty_card_queue_set(false),
1855   _is_alive_closure_cm(this),
1856   _is_alive_closure_stw(this),
1857   _ref_processor_cm(NULL),
1858   _ref_processor_stw(NULL),
1859   _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
1860   _bot_shared(NULL),
1861   _evac_failure_scan_stack(NULL),
1862   _mark_in_progress(false),
1863   _cg1r(NULL),
1864   _g1mm(NULL),
1865   _refine_cte_cl(NULL),
1866   _full_collection(false),
1867   _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1868   _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1869   _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1870   _humongous_is_live(),
1871   _has_humongous_reclaim_candidates(false),
1872   _free_regions_coming(false),
1873   _young_list(new YoungList(this)),
1874   _gc_time_stamp(0),
1875   _survivor_plab_stats(YoungPLABSize, PLABWeight),
1876   _old_plab_stats(OldPLABSize, PLABWeight),
1877   _expand_heap_after_alloc_failure(true),
1878   _surviving_young_words(NULL),
1879   _old_marking_cycles_started(0),
1880   _old_marking_cycles_completed(0),
1881   _concurrent_cycle_started(false),
1882   _heap_summary_sent(false),
1883   _in_cset_fast_test(),
1884   _dirty_cards_region_list(NULL),
1885   _worker_cset_start_region(NULL),
1886   _worker_cset_start_region_time_stamp(NULL),
1887   _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1888   _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
1889   _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1890   _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) {
1891 
1892   _g1h = this;
1893   if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
1894     vm_exit_during_initialization("Failed necessary allocation.");
1895   }
1896 
1897   _allocator = G1Allocator::create_allocator(_g1h);
1898   _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1899 
1900   int n_queues = MAX2((int)ParallelGCThreads, 1);
1901   _task_queues = new RefToScanQueueSet(n_queues);
1902 
1903   uint n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1904   assert(n_rem_sets > 0, "Invariant.");
1905 
1906   _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1907   _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC);
1908   _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1909 
1910   for (int i = 0; i < n_queues; i++) {
1911     RefToScanQueue* q = new RefToScanQueue();
1912     q->initialize();
1913     _task_queues->register_queue(i, q);
1914     ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1915   }
1916   clear_cset_start_regions();
1917 
1918   // Initialize the G1EvacuationFailureALot counters and flags.
1919   NOT_PRODUCT(reset_evacuation_should_fail();)
1920 
1921   guarantee(_task_queues != NULL, "task_queues allocation failure.");
1922 }
1923 
1924 jint G1CollectedHeap::initialize() {
1925   CollectedHeap::pre_initialize();
1926   os::enable_vtime();
1927 
1928   G1Log::init();
1929 
1930   // Necessary to satisfy locking discipline assertions.
1931 
1932   MutexLocker x(Heap_lock);
1933 
1934   // We have to initialize the printer before committing the heap, as
1935   // it will be used then.
1936   _hr_printer.set_active(G1PrintHeapRegions);
1937 
1938   // While there are no constraints in the GC code that HeapWordSize
1939   // be any particular value, there are multiple other areas in the
1940   // system which believe this to be true (e.g. oop->object_size in some
1941   // cases incorrectly returns the size in wordSize units rather than
1942   // HeapWordSize).
1943   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1944 
1945   size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1946   size_t max_byte_size = collector_policy()->max_heap_byte_size();
1947   size_t heap_alignment = collector_policy()->heap_alignment();
1948 
1949   // Ensure that the sizes are properly aligned.
1950   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1951   Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1952   Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1953 
1954   _refine_cte_cl = new RefineCardTableEntryClosure();
1955 
1956   _cg1r = new ConcurrentG1Refine(this, _refine_cte_cl);
1957 
1958   // Reserve the maximum.
1959 
1960   // When compressed oops are enabled, the preferred heap base
1961   // is calculated by subtracting the requested size from the
1962   // 32Gb boundary and using the result as the base address for
1963   // heap reservation. If the requested size is not aligned to
1964   // HeapRegion::GrainBytes (i.e. the alignment that is passed
1965   // into the ReservedHeapSpace constructor) then the actual
1966   // base of the reserved heap may end up differing from the
1967   // address that was requested (i.e. the preferred heap base).
1968   // If this happens then we could end up using a non-optimal
1969   // compressed oops mode.
1970 
1971   ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1972                                                  heap_alignment);
1973 
1974   initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
1975 
1976   // Create the gen rem set (and barrier set) for the entire reserved region.
1977   _rem_set = collector_policy()->create_rem_set(reserved_region(), 2);
1978   set_barrier_set(rem_set()->bs());
1979   if (!barrier_set()->is_a(BarrierSet::G1SATBCTLogging)) {
1980     vm_exit_during_initialization("G1 requires a G1SATBLoggingCardTableModRefBS");
1981     return JNI_ENOMEM;
1982   }
1983 
1984   // Also create a G1 rem set.
1985   _g1_rem_set = new G1RemSet(this, g1_barrier_set());
1986 
1987   // Carve out the G1 part of the heap.
1988 
1989   ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1990   G1RegionToSpaceMapper* heap_storage =
1991     G1RegionToSpaceMapper::create_mapper(g1_rs,
1992                                          UseLargePages ? os::large_page_size() : os::vm_page_size(),
1993                                          HeapRegion::GrainBytes,
1994                                          1,
1995                                          mtJavaHeap);
1996   heap_storage->set_mapping_changed_listener(&_listener);
1997 
1998   // Reserve space for the block offset table. We do not support automatic uncommit
1999   // for the card table at this time. BOT only.
2000   ReservedSpace bot_rs(G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize));
2001   G1RegionToSpaceMapper* bot_storage =
2002     G1RegionToSpaceMapper::create_mapper(bot_rs,
2003                                          os::vm_page_size(),
2004                                          HeapRegion::GrainBytes,
2005                                          G1BlockOffsetSharedArray::N_bytes,
2006                                          mtGC);
2007 
2008   ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize));
2009   G1RegionToSpaceMapper* cardtable_storage =
2010     G1RegionToSpaceMapper::create_mapper(cardtable_rs,
2011                                          os::vm_page_size(),
2012                                          HeapRegion::GrainBytes,
2013                                          G1BlockOffsetSharedArray::N_bytes,
2014                                          mtGC);
2015 
2016   // Reserve space for the card counts table.
2017   ReservedSpace card_counts_rs(G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize));
2018   G1RegionToSpaceMapper* card_counts_storage =
2019     G1RegionToSpaceMapper::create_mapper(card_counts_rs,
2020                                          os::vm_page_size(),
2021                                          HeapRegion::GrainBytes,
2022                                          G1BlockOffsetSharedArray::N_bytes,
2023                                          mtGC);
2024 
2025   // Reserve space for prev and next bitmap.
2026   size_t bitmap_size = CMBitMap::compute_size(g1_rs.size());
2027 
2028   ReservedSpace prev_bitmap_rs(ReservedSpace::allocation_align_size_up(bitmap_size));
2029   G1RegionToSpaceMapper* prev_bitmap_storage =
2030     G1RegionToSpaceMapper::create_mapper(prev_bitmap_rs,
2031                                          os::vm_page_size(),
2032                                          HeapRegion::GrainBytes,
2033                                          CMBitMap::mark_distance(),
2034                                          mtGC);
2035 
2036   ReservedSpace next_bitmap_rs(ReservedSpace::allocation_align_size_up(bitmap_size));
2037   G1RegionToSpaceMapper* next_bitmap_storage =
2038     G1RegionToSpaceMapper::create_mapper(next_bitmap_rs,
2039                                          os::vm_page_size(),
2040                                          HeapRegion::GrainBytes,
2041                                          CMBitMap::mark_distance(),
2042                                          mtGC);
2043 
2044   _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
2045   g1_barrier_set()->initialize(cardtable_storage);
2046    // Do later initialization work for concurrent refinement.
2047   _cg1r->init(card_counts_storage);
2048 
2049   // 6843694 - ensure that the maximum region index can fit
2050   // in the remembered set structures.
2051   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
2052   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
2053 
2054   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
2055   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
2056   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
2057             "too many cards per region");
2058 
2059   FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
2060 
2061   _bot_shared = new G1BlockOffsetSharedArray(reserved_region(), bot_storage);
2062 
2063   _g1h = this;
2064 
2065   _in_cset_fast_test.initialize(_hrm.reserved().start(), _hrm.reserved().end(), HeapRegion::GrainBytes);
2066   _humongous_is_live.initialize(_hrm.reserved().start(), _hrm.reserved().end(), HeapRegion::GrainBytes);
2067 
2068   // Create the ConcurrentMark data structure and thread.
2069   // (Must do this late, so that "max_regions" is defined.)
2070   _cm = new ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
2071   if (_cm == NULL || !_cm->completed_initialization()) {
2072     vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark");
2073     return JNI_ENOMEM;
2074   }
2075   _cmThread = _cm->cmThread();
2076 
2077   // Initialize the from_card cache structure of HeapRegionRemSet.
2078   HeapRegionRemSet::init_heap(max_regions());
2079 
2080   // Now expand into the initial heap size.
2081   if (!expand(init_byte_size)) {
2082     vm_shutdown_during_initialization("Failed to allocate initial heap.");
2083     return JNI_ENOMEM;
2084   }
2085 
2086   // Perform any initialization actions delegated to the policy.
2087   g1_policy()->init();
2088 
2089   JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
2090                                                SATB_Q_FL_lock,
2091                                                G1SATBProcessCompletedThreshold,
2092                                                Shared_SATB_Q_lock);
2093 
2094   JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl,
2095                                                 DirtyCardQ_CBL_mon,
2096                                                 DirtyCardQ_FL_lock,
2097                                                 concurrent_g1_refine()->yellow_zone(),
2098                                                 concurrent_g1_refine()->red_zone(),
2099                                                 Shared_DirtyCardQ_lock);
2100 
2101   dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code
2102                                     DirtyCardQ_CBL_mon,
2103                                     DirtyCardQ_FL_lock,
2104                                     -1, // never trigger processing
2105                                     -1, // no limit on length
2106                                     Shared_DirtyCardQ_lock,
2107                                     &JavaThread::dirty_card_queue_set());
2108 
2109   // Initialize the card queue set used to hold cards containing
2110   // references into the collection set.
2111   _into_cset_dirty_card_queue_set.initialize(NULL, // Should never be called by the Java code
2112                                              DirtyCardQ_CBL_mon,
2113                                              DirtyCardQ_FL_lock,
2114                                              -1, // never trigger processing
2115                                              -1, // no limit on length
2116                                              Shared_DirtyCardQ_lock,
2117                                              &JavaThread::dirty_card_queue_set());
2118 
2119   // In case we're keeping closure specialization stats, initialize those
2120   // counts and that mechanism.
2121   SpecializationStats::clear();
2122 
2123   // Here we allocate the dummy HeapRegion that is required by the
2124   // G1AllocRegion class.
2125   HeapRegion* dummy_region = _hrm.get_dummy_region();
2126 
2127   // We'll re-use the same region whether the alloc region will
2128   // require BOT updates or not and, if it doesn't, then a non-young
2129   // region will complain that it cannot support allocations without
2130   // BOT updates. So we'll tag the dummy region as eden to avoid that.
2131   dummy_region->set_eden();
2132   // Make sure it's full.
2133   dummy_region->set_top(dummy_region->end());
2134   G1AllocRegion::setup(this, dummy_region);
2135 
2136   _allocator->init_mutator_alloc_region();
2137 
2138   // Do create of the monitoring and management support so that
2139   // values in the heap have been properly initialized.
2140   _g1mm = new G1MonitoringSupport(this);
2141 
2142   G1StringDedup::initialize();
2143 
2144   return JNI_OK;
2145 }
2146 
2147 void G1CollectedHeap::stop() {
2148   // Stop all concurrent threads. We do this to make sure these threads
2149   // do not continue to execute and access resources (e.g. gclog_or_tty)
2150   // that are destroyed during shutdown.
2151   _cg1r->stop();
2152   _cmThread->stop();
2153   if (G1StringDedup::is_enabled()) {
2154     G1StringDedup::stop();
2155   }
2156 }
2157 
2158 void G1CollectedHeap::clear_humongous_is_live_table() {
2159   guarantee(G1ReclaimDeadHumongousObjectsAtYoungGC, "Should only be called if true");
2160   _humongous_is_live.clear();
2161 }
2162 
2163 size_t G1CollectedHeap::conservative_max_heap_alignment() {
2164   return HeapRegion::max_region_size();
2165 }
2166 
2167 void G1CollectedHeap::ref_processing_init() {
2168   // Reference processing in G1 currently works as follows:
2169   //
2170   // * There are two reference processor instances. One is
2171   //   used to record and process discovered references
2172   //   during concurrent marking; the other is used to
2173   //   record and process references during STW pauses
2174   //   (both full and incremental).
2175   // * Both ref processors need to 'span' the entire heap as
2176   //   the regions in the collection set may be dotted around.
2177   //
2178   // * For the concurrent marking ref processor:
2179   //   * Reference discovery is enabled at initial marking.
2180   //   * Reference discovery is disabled and the discovered
2181   //     references processed etc during remarking.
2182   //   * Reference discovery is MT (see below).
2183   //   * Reference discovery requires a barrier (see below).
2184   //   * Reference processing may or may not be MT
2185   //     (depending on the value of ParallelRefProcEnabled
2186   //     and ParallelGCThreads).
2187   //   * A full GC disables reference discovery by the CM
2188   //     ref processor and abandons any entries on it's
2189   //     discovered lists.
2190   //
2191   // * For the STW processor:
2192   //   * Non MT discovery is enabled at the start of a full GC.
2193   //   * Processing and enqueueing during a full GC is non-MT.
2194   //   * During a full GC, references are processed after marking.
2195   //
2196   //   * Discovery (may or may not be MT) is enabled at the start
2197   //     of an incremental evacuation pause.
2198   //   * References are processed near the end of a STW evacuation pause.
2199   //   * For both types of GC:
2200   //     * Discovery is atomic - i.e. not concurrent.
2201   //     * Reference discovery will not need a barrier.
2202 
2203   SharedHeap::ref_processing_init();
2204   MemRegion mr = reserved_region();
2205 
2206   // Concurrent Mark ref processor
2207   _ref_processor_cm =
2208     new ReferenceProcessor(mr,    // span
2209                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2210                                 // mt processing
2211                            (int) ParallelGCThreads,
2212                                 // degree of mt processing
2213                            (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2214                                 // mt discovery
2215                            (int) MAX2(ParallelGCThreads, ConcGCThreads),
2216                                 // degree of mt discovery
2217                            false,
2218                                 // Reference discovery is not atomic
2219                            &_is_alive_closure_cm);
2220                                 // is alive closure
2221                                 // (for efficiency/performance)
2222 
2223   // STW ref processor
2224   _ref_processor_stw =
2225     new ReferenceProcessor(mr,    // span
2226                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2227                                 // mt processing
2228                            MAX2((int)ParallelGCThreads, 1),
2229                                 // degree of mt processing
2230                            (ParallelGCThreads > 1),
2231                                 // mt discovery
2232                            MAX2((int)ParallelGCThreads, 1),
2233                                 // degree of mt discovery
2234                            true,
2235                                 // Reference discovery is atomic
2236                            &_is_alive_closure_stw);
2237                                 // is alive closure
2238                                 // (for efficiency/performance)
2239 }
2240 
2241 size_t G1CollectedHeap::capacity() const {
2242   return _hrm.length() * HeapRegion::GrainBytes;
2243 }
2244 
2245 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2246   assert(!hr->is_continues_humongous(), "pre-condition");
2247   hr->reset_gc_time_stamp();
2248   if (hr->is_starts_humongous()) {
2249     uint first_index = hr->hrm_index() + 1;
2250     uint last_index = hr->last_hc_index();
2251     for (uint i = first_index; i < last_index; i += 1) {
2252       HeapRegion* chr = region_at(i);
2253       assert(chr->is_continues_humongous(), "sanity");
2254       chr->reset_gc_time_stamp();
2255     }
2256   }
2257 }
2258 
2259 #ifndef PRODUCT
2260 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2261 private:
2262   unsigned _gc_time_stamp;
2263   bool _failures;
2264 
2265 public:
2266   CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2267     _gc_time_stamp(gc_time_stamp), _failures(false) { }
2268 
2269   virtual bool doHeapRegion(HeapRegion* hr) {
2270     unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2271     if (_gc_time_stamp != region_gc_time_stamp) {
2272       gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, "
2273                              "expected %d", HR_FORMAT_PARAMS(hr),
2274                              region_gc_time_stamp, _gc_time_stamp);
2275       _failures = true;
2276     }
2277     return false;
2278   }
2279 
2280   bool failures() { return _failures; }
2281 };
2282 
2283 void G1CollectedHeap::check_gc_time_stamps() {
2284   CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2285   heap_region_iterate(&cl);
2286   guarantee(!cl.failures(), "all GC time stamps should have been reset");
2287 }
2288 #endif // PRODUCT
2289 
2290 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2291                                                  DirtyCardQueue* into_cset_dcq,
2292                                                  bool concurrent,
2293                                                  uint worker_i) {
2294   // Clean cards in the hot card cache
2295   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
2296   hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq);
2297 
2298   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2299   int n_completed_buffers = 0;
2300   while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2301     n_completed_buffers++;
2302   }
2303   g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers);
2304   dcqs.clear_n_completed_buffers();
2305   assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2306 }
2307 
2308 
2309 // Computes the sum of the storage used by the various regions.
2310 size_t G1CollectedHeap::used() const {
2311   return _allocator->used();
2312 }
2313 
2314 size_t G1CollectedHeap::used_unlocked() const {
2315   return _allocator->used_unlocked();
2316 }
2317 
2318 class SumUsedClosure: public HeapRegionClosure {
2319   size_t _used;
2320 public:
2321   SumUsedClosure() : _used(0) {}
2322   bool doHeapRegion(HeapRegion* r) {
2323     if (!r->is_continues_humongous()) {
2324       _used += r->used();
2325     }
2326     return false;
2327   }
2328   size_t result() { return _used; }
2329 };
2330 
2331 size_t G1CollectedHeap::recalculate_used() const {
2332   double recalculate_used_start = os::elapsedTime();
2333 
2334   SumUsedClosure blk;
2335   heap_region_iterate(&blk);
2336 
2337   g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2338   return blk.result();
2339 }
2340 
2341 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2342   switch (cause) {
2343     case GCCause::_gc_locker:               return GCLockerInvokesConcurrent;
2344     case GCCause::_java_lang_system_gc:     return ExplicitGCInvokesConcurrent;
2345     case GCCause::_g1_humongous_allocation: return true;
2346     default:                                return false;
2347   }
2348 }
2349 
2350 #ifndef PRODUCT
2351 void G1CollectedHeap::allocate_dummy_regions() {
2352   // Let's fill up most of the region
2353   size_t word_size = HeapRegion::GrainWords - 1024;
2354   // And as a result the region we'll allocate will be humongous.
2355   guarantee(is_humongous(word_size), "sanity");
2356 
2357   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2358     // Let's use the existing mechanism for the allocation
2359     HeapWord* dummy_obj = humongous_obj_allocate(word_size,
2360                                                  AllocationContext::system());
2361     if (dummy_obj != NULL) {
2362       MemRegion mr(dummy_obj, word_size);
2363       CollectedHeap::fill_with_object(mr);
2364     } else {
2365       // If we can't allocate once, we probably cannot allocate
2366       // again. Let's get out of the loop.
2367       break;
2368     }
2369   }
2370 }
2371 #endif // !PRODUCT
2372 
2373 void G1CollectedHeap::increment_old_marking_cycles_started() {
2374   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2375     _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2376     err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2377     _old_marking_cycles_started, _old_marking_cycles_completed));
2378 
2379   _old_marking_cycles_started++;
2380 }
2381 
2382 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2383   MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2384 
2385   // We assume that if concurrent == true, then the caller is a
2386   // concurrent thread that was joined the Suspendible Thread
2387   // Set. If there's ever a cheap way to check this, we should add an
2388   // assert here.
2389 
2390   // Given that this method is called at the end of a Full GC or of a
2391   // concurrent cycle, and those can be nested (i.e., a Full GC can
2392   // interrupt a concurrent cycle), the number of full collections
2393   // completed should be either one (in the case where there was no
2394   // nesting) or two (when a Full GC interrupted a concurrent cycle)
2395   // behind the number of full collections started.
2396 
2397   // This is the case for the inner caller, i.e. a Full GC.
2398   assert(concurrent ||
2399          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2400          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2401          err_msg("for inner caller (Full GC): _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   // This is the case for the outer caller, i.e. the concurrent cycle.
2406   assert(!concurrent ||
2407          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2408          err_msg("for outer caller (concurrent cycle): "
2409                  "_old_marking_cycles_started = %u "
2410                  "is inconsistent with _old_marking_cycles_completed = %u",
2411                  _old_marking_cycles_started, _old_marking_cycles_completed));
2412 
2413   _old_marking_cycles_completed += 1;
2414 
2415   // We need to clear the "in_progress" flag in the CM thread before
2416   // we wake up any waiters (especially when ExplicitInvokesConcurrent
2417   // is set) so that if a waiter requests another System.gc() it doesn't
2418   // incorrectly see that a marking cycle is still in progress.
2419   if (concurrent) {
2420     _cmThread->clear_in_progress();
2421   }
2422 
2423   // This notify_all() will ensure that a thread that called
2424   // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2425   // and it's waiting for a full GC to finish will be woken up. It is
2426   // waiting in VM_G1IncCollectionPause::doit_epilogue().
2427   FullGCCount_lock->notify_all();
2428 }
2429 
2430 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) {
2431   _concurrent_cycle_started = true;
2432   _gc_timer_cm->register_gc_start(start_time);
2433 
2434   _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start());
2435   trace_heap_before_gc(_gc_tracer_cm);
2436 }
2437 
2438 void G1CollectedHeap::register_concurrent_cycle_end() {
2439   if (_concurrent_cycle_started) {
2440     if (_cm->has_aborted()) {
2441       _gc_tracer_cm->report_concurrent_mode_failure();
2442     }
2443 
2444     _gc_timer_cm->register_gc_end();
2445     _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
2446 
2447     // Clear state variables to prepare for the next concurrent cycle.
2448     _concurrent_cycle_started = false;
2449     _heap_summary_sent = false;
2450   }
2451 }
2452 
2453 void G1CollectedHeap::trace_heap_after_concurrent_cycle() {
2454   if (_concurrent_cycle_started) {
2455     // This function can be called when:
2456     //  the cleanup pause is run
2457     //  the concurrent cycle is aborted before the cleanup pause.
2458     //  the concurrent cycle is aborted after the cleanup pause,
2459     //   but before the concurrent cycle end has been registered.
2460     // Make sure that we only send the heap information once.
2461     if (!_heap_summary_sent) {
2462       trace_heap_after_gc(_gc_tracer_cm);
2463       _heap_summary_sent = true;
2464     }
2465   }
2466 }
2467 
2468 G1YCType G1CollectedHeap::yc_type() {
2469   bool is_young = g1_policy()->gcs_are_young();
2470   bool is_initial_mark = g1_policy()->during_initial_mark_pause();
2471   bool is_during_mark = mark_in_progress();
2472 
2473   if (is_initial_mark) {
2474     return InitialMark;
2475   } else if (is_during_mark) {
2476     return DuringMark;
2477   } else if (is_young) {
2478     return Normal;
2479   } else {
2480     return Mixed;
2481   }
2482 }
2483 
2484 void G1CollectedHeap::collect(GCCause::Cause cause) {
2485   assert_heap_not_locked();
2486 
2487   unsigned int gc_count_before;
2488   unsigned int old_marking_count_before;
2489   bool retry_gc;
2490 
2491   do {
2492     retry_gc = false;
2493 
2494     {
2495       MutexLocker ml(Heap_lock);
2496 
2497       // Read the GC count while holding the Heap_lock
2498       gc_count_before = total_collections();
2499       old_marking_count_before = _old_marking_cycles_started;
2500     }
2501 
2502     if (should_do_concurrent_full_gc(cause)) {
2503       // Schedule an initial-mark evacuation pause that will start a
2504       // concurrent cycle. We're setting word_size to 0 which means that
2505       // we are not requesting a post-GC allocation.
2506       VM_G1IncCollectionPause op(gc_count_before,
2507                                  0,     /* word_size */
2508                                  true,  /* should_initiate_conc_mark */
2509                                  g1_policy()->max_pause_time_ms(),
2510                                  cause);
2511       op.set_allocation_context(AllocationContext::current());
2512 
2513       VMThread::execute(&op);
2514       if (!op.pause_succeeded()) {
2515         if (old_marking_count_before == _old_marking_cycles_started) {
2516           retry_gc = op.should_retry_gc();
2517         } else {
2518           // A Full GC happened while we were trying to schedule the
2519           // initial-mark GC. No point in starting a new cycle given
2520           // that the whole heap was collected anyway.
2521         }
2522 
2523         if (retry_gc) {
2524           if (GC_locker::is_active_and_needs_gc()) {
2525             GC_locker::stall_until_clear();
2526           }
2527         }
2528       }
2529     } else {
2530       if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2531           DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2532 
2533         // Schedule a standard evacuation pause. We're setting word_size
2534         // to 0 which means that we are not requesting a post-GC allocation.
2535         VM_G1IncCollectionPause op(gc_count_before,
2536                                    0,     /* word_size */
2537                                    false, /* should_initiate_conc_mark */
2538                                    g1_policy()->max_pause_time_ms(),
2539                                    cause);
2540         VMThread::execute(&op);
2541       } else {
2542         // Schedule a Full GC.
2543         VM_G1CollectFull op(gc_count_before, old_marking_count_before, cause);
2544         VMThread::execute(&op);
2545       }
2546     }
2547   } while (retry_gc);
2548 }
2549 
2550 bool G1CollectedHeap::is_in(const void* p) const {
2551   if (_hrm.reserved().contains(p)) {
2552     // Given that we know that p is in the reserved space,
2553     // heap_region_containing_raw() should successfully
2554     // return the containing region.
2555     HeapRegion* hr = heap_region_containing_raw(p);
2556     return hr->is_in(p);
2557   } else {
2558     return false;
2559   }
2560 }
2561 
2562 #ifdef ASSERT
2563 bool G1CollectedHeap::is_in_exact(const void* p) const {
2564   bool contains = reserved_region().contains(p);
2565   bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2566   if (contains && available) {
2567     return true;
2568   } else {
2569     return false;
2570   }
2571 }
2572 #endif
2573 
2574 // Iteration functions.
2575 
2576 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion.
2577 
2578 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2579   ExtendedOopClosure* _cl;
2580 public:
2581   IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {}
2582   bool doHeapRegion(HeapRegion* r) {
2583     if (!r->is_continues_humongous()) {
2584       r->oop_iterate(_cl);
2585     }
2586     return false;
2587   }
2588 };
2589 
2590 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) {
2591   IterateOopClosureRegionClosure blk(cl);
2592   heap_region_iterate(&blk);
2593 }
2594 
2595 // Iterates an ObjectClosure over all objects within a HeapRegion.
2596 
2597 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2598   ObjectClosure* _cl;
2599 public:
2600   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2601   bool doHeapRegion(HeapRegion* r) {
2602     if (!r->is_continues_humongous()) {
2603       r->object_iterate(_cl);
2604     }
2605     return false;
2606   }
2607 };
2608 
2609 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2610   IterateObjectClosureRegionClosure blk(cl);
2611   heap_region_iterate(&blk);
2612 }
2613 
2614 // Calls a SpaceClosure on a HeapRegion.
2615 
2616 class SpaceClosureRegionClosure: public HeapRegionClosure {
2617   SpaceClosure* _cl;
2618 public:
2619   SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2620   bool doHeapRegion(HeapRegion* r) {
2621     _cl->do_space(r);
2622     return false;
2623   }
2624 };
2625 
2626 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2627   SpaceClosureRegionClosure blk(cl);
2628   heap_region_iterate(&blk);
2629 }
2630 
2631 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2632   _hrm.iterate(cl);
2633 }
2634 
2635 void
2636 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
2637                                                  uint worker_id,
2638                                                  uint num_workers,
2639                                                  jint claim_value) const {
2640   _hrm.par_iterate(cl, worker_id, num_workers, claim_value);
2641 }
2642 
2643 class ResetClaimValuesClosure: public HeapRegionClosure {
2644 public:
2645   bool doHeapRegion(HeapRegion* r) {
2646     r->set_claim_value(HeapRegion::InitialClaimValue);
2647     return false;
2648   }
2649 };
2650 
2651 void G1CollectedHeap::reset_heap_region_claim_values() {
2652   ResetClaimValuesClosure blk;
2653   heap_region_iterate(&blk);
2654 }
2655 
2656 void G1CollectedHeap::reset_cset_heap_region_claim_values() {
2657   ResetClaimValuesClosure blk;
2658   collection_set_iterate(&blk);
2659 }
2660 
2661 #ifdef ASSERT
2662 // This checks whether all regions in the heap have the correct claim
2663 // value. I also piggy-backed on this a check to ensure that the
2664 // humongous_start_region() information on "continues humongous"
2665 // regions is correct.
2666 
2667 class CheckClaimValuesClosure : public HeapRegionClosure {
2668 private:
2669   jint _claim_value;
2670   uint _failures;
2671   HeapRegion* _sh_region;
2672 
2673 public:
2674   CheckClaimValuesClosure(jint claim_value) :
2675     _claim_value(claim_value), _failures(0), _sh_region(NULL) { }
2676   bool doHeapRegion(HeapRegion* r) {
2677     if (r->claim_value() != _claim_value) {
2678       gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2679                              "claim value = %d, should be %d",
2680                              HR_FORMAT_PARAMS(r),
2681                              r->claim_value(), _claim_value);
2682       ++_failures;
2683     }
2684     if (!r->is_humongous()) {
2685       _sh_region = NULL;
2686     } else if (r->is_starts_humongous()) {
2687       _sh_region = r;
2688     } else if (r->is_continues_humongous()) {
2689       if (r->humongous_start_region() != _sh_region) {
2690         gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2691                                "HS = "PTR_FORMAT", should be "PTR_FORMAT,
2692                                HR_FORMAT_PARAMS(r),
2693                                r->humongous_start_region(),
2694                                _sh_region);
2695         ++_failures;
2696       }
2697     }
2698     return false;
2699   }
2700   uint failures() { return _failures; }
2701 };
2702 
2703 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
2704   CheckClaimValuesClosure cl(claim_value);
2705   heap_region_iterate(&cl);
2706   return cl.failures() == 0;
2707 }
2708 
2709 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure {
2710 private:
2711   jint _claim_value;
2712   uint _failures;
2713 
2714 public:
2715   CheckClaimValuesInCSetHRClosure(jint claim_value) :
2716     _claim_value(claim_value), _failures(0) { }
2717 
2718   uint failures() { return _failures; }
2719 
2720   bool doHeapRegion(HeapRegion* hr) {
2721     assert(hr->in_collection_set(), "how?");
2722     assert(!hr->is_humongous(), "H-region in CSet");
2723     if (hr->claim_value() != _claim_value) {
2724       gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", "
2725                              "claim value = %d, should be %d",
2726                              HR_FORMAT_PARAMS(hr),
2727                              hr->claim_value(), _claim_value);
2728       _failures += 1;
2729     }
2730     return false;
2731   }
2732 };
2733 
2734 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) {
2735   CheckClaimValuesInCSetHRClosure cl(claim_value);
2736   collection_set_iterate(&cl);
2737   return cl.failures() == 0;
2738 }
2739 #endif // ASSERT
2740 
2741 // Clear the cached CSet starting regions and (more importantly)
2742 // the time stamps. Called when we reset the GC time stamp.
2743 void G1CollectedHeap::clear_cset_start_regions() {
2744   assert(_worker_cset_start_region != NULL, "sanity");
2745   assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2746 
2747   int n_queues = MAX2((int)ParallelGCThreads, 1);
2748   for (int i = 0; i < n_queues; i++) {
2749     _worker_cset_start_region[i] = NULL;
2750     _worker_cset_start_region_time_stamp[i] = 0;
2751   }
2752 }
2753 
2754 // Given the id of a worker, obtain or calculate a suitable
2755 // starting region for iterating over the current collection set.
2756 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) {
2757   assert(get_gc_time_stamp() > 0, "should have been updated by now");
2758 
2759   HeapRegion* result = NULL;
2760   unsigned gc_time_stamp = get_gc_time_stamp();
2761 
2762   if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2763     // Cached starting region for current worker was set
2764     // during the current pause - so it's valid.
2765     // Note: the cached starting heap region may be NULL
2766     // (when the collection set is empty).
2767     result = _worker_cset_start_region[worker_i];
2768     assert(result == NULL || result->in_collection_set(), "sanity");
2769     return result;
2770   }
2771 
2772   // The cached entry was not valid so let's calculate
2773   // a suitable starting heap region for this worker.
2774 
2775   // We want the parallel threads to start their collection
2776   // set iteration at different collection set regions to
2777   // avoid contention.
2778   // If we have:
2779   //          n collection set regions
2780   //          p threads
2781   // Then thread t will start at region floor ((t * n) / p)
2782 
2783   result = g1_policy()->collection_set();
2784   if (G1CollectedHeap::use_parallel_gc_threads()) {
2785     uint cs_size = g1_policy()->cset_region_length();
2786     uint active_workers = workers()->active_workers();
2787     assert(UseDynamicNumberOfGCThreads ||
2788              active_workers == workers()->total_workers(),
2789              "Unless dynamic should use total workers");
2790 
2791     uint end_ind   = (cs_size * worker_i) / active_workers;
2792     uint start_ind = 0;
2793 
2794     if (worker_i > 0 &&
2795         _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2796       // Previous workers starting region is valid
2797       // so let's iterate from there
2798       start_ind = (cs_size * (worker_i - 1)) / active_workers;
2799       result = _worker_cset_start_region[worker_i - 1];
2800     }
2801 
2802     for (uint i = start_ind; i < end_ind; i++) {
2803       result = result->next_in_collection_set();
2804     }
2805   }
2806 
2807   // Note: the calculated starting heap region may be NULL
2808   // (when the collection set is empty).
2809   assert(result == NULL || result->in_collection_set(), "sanity");
2810   assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2811          "should be updated only once per pause");
2812   _worker_cset_start_region[worker_i] = result;
2813   OrderAccess::storestore();
2814   _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2815   return result;
2816 }
2817 
2818 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2819   HeapRegion* r = g1_policy()->collection_set();
2820   while (r != NULL) {
2821     HeapRegion* next = r->next_in_collection_set();
2822     if (cl->doHeapRegion(r)) {
2823       cl->incomplete();
2824       return;
2825     }
2826     r = next;
2827   }
2828 }
2829 
2830 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2831                                                   HeapRegionClosure *cl) {
2832   if (r == NULL) {
2833     // The CSet is empty so there's nothing to do.
2834     return;
2835   }
2836 
2837   assert(r->in_collection_set(),
2838          "Start region must be a member of the collection set.");
2839   HeapRegion* cur = r;
2840   while (cur != NULL) {
2841     HeapRegion* next = cur->next_in_collection_set();
2842     if (cl->doHeapRegion(cur) && false) {
2843       cl->incomplete();
2844       return;
2845     }
2846     cur = next;
2847   }
2848   cur = g1_policy()->collection_set();
2849   while (cur != r) {
2850     HeapRegion* next = cur->next_in_collection_set();
2851     if (cl->doHeapRegion(cur) && false) {
2852       cl->incomplete();
2853       return;
2854     }
2855     cur = next;
2856   }
2857 }
2858 
2859 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const {
2860   HeapRegion* result = _hrm.next_region_in_heap(from);
2861   while (result != NULL && result->is_humongous()) {
2862     result = _hrm.next_region_in_heap(result);
2863   }
2864   return result;
2865 }
2866 
2867 Space* G1CollectedHeap::space_containing(const void* addr) const {
2868   return heap_region_containing(addr);
2869 }
2870 
2871 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2872   Space* sp = space_containing(addr);
2873   return sp->block_start(addr);
2874 }
2875 
2876 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2877   Space* sp = space_containing(addr);
2878   return sp->block_size(addr);
2879 }
2880 
2881 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2882   Space* sp = space_containing(addr);
2883   return sp->block_is_obj(addr);
2884 }
2885 
2886 bool G1CollectedHeap::supports_tlab_allocation() const {
2887   return true;
2888 }
2889 
2890 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2891   return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes;
2892 }
2893 
2894 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2895   return young_list()->eden_used_bytes();
2896 }
2897 
2898 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2899 // must be smaller than the humongous object limit.
2900 size_t G1CollectedHeap::max_tlab_size() const {
2901   return align_size_down(_humongous_object_threshold_in_words - 1, MinObjAlignment);
2902 }
2903 
2904 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2905   // Return the remaining space in the cur alloc region, but not less than
2906   // the min TLAB size.
2907 
2908   // Also, this value can be at most the humongous object threshold,
2909   // since we can't allow tlabs to grow big enough to accommodate
2910   // humongous objects.
2911 
2912   HeapRegion* hr = _allocator->mutator_alloc_region(AllocationContext::current())->get();
2913   size_t max_tlab = max_tlab_size() * wordSize;
2914   if (hr == NULL) {
2915     return max_tlab;
2916   } else {
2917     return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab);
2918   }
2919 }
2920 
2921 size_t G1CollectedHeap::max_capacity() const {
2922   return _hrm.reserved().byte_size();
2923 }
2924 
2925 jlong G1CollectedHeap::millis_since_last_gc() {
2926   // assert(false, "NYI");
2927   return 0;
2928 }
2929 
2930 void G1CollectedHeap::prepare_for_verify() {
2931   if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
2932     ensure_parsability(false);
2933   }
2934   g1_rem_set()->prepare_for_verify();
2935 }
2936 
2937 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr,
2938                                               VerifyOption vo) {
2939   switch (vo) {
2940   case VerifyOption_G1UsePrevMarking:
2941     return hr->obj_allocated_since_prev_marking(obj);
2942   case VerifyOption_G1UseNextMarking:
2943     return hr->obj_allocated_since_next_marking(obj);
2944   case VerifyOption_G1UseMarkWord:
2945     return false;
2946   default:
2947     ShouldNotReachHere();
2948   }
2949   return false; // keep some compilers happy
2950 }
2951 
2952 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) {
2953   switch (vo) {
2954   case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start();
2955   case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start();
2956   case VerifyOption_G1UseMarkWord:    return NULL;
2957   default:                            ShouldNotReachHere();
2958   }
2959   return NULL; // keep some compilers happy
2960 }
2961 
2962 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) {
2963   switch (vo) {
2964   case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj);
2965   case VerifyOption_G1UseNextMarking: return isMarkedNext(obj);
2966   case VerifyOption_G1UseMarkWord:    return obj->is_gc_marked();
2967   default:                            ShouldNotReachHere();
2968   }
2969   return false; // keep some compilers happy
2970 }
2971 
2972 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) {
2973   switch (vo) {
2974   case VerifyOption_G1UsePrevMarking: return "PTAMS";
2975   case VerifyOption_G1UseNextMarking: return "NTAMS";
2976   case VerifyOption_G1UseMarkWord:    return "NONE";
2977   default:                            ShouldNotReachHere();
2978   }
2979   return NULL; // keep some compilers happy
2980 }
2981 
2982 class VerifyRootsClosure: public OopClosure {
2983 private:
2984   G1CollectedHeap* _g1h;
2985   VerifyOption     _vo;
2986   bool             _failures;
2987 public:
2988   // _vo == UsePrevMarking -> use "prev" marking information,
2989   // _vo == UseNextMarking -> use "next" marking information,
2990   // _vo == UseMarkWord    -> use mark word from object header.
2991   VerifyRootsClosure(VerifyOption vo) :
2992     _g1h(G1CollectedHeap::heap()),
2993     _vo(vo),
2994     _failures(false) { }
2995 
2996   bool failures() { return _failures; }
2997 
2998   template <class T> void do_oop_nv(T* p) {
2999     T heap_oop = oopDesc::load_heap_oop(p);
3000     if (!oopDesc::is_null(heap_oop)) {
3001       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3002       if (_g1h->is_obj_dead_cond(obj, _vo)) {
3003         gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
3004                               "points to dead obj "PTR_FORMAT, p, (void*) obj);
3005         if (_vo == VerifyOption_G1UseMarkWord) {
3006           gclog_or_tty->print_cr("  Mark word: "PTR_FORMAT, (void*)(obj->mark()));
3007         }
3008         obj->print_on(gclog_or_tty);
3009         _failures = true;
3010       }
3011     }
3012   }
3013 
3014   void do_oop(oop* p)       { do_oop_nv(p); }
3015   void do_oop(narrowOop* p) { do_oop_nv(p); }
3016 };
3017 
3018 class G1VerifyCodeRootOopClosure: public OopClosure {
3019   G1CollectedHeap* _g1h;
3020   OopClosure* _root_cl;
3021   nmethod* _nm;
3022   VerifyOption _vo;
3023   bool _failures;
3024 
3025   template <class T> void do_oop_work(T* p) {
3026     // First verify that this root is live
3027     _root_cl->do_oop(p);
3028 
3029     if (!G1VerifyHeapRegionCodeRoots) {
3030       // We're not verifying the code roots attached to heap region.
3031       return;
3032     }
3033 
3034     // Don't check the code roots during marking verification in a full GC
3035     if (_vo == VerifyOption_G1UseMarkWord) {
3036       return;
3037     }
3038 
3039     // Now verify that the current nmethod (which contains p) is
3040     // in the code root list of the heap region containing the
3041     // object referenced by p.
3042 
3043     T heap_oop = oopDesc::load_heap_oop(p);
3044     if (!oopDesc::is_null(heap_oop)) {
3045       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3046 
3047       // Now fetch the region containing the object
3048       HeapRegion* hr = _g1h->heap_region_containing(obj);
3049       HeapRegionRemSet* hrrs = hr->rem_set();
3050       // Verify that the strong code root list for this region
3051       // contains the nmethod
3052       if (!hrrs->strong_code_roots_list_contains(_nm)) {
3053         gclog_or_tty->print_cr("Code root location "PTR_FORMAT" "
3054                               "from nmethod "PTR_FORMAT" not in strong "
3055                               "code roots for region ["PTR_FORMAT","PTR_FORMAT")",
3056                               p, _nm, hr->bottom(), hr->end());
3057         _failures = true;
3058       }
3059     }
3060   }
3061 
3062 public:
3063   G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo):
3064     _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {}
3065 
3066   void do_oop(oop* p) { do_oop_work(p); }
3067   void do_oop(narrowOop* p) { do_oop_work(p); }
3068 
3069   void set_nmethod(nmethod* nm) { _nm = nm; }
3070   bool failures() { return _failures; }
3071 };
3072 
3073 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure {
3074   G1VerifyCodeRootOopClosure* _oop_cl;
3075 
3076 public:
3077   G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl):
3078     _oop_cl(oop_cl) {}
3079 
3080   void do_code_blob(CodeBlob* cb) {
3081     nmethod* nm = cb->as_nmethod_or_null();
3082     if (nm != NULL) {
3083       _oop_cl->set_nmethod(nm);
3084       nm->oops_do(_oop_cl);
3085     }
3086   }
3087 };
3088 
3089 class YoungRefCounterClosure : public OopClosure {
3090   G1CollectedHeap* _g1h;
3091   int              _count;
3092  public:
3093   YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {}
3094   void do_oop(oop* p)       { if (_g1h->is_in_young(*p)) { _count++; } }
3095   void do_oop(narrowOop* p) { ShouldNotReachHere(); }
3096 
3097   int count() { return _count; }
3098   void reset_count() { _count = 0; };
3099 };
3100 
3101 class VerifyKlassClosure: public KlassClosure {
3102   YoungRefCounterClosure _young_ref_counter_closure;
3103   OopClosure *_oop_closure;
3104  public:
3105   VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {}
3106   void do_klass(Klass* k) {
3107     k->oops_do(_oop_closure);
3108 
3109     _young_ref_counter_closure.reset_count();
3110     k->oops_do(&_young_ref_counter_closure);
3111     if (_young_ref_counter_closure.count() > 0) {
3112       guarantee(k->has_modified_oops(), err_msg("Klass " PTR_FORMAT ", has young refs but is not dirty.", k));
3113     }
3114   }
3115 };
3116 
3117 class VerifyLivenessOopClosure: public OopClosure {
3118   G1CollectedHeap* _g1h;
3119   VerifyOption _vo;
3120 public:
3121   VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
3122     _g1h(g1h), _vo(vo)
3123   { }
3124   void do_oop(narrowOop *p) { do_oop_work(p); }
3125   void do_oop(      oop *p) { do_oop_work(p); }
3126 
3127   template <class T> void do_oop_work(T *p) {
3128     oop obj = oopDesc::load_decode_heap_oop(p);
3129     guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
3130               "Dead object referenced by a not dead object");
3131   }
3132 };
3133 
3134 class VerifyObjsInRegionClosure: public ObjectClosure {
3135 private:
3136   G1CollectedHeap* _g1h;
3137   size_t _live_bytes;
3138   HeapRegion *_hr;
3139   VerifyOption _vo;
3140 public:
3141   // _vo == UsePrevMarking -> use "prev" marking information,
3142   // _vo == UseNextMarking -> use "next" marking information,
3143   // _vo == UseMarkWord    -> use mark word from object header.
3144   VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
3145     : _live_bytes(0), _hr(hr), _vo(vo) {
3146     _g1h = G1CollectedHeap::heap();
3147   }
3148   void do_object(oop o) {
3149     VerifyLivenessOopClosure isLive(_g1h, _vo);
3150     assert(o != NULL, "Huh?");
3151     if (!_g1h->is_obj_dead_cond(o, _vo)) {
3152       // If the object is alive according to the mark word,
3153       // then verify that the marking information agrees.
3154       // Note we can't verify the contra-positive of the
3155       // above: if the object is dead (according to the mark
3156       // word), it may not be marked, or may have been marked
3157       // but has since became dead, or may have been allocated
3158       // since the last marking.
3159       if (_vo == VerifyOption_G1UseMarkWord) {
3160         guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
3161       }
3162 
3163       o->oop_iterate_no_header(&isLive);
3164       if (!_hr->obj_allocated_since_prev_marking(o)) {
3165         size_t obj_size = o->size();    // Make sure we don't overflow
3166         _live_bytes += (obj_size * HeapWordSize);
3167       }
3168     }
3169   }
3170   size_t live_bytes() { return _live_bytes; }
3171 };
3172 
3173 class PrintObjsInRegionClosure : public ObjectClosure {
3174   HeapRegion *_hr;
3175   G1CollectedHeap *_g1;
3176 public:
3177   PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
3178     _g1 = G1CollectedHeap::heap();
3179   };
3180 
3181   void do_object(oop o) {
3182     if (o != NULL) {
3183       HeapWord *start = (HeapWord *) o;
3184       size_t word_sz = o->size();
3185       gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
3186                           " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
3187                           (void*) o, word_sz,
3188                           _g1->isMarkedPrev(o),
3189                           _g1->isMarkedNext(o),
3190                           _hr->obj_allocated_since_prev_marking(o));
3191       HeapWord *end = start + word_sz;
3192       HeapWord *cur;
3193       int *val;
3194       for (cur = start; cur < end; cur++) {
3195         val = (int *) cur;
3196         gclog_or_tty->print("\t "PTR_FORMAT":%d\n", val, *val);
3197       }
3198     }
3199   }
3200 };
3201 
3202 class VerifyRegionClosure: public HeapRegionClosure {
3203 private:
3204   bool             _par;
3205   VerifyOption     _vo;
3206   bool             _failures;
3207 public:
3208   // _vo == UsePrevMarking -> use "prev" marking information,
3209   // _vo == UseNextMarking -> use "next" marking information,
3210   // _vo == UseMarkWord    -> use mark word from object header.
3211   VerifyRegionClosure(bool par, VerifyOption vo)
3212     : _par(par),
3213       _vo(vo),
3214       _failures(false) {}
3215 
3216   bool failures() {
3217     return _failures;
3218   }
3219 
3220   bool doHeapRegion(HeapRegion* r) {
3221     if (!r->is_continues_humongous()) {
3222       bool failures = false;
3223       r->verify(_vo, &failures);
3224       if (failures) {
3225         _failures = true;
3226       } else {
3227         VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
3228         r->object_iterate(&not_dead_yet_cl);
3229         if (_vo != VerifyOption_G1UseNextMarking) {
3230           if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
3231             gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
3232                                    "max_live_bytes "SIZE_FORMAT" "
3233                                    "< calculated "SIZE_FORMAT,
3234                                    r->bottom(), r->end(),
3235                                    r->max_live_bytes(),
3236                                  not_dead_yet_cl.live_bytes());
3237             _failures = true;
3238           }
3239         } else {
3240           // When vo == UseNextMarking we cannot currently do a sanity
3241           // check on the live bytes as the calculation has not been
3242           // finalized yet.
3243         }
3244       }
3245     }
3246     return false; // stop the region iteration if we hit a failure
3247   }
3248 };
3249 
3250 // This is the task used for parallel verification of the heap regions
3251 
3252 class G1ParVerifyTask: public AbstractGangTask {
3253 private:
3254   G1CollectedHeap* _g1h;
3255   VerifyOption     _vo;
3256   bool             _failures;
3257 
3258 public:
3259   // _vo == UsePrevMarking -> use "prev" marking information,
3260   // _vo == UseNextMarking -> use "next" marking information,
3261   // _vo == UseMarkWord    -> use mark word from object header.
3262   G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
3263     AbstractGangTask("Parallel verify task"),
3264     _g1h(g1h),
3265     _vo(vo),
3266     _failures(false) { }
3267 
3268   bool failures() {
3269     return _failures;
3270   }
3271 
3272   void work(uint worker_id) {
3273     HandleMark hm;
3274     VerifyRegionClosure blk(true, _vo);
3275     _g1h->heap_region_par_iterate_chunked(&blk, worker_id,
3276                                           _g1h->workers()->active_workers(),
3277                                           HeapRegion::ParVerifyClaimValue);
3278     if (blk.failures()) {
3279       _failures = true;
3280     }
3281   }
3282 };
3283 
3284 void G1CollectedHeap::verify(bool silent, VerifyOption vo) {
3285   if (SafepointSynchronize::is_at_safepoint()) {
3286     assert(Thread::current()->is_VM_thread(),
3287            "Expected to be executed serially by the VM thread at this point");
3288 
3289     if (!silent) { gclog_or_tty->print("Roots "); }
3290     VerifyRootsClosure rootsCl(vo);
3291     VerifyKlassClosure klassCl(this, &rootsCl);
3292     CLDToKlassAndOopClosure cldCl(&klassCl, &rootsCl, false);
3293 
3294     // We apply the relevant closures to all the oops in the
3295     // system dictionary, class loader data graph, the string table
3296     // and the nmethods in the code cache.
3297     G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo);
3298     G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl);
3299 
3300     process_all_roots(true,            // activate StrongRootsScope
3301                       SO_AllCodeCache, // roots scanning options
3302                       &rootsCl,
3303                       &cldCl,
3304                       &blobsCl);
3305 
3306     bool failures = rootsCl.failures() || codeRootsCl.failures();
3307 
3308     if (vo != VerifyOption_G1UseMarkWord) {
3309       // If we're verifying during a full GC then the region sets
3310       // will have been torn down at the start of the GC. Therefore
3311       // verifying the region sets will fail. So we only verify
3312       // the region sets when not in a full GC.
3313       if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3314       verify_region_sets();
3315     }
3316 
3317     if (!silent) { gclog_or_tty->print("HeapRegions "); }
3318     if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3319       assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3320              "sanity check");
3321 
3322       G1ParVerifyTask task(this, vo);
3323       assert(UseDynamicNumberOfGCThreads ||
3324         workers()->active_workers() == workers()->total_workers(),
3325         "If not dynamic should be using all the workers");
3326       int n_workers = workers()->active_workers();
3327       set_par_threads(n_workers);
3328       workers()->run_task(&task);
3329       set_par_threads(0);
3330       if (task.failures()) {
3331         failures = true;
3332       }
3333 
3334       // Checks that the expected amount of parallel work was done.
3335       // The implication is that n_workers is > 0.
3336       assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
3337              "sanity check");
3338 
3339       reset_heap_region_claim_values();
3340 
3341       assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3342              "sanity check");
3343     } else {
3344       VerifyRegionClosure blk(false, vo);
3345       heap_region_iterate(&blk);
3346       if (blk.failures()) {
3347         failures = true;
3348       }
3349     }
3350     if (!silent) gclog_or_tty->print("RemSet ");
3351     rem_set()->verify();
3352 
3353     if (G1StringDedup::is_enabled()) {
3354       if (!silent) gclog_or_tty->print("StrDedup ");
3355       G1StringDedup::verify();
3356     }
3357 
3358     if (failures) {
3359       gclog_or_tty->print_cr("Heap:");
3360       // It helps to have the per-region information in the output to
3361       // help us track down what went wrong. This is why we call
3362       // print_extended_on() instead of print_on().
3363       print_extended_on(gclog_or_tty);
3364       gclog_or_tty->cr();
3365 #ifndef PRODUCT
3366       if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3367         concurrent_mark()->print_reachable("at-verification-failure",
3368                                            vo, false /* all */);
3369       }
3370 #endif
3371       gclog_or_tty->flush();
3372     }
3373     guarantee(!failures, "there should not have been any failures");
3374   } else {
3375     if (!silent) {
3376       gclog_or_tty->print("(SKIPPING Roots, HeapRegionSets, HeapRegions, RemSet");
3377       if (G1StringDedup::is_enabled()) {
3378         gclog_or_tty->print(", StrDedup");
3379       }
3380       gclog_or_tty->print(") ");
3381     }
3382   }
3383 }
3384 
3385 void G1CollectedHeap::verify(bool silent) {
3386   verify(silent, VerifyOption_G1UsePrevMarking);
3387 }
3388 
3389 double G1CollectedHeap::verify(bool guard, const char* msg) {
3390   double verify_time_ms = 0.0;
3391 
3392   if (guard && total_collections() >= VerifyGCStartAt) {
3393     double verify_start = os::elapsedTime();
3394     HandleMark hm;  // Discard invalid handles created during verification
3395     prepare_for_verify();
3396     Universe::verify(VerifyOption_G1UsePrevMarking, msg);
3397     verify_time_ms = (os::elapsedTime() - verify_start) * 1000;
3398   }
3399 
3400   return verify_time_ms;
3401 }
3402 
3403 void G1CollectedHeap::verify_before_gc() {
3404   double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:");
3405   g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms);
3406 }
3407 
3408 void G1CollectedHeap::verify_after_gc() {
3409   double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:");
3410   g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms);
3411 }
3412 
3413 class PrintRegionClosure: public HeapRegionClosure {
3414   outputStream* _st;
3415 public:
3416   PrintRegionClosure(outputStream* st) : _st(st) {}
3417   bool doHeapRegion(HeapRegion* r) {
3418     r->print_on(_st);
3419     return false;
3420   }
3421 };
3422 
3423 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3424                                        const HeapRegion* hr,
3425                                        const VerifyOption vo) const {
3426   switch (vo) {
3427   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
3428   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
3429   case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked();
3430   default:                            ShouldNotReachHere();
3431   }
3432   return false; // keep some compilers happy
3433 }
3434 
3435 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3436                                        const VerifyOption vo) const {
3437   switch (vo) {
3438   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
3439   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
3440   case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked();
3441   default:                            ShouldNotReachHere();
3442   }
3443   return false; // keep some compilers happy
3444 }
3445 
3446 void G1CollectedHeap::print_on(outputStream* st) const {
3447   st->print(" %-20s", "garbage-first heap");
3448   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3449             capacity()/K, used_unlocked()/K);
3450   st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3451             _hrm.reserved().start(),
3452             _hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords,
3453             _hrm.reserved().end());
3454   st->cr();
3455   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3456   uint young_regions = _young_list->length();
3457   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3458             (size_t) young_regions * HeapRegion::GrainBytes / K);
3459   uint survivor_regions = g1_policy()->recorded_survivor_regions();
3460   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3461             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3462   st->cr();
3463   MetaspaceAux::print_on(st);
3464 }
3465 
3466 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3467   print_on(st);
3468 
3469   // Print the per-region information.
3470   st->cr();
3471   st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3472                "HS=humongous(starts), HC=humongous(continues), "
3473                "CS=collection set, F=free, TS=gc time stamp, "
3474                "PTAMS=previous top-at-mark-start, "
3475                "NTAMS=next top-at-mark-start)");
3476   PrintRegionClosure blk(st);
3477   heap_region_iterate(&blk);
3478 }
3479 
3480 void G1CollectedHeap::print_on_error(outputStream* st) const {
3481   this->CollectedHeap::print_on_error(st);
3482 
3483   if (_cm != NULL) {
3484     st->cr();
3485     _cm->print_on_error(st);
3486   }
3487 }
3488 
3489 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3490   if (G1CollectedHeap::use_parallel_gc_threads()) {
3491     workers()->print_worker_threads_on(st);
3492   }
3493   _cmThread->print_on(st);
3494   st->cr();
3495   _cm->print_worker_threads_on(st);
3496   _cg1r->print_worker_threads_on(st);
3497   if (G1StringDedup::is_enabled()) {
3498     G1StringDedup::print_worker_threads_on(st);
3499   }
3500 }
3501 
3502 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3503   if (G1CollectedHeap::use_parallel_gc_threads()) {
3504     workers()->threads_do(tc);
3505   }
3506   tc->do_thread(_cmThread);
3507   _cg1r->threads_do(tc);
3508   if (G1StringDedup::is_enabled()) {
3509     G1StringDedup::threads_do(tc);
3510   }
3511 }
3512 
3513 void G1CollectedHeap::print_tracing_info() const {
3514   // We'll overload this to mean "trace GC pause statistics."
3515   if (TraceYoungGenTime || TraceOldGenTime) {
3516     // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3517     // to that.
3518     g1_policy()->print_tracing_info();
3519   }
3520   if (G1SummarizeRSetStats) {
3521     g1_rem_set()->print_summary_info();
3522   }
3523   if (G1SummarizeConcMark) {
3524     concurrent_mark()->print_summary_info();
3525   }
3526   g1_policy()->print_yg_surv_rate_info();
3527   SpecializationStats::print();
3528 }
3529 
3530 #ifndef PRODUCT
3531 // Helpful for debugging RSet issues.
3532 
3533 class PrintRSetsClosure : public HeapRegionClosure {
3534 private:
3535   const char* _msg;
3536   size_t _occupied_sum;
3537 
3538 public:
3539   bool doHeapRegion(HeapRegion* r) {
3540     HeapRegionRemSet* hrrs = r->rem_set();
3541     size_t occupied = hrrs->occupied();
3542     _occupied_sum += occupied;
3543 
3544     gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3545                            HR_FORMAT_PARAMS(r));
3546     if (occupied == 0) {
3547       gclog_or_tty->print_cr("  RSet is empty");
3548     } else {
3549       hrrs->print();
3550     }
3551     gclog_or_tty->print_cr("----------");
3552     return false;
3553   }
3554 
3555   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3556     gclog_or_tty->cr();
3557     gclog_or_tty->print_cr("========================================");
3558     gclog_or_tty->print_cr("%s", msg);
3559     gclog_or_tty->cr();
3560   }
3561 
3562   ~PrintRSetsClosure() {
3563     gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3564     gclog_or_tty->print_cr("========================================");
3565     gclog_or_tty->cr();
3566   }
3567 };
3568 
3569 void G1CollectedHeap::print_cset_rsets() {
3570   PrintRSetsClosure cl("Printing CSet RSets");
3571   collection_set_iterate(&cl);
3572 }
3573 
3574 void G1CollectedHeap::print_all_rsets() {
3575   PrintRSetsClosure cl("Printing All RSets");;
3576   heap_region_iterate(&cl);
3577 }
3578 #endif // PRODUCT
3579 
3580 G1CollectedHeap* G1CollectedHeap::heap() {
3581   assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3582          "not a garbage-first heap");
3583   return _g1h;
3584 }
3585 
3586 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3587   // always_do_update_barrier = false;
3588   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3589   // Fill TLAB's and such
3590   accumulate_statistics_all_tlabs();
3591   ensure_parsability(true);
3592 
3593   if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) &&
3594       (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3595     g1_rem_set()->print_periodic_summary_info("Before GC RS summary");
3596   }
3597 }
3598 
3599 void G1CollectedHeap::gc_epilogue(bool full) {
3600 
3601   if (G1SummarizeRSetStats &&
3602       (G1SummarizeRSetStatsPeriod > 0) &&
3603       // we are at the end of the GC. Total collections has already been increased.
3604       ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) {
3605     g1_rem_set()->print_periodic_summary_info("After GC RS summary");
3606   }
3607 
3608   // FIXME: what is this about?
3609   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3610   // is set.
3611   COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3612                         "derived pointer present"));
3613   // always_do_update_barrier = true;
3614 
3615   resize_all_tlabs();
3616   allocation_context_stats().update(full);
3617 
3618   // We have just completed a GC. Update the soft reference
3619   // policy with the new heap occupancy
3620   Universe::update_heap_info_at_gc();
3621 }
3622 
3623 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3624                                                unsigned int gc_count_before,
3625                                                bool* succeeded,
3626                                                GCCause::Cause gc_cause) {
3627   assert_heap_not_locked_and_not_at_safepoint();
3628   g1_policy()->record_stop_world_start();
3629   VM_G1IncCollectionPause op(gc_count_before,
3630                              word_size,
3631                              false, /* should_initiate_conc_mark */
3632                              g1_policy()->max_pause_time_ms(),
3633                              gc_cause);
3634 
3635   op.set_allocation_context(AllocationContext::current());
3636   VMThread::execute(&op);
3637 
3638   HeapWord* result = op.result();
3639   bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3640   assert(result == NULL || ret_succeeded,
3641          "the result should be NULL if the VM did not succeed");
3642   *succeeded = ret_succeeded;
3643 
3644   assert_heap_not_locked();
3645   return result;
3646 }
3647 
3648 void
3649 G1CollectedHeap::doConcurrentMark() {
3650   MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3651   if (!_cmThread->in_progress()) {
3652     _cmThread->set_started();
3653     CGC_lock->notify();
3654   }
3655 }
3656 
3657 size_t G1CollectedHeap::pending_card_num() {
3658   size_t extra_cards = 0;
3659   JavaThread *curr = Threads::first();
3660   while (curr != NULL) {
3661     DirtyCardQueue& dcq = curr->dirty_card_queue();
3662     extra_cards += dcq.size();
3663     curr = curr->next();
3664   }
3665   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3666   size_t buffer_size = dcqs.buffer_size();
3667   size_t buffer_num = dcqs.completed_buffers_num();
3668 
3669   // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
3670   // in bytes - not the number of 'entries'. We need to convert
3671   // into a number of cards.
3672   return (buffer_size * buffer_num + extra_cards) / oopSize;
3673 }
3674 
3675 size_t G1CollectedHeap::cards_scanned() {
3676   return g1_rem_set()->cardsScanned();
3677 }
3678 
3679 bool G1CollectedHeap::humongous_region_is_always_live(uint index) {
3680   HeapRegion* region = region_at(index);
3681   assert(region->is_starts_humongous(), "Must start a humongous object");
3682   return oop(region->bottom())->is_objArray() || !region->rem_set()->is_empty();
3683 }
3684 
3685 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
3686  private:
3687   size_t _total_humongous;
3688   size_t _candidate_humongous;
3689  public:
3690   RegisterHumongousWithInCSetFastTestClosure() : _total_humongous(0), _candidate_humongous(0) {
3691   }
3692 
3693   virtual bool doHeapRegion(HeapRegion* r) {
3694     if (!r->is_starts_humongous()) {
3695       return false;
3696     }
3697     G1CollectedHeap* g1h = G1CollectedHeap::heap();
3698 
3699     uint region_idx = r->hrm_index();
3700     bool is_candidate = !g1h->humongous_region_is_always_live(region_idx);
3701     // Is_candidate already filters out humongous regions with some remembered set.
3702     // This will not lead to humongous object that we mistakenly keep alive because
3703     // during young collection the remembered sets will only be added to.
3704     if (is_candidate) {
3705       g1h->register_humongous_region_with_in_cset_fast_test(region_idx);
3706       _candidate_humongous++;
3707     }
3708     _total_humongous++;
3709 
3710     return false;
3711   }
3712 
3713   size_t total_humongous() const { return _total_humongous; }
3714   size_t candidate_humongous() const { return _candidate_humongous; }
3715 };
3716 
3717 void G1CollectedHeap::register_humongous_regions_with_in_cset_fast_test() {
3718   if (!G1ReclaimDeadHumongousObjectsAtYoungGC) {
3719     g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0, 0);
3720     return;
3721   }
3722 
3723   RegisterHumongousWithInCSetFastTestClosure cl;
3724   heap_region_iterate(&cl);
3725   g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(cl.total_humongous(),
3726                                                                   cl.candidate_humongous());
3727   _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
3728 
3729   if (_has_humongous_reclaim_candidates) {
3730     clear_humongous_is_live_table();
3731   }
3732 }
3733 
3734 void
3735 G1CollectedHeap::setup_surviving_young_words() {
3736   assert(_surviving_young_words == NULL, "pre-condition");
3737   uint array_length = g1_policy()->young_cset_region_length();
3738   _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3739   if (_surviving_young_words == NULL) {
3740     vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR,
3741                           "Not enough space for young surv words summary.");
3742   }
3743   memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3744 #ifdef ASSERT
3745   for (uint i = 0;  i < array_length; ++i) {
3746     assert( _surviving_young_words[i] == 0, "memset above" );
3747   }
3748 #endif // !ASSERT
3749 }
3750 
3751 void
3752 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3753   MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3754   uint array_length = g1_policy()->young_cset_region_length();
3755   for (uint i = 0; i < array_length; ++i) {
3756     _surviving_young_words[i] += surv_young_words[i];
3757   }
3758 }
3759 
3760 void
3761 G1CollectedHeap::cleanup_surviving_young_words() {
3762   guarantee( _surviving_young_words != NULL, "pre-condition" );
3763   FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC);
3764   _surviving_young_words = NULL;
3765 }
3766 
3767 #ifdef ASSERT
3768 class VerifyCSetClosure: public HeapRegionClosure {
3769 public:
3770   bool doHeapRegion(HeapRegion* hr) {
3771     // Here we check that the CSet region's RSet is ready for parallel
3772     // iteration. The fields that we'll verify are only manipulated
3773     // when the region is part of a CSet and is collected. Afterwards,
3774     // we reset these fields when we clear the region's RSet (when the
3775     // region is freed) so they are ready when the region is
3776     // re-allocated. The only exception to this is if there's an
3777     // evacuation failure and instead of freeing the region we leave
3778     // it in the heap. In that case, we reset these fields during
3779     // evacuation failure handling.
3780     guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3781 
3782     // Here's a good place to add any other checks we'd like to
3783     // perform on CSet regions.
3784     return false;
3785   }
3786 };
3787 #endif // ASSERT
3788 
3789 #if TASKQUEUE_STATS
3790 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3791   st->print_raw_cr("GC Task Stats");
3792   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3793   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3794 }
3795 
3796 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3797   print_taskqueue_stats_hdr(st);
3798 
3799   TaskQueueStats totals;
3800   const int n = workers() != NULL ? workers()->total_workers() : 1;
3801   for (int i = 0; i < n; ++i) {
3802     st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3803     totals += task_queue(i)->stats;
3804   }
3805   st->print_raw("tot "); totals.print(st); st->cr();
3806 
3807   DEBUG_ONLY(totals.verify());
3808 }
3809 
3810 void G1CollectedHeap::reset_taskqueue_stats() {
3811   const int n = workers() != NULL ? workers()->total_workers() : 1;
3812   for (int i = 0; i < n; ++i) {
3813     task_queue(i)->stats.reset();
3814   }
3815 }
3816 #endif // TASKQUEUE_STATS
3817 
3818 void G1CollectedHeap::log_gc_header() {
3819   if (!G1Log::fine()) {
3820     return;
3821   }
3822 
3823   gclog_or_tty->gclog_stamp(_gc_tracer_stw->gc_id());
3824 
3825   GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
3826     .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)")
3827     .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : "");
3828 
3829   gclog_or_tty->print("[%s", (const char*)gc_cause_str);
3830 }
3831 
3832 void G1CollectedHeap::log_gc_footer(double pause_time_sec) {
3833   if (!G1Log::fine()) {
3834     return;
3835   }
3836 
3837   if (G1Log::finer()) {
3838     if (evacuation_failed()) {
3839       gclog_or_tty->print(" (to-space exhausted)");
3840     }
3841     gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3842     g1_policy()->phase_times()->note_gc_end();
3843     g1_policy()->phase_times()->print(pause_time_sec);
3844     g1_policy()->print_detailed_heap_transition();
3845   } else {
3846     if (evacuation_failed()) {
3847       gclog_or_tty->print("--");
3848     }
3849     g1_policy()->print_heap_transition();
3850     gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3851   }
3852   gclog_or_tty->flush();
3853 }
3854 
3855 bool
3856 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3857   assert_at_safepoint(true /* should_be_vm_thread */);
3858   guarantee(!is_gc_active(), "collection is not reentrant");
3859 
3860   if (GC_locker::check_active_before_gc()) {
3861     return false;
3862   }
3863 
3864   _gc_timer_stw->register_gc_start();
3865 
3866   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3867 
3868   SvcGCMarker sgcm(SvcGCMarker::MINOR);
3869   ResourceMark rm;
3870 
3871   print_heap_before_gc();
3872   trace_heap_before_gc(_gc_tracer_stw);
3873 
3874   verify_region_sets_optional();
3875   verify_dirty_young_regions();
3876 
3877   // This call will decide whether this pause is an initial-mark
3878   // pause. If it is, during_initial_mark_pause() will return true
3879   // for the duration of this pause.
3880   g1_policy()->decide_on_conc_mark_initiation();
3881 
3882   // We do not allow initial-mark to be piggy-backed on a mixed GC.
3883   assert(!g1_policy()->during_initial_mark_pause() ||
3884           g1_policy()->gcs_are_young(), "sanity");
3885 
3886   // We also do not allow mixed GCs during marking.
3887   assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3888 
3889   // Record whether this pause is an initial mark. When the current
3890   // thread has completed its logging output and it's safe to signal
3891   // the CM thread, the flag's value in the policy has been reset.
3892   bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3893 
3894   // Inner scope for scope based logging, timers, and stats collection
3895   {
3896     EvacuationInfo evacuation_info;
3897 
3898     if (g1_policy()->during_initial_mark_pause()) {
3899       // We are about to start a marking cycle, so we increment the
3900       // full collection counter.
3901       increment_old_marking_cycles_started();
3902       register_concurrent_cycle_start(_gc_timer_stw->gc_start());
3903     }
3904 
3905     _gc_tracer_stw->report_yc_type(yc_type());
3906 
3907     TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3908 
3909     int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
3910                                 workers()->active_workers() : 1);
3911     double pause_start_sec = os::elapsedTime();
3912     g1_policy()->phase_times()->note_gc_start(active_workers);
3913     log_gc_header();
3914 
3915     TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3916     TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3917 
3918     // If the secondary_free_list is not empty, append it to the
3919     // free_list. No need to wait for the cleanup operation to finish;
3920     // the region allocation code will check the secondary_free_list
3921     // and wait if necessary. If the G1StressConcRegionFreeing flag is
3922     // set, skip this step so that the region allocation code has to
3923     // get entries from the secondary_free_list.
3924     if (!G1StressConcRegionFreeing) {
3925       append_secondary_free_list_if_not_empty_with_lock();
3926     }
3927 
3928     assert(check_young_list_well_formed(), "young list should be well formed");
3929     assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3930            "sanity check");
3931 
3932     // Don't dynamically change the number of GC threads this early.  A value of
3933     // 0 is used to indicate serial work.  When parallel work is done,
3934     // it will be set.
3935 
3936     { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3937       IsGCActiveMark x;
3938 
3939       gc_prologue(false);
3940       increment_total_collections(false /* full gc */);
3941       increment_gc_time_stamp();
3942 
3943       verify_before_gc();
3944 
3945       check_bitmaps("GC Start");
3946 
3947       COMPILER2_PRESENT(DerivedPointerTable::clear());
3948 
3949       // Please see comment in g1CollectedHeap.hpp and
3950       // G1CollectedHeap::ref_processing_init() to see how
3951       // reference processing currently works in G1.
3952 
3953       // Enable discovery in the STW reference processor
3954       ref_processor_stw()->enable_discovery(true /*verify_disabled*/,
3955                                             true /*verify_no_refs*/);
3956 
3957       {
3958         // We want to temporarily turn off discovery by the
3959         // CM ref processor, if necessary, and turn it back on
3960         // on again later if we do. Using a scoped
3961         // NoRefDiscovery object will do this.
3962         NoRefDiscovery no_cm_discovery(ref_processor_cm());
3963 
3964         // Forget the current alloc region (we might even choose it to be part
3965         // of the collection set!).
3966         _allocator->release_mutator_alloc_region();
3967 
3968         // We should call this after we retire the mutator alloc
3969         // region(s) so that all the ALLOC / RETIRE events are generated
3970         // before the start GC event.
3971         _hr_printer.start_gc(false /* full */, (size_t) total_collections());
3972 
3973         // This timing is only used by the ergonomics to handle our pause target.
3974         // It is unclear why this should not include the full pause. We will
3975         // investigate this in CR 7178365.
3976         //
3977         // Preserving the old comment here if that helps the investigation:
3978         //
3979         // The elapsed time induced by the start time below deliberately elides
3980         // the possible verification above.
3981         double sample_start_time_sec = os::elapsedTime();
3982 
3983 #if YOUNG_LIST_VERBOSE
3984         gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
3985         _young_list->print();
3986         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3987 #endif // YOUNG_LIST_VERBOSE
3988 
3989         g1_policy()->record_collection_pause_start(sample_start_time_sec);
3990 
3991         double scan_wait_start = os::elapsedTime();
3992         // We have to wait until the CM threads finish scanning the
3993         // root regions as it's the only way to ensure that all the
3994         // objects on them have been correctly scanned before we start
3995         // moving them during the GC.
3996         bool waited = _cm->root_regions()->wait_until_scan_finished();
3997         double wait_time_ms = 0.0;
3998         if (waited) {
3999           double scan_wait_end = os::elapsedTime();
4000           wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
4001         }
4002         g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
4003 
4004 #if YOUNG_LIST_VERBOSE
4005         gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
4006         _young_list->print();
4007 #endif // YOUNG_LIST_VERBOSE
4008 
4009         if (g1_policy()->during_initial_mark_pause()) {
4010           concurrent_mark()->checkpointRootsInitialPre();
4011         }
4012 
4013 #if YOUNG_LIST_VERBOSE
4014         gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
4015         _young_list->print();
4016         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4017 #endif // YOUNG_LIST_VERBOSE
4018 
4019         g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info);
4020 
4021         register_humongous_regions_with_in_cset_fast_test();
4022 
4023         _cm->note_start_of_gc();
4024         // We should not verify the per-thread SATB buffers given that
4025         // we have not filtered them yet (we'll do so during the
4026         // GC). We also call this after finalize_cset() to
4027         // ensure that the CSet has been finalized.
4028         _cm->verify_no_cset_oops(true  /* verify_stacks */,
4029                                  true  /* verify_enqueued_buffers */,
4030                                  false /* verify_thread_buffers */,
4031                                  true  /* verify_fingers */);
4032 
4033         if (_hr_printer.is_active()) {
4034           HeapRegion* hr = g1_policy()->collection_set();
4035           while (hr != NULL) {
4036             _hr_printer.cset(hr);
4037             hr = hr->next_in_collection_set();
4038           }
4039         }
4040 
4041 #ifdef ASSERT
4042         VerifyCSetClosure cl;
4043         collection_set_iterate(&cl);
4044 #endif // ASSERT
4045 
4046         setup_surviving_young_words();
4047 
4048         // Initialize the GC alloc regions.
4049         _allocator->init_gc_alloc_regions(evacuation_info);
4050 
4051         // Actually do the work...
4052         evacuate_collection_set(evacuation_info);
4053 
4054         // We do this to mainly verify the per-thread SATB buffers
4055         // (which have been filtered by now) since we didn't verify
4056         // them earlier. No point in re-checking the stacks / enqueued
4057         // buffers given that the CSet has not changed since last time
4058         // we checked.
4059         _cm->verify_no_cset_oops(false /* verify_stacks */,
4060                                  false /* verify_enqueued_buffers */,
4061                                  true  /* verify_thread_buffers */,
4062                                  true  /* verify_fingers */);
4063 
4064         free_collection_set(g1_policy()->collection_set(), evacuation_info);
4065 
4066         eagerly_reclaim_humongous_regions();
4067 
4068         g1_policy()->clear_collection_set();
4069 
4070         cleanup_surviving_young_words();
4071 
4072         // Start a new incremental collection set for the next pause.
4073         g1_policy()->start_incremental_cset_building();
4074 
4075         clear_cset_fast_test();
4076 
4077         _young_list->reset_sampled_info();
4078 
4079         // Don't check the whole heap at this point as the
4080         // GC alloc regions from this pause have been tagged
4081         // as survivors and moved on to the survivor list.
4082         // Survivor regions will fail the !is_young() check.
4083         assert(check_young_list_empty(false /* check_heap */),
4084           "young list should be empty");
4085 
4086 #if YOUNG_LIST_VERBOSE
4087         gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
4088         _young_list->print();
4089 #endif // YOUNG_LIST_VERBOSE
4090 
4091         g1_policy()->record_survivor_regions(_young_list->survivor_length(),
4092                                              _young_list->first_survivor_region(),
4093                                              _young_list->last_survivor_region());
4094 
4095         _young_list->reset_auxilary_lists();
4096 
4097         if (evacuation_failed()) {
4098           _allocator->set_used(recalculate_used());
4099           uint n_queues = MAX2((int)ParallelGCThreads, 1);
4100           for (uint i = 0; i < n_queues; i++) {
4101             if (_evacuation_failed_info_array[i].has_failed()) {
4102               _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
4103             }
4104           }
4105         } else {
4106           // The "used" of the the collection set have already been subtracted
4107           // when they were freed.  Add in the bytes evacuated.
4108           _allocator->increase_used(g1_policy()->bytes_copied_during_gc());
4109         }
4110 
4111         if (g1_policy()->during_initial_mark_pause()) {
4112           // We have to do this before we notify the CM threads that
4113           // they can start working to make sure that all the
4114           // appropriate initialization is done on the CM object.
4115           concurrent_mark()->checkpointRootsInitialPost();
4116           set_marking_started();
4117           // Note that we don't actually trigger the CM thread at
4118           // this point. We do that later when we're sure that
4119           // the current thread has completed its logging output.
4120         }
4121 
4122         allocate_dummy_regions();
4123 
4124 #if YOUNG_LIST_VERBOSE
4125         gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
4126         _young_list->print();
4127         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4128 #endif // YOUNG_LIST_VERBOSE
4129 
4130         _allocator->init_mutator_alloc_region();
4131 
4132         {
4133           size_t expand_bytes = g1_policy()->expansion_amount();
4134           if (expand_bytes > 0) {
4135             size_t bytes_before = capacity();
4136             // No need for an ergo verbose message here,
4137             // expansion_amount() does this when it returns a value > 0.
4138             if (!expand(expand_bytes)) {
4139               // We failed to expand the heap. Cannot do anything about it.
4140             }
4141           }
4142         }
4143 
4144         // We redo the verification but now wrt to the new CSet which
4145         // has just got initialized after the previous CSet was freed.
4146         _cm->verify_no_cset_oops(true  /* verify_stacks */,
4147                                  true  /* verify_enqueued_buffers */,
4148                                  true  /* verify_thread_buffers */,
4149                                  true  /* verify_fingers */);
4150         _cm->note_end_of_gc();
4151 
4152         // This timing is only used by the ergonomics to handle our pause target.
4153         // It is unclear why this should not include the full pause. We will
4154         // investigate this in CR 7178365.
4155         double sample_end_time_sec = os::elapsedTime();
4156         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
4157         g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info);
4158 
4159         MemoryService::track_memory_usage();
4160 
4161         // In prepare_for_verify() below we'll need to scan the deferred
4162         // update buffers to bring the RSets up-to-date if
4163         // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
4164         // the update buffers we'll probably need to scan cards on the
4165         // regions we just allocated to (i.e., the GC alloc
4166         // regions). However, during the last GC we called
4167         // set_saved_mark() on all the GC alloc regions, so card
4168         // scanning might skip the [saved_mark_word()...top()] area of
4169         // those regions (i.e., the area we allocated objects into
4170         // during the last GC). But it shouldn't. Given that
4171         // saved_mark_word() is conditional on whether the GC time stamp
4172         // on the region is current or not, by incrementing the GC time
4173         // stamp here we invalidate all the GC time stamps on all the
4174         // regions and saved_mark_word() will simply return top() for
4175         // all the regions. This is a nicer way of ensuring this rather
4176         // than iterating over the regions and fixing them. In fact, the
4177         // GC time stamp increment here also ensures that
4178         // saved_mark_word() will return top() between pauses, i.e.,
4179         // during concurrent refinement. So we don't need the
4180         // is_gc_active() check to decided which top to use when
4181         // scanning cards (see CR 7039627).
4182         increment_gc_time_stamp();
4183 
4184         verify_after_gc();
4185         check_bitmaps("GC End");
4186 
4187         assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
4188         ref_processor_stw()->verify_no_references_recorded();
4189 
4190         // CM reference discovery will be re-enabled if necessary.
4191       }
4192 
4193       // We should do this after we potentially expand the heap so
4194       // that all the COMMIT events are generated before the end GC
4195       // event, and after we retire the GC alloc regions so that all
4196       // RETIRE events are generated before the end GC event.
4197       _hr_printer.end_gc(false /* full */, (size_t) total_collections());
4198 
4199 #ifdef TRACESPINNING
4200       ParallelTaskTerminator::print_termination_counts();
4201 #endif
4202 
4203       gc_epilogue(false);
4204     }
4205 
4206     // Print the remainder of the GC log output.
4207     log_gc_footer(os::elapsedTime() - pause_start_sec);
4208 
4209     // It is not yet to safe to tell the concurrent mark to
4210     // start as we have some optional output below. We don't want the
4211     // output from the concurrent mark thread interfering with this
4212     // logging output either.
4213 
4214     _hrm.verify_optional();
4215     verify_region_sets_optional();
4216 
4217     TASKQUEUE_STATS_ONLY(if (PrintTaskqueue) print_taskqueue_stats());
4218     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
4219 
4220     print_heap_after_gc();
4221     trace_heap_after_gc(_gc_tracer_stw);
4222 
4223     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
4224     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
4225     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
4226     // before any GC notifications are raised.
4227     g1mm()->update_sizes();
4228 
4229     _gc_tracer_stw->report_evacuation_info(&evacuation_info);
4230     _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
4231     _gc_timer_stw->register_gc_end();
4232     _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
4233   }
4234   // It should now be safe to tell the concurrent mark thread to start
4235   // without its logging output interfering with the logging output
4236   // that came from the pause.
4237 
4238   if (should_start_conc_mark) {
4239     // CAUTION: after the doConcurrentMark() call below,
4240     // the concurrent marking thread(s) could be running
4241     // concurrently with us. Make sure that anything after
4242     // this point does not assume that we are the only GC thread
4243     // running. Note: of course, the actual marking work will
4244     // not start until the safepoint itself is released in
4245     // SuspendibleThreadSet::desynchronize().
4246     doConcurrentMark();
4247   }
4248 
4249   return true;
4250 }
4251 
4252 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
4253 {
4254   size_t gclab_word_size;
4255   switch (purpose) {
4256     case GCAllocForSurvived:
4257       gclab_word_size = _survivor_plab_stats.desired_plab_sz();
4258       break;
4259     case GCAllocForTenured:
4260       gclab_word_size = _old_plab_stats.desired_plab_sz();
4261       break;
4262     default:
4263       assert(false, "unknown GCAllocPurpose");
4264       gclab_word_size = _old_plab_stats.desired_plab_sz();
4265       break;
4266   }
4267 
4268   // Prevent humongous PLAB sizes for two reasons:
4269   // * PLABs are allocated using a similar paths as oops, but should
4270   //   never be in a humongous region
4271   // * Allowing humongous PLABs needlessly churns the region free lists
4272   return MIN2(_humongous_object_threshold_in_words, gclab_word_size);
4273 }
4274 
4275 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4276   _drain_in_progress = false;
4277   set_evac_failure_closure(cl);
4278   _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4279 }
4280 
4281 void G1CollectedHeap::finalize_for_evac_failure() {
4282   assert(_evac_failure_scan_stack != NULL &&
4283          _evac_failure_scan_stack->length() == 0,
4284          "Postcondition");
4285   assert(!_drain_in_progress, "Postcondition");
4286   delete _evac_failure_scan_stack;
4287   _evac_failure_scan_stack = NULL;
4288 }
4289 
4290 void G1CollectedHeap::remove_self_forwarding_pointers() {
4291   assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4292 
4293   double remove_self_forwards_start = os::elapsedTime();
4294 
4295   G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4296 
4297   if (G1CollectedHeap::use_parallel_gc_threads()) {
4298     set_par_threads();
4299     workers()->run_task(&rsfp_task);
4300     set_par_threads(0);
4301   } else {
4302     rsfp_task.work(0);
4303   }
4304 
4305   assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity");
4306 
4307   // Reset the claim values in the regions in the collection set.
4308   reset_cset_heap_region_claim_values();
4309 
4310   assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4311 
4312   // Now restore saved marks, if any.
4313   assert(_objs_with_preserved_marks.size() ==
4314             _preserved_marks_of_objs.size(), "Both or none.");
4315   while (!_objs_with_preserved_marks.is_empty()) {
4316     oop obj = _objs_with_preserved_marks.pop();
4317     markOop m = _preserved_marks_of_objs.pop();
4318     obj->set_mark(m);
4319   }
4320   _objs_with_preserved_marks.clear(true);
4321   _preserved_marks_of_objs.clear(true);
4322 
4323   g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
4324 }
4325 
4326 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4327   _evac_failure_scan_stack->push(obj);
4328 }
4329 
4330 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4331   assert(_evac_failure_scan_stack != NULL, "precondition");
4332 
4333   while (_evac_failure_scan_stack->length() > 0) {
4334      oop obj = _evac_failure_scan_stack->pop();
4335      _evac_failure_closure->set_region(heap_region_containing(obj));
4336      obj->oop_iterate_backwards(_evac_failure_closure);
4337   }
4338 }
4339 
4340 oop
4341 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state,
4342                                                oop old) {
4343   assert(obj_in_cs(old),
4344          err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4345                  (HeapWord*) old));
4346   markOop m = old->mark();
4347   oop forward_ptr = old->forward_to_atomic(old);
4348   if (forward_ptr == NULL) {
4349     // Forward-to-self succeeded.
4350     assert(_par_scan_state != NULL, "par scan state");
4351     OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4352     uint queue_num = _par_scan_state->queue_num();
4353 
4354     _evacuation_failed = true;
4355     _evacuation_failed_info_array[queue_num].register_copy_failure(old->size());
4356     if (_evac_failure_closure != cl) {
4357       MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4358       assert(!_drain_in_progress,
4359              "Should only be true while someone holds the lock.");
4360       // Set the global evac-failure closure to the current thread's.
4361       assert(_evac_failure_closure == NULL, "Or locking has failed.");
4362       set_evac_failure_closure(cl);
4363       // Now do the common part.
4364       handle_evacuation_failure_common(old, m);
4365       // Reset to NULL.
4366       set_evac_failure_closure(NULL);
4367     } else {
4368       // The lock is already held, and this is recursive.
4369       assert(_drain_in_progress, "This should only be the recursive case.");
4370       handle_evacuation_failure_common(old, m);
4371     }
4372     return old;
4373   } else {
4374     // Forward-to-self failed. Either someone else managed to allocate
4375     // space for this object (old != forward_ptr) or they beat us in
4376     // self-forwarding it (old == forward_ptr).
4377     assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4378            err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4379                    "should not be in the CSet",
4380                    (HeapWord*) old, (HeapWord*) forward_ptr));
4381     return forward_ptr;
4382   }
4383 }
4384 
4385 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4386   preserve_mark_if_necessary(old, m);
4387 
4388   HeapRegion* r = heap_region_containing(old);
4389   if (!r->evacuation_failed()) {
4390     r->set_evacuation_failed(true);
4391     _hr_printer.evac_failure(r);
4392   }
4393 
4394   push_on_evac_failure_scan_stack(old);
4395 
4396   if (!_drain_in_progress) {
4397     // prevent recursion in copy_to_survivor_space()
4398     _drain_in_progress = true;
4399     drain_evac_failure_scan_stack();
4400     _drain_in_progress = false;
4401   }
4402 }
4403 
4404 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4405   assert(evacuation_failed(), "Oversaving!");
4406   // We want to call the "for_promotion_failure" version only in the
4407   // case of a promotion failure.
4408   if (m->must_be_preserved_for_promotion_failure(obj)) {
4409     _objs_with_preserved_marks.push(obj);
4410     _preserved_marks_of_objs.push(m);
4411   }
4412 }
4413 
4414 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
4415                                                   size_t word_size,
4416                                                   AllocationContext_t context) {
4417   if (purpose == GCAllocForSurvived) {
4418     HeapWord* result = survivor_attempt_allocation(word_size, context);
4419     if (result != NULL) {
4420       return result;
4421     } else {
4422       // Let's try to allocate in the old gen in case we can fit the
4423       // object there.
4424       return old_attempt_allocation(word_size, context);
4425     }
4426   } else {
4427     assert(purpose ==  GCAllocForTenured, "sanity");
4428     HeapWord* result = old_attempt_allocation(word_size, context);
4429     if (result != NULL) {
4430       return result;
4431     } else {
4432       // Let's try to allocate in the survivors in case we can fit the
4433       // object there.
4434       return survivor_attempt_allocation(word_size, context);
4435     }
4436   }
4437 
4438   ShouldNotReachHere();
4439   // Trying to keep some compilers happy.
4440   return NULL;
4441 }
4442 
4443 void G1ParCopyHelper::mark_object(oop obj) {
4444   assert(!_g1->heap_region_containing(obj)->in_collection_set(), "should not mark objects in the CSet");
4445 
4446   // We know that the object is not moving so it's safe to read its size.
4447   _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4448 }
4449 
4450 void G1ParCopyHelper::mark_forwarded_object(oop from_obj, oop to_obj) {
4451   assert(from_obj->is_forwarded(), "from obj should be forwarded");
4452   assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4453   assert(from_obj != to_obj, "should not be self-forwarded");
4454 
4455   assert(_g1->heap_region_containing(from_obj)->in_collection_set(), "from obj should be in the CSet");
4456   assert(!_g1->heap_region_containing(to_obj)->in_collection_set(), "should not mark objects in the CSet");
4457 
4458   // The object might be in the process of being copied by another
4459   // worker so we cannot trust that its to-space image is
4460   // well-formed. So we have to read its size from its from-space
4461   // image which we know should not be changing.
4462   _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4463 }
4464 
4465 template <class T>
4466 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) {
4467   if (_g1->heap_region_containing_raw(new_obj)->is_young()) {
4468     _scanned_klass->record_modified_oops();
4469   }
4470 }
4471 
4472 template <G1Barrier barrier, G1Mark do_mark_object>
4473 template <class T>
4474 void G1ParCopyClosure<barrier, do_mark_object>::do_oop_work(T* p) {
4475   T heap_oop = oopDesc::load_heap_oop(p);
4476 
4477   if (oopDesc::is_null(heap_oop)) {
4478     return;
4479   }
4480 
4481   oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
4482 
4483   assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4484 
4485   G1CollectedHeap::in_cset_state_t state = _g1->in_cset_state(obj);
4486 
4487   if (state == G1CollectedHeap::InCSet) {
4488     oop forwardee;
4489     if (obj->is_forwarded()) {
4490       forwardee = obj->forwardee();
4491     } else {
4492       forwardee = _par_scan_state->copy_to_survivor_space(obj);
4493     }
4494     assert(forwardee != NULL, "forwardee should not be NULL");
4495     oopDesc::encode_store_heap_oop(p, forwardee);
4496     if (do_mark_object != G1MarkNone && forwardee != obj) {
4497       // If the object is self-forwarded we don't need to explicitly
4498       // mark it, the evacuation failure protocol will do so.
4499       mark_forwarded_object(obj, forwardee);
4500     }
4501 
4502     if (barrier == G1BarrierKlass) {
4503       do_klass_barrier(p, forwardee);
4504     }
4505   } else {
4506     if (state == G1CollectedHeap::IsHumongous) {
4507       _g1->set_humongous_is_live(obj);
4508     }
4509     // The object is not in collection set. If we're a root scanning
4510     // closure during an initial mark pause then attempt to mark the object.
4511     if (do_mark_object == G1MarkFromRoot) {
4512       mark_object(obj);
4513     }
4514   }
4515 
4516   if (barrier == G1BarrierEvac) {
4517     _par_scan_state->update_rs(_from, p, _worker_id);
4518   }
4519 }
4520 
4521 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(oop* p);
4522 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(narrowOop* p);
4523 
4524 class G1ParEvacuateFollowersClosure : public VoidClosure {
4525 protected:
4526   G1CollectedHeap*              _g1h;
4527   G1ParScanThreadState*         _par_scan_state;
4528   RefToScanQueueSet*            _queues;
4529   ParallelTaskTerminator*       _terminator;
4530 
4531   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
4532   RefToScanQueueSet*      queues()         { return _queues; }
4533   ParallelTaskTerminator* terminator()     { return _terminator; }
4534 
4535 public:
4536   G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4537                                 G1ParScanThreadState* par_scan_state,
4538                                 RefToScanQueueSet* queues,
4539                                 ParallelTaskTerminator* terminator)
4540     : _g1h(g1h), _par_scan_state(par_scan_state),
4541       _queues(queues), _terminator(terminator) {}
4542 
4543   void do_void();
4544 
4545 private:
4546   inline bool offer_termination();
4547 };
4548 
4549 bool G1ParEvacuateFollowersClosure::offer_termination() {
4550   G1ParScanThreadState* const pss = par_scan_state();
4551   pss->start_term_time();
4552   const bool res = terminator()->offer_termination();
4553   pss->end_term_time();
4554   return res;
4555 }
4556 
4557 void G1ParEvacuateFollowersClosure::do_void() {
4558   G1ParScanThreadState* const pss = par_scan_state();
4559   pss->trim_queue();
4560   do {
4561     pss->steal_and_trim_queue(queues());
4562   } while (!offer_termination());
4563 }
4564 
4565 class G1KlassScanClosure : public KlassClosure {
4566  G1ParCopyHelper* _closure;
4567  bool             _process_only_dirty;
4568  int              _count;
4569  public:
4570   G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty)
4571       : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {}
4572   void do_klass(Klass* klass) {
4573     // If the klass has not been dirtied we know that there's
4574     // no references into  the young gen and we can skip it.
4575    if (!_process_only_dirty || klass->has_modified_oops()) {
4576       // Clean the klass since we're going to scavenge all the metadata.
4577       klass->clear_modified_oops();
4578 
4579       // Tell the closure that this klass is the Klass to scavenge
4580       // and is the one to dirty if oops are left pointing into the young gen.
4581       _closure->set_scanned_klass(klass);
4582 
4583       klass->oops_do(_closure);
4584 
4585       _closure->set_scanned_klass(NULL);
4586     }
4587     _count++;
4588   }
4589 };
4590 
4591 class G1CodeBlobClosure : public CodeBlobClosure {
4592   class HeapRegionGatheringOopClosure : public OopClosure {
4593     G1CollectedHeap* _g1h;
4594     OopClosure* _work;
4595     nmethod* _nm;
4596 
4597     template <typename T>
4598     void do_oop_work(T* p) {
4599       _work->do_oop(p);
4600       T oop_or_narrowoop = oopDesc::load_heap_oop(p);
4601       if (!oopDesc::is_null(oop_or_narrowoop)) {
4602         oop o = oopDesc::decode_heap_oop_not_null(oop_or_narrowoop);
4603         HeapRegion* hr = _g1h->heap_region_containing_raw(o);
4604         assert(!_g1h->obj_in_cs(o) || hr->rem_set()->strong_code_roots_list_contains(_nm), "if o still in CS then evacuation failed and nm must already be in the remset");
4605         hr->add_strong_code_root(_nm);
4606       }
4607     }
4608 
4609   public:
4610     HeapRegionGatheringOopClosure(OopClosure* oc) : _g1h(G1CollectedHeap::heap()), _work(oc), _nm(NULL) {}
4611 
4612     void do_oop(oop* o) {
4613       do_oop_work(o);
4614     }
4615 
4616     void do_oop(narrowOop* o) {
4617       do_oop_work(o);
4618     }
4619 
4620     void set_nm(nmethod* nm) {
4621       _nm = nm;
4622     }
4623   };
4624 
4625   HeapRegionGatheringOopClosure _oc;
4626 public:
4627   G1CodeBlobClosure(OopClosure* oc) : _oc(oc) {}
4628 
4629   void do_code_blob(CodeBlob* cb) {
4630     nmethod* nm = cb->as_nmethod_or_null();
4631     if (nm != NULL) {
4632       if (!nm->test_set_oops_do_mark()) {
4633         _oc.set_nm(nm);
4634         nm->oops_do(&_oc);
4635         nm->fix_oop_relocations();
4636       }
4637     }
4638   }
4639 };
4640 
4641 class G1ParTask : public AbstractGangTask {
4642 protected:
4643   G1CollectedHeap*       _g1h;
4644   RefToScanQueueSet      *_queues;
4645   ParallelTaskTerminator _terminator;
4646   uint _n_workers;
4647 
4648   Mutex _stats_lock;
4649   Mutex* stats_lock() { return &_stats_lock; }
4650 
4651 public:
4652   G1ParTask(G1CollectedHeap* g1h, RefToScanQueueSet *task_queues)
4653     : AbstractGangTask("G1 collection"),
4654       _g1h(g1h),
4655       _queues(task_queues),
4656       _terminator(0, _queues),
4657       _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4658   {}
4659 
4660   RefToScanQueueSet* queues() { return _queues; }
4661 
4662   RefToScanQueue *work_queue(int i) {
4663     return queues()->queue(i);
4664   }
4665 
4666   ParallelTaskTerminator* terminator() { return &_terminator; }
4667 
4668   virtual void set_for_termination(int active_workers) {
4669     // This task calls set_n_termination() in par_non_clean_card_iterate_work()
4670     // in the young space (_par_seq_tasks) in the G1 heap
4671     // for SequentialSubTasksDone.
4672     // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap
4673     // both of which need setting by set_n_termination().
4674     _g1h->SharedHeap::set_n_termination(active_workers);
4675     _g1h->set_n_termination(active_workers);
4676     terminator()->reset_for_reuse(active_workers);
4677     _n_workers = active_workers;
4678   }
4679 
4680   // Helps out with CLD processing.
4681   //
4682   // During InitialMark we need to:
4683   // 1) Scavenge all CLDs for the young GC.
4684   // 2) Mark all objects directly reachable from strong CLDs.
4685   template <G1Mark do_mark_object>
4686   class G1CLDClosure : public CLDClosure {
4687     G1ParCopyClosure<G1BarrierNone,  do_mark_object>* _oop_closure;
4688     G1ParCopyClosure<G1BarrierKlass, do_mark_object>  _oop_in_klass_closure;
4689     G1KlassScanClosure                                _klass_in_cld_closure;
4690     bool                                              _claim;
4691 
4692    public:
4693     G1CLDClosure(G1ParCopyClosure<G1BarrierNone, do_mark_object>* oop_closure,
4694                  bool only_young, bool claim)
4695         : _oop_closure(oop_closure),
4696           _oop_in_klass_closure(oop_closure->g1(),
4697                                 oop_closure->pss(),
4698                                 oop_closure->rp()),
4699           _klass_in_cld_closure(&_oop_in_klass_closure, only_young),
4700           _claim(claim) {
4701 
4702     }
4703 
4704     void do_cld(ClassLoaderData* cld) {
4705       cld->oops_do(_oop_closure, &_klass_in_cld_closure, _claim);
4706     }
4707   };
4708 
4709   void work(uint worker_id) {
4710     if (worker_id >= _n_workers) return;  // no work needed this round
4711 
4712     double start_time_ms = os::elapsedTime() * 1000.0;
4713     _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms);
4714 
4715     {
4716       ResourceMark rm;
4717       HandleMark   hm;
4718 
4719       ReferenceProcessor*             rp = _g1h->ref_processor_stw();
4720 
4721       G1ParScanThreadState            pss(_g1h, worker_id, rp);
4722       G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
4723 
4724       pss.set_evac_failure_closure(&evac_failure_cl);
4725 
4726       bool only_young = _g1h->g1_policy()->gcs_are_young();
4727 
4728       // Non-IM young GC.
4729       G1ParCopyClosure<G1BarrierNone, G1MarkNone>             scan_only_root_cl(_g1h, &pss, rp);
4730       G1CLDClosure<G1MarkNone>                                scan_only_cld_cl(&scan_only_root_cl,
4731                                                                                only_young, // Only process dirty klasses.
4732                                                                                false);     // No need to claim CLDs.
4733       // IM young GC.
4734       //    Strong roots closures.
4735       G1ParCopyClosure<G1BarrierNone, G1MarkFromRoot>         scan_mark_root_cl(_g1h, &pss, rp);
4736       G1CLDClosure<G1MarkFromRoot>                            scan_mark_cld_cl(&scan_mark_root_cl,
4737                                                                                false, // Process all klasses.
4738                                                                                true); // Need to claim CLDs.
4739       //    Weak roots closures.
4740       G1ParCopyClosure<G1BarrierNone, G1MarkPromotedFromRoot> scan_mark_weak_root_cl(_g1h, &pss, rp);
4741       G1CLDClosure<G1MarkPromotedFromRoot>                    scan_mark_weak_cld_cl(&scan_mark_weak_root_cl,
4742                                                                                     false, // Process all klasses.
4743                                                                                     true); // Need to claim CLDs.
4744 
4745       G1CodeBlobClosure scan_only_code_cl(&scan_only_root_cl);
4746       G1CodeBlobClosure scan_mark_code_cl(&scan_mark_root_cl);
4747       // IM Weak code roots are handled later.
4748 
4749       OopClosure* strong_root_cl;
4750       OopClosure* weak_root_cl;
4751       CLDClosure* strong_cld_cl;
4752       CLDClosure* weak_cld_cl;
4753       CodeBlobClosure* strong_code_cl;
4754 
4755       if (_g1h->g1_policy()->during_initial_mark_pause()) {
4756         // We also need to mark copied objects.
4757         strong_root_cl = &scan_mark_root_cl;
4758         strong_cld_cl  = &scan_mark_cld_cl;
4759         strong_code_cl = &scan_mark_code_cl;
4760         if (ClassUnloadingWithConcurrentMark) {
4761           weak_root_cl = &scan_mark_weak_root_cl;
4762           weak_cld_cl  = &scan_mark_weak_cld_cl;
4763         } else {
4764           weak_root_cl = &scan_mark_root_cl;
4765           weak_cld_cl  = &scan_mark_cld_cl;
4766         }
4767       } else {
4768         strong_root_cl = &scan_only_root_cl;
4769         weak_root_cl   = &scan_only_root_cl;
4770         strong_cld_cl  = &scan_only_cld_cl;
4771         weak_cld_cl    = &scan_only_cld_cl;
4772         strong_code_cl = &scan_only_code_cl;
4773       }
4774 
4775 
4776       G1ParPushHeapRSClosure  push_heap_rs_cl(_g1h, &pss);
4777 
4778       pss.start_strong_roots();
4779       _g1h->g1_process_roots(strong_root_cl,
4780                              weak_root_cl,
4781                              &push_heap_rs_cl,
4782                              strong_cld_cl,
4783                              weak_cld_cl,
4784                              strong_code_cl,
4785                              worker_id);
4786 
4787       pss.end_strong_roots();
4788 
4789       {
4790         double start = os::elapsedTime();
4791         G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4792         evac.do_void();
4793         double elapsed_ms = (os::elapsedTime()-start)*1000.0;
4794         double term_ms = pss.term_time()*1000.0;
4795         _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms);
4796         _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts());
4797       }
4798       _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4799       _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4800 
4801       if (PrintTerminationStats) {
4802         MutexLocker x(stats_lock());
4803         pss.print_termination_stats(worker_id);
4804       }
4805 
4806       assert(pss.queue_is_empty(), "should be empty");
4807 
4808       // Close the inner scope so that the ResourceMark and HandleMark
4809       // destructors are executed here and are included as part of the
4810       // "GC Worker Time".
4811     }
4812 
4813     double end_time_ms = os::elapsedTime() * 1000.0;
4814     _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms);
4815   }
4816 };
4817 
4818 // *** Common G1 Evacuation Stuff
4819 
4820 // This method is run in a GC worker.
4821 
4822 void
4823 G1CollectedHeap::
4824 g1_process_roots(OopClosure* scan_non_heap_roots,
4825                  OopClosure* scan_non_heap_weak_roots,
4826                  OopsInHeapRegionClosure* scan_rs,
4827                  CLDClosure* scan_strong_clds,
4828                  CLDClosure* scan_weak_clds,
4829                  CodeBlobClosure* scan_strong_code,
4830                  uint worker_i) {
4831 
4832   // First scan the shared roots.
4833   double ext_roots_start = os::elapsedTime();
4834   double closure_app_time_sec = 0.0;
4835 
4836   bool during_im = _g1h->g1_policy()->during_initial_mark_pause();
4837   bool trace_metadata = during_im && ClassUnloadingWithConcurrentMark;
4838 
4839   BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
4840   BufferingOopClosure buf_scan_non_heap_weak_roots(scan_non_heap_weak_roots);
4841 
4842   process_roots(false, // no scoping; this is parallel code
4843                 SharedHeap::SO_None,
4844                 &buf_scan_non_heap_roots,
4845                 &buf_scan_non_heap_weak_roots,
4846                 scan_strong_clds,
4847                 // Unloading Initial Marks handle the weak CLDs separately.
4848                 (trace_metadata ? NULL : scan_weak_clds),
4849                 scan_strong_code);
4850 
4851   // Now the CM ref_processor roots.
4852   if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
4853     // We need to treat the discovered reference lists of the
4854     // concurrent mark ref processor as roots and keep entries
4855     // (which are added by the marking threads) on them live
4856     // until they can be processed at the end of marking.
4857     ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
4858   }
4859 
4860   if (trace_metadata) {
4861     // Barrier to make sure all workers passed
4862     // the strong CLD and strong nmethods phases.
4863     active_strong_roots_scope()->wait_until_all_workers_done_with_threads(n_par_threads());
4864 
4865     // Now take the complement of the strong CLDs.
4866     ClassLoaderDataGraph::roots_cld_do(NULL, scan_weak_clds);
4867   }
4868 
4869   // Finish up any enqueued closure apps (attributed as object copy time).
4870   buf_scan_non_heap_roots.done();
4871   buf_scan_non_heap_weak_roots.done();
4872 
4873   double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds()
4874       + buf_scan_non_heap_weak_roots.closure_app_seconds();
4875 
4876   g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
4877 
4878   double ext_root_time_ms =
4879     ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0;
4880 
4881   g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
4882 
4883   // During conc marking we have to filter the per-thread SATB buffers
4884   // to make sure we remove any oops into the CSet (which will show up
4885   // as implicitly live).
4886   double satb_filtering_ms = 0.0;
4887   if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) {
4888     if (mark_in_progress()) {
4889       double satb_filter_start = os::elapsedTime();
4890 
4891       JavaThread::satb_mark_queue_set().filter_thread_buffers();
4892 
4893       satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0;
4894     }
4895   }
4896   g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms);
4897 
4898   // Now scan the complement of the collection set.
4899   G1CodeBlobClosure scavenge_cs_nmethods(scan_non_heap_weak_roots);
4900 
4901   g1_rem_set()->oops_into_collection_set_do(scan_rs, &scavenge_cs_nmethods, worker_i);
4902 
4903   _process_strong_tasks->all_tasks_completed();
4904 }
4905 
4906 class G1StringSymbolTableUnlinkTask : public AbstractGangTask {
4907 private:
4908   BoolObjectClosure* _is_alive;
4909   int _initial_string_table_size;
4910   int _initial_symbol_table_size;
4911 
4912   bool  _process_strings;
4913   int _strings_processed;
4914   int _strings_removed;
4915 
4916   bool  _process_symbols;
4917   int _symbols_processed;
4918   int _symbols_removed;
4919 
4920   bool _do_in_parallel;
4921 public:
4922   G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) :
4923     AbstractGangTask("String/Symbol Unlinking"),
4924     _is_alive(is_alive),
4925     _do_in_parallel(G1CollectedHeap::use_parallel_gc_threads()),
4926     _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
4927     _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) {
4928 
4929     _initial_string_table_size = StringTable::the_table()->table_size();
4930     _initial_symbol_table_size = SymbolTable::the_table()->table_size();
4931     if (process_strings) {
4932       StringTable::clear_parallel_claimed_index();
4933     }
4934     if (process_symbols) {
4935       SymbolTable::clear_parallel_claimed_index();
4936     }
4937   }
4938 
4939   ~G1StringSymbolTableUnlinkTask() {
4940     guarantee(!_process_strings || !_do_in_parallel || StringTable::parallel_claimed_index() >= _initial_string_table_size,
4941               err_msg("claim value %d after unlink less than initial string table size %d",
4942                       StringTable::parallel_claimed_index(), _initial_string_table_size));
4943     guarantee(!_process_symbols || !_do_in_parallel || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
4944               err_msg("claim value %d after unlink less than initial symbol table size %d",
4945                       SymbolTable::parallel_claimed_index(), _initial_symbol_table_size));
4946 
4947     if (G1TraceStringSymbolTableScrubbing) {
4948       gclog_or_tty->print_cr("Cleaned string and symbol table, "
4949                              "strings: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed, "
4950                              "symbols: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed",
4951                              strings_processed(), strings_removed(),
4952                              symbols_processed(), symbols_removed());
4953     }
4954   }
4955 
4956   void work(uint worker_id) {
4957     if (_do_in_parallel) {
4958       int strings_processed = 0;
4959       int strings_removed = 0;
4960       int symbols_processed = 0;
4961       int symbols_removed = 0;
4962       if (_process_strings) {
4963         StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
4964         Atomic::add(strings_processed, &_strings_processed);
4965         Atomic::add(strings_removed, &_strings_removed);
4966       }
4967       if (_process_symbols) {
4968         SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
4969         Atomic::add(symbols_processed, &_symbols_processed);
4970         Atomic::add(symbols_removed, &_symbols_removed);
4971       }
4972     } else {
4973       if (_process_strings) {
4974         StringTable::unlink(_is_alive, &_strings_processed, &_strings_removed);
4975       }
4976       if (_process_symbols) {
4977         SymbolTable::unlink(&_symbols_processed, &_symbols_removed);
4978       }
4979     }
4980   }
4981 
4982   size_t strings_processed() const { return (size_t)_strings_processed; }
4983   size_t strings_removed()   const { return (size_t)_strings_removed; }
4984 
4985   size_t symbols_processed() const { return (size_t)_symbols_processed; }
4986   size_t symbols_removed()   const { return (size_t)_symbols_removed; }
4987 };
4988 
4989 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
4990 private:
4991   static Monitor* _lock;
4992 
4993   BoolObjectClosure* const _is_alive;
4994   const bool               _unloading_occurred;
4995   const uint               _num_workers;
4996 
4997   // Variables used to claim nmethods.
4998   nmethod* _first_nmethod;
4999   volatile nmethod* _claimed_nmethod;
5000 
5001   // The list of nmethods that need to be processed by the second pass.
5002   volatile nmethod* _postponed_list;
5003   volatile uint     _num_entered_barrier;
5004 
5005  public:
5006   G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
5007       _is_alive(is_alive),
5008       _unloading_occurred(unloading_occurred),
5009       _num_workers(num_workers),
5010       _first_nmethod(NULL),
5011       _claimed_nmethod(NULL),
5012       _postponed_list(NULL),
5013       _num_entered_barrier(0)
5014   {
5015     nmethod::increase_unloading_clock();
5016     _first_nmethod = CodeCache::alive_nmethod(CodeCache::first());
5017     _claimed_nmethod = (volatile nmethod*)_first_nmethod;
5018   }
5019 
5020   ~G1CodeCacheUnloadingTask() {
5021     CodeCache::verify_clean_inline_caches();
5022 
5023     CodeCache::set_needs_cache_clean(false);
5024     guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
5025 
5026     CodeCache::verify_icholder_relocations();
5027   }
5028 
5029  private:
5030   void add_to_postponed_list(nmethod* nm) {
5031       nmethod* old;
5032       do {
5033         old = (nmethod*)_postponed_list;
5034         nm->set_unloading_next(old);
5035       } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old);
5036   }
5037 
5038   void clean_nmethod(nmethod* nm) {
5039     bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
5040 
5041     if (postponed) {
5042       // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
5043       add_to_postponed_list(nm);
5044     }
5045 
5046     // Mark that this thread has been cleaned/unloaded.
5047     // After this call, it will be safe to ask if this nmethod was unloaded or not.
5048     nm->set_unloading_clock(nmethod::global_unloading_clock());
5049   }
5050 
5051   void clean_nmethod_postponed(nmethod* nm) {
5052     nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
5053   }
5054 
5055   static const int MaxClaimNmethods = 16;
5056 
5057   void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) {
5058     nmethod* first;
5059     nmethod* last;
5060 
5061     do {
5062       *num_claimed_nmethods = 0;
5063 
5064       first = last = (nmethod*)_claimed_nmethod;
5065 
5066       if (first != NULL) {
5067         for (int i = 0; i < MaxClaimNmethods; i++) {
5068           last = CodeCache::alive_nmethod(CodeCache::next(last));
5069 
5070           if (last == NULL) {
5071             break;
5072           }
5073 
5074           claimed_nmethods[i] = last;
5075           (*num_claimed_nmethods)++;
5076         }
5077       }
5078 
5079     } while ((nmethod*)Atomic::cmpxchg_ptr(last, &_claimed_nmethod, first) != first);
5080   }
5081 
5082   nmethod* claim_postponed_nmethod() {
5083     nmethod* claim;
5084     nmethod* next;
5085 
5086     do {
5087       claim = (nmethod*)_postponed_list;
5088       if (claim == NULL) {
5089         return NULL;
5090       }
5091 
5092       next = claim->unloading_next();
5093 
5094     } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim);
5095 
5096     return claim;
5097   }
5098 
5099  public:
5100   // Mark that we're done with the first pass of nmethod cleaning.
5101   void barrier_mark(uint worker_id) {
5102     MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
5103     _num_entered_barrier++;
5104     if (_num_entered_barrier == _num_workers) {
5105       ml.notify_all();
5106     }
5107   }
5108 
5109   // See if we have to wait for the other workers to
5110   // finish their first-pass nmethod cleaning work.
5111   void barrier_wait(uint worker_id) {
5112     if (_num_entered_barrier < _num_workers) {
5113       MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
5114       while (_num_entered_barrier < _num_workers) {
5115           ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
5116       }
5117     }
5118   }
5119 
5120   // Cleaning and unloading of nmethods. Some work has to be postponed
5121   // to the second pass, when we know which nmethods survive.
5122   void work_first_pass(uint worker_id) {
5123     // The first nmethods is claimed by the first worker.
5124     if (worker_id == 0 && _first_nmethod != NULL) {
5125       clean_nmethod(_first_nmethod);
5126       _first_nmethod = NULL;
5127     }
5128 
5129     int num_claimed_nmethods;
5130     nmethod* claimed_nmethods[MaxClaimNmethods];
5131 
5132     while (true) {
5133       claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
5134 
5135       if (num_claimed_nmethods == 0) {
5136         break;
5137       }
5138 
5139       for (int i = 0; i < num_claimed_nmethods; i++) {
5140         clean_nmethod(claimed_nmethods[i]);
5141       }
5142     }
5143   }
5144 
5145   void work_second_pass(uint worker_id) {
5146     nmethod* nm;
5147     // Take care of postponed nmethods.
5148     while ((nm = claim_postponed_nmethod()) != NULL) {
5149       clean_nmethod_postponed(nm);
5150     }
5151   }
5152 };
5153 
5154 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock");
5155 
5156 class G1KlassCleaningTask : public StackObj {
5157   BoolObjectClosure*                      _is_alive;
5158   volatile jint                           _clean_klass_tree_claimed;
5159   ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
5160 
5161  public:
5162   G1KlassCleaningTask(BoolObjectClosure* is_alive) :
5163       _is_alive(is_alive),
5164       _clean_klass_tree_claimed(0),
5165       _klass_iterator() {
5166   }
5167 
5168  private:
5169   bool claim_clean_klass_tree_task() {
5170     if (_clean_klass_tree_claimed) {
5171       return false;
5172     }
5173 
5174     return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0;
5175   }
5176 
5177   InstanceKlass* claim_next_klass() {
5178     Klass* klass;
5179     do {
5180       klass =_klass_iterator.next_klass();
5181     } while (klass != NULL && !klass->oop_is_instance());
5182 
5183     return (InstanceKlass*)klass;
5184   }
5185 
5186 public:
5187 
5188   void clean_klass(InstanceKlass* ik) {
5189     ik->clean_implementors_list(_is_alive);
5190     ik->clean_method_data(_is_alive);
5191 
5192     // G1 specific cleanup work that has
5193     // been moved here to be done in parallel.
5194     ik->clean_dependent_nmethods();
5195   }
5196 
5197   void work() {
5198     ResourceMark rm;
5199 
5200     // One worker will clean the subklass/sibling klass tree.
5201     if (claim_clean_klass_tree_task()) {
5202       Klass::clean_subklass_tree(_is_alive);
5203     }
5204 
5205     // All workers will help cleaning the classes,
5206     InstanceKlass* klass;
5207     while ((klass = claim_next_klass()) != NULL) {
5208       clean_klass(klass);
5209     }
5210   }
5211 };
5212 
5213 // To minimize the remark pause times, the tasks below are done in parallel.
5214 class G1ParallelCleaningTask : public AbstractGangTask {
5215 private:
5216   G1StringSymbolTableUnlinkTask _string_symbol_task;
5217   G1CodeCacheUnloadingTask      _code_cache_task;
5218   G1KlassCleaningTask           _klass_cleaning_task;
5219 
5220 public:
5221   // The constructor is run in the VMThread.
5222   G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) :
5223       AbstractGangTask("Parallel Cleaning"),
5224       _string_symbol_task(is_alive, process_strings, process_symbols),
5225       _code_cache_task(num_workers, is_alive, unloading_occurred),
5226       _klass_cleaning_task(is_alive) {
5227   }
5228 
5229   // The parallel work done by all worker threads.
5230   void work(uint worker_id) {
5231     // Do first pass of code cache cleaning.
5232     _code_cache_task.work_first_pass(worker_id);
5233 
5234     // Let the threads mark that the first pass is done.
5235     _code_cache_task.barrier_mark(worker_id);
5236 
5237     // Clean the Strings and Symbols.
5238     _string_symbol_task.work(worker_id);
5239 
5240     // Wait for all workers to finish the first code cache cleaning pass.
5241     _code_cache_task.barrier_wait(worker_id);
5242 
5243     // Do the second code cache cleaning work, which realize on
5244     // the liveness information gathered during the first pass.
5245     _code_cache_task.work_second_pass(worker_id);
5246 
5247     // Clean all klasses that were not unloaded.
5248     _klass_cleaning_task.work();
5249   }
5250 };
5251 
5252 
5253 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive,
5254                                         bool process_strings,
5255                                         bool process_symbols,
5256                                         bool class_unloading_occurred) {
5257   uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5258                     workers()->active_workers() : 1);
5259 
5260   G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols,
5261                                         n_workers, class_unloading_occurred);
5262   if (G1CollectedHeap::use_parallel_gc_threads()) {
5263     set_par_threads(n_workers);
5264     workers()->run_task(&g1_unlink_task);
5265     set_par_threads(0);
5266   } else {
5267     g1_unlink_task.work(0);
5268   }
5269 }
5270 
5271 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive,
5272                                                      bool process_strings, bool process_symbols) {
5273   {
5274     uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5275                      _g1h->workers()->active_workers() : 1);
5276     G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols);
5277     if (G1CollectedHeap::use_parallel_gc_threads()) {
5278       set_par_threads(n_workers);
5279       workers()->run_task(&g1_unlink_task);
5280       set_par_threads(0);
5281     } else {
5282       g1_unlink_task.work(0);
5283     }
5284   }
5285 
5286   if (G1StringDedup::is_enabled()) {
5287     G1StringDedup::unlink(is_alive);
5288   }
5289 }
5290 
5291 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
5292  private:
5293   DirtyCardQueueSet* _queue;
5294  public:
5295   G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue) : AbstractGangTask("Redirty Cards"), _queue(queue) { }
5296 
5297   virtual void work(uint worker_id) {
5298     double start_time = os::elapsedTime();
5299 
5300     RedirtyLoggedCardTableEntryClosure cl;
5301     if (G1CollectedHeap::heap()->use_parallel_gc_threads()) {
5302       _queue->par_apply_closure_to_all_completed_buffers(&cl);
5303     } else {
5304       _queue->apply_closure_to_all_completed_buffers(&cl);
5305     }
5306 
5307     G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
5308     timer->record_redirty_logged_cards_time_ms(worker_id, (os::elapsedTime() - start_time) * 1000.0);
5309     timer->record_redirty_logged_cards_processed_cards(worker_id, cl.num_processed());
5310   }
5311 };
5312 
5313 void G1CollectedHeap::redirty_logged_cards() {
5314   double redirty_logged_cards_start = os::elapsedTime();
5315 
5316   uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5317                    _g1h->workers()->active_workers() : 1);
5318 
5319   G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set());
5320   dirty_card_queue_set().reset_for_par_iteration();
5321   if (use_parallel_gc_threads()) {
5322     set_par_threads(n_workers);
5323     workers()->run_task(&redirty_task);
5324     set_par_threads(0);
5325   } else {
5326     redirty_task.work(0);
5327   }
5328 
5329   DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5330   dcq.merge_bufferlists(&dirty_card_queue_set());
5331   assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5332 
5333   g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
5334 }
5335 
5336 // Weak Reference Processing support
5337 
5338 // An always "is_alive" closure that is used to preserve referents.
5339 // If the object is non-null then it's alive.  Used in the preservation
5340 // of referent objects that are pointed to by reference objects
5341 // discovered by the CM ref processor.
5342 class G1AlwaysAliveClosure: public BoolObjectClosure {
5343   G1CollectedHeap* _g1;
5344 public:
5345   G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5346   bool do_object_b(oop p) {
5347     if (p != NULL) {
5348       return true;
5349     }
5350     return false;
5351   }
5352 };
5353 
5354 bool G1STWIsAliveClosure::do_object_b(oop p) {
5355   // An object is reachable if it is outside the collection set,
5356   // or is inside and copied.
5357   return !_g1->obj_in_cs(p) || p->is_forwarded();
5358 }
5359 
5360 // Non Copying Keep Alive closure
5361 class G1KeepAliveClosure: public OopClosure {
5362   G1CollectedHeap* _g1;
5363 public:
5364   G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5365   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
5366   void do_oop(oop* p) {
5367     oop obj = *p;
5368     assert(obj != NULL, "the caller should have filtered out NULL values");
5369 
5370     G1CollectedHeap::in_cset_state_t cset_state = _g1->in_cset_state(obj);
5371     if (cset_state == G1CollectedHeap::InNeither) {
5372       return;
5373     }
5374     if (cset_state == G1CollectedHeap::InCSet) {
5375       assert( obj->is_forwarded(), "invariant" );
5376       *p = obj->forwardee();
5377     } else {
5378       assert(!obj->is_forwarded(), "invariant" );
5379       assert(cset_state == G1CollectedHeap::IsHumongous,
5380              err_msg("Only allowed InCSet state is IsHumongous, but is %d", cset_state));
5381       _g1->set_humongous_is_live(obj);
5382     }
5383   }
5384 };
5385 
5386 // Copying Keep Alive closure - can be called from both
5387 // serial and parallel code as long as different worker
5388 // threads utilize different G1ParScanThreadState instances
5389 // and different queues.
5390 
5391 class G1CopyingKeepAliveClosure: public OopClosure {
5392   G1CollectedHeap*         _g1h;
5393   OopClosure*              _copy_non_heap_obj_cl;
5394   G1ParScanThreadState*    _par_scan_state;
5395 
5396 public:
5397   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
5398                             OopClosure* non_heap_obj_cl,
5399                             G1ParScanThreadState* pss):
5400     _g1h(g1h),
5401     _copy_non_heap_obj_cl(non_heap_obj_cl),
5402     _par_scan_state(pss)
5403   {}
5404 
5405   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
5406   virtual void do_oop(      oop* p) { do_oop_work(p); }
5407 
5408   template <class T> void do_oop_work(T* p) {
5409     oop obj = oopDesc::load_decode_heap_oop(p);
5410 
5411     if (_g1h->is_in_cset_or_humongous(obj)) {
5412       // If the referent object has been forwarded (either copied
5413       // to a new location or to itself in the event of an
5414       // evacuation failure) then we need to update the reference
5415       // field and, if both reference and referent are in the G1
5416       // heap, update the RSet for the referent.
5417       //
5418       // If the referent has not been forwarded then we have to keep
5419       // it alive by policy. Therefore we have copy the referent.
5420       //
5421       // If the reference field is in the G1 heap then we can push
5422       // on the PSS queue. When the queue is drained (after each
5423       // phase of reference processing) the object and it's followers
5424       // will be copied, the reference field set to point to the
5425       // new location, and the RSet updated. Otherwise we need to
5426       // use the the non-heap or metadata closures directly to copy
5427       // the referent object and update the pointer, while avoiding
5428       // updating the RSet.
5429 
5430       if (_g1h->is_in_g1_reserved(p)) {
5431         _par_scan_state->push_on_queue(p);
5432       } else {
5433         assert(!Metaspace::contains((const void*)p),
5434                err_msg("Unexpectedly found a pointer from metadata: "
5435                               PTR_FORMAT, p));
5436         _copy_non_heap_obj_cl->do_oop(p);
5437       }
5438     }
5439   }
5440 };
5441 
5442 // Serial drain queue closure. Called as the 'complete_gc'
5443 // closure for each discovered list in some of the
5444 // reference processing phases.
5445 
5446 class G1STWDrainQueueClosure: public VoidClosure {
5447 protected:
5448   G1CollectedHeap* _g1h;
5449   G1ParScanThreadState* _par_scan_state;
5450 
5451   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
5452 
5453 public:
5454   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
5455     _g1h(g1h),
5456     _par_scan_state(pss)
5457   { }
5458 
5459   void do_void() {
5460     G1ParScanThreadState* const pss = par_scan_state();
5461     pss->trim_queue();
5462   }
5463 };
5464 
5465 // Parallel Reference Processing closures
5466 
5467 // Implementation of AbstractRefProcTaskExecutor for parallel reference
5468 // processing during G1 evacuation pauses.
5469 
5470 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5471 private:
5472   G1CollectedHeap*   _g1h;
5473   RefToScanQueueSet* _queues;
5474   FlexibleWorkGang*  _workers;
5475   int                _active_workers;
5476 
5477 public:
5478   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5479                         FlexibleWorkGang* workers,
5480                         RefToScanQueueSet *task_queues,
5481                         int n_workers) :
5482     _g1h(g1h),
5483     _queues(task_queues),
5484     _workers(workers),
5485     _active_workers(n_workers)
5486   {
5487     assert(n_workers > 0, "shouldn't call this otherwise");
5488   }
5489 
5490   // Executes the given task using concurrent marking worker threads.
5491   virtual void execute(ProcessTask& task);
5492   virtual void execute(EnqueueTask& task);
5493 };
5494 
5495 // Gang task for possibly parallel reference processing
5496 
5497 class G1STWRefProcTaskProxy: public AbstractGangTask {
5498   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5499   ProcessTask&     _proc_task;
5500   G1CollectedHeap* _g1h;
5501   RefToScanQueueSet *_task_queues;
5502   ParallelTaskTerminator* _terminator;
5503 
5504 public:
5505   G1STWRefProcTaskProxy(ProcessTask& proc_task,
5506                      G1CollectedHeap* g1h,
5507                      RefToScanQueueSet *task_queues,
5508                      ParallelTaskTerminator* terminator) :
5509     AbstractGangTask("Process reference objects in parallel"),
5510     _proc_task(proc_task),
5511     _g1h(g1h),
5512     _task_queues(task_queues),
5513     _terminator(terminator)
5514   {}
5515 
5516   virtual void work(uint worker_id) {
5517     // The reference processing task executed by a single worker.
5518     ResourceMark rm;
5519     HandleMark   hm;
5520 
5521     G1STWIsAliveClosure is_alive(_g1h);
5522 
5523     G1ParScanThreadState            pss(_g1h, worker_id, NULL);
5524     G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5525 
5526     pss.set_evac_failure_closure(&evac_failure_cl);
5527 
5528     G1ParScanExtRootClosure        only_copy_non_heap_cl(_g1h, &pss, NULL);
5529 
5530     G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5531 
5532     OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5533 
5534     if (_g1h->g1_policy()->during_initial_mark_pause()) {
5535       // We also need to mark copied objects.
5536       copy_non_heap_cl = &copy_mark_non_heap_cl;
5537     }
5538 
5539     // Keep alive closure.
5540     G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5541 
5542     // Complete GC closure
5543     G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5544 
5545     // Call the reference processing task's work routine.
5546     _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5547 
5548     // Note we cannot assert that the refs array is empty here as not all
5549     // of the processing tasks (specifically phase2 - pp2_work) execute
5550     // the complete_gc closure (which ordinarily would drain the queue) so
5551     // the queue may not be empty.
5552   }
5553 };
5554 
5555 // Driver routine for parallel reference processing.
5556 // Creates an instance of the ref processing gang
5557 // task and has the worker threads execute it.
5558 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5559   assert(_workers != NULL, "Need parallel worker threads.");
5560 
5561   ParallelTaskTerminator terminator(_active_workers, _queues);
5562   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5563 
5564   _g1h->set_par_threads(_active_workers);
5565   _workers->run_task(&proc_task_proxy);
5566   _g1h->set_par_threads(0);
5567 }
5568 
5569 // Gang task for parallel reference enqueueing.
5570 
5571 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5572   typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5573   EnqueueTask& _enq_task;
5574 
5575 public:
5576   G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5577     AbstractGangTask("Enqueue reference objects in parallel"),
5578     _enq_task(enq_task)
5579   { }
5580 
5581   virtual void work(uint worker_id) {
5582     _enq_task.work(worker_id);
5583   }
5584 };
5585 
5586 // Driver routine for parallel reference enqueueing.
5587 // Creates an instance of the ref enqueueing gang
5588 // task and has the worker threads execute it.
5589 
5590 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5591   assert(_workers != NULL, "Need parallel worker threads.");
5592 
5593   G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5594 
5595   _g1h->set_par_threads(_active_workers);
5596   _workers->run_task(&enq_task_proxy);
5597   _g1h->set_par_threads(0);
5598 }
5599 
5600 // End of weak reference support closures
5601 
5602 // Abstract task used to preserve (i.e. copy) any referent objects
5603 // that are in the collection set and are pointed to by reference
5604 // objects discovered by the CM ref processor.
5605 
5606 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5607 protected:
5608   G1CollectedHeap* _g1h;
5609   RefToScanQueueSet      *_queues;
5610   ParallelTaskTerminator _terminator;
5611   uint _n_workers;
5612 
5613 public:
5614   G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
5615     AbstractGangTask("ParPreserveCMReferents"),
5616     _g1h(g1h),
5617     _queues(task_queues),
5618     _terminator(workers, _queues),
5619     _n_workers(workers)
5620   { }
5621 
5622   void work(uint worker_id) {
5623     ResourceMark rm;
5624     HandleMark   hm;
5625 
5626     G1ParScanThreadState            pss(_g1h, worker_id, NULL);
5627     G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5628 
5629     pss.set_evac_failure_closure(&evac_failure_cl);
5630 
5631     assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5632 
5633     G1ParScanExtRootClosure        only_copy_non_heap_cl(_g1h, &pss, NULL);
5634 
5635     G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5636 
5637     OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5638 
5639     if (_g1h->g1_policy()->during_initial_mark_pause()) {
5640       // We also need to mark copied objects.
5641       copy_non_heap_cl = &copy_mark_non_heap_cl;
5642     }
5643 
5644     // Is alive closure
5645     G1AlwaysAliveClosure always_alive(_g1h);
5646 
5647     // Copying keep alive closure. Applied to referent objects that need
5648     // to be copied.
5649     G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5650 
5651     ReferenceProcessor* rp = _g1h->ref_processor_cm();
5652 
5653     uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5654     uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5655 
5656     // limit is set using max_num_q() - which was set using ParallelGCThreads.
5657     // So this must be true - but assert just in case someone decides to
5658     // change the worker ids.
5659     assert(0 <= worker_id && worker_id < limit, "sanity");
5660     assert(!rp->discovery_is_atomic(), "check this code");
5661 
5662     // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5663     for (uint idx = worker_id; idx < limit; idx += stride) {
5664       DiscoveredList& ref_list = rp->discovered_refs()[idx];
5665 
5666       DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5667       while (iter.has_next()) {
5668         // Since discovery is not atomic for the CM ref processor, we
5669         // can see some null referent objects.
5670         iter.load_ptrs(DEBUG_ONLY(true));
5671         oop ref = iter.obj();
5672 
5673         // This will filter nulls.
5674         if (iter.is_referent_alive()) {
5675           iter.make_referent_alive();
5676         }
5677         iter.move_to_next();
5678       }
5679     }
5680 
5681     // Drain the queue - which may cause stealing
5682     G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5683     drain_queue.do_void();
5684     // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5685     assert(pss.queue_is_empty(), "should be");
5686   }
5687 };
5688 
5689 // Weak Reference processing during an evacuation pause (part 1).
5690 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) {
5691   double ref_proc_start = os::elapsedTime();
5692 
5693   ReferenceProcessor* rp = _ref_processor_stw;
5694   assert(rp->discovery_enabled(), "should have been enabled");
5695 
5696   // Any reference objects, in the collection set, that were 'discovered'
5697   // by the CM ref processor should have already been copied (either by
5698   // applying the external root copy closure to the discovered lists, or
5699   // by following an RSet entry).
5700   //
5701   // But some of the referents, that are in the collection set, that these
5702   // reference objects point to may not have been copied: the STW ref
5703   // processor would have seen that the reference object had already
5704   // been 'discovered' and would have skipped discovering the reference,
5705   // but would not have treated the reference object as a regular oop.
5706   // As a result the copy closure would not have been applied to the
5707   // referent object.
5708   //
5709   // We need to explicitly copy these referent objects - the references
5710   // will be processed at the end of remarking.
5711   //
5712   // We also need to do this copying before we process the reference
5713   // objects discovered by the STW ref processor in case one of these
5714   // referents points to another object which is also referenced by an
5715   // object discovered by the STW ref processor.
5716 
5717   assert(!G1CollectedHeap::use_parallel_gc_threads() ||
5718            no_of_gc_workers == workers()->active_workers(),
5719            "Need to reset active GC workers");
5720 
5721   set_par_threads(no_of_gc_workers);
5722   G1ParPreserveCMReferentsTask keep_cm_referents(this,
5723                                                  no_of_gc_workers,
5724                                                  _task_queues);
5725 
5726   if (G1CollectedHeap::use_parallel_gc_threads()) {
5727     workers()->run_task(&keep_cm_referents);
5728   } else {
5729     keep_cm_referents.work(0);
5730   }
5731 
5732   set_par_threads(0);
5733 
5734   // Closure to test whether a referent is alive.
5735   G1STWIsAliveClosure is_alive(this);
5736 
5737   // Even when parallel reference processing is enabled, the processing
5738   // of JNI refs is serial and performed serially by the current thread
5739   // rather than by a worker. The following PSS will be used for processing
5740   // JNI refs.
5741 
5742   // Use only a single queue for this PSS.
5743   G1ParScanThreadState            pss(this, 0, NULL);
5744 
5745   // We do not embed a reference processor in the copying/scanning
5746   // closures while we're actually processing the discovered
5747   // reference objects.
5748   G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5749 
5750   pss.set_evac_failure_closure(&evac_failure_cl);
5751 
5752   assert(pss.queue_is_empty(), "pre-condition");
5753 
5754   G1ParScanExtRootClosure        only_copy_non_heap_cl(this, &pss, NULL);
5755 
5756   G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5757 
5758   OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5759 
5760   if (_g1h->g1_policy()->during_initial_mark_pause()) {
5761     // We also need to mark copied objects.
5762     copy_non_heap_cl = &copy_mark_non_heap_cl;
5763   }
5764 
5765   // Keep alive closure.
5766   G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, &pss);
5767 
5768   // Serial Complete GC closure
5769   G1STWDrainQueueClosure drain_queue(this, &pss);
5770 
5771   // Setup the soft refs policy...
5772   rp->setup_policy(false);
5773 
5774   ReferenceProcessorStats stats;
5775   if (!rp->processing_is_mt()) {
5776     // Serial reference processing...
5777     stats = rp->process_discovered_references(&is_alive,
5778                                               &keep_alive,
5779                                               &drain_queue,
5780                                               NULL,
5781                                               _gc_timer_stw,
5782                                               _gc_tracer_stw->gc_id());
5783   } else {
5784     // Parallel reference processing
5785     assert(rp->num_q() == no_of_gc_workers, "sanity");
5786     assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5787 
5788     G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5789     stats = rp->process_discovered_references(&is_alive,
5790                                               &keep_alive,
5791                                               &drain_queue,
5792                                               &par_task_executor,
5793                                               _gc_timer_stw,
5794                                               _gc_tracer_stw->gc_id());
5795   }
5796 
5797   _gc_tracer_stw->report_gc_reference_stats(stats);
5798 
5799   // We have completed copying any necessary live referent objects.
5800   assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5801 
5802   double ref_proc_time = os::elapsedTime() - ref_proc_start;
5803   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5804 }
5805 
5806 // Weak Reference processing during an evacuation pause (part 2).
5807 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) {
5808   double ref_enq_start = os::elapsedTime();
5809 
5810   ReferenceProcessor* rp = _ref_processor_stw;
5811   assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5812 
5813   // Now enqueue any remaining on the discovered lists on to
5814   // the pending list.
5815   if (!rp->processing_is_mt()) {
5816     // Serial reference processing...
5817     rp->enqueue_discovered_references();
5818   } else {
5819     // Parallel reference enqueueing
5820 
5821     assert(no_of_gc_workers == workers()->active_workers(),
5822            "Need to reset active workers");
5823     assert(rp->num_q() == no_of_gc_workers, "sanity");
5824     assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5825 
5826     G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5827     rp->enqueue_discovered_references(&par_task_executor);
5828   }
5829 
5830   rp->verify_no_references_recorded();
5831   assert(!rp->discovery_enabled(), "should have been disabled");
5832 
5833   // FIXME
5834   // CM's reference processing also cleans up the string and symbol tables.
5835   // Should we do that here also? We could, but it is a serial operation
5836   // and could significantly increase the pause time.
5837 
5838   double ref_enq_time = os::elapsedTime() - ref_enq_start;
5839   g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5840 }
5841 
5842 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) {
5843   _expand_heap_after_alloc_failure = true;
5844   _evacuation_failed = false;
5845 
5846   // Should G1EvacuationFailureALot be in effect for this GC?
5847   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
5848 
5849   g1_rem_set()->prepare_for_oops_into_collection_set_do();
5850 
5851   // Disable the hot card cache.
5852   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
5853   hot_card_cache->reset_hot_cache_claimed_index();
5854   hot_card_cache->set_use_cache(false);
5855 
5856   uint n_workers;
5857   if (G1CollectedHeap::use_parallel_gc_threads()) {
5858     n_workers =
5859       AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
5860                                      workers()->active_workers(),
5861                                      Threads::number_of_non_daemon_threads());
5862     assert(UseDynamicNumberOfGCThreads ||
5863            n_workers == workers()->total_workers(),
5864            "If not dynamic should be using all the  workers");
5865     workers()->set_active_workers(n_workers);
5866     set_par_threads(n_workers);
5867   } else {
5868     assert(n_par_threads() == 0,
5869            "Should be the original non-parallel value");
5870     n_workers = 1;
5871   }
5872 
5873   G1ParTask g1_par_task(this, _task_queues);
5874 
5875   init_for_evac_failure(NULL);
5876 
5877   rem_set()->prepare_for_younger_refs_iterate(true);
5878 
5879   assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5880   double start_par_time_sec = os::elapsedTime();
5881   double end_par_time_sec;
5882 
5883   {
5884     StrongRootsScope srs(this);
5885     // InitialMark needs claim bits to keep track of the marked-through CLDs.
5886     if (g1_policy()->during_initial_mark_pause()) {
5887       ClassLoaderDataGraph::clear_claimed_marks();
5888     }
5889 
5890     if (G1CollectedHeap::use_parallel_gc_threads()) {
5891       // The individual threads will set their evac-failure closures.
5892       if (PrintTerminationStats) G1ParScanThreadState::print_termination_stats_hdr();
5893       // These tasks use ShareHeap::_process_strong_tasks
5894       assert(UseDynamicNumberOfGCThreads ||
5895              workers()->active_workers() == workers()->total_workers(),
5896              "If not dynamic should be using all the  workers");
5897       workers()->run_task(&g1_par_task);
5898     } else {
5899       g1_par_task.set_for_termination(n_workers);
5900       g1_par_task.work(0);
5901     }
5902     end_par_time_sec = os::elapsedTime();
5903 
5904     // Closing the inner scope will execute the destructor
5905     // for the StrongRootsScope object. We record the current
5906     // elapsed time before closing the scope so that time
5907     // taken for the SRS destructor is NOT included in the
5908     // reported parallel time.
5909   }
5910 
5911   double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5912   g1_policy()->phase_times()->record_par_time(par_time_ms);
5913 
5914   double code_root_fixup_time_ms =
5915         (os::elapsedTime() - end_par_time_sec) * 1000.0;
5916   g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms);
5917 
5918   set_par_threads(0);
5919 
5920   // Process any discovered reference objects - we have
5921   // to do this _before_ we retire the GC alloc regions
5922   // as we may have to copy some 'reachable' referent
5923   // objects (and their reachable sub-graphs) that were
5924   // not copied during the pause.
5925   process_discovered_references(n_workers);
5926 
5927   // Weak root processing.
5928   {
5929     G1STWIsAliveClosure is_alive(this);
5930     G1KeepAliveClosure keep_alive(this);
5931     JNIHandles::weak_oops_do(&is_alive, &keep_alive);
5932     if (G1StringDedup::is_enabled()) {
5933       G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive);
5934     }
5935   }
5936 
5937   _allocator->release_gc_alloc_regions(n_workers, evacuation_info);
5938   g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5939 
5940   // Reset and re-enable the hot card cache.
5941   // Note the counts for the cards in the regions in the
5942   // collection set are reset when the collection set is freed.
5943   hot_card_cache->reset_hot_cache();
5944   hot_card_cache->set_use_cache(true);
5945 
5946   purge_code_root_memory();
5947 
5948   if (g1_policy()->during_initial_mark_pause()) {
5949     // Reset the claim values set during marking the strong code roots
5950     reset_heap_region_claim_values();
5951   }
5952 
5953   finalize_for_evac_failure();
5954 
5955   if (evacuation_failed()) {
5956     remove_self_forwarding_pointers();
5957 
5958     // Reset the G1EvacuationFailureALot counters and flags
5959     // Note: the values are reset only when an actual
5960     // evacuation failure occurs.
5961     NOT_PRODUCT(reset_evacuation_should_fail();)
5962   }
5963 
5964   // Enqueue any remaining references remaining on the STW
5965   // reference processor's discovered lists. We need to do
5966   // this after the card table is cleaned (and verified) as
5967   // the act of enqueueing entries on to the pending list
5968   // will log these updates (and dirty their associated
5969   // cards). We need these updates logged to update any
5970   // RSets.
5971   enqueue_discovered_references(n_workers);
5972 
5973   redirty_logged_cards();
5974   COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5975 }
5976 
5977 void G1CollectedHeap::free_region(HeapRegion* hr,
5978                                   FreeRegionList* free_list,
5979                                   bool par,
5980                                   bool locked) {
5981   assert(!hr->is_free(), "the region should not be free");
5982   assert(!hr->is_empty(), "the region should not be empty");
5983   assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
5984   assert(free_list != NULL, "pre-condition");
5985 
5986   if (G1VerifyBitmaps) {
5987     MemRegion mr(hr->bottom(), hr->end());
5988     concurrent_mark()->clearRangePrevBitmap(mr);
5989   }
5990 
5991   // Clear the card counts for this region.
5992   // Note: we only need to do this if the region is not young
5993   // (since we don't refine cards in young regions).
5994   if (!hr->is_young()) {
5995     _cg1r->hot_card_cache()->reset_card_counts(hr);
5996   }
5997   hr->hr_clear(par, true /* clear_space */, locked /* locked */);
5998   free_list->add_ordered(hr);
5999 }
6000 
6001 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
6002                                      FreeRegionList* free_list,
6003                                      bool par) {
6004   assert(hr->is_starts_humongous(), "this is only for starts humongous regions");
6005   assert(free_list != NULL, "pre-condition");
6006 
6007   size_t hr_capacity = hr->capacity();
6008   // We need to read this before we make the region non-humongous,
6009   // otherwise the information will be gone.
6010   uint last_index = hr->last_hc_index();
6011   hr->clear_humongous();
6012   free_region(hr, free_list, par);
6013 
6014   uint i = hr->hrm_index() + 1;
6015   while (i < last_index) {
6016     HeapRegion* curr_hr = region_at(i);
6017     assert(curr_hr->is_continues_humongous(), "invariant");
6018     curr_hr->clear_humongous();
6019     free_region(curr_hr, free_list, par);
6020     i += 1;
6021   }
6022 }
6023 
6024 void G1CollectedHeap::remove_from_old_sets(const HeapRegionSetCount& old_regions_removed,
6025                                        const HeapRegionSetCount& humongous_regions_removed) {
6026   if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 0) {
6027     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
6028     _old_set.bulk_remove(old_regions_removed);
6029     _humongous_set.bulk_remove(humongous_regions_removed);
6030   }
6031 
6032 }
6033 
6034 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
6035   assert(list != NULL, "list can't be null");
6036   if (!list->is_empty()) {
6037     MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
6038     _hrm.insert_list_into_free_list(list);
6039   }
6040 }
6041 
6042 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
6043   _allocator->decrease_used(bytes);
6044 }
6045 
6046 class G1ParCleanupCTTask : public AbstractGangTask {
6047   G1SATBCardTableModRefBS* _ct_bs;
6048   G1CollectedHeap* _g1h;
6049   HeapRegion* volatile _su_head;
6050 public:
6051   G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs,
6052                      G1CollectedHeap* g1h) :
6053     AbstractGangTask("G1 Par Cleanup CT Task"),
6054     _ct_bs(ct_bs), _g1h(g1h) { }
6055 
6056   void work(uint worker_id) {
6057     HeapRegion* r;
6058     while (r = _g1h->pop_dirty_cards_region()) {
6059       clear_cards(r);
6060     }
6061   }
6062 
6063   void clear_cards(HeapRegion* r) {
6064     // Cards of the survivors should have already been dirtied.
6065     if (!r->is_survivor()) {
6066       _ct_bs->clear(MemRegion(r->bottom(), r->end()));
6067     }
6068   }
6069 };
6070 
6071 #ifndef PRODUCT
6072 class G1VerifyCardTableCleanup: public HeapRegionClosure {
6073   G1CollectedHeap* _g1h;
6074   G1SATBCardTableModRefBS* _ct_bs;
6075 public:
6076   G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs)
6077     : _g1h(g1h), _ct_bs(ct_bs) { }
6078   virtual bool doHeapRegion(HeapRegion* r) {
6079     if (r->is_survivor()) {
6080       _g1h->verify_dirty_region(r);
6081     } else {
6082       _g1h->verify_not_dirty_region(r);
6083     }
6084     return false;
6085   }
6086 };
6087 
6088 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
6089   // All of the region should be clean.
6090   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6091   MemRegion mr(hr->bottom(), hr->end());
6092   ct_bs->verify_not_dirty_region(mr);
6093 }
6094 
6095 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
6096   // We cannot guarantee that [bottom(),end()] is dirty.  Threads
6097   // dirty allocated blocks as they allocate them. The thread that
6098   // retires each region and replaces it with a new one will do a
6099   // maximal allocation to fill in [pre_dummy_top(),end()] but will
6100   // not dirty that area (one less thing to have to do while holding
6101   // a lock). So we can only verify that [bottom(),pre_dummy_top()]
6102   // is dirty.
6103   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6104   MemRegion mr(hr->bottom(), hr->pre_dummy_top());
6105   if (hr->is_young()) {
6106     ct_bs->verify_g1_young_region(mr);
6107   } else {
6108     ct_bs->verify_dirty_region(mr);
6109   }
6110 }
6111 
6112 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
6113   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6114   for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
6115     verify_dirty_region(hr);
6116   }
6117 }
6118 
6119 void G1CollectedHeap::verify_dirty_young_regions() {
6120   verify_dirty_young_list(_young_list->first_region());
6121 }
6122 
6123 bool G1CollectedHeap::verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
6124                                                HeapWord* tams, HeapWord* end) {
6125   guarantee(tams <= end,
6126             err_msg("tams: "PTR_FORMAT" end: "PTR_FORMAT, tams, end));
6127   HeapWord* result = bitmap->getNextMarkedWordAddress(tams, end);
6128   if (result < end) {
6129     gclog_or_tty->cr();
6130     gclog_or_tty->print_cr("## wrong marked address on %s bitmap: "PTR_FORMAT,
6131                            bitmap_name, result);
6132     gclog_or_tty->print_cr("## %s tams: "PTR_FORMAT" end: "PTR_FORMAT,
6133                            bitmap_name, tams, end);
6134     return false;
6135   }
6136   return true;
6137 }
6138 
6139 bool G1CollectedHeap::verify_bitmaps(const char* caller, HeapRegion* hr) {
6140   CMBitMapRO* prev_bitmap = concurrent_mark()->prevMarkBitMap();
6141   CMBitMapRO* next_bitmap = (CMBitMapRO*) concurrent_mark()->nextMarkBitMap();
6142 
6143   HeapWord* bottom = hr->bottom();
6144   HeapWord* ptams  = hr->prev_top_at_mark_start();
6145   HeapWord* ntams  = hr->next_top_at_mark_start();
6146   HeapWord* end    = hr->end();
6147 
6148   bool res_p = verify_no_bits_over_tams("prev", prev_bitmap, ptams, end);
6149 
6150   bool res_n = true;
6151   // We reset mark_in_progress() before we reset _cmThread->in_progress() and in this window
6152   // we do the clearing of the next bitmap concurrently. Thus, we can not verify the bitmap
6153   // if we happen to be in that state.
6154   if (mark_in_progress() || !_cmThread->in_progress()) {
6155     res_n = verify_no_bits_over_tams("next", next_bitmap, ntams, end);
6156   }
6157   if (!res_p || !res_n) {
6158     gclog_or_tty->print_cr("#### Bitmap verification failed for "HR_FORMAT,
6159                            HR_FORMAT_PARAMS(hr));
6160     gclog_or_tty->print_cr("#### Caller: %s", caller);
6161     return false;
6162   }
6163   return true;
6164 }
6165 
6166 void G1CollectedHeap::check_bitmaps(const char* caller, HeapRegion* hr) {
6167   if (!G1VerifyBitmaps) return;
6168 
6169   guarantee(verify_bitmaps(caller, hr), "bitmap verification");
6170 }
6171 
6172 class G1VerifyBitmapClosure : public HeapRegionClosure {
6173 private:
6174   const char* _caller;
6175   G1CollectedHeap* _g1h;
6176   bool _failures;
6177 
6178 public:
6179   G1VerifyBitmapClosure(const char* caller, G1CollectedHeap* g1h) :
6180     _caller(caller), _g1h(g1h), _failures(false) { }
6181 
6182   bool failures() { return _failures; }
6183 
6184   virtual bool doHeapRegion(HeapRegion* hr) {
6185     if (hr->is_continues_humongous()) return false;
6186 
6187     bool result = _g1h->verify_bitmaps(_caller, hr);
6188     if (!result) {
6189       _failures = true;
6190     }
6191     return false;
6192   }
6193 };
6194 
6195 void G1CollectedHeap::check_bitmaps(const char* caller) {
6196   if (!G1VerifyBitmaps) return;
6197 
6198   G1VerifyBitmapClosure cl(caller, this);
6199   heap_region_iterate(&cl);
6200   guarantee(!cl.failures(), "bitmap verification");
6201 }
6202 #endif // PRODUCT
6203 
6204 void G1CollectedHeap::cleanUpCardTable() {
6205   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6206   double start = os::elapsedTime();
6207 
6208   {
6209     // Iterate over the dirty cards region list.
6210     G1ParCleanupCTTask cleanup_task(ct_bs, this);
6211 
6212     if (G1CollectedHeap::use_parallel_gc_threads()) {
6213       set_par_threads();
6214       workers()->run_task(&cleanup_task);
6215       set_par_threads(0);
6216     } else {
6217       while (_dirty_cards_region_list) {
6218         HeapRegion* r = _dirty_cards_region_list;
6219         cleanup_task.clear_cards(r);
6220         _dirty_cards_region_list = r->get_next_dirty_cards_region();
6221         if (_dirty_cards_region_list == r) {
6222           // The last region.
6223           _dirty_cards_region_list = NULL;
6224         }
6225         r->set_next_dirty_cards_region(NULL);
6226       }
6227     }
6228 #ifndef PRODUCT
6229     if (G1VerifyCTCleanup || VerifyAfterGC) {
6230       G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
6231       heap_region_iterate(&cleanup_verifier);
6232     }
6233 #endif
6234   }
6235 
6236   double elapsed = os::elapsedTime() - start;
6237   g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
6238 }
6239 
6240 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) {
6241   size_t pre_used = 0;
6242   FreeRegionList local_free_list("Local List for CSet Freeing");
6243 
6244   double young_time_ms     = 0.0;
6245   double non_young_time_ms = 0.0;
6246 
6247   // Since the collection set is a superset of the the young list,
6248   // all we need to do to clear the young list is clear its
6249   // head and length, and unlink any young regions in the code below
6250   _young_list->clear();
6251 
6252   G1CollectorPolicy* policy = g1_policy();
6253 
6254   double start_sec = os::elapsedTime();
6255   bool non_young = true;
6256 
6257   HeapRegion* cur = cs_head;
6258   int age_bound = -1;
6259   size_t rs_lengths = 0;
6260 
6261   while (cur != NULL) {
6262     assert(!is_on_master_free_list(cur), "sanity");
6263     if (non_young) {
6264       if (cur->is_young()) {
6265         double end_sec = os::elapsedTime();
6266         double elapsed_ms = (end_sec - start_sec) * 1000.0;
6267         non_young_time_ms += elapsed_ms;
6268 
6269         start_sec = os::elapsedTime();
6270         non_young = false;
6271       }
6272     } else {
6273       if (!cur->is_young()) {
6274         double end_sec = os::elapsedTime();
6275         double elapsed_ms = (end_sec - start_sec) * 1000.0;
6276         young_time_ms += elapsed_ms;
6277 
6278         start_sec = os::elapsedTime();
6279         non_young = true;
6280       }
6281     }
6282 
6283     rs_lengths += cur->rem_set()->occupied_locked();
6284 
6285     HeapRegion* next = cur->next_in_collection_set();
6286     assert(cur->in_collection_set(), "bad CS");
6287     cur->set_next_in_collection_set(NULL);
6288     cur->set_in_collection_set(false);
6289 
6290     if (cur->is_young()) {
6291       int index = cur->young_index_in_cset();
6292       assert(index != -1, "invariant");
6293       assert((uint) index < policy->young_cset_region_length(), "invariant");
6294       size_t words_survived = _surviving_young_words[index];
6295       cur->record_surv_words_in_group(words_survived);
6296 
6297       // At this point the we have 'popped' cur from the collection set
6298       // (linked via next_in_collection_set()) but it is still in the
6299       // young list (linked via next_young_region()). Clear the
6300       // _next_young_region field.
6301       cur->set_next_young_region(NULL);
6302     } else {
6303       int index = cur->young_index_in_cset();
6304       assert(index == -1, "invariant");
6305     }
6306 
6307     assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
6308             (!cur->is_young() && cur->young_index_in_cset() == -1),
6309             "invariant" );
6310 
6311     if (!cur->evacuation_failed()) {
6312       MemRegion used_mr = cur->used_region();
6313 
6314       // And the region is empty.
6315       assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
6316       pre_used += cur->used();
6317       free_region(cur, &local_free_list, false /* par */, true /* locked */);
6318     } else {
6319       cur->uninstall_surv_rate_group();
6320       if (cur->is_young()) {
6321         cur->set_young_index_in_cset(-1);
6322       }
6323       cur->set_evacuation_failed(false);
6324       // The region is now considered to be old.
6325       cur->set_old();
6326       _old_set.add(cur);
6327       evacuation_info.increment_collectionset_used_after(cur->used());
6328     }
6329     cur = next;
6330   }
6331 
6332   evacuation_info.set_regions_freed(local_free_list.length());
6333   policy->record_max_rs_lengths(rs_lengths);
6334   policy->cset_regions_freed();
6335 
6336   double end_sec = os::elapsedTime();
6337   double elapsed_ms = (end_sec - start_sec) * 1000.0;
6338 
6339   if (non_young) {
6340     non_young_time_ms += elapsed_ms;
6341   } else {
6342     young_time_ms += elapsed_ms;
6343   }
6344 
6345   prepend_to_freelist(&local_free_list);
6346   decrement_summary_bytes(pre_used);
6347   policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
6348   policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
6349 }
6350 
6351 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
6352  private:
6353   FreeRegionList* _free_region_list;
6354   HeapRegionSet* _proxy_set;
6355   HeapRegionSetCount _humongous_regions_removed;
6356   size_t _freed_bytes;
6357  public:
6358 
6359   G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
6360     _free_region_list(free_region_list), _humongous_regions_removed(), _freed_bytes(0) {
6361   }
6362 
6363   virtual bool doHeapRegion(HeapRegion* r) {
6364     if (!r->is_starts_humongous()) {
6365       return false;
6366     }
6367 
6368     G1CollectedHeap* g1h = G1CollectedHeap::heap();
6369 
6370     oop obj = (oop)r->bottom();
6371     CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap();
6372 
6373     // The following checks whether the humongous object is live are sufficient.
6374     // The main additional check (in addition to having a reference from the roots
6375     // or the young gen) is whether the humongous object has a remembered set entry.
6376     //
6377     // A humongous object cannot be live if there is no remembered set for it
6378     // because:
6379     // - there can be no references from within humongous starts regions referencing
6380     // the object because we never allocate other objects into them.
6381     // (I.e. there are no intra-region references that may be missed by the
6382     // remembered set)
6383     // - as soon there is a remembered set entry to the humongous starts region
6384     // (i.e. it has "escaped" to an old object) this remembered set entry will stay
6385     // until the end of a concurrent mark.
6386     //
6387     // It is not required to check whether the object has been found dead by marking
6388     // or not, in fact it would prevent reclamation within a concurrent cycle, as
6389     // all objects allocated during that time are considered live.
6390     // SATB marking is even more conservative than the remembered set.
6391     // So if at this point in the collection there is no remembered set entry,
6392     // nobody has a reference to it.
6393     // At the start of collection we flush all refinement logs, and remembered sets
6394     // are completely up-to-date wrt to references to the humongous object.
6395     //
6396     // Other implementation considerations:
6397     // - never consider object arrays: while they are a valid target, they have not
6398     // been observed to be used as temporary objects.
6399     // - they would also pose considerable effort for cleaning up the the remembered
6400     // sets.
6401     // While this cleanup is not strictly necessary to be done (or done instantly),
6402     // given that their occurrence is very low, this saves us this additional
6403     // complexity.
6404     uint region_idx = r->hrm_index();
6405     if (g1h->humongous_is_live(region_idx) ||
6406         g1h->humongous_region_is_always_live(region_idx)) {
6407 
6408       if (G1TraceReclaimDeadHumongousObjectsAtYoungGC) {
6409         gclog_or_tty->print_cr("Live humongous %d region %d with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is marked %d live-other %d obj array %d",
6410                                r->is_humongous(),
6411                                region_idx,
6412                                r->rem_set()->occupied(),
6413                                r->rem_set()->strong_code_roots_list_length(),
6414                                next_bitmap->isMarked(r->bottom()),
6415                                g1h->humongous_is_live(region_idx),
6416                                obj->is_objArray()
6417                               );
6418       }
6419 
6420       return false;
6421     }
6422 
6423     guarantee(!obj->is_objArray(),
6424               err_msg("Eagerly reclaiming object arrays is not supported, but the object "PTR_FORMAT" is.",
6425                       r->bottom()));
6426 
6427     if (G1TraceReclaimDeadHumongousObjectsAtYoungGC) {
6428       gclog_or_tty->print_cr("Reclaim humongous region %d start "PTR_FORMAT" region %d length "UINT32_FORMAT" with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is marked %d live-other %d obj array %d",
6429                              r->is_humongous(),
6430                              r->bottom(),
6431                              region_idx,
6432                              r->region_num(),
6433                              r->rem_set()->occupied(),
6434                              r->rem_set()->strong_code_roots_list_length(),
6435                              next_bitmap->isMarked(r->bottom()),
6436                              g1h->humongous_is_live(region_idx),
6437                              obj->is_objArray()
6438                             );
6439     }
6440     // Need to clear mark bit of the humongous object if already set.
6441     if (next_bitmap->isMarked(r->bottom())) {
6442       next_bitmap->clear(r->bottom());
6443     }
6444     _freed_bytes += r->used();
6445     r->set_containing_set(NULL);
6446     _humongous_regions_removed.increment(1u, r->capacity());
6447     g1h->free_humongous_region(r, _free_region_list, false);
6448 
6449     return false;
6450   }
6451 
6452   HeapRegionSetCount& humongous_free_count() {
6453     return _humongous_regions_removed;
6454   }
6455 
6456   size_t bytes_freed() const {
6457     return _freed_bytes;
6458   }
6459 
6460   size_t humongous_reclaimed() const {
6461     return _humongous_regions_removed.length();
6462   }
6463 };
6464 
6465 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
6466   assert_at_safepoint(true);
6467 
6468   if (!G1ReclaimDeadHumongousObjectsAtYoungGC || !_has_humongous_reclaim_candidates) {
6469     g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
6470     return;
6471   }
6472 
6473   double start_time = os::elapsedTime();
6474 
6475   FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
6476 
6477   G1FreeHumongousRegionClosure cl(&local_cleanup_list);
6478   heap_region_iterate(&cl);
6479 
6480   HeapRegionSetCount empty_set;
6481   remove_from_old_sets(empty_set, cl.humongous_free_count());
6482 
6483   G1HRPrinter* hr_printer = _g1h->hr_printer();
6484   if (hr_printer->is_active()) {
6485     FreeRegionListIterator iter(&local_cleanup_list);
6486     while (iter.more_available()) {
6487       HeapRegion* hr = iter.get_next();
6488       hr_printer->cleanup(hr);
6489     }
6490   }
6491 
6492   prepend_to_freelist(&local_cleanup_list);
6493   decrement_summary_bytes(cl.bytes_freed());
6494 
6495   g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
6496                                                                     cl.humongous_reclaimed());
6497 }
6498 
6499 // This routine is similar to the above but does not record
6500 // any policy statistics or update free lists; we are abandoning
6501 // the current incremental collection set in preparation of a
6502 // full collection. After the full GC we will start to build up
6503 // the incremental collection set again.
6504 // This is only called when we're doing a full collection
6505 // and is immediately followed by the tearing down of the young list.
6506 
6507 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
6508   HeapRegion* cur = cs_head;
6509 
6510   while (cur != NULL) {
6511     HeapRegion* next = cur->next_in_collection_set();
6512     assert(cur->in_collection_set(), "bad CS");
6513     cur->set_next_in_collection_set(NULL);
6514     cur->set_in_collection_set(false);
6515     cur->set_young_index_in_cset(-1);
6516     cur = next;
6517   }
6518 }
6519 
6520 void G1CollectedHeap::set_free_regions_coming() {
6521   if (G1ConcRegionFreeingVerbose) {
6522     gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6523                            "setting free regions coming");
6524   }
6525 
6526   assert(!free_regions_coming(), "pre-condition");
6527   _free_regions_coming = true;
6528 }
6529 
6530 void G1CollectedHeap::reset_free_regions_coming() {
6531   assert(free_regions_coming(), "pre-condition");
6532 
6533   {
6534     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6535     _free_regions_coming = false;
6536     SecondaryFreeList_lock->notify_all();
6537   }
6538 
6539   if (G1ConcRegionFreeingVerbose) {
6540     gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6541                            "reset free regions coming");
6542   }
6543 }
6544 
6545 void G1CollectedHeap::wait_while_free_regions_coming() {
6546   // Most of the time we won't have to wait, so let's do a quick test
6547   // first before we take the lock.
6548   if (!free_regions_coming()) {
6549     return;
6550   }
6551 
6552   if (G1ConcRegionFreeingVerbose) {
6553     gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6554                            "waiting for free regions");
6555   }
6556 
6557   {
6558     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6559     while (free_regions_coming()) {
6560       SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
6561     }
6562   }
6563 
6564   if (G1ConcRegionFreeingVerbose) {
6565     gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6566                            "done waiting for free regions");
6567   }
6568 }
6569 
6570 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
6571   assert(heap_lock_held_for_gc(),
6572               "the heap lock should already be held by or for this thread");
6573   _young_list->push_region(hr);
6574 }
6575 
6576 class NoYoungRegionsClosure: public HeapRegionClosure {
6577 private:
6578   bool _success;
6579 public:
6580   NoYoungRegionsClosure() : _success(true) { }
6581   bool doHeapRegion(HeapRegion* r) {
6582     if (r->is_young()) {
6583       gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
6584                              r->bottom(), r->end());
6585       _success = false;
6586     }
6587     return false;
6588   }
6589   bool success() { return _success; }
6590 };
6591 
6592 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
6593   bool ret = _young_list->check_list_empty(check_sample);
6594 
6595   if (check_heap) {
6596     NoYoungRegionsClosure closure;
6597     heap_region_iterate(&closure);
6598     ret = ret && closure.success();
6599   }
6600 
6601   return ret;
6602 }
6603 
6604 class TearDownRegionSetsClosure : public HeapRegionClosure {
6605 private:
6606   HeapRegionSet *_old_set;
6607 
6608 public:
6609   TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
6610 
6611   bool doHeapRegion(HeapRegion* r) {
6612     if (r->is_old()) {
6613       _old_set->remove(r);
6614     } else {
6615       // We ignore free regions, we'll empty the free list afterwards.
6616       // We ignore young regions, we'll empty the young list afterwards.
6617       // We ignore humongous regions, we're not tearing down the
6618       // humongous regions set.
6619       assert(r->is_free() || r->is_young() || r->is_humongous(),
6620              "it cannot be another type");
6621     }
6622     return false;
6623   }
6624 
6625   ~TearDownRegionSetsClosure() {
6626     assert(_old_set->is_empty(), "post-condition");
6627   }
6628 };
6629 
6630 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6631   assert_at_safepoint(true /* should_be_vm_thread */);
6632 
6633   if (!free_list_only) {
6634     TearDownRegionSetsClosure cl(&_old_set);
6635     heap_region_iterate(&cl);
6636 
6637     // Note that emptying the _young_list is postponed and instead done as
6638     // the first step when rebuilding the regions sets again. The reason for
6639     // this is that during a full GC string deduplication needs to know if
6640     // a collected region was young or old when the full GC was initiated.
6641   }
6642   _hrm.remove_all_free_regions();
6643 }
6644 
6645 class RebuildRegionSetsClosure : public HeapRegionClosure {
6646 private:
6647   bool            _free_list_only;
6648   HeapRegionSet*   _old_set;
6649   HeapRegionManager*   _hrm;
6650   size_t          _total_used;
6651 
6652 public:
6653   RebuildRegionSetsClosure(bool free_list_only,
6654                            HeapRegionSet* old_set, HeapRegionManager* hrm) :
6655     _free_list_only(free_list_only),
6656     _old_set(old_set), _hrm(hrm), _total_used(0) {
6657     assert(_hrm->num_free_regions() == 0, "pre-condition");
6658     if (!free_list_only) {
6659       assert(_old_set->is_empty(), "pre-condition");
6660     }
6661   }
6662 
6663   bool doHeapRegion(HeapRegion* r) {
6664     if (r->is_continues_humongous()) {
6665       return false;
6666     }
6667 
6668     if (r->is_empty()) {
6669       // Add free regions to the free list
6670       r->set_free();
6671       r->set_allocation_context(AllocationContext::system());
6672       _hrm->insert_into_free_list(r);
6673     } else if (!_free_list_only) {
6674       assert(!r->is_young(), "we should not come across young regions");
6675 
6676       if (r->is_humongous()) {
6677         // We ignore humongous regions, we left the humongous set unchanged
6678       } else {
6679         // Objects that were compacted would have ended up on regions
6680         // that were previously old or free.
6681         assert(r->is_free() || r->is_old(), "invariant");
6682         // We now consider them old, so register as such.
6683         r->set_old();
6684         _old_set->add(r);
6685       }
6686       _total_used += r->used();
6687     }
6688 
6689     return false;
6690   }
6691 
6692   size_t total_used() {
6693     return _total_used;
6694   }
6695 };
6696 
6697 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6698   assert_at_safepoint(true /* should_be_vm_thread */);
6699 
6700   if (!free_list_only) {
6701     _young_list->empty_list();
6702   }
6703 
6704   RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
6705   heap_region_iterate(&cl);
6706 
6707   if (!free_list_only) {
6708     _allocator->set_used(cl.total_used());
6709   }
6710   assert(_allocator->used_unlocked() == recalculate_used(),
6711          err_msg("inconsistent _allocator->used_unlocked(), "
6712                  "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6713                  _allocator->used_unlocked(), recalculate_used()));
6714 }
6715 
6716 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6717   _refine_cte_cl->set_concurrent(concurrent);
6718 }
6719 
6720 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6721   HeapRegion* hr = heap_region_containing(p);
6722   return hr->is_in(p);
6723 }
6724 
6725 // Methods for the mutator alloc region
6726 
6727 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6728                                                       bool force) {
6729   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6730   assert(!force || g1_policy()->can_expand_young_list(),
6731          "if force is true we should be able to expand the young list");
6732   bool young_list_full = g1_policy()->is_young_list_full();
6733   if (force || !young_list_full) {
6734     HeapRegion* new_alloc_region = new_region(word_size,
6735                                               false /* is_old */,
6736                                               false /* do_expand */);
6737     if (new_alloc_region != NULL) {
6738       set_region_short_lived_locked(new_alloc_region);
6739       _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6740       check_bitmaps("Mutator Region Allocation", new_alloc_region);
6741       return new_alloc_region;
6742     }
6743   }
6744   return NULL;
6745 }
6746 
6747 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6748                                                   size_t allocated_bytes) {
6749   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6750   assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
6751 
6752   g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6753   _allocator->increase_used(allocated_bytes);
6754   _hr_printer.retire(alloc_region);
6755   // We update the eden sizes here, when the region is retired,
6756   // instead of when it's allocated, since this is the point that its
6757   // used space has been recored in _summary_bytes_used.
6758   g1mm()->update_eden_size();
6759 }
6760 
6761 void G1CollectedHeap::set_par_threads() {
6762   // Don't change the number of workers.  Use the value previously set
6763   // in the workgroup.
6764   assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise");
6765   uint n_workers = workers()->active_workers();
6766   assert(UseDynamicNumberOfGCThreads ||
6767            n_workers == workers()->total_workers(),
6768       "Otherwise should be using the total number of workers");
6769   if (n_workers == 0) {
6770     assert(false, "Should have been set in prior evacuation pause.");
6771     n_workers = ParallelGCThreads;
6772     workers()->set_active_workers(n_workers);
6773   }
6774   set_par_threads(n_workers);
6775 }
6776 
6777 // Methods for the GC alloc regions
6778 
6779 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6780                                                  uint count,
6781                                                  GCAllocPurpose ap) {
6782   assert(FreeList_lock->owned_by_self(), "pre-condition");
6783 
6784   if (count < g1_policy()->max_regions(ap)) {
6785     bool survivor = (ap == GCAllocForSurvived);
6786     HeapRegion* new_alloc_region = new_region(word_size,
6787                                               !survivor,
6788                                               true /* do_expand */);
6789     if (new_alloc_region != NULL) {
6790       // We really only need to do this for old regions given that we
6791       // should never scan survivors. But it doesn't hurt to do it
6792       // for survivors too.
6793       new_alloc_region->record_top_and_timestamp();
6794       if (survivor) {
6795         new_alloc_region->set_survivor();
6796         _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6797         check_bitmaps("Survivor Region Allocation", new_alloc_region);
6798       } else {
6799         new_alloc_region->set_old();
6800         _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6801         check_bitmaps("Old Region Allocation", new_alloc_region);
6802       }
6803       bool during_im = g1_policy()->during_initial_mark_pause();
6804       new_alloc_region->note_start_of_copying(during_im);
6805       return new_alloc_region;
6806     } else {
6807       g1_policy()->note_alloc_region_limit_reached(ap);
6808     }
6809   }
6810   return NULL;
6811 }
6812 
6813 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6814                                              size_t allocated_bytes,
6815                                              GCAllocPurpose ap) {
6816   bool during_im = g1_policy()->during_initial_mark_pause();
6817   alloc_region->note_end_of_copying(during_im);
6818   g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6819   if (ap == GCAllocForSurvived) {
6820     young_list()->add_survivor_region(alloc_region);
6821   } else {
6822     _old_set.add(alloc_region);
6823   }
6824   _hr_printer.retire(alloc_region);
6825 }
6826 
6827 // Heap region set verification
6828 
6829 class VerifyRegionListsClosure : public HeapRegionClosure {
6830 private:
6831   HeapRegionSet*   _old_set;
6832   HeapRegionSet*   _humongous_set;
6833   HeapRegionManager*   _hrm;
6834 
6835 public:
6836   HeapRegionSetCount _old_count;
6837   HeapRegionSetCount _humongous_count;
6838   HeapRegionSetCount _free_count;
6839 
6840   VerifyRegionListsClosure(HeapRegionSet* old_set,
6841                            HeapRegionSet* humongous_set,
6842                            HeapRegionManager* hrm) :
6843     _old_set(old_set), _humongous_set(humongous_set), _hrm(hrm),
6844     _old_count(), _humongous_count(), _free_count(){ }
6845 
6846   bool doHeapRegion(HeapRegion* hr) {
6847     if (hr->is_continues_humongous()) {
6848       return false;
6849     }
6850 
6851     if (hr->is_young()) {
6852       // TODO
6853     } else if (hr->is_starts_humongous()) {
6854       assert(hr->containing_set() == _humongous_set, err_msg("Heap region %u is starts humongous but not in humongous set.", hr->hrm_index()));
6855       _humongous_count.increment(1u, hr->capacity());
6856     } else if (hr->is_empty()) {
6857       assert(_hrm->is_free(hr), err_msg("Heap region %u is empty but not on the free list.", hr->hrm_index()));
6858       _free_count.increment(1u, hr->capacity());
6859     } else if (hr->is_old()) {
6860       assert(hr->containing_set() == _old_set, err_msg("Heap region %u is old but not in the old set.", hr->hrm_index()));
6861       _old_count.increment(1u, hr->capacity());
6862     } else {
6863       ShouldNotReachHere();
6864     }
6865     return false;
6866   }
6867 
6868   void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, HeapRegionManager* free_list) {
6869     guarantee(old_set->length() == _old_count.length(), err_msg("Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length()));
6870     guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), err_msg("Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6871         old_set->total_capacity_bytes(), _old_count.capacity()));
6872 
6873     guarantee(humongous_set->length() == _humongous_count.length(), err_msg("Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length()));
6874     guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), err_msg("Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6875         humongous_set->total_capacity_bytes(), _humongous_count.capacity()));
6876 
6877     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()));
6878     guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), err_msg("Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6879         free_list->total_capacity_bytes(), _free_count.capacity()));
6880   }
6881 };
6882 
6883 void G1CollectedHeap::verify_region_sets() {
6884   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6885 
6886   // First, check the explicit lists.
6887   _hrm.verify();
6888   {
6889     // Given that a concurrent operation might be adding regions to
6890     // the secondary free list we have to take the lock before
6891     // verifying it.
6892     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6893     _secondary_free_list.verify_list();
6894   }
6895 
6896   // If a concurrent region freeing operation is in progress it will
6897   // be difficult to correctly attributed any free regions we come
6898   // across to the correct free list given that they might belong to
6899   // one of several (free_list, secondary_free_list, any local lists,
6900   // etc.). So, if that's the case we will skip the rest of the
6901   // verification operation. Alternatively, waiting for the concurrent
6902   // operation to complete will have a non-trivial effect on the GC's
6903   // operation (no concurrent operation will last longer than the
6904   // interval between two calls to verification) and it might hide
6905   // any issues that we would like to catch during testing.
6906   if (free_regions_coming()) {
6907     return;
6908   }
6909 
6910   // Make sure we append the secondary_free_list on the free_list so
6911   // that all free regions we will come across can be safely
6912   // attributed to the free_list.
6913   append_secondary_free_list_if_not_empty_with_lock();
6914 
6915   // Finally, make sure that the region accounting in the lists is
6916   // consistent with what we see in the heap.
6917 
6918   VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_hrm);
6919   heap_region_iterate(&cl);
6920   cl.verify_counts(&_old_set, &_humongous_set, &_hrm);
6921 }
6922 
6923 // Optimized nmethod scanning
6924 
6925 class RegisterNMethodOopClosure: 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->is_continues_humongous(),
6935              err_msg("trying to add 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       // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
6940       hr->add_strong_code_root_locked(_nm);
6941     }
6942   }
6943 
6944 public:
6945   RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6946     _g1h(g1h), _nm(nm) {}
6947 
6948   void do_oop(oop* p)       { do_oop_work(p); }
6949   void do_oop(narrowOop* p) { do_oop_work(p); }
6950 };
6951 
6952 class UnregisterNMethodOopClosure: public OopClosure {
6953   G1CollectedHeap* _g1h;
6954   nmethod* _nm;
6955 
6956   template <class T> void do_oop_work(T* p) {
6957     T heap_oop = oopDesc::load_heap_oop(p);
6958     if (!oopDesc::is_null(heap_oop)) {
6959       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6960       HeapRegion* hr = _g1h->heap_region_containing(obj);
6961       assert(!hr->is_continues_humongous(),
6962              err_msg("trying to remove code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6963                      " starting at "HR_FORMAT,
6964                      _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6965 
6966       hr->remove_strong_code_root(_nm);
6967     }
6968   }
6969 
6970 public:
6971   UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6972     _g1h(g1h), _nm(nm) {}
6973 
6974   void do_oop(oop* p)       { do_oop_work(p); }
6975   void do_oop(narrowOop* p) { do_oop_work(p); }
6976 };
6977 
6978 void G1CollectedHeap::register_nmethod(nmethod* nm) {
6979   CollectedHeap::register_nmethod(nm);
6980 
6981   guarantee(nm != NULL, "sanity");
6982   RegisterNMethodOopClosure reg_cl(this, nm);
6983   nm->oops_do(&reg_cl);
6984 }
6985 
6986 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
6987   CollectedHeap::unregister_nmethod(nm);
6988 
6989   guarantee(nm != NULL, "sanity");
6990   UnregisterNMethodOopClosure reg_cl(this, nm);
6991   nm->oops_do(&reg_cl, true);
6992 }
6993 
6994 void G1CollectedHeap::purge_code_root_memory() {
6995   double purge_start = os::elapsedTime();
6996   G1CodeRootSet::purge();
6997   double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
6998   g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
6999 }
7000 
7001 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
7002   G1CollectedHeap* _g1h;
7003 
7004 public:
7005   RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
7006     _g1h(g1h) {}
7007 
7008   void do_code_blob(CodeBlob* cb) {
7009     nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
7010     if (nm == NULL) {
7011       return;
7012     }
7013 
7014     if (ScavengeRootsInCode) {
7015       _g1h->register_nmethod(nm);
7016     }
7017   }
7018 };
7019 
7020 void G1CollectedHeap::rebuild_strong_code_roots() {
7021   RebuildStrongCodeRootClosure blob_cl(this);
7022   CodeCache::blobs_do(&blob_cl);
7023 }