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() for parallelism.
  94 // The number of GC workers is passed to heap_region_par_iterate().
  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, bool zero_filled) {
 393   // The from card cache is not the memory that is actually committed. So we cannot
 394   // take advantage of the zero_filled parameter.
 395   reset_from_card_cache(start_idx, num_regions);
 396 }
 397 
 398 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
 399 {
 400   // Claim the right to put the region on the dirty cards region list
 401   // by installing a self pointer.
 402   HeapRegion* next = hr->get_next_dirty_cards_region();
 403   if (next == NULL) {
 404     HeapRegion* res = (HeapRegion*)
 405       Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
 406                           NULL);
 407     if (res == NULL) {
 408       HeapRegion* head;
 409       do {
 410         // Put the region to the dirty cards region list.
 411         head = _dirty_cards_region_list;
 412         next = (HeapRegion*)
 413           Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
 414         if (next == head) {
 415           assert(hr->get_next_dirty_cards_region() == hr,
 416                  "hr->get_next_dirty_cards_region() != hr");
 417           if (next == NULL) {
 418             // The last region in the list points to itself.
 419             hr->set_next_dirty_cards_region(hr);
 420           } else {
 421             hr->set_next_dirty_cards_region(next);
 422           }
 423         }
 424       } while (next != head);
 425     }
 426   }
 427 }
 428 
 429 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
 430 {
 431   HeapRegion* head;
 432   HeapRegion* hr;
 433   do {
 434     head = _dirty_cards_region_list;
 435     if (head == NULL) {
 436       return NULL;
 437     }
 438     HeapRegion* new_head = head->get_next_dirty_cards_region();
 439     if (head == new_head) {
 440       // The last region.
 441       new_head = NULL;
 442     }
 443     hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
 444                                           head);
 445   } while (hr != head);
 446   assert(hr != NULL, "invariant");
 447   hr->set_next_dirty_cards_region(NULL);
 448   return hr;
 449 }
 450 
 451 #ifdef ASSERT
 452 // A region is added to the collection set as it is retired
 453 // so an address p can point to a region which will be in the
 454 // collection set but has not yet been retired.  This method
 455 // therefore is only accurate during a GC pause after all
 456 // regions have been retired.  It is used for debugging
 457 // to check if an nmethod has references to objects that can
 458 // be move during a partial collection.  Though it can be
 459 // inaccurate, it is sufficient for G1 because the conservative
 460 // implementation of is_scavengable() for G1 will indicate that
 461 // all nmethods must be scanned during a partial collection.
 462 bool G1CollectedHeap::is_in_partial_collection(const void* p) {
 463   if (p == NULL) {
 464     return false;
 465   }
 466   return heap_region_containing(p)->in_collection_set();
 467 }
 468 #endif
 469 
 470 // Returns true if the reference points to an object that
 471 // can move in an incremental collection.
 472 bool G1CollectedHeap::is_scavengable(const void* p) {
 473   HeapRegion* hr = heap_region_containing(p);
 474   return !hr->is_humongous();
 475 }
 476 
 477 void G1CollectedHeap::check_ct_logs_at_safepoint() {
 478   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
 479   CardTableModRefBS* ct_bs = g1_barrier_set();
 480 
 481   // Count the dirty cards at the start.
 482   CountNonCleanMemRegionClosure count1(this);
 483   ct_bs->mod_card_iterate(&count1);
 484   int orig_count = count1.n();
 485 
 486   // First clear the logged cards.
 487   ClearLoggedCardTableEntryClosure clear;
 488   dcqs.apply_closure_to_all_completed_buffers(&clear);
 489   dcqs.iterate_closure_all_threads(&clear, false);
 490   clear.print_histo();
 491 
 492   // Now ensure that there's no dirty cards.
 493   CountNonCleanMemRegionClosure count2(this);
 494   ct_bs->mod_card_iterate(&count2);
 495   if (count2.n() != 0) {
 496     gclog_or_tty->print_cr("Card table has %d entries; %d originally",
 497                            count2.n(), orig_count);
 498   }
 499   guarantee(count2.n() == 0, "Card table should be clean.");
 500 
 501   RedirtyLoggedCardTableEntryClosure redirty;
 502   dcqs.apply_closure_to_all_completed_buffers(&redirty);
 503   dcqs.iterate_closure_all_threads(&redirty, false);
 504   gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
 505                          clear.num_processed(), orig_count);
 506   guarantee(redirty.num_processed() == clear.num_processed(),
 507             err_msg("Redirtied "SIZE_FORMAT" cards, bug cleared "SIZE_FORMAT,
 508                     redirty.num_processed(), clear.num_processed()));
 509 
 510   CountNonCleanMemRegionClosure count3(this);
 511   ct_bs->mod_card_iterate(&count3);
 512   if (count3.n() != orig_count) {
 513     gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
 514                            orig_count, count3.n());
 515     guarantee(count3.n() >= orig_count, "Should have restored them all.");
 516   }
 517 }
 518 
 519 // Private class members.
 520 
 521 G1CollectedHeap* G1CollectedHeap::_g1h;
 522 
 523 // Private methods.
 524 
 525 HeapRegion*
 526 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
 527   MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
 528   while (!_secondary_free_list.is_empty() || free_regions_coming()) {
 529     if (!_secondary_free_list.is_empty()) {
 530       if (G1ConcRegionFreeingVerbose) {
 531         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 532                                "secondary_free_list has %u entries",
 533                                _secondary_free_list.length());
 534       }
 535       // It looks as if there are free regions available on the
 536       // secondary_free_list. Let's move them to the free_list and try
 537       // again to allocate from it.
 538       append_secondary_free_list();
 539 
 540       assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not "
 541              "empty we should have moved at least one entry to the free_list");
 542       HeapRegion* res = _hrm.allocate_free_region(is_old);
 543       if (G1ConcRegionFreeingVerbose) {
 544         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 545                                "allocated "HR_FORMAT" from secondary_free_list",
 546                                HR_FORMAT_PARAMS(res));
 547       }
 548       return res;
 549     }
 550 
 551     // Wait here until we get notified either when (a) there are no
 552     // more free regions coming or (b) some regions have been moved on
 553     // the secondary_free_list.
 554     SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
 555   }
 556 
 557   if (G1ConcRegionFreeingVerbose) {
 558     gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 559                            "could not allocate from secondary_free_list");
 560   }
 561   return NULL;
 562 }
 563 
 564 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
 565   assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
 566          "the only time we use this to allocate a humongous region is "
 567          "when we are allocating a single humongous region");
 568 
 569   HeapRegion* res;
 570   if (G1StressConcRegionFreeing) {
 571     if (!_secondary_free_list.is_empty()) {
 572       if (G1ConcRegionFreeingVerbose) {
 573         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 574                                "forced to look at the secondary_free_list");
 575       }
 576       res = new_region_try_secondary_free_list(is_old);
 577       if (res != NULL) {
 578         return res;
 579       }
 580     }
 581   }
 582 
 583   res = _hrm.allocate_free_region(is_old);
 584 
 585   if (res == NULL) {
 586     if (G1ConcRegionFreeingVerbose) {
 587       gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 588                              "res == NULL, trying the secondary_free_list");
 589     }
 590     res = new_region_try_secondary_free_list(is_old);
 591   }
 592   if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
 593     // Currently, only attempts to allocate GC alloc regions set
 594     // do_expand to true. So, we should only reach here during a
 595     // safepoint. If this assumption changes we might have to
 596     // reconsider the use of _expand_heap_after_alloc_failure.
 597     assert(SafepointSynchronize::is_at_safepoint(), "invariant");
 598 
 599     ergo_verbose1(ErgoHeapSizing,
 600                   "attempt heap expansion",
 601                   ergo_format_reason("region allocation request failed")
 602                   ergo_format_byte("allocation request"),
 603                   word_size * HeapWordSize);
 604     if (expand(word_size * HeapWordSize)) {
 605       // Given that expand() succeeded in expanding the heap, and we
 606       // always expand the heap by an amount aligned to the heap
 607       // region size, the free list should in theory not be empty.
 608       // In either case allocate_free_region() will check for NULL.
 609       res = _hrm.allocate_free_region(is_old);
 610     } else {
 611       _expand_heap_after_alloc_failure = false;
 612     }
 613   }
 614   return res;
 615 }
 616 
 617 HeapWord*
 618 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
 619                                                            uint num_regions,
 620                                                            size_t word_size,
 621                                                            AllocationContext_t context) {
 622   assert(first != G1_NO_HRM_INDEX, "pre-condition");
 623   assert(is_humongous(word_size), "word_size should be humongous");
 624   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 625 
 626   // Index of last region in the series + 1.
 627   uint last = first + num_regions;
 628 
 629   // We need to initialize the region(s) we just discovered. This is
 630   // a bit tricky given that it can happen concurrently with
 631   // refinement threads refining cards on these regions and
 632   // potentially wanting to refine the BOT as they are scanning
 633   // those cards (this can happen shortly after a cleanup; see CR
 634   // 6991377). So we have to set up the region(s) carefully and in
 635   // a specific order.
 636 
 637   // The word size sum of all the regions we will allocate.
 638   size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
 639   assert(word_size <= word_size_sum, "sanity");
 640 
 641   // This will be the "starts humongous" region.
 642   HeapRegion* first_hr = region_at(first);
 643   // The header of the new object will be placed at the bottom of
 644   // the first region.
 645   HeapWord* new_obj = first_hr->bottom();
 646   // This will be the new end of the first region in the series that
 647   // should also match the end of the last region in the series.
 648   HeapWord* new_end = new_obj + word_size_sum;
 649   // This will be the new top of the first region that will reflect
 650   // this allocation.
 651   HeapWord* new_top = new_obj + word_size;
 652 
 653   // First, we need to zero the header of the space that we will be
 654   // allocating. When we update top further down, some refinement
 655   // threads might try to scan the region. By zeroing the header we
 656   // ensure that any thread that will try to scan the region will
 657   // come across the zero klass word and bail out.
 658   //
 659   // NOTE: It would not have been correct to have used
 660   // CollectedHeap::fill_with_object() and make the space look like
 661   // an int array. The thread that is doing the allocation will
 662   // later update the object header to a potentially different array
 663   // type and, for a very short period of time, the klass and length
 664   // fields will be inconsistent. This could cause a refinement
 665   // thread to calculate the object size incorrectly.
 666   Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
 667 
 668   // We will set up the first region as "starts humongous". This
 669   // will also update the BOT covering all the regions to reflect
 670   // that there is a single object that starts at the bottom of the
 671   // first region.
 672   first_hr->set_starts_humongous(new_top, new_end);
 673   first_hr->set_allocation_context(context);
 674   // Then, if there are any, we will set up the "continues
 675   // humongous" regions.
 676   HeapRegion* hr = NULL;
 677   for (uint i = first + 1; i < last; ++i) {
 678     hr = region_at(i);
 679     hr->set_continues_humongous(first_hr);
 680     hr->set_allocation_context(context);
 681   }
 682   // If we have "continues humongous" regions (hr != NULL), then the
 683   // end of the last one should match new_end.
 684   assert(hr == NULL || hr->end() == new_end, "sanity");
 685 
 686   // Up to this point no concurrent thread would have been able to
 687   // do any scanning on any region in this series. All the top
 688   // fields still point to bottom, so the intersection between
 689   // [bottom,top] and [card_start,card_end] will be empty. Before we
 690   // update the top fields, we'll do a storestore to make sure that
 691   // no thread sees the update to top before the zeroing of the
 692   // object header and the BOT initialization.
 693   OrderAccess::storestore();
 694 
 695   // Now that the BOT and the object header have been initialized,
 696   // we can update top of the "starts humongous" region.
 697   assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
 698          "new_top should be in this region");
 699   first_hr->set_top(new_top);
 700   if (_hr_printer.is_active()) {
 701     HeapWord* bottom = first_hr->bottom();
 702     HeapWord* end = first_hr->orig_end();
 703     if ((first + 1) == last) {
 704       // the series has a single humongous region
 705       _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
 706     } else {
 707       // the series has more than one humongous regions
 708       _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
 709     }
 710   }
 711 
 712   // Now, we will update the top fields of the "continues humongous"
 713   // regions. The reason we need to do this is that, otherwise,
 714   // these regions would look empty and this will confuse parts of
 715   // G1. For example, the code that looks for a consecutive number
 716   // of empty regions will consider them empty and try to
 717   // re-allocate them. We can extend is_empty() to also include
 718   // !is_continues_humongous(), but it is easier to just update the top
 719   // fields here. The way we set top for all regions (i.e., top ==
 720   // end for all regions but the last one, top == new_top for the
 721   // last one) is actually used when we will free up the humongous
 722   // region in free_humongous_region().
 723   hr = NULL;
 724   for (uint i = first + 1; i < last; ++i) {
 725     hr = region_at(i);
 726     if ((i + 1) == last) {
 727       // last continues humongous region
 728       assert(hr->bottom() < new_top && new_top <= hr->end(),
 729              "new_top should fall on this region");
 730       hr->set_top(new_top);
 731       _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
 732     } else {
 733       // not last one
 734       assert(new_top > hr->end(), "new_top should be above this region");
 735       hr->set_top(hr->end());
 736       _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
 737     }
 738   }
 739   // If we have continues humongous regions (hr != NULL), then the
 740   // end of the last one should match new_end and its top should
 741   // match new_top.
 742   assert(hr == NULL ||
 743          (hr->end() == new_end && hr->top() == new_top), "sanity");
 744   check_bitmaps("Humongous Region Allocation", first_hr);
 745 
 746   assert(first_hr->used() == word_size * HeapWordSize, "invariant");
 747   _allocator->increase_used(first_hr->used());
 748   _humongous_set.add(first_hr);
 749 
 750   return new_obj;
 751 }
 752 
 753 // If could fit into free regions w/o expansion, try.
 754 // Otherwise, if can expand, do so.
 755 // Otherwise, if using ex regions might help, try with ex given back.
 756 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) {
 757   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 758 
 759   verify_region_sets_optional();
 760 
 761   uint first = G1_NO_HRM_INDEX;
 762   uint obj_regions = (uint)(align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords);
 763 
 764   if (obj_regions == 1) {
 765     // Only one region to allocate, try to use a fast path by directly allocating
 766     // from the free lists. Do not try to expand here, we will potentially do that
 767     // later.
 768     HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
 769     if (hr != NULL) {
 770       first = hr->hrm_index();
 771     }
 772   } else {
 773     // We can't allocate humongous regions spanning more than one region while
 774     // cleanupComplete() is running, since some of the regions we find to be
 775     // empty might not yet be added to the free list. It is not straightforward
 776     // to know in which list they are on so that we can remove them. We only
 777     // need to do this if we need to allocate more than one region to satisfy the
 778     // current humongous allocation request. If we are only allocating one region
 779     // we use the one-region region allocation code (see above), that already
 780     // potentially waits for regions from the secondary free list.
 781     wait_while_free_regions_coming();
 782     append_secondary_free_list_if_not_empty_with_lock();
 783 
 784     // Policy: Try only empty regions (i.e. already committed first). Maybe we
 785     // are lucky enough to find some.
 786     first = _hrm.find_contiguous_only_empty(obj_regions);
 787     if (first != G1_NO_HRM_INDEX) {
 788       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 789     }
 790   }
 791 
 792   if (first == G1_NO_HRM_INDEX) {
 793     // Policy: We could not find enough regions for the humongous object in the
 794     // free list. Look through the heap to find a mix of free and uncommitted regions.
 795     // If so, try expansion.
 796     first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
 797     if (first != G1_NO_HRM_INDEX) {
 798       // We found something. Make sure these regions are committed, i.e. expand
 799       // the heap. Alternatively we could do a defragmentation GC.
 800       ergo_verbose1(ErgoHeapSizing,
 801                     "attempt heap expansion",
 802                     ergo_format_reason("humongous allocation request failed")
 803                     ergo_format_byte("allocation request"),
 804                     word_size * HeapWordSize);
 805 
 806       _hrm.expand_at(first, obj_regions);
 807       g1_policy()->record_new_heap_size(num_regions());
 808 
 809 #ifdef ASSERT
 810       for (uint i = first; i < first + obj_regions; ++i) {
 811         HeapRegion* hr = region_at(i);
 812         assert(hr->is_free(), "sanity");
 813         assert(hr->is_empty(), "sanity");
 814         assert(is_on_master_free_list(hr), "sanity");
 815       }
 816 #endif
 817       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 818     } else {
 819       // Policy: Potentially trigger a defragmentation GC.
 820     }
 821   }
 822 
 823   HeapWord* result = NULL;
 824   if (first != G1_NO_HRM_INDEX) {
 825     result = humongous_obj_allocate_initialize_regions(first, obj_regions,
 826                                                        word_size, context);
 827     assert(result != NULL, "it should always return a valid result");
 828 
 829     // A successful humongous object allocation changes the used space
 830     // information of the old generation so we need to recalculate the
 831     // sizes and update the jstat counters here.
 832     g1mm()->update_sizes();
 833   }
 834 
 835   verify_region_sets_optional();
 836 
 837   return result;
 838 }
 839 
 840 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
 841   assert_heap_not_locked_and_not_at_safepoint();
 842   assert(!is_humongous(word_size), "we do not allow humongous TLABs");
 843 
 844   unsigned int dummy_gc_count_before;
 845   int dummy_gclocker_retry_count = 0;
 846   return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
 847 }
 848 
 849 HeapWord*
 850 G1CollectedHeap::mem_allocate(size_t word_size,
 851                               bool*  gc_overhead_limit_was_exceeded) {
 852   assert_heap_not_locked_and_not_at_safepoint();
 853 
 854   // Loop until the allocation is satisfied, or unsatisfied after GC.
 855   for (int try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 856     unsigned int gc_count_before;
 857 
 858     HeapWord* result = NULL;
 859     if (!is_humongous(word_size)) {
 860       result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
 861     } else {
 862       result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
 863     }
 864     if (result != NULL) {
 865       return result;
 866     }
 867 
 868     // Create the garbage collection operation...
 869     VM_G1CollectForAllocation op(gc_count_before, word_size);
 870     op.set_allocation_context(AllocationContext::current());
 871 
 872     // ...and get the VM thread to execute it.
 873     VMThread::execute(&op);
 874 
 875     if (op.prologue_succeeded() && op.pause_succeeded()) {
 876       // If the operation was successful we'll return the result even
 877       // if it is NULL. If the allocation attempt failed immediately
 878       // after a Full GC, it's unlikely we'll be able to allocate now.
 879       HeapWord* result = op.result();
 880       if (result != NULL && !is_humongous(word_size)) {
 881         // Allocations that take place on VM operations do not do any
 882         // card dirtying and we have to do it here. We only have to do
 883         // this for non-humongous allocations, though.
 884         dirty_young_block(result, word_size);
 885       }
 886       return result;
 887     } else {
 888       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 889         return NULL;
 890       }
 891       assert(op.result() == NULL,
 892              "the result should be NULL if the VM op did not succeed");
 893     }
 894 
 895     // Give a warning if we seem to be looping forever.
 896     if ((QueuedAllocationWarningCount > 0) &&
 897         (try_count % QueuedAllocationWarningCount == 0)) {
 898       warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
 899     }
 900   }
 901 
 902   ShouldNotReachHere();
 903   return NULL;
 904 }
 905 
 906 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
 907                                                    AllocationContext_t context,
 908                                                    unsigned int *gc_count_before_ret,
 909                                                    int* gclocker_retry_count_ret) {
 910   // Make sure you read the note in attempt_allocation_humongous().
 911 
 912   assert_heap_not_locked_and_not_at_safepoint();
 913   assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
 914          "be called for humongous allocation requests");
 915 
 916   // We should only get here after the first-level allocation attempt
 917   // (attempt_allocation()) failed to allocate.
 918 
 919   // We will loop until a) we manage to successfully perform the
 920   // allocation or b) we successfully schedule a collection which
 921   // fails to perform the allocation. b) is the only case when we'll
 922   // return NULL.
 923   HeapWord* result = NULL;
 924   for (int try_count = 1; /* we'll return */; try_count += 1) {
 925     bool should_try_gc;
 926     unsigned int gc_count_before;
 927 
 928     {
 929       MutexLockerEx x(Heap_lock);
 930       result = _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size,
 931                                                                                     false /* bot_updates */);
 932       if (result != NULL) {
 933         return result;
 934       }
 935 
 936       // If we reach here, attempt_allocation_locked() above failed to
 937       // allocate a new region. So the mutator alloc region should be NULL.
 938       assert(_allocator->mutator_alloc_region(context)->get() == NULL, "only way to get here");
 939 
 940       if (GC_locker::is_active_and_needs_gc()) {
 941         if (g1_policy()->can_expand_young_list()) {
 942           // No need for an ergo verbose message here,
 943           // can_expand_young_list() does this when it returns true.
 944           result = _allocator->mutator_alloc_region(context)->attempt_allocation_force(word_size,
 945                                                                                        false /* bot_updates */);
 946           if (result != NULL) {
 947             return result;
 948           }
 949         }
 950         should_try_gc = false;
 951       } else {
 952         // The GCLocker may not be active but the GCLocker initiated
 953         // GC may not yet have been performed (GCLocker::needs_gc()
 954         // returns true). In this case we do not try this GC and
 955         // wait until the GCLocker initiated GC is performed, and
 956         // then retry the allocation.
 957         if (GC_locker::needs_gc()) {
 958           should_try_gc = false;
 959         } else {
 960           // Read the GC count while still holding the Heap_lock.
 961           gc_count_before = total_collections();
 962           should_try_gc = true;
 963         }
 964       }
 965     }
 966 
 967     if (should_try_gc) {
 968       bool succeeded;
 969       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 970           GCCause::_g1_inc_collection_pause);
 971       if (result != NULL) {
 972         assert(succeeded, "only way to get back a non-NULL result");
 973         return result;
 974       }
 975 
 976       if (succeeded) {
 977         // If we get here we successfully scheduled a collection which
 978         // failed to allocate. No point in trying to allocate
 979         // further. We'll just return NULL.
 980         MutexLockerEx x(Heap_lock);
 981         *gc_count_before_ret = total_collections();
 982         return NULL;
 983       }
 984     } else {
 985       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
 986         MutexLockerEx x(Heap_lock);
 987         *gc_count_before_ret = total_collections();
 988         return NULL;
 989       }
 990       // The GCLocker is either active or the GCLocker initiated
 991       // GC has not yet been performed. Stall until it is and
 992       // then retry the allocation.
 993       GC_locker::stall_until_clear();
 994       (*gclocker_retry_count_ret) += 1;
 995     }
 996 
 997     // We can reach here if we were unsuccessful in scheduling a
 998     // collection (because another thread beat us to it) or if we were
 999     // stalled due to the GC locker. In either can we should retry the
1000     // allocation attempt in case another thread successfully
1001     // performed a collection and reclaimed enough space. We do the
1002     // first attempt (without holding the Heap_lock) here and the
1003     // follow-on attempt will be at the start of the next loop
1004     // iteration (after taking the Heap_lock).
1005     result = _allocator->mutator_alloc_region(context)->attempt_allocation(word_size,
1006                                                                            false /* bot_updates */);
1007     if (result != NULL) {
1008       return result;
1009     }
1010 
1011     // Give a warning if we seem to be looping forever.
1012     if ((QueuedAllocationWarningCount > 0) &&
1013         (try_count % QueuedAllocationWarningCount == 0)) {
1014       warning("G1CollectedHeap::attempt_allocation_slow() "
1015               "retries %d times", try_count);
1016     }
1017   }
1018 
1019   ShouldNotReachHere();
1020   return NULL;
1021 }
1022 
1023 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
1024                                                         unsigned int * gc_count_before_ret,
1025                                                         int* gclocker_retry_count_ret) {
1026   // The structure of this method has a lot of similarities to
1027   // attempt_allocation_slow(). The reason these two were not merged
1028   // into a single one is that such a method would require several "if
1029   // allocation is not humongous do this, otherwise do that"
1030   // conditional paths which would obscure its flow. In fact, an early
1031   // version of this code did use a unified method which was harder to
1032   // follow and, as a result, it had subtle bugs that were hard to
1033   // track down. So keeping these two methods separate allows each to
1034   // be more readable. It will be good to keep these two in sync as
1035   // much as possible.
1036 
1037   assert_heap_not_locked_and_not_at_safepoint();
1038   assert(is_humongous(word_size), "attempt_allocation_humongous() "
1039          "should only be called for humongous allocations");
1040 
1041   // Humongous objects can exhaust the heap quickly, so we should check if we
1042   // need to start a marking cycle at each humongous object allocation. We do
1043   // the check before we do the actual allocation. The reason for doing it
1044   // before the allocation is that we avoid having to keep track of the newly
1045   // allocated memory while we do a GC.
1046   if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
1047                                            word_size)) {
1048     collect(GCCause::_g1_humongous_allocation);
1049   }
1050 
1051   // We will loop until a) we manage to successfully perform the
1052   // allocation or b) we successfully schedule a collection which
1053   // fails to perform the allocation. b) is the only case when we'll
1054   // return NULL.
1055   HeapWord* result = NULL;
1056   for (int try_count = 1; /* we'll return */; try_count += 1) {
1057     bool should_try_gc;
1058     unsigned int gc_count_before;
1059 
1060     {
1061       MutexLockerEx x(Heap_lock);
1062 
1063       // Given that humongous objects are not allocated in young
1064       // regions, we'll first try to do the allocation without doing a
1065       // collection hoping that there's enough space in the heap.
1066       result = humongous_obj_allocate(word_size, AllocationContext::current());
1067       if (result != NULL) {
1068         return result;
1069       }
1070 
1071       if (GC_locker::is_active_and_needs_gc()) {
1072         should_try_gc = false;
1073       } else {
1074          // The GCLocker may not be active but the GCLocker initiated
1075         // GC may not yet have been performed (GCLocker::needs_gc()
1076         // returns true). In this case we do not try this GC and
1077         // wait until the GCLocker initiated GC is performed, and
1078         // then retry the allocation.
1079         if (GC_locker::needs_gc()) {
1080           should_try_gc = false;
1081         } else {
1082           // Read the GC count while still holding the Heap_lock.
1083           gc_count_before = total_collections();
1084           should_try_gc = true;
1085         }
1086       }
1087     }
1088 
1089     if (should_try_gc) {
1090       // If we failed to allocate the humongous object, we should try to
1091       // do a collection pause (if we're allowed) in case it reclaims
1092       // enough space for the allocation to succeed after the pause.
1093 
1094       bool succeeded;
1095       result = do_collection_pause(word_size, gc_count_before, &succeeded,
1096           GCCause::_g1_humongous_allocation);
1097       if (result != NULL) {
1098         assert(succeeded, "only way to get back a non-NULL result");
1099         return result;
1100       }
1101 
1102       if (succeeded) {
1103         // If we get here we successfully scheduled a collection which
1104         // failed to allocate. No point in trying to allocate
1105         // further. We'll just return NULL.
1106         MutexLockerEx x(Heap_lock);
1107         *gc_count_before_ret = total_collections();
1108         return NULL;
1109       }
1110     } else {
1111       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1112         MutexLockerEx x(Heap_lock);
1113         *gc_count_before_ret = total_collections();
1114         return NULL;
1115       }
1116       // The GCLocker is either active or the GCLocker initiated
1117       // GC has not yet been performed. Stall until it is and
1118       // then retry the allocation.
1119       GC_locker::stall_until_clear();
1120       (*gclocker_retry_count_ret) += 1;
1121     }
1122 
1123     // We can reach here if we were unsuccessful in scheduling a
1124     // collection (because another thread beat us to it) or if we were
1125     // stalled due to the GC locker. In either can we should retry the
1126     // allocation attempt in case another thread successfully
1127     // performed a collection and reclaimed enough space.  Give a
1128     // warning if we seem to be looping forever.
1129 
1130     if ((QueuedAllocationWarningCount > 0) &&
1131         (try_count % QueuedAllocationWarningCount == 0)) {
1132       warning("G1CollectedHeap::attempt_allocation_humongous() "
1133               "retries %d times", try_count);
1134     }
1135   }
1136 
1137   ShouldNotReachHere();
1138   return NULL;
1139 }
1140 
1141 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1142                                                            AllocationContext_t context,
1143                                                            bool expect_null_mutator_alloc_region) {
1144   assert_at_safepoint(true /* should_be_vm_thread */);
1145   assert(_allocator->mutator_alloc_region(context)->get() == NULL ||
1146                                              !expect_null_mutator_alloc_region,
1147          "the current alloc region was unexpectedly found to be non-NULL");
1148 
1149   if (!is_humongous(word_size)) {
1150     return _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size,
1151                                                       false /* bot_updates */);
1152   } else {
1153     HeapWord* result = humongous_obj_allocate(word_size, context);
1154     if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1155       g1_policy()->set_initiate_conc_mark_if_possible();
1156     }
1157     return result;
1158   }
1159 
1160   ShouldNotReachHere();
1161 }
1162 
1163 class PostMCRemSetClearClosure: public HeapRegionClosure {
1164   G1CollectedHeap* _g1h;
1165   ModRefBarrierSet* _mr_bs;
1166 public:
1167   PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1168     _g1h(g1h), _mr_bs(mr_bs) {}
1169 
1170   bool doHeapRegion(HeapRegion* r) {
1171     HeapRegionRemSet* hrrs = r->rem_set();
1172 
1173     if (r->is_continues_humongous()) {
1174       // We'll assert that the strong code root list and RSet is empty
1175       assert(hrrs->strong_code_roots_list_length() == 0, "sanity");
1176       assert(hrrs->occupied() == 0, "RSet should be empty");
1177       return false;
1178     }
1179 
1180     _g1h->reset_gc_time_stamps(r);
1181     hrrs->clear();
1182     // You might think here that we could clear just the cards
1183     // corresponding to the used region.  But no: if we leave a dirty card
1184     // in a region we might allocate into, then it would prevent that card
1185     // from being enqueued, and cause it to be missed.
1186     // Re: the performance cost: we shouldn't be doing full GC anyway!
1187     _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1188 
1189     return false;
1190   }
1191 };
1192 
1193 void G1CollectedHeap::clear_rsets_post_compaction() {
1194   PostMCRemSetClearClosure rs_clear(this, g1_barrier_set());
1195   heap_region_iterate(&rs_clear);
1196 }
1197 
1198 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1199   G1CollectedHeap*   _g1h;
1200   UpdateRSOopClosure _cl;
1201   int                _worker_i;
1202 public:
1203   RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1204     _cl(g1->g1_rem_set(), worker_i),
1205     _worker_i(worker_i),
1206     _g1h(g1)
1207   { }
1208 
1209   bool doHeapRegion(HeapRegion* r) {
1210     if (!r->is_continues_humongous()) {
1211       _cl.set_from(r);
1212       r->oop_iterate(&_cl);
1213     }
1214     return false;
1215   }
1216 };
1217 
1218 class ParRebuildRSTask: public AbstractGangTask {
1219   G1CollectedHeap* _g1;
1220   HeapRegionClaimer _hrclaimer;
1221 
1222 public:
1223   ParRebuildRSTask(G1CollectedHeap* g1) :
1224       AbstractGangTask("ParRebuildRSTask"), _g1(g1), _hrclaimer(g1->workers()->active_workers()) {}
1225 
1226   void work(uint worker_id) {
1227     RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1228     _g1->heap_region_par_iterate(&rebuild_rs, worker_id, &_hrclaimer);
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(UseDynamicNumberOfGCThreads ||
1459                workers()->active_workers() == workers()->total_workers(),
1460                "Unless dynamic should use total workers");
1461         // Use the most recent number of  active workers
1462         assert(workers()->active_workers() > 0,
1463                "Active workers not properly set");
1464         set_par_threads(workers()->active_workers());
1465         workers()->run_task(&rebuild_rs_task);
1466         set_par_threads(0);
1467       } else {
1468         RebuildRSOutOfRegionClosure rebuild_rs(this);
1469         heap_region_iterate(&rebuild_rs);
1470       }
1471 
1472       // Rebuild the strong code root lists for each region
1473       rebuild_strong_code_roots();
1474 
1475       if (true) { // FIXME
1476         MetaspaceGC::compute_new_size();
1477       }
1478 
1479 #ifdef TRACESPINNING
1480       ParallelTaskTerminator::print_termination_counts();
1481 #endif
1482 
1483       // Discard all rset updates
1484       JavaThread::dirty_card_queue_set().abandon_logs();
1485       assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1486 
1487       _young_list->reset_sampled_info();
1488       // At this point there should be no regions in the
1489       // entire heap tagged as young.
1490       assert(check_young_list_empty(true /* check_heap */),
1491              "young list should be empty at this point");
1492 
1493       // Update the number of full collections that have been completed.
1494       increment_old_marking_cycles_completed(false /* concurrent */);
1495 
1496       _hrm.verify_optional();
1497       verify_region_sets_optional();
1498 
1499       verify_after_gc();
1500 
1501       // Clear the previous marking bitmap, if needed for bitmap verification.
1502       // Note we cannot do this when we clear the next marking bitmap in
1503       // ConcurrentMark::abort() above since VerifyDuringGC verifies the
1504       // objects marked during a full GC against the previous bitmap.
1505       // But we need to clear it before calling check_bitmaps below since
1506       // the full GC has compacted objects and updated TAMS but not updated
1507       // the prev bitmap.
1508       if (G1VerifyBitmaps) {
1509         ((CMBitMap*) concurrent_mark()->prevMarkBitMap())->clearAll();
1510       }
1511       check_bitmaps("Full GC End");
1512 
1513       // Start a new incremental collection set for the next pause
1514       assert(g1_policy()->collection_set() == NULL, "must be");
1515       g1_policy()->start_incremental_cset_building();
1516 
1517       clear_cset_fast_test();
1518 
1519       _allocator->init_mutator_alloc_region();
1520 
1521       double end = os::elapsedTime();
1522       g1_policy()->record_full_collection_end();
1523 
1524       if (G1Log::fine()) {
1525         g1_policy()->print_heap_transition();
1526       }
1527 
1528       // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1529       // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1530       // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1531       // before any GC notifications are raised.
1532       g1mm()->update_sizes();
1533 
1534       gc_epilogue(true);
1535     }
1536 
1537     if (G1Log::finer()) {
1538       g1_policy()->print_detailed_heap_transition(true /* full */);
1539     }
1540 
1541     print_heap_after_gc();
1542     trace_heap_after_gc(gc_tracer);
1543 
1544     post_full_gc_dump(gc_timer);
1545 
1546     gc_timer->register_gc_end();
1547     gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
1548   }
1549 
1550   return true;
1551 }
1552 
1553 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1554   // do_collection() will return whether it succeeded in performing
1555   // the GC. Currently, there is no facility on the
1556   // do_full_collection() API to notify the caller than the collection
1557   // did not succeed (e.g., because it was locked out by the GC
1558   // locker). So, right now, we'll ignore the return value.
1559   bool dummy = do_collection(true,                /* explicit_gc */
1560                              clear_all_soft_refs,
1561                              0                    /* word_size */);
1562 }
1563 
1564 // This code is mostly copied from TenuredGeneration.
1565 void
1566 G1CollectedHeap::
1567 resize_if_necessary_after_full_collection(size_t word_size) {
1568   // Include the current allocation, if any, and bytes that will be
1569   // pre-allocated to support collections, as "used".
1570   const size_t used_after_gc = used();
1571   const size_t capacity_after_gc = capacity();
1572   const size_t free_after_gc = capacity_after_gc - used_after_gc;
1573 
1574   // This is enforced in arguments.cpp.
1575   assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1576          "otherwise the code below doesn't make sense");
1577 
1578   // We don't have floating point command-line arguments
1579   const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1580   const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1581   const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1582   const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1583 
1584   const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1585   const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1586 
1587   // We have to be careful here as these two calculations can overflow
1588   // 32-bit size_t's.
1589   double used_after_gc_d = (double) used_after_gc;
1590   double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1591   double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1592 
1593   // Let's make sure that they are both under the max heap size, which
1594   // by default will make them fit into a size_t.
1595   double desired_capacity_upper_bound = (double) max_heap_size;
1596   minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1597                                     desired_capacity_upper_bound);
1598   maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1599                                     desired_capacity_upper_bound);
1600 
1601   // We can now safely turn them into size_t's.
1602   size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1603   size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1604 
1605   // This assert only makes sense here, before we adjust them
1606   // with respect to the min and max heap size.
1607   assert(minimum_desired_capacity <= maximum_desired_capacity,
1608          err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1609                  "maximum_desired_capacity = "SIZE_FORMAT,
1610                  minimum_desired_capacity, maximum_desired_capacity));
1611 
1612   // Should not be greater than the heap max size. No need to adjust
1613   // it with respect to the heap min size as it's a lower bound (i.e.,
1614   // we'll try to make the capacity larger than it, not smaller).
1615   minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1616   // Should not be less than the heap min size. No need to adjust it
1617   // with respect to the heap max size as it's an upper bound (i.e.,
1618   // we'll try to make the capacity smaller than it, not greater).
1619   maximum_desired_capacity =  MAX2(maximum_desired_capacity, min_heap_size);
1620 
1621   if (capacity_after_gc < minimum_desired_capacity) {
1622     // Don't expand unless it's significant
1623     size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1624     ergo_verbose4(ErgoHeapSizing,
1625                   "attempt heap expansion",
1626                   ergo_format_reason("capacity lower than "
1627                                      "min desired capacity after Full GC")
1628                   ergo_format_byte("capacity")
1629                   ergo_format_byte("occupancy")
1630                   ergo_format_byte_perc("min desired capacity"),
1631                   capacity_after_gc, used_after_gc,
1632                   minimum_desired_capacity, (double) MinHeapFreeRatio);
1633     expand(expand_bytes);
1634 
1635     // No expansion, now see if we want to shrink
1636   } else if (capacity_after_gc > maximum_desired_capacity) {
1637     // Capacity too large, compute shrinking size
1638     size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1639     ergo_verbose4(ErgoHeapSizing,
1640                   "attempt heap shrinking",
1641                   ergo_format_reason("capacity higher than "
1642                                      "max desired capacity after Full GC")
1643                   ergo_format_byte("capacity")
1644                   ergo_format_byte("occupancy")
1645                   ergo_format_byte_perc("max desired capacity"),
1646                   capacity_after_gc, used_after_gc,
1647                   maximum_desired_capacity, (double) MaxHeapFreeRatio);
1648     shrink(shrink_bytes);
1649   }
1650 }
1651 
1652 
1653 HeapWord*
1654 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1655                                            AllocationContext_t context,
1656                                            bool* succeeded) {
1657   assert_at_safepoint(true /* should_be_vm_thread */);
1658 
1659   *succeeded = true;
1660   // Let's attempt the allocation first.
1661   HeapWord* result =
1662     attempt_allocation_at_safepoint(word_size,
1663                                     context,
1664                                     false /* expect_null_mutator_alloc_region */);
1665   if (result != NULL) {
1666     assert(*succeeded, "sanity");
1667     return result;
1668   }
1669 
1670   // In a G1 heap, we're supposed to keep allocation from failing by
1671   // incremental pauses.  Therefore, at least for now, we'll favor
1672   // expansion over collection.  (This might change in the future if we can
1673   // do something smarter than full collection to satisfy a failed alloc.)
1674   result = expand_and_allocate(word_size, context);
1675   if (result != NULL) {
1676     assert(*succeeded, "sanity");
1677     return result;
1678   }
1679 
1680   // Expansion didn't work, we'll try to do a Full GC.
1681   bool gc_succeeded = do_collection(false, /* explicit_gc */
1682                                     false, /* clear_all_soft_refs */
1683                                     word_size);
1684   if (!gc_succeeded) {
1685     *succeeded = false;
1686     return NULL;
1687   }
1688 
1689   // Retry the allocation
1690   result = attempt_allocation_at_safepoint(word_size,
1691                                            context,
1692                                            true /* expect_null_mutator_alloc_region */);
1693   if (result != NULL) {
1694     assert(*succeeded, "sanity");
1695     return result;
1696   }
1697 
1698   // Then, try a Full GC that will collect all soft references.
1699   gc_succeeded = do_collection(false, /* explicit_gc */
1700                                true,  /* clear_all_soft_refs */
1701                                word_size);
1702   if (!gc_succeeded) {
1703     *succeeded = false;
1704     return NULL;
1705   }
1706 
1707   // Retry the allocation once more
1708   result = attempt_allocation_at_safepoint(word_size,
1709                                            context,
1710                                            true /* expect_null_mutator_alloc_region */);
1711   if (result != NULL) {
1712     assert(*succeeded, "sanity");
1713     return result;
1714   }
1715 
1716   assert(!collector_policy()->should_clear_all_soft_refs(),
1717          "Flag should have been handled and cleared prior to this point");
1718 
1719   // What else?  We might try synchronous finalization later.  If the total
1720   // space available is large enough for the allocation, then a more
1721   // complete compaction phase than we've tried so far might be
1722   // appropriate.
1723   assert(*succeeded, "sanity");
1724   return NULL;
1725 }
1726 
1727 // Attempting to expand the heap sufficiently
1728 // to support an allocation of the given "word_size".  If
1729 // successful, perform the allocation and return the address of the
1730 // allocated block, or else "NULL".
1731 
1732 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) {
1733   assert_at_safepoint(true /* should_be_vm_thread */);
1734 
1735   verify_region_sets_optional();
1736 
1737   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1738   ergo_verbose1(ErgoHeapSizing,
1739                 "attempt heap expansion",
1740                 ergo_format_reason("allocation request failed")
1741                 ergo_format_byte("allocation request"),
1742                 word_size * HeapWordSize);
1743   if (expand(expand_bytes)) {
1744     _hrm.verify_optional();
1745     verify_region_sets_optional();
1746     return attempt_allocation_at_safepoint(word_size,
1747                                            context,
1748                                            false /* expect_null_mutator_alloc_region */);
1749   }
1750   return NULL;
1751 }
1752 
1753 bool G1CollectedHeap::expand(size_t expand_bytes) {
1754   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1755   aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1756                                        HeapRegion::GrainBytes);
1757   ergo_verbose2(ErgoHeapSizing,
1758                 "expand the heap",
1759                 ergo_format_byte("requested expansion amount")
1760                 ergo_format_byte("attempted expansion amount"),
1761                 expand_bytes, aligned_expand_bytes);
1762 
1763   if (is_maximal_no_gc()) {
1764     ergo_verbose0(ErgoHeapSizing,
1765                       "did not expand the heap",
1766                       ergo_format_reason("heap already fully expanded"));
1767     return false;
1768   }
1769 
1770   uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1771   assert(regions_to_expand > 0, "Must expand by at least one region");
1772 
1773   uint expanded_by = _hrm.expand_by(regions_to_expand);
1774 
1775   if (expanded_by > 0) {
1776     size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1777     assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1778     g1_policy()->record_new_heap_size(num_regions());
1779   } else {
1780     ergo_verbose0(ErgoHeapSizing,
1781                   "did not expand the heap",
1782                   ergo_format_reason("heap expansion operation failed"));
1783     // The expansion of the virtual storage space was unsuccessful.
1784     // Let's see if it was because we ran out of swap.
1785     if (G1ExitOnExpansionFailure &&
1786         _hrm.available() >= regions_to_expand) {
1787       // We had head room...
1788       vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1789     }
1790   }
1791   return regions_to_expand > 0;
1792 }
1793 
1794 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1795   size_t aligned_shrink_bytes =
1796     ReservedSpace::page_align_size_down(shrink_bytes);
1797   aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1798                                          HeapRegion::GrainBytes);
1799   uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1800 
1801   uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1802   size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1803 
1804   ergo_verbose3(ErgoHeapSizing,
1805                 "shrink the heap",
1806                 ergo_format_byte("requested shrinking amount")
1807                 ergo_format_byte("aligned shrinking amount")
1808                 ergo_format_byte("attempted shrinking amount"),
1809                 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1810   if (num_regions_removed > 0) {
1811     g1_policy()->record_new_heap_size(num_regions());
1812   } else {
1813     ergo_verbose0(ErgoHeapSizing,
1814                   "did not shrink the heap",
1815                   ergo_format_reason("heap shrinking operation failed"));
1816   }
1817 }
1818 
1819 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1820   verify_region_sets_optional();
1821 
1822   // We should only reach here at the end of a Full GC which means we
1823   // should not not be holding to any GC alloc regions. The method
1824   // below will make sure of that and do any remaining clean up.
1825   _allocator->abandon_gc_alloc_regions();
1826 
1827   // Instead of tearing down / rebuilding the free lists here, we
1828   // could instead use the remove_all_pending() method on free_list to
1829   // remove only the ones that we need to remove.
1830   tear_down_region_sets(true /* free_list_only */);
1831   shrink_helper(shrink_bytes);
1832   rebuild_region_sets(true /* free_list_only */);
1833 
1834   _hrm.verify_optional();
1835   verify_region_sets_optional();
1836 }
1837 
1838 // Public methods.
1839 
1840 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1841 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1842 #endif // _MSC_VER
1843 
1844 
1845 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1846   SharedHeap(policy_),
1847   _g1_policy(policy_),
1848   _dirty_card_queue_set(false),
1849   _into_cset_dirty_card_queue_set(false),
1850   _is_alive_closure_cm(this),
1851   _is_alive_closure_stw(this),
1852   _ref_processor_cm(NULL),
1853   _ref_processor_stw(NULL),
1854   _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
1855   _bot_shared(NULL),
1856   _evac_failure_scan_stack(NULL),
1857   _mark_in_progress(false),
1858   _cg1r(NULL),
1859   _g1mm(NULL),
1860   _refine_cte_cl(NULL),
1861   _full_collection(false),
1862   _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1863   _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1864   _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1865   _humongous_is_live(),
1866   _has_humongous_reclaim_candidates(false),
1867   _free_regions_coming(false),
1868   _young_list(new YoungList(this)),
1869   _gc_time_stamp(0),
1870   _survivor_plab_stats(YoungPLABSize, PLABWeight),
1871   _old_plab_stats(OldPLABSize, PLABWeight),
1872   _expand_heap_after_alloc_failure(true),
1873   _surviving_young_words(NULL),
1874   _old_marking_cycles_started(0),
1875   _old_marking_cycles_completed(0),
1876   _concurrent_cycle_started(false),
1877   _heap_summary_sent(false),
1878   _in_cset_fast_test(),
1879   _dirty_cards_region_list(NULL),
1880   _worker_cset_start_region(NULL),
1881   _worker_cset_start_region_time_stamp(NULL),
1882   _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1883   _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
1884   _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1885   _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) {
1886 
1887   _g1h = this;
1888   if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
1889     vm_exit_during_initialization("Failed necessary allocation.");
1890   }
1891 
1892   _allocator = G1Allocator::create_allocator(_g1h);
1893   _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1894 
1895   int n_queues = MAX2((int)ParallelGCThreads, 1);
1896   _task_queues = new RefToScanQueueSet(n_queues);
1897 
1898   uint n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1899   assert(n_rem_sets > 0, "Invariant.");
1900 
1901   _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1902   _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC);
1903   _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1904 
1905   for (int i = 0; i < n_queues; i++) {
1906     RefToScanQueue* q = new RefToScanQueue();
1907     q->initialize();
1908     _task_queues->register_queue(i, q);
1909     ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1910   }
1911   clear_cset_start_regions();
1912 
1913   // Initialize the G1EvacuationFailureALot counters and flags.
1914   NOT_PRODUCT(reset_evacuation_should_fail();)
1915 
1916   guarantee(_task_queues != NULL, "task_queues allocation failure.");
1917 }
1918 
1919 jint G1CollectedHeap::initialize() {
1920   CollectedHeap::pre_initialize();
1921   os::enable_vtime();
1922 
1923   G1Log::init();
1924 
1925   // Necessary to satisfy locking discipline assertions.
1926 
1927   MutexLocker x(Heap_lock);
1928 
1929   // We have to initialize the printer before committing the heap, as
1930   // it will be used then.
1931   _hr_printer.set_active(G1PrintHeapRegions);
1932 
1933   // While there are no constraints in the GC code that HeapWordSize
1934   // be any particular value, there are multiple other areas in the
1935   // system which believe this to be true (e.g. oop->object_size in some
1936   // cases incorrectly returns the size in wordSize units rather than
1937   // HeapWordSize).
1938   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1939 
1940   size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1941   size_t max_byte_size = collector_policy()->max_heap_byte_size();
1942   size_t heap_alignment = collector_policy()->heap_alignment();
1943 
1944   // Ensure that the sizes are properly aligned.
1945   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1946   Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1947   Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1948 
1949   _refine_cte_cl = new RefineCardTableEntryClosure();
1950 
1951   _cg1r = new ConcurrentG1Refine(this, _refine_cte_cl);
1952 
1953   // Reserve the maximum.
1954 
1955   // When compressed oops are enabled, the preferred heap base
1956   // is calculated by subtracting the requested size from the
1957   // 32Gb boundary and using the result as the base address for
1958   // heap reservation. If the requested size is not aligned to
1959   // HeapRegion::GrainBytes (i.e. the alignment that is passed
1960   // into the ReservedHeapSpace constructor) then the actual
1961   // base of the reserved heap may end up differing from the
1962   // address that was requested (i.e. the preferred heap base).
1963   // If this happens then we could end up using a non-optimal
1964   // compressed oops mode.
1965 
1966   ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1967                                                  heap_alignment);
1968 
1969   initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
1970 
1971   // Create the gen rem set (and barrier set) for the entire reserved region.
1972   _rem_set = collector_policy()->create_rem_set(reserved_region(), 2);
1973   set_barrier_set(rem_set()->bs());
1974   if (!barrier_set()->is_a(BarrierSet::G1SATBCTLogging)) {
1975     vm_exit_during_initialization("G1 requires a G1SATBLoggingCardTableModRefBS");
1976     return JNI_ENOMEM;
1977   }
1978 
1979   // Also create a G1 rem set.
1980   _g1_rem_set = new G1RemSet(this, g1_barrier_set());
1981 
1982   // Carve out the G1 part of the heap.
1983 
1984   ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1985   G1RegionToSpaceMapper* heap_storage =
1986     G1RegionToSpaceMapper::create_mapper(g1_rs,
1987                                          UseLargePages ? os::large_page_size() : os::vm_page_size(),
1988                                          HeapRegion::GrainBytes,
1989                                          1,
1990                                          mtJavaHeap);
1991   heap_storage->set_mapping_changed_listener(&_listener);
1992 
1993   // Reserve space for the block offset table. We do not support automatic uncommit
1994   // for the card table at this time. BOT only.
1995   ReservedSpace bot_rs(G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize));
1996   G1RegionToSpaceMapper* bot_storage =
1997     G1RegionToSpaceMapper::create_mapper(bot_rs,
1998                                          os::vm_page_size(),
1999                                          HeapRegion::GrainBytes,
2000                                          G1BlockOffsetSharedArray::N_bytes,
2001                                          mtGC);
2002 
2003   ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize));
2004   G1RegionToSpaceMapper* cardtable_storage =
2005     G1RegionToSpaceMapper::create_mapper(cardtable_rs,
2006                                          os::vm_page_size(),
2007                                          HeapRegion::GrainBytes,
2008                                          G1BlockOffsetSharedArray::N_bytes,
2009                                          mtGC);
2010 
2011   // Reserve space for the card counts table.
2012   ReservedSpace card_counts_rs(G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize));
2013   G1RegionToSpaceMapper* card_counts_storage =
2014     G1RegionToSpaceMapper::create_mapper(card_counts_rs,
2015                                          os::vm_page_size(),
2016                                          HeapRegion::GrainBytes,
2017                                          G1BlockOffsetSharedArray::N_bytes,
2018                                          mtGC);
2019 
2020   // Reserve space for prev and next bitmap.
2021   size_t bitmap_size = CMBitMap::compute_size(g1_rs.size());
2022 
2023   ReservedSpace prev_bitmap_rs(ReservedSpace::allocation_align_size_up(bitmap_size));
2024   G1RegionToSpaceMapper* prev_bitmap_storage =
2025     G1RegionToSpaceMapper::create_mapper(prev_bitmap_rs,
2026                                          os::vm_page_size(),
2027                                          HeapRegion::GrainBytes,
2028                                          CMBitMap::mark_distance(),
2029                                          mtGC);
2030 
2031   ReservedSpace next_bitmap_rs(ReservedSpace::allocation_align_size_up(bitmap_size));
2032   G1RegionToSpaceMapper* next_bitmap_storage =
2033     G1RegionToSpaceMapper::create_mapper(next_bitmap_rs,
2034                                          os::vm_page_size(),
2035                                          HeapRegion::GrainBytes,
2036                                          CMBitMap::mark_distance(),
2037                                          mtGC);
2038 
2039   _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
2040   g1_barrier_set()->initialize(cardtable_storage);
2041    // Do later initialization work for concurrent refinement.
2042   _cg1r->init(card_counts_storage);
2043 
2044   // 6843694 - ensure that the maximum region index can fit
2045   // in the remembered set structures.
2046   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
2047   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
2048 
2049   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
2050   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
2051   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
2052             "too many cards per region");
2053 
2054   FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
2055 
2056   _bot_shared = new G1BlockOffsetSharedArray(reserved_region(), bot_storage);
2057 
2058   _g1h = this;
2059 
2060   _in_cset_fast_test.initialize(_hrm.reserved().start(), _hrm.reserved().end(), HeapRegion::GrainBytes);
2061   _humongous_is_live.initialize(_hrm.reserved().start(), _hrm.reserved().end(), HeapRegion::GrainBytes);
2062 
2063   // Create the ConcurrentMark data structure and thread.
2064   // (Must do this late, so that "max_regions" is defined.)
2065   _cm = new ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
2066   if (_cm == NULL || !_cm->completed_initialization()) {
2067     vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark");
2068     return JNI_ENOMEM;
2069   }
2070   _cmThread = _cm->cmThread();
2071 
2072   // Initialize the from_card cache structure of HeapRegionRemSet.
2073   HeapRegionRemSet::init_heap(max_regions());
2074 
2075   // Now expand into the initial heap size.
2076   if (!expand(init_byte_size)) {
2077     vm_shutdown_during_initialization("Failed to allocate initial heap.");
2078     return JNI_ENOMEM;
2079   }
2080 
2081   // Perform any initialization actions delegated to the policy.
2082   g1_policy()->init();
2083 
2084   JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
2085                                                SATB_Q_FL_lock,
2086                                                G1SATBProcessCompletedThreshold,
2087                                                Shared_SATB_Q_lock);
2088 
2089   JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl,
2090                                                 DirtyCardQ_CBL_mon,
2091                                                 DirtyCardQ_FL_lock,
2092                                                 concurrent_g1_refine()->yellow_zone(),
2093                                                 concurrent_g1_refine()->red_zone(),
2094                                                 Shared_DirtyCardQ_lock);
2095 
2096   dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code
2097                                     DirtyCardQ_CBL_mon,
2098                                     DirtyCardQ_FL_lock,
2099                                     -1, // never trigger processing
2100                                     -1, // no limit on length
2101                                     Shared_DirtyCardQ_lock,
2102                                     &JavaThread::dirty_card_queue_set());
2103 
2104   // Initialize the card queue set used to hold cards containing
2105   // references into the collection set.
2106   _into_cset_dirty_card_queue_set.initialize(NULL, // Should never be called by the Java code
2107                                              DirtyCardQ_CBL_mon,
2108                                              DirtyCardQ_FL_lock,
2109                                              -1, // never trigger processing
2110                                              -1, // no limit on length
2111                                              Shared_DirtyCardQ_lock,
2112                                              &JavaThread::dirty_card_queue_set());
2113 
2114   // In case we're keeping closure specialization stats, initialize those
2115   // counts and that mechanism.
2116   SpecializationStats::clear();
2117 
2118   // Here we allocate the dummy HeapRegion that is required by the
2119   // G1AllocRegion class.
2120   HeapRegion* dummy_region = _hrm.get_dummy_region();
2121 
2122   // We'll re-use the same region whether the alloc region will
2123   // require BOT updates or not and, if it doesn't, then a non-young
2124   // region will complain that it cannot support allocations without
2125   // BOT updates. So we'll tag the dummy region as eden to avoid that.
2126   dummy_region->set_eden();
2127   // Make sure it's full.
2128   dummy_region->set_top(dummy_region->end());
2129   G1AllocRegion::setup(this, dummy_region);
2130 
2131   _allocator->init_mutator_alloc_region();
2132 
2133   // Do create of the monitoring and management support so that
2134   // values in the heap have been properly initialized.
2135   _g1mm = new G1MonitoringSupport(this);
2136 
2137   G1StringDedup::initialize();
2138 
2139   return JNI_OK;
2140 }
2141 
2142 void G1CollectedHeap::stop() {
2143   // Stop all concurrent threads. We do this to make sure these threads
2144   // do not continue to execute and access resources (e.g. gclog_or_tty)
2145   // that are destroyed during shutdown.
2146   _cg1r->stop();
2147   _cmThread->stop();
2148   if (G1StringDedup::is_enabled()) {
2149     G1StringDedup::stop();
2150   }
2151 }
2152 
2153 void G1CollectedHeap::clear_humongous_is_live_table() {
2154   guarantee(G1ReclaimDeadHumongousObjectsAtYoungGC, "Should only be called if true");
2155   _humongous_is_live.clear();
2156 }
2157 
2158 size_t G1CollectedHeap::conservative_max_heap_alignment() {
2159   return HeapRegion::max_region_size();
2160 }
2161 
2162 void G1CollectedHeap::ref_processing_init() {
2163   // Reference processing in G1 currently works as follows:
2164   //
2165   // * There are two reference processor instances. One is
2166   //   used to record and process discovered references
2167   //   during concurrent marking; the other is used to
2168   //   record and process references during STW pauses
2169   //   (both full and incremental).
2170   // * Both ref processors need to 'span' the entire heap as
2171   //   the regions in the collection set may be dotted around.
2172   //
2173   // * For the concurrent marking ref processor:
2174   //   * Reference discovery is enabled at initial marking.
2175   //   * Reference discovery is disabled and the discovered
2176   //     references processed etc during remarking.
2177   //   * Reference discovery is MT (see below).
2178   //   * Reference discovery requires a barrier (see below).
2179   //   * Reference processing may or may not be MT
2180   //     (depending on the value of ParallelRefProcEnabled
2181   //     and ParallelGCThreads).
2182   //   * A full GC disables reference discovery by the CM
2183   //     ref processor and abandons any entries on it's
2184   //     discovered lists.
2185   //
2186   // * For the STW processor:
2187   //   * Non MT discovery is enabled at the start of a full GC.
2188   //   * Processing and enqueueing during a full GC is non-MT.
2189   //   * During a full GC, references are processed after marking.
2190   //
2191   //   * Discovery (may or may not be MT) is enabled at the start
2192   //     of an incremental evacuation pause.
2193   //   * References are processed near the end of a STW evacuation pause.
2194   //   * For both types of GC:
2195   //     * Discovery is atomic - i.e. not concurrent.
2196   //     * Reference discovery will not need a barrier.
2197 
2198   SharedHeap::ref_processing_init();
2199   MemRegion mr = reserved_region();
2200 
2201   // Concurrent Mark ref processor
2202   _ref_processor_cm =
2203     new ReferenceProcessor(mr,    // span
2204                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2205                                 // mt processing
2206                            (int) ParallelGCThreads,
2207                                 // degree of mt processing
2208                            (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2209                                 // mt discovery
2210                            (int) MAX2(ParallelGCThreads, ConcGCThreads),
2211                                 // degree of mt discovery
2212                            false,
2213                                 // Reference discovery is not atomic
2214                            &_is_alive_closure_cm);
2215                                 // is alive closure
2216                                 // (for efficiency/performance)
2217 
2218   // STW ref processor
2219   _ref_processor_stw =
2220     new ReferenceProcessor(mr,    // span
2221                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2222                                 // mt processing
2223                            MAX2((int)ParallelGCThreads, 1),
2224                                 // degree of mt processing
2225                            (ParallelGCThreads > 1),
2226                                 // mt discovery
2227                            MAX2((int)ParallelGCThreads, 1),
2228                                 // degree of mt discovery
2229                            true,
2230                                 // Reference discovery is atomic
2231                            &_is_alive_closure_stw);
2232                                 // is alive closure
2233                                 // (for efficiency/performance)
2234 }
2235 
2236 size_t G1CollectedHeap::capacity() const {
2237   return _hrm.length() * HeapRegion::GrainBytes;
2238 }
2239 
2240 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2241   assert(!hr->is_continues_humongous(), "pre-condition");
2242   hr->reset_gc_time_stamp();
2243   if (hr->is_starts_humongous()) {
2244     uint first_index = hr->hrm_index() + 1;
2245     uint last_index = hr->last_hc_index();
2246     for (uint i = first_index; i < last_index; i += 1) {
2247       HeapRegion* chr = region_at(i);
2248       assert(chr->is_continues_humongous(), "sanity");
2249       chr->reset_gc_time_stamp();
2250     }
2251   }
2252 }
2253 
2254 #ifndef PRODUCT
2255 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2256 private:
2257   unsigned _gc_time_stamp;
2258   bool _failures;
2259 
2260 public:
2261   CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2262     _gc_time_stamp(gc_time_stamp), _failures(false) { }
2263 
2264   virtual bool doHeapRegion(HeapRegion* hr) {
2265     unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2266     if (_gc_time_stamp != region_gc_time_stamp) {
2267       gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, "
2268                              "expected %d", HR_FORMAT_PARAMS(hr),
2269                              region_gc_time_stamp, _gc_time_stamp);
2270       _failures = true;
2271     }
2272     return false;
2273   }
2274 
2275   bool failures() { return _failures; }
2276 };
2277 
2278 void G1CollectedHeap::check_gc_time_stamps() {
2279   CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2280   heap_region_iterate(&cl);
2281   guarantee(!cl.failures(), "all GC time stamps should have been reset");
2282 }
2283 #endif // PRODUCT
2284 
2285 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2286                                                  DirtyCardQueue* into_cset_dcq,
2287                                                  bool concurrent,
2288                                                  uint worker_i) {
2289   // Clean cards in the hot card cache
2290   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
2291   hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq);
2292 
2293   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2294   int n_completed_buffers = 0;
2295   while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2296     n_completed_buffers++;
2297   }
2298   g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers);
2299   dcqs.clear_n_completed_buffers();
2300   assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2301 }
2302 
2303 
2304 // Computes the sum of the storage used by the various regions.
2305 size_t G1CollectedHeap::used() const {
2306   return _allocator->used();
2307 }
2308 
2309 size_t G1CollectedHeap::used_unlocked() const {
2310   return _allocator->used_unlocked();
2311 }
2312 
2313 class SumUsedClosure: public HeapRegionClosure {
2314   size_t _used;
2315 public:
2316   SumUsedClosure() : _used(0) {}
2317   bool doHeapRegion(HeapRegion* r) {
2318     if (!r->is_continues_humongous()) {
2319       _used += r->used();
2320     }
2321     return false;
2322   }
2323   size_t result() { return _used; }
2324 };
2325 
2326 size_t G1CollectedHeap::recalculate_used() const {
2327   double recalculate_used_start = os::elapsedTime();
2328 
2329   SumUsedClosure blk;
2330   heap_region_iterate(&blk);
2331 
2332   g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2333   return blk.result();
2334 }
2335 
2336 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2337   switch (cause) {
2338     case GCCause::_gc_locker:               return GCLockerInvokesConcurrent;
2339     case GCCause::_java_lang_system_gc:     return ExplicitGCInvokesConcurrent;
2340     case GCCause::_g1_humongous_allocation: return true;
2341     case GCCause::_update_allocation_context_stats_inc: return true;
2342     default:                                return false;
2343   }
2344 }
2345 
2346 #ifndef PRODUCT
2347 void G1CollectedHeap::allocate_dummy_regions() {
2348   // Let's fill up most of the region
2349   size_t word_size = HeapRegion::GrainWords - 1024;
2350   // And as a result the region we'll allocate will be humongous.
2351   guarantee(is_humongous(word_size), "sanity");
2352 
2353   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2354     // Let's use the existing mechanism for the allocation
2355     HeapWord* dummy_obj = humongous_obj_allocate(word_size,
2356                                                  AllocationContext::system());
2357     if (dummy_obj != NULL) {
2358       MemRegion mr(dummy_obj, word_size);
2359       CollectedHeap::fill_with_object(mr);
2360     } else {
2361       // If we can't allocate once, we probably cannot allocate
2362       // again. Let's get out of the loop.
2363       break;
2364     }
2365   }
2366 }
2367 #endif // !PRODUCT
2368 
2369 void G1CollectedHeap::increment_old_marking_cycles_started() {
2370   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2371     _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2372     err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2373     _old_marking_cycles_started, _old_marking_cycles_completed));
2374 
2375   _old_marking_cycles_started++;
2376 }
2377 
2378 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2379   MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2380 
2381   // We assume that if concurrent == true, then the caller is a
2382   // concurrent thread that was joined the Suspendible Thread
2383   // Set. If there's ever a cheap way to check this, we should add an
2384   // assert here.
2385 
2386   // Given that this method is called at the end of a Full GC or of a
2387   // concurrent cycle, and those can be nested (i.e., a Full GC can
2388   // interrupt a concurrent cycle), the number of full collections
2389   // completed should be either one (in the case where there was no
2390   // nesting) or two (when a Full GC interrupted a concurrent cycle)
2391   // behind the number of full collections started.
2392 
2393   // This is the case for the inner caller, i.e. a Full GC.
2394   assert(concurrent ||
2395          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2396          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2397          err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
2398                  "is inconsistent with _old_marking_cycles_completed = %u",
2399                  _old_marking_cycles_started, _old_marking_cycles_completed));
2400 
2401   // This is the case for the outer caller, i.e. the concurrent cycle.
2402   assert(!concurrent ||
2403          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2404          err_msg("for outer caller (concurrent cycle): "
2405                  "_old_marking_cycles_started = %u "
2406                  "is inconsistent with _old_marking_cycles_completed = %u",
2407                  _old_marking_cycles_started, _old_marking_cycles_completed));
2408 
2409   _old_marking_cycles_completed += 1;
2410 
2411   // We need to clear the "in_progress" flag in the CM thread before
2412   // we wake up any waiters (especially when ExplicitInvokesConcurrent
2413   // is set) so that if a waiter requests another System.gc() it doesn't
2414   // incorrectly see that a marking cycle is still in progress.
2415   if (concurrent) {
2416     _cmThread->clear_in_progress();
2417   }
2418 
2419   // This notify_all() will ensure that a thread that called
2420   // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2421   // and it's waiting for a full GC to finish will be woken up. It is
2422   // waiting in VM_G1IncCollectionPause::doit_epilogue().
2423   FullGCCount_lock->notify_all();
2424 }
2425 
2426 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) {
2427   _concurrent_cycle_started = true;
2428   _gc_timer_cm->register_gc_start(start_time);
2429 
2430   _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start());
2431   trace_heap_before_gc(_gc_tracer_cm);
2432 }
2433 
2434 void G1CollectedHeap::register_concurrent_cycle_end() {
2435   if (_concurrent_cycle_started) {
2436     if (_cm->has_aborted()) {
2437       _gc_tracer_cm->report_concurrent_mode_failure();
2438     }
2439 
2440     _gc_timer_cm->register_gc_end();
2441     _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
2442 
2443     // Clear state variables to prepare for the next concurrent cycle.
2444     _concurrent_cycle_started = false;
2445     _heap_summary_sent = false;
2446   }
2447 }
2448 
2449 void G1CollectedHeap::trace_heap_after_concurrent_cycle() {
2450   if (_concurrent_cycle_started) {
2451     // This function can be called when:
2452     //  the cleanup pause is run
2453     //  the concurrent cycle is aborted before the cleanup pause.
2454     //  the concurrent cycle is aborted after the cleanup pause,
2455     //   but before the concurrent cycle end has been registered.
2456     // Make sure that we only send the heap information once.
2457     if (!_heap_summary_sent) {
2458       trace_heap_after_gc(_gc_tracer_cm);
2459       _heap_summary_sent = true;
2460     }
2461   }
2462 }
2463 
2464 G1YCType G1CollectedHeap::yc_type() {
2465   bool is_young = g1_policy()->gcs_are_young();
2466   bool is_initial_mark = g1_policy()->during_initial_mark_pause();
2467   bool is_during_mark = mark_in_progress();
2468 
2469   if (is_initial_mark) {
2470     return InitialMark;
2471   } else if (is_during_mark) {
2472     return DuringMark;
2473   } else if (is_young) {
2474     return Normal;
2475   } else {
2476     return Mixed;
2477   }
2478 }
2479 
2480 void G1CollectedHeap::collect(GCCause::Cause cause) {
2481   assert_heap_not_locked();
2482 
2483   unsigned int gc_count_before;
2484   unsigned int old_marking_count_before;
2485   bool retry_gc;
2486 
2487   do {
2488     retry_gc = false;
2489 
2490     {
2491       MutexLocker ml(Heap_lock);
2492 
2493       // Read the GC count while holding the Heap_lock
2494       gc_count_before = total_collections();
2495       old_marking_count_before = _old_marking_cycles_started;
2496     }
2497 
2498     if (should_do_concurrent_full_gc(cause)) {
2499       // Schedule an initial-mark evacuation pause that will start a
2500       // concurrent cycle. We're setting word_size to 0 which means that
2501       // we are not requesting a post-GC allocation.
2502       VM_G1IncCollectionPause op(gc_count_before,
2503                                  0,     /* word_size */
2504                                  true,  /* should_initiate_conc_mark */
2505                                  g1_policy()->max_pause_time_ms(),
2506                                  cause);
2507       op.set_allocation_context(AllocationContext::current());
2508 
2509       VMThread::execute(&op);
2510       if (!op.pause_succeeded()) {
2511         if (old_marking_count_before == _old_marking_cycles_started) {
2512           retry_gc = op.should_retry_gc();
2513         } else {
2514           // A Full GC happened while we were trying to schedule the
2515           // initial-mark GC. No point in starting a new cycle given
2516           // that the whole heap was collected anyway.
2517         }
2518 
2519         if (retry_gc) {
2520           if (GC_locker::is_active_and_needs_gc()) {
2521             GC_locker::stall_until_clear();
2522           }
2523         }
2524       }
2525     } else {
2526       if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2527           DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2528 
2529         // Schedule a standard evacuation pause. We're setting word_size
2530         // to 0 which means that we are not requesting a post-GC allocation.
2531         VM_G1IncCollectionPause op(gc_count_before,
2532                                    0,     /* word_size */
2533                                    false, /* should_initiate_conc_mark */
2534                                    g1_policy()->max_pause_time_ms(),
2535                                    cause);
2536         VMThread::execute(&op);
2537       } else {
2538         // Schedule a Full GC.
2539         VM_G1CollectFull op(gc_count_before, old_marking_count_before, cause);
2540         VMThread::execute(&op);
2541       }
2542     }
2543   } while (retry_gc);
2544 }
2545 
2546 bool G1CollectedHeap::is_in(const void* p) const {
2547   if (_hrm.reserved().contains(p)) {
2548     // Given that we know that p is in the reserved space,
2549     // heap_region_containing_raw() should successfully
2550     // return the containing region.
2551     HeapRegion* hr = heap_region_containing_raw(p);
2552     return hr->is_in(p);
2553   } else {
2554     return false;
2555   }
2556 }
2557 
2558 #ifdef ASSERT
2559 bool G1CollectedHeap::is_in_exact(const void* p) const {
2560   bool contains = reserved_region().contains(p);
2561   bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2562   if (contains && available) {
2563     return true;
2564   } else {
2565     return false;
2566   }
2567 }
2568 #endif
2569 
2570 // Iteration functions.
2571 
2572 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion.
2573 
2574 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2575   ExtendedOopClosure* _cl;
2576 public:
2577   IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {}
2578   bool doHeapRegion(HeapRegion* r) {
2579     if (!r->is_continues_humongous()) {
2580       r->oop_iterate(_cl);
2581     }
2582     return false;
2583   }
2584 };
2585 
2586 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) {
2587   IterateOopClosureRegionClosure blk(cl);
2588   heap_region_iterate(&blk);
2589 }
2590 
2591 // Iterates an ObjectClosure over all objects within a HeapRegion.
2592 
2593 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2594   ObjectClosure* _cl;
2595 public:
2596   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2597   bool doHeapRegion(HeapRegion* r) {
2598     if (!r->is_continues_humongous()) {
2599       r->object_iterate(_cl);
2600     }
2601     return false;
2602   }
2603 };
2604 
2605 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2606   IterateObjectClosureRegionClosure blk(cl);
2607   heap_region_iterate(&blk);
2608 }
2609 
2610 // Calls a SpaceClosure on a HeapRegion.
2611 
2612 class SpaceClosureRegionClosure: public HeapRegionClosure {
2613   SpaceClosure* _cl;
2614 public:
2615   SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2616   bool doHeapRegion(HeapRegion* r) {
2617     _cl->do_space(r);
2618     return false;
2619   }
2620 };
2621 
2622 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2623   SpaceClosureRegionClosure blk(cl);
2624   heap_region_iterate(&blk);
2625 }
2626 
2627 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2628   _hrm.iterate(cl);
2629 }
2630 
2631 void
2632 G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl,
2633                                          uint worker_id,
2634                                          HeapRegionClaimer *hrclaimer) const {
2635   _hrm.par_iterate(cl, worker_id, hrclaimer);
2636 }
2637 
2638 // Clear the cached CSet starting regions and (more importantly)
2639 // the time stamps. Called when we reset the GC time stamp.
2640 void G1CollectedHeap::clear_cset_start_regions() {
2641   assert(_worker_cset_start_region != NULL, "sanity");
2642   assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2643 
2644   int n_queues = MAX2((int)ParallelGCThreads, 1);
2645   for (int i = 0; i < n_queues; i++) {
2646     _worker_cset_start_region[i] = NULL;
2647     _worker_cset_start_region_time_stamp[i] = 0;
2648   }
2649 }
2650 
2651 // Given the id of a worker, obtain or calculate a suitable
2652 // starting region for iterating over the current collection set.
2653 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) {
2654   assert(get_gc_time_stamp() > 0, "should have been updated by now");
2655 
2656   HeapRegion* result = NULL;
2657   unsigned gc_time_stamp = get_gc_time_stamp();
2658 
2659   if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2660     // Cached starting region for current worker was set
2661     // during the current pause - so it's valid.
2662     // Note: the cached starting heap region may be NULL
2663     // (when the collection set is empty).
2664     result = _worker_cset_start_region[worker_i];
2665     assert(result == NULL || result->in_collection_set(), "sanity");
2666     return result;
2667   }
2668 
2669   // The cached entry was not valid so let's calculate
2670   // a suitable starting heap region for this worker.
2671 
2672   // We want the parallel threads to start their collection
2673   // set iteration at different collection set regions to
2674   // avoid contention.
2675   // If we have:
2676   //          n collection set regions
2677   //          p threads
2678   // Then thread t will start at region floor ((t * n) / p)
2679 
2680   result = g1_policy()->collection_set();
2681   if (G1CollectedHeap::use_parallel_gc_threads()) {
2682     uint cs_size = g1_policy()->cset_region_length();
2683     uint active_workers = workers()->active_workers();
2684     assert(UseDynamicNumberOfGCThreads ||
2685              active_workers == workers()->total_workers(),
2686              "Unless dynamic should use total workers");
2687 
2688     uint end_ind   = (cs_size * worker_i) / active_workers;
2689     uint start_ind = 0;
2690 
2691     if (worker_i > 0 &&
2692         _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2693       // Previous workers starting region is valid
2694       // so let's iterate from there
2695       start_ind = (cs_size * (worker_i - 1)) / active_workers;
2696       result = _worker_cset_start_region[worker_i - 1];
2697     }
2698 
2699     for (uint i = start_ind; i < end_ind; i++) {
2700       result = result->next_in_collection_set();
2701     }
2702   }
2703 
2704   // Note: the calculated starting heap region may be NULL
2705   // (when the collection set is empty).
2706   assert(result == NULL || result->in_collection_set(), "sanity");
2707   assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2708          "should be updated only once per pause");
2709   _worker_cset_start_region[worker_i] = result;
2710   OrderAccess::storestore();
2711   _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2712   return result;
2713 }
2714 
2715 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2716   HeapRegion* r = g1_policy()->collection_set();
2717   while (r != NULL) {
2718     HeapRegion* next = r->next_in_collection_set();
2719     if (cl->doHeapRegion(r)) {
2720       cl->incomplete();
2721       return;
2722     }
2723     r = next;
2724   }
2725 }
2726 
2727 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2728                                                   HeapRegionClosure *cl) {
2729   if (r == NULL) {
2730     // The CSet is empty so there's nothing to do.
2731     return;
2732   }
2733 
2734   assert(r->in_collection_set(),
2735          "Start region must be a member of the collection set.");
2736   HeapRegion* cur = r;
2737   while (cur != NULL) {
2738     HeapRegion* next = cur->next_in_collection_set();
2739     if (cl->doHeapRegion(cur) && false) {
2740       cl->incomplete();
2741       return;
2742     }
2743     cur = next;
2744   }
2745   cur = g1_policy()->collection_set();
2746   while (cur != r) {
2747     HeapRegion* next = cur->next_in_collection_set();
2748     if (cl->doHeapRegion(cur) && false) {
2749       cl->incomplete();
2750       return;
2751     }
2752     cur = next;
2753   }
2754 }
2755 
2756 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const {
2757   HeapRegion* result = _hrm.next_region_in_heap(from);
2758   while (result != NULL && result->is_humongous()) {
2759     result = _hrm.next_region_in_heap(result);
2760   }
2761   return result;
2762 }
2763 
2764 Space* G1CollectedHeap::space_containing(const void* addr) const {
2765   return heap_region_containing(addr);
2766 }
2767 
2768 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2769   Space* sp = space_containing(addr);
2770   return sp->block_start(addr);
2771 }
2772 
2773 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2774   Space* sp = space_containing(addr);
2775   return sp->block_size(addr);
2776 }
2777 
2778 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2779   Space* sp = space_containing(addr);
2780   return sp->block_is_obj(addr);
2781 }
2782 
2783 bool G1CollectedHeap::supports_tlab_allocation() const {
2784   return true;
2785 }
2786 
2787 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2788   return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes;
2789 }
2790 
2791 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2792   return young_list()->eden_used_bytes();
2793 }
2794 
2795 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2796 // must be smaller than the humongous object limit.
2797 size_t G1CollectedHeap::max_tlab_size() const {
2798   return align_size_down(_humongous_object_threshold_in_words - 1, MinObjAlignment);
2799 }
2800 
2801 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2802   // Return the remaining space in the cur alloc region, but not less than
2803   // the min TLAB size.
2804 
2805   // Also, this value can be at most the humongous object threshold,
2806   // since we can't allow tlabs to grow big enough to accommodate
2807   // humongous objects.
2808 
2809   HeapRegion* hr = _allocator->mutator_alloc_region(AllocationContext::current())->get();
2810   size_t max_tlab = max_tlab_size() * wordSize;
2811   if (hr == NULL) {
2812     return max_tlab;
2813   } else {
2814     return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab);
2815   }
2816 }
2817 
2818 size_t G1CollectedHeap::max_capacity() const {
2819   return _hrm.reserved().byte_size();
2820 }
2821 
2822 jlong G1CollectedHeap::millis_since_last_gc() {
2823   // assert(false, "NYI");
2824   return 0;
2825 }
2826 
2827 void G1CollectedHeap::prepare_for_verify() {
2828   if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
2829     ensure_parsability(false);
2830   }
2831   g1_rem_set()->prepare_for_verify();
2832 }
2833 
2834 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr,
2835                                               VerifyOption vo) {
2836   switch (vo) {
2837   case VerifyOption_G1UsePrevMarking:
2838     return hr->obj_allocated_since_prev_marking(obj);
2839   case VerifyOption_G1UseNextMarking:
2840     return hr->obj_allocated_since_next_marking(obj);
2841   case VerifyOption_G1UseMarkWord:
2842     return false;
2843   default:
2844     ShouldNotReachHere();
2845   }
2846   return false; // keep some compilers happy
2847 }
2848 
2849 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) {
2850   switch (vo) {
2851   case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start();
2852   case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start();
2853   case VerifyOption_G1UseMarkWord:    return NULL;
2854   default:                            ShouldNotReachHere();
2855   }
2856   return NULL; // keep some compilers happy
2857 }
2858 
2859 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) {
2860   switch (vo) {
2861   case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj);
2862   case VerifyOption_G1UseNextMarking: return isMarkedNext(obj);
2863   case VerifyOption_G1UseMarkWord:    return obj->is_gc_marked();
2864   default:                            ShouldNotReachHere();
2865   }
2866   return false; // keep some compilers happy
2867 }
2868 
2869 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) {
2870   switch (vo) {
2871   case VerifyOption_G1UsePrevMarking: return "PTAMS";
2872   case VerifyOption_G1UseNextMarking: return "NTAMS";
2873   case VerifyOption_G1UseMarkWord:    return "NONE";
2874   default:                            ShouldNotReachHere();
2875   }
2876   return NULL; // keep some compilers happy
2877 }
2878 
2879 class VerifyRootsClosure: public OopClosure {
2880 private:
2881   G1CollectedHeap* _g1h;
2882   VerifyOption     _vo;
2883   bool             _failures;
2884 public:
2885   // _vo == UsePrevMarking -> use "prev" marking information,
2886   // _vo == UseNextMarking -> use "next" marking information,
2887   // _vo == UseMarkWord    -> use mark word from object header.
2888   VerifyRootsClosure(VerifyOption vo) :
2889     _g1h(G1CollectedHeap::heap()),
2890     _vo(vo),
2891     _failures(false) { }
2892 
2893   bool failures() { return _failures; }
2894 
2895   template <class T> void do_oop_nv(T* p) {
2896     T heap_oop = oopDesc::load_heap_oop(p);
2897     if (!oopDesc::is_null(heap_oop)) {
2898       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2899       if (_g1h->is_obj_dead_cond(obj, _vo)) {
2900         gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
2901                               "points to dead obj "PTR_FORMAT, p, (void*) obj);
2902         if (_vo == VerifyOption_G1UseMarkWord) {
2903           gclog_or_tty->print_cr("  Mark word: "PTR_FORMAT, (void*)(obj->mark()));
2904         }
2905         obj->print_on(gclog_or_tty);
2906         _failures = true;
2907       }
2908     }
2909   }
2910 
2911   void do_oop(oop* p)       { do_oop_nv(p); }
2912   void do_oop(narrowOop* p) { do_oop_nv(p); }
2913 };
2914 
2915 class G1VerifyCodeRootOopClosure: public OopClosure {
2916   G1CollectedHeap* _g1h;
2917   OopClosure* _root_cl;
2918   nmethod* _nm;
2919   VerifyOption _vo;
2920   bool _failures;
2921 
2922   template <class T> void do_oop_work(T* p) {
2923     // First verify that this root is live
2924     _root_cl->do_oop(p);
2925 
2926     if (!G1VerifyHeapRegionCodeRoots) {
2927       // We're not verifying the code roots attached to heap region.
2928       return;
2929     }
2930 
2931     // Don't check the code roots during marking verification in a full GC
2932     if (_vo == VerifyOption_G1UseMarkWord) {
2933       return;
2934     }
2935 
2936     // Now verify that the current nmethod (which contains p) is
2937     // in the code root list of the heap region containing the
2938     // object referenced by p.
2939 
2940     T heap_oop = oopDesc::load_heap_oop(p);
2941     if (!oopDesc::is_null(heap_oop)) {
2942       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2943 
2944       // Now fetch the region containing the object
2945       HeapRegion* hr = _g1h->heap_region_containing(obj);
2946       HeapRegionRemSet* hrrs = hr->rem_set();
2947       // Verify that the strong code root list for this region
2948       // contains the nmethod
2949       if (!hrrs->strong_code_roots_list_contains(_nm)) {
2950         gclog_or_tty->print_cr("Code root location "PTR_FORMAT" "
2951                               "from nmethod "PTR_FORMAT" not in strong "
2952                               "code roots for region ["PTR_FORMAT","PTR_FORMAT")",
2953                               p, _nm, hr->bottom(), hr->end());
2954         _failures = true;
2955       }
2956     }
2957   }
2958 
2959 public:
2960   G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo):
2961     _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {}
2962 
2963   void do_oop(oop* p) { do_oop_work(p); }
2964   void do_oop(narrowOop* p) { do_oop_work(p); }
2965 
2966   void set_nmethod(nmethod* nm) { _nm = nm; }
2967   bool failures() { return _failures; }
2968 };
2969 
2970 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure {
2971   G1VerifyCodeRootOopClosure* _oop_cl;
2972 
2973 public:
2974   G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl):
2975     _oop_cl(oop_cl) {}
2976 
2977   void do_code_blob(CodeBlob* cb) {
2978     nmethod* nm = cb->as_nmethod_or_null();
2979     if (nm != NULL) {
2980       _oop_cl->set_nmethod(nm);
2981       nm->oops_do(_oop_cl);
2982     }
2983   }
2984 };
2985 
2986 class YoungRefCounterClosure : public OopClosure {
2987   G1CollectedHeap* _g1h;
2988   int              _count;
2989  public:
2990   YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {}
2991   void do_oop(oop* p)       { if (_g1h->is_in_young(*p)) { _count++; } }
2992   void do_oop(narrowOop* p) { ShouldNotReachHere(); }
2993 
2994   int count() { return _count; }
2995   void reset_count() { _count = 0; };
2996 };
2997 
2998 class VerifyKlassClosure: public KlassClosure {
2999   YoungRefCounterClosure _young_ref_counter_closure;
3000   OopClosure *_oop_closure;
3001  public:
3002   VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {}
3003   void do_klass(Klass* k) {
3004     k->oops_do(_oop_closure);
3005 
3006     _young_ref_counter_closure.reset_count();
3007     k->oops_do(&_young_ref_counter_closure);
3008     if (_young_ref_counter_closure.count() > 0) {
3009       guarantee(k->has_modified_oops(), err_msg("Klass " PTR_FORMAT ", has young refs but is not dirty.", k));
3010     }
3011   }
3012 };
3013 
3014 class VerifyLivenessOopClosure: public OopClosure {
3015   G1CollectedHeap* _g1h;
3016   VerifyOption _vo;
3017 public:
3018   VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
3019     _g1h(g1h), _vo(vo)
3020   { }
3021   void do_oop(narrowOop *p) { do_oop_work(p); }
3022   void do_oop(      oop *p) { do_oop_work(p); }
3023 
3024   template <class T> void do_oop_work(T *p) {
3025     oop obj = oopDesc::load_decode_heap_oop(p);
3026     guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
3027               "Dead object referenced by a not dead object");
3028   }
3029 };
3030 
3031 class VerifyObjsInRegionClosure: public ObjectClosure {
3032 private:
3033   G1CollectedHeap* _g1h;
3034   size_t _live_bytes;
3035   HeapRegion *_hr;
3036   VerifyOption _vo;
3037 public:
3038   // _vo == UsePrevMarking -> use "prev" marking information,
3039   // _vo == UseNextMarking -> use "next" marking information,
3040   // _vo == UseMarkWord    -> use mark word from object header.
3041   VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
3042     : _live_bytes(0), _hr(hr), _vo(vo) {
3043     _g1h = G1CollectedHeap::heap();
3044   }
3045   void do_object(oop o) {
3046     VerifyLivenessOopClosure isLive(_g1h, _vo);
3047     assert(o != NULL, "Huh?");
3048     if (!_g1h->is_obj_dead_cond(o, _vo)) {
3049       // If the object is alive according to the mark word,
3050       // then verify that the marking information agrees.
3051       // Note we can't verify the contra-positive of the
3052       // above: if the object is dead (according to the mark
3053       // word), it may not be marked, or may have been marked
3054       // but has since became dead, or may have been allocated
3055       // since the last marking.
3056       if (_vo == VerifyOption_G1UseMarkWord) {
3057         guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
3058       }
3059 
3060       o->oop_iterate_no_header(&isLive);
3061       if (!_hr->obj_allocated_since_prev_marking(o)) {
3062         size_t obj_size = o->size();    // Make sure we don't overflow
3063         _live_bytes += (obj_size * HeapWordSize);
3064       }
3065     }
3066   }
3067   size_t live_bytes() { return _live_bytes; }
3068 };
3069 
3070 class PrintObjsInRegionClosure : public ObjectClosure {
3071   HeapRegion *_hr;
3072   G1CollectedHeap *_g1;
3073 public:
3074   PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
3075     _g1 = G1CollectedHeap::heap();
3076   };
3077 
3078   void do_object(oop o) {
3079     if (o != NULL) {
3080       HeapWord *start = (HeapWord *) o;
3081       size_t word_sz = o->size();
3082       gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
3083                           " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
3084                           (void*) o, word_sz,
3085                           _g1->isMarkedPrev(o),
3086                           _g1->isMarkedNext(o),
3087                           _hr->obj_allocated_since_prev_marking(o));
3088       HeapWord *end = start + word_sz;
3089       HeapWord *cur;
3090       int *val;
3091       for (cur = start; cur < end; cur++) {
3092         val = (int *) cur;
3093         gclog_or_tty->print("\t "PTR_FORMAT":%d\n", val, *val);
3094       }
3095     }
3096   }
3097 };
3098 
3099 class VerifyRegionClosure: public HeapRegionClosure {
3100 private:
3101   bool             _par;
3102   VerifyOption     _vo;
3103   bool             _failures;
3104 public:
3105   // _vo == UsePrevMarking -> use "prev" marking information,
3106   // _vo == UseNextMarking -> use "next" marking information,
3107   // _vo == UseMarkWord    -> use mark word from object header.
3108   VerifyRegionClosure(bool par, VerifyOption vo)
3109     : _par(par),
3110       _vo(vo),
3111       _failures(false) {}
3112 
3113   bool failures() {
3114     return _failures;
3115   }
3116 
3117   bool doHeapRegion(HeapRegion* r) {
3118     if (!r->is_continues_humongous()) {
3119       bool failures = false;
3120       r->verify(_vo, &failures);
3121       if (failures) {
3122         _failures = true;
3123       } else {
3124         VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
3125         r->object_iterate(&not_dead_yet_cl);
3126         if (_vo != VerifyOption_G1UseNextMarking) {
3127           if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
3128             gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
3129                                    "max_live_bytes "SIZE_FORMAT" "
3130                                    "< calculated "SIZE_FORMAT,
3131                                    r->bottom(), r->end(),
3132                                    r->max_live_bytes(),
3133                                  not_dead_yet_cl.live_bytes());
3134             _failures = true;
3135           }
3136         } else {
3137           // When vo == UseNextMarking we cannot currently do a sanity
3138           // check on the live bytes as the calculation has not been
3139           // finalized yet.
3140         }
3141       }
3142     }
3143     return false; // stop the region iteration if we hit a failure
3144   }
3145 };
3146 
3147 // This is the task used for parallel verification of the heap regions
3148 
3149 class G1ParVerifyTask: public AbstractGangTask {
3150 private:
3151   G1CollectedHeap*  _g1h;
3152   VerifyOption      _vo;
3153   bool              _failures;
3154   HeapRegionClaimer _hrclaimer;
3155 
3156 public:
3157   // _vo == UsePrevMarking -> use "prev" marking information,
3158   // _vo == UseNextMarking -> use "next" marking information,
3159   // _vo == UseMarkWord    -> use mark word from object header.
3160   G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
3161       AbstractGangTask("Parallel verify task"),
3162       _g1h(g1h),
3163       _vo(vo),
3164       _failures(false),
3165       _hrclaimer(g1h->workers()->active_workers()) {}
3166 
3167   bool failures() {
3168     return _failures;
3169   }
3170 
3171   void work(uint worker_id) {
3172     HandleMark hm;
3173     VerifyRegionClosure blk(true, _vo);
3174     _g1h->heap_region_par_iterate(&blk, worker_id, &_hrclaimer);
3175     if (blk.failures()) {
3176       _failures = true;
3177     }
3178   }
3179 };
3180 
3181 void G1CollectedHeap::verify(bool silent, VerifyOption vo) {
3182   if (SafepointSynchronize::is_at_safepoint()) {
3183     assert(Thread::current()->is_VM_thread(),
3184            "Expected to be executed serially by the VM thread at this point");
3185 
3186     if (!silent) { gclog_or_tty->print("Roots "); }
3187     VerifyRootsClosure rootsCl(vo);
3188     VerifyKlassClosure klassCl(this, &rootsCl);
3189     CLDToKlassAndOopClosure cldCl(&klassCl, &rootsCl, false);
3190 
3191     // We apply the relevant closures to all the oops in the
3192     // system dictionary, class loader data graph, the string table
3193     // and the nmethods in the code cache.
3194     G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo);
3195     G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl);
3196 
3197     process_all_roots(true,            // activate StrongRootsScope
3198                       SO_AllCodeCache, // roots scanning options
3199                       &rootsCl,
3200                       &cldCl,
3201                       &blobsCl);
3202 
3203     bool failures = rootsCl.failures() || codeRootsCl.failures();
3204 
3205     if (vo != VerifyOption_G1UseMarkWord) {
3206       // If we're verifying during a full GC then the region sets
3207       // will have been torn down at the start of the GC. Therefore
3208       // verifying the region sets will fail. So we only verify
3209       // the region sets when not in a full GC.
3210       if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3211       verify_region_sets();
3212     }
3213 
3214     if (!silent) { gclog_or_tty->print("HeapRegions "); }
3215     if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3216 
3217       G1ParVerifyTask task(this, vo);
3218       assert(UseDynamicNumberOfGCThreads ||
3219         workers()->active_workers() == workers()->total_workers(),
3220         "If not dynamic should be using all the workers");
3221       int n_workers = workers()->active_workers();
3222       set_par_threads(n_workers);
3223       workers()->run_task(&task);
3224       set_par_threads(0);
3225       if (task.failures()) {
3226         failures = true;
3227       }
3228 
3229     } else {
3230       VerifyRegionClosure blk(false, vo);
3231       heap_region_iterate(&blk);
3232       if (blk.failures()) {
3233         failures = true;
3234       }
3235     }
3236     if (!silent) gclog_or_tty->print("RemSet ");
3237     rem_set()->verify();
3238 
3239     if (G1StringDedup::is_enabled()) {
3240       if (!silent) gclog_or_tty->print("StrDedup ");
3241       G1StringDedup::verify();
3242     }
3243 
3244     if (failures) {
3245       gclog_or_tty->print_cr("Heap:");
3246       // It helps to have the per-region information in the output to
3247       // help us track down what went wrong. This is why we call
3248       // print_extended_on() instead of print_on().
3249       print_extended_on(gclog_or_tty);
3250       gclog_or_tty->cr();
3251 #ifndef PRODUCT
3252       if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3253         concurrent_mark()->print_reachable("at-verification-failure",
3254                                            vo, false /* all */);
3255       }
3256 #endif
3257       gclog_or_tty->flush();
3258     }
3259     guarantee(!failures, "there should not have been any failures");
3260   } else {
3261     if (!silent) {
3262       gclog_or_tty->print("(SKIPPING Roots, HeapRegionSets, HeapRegions, RemSet");
3263       if (G1StringDedup::is_enabled()) {
3264         gclog_or_tty->print(", StrDedup");
3265       }
3266       gclog_or_tty->print(") ");
3267     }
3268   }
3269 }
3270 
3271 void G1CollectedHeap::verify(bool silent) {
3272   verify(silent, VerifyOption_G1UsePrevMarking);
3273 }
3274 
3275 double G1CollectedHeap::verify(bool guard, const char* msg) {
3276   double verify_time_ms = 0.0;
3277 
3278   if (guard && total_collections() >= VerifyGCStartAt) {
3279     double verify_start = os::elapsedTime();
3280     HandleMark hm;  // Discard invalid handles created during verification
3281     prepare_for_verify();
3282     Universe::verify(VerifyOption_G1UsePrevMarking, msg);
3283     verify_time_ms = (os::elapsedTime() - verify_start) * 1000;
3284   }
3285 
3286   return verify_time_ms;
3287 }
3288 
3289 void G1CollectedHeap::verify_before_gc() {
3290   double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:");
3291   g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms);
3292 }
3293 
3294 void G1CollectedHeap::verify_after_gc() {
3295   double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:");
3296   g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms);
3297 }
3298 
3299 class PrintRegionClosure: public HeapRegionClosure {
3300   outputStream* _st;
3301 public:
3302   PrintRegionClosure(outputStream* st) : _st(st) {}
3303   bool doHeapRegion(HeapRegion* r) {
3304     r->print_on(_st);
3305     return false;
3306   }
3307 };
3308 
3309 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3310                                        const HeapRegion* hr,
3311                                        const VerifyOption vo) const {
3312   switch (vo) {
3313   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
3314   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
3315   case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked();
3316   default:                            ShouldNotReachHere();
3317   }
3318   return false; // keep some compilers happy
3319 }
3320 
3321 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3322                                        const VerifyOption vo) const {
3323   switch (vo) {
3324   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
3325   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
3326   case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked();
3327   default:                            ShouldNotReachHere();
3328   }
3329   return false; // keep some compilers happy
3330 }
3331 
3332 void G1CollectedHeap::print_on(outputStream* st) const {
3333   st->print(" %-20s", "garbage-first heap");
3334   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3335             capacity()/K, used_unlocked()/K);
3336   st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3337             _hrm.reserved().start(),
3338             _hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords,
3339             _hrm.reserved().end());
3340   st->cr();
3341   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3342   uint young_regions = _young_list->length();
3343   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3344             (size_t) young_regions * HeapRegion::GrainBytes / K);
3345   uint survivor_regions = g1_policy()->recorded_survivor_regions();
3346   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3347             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3348   st->cr();
3349   MetaspaceAux::print_on(st);
3350 }
3351 
3352 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3353   print_on(st);
3354 
3355   // Print the per-region information.
3356   st->cr();
3357   st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3358                "HS=humongous(starts), HC=humongous(continues), "
3359                "CS=collection set, F=free, TS=gc time stamp, "
3360                "PTAMS=previous top-at-mark-start, "
3361                "NTAMS=next top-at-mark-start)");
3362   PrintRegionClosure blk(st);
3363   heap_region_iterate(&blk);
3364 }
3365 
3366 void G1CollectedHeap::print_on_error(outputStream* st) const {
3367   this->CollectedHeap::print_on_error(st);
3368 
3369   if (_cm != NULL) {
3370     st->cr();
3371     _cm->print_on_error(st);
3372   }
3373 }
3374 
3375 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3376   if (G1CollectedHeap::use_parallel_gc_threads()) {
3377     workers()->print_worker_threads_on(st);
3378   }
3379   _cmThread->print_on(st);
3380   st->cr();
3381   _cm->print_worker_threads_on(st);
3382   _cg1r->print_worker_threads_on(st);
3383   if (G1StringDedup::is_enabled()) {
3384     G1StringDedup::print_worker_threads_on(st);
3385   }
3386 }
3387 
3388 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3389   if (G1CollectedHeap::use_parallel_gc_threads()) {
3390     workers()->threads_do(tc);
3391   }
3392   tc->do_thread(_cmThread);
3393   _cg1r->threads_do(tc);
3394   if (G1StringDedup::is_enabled()) {
3395     G1StringDedup::threads_do(tc);
3396   }
3397 }
3398 
3399 void G1CollectedHeap::print_tracing_info() const {
3400   // We'll overload this to mean "trace GC pause statistics."
3401   if (TraceYoungGenTime || TraceOldGenTime) {
3402     // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3403     // to that.
3404     g1_policy()->print_tracing_info();
3405   }
3406   if (G1SummarizeRSetStats) {
3407     g1_rem_set()->print_summary_info();
3408   }
3409   if (G1SummarizeConcMark) {
3410     concurrent_mark()->print_summary_info();
3411   }
3412   g1_policy()->print_yg_surv_rate_info();
3413   SpecializationStats::print();
3414 }
3415 
3416 #ifndef PRODUCT
3417 // Helpful for debugging RSet issues.
3418 
3419 class PrintRSetsClosure : public HeapRegionClosure {
3420 private:
3421   const char* _msg;
3422   size_t _occupied_sum;
3423 
3424 public:
3425   bool doHeapRegion(HeapRegion* r) {
3426     HeapRegionRemSet* hrrs = r->rem_set();
3427     size_t occupied = hrrs->occupied();
3428     _occupied_sum += occupied;
3429 
3430     gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3431                            HR_FORMAT_PARAMS(r));
3432     if (occupied == 0) {
3433       gclog_or_tty->print_cr("  RSet is empty");
3434     } else {
3435       hrrs->print();
3436     }
3437     gclog_or_tty->print_cr("----------");
3438     return false;
3439   }
3440 
3441   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3442     gclog_or_tty->cr();
3443     gclog_or_tty->print_cr("========================================");
3444     gclog_or_tty->print_cr("%s", msg);
3445     gclog_or_tty->cr();
3446   }
3447 
3448   ~PrintRSetsClosure() {
3449     gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3450     gclog_or_tty->print_cr("========================================");
3451     gclog_or_tty->cr();
3452   }
3453 };
3454 
3455 void G1CollectedHeap::print_cset_rsets() {
3456   PrintRSetsClosure cl("Printing CSet RSets");
3457   collection_set_iterate(&cl);
3458 }
3459 
3460 void G1CollectedHeap::print_all_rsets() {
3461   PrintRSetsClosure cl("Printing All RSets");;
3462   heap_region_iterate(&cl);
3463 }
3464 #endif // PRODUCT
3465 
3466 G1CollectedHeap* G1CollectedHeap::heap() {
3467   assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3468          "not a garbage-first heap");
3469   return _g1h;
3470 }
3471 
3472 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3473   // always_do_update_barrier = false;
3474   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3475   // Fill TLAB's and such
3476   accumulate_statistics_all_tlabs();
3477   ensure_parsability(true);
3478 
3479   if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) &&
3480       (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3481     g1_rem_set()->print_periodic_summary_info("Before GC RS summary");
3482   }
3483 }
3484 
3485 void G1CollectedHeap::gc_epilogue(bool full) {
3486 
3487   if (G1SummarizeRSetStats &&
3488       (G1SummarizeRSetStatsPeriod > 0) &&
3489       // we are at the end of the GC. Total collections has already been increased.
3490       ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) {
3491     g1_rem_set()->print_periodic_summary_info("After GC RS summary");
3492   }
3493 
3494   // FIXME: what is this about?
3495   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3496   // is set.
3497   COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3498                         "derived pointer present"));
3499   // always_do_update_barrier = true;
3500 
3501   resize_all_tlabs();
3502   allocation_context_stats().update(full);
3503 
3504   // We have just completed a GC. Update the soft reference
3505   // policy with the new heap occupancy
3506   Universe::update_heap_info_at_gc();
3507 }
3508 
3509 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3510                                                unsigned int gc_count_before,
3511                                                bool* succeeded,
3512                                                GCCause::Cause gc_cause) {
3513   assert_heap_not_locked_and_not_at_safepoint();
3514   g1_policy()->record_stop_world_start();
3515   VM_G1IncCollectionPause op(gc_count_before,
3516                              word_size,
3517                              false, /* should_initiate_conc_mark */
3518                              g1_policy()->max_pause_time_ms(),
3519                              gc_cause);
3520 
3521   op.set_allocation_context(AllocationContext::current());
3522   VMThread::execute(&op);
3523 
3524   HeapWord* result = op.result();
3525   bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3526   assert(result == NULL || ret_succeeded,
3527          "the result should be NULL if the VM did not succeed");
3528   *succeeded = ret_succeeded;
3529 
3530   assert_heap_not_locked();
3531   return result;
3532 }
3533 
3534 void
3535 G1CollectedHeap::doConcurrentMark() {
3536   MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3537   if (!_cmThread->in_progress()) {
3538     _cmThread->set_started();
3539     CGC_lock->notify();
3540   }
3541 }
3542 
3543 size_t G1CollectedHeap::pending_card_num() {
3544   size_t extra_cards = 0;
3545   JavaThread *curr = Threads::first();
3546   while (curr != NULL) {
3547     DirtyCardQueue& dcq = curr->dirty_card_queue();
3548     extra_cards += dcq.size();
3549     curr = curr->next();
3550   }
3551   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3552   size_t buffer_size = dcqs.buffer_size();
3553   size_t buffer_num = dcqs.completed_buffers_num();
3554 
3555   // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
3556   // in bytes - not the number of 'entries'. We need to convert
3557   // into a number of cards.
3558   return (buffer_size * buffer_num + extra_cards) / oopSize;
3559 }
3560 
3561 size_t G1CollectedHeap::cards_scanned() {
3562   return g1_rem_set()->cardsScanned();
3563 }
3564 
3565 bool G1CollectedHeap::humongous_region_is_always_live(uint index) {
3566   HeapRegion* region = region_at(index);
3567   assert(region->is_starts_humongous(), "Must start a humongous object");
3568   return oop(region->bottom())->is_objArray() || !region->rem_set()->is_empty();
3569 }
3570 
3571 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
3572  private:
3573   size_t _total_humongous;
3574   size_t _candidate_humongous;
3575  public:
3576   RegisterHumongousWithInCSetFastTestClosure() : _total_humongous(0), _candidate_humongous(0) {
3577   }
3578 
3579   virtual bool doHeapRegion(HeapRegion* r) {
3580     if (!r->is_starts_humongous()) {
3581       return false;
3582     }
3583     G1CollectedHeap* g1h = G1CollectedHeap::heap();
3584 
3585     uint region_idx = r->hrm_index();
3586     bool is_candidate = !g1h->humongous_region_is_always_live(region_idx);
3587     // Is_candidate already filters out humongous regions with some remembered set.
3588     // This will not lead to humongous object that we mistakenly keep alive because
3589     // during young collection the remembered sets will only be added to.
3590     if (is_candidate) {
3591       g1h->register_humongous_region_with_in_cset_fast_test(region_idx);
3592       _candidate_humongous++;
3593     }
3594     _total_humongous++;
3595 
3596     return false;
3597   }
3598 
3599   size_t total_humongous() const { return _total_humongous; }
3600   size_t candidate_humongous() const { return _candidate_humongous; }
3601 };
3602 
3603 void G1CollectedHeap::register_humongous_regions_with_in_cset_fast_test() {
3604   if (!G1ReclaimDeadHumongousObjectsAtYoungGC) {
3605     g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0, 0);
3606     return;
3607   }
3608 
3609   RegisterHumongousWithInCSetFastTestClosure cl;
3610   heap_region_iterate(&cl);
3611   g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(cl.total_humongous(),
3612                                                                   cl.candidate_humongous());
3613   _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
3614 
3615   if (_has_humongous_reclaim_candidates || G1TraceReclaimDeadHumongousObjectsAtYoungGC) {
3616     clear_humongous_is_live_table();
3617   }
3618 }
3619 
3620 void
3621 G1CollectedHeap::setup_surviving_young_words() {
3622   assert(_surviving_young_words == NULL, "pre-condition");
3623   uint array_length = g1_policy()->young_cset_region_length();
3624   _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3625   if (_surviving_young_words == NULL) {
3626     vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR,
3627                           "Not enough space for young surv words summary.");
3628   }
3629   memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3630 #ifdef ASSERT
3631   for (uint i = 0;  i < array_length; ++i) {
3632     assert( _surviving_young_words[i] == 0, "memset above" );
3633   }
3634 #endif // !ASSERT
3635 }
3636 
3637 void
3638 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3639   MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3640   uint array_length = g1_policy()->young_cset_region_length();
3641   for (uint i = 0; i < array_length; ++i) {
3642     _surviving_young_words[i] += surv_young_words[i];
3643   }
3644 }
3645 
3646 void
3647 G1CollectedHeap::cleanup_surviving_young_words() {
3648   guarantee( _surviving_young_words != NULL, "pre-condition" );
3649   FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC);
3650   _surviving_young_words = NULL;
3651 }
3652 
3653 #ifdef ASSERT
3654 class VerifyCSetClosure: public HeapRegionClosure {
3655 public:
3656   bool doHeapRegion(HeapRegion* hr) {
3657     // Here we check that the CSet region's RSet is ready for parallel
3658     // iteration. The fields that we'll verify are only manipulated
3659     // when the region is part of a CSet and is collected. Afterwards,
3660     // we reset these fields when we clear the region's RSet (when the
3661     // region is freed) so they are ready when the region is
3662     // re-allocated. The only exception to this is if there's an
3663     // evacuation failure and instead of freeing the region we leave
3664     // it in the heap. In that case, we reset these fields during
3665     // evacuation failure handling.
3666     guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3667 
3668     // Here's a good place to add any other checks we'd like to
3669     // perform on CSet regions.
3670     return false;
3671   }
3672 };
3673 #endif // ASSERT
3674 
3675 #if TASKQUEUE_STATS
3676 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3677   st->print_raw_cr("GC Task Stats");
3678   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3679   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3680 }
3681 
3682 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3683   print_taskqueue_stats_hdr(st);
3684 
3685   TaskQueueStats totals;
3686   const int n = workers() != NULL ? workers()->total_workers() : 1;
3687   for (int i = 0; i < n; ++i) {
3688     st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3689     totals += task_queue(i)->stats;
3690   }
3691   st->print_raw("tot "); totals.print(st); st->cr();
3692 
3693   DEBUG_ONLY(totals.verify());
3694 }
3695 
3696 void G1CollectedHeap::reset_taskqueue_stats() {
3697   const int n = workers() != NULL ? workers()->total_workers() : 1;
3698   for (int i = 0; i < n; ++i) {
3699     task_queue(i)->stats.reset();
3700   }
3701 }
3702 #endif // TASKQUEUE_STATS
3703 
3704 void G1CollectedHeap::log_gc_header() {
3705   if (!G1Log::fine()) {
3706     return;
3707   }
3708 
3709   gclog_or_tty->gclog_stamp(_gc_tracer_stw->gc_id());
3710 
3711   GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
3712     .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)")
3713     .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : "");
3714 
3715   gclog_or_tty->print("[%s", (const char*)gc_cause_str);
3716 }
3717 
3718 void G1CollectedHeap::log_gc_footer(double pause_time_sec) {
3719   if (!G1Log::fine()) {
3720     return;
3721   }
3722 
3723   if (G1Log::finer()) {
3724     if (evacuation_failed()) {
3725       gclog_or_tty->print(" (to-space exhausted)");
3726     }
3727     gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3728     g1_policy()->phase_times()->note_gc_end();
3729     g1_policy()->phase_times()->print(pause_time_sec);
3730     g1_policy()->print_detailed_heap_transition();
3731   } else {
3732     if (evacuation_failed()) {
3733       gclog_or_tty->print("--");
3734     }
3735     g1_policy()->print_heap_transition();
3736     gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3737   }
3738   gclog_or_tty->flush();
3739 }
3740 
3741 bool
3742 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3743   assert_at_safepoint(true /* should_be_vm_thread */);
3744   guarantee(!is_gc_active(), "collection is not reentrant");
3745 
3746   if (GC_locker::check_active_before_gc()) {
3747     return false;
3748   }
3749 
3750   _gc_timer_stw->register_gc_start();
3751 
3752   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3753 
3754   SvcGCMarker sgcm(SvcGCMarker::MINOR);
3755   ResourceMark rm;
3756 
3757   print_heap_before_gc();
3758   trace_heap_before_gc(_gc_tracer_stw);
3759 
3760   verify_region_sets_optional();
3761   verify_dirty_young_regions();
3762 
3763   // This call will decide whether this pause is an initial-mark
3764   // pause. If it is, during_initial_mark_pause() will return true
3765   // for the duration of this pause.
3766   g1_policy()->decide_on_conc_mark_initiation();
3767 
3768   // We do not allow initial-mark to be piggy-backed on a mixed GC.
3769   assert(!g1_policy()->during_initial_mark_pause() ||
3770           g1_policy()->gcs_are_young(), "sanity");
3771 
3772   // We also do not allow mixed GCs during marking.
3773   assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3774 
3775   // Record whether this pause is an initial mark. When the current
3776   // thread has completed its logging output and it's safe to signal
3777   // the CM thread, the flag's value in the policy has been reset.
3778   bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3779 
3780   // Inner scope for scope based logging, timers, and stats collection
3781   {
3782     EvacuationInfo evacuation_info;
3783 
3784     if (g1_policy()->during_initial_mark_pause()) {
3785       // We are about to start a marking cycle, so we increment the
3786       // full collection counter.
3787       increment_old_marking_cycles_started();
3788       register_concurrent_cycle_start(_gc_timer_stw->gc_start());
3789     }
3790 
3791     _gc_tracer_stw->report_yc_type(yc_type());
3792 
3793     TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3794 
3795     int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
3796                                 workers()->active_workers() : 1);
3797     double pause_start_sec = os::elapsedTime();
3798     g1_policy()->phase_times()->note_gc_start(active_workers);
3799     log_gc_header();
3800 
3801     TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3802     TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3803 
3804     // If the secondary_free_list is not empty, append it to the
3805     // free_list. No need to wait for the cleanup operation to finish;
3806     // the region allocation code will check the secondary_free_list
3807     // and wait if necessary. If the G1StressConcRegionFreeing flag is
3808     // set, skip this step so that the region allocation code has to
3809     // get entries from the secondary_free_list.
3810     if (!G1StressConcRegionFreeing) {
3811       append_secondary_free_list_if_not_empty_with_lock();
3812     }
3813 
3814     assert(check_young_list_well_formed(), "young list should be well formed");
3815 
3816     // Don't dynamically change the number of GC threads this early.  A value of
3817     // 0 is used to indicate serial work.  When parallel work is done,
3818     // it will be set.
3819 
3820     { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3821       IsGCActiveMark x;
3822 
3823       gc_prologue(false);
3824       increment_total_collections(false /* full gc */);
3825       increment_gc_time_stamp();
3826 
3827       verify_before_gc();
3828 
3829       check_bitmaps("GC Start");
3830 
3831       COMPILER2_PRESENT(DerivedPointerTable::clear());
3832 
3833       // Please see comment in g1CollectedHeap.hpp and
3834       // G1CollectedHeap::ref_processing_init() to see how
3835       // reference processing currently works in G1.
3836 
3837       // Enable discovery in the STW reference processor
3838       ref_processor_stw()->enable_discovery(true /*verify_disabled*/,
3839                                             true /*verify_no_refs*/);
3840 
3841       {
3842         // We want to temporarily turn off discovery by the
3843         // CM ref processor, if necessary, and turn it back on
3844         // on again later if we do. Using a scoped
3845         // NoRefDiscovery object will do this.
3846         NoRefDiscovery no_cm_discovery(ref_processor_cm());
3847 
3848         // Forget the current alloc region (we might even choose it to be part
3849         // of the collection set!).
3850         _allocator->release_mutator_alloc_region();
3851 
3852         // We should call this after we retire the mutator alloc
3853         // region(s) so that all the ALLOC / RETIRE events are generated
3854         // before the start GC event.
3855         _hr_printer.start_gc(false /* full */, (size_t) total_collections());
3856 
3857         // This timing is only used by the ergonomics to handle our pause target.
3858         // It is unclear why this should not include the full pause. We will
3859         // investigate this in CR 7178365.
3860         //
3861         // Preserving the old comment here if that helps the investigation:
3862         //
3863         // The elapsed time induced by the start time below deliberately elides
3864         // the possible verification above.
3865         double sample_start_time_sec = os::elapsedTime();
3866 
3867 #if YOUNG_LIST_VERBOSE
3868         gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
3869         _young_list->print();
3870         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3871 #endif // YOUNG_LIST_VERBOSE
3872 
3873         g1_policy()->record_collection_pause_start(sample_start_time_sec);
3874 
3875         double scan_wait_start = os::elapsedTime();
3876         // We have to wait until the CM threads finish scanning the
3877         // root regions as it's the only way to ensure that all the
3878         // objects on them have been correctly scanned before we start
3879         // moving them during the GC.
3880         bool waited = _cm->root_regions()->wait_until_scan_finished();
3881         double wait_time_ms = 0.0;
3882         if (waited) {
3883           double scan_wait_end = os::elapsedTime();
3884           wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
3885         }
3886         g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
3887 
3888 #if YOUNG_LIST_VERBOSE
3889         gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
3890         _young_list->print();
3891 #endif // YOUNG_LIST_VERBOSE
3892 
3893         if (g1_policy()->during_initial_mark_pause()) {
3894           concurrent_mark()->checkpointRootsInitialPre();
3895         }
3896 
3897 #if YOUNG_LIST_VERBOSE
3898         gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
3899         _young_list->print();
3900         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3901 #endif // YOUNG_LIST_VERBOSE
3902 
3903         g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info);
3904 
3905         register_humongous_regions_with_in_cset_fast_test();
3906 
3907         _cm->note_start_of_gc();
3908         // We should not verify the per-thread SATB buffers given that
3909         // we have not filtered them yet (we'll do so during the
3910         // GC). We also call this after finalize_cset() to
3911         // ensure that the CSet has been finalized.
3912         _cm->verify_no_cset_oops(true  /* verify_stacks */,
3913                                  true  /* verify_enqueued_buffers */,
3914                                  false /* verify_thread_buffers */,
3915                                  true  /* verify_fingers */);
3916 
3917         if (_hr_printer.is_active()) {
3918           HeapRegion* hr = g1_policy()->collection_set();
3919           while (hr != NULL) {
3920             _hr_printer.cset(hr);
3921             hr = hr->next_in_collection_set();
3922           }
3923         }
3924 
3925 #ifdef ASSERT
3926         VerifyCSetClosure cl;
3927         collection_set_iterate(&cl);
3928 #endif // ASSERT
3929 
3930         setup_surviving_young_words();
3931 
3932         // Initialize the GC alloc regions.
3933         _allocator->init_gc_alloc_regions(evacuation_info);
3934 
3935         // Actually do the work...
3936         evacuate_collection_set(evacuation_info);
3937 
3938         // We do this to mainly verify the per-thread SATB buffers
3939         // (which have been filtered by now) since we didn't verify
3940         // them earlier. No point in re-checking the stacks / enqueued
3941         // buffers given that the CSet has not changed since last time
3942         // we checked.
3943         _cm->verify_no_cset_oops(false /* verify_stacks */,
3944                                  false /* verify_enqueued_buffers */,
3945                                  true  /* verify_thread_buffers */,
3946                                  true  /* verify_fingers */);
3947 
3948         free_collection_set(g1_policy()->collection_set(), evacuation_info);
3949 
3950         eagerly_reclaim_humongous_regions();
3951 
3952         g1_policy()->clear_collection_set();
3953 
3954         cleanup_surviving_young_words();
3955 
3956         // Start a new incremental collection set for the next pause.
3957         g1_policy()->start_incremental_cset_building();
3958 
3959         clear_cset_fast_test();
3960 
3961         _young_list->reset_sampled_info();
3962 
3963         // Don't check the whole heap at this point as the
3964         // GC alloc regions from this pause have been tagged
3965         // as survivors and moved on to the survivor list.
3966         // Survivor regions will fail the !is_young() check.
3967         assert(check_young_list_empty(false /* check_heap */),
3968           "young list should be empty");
3969 
3970 #if YOUNG_LIST_VERBOSE
3971         gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
3972         _young_list->print();
3973 #endif // YOUNG_LIST_VERBOSE
3974 
3975         g1_policy()->record_survivor_regions(_young_list->survivor_length(),
3976                                              _young_list->first_survivor_region(),
3977                                              _young_list->last_survivor_region());
3978 
3979         _young_list->reset_auxilary_lists();
3980 
3981         if (evacuation_failed()) {
3982           _allocator->set_used(recalculate_used());
3983           uint n_queues = MAX2((int)ParallelGCThreads, 1);
3984           for (uint i = 0; i < n_queues; i++) {
3985             if (_evacuation_failed_info_array[i].has_failed()) {
3986               _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
3987             }
3988           }
3989         } else {
3990           // The "used" of the the collection set have already been subtracted
3991           // when they were freed.  Add in the bytes evacuated.
3992           _allocator->increase_used(g1_policy()->bytes_copied_during_gc());
3993         }
3994 
3995         if (g1_policy()->during_initial_mark_pause()) {
3996           // We have to do this before we notify the CM threads that
3997           // they can start working to make sure that all the
3998           // appropriate initialization is done on the CM object.
3999           concurrent_mark()->checkpointRootsInitialPost();
4000           set_marking_started();
4001           // Note that we don't actually trigger the CM thread at
4002           // this point. We do that later when we're sure that
4003           // the current thread has completed its logging output.
4004         }
4005 
4006         allocate_dummy_regions();
4007 
4008 #if YOUNG_LIST_VERBOSE
4009         gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
4010         _young_list->print();
4011         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4012 #endif // YOUNG_LIST_VERBOSE
4013 
4014         _allocator->init_mutator_alloc_region();
4015 
4016         {
4017           size_t expand_bytes = g1_policy()->expansion_amount();
4018           if (expand_bytes > 0) {
4019             size_t bytes_before = capacity();
4020             // No need for an ergo verbose message here,
4021             // expansion_amount() does this when it returns a value > 0.
4022             if (!expand(expand_bytes)) {
4023               // We failed to expand the heap. Cannot do anything about it.
4024             }
4025           }
4026         }
4027 
4028         // We redo the verification but now wrt to the new CSet which
4029         // has just got initialized after the previous CSet was freed.
4030         _cm->verify_no_cset_oops(true  /* verify_stacks */,
4031                                  true  /* verify_enqueued_buffers */,
4032                                  true  /* verify_thread_buffers */,
4033                                  true  /* verify_fingers */);
4034         _cm->note_end_of_gc();
4035 
4036         // This timing is only used by the ergonomics to handle our pause target.
4037         // It is unclear why this should not include the full pause. We will
4038         // investigate this in CR 7178365.
4039         double sample_end_time_sec = os::elapsedTime();
4040         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
4041         g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info);
4042 
4043         MemoryService::track_memory_usage();
4044 
4045         // In prepare_for_verify() below we'll need to scan the deferred
4046         // update buffers to bring the RSets up-to-date if
4047         // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
4048         // the update buffers we'll probably need to scan cards on the
4049         // regions we just allocated to (i.e., the GC alloc
4050         // regions). However, during the last GC we called
4051         // set_saved_mark() on all the GC alloc regions, so card
4052         // scanning might skip the [saved_mark_word()...top()] area of
4053         // those regions (i.e., the area we allocated objects into
4054         // during the last GC). But it shouldn't. Given that
4055         // saved_mark_word() is conditional on whether the GC time stamp
4056         // on the region is current or not, by incrementing the GC time
4057         // stamp here we invalidate all the GC time stamps on all the
4058         // regions and saved_mark_word() will simply return top() for
4059         // all the regions. This is a nicer way of ensuring this rather
4060         // than iterating over the regions and fixing them. In fact, the
4061         // GC time stamp increment here also ensures that
4062         // saved_mark_word() will return top() between pauses, i.e.,
4063         // during concurrent refinement. So we don't need the
4064         // is_gc_active() check to decided which top to use when
4065         // scanning cards (see CR 7039627).
4066         increment_gc_time_stamp();
4067 
4068         verify_after_gc();
4069         check_bitmaps("GC End");
4070 
4071         assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
4072         ref_processor_stw()->verify_no_references_recorded();
4073 
4074         // CM reference discovery will be re-enabled if necessary.
4075       }
4076 
4077       // We should do this after we potentially expand the heap so
4078       // that all the COMMIT events are generated before the end GC
4079       // event, and after we retire the GC alloc regions so that all
4080       // RETIRE events are generated before the end GC event.
4081       _hr_printer.end_gc(false /* full */, (size_t) total_collections());
4082 
4083 #ifdef TRACESPINNING
4084       ParallelTaskTerminator::print_termination_counts();
4085 #endif
4086 
4087       gc_epilogue(false);
4088     }
4089 
4090     // Print the remainder of the GC log output.
4091     log_gc_footer(os::elapsedTime() - pause_start_sec);
4092 
4093     // It is not yet to safe to tell the concurrent mark to
4094     // start as we have some optional output below. We don't want the
4095     // output from the concurrent mark thread interfering with this
4096     // logging output either.
4097 
4098     _hrm.verify_optional();
4099     verify_region_sets_optional();
4100 
4101     TASKQUEUE_STATS_ONLY(if (PrintTaskqueue) print_taskqueue_stats());
4102     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
4103 
4104     print_heap_after_gc();
4105     trace_heap_after_gc(_gc_tracer_stw);
4106 
4107     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
4108     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
4109     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
4110     // before any GC notifications are raised.
4111     g1mm()->update_sizes();
4112 
4113     _gc_tracer_stw->report_evacuation_info(&evacuation_info);
4114     _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
4115     _gc_timer_stw->register_gc_end();
4116     _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
4117   }
4118   // It should now be safe to tell the concurrent mark thread to start
4119   // without its logging output interfering with the logging output
4120   // that came from the pause.
4121 
4122   if (should_start_conc_mark) {
4123     // CAUTION: after the doConcurrentMark() call below,
4124     // the concurrent marking thread(s) could be running
4125     // concurrently with us. Make sure that anything after
4126     // this point does not assume that we are the only GC thread
4127     // running. Note: of course, the actual marking work will
4128     // not start until the safepoint itself is released in
4129     // SuspendibleThreadSet::desynchronize().
4130     doConcurrentMark();
4131   }
4132 
4133   return true;
4134 }
4135 
4136 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
4137 {
4138   size_t gclab_word_size;
4139   switch (purpose) {
4140     case GCAllocForSurvived:
4141       gclab_word_size = _survivor_plab_stats.desired_plab_sz();
4142       break;
4143     case GCAllocForTenured:
4144       gclab_word_size = _old_plab_stats.desired_plab_sz();
4145       break;
4146     default:
4147       assert(false, "unknown GCAllocPurpose");
4148       gclab_word_size = _old_plab_stats.desired_plab_sz();
4149       break;
4150   }
4151 
4152   // Prevent humongous PLAB sizes for two reasons:
4153   // * PLABs are allocated using a similar paths as oops, but should
4154   //   never be in a humongous region
4155   // * Allowing humongous PLABs needlessly churns the region free lists
4156   return MIN2(_humongous_object_threshold_in_words, gclab_word_size);
4157 }
4158 
4159 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4160   _drain_in_progress = false;
4161   set_evac_failure_closure(cl);
4162   _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4163 }
4164 
4165 void G1CollectedHeap::finalize_for_evac_failure() {
4166   assert(_evac_failure_scan_stack != NULL &&
4167          _evac_failure_scan_stack->length() == 0,
4168          "Postcondition");
4169   assert(!_drain_in_progress, "Postcondition");
4170   delete _evac_failure_scan_stack;
4171   _evac_failure_scan_stack = NULL;
4172 }
4173 
4174 void G1CollectedHeap::remove_self_forwarding_pointers() {
4175   double remove_self_forwards_start = os::elapsedTime();
4176 
4177   set_par_threads();
4178   G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4179   workers()->run_task(&rsfp_task);
4180   set_par_threads(0);
4181 
4182   // Now restore saved marks, if any.
4183   assert(_objs_with_preserved_marks.size() ==
4184             _preserved_marks_of_objs.size(), "Both or none.");
4185   while (!_objs_with_preserved_marks.is_empty()) {
4186     oop obj = _objs_with_preserved_marks.pop();
4187     markOop m = _preserved_marks_of_objs.pop();
4188     obj->set_mark(m);
4189   }
4190   _objs_with_preserved_marks.clear(true);
4191   _preserved_marks_of_objs.clear(true);
4192 
4193   g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
4194 }
4195 
4196 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4197   _evac_failure_scan_stack->push(obj);
4198 }
4199 
4200 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4201   assert(_evac_failure_scan_stack != NULL, "precondition");
4202 
4203   while (_evac_failure_scan_stack->length() > 0) {
4204      oop obj = _evac_failure_scan_stack->pop();
4205      _evac_failure_closure->set_region(heap_region_containing(obj));
4206      obj->oop_iterate_backwards(_evac_failure_closure);
4207   }
4208 }
4209 
4210 oop
4211 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state,
4212                                                oop old) {
4213   assert(obj_in_cs(old),
4214          err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4215                  (HeapWord*) old));
4216   markOop m = old->mark();
4217   oop forward_ptr = old->forward_to_atomic(old);
4218   if (forward_ptr == NULL) {
4219     // Forward-to-self succeeded.
4220     assert(_par_scan_state != NULL, "par scan state");
4221     OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4222     uint queue_num = _par_scan_state->queue_num();
4223 
4224     _evacuation_failed = true;
4225     _evacuation_failed_info_array[queue_num].register_copy_failure(old->size());
4226     if (_evac_failure_closure != cl) {
4227       MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4228       assert(!_drain_in_progress,
4229              "Should only be true while someone holds the lock.");
4230       // Set the global evac-failure closure to the current thread's.
4231       assert(_evac_failure_closure == NULL, "Or locking has failed.");
4232       set_evac_failure_closure(cl);
4233       // Now do the common part.
4234       handle_evacuation_failure_common(old, m);
4235       // Reset to NULL.
4236       set_evac_failure_closure(NULL);
4237     } else {
4238       // The lock is already held, and this is recursive.
4239       assert(_drain_in_progress, "This should only be the recursive case.");
4240       handle_evacuation_failure_common(old, m);
4241     }
4242     return old;
4243   } else {
4244     // Forward-to-self failed. Either someone else managed to allocate
4245     // space for this object (old != forward_ptr) or they beat us in
4246     // self-forwarding it (old == forward_ptr).
4247     assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4248            err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4249                    "should not be in the CSet",
4250                    (HeapWord*) old, (HeapWord*) forward_ptr));
4251     return forward_ptr;
4252   }
4253 }
4254 
4255 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4256   preserve_mark_if_necessary(old, m);
4257 
4258   HeapRegion* r = heap_region_containing(old);
4259   if (!r->evacuation_failed()) {
4260     r->set_evacuation_failed(true);
4261     _hr_printer.evac_failure(r);
4262   }
4263 
4264   push_on_evac_failure_scan_stack(old);
4265 
4266   if (!_drain_in_progress) {
4267     // prevent recursion in copy_to_survivor_space()
4268     _drain_in_progress = true;
4269     drain_evac_failure_scan_stack();
4270     _drain_in_progress = false;
4271   }
4272 }
4273 
4274 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4275   assert(evacuation_failed(), "Oversaving!");
4276   // We want to call the "for_promotion_failure" version only in the
4277   // case of a promotion failure.
4278   if (m->must_be_preserved_for_promotion_failure(obj)) {
4279     _objs_with_preserved_marks.push(obj);
4280     _preserved_marks_of_objs.push(m);
4281   }
4282 }
4283 
4284 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
4285                                                   size_t word_size,
4286                                                   AllocationContext_t context) {
4287   if (purpose == GCAllocForSurvived) {
4288     HeapWord* result = survivor_attempt_allocation(word_size, context);
4289     if (result != NULL) {
4290       return result;
4291     } else {
4292       // Let's try to allocate in the old gen in case we can fit the
4293       // object there.
4294       return old_attempt_allocation(word_size, context);
4295     }
4296   } else {
4297     assert(purpose ==  GCAllocForTenured, "sanity");
4298     HeapWord* result = old_attempt_allocation(word_size, context);
4299     if (result != NULL) {
4300       return result;
4301     } else {
4302       // Let's try to allocate in the survivors in case we can fit the
4303       // object there.
4304       return survivor_attempt_allocation(word_size, context);
4305     }
4306   }
4307 
4308   ShouldNotReachHere();
4309   // Trying to keep some compilers happy.
4310   return NULL;
4311 }
4312 
4313 void G1ParCopyHelper::mark_object(oop obj) {
4314   assert(!_g1->heap_region_containing(obj)->in_collection_set(), "should not mark objects in the CSet");
4315 
4316   // We know that the object is not moving so it's safe to read its size.
4317   _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4318 }
4319 
4320 void G1ParCopyHelper::mark_forwarded_object(oop from_obj, oop to_obj) {
4321   assert(from_obj->is_forwarded(), "from obj should be forwarded");
4322   assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4323   assert(from_obj != to_obj, "should not be self-forwarded");
4324 
4325   assert(_g1->heap_region_containing(from_obj)->in_collection_set(), "from obj should be in the CSet");
4326   assert(!_g1->heap_region_containing(to_obj)->in_collection_set(), "should not mark objects in the CSet");
4327 
4328   // The object might be in the process of being copied by another
4329   // worker so we cannot trust that its to-space image is
4330   // well-formed. So we have to read its size from its from-space
4331   // image which we know should not be changing.
4332   _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4333 }
4334 
4335 template <class T>
4336 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) {
4337   if (_g1->heap_region_containing_raw(new_obj)->is_young()) {
4338     _scanned_klass->record_modified_oops();
4339   }
4340 }
4341 
4342 template <G1Barrier barrier, G1Mark do_mark_object>
4343 template <class T>
4344 void G1ParCopyClosure<barrier, do_mark_object>::do_oop_work(T* p) {
4345   T heap_oop = oopDesc::load_heap_oop(p);
4346 
4347   if (oopDesc::is_null(heap_oop)) {
4348     return;
4349   }
4350 
4351   oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
4352 
4353   assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4354 
4355   G1CollectedHeap::in_cset_state_t state = _g1->in_cset_state(obj);
4356 
4357   if (state == G1CollectedHeap::InCSet) {
4358     oop forwardee;
4359     if (obj->is_forwarded()) {
4360       forwardee = obj->forwardee();
4361     } else {
4362       forwardee = _par_scan_state->copy_to_survivor_space(obj);
4363     }
4364     assert(forwardee != NULL, "forwardee should not be NULL");
4365     oopDesc::encode_store_heap_oop(p, forwardee);
4366     if (do_mark_object != G1MarkNone && forwardee != obj) {
4367       // If the object is self-forwarded we don't need to explicitly
4368       // mark it, the evacuation failure protocol will do so.
4369       mark_forwarded_object(obj, forwardee);
4370     }
4371 
4372     if (barrier == G1BarrierKlass) {
4373       do_klass_barrier(p, forwardee);
4374     }
4375   } else {
4376     if (state == G1CollectedHeap::IsHumongous) {
4377       _g1->set_humongous_is_live(obj);
4378     }
4379     // The object is not in collection set. If we're a root scanning
4380     // closure during an initial mark pause then attempt to mark the object.
4381     if (do_mark_object == G1MarkFromRoot) {
4382       mark_object(obj);
4383     }
4384   }
4385 
4386   if (barrier == G1BarrierEvac) {
4387     _par_scan_state->update_rs(_from, p, _worker_id);
4388   }
4389 }
4390 
4391 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(oop* p);
4392 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(narrowOop* p);
4393 
4394 class G1ParEvacuateFollowersClosure : public VoidClosure {
4395 protected:
4396   G1CollectedHeap*              _g1h;
4397   G1ParScanThreadState*         _par_scan_state;
4398   RefToScanQueueSet*            _queues;
4399   ParallelTaskTerminator*       _terminator;
4400 
4401   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
4402   RefToScanQueueSet*      queues()         { return _queues; }
4403   ParallelTaskTerminator* terminator()     { return _terminator; }
4404 
4405 public:
4406   G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4407                                 G1ParScanThreadState* par_scan_state,
4408                                 RefToScanQueueSet* queues,
4409                                 ParallelTaskTerminator* terminator)
4410     : _g1h(g1h), _par_scan_state(par_scan_state),
4411       _queues(queues), _terminator(terminator) {}
4412 
4413   void do_void();
4414 
4415 private:
4416   inline bool offer_termination();
4417 };
4418 
4419 bool G1ParEvacuateFollowersClosure::offer_termination() {
4420   G1ParScanThreadState* const pss = par_scan_state();
4421   pss->start_term_time();
4422   const bool res = terminator()->offer_termination();
4423   pss->end_term_time();
4424   return res;
4425 }
4426 
4427 void G1ParEvacuateFollowersClosure::do_void() {
4428   G1ParScanThreadState* const pss = par_scan_state();
4429   pss->trim_queue();
4430   do {
4431     pss->steal_and_trim_queue(queues());
4432   } while (!offer_termination());
4433 }
4434 
4435 class G1KlassScanClosure : public KlassClosure {
4436  G1ParCopyHelper* _closure;
4437  bool             _process_only_dirty;
4438  int              _count;
4439  public:
4440   G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty)
4441       : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {}
4442   void do_klass(Klass* klass) {
4443     // If the klass has not been dirtied we know that there's
4444     // no references into  the young gen and we can skip it.
4445    if (!_process_only_dirty || klass->has_modified_oops()) {
4446       // Clean the klass since we're going to scavenge all the metadata.
4447       klass->clear_modified_oops();
4448 
4449       // Tell the closure that this klass is the Klass to scavenge
4450       // and is the one to dirty if oops are left pointing into the young gen.
4451       _closure->set_scanned_klass(klass);
4452 
4453       klass->oops_do(_closure);
4454 
4455       _closure->set_scanned_klass(NULL);
4456     }
4457     _count++;
4458   }
4459 };
4460 
4461 class G1CodeBlobClosure : public CodeBlobClosure {
4462   class HeapRegionGatheringOopClosure : public OopClosure {
4463     G1CollectedHeap* _g1h;
4464     OopClosure* _work;
4465     nmethod* _nm;
4466 
4467     template <typename T>
4468     void do_oop_work(T* p) {
4469       _work->do_oop(p);
4470       T oop_or_narrowoop = oopDesc::load_heap_oop(p);
4471       if (!oopDesc::is_null(oop_or_narrowoop)) {
4472         oop o = oopDesc::decode_heap_oop_not_null(oop_or_narrowoop);
4473         HeapRegion* hr = _g1h->heap_region_containing_raw(o);
4474         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");
4475         hr->add_strong_code_root(_nm);
4476       }
4477     }
4478 
4479   public:
4480     HeapRegionGatheringOopClosure(OopClosure* oc) : _g1h(G1CollectedHeap::heap()), _work(oc), _nm(NULL) {}
4481 
4482     void do_oop(oop* o) {
4483       do_oop_work(o);
4484     }
4485 
4486     void do_oop(narrowOop* o) {
4487       do_oop_work(o);
4488     }
4489 
4490     void set_nm(nmethod* nm) {
4491       _nm = nm;
4492     }
4493   };
4494 
4495   HeapRegionGatheringOopClosure _oc;
4496 public:
4497   G1CodeBlobClosure(OopClosure* oc) : _oc(oc) {}
4498 
4499   void do_code_blob(CodeBlob* cb) {
4500     nmethod* nm = cb->as_nmethod_or_null();
4501     if (nm != NULL) {
4502       if (!nm->test_set_oops_do_mark()) {
4503         _oc.set_nm(nm);
4504         nm->oops_do(&_oc);
4505         nm->fix_oop_relocations();
4506       }
4507     }
4508   }
4509 };
4510 
4511 class G1ParTask : public AbstractGangTask {
4512 protected:
4513   G1CollectedHeap*       _g1h;
4514   RefToScanQueueSet      *_queues;
4515   ParallelTaskTerminator _terminator;
4516   uint _n_workers;
4517 
4518   Mutex _stats_lock;
4519   Mutex* stats_lock() { return &_stats_lock; }
4520 
4521 public:
4522   G1ParTask(G1CollectedHeap* g1h, RefToScanQueueSet *task_queues)
4523     : AbstractGangTask("G1 collection"),
4524       _g1h(g1h),
4525       _queues(task_queues),
4526       _terminator(0, _queues),
4527       _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4528   {}
4529 
4530   RefToScanQueueSet* queues() { return _queues; }
4531 
4532   RefToScanQueue *work_queue(int i) {
4533     return queues()->queue(i);
4534   }
4535 
4536   ParallelTaskTerminator* terminator() { return &_terminator; }
4537 
4538   virtual void set_for_termination(int active_workers) {
4539     // This task calls set_n_termination() in par_non_clean_card_iterate_work()
4540     // in the young space (_par_seq_tasks) in the G1 heap
4541     // for SequentialSubTasksDone.
4542     // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap
4543     // both of which need setting by set_n_termination().
4544     _g1h->SharedHeap::set_n_termination(active_workers);
4545     _g1h->set_n_termination(active_workers);
4546     terminator()->reset_for_reuse(active_workers);
4547     _n_workers = active_workers;
4548   }
4549 
4550   // Helps out with CLD processing.
4551   //
4552   // During InitialMark we need to:
4553   // 1) Scavenge all CLDs for the young GC.
4554   // 2) Mark all objects directly reachable from strong CLDs.
4555   template <G1Mark do_mark_object>
4556   class G1CLDClosure : public CLDClosure {
4557     G1ParCopyClosure<G1BarrierNone,  do_mark_object>* _oop_closure;
4558     G1ParCopyClosure<G1BarrierKlass, do_mark_object>  _oop_in_klass_closure;
4559     G1KlassScanClosure                                _klass_in_cld_closure;
4560     bool                                              _claim;
4561 
4562    public:
4563     G1CLDClosure(G1ParCopyClosure<G1BarrierNone, do_mark_object>* oop_closure,
4564                  bool only_young, bool claim)
4565         : _oop_closure(oop_closure),
4566           _oop_in_klass_closure(oop_closure->g1(),
4567                                 oop_closure->pss(),
4568                                 oop_closure->rp()),
4569           _klass_in_cld_closure(&_oop_in_klass_closure, only_young),
4570           _claim(claim) {
4571 
4572     }
4573 
4574     void do_cld(ClassLoaderData* cld) {
4575       cld->oops_do(_oop_closure, &_klass_in_cld_closure, _claim);
4576     }
4577   };
4578 
4579   void work(uint worker_id) {
4580     if (worker_id >= _n_workers) return;  // no work needed this round
4581 
4582     double start_time_ms = os::elapsedTime() * 1000.0;
4583     _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms);
4584 
4585     {
4586       ResourceMark rm;
4587       HandleMark   hm;
4588 
4589       ReferenceProcessor*             rp = _g1h->ref_processor_stw();
4590 
4591       G1ParScanThreadState            pss(_g1h, worker_id, rp);
4592       G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
4593 
4594       pss.set_evac_failure_closure(&evac_failure_cl);
4595 
4596       bool only_young = _g1h->g1_policy()->gcs_are_young();
4597 
4598       // Non-IM young GC.
4599       G1ParCopyClosure<G1BarrierNone, G1MarkNone>             scan_only_root_cl(_g1h, &pss, rp);
4600       G1CLDClosure<G1MarkNone>                                scan_only_cld_cl(&scan_only_root_cl,
4601                                                                                only_young, // Only process dirty klasses.
4602                                                                                false);     // No need to claim CLDs.
4603       // IM young GC.
4604       //    Strong roots closures.
4605       G1ParCopyClosure<G1BarrierNone, G1MarkFromRoot>         scan_mark_root_cl(_g1h, &pss, rp);
4606       G1CLDClosure<G1MarkFromRoot>                            scan_mark_cld_cl(&scan_mark_root_cl,
4607                                                                                false, // Process all klasses.
4608                                                                                true); // Need to claim CLDs.
4609       //    Weak roots closures.
4610       G1ParCopyClosure<G1BarrierNone, G1MarkPromotedFromRoot> scan_mark_weak_root_cl(_g1h, &pss, rp);
4611       G1CLDClosure<G1MarkPromotedFromRoot>                    scan_mark_weak_cld_cl(&scan_mark_weak_root_cl,
4612                                                                                     false, // Process all klasses.
4613                                                                                     true); // Need to claim CLDs.
4614 
4615       G1CodeBlobClosure scan_only_code_cl(&scan_only_root_cl);
4616       G1CodeBlobClosure scan_mark_code_cl(&scan_mark_root_cl);
4617       // IM Weak code roots are handled later.
4618 
4619       OopClosure* strong_root_cl;
4620       OopClosure* weak_root_cl;
4621       CLDClosure* strong_cld_cl;
4622       CLDClosure* weak_cld_cl;
4623       CodeBlobClosure* strong_code_cl;
4624 
4625       if (_g1h->g1_policy()->during_initial_mark_pause()) {
4626         // We also need to mark copied objects.
4627         strong_root_cl = &scan_mark_root_cl;
4628         strong_cld_cl  = &scan_mark_cld_cl;
4629         strong_code_cl = &scan_mark_code_cl;
4630         if (ClassUnloadingWithConcurrentMark) {
4631           weak_root_cl = &scan_mark_weak_root_cl;
4632           weak_cld_cl  = &scan_mark_weak_cld_cl;
4633         } else {
4634           weak_root_cl = &scan_mark_root_cl;
4635           weak_cld_cl  = &scan_mark_cld_cl;
4636         }
4637       } else {
4638         strong_root_cl = &scan_only_root_cl;
4639         weak_root_cl   = &scan_only_root_cl;
4640         strong_cld_cl  = &scan_only_cld_cl;
4641         weak_cld_cl    = &scan_only_cld_cl;
4642         strong_code_cl = &scan_only_code_cl;
4643       }
4644 
4645 
4646       G1ParPushHeapRSClosure  push_heap_rs_cl(_g1h, &pss);
4647 
4648       pss.start_strong_roots();
4649       _g1h->g1_process_roots(strong_root_cl,
4650                              weak_root_cl,
4651                              &push_heap_rs_cl,
4652                              strong_cld_cl,
4653                              weak_cld_cl,
4654                              strong_code_cl,
4655                              worker_id);
4656 
4657       pss.end_strong_roots();
4658 
4659       {
4660         double start = os::elapsedTime();
4661         G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4662         evac.do_void();
4663         double elapsed_ms = (os::elapsedTime()-start)*1000.0;
4664         double term_ms = pss.term_time()*1000.0;
4665         _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms);
4666         _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts());
4667       }
4668       _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4669       _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4670 
4671       if (PrintTerminationStats) {
4672         MutexLocker x(stats_lock());
4673         pss.print_termination_stats(worker_id);
4674       }
4675 
4676       assert(pss.queue_is_empty(), "should be empty");
4677 
4678       // Close the inner scope so that the ResourceMark and HandleMark
4679       // destructors are executed here and are included as part of the
4680       // "GC Worker Time".
4681     }
4682 
4683     double end_time_ms = os::elapsedTime() * 1000.0;
4684     _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms);
4685   }
4686 };
4687 
4688 // *** Common G1 Evacuation Stuff
4689 
4690 // This method is run in a GC worker.
4691 
4692 void
4693 G1CollectedHeap::
4694 g1_process_roots(OopClosure* scan_non_heap_roots,
4695                  OopClosure* scan_non_heap_weak_roots,
4696                  OopsInHeapRegionClosure* scan_rs,
4697                  CLDClosure* scan_strong_clds,
4698                  CLDClosure* scan_weak_clds,
4699                  CodeBlobClosure* scan_strong_code,
4700                  uint worker_i) {
4701 
4702   // First scan the shared roots.
4703   double ext_roots_start = os::elapsedTime();
4704   double closure_app_time_sec = 0.0;
4705 
4706   bool during_im = _g1h->g1_policy()->during_initial_mark_pause();
4707   bool trace_metadata = during_im && ClassUnloadingWithConcurrentMark;
4708 
4709   BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
4710   BufferingOopClosure buf_scan_non_heap_weak_roots(scan_non_heap_weak_roots);
4711 
4712   process_roots(false, // no scoping; this is parallel code
4713                 SharedHeap::SO_None,
4714                 &buf_scan_non_heap_roots,
4715                 &buf_scan_non_heap_weak_roots,
4716                 scan_strong_clds,
4717                 // Unloading Initial Marks handle the weak CLDs separately.
4718                 (trace_metadata ? NULL : scan_weak_clds),
4719                 scan_strong_code);
4720 
4721   // Now the CM ref_processor roots.
4722   if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
4723     // We need to treat the discovered reference lists of the
4724     // concurrent mark ref processor as roots and keep entries
4725     // (which are added by the marking threads) on them live
4726     // until they can be processed at the end of marking.
4727     ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
4728   }
4729 
4730   if (trace_metadata) {
4731     // Barrier to make sure all workers passed
4732     // the strong CLD and strong nmethods phases.
4733     active_strong_roots_scope()->wait_until_all_workers_done_with_threads(n_par_threads());
4734 
4735     // Now take the complement of the strong CLDs.
4736     ClassLoaderDataGraph::roots_cld_do(NULL, scan_weak_clds);
4737   }
4738 
4739   // Finish up any enqueued closure apps (attributed as object copy time).
4740   buf_scan_non_heap_roots.done();
4741   buf_scan_non_heap_weak_roots.done();
4742 
4743   double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds()
4744       + buf_scan_non_heap_weak_roots.closure_app_seconds();
4745 
4746   g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
4747 
4748   double ext_root_time_ms =
4749     ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0;
4750 
4751   g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
4752 
4753   // During conc marking we have to filter the per-thread SATB buffers
4754   // to make sure we remove any oops into the CSet (which will show up
4755   // as implicitly live).
4756   double satb_filtering_ms = 0.0;
4757   if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) {
4758     if (mark_in_progress()) {
4759       double satb_filter_start = os::elapsedTime();
4760 
4761       JavaThread::satb_mark_queue_set().filter_thread_buffers();
4762 
4763       satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0;
4764     }
4765   }
4766   g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms);
4767 
4768   // Now scan the complement of the collection set.
4769   G1CodeBlobClosure scavenge_cs_nmethods(scan_non_heap_weak_roots);
4770 
4771   g1_rem_set()->oops_into_collection_set_do(scan_rs, &scavenge_cs_nmethods, worker_i);
4772 
4773   _process_strong_tasks->all_tasks_completed();
4774 }
4775 
4776 class G1StringSymbolTableUnlinkTask : public AbstractGangTask {
4777 private:
4778   BoolObjectClosure* _is_alive;
4779   int _initial_string_table_size;
4780   int _initial_symbol_table_size;
4781 
4782   bool  _process_strings;
4783   int _strings_processed;
4784   int _strings_removed;
4785 
4786   bool  _process_symbols;
4787   int _symbols_processed;
4788   int _symbols_removed;
4789 
4790   bool _do_in_parallel;
4791 public:
4792   G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) :
4793     AbstractGangTask("String/Symbol Unlinking"),
4794     _is_alive(is_alive),
4795     _do_in_parallel(G1CollectedHeap::use_parallel_gc_threads()),
4796     _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
4797     _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) {
4798 
4799     _initial_string_table_size = StringTable::the_table()->table_size();
4800     _initial_symbol_table_size = SymbolTable::the_table()->table_size();
4801     if (process_strings) {
4802       StringTable::clear_parallel_claimed_index();
4803     }
4804     if (process_symbols) {
4805       SymbolTable::clear_parallel_claimed_index();
4806     }
4807   }
4808 
4809   ~G1StringSymbolTableUnlinkTask() {
4810     guarantee(!_process_strings || !_do_in_parallel || StringTable::parallel_claimed_index() >= _initial_string_table_size,
4811               err_msg("claim value %d after unlink less than initial string table size %d",
4812                       StringTable::parallel_claimed_index(), _initial_string_table_size));
4813     guarantee(!_process_symbols || !_do_in_parallel || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
4814               err_msg("claim value %d after unlink less than initial symbol table size %d",
4815                       SymbolTable::parallel_claimed_index(), _initial_symbol_table_size));
4816 
4817     if (G1TraceStringSymbolTableScrubbing) {
4818       gclog_or_tty->print_cr("Cleaned string and symbol table, "
4819                              "strings: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed, "
4820                              "symbols: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed",
4821                              strings_processed(), strings_removed(),
4822                              symbols_processed(), symbols_removed());
4823     }
4824   }
4825 
4826   void work(uint worker_id) {
4827     if (_do_in_parallel) {
4828       int strings_processed = 0;
4829       int strings_removed = 0;
4830       int symbols_processed = 0;
4831       int symbols_removed = 0;
4832       if (_process_strings) {
4833         StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
4834         Atomic::add(strings_processed, &_strings_processed);
4835         Atomic::add(strings_removed, &_strings_removed);
4836       }
4837       if (_process_symbols) {
4838         SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
4839         Atomic::add(symbols_processed, &_symbols_processed);
4840         Atomic::add(symbols_removed, &_symbols_removed);
4841       }
4842     } else {
4843       if (_process_strings) {
4844         StringTable::unlink(_is_alive, &_strings_processed, &_strings_removed);
4845       }
4846       if (_process_symbols) {
4847         SymbolTable::unlink(&_symbols_processed, &_symbols_removed);
4848       }
4849     }
4850   }
4851 
4852   size_t strings_processed() const { return (size_t)_strings_processed; }
4853   size_t strings_removed()   const { return (size_t)_strings_removed; }
4854 
4855   size_t symbols_processed() const { return (size_t)_symbols_processed; }
4856   size_t symbols_removed()   const { return (size_t)_symbols_removed; }
4857 };
4858 
4859 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
4860 private:
4861   static Monitor* _lock;
4862 
4863   BoolObjectClosure* const _is_alive;
4864   const bool               _unloading_occurred;
4865   const uint               _num_workers;
4866 
4867   // Variables used to claim nmethods.
4868   nmethod* _first_nmethod;
4869   volatile nmethod* _claimed_nmethod;
4870 
4871   // The list of nmethods that need to be processed by the second pass.
4872   volatile nmethod* _postponed_list;
4873   volatile uint     _num_entered_barrier;
4874 
4875  public:
4876   G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
4877       _is_alive(is_alive),
4878       _unloading_occurred(unloading_occurred),
4879       _num_workers(num_workers),
4880       _first_nmethod(NULL),
4881       _claimed_nmethod(NULL),
4882       _postponed_list(NULL),
4883       _num_entered_barrier(0)
4884   {
4885     nmethod::increase_unloading_clock();
4886     // Get first alive nmethod
4887     NMethodIterator iter = NMethodIterator();
4888     if(iter.next_alive()) {
4889       _first_nmethod = iter.method();
4890     }
4891     _claimed_nmethod = (volatile nmethod*)_first_nmethod;
4892   }
4893 
4894   ~G1CodeCacheUnloadingTask() {
4895     CodeCache::verify_clean_inline_caches();
4896 
4897     CodeCache::set_needs_cache_clean(false);
4898     guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
4899 
4900     CodeCache::verify_icholder_relocations();
4901   }
4902 
4903  private:
4904   void add_to_postponed_list(nmethod* nm) {
4905       nmethod* old;
4906       do {
4907         old = (nmethod*)_postponed_list;
4908         nm->set_unloading_next(old);
4909       } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old);
4910   }
4911 
4912   void clean_nmethod(nmethod* nm) {
4913     bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
4914 
4915     if (postponed) {
4916       // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
4917       add_to_postponed_list(nm);
4918     }
4919 
4920     // Mark that this thread has been cleaned/unloaded.
4921     // After this call, it will be safe to ask if this nmethod was unloaded or not.
4922     nm->set_unloading_clock(nmethod::global_unloading_clock());
4923   }
4924 
4925   void clean_nmethod_postponed(nmethod* nm) {
4926     nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
4927   }
4928 
4929   static const int MaxClaimNmethods = 16;
4930 
4931   void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) {
4932     nmethod* first;
4933     NMethodIterator last;
4934 
4935     do {
4936       *num_claimed_nmethods = 0;
4937 
4938       first = (nmethod*)_claimed_nmethod;
4939       last = NMethodIterator(first);
4940 
4941       if (first != NULL) {
4942 
4943         for (int i = 0; i < MaxClaimNmethods; i++) {
4944           if (!last.next_alive()) {
4945             break;
4946           }
4947           claimed_nmethods[i] = last.method();
4948           (*num_claimed_nmethods)++;
4949         }
4950       }
4951 
4952     } while ((nmethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first);
4953   }
4954 
4955   nmethod* claim_postponed_nmethod() {
4956     nmethod* claim;
4957     nmethod* next;
4958 
4959     do {
4960       claim = (nmethod*)_postponed_list;
4961       if (claim == NULL) {
4962         return NULL;
4963       }
4964 
4965       next = claim->unloading_next();
4966 
4967     } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim);
4968 
4969     return claim;
4970   }
4971 
4972  public:
4973   // Mark that we're done with the first pass of nmethod cleaning.
4974   void barrier_mark(uint worker_id) {
4975     MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
4976     _num_entered_barrier++;
4977     if (_num_entered_barrier == _num_workers) {
4978       ml.notify_all();
4979     }
4980   }
4981 
4982   // See if we have to wait for the other workers to
4983   // finish their first-pass nmethod cleaning work.
4984   void barrier_wait(uint worker_id) {
4985     if (_num_entered_barrier < _num_workers) {
4986       MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
4987       while (_num_entered_barrier < _num_workers) {
4988           ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
4989       }
4990     }
4991   }
4992 
4993   // Cleaning and unloading of nmethods. Some work has to be postponed
4994   // to the second pass, when we know which nmethods survive.
4995   void work_first_pass(uint worker_id) {
4996     // The first nmethods is claimed by the first worker.
4997     if (worker_id == 0 && _first_nmethod != NULL) {
4998       clean_nmethod(_first_nmethod);
4999       _first_nmethod = NULL;
5000     }
5001 
5002     int num_claimed_nmethods;
5003     nmethod* claimed_nmethods[MaxClaimNmethods];
5004 
5005     while (true) {
5006       claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
5007 
5008       if (num_claimed_nmethods == 0) {
5009         break;
5010       }
5011 
5012       for (int i = 0; i < num_claimed_nmethods; i++) {
5013         clean_nmethod(claimed_nmethods[i]);
5014       }
5015     }
5016   }
5017 
5018   void work_second_pass(uint worker_id) {
5019     nmethod* nm;
5020     // Take care of postponed nmethods.
5021     while ((nm = claim_postponed_nmethod()) != NULL) {
5022       clean_nmethod_postponed(nm);
5023     }
5024   }
5025 };
5026 
5027 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock");
5028 
5029 class G1KlassCleaningTask : public StackObj {
5030   BoolObjectClosure*                      _is_alive;
5031   volatile jint                           _clean_klass_tree_claimed;
5032   ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
5033 
5034  public:
5035   G1KlassCleaningTask(BoolObjectClosure* is_alive) :
5036       _is_alive(is_alive),
5037       _clean_klass_tree_claimed(0),
5038       _klass_iterator() {
5039   }
5040 
5041  private:
5042   bool claim_clean_klass_tree_task() {
5043     if (_clean_klass_tree_claimed) {
5044       return false;
5045     }
5046 
5047     return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0;
5048   }
5049 
5050   InstanceKlass* claim_next_klass() {
5051     Klass* klass;
5052     do {
5053       klass =_klass_iterator.next_klass();
5054     } while (klass != NULL && !klass->oop_is_instance());
5055 
5056     return (InstanceKlass*)klass;
5057   }
5058 
5059 public:
5060 
5061   void clean_klass(InstanceKlass* ik) {
5062     ik->clean_implementors_list(_is_alive);
5063     ik->clean_method_data(_is_alive);
5064 
5065     // G1 specific cleanup work that has
5066     // been moved here to be done in parallel.
5067     ik->clean_dependent_nmethods();
5068   }
5069 
5070   void work() {
5071     ResourceMark rm;
5072 
5073     // One worker will clean the subklass/sibling klass tree.
5074     if (claim_clean_klass_tree_task()) {
5075       Klass::clean_subklass_tree(_is_alive);
5076     }
5077 
5078     // All workers will help cleaning the classes,
5079     InstanceKlass* klass;
5080     while ((klass = claim_next_klass()) != NULL) {
5081       clean_klass(klass);
5082     }
5083   }
5084 };
5085 
5086 // To minimize the remark pause times, the tasks below are done in parallel.
5087 class G1ParallelCleaningTask : public AbstractGangTask {
5088 private:
5089   G1StringSymbolTableUnlinkTask _string_symbol_task;
5090   G1CodeCacheUnloadingTask      _code_cache_task;
5091   G1KlassCleaningTask           _klass_cleaning_task;
5092 
5093 public:
5094   // The constructor is run in the VMThread.
5095   G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) :
5096       AbstractGangTask("Parallel Cleaning"),
5097       _string_symbol_task(is_alive, process_strings, process_symbols),
5098       _code_cache_task(num_workers, is_alive, unloading_occurred),
5099       _klass_cleaning_task(is_alive) {
5100   }
5101 
5102   // The parallel work done by all worker threads.
5103   void work(uint worker_id) {
5104     // Do first pass of code cache cleaning.
5105     _code_cache_task.work_first_pass(worker_id);
5106 
5107     // Let the threads mark that the first pass is done.
5108     _code_cache_task.barrier_mark(worker_id);
5109 
5110     // Clean the Strings and Symbols.
5111     _string_symbol_task.work(worker_id);
5112 
5113     // Wait for all workers to finish the first code cache cleaning pass.
5114     _code_cache_task.barrier_wait(worker_id);
5115 
5116     // Do the second code cache cleaning work, which realize on
5117     // the liveness information gathered during the first pass.
5118     _code_cache_task.work_second_pass(worker_id);
5119 
5120     // Clean all klasses that were not unloaded.
5121     _klass_cleaning_task.work();
5122   }
5123 };
5124 
5125 
5126 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive,
5127                                         bool process_strings,
5128                                         bool process_symbols,
5129                                         bool class_unloading_occurred) {
5130   uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5131                     workers()->active_workers() : 1);
5132 
5133   G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols,
5134                                         n_workers, class_unloading_occurred);
5135   if (G1CollectedHeap::use_parallel_gc_threads()) {
5136     set_par_threads(n_workers);
5137     workers()->run_task(&g1_unlink_task);
5138     set_par_threads(0);
5139   } else {
5140     g1_unlink_task.work(0);
5141   }
5142 }
5143 
5144 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive,
5145                                                      bool process_strings, bool process_symbols) {
5146   {
5147     uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5148                      _g1h->workers()->active_workers() : 1);
5149     G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols);
5150     if (G1CollectedHeap::use_parallel_gc_threads()) {
5151       set_par_threads(n_workers);
5152       workers()->run_task(&g1_unlink_task);
5153       set_par_threads(0);
5154     } else {
5155       g1_unlink_task.work(0);
5156     }
5157   }
5158 
5159   if (G1StringDedup::is_enabled()) {
5160     G1StringDedup::unlink(is_alive);
5161   }
5162 }
5163 
5164 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
5165  private:
5166   DirtyCardQueueSet* _queue;
5167  public:
5168   G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue) : AbstractGangTask("Redirty Cards"), _queue(queue) { }
5169 
5170   virtual void work(uint worker_id) {
5171     double start_time = os::elapsedTime();
5172 
5173     RedirtyLoggedCardTableEntryClosure cl;
5174     if (G1CollectedHeap::heap()->use_parallel_gc_threads()) {
5175       _queue->par_apply_closure_to_all_completed_buffers(&cl);
5176     } else {
5177       _queue->apply_closure_to_all_completed_buffers(&cl);
5178     }
5179 
5180     G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
5181     timer->record_redirty_logged_cards_time_ms(worker_id, (os::elapsedTime() - start_time) * 1000.0);
5182     timer->record_redirty_logged_cards_processed_cards(worker_id, cl.num_processed());
5183   }
5184 };
5185 
5186 void G1CollectedHeap::redirty_logged_cards() {
5187   double redirty_logged_cards_start = os::elapsedTime();
5188 
5189   uint n_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5190                    _g1h->workers()->active_workers() : 1);
5191 
5192   G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set());
5193   dirty_card_queue_set().reset_for_par_iteration();
5194   if (use_parallel_gc_threads()) {
5195     set_par_threads(n_workers);
5196     workers()->run_task(&redirty_task);
5197     set_par_threads(0);
5198   } else {
5199     redirty_task.work(0);
5200   }
5201 
5202   DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5203   dcq.merge_bufferlists(&dirty_card_queue_set());
5204   assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5205 
5206   g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
5207 }
5208 
5209 // Weak Reference Processing support
5210 
5211 // An always "is_alive" closure that is used to preserve referents.
5212 // If the object is non-null then it's alive.  Used in the preservation
5213 // of referent objects that are pointed to by reference objects
5214 // discovered by the CM ref processor.
5215 class G1AlwaysAliveClosure: public BoolObjectClosure {
5216   G1CollectedHeap* _g1;
5217 public:
5218   G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5219   bool do_object_b(oop p) {
5220     if (p != NULL) {
5221       return true;
5222     }
5223     return false;
5224   }
5225 };
5226 
5227 bool G1STWIsAliveClosure::do_object_b(oop p) {
5228   // An object is reachable if it is outside the collection set,
5229   // or is inside and copied.
5230   return !_g1->obj_in_cs(p) || p->is_forwarded();
5231 }
5232 
5233 // Non Copying Keep Alive closure
5234 class G1KeepAliveClosure: public OopClosure {
5235   G1CollectedHeap* _g1;
5236 public:
5237   G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
5238   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
5239   void do_oop(oop* p) {
5240     oop obj = *p;
5241     assert(obj != NULL, "the caller should have filtered out NULL values");
5242 
5243     G1CollectedHeap::in_cset_state_t cset_state = _g1->in_cset_state(obj);
5244     if (cset_state == G1CollectedHeap::InNeither) {
5245       return;
5246     }
5247     if (cset_state == G1CollectedHeap::InCSet) {
5248       assert( obj->is_forwarded(), "invariant" );
5249       *p = obj->forwardee();
5250     } else {
5251       assert(!obj->is_forwarded(), "invariant" );
5252       assert(cset_state == G1CollectedHeap::IsHumongous,
5253              err_msg("Only allowed InCSet state is IsHumongous, but is %d", cset_state));
5254       _g1->set_humongous_is_live(obj);
5255     }
5256   }
5257 };
5258 
5259 // Copying Keep Alive closure - can be called from both
5260 // serial and parallel code as long as different worker
5261 // threads utilize different G1ParScanThreadState instances
5262 // and different queues.
5263 
5264 class G1CopyingKeepAliveClosure: public OopClosure {
5265   G1CollectedHeap*         _g1h;
5266   OopClosure*              _copy_non_heap_obj_cl;
5267   G1ParScanThreadState*    _par_scan_state;
5268 
5269 public:
5270   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
5271                             OopClosure* non_heap_obj_cl,
5272                             G1ParScanThreadState* pss):
5273     _g1h(g1h),
5274     _copy_non_heap_obj_cl(non_heap_obj_cl),
5275     _par_scan_state(pss)
5276   {}
5277 
5278   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
5279   virtual void do_oop(      oop* p) { do_oop_work(p); }
5280 
5281   template <class T> void do_oop_work(T* p) {
5282     oop obj = oopDesc::load_decode_heap_oop(p);
5283 
5284     if (_g1h->is_in_cset_or_humongous(obj)) {
5285       // If the referent object has been forwarded (either copied
5286       // to a new location or to itself in the event of an
5287       // evacuation failure) then we need to update the reference
5288       // field and, if both reference and referent are in the G1
5289       // heap, update the RSet for the referent.
5290       //
5291       // If the referent has not been forwarded then we have to keep
5292       // it alive by policy. Therefore we have copy the referent.
5293       //
5294       // If the reference field is in the G1 heap then we can push
5295       // on the PSS queue. When the queue is drained (after each
5296       // phase of reference processing) the object and it's followers
5297       // will be copied, the reference field set to point to the
5298       // new location, and the RSet updated. Otherwise we need to
5299       // use the the non-heap or metadata closures directly to copy
5300       // the referent object and update the pointer, while avoiding
5301       // updating the RSet.
5302 
5303       if (_g1h->is_in_g1_reserved(p)) {
5304         _par_scan_state->push_on_queue(p);
5305       } else {
5306         assert(!Metaspace::contains((const void*)p),
5307                err_msg("Unexpectedly found a pointer from metadata: "
5308                               PTR_FORMAT, p));
5309         _copy_non_heap_obj_cl->do_oop(p);
5310       }
5311     }
5312   }
5313 };
5314 
5315 // Serial drain queue closure. Called as the 'complete_gc'
5316 // closure for each discovered list in some of the
5317 // reference processing phases.
5318 
5319 class G1STWDrainQueueClosure: public VoidClosure {
5320 protected:
5321   G1CollectedHeap* _g1h;
5322   G1ParScanThreadState* _par_scan_state;
5323 
5324   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
5325 
5326 public:
5327   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
5328     _g1h(g1h),
5329     _par_scan_state(pss)
5330   { }
5331 
5332   void do_void() {
5333     G1ParScanThreadState* const pss = par_scan_state();
5334     pss->trim_queue();
5335   }
5336 };
5337 
5338 // Parallel Reference Processing closures
5339 
5340 // Implementation of AbstractRefProcTaskExecutor for parallel reference
5341 // processing during G1 evacuation pauses.
5342 
5343 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5344 private:
5345   G1CollectedHeap*   _g1h;
5346   RefToScanQueueSet* _queues;
5347   FlexibleWorkGang*  _workers;
5348   int                _active_workers;
5349 
5350 public:
5351   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5352                         FlexibleWorkGang* workers,
5353                         RefToScanQueueSet *task_queues,
5354                         int n_workers) :
5355     _g1h(g1h),
5356     _queues(task_queues),
5357     _workers(workers),
5358     _active_workers(n_workers)
5359   {
5360     assert(n_workers > 0, "shouldn't call this otherwise");
5361   }
5362 
5363   // Executes the given task using concurrent marking worker threads.
5364   virtual void execute(ProcessTask& task);
5365   virtual void execute(EnqueueTask& task);
5366 };
5367 
5368 // Gang task for possibly parallel reference processing
5369 
5370 class G1STWRefProcTaskProxy: public AbstractGangTask {
5371   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5372   ProcessTask&     _proc_task;
5373   G1CollectedHeap* _g1h;
5374   RefToScanQueueSet *_task_queues;
5375   ParallelTaskTerminator* _terminator;
5376 
5377 public:
5378   G1STWRefProcTaskProxy(ProcessTask& proc_task,
5379                      G1CollectedHeap* g1h,
5380                      RefToScanQueueSet *task_queues,
5381                      ParallelTaskTerminator* terminator) :
5382     AbstractGangTask("Process reference objects in parallel"),
5383     _proc_task(proc_task),
5384     _g1h(g1h),
5385     _task_queues(task_queues),
5386     _terminator(terminator)
5387   {}
5388 
5389   virtual void work(uint worker_id) {
5390     // The reference processing task executed by a single worker.
5391     ResourceMark rm;
5392     HandleMark   hm;
5393 
5394     G1STWIsAliveClosure is_alive(_g1h);
5395 
5396     G1ParScanThreadState            pss(_g1h, worker_id, NULL);
5397     G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5398 
5399     pss.set_evac_failure_closure(&evac_failure_cl);
5400 
5401     G1ParScanExtRootClosure        only_copy_non_heap_cl(_g1h, &pss, NULL);
5402 
5403     G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5404 
5405     OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5406 
5407     if (_g1h->g1_policy()->during_initial_mark_pause()) {
5408       // We also need to mark copied objects.
5409       copy_non_heap_cl = &copy_mark_non_heap_cl;
5410     }
5411 
5412     // Keep alive closure.
5413     G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5414 
5415     // Complete GC closure
5416     G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5417 
5418     // Call the reference processing task's work routine.
5419     _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5420 
5421     // Note we cannot assert that the refs array is empty here as not all
5422     // of the processing tasks (specifically phase2 - pp2_work) execute
5423     // the complete_gc closure (which ordinarily would drain the queue) so
5424     // the queue may not be empty.
5425   }
5426 };
5427 
5428 // Driver routine for parallel reference processing.
5429 // Creates an instance of the ref processing gang
5430 // task and has the worker threads execute it.
5431 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5432   assert(_workers != NULL, "Need parallel worker threads.");
5433 
5434   ParallelTaskTerminator terminator(_active_workers, _queues);
5435   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5436 
5437   _g1h->set_par_threads(_active_workers);
5438   _workers->run_task(&proc_task_proxy);
5439   _g1h->set_par_threads(0);
5440 }
5441 
5442 // Gang task for parallel reference enqueueing.
5443 
5444 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5445   typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5446   EnqueueTask& _enq_task;
5447 
5448 public:
5449   G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5450     AbstractGangTask("Enqueue reference objects in parallel"),
5451     _enq_task(enq_task)
5452   { }
5453 
5454   virtual void work(uint worker_id) {
5455     _enq_task.work(worker_id);
5456   }
5457 };
5458 
5459 // Driver routine for parallel reference enqueueing.
5460 // Creates an instance of the ref enqueueing gang
5461 // task and has the worker threads execute it.
5462 
5463 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5464   assert(_workers != NULL, "Need parallel worker threads.");
5465 
5466   G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5467 
5468   _g1h->set_par_threads(_active_workers);
5469   _workers->run_task(&enq_task_proxy);
5470   _g1h->set_par_threads(0);
5471 }
5472 
5473 // End of weak reference support closures
5474 
5475 // Abstract task used to preserve (i.e. copy) any referent objects
5476 // that are in the collection set and are pointed to by reference
5477 // objects discovered by the CM ref processor.
5478 
5479 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5480 protected:
5481   G1CollectedHeap* _g1h;
5482   RefToScanQueueSet      *_queues;
5483   ParallelTaskTerminator _terminator;
5484   uint _n_workers;
5485 
5486 public:
5487   G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
5488     AbstractGangTask("ParPreserveCMReferents"),
5489     _g1h(g1h),
5490     _queues(task_queues),
5491     _terminator(workers, _queues),
5492     _n_workers(workers)
5493   { }
5494 
5495   void work(uint worker_id) {
5496     ResourceMark rm;
5497     HandleMark   hm;
5498 
5499     G1ParScanThreadState            pss(_g1h, worker_id, NULL);
5500     G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5501 
5502     pss.set_evac_failure_closure(&evac_failure_cl);
5503 
5504     assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5505 
5506     G1ParScanExtRootClosure        only_copy_non_heap_cl(_g1h, &pss, NULL);
5507 
5508     G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5509 
5510     OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5511 
5512     if (_g1h->g1_policy()->during_initial_mark_pause()) {
5513       // We also need to mark copied objects.
5514       copy_non_heap_cl = &copy_mark_non_heap_cl;
5515     }
5516 
5517     // Is alive closure
5518     G1AlwaysAliveClosure always_alive(_g1h);
5519 
5520     // Copying keep alive closure. Applied to referent objects that need
5521     // to be copied.
5522     G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5523 
5524     ReferenceProcessor* rp = _g1h->ref_processor_cm();
5525 
5526     uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5527     uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5528 
5529     // limit is set using max_num_q() - which was set using ParallelGCThreads.
5530     // So this must be true - but assert just in case someone decides to
5531     // change the worker ids.
5532     assert(0 <= worker_id && worker_id < limit, "sanity");
5533     assert(!rp->discovery_is_atomic(), "check this code");
5534 
5535     // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5536     for (uint idx = worker_id; idx < limit; idx += stride) {
5537       DiscoveredList& ref_list = rp->discovered_refs()[idx];
5538 
5539       DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5540       while (iter.has_next()) {
5541         // Since discovery is not atomic for the CM ref processor, we
5542         // can see some null referent objects.
5543         iter.load_ptrs(DEBUG_ONLY(true));
5544         oop ref = iter.obj();
5545 
5546         // This will filter nulls.
5547         if (iter.is_referent_alive()) {
5548           iter.make_referent_alive();
5549         }
5550         iter.move_to_next();
5551       }
5552     }
5553 
5554     // Drain the queue - which may cause stealing
5555     G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5556     drain_queue.do_void();
5557     // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5558     assert(pss.queue_is_empty(), "should be");
5559   }
5560 };
5561 
5562 // Weak Reference processing during an evacuation pause (part 1).
5563 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) {
5564   double ref_proc_start = os::elapsedTime();
5565 
5566   ReferenceProcessor* rp = _ref_processor_stw;
5567   assert(rp->discovery_enabled(), "should have been enabled");
5568 
5569   // Any reference objects, in the collection set, that were 'discovered'
5570   // by the CM ref processor should have already been copied (either by
5571   // applying the external root copy closure to the discovered lists, or
5572   // by following an RSet entry).
5573   //
5574   // But some of the referents, that are in the collection set, that these
5575   // reference objects point to may not have been copied: the STW ref
5576   // processor would have seen that the reference object had already
5577   // been 'discovered' and would have skipped discovering the reference,
5578   // but would not have treated the reference object as a regular oop.
5579   // As a result the copy closure would not have been applied to the
5580   // referent object.
5581   //
5582   // We need to explicitly copy these referent objects - the references
5583   // will be processed at the end of remarking.
5584   //
5585   // We also need to do this copying before we process the reference
5586   // objects discovered by the STW ref processor in case one of these
5587   // referents points to another object which is also referenced by an
5588   // object discovered by the STW ref processor.
5589 
5590   assert(!G1CollectedHeap::use_parallel_gc_threads() ||
5591            no_of_gc_workers == workers()->active_workers(),
5592            "Need to reset active GC workers");
5593 
5594   set_par_threads(no_of_gc_workers);
5595   G1ParPreserveCMReferentsTask keep_cm_referents(this,
5596                                                  no_of_gc_workers,
5597                                                  _task_queues);
5598 
5599   if (G1CollectedHeap::use_parallel_gc_threads()) {
5600     workers()->run_task(&keep_cm_referents);
5601   } else {
5602     keep_cm_referents.work(0);
5603   }
5604 
5605   set_par_threads(0);
5606 
5607   // Closure to test whether a referent is alive.
5608   G1STWIsAliveClosure is_alive(this);
5609 
5610   // Even when parallel reference processing is enabled, the processing
5611   // of JNI refs is serial and performed serially by the current thread
5612   // rather than by a worker. The following PSS will be used for processing
5613   // JNI refs.
5614 
5615   // Use only a single queue for this PSS.
5616   G1ParScanThreadState            pss(this, 0, NULL);
5617 
5618   // We do not embed a reference processor in the copying/scanning
5619   // closures while we're actually processing the discovered
5620   // reference objects.
5621   G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5622 
5623   pss.set_evac_failure_closure(&evac_failure_cl);
5624 
5625   assert(pss.queue_is_empty(), "pre-condition");
5626 
5627   G1ParScanExtRootClosure        only_copy_non_heap_cl(this, &pss, NULL);
5628 
5629   G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5630 
5631   OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5632 
5633   if (_g1h->g1_policy()->during_initial_mark_pause()) {
5634     // We also need to mark copied objects.
5635     copy_non_heap_cl = &copy_mark_non_heap_cl;
5636   }
5637 
5638   // Keep alive closure.
5639   G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, &pss);
5640 
5641   // Serial Complete GC closure
5642   G1STWDrainQueueClosure drain_queue(this, &pss);
5643 
5644   // Setup the soft refs policy...
5645   rp->setup_policy(false);
5646 
5647   ReferenceProcessorStats stats;
5648   if (!rp->processing_is_mt()) {
5649     // Serial reference processing...
5650     stats = rp->process_discovered_references(&is_alive,
5651                                               &keep_alive,
5652                                               &drain_queue,
5653                                               NULL,
5654                                               _gc_timer_stw,
5655                                               _gc_tracer_stw->gc_id());
5656   } else {
5657     // Parallel reference processing
5658     assert(rp->num_q() == no_of_gc_workers, "sanity");
5659     assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5660 
5661     G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5662     stats = rp->process_discovered_references(&is_alive,
5663                                               &keep_alive,
5664                                               &drain_queue,
5665                                               &par_task_executor,
5666                                               _gc_timer_stw,
5667                                               _gc_tracer_stw->gc_id());
5668   }
5669 
5670   _gc_tracer_stw->report_gc_reference_stats(stats);
5671 
5672   // We have completed copying any necessary live referent objects.
5673   assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5674 
5675   double ref_proc_time = os::elapsedTime() - ref_proc_start;
5676   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5677 }
5678 
5679 // Weak Reference processing during an evacuation pause (part 2).
5680 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) {
5681   double ref_enq_start = os::elapsedTime();
5682 
5683   ReferenceProcessor* rp = _ref_processor_stw;
5684   assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5685 
5686   // Now enqueue any remaining on the discovered lists on to
5687   // the pending list.
5688   if (!rp->processing_is_mt()) {
5689     // Serial reference processing...
5690     rp->enqueue_discovered_references();
5691   } else {
5692     // Parallel reference enqueueing
5693 
5694     assert(no_of_gc_workers == workers()->active_workers(),
5695            "Need to reset active workers");
5696     assert(rp->num_q() == no_of_gc_workers, "sanity");
5697     assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5698 
5699     G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5700     rp->enqueue_discovered_references(&par_task_executor);
5701   }
5702 
5703   rp->verify_no_references_recorded();
5704   assert(!rp->discovery_enabled(), "should have been disabled");
5705 
5706   // FIXME
5707   // CM's reference processing also cleans up the string and symbol tables.
5708   // Should we do that here also? We could, but it is a serial operation
5709   // and could significantly increase the pause time.
5710 
5711   double ref_enq_time = os::elapsedTime() - ref_enq_start;
5712   g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5713 }
5714 
5715 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) {
5716   _expand_heap_after_alloc_failure = true;
5717   _evacuation_failed = false;
5718 
5719   // Should G1EvacuationFailureALot be in effect for this GC?
5720   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
5721 
5722   g1_rem_set()->prepare_for_oops_into_collection_set_do();
5723 
5724   // Disable the hot card cache.
5725   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
5726   hot_card_cache->reset_hot_cache_claimed_index();
5727   hot_card_cache->set_use_cache(false);
5728 
5729   uint n_workers;
5730   if (G1CollectedHeap::use_parallel_gc_threads()) {
5731     n_workers =
5732       AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
5733                                      workers()->active_workers(),
5734                                      Threads::number_of_non_daemon_threads());
5735     assert(UseDynamicNumberOfGCThreads ||
5736            n_workers == workers()->total_workers(),
5737            "If not dynamic should be using all the  workers");
5738     workers()->set_active_workers(n_workers);
5739     set_par_threads(n_workers);
5740   } else {
5741     assert(n_par_threads() == 0,
5742            "Should be the original non-parallel value");
5743     n_workers = 1;
5744   }
5745 
5746   G1ParTask g1_par_task(this, _task_queues);
5747 
5748   init_for_evac_failure(NULL);
5749 
5750   rem_set()->prepare_for_younger_refs_iterate(true);
5751 
5752   assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5753   double start_par_time_sec = os::elapsedTime();
5754   double end_par_time_sec;
5755 
5756   {
5757     StrongRootsScope srs(this);
5758     // InitialMark needs claim bits to keep track of the marked-through CLDs.
5759     if (g1_policy()->during_initial_mark_pause()) {
5760       ClassLoaderDataGraph::clear_claimed_marks();
5761     }
5762 
5763     if (G1CollectedHeap::use_parallel_gc_threads()) {
5764       // The individual threads will set their evac-failure closures.
5765       if (PrintTerminationStats) G1ParScanThreadState::print_termination_stats_hdr();
5766       // These tasks use ShareHeap::_process_strong_tasks
5767       assert(UseDynamicNumberOfGCThreads ||
5768              workers()->active_workers() == workers()->total_workers(),
5769              "If not dynamic should be using all the  workers");
5770       workers()->run_task(&g1_par_task);
5771     } else {
5772       g1_par_task.set_for_termination(n_workers);
5773       g1_par_task.work(0);
5774     }
5775     end_par_time_sec = os::elapsedTime();
5776 
5777     // Closing the inner scope will execute the destructor
5778     // for the StrongRootsScope object. We record the current
5779     // elapsed time before closing the scope so that time
5780     // taken for the SRS destructor is NOT included in the
5781     // reported parallel time.
5782   }
5783 
5784   double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5785   g1_policy()->phase_times()->record_par_time(par_time_ms);
5786 
5787   double code_root_fixup_time_ms =
5788         (os::elapsedTime() - end_par_time_sec) * 1000.0;
5789   g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms);
5790 
5791   set_par_threads(0);
5792 
5793   // Process any discovered reference objects - we have
5794   // to do this _before_ we retire the GC alloc regions
5795   // as we may have to copy some 'reachable' referent
5796   // objects (and their reachable sub-graphs) that were
5797   // not copied during the pause.
5798   process_discovered_references(n_workers);
5799 
5800   // Weak root processing.
5801   {
5802     G1STWIsAliveClosure is_alive(this);
5803     G1KeepAliveClosure keep_alive(this);
5804     JNIHandles::weak_oops_do(&is_alive, &keep_alive);
5805     if (G1StringDedup::is_enabled()) {
5806       G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive);
5807     }
5808   }
5809 
5810   _allocator->release_gc_alloc_regions(n_workers, evacuation_info);
5811   g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5812 
5813   // Reset and re-enable the hot card cache.
5814   // Note the counts for the cards in the regions in the
5815   // collection set are reset when the collection set is freed.
5816   hot_card_cache->reset_hot_cache();
5817   hot_card_cache->set_use_cache(true);
5818 
5819   purge_code_root_memory();
5820 
5821   finalize_for_evac_failure();
5822 
5823   if (evacuation_failed()) {
5824     remove_self_forwarding_pointers();
5825 
5826     // Reset the G1EvacuationFailureALot counters and flags
5827     // Note: the values are reset only when an actual
5828     // evacuation failure occurs.
5829     NOT_PRODUCT(reset_evacuation_should_fail();)
5830   }
5831 
5832   // Enqueue any remaining references remaining on the STW
5833   // reference processor's discovered lists. We need to do
5834   // this after the card table is cleaned (and verified) as
5835   // the act of enqueueing entries on to the pending list
5836   // will log these updates (and dirty their associated
5837   // cards). We need these updates logged to update any
5838   // RSets.
5839   enqueue_discovered_references(n_workers);
5840 
5841   redirty_logged_cards();
5842   COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5843 }
5844 
5845 void G1CollectedHeap::free_region(HeapRegion* hr,
5846                                   FreeRegionList* free_list,
5847                                   bool par,
5848                                   bool locked) {
5849   assert(!hr->is_free(), "the region should not be free");
5850   assert(!hr->is_empty(), "the region should not be empty");
5851   assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
5852   assert(free_list != NULL, "pre-condition");
5853 
5854   if (G1VerifyBitmaps) {
5855     MemRegion mr(hr->bottom(), hr->end());
5856     concurrent_mark()->clearRangePrevBitmap(mr);
5857   }
5858 
5859   // Clear the card counts for this region.
5860   // Note: we only need to do this if the region is not young
5861   // (since we don't refine cards in young regions).
5862   if (!hr->is_young()) {
5863     _cg1r->hot_card_cache()->reset_card_counts(hr);
5864   }
5865   hr->hr_clear(par, true /* clear_space */, locked /* locked */);
5866   free_list->add_ordered(hr);
5867 }
5868 
5869 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
5870                                      FreeRegionList* free_list,
5871                                      bool par) {
5872   assert(hr->is_starts_humongous(), "this is only for starts humongous regions");
5873   assert(free_list != NULL, "pre-condition");
5874 
5875   size_t hr_capacity = hr->capacity();
5876   // We need to read this before we make the region non-humongous,
5877   // otherwise the information will be gone.
5878   uint last_index = hr->last_hc_index();
5879   hr->clear_humongous();
5880   free_region(hr, free_list, par);
5881 
5882   uint i = hr->hrm_index() + 1;
5883   while (i < last_index) {
5884     HeapRegion* curr_hr = region_at(i);
5885     assert(curr_hr->is_continues_humongous(), "invariant");
5886     curr_hr->clear_humongous();
5887     free_region(curr_hr, free_list, par);
5888     i += 1;
5889   }
5890 }
5891 
5892 void G1CollectedHeap::remove_from_old_sets(const HeapRegionSetCount& old_regions_removed,
5893                                        const HeapRegionSetCount& humongous_regions_removed) {
5894   if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 0) {
5895     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5896     _old_set.bulk_remove(old_regions_removed);
5897     _humongous_set.bulk_remove(humongous_regions_removed);
5898   }
5899 
5900 }
5901 
5902 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
5903   assert(list != NULL, "list can't be null");
5904   if (!list->is_empty()) {
5905     MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
5906     _hrm.insert_list_into_free_list(list);
5907   }
5908 }
5909 
5910 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
5911   _allocator->decrease_used(bytes);
5912 }
5913 
5914 class G1ParCleanupCTTask : public AbstractGangTask {
5915   G1SATBCardTableModRefBS* _ct_bs;
5916   G1CollectedHeap* _g1h;
5917   HeapRegion* volatile _su_head;
5918 public:
5919   G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs,
5920                      G1CollectedHeap* g1h) :
5921     AbstractGangTask("G1 Par Cleanup CT Task"),
5922     _ct_bs(ct_bs), _g1h(g1h) { }
5923 
5924   void work(uint worker_id) {
5925     HeapRegion* r;
5926     while (r = _g1h->pop_dirty_cards_region()) {
5927       clear_cards(r);
5928     }
5929   }
5930 
5931   void clear_cards(HeapRegion* r) {
5932     // Cards of the survivors should have already been dirtied.
5933     if (!r->is_survivor()) {
5934       _ct_bs->clear(MemRegion(r->bottom(), r->end()));
5935     }
5936   }
5937 };
5938 
5939 #ifndef PRODUCT
5940 class G1VerifyCardTableCleanup: public HeapRegionClosure {
5941   G1CollectedHeap* _g1h;
5942   G1SATBCardTableModRefBS* _ct_bs;
5943 public:
5944   G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs)
5945     : _g1h(g1h), _ct_bs(ct_bs) { }
5946   virtual bool doHeapRegion(HeapRegion* r) {
5947     if (r->is_survivor()) {
5948       _g1h->verify_dirty_region(r);
5949     } else {
5950       _g1h->verify_not_dirty_region(r);
5951     }
5952     return false;
5953   }
5954 };
5955 
5956 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
5957   // All of the region should be clean.
5958   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5959   MemRegion mr(hr->bottom(), hr->end());
5960   ct_bs->verify_not_dirty_region(mr);
5961 }
5962 
5963 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
5964   // We cannot guarantee that [bottom(),end()] is dirty.  Threads
5965   // dirty allocated blocks as they allocate them. The thread that
5966   // retires each region and replaces it with a new one will do a
5967   // maximal allocation to fill in [pre_dummy_top(),end()] but will
5968   // not dirty that area (one less thing to have to do while holding
5969   // a lock). So we can only verify that [bottom(),pre_dummy_top()]
5970   // is dirty.
5971   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5972   MemRegion mr(hr->bottom(), hr->pre_dummy_top());
5973   if (hr->is_young()) {
5974     ct_bs->verify_g1_young_region(mr);
5975   } else {
5976     ct_bs->verify_dirty_region(mr);
5977   }
5978 }
5979 
5980 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
5981   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5982   for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
5983     verify_dirty_region(hr);
5984   }
5985 }
5986 
5987 void G1CollectedHeap::verify_dirty_young_regions() {
5988   verify_dirty_young_list(_young_list->first_region());
5989 }
5990 
5991 bool G1CollectedHeap::verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
5992                                                HeapWord* tams, HeapWord* end) {
5993   guarantee(tams <= end,
5994             err_msg("tams: "PTR_FORMAT" end: "PTR_FORMAT, tams, end));
5995   HeapWord* result = bitmap->getNextMarkedWordAddress(tams, end);
5996   if (result < end) {
5997     gclog_or_tty->cr();
5998     gclog_or_tty->print_cr("## wrong marked address on %s bitmap: "PTR_FORMAT,
5999                            bitmap_name, result);
6000     gclog_or_tty->print_cr("## %s tams: "PTR_FORMAT" end: "PTR_FORMAT,
6001                            bitmap_name, tams, end);
6002     return false;
6003   }
6004   return true;
6005 }
6006 
6007 bool G1CollectedHeap::verify_bitmaps(const char* caller, HeapRegion* hr) {
6008   CMBitMapRO* prev_bitmap = concurrent_mark()->prevMarkBitMap();
6009   CMBitMapRO* next_bitmap = (CMBitMapRO*) concurrent_mark()->nextMarkBitMap();
6010 
6011   HeapWord* bottom = hr->bottom();
6012   HeapWord* ptams  = hr->prev_top_at_mark_start();
6013   HeapWord* ntams  = hr->next_top_at_mark_start();
6014   HeapWord* end    = hr->end();
6015 
6016   bool res_p = verify_no_bits_over_tams("prev", prev_bitmap, ptams, end);
6017 
6018   bool res_n = true;
6019   // We reset mark_in_progress() before we reset _cmThread->in_progress() and in this window
6020   // we do the clearing of the next bitmap concurrently. Thus, we can not verify the bitmap
6021   // if we happen to be in that state.
6022   if (mark_in_progress() || !_cmThread->in_progress()) {
6023     res_n = verify_no_bits_over_tams("next", next_bitmap, ntams, end);
6024   }
6025   if (!res_p || !res_n) {
6026     gclog_or_tty->print_cr("#### Bitmap verification failed for "HR_FORMAT,
6027                            HR_FORMAT_PARAMS(hr));
6028     gclog_or_tty->print_cr("#### Caller: %s", caller);
6029     return false;
6030   }
6031   return true;
6032 }
6033 
6034 void G1CollectedHeap::check_bitmaps(const char* caller, HeapRegion* hr) {
6035   if (!G1VerifyBitmaps) return;
6036 
6037   guarantee(verify_bitmaps(caller, hr), "bitmap verification");
6038 }
6039 
6040 class G1VerifyBitmapClosure : public HeapRegionClosure {
6041 private:
6042   const char* _caller;
6043   G1CollectedHeap* _g1h;
6044   bool _failures;
6045 
6046 public:
6047   G1VerifyBitmapClosure(const char* caller, G1CollectedHeap* g1h) :
6048     _caller(caller), _g1h(g1h), _failures(false) { }
6049 
6050   bool failures() { return _failures; }
6051 
6052   virtual bool doHeapRegion(HeapRegion* hr) {
6053     if (hr->is_continues_humongous()) return false;
6054 
6055     bool result = _g1h->verify_bitmaps(_caller, hr);
6056     if (!result) {
6057       _failures = true;
6058     }
6059     return false;
6060   }
6061 };
6062 
6063 void G1CollectedHeap::check_bitmaps(const char* caller) {
6064   if (!G1VerifyBitmaps) return;
6065 
6066   G1VerifyBitmapClosure cl(caller, this);
6067   heap_region_iterate(&cl);
6068   guarantee(!cl.failures(), "bitmap verification");
6069 }
6070 #endif // PRODUCT
6071 
6072 void G1CollectedHeap::cleanUpCardTable() {
6073   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
6074   double start = os::elapsedTime();
6075 
6076   {
6077     // Iterate over the dirty cards region list.
6078     G1ParCleanupCTTask cleanup_task(ct_bs, this);
6079 
6080     if (G1CollectedHeap::use_parallel_gc_threads()) {
6081       set_par_threads();
6082       workers()->run_task(&cleanup_task);
6083       set_par_threads(0);
6084     } else {
6085       while (_dirty_cards_region_list) {
6086         HeapRegion* r = _dirty_cards_region_list;
6087         cleanup_task.clear_cards(r);
6088         _dirty_cards_region_list = r->get_next_dirty_cards_region();
6089         if (_dirty_cards_region_list == r) {
6090           // The last region.
6091           _dirty_cards_region_list = NULL;
6092         }
6093         r->set_next_dirty_cards_region(NULL);
6094       }
6095     }
6096 #ifndef PRODUCT
6097     if (G1VerifyCTCleanup || VerifyAfterGC) {
6098       G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
6099       heap_region_iterate(&cleanup_verifier);
6100     }
6101 #endif
6102   }
6103 
6104   double elapsed = os::elapsedTime() - start;
6105   g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
6106 }
6107 
6108 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) {
6109   size_t pre_used = 0;
6110   FreeRegionList local_free_list("Local List for CSet Freeing");
6111 
6112   double young_time_ms     = 0.0;
6113   double non_young_time_ms = 0.0;
6114 
6115   // Since the collection set is a superset of the the young list,
6116   // all we need to do to clear the young list is clear its
6117   // head and length, and unlink any young regions in the code below
6118   _young_list->clear();
6119 
6120   G1CollectorPolicy* policy = g1_policy();
6121 
6122   double start_sec = os::elapsedTime();
6123   bool non_young = true;
6124 
6125   HeapRegion* cur = cs_head;
6126   int age_bound = -1;
6127   size_t rs_lengths = 0;
6128 
6129   while (cur != NULL) {
6130     assert(!is_on_master_free_list(cur), "sanity");
6131     if (non_young) {
6132       if (cur->is_young()) {
6133         double end_sec = os::elapsedTime();
6134         double elapsed_ms = (end_sec - start_sec) * 1000.0;
6135         non_young_time_ms += elapsed_ms;
6136 
6137         start_sec = os::elapsedTime();
6138         non_young = false;
6139       }
6140     } else {
6141       if (!cur->is_young()) {
6142         double end_sec = os::elapsedTime();
6143         double elapsed_ms = (end_sec - start_sec) * 1000.0;
6144         young_time_ms += elapsed_ms;
6145 
6146         start_sec = os::elapsedTime();
6147         non_young = true;
6148       }
6149     }
6150 
6151     rs_lengths += cur->rem_set()->occupied_locked();
6152 
6153     HeapRegion* next = cur->next_in_collection_set();
6154     assert(cur->in_collection_set(), "bad CS");
6155     cur->set_next_in_collection_set(NULL);
6156     cur->set_in_collection_set(false);
6157 
6158     if (cur->is_young()) {
6159       int index = cur->young_index_in_cset();
6160       assert(index != -1, "invariant");
6161       assert((uint) index < policy->young_cset_region_length(), "invariant");
6162       size_t words_survived = _surviving_young_words[index];
6163       cur->record_surv_words_in_group(words_survived);
6164 
6165       // At this point the we have 'popped' cur from the collection set
6166       // (linked via next_in_collection_set()) but it is still in the
6167       // young list (linked via next_young_region()). Clear the
6168       // _next_young_region field.
6169       cur->set_next_young_region(NULL);
6170     } else {
6171       int index = cur->young_index_in_cset();
6172       assert(index == -1, "invariant");
6173     }
6174 
6175     assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
6176             (!cur->is_young() && cur->young_index_in_cset() == -1),
6177             "invariant" );
6178 
6179     if (!cur->evacuation_failed()) {
6180       MemRegion used_mr = cur->used_region();
6181 
6182       // And the region is empty.
6183       assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
6184       pre_used += cur->used();
6185       free_region(cur, &local_free_list, false /* par */, true /* locked */);
6186     } else {
6187       cur->uninstall_surv_rate_group();
6188       if (cur->is_young()) {
6189         cur->set_young_index_in_cset(-1);
6190       }
6191       cur->set_evacuation_failed(false);
6192       // The region is now considered to be old.
6193       cur->set_old();
6194       _old_set.add(cur);
6195       evacuation_info.increment_collectionset_used_after(cur->used());
6196     }
6197     cur = next;
6198   }
6199 
6200   evacuation_info.set_regions_freed(local_free_list.length());
6201   policy->record_max_rs_lengths(rs_lengths);
6202   policy->cset_regions_freed();
6203 
6204   double end_sec = os::elapsedTime();
6205   double elapsed_ms = (end_sec - start_sec) * 1000.0;
6206 
6207   if (non_young) {
6208     non_young_time_ms += elapsed_ms;
6209   } else {
6210     young_time_ms += elapsed_ms;
6211   }
6212 
6213   prepend_to_freelist(&local_free_list);
6214   decrement_summary_bytes(pre_used);
6215   policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
6216   policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
6217 }
6218 
6219 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
6220  private:
6221   FreeRegionList* _free_region_list;
6222   HeapRegionSet* _proxy_set;
6223   HeapRegionSetCount _humongous_regions_removed;
6224   size_t _freed_bytes;
6225  public:
6226 
6227   G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
6228     _free_region_list(free_region_list), _humongous_regions_removed(), _freed_bytes(0) {
6229   }
6230 
6231   virtual bool doHeapRegion(HeapRegion* r) {
6232     if (!r->is_starts_humongous()) {
6233       return false;
6234     }
6235 
6236     G1CollectedHeap* g1h = G1CollectedHeap::heap();
6237 
6238     oop obj = (oop)r->bottom();
6239     CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap();
6240 
6241     // The following checks whether the humongous object is live are sufficient.
6242     // The main additional check (in addition to having a reference from the roots
6243     // or the young gen) is whether the humongous object has a remembered set entry.
6244     //
6245     // A humongous object cannot be live if there is no remembered set for it
6246     // because:
6247     // - there can be no references from within humongous starts regions referencing
6248     // the object because we never allocate other objects into them.
6249     // (I.e. there are no intra-region references that may be missed by the
6250     // remembered set)
6251     // - as soon there is a remembered set entry to the humongous starts region
6252     // (i.e. it has "escaped" to an old object) this remembered set entry will stay
6253     // until the end of a concurrent mark.
6254     //
6255     // It is not required to check whether the object has been found dead by marking
6256     // or not, in fact it would prevent reclamation within a concurrent cycle, as
6257     // all objects allocated during that time are considered live.
6258     // SATB marking is even more conservative than the remembered set.
6259     // So if at this point in the collection there is no remembered set entry,
6260     // nobody has a reference to it.
6261     // At the start of collection we flush all refinement logs, and remembered sets
6262     // are completely up-to-date wrt to references to the humongous object.
6263     //
6264     // Other implementation considerations:
6265     // - never consider object arrays: while they are a valid target, they have not
6266     // been observed to be used as temporary objects.
6267     // - they would also pose considerable effort for cleaning up the the remembered
6268     // sets.
6269     // While this cleanup is not strictly necessary to be done (or done instantly),
6270     // given that their occurrence is very low, this saves us this additional
6271     // complexity.
6272     uint region_idx = r->hrm_index();
6273     if (g1h->humongous_is_live(region_idx) ||
6274         g1h->humongous_region_is_always_live(region_idx)) {
6275 
6276       if (G1TraceReclaimDeadHumongousObjectsAtYoungGC) {
6277         gclog_or_tty->print_cr("Live humongous %d region %d size "SIZE_FORMAT" with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is marked %d live-other %d obj array %d",
6278                                r->is_humongous(),
6279                                region_idx,
6280                                obj->size()*HeapWordSize,
6281                                r->rem_set()->occupied(),
6282                                r->rem_set()->strong_code_roots_list_length(),
6283                                next_bitmap->isMarked(r->bottom()),
6284                                g1h->humongous_is_live(region_idx),
6285                                obj->is_objArray()
6286                               );
6287       }
6288 
6289       return false;
6290     }
6291 
6292     guarantee(!obj->is_objArray(),
6293               err_msg("Eagerly reclaiming object arrays is not supported, but the object "PTR_FORMAT" is.",
6294                       r->bottom()));
6295 
6296     if (G1TraceReclaimDeadHumongousObjectsAtYoungGC) {
6297       gclog_or_tty->print_cr("Reclaim humongous region %d size "SIZE_FORMAT" 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",
6298                              r->is_humongous(),
6299                              obj->size()*HeapWordSize,
6300                              r->bottom(),
6301                              region_idx,
6302                              r->region_num(),
6303                              r->rem_set()->occupied(),
6304                              r->rem_set()->strong_code_roots_list_length(),
6305                              next_bitmap->isMarked(r->bottom()),
6306                              g1h->humongous_is_live(region_idx),
6307                              obj->is_objArray()
6308                             );
6309     }
6310     // Need to clear mark bit of the humongous object if already set.
6311     if (next_bitmap->isMarked(r->bottom())) {
6312       next_bitmap->clear(r->bottom());
6313     }
6314     _freed_bytes += r->used();
6315     r->set_containing_set(NULL);
6316     _humongous_regions_removed.increment(1u, r->capacity());
6317     g1h->free_humongous_region(r, _free_region_list, false);
6318 
6319     return false;
6320   }
6321 
6322   HeapRegionSetCount& humongous_free_count() {
6323     return _humongous_regions_removed;
6324   }
6325 
6326   size_t bytes_freed() const {
6327     return _freed_bytes;
6328   }
6329 
6330   size_t humongous_reclaimed() const {
6331     return _humongous_regions_removed.length();
6332   }
6333 };
6334 
6335 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
6336   assert_at_safepoint(true);
6337 
6338   if (!G1ReclaimDeadHumongousObjectsAtYoungGC ||
6339       (!_has_humongous_reclaim_candidates && !G1TraceReclaimDeadHumongousObjectsAtYoungGC)) {
6340     g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
6341     return;
6342   }
6343 
6344   double start_time = os::elapsedTime();
6345 
6346   FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
6347 
6348   G1FreeHumongousRegionClosure cl(&local_cleanup_list);
6349   heap_region_iterate(&cl);
6350 
6351   HeapRegionSetCount empty_set;
6352   remove_from_old_sets(empty_set, cl.humongous_free_count());
6353 
6354   G1HRPrinter* hr_printer = _g1h->hr_printer();
6355   if (hr_printer->is_active()) {
6356     FreeRegionListIterator iter(&local_cleanup_list);
6357     while (iter.more_available()) {
6358       HeapRegion* hr = iter.get_next();
6359       hr_printer->cleanup(hr);
6360     }
6361   }
6362 
6363   prepend_to_freelist(&local_cleanup_list);
6364   decrement_summary_bytes(cl.bytes_freed());
6365 
6366   g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
6367                                                                     cl.humongous_reclaimed());
6368 }
6369 
6370 // This routine is similar to the above but does not record
6371 // any policy statistics or update free lists; we are abandoning
6372 // the current incremental collection set in preparation of a
6373 // full collection. After the full GC we will start to build up
6374 // the incremental collection set again.
6375 // This is only called when we're doing a full collection
6376 // and is immediately followed by the tearing down of the young list.
6377 
6378 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
6379   HeapRegion* cur = cs_head;
6380 
6381   while (cur != NULL) {
6382     HeapRegion* next = cur->next_in_collection_set();
6383     assert(cur->in_collection_set(), "bad CS");
6384     cur->set_next_in_collection_set(NULL);
6385     cur->set_in_collection_set(false);
6386     cur->set_young_index_in_cset(-1);
6387     cur = next;
6388   }
6389 }
6390 
6391 void G1CollectedHeap::set_free_regions_coming() {
6392   if (G1ConcRegionFreeingVerbose) {
6393     gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6394                            "setting free regions coming");
6395   }
6396 
6397   assert(!free_regions_coming(), "pre-condition");
6398   _free_regions_coming = true;
6399 }
6400 
6401 void G1CollectedHeap::reset_free_regions_coming() {
6402   assert(free_regions_coming(), "pre-condition");
6403 
6404   {
6405     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6406     _free_regions_coming = false;
6407     SecondaryFreeList_lock->notify_all();
6408   }
6409 
6410   if (G1ConcRegionFreeingVerbose) {
6411     gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6412                            "reset free regions coming");
6413   }
6414 }
6415 
6416 void G1CollectedHeap::wait_while_free_regions_coming() {
6417   // Most of the time we won't have to wait, so let's do a quick test
6418   // first before we take the lock.
6419   if (!free_regions_coming()) {
6420     return;
6421   }
6422 
6423   if (G1ConcRegionFreeingVerbose) {
6424     gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6425                            "waiting for free regions");
6426   }
6427 
6428   {
6429     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6430     while (free_regions_coming()) {
6431       SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
6432     }
6433   }
6434 
6435   if (G1ConcRegionFreeingVerbose) {
6436     gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6437                            "done waiting for free regions");
6438   }
6439 }
6440 
6441 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
6442   assert(heap_lock_held_for_gc(),
6443               "the heap lock should already be held by or for this thread");
6444   _young_list->push_region(hr);
6445 }
6446 
6447 class NoYoungRegionsClosure: public HeapRegionClosure {
6448 private:
6449   bool _success;
6450 public:
6451   NoYoungRegionsClosure() : _success(true) { }
6452   bool doHeapRegion(HeapRegion* r) {
6453     if (r->is_young()) {
6454       gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
6455                              r->bottom(), r->end());
6456       _success = false;
6457     }
6458     return false;
6459   }
6460   bool success() { return _success; }
6461 };
6462 
6463 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
6464   bool ret = _young_list->check_list_empty(check_sample);
6465 
6466   if (check_heap) {
6467     NoYoungRegionsClosure closure;
6468     heap_region_iterate(&closure);
6469     ret = ret && closure.success();
6470   }
6471 
6472   return ret;
6473 }
6474 
6475 class TearDownRegionSetsClosure : public HeapRegionClosure {
6476 private:
6477   HeapRegionSet *_old_set;
6478 
6479 public:
6480   TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
6481 
6482   bool doHeapRegion(HeapRegion* r) {
6483     if (r->is_old()) {
6484       _old_set->remove(r);
6485     } else {
6486       // We ignore free regions, we'll empty the free list afterwards.
6487       // We ignore young regions, we'll empty the young list afterwards.
6488       // We ignore humongous regions, we're not tearing down the
6489       // humongous regions set.
6490       assert(r->is_free() || r->is_young() || r->is_humongous(),
6491              "it cannot be another type");
6492     }
6493     return false;
6494   }
6495 
6496   ~TearDownRegionSetsClosure() {
6497     assert(_old_set->is_empty(), "post-condition");
6498   }
6499 };
6500 
6501 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6502   assert_at_safepoint(true /* should_be_vm_thread */);
6503 
6504   if (!free_list_only) {
6505     TearDownRegionSetsClosure cl(&_old_set);
6506     heap_region_iterate(&cl);
6507 
6508     // Note that emptying the _young_list is postponed and instead done as
6509     // the first step when rebuilding the regions sets again. The reason for
6510     // this is that during a full GC string deduplication needs to know if
6511     // a collected region was young or old when the full GC was initiated.
6512   }
6513   _hrm.remove_all_free_regions();
6514 }
6515 
6516 class RebuildRegionSetsClosure : public HeapRegionClosure {
6517 private:
6518   bool            _free_list_only;
6519   HeapRegionSet*   _old_set;
6520   HeapRegionManager*   _hrm;
6521   size_t          _total_used;
6522 
6523 public:
6524   RebuildRegionSetsClosure(bool free_list_only,
6525                            HeapRegionSet* old_set, HeapRegionManager* hrm) :
6526     _free_list_only(free_list_only),
6527     _old_set(old_set), _hrm(hrm), _total_used(0) {
6528     assert(_hrm->num_free_regions() == 0, "pre-condition");
6529     if (!free_list_only) {
6530       assert(_old_set->is_empty(), "pre-condition");
6531     }
6532   }
6533 
6534   bool doHeapRegion(HeapRegion* r) {
6535     if (r->is_continues_humongous()) {
6536       return false;
6537     }
6538 
6539     if (r->is_empty()) {
6540       // Add free regions to the free list
6541       r->set_free();
6542       r->set_allocation_context(AllocationContext::system());
6543       _hrm->insert_into_free_list(r);
6544     } else if (!_free_list_only) {
6545       assert(!r->is_young(), "we should not come across young regions");
6546 
6547       if (r->is_humongous()) {
6548         // We ignore humongous regions, we left the humongous set unchanged
6549       } else {
6550         // Objects that were compacted would have ended up on regions
6551         // that were previously old or free.
6552         assert(r->is_free() || r->is_old(), "invariant");
6553         // We now consider them old, so register as such.
6554         r->set_old();
6555         _old_set->add(r);
6556       }
6557       _total_used += r->used();
6558     }
6559 
6560     return false;
6561   }
6562 
6563   size_t total_used() {
6564     return _total_used;
6565   }
6566 };
6567 
6568 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6569   assert_at_safepoint(true /* should_be_vm_thread */);
6570 
6571   if (!free_list_only) {
6572     _young_list->empty_list();
6573   }
6574 
6575   RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
6576   heap_region_iterate(&cl);
6577 
6578   if (!free_list_only) {
6579     _allocator->set_used(cl.total_used());
6580   }
6581   assert(_allocator->used_unlocked() == recalculate_used(),
6582          err_msg("inconsistent _allocator->used_unlocked(), "
6583                  "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6584                  _allocator->used_unlocked(), recalculate_used()));
6585 }
6586 
6587 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6588   _refine_cte_cl->set_concurrent(concurrent);
6589 }
6590 
6591 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6592   HeapRegion* hr = heap_region_containing(p);
6593   return hr->is_in(p);
6594 }
6595 
6596 // Methods for the mutator alloc region
6597 
6598 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6599                                                       bool force) {
6600   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6601   assert(!force || g1_policy()->can_expand_young_list(),
6602          "if force is true we should be able to expand the young list");
6603   bool young_list_full = g1_policy()->is_young_list_full();
6604   if (force || !young_list_full) {
6605     HeapRegion* new_alloc_region = new_region(word_size,
6606                                               false /* is_old */,
6607                                               false /* do_expand */);
6608     if (new_alloc_region != NULL) {
6609       set_region_short_lived_locked(new_alloc_region);
6610       _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6611       check_bitmaps("Mutator Region Allocation", new_alloc_region);
6612       return new_alloc_region;
6613     }
6614   }
6615   return NULL;
6616 }
6617 
6618 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6619                                                   size_t allocated_bytes) {
6620   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6621   assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
6622 
6623   g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6624   _allocator->increase_used(allocated_bytes);
6625   _hr_printer.retire(alloc_region);
6626   // We update the eden sizes here, when the region is retired,
6627   // instead of when it's allocated, since this is the point that its
6628   // used space has been recored in _summary_bytes_used.
6629   g1mm()->update_eden_size();
6630 }
6631 
6632 void G1CollectedHeap::set_par_threads() {
6633   // Don't change the number of workers.  Use the value previously set
6634   // in the workgroup.
6635   assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise");
6636   uint n_workers = workers()->active_workers();
6637   assert(UseDynamicNumberOfGCThreads ||
6638            n_workers == workers()->total_workers(),
6639       "Otherwise should be using the total number of workers");
6640   if (n_workers == 0) {
6641     assert(false, "Should have been set in prior evacuation pause.");
6642     n_workers = ParallelGCThreads;
6643     workers()->set_active_workers(n_workers);
6644   }
6645   set_par_threads(n_workers);
6646 }
6647 
6648 // Methods for the GC alloc regions
6649 
6650 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6651                                                  uint count,
6652                                                  GCAllocPurpose ap) {
6653   assert(FreeList_lock->owned_by_self(), "pre-condition");
6654 
6655   if (count < g1_policy()->max_regions(ap)) {
6656     bool survivor = (ap == GCAllocForSurvived);
6657     HeapRegion* new_alloc_region = new_region(word_size,
6658                                               !survivor,
6659                                               true /* do_expand */);
6660     if (new_alloc_region != NULL) {
6661       // We really only need to do this for old regions given that we
6662       // should never scan survivors. But it doesn't hurt to do it
6663       // for survivors too.
6664       new_alloc_region->record_top_and_timestamp();
6665       if (survivor) {
6666         new_alloc_region->set_survivor();
6667         _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6668         check_bitmaps("Survivor Region Allocation", new_alloc_region);
6669       } else {
6670         new_alloc_region->set_old();
6671         _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6672         check_bitmaps("Old Region Allocation", new_alloc_region);
6673       }
6674       bool during_im = g1_policy()->during_initial_mark_pause();
6675       new_alloc_region->note_start_of_copying(during_im);
6676       return new_alloc_region;
6677     } else {
6678       g1_policy()->note_alloc_region_limit_reached(ap);
6679     }
6680   }
6681   return NULL;
6682 }
6683 
6684 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6685                                              size_t allocated_bytes,
6686                                              GCAllocPurpose ap) {
6687   bool during_im = g1_policy()->during_initial_mark_pause();
6688   alloc_region->note_end_of_copying(during_im);
6689   g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6690   if (ap == GCAllocForSurvived) {
6691     young_list()->add_survivor_region(alloc_region);
6692   } else {
6693     _old_set.add(alloc_region);
6694   }
6695   _hr_printer.retire(alloc_region);
6696 }
6697 
6698 // Heap region set verification
6699 
6700 class VerifyRegionListsClosure : public HeapRegionClosure {
6701 private:
6702   HeapRegionSet*   _old_set;
6703   HeapRegionSet*   _humongous_set;
6704   HeapRegionManager*   _hrm;
6705 
6706 public:
6707   HeapRegionSetCount _old_count;
6708   HeapRegionSetCount _humongous_count;
6709   HeapRegionSetCount _free_count;
6710 
6711   VerifyRegionListsClosure(HeapRegionSet* old_set,
6712                            HeapRegionSet* humongous_set,
6713                            HeapRegionManager* hrm) :
6714     _old_set(old_set), _humongous_set(humongous_set), _hrm(hrm),
6715     _old_count(), _humongous_count(), _free_count(){ }
6716 
6717   bool doHeapRegion(HeapRegion* hr) {
6718     if (hr->is_continues_humongous()) {
6719       return false;
6720     }
6721 
6722     if (hr->is_young()) {
6723       // TODO
6724     } else if (hr->is_starts_humongous()) {
6725       assert(hr->containing_set() == _humongous_set, err_msg("Heap region %u is starts humongous but not in humongous set.", hr->hrm_index()));
6726       _humongous_count.increment(1u, hr->capacity());
6727     } else if (hr->is_empty()) {
6728       assert(_hrm->is_free(hr), err_msg("Heap region %u is empty but not on the free list.", hr->hrm_index()));
6729       _free_count.increment(1u, hr->capacity());
6730     } else if (hr->is_old()) {
6731       assert(hr->containing_set() == _old_set, err_msg("Heap region %u is old but not in the old set.", hr->hrm_index()));
6732       _old_count.increment(1u, hr->capacity());
6733     } else {
6734       ShouldNotReachHere();
6735     }
6736     return false;
6737   }
6738 
6739   void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, HeapRegionManager* free_list) {
6740     guarantee(old_set->length() == _old_count.length(), err_msg("Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length()));
6741     guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), err_msg("Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6742         old_set->total_capacity_bytes(), _old_count.capacity()));
6743 
6744     guarantee(humongous_set->length() == _humongous_count.length(), err_msg("Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length()));
6745     guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), err_msg("Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6746         humongous_set->total_capacity_bytes(), _humongous_count.capacity()));
6747 
6748     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()));
6749     guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), err_msg("Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6750         free_list->total_capacity_bytes(), _free_count.capacity()));
6751   }
6752 };
6753 
6754 void G1CollectedHeap::verify_region_sets() {
6755   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6756 
6757   // First, check the explicit lists.
6758   _hrm.verify();
6759   {
6760     // Given that a concurrent operation might be adding regions to
6761     // the secondary free list we have to take the lock before
6762     // verifying it.
6763     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6764     _secondary_free_list.verify_list();
6765   }
6766 
6767   // If a concurrent region freeing operation is in progress it will
6768   // be difficult to correctly attributed any free regions we come
6769   // across to the correct free list given that they might belong to
6770   // one of several (free_list, secondary_free_list, any local lists,
6771   // etc.). So, if that's the case we will skip the rest of the
6772   // verification operation. Alternatively, waiting for the concurrent
6773   // operation to complete will have a non-trivial effect on the GC's
6774   // operation (no concurrent operation will last longer than the
6775   // interval between two calls to verification) and it might hide
6776   // any issues that we would like to catch during testing.
6777   if (free_regions_coming()) {
6778     return;
6779   }
6780 
6781   // Make sure we append the secondary_free_list on the free_list so
6782   // that all free regions we will come across can be safely
6783   // attributed to the free_list.
6784   append_secondary_free_list_if_not_empty_with_lock();
6785 
6786   // Finally, make sure that the region accounting in the lists is
6787   // consistent with what we see in the heap.
6788 
6789   VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_hrm);
6790   heap_region_iterate(&cl);
6791   cl.verify_counts(&_old_set, &_humongous_set, &_hrm);
6792 }
6793 
6794 // Optimized nmethod scanning
6795 
6796 class RegisterNMethodOopClosure: public OopClosure {
6797   G1CollectedHeap* _g1h;
6798   nmethod* _nm;
6799 
6800   template <class T> void do_oop_work(T* p) {
6801     T heap_oop = oopDesc::load_heap_oop(p);
6802     if (!oopDesc::is_null(heap_oop)) {
6803       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6804       HeapRegion* hr = _g1h->heap_region_containing(obj);
6805       assert(!hr->is_continues_humongous(),
6806              err_msg("trying to add code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6807                      " starting at "HR_FORMAT,
6808                      _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6809 
6810       // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
6811       hr->add_strong_code_root_locked(_nm);
6812     }
6813   }
6814 
6815 public:
6816   RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6817     _g1h(g1h), _nm(nm) {}
6818 
6819   void do_oop(oop* p)       { do_oop_work(p); }
6820   void do_oop(narrowOop* p) { do_oop_work(p); }
6821 };
6822 
6823 class UnregisterNMethodOopClosure: public OopClosure {
6824   G1CollectedHeap* _g1h;
6825   nmethod* _nm;
6826 
6827   template <class T> void do_oop_work(T* p) {
6828     T heap_oop = oopDesc::load_heap_oop(p);
6829     if (!oopDesc::is_null(heap_oop)) {
6830       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6831       HeapRegion* hr = _g1h->heap_region_containing(obj);
6832       assert(!hr->is_continues_humongous(),
6833              err_msg("trying to remove code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6834                      " starting at "HR_FORMAT,
6835                      _nm, HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6836 
6837       hr->remove_strong_code_root(_nm);
6838     }
6839   }
6840 
6841 public:
6842   UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6843     _g1h(g1h), _nm(nm) {}
6844 
6845   void do_oop(oop* p)       { do_oop_work(p); }
6846   void do_oop(narrowOop* p) { do_oop_work(p); }
6847 };
6848 
6849 void G1CollectedHeap::register_nmethod(nmethod* nm) {
6850   CollectedHeap::register_nmethod(nm);
6851 
6852   guarantee(nm != NULL, "sanity");
6853   RegisterNMethodOopClosure reg_cl(this, nm);
6854   nm->oops_do(&reg_cl);
6855 }
6856 
6857 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
6858   CollectedHeap::unregister_nmethod(nm);
6859 
6860   guarantee(nm != NULL, "sanity");
6861   UnregisterNMethodOopClosure reg_cl(this, nm);
6862   nm->oops_do(&reg_cl, true);
6863 }
6864 
6865 void G1CollectedHeap::purge_code_root_memory() {
6866   double purge_start = os::elapsedTime();
6867   G1CodeRootSet::purge();
6868   double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
6869   g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
6870 }
6871 
6872 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
6873   G1CollectedHeap* _g1h;
6874 
6875 public:
6876   RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
6877     _g1h(g1h) {}
6878 
6879   void do_code_blob(CodeBlob* cb) {
6880     nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
6881     if (nm == NULL) {
6882       return;
6883     }
6884 
6885     if (ScavengeRootsInCode) {
6886       _g1h->register_nmethod(nm);
6887     }
6888   }
6889 };
6890 
6891 void G1CollectedHeap::rebuild_strong_code_roots() {
6892   RebuildStrongCodeRootClosure blob_cl(this);
6893   CodeCache::blobs_do(&blob_cl);
6894 }