1 /*
   2  * Copyright (c) 2001, 2013, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "code/codeCache.hpp"
  27 #include "code/icBuffer.hpp"
  28 #include "gc_implementation/g1/bufferingOopClosure.hpp"
  29 #include "gc_implementation/g1/concurrentG1Refine.hpp"
  30 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
  31 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
  32 #include "gc_implementation/g1/g1AllocRegion.inline.hpp"
  33 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
  34 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
  35 #include "gc_implementation/g1/g1ErgoVerbose.hpp"
  36 #include "gc_implementation/g1/g1EvacFailure.hpp"
  37 #include "gc_implementation/g1/g1GCPhaseTimes.hpp"
  38 #include "gc_implementation/g1/g1Log.hpp"
  39 #include "gc_implementation/g1/g1MarkSweep.hpp"
  40 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
  41 #include "gc_implementation/g1/g1RemSet.inline.hpp"
  42 #include "gc_implementation/g1/g1YCTypes.hpp"
  43 #include "gc_implementation/g1/heapRegion.inline.hpp"
  44 #include "gc_implementation/g1/heapRegionRemSet.hpp"
  45 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
  46 #include "gc_implementation/g1/vm_operations_g1.hpp"
  47 #include "gc_implementation/shared/gcHeapSummary.hpp"
  48 #include "gc_implementation/shared/gcTimer.hpp"
  49 #include "gc_implementation/shared/gcTrace.hpp"
  50 #include "gc_implementation/shared/gcTraceTime.hpp"
  51 #include "gc_implementation/shared/isGCActiveMark.hpp"
  52 #include "memory/gcLocker.inline.hpp"
  53 #include "memory/genOopClosures.inline.hpp"
  54 #include "memory/generationSpec.hpp"
  55 #include "memory/referenceProcessor.hpp"
  56 #include "oops/oop.inline.hpp"
  57 #include "oops/oop.pcgc.inline.hpp"
  58 #include "runtime/vmThread.hpp"
  59 
  60 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
  61 
  62 // turn it on so that the contents of the young list (scan-only /
  63 // to-be-collected) are printed at "strategic" points before / during
  64 // / after the collection --- this is useful for debugging
  65 #define YOUNG_LIST_VERBOSE 0
  66 // CURRENT STATUS
  67 // This file is under construction.  Search for "FIXME".
  68 
  69 // INVARIANTS/NOTES
  70 //
  71 // All allocation activity covered by the G1CollectedHeap interface is
  72 // serialized by acquiring the HeapLock.  This happens in mem_allocate
  73 // and allocate_new_tlab, which are the "entry" points to the
  74 // allocation code from the rest of the JVM.  (Note that this does not
  75 // apply to TLAB allocation, which is not part of this interface: it
  76 // is done by clients of this interface.)
  77 
  78 // Notes on implementation of parallelism in different tasks.
  79 //
  80 // G1ParVerifyTask uses heap_region_par_iterate_chunked() for parallelism.
  81 // The number of GC workers is passed to heap_region_par_iterate_chunked().
  82 // It does use run_task() which sets _n_workers in the task.
  83 // G1ParTask executes g1_process_strong_roots() ->
  84 // SharedHeap::process_strong_roots() which calls eventually to
  85 // CardTableModRefBS::par_non_clean_card_iterate_work() which uses
  86 // SequentialSubTasksDone.  SharedHeap::process_strong_roots() also
  87 // directly uses SubTasksDone (_process_strong_tasks field in SharedHeap).
  88 //
  89 
  90 // Local to this file.
  91 
  92 class RefineCardTableEntryClosure: public CardTableEntryClosure {
  93   SuspendibleThreadSet* _sts;
  94   G1RemSet* _g1rs;
  95   ConcurrentG1Refine* _cg1r;
  96   bool _concurrent;
  97 public:
  98   RefineCardTableEntryClosure(SuspendibleThreadSet* sts,
  99                               G1RemSet* g1rs,
 100                               ConcurrentG1Refine* cg1r) :
 101     _sts(sts), _g1rs(g1rs), _cg1r(cg1r), _concurrent(true)
 102   {}
 103   bool do_card_ptr(jbyte* card_ptr, int worker_i) {
 104     bool oops_into_cset = _g1rs->refine_card(card_ptr, worker_i, false);
 105     // This path is executed by the concurrent refine or mutator threads,
 106     // concurrently, and so we do not care if card_ptr contains references
 107     // that point into the collection set.
 108     assert(!oops_into_cset, "should be");
 109 
 110     if (_concurrent && _sts->should_yield()) {
 111       // Caller will actually yield.
 112       return false;
 113     }
 114     // Otherwise, we finished successfully; return true.
 115     return true;
 116   }
 117   void set_concurrent(bool b) { _concurrent = b; }
 118 };
 119 
 120 
 121 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure {
 122   int _calls;
 123   G1CollectedHeap* _g1h;
 124   CardTableModRefBS* _ctbs;
 125   int _histo[256];
 126 public:
 127   ClearLoggedCardTableEntryClosure() :
 128     _calls(0)
 129   {
 130     _g1h = G1CollectedHeap::heap();
 131     _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
 132     for (int i = 0; i < 256; i++) _histo[i] = 0;
 133   }
 134   bool do_card_ptr(jbyte* card_ptr, int worker_i) {
 135     if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
 136       _calls++;
 137       unsigned char* ujb = (unsigned char*)card_ptr;
 138       int ind = (int)(*ujb);
 139       _histo[ind]++;
 140       *card_ptr = -1;
 141     }
 142     return true;
 143   }
 144   int calls() { return _calls; }
 145   void print_histo() {
 146     gclog_or_tty->print_cr("Card table value histogram:");
 147     for (int i = 0; i < 256; i++) {
 148       if (_histo[i] != 0) {
 149         gclog_or_tty->print_cr("  %d: %d", i, _histo[i]);
 150       }
 151     }
 152   }
 153 };
 154 
 155 class RedirtyLoggedCardTableEntryClosure: public CardTableEntryClosure {
 156   int _calls;
 157   G1CollectedHeap* _g1h;
 158   CardTableModRefBS* _ctbs;
 159 public:
 160   RedirtyLoggedCardTableEntryClosure() :
 161     _calls(0)
 162   {
 163     _g1h = G1CollectedHeap::heap();
 164     _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
 165   }
 166   bool do_card_ptr(jbyte* card_ptr, int worker_i) {
 167     if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
 168       _calls++;
 169       *card_ptr = 0;
 170     }
 171     return true;
 172   }
 173   int calls() { return _calls; }
 174 };
 175 
 176 class RedirtyLoggedCardTableEntryFastClosure : public CardTableEntryClosure {
 177 public:
 178   bool do_card_ptr(jbyte* card_ptr, int worker_i) {
 179     *card_ptr = CardTableModRefBS::dirty_card_val();
 180     return true;
 181   }
 182 };
 183 
 184 YoungList::YoungList(G1CollectedHeap* g1h) :
 185     _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0),
 186     _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) {
 187   guarantee(check_list_empty(false), "just making sure...");
 188 }
 189 
 190 void YoungList::push_region(HeapRegion *hr) {
 191   assert(!hr->is_young(), "should not already be young");
 192   assert(hr->get_next_young_region() == NULL, "cause it should!");
 193 
 194   hr->set_next_young_region(_head);
 195   _head = hr;
 196 
 197   _g1h->g1_policy()->set_region_eden(hr, (int) _length);
 198   ++_length;
 199 }
 200 
 201 void YoungList::add_survivor_region(HeapRegion* hr) {
 202   assert(hr->is_survivor(), "should be flagged as survivor region");
 203   assert(hr->get_next_young_region() == NULL, "cause it should!");
 204 
 205   hr->set_next_young_region(_survivor_head);
 206   if (_survivor_head == NULL) {
 207     _survivor_tail = hr;
 208   }
 209   _survivor_head = hr;
 210   ++_survivor_length;
 211 }
 212 
 213 void YoungList::empty_list(HeapRegion* list) {
 214   while (list != NULL) {
 215     HeapRegion* next = list->get_next_young_region();
 216     list->set_next_young_region(NULL);
 217     list->uninstall_surv_rate_group();
 218     list->set_not_young();
 219     list = next;
 220   }
 221 }
 222 
 223 void YoungList::empty_list() {
 224   assert(check_list_well_formed(), "young list should be well formed");
 225 
 226   empty_list(_head);
 227   _head = NULL;
 228   _length = 0;
 229 
 230   empty_list(_survivor_head);
 231   _survivor_head = NULL;
 232   _survivor_tail = NULL;
 233   _survivor_length = 0;
 234 
 235   _last_sampled_rs_lengths = 0;
 236 
 237   assert(check_list_empty(false), "just making sure...");
 238 }
 239 
 240 bool YoungList::check_list_well_formed() {
 241   bool ret = true;
 242 
 243   uint length = 0;
 244   HeapRegion* curr = _head;
 245   HeapRegion* last = NULL;
 246   while (curr != NULL) {
 247     if (!curr->is_young()) {
 248       gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
 249                              "incorrectly tagged (y: %d, surv: %d)",
 250                              curr->bottom(), curr->end(),
 251                              curr->is_young(), curr->is_survivor());
 252       ret = false;
 253     }
 254     ++length;
 255     last = curr;
 256     curr = curr->get_next_young_region();
 257   }
 258   ret = ret && (length == _length);
 259 
 260   if (!ret) {
 261     gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
 262     gclog_or_tty->print_cr("###   list has %u entries, _length is %u",
 263                            length, _length);
 264   }
 265 
 266   return ret;
 267 }
 268 
 269 bool YoungList::check_list_empty(bool check_sample) {
 270   bool ret = true;
 271 
 272   if (_length != 0) {
 273     gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u",
 274                   _length);
 275     ret = false;
 276   }
 277   if (check_sample && _last_sampled_rs_lengths != 0) {
 278     gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
 279     ret = false;
 280   }
 281   if (_head != NULL) {
 282     gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
 283     ret = false;
 284   }
 285   if (!ret) {
 286     gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
 287   }
 288 
 289   return ret;
 290 }
 291 
 292 void
 293 YoungList::rs_length_sampling_init() {
 294   _sampled_rs_lengths = 0;
 295   _curr               = _head;
 296 }
 297 
 298 bool
 299 YoungList::rs_length_sampling_more() {
 300   return _curr != NULL;
 301 }
 302 
 303 void
 304 YoungList::rs_length_sampling_next() {
 305   assert( _curr != NULL, "invariant" );
 306   size_t rs_length = _curr->rem_set()->occupied();
 307 
 308   _sampled_rs_lengths += rs_length;
 309 
 310   // The current region may not yet have been added to the
 311   // incremental collection set (it gets added when it is
 312   // retired as the current allocation region).
 313   if (_curr->in_collection_set()) {
 314     // Update the collection set policy information for this region
 315     _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
 316   }
 317 
 318   _curr = _curr->get_next_young_region();
 319   if (_curr == NULL) {
 320     _last_sampled_rs_lengths = _sampled_rs_lengths;
 321     // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
 322   }
 323 }
 324 
 325 void
 326 YoungList::reset_auxilary_lists() {
 327   guarantee( is_empty(), "young list should be empty" );
 328   assert(check_list_well_formed(), "young list should be well formed");
 329 
 330   // Add survivor regions to SurvRateGroup.
 331   _g1h->g1_policy()->note_start_adding_survivor_regions();
 332   _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
 333 
 334   int young_index_in_cset = 0;
 335   for (HeapRegion* curr = _survivor_head;
 336        curr != NULL;
 337        curr = curr->get_next_young_region()) {
 338     _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
 339 
 340     // The region is a non-empty survivor so let's add it to
 341     // the incremental collection set for the next evacuation
 342     // pause.
 343     _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
 344     young_index_in_cset += 1;
 345   }
 346   assert((uint) young_index_in_cset == _survivor_length, "post-condition");
 347   _g1h->g1_policy()->note_stop_adding_survivor_regions();
 348 
 349   _head   = _survivor_head;
 350   _length = _survivor_length;
 351   if (_survivor_head != NULL) {
 352     assert(_survivor_tail != NULL, "cause it shouldn't be");
 353     assert(_survivor_length > 0, "invariant");
 354     _survivor_tail->set_next_young_region(NULL);
 355   }
 356 
 357   // Don't clear the survivor list handles until the start of
 358   // the next evacuation pause - we need it in order to re-tag
 359   // the survivor regions from this evacuation pause as 'young'
 360   // at the start of the next.
 361 
 362   _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
 363 
 364   assert(check_list_well_formed(), "young list should be well formed");
 365 }
 366 
 367 void YoungList::print() {
 368   HeapRegion* lists[] = {_head,   _survivor_head};
 369   const char* names[] = {"YOUNG", "SURVIVOR"};
 370 
 371   for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) {
 372     gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
 373     HeapRegion *curr = lists[list];
 374     if (curr == NULL)
 375       gclog_or_tty->print_cr("  empty");
 376     while (curr != NULL) {
 377       gclog_or_tty->print_cr("  "HR_FORMAT", P: "PTR_FORMAT "N: "PTR_FORMAT", age: %4d",
 378                              HR_FORMAT_PARAMS(curr),
 379                              curr->prev_top_at_mark_start(),
 380                              curr->next_top_at_mark_start(),
 381                              curr->age_in_surv_rate_group_cond());
 382       curr = curr->get_next_young_region();
 383     }
 384   }
 385 
 386   gclog_or_tty->print_cr("");
 387 }
 388 
 389 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
 390 {
 391   // Claim the right to put the region on the dirty cards region list
 392   // by installing a self pointer.
 393   HeapRegion* next = hr->get_next_dirty_cards_region();
 394   if (next == NULL) {
 395     HeapRegion* res = (HeapRegion*)
 396       Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
 397                           NULL);
 398     if (res == NULL) {
 399       HeapRegion* head;
 400       do {
 401         // Put the region to the dirty cards region list.
 402         head = _dirty_cards_region_list;
 403         next = (HeapRegion*)
 404           Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
 405         if (next == head) {
 406           assert(hr->get_next_dirty_cards_region() == hr,
 407                  "hr->get_next_dirty_cards_region() != hr");
 408           if (next == NULL) {
 409             // The last region in the list points to itself.
 410             hr->set_next_dirty_cards_region(hr);
 411           } else {
 412             hr->set_next_dirty_cards_region(next);
 413           }
 414         }
 415       } while (next != head);
 416     }
 417   }
 418 }
 419 
 420 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
 421 {
 422   HeapRegion* head;
 423   HeapRegion* hr;
 424   do {
 425     head = _dirty_cards_region_list;
 426     if (head == NULL) {
 427       return NULL;
 428     }
 429     HeapRegion* new_head = head->get_next_dirty_cards_region();
 430     if (head == new_head) {
 431       // The last region.
 432       new_head = NULL;
 433     }
 434     hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
 435                                           head);
 436   } while (hr != head);
 437   assert(hr != NULL, "invariant");
 438   hr->set_next_dirty_cards_region(NULL);
 439   return hr;
 440 }
 441 
 442 void G1CollectedHeap::stop_conc_gc_threads() {
 443   _cg1r->stop();
 444   _cmThread->stop();
 445 }
 446 
 447 #ifdef ASSERT
 448 // A region is added to the collection set as it is retired
 449 // so an address p can point to a region which will be in the
 450 // collection set but has not yet been retired.  This method
 451 // therefore is only accurate during a GC pause after all
 452 // regions have been retired.  It is used for debugging
 453 // to check if an nmethod has references to objects that can
 454 // be move during a partial collection.  Though it can be
 455 // inaccurate, it is sufficient for G1 because the conservative
 456 // implementation of is_scavengable() for G1 will indicate that
 457 // all nmethods must be scanned during a partial collection.
 458 bool G1CollectedHeap::is_in_partial_collection(const void* p) {
 459   HeapRegion* hr = heap_region_containing(p);
 460   return hr != NULL && hr->in_collection_set();
 461 }
 462 #endif
 463 
 464 // Returns true if the reference points to an object that
 465 // can move in an incremental collection.
 466 bool G1CollectedHeap::is_scavengable(const void* p) {
 467   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 468   G1CollectorPolicy* g1p = g1h->g1_policy();
 469   HeapRegion* hr = heap_region_containing(p);
 470   if (hr == NULL) {
 471      // null
 472      assert(p == NULL, err_msg("Not NULL " PTR_FORMAT ,p));
 473      return false;
 474   } else {
 475     return !hr->isHumongous();
 476   }
 477 }
 478 
 479 void G1CollectedHeap::check_ct_logs_at_safepoint() {
 480   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
 481   CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
 482 
 483   // Count the dirty cards at the start.
 484   CountNonCleanMemRegionClosure count1(this);
 485   ct_bs->mod_card_iterate(&count1);
 486   int orig_count = count1.n();
 487 
 488   // First clear the logged cards.
 489   ClearLoggedCardTableEntryClosure clear;
 490   dcqs.set_closure(&clear);
 491   dcqs.apply_closure_to_all_completed_buffers();
 492   dcqs.iterate_closure_all_threads(false);
 493   clear.print_histo();
 494 
 495   // Now ensure that there's no dirty cards.
 496   CountNonCleanMemRegionClosure count2(this);
 497   ct_bs->mod_card_iterate(&count2);
 498   if (count2.n() != 0) {
 499     gclog_or_tty->print_cr("Card table has %d entries; %d originally",
 500                            count2.n(), orig_count);
 501   }
 502   guarantee(count2.n() == 0, "Card table should be clean.");
 503 
 504   RedirtyLoggedCardTableEntryClosure redirty;
 505   JavaThread::dirty_card_queue_set().set_closure(&redirty);
 506   dcqs.apply_closure_to_all_completed_buffers();
 507   dcqs.iterate_closure_all_threads(false);
 508   gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
 509                          clear.calls(), orig_count);
 510   guarantee(redirty.calls() == clear.calls(),
 511             "Or else mechanism is broken.");
 512 
 513   CountNonCleanMemRegionClosure count3(this);
 514   ct_bs->mod_card_iterate(&count3);
 515   if (count3.n() != orig_count) {
 516     gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
 517                            orig_count, count3.n());
 518     guarantee(count3.n() >= orig_count, "Should have restored them all.");
 519   }
 520 
 521   JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
 522 }
 523 
 524 // Private class members.
 525 
 526 G1CollectedHeap* G1CollectedHeap::_g1h;
 527 
 528 // Private methods.
 529 
 530 HeapRegion*
 531 G1CollectedHeap::new_region_try_secondary_free_list() {
 532   MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
 533   while (!_secondary_free_list.is_empty() || free_regions_coming()) {
 534     if (!_secondary_free_list.is_empty()) {
 535       if (G1ConcRegionFreeingVerbose) {
 536         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 537                                "secondary_free_list has %u entries",
 538                                _secondary_free_list.length());
 539       }
 540       // It looks as if there are free regions available on the
 541       // secondary_free_list. Let's move them to the free_list and try
 542       // again to allocate from it.
 543       append_secondary_free_list();
 544 
 545       assert(!_free_list.is_empty(), "if the secondary_free_list was not "
 546              "empty we should have moved at least one entry to the free_list");
 547       HeapRegion* res = _free_list.remove_head();
 548       if (G1ConcRegionFreeingVerbose) {
 549         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 550                                "allocated "HR_FORMAT" from secondary_free_list",
 551                                HR_FORMAT_PARAMS(res));
 552       }
 553       return res;
 554     }
 555 
 556     // Wait here until we get notified either when (a) there are no
 557     // more free regions coming or (b) some regions have been moved on
 558     // the secondary_free_list.
 559     SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
 560   }
 561 
 562   if (G1ConcRegionFreeingVerbose) {
 563     gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 564                            "could not allocate from secondary_free_list");
 565   }
 566   return NULL;
 567 }
 568 
 569 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool do_expand) {
 570   assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords,
 571          "the only time we use this to allocate a humongous region is "
 572          "when we are allocating a single humongous region");
 573 
 574   HeapRegion* res;
 575   if (G1StressConcRegionFreeing) {
 576     if (!_secondary_free_list.is_empty()) {
 577       if (G1ConcRegionFreeingVerbose) {
 578         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 579                                "forced to look at the secondary_free_list");
 580       }
 581       res = new_region_try_secondary_free_list();
 582       if (res != NULL) {
 583         return res;
 584       }
 585     }
 586   }
 587   res = _free_list.remove_head_or_null();
 588   if (res == NULL) {
 589     if (G1ConcRegionFreeingVerbose) {
 590       gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 591                              "res == NULL, trying the secondary_free_list");
 592     }
 593     res = new_region_try_secondary_free_list();
 594   }
 595   if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
 596     // Currently, only attempts to allocate GC alloc regions set
 597     // do_expand to true. So, we should only reach here during a
 598     // safepoint. If this assumption changes we might have to
 599     // reconsider the use of _expand_heap_after_alloc_failure.
 600     assert(SafepointSynchronize::is_at_safepoint(), "invariant");
 601 
 602     ergo_verbose1(ErgoHeapSizing,
 603                   "attempt heap expansion",
 604                   ergo_format_reason("region allocation request failed")
 605                   ergo_format_byte("allocation request"),
 606                   word_size * HeapWordSize);
 607     if (expand(word_size * HeapWordSize)) {
 608       // Given that expand() succeeded in expanding the heap, and we
 609       // always expand the heap by an amount aligned to the heap
 610       // region size, the free list should in theory not be empty. So
 611       // it would probably be OK to use remove_head(). But the extra
 612       // check for NULL is unlikely to be a performance issue here (we
 613       // just expanded the heap!) so let's just be conservative and
 614       // use remove_head_or_null().
 615       res = _free_list.remove_head_or_null();
 616     } else {
 617       _expand_heap_after_alloc_failure = false;
 618     }
 619   }
 620   return res;
 621 }
 622 
 623 uint G1CollectedHeap::humongous_obj_allocate_find_first(uint num_regions,
 624                                                         size_t word_size) {
 625   assert(isHumongous(word_size), "word_size should be humongous");
 626   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 627 
 628   uint first = G1_NULL_HRS_INDEX;
 629   if (num_regions == 1) {
 630     // Only one region to allocate, no need to go through the slower
 631     // path. The caller will attempt the expansion if this fails, so
 632     // let's not try to expand here too.
 633     HeapRegion* hr = new_region(word_size, false /* do_expand */);
 634     if (hr != NULL) {
 635       first = hr->hrs_index();
 636     } else {
 637       first = G1_NULL_HRS_INDEX;
 638     }
 639   } else {
 640     // We can't allocate humongous regions while cleanupComplete() is
 641     // running, since some of the regions we find to be empty might not
 642     // yet be added to the free list and it is not straightforward to
 643     // know which list they are on so that we can remove them. Note
 644     // that we only need to do this if we need to allocate more than
 645     // one region to satisfy the current humongous allocation
 646     // request. If we are only allocating one region we use the common
 647     // region allocation code (see above).
 648     wait_while_free_regions_coming();
 649     append_secondary_free_list_if_not_empty_with_lock();
 650 
 651     if (free_regions() >= num_regions) {
 652       first = _hrs.find_contiguous(num_regions);
 653       if (first != G1_NULL_HRS_INDEX) {
 654         for (uint i = first; i < first + num_regions; ++i) {
 655           HeapRegion* hr = region_at(i);
 656           assert(hr->is_empty(), "sanity");
 657           assert(is_on_master_free_list(hr), "sanity");
 658           hr->set_pending_removal(true);
 659         }
 660         _free_list.remove_all_pending(num_regions);
 661       }
 662     }
 663   }
 664   return first;
 665 }
 666 
 667 HeapWord*
 668 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
 669                                                            uint num_regions,
 670                                                            size_t word_size) {
 671   assert(first != G1_NULL_HRS_INDEX, "pre-condition");
 672   assert(isHumongous(word_size), "word_size should be humongous");
 673   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 674 
 675   // Index of last region in the series + 1.
 676   uint last = first + num_regions;
 677 
 678   // We need to initialize the region(s) we just discovered. This is
 679   // a bit tricky given that it can happen concurrently with
 680   // refinement threads refining cards on these regions and
 681   // potentially wanting to refine the BOT as they are scanning
 682   // those cards (this can happen shortly after a cleanup; see CR
 683   // 6991377). So we have to set up the region(s) carefully and in
 684   // a specific order.
 685 
 686   // The word size sum of all the regions we will allocate.
 687   size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
 688   assert(word_size <= word_size_sum, "sanity");
 689 
 690   // This will be the "starts humongous" region.
 691   HeapRegion* first_hr = region_at(first);
 692   // The header of the new object will be placed at the bottom of
 693   // the first region.
 694   HeapWord* new_obj = first_hr->bottom();
 695   // This will be the new end of the first region in the series that
 696   // should also match the end of the last region in the series.
 697   HeapWord* new_end = new_obj + word_size_sum;
 698   // This will be the new top of the first region that will reflect
 699   // this allocation.
 700   HeapWord* new_top = new_obj + word_size;
 701 
 702   // First, we need to zero the header of the space that we will be
 703   // allocating. When we update top further down, some refinement
 704   // threads might try to scan the region. By zeroing the header we
 705   // ensure that any thread that will try to scan the region will
 706   // come across the zero klass word and bail out.
 707   //
 708   // NOTE: It would not have been correct to have used
 709   // CollectedHeap::fill_with_object() and make the space look like
 710   // an int array. The thread that is doing the allocation will
 711   // later update the object header to a potentially different array
 712   // type and, for a very short period of time, the klass and length
 713   // fields will be inconsistent. This could cause a refinement
 714   // thread to calculate the object size incorrectly.
 715   Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
 716 
 717   // We will set up the first region as "starts humongous". This
 718   // will also update the BOT covering all the regions to reflect
 719   // that there is a single object that starts at the bottom of the
 720   // first region.
 721   first_hr->set_startsHumongous(new_top, new_end);
 722 
 723   // Then, if there are any, we will set up the "continues
 724   // humongous" regions.
 725   HeapRegion* hr = NULL;
 726   for (uint i = first + 1; i < last; ++i) {
 727     hr = region_at(i);
 728     hr->set_continuesHumongous(first_hr);
 729   }
 730   // If we have "continues humongous" regions (hr != NULL), then the
 731   // end of the last one should match new_end.
 732   assert(hr == NULL || hr->end() == new_end, "sanity");
 733 
 734   // Up to this point no concurrent thread would have been able to
 735   // do any scanning on any region in this series. All the top
 736   // fields still point to bottom, so the intersection between
 737   // [bottom,top] and [card_start,card_end] will be empty. Before we
 738   // update the top fields, we'll do a storestore to make sure that
 739   // no thread sees the update to top before the zeroing of the
 740   // object header and the BOT initialization.
 741   OrderAccess::storestore();
 742 
 743   // Now that the BOT and the object header have been initialized,
 744   // we can update top of the "starts humongous" region.
 745   assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
 746          "new_top should be in this region");
 747   first_hr->set_top(new_top);
 748   if (_hr_printer.is_active()) {
 749     HeapWord* bottom = first_hr->bottom();
 750     HeapWord* end = first_hr->orig_end();
 751     if ((first + 1) == last) {
 752       // the series has a single humongous region
 753       _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
 754     } else {
 755       // the series has more than one humongous regions
 756       _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
 757     }
 758   }
 759 
 760   // Now, we will update the top fields of the "continues humongous"
 761   // regions. The reason we need to do this is that, otherwise,
 762   // these regions would look empty and this will confuse parts of
 763   // G1. For example, the code that looks for a consecutive number
 764   // of empty regions will consider them empty and try to
 765   // re-allocate them. We can extend is_empty() to also include
 766   // !continuesHumongous(), but it is easier to just update the top
 767   // fields here. The way we set top for all regions (i.e., top ==
 768   // end for all regions but the last one, top == new_top for the
 769   // last one) is actually used when we will free up the humongous
 770   // region in free_humongous_region().
 771   hr = NULL;
 772   for (uint i = first + 1; i < last; ++i) {
 773     hr = region_at(i);
 774     if ((i + 1) == last) {
 775       // last continues humongous region
 776       assert(hr->bottom() < new_top && new_top <= hr->end(),
 777              "new_top should fall on this region");
 778       hr->set_top(new_top);
 779       _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
 780     } else {
 781       // not last one
 782       assert(new_top > hr->end(), "new_top should be above this region");
 783       hr->set_top(hr->end());
 784       _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
 785     }
 786   }
 787   // If we have continues humongous regions (hr != NULL), then the
 788   // end of the last one should match new_end and its top should
 789   // match new_top.
 790   assert(hr == NULL ||
 791          (hr->end() == new_end && hr->top() == new_top), "sanity");
 792 
 793   assert(first_hr->used() == word_size * HeapWordSize, "invariant");
 794   _summary_bytes_used += first_hr->used();
 795   _humongous_set.add(first_hr);
 796 
 797   return new_obj;
 798 }
 799 
 800 // If could fit into free regions w/o expansion, try.
 801 // Otherwise, if can expand, do so.
 802 // Otherwise, if using ex regions might help, try with ex given back.
 803 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
 804   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 805 
 806   verify_region_sets_optional();
 807 
 808   size_t word_size_rounded = round_to(word_size, HeapRegion::GrainWords);
 809   uint num_regions = (uint) (word_size_rounded / HeapRegion::GrainWords);
 810   uint x_num = expansion_regions();
 811   uint fs = _hrs.free_suffix();
 812   uint first = humongous_obj_allocate_find_first(num_regions, word_size);
 813   if (first == G1_NULL_HRS_INDEX) {
 814     // The only thing we can do now is attempt expansion.
 815     if (fs + x_num >= num_regions) {
 816       // If the number of regions we're trying to allocate for this
 817       // object is at most the number of regions in the free suffix,
 818       // then the call to humongous_obj_allocate_find_first() above
 819       // should have succeeded and we wouldn't be here.
 820       //
 821       // We should only be trying to expand when the free suffix is
 822       // not sufficient for the object _and_ we have some expansion
 823       // room available.
 824       assert(num_regions > fs, "earlier allocation should have succeeded");
 825 
 826       ergo_verbose1(ErgoHeapSizing,
 827                     "attempt heap expansion",
 828                     ergo_format_reason("humongous allocation request failed")
 829                     ergo_format_byte("allocation request"),
 830                     word_size * HeapWordSize);
 831       if (expand((num_regions - fs) * HeapRegion::GrainBytes)) {
 832         // Even though the heap was expanded, it might not have
 833         // reached the desired size. So, we cannot assume that the
 834         // allocation will succeed.
 835         first = humongous_obj_allocate_find_first(num_regions, word_size);
 836       }
 837     }
 838   }
 839 
 840   HeapWord* result = NULL;
 841   if (first != G1_NULL_HRS_INDEX) {
 842     result =
 843       humongous_obj_allocate_initialize_regions(first, num_regions, word_size);
 844     assert(result != NULL, "it should always return a valid result");
 845 
 846     // A successful humongous object allocation changes the used space
 847     // information of the old generation so we need to recalculate the
 848     // sizes and update the jstat counters here.
 849     g1mm()->update_sizes();
 850   }
 851 
 852   verify_region_sets_optional();
 853 
 854   return result;
 855 }
 856 
 857 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
 858   assert_heap_not_locked_and_not_at_safepoint();
 859   assert(!isHumongous(word_size), "we do not allow humongous TLABs");
 860 
 861   unsigned int dummy_gc_count_before;
 862   int dummy_gclocker_retry_count = 0;
 863   return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
 864 }
 865 
 866 HeapWord*
 867 G1CollectedHeap::mem_allocate(size_t word_size,
 868                               bool*  gc_overhead_limit_was_exceeded) {
 869   assert_heap_not_locked_and_not_at_safepoint();
 870 
 871   // Loop until the allocation is satisfied, or unsatisfied after GC.
 872   for (int try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 873     unsigned int gc_count_before;
 874 
 875     HeapWord* result = NULL;
 876     if (!isHumongous(word_size)) {
 877       result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
 878     } else {
 879       result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
 880     }
 881     if (result != NULL) {
 882       return result;
 883     }
 884 
 885     // Create the garbage collection operation...
 886     VM_G1CollectForAllocation op(gc_count_before, word_size);
 887     // ...and get the VM thread to execute it.
 888     VMThread::execute(&op);
 889 
 890     if (op.prologue_succeeded() && op.pause_succeeded()) {
 891       // If the operation was successful we'll return the result even
 892       // if it is NULL. If the allocation attempt failed immediately
 893       // after a Full GC, it's unlikely we'll be able to allocate now.
 894       HeapWord* result = op.result();
 895       if (result != NULL && !isHumongous(word_size)) {
 896         // Allocations that take place on VM operations do not do any
 897         // card dirtying and we have to do it here. We only have to do
 898         // this for non-humongous allocations, though.
 899         dirty_young_block(result, word_size);
 900       }
 901       return result;
 902     } else {
 903       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 904         return NULL;
 905       }
 906       assert(op.result() == NULL,
 907              "the result should be NULL if the VM op did not succeed");
 908     }
 909 
 910     // Give a warning if we seem to be looping forever.
 911     if ((QueuedAllocationWarningCount > 0) &&
 912         (try_count % QueuedAllocationWarningCount == 0)) {
 913       warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
 914     }
 915   }
 916 
 917   ShouldNotReachHere();
 918   return NULL;
 919 }
 920 
 921 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
 922                                            unsigned int *gc_count_before_ret,
 923                                            int* gclocker_retry_count_ret) {
 924   // Make sure you read the note in attempt_allocation_humongous().
 925 
 926   assert_heap_not_locked_and_not_at_safepoint();
 927   assert(!isHumongous(word_size), "attempt_allocation_slow() should not "
 928          "be called for humongous allocation requests");
 929 
 930   // We should only get here after the first-level allocation attempt
 931   // (attempt_allocation()) failed to allocate.
 932 
 933   // We will loop until a) we manage to successfully perform the
 934   // allocation or b) we successfully schedule a collection which
 935   // fails to perform the allocation. b) is the only case when we'll
 936   // return NULL.
 937   HeapWord* result = NULL;
 938   for (int try_count = 1; /* we'll return */; try_count += 1) {
 939     bool should_try_gc;
 940     unsigned int gc_count_before;
 941 
 942     {
 943       MutexLockerEx x(Heap_lock);
 944 
 945       result = _mutator_alloc_region.attempt_allocation_locked(word_size,
 946                                                       false /* bot_updates */);
 947       if (result != NULL) {
 948         return result;
 949       }
 950 
 951       // If we reach here, attempt_allocation_locked() above failed to
 952       // allocate a new region. So the mutator alloc region should be NULL.
 953       assert(_mutator_alloc_region.get() == NULL, "only way to get here");
 954 
 955       if (GC_locker::is_active_and_needs_gc()) {
 956         if (g1_policy()->can_expand_young_list()) {
 957           // No need for an ergo verbose message here,
 958           // can_expand_young_list() does this when it returns true.
 959           result = _mutator_alloc_region.attempt_allocation_force(word_size,
 960                                                       false /* bot_updates */);
 961           if (result != NULL) {
 962             return result;
 963           }
 964         }
 965         should_try_gc = false;
 966       } else {
 967         // The GCLocker may not be active but the GCLocker initiated
 968         // GC may not yet have been performed (GCLocker::needs_gc()
 969         // returns true). In this case we do not try this GC and
 970         // wait until the GCLocker initiated GC is performed, and
 971         // then retry the allocation.
 972         if (GC_locker::needs_gc()) {
 973           should_try_gc = false;
 974         } else {
 975           // Read the GC count while still holding the Heap_lock.
 976           gc_count_before = total_collections();
 977           should_try_gc = true;
 978         }
 979       }
 980     }
 981 
 982     if (should_try_gc) {
 983       bool succeeded;
 984       result = do_collection_pause(word_size, gc_count_before, &succeeded);
 985       if (result != NULL) {
 986         assert(succeeded, "only way to get back a non-NULL result");
 987         return result;
 988       }
 989 
 990       if (succeeded) {
 991         // If we get here we successfully scheduled a collection which
 992         // failed to allocate. No point in trying to allocate
 993         // further. We'll just return NULL.
 994         MutexLockerEx x(Heap_lock);
 995         *gc_count_before_ret = total_collections();
 996         return NULL;
 997       }
 998     } else {
 999       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1000         MutexLockerEx x(Heap_lock);
1001         *gc_count_before_ret = total_collections();
1002         return NULL;
1003       }
1004       // The GCLocker is either active or the GCLocker initiated
1005       // GC has not yet been performed. Stall until it is and
1006       // then retry the allocation.
1007       GC_locker::stall_until_clear();
1008       (*gclocker_retry_count_ret) += 1;
1009     }
1010 
1011     // We can reach here if we were unsuccessful in scheduling a
1012     // collection (because another thread beat us to it) or if we were
1013     // stalled due to the GC locker. In either can we should retry the
1014     // allocation attempt in case another thread successfully
1015     // performed a collection and reclaimed enough space. We do the
1016     // first attempt (without holding the Heap_lock) here and the
1017     // follow-on attempt will be at the start of the next loop
1018     // iteration (after taking the Heap_lock).
1019     result = _mutator_alloc_region.attempt_allocation(word_size,
1020                                                       false /* bot_updates */);
1021     if (result != NULL) {
1022       return result;
1023     }
1024 
1025     // Give a warning if we seem to be looping forever.
1026     if ((QueuedAllocationWarningCount > 0) &&
1027         (try_count % QueuedAllocationWarningCount == 0)) {
1028       warning("G1CollectedHeap::attempt_allocation_slow() "
1029               "retries %d times", try_count);
1030     }
1031   }
1032 
1033   ShouldNotReachHere();
1034   return NULL;
1035 }
1036 
1037 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
1038                                           unsigned int * gc_count_before_ret,
1039                                           int* gclocker_retry_count_ret) {
1040   // The structure of this method has a lot of similarities to
1041   // attempt_allocation_slow(). The reason these two were not merged
1042   // into a single one is that such a method would require several "if
1043   // allocation is not humongous do this, otherwise do that"
1044   // conditional paths which would obscure its flow. In fact, an early
1045   // version of this code did use a unified method which was harder to
1046   // follow and, as a result, it had subtle bugs that were hard to
1047   // track down. So keeping these two methods separate allows each to
1048   // be more readable. It will be good to keep these two in sync as
1049   // much as possible.
1050 
1051   assert_heap_not_locked_and_not_at_safepoint();
1052   assert(isHumongous(word_size), "attempt_allocation_humongous() "
1053          "should only be called for humongous allocations");
1054 
1055   // Humongous objects can exhaust the heap quickly, so we should check if we
1056   // need to start a marking cycle at each humongous object allocation. We do
1057   // the check before we do the actual allocation. The reason for doing it
1058   // before the allocation is that we avoid having to keep track of the newly
1059   // allocated memory while we do a GC.
1060   if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
1061                                            word_size)) {
1062     collect(GCCause::_g1_humongous_allocation);
1063   }
1064 
1065   // We will loop until a) we manage to successfully perform the
1066   // allocation or b) we successfully schedule a collection which
1067   // fails to perform the allocation. b) is the only case when we'll
1068   // return NULL.
1069   HeapWord* result = NULL;
1070   for (int try_count = 1; /* we'll return */; try_count += 1) {
1071     bool should_try_gc;
1072     unsigned int gc_count_before;
1073 
1074     {
1075       MutexLockerEx x(Heap_lock);
1076 
1077       // Given that humongous objects are not allocated in young
1078       // regions, we'll first try to do the allocation without doing a
1079       // collection hoping that there's enough space in the heap.
1080       result = humongous_obj_allocate(word_size);
1081       if (result != NULL) {
1082         return result;
1083       }
1084 
1085       if (GC_locker::is_active_and_needs_gc()) {
1086         should_try_gc = false;
1087       } else {
1088          // The GCLocker may not be active but the GCLocker initiated
1089         // GC may not yet have been performed (GCLocker::needs_gc()
1090         // returns true). In this case we do not try this GC and
1091         // wait until the GCLocker initiated GC is performed, and
1092         // then retry the allocation.
1093         if (GC_locker::needs_gc()) {
1094           should_try_gc = false;
1095         } else {
1096           // Read the GC count while still holding the Heap_lock.
1097           gc_count_before = total_collections();
1098           should_try_gc = true;
1099         }
1100       }
1101     }
1102 
1103     if (should_try_gc) {
1104       // If we failed to allocate the humongous object, we should try to
1105       // do a collection pause (if we're allowed) in case it reclaims
1106       // enough space for the allocation to succeed after the pause.
1107 
1108       bool succeeded;
1109       result = do_collection_pause(word_size, gc_count_before, &succeeded);
1110       if (result != NULL) {
1111         assert(succeeded, "only way to get back a non-NULL result");
1112         return result;
1113       }
1114 
1115       if (succeeded) {
1116         // If we get here we successfully scheduled a collection which
1117         // failed to allocate. No point in trying to allocate
1118         // further. We'll just return NULL.
1119         MutexLockerEx x(Heap_lock);
1120         *gc_count_before_ret = total_collections();
1121         return NULL;
1122       }
1123     } else {
1124       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1125         MutexLockerEx x(Heap_lock);
1126         *gc_count_before_ret = total_collections();
1127         return NULL;
1128       }
1129       // The GCLocker is either active or the GCLocker initiated
1130       // GC has not yet been performed. Stall until it is and
1131       // then retry the allocation.
1132       GC_locker::stall_until_clear();
1133       (*gclocker_retry_count_ret) += 1;
1134     }
1135 
1136     // We can reach here if we were unsuccessful in scheduling a
1137     // collection (because another thread beat us to it) or if we were
1138     // stalled due to the GC locker. In either can we should retry the
1139     // allocation attempt in case another thread successfully
1140     // performed a collection and reclaimed enough space.  Give a
1141     // warning if we seem to be looping forever.
1142 
1143     if ((QueuedAllocationWarningCount > 0) &&
1144         (try_count % QueuedAllocationWarningCount == 0)) {
1145       warning("G1CollectedHeap::attempt_allocation_humongous() "
1146               "retries %d times", try_count);
1147     }
1148   }
1149 
1150   ShouldNotReachHere();
1151   return NULL;
1152 }
1153 
1154 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1155                                        bool expect_null_mutator_alloc_region) {
1156   assert_at_safepoint(true /* should_be_vm_thread */);
1157   assert(_mutator_alloc_region.get() == NULL ||
1158                                              !expect_null_mutator_alloc_region,
1159          "the current alloc region was unexpectedly found to be non-NULL");
1160 
1161   if (!isHumongous(word_size)) {
1162     return _mutator_alloc_region.attempt_allocation_locked(word_size,
1163                                                       false /* bot_updates */);
1164   } else {
1165     HeapWord* result = humongous_obj_allocate(word_size);
1166     if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1167       g1_policy()->set_initiate_conc_mark_if_possible();
1168     }
1169     return result;
1170   }
1171 
1172   ShouldNotReachHere();
1173 }
1174 
1175 class PostMCRemSetClearClosure: public HeapRegionClosure {
1176   G1CollectedHeap* _g1h;
1177   ModRefBarrierSet* _mr_bs;
1178 public:
1179   PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1180     _g1h(g1h), _mr_bs(mr_bs) {}
1181 
1182   bool doHeapRegion(HeapRegion* r) {
1183     HeapRegionRemSet* hrrs = r->rem_set();
1184 
1185     if (r->continuesHumongous()) {
1186       // We'll assert that the strong code root list and RSet is empty
1187       assert(hrrs->strong_code_roots_list_length() == 0, "sanity");
1188       assert(hrrs->occupied() == 0, "RSet should be empty");
1189       return false;
1190     }
1191 
1192     _g1h->reset_gc_time_stamps(r);
1193     hrrs->clear();
1194     // You might think here that we could clear just the cards
1195     // corresponding to the used region.  But no: if we leave a dirty card
1196     // in a region we might allocate into, then it would prevent that card
1197     // from being enqueued, and cause it to be missed.
1198     // Re: the performance cost: we shouldn't be doing full GC anyway!
1199     _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1200 
1201     return false;
1202   }
1203 };
1204 
1205 void G1CollectedHeap::clear_rsets_post_compaction() {
1206   PostMCRemSetClearClosure rs_clear(this, mr_bs());
1207   heap_region_iterate(&rs_clear);
1208 }
1209 
1210 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1211   G1CollectedHeap*   _g1h;
1212   UpdateRSOopClosure _cl;
1213   int                _worker_i;
1214 public:
1215   RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1216     _cl(g1->g1_rem_set(), worker_i),
1217     _worker_i(worker_i),
1218     _g1h(g1)
1219   { }
1220 
1221   bool doHeapRegion(HeapRegion* r) {
1222     if (!r->continuesHumongous()) {
1223       _cl.set_from(r);
1224       r->oop_iterate(&_cl);
1225     }
1226     return false;
1227   }
1228 };
1229 
1230 class ParRebuildRSTask: public AbstractGangTask {
1231   G1CollectedHeap* _g1;
1232 public:
1233   ParRebuildRSTask(G1CollectedHeap* g1)
1234     : AbstractGangTask("ParRebuildRSTask"),
1235       _g1(g1)
1236   { }
1237 
1238   void work(uint worker_id) {
1239     RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1240     _g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id,
1241                                           _g1->workers()->active_workers(),
1242                                          HeapRegion::RebuildRSClaimValue);
1243   }
1244 };
1245 
1246 class PostCompactionPrinterClosure: public HeapRegionClosure {
1247 private:
1248   G1HRPrinter* _hr_printer;
1249 public:
1250   bool doHeapRegion(HeapRegion* hr) {
1251     assert(!hr->is_young(), "not expecting to find young regions");
1252     // We only generate output for non-empty regions.
1253     if (!hr->is_empty()) {
1254       if (!hr->isHumongous()) {
1255         _hr_printer->post_compaction(hr, G1HRPrinter::Old);
1256       } else if (hr->startsHumongous()) {
1257         if (hr->region_num() == 1) {
1258           // single humongous region
1259           _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
1260         } else {
1261           _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
1262         }
1263       } else {
1264         assert(hr->continuesHumongous(), "only way to get here");
1265         _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1266       }
1267     }
1268     return false;
1269   }
1270 
1271   PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1272     : _hr_printer(hr_printer) { }
1273 };
1274 
1275 void G1CollectedHeap::print_hrs_post_compaction() {
1276   PostCompactionPrinterClosure cl(hr_printer());
1277   heap_region_iterate(&cl);
1278 }
1279 
1280 bool G1CollectedHeap::do_collection(bool explicit_gc,
1281                                     bool clear_all_soft_refs,
1282                                     size_t word_size) {
1283   assert_at_safepoint(true /* should_be_vm_thread */);
1284 
1285   if (GC_locker::check_active_before_gc()) {
1286     return false;
1287   }
1288 
1289   STWGCTimer* gc_timer = G1MarkSweep::gc_timer();
1290   gc_timer->register_gc_start(os::elapsed_counter());
1291 
1292   SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer();
1293   gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start());
1294 
1295   SvcGCMarker sgcm(SvcGCMarker::FULL);
1296   ResourceMark rm;
1297 
1298   print_heap_before_gc();
1299   trace_heap_before_gc(gc_tracer);
1300 
1301   size_t metadata_prev_used = MetaspaceAux::allocated_used_bytes();
1302 
1303   HRSPhaseSetter x(HRSPhaseFullGC);
1304   verify_region_sets_optional();
1305 
1306   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1307                            collector_policy()->should_clear_all_soft_refs();
1308 
1309   ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1310 
1311   {
1312     IsGCActiveMark x;
1313 
1314     // Timing
1315     assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant");
1316     gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps);
1317     TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
1318 
1319     {
1320       GCTraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, NULL);
1321       TraceCollectorStats tcs(g1mm()->full_collection_counters());
1322       TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1323 
1324       double start = os::elapsedTime();
1325       g1_policy()->record_full_collection_start();
1326 
1327       // Note: When we have a more flexible GC logging framework that
1328       // allows us to add optional attributes to a GC log record we
1329       // could consider timing and reporting how long we wait in the
1330       // following two methods.
1331       wait_while_free_regions_coming();
1332       // If we start the compaction before the CM threads finish
1333       // scanning the root regions we might trip them over as we'll
1334       // be moving objects / updating references. So let's wait until
1335       // they are done. By telling them to abort, they should complete
1336       // early.
1337       _cm->root_regions()->abort();
1338       _cm->root_regions()->wait_until_scan_finished();
1339       append_secondary_free_list_if_not_empty_with_lock();
1340 
1341       gc_prologue(true);
1342       increment_total_collections(true /* full gc */);
1343       increment_old_marking_cycles_started();
1344 
1345       assert(used() == recalculate_used(), "Should be equal");
1346 
1347       verify_before_gc();
1348 
1349       pre_full_gc_dump(gc_timer);
1350 
1351       COMPILER2_PRESENT(DerivedPointerTable::clear());
1352 
1353       // Disable discovery and empty the discovered lists
1354       // for the CM ref processor.
1355       ref_processor_cm()->disable_discovery();
1356       ref_processor_cm()->abandon_partial_discovery();
1357       ref_processor_cm()->verify_no_references_recorded();
1358 
1359       // Abandon current iterations of concurrent marking and concurrent
1360       // refinement, if any are in progress. We have to do this before
1361       // wait_until_scan_finished() below.
1362       concurrent_mark()->abort();
1363 
1364       // Make sure we'll choose a new allocation region afterwards.
1365       release_mutator_alloc_region();
1366       abandon_gc_alloc_regions();
1367       g1_rem_set()->cleanupHRRS();
1368 
1369       // We should call this after we retire any currently active alloc
1370       // regions so that all the ALLOC / RETIRE events are generated
1371       // before the start GC event.
1372       _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1373 
1374       // We may have added regions to the current incremental collection
1375       // set between the last GC or pause and now. We need to clear the
1376       // incremental collection set and then start rebuilding it afresh
1377       // after this full GC.
1378       abandon_collection_set(g1_policy()->inc_cset_head());
1379       g1_policy()->clear_incremental_cset();
1380       g1_policy()->stop_incremental_cset_building();
1381 
1382       tear_down_region_sets(false /* free_list_only */);
1383       g1_policy()->set_gcs_are_young(true);
1384 
1385       // See the comments in g1CollectedHeap.hpp and
1386       // G1CollectedHeap::ref_processing_init() about
1387       // how reference processing currently works in G1.
1388 
1389       // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1390       ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1391 
1392       // Temporarily clear the STW ref processor's _is_alive_non_header field.
1393       ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1394 
1395       ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
1396       ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1397 
1398       // Do collection work
1399       {
1400         HandleMark hm;  // Discard invalid handles created during gc
1401         G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1402       }
1403 
1404       assert(free_regions() == 0, "we should not have added any free regions");
1405       rebuild_region_sets(false /* free_list_only */);
1406 
1407       // Enqueue any discovered reference objects that have
1408       // not been removed from the discovered lists.
1409       ref_processor_stw()->enqueue_discovered_references();
1410 
1411       COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1412 
1413       MemoryService::track_memory_usage();
1414 
1415       assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1416       ref_processor_stw()->verify_no_references_recorded();
1417 
1418       // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1419       ClassLoaderDataGraph::purge();
1420       MetaspaceAux::verify_metrics();
1421 
1422       // Note: since we've just done a full GC, concurrent
1423       // marking is no longer active. Therefore we need not
1424       // re-enable reference discovery for the CM ref processor.
1425       // That will be done at the start of the next marking cycle.
1426       assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1427       ref_processor_cm()->verify_no_references_recorded();
1428 
1429       reset_gc_time_stamp();
1430       // Since everything potentially moved, we will clear all remembered
1431       // sets, and clear all cards.  Later we will rebuild remembered
1432       // sets. We will also reset the GC time stamps of the regions.
1433       clear_rsets_post_compaction();
1434       check_gc_time_stamps();
1435 
1436       // Resize the heap if necessary.
1437       resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1438 
1439       if (_hr_printer.is_active()) {
1440         // We should do this after we potentially resize the heap so
1441         // that all the COMMIT / UNCOMMIT events are generated before
1442         // the end GC event.
1443 
1444         print_hrs_post_compaction();
1445         _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1446       }
1447 
1448       G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
1449       if (hot_card_cache->use_cache()) {
1450         hot_card_cache->reset_card_counts();
1451         hot_card_cache->reset_hot_cache();
1452       }
1453 
1454       // Rebuild remembered sets of all regions.
1455       if (G1CollectedHeap::use_parallel_gc_threads()) {
1456         uint n_workers =
1457           AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1458                                                   workers()->active_workers(),
1459                                                   Threads::number_of_non_daemon_threads());
1460         assert(UseDynamicNumberOfGCThreads ||
1461                n_workers == workers()->total_workers(),
1462                "If not dynamic should be using all the  workers");
1463         workers()->set_active_workers(n_workers);
1464         // Set parallel threads in the heap (_n_par_threads) only
1465         // before a parallel phase and always reset it to 0 after
1466         // the phase so that the number of parallel threads does
1467         // no get carried forward to a serial phase where there
1468         // may be code that is "possibly_parallel".
1469         set_par_threads(n_workers);
1470 
1471         ParRebuildRSTask rebuild_rs_task(this);
1472         assert(check_heap_region_claim_values(
1473                HeapRegion::InitialClaimValue), "sanity check");
1474         assert(UseDynamicNumberOfGCThreads ||
1475                workers()->active_workers() == workers()->total_workers(),
1476                "Unless dynamic should use total workers");
1477         // Use the most recent number of  active workers
1478         assert(workers()->active_workers() > 0,
1479                "Active workers not properly set");
1480         set_par_threads(workers()->active_workers());
1481         workers()->run_task(&rebuild_rs_task);
1482         set_par_threads(0);
1483         assert(check_heap_region_claim_values(
1484                HeapRegion::RebuildRSClaimValue), "sanity check");
1485         reset_heap_region_claim_values();
1486       } else {
1487         RebuildRSOutOfRegionClosure rebuild_rs(this);
1488         heap_region_iterate(&rebuild_rs);
1489       }
1490 
1491       // Rebuild the strong code root lists for each region
1492       rebuild_strong_code_roots();
1493 
1494       if (true) { // FIXME
1495         MetaspaceGC::compute_new_size();
1496       }
1497 
1498 #ifdef TRACESPINNING
1499       ParallelTaskTerminator::print_termination_counts();
1500 #endif
1501 
1502       // Discard all rset updates
1503       JavaThread::dirty_card_queue_set().abandon_logs();
1504       assert(!G1DeferredRSUpdate
1505              || (G1DeferredRSUpdate &&
1506                 (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any");
1507 
1508       _young_list->reset_sampled_info();
1509       // At this point there should be no regions in the
1510       // entire heap tagged as young.
1511       assert(check_young_list_empty(true /* check_heap */),
1512              "young list should be empty at this point");
1513 
1514       // Update the number of full collections that have been completed.
1515       increment_old_marking_cycles_completed(false /* concurrent */);
1516 
1517       _hrs.verify_optional();
1518       verify_region_sets_optional();
1519 
1520       verify_after_gc();
1521 
1522       // Start a new incremental collection set for the next pause
1523       assert(g1_policy()->collection_set() == NULL, "must be");
1524       g1_policy()->start_incremental_cset_building();
1525 
1526       // Clear the _cset_fast_test bitmap in anticipation of adding
1527       // regions to the incremental collection set for the next
1528       // evacuation pause.
1529       clear_cset_fast_test();
1530 
1531       init_mutator_alloc_region();
1532 
1533       double end = os::elapsedTime();
1534       g1_policy()->record_full_collection_end();
1535 
1536       if (G1Log::fine()) {
1537         g1_policy()->print_heap_transition();
1538       }
1539 
1540       // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1541       // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1542       // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1543       // before any GC notifications are raised.
1544       g1mm()->update_sizes();
1545 
1546       gc_epilogue(true);
1547     }
1548 
1549     if (G1Log::finer()) {
1550       g1_policy()->print_detailed_heap_transition(true /* full */);
1551     }
1552 
1553     print_heap_after_gc();
1554     trace_heap_after_gc(gc_tracer);
1555 
1556     post_full_gc_dump(gc_timer);
1557 
1558     gc_timer->register_gc_end(os::elapsed_counter());
1559     gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
1560   }
1561 
1562   return true;
1563 }
1564 
1565 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1566   // do_collection() will return whether it succeeded in performing
1567   // the GC. Currently, there is no facility on the
1568   // do_full_collection() API to notify the caller than the collection
1569   // did not succeed (e.g., because it was locked out by the GC
1570   // locker). So, right now, we'll ignore the return value.
1571   bool dummy = do_collection(true,                /* explicit_gc */
1572                              clear_all_soft_refs,
1573                              0                    /* word_size */);
1574 }
1575 
1576 // This code is mostly copied from TenuredGeneration.
1577 void
1578 G1CollectedHeap::
1579 resize_if_necessary_after_full_collection(size_t word_size) {
1580   assert(MinHeapFreeRatio <= MaxHeapFreeRatio, "sanity check");
1581 
1582   // Include the current allocation, if any, and bytes that will be
1583   // pre-allocated to support collections, as "used".
1584   const size_t used_after_gc = used();
1585   const size_t capacity_after_gc = capacity();
1586   const size_t free_after_gc = capacity_after_gc - used_after_gc;
1587 
1588   // This is enforced in arguments.cpp.
1589   assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1590          "otherwise the code below doesn't make sense");
1591 
1592   // We don't have floating point command-line arguments
1593   const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1594   const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1595   const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1596   const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1597 
1598   const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1599   const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1600 
1601   // We have to be careful here as these two calculations can overflow
1602   // 32-bit size_t's.
1603   double used_after_gc_d = (double) used_after_gc;
1604   double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1605   double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1606 
1607   // Let's make sure that they are both under the max heap size, which
1608   // by default will make them fit into a size_t.
1609   double desired_capacity_upper_bound = (double) max_heap_size;
1610   minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1611                                     desired_capacity_upper_bound);
1612   maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1613                                     desired_capacity_upper_bound);
1614 
1615   // We can now safely turn them into size_t's.
1616   size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1617   size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1618 
1619   // This assert only makes sense here, before we adjust them
1620   // with respect to the min and max heap size.
1621   assert(minimum_desired_capacity <= maximum_desired_capacity,
1622          err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1623                  "maximum_desired_capacity = "SIZE_FORMAT,
1624                  minimum_desired_capacity, maximum_desired_capacity));
1625 
1626   // Should not be greater than the heap max size. No need to adjust
1627   // it with respect to the heap min size as it's a lower bound (i.e.,
1628   // we'll try to make the capacity larger than it, not smaller).
1629   minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1630   // Should not be less than the heap min size. No need to adjust it
1631   // with respect to the heap max size as it's an upper bound (i.e.,
1632   // we'll try to make the capacity smaller than it, not greater).
1633   maximum_desired_capacity =  MAX2(maximum_desired_capacity, min_heap_size);
1634 
1635   if (capacity_after_gc < minimum_desired_capacity) {
1636     // Don't expand unless it's significant
1637     size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1638     ergo_verbose4(ErgoHeapSizing,
1639                   "attempt heap expansion",
1640                   ergo_format_reason("capacity lower than "
1641                                      "min desired capacity after Full GC")
1642                   ergo_format_byte("capacity")
1643                   ergo_format_byte("occupancy")
1644                   ergo_format_byte_perc("min desired capacity"),
1645                   capacity_after_gc, used_after_gc,
1646                   minimum_desired_capacity, (double) MinHeapFreeRatio);
1647     expand(expand_bytes);
1648 
1649     // No expansion, now see if we want to shrink
1650   } else if (capacity_after_gc > maximum_desired_capacity) {
1651     // Capacity too large, compute shrinking size
1652     size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1653     ergo_verbose4(ErgoHeapSizing,
1654                   "attempt heap shrinking",
1655                   ergo_format_reason("capacity higher than "
1656                                      "max desired capacity after Full GC")
1657                   ergo_format_byte("capacity")
1658                   ergo_format_byte("occupancy")
1659                   ergo_format_byte_perc("max desired capacity"),
1660                   capacity_after_gc, used_after_gc,
1661                   maximum_desired_capacity, (double) MaxHeapFreeRatio);
1662     shrink(shrink_bytes);
1663   }
1664 }
1665 
1666 
1667 HeapWord*
1668 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1669                                            bool* succeeded) {
1670   assert_at_safepoint(true /* should_be_vm_thread */);
1671 
1672   *succeeded = true;
1673   // Let's attempt the allocation first.
1674   HeapWord* result =
1675     attempt_allocation_at_safepoint(word_size,
1676                                  false /* expect_null_mutator_alloc_region */);
1677   if (result != NULL) {
1678     assert(*succeeded, "sanity");
1679     return result;
1680   }
1681 
1682   // In a G1 heap, we're supposed to keep allocation from failing by
1683   // incremental pauses.  Therefore, at least for now, we'll favor
1684   // expansion over collection.  (This might change in the future if we can
1685   // do something smarter than full collection to satisfy a failed alloc.)
1686   result = expand_and_allocate(word_size);
1687   if (result != NULL) {
1688     assert(*succeeded, "sanity");
1689     return result;
1690   }
1691 
1692   // Expansion didn't work, we'll try to do a Full GC.
1693   bool gc_succeeded = do_collection(false, /* explicit_gc */
1694                                     false, /* clear_all_soft_refs */
1695                                     word_size);
1696   if (!gc_succeeded) {
1697     *succeeded = false;
1698     return NULL;
1699   }
1700 
1701   // Retry the allocation
1702   result = attempt_allocation_at_safepoint(word_size,
1703                                   true /* expect_null_mutator_alloc_region */);
1704   if (result != NULL) {
1705     assert(*succeeded, "sanity");
1706     return result;
1707   }
1708 
1709   // Then, try a Full GC that will collect all soft references.
1710   gc_succeeded = do_collection(false, /* explicit_gc */
1711                                true,  /* clear_all_soft_refs */
1712                                word_size);
1713   if (!gc_succeeded) {
1714     *succeeded = false;
1715     return NULL;
1716   }
1717 
1718   // Retry the allocation once more
1719   result = attempt_allocation_at_safepoint(word_size,
1720                                   true /* expect_null_mutator_alloc_region */);
1721   if (result != NULL) {
1722     assert(*succeeded, "sanity");
1723     return result;
1724   }
1725 
1726   assert(!collector_policy()->should_clear_all_soft_refs(),
1727          "Flag should have been handled and cleared prior to this point");
1728 
1729   // What else?  We might try synchronous finalization later.  If the total
1730   // space available is large enough for the allocation, then a more
1731   // complete compaction phase than we've tried so far might be
1732   // appropriate.
1733   assert(*succeeded, "sanity");
1734   return NULL;
1735 }
1736 
1737 // Attempting to expand the heap sufficiently
1738 // to support an allocation of the given "word_size".  If
1739 // successful, perform the allocation and return the address of the
1740 // allocated block, or else "NULL".
1741 
1742 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1743   assert_at_safepoint(true /* should_be_vm_thread */);
1744 
1745   verify_region_sets_optional();
1746 
1747   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1748   ergo_verbose1(ErgoHeapSizing,
1749                 "attempt heap expansion",
1750                 ergo_format_reason("allocation request failed")
1751                 ergo_format_byte("allocation request"),
1752                 word_size * HeapWordSize);
1753   if (expand(expand_bytes)) {
1754     _hrs.verify_optional();
1755     verify_region_sets_optional();
1756     return attempt_allocation_at_safepoint(word_size,
1757                                  false /* expect_null_mutator_alloc_region */);
1758   }
1759   return NULL;
1760 }
1761 
1762 void G1CollectedHeap::update_committed_space(HeapWord* old_end,
1763                                              HeapWord* new_end) {
1764   assert(old_end != new_end, "don't call this otherwise");
1765   assert((HeapWord*) _g1_storage.high() == new_end, "invariant");
1766 
1767   // Update the committed mem region.
1768   _g1_committed.set_end(new_end);
1769   // Tell the card table about the update.
1770   Universe::heap()->barrier_set()->resize_covered_region(_g1_committed);
1771   // Tell the BOT about the update.
1772   _bot_shared->resize(_g1_committed.word_size());
1773   // Tell the hot card cache about the update
1774   _cg1r->hot_card_cache()->resize_card_counts(capacity());
1775 }
1776 
1777 bool G1CollectedHeap::expand(size_t expand_bytes) {
1778   size_t old_mem_size = _g1_storage.committed_size();
1779   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1780   aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1781                                        HeapRegion::GrainBytes);
1782   ergo_verbose2(ErgoHeapSizing,
1783                 "expand the heap",
1784                 ergo_format_byte("requested expansion amount")
1785                 ergo_format_byte("attempted expansion amount"),
1786                 expand_bytes, aligned_expand_bytes);
1787 
1788   // First commit the memory.
1789   HeapWord* old_end = (HeapWord*) _g1_storage.high();
1790   bool successful = _g1_storage.expand_by(aligned_expand_bytes);
1791   if (successful) {
1792     // Then propagate this update to the necessary data structures.
1793     HeapWord* new_end = (HeapWord*) _g1_storage.high();
1794     update_committed_space(old_end, new_end);
1795 
1796     FreeRegionList expansion_list("Local Expansion List");
1797     MemRegion mr = _hrs.expand_by(old_end, new_end, &expansion_list);
1798     assert(mr.start() == old_end, "post-condition");
1799     // mr might be a smaller region than what was requested if
1800     // expand_by() was unable to allocate the HeapRegion instances
1801     assert(mr.end() <= new_end, "post-condition");
1802 
1803     size_t actual_expand_bytes = mr.byte_size();
1804     assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1805     assert(actual_expand_bytes == expansion_list.total_capacity_bytes(),
1806            "post-condition");
1807     if (actual_expand_bytes < aligned_expand_bytes) {
1808       // We could not expand _hrs to the desired size. In this case we
1809       // need to shrink the committed space accordingly.
1810       assert(mr.end() < new_end, "invariant");
1811 
1812       size_t diff_bytes = aligned_expand_bytes - actual_expand_bytes;
1813       // First uncommit the memory.
1814       _g1_storage.shrink_by(diff_bytes);
1815       // Then propagate this update to the necessary data structures.
1816       update_committed_space(new_end, mr.end());
1817     }
1818     _free_list.add_as_tail(&expansion_list);
1819 
1820     if (_hr_printer.is_active()) {
1821       HeapWord* curr = mr.start();
1822       while (curr < mr.end()) {
1823         HeapWord* curr_end = curr + HeapRegion::GrainWords;
1824         _hr_printer.commit(curr, curr_end);
1825         curr = curr_end;
1826       }
1827       assert(curr == mr.end(), "post-condition");
1828     }
1829     g1_policy()->record_new_heap_size(n_regions());
1830   } else {
1831     ergo_verbose0(ErgoHeapSizing,
1832                   "did not expand the heap",
1833                   ergo_format_reason("heap expansion operation failed"));
1834     // The expansion of the virtual storage space was unsuccessful.
1835     // Let's see if it was because we ran out of swap.
1836     if (G1ExitOnExpansionFailure &&
1837         _g1_storage.uncommitted_size() >= aligned_expand_bytes) {
1838       // We had head room...
1839       vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1840     }
1841   }
1842   return successful;
1843 }
1844 
1845 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1846   size_t old_mem_size = _g1_storage.committed_size();
1847   size_t aligned_shrink_bytes =
1848     ReservedSpace::page_align_size_down(shrink_bytes);
1849   aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1850                                          HeapRegion::GrainBytes);
1851   uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1852 
1853   uint num_regions_removed = _hrs.shrink_by(num_regions_to_remove);
1854   HeapWord* old_end = (HeapWord*) _g1_storage.high();
1855   size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1856 
1857   ergo_verbose3(ErgoHeapSizing,
1858                 "shrink the heap",
1859                 ergo_format_byte("requested shrinking amount")
1860                 ergo_format_byte("aligned shrinking amount")
1861                 ergo_format_byte("attempted shrinking amount"),
1862                 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1863   if (num_regions_removed > 0) {
1864     _g1_storage.shrink_by(shrunk_bytes);
1865     HeapWord* new_end = (HeapWord*) _g1_storage.high();
1866 
1867     if (_hr_printer.is_active()) {
1868       HeapWord* curr = old_end;
1869       while (curr > new_end) {
1870         HeapWord* curr_end = curr;
1871         curr -= HeapRegion::GrainWords;
1872         _hr_printer.uncommit(curr, curr_end);
1873       }
1874     }
1875 
1876     _expansion_regions += num_regions_removed;
1877     update_committed_space(old_end, new_end);
1878     HeapRegionRemSet::shrink_heap(n_regions());
1879     g1_policy()->record_new_heap_size(n_regions());
1880   } else {
1881     ergo_verbose0(ErgoHeapSizing,
1882                   "did not shrink the heap",
1883                   ergo_format_reason("heap shrinking operation failed"));
1884   }
1885 }
1886 
1887 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1888   verify_region_sets_optional();
1889 
1890   // We should only reach here at the end of a Full GC which means we
1891   // should not not be holding to any GC alloc regions. The method
1892   // below will make sure of that and do any remaining clean up.
1893   abandon_gc_alloc_regions();
1894 
1895   // Instead of tearing down / rebuilding the free lists here, we
1896   // could instead use the remove_all_pending() method on free_list to
1897   // remove only the ones that we need to remove.
1898   tear_down_region_sets(true /* free_list_only */);
1899   shrink_helper(shrink_bytes);
1900   rebuild_region_sets(true /* free_list_only */);
1901 
1902   _hrs.verify_optional();
1903   verify_region_sets_optional();
1904 }
1905 
1906 // Public methods.
1907 
1908 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1909 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1910 #endif // _MSC_VER
1911 
1912 
1913 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1914   SharedHeap(policy_),
1915   _g1_policy(policy_),
1916   _dirty_card_queue_set(false),
1917   _into_cset_dirty_card_queue_set(false),
1918   _is_alive_closure_cm(this),
1919   _is_alive_closure_stw(this),
1920   _ref_processor_cm(NULL),
1921   _ref_processor_stw(NULL),
1922   _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
1923   _bot_shared(NULL),
1924   _evac_failure_scan_stack(NULL),
1925   _mark_in_progress(false),
1926   _cg1r(NULL), _summary_bytes_used(0),
1927   _g1mm(NULL),
1928   _refine_cte_cl(NULL),
1929   _full_collection(false),
1930   _free_list("Master Free List"),
1931   _secondary_free_list("Secondary Free List"),
1932   _old_set("Old Set"),
1933   _humongous_set("Master Humongous Set"),
1934   _free_regions_coming(false),
1935   _young_list(new YoungList(this)),
1936   _gc_time_stamp(0),
1937   _retained_old_gc_alloc_region(NULL),
1938   _survivor_plab_stats(YoungPLABSize, PLABWeight),
1939   _old_plab_stats(OldPLABSize, PLABWeight),
1940   _expand_heap_after_alloc_failure(true),
1941   _surviving_young_words(NULL),
1942   _old_marking_cycles_started(0),
1943   _old_marking_cycles_completed(0),
1944   _concurrent_cycle_started(false),
1945   _in_cset_fast_test(NULL),
1946   _in_cset_fast_test_base(NULL),
1947   _dirty_cards_region_list(NULL),
1948   _worker_cset_start_region(NULL),
1949   _worker_cset_start_region_time_stamp(NULL),
1950   _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1951   _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
1952   _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1953   _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) {
1954 
1955   _g1h = this;
1956   if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
1957     vm_exit_during_initialization("Failed necessary allocation.");
1958   }
1959 
1960   _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1961 
1962   int n_queues = MAX2((int)ParallelGCThreads, 1);
1963   _task_queues = new RefToScanQueueSet(n_queues);
1964 
1965   int n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1966   assert(n_rem_sets > 0, "Invariant.");
1967 
1968   _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1969   _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC);
1970   _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1971 
1972   for (int i = 0; i < n_queues; i++) {
1973     RefToScanQueue* q = new RefToScanQueue();
1974     q->initialize();
1975     _task_queues->register_queue(i, q);
1976     ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1977   }
1978   clear_cset_start_regions();
1979 
1980   // Initialize the G1EvacuationFailureALot counters and flags.
1981   NOT_PRODUCT(reset_evacuation_should_fail();)
1982 
1983   guarantee(_task_queues != NULL, "task_queues allocation failure.");
1984 }
1985 
1986 jint G1CollectedHeap::initialize() {
1987   CollectedHeap::pre_initialize();
1988   os::enable_vtime();
1989 
1990   G1Log::init();
1991 
1992   // Necessary to satisfy locking discipline assertions.
1993 
1994   MutexLocker x(Heap_lock);
1995 
1996   // We have to initialize the printer before committing the heap, as
1997   // it will be used then.
1998   _hr_printer.set_active(G1PrintHeapRegions);
1999 
2000   // While there are no constraints in the GC code that HeapWordSize
2001   // be any particular value, there are multiple other areas in the
2002   // system which believe this to be true (e.g. oop->object_size in some
2003   // cases incorrectly returns the size in wordSize units rather than
2004   // HeapWordSize).
2005   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
2006 
2007   size_t init_byte_size = collector_policy()->initial_heap_byte_size();
2008   size_t max_byte_size = collector_policy()->max_heap_byte_size();
2009 
2010   // Ensure that the sizes are properly aligned.
2011   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
2012   Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
2013 
2014   _cg1r = new ConcurrentG1Refine(this);
2015 
2016   // Reserve the maximum.
2017 
2018   // When compressed oops are enabled, the preferred heap base
2019   // is calculated by subtracting the requested size from the
2020   // 32Gb boundary and using the result as the base address for
2021   // heap reservation. If the requested size is not aligned to
2022   // HeapRegion::GrainBytes (i.e. the alignment that is passed
2023   // into the ReservedHeapSpace constructor) then the actual
2024   // base of the reserved heap may end up differing from the
2025   // address that was requested (i.e. the preferred heap base).
2026   // If this happens then we could end up using a non-optimal
2027   // compressed oops mode.
2028 
2029   // Since max_byte_size is aligned to the size of a heap region (checked
2030   // above).
2031   Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
2032 
2033   ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
2034                                                  HeapRegion::GrainBytes);
2035 
2036   // It is important to do this in a way such that concurrent readers can't
2037   // temporarily think something is in the heap.  (I've actually seen this
2038   // happen in asserts: DLD.)
2039   _reserved.set_word_size(0);
2040   _reserved.set_start((HeapWord*)heap_rs.base());
2041   _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size()));
2042 
2043   _expansion_regions = (uint) (max_byte_size / HeapRegion::GrainBytes);
2044 
2045   // Create the gen rem set (and barrier set) for the entire reserved region.
2046   _rem_set = collector_policy()->create_rem_set(_reserved, 2);
2047   set_barrier_set(rem_set()->bs());
2048   if (barrier_set()->is_a(BarrierSet::ModRef)) {
2049     _mr_bs = (ModRefBarrierSet*)_barrier_set;
2050   } else {
2051     vm_exit_during_initialization("G1 requires a mod ref bs.");
2052     return JNI_ENOMEM;
2053   }
2054 
2055   // Also create a G1 rem set.
2056   if (mr_bs()->is_a(BarrierSet::CardTableModRef)) {
2057     _g1_rem_set = new G1RemSet(this, (CardTableModRefBS*)mr_bs());
2058   } else {
2059     vm_exit_during_initialization("G1 requires a cardtable mod ref bs.");
2060     return JNI_ENOMEM;
2061   }
2062 
2063   // Carve out the G1 part of the heap.
2064 
2065   ReservedSpace g1_rs   = heap_rs.first_part(max_byte_size);
2066   _g1_reserved = MemRegion((HeapWord*)g1_rs.base(),
2067                            g1_rs.size()/HeapWordSize);
2068 
2069   _g1_storage.initialize(g1_rs, 0);
2070   _g1_committed = MemRegion((HeapWord*)_g1_storage.low(), (size_t) 0);
2071   _hrs.initialize((HeapWord*) _g1_reserved.start(),
2072                   (HeapWord*) _g1_reserved.end(),
2073                   _expansion_regions);
2074 
2075   // Do later initialization work for concurrent refinement.
2076   _cg1r->init();
2077 
2078   // 6843694 - ensure that the maximum region index can fit
2079   // in the remembered set structures.
2080   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
2081   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
2082 
2083   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
2084   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
2085   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
2086             "too many cards per region");
2087 
2088   HeapRegionSet::set_unrealistically_long_length(max_regions() + 1);
2089 
2090   _bot_shared = new G1BlockOffsetSharedArray(_reserved,
2091                                              heap_word_size(init_byte_size));
2092 
2093   _g1h = this;
2094 
2095   _in_cset_fast_test_length = max_regions();
2096   _in_cset_fast_test_base =
2097                    NEW_C_HEAP_ARRAY(bool, (size_t) _in_cset_fast_test_length, mtGC);
2098 
2099   // We're biasing _in_cset_fast_test to avoid subtracting the
2100   // beginning of the heap every time we want to index; basically
2101   // it's the same with what we do with the card table.
2102   _in_cset_fast_test = _in_cset_fast_test_base -
2103                ((uintx) _g1_reserved.start() >> HeapRegion::LogOfHRGrainBytes);
2104 
2105   // Clear the _cset_fast_test bitmap in anticipation of adding
2106   // regions to the incremental collection set for the first
2107   // evacuation pause.
2108   clear_cset_fast_test();
2109 
2110   // Create the ConcurrentMark data structure and thread.
2111   // (Must do this late, so that "max_regions" is defined.)
2112   _cm = new ConcurrentMark(this, heap_rs);
2113   if (_cm == NULL || !_cm->completed_initialization()) {
2114     vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark");
2115     return JNI_ENOMEM;
2116   }
2117   _cmThread = _cm->cmThread();
2118 
2119   // Initialize the from_card cache structure of HeapRegionRemSet.
2120   HeapRegionRemSet::init_heap(max_regions());
2121 
2122   // Now expand into the initial heap size.
2123   if (!expand(init_byte_size)) {
2124     vm_shutdown_during_initialization("Failed to allocate initial heap.");
2125     return JNI_ENOMEM;
2126   }
2127 
2128   // Perform any initialization actions delegated to the policy.
2129   g1_policy()->init();
2130 
2131   _refine_cte_cl =
2132     new RefineCardTableEntryClosure(ConcurrentG1RefineThread::sts(),
2133                                     g1_rem_set(),
2134                                     concurrent_g1_refine());
2135   JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
2136 
2137   JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
2138                                                SATB_Q_FL_lock,
2139                                                G1SATBProcessCompletedThreshold,
2140                                                Shared_SATB_Q_lock);
2141 
2142   JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
2143                                                 DirtyCardQ_FL_lock,
2144                                                 concurrent_g1_refine()->yellow_zone(),
2145                                                 concurrent_g1_refine()->red_zone(),
2146                                                 Shared_DirtyCardQ_lock);
2147 
2148   if (G1DeferredRSUpdate) {
2149     dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
2150                                       DirtyCardQ_FL_lock,
2151                                       -1, // never trigger processing
2152                                       -1, // no limit on length
2153                                       Shared_DirtyCardQ_lock,
2154                                       &JavaThread::dirty_card_queue_set());
2155   }
2156 
2157   // Initialize the card queue set used to hold cards containing
2158   // references into the collection set.
2159   _into_cset_dirty_card_queue_set.initialize(DirtyCardQ_CBL_mon,
2160                                              DirtyCardQ_FL_lock,
2161                                              -1, // never trigger processing
2162                                              -1, // no limit on length
2163                                              Shared_DirtyCardQ_lock,
2164                                              &JavaThread::dirty_card_queue_set());
2165 
2166   // In case we're keeping closure specialization stats, initialize those
2167   // counts and that mechanism.
2168   SpecializationStats::clear();
2169 
2170   // Here we allocate the dummy full region that is required by the
2171   // G1AllocRegion class. If we don't pass an address in the reserved
2172   // space here, lots of asserts fire.
2173 
2174   HeapRegion* dummy_region = new_heap_region(0 /* index of bottom region */,
2175                                              _g1_reserved.start());
2176   // We'll re-use the same region whether the alloc region will
2177   // require BOT updates or not and, if it doesn't, then a non-young
2178   // region will complain that it cannot support allocations without
2179   // BOT updates. So we'll tag the dummy region as young to avoid that.
2180   dummy_region->set_young();
2181   // Make sure it's full.
2182   dummy_region->set_top(dummy_region->end());
2183   G1AllocRegion::setup(this, dummy_region);
2184 
2185   init_mutator_alloc_region();
2186 
2187   // Do create of the monitoring and management support so that
2188   // values in the heap have been properly initialized.
2189   _g1mm = new G1MonitoringSupport(this);
2190 
2191   return JNI_OK;
2192 }
2193 
2194 void G1CollectedHeap::ref_processing_init() {
2195   // Reference processing in G1 currently works as follows:
2196   //
2197   // * There are two reference processor instances. One is
2198   //   used to record and process discovered references
2199   //   during concurrent marking; the other is used to
2200   //   record and process references during STW pauses
2201   //   (both full and incremental).
2202   // * Both ref processors need to 'span' the entire heap as
2203   //   the regions in the collection set may be dotted around.
2204   //
2205   // * For the concurrent marking ref processor:
2206   //   * Reference discovery is enabled at initial marking.
2207   //   * Reference discovery is disabled and the discovered
2208   //     references processed etc during remarking.
2209   //   * Reference discovery is MT (see below).
2210   //   * Reference discovery requires a barrier (see below).
2211   //   * Reference processing may or may not be MT
2212   //     (depending on the value of ParallelRefProcEnabled
2213   //     and ParallelGCThreads).
2214   //   * A full GC disables reference discovery by the CM
2215   //     ref processor and abandons any entries on it's
2216   //     discovered lists.
2217   //
2218   // * For the STW processor:
2219   //   * Non MT discovery is enabled at the start of a full GC.
2220   //   * Processing and enqueueing during a full GC is non-MT.
2221   //   * During a full GC, references are processed after marking.
2222   //
2223   //   * Discovery (may or may not be MT) is enabled at the start
2224   //     of an incremental evacuation pause.
2225   //   * References are processed near the end of a STW evacuation pause.
2226   //   * For both types of GC:
2227   //     * Discovery is atomic - i.e. not concurrent.
2228   //     * Reference discovery will not need a barrier.
2229 
2230   SharedHeap::ref_processing_init();
2231   MemRegion mr = reserved_region();
2232 
2233   // Concurrent Mark ref processor
2234   _ref_processor_cm =
2235     new ReferenceProcessor(mr,    // span
2236                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2237                                 // mt processing
2238                            (int) ParallelGCThreads,
2239                                 // degree of mt processing
2240                            (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2241                                 // mt discovery
2242                            (int) MAX2(ParallelGCThreads, ConcGCThreads),
2243                                 // degree of mt discovery
2244                            false,
2245                                 // Reference discovery is not atomic
2246                            &_is_alive_closure_cm,
2247                                 // is alive closure
2248                                 // (for efficiency/performance)
2249                            true);
2250                                 // Setting next fields of discovered
2251                                 // lists requires a barrier.
2252 
2253   // STW ref processor
2254   _ref_processor_stw =
2255     new ReferenceProcessor(mr,    // span
2256                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2257                                 // mt processing
2258                            MAX2((int)ParallelGCThreads, 1),
2259                                 // degree of mt processing
2260                            (ParallelGCThreads > 1),
2261                                 // mt discovery
2262                            MAX2((int)ParallelGCThreads, 1),
2263                                 // degree of mt discovery
2264                            true,
2265                                 // Reference discovery is atomic
2266                            &_is_alive_closure_stw,
2267                                 // is alive closure
2268                                 // (for efficiency/performance)
2269                            false);
2270                                 // Setting next fields of discovered
2271                                 // lists requires a barrier.
2272 }
2273 
2274 size_t G1CollectedHeap::capacity() const {
2275   return _g1_committed.byte_size();
2276 }
2277 
2278 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2279   assert(!hr->continuesHumongous(), "pre-condition");
2280   hr->reset_gc_time_stamp();
2281   if (hr->startsHumongous()) {
2282     uint first_index = hr->hrs_index() + 1;
2283     uint last_index = hr->last_hc_index();
2284     for (uint i = first_index; i < last_index; i += 1) {
2285       HeapRegion* chr = region_at(i);
2286       assert(chr->continuesHumongous(), "sanity");
2287       chr->reset_gc_time_stamp();
2288     }
2289   }
2290 }
2291 
2292 #ifndef PRODUCT
2293 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2294 private:
2295   unsigned _gc_time_stamp;
2296   bool _failures;
2297 
2298 public:
2299   CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2300     _gc_time_stamp(gc_time_stamp), _failures(false) { }
2301 
2302   virtual bool doHeapRegion(HeapRegion* hr) {
2303     unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2304     if (_gc_time_stamp != region_gc_time_stamp) {
2305       gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, "
2306                              "expected %d", HR_FORMAT_PARAMS(hr),
2307                              region_gc_time_stamp, _gc_time_stamp);
2308       _failures = true;
2309     }
2310     return false;
2311   }
2312 
2313   bool failures() { return _failures; }
2314 };
2315 
2316 void G1CollectedHeap::check_gc_time_stamps() {
2317   CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2318   heap_region_iterate(&cl);
2319   guarantee(!cl.failures(), "all GC time stamps should have been reset");
2320 }
2321 #endif // PRODUCT
2322 
2323 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2324                                                  DirtyCardQueue* into_cset_dcq,
2325                                                  bool concurrent,
2326                                                  int worker_i) {
2327   // Clean cards in the hot card cache
2328   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
2329   hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq);
2330 
2331   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2332   int n_completed_buffers = 0;
2333   while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2334     n_completed_buffers++;
2335   }
2336   g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers);
2337   dcqs.clear_n_completed_buffers();
2338   assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2339 }
2340 
2341 
2342 // Computes the sum of the storage used by the various regions.
2343 
2344 size_t G1CollectedHeap::used() const {
2345   assert(Heap_lock->owner() != NULL,
2346          "Should be owned on this thread's behalf.");
2347   size_t result = _summary_bytes_used;
2348   // Read only once in case it is set to NULL concurrently
2349   HeapRegion* hr = _mutator_alloc_region.get();
2350   if (hr != NULL)
2351     result += hr->used();
2352   return result;
2353 }
2354 
2355 size_t G1CollectedHeap::used_unlocked() const {
2356   size_t result = _summary_bytes_used;
2357   return result;
2358 }
2359 
2360 class SumUsedClosure: public HeapRegionClosure {
2361   size_t _used;
2362 public:
2363   SumUsedClosure() : _used(0) {}
2364   bool doHeapRegion(HeapRegion* r) {
2365     if (!r->continuesHumongous()) {
2366       _used += r->used();
2367     }
2368     return false;
2369   }
2370   size_t result() { return _used; }
2371 };
2372 
2373 size_t G1CollectedHeap::recalculate_used() const {
2374   SumUsedClosure blk;
2375   heap_region_iterate(&blk);
2376   return blk.result();
2377 }
2378 
2379 size_t G1CollectedHeap::unsafe_max_alloc() {
2380   if (free_regions() > 0) return HeapRegion::GrainBytes;
2381   // otherwise, is there space in the current allocation region?
2382 
2383   // We need to store the current allocation region in a local variable
2384   // here. The problem is that this method doesn't take any locks and
2385   // there may be other threads which overwrite the current allocation
2386   // region field. attempt_allocation(), for example, sets it to NULL
2387   // and this can happen *after* the NULL check here but before the call
2388   // to free(), resulting in a SIGSEGV. Note that this doesn't appear
2389   // to be a problem in the optimized build, since the two loads of the
2390   // current allocation region field are optimized away.
2391   HeapRegion* hr = _mutator_alloc_region.get();
2392   if (hr == NULL) {
2393     return 0;
2394   }
2395   return hr->free();
2396 }
2397 
2398 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2399   switch (cause) {
2400     case GCCause::_gc_locker:               return GCLockerInvokesConcurrent;
2401     case GCCause::_java_lang_system_gc:     return ExplicitGCInvokesConcurrent;
2402     case GCCause::_g1_humongous_allocation: return true;
2403     default:                                return false;
2404   }
2405 }
2406 
2407 #ifndef PRODUCT
2408 void G1CollectedHeap::allocate_dummy_regions() {
2409   // Let's fill up most of the region
2410   size_t word_size = HeapRegion::GrainWords - 1024;
2411   // And as a result the region we'll allocate will be humongous.
2412   guarantee(isHumongous(word_size), "sanity");
2413 
2414   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2415     // Let's use the existing mechanism for the allocation
2416     HeapWord* dummy_obj = humongous_obj_allocate(word_size);
2417     if (dummy_obj != NULL) {
2418       MemRegion mr(dummy_obj, word_size);
2419       CollectedHeap::fill_with_object(mr);
2420     } else {
2421       // If we can't allocate once, we probably cannot allocate
2422       // again. Let's get out of the loop.
2423       break;
2424     }
2425   }
2426 }
2427 #endif // !PRODUCT
2428 
2429 void G1CollectedHeap::increment_old_marking_cycles_started() {
2430   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2431     _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2432     err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2433     _old_marking_cycles_started, _old_marking_cycles_completed));
2434 
2435   _old_marking_cycles_started++;
2436 }
2437 
2438 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2439   MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2440 
2441   // We assume that if concurrent == true, then the caller is a
2442   // concurrent thread that was joined the Suspendible Thread
2443   // Set. If there's ever a cheap way to check this, we should add an
2444   // assert here.
2445 
2446   // Given that this method is called at the end of a Full GC or of a
2447   // concurrent cycle, and those can be nested (i.e., a Full GC can
2448   // interrupt a concurrent cycle), the number of full collections
2449   // completed should be either one (in the case where there was no
2450   // nesting) or two (when a Full GC interrupted a concurrent cycle)
2451   // behind the number of full collections started.
2452 
2453   // This is the case for the inner caller, i.e. a Full GC.
2454   assert(concurrent ||
2455          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2456          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2457          err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
2458                  "is inconsistent with _old_marking_cycles_completed = %u",
2459                  _old_marking_cycles_started, _old_marking_cycles_completed));
2460 
2461   // This is the case for the outer caller, i.e. the concurrent cycle.
2462   assert(!concurrent ||
2463          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2464          err_msg("for outer caller (concurrent cycle): "
2465                  "_old_marking_cycles_started = %u "
2466                  "is inconsistent with _old_marking_cycles_completed = %u",
2467                  _old_marking_cycles_started, _old_marking_cycles_completed));
2468 
2469   _old_marking_cycles_completed += 1;
2470 
2471   // We need to clear the "in_progress" flag in the CM thread before
2472   // we wake up any waiters (especially when ExplicitInvokesConcurrent
2473   // is set) so that if a waiter requests another System.gc() it doesn't
2474   // incorrectly see that a marking cycle is still in progress.
2475   if (concurrent) {
2476     _cmThread->clear_in_progress();
2477   }
2478 
2479   // This notify_all() will ensure that a thread that called
2480   // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2481   // and it's waiting for a full GC to finish will be woken up. It is
2482   // waiting in VM_G1IncCollectionPause::doit_epilogue().
2483   FullGCCount_lock->notify_all();
2484 }
2485 
2486 void G1CollectedHeap::register_concurrent_cycle_start(jlong start_time) {
2487   _concurrent_cycle_started = true;
2488   _gc_timer_cm->register_gc_start(start_time);
2489 
2490   _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start());
2491   trace_heap_before_gc(_gc_tracer_cm);
2492 }
2493 
2494 void G1CollectedHeap::register_concurrent_cycle_end() {
2495   if (_concurrent_cycle_started) {
2496     _gc_timer_cm->register_gc_end(os::elapsed_counter());
2497 
2498     if (_cm->has_aborted()) {
2499       _gc_tracer_cm->report_concurrent_mode_failure();
2500     }
2501     _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
2502 
2503     _concurrent_cycle_started = false;
2504   }
2505 }
2506 
2507 void G1CollectedHeap::trace_heap_after_concurrent_cycle() {
2508   if (_concurrent_cycle_started) {
2509     trace_heap_after_gc(_gc_tracer_cm);
2510   }
2511 }
2512 
2513 G1YCType G1CollectedHeap::yc_type() {
2514   bool is_young = g1_policy()->gcs_are_young();
2515   bool is_initial_mark = g1_policy()->during_initial_mark_pause();
2516   bool is_during_mark = mark_in_progress();
2517 
2518   if (is_initial_mark) {
2519     return InitialMark;
2520   } else if (is_during_mark) {
2521     return DuringMark;
2522   } else if (is_young) {
2523     return Normal;
2524   } else {
2525     return Mixed;
2526   }
2527 }
2528 
2529 void G1CollectedHeap::collect(GCCause::Cause cause) {
2530   assert_heap_not_locked();
2531 
2532   unsigned int gc_count_before;
2533   unsigned int old_marking_count_before;
2534   bool retry_gc;
2535 
2536   do {
2537     retry_gc = false;
2538 
2539     {
2540       MutexLocker ml(Heap_lock);
2541 
2542       // Read the GC count while holding the Heap_lock
2543       gc_count_before = total_collections();
2544       old_marking_count_before = _old_marking_cycles_started;
2545     }
2546 
2547     if (should_do_concurrent_full_gc(cause)) {
2548       // Schedule an initial-mark evacuation pause that will start a
2549       // concurrent cycle. We're setting word_size to 0 which means that
2550       // we are not requesting a post-GC allocation.
2551       VM_G1IncCollectionPause op(gc_count_before,
2552                                  0,     /* word_size */
2553                                  true,  /* should_initiate_conc_mark */
2554                                  g1_policy()->max_pause_time_ms(),
2555                                  cause);
2556 
2557       VMThread::execute(&op);
2558       if (!op.pause_succeeded()) {
2559         if (old_marking_count_before == _old_marking_cycles_started) {
2560           retry_gc = op.should_retry_gc();
2561         } else {
2562           // A Full GC happened while we were trying to schedule the
2563           // initial-mark GC. No point in starting a new cycle given
2564           // that the whole heap was collected anyway.
2565         }
2566 
2567         if (retry_gc) {
2568           if (GC_locker::is_active_and_needs_gc()) {
2569             GC_locker::stall_until_clear();
2570           }
2571         }
2572       }
2573     } else {
2574       if (cause == GCCause::_gc_locker
2575           DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2576 
2577         // Schedule a standard evacuation pause. We're setting word_size
2578         // to 0 which means that we are not requesting a post-GC allocation.
2579         VM_G1IncCollectionPause op(gc_count_before,
2580                                    0,     /* word_size */
2581                                    false, /* should_initiate_conc_mark */
2582                                    g1_policy()->max_pause_time_ms(),
2583                                    cause);
2584         VMThread::execute(&op);
2585       } else {
2586         // Schedule a Full GC.
2587         VM_G1CollectFull op(gc_count_before, old_marking_count_before, cause);
2588         VMThread::execute(&op);
2589       }
2590     }
2591   } while (retry_gc);
2592 }
2593 
2594 bool G1CollectedHeap::is_in(const void* p) const {
2595   if (_g1_committed.contains(p)) {
2596     // Given that we know that p is in the committed space,
2597     // heap_region_containing_raw() should successfully
2598     // return the containing region.
2599     HeapRegion* hr = heap_region_containing_raw(p);
2600     return hr->is_in(p);
2601   } else {
2602     return false;
2603   }
2604 }
2605 
2606 // Iteration functions.
2607 
2608 // Iterates an OopClosure over all ref-containing fields of objects
2609 // within a HeapRegion.
2610 
2611 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2612   MemRegion _mr;
2613   ExtendedOopClosure* _cl;
2614 public:
2615   IterateOopClosureRegionClosure(MemRegion mr, ExtendedOopClosure* cl)
2616     : _mr(mr), _cl(cl) {}
2617   bool doHeapRegion(HeapRegion* r) {
2618     if (!r->continuesHumongous()) {
2619       r->oop_iterate(_cl);
2620     }
2621     return false;
2622   }
2623 };
2624 
2625 void G1CollectedHeap::oop_iterate(ExtendedOopClosure* cl) {
2626   IterateOopClosureRegionClosure blk(_g1_committed, cl);
2627   heap_region_iterate(&blk);
2628 }
2629 
2630 void G1CollectedHeap::oop_iterate(MemRegion mr, ExtendedOopClosure* cl) {
2631   IterateOopClosureRegionClosure blk(mr, cl);
2632   heap_region_iterate(&blk);
2633 }
2634 
2635 // Iterates an ObjectClosure over all objects within a HeapRegion.
2636 
2637 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2638   ObjectClosure* _cl;
2639 public:
2640   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2641   bool doHeapRegion(HeapRegion* r) {
2642     if (! r->continuesHumongous()) {
2643       r->object_iterate(_cl);
2644     }
2645     return false;
2646   }
2647 };
2648 
2649 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2650   IterateObjectClosureRegionClosure blk(cl);
2651   heap_region_iterate(&blk);
2652 }
2653 
2654 // Calls a SpaceClosure on a HeapRegion.
2655 
2656 class SpaceClosureRegionClosure: public HeapRegionClosure {
2657   SpaceClosure* _cl;
2658 public:
2659   SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2660   bool doHeapRegion(HeapRegion* r) {
2661     _cl->do_space(r);
2662     return false;
2663   }
2664 };
2665 
2666 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2667   SpaceClosureRegionClosure blk(cl);
2668   heap_region_iterate(&blk);
2669 }
2670 
2671 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2672   _hrs.iterate(cl);
2673 }
2674 
2675 void
2676 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
2677                                                  uint worker_id,
2678                                                  uint no_of_par_workers,
2679                                                  jint claim_value) {
2680   const uint regions = n_regions();
2681   const uint max_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
2682                              no_of_par_workers :
2683                              1);
2684   assert(UseDynamicNumberOfGCThreads ||
2685          no_of_par_workers == workers()->total_workers(),
2686          "Non dynamic should use fixed number of workers");
2687   // try to spread out the starting points of the workers
2688   const HeapRegion* start_hr =
2689                         start_region_for_worker(worker_id, no_of_par_workers);
2690   const uint start_index = start_hr->hrs_index();
2691 
2692   // each worker will actually look at all regions
2693   for (uint count = 0; count < regions; ++count) {
2694     const uint index = (start_index + count) % regions;
2695     assert(0 <= index && index < regions, "sanity");
2696     HeapRegion* r = region_at(index);
2697     // we'll ignore "continues humongous" regions (we'll process them
2698     // when we come across their corresponding "start humongous"
2699     // region) and regions already claimed
2700     if (r->claim_value() == claim_value || r->continuesHumongous()) {
2701       continue;
2702     }
2703     // OK, try to claim it
2704     if (r->claimHeapRegion(claim_value)) {
2705       // success!
2706       assert(!r->continuesHumongous(), "sanity");
2707       if (r->startsHumongous()) {
2708         // If the region is "starts humongous" we'll iterate over its
2709         // "continues humongous" first; in fact we'll do them
2710         // first. The order is important. In on case, calling the
2711         // closure on the "starts humongous" region might de-allocate
2712         // and clear all its "continues humongous" regions and, as a
2713         // result, we might end up processing them twice. So, we'll do
2714         // them first (notice: most closures will ignore them anyway) and
2715         // then we'll do the "starts humongous" region.
2716         for (uint ch_index = index + 1; ch_index < regions; ++ch_index) {
2717           HeapRegion* chr = region_at(ch_index);
2718 
2719           // if the region has already been claimed or it's not
2720           // "continues humongous" we're done
2721           if (chr->claim_value() == claim_value ||
2722               !chr->continuesHumongous()) {
2723             break;
2724           }
2725 
2726           // No one should have claimed it directly. We can given
2727           // that we claimed its "starts humongous" region.
2728           assert(chr->claim_value() != claim_value, "sanity");
2729           assert(chr->humongous_start_region() == r, "sanity");
2730 
2731           if (chr->claimHeapRegion(claim_value)) {
2732             // we should always be able to claim it; no one else should
2733             // be trying to claim this region
2734 
2735             bool res2 = cl->doHeapRegion(chr);
2736             assert(!res2, "Should not abort");
2737 
2738             // Right now, this holds (i.e., no closure that actually
2739             // does something with "continues humongous" regions
2740             // clears them). We might have to weaken it in the future,
2741             // but let's leave these two asserts here for extra safety.
2742             assert(chr->continuesHumongous(), "should still be the case");
2743             assert(chr->humongous_start_region() == r, "sanity");
2744           } else {
2745             guarantee(false, "we should not reach here");
2746           }
2747         }
2748       }
2749 
2750       assert(!r->continuesHumongous(), "sanity");
2751       bool res = cl->doHeapRegion(r);
2752       assert(!res, "Should not abort");
2753     }
2754   }
2755 }
2756 
2757 class ResetClaimValuesClosure: public HeapRegionClosure {
2758 public:
2759   bool doHeapRegion(HeapRegion* r) {
2760     r->set_claim_value(HeapRegion::InitialClaimValue);
2761     return false;
2762   }
2763 };
2764 
2765 void G1CollectedHeap::reset_heap_region_claim_values() {
2766   ResetClaimValuesClosure blk;
2767   heap_region_iterate(&blk);
2768 }
2769 
2770 void G1CollectedHeap::reset_cset_heap_region_claim_values() {
2771   ResetClaimValuesClosure blk;
2772   collection_set_iterate(&blk);
2773 }
2774 
2775 #ifdef ASSERT
2776 // This checks whether all regions in the heap have the correct claim
2777 // value. I also piggy-backed on this a check to ensure that the
2778 // humongous_start_region() information on "continues humongous"
2779 // regions is correct.
2780 
2781 class CheckClaimValuesClosure : public HeapRegionClosure {
2782 private:
2783   jint _claim_value;
2784   uint _failures;
2785   HeapRegion* _sh_region;
2786 
2787 public:
2788   CheckClaimValuesClosure(jint claim_value) :
2789     _claim_value(claim_value), _failures(0), _sh_region(NULL) { }
2790   bool doHeapRegion(HeapRegion* r) {
2791     if (r->claim_value() != _claim_value) {
2792       gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2793                              "claim value = %d, should be %d",
2794                              HR_FORMAT_PARAMS(r),
2795                              r->claim_value(), _claim_value);
2796       ++_failures;
2797     }
2798     if (!r->isHumongous()) {
2799       _sh_region = NULL;
2800     } else if (r->startsHumongous()) {
2801       _sh_region = r;
2802     } else if (r->continuesHumongous()) {
2803       if (r->humongous_start_region() != _sh_region) {
2804         gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2805                                "HS = "PTR_FORMAT", should be "PTR_FORMAT,
2806                                HR_FORMAT_PARAMS(r),
2807                                r->humongous_start_region(),
2808                                _sh_region);
2809         ++_failures;
2810       }
2811     }
2812     return false;
2813   }
2814   uint failures() { return _failures; }
2815 };
2816 
2817 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
2818   CheckClaimValuesClosure cl(claim_value);
2819   heap_region_iterate(&cl);
2820   return cl.failures() == 0;
2821 }
2822 
2823 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure {
2824 private:
2825   jint _claim_value;
2826   uint _failures;
2827 
2828 public:
2829   CheckClaimValuesInCSetHRClosure(jint claim_value) :
2830     _claim_value(claim_value), _failures(0) { }
2831 
2832   uint failures() { return _failures; }
2833 
2834   bool doHeapRegion(HeapRegion* hr) {
2835     assert(hr->in_collection_set(), "how?");
2836     assert(!hr->isHumongous(), "H-region in CSet");
2837     if (hr->claim_value() != _claim_value) {
2838       gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", "
2839                              "claim value = %d, should be %d",
2840                              HR_FORMAT_PARAMS(hr),
2841                              hr->claim_value(), _claim_value);
2842       _failures += 1;
2843     }
2844     return false;
2845   }
2846 };
2847 
2848 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) {
2849   CheckClaimValuesInCSetHRClosure cl(claim_value);
2850   collection_set_iterate(&cl);
2851   return cl.failures() == 0;
2852 }
2853 #endif // ASSERT
2854 
2855 // Clear the cached CSet starting regions and (more importantly)
2856 // the time stamps. Called when we reset the GC time stamp.
2857 void G1CollectedHeap::clear_cset_start_regions() {
2858   assert(_worker_cset_start_region != NULL, "sanity");
2859   assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2860 
2861   int n_queues = MAX2((int)ParallelGCThreads, 1);
2862   for (int i = 0; i < n_queues; i++) {
2863     _worker_cset_start_region[i] = NULL;
2864     _worker_cset_start_region_time_stamp[i] = 0;
2865   }
2866 }
2867 
2868 // Given the id of a worker, obtain or calculate a suitable
2869 // starting region for iterating over the current collection set.
2870 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(int worker_i) {
2871   assert(get_gc_time_stamp() > 0, "should have been updated by now");
2872 
2873   HeapRegion* result = NULL;
2874   unsigned gc_time_stamp = get_gc_time_stamp();
2875 
2876   if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2877     // Cached starting region for current worker was set
2878     // during the current pause - so it's valid.
2879     // Note: the cached starting heap region may be NULL
2880     // (when the collection set is empty).
2881     result = _worker_cset_start_region[worker_i];
2882     assert(result == NULL || result->in_collection_set(), "sanity");
2883     return result;
2884   }
2885 
2886   // The cached entry was not valid so let's calculate
2887   // a suitable starting heap region for this worker.
2888 
2889   // We want the parallel threads to start their collection
2890   // set iteration at different collection set regions to
2891   // avoid contention.
2892   // If we have:
2893   //          n collection set regions
2894   //          p threads
2895   // Then thread t will start at region floor ((t * n) / p)
2896 
2897   result = g1_policy()->collection_set();
2898   if (G1CollectedHeap::use_parallel_gc_threads()) {
2899     uint cs_size = g1_policy()->cset_region_length();
2900     uint active_workers = workers()->active_workers();
2901     assert(UseDynamicNumberOfGCThreads ||
2902              active_workers == workers()->total_workers(),
2903              "Unless dynamic should use total workers");
2904 
2905     uint end_ind   = (cs_size * worker_i) / active_workers;
2906     uint start_ind = 0;
2907 
2908     if (worker_i > 0 &&
2909         _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2910       // Previous workers starting region is valid
2911       // so let's iterate from there
2912       start_ind = (cs_size * (worker_i - 1)) / active_workers;
2913       result = _worker_cset_start_region[worker_i - 1];
2914     }
2915 
2916     for (uint i = start_ind; i < end_ind; i++) {
2917       result = result->next_in_collection_set();
2918     }
2919   }
2920 
2921   // Note: the calculated starting heap region may be NULL
2922   // (when the collection set is empty).
2923   assert(result == NULL || result->in_collection_set(), "sanity");
2924   assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2925          "should be updated only once per pause");
2926   _worker_cset_start_region[worker_i] = result;
2927   OrderAccess::storestore();
2928   _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2929   return result;
2930 }
2931 
2932 HeapRegion* G1CollectedHeap::start_region_for_worker(uint worker_i,
2933                                                      uint no_of_par_workers) {
2934   uint worker_num =
2935            G1CollectedHeap::use_parallel_gc_threads() ? no_of_par_workers : 1U;
2936   assert(UseDynamicNumberOfGCThreads ||
2937          no_of_par_workers == workers()->total_workers(),
2938          "Non dynamic should use fixed number of workers");
2939   const uint start_index = n_regions() * worker_i / worker_num;
2940   return region_at(start_index);
2941 }
2942 
2943 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2944   HeapRegion* r = g1_policy()->collection_set();
2945   while (r != NULL) {
2946     HeapRegion* next = r->next_in_collection_set();
2947     if (cl->doHeapRegion(r)) {
2948       cl->incomplete();
2949       return;
2950     }
2951     r = next;
2952   }
2953 }
2954 
2955 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2956                                                   HeapRegionClosure *cl) {
2957   if (r == NULL) {
2958     // The CSet is empty so there's nothing to do.
2959     return;
2960   }
2961 
2962   assert(r->in_collection_set(),
2963          "Start region must be a member of the collection set.");
2964   HeapRegion* cur = r;
2965   while (cur != NULL) {
2966     HeapRegion* next = cur->next_in_collection_set();
2967     if (cl->doHeapRegion(cur) && false) {
2968       cl->incomplete();
2969       return;
2970     }
2971     cur = next;
2972   }
2973   cur = g1_policy()->collection_set();
2974   while (cur != r) {
2975     HeapRegion* next = cur->next_in_collection_set();
2976     if (cl->doHeapRegion(cur) && false) {
2977       cl->incomplete();
2978       return;
2979     }
2980     cur = next;
2981   }
2982 }
2983 
2984 CompactibleSpace* G1CollectedHeap::first_compactible_space() {
2985   return n_regions() > 0 ? region_at(0) : NULL;
2986 }
2987 
2988 
2989 Space* G1CollectedHeap::space_containing(const void* addr) const {
2990   Space* res = heap_region_containing(addr);
2991   return res;
2992 }
2993 
2994 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2995   Space* sp = space_containing(addr);
2996   if (sp != NULL) {
2997     return sp->block_start(addr);
2998   }
2999   return NULL;
3000 }
3001 
3002 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
3003   Space* sp = space_containing(addr);
3004   assert(sp != NULL, "block_size of address outside of heap");
3005   return sp->block_size(addr);
3006 }
3007 
3008 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
3009   Space* sp = space_containing(addr);
3010   return sp->block_is_obj(addr);
3011 }
3012 
3013 bool G1CollectedHeap::supports_tlab_allocation() const {
3014   return true;
3015 }
3016 
3017 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
3018   return HeapRegion::GrainBytes;
3019 }
3020 
3021 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
3022   // Return the remaining space in the cur alloc region, but not less than
3023   // the min TLAB size.
3024 
3025   // Also, this value can be at most the humongous object threshold,
3026   // since we can't allow tlabs to grow big enough to accommodate
3027   // humongous objects.
3028 
3029   HeapRegion* hr = _mutator_alloc_region.get();
3030   size_t max_tlab_size = _humongous_object_threshold_in_words * wordSize;
3031   if (hr == NULL) {
3032     return max_tlab_size;
3033   } else {
3034     return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab_size);
3035   }
3036 }
3037 
3038 size_t G1CollectedHeap::max_capacity() const {
3039   return _g1_reserved.byte_size();
3040 }
3041 
3042 jlong G1CollectedHeap::millis_since_last_gc() {
3043   // assert(false, "NYI");
3044   return 0;
3045 }
3046 
3047 void G1CollectedHeap::prepare_for_verify() {
3048   if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
3049     ensure_parsability(false);
3050   }
3051   g1_rem_set()->prepare_for_verify();
3052 }
3053 
3054 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr,
3055                                               VerifyOption vo) {
3056   switch (vo) {
3057   case VerifyOption_G1UsePrevMarking:
3058     return hr->obj_allocated_since_prev_marking(obj);
3059   case VerifyOption_G1UseNextMarking:
3060     return hr->obj_allocated_since_next_marking(obj);
3061   case VerifyOption_G1UseMarkWord:
3062     return false;
3063   default:
3064     ShouldNotReachHere();
3065   }
3066   return false; // keep some compilers happy
3067 }
3068 
3069 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) {
3070   switch (vo) {
3071   case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start();
3072   case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start();
3073   case VerifyOption_G1UseMarkWord:    return NULL;
3074   default:                            ShouldNotReachHere();
3075   }
3076   return NULL; // keep some compilers happy
3077 }
3078 
3079 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) {
3080   switch (vo) {
3081   case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj);
3082   case VerifyOption_G1UseNextMarking: return isMarkedNext(obj);
3083   case VerifyOption_G1UseMarkWord:    return obj->is_gc_marked();
3084   default:                            ShouldNotReachHere();
3085   }
3086   return false; // keep some compilers happy
3087 }
3088 
3089 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) {
3090   switch (vo) {
3091   case VerifyOption_G1UsePrevMarking: return "PTAMS";
3092   case VerifyOption_G1UseNextMarking: return "NTAMS";
3093   case VerifyOption_G1UseMarkWord:    return "NONE";
3094   default:                            ShouldNotReachHere();
3095   }
3096   return NULL; // keep some compilers happy
3097 }
3098 
3099 // TODO: VerifyRootsClosure extends OopsInGenClosure so that we can
3100 //       pass it as the perm_blk to SharedHeap::process_strong_roots.
3101 //       When process_strong_roots stop calling perm_blk->younger_refs_iterate
3102 //       we can change this closure to extend the simpler OopClosure.
3103 class VerifyRootsClosure: public OopsInGenClosure {
3104 private:
3105   G1CollectedHeap* _g1h;
3106   VerifyOption     _vo;
3107   bool             _failures;
3108 public:
3109   // _vo == UsePrevMarking -> use "prev" marking information,
3110   // _vo == UseNextMarking -> use "next" marking information,
3111   // _vo == UseMarkWord    -> use mark word from object header.
3112   VerifyRootsClosure(VerifyOption vo) :
3113     _g1h(G1CollectedHeap::heap()),
3114     _vo(vo),
3115     _failures(false) { }
3116 
3117   bool failures() { return _failures; }
3118 
3119   template <class T> void do_oop_nv(T* p) {
3120     T heap_oop = oopDesc::load_heap_oop(p);
3121     if (!oopDesc::is_null(heap_oop)) {
3122       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3123       if (_g1h->is_obj_dead_cond(obj, _vo)) {
3124         gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
3125                               "points to dead obj "PTR_FORMAT, p, (void*) obj);
3126         if (_vo == VerifyOption_G1UseMarkWord) {
3127           gclog_or_tty->print_cr("  Mark word: "PTR_FORMAT, (void*)(obj->mark()));
3128         }
3129         obj->print_on(gclog_or_tty);
3130         _failures = true;
3131       }
3132     }
3133   }
3134 
3135   void do_oop(oop* p)       { do_oop_nv(p); }
3136   void do_oop(narrowOop* p) { do_oop_nv(p); }
3137 };
3138 
3139 class G1VerifyCodeRootOopClosure: public OopsInGenClosure {
3140   G1CollectedHeap* _g1h;
3141   OopClosure* _root_cl;
3142   nmethod* _nm;
3143   VerifyOption _vo;
3144   bool _failures;
3145 
3146   template <class T> void do_oop_work(T* p) {
3147     // First verify that this root is live
3148     _root_cl->do_oop(p);
3149 
3150     if (!G1VerifyHeapRegionCodeRoots) {
3151       // We're not verifying the code roots attached to heap region.
3152       return;
3153     }
3154 
3155     // Don't check the code roots during marking verification in a full GC
3156     if (_vo == VerifyOption_G1UseMarkWord) {
3157       return;
3158     }
3159 
3160     // Now verify that the current nmethod (which contains p) is
3161     // in the code root list of the heap region containing the
3162     // object referenced by p.
3163 
3164     T heap_oop = oopDesc::load_heap_oop(p);
3165     if (!oopDesc::is_null(heap_oop)) {
3166       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3167 
3168       // Now fetch the region containing the object
3169       HeapRegion* hr = _g1h->heap_region_containing(obj);
3170       HeapRegionRemSet* hrrs = hr->rem_set();
3171       // Verify that the strong code root list for this region
3172       // contains the nmethod
3173       if (!hrrs->strong_code_roots_list_contains(_nm)) {
3174         gclog_or_tty->print_cr("Code root location "PTR_FORMAT" "
3175                               "from nmethod "PTR_FORMAT" not in strong "
3176                               "code roots for region ["PTR_FORMAT","PTR_FORMAT")",
3177                               p, _nm, hr->bottom(), hr->end());
3178         _failures = true;
3179       }
3180     }
3181   }
3182 
3183 public:
3184   G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo):
3185     _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {}
3186 
3187   void do_oop(oop* p) { do_oop_work(p); }
3188   void do_oop(narrowOop* p) { do_oop_work(p); }
3189 
3190   void set_nmethod(nmethod* nm) { _nm = nm; }
3191   bool failures() { return _failures; }
3192 };
3193 
3194 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure {
3195   G1VerifyCodeRootOopClosure* _oop_cl;
3196 
3197 public:
3198   G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl):
3199     _oop_cl(oop_cl) {}
3200 
3201   void do_code_blob(CodeBlob* cb) {
3202     nmethod* nm = cb->as_nmethod_or_null();
3203     if (nm != NULL) {
3204       _oop_cl->set_nmethod(nm);
3205       nm->oops_do(_oop_cl);
3206     }
3207   }
3208 };
3209 
3210 class YoungRefCounterClosure : public OopClosure {
3211   G1CollectedHeap* _g1h;
3212   int              _count;
3213  public:
3214   YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {}
3215   void do_oop(oop* p)       { if (_g1h->is_in_young(*p)) { _count++; } }
3216   void do_oop(narrowOop* p) { ShouldNotReachHere(); }
3217 
3218   int count() { return _count; }
3219   void reset_count() { _count = 0; };
3220 };
3221 
3222 class VerifyKlassClosure: public KlassClosure {
3223   YoungRefCounterClosure _young_ref_counter_closure;
3224   OopClosure *_oop_closure;
3225  public:
3226   VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {}
3227   void do_klass(Klass* k) {
3228     k->oops_do(_oop_closure);
3229 
3230     _young_ref_counter_closure.reset_count();
3231     k->oops_do(&_young_ref_counter_closure);
3232     if (_young_ref_counter_closure.count() > 0) {
3233       guarantee(k->has_modified_oops(), err_msg("Klass %p, has young refs but is not dirty.", k));
3234     }
3235   }
3236 };
3237 
3238 class VerifyLivenessOopClosure: public OopClosure {
3239   G1CollectedHeap* _g1h;
3240   VerifyOption _vo;
3241 public:
3242   VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
3243     _g1h(g1h), _vo(vo)
3244   { }
3245   void do_oop(narrowOop *p) { do_oop_work(p); }
3246   void do_oop(      oop *p) { do_oop_work(p); }
3247 
3248   template <class T> void do_oop_work(T *p) {
3249     oop obj = oopDesc::load_decode_heap_oop(p);
3250     guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
3251               "Dead object referenced by a not dead object");
3252   }
3253 };
3254 
3255 class VerifyObjsInRegionClosure: public ObjectClosure {
3256 private:
3257   G1CollectedHeap* _g1h;
3258   size_t _live_bytes;
3259   HeapRegion *_hr;
3260   VerifyOption _vo;
3261 public:
3262   // _vo == UsePrevMarking -> use "prev" marking information,
3263   // _vo == UseNextMarking -> use "next" marking information,
3264   // _vo == UseMarkWord    -> use mark word from object header.
3265   VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
3266     : _live_bytes(0), _hr(hr), _vo(vo) {
3267     _g1h = G1CollectedHeap::heap();
3268   }
3269   void do_object(oop o) {
3270     VerifyLivenessOopClosure isLive(_g1h, _vo);
3271     assert(o != NULL, "Huh?");
3272     if (!_g1h->is_obj_dead_cond(o, _vo)) {
3273       // If the object is alive according to the mark word,
3274       // then verify that the marking information agrees.
3275       // Note we can't verify the contra-positive of the
3276       // above: if the object is dead (according to the mark
3277       // word), it may not be marked, or may have been marked
3278       // but has since became dead, or may have been allocated
3279       // since the last marking.
3280       if (_vo == VerifyOption_G1UseMarkWord) {
3281         guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
3282       }
3283 
3284       o->oop_iterate_no_header(&isLive);
3285       if (!_hr->obj_allocated_since_prev_marking(o)) {
3286         size_t obj_size = o->size();    // Make sure we don't overflow
3287         _live_bytes += (obj_size * HeapWordSize);
3288       }
3289     }
3290   }
3291   size_t live_bytes() { return _live_bytes; }
3292 };
3293 
3294 class PrintObjsInRegionClosure : public ObjectClosure {
3295   HeapRegion *_hr;
3296   G1CollectedHeap *_g1;
3297 public:
3298   PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
3299     _g1 = G1CollectedHeap::heap();
3300   };
3301 
3302   void do_object(oop o) {
3303     if (o != NULL) {
3304       HeapWord *start = (HeapWord *) o;
3305       size_t word_sz = o->size();
3306       gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
3307                           " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
3308                           (void*) o, word_sz,
3309                           _g1->isMarkedPrev(o),
3310                           _g1->isMarkedNext(o),
3311                           _hr->obj_allocated_since_prev_marking(o));
3312       HeapWord *end = start + word_sz;
3313       HeapWord *cur;
3314       int *val;
3315       for (cur = start; cur < end; cur++) {
3316         val = (int *) cur;
3317         gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val);
3318       }
3319     }
3320   }
3321 };
3322 
3323 class VerifyRegionClosure: public HeapRegionClosure {
3324 private:
3325   bool             _par;
3326   VerifyOption     _vo;
3327   bool             _failures;
3328 public:
3329   // _vo == UsePrevMarking -> use "prev" marking information,
3330   // _vo == UseNextMarking -> use "next" marking information,
3331   // _vo == UseMarkWord    -> use mark word from object header.
3332   VerifyRegionClosure(bool par, VerifyOption vo)
3333     : _par(par),
3334       _vo(vo),
3335       _failures(false) {}
3336 
3337   bool failures() {
3338     return _failures;
3339   }
3340 
3341   bool doHeapRegion(HeapRegion* r) {
3342     if (!r->continuesHumongous()) {
3343       bool failures = false;
3344       r->verify(_vo, &failures);
3345       if (failures) {
3346         _failures = true;
3347       } else {
3348         VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
3349         r->object_iterate(&not_dead_yet_cl);
3350         if (_vo != VerifyOption_G1UseNextMarking) {
3351           if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
3352             gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
3353                                    "max_live_bytes "SIZE_FORMAT" "
3354                                    "< calculated "SIZE_FORMAT,
3355                                    r->bottom(), r->end(),
3356                                    r->max_live_bytes(),
3357                                  not_dead_yet_cl.live_bytes());
3358             _failures = true;
3359           }
3360         } else {
3361           // When vo == UseNextMarking we cannot currently do a sanity
3362           // check on the live bytes as the calculation has not been
3363           // finalized yet.
3364         }
3365       }
3366     }
3367     return false; // stop the region iteration if we hit a failure
3368   }
3369 };
3370 
3371 // This is the task used for parallel verification of the heap regions
3372 
3373 class G1ParVerifyTask: public AbstractGangTask {
3374 private:
3375   G1CollectedHeap* _g1h;
3376   VerifyOption     _vo;
3377   bool             _failures;
3378 
3379 public:
3380   // _vo == UsePrevMarking -> use "prev" marking information,
3381   // _vo == UseNextMarking -> use "next" marking information,
3382   // _vo == UseMarkWord    -> use mark word from object header.
3383   G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
3384     AbstractGangTask("Parallel verify task"),
3385     _g1h(g1h),
3386     _vo(vo),
3387     _failures(false) { }
3388 
3389   bool failures() {
3390     return _failures;
3391   }
3392 
3393   void work(uint worker_id) {
3394     HandleMark hm;
3395     VerifyRegionClosure blk(true, _vo);
3396     _g1h->heap_region_par_iterate_chunked(&blk, worker_id,
3397                                           _g1h->workers()->active_workers(),
3398                                           HeapRegion::ParVerifyClaimValue);
3399     if (blk.failures()) {
3400       _failures = true;
3401     }
3402   }
3403 };
3404 
3405 void G1CollectedHeap::verify(bool silent, VerifyOption vo) {
3406   if (SafepointSynchronize::is_at_safepoint()) {
3407     assert(Thread::current()->is_VM_thread(),
3408            "Expected to be executed serially by the VM thread at this point");
3409 
3410     if (!silent) { gclog_or_tty->print("Roots "); }
3411     VerifyRootsClosure rootsCl(vo);
3412     G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo);
3413     G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl);
3414     VerifyKlassClosure klassCl(this, &rootsCl);
3415 
3416     // We apply the relevant closures to all the oops in the
3417     // system dictionary, the string table and the code cache.
3418     const int so = SO_AllClasses | SO_Strings | SO_CodeCache;
3419 
3420     // Need cleared claim bits for the strong roots processing
3421     ClassLoaderDataGraph::clear_claimed_marks();
3422 
3423     process_strong_roots(true,      // activate StrongRootsScope
3424                          false,     // we set "is scavenging" to false,
3425                                     // so we don't reset the dirty cards.
3426                          ScanningOption(so),  // roots scanning options
3427                          &rootsCl,
3428                          &blobsCl,
3429                          &klassCl
3430                          );
3431 
3432     bool failures = rootsCl.failures() || codeRootsCl.failures();
3433 
3434     if (vo != VerifyOption_G1UseMarkWord) {
3435       // If we're verifying during a full GC then the region sets
3436       // will have been torn down at the start of the GC. Therefore
3437       // verifying the region sets will fail. So we only verify
3438       // the region sets when not in a full GC.
3439       if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3440       verify_region_sets();
3441     }
3442 
3443     if (!silent) { gclog_or_tty->print("HeapRegions "); }
3444     if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3445       assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3446              "sanity check");
3447 
3448       G1ParVerifyTask task(this, vo);
3449       assert(UseDynamicNumberOfGCThreads ||
3450         workers()->active_workers() == workers()->total_workers(),
3451         "If not dynamic should be using all the workers");
3452       int n_workers = workers()->active_workers();
3453       set_par_threads(n_workers);
3454       workers()->run_task(&task);
3455       set_par_threads(0);
3456       if (task.failures()) {
3457         failures = true;
3458       }
3459 
3460       // Checks that the expected amount of parallel work was done.
3461       // The implication is that n_workers is > 0.
3462       assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
3463              "sanity check");
3464 
3465       reset_heap_region_claim_values();
3466 
3467       assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3468              "sanity check");
3469     } else {
3470       VerifyRegionClosure blk(false, vo);
3471       heap_region_iterate(&blk);
3472       if (blk.failures()) {
3473         failures = true;
3474       }
3475     }
3476     if (!silent) gclog_or_tty->print("RemSet ");
3477     rem_set()->verify();
3478 
3479     if (failures) {
3480       gclog_or_tty->print_cr("Heap:");
3481       // It helps to have the per-region information in the output to
3482       // help us track down what went wrong. This is why we call
3483       // print_extended_on() instead of print_on().
3484       print_extended_on(gclog_or_tty);
3485       gclog_or_tty->print_cr("");
3486 #ifndef PRODUCT
3487       if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3488         concurrent_mark()->print_reachable("at-verification-failure",
3489                                            vo, false /* all */);
3490       }
3491 #endif
3492       gclog_or_tty->flush();
3493     }
3494     guarantee(!failures, "there should not have been any failures");
3495   } else {
3496     if (!silent)
3497       gclog_or_tty->print("(SKIPPING roots, heapRegionSets, heapRegions, remset) ");
3498   }
3499 }
3500 
3501 void G1CollectedHeap::verify(bool silent) {
3502   verify(silent, VerifyOption_G1UsePrevMarking);
3503 }
3504 
3505 double G1CollectedHeap::verify(bool guard, const char* msg) {
3506   double verify_time_ms = 0.0;
3507 
3508   if (guard && total_collections() >= VerifyGCStartAt) {
3509     double verify_start = os::elapsedTime();
3510     HandleMark hm;  // Discard invalid handles created during verification
3511     prepare_for_verify();
3512     Universe::verify(VerifyOption_G1UsePrevMarking, msg);
3513     verify_time_ms = (os::elapsedTime() - verify_start) * 1000;
3514   }
3515 
3516   return verify_time_ms;
3517 }
3518 
3519 void G1CollectedHeap::verify_before_gc() {
3520   double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:");
3521   g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms);
3522 }
3523 
3524 void G1CollectedHeap::verify_after_gc() {
3525   double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:");
3526   g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms);
3527 }
3528 
3529 class PrintRegionClosure: public HeapRegionClosure {
3530   outputStream* _st;
3531 public:
3532   PrintRegionClosure(outputStream* st) : _st(st) {}
3533   bool doHeapRegion(HeapRegion* r) {
3534     r->print_on(_st);
3535     return false;
3536   }
3537 };
3538 
3539 void G1CollectedHeap::print_on(outputStream* st) const {
3540   st->print(" %-20s", "garbage-first heap");
3541   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3542             capacity()/K, used_unlocked()/K);
3543   st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3544             _g1_storage.low_boundary(),
3545             _g1_storage.high(),
3546             _g1_storage.high_boundary());
3547   st->cr();
3548   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3549   uint young_regions = _young_list->length();
3550   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3551             (size_t) young_regions * HeapRegion::GrainBytes / K);
3552   uint survivor_regions = g1_policy()->recorded_survivor_regions();
3553   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3554             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3555   st->cr();
3556   MetaspaceAux::print_on(st);
3557 }
3558 
3559 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3560   print_on(st);
3561 
3562   // Print the per-region information.
3563   st->cr();
3564   st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3565                "HS=humongous(starts), HC=humongous(continues), "
3566                "CS=collection set, F=free, TS=gc time stamp, "
3567                "PTAMS=previous top-at-mark-start, "
3568                "NTAMS=next top-at-mark-start)");
3569   PrintRegionClosure blk(st);
3570   heap_region_iterate(&blk);
3571 }
3572 
3573 void G1CollectedHeap::print_on_error(outputStream* st) const {
3574   this->CollectedHeap::print_on_error(st);
3575 
3576   if (_cm != NULL) {
3577     st->cr();
3578     _cm->print_on_error(st);
3579   }
3580 }
3581 
3582 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3583   if (G1CollectedHeap::use_parallel_gc_threads()) {
3584     workers()->print_worker_threads_on(st);
3585   }
3586   _cmThread->print_on(st);
3587   st->cr();
3588   _cm->print_worker_threads_on(st);
3589   _cg1r->print_worker_threads_on(st);
3590 }
3591 
3592 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3593   if (G1CollectedHeap::use_parallel_gc_threads()) {
3594     workers()->threads_do(tc);
3595   }
3596   tc->do_thread(_cmThread);
3597   _cg1r->threads_do(tc);
3598 }
3599 
3600 void G1CollectedHeap::print_tracing_info() const {
3601   // We'll overload this to mean "trace GC pause statistics."
3602   if (TraceGen0Time || TraceGen1Time) {
3603     // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3604     // to that.
3605     g1_policy()->print_tracing_info();
3606   }
3607   if (G1SummarizeRSetStats) {
3608     g1_rem_set()->print_summary_info();
3609   }
3610   if (G1SummarizeConcMark) {
3611     concurrent_mark()->print_summary_info();
3612   }
3613   g1_policy()->print_yg_surv_rate_info();
3614   SpecializationStats::print();
3615 }
3616 
3617 #ifndef PRODUCT
3618 // Helpful for debugging RSet issues.
3619 
3620 class PrintRSetsClosure : public HeapRegionClosure {
3621 private:
3622   const char* _msg;
3623   size_t _occupied_sum;
3624 
3625 public:
3626   bool doHeapRegion(HeapRegion* r) {
3627     HeapRegionRemSet* hrrs = r->rem_set();
3628     size_t occupied = hrrs->occupied();
3629     _occupied_sum += occupied;
3630 
3631     gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3632                            HR_FORMAT_PARAMS(r));
3633     if (occupied == 0) {
3634       gclog_or_tty->print_cr("  RSet is empty");
3635     } else {
3636       hrrs->print();
3637     }
3638     gclog_or_tty->print_cr("----------");
3639     return false;
3640   }
3641 
3642   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3643     gclog_or_tty->cr();
3644     gclog_or_tty->print_cr("========================================");
3645     gclog_or_tty->print_cr(msg);
3646     gclog_or_tty->cr();
3647   }
3648 
3649   ~PrintRSetsClosure() {
3650     gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3651     gclog_or_tty->print_cr("========================================");
3652     gclog_or_tty->cr();
3653   }
3654 };
3655 
3656 void G1CollectedHeap::print_cset_rsets() {
3657   PrintRSetsClosure cl("Printing CSet RSets");
3658   collection_set_iterate(&cl);
3659 }
3660 
3661 void G1CollectedHeap::print_all_rsets() {
3662   PrintRSetsClosure cl("Printing All RSets");;
3663   heap_region_iterate(&cl);
3664 }
3665 #endif // PRODUCT
3666 
3667 G1CollectedHeap* G1CollectedHeap::heap() {
3668   assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3669          "not a garbage-first heap");
3670   return _g1h;
3671 }
3672 
3673 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3674   // always_do_update_barrier = false;
3675   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3676   // Fill TLAB's and such
3677   ensure_parsability(true);
3678 }
3679 
3680 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) {
3681 
3682   if (G1SummarizeRSetStats &&
3683       (G1SummarizeRSetStatsPeriod > 0) &&
3684       // we are at the end of the GC. Total collections has already been increased.
3685       ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) {
3686     g1_rem_set()->print_periodic_summary_info();
3687   }
3688 
3689   // FIXME: what is this about?
3690   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3691   // is set.
3692   COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3693                         "derived pointer present"));
3694   // always_do_update_barrier = true;
3695 
3696   // We have just completed a GC. Update the soft reference
3697   // policy with the new heap occupancy
3698   Universe::update_heap_info_at_gc();
3699 }
3700 
3701 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3702                                                unsigned int gc_count_before,
3703                                                bool* succeeded) {
3704   assert_heap_not_locked_and_not_at_safepoint();
3705   g1_policy()->record_stop_world_start();
3706   VM_G1IncCollectionPause op(gc_count_before,
3707                              word_size,
3708                              false, /* should_initiate_conc_mark */
3709                              g1_policy()->max_pause_time_ms(),
3710                              GCCause::_g1_inc_collection_pause);
3711   VMThread::execute(&op);
3712 
3713   HeapWord* result = op.result();
3714   bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3715   assert(result == NULL || ret_succeeded,
3716          "the result should be NULL if the VM did not succeed");
3717   *succeeded = ret_succeeded;
3718 
3719   assert_heap_not_locked();
3720   return result;
3721 }
3722 
3723 void
3724 G1CollectedHeap::doConcurrentMark() {
3725   MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3726   if (!_cmThread->in_progress()) {
3727     _cmThread->set_started();
3728     CGC_lock->notify();
3729   }
3730 }
3731 
3732 size_t G1CollectedHeap::pending_card_num() {
3733   size_t extra_cards = 0;
3734   JavaThread *curr = Threads::first();
3735   while (curr != NULL) {
3736     DirtyCardQueue& dcq = curr->dirty_card_queue();
3737     extra_cards += dcq.size();
3738     curr = curr->next();
3739   }
3740   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3741   size_t buffer_size = dcqs.buffer_size();
3742   size_t buffer_num = dcqs.completed_buffers_num();
3743 
3744   // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
3745   // in bytes - not the number of 'entries'. We need to convert
3746   // into a number of cards.
3747   return (buffer_size * buffer_num + extra_cards) / oopSize;
3748 }
3749 
3750 size_t G1CollectedHeap::cards_scanned() {
3751   return g1_rem_set()->cardsScanned();
3752 }
3753 
3754 void
3755 G1CollectedHeap::setup_surviving_young_words() {
3756   assert(_surviving_young_words == NULL, "pre-condition");
3757   uint array_length = g1_policy()->young_cset_region_length();
3758   _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3759   if (_surviving_young_words == NULL) {
3760     vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR,
3761                           "Not enough space for young surv words summary.");
3762   }
3763   memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3764 #ifdef ASSERT
3765   for (uint i = 0;  i < array_length; ++i) {
3766     assert( _surviving_young_words[i] == 0, "memset above" );
3767   }
3768 #endif // !ASSERT
3769 }
3770 
3771 void
3772 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3773   MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3774   uint array_length = g1_policy()->young_cset_region_length();
3775   for (uint i = 0; i < array_length; ++i) {
3776     _surviving_young_words[i] += surv_young_words[i];
3777   }
3778 }
3779 
3780 void
3781 G1CollectedHeap::cleanup_surviving_young_words() {
3782   guarantee( _surviving_young_words != NULL, "pre-condition" );
3783   FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC);
3784   _surviving_young_words = NULL;
3785 }
3786 
3787 #ifdef ASSERT
3788 class VerifyCSetClosure: public HeapRegionClosure {
3789 public:
3790   bool doHeapRegion(HeapRegion* hr) {
3791     // Here we check that the CSet region's RSet is ready for parallel
3792     // iteration. The fields that we'll verify are only manipulated
3793     // when the region is part of a CSet and is collected. Afterwards,
3794     // we reset these fields when we clear the region's RSet (when the
3795     // region is freed) so they are ready when the region is
3796     // re-allocated. The only exception to this is if there's an
3797     // evacuation failure and instead of freeing the region we leave
3798     // it in the heap. In that case, we reset these fields during
3799     // evacuation failure handling.
3800     guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3801 
3802     // Here's a good place to add any other checks we'd like to
3803     // perform on CSet regions.
3804     return false;
3805   }
3806 };
3807 #endif // ASSERT
3808 
3809 #if TASKQUEUE_STATS
3810 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3811   st->print_raw_cr("GC Task Stats");
3812   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3813   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3814 }
3815 
3816 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3817   print_taskqueue_stats_hdr(st);
3818 
3819   TaskQueueStats totals;
3820   const int n = workers() != NULL ? workers()->total_workers() : 1;
3821   for (int i = 0; i < n; ++i) {
3822     st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3823     totals += task_queue(i)->stats;
3824   }
3825   st->print_raw("tot "); totals.print(st); st->cr();
3826 
3827   DEBUG_ONLY(totals.verify());
3828 }
3829 
3830 void G1CollectedHeap::reset_taskqueue_stats() {
3831   const int n = workers() != NULL ? workers()->total_workers() : 1;
3832   for (int i = 0; i < n; ++i) {
3833     task_queue(i)->stats.reset();
3834   }
3835 }
3836 #endif // TASKQUEUE_STATS
3837 
3838 void G1CollectedHeap::log_gc_header() {
3839   if (!G1Log::fine()) {
3840     return;
3841   }
3842 
3843   gclog_or_tty->date_stamp(PrintGCDateStamps);
3844   gclog_or_tty->stamp(PrintGCTimeStamps);
3845 
3846   GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
3847     .append(g1_policy()->gcs_are_young() ? "(young)" : "(mixed)")
3848     .append(g1_policy()->during_initial_mark_pause() ? " (initial-mark)" : "");
3849 
3850   gclog_or_tty->print("[%s", (const char*)gc_cause_str);
3851 }
3852 
3853 void G1CollectedHeap::log_gc_footer(double pause_time_sec) {
3854   if (!G1Log::fine()) {
3855     return;
3856   }
3857 
3858   if (G1Log::finer()) {
3859     if (evacuation_failed()) {
3860       gclog_or_tty->print(" (to-space exhausted)");
3861     }
3862     gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3863     g1_policy()->phase_times()->note_gc_end();
3864     g1_policy()->phase_times()->print(pause_time_sec);
3865     g1_policy()->print_detailed_heap_transition();
3866   } else {
3867     if (evacuation_failed()) {
3868       gclog_or_tty->print("--");
3869     }
3870     g1_policy()->print_heap_transition();
3871     gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3872   }
3873   gclog_or_tty->flush();
3874 }
3875 
3876 bool
3877 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3878   assert_at_safepoint(true /* should_be_vm_thread */);
3879   guarantee(!is_gc_active(), "collection is not reentrant");
3880 
3881   if (GC_locker::check_active_before_gc()) {
3882     return false;
3883   }
3884 
3885   _gc_timer_stw->register_gc_start(os::elapsed_counter());
3886 
3887   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3888 
3889   SvcGCMarker sgcm(SvcGCMarker::MINOR);
3890   ResourceMark rm;
3891 
3892   print_heap_before_gc();
3893   trace_heap_before_gc(_gc_tracer_stw);
3894 
3895   HRSPhaseSetter x(HRSPhaseEvacuation);
3896   verify_region_sets_optional();
3897   verify_dirty_young_regions();
3898 
3899   // This call will decide whether this pause is an initial-mark
3900   // pause. If it is, during_initial_mark_pause() will return true
3901   // for the duration of this pause.
3902   g1_policy()->decide_on_conc_mark_initiation();
3903 
3904   // We do not allow initial-mark to be piggy-backed on a mixed GC.
3905   assert(!g1_policy()->during_initial_mark_pause() ||
3906           g1_policy()->gcs_are_young(), "sanity");
3907 
3908   // We also do not allow mixed GCs during marking.
3909   assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3910 
3911   // Record whether this pause is an initial mark. When the current
3912   // thread has completed its logging output and it's safe to signal
3913   // the CM thread, the flag's value in the policy has been reset.
3914   bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3915 
3916   // Inner scope for scope based logging, timers, and stats collection
3917   {
3918     EvacuationInfo evacuation_info;
3919 
3920     if (g1_policy()->during_initial_mark_pause()) {
3921       // We are about to start a marking cycle, so we increment the
3922       // full collection counter.
3923       increment_old_marking_cycles_started();
3924       register_concurrent_cycle_start(_gc_timer_stw->gc_start());
3925     }
3926 
3927     _gc_tracer_stw->report_yc_type(yc_type());
3928 
3929     TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3930 
3931     int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
3932                                 workers()->active_workers() : 1);
3933     double pause_start_sec = os::elapsedTime();
3934     g1_policy()->phase_times()->note_gc_start(active_workers);
3935     log_gc_header();
3936 
3937     TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3938     TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3939 
3940     // If the secondary_free_list is not empty, append it to the
3941     // free_list. No need to wait for the cleanup operation to finish;
3942     // the region allocation code will check the secondary_free_list
3943     // and wait if necessary. If the G1StressConcRegionFreeing flag is
3944     // set, skip this step so that the region allocation code has to
3945     // get entries from the secondary_free_list.
3946     if (!G1StressConcRegionFreeing) {
3947       append_secondary_free_list_if_not_empty_with_lock();
3948     }
3949 
3950     assert(check_young_list_well_formed(), "young list should be well formed");
3951     assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3952            "sanity check");
3953 
3954     // Don't dynamically change the number of GC threads this early.  A value of
3955     // 0 is used to indicate serial work.  When parallel work is done,
3956     // it will be set.
3957 
3958     { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3959       IsGCActiveMark x;
3960 
3961       gc_prologue(false);
3962       increment_total_collections(false /* full gc */);
3963       increment_gc_time_stamp();
3964 
3965       verify_before_gc();
3966 
3967       COMPILER2_PRESENT(DerivedPointerTable::clear());
3968 
3969       // Please see comment in g1CollectedHeap.hpp and
3970       // G1CollectedHeap::ref_processing_init() to see how
3971       // reference processing currently works in G1.
3972 
3973       // Enable discovery in the STW reference processor
3974       ref_processor_stw()->enable_discovery(true /*verify_disabled*/,
3975                                             true /*verify_no_refs*/);
3976 
3977       {
3978         // We want to temporarily turn off discovery by the
3979         // CM ref processor, if necessary, and turn it back on
3980         // on again later if we do. Using a scoped
3981         // NoRefDiscovery object will do this.
3982         NoRefDiscovery no_cm_discovery(ref_processor_cm());
3983 
3984         // Forget the current alloc region (we might even choose it to be part
3985         // of the collection set!).
3986         release_mutator_alloc_region();
3987 
3988         // We should call this after we retire the mutator alloc
3989         // region(s) so that all the ALLOC / RETIRE events are generated
3990         // before the start GC event.
3991         _hr_printer.start_gc(false /* full */, (size_t) total_collections());
3992 
3993         // This timing is only used by the ergonomics to handle our pause target.
3994         // It is unclear why this should not include the full pause. We will
3995         // investigate this in CR 7178365.
3996         //
3997         // Preserving the old comment here if that helps the investigation:
3998         //
3999         // The elapsed time induced by the start time below deliberately elides
4000         // the possible verification above.
4001         double sample_start_time_sec = os::elapsedTime();
4002 
4003 #if YOUNG_LIST_VERBOSE
4004         gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
4005         _young_list->print();
4006         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4007 #endif // YOUNG_LIST_VERBOSE
4008 
4009         g1_policy()->record_collection_pause_start(sample_start_time_sec);
4010 
4011         double scan_wait_start = os::elapsedTime();
4012         // We have to wait until the CM threads finish scanning the
4013         // root regions as it's the only way to ensure that all the
4014         // objects on them have been correctly scanned before we start
4015         // moving them during the GC.
4016         bool waited = _cm->root_regions()->wait_until_scan_finished();
4017         double wait_time_ms = 0.0;
4018         if (waited) {
4019           double scan_wait_end = os::elapsedTime();
4020           wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
4021         }
4022         g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
4023 
4024 #if YOUNG_LIST_VERBOSE
4025         gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
4026         _young_list->print();
4027 #endif // YOUNG_LIST_VERBOSE
4028 
4029         if (g1_policy()->during_initial_mark_pause()) {
4030           concurrent_mark()->checkpointRootsInitialPre();
4031         }
4032 
4033 #if YOUNG_LIST_VERBOSE
4034         gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
4035         _young_list->print();
4036         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4037 #endif // YOUNG_LIST_VERBOSE
4038 
4039         g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info);
4040 
4041         _cm->note_start_of_gc();
4042         // We should not verify the per-thread SATB buffers given that
4043         // we have not filtered them yet (we'll do so during the
4044         // GC). We also call this after finalize_cset() to
4045         // ensure that the CSet has been finalized.
4046         _cm->verify_no_cset_oops(true  /* verify_stacks */,
4047                                  true  /* verify_enqueued_buffers */,
4048                                  false /* verify_thread_buffers */,
4049                                  true  /* verify_fingers */);
4050 
4051         if (_hr_printer.is_active()) {
4052           HeapRegion* hr = g1_policy()->collection_set();
4053           while (hr != NULL) {
4054             G1HRPrinter::RegionType type;
4055             if (!hr->is_young()) {
4056               type = G1HRPrinter::Old;
4057             } else if (hr->is_survivor()) {
4058               type = G1HRPrinter::Survivor;
4059             } else {
4060               type = G1HRPrinter::Eden;
4061             }
4062             _hr_printer.cset(hr);
4063             hr = hr->next_in_collection_set();
4064           }
4065         }
4066 
4067 #ifdef ASSERT
4068         VerifyCSetClosure cl;
4069         collection_set_iterate(&cl);
4070 #endif // ASSERT
4071 
4072         setup_surviving_young_words();
4073 
4074         // Initialize the GC alloc regions.
4075         init_gc_alloc_regions(evacuation_info);
4076 
4077         // Actually do the work...
4078         evacuate_collection_set(evacuation_info);
4079 
4080         // We do this to mainly verify the per-thread SATB buffers
4081         // (which have been filtered by now) since we didn't verify
4082         // them earlier. No point in re-checking the stacks / enqueued
4083         // buffers given that the CSet has not changed since last time
4084         // we checked.
4085         _cm->verify_no_cset_oops(false /* verify_stacks */,
4086                                  false /* verify_enqueued_buffers */,
4087                                  true  /* verify_thread_buffers */,
4088                                  true  /* verify_fingers */);
4089 
4090         free_collection_set(g1_policy()->collection_set(), evacuation_info);
4091         g1_policy()->clear_collection_set();
4092 
4093         cleanup_surviving_young_words();
4094 
4095         // Start a new incremental collection set for the next pause.
4096         g1_policy()->start_incremental_cset_building();
4097 
4098         // Clear the _cset_fast_test bitmap in anticipation of adding
4099         // regions to the incremental collection set for the next
4100         // evacuation pause.
4101         clear_cset_fast_test();
4102 
4103         _young_list->reset_sampled_info();
4104 
4105         // Don't check the whole heap at this point as the
4106         // GC alloc regions from this pause have been tagged
4107         // as survivors and moved on to the survivor list.
4108         // Survivor regions will fail the !is_young() check.
4109         assert(check_young_list_empty(false /* check_heap */),
4110           "young list should be empty");
4111 
4112 #if YOUNG_LIST_VERBOSE
4113         gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
4114         _young_list->print();
4115 #endif // YOUNG_LIST_VERBOSE
4116 
4117         g1_policy()->record_survivor_regions(_young_list->survivor_length(),
4118                                              _young_list->first_survivor_region(),
4119                                              _young_list->last_survivor_region());
4120 
4121         _young_list->reset_auxilary_lists();
4122 
4123         if (evacuation_failed()) {
4124           _summary_bytes_used = recalculate_used();
4125           uint n_queues = MAX2((int)ParallelGCThreads, 1);
4126           for (uint i = 0; i < n_queues; i++) {
4127             if (_evacuation_failed_info_array[i].has_failed()) {
4128               _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
4129             }
4130           }
4131         } else {
4132           // The "used" of the the collection set have already been subtracted
4133           // when they were freed.  Add in the bytes evacuated.
4134           _summary_bytes_used += g1_policy()->bytes_copied_during_gc();
4135         }
4136 
4137         if (g1_policy()->during_initial_mark_pause()) {
4138           // We have to do this before we notify the CM threads that
4139           // they can start working to make sure that all the
4140           // appropriate initialization is done on the CM object.
4141           concurrent_mark()->checkpointRootsInitialPost();
4142           set_marking_started();
4143           // Note that we don't actually trigger the CM thread at
4144           // this point. We do that later when we're sure that
4145           // the current thread has completed its logging output.
4146         }
4147 
4148         allocate_dummy_regions();
4149 
4150 #if YOUNG_LIST_VERBOSE
4151         gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
4152         _young_list->print();
4153         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
4154 #endif // YOUNG_LIST_VERBOSE
4155 
4156         init_mutator_alloc_region();
4157 
4158         {
4159           size_t expand_bytes = g1_policy()->expansion_amount();
4160           if (expand_bytes > 0) {
4161             size_t bytes_before = capacity();
4162             // No need for an ergo verbose message here,
4163             // expansion_amount() does this when it returns a value > 0.
4164             if (!expand(expand_bytes)) {
4165               // We failed to expand the heap so let's verify that
4166               // committed/uncommitted amount match the backing store
4167               assert(capacity() == _g1_storage.committed_size(), "committed size mismatch");
4168               assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch");
4169             }
4170           }
4171         }
4172 
4173         // We redo the verification but now wrt to the new CSet which
4174         // has just got initialized after the previous CSet was freed.
4175         _cm->verify_no_cset_oops(true  /* verify_stacks */,
4176                                  true  /* verify_enqueued_buffers */,
4177                                  true  /* verify_thread_buffers */,
4178                                  true  /* verify_fingers */);
4179         _cm->note_end_of_gc();
4180 
4181         // This timing is only used by the ergonomics to handle our pause target.
4182         // It is unclear why this should not include the full pause. We will
4183         // investigate this in CR 7178365.
4184         double sample_end_time_sec = os::elapsedTime();
4185         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
4186         g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info);
4187 
4188         MemoryService::track_memory_usage();
4189 
4190         // In prepare_for_verify() below we'll need to scan the deferred
4191         // update buffers to bring the RSets up-to-date if
4192         // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
4193         // the update buffers we'll probably need to scan cards on the
4194         // regions we just allocated to (i.e., the GC alloc
4195         // regions). However, during the last GC we called
4196         // set_saved_mark() on all the GC alloc regions, so card
4197         // scanning might skip the [saved_mark_word()...top()] area of
4198         // those regions (i.e., the area we allocated objects into
4199         // during the last GC). But it shouldn't. Given that
4200         // saved_mark_word() is conditional on whether the GC time stamp
4201         // on the region is current or not, by incrementing the GC time
4202         // stamp here we invalidate all the GC time stamps on all the
4203         // regions and saved_mark_word() will simply return top() for
4204         // all the regions. This is a nicer way of ensuring this rather
4205         // than iterating over the regions and fixing them. In fact, the
4206         // GC time stamp increment here also ensures that
4207         // saved_mark_word() will return top() between pauses, i.e.,
4208         // during concurrent refinement. So we don't need the
4209         // is_gc_active() check to decided which top to use when
4210         // scanning cards (see CR 7039627).
4211         increment_gc_time_stamp();
4212 
4213         verify_after_gc();
4214 
4215         assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
4216         ref_processor_stw()->verify_no_references_recorded();
4217 
4218         // CM reference discovery will be re-enabled if necessary.
4219       }
4220 
4221       // We should do this after we potentially expand the heap so
4222       // that all the COMMIT events are generated before the end GC
4223       // event, and after we retire the GC alloc regions so that all
4224       // RETIRE events are generated before the end GC event.
4225       _hr_printer.end_gc(false /* full */, (size_t) total_collections());
4226 
4227       if (mark_in_progress()) {
4228         concurrent_mark()->update_g1_committed();
4229       }
4230 
4231 #ifdef TRACESPINNING
4232       ParallelTaskTerminator::print_termination_counts();
4233 #endif
4234 
4235       gc_epilogue(false);
4236     }
4237 
4238     // Print the remainder of the GC log output.
4239     log_gc_footer(os::elapsedTime() - pause_start_sec);
4240 
4241     // It is not yet to safe to tell the concurrent mark to
4242     // start as we have some optional output below. We don't want the
4243     // output from the concurrent mark thread interfering with this
4244     // logging output either.
4245 
4246     _hrs.verify_optional();
4247     verify_region_sets_optional();
4248 
4249     TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
4250     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
4251 
4252     print_heap_after_gc();
4253     trace_heap_after_gc(_gc_tracer_stw);
4254 
4255     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
4256     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
4257     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
4258     // before any GC notifications are raised.
4259     g1mm()->update_sizes();
4260 
4261     _gc_tracer_stw->report_evacuation_info(&evacuation_info);
4262     _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
4263     _gc_timer_stw->register_gc_end(os::elapsed_counter());
4264     _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
4265   }
4266   // It should now be safe to tell the concurrent mark thread to start
4267   // without its logging output interfering with the logging output
4268   // that came from the pause.
4269 
4270   if (should_start_conc_mark) {
4271     // CAUTION: after the doConcurrentMark() call below,
4272     // the concurrent marking thread(s) could be running
4273     // concurrently with us. Make sure that anything after
4274     // this point does not assume that we are the only GC thread
4275     // running. Note: of course, the actual marking work will
4276     // not start until the safepoint itself is released in
4277     // ConcurrentGCThread::safepoint_desynchronize().
4278     doConcurrentMark();
4279   }
4280 
4281   return true;
4282 }
4283 
4284 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
4285 {
4286   size_t gclab_word_size;
4287   switch (purpose) {
4288     case GCAllocForSurvived:
4289       gclab_word_size = _survivor_plab_stats.desired_plab_sz();
4290       break;
4291     case GCAllocForTenured:
4292       gclab_word_size = _old_plab_stats.desired_plab_sz();
4293       break;
4294     default:
4295       assert(false, "unknown GCAllocPurpose");
4296       gclab_word_size = _old_plab_stats.desired_plab_sz();
4297       break;
4298   }
4299 
4300   // Prevent humongous PLAB sizes for two reasons:
4301   // * PLABs are allocated using a similar paths as oops, but should
4302   //   never be in a humongous region
4303   // * Allowing humongous PLABs needlessly churns the region free lists
4304   return MIN2(_humongous_object_threshold_in_words, gclab_word_size);
4305 }
4306 
4307 void G1CollectedHeap::init_mutator_alloc_region() {
4308   assert(_mutator_alloc_region.get() == NULL, "pre-condition");
4309   _mutator_alloc_region.init();
4310 }
4311 
4312 void G1CollectedHeap::release_mutator_alloc_region() {
4313   _mutator_alloc_region.release();
4314   assert(_mutator_alloc_region.get() == NULL, "post-condition");
4315 }
4316 
4317 void G1CollectedHeap::init_gc_alloc_regions(EvacuationInfo& evacuation_info) {
4318   assert_at_safepoint(true /* should_be_vm_thread */);
4319 
4320   _survivor_gc_alloc_region.init();
4321   _old_gc_alloc_region.init();
4322   HeapRegion* retained_region = _retained_old_gc_alloc_region;
4323   _retained_old_gc_alloc_region = NULL;
4324 
4325   // We will discard the current GC alloc region if:
4326   // a) it's in the collection set (it can happen!),
4327   // b) it's already full (no point in using it),
4328   // c) it's empty (this means that it was emptied during
4329   // a cleanup and it should be on the free list now), or
4330   // d) it's humongous (this means that it was emptied
4331   // during a cleanup and was added to the free list, but
4332   // has been subsequently used to allocate a humongous
4333   // object that may be less than the region size).
4334   if (retained_region != NULL &&
4335       !retained_region->in_collection_set() &&
4336       !(retained_region->top() == retained_region->end()) &&
4337       !retained_region->is_empty() &&
4338       !retained_region->isHumongous()) {
4339     retained_region->set_saved_mark();
4340     // The retained region was added to the old region set when it was
4341     // retired. We have to remove it now, since we don't allow regions
4342     // we allocate to in the region sets. We'll re-add it later, when
4343     // it's retired again.
4344     _old_set.remove(retained_region);
4345     bool during_im = g1_policy()->during_initial_mark_pause();
4346     retained_region->note_start_of_copying(during_im);
4347     _old_gc_alloc_region.set(retained_region);
4348     _hr_printer.reuse(retained_region);
4349     evacuation_info.set_alloc_regions_used_before(retained_region->used());
4350   }
4351 }
4352 
4353 void G1CollectedHeap::release_gc_alloc_regions(uint no_of_gc_workers, EvacuationInfo& evacuation_info) {
4354   evacuation_info.set_allocation_regions(_survivor_gc_alloc_region.count() +
4355                                          _old_gc_alloc_region.count());
4356   _survivor_gc_alloc_region.release();
4357   // If we have an old GC alloc region to release, we'll save it in
4358   // _retained_old_gc_alloc_region. If we don't
4359   // _retained_old_gc_alloc_region will become NULL. This is what we
4360   // want either way so no reason to check explicitly for either
4361   // condition.
4362   _retained_old_gc_alloc_region = _old_gc_alloc_region.release();
4363 
4364   if (ResizePLAB) {
4365     _survivor_plab_stats.adjust_desired_plab_sz(no_of_gc_workers);
4366     _old_plab_stats.adjust_desired_plab_sz(no_of_gc_workers);
4367   }
4368 }
4369 
4370 void G1CollectedHeap::abandon_gc_alloc_regions() {
4371   assert(_survivor_gc_alloc_region.get() == NULL, "pre-condition");
4372   assert(_old_gc_alloc_region.get() == NULL, "pre-condition");
4373   _retained_old_gc_alloc_region = NULL;
4374 }
4375 
4376 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4377   _drain_in_progress = false;
4378   set_evac_failure_closure(cl);
4379   _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4380 }
4381 
4382 void G1CollectedHeap::finalize_for_evac_failure() {
4383   assert(_evac_failure_scan_stack != NULL &&
4384          _evac_failure_scan_stack->length() == 0,
4385          "Postcondition");
4386   assert(!_drain_in_progress, "Postcondition");
4387   delete _evac_failure_scan_stack;
4388   _evac_failure_scan_stack = NULL;
4389 }
4390 
4391 void G1CollectedHeap::remove_self_forwarding_pointers() {
4392   assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4393 
4394   G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4395 
4396   if (G1CollectedHeap::use_parallel_gc_threads()) {
4397     set_par_threads();
4398     workers()->run_task(&rsfp_task);
4399     set_par_threads(0);
4400   } else {
4401     rsfp_task.work(0);
4402   }
4403 
4404   assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity");
4405 
4406   // Reset the claim values in the regions in the collection set.
4407   reset_cset_heap_region_claim_values();
4408 
4409   assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4410 
4411   // Now restore saved marks, if any.
4412   assert(_objs_with_preserved_marks.size() ==
4413             _preserved_marks_of_objs.size(), "Both or none.");
4414   while (!_objs_with_preserved_marks.is_empty()) {
4415     oop obj = _objs_with_preserved_marks.pop();
4416     markOop m = _preserved_marks_of_objs.pop();
4417     obj->set_mark(m);
4418   }
4419   _objs_with_preserved_marks.clear(true);
4420   _preserved_marks_of_objs.clear(true);
4421 }
4422 
4423 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4424   _evac_failure_scan_stack->push(obj);
4425 }
4426 
4427 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4428   assert(_evac_failure_scan_stack != NULL, "precondition");
4429 
4430   while (_evac_failure_scan_stack->length() > 0) {
4431      oop obj = _evac_failure_scan_stack->pop();
4432      _evac_failure_closure->set_region(heap_region_containing(obj));
4433      obj->oop_iterate_backwards(_evac_failure_closure);
4434   }
4435 }
4436 
4437 oop
4438 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state,
4439                                                oop old) {
4440   assert(obj_in_cs(old),
4441          err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4442                  (HeapWord*) old));
4443   markOop m = old->mark();
4444   oop forward_ptr = old->forward_to_atomic(old);
4445   if (forward_ptr == NULL) {
4446     // Forward-to-self succeeded.
4447     assert(_par_scan_state != NULL, "par scan state");
4448     OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4449     uint queue_num = _par_scan_state->queue_num();
4450 
4451     _evacuation_failed = true;
4452     _evacuation_failed_info_array[queue_num].register_copy_failure(old->size());
4453     if (_evac_failure_closure != cl) {
4454       MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4455       assert(!_drain_in_progress,
4456              "Should only be true while someone holds the lock.");
4457       // Set the global evac-failure closure to the current thread's.
4458       assert(_evac_failure_closure == NULL, "Or locking has failed.");
4459       set_evac_failure_closure(cl);
4460       // Now do the common part.
4461       handle_evacuation_failure_common(old, m);
4462       // Reset to NULL.
4463       set_evac_failure_closure(NULL);
4464     } else {
4465       // The lock is already held, and this is recursive.
4466       assert(_drain_in_progress, "This should only be the recursive case.");
4467       handle_evacuation_failure_common(old, m);
4468     }
4469     return old;
4470   } else {
4471     // Forward-to-self failed. Either someone else managed to allocate
4472     // space for this object (old != forward_ptr) or they beat us in
4473     // self-forwarding it (old == forward_ptr).
4474     assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4475            err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4476                    "should not be in the CSet",
4477                    (HeapWord*) old, (HeapWord*) forward_ptr));
4478     return forward_ptr;
4479   }
4480 }
4481 
4482 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4483   preserve_mark_if_necessary(old, m);
4484 
4485   HeapRegion* r = heap_region_containing(old);
4486   if (!r->evacuation_failed()) {
4487     r->set_evacuation_failed(true);
4488     _hr_printer.evac_failure(r);
4489   }
4490 
4491   push_on_evac_failure_scan_stack(old);
4492 
4493   if (!_drain_in_progress) {
4494     // prevent recursion in copy_to_survivor_space()
4495     _drain_in_progress = true;
4496     drain_evac_failure_scan_stack();
4497     _drain_in_progress = false;
4498   }
4499 }
4500 
4501 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4502   assert(evacuation_failed(), "Oversaving!");
4503   // We want to call the "for_promotion_failure" version only in the
4504   // case of a promotion failure.
4505   if (m->must_be_preserved_for_promotion_failure(obj)) {
4506     _objs_with_preserved_marks.push(obj);
4507     _preserved_marks_of_objs.push(m);
4508   }
4509 }
4510 
4511 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
4512                                                   size_t word_size) {
4513   if (purpose == GCAllocForSurvived) {
4514     HeapWord* result = survivor_attempt_allocation(word_size);
4515     if (result != NULL) {
4516       return result;
4517     } else {
4518       // Let's try to allocate in the old gen in case we can fit the
4519       // object there.
4520       return old_attempt_allocation(word_size);
4521     }
4522   } else {
4523     assert(purpose ==  GCAllocForTenured, "sanity");
4524     HeapWord* result = old_attempt_allocation(word_size);
4525     if (result != NULL) {
4526       return result;
4527     } else {
4528       // Let's try to allocate in the survivors in case we can fit the
4529       // object there.
4530       return survivor_attempt_allocation(word_size);
4531     }
4532   }
4533 
4534   ShouldNotReachHere();
4535   // Trying to keep some compilers happy.
4536   return NULL;
4537 }
4538 
4539 G1ParGCAllocBuffer::G1ParGCAllocBuffer(size_t gclab_word_size) :
4540   ParGCAllocBuffer(gclab_word_size), _retired(false) { }
4541 
4542 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, uint queue_num)
4543   : _g1h(g1h),
4544     _refs(g1h->task_queue(queue_num)),
4545     _dcq(&g1h->dirty_card_queue_set()),
4546     _ct_bs((CardTableModRefBS*)_g1h->barrier_set()),
4547     _g1_rem(g1h->g1_rem_set()),
4548     _hash_seed(17), _queue_num(queue_num),
4549     _term_attempts(0),
4550     _surviving_alloc_buffer(g1h->desired_plab_sz(GCAllocForSurvived)),
4551     _tenured_alloc_buffer(g1h->desired_plab_sz(GCAllocForTenured)),
4552     _age_table(false),
4553     _strong_roots_time(0), _term_time(0),
4554     _alloc_buffer_waste(0), _undo_waste(0) {
4555   // we allocate G1YoungSurvRateNumRegions plus one entries, since
4556   // we "sacrifice" entry 0 to keep track of surviving bytes for
4557   // non-young regions (where the age is -1)
4558   // We also add a few elements at the beginning and at the end in
4559   // an attempt to eliminate cache contention
4560   uint real_length = 1 + _g1h->g1_policy()->young_cset_region_length();
4561   uint array_length = PADDING_ELEM_NUM +
4562                       real_length +
4563                       PADDING_ELEM_NUM;
4564   _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length, mtGC);
4565   if (_surviving_young_words_base == NULL)
4566     vm_exit_out_of_memory(array_length * sizeof(size_t), OOM_MALLOC_ERROR,
4567                           "Not enough space for young surv histo.");
4568   _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM;
4569   memset(_surviving_young_words, 0, (size_t) real_length * sizeof(size_t));
4570 
4571   _alloc_buffers[GCAllocForSurvived] = &_surviving_alloc_buffer;
4572   _alloc_buffers[GCAllocForTenured]  = &_tenured_alloc_buffer;
4573 
4574   _start = os::elapsedTime();
4575 }
4576 
4577 void
4578 G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st)
4579 {
4580   st->print_raw_cr("GC Termination Stats");
4581   st->print_raw_cr("     elapsed  --strong roots-- -------termination-------"
4582                    " ------waste (KiB)------");
4583   st->print_raw_cr("thr     ms        ms      %        ms      %    attempts"
4584                    "  total   alloc    undo");
4585   st->print_raw_cr("--- --------- --------- ------ --------- ------ --------"
4586                    " ------- ------- -------");
4587 }
4588 
4589 void
4590 G1ParScanThreadState::print_termination_stats(int i,
4591                                               outputStream* const st) const
4592 {
4593   const double elapsed_ms = elapsed_time() * 1000.0;
4594   const double s_roots_ms = strong_roots_time() * 1000.0;
4595   const double term_ms    = term_time() * 1000.0;
4596   st->print_cr("%3d %9.2f %9.2f %6.2f "
4597                "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
4598                SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
4599                i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms,
4600                term_ms, term_ms * 100 / elapsed_ms, term_attempts(),
4601                (alloc_buffer_waste() + undo_waste()) * HeapWordSize / K,
4602                alloc_buffer_waste() * HeapWordSize / K,
4603                undo_waste() * HeapWordSize / K);
4604 }
4605 
4606 #ifdef ASSERT
4607 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const {
4608   assert(ref != NULL, "invariant");
4609   assert(UseCompressedOops, "sanity");
4610   assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, ref));
4611   oop p = oopDesc::load_decode_heap_oop(ref);
4612   assert(_g1h->is_in_g1_reserved(p),
4613          err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4614   return true;
4615 }
4616 
4617 bool G1ParScanThreadState::verify_ref(oop* ref) const {
4618   assert(ref != NULL, "invariant");
4619   if (has_partial_array_mask(ref)) {
4620     // Must be in the collection set--it's already been copied.
4621     oop p = clear_partial_array_mask(ref);
4622     assert(_g1h->obj_in_cs(p),
4623            err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4624   } else {
4625     oop p = oopDesc::load_decode_heap_oop(ref);
4626     assert(_g1h->is_in_g1_reserved(p),
4627            err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4628   }
4629   return true;
4630 }
4631 
4632 bool G1ParScanThreadState::verify_task(StarTask ref) const {
4633   if (ref.is_narrow()) {
4634     return verify_ref((narrowOop*) ref);
4635   } else {
4636     return verify_ref((oop*) ref);
4637   }
4638 }
4639 #endif // ASSERT
4640 
4641 void G1ParScanThreadState::trim_queue() {
4642   assert(_evac_cl != NULL, "not set");
4643   assert(_evac_failure_cl != NULL, "not set");
4644   assert(_partial_scan_cl != NULL, "not set");
4645 
4646   StarTask ref;
4647   do {
4648     // Drain the overflow stack first, so other threads can steal.
4649     while (refs()->pop_overflow(ref)) {
4650       deal_with_reference(ref);
4651     }
4652 
4653     while (refs()->pop_local(ref)) {
4654       deal_with_reference(ref);
4655     }
4656   } while (!refs()->is_empty());
4657 }
4658 
4659 G1ParClosureSuper::G1ParClosureSuper(G1CollectedHeap* g1,
4660                                      G1ParScanThreadState* par_scan_state) :
4661   _g1(g1), _g1_rem(_g1->g1_rem_set()), _cm(_g1->concurrent_mark()),
4662   _par_scan_state(par_scan_state),
4663   _worker_id(par_scan_state->queue_num()),
4664   _during_initial_mark(_g1->g1_policy()->during_initial_mark_pause()),
4665   _mark_in_progress(_g1->mark_in_progress()) { }
4666 
4667 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4668 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>::mark_object(oop obj) {
4669 #ifdef ASSERT
4670   HeapRegion* hr = _g1->heap_region_containing(obj);
4671   assert(hr != NULL, "sanity");
4672   assert(!hr->in_collection_set(), "should not mark objects in the CSet");
4673 #endif // ASSERT
4674 
4675   // We know that the object is not moving so it's safe to read its size.
4676   _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4677 }
4678 
4679 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4680 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4681   ::mark_forwarded_object(oop from_obj, oop to_obj) {
4682 #ifdef ASSERT
4683   assert(from_obj->is_forwarded(), "from obj should be forwarded");
4684   assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4685   assert(from_obj != to_obj, "should not be self-forwarded");
4686 
4687   HeapRegion* from_hr = _g1->heap_region_containing(from_obj);
4688   assert(from_hr != NULL, "sanity");
4689   assert(from_hr->in_collection_set(), "from obj should be in the CSet");
4690 
4691   HeapRegion* to_hr = _g1->heap_region_containing(to_obj);
4692   assert(to_hr != NULL, "sanity");
4693   assert(!to_hr->in_collection_set(), "should not mark objects in the CSet");
4694 #endif // ASSERT
4695 
4696   // The object might be in the process of being copied by another
4697   // worker so we cannot trust that its to-space image is
4698   // well-formed. So we have to read its size from its from-space
4699   // image which we know should not be changing.
4700   _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4701 }
4702 
4703 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4704 oop G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4705   ::copy_to_survivor_space(oop old) {
4706   size_t word_sz = old->size();
4707   HeapRegion* from_region = _g1->heap_region_containing_raw(old);
4708   // +1 to make the -1 indexes valid...
4709   int       young_index = from_region->young_index_in_cset()+1;
4710   assert( (from_region->is_young() && young_index >  0) ||
4711          (!from_region->is_young() && young_index == 0), "invariant" );
4712   G1CollectorPolicy* g1p = _g1->g1_policy();
4713   markOop m = old->mark();
4714   int age = m->has_displaced_mark_helper() ? m->displaced_mark_helper()->age()
4715                                            : m->age();
4716   GCAllocPurpose alloc_purpose = g1p->evacuation_destination(from_region, age,
4717                                                              word_sz);
4718   HeapWord* obj_ptr = _par_scan_state->allocate(alloc_purpose, word_sz);
4719 #ifndef PRODUCT
4720   // Should this evacuation fail?
4721   if (_g1->evacuation_should_fail()) {
4722     if (obj_ptr != NULL) {
4723       _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz);
4724       obj_ptr = NULL;
4725     }
4726   }
4727 #endif // !PRODUCT
4728 
4729   if (obj_ptr == NULL) {
4730     // This will either forward-to-self, or detect that someone else has
4731     // installed a forwarding pointer.
4732     return _g1->handle_evacuation_failure_par(_par_scan_state, old);
4733   }
4734 
4735   oop obj = oop(obj_ptr);
4736 
4737   // We're going to allocate linearly, so might as well prefetch ahead.
4738   Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
4739 
4740   oop forward_ptr = old->forward_to_atomic(obj);
4741   if (forward_ptr == NULL) {
4742     Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
4743     if (g1p->track_object_age(alloc_purpose)) {
4744       // We could simply do obj->incr_age(). However, this causes a
4745       // performance issue. obj->incr_age() will first check whether
4746       // the object has a displaced mark by checking its mark word;
4747       // getting the mark word from the new location of the object
4748       // stalls. So, given that we already have the mark word and we
4749       // are about to install it anyway, it's better to increase the
4750       // age on the mark word, when the object does not have a
4751       // displaced mark word. We're not expecting many objects to have
4752       // a displaced marked word, so that case is not optimized
4753       // further (it could be...) and we simply call obj->incr_age().
4754 
4755       if (m->has_displaced_mark_helper()) {
4756         // in this case, we have to install the mark word first,
4757         // otherwise obj looks to be forwarded (the old mark word,
4758         // which contains the forward pointer, was copied)
4759         obj->set_mark(m);
4760         obj->incr_age();
4761       } else {
4762         m = m->incr_age();
4763         obj->set_mark(m);
4764       }
4765       _par_scan_state->age_table()->add(obj, word_sz);
4766     } else {
4767       obj->set_mark(m);
4768     }
4769 
4770     size_t* surv_young_words = _par_scan_state->surviving_young_words();
4771     surv_young_words[young_index] += word_sz;
4772 
4773     if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
4774       // We keep track of the next start index in the length field of
4775       // the to-space object. The actual length can be found in the
4776       // length field of the from-space object.
4777       arrayOop(obj)->set_length(0);
4778       oop* old_p = set_partial_array_mask(old);
4779       _par_scan_state->push_on_queue(old_p);
4780     } else {
4781       // No point in using the slower heap_region_containing() method,
4782       // given that we know obj is in the heap.
4783       _scanner.set_region(_g1->heap_region_containing_raw(obj));
4784       obj->oop_iterate_backwards(&_scanner);
4785     }
4786   } else {
4787     _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz);
4788     obj = forward_ptr;
4789   }
4790   return obj;
4791 }
4792 
4793 template <class T>
4794 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) {
4795   if (_g1->heap_region_containing_raw(new_obj)->is_young()) {
4796     _scanned_klass->record_modified_oops();
4797   }
4798 }
4799 
4800 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4801 template <class T>
4802 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4803 ::do_oop_work(T* p) {
4804   oop obj = oopDesc::load_decode_heap_oop(p);
4805   assert(barrier != G1BarrierRS || obj != NULL,
4806          "Precondition: G1BarrierRS implies obj is non-NULL");
4807 
4808   assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4809 
4810   // here the null check is implicit in the cset_fast_test() test
4811   if (_g1->in_cset_fast_test(obj)) {
4812     oop forwardee;
4813     if (obj->is_forwarded()) {
4814       forwardee = obj->forwardee();
4815     } else {
4816       forwardee = copy_to_survivor_space(obj);
4817     }
4818     assert(forwardee != NULL, "forwardee should not be NULL");
4819     oopDesc::encode_store_heap_oop(p, forwardee);
4820     if (do_mark_object && forwardee != obj) {
4821       // If the object is self-forwarded we don't need to explicitly
4822       // mark it, the evacuation failure protocol will do so.
4823       mark_forwarded_object(obj, forwardee);
4824     }
4825 
4826     // When scanning the RS, we only care about objs in CS.
4827     if (barrier == G1BarrierRS) {
4828       _par_scan_state->update_rs(_from, p, _worker_id);
4829     } else if (barrier == G1BarrierKlass) {
4830       do_klass_barrier(p, forwardee);
4831     }
4832   } else {
4833     // The object is not in collection set. If we're a root scanning
4834     // closure during an initial mark pause (i.e. do_mark_object will
4835     // be true) then attempt to mark the object.
4836     if (do_mark_object && _g1->is_in_g1_reserved(obj)) {
4837       mark_object(obj);
4838     }
4839   }
4840 
4841   if (barrier == G1BarrierEvac && obj != NULL) {
4842     _par_scan_state->update_rs(_from, p, _worker_id);
4843   }
4844 
4845   if (do_gen_barrier && obj != NULL) {
4846     par_do_barrier(p);
4847   }
4848 }
4849 
4850 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(oop* p);
4851 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(narrowOop* p);
4852 
4853 template <class T> void G1ParScanPartialArrayClosure::do_oop_nv(T* p) {
4854   assert(has_partial_array_mask(p), "invariant");
4855   oop from_obj = clear_partial_array_mask(p);
4856 
4857   assert(Universe::heap()->is_in_reserved(from_obj), "must be in heap.");
4858   assert(from_obj->is_objArray(), "must be obj array");
4859   objArrayOop from_obj_array = objArrayOop(from_obj);
4860   // The from-space object contains the real length.
4861   int length                 = from_obj_array->length();
4862 
4863   assert(from_obj->is_forwarded(), "must be forwarded");
4864   oop to_obj                 = from_obj->forwardee();
4865   assert(from_obj != to_obj, "should not be chunking self-forwarded objects");
4866   objArrayOop to_obj_array   = objArrayOop(to_obj);
4867   // We keep track of the next start index in the length field of the
4868   // to-space object.
4869   int next_index             = to_obj_array->length();
4870   assert(0 <= next_index && next_index < length,
4871          err_msg("invariant, next index: %d, length: %d", next_index, length));
4872 
4873   int start                  = next_index;
4874   int end                    = length;
4875   int remainder              = end - start;
4876   // We'll try not to push a range that's smaller than ParGCArrayScanChunk.
4877   if (remainder > 2 * ParGCArrayScanChunk) {
4878     end = start + ParGCArrayScanChunk;
4879     to_obj_array->set_length(end);
4880     // Push the remainder before we process the range in case another
4881     // worker has run out of things to do and can steal it.
4882     oop* from_obj_p = set_partial_array_mask(from_obj);
4883     _par_scan_state->push_on_queue(from_obj_p);
4884   } else {
4885     assert(length == end, "sanity");
4886     // We'll process the final range for this object. Restore the length
4887     // so that the heap remains parsable in case of evacuation failure.
4888     to_obj_array->set_length(end);
4889   }
4890   _scanner.set_region(_g1->heap_region_containing_raw(to_obj));
4891   // Process indexes [start,end). It will also process the header
4892   // along with the first chunk (i.e., the chunk with start == 0).
4893   // Note that at this point the length field of to_obj_array is not
4894   // correct given that we are using it to keep track of the next
4895   // start index. oop_iterate_range() (thankfully!) ignores the length
4896   // field and only relies on the start / end parameters.  It does
4897   // however return the size of the object which will be incorrect. So
4898   // we have to ignore it even if we wanted to use it.
4899   to_obj_array->oop_iterate_range(&_scanner, start, end);
4900 }
4901 
4902 class G1ParEvacuateFollowersClosure : public VoidClosure {
4903 protected:
4904   G1CollectedHeap*              _g1h;
4905   G1ParScanThreadState*         _par_scan_state;
4906   RefToScanQueueSet*            _queues;
4907   ParallelTaskTerminator*       _terminator;
4908 
4909   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
4910   RefToScanQueueSet*      queues()         { return _queues; }
4911   ParallelTaskTerminator* terminator()     { return _terminator; }
4912 
4913 public:
4914   G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4915                                 G1ParScanThreadState* par_scan_state,
4916                                 RefToScanQueueSet* queues,
4917                                 ParallelTaskTerminator* terminator)
4918     : _g1h(g1h), _par_scan_state(par_scan_state),
4919       _queues(queues), _terminator(terminator) {}
4920 
4921   void do_void();
4922 
4923 private:
4924   inline bool offer_termination();
4925 };
4926 
4927 bool G1ParEvacuateFollowersClosure::offer_termination() {
4928   G1ParScanThreadState* const pss = par_scan_state();
4929   pss->start_term_time();
4930   const bool res = terminator()->offer_termination();
4931   pss->end_term_time();
4932   return res;
4933 }
4934 
4935 void G1ParEvacuateFollowersClosure::do_void() {
4936   StarTask stolen_task;
4937   G1ParScanThreadState* const pss = par_scan_state();
4938   pss->trim_queue();
4939 
4940   do {
4941     while (queues()->steal(pss->queue_num(), pss->hash_seed(), stolen_task)) {
4942       assert(pss->verify_task(stolen_task), "sanity");
4943       if (stolen_task.is_narrow()) {
4944         pss->deal_with_reference((narrowOop*) stolen_task);
4945       } else {
4946         pss->deal_with_reference((oop*) stolen_task);
4947       }
4948 
4949       // We've just processed a reference and we might have made
4950       // available new entries on the queues. So we have to make sure
4951       // we drain the queues as necessary.
4952       pss->trim_queue();
4953     }
4954   } while (!offer_termination());
4955 
4956   pss->retire_alloc_buffers();
4957 }
4958 
4959 class G1KlassScanClosure : public KlassClosure {
4960  G1ParCopyHelper* _closure;
4961  bool             _process_only_dirty;
4962  int              _count;
4963  public:
4964   G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty)
4965       : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {}
4966   void do_klass(Klass* klass) {
4967     // If the klass has not been dirtied we know that there's
4968     // no references into  the young gen and we can skip it.
4969    if (!_process_only_dirty || klass->has_modified_oops()) {
4970       // Clean the klass since we're going to scavenge all the metadata.
4971       klass->clear_modified_oops();
4972 
4973       // Tell the closure that this klass is the Klass to scavenge
4974       // and is the one to dirty if oops are left pointing into the young gen.
4975       _closure->set_scanned_klass(klass);
4976 
4977       klass->oops_do(_closure);
4978 
4979       _closure->set_scanned_klass(NULL);
4980     }
4981     _count++;
4982   }
4983 };
4984 
4985 class G1ParTask : public AbstractGangTask {
4986 protected:
4987   G1CollectedHeap*       _g1h;
4988   RefToScanQueueSet      *_queues;
4989   ParallelTaskTerminator _terminator;
4990   uint _n_workers;
4991 
4992   Mutex _stats_lock;
4993   Mutex* stats_lock() { return &_stats_lock; }
4994 
4995   size_t getNCards() {
4996     return (_g1h->capacity() + G1BlockOffsetSharedArray::N_bytes - 1)
4997       / G1BlockOffsetSharedArray::N_bytes;
4998   }
4999 
5000 public:
5001   G1ParTask(G1CollectedHeap* g1h,
5002             RefToScanQueueSet *task_queues)
5003     : AbstractGangTask("G1 collection"),
5004       _g1h(g1h),
5005       _queues(task_queues),
5006       _terminator(0, _queues),
5007       _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
5008   {}
5009 
5010   RefToScanQueueSet* queues() { return _queues; }
5011 
5012   RefToScanQueue *work_queue(int i) {
5013     return queues()->queue(i);
5014   }
5015 
5016   ParallelTaskTerminator* terminator() { return &_terminator; }
5017 
5018   virtual void set_for_termination(int active_workers) {
5019     // This task calls set_n_termination() in par_non_clean_card_iterate_work()
5020     // in the young space (_par_seq_tasks) in the G1 heap
5021     // for SequentialSubTasksDone.
5022     // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap
5023     // both of which need setting by set_n_termination().
5024     _g1h->SharedHeap::set_n_termination(active_workers);
5025     _g1h->set_n_termination(active_workers);
5026     terminator()->reset_for_reuse(active_workers);
5027     _n_workers = active_workers;
5028   }
5029 
5030   void work(uint worker_id) {
5031     if (worker_id >= _n_workers) return;  // no work needed this round
5032 
5033     double start_time_ms = os::elapsedTime() * 1000.0;
5034     _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms);
5035 
5036     {
5037       ResourceMark rm;
5038       HandleMark   hm;
5039 
5040       ReferenceProcessor*             rp = _g1h->ref_processor_stw();
5041 
5042       G1ParScanThreadState            pss(_g1h, worker_id);
5043       G1ParScanHeapEvacClosure        scan_evac_cl(_g1h, &pss, rp);
5044       G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
5045       G1ParScanPartialArrayClosure    partial_scan_cl(_g1h, &pss, rp);
5046 
5047       pss.set_evac_closure(&scan_evac_cl);
5048       pss.set_evac_failure_closure(&evac_failure_cl);
5049       pss.set_partial_scan_closure(&partial_scan_cl);
5050 
5051       G1ParScanExtRootClosure        only_scan_root_cl(_g1h, &pss, rp);
5052       G1ParScanMetadataClosure       only_scan_metadata_cl(_g1h, &pss, rp);
5053 
5054       G1ParScanAndMarkExtRootClosure scan_mark_root_cl(_g1h, &pss, rp);
5055       G1ParScanAndMarkMetadataClosure scan_mark_metadata_cl(_g1h, &pss, rp);
5056 
5057       bool only_young                 = _g1h->g1_policy()->gcs_are_young();
5058       G1KlassScanClosure              scan_mark_klasses_cl_s(&scan_mark_metadata_cl, false);
5059       G1KlassScanClosure              only_scan_klasses_cl_s(&only_scan_metadata_cl, only_young);
5060 
5061       OopClosure*                    scan_root_cl = &only_scan_root_cl;
5062       G1KlassScanClosure*            scan_klasses_cl = &only_scan_klasses_cl_s;
5063 
5064       if (_g1h->g1_policy()->during_initial_mark_pause()) {
5065         // We also need to mark copied objects.
5066         scan_root_cl = &scan_mark_root_cl;
5067         scan_klasses_cl = &scan_mark_klasses_cl_s;
5068       }
5069 
5070       G1ParPushHeapRSClosure          push_heap_rs_cl(_g1h, &pss);
5071 
5072       // Don't scan the scavengable methods in the code cache as part
5073       // of strong root scanning. The code roots that point into a
5074       // region in the collection set are scanned when we scan the
5075       // region's RSet.
5076       int so = SharedHeap::SO_AllClasses | SharedHeap::SO_Strings;
5077 
5078       pss.start_strong_roots();
5079       _g1h->g1_process_strong_roots(/* is scavenging */ true,
5080                                     SharedHeap::ScanningOption(so),
5081                                     scan_root_cl,
5082                                     &push_heap_rs_cl,
5083                                     scan_klasses_cl,
5084                                     worker_id);
5085       pss.end_strong_roots();
5086 
5087       {
5088         double start = os::elapsedTime();
5089         G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
5090         evac.do_void();
5091         double elapsed_ms = (os::elapsedTime()-start)*1000.0;
5092         double term_ms = pss.term_time()*1000.0;
5093         _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms);
5094         _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts());
5095       }
5096       _g1h->g1_policy()->record_thread_age_table(pss.age_table());
5097       _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
5098 
5099       if (ParallelGCVerbose) {
5100         MutexLocker x(stats_lock());
5101         pss.print_termination_stats(worker_id);
5102       }
5103 
5104       assert(pss.refs()->is_empty(), "should be empty");
5105 
5106       // Close the inner scope so that the ResourceMark and HandleMark
5107       // destructors are executed here and are included as part of the
5108       // "GC Worker Time".
5109     }
5110 
5111     double end_time_ms = os::elapsedTime() * 1000.0;
5112     _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms);
5113   }
5114 };
5115 
5116 // *** Common G1 Evacuation Stuff
5117 
5118 // This method is run in a GC worker.
5119 
5120 void
5121 G1CollectedHeap::
5122 g1_process_strong_roots(bool is_scavenging,
5123                         ScanningOption so,
5124                         OopClosure* scan_non_heap_roots,
5125                         OopsInHeapRegionClosure* scan_rs,
5126                         G1KlassScanClosure* scan_klasses,
5127                         int worker_i) {
5128 
5129   // First scan the strong roots
5130   double ext_roots_start = os::elapsedTime();
5131   double closure_app_time_sec = 0.0;
5132 
5133   BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
5134 
5135   assert(so & SO_CodeCache || scan_rs != NULL, "must scan code roots somehow");
5136   // Walk the code cache/strong code roots w/o buffering, because StarTask
5137   // cannot handle unaligned oop locations.
5138   CodeBlobToOopClosure eager_scan_code_roots(scan_non_heap_roots, true /* do_marking */);
5139 
5140   process_strong_roots(false, // no scoping; this is parallel code
5141                        is_scavenging, so,
5142                        &buf_scan_non_heap_roots,
5143                        &eager_scan_code_roots,
5144                        scan_klasses
5145                        );
5146 
5147   // Now the CM ref_processor roots.
5148   if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
5149     // We need to treat the discovered reference lists of the
5150     // concurrent mark ref processor as roots and keep entries
5151     // (which are added by the marking threads) on them live
5152     // until they can be processed at the end of marking.
5153     ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
5154   }
5155 
5156   // Finish up any enqueued closure apps (attributed as object copy time).
5157   buf_scan_non_heap_roots.done();
5158 
5159   double obj_copy_time_sec = buf_scan_non_heap_roots.closure_app_seconds();
5160 
5161   g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
5162 
5163   double ext_root_time_ms =
5164     ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0;
5165 
5166   g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
5167 
5168   // During conc marking we have to filter the per-thread SATB buffers
5169   // to make sure we remove any oops into the CSet (which will show up
5170   // as implicitly live).
5171   double satb_filtering_ms = 0.0;
5172   if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) {
5173     if (mark_in_progress()) {
5174       double satb_filter_start = os::elapsedTime();
5175 
5176       JavaThread::satb_mark_queue_set().filter_thread_buffers();
5177 
5178       satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0;
5179     }
5180   }
5181   g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms);
5182 
5183   // If this is an initial mark pause, and we're not scanning
5184   // the entire code cache, we need to mark the oops in the
5185   // strong code root lists for the regions that are not in
5186   // the collection set.
5187   // Note all threads participate in this set of root tasks.
5188   double mark_strong_code_roots_ms = 0.0;
5189   if (g1_policy()->during_initial_mark_pause() && !(so & SO_CodeCache)) {
5190     double mark_strong_roots_start = os::elapsedTime();
5191     mark_strong_code_roots(worker_i);
5192     mark_strong_code_roots_ms = (os::elapsedTime() - mark_strong_roots_start) * 1000.0;
5193   }
5194   g1_policy()->phase_times()->record_strong_code_root_mark_time(worker_i, mark_strong_code_roots_ms);
5195 
5196   // Now scan the complement of the collection set.
5197   if (scan_rs != NULL) {
5198     g1_rem_set()->oops_into_collection_set_do(scan_rs, &eager_scan_code_roots, worker_i);
5199   }
5200   _process_strong_tasks->all_tasks_completed();
5201 }
5202 
5203 void
5204 G1CollectedHeap::g1_process_weak_roots(OopClosure* root_closure) {
5205   CodeBlobToOopClosure roots_in_blobs(root_closure, /*do_marking=*/ false);
5206   SharedHeap::process_weak_roots(root_closure, &roots_in_blobs);
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 
5242     if (_g1->obj_in_cs(obj)) {
5243       assert( obj->is_forwarded(), "invariant" );
5244       *p = obj->forwardee();
5245     }
5246   }
5247 };
5248 
5249 // Copying Keep Alive closure - can be called from both
5250 // serial and parallel code as long as different worker
5251 // threads utilize different G1ParScanThreadState instances
5252 // and different queues.
5253 
5254 class G1CopyingKeepAliveClosure: public OopClosure {
5255   G1CollectedHeap*         _g1h;
5256   OopClosure*              _copy_non_heap_obj_cl;
5257   OopsInHeapRegionClosure* _copy_metadata_obj_cl;
5258   G1ParScanThreadState*    _par_scan_state;
5259 
5260 public:
5261   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
5262                             OopClosure* non_heap_obj_cl,
5263                             OopsInHeapRegionClosure* metadata_obj_cl,
5264                             G1ParScanThreadState* pss):
5265     _g1h(g1h),
5266     _copy_non_heap_obj_cl(non_heap_obj_cl),
5267     _copy_metadata_obj_cl(metadata_obj_cl),
5268     _par_scan_state(pss)
5269   {}
5270 
5271   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
5272   virtual void do_oop(      oop* p) { do_oop_work(p); }
5273 
5274   template <class T> void do_oop_work(T* p) {
5275     oop obj = oopDesc::load_decode_heap_oop(p);
5276 
5277     if (_g1h->obj_in_cs(obj)) {
5278       // If the referent object has been forwarded (either copied
5279       // to a new location or to itself in the event of an
5280       // evacuation failure) then we need to update the reference
5281       // field and, if both reference and referent are in the G1
5282       // heap, update the RSet for the referent.
5283       //
5284       // If the referent has not been forwarded then we have to keep
5285       // it alive by policy. Therefore we have copy the referent.
5286       //
5287       // If the reference field is in the G1 heap then we can push
5288       // on the PSS queue. When the queue is drained (after each
5289       // phase of reference processing) the object and it's followers
5290       // will be copied, the reference field set to point to the
5291       // new location, and the RSet updated. Otherwise we need to
5292       // use the the non-heap or metadata closures directly to copy
5293       // the referent object and update the pointer, while avoiding
5294       // updating the RSet.
5295 
5296       if (_g1h->is_in_g1_reserved(p)) {
5297         _par_scan_state->push_on_queue(p);
5298       } else {
5299         assert(!ClassLoaderDataGraph::contains((address)p),
5300                err_msg("Otherwise need to call _copy_metadata_obj_cl->do_oop(p) "
5301                               PTR_FORMAT, p));
5302           _copy_non_heap_obj_cl->do_oop(p);
5303         }
5304       }
5305     }
5306 };
5307 
5308 // Serial drain queue closure. Called as the 'complete_gc'
5309 // closure for each discovered list in some of the
5310 // reference processing phases.
5311 
5312 class G1STWDrainQueueClosure: public VoidClosure {
5313 protected:
5314   G1CollectedHeap* _g1h;
5315   G1ParScanThreadState* _par_scan_state;
5316 
5317   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
5318 
5319 public:
5320   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
5321     _g1h(g1h),
5322     _par_scan_state(pss)
5323   { }
5324 
5325   void do_void() {
5326     G1ParScanThreadState* const pss = par_scan_state();
5327     pss->trim_queue();
5328   }
5329 };
5330 
5331 // Parallel Reference Processing closures
5332 
5333 // Implementation of AbstractRefProcTaskExecutor for parallel reference
5334 // processing during G1 evacuation pauses.
5335 
5336 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5337 private:
5338   G1CollectedHeap*   _g1h;
5339   RefToScanQueueSet* _queues;
5340   FlexibleWorkGang*  _workers;
5341   int                _active_workers;
5342 
5343 public:
5344   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5345                         FlexibleWorkGang* workers,
5346                         RefToScanQueueSet *task_queues,
5347                         int n_workers) :
5348     _g1h(g1h),
5349     _queues(task_queues),
5350     _workers(workers),
5351     _active_workers(n_workers)
5352   {
5353     assert(n_workers > 0, "shouldn't call this otherwise");
5354   }
5355 
5356   // Executes the given task using concurrent marking worker threads.
5357   virtual void execute(ProcessTask& task);
5358   virtual void execute(EnqueueTask& task);
5359 };
5360 
5361 // Gang task for possibly parallel reference processing
5362 
5363 class G1STWRefProcTaskProxy: public AbstractGangTask {
5364   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5365   ProcessTask&     _proc_task;
5366   G1CollectedHeap* _g1h;
5367   RefToScanQueueSet *_task_queues;
5368   ParallelTaskTerminator* _terminator;
5369 
5370 public:
5371   G1STWRefProcTaskProxy(ProcessTask& proc_task,
5372                      G1CollectedHeap* g1h,
5373                      RefToScanQueueSet *task_queues,
5374                      ParallelTaskTerminator* terminator) :
5375     AbstractGangTask("Process reference objects in parallel"),
5376     _proc_task(proc_task),
5377     _g1h(g1h),
5378     _task_queues(task_queues),
5379     _terminator(terminator)
5380   {}
5381 
5382   virtual void work(uint worker_id) {
5383     // The reference processing task executed by a single worker.
5384     ResourceMark rm;
5385     HandleMark   hm;
5386 
5387     G1STWIsAliveClosure is_alive(_g1h);
5388 
5389     G1ParScanThreadState pss(_g1h, worker_id);
5390 
5391     G1ParScanHeapEvacClosure        scan_evac_cl(_g1h, &pss, NULL);
5392     G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5393     G1ParScanPartialArrayClosure    partial_scan_cl(_g1h, &pss, NULL);
5394 
5395     pss.set_evac_closure(&scan_evac_cl);
5396     pss.set_evac_failure_closure(&evac_failure_cl);
5397     pss.set_partial_scan_closure(&partial_scan_cl);
5398 
5399     G1ParScanExtRootClosure        only_copy_non_heap_cl(_g1h, &pss, NULL);
5400     G1ParScanMetadataClosure       only_copy_metadata_cl(_g1h, &pss, NULL);
5401 
5402     G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5403     G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(_g1h, &pss, NULL);
5404 
5405     OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5406     OopsInHeapRegionClosure*       copy_metadata_cl = &only_copy_metadata_cl;
5407 
5408     if (_g1h->g1_policy()->during_initial_mark_pause()) {
5409       // We also need to mark copied objects.
5410       copy_non_heap_cl = &copy_mark_non_heap_cl;
5411       copy_metadata_cl = &copy_mark_metadata_cl;
5412     }
5413 
5414     // Keep alive closure.
5415     G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_metadata_cl, &pss);
5416 
5417     // Complete GC closure
5418     G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5419 
5420     // Call the reference processing task's work routine.
5421     _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5422 
5423     // Note we cannot assert that the refs array is empty here as not all
5424     // of the processing tasks (specifically phase2 - pp2_work) execute
5425     // the complete_gc closure (which ordinarily would drain the queue) so
5426     // the queue may not be empty.
5427   }
5428 };
5429 
5430 // Driver routine for parallel reference processing.
5431 // Creates an instance of the ref processing gang
5432 // task and has the worker threads execute it.
5433 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5434   assert(_workers != NULL, "Need parallel worker threads.");
5435 
5436   ParallelTaskTerminator terminator(_active_workers, _queues);
5437   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5438 
5439   _g1h->set_par_threads(_active_workers);
5440   _workers->run_task(&proc_task_proxy);
5441   _g1h->set_par_threads(0);
5442 }
5443 
5444 // Gang task for parallel reference enqueueing.
5445 
5446 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5447   typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5448   EnqueueTask& _enq_task;
5449 
5450 public:
5451   G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5452     AbstractGangTask("Enqueue reference objects in parallel"),
5453     _enq_task(enq_task)
5454   { }
5455 
5456   virtual void work(uint worker_id) {
5457     _enq_task.work(worker_id);
5458   }
5459 };
5460 
5461 // Driver routine for parallel reference enqueueing.
5462 // Creates an instance of the ref enqueueing gang
5463 // task and has the worker threads execute it.
5464 
5465 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5466   assert(_workers != NULL, "Need parallel worker threads.");
5467 
5468   G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5469 
5470   _g1h->set_par_threads(_active_workers);
5471   _workers->run_task(&enq_task_proxy);
5472   _g1h->set_par_threads(0);
5473 }
5474 
5475 // End of weak reference support closures
5476 
5477 // Abstract task used to preserve (i.e. copy) any referent objects
5478 // that are in the collection set and are pointed to by reference
5479 // objects discovered by the CM ref processor.
5480 
5481 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5482 protected:
5483   G1CollectedHeap* _g1h;
5484   RefToScanQueueSet      *_queues;
5485   ParallelTaskTerminator _terminator;
5486   uint _n_workers;
5487 
5488 public:
5489   G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
5490     AbstractGangTask("ParPreserveCMReferents"),
5491     _g1h(g1h),
5492     _queues(task_queues),
5493     _terminator(workers, _queues),
5494     _n_workers(workers)
5495   { }
5496 
5497   void work(uint worker_id) {
5498     ResourceMark rm;
5499     HandleMark   hm;
5500 
5501     G1ParScanThreadState            pss(_g1h, worker_id);
5502     G1ParScanHeapEvacClosure        scan_evac_cl(_g1h, &pss, NULL);
5503     G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5504     G1ParScanPartialArrayClosure    partial_scan_cl(_g1h, &pss, NULL);
5505 
5506     pss.set_evac_closure(&scan_evac_cl);
5507     pss.set_evac_failure_closure(&evac_failure_cl);
5508     pss.set_partial_scan_closure(&partial_scan_cl);
5509 
5510     assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5511 
5512 
5513     G1ParScanExtRootClosure        only_copy_non_heap_cl(_g1h, &pss, NULL);
5514     G1ParScanMetadataClosure       only_copy_metadata_cl(_g1h, &pss, NULL);
5515 
5516     G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5517     G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(_g1h, &pss, NULL);
5518 
5519     OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5520     OopsInHeapRegionClosure*       copy_metadata_cl = &only_copy_metadata_cl;
5521 
5522     if (_g1h->g1_policy()->during_initial_mark_pause()) {
5523       // We also need to mark copied objects.
5524       copy_non_heap_cl = &copy_mark_non_heap_cl;
5525       copy_metadata_cl = &copy_mark_metadata_cl;
5526     }
5527 
5528     // Is alive closure
5529     G1AlwaysAliveClosure always_alive(_g1h);
5530 
5531     // Copying keep alive closure. Applied to referent objects that need
5532     // to be copied.
5533     G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_metadata_cl, &pss);
5534 
5535     ReferenceProcessor* rp = _g1h->ref_processor_cm();
5536 
5537     uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5538     uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5539 
5540     // limit is set using max_num_q() - which was set using ParallelGCThreads.
5541     // So this must be true - but assert just in case someone decides to
5542     // change the worker ids.
5543     assert(0 <= worker_id && worker_id < limit, "sanity");
5544     assert(!rp->discovery_is_atomic(), "check this code");
5545 
5546     // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5547     for (uint idx = worker_id; idx < limit; idx += stride) {
5548       DiscoveredList& ref_list = rp->discovered_refs()[idx];
5549 
5550       DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5551       while (iter.has_next()) {
5552         // Since discovery is not atomic for the CM ref processor, we
5553         // can see some null referent objects.
5554         iter.load_ptrs(DEBUG_ONLY(true));
5555         oop ref = iter.obj();
5556 
5557         // This will filter nulls.
5558         if (iter.is_referent_alive()) {
5559           iter.make_referent_alive();
5560         }
5561         iter.move_to_next();
5562       }
5563     }
5564 
5565     // Drain the queue - which may cause stealing
5566     G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5567     drain_queue.do_void();
5568     // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5569     assert(pss.refs()->is_empty(), "should be");
5570   }
5571 };
5572 
5573 // Weak Reference processing during an evacuation pause (part 1).
5574 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) {
5575   double ref_proc_start = os::elapsedTime();
5576 
5577   ReferenceProcessor* rp = _ref_processor_stw;
5578   assert(rp->discovery_enabled(), "should have been enabled");
5579 
5580   // Any reference objects, in the collection set, that were 'discovered'
5581   // by the CM ref processor should have already been copied (either by
5582   // applying the external root copy closure to the discovered lists, or
5583   // by following an RSet entry).
5584   //
5585   // But some of the referents, that are in the collection set, that these
5586   // reference objects point to may not have been copied: the STW ref
5587   // processor would have seen that the reference object had already
5588   // been 'discovered' and would have skipped discovering the reference,
5589   // but would not have treated the reference object as a regular oop.
5590   // As a result the copy closure would not have been applied to the
5591   // referent object.
5592   //
5593   // We need to explicitly copy these referent objects - the references
5594   // will be processed at the end of remarking.
5595   //
5596   // We also need to do this copying before we process the reference
5597   // objects discovered by the STW ref processor in case one of these
5598   // referents points to another object which is also referenced by an
5599   // object discovered by the STW ref processor.
5600 
5601   assert(!G1CollectedHeap::use_parallel_gc_threads() ||
5602            no_of_gc_workers == workers()->active_workers(),
5603            "Need to reset active GC workers");
5604 
5605   set_par_threads(no_of_gc_workers);
5606   G1ParPreserveCMReferentsTask keep_cm_referents(this,
5607                                                  no_of_gc_workers,
5608                                                  _task_queues);
5609 
5610   if (G1CollectedHeap::use_parallel_gc_threads()) {
5611     workers()->run_task(&keep_cm_referents);
5612   } else {
5613     keep_cm_referents.work(0);
5614   }
5615 
5616   set_par_threads(0);
5617 
5618   // Closure to test whether a referent is alive.
5619   G1STWIsAliveClosure is_alive(this);
5620 
5621   // Even when parallel reference processing is enabled, the processing
5622   // of JNI refs is serial and performed serially by the current thread
5623   // rather than by a worker. The following PSS will be used for processing
5624   // JNI refs.
5625 
5626   // Use only a single queue for this PSS.
5627   G1ParScanThreadState pss(this, 0);
5628 
5629   // We do not embed a reference processor in the copying/scanning
5630   // closures while we're actually processing the discovered
5631   // reference objects.
5632   G1ParScanHeapEvacClosure        scan_evac_cl(this, &pss, NULL);
5633   G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5634   G1ParScanPartialArrayClosure    partial_scan_cl(this, &pss, NULL);
5635 
5636   pss.set_evac_closure(&scan_evac_cl);
5637   pss.set_evac_failure_closure(&evac_failure_cl);
5638   pss.set_partial_scan_closure(&partial_scan_cl);
5639 
5640   assert(pss.refs()->is_empty(), "pre-condition");
5641 
5642   G1ParScanExtRootClosure        only_copy_non_heap_cl(this, &pss, NULL);
5643   G1ParScanMetadataClosure       only_copy_metadata_cl(this, &pss, NULL);
5644 
5645   G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5646   G1ParScanAndMarkMetadataClosure copy_mark_metadata_cl(this, &pss, NULL);
5647 
5648   OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5649   OopsInHeapRegionClosure*       copy_metadata_cl = &only_copy_metadata_cl;
5650 
5651   if (_g1h->g1_policy()->during_initial_mark_pause()) {
5652     // We also need to mark copied objects.
5653     copy_non_heap_cl = &copy_mark_non_heap_cl;
5654     copy_metadata_cl = &copy_mark_metadata_cl;
5655   }
5656 
5657   // Keep alive closure.
5658   G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, copy_metadata_cl, &pss);
5659 
5660   // Serial Complete GC closure
5661   G1STWDrainQueueClosure drain_queue(this, &pss);
5662 
5663   // Setup the soft refs policy...
5664   rp->setup_policy(false);
5665 
5666   ReferenceProcessorStats stats;
5667   if (!rp->processing_is_mt()) {
5668     // Serial reference processing...
5669     stats = rp->process_discovered_references(&is_alive,
5670                                               &keep_alive,
5671                                               &drain_queue,
5672                                               NULL,
5673                                               _gc_timer_stw);
5674   } else {
5675     // Parallel reference processing
5676     assert(rp->num_q() == no_of_gc_workers, "sanity");
5677     assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5678 
5679     G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5680     stats = rp->process_discovered_references(&is_alive,
5681                                               &keep_alive,
5682                                               &drain_queue,
5683                                               &par_task_executor,
5684                                               _gc_timer_stw);
5685   }
5686 
5687   _gc_tracer_stw->report_gc_reference_stats(stats);
5688   // We have completed copying any necessary live referent objects
5689   // (that were not copied during the actual pause) so we can
5690   // retire any active alloc buffers
5691   pss.retire_alloc_buffers();
5692   assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5693 
5694   double ref_proc_time = os::elapsedTime() - ref_proc_start;
5695   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5696 }
5697 
5698 // Weak Reference processing during an evacuation pause (part 2).
5699 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) {
5700   double ref_enq_start = os::elapsedTime();
5701 
5702   ReferenceProcessor* rp = _ref_processor_stw;
5703   assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5704 
5705   // Now enqueue any remaining on the discovered lists on to
5706   // the pending list.
5707   if (!rp->processing_is_mt()) {
5708     // Serial reference processing...
5709     rp->enqueue_discovered_references();
5710   } else {
5711     // Parallel reference enqueueing
5712 
5713     assert(no_of_gc_workers == workers()->active_workers(),
5714            "Need to reset active workers");
5715     assert(rp->num_q() == no_of_gc_workers, "sanity");
5716     assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5717 
5718     G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5719     rp->enqueue_discovered_references(&par_task_executor);
5720   }
5721 
5722   rp->verify_no_references_recorded();
5723   assert(!rp->discovery_enabled(), "should have been disabled");
5724 
5725   // FIXME
5726   // CM's reference processing also cleans up the string and symbol tables.
5727   // Should we do that here also? We could, but it is a serial operation
5728   // and could significantly increase the pause time.
5729 
5730   double ref_enq_time = os::elapsedTime() - ref_enq_start;
5731   g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5732 }
5733 
5734 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) {
5735   _expand_heap_after_alloc_failure = true;
5736   _evacuation_failed = false;
5737 
5738   // Should G1EvacuationFailureALot be in effect for this GC?
5739   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
5740 
5741   g1_rem_set()->prepare_for_oops_into_collection_set_do();
5742 
5743   // Disable the hot card cache.
5744   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
5745   hot_card_cache->reset_hot_cache_claimed_index();
5746   hot_card_cache->set_use_cache(false);
5747 
5748   uint n_workers;
5749   if (G1CollectedHeap::use_parallel_gc_threads()) {
5750     n_workers =
5751       AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
5752                                      workers()->active_workers(),
5753                                      Threads::number_of_non_daemon_threads());
5754     assert(UseDynamicNumberOfGCThreads ||
5755            n_workers == workers()->total_workers(),
5756            "If not dynamic should be using all the  workers");
5757     workers()->set_active_workers(n_workers);
5758     set_par_threads(n_workers);
5759   } else {
5760     assert(n_par_threads() == 0,
5761            "Should be the original non-parallel value");
5762     n_workers = 1;
5763   }
5764 
5765   G1ParTask g1_par_task(this, _task_queues);
5766 
5767   init_for_evac_failure(NULL);
5768 
5769   rem_set()->prepare_for_younger_refs_iterate(true);
5770 
5771   assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5772   double start_par_time_sec = os::elapsedTime();
5773   double end_par_time_sec;
5774 
5775   {
5776     StrongRootsScope srs(this);
5777 
5778     if (G1CollectedHeap::use_parallel_gc_threads()) {
5779       // The individual threads will set their evac-failure closures.
5780       if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
5781       // These tasks use ShareHeap::_process_strong_tasks
5782       assert(UseDynamicNumberOfGCThreads ||
5783              workers()->active_workers() == workers()->total_workers(),
5784              "If not dynamic should be using all the  workers");
5785       workers()->run_task(&g1_par_task);
5786     } else {
5787       g1_par_task.set_for_termination(n_workers);
5788       g1_par_task.work(0);
5789     }
5790     end_par_time_sec = os::elapsedTime();
5791 
5792     // Closing the inner scope will execute the destructor
5793     // for the StrongRootsScope object. We record the current
5794     // elapsed time before closing the scope so that time
5795     // taken for the SRS destructor is NOT included in the
5796     // reported parallel time.
5797   }
5798 
5799   double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5800   g1_policy()->phase_times()->record_par_time(par_time_ms);
5801 
5802   double code_root_fixup_time_ms =
5803         (os::elapsedTime() - end_par_time_sec) * 1000.0;
5804   g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms);
5805 
5806   set_par_threads(0);
5807 
5808   // Process any discovered reference objects - we have
5809   // to do this _before_ we retire the GC alloc regions
5810   // as we may have to copy some 'reachable' referent
5811   // objects (and their reachable sub-graphs) that were
5812   // not copied during the pause.
5813   process_discovered_references(n_workers);
5814 
5815   // Weak root processing.
5816   {
5817     G1STWIsAliveClosure is_alive(this);
5818     G1KeepAliveClosure keep_alive(this);
5819     JNIHandles::weak_oops_do(&is_alive, &keep_alive);
5820   }
5821 
5822   release_gc_alloc_regions(n_workers, evacuation_info);
5823   g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5824 
5825   // Reset and re-enable the hot card cache.
5826   // Note the counts for the cards in the regions in the
5827   // collection set are reset when the collection set is freed.
5828   hot_card_cache->reset_hot_cache();
5829   hot_card_cache->set_use_cache(true);
5830 
5831   // Migrate the strong code roots attached to each region in
5832   // the collection set. Ideally we would like to do this
5833   // after we have finished the scanning/evacuation of the
5834   // strong code roots for a particular heap region.
5835   migrate_strong_code_roots();
5836 
5837   if (g1_policy()->during_initial_mark_pause()) {
5838     // Reset the claim values set during marking the strong code roots
5839     reset_heap_region_claim_values();
5840   }
5841 
5842   finalize_for_evac_failure();
5843 
5844   if (evacuation_failed()) {
5845     remove_self_forwarding_pointers();
5846 
5847     // Reset the G1EvacuationFailureALot counters and flags
5848     // Note: the values are reset only when an actual
5849     // evacuation failure occurs.
5850     NOT_PRODUCT(reset_evacuation_should_fail();)
5851   }
5852 
5853   // Enqueue any remaining references remaining on the STW
5854   // reference processor's discovered lists. We need to do
5855   // this after the card table is cleaned (and verified) as
5856   // the act of enqueueing entries on to the pending list
5857   // will log these updates (and dirty their associated
5858   // cards). We need these updates logged to update any
5859   // RSets.
5860   enqueue_discovered_references(n_workers);
5861 
5862   if (G1DeferredRSUpdate) {
5863     RedirtyLoggedCardTableEntryFastClosure redirty;
5864     dirty_card_queue_set().set_closure(&redirty);
5865     dirty_card_queue_set().apply_closure_to_all_completed_buffers();
5866 
5867     DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5868     dcq.merge_bufferlists(&dirty_card_queue_set());
5869     assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5870   }
5871   COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5872 }
5873 
5874 void G1CollectedHeap::free_region_if_empty(HeapRegion* hr,
5875                                      size_t* pre_used,
5876                                      FreeRegionList* free_list,
5877                                      OldRegionSet* old_proxy_set,
5878                                      HumongousRegionSet* humongous_proxy_set,
5879                                      HRRSCleanupTask* hrrs_cleanup_task,
5880                                      bool par) {
5881   if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) {
5882     if (hr->isHumongous()) {
5883       assert(hr->startsHumongous(), "we should only see starts humongous");
5884       free_humongous_region(hr, pre_used, free_list, humongous_proxy_set, par);
5885     } else {
5886       _old_set.remove_with_proxy(hr, old_proxy_set);
5887       free_region(hr, pre_used, free_list, par);
5888     }
5889   } else {
5890     hr->rem_set()->do_cleanup_work(hrrs_cleanup_task);
5891   }
5892 }
5893 
5894 void G1CollectedHeap::free_region(HeapRegion* hr,
5895                                   size_t* pre_used,
5896                                   FreeRegionList* free_list,
5897                                   bool par) {
5898   assert(!hr->isHumongous(), "this is only for non-humongous regions");
5899   assert(!hr->is_empty(), "the region should not be empty");
5900   assert(free_list != NULL, "pre-condition");
5901 
5902   // Clear the card counts for this region.
5903   // Note: we only need to do this if the region is not young
5904   // (since we don't refine cards in young regions).
5905   if (!hr->is_young()) {
5906     _cg1r->hot_card_cache()->reset_card_counts(hr);
5907   }
5908   *pre_used += hr->used();
5909   hr->hr_clear(par, true /* clear_space */);
5910   free_list->add_as_head(hr);
5911 }
5912 
5913 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
5914                                      size_t* pre_used,
5915                                      FreeRegionList* free_list,
5916                                      HumongousRegionSet* humongous_proxy_set,
5917                                      bool par) {
5918   assert(hr->startsHumongous(), "this is only for starts humongous regions");
5919   assert(free_list != NULL, "pre-condition");
5920   assert(humongous_proxy_set != NULL, "pre-condition");
5921 
5922   size_t hr_used = hr->used();
5923   size_t hr_capacity = hr->capacity();
5924   size_t hr_pre_used = 0;
5925   _humongous_set.remove_with_proxy(hr, humongous_proxy_set);
5926   // We need to read this before we make the region non-humongous,
5927   // otherwise the information will be gone.
5928   uint last_index = hr->last_hc_index();
5929   hr->set_notHumongous();
5930   free_region(hr, &hr_pre_used, free_list, par);
5931 
5932   uint i = hr->hrs_index() + 1;
5933   while (i < last_index) {
5934     HeapRegion* curr_hr = region_at(i);
5935     assert(curr_hr->continuesHumongous(), "invariant");
5936     curr_hr->set_notHumongous();
5937     free_region(curr_hr, &hr_pre_used, free_list, par);
5938     i += 1;
5939   }
5940   assert(hr_pre_used == hr_used,
5941          err_msg("hr_pre_used: "SIZE_FORMAT" and hr_used: "SIZE_FORMAT" "
5942                  "should be the same", hr_pre_used, hr_used));
5943   *pre_used += hr_pre_used;
5944 }
5945 
5946 void G1CollectedHeap::update_sets_after_freeing_regions(size_t pre_used,
5947                                        FreeRegionList* free_list,
5948                                        OldRegionSet* old_proxy_set,
5949                                        HumongousRegionSet* humongous_proxy_set,
5950                                        bool par) {
5951   if (pre_used > 0) {
5952     Mutex* lock = (par) ? ParGCRareEvent_lock : NULL;
5953     MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag);
5954     assert(_summary_bytes_used >= pre_used,
5955            err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" "
5956                    "should be >= pre_used: "SIZE_FORMAT,
5957                    _summary_bytes_used, pre_used));
5958     _summary_bytes_used -= pre_used;
5959   }
5960   if (free_list != NULL && !free_list->is_empty()) {
5961     MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
5962     _free_list.add_as_head(free_list);
5963   }
5964   if (old_proxy_set != NULL && !old_proxy_set->is_empty()) {
5965     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5966     _old_set.update_from_proxy(old_proxy_set);
5967   }
5968   if (humongous_proxy_set != NULL && !humongous_proxy_set->is_empty()) {
5969     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5970     _humongous_set.update_from_proxy(humongous_proxy_set);
5971   }
5972 }
5973 
5974 class G1ParCleanupCTTask : public AbstractGangTask {
5975   CardTableModRefBS* _ct_bs;
5976   G1CollectedHeap* _g1h;
5977   HeapRegion* volatile _su_head;
5978 public:
5979   G1ParCleanupCTTask(CardTableModRefBS* ct_bs,
5980                      G1CollectedHeap* g1h) :
5981     AbstractGangTask("G1 Par Cleanup CT Task"),
5982     _ct_bs(ct_bs), _g1h(g1h) { }
5983 
5984   void work(uint worker_id) {
5985     HeapRegion* r;
5986     while (r = _g1h->pop_dirty_cards_region()) {
5987       clear_cards(r);
5988     }
5989   }
5990 
5991   void clear_cards(HeapRegion* r) {
5992     // Cards of the survivors should have already been dirtied.
5993     if (!r->is_survivor()) {
5994       _ct_bs->clear(MemRegion(r->bottom(), r->end()));
5995     }
5996   }
5997 };
5998 
5999 #ifndef PRODUCT
6000 class G1VerifyCardTableCleanup: public HeapRegionClosure {
6001   G1CollectedHeap* _g1h;
6002   CardTableModRefBS* _ct_bs;
6003 public:
6004   G1VerifyCardTableCleanup(G1CollectedHeap* g1h, CardTableModRefBS* ct_bs)
6005     : _g1h(g1h), _ct_bs(ct_bs) { }
6006   virtual bool doHeapRegion(HeapRegion* r) {
6007     if (r->is_survivor()) {
6008       _g1h->verify_dirty_region(r);
6009     } else {
6010       _g1h->verify_not_dirty_region(r);
6011     }
6012     return false;
6013   }
6014 };
6015 
6016 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
6017   // All of the region should be clean.
6018   CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
6019   MemRegion mr(hr->bottom(), hr->end());
6020   ct_bs->verify_not_dirty_region(mr);
6021 }
6022 
6023 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
6024   // We cannot guarantee that [bottom(),end()] is dirty.  Threads
6025   // dirty allocated blocks as they allocate them. The thread that
6026   // retires each region and replaces it with a new one will do a
6027   // maximal allocation to fill in [pre_dummy_top(),end()] but will
6028   // not dirty that area (one less thing to have to do while holding
6029   // a lock). So we can only verify that [bottom(),pre_dummy_top()]
6030   // is dirty.
6031   CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set();
6032   MemRegion mr(hr->bottom(), hr->pre_dummy_top());
6033   ct_bs->verify_dirty_region(mr);
6034 }
6035 
6036 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
6037   CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set();
6038   for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
6039     verify_dirty_region(hr);
6040   }
6041 }
6042 
6043 void G1CollectedHeap::verify_dirty_young_regions() {
6044   verify_dirty_young_list(_young_list->first_region());
6045 }
6046 #endif
6047 
6048 void G1CollectedHeap::cleanUpCardTable() {
6049   CardTableModRefBS* ct_bs = (CardTableModRefBS*) (barrier_set());
6050   double start = os::elapsedTime();
6051 
6052   {
6053     // Iterate over the dirty cards region list.
6054     G1ParCleanupCTTask cleanup_task(ct_bs, this);
6055 
6056     if (G1CollectedHeap::use_parallel_gc_threads()) {
6057       set_par_threads();
6058       workers()->run_task(&cleanup_task);
6059       set_par_threads(0);
6060     } else {
6061       while (_dirty_cards_region_list) {
6062         HeapRegion* r = _dirty_cards_region_list;
6063         cleanup_task.clear_cards(r);
6064         _dirty_cards_region_list = r->get_next_dirty_cards_region();
6065         if (_dirty_cards_region_list == r) {
6066           // The last region.
6067           _dirty_cards_region_list = NULL;
6068         }
6069         r->set_next_dirty_cards_region(NULL);
6070       }
6071     }
6072 #ifndef PRODUCT
6073     if (G1VerifyCTCleanup || VerifyAfterGC) {
6074       G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
6075       heap_region_iterate(&cleanup_verifier);
6076     }
6077 #endif
6078   }
6079 
6080   double elapsed = os::elapsedTime() - start;
6081   g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
6082 }
6083 
6084 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) {
6085   size_t pre_used = 0;
6086   FreeRegionList local_free_list("Local List for CSet Freeing");
6087 
6088   double young_time_ms     = 0.0;
6089   double non_young_time_ms = 0.0;
6090 
6091   // Since the collection set is a superset of the the young list,
6092   // all we need to do to clear the young list is clear its
6093   // head and length, and unlink any young regions in the code below
6094   _young_list->clear();
6095 
6096   G1CollectorPolicy* policy = g1_policy();
6097 
6098   double start_sec = os::elapsedTime();
6099   bool non_young = true;
6100 
6101   HeapRegion* cur = cs_head;
6102   int age_bound = -1;
6103   size_t rs_lengths = 0;
6104 
6105   while (cur != NULL) {
6106     assert(!is_on_master_free_list(cur), "sanity");
6107     if (non_young) {
6108       if (cur->is_young()) {
6109         double end_sec = os::elapsedTime();
6110         double elapsed_ms = (end_sec - start_sec) * 1000.0;
6111         non_young_time_ms += elapsed_ms;
6112 
6113         start_sec = os::elapsedTime();
6114         non_young = false;
6115       }
6116     } else {
6117       if (!cur->is_young()) {
6118         double end_sec = os::elapsedTime();
6119         double elapsed_ms = (end_sec - start_sec) * 1000.0;
6120         young_time_ms += elapsed_ms;
6121 
6122         start_sec = os::elapsedTime();
6123         non_young = true;
6124       }
6125     }
6126 
6127     rs_lengths += cur->rem_set()->occupied();
6128 
6129     HeapRegion* next = cur->next_in_collection_set();
6130     assert(cur->in_collection_set(), "bad CS");
6131     cur->set_next_in_collection_set(NULL);
6132     cur->set_in_collection_set(false);
6133 
6134     if (cur->is_young()) {
6135       int index = cur->young_index_in_cset();
6136       assert(index != -1, "invariant");
6137       assert((uint) index < policy->young_cset_region_length(), "invariant");
6138       size_t words_survived = _surviving_young_words[index];
6139       cur->record_surv_words_in_group(words_survived);
6140 
6141       // At this point the we have 'popped' cur from the collection set
6142       // (linked via next_in_collection_set()) but it is still in the
6143       // young list (linked via next_young_region()). Clear the
6144       // _next_young_region field.
6145       cur->set_next_young_region(NULL);
6146     } else {
6147       int index = cur->young_index_in_cset();
6148       assert(index == -1, "invariant");
6149     }
6150 
6151     assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
6152             (!cur->is_young() && cur->young_index_in_cset() == -1),
6153             "invariant" );
6154 
6155     if (!cur->evacuation_failed()) {
6156       MemRegion used_mr = cur->used_region();
6157 
6158       // And the region is empty.
6159       assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
6160       free_region(cur, &pre_used, &local_free_list, false /* par */);
6161     } else {
6162       cur->uninstall_surv_rate_group();
6163       if (cur->is_young()) {
6164         cur->set_young_index_in_cset(-1);
6165       }
6166       cur->set_not_young();
6167       cur->set_evacuation_failed(false);
6168       // The region is now considered to be old.
6169       _old_set.add(cur);
6170       evacuation_info.increment_collectionset_used_after(cur->used());
6171     }
6172     cur = next;
6173   }
6174 
6175   evacuation_info.set_regions_freed(local_free_list.length());
6176   policy->record_max_rs_lengths(rs_lengths);
6177   policy->cset_regions_freed();
6178 
6179   double end_sec = os::elapsedTime();
6180   double elapsed_ms = (end_sec - start_sec) * 1000.0;
6181 
6182   if (non_young) {
6183     non_young_time_ms += elapsed_ms;
6184   } else {
6185     young_time_ms += elapsed_ms;
6186   }
6187 
6188   update_sets_after_freeing_regions(pre_used, &local_free_list,
6189                                     NULL /* old_proxy_set */,
6190                                     NULL /* humongous_proxy_set */,
6191                                     false /* par */);
6192   policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
6193   policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
6194 }
6195 
6196 // This routine is similar to the above but does not record
6197 // any policy statistics or update free lists; we are abandoning
6198 // the current incremental collection set in preparation of a
6199 // full collection. After the full GC we will start to build up
6200 // the incremental collection set again.
6201 // This is only called when we're doing a full collection
6202 // and is immediately followed by the tearing down of the young list.
6203 
6204 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
6205   HeapRegion* cur = cs_head;
6206 
6207   while (cur != NULL) {
6208     HeapRegion* next = cur->next_in_collection_set();
6209     assert(cur->in_collection_set(), "bad CS");
6210     cur->set_next_in_collection_set(NULL);
6211     cur->set_in_collection_set(false);
6212     cur->set_young_index_in_cset(-1);
6213     cur = next;
6214   }
6215 }
6216 
6217 void G1CollectedHeap::set_free_regions_coming() {
6218   if (G1ConcRegionFreeingVerbose) {
6219     gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6220                            "setting free regions coming");
6221   }
6222 
6223   assert(!free_regions_coming(), "pre-condition");
6224   _free_regions_coming = true;
6225 }
6226 
6227 void G1CollectedHeap::reset_free_regions_coming() {
6228   assert(free_regions_coming(), "pre-condition");
6229 
6230   {
6231     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6232     _free_regions_coming = false;
6233     SecondaryFreeList_lock->notify_all();
6234   }
6235 
6236   if (G1ConcRegionFreeingVerbose) {
6237     gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6238                            "reset free regions coming");
6239   }
6240 }
6241 
6242 void G1CollectedHeap::wait_while_free_regions_coming() {
6243   // Most of the time we won't have to wait, so let's do a quick test
6244   // first before we take the lock.
6245   if (!free_regions_coming()) {
6246     return;
6247   }
6248 
6249   if (G1ConcRegionFreeingVerbose) {
6250     gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6251                            "waiting for free regions");
6252   }
6253 
6254   {
6255     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6256     while (free_regions_coming()) {
6257       SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
6258     }
6259   }
6260 
6261   if (G1ConcRegionFreeingVerbose) {
6262     gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6263                            "done waiting for free regions");
6264   }
6265 }
6266 
6267 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
6268   assert(heap_lock_held_for_gc(),
6269               "the heap lock should already be held by or for this thread");
6270   _young_list->push_region(hr);
6271 }
6272 
6273 class NoYoungRegionsClosure: public HeapRegionClosure {
6274 private:
6275   bool _success;
6276 public:
6277   NoYoungRegionsClosure() : _success(true) { }
6278   bool doHeapRegion(HeapRegion* r) {
6279     if (r->is_young()) {
6280       gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
6281                              r->bottom(), r->end());
6282       _success = false;
6283     }
6284     return false;
6285   }
6286   bool success() { return _success; }
6287 };
6288 
6289 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
6290   bool ret = _young_list->check_list_empty(check_sample);
6291 
6292   if (check_heap) {
6293     NoYoungRegionsClosure closure;
6294     heap_region_iterate(&closure);
6295     ret = ret && closure.success();
6296   }
6297 
6298   return ret;
6299 }
6300 
6301 class TearDownRegionSetsClosure : public HeapRegionClosure {
6302 private:
6303   OldRegionSet *_old_set;
6304 
6305 public:
6306   TearDownRegionSetsClosure(OldRegionSet* old_set) : _old_set(old_set) { }
6307 
6308   bool doHeapRegion(HeapRegion* r) {
6309     if (r->is_empty()) {
6310       // We ignore empty regions, we'll empty the free list afterwards
6311     } else if (r->is_young()) {
6312       // We ignore young regions, we'll empty the young list afterwards
6313     } else if (r->isHumongous()) {
6314       // We ignore humongous regions, we're not tearing down the
6315       // humongous region set
6316     } else {
6317       // The rest should be old
6318       _old_set->remove(r);
6319     }
6320     return false;
6321   }
6322 
6323   ~TearDownRegionSetsClosure() {
6324     assert(_old_set->is_empty(), "post-condition");
6325   }
6326 };
6327 
6328 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6329   assert_at_safepoint(true /* should_be_vm_thread */);
6330 
6331   if (!free_list_only) {
6332     TearDownRegionSetsClosure cl(&_old_set);
6333     heap_region_iterate(&cl);
6334 
6335     // Need to do this after the heap iteration to be able to
6336     // recognize the young regions and ignore them during the iteration.
6337     _young_list->empty_list();
6338   }
6339   _free_list.remove_all();
6340 }
6341 
6342 class RebuildRegionSetsClosure : public HeapRegionClosure {
6343 private:
6344   bool            _free_list_only;
6345   OldRegionSet*   _old_set;
6346   FreeRegionList* _free_list;
6347   size_t          _total_used;
6348 
6349 public:
6350   RebuildRegionSetsClosure(bool free_list_only,
6351                            OldRegionSet* old_set, FreeRegionList* free_list) :
6352     _free_list_only(free_list_only),
6353     _old_set(old_set), _free_list(free_list), _total_used(0) {
6354     assert(_free_list->is_empty(), "pre-condition");
6355     if (!free_list_only) {
6356       assert(_old_set->is_empty(), "pre-condition");
6357     }
6358   }
6359 
6360   bool doHeapRegion(HeapRegion* r) {
6361     if (r->continuesHumongous()) {
6362       return false;
6363     }
6364 
6365     if (r->is_empty()) {
6366       // Add free regions to the free list
6367       _free_list->add_as_tail(r);
6368     } else if (!_free_list_only) {
6369       assert(!r->is_young(), "we should not come across young regions");
6370 
6371       if (r->isHumongous()) {
6372         // We ignore humongous regions, we left the humongous set unchanged
6373       } else {
6374         // The rest should be old, add them to the old set
6375         _old_set->add(r);
6376       }
6377       _total_used += r->used();
6378     }
6379 
6380     return false;
6381   }
6382 
6383   size_t total_used() {
6384     return _total_used;
6385   }
6386 };
6387 
6388 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6389   assert_at_safepoint(true /* should_be_vm_thread */);
6390 
6391   RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_free_list);
6392   heap_region_iterate(&cl);
6393 
6394   if (!free_list_only) {
6395     _summary_bytes_used = cl.total_used();
6396   }
6397   assert(_summary_bytes_used == recalculate_used(),
6398          err_msg("inconsistent _summary_bytes_used, "
6399                  "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6400                  _summary_bytes_used, recalculate_used()));
6401 }
6402 
6403 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6404   _refine_cte_cl->set_concurrent(concurrent);
6405 }
6406 
6407 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6408   HeapRegion* hr = heap_region_containing(p);
6409   if (hr == NULL) {
6410     return false;
6411   } else {
6412     return hr->is_in(p);
6413   }
6414 }
6415 
6416 // Methods for the mutator alloc region
6417 
6418 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6419                                                       bool force) {
6420   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6421   assert(!force || g1_policy()->can_expand_young_list(),
6422          "if force is true we should be able to expand the young list");
6423   bool young_list_full = g1_policy()->is_young_list_full();
6424   if (force || !young_list_full) {
6425     HeapRegion* new_alloc_region = new_region(word_size,
6426                                               false /* do_expand */);
6427     if (new_alloc_region != NULL) {
6428       set_region_short_lived_locked(new_alloc_region);
6429       _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6430       return new_alloc_region;
6431     }
6432   }
6433   return NULL;
6434 }
6435 
6436 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6437                                                   size_t allocated_bytes) {
6438   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6439   assert(alloc_region->is_young(), "all mutator alloc regions should be young");
6440 
6441   g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6442   _summary_bytes_used += allocated_bytes;
6443   _hr_printer.retire(alloc_region);
6444   // We update the eden sizes here, when the region is retired,
6445   // instead of when it's allocated, since this is the point that its
6446   // used space has been recored in _summary_bytes_used.
6447   g1mm()->update_eden_size();
6448 }
6449 
6450 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
6451                                                     bool force) {
6452   return _g1h->new_mutator_alloc_region(word_size, force);
6453 }
6454 
6455 void G1CollectedHeap::set_par_threads() {
6456   // Don't change the number of workers.  Use the value previously set
6457   // in the workgroup.
6458   assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise");
6459   uint n_workers = workers()->active_workers();
6460   assert(UseDynamicNumberOfGCThreads ||
6461            n_workers == workers()->total_workers(),
6462       "Otherwise should be using the total number of workers");
6463   if (n_workers == 0) {
6464     assert(false, "Should have been set in prior evacuation pause.");
6465     n_workers = ParallelGCThreads;
6466     workers()->set_active_workers(n_workers);
6467   }
6468   set_par_threads(n_workers);
6469 }
6470 
6471 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
6472                                        size_t allocated_bytes) {
6473   _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
6474 }
6475 
6476 // Methods for the GC alloc regions
6477 
6478 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6479                                                  uint count,
6480                                                  GCAllocPurpose ap) {
6481   assert(FreeList_lock->owned_by_self(), "pre-condition");
6482 
6483   if (count < g1_policy()->max_regions(ap)) {
6484     HeapRegion* new_alloc_region = new_region(word_size,
6485                                               true /* do_expand */);
6486     if (new_alloc_region != NULL) {
6487       // We really only need to do this for old regions given that we
6488       // should never scan survivors. But it doesn't hurt to do it
6489       // for survivors too.
6490       new_alloc_region->set_saved_mark();
6491       if (ap == GCAllocForSurvived) {
6492         new_alloc_region->set_survivor();
6493         _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6494       } else {
6495         _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6496       }
6497       bool during_im = g1_policy()->during_initial_mark_pause();
6498       new_alloc_region->note_start_of_copying(during_im);
6499       return new_alloc_region;
6500     } else {
6501       g1_policy()->note_alloc_region_limit_reached(ap);
6502     }
6503   }
6504   return NULL;
6505 }
6506 
6507 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6508                                              size_t allocated_bytes,
6509                                              GCAllocPurpose ap) {
6510   bool during_im = g1_policy()->during_initial_mark_pause();
6511   alloc_region->note_end_of_copying(during_im);
6512   g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6513   if (ap == GCAllocForSurvived) {
6514     young_list()->add_survivor_region(alloc_region);
6515   } else {
6516     _old_set.add(alloc_region);
6517   }
6518   _hr_printer.retire(alloc_region);
6519 }
6520 
6521 HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size,
6522                                                        bool force) {
6523   assert(!force, "not supported for GC alloc regions");
6524   return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForSurvived);
6525 }
6526 
6527 void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region,
6528                                           size_t allocated_bytes) {
6529   _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6530                                GCAllocForSurvived);
6531 }
6532 
6533 HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size,
6534                                                   bool force) {
6535   assert(!force, "not supported for GC alloc regions");
6536   return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForTenured);
6537 }
6538 
6539 void OldGCAllocRegion::retire_region(HeapRegion* alloc_region,
6540                                      size_t allocated_bytes) {
6541   _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6542                                GCAllocForTenured);
6543 }
6544 // Heap region set verification
6545 
6546 class VerifyRegionListsClosure : public HeapRegionClosure {
6547 private:
6548   FreeRegionList*     _free_list;
6549   OldRegionSet*       _old_set;
6550   HumongousRegionSet* _humongous_set;
6551   uint                _region_count;
6552 
6553 public:
6554   VerifyRegionListsClosure(OldRegionSet* old_set,
6555                            HumongousRegionSet* humongous_set,
6556                            FreeRegionList* free_list) :
6557     _old_set(old_set), _humongous_set(humongous_set),
6558     _free_list(free_list), _region_count(0) { }
6559 
6560   uint region_count() { return _region_count; }
6561 
6562   bool doHeapRegion(HeapRegion* hr) {
6563     _region_count += 1;
6564 
6565     if (hr->continuesHumongous()) {
6566       return false;
6567     }
6568 
6569     if (hr->is_young()) {
6570       // TODO
6571     } else if (hr->startsHumongous()) {
6572       _humongous_set->verify_next_region(hr);
6573     } else if (hr->is_empty()) {
6574       _free_list->verify_next_region(hr);
6575     } else {
6576       _old_set->verify_next_region(hr);
6577     }
6578     return false;
6579   }
6580 };
6581 
6582 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
6583                                              HeapWord* bottom) {
6584   HeapWord* end = bottom + HeapRegion::GrainWords;
6585   MemRegion mr(bottom, end);
6586   assert(_g1_reserved.contains(mr), "invariant");
6587   // This might return NULL if the allocation fails
6588   return new HeapRegion(hrs_index, _bot_shared, mr);
6589 }
6590 
6591 void G1CollectedHeap::verify_region_sets() {
6592   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6593 
6594   // First, check the explicit lists.
6595   _free_list.verify();
6596   {
6597     // Given that a concurrent operation might be adding regions to
6598     // the secondary free list we have to take the lock before
6599     // verifying it.
6600     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6601     _secondary_free_list.verify();
6602   }
6603   _old_set.verify();
6604   _humongous_set.verify();
6605 
6606   // If a concurrent region freeing operation is in progress it will
6607   // be difficult to correctly attributed any free regions we come
6608   // across to the correct free list given that they might belong to
6609   // one of several (free_list, secondary_free_list, any local lists,
6610   // etc.). So, if that's the case we will skip the rest of the
6611   // verification operation. Alternatively, waiting for the concurrent
6612   // operation to complete will have a non-trivial effect on the GC's
6613   // operation (no concurrent operation will last longer than the
6614   // interval between two calls to verification) and it might hide
6615   // any issues that we would like to catch during testing.
6616   if (free_regions_coming()) {
6617     return;
6618   }
6619 
6620   // Make sure we append the secondary_free_list on the free_list so
6621   // that all free regions we will come across can be safely
6622   // attributed to the free_list.
6623   append_secondary_free_list_if_not_empty_with_lock();
6624 
6625   // Finally, make sure that the region accounting in the lists is
6626   // consistent with what we see in the heap.
6627   _old_set.verify_start();
6628   _humongous_set.verify_start();
6629   _free_list.verify_start();
6630 
6631   VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_free_list);
6632   heap_region_iterate(&cl);
6633 
6634   _old_set.verify_end();
6635   _humongous_set.verify_end();
6636   _free_list.verify_end();
6637 }
6638 
6639 // Optimized nmethod scanning
6640 
6641 class RegisterNMethodOopClosure: public OopClosure {
6642   G1CollectedHeap* _g1h;
6643   nmethod* _nm;
6644 
6645   template <class T> void do_oop_work(T* p) {
6646     T heap_oop = oopDesc::load_heap_oop(p);
6647     if (!oopDesc::is_null(heap_oop)) {
6648       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6649       HeapRegion* hr = _g1h->heap_region_containing(obj);
6650       assert(!hr->isHumongous(), "code root in humongous region?");
6651 
6652       // HeapRegion::add_strong_code_root() avoids adding duplicate
6653       // entries but having duplicates is  OK since we "mark" nmethods
6654       // as visited when we scan the strong code root lists during the GC.
6655       hr->add_strong_code_root(_nm);
6656       assert(hr->rem_set()->strong_code_roots_list_contains(_nm), "add failed?");
6657     }
6658   }
6659 
6660 public:
6661   RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6662     _g1h(g1h), _nm(nm) {}
6663 
6664   void do_oop(oop* p)       { do_oop_work(p); }
6665   void do_oop(narrowOop* p) { do_oop_work(p); }
6666 };
6667 
6668 class UnregisterNMethodOopClosure: public OopClosure {
6669   G1CollectedHeap* _g1h;
6670   nmethod* _nm;
6671 
6672   template <class T> void do_oop_work(T* p) {
6673     T heap_oop = oopDesc::load_heap_oop(p);
6674     if (!oopDesc::is_null(heap_oop)) {
6675       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6676       HeapRegion* hr = _g1h->heap_region_containing(obj);
6677       assert(!hr->isHumongous(), "code root in humongous region?");
6678       hr->remove_strong_code_root(_nm);
6679       assert(!hr->rem_set()->strong_code_roots_list_contains(_nm), "remove failed?");
6680     }
6681   }
6682 
6683 public:
6684   UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6685     _g1h(g1h), _nm(nm) {}
6686 
6687   void do_oop(oop* p)       { do_oop_work(p); }
6688   void do_oop(narrowOop* p) { do_oop_work(p); }
6689 };
6690 
6691 void G1CollectedHeap::register_nmethod(nmethod* nm) {
6692   CollectedHeap::register_nmethod(nm);
6693 
6694   guarantee(nm != NULL, "sanity");
6695   RegisterNMethodOopClosure reg_cl(this, nm);
6696   nm->oops_do(&reg_cl);
6697 }
6698 
6699 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
6700   CollectedHeap::unregister_nmethod(nm);
6701 
6702   guarantee(nm != NULL, "sanity");
6703   UnregisterNMethodOopClosure reg_cl(this, nm);
6704   nm->oops_do(&reg_cl, true);
6705 }
6706 
6707 class MigrateCodeRootsHeapRegionClosure: public HeapRegionClosure {
6708 public:
6709   bool doHeapRegion(HeapRegion *hr) {
6710     assert(!hr->isHumongous(), "humongous region in collection set?");
6711     hr->migrate_strong_code_roots();
6712     return false;
6713   }
6714 };
6715 
6716 void G1CollectedHeap::migrate_strong_code_roots() {
6717   MigrateCodeRootsHeapRegionClosure cl;
6718   double migrate_start = os::elapsedTime();
6719   collection_set_iterate(&cl);
6720   double migration_time_ms = (os::elapsedTime() - migrate_start) * 1000.0;
6721   g1_policy()->phase_times()->record_strong_code_root_migration_time(migration_time_ms);
6722 }
6723 
6724 // Mark all the code roots that point into regions *not* in the
6725 // collection set.
6726 //
6727 // Note we do not want to use a "marking" CodeBlobToOopClosure while
6728 // walking the the code roots lists of regions not in the collection
6729 // set. Suppose we have an nmethod (M) that points to objects in two
6730 // separate regions - one in the collection set (R1) and one not (R2).
6731 // Using a "marking" CodeBlobToOopClosure here would result in "marking"
6732 // nmethod M when walking the code roots for R1. When we come to scan
6733 // the code roots for R2, we would see that M is already marked and it
6734 // would be skipped and the objects in R2 that are referenced from M
6735 // would not be evacuated.
6736 
6737 class MarkStrongCodeRootCodeBlobClosure: public CodeBlobClosure {
6738 
6739   class MarkStrongCodeRootOopClosure: public OopClosure {
6740     ConcurrentMark* _cm;
6741     HeapRegion* _hr;
6742     uint _worker_id;
6743 
6744     template <class T> void do_oop_work(T* p) {
6745       T heap_oop = oopDesc::load_heap_oop(p);
6746       if (!oopDesc::is_null(heap_oop)) {
6747         oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6748         // Only mark objects in the region (which is assumed
6749         // to be not in the collection set).
6750         if (_hr->is_in(obj)) {
6751           _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
6752         }
6753       }
6754     }
6755 
6756   public:
6757     MarkStrongCodeRootOopClosure(ConcurrentMark* cm, HeapRegion* hr, uint worker_id) :
6758       _cm(cm), _hr(hr), _worker_id(worker_id) {
6759       assert(!_hr->in_collection_set(), "sanity");
6760     }
6761 
6762     void do_oop(narrowOop* p) { do_oop_work(p); }
6763     void do_oop(oop* p)       { do_oop_work(p); }
6764   };
6765 
6766   MarkStrongCodeRootOopClosure _oop_cl;
6767 
6768 public:
6769   MarkStrongCodeRootCodeBlobClosure(ConcurrentMark* cm, HeapRegion* hr, uint worker_id):
6770     _oop_cl(cm, hr, worker_id) {}
6771 
6772   void do_code_blob(CodeBlob* cb) {
6773     nmethod* nm = (cb == NULL) ? NULL : cb->as_nmethod_or_null();
6774     if (nm != NULL) {
6775       nm->oops_do(&_oop_cl);
6776     }
6777   }
6778 };
6779 
6780 class MarkStrongCodeRootsHRClosure: public HeapRegionClosure {
6781   G1CollectedHeap* _g1h;
6782   uint _worker_id;
6783 
6784 public:
6785   MarkStrongCodeRootsHRClosure(G1CollectedHeap* g1h, uint worker_id) :
6786     _g1h(g1h), _worker_id(worker_id) {}
6787 
6788   bool doHeapRegion(HeapRegion *hr) {
6789     HeapRegionRemSet* hrrs = hr->rem_set();
6790     if (hr->isHumongous()) {
6791       // Code roots should never be attached to a humongous region
6792       assert(hrrs->strong_code_roots_list_length() == 0, "sanity");
6793       return false;
6794     }
6795 
6796     if (hr->in_collection_set()) {
6797       // Don't mark code roots into regions in the collection set here.
6798       // They will be marked when we scan them.
6799       return false;
6800     }
6801 
6802     MarkStrongCodeRootCodeBlobClosure cb_cl(_g1h->concurrent_mark(), hr, _worker_id);
6803     hr->strong_code_roots_do(&cb_cl);
6804     return false;
6805   }
6806 };
6807 
6808 void G1CollectedHeap::mark_strong_code_roots(uint worker_id) {
6809   MarkStrongCodeRootsHRClosure cl(this, worker_id);
6810   if (G1CollectedHeap::use_parallel_gc_threads()) {
6811     heap_region_par_iterate_chunked(&cl,
6812                                     worker_id,
6813                                     workers()->active_workers(),
6814                                     HeapRegion::ParMarkRootClaimValue);
6815   } else {
6816     heap_region_iterate(&cl);
6817   }
6818 }
6819 
6820 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
6821   G1CollectedHeap* _g1h;
6822 
6823 public:
6824   RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
6825     _g1h(g1h) {}
6826 
6827   void do_code_blob(CodeBlob* cb) {
6828     nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
6829     if (nm == NULL) {
6830       return;
6831     }
6832 
6833     if (ScavengeRootsInCode && nm->detect_scavenge_root_oops()) {
6834       _g1h->register_nmethod(nm);
6835     }
6836   }
6837 };
6838 
6839 void G1CollectedHeap::rebuild_strong_code_roots() {
6840   RebuildStrongCodeRootClosure blob_cl(this);
6841   CodeCache::blobs_do(&blob_cl);
6842 }
--- EOF ---