1 /*
   2  * Copyright (c) 2001, 2011, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "code/icBuffer.hpp"
  27 #include "gc_implementation/g1/bufferingOopClosure.hpp"
  28 #include "gc_implementation/g1/concurrentG1Refine.hpp"
  29 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
  30 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
  31 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
  32 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
  33 #include "gc_implementation/g1/g1MarkSweep.hpp"
  34 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
  35 #include "gc_implementation/g1/g1RemSet.inline.hpp"
  36 #include "gc_implementation/g1/heapRegionRemSet.hpp"
  37 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
  38 #include "gc_implementation/g1/vm_operations_g1.hpp"
  39 #include "gc_implementation/shared/isGCActiveMark.hpp"
  40 #include "memory/gcLocker.inline.hpp"
  41 #include "memory/genOopClosures.inline.hpp"
  42 #include "memory/generationSpec.hpp"
  43 #include "oops/oop.inline.hpp"
  44 #include "oops/oop.pcgc.inline.hpp"
  45 #include "runtime/aprofiler.hpp"
  46 #include "runtime/vmThread.hpp"
  47 
  48 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
  49 
  50 // turn it on so that the contents of the young list (scan-only /
  51 // to-be-collected) are printed at "strategic" points before / during
  52 // / after the collection --- this is useful for debugging
  53 #define YOUNG_LIST_VERBOSE 0
  54 // CURRENT STATUS
  55 // This file is under construction.  Search for "FIXME".
  56 
  57 // INVARIANTS/NOTES
  58 //
  59 // All allocation activity covered by the G1CollectedHeap interface is
  60 // serialized by acquiring the HeapLock.  This happens in mem_allocate
  61 // and allocate_new_tlab, which are the "entry" points to the
  62 // allocation code from the rest of the JVM.  (Note that this does not
  63 // apply to TLAB allocation, which is not part of this interface: it
  64 // is done by clients of this interface.)
  65 
  66 // Local to this file.
  67 
  68 class RefineCardTableEntryClosure: public CardTableEntryClosure {
  69   SuspendibleThreadSet* _sts;
  70   G1RemSet* _g1rs;
  71   ConcurrentG1Refine* _cg1r;
  72   bool _concurrent;
  73 public:
  74   RefineCardTableEntryClosure(SuspendibleThreadSet* sts,
  75                               G1RemSet* g1rs,
  76                               ConcurrentG1Refine* cg1r) :
  77     _sts(sts), _g1rs(g1rs), _cg1r(cg1r), _concurrent(true)
  78   {}
  79   bool do_card_ptr(jbyte* card_ptr, int worker_i) {
  80     bool oops_into_cset = _g1rs->concurrentRefineOneCard(card_ptr, worker_i, false);
  81     // This path is executed by the concurrent refine or mutator threads,
  82     // concurrently, and so we do not care if card_ptr contains references
  83     // that point into the collection set.
  84     assert(!oops_into_cset, "should be");
  85 
  86     if (_concurrent && _sts->should_yield()) {
  87       // Caller will actually yield.
  88       return false;
  89     }
  90     // Otherwise, we finished successfully; return true.
  91     return true;
  92   }
  93   void set_concurrent(bool b) { _concurrent = b; }
  94 };
  95 
  96 
  97 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure {
  98   int _calls;
  99   G1CollectedHeap* _g1h;
 100   CardTableModRefBS* _ctbs;
 101   int _histo[256];
 102 public:
 103   ClearLoggedCardTableEntryClosure() :
 104     _calls(0)
 105   {
 106     _g1h = G1CollectedHeap::heap();
 107     _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
 108     for (int i = 0; i < 256; i++) _histo[i] = 0;
 109   }
 110   bool do_card_ptr(jbyte* card_ptr, int worker_i) {
 111     if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
 112       _calls++;
 113       unsigned char* ujb = (unsigned char*)card_ptr;
 114       int ind = (int)(*ujb);
 115       _histo[ind]++;
 116       *card_ptr = -1;
 117     }
 118     return true;
 119   }
 120   int calls() { return _calls; }
 121   void print_histo() {
 122     gclog_or_tty->print_cr("Card table value histogram:");
 123     for (int i = 0; i < 256; i++) {
 124       if (_histo[i] != 0) {
 125         gclog_or_tty->print_cr("  %d: %d", i, _histo[i]);
 126       }
 127     }
 128   }
 129 };
 130 
 131 class RedirtyLoggedCardTableEntryClosure: public CardTableEntryClosure {
 132   int _calls;
 133   G1CollectedHeap* _g1h;
 134   CardTableModRefBS* _ctbs;
 135 public:
 136   RedirtyLoggedCardTableEntryClosure() :
 137     _calls(0)
 138   {
 139     _g1h = G1CollectedHeap::heap();
 140     _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
 141   }
 142   bool do_card_ptr(jbyte* card_ptr, int worker_i) {
 143     if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
 144       _calls++;
 145       *card_ptr = 0;
 146     }
 147     return true;
 148   }
 149   int calls() { return _calls; }
 150 };
 151 
 152 class RedirtyLoggedCardTableEntryFastClosure : public CardTableEntryClosure {
 153 public:
 154   bool do_card_ptr(jbyte* card_ptr, int worker_i) {
 155     *card_ptr = CardTableModRefBS::dirty_card_val();
 156     return true;
 157   }
 158 };
 159 
 160 YoungList::YoungList(G1CollectedHeap* g1h)
 161   : _g1h(g1h), _head(NULL),
 162     _length(0),
 163     _last_sampled_rs_lengths(0),
 164     _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0)
 165 {
 166   guarantee( check_list_empty(false), "just making sure..." );
 167 }
 168 
 169 void YoungList::push_region(HeapRegion *hr) {
 170   assert(!hr->is_young(), "should not already be young");
 171   assert(hr->get_next_young_region() == NULL, "cause it should!");
 172 
 173   hr->set_next_young_region(_head);
 174   _head = hr;
 175 
 176   hr->set_young();
 177   double yg_surv_rate = _g1h->g1_policy()->predict_yg_surv_rate((int)_length);
 178   ++_length;
 179 }
 180 
 181 void YoungList::add_survivor_region(HeapRegion* hr) {
 182   assert(hr->is_survivor(), "should be flagged as survivor region");
 183   assert(hr->get_next_young_region() == NULL, "cause it should!");
 184 
 185   hr->set_next_young_region(_survivor_head);
 186   if (_survivor_head == NULL) {
 187     _survivor_tail = hr;
 188   }
 189   _survivor_head = hr;
 190 
 191   ++_survivor_length;
 192 }
 193 
 194 void YoungList::empty_list(HeapRegion* list) {
 195   while (list != NULL) {
 196     HeapRegion* next = list->get_next_young_region();
 197     list->set_next_young_region(NULL);
 198     list->uninstall_surv_rate_group();
 199     list->set_not_young();
 200     list = next;
 201   }
 202 }
 203 
 204 void YoungList::empty_list() {
 205   assert(check_list_well_formed(), "young list should be well formed");
 206 
 207   empty_list(_head);
 208   _head = NULL;
 209   _length = 0;
 210 
 211   empty_list(_survivor_head);
 212   _survivor_head = NULL;
 213   _survivor_tail = NULL;
 214   _survivor_length = 0;
 215 
 216   _last_sampled_rs_lengths = 0;
 217 
 218   assert(check_list_empty(false), "just making sure...");
 219 }
 220 
 221 bool YoungList::check_list_well_formed() {
 222   bool ret = true;
 223 
 224   size_t length = 0;
 225   HeapRegion* curr = _head;
 226   HeapRegion* last = NULL;
 227   while (curr != NULL) {
 228     if (!curr->is_young()) {
 229       gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
 230                              "incorrectly tagged (y: %d, surv: %d)",
 231                              curr->bottom(), curr->end(),
 232                              curr->is_young(), curr->is_survivor());
 233       ret = false;
 234     }
 235     ++length;
 236     last = curr;
 237     curr = curr->get_next_young_region();
 238   }
 239   ret = ret && (length == _length);
 240 
 241   if (!ret) {
 242     gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
 243     gclog_or_tty->print_cr("###   list has %d entries, _length is %d",
 244                            length, _length);
 245   }
 246 
 247   return ret;
 248 }
 249 
 250 bool YoungList::check_list_empty(bool check_sample) {
 251   bool ret = true;
 252 
 253   if (_length != 0) {
 254     gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %d",
 255                   _length);
 256     ret = false;
 257   }
 258   if (check_sample && _last_sampled_rs_lengths != 0) {
 259     gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
 260     ret = false;
 261   }
 262   if (_head != NULL) {
 263     gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
 264     ret = false;
 265   }
 266   if (!ret) {
 267     gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
 268   }
 269 
 270   return ret;
 271 }
 272 
 273 void
 274 YoungList::rs_length_sampling_init() {
 275   _sampled_rs_lengths = 0;
 276   _curr               = _head;
 277 }
 278 
 279 bool
 280 YoungList::rs_length_sampling_more() {
 281   return _curr != NULL;
 282 }
 283 
 284 void
 285 YoungList::rs_length_sampling_next() {
 286   assert( _curr != NULL, "invariant" );
 287   size_t rs_length = _curr->rem_set()->occupied();
 288 
 289   _sampled_rs_lengths += rs_length;
 290 
 291   // The current region may not yet have been added to the
 292   // incremental collection set (it gets added when it is
 293   // retired as the current allocation region).
 294   if (_curr->in_collection_set()) {
 295     // Update the collection set policy information for this region
 296     _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
 297   }
 298 
 299   _curr = _curr->get_next_young_region();
 300   if (_curr == NULL) {
 301     _last_sampled_rs_lengths = _sampled_rs_lengths;
 302     // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
 303   }
 304 }
 305 
 306 void
 307 YoungList::reset_auxilary_lists() {
 308   guarantee( is_empty(), "young list should be empty" );
 309   assert(check_list_well_formed(), "young list should be well formed");
 310 
 311   // Add survivor regions to SurvRateGroup.
 312   _g1h->g1_policy()->note_start_adding_survivor_regions();
 313   _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
 314 
 315   for (HeapRegion* curr = _survivor_head;
 316        curr != NULL;
 317        curr = curr->get_next_young_region()) {
 318     _g1h->g1_policy()->set_region_survivors(curr);
 319 
 320     // The region is a non-empty survivor so let's add it to
 321     // the incremental collection set for the next evacuation
 322     // pause.
 323     _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
 324   }
 325   _g1h->g1_policy()->note_stop_adding_survivor_regions();
 326 
 327   _head   = _survivor_head;
 328   _length = _survivor_length;
 329   if (_survivor_head != NULL) {
 330     assert(_survivor_tail != NULL, "cause it shouldn't be");
 331     assert(_survivor_length > 0, "invariant");
 332     _survivor_tail->set_next_young_region(NULL);
 333   }
 334 
 335   // Don't clear the survivor list handles until the start of
 336   // the next evacuation pause - we need it in order to re-tag
 337   // the survivor regions from this evacuation pause as 'young'
 338   // at the start of the next.
 339 
 340   _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
 341 
 342   assert(check_list_well_formed(), "young list should be well formed");
 343 }
 344 
 345 void YoungList::print() {
 346   HeapRegion* lists[] = {_head,   _survivor_head};
 347   const char* names[] = {"YOUNG", "SURVIVOR"};
 348 
 349   for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) {
 350     gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
 351     HeapRegion *curr = lists[list];
 352     if (curr == NULL)
 353       gclog_or_tty->print_cr("  empty");
 354     while (curr != NULL) {
 355       gclog_or_tty->print_cr("  [%08x-%08x], t: %08x, P: %08x, N: %08x, C: %08x, "
 356                              "age: %4d, y: %d, surv: %d",
 357                              curr->bottom(), curr->end(),
 358                              curr->top(),
 359                              curr->prev_top_at_mark_start(),
 360                              curr->next_top_at_mark_start(),
 361                              curr->top_at_conc_mark_count(),
 362                              curr->age_in_surv_rate_group_cond(),
 363                              curr->is_young(),
 364                              curr->is_survivor());
 365       curr = curr->get_next_young_region();
 366     }
 367   }
 368 
 369   gclog_or_tty->print_cr("");
 370 }
 371 
 372 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
 373 {
 374   // Claim the right to put the region on the dirty cards region list
 375   // by installing a self pointer.
 376   HeapRegion* next = hr->get_next_dirty_cards_region();
 377   if (next == NULL) {
 378     HeapRegion* res = (HeapRegion*)
 379       Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
 380                           NULL);
 381     if (res == NULL) {
 382       HeapRegion* head;
 383       do {
 384         // Put the region to the dirty cards region list.
 385         head = _dirty_cards_region_list;
 386         next = (HeapRegion*)
 387           Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
 388         if (next == head) {
 389           assert(hr->get_next_dirty_cards_region() == hr,
 390                  "hr->get_next_dirty_cards_region() != hr");
 391           if (next == NULL) {
 392             // The last region in the list points to itself.
 393             hr->set_next_dirty_cards_region(hr);
 394           } else {
 395             hr->set_next_dirty_cards_region(next);
 396           }
 397         }
 398       } while (next != head);
 399     }
 400   }
 401 }
 402 
 403 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
 404 {
 405   HeapRegion* head;
 406   HeapRegion* hr;
 407   do {
 408     head = _dirty_cards_region_list;
 409     if (head == NULL) {
 410       return NULL;
 411     }
 412     HeapRegion* new_head = head->get_next_dirty_cards_region();
 413     if (head == new_head) {
 414       // The last region.
 415       new_head = NULL;
 416     }
 417     hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
 418                                           head);
 419   } while (hr != head);
 420   assert(hr != NULL, "invariant");
 421   hr->set_next_dirty_cards_region(NULL);
 422   return hr;
 423 }
 424 
 425 void G1CollectedHeap::stop_conc_gc_threads() {
 426   _cg1r->stop();
 427   _cmThread->stop();
 428 }
 429 
 430 void G1CollectedHeap::check_ct_logs_at_safepoint() {
 431   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
 432   CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
 433 
 434   // Count the dirty cards at the start.
 435   CountNonCleanMemRegionClosure count1(this);
 436   ct_bs->mod_card_iterate(&count1);
 437   int orig_count = count1.n();
 438 
 439   // First clear the logged cards.
 440   ClearLoggedCardTableEntryClosure clear;
 441   dcqs.set_closure(&clear);
 442   dcqs.apply_closure_to_all_completed_buffers();
 443   dcqs.iterate_closure_all_threads(false);
 444   clear.print_histo();
 445 
 446   // Now ensure that there's no dirty cards.
 447   CountNonCleanMemRegionClosure count2(this);
 448   ct_bs->mod_card_iterate(&count2);
 449   if (count2.n() != 0) {
 450     gclog_or_tty->print_cr("Card table has %d entries; %d originally",
 451                            count2.n(), orig_count);
 452   }
 453   guarantee(count2.n() == 0, "Card table should be clean.");
 454 
 455   RedirtyLoggedCardTableEntryClosure redirty;
 456   JavaThread::dirty_card_queue_set().set_closure(&redirty);
 457   dcqs.apply_closure_to_all_completed_buffers();
 458   dcqs.iterate_closure_all_threads(false);
 459   gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
 460                          clear.calls(), orig_count);
 461   guarantee(redirty.calls() == clear.calls(),
 462             "Or else mechanism is broken.");
 463 
 464   CountNonCleanMemRegionClosure count3(this);
 465   ct_bs->mod_card_iterate(&count3);
 466   if (count3.n() != orig_count) {
 467     gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
 468                            orig_count, count3.n());
 469     guarantee(count3.n() >= orig_count, "Should have restored them all.");
 470   }
 471 
 472   JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
 473 }
 474 
 475 // Private class members.
 476 
 477 G1CollectedHeap* G1CollectedHeap::_g1h;
 478 
 479 // Private methods.
 480 
 481 HeapRegion*
 482 G1CollectedHeap::new_region_try_secondary_free_list() {
 483   MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
 484   while (!_secondary_free_list.is_empty() || free_regions_coming()) {
 485     if (!_secondary_free_list.is_empty()) {
 486       if (G1ConcRegionFreeingVerbose) {
 487         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 488                                "secondary_free_list has "SIZE_FORMAT" entries",
 489                                _secondary_free_list.length());
 490       }
 491       // It looks as if there are free regions available on the
 492       // secondary_free_list. Let's move them to the free_list and try
 493       // again to allocate from it.
 494       append_secondary_free_list();
 495 
 496       assert(!_free_list.is_empty(), "if the secondary_free_list was not "
 497              "empty we should have moved at least one entry to the free_list");
 498       HeapRegion* res = _free_list.remove_head();
 499       if (G1ConcRegionFreeingVerbose) {
 500         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 501                                "allocated "HR_FORMAT" from secondary_free_list",
 502                                HR_FORMAT_PARAMS(res));
 503       }
 504       return res;
 505     }
 506 
 507     // Wait here until we get notifed either when (a) there are no
 508     // more free regions coming or (b) some regions have been moved on
 509     // the secondary_free_list.
 510     SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
 511   }
 512 
 513   if (G1ConcRegionFreeingVerbose) {
 514     gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 515                            "could not allocate from secondary_free_list");
 516   }
 517   return NULL;
 518 }
 519 
 520 HeapRegion* G1CollectedHeap::new_region_work(size_t word_size,
 521                                              bool do_expand) {
 522   assert(!isHumongous(word_size) ||
 523                                   word_size <= (size_t) HeapRegion::GrainWords,
 524          "the only time we use this to allocate a humongous region is "
 525          "when we are allocating a single humongous region");
 526 
 527   HeapRegion* res;
 528   if (G1StressConcRegionFreeing) {
 529     if (!_secondary_free_list.is_empty()) {
 530       if (G1ConcRegionFreeingVerbose) {
 531         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 532                                "forced to look at the secondary_free_list");
 533       }
 534       res = new_region_try_secondary_free_list();
 535       if (res != NULL) {
 536         return res;
 537       }
 538     }
 539   }
 540   res = _free_list.remove_head_or_null();
 541   if (res == NULL) {
 542     if (G1ConcRegionFreeingVerbose) {
 543       gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 544                              "res == NULL, trying the secondary_free_list");
 545     }
 546     res = new_region_try_secondary_free_list();
 547   }
 548   if (res == NULL && do_expand) {
 549     if (expand(word_size * HeapWordSize)) {
 550       // The expansion succeeded and so we should have at least one
 551       // region on the free list.
 552       res = _free_list.remove_head();
 553     }
 554   }
 555   if (res != NULL) {
 556     if (G1PrintHeapRegions) {
 557       gclog_or_tty->print_cr("new alloc region %d:["PTR_FORMAT","PTR_FORMAT"], "
 558                              "top "PTR_FORMAT, res->hrs_index(),
 559                              res->bottom(), res->end(), res->top());
 560     }
 561   }
 562   return res;
 563 }
 564 
 565 HeapRegion* G1CollectedHeap::new_gc_alloc_region(int purpose,
 566                                                  size_t word_size) {
 567   HeapRegion* alloc_region = NULL;
 568   if (_gc_alloc_region_counts[purpose] < g1_policy()->max_regions(purpose)) {
 569     alloc_region = new_region_work(word_size, true /* do_expand */);
 570     if (purpose == GCAllocForSurvived && alloc_region != NULL) {
 571       alloc_region->set_survivor();
 572     }
 573     ++_gc_alloc_region_counts[purpose];
 574   } else {
 575     g1_policy()->note_alloc_region_limit_reached(purpose);
 576   }
 577   return alloc_region;
 578 }
 579 
 580 int G1CollectedHeap::humongous_obj_allocate_find_first(size_t num_regions,
 581                                                        size_t word_size) {
 582   assert(isHumongous(word_size), "word_size should be humongous");
 583   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 584 
 585   int first = -1;
 586   if (num_regions == 1) {
 587     // Only one region to allocate, no need to go through the slower
 588     // path. The caller will attempt the expasion if this fails, so
 589     // let's not try to expand here too.
 590     HeapRegion* hr = new_region_work(word_size, false /* do_expand */);
 591     if (hr != NULL) {
 592       first = hr->hrs_index();
 593     } else {
 594       first = -1;
 595     }
 596   } else {
 597     // We can't allocate humongous regions while cleanupComplete() is
 598     // running, since some of the regions we find to be empty might not
 599     // yet be added to the free list and it is not straightforward to
 600     // know which list they are on so that we can remove them. Note
 601     // that we only need to do this if we need to allocate more than
 602     // one region to satisfy the current humongous allocation
 603     // request. If we are only allocating one region we use the common
 604     // region allocation code (see above).
 605     wait_while_free_regions_coming();
 606     append_secondary_free_list_if_not_empty_with_lock();
 607 
 608     if (free_regions() >= num_regions) {
 609       first = _hrs->find_contiguous(num_regions);
 610       if (first != -1) {
 611         for (int i = first; i < first + (int) num_regions; ++i) {
 612           HeapRegion* hr = _hrs->at(i);
 613           assert(hr->is_empty(), "sanity");
 614           assert(is_on_master_free_list(hr), "sanity");
 615           hr->set_pending_removal(true);
 616         }
 617         _free_list.remove_all_pending(num_regions);
 618       }
 619     }
 620   }
 621   return first;
 622 }
 623 
 624 HeapWord*
 625 G1CollectedHeap::humongous_obj_allocate_initialize_regions(int first,
 626                                                            size_t num_regions,
 627                                                            size_t word_size) {
 628   assert(first != -1, "pre-condition");
 629   assert(isHumongous(word_size), "word_size should be humongous");
 630   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 631 
 632   // Index of last region in the series + 1.
 633   int last = first + (int) num_regions;
 634 
 635   // We need to initialize the region(s) we just discovered. This is
 636   // a bit tricky given that it can happen concurrently with
 637   // refinement threads refining cards on these regions and
 638   // potentially wanting to refine the BOT as they are scanning
 639   // those cards (this can happen shortly after a cleanup; see CR
 640   // 6991377). So we have to set up the region(s) carefully and in
 641   // a specific order.
 642 
 643   // The word size sum of all the regions we will allocate.
 644   size_t word_size_sum = num_regions * HeapRegion::GrainWords;
 645   assert(word_size <= word_size_sum, "sanity");
 646 
 647   // This will be the "starts humongous" region.
 648   HeapRegion* first_hr = _hrs->at(first);
 649   // The header of the new object will be placed at the bottom of
 650   // the first region.
 651   HeapWord* new_obj = first_hr->bottom();
 652   // This will be the new end of the first region in the series that
 653   // should also match the end of the last region in the seriers.
 654   HeapWord* new_end = new_obj + word_size_sum;
 655   // This will be the new top of the first region that will reflect
 656   // this allocation.
 657   HeapWord* new_top = new_obj + word_size;
 658 
 659   // First, we need to zero the header of the space that we will be
 660   // allocating. When we update top further down, some refinement
 661   // threads might try to scan the region. By zeroing the header we
 662   // ensure that any thread that will try to scan the region will
 663   // come across the zero klass word and bail out.
 664   //
 665   // NOTE: It would not have been correct to have used
 666   // CollectedHeap::fill_with_object() and make the space look like
 667   // an int array. The thread that is doing the allocation will
 668   // later update the object header to a potentially different array
 669   // type and, for a very short period of time, the klass and length
 670   // fields will be inconsistent. This could cause a refinement
 671   // thread to calculate the object size incorrectly.
 672   Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
 673 
 674   // We will set up the first region as "starts humongous". This
 675   // will also update the BOT covering all the regions to reflect
 676   // that there is a single object that starts at the bottom of the
 677   // first region.
 678   first_hr->set_startsHumongous(new_top, new_end);
 679 
 680   // Then, if there are any, we will set up the "continues
 681   // humongous" regions.
 682   HeapRegion* hr = NULL;
 683   for (int i = first + 1; i < last; ++i) {
 684     hr = _hrs->at(i);
 685     hr->set_continuesHumongous(first_hr);
 686   }
 687   // If we have "continues humongous" regions (hr != NULL), then the
 688   // end of the last one should match new_end.
 689   assert(hr == NULL || hr->end() == new_end, "sanity");
 690 
 691   // Up to this point no concurrent thread would have been able to
 692   // do any scanning on any region in this series. All the top
 693   // fields still point to bottom, so the intersection between
 694   // [bottom,top] and [card_start,card_end] will be empty. Before we
 695   // update the top fields, we'll do a storestore to make sure that
 696   // no thread sees the update to top before the zeroing of the
 697   // object header and the BOT initialization.
 698   OrderAccess::storestore();
 699 
 700   // Now that the BOT and the object header have been initialized,
 701   // we can update top of the "starts humongous" region.
 702   assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
 703          "new_top should be in this region");
 704   first_hr->set_top(new_top);
 705 
 706   // Now, we will update the top fields of the "continues humongous"
 707   // regions. The reason we need to do this is that, otherwise,
 708   // these regions would look empty and this will confuse parts of
 709   // G1. For example, the code that looks for a consecutive number
 710   // of empty regions will consider them empty and try to
 711   // re-allocate them. We can extend is_empty() to also include
 712   // !continuesHumongous(), but it is easier to just update the top
 713   // fields here. The way we set top for all regions (i.e., top ==
 714   // end for all regions but the last one, top == new_top for the
 715   // last one) is actually used when we will free up the humongous
 716   // region in free_humongous_region().
 717   hr = NULL;
 718   for (int i = first + 1; i < last; ++i) {
 719     hr = _hrs->at(i);
 720     if ((i + 1) == last) {
 721       // last continues humongous region
 722       assert(hr->bottom() < new_top && new_top <= hr->end(),
 723              "new_top should fall on this region");
 724       hr->set_top(new_top);
 725     } else {
 726       // not last one
 727       assert(new_top > hr->end(), "new_top should be above this region");
 728       hr->set_top(hr->end());
 729     }
 730   }
 731   // If we have continues humongous regions (hr != NULL), then the
 732   // end of the last one should match new_end and its top should
 733   // match new_top.
 734   assert(hr == NULL ||
 735          (hr->end() == new_end && hr->top() == new_top), "sanity");
 736 
 737   assert(first_hr->used() == word_size * HeapWordSize, "invariant");
 738   _summary_bytes_used += first_hr->used();
 739   _humongous_set.add(first_hr);
 740 
 741   return new_obj;
 742 }
 743 
 744 // If could fit into free regions w/o expansion, try.
 745 // Otherwise, if can expand, do so.
 746 // Otherwise, if using ex regions might help, try with ex given back.
 747 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
 748   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 749 
 750   verify_region_sets_optional();
 751 
 752   size_t num_regions =
 753          round_to(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
 754   size_t x_size = expansion_regions();
 755   size_t fs = _hrs->free_suffix();
 756   int first = humongous_obj_allocate_find_first(num_regions, word_size);
 757   if (first == -1) {
 758     // The only thing we can do now is attempt expansion.
 759     if (fs + x_size >= num_regions) {
 760       // If the number of regions we're trying to allocate for this
 761       // object is at most the number of regions in the free suffix,
 762       // then the call to humongous_obj_allocate_find_first() above
 763       // should have succeeded and we wouldn't be here.
 764       //
 765       // We should only be trying to expand when the free suffix is
 766       // not sufficient for the object _and_ we have some expansion
 767       // room available.
 768       assert(num_regions > fs, "earlier allocation should have succeeded");
 769 
 770       if (expand((num_regions - fs) * HeapRegion::GrainBytes)) {
 771         first = humongous_obj_allocate_find_first(num_regions, word_size);
 772         // If the expansion was successful then the allocation
 773         // should have been successful.
 774         assert(first != -1, "this should have worked");
 775       }
 776     }
 777   }
 778 
 779   HeapWord* result = NULL;
 780   if (first != -1) {
 781     result =
 782       humongous_obj_allocate_initialize_regions(first, num_regions, word_size);
 783     assert(result != NULL, "it should always return a valid result");
 784   }
 785 
 786   verify_region_sets_optional();
 787 
 788   return result;
 789 }
 790 
 791 void
 792 G1CollectedHeap::retire_cur_alloc_region(HeapRegion* cur_alloc_region) {
 793   // Other threads might still be trying to allocate using CASes out
 794   // of the region we are retiring, as they can do so without holding
 795   // the Heap_lock. So we first have to make sure that noone else can
 796   // allocate in it by doing a maximal allocation. Even if our CAS
 797   // attempt fails a few times, we'll succeed sooner or later given
 798   // that a failed CAS attempt mean that the region is getting closed
 799   // to being full (someone else succeeded in allocating into it).
 800   size_t free_word_size = cur_alloc_region->free() / HeapWordSize;
 801 
 802   // This is the minimum free chunk we can turn into a dummy
 803   // object. If the free space falls below this, then noone can
 804   // allocate in this region anyway (all allocation requests will be
 805   // of a size larger than this) so we won't have to perform the dummy
 806   // allocation.
 807   size_t min_word_size_to_fill = CollectedHeap::min_fill_size();
 808 
 809   while (free_word_size >= min_word_size_to_fill) {
 810     HeapWord* dummy =
 811       cur_alloc_region->par_allocate_no_bot_updates(free_word_size);
 812     if (dummy != NULL) {
 813       // If the allocation was successful we should fill in the space.
 814       CollectedHeap::fill_with_object(dummy, free_word_size);
 815       break;
 816     }
 817 
 818     free_word_size = cur_alloc_region->free() / HeapWordSize;
 819     // It's also possible that someone else beats us to the
 820     // allocation and they fill up the region. In that case, we can
 821     // just get out of the loop
 822   }
 823   assert(cur_alloc_region->free() / HeapWordSize < min_word_size_to_fill,
 824          "sanity");
 825 
 826   retire_cur_alloc_region_common(cur_alloc_region);
 827   assert(_cur_alloc_region == NULL, "post-condition");
 828 }
 829 
 830 // See the comment in the .hpp file about the locking protocol and
 831 // assumptions of this method (and other related ones).
 832 HeapWord*
 833 G1CollectedHeap::replace_cur_alloc_region_and_allocate(size_t word_size,
 834                                                        bool at_safepoint,
 835                                                        bool do_dirtying,
 836                                                        bool can_expand) {
 837   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 838   assert(_cur_alloc_region == NULL,
 839          "replace_cur_alloc_region_and_allocate() should only be called "
 840          "after retiring the previous current alloc region");
 841   assert(SafepointSynchronize::is_at_safepoint() == at_safepoint,
 842          "at_safepoint and is_at_safepoint() should be a tautology");
 843   assert(!can_expand || g1_policy()->can_expand_young_list(),
 844          "we should not call this method with can_expand == true if "
 845          "we are not allowed to expand the young gen");
 846 
 847   if (can_expand || !g1_policy()->is_young_list_full()) {
 848     HeapRegion* new_cur_alloc_region = new_alloc_region(word_size);
 849     if (new_cur_alloc_region != NULL) {
 850       assert(new_cur_alloc_region->is_empty(),
 851              "the newly-allocated region should be empty, "
 852              "as right now we only allocate new regions out of the free list");
 853       g1_policy()->update_region_num(true /* next_is_young */);
 854       set_region_short_lived_locked(new_cur_alloc_region);
 855 
 856       assert(!new_cur_alloc_region->isHumongous(),
 857              "Catch a regression of this bug.");
 858 
 859       // We need to ensure that the stores to _cur_alloc_region and,
 860       // subsequently, to top do not float above the setting of the
 861       // young type.
 862       OrderAccess::storestore();
 863 
 864       // Now, perform the allocation out of the region we just
 865       // allocated. Note that noone else can access that region at
 866       // this point (as _cur_alloc_region has not been updated yet),
 867       // so we can just go ahead and do the allocation without any
 868       // atomics (and we expect this allocation attempt to
 869       // suceeded). Given that other threads can attempt an allocation
 870       // with a CAS and without needing the Heap_lock, if we assigned
 871       // the new region to _cur_alloc_region before first allocating
 872       // into it other threads might have filled up the new region
 873       // before we got a chance to do the allocation ourselves. In
 874       // that case, we would have needed to retire the region, grab a
 875       // new one, and go through all this again. Allocating out of the
 876       // new region before assigning it to _cur_alloc_region avoids
 877       // all this.
 878       HeapWord* result =
 879                      new_cur_alloc_region->allocate_no_bot_updates(word_size);
 880       assert(result != NULL, "we just allocate out of an empty region "
 881              "so allocation should have been successful");
 882       assert(is_in(result), "result should be in the heap");
 883 
 884       // Now make sure that the store to _cur_alloc_region does not
 885       // float above the store to top.
 886       OrderAccess::storestore();
 887       _cur_alloc_region = new_cur_alloc_region;
 888 
 889       if (!at_safepoint) {
 890         Heap_lock->unlock();
 891       }
 892 
 893       // do the dirtying, if necessary, after we release the Heap_lock
 894       if (do_dirtying) {
 895         dirty_young_block(result, word_size);
 896       }
 897       return result;
 898     }
 899   }
 900 
 901   assert(_cur_alloc_region == NULL, "we failed to allocate a new current "
 902          "alloc region, it should still be NULL");
 903   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 904   return NULL;
 905 }
 906 
 907 // See the comment in the .hpp file about the locking protocol and
 908 // assumptions of this method (and other related ones).
 909 HeapWord*
 910 G1CollectedHeap::attempt_allocation_slow(size_t word_size) {
 911   assert_heap_locked_and_not_at_safepoint();
 912   assert(!isHumongous(word_size), "attempt_allocation_slow() should not be "
 913          "used for humongous allocations");
 914 
 915   // We should only reach here when we were unable to allocate
 916   // otherwise. So, we should have not active current alloc region.
 917   assert(_cur_alloc_region == NULL, "current alloc region should be NULL");
 918 
 919   // We will loop while succeeded is false, which means that we tried
 920   // to do a collection, but the VM op did not succeed. So, when we
 921   // exit the loop, either one of the allocation attempts was
 922   // successful, or we succeeded in doing the VM op but which was
 923   // unable to allocate after the collection.
 924   for (int try_count = 1; /* we'll return or break */; try_count += 1) {
 925     bool succeeded = true;
 926 
 927     // Every time we go round the loop we should be holding the Heap_lock.
 928     assert_heap_locked();
 929 
 930     if (GC_locker::is_active_and_needs_gc()) {
 931       // We are locked out of GC because of the GC locker. We can
 932       // allocate a new region only if we can expand the young gen.
 933 
 934       if (g1_policy()->can_expand_young_list()) {
 935         // Yes, we are allowed to expand the young gen. Let's try to
 936         // allocate a new current alloc region.
 937         HeapWord* result =
 938           replace_cur_alloc_region_and_allocate(word_size,
 939                                                 false, /* at_safepoint */
 940                                                 true,  /* do_dirtying */
 941                                                 true   /* can_expand */);
 942         if (result != NULL) {
 943           assert_heap_not_locked();
 944           return result;
 945         }
 946       }
 947       // We could not expand the young gen further (or we could but we
 948       // failed to allocate a new region). We'll stall until the GC
 949       // locker forces a GC.
 950 
 951       // If this thread is not in a jni critical section, we stall
 952       // the requestor until the critical section has cleared and
 953       // GC allowed. When the critical section clears, a GC is
 954       // initiated by the last thread exiting the critical section; so
 955       // we retry the allocation sequence from the beginning of the loop,
 956       // rather than causing more, now probably unnecessary, GC attempts.
 957       JavaThread* jthr = JavaThread::current();
 958       assert(jthr != NULL, "sanity");
 959       if (jthr->in_critical()) {
 960         if (CheckJNICalls) {
 961           fatal("Possible deadlock due to allocating while"
 962                 " in jni critical section");
 963         }
 964         // We are returning NULL so the protocol is that we're still
 965         // holding the Heap_lock.
 966         assert_heap_locked();
 967         return NULL;
 968       }
 969 
 970       Heap_lock->unlock();
 971       GC_locker::stall_until_clear();
 972 
 973       // No need to relock the Heap_lock. We'll fall off to the code
 974       // below the else-statement which assumes that we are not
 975       // holding the Heap_lock.
 976     } else {
 977       // We are not locked out. So, let's try to do a GC. The VM op
 978       // will retry the allocation before it completes.
 979 
 980       // Read the GC count while holding the Heap_lock
 981       unsigned int gc_count_before = SharedHeap::heap()->total_collections();
 982 
 983       Heap_lock->unlock();
 984 
 985       HeapWord* result =
 986         do_collection_pause(word_size, gc_count_before, &succeeded);
 987       assert_heap_not_locked();
 988       if (result != NULL) {
 989         assert(succeeded, "the VM op should have succeeded");
 990 
 991         // Allocations that take place on VM operations do not do any
 992         // card dirtying and we have to do it here.
 993         dirty_young_block(result, word_size);
 994         return result;
 995       }
 996     }
 997 
 998     // Both paths that get us here from above unlock the Heap_lock.
 999     assert_heap_not_locked();
1000 
1001     // We can reach here when we were unsuccessful in doing a GC,
1002     // because another thread beat us to it, or because we were locked
1003     // out of GC due to the GC locker. In either case a new alloc
1004     // region might be available so we will retry the allocation.
1005     HeapWord* result = attempt_allocation(word_size);
1006     if (result != NULL) {
1007       assert_heap_not_locked();
1008       return result;
1009     }
1010 
1011     // So far our attempts to allocate failed. The only time we'll go
1012     // around the loop and try again is if we tried to do a GC and the
1013     // VM op that we tried to schedule was not successful because
1014     // another thread beat us to it. If that happened it's possible
1015     // that by the time we grabbed the Heap_lock again and tried to
1016     // allocate other threads filled up the young generation, which
1017     // means that the allocation attempt after the GC also failed. So,
1018     // it's worth trying to schedule another GC pause.
1019     if (succeeded) {
1020       break;
1021     }
1022 
1023     // Give a warning if we seem to be looping forever.
1024     if ((QueuedAllocationWarningCount > 0) &&
1025         (try_count % QueuedAllocationWarningCount == 0)) {
1026       warning("G1CollectedHeap::attempt_allocation_slow() "
1027               "retries %d times", try_count);
1028     }
1029   }
1030 
1031   assert_heap_locked();
1032   return NULL;
1033 }
1034 
1035 // See the comment in the .hpp file about the locking protocol and
1036 // assumptions of this method (and other related ones).
1037 HeapWord*
1038 G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
1039                                               bool at_safepoint) {
1040   // This is the method that will allocate a humongous object. All
1041   // allocation paths that attempt to allocate a humongous object
1042   // should eventually reach here. Currently, the only paths are from
1043   // mem_allocate() and attempt_allocation_at_safepoint().
1044   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
1045   assert(isHumongous(word_size), "attempt_allocation_humongous() "
1046          "should only be used for humongous allocations");
1047   assert(SafepointSynchronize::is_at_safepoint() == at_safepoint,
1048          "at_safepoint and is_at_safepoint() should be a tautology");
1049 
1050   HeapWord* result = NULL;
1051 
1052   // We will loop while succeeded is false, which means that we tried
1053   // to do a collection, but the VM op did not succeed. So, when we
1054   // exit the loop, either one of the allocation attempts was
1055   // successful, or we succeeded in doing the VM op but which was
1056   // unable to allocate after the collection.
1057   for (int try_count = 1; /* we'll return or break */; try_count += 1) {
1058     bool succeeded = true;
1059 
1060     // Given that humongous objects are not allocated in young
1061     // regions, we'll first try to do the allocation without doing a
1062     // collection hoping that there's enough space in the heap.
1063     result = humongous_obj_allocate(word_size);
1064     assert(_cur_alloc_region == NULL || !_cur_alloc_region->isHumongous(),
1065            "catch a regression of this bug.");
1066     if (result != NULL) {
1067       if (!at_safepoint) {
1068         // If we're not at a safepoint, unlock the Heap_lock.
1069         Heap_lock->unlock();
1070       }
1071       return result;
1072     }
1073 
1074     // If we failed to allocate the humongous object, we should try to
1075     // do a collection pause (if we're allowed) in case it reclaims
1076     // enough space for the allocation to succeed after the pause.
1077     if (!at_safepoint) {
1078       // Read the GC count while holding the Heap_lock
1079       unsigned int gc_count_before = SharedHeap::heap()->total_collections();
1080 
1081       // If we're allowed to do a collection we're not at a
1082       // safepoint, so it is safe to unlock the Heap_lock.
1083       Heap_lock->unlock();
1084 
1085       result = do_collection_pause(word_size, gc_count_before, &succeeded);
1086       assert_heap_not_locked();
1087       if (result != NULL) {
1088         assert(succeeded, "the VM op should have succeeded");
1089         return result;
1090       }
1091 
1092       // If we get here, the VM operation either did not succeed
1093       // (i.e., another thread beat us to it) or it succeeded but
1094       // failed to allocate the object.
1095 
1096       // If we're allowed to do a collection we're not at a
1097       // safepoint, so it is safe to lock the Heap_lock.
1098       Heap_lock->lock();
1099     }
1100 
1101     assert(result == NULL, "otherwise we should have exited the loop earlier");
1102 
1103     // So far our attempts to allocate failed. The only time we'll go
1104     // around the loop and try again is if we tried to do a GC and the
1105     // VM op that we tried to schedule was not successful because
1106     // another thread beat us to it. That way it's possible that some
1107     // space was freed up by the thread that successfully scheduled a
1108     // GC. So it's worth trying to allocate again.
1109     if (succeeded) {
1110       break;
1111     }
1112 
1113     // Give a warning if we seem to be looping forever.
1114     if ((QueuedAllocationWarningCount > 0) &&
1115         (try_count % QueuedAllocationWarningCount == 0)) {
1116       warning("G1CollectedHeap::attempt_allocation_humongous "
1117               "retries %d times", try_count);
1118     }
1119   }
1120 
1121   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
1122   return NULL;
1123 }
1124 
1125 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1126                                            bool expect_null_cur_alloc_region) {
1127   assert_at_safepoint(true /* should_be_vm_thread */);
1128   assert(_cur_alloc_region == NULL || !expect_null_cur_alloc_region,
1129          err_msg("the current alloc region was unexpectedly found "
1130                  "to be non-NULL, cur alloc region: "PTR_FORMAT" "
1131                  "expect_null_cur_alloc_region: %d word_size: "SIZE_FORMAT,
1132                  _cur_alloc_region, expect_null_cur_alloc_region, word_size));
1133 
1134   if (!isHumongous(word_size)) {
1135     if (!expect_null_cur_alloc_region) {
1136       HeapRegion* cur_alloc_region = _cur_alloc_region;
1137       if (cur_alloc_region != NULL) {
1138         // We are at a safepoint so no reason to use the MT-safe version.
1139         HeapWord* result = cur_alloc_region->allocate_no_bot_updates(word_size);
1140         if (result != NULL) {
1141           assert(is_in(result), "result should be in the heap");
1142 
1143           // We will not do any dirtying here. This is guaranteed to be
1144           // called during a safepoint and the thread that scheduled the
1145           // pause will do the dirtying if we return a non-NULL result.
1146           return result;
1147         }
1148 
1149         retire_cur_alloc_region_common(cur_alloc_region);
1150       }
1151     }
1152 
1153     assert(_cur_alloc_region == NULL,
1154            "at this point we should have no cur alloc region");
1155     return replace_cur_alloc_region_and_allocate(word_size,
1156                                                  true, /* at_safepoint */
1157                                                  false /* do_dirtying */,
1158                                                  false /* can_expand */);
1159   } else {
1160     return attempt_allocation_humongous(word_size,
1161                                         true /* at_safepoint */);
1162   }
1163 
1164   ShouldNotReachHere();
1165 }
1166 
1167 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
1168   assert_heap_not_locked_and_not_at_safepoint();
1169   assert(!isHumongous(word_size), "we do not allow TLABs of humongous size");
1170 
1171   // First attempt: Try allocating out of the current alloc region
1172   // using a CAS. If that fails, take the Heap_lock and retry the
1173   // allocation, potentially replacing the current alloc region.
1174   HeapWord* result = attempt_allocation(word_size);
1175   if (result != NULL) {
1176     assert_heap_not_locked();
1177     return result;
1178   }
1179 
1180   // Second attempt: Go to the slower path where we might try to
1181   // schedule a collection.
1182   result = attempt_allocation_slow(word_size);
1183   if (result != NULL) {
1184     assert_heap_not_locked();
1185     return result;
1186   }
1187 
1188   assert_heap_locked();
1189   // Need to unlock the Heap_lock before returning.
1190   Heap_lock->unlock();
1191   return NULL;
1192 }
1193 
1194 HeapWord*
1195 G1CollectedHeap::mem_allocate(size_t word_size,
1196                               bool   is_noref,
1197                               bool   is_tlab,
1198                               bool*  gc_overhead_limit_was_exceeded) {
1199   assert_heap_not_locked_and_not_at_safepoint();
1200   assert(!is_tlab, "mem_allocate() this should not be called directly "
1201          "to allocate TLABs");
1202 
1203   // Loop until the allocation is satisified,
1204   // or unsatisfied after GC.
1205   for (int try_count = 1; /* we'll return */; try_count += 1) {
1206     unsigned int gc_count_before;
1207     {
1208       if (!isHumongous(word_size)) {
1209         // First attempt: Try allocating out of the current alloc region
1210         // using a CAS. If that fails, take the Heap_lock and retry the
1211         // allocation, potentially replacing the current alloc region.
1212         HeapWord* result = attempt_allocation(word_size);
1213         if (result != NULL) {
1214           assert_heap_not_locked();
1215           return result;
1216         }
1217 
1218         assert_heap_locked();
1219 
1220         // Second attempt: Go to the slower path where we might try to
1221         // schedule a collection.
1222         result = attempt_allocation_slow(word_size);
1223         if (result != NULL) {
1224           assert_heap_not_locked();
1225           return result;
1226         }
1227       } else {
1228         // attempt_allocation_humongous() requires the Heap_lock to be held.
1229         Heap_lock->lock();
1230 
1231         HeapWord* result = attempt_allocation_humongous(word_size,
1232                                                      false /* at_safepoint */);
1233         if (result != NULL) {
1234           assert_heap_not_locked();
1235           return result;
1236         }
1237       }
1238 
1239       assert_heap_locked();
1240       // Read the gc count while the heap lock is held.
1241       gc_count_before = SharedHeap::heap()->total_collections();
1242 
1243       // Release the Heap_lock before attempting the collection.
1244       Heap_lock->unlock();
1245     }
1246 
1247     // Create the garbage collection operation...
1248     VM_G1CollectForAllocation op(gc_count_before, word_size);
1249     // ...and get the VM thread to execute it.
1250     VMThread::execute(&op);
1251 
1252     assert_heap_not_locked();
1253     if (op.prologue_succeeded() && op.pause_succeeded()) {
1254       // If the operation was successful we'll return the result even
1255       // if it is NULL. If the allocation attempt failed immediately
1256       // after a Full GC, it's unlikely we'll be able to allocate now.
1257       HeapWord* result = op.result();
1258       if (result != NULL && !isHumongous(word_size)) {
1259         // Allocations that take place on VM operations do not do any
1260         // card dirtying and we have to do it here. We only have to do
1261         // this for non-humongous allocations, though.
1262         dirty_young_block(result, word_size);
1263       }
1264       return result;
1265     } else {
1266       assert(op.result() == NULL,
1267              "the result should be NULL if the VM op did not succeed");
1268     }
1269 
1270     // Give a warning if we seem to be looping forever.
1271     if ((QueuedAllocationWarningCount > 0) &&
1272         (try_count % QueuedAllocationWarningCount == 0)) {
1273       warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
1274     }
1275   }
1276 
1277   ShouldNotReachHere();
1278 }
1279 
1280 void G1CollectedHeap::abandon_cur_alloc_region() {
1281   assert_at_safepoint(true /* should_be_vm_thread */);
1282 
1283   HeapRegion* cur_alloc_region = _cur_alloc_region;
1284   if (cur_alloc_region != NULL) {
1285     assert(!cur_alloc_region->is_empty(),
1286            "the current alloc region can never be empty");
1287     assert(cur_alloc_region->is_young(),
1288            "the current alloc region should be young");
1289 
1290     retire_cur_alloc_region_common(cur_alloc_region);
1291   }
1292   assert(_cur_alloc_region == NULL, "post-condition");
1293 }
1294 
1295 void G1CollectedHeap::abandon_gc_alloc_regions() {
1296   // first, make sure that the GC alloc region list is empty (it should!)
1297   assert(_gc_alloc_region_list == NULL, "invariant");
1298   release_gc_alloc_regions(true /* totally */);
1299 }
1300 
1301 class PostMCRemSetClearClosure: public HeapRegionClosure {
1302   ModRefBarrierSet* _mr_bs;
1303 public:
1304   PostMCRemSetClearClosure(ModRefBarrierSet* mr_bs) : _mr_bs(mr_bs) {}
1305   bool doHeapRegion(HeapRegion* r) {
1306     r->reset_gc_time_stamp();
1307     if (r->continuesHumongous())
1308       return false;
1309     HeapRegionRemSet* hrrs = r->rem_set();
1310     if (hrrs != NULL) hrrs->clear();
1311     // You might think here that we could clear just the cards
1312     // corresponding to the used region.  But no: if we leave a dirty card
1313     // in a region we might allocate into, then it would prevent that card
1314     // from being enqueued, and cause it to be missed.
1315     // Re: the performance cost: we shouldn't be doing full GC anyway!
1316     _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1317     return false;
1318   }
1319 };
1320 
1321 
1322 class PostMCRemSetInvalidateClosure: public HeapRegionClosure {
1323   ModRefBarrierSet* _mr_bs;
1324 public:
1325   PostMCRemSetInvalidateClosure(ModRefBarrierSet* mr_bs) : _mr_bs(mr_bs) {}
1326   bool doHeapRegion(HeapRegion* r) {
1327     if (r->continuesHumongous()) return false;
1328     if (r->used_region().word_size() != 0) {
1329       _mr_bs->invalidate(r->used_region(), true /*whole heap*/);
1330     }
1331     return false;
1332   }
1333 };
1334 
1335 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1336   G1CollectedHeap*   _g1h;
1337   UpdateRSOopClosure _cl;
1338   int                _worker_i;
1339 public:
1340   RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1341     _cl(g1->g1_rem_set(), worker_i),
1342     _worker_i(worker_i),
1343     _g1h(g1)
1344   { }
1345 
1346   bool doHeapRegion(HeapRegion* r) {
1347     if (!r->continuesHumongous()) {
1348       _cl.set_from(r);
1349       r->oop_iterate(&_cl);
1350     }
1351     return false;
1352   }
1353 };
1354 
1355 class ParRebuildRSTask: public AbstractGangTask {
1356   G1CollectedHeap* _g1;
1357 public:
1358   ParRebuildRSTask(G1CollectedHeap* g1)
1359     : AbstractGangTask("ParRebuildRSTask"),
1360       _g1(g1)
1361   { }
1362 
1363   void work(int i) {
1364     RebuildRSOutOfRegionClosure rebuild_rs(_g1, i);
1365     _g1->heap_region_par_iterate_chunked(&rebuild_rs, i,
1366                                          HeapRegion::RebuildRSClaimValue);
1367   }
1368 };
1369 
1370 bool G1CollectedHeap::do_collection(bool explicit_gc,
1371                                     bool clear_all_soft_refs,
1372                                     size_t word_size) {
1373   assert_at_safepoint(true /* should_be_vm_thread */);
1374 
1375   if (GC_locker::check_active_before_gc()) {
1376     return false;
1377   }
1378 
1379   SvcGCMarker sgcm(SvcGCMarker::FULL);
1380   ResourceMark rm;
1381 
1382   if (PrintHeapAtGC) {
1383     Universe::print_heap_before_gc();
1384   }
1385 
1386   verify_region_sets_optional();
1387 
1388   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1389                            collector_policy()->should_clear_all_soft_refs();
1390 
1391   ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1392 
1393   {
1394     IsGCActiveMark x;
1395 
1396     // Timing
1397     bool system_gc = (gc_cause() == GCCause::_java_lang_system_gc);
1398     assert(!system_gc || explicit_gc, "invariant");
1399     gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
1400     TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
1401     TraceTime t(system_gc ? "Full GC (System.gc())" : "Full GC",
1402                 PrintGC, true, gclog_or_tty);
1403 
1404     TraceMemoryManagerStats tms(true /* fullGC */);
1405 
1406     double start = os::elapsedTime();
1407     g1_policy()->record_full_collection_start();
1408 
1409     wait_while_free_regions_coming();
1410     append_secondary_free_list_if_not_empty_with_lock();
1411 
1412     gc_prologue(true);
1413     increment_total_collections(true /* full gc */);
1414 
1415     size_t g1h_prev_used = used();
1416     assert(used() == recalculate_used(), "Should be equal");
1417 
1418     if (VerifyBeforeGC && total_collections() >= VerifyGCStartAt) {
1419       HandleMark hm;  // Discard invalid handles created during verification
1420       prepare_for_verify();
1421       gclog_or_tty->print(" VerifyBeforeGC:");
1422       Universe::verify(true);
1423     }
1424 
1425     COMPILER2_PRESENT(DerivedPointerTable::clear());
1426 
1427     // We want to discover references, but not process them yet.
1428     // This mode is disabled in
1429     // instanceRefKlass::process_discovered_references if the
1430     // generation does some collection work, or
1431     // instanceRefKlass::enqueue_discovered_references if the
1432     // generation returns without doing any work.
1433     ref_processor()->disable_discovery();
1434     ref_processor()->abandon_partial_discovery();
1435     ref_processor()->verify_no_references_recorded();
1436 
1437     // Abandon current iterations of concurrent marking and concurrent
1438     // refinement, if any are in progress.
1439     concurrent_mark()->abort();
1440 
1441     // Make sure we'll choose a new allocation region afterwards.
1442     abandon_cur_alloc_region();
1443     abandon_gc_alloc_regions();
1444     assert(_cur_alloc_region == NULL, "Invariant.");
1445     g1_rem_set()->cleanupHRRS();
1446     tear_down_region_lists();
1447 
1448     // We may have added regions to the current incremental collection
1449     // set between the last GC or pause and now. We need to clear the
1450     // incremental collection set and then start rebuilding it afresh
1451     // after this full GC.
1452     abandon_collection_set(g1_policy()->inc_cset_head());
1453     g1_policy()->clear_incremental_cset();
1454     g1_policy()->stop_incremental_cset_building();
1455 
1456     if (g1_policy()->in_young_gc_mode()) {
1457       empty_young_list();
1458       g1_policy()->set_full_young_gcs(true);
1459     }
1460 
1461     // See the comment in G1CollectedHeap::ref_processing_init() about
1462     // how reference processing currently works in G1.
1463 
1464     // Temporarily make reference _discovery_ single threaded (non-MT).
1465     ReferenceProcessorMTMutator rp_disc_ser(ref_processor(), false);
1466 
1467     // Temporarily make refs discovery atomic
1468     ReferenceProcessorAtomicMutator rp_disc_atomic(ref_processor(), true);
1469 
1470     // Temporarily clear _is_alive_non_header
1471     ReferenceProcessorIsAliveMutator rp_is_alive_null(ref_processor(), NULL);
1472 
1473     ref_processor()->enable_discovery();
1474     ref_processor()->setup_policy(do_clear_all_soft_refs);
1475 
1476     // Do collection work
1477     {
1478       HandleMark hm;  // Discard invalid handles created during gc
1479       G1MarkSweep::invoke_at_safepoint(ref_processor(), do_clear_all_soft_refs);
1480     }
1481     assert(free_regions() == 0, "we should not have added any free regions");
1482     rebuild_region_lists();
1483 
1484     _summary_bytes_used = recalculate_used();
1485 
1486     ref_processor()->enqueue_discovered_references();
1487 
1488     COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1489 
1490     MemoryService::track_memory_usage();
1491 
1492     if (VerifyAfterGC && total_collections() >= VerifyGCStartAt) {
1493       HandleMark hm;  // Discard invalid handles created during verification
1494       gclog_or_tty->print(" VerifyAfterGC:");
1495       prepare_for_verify();
1496       Universe::verify(false);
1497     }
1498     NOT_PRODUCT(ref_processor()->verify_no_references_recorded());
1499 
1500     reset_gc_time_stamp();
1501     // Since everything potentially moved, we will clear all remembered
1502     // sets, and clear all cards.  Later we will rebuild remebered
1503     // sets. We will also reset the GC time stamps of the regions.
1504     PostMCRemSetClearClosure rs_clear(mr_bs());
1505     heap_region_iterate(&rs_clear);
1506 
1507     // Resize the heap if necessary.
1508     resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1509 
1510     if (_cg1r->use_cache()) {
1511       _cg1r->clear_and_record_card_counts();
1512       _cg1r->clear_hot_cache();
1513     }
1514 
1515     // Rebuild remembered sets of all regions.
1516 
1517     if (G1CollectedHeap::use_parallel_gc_threads()) {
1518       ParRebuildRSTask rebuild_rs_task(this);
1519       assert(check_heap_region_claim_values(
1520              HeapRegion::InitialClaimValue), "sanity check");
1521       set_par_threads(workers()->total_workers());
1522       workers()->run_task(&rebuild_rs_task);
1523       set_par_threads(0);
1524       assert(check_heap_region_claim_values(
1525              HeapRegion::RebuildRSClaimValue), "sanity check");
1526       reset_heap_region_claim_values();
1527     } else {
1528       RebuildRSOutOfRegionClosure rebuild_rs(this);
1529       heap_region_iterate(&rebuild_rs);
1530     }
1531 
1532     if (PrintGC) {
1533       print_size_transition(gclog_or_tty, g1h_prev_used, used(), capacity());
1534     }
1535 
1536     if (true) { // FIXME
1537       // Ask the permanent generation to adjust size for full collections
1538       perm()->compute_new_size();
1539     }
1540 
1541     // Start a new incremental collection set for the next pause
1542     assert(g1_policy()->collection_set() == NULL, "must be");
1543     g1_policy()->start_incremental_cset_building();
1544 
1545     // Clear the _cset_fast_test bitmap in anticipation of adding
1546     // regions to the incremental collection set for the next
1547     // evacuation pause.
1548     clear_cset_fast_test();
1549 
1550     double end = os::elapsedTime();
1551     g1_policy()->record_full_collection_end();
1552 
1553 #ifdef TRACESPINNING
1554     ParallelTaskTerminator::print_termination_counts();
1555 #endif
1556 
1557     gc_epilogue(true);
1558 
1559     // Discard all rset updates
1560     JavaThread::dirty_card_queue_set().abandon_logs();
1561     assert(!G1DeferredRSUpdate
1562            || (G1DeferredRSUpdate && (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any");
1563   }
1564 
1565   if (g1_policy()->in_young_gc_mode()) {
1566     _young_list->reset_sampled_info();
1567     // At this point there should be no regions in the
1568     // entire heap tagged as young.
1569     assert( check_young_list_empty(true /* check_heap */),
1570             "young list should be empty at this point");
1571   }
1572 
1573   // Update the number of full collections that have been completed.
1574   increment_full_collections_completed(false /* concurrent */);
1575 
1576   verify_region_sets_optional();
1577 
1578   if (PrintHeapAtGC) {
1579     Universe::print_heap_after_gc();
1580   }
1581 
1582   return true;
1583 }
1584 
1585 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1586   // do_collection() will return whether it succeeded in performing
1587   // the GC. Currently, there is no facility on the
1588   // do_full_collection() API to notify the caller than the collection
1589   // did not succeed (e.g., because it was locked out by the GC
1590   // locker). So, right now, we'll ignore the return value.
1591   bool dummy = do_collection(true,                /* explicit_gc */
1592                              clear_all_soft_refs,
1593                              0                    /* word_size */);
1594 }
1595 
1596 // This code is mostly copied from TenuredGeneration.
1597 void
1598 G1CollectedHeap::
1599 resize_if_necessary_after_full_collection(size_t word_size) {
1600   assert(MinHeapFreeRatio <= MaxHeapFreeRatio, "sanity check");
1601 
1602   // Include the current allocation, if any, and bytes that will be
1603   // pre-allocated to support collections, as "used".
1604   const size_t used_after_gc = used();
1605   const size_t capacity_after_gc = capacity();
1606   const size_t free_after_gc = capacity_after_gc - used_after_gc;
1607 
1608   // This is enforced in arguments.cpp.
1609   assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1610          "otherwise the code below doesn't make sense");
1611 
1612   // We don't have floating point command-line arguments
1613   const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1614   const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1615   const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1616   const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1617 
1618   const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1619   const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1620 
1621   // We have to be careful here as these two calculations can overflow
1622   // 32-bit size_t's.
1623   double used_after_gc_d = (double) used_after_gc;
1624   double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1625   double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1626 
1627   // Let's make sure that they are both under the max heap size, which
1628   // by default will make them fit into a size_t.
1629   double desired_capacity_upper_bound = (double) max_heap_size;
1630   minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1631                                     desired_capacity_upper_bound);
1632   maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1633                                     desired_capacity_upper_bound);
1634 
1635   // We can now safely turn them into size_t's.
1636   size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1637   size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1638 
1639   // This assert only makes sense here, before we adjust them
1640   // with respect to the min and max heap size.
1641   assert(minimum_desired_capacity <= maximum_desired_capacity,
1642          err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1643                  "maximum_desired_capacity = "SIZE_FORMAT,
1644                  minimum_desired_capacity, maximum_desired_capacity));
1645 
1646   // Should not be greater than the heap max size. No need to adjust
1647   // it with respect to the heap min size as it's a lower bound (i.e.,
1648   // we'll try to make the capacity larger than it, not smaller).
1649   minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1650   // Should not be less than the heap min size. No need to adjust it
1651   // with respect to the heap max size as it's an upper bound (i.e.,
1652   // we'll try to make the capacity smaller than it, not greater).
1653   maximum_desired_capacity =  MAX2(maximum_desired_capacity, min_heap_size);
1654 
1655   if (PrintGC && Verbose) {
1656     const double free_percentage =
1657       (double) free_after_gc / (double) capacity_after_gc;
1658     gclog_or_tty->print_cr("Computing new size after full GC ");
1659     gclog_or_tty->print_cr("  "
1660                            "  minimum_free_percentage: %6.2f",
1661                            minimum_free_percentage);
1662     gclog_or_tty->print_cr("  "
1663                            "  maximum_free_percentage: %6.2f",
1664                            maximum_free_percentage);
1665     gclog_or_tty->print_cr("  "
1666                            "  capacity: %6.1fK"
1667                            "  minimum_desired_capacity: %6.1fK"
1668                            "  maximum_desired_capacity: %6.1fK",
1669                            (double) capacity_after_gc / (double) K,
1670                            (double) minimum_desired_capacity / (double) K,
1671                            (double) maximum_desired_capacity / (double) K);
1672     gclog_or_tty->print_cr("  "
1673                            "  free_after_gc: %6.1fK"
1674                            "  used_after_gc: %6.1fK",
1675                            (double) free_after_gc / (double) K,
1676                            (double) used_after_gc / (double) K);
1677     gclog_or_tty->print_cr("  "
1678                            "   free_percentage: %6.2f",
1679                            free_percentage);
1680   }
1681   if (capacity_after_gc < minimum_desired_capacity) {
1682     // Don't expand unless it's significant
1683     size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1684     if (expand(expand_bytes)) {
1685       if (PrintGC && Verbose) {
1686         gclog_or_tty->print_cr("  "
1687                                "  expanding:"
1688                                "  max_heap_size: %6.1fK"
1689                                "  minimum_desired_capacity: %6.1fK"
1690                                "  expand_bytes: %6.1fK",
1691                                (double) max_heap_size / (double) K,
1692                                (double) minimum_desired_capacity / (double) K,
1693                                (double) expand_bytes / (double) K);
1694       }
1695     }
1696 
1697     // No expansion, now see if we want to shrink
1698   } else if (capacity_after_gc > maximum_desired_capacity) {
1699     // Capacity too large, compute shrinking size
1700     size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1701     shrink(shrink_bytes);
1702     if (PrintGC && Verbose) {
1703       gclog_or_tty->print_cr("  "
1704                              "  shrinking:"
1705                              "  min_heap_size: %6.1fK"
1706                              "  maximum_desired_capacity: %6.1fK"
1707                              "  shrink_bytes: %6.1fK",
1708                              (double) min_heap_size / (double) K,
1709                              (double) maximum_desired_capacity / (double) K,
1710                              (double) shrink_bytes / (double) K);
1711     }
1712   }
1713 }
1714 
1715 
1716 HeapWord*
1717 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1718                                            bool* succeeded) {
1719   assert_at_safepoint(true /* should_be_vm_thread */);
1720 
1721   *succeeded = true;
1722   // Let's attempt the allocation first.
1723   HeapWord* result = attempt_allocation_at_safepoint(word_size,
1724                                      false /* expect_null_cur_alloc_region */);
1725   if (result != NULL) {
1726     assert(*succeeded, "sanity");
1727     return result;
1728   }
1729 
1730   // In a G1 heap, we're supposed to keep allocation from failing by
1731   // incremental pauses.  Therefore, at least for now, we'll favor
1732   // expansion over collection.  (This might change in the future if we can
1733   // do something smarter than full collection to satisfy a failed alloc.)
1734   result = expand_and_allocate(word_size);
1735   if (result != NULL) {
1736     assert(*succeeded, "sanity");
1737     return result;
1738   }
1739 
1740   // Expansion didn't work, we'll try to do a Full GC.
1741   bool gc_succeeded = do_collection(false, /* explicit_gc */
1742                                     false, /* clear_all_soft_refs */
1743                                     word_size);
1744   if (!gc_succeeded) {
1745     *succeeded = false;
1746     return NULL;
1747   }
1748 
1749   // Retry the allocation
1750   result = attempt_allocation_at_safepoint(word_size,
1751                                       true /* expect_null_cur_alloc_region */);
1752   if (result != NULL) {
1753     assert(*succeeded, "sanity");
1754     return result;
1755   }
1756 
1757   // Then, try a Full GC that will collect all soft references.
1758   gc_succeeded = do_collection(false, /* explicit_gc */
1759                                true,  /* clear_all_soft_refs */
1760                                word_size);
1761   if (!gc_succeeded) {
1762     *succeeded = false;
1763     return NULL;
1764   }
1765 
1766   // Retry the allocation once more
1767   result = attempt_allocation_at_safepoint(word_size,
1768                                       true /* expect_null_cur_alloc_region */);
1769   if (result != NULL) {
1770     assert(*succeeded, "sanity");
1771     return result;
1772   }
1773 
1774   assert(!collector_policy()->should_clear_all_soft_refs(),
1775          "Flag should have been handled and cleared prior to this point");
1776 
1777   // What else?  We might try synchronous finalization later.  If the total
1778   // space available is large enough for the allocation, then a more
1779   // complete compaction phase than we've tried so far might be
1780   // appropriate.
1781   assert(*succeeded, "sanity");
1782   return NULL;
1783 }
1784 
1785 // Attempting to expand the heap sufficiently
1786 // to support an allocation of the given "word_size".  If
1787 // successful, perform the allocation and return the address of the
1788 // allocated block, or else "NULL".
1789 
1790 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1791   assert_at_safepoint(true /* should_be_vm_thread */);
1792 
1793   verify_region_sets_optional();
1794 
1795   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1796   if (expand(expand_bytes)) {
1797     verify_region_sets_optional();
1798     return attempt_allocation_at_safepoint(word_size,
1799                                           false /* expect_null_cur_alloc_region */);
1800   }
1801   return NULL;
1802 }
1803 
1804 bool G1CollectedHeap::expand(size_t expand_bytes) {
1805   size_t old_mem_size = _g1_storage.committed_size();
1806   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1807   aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1808                                        HeapRegion::GrainBytes);
1809 
1810   if (Verbose && PrintGC) {
1811     gclog_or_tty->print("Expanding garbage-first heap from %ldK by %ldK",
1812                            old_mem_size/K, aligned_expand_bytes/K);
1813   }
1814 
1815   HeapWord* old_end = (HeapWord*)_g1_storage.high();
1816   bool successful = _g1_storage.expand_by(aligned_expand_bytes);
1817   if (successful) {
1818     HeapWord* new_end = (HeapWord*)_g1_storage.high();
1819 
1820     // Expand the committed region.
1821     _g1_committed.set_end(new_end);
1822 
1823     // Tell the cardtable about the expansion.
1824     Universe::heap()->barrier_set()->resize_covered_region(_g1_committed);
1825 
1826     // And the offset table as well.
1827     _bot_shared->resize(_g1_committed.word_size());
1828 
1829     expand_bytes = aligned_expand_bytes;
1830     HeapWord* base = old_end;
1831 
1832     // Create the heap regions for [old_end, new_end)
1833     while (expand_bytes > 0) {
1834       HeapWord* high = base + HeapRegion::GrainWords;
1835 
1836       // Create a new HeapRegion.
1837       MemRegion mr(base, high);
1838       bool is_zeroed = !_g1_max_committed.contains(base);
1839       HeapRegion* hr = new HeapRegion(_bot_shared, mr, is_zeroed);
1840 
1841       // Add it to the HeapRegionSeq.
1842       _hrs->insert(hr);
1843       _free_list.add_as_tail(hr);
1844 
1845       // And we used up an expansion region to create it.
1846       _expansion_regions--;
1847 
1848       expand_bytes -= HeapRegion::GrainBytes;
1849       base += HeapRegion::GrainWords;
1850     }
1851     assert(base == new_end, "sanity");
1852 
1853     // Now update max_committed if necessary.
1854     _g1_max_committed.set_end(MAX2(_g1_max_committed.end(), new_end));
1855 
1856   } else {
1857     // The expansion of the virtual storage space was unsuccessful.
1858     // Let's see if it was because we ran out of swap.
1859     if (G1ExitOnExpansionFailure &&
1860         _g1_storage.uncommitted_size() >= aligned_expand_bytes) {
1861       // We had head room...
1862       vm_exit_out_of_memory(aligned_expand_bytes, "G1 heap expansion");
1863     }
1864   }
1865 
1866   if (Verbose && PrintGC) {
1867     size_t new_mem_size = _g1_storage.committed_size();
1868     gclog_or_tty->print_cr("...%s, expanded to %ldK",
1869                            (successful ? "Successful" : "Failed"),
1870                            new_mem_size/K);
1871   }
1872   return successful;
1873 }
1874 
1875 void G1CollectedHeap::shrink_helper(size_t shrink_bytes)
1876 {
1877   size_t old_mem_size = _g1_storage.committed_size();
1878   size_t aligned_shrink_bytes =
1879     ReservedSpace::page_align_size_down(shrink_bytes);
1880   aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1881                                          HeapRegion::GrainBytes);
1882   size_t num_regions_deleted = 0;
1883   MemRegion mr = _hrs->shrink_by(aligned_shrink_bytes, num_regions_deleted);
1884 
1885   assert(mr.end() == (HeapWord*)_g1_storage.high(), "Bad shrink!");
1886   if (mr.byte_size() > 0)
1887     _g1_storage.shrink_by(mr.byte_size());
1888   assert(mr.start() == (HeapWord*)_g1_storage.high(), "Bad shrink!");
1889 
1890   _g1_committed.set_end(mr.start());
1891   _expansion_regions += num_regions_deleted;
1892 
1893   // Tell the cardtable about it.
1894   Universe::heap()->barrier_set()->resize_covered_region(_g1_committed);
1895 
1896   // And the offset table as well.
1897   _bot_shared->resize(_g1_committed.word_size());
1898 
1899   HeapRegionRemSet::shrink_heap(n_regions());
1900 
1901   if (Verbose && PrintGC) {
1902     size_t new_mem_size = _g1_storage.committed_size();
1903     gclog_or_tty->print_cr("Shrinking garbage-first heap from %ldK by %ldK to %ldK",
1904                            old_mem_size/K, aligned_shrink_bytes/K,
1905                            new_mem_size/K);
1906   }
1907 }
1908 
1909 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1910   verify_region_sets_optional();
1911 
1912   release_gc_alloc_regions(true /* totally */);
1913   // Instead of tearing down / rebuilding the free lists here, we
1914   // could instead use the remove_all_pending() method on free_list to
1915   // remove only the ones that we need to remove.
1916   tear_down_region_lists();  // We will rebuild them in a moment.
1917   shrink_helper(shrink_bytes);
1918   rebuild_region_lists();
1919 
1920   verify_region_sets_optional();
1921 }
1922 
1923 // Public methods.
1924 
1925 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1926 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1927 #endif // _MSC_VER
1928 
1929 
1930 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1931   SharedHeap(policy_),
1932   _g1_policy(policy_),
1933   _dirty_card_queue_set(false),
1934   _into_cset_dirty_card_queue_set(false),
1935   _is_alive_closure(this),
1936   _ref_processor(NULL),
1937   _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
1938   _bot_shared(NULL),
1939   _objs_with_preserved_marks(NULL), _preserved_marks_of_objs(NULL),
1940   _evac_failure_scan_stack(NULL) ,
1941   _mark_in_progress(false),
1942   _cg1r(NULL), _summary_bytes_used(0),
1943   _cur_alloc_region(NULL),
1944   _refine_cte_cl(NULL),
1945   _full_collection(false),
1946   _free_list("Master Free List"),
1947   _secondary_free_list("Secondary Free List"),
1948   _humongous_set("Master Humongous Set"),
1949   _free_regions_coming(false),
1950   _young_list(new YoungList(this)),
1951   _gc_time_stamp(0),
1952   _surviving_young_words(NULL),
1953   _full_collections_completed(0),
1954   _in_cset_fast_test(NULL),
1955   _in_cset_fast_test_base(NULL),
1956   _dirty_cards_region_list(NULL) {
1957   _g1h = this; // To catch bugs.
1958   if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
1959     vm_exit_during_initialization("Failed necessary allocation.");
1960   }
1961 
1962   _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1963 
1964   int n_queues = MAX2((int)ParallelGCThreads, 1);
1965   _task_queues = new RefToScanQueueSet(n_queues);
1966 
1967   int n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1968   assert(n_rem_sets > 0, "Invariant.");
1969 
1970   HeapRegionRemSetIterator** iter_arr =
1971     NEW_C_HEAP_ARRAY(HeapRegionRemSetIterator*, n_queues);
1972   for (int i = 0; i < n_queues; i++) {
1973     iter_arr[i] = new HeapRegionRemSetIterator();
1974   }
1975   _rem_set_iterator = iter_arr;
1976 
1977   for (int i = 0; i < n_queues; i++) {
1978     RefToScanQueue* q = new RefToScanQueue();
1979     q->initialize();
1980     _task_queues->register_queue(i, q);
1981   }
1982 
1983   for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
1984     _gc_alloc_regions[ap]          = NULL;
1985     _gc_alloc_region_counts[ap]    = 0;
1986     _retained_gc_alloc_regions[ap] = NULL;
1987     // by default, we do not retain a GC alloc region for each ap;
1988     // we'll override this, when appropriate, below
1989     _retain_gc_alloc_region[ap]    = false;
1990   }
1991 
1992   // We will try to remember the last half-full tenured region we
1993   // allocated to at the end of a collection so that we can re-use it
1994   // during the next collection.
1995   _retain_gc_alloc_region[GCAllocForTenured]  = true;
1996 
1997   guarantee(_task_queues != NULL, "task_queues allocation failure.");
1998 }
1999 
2000 jint G1CollectedHeap::initialize() {
2001   CollectedHeap::pre_initialize();
2002   os::enable_vtime();
2003 
2004   // Necessary to satisfy locking discipline assertions.
2005 
2006   MutexLocker x(Heap_lock);
2007 
2008   // While there are no constraints in the GC code that HeapWordSize
2009   // be any particular value, there are multiple other areas in the
2010   // system which believe this to be true (e.g. oop->object_size in some
2011   // cases incorrectly returns the size in wordSize units rather than
2012   // HeapWordSize).
2013   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
2014 
2015   size_t init_byte_size = collector_policy()->initial_heap_byte_size();
2016   size_t max_byte_size = collector_policy()->max_heap_byte_size();
2017 
2018   // Ensure that the sizes are properly aligned.
2019   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
2020   Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
2021 
2022   _cg1r = new ConcurrentG1Refine();
2023 
2024   // Reserve the maximum.
2025   PermanentGenerationSpec* pgs = collector_policy()->permanent_generation();
2026   // Includes the perm-gen.
2027 
2028   const size_t total_reserved = max_byte_size + pgs->max_size();
2029   char* addr = Universe::preferred_heap_base(total_reserved, Universe::UnscaledNarrowOop);
2030 
2031   ReservedSpace heap_rs(max_byte_size + pgs->max_size(),
2032                         HeapRegion::GrainBytes,
2033                         UseLargePages, addr);
2034 
2035   if (UseCompressedOops) {
2036     if (addr != NULL && !heap_rs.is_reserved()) {
2037       // Failed to reserve at specified address - the requested memory
2038       // region is taken already, for example, by 'java' launcher.
2039       // Try again to reserver heap higher.
2040       addr = Universe::preferred_heap_base(total_reserved, Universe::ZeroBasedNarrowOop);
2041       ReservedSpace heap_rs0(total_reserved, HeapRegion::GrainBytes,
2042                              UseLargePages, addr);
2043       if (addr != NULL && !heap_rs0.is_reserved()) {
2044         // Failed to reserve at specified address again - give up.
2045         addr = Universe::preferred_heap_base(total_reserved, Universe::HeapBasedNarrowOop);
2046         assert(addr == NULL, "");
2047         ReservedSpace heap_rs1(total_reserved, HeapRegion::GrainBytes,
2048                                UseLargePages, addr);
2049         heap_rs = heap_rs1;
2050       } else {
2051         heap_rs = heap_rs0;
2052       }
2053     }
2054   }
2055 
2056   if (!heap_rs.is_reserved()) {
2057     vm_exit_during_initialization("Could not reserve enough space for object heap");
2058     return JNI_ENOMEM;
2059   }
2060 
2061   // It is important to do this in a way such that concurrent readers can't
2062   // temporarily think somethings in the heap.  (I've actually seen this
2063   // happen in asserts: DLD.)
2064   _reserved.set_word_size(0);
2065   _reserved.set_start((HeapWord*)heap_rs.base());
2066   _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size()));
2067 
2068   _expansion_regions = max_byte_size/HeapRegion::GrainBytes;
2069 
2070   // Create the gen rem set (and barrier set) for the entire reserved region.
2071   _rem_set = collector_policy()->create_rem_set(_reserved, 2);
2072   set_barrier_set(rem_set()->bs());
2073   if (barrier_set()->is_a(BarrierSet::ModRef)) {
2074     _mr_bs = (ModRefBarrierSet*)_barrier_set;
2075   } else {
2076     vm_exit_during_initialization("G1 requires a mod ref bs.");
2077     return JNI_ENOMEM;
2078   }
2079 
2080   // Also create a G1 rem set.
2081   if (mr_bs()->is_a(BarrierSet::CardTableModRef)) {
2082     _g1_rem_set = new G1RemSet(this, (CardTableModRefBS*)mr_bs());
2083   } else {
2084     vm_exit_during_initialization("G1 requires a cardtable mod ref bs.");
2085     return JNI_ENOMEM;
2086   }
2087 
2088   // Carve out the G1 part of the heap.
2089 
2090   ReservedSpace g1_rs   = heap_rs.first_part(max_byte_size);
2091   _g1_reserved = MemRegion((HeapWord*)g1_rs.base(),
2092                            g1_rs.size()/HeapWordSize);
2093   ReservedSpace perm_gen_rs = heap_rs.last_part(max_byte_size);
2094 
2095   _perm_gen = pgs->init(perm_gen_rs, pgs->init_size(), rem_set());
2096 
2097   _g1_storage.initialize(g1_rs, 0);
2098   _g1_committed = MemRegion((HeapWord*)_g1_storage.low(), (size_t) 0);
2099   _g1_max_committed = _g1_committed;
2100   _hrs = new HeapRegionSeq(_expansion_regions);
2101   guarantee(_hrs != NULL, "Couldn't allocate HeapRegionSeq");
2102   guarantee(_cur_alloc_region == NULL, "from constructor");
2103 
2104   // 6843694 - ensure that the maximum region index can fit
2105   // in the remembered set structures.
2106   const size_t max_region_idx = ((size_t)1 << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
2107   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
2108 
2109   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
2110   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
2111   guarantee((size_t) HeapRegion::CardsPerRegion < max_cards_per_region,
2112             "too many cards per region");
2113 
2114   HeapRegionSet::set_unrealistically_long_length(max_regions() + 1);
2115 
2116   _bot_shared = new G1BlockOffsetSharedArray(_reserved,
2117                                              heap_word_size(init_byte_size));
2118 
2119   _g1h = this;
2120 
2121    _in_cset_fast_test_length = max_regions();
2122    _in_cset_fast_test_base = NEW_C_HEAP_ARRAY(bool, _in_cset_fast_test_length);
2123 
2124    // We're biasing _in_cset_fast_test to avoid subtracting the
2125    // beginning of the heap every time we want to index; basically
2126    // it's the same with what we do with the card table.
2127    _in_cset_fast_test = _in_cset_fast_test_base -
2128                 ((size_t) _g1_reserved.start() >> HeapRegion::LogOfHRGrainBytes);
2129 
2130    // Clear the _cset_fast_test bitmap in anticipation of adding
2131    // regions to the incremental collection set for the first
2132    // evacuation pause.
2133    clear_cset_fast_test();
2134 
2135   // Create the ConcurrentMark data structure and thread.
2136   // (Must do this late, so that "max_regions" is defined.)
2137   _cm       = new ConcurrentMark(heap_rs, (int) max_regions());
2138   _cmThread = _cm->cmThread();
2139 
2140   // Initialize the from_card cache structure of HeapRegionRemSet.
2141   HeapRegionRemSet::init_heap(max_regions());
2142 
2143   // Now expand into the initial heap size.
2144   if (!expand(init_byte_size)) {
2145     vm_exit_during_initialization("Failed to allocate initial heap.");
2146     return JNI_ENOMEM;
2147   }
2148 
2149   // Perform any initialization actions delegated to the policy.
2150   g1_policy()->init();
2151 
2152   g1_policy()->note_start_of_mark_thread();
2153 
2154   _refine_cte_cl =
2155     new RefineCardTableEntryClosure(ConcurrentG1RefineThread::sts(),
2156                                     g1_rem_set(),
2157                                     concurrent_g1_refine());
2158   JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
2159 
2160   JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
2161                                                SATB_Q_FL_lock,
2162                                                G1SATBProcessCompletedThreshold,
2163                                                Shared_SATB_Q_lock);
2164 
2165   JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
2166                                                 DirtyCardQ_FL_lock,
2167                                                 concurrent_g1_refine()->yellow_zone(),
2168                                                 concurrent_g1_refine()->red_zone(),
2169                                                 Shared_DirtyCardQ_lock);
2170 
2171   if (G1DeferredRSUpdate) {
2172     dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
2173                                       DirtyCardQ_FL_lock,
2174                                       -1, // never trigger processing
2175                                       -1, // no limit on length
2176                                       Shared_DirtyCardQ_lock,
2177                                       &JavaThread::dirty_card_queue_set());
2178   }
2179 
2180   // Initialize the card queue set used to hold cards containing
2181   // references into the collection set.
2182   _into_cset_dirty_card_queue_set.initialize(DirtyCardQ_CBL_mon,
2183                                              DirtyCardQ_FL_lock,
2184                                              -1, // never trigger processing
2185                                              -1, // no limit on length
2186                                              Shared_DirtyCardQ_lock,
2187                                              &JavaThread::dirty_card_queue_set());
2188 
2189   // In case we're keeping closure specialization stats, initialize those
2190   // counts and that mechanism.
2191   SpecializationStats::clear();
2192 
2193   _gc_alloc_region_list = NULL;
2194 
2195   // Do later initialization work for concurrent refinement.
2196   _cg1r->init();
2197 
2198   return JNI_OK;
2199 }
2200 
2201 void G1CollectedHeap::ref_processing_init() {
2202   // Reference processing in G1 currently works as follows:
2203   //
2204   // * There is only one reference processor instance that
2205   //   'spans' the entire heap. It is created by the code
2206   //   below.
2207   // * Reference discovery is not enabled during an incremental
2208   //   pause (see 6484982).
2209   // * Discoverered refs are not enqueued nor are they processed
2210   //   during an incremental pause (see 6484982).
2211   // * Reference discovery is enabled at initial marking.
2212   // * Reference discovery is disabled and the discovered
2213   //   references processed etc during remarking.
2214   // * Reference discovery is MT (see below).
2215   // * Reference discovery requires a barrier (see below).
2216   // * Reference processing is currently not MT (see 6608385).
2217   // * A full GC enables (non-MT) reference discovery and
2218   //   processes any discovered references.
2219 
2220   SharedHeap::ref_processing_init();
2221   MemRegion mr = reserved_region();
2222   _ref_processor = ReferenceProcessor::create_ref_processor(
2223                                          mr,    // span
2224                                          false, // Reference discovery is not atomic
2225                                          true,  // mt_discovery
2226                                          &_is_alive_closure, // is alive closure
2227                                                              // for efficiency
2228                                          ParallelGCThreads,
2229                                          ParallelRefProcEnabled,
2230                                          true); // Setting next fields of discovered
2231                                                 // lists requires a barrier.
2232 }
2233 
2234 size_t G1CollectedHeap::capacity() const {
2235   return _g1_committed.byte_size();
2236 }
2237 
2238 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2239                                                  DirtyCardQueue* into_cset_dcq,
2240                                                  bool concurrent,
2241                                                  int worker_i) {
2242   // Clean cards in the hot card cache
2243   concurrent_g1_refine()->clean_up_cache(worker_i, g1_rem_set(), into_cset_dcq);
2244 
2245   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2246   int n_completed_buffers = 0;
2247   while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2248     n_completed_buffers++;
2249   }
2250   g1_policy()->record_update_rs_processed_buffers(worker_i,
2251                                                   (double) n_completed_buffers);
2252   dcqs.clear_n_completed_buffers();
2253   assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2254 }
2255 
2256 
2257 // Computes the sum of the storage used by the various regions.
2258 
2259 size_t G1CollectedHeap::used() const {
2260   assert(Heap_lock->owner() != NULL,
2261          "Should be owned on this thread's behalf.");
2262   size_t result = _summary_bytes_used;
2263   // Read only once in case it is set to NULL concurrently
2264   HeapRegion* hr = _cur_alloc_region;
2265   if (hr != NULL)
2266     result += hr->used();
2267   return result;
2268 }
2269 
2270 size_t G1CollectedHeap::used_unlocked() const {
2271   size_t result = _summary_bytes_used;
2272   return result;
2273 }
2274 
2275 class SumUsedClosure: public HeapRegionClosure {
2276   size_t _used;
2277 public:
2278   SumUsedClosure() : _used(0) {}
2279   bool doHeapRegion(HeapRegion* r) {
2280     if (!r->continuesHumongous()) {
2281       _used += r->used();
2282     }
2283     return false;
2284   }
2285   size_t result() { return _used; }
2286 };
2287 
2288 size_t G1CollectedHeap::recalculate_used() const {
2289   SumUsedClosure blk;
2290   _hrs->iterate(&blk);
2291   return blk.result();
2292 }
2293 
2294 #ifndef PRODUCT
2295 class SumUsedRegionsClosure: public HeapRegionClosure {
2296   size_t _num;
2297 public:
2298   SumUsedRegionsClosure() : _num(0) {}
2299   bool doHeapRegion(HeapRegion* r) {
2300     if (r->continuesHumongous() || r->used() > 0 || r->is_gc_alloc_region()) {
2301       _num += 1;
2302     }
2303     return false;
2304   }
2305   size_t result() { return _num; }
2306 };
2307 
2308 size_t G1CollectedHeap::recalculate_used_regions() const {
2309   SumUsedRegionsClosure blk;
2310   _hrs->iterate(&blk);
2311   return blk.result();
2312 }
2313 #endif // PRODUCT
2314 
2315 size_t G1CollectedHeap::unsafe_max_alloc() {
2316   if (free_regions() > 0) return HeapRegion::GrainBytes;
2317   // otherwise, is there space in the current allocation region?
2318 
2319   // We need to store the current allocation region in a local variable
2320   // here. The problem is that this method doesn't take any locks and
2321   // there may be other threads which overwrite the current allocation
2322   // region field. attempt_allocation(), for example, sets it to NULL
2323   // and this can happen *after* the NULL check here but before the call
2324   // to free(), resulting in a SIGSEGV. Note that this doesn't appear
2325   // to be a problem in the optimized build, since the two loads of the
2326   // current allocation region field are optimized away.
2327   HeapRegion* car = _cur_alloc_region;
2328 
2329   // FIXME: should iterate over all regions?
2330   if (car == NULL) {
2331     return 0;
2332   }
2333   return car->free();
2334 }
2335 
2336 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2337   return
2338     ((cause == GCCause::_gc_locker           && GCLockerInvokesConcurrent) ||
2339      (cause == GCCause::_java_lang_system_gc && ExplicitGCInvokesConcurrent));
2340 }
2341 
2342 void G1CollectedHeap::increment_full_collections_completed(bool concurrent) {
2343   MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2344 
2345   // We assume that if concurrent == true, then the caller is a
2346   // concurrent thread that was joined the Suspendible Thread
2347   // Set. If there's ever a cheap way to check this, we should add an
2348   // assert here.
2349 
2350   // We have already incremented _total_full_collections at the start
2351   // of the GC, so total_full_collections() represents how many full
2352   // collections have been started.
2353   unsigned int full_collections_started = total_full_collections();
2354 
2355   // Given that this method is called at the end of a Full GC or of a
2356   // concurrent cycle, and those can be nested (i.e., a Full GC can
2357   // interrupt a concurrent cycle), the number of full collections
2358   // completed should be either one (in the case where there was no
2359   // nesting) or two (when a Full GC interrupted a concurrent cycle)
2360   // behind the number of full collections started.
2361 
2362   // This is the case for the inner caller, i.e. a Full GC.
2363   assert(concurrent ||
2364          (full_collections_started == _full_collections_completed + 1) ||
2365          (full_collections_started == _full_collections_completed + 2),
2366          err_msg("for inner caller (Full GC): full_collections_started = %u "
2367                  "is inconsistent with _full_collections_completed = %u",
2368                  full_collections_started, _full_collections_completed));
2369 
2370   // This is the case for the outer caller, i.e. the concurrent cycle.
2371   assert(!concurrent ||
2372          (full_collections_started == _full_collections_completed + 1),
2373          err_msg("for outer caller (concurrent cycle): "
2374                  "full_collections_started = %u "
2375                  "is inconsistent with _full_collections_completed = %u",
2376                  full_collections_started, _full_collections_completed));
2377 
2378   _full_collections_completed += 1;
2379 
2380   // We need to clear the "in_progress" flag in the CM thread before
2381   // we wake up any waiters (especially when ExplicitInvokesConcurrent
2382   // is set) so that if a waiter requests another System.gc() it doesn't
2383   // incorrectly see that a marking cyle is still in progress.
2384   if (concurrent) {
2385     _cmThread->clear_in_progress();
2386   }
2387 
2388   // This notify_all() will ensure that a thread that called
2389   // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2390   // and it's waiting for a full GC to finish will be woken up. It is
2391   // waiting in VM_G1IncCollectionPause::doit_epilogue().
2392   FullGCCount_lock->notify_all();
2393 }
2394 
2395 void G1CollectedHeap::collect_as_vm_thread(GCCause::Cause cause) {
2396   assert_at_safepoint(true /* should_be_vm_thread */);
2397   GCCauseSetter gcs(this, cause);
2398   switch (cause) {
2399     case GCCause::_heap_inspection:
2400     case GCCause::_heap_dump: {
2401       HandleMark hm;
2402       do_full_collection(false);         // don't clear all soft refs
2403       break;
2404     }
2405     default: // XXX FIX ME
2406       ShouldNotReachHere(); // Unexpected use of this function
2407   }
2408 }
2409 
2410 void G1CollectedHeap::collect(GCCause::Cause cause) {
2411   // The caller doesn't have the Heap_lock
2412   assert(!Heap_lock->owned_by_self(), "this thread should not own the Heap_lock");
2413 
2414   unsigned int gc_count_before;
2415   unsigned int full_gc_count_before;
2416   {
2417     MutexLocker ml(Heap_lock);
2418 
2419     // Read the GC count while holding the Heap_lock
2420     gc_count_before = SharedHeap::heap()->total_collections();
2421     full_gc_count_before = SharedHeap::heap()->total_full_collections();
2422   }
2423 
2424   if (should_do_concurrent_full_gc(cause)) {
2425     // Schedule an initial-mark evacuation pause that will start a
2426     // concurrent cycle. We're setting word_size to 0 which means that
2427     // we are not requesting a post-GC allocation.
2428     VM_G1IncCollectionPause op(gc_count_before,
2429                                0,     /* word_size */
2430                                true,  /* should_initiate_conc_mark */
2431                                g1_policy()->max_pause_time_ms(),
2432                                cause);
2433     VMThread::execute(&op);
2434   } else {
2435     if (cause == GCCause::_gc_locker
2436         DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2437 
2438       // Schedule a standard evacuation pause. We're setting word_size
2439       // to 0 which means that we are not requesting a post-GC allocation.
2440       VM_G1IncCollectionPause op(gc_count_before,
2441                                  0,     /* word_size */
2442                                  false, /* should_initiate_conc_mark */
2443                                  g1_policy()->max_pause_time_ms(),
2444                                  cause);
2445       VMThread::execute(&op);
2446     } else {
2447       // Schedule a Full GC.
2448       VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2449       VMThread::execute(&op);
2450     }
2451   }
2452 }
2453 
2454 bool G1CollectedHeap::is_in(const void* p) const {
2455   if (_g1_committed.contains(p)) {
2456     HeapRegion* hr = _hrs->addr_to_region(p);
2457     return hr->is_in(p);
2458   } else {
2459     return _perm_gen->as_gen()->is_in(p);
2460   }
2461 }
2462 
2463 // Iteration functions.
2464 
2465 // Iterates an OopClosure over all ref-containing fields of objects
2466 // within a HeapRegion.
2467 
2468 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2469   MemRegion _mr;
2470   OopClosure* _cl;
2471 public:
2472   IterateOopClosureRegionClosure(MemRegion mr, OopClosure* cl)
2473     : _mr(mr), _cl(cl) {}
2474   bool doHeapRegion(HeapRegion* r) {
2475     if (! r->continuesHumongous()) {
2476       r->oop_iterate(_cl);
2477     }
2478     return false;
2479   }
2480 };
2481 
2482 void G1CollectedHeap::oop_iterate(OopClosure* cl, bool do_perm) {
2483   IterateOopClosureRegionClosure blk(_g1_committed, cl);
2484   _hrs->iterate(&blk);
2485   if (do_perm) {
2486     perm_gen()->oop_iterate(cl);
2487   }
2488 }
2489 
2490 void G1CollectedHeap::oop_iterate(MemRegion mr, OopClosure* cl, bool do_perm) {
2491   IterateOopClosureRegionClosure blk(mr, cl);
2492   _hrs->iterate(&blk);
2493   if (do_perm) {
2494     perm_gen()->oop_iterate(cl);
2495   }
2496 }
2497 
2498 // Iterates an ObjectClosure over all objects within a HeapRegion.
2499 
2500 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2501   ObjectClosure* _cl;
2502 public:
2503   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2504   bool doHeapRegion(HeapRegion* r) {
2505     if (! r->continuesHumongous()) {
2506       r->object_iterate(_cl);
2507     }
2508     return false;
2509   }
2510 };
2511 
2512 void G1CollectedHeap::object_iterate(ObjectClosure* cl, bool do_perm) {
2513   IterateObjectClosureRegionClosure blk(cl);
2514   _hrs->iterate(&blk);
2515   if (do_perm) {
2516     perm_gen()->object_iterate(cl);
2517   }
2518 }
2519 
2520 void G1CollectedHeap::object_iterate_since_last_GC(ObjectClosure* cl) {
2521   // FIXME: is this right?
2522   guarantee(false, "object_iterate_since_last_GC not supported by G1 heap");
2523 }
2524 
2525 // Calls a SpaceClosure on a HeapRegion.
2526 
2527 class SpaceClosureRegionClosure: public HeapRegionClosure {
2528   SpaceClosure* _cl;
2529 public:
2530   SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2531   bool doHeapRegion(HeapRegion* r) {
2532     _cl->do_space(r);
2533     return false;
2534   }
2535 };
2536 
2537 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2538   SpaceClosureRegionClosure blk(cl);
2539   _hrs->iterate(&blk);
2540 }
2541 
2542 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) {
2543   _hrs->iterate(cl);
2544 }
2545 
2546 void G1CollectedHeap::heap_region_iterate_from(HeapRegion* r,
2547                                                HeapRegionClosure* cl) {
2548   _hrs->iterate_from(r, cl);
2549 }
2550 
2551 void
2552 G1CollectedHeap::heap_region_iterate_from(int idx, HeapRegionClosure* cl) {
2553   _hrs->iterate_from(idx, cl);
2554 }
2555 
2556 HeapRegion* G1CollectedHeap::region_at(size_t idx) { return _hrs->at(idx); }
2557 
2558 void
2559 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
2560                                                  int worker,
2561                                                  jint claim_value) {
2562   const size_t regions = n_regions();
2563   const size_t worker_num = (G1CollectedHeap::use_parallel_gc_threads() ? ParallelGCThreads : 1);
2564   // try to spread out the starting points of the workers
2565   const size_t start_index = regions / worker_num * (size_t) worker;
2566 
2567   // each worker will actually look at all regions
2568   for (size_t count = 0; count < regions; ++count) {
2569     const size_t index = (start_index + count) % regions;
2570     assert(0 <= index && index < regions, "sanity");
2571     HeapRegion* r = region_at(index);
2572     // we'll ignore "continues humongous" regions (we'll process them
2573     // when we come across their corresponding "start humongous"
2574     // region) and regions already claimed
2575     if (r->claim_value() == claim_value || r->continuesHumongous()) {
2576       continue;
2577     }
2578     // OK, try to claim it
2579     if (r->claimHeapRegion(claim_value)) {
2580       // success!
2581       assert(!r->continuesHumongous(), "sanity");
2582       if (r->startsHumongous()) {
2583         // If the region is "starts humongous" we'll iterate over its
2584         // "continues humongous" first; in fact we'll do them
2585         // first. The order is important. In on case, calling the
2586         // closure on the "starts humongous" region might de-allocate
2587         // and clear all its "continues humongous" regions and, as a
2588         // result, we might end up processing them twice. So, we'll do
2589         // them first (notice: most closures will ignore them anyway) and
2590         // then we'll do the "starts humongous" region.
2591         for (size_t ch_index = index + 1; ch_index < regions; ++ch_index) {
2592           HeapRegion* chr = region_at(ch_index);
2593 
2594           // if the region has already been claimed or it's not
2595           // "continues humongous" we're done
2596           if (chr->claim_value() == claim_value ||
2597               !chr->continuesHumongous()) {
2598             break;
2599           }
2600 
2601           // Noone should have claimed it directly. We can given
2602           // that we claimed its "starts humongous" region.
2603           assert(chr->claim_value() != claim_value, "sanity");
2604           assert(chr->humongous_start_region() == r, "sanity");
2605 
2606           if (chr->claimHeapRegion(claim_value)) {
2607             // we should always be able to claim it; noone else should
2608             // be trying to claim this region
2609 
2610             bool res2 = cl->doHeapRegion(chr);
2611             assert(!res2, "Should not abort");
2612 
2613             // Right now, this holds (i.e., no closure that actually
2614             // does something with "continues humongous" regions
2615             // clears them). We might have to weaken it in the future,
2616             // but let's leave these two asserts here for extra safety.
2617             assert(chr->continuesHumongous(), "should still be the case");
2618             assert(chr->humongous_start_region() == r, "sanity");
2619           } else {
2620             guarantee(false, "we should not reach here");
2621           }
2622         }
2623       }
2624 
2625       assert(!r->continuesHumongous(), "sanity");
2626       bool res = cl->doHeapRegion(r);
2627       assert(!res, "Should not abort");
2628     }
2629   }
2630 }
2631 
2632 class ResetClaimValuesClosure: public HeapRegionClosure {
2633 public:
2634   bool doHeapRegion(HeapRegion* r) {
2635     r->set_claim_value(HeapRegion::InitialClaimValue);
2636     return false;
2637   }
2638 };
2639 
2640 void
2641 G1CollectedHeap::reset_heap_region_claim_values() {
2642   ResetClaimValuesClosure blk;
2643   heap_region_iterate(&blk);
2644 }
2645 
2646 #ifdef ASSERT
2647 // This checks whether all regions in the heap have the correct claim
2648 // value. I also piggy-backed on this a check to ensure that the
2649 // humongous_start_region() information on "continues humongous"
2650 // regions is correct.
2651 
2652 class CheckClaimValuesClosure : public HeapRegionClosure {
2653 private:
2654   jint _claim_value;
2655   size_t _failures;
2656   HeapRegion* _sh_region;
2657 public:
2658   CheckClaimValuesClosure(jint claim_value) :
2659     _claim_value(claim_value), _failures(0), _sh_region(NULL) { }
2660   bool doHeapRegion(HeapRegion* r) {
2661     if (r->claim_value() != _claim_value) {
2662       gclog_or_tty->print_cr("Region ["PTR_FORMAT","PTR_FORMAT"), "
2663                              "claim value = %d, should be %d",
2664                              r->bottom(), r->end(), r->claim_value(),
2665                              _claim_value);
2666       ++_failures;
2667     }
2668     if (!r->isHumongous()) {
2669       _sh_region = NULL;
2670     } else if (r->startsHumongous()) {
2671       _sh_region = r;
2672     } else if (r->continuesHumongous()) {
2673       if (r->humongous_start_region() != _sh_region) {
2674         gclog_or_tty->print_cr("Region ["PTR_FORMAT","PTR_FORMAT"), "
2675                                "HS = "PTR_FORMAT", should be "PTR_FORMAT,
2676                                r->bottom(), r->end(),
2677                                r->humongous_start_region(),
2678                                _sh_region);
2679         ++_failures;
2680       }
2681     }
2682     return false;
2683   }
2684   size_t failures() {
2685     return _failures;
2686   }
2687 };
2688 
2689 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
2690   CheckClaimValuesClosure cl(claim_value);
2691   heap_region_iterate(&cl);
2692   return cl.failures() == 0;
2693 }
2694 #endif // ASSERT
2695 
2696 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2697   HeapRegion* r = g1_policy()->collection_set();
2698   while (r != NULL) {
2699     HeapRegion* next = r->next_in_collection_set();
2700     if (cl->doHeapRegion(r)) {
2701       cl->incomplete();
2702       return;
2703     }
2704     r = next;
2705   }
2706 }
2707 
2708 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2709                                                   HeapRegionClosure *cl) {
2710   if (r == NULL) {
2711     // The CSet is empty so there's nothing to do.
2712     return;
2713   }
2714 
2715   assert(r->in_collection_set(),
2716          "Start region must be a member of the collection set.");
2717   HeapRegion* cur = r;
2718   while (cur != NULL) {
2719     HeapRegion* next = cur->next_in_collection_set();
2720     if (cl->doHeapRegion(cur) && false) {
2721       cl->incomplete();
2722       return;
2723     }
2724     cur = next;
2725   }
2726   cur = g1_policy()->collection_set();
2727   while (cur != r) {
2728     HeapRegion* next = cur->next_in_collection_set();
2729     if (cl->doHeapRegion(cur) && false) {
2730       cl->incomplete();
2731       return;
2732     }
2733     cur = next;
2734   }
2735 }
2736 
2737 CompactibleSpace* G1CollectedHeap::first_compactible_space() {
2738   return _hrs->length() > 0 ? _hrs->at(0) : NULL;
2739 }
2740 
2741 
2742 Space* G1CollectedHeap::space_containing(const void* addr) const {
2743   Space* res = heap_region_containing(addr);
2744   if (res == NULL)
2745     res = perm_gen()->space_containing(addr);
2746   return res;
2747 }
2748 
2749 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2750   Space* sp = space_containing(addr);
2751   if (sp != NULL) {
2752     return sp->block_start(addr);
2753   }
2754   return NULL;
2755 }
2756 
2757 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2758   Space* sp = space_containing(addr);
2759   assert(sp != NULL, "block_size of address outside of heap");
2760   return sp->block_size(addr);
2761 }
2762 
2763 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2764   Space* sp = space_containing(addr);
2765   return sp->block_is_obj(addr);
2766 }
2767 
2768 bool G1CollectedHeap::supports_tlab_allocation() const {
2769   return true;
2770 }
2771 
2772 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2773   return HeapRegion::GrainBytes;
2774 }
2775 
2776 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2777   // Return the remaining space in the cur alloc region, but not less than
2778   // the min TLAB size.
2779 
2780   // Also, this value can be at most the humongous object threshold,
2781   // since we can't allow tlabs to grow big enough to accomodate
2782   // humongous objects.
2783 
2784   // We need to store the cur alloc region locally, since it might change
2785   // between when we test for NULL and when we use it later.
2786   ContiguousSpace* cur_alloc_space = _cur_alloc_region;
2787   size_t max_tlab_size = _humongous_object_threshold_in_words * wordSize;
2788 
2789   if (cur_alloc_space == NULL) {
2790     return max_tlab_size;
2791   } else {
2792     return MIN2(MAX2(cur_alloc_space->free(), (size_t)MinTLABSize),
2793                 max_tlab_size);
2794   }
2795 }
2796 
2797 size_t G1CollectedHeap::large_typearray_limit() {
2798   // FIXME
2799   return HeapRegion::GrainBytes/HeapWordSize;
2800 }
2801 
2802 size_t G1CollectedHeap::max_capacity() const {
2803   return _g1_reserved.byte_size();
2804 }
2805 
2806 jlong G1CollectedHeap::millis_since_last_gc() {
2807   // assert(false, "NYI");
2808   return 0;
2809 }
2810 
2811 void G1CollectedHeap::prepare_for_verify() {
2812   if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
2813     ensure_parsability(false);
2814   }
2815   g1_rem_set()->prepare_for_verify();
2816 }
2817 
2818 class VerifyLivenessOopClosure: public OopClosure {
2819   G1CollectedHeap* g1h;
2820 public:
2821   VerifyLivenessOopClosure(G1CollectedHeap* _g1h) {
2822     g1h = _g1h;
2823   }
2824   void do_oop(narrowOop *p) { do_oop_work(p); }
2825   void do_oop(      oop *p) { do_oop_work(p); }
2826 
2827   template <class T> void do_oop_work(T *p) {
2828     oop obj = oopDesc::load_decode_heap_oop(p);
2829     guarantee(obj == NULL || !g1h->is_obj_dead(obj),
2830               "Dead object referenced by a not dead object");
2831   }
2832 };
2833 
2834 class VerifyObjsInRegionClosure: public ObjectClosure {
2835 private:
2836   G1CollectedHeap* _g1h;
2837   size_t _live_bytes;
2838   HeapRegion *_hr;
2839   bool _use_prev_marking;
2840 public:
2841   // use_prev_marking == true  -> use "prev" marking information,
2842   // use_prev_marking == false -> use "next" marking information
2843   VerifyObjsInRegionClosure(HeapRegion *hr, bool use_prev_marking)
2844     : _live_bytes(0), _hr(hr), _use_prev_marking(use_prev_marking) {
2845     _g1h = G1CollectedHeap::heap();
2846   }
2847   void do_object(oop o) {
2848     VerifyLivenessOopClosure isLive(_g1h);
2849     assert(o != NULL, "Huh?");
2850     if (!_g1h->is_obj_dead_cond(o, _use_prev_marking)) {
2851       o->oop_iterate(&isLive);
2852       if (!_hr->obj_allocated_since_prev_marking(o)) {
2853         size_t obj_size = o->size();    // Make sure we don't overflow
2854         _live_bytes += (obj_size * HeapWordSize);
2855       }
2856     }
2857   }
2858   size_t live_bytes() { return _live_bytes; }
2859 };
2860 
2861 class PrintObjsInRegionClosure : public ObjectClosure {
2862   HeapRegion *_hr;
2863   G1CollectedHeap *_g1;
2864 public:
2865   PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
2866     _g1 = G1CollectedHeap::heap();
2867   };
2868 
2869   void do_object(oop o) {
2870     if (o != NULL) {
2871       HeapWord *start = (HeapWord *) o;
2872       size_t word_sz = o->size();
2873       gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
2874                           " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
2875                           (void*) o, word_sz,
2876                           _g1->isMarkedPrev(o),
2877                           _g1->isMarkedNext(o),
2878                           _hr->obj_allocated_since_prev_marking(o));
2879       HeapWord *end = start + word_sz;
2880       HeapWord *cur;
2881       int *val;
2882       for (cur = start; cur < end; cur++) {
2883         val = (int *) cur;
2884         gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val);
2885       }
2886     }
2887   }
2888 };
2889 
2890 class VerifyRegionClosure: public HeapRegionClosure {
2891 private:
2892   bool _allow_dirty;
2893   bool _par;
2894   bool _use_prev_marking;
2895   bool _failures;
2896 public:
2897   // use_prev_marking == true  -> use "prev" marking information,
2898   // use_prev_marking == false -> use "next" marking information
2899   VerifyRegionClosure(bool allow_dirty, bool par, bool use_prev_marking)
2900     : _allow_dirty(allow_dirty),
2901       _par(par),
2902       _use_prev_marking(use_prev_marking),
2903       _failures(false) {}
2904 
2905   bool failures() {
2906     return _failures;
2907   }
2908 
2909   bool doHeapRegion(HeapRegion* r) {
2910     guarantee(_par || r->claim_value() == HeapRegion::InitialClaimValue,
2911               "Should be unclaimed at verify points.");
2912     if (!r->continuesHumongous()) {
2913       bool failures = false;
2914       r->verify(_allow_dirty, _use_prev_marking, &failures);
2915       if (failures) {
2916         _failures = true;
2917       } else {
2918         VerifyObjsInRegionClosure not_dead_yet_cl(r, _use_prev_marking);
2919         r->object_iterate(&not_dead_yet_cl);
2920         if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
2921           gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
2922                                  "max_live_bytes "SIZE_FORMAT" "
2923                                  "< calculated "SIZE_FORMAT,
2924                                  r->bottom(), r->end(),
2925                                  r->max_live_bytes(),
2926                                  not_dead_yet_cl.live_bytes());
2927           _failures = true;
2928         }
2929       }
2930     }
2931     return false; // stop the region iteration if we hit a failure
2932   }
2933 };
2934 
2935 class VerifyRootsClosure: public OopsInGenClosure {
2936 private:
2937   G1CollectedHeap* _g1h;
2938   bool             _use_prev_marking;
2939   bool             _failures;
2940 public:
2941   // use_prev_marking == true  -> use "prev" marking information,
2942   // use_prev_marking == false -> use "next" marking information
2943   VerifyRootsClosure(bool use_prev_marking) :
2944     _g1h(G1CollectedHeap::heap()),
2945     _use_prev_marking(use_prev_marking),
2946     _failures(false) { }
2947 
2948   bool failures() { return _failures; }
2949 
2950   template <class T> void do_oop_nv(T* p) {
2951     T heap_oop = oopDesc::load_heap_oop(p);
2952     if (!oopDesc::is_null(heap_oop)) {
2953       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2954       if (_g1h->is_obj_dead_cond(obj, _use_prev_marking)) {
2955         gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
2956                               "points to dead obj "PTR_FORMAT, p, (void*) obj);
2957         obj->print_on(gclog_or_tty);
2958         _failures = true;
2959       }
2960     }
2961   }
2962 
2963   void do_oop(oop* p)       { do_oop_nv(p); }
2964   void do_oop(narrowOop* p) { do_oop_nv(p); }
2965 };
2966 
2967 // This is the task used for parallel heap verification.
2968 
2969 class G1ParVerifyTask: public AbstractGangTask {
2970 private:
2971   G1CollectedHeap* _g1h;
2972   bool _allow_dirty;
2973   bool _use_prev_marking;
2974   bool _failures;
2975 
2976 public:
2977   // use_prev_marking == true  -> use "prev" marking information,
2978   // use_prev_marking == false -> use "next" marking information
2979   G1ParVerifyTask(G1CollectedHeap* g1h, bool allow_dirty,
2980                   bool use_prev_marking) :
2981     AbstractGangTask("Parallel verify task"),
2982     _g1h(g1h),
2983     _allow_dirty(allow_dirty),
2984     _use_prev_marking(use_prev_marking),
2985     _failures(false) { }
2986 
2987   bool failures() {
2988     return _failures;
2989   }
2990 
2991   void work(int worker_i) {
2992     HandleMark hm;
2993     VerifyRegionClosure blk(_allow_dirty, true, _use_prev_marking);
2994     _g1h->heap_region_par_iterate_chunked(&blk, worker_i,
2995                                           HeapRegion::ParVerifyClaimValue);
2996     if (blk.failures()) {
2997       _failures = true;
2998     }
2999   }
3000 };
3001 
3002 void G1CollectedHeap::verify(bool allow_dirty, bool silent) {
3003   verify(allow_dirty, silent, /* use_prev_marking */ true);
3004 }
3005 
3006 void G1CollectedHeap::verify(bool allow_dirty,
3007                              bool silent,
3008                              bool use_prev_marking) {
3009   if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
3010     if (!silent) { gclog_or_tty->print("roots "); }
3011     VerifyRootsClosure rootsCl(use_prev_marking);
3012     CodeBlobToOopClosure blobsCl(&rootsCl, /*do_marking=*/ false);
3013     process_strong_roots(true,  // activate StrongRootsScope
3014                          false,
3015                          SharedHeap::SO_AllClasses,
3016                          &rootsCl,
3017                          &blobsCl,
3018                          &rootsCl);
3019     bool failures = rootsCl.failures();
3020     rem_set()->invalidate(perm_gen()->used_region(), false);
3021     if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3022     verify_region_sets();
3023     if (!silent) { gclog_or_tty->print("HeapRegions "); }
3024     if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3025       assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3026              "sanity check");
3027 
3028       G1ParVerifyTask task(this, allow_dirty, use_prev_marking);
3029       int n_workers = workers()->total_workers();
3030       set_par_threads(n_workers);
3031       workers()->run_task(&task);
3032       set_par_threads(0);
3033       if (task.failures()) {
3034         failures = true;
3035       }
3036 
3037       assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
3038              "sanity check");
3039 
3040       reset_heap_region_claim_values();
3041 
3042       assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3043              "sanity check");
3044     } else {
3045       VerifyRegionClosure blk(allow_dirty, false, use_prev_marking);
3046       _hrs->iterate(&blk);
3047       if (blk.failures()) {
3048         failures = true;
3049       }
3050     }
3051     if (!silent) gclog_or_tty->print("RemSet ");
3052     rem_set()->verify();
3053 
3054     if (failures) {
3055       gclog_or_tty->print_cr("Heap:");
3056       print_on(gclog_or_tty, true /* extended */);
3057       gclog_or_tty->print_cr("");
3058 #ifndef PRODUCT
3059       if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3060         concurrent_mark()->print_reachable("at-verification-failure",
3061                                            use_prev_marking, false /* all */);
3062       }
3063 #endif
3064       gclog_or_tty->flush();
3065     }
3066     guarantee(!failures, "there should not have been any failures");
3067   } else {
3068     if (!silent) gclog_or_tty->print("(SKIPPING roots, heapRegions, remset) ");
3069   }
3070 }
3071 
3072 class PrintRegionClosure: public HeapRegionClosure {
3073   outputStream* _st;
3074 public:
3075   PrintRegionClosure(outputStream* st) : _st(st) {}
3076   bool doHeapRegion(HeapRegion* r) {
3077     r->print_on(_st);
3078     return false;
3079   }
3080 };
3081 
3082 void G1CollectedHeap::print() const { print_on(tty); }
3083 
3084 void G1CollectedHeap::print_on(outputStream* st) const {
3085   print_on(st, PrintHeapAtGCExtended);
3086 }
3087 
3088 void G1CollectedHeap::print_on(outputStream* st, bool extended) const {
3089   st->print(" %-20s", "garbage-first heap");
3090   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3091             capacity()/K, used_unlocked()/K);
3092   st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3093             _g1_storage.low_boundary(),
3094             _g1_storage.high(),
3095             _g1_storage.high_boundary());
3096   st->cr();
3097   st->print("  region size " SIZE_FORMAT "K, ",
3098             HeapRegion::GrainBytes/K);
3099   size_t young_regions = _young_list->length();
3100   st->print(SIZE_FORMAT " young (" SIZE_FORMAT "K), ",
3101             young_regions, young_regions * HeapRegion::GrainBytes / K);
3102   size_t survivor_regions = g1_policy()->recorded_survivor_regions();
3103   st->print(SIZE_FORMAT " survivors (" SIZE_FORMAT "K)",
3104             survivor_regions, survivor_regions * HeapRegion::GrainBytes / K);
3105   st->cr();
3106   perm()->as_gen()->print_on(st);
3107   if (extended) {
3108     st->cr();
3109     print_on_extended(st);
3110   }
3111 }
3112 
3113 void G1CollectedHeap::print_on_extended(outputStream* st) const {
3114   PrintRegionClosure blk(st);
3115   _hrs->iterate(&blk);
3116 }
3117 
3118 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3119   if (G1CollectedHeap::use_parallel_gc_threads()) {
3120     workers()->print_worker_threads_on(st);
3121   }
3122   _cmThread->print_on(st);
3123   st->cr();
3124   _cm->print_worker_threads_on(st);
3125   _cg1r->print_worker_threads_on(st);
3126   st->cr();
3127 }
3128 
3129 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3130   if (G1CollectedHeap::use_parallel_gc_threads()) {
3131     workers()->threads_do(tc);
3132   }
3133   tc->do_thread(_cmThread);
3134   _cg1r->threads_do(tc);
3135 }
3136 
3137 void G1CollectedHeap::print_tracing_info() const {
3138   // We'll overload this to mean "trace GC pause statistics."
3139   if (TraceGen0Time || TraceGen1Time) {
3140     // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3141     // to that.
3142     g1_policy()->print_tracing_info();
3143   }
3144   if (G1SummarizeRSetStats) {
3145     g1_rem_set()->print_summary_info();
3146   }
3147   if (G1SummarizeConcMark) {
3148     concurrent_mark()->print_summary_info();
3149   }
3150   g1_policy()->print_yg_surv_rate_info();
3151   SpecializationStats::print();
3152 }
3153 
3154 int G1CollectedHeap::addr_to_arena_id(void* addr) const {
3155   HeapRegion* hr = heap_region_containing(addr);
3156   if (hr == NULL) {
3157     return 0;
3158   } else {
3159     return 1;
3160   }
3161 }
3162 
3163 G1CollectedHeap* G1CollectedHeap::heap() {
3164   assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3165          "not a garbage-first heap");
3166   return _g1h;
3167 }
3168 
3169 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3170   // always_do_update_barrier = false;
3171   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3172   // Call allocation profiler
3173   AllocationProfiler::iterate_since_last_gc();
3174   // Fill TLAB's and such
3175   ensure_parsability(true);
3176 }
3177 
3178 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) {
3179   // FIXME: what is this about?
3180   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3181   // is set.
3182   COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3183                         "derived pointer present"));
3184   // always_do_update_barrier = true;
3185 }
3186 
3187 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3188                                                unsigned int gc_count_before,
3189                                                bool* succeeded) {
3190   assert_heap_not_locked_and_not_at_safepoint();
3191   g1_policy()->record_stop_world_start();
3192   VM_G1IncCollectionPause op(gc_count_before,
3193                              word_size,
3194                              false, /* should_initiate_conc_mark */
3195                              g1_policy()->max_pause_time_ms(),
3196                              GCCause::_g1_inc_collection_pause);
3197   VMThread::execute(&op);
3198 
3199   HeapWord* result = op.result();
3200   bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3201   assert(result == NULL || ret_succeeded,
3202          "the result should be NULL if the VM did not succeed");
3203   *succeeded = ret_succeeded;
3204 
3205   assert_heap_not_locked();
3206   return result;
3207 }
3208 
3209 void
3210 G1CollectedHeap::doConcurrentMark() {
3211   MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3212   if (!_cmThread->in_progress()) {
3213     _cmThread->set_started();
3214     CGC_lock->notify();
3215   }
3216 }
3217 
3218 class VerifyMarkedObjsClosure: public ObjectClosure {
3219     G1CollectedHeap* _g1h;
3220     public:
3221     VerifyMarkedObjsClosure(G1CollectedHeap* g1h) : _g1h(g1h) {}
3222     void do_object(oop obj) {
3223       assert(obj->mark()->is_marked() ? !_g1h->is_obj_dead(obj) : true,
3224              "markandsweep mark should agree with concurrent deadness");
3225     }
3226 };
3227 
3228 void
3229 G1CollectedHeap::checkConcurrentMark() {
3230     VerifyMarkedObjsClosure verifycl(this);
3231     //    MutexLockerEx x(getMarkBitMapLock(),
3232     //              Mutex::_no_safepoint_check_flag);
3233     object_iterate(&verifycl, false);
3234 }
3235 
3236 void G1CollectedHeap::do_sync_mark() {
3237   _cm->checkpointRootsInitial();
3238   _cm->markFromRoots();
3239   _cm->checkpointRootsFinal(false);
3240 }
3241 
3242 // <NEW PREDICTION>
3243 
3244 double G1CollectedHeap::predict_region_elapsed_time_ms(HeapRegion *hr,
3245                                                        bool young) {
3246   return _g1_policy->predict_region_elapsed_time_ms(hr, young);
3247 }
3248 
3249 void G1CollectedHeap::check_if_region_is_too_expensive(double
3250                                                            predicted_time_ms) {
3251   _g1_policy->check_if_region_is_too_expensive(predicted_time_ms);
3252 }
3253 
3254 size_t G1CollectedHeap::pending_card_num() {
3255   size_t extra_cards = 0;
3256   JavaThread *curr = Threads::first();
3257   while (curr != NULL) {
3258     DirtyCardQueue& dcq = curr->dirty_card_queue();
3259     extra_cards += dcq.size();
3260     curr = curr->next();
3261   }
3262   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3263   size_t buffer_size = dcqs.buffer_size();
3264   size_t buffer_num = dcqs.completed_buffers_num();
3265   return buffer_size * buffer_num + extra_cards;
3266 }
3267 
3268 size_t G1CollectedHeap::max_pending_card_num() {
3269   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3270   size_t buffer_size = dcqs.buffer_size();
3271   size_t buffer_num  = dcqs.completed_buffers_num();
3272   int thread_num  = Threads::number_of_threads();
3273   return (buffer_num + thread_num) * buffer_size;
3274 }
3275 
3276 size_t G1CollectedHeap::cards_scanned() {
3277   return g1_rem_set()->cardsScanned();
3278 }
3279 
3280 void
3281 G1CollectedHeap::setup_surviving_young_words() {
3282   guarantee( _surviving_young_words == NULL, "pre-condition" );
3283   size_t array_length = g1_policy()->young_cset_length();
3284   _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, array_length);
3285   if (_surviving_young_words == NULL) {
3286     vm_exit_out_of_memory(sizeof(size_t) * array_length,
3287                           "Not enough space for young surv words summary.");
3288   }
3289   memset(_surviving_young_words, 0, array_length * sizeof(size_t));
3290 #ifdef ASSERT
3291   for (size_t i = 0;  i < array_length; ++i) {
3292     assert( _surviving_young_words[i] == 0, "memset above" );
3293   }
3294 #endif // !ASSERT
3295 }
3296 
3297 void
3298 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3299   MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3300   size_t array_length = g1_policy()->young_cset_length();
3301   for (size_t i = 0; i < array_length; ++i)
3302     _surviving_young_words[i] += surv_young_words[i];
3303 }
3304 
3305 void
3306 G1CollectedHeap::cleanup_surviving_young_words() {
3307   guarantee( _surviving_young_words != NULL, "pre-condition" );
3308   FREE_C_HEAP_ARRAY(size_t, _surviving_young_words);
3309   _surviving_young_words = NULL;
3310 }
3311 
3312 // </NEW PREDICTION>
3313 
3314 struct PrepareForRSScanningClosure : public HeapRegionClosure {
3315   bool doHeapRegion(HeapRegion *r) {
3316     r->rem_set()->set_iter_claimed(0);
3317     return false;
3318   }
3319 };
3320 
3321 #if TASKQUEUE_STATS
3322 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3323   st->print_raw_cr("GC Task Stats");
3324   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3325   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3326 }
3327 
3328 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3329   print_taskqueue_stats_hdr(st);
3330 
3331   TaskQueueStats totals;
3332   const int n = workers() != NULL ? workers()->total_workers() : 1;
3333   for (int i = 0; i < n; ++i) {
3334     st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3335     totals += task_queue(i)->stats;
3336   }
3337   st->print_raw("tot "); totals.print(st); st->cr();
3338 
3339   DEBUG_ONLY(totals.verify());
3340 }
3341 
3342 void G1CollectedHeap::reset_taskqueue_stats() {
3343   const int n = workers() != NULL ? workers()->total_workers() : 1;
3344   for (int i = 0; i < n; ++i) {
3345     task_queue(i)->stats.reset();
3346   }
3347 }
3348 #endif // TASKQUEUE_STATS
3349 
3350 bool
3351 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3352   assert_at_safepoint(true /* should_be_vm_thread */);
3353   guarantee(!is_gc_active(), "collection is not reentrant");
3354 
3355   if (GC_locker::check_active_before_gc()) {
3356     return false;
3357   }
3358 
3359   SvcGCMarker sgcm(SvcGCMarker::MINOR);
3360   ResourceMark rm;
3361 
3362   if (PrintHeapAtGC) {
3363     Universe::print_heap_before_gc();
3364   }
3365 
3366   verify_region_sets_optional();
3367 
3368   {
3369     // This call will decide whether this pause is an initial-mark
3370     // pause. If it is, during_initial_mark_pause() will return true
3371     // for the duration of this pause.
3372     g1_policy()->decide_on_conc_mark_initiation();
3373 
3374     char verbose_str[128];
3375     sprintf(verbose_str, "GC pause ");
3376     if (g1_policy()->in_young_gc_mode()) {
3377       if (g1_policy()->full_young_gcs())
3378         strcat(verbose_str, "(young)");
3379       else
3380         strcat(verbose_str, "(partial)");
3381     }
3382     if (g1_policy()->during_initial_mark_pause()) {
3383       strcat(verbose_str, " (initial-mark)");
3384       // We are about to start a marking cycle, so we increment the
3385       // full collection counter.
3386       increment_total_full_collections();
3387     }
3388 
3389     // if PrintGCDetails is on, we'll print long statistics information
3390     // in the collector policy code, so let's not print this as the output
3391     // is messy if we do.
3392     gclog_or_tty->date_stamp(PrintGC && PrintGCDateStamps);
3393     TraceCPUTime tcpu(PrintGCDetails, true, gclog_or_tty);
3394     TraceTime t(verbose_str, PrintGC && !PrintGCDetails, true, gclog_or_tty);
3395 
3396     TraceMemoryManagerStats tms(false /* fullGC */);
3397 
3398     // If the secondary_free_list is not empty, append it to the
3399     // free_list. No need to wait for the cleanup operation to finish;
3400     // the region allocation code will check the secondary_free_list
3401     // and wait if necessary. If the G1StressConcRegionFreeing flag is
3402     // set, skip this step so that the region allocation code has to
3403     // get entries from the secondary_free_list.
3404     if (!G1StressConcRegionFreeing) {
3405       append_secondary_free_list_if_not_empty_with_lock();
3406     }
3407 
3408     increment_gc_time_stamp();
3409 
3410     if (g1_policy()->in_young_gc_mode()) {
3411       assert(check_young_list_well_formed(),
3412              "young list should be well formed");
3413     }
3414 
3415     { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3416       IsGCActiveMark x;
3417 
3418       gc_prologue(false);
3419       increment_total_collections(false /* full gc */);
3420 
3421 #if G1_REM_SET_LOGGING
3422       gclog_or_tty->print_cr("\nJust chose CS, heap:");
3423       print();
3424 #endif
3425 
3426       if (VerifyBeforeGC && total_collections() >= VerifyGCStartAt) {
3427         HandleMark hm;  // Discard invalid handles created during verification
3428         prepare_for_verify();
3429         gclog_or_tty->print(" VerifyBeforeGC:");
3430         Universe::verify(false);
3431       }
3432 
3433       COMPILER2_PRESENT(DerivedPointerTable::clear());
3434 
3435       // Please see comment in G1CollectedHeap::ref_processing_init()
3436       // to see how reference processing currently works in G1.
3437       //
3438       // We want to turn off ref discovery, if necessary, and turn it back on
3439       // on again later if we do. XXX Dubious: why is discovery disabled?
3440       bool was_enabled = ref_processor()->discovery_enabled();
3441       if (was_enabled) ref_processor()->disable_discovery();
3442 
3443       // Forget the current alloc region (we might even choose it to be part
3444       // of the collection set!).
3445       abandon_cur_alloc_region();
3446 
3447       // The elapsed time induced by the start time below deliberately elides
3448       // the possible verification above.
3449       double start_time_sec = os::elapsedTime();
3450       size_t start_used_bytes = used();
3451 
3452 #if YOUNG_LIST_VERBOSE
3453       gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
3454       _young_list->print();
3455       g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3456 #endif // YOUNG_LIST_VERBOSE
3457 
3458       g1_policy()->record_collection_pause_start(start_time_sec,
3459                                                  start_used_bytes);
3460 
3461 #if YOUNG_LIST_VERBOSE
3462       gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
3463       _young_list->print();
3464 #endif // YOUNG_LIST_VERBOSE
3465 
3466       if (g1_policy()->during_initial_mark_pause()) {
3467         concurrent_mark()->checkpointRootsInitialPre();
3468       }
3469       save_marks();
3470 
3471       // We must do this before any possible evacuation that should propagate
3472       // marks.
3473       if (mark_in_progress()) {
3474         double start_time_sec = os::elapsedTime();
3475 
3476         _cm->drainAllSATBBuffers();
3477         double finish_mark_ms = (os::elapsedTime() - start_time_sec) * 1000.0;
3478         g1_policy()->record_satb_drain_time(finish_mark_ms);
3479       }
3480       // Record the number of elements currently on the mark stack, so we
3481       // only iterate over these.  (Since evacuation may add to the mark
3482       // stack, doing more exposes race conditions.)  If no mark is in
3483       // progress, this will be zero.
3484       _cm->set_oops_do_bound();
3485 
3486       if (mark_in_progress())
3487         concurrent_mark()->newCSet();
3488 
3489 #if YOUNG_LIST_VERBOSE
3490       gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
3491       _young_list->print();
3492       g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3493 #endif // YOUNG_LIST_VERBOSE
3494 
3495       g1_policy()->choose_collection_set(target_pause_time_ms);
3496 
3497       // Nothing to do if we were unable to choose a collection set.
3498 #if G1_REM_SET_LOGGING
3499       gclog_or_tty->print_cr("\nAfter pause, heap:");
3500       print();
3501 #endif
3502       PrepareForRSScanningClosure prepare_for_rs_scan;
3503       collection_set_iterate(&prepare_for_rs_scan);
3504 
3505       setup_surviving_young_words();
3506 
3507       // Set up the gc allocation regions.
3508       get_gc_alloc_regions();
3509 
3510       // Actually do the work...
3511       evacuate_collection_set();
3512 
3513       free_collection_set(g1_policy()->collection_set());
3514       g1_policy()->clear_collection_set();
3515 
3516       cleanup_surviving_young_words();
3517 
3518       // Start a new incremental collection set for the next pause.
3519       g1_policy()->start_incremental_cset_building();
3520 
3521       // Clear the _cset_fast_test bitmap in anticipation of adding
3522       // regions to the incremental collection set for the next
3523       // evacuation pause.
3524       clear_cset_fast_test();
3525 
3526       if (g1_policy()->in_young_gc_mode()) {
3527         _young_list->reset_sampled_info();
3528 
3529         // Don't check the whole heap at this point as the
3530         // GC alloc regions from this pause have been tagged
3531         // as survivors and moved on to the survivor list.
3532         // Survivor regions will fail the !is_young() check.
3533         assert(check_young_list_empty(false /* check_heap */),
3534                "young list should be empty");
3535 
3536 #if YOUNG_LIST_VERBOSE
3537         gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
3538         _young_list->print();
3539 #endif // YOUNG_LIST_VERBOSE
3540 
3541         g1_policy()->record_survivor_regions(_young_list->survivor_length(),
3542                                           _young_list->first_survivor_region(),
3543                                           _young_list->last_survivor_region());
3544 
3545         _young_list->reset_auxilary_lists();
3546       }
3547 
3548       if (evacuation_failed()) {
3549         _summary_bytes_used = recalculate_used();
3550       } else {
3551         // The "used" of the the collection set have already been subtracted
3552         // when they were freed.  Add in the bytes evacuated.
3553         _summary_bytes_used += g1_policy()->bytes_in_to_space();
3554       }
3555 
3556       if (g1_policy()->in_young_gc_mode() &&
3557           g1_policy()->during_initial_mark_pause()) {
3558         concurrent_mark()->checkpointRootsInitialPost();
3559         set_marking_started();
3560         // CAUTION: after the doConcurrentMark() call below,
3561         // the concurrent marking thread(s) could be running
3562         // concurrently with us. Make sure that anything after
3563         // this point does not assume that we are the only GC thread
3564         // running. Note: of course, the actual marking work will
3565         // not start until the safepoint itself is released in
3566         // ConcurrentGCThread::safepoint_desynchronize().
3567         doConcurrentMark();
3568       }
3569 
3570 #if YOUNG_LIST_VERBOSE
3571       gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
3572       _young_list->print();
3573       g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3574 #endif // YOUNG_LIST_VERBOSE
3575 
3576       double end_time_sec = os::elapsedTime();
3577       double pause_time_ms = (end_time_sec - start_time_sec) * MILLIUNITS;
3578       g1_policy()->record_pause_time_ms(pause_time_ms);
3579       g1_policy()->record_collection_pause_end();
3580 
3581       MemoryService::track_memory_usage();
3582 
3583       if (VerifyAfterGC && total_collections() >= VerifyGCStartAt) {
3584         HandleMark hm;  // Discard invalid handles created during verification
3585         gclog_or_tty->print(" VerifyAfterGC:");
3586         prepare_for_verify();
3587         Universe::verify(false);
3588       }
3589 
3590       if (was_enabled) ref_processor()->enable_discovery();
3591 
3592       {
3593         size_t expand_bytes = g1_policy()->expansion_amount();
3594         if (expand_bytes > 0) {
3595           size_t bytes_before = capacity();
3596           if (!expand(expand_bytes)) {
3597             // We failed to expand the heap so let's verify that
3598             // committed/uncommitted amount match the backing store
3599             assert(capacity() == _g1_storage.committed_size(), "committed size mismatch");
3600             assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch");
3601           }
3602         }
3603       }
3604 
3605       if (mark_in_progress()) {
3606         concurrent_mark()->update_g1_committed();
3607       }
3608 
3609 #ifdef TRACESPINNING
3610       ParallelTaskTerminator::print_termination_counts();
3611 #endif
3612 
3613       gc_epilogue(false);
3614     }
3615 
3616     if (ExitAfterGCNum > 0 && total_collections() == ExitAfterGCNum) {
3617       gclog_or_tty->print_cr("Stopping after GC #%d", ExitAfterGCNum);
3618       print_tracing_info();
3619       vm_exit(-1);
3620     }
3621   }
3622 
3623   verify_region_sets_optional();
3624 
3625   TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
3626   TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3627 
3628   if (PrintHeapAtGC) {
3629     Universe::print_heap_after_gc();
3630   }
3631   if (G1SummarizeRSetStats &&
3632       (G1SummarizeRSetStatsPeriod > 0) &&
3633       (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3634     g1_rem_set()->print_summary_info();
3635   }
3636 
3637   return true;
3638 }
3639 
3640 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
3641 {
3642   size_t gclab_word_size;
3643   switch (purpose) {
3644     case GCAllocForSurvived:
3645       gclab_word_size = YoungPLABSize;
3646       break;
3647     case GCAllocForTenured:
3648       gclab_word_size = OldPLABSize;
3649       break;
3650     default:
3651       assert(false, "unknown GCAllocPurpose");
3652       gclab_word_size = OldPLABSize;
3653       break;
3654   }
3655   return gclab_word_size;
3656 }
3657 
3658 
3659 void G1CollectedHeap::set_gc_alloc_region(int purpose, HeapRegion* r) {
3660   assert(purpose >= 0 && purpose < GCAllocPurposeCount, "invalid purpose");
3661   // make sure we don't call set_gc_alloc_region() multiple times on
3662   // the same region
3663   assert(r == NULL || !r->is_gc_alloc_region(),
3664          "shouldn't already be a GC alloc region");
3665   assert(r == NULL || !r->isHumongous(),
3666          "humongous regions shouldn't be used as GC alloc regions");
3667 
3668   HeapWord* original_top = NULL;
3669   if (r != NULL)
3670     original_top = r->top();
3671 
3672   // We will want to record the used space in r as being there before gc.
3673   // One we install it as a GC alloc region it's eligible for allocation.
3674   // So record it now and use it later.
3675   size_t r_used = 0;
3676   if (r != NULL) {
3677     r_used = r->used();
3678 
3679     if (G1CollectedHeap::use_parallel_gc_threads()) {
3680       // need to take the lock to guard against two threads calling
3681       // get_gc_alloc_region concurrently (very unlikely but...)
3682       MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3683       r->save_marks();
3684     }
3685   }
3686   HeapRegion* old_alloc_region = _gc_alloc_regions[purpose];
3687   _gc_alloc_regions[purpose] = r;
3688   if (old_alloc_region != NULL) {
3689     // Replace aliases too.
3690     for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
3691       if (_gc_alloc_regions[ap] == old_alloc_region) {
3692         _gc_alloc_regions[ap] = r;
3693       }
3694     }
3695   }
3696   if (r != NULL) {
3697     push_gc_alloc_region(r);
3698     if (mark_in_progress() && original_top != r->next_top_at_mark_start()) {
3699       // We are using a region as a GC alloc region after it has been used
3700       // as a mutator allocation region during the current marking cycle.
3701       // The mutator-allocated objects are currently implicitly marked, but
3702       // when we move hr->next_top_at_mark_start() forward at the the end
3703       // of the GC pause, they won't be.  We therefore mark all objects in
3704       // the "gap".  We do this object-by-object, since marking densely
3705       // does not currently work right with marking bitmap iteration.  This
3706       // means we rely on TLAB filling at the start of pauses, and no
3707       // "resuscitation" of filled TLAB's.  If we want to do this, we need
3708       // to fix the marking bitmap iteration.
3709       HeapWord* curhw = r->next_top_at_mark_start();
3710       HeapWord* t = original_top;
3711 
3712       while (curhw < t) {
3713         oop cur = (oop)curhw;
3714         // We'll assume parallel for generality.  This is rare code.
3715         concurrent_mark()->markAndGrayObjectIfNecessary(cur); // can't we just mark them?
3716         curhw = curhw + cur->size();
3717       }
3718       assert(curhw == t, "Should have parsed correctly.");
3719     }
3720     if (G1PolicyVerbose > 1) {
3721       gclog_or_tty->print("New alloc region ["PTR_FORMAT", "PTR_FORMAT", " PTR_FORMAT") "
3722                           "for survivors:", r->bottom(), original_top, r->end());
3723       r->print();
3724     }
3725     g1_policy()->record_before_bytes(r_used);
3726   }
3727 }
3728 
3729 void G1CollectedHeap::push_gc_alloc_region(HeapRegion* hr) {
3730   assert(Thread::current()->is_VM_thread() ||
3731          FreeList_lock->owned_by_self(), "Precondition");
3732   assert(!hr->is_gc_alloc_region() && !hr->in_collection_set(),
3733          "Precondition.");
3734   hr->set_is_gc_alloc_region(true);
3735   hr->set_next_gc_alloc_region(_gc_alloc_region_list);
3736   _gc_alloc_region_list = hr;
3737 }
3738 
3739 #ifdef G1_DEBUG
3740 class FindGCAllocRegion: public HeapRegionClosure {
3741 public:
3742   bool doHeapRegion(HeapRegion* r) {
3743     if (r->is_gc_alloc_region()) {
3744       gclog_or_tty->print_cr("Region %d ["PTR_FORMAT"...] is still a gc_alloc_region.",
3745                              r->hrs_index(), r->bottom());
3746     }
3747     return false;
3748   }
3749 };
3750 #endif // G1_DEBUG
3751 
3752 void G1CollectedHeap::forget_alloc_region_list() {
3753   assert_at_safepoint(true /* should_be_vm_thread */);
3754   while (_gc_alloc_region_list != NULL) {
3755     HeapRegion* r = _gc_alloc_region_list;
3756     assert(r->is_gc_alloc_region(), "Invariant.");
3757     // We need HeapRegion::oops_on_card_seq_iterate_careful() to work on
3758     // newly allocated data in order to be able to apply deferred updates
3759     // before the GC is done for verification purposes (i.e to allow
3760     // G1HRRSFlushLogBuffersOnVerify). It's safe thing to do after the
3761     // collection.
3762     r->ContiguousSpace::set_saved_mark();
3763     _gc_alloc_region_list = r->next_gc_alloc_region();
3764     r->set_next_gc_alloc_region(NULL);
3765     r->set_is_gc_alloc_region(false);
3766     if (r->is_survivor()) {
3767       if (r->is_empty()) {
3768         r->set_not_young();
3769       } else {
3770         _young_list->add_survivor_region(r);
3771       }
3772     }
3773   }
3774 #ifdef G1_DEBUG
3775   FindGCAllocRegion fa;
3776   heap_region_iterate(&fa);
3777 #endif // G1_DEBUG
3778 }
3779 
3780 
3781 bool G1CollectedHeap::check_gc_alloc_regions() {
3782   // TODO: allocation regions check
3783   return true;
3784 }
3785 
3786 void G1CollectedHeap::get_gc_alloc_regions() {
3787   // First, let's check that the GC alloc region list is empty (it should)
3788   assert(_gc_alloc_region_list == NULL, "invariant");
3789 
3790   for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
3791     assert(_gc_alloc_regions[ap] == NULL, "invariant");
3792     assert(_gc_alloc_region_counts[ap] == 0, "invariant");
3793 
3794     // Create new GC alloc regions.
3795     HeapRegion* alloc_region = _retained_gc_alloc_regions[ap];
3796     _retained_gc_alloc_regions[ap] = NULL;
3797 
3798     if (alloc_region != NULL) {
3799       assert(_retain_gc_alloc_region[ap], "only way to retain a GC region");
3800 
3801       // let's make sure that the GC alloc region is not tagged as such
3802       // outside a GC operation
3803       assert(!alloc_region->is_gc_alloc_region(), "sanity");
3804 
3805       if (alloc_region->in_collection_set() ||
3806           alloc_region->top() == alloc_region->end() ||
3807           alloc_region->top() == alloc_region->bottom() ||
3808           alloc_region->isHumongous()) {
3809         // we will discard the current GC alloc region if
3810         // * it's in the collection set (it can happen!),
3811         // * it's already full (no point in using it),
3812         // * it's empty (this means that it was emptied during
3813         // a cleanup and it should be on the free list now), or
3814         // * it's humongous (this means that it was emptied
3815         // during a cleanup and was added to the free list, but
3816         // has been subseqently used to allocate a humongous
3817         // object that may be less than the region size).
3818 
3819         alloc_region = NULL;
3820       }
3821     }
3822 
3823     if (alloc_region == NULL) {
3824       // we will get a new GC alloc region
3825       alloc_region = new_gc_alloc_region(ap, HeapRegion::GrainWords);
3826     } else {
3827       // the region was retained from the last collection
3828       ++_gc_alloc_region_counts[ap];
3829       if (G1PrintHeapRegions) {
3830         gclog_or_tty->print_cr("new alloc region %d:["PTR_FORMAT", "PTR_FORMAT"], "
3831                                "top "PTR_FORMAT,
3832                                alloc_region->hrs_index(), alloc_region->bottom(), alloc_region->end(), alloc_region->top());
3833       }
3834     }
3835 
3836     if (alloc_region != NULL) {
3837       assert(_gc_alloc_regions[ap] == NULL, "pre-condition");
3838       set_gc_alloc_region(ap, alloc_region);
3839     }
3840 
3841     assert(_gc_alloc_regions[ap] == NULL ||
3842            _gc_alloc_regions[ap]->is_gc_alloc_region(),
3843            "the GC alloc region should be tagged as such");
3844     assert(_gc_alloc_regions[ap] == NULL ||
3845            _gc_alloc_regions[ap] == _gc_alloc_region_list,
3846            "the GC alloc region should be the same as the GC alloc list head");
3847   }
3848   // Set alternative regions for allocation purposes that have reached
3849   // their limit.
3850   for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
3851     GCAllocPurpose alt_purpose = g1_policy()->alternative_purpose(ap);
3852     if (_gc_alloc_regions[ap] == NULL && alt_purpose != ap) {
3853       _gc_alloc_regions[ap] = _gc_alloc_regions[alt_purpose];
3854     }
3855   }
3856   assert(check_gc_alloc_regions(), "alloc regions messed up");
3857 }
3858 
3859 void G1CollectedHeap::release_gc_alloc_regions(bool totally) {
3860   // We keep a separate list of all regions that have been alloc regions in
3861   // the current collection pause. Forget that now. This method will
3862   // untag the GC alloc regions and tear down the GC alloc region
3863   // list. It's desirable that no regions are tagged as GC alloc
3864   // outside GCs.
3865 
3866   forget_alloc_region_list();
3867 
3868   // The current alloc regions contain objs that have survived
3869   // collection. Make them no longer GC alloc regions.
3870   for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
3871     HeapRegion* r = _gc_alloc_regions[ap];
3872     _retained_gc_alloc_regions[ap] = NULL;
3873     _gc_alloc_region_counts[ap] = 0;
3874 
3875     if (r != NULL) {
3876       // we retain nothing on _gc_alloc_regions between GCs
3877       set_gc_alloc_region(ap, NULL);
3878 
3879       if (r->is_empty()) {
3880         // We didn't actually allocate anything in it; let's just put
3881         // it back on the free list.
3882         _free_list.add_as_tail(r);
3883       } else if (_retain_gc_alloc_region[ap] && !totally) {
3884         // retain it so that we can use it at the beginning of the next GC
3885         _retained_gc_alloc_regions[ap] = r;
3886       }
3887     }
3888   }
3889 }
3890 
3891 #ifndef PRODUCT
3892 // Useful for debugging
3893 
3894 void G1CollectedHeap::print_gc_alloc_regions() {
3895   gclog_or_tty->print_cr("GC alloc regions");
3896   for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
3897     HeapRegion* r = _gc_alloc_regions[ap];
3898     if (r == NULL) {
3899       gclog_or_tty->print_cr("  %2d : "PTR_FORMAT, ap, NULL);
3900     } else {
3901       gclog_or_tty->print_cr("  %2d : "PTR_FORMAT" "SIZE_FORMAT,
3902                              ap, r->bottom(), r->used());
3903     }
3904   }
3905 }
3906 #endif // PRODUCT
3907 
3908 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
3909   _drain_in_progress = false;
3910   set_evac_failure_closure(cl);
3911   _evac_failure_scan_stack = new (ResourceObj::C_HEAP) GrowableArray<oop>(40, true);
3912 }
3913 
3914 void G1CollectedHeap::finalize_for_evac_failure() {
3915   assert(_evac_failure_scan_stack != NULL &&
3916          _evac_failure_scan_stack->length() == 0,
3917          "Postcondition");
3918   assert(!_drain_in_progress, "Postcondition");
3919   delete _evac_failure_scan_stack;
3920   _evac_failure_scan_stack = NULL;
3921 }
3922 
3923 
3924 
3925 // *** Sequential G1 Evacuation
3926 
3927 class G1IsAliveClosure: public BoolObjectClosure {
3928   G1CollectedHeap* _g1;
3929 public:
3930   G1IsAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3931   void do_object(oop p) { assert(false, "Do not call."); }
3932   bool do_object_b(oop p) {
3933     // It is reachable if it is outside the collection set, or is inside
3934     // and forwarded.
3935 
3936 #ifdef G1_DEBUG
3937     gclog_or_tty->print_cr("is alive "PTR_FORMAT" in CS %d forwarded %d overall %d",
3938                            (void*) p, _g1->obj_in_cs(p), p->is_forwarded(),
3939                            !_g1->obj_in_cs(p) || p->is_forwarded());
3940 #endif // G1_DEBUG
3941 
3942     return !_g1->obj_in_cs(p) || p->is_forwarded();
3943   }
3944 };
3945 
3946 class G1KeepAliveClosure: public OopClosure {
3947   G1CollectedHeap* _g1;
3948 public:
3949   G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3950   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
3951   void do_oop(      oop* p) {
3952     oop obj = *p;
3953 #ifdef G1_DEBUG
3954     if (PrintGC && Verbose) {
3955       gclog_or_tty->print_cr("keep alive *"PTR_FORMAT" = "PTR_FORMAT" "PTR_FORMAT,
3956                              p, (void*) obj, (void*) *p);
3957     }
3958 #endif // G1_DEBUG
3959 
3960     if (_g1->obj_in_cs(obj)) {
3961       assert( obj->is_forwarded(), "invariant" );
3962       *p = obj->forwardee();
3963 #ifdef G1_DEBUG
3964       gclog_or_tty->print_cr("     in CSet: moved "PTR_FORMAT" -> "PTR_FORMAT,
3965                              (void*) obj, (void*) *p);
3966 #endif // G1_DEBUG
3967     }
3968   }
3969 };
3970 
3971 class UpdateRSetDeferred : public OopsInHeapRegionClosure {
3972 private:
3973   G1CollectedHeap* _g1;
3974   DirtyCardQueue *_dcq;
3975   CardTableModRefBS* _ct_bs;
3976 
3977 public:
3978   UpdateRSetDeferred(G1CollectedHeap* g1, DirtyCardQueue* dcq) :
3979     _g1(g1), _ct_bs((CardTableModRefBS*)_g1->barrier_set()), _dcq(dcq) {}
3980 
3981   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
3982   virtual void do_oop(      oop* p) { do_oop_work(p); }
3983   template <class T> void do_oop_work(T* p) {
3984     assert(_from->is_in_reserved(p), "paranoia");
3985     if (!_from->is_in_reserved(oopDesc::load_decode_heap_oop(p)) &&
3986         !_from->is_survivor()) {
3987       size_t card_index = _ct_bs->index_for(p);
3988       if (_ct_bs->mark_card_deferred(card_index)) {
3989         _dcq->enqueue((jbyte*)_ct_bs->byte_for_index(card_index));
3990       }
3991     }
3992   }
3993 };
3994 
3995 class RemoveSelfPointerClosure: public ObjectClosure {
3996 private:
3997   G1CollectedHeap* _g1;
3998   ConcurrentMark* _cm;
3999   HeapRegion* _hr;
4000   size_t _prev_marked_bytes;
4001   size_t _next_marked_bytes;
4002   OopsInHeapRegionClosure *_cl;
4003 public:
4004   RemoveSelfPointerClosure(G1CollectedHeap* g1, HeapRegion* hr,
4005                            OopsInHeapRegionClosure* cl) :
4006     _g1(g1), _hr(hr), _cm(_g1->concurrent_mark()),  _prev_marked_bytes(0),
4007     _next_marked_bytes(0), _cl(cl) {}
4008 
4009   size_t prev_marked_bytes() { return _prev_marked_bytes; }
4010   size_t next_marked_bytes() { return _next_marked_bytes; }
4011 
4012   // <original comment>
4013   // The original idea here was to coalesce evacuated and dead objects.
4014   // However that caused complications with the block offset table (BOT).
4015   // In particular if there were two TLABs, one of them partially refined.
4016   // |----- TLAB_1--------|----TLAB_2-~~~(partially refined part)~~~|
4017   // The BOT entries of the unrefined part of TLAB_2 point to the start
4018   // of TLAB_2. If the last object of the TLAB_1 and the first object
4019   // of TLAB_2 are coalesced, then the cards of the unrefined part
4020   // would point into middle of the filler object.
4021   // The current approach is to not coalesce and leave the BOT contents intact.
4022   // </original comment>
4023   //
4024   // We now reset the BOT when we start the object iteration over the
4025   // region and refine its entries for every object we come across. So
4026   // the above comment is not really relevant and we should be able
4027   // to coalesce dead objects if we want to.
4028   void do_object(oop obj) {
4029     HeapWord* obj_addr = (HeapWord*) obj;
4030     assert(_hr->is_in(obj_addr), "sanity");
4031     size_t obj_size = obj->size();
4032     _hr->update_bot_for_object(obj_addr, obj_size);
4033     if (obj->is_forwarded() && obj->forwardee() == obj) {
4034       // The object failed to move.
4035       assert(!_g1->is_obj_dead(obj), "We should not be preserving dead objs.");
4036       _cm->markPrev(obj);
4037       assert(_cm->isPrevMarked(obj), "Should be marked!");
4038       _prev_marked_bytes += (obj_size * HeapWordSize);
4039       if (_g1->mark_in_progress() && !_g1->is_obj_ill(obj)) {
4040         _cm->markAndGrayObjectIfNecessary(obj);
4041       }
4042       obj->set_mark(markOopDesc::prototype());
4043       // While we were processing RSet buffers during the
4044       // collection, we actually didn't scan any cards on the
4045       // collection set, since we didn't want to update remebered
4046       // sets with entries that point into the collection set, given
4047       // that live objects fromthe collection set are about to move
4048       // and such entries will be stale very soon. This change also
4049       // dealt with a reliability issue which involved scanning a
4050       // card in the collection set and coming across an array that
4051       // was being chunked and looking malformed. The problem is
4052       // that, if evacuation fails, we might have remembered set
4053       // entries missing given that we skipped cards on the
4054       // collection set. So, we'll recreate such entries now.
4055       obj->oop_iterate(_cl);
4056       assert(_cm->isPrevMarked(obj), "Should be marked!");
4057     } else {
4058       // The object has been either evacuated or is dead. Fill it with a
4059       // dummy object.
4060       MemRegion mr((HeapWord*)obj, obj_size);
4061       CollectedHeap::fill_with_object(mr);
4062       _cm->clearRangeBothMaps(mr);
4063     }
4064   }
4065 };
4066 
4067 void G1CollectedHeap::remove_self_forwarding_pointers() {
4068   UpdateRSetImmediate immediate_update(_g1h->g1_rem_set());
4069   DirtyCardQueue dcq(&_g1h->dirty_card_queue_set());
4070   UpdateRSetDeferred deferred_update(_g1h, &dcq);
4071   OopsInHeapRegionClosure *cl;
4072   if (G1DeferredRSUpdate) {
4073     cl = &deferred_update;
4074   } else {
4075     cl = &immediate_update;
4076   }
4077   HeapRegion* cur = g1_policy()->collection_set();
4078   while (cur != NULL) {
4079     assert(g1_policy()->assertMarkedBytesDataOK(), "Should be!");
4080     assert(!cur->isHumongous(), "sanity");
4081 
4082     if (cur->evacuation_failed()) {
4083       assert(cur->in_collection_set(), "bad CS");
4084       RemoveSelfPointerClosure rspc(_g1h, cur, cl);
4085 
4086       cur->reset_bot();
4087       cl->set_region(cur);
4088       cur->object_iterate(&rspc);
4089 
4090       // A number of manipulations to make the TAMS be the current top,
4091       // and the marked bytes be the ones observed in the iteration.
4092       if (_g1h->concurrent_mark()->at_least_one_mark_complete()) {
4093         // The comments below are the postconditions achieved by the
4094         // calls.  Note especially the last such condition, which says that
4095         // the count of marked bytes has been properly restored.
4096         cur->note_start_of_marking(false);
4097         // _next_top_at_mark_start == top, _next_marked_bytes == 0
4098         cur->add_to_marked_bytes(rspc.prev_marked_bytes());
4099         // _next_marked_bytes == prev_marked_bytes.
4100         cur->note_end_of_marking();
4101         // _prev_top_at_mark_start == top(),
4102         // _prev_marked_bytes == prev_marked_bytes
4103       }
4104       // If there is no mark in progress, we modified the _next variables
4105       // above needlessly, but harmlessly.
4106       if (_g1h->mark_in_progress()) {
4107         cur->note_start_of_marking(false);
4108         // _next_top_at_mark_start == top, _next_marked_bytes == 0
4109         // _next_marked_bytes == next_marked_bytes.
4110       }
4111 
4112       // Now make sure the region has the right index in the sorted array.
4113       g1_policy()->note_change_in_marked_bytes(cur);
4114     }
4115     cur = cur->next_in_collection_set();
4116   }
4117   assert(g1_policy()->assertMarkedBytesDataOK(), "Should be!");
4118 
4119   // Now restore saved marks, if any.
4120   if (_objs_with_preserved_marks != NULL) {
4121     assert(_preserved_marks_of_objs != NULL, "Both or none.");
4122     guarantee(_objs_with_preserved_marks->length() ==
4123               _preserved_marks_of_objs->length(), "Both or none.");
4124     for (int i = 0; i < _objs_with_preserved_marks->length(); i++) {
4125       oop obj   = _objs_with_preserved_marks->at(i);
4126       markOop m = _preserved_marks_of_objs->at(i);
4127       obj->set_mark(m);
4128     }
4129     // Delete the preserved marks growable arrays (allocated on the C heap).
4130     delete _objs_with_preserved_marks;
4131     delete _preserved_marks_of_objs;
4132     _objs_with_preserved_marks = NULL;
4133     _preserved_marks_of_objs = NULL;
4134   }
4135 }
4136 
4137 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4138   _evac_failure_scan_stack->push(obj);
4139 }
4140 
4141 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4142   assert(_evac_failure_scan_stack != NULL, "precondition");
4143 
4144   while (_evac_failure_scan_stack->length() > 0) {
4145      oop obj = _evac_failure_scan_stack->pop();
4146      _evac_failure_closure->set_region(heap_region_containing(obj));
4147      obj->oop_iterate_backwards(_evac_failure_closure);
4148   }
4149 }
4150 
4151 oop
4152 G1CollectedHeap::handle_evacuation_failure_par(OopsInHeapRegionClosure* cl,
4153                                                oop old) {
4154   markOop m = old->mark();
4155   oop forward_ptr = old->forward_to_atomic(old);
4156   if (forward_ptr == NULL) {
4157     // Forward-to-self succeeded.
4158     if (_evac_failure_closure != cl) {
4159       MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4160       assert(!_drain_in_progress,
4161              "Should only be true while someone holds the lock.");
4162       // Set the global evac-failure closure to the current thread's.
4163       assert(_evac_failure_closure == NULL, "Or locking has failed.");
4164       set_evac_failure_closure(cl);
4165       // Now do the common part.
4166       handle_evacuation_failure_common(old, m);
4167       // Reset to NULL.
4168       set_evac_failure_closure(NULL);
4169     } else {
4170       // The lock is already held, and this is recursive.
4171       assert(_drain_in_progress, "This should only be the recursive case.");
4172       handle_evacuation_failure_common(old, m);
4173     }
4174     return old;
4175   } else {
4176     // Someone else had a place to copy it.
4177     return forward_ptr;
4178   }
4179 }
4180 
4181 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4182   set_evacuation_failed(true);
4183 
4184   preserve_mark_if_necessary(old, m);
4185 
4186   HeapRegion* r = heap_region_containing(old);
4187   if (!r->evacuation_failed()) {
4188     r->set_evacuation_failed(true);
4189     if (G1PrintHeapRegions) {
4190       gclog_or_tty->print("overflow in heap region "PTR_FORMAT" "
4191                           "["PTR_FORMAT","PTR_FORMAT")\n",
4192                           r, r->bottom(), r->end());
4193     }
4194   }
4195 
4196   push_on_evac_failure_scan_stack(old);
4197 
4198   if (!_drain_in_progress) {
4199     // prevent recursion in copy_to_survivor_space()
4200     _drain_in_progress = true;
4201     drain_evac_failure_scan_stack();
4202     _drain_in_progress = false;
4203   }
4204 }
4205 
4206 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4207   assert(evacuation_failed(), "Oversaving!");
4208   // We want to call the "for_promotion_failure" version only in the
4209   // case of a promotion failure.
4210   if (m->must_be_preserved_for_promotion_failure(obj)) {
4211     if (_objs_with_preserved_marks == NULL) {
4212       assert(_preserved_marks_of_objs == NULL, "Both or none.");
4213       _objs_with_preserved_marks =
4214         new (ResourceObj::C_HEAP) GrowableArray<oop>(40, true);
4215       _preserved_marks_of_objs =
4216         new (ResourceObj::C_HEAP) GrowableArray<markOop>(40, true);
4217     }
4218     _objs_with_preserved_marks->push(obj);
4219     _preserved_marks_of_objs->push(m);
4220   }
4221 }
4222 
4223 // *** Parallel G1 Evacuation
4224 
4225 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
4226                                                   size_t word_size) {
4227   assert(!isHumongous(word_size),
4228          err_msg("we should not be seeing humongous allocation requests "
4229                  "during GC, word_size = "SIZE_FORMAT, word_size));
4230 
4231   HeapRegion* alloc_region = _gc_alloc_regions[purpose];
4232   // let the caller handle alloc failure
4233   if (alloc_region == NULL) return NULL;
4234 
4235   HeapWord* block = alloc_region->par_allocate(word_size);
4236   if (block == NULL) {
4237     block = allocate_during_gc_slow(purpose, alloc_region, true, word_size);
4238   }
4239   return block;
4240 }
4241 
4242 void G1CollectedHeap::retire_alloc_region(HeapRegion* alloc_region,
4243                                             bool par) {
4244   // Another thread might have obtained alloc_region for the given
4245   // purpose, and might be attempting to allocate in it, and might
4246   // succeed.  Therefore, we can't do the "finalization" stuff on the
4247   // region below until we're sure the last allocation has happened.
4248   // We ensure this by allocating the remaining space with a garbage
4249   // object.
4250   if (par) par_allocate_remaining_space(alloc_region);
4251   // Now we can do the post-GC stuff on the region.
4252   alloc_region->note_end_of_copying();
4253   g1_policy()->record_after_bytes(alloc_region->used());
4254 }
4255 
4256 HeapWord*
4257 G1CollectedHeap::allocate_during_gc_slow(GCAllocPurpose purpose,
4258                                          HeapRegion*    alloc_region,
4259                                          bool           par,
4260                                          size_t         word_size) {
4261   assert(!isHumongous(word_size),
4262          err_msg("we should not be seeing humongous allocation requests "
4263                  "during GC, word_size = "SIZE_FORMAT, word_size));
4264 
4265   // We need to make sure we serialize calls to this method. Given
4266   // that the FreeList_lock guards accesses to the free_list anyway,
4267   // and we need to potentially remove a region from it, we'll use it
4268   // to protect the whole call.
4269   MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4270 
4271   HeapWord* block = NULL;
4272   // In the parallel case, a previous thread to obtain the lock may have
4273   // already assigned a new gc_alloc_region.
4274   if (alloc_region != _gc_alloc_regions[purpose]) {
4275     assert(par, "But should only happen in parallel case.");
4276     alloc_region = _gc_alloc_regions[purpose];
4277     if (alloc_region == NULL) return NULL;
4278     block = alloc_region->par_allocate(word_size);
4279     if (block != NULL) return block;
4280     // Otherwise, continue; this new region is empty, too.
4281   }
4282   assert(alloc_region != NULL, "We better have an allocation region");
4283   retire_alloc_region(alloc_region, par);
4284 
4285   if (_gc_alloc_region_counts[purpose] >= g1_policy()->max_regions(purpose)) {
4286     // Cannot allocate more regions for the given purpose.
4287     GCAllocPurpose alt_purpose = g1_policy()->alternative_purpose(purpose);
4288     // Is there an alternative?
4289     if (purpose != alt_purpose) {
4290       HeapRegion* alt_region = _gc_alloc_regions[alt_purpose];
4291       // Has not the alternative region been aliased?
4292       if (alloc_region != alt_region && alt_region != NULL) {
4293         // Try to allocate in the alternative region.
4294         if (par) {
4295           block = alt_region->par_allocate(word_size);
4296         } else {
4297           block = alt_region->allocate(word_size);
4298         }
4299         // Make an alias.
4300         _gc_alloc_regions[purpose] = _gc_alloc_regions[alt_purpose];
4301         if (block != NULL) {
4302           return block;
4303         }
4304         retire_alloc_region(alt_region, par);
4305       }
4306       // Both the allocation region and the alternative one are full
4307       // and aliased, replace them with a new allocation region.
4308       purpose = alt_purpose;
4309     } else {
4310       set_gc_alloc_region(purpose, NULL);
4311       return NULL;
4312     }
4313   }
4314 
4315   // Now allocate a new region for allocation.
4316   alloc_region = new_gc_alloc_region(purpose, word_size);
4317 
4318   // let the caller handle alloc failure
4319   if (alloc_region != NULL) {
4320 
4321     assert(check_gc_alloc_regions(), "alloc regions messed up");
4322     assert(alloc_region->saved_mark_at_top(),
4323            "Mark should have been saved already.");
4324     // This must be done last: once it's installed, other regions may
4325     // allocate in it (without holding the lock.)
4326     set_gc_alloc_region(purpose, alloc_region);
4327 
4328     if (par) {
4329       block = alloc_region->par_allocate(word_size);
4330     } else {
4331       block = alloc_region->allocate(word_size);
4332     }
4333     // Caller handles alloc failure.
4334   } else {
4335     // This sets other apis using the same old alloc region to NULL, also.
4336     set_gc_alloc_region(purpose, NULL);
4337   }
4338   return block;  // May be NULL.
4339 }
4340 
4341 void G1CollectedHeap::par_allocate_remaining_space(HeapRegion* r) {
4342   HeapWord* block = NULL;
4343   size_t free_words;
4344   do {
4345     free_words = r->free()/HeapWordSize;
4346     // If there's too little space, no one can allocate, so we're done.
4347     if (free_words < CollectedHeap::min_fill_size()) return;
4348     // Otherwise, try to claim it.
4349     block = r->par_allocate(free_words);
4350   } while (block == NULL);
4351   fill_with_object(block, free_words);
4352 }
4353 
4354 #ifndef PRODUCT
4355 bool GCLabBitMapClosure::do_bit(size_t offset) {
4356   HeapWord* addr = _bitmap->offsetToHeapWord(offset);
4357   guarantee(_cm->isMarked(oop(addr)), "it should be!");
4358   return true;
4359 }
4360 #endif // PRODUCT
4361 
4362 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, int queue_num)
4363   : _g1h(g1h),
4364     _refs(g1h->task_queue(queue_num)),
4365     _dcq(&g1h->dirty_card_queue_set()),
4366     _ct_bs((CardTableModRefBS*)_g1h->barrier_set()),
4367     _g1_rem(g1h->g1_rem_set()),
4368     _hash_seed(17), _queue_num(queue_num),
4369     _term_attempts(0),
4370     _surviving_alloc_buffer(g1h->desired_plab_sz(GCAllocForSurvived)),
4371     _tenured_alloc_buffer(g1h->desired_plab_sz(GCAllocForTenured)),
4372     _age_table(false),
4373     _strong_roots_time(0), _term_time(0),
4374     _alloc_buffer_waste(0), _undo_waste(0)
4375 {
4376   // we allocate G1YoungSurvRateNumRegions plus one entries, since
4377   // we "sacrifice" entry 0 to keep track of surviving bytes for
4378   // non-young regions (where the age is -1)
4379   // We also add a few elements at the beginning and at the end in
4380   // an attempt to eliminate cache contention
4381   size_t real_length = 1 + _g1h->g1_policy()->young_cset_length();
4382   size_t array_length = PADDING_ELEM_NUM +
4383                         real_length +
4384                         PADDING_ELEM_NUM;
4385   _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length);
4386   if (_surviving_young_words_base == NULL)
4387     vm_exit_out_of_memory(array_length * sizeof(size_t),
4388                           "Not enough space for young surv histo.");
4389   _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM;
4390   memset(_surviving_young_words, 0, real_length * sizeof(size_t));
4391 
4392   _alloc_buffers[GCAllocForSurvived] = &_surviving_alloc_buffer;
4393   _alloc_buffers[GCAllocForTenured]  = &_tenured_alloc_buffer;
4394 
4395   _start = os::elapsedTime();
4396 }
4397 
4398 void
4399 G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st)
4400 {
4401   st->print_raw_cr("GC Termination Stats");
4402   st->print_raw_cr("     elapsed  --strong roots-- -------termination-------"
4403                    " ------waste (KiB)------");
4404   st->print_raw_cr("thr     ms        ms      %        ms      %    attempts"
4405                    "  total   alloc    undo");
4406   st->print_raw_cr("--- --------- --------- ------ --------- ------ --------"
4407                    " ------- ------- -------");
4408 }
4409 
4410 void
4411 G1ParScanThreadState::print_termination_stats(int i,
4412                                               outputStream* const st) const
4413 {
4414   const double elapsed_ms = elapsed_time() * 1000.0;
4415   const double s_roots_ms = strong_roots_time() * 1000.0;
4416   const double term_ms    = term_time() * 1000.0;
4417   st->print_cr("%3d %9.2f %9.2f %6.2f "
4418                "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
4419                SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
4420                i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms,
4421                term_ms, term_ms * 100 / elapsed_ms, term_attempts(),
4422                (alloc_buffer_waste() + undo_waste()) * HeapWordSize / K,
4423                alloc_buffer_waste() * HeapWordSize / K,
4424                undo_waste() * HeapWordSize / K);
4425 }
4426 
4427 #ifdef ASSERT
4428 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const {
4429   assert(ref != NULL, "invariant");
4430   assert(UseCompressedOops, "sanity");
4431   assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, ref));
4432   oop p = oopDesc::load_decode_heap_oop(ref);
4433   assert(_g1h->is_in_g1_reserved(p),
4434          err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4435   return true;
4436 }
4437 
4438 bool G1ParScanThreadState::verify_ref(oop* ref) const {
4439   assert(ref != NULL, "invariant");
4440   if (has_partial_array_mask(ref)) {
4441     // Must be in the collection set--it's already been copied.
4442     oop p = clear_partial_array_mask(ref);
4443     assert(_g1h->obj_in_cs(p),
4444            err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4445   } else {
4446     oop p = oopDesc::load_decode_heap_oop(ref);
4447     assert(_g1h->is_in_g1_reserved(p),
4448            err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4449   }
4450   return true;
4451 }
4452 
4453 bool G1ParScanThreadState::verify_task(StarTask ref) const {
4454   if (ref.is_narrow()) {
4455     return verify_ref((narrowOop*) ref);
4456   } else {
4457     return verify_ref((oop*) ref);
4458   }
4459 }
4460 #endif // ASSERT
4461 
4462 void G1ParScanThreadState::trim_queue() {
4463   StarTask ref;
4464   do {
4465     // Drain the overflow stack first, so other threads can steal.
4466     while (refs()->pop_overflow(ref)) {
4467       deal_with_reference(ref);
4468     }
4469     while (refs()->pop_local(ref)) {
4470       deal_with_reference(ref);
4471     }
4472   } while (!refs()->is_empty());
4473 }
4474 
4475 G1ParClosureSuper::G1ParClosureSuper(G1CollectedHeap* g1, G1ParScanThreadState* par_scan_state) :
4476   _g1(g1), _g1_rem(_g1->g1_rem_set()), _cm(_g1->concurrent_mark()),
4477   _par_scan_state(par_scan_state) { }
4478 
4479 template <class T> void G1ParCopyHelper::mark_forwardee(T* p) {
4480   // This is called _after_ do_oop_work has been called, hence after
4481   // the object has been relocated to its new location and *p points
4482   // to its new location.
4483 
4484   T heap_oop = oopDesc::load_heap_oop(p);
4485   if (!oopDesc::is_null(heap_oop)) {
4486     oop obj = oopDesc::decode_heap_oop(heap_oop);
4487     assert((_g1->evacuation_failed()) || (!_g1->obj_in_cs(obj)),
4488            "shouldn't still be in the CSet if evacuation didn't fail.");
4489     HeapWord* addr = (HeapWord*)obj;
4490     if (_g1->is_in_g1_reserved(addr))
4491       _cm->grayRoot(oop(addr));
4492   }
4493 }
4494 
4495 oop G1ParCopyHelper::copy_to_survivor_space(oop old) {
4496   size_t    word_sz = old->size();
4497   HeapRegion* from_region = _g1->heap_region_containing_raw(old);
4498   // +1 to make the -1 indexes valid...
4499   int       young_index = from_region->young_index_in_cset()+1;
4500   assert( (from_region->is_young() && young_index > 0) ||
4501           (!from_region->is_young() && young_index == 0), "invariant" );
4502   G1CollectorPolicy* g1p = _g1->g1_policy();
4503   markOop m = old->mark();
4504   int age = m->has_displaced_mark_helper() ? m->displaced_mark_helper()->age()
4505                                            : m->age();
4506   GCAllocPurpose alloc_purpose = g1p->evacuation_destination(from_region, age,
4507                                                              word_sz);
4508   HeapWord* obj_ptr = _par_scan_state->allocate(alloc_purpose, word_sz);
4509   oop       obj     = oop(obj_ptr);
4510 
4511   if (obj_ptr == NULL) {
4512     // This will either forward-to-self, or detect that someone else has
4513     // installed a forwarding pointer.
4514     OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4515     return _g1->handle_evacuation_failure_par(cl, old);
4516   }
4517 
4518   // We're going to allocate linearly, so might as well prefetch ahead.
4519   Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
4520 
4521   oop forward_ptr = old->forward_to_atomic(obj);
4522   if (forward_ptr == NULL) {
4523     Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
4524     if (g1p->track_object_age(alloc_purpose)) {
4525       // We could simply do obj->incr_age(). However, this causes a
4526       // performance issue. obj->incr_age() will first check whether
4527       // the object has a displaced mark by checking its mark word;
4528       // getting the mark word from the new location of the object
4529       // stalls. So, given that we already have the mark word and we
4530       // are about to install it anyway, it's better to increase the
4531       // age on the mark word, when the object does not have a
4532       // displaced mark word. We're not expecting many objects to have
4533       // a displaced marked word, so that case is not optimized
4534       // further (it could be...) and we simply call obj->incr_age().
4535 
4536       if (m->has_displaced_mark_helper()) {
4537         // in this case, we have to install the mark word first,
4538         // otherwise obj looks to be forwarded (the old mark word,
4539         // which contains the forward pointer, was copied)
4540         obj->set_mark(m);
4541         obj->incr_age();
4542       } else {
4543         m = m->incr_age();
4544         obj->set_mark(m);
4545       }
4546       _par_scan_state->age_table()->add(obj, word_sz);
4547     } else {
4548       obj->set_mark(m);
4549     }
4550 
4551     // preserve "next" mark bit
4552     if (_g1->mark_in_progress() && !_g1->is_obj_ill(old)) {
4553       if (!use_local_bitmaps ||
4554           !_par_scan_state->alloc_buffer(alloc_purpose)->mark(obj_ptr)) {
4555         // if we couldn't mark it on the local bitmap (this happens when
4556         // the object was not allocated in the GCLab), we have to bite
4557         // the bullet and do the standard parallel mark
4558         _cm->markAndGrayObjectIfNecessary(obj);
4559       }
4560 #if 1
4561       if (_g1->isMarkedNext(old)) {
4562         _cm->nextMarkBitMap()->parClear((HeapWord*)old);
4563       }
4564 #endif
4565     }
4566 
4567     size_t* surv_young_words = _par_scan_state->surviving_young_words();
4568     surv_young_words[young_index] += word_sz;
4569 
4570     if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
4571       arrayOop(old)->set_length(0);
4572       oop* old_p = set_partial_array_mask(old);
4573       _par_scan_state->push_on_queue(old_p);
4574     } else {
4575       // No point in using the slower heap_region_containing() method,
4576       // given that we know obj is in the heap.
4577       _scanner->set_region(_g1->heap_region_containing_raw(obj));
4578       obj->oop_iterate_backwards(_scanner);
4579     }
4580   } else {
4581     _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz);
4582     obj = forward_ptr;
4583   }
4584   return obj;
4585 }
4586 
4587 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_forwardee>
4588 template <class T>
4589 void G1ParCopyClosure <do_gen_barrier, barrier, do_mark_forwardee>
4590 ::do_oop_work(T* p) {
4591   oop obj = oopDesc::load_decode_heap_oop(p);
4592   assert(barrier != G1BarrierRS || obj != NULL,
4593          "Precondition: G1BarrierRS implies obj is nonNull");
4594 
4595   // here the null check is implicit in the cset_fast_test() test
4596   if (_g1->in_cset_fast_test(obj)) {
4597 #if G1_REM_SET_LOGGING
4598     gclog_or_tty->print_cr("Loc "PTR_FORMAT" contains pointer "PTR_FORMAT" "
4599                            "into CS.", p, (void*) obj);
4600 #endif
4601     if (obj->is_forwarded()) {
4602       oopDesc::encode_store_heap_oop(p, obj->forwardee());
4603     } else {
4604       oop copy_oop = copy_to_survivor_space(obj);
4605       oopDesc::encode_store_heap_oop(p, copy_oop);
4606     }
4607     // When scanning the RS, we only care about objs in CS.
4608     if (barrier == G1BarrierRS) {
4609       _par_scan_state->update_rs(_from, p, _par_scan_state->queue_num());
4610     }
4611   }
4612 
4613   if (barrier == G1BarrierEvac && obj != NULL) {
4614     _par_scan_state->update_rs(_from, p, _par_scan_state->queue_num());
4615   }
4616 
4617   if (do_gen_barrier && obj != NULL) {
4618     par_do_barrier(p);
4619   }
4620 }
4621 
4622 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(oop* p);
4623 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(narrowOop* p);
4624 
4625 template <class T> void G1ParScanPartialArrayClosure::do_oop_nv(T* p) {
4626   assert(has_partial_array_mask(p), "invariant");
4627   oop old = clear_partial_array_mask(p);
4628   assert(old->is_objArray(), "must be obj array");
4629   assert(old->is_forwarded(), "must be forwarded");
4630   assert(Universe::heap()->is_in_reserved(old), "must be in heap.");
4631 
4632   objArrayOop obj = objArrayOop(old->forwardee());
4633   assert((void*)old != (void*)old->forwardee(), "self forwarding here?");
4634   // Process ParGCArrayScanChunk elements now
4635   // and push the remainder back onto queue
4636   int start     = arrayOop(old)->length();
4637   int end       = obj->length();
4638   int remainder = end - start;
4639   assert(start <= end, "just checking");
4640   if (remainder > 2 * ParGCArrayScanChunk) {
4641     // Test above combines last partial chunk with a full chunk
4642     end = start + ParGCArrayScanChunk;
4643     arrayOop(old)->set_length(end);
4644     // Push remainder.
4645     oop* old_p = set_partial_array_mask(old);
4646     assert(arrayOop(old)->length() < obj->length(), "Empty push?");
4647     _par_scan_state->push_on_queue(old_p);
4648   } else {
4649     // Restore length so that the heap remains parsable in
4650     // case of evacuation failure.
4651     arrayOop(old)->set_length(end);
4652   }
4653   _scanner.set_region(_g1->heap_region_containing_raw(obj));
4654   // process our set of indices (include header in first chunk)
4655   obj->oop_iterate_range(&_scanner, start, end);
4656 }
4657 
4658 class G1ParEvacuateFollowersClosure : public VoidClosure {
4659 protected:
4660   G1CollectedHeap*              _g1h;
4661   G1ParScanThreadState*         _par_scan_state;
4662   RefToScanQueueSet*            _queues;
4663   ParallelTaskTerminator*       _terminator;
4664 
4665   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
4666   RefToScanQueueSet*      queues()         { return _queues; }
4667   ParallelTaskTerminator* terminator()     { return _terminator; }
4668 
4669 public:
4670   G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4671                                 G1ParScanThreadState* par_scan_state,
4672                                 RefToScanQueueSet* queues,
4673                                 ParallelTaskTerminator* terminator)
4674     : _g1h(g1h), _par_scan_state(par_scan_state),
4675       _queues(queues), _terminator(terminator) {}
4676 
4677   void do_void();
4678 
4679 private:
4680   inline bool offer_termination();
4681 };
4682 
4683 bool G1ParEvacuateFollowersClosure::offer_termination() {
4684   G1ParScanThreadState* const pss = par_scan_state();
4685   pss->start_term_time();
4686   const bool res = terminator()->offer_termination();
4687   pss->end_term_time();
4688   return res;
4689 }
4690 
4691 void G1ParEvacuateFollowersClosure::do_void() {
4692   StarTask stolen_task;
4693   G1ParScanThreadState* const pss = par_scan_state();
4694   pss->trim_queue();
4695 
4696   do {
4697     while (queues()->steal(pss->queue_num(), pss->hash_seed(), stolen_task)) {
4698       assert(pss->verify_task(stolen_task), "sanity");
4699       if (stolen_task.is_narrow()) {
4700         pss->deal_with_reference((narrowOop*) stolen_task);
4701       } else {
4702         pss->deal_with_reference((oop*) stolen_task);
4703       }
4704 
4705       // We've just processed a reference and we might have made
4706       // available new entries on the queues. So we have to make sure
4707       // we drain the queues as necessary.
4708       pss->trim_queue();
4709     }
4710   } while (!offer_termination());
4711 
4712   pss->retire_alloc_buffers();
4713 }
4714 
4715 class G1ParTask : public AbstractGangTask {
4716 protected:
4717   G1CollectedHeap*       _g1h;
4718   RefToScanQueueSet      *_queues;
4719   ParallelTaskTerminator _terminator;
4720   int _n_workers;
4721 
4722   Mutex _stats_lock;
4723   Mutex* stats_lock() { return &_stats_lock; }
4724 
4725   size_t getNCards() {
4726     return (_g1h->capacity() + G1BlockOffsetSharedArray::N_bytes - 1)
4727       / G1BlockOffsetSharedArray::N_bytes;
4728   }
4729 
4730 public:
4731   G1ParTask(G1CollectedHeap* g1h, int workers, RefToScanQueueSet *task_queues)
4732     : AbstractGangTask("G1 collection"),
4733       _g1h(g1h),
4734       _queues(task_queues),
4735       _terminator(workers, _queues),
4736       _stats_lock(Mutex::leaf, "parallel G1 stats lock", true),
4737       _n_workers(workers)
4738   {}
4739 
4740   RefToScanQueueSet* queues() { return _queues; }
4741 
4742   RefToScanQueue *work_queue(int i) {
4743     return queues()->queue(i);
4744   }
4745 
4746   void work(int i) {
4747     if (i >= _n_workers) return;  // no work needed this round
4748 
4749     double start_time_ms = os::elapsedTime() * 1000.0;
4750     _g1h->g1_policy()->record_gc_worker_start_time(i, start_time_ms);
4751 
4752     ResourceMark rm;
4753     HandleMark   hm;
4754 
4755     G1ParScanThreadState            pss(_g1h, i);
4756     G1ParScanHeapEvacClosure        scan_evac_cl(_g1h, &pss);
4757     G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss);
4758     G1ParScanPartialArrayClosure    partial_scan_cl(_g1h, &pss);
4759 
4760     pss.set_evac_closure(&scan_evac_cl);
4761     pss.set_evac_failure_closure(&evac_failure_cl);
4762     pss.set_partial_scan_closure(&partial_scan_cl);
4763 
4764     G1ParScanExtRootClosure         only_scan_root_cl(_g1h, &pss);
4765     G1ParScanPermClosure            only_scan_perm_cl(_g1h, &pss);
4766     G1ParScanHeapRSClosure          only_scan_heap_rs_cl(_g1h, &pss);
4767     G1ParPushHeapRSClosure          push_heap_rs_cl(_g1h, &pss);
4768 
4769     G1ParScanAndMarkExtRootClosure  scan_mark_root_cl(_g1h, &pss);
4770     G1ParScanAndMarkPermClosure     scan_mark_perm_cl(_g1h, &pss);
4771     G1ParScanAndMarkHeapRSClosure   scan_mark_heap_rs_cl(_g1h, &pss);
4772 
4773     OopsInHeapRegionClosure        *scan_root_cl;
4774     OopsInHeapRegionClosure        *scan_perm_cl;
4775 
4776     if (_g1h->g1_policy()->during_initial_mark_pause()) {
4777       scan_root_cl = &scan_mark_root_cl;
4778       scan_perm_cl = &scan_mark_perm_cl;
4779     } else {
4780       scan_root_cl = &only_scan_root_cl;
4781       scan_perm_cl = &only_scan_perm_cl;
4782     }
4783 
4784     pss.start_strong_roots();
4785     _g1h->g1_process_strong_roots(/* not collecting perm */ false,
4786                                   SharedHeap::SO_AllClasses,
4787                                   scan_root_cl,
4788                                   &push_heap_rs_cl,
4789                                   scan_perm_cl,
4790                                   i);
4791     pss.end_strong_roots();
4792     {
4793       double start = os::elapsedTime();
4794       G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4795       evac.do_void();
4796       double elapsed_ms = (os::elapsedTime()-start)*1000.0;
4797       double term_ms = pss.term_time()*1000.0;
4798       _g1h->g1_policy()->record_obj_copy_time(i, elapsed_ms-term_ms);
4799       _g1h->g1_policy()->record_termination(i, term_ms, pss.term_attempts());
4800     }
4801     _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4802     _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4803 
4804     // Clean up any par-expanded rem sets.
4805     HeapRegionRemSet::par_cleanup();
4806 
4807     if (ParallelGCVerbose) {
4808       MutexLocker x(stats_lock());
4809       pss.print_termination_stats(i);
4810     }
4811 
4812     assert(pss.refs()->is_empty(), "should be empty");
4813     double end_time_ms = os::elapsedTime() * 1000.0;
4814     _g1h->g1_policy()->record_gc_worker_end_time(i, end_time_ms);
4815   }
4816 };
4817 
4818 // *** Common G1 Evacuation Stuff
4819 
4820 // This method is run in a GC worker.
4821 
4822 void
4823 G1CollectedHeap::
4824 g1_process_strong_roots(bool collecting_perm_gen,
4825                         SharedHeap::ScanningOption so,
4826                         OopClosure* scan_non_heap_roots,
4827                         OopsInHeapRegionClosure* scan_rs,
4828                         OopsInGenClosure* scan_perm,
4829                         int worker_i) {
4830   // First scan the strong roots, including the perm gen.
4831   double ext_roots_start = os::elapsedTime();
4832   double closure_app_time_sec = 0.0;
4833 
4834   BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
4835   BufferingOopsInGenClosure buf_scan_perm(scan_perm);
4836   buf_scan_perm.set_generation(perm_gen());
4837 
4838   // Walk the code cache w/o buffering, because StarTask cannot handle
4839   // unaligned oop locations.
4840   CodeBlobToOopClosure eager_scan_code_roots(scan_non_heap_roots, /*do_marking=*/ true);
4841 
4842   process_strong_roots(false, // no scoping; this is parallel code
4843                        collecting_perm_gen, so,
4844                        &buf_scan_non_heap_roots,
4845                        &eager_scan_code_roots,
4846                        &buf_scan_perm);
4847 
4848   // Finish up any enqueued closure apps.
4849   buf_scan_non_heap_roots.done();
4850   buf_scan_perm.done();
4851   double ext_roots_end = os::elapsedTime();
4852   g1_policy()->reset_obj_copy_time(worker_i);
4853   double obj_copy_time_sec =
4854     buf_scan_non_heap_roots.closure_app_seconds() +
4855     buf_scan_perm.closure_app_seconds();
4856   g1_policy()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
4857   double ext_root_time_ms =
4858     ((ext_roots_end - ext_roots_start) - obj_copy_time_sec) * 1000.0;
4859   g1_policy()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
4860 
4861   // Scan strong roots in mark stack.
4862   if (!_process_strong_tasks->is_task_claimed(G1H_PS_mark_stack_oops_do)) {
4863     concurrent_mark()->oops_do(scan_non_heap_roots);
4864   }
4865   double mark_stack_scan_ms = (os::elapsedTime() - ext_roots_end) * 1000.0;
4866   g1_policy()->record_mark_stack_scan_time(worker_i, mark_stack_scan_ms);
4867 
4868   // XXX What should this be doing in the parallel case?
4869   g1_policy()->record_collection_pause_end_CH_strong_roots();
4870   // Now scan the complement of the collection set.
4871   if (scan_rs != NULL) {
4872     g1_rem_set()->oops_into_collection_set_do(scan_rs, worker_i);
4873   }
4874   // Finish with the ref_processor roots.
4875   if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
4876     // We need to treat the discovered reference lists as roots and
4877     // keep entries (which are added by the marking threads) on them
4878     // live until they can be processed at the end of marking.
4879     ref_processor()->weak_oops_do(scan_non_heap_roots);
4880     ref_processor()->oops_do(scan_non_heap_roots);
4881   }
4882   g1_policy()->record_collection_pause_end_G1_strong_roots();
4883   _process_strong_tasks->all_tasks_completed();
4884 }
4885 
4886 void
4887 G1CollectedHeap::g1_process_weak_roots(OopClosure* root_closure,
4888                                        OopClosure* non_root_closure) {
4889   CodeBlobToOopClosure roots_in_blobs(root_closure, /*do_marking=*/ false);
4890   SharedHeap::process_weak_roots(root_closure, &roots_in_blobs, non_root_closure);
4891 }
4892 
4893 
4894 class SaveMarksClosure: public HeapRegionClosure {
4895 public:
4896   bool doHeapRegion(HeapRegion* r) {
4897     r->save_marks();
4898     return false;
4899   }
4900 };
4901 
4902 void G1CollectedHeap::save_marks() {
4903   if (!CollectedHeap::use_parallel_gc_threads()) {
4904     SaveMarksClosure sm;
4905     heap_region_iterate(&sm);
4906   }
4907   // We do this even in the parallel case
4908   perm_gen()->save_marks();
4909 }
4910 
4911 void G1CollectedHeap::evacuate_collection_set() {
4912   set_evacuation_failed(false);
4913 
4914   g1_rem_set()->prepare_for_oops_into_collection_set_do();
4915   concurrent_g1_refine()->set_use_cache(false);
4916   concurrent_g1_refine()->clear_hot_cache_claimed_index();
4917 
4918   int n_workers = (ParallelGCThreads > 0 ? workers()->total_workers() : 1);
4919   set_par_threads(n_workers);
4920   G1ParTask g1_par_task(this, n_workers, _task_queues);
4921 
4922   init_for_evac_failure(NULL);
4923 
4924   rem_set()->prepare_for_younger_refs_iterate(true);
4925 
4926   assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
4927   double start_par = os::elapsedTime();
4928   if (G1CollectedHeap::use_parallel_gc_threads()) {
4929     // The individual threads will set their evac-failure closures.
4930     StrongRootsScope srs(this);
4931     if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
4932     workers()->run_task(&g1_par_task);
4933   } else {
4934     StrongRootsScope srs(this);
4935     g1_par_task.work(0);
4936   }
4937 
4938   double par_time = (os::elapsedTime() - start_par) * 1000.0;
4939   g1_policy()->record_par_time(par_time);
4940   set_par_threads(0);
4941   // Is this the right thing to do here?  We don't save marks
4942   // on individual heap regions when we allocate from
4943   // them in parallel, so this seems like the correct place for this.
4944   retire_all_alloc_regions();
4945 
4946   // Weak root processing.
4947   // Note: when JSR 292 is enabled and code blobs can contain
4948   // non-perm oops then we will need to process the code blobs
4949   // here too.
4950   {
4951     G1IsAliveClosure is_alive(this);
4952     G1KeepAliveClosure keep_alive(this);
4953     JNIHandles::weak_oops_do(&is_alive, &keep_alive);
4954   }
4955   release_gc_alloc_regions(false /* totally */);
4956   g1_rem_set()->cleanup_after_oops_into_collection_set_do();
4957 
4958   concurrent_g1_refine()->clear_hot_cache();
4959   concurrent_g1_refine()->set_use_cache(true);
4960 
4961   finalize_for_evac_failure();
4962 
4963   // Must do this before removing self-forwarding pointers, which clears
4964   // the per-region evac-failure flags.
4965   concurrent_mark()->complete_marking_in_collection_set();
4966 
4967   if (evacuation_failed()) {
4968     remove_self_forwarding_pointers();
4969     if (PrintGCDetails) {
4970       gclog_or_tty->print(" (to-space overflow)");
4971     } else if (PrintGC) {
4972       gclog_or_tty->print("--");
4973     }
4974   }
4975 
4976   if (G1DeferredRSUpdate) {
4977     RedirtyLoggedCardTableEntryFastClosure redirty;
4978     dirty_card_queue_set().set_closure(&redirty);
4979     dirty_card_queue_set().apply_closure_to_all_completed_buffers();
4980 
4981     DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
4982     dcq.merge_bufferlists(&dirty_card_queue_set());
4983     assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
4984   }
4985   COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
4986 }
4987 
4988 void G1CollectedHeap::free_region_if_empty(HeapRegion* hr,
4989                                      size_t* pre_used,
4990                                      FreeRegionList* free_list,
4991                                      HumongousRegionSet* humongous_proxy_set,
4992                                      HRRSCleanupTask* hrrs_cleanup_task,
4993                                      bool par) {
4994   if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) {
4995     if (hr->isHumongous()) {
4996       assert(hr->startsHumongous(), "we should only see starts humongous");
4997       free_humongous_region(hr, pre_used, free_list, humongous_proxy_set, par);
4998     } else {
4999       free_region(hr, pre_used, free_list, par);
5000     }
5001   } else {
5002     hr->rem_set()->do_cleanup_work(hrrs_cleanup_task);
5003   }
5004 }
5005 
5006 void G1CollectedHeap::free_region(HeapRegion* hr,
5007                                   size_t* pre_used,
5008                                   FreeRegionList* free_list,
5009                                   bool par) {
5010   assert(!hr->isHumongous(), "this is only for non-humongous regions");
5011   assert(!hr->is_empty(), "the region should not be empty");
5012   assert(free_list != NULL, "pre-condition");
5013 
5014   *pre_used += hr->used();
5015   hr->hr_clear(par, true /* clear_space */);
5016   free_list->add_as_tail(hr);
5017 }
5018 
5019 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
5020                                      size_t* pre_used,
5021                                      FreeRegionList* free_list,
5022                                      HumongousRegionSet* humongous_proxy_set,
5023                                      bool par) {
5024   assert(hr->startsHumongous(), "this is only for starts humongous regions");
5025   assert(free_list != NULL, "pre-condition");
5026   assert(humongous_proxy_set != NULL, "pre-condition");
5027 
5028   size_t hr_used = hr->used();
5029   size_t hr_capacity = hr->capacity();
5030   size_t hr_pre_used = 0;
5031   _humongous_set.remove_with_proxy(hr, humongous_proxy_set);
5032   hr->set_notHumongous();
5033   free_region(hr, &hr_pre_used, free_list, par);
5034 
5035   int i = hr->hrs_index() + 1;
5036   size_t num = 1;
5037   while ((size_t) i < n_regions()) {
5038     HeapRegion* curr_hr = _hrs->at(i);
5039     if (!curr_hr->continuesHumongous()) {
5040       break;
5041     }
5042     curr_hr->set_notHumongous();
5043     free_region(curr_hr, &hr_pre_used, free_list, par);
5044     num += 1;
5045     i += 1;
5046   }
5047   assert(hr_pre_used == hr_used,
5048          err_msg("hr_pre_used: "SIZE_FORMAT" and hr_used: "SIZE_FORMAT" "
5049                  "should be the same", hr_pre_used, hr_used));
5050   *pre_used += hr_pre_used;
5051 }
5052 
5053 void G1CollectedHeap::update_sets_after_freeing_regions(size_t pre_used,
5054                                        FreeRegionList* free_list,
5055                                        HumongousRegionSet* humongous_proxy_set,
5056                                        bool par) {
5057   if (pre_used > 0) {
5058     Mutex* lock = (par) ? ParGCRareEvent_lock : NULL;
5059     MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag);
5060     assert(_summary_bytes_used >= pre_used,
5061            err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" "
5062                    "should be >= pre_used: "SIZE_FORMAT,
5063                    _summary_bytes_used, pre_used));
5064     _summary_bytes_used -= pre_used;
5065   }
5066   if (free_list != NULL && !free_list->is_empty()) {
5067     MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
5068     _free_list.add_as_tail(free_list);
5069   }
5070   if (humongous_proxy_set != NULL && !humongous_proxy_set->is_empty()) {
5071     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5072     _humongous_set.update_from_proxy(humongous_proxy_set);
5073   }
5074 }
5075 
5076 void G1CollectedHeap::dirtyCardsForYoungRegions(CardTableModRefBS* ct_bs, HeapRegion* list) {
5077   while (list != NULL) {
5078     guarantee( list->is_young(), "invariant" );
5079 
5080     HeapWord* bottom = list->bottom();
5081     HeapWord* end = list->end();
5082     MemRegion mr(bottom, end);
5083     ct_bs->dirty(mr);
5084 
5085     list = list->get_next_young_region();
5086   }
5087 }
5088 
5089 
5090 class G1ParCleanupCTTask : public AbstractGangTask {
5091   CardTableModRefBS* _ct_bs;
5092   G1CollectedHeap* _g1h;
5093   HeapRegion* volatile _su_head;
5094 public:
5095   G1ParCleanupCTTask(CardTableModRefBS* ct_bs,
5096                      G1CollectedHeap* g1h,
5097                      HeapRegion* survivor_list) :
5098     AbstractGangTask("G1 Par Cleanup CT Task"),
5099     _ct_bs(ct_bs),
5100     _g1h(g1h),
5101     _su_head(survivor_list)
5102   { }
5103 
5104   void work(int i) {
5105     HeapRegion* r;
5106     while (r = _g1h->pop_dirty_cards_region()) {
5107       clear_cards(r);
5108     }
5109     // Redirty the cards of the survivor regions.
5110     dirty_list(&this->_su_head);
5111   }
5112 
5113   void clear_cards(HeapRegion* r) {
5114     // Cards for Survivor regions will be dirtied later.
5115     if (!r->is_survivor()) {
5116       _ct_bs->clear(MemRegion(r->bottom(), r->end()));
5117     }
5118   }
5119 
5120   void dirty_list(HeapRegion* volatile * head_ptr) {
5121     HeapRegion* head;
5122     do {
5123       // Pop region off the list.
5124       head = *head_ptr;
5125       if (head != NULL) {
5126         HeapRegion* r = (HeapRegion*)
5127           Atomic::cmpxchg_ptr(head->get_next_young_region(), head_ptr, head);
5128         if (r == head) {
5129           assert(!r->isHumongous(), "Humongous regions shouldn't be on survivor list");
5130           _ct_bs->dirty(MemRegion(r->bottom(), r->end()));
5131         }
5132       }
5133     } while (*head_ptr != NULL);
5134   }
5135 };
5136 
5137 
5138 #ifndef PRODUCT
5139 class G1VerifyCardTableCleanup: public HeapRegionClosure {
5140   CardTableModRefBS* _ct_bs;
5141 public:
5142   G1VerifyCardTableCleanup(CardTableModRefBS* ct_bs)
5143     : _ct_bs(ct_bs)
5144   { }
5145   virtual bool doHeapRegion(HeapRegion* r)
5146   {
5147     MemRegion mr(r->bottom(), r->end());
5148     if (r->is_survivor()) {
5149       _ct_bs->verify_dirty_region(mr);
5150     } else {
5151       _ct_bs->verify_clean_region(mr);
5152     }
5153     return false;
5154   }
5155 };
5156 #endif
5157 
5158 void G1CollectedHeap::cleanUpCardTable() {
5159   CardTableModRefBS* ct_bs = (CardTableModRefBS*) (barrier_set());
5160   double start = os::elapsedTime();
5161 
5162   // Iterate over the dirty cards region list.
5163   G1ParCleanupCTTask cleanup_task(ct_bs, this,
5164                                   _young_list->first_survivor_region());
5165 
5166   if (ParallelGCThreads > 0) {
5167     set_par_threads(workers()->total_workers());
5168     workers()->run_task(&cleanup_task);
5169     set_par_threads(0);
5170   } else {
5171     while (_dirty_cards_region_list) {
5172       HeapRegion* r = _dirty_cards_region_list;
5173       cleanup_task.clear_cards(r);
5174       _dirty_cards_region_list = r->get_next_dirty_cards_region();
5175       if (_dirty_cards_region_list == r) {
5176         // The last region.
5177         _dirty_cards_region_list = NULL;
5178       }
5179       r->set_next_dirty_cards_region(NULL);
5180     }
5181     // now, redirty the cards of the survivor regions
5182     // (it seemed faster to do it this way, instead of iterating over
5183     // all regions and then clearing / dirtying as appropriate)
5184     dirtyCardsForYoungRegions(ct_bs, _young_list->first_survivor_region());
5185   }
5186 
5187   double elapsed = os::elapsedTime() - start;
5188   g1_policy()->record_clear_ct_time( elapsed * 1000.0);
5189 #ifndef PRODUCT
5190   if (G1VerifyCTCleanup || VerifyAfterGC) {
5191     G1VerifyCardTableCleanup cleanup_verifier(ct_bs);
5192     heap_region_iterate(&cleanup_verifier);
5193   }
5194 #endif
5195 }
5196 
5197 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head) {
5198   size_t pre_used = 0;
5199   FreeRegionList local_free_list("Local List for CSet Freeing");
5200 
5201   double young_time_ms     = 0.0;
5202   double non_young_time_ms = 0.0;
5203 
5204   // Since the collection set is a superset of the the young list,
5205   // all we need to do to clear the young list is clear its
5206   // head and length, and unlink any young regions in the code below
5207   _young_list->clear();
5208 
5209   G1CollectorPolicy* policy = g1_policy();
5210 
5211   double start_sec = os::elapsedTime();
5212   bool non_young = true;
5213 
5214   HeapRegion* cur = cs_head;
5215   int age_bound = -1;
5216   size_t rs_lengths = 0;
5217 
5218   while (cur != NULL) {
5219     assert(!is_on_master_free_list(cur), "sanity");
5220 
5221     if (non_young) {
5222       if (cur->is_young()) {
5223         double end_sec = os::elapsedTime();
5224         double elapsed_ms = (end_sec - start_sec) * 1000.0;
5225         non_young_time_ms += elapsed_ms;
5226 
5227         start_sec = os::elapsedTime();
5228         non_young = false;
5229       }
5230     } else {
5231       double end_sec = os::elapsedTime();
5232       double elapsed_ms = (end_sec - start_sec) * 1000.0;
5233       young_time_ms += elapsed_ms;
5234 
5235       start_sec = os::elapsedTime();
5236       non_young = true;
5237     }
5238 
5239     rs_lengths += cur->rem_set()->occupied();
5240 
5241     HeapRegion* next = cur->next_in_collection_set();
5242     assert(cur->in_collection_set(), "bad CS");
5243     cur->set_next_in_collection_set(NULL);
5244     cur->set_in_collection_set(false);
5245 
5246     if (cur->is_young()) {
5247       int index = cur->young_index_in_cset();
5248       guarantee( index != -1, "invariant" );
5249       guarantee( (size_t)index < policy->young_cset_length(), "invariant" );
5250       size_t words_survived = _surviving_young_words[index];
5251       cur->record_surv_words_in_group(words_survived);
5252 
5253       // At this point the we have 'popped' cur from the collection set
5254       // (linked via next_in_collection_set()) but it is still in the
5255       // young list (linked via next_young_region()). Clear the
5256       // _next_young_region field.
5257       cur->set_next_young_region(NULL);
5258     } else {
5259       int index = cur->young_index_in_cset();
5260       guarantee( index == -1, "invariant" );
5261     }
5262 
5263     assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
5264             (!cur->is_young() && cur->young_index_in_cset() == -1),
5265             "invariant" );
5266 
5267     if (!cur->evacuation_failed()) {
5268       // And the region is empty.
5269       assert(!cur->is_empty(), "Should not have empty regions in a CS.");
5270       free_region(cur, &pre_used, &local_free_list, false /* par */);
5271     } else {
5272       cur->uninstall_surv_rate_group();
5273       if (cur->is_young())
5274         cur->set_young_index_in_cset(-1);
5275       cur->set_not_young();
5276       cur->set_evacuation_failed(false);
5277     }
5278     cur = next;
5279   }
5280 
5281   policy->record_max_rs_lengths(rs_lengths);
5282   policy->cset_regions_freed();
5283 
5284   double end_sec = os::elapsedTime();
5285   double elapsed_ms = (end_sec - start_sec) * 1000.0;
5286   if (non_young)
5287     non_young_time_ms += elapsed_ms;
5288   else
5289     young_time_ms += elapsed_ms;
5290 
5291   update_sets_after_freeing_regions(pre_used, &local_free_list,
5292                                     NULL /* humongous_proxy_set */,
5293                                     false /* par */);
5294   policy->record_young_free_cset_time_ms(young_time_ms);
5295   policy->record_non_young_free_cset_time_ms(non_young_time_ms);
5296 }
5297 
5298 // This routine is similar to the above but does not record
5299 // any policy statistics or update free lists; we are abandoning
5300 // the current incremental collection set in preparation of a
5301 // full collection. After the full GC we will start to build up
5302 // the incremental collection set again.
5303 // This is only called when we're doing a full collection
5304 // and is immediately followed by the tearing down of the young list.
5305 
5306 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
5307   HeapRegion* cur = cs_head;
5308 
5309   while (cur != NULL) {
5310     HeapRegion* next = cur->next_in_collection_set();
5311     assert(cur->in_collection_set(), "bad CS");
5312     cur->set_next_in_collection_set(NULL);
5313     cur->set_in_collection_set(false);
5314     cur->set_young_index_in_cset(-1);
5315     cur = next;
5316   }
5317 }
5318 
5319 void G1CollectedHeap::set_free_regions_coming() {
5320   if (G1ConcRegionFreeingVerbose) {
5321     gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
5322                            "setting free regions coming");
5323   }
5324 
5325   assert(!free_regions_coming(), "pre-condition");
5326   _free_regions_coming = true;
5327 }
5328 
5329 void G1CollectedHeap::reset_free_regions_coming() {
5330   {
5331     assert(free_regions_coming(), "pre-condition");
5332     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5333     _free_regions_coming = false;
5334     SecondaryFreeList_lock->notify_all();
5335   }
5336 
5337   if (G1ConcRegionFreeingVerbose) {
5338     gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
5339                            "reset free regions coming");
5340   }
5341 }
5342 
5343 void G1CollectedHeap::wait_while_free_regions_coming() {
5344   // Most of the time we won't have to wait, so let's do a quick test
5345   // first before we take the lock.
5346   if (!free_regions_coming()) {
5347     return;
5348   }
5349 
5350   if (G1ConcRegionFreeingVerbose) {
5351     gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
5352                            "waiting for free regions");
5353   }
5354 
5355   {
5356     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5357     while (free_regions_coming()) {
5358       SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
5359     }
5360   }
5361 
5362   if (G1ConcRegionFreeingVerbose) {
5363     gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
5364                            "done waiting for free regions");
5365   }
5366 }
5367 
5368 size_t G1CollectedHeap::n_regions() {
5369   return _hrs->length();
5370 }
5371 
5372 size_t G1CollectedHeap::max_regions() {
5373   return
5374     (size_t)align_size_up(max_capacity(), HeapRegion::GrainBytes) /
5375     HeapRegion::GrainBytes;
5376 }
5377 
5378 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
5379   assert(heap_lock_held_for_gc(),
5380               "the heap lock should already be held by or for this thread");
5381   _young_list->push_region(hr);
5382   g1_policy()->set_region_short_lived(hr);
5383 }
5384 
5385 class NoYoungRegionsClosure: public HeapRegionClosure {
5386 private:
5387   bool _success;
5388 public:
5389   NoYoungRegionsClosure() : _success(true) { }
5390   bool doHeapRegion(HeapRegion* r) {
5391     if (r->is_young()) {
5392       gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
5393                              r->bottom(), r->end());
5394       _success = false;
5395     }
5396     return false;
5397   }
5398   bool success() { return _success; }
5399 };
5400 
5401 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
5402   bool ret = _young_list->check_list_empty(check_sample);
5403 
5404   if (check_heap) {
5405     NoYoungRegionsClosure closure;
5406     heap_region_iterate(&closure);
5407     ret = ret && closure.success();
5408   }
5409 
5410   return ret;
5411 }
5412 
5413 void G1CollectedHeap::empty_young_list() {
5414   assert(heap_lock_held_for_gc(),
5415               "the heap lock should already be held by or for this thread");
5416   assert(g1_policy()->in_young_gc_mode(), "should be in young GC mode");
5417 
5418   _young_list->empty_list();
5419 }
5420 
5421 bool G1CollectedHeap::all_alloc_regions_no_allocs_since_save_marks() {
5422   bool no_allocs = true;
5423   for (int ap = 0; ap < GCAllocPurposeCount && no_allocs; ++ap) {
5424     HeapRegion* r = _gc_alloc_regions[ap];
5425     no_allocs = r == NULL || r->saved_mark_at_top();
5426   }
5427   return no_allocs;
5428 }
5429 
5430 void G1CollectedHeap::retire_all_alloc_regions() {
5431   for (int ap = 0; ap < GCAllocPurposeCount; ++ap) {
5432     HeapRegion* r = _gc_alloc_regions[ap];
5433     if (r != NULL) {
5434       // Check for aliases.
5435       bool has_processed_alias = false;
5436       for (int i = 0; i < ap; ++i) {
5437         if (_gc_alloc_regions[i] == r) {
5438           has_processed_alias = true;
5439           break;
5440         }
5441       }
5442       if (!has_processed_alias) {
5443         retire_alloc_region(r, false /* par */);
5444       }
5445     }
5446   }
5447 }
5448 
5449 // Done at the start of full GC.
5450 void G1CollectedHeap::tear_down_region_lists() {
5451   _free_list.remove_all();
5452 }
5453 
5454 class RegionResetter: public HeapRegionClosure {
5455   G1CollectedHeap* _g1h;
5456   FreeRegionList _local_free_list;
5457 
5458 public:
5459   RegionResetter() : _g1h(G1CollectedHeap::heap()),
5460                      _local_free_list("Local Free List for RegionResetter") { }
5461 
5462   bool doHeapRegion(HeapRegion* r) {
5463     if (r->continuesHumongous()) return false;
5464     if (r->top() > r->bottom()) {
5465       if (r->top() < r->end()) {
5466         Copy::fill_to_words(r->top(),
5467                           pointer_delta(r->end(), r->top()));
5468       }
5469     } else {
5470       assert(r->is_empty(), "tautology");
5471       _local_free_list.add_as_tail(r);
5472     }
5473     return false;
5474   }
5475 
5476   void update_free_lists() {
5477     _g1h->update_sets_after_freeing_regions(0, &_local_free_list, NULL,
5478                                             false /* par */);
5479   }
5480 };
5481 
5482 // Done at the end of full GC.
5483 void G1CollectedHeap::rebuild_region_lists() {
5484   // This needs to go at the end of the full GC.
5485   RegionResetter rs;
5486   heap_region_iterate(&rs);
5487   rs.update_free_lists();
5488 }
5489 
5490 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
5491   _refine_cte_cl->set_concurrent(concurrent);
5492 }
5493 
5494 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
5495   HeapRegion* hr = heap_region_containing(p);
5496   if (hr == NULL) {
5497     return is_in_permanent(p);
5498   } else {
5499     return hr->is_in(p);
5500   }
5501 }
5502 
5503 class VerifyRegionListsClosure : public HeapRegionClosure {
5504 private:
5505   HumongousRegionSet* _humongous_set;
5506   FreeRegionList*     _free_list;
5507   size_t              _region_count;
5508 
5509 public:
5510   VerifyRegionListsClosure(HumongousRegionSet* humongous_set,
5511                            FreeRegionList* free_list) :
5512     _humongous_set(humongous_set), _free_list(free_list),
5513     _region_count(0) { }
5514 
5515   size_t region_count()      { return _region_count;      }
5516 
5517   bool doHeapRegion(HeapRegion* hr) {
5518     _region_count += 1;
5519 
5520     if (hr->continuesHumongous()) {
5521       return false;
5522     }
5523 
5524     if (hr->is_young()) {
5525       // TODO
5526     } else if (hr->startsHumongous()) {
5527       _humongous_set->verify_next_region(hr);
5528     } else if (hr->is_empty()) {
5529       _free_list->verify_next_region(hr);
5530     }
5531     return false;
5532   }
5533 };
5534 
5535 void G1CollectedHeap::verify_region_sets() {
5536   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5537 
5538   // First, check the explicit lists.
5539   _free_list.verify();
5540   {
5541     // Given that a concurrent operation might be adding regions to
5542     // the secondary free list we have to take the lock before
5543     // verifying it.
5544     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5545     _secondary_free_list.verify();
5546   }
5547   _humongous_set.verify();
5548 
5549   // If a concurrent region freeing operation is in progress it will
5550   // be difficult to correctly attributed any free regions we come
5551   // across to the correct free list given that they might belong to
5552   // one of several (free_list, secondary_free_list, any local lists,
5553   // etc.). So, if that's the case we will skip the rest of the
5554   // verification operation. Alternatively, waiting for the concurrent
5555   // operation to complete will have a non-trivial effect on the GC's
5556   // operation (no concurrent operation will last longer than the
5557   // interval between two calls to verification) and it might hide
5558   // any issues that we would like to catch during testing.
5559   if (free_regions_coming()) {
5560     return;
5561   }
5562 
5563   // Make sure we append the secondary_free_list on the free_list so
5564   // that all free regions we will come across can be safely
5565   // attributed to the free_list.
5566   append_secondary_free_list_if_not_empty_with_lock();
5567 
5568   // Finally, make sure that the region accounting in the lists is
5569   // consistent with what we see in the heap.
5570   _humongous_set.verify_start();
5571   _free_list.verify_start();
5572 
5573   VerifyRegionListsClosure cl(&_humongous_set, &_free_list);
5574   heap_region_iterate(&cl);
5575 
5576   _humongous_set.verify_end();
5577   _free_list.verify_end();
5578 }