rev 3484 : 7178363: G1: Remove the serial code for PrintGCDetails and make it a special case of the parallel code
Summary: Introduced the WorkerDataArray class.
Reviewed-by: mgerdin

   1 /*
   2  * Copyright (c) 2001, 2012, 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/g1AllocRegion.inline.hpp"
  32 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
  33 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
  34 #include "gc_implementation/g1/g1ErgoVerbose.hpp"
  35 #include "gc_implementation/g1/g1EvacFailure.hpp"
  36 #include "gc_implementation/g1/g1GCPhaseTimes.hpp"
  37 #include "gc_implementation/g1/g1Log.hpp"
  38 #include "gc_implementation/g1/g1MarkSweep.hpp"
  39 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
  40 #include "gc_implementation/g1/g1RemSet.inline.hpp"
  41 #include "gc_implementation/g1/heapRegion.inline.hpp"
  42 #include "gc_implementation/g1/heapRegionRemSet.hpp"
  43 #include "gc_implementation/g1/heapRegionSeq.inline.hpp"
  44 #include "gc_implementation/g1/vm_operations_g1.hpp"
  45 #include "gc_implementation/shared/isGCActiveMark.hpp"
  46 #include "memory/gcLocker.inline.hpp"
  47 #include "memory/genOopClosures.inline.hpp"
  48 #include "memory/generationSpec.hpp"
  49 #include "memory/referenceProcessor.hpp"
  50 #include "oops/oop.inline.hpp"
  51 #include "oops/oop.pcgc.inline.hpp"
  52 #include "runtime/aprofiler.hpp"
  53 #include "runtime/vmThread.hpp"
  54 
  55 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
  56 
  57 // turn it on so that the contents of the young list (scan-only /
  58 // to-be-collected) are printed at "strategic" points before / during
  59 // / after the collection --- this is useful for debugging
  60 #define YOUNG_LIST_VERBOSE 0
  61 // CURRENT STATUS
  62 // This file is under construction.  Search for "FIXME".
  63 
  64 // INVARIANTS/NOTES
  65 //
  66 // All allocation activity covered by the G1CollectedHeap interface is
  67 // serialized by acquiring the HeapLock.  This happens in mem_allocate
  68 // and allocate_new_tlab, which are the "entry" points to the
  69 // allocation code from the rest of the JVM.  (Note that this does not
  70 // apply to TLAB allocation, which is not part of this interface: it
  71 // is done by clients of this interface.)
  72 
  73 // Notes on implementation of parallelism in different tasks.
  74 //
  75 // G1ParVerifyTask uses heap_region_par_iterate_chunked() for parallelism.
  76 // The number of GC workers is passed to heap_region_par_iterate_chunked().
  77 // It does use run_task() which sets _n_workers in the task.
  78 // G1ParTask executes g1_process_strong_roots() ->
  79 // SharedHeap::process_strong_roots() which calls eventuall to
  80 // CardTableModRefBS::par_non_clean_card_iterate_work() which uses
  81 // SequentialSubTasksDone.  SharedHeap::process_strong_roots() also
  82 // directly uses SubTasksDone (_process_strong_tasks field in SharedHeap).
  83 //
  84 
  85 // Local to this file.
  86 
  87 class RefineCardTableEntryClosure: public CardTableEntryClosure {
  88   SuspendibleThreadSet* _sts;
  89   G1RemSet* _g1rs;
  90   ConcurrentG1Refine* _cg1r;
  91   bool _concurrent;
  92 public:
  93   RefineCardTableEntryClosure(SuspendibleThreadSet* sts,
  94                               G1RemSet* g1rs,
  95                               ConcurrentG1Refine* cg1r) :
  96     _sts(sts), _g1rs(g1rs), _cg1r(cg1r), _concurrent(true)
  97   {}
  98   bool do_card_ptr(jbyte* card_ptr, int worker_i) {
  99     bool oops_into_cset = _g1rs->concurrentRefineOneCard(card_ptr, worker_i, false);
 100     // This path is executed by the concurrent refine or mutator threads,
 101     // concurrently, and so we do not care if card_ptr contains references
 102     // that point into the collection set.
 103     assert(!oops_into_cset, "should be");
 104 
 105     if (_concurrent && _sts->should_yield()) {
 106       // Caller will actually yield.
 107       return false;
 108     }
 109     // Otherwise, we finished successfully; return true.
 110     return true;
 111   }
 112   void set_concurrent(bool b) { _concurrent = b; }
 113 };
 114 
 115 
 116 class ClearLoggedCardTableEntryClosure: public CardTableEntryClosure {
 117   int _calls;
 118   G1CollectedHeap* _g1h;
 119   CardTableModRefBS* _ctbs;
 120   int _histo[256];
 121 public:
 122   ClearLoggedCardTableEntryClosure() :
 123     _calls(0)
 124   {
 125     _g1h = G1CollectedHeap::heap();
 126     _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
 127     for (int i = 0; i < 256; i++) _histo[i] = 0;
 128   }
 129   bool do_card_ptr(jbyte* card_ptr, int worker_i) {
 130     if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
 131       _calls++;
 132       unsigned char* ujb = (unsigned char*)card_ptr;
 133       int ind = (int)(*ujb);
 134       _histo[ind]++;
 135       *card_ptr = -1;
 136     }
 137     return true;
 138   }
 139   int calls() { return _calls; }
 140   void print_histo() {
 141     gclog_or_tty->print_cr("Card table value histogram:");
 142     for (int i = 0; i < 256; i++) {
 143       if (_histo[i] != 0) {
 144         gclog_or_tty->print_cr("  %d: %d", i, _histo[i]);
 145       }
 146     }
 147   }
 148 };
 149 
 150 class RedirtyLoggedCardTableEntryClosure: public CardTableEntryClosure {
 151   int _calls;
 152   G1CollectedHeap* _g1h;
 153   CardTableModRefBS* _ctbs;
 154 public:
 155   RedirtyLoggedCardTableEntryClosure() :
 156     _calls(0)
 157   {
 158     _g1h = G1CollectedHeap::heap();
 159     _ctbs = (CardTableModRefBS*)_g1h->barrier_set();
 160   }
 161   bool do_card_ptr(jbyte* card_ptr, int worker_i) {
 162     if (_g1h->is_in_reserved(_ctbs->addr_for(card_ptr))) {
 163       _calls++;
 164       *card_ptr = 0;
 165     }
 166     return true;
 167   }
 168   int calls() { return _calls; }
 169 };
 170 
 171 class RedirtyLoggedCardTableEntryFastClosure : public CardTableEntryClosure {
 172 public:
 173   bool do_card_ptr(jbyte* card_ptr, int worker_i) {
 174     *card_ptr = CardTableModRefBS::dirty_card_val();
 175     return true;
 176   }
 177 };
 178 
 179 YoungList::YoungList(G1CollectedHeap* g1h) :
 180     _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0),
 181     _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) {
 182   guarantee(check_list_empty(false), "just making sure...");
 183 }
 184 
 185 void YoungList::push_region(HeapRegion *hr) {
 186   assert(!hr->is_young(), "should not already be young");
 187   assert(hr->get_next_young_region() == NULL, "cause it should!");
 188 
 189   hr->set_next_young_region(_head);
 190   _head = hr;
 191 
 192   _g1h->g1_policy()->set_region_eden(hr, (int) _length);
 193   ++_length;
 194 }
 195 
 196 void YoungList::add_survivor_region(HeapRegion* hr) {
 197   assert(hr->is_survivor(), "should be flagged as survivor region");
 198   assert(hr->get_next_young_region() == NULL, "cause it should!");
 199 
 200   hr->set_next_young_region(_survivor_head);
 201   if (_survivor_head == NULL) {
 202     _survivor_tail = hr;
 203   }
 204   _survivor_head = hr;
 205   ++_survivor_length;
 206 }
 207 
 208 void YoungList::empty_list(HeapRegion* list) {
 209   while (list != NULL) {
 210     HeapRegion* next = list->get_next_young_region();
 211     list->set_next_young_region(NULL);
 212     list->uninstall_surv_rate_group();
 213     list->set_not_young();
 214     list = next;
 215   }
 216 }
 217 
 218 void YoungList::empty_list() {
 219   assert(check_list_well_formed(), "young list should be well formed");
 220 
 221   empty_list(_head);
 222   _head = NULL;
 223   _length = 0;
 224 
 225   empty_list(_survivor_head);
 226   _survivor_head = NULL;
 227   _survivor_tail = NULL;
 228   _survivor_length = 0;
 229 
 230   _last_sampled_rs_lengths = 0;
 231 
 232   assert(check_list_empty(false), "just making sure...");
 233 }
 234 
 235 bool YoungList::check_list_well_formed() {
 236   bool ret = true;
 237 
 238   uint length = 0;
 239   HeapRegion* curr = _head;
 240   HeapRegion* last = NULL;
 241   while (curr != NULL) {
 242     if (!curr->is_young()) {
 243       gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
 244                              "incorrectly tagged (y: %d, surv: %d)",
 245                              curr->bottom(), curr->end(),
 246                              curr->is_young(), curr->is_survivor());
 247       ret = false;
 248     }
 249     ++length;
 250     last = curr;
 251     curr = curr->get_next_young_region();
 252   }
 253   ret = ret && (length == _length);
 254 
 255   if (!ret) {
 256     gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
 257     gclog_or_tty->print_cr("###   list has %u entries, _length is %u",
 258                            length, _length);
 259   }
 260 
 261   return ret;
 262 }
 263 
 264 bool YoungList::check_list_empty(bool check_sample) {
 265   bool ret = true;
 266 
 267   if (_length != 0) {
 268     gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u",
 269                   _length);
 270     ret = false;
 271   }
 272   if (check_sample && _last_sampled_rs_lengths != 0) {
 273     gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
 274     ret = false;
 275   }
 276   if (_head != NULL) {
 277     gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
 278     ret = false;
 279   }
 280   if (!ret) {
 281     gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
 282   }
 283 
 284   return ret;
 285 }
 286 
 287 void
 288 YoungList::rs_length_sampling_init() {
 289   _sampled_rs_lengths = 0;
 290   _curr               = _head;
 291 }
 292 
 293 bool
 294 YoungList::rs_length_sampling_more() {
 295   return _curr != NULL;
 296 }
 297 
 298 void
 299 YoungList::rs_length_sampling_next() {
 300   assert( _curr != NULL, "invariant" );
 301   size_t rs_length = _curr->rem_set()->occupied();
 302 
 303   _sampled_rs_lengths += rs_length;
 304 
 305   // The current region may not yet have been added to the
 306   // incremental collection set (it gets added when it is
 307   // retired as the current allocation region).
 308   if (_curr->in_collection_set()) {
 309     // Update the collection set policy information for this region
 310     _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
 311   }
 312 
 313   _curr = _curr->get_next_young_region();
 314   if (_curr == NULL) {
 315     _last_sampled_rs_lengths = _sampled_rs_lengths;
 316     // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
 317   }
 318 }
 319 
 320 void
 321 YoungList::reset_auxilary_lists() {
 322   guarantee( is_empty(), "young list should be empty" );
 323   assert(check_list_well_formed(), "young list should be well formed");
 324 
 325   // Add survivor regions to SurvRateGroup.
 326   _g1h->g1_policy()->note_start_adding_survivor_regions();
 327   _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
 328 
 329   int young_index_in_cset = 0;
 330   for (HeapRegion* curr = _survivor_head;
 331        curr != NULL;
 332        curr = curr->get_next_young_region()) {
 333     _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
 334 
 335     // The region is a non-empty survivor so let's add it to
 336     // the incremental collection set for the next evacuation
 337     // pause.
 338     _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
 339     young_index_in_cset += 1;
 340   }
 341   assert((uint) young_index_in_cset == _survivor_length, "post-condition");
 342   _g1h->g1_policy()->note_stop_adding_survivor_regions();
 343 
 344   _head   = _survivor_head;
 345   _length = _survivor_length;
 346   if (_survivor_head != NULL) {
 347     assert(_survivor_tail != NULL, "cause it shouldn't be");
 348     assert(_survivor_length > 0, "invariant");
 349     _survivor_tail->set_next_young_region(NULL);
 350   }
 351 
 352   // Don't clear the survivor list handles until the start of
 353   // the next evacuation pause - we need it in order to re-tag
 354   // the survivor regions from this evacuation pause as 'young'
 355   // at the start of the next.
 356 
 357   _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
 358 
 359   assert(check_list_well_formed(), "young list should be well formed");
 360 }
 361 
 362 void YoungList::print() {
 363   HeapRegion* lists[] = {_head,   _survivor_head};
 364   const char* names[] = {"YOUNG", "SURVIVOR"};
 365 
 366   for (unsigned int list = 0; list < ARRAY_SIZE(lists); ++list) {
 367     gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
 368     HeapRegion *curr = lists[list];
 369     if (curr == NULL)
 370       gclog_or_tty->print_cr("  empty");
 371     while (curr != NULL) {
 372       gclog_or_tty->print_cr("  "HR_FORMAT", P: "PTR_FORMAT "N: "PTR_FORMAT", age: %4d",
 373                              HR_FORMAT_PARAMS(curr),
 374                              curr->prev_top_at_mark_start(),
 375                              curr->next_top_at_mark_start(),
 376                              curr->age_in_surv_rate_group_cond());
 377       curr = curr->get_next_young_region();
 378     }
 379   }
 380 
 381   gclog_or_tty->print_cr("");
 382 }
 383 
 384 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
 385 {
 386   // Claim the right to put the region on the dirty cards region list
 387   // by installing a self pointer.
 388   HeapRegion* next = hr->get_next_dirty_cards_region();
 389   if (next == NULL) {
 390     HeapRegion* res = (HeapRegion*)
 391       Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
 392                           NULL);
 393     if (res == NULL) {
 394       HeapRegion* head;
 395       do {
 396         // Put the region to the dirty cards region list.
 397         head = _dirty_cards_region_list;
 398         next = (HeapRegion*)
 399           Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
 400         if (next == head) {
 401           assert(hr->get_next_dirty_cards_region() == hr,
 402                  "hr->get_next_dirty_cards_region() != hr");
 403           if (next == NULL) {
 404             // The last region in the list points to itself.
 405             hr->set_next_dirty_cards_region(hr);
 406           } else {
 407             hr->set_next_dirty_cards_region(next);
 408           }
 409         }
 410       } while (next != head);
 411     }
 412   }
 413 }
 414 
 415 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
 416 {
 417   HeapRegion* head;
 418   HeapRegion* hr;
 419   do {
 420     head = _dirty_cards_region_list;
 421     if (head == NULL) {
 422       return NULL;
 423     }
 424     HeapRegion* new_head = head->get_next_dirty_cards_region();
 425     if (head == new_head) {
 426       // The last region.
 427       new_head = NULL;
 428     }
 429     hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
 430                                           head);
 431   } while (hr != head);
 432   assert(hr != NULL, "invariant");
 433   hr->set_next_dirty_cards_region(NULL);
 434   return hr;
 435 }
 436 
 437 void G1CollectedHeap::stop_conc_gc_threads() {
 438   _cg1r->stop();
 439   _cmThread->stop();
 440 }
 441 
 442 #ifdef ASSERT
 443 // A region is added to the collection set as it is retired
 444 // so an address p can point to a region which will be in the
 445 // collection set but has not yet been retired.  This method
 446 // therefore is only accurate during a GC pause after all
 447 // regions have been retired.  It is used for debugging
 448 // to check if an nmethod has references to objects that can
 449 // be move during a partial collection.  Though it can be
 450 // inaccurate, it is sufficient for G1 because the conservative
 451 // implementation of is_scavengable() for G1 will indicate that
 452 // all nmethods must be scanned during a partial collection.
 453 bool G1CollectedHeap::is_in_partial_collection(const void* p) {
 454   HeapRegion* hr = heap_region_containing(p);
 455   return hr != NULL && hr->in_collection_set();
 456 }
 457 #endif
 458 
 459 // Returns true if the reference points to an object that
 460 // can move in an incremental collecction.
 461 bool G1CollectedHeap::is_scavengable(const void* p) {
 462   G1CollectedHeap* g1h = G1CollectedHeap::heap();
 463   G1CollectorPolicy* g1p = g1h->g1_policy();
 464   HeapRegion* hr = heap_region_containing(p);
 465   if (hr == NULL) {
 466      // perm gen (or null)
 467      return false;
 468   } else {
 469     return !hr->isHumongous();
 470   }
 471 }
 472 
 473 void G1CollectedHeap::check_ct_logs_at_safepoint() {
 474   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
 475   CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
 476 
 477   // Count the dirty cards at the start.
 478   CountNonCleanMemRegionClosure count1(this);
 479   ct_bs->mod_card_iterate(&count1);
 480   int orig_count = count1.n();
 481 
 482   // First clear the logged cards.
 483   ClearLoggedCardTableEntryClosure clear;
 484   dcqs.set_closure(&clear);
 485   dcqs.apply_closure_to_all_completed_buffers();
 486   dcqs.iterate_closure_all_threads(false);
 487   clear.print_histo();
 488 
 489   // Now ensure that there's no dirty cards.
 490   CountNonCleanMemRegionClosure count2(this);
 491   ct_bs->mod_card_iterate(&count2);
 492   if (count2.n() != 0) {
 493     gclog_or_tty->print_cr("Card table has %d entries; %d originally",
 494                            count2.n(), orig_count);
 495   }
 496   guarantee(count2.n() == 0, "Card table should be clean.");
 497 
 498   RedirtyLoggedCardTableEntryClosure redirty;
 499   JavaThread::dirty_card_queue_set().set_closure(&redirty);
 500   dcqs.apply_closure_to_all_completed_buffers();
 501   dcqs.iterate_closure_all_threads(false);
 502   gclog_or_tty->print_cr("Log entries = %d, dirty cards = %d.",
 503                          clear.calls(), orig_count);
 504   guarantee(redirty.calls() == clear.calls(),
 505             "Or else mechanism is broken.");
 506 
 507   CountNonCleanMemRegionClosure count3(this);
 508   ct_bs->mod_card_iterate(&count3);
 509   if (count3.n() != orig_count) {
 510     gclog_or_tty->print_cr("Should have restored them all: orig = %d, final = %d.",
 511                            orig_count, count3.n());
 512     guarantee(count3.n() >= orig_count, "Should have restored them all.");
 513   }
 514 
 515   JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
 516 }
 517 
 518 // Private class members.
 519 
 520 G1CollectedHeap* G1CollectedHeap::_g1h;
 521 
 522 // Private methods.
 523 
 524 HeapRegion*
 525 G1CollectedHeap::new_region_try_secondary_free_list() {
 526   MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
 527   while (!_secondary_free_list.is_empty() || free_regions_coming()) {
 528     if (!_secondary_free_list.is_empty()) {
 529       if (G1ConcRegionFreeingVerbose) {
 530         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 531                                "secondary_free_list has %u entries",
 532                                _secondary_free_list.length());
 533       }
 534       // It looks as if there are free regions available on the
 535       // secondary_free_list. Let's move them to the free_list and try
 536       // again to allocate from it.
 537       append_secondary_free_list();
 538 
 539       assert(!_free_list.is_empty(), "if the secondary_free_list was not "
 540              "empty we should have moved at least one entry to the free_list");
 541       HeapRegion* res = _free_list.remove_head();
 542       if (G1ConcRegionFreeingVerbose) {
 543         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 544                                "allocated "HR_FORMAT" from secondary_free_list",
 545                                HR_FORMAT_PARAMS(res));
 546       }
 547       return res;
 548     }
 549 
 550     // Wait here until we get notifed either when (a) there are no
 551     // more free regions coming or (b) some regions have been moved on
 552     // the secondary_free_list.
 553     SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
 554   }
 555 
 556   if (G1ConcRegionFreeingVerbose) {
 557     gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 558                            "could not allocate from secondary_free_list");
 559   }
 560   return NULL;
 561 }
 562 
 563 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool do_expand) {
 564   assert(!isHumongous(word_size) || word_size <= HeapRegion::GrainWords,
 565          "the only time we use this to allocate a humongous region is "
 566          "when we are allocating a single humongous region");
 567 
 568   HeapRegion* res;
 569   if (G1StressConcRegionFreeing) {
 570     if (!_secondary_free_list.is_empty()) {
 571       if (G1ConcRegionFreeingVerbose) {
 572         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 573                                "forced to look at the secondary_free_list");
 574       }
 575       res = new_region_try_secondary_free_list();
 576       if (res != NULL) {
 577         return res;
 578       }
 579     }
 580   }
 581   res = _free_list.remove_head_or_null();
 582   if (res == NULL) {
 583     if (G1ConcRegionFreeingVerbose) {
 584       gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 585                              "res == NULL, trying the secondary_free_list");
 586     }
 587     res = new_region_try_secondary_free_list();
 588   }
 589   if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
 590     // Currently, only attempts to allocate GC alloc regions set
 591     // do_expand to true. So, we should only reach here during a
 592     // safepoint. If this assumption changes we might have to
 593     // reconsider the use of _expand_heap_after_alloc_failure.
 594     assert(SafepointSynchronize::is_at_safepoint(), "invariant");
 595 
 596     ergo_verbose1(ErgoHeapSizing,
 597                   "attempt heap expansion",
 598                   ergo_format_reason("region allocation request failed")
 599                   ergo_format_byte("allocation request"),
 600                   word_size * HeapWordSize);
 601     if (expand(word_size * HeapWordSize)) {
 602       // Given that expand() succeeded in expanding the heap, and we
 603       // always expand the heap by an amount aligned to the heap
 604       // region size, the free list should in theory not be empty. So
 605       // it would probably be OK to use remove_head(). But the extra
 606       // check for NULL is unlikely to be a performance issue here (we
 607       // just expanded the heap!) so let's just be conservative and
 608       // use remove_head_or_null().
 609       res = _free_list.remove_head_or_null();
 610     } else {
 611       _expand_heap_after_alloc_failure = false;
 612     }
 613   }
 614   return res;
 615 }
 616 
 617 uint G1CollectedHeap::humongous_obj_allocate_find_first(uint num_regions,
 618                                                         size_t word_size) {
 619   assert(isHumongous(word_size), "word_size should be humongous");
 620   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 621 
 622   uint first = G1_NULL_HRS_INDEX;
 623   if (num_regions == 1) {
 624     // Only one region to allocate, no need to go through the slower
 625     // path. The caller will attempt the expasion if this fails, so
 626     // let's not try to expand here too.
 627     HeapRegion* hr = new_region(word_size, false /* do_expand */);
 628     if (hr != NULL) {
 629       first = hr->hrs_index();
 630     } else {
 631       first = G1_NULL_HRS_INDEX;
 632     }
 633   } else {
 634     // We can't allocate humongous regions while cleanupComplete() is
 635     // running, since some of the regions we find to be empty might not
 636     // yet be added to the free list and it is not straightforward to
 637     // know which list they are on so that we can remove them. Note
 638     // that we only need to do this if we need to allocate more than
 639     // one region to satisfy the current humongous allocation
 640     // request. If we are only allocating one region we use the common
 641     // region allocation code (see above).
 642     wait_while_free_regions_coming();
 643     append_secondary_free_list_if_not_empty_with_lock();
 644 
 645     if (free_regions() >= num_regions) {
 646       first = _hrs.find_contiguous(num_regions);
 647       if (first != G1_NULL_HRS_INDEX) {
 648         for (uint i = first; i < first + num_regions; ++i) {
 649           HeapRegion* hr = region_at(i);
 650           assert(hr->is_empty(), "sanity");
 651           assert(is_on_master_free_list(hr), "sanity");
 652           hr->set_pending_removal(true);
 653         }
 654         _free_list.remove_all_pending(num_regions);
 655       }
 656     }
 657   }
 658   return first;
 659 }
 660 
 661 HeapWord*
 662 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
 663                                                            uint num_regions,
 664                                                            size_t word_size) {
 665   assert(first != G1_NULL_HRS_INDEX, "pre-condition");
 666   assert(isHumongous(word_size), "word_size should be humongous");
 667   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 668 
 669   // Index of last region in the series + 1.
 670   uint last = first + num_regions;
 671 
 672   // We need to initialize the region(s) we just discovered. This is
 673   // a bit tricky given that it can happen concurrently with
 674   // refinement threads refining cards on these regions and
 675   // potentially wanting to refine the BOT as they are scanning
 676   // those cards (this can happen shortly after a cleanup; see CR
 677   // 6991377). So we have to set up the region(s) carefully and in
 678   // a specific order.
 679 
 680   // The word size sum of all the regions we will allocate.
 681   size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
 682   assert(word_size <= word_size_sum, "sanity");
 683 
 684   // This will be the "starts humongous" region.
 685   HeapRegion* first_hr = region_at(first);
 686   // The header of the new object will be placed at the bottom of
 687   // the first region.
 688   HeapWord* new_obj = first_hr->bottom();
 689   // This will be the new end of the first region in the series that
 690   // should also match the end of the last region in the seriers.
 691   HeapWord* new_end = new_obj + word_size_sum;
 692   // This will be the new top of the first region that will reflect
 693   // this allocation.
 694   HeapWord* new_top = new_obj + word_size;
 695 
 696   // First, we need to zero the header of the space that we will be
 697   // allocating. When we update top further down, some refinement
 698   // threads might try to scan the region. By zeroing the header we
 699   // ensure that any thread that will try to scan the region will
 700   // come across the zero klass word and bail out.
 701   //
 702   // NOTE: It would not have been correct to have used
 703   // CollectedHeap::fill_with_object() and make the space look like
 704   // an int array. The thread that is doing the allocation will
 705   // later update the object header to a potentially different array
 706   // type and, for a very short period of time, the klass and length
 707   // fields will be inconsistent. This could cause a refinement
 708   // thread to calculate the object size incorrectly.
 709   Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
 710 
 711   // We will set up the first region as "starts humongous". This
 712   // will also update the BOT covering all the regions to reflect
 713   // that there is a single object that starts at the bottom of the
 714   // first region.
 715   first_hr->set_startsHumongous(new_top, new_end);
 716 
 717   // Then, if there are any, we will set up the "continues
 718   // humongous" regions.
 719   HeapRegion* hr = NULL;
 720   for (uint i = first + 1; i < last; ++i) {
 721     hr = region_at(i);
 722     hr->set_continuesHumongous(first_hr);
 723   }
 724   // If we have "continues humongous" regions (hr != NULL), then the
 725   // end of the last one should match new_end.
 726   assert(hr == NULL || hr->end() == new_end, "sanity");
 727 
 728   // Up to this point no concurrent thread would have been able to
 729   // do any scanning on any region in this series. All the top
 730   // fields still point to bottom, so the intersection between
 731   // [bottom,top] and [card_start,card_end] will be empty. Before we
 732   // update the top fields, we'll do a storestore to make sure that
 733   // no thread sees the update to top before the zeroing of the
 734   // object header and the BOT initialization.
 735   OrderAccess::storestore();
 736 
 737   // Now that the BOT and the object header have been initialized,
 738   // we can update top of the "starts humongous" region.
 739   assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
 740          "new_top should be in this region");
 741   first_hr->set_top(new_top);
 742   if (_hr_printer.is_active()) {
 743     HeapWord* bottom = first_hr->bottom();
 744     HeapWord* end = first_hr->orig_end();
 745     if ((first + 1) == last) {
 746       // the series has a single humongous region
 747       _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
 748     } else {
 749       // the series has more than one humongous regions
 750       _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
 751     }
 752   }
 753 
 754   // Now, we will update the top fields of the "continues humongous"
 755   // regions. The reason we need to do this is that, otherwise,
 756   // these regions would look empty and this will confuse parts of
 757   // G1. For example, the code that looks for a consecutive number
 758   // of empty regions will consider them empty and try to
 759   // re-allocate them. We can extend is_empty() to also include
 760   // !continuesHumongous(), but it is easier to just update the top
 761   // fields here. The way we set top for all regions (i.e., top ==
 762   // end for all regions but the last one, top == new_top for the
 763   // last one) is actually used when we will free up the humongous
 764   // region in free_humongous_region().
 765   hr = NULL;
 766   for (uint i = first + 1; i < last; ++i) {
 767     hr = region_at(i);
 768     if ((i + 1) == last) {
 769       // last continues humongous region
 770       assert(hr->bottom() < new_top && new_top <= hr->end(),
 771              "new_top should fall on this region");
 772       hr->set_top(new_top);
 773       _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
 774     } else {
 775       // not last one
 776       assert(new_top > hr->end(), "new_top should be above this region");
 777       hr->set_top(hr->end());
 778       _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
 779     }
 780   }
 781   // If we have continues humongous regions (hr != NULL), then the
 782   // end of the last one should match new_end and its top should
 783   // match new_top.
 784   assert(hr == NULL ||
 785          (hr->end() == new_end && hr->top() == new_top), "sanity");
 786 
 787   assert(first_hr->used() == word_size * HeapWordSize, "invariant");
 788   _summary_bytes_used += first_hr->used();
 789   _humongous_set.add(first_hr);
 790 
 791   return new_obj;
 792 }
 793 
 794 // If could fit into free regions w/o expansion, try.
 795 // Otherwise, if can expand, do so.
 796 // Otherwise, if using ex regions might help, try with ex given back.
 797 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
 798   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 799 
 800   verify_region_sets_optional();
 801 
 802   size_t word_size_rounded = round_to(word_size, HeapRegion::GrainWords);
 803   uint num_regions = (uint) (word_size_rounded / HeapRegion::GrainWords);
 804   uint x_num = expansion_regions();
 805   uint fs = _hrs.free_suffix();
 806   uint first = humongous_obj_allocate_find_first(num_regions, word_size);
 807   if (first == G1_NULL_HRS_INDEX) {
 808     // The only thing we can do now is attempt expansion.
 809     if (fs + x_num >= num_regions) {
 810       // If the number of regions we're trying to allocate for this
 811       // object is at most the number of regions in the free suffix,
 812       // then the call to humongous_obj_allocate_find_first() above
 813       // should have succeeded and we wouldn't be here.
 814       //
 815       // We should only be trying to expand when the free suffix is
 816       // not sufficient for the object _and_ we have some expansion
 817       // room available.
 818       assert(num_regions > fs, "earlier allocation should have succeeded");
 819 
 820       ergo_verbose1(ErgoHeapSizing,
 821                     "attempt heap expansion",
 822                     ergo_format_reason("humongous allocation request failed")
 823                     ergo_format_byte("allocation request"),
 824                     word_size * HeapWordSize);
 825       if (expand((num_regions - fs) * HeapRegion::GrainBytes)) {
 826         // Even though the heap was expanded, it might not have
 827         // reached the desired size. So, we cannot assume that the
 828         // allocation will succeed.
 829         first = humongous_obj_allocate_find_first(num_regions, word_size);
 830       }
 831     }
 832   }
 833 
 834   HeapWord* result = NULL;
 835   if (first != G1_NULL_HRS_INDEX) {
 836     result =
 837       humongous_obj_allocate_initialize_regions(first, num_regions, word_size);
 838     assert(result != NULL, "it should always return a valid result");
 839 
 840     // A successful humongous object allocation changes the used space
 841     // information of the old generation so we need to recalculate the
 842     // sizes and update the jstat counters here.
 843     g1mm()->update_sizes();
 844   }
 845 
 846   verify_region_sets_optional();
 847 
 848   return result;
 849 }
 850 
 851 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
 852   assert_heap_not_locked_and_not_at_safepoint();
 853   assert(!isHumongous(word_size), "we do not allow humongous TLABs");
 854 
 855   unsigned int dummy_gc_count_before;
 856   return attempt_allocation(word_size, &dummy_gc_count_before);
 857 }
 858 
 859 HeapWord*
 860 G1CollectedHeap::mem_allocate(size_t word_size,
 861                               bool*  gc_overhead_limit_was_exceeded) {
 862   assert_heap_not_locked_and_not_at_safepoint();
 863 
 864   // Loop until the allocation is satisified, or unsatisfied after GC.
 865   for (int try_count = 1; /* we'll return */; try_count += 1) {
 866     unsigned int gc_count_before;
 867 
 868     HeapWord* result = NULL;
 869     if (!isHumongous(word_size)) {
 870       result = attempt_allocation(word_size, &gc_count_before);
 871     } else {
 872       result = attempt_allocation_humongous(word_size, &gc_count_before);
 873     }
 874     if (result != NULL) {
 875       return result;
 876     }
 877 
 878     // Create the garbage collection operation...
 879     VM_G1CollectForAllocation op(gc_count_before, word_size);
 880     // ...and get the VM thread to execute it.
 881     VMThread::execute(&op);
 882 
 883     if (op.prologue_succeeded() && op.pause_succeeded()) {
 884       // If the operation was successful we'll return the result even
 885       // if it is NULL. If the allocation attempt failed immediately
 886       // after a Full GC, it's unlikely we'll be able to allocate now.
 887       HeapWord* result = op.result();
 888       if (result != NULL && !isHumongous(word_size)) {
 889         // Allocations that take place on VM operations do not do any
 890         // card dirtying and we have to do it here. We only have to do
 891         // this for non-humongous allocations, though.
 892         dirty_young_block(result, word_size);
 893       }
 894       return result;
 895     } else {
 896       assert(op.result() == NULL,
 897              "the result should be NULL if the VM op did not succeed");
 898     }
 899 
 900     // Give a warning if we seem to be looping forever.
 901     if ((QueuedAllocationWarningCount > 0) &&
 902         (try_count % QueuedAllocationWarningCount == 0)) {
 903       warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
 904     }
 905   }
 906 
 907   ShouldNotReachHere();
 908   return NULL;
 909 }
 910 
 911 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
 912                                            unsigned int *gc_count_before_ret) {
 913   // Make sure you read the note in attempt_allocation_humongous().
 914 
 915   assert_heap_not_locked_and_not_at_safepoint();
 916   assert(!isHumongous(word_size), "attempt_allocation_slow() should not "
 917          "be called for humongous allocation requests");
 918 
 919   // We should only get here after the first-level allocation attempt
 920   // (attempt_allocation()) failed to allocate.
 921 
 922   // We will loop until a) we manage to successfully perform the
 923   // allocation or b) we successfully schedule a collection which
 924   // fails to perform the allocation. b) is the only case when we'll
 925   // return NULL.
 926   HeapWord* result = NULL;
 927   for (int try_count = 1; /* we'll return */; try_count += 1) {
 928     bool should_try_gc;
 929     unsigned int gc_count_before;
 930 
 931     {
 932       MutexLockerEx x(Heap_lock);
 933 
 934       result = _mutator_alloc_region.attempt_allocation_locked(word_size,
 935                                                       false /* bot_updates */);
 936       if (result != NULL) {
 937         return result;
 938       }
 939 
 940       // If we reach here, attempt_allocation_locked() above failed to
 941       // allocate a new region. So the mutator alloc region should be NULL.
 942       assert(_mutator_alloc_region.get() == NULL, "only way to get here");
 943 
 944       if (GC_locker::is_active_and_needs_gc()) {
 945         if (g1_policy()->can_expand_young_list()) {
 946           // No need for an ergo verbose message here,
 947           // can_expand_young_list() does this when it returns true.
 948           result = _mutator_alloc_region.attempt_allocation_force(word_size,
 949                                                       false /* bot_updates */);
 950           if (result != NULL) {
 951             return result;
 952           }
 953         }
 954         should_try_gc = false;
 955       } else {
 956         // The GCLocker may not be active but the GCLocker initiated
 957         // GC may not yet have been performed (GCLocker::needs_gc()
 958         // returns true). In this case we do not try this GC and
 959         // wait until the GCLocker initiated GC is performed, and
 960         // then retry the allocation.
 961         if (GC_locker::needs_gc()) {
 962           should_try_gc = false;
 963         } else {
 964           // Read the GC count while still holding the Heap_lock.
 965           gc_count_before = total_collections();
 966           should_try_gc = true;
 967         }
 968       }
 969     }
 970 
 971     if (should_try_gc) {
 972       bool succeeded;
 973       result = do_collection_pause(word_size, gc_count_before, &succeeded);
 974       if (result != NULL) {
 975         assert(succeeded, "only way to get back a non-NULL result");
 976         return result;
 977       }
 978 
 979       if (succeeded) {
 980         // If we get here we successfully scheduled a collection which
 981         // failed to allocate. No point in trying to allocate
 982         // further. We'll just return NULL.
 983         MutexLockerEx x(Heap_lock);
 984         *gc_count_before_ret = total_collections();
 985         return NULL;
 986       }
 987     } else {
 988       // The GCLocker is either active or the GCLocker initiated
 989       // GC has not yet been performed. Stall until it is and
 990       // then retry the allocation.
 991       GC_locker::stall_until_clear();
 992     }
 993 
 994     // We can reach here if we were unsuccessul in scheduling a
 995     // collection (because another thread beat us to it) or if we were
 996     // stalled due to the GC locker. In either can we should retry the
 997     // allocation attempt in case another thread successfully
 998     // performed a collection and reclaimed enough space. We do the
 999     // first attempt (without holding the Heap_lock) here and the
1000     // follow-on attempt will be at the start of the next loop
1001     // iteration (after taking the Heap_lock).
1002     result = _mutator_alloc_region.attempt_allocation(word_size,
1003                                                       false /* bot_updates */);
1004     if (result != NULL) {
1005       return result;
1006     }
1007 
1008     // Give a warning if we seem to be looping forever.
1009     if ((QueuedAllocationWarningCount > 0) &&
1010         (try_count % QueuedAllocationWarningCount == 0)) {
1011       warning("G1CollectedHeap::attempt_allocation_slow() "
1012               "retries %d times", try_count);
1013     }
1014   }
1015 
1016   ShouldNotReachHere();
1017   return NULL;
1018 }
1019 
1020 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
1021                                           unsigned int * gc_count_before_ret) {
1022   // The structure of this method has a lot of similarities to
1023   // attempt_allocation_slow(). The reason these two were not merged
1024   // into a single one is that such a method would require several "if
1025   // allocation is not humongous do this, otherwise do that"
1026   // conditional paths which would obscure its flow. In fact, an early
1027   // version of this code did use a unified method which was harder to
1028   // follow and, as a result, it had subtle bugs that were hard to
1029   // track down. So keeping these two methods separate allows each to
1030   // be more readable. It will be good to keep these two in sync as
1031   // much as possible.
1032 
1033   assert_heap_not_locked_and_not_at_safepoint();
1034   assert(isHumongous(word_size), "attempt_allocation_humongous() "
1035          "should only be called for humongous allocations");
1036 
1037   // Humongous objects can exhaust the heap quickly, so we should check if we
1038   // need to start a marking cycle at each humongous object allocation. We do
1039   // the check before we do the actual allocation. The reason for doing it
1040   // before the allocation is that we avoid having to keep track of the newly
1041   // allocated memory while we do a GC.
1042   if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
1043                                            word_size)) {
1044     collect(GCCause::_g1_humongous_allocation);
1045   }
1046 
1047   // We will loop until a) we manage to successfully perform the
1048   // allocation or b) we successfully schedule a collection which
1049   // fails to perform the allocation. b) is the only case when we'll
1050   // return NULL.
1051   HeapWord* result = NULL;
1052   for (int try_count = 1; /* we'll return */; try_count += 1) {
1053     bool should_try_gc;
1054     unsigned int gc_count_before;
1055 
1056     {
1057       MutexLockerEx x(Heap_lock);
1058 
1059       // Given that humongous objects are not allocated in young
1060       // regions, we'll first try to do the allocation without doing a
1061       // collection hoping that there's enough space in the heap.
1062       result = humongous_obj_allocate(word_size);
1063       if (result != NULL) {
1064         return result;
1065       }
1066 
1067       if (GC_locker::is_active_and_needs_gc()) {
1068         should_try_gc = false;
1069       } else {
1070          // The GCLocker may not be active but the GCLocker initiated
1071         // GC may not yet have been performed (GCLocker::needs_gc()
1072         // returns true). In this case we do not try this GC and
1073         // wait until the GCLocker initiated GC is performed, and
1074         // then retry the allocation.
1075         if (GC_locker::needs_gc()) {
1076           should_try_gc = false;
1077         } else {
1078           // Read the GC count while still holding the Heap_lock.
1079           gc_count_before = total_collections();
1080           should_try_gc = true;
1081         }
1082       }
1083     }
1084 
1085     if (should_try_gc) {
1086       // If we failed to allocate the humongous object, we should try to
1087       // do a collection pause (if we're allowed) in case it reclaims
1088       // enough space for the allocation to succeed after the pause.
1089 
1090       bool succeeded;
1091       result = do_collection_pause(word_size, gc_count_before, &succeeded);
1092       if (result != NULL) {
1093         assert(succeeded, "only way to get back a non-NULL result");
1094         return result;
1095       }
1096 
1097       if (succeeded) {
1098         // If we get here we successfully scheduled a collection which
1099         // failed to allocate. No point in trying to allocate
1100         // further. We'll just return NULL.
1101         MutexLockerEx x(Heap_lock);
1102         *gc_count_before_ret = total_collections();
1103         return NULL;
1104       }
1105     } else {
1106       // The GCLocker is either active or the GCLocker initiated
1107       // GC has not yet been performed. Stall until it is and
1108       // then retry the allocation.
1109       GC_locker::stall_until_clear();
1110     }
1111 
1112     // We can reach here if we were unsuccessul in scheduling a
1113     // collection (because another thread beat us to it) or if we were
1114     // stalled due to the GC locker. In either can we should retry the
1115     // allocation attempt in case another thread successfully
1116     // performed a collection and reclaimed enough space.  Give a
1117     // warning if we seem to be looping forever.
1118 
1119     if ((QueuedAllocationWarningCount > 0) &&
1120         (try_count % QueuedAllocationWarningCount == 0)) {
1121       warning("G1CollectedHeap::attempt_allocation_humongous() "
1122               "retries %d times", try_count);
1123     }
1124   }
1125 
1126   ShouldNotReachHere();
1127   return NULL;
1128 }
1129 
1130 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1131                                        bool expect_null_mutator_alloc_region) {
1132   assert_at_safepoint(true /* should_be_vm_thread */);
1133   assert(_mutator_alloc_region.get() == NULL ||
1134                                              !expect_null_mutator_alloc_region,
1135          "the current alloc region was unexpectedly found to be non-NULL");
1136 
1137   if (!isHumongous(word_size)) {
1138     return _mutator_alloc_region.attempt_allocation_locked(word_size,
1139                                                       false /* bot_updates */);
1140   } else {
1141     HeapWord* result = humongous_obj_allocate(word_size);
1142     if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1143       g1_policy()->set_initiate_conc_mark_if_possible();
1144     }
1145     return result;
1146   }
1147 
1148   ShouldNotReachHere();
1149 }
1150 
1151 class PostMCRemSetClearClosure: public HeapRegionClosure {
1152   ModRefBarrierSet* _mr_bs;
1153 public:
1154   PostMCRemSetClearClosure(ModRefBarrierSet* mr_bs) : _mr_bs(mr_bs) {}
1155   bool doHeapRegion(HeapRegion* r) {
1156     r->reset_gc_time_stamp();
1157     if (r->continuesHumongous())
1158       return false;
1159     HeapRegionRemSet* hrrs = r->rem_set();
1160     if (hrrs != NULL) hrrs->clear();
1161     // You might think here that we could clear just the cards
1162     // corresponding to the used region.  But no: if we leave a dirty card
1163     // in a region we might allocate into, then it would prevent that card
1164     // from being enqueued, and cause it to be missed.
1165     // Re: the performance cost: we shouldn't be doing full GC anyway!
1166     _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1167     return false;
1168   }
1169 };
1170 
1171 
1172 class PostMCRemSetInvalidateClosure: public HeapRegionClosure {
1173   ModRefBarrierSet* _mr_bs;
1174 public:
1175   PostMCRemSetInvalidateClosure(ModRefBarrierSet* mr_bs) : _mr_bs(mr_bs) {}
1176   bool doHeapRegion(HeapRegion* r) {
1177     if (r->continuesHumongous()) return false;
1178     if (r->used_region().word_size() != 0) {
1179       _mr_bs->invalidate(r->used_region(), true /*whole heap*/);
1180     }
1181     return false;
1182   }
1183 };
1184 
1185 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1186   G1CollectedHeap*   _g1h;
1187   UpdateRSOopClosure _cl;
1188   int                _worker_i;
1189 public:
1190   RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, int worker_i = 0) :
1191     _cl(g1->g1_rem_set(), worker_i),
1192     _worker_i(worker_i),
1193     _g1h(g1)
1194   { }
1195 
1196   bool doHeapRegion(HeapRegion* r) {
1197     if (!r->continuesHumongous()) {
1198       _cl.set_from(r);
1199       r->oop_iterate(&_cl);
1200     }
1201     return false;
1202   }
1203 };
1204 
1205 class ParRebuildRSTask: public AbstractGangTask {
1206   G1CollectedHeap* _g1;
1207 public:
1208   ParRebuildRSTask(G1CollectedHeap* g1)
1209     : AbstractGangTask("ParRebuildRSTask"),
1210       _g1(g1)
1211   { }
1212 
1213   void work(uint worker_id) {
1214     RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1215     _g1->heap_region_par_iterate_chunked(&rebuild_rs, worker_id,
1216                                           _g1->workers()->active_workers(),
1217                                          HeapRegion::RebuildRSClaimValue);
1218   }
1219 };
1220 
1221 class PostCompactionPrinterClosure: public HeapRegionClosure {
1222 private:
1223   G1HRPrinter* _hr_printer;
1224 public:
1225   bool doHeapRegion(HeapRegion* hr) {
1226     assert(!hr->is_young(), "not expecting to find young regions");
1227     // We only generate output for non-empty regions.
1228     if (!hr->is_empty()) {
1229       if (!hr->isHumongous()) {
1230         _hr_printer->post_compaction(hr, G1HRPrinter::Old);
1231       } else if (hr->startsHumongous()) {
1232         if (hr->capacity() == HeapRegion::GrainBytes) {
1233           // single humongous region
1234           _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
1235         } else {
1236           _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
1237         }
1238       } else {
1239         assert(hr->continuesHumongous(), "only way to get here");
1240         _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1241       }
1242     }
1243     return false;
1244   }
1245 
1246   PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1247     : _hr_printer(hr_printer) { }
1248 };
1249 
1250 bool G1CollectedHeap::do_collection(bool explicit_gc,
1251                                     bool clear_all_soft_refs,
1252                                     size_t word_size) {
1253   assert_at_safepoint(true /* should_be_vm_thread */);
1254 
1255   if (GC_locker::check_active_before_gc()) {
1256     return false;
1257   }
1258 
1259   SvcGCMarker sgcm(SvcGCMarker::FULL);
1260   ResourceMark rm;
1261 
1262   print_heap_before_gc();
1263 
1264   HRSPhaseSetter x(HRSPhaseFullGC);
1265   verify_region_sets_optional();
1266 
1267   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1268                            collector_policy()->should_clear_all_soft_refs();
1269 
1270   ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1271 
1272   {
1273     IsGCActiveMark x;
1274 
1275     // Timing
1276     assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant");
1277     gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps);
1278     TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
1279 
1280     TraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, gclog_or_tty);
1281     TraceCollectorStats tcs(g1mm()->full_collection_counters());
1282     TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1283 
1284     double start = os::elapsedTime();
1285     g1_policy()->record_full_collection_start();
1286 
1287     // Note: When we have a more flexible GC logging framework that
1288     // allows us to add optional attributes to a GC log record we
1289     // could consider timing and reporting how long we wait in the
1290     // following two methods.
1291     wait_while_free_regions_coming();
1292     // If we start the compaction before the CM threads finish
1293     // scanning the root regions we might trip them over as we'll
1294     // be moving objects / updating references. So let's wait until
1295     // they are done. By telling them to abort, they should complete
1296     // early.
1297     _cm->root_regions()->abort();
1298     _cm->root_regions()->wait_until_scan_finished();
1299     append_secondary_free_list_if_not_empty_with_lock();
1300 
1301     gc_prologue(true);
1302     increment_total_collections(true /* full gc */);
1303     increment_old_marking_cycles_started();
1304 
1305     size_t g1h_prev_used = used();
1306     assert(used() == recalculate_used(), "Should be equal");
1307 
1308     if (VerifyBeforeGC && total_collections() >= VerifyGCStartAt) {
1309       HandleMark hm;  // Discard invalid handles created during verification
1310       gclog_or_tty->print(" VerifyBeforeGC:");
1311       prepare_for_verify();
1312       Universe::verify(/* silent      */ false,
1313                        /* option      */ VerifyOption_G1UsePrevMarking);
1314 
1315     }
1316     pre_full_gc_dump();
1317 
1318     COMPILER2_PRESENT(DerivedPointerTable::clear());
1319 
1320     // Disable discovery and empty the discovered lists
1321     // for the CM ref processor.
1322     ref_processor_cm()->disable_discovery();
1323     ref_processor_cm()->abandon_partial_discovery();
1324     ref_processor_cm()->verify_no_references_recorded();
1325 
1326     // Abandon current iterations of concurrent marking and concurrent
1327     // refinement, if any are in progress. We have to do this before
1328     // wait_until_scan_finished() below.
1329     concurrent_mark()->abort();
1330 
1331     // Make sure we'll choose a new allocation region afterwards.
1332     release_mutator_alloc_region();
1333     abandon_gc_alloc_regions();
1334     g1_rem_set()->cleanupHRRS();
1335 
1336     // We should call this after we retire any currently active alloc
1337     // regions so that all the ALLOC / RETIRE events are generated
1338     // before the start GC event.
1339     _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1340 
1341     // We may have added regions to the current incremental collection
1342     // set between the last GC or pause and now. We need to clear the
1343     // incremental collection set and then start rebuilding it afresh
1344     // after this full GC.
1345     abandon_collection_set(g1_policy()->inc_cset_head());
1346     g1_policy()->clear_incremental_cset();
1347     g1_policy()->stop_incremental_cset_building();
1348 
1349     tear_down_region_sets(false /* free_list_only */);
1350     g1_policy()->set_gcs_are_young(true);
1351 
1352     // See the comments in g1CollectedHeap.hpp and
1353     // G1CollectedHeap::ref_processing_init() about
1354     // how reference processing currently works in G1.
1355 
1356     // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1357     ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1358 
1359     // Temporarily clear the STW ref processor's _is_alive_non_header field.
1360     ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1361 
1362     ref_processor_stw()->enable_discovery(true /*verify_disabled*/, true /*verify_no_refs*/);
1363     ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1364 
1365     // Do collection work
1366     {
1367       HandleMark hm;  // Discard invalid handles created during gc
1368       G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1369     }
1370 
1371     assert(free_regions() == 0, "we should not have added any free regions");
1372     rebuild_region_sets(false /* free_list_only */);
1373 
1374     // Enqueue any discovered reference objects that have
1375     // not been removed from the discovered lists.
1376     ref_processor_stw()->enqueue_discovered_references();
1377 
1378     COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1379 
1380     MemoryService::track_memory_usage();
1381 
1382     if (VerifyAfterGC && total_collections() >= VerifyGCStartAt) {
1383       HandleMark hm;  // Discard invalid handles created during verification
1384       gclog_or_tty->print(" VerifyAfterGC:");
1385       prepare_for_verify();
1386       Universe::verify(/* silent      */ false,
1387                        /* option      */ VerifyOption_G1UsePrevMarking);
1388 
1389     }
1390 
1391     assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1392     ref_processor_stw()->verify_no_references_recorded();
1393 
1394     // Note: since we've just done a full GC, concurrent
1395     // marking is no longer active. Therefore we need not
1396     // re-enable reference discovery for the CM ref processor.
1397     // That will be done at the start of the next marking cycle.
1398     assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1399     ref_processor_cm()->verify_no_references_recorded();
1400 
1401     reset_gc_time_stamp();
1402     // Since everything potentially moved, we will clear all remembered
1403     // sets, and clear all cards.  Later we will rebuild remebered
1404     // sets. We will also reset the GC time stamps of the regions.
1405     PostMCRemSetClearClosure rs_clear(mr_bs());
1406     heap_region_iterate(&rs_clear);
1407 
1408     // Resize the heap if necessary.
1409     resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1410 
1411     if (_hr_printer.is_active()) {
1412       // We should do this after we potentially resize the heap so
1413       // that all the COMMIT / UNCOMMIT events are generated before
1414       // the end GC event.
1415 
1416       PostCompactionPrinterClosure cl(hr_printer());
1417       heap_region_iterate(&cl);
1418 
1419       _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1420     }
1421 
1422     if (_cg1r->use_cache()) {
1423       _cg1r->clear_and_record_card_counts();
1424       _cg1r->clear_hot_cache();
1425     }
1426 
1427     // Rebuild remembered sets of all regions.
1428     if (G1CollectedHeap::use_parallel_gc_threads()) {
1429       uint n_workers =
1430         AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1431                                        workers()->active_workers(),
1432                                        Threads::number_of_non_daemon_threads());
1433       assert(UseDynamicNumberOfGCThreads ||
1434              n_workers == workers()->total_workers(),
1435              "If not dynamic should be using all the  workers");
1436       workers()->set_active_workers(n_workers);
1437       // Set parallel threads in the heap (_n_par_threads) only
1438       // before a parallel phase and always reset it to 0 after
1439       // the phase so that the number of parallel threads does
1440       // no get carried forward to a serial phase where there
1441       // may be code that is "possibly_parallel".
1442       set_par_threads(n_workers);
1443 
1444       ParRebuildRSTask rebuild_rs_task(this);
1445       assert(check_heap_region_claim_values(
1446              HeapRegion::InitialClaimValue), "sanity check");
1447       assert(UseDynamicNumberOfGCThreads ||
1448              workers()->active_workers() == workers()->total_workers(),
1449         "Unless dynamic should use total workers");
1450       // Use the most recent number of  active workers
1451       assert(workers()->active_workers() > 0,
1452         "Active workers not properly set");
1453       set_par_threads(workers()->active_workers());
1454       workers()->run_task(&rebuild_rs_task);
1455       set_par_threads(0);
1456       assert(check_heap_region_claim_values(
1457              HeapRegion::RebuildRSClaimValue), "sanity check");
1458       reset_heap_region_claim_values();
1459     } else {
1460       RebuildRSOutOfRegionClosure rebuild_rs(this);
1461       heap_region_iterate(&rebuild_rs);
1462     }
1463 
1464     if (G1Log::fine()) {
1465       print_size_transition(gclog_or_tty, g1h_prev_used, used(), capacity());
1466     }
1467 
1468     if (true) { // FIXME
1469       // Ask the permanent generation to adjust size for full collections
1470       perm()->compute_new_size();
1471     }
1472 
1473     // Start a new incremental collection set for the next pause
1474     assert(g1_policy()->collection_set() == NULL, "must be");
1475     g1_policy()->start_incremental_cset_building();
1476 
1477     // Clear the _cset_fast_test bitmap in anticipation of adding
1478     // regions to the incremental collection set for the next
1479     // evacuation pause.
1480     clear_cset_fast_test();
1481 
1482     init_mutator_alloc_region();
1483 
1484     double end = os::elapsedTime();
1485     g1_policy()->record_full_collection_end();
1486 
1487 #ifdef TRACESPINNING
1488     ParallelTaskTerminator::print_termination_counts();
1489 #endif
1490 
1491     gc_epilogue(true);
1492 
1493     // Discard all rset updates
1494     JavaThread::dirty_card_queue_set().abandon_logs();
1495     assert(!G1DeferredRSUpdate
1496            || (G1DeferredRSUpdate && (dirty_card_queue_set().completed_buffers_num() == 0)), "Should not be any");
1497 
1498     _young_list->reset_sampled_info();
1499     // At this point there should be no regions in the
1500     // entire heap tagged as young.
1501     assert( check_young_list_empty(true /* check_heap */),
1502       "young list should be empty at this point");
1503 
1504     // Update the number of full collections that have been completed.
1505     increment_old_marking_cycles_completed(false /* concurrent */);
1506 
1507     _hrs.verify_optional();
1508     verify_region_sets_optional();
1509 
1510     print_heap_after_gc();
1511 
1512     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1513     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1514     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1515     // before any GC notifications are raised.
1516     g1mm()->update_sizes();
1517   }
1518 
1519   post_full_gc_dump();
1520 
1521   return true;
1522 }
1523 
1524 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1525   // do_collection() will return whether it succeeded in performing
1526   // the GC. Currently, there is no facility on the
1527   // do_full_collection() API to notify the caller than the collection
1528   // did not succeed (e.g., because it was locked out by the GC
1529   // locker). So, right now, we'll ignore the return value.
1530   bool dummy = do_collection(true,                /* explicit_gc */
1531                              clear_all_soft_refs,
1532                              0                    /* word_size */);
1533 }
1534 
1535 // This code is mostly copied from TenuredGeneration.
1536 void
1537 G1CollectedHeap::
1538 resize_if_necessary_after_full_collection(size_t word_size) {
1539   assert(MinHeapFreeRatio <= MaxHeapFreeRatio, "sanity check");
1540 
1541   // Include the current allocation, if any, and bytes that will be
1542   // pre-allocated to support collections, as "used".
1543   const size_t used_after_gc = used();
1544   const size_t capacity_after_gc = capacity();
1545   const size_t free_after_gc = capacity_after_gc - used_after_gc;
1546 
1547   // This is enforced in arguments.cpp.
1548   assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1549          "otherwise the code below doesn't make sense");
1550 
1551   // We don't have floating point command-line arguments
1552   const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1553   const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1554   const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1555   const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1556 
1557   const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1558   const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1559 
1560   // We have to be careful here as these two calculations can overflow
1561   // 32-bit size_t's.
1562   double used_after_gc_d = (double) used_after_gc;
1563   double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1564   double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1565 
1566   // Let's make sure that they are both under the max heap size, which
1567   // by default will make them fit into a size_t.
1568   double desired_capacity_upper_bound = (double) max_heap_size;
1569   minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1570                                     desired_capacity_upper_bound);
1571   maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1572                                     desired_capacity_upper_bound);
1573 
1574   // We can now safely turn them into size_t's.
1575   size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1576   size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1577 
1578   // This assert only makes sense here, before we adjust them
1579   // with respect to the min and max heap size.
1580   assert(minimum_desired_capacity <= maximum_desired_capacity,
1581          err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1582                  "maximum_desired_capacity = "SIZE_FORMAT,
1583                  minimum_desired_capacity, maximum_desired_capacity));
1584 
1585   // Should not be greater than the heap max size. No need to adjust
1586   // it with respect to the heap min size as it's a lower bound (i.e.,
1587   // we'll try to make the capacity larger than it, not smaller).
1588   minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1589   // Should not be less than the heap min size. No need to adjust it
1590   // with respect to the heap max size as it's an upper bound (i.e.,
1591   // we'll try to make the capacity smaller than it, not greater).
1592   maximum_desired_capacity =  MAX2(maximum_desired_capacity, min_heap_size);
1593 
1594   if (capacity_after_gc < minimum_desired_capacity) {
1595     // Don't expand unless it's significant
1596     size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1597     ergo_verbose4(ErgoHeapSizing,
1598                   "attempt heap expansion",
1599                   ergo_format_reason("capacity lower than "
1600                                      "min desired capacity after Full GC")
1601                   ergo_format_byte("capacity")
1602                   ergo_format_byte("occupancy")
1603                   ergo_format_byte_perc("min desired capacity"),
1604                   capacity_after_gc, used_after_gc,
1605                   minimum_desired_capacity, (double) MinHeapFreeRatio);
1606     expand(expand_bytes);
1607 
1608     // No expansion, now see if we want to shrink
1609   } else if (capacity_after_gc > maximum_desired_capacity) {
1610     // Capacity too large, compute shrinking size
1611     size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1612     ergo_verbose4(ErgoHeapSizing,
1613                   "attempt heap shrinking",
1614                   ergo_format_reason("capacity higher than "
1615                                      "max desired capacity after Full GC")
1616                   ergo_format_byte("capacity")
1617                   ergo_format_byte("occupancy")
1618                   ergo_format_byte_perc("max desired capacity"),
1619                   capacity_after_gc, used_after_gc,
1620                   maximum_desired_capacity, (double) MaxHeapFreeRatio);
1621     shrink(shrink_bytes);
1622   }
1623 }
1624 
1625 
1626 HeapWord*
1627 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1628                                            bool* succeeded) {
1629   assert_at_safepoint(true /* should_be_vm_thread */);
1630 
1631   *succeeded = true;
1632   // Let's attempt the allocation first.
1633   HeapWord* result =
1634     attempt_allocation_at_safepoint(word_size,
1635                                  false /* expect_null_mutator_alloc_region */);
1636   if (result != NULL) {
1637     assert(*succeeded, "sanity");
1638     return result;
1639   }
1640 
1641   // In a G1 heap, we're supposed to keep allocation from failing by
1642   // incremental pauses.  Therefore, at least for now, we'll favor
1643   // expansion over collection.  (This might change in the future if we can
1644   // do something smarter than full collection to satisfy a failed alloc.)
1645   result = expand_and_allocate(word_size);
1646   if (result != NULL) {
1647     assert(*succeeded, "sanity");
1648     return result;
1649   }
1650 
1651   // Expansion didn't work, we'll try to do a Full GC.
1652   bool gc_succeeded = do_collection(false, /* explicit_gc */
1653                                     false, /* clear_all_soft_refs */
1654                                     word_size);
1655   if (!gc_succeeded) {
1656     *succeeded = false;
1657     return NULL;
1658   }
1659 
1660   // Retry the allocation
1661   result = attempt_allocation_at_safepoint(word_size,
1662                                   true /* expect_null_mutator_alloc_region */);
1663   if (result != NULL) {
1664     assert(*succeeded, "sanity");
1665     return result;
1666   }
1667 
1668   // Then, try a Full GC that will collect all soft references.
1669   gc_succeeded = do_collection(false, /* explicit_gc */
1670                                true,  /* clear_all_soft_refs */
1671                                word_size);
1672   if (!gc_succeeded) {
1673     *succeeded = false;
1674     return NULL;
1675   }
1676 
1677   // Retry the allocation once more
1678   result = attempt_allocation_at_safepoint(word_size,
1679                                   true /* expect_null_mutator_alloc_region */);
1680   if (result != NULL) {
1681     assert(*succeeded, "sanity");
1682     return result;
1683   }
1684 
1685   assert(!collector_policy()->should_clear_all_soft_refs(),
1686          "Flag should have been handled and cleared prior to this point");
1687 
1688   // What else?  We might try synchronous finalization later.  If the total
1689   // space available is large enough for the allocation, then a more
1690   // complete compaction phase than we've tried so far might be
1691   // appropriate.
1692   assert(*succeeded, "sanity");
1693   return NULL;
1694 }
1695 
1696 // Attempting to expand the heap sufficiently
1697 // to support an allocation of the given "word_size".  If
1698 // successful, perform the allocation and return the address of the
1699 // allocated block, or else "NULL".
1700 
1701 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1702   assert_at_safepoint(true /* should_be_vm_thread */);
1703 
1704   verify_region_sets_optional();
1705 
1706   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1707   ergo_verbose1(ErgoHeapSizing,
1708                 "attempt heap expansion",
1709                 ergo_format_reason("allocation request failed")
1710                 ergo_format_byte("allocation request"),
1711                 word_size * HeapWordSize);
1712   if (expand(expand_bytes)) {
1713     _hrs.verify_optional();
1714     verify_region_sets_optional();
1715     return attempt_allocation_at_safepoint(word_size,
1716                                  false /* expect_null_mutator_alloc_region */);
1717   }
1718   return NULL;
1719 }
1720 
1721 void G1CollectedHeap::update_committed_space(HeapWord* old_end,
1722                                              HeapWord* new_end) {
1723   assert(old_end != new_end, "don't call this otherwise");
1724   assert((HeapWord*) _g1_storage.high() == new_end, "invariant");
1725 
1726   // Update the committed mem region.
1727   _g1_committed.set_end(new_end);
1728   // Tell the card table about the update.
1729   Universe::heap()->barrier_set()->resize_covered_region(_g1_committed);
1730   // Tell the BOT about the update.
1731   _bot_shared->resize(_g1_committed.word_size());
1732 }
1733 
1734 bool G1CollectedHeap::expand(size_t expand_bytes) {
1735   size_t old_mem_size = _g1_storage.committed_size();
1736   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1737   aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1738                                        HeapRegion::GrainBytes);
1739   ergo_verbose2(ErgoHeapSizing,
1740                 "expand the heap",
1741                 ergo_format_byte("requested expansion amount")
1742                 ergo_format_byte("attempted expansion amount"),
1743                 expand_bytes, aligned_expand_bytes);
1744 
1745   // First commit the memory.
1746   HeapWord* old_end = (HeapWord*) _g1_storage.high();
1747   bool successful = _g1_storage.expand_by(aligned_expand_bytes);
1748   if (successful) {
1749     // Then propagate this update to the necessary data structures.
1750     HeapWord* new_end = (HeapWord*) _g1_storage.high();
1751     update_committed_space(old_end, new_end);
1752 
1753     FreeRegionList expansion_list("Local Expansion List");
1754     MemRegion mr = _hrs.expand_by(old_end, new_end, &expansion_list);
1755     assert(mr.start() == old_end, "post-condition");
1756     // mr might be a smaller region than what was requested if
1757     // expand_by() was unable to allocate the HeapRegion instances
1758     assert(mr.end() <= new_end, "post-condition");
1759 
1760     size_t actual_expand_bytes = mr.byte_size();
1761     assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1762     assert(actual_expand_bytes == expansion_list.total_capacity_bytes(),
1763            "post-condition");
1764     if (actual_expand_bytes < aligned_expand_bytes) {
1765       // We could not expand _hrs to the desired size. In this case we
1766       // need to shrink the committed space accordingly.
1767       assert(mr.end() < new_end, "invariant");
1768 
1769       size_t diff_bytes = aligned_expand_bytes - actual_expand_bytes;
1770       // First uncommit the memory.
1771       _g1_storage.shrink_by(diff_bytes);
1772       // Then propagate this update to the necessary data structures.
1773       update_committed_space(new_end, mr.end());
1774     }
1775     _free_list.add_as_tail(&expansion_list);
1776 
1777     if (_hr_printer.is_active()) {
1778       HeapWord* curr = mr.start();
1779       while (curr < mr.end()) {
1780         HeapWord* curr_end = curr + HeapRegion::GrainWords;
1781         _hr_printer.commit(curr, curr_end);
1782         curr = curr_end;
1783       }
1784       assert(curr == mr.end(), "post-condition");
1785     }
1786     g1_policy()->record_new_heap_size(n_regions());
1787   } else {
1788     ergo_verbose0(ErgoHeapSizing,
1789                   "did not expand the heap",
1790                   ergo_format_reason("heap expansion operation failed"));
1791     // The expansion of the virtual storage space was unsuccessful.
1792     // Let's see if it was because we ran out of swap.
1793     if (G1ExitOnExpansionFailure &&
1794         _g1_storage.uncommitted_size() >= aligned_expand_bytes) {
1795       // We had head room...
1796       vm_exit_out_of_memory(aligned_expand_bytes, "G1 heap expansion");
1797     }
1798   }
1799   return successful;
1800 }
1801 
1802 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1803   size_t old_mem_size = _g1_storage.committed_size();
1804   size_t aligned_shrink_bytes =
1805     ReservedSpace::page_align_size_down(shrink_bytes);
1806   aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1807                                          HeapRegion::GrainBytes);
1808   uint num_regions_deleted = 0;
1809   MemRegion mr = _hrs.shrink_by(aligned_shrink_bytes, &num_regions_deleted);
1810   HeapWord* old_end = (HeapWord*) _g1_storage.high();
1811   assert(mr.end() == old_end, "post-condition");
1812 
1813   ergo_verbose3(ErgoHeapSizing,
1814                 "shrink the heap",
1815                 ergo_format_byte("requested shrinking amount")
1816                 ergo_format_byte("aligned shrinking amount")
1817                 ergo_format_byte("attempted shrinking amount"),
1818                 shrink_bytes, aligned_shrink_bytes, mr.byte_size());
1819   if (mr.byte_size() > 0) {
1820     if (_hr_printer.is_active()) {
1821       HeapWord* curr = mr.end();
1822       while (curr > mr.start()) {
1823         HeapWord* curr_end = curr;
1824         curr -= HeapRegion::GrainWords;
1825         _hr_printer.uncommit(curr, curr_end);
1826       }
1827       assert(curr == mr.start(), "post-condition");
1828     }
1829 
1830     _g1_storage.shrink_by(mr.byte_size());
1831     HeapWord* new_end = (HeapWord*) _g1_storage.high();
1832     assert(mr.start() == new_end, "post-condition");
1833 
1834     _expansion_regions += num_regions_deleted;
1835     update_committed_space(old_end, new_end);
1836     HeapRegionRemSet::shrink_heap(n_regions());
1837     g1_policy()->record_new_heap_size(n_regions());
1838   } else {
1839     ergo_verbose0(ErgoHeapSizing,
1840                   "did not shrink the heap",
1841                   ergo_format_reason("heap shrinking operation failed"));
1842   }
1843 }
1844 
1845 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1846   verify_region_sets_optional();
1847 
1848   // We should only reach here at the end of a Full GC which means we
1849   // should not not be holding to any GC alloc regions. The method
1850   // below will make sure of that and do any remaining clean up.
1851   abandon_gc_alloc_regions();
1852 
1853   // Instead of tearing down / rebuilding the free lists here, we
1854   // could instead use the remove_all_pending() method on free_list to
1855   // remove only the ones that we need to remove.
1856   tear_down_region_sets(true /* free_list_only */);
1857   shrink_helper(shrink_bytes);
1858   rebuild_region_sets(true /* free_list_only */);
1859 
1860   _hrs.verify_optional();
1861   verify_region_sets_optional();
1862 }
1863 
1864 // Public methods.
1865 
1866 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1867 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1868 #endif // _MSC_VER
1869 
1870 
1871 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1872   SharedHeap(policy_),
1873   _g1_policy(policy_),
1874   _dirty_card_queue_set(false),
1875   _into_cset_dirty_card_queue_set(false),
1876   _is_alive_closure_cm(this),
1877   _is_alive_closure_stw(this),
1878   _ref_processor_cm(NULL),
1879   _ref_processor_stw(NULL),
1880   _process_strong_tasks(new SubTasksDone(G1H_PS_NumElements)),
1881   _bot_shared(NULL),
1882   _objs_with_preserved_marks(NULL), _preserved_marks_of_objs(NULL),
1883   _evac_failure_scan_stack(NULL) ,
1884   _mark_in_progress(false),
1885   _cg1r(NULL), _summary_bytes_used(0),
1886   _g1mm(NULL),
1887   _refine_cte_cl(NULL),
1888   _full_collection(false),
1889   _free_list("Master Free List"),
1890   _secondary_free_list("Secondary Free List"),
1891   _old_set("Old Set"),
1892   _humongous_set("Master Humongous Set"),
1893   _free_regions_coming(false),
1894   _young_list(new YoungList(this)),
1895   _gc_time_stamp(0),
1896   _retained_old_gc_alloc_region(NULL),
1897   _expand_heap_after_alloc_failure(true),
1898   _surviving_young_words(NULL),
1899   _old_marking_cycles_started(0),
1900   _old_marking_cycles_completed(0),
1901   _in_cset_fast_test(NULL),
1902   _in_cset_fast_test_base(NULL),
1903   _dirty_cards_region_list(NULL),
1904   _worker_cset_start_region(NULL),
1905   _worker_cset_start_region_time_stamp(NULL) {
1906   _g1h = this; // To catch bugs.
1907   if (_process_strong_tasks == NULL || !_process_strong_tasks->valid()) {
1908     vm_exit_during_initialization("Failed necessary allocation.");
1909   }
1910 
1911   _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1912 
1913   int n_queues = MAX2((int)ParallelGCThreads, 1);
1914   _task_queues = new RefToScanQueueSet(n_queues);
1915 
1916   int n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1917   assert(n_rem_sets > 0, "Invariant.");
1918 
1919   HeapRegionRemSetIterator** iter_arr =
1920     NEW_C_HEAP_ARRAY(HeapRegionRemSetIterator*, n_queues, mtGC);
1921   for (int i = 0; i < n_queues; i++) {
1922     iter_arr[i] = new HeapRegionRemSetIterator();
1923   }
1924   _rem_set_iterator = iter_arr;
1925 
1926   _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1927   _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(unsigned int, n_queues, mtGC);
1928 
1929   for (int i = 0; i < n_queues; i++) {
1930     RefToScanQueue* q = new RefToScanQueue();
1931     q->initialize();
1932     _task_queues->register_queue(i, q);
1933   }
1934 
1935   clear_cset_start_regions();
1936 
1937   guarantee(_task_queues != NULL, "task_queues allocation failure.");
1938 }
1939 
1940 jint G1CollectedHeap::initialize() {
1941   CollectedHeap::pre_initialize();
1942   os::enable_vtime();
1943 
1944   G1Log::init();
1945 
1946   // Necessary to satisfy locking discipline assertions.
1947 
1948   MutexLocker x(Heap_lock);
1949 
1950   // We have to initialize the printer before committing the heap, as
1951   // it will be used then.
1952   _hr_printer.set_active(G1PrintHeapRegions);
1953 
1954   // While there are no constraints in the GC code that HeapWordSize
1955   // be any particular value, there are multiple other areas in the
1956   // system which believe this to be true (e.g. oop->object_size in some
1957   // cases incorrectly returns the size in wordSize units rather than
1958   // HeapWordSize).
1959   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1960 
1961   size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1962   size_t max_byte_size = collector_policy()->max_heap_byte_size();
1963 
1964   // Ensure that the sizes are properly aligned.
1965   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1966   Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1967 
1968   _cg1r = new ConcurrentG1Refine();
1969 
1970   // Reserve the maximum.
1971   PermanentGenerationSpec* pgs = collector_policy()->permanent_generation();
1972   // Includes the perm-gen.
1973 
1974   // When compressed oops are enabled, the preferred heap base
1975   // is calculated by subtracting the requested size from the
1976   // 32Gb boundary and using the result as the base address for
1977   // heap reservation. If the requested size is not aligned to
1978   // HeapRegion::GrainBytes (i.e. the alignment that is passed
1979   // into the ReservedHeapSpace constructor) then the actual
1980   // base of the reserved heap may end up differing from the
1981   // address that was requested (i.e. the preferred heap base).
1982   // If this happens then we could end up using a non-optimal
1983   // compressed oops mode.
1984 
1985   // Since max_byte_size is aligned to the size of a heap region (checked
1986   // above), we also need to align the perm gen size as it might not be.
1987   const size_t total_reserved = max_byte_size +
1988                                 align_size_up(pgs->max_size(), HeapRegion::GrainBytes);
1989   Universe::check_alignment(total_reserved, HeapRegion::GrainBytes, "g1 heap and perm");
1990 
1991   char* addr = Universe::preferred_heap_base(total_reserved, Universe::UnscaledNarrowOop);
1992 
1993   ReservedHeapSpace heap_rs(total_reserved, HeapRegion::GrainBytes,
1994                             UseLargePages, addr);
1995 
1996   if (UseCompressedOops) {
1997     if (addr != NULL && !heap_rs.is_reserved()) {
1998       // Failed to reserve at specified address - the requested memory
1999       // region is taken already, for example, by 'java' launcher.
2000       // Try again to reserver heap higher.
2001       addr = Universe::preferred_heap_base(total_reserved, Universe::ZeroBasedNarrowOop);
2002 
2003       ReservedHeapSpace heap_rs0(total_reserved, HeapRegion::GrainBytes,
2004                                  UseLargePages, addr);
2005 
2006       if (addr != NULL && !heap_rs0.is_reserved()) {
2007         // Failed to reserve at specified address again - give up.
2008         addr = Universe::preferred_heap_base(total_reserved, Universe::HeapBasedNarrowOop);
2009         assert(addr == NULL, "");
2010 
2011         ReservedHeapSpace heap_rs1(total_reserved, HeapRegion::GrainBytes,
2012                                    UseLargePages, addr);
2013         heap_rs = heap_rs1;
2014       } else {
2015         heap_rs = heap_rs0;
2016       }
2017     }
2018   }
2019 
2020   if (!heap_rs.is_reserved()) {
2021     vm_exit_during_initialization("Could not reserve enough space for object heap");
2022     return JNI_ENOMEM;
2023   }
2024 
2025   // It is important to do this in a way such that concurrent readers can't
2026   // temporarily think somethings in the heap.  (I've actually seen this
2027   // happen in asserts: DLD.)
2028   _reserved.set_word_size(0);
2029   _reserved.set_start((HeapWord*)heap_rs.base());
2030   _reserved.set_end((HeapWord*)(heap_rs.base() + heap_rs.size()));
2031 
2032   _expansion_regions = (uint) (max_byte_size / HeapRegion::GrainBytes);
2033 
2034   // Create the gen rem set (and barrier set) for the entire reserved region.
2035   _rem_set = collector_policy()->create_rem_set(_reserved, 2);
2036   set_barrier_set(rem_set()->bs());
2037   if (barrier_set()->is_a(BarrierSet::ModRef)) {
2038     _mr_bs = (ModRefBarrierSet*)_barrier_set;
2039   } else {
2040     vm_exit_during_initialization("G1 requires a mod ref bs.");
2041     return JNI_ENOMEM;
2042   }
2043 
2044   // Also create a G1 rem set.
2045   if (mr_bs()->is_a(BarrierSet::CardTableModRef)) {
2046     _g1_rem_set = new G1RemSet(this, (CardTableModRefBS*)mr_bs());
2047   } else {
2048     vm_exit_during_initialization("G1 requires a cardtable mod ref bs.");
2049     return JNI_ENOMEM;
2050   }
2051 
2052   // Carve out the G1 part of the heap.
2053 
2054   ReservedSpace g1_rs   = heap_rs.first_part(max_byte_size);
2055   _g1_reserved = MemRegion((HeapWord*)g1_rs.base(),
2056                            g1_rs.size()/HeapWordSize);
2057   ReservedSpace perm_gen_rs = heap_rs.last_part(max_byte_size);
2058 
2059   _perm_gen = pgs->init(perm_gen_rs, pgs->init_size(), rem_set());
2060 
2061   _g1_storage.initialize(g1_rs, 0);
2062   _g1_committed = MemRegion((HeapWord*)_g1_storage.low(), (size_t) 0);
2063   _hrs.initialize((HeapWord*) _g1_reserved.start(),
2064                   (HeapWord*) _g1_reserved.end(),
2065                   _expansion_regions);
2066 
2067   // 6843694 - ensure that the maximum region index can fit
2068   // in the remembered set structures.
2069   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
2070   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
2071 
2072   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
2073   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
2074   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
2075             "too many cards per region");
2076 
2077   HeapRegionSet::set_unrealistically_long_length(max_regions() + 1);
2078 
2079   _bot_shared = new G1BlockOffsetSharedArray(_reserved,
2080                                              heap_word_size(init_byte_size));
2081 
2082   _g1h = this;
2083 
2084    _in_cset_fast_test_length = max_regions();
2085    _in_cset_fast_test_base =
2086                    NEW_C_HEAP_ARRAY(bool, (size_t) _in_cset_fast_test_length, mtGC);
2087 
2088    // We're biasing _in_cset_fast_test to avoid subtracting the
2089    // beginning of the heap every time we want to index; basically
2090    // it's the same with what we do with the card table.
2091    _in_cset_fast_test = _in_cset_fast_test_base -
2092                ((uintx) _g1_reserved.start() >> HeapRegion::LogOfHRGrainBytes);
2093 
2094    // Clear the _cset_fast_test bitmap in anticipation of adding
2095    // regions to the incremental collection set for the first
2096    // evacuation pause.
2097    clear_cset_fast_test();
2098 
2099   // Create the ConcurrentMark data structure and thread.
2100   // (Must do this late, so that "max_regions" is defined.)
2101   _cm       = new ConcurrentMark(heap_rs, max_regions());
2102   _cmThread = _cm->cmThread();
2103 
2104   // Initialize the from_card cache structure of HeapRegionRemSet.
2105   HeapRegionRemSet::init_heap(max_regions());
2106 
2107   // Now expand into the initial heap size.
2108   if (!expand(init_byte_size)) {
2109     vm_exit_during_initialization("Failed to allocate initial heap.");
2110     return JNI_ENOMEM;
2111   }
2112 
2113   // Perform any initialization actions delegated to the policy.
2114   g1_policy()->init();
2115 
2116   _refine_cte_cl =
2117     new RefineCardTableEntryClosure(ConcurrentG1RefineThread::sts(),
2118                                     g1_rem_set(),
2119                                     concurrent_g1_refine());
2120   JavaThread::dirty_card_queue_set().set_closure(_refine_cte_cl);
2121 
2122   JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
2123                                                SATB_Q_FL_lock,
2124                                                G1SATBProcessCompletedThreshold,
2125                                                Shared_SATB_Q_lock);
2126 
2127   JavaThread::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
2128                                                 DirtyCardQ_FL_lock,
2129                                                 concurrent_g1_refine()->yellow_zone(),
2130                                                 concurrent_g1_refine()->red_zone(),
2131                                                 Shared_DirtyCardQ_lock);
2132 
2133   if (G1DeferredRSUpdate) {
2134     dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
2135                                       DirtyCardQ_FL_lock,
2136                                       -1, // never trigger processing
2137                                       -1, // no limit on length
2138                                       Shared_DirtyCardQ_lock,
2139                                       &JavaThread::dirty_card_queue_set());
2140   }
2141 
2142   // Initialize the card queue set used to hold cards containing
2143   // references into the collection set.
2144   _into_cset_dirty_card_queue_set.initialize(DirtyCardQ_CBL_mon,
2145                                              DirtyCardQ_FL_lock,
2146                                              -1, // never trigger processing
2147                                              -1, // no limit on length
2148                                              Shared_DirtyCardQ_lock,
2149                                              &JavaThread::dirty_card_queue_set());
2150 
2151   // In case we're keeping closure specialization stats, initialize those
2152   // counts and that mechanism.
2153   SpecializationStats::clear();
2154 
2155   // Do later initialization work for concurrent refinement.
2156   _cg1r->init();
2157 
2158   // Here we allocate the dummy full region that is required by the
2159   // G1AllocRegion class. If we don't pass an address in the reserved
2160   // space here, lots of asserts fire.
2161 
2162   HeapRegion* dummy_region = new_heap_region(0 /* index of bottom region */,
2163                                              _g1_reserved.start());
2164   // We'll re-use the same region whether the alloc region will
2165   // require BOT updates or not and, if it doesn't, then a non-young
2166   // region will complain that it cannot support allocations without
2167   // BOT updates. So we'll tag the dummy region as young to avoid that.
2168   dummy_region->set_young();
2169   // Make sure it's full.
2170   dummy_region->set_top(dummy_region->end());
2171   G1AllocRegion::setup(this, dummy_region);
2172 
2173   init_mutator_alloc_region();
2174 
2175   // Do create of the monitoring and management support so that
2176   // values in the heap have been properly initialized.
2177   _g1mm = new G1MonitoringSupport(this);
2178 
2179   return JNI_OK;
2180 }
2181 
2182 void G1CollectedHeap::ref_processing_init() {
2183   // Reference processing in G1 currently works as follows:
2184   //
2185   // * There are two reference processor instances. One is
2186   //   used to record and process discovered references
2187   //   during concurrent marking; the other is used to
2188   //   record and process references during STW pauses
2189   //   (both full and incremental).
2190   // * Both ref processors need to 'span' the entire heap as
2191   //   the regions in the collection set may be dotted around.
2192   //
2193   // * For the concurrent marking ref processor:
2194   //   * Reference discovery is enabled at initial marking.
2195   //   * Reference discovery is disabled and the discovered
2196   //     references processed etc during remarking.
2197   //   * Reference discovery is MT (see below).
2198   //   * Reference discovery requires a barrier (see below).
2199   //   * Reference processing may or may not be MT
2200   //     (depending on the value of ParallelRefProcEnabled
2201   //     and ParallelGCThreads).
2202   //   * A full GC disables reference discovery by the CM
2203   //     ref processor and abandons any entries on it's
2204   //     discovered lists.
2205   //
2206   // * For the STW processor:
2207   //   * Non MT discovery is enabled at the start of a full GC.
2208   //   * Processing and enqueueing during a full GC is non-MT.
2209   //   * During a full GC, references are processed after marking.
2210   //
2211   //   * Discovery (may or may not be MT) is enabled at the start
2212   //     of an incremental evacuation pause.
2213   //   * References are processed near the end of a STW evacuation pause.
2214   //   * For both types of GC:
2215   //     * Discovery is atomic - i.e. not concurrent.
2216   //     * Reference discovery will not need a barrier.
2217 
2218   SharedHeap::ref_processing_init();
2219   MemRegion mr = reserved_region();
2220 
2221   // Concurrent Mark ref processor
2222   _ref_processor_cm =
2223     new ReferenceProcessor(mr,    // span
2224                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2225                                 // mt processing
2226                            (int) ParallelGCThreads,
2227                                 // degree of mt processing
2228                            (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2229                                 // mt discovery
2230                            (int) MAX2(ParallelGCThreads, ConcGCThreads),
2231                                 // degree of mt discovery
2232                            false,
2233                                 // Reference discovery is not atomic
2234                            &_is_alive_closure_cm,
2235                                 // is alive closure
2236                                 // (for efficiency/performance)
2237                            true);
2238                                 // Setting next fields of discovered
2239                                 // lists requires a barrier.
2240 
2241   // STW ref processor
2242   _ref_processor_stw =
2243     new ReferenceProcessor(mr,    // span
2244                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2245                                 // mt processing
2246                            MAX2((int)ParallelGCThreads, 1),
2247                                 // degree of mt processing
2248                            (ParallelGCThreads > 1),
2249                                 // mt discovery
2250                            MAX2((int)ParallelGCThreads, 1),
2251                                 // degree of mt discovery
2252                            true,
2253                                 // Reference discovery is atomic
2254                            &_is_alive_closure_stw,
2255                                 // is alive closure
2256                                 // (for efficiency/performance)
2257                            false);
2258                                 // Setting next fields of discovered
2259                                 // lists requires a barrier.
2260 }
2261 
2262 size_t G1CollectedHeap::capacity() const {
2263   return _g1_committed.byte_size();
2264 }
2265 
2266 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2267                                                  DirtyCardQueue* into_cset_dcq,
2268                                                  bool concurrent,
2269                                                  int worker_i) {
2270   // Clean cards in the hot card cache
2271   concurrent_g1_refine()->clean_up_cache(worker_i, g1_rem_set(), into_cset_dcq);
2272 
2273   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2274   int n_completed_buffers = 0;
2275   while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2276     n_completed_buffers++;
2277   }
2278   g1_policy()->phase_times()->record_update_rs_processed_buffers(worker_i, n_completed_buffers);

2279   dcqs.clear_n_completed_buffers();
2280   assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2281 }
2282 
2283 
2284 // Computes the sum of the storage used by the various regions.
2285 
2286 size_t G1CollectedHeap::used() const {
2287   assert(Heap_lock->owner() != NULL,
2288          "Should be owned on this thread's behalf.");
2289   size_t result = _summary_bytes_used;
2290   // Read only once in case it is set to NULL concurrently
2291   HeapRegion* hr = _mutator_alloc_region.get();
2292   if (hr != NULL)
2293     result += hr->used();
2294   return result;
2295 }
2296 
2297 size_t G1CollectedHeap::used_unlocked() const {
2298   size_t result = _summary_bytes_used;
2299   return result;
2300 }
2301 
2302 class SumUsedClosure: public HeapRegionClosure {
2303   size_t _used;
2304 public:
2305   SumUsedClosure() : _used(0) {}
2306   bool doHeapRegion(HeapRegion* r) {
2307     if (!r->continuesHumongous()) {
2308       _used += r->used();
2309     }
2310     return false;
2311   }
2312   size_t result() { return _used; }
2313 };
2314 
2315 size_t G1CollectedHeap::recalculate_used() const {
2316   SumUsedClosure blk;
2317   heap_region_iterate(&blk);
2318   return blk.result();
2319 }
2320 
2321 size_t G1CollectedHeap::unsafe_max_alloc() {
2322   if (free_regions() > 0) return HeapRegion::GrainBytes;
2323   // otherwise, is there space in the current allocation region?
2324 
2325   // We need to store the current allocation region in a local variable
2326   // here. The problem is that this method doesn't take any locks and
2327   // there may be other threads which overwrite the current allocation
2328   // region field. attempt_allocation(), for example, sets it to NULL
2329   // and this can happen *after* the NULL check here but before the call
2330   // to free(), resulting in a SIGSEGV. Note that this doesn't appear
2331   // to be a problem in the optimized build, since the two loads of the
2332   // current allocation region field are optimized away.
2333   HeapRegion* hr = _mutator_alloc_region.get();
2334   if (hr == NULL) {
2335     return 0;
2336   }
2337   return hr->free();
2338 }
2339 
2340 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2341   switch (cause) {
2342     case GCCause::_gc_locker:               return GCLockerInvokesConcurrent;
2343     case GCCause::_java_lang_system_gc:     return ExplicitGCInvokesConcurrent;
2344     case GCCause::_g1_humongous_allocation: return true;
2345     default:                                return false;
2346   }
2347 }
2348 
2349 #ifndef PRODUCT
2350 void G1CollectedHeap::allocate_dummy_regions() {
2351   // Let's fill up most of the region
2352   size_t word_size = HeapRegion::GrainWords - 1024;
2353   // And as a result the region we'll allocate will be humongous.
2354   guarantee(isHumongous(word_size), "sanity");
2355 
2356   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2357     // Let's use the existing mechanism for the allocation
2358     HeapWord* dummy_obj = humongous_obj_allocate(word_size);
2359     if (dummy_obj != NULL) {
2360       MemRegion mr(dummy_obj, word_size);
2361       CollectedHeap::fill_with_object(mr);
2362     } else {
2363       // If we can't allocate once, we probably cannot allocate
2364       // again. Let's get out of the loop.
2365       break;
2366     }
2367   }
2368 }
2369 #endif // !PRODUCT
2370 
2371 void G1CollectedHeap::increment_old_marking_cycles_started() {
2372   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2373     _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2374     err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2375     _old_marking_cycles_started, _old_marking_cycles_completed));
2376 
2377   _old_marking_cycles_started++;
2378 }
2379 
2380 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2381   MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2382 
2383   // We assume that if concurrent == true, then the caller is a
2384   // concurrent thread that was joined the Suspendible Thread
2385   // Set. If there's ever a cheap way to check this, we should add an
2386   // assert here.
2387 
2388   // Given that this method is called at the end of a Full GC or of a
2389   // concurrent cycle, and those can be nested (i.e., a Full GC can
2390   // interrupt a concurrent cycle), the number of full collections
2391   // completed should be either one (in the case where there was no
2392   // nesting) or two (when a Full GC interrupted a concurrent cycle)
2393   // behind the number of full collections started.
2394 
2395   // This is the case for the inner caller, i.e. a Full GC.
2396   assert(concurrent ||
2397          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2398          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2399          err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
2400                  "is inconsistent with _old_marking_cycles_completed = %u",
2401                  _old_marking_cycles_started, _old_marking_cycles_completed));
2402 
2403   // This is the case for the outer caller, i.e. the concurrent cycle.
2404   assert(!concurrent ||
2405          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2406          err_msg("for outer caller (concurrent cycle): "
2407                  "_old_marking_cycles_started = %u "
2408                  "is inconsistent with _old_marking_cycles_completed = %u",
2409                  _old_marking_cycles_started, _old_marking_cycles_completed));
2410 
2411   _old_marking_cycles_completed += 1;
2412 
2413   // We need to clear the "in_progress" flag in the CM thread before
2414   // we wake up any waiters (especially when ExplicitInvokesConcurrent
2415   // is set) so that if a waiter requests another System.gc() it doesn't
2416   // incorrectly see that a marking cyle is still in progress.
2417   if (concurrent) {
2418     _cmThread->clear_in_progress();
2419   }
2420 
2421   // This notify_all() will ensure that a thread that called
2422   // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2423   // and it's waiting for a full GC to finish will be woken up. It is
2424   // waiting in VM_G1IncCollectionPause::doit_epilogue().
2425   FullGCCount_lock->notify_all();
2426 }
2427 
2428 void G1CollectedHeap::collect_as_vm_thread(GCCause::Cause cause) {
2429   assert_at_safepoint(true /* should_be_vm_thread */);
2430   GCCauseSetter gcs(this, cause);
2431   switch (cause) {
2432     case GCCause::_heap_inspection:
2433     case GCCause::_heap_dump: {
2434       HandleMark hm;
2435       do_full_collection(false);         // don't clear all soft refs
2436       break;
2437     }
2438     default: // XXX FIX ME
2439       ShouldNotReachHere(); // Unexpected use of this function
2440   }
2441 }
2442 
2443 void G1CollectedHeap::collect(GCCause::Cause cause) {
2444   assert_heap_not_locked();
2445 
2446   unsigned int gc_count_before;
2447   unsigned int old_marking_count_before;
2448   bool retry_gc;
2449 
2450   do {
2451     retry_gc = false;
2452 
2453     {
2454       MutexLocker ml(Heap_lock);
2455 
2456       // Read the GC count while holding the Heap_lock
2457       gc_count_before = total_collections();
2458       old_marking_count_before = _old_marking_cycles_started;
2459     }
2460 
2461     if (should_do_concurrent_full_gc(cause)) {
2462       // Schedule an initial-mark evacuation pause that will start a
2463       // concurrent cycle. We're setting word_size to 0 which means that
2464       // we are not requesting a post-GC allocation.
2465       VM_G1IncCollectionPause op(gc_count_before,
2466                                  0,     /* word_size */
2467                                  true,  /* should_initiate_conc_mark */
2468                                  g1_policy()->max_pause_time_ms(),
2469                                  cause);
2470 
2471       VMThread::execute(&op);
2472       if (!op.pause_succeeded()) {
2473         if (old_marking_count_before == _old_marking_cycles_started) {
2474           retry_gc = op.should_retry_gc();
2475         } else {
2476           // A Full GC happened while we were trying to schedule the
2477           // initial-mark GC. No point in starting a new cycle given
2478           // that the whole heap was collected anyway.
2479         }
2480 
2481         if (retry_gc) {
2482           if (GC_locker::is_active_and_needs_gc()) {
2483             GC_locker::stall_until_clear();
2484           }
2485         }
2486       }
2487     } else {
2488       if (cause == GCCause::_gc_locker
2489           DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2490 
2491         // Schedule a standard evacuation pause. We're setting word_size
2492         // to 0 which means that we are not requesting a post-GC allocation.
2493         VM_G1IncCollectionPause op(gc_count_before,
2494                                    0,     /* word_size */
2495                                    false, /* should_initiate_conc_mark */
2496                                    g1_policy()->max_pause_time_ms(),
2497                                    cause);
2498         VMThread::execute(&op);
2499       } else {
2500         // Schedule a Full GC.
2501         VM_G1CollectFull op(gc_count_before, old_marking_count_before, cause);
2502         VMThread::execute(&op);
2503       }
2504     }
2505   } while (retry_gc);
2506 }
2507 
2508 bool G1CollectedHeap::is_in(const void* p) const {
2509   if (_g1_committed.contains(p)) {
2510     // Given that we know that p is in the committed space,
2511     // heap_region_containing_raw() should successfully
2512     // return the containing region.
2513     HeapRegion* hr = heap_region_containing_raw(p);
2514     return hr->is_in(p);
2515   } else {
2516     return _perm_gen->as_gen()->is_in(p);
2517   }
2518 }
2519 
2520 // Iteration functions.
2521 
2522 // Iterates an OopClosure over all ref-containing fields of objects
2523 // within a HeapRegion.
2524 
2525 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2526   MemRegion _mr;
2527   OopClosure* _cl;
2528 public:
2529   IterateOopClosureRegionClosure(MemRegion mr, OopClosure* cl)
2530     : _mr(mr), _cl(cl) {}
2531   bool doHeapRegion(HeapRegion* r) {
2532     if (! r->continuesHumongous()) {
2533       r->oop_iterate(_cl);
2534     }
2535     return false;
2536   }
2537 };
2538 
2539 void G1CollectedHeap::oop_iterate(OopClosure* cl, bool do_perm) {
2540   IterateOopClosureRegionClosure blk(_g1_committed, cl);
2541   heap_region_iterate(&blk);
2542   if (do_perm) {
2543     perm_gen()->oop_iterate(cl);
2544   }
2545 }
2546 
2547 void G1CollectedHeap::oop_iterate(MemRegion mr, OopClosure* cl, bool do_perm) {
2548   IterateOopClosureRegionClosure blk(mr, cl);
2549   heap_region_iterate(&blk);
2550   if (do_perm) {
2551     perm_gen()->oop_iterate(cl);
2552   }
2553 }
2554 
2555 // Iterates an ObjectClosure over all objects within a HeapRegion.
2556 
2557 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2558   ObjectClosure* _cl;
2559 public:
2560   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2561   bool doHeapRegion(HeapRegion* r) {
2562     if (! r->continuesHumongous()) {
2563       r->object_iterate(_cl);
2564     }
2565     return false;
2566   }
2567 };
2568 
2569 void G1CollectedHeap::object_iterate(ObjectClosure* cl, bool do_perm) {
2570   IterateObjectClosureRegionClosure blk(cl);
2571   heap_region_iterate(&blk);
2572   if (do_perm) {
2573     perm_gen()->object_iterate(cl);
2574   }
2575 }
2576 
2577 void G1CollectedHeap::object_iterate_since_last_GC(ObjectClosure* cl) {
2578   // FIXME: is this right?
2579   guarantee(false, "object_iterate_since_last_GC not supported by G1 heap");
2580 }
2581 
2582 // Calls a SpaceClosure on a HeapRegion.
2583 
2584 class SpaceClosureRegionClosure: public HeapRegionClosure {
2585   SpaceClosure* _cl;
2586 public:
2587   SpaceClosureRegionClosure(SpaceClosure* cl) : _cl(cl) {}
2588   bool doHeapRegion(HeapRegion* r) {
2589     _cl->do_space(r);
2590     return false;
2591   }
2592 };
2593 
2594 void G1CollectedHeap::space_iterate(SpaceClosure* cl) {
2595   SpaceClosureRegionClosure blk(cl);
2596   heap_region_iterate(&blk);
2597 }
2598 
2599 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2600   _hrs.iterate(cl);
2601 }
2602 
2603 void G1CollectedHeap::heap_region_iterate_from(HeapRegion* r,
2604                                                HeapRegionClosure* cl) const {
2605   _hrs.iterate_from(r, cl);
2606 }
2607 
2608 void
2609 G1CollectedHeap::heap_region_par_iterate_chunked(HeapRegionClosure* cl,
2610                                                  uint worker,
2611                                                  uint no_of_par_workers,
2612                                                  jint claim_value) {
2613   const uint regions = n_regions();
2614   const uint max_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
2615                              no_of_par_workers :
2616                              1);
2617   assert(UseDynamicNumberOfGCThreads ||
2618          no_of_par_workers == workers()->total_workers(),
2619          "Non dynamic should use fixed number of workers");
2620   // try to spread out the starting points of the workers
2621   const uint start_index = regions / max_workers * worker;
2622 
2623   // each worker will actually look at all regions
2624   for (uint count = 0; count < regions; ++count) {
2625     const uint index = (start_index + count) % regions;
2626     assert(0 <= index && index < regions, "sanity");
2627     HeapRegion* r = region_at(index);
2628     // we'll ignore "continues humongous" regions (we'll process them
2629     // when we come across their corresponding "start humongous"
2630     // region) and regions already claimed
2631     if (r->claim_value() == claim_value || r->continuesHumongous()) {
2632       continue;
2633     }
2634     // OK, try to claim it
2635     if (r->claimHeapRegion(claim_value)) {
2636       // success!
2637       assert(!r->continuesHumongous(), "sanity");
2638       if (r->startsHumongous()) {
2639         // If the region is "starts humongous" we'll iterate over its
2640         // "continues humongous" first; in fact we'll do them
2641         // first. The order is important. In on case, calling the
2642         // closure on the "starts humongous" region might de-allocate
2643         // and clear all its "continues humongous" regions and, as a
2644         // result, we might end up processing them twice. So, we'll do
2645         // them first (notice: most closures will ignore them anyway) and
2646         // then we'll do the "starts humongous" region.
2647         for (uint ch_index = index + 1; ch_index < regions; ++ch_index) {
2648           HeapRegion* chr = region_at(ch_index);
2649 
2650           // if the region has already been claimed or it's not
2651           // "continues humongous" we're done
2652           if (chr->claim_value() == claim_value ||
2653               !chr->continuesHumongous()) {
2654             break;
2655           }
2656 
2657           // Noone should have claimed it directly. We can given
2658           // that we claimed its "starts humongous" region.
2659           assert(chr->claim_value() != claim_value, "sanity");
2660           assert(chr->humongous_start_region() == r, "sanity");
2661 
2662           if (chr->claimHeapRegion(claim_value)) {
2663             // we should always be able to claim it; noone else should
2664             // be trying to claim this region
2665 
2666             bool res2 = cl->doHeapRegion(chr);
2667             assert(!res2, "Should not abort");
2668 
2669             // Right now, this holds (i.e., no closure that actually
2670             // does something with "continues humongous" regions
2671             // clears them). We might have to weaken it in the future,
2672             // but let's leave these two asserts here for extra safety.
2673             assert(chr->continuesHumongous(), "should still be the case");
2674             assert(chr->humongous_start_region() == r, "sanity");
2675           } else {
2676             guarantee(false, "we should not reach here");
2677           }
2678         }
2679       }
2680 
2681       assert(!r->continuesHumongous(), "sanity");
2682       bool res = cl->doHeapRegion(r);
2683       assert(!res, "Should not abort");
2684     }
2685   }
2686 }
2687 
2688 class ResetClaimValuesClosure: public HeapRegionClosure {
2689 public:
2690   bool doHeapRegion(HeapRegion* r) {
2691     r->set_claim_value(HeapRegion::InitialClaimValue);
2692     return false;
2693   }
2694 };
2695 
2696 void G1CollectedHeap::reset_heap_region_claim_values() {
2697   ResetClaimValuesClosure blk;
2698   heap_region_iterate(&blk);
2699 }
2700 
2701 void G1CollectedHeap::reset_cset_heap_region_claim_values() {
2702   ResetClaimValuesClosure blk;
2703   collection_set_iterate(&blk);
2704 }
2705 
2706 #ifdef ASSERT
2707 // This checks whether all regions in the heap have the correct claim
2708 // value. I also piggy-backed on this a check to ensure that the
2709 // humongous_start_region() information on "continues humongous"
2710 // regions is correct.
2711 
2712 class CheckClaimValuesClosure : public HeapRegionClosure {
2713 private:
2714   jint _claim_value;
2715   uint _failures;
2716   HeapRegion* _sh_region;
2717 
2718 public:
2719   CheckClaimValuesClosure(jint claim_value) :
2720     _claim_value(claim_value), _failures(0), _sh_region(NULL) { }
2721   bool doHeapRegion(HeapRegion* r) {
2722     if (r->claim_value() != _claim_value) {
2723       gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2724                              "claim value = %d, should be %d",
2725                              HR_FORMAT_PARAMS(r),
2726                              r->claim_value(), _claim_value);
2727       ++_failures;
2728     }
2729     if (!r->isHumongous()) {
2730       _sh_region = NULL;
2731     } else if (r->startsHumongous()) {
2732       _sh_region = r;
2733     } else if (r->continuesHumongous()) {
2734       if (r->humongous_start_region() != _sh_region) {
2735         gclog_or_tty->print_cr("Region " HR_FORMAT ", "
2736                                "HS = "PTR_FORMAT", should be "PTR_FORMAT,
2737                                HR_FORMAT_PARAMS(r),
2738                                r->humongous_start_region(),
2739                                _sh_region);
2740         ++_failures;
2741       }
2742     }
2743     return false;
2744   }
2745   uint failures() { return _failures; }
2746 };
2747 
2748 bool G1CollectedHeap::check_heap_region_claim_values(jint claim_value) {
2749   CheckClaimValuesClosure cl(claim_value);
2750   heap_region_iterate(&cl);
2751   return cl.failures() == 0;
2752 }
2753 
2754 class CheckClaimValuesInCSetHRClosure: public HeapRegionClosure {
2755 private:
2756   jint _claim_value;
2757   uint _failures;
2758 
2759 public:
2760   CheckClaimValuesInCSetHRClosure(jint claim_value) :
2761     _claim_value(claim_value), _failures(0) { }
2762 
2763   uint failures() { return _failures; }
2764 
2765   bool doHeapRegion(HeapRegion* hr) {
2766     assert(hr->in_collection_set(), "how?");
2767     assert(!hr->isHumongous(), "H-region in CSet");
2768     if (hr->claim_value() != _claim_value) {
2769       gclog_or_tty->print_cr("CSet Region " HR_FORMAT ", "
2770                              "claim value = %d, should be %d",
2771                              HR_FORMAT_PARAMS(hr),
2772                              hr->claim_value(), _claim_value);
2773       _failures += 1;
2774     }
2775     return false;
2776   }
2777 };
2778 
2779 bool G1CollectedHeap::check_cset_heap_region_claim_values(jint claim_value) {
2780   CheckClaimValuesInCSetHRClosure cl(claim_value);
2781   collection_set_iterate(&cl);
2782   return cl.failures() == 0;
2783 }
2784 #endif // ASSERT
2785 
2786 // Clear the cached CSet starting regions and (more importantly)
2787 // the time stamps. Called when we reset the GC time stamp.
2788 void G1CollectedHeap::clear_cset_start_regions() {
2789   assert(_worker_cset_start_region != NULL, "sanity");
2790   assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2791 
2792   int n_queues = MAX2((int)ParallelGCThreads, 1);
2793   for (int i = 0; i < n_queues; i++) {
2794     _worker_cset_start_region[i] = NULL;
2795     _worker_cset_start_region_time_stamp[i] = 0;
2796   }
2797 }
2798 
2799 // Given the id of a worker, obtain or calculate a suitable
2800 // starting region for iterating over the current collection set.
2801 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(int worker_i) {
2802   assert(get_gc_time_stamp() > 0, "should have been updated by now");
2803 
2804   HeapRegion* result = NULL;
2805   unsigned gc_time_stamp = get_gc_time_stamp();
2806 
2807   if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2808     // Cached starting region for current worker was set
2809     // during the current pause - so it's valid.
2810     // Note: the cached starting heap region may be NULL
2811     // (when the collection set is empty).
2812     result = _worker_cset_start_region[worker_i];
2813     assert(result == NULL || result->in_collection_set(), "sanity");
2814     return result;
2815   }
2816 
2817   // The cached entry was not valid so let's calculate
2818   // a suitable starting heap region for this worker.
2819 
2820   // We want the parallel threads to start their collection
2821   // set iteration at different collection set regions to
2822   // avoid contention.
2823   // If we have:
2824   //          n collection set regions
2825   //          p threads
2826   // Then thread t will start at region floor ((t * n) / p)
2827 
2828   result = g1_policy()->collection_set();
2829   if (G1CollectedHeap::use_parallel_gc_threads()) {
2830     uint cs_size = g1_policy()->cset_region_length();
2831     uint active_workers = workers()->active_workers();
2832     assert(UseDynamicNumberOfGCThreads ||
2833              active_workers == workers()->total_workers(),
2834              "Unless dynamic should use total workers");
2835 
2836     uint end_ind   = (cs_size * worker_i) / active_workers;
2837     uint start_ind = 0;
2838 
2839     if (worker_i > 0 &&
2840         _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2841       // Previous workers starting region is valid
2842       // so let's iterate from there
2843       start_ind = (cs_size * (worker_i - 1)) / active_workers;
2844       result = _worker_cset_start_region[worker_i - 1];
2845     }
2846 
2847     for (uint i = start_ind; i < end_ind; i++) {
2848       result = result->next_in_collection_set();
2849     }
2850   }
2851 
2852   // Note: the calculated starting heap region may be NULL
2853   // (when the collection set is empty).
2854   assert(result == NULL || result->in_collection_set(), "sanity");
2855   assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2856          "should be updated only once per pause");
2857   _worker_cset_start_region[worker_i] = result;
2858   OrderAccess::storestore();
2859   _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2860   return result;
2861 }
2862 
2863 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2864   HeapRegion* r = g1_policy()->collection_set();
2865   while (r != NULL) {
2866     HeapRegion* next = r->next_in_collection_set();
2867     if (cl->doHeapRegion(r)) {
2868       cl->incomplete();
2869       return;
2870     }
2871     r = next;
2872   }
2873 }
2874 
2875 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2876                                                   HeapRegionClosure *cl) {
2877   if (r == NULL) {
2878     // The CSet is empty so there's nothing to do.
2879     return;
2880   }
2881 
2882   assert(r->in_collection_set(),
2883          "Start region must be a member of the collection set.");
2884   HeapRegion* cur = r;
2885   while (cur != NULL) {
2886     HeapRegion* next = cur->next_in_collection_set();
2887     if (cl->doHeapRegion(cur) && false) {
2888       cl->incomplete();
2889       return;
2890     }
2891     cur = next;
2892   }
2893   cur = g1_policy()->collection_set();
2894   while (cur != r) {
2895     HeapRegion* next = cur->next_in_collection_set();
2896     if (cl->doHeapRegion(cur) && false) {
2897       cl->incomplete();
2898       return;
2899     }
2900     cur = next;
2901   }
2902 }
2903 
2904 CompactibleSpace* G1CollectedHeap::first_compactible_space() {
2905   return n_regions() > 0 ? region_at(0) : NULL;
2906 }
2907 
2908 
2909 Space* G1CollectedHeap::space_containing(const void* addr) const {
2910   Space* res = heap_region_containing(addr);
2911   if (res == NULL)
2912     res = perm_gen()->space_containing(addr);
2913   return res;
2914 }
2915 
2916 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2917   Space* sp = space_containing(addr);
2918   if (sp != NULL) {
2919     return sp->block_start(addr);
2920   }
2921   return NULL;
2922 }
2923 
2924 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2925   Space* sp = space_containing(addr);
2926   assert(sp != NULL, "block_size of address outside of heap");
2927   return sp->block_size(addr);
2928 }
2929 
2930 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2931   Space* sp = space_containing(addr);
2932   return sp->block_is_obj(addr);
2933 }
2934 
2935 bool G1CollectedHeap::supports_tlab_allocation() const {
2936   return true;
2937 }
2938 
2939 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2940   return HeapRegion::GrainBytes;
2941 }
2942 
2943 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2944   // Return the remaining space in the cur alloc region, but not less than
2945   // the min TLAB size.
2946 
2947   // Also, this value can be at most the humongous object threshold,
2948   // since we can't allow tlabs to grow big enough to accomodate
2949   // humongous objects.
2950 
2951   HeapRegion* hr = _mutator_alloc_region.get();
2952   size_t max_tlab_size = _humongous_object_threshold_in_words * wordSize;
2953   if (hr == NULL) {
2954     return max_tlab_size;
2955   } else {
2956     return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab_size);
2957   }
2958 }
2959 
2960 size_t G1CollectedHeap::max_capacity() const {
2961   return _g1_reserved.byte_size();
2962 }
2963 
2964 jlong G1CollectedHeap::millis_since_last_gc() {
2965   // assert(false, "NYI");
2966   return 0;
2967 }
2968 
2969 void G1CollectedHeap::prepare_for_verify() {
2970   if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
2971     ensure_parsability(false);
2972   }
2973   g1_rem_set()->prepare_for_verify();
2974 }
2975 
2976 class VerifyLivenessOopClosure: public OopClosure {
2977   G1CollectedHeap* _g1h;
2978   VerifyOption _vo;
2979 public:
2980   VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
2981     _g1h(g1h), _vo(vo)
2982   { }
2983   void do_oop(narrowOop *p) { do_oop_work(p); }
2984   void do_oop(      oop *p) { do_oop_work(p); }
2985 
2986   template <class T> void do_oop_work(T *p) {
2987     oop obj = oopDesc::load_decode_heap_oop(p);
2988     guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
2989               "Dead object referenced by a not dead object");
2990   }
2991 };
2992 
2993 class VerifyObjsInRegionClosure: public ObjectClosure {
2994 private:
2995   G1CollectedHeap* _g1h;
2996   size_t _live_bytes;
2997   HeapRegion *_hr;
2998   VerifyOption _vo;
2999 public:
3000   // _vo == UsePrevMarking -> use "prev" marking information,
3001   // _vo == UseNextMarking -> use "next" marking information,
3002   // _vo == UseMarkWord    -> use mark word from object header.
3003   VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
3004     : _live_bytes(0), _hr(hr), _vo(vo) {
3005     _g1h = G1CollectedHeap::heap();
3006   }
3007   void do_object(oop o) {
3008     VerifyLivenessOopClosure isLive(_g1h, _vo);
3009     assert(o != NULL, "Huh?");
3010     if (!_g1h->is_obj_dead_cond(o, _vo)) {
3011       // If the object is alive according to the mark word,
3012       // then verify that the marking information agrees.
3013       // Note we can't verify the contra-positive of the
3014       // above: if the object is dead (according to the mark
3015       // word), it may not be marked, or may have been marked
3016       // but has since became dead, or may have been allocated
3017       // since the last marking.
3018       if (_vo == VerifyOption_G1UseMarkWord) {
3019         guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
3020       }
3021 
3022       o->oop_iterate(&isLive);
3023       if (!_hr->obj_allocated_since_prev_marking(o)) {
3024         size_t obj_size = o->size();    // Make sure we don't overflow
3025         _live_bytes += (obj_size * HeapWordSize);
3026       }
3027     }
3028   }
3029   size_t live_bytes() { return _live_bytes; }
3030 };
3031 
3032 class PrintObjsInRegionClosure : public ObjectClosure {
3033   HeapRegion *_hr;
3034   G1CollectedHeap *_g1;
3035 public:
3036   PrintObjsInRegionClosure(HeapRegion *hr) : _hr(hr) {
3037     _g1 = G1CollectedHeap::heap();
3038   };
3039 
3040   void do_object(oop o) {
3041     if (o != NULL) {
3042       HeapWord *start = (HeapWord *) o;
3043       size_t word_sz = o->size();
3044       gclog_or_tty->print("\nPrinting obj "PTR_FORMAT" of size " SIZE_FORMAT
3045                           " isMarkedPrev %d isMarkedNext %d isAllocSince %d\n",
3046                           (void*) o, word_sz,
3047                           _g1->isMarkedPrev(o),
3048                           _g1->isMarkedNext(o),
3049                           _hr->obj_allocated_since_prev_marking(o));
3050       HeapWord *end = start + word_sz;
3051       HeapWord *cur;
3052       int *val;
3053       for (cur = start; cur < end; cur++) {
3054         val = (int *) cur;
3055         gclog_or_tty->print("\t "PTR_FORMAT":"PTR_FORMAT"\n", val, *val);
3056       }
3057     }
3058   }
3059 };
3060 
3061 class VerifyRegionClosure: public HeapRegionClosure {
3062 private:
3063   bool         _par;
3064   VerifyOption _vo;
3065   bool         _failures;
3066 public:
3067   // _vo == UsePrevMarking -> use "prev" marking information,
3068   // _vo == UseNextMarking -> use "next" marking information,
3069   // _vo == UseMarkWord    -> use mark word from object header.
3070   VerifyRegionClosure(bool par, VerifyOption vo)
3071     : _par(par),
3072       _vo(vo),
3073       _failures(false) {}
3074 
3075   bool failures() {
3076     return _failures;
3077   }
3078 
3079   bool doHeapRegion(HeapRegion* r) {
3080     guarantee(_par || r->claim_value() == HeapRegion::InitialClaimValue,
3081               "Should be unclaimed at verify points.");
3082     if (!r->continuesHumongous()) {
3083       bool failures = false;
3084       r->verify(_vo, &failures);
3085       if (failures) {
3086         _failures = true;
3087       } else {
3088         VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
3089         r->object_iterate(&not_dead_yet_cl);
3090         if (_vo != VerifyOption_G1UseNextMarking) {
3091           if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
3092             gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
3093                                    "max_live_bytes "SIZE_FORMAT" "
3094                                    "< calculated "SIZE_FORMAT,
3095                                    r->bottom(), r->end(),
3096                                    r->max_live_bytes(),
3097                                  not_dead_yet_cl.live_bytes());
3098             _failures = true;
3099           }
3100         } else {
3101           // When vo == UseNextMarking we cannot currently do a sanity
3102           // check on the live bytes as the calculation has not been
3103           // finalized yet.
3104         }
3105       }
3106     }
3107     return false; // stop the region iteration if we hit a failure
3108   }
3109 };
3110 
3111 class VerifyRootsClosure: public OopsInGenClosure {
3112 private:
3113   G1CollectedHeap* _g1h;
3114   VerifyOption     _vo;
3115   bool             _failures;
3116 public:
3117   // _vo == UsePrevMarking -> use "prev" marking information,
3118   // _vo == UseNextMarking -> use "next" marking information,
3119   // _vo == UseMarkWord    -> use mark word from object header.
3120   VerifyRootsClosure(VerifyOption vo) :
3121     _g1h(G1CollectedHeap::heap()),
3122     _vo(vo),
3123     _failures(false) { }
3124 
3125   bool failures() { return _failures; }
3126 
3127   template <class T> void do_oop_nv(T* p) {
3128     T heap_oop = oopDesc::load_heap_oop(p);
3129     if (!oopDesc::is_null(heap_oop)) {
3130       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
3131       if (_g1h->is_obj_dead_cond(obj, _vo)) {
3132         gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
3133                               "points to dead obj "PTR_FORMAT, p, (void*) obj);
3134         if (_vo == VerifyOption_G1UseMarkWord) {
3135           gclog_or_tty->print_cr("  Mark word: "PTR_FORMAT, (void*)(obj->mark()));
3136         }
3137         obj->print_on(gclog_or_tty);
3138         _failures = true;
3139       }
3140     }
3141   }
3142 
3143   void do_oop(oop* p)       { do_oop_nv(p); }
3144   void do_oop(narrowOop* p) { do_oop_nv(p); }
3145 };
3146 
3147 // This is the task used for parallel heap verification.
3148 
3149 class G1ParVerifyTask: public AbstractGangTask {
3150 private:
3151   G1CollectedHeap* _g1h;
3152   VerifyOption     _vo;
3153   bool             _failures;
3154 
3155 public:
3156   // _vo == UsePrevMarking -> use "prev" marking information,
3157   // _vo == UseNextMarking -> use "next" marking information,
3158   // _vo == UseMarkWord    -> use mark word from object header.
3159   G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
3160     AbstractGangTask("Parallel verify task"),
3161     _g1h(g1h),
3162     _vo(vo),
3163     _failures(false) { }
3164 
3165   bool failures() {
3166     return _failures;
3167   }
3168 
3169   void work(uint worker_id) {
3170     HandleMark hm;
3171     VerifyRegionClosure blk(true, _vo);
3172     _g1h->heap_region_par_iterate_chunked(&blk, worker_id,
3173                                           _g1h->workers()->active_workers(),
3174                                           HeapRegion::ParVerifyClaimValue);
3175     if (blk.failures()) {
3176       _failures = true;
3177     }
3178   }
3179 };
3180 
3181 void G1CollectedHeap::verify(bool silent) {
3182   verify(silent, VerifyOption_G1UsePrevMarking);
3183 }
3184 
3185 void G1CollectedHeap::verify(bool silent,
3186                              VerifyOption vo) {
3187   if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
3188     if (!silent) { gclog_or_tty->print("Roots (excluding permgen) "); }
3189     VerifyRootsClosure rootsCl(vo);
3190 
3191     assert(Thread::current()->is_VM_thread(),
3192       "Expected to be executed serially by the VM thread at this point");
3193 
3194     CodeBlobToOopClosure blobsCl(&rootsCl, /*do_marking=*/ false);
3195 
3196     // We apply the relevant closures to all the oops in the
3197     // system dictionary, the string table and the code cache.
3198     const int so = SO_AllClasses | SO_Strings | SO_CodeCache;
3199 
3200     process_strong_roots(true,      // activate StrongRootsScope
3201                          true,      // we set "collecting perm gen" to true,
3202                                     // so we don't reset the dirty cards in the perm gen.
3203                          ScanningOption(so),  // roots scanning options
3204                          &rootsCl,
3205                          &blobsCl,
3206                          &rootsCl);
3207 
3208     // If we're verifying after the marking phase of a Full GC then we can't
3209     // treat the perm gen as roots into the G1 heap. Some of the objects in
3210     // the perm gen may be dead and hence not marked. If one of these dead
3211     // objects is considered to be a root then we may end up with a false
3212     // "Root location <x> points to dead ob <y>" failure.
3213     if (vo != VerifyOption_G1UseMarkWord) {
3214       // Since we used "collecting_perm_gen" == true above, we will not have
3215       // checked the refs from perm into the G1-collected heap. We check those
3216       // references explicitly below. Whether the relevant cards are dirty
3217       // is checked further below in the rem set verification.
3218       if (!silent) { gclog_or_tty->print("Permgen roots "); }
3219       perm_gen()->oop_iterate(&rootsCl);
3220     }
3221     bool failures = rootsCl.failures();
3222 
3223     if (vo != VerifyOption_G1UseMarkWord) {
3224       // If we're verifying during a full GC then the region sets
3225       // will have been torn down at the start of the GC. Therefore
3226       // verifying the region sets will fail. So we only verify
3227       // the region sets when not in a full GC.
3228       if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3229       verify_region_sets();
3230     }
3231 
3232     if (!silent) { gclog_or_tty->print("HeapRegions "); }
3233     if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3234       assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3235              "sanity check");
3236 
3237       G1ParVerifyTask task(this, vo);
3238       assert(UseDynamicNumberOfGCThreads ||
3239         workers()->active_workers() == workers()->total_workers(),
3240         "If not dynamic should be using all the workers");
3241       int n_workers = workers()->active_workers();
3242       set_par_threads(n_workers);
3243       workers()->run_task(&task);
3244       set_par_threads(0);
3245       if (task.failures()) {
3246         failures = true;
3247       }
3248 
3249       // Checks that the expected amount of parallel work was done.
3250       // The implication is that n_workers is > 0.
3251       assert(check_heap_region_claim_values(HeapRegion::ParVerifyClaimValue),
3252              "sanity check");
3253 
3254       reset_heap_region_claim_values();
3255 
3256       assert(check_heap_region_claim_values(HeapRegion::InitialClaimValue),
3257              "sanity check");
3258     } else {
3259       VerifyRegionClosure blk(false, vo);
3260       heap_region_iterate(&blk);
3261       if (blk.failures()) {
3262         failures = true;
3263       }
3264     }
3265     if (!silent) gclog_or_tty->print("RemSet ");
3266     rem_set()->verify();
3267 
3268     if (failures) {
3269       gclog_or_tty->print_cr("Heap:");
3270       // It helps to have the per-region information in the output to
3271       // help us track down what went wrong. This is why we call
3272       // print_extended_on() instead of print_on().
3273       print_extended_on(gclog_or_tty);
3274       gclog_or_tty->print_cr("");
3275 #ifndef PRODUCT
3276       if (VerifyDuringGC && G1VerifyDuringGCPrintReachable) {
3277         concurrent_mark()->print_reachable("at-verification-failure",
3278                                            vo, false /* all */);
3279       }
3280 #endif
3281       gclog_or_tty->flush();
3282     }
3283     guarantee(!failures, "there should not have been any failures");
3284   } else {
3285     if (!silent) gclog_or_tty->print("(SKIPPING roots, heapRegions, remset) ");
3286   }
3287 }
3288 
3289 class PrintRegionClosure: public HeapRegionClosure {
3290   outputStream* _st;
3291 public:
3292   PrintRegionClosure(outputStream* st) : _st(st) {}
3293   bool doHeapRegion(HeapRegion* r) {
3294     r->print_on(_st);
3295     return false;
3296   }
3297 };
3298 
3299 void G1CollectedHeap::print_on(outputStream* st) const {
3300   st->print(" %-20s", "garbage-first heap");
3301   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3302             capacity()/K, used_unlocked()/K);
3303   st->print(" [" INTPTR_FORMAT ", " INTPTR_FORMAT ", " INTPTR_FORMAT ")",
3304             _g1_storage.low_boundary(),
3305             _g1_storage.high(),
3306             _g1_storage.high_boundary());
3307   st->cr();
3308   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3309   uint young_regions = _young_list->length();
3310   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3311             (size_t) young_regions * HeapRegion::GrainBytes / K);
3312   uint survivor_regions = g1_policy()->recorded_survivor_regions();
3313   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3314             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3315   st->cr();
3316   perm()->as_gen()->print_on(st);
3317 }
3318 
3319 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3320   print_on(st);
3321 
3322   // Print the per-region information.
3323   st->cr();
3324   st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3325                "HS=humongous(starts), HC=humongous(continues), "
3326                "CS=collection set, F=free, TS=gc time stamp, "
3327                "PTAMS=previous top-at-mark-start, "
3328                "NTAMS=next top-at-mark-start)");
3329   PrintRegionClosure blk(st);
3330   heap_region_iterate(&blk);
3331 }
3332 
3333 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3334   if (G1CollectedHeap::use_parallel_gc_threads()) {
3335     workers()->print_worker_threads_on(st);
3336   }
3337   _cmThread->print_on(st);
3338   st->cr();
3339   _cm->print_worker_threads_on(st);
3340   _cg1r->print_worker_threads_on(st);
3341   st->cr();
3342 }
3343 
3344 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3345   if (G1CollectedHeap::use_parallel_gc_threads()) {
3346     workers()->threads_do(tc);
3347   }
3348   tc->do_thread(_cmThread);
3349   _cg1r->threads_do(tc);
3350 }
3351 
3352 void G1CollectedHeap::print_tracing_info() const {
3353   // We'll overload this to mean "trace GC pause statistics."
3354   if (TraceGen0Time || TraceGen1Time) {
3355     // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3356     // to that.
3357     g1_policy()->print_tracing_info();
3358   }
3359   if (G1SummarizeRSetStats) {
3360     g1_rem_set()->print_summary_info();
3361   }
3362   if (G1SummarizeConcMark) {
3363     concurrent_mark()->print_summary_info();
3364   }
3365   g1_policy()->print_yg_surv_rate_info();
3366   SpecializationStats::print();
3367 }
3368 
3369 #ifndef PRODUCT
3370 // Helpful for debugging RSet issues.
3371 
3372 class PrintRSetsClosure : public HeapRegionClosure {
3373 private:
3374   const char* _msg;
3375   size_t _occupied_sum;
3376 
3377 public:
3378   bool doHeapRegion(HeapRegion* r) {
3379     HeapRegionRemSet* hrrs = r->rem_set();
3380     size_t occupied = hrrs->occupied();
3381     _occupied_sum += occupied;
3382 
3383     gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3384                            HR_FORMAT_PARAMS(r));
3385     if (occupied == 0) {
3386       gclog_or_tty->print_cr("  RSet is empty");
3387     } else {
3388       hrrs->print();
3389     }
3390     gclog_or_tty->print_cr("----------");
3391     return false;
3392   }
3393 
3394   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3395     gclog_or_tty->cr();
3396     gclog_or_tty->print_cr("========================================");
3397     gclog_or_tty->print_cr(msg);
3398     gclog_or_tty->cr();
3399   }
3400 
3401   ~PrintRSetsClosure() {
3402     gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3403     gclog_or_tty->print_cr("========================================");
3404     gclog_or_tty->cr();
3405   }
3406 };
3407 
3408 void G1CollectedHeap::print_cset_rsets() {
3409   PrintRSetsClosure cl("Printing CSet RSets");
3410   collection_set_iterate(&cl);
3411 }
3412 
3413 void G1CollectedHeap::print_all_rsets() {
3414   PrintRSetsClosure cl("Printing All RSets");;
3415   heap_region_iterate(&cl);
3416 }
3417 #endif // PRODUCT
3418 
3419 G1CollectedHeap* G1CollectedHeap::heap() {
3420   assert(_sh->kind() == CollectedHeap::G1CollectedHeap,
3421          "not a garbage-first heap");
3422   return _g1h;
3423 }
3424 
3425 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3426   // always_do_update_barrier = false;
3427   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3428   // Call allocation profiler
3429   AllocationProfiler::iterate_since_last_gc();
3430   // Fill TLAB's and such
3431   ensure_parsability(true);
3432 }
3433 
3434 void G1CollectedHeap::gc_epilogue(bool full /* Ignored */) {
3435   // FIXME: what is this about?
3436   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3437   // is set.
3438   COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3439                         "derived pointer present"));
3440   // always_do_update_barrier = true;
3441 
3442   // We have just completed a GC. Update the soft reference
3443   // policy with the new heap occupancy
3444   Universe::update_heap_info_at_gc();
3445 }
3446 
3447 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3448                                                unsigned int gc_count_before,
3449                                                bool* succeeded) {
3450   assert_heap_not_locked_and_not_at_safepoint();
3451   g1_policy()->record_stop_world_start();
3452   VM_G1IncCollectionPause op(gc_count_before,
3453                              word_size,
3454                              false, /* should_initiate_conc_mark */
3455                              g1_policy()->max_pause_time_ms(),
3456                              GCCause::_g1_inc_collection_pause);
3457   VMThread::execute(&op);
3458 
3459   HeapWord* result = op.result();
3460   bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3461   assert(result == NULL || ret_succeeded,
3462          "the result should be NULL if the VM did not succeed");
3463   *succeeded = ret_succeeded;
3464 
3465   assert_heap_not_locked();
3466   return result;
3467 }
3468 
3469 void
3470 G1CollectedHeap::doConcurrentMark() {
3471   MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3472   if (!_cmThread->in_progress()) {
3473     _cmThread->set_started();
3474     CGC_lock->notify();
3475   }
3476 }
3477 
3478 size_t G1CollectedHeap::pending_card_num() {
3479   size_t extra_cards = 0;
3480   JavaThread *curr = Threads::first();
3481   while (curr != NULL) {
3482     DirtyCardQueue& dcq = curr->dirty_card_queue();
3483     extra_cards += dcq.size();
3484     curr = curr->next();
3485   }
3486   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3487   size_t buffer_size = dcqs.buffer_size();
3488   size_t buffer_num = dcqs.completed_buffers_num();
3489   return buffer_size * buffer_num + extra_cards;
3490 }
3491 
3492 size_t G1CollectedHeap::max_pending_card_num() {
3493   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3494   size_t buffer_size = dcqs.buffer_size();
3495   size_t buffer_num  = dcqs.completed_buffers_num();
3496   int thread_num  = Threads::number_of_threads();
3497   return (buffer_num + thread_num) * buffer_size;
3498 }
3499 
3500 size_t G1CollectedHeap::cards_scanned() {
3501   return g1_rem_set()->cardsScanned();
3502 }
3503 
3504 void
3505 G1CollectedHeap::setup_surviving_young_words() {
3506   assert(_surviving_young_words == NULL, "pre-condition");
3507   uint array_length = g1_policy()->young_cset_region_length();
3508   _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3509   if (_surviving_young_words == NULL) {
3510     vm_exit_out_of_memory(sizeof(size_t) * array_length,
3511                           "Not enough space for young surv words summary.");
3512   }
3513   memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3514 #ifdef ASSERT
3515   for (uint i = 0;  i < array_length; ++i) {
3516     assert( _surviving_young_words[i] == 0, "memset above" );
3517   }
3518 #endif // !ASSERT
3519 }
3520 
3521 void
3522 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3523   MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3524   uint array_length = g1_policy()->young_cset_region_length();
3525   for (uint i = 0; i < array_length; ++i) {
3526     _surviving_young_words[i] += surv_young_words[i];
3527   }
3528 }
3529 
3530 void
3531 G1CollectedHeap::cleanup_surviving_young_words() {
3532   guarantee( _surviving_young_words != NULL, "pre-condition" );
3533   FREE_C_HEAP_ARRAY(size_t, _surviving_young_words, mtGC);
3534   _surviving_young_words = NULL;
3535 }
3536 
3537 #ifdef ASSERT
3538 class VerifyCSetClosure: public HeapRegionClosure {
3539 public:
3540   bool doHeapRegion(HeapRegion* hr) {
3541     // Here we check that the CSet region's RSet is ready for parallel
3542     // iteration. The fields that we'll verify are only manipulated
3543     // when the region is part of a CSet and is collected. Afterwards,
3544     // we reset these fields when we clear the region's RSet (when the
3545     // region is freed) so they are ready when the region is
3546     // re-allocated. The only exception to this is if there's an
3547     // evacuation failure and instead of freeing the region we leave
3548     // it in the heap. In that case, we reset these fields during
3549     // evacuation failure handling.
3550     guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3551 
3552     // Here's a good place to add any other checks we'd like to
3553     // perform on CSet regions.
3554     return false;
3555   }
3556 };
3557 #endif // ASSERT
3558 
3559 #if TASKQUEUE_STATS
3560 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3561   st->print_raw_cr("GC Task Stats");
3562   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3563   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3564 }
3565 
3566 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3567   print_taskqueue_stats_hdr(st);
3568 
3569   TaskQueueStats totals;
3570   const int n = workers() != NULL ? workers()->total_workers() : 1;
3571   for (int i = 0; i < n; ++i) {
3572     st->print("%3d ", i); task_queue(i)->stats.print(st); st->cr();
3573     totals += task_queue(i)->stats;
3574   }
3575   st->print_raw("tot "); totals.print(st); st->cr();
3576 
3577   DEBUG_ONLY(totals.verify());
3578 }
3579 
3580 void G1CollectedHeap::reset_taskqueue_stats() {
3581   const int n = workers() != NULL ? workers()->total_workers() : 1;
3582   for (int i = 0; i < n; ++i) {
3583     task_queue(i)->stats.reset();
3584   }
3585 }
3586 #endif // TASKQUEUE_STATS
3587 
3588 bool
3589 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3590   assert_at_safepoint(true /* should_be_vm_thread */);
3591   guarantee(!is_gc_active(), "collection is not reentrant");
3592 
3593   if (GC_locker::check_active_before_gc()) {
3594     return false;
3595   }
3596 
3597   SvcGCMarker sgcm(SvcGCMarker::MINOR);
3598   ResourceMark rm;
3599 
3600   print_heap_before_gc();
3601 
3602   HRSPhaseSetter x(HRSPhaseEvacuation);
3603   verify_region_sets_optional();
3604   verify_dirty_young_regions();
3605 
3606   // This call will decide whether this pause is an initial-mark
3607   // pause. If it is, during_initial_mark_pause() will return true
3608   // for the duration of this pause.
3609   g1_policy()->decide_on_conc_mark_initiation();
3610 
3611   // We do not allow initial-mark to be piggy-backed on a mixed GC.
3612   assert(!g1_policy()->during_initial_mark_pause() ||
3613           g1_policy()->gcs_are_young(), "sanity");
3614 
3615   // We also do not allow mixed GCs during marking.
3616   assert(!mark_in_progress() || g1_policy()->gcs_are_young(), "sanity");
3617 
3618   // Record whether this pause is an initial mark. When the current
3619   // thread has completed its logging output and it's safe to signal
3620   // the CM thread, the flag's value in the policy has been reset.
3621   bool should_start_conc_mark = g1_policy()->during_initial_mark_pause();
3622 
3623   // Inner scope for scope based logging, timers, and stats collection
3624   {
3625     if (g1_policy()->during_initial_mark_pause()) {
3626       // We are about to start a marking cycle, so we increment the
3627       // full collection counter.
3628       increment_old_marking_cycles_started();
3629     }
3630     // if the log level is "finer" is on, we'll print long statistics information
3631     // in the collector policy code, so let's not print this as the output
3632     // is messy if we do.
3633     gclog_or_tty->date_stamp(G1Log::fine() && PrintGCDateStamps);
3634     TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3635 
3636     int active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
3637                                 workers()->active_workers() : 1);
3638     g1_policy()->phase_times()->note_gc_start(os::elapsedTime(), active_workers,
3639       g1_policy()->gcs_are_young(), g1_policy()->during_initial_mark_pause(), gc_cause());
3640 
3641     TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3642     TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3643 
3644     // If the secondary_free_list is not empty, append it to the
3645     // free_list. No need to wait for the cleanup operation to finish;
3646     // the region allocation code will check the secondary_free_list
3647     // and wait if necessary. If the G1StressConcRegionFreeing flag is
3648     // set, skip this step so that the region allocation code has to
3649     // get entries from the secondary_free_list.
3650     if (!G1StressConcRegionFreeing) {
3651       append_secondary_free_list_if_not_empty_with_lock();
3652     }
3653 
3654     assert(check_young_list_well_formed(),
3655       "young list should be well formed");
3656 
3657     // Don't dynamically change the number of GC threads this early.  A value of
3658     // 0 is used to indicate serial work.  When parallel work is done,
3659     // it will be set.
3660 
3661     { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3662       IsGCActiveMark x;
3663 
3664       gc_prologue(false);
3665       increment_total_collections(false /* full gc */);
3666       increment_gc_time_stamp();
3667 
3668       if (VerifyBeforeGC && total_collections() >= VerifyGCStartAt) {
3669         HandleMark hm;  // Discard invalid handles created during verification
3670         gclog_or_tty->print(" VerifyBeforeGC:");
3671         prepare_for_verify();
3672         Universe::verify(/* silent      */ false,
3673                          /* option      */ VerifyOption_G1UsePrevMarking);
3674       }
3675 
3676       COMPILER2_PRESENT(DerivedPointerTable::clear());
3677 
3678       // Please see comment in g1CollectedHeap.hpp and
3679       // G1CollectedHeap::ref_processing_init() to see how
3680       // reference processing currently works in G1.
3681 
3682       // Enable discovery in the STW reference processor
3683       ref_processor_stw()->enable_discovery(true /*verify_disabled*/,
3684                                             true /*verify_no_refs*/);
3685 
3686       {
3687         // We want to temporarily turn off discovery by the
3688         // CM ref processor, if necessary, and turn it back on
3689         // on again later if we do. Using a scoped
3690         // NoRefDiscovery object will do this.
3691         NoRefDiscovery no_cm_discovery(ref_processor_cm());
3692 
3693         // Forget the current alloc region (we might even choose it to be part
3694         // of the collection set!).
3695         release_mutator_alloc_region();
3696 
3697         // We should call this after we retire the mutator alloc
3698         // region(s) so that all the ALLOC / RETIRE events are generated
3699         // before the start GC event.
3700         _hr_printer.start_gc(false /* full */, (size_t) total_collections());
3701 
3702         // This timing is only used by the ergonomics to handle our pause target.
3703         // It is unclear why this should not include the full pause. We will
3704         // investigate this in CR 7178365.
3705         //
3706         // Preserving the old comment here if that helps the investigation:
3707         //
3708         // The elapsed time induced by the start time below deliberately elides
3709         // the possible verification above.
3710         double sample_start_time_sec = os::elapsedTime();
3711         size_t start_used_bytes = used();
3712 
3713 #if YOUNG_LIST_VERBOSE
3714         gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
3715         _young_list->print();
3716         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3717 #endif // YOUNG_LIST_VERBOSE
3718 
3719         g1_policy()->record_collection_pause_start(sample_start_time_sec,
3720                                                    start_used_bytes);
3721 
3722         double scan_wait_start = os::elapsedTime();
3723         // We have to wait until the CM threads finish scanning the
3724         // root regions as it's the only way to ensure that all the
3725         // objects on them have been correctly scanned before we start
3726         // moving them during the GC.
3727         bool waited = _cm->root_regions()->wait_until_scan_finished();
3728         double wait_time_ms = 0.0;
3729         if (waited) {
3730           double scan_wait_end = os::elapsedTime();
3731           wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
3732         }
3733         g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
3734 
3735 #if YOUNG_LIST_VERBOSE
3736         gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
3737         _young_list->print();
3738 #endif // YOUNG_LIST_VERBOSE
3739 
3740         if (g1_policy()->during_initial_mark_pause()) {
3741           concurrent_mark()->checkpointRootsInitialPre();
3742         }
3743         perm_gen()->save_marks();
3744 
3745 #if YOUNG_LIST_VERBOSE
3746         gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
3747         _young_list->print();
3748         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3749 #endif // YOUNG_LIST_VERBOSE
3750 
3751         g1_policy()->finalize_cset(target_pause_time_ms);
3752 
3753         _cm->note_start_of_gc();
3754         // We should not verify the per-thread SATB buffers given that
3755         // we have not filtered them yet (we'll do so during the
3756         // GC). We also call this after finalize_cset() to
3757         // ensure that the CSet has been finalized.
3758         _cm->verify_no_cset_oops(true  /* verify_stacks */,
3759                                  true  /* verify_enqueued_buffers */,
3760                                  false /* verify_thread_buffers */,
3761                                  true  /* verify_fingers */);
3762 
3763         if (_hr_printer.is_active()) {
3764           HeapRegion* hr = g1_policy()->collection_set();
3765           while (hr != NULL) {
3766             G1HRPrinter::RegionType type;
3767             if (!hr->is_young()) {
3768               type = G1HRPrinter::Old;
3769             } else if (hr->is_survivor()) {
3770               type = G1HRPrinter::Survivor;
3771             } else {
3772               type = G1HRPrinter::Eden;
3773             }
3774             _hr_printer.cset(hr);
3775             hr = hr->next_in_collection_set();
3776           }
3777         }
3778 
3779 #ifdef ASSERT
3780         VerifyCSetClosure cl;
3781         collection_set_iterate(&cl);
3782 #endif // ASSERT
3783 
3784         setup_surviving_young_words();
3785 
3786         // Initialize the GC alloc regions.
3787         init_gc_alloc_regions();
3788 
3789         // Actually do the work...
3790         evacuate_collection_set();
3791 
3792         // We do this to mainly verify the per-thread SATB buffers
3793         // (which have been filtered by now) since we didn't verify
3794         // them earlier. No point in re-checking the stacks / enqueued
3795         // buffers given that the CSet has not changed since last time
3796         // we checked.
3797         _cm->verify_no_cset_oops(false /* verify_stacks */,
3798                                  false /* verify_enqueued_buffers */,
3799                                  true  /* verify_thread_buffers */,
3800                                  true  /* verify_fingers */);
3801 
3802         free_collection_set(g1_policy()->collection_set());
3803         g1_policy()->clear_collection_set();
3804 
3805         cleanup_surviving_young_words();
3806 
3807         // Start a new incremental collection set for the next pause.
3808         g1_policy()->start_incremental_cset_building();
3809 
3810         // Clear the _cset_fast_test bitmap in anticipation of adding
3811         // regions to the incremental collection set for the next
3812         // evacuation pause.
3813         clear_cset_fast_test();
3814 
3815         _young_list->reset_sampled_info();
3816 
3817         // Don't check the whole heap at this point as the
3818         // GC alloc regions from this pause have been tagged
3819         // as survivors and moved on to the survivor list.
3820         // Survivor regions will fail the !is_young() check.
3821         assert(check_young_list_empty(false /* check_heap */),
3822           "young list should be empty");
3823 
3824 #if YOUNG_LIST_VERBOSE
3825         gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
3826         _young_list->print();
3827 #endif // YOUNG_LIST_VERBOSE
3828 
3829         g1_policy()->record_survivor_regions(_young_list->survivor_length(),
3830                                             _young_list->first_survivor_region(),
3831                                             _young_list->last_survivor_region());
3832 
3833         _young_list->reset_auxilary_lists();
3834 
3835         if (evacuation_failed()) {
3836           _summary_bytes_used = recalculate_used();
3837         } else {
3838           // The "used" of the the collection set have already been subtracted
3839           // when they were freed.  Add in the bytes evacuated.
3840           _summary_bytes_used += g1_policy()->bytes_copied_during_gc();
3841         }
3842 
3843         if (g1_policy()->during_initial_mark_pause()) {
3844           // We have to do this before we notify the CM threads that
3845           // they can start working to make sure that all the
3846           // appropriate initialization is done on the CM object.
3847           concurrent_mark()->checkpointRootsInitialPost();
3848           set_marking_started();
3849           // Note that we don't actually trigger the CM thread at
3850           // this point. We do that later when we're sure that
3851           // the current thread has completed its logging output.
3852         }
3853 
3854         allocate_dummy_regions();
3855 
3856 #if YOUNG_LIST_VERBOSE
3857         gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
3858         _young_list->print();
3859         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3860 #endif // YOUNG_LIST_VERBOSE
3861 
3862         init_mutator_alloc_region();
3863 
3864         {
3865           size_t expand_bytes = g1_policy()->expansion_amount();
3866           if (expand_bytes > 0) {
3867             size_t bytes_before = capacity();
3868             // No need for an ergo verbose message here,
3869             // expansion_amount() does this when it returns a value > 0.
3870             if (!expand(expand_bytes)) {
3871               // We failed to expand the heap so let's verify that
3872               // committed/uncommitted amount match the backing store
3873               assert(capacity() == _g1_storage.committed_size(), "committed size mismatch");
3874               assert(max_capacity() == _g1_storage.reserved_size(), "reserved size mismatch");
3875             }
3876           }
3877         }
3878 
3879         // We redo the verificaiton but now wrt to the new CSet which
3880         // has just got initialized after the previous CSet was freed.
3881         _cm->verify_no_cset_oops(true  /* verify_stacks */,
3882                                  true  /* verify_enqueued_buffers */,
3883                                  true  /* verify_thread_buffers */,
3884                                  true  /* verify_fingers */);
3885         _cm->note_end_of_gc();
3886 




3887         // This timing is only used by the ergonomics to handle our pause target.
3888         // It is unclear why this should not include the full pause. We will
3889         // investigate this in CR 7178365.
3890         double sample_end_time_sec = os::elapsedTime();
3891         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3892         g1_policy()->record_collection_pause_end(pause_time_ms);
3893 
3894         MemoryService::track_memory_usage();
3895 
3896         // In prepare_for_verify() below we'll need to scan the deferred
3897         // update buffers to bring the RSets up-to-date if
3898         // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
3899         // the update buffers we'll probably need to scan cards on the
3900         // regions we just allocated to (i.e., the GC alloc
3901         // regions). However, during the last GC we called
3902         // set_saved_mark() on all the GC alloc regions, so card
3903         // scanning might skip the [saved_mark_word()...top()] area of
3904         // those regions (i.e., the area we allocated objects into
3905         // during the last GC). But it shouldn't. Given that
3906         // saved_mark_word() is conditional on whether the GC time stamp
3907         // on the region is current or not, by incrementing the GC time
3908         // stamp here we invalidate all the GC time stamps on all the
3909         // regions and saved_mark_word() will simply return top() for
3910         // all the regions. This is a nicer way of ensuring this rather
3911         // than iterating over the regions and fixing them. In fact, the
3912         // GC time stamp increment here also ensures that
3913         // saved_mark_word() will return top() between pauses, i.e.,
3914         // during concurrent refinement. So we don't need the
3915         // is_gc_active() check to decided which top to use when
3916         // scanning cards (see CR 7039627).
3917         increment_gc_time_stamp();
3918 
3919         if (VerifyAfterGC && total_collections() >= VerifyGCStartAt) {
3920           HandleMark hm;  // Discard invalid handles created during verification
3921           gclog_or_tty->print(" VerifyAfterGC:");
3922           prepare_for_verify();
3923           Universe::verify(/* silent      */ false,
3924                            /* option      */ VerifyOption_G1UsePrevMarking);
3925         }
3926 
3927         assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
3928         ref_processor_stw()->verify_no_references_recorded();
3929 
3930         // CM reference discovery will be re-enabled if necessary.
3931       }
3932 
3933       // We should do this after we potentially expand the heap so
3934       // that all the COMMIT events are generated before the end GC
3935       // event, and after we retire the GC alloc regions so that all
3936       // RETIRE events are generated before the end GC event.
3937       _hr_printer.end_gc(false /* full */, (size_t) total_collections());
3938 
3939       if (mark_in_progress()) {
3940         concurrent_mark()->update_g1_committed();
3941       }
3942 
3943 #ifdef TRACESPINNING
3944       ParallelTaskTerminator::print_termination_counts();
3945 #endif
3946 
3947       gc_epilogue(false);
3948 
3949       g1_policy()->phase_times()->note_gc_end(os::elapsedTime());
3950 
3951       // We have to do this after we decide whether to expand the heap or not.
3952       g1_policy()->print_heap_transition();
3953     }
3954 
3955     // It is not yet to safe to tell the concurrent mark to
3956     // start as we have some optional output below. We don't want the
3957     // output from the concurrent mark thread interfering with this
3958     // logging output either.
3959 
3960     _hrs.verify_optional();
3961     verify_region_sets_optional();
3962 
3963     TASKQUEUE_STATS_ONLY(if (ParallelGCVerbose) print_taskqueue_stats());
3964     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3965 
3966     print_heap_after_gc();
3967 
3968     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3969     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3970     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3971     // before any GC notifications are raised.
3972     g1mm()->update_sizes();
3973   }
3974 
3975   if (G1SummarizeRSetStats &&
3976       (G1SummarizeRSetStatsPeriod > 0) &&
3977       (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3978     g1_rem_set()->print_summary_info();
3979   }
3980 
3981   // It should now be safe to tell the concurrent mark thread to start
3982   // without its logging output interfering with the logging output
3983   // that came from the pause.
3984 
3985   if (should_start_conc_mark) {
3986     // CAUTION: after the doConcurrentMark() call below,
3987     // the concurrent marking thread(s) could be running
3988     // concurrently with us. Make sure that anything after
3989     // this point does not assume that we are the only GC thread
3990     // running. Note: of course, the actual marking work will
3991     // not start until the safepoint itself is released in
3992     // ConcurrentGCThread::safepoint_desynchronize().
3993     doConcurrentMark();
3994   }
3995 
3996   return true;
3997 }
3998 
3999 size_t G1CollectedHeap::desired_plab_sz(GCAllocPurpose purpose)
4000 {
4001   size_t gclab_word_size;
4002   switch (purpose) {
4003     case GCAllocForSurvived:
4004       gclab_word_size = YoungPLABSize;
4005       break;
4006     case GCAllocForTenured:
4007       gclab_word_size = OldPLABSize;
4008       break;
4009     default:
4010       assert(false, "unknown GCAllocPurpose");
4011       gclab_word_size = OldPLABSize;
4012       break;
4013   }
4014   return gclab_word_size;
4015 }
4016 
4017 void G1CollectedHeap::init_mutator_alloc_region() {
4018   assert(_mutator_alloc_region.get() == NULL, "pre-condition");
4019   _mutator_alloc_region.init();
4020 }
4021 
4022 void G1CollectedHeap::release_mutator_alloc_region() {
4023   _mutator_alloc_region.release();
4024   assert(_mutator_alloc_region.get() == NULL, "post-condition");
4025 }
4026 
4027 void G1CollectedHeap::init_gc_alloc_regions() {
4028   assert_at_safepoint(true /* should_be_vm_thread */);
4029 
4030   _survivor_gc_alloc_region.init();
4031   _old_gc_alloc_region.init();
4032   HeapRegion* retained_region = _retained_old_gc_alloc_region;
4033   _retained_old_gc_alloc_region = NULL;
4034 
4035   // We will discard the current GC alloc region if:
4036   // a) it's in the collection set (it can happen!),
4037   // b) it's already full (no point in using it),
4038   // c) it's empty (this means that it was emptied during
4039   // a cleanup and it should be on the free list now), or
4040   // d) it's humongous (this means that it was emptied
4041   // during a cleanup and was added to the free list, but
4042   // has been subseqently used to allocate a humongous
4043   // object that may be less than the region size).
4044   if (retained_region != NULL &&
4045       !retained_region->in_collection_set() &&
4046       !(retained_region->top() == retained_region->end()) &&
4047       !retained_region->is_empty() &&
4048       !retained_region->isHumongous()) {
4049     retained_region->set_saved_mark();
4050     // The retained region was added to the old region set when it was
4051     // retired. We have to remove it now, since we don't allow regions
4052     // we allocate to in the region sets. We'll re-add it later, when
4053     // it's retired again.
4054     _old_set.remove(retained_region);
4055     bool during_im = g1_policy()->during_initial_mark_pause();
4056     retained_region->note_start_of_copying(during_im);
4057     _old_gc_alloc_region.set(retained_region);
4058     _hr_printer.reuse(retained_region);
4059   }
4060 }
4061 
4062 void G1CollectedHeap::release_gc_alloc_regions() {
4063   _survivor_gc_alloc_region.release();
4064   // If we have an old GC alloc region to release, we'll save it in
4065   // _retained_old_gc_alloc_region. If we don't
4066   // _retained_old_gc_alloc_region will become NULL. This is what we
4067   // want either way so no reason to check explicitly for either
4068   // condition.
4069   _retained_old_gc_alloc_region = _old_gc_alloc_region.release();
4070 }
4071 
4072 void G1CollectedHeap::abandon_gc_alloc_regions() {
4073   assert(_survivor_gc_alloc_region.get() == NULL, "pre-condition");
4074   assert(_old_gc_alloc_region.get() == NULL, "pre-condition");
4075   _retained_old_gc_alloc_region = NULL;
4076 }
4077 
4078 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4079   _drain_in_progress = false;
4080   set_evac_failure_closure(cl);
4081   _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4082 }
4083 
4084 void G1CollectedHeap::finalize_for_evac_failure() {
4085   assert(_evac_failure_scan_stack != NULL &&
4086          _evac_failure_scan_stack->length() == 0,
4087          "Postcondition");
4088   assert(!_drain_in_progress, "Postcondition");
4089   delete _evac_failure_scan_stack;
4090   _evac_failure_scan_stack = NULL;
4091 }
4092 
4093 void G1CollectedHeap::remove_self_forwarding_pointers() {
4094   assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4095 
4096   G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4097 
4098   if (G1CollectedHeap::use_parallel_gc_threads()) {
4099     set_par_threads();
4100     workers()->run_task(&rsfp_task);
4101     set_par_threads(0);
4102   } else {
4103     rsfp_task.work(0);
4104   }
4105 
4106   assert(check_cset_heap_region_claim_values(HeapRegion::ParEvacFailureClaimValue), "sanity");
4107 
4108   // Reset the claim values in the regions in the collection set.
4109   reset_cset_heap_region_claim_values();
4110 
4111   assert(check_cset_heap_region_claim_values(HeapRegion::InitialClaimValue), "sanity");
4112 
4113   // Now restore saved marks, if any.
4114   if (_objs_with_preserved_marks != NULL) {
4115     assert(_preserved_marks_of_objs != NULL, "Both or none.");
4116     guarantee(_objs_with_preserved_marks->length() ==
4117               _preserved_marks_of_objs->length(), "Both or none.");
4118     for (int i = 0; i < _objs_with_preserved_marks->length(); i++) {
4119       oop obj   = _objs_with_preserved_marks->at(i);
4120       markOop m = _preserved_marks_of_objs->at(i);
4121       obj->set_mark(m);
4122     }
4123 
4124     // Delete the preserved marks growable arrays (allocated on the C heap).
4125     delete _objs_with_preserved_marks;
4126     delete _preserved_marks_of_objs;
4127     _objs_with_preserved_marks = NULL;
4128     _preserved_marks_of_objs = NULL;
4129   }
4130 }
4131 
4132 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4133   _evac_failure_scan_stack->push(obj);
4134 }
4135 
4136 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4137   assert(_evac_failure_scan_stack != NULL, "precondition");
4138 
4139   while (_evac_failure_scan_stack->length() > 0) {
4140      oop obj = _evac_failure_scan_stack->pop();
4141      _evac_failure_closure->set_region(heap_region_containing(obj));
4142      obj->oop_iterate_backwards(_evac_failure_closure);
4143   }
4144 }
4145 
4146 oop
4147 G1CollectedHeap::handle_evacuation_failure_par(OopsInHeapRegionClosure* cl,
4148                                                oop old) {
4149   assert(obj_in_cs(old),
4150          err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4151                  (HeapWord*) old));
4152   markOop m = old->mark();
4153   oop forward_ptr = old->forward_to_atomic(old);
4154   if (forward_ptr == NULL) {
4155     // Forward-to-self succeeded.
4156 
4157     if (_evac_failure_closure != cl) {
4158       MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4159       assert(!_drain_in_progress,
4160              "Should only be true while someone holds the lock.");
4161       // Set the global evac-failure closure to the current thread's.
4162       assert(_evac_failure_closure == NULL, "Or locking has failed.");
4163       set_evac_failure_closure(cl);
4164       // Now do the common part.
4165       handle_evacuation_failure_common(old, m);
4166       // Reset to NULL.
4167       set_evac_failure_closure(NULL);
4168     } else {
4169       // The lock is already held, and this is recursive.
4170       assert(_drain_in_progress, "This should only be the recursive case.");
4171       handle_evacuation_failure_common(old, m);
4172     }
4173     return old;
4174   } else {
4175     // Forward-to-self failed. Either someone else managed to allocate
4176     // space for this object (old != forward_ptr) or they beat us in
4177     // self-forwarding it (old == forward_ptr).
4178     assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4179            err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4180                    "should not be in the CSet",
4181                    (HeapWord*) old, (HeapWord*) forward_ptr));
4182     return forward_ptr;
4183   }
4184 }
4185 
4186 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4187   set_evacuation_failed(true);
4188 
4189   preserve_mark_if_necessary(old, m);
4190 
4191   HeapRegion* r = heap_region_containing(old);
4192   if (!r->evacuation_failed()) {
4193     r->set_evacuation_failed(true);
4194     _hr_printer.evac_failure(r);
4195   }
4196 
4197   push_on_evac_failure_scan_stack(old);
4198 
4199   if (!_drain_in_progress) {
4200     // prevent recursion in copy_to_survivor_space()
4201     _drain_in_progress = true;
4202     drain_evac_failure_scan_stack();
4203     _drain_in_progress = false;
4204   }
4205 }
4206 
4207 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4208   assert(evacuation_failed(), "Oversaving!");
4209   // We want to call the "for_promotion_failure" version only in the
4210   // case of a promotion failure.
4211   if (m->must_be_preserved_for_promotion_failure(obj)) {
4212     if (_objs_with_preserved_marks == NULL) {
4213       assert(_preserved_marks_of_objs == NULL, "Both or none.");
4214       _objs_with_preserved_marks =
4215         new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4216       _preserved_marks_of_objs =
4217         new (ResourceObj::C_HEAP, mtGC) GrowableArray<markOop>(40, true);
4218     }
4219     _objs_with_preserved_marks->push(obj);
4220     _preserved_marks_of_objs->push(m);
4221   }
4222 }
4223 
4224 HeapWord* G1CollectedHeap::par_allocate_during_gc(GCAllocPurpose purpose,
4225                                                   size_t word_size) {
4226   if (purpose == GCAllocForSurvived) {
4227     HeapWord* result = survivor_attempt_allocation(word_size);
4228     if (result != NULL) {
4229       return result;
4230     } else {
4231       // Let's try to allocate in the old gen in case we can fit the
4232       // object there.
4233       return old_attempt_allocation(word_size);
4234     }
4235   } else {
4236     assert(purpose ==  GCAllocForTenured, "sanity");
4237     HeapWord* result = old_attempt_allocation(word_size);
4238     if (result != NULL) {
4239       return result;
4240     } else {
4241       // Let's try to allocate in the survivors in case we can fit the
4242       // object there.
4243       return survivor_attempt_allocation(word_size);
4244     }
4245   }
4246 
4247   ShouldNotReachHere();
4248   // Trying to keep some compilers happy.
4249   return NULL;
4250 }
4251 
4252 G1ParGCAllocBuffer::G1ParGCAllocBuffer(size_t gclab_word_size) :
4253   ParGCAllocBuffer(gclab_word_size), _retired(false) { }
4254 
4255 G1ParScanThreadState::G1ParScanThreadState(G1CollectedHeap* g1h, uint queue_num)
4256   : _g1h(g1h),
4257     _refs(g1h->task_queue(queue_num)),
4258     _dcq(&g1h->dirty_card_queue_set()),
4259     _ct_bs((CardTableModRefBS*)_g1h->barrier_set()),
4260     _g1_rem(g1h->g1_rem_set()),
4261     _hash_seed(17), _queue_num(queue_num),
4262     _term_attempts(0),
4263     _surviving_alloc_buffer(g1h->desired_plab_sz(GCAllocForSurvived)),
4264     _tenured_alloc_buffer(g1h->desired_plab_sz(GCAllocForTenured)),
4265     _age_table(false),
4266     _strong_roots_time(0), _term_time(0),
4267     _alloc_buffer_waste(0), _undo_waste(0) {
4268   // we allocate G1YoungSurvRateNumRegions plus one entries, since
4269   // we "sacrifice" entry 0 to keep track of surviving bytes for
4270   // non-young regions (where the age is -1)
4271   // We also add a few elements at the beginning and at the end in
4272   // an attempt to eliminate cache contention
4273   uint real_length = 1 + _g1h->g1_policy()->young_cset_region_length();
4274   uint array_length = PADDING_ELEM_NUM +
4275                       real_length +
4276                       PADDING_ELEM_NUM;
4277   _surviving_young_words_base = NEW_C_HEAP_ARRAY(size_t, array_length, mtGC);
4278   if (_surviving_young_words_base == NULL)
4279     vm_exit_out_of_memory(array_length * sizeof(size_t),
4280                           "Not enough space for young surv histo.");
4281   _surviving_young_words = _surviving_young_words_base + PADDING_ELEM_NUM;
4282   memset(_surviving_young_words, 0, (size_t) real_length * sizeof(size_t));
4283 
4284   _alloc_buffers[GCAllocForSurvived] = &_surviving_alloc_buffer;
4285   _alloc_buffers[GCAllocForTenured]  = &_tenured_alloc_buffer;
4286 
4287   _start = os::elapsedTime();
4288 }
4289 
4290 void
4291 G1ParScanThreadState::print_termination_stats_hdr(outputStream* const st)
4292 {
4293   st->print_raw_cr("GC Termination Stats");
4294   st->print_raw_cr("     elapsed  --strong roots-- -------termination-------"
4295                    " ------waste (KiB)------");
4296   st->print_raw_cr("thr     ms        ms      %        ms      %    attempts"
4297                    "  total   alloc    undo");
4298   st->print_raw_cr("--- --------- --------- ------ --------- ------ --------"
4299                    " ------- ------- -------");
4300 }
4301 
4302 void
4303 G1ParScanThreadState::print_termination_stats(int i,
4304                                               outputStream* const st) const
4305 {
4306   const double elapsed_ms = elapsed_time() * 1000.0;
4307   const double s_roots_ms = strong_roots_time() * 1000.0;
4308   const double term_ms    = term_time() * 1000.0;
4309   st->print_cr("%3d %9.2f %9.2f %6.2f "
4310                "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
4311                SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
4312                i, elapsed_ms, s_roots_ms, s_roots_ms * 100 / elapsed_ms,
4313                term_ms, term_ms * 100 / elapsed_ms, term_attempts(),
4314                (alloc_buffer_waste() + undo_waste()) * HeapWordSize / K,
4315                alloc_buffer_waste() * HeapWordSize / K,
4316                undo_waste() * HeapWordSize / K);
4317 }
4318 
4319 #ifdef ASSERT
4320 bool G1ParScanThreadState::verify_ref(narrowOop* ref) const {
4321   assert(ref != NULL, "invariant");
4322   assert(UseCompressedOops, "sanity");
4323   assert(!has_partial_array_mask(ref), err_msg("ref=" PTR_FORMAT, ref));
4324   oop p = oopDesc::load_decode_heap_oop(ref);
4325   assert(_g1h->is_in_g1_reserved(p),
4326          err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4327   return true;
4328 }
4329 
4330 bool G1ParScanThreadState::verify_ref(oop* ref) const {
4331   assert(ref != NULL, "invariant");
4332   if (has_partial_array_mask(ref)) {
4333     // Must be in the collection set--it's already been copied.
4334     oop p = clear_partial_array_mask(ref);
4335     assert(_g1h->obj_in_cs(p),
4336            err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4337   } else {
4338     oop p = oopDesc::load_decode_heap_oop(ref);
4339     assert(_g1h->is_in_g1_reserved(p),
4340            err_msg("ref=" PTR_FORMAT " p=" PTR_FORMAT, ref, intptr_t(p)));
4341   }
4342   return true;
4343 }
4344 
4345 bool G1ParScanThreadState::verify_task(StarTask ref) const {
4346   if (ref.is_narrow()) {
4347     return verify_ref((narrowOop*) ref);
4348   } else {
4349     return verify_ref((oop*) ref);
4350   }
4351 }
4352 #endif // ASSERT
4353 
4354 void G1ParScanThreadState::trim_queue() {
4355   assert(_evac_cl != NULL, "not set");
4356   assert(_evac_failure_cl != NULL, "not set");
4357   assert(_partial_scan_cl != NULL, "not set");
4358 
4359   StarTask ref;
4360   do {
4361     // Drain the overflow stack first, so other threads can steal.
4362     while (refs()->pop_overflow(ref)) {
4363       deal_with_reference(ref);
4364     }
4365 
4366     while (refs()->pop_local(ref)) {
4367       deal_with_reference(ref);
4368     }
4369   } while (!refs()->is_empty());
4370 }
4371 
4372 G1ParClosureSuper::G1ParClosureSuper(G1CollectedHeap* g1,
4373                                      G1ParScanThreadState* par_scan_state) :
4374   _g1(g1), _g1_rem(_g1->g1_rem_set()), _cm(_g1->concurrent_mark()),
4375   _par_scan_state(par_scan_state),
4376   _worker_id(par_scan_state->queue_num()),
4377   _during_initial_mark(_g1->g1_policy()->during_initial_mark_pause()),
4378   _mark_in_progress(_g1->mark_in_progress()) { }
4379 
4380 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4381 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>::mark_object(oop obj) {
4382 #ifdef ASSERT
4383   HeapRegion* hr = _g1->heap_region_containing(obj);
4384   assert(hr != NULL, "sanity");
4385   assert(!hr->in_collection_set(), "should not mark objects in the CSet");
4386 #endif // ASSERT
4387 
4388   // We know that the object is not moving so it's safe to read its size.
4389   _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4390 }
4391 
4392 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4393 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4394   ::mark_forwarded_object(oop from_obj, oop to_obj) {
4395 #ifdef ASSERT
4396   assert(from_obj->is_forwarded(), "from obj should be forwarded");
4397   assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4398   assert(from_obj != to_obj, "should not be self-forwarded");
4399 
4400   HeapRegion* from_hr = _g1->heap_region_containing(from_obj);
4401   assert(from_hr != NULL, "sanity");
4402   assert(from_hr->in_collection_set(), "from obj should be in the CSet");
4403 
4404   HeapRegion* to_hr = _g1->heap_region_containing(to_obj);
4405   assert(to_hr != NULL, "sanity");
4406   assert(!to_hr->in_collection_set(), "should not mark objects in the CSet");
4407 #endif // ASSERT
4408 
4409   // The object might be in the process of being copied by another
4410   // worker so we cannot trust that its to-space image is
4411   // well-formed. So we have to read its size from its from-space
4412   // image which we know should not be changing.
4413   _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4414 }
4415 
4416 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4417 oop G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4418   ::copy_to_survivor_space(oop old) {
4419   size_t word_sz = old->size();
4420   HeapRegion* from_region = _g1->heap_region_containing_raw(old);
4421   // +1 to make the -1 indexes valid...
4422   int       young_index = from_region->young_index_in_cset()+1;
4423   assert( (from_region->is_young() && young_index >  0) ||
4424          (!from_region->is_young() && young_index == 0), "invariant" );
4425   G1CollectorPolicy* g1p = _g1->g1_policy();
4426   markOop m = old->mark();
4427   int age = m->has_displaced_mark_helper() ? m->displaced_mark_helper()->age()
4428                                            : m->age();
4429   GCAllocPurpose alloc_purpose = g1p->evacuation_destination(from_region, age,
4430                                                              word_sz);
4431   HeapWord* obj_ptr = _par_scan_state->allocate(alloc_purpose, word_sz);
4432   oop       obj     = oop(obj_ptr);
4433 
4434   if (obj_ptr == NULL) {
4435     // This will either forward-to-self, or detect that someone else has
4436     // installed a forwarding pointer.
4437     OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4438     return _g1->handle_evacuation_failure_par(cl, old);
4439   }
4440 
4441   // We're going to allocate linearly, so might as well prefetch ahead.
4442   Prefetch::write(obj_ptr, PrefetchCopyIntervalInBytes);
4443 
4444   oop forward_ptr = old->forward_to_atomic(obj);
4445   if (forward_ptr == NULL) {
4446     Copy::aligned_disjoint_words((HeapWord*) old, obj_ptr, word_sz);
4447     if (g1p->track_object_age(alloc_purpose)) {
4448       // We could simply do obj->incr_age(). However, this causes a
4449       // performance issue. obj->incr_age() will first check whether
4450       // the object has a displaced mark by checking its mark word;
4451       // getting the mark word from the new location of the object
4452       // stalls. So, given that we already have the mark word and we
4453       // are about to install it anyway, it's better to increase the
4454       // age on the mark word, when the object does not have a
4455       // displaced mark word. We're not expecting many objects to have
4456       // a displaced marked word, so that case is not optimized
4457       // further (it could be...) and we simply call obj->incr_age().
4458 
4459       if (m->has_displaced_mark_helper()) {
4460         // in this case, we have to install the mark word first,
4461         // otherwise obj looks to be forwarded (the old mark word,
4462         // which contains the forward pointer, was copied)
4463         obj->set_mark(m);
4464         obj->incr_age();
4465       } else {
4466         m = m->incr_age();
4467         obj->set_mark(m);
4468       }
4469       _par_scan_state->age_table()->add(obj, word_sz);
4470     } else {
4471       obj->set_mark(m);
4472     }
4473 
4474     size_t* surv_young_words = _par_scan_state->surviving_young_words();
4475     surv_young_words[young_index] += word_sz;
4476 
4477     if (obj->is_objArray() && arrayOop(obj)->length() >= ParGCArrayScanChunk) {
4478       // We keep track of the next start index in the length field of
4479       // the to-space object. The actual length can be found in the
4480       // length field of the from-space object.
4481       arrayOop(obj)->set_length(0);
4482       oop* old_p = set_partial_array_mask(old);
4483       _par_scan_state->push_on_queue(old_p);
4484     } else {
4485       // No point in using the slower heap_region_containing() method,
4486       // given that we know obj is in the heap.
4487       _scanner.set_region(_g1->heap_region_containing_raw(obj));
4488       obj->oop_iterate_backwards(&_scanner);
4489     }
4490   } else {
4491     _par_scan_state->undo_allocation(alloc_purpose, obj_ptr, word_sz);
4492     obj = forward_ptr;
4493   }
4494   return obj;
4495 }
4496 
4497 template <bool do_gen_barrier, G1Barrier barrier, bool do_mark_object>
4498 template <class T>
4499 void G1ParCopyClosure<do_gen_barrier, barrier, do_mark_object>
4500 ::do_oop_work(T* p) {
4501   oop obj = oopDesc::load_decode_heap_oop(p);
4502   assert(barrier != G1BarrierRS || obj != NULL,
4503          "Precondition: G1BarrierRS implies obj is non-NULL");
4504 
4505   assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4506 
4507   // here the null check is implicit in the cset_fast_test() test
4508   if (_g1->in_cset_fast_test(obj)) {
4509     oop forwardee;
4510     if (obj->is_forwarded()) {
4511       forwardee = obj->forwardee();
4512     } else {
4513       forwardee = copy_to_survivor_space(obj);
4514     }
4515     assert(forwardee != NULL, "forwardee should not be NULL");
4516     oopDesc::encode_store_heap_oop(p, forwardee);
4517     if (do_mark_object && forwardee != obj) {
4518       // If the object is self-forwarded we don't need to explicitly
4519       // mark it, the evacuation failure protocol will do so.
4520       mark_forwarded_object(obj, forwardee);
4521     }
4522 
4523     // When scanning the RS, we only care about objs in CS.
4524     if (barrier == G1BarrierRS) {
4525       _par_scan_state->update_rs(_from, p, _worker_id);
4526     }
4527   } else {
4528     // The object is not in collection set. If we're a root scanning
4529     // closure during an initial mark pause (i.e. do_mark_object will
4530     // be true) then attempt to mark the object.
4531     if (do_mark_object && _g1->is_in_g1_reserved(obj)) {
4532       mark_object(obj);
4533     }
4534   }
4535 
4536   if (barrier == G1BarrierEvac && obj != NULL) {
4537     _par_scan_state->update_rs(_from, p, _worker_id);
4538   }
4539 
4540   if (do_gen_barrier && obj != NULL) {
4541     par_do_barrier(p);
4542   }
4543 }
4544 
4545 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(oop* p);
4546 template void G1ParCopyClosure<false, G1BarrierEvac, false>::do_oop_work(narrowOop* p);
4547 
4548 template <class T> void G1ParScanPartialArrayClosure::do_oop_nv(T* p) {
4549   assert(has_partial_array_mask(p), "invariant");
4550   oop from_obj = clear_partial_array_mask(p);
4551 
4552   assert(Universe::heap()->is_in_reserved(from_obj), "must be in heap.");
4553   assert(from_obj->is_objArray(), "must be obj array");
4554   objArrayOop from_obj_array = objArrayOop(from_obj);
4555   // The from-space object contains the real length.
4556   int length                 = from_obj_array->length();
4557 
4558   assert(from_obj->is_forwarded(), "must be forwarded");
4559   oop to_obj                 = from_obj->forwardee();
4560   assert(from_obj != to_obj, "should not be chunking self-forwarded objects");
4561   objArrayOop to_obj_array   = objArrayOop(to_obj);
4562   // We keep track of the next start index in the length field of the
4563   // to-space object.
4564   int next_index             = to_obj_array->length();
4565   assert(0 <= next_index && next_index < length,
4566          err_msg("invariant, next index: %d, length: %d", next_index, length));
4567 
4568   int start                  = next_index;
4569   int end                    = length;
4570   int remainder              = end - start;
4571   // We'll try not to push a range that's smaller than ParGCArrayScanChunk.
4572   if (remainder > 2 * ParGCArrayScanChunk) {
4573     end = start + ParGCArrayScanChunk;
4574     to_obj_array->set_length(end);
4575     // Push the remainder before we process the range in case another
4576     // worker has run out of things to do and can steal it.
4577     oop* from_obj_p = set_partial_array_mask(from_obj);
4578     _par_scan_state->push_on_queue(from_obj_p);
4579   } else {
4580     assert(length == end, "sanity");
4581     // We'll process the final range for this object. Restore the length
4582     // so that the heap remains parsable in case of evacuation failure.
4583     to_obj_array->set_length(end);
4584   }
4585   _scanner.set_region(_g1->heap_region_containing_raw(to_obj));
4586   // Process indexes [start,end). It will also process the header
4587   // along with the first chunk (i.e., the chunk with start == 0).
4588   // Note that at this point the length field of to_obj_array is not
4589   // correct given that we are using it to keep track of the next
4590   // start index. oop_iterate_range() (thankfully!) ignores the length
4591   // field and only relies on the start / end parameters.  It does
4592   // however return the size of the object which will be incorrect. So
4593   // we have to ignore it even if we wanted to use it.
4594   to_obj_array->oop_iterate_range(&_scanner, start, end);
4595 }
4596 
4597 class G1ParEvacuateFollowersClosure : public VoidClosure {
4598 protected:
4599   G1CollectedHeap*              _g1h;
4600   G1ParScanThreadState*         _par_scan_state;
4601   RefToScanQueueSet*            _queues;
4602   ParallelTaskTerminator*       _terminator;
4603 
4604   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
4605   RefToScanQueueSet*      queues()         { return _queues; }
4606   ParallelTaskTerminator* terminator()     { return _terminator; }
4607 
4608 public:
4609   G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4610                                 G1ParScanThreadState* par_scan_state,
4611                                 RefToScanQueueSet* queues,
4612                                 ParallelTaskTerminator* terminator)
4613     : _g1h(g1h), _par_scan_state(par_scan_state),
4614       _queues(queues), _terminator(terminator) {}
4615 
4616   void do_void();
4617 
4618 private:
4619   inline bool offer_termination();
4620 };
4621 
4622 bool G1ParEvacuateFollowersClosure::offer_termination() {
4623   G1ParScanThreadState* const pss = par_scan_state();
4624   pss->start_term_time();
4625   const bool res = terminator()->offer_termination();
4626   pss->end_term_time();
4627   return res;
4628 }
4629 
4630 void G1ParEvacuateFollowersClosure::do_void() {
4631   StarTask stolen_task;
4632   G1ParScanThreadState* const pss = par_scan_state();
4633   pss->trim_queue();
4634 
4635   do {
4636     while (queues()->steal(pss->queue_num(), pss->hash_seed(), stolen_task)) {
4637       assert(pss->verify_task(stolen_task), "sanity");
4638       if (stolen_task.is_narrow()) {
4639         pss->deal_with_reference((narrowOop*) stolen_task);
4640       } else {
4641         pss->deal_with_reference((oop*) stolen_task);
4642       }
4643 
4644       // We've just processed a reference and we might have made
4645       // available new entries on the queues. So we have to make sure
4646       // we drain the queues as necessary.
4647       pss->trim_queue();
4648     }
4649   } while (!offer_termination());
4650 
4651   pss->retire_alloc_buffers();
4652 }
4653 
4654 class G1ParTask : public AbstractGangTask {
4655 protected:
4656   G1CollectedHeap*       _g1h;
4657   RefToScanQueueSet      *_queues;
4658   ParallelTaskTerminator _terminator;
4659   uint _n_workers;
4660 
4661   Mutex _stats_lock;
4662   Mutex* stats_lock() { return &_stats_lock; }
4663 
4664   size_t getNCards() {
4665     return (_g1h->capacity() + G1BlockOffsetSharedArray::N_bytes - 1)
4666       / G1BlockOffsetSharedArray::N_bytes;
4667   }
4668 
4669 public:
4670   G1ParTask(G1CollectedHeap* g1h,
4671             RefToScanQueueSet *task_queues)
4672     : AbstractGangTask("G1 collection"),
4673       _g1h(g1h),
4674       _queues(task_queues),
4675       _terminator(0, _queues),
4676       _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4677   {}
4678 
4679   RefToScanQueueSet* queues() { return _queues; }
4680 
4681   RefToScanQueue *work_queue(int i) {
4682     return queues()->queue(i);
4683   }
4684 
4685   ParallelTaskTerminator* terminator() { return &_terminator; }
4686 
4687   virtual void set_for_termination(int active_workers) {
4688     // This task calls set_n_termination() in par_non_clean_card_iterate_work()
4689     // in the young space (_par_seq_tasks) in the G1 heap
4690     // for SequentialSubTasksDone.
4691     // This task also uses SubTasksDone in SharedHeap and G1CollectedHeap
4692     // both of which need setting by set_n_termination().
4693     _g1h->SharedHeap::set_n_termination(active_workers);
4694     _g1h->set_n_termination(active_workers);
4695     terminator()->reset_for_reuse(active_workers);
4696     _n_workers = active_workers;
4697   }
4698 
4699   void work(uint worker_id) {
4700     if (worker_id >= _n_workers) return;  // no work needed this round
4701 
4702     double start_time_ms = os::elapsedTime() * 1000.0;
4703     _g1h->g1_policy()->phase_times()->record_gc_worker_start_time(worker_id, start_time_ms);
4704 
4705     {
4706       ResourceMark rm;
4707       HandleMark   hm;
4708 
4709       ReferenceProcessor*             rp = _g1h->ref_processor_stw();
4710 
4711       G1ParScanThreadState            pss(_g1h, worker_id);
4712       G1ParScanHeapEvacClosure        scan_evac_cl(_g1h, &pss, rp);
4713       G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
4714       G1ParScanPartialArrayClosure    partial_scan_cl(_g1h, &pss, rp);
4715 
4716       pss.set_evac_closure(&scan_evac_cl);
4717       pss.set_evac_failure_closure(&evac_failure_cl);
4718       pss.set_partial_scan_closure(&partial_scan_cl);
4719 
4720       G1ParScanExtRootClosure        only_scan_root_cl(_g1h, &pss, rp);
4721       G1ParScanPermClosure           only_scan_perm_cl(_g1h, &pss, rp);
4722 
4723       G1ParScanAndMarkExtRootClosure scan_mark_root_cl(_g1h, &pss, rp);
4724       G1ParScanAndMarkPermClosure    scan_mark_perm_cl(_g1h, &pss, rp);
4725 
4726       OopClosure*                    scan_root_cl = &only_scan_root_cl;
4727       OopsInHeapRegionClosure*       scan_perm_cl = &only_scan_perm_cl;
4728 
4729       if (_g1h->g1_policy()->during_initial_mark_pause()) {
4730         // We also need to mark copied objects.
4731         scan_root_cl = &scan_mark_root_cl;
4732         scan_perm_cl = &scan_mark_perm_cl;
4733       }
4734 
4735       G1ParPushHeapRSClosure          push_heap_rs_cl(_g1h, &pss);
4736 
4737       pss.start_strong_roots();
4738       _g1h->g1_process_strong_roots(/* not collecting perm */ false,
4739                                     SharedHeap::SO_AllClasses,
4740                                     scan_root_cl,
4741                                     &push_heap_rs_cl,
4742                                     scan_perm_cl,
4743                                     worker_id);
4744       pss.end_strong_roots();
4745 
4746       {
4747         double start = os::elapsedTime();
4748         G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4749         evac.do_void();
4750         double elapsed_ms = (os::elapsedTime()-start)*1000.0;
4751         double term_ms = pss.term_time()*1000.0;
4752         _g1h->g1_policy()->phase_times()->add_obj_copy_time(worker_id, elapsed_ms-term_ms);
4753         _g1h->g1_policy()->phase_times()->record_termination(worker_id, term_ms, pss.term_attempts());
4754       }
4755       _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4756       _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4757 
4758       if (ParallelGCVerbose) {
4759         MutexLocker x(stats_lock());
4760         pss.print_termination_stats(worker_id);
4761       }
4762 
4763       assert(pss.refs()->is_empty(), "should be empty");
4764 
4765       // Close the inner scope so that the ResourceMark and HandleMark
4766       // destructors are executed here and are included as part of the
4767       // "GC Worker Time".
4768     }
4769 
4770     double end_time_ms = os::elapsedTime() * 1000.0;
4771     _g1h->g1_policy()->phase_times()->record_gc_worker_end_time(worker_id, end_time_ms);
4772   }
4773 };
4774 
4775 // *** Common G1 Evacuation Stuff
4776 
4777 // Closures that support the filtering of CodeBlobs scanned during
4778 // external root scanning.
4779 
4780 // Closure applied to reference fields in code blobs (specifically nmethods)
4781 // to determine whether an nmethod contains references that point into
4782 // the collection set. Used as a predicate when walking code roots so
4783 // that only nmethods that point into the collection set are added to the
4784 // 'marked' list.
4785 
4786 class G1FilteredCodeBlobToOopClosure : public CodeBlobToOopClosure {
4787 
4788   class G1PointsIntoCSOopClosure : public OopClosure {
4789     G1CollectedHeap* _g1;
4790     bool _points_into_cs;
4791   public:
4792     G1PointsIntoCSOopClosure(G1CollectedHeap* g1) :
4793       _g1(g1), _points_into_cs(false) { }
4794 
4795     bool points_into_cs() const { return _points_into_cs; }
4796 
4797     template <class T>
4798     void do_oop_nv(T* p) {
4799       if (!_points_into_cs) {
4800         T heap_oop = oopDesc::load_heap_oop(p);
4801         if (!oopDesc::is_null(heap_oop) &&
4802             _g1->in_cset_fast_test(oopDesc::decode_heap_oop_not_null(heap_oop))) {
4803           _points_into_cs = true;
4804         }
4805       }
4806     }
4807 
4808     virtual void do_oop(oop* p)        { do_oop_nv(p); }
4809     virtual void do_oop(narrowOop* p)  { do_oop_nv(p); }
4810   };
4811 
4812   G1CollectedHeap* _g1;
4813 
4814 public:
4815   G1FilteredCodeBlobToOopClosure(G1CollectedHeap* g1, OopClosure* cl) :
4816     CodeBlobToOopClosure(cl, true), _g1(g1) { }
4817 
4818   virtual void do_code_blob(CodeBlob* cb) {
4819     nmethod* nm = cb->as_nmethod_or_null();
4820     if (nm != NULL && !(nm->test_oops_do_mark())) {
4821       G1PointsIntoCSOopClosure predicate_cl(_g1);
4822       nm->oops_do(&predicate_cl);
4823 
4824       if (predicate_cl.points_into_cs()) {
4825         // At least one of the reference fields or the oop relocations
4826         // in the nmethod points into the collection set. We have to
4827         // 'mark' this nmethod.
4828         // Note: Revisit the following if CodeBlobToOopClosure::do_code_blob()
4829         // or MarkingCodeBlobClosure::do_code_blob() change.
4830         if (!nm->test_set_oops_do_mark()) {
4831           do_newly_marked_nmethod(nm);
4832         }
4833       }
4834     }
4835   }
4836 };
4837 
4838 // This method is run in a GC worker.
4839 
4840 void
4841 G1CollectedHeap::
4842 g1_process_strong_roots(bool collecting_perm_gen,
4843                         ScanningOption so,
4844                         OopClosure* scan_non_heap_roots,
4845                         OopsInHeapRegionClosure* scan_rs,
4846                         OopsInGenClosure* scan_perm,
4847                         int worker_i) {
4848 
4849   // First scan the strong roots, including the perm gen.
4850   double ext_roots_start = os::elapsedTime();
4851   double closure_app_time_sec = 0.0;
4852 
4853   BufferingOopClosure buf_scan_non_heap_roots(scan_non_heap_roots);
4854   BufferingOopsInGenClosure buf_scan_perm(scan_perm);
4855   buf_scan_perm.set_generation(perm_gen());
4856 
4857   // Walk the code cache w/o buffering, because StarTask cannot handle
4858   // unaligned oop locations.
4859   G1FilteredCodeBlobToOopClosure eager_scan_code_roots(this, scan_non_heap_roots);
4860 
4861   process_strong_roots(false, // no scoping; this is parallel code
4862                        collecting_perm_gen, so,
4863                        &buf_scan_non_heap_roots,
4864                        &eager_scan_code_roots,
4865                        &buf_scan_perm);
4866 
4867   // Now the CM ref_processor roots.
4868   if (!_process_strong_tasks->is_task_claimed(G1H_PS_refProcessor_oops_do)) {
4869     // We need to treat the discovered reference lists of the
4870     // concurrent mark ref processor as roots and keep entries
4871     // (which are added by the marking threads) on them live
4872     // until they can be processed at the end of marking.
4873     ref_processor_cm()->weak_oops_do(&buf_scan_non_heap_roots);
4874   }
4875 
4876   // Finish up any enqueued closure apps (attributed as object copy time).
4877   buf_scan_non_heap_roots.done();
4878   buf_scan_perm.done();
4879 



4880   double obj_copy_time_sec = buf_scan_perm.closure_app_seconds() +
4881                                 buf_scan_non_heap_roots.closure_app_seconds();
4882   g1_policy()->phase_times()->record_obj_copy_time(worker_i, obj_copy_time_sec * 1000.0);
4883 
4884   double ext_root_time_ms =
4885     ((os::elapsedTime() - ext_roots_start) - obj_copy_time_sec) * 1000.0;
4886 
4887   g1_policy()->phase_times()->record_ext_root_scan_time(worker_i, ext_root_time_ms);
4888 
4889   // During conc marking we have to filter the per-thread SATB buffers
4890   // to make sure we remove any oops into the CSet (which will show up
4891   // as implicitly live).
4892   double satb_filtering_ms = 0.0;
4893   if (!_process_strong_tasks->is_task_claimed(G1H_PS_filter_satb_buffers)) {
4894     if (mark_in_progress()) {
4895       double satb_filter_start = os::elapsedTime();
4896 
4897       JavaThread::satb_mark_queue_set().filter_thread_buffers();
4898 
4899       satb_filtering_ms = (os::elapsedTime() - satb_filter_start) * 1000.0;
4900     }
4901   }

4902   g1_policy()->phase_times()->record_satb_filtering_time(worker_i, satb_filtering_ms);
4903 
4904   // Now scan the complement of the collection set.
4905   if (scan_rs != NULL) {
4906     g1_rem_set()->oops_into_collection_set_do(scan_rs, worker_i);
4907   }
4908 
4909   _process_strong_tasks->all_tasks_completed();
4910 }
4911 
4912 void
4913 G1CollectedHeap::g1_process_weak_roots(OopClosure* root_closure,
4914                                        OopClosure* non_root_closure) {
4915   CodeBlobToOopClosure roots_in_blobs(root_closure, /*do_marking=*/ false);
4916   SharedHeap::process_weak_roots(root_closure, &roots_in_blobs, non_root_closure);
4917 }
4918 
4919 // Weak Reference Processing support
4920 
4921 // An always "is_alive" closure that is used to preserve referents.
4922 // If the object is non-null then it's alive.  Used in the preservation
4923 // of referent objects that are pointed to by reference objects
4924 // discovered by the CM ref processor.
4925 class G1AlwaysAliveClosure: public BoolObjectClosure {
4926   G1CollectedHeap* _g1;
4927 public:
4928   G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
4929   void do_object(oop p) { assert(false, "Do not call."); }
4930   bool do_object_b(oop p) {
4931     if (p != NULL) {
4932       return true;
4933     }
4934     return false;
4935   }
4936 };
4937 
4938 bool G1STWIsAliveClosure::do_object_b(oop p) {
4939   // An object is reachable if it is outside the collection set,
4940   // or is inside and copied.
4941   return !_g1->obj_in_cs(p) || p->is_forwarded();
4942 }
4943 
4944 // Non Copying Keep Alive closure
4945 class G1KeepAliveClosure: public OopClosure {
4946   G1CollectedHeap* _g1;
4947 public:
4948   G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
4949   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
4950   void do_oop(      oop* p) {
4951     oop obj = *p;
4952 
4953     if (_g1->obj_in_cs(obj)) {
4954       assert( obj->is_forwarded(), "invariant" );
4955       *p = obj->forwardee();
4956     }
4957   }
4958 };
4959 
4960 // Copying Keep Alive closure - can be called from both
4961 // serial and parallel code as long as different worker
4962 // threads utilize different G1ParScanThreadState instances
4963 // and different queues.
4964 
4965 class G1CopyingKeepAliveClosure: public OopClosure {
4966   G1CollectedHeap*         _g1h;
4967   OopClosure*              _copy_non_heap_obj_cl;
4968   OopsInHeapRegionClosure* _copy_perm_obj_cl;
4969   G1ParScanThreadState*    _par_scan_state;
4970 
4971 public:
4972   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
4973                             OopClosure* non_heap_obj_cl,
4974                             OopsInHeapRegionClosure* perm_obj_cl,
4975                             G1ParScanThreadState* pss):
4976     _g1h(g1h),
4977     _copy_non_heap_obj_cl(non_heap_obj_cl),
4978     _copy_perm_obj_cl(perm_obj_cl),
4979     _par_scan_state(pss)
4980   {}
4981 
4982   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
4983   virtual void do_oop(      oop* p) { do_oop_work(p); }
4984 
4985   template <class T> void do_oop_work(T* p) {
4986     oop obj = oopDesc::load_decode_heap_oop(p);
4987 
4988     if (_g1h->obj_in_cs(obj)) {
4989       // If the referent object has been forwarded (either copied
4990       // to a new location or to itself in the event of an
4991       // evacuation failure) then we need to update the reference
4992       // field and, if both reference and referent are in the G1
4993       // heap, update the RSet for the referent.
4994       //
4995       // If the referent has not been forwarded then we have to keep
4996       // it alive by policy. Therefore we have copy the referent.
4997       //
4998       // If the reference field is in the G1 heap then we can push
4999       // on the PSS queue. When the queue is drained (after each
5000       // phase of reference processing) the object and it's followers
5001       // will be copied, the reference field set to point to the
5002       // new location, and the RSet updated. Otherwise we need to
5003       // use the the non-heap or perm closures directly to copy
5004       // the refernt object and update the pointer, while avoiding
5005       // updating the RSet.
5006 
5007       if (_g1h->is_in_g1_reserved(p)) {
5008         _par_scan_state->push_on_queue(p);
5009       } else {
5010         // The reference field is not in the G1 heap.
5011         if (_g1h->perm_gen()->is_in(p)) {
5012           _copy_perm_obj_cl->do_oop(p);
5013         } else {
5014           _copy_non_heap_obj_cl->do_oop(p);
5015         }
5016       }
5017     }
5018   }
5019 };
5020 
5021 // Serial drain queue closure. Called as the 'complete_gc'
5022 // closure for each discovered list in some of the
5023 // reference processing phases.
5024 
5025 class G1STWDrainQueueClosure: public VoidClosure {
5026 protected:
5027   G1CollectedHeap* _g1h;
5028   G1ParScanThreadState* _par_scan_state;
5029 
5030   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
5031 
5032 public:
5033   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
5034     _g1h(g1h),
5035     _par_scan_state(pss)
5036   { }
5037 
5038   void do_void() {
5039     G1ParScanThreadState* const pss = par_scan_state();
5040     pss->trim_queue();
5041   }
5042 };
5043 
5044 // Parallel Reference Processing closures
5045 
5046 // Implementation of AbstractRefProcTaskExecutor for parallel reference
5047 // processing during G1 evacuation pauses.
5048 
5049 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5050 private:
5051   G1CollectedHeap*   _g1h;
5052   RefToScanQueueSet* _queues;
5053   FlexibleWorkGang*  _workers;
5054   int                _active_workers;
5055 
5056 public:
5057   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5058                         FlexibleWorkGang* workers,
5059                         RefToScanQueueSet *task_queues,
5060                         int n_workers) :
5061     _g1h(g1h),
5062     _queues(task_queues),
5063     _workers(workers),
5064     _active_workers(n_workers)
5065   {
5066     assert(n_workers > 0, "shouldn't call this otherwise");
5067   }
5068 
5069   // Executes the given task using concurrent marking worker threads.
5070   virtual void execute(ProcessTask& task);
5071   virtual void execute(EnqueueTask& task);
5072 };
5073 
5074 // Gang task for possibly parallel reference processing
5075 
5076 class G1STWRefProcTaskProxy: public AbstractGangTask {
5077   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5078   ProcessTask&     _proc_task;
5079   G1CollectedHeap* _g1h;
5080   RefToScanQueueSet *_task_queues;
5081   ParallelTaskTerminator* _terminator;
5082 
5083 public:
5084   G1STWRefProcTaskProxy(ProcessTask& proc_task,
5085                      G1CollectedHeap* g1h,
5086                      RefToScanQueueSet *task_queues,
5087                      ParallelTaskTerminator* terminator) :
5088     AbstractGangTask("Process reference objects in parallel"),
5089     _proc_task(proc_task),
5090     _g1h(g1h),
5091     _task_queues(task_queues),
5092     _terminator(terminator)
5093   {}
5094 
5095   virtual void work(uint worker_id) {
5096     // The reference processing task executed by a single worker.
5097     ResourceMark rm;
5098     HandleMark   hm;
5099 
5100     G1STWIsAliveClosure is_alive(_g1h);
5101 
5102     G1ParScanThreadState pss(_g1h, worker_id);
5103 
5104     G1ParScanHeapEvacClosure        scan_evac_cl(_g1h, &pss, NULL);
5105     G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5106     G1ParScanPartialArrayClosure    partial_scan_cl(_g1h, &pss, NULL);
5107 
5108     pss.set_evac_closure(&scan_evac_cl);
5109     pss.set_evac_failure_closure(&evac_failure_cl);
5110     pss.set_partial_scan_closure(&partial_scan_cl);
5111 
5112     G1ParScanExtRootClosure        only_copy_non_heap_cl(_g1h, &pss, NULL);
5113     G1ParScanPermClosure           only_copy_perm_cl(_g1h, &pss, NULL);
5114 
5115     G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5116     G1ParScanAndMarkPermClosure    copy_mark_perm_cl(_g1h, &pss, NULL);
5117 
5118     OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5119     OopsInHeapRegionClosure*       copy_perm_cl = &only_copy_perm_cl;
5120 
5121     if (_g1h->g1_policy()->during_initial_mark_pause()) {
5122       // We also need to mark copied objects.
5123       copy_non_heap_cl = &copy_mark_non_heap_cl;
5124       copy_perm_cl = &copy_mark_perm_cl;
5125     }
5126 
5127     // Keep alive closure.
5128     G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_perm_cl, &pss);
5129 
5130     // Complete GC closure
5131     G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5132 
5133     // Call the reference processing task's work routine.
5134     _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5135 
5136     // Note we cannot assert that the refs array is empty here as not all
5137     // of the processing tasks (specifically phase2 - pp2_work) execute
5138     // the complete_gc closure (which ordinarily would drain the queue) so
5139     // the queue may not be empty.
5140   }
5141 };
5142 
5143 // Driver routine for parallel reference processing.
5144 // Creates an instance of the ref processing gang
5145 // task and has the worker threads execute it.
5146 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5147   assert(_workers != NULL, "Need parallel worker threads.");
5148 
5149   ParallelTaskTerminator terminator(_active_workers, _queues);
5150   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5151 
5152   _g1h->set_par_threads(_active_workers);
5153   _workers->run_task(&proc_task_proxy);
5154   _g1h->set_par_threads(0);
5155 }
5156 
5157 // Gang task for parallel reference enqueueing.
5158 
5159 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5160   typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5161   EnqueueTask& _enq_task;
5162 
5163 public:
5164   G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5165     AbstractGangTask("Enqueue reference objects in parallel"),
5166     _enq_task(enq_task)
5167   { }
5168 
5169   virtual void work(uint worker_id) {
5170     _enq_task.work(worker_id);
5171   }
5172 };
5173 
5174 // Driver routine for parallel reference enqueing.
5175 // Creates an instance of the ref enqueueing gang
5176 // task and has the worker threads execute it.
5177 
5178 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5179   assert(_workers != NULL, "Need parallel worker threads.");
5180 
5181   G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5182 
5183   _g1h->set_par_threads(_active_workers);
5184   _workers->run_task(&enq_task_proxy);
5185   _g1h->set_par_threads(0);
5186 }
5187 
5188 // End of weak reference support closures
5189 
5190 // Abstract task used to preserve (i.e. copy) any referent objects
5191 // that are in the collection set and are pointed to by reference
5192 // objects discovered by the CM ref processor.
5193 
5194 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5195 protected:
5196   G1CollectedHeap* _g1h;
5197   RefToScanQueueSet      *_queues;
5198   ParallelTaskTerminator _terminator;
5199   uint _n_workers;
5200 
5201 public:
5202   G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h,int workers, RefToScanQueueSet *task_queues) :
5203     AbstractGangTask("ParPreserveCMReferents"),
5204     _g1h(g1h),
5205     _queues(task_queues),
5206     _terminator(workers, _queues),
5207     _n_workers(workers)
5208   { }
5209 
5210   void work(uint worker_id) {
5211     ResourceMark rm;
5212     HandleMark   hm;
5213 
5214     G1ParScanThreadState            pss(_g1h, worker_id);
5215     G1ParScanHeapEvacClosure        scan_evac_cl(_g1h, &pss, NULL);
5216     G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5217     G1ParScanPartialArrayClosure    partial_scan_cl(_g1h, &pss, NULL);
5218 
5219     pss.set_evac_closure(&scan_evac_cl);
5220     pss.set_evac_failure_closure(&evac_failure_cl);
5221     pss.set_partial_scan_closure(&partial_scan_cl);
5222 
5223     assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5224 
5225 
5226     G1ParScanExtRootClosure        only_copy_non_heap_cl(_g1h, &pss, NULL);
5227     G1ParScanPermClosure           only_copy_perm_cl(_g1h, &pss, NULL);
5228 
5229     G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5230     G1ParScanAndMarkPermClosure    copy_mark_perm_cl(_g1h, &pss, NULL);
5231 
5232     OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5233     OopsInHeapRegionClosure*       copy_perm_cl = &only_copy_perm_cl;
5234 
5235     if (_g1h->g1_policy()->during_initial_mark_pause()) {
5236       // We also need to mark copied objects.
5237       copy_non_heap_cl = &copy_mark_non_heap_cl;
5238       copy_perm_cl = &copy_mark_perm_cl;
5239     }
5240 
5241     // Is alive closure
5242     G1AlwaysAliveClosure always_alive(_g1h);
5243 
5244     // Copying keep alive closure. Applied to referent objects that need
5245     // to be copied.
5246     G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, copy_perm_cl, &pss);
5247 
5248     ReferenceProcessor* rp = _g1h->ref_processor_cm();
5249 
5250     uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5251     uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5252 
5253     // limit is set using max_num_q() - which was set using ParallelGCThreads.
5254     // So this must be true - but assert just in case someone decides to
5255     // change the worker ids.
5256     assert(0 <= worker_id && worker_id < limit, "sanity");
5257     assert(!rp->discovery_is_atomic(), "check this code");
5258 
5259     // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5260     for (uint idx = worker_id; idx < limit; idx += stride) {
5261       DiscoveredList& ref_list = rp->discovered_refs()[idx];
5262 
5263       DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5264       while (iter.has_next()) {
5265         // Since discovery is not atomic for the CM ref processor, we
5266         // can see some null referent objects.
5267         iter.load_ptrs(DEBUG_ONLY(true));
5268         oop ref = iter.obj();
5269 
5270         // This will filter nulls.
5271         if (iter.is_referent_alive()) {
5272           iter.make_referent_alive();
5273         }
5274         iter.move_to_next();
5275       }
5276     }
5277 
5278     // Drain the queue - which may cause stealing
5279     G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5280     drain_queue.do_void();
5281     // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5282     assert(pss.refs()->is_empty(), "should be");
5283   }
5284 };
5285 
5286 // Weak Reference processing during an evacuation pause (part 1).
5287 void G1CollectedHeap::process_discovered_references() {
5288   double ref_proc_start = os::elapsedTime();
5289 
5290   ReferenceProcessor* rp = _ref_processor_stw;
5291   assert(rp->discovery_enabled(), "should have been enabled");
5292 
5293   // Any reference objects, in the collection set, that were 'discovered'
5294   // by the CM ref processor should have already been copied (either by
5295   // applying the external root copy closure to the discovered lists, or
5296   // by following an RSet entry).
5297   //
5298   // But some of the referents, that are in the collection set, that these
5299   // reference objects point to may not have been copied: the STW ref
5300   // processor would have seen that the reference object had already
5301   // been 'discovered' and would have skipped discovering the reference,
5302   // but would not have treated the reference object as a regular oop.
5303   // As a reult the copy closure would not have been applied to the
5304   // referent object.
5305   //
5306   // We need to explicitly copy these referent objects - the references
5307   // will be processed at the end of remarking.
5308   //
5309   // We also need to do this copying before we process the reference
5310   // objects discovered by the STW ref processor in case one of these
5311   // referents points to another object which is also referenced by an
5312   // object discovered by the STW ref processor.
5313 
5314   uint active_workers = (G1CollectedHeap::use_parallel_gc_threads() ?
5315                         workers()->active_workers() : 1);
5316 
5317   assert(!G1CollectedHeap::use_parallel_gc_threads() ||
5318            active_workers == workers()->active_workers(),
5319            "Need to reset active_workers");
5320 
5321   set_par_threads(active_workers);
5322   G1ParPreserveCMReferentsTask keep_cm_referents(this, active_workers, _task_queues);
5323 
5324   if (G1CollectedHeap::use_parallel_gc_threads()) {
5325     workers()->run_task(&keep_cm_referents);
5326   } else {
5327     keep_cm_referents.work(0);
5328   }
5329 
5330   set_par_threads(0);
5331 
5332   // Closure to test whether a referent is alive.
5333   G1STWIsAliveClosure is_alive(this);
5334 
5335   // Even when parallel reference processing is enabled, the processing
5336   // of JNI refs is serial and performed serially by the current thread
5337   // rather than by a worker. The following PSS will be used for processing
5338   // JNI refs.
5339 
5340   // Use only a single queue for this PSS.
5341   G1ParScanThreadState pss(this, 0);
5342 
5343   // We do not embed a reference processor in the copying/scanning
5344   // closures while we're actually processing the discovered
5345   // reference objects.
5346   G1ParScanHeapEvacClosure        scan_evac_cl(this, &pss, NULL);
5347   G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5348   G1ParScanPartialArrayClosure    partial_scan_cl(this, &pss, NULL);
5349 
5350   pss.set_evac_closure(&scan_evac_cl);
5351   pss.set_evac_failure_closure(&evac_failure_cl);
5352   pss.set_partial_scan_closure(&partial_scan_cl);
5353 
5354   assert(pss.refs()->is_empty(), "pre-condition");
5355 
5356   G1ParScanExtRootClosure        only_copy_non_heap_cl(this, &pss, NULL);
5357   G1ParScanPermClosure           only_copy_perm_cl(this, &pss, NULL);
5358 
5359   G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5360   G1ParScanAndMarkPermClosure    copy_mark_perm_cl(this, &pss, NULL);
5361 
5362   OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5363   OopsInHeapRegionClosure*       copy_perm_cl = &only_copy_perm_cl;
5364 
5365   if (_g1h->g1_policy()->during_initial_mark_pause()) {
5366     // We also need to mark copied objects.
5367     copy_non_heap_cl = &copy_mark_non_heap_cl;
5368     copy_perm_cl = &copy_mark_perm_cl;
5369   }
5370 
5371   // Keep alive closure.
5372   G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, copy_perm_cl, &pss);
5373 
5374   // Serial Complete GC closure
5375   G1STWDrainQueueClosure drain_queue(this, &pss);
5376 
5377   // Setup the soft refs policy...
5378   rp->setup_policy(false);
5379 
5380   if (!rp->processing_is_mt()) {
5381     // Serial reference processing...
5382     rp->process_discovered_references(&is_alive,
5383                                       &keep_alive,
5384                                       &drain_queue,
5385                                       NULL);
5386   } else {
5387     // Parallel reference processing
5388     assert(rp->num_q() == active_workers, "sanity");
5389     assert(active_workers <= rp->max_num_q(), "sanity");
5390 
5391     G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, active_workers);
5392     rp->process_discovered_references(&is_alive, &keep_alive, &drain_queue, &par_task_executor);
5393   }
5394 
5395   // We have completed copying any necessary live referent objects
5396   // (that were not copied during the actual pause) so we can
5397   // retire any active alloc buffers
5398   pss.retire_alloc_buffers();
5399   assert(pss.refs()->is_empty(), "both queue and overflow should be empty");
5400 
5401   double ref_proc_time = os::elapsedTime() - ref_proc_start;
5402   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5403 }
5404 
5405 // Weak Reference processing during an evacuation pause (part 2).
5406 void G1CollectedHeap::enqueue_discovered_references() {
5407   double ref_enq_start = os::elapsedTime();
5408 
5409   ReferenceProcessor* rp = _ref_processor_stw;
5410   assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5411 
5412   // Now enqueue any remaining on the discovered lists on to
5413   // the pending list.
5414   if (!rp->processing_is_mt()) {
5415     // Serial reference processing...
5416     rp->enqueue_discovered_references();
5417   } else {
5418     // Parallel reference enqueuing
5419 
5420     uint active_workers = (ParallelGCThreads > 0 ? workers()->active_workers() : 1);
5421     assert(active_workers == workers()->active_workers(),
5422            "Need to reset active_workers");
5423     assert(rp->num_q() == active_workers, "sanity");
5424     assert(active_workers <= rp->max_num_q(), "sanity");
5425 
5426     G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, active_workers);
5427     rp->enqueue_discovered_references(&par_task_executor);
5428   }
5429 
5430   rp->verify_no_references_recorded();
5431   assert(!rp->discovery_enabled(), "should have been disabled");
5432 
5433   // FIXME
5434   // CM's reference processing also cleans up the string and symbol tables.
5435   // Should we do that here also? We could, but it is a serial operation
5436   // and could signicantly increase the pause time.
5437 
5438   double ref_enq_time = os::elapsedTime() - ref_enq_start;
5439   g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5440 }
5441 
5442 void G1CollectedHeap::evacuate_collection_set() {
5443   _expand_heap_after_alloc_failure = true;
5444   set_evacuation_failed(false);
5445 
5446   g1_rem_set()->prepare_for_oops_into_collection_set_do();
5447   concurrent_g1_refine()->set_use_cache(false);
5448   concurrent_g1_refine()->clear_hot_cache_claimed_index();
5449 
5450   uint n_workers;
5451   if (G1CollectedHeap::use_parallel_gc_threads()) {
5452     n_workers =
5453       AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
5454                                      workers()->active_workers(),
5455                                      Threads::number_of_non_daemon_threads());
5456     assert(UseDynamicNumberOfGCThreads ||
5457            n_workers == workers()->total_workers(),
5458            "If not dynamic should be using all the  workers");
5459     workers()->set_active_workers(n_workers);
5460     set_par_threads(n_workers);
5461   } else {
5462     assert(n_par_threads() == 0,
5463            "Should be the original non-parallel value");
5464     n_workers = 1;
5465   }
5466 
5467   G1ParTask g1_par_task(this, _task_queues);
5468 
5469   init_for_evac_failure(NULL);
5470 
5471   rem_set()->prepare_for_younger_refs_iterate(true);
5472 
5473   assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5474   double start_par_time_sec = os::elapsedTime();
5475   double end_par_time_sec;
5476 
5477   {
5478     StrongRootsScope srs(this);
5479 
5480     if (G1CollectedHeap::use_parallel_gc_threads()) {
5481       // The individual threads will set their evac-failure closures.
5482       if (ParallelGCVerbose) G1ParScanThreadState::print_termination_stats_hdr();
5483       // These tasks use ShareHeap::_process_strong_tasks
5484       assert(UseDynamicNumberOfGCThreads ||
5485              workers()->active_workers() == workers()->total_workers(),
5486              "If not dynamic should be using all the  workers");
5487       workers()->run_task(&g1_par_task);
5488     } else {
5489       g1_par_task.set_for_termination(n_workers);
5490       g1_par_task.work(0);
5491     }
5492     end_par_time_sec = os::elapsedTime();
5493 
5494     // Closing the inner scope will execute the destructor
5495     // for the StrongRootsScope object. We record the current
5496     // elapsed time before closing the scope so that time
5497     // taken for the SRS destructor is NOT included in the
5498     // reported parallel time.
5499   }
5500 
5501   double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5502   g1_policy()->phase_times()->record_par_time(par_time_ms);
5503 
5504   double code_root_fixup_time_ms =
5505         (os::elapsedTime() - end_par_time_sec) * 1000.0;
5506   g1_policy()->phase_times()->record_code_root_fixup_time(code_root_fixup_time_ms);
5507 
5508   set_par_threads(0);
5509 
5510   // Process any discovered reference objects - we have
5511   // to do this _before_ we retire the GC alloc regions
5512   // as we may have to copy some 'reachable' referent
5513   // objects (and their reachable sub-graphs) that were
5514   // not copied during the pause.
5515   process_discovered_references();
5516 
5517   // Weak root processing.
5518   // Note: when JSR 292 is enabled and code blobs can contain
5519   // non-perm oops then we will need to process the code blobs
5520   // here too.
5521   {
5522     G1STWIsAliveClosure is_alive(this);
5523     G1KeepAliveClosure keep_alive(this);
5524     JNIHandles::weak_oops_do(&is_alive, &keep_alive);
5525   }
5526 
5527   release_gc_alloc_regions();
5528   g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5529 
5530   concurrent_g1_refine()->clear_hot_cache();
5531   concurrent_g1_refine()->set_use_cache(true);
5532 
5533   finalize_for_evac_failure();
5534 
5535   if (evacuation_failed()) {
5536     remove_self_forwarding_pointers();
5537     if (G1Log::finer()) {
5538       gclog_or_tty->print(" (to-space exhausted)");
5539     } else if (G1Log::fine()) {
5540       gclog_or_tty->print("--");
5541     }
5542   }
5543 
5544   // Enqueue any remaining references remaining on the STW
5545   // reference processor's discovered lists. We need to do
5546   // this after the card table is cleaned (and verified) as
5547   // the act of enqueuing entries on to the pending list
5548   // will log these updates (and dirty their associated
5549   // cards). We need these updates logged to update any
5550   // RSets.
5551   enqueue_discovered_references();
5552 
5553   if (G1DeferredRSUpdate) {
5554     RedirtyLoggedCardTableEntryFastClosure redirty;
5555     dirty_card_queue_set().set_closure(&redirty);
5556     dirty_card_queue_set().apply_closure_to_all_completed_buffers();
5557 
5558     DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
5559     dcq.merge_bufferlists(&dirty_card_queue_set());
5560     assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
5561   }
5562   COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5563 }
5564 
5565 void G1CollectedHeap::free_region_if_empty(HeapRegion* hr,
5566                                      size_t* pre_used,
5567                                      FreeRegionList* free_list,
5568                                      OldRegionSet* old_proxy_set,
5569                                      HumongousRegionSet* humongous_proxy_set,
5570                                      HRRSCleanupTask* hrrs_cleanup_task,
5571                                      bool par) {
5572   if (hr->used() > 0 && hr->max_live_bytes() == 0 && !hr->is_young()) {
5573     if (hr->isHumongous()) {
5574       assert(hr->startsHumongous(), "we should only see starts humongous");
5575       free_humongous_region(hr, pre_used, free_list, humongous_proxy_set, par);
5576     } else {
5577       _old_set.remove_with_proxy(hr, old_proxy_set);
5578       free_region(hr, pre_used, free_list, par);
5579     }
5580   } else {
5581     hr->rem_set()->do_cleanup_work(hrrs_cleanup_task);
5582   }
5583 }
5584 
5585 void G1CollectedHeap::free_region(HeapRegion* hr,
5586                                   size_t* pre_used,
5587                                   FreeRegionList* free_list,
5588                                   bool par) {
5589   assert(!hr->isHumongous(), "this is only for non-humongous regions");
5590   assert(!hr->is_empty(), "the region should not be empty");
5591   assert(free_list != NULL, "pre-condition");
5592 
5593   *pre_used += hr->used();
5594   hr->hr_clear(par, true /* clear_space */);
5595   free_list->add_as_head(hr);
5596 }
5597 
5598 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
5599                                      size_t* pre_used,
5600                                      FreeRegionList* free_list,
5601                                      HumongousRegionSet* humongous_proxy_set,
5602                                      bool par) {
5603   assert(hr->startsHumongous(), "this is only for starts humongous regions");
5604   assert(free_list != NULL, "pre-condition");
5605   assert(humongous_proxy_set != NULL, "pre-condition");
5606 
5607   size_t hr_used = hr->used();
5608   size_t hr_capacity = hr->capacity();
5609   size_t hr_pre_used = 0;
5610   _humongous_set.remove_with_proxy(hr, humongous_proxy_set);
5611   hr->set_notHumongous();
5612   free_region(hr, &hr_pre_used, free_list, par);
5613 
5614   uint i = hr->hrs_index() + 1;
5615   uint num = 1;
5616   while (i < n_regions()) {
5617     HeapRegion* curr_hr = region_at(i);
5618     if (!curr_hr->continuesHumongous()) {
5619       break;
5620     }
5621     curr_hr->set_notHumongous();
5622     free_region(curr_hr, &hr_pre_used, free_list, par);
5623     num += 1;
5624     i += 1;
5625   }
5626   assert(hr_pre_used == hr_used,
5627          err_msg("hr_pre_used: "SIZE_FORMAT" and hr_used: "SIZE_FORMAT" "
5628                  "should be the same", hr_pre_used, hr_used));
5629   *pre_used += hr_pre_used;
5630 }
5631 
5632 void G1CollectedHeap::update_sets_after_freeing_regions(size_t pre_used,
5633                                        FreeRegionList* free_list,
5634                                        OldRegionSet* old_proxy_set,
5635                                        HumongousRegionSet* humongous_proxy_set,
5636                                        bool par) {
5637   if (pre_used > 0) {
5638     Mutex* lock = (par) ? ParGCRareEvent_lock : NULL;
5639     MutexLockerEx x(lock, Mutex::_no_safepoint_check_flag);
5640     assert(_summary_bytes_used >= pre_used,
5641            err_msg("invariant: _summary_bytes_used: "SIZE_FORMAT" "
5642                    "should be >= pre_used: "SIZE_FORMAT,
5643                    _summary_bytes_used, pre_used));
5644     _summary_bytes_used -= pre_used;
5645   }
5646   if (free_list != NULL && !free_list->is_empty()) {
5647     MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
5648     _free_list.add_as_head(free_list);
5649   }
5650   if (old_proxy_set != NULL && !old_proxy_set->is_empty()) {
5651     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5652     _old_set.update_from_proxy(old_proxy_set);
5653   }
5654   if (humongous_proxy_set != NULL && !humongous_proxy_set->is_empty()) {
5655     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5656     _humongous_set.update_from_proxy(humongous_proxy_set);
5657   }
5658 }
5659 
5660 class G1ParCleanupCTTask : public AbstractGangTask {
5661   CardTableModRefBS* _ct_bs;
5662   G1CollectedHeap* _g1h;
5663   HeapRegion* volatile _su_head;
5664 public:
5665   G1ParCleanupCTTask(CardTableModRefBS* ct_bs,
5666                      G1CollectedHeap* g1h) :
5667     AbstractGangTask("G1 Par Cleanup CT Task"),
5668     _ct_bs(ct_bs), _g1h(g1h) { }
5669 
5670   void work(uint worker_id) {
5671     HeapRegion* r;
5672     while (r = _g1h->pop_dirty_cards_region()) {
5673       clear_cards(r);
5674     }
5675   }
5676 
5677   void clear_cards(HeapRegion* r) {
5678     // Cards of the survivors should have already been dirtied.
5679     if (!r->is_survivor()) {
5680       _ct_bs->clear(MemRegion(r->bottom(), r->end()));
5681     }
5682   }
5683 };
5684 
5685 #ifndef PRODUCT
5686 class G1VerifyCardTableCleanup: public HeapRegionClosure {
5687   G1CollectedHeap* _g1h;
5688   CardTableModRefBS* _ct_bs;
5689 public:
5690   G1VerifyCardTableCleanup(G1CollectedHeap* g1h, CardTableModRefBS* ct_bs)
5691     : _g1h(g1h), _ct_bs(ct_bs) { }
5692   virtual bool doHeapRegion(HeapRegion* r) {
5693     if (r->is_survivor()) {
5694       _g1h->verify_dirty_region(r);
5695     } else {
5696       _g1h->verify_not_dirty_region(r);
5697     }
5698     return false;
5699   }
5700 };
5701 
5702 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
5703   // All of the region should be clean.
5704   CardTableModRefBS* ct_bs = (CardTableModRefBS*)barrier_set();
5705   MemRegion mr(hr->bottom(), hr->end());
5706   ct_bs->verify_not_dirty_region(mr);
5707 }
5708 
5709 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
5710   // We cannot guarantee that [bottom(),end()] is dirty.  Threads
5711   // dirty allocated blocks as they allocate them. The thread that
5712   // retires each region and replaces it with a new one will do a
5713   // maximal allocation to fill in [pre_dummy_top(),end()] but will
5714   // not dirty that area (one less thing to have to do while holding
5715   // a lock). So we can only verify that [bottom(),pre_dummy_top()]
5716   // is dirty.
5717   CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set();
5718   MemRegion mr(hr->bottom(), hr->pre_dummy_top());
5719   ct_bs->verify_dirty_region(mr);
5720 }
5721 
5722 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
5723   CardTableModRefBS* ct_bs = (CardTableModRefBS*) barrier_set();
5724   for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
5725     verify_dirty_region(hr);
5726   }
5727 }
5728 
5729 void G1CollectedHeap::verify_dirty_young_regions() {
5730   verify_dirty_young_list(_young_list->first_region());
5731   verify_dirty_young_list(_young_list->first_survivor_region());
5732 }
5733 #endif
5734 
5735 void G1CollectedHeap::cleanUpCardTable() {
5736   CardTableModRefBS* ct_bs = (CardTableModRefBS*) (barrier_set());
5737   double start = os::elapsedTime();
5738 
5739   {
5740     // Iterate over the dirty cards region list.
5741     G1ParCleanupCTTask cleanup_task(ct_bs, this);
5742 
5743     if (G1CollectedHeap::use_parallel_gc_threads()) {
5744       set_par_threads();
5745       workers()->run_task(&cleanup_task);
5746       set_par_threads(0);
5747     } else {
5748       while (_dirty_cards_region_list) {
5749         HeapRegion* r = _dirty_cards_region_list;
5750         cleanup_task.clear_cards(r);
5751         _dirty_cards_region_list = r->get_next_dirty_cards_region();
5752         if (_dirty_cards_region_list == r) {
5753           // The last region.
5754           _dirty_cards_region_list = NULL;
5755         }
5756         r->set_next_dirty_cards_region(NULL);
5757       }
5758     }
5759 #ifndef PRODUCT
5760     if (G1VerifyCTCleanup || VerifyAfterGC) {
5761       G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
5762       heap_region_iterate(&cleanup_verifier);
5763     }
5764 #endif
5765   }
5766 
5767   double elapsed = os::elapsedTime() - start;
5768   g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
5769 }
5770 
5771 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head) {
5772   size_t pre_used = 0;
5773   FreeRegionList local_free_list("Local List for CSet Freeing");
5774 
5775   double young_time_ms     = 0.0;
5776   double non_young_time_ms = 0.0;
5777 
5778   // Since the collection set is a superset of the the young list,
5779   // all we need to do to clear the young list is clear its
5780   // head and length, and unlink any young regions in the code below
5781   _young_list->clear();
5782 
5783   G1CollectorPolicy* policy = g1_policy();
5784 
5785   double start_sec = os::elapsedTime();
5786   bool non_young = true;
5787 
5788   HeapRegion* cur = cs_head;
5789   int age_bound = -1;
5790   size_t rs_lengths = 0;
5791 
5792   while (cur != NULL) {
5793     assert(!is_on_master_free_list(cur), "sanity");
5794     if (non_young) {
5795       if (cur->is_young()) {
5796         double end_sec = os::elapsedTime();
5797         double elapsed_ms = (end_sec - start_sec) * 1000.0;
5798         non_young_time_ms += elapsed_ms;
5799 
5800         start_sec = os::elapsedTime();
5801         non_young = false;
5802       }
5803     } else {
5804       if (!cur->is_young()) {
5805         double end_sec = os::elapsedTime();
5806         double elapsed_ms = (end_sec - start_sec) * 1000.0;
5807         young_time_ms += elapsed_ms;
5808 
5809         start_sec = os::elapsedTime();
5810         non_young = true;
5811       }
5812     }
5813 
5814     rs_lengths += cur->rem_set()->occupied();
5815 
5816     HeapRegion* next = cur->next_in_collection_set();
5817     assert(cur->in_collection_set(), "bad CS");
5818     cur->set_next_in_collection_set(NULL);
5819     cur->set_in_collection_set(false);
5820 
5821     if (cur->is_young()) {
5822       int index = cur->young_index_in_cset();
5823       assert(index != -1, "invariant");
5824       assert((uint) index < policy->young_cset_region_length(), "invariant");
5825       size_t words_survived = _surviving_young_words[index];
5826       cur->record_surv_words_in_group(words_survived);
5827 
5828       // At this point the we have 'popped' cur from the collection set
5829       // (linked via next_in_collection_set()) but it is still in the
5830       // young list (linked via next_young_region()). Clear the
5831       // _next_young_region field.
5832       cur->set_next_young_region(NULL);
5833     } else {
5834       int index = cur->young_index_in_cset();
5835       assert(index == -1, "invariant");
5836     }
5837 
5838     assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
5839             (!cur->is_young() && cur->young_index_in_cset() == -1),
5840             "invariant" );
5841 
5842     if (!cur->evacuation_failed()) {
5843       MemRegion used_mr = cur->used_region();
5844 
5845       // And the region is empty.
5846       assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
5847       free_region(cur, &pre_used, &local_free_list, false /* par */);
5848     } else {
5849       cur->uninstall_surv_rate_group();
5850       if (cur->is_young()) {
5851         cur->set_young_index_in_cset(-1);
5852       }
5853       cur->set_not_young();
5854       cur->set_evacuation_failed(false);
5855       // The region is now considered to be old.
5856       _old_set.add(cur);
5857     }
5858     cur = next;
5859   }
5860 
5861   policy->record_max_rs_lengths(rs_lengths);
5862   policy->cset_regions_freed();
5863 
5864   double end_sec = os::elapsedTime();
5865   double elapsed_ms = (end_sec - start_sec) * 1000.0;
5866 
5867   if (non_young) {
5868     non_young_time_ms += elapsed_ms;
5869   } else {
5870     young_time_ms += elapsed_ms;
5871   }
5872 
5873   update_sets_after_freeing_regions(pre_used, &local_free_list,
5874                                     NULL /* old_proxy_set */,
5875                                     NULL /* humongous_proxy_set */,
5876                                     false /* par */);
5877   policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
5878   policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
5879 }
5880 
5881 // This routine is similar to the above but does not record
5882 // any policy statistics or update free lists; we are abandoning
5883 // the current incremental collection set in preparation of a
5884 // full collection. After the full GC we will start to build up
5885 // the incremental collection set again.
5886 // This is only called when we're doing a full collection
5887 // and is immediately followed by the tearing down of the young list.
5888 
5889 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
5890   HeapRegion* cur = cs_head;
5891 
5892   while (cur != NULL) {
5893     HeapRegion* next = cur->next_in_collection_set();
5894     assert(cur->in_collection_set(), "bad CS");
5895     cur->set_next_in_collection_set(NULL);
5896     cur->set_in_collection_set(false);
5897     cur->set_young_index_in_cset(-1);
5898     cur = next;
5899   }
5900 }
5901 
5902 void G1CollectedHeap::set_free_regions_coming() {
5903   if (G1ConcRegionFreeingVerbose) {
5904     gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
5905                            "setting free regions coming");
5906   }
5907 
5908   assert(!free_regions_coming(), "pre-condition");
5909   _free_regions_coming = true;
5910 }
5911 
5912 void G1CollectedHeap::reset_free_regions_coming() {
5913   assert(free_regions_coming(), "pre-condition");
5914 
5915   {
5916     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5917     _free_regions_coming = false;
5918     SecondaryFreeList_lock->notify_all();
5919   }
5920 
5921   if (G1ConcRegionFreeingVerbose) {
5922     gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
5923                            "reset free regions coming");
5924   }
5925 }
5926 
5927 void G1CollectedHeap::wait_while_free_regions_coming() {
5928   // Most of the time we won't have to wait, so let's do a quick test
5929   // first before we take the lock.
5930   if (!free_regions_coming()) {
5931     return;
5932   }
5933 
5934   if (G1ConcRegionFreeingVerbose) {
5935     gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
5936                            "waiting for free regions");
5937   }
5938 
5939   {
5940     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5941     while (free_regions_coming()) {
5942       SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
5943     }
5944   }
5945 
5946   if (G1ConcRegionFreeingVerbose) {
5947     gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
5948                            "done waiting for free regions");
5949   }
5950 }
5951 
5952 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
5953   assert(heap_lock_held_for_gc(),
5954               "the heap lock should already be held by or for this thread");
5955   _young_list->push_region(hr);
5956 }
5957 
5958 class NoYoungRegionsClosure: public HeapRegionClosure {
5959 private:
5960   bool _success;
5961 public:
5962   NoYoungRegionsClosure() : _success(true) { }
5963   bool doHeapRegion(HeapRegion* r) {
5964     if (r->is_young()) {
5965       gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
5966                              r->bottom(), r->end());
5967       _success = false;
5968     }
5969     return false;
5970   }
5971   bool success() { return _success; }
5972 };
5973 
5974 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
5975   bool ret = _young_list->check_list_empty(check_sample);
5976 
5977   if (check_heap) {
5978     NoYoungRegionsClosure closure;
5979     heap_region_iterate(&closure);
5980     ret = ret && closure.success();
5981   }
5982 
5983   return ret;
5984 }
5985 
5986 class TearDownRegionSetsClosure : public HeapRegionClosure {
5987 private:
5988   OldRegionSet *_old_set;
5989 
5990 public:
5991   TearDownRegionSetsClosure(OldRegionSet* old_set) : _old_set(old_set) { }
5992 
5993   bool doHeapRegion(HeapRegion* r) {
5994     if (r->is_empty()) {
5995       // We ignore empty regions, we'll empty the free list afterwards
5996     } else if (r->is_young()) {
5997       // We ignore young regions, we'll empty the young list afterwards
5998     } else if (r->isHumongous()) {
5999       // We ignore humongous regions, we're not tearing down the
6000       // humongous region set
6001     } else {
6002       // The rest should be old
6003       _old_set->remove(r);
6004     }
6005     return false;
6006   }
6007 
6008   ~TearDownRegionSetsClosure() {
6009     assert(_old_set->is_empty(), "post-condition");
6010   }
6011 };
6012 
6013 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6014   assert_at_safepoint(true /* should_be_vm_thread */);
6015 
6016   if (!free_list_only) {
6017     TearDownRegionSetsClosure cl(&_old_set);
6018     heap_region_iterate(&cl);
6019 
6020     // Need to do this after the heap iteration to be able to
6021     // recognize the young regions and ignore them during the iteration.
6022     _young_list->empty_list();
6023   }
6024   _free_list.remove_all();
6025 }
6026 
6027 class RebuildRegionSetsClosure : public HeapRegionClosure {
6028 private:
6029   bool            _free_list_only;
6030   OldRegionSet*   _old_set;
6031   FreeRegionList* _free_list;
6032   size_t          _total_used;
6033 
6034 public:
6035   RebuildRegionSetsClosure(bool free_list_only,
6036                            OldRegionSet* old_set, FreeRegionList* free_list) :
6037     _free_list_only(free_list_only),
6038     _old_set(old_set), _free_list(free_list), _total_used(0) {
6039     assert(_free_list->is_empty(), "pre-condition");
6040     if (!free_list_only) {
6041       assert(_old_set->is_empty(), "pre-condition");
6042     }
6043   }
6044 
6045   bool doHeapRegion(HeapRegion* r) {
6046     if (r->continuesHumongous()) {
6047       return false;
6048     }
6049 
6050     if (r->is_empty()) {
6051       // Add free regions to the free list
6052       _free_list->add_as_tail(r);
6053     } else if (!_free_list_only) {
6054       assert(!r->is_young(), "we should not come across young regions");
6055 
6056       if (r->isHumongous()) {
6057         // We ignore humongous regions, we left the humongous set unchanged
6058       } else {
6059         // The rest should be old, add them to the old set
6060         _old_set->add(r);
6061       }
6062       _total_used += r->used();
6063     }
6064 
6065     return false;
6066   }
6067 
6068   size_t total_used() {
6069     return _total_used;
6070   }
6071 };
6072 
6073 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6074   assert_at_safepoint(true /* should_be_vm_thread */);
6075 
6076   RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_free_list);
6077   heap_region_iterate(&cl);
6078 
6079   if (!free_list_only) {
6080     _summary_bytes_used = cl.total_used();
6081   }
6082   assert(_summary_bytes_used == recalculate_used(),
6083          err_msg("inconsistent _summary_bytes_used, "
6084                  "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6085                  _summary_bytes_used, recalculate_used()));
6086 }
6087 
6088 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6089   _refine_cte_cl->set_concurrent(concurrent);
6090 }
6091 
6092 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6093   HeapRegion* hr = heap_region_containing(p);
6094   if (hr == NULL) {
6095     return is_in_permanent(p);
6096   } else {
6097     return hr->is_in(p);
6098   }
6099 }
6100 
6101 // Methods for the mutator alloc region
6102 
6103 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6104                                                       bool force) {
6105   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6106   assert(!force || g1_policy()->can_expand_young_list(),
6107          "if force is true we should be able to expand the young list");
6108   bool young_list_full = g1_policy()->is_young_list_full();
6109   if (force || !young_list_full) {
6110     HeapRegion* new_alloc_region = new_region(word_size,
6111                                               false /* do_expand */);
6112     if (new_alloc_region != NULL) {
6113       set_region_short_lived_locked(new_alloc_region);
6114       _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6115       return new_alloc_region;
6116     }
6117   }
6118   return NULL;
6119 }
6120 
6121 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6122                                                   size_t allocated_bytes) {
6123   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6124   assert(alloc_region->is_young(), "all mutator alloc regions should be young");
6125 
6126   g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6127   _summary_bytes_used += allocated_bytes;
6128   _hr_printer.retire(alloc_region);
6129   // We update the eden sizes here, when the region is retired,
6130   // instead of when it's allocated, since this is the point that its
6131   // used space has been recored in _summary_bytes_used.
6132   g1mm()->update_eden_size();
6133 }
6134 
6135 HeapRegion* MutatorAllocRegion::allocate_new_region(size_t word_size,
6136                                                     bool force) {
6137   return _g1h->new_mutator_alloc_region(word_size, force);
6138 }
6139 
6140 void G1CollectedHeap::set_par_threads() {
6141   // Don't change the number of workers.  Use the value previously set
6142   // in the workgroup.
6143   assert(G1CollectedHeap::use_parallel_gc_threads(), "shouldn't be here otherwise");
6144   uint n_workers = workers()->active_workers();
6145   assert(UseDynamicNumberOfGCThreads ||
6146            n_workers == workers()->total_workers(),
6147       "Otherwise should be using the total number of workers");
6148   if (n_workers == 0) {
6149     assert(false, "Should have been set in prior evacuation pause.");
6150     n_workers = ParallelGCThreads;
6151     workers()->set_active_workers(n_workers);
6152   }
6153   set_par_threads(n_workers);
6154 }
6155 
6156 void MutatorAllocRegion::retire_region(HeapRegion* alloc_region,
6157                                        size_t allocated_bytes) {
6158   _g1h->retire_mutator_alloc_region(alloc_region, allocated_bytes);
6159 }
6160 
6161 // Methods for the GC alloc regions
6162 
6163 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6164                                                  uint count,
6165                                                  GCAllocPurpose ap) {
6166   assert(FreeList_lock->owned_by_self(), "pre-condition");
6167 
6168   if (count < g1_policy()->max_regions(ap)) {
6169     HeapRegion* new_alloc_region = new_region(word_size,
6170                                               true /* do_expand */);
6171     if (new_alloc_region != NULL) {
6172       // We really only need to do this for old regions given that we
6173       // should never scan survivors. But it doesn't hurt to do it
6174       // for survivors too.
6175       new_alloc_region->set_saved_mark();
6176       if (ap == GCAllocForSurvived) {
6177         new_alloc_region->set_survivor();
6178         _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6179       } else {
6180         _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6181       }
6182       bool during_im = g1_policy()->during_initial_mark_pause();
6183       new_alloc_region->note_start_of_copying(during_im);
6184       return new_alloc_region;
6185     } else {
6186       g1_policy()->note_alloc_region_limit_reached(ap);
6187     }
6188   }
6189   return NULL;
6190 }
6191 
6192 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6193                                              size_t allocated_bytes,
6194                                              GCAllocPurpose ap) {
6195   bool during_im = g1_policy()->during_initial_mark_pause();
6196   alloc_region->note_end_of_copying(during_im);
6197   g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6198   if (ap == GCAllocForSurvived) {
6199     young_list()->add_survivor_region(alloc_region);
6200   } else {
6201     _old_set.add(alloc_region);
6202   }
6203   _hr_printer.retire(alloc_region);
6204 }
6205 
6206 HeapRegion* SurvivorGCAllocRegion::allocate_new_region(size_t word_size,
6207                                                        bool force) {
6208   assert(!force, "not supported for GC alloc regions");
6209   return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForSurvived);
6210 }
6211 
6212 void SurvivorGCAllocRegion::retire_region(HeapRegion* alloc_region,
6213                                           size_t allocated_bytes) {
6214   _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6215                                GCAllocForSurvived);
6216 }
6217 
6218 HeapRegion* OldGCAllocRegion::allocate_new_region(size_t word_size,
6219                                                   bool force) {
6220   assert(!force, "not supported for GC alloc regions");
6221   return _g1h->new_gc_alloc_region(word_size, count(), GCAllocForTenured);
6222 }
6223 
6224 void OldGCAllocRegion::retire_region(HeapRegion* alloc_region,
6225                                      size_t allocated_bytes) {
6226   _g1h->retire_gc_alloc_region(alloc_region, allocated_bytes,
6227                                GCAllocForTenured);
6228 }
6229 // Heap region set verification
6230 
6231 class VerifyRegionListsClosure : public HeapRegionClosure {
6232 private:
6233   FreeRegionList*     _free_list;
6234   OldRegionSet*       _old_set;
6235   HumongousRegionSet* _humongous_set;
6236   uint                _region_count;
6237 
6238 public:
6239   VerifyRegionListsClosure(OldRegionSet* old_set,
6240                            HumongousRegionSet* humongous_set,
6241                            FreeRegionList* free_list) :
6242     _old_set(old_set), _humongous_set(humongous_set),
6243     _free_list(free_list), _region_count(0) { }
6244 
6245   uint region_count() { return _region_count; }
6246 
6247   bool doHeapRegion(HeapRegion* hr) {
6248     _region_count += 1;
6249 
6250     if (hr->continuesHumongous()) {
6251       return false;
6252     }
6253 
6254     if (hr->is_young()) {
6255       // TODO
6256     } else if (hr->startsHumongous()) {
6257       _humongous_set->verify_next_region(hr);
6258     } else if (hr->is_empty()) {
6259       _free_list->verify_next_region(hr);
6260     } else {
6261       _old_set->verify_next_region(hr);
6262     }
6263     return false;
6264   }
6265 };
6266 
6267 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
6268                                              HeapWord* bottom) {
6269   HeapWord* end = bottom + HeapRegion::GrainWords;
6270   MemRegion mr(bottom, end);
6271   assert(_g1_reserved.contains(mr), "invariant");
6272   // This might return NULL if the allocation fails
6273   return new HeapRegion(hrs_index, _bot_shared, mr, true /* is_zeroed */);
6274 }
6275 
6276 void G1CollectedHeap::verify_region_sets() {
6277   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6278 
6279   // First, check the explicit lists.
6280   _free_list.verify();
6281   {
6282     // Given that a concurrent operation might be adding regions to
6283     // the secondary free list we have to take the lock before
6284     // verifying it.
6285     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6286     _secondary_free_list.verify();
6287   }
6288   _old_set.verify();
6289   _humongous_set.verify();
6290 
6291   // If a concurrent region freeing operation is in progress it will
6292   // be difficult to correctly attributed any free regions we come
6293   // across to the correct free list given that they might belong to
6294   // one of several (free_list, secondary_free_list, any local lists,
6295   // etc.). So, if that's the case we will skip the rest of the
6296   // verification operation. Alternatively, waiting for the concurrent
6297   // operation to complete will have a non-trivial effect on the GC's
6298   // operation (no concurrent operation will last longer than the
6299   // interval between two calls to verification) and it might hide
6300   // any issues that we would like to catch during testing.
6301   if (free_regions_coming()) {
6302     return;
6303   }
6304 
6305   // Make sure we append the secondary_free_list on the free_list so
6306   // that all free regions we will come across can be safely
6307   // attributed to the free_list.
6308   append_secondary_free_list_if_not_empty_with_lock();
6309 
6310   // Finally, make sure that the region accounting in the lists is
6311   // consistent with what we see in the heap.
6312   _old_set.verify_start();
6313   _humongous_set.verify_start();
6314   _free_list.verify_start();
6315 
6316   VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_free_list);
6317   heap_region_iterate(&cl);
6318 
6319   _old_set.verify_end();
6320   _humongous_set.verify_end();
6321   _free_list.verify_end();
6322 }
--- EOF ---