1 /*
   2  * Copyright (c) 2001, 2015, 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 "classfile/metadataOnStackMark.hpp"
  27 #include "classfile/stringTable.hpp"
  28 #include "code/codeCache.hpp"
  29 #include "code/icBuffer.hpp"
  30 #include "gc_implementation/g1/bufferingOopClosure.hpp"
  31 #include "gc_implementation/g1/concurrentG1Refine.hpp"
  32 #include "gc_implementation/g1/concurrentG1RefineThread.hpp"
  33 #include "gc_implementation/g1/concurrentMarkThread.inline.hpp"
  34 #include "gc_implementation/g1/g1AllocRegion.inline.hpp"
  35 #include "gc_implementation/g1/g1CollectedHeap.inline.hpp"
  36 #include "gc_implementation/g1/g1CollectorPolicy.hpp"
  37 #include "gc_implementation/g1/g1CollectorState.hpp"
  38 #include "gc_implementation/g1/g1ErgoVerbose.hpp"
  39 #include "gc_implementation/g1/g1EvacFailure.hpp"
  40 #include "gc_implementation/g1/g1GCPhaseTimes.hpp"
  41 #include "gc_implementation/g1/g1Log.hpp"
  42 #include "gc_implementation/g1/g1MarkSweep.hpp"
  43 #include "gc_implementation/g1/g1OopClosures.inline.hpp"
  44 #include "gc_implementation/g1/g1ParScanThreadState.inline.hpp"
  45 #include "gc_implementation/g1/g1RegionToSpaceMapper.hpp"
  46 #include "gc_implementation/g1/g1RemSet.inline.hpp"
  47 #include "gc_implementation/g1/g1RootProcessor.hpp"
  48 #include "gc_implementation/g1/g1StringDedup.hpp"
  49 #include "gc_implementation/g1/g1YCTypes.hpp"
  50 #include "gc_implementation/g1/heapRegion.inline.hpp"
  51 #include "gc_implementation/g1/heapRegionRemSet.hpp"
  52 #include "gc_implementation/g1/heapRegionSet.inline.hpp"
  53 #include "gc_implementation/g1/vm_operations_g1.hpp"
  54 #include "gc_implementation/shared/gcHeapSummary.hpp"
  55 #include "gc_implementation/shared/gcTimer.hpp"
  56 #include "gc_implementation/shared/gcTrace.hpp"
  57 #include "gc_implementation/shared/gcTraceTime.hpp"
  58 #include "gc_implementation/shared/isGCActiveMark.hpp"
  59 #include "memory/allocation.hpp"
  60 #include "memory/gcLocker.inline.hpp"
  61 #include "memory/generationSpec.hpp"
  62 #include "memory/iterator.hpp"
  63 #include "memory/referenceProcessor.hpp"
  64 #include "oops/oop.inline.hpp"
  65 #include "runtime/atomic.inline.hpp"
  66 #include "runtime/orderAccess.inline.hpp"
  67 #include "runtime/vmThread.hpp"
  68 #include "utilities/globalDefinitions.hpp"
  69 #include "utilities/stack.inline.hpp"
  70 #include "utilities/taskqueue.inline.hpp"
  71 
  72 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
  73 
  74 // turn it on so that the contents of the young list (scan-only /
  75 // to-be-collected) are printed at "strategic" points before / during
  76 // / after the collection --- this is useful for debugging
  77 #define YOUNG_LIST_VERBOSE 0
  78 // CURRENT STATUS
  79 // This file is under construction.  Search for "FIXME".
  80 
  81 // INVARIANTS/NOTES
  82 //
  83 // All allocation activity covered by the G1CollectedHeap interface is
  84 // serialized by acquiring the HeapLock.  This happens in mem_allocate
  85 // and allocate_new_tlab, which are the "entry" points to the
  86 // allocation code from the rest of the JVM.  (Note that this does not
  87 // apply to TLAB allocation, which is not part of this interface: it
  88 // is done by clients of this interface.)
  89 
  90 // Local to this file.
  91 
  92 class RefineCardTableEntryClosure: public CardTableEntryClosure {
  93   bool _concurrent;
  94 public:
  95   RefineCardTableEntryClosure() : _concurrent(true) { }
  96 
  97   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
  98     bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, false);
  99     // This path is executed by the concurrent refine or mutator threads,
 100     // concurrently, and so we do not care if card_ptr contains references
 101     // that point into the collection set.
 102     assert(!oops_into_cset, "should be");
 103 
 104     if (_concurrent && SuspendibleThreadSet::should_yield()) {
 105       // Caller will actually yield.
 106       return false;
 107     }
 108     // Otherwise, we finished successfully; return true.
 109     return true;
 110   }
 111 
 112   void set_concurrent(bool b) { _concurrent = b; }
 113 };
 114 
 115 
 116 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
 117  private:
 118   size_t _num_processed;
 119 
 120  public:
 121   RedirtyLoggedCardTableEntryClosure() : CardTableEntryClosure(), _num_processed(0) { }
 122 
 123   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
 124     *card_ptr = CardTableModRefBS::dirty_card_val();
 125     _num_processed++;
 126     return true;
 127   }
 128 
 129   size_t num_processed() const { return _num_processed; }
 130 };
 131 
 132 YoungList::YoungList(G1CollectedHeap* g1h) :
 133     _g1h(g1h), _head(NULL), _length(0), _last_sampled_rs_lengths(0),
 134     _survivor_head(NULL), _survivor_tail(NULL), _survivor_length(0) {
 135   guarantee(check_list_empty(false), "just making sure...");
 136 }
 137 
 138 void YoungList::push_region(HeapRegion *hr) {
 139   assert(!hr->is_young(), "should not already be young");
 140   assert(hr->get_next_young_region() == NULL, "cause it should!");
 141 
 142   hr->set_next_young_region(_head);
 143   _head = hr;
 144 
 145   _g1h->g1_policy()->set_region_eden(hr, (int) _length);
 146   ++_length;
 147 }
 148 
 149 void YoungList::add_survivor_region(HeapRegion* hr) {
 150   assert(hr->is_survivor(), "should be flagged as survivor region");
 151   assert(hr->get_next_young_region() == NULL, "cause it should!");
 152 
 153   hr->set_next_young_region(_survivor_head);
 154   if (_survivor_head == NULL) {
 155     _survivor_tail = hr;
 156   }
 157   _survivor_head = hr;
 158   ++_survivor_length;
 159 }
 160 
 161 void YoungList::empty_list(HeapRegion* list) {
 162   while (list != NULL) {
 163     HeapRegion* next = list->get_next_young_region();
 164     list->set_next_young_region(NULL);
 165     list->uninstall_surv_rate_group();
 166     // This is called before a Full GC and all the non-empty /
 167     // non-humongous regions at the end of the Full GC will end up as
 168     // old anyway.
 169     list->set_old();
 170     list = next;
 171   }
 172 }
 173 
 174 void YoungList::empty_list() {
 175   assert(check_list_well_formed(), "young list should be well formed");
 176 
 177   empty_list(_head);
 178   _head = NULL;
 179   _length = 0;
 180 
 181   empty_list(_survivor_head);
 182   _survivor_head = NULL;
 183   _survivor_tail = NULL;
 184   _survivor_length = 0;
 185 
 186   _last_sampled_rs_lengths = 0;
 187 
 188   assert(check_list_empty(false), "just making sure...");
 189 }
 190 
 191 bool YoungList::check_list_well_formed() {
 192   bool ret = true;
 193 
 194   uint length = 0;
 195   HeapRegion* curr = _head;
 196   HeapRegion* last = NULL;
 197   while (curr != NULL) {
 198     if (!curr->is_young()) {
 199       gclog_or_tty->print_cr("### YOUNG REGION "PTR_FORMAT"-"PTR_FORMAT" "
 200                              "incorrectly tagged (y: %d, surv: %d)",
 201                              p2i(curr->bottom()), p2i(curr->end()),
 202                              curr->is_young(), curr->is_survivor());
 203       ret = false;
 204     }
 205     ++length;
 206     last = curr;
 207     curr = curr->get_next_young_region();
 208   }
 209   ret = ret && (length == _length);
 210 
 211   if (!ret) {
 212     gclog_or_tty->print_cr("### YOUNG LIST seems not well formed!");
 213     gclog_or_tty->print_cr("###   list has %u entries, _length is %u",
 214                            length, _length);
 215   }
 216 
 217   return ret;
 218 }
 219 
 220 bool YoungList::check_list_empty(bool check_sample) {
 221   bool ret = true;
 222 
 223   if (_length != 0) {
 224     gclog_or_tty->print_cr("### YOUNG LIST should have 0 length, not %u",
 225                   _length);
 226     ret = false;
 227   }
 228   if (check_sample && _last_sampled_rs_lengths != 0) {
 229     gclog_or_tty->print_cr("### YOUNG LIST has non-zero last sampled RS lengths");
 230     ret = false;
 231   }
 232   if (_head != NULL) {
 233     gclog_or_tty->print_cr("### YOUNG LIST does not have a NULL head");
 234     ret = false;
 235   }
 236   if (!ret) {
 237     gclog_or_tty->print_cr("### YOUNG LIST does not seem empty");
 238   }
 239 
 240   return ret;
 241 }
 242 
 243 void
 244 YoungList::rs_length_sampling_init() {
 245   _sampled_rs_lengths = 0;
 246   _curr               = _head;
 247 }
 248 
 249 bool
 250 YoungList::rs_length_sampling_more() {
 251   return _curr != NULL;
 252 }
 253 
 254 void
 255 YoungList::rs_length_sampling_next() {
 256   assert( _curr != NULL, "invariant" );
 257   size_t rs_length = _curr->rem_set()->occupied();
 258 
 259   _sampled_rs_lengths += rs_length;
 260 
 261   // The current region may not yet have been added to the
 262   // incremental collection set (it gets added when it is
 263   // retired as the current allocation region).
 264   if (_curr->in_collection_set()) {
 265     // Update the collection set policy information for this region
 266     _g1h->g1_policy()->update_incremental_cset_info(_curr, rs_length);
 267   }
 268 
 269   _curr = _curr->get_next_young_region();
 270   if (_curr == NULL) {
 271     _last_sampled_rs_lengths = _sampled_rs_lengths;
 272     // gclog_or_tty->print_cr("last sampled RS lengths = %d", _last_sampled_rs_lengths);
 273   }
 274 }
 275 
 276 void
 277 YoungList::reset_auxilary_lists() {
 278   guarantee( is_empty(), "young list should be empty" );
 279   assert(check_list_well_formed(), "young list should be well formed");
 280 
 281   // Add survivor regions to SurvRateGroup.
 282   _g1h->g1_policy()->note_start_adding_survivor_regions();
 283   _g1h->g1_policy()->finished_recalculating_age_indexes(true /* is_survivors */);
 284 
 285   int young_index_in_cset = 0;
 286   for (HeapRegion* curr = _survivor_head;
 287        curr != NULL;
 288        curr = curr->get_next_young_region()) {
 289     _g1h->g1_policy()->set_region_survivor(curr, young_index_in_cset);
 290 
 291     // The region is a non-empty survivor so let's add it to
 292     // the incremental collection set for the next evacuation
 293     // pause.
 294     _g1h->g1_policy()->add_region_to_incremental_cset_rhs(curr);
 295     young_index_in_cset += 1;
 296   }
 297   assert((uint) young_index_in_cset == _survivor_length, "post-condition");
 298   _g1h->g1_policy()->note_stop_adding_survivor_regions();
 299 
 300   _head   = _survivor_head;
 301   _length = _survivor_length;
 302   if (_survivor_head != NULL) {
 303     assert(_survivor_tail != NULL, "cause it shouldn't be");
 304     assert(_survivor_length > 0, "invariant");
 305     _survivor_tail->set_next_young_region(NULL);
 306   }
 307 
 308   // Don't clear the survivor list handles until the start of
 309   // the next evacuation pause - we need it in order to re-tag
 310   // the survivor regions from this evacuation pause as 'young'
 311   // at the start of the next.
 312 
 313   _g1h->g1_policy()->finished_recalculating_age_indexes(false /* is_survivors */);
 314 
 315   assert(check_list_well_formed(), "young list should be well formed");
 316 }
 317 
 318 void YoungList::print() {
 319   HeapRegion* lists[] = {_head,   _survivor_head};
 320   const char* names[] = {"YOUNG", "SURVIVOR"};
 321 
 322   for (uint list = 0; list < ARRAY_SIZE(lists); ++list) {
 323     gclog_or_tty->print_cr("%s LIST CONTENTS", names[list]);
 324     HeapRegion *curr = lists[list];
 325     if (curr == NULL)
 326       gclog_or_tty->print_cr("  empty");
 327     while (curr != NULL) {
 328       gclog_or_tty->print_cr("  "HR_FORMAT", P: "PTR_FORMAT ", N: "PTR_FORMAT", age: %4d",
 329                              HR_FORMAT_PARAMS(curr),
 330                              p2i(curr->prev_top_at_mark_start()),
 331                              p2i(curr->next_top_at_mark_start()),
 332                              curr->age_in_surv_rate_group_cond());
 333       curr = curr->get_next_young_region();
 334     }
 335   }
 336 
 337   gclog_or_tty->cr();
 338 }
 339 
 340 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
 341   HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
 342 }
 343 
 344 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
 345   // The from card cache is not the memory that is actually committed. So we cannot
 346   // take advantage of the zero_filled parameter.
 347   reset_from_card_cache(start_idx, num_regions);
 348 }
 349 
 350 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
 351 {
 352   // Claim the right to put the region on the dirty cards region list
 353   // by installing a self pointer.
 354   HeapRegion* next = hr->get_next_dirty_cards_region();
 355   if (next == NULL) {
 356     HeapRegion* res = (HeapRegion*)
 357       Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
 358                           NULL);
 359     if (res == NULL) {
 360       HeapRegion* head;
 361       do {
 362         // Put the region to the dirty cards region list.
 363         head = _dirty_cards_region_list;
 364         next = (HeapRegion*)
 365           Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
 366         if (next == head) {
 367           assert(hr->get_next_dirty_cards_region() == hr,
 368                  "hr->get_next_dirty_cards_region() != hr");
 369           if (next == NULL) {
 370             // The last region in the list points to itself.
 371             hr->set_next_dirty_cards_region(hr);
 372           } else {
 373             hr->set_next_dirty_cards_region(next);
 374           }
 375         }
 376       } while (next != head);
 377     }
 378   }
 379 }
 380 
 381 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
 382 {
 383   HeapRegion* head;
 384   HeapRegion* hr;
 385   do {
 386     head = _dirty_cards_region_list;
 387     if (head == NULL) {
 388       return NULL;
 389     }
 390     HeapRegion* new_head = head->get_next_dirty_cards_region();
 391     if (head == new_head) {
 392       // The last region.
 393       new_head = NULL;
 394     }
 395     hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
 396                                           head);
 397   } while (hr != head);
 398   assert(hr != NULL, "invariant");
 399   hr->set_next_dirty_cards_region(NULL);
 400   return hr;
 401 }
 402 
 403 // Returns true if the reference points to an object that
 404 // can move in an incremental collection.
 405 bool G1CollectedHeap::is_scavengable(const void* p) {
 406   HeapRegion* hr = heap_region_containing(p);
 407   return !hr->is_humongous();
 408 }
 409 
 410 // Private methods.
 411 
 412 HeapRegion*
 413 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
 414   MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
 415   while (!_secondary_free_list.is_empty() || free_regions_coming()) {
 416     if (!_secondary_free_list.is_empty()) {
 417       if (G1ConcRegionFreeingVerbose) {
 418         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 419                                "secondary_free_list has %u entries",
 420                                _secondary_free_list.length());
 421       }
 422       // It looks as if there are free regions available on the
 423       // secondary_free_list. Let's move them to the free_list and try
 424       // again to allocate from it.
 425       append_secondary_free_list();
 426 
 427       assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not "
 428              "empty we should have moved at least one entry to the free_list");
 429       HeapRegion* res = _hrm.allocate_free_region(is_old);
 430       if (G1ConcRegionFreeingVerbose) {
 431         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 432                                "allocated "HR_FORMAT" from secondary_free_list",
 433                                HR_FORMAT_PARAMS(res));
 434       }
 435       return res;
 436     }
 437 
 438     // Wait here until we get notified either when (a) there are no
 439     // more free regions coming or (b) some regions have been moved on
 440     // the secondary_free_list.
 441     SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
 442   }
 443 
 444   if (G1ConcRegionFreeingVerbose) {
 445     gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 446                            "could not allocate from secondary_free_list");
 447   }
 448   return NULL;
 449 }
 450 
 451 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
 452   assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
 453          "the only time we use this to allocate a humongous region is "
 454          "when we are allocating a single humongous region");
 455 
 456   HeapRegion* res;
 457   if (G1StressConcRegionFreeing) {
 458     if (!_secondary_free_list.is_empty()) {
 459       if (G1ConcRegionFreeingVerbose) {
 460         gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 461                                "forced to look at the secondary_free_list");
 462       }
 463       res = new_region_try_secondary_free_list(is_old);
 464       if (res != NULL) {
 465         return res;
 466       }
 467     }
 468   }
 469 
 470   res = _hrm.allocate_free_region(is_old);
 471 
 472   if (res == NULL) {
 473     if (G1ConcRegionFreeingVerbose) {
 474       gclog_or_tty->print_cr("G1ConcRegionFreeing [region alloc] : "
 475                              "res == NULL, trying the secondary_free_list");
 476     }
 477     res = new_region_try_secondary_free_list(is_old);
 478   }
 479   if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
 480     // Currently, only attempts to allocate GC alloc regions set
 481     // do_expand to true. So, we should only reach here during a
 482     // safepoint. If this assumption changes we might have to
 483     // reconsider the use of _expand_heap_after_alloc_failure.
 484     assert(SafepointSynchronize::is_at_safepoint(), "invariant");
 485 
 486     ergo_verbose1(ErgoHeapSizing,
 487                   "attempt heap expansion",
 488                   ergo_format_reason("region allocation request failed")
 489                   ergo_format_byte("allocation request"),
 490                   word_size * HeapWordSize);
 491     if (expand(word_size * HeapWordSize)) {
 492       // Given that expand() succeeded in expanding the heap, and we
 493       // always expand the heap by an amount aligned to the heap
 494       // region size, the free list should in theory not be empty.
 495       // In either case allocate_free_region() will check for NULL.
 496       res = _hrm.allocate_free_region(is_old);
 497     } else {
 498       _expand_heap_after_alloc_failure = false;
 499     }
 500   }
 501   return res;
 502 }
 503 
 504 HeapWord*
 505 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
 506                                                            uint num_regions,
 507                                                            size_t word_size,
 508                                                            AllocationContext_t context) {
 509   assert(first != G1_NO_HRM_INDEX, "pre-condition");
 510   assert(is_humongous(word_size), "word_size should be humongous");
 511   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 512 
 513   // Index of last region in the series + 1.
 514   uint last = first + num_regions;
 515 
 516   // We need to initialize the region(s) we just discovered. This is
 517   // a bit tricky given that it can happen concurrently with
 518   // refinement threads refining cards on these regions and
 519   // potentially wanting to refine the BOT as they are scanning
 520   // those cards (this can happen shortly after a cleanup; see CR
 521   // 6991377). So we have to set up the region(s) carefully and in
 522   // a specific order.
 523 
 524   // The word size sum of all the regions we will allocate.
 525   size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
 526   assert(word_size <= word_size_sum, "sanity");
 527 
 528   // This will be the "starts humongous" region.
 529   HeapRegion* first_hr = region_at(first);
 530   // The header of the new object will be placed at the bottom of
 531   // the first region.
 532   HeapWord* new_obj = first_hr->bottom();
 533   // This will be the new end of the first region in the series that
 534   // should also match the end of the last region in the series.
 535   HeapWord* new_end = new_obj + word_size_sum;
 536   // This will be the new top of the first region that will reflect
 537   // this allocation.
 538   HeapWord* new_top = new_obj + word_size;
 539 
 540   // First, we need to zero the header of the space that we will be
 541   // allocating. When we update top further down, some refinement
 542   // threads might try to scan the region. By zeroing the header we
 543   // ensure that any thread that will try to scan the region will
 544   // come across the zero klass word and bail out.
 545   //
 546   // NOTE: It would not have been correct to have used
 547   // CollectedHeap::fill_with_object() and make the space look like
 548   // an int array. The thread that is doing the allocation will
 549   // later update the object header to a potentially different array
 550   // type and, for a very short period of time, the klass and length
 551   // fields will be inconsistent. This could cause a refinement
 552   // thread to calculate the object size incorrectly.
 553   Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
 554 
 555   // We will set up the first region as "starts humongous". This
 556   // will also update the BOT covering all the regions to reflect
 557   // that there is a single object that starts at the bottom of the
 558   // first region.
 559   first_hr->set_starts_humongous(new_top, new_end);
 560   first_hr->set_allocation_context(context);
 561   // Then, if there are any, we will set up the "continues
 562   // humongous" regions.
 563   HeapRegion* hr = NULL;
 564   for (uint i = first + 1; i < last; ++i) {
 565     hr = region_at(i);
 566     hr->set_continues_humongous(first_hr);
 567     hr->set_allocation_context(context);
 568   }
 569   // If we have "continues humongous" regions (hr != NULL), then the
 570   // end of the last one should match new_end.
 571   assert(hr == NULL || hr->end() == new_end, "sanity");
 572 
 573   // Up to this point no concurrent thread would have been able to
 574   // do any scanning on any region in this series. All the top
 575   // fields still point to bottom, so the intersection between
 576   // [bottom,top] and [card_start,card_end] will be empty. Before we
 577   // update the top fields, we'll do a storestore to make sure that
 578   // no thread sees the update to top before the zeroing of the
 579   // object header and the BOT initialization.
 580   OrderAccess::storestore();
 581 
 582   // Now that the BOT and the object header have been initialized,
 583   // we can update top of the "starts humongous" region.
 584   assert(first_hr->bottom() < new_top && new_top <= first_hr->end(),
 585          "new_top should be in this region");
 586   first_hr->set_top(new_top);
 587   if (_hr_printer.is_active()) {
 588     HeapWord* bottom = first_hr->bottom();
 589     HeapWord* end = first_hr->orig_end();
 590     if ((first + 1) == last) {
 591       // the series has a single humongous region
 592       _hr_printer.alloc(G1HRPrinter::SingleHumongous, first_hr, new_top);
 593     } else {
 594       // the series has more than one humongous regions
 595       _hr_printer.alloc(G1HRPrinter::StartsHumongous, first_hr, end);
 596     }
 597   }
 598 
 599   // Now, we will update the top fields of the "continues humongous"
 600   // regions. The reason we need to do this is that, otherwise,
 601   // these regions would look empty and this will confuse parts of
 602   // G1. For example, the code that looks for a consecutive number
 603   // of empty regions will consider them empty and try to
 604   // re-allocate them. We can extend is_empty() to also include
 605   // !is_continues_humongous(), but it is easier to just update the top
 606   // fields here. The way we set top for all regions (i.e., top ==
 607   // end for all regions but the last one, top == new_top for the
 608   // last one) is actually used when we will free up the humongous
 609   // region in free_humongous_region().
 610   hr = NULL;
 611   for (uint i = first + 1; i < last; ++i) {
 612     hr = region_at(i);
 613     if ((i + 1) == last) {
 614       // last continues humongous region
 615       assert(hr->bottom() < new_top && new_top <= hr->end(),
 616              "new_top should fall on this region");
 617       hr->set_top(new_top);
 618       _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, new_top);
 619     } else {
 620       // not last one
 621       assert(new_top > hr->end(), "new_top should be above this region");
 622       hr->set_top(hr->end());
 623       _hr_printer.alloc(G1HRPrinter::ContinuesHumongous, hr, hr->end());
 624     }
 625   }
 626   // If we have continues humongous regions (hr != NULL), then the
 627   // end of the last one should match new_end and its top should
 628   // match new_top.
 629   assert(hr == NULL ||
 630          (hr->end() == new_end && hr->top() == new_top), "sanity");
 631   check_bitmaps("Humongous Region Allocation", first_hr);
 632 
 633   assert(first_hr->used() == word_size * HeapWordSize, "invariant");
 634   _allocator->increase_used(first_hr->used());
 635   _humongous_set.add(first_hr);
 636 
 637   return new_obj;
 638 }
 639 
 640 // If could fit into free regions w/o expansion, try.
 641 // Otherwise, if can expand, do so.
 642 // Otherwise, if using ex regions might help, try with ex given back.
 643 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) {
 644   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 645 
 646   verify_region_sets_optional();
 647 
 648   uint first = G1_NO_HRM_INDEX;
 649   uint obj_regions = (uint)(align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords);
 650 
 651   if (obj_regions == 1) {
 652     // Only one region to allocate, try to use a fast path by directly allocating
 653     // from the free lists. Do not try to expand here, we will potentially do that
 654     // later.
 655     HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
 656     if (hr != NULL) {
 657       first = hr->hrm_index();
 658     }
 659   } else {
 660     // We can't allocate humongous regions spanning more than one region while
 661     // cleanupComplete() is running, since some of the regions we find to be
 662     // empty might not yet be added to the free list. It is not straightforward
 663     // to know in which list they are on so that we can remove them. We only
 664     // need to do this if we need to allocate more than one region to satisfy the
 665     // current humongous allocation request. If we are only allocating one region
 666     // we use the one-region region allocation code (see above), that already
 667     // potentially waits for regions from the secondary free list.
 668     wait_while_free_regions_coming();
 669     append_secondary_free_list_if_not_empty_with_lock();
 670 
 671     // Policy: Try only empty regions (i.e. already committed first). Maybe we
 672     // are lucky enough to find some.
 673     first = _hrm.find_contiguous_only_empty(obj_regions);
 674     if (first != G1_NO_HRM_INDEX) {
 675       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 676     }
 677   }
 678 
 679   if (first == G1_NO_HRM_INDEX) {
 680     // Policy: We could not find enough regions for the humongous object in the
 681     // free list. Look through the heap to find a mix of free and uncommitted regions.
 682     // If so, try expansion.
 683     first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
 684     if (first != G1_NO_HRM_INDEX) {
 685       // We found something. Make sure these regions are committed, i.e. expand
 686       // the heap. Alternatively we could do a defragmentation GC.
 687       ergo_verbose1(ErgoHeapSizing,
 688                     "attempt heap expansion",
 689                     ergo_format_reason("humongous allocation request failed")
 690                     ergo_format_byte("allocation request"),
 691                     word_size * HeapWordSize);
 692 
 693       _hrm.expand_at(first, obj_regions);
 694       g1_policy()->record_new_heap_size(num_regions());
 695 
 696 #ifdef ASSERT
 697       for (uint i = first; i < first + obj_regions; ++i) {
 698         HeapRegion* hr = region_at(i);
 699         assert(hr->is_free(), "sanity");
 700         assert(hr->is_empty(), "sanity");
 701         assert(is_on_master_free_list(hr), "sanity");
 702       }
 703 #endif
 704       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 705     } else {
 706       // Policy: Potentially trigger a defragmentation GC.
 707     }
 708   }
 709 
 710   HeapWord* result = NULL;
 711   if (first != G1_NO_HRM_INDEX) {
 712     result = humongous_obj_allocate_initialize_regions(first, obj_regions,
 713                                                        word_size, context);
 714     assert(result != NULL, "it should always return a valid result");
 715 
 716     // A successful humongous object allocation changes the used space
 717     // information of the old generation so we need to recalculate the
 718     // sizes and update the jstat counters here.
 719     g1mm()->update_sizes();
 720   }
 721 
 722   verify_region_sets_optional();
 723 
 724   return result;
 725 }
 726 
 727 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
 728   assert_heap_not_locked_and_not_at_safepoint();
 729   assert(!is_humongous(word_size), "we do not allow humongous TLABs");
 730 
 731   uint dummy_gc_count_before;
 732   uint dummy_gclocker_retry_count = 0;
 733   return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
 734 }
 735 
 736 HeapWord*
 737 G1CollectedHeap::mem_allocate(size_t word_size,
 738                               bool*  gc_overhead_limit_was_exceeded) {
 739   assert_heap_not_locked_and_not_at_safepoint();
 740 
 741   // Loop until the allocation is satisfied, or unsatisfied after GC.
 742   for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 743     uint gc_count_before;
 744 
 745     HeapWord* result = NULL;
 746     if (!is_humongous(word_size)) {
 747       result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
 748     } else {
 749       result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
 750     }
 751     if (result != NULL) {
 752       return result;
 753     }
 754 
 755     // Create the garbage collection operation...
 756     VM_G1CollectForAllocation op(gc_count_before, word_size);
 757     op.set_allocation_context(AllocationContext::current());
 758 
 759     // ...and get the VM thread to execute it.
 760     VMThread::execute(&op);
 761 
 762     if (op.prologue_succeeded() && op.pause_succeeded()) {
 763       // If the operation was successful we'll return the result even
 764       // if it is NULL. If the allocation attempt failed immediately
 765       // after a Full GC, it's unlikely we'll be able to allocate now.
 766       HeapWord* result = op.result();
 767       if (result != NULL && !is_humongous(word_size)) {
 768         // Allocations that take place on VM operations do not do any
 769         // card dirtying and we have to do it here. We only have to do
 770         // this for non-humongous allocations, though.
 771         dirty_young_block(result, word_size);
 772       }
 773       return result;
 774     } else {
 775       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 776         return NULL;
 777       }
 778       assert(op.result() == NULL,
 779              "the result should be NULL if the VM op did not succeed");
 780     }
 781 
 782     // Give a warning if we seem to be looping forever.
 783     if ((QueuedAllocationWarningCount > 0) &&
 784         (try_count % QueuedAllocationWarningCount == 0)) {
 785       warning("G1CollectedHeap::mem_allocate retries %d times", try_count);
 786     }
 787   }
 788 
 789   ShouldNotReachHere();
 790   return NULL;
 791 }
 792 
 793 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
 794                                                    AllocationContext_t context,
 795                                                    uint* gc_count_before_ret,
 796                                                    uint* gclocker_retry_count_ret) {
 797   // Make sure you read the note in attempt_allocation_humongous().
 798 
 799   assert_heap_not_locked_and_not_at_safepoint();
 800   assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
 801          "be called for humongous allocation requests");
 802 
 803   // We should only get here after the first-level allocation attempt
 804   // (attempt_allocation()) failed to allocate.
 805 
 806   // We will loop until a) we manage to successfully perform the
 807   // allocation or b) we successfully schedule a collection which
 808   // fails to perform the allocation. b) is the only case when we'll
 809   // return NULL.
 810   HeapWord* result = NULL;
 811   for (int try_count = 1; /* we'll return */; try_count += 1) {
 812     bool should_try_gc;
 813     uint gc_count_before;
 814 
 815     {
 816       MutexLockerEx x(Heap_lock);
 817       result = _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size,
 818                                                                                     false /* bot_updates */);
 819       if (result != NULL) {
 820         return result;
 821       }
 822 
 823       // If we reach here, attempt_allocation_locked() above failed to
 824       // allocate a new region. So the mutator alloc region should be NULL.
 825       assert(_allocator->mutator_alloc_region(context)->get() == NULL, "only way to get here");
 826 
 827       if (GC_locker::is_active_and_needs_gc()) {
 828         if (g1_policy()->can_expand_young_list()) {
 829           // No need for an ergo verbose message here,
 830           // can_expand_young_list() does this when it returns true.
 831           result = _allocator->mutator_alloc_region(context)->attempt_allocation_force(word_size,
 832                                                                                        false /* bot_updates */);
 833           if (result != NULL) {
 834             return result;
 835           }
 836         }
 837         should_try_gc = false;
 838       } else {
 839         // The GCLocker may not be active but the GCLocker initiated
 840         // GC may not yet have been performed (GCLocker::needs_gc()
 841         // returns true). In this case we do not try this GC and
 842         // wait until the GCLocker initiated GC is performed, and
 843         // then retry the allocation.
 844         if (GC_locker::needs_gc()) {
 845           should_try_gc = false;
 846         } else {
 847           // Read the GC count while still holding the Heap_lock.
 848           gc_count_before = total_collections();
 849           should_try_gc = true;
 850         }
 851       }
 852     }
 853 
 854     if (should_try_gc) {
 855       bool succeeded;
 856       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 857           GCCause::_g1_inc_collection_pause);
 858       if (result != NULL) {
 859         assert(succeeded, "only way to get back a non-NULL result");
 860         return result;
 861       }
 862 
 863       if (succeeded) {
 864         // If we get here we successfully scheduled a collection which
 865         // failed to allocate. No point in trying to allocate
 866         // further. We'll just return NULL.
 867         MutexLockerEx x(Heap_lock);
 868         *gc_count_before_ret = total_collections();
 869         return NULL;
 870       }
 871     } else {
 872       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
 873         MutexLockerEx x(Heap_lock);
 874         *gc_count_before_ret = total_collections();
 875         return NULL;
 876       }
 877       // The GCLocker is either active or the GCLocker initiated
 878       // GC has not yet been performed. Stall until it is and
 879       // then retry the allocation.
 880       GC_locker::stall_until_clear();
 881       (*gclocker_retry_count_ret) += 1;
 882     }
 883 
 884     // We can reach here if we were unsuccessful in scheduling a
 885     // collection (because another thread beat us to it) or if we were
 886     // stalled due to the GC locker. In either can we should retry the
 887     // allocation attempt in case another thread successfully
 888     // performed a collection and reclaimed enough space. We do the
 889     // first attempt (without holding the Heap_lock) here and the
 890     // follow-on attempt will be at the start of the next loop
 891     // iteration (after taking the Heap_lock).
 892     result = _allocator->mutator_alloc_region(context)->attempt_allocation(word_size,
 893                                                                            false /* bot_updates */);
 894     if (result != NULL) {
 895       return result;
 896     }
 897 
 898     // Give a warning if we seem to be looping forever.
 899     if ((QueuedAllocationWarningCount > 0) &&
 900         (try_count % QueuedAllocationWarningCount == 0)) {
 901       warning("G1CollectedHeap::attempt_allocation_slow() "
 902               "retries %d times", try_count);
 903     }
 904   }
 905 
 906   ShouldNotReachHere();
 907   return NULL;
 908 }
 909 
 910 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
 911                                                         uint* gc_count_before_ret,
 912                                                         uint* gclocker_retry_count_ret) {
 913   // The structure of this method has a lot of similarities to
 914   // attempt_allocation_slow(). The reason these two were not merged
 915   // into a single one is that such a method would require several "if
 916   // allocation is not humongous do this, otherwise do that"
 917   // conditional paths which would obscure its flow. In fact, an early
 918   // version of this code did use a unified method which was harder to
 919   // follow and, as a result, it had subtle bugs that were hard to
 920   // track down. So keeping these two methods separate allows each to
 921   // be more readable. It will be good to keep these two in sync as
 922   // much as possible.
 923 
 924   assert_heap_not_locked_and_not_at_safepoint();
 925   assert(is_humongous(word_size), "attempt_allocation_humongous() "
 926          "should only be called for humongous allocations");
 927 
 928   // Humongous objects can exhaust the heap quickly, so we should check if we
 929   // need to start a marking cycle at each humongous object allocation. We do
 930   // the check before we do the actual allocation. The reason for doing it
 931   // before the allocation is that we avoid having to keep track of the newly
 932   // allocated memory while we do a GC.
 933   if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
 934                                            word_size)) {
 935     collect(GCCause::_g1_humongous_allocation);
 936   }
 937 
 938   // We will loop until a) we manage to successfully perform the
 939   // allocation or b) we successfully schedule a collection which
 940   // fails to perform the allocation. b) is the only case when we'll
 941   // return NULL.
 942   HeapWord* result = NULL;
 943   for (int try_count = 1; /* we'll return */; try_count += 1) {
 944     bool should_try_gc;
 945     uint gc_count_before;
 946 
 947     {
 948       MutexLockerEx x(Heap_lock);
 949 
 950       // Given that humongous objects are not allocated in young
 951       // regions, we'll first try to do the allocation without doing a
 952       // collection hoping that there's enough space in the heap.
 953       result = humongous_obj_allocate(word_size, AllocationContext::current());
 954       if (result != NULL) {
 955         return result;
 956       }
 957 
 958       if (GC_locker::is_active_and_needs_gc()) {
 959         should_try_gc = false;
 960       } else {
 961          // The GCLocker may not be active but the GCLocker initiated
 962         // GC may not yet have been performed (GCLocker::needs_gc()
 963         // returns true). In this case we do not try this GC and
 964         // wait until the GCLocker initiated GC is performed, and
 965         // then retry the allocation.
 966         if (GC_locker::needs_gc()) {
 967           should_try_gc = false;
 968         } else {
 969           // Read the GC count while still holding the Heap_lock.
 970           gc_count_before = total_collections();
 971           should_try_gc = true;
 972         }
 973       }
 974     }
 975 
 976     if (should_try_gc) {
 977       // If we failed to allocate the humongous object, we should try to
 978       // do a collection pause (if we're allowed) in case it reclaims
 979       // enough space for the allocation to succeed after the pause.
 980 
 981       bool succeeded;
 982       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 983           GCCause::_g1_humongous_allocation);
 984       if (result != NULL) {
 985         assert(succeeded, "only way to get back a non-NULL result");
 986         return result;
 987       }
 988 
 989       if (succeeded) {
 990         // If we get here we successfully scheduled a collection which
 991         // failed to allocate. No point in trying to allocate
 992         // further. We'll just return NULL.
 993         MutexLockerEx x(Heap_lock);
 994         *gc_count_before_ret = total_collections();
 995         return NULL;
 996       }
 997     } else {
 998       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
 999         MutexLockerEx x(Heap_lock);
1000         *gc_count_before_ret = total_collections();
1001         return NULL;
1002       }
1003       // The GCLocker is either active or the GCLocker initiated
1004       // GC has not yet been performed. Stall until it is and
1005       // then retry the allocation.
1006       GC_locker::stall_until_clear();
1007       (*gclocker_retry_count_ret) += 1;
1008     }
1009 
1010     // We can reach here if we were unsuccessful in scheduling a
1011     // collection (because another thread beat us to it) or if we were
1012     // stalled due to the GC locker. In either can we should retry the
1013     // allocation attempt in case another thread successfully
1014     // performed a collection and reclaimed enough space.  Give a
1015     // warning if we seem to be looping forever.
1016 
1017     if ((QueuedAllocationWarningCount > 0) &&
1018         (try_count % QueuedAllocationWarningCount == 0)) {
1019       warning("G1CollectedHeap::attempt_allocation_humongous() "
1020               "retries %d times", try_count);
1021     }
1022   }
1023 
1024   ShouldNotReachHere();
1025   return NULL;
1026 }
1027 
1028 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1029                                                            AllocationContext_t context,
1030                                                            bool expect_null_mutator_alloc_region) {
1031   assert_at_safepoint(true /* should_be_vm_thread */);
1032   assert(_allocator->mutator_alloc_region(context)->get() == NULL ||
1033                                              !expect_null_mutator_alloc_region,
1034          "the current alloc region was unexpectedly found to be non-NULL");
1035 
1036   if (!is_humongous(word_size)) {
1037     return _allocator->mutator_alloc_region(context)->attempt_allocation_locked(word_size,
1038                                                       false /* bot_updates */);
1039   } else {
1040     HeapWord* result = humongous_obj_allocate(word_size, context);
1041     if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1042       collector_state()->set_initiate_conc_mark_if_possible(true);
1043     }
1044     return result;
1045   }
1046 
1047   ShouldNotReachHere();
1048 }
1049 
1050 class PostMCRemSetClearClosure: public HeapRegionClosure {
1051   G1CollectedHeap* _g1h;
1052   ModRefBarrierSet* _mr_bs;
1053 public:
1054   PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1055     _g1h(g1h), _mr_bs(mr_bs) {}
1056 
1057   bool doHeapRegion(HeapRegion* r) {
1058     HeapRegionRemSet* hrrs = r->rem_set();
1059 
1060     if (r->is_continues_humongous()) {
1061       // We'll assert that the strong code root list and RSet is empty
1062       assert(hrrs->strong_code_roots_list_length() == 0, "sanity");
1063       assert(hrrs->occupied() == 0, "RSet should be empty");
1064       return false;
1065     }
1066 
1067     _g1h->reset_gc_time_stamps(r);
1068     hrrs->clear();
1069     // You might think here that we could clear just the cards
1070     // corresponding to the used region.  But no: if we leave a dirty card
1071     // in a region we might allocate into, then it would prevent that card
1072     // from being enqueued, and cause it to be missed.
1073     // Re: the performance cost: we shouldn't be doing full GC anyway!
1074     _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1075 
1076     return false;
1077   }
1078 };
1079 
1080 void G1CollectedHeap::clear_rsets_post_compaction() {
1081   PostMCRemSetClearClosure rs_clear(this, g1_barrier_set());
1082   heap_region_iterate(&rs_clear);
1083 }
1084 
1085 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1086   G1CollectedHeap*   _g1h;
1087   UpdateRSOopClosure _cl;
1088 public:
1089   RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, uint worker_i = 0) :
1090     _cl(g1->g1_rem_set(), worker_i),
1091     _g1h(g1)
1092   { }
1093 
1094   bool doHeapRegion(HeapRegion* r) {
1095     if (!r->is_continues_humongous()) {
1096       _cl.set_from(r);
1097       r->oop_iterate(&_cl);
1098     }
1099     return false;
1100   }
1101 };
1102 
1103 class ParRebuildRSTask: public AbstractGangTask {
1104   G1CollectedHeap* _g1;
1105   HeapRegionClaimer _hrclaimer;
1106 
1107 public:
1108   ParRebuildRSTask(G1CollectedHeap* g1) :
1109       AbstractGangTask("ParRebuildRSTask"), _g1(g1), _hrclaimer(g1->workers()->active_workers()) {}
1110 
1111   void work(uint worker_id) {
1112     RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1113     _g1->heap_region_par_iterate(&rebuild_rs, worker_id, &_hrclaimer);
1114   }
1115 };
1116 
1117 class PostCompactionPrinterClosure: public HeapRegionClosure {
1118 private:
1119   G1HRPrinter* _hr_printer;
1120 public:
1121   bool doHeapRegion(HeapRegion* hr) {
1122     assert(!hr->is_young(), "not expecting to find young regions");
1123     if (hr->is_free()) {
1124       // We only generate output for non-empty regions.
1125     } else if (hr->is_starts_humongous()) {
1126       if (hr->region_num() == 1) {
1127         // single humongous region
1128         _hr_printer->post_compaction(hr, G1HRPrinter::SingleHumongous);
1129       } else {
1130         _hr_printer->post_compaction(hr, G1HRPrinter::StartsHumongous);
1131       }
1132     } else if (hr->is_continues_humongous()) {
1133       _hr_printer->post_compaction(hr, G1HRPrinter::ContinuesHumongous);
1134     } else if (hr->is_old()) {
1135       _hr_printer->post_compaction(hr, G1HRPrinter::Old);
1136     } else {
1137       ShouldNotReachHere();
1138     }
1139     return false;
1140   }
1141 
1142   PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1143     : _hr_printer(hr_printer) { }
1144 };
1145 
1146 void G1CollectedHeap::print_hrm_post_compaction() {
1147   PostCompactionPrinterClosure cl(hr_printer());
1148   heap_region_iterate(&cl);
1149 }
1150 
1151 bool G1CollectedHeap::do_collection(bool explicit_gc,
1152                                     bool clear_all_soft_refs,
1153                                     size_t word_size) {
1154   assert_at_safepoint(true /* should_be_vm_thread */);
1155 
1156   if (GC_locker::check_active_before_gc()) {
1157     return false;
1158   }
1159 
1160   STWGCTimer* gc_timer = G1MarkSweep::gc_timer();
1161   gc_timer->register_gc_start();
1162 
1163   SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer();
1164   gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start());
1165 
1166   SvcGCMarker sgcm(SvcGCMarker::FULL);
1167   ResourceMark rm;
1168 
1169   G1Log::update_level();
1170   print_heap_before_gc();
1171   trace_heap_before_gc(gc_tracer);
1172 
1173   size_t metadata_prev_used = MetaspaceAux::used_bytes();
1174 
1175   verify_region_sets_optional();
1176 
1177   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1178                            collector_policy()->should_clear_all_soft_refs();
1179 
1180   ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1181 
1182   {
1183     IsGCActiveMark x;
1184 
1185     // Timing
1186     assert(gc_cause() != GCCause::_java_lang_system_gc || explicit_gc, "invariant");
1187     TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
1188 
1189     {
1190       GCTraceTime t(GCCauseString("Full GC", gc_cause()), G1Log::fine(), true, NULL, gc_tracer->gc_id());
1191       TraceCollectorStats tcs(g1mm()->full_collection_counters());
1192       TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1193 
1194       g1_policy()->record_full_collection_start();
1195 
1196       // Note: When we have a more flexible GC logging framework that
1197       // allows us to add optional attributes to a GC log record we
1198       // could consider timing and reporting how long we wait in the
1199       // following two methods.
1200       wait_while_free_regions_coming();
1201       // If we start the compaction before the CM threads finish
1202       // scanning the root regions we might trip them over as we'll
1203       // be moving objects / updating references. So let's wait until
1204       // they are done. By telling them to abort, they should complete
1205       // early.
1206       _cm->root_regions()->abort();
1207       _cm->root_regions()->wait_until_scan_finished();
1208       append_secondary_free_list_if_not_empty_with_lock();
1209 
1210       gc_prologue(true);
1211       increment_total_collections(true /* full gc */);
1212       increment_old_marking_cycles_started();
1213 
1214       assert(used() == recalculate_used(), "Should be equal");
1215 
1216       verify_before_gc();
1217 
1218       check_bitmaps("Full GC Start");
1219       pre_full_gc_dump(gc_timer);
1220 
1221       COMPILER2_PRESENT(DerivedPointerTable::clear());
1222 
1223       // Disable discovery and empty the discovered lists
1224       // for the CM ref processor.
1225       ref_processor_cm()->disable_discovery();
1226       ref_processor_cm()->abandon_partial_discovery();
1227       ref_processor_cm()->verify_no_references_recorded();
1228 
1229       // Abandon current iterations of concurrent marking and concurrent
1230       // refinement, if any are in progress. We have to do this before
1231       // wait_until_scan_finished() below.
1232       concurrent_mark()->abort();
1233 
1234       // Make sure we'll choose a new allocation region afterwards.
1235       _allocator->release_mutator_alloc_region();
1236       _allocator->abandon_gc_alloc_regions();
1237       g1_rem_set()->cleanupHRRS();
1238 
1239       // We should call this after we retire any currently active alloc
1240       // regions so that all the ALLOC / RETIRE events are generated
1241       // before the start GC event.
1242       _hr_printer.start_gc(true /* full */, (size_t) total_collections());
1243 
1244       // We may have added regions to the current incremental collection
1245       // set between the last GC or pause and now. We need to clear the
1246       // incremental collection set and then start rebuilding it afresh
1247       // after this full GC.
1248       abandon_collection_set(g1_policy()->inc_cset_head());
1249       g1_policy()->clear_incremental_cset();
1250       g1_policy()->stop_incremental_cset_building();
1251 
1252       tear_down_region_sets(false /* free_list_only */);
1253       collector_state()->set_gcs_are_young(true);
1254 
1255       // See the comments in g1CollectedHeap.hpp and
1256       // G1CollectedHeap::ref_processing_init() about
1257       // how reference processing currently works in G1.
1258 
1259       // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1260       ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1261 
1262       // Temporarily clear the STW ref processor's _is_alive_non_header field.
1263       ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1264 
1265       ref_processor_stw()->enable_discovery();
1266       ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1267 
1268       // Do collection work
1269       {
1270         HandleMark hm;  // Discard invalid handles created during gc
1271         G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1272       }
1273 
1274       assert(num_free_regions() == 0, "we should not have added any free regions");
1275       rebuild_region_sets(false /* free_list_only */);
1276 
1277       // Enqueue any discovered reference objects that have
1278       // not been removed from the discovered lists.
1279       ref_processor_stw()->enqueue_discovered_references();
1280 
1281       COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
1282 
1283       MemoryService::track_memory_usage();
1284 
1285       assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1286       ref_processor_stw()->verify_no_references_recorded();
1287 
1288       // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1289       ClassLoaderDataGraph::purge();
1290       MetaspaceAux::verify_metrics();
1291 
1292       // Note: since we've just done a full GC, concurrent
1293       // marking is no longer active. Therefore we need not
1294       // re-enable reference discovery for the CM ref processor.
1295       // That will be done at the start of the next marking cycle.
1296       assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1297       ref_processor_cm()->verify_no_references_recorded();
1298 
1299       reset_gc_time_stamp();
1300       // Since everything potentially moved, we will clear all remembered
1301       // sets, and clear all cards.  Later we will rebuild remembered
1302       // sets. We will also reset the GC time stamps of the regions.
1303       clear_rsets_post_compaction();
1304       check_gc_time_stamps();
1305 
1306       // Resize the heap if necessary.
1307       resize_if_necessary_after_full_collection(explicit_gc ? 0 : word_size);
1308 
1309       if (_hr_printer.is_active()) {
1310         // We should do this after we potentially resize the heap so
1311         // that all the COMMIT / UNCOMMIT events are generated before
1312         // the end GC event.
1313 
1314         print_hrm_post_compaction();
1315         _hr_printer.end_gc(true /* full */, (size_t) total_collections());
1316       }
1317 
1318       G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
1319       if (hot_card_cache->use_cache()) {
1320         hot_card_cache->reset_card_counts();
1321         hot_card_cache->reset_hot_cache();
1322       }
1323 
1324       // Rebuild remembered sets of all regions.
1325       uint n_workers =
1326         AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1327                                                 workers()->active_workers(),
1328                                                 Threads::number_of_non_daemon_threads());
1329       assert(UseDynamicNumberOfGCThreads ||
1330              n_workers == workers()->total_workers(),
1331              "If not dynamic should be using all the  workers");
1332       workers()->set_active_workers(n_workers);
1333       // Set parallel threads in the heap (_n_par_threads) only
1334       // before a parallel phase and always reset it to 0 after
1335       // the phase so that the number of parallel threads does
1336       // no get carried forward to a serial phase where there
1337       // may be code that is "possibly_parallel".
1338       set_par_threads(n_workers);
1339 
1340       ParRebuildRSTask rebuild_rs_task(this);
1341       assert(UseDynamicNumberOfGCThreads ||
1342              workers()->active_workers() == workers()->total_workers(),
1343              "Unless dynamic should use total workers");
1344       // Use the most recent number of  active workers
1345       assert(workers()->active_workers() > 0,
1346              "Active workers not properly set");
1347       set_par_threads(workers()->active_workers());
1348       workers()->run_task(&rebuild_rs_task);
1349       set_par_threads(0);
1350 
1351       // Rebuild the strong code root lists for each region
1352       rebuild_strong_code_roots();
1353 
1354       if (true) { // FIXME
1355         MetaspaceGC::compute_new_size();
1356       }
1357 
1358 #ifdef TRACESPINNING
1359       ParallelTaskTerminator::print_termination_counts();
1360 #endif
1361 
1362       // Discard all rset updates
1363       JavaThread::dirty_card_queue_set().abandon_logs();
1364       assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1365 
1366       _young_list->reset_sampled_info();
1367       // At this point there should be no regions in the
1368       // entire heap tagged as young.
1369       assert(check_young_list_empty(true /* check_heap */),
1370              "young list should be empty at this point");
1371 
1372       // Update the number of full collections that have been completed.
1373       increment_old_marking_cycles_completed(false /* concurrent */);
1374 
1375       _hrm.verify_optional();
1376       verify_region_sets_optional();
1377 
1378       verify_after_gc();
1379 
1380       // Clear the previous marking bitmap, if needed for bitmap verification.
1381       // Note we cannot do this when we clear the next marking bitmap in
1382       // ConcurrentMark::abort() above since VerifyDuringGC verifies the
1383       // objects marked during a full GC against the previous bitmap.
1384       // But we need to clear it before calling check_bitmaps below since
1385       // the full GC has compacted objects and updated TAMS but not updated
1386       // the prev bitmap.
1387       if (G1VerifyBitmaps) {
1388         ((CMBitMap*) concurrent_mark()->prevMarkBitMap())->clearAll();
1389       }
1390       check_bitmaps("Full GC End");
1391 
1392       // Start a new incremental collection set for the next pause
1393       assert(g1_policy()->collection_set() == NULL, "must be");
1394       g1_policy()->start_incremental_cset_building();
1395 
1396       clear_cset_fast_test();
1397 
1398       _allocator->init_mutator_alloc_region();
1399 
1400       g1_policy()->record_full_collection_end();
1401 
1402       if (G1Log::fine()) {
1403         g1_policy()->print_heap_transition();
1404       }
1405 
1406       // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1407       // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1408       // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1409       // before any GC notifications are raised.
1410       g1mm()->update_sizes();
1411 
1412       gc_epilogue(true);
1413     }
1414 
1415     if (G1Log::finer()) {
1416       g1_policy()->print_detailed_heap_transition(true /* full */);
1417     }
1418 
1419     print_heap_after_gc();
1420     trace_heap_after_gc(gc_tracer);
1421 
1422     post_full_gc_dump(gc_timer);
1423 
1424     gc_timer->register_gc_end();
1425     gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
1426   }
1427 
1428   return true;
1429 }
1430 
1431 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1432   // do_collection() will return whether it succeeded in performing
1433   // the GC. Currently, there is no facility on the
1434   // do_full_collection() API to notify the caller than the collection
1435   // did not succeed (e.g., because it was locked out by the GC
1436   // locker). So, right now, we'll ignore the return value.
1437   bool dummy = do_collection(true,                /* explicit_gc */
1438                              clear_all_soft_refs,
1439                              0                    /* word_size */);
1440 }
1441 
1442 // This code is mostly copied from TenuredGeneration.
1443 void
1444 G1CollectedHeap::
1445 resize_if_necessary_after_full_collection(size_t word_size) {
1446   // Include the current allocation, if any, and bytes that will be
1447   // pre-allocated to support collections, as "used".
1448   const size_t used_after_gc = used();
1449   const size_t capacity_after_gc = capacity();
1450   const size_t free_after_gc = capacity_after_gc - used_after_gc;
1451 
1452   // This is enforced in arguments.cpp.
1453   assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1454          "otherwise the code below doesn't make sense");
1455 
1456   // We don't have floating point command-line arguments
1457   const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1458   const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1459   const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1460   const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1461 
1462   const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1463   const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1464 
1465   // We have to be careful here as these two calculations can overflow
1466   // 32-bit size_t's.
1467   double used_after_gc_d = (double) used_after_gc;
1468   double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1469   double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1470 
1471   // Let's make sure that they are both under the max heap size, which
1472   // by default will make them fit into a size_t.
1473   double desired_capacity_upper_bound = (double) max_heap_size;
1474   minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1475                                     desired_capacity_upper_bound);
1476   maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1477                                     desired_capacity_upper_bound);
1478 
1479   // We can now safely turn them into size_t's.
1480   size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1481   size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1482 
1483   // This assert only makes sense here, before we adjust them
1484   // with respect to the min and max heap size.
1485   assert(minimum_desired_capacity <= maximum_desired_capacity,
1486          err_msg("minimum_desired_capacity = "SIZE_FORMAT", "
1487                  "maximum_desired_capacity = "SIZE_FORMAT,
1488                  minimum_desired_capacity, maximum_desired_capacity));
1489 
1490   // Should not be greater than the heap max size. No need to adjust
1491   // it with respect to the heap min size as it's a lower bound (i.e.,
1492   // we'll try to make the capacity larger than it, not smaller).
1493   minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1494   // Should not be less than the heap min size. No need to adjust it
1495   // with respect to the heap max size as it's an upper bound (i.e.,
1496   // we'll try to make the capacity smaller than it, not greater).
1497   maximum_desired_capacity =  MAX2(maximum_desired_capacity, min_heap_size);
1498 
1499   if (capacity_after_gc < minimum_desired_capacity) {
1500     // Don't expand unless it's significant
1501     size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1502     ergo_verbose4(ErgoHeapSizing,
1503                   "attempt heap expansion",
1504                   ergo_format_reason("capacity lower than "
1505                                      "min desired capacity after Full GC")
1506                   ergo_format_byte("capacity")
1507                   ergo_format_byte("occupancy")
1508                   ergo_format_byte_perc("min desired capacity"),
1509                   capacity_after_gc, used_after_gc,
1510                   minimum_desired_capacity, (double) MinHeapFreeRatio);
1511     expand(expand_bytes);
1512 
1513     // No expansion, now see if we want to shrink
1514   } else if (capacity_after_gc > maximum_desired_capacity) {
1515     // Capacity too large, compute shrinking size
1516     size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1517     ergo_verbose4(ErgoHeapSizing,
1518                   "attempt heap shrinking",
1519                   ergo_format_reason("capacity higher than "
1520                                      "max desired capacity after Full GC")
1521                   ergo_format_byte("capacity")
1522                   ergo_format_byte("occupancy")
1523                   ergo_format_byte_perc("max desired capacity"),
1524                   capacity_after_gc, used_after_gc,
1525                   maximum_desired_capacity, (double) MaxHeapFreeRatio);
1526     shrink(shrink_bytes);
1527   }
1528 }
1529 
1530 
1531 HeapWord*
1532 G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1533                                            AllocationContext_t context,
1534                                            bool* succeeded) {
1535   assert_at_safepoint(true /* should_be_vm_thread */);
1536 
1537   *succeeded = true;
1538   // Let's attempt the allocation first.
1539   HeapWord* result =
1540     attempt_allocation_at_safepoint(word_size,
1541                                     context,
1542                                     false /* expect_null_mutator_alloc_region */);
1543   if (result != NULL) {
1544     assert(*succeeded, "sanity");
1545     return result;
1546   }
1547 
1548   // In a G1 heap, we're supposed to keep allocation from failing by
1549   // incremental pauses.  Therefore, at least for now, we'll favor
1550   // expansion over collection.  (This might change in the future if we can
1551   // do something smarter than full collection to satisfy a failed alloc.)
1552   result = expand_and_allocate(word_size, context);
1553   if (result != NULL) {
1554     assert(*succeeded, "sanity");
1555     return result;
1556   }
1557 
1558   // Expansion didn't work, we'll try to do a Full GC.
1559   bool gc_succeeded = do_collection(false, /* explicit_gc */
1560                                     false, /* clear_all_soft_refs */
1561                                     word_size);
1562   if (!gc_succeeded) {
1563     *succeeded = false;
1564     return NULL;
1565   }
1566 
1567   // Retry the allocation
1568   result = attempt_allocation_at_safepoint(word_size,
1569                                            context,
1570                                            true /* expect_null_mutator_alloc_region */);
1571   if (result != NULL) {
1572     assert(*succeeded, "sanity");
1573     return result;
1574   }
1575 
1576   // Then, try a Full GC that will collect all soft references.
1577   gc_succeeded = do_collection(false, /* explicit_gc */
1578                                true,  /* clear_all_soft_refs */
1579                                word_size);
1580   if (!gc_succeeded) {
1581     *succeeded = false;
1582     return NULL;
1583   }
1584 
1585   // Retry the allocation once more
1586   result = attempt_allocation_at_safepoint(word_size,
1587                                            context,
1588                                            true /* expect_null_mutator_alloc_region */);
1589   if (result != NULL) {
1590     assert(*succeeded, "sanity");
1591     return result;
1592   }
1593 
1594   assert(!collector_policy()->should_clear_all_soft_refs(),
1595          "Flag should have been handled and cleared prior to this point");
1596 
1597   // What else?  We might try synchronous finalization later.  If the total
1598   // space available is large enough for the allocation, then a more
1599   // complete compaction phase than we've tried so far might be
1600   // appropriate.
1601   assert(*succeeded, "sanity");
1602   return NULL;
1603 }
1604 
1605 // Attempting to expand the heap sufficiently
1606 // to support an allocation of the given "word_size".  If
1607 // successful, perform the allocation and return the address of the
1608 // allocated block, or else "NULL".
1609 
1610 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) {
1611   assert_at_safepoint(true /* should_be_vm_thread */);
1612 
1613   verify_region_sets_optional();
1614 
1615   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1616   ergo_verbose1(ErgoHeapSizing,
1617                 "attempt heap expansion",
1618                 ergo_format_reason("allocation request failed")
1619                 ergo_format_byte("allocation request"),
1620                 word_size * HeapWordSize);
1621   if (expand(expand_bytes)) {
1622     _hrm.verify_optional();
1623     verify_region_sets_optional();
1624     return attempt_allocation_at_safepoint(word_size,
1625                                            context,
1626                                            false /* expect_null_mutator_alloc_region */);
1627   }
1628   return NULL;
1629 }
1630 
1631 bool G1CollectedHeap::expand(size_t expand_bytes) {
1632   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1633   aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1634                                        HeapRegion::GrainBytes);
1635   ergo_verbose2(ErgoHeapSizing,
1636                 "expand the heap",
1637                 ergo_format_byte("requested expansion amount")
1638                 ergo_format_byte("attempted expansion amount"),
1639                 expand_bytes, aligned_expand_bytes);
1640 
1641   if (is_maximal_no_gc()) {
1642     ergo_verbose0(ErgoHeapSizing,
1643                       "did not expand the heap",
1644                       ergo_format_reason("heap already fully expanded"));
1645     return false;
1646   }
1647 
1648   uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1649   assert(regions_to_expand > 0, "Must expand by at least one region");
1650 
1651   uint expanded_by = _hrm.expand_by(regions_to_expand);
1652 
1653   if (expanded_by > 0) {
1654     size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1655     assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1656     g1_policy()->record_new_heap_size(num_regions());
1657   } else {
1658     ergo_verbose0(ErgoHeapSizing,
1659                   "did not expand the heap",
1660                   ergo_format_reason("heap expansion operation failed"));
1661     // The expansion of the virtual storage space was unsuccessful.
1662     // Let's see if it was because we ran out of swap.
1663     if (G1ExitOnExpansionFailure &&
1664         _hrm.available() >= regions_to_expand) {
1665       // We had head room...
1666       vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1667     }
1668   }
1669   return regions_to_expand > 0;
1670 }
1671 
1672 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1673   size_t aligned_shrink_bytes =
1674     ReservedSpace::page_align_size_down(shrink_bytes);
1675   aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1676                                          HeapRegion::GrainBytes);
1677   uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1678 
1679   uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1680   size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1681 
1682   ergo_verbose3(ErgoHeapSizing,
1683                 "shrink the heap",
1684                 ergo_format_byte("requested shrinking amount")
1685                 ergo_format_byte("aligned shrinking amount")
1686                 ergo_format_byte("attempted shrinking amount"),
1687                 shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1688   if (num_regions_removed > 0) {
1689     g1_policy()->record_new_heap_size(num_regions());
1690   } else {
1691     ergo_verbose0(ErgoHeapSizing,
1692                   "did not shrink the heap",
1693                   ergo_format_reason("heap shrinking operation failed"));
1694   }
1695 }
1696 
1697 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1698   verify_region_sets_optional();
1699 
1700   // We should only reach here at the end of a Full GC which means we
1701   // should not not be holding to any GC alloc regions. The method
1702   // below will make sure of that and do any remaining clean up.
1703   _allocator->abandon_gc_alloc_regions();
1704 
1705   // Instead of tearing down / rebuilding the free lists here, we
1706   // could instead use the remove_all_pending() method on free_list to
1707   // remove only the ones that we need to remove.
1708   tear_down_region_sets(true /* free_list_only */);
1709   shrink_helper(shrink_bytes);
1710   rebuild_region_sets(true /* free_list_only */);
1711 
1712   _hrm.verify_optional();
1713   verify_region_sets_optional();
1714 }
1715 
1716 // Public methods.
1717 
1718 #ifdef _MSC_VER // the use of 'this' below gets a warning, make it go away
1719 #pragma warning( disable:4355 ) // 'this' : used in base member initializer list
1720 #endif // _MSC_VER
1721 
1722 
1723 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1724   CollectedHeap(),
1725   _g1_policy(policy_),
1726   _dirty_card_queue_set(false),
1727   _into_cset_dirty_card_queue_set(false),
1728   _is_alive_closure_cm(this),
1729   _is_alive_closure_stw(this),
1730   _ref_processor_cm(NULL),
1731   _ref_processor_stw(NULL),
1732   _bot_shared(NULL),
1733   _evac_failure_scan_stack(NULL),
1734   _cg1r(NULL),
1735   _g1mm(NULL),
1736   _refine_cte_cl(NULL),
1737   _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1738   _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1739   _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1740   _humongous_reclaim_candidates(),
1741   _has_humongous_reclaim_candidates(false),
1742   _free_regions_coming(false),
1743   _young_list(new YoungList(this)),
1744   _gc_time_stamp(0),
1745   _survivor_plab_stats(YoungPLABSize, PLABWeight),
1746   _old_plab_stats(OldPLABSize, PLABWeight),
1747   _expand_heap_after_alloc_failure(true),
1748   _surviving_young_words(NULL),
1749   _old_marking_cycles_started(0),
1750   _old_marking_cycles_completed(0),
1751   _heap_summary_sent(false),
1752   _in_cset_fast_test(),
1753   _dirty_cards_region_list(NULL),
1754   _worker_cset_start_region(NULL),
1755   _worker_cset_start_region_time_stamp(NULL),
1756   _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1757   _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
1758   _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1759   _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) {
1760 
1761   _workers = new FlexibleWorkGang("GC Thread", ParallelGCThreads,
1762                           /* are_GC_task_threads */true,
1763                           /* are_ConcurrentGC_threads */false);
1764   _workers->initialize_workers();
1765 
1766   _allocator = G1Allocator::create_allocator(this);
1767   _humongous_object_threshold_in_words = HeapRegion::GrainWords / 2;
1768 
1769   int n_queues = MAX2((int)ParallelGCThreads, 1);
1770   _task_queues = new RefToScanQueueSet(n_queues);
1771 
1772   uint n_rem_sets = HeapRegionRemSet::num_par_rem_sets();
1773   assert(n_rem_sets > 0, "Invariant.");
1774 
1775   _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1776   _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(uint, n_queues, mtGC);
1777   _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1778 
1779   for (int i = 0; i < n_queues; i++) {
1780     RefToScanQueue* q = new RefToScanQueue();
1781     q->initialize();
1782     _task_queues->register_queue(i, q);
1783     ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1784   }
1785   clear_cset_start_regions();
1786 
1787   // Initialize the G1EvacuationFailureALot counters and flags.
1788   NOT_PRODUCT(reset_evacuation_should_fail();)
1789 
1790   guarantee(_task_queues != NULL, "task_queues allocation failure.");
1791 }
1792 
1793 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1794                                                                  size_t size,
1795                                                                  size_t translation_factor) {
1796   size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1797   // Allocate a new reserved space, preferring to use large pages.
1798   ReservedSpace rs(size, preferred_page_size);
1799   G1RegionToSpaceMapper* result  =
1800     G1RegionToSpaceMapper::create_mapper(rs,
1801                                          size,
1802                                          rs.alignment(),
1803                                          HeapRegion::GrainBytes,
1804                                          translation_factor,
1805                                          mtGC);
1806   if (TracePageSizes) {
1807     gclog_or_tty->print_cr("G1 '%s': pg_sz=" SIZE_FORMAT " base=" PTR_FORMAT " size=" SIZE_FORMAT " alignment=" SIZE_FORMAT " reqsize=" SIZE_FORMAT,
1808                            description, preferred_page_size, p2i(rs.base()), rs.size(), rs.alignment(), size);
1809   }
1810   return result;
1811 }
1812 
1813 jint G1CollectedHeap::initialize() {
1814   CollectedHeap::pre_initialize();
1815   os::enable_vtime();
1816 
1817   G1Log::init();
1818 
1819   // Necessary to satisfy locking discipline assertions.
1820 
1821   MutexLocker x(Heap_lock);
1822 
1823   // We have to initialize the printer before committing the heap, as
1824   // it will be used then.
1825   _hr_printer.set_active(G1PrintHeapRegions);
1826 
1827   // While there are no constraints in the GC code that HeapWordSize
1828   // be any particular value, there are multiple other areas in the
1829   // system which believe this to be true (e.g. oop->object_size in some
1830   // cases incorrectly returns the size in wordSize units rather than
1831   // HeapWordSize).
1832   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1833 
1834   size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1835   size_t max_byte_size = collector_policy()->max_heap_byte_size();
1836   size_t heap_alignment = collector_policy()->heap_alignment();
1837 
1838   // Ensure that the sizes are properly aligned.
1839   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1840   Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1841   Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1842 
1843   _refine_cte_cl = new RefineCardTableEntryClosure();
1844 
1845   _cg1r = new ConcurrentG1Refine(this, _refine_cte_cl);
1846 
1847   // Reserve the maximum.
1848 
1849   // When compressed oops are enabled, the preferred heap base
1850   // is calculated by subtracting the requested size from the
1851   // 32Gb boundary and using the result as the base address for
1852   // heap reservation. If the requested size is not aligned to
1853   // HeapRegion::GrainBytes (i.e. the alignment that is passed
1854   // into the ReservedHeapSpace constructor) then the actual
1855   // base of the reserved heap may end up differing from the
1856   // address that was requested (i.e. the preferred heap base).
1857   // If this happens then we could end up using a non-optimal
1858   // compressed oops mode.
1859 
1860   ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1861                                                  heap_alignment);
1862 
1863   initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
1864 
1865   // Create the barrier set for the entire reserved region.
1866   G1SATBCardTableLoggingModRefBS* bs
1867     = new G1SATBCardTableLoggingModRefBS(reserved_region());
1868   bs->initialize();
1869   assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity");
1870   set_barrier_set(bs);
1871 
1872   // Also create a G1 rem set.
1873   _g1_rem_set = new G1RemSet(this, g1_barrier_set());
1874 
1875   // Carve out the G1 part of the heap.
1876 
1877   ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1878   size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
1879   G1RegionToSpaceMapper* heap_storage =
1880     G1RegionToSpaceMapper::create_mapper(g1_rs,
1881                                          g1_rs.size(),
1882                                          page_size,
1883                                          HeapRegion::GrainBytes,
1884                                          1,
1885                                          mtJavaHeap);
1886   os::trace_page_sizes("G1 Heap", collector_policy()->min_heap_byte_size(),
1887                        max_byte_size, page_size,
1888                        heap_rs.base(),
1889                        heap_rs.size());
1890   heap_storage->set_mapping_changed_listener(&_listener);
1891 
1892   // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1893   G1RegionToSpaceMapper* bot_storage =
1894     create_aux_memory_mapper("Block offset table",
1895                              G1BlockOffsetSharedArray::compute_size(g1_rs.size() / HeapWordSize),
1896                              G1BlockOffsetSharedArray::heap_map_factor());
1897 
1898   ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize));
1899   G1RegionToSpaceMapper* cardtable_storage =
1900     create_aux_memory_mapper("Card table",
1901                              G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize),
1902                              G1SATBCardTableLoggingModRefBS::heap_map_factor());
1903 
1904   G1RegionToSpaceMapper* card_counts_storage =
1905     create_aux_memory_mapper("Card counts table",
1906                              G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1907                              G1CardCounts::heap_map_factor());
1908 
1909   size_t bitmap_size = CMBitMap::compute_size(g1_rs.size());
1910   G1RegionToSpaceMapper* prev_bitmap_storage =
1911     create_aux_memory_mapper("Prev Bitmap", bitmap_size, CMBitMap::heap_map_factor());
1912   G1RegionToSpaceMapper* next_bitmap_storage =
1913     create_aux_memory_mapper("Next Bitmap", bitmap_size, CMBitMap::heap_map_factor());
1914 
1915   _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1916   g1_barrier_set()->initialize(cardtable_storage);
1917    // Do later initialization work for concurrent refinement.
1918   _cg1r->init(card_counts_storage);
1919 
1920   // 6843694 - ensure that the maximum region index can fit
1921   // in the remembered set structures.
1922   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1923   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1924 
1925   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1926   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1927   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1928             "too many cards per region");
1929 
1930   FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
1931 
1932   _bot_shared = new G1BlockOffsetSharedArray(reserved_region(), bot_storage);
1933 
1934   {
1935     HeapWord* start = _hrm.reserved().start();
1936     HeapWord* end = _hrm.reserved().end();
1937     size_t granularity = HeapRegion::GrainBytes;
1938 
1939     _in_cset_fast_test.initialize(start, end, granularity);
1940     _humongous_reclaim_candidates.initialize(start, end, granularity);
1941   }
1942 
1943   // Create the ConcurrentMark data structure and thread.
1944   // (Must do this late, so that "max_regions" is defined.)
1945   _cm = new ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1946   if (_cm == NULL || !_cm->completed_initialization()) {
1947     vm_shutdown_during_initialization("Could not create/initialize ConcurrentMark");
1948     return JNI_ENOMEM;
1949   }
1950   _cmThread = _cm->cmThread();
1951 
1952   // Initialize the from_card cache structure of HeapRegionRemSet.
1953   HeapRegionRemSet::init_heap(max_regions());
1954 
1955   // Now expand into the initial heap size.
1956   if (!expand(init_byte_size)) {
1957     vm_shutdown_during_initialization("Failed to allocate initial heap.");
1958     return JNI_ENOMEM;
1959   }
1960 
1961   // Perform any initialization actions delegated to the policy.
1962   g1_policy()->init();
1963 
1964   JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
1965                                                SATB_Q_FL_lock,
1966                                                G1SATBProcessCompletedThreshold,
1967                                                Shared_SATB_Q_lock);
1968 
1969   JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl,
1970                                                 DirtyCardQ_CBL_mon,
1971                                                 DirtyCardQ_FL_lock,
1972                                                 concurrent_g1_refine()->yellow_zone(),
1973                                                 concurrent_g1_refine()->red_zone(),
1974                                                 Shared_DirtyCardQ_lock);
1975 
1976   dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code
1977                                     DirtyCardQ_CBL_mon,
1978                                     DirtyCardQ_FL_lock,
1979                                     -1, // never trigger processing
1980                                     -1, // no limit on length
1981                                     Shared_DirtyCardQ_lock,
1982                                     &JavaThread::dirty_card_queue_set());
1983 
1984   // Initialize the card queue set used to hold cards containing
1985   // references into the collection set.
1986   _into_cset_dirty_card_queue_set.initialize(NULL, // Should never be called by the Java code
1987                                              DirtyCardQ_CBL_mon,
1988                                              DirtyCardQ_FL_lock,
1989                                              -1, // never trigger processing
1990                                              -1, // no limit on length
1991                                              Shared_DirtyCardQ_lock,
1992                                              &JavaThread::dirty_card_queue_set());
1993 
1994   // Here we allocate the dummy HeapRegion that is required by the
1995   // G1AllocRegion class.
1996   HeapRegion* dummy_region = _hrm.get_dummy_region();
1997 
1998   // We'll re-use the same region whether the alloc region will
1999   // require BOT updates or not and, if it doesn't, then a non-young
2000   // region will complain that it cannot support allocations without
2001   // BOT updates. So we'll tag the dummy region as eden to avoid that.
2002   dummy_region->set_eden();
2003   // Make sure it's full.
2004   dummy_region->set_top(dummy_region->end());
2005   G1AllocRegion::setup(this, dummy_region);
2006 
2007   _allocator->init_mutator_alloc_region();
2008 
2009   // Do create of the monitoring and management support so that
2010   // values in the heap have been properly initialized.
2011   _g1mm = new G1MonitoringSupport(this);
2012 
2013   G1StringDedup::initialize();
2014 
2015   return JNI_OK;
2016 }
2017 
2018 void G1CollectedHeap::stop() {
2019   // Stop all concurrent threads. We do this to make sure these threads
2020   // do not continue to execute and access resources (e.g. gclog_or_tty)
2021   // that are destroyed during shutdown.
2022   _cg1r->stop();
2023   _cmThread->stop();
2024   if (G1StringDedup::is_enabled()) {
2025     G1StringDedup::stop();
2026   }
2027 }
2028 
2029 size_t G1CollectedHeap::conservative_max_heap_alignment() {
2030   return HeapRegion::max_region_size();
2031 }
2032 
2033 void G1CollectedHeap::post_initialize() {
2034   CollectedHeap::post_initialize();
2035   ref_processing_init();
2036 }
2037 
2038 void G1CollectedHeap::ref_processing_init() {
2039   // Reference processing in G1 currently works as follows:
2040   //
2041   // * There are two reference processor instances. One is
2042   //   used to record and process discovered references
2043   //   during concurrent marking; the other is used to
2044   //   record and process references during STW pauses
2045   //   (both full and incremental).
2046   // * Both ref processors need to 'span' the entire heap as
2047   //   the regions in the collection set may be dotted around.
2048   //
2049   // * For the concurrent marking ref processor:
2050   //   * Reference discovery is enabled at initial marking.
2051   //   * Reference discovery is disabled and the discovered
2052   //     references processed etc during remarking.
2053   //   * Reference discovery is MT (see below).
2054   //   * Reference discovery requires a barrier (see below).
2055   //   * Reference processing may or may not be MT
2056   //     (depending on the value of ParallelRefProcEnabled
2057   //     and ParallelGCThreads).
2058   //   * A full GC disables reference discovery by the CM
2059   //     ref processor and abandons any entries on it's
2060   //     discovered lists.
2061   //
2062   // * For the STW processor:
2063   //   * Non MT discovery is enabled at the start of a full GC.
2064   //   * Processing and enqueueing during a full GC is non-MT.
2065   //   * During a full GC, references are processed after marking.
2066   //
2067   //   * Discovery (may or may not be MT) is enabled at the start
2068   //     of an incremental evacuation pause.
2069   //   * References are processed near the end of a STW evacuation pause.
2070   //   * For both types of GC:
2071   //     * Discovery is atomic - i.e. not concurrent.
2072   //     * Reference discovery will not need a barrier.
2073 
2074   MemRegion mr = reserved_region();
2075 
2076   // Concurrent Mark ref processor
2077   _ref_processor_cm =
2078     new ReferenceProcessor(mr,    // span
2079                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2080                                 // mt processing
2081                            (int) ParallelGCThreads,
2082                                 // degree of mt processing
2083                            (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2084                                 // mt discovery
2085                            (int) MAX2(ParallelGCThreads, ConcGCThreads),
2086                                 // degree of mt discovery
2087                            false,
2088                                 // Reference discovery is not atomic
2089                            &_is_alive_closure_cm);
2090                                 // is alive closure
2091                                 // (for efficiency/performance)
2092 
2093   // STW ref processor
2094   _ref_processor_stw =
2095     new ReferenceProcessor(mr,    // span
2096                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2097                                 // mt processing
2098                            MAX2((int)ParallelGCThreads, 1),
2099                                 // degree of mt processing
2100                            (ParallelGCThreads > 1),
2101                                 // mt discovery
2102                            MAX2((int)ParallelGCThreads, 1),
2103                                 // degree of mt discovery
2104                            true,
2105                                 // Reference discovery is atomic
2106                            &_is_alive_closure_stw);
2107                                 // is alive closure
2108                                 // (for efficiency/performance)
2109 }
2110 
2111 size_t G1CollectedHeap::capacity() const {
2112   return _hrm.length() * HeapRegion::GrainBytes;
2113 }
2114 
2115 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2116   assert(!hr->is_continues_humongous(), "pre-condition");
2117   hr->reset_gc_time_stamp();
2118   if (hr->is_starts_humongous()) {
2119     uint first_index = hr->hrm_index() + 1;
2120     uint last_index = hr->last_hc_index();
2121     for (uint i = first_index; i < last_index; i += 1) {
2122       HeapRegion* chr = region_at(i);
2123       assert(chr->is_continues_humongous(), "sanity");
2124       chr->reset_gc_time_stamp();
2125     }
2126   }
2127 }
2128 
2129 #ifndef PRODUCT
2130 
2131 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2132 private:
2133   unsigned _gc_time_stamp;
2134   bool _failures;
2135 
2136 public:
2137   CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2138     _gc_time_stamp(gc_time_stamp), _failures(false) { }
2139 
2140   virtual bool doHeapRegion(HeapRegion* hr) {
2141     unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2142     if (_gc_time_stamp != region_gc_time_stamp) {
2143       gclog_or_tty->print_cr("Region "HR_FORMAT" has GC time stamp = %d, "
2144                              "expected %d", HR_FORMAT_PARAMS(hr),
2145                              region_gc_time_stamp, _gc_time_stamp);
2146       _failures = true;
2147     }
2148     return false;
2149   }
2150 
2151   bool failures() { return _failures; }
2152 };
2153 
2154 void G1CollectedHeap::check_gc_time_stamps() {
2155   CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2156   heap_region_iterate(&cl);
2157   guarantee(!cl.failures(), "all GC time stamps should have been reset");
2158 }
2159 #endif // PRODUCT
2160 
2161 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl,
2162                                                  DirtyCardQueue* into_cset_dcq,
2163                                                  bool concurrent,
2164                                                  uint worker_i) {
2165   // Clean cards in the hot card cache
2166   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
2167   hot_card_cache->drain(worker_i, g1_rem_set(), into_cset_dcq);
2168 
2169   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2170   size_t n_completed_buffers = 0;
2171   while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2172     n_completed_buffers++;
2173   }
2174   g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers);
2175   dcqs.clear_n_completed_buffers();
2176   assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2177 }
2178 
2179 
2180 // Computes the sum of the storage used by the various regions.
2181 size_t G1CollectedHeap::used() const {
2182   return _allocator->used();
2183 }
2184 
2185 size_t G1CollectedHeap::used_unlocked() const {
2186   return _allocator->used_unlocked();
2187 }
2188 
2189 class SumUsedClosure: public HeapRegionClosure {
2190   size_t _used;
2191 public:
2192   SumUsedClosure() : _used(0) {}
2193   bool doHeapRegion(HeapRegion* r) {
2194     if (!r->is_continues_humongous()) {
2195       _used += r->used();
2196     }
2197     return false;
2198   }
2199   size_t result() { return _used; }
2200 };
2201 
2202 size_t G1CollectedHeap::recalculate_used() const {
2203   double recalculate_used_start = os::elapsedTime();
2204 
2205   SumUsedClosure blk;
2206   heap_region_iterate(&blk);
2207 
2208   g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2209   return blk.result();
2210 }
2211 
2212 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2213   switch (cause) {
2214     case GCCause::_gc_locker:               return GCLockerInvokesConcurrent;
2215     case GCCause::_java_lang_system_gc:     return ExplicitGCInvokesConcurrent;
2216     case GCCause::_g1_humongous_allocation: return true;
2217     case GCCause::_update_allocation_context_stats_inc: return true;
2218     case GCCause::_wb_conc_mark:            return true;
2219     default:                                return false;
2220   }
2221 }
2222 
2223 #ifndef PRODUCT
2224 void G1CollectedHeap::allocate_dummy_regions() {
2225   // Let's fill up most of the region
2226   size_t word_size = HeapRegion::GrainWords - 1024;
2227   // And as a result the region we'll allocate will be humongous.
2228   guarantee(is_humongous(word_size), "sanity");
2229 
2230   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2231     // Let's use the existing mechanism for the allocation
2232     HeapWord* dummy_obj = humongous_obj_allocate(word_size,
2233                                                  AllocationContext::system());
2234     if (dummy_obj != NULL) {
2235       MemRegion mr(dummy_obj, word_size);
2236       CollectedHeap::fill_with_object(mr);
2237     } else {
2238       // If we can't allocate once, we probably cannot allocate
2239       // again. Let's get out of the loop.
2240       break;
2241     }
2242   }
2243 }
2244 #endif // !PRODUCT
2245 
2246 void G1CollectedHeap::increment_old_marking_cycles_started() {
2247   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2248     _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2249     err_msg("Wrong marking cycle count (started: %d, completed: %d)",
2250     _old_marking_cycles_started, _old_marking_cycles_completed));
2251 
2252   _old_marking_cycles_started++;
2253 }
2254 
2255 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2256   MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2257 
2258   // We assume that if concurrent == true, then the caller is a
2259   // concurrent thread that was joined the Suspendible Thread
2260   // Set. If there's ever a cheap way to check this, we should add an
2261   // assert here.
2262 
2263   // Given that this method is called at the end of a Full GC or of a
2264   // concurrent cycle, and those can be nested (i.e., a Full GC can
2265   // interrupt a concurrent cycle), the number of full collections
2266   // completed should be either one (in the case where there was no
2267   // nesting) or two (when a Full GC interrupted a concurrent cycle)
2268   // behind the number of full collections started.
2269 
2270   // This is the case for the inner caller, i.e. a Full GC.
2271   assert(concurrent ||
2272          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2273          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2274          err_msg("for inner caller (Full GC): _old_marking_cycles_started = %u "
2275                  "is inconsistent with _old_marking_cycles_completed = %u",
2276                  _old_marking_cycles_started, _old_marking_cycles_completed));
2277 
2278   // This is the case for the outer caller, i.e. the concurrent cycle.
2279   assert(!concurrent ||
2280          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2281          err_msg("for outer caller (concurrent cycle): "
2282                  "_old_marking_cycles_started = %u "
2283                  "is inconsistent with _old_marking_cycles_completed = %u",
2284                  _old_marking_cycles_started, _old_marking_cycles_completed));
2285 
2286   _old_marking_cycles_completed += 1;
2287 
2288   // We need to clear the "in_progress" flag in the CM thread before
2289   // we wake up any waiters (especially when ExplicitInvokesConcurrent
2290   // is set) so that if a waiter requests another System.gc() it doesn't
2291   // incorrectly see that a marking cycle is still in progress.
2292   if (concurrent) {
2293     _cmThread->clear_in_progress();
2294   }
2295 
2296   // This notify_all() will ensure that a thread that called
2297   // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2298   // and it's waiting for a full GC to finish will be woken up. It is
2299   // waiting in VM_G1IncCollectionPause::doit_epilogue().
2300   FullGCCount_lock->notify_all();
2301 }
2302 
2303 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) {
2304   collector_state()->set_concurrent_cycle_started(true);
2305   _gc_timer_cm->register_gc_start(start_time);
2306 
2307   _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start());
2308   trace_heap_before_gc(_gc_tracer_cm);
2309 }
2310 
2311 void G1CollectedHeap::register_concurrent_cycle_end() {
2312   if (collector_state()->concurrent_cycle_started()) {
2313     if (_cm->has_aborted()) {
2314       _gc_tracer_cm->report_concurrent_mode_failure();
2315     }
2316 
2317     _gc_timer_cm->register_gc_end();
2318     _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
2319 
2320     // Clear state variables to prepare for the next concurrent cycle.
2321      collector_state()->set_concurrent_cycle_started(false);
2322     _heap_summary_sent = false;
2323   }
2324 }
2325 
2326 void G1CollectedHeap::trace_heap_after_concurrent_cycle() {
2327   if (collector_state()->concurrent_cycle_started()) {
2328     // This function can be called when:
2329     //  the cleanup pause is run
2330     //  the concurrent cycle is aborted before the cleanup pause.
2331     //  the concurrent cycle is aborted after the cleanup pause,
2332     //   but before the concurrent cycle end has been registered.
2333     // Make sure that we only send the heap information once.
2334     if (!_heap_summary_sent) {
2335       trace_heap_after_gc(_gc_tracer_cm);
2336       _heap_summary_sent = true;
2337     }
2338   }
2339 }
2340 
2341 G1YCType G1CollectedHeap::yc_type() {
2342   bool is_young = collector_state()->gcs_are_young();
2343   bool is_initial_mark = collector_state()->during_initial_mark_pause();
2344   bool is_during_mark = collector_state()->mark_in_progress();
2345 
2346   if (is_initial_mark) {
2347     return InitialMark;
2348   } else if (is_during_mark) {
2349     return DuringMark;
2350   } else if (is_young) {
2351     return Normal;
2352   } else {
2353     return Mixed;
2354   }
2355 }
2356 
2357 void G1CollectedHeap::collect(GCCause::Cause cause) {
2358   assert_heap_not_locked();
2359 
2360   uint gc_count_before;
2361   uint old_marking_count_before;
2362   uint full_gc_count_before;
2363   bool retry_gc;
2364 
2365   do {
2366     retry_gc = false;
2367 
2368     {
2369       MutexLocker ml(Heap_lock);
2370 
2371       // Read the GC count while holding the Heap_lock
2372       gc_count_before = total_collections();
2373       full_gc_count_before = total_full_collections();
2374       old_marking_count_before = _old_marking_cycles_started;
2375     }
2376 
2377     if (should_do_concurrent_full_gc(cause)) {
2378       // Schedule an initial-mark evacuation pause that will start a
2379       // concurrent cycle. We're setting word_size to 0 which means that
2380       // we are not requesting a post-GC allocation.
2381       VM_G1IncCollectionPause op(gc_count_before,
2382                                  0,     /* word_size */
2383                                  true,  /* should_initiate_conc_mark */
2384                                  g1_policy()->max_pause_time_ms(),
2385                                  cause);
2386       op.set_allocation_context(AllocationContext::current());
2387 
2388       VMThread::execute(&op);
2389       if (!op.pause_succeeded()) {
2390         if (old_marking_count_before == _old_marking_cycles_started) {
2391           retry_gc = op.should_retry_gc();
2392         } else {
2393           // A Full GC happened while we were trying to schedule the
2394           // initial-mark GC. No point in starting a new cycle given
2395           // that the whole heap was collected anyway.
2396         }
2397 
2398         if (retry_gc) {
2399           if (GC_locker::is_active_and_needs_gc()) {
2400             GC_locker::stall_until_clear();
2401           }
2402         }
2403       }
2404     } else {
2405       if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2406           DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2407 
2408         // Schedule a standard evacuation pause. We're setting word_size
2409         // to 0 which means that we are not requesting a post-GC allocation.
2410         VM_G1IncCollectionPause op(gc_count_before,
2411                                    0,     /* word_size */
2412                                    false, /* should_initiate_conc_mark */
2413                                    g1_policy()->max_pause_time_ms(),
2414                                    cause);
2415         VMThread::execute(&op);
2416       } else {
2417         // Schedule a Full GC.
2418         VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2419         VMThread::execute(&op);
2420       }
2421     }
2422   } while (retry_gc);
2423 }
2424 
2425 bool G1CollectedHeap::is_in(const void* p) const {
2426   if (_hrm.reserved().contains(p)) {
2427     // Given that we know that p is in the reserved space,
2428     // heap_region_containing_raw() should successfully
2429     // return the containing region.
2430     HeapRegion* hr = heap_region_containing_raw(p);
2431     return hr->is_in(p);
2432   } else {
2433     return false;
2434   }
2435 }
2436 
2437 #ifdef ASSERT
2438 bool G1CollectedHeap::is_in_exact(const void* p) const {
2439   bool contains = reserved_region().contains(p);
2440   bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2441   if (contains && available) {
2442     return true;
2443   } else {
2444     return false;
2445   }
2446 }
2447 #endif
2448 
2449 // Iteration functions.
2450 
2451 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion.
2452 
2453 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2454   ExtendedOopClosure* _cl;
2455 public:
2456   IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {}
2457   bool doHeapRegion(HeapRegion* r) {
2458     if (!r->is_continues_humongous()) {
2459       r->oop_iterate(_cl);
2460     }
2461     return false;
2462   }
2463 };
2464 
2465 // Iterates an ObjectClosure over all objects within a HeapRegion.
2466 
2467 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2468   ObjectClosure* _cl;
2469 public:
2470   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2471   bool doHeapRegion(HeapRegion* r) {
2472     if (!r->is_continues_humongous()) {
2473       r->object_iterate(_cl);
2474     }
2475     return false;
2476   }
2477 };
2478 
2479 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2480   IterateObjectClosureRegionClosure blk(cl);
2481   heap_region_iterate(&blk);
2482 }
2483 
2484 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2485   _hrm.iterate(cl);
2486 }
2487 
2488 void
2489 G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl,
2490                                          uint worker_id,
2491                                          HeapRegionClaimer *hrclaimer,
2492                                          bool concurrent) const {
2493   _hrm.par_iterate(cl, worker_id, hrclaimer, concurrent);
2494 }
2495 
2496 // Clear the cached CSet starting regions and (more importantly)
2497 // the time stamps. Called when we reset the GC time stamp.
2498 void G1CollectedHeap::clear_cset_start_regions() {
2499   assert(_worker_cset_start_region != NULL, "sanity");
2500   assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2501 
2502   int n_queues = MAX2((int)ParallelGCThreads, 1);
2503   for (int i = 0; i < n_queues; i++) {
2504     _worker_cset_start_region[i] = NULL;
2505     _worker_cset_start_region_time_stamp[i] = 0;
2506   }
2507 }
2508 
2509 // Given the id of a worker, obtain or calculate a suitable
2510 // starting region for iterating over the current collection set.
2511 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) {
2512   assert(get_gc_time_stamp() > 0, "should have been updated by now");
2513 
2514   HeapRegion* result = NULL;
2515   unsigned gc_time_stamp = get_gc_time_stamp();
2516 
2517   if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2518     // Cached starting region for current worker was set
2519     // during the current pause - so it's valid.
2520     // Note: the cached starting heap region may be NULL
2521     // (when the collection set is empty).
2522     result = _worker_cset_start_region[worker_i];
2523     assert(result == NULL || result->in_collection_set(), "sanity");
2524     return result;
2525   }
2526 
2527   // The cached entry was not valid so let's calculate
2528   // a suitable starting heap region for this worker.
2529 
2530   // We want the parallel threads to start their collection
2531   // set iteration at different collection set regions to
2532   // avoid contention.
2533   // If we have:
2534   //          n collection set regions
2535   //          p threads
2536   // Then thread t will start at region floor ((t * n) / p)
2537 
2538   result = g1_policy()->collection_set();
2539   uint cs_size = g1_policy()->cset_region_length();
2540   uint active_workers = workers()->active_workers();
2541   assert(UseDynamicNumberOfGCThreads ||
2542            active_workers == workers()->total_workers(),
2543            "Unless dynamic should use total workers");
2544 
2545   uint end_ind   = (cs_size * worker_i) / active_workers;
2546   uint start_ind = 0;
2547 
2548   if (worker_i > 0 &&
2549       _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2550     // Previous workers starting region is valid
2551     // so let's iterate from there
2552     start_ind = (cs_size * (worker_i - 1)) / active_workers;
2553     result = _worker_cset_start_region[worker_i - 1];
2554   }
2555 
2556   for (uint i = start_ind; i < end_ind; i++) {
2557     result = result->next_in_collection_set();
2558   }
2559 
2560   // Note: the calculated starting heap region may be NULL
2561   // (when the collection set is empty).
2562   assert(result == NULL || result->in_collection_set(), "sanity");
2563   assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2564          "should be updated only once per pause");
2565   _worker_cset_start_region[worker_i] = result;
2566   OrderAccess::storestore();
2567   _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2568   return result;
2569 }
2570 
2571 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2572   HeapRegion* r = g1_policy()->collection_set();
2573   while (r != NULL) {
2574     HeapRegion* next = r->next_in_collection_set();
2575     if (cl->doHeapRegion(r)) {
2576       cl->incomplete();
2577       return;
2578     }
2579     r = next;
2580   }
2581 }
2582 
2583 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2584                                                   HeapRegionClosure *cl) {
2585   if (r == NULL) {
2586     // The CSet is empty so there's nothing to do.
2587     return;
2588   }
2589 
2590   assert(r->in_collection_set(),
2591          "Start region must be a member of the collection set.");
2592   HeapRegion* cur = r;
2593   while (cur != NULL) {
2594     HeapRegion* next = cur->next_in_collection_set();
2595     if (cl->doHeapRegion(cur) && false) {
2596       cl->incomplete();
2597       return;
2598     }
2599     cur = next;
2600   }
2601   cur = g1_policy()->collection_set();
2602   while (cur != r) {
2603     HeapRegion* next = cur->next_in_collection_set();
2604     if (cl->doHeapRegion(cur) && false) {
2605       cl->incomplete();
2606       return;
2607     }
2608     cur = next;
2609   }
2610 }
2611 
2612 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const {
2613   HeapRegion* result = _hrm.next_region_in_heap(from);
2614   while (result != NULL && result->is_humongous()) {
2615     result = _hrm.next_region_in_heap(result);
2616   }
2617   return result;
2618 }
2619 
2620 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2621   HeapRegion* hr = heap_region_containing(addr);
2622   return hr->block_start(addr);
2623 }
2624 
2625 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2626   HeapRegion* hr = heap_region_containing(addr);
2627   return hr->block_size(addr);
2628 }
2629 
2630 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2631   HeapRegion* hr = heap_region_containing(addr);
2632   return hr->block_is_obj(addr);
2633 }
2634 
2635 bool G1CollectedHeap::supports_tlab_allocation() const {
2636   return true;
2637 }
2638 
2639 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2640   return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes;
2641 }
2642 
2643 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2644   return young_list()->eden_used_bytes();
2645 }
2646 
2647 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2648 // must be smaller than the humongous object limit.
2649 size_t G1CollectedHeap::max_tlab_size() const {
2650   return align_size_down(_humongous_object_threshold_in_words - 1, MinObjAlignment);
2651 }
2652 
2653 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2654   // Return the remaining space in the cur alloc region, but not less than
2655   // the min TLAB size.
2656 
2657   // Also, this value can be at most the humongous object threshold,
2658   // since we can't allow tlabs to grow big enough to accommodate
2659   // humongous objects.
2660 
2661   HeapRegion* hr = _allocator->mutator_alloc_region(AllocationContext::current())->get();
2662   size_t max_tlab = max_tlab_size() * wordSize;
2663   if (hr == NULL) {
2664     return max_tlab;
2665   } else {
2666     return MIN2(MAX2(hr->free(), (size_t) MinTLABSize), max_tlab);
2667   }
2668 }
2669 
2670 size_t G1CollectedHeap::max_capacity() const {
2671   return _hrm.reserved().byte_size();
2672 }
2673 
2674 jlong G1CollectedHeap::millis_since_last_gc() {
2675   // assert(false, "NYI");
2676   return 0;
2677 }
2678 
2679 void G1CollectedHeap::prepare_for_verify() {
2680   if (SafepointSynchronize::is_at_safepoint() || ! UseTLAB) {
2681     ensure_parsability(false);
2682   }
2683   g1_rem_set()->prepare_for_verify();
2684 }
2685 
2686 bool G1CollectedHeap::allocated_since_marking(oop obj, HeapRegion* hr,
2687                                               VerifyOption vo) {
2688   switch (vo) {
2689   case VerifyOption_G1UsePrevMarking:
2690     return hr->obj_allocated_since_prev_marking(obj);
2691   case VerifyOption_G1UseNextMarking:
2692     return hr->obj_allocated_since_next_marking(obj);
2693   case VerifyOption_G1UseMarkWord:
2694     return false;
2695   default:
2696     ShouldNotReachHere();
2697   }
2698   return false; // keep some compilers happy
2699 }
2700 
2701 HeapWord* G1CollectedHeap::top_at_mark_start(HeapRegion* hr, VerifyOption vo) {
2702   switch (vo) {
2703   case VerifyOption_G1UsePrevMarking: return hr->prev_top_at_mark_start();
2704   case VerifyOption_G1UseNextMarking: return hr->next_top_at_mark_start();
2705   case VerifyOption_G1UseMarkWord:    return NULL;
2706   default:                            ShouldNotReachHere();
2707   }
2708   return NULL; // keep some compilers happy
2709 }
2710 
2711 bool G1CollectedHeap::is_marked(oop obj, VerifyOption vo) {
2712   switch (vo) {
2713   case VerifyOption_G1UsePrevMarking: return isMarkedPrev(obj);
2714   case VerifyOption_G1UseNextMarking: return isMarkedNext(obj);
2715   case VerifyOption_G1UseMarkWord:    return obj->is_gc_marked();
2716   default:                            ShouldNotReachHere();
2717   }
2718   return false; // keep some compilers happy
2719 }
2720 
2721 const char* G1CollectedHeap::top_at_mark_start_str(VerifyOption vo) {
2722   switch (vo) {
2723   case VerifyOption_G1UsePrevMarking: return "PTAMS";
2724   case VerifyOption_G1UseNextMarking: return "NTAMS";
2725   case VerifyOption_G1UseMarkWord:    return "NONE";
2726   default:                            ShouldNotReachHere();
2727   }
2728   return NULL; // keep some compilers happy
2729 }
2730 
2731 class VerifyRootsClosure: public OopClosure {
2732 private:
2733   G1CollectedHeap* _g1h;
2734   VerifyOption     _vo;
2735   bool             _failures;
2736 public:
2737   // _vo == UsePrevMarking -> use "prev" marking information,
2738   // _vo == UseNextMarking -> use "next" marking information,
2739   // _vo == UseMarkWord    -> use mark word from object header.
2740   VerifyRootsClosure(VerifyOption vo) :
2741     _g1h(G1CollectedHeap::heap()),
2742     _vo(vo),
2743     _failures(false) { }
2744 
2745   bool failures() { return _failures; }
2746 
2747   template <class T> void do_oop_nv(T* p) {
2748     T heap_oop = oopDesc::load_heap_oop(p);
2749     if (!oopDesc::is_null(heap_oop)) {
2750       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2751       if (_g1h->is_obj_dead_cond(obj, _vo)) {
2752         gclog_or_tty->print_cr("Root location "PTR_FORMAT" "
2753                                "points to dead obj "PTR_FORMAT, p2i(p), p2i(obj));
2754         if (_vo == VerifyOption_G1UseMarkWord) {
2755           gclog_or_tty->print_cr("  Mark word: "INTPTR_FORMAT, (intptr_t)obj->mark());
2756         }
2757         obj->print_on(gclog_or_tty);
2758         _failures = true;
2759       }
2760     }
2761   }
2762 
2763   void do_oop(oop* p)       { do_oop_nv(p); }
2764   void do_oop(narrowOop* p) { do_oop_nv(p); }
2765 };
2766 
2767 class G1VerifyCodeRootOopClosure: public OopClosure {
2768   G1CollectedHeap* _g1h;
2769   OopClosure* _root_cl;
2770   nmethod* _nm;
2771   VerifyOption _vo;
2772   bool _failures;
2773 
2774   template <class T> void do_oop_work(T* p) {
2775     // First verify that this root is live
2776     _root_cl->do_oop(p);
2777 
2778     if (!G1VerifyHeapRegionCodeRoots) {
2779       // We're not verifying the code roots attached to heap region.
2780       return;
2781     }
2782 
2783     // Don't check the code roots during marking verification in a full GC
2784     if (_vo == VerifyOption_G1UseMarkWord) {
2785       return;
2786     }
2787 
2788     // Now verify that the current nmethod (which contains p) is
2789     // in the code root list of the heap region containing the
2790     // object referenced by p.
2791 
2792     T heap_oop = oopDesc::load_heap_oop(p);
2793     if (!oopDesc::is_null(heap_oop)) {
2794       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
2795 
2796       // Now fetch the region containing the object
2797       HeapRegion* hr = _g1h->heap_region_containing(obj);
2798       HeapRegionRemSet* hrrs = hr->rem_set();
2799       // Verify that the strong code root list for this region
2800       // contains the nmethod
2801       if (!hrrs->strong_code_roots_list_contains(_nm)) {
2802         gclog_or_tty->print_cr("Code root location "PTR_FORMAT" "
2803                               "from nmethod "PTR_FORMAT" not in strong "
2804                               "code roots for region ["PTR_FORMAT","PTR_FORMAT")",
2805                                p2i(p), p2i(_nm), p2i(hr->bottom()), p2i(hr->end()));
2806         _failures = true;
2807       }
2808     }
2809   }
2810 
2811 public:
2812   G1VerifyCodeRootOopClosure(G1CollectedHeap* g1h, OopClosure* root_cl, VerifyOption vo):
2813     _g1h(g1h), _root_cl(root_cl), _vo(vo), _nm(NULL), _failures(false) {}
2814 
2815   void do_oop(oop* p) { do_oop_work(p); }
2816   void do_oop(narrowOop* p) { do_oop_work(p); }
2817 
2818   void set_nmethod(nmethod* nm) { _nm = nm; }
2819   bool failures() { return _failures; }
2820 };
2821 
2822 class G1VerifyCodeRootBlobClosure: public CodeBlobClosure {
2823   G1VerifyCodeRootOopClosure* _oop_cl;
2824 
2825 public:
2826   G1VerifyCodeRootBlobClosure(G1VerifyCodeRootOopClosure* oop_cl):
2827     _oop_cl(oop_cl) {}
2828 
2829   void do_code_blob(CodeBlob* cb) {
2830     nmethod* nm = cb->as_nmethod_or_null();
2831     if (nm != NULL) {
2832       _oop_cl->set_nmethod(nm);
2833       nm->oops_do(_oop_cl);
2834     }
2835   }
2836 };
2837 
2838 class YoungRefCounterClosure : public OopClosure {
2839   G1CollectedHeap* _g1h;
2840   int              _count;
2841  public:
2842   YoungRefCounterClosure(G1CollectedHeap* g1h) : _g1h(g1h), _count(0) {}
2843   void do_oop(oop* p)       { if (_g1h->is_in_young(*p)) { _count++; } }
2844   void do_oop(narrowOop* p) { ShouldNotReachHere(); }
2845 
2846   int count() { return _count; }
2847   void reset_count() { _count = 0; };
2848 };
2849 
2850 class VerifyKlassClosure: public KlassClosure {
2851   YoungRefCounterClosure _young_ref_counter_closure;
2852   OopClosure *_oop_closure;
2853  public:
2854   VerifyKlassClosure(G1CollectedHeap* g1h, OopClosure* cl) : _young_ref_counter_closure(g1h), _oop_closure(cl) {}
2855   void do_klass(Klass* k) {
2856     k->oops_do(_oop_closure);
2857 
2858     _young_ref_counter_closure.reset_count();
2859     k->oops_do(&_young_ref_counter_closure);
2860     if (_young_ref_counter_closure.count() > 0) {
2861       guarantee(k->has_modified_oops(), err_msg("Klass " PTR_FORMAT ", has young refs but is not dirty.", p2i(k)));
2862     }
2863   }
2864 };
2865 
2866 class VerifyLivenessOopClosure: public OopClosure {
2867   G1CollectedHeap* _g1h;
2868   VerifyOption _vo;
2869 public:
2870   VerifyLivenessOopClosure(G1CollectedHeap* g1h, VerifyOption vo):
2871     _g1h(g1h), _vo(vo)
2872   { }
2873   void do_oop(narrowOop *p) { do_oop_work(p); }
2874   void do_oop(      oop *p) { do_oop_work(p); }
2875 
2876   template <class T> void do_oop_work(T *p) {
2877     oop obj = oopDesc::load_decode_heap_oop(p);
2878     guarantee(obj == NULL || !_g1h->is_obj_dead_cond(obj, _vo),
2879               "Dead object referenced by a not dead object");
2880   }
2881 };
2882 
2883 class VerifyObjsInRegionClosure: public ObjectClosure {
2884 private:
2885   G1CollectedHeap* _g1h;
2886   size_t _live_bytes;
2887   HeapRegion *_hr;
2888   VerifyOption _vo;
2889 public:
2890   // _vo == UsePrevMarking -> use "prev" marking information,
2891   // _vo == UseNextMarking -> use "next" marking information,
2892   // _vo == UseMarkWord    -> use mark word from object header.
2893   VerifyObjsInRegionClosure(HeapRegion *hr, VerifyOption vo)
2894     : _live_bytes(0), _hr(hr), _vo(vo) {
2895     _g1h = G1CollectedHeap::heap();
2896   }
2897   void do_object(oop o) {
2898     VerifyLivenessOopClosure isLive(_g1h, _vo);
2899     assert(o != NULL, "Huh?");
2900     if (!_g1h->is_obj_dead_cond(o, _vo)) {
2901       // If the object is alive according to the mark word,
2902       // then verify that the marking information agrees.
2903       // Note we can't verify the contra-positive of the
2904       // above: if the object is dead (according to the mark
2905       // word), it may not be marked, or may have been marked
2906       // but has since became dead, or may have been allocated
2907       // since the last marking.
2908       if (_vo == VerifyOption_G1UseMarkWord) {
2909         guarantee(!_g1h->is_obj_dead(o), "mark word and concurrent mark mismatch");
2910       }
2911 
2912       o->oop_iterate_no_header(&isLive);
2913       if (!_hr->obj_allocated_since_prev_marking(o)) {
2914         size_t obj_size = o->size();    // Make sure we don't overflow
2915         _live_bytes += (obj_size * HeapWordSize);
2916       }
2917     }
2918   }
2919   size_t live_bytes() { return _live_bytes; }
2920 };
2921 
2922 class VerifyRegionClosure: public HeapRegionClosure {
2923 private:
2924   bool             _par;
2925   VerifyOption     _vo;
2926   bool             _failures;
2927 public:
2928   // _vo == UsePrevMarking -> use "prev" marking information,
2929   // _vo == UseNextMarking -> use "next" marking information,
2930   // _vo == UseMarkWord    -> use mark word from object header.
2931   VerifyRegionClosure(bool par, VerifyOption vo)
2932     : _par(par),
2933       _vo(vo),
2934       _failures(false) {}
2935 
2936   bool failures() {
2937     return _failures;
2938   }
2939 
2940   bool doHeapRegion(HeapRegion* r) {
2941     if (!r->is_continues_humongous()) {
2942       bool failures = false;
2943       r->verify(_vo, &failures);
2944       if (failures) {
2945         _failures = true;
2946       } else {
2947         VerifyObjsInRegionClosure not_dead_yet_cl(r, _vo);
2948         r->object_iterate(&not_dead_yet_cl);
2949         if (_vo != VerifyOption_G1UseNextMarking) {
2950           if (r->max_live_bytes() < not_dead_yet_cl.live_bytes()) {
2951             gclog_or_tty->print_cr("["PTR_FORMAT","PTR_FORMAT"] "
2952                                    "max_live_bytes "SIZE_FORMAT" "
2953                                    "< calculated "SIZE_FORMAT,
2954                                    p2i(r->bottom()), p2i(r->end()),
2955                                    r->max_live_bytes(),
2956                                  not_dead_yet_cl.live_bytes());
2957             _failures = true;
2958           }
2959         } else {
2960           // When vo == UseNextMarking we cannot currently do a sanity
2961           // check on the live bytes as the calculation has not been
2962           // finalized yet.
2963         }
2964       }
2965     }
2966     return false; // stop the region iteration if we hit a failure
2967   }
2968 };
2969 
2970 // This is the task used for parallel verification of the heap regions
2971 
2972 class G1ParVerifyTask: public AbstractGangTask {
2973 private:
2974   G1CollectedHeap*  _g1h;
2975   VerifyOption      _vo;
2976   bool              _failures;
2977   HeapRegionClaimer _hrclaimer;
2978 
2979 public:
2980   // _vo == UsePrevMarking -> use "prev" marking information,
2981   // _vo == UseNextMarking -> use "next" marking information,
2982   // _vo == UseMarkWord    -> use mark word from object header.
2983   G1ParVerifyTask(G1CollectedHeap* g1h, VerifyOption vo) :
2984       AbstractGangTask("Parallel verify task"),
2985       _g1h(g1h),
2986       _vo(vo),
2987       _failures(false),
2988       _hrclaimer(g1h->workers()->active_workers()) {}
2989 
2990   bool failures() {
2991     return _failures;
2992   }
2993 
2994   void work(uint worker_id) {
2995     HandleMark hm;
2996     VerifyRegionClosure blk(true, _vo);
2997     _g1h->heap_region_par_iterate(&blk, worker_id, &_hrclaimer);
2998     if (blk.failures()) {
2999       _failures = true;
3000     }
3001   }
3002 };
3003 
3004 void G1CollectedHeap::verify(bool silent, VerifyOption vo) {
3005   if (SafepointSynchronize::is_at_safepoint()) {
3006     assert(Thread::current()->is_VM_thread(),
3007            "Expected to be executed serially by the VM thread at this point");
3008 
3009     if (!silent) { gclog_or_tty->print("Roots "); }
3010     VerifyRootsClosure rootsCl(vo);
3011     VerifyKlassClosure klassCl(this, &rootsCl);
3012     CLDToKlassAndOopClosure cldCl(&klassCl, &rootsCl, false);
3013 
3014     // We apply the relevant closures to all the oops in the
3015     // system dictionary, class loader data graph, the string table
3016     // and the nmethods in the code cache.
3017     G1VerifyCodeRootOopClosure codeRootsCl(this, &rootsCl, vo);
3018     G1VerifyCodeRootBlobClosure blobsCl(&codeRootsCl);
3019 
3020     {
3021       G1RootProcessor root_processor(this);
3022       root_processor.process_all_roots(&rootsCl,
3023                       &cldCl,
3024                       &blobsCl);
3025     }
3026 
3027     bool failures = rootsCl.failures() || codeRootsCl.failures();
3028 
3029     if (vo != VerifyOption_G1UseMarkWord) {
3030       // If we're verifying during a full GC then the region sets
3031       // will have been torn down at the start of the GC. Therefore
3032       // verifying the region sets will fail. So we only verify
3033       // the region sets when not in a full GC.
3034       if (!silent) { gclog_or_tty->print("HeapRegionSets "); }
3035       verify_region_sets();
3036     }
3037 
3038     if (!silent) { gclog_or_tty->print("HeapRegions "); }
3039     if (GCParallelVerificationEnabled && ParallelGCThreads > 1) {
3040 
3041       G1ParVerifyTask task(this, vo);
3042       assert(UseDynamicNumberOfGCThreads ||
3043         workers()->active_workers() == workers()->total_workers(),
3044         "If not dynamic should be using all the workers");
3045       uint n_workers = workers()->active_workers();
3046       set_par_threads(n_workers);
3047       workers()->run_task(&task);
3048       set_par_threads(0);
3049       if (task.failures()) {
3050         failures = true;
3051       }
3052 
3053     } else {
3054       VerifyRegionClosure blk(false, vo);
3055       heap_region_iterate(&blk);
3056       if (blk.failures()) {
3057         failures = true;
3058       }
3059     }
3060 
3061     if (G1StringDedup::is_enabled()) {
3062       if (!silent) gclog_or_tty->print("StrDedup ");
3063       G1StringDedup::verify();
3064     }
3065 
3066     if (failures) {
3067       gclog_or_tty->print_cr("Heap:");
3068       // It helps to have the per-region information in the output to
3069       // help us track down what went wrong. This is why we call
3070       // print_extended_on() instead of print_on().
3071       print_extended_on(gclog_or_tty);
3072       gclog_or_tty->cr();
3073       gclog_or_tty->flush();
3074     }
3075     guarantee(!failures, "there should not have been any failures");
3076   } else {
3077     if (!silent) {
3078       gclog_or_tty->print("(SKIPPING Roots, HeapRegionSets, HeapRegions, RemSet");
3079       if (G1StringDedup::is_enabled()) {
3080         gclog_or_tty->print(", StrDedup");
3081       }
3082       gclog_or_tty->print(") ");
3083     }
3084   }
3085 }
3086 
3087 void G1CollectedHeap::verify(bool silent) {
3088   verify(silent, VerifyOption_G1UsePrevMarking);
3089 }
3090 
3091 double G1CollectedHeap::verify(bool guard, const char* msg) {
3092   double verify_time_ms = 0.0;
3093 
3094   if (guard && total_collections() >= VerifyGCStartAt) {
3095     double verify_start = os::elapsedTime();
3096     HandleMark hm;  // Discard invalid handles created during verification
3097     prepare_for_verify();
3098     Universe::verify(VerifyOption_G1UsePrevMarking, msg);
3099     verify_time_ms = (os::elapsedTime() - verify_start) * 1000;
3100   }
3101 
3102   return verify_time_ms;
3103 }
3104 
3105 void G1CollectedHeap::verify_before_gc() {
3106   double verify_time_ms = verify(VerifyBeforeGC, " VerifyBeforeGC:");
3107   g1_policy()->phase_times()->record_verify_before_time_ms(verify_time_ms);
3108 }
3109 
3110 void G1CollectedHeap::verify_after_gc() {
3111   double verify_time_ms = verify(VerifyAfterGC, " VerifyAfterGC:");
3112   g1_policy()->phase_times()->record_verify_after_time_ms(verify_time_ms);
3113 }
3114 
3115 class PrintRegionClosure: public HeapRegionClosure {
3116   outputStream* _st;
3117 public:
3118   PrintRegionClosure(outputStream* st) : _st(st) {}
3119   bool doHeapRegion(HeapRegion* r) {
3120     r->print_on(_st);
3121     return false;
3122   }
3123 };
3124 
3125 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3126                                        const HeapRegion* hr,
3127                                        const VerifyOption vo) const {
3128   switch (vo) {
3129   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
3130   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
3131   case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked();
3132   default:                            ShouldNotReachHere();
3133   }
3134   return false; // keep some compilers happy
3135 }
3136 
3137 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
3138                                        const VerifyOption vo) const {
3139   switch (vo) {
3140   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
3141   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
3142   case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked();
3143   default:                            ShouldNotReachHere();
3144   }
3145   return false; // keep some compilers happy
3146 }
3147 
3148 void G1CollectedHeap::print_on(outputStream* st) const {
3149   st->print(" %-20s", "garbage-first heap");
3150   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
3151             capacity()/K, used_unlocked()/K);
3152   st->print(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")",
3153             p2i(_hrm.reserved().start()),
3154             p2i(_hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords),
3155             p2i(_hrm.reserved().end()));
3156   st->cr();
3157   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
3158   uint young_regions = _young_list->length();
3159   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
3160             (size_t) young_regions * HeapRegion::GrainBytes / K);
3161   uint survivor_regions = g1_policy()->recorded_survivor_regions();
3162   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
3163             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
3164   st->cr();
3165   MetaspaceAux::print_on(st);
3166 }
3167 
3168 void G1CollectedHeap::print_extended_on(outputStream* st) const {
3169   print_on(st);
3170 
3171   // Print the per-region information.
3172   st->cr();
3173   st->print_cr("Heap Regions: (Y=young(eden), SU=young(survivor), "
3174                "HS=humongous(starts), HC=humongous(continues), "
3175                "CS=collection set, F=free, TS=gc time stamp, "
3176                "PTAMS=previous top-at-mark-start, "
3177                "NTAMS=next top-at-mark-start)");
3178   PrintRegionClosure blk(st);
3179   heap_region_iterate(&blk);
3180 }
3181 
3182 void G1CollectedHeap::print_on_error(outputStream* st) const {
3183   this->CollectedHeap::print_on_error(st);
3184 
3185   if (_cm != NULL) {
3186     st->cr();
3187     _cm->print_on_error(st);
3188   }
3189 }
3190 
3191 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
3192   workers()->print_worker_threads_on(st);
3193   _cmThread->print_on(st);
3194   st->cr();
3195   _cm->print_worker_threads_on(st);
3196   _cg1r->print_worker_threads_on(st);
3197   if (G1StringDedup::is_enabled()) {
3198     G1StringDedup::print_worker_threads_on(st);
3199   }
3200 }
3201 
3202 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
3203   workers()->threads_do(tc);
3204   tc->do_thread(_cmThread);
3205   _cg1r->threads_do(tc);
3206   if (G1StringDedup::is_enabled()) {
3207     G1StringDedup::threads_do(tc);
3208   }
3209 }
3210 
3211 void G1CollectedHeap::print_tracing_info() const {
3212   // We'll overload this to mean "trace GC pause statistics."
3213   if (TraceYoungGenTime || TraceOldGenTime) {
3214     // The "G1CollectorPolicy" is keeping track of these stats, so delegate
3215     // to that.
3216     g1_policy()->print_tracing_info();
3217   }
3218   if (G1SummarizeRSetStats) {
3219     g1_rem_set()->print_summary_info();
3220   }
3221   if (G1SummarizeConcMark) {
3222     concurrent_mark()->print_summary_info();
3223   }
3224   g1_policy()->print_yg_surv_rate_info();
3225 }
3226 
3227 #ifndef PRODUCT
3228 // Helpful for debugging RSet issues.
3229 
3230 class PrintRSetsClosure : public HeapRegionClosure {
3231 private:
3232   const char* _msg;
3233   size_t _occupied_sum;
3234 
3235 public:
3236   bool doHeapRegion(HeapRegion* r) {
3237     HeapRegionRemSet* hrrs = r->rem_set();
3238     size_t occupied = hrrs->occupied();
3239     _occupied_sum += occupied;
3240 
3241     gclog_or_tty->print_cr("Printing RSet for region "HR_FORMAT,
3242                            HR_FORMAT_PARAMS(r));
3243     if (occupied == 0) {
3244       gclog_or_tty->print_cr("  RSet is empty");
3245     } else {
3246       hrrs->print();
3247     }
3248     gclog_or_tty->print_cr("----------");
3249     return false;
3250   }
3251 
3252   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
3253     gclog_or_tty->cr();
3254     gclog_or_tty->print_cr("========================================");
3255     gclog_or_tty->print_cr("%s", msg);
3256     gclog_or_tty->cr();
3257   }
3258 
3259   ~PrintRSetsClosure() {
3260     gclog_or_tty->print_cr("Occupied Sum: "SIZE_FORMAT, _occupied_sum);
3261     gclog_or_tty->print_cr("========================================");
3262     gclog_or_tty->cr();
3263   }
3264 };
3265 
3266 void G1CollectedHeap::print_cset_rsets() {
3267   PrintRSetsClosure cl("Printing CSet RSets");
3268   collection_set_iterate(&cl);
3269 }
3270 
3271 void G1CollectedHeap::print_all_rsets() {
3272   PrintRSetsClosure cl("Printing All RSets");;
3273   heap_region_iterate(&cl);
3274 }
3275 #endif // PRODUCT
3276 
3277 G1CollectedHeap* G1CollectedHeap::heap() {
3278   CollectedHeap* heap = Universe::heap();
3279   assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
3280   assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap");
3281   return (G1CollectedHeap*)heap;
3282 }
3283 
3284 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
3285   // always_do_update_barrier = false;
3286   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
3287   // Fill TLAB's and such
3288   accumulate_statistics_all_tlabs();
3289   ensure_parsability(true);
3290 
3291   if (G1SummarizeRSetStats && (G1SummarizeRSetStatsPeriod > 0) &&
3292       (total_collections() % G1SummarizeRSetStatsPeriod == 0)) {
3293     g1_rem_set()->print_periodic_summary_info("Before GC RS summary");
3294   }
3295 }
3296 
3297 void G1CollectedHeap::gc_epilogue(bool full) {
3298 
3299   if (G1SummarizeRSetStats &&
3300       (G1SummarizeRSetStatsPeriod > 0) &&
3301       // we are at the end of the GC. Total collections has already been increased.
3302       ((total_collections() - 1) % G1SummarizeRSetStatsPeriod == 0)) {
3303     g1_rem_set()->print_periodic_summary_info("After GC RS summary");
3304   }
3305 
3306   // FIXME: what is this about?
3307   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
3308   // is set.
3309   COMPILER2_PRESENT(assert(DerivedPointerTable::is_empty(),
3310                         "derived pointer present"));
3311   // always_do_update_barrier = true;
3312 
3313   resize_all_tlabs();
3314   allocation_context_stats().update(full);
3315 
3316   // We have just completed a GC. Update the soft reference
3317   // policy with the new heap occupancy
3318   Universe::update_heap_info_at_gc();
3319 }
3320 
3321 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
3322                                                uint gc_count_before,
3323                                                bool* succeeded,
3324                                                GCCause::Cause gc_cause) {
3325   assert_heap_not_locked_and_not_at_safepoint();
3326   g1_policy()->record_stop_world_start();
3327   VM_G1IncCollectionPause op(gc_count_before,
3328                              word_size,
3329                              false, /* should_initiate_conc_mark */
3330                              g1_policy()->max_pause_time_ms(),
3331                              gc_cause);
3332 
3333   op.set_allocation_context(AllocationContext::current());
3334   VMThread::execute(&op);
3335 
3336   HeapWord* result = op.result();
3337   bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
3338   assert(result == NULL || ret_succeeded,
3339          "the result should be NULL if the VM did not succeed");
3340   *succeeded = ret_succeeded;
3341 
3342   assert_heap_not_locked();
3343   return result;
3344 }
3345 
3346 void
3347 G1CollectedHeap::doConcurrentMark() {
3348   MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
3349   if (!_cmThread->in_progress()) {
3350     _cmThread->set_started();
3351     CGC_lock->notify();
3352   }
3353 }
3354 
3355 size_t G1CollectedHeap::pending_card_num() {
3356   size_t extra_cards = 0;
3357   JavaThread *curr = Threads::first();
3358   while (curr != NULL) {
3359     DirtyCardQueue& dcq = curr->dirty_card_queue();
3360     extra_cards += dcq.size();
3361     curr = curr->next();
3362   }
3363   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
3364   size_t buffer_size = dcqs.buffer_size();
3365   size_t buffer_num = dcqs.completed_buffers_num();
3366 
3367   // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
3368   // in bytes - not the number of 'entries'. We need to convert
3369   // into a number of cards.
3370   return (buffer_size * buffer_num + extra_cards) / oopSize;
3371 }
3372 
3373 size_t G1CollectedHeap::cards_scanned() {
3374   return g1_rem_set()->cardsScanned();
3375 }
3376 
3377 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
3378  private:
3379   size_t _total_humongous;
3380   size_t _candidate_humongous;
3381 
3382   DirtyCardQueue _dcq;
3383 
3384   // We don't nominate objects with many remembered set entries, on
3385   // the assumption that such objects are likely still live.
3386   bool is_remset_small(HeapRegion* region) const {
3387     HeapRegionRemSet* const rset = region->rem_set();
3388     return G1EagerReclaimHumongousObjectsWithStaleRefs
3389       ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries)
3390       : rset->is_empty();
3391   }
3392 
3393   bool is_typeArray_region(HeapRegion* region) const {
3394     return oop(region->bottom())->is_typeArray();
3395   }
3396 
3397   bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const {
3398     assert(region->is_starts_humongous(), "Must start a humongous object");
3399 
3400     // Candidate selection must satisfy the following constraints
3401     // while concurrent marking is in progress:
3402     //
3403     // * In order to maintain SATB invariants, an object must not be
3404     // reclaimed if it was allocated before the start of marking and
3405     // has not had its references scanned.  Such an object must have
3406     // its references (including type metadata) scanned to ensure no
3407     // live objects are missed by the marking process.  Objects
3408     // allocated after the start of concurrent marking don't need to
3409     // be scanned.
3410     //
3411     // * An object must not be reclaimed if it is on the concurrent
3412     // mark stack.  Objects allocated after the start of concurrent
3413     // marking are never pushed on the mark stack.
3414     //
3415     // Nominating only objects allocated after the start of concurrent
3416     // marking is sufficient to meet both constraints.  This may miss
3417     // some objects that satisfy the constraints, but the marking data
3418     // structures don't support efficiently performing the needed
3419     // additional tests or scrubbing of the mark stack.
3420     //
3421     // However, we presently only nominate is_typeArray() objects.
3422     // A humongous object containing references induces remembered
3423     // set entries on other regions.  In order to reclaim such an
3424     // object, those remembered sets would need to be cleaned up.
3425     //
3426     // We also treat is_typeArray() objects specially, allowing them
3427     // to be reclaimed even if allocated before the start of
3428     // concurrent mark.  For this we rely on mark stack insertion to
3429     // exclude is_typeArray() objects, preventing reclaiming an object
3430     // that is in the mark stack.  We also rely on the metadata for
3431     // such objects to be built-in and so ensured to be kept live.
3432     // Frequent allocation and drop of large binary blobs is an
3433     // important use case for eager reclaim, and this special handling
3434     // may reduce needed headroom.
3435 
3436     return is_typeArray_region(region) && is_remset_small(region);
3437   }
3438 
3439  public:
3440   RegisterHumongousWithInCSetFastTestClosure()
3441   : _total_humongous(0),
3442     _candidate_humongous(0),
3443     _dcq(&JavaThread::dirty_card_queue_set()) {
3444   }
3445 
3446   virtual bool doHeapRegion(HeapRegion* r) {
3447     if (!r->is_starts_humongous()) {
3448       return false;
3449     }
3450     G1CollectedHeap* g1h = G1CollectedHeap::heap();
3451 
3452     bool is_candidate = humongous_region_is_candidate(g1h, r);
3453     uint rindex = r->hrm_index();
3454     g1h->set_humongous_reclaim_candidate(rindex, is_candidate);
3455     if (is_candidate) {
3456       _candidate_humongous++;
3457       g1h->register_humongous_region_with_cset(rindex);
3458     // Is_candidate already filters out humongous object with large remembered sets.
3459     // If we have a humongous object with a few remembered sets, we simply flush these
3460     // remembered set entries into the DCQS. That will result in automatic
3461     // re-evaluation of their remembered set entries during the following evacuation
3462     // phase.
3463       if (!r->rem_set()->is_empty()) {
3464         guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
3465                   "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
3466         G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set();
3467         HeapRegionRemSetIterator hrrs(r->rem_set());
3468         size_t card_index;
3469         while (hrrs.has_next(card_index)) {
3470           jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index);
3471           // The remembered set might contain references to already freed
3472           // regions. Filter out such entries to avoid failing card table
3473           // verification.
3474           if (!g1h->heap_region_containing(bs->addr_for(card_ptr))->is_free()) {
3475           if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
3476             *card_ptr = CardTableModRefBS::dirty_card_val();
3477             _dcq.enqueue(card_ptr);
3478           }
3479         }
3480         }
3481         r->rem_set()->clear_locked();
3482       }
3483       assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
3484     }
3485     _total_humongous++;
3486 
3487     return false;
3488   }
3489 
3490   size_t total_humongous() const { return _total_humongous; }
3491   size_t candidate_humongous() const { return _candidate_humongous; }
3492 
3493   void flush_rem_set_entries() { _dcq.flush(); }
3494 };
3495 
3496 void G1CollectedHeap::register_humongous_regions_with_cset() {
3497   if (!G1EagerReclaimHumongousObjects) {
3498     g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
3499     return;
3500   }
3501   double time = os::elapsed_counter();
3502 
3503   // Collect reclaim candidate information and register candidates with cset.
3504   RegisterHumongousWithInCSetFastTestClosure cl;
3505   heap_region_iterate(&cl);
3506 
3507   time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
3508   g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
3509                                                                   cl.total_humongous(),
3510                                                                   cl.candidate_humongous());
3511   _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
3512 
3513   // Finally flush all remembered set entries to re-check into the global DCQS.
3514   cl.flush_rem_set_entries();
3515 }
3516 
3517 void
3518 G1CollectedHeap::setup_surviving_young_words() {
3519   assert(_surviving_young_words == NULL, "pre-condition");
3520   uint array_length = g1_policy()->young_cset_region_length();
3521   _surviving_young_words = NEW_C_HEAP_ARRAY(size_t, (size_t) array_length, mtGC);
3522   if (_surviving_young_words == NULL) {
3523     vm_exit_out_of_memory(sizeof(size_t) * array_length, OOM_MALLOC_ERROR,
3524                           "Not enough space for young surv words summary.");
3525   }
3526   memset(_surviving_young_words, 0, (size_t) array_length * sizeof(size_t));
3527 #ifdef ASSERT
3528   for (uint i = 0;  i < array_length; ++i) {
3529     assert( _surviving_young_words[i] == 0, "memset above" );
3530   }
3531 #endif // !ASSERT
3532 }
3533 
3534 void
3535 G1CollectedHeap::update_surviving_young_words(size_t* surv_young_words) {
3536   MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3537   uint array_length = g1_policy()->young_cset_region_length();
3538   for (uint i = 0; i < array_length; ++i) {
3539     _surviving_young_words[i] += surv_young_words[i];
3540   }
3541 }
3542 
3543 void
3544 G1CollectedHeap::cleanup_surviving_young_words() {
3545   guarantee( _surviving_young_words != NULL, "pre-condition" );
3546   FREE_C_HEAP_ARRAY(size_t, _surviving_young_words);
3547   _surviving_young_words = NULL;
3548 }
3549 
3550 #ifdef ASSERT
3551 class VerifyCSetClosure: public HeapRegionClosure {
3552 public:
3553   bool doHeapRegion(HeapRegion* hr) {
3554     // Here we check that the CSet region's RSet is ready for parallel
3555     // iteration. The fields that we'll verify are only manipulated
3556     // when the region is part of a CSet and is collected. Afterwards,
3557     // we reset these fields when we clear the region's RSet (when the
3558     // region is freed) so they are ready when the region is
3559     // re-allocated. The only exception to this is if there's an
3560     // evacuation failure and instead of freeing the region we leave
3561     // it in the heap. In that case, we reset these fields during
3562     // evacuation failure handling.
3563     guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3564 
3565     // Here's a good place to add any other checks we'd like to
3566     // perform on CSet regions.
3567     return false;
3568   }
3569 };
3570 #endif // ASSERT
3571 
3572 #if TASKQUEUE_STATS
3573 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3574   st->print_raw_cr("GC Task Stats");
3575   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3576   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3577 }
3578 
3579 void G1CollectedHeap::print_taskqueue_stats(outputStream* const st) const {
3580   print_taskqueue_stats_hdr(st);
3581 
3582   TaskQueueStats totals;
3583   const uint n = workers()->total_workers();
3584   for (uint i = 0; i < n; ++i) {
3585     st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
3586     totals += task_queue(i)->stats;
3587   }
3588   st->print_raw("tot "); totals.print(st); st->cr();
3589 
3590   DEBUG_ONLY(totals.verify());
3591 }
3592 
3593 void G1CollectedHeap::reset_taskqueue_stats() {
3594   const uint n = workers()->total_workers();
3595   for (uint i = 0; i < n; ++i) {
3596     task_queue(i)->stats.reset();
3597   }
3598 }
3599 #endif // TASKQUEUE_STATS
3600 
3601 void G1CollectedHeap::log_gc_header() {
3602   if (!G1Log::fine()) {
3603     return;
3604   }
3605 
3606   gclog_or_tty->gclog_stamp(_gc_tracer_stw->gc_id());
3607 
3608   GCCauseString gc_cause_str = GCCauseString("GC pause", gc_cause())
3609     .append(collector_state()->gcs_are_young() ? "(young)" : "(mixed)")
3610     .append(collector_state()->during_initial_mark_pause() ? " (initial-mark)" : "");
3611 
3612   gclog_or_tty->print("[%s", (const char*)gc_cause_str);
3613 }
3614 
3615 void G1CollectedHeap::log_gc_footer(double pause_time_sec) {
3616   if (!G1Log::fine()) {
3617     return;
3618   }
3619 
3620   if (G1Log::finer()) {
3621     if (evacuation_failed()) {
3622       gclog_or_tty->print(" (to-space exhausted)");
3623     }
3624     gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3625     g1_policy()->phase_times()->note_gc_end();
3626     g1_policy()->phase_times()->print(pause_time_sec);
3627     g1_policy()->print_detailed_heap_transition();
3628   } else {
3629     if (evacuation_failed()) {
3630       gclog_or_tty->print("--");
3631     }
3632     g1_policy()->print_heap_transition();
3633     gclog_or_tty->print_cr(", %3.7f secs]", pause_time_sec);
3634   }
3635   gclog_or_tty->flush();
3636 }
3637 
3638 bool
3639 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3640   assert_at_safepoint(true /* should_be_vm_thread */);
3641   guarantee(!is_gc_active(), "collection is not reentrant");
3642 
3643   if (GC_locker::check_active_before_gc()) {
3644     return false;
3645   }
3646 
3647   _gc_timer_stw->register_gc_start();
3648 
3649   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3650 
3651   SvcGCMarker sgcm(SvcGCMarker::MINOR);
3652   ResourceMark rm;
3653 
3654   G1Log::update_level();
3655   print_heap_before_gc();
3656   trace_heap_before_gc(_gc_tracer_stw);
3657 
3658   verify_region_sets_optional();
3659   verify_dirty_young_regions();
3660 
3661   // This call will decide whether this pause is an initial-mark
3662   // pause. If it is, during_initial_mark_pause() will return true
3663   // for the duration of this pause.
3664   g1_policy()->decide_on_conc_mark_initiation();
3665 
3666   // We do not allow initial-mark to be piggy-backed on a mixed GC.
3667   assert(!collector_state()->during_initial_mark_pause() ||
3668           collector_state()->gcs_are_young(), "sanity");
3669 
3670   // We also do not allow mixed GCs during marking.
3671   assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity");
3672 
3673   // Record whether this pause is an initial mark. When the current
3674   // thread has completed its logging output and it's safe to signal
3675   // the CM thread, the flag's value in the policy has been reset.
3676   bool should_start_conc_mark = collector_state()->during_initial_mark_pause();
3677 
3678   // Inner scope for scope based logging, timers, and stats collection
3679   {
3680     EvacuationInfo evacuation_info;
3681 
3682     if (collector_state()->during_initial_mark_pause()) {
3683       // We are about to start a marking cycle, so we increment the
3684       // full collection counter.
3685       increment_old_marking_cycles_started();
3686       register_concurrent_cycle_start(_gc_timer_stw->gc_start());
3687     }
3688 
3689     _gc_tracer_stw->report_yc_type(yc_type());
3690 
3691     TraceCPUTime tcpu(G1Log::finer(), true, gclog_or_tty);
3692 
3693     uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
3694                                                                   workers()->active_workers(),
3695                                                                   Threads::number_of_non_daemon_threads());
3696     assert(UseDynamicNumberOfGCThreads ||
3697            active_workers == workers()->total_workers(),
3698            "If not dynamic should be using all the  workers");
3699     workers()->set_active_workers(active_workers);
3700 
3701     double pause_start_sec = os::elapsedTime();
3702     g1_policy()->phase_times()->note_gc_start(active_workers, collector_state()->mark_in_progress());
3703     log_gc_header();
3704 
3705     TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3706     TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3707 
3708     // If the secondary_free_list is not empty, append it to the
3709     // free_list. No need to wait for the cleanup operation to finish;
3710     // the region allocation code will check the secondary_free_list
3711     // and wait if necessary. If the G1StressConcRegionFreeing flag is
3712     // set, skip this step so that the region allocation code has to
3713     // get entries from the secondary_free_list.
3714     if (!G1StressConcRegionFreeing) {
3715       append_secondary_free_list_if_not_empty_with_lock();
3716     }
3717 
3718     assert(check_young_list_well_formed(), "young list should be well formed");
3719 
3720     // Don't dynamically change the number of GC threads this early.  A value of
3721     // 0 is used to indicate serial work.  When parallel work is done,
3722     // it will be set.
3723 
3724     { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3725       IsGCActiveMark x;
3726 
3727       gc_prologue(false);
3728       increment_total_collections(false /* full gc */);
3729       increment_gc_time_stamp();
3730 
3731       verify_before_gc();
3732 
3733       check_bitmaps("GC Start");
3734 
3735       COMPILER2_PRESENT(DerivedPointerTable::clear());
3736 
3737       // Please see comment in g1CollectedHeap.hpp and
3738       // G1CollectedHeap::ref_processing_init() to see how
3739       // reference processing currently works in G1.
3740 
3741       // Enable discovery in the STW reference processor
3742       ref_processor_stw()->enable_discovery();
3743 
3744       {
3745         // We want to temporarily turn off discovery by the
3746         // CM ref processor, if necessary, and turn it back on
3747         // on again later if we do. Using a scoped
3748         // NoRefDiscovery object will do this.
3749         NoRefDiscovery no_cm_discovery(ref_processor_cm());
3750 
3751         // Forget the current alloc region (we might even choose it to be part
3752         // of the collection set!).
3753         _allocator->release_mutator_alloc_region();
3754 
3755         // We should call this after we retire the mutator alloc
3756         // region(s) so that all the ALLOC / RETIRE events are generated
3757         // before the start GC event.
3758         _hr_printer.start_gc(false /* full */, (size_t) total_collections());
3759 
3760         // This timing is only used by the ergonomics to handle our pause target.
3761         // It is unclear why this should not include the full pause. We will
3762         // investigate this in CR 7178365.
3763         //
3764         // Preserving the old comment here if that helps the investigation:
3765         //
3766         // The elapsed time induced by the start time below deliberately elides
3767         // the possible verification above.
3768         double sample_start_time_sec = os::elapsedTime();
3769 
3770 #if YOUNG_LIST_VERBOSE
3771         gclog_or_tty->print_cr("\nBefore recording pause start.\nYoung_list:");
3772         _young_list->print();
3773         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3774 #endif // YOUNG_LIST_VERBOSE
3775 
3776         g1_policy()->record_collection_pause_start(sample_start_time_sec);
3777 
3778         double scan_wait_start = os::elapsedTime();
3779         // We have to wait until the CM threads finish scanning the
3780         // root regions as it's the only way to ensure that all the
3781         // objects on them have been correctly scanned before we start
3782         // moving them during the GC.
3783         bool waited = _cm->root_regions()->wait_until_scan_finished();
3784         double wait_time_ms = 0.0;
3785         if (waited) {
3786           double scan_wait_end = os::elapsedTime();
3787           wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
3788         }
3789         g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
3790 
3791 #if YOUNG_LIST_VERBOSE
3792         gclog_or_tty->print_cr("\nAfter recording pause start.\nYoung_list:");
3793         _young_list->print();
3794 #endif // YOUNG_LIST_VERBOSE
3795 
3796         if (collector_state()->during_initial_mark_pause()) {
3797           concurrent_mark()->checkpointRootsInitialPre();
3798         }
3799 
3800 #if YOUNG_LIST_VERBOSE
3801         gclog_or_tty->print_cr("\nBefore choosing collection set.\nYoung_list:");
3802         _young_list->print();
3803         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3804 #endif // YOUNG_LIST_VERBOSE
3805 
3806         g1_policy()->finalize_cset(target_pause_time_ms, evacuation_info);
3807 
3808         register_humongous_regions_with_cset();
3809 
3810         assert(check_cset_fast_test(), "Inconsistency in the InCSetState table.");
3811 
3812         _cm->note_start_of_gc();
3813         // We call this after finalize_cset() to
3814         // ensure that the CSet has been finalized.
3815         _cm->verify_no_cset_oops();
3816 
3817         if (_hr_printer.is_active()) {
3818           HeapRegion* hr = g1_policy()->collection_set();
3819           while (hr != NULL) {
3820             _hr_printer.cset(hr);
3821             hr = hr->next_in_collection_set();
3822           }
3823         }
3824 
3825 #ifdef ASSERT
3826         VerifyCSetClosure cl;
3827         collection_set_iterate(&cl);
3828 #endif // ASSERT
3829 
3830         setup_surviving_young_words();
3831 
3832         // Initialize the GC alloc regions.
3833         _allocator->init_gc_alloc_regions(evacuation_info);
3834 
3835         // Actually do the work...
3836         evacuate_collection_set(evacuation_info);
3837 
3838         free_collection_set(g1_policy()->collection_set(), evacuation_info);
3839 
3840         eagerly_reclaim_humongous_regions();
3841 
3842         g1_policy()->clear_collection_set();
3843 
3844         cleanup_surviving_young_words();
3845 
3846         // Start a new incremental collection set for the next pause.
3847         g1_policy()->start_incremental_cset_building();
3848 
3849         clear_cset_fast_test();
3850 
3851         _young_list->reset_sampled_info();
3852 
3853         // Don't check the whole heap at this point as the
3854         // GC alloc regions from this pause have been tagged
3855         // as survivors and moved on to the survivor list.
3856         // Survivor regions will fail the !is_young() check.
3857         assert(check_young_list_empty(false /* check_heap */),
3858           "young list should be empty");
3859 
3860 #if YOUNG_LIST_VERBOSE
3861         gclog_or_tty->print_cr("Before recording survivors.\nYoung List:");
3862         _young_list->print();
3863 #endif // YOUNG_LIST_VERBOSE
3864 
3865         g1_policy()->record_survivor_regions(_young_list->survivor_length(),
3866                                              _young_list->first_survivor_region(),
3867                                              _young_list->last_survivor_region());
3868 
3869         _young_list->reset_auxilary_lists();
3870 
3871         if (evacuation_failed()) {
3872           _allocator->set_used(recalculate_used());
3873           uint n_queues = MAX2((int)ParallelGCThreads, 1);
3874           for (uint i = 0; i < n_queues; i++) {
3875             if (_evacuation_failed_info_array[i].has_failed()) {
3876               _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
3877             }
3878           }
3879         } else {
3880           // The "used" of the the collection set have already been subtracted
3881           // when they were freed.  Add in the bytes evacuated.
3882           _allocator->increase_used(g1_policy()->bytes_copied_during_gc());
3883         }
3884 
3885         if (collector_state()->during_initial_mark_pause()) {
3886           // We have to do this before we notify the CM threads that
3887           // they can start working to make sure that all the
3888           // appropriate initialization is done on the CM object.
3889           concurrent_mark()->checkpointRootsInitialPost();
3890           collector_state()->set_mark_in_progress(true);
3891           // Note that we don't actually trigger the CM thread at
3892           // this point. We do that later when we're sure that
3893           // the current thread has completed its logging output.
3894         }
3895 
3896         allocate_dummy_regions();
3897 
3898 #if YOUNG_LIST_VERBOSE
3899         gclog_or_tty->print_cr("\nEnd of the pause.\nYoung_list:");
3900         _young_list->print();
3901         g1_policy()->print_collection_set(g1_policy()->inc_cset_head(), gclog_or_tty);
3902 #endif // YOUNG_LIST_VERBOSE
3903 
3904         _allocator->init_mutator_alloc_region();
3905 
3906         {
3907           size_t expand_bytes = g1_policy()->expansion_amount();
3908           if (expand_bytes > 0) {
3909             size_t bytes_before = capacity();
3910             // No need for an ergo verbose message here,
3911             // expansion_amount() does this when it returns a value > 0.
3912             if (!expand(expand_bytes)) {
3913               // We failed to expand the heap. Cannot do anything about it.
3914             }
3915           }
3916         }
3917 
3918         // We redo the verification but now wrt to the new CSet which
3919         // has just got initialized after the previous CSet was freed.
3920         _cm->verify_no_cset_oops();
3921         _cm->note_end_of_gc();
3922 
3923         // This timing is only used by the ergonomics to handle our pause target.
3924         // It is unclear why this should not include the full pause. We will
3925         // investigate this in CR 7178365.
3926         double sample_end_time_sec = os::elapsedTime();
3927         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3928         g1_policy()->record_collection_pause_end(pause_time_ms, evacuation_info);
3929 
3930         MemoryService::track_memory_usage();
3931 
3932         // In prepare_for_verify() below we'll need to scan the deferred
3933         // update buffers to bring the RSets up-to-date if
3934         // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
3935         // the update buffers we'll probably need to scan cards on the
3936         // regions we just allocated to (i.e., the GC alloc
3937         // regions). However, during the last GC we called
3938         // set_saved_mark() on all the GC alloc regions, so card
3939         // scanning might skip the [saved_mark_word()...top()] area of
3940         // those regions (i.e., the area we allocated objects into
3941         // during the last GC). But it shouldn't. Given that
3942         // saved_mark_word() is conditional on whether the GC time stamp
3943         // on the region is current or not, by incrementing the GC time
3944         // stamp here we invalidate all the GC time stamps on all the
3945         // regions and saved_mark_word() will simply return top() for
3946         // all the regions. This is a nicer way of ensuring this rather
3947         // than iterating over the regions and fixing them. In fact, the
3948         // GC time stamp increment here also ensures that
3949         // saved_mark_word() will return top() between pauses, i.e.,
3950         // during concurrent refinement. So we don't need the
3951         // is_gc_active() check to decided which top to use when
3952         // scanning cards (see CR 7039627).
3953         increment_gc_time_stamp();
3954 
3955         verify_after_gc();
3956         check_bitmaps("GC End");
3957 
3958         assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
3959         ref_processor_stw()->verify_no_references_recorded();
3960 
3961         // CM reference discovery will be re-enabled if necessary.
3962       }
3963 
3964       // We should do this after we potentially expand the heap so
3965       // that all the COMMIT events are generated before the end GC
3966       // event, and after we retire the GC alloc regions so that all
3967       // RETIRE events are generated before the end GC event.
3968       _hr_printer.end_gc(false /* full */, (size_t) total_collections());
3969 
3970 #ifdef TRACESPINNING
3971       ParallelTaskTerminator::print_termination_counts();
3972 #endif
3973 
3974       gc_epilogue(false);
3975     }
3976 
3977     // Print the remainder of the GC log output.
3978     log_gc_footer(os::elapsedTime() - pause_start_sec);
3979 
3980     // It is not yet to safe to tell the concurrent mark to
3981     // start as we have some optional output below. We don't want the
3982     // output from the concurrent mark thread interfering with this
3983     // logging output either.
3984 
3985     _hrm.verify_optional();
3986     verify_region_sets_optional();
3987 
3988     TASKQUEUE_STATS_ONLY(if (PrintTaskqueue) print_taskqueue_stats());
3989     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3990 
3991     print_heap_after_gc();
3992     trace_heap_after_gc(_gc_tracer_stw);
3993 
3994     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3995     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3996     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3997     // before any GC notifications are raised.
3998     g1mm()->update_sizes();
3999 
4000     _gc_tracer_stw->report_evacuation_info(&evacuation_info);
4001     _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
4002     _gc_timer_stw->register_gc_end();
4003     _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
4004   }
4005   // It should now be safe to tell the concurrent mark thread to start
4006   // without its logging output interfering with the logging output
4007   // that came from the pause.
4008 
4009   if (should_start_conc_mark) {
4010     // CAUTION: after the doConcurrentMark() call below,
4011     // the concurrent marking thread(s) could be running
4012     // concurrently with us. Make sure that anything after
4013     // this point does not assume that we are the only GC thread
4014     // running. Note: of course, the actual marking work will
4015     // not start until the safepoint itself is released in
4016     // SuspendibleThreadSet::desynchronize().
4017     doConcurrentMark();
4018   }
4019 
4020   return true;
4021 }
4022 
4023 void G1CollectedHeap::init_for_evac_failure(OopsInHeapRegionClosure* cl) {
4024   _drain_in_progress = false;
4025   set_evac_failure_closure(cl);
4026   _evac_failure_scan_stack = new (ResourceObj::C_HEAP, mtGC) GrowableArray<oop>(40, true);
4027 }
4028 
4029 void G1CollectedHeap::finalize_for_evac_failure() {
4030   assert(_evac_failure_scan_stack != NULL &&
4031          _evac_failure_scan_stack->length() == 0,
4032          "Postcondition");
4033   assert(!_drain_in_progress, "Postcondition");
4034   delete _evac_failure_scan_stack;
4035   _evac_failure_scan_stack = NULL;
4036 }
4037 
4038 void G1CollectedHeap::remove_self_forwarding_pointers() {
4039   double remove_self_forwards_start = os::elapsedTime();
4040 
4041   set_par_threads();
4042   G1ParRemoveSelfForwardPtrsTask rsfp_task(this);
4043   workers()->run_task(&rsfp_task);
4044   set_par_threads(0);
4045 
4046   // Now restore saved marks, if any.
4047   assert(_objs_with_preserved_marks.size() ==
4048             _preserved_marks_of_objs.size(), "Both or none.");
4049   while (!_objs_with_preserved_marks.is_empty()) {
4050     oop obj = _objs_with_preserved_marks.pop();
4051     markOop m = _preserved_marks_of_objs.pop();
4052     obj->set_mark(m);
4053   }
4054   _objs_with_preserved_marks.clear(true);
4055   _preserved_marks_of_objs.clear(true);
4056 
4057   g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
4058 }
4059 
4060 void G1CollectedHeap::push_on_evac_failure_scan_stack(oop obj) {
4061   _evac_failure_scan_stack->push(obj);
4062 }
4063 
4064 void G1CollectedHeap::drain_evac_failure_scan_stack() {
4065   assert(_evac_failure_scan_stack != NULL, "precondition");
4066 
4067   while (_evac_failure_scan_stack->length() > 0) {
4068      oop obj = _evac_failure_scan_stack->pop();
4069      _evac_failure_closure->set_region(heap_region_containing(obj));
4070      obj->oop_iterate_backwards(_evac_failure_closure);
4071   }
4072 }
4073 
4074 oop
4075 G1CollectedHeap::handle_evacuation_failure_par(G1ParScanThreadState* _par_scan_state,
4076                                                oop old) {
4077   assert(obj_in_cs(old),
4078          err_msg("obj: "PTR_FORMAT" should still be in the CSet",
4079                  p2i(old)));
4080   markOop m = old->mark();
4081   oop forward_ptr = old->forward_to_atomic(old);
4082   if (forward_ptr == NULL) {
4083     // Forward-to-self succeeded.
4084     assert(_par_scan_state != NULL, "par scan state");
4085     OopsInHeapRegionClosure* cl = _par_scan_state->evac_failure_closure();
4086     uint queue_num = _par_scan_state->queue_num();
4087 
4088     _evacuation_failed = true;
4089     _evacuation_failed_info_array[queue_num].register_copy_failure(old->size());
4090     if (_evac_failure_closure != cl) {
4091       MutexLockerEx x(EvacFailureStack_lock, Mutex::_no_safepoint_check_flag);
4092       assert(!_drain_in_progress,
4093              "Should only be true while someone holds the lock.");
4094       // Set the global evac-failure closure to the current thread's.
4095       assert(_evac_failure_closure == NULL, "Or locking has failed.");
4096       set_evac_failure_closure(cl);
4097       // Now do the common part.
4098       handle_evacuation_failure_common(old, m);
4099       // Reset to NULL.
4100       set_evac_failure_closure(NULL);
4101     } else {
4102       // The lock is already held, and this is recursive.
4103       assert(_drain_in_progress, "This should only be the recursive case.");
4104       handle_evacuation_failure_common(old, m);
4105     }
4106     return old;
4107   } else {
4108     // Forward-to-self failed. Either someone else managed to allocate
4109     // space for this object (old != forward_ptr) or they beat us in
4110     // self-forwarding it (old == forward_ptr).
4111     assert(old == forward_ptr || !obj_in_cs(forward_ptr),
4112            err_msg("obj: "PTR_FORMAT" forwarded to: "PTR_FORMAT" "
4113                    "should not be in the CSet",
4114                    p2i(old), p2i(forward_ptr)));
4115     return forward_ptr;
4116   }
4117 }
4118 
4119 void G1CollectedHeap::handle_evacuation_failure_common(oop old, markOop m) {
4120   preserve_mark_if_necessary(old, m);
4121 
4122   HeapRegion* r = heap_region_containing(old);
4123   if (!r->evacuation_failed()) {
4124     r->set_evacuation_failed(true);
4125     _hr_printer.evac_failure(r);
4126   }
4127 
4128   push_on_evac_failure_scan_stack(old);
4129 
4130   if (!_drain_in_progress) {
4131     // prevent recursion in copy_to_survivor_space()
4132     _drain_in_progress = true;
4133     drain_evac_failure_scan_stack();
4134     _drain_in_progress = false;
4135   }
4136 }
4137 
4138 void G1CollectedHeap::preserve_mark_if_necessary(oop obj, markOop m) {
4139   assert(evacuation_failed(), "Oversaving!");
4140   // We want to call the "for_promotion_failure" version only in the
4141   // case of a promotion failure.
4142   if (m->must_be_preserved_for_promotion_failure(obj)) {
4143     _objs_with_preserved_marks.push(obj);
4144     _preserved_marks_of_objs.push(m);
4145   }
4146 }
4147 
4148 void G1ParCopyHelper::mark_object(oop obj) {
4149   assert(!_g1->heap_region_containing(obj)->in_collection_set(), "should not mark objects in the CSet");
4150 
4151   // We know that the object is not moving so it's safe to read its size.
4152   _cm->grayRoot(obj, (size_t) obj->size(), _worker_id);
4153 }
4154 
4155 void G1ParCopyHelper::mark_forwarded_object(oop from_obj, oop to_obj) {
4156   assert(from_obj->is_forwarded(), "from obj should be forwarded");
4157   assert(from_obj->forwardee() == to_obj, "to obj should be the forwardee");
4158   assert(from_obj != to_obj, "should not be self-forwarded");
4159 
4160   assert(_g1->heap_region_containing(from_obj)->in_collection_set(), "from obj should be in the CSet");
4161   assert(!_g1->heap_region_containing(to_obj)->in_collection_set(), "should not mark objects in the CSet");
4162 
4163   // The object might be in the process of being copied by another
4164   // worker so we cannot trust that its to-space image is
4165   // well-formed. So we have to read its size from its from-space
4166   // image which we know should not be changing.
4167   _cm->grayRoot(to_obj, (size_t) from_obj->size(), _worker_id);
4168 }
4169 
4170 template <class T>
4171 void G1ParCopyHelper::do_klass_barrier(T* p, oop new_obj) {
4172   if (_g1->heap_region_containing_raw(new_obj)->is_young()) {
4173     _scanned_klass->record_modified_oops();
4174   }
4175 }
4176 
4177 template <G1Barrier barrier, G1Mark do_mark_object>
4178 template <class T>
4179 void G1ParCopyClosure<barrier, do_mark_object>::do_oop_work(T* p) {
4180   T heap_oop = oopDesc::load_heap_oop(p);
4181 
4182   if (oopDesc::is_null(heap_oop)) {
4183     return;
4184   }
4185 
4186   oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
4187 
4188   assert(_worker_id == _par_scan_state->queue_num(), "sanity");
4189 
4190   const InCSetState state = _g1->in_cset_state(obj);
4191   if (state.is_in_cset()) {
4192     oop forwardee;
4193     markOop m = obj->mark();
4194     if (m->is_marked()) {
4195       forwardee = (oop) m->decode_pointer();
4196     } else {
4197       forwardee = _par_scan_state->copy_to_survivor_space(state, obj, m);
4198     }
4199     assert(forwardee != NULL, "forwardee should not be NULL");
4200     oopDesc::encode_store_heap_oop(p, forwardee);
4201     if (do_mark_object != G1MarkNone && forwardee != obj) {
4202       // If the object is self-forwarded we don't need to explicitly
4203       // mark it, the evacuation failure protocol will do so.
4204       mark_forwarded_object(obj, forwardee);
4205     }
4206 
4207     if (barrier == G1BarrierKlass) {
4208       do_klass_barrier(p, forwardee);
4209     }
4210   } else {
4211     if (state.is_humongous()) {
4212       _g1->set_humongous_is_live(obj);
4213     }
4214     // The object is not in collection set. If we're a root scanning
4215     // closure during an initial mark pause then attempt to mark the object.
4216     if (do_mark_object == G1MarkFromRoot) {
4217       mark_object(obj);
4218     }
4219   }
4220 
4221   if (barrier == G1BarrierEvac) {
4222     _par_scan_state->update_rs(_from, p, _worker_id);
4223   }
4224 }
4225 
4226 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(oop* p);
4227 template void G1ParCopyClosure<G1BarrierEvac, G1MarkNone>::do_oop_work(narrowOop* p);
4228 
4229 class G1ParEvacuateFollowersClosure : public VoidClosure {
4230 protected:
4231   G1CollectedHeap*              _g1h;
4232   G1ParScanThreadState*         _par_scan_state;
4233   RefToScanQueueSet*            _queues;
4234   ParallelTaskTerminator*       _terminator;
4235 
4236   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
4237   RefToScanQueueSet*      queues()         { return _queues; }
4238   ParallelTaskTerminator* terminator()     { return _terminator; }
4239 
4240 public:
4241   G1ParEvacuateFollowersClosure(G1CollectedHeap* g1h,
4242                                 G1ParScanThreadState* par_scan_state,
4243                                 RefToScanQueueSet* queues,
4244                                 ParallelTaskTerminator* terminator)
4245     : _g1h(g1h), _par_scan_state(par_scan_state),
4246       _queues(queues), _terminator(terminator) {}
4247 
4248   void do_void();
4249 
4250 private:
4251   inline bool offer_termination();
4252 };
4253 
4254 bool G1ParEvacuateFollowersClosure::offer_termination() {
4255   G1ParScanThreadState* const pss = par_scan_state();
4256   pss->start_term_time();
4257   const bool res = terminator()->offer_termination();
4258   pss->end_term_time();
4259   return res;
4260 }
4261 
4262 void G1ParEvacuateFollowersClosure::do_void() {
4263   G1ParScanThreadState* const pss = par_scan_state();
4264   pss->trim_queue();
4265   do {
4266     pss->steal_and_trim_queue(queues());
4267   } while (!offer_termination());
4268 }
4269 
4270 class G1KlassScanClosure : public KlassClosure {
4271  G1ParCopyHelper* _closure;
4272  bool             _process_only_dirty;
4273  int              _count;
4274  public:
4275   G1KlassScanClosure(G1ParCopyHelper* closure, bool process_only_dirty)
4276       : _process_only_dirty(process_only_dirty), _closure(closure), _count(0) {}
4277   void do_klass(Klass* klass) {
4278     // If the klass has not been dirtied we know that there's
4279     // no references into  the young gen and we can skip it.
4280    if (!_process_only_dirty || klass->has_modified_oops()) {
4281       // Clean the klass since we're going to scavenge all the metadata.
4282       klass->clear_modified_oops();
4283 
4284       // Tell the closure that this klass is the Klass to scavenge
4285       // and is the one to dirty if oops are left pointing into the young gen.
4286       _closure->set_scanned_klass(klass);
4287 
4288       klass->oops_do(_closure);
4289 
4290       _closure->set_scanned_klass(NULL);
4291     }
4292     _count++;
4293   }
4294 };
4295 
4296 class G1ParTask : public AbstractGangTask {
4297 protected:
4298   G1CollectedHeap*       _g1h;
4299   RefToScanQueueSet      *_queues;
4300   G1RootProcessor*       _root_processor;
4301   ParallelTaskTerminator _terminator;
4302   uint _n_workers;
4303 
4304   Mutex _stats_lock;
4305   Mutex* stats_lock() { return &_stats_lock; }
4306 
4307 public:
4308   G1ParTask(G1CollectedHeap* g1h, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor)
4309     : AbstractGangTask("G1 collection"),
4310       _g1h(g1h),
4311       _queues(task_queues),
4312       _root_processor(root_processor),
4313       _terminator(0, _queues),
4314       _stats_lock(Mutex::leaf, "parallel G1 stats lock", true)
4315   {}
4316 
4317   RefToScanQueueSet* queues() { return _queues; }
4318 
4319   RefToScanQueue *work_queue(int i) {
4320     return queues()->queue(i);
4321   }
4322 
4323   ParallelTaskTerminator* terminator() { return &_terminator; }
4324 
4325   virtual void set_for_termination(uint active_workers) {
4326     _root_processor->set_num_workers(active_workers);
4327     terminator()->reset_for_reuse(active_workers);
4328     _n_workers = active_workers;
4329   }
4330 
4331   // Helps out with CLD processing.
4332   //
4333   // During InitialMark we need to:
4334   // 1) Scavenge all CLDs for the young GC.
4335   // 2) Mark all objects directly reachable from strong CLDs.
4336   template <G1Mark do_mark_object>
4337   class G1CLDClosure : public CLDClosure {
4338     G1ParCopyClosure<G1BarrierNone,  do_mark_object>* _oop_closure;
4339     G1ParCopyClosure<G1BarrierKlass, do_mark_object>  _oop_in_klass_closure;
4340     G1KlassScanClosure                                _klass_in_cld_closure;
4341     bool                                              _claim;
4342 
4343    public:
4344     G1CLDClosure(G1ParCopyClosure<G1BarrierNone, do_mark_object>* oop_closure,
4345                  bool only_young, bool claim)
4346         : _oop_closure(oop_closure),
4347           _oop_in_klass_closure(oop_closure->g1(),
4348                                 oop_closure->pss(),
4349                                 oop_closure->rp()),
4350           _klass_in_cld_closure(&_oop_in_klass_closure, only_young),
4351           _claim(claim) {
4352 
4353     }
4354 
4355     void do_cld(ClassLoaderData* cld) {
4356       cld->oops_do(_oop_closure, &_klass_in_cld_closure, _claim);
4357     }
4358   };
4359 
4360   void work(uint worker_id) {
4361     if (worker_id >= _n_workers) return;  // no work needed this round
4362 
4363     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, os::elapsedTime());
4364 
4365     {
4366       ResourceMark rm;
4367       HandleMark   hm;
4368 
4369       ReferenceProcessor*             rp = _g1h->ref_processor_stw();
4370 
4371       G1ParScanThreadState            pss(_g1h, worker_id, rp);
4372       G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, rp);
4373 
4374       pss.set_evac_failure_closure(&evac_failure_cl);
4375 
4376       bool only_young = _g1h->collector_state()->gcs_are_young();
4377 
4378       // Non-IM young GC.
4379       G1ParCopyClosure<G1BarrierNone, G1MarkNone>             scan_only_root_cl(_g1h, &pss, rp);
4380       G1CLDClosure<G1MarkNone>                                scan_only_cld_cl(&scan_only_root_cl,
4381                                                                                only_young, // Only process dirty klasses.
4382                                                                                false);     // No need to claim CLDs.
4383       // IM young GC.
4384       //    Strong roots closures.
4385       G1ParCopyClosure<G1BarrierNone, G1MarkFromRoot>         scan_mark_root_cl(_g1h, &pss, rp);
4386       G1CLDClosure<G1MarkFromRoot>                            scan_mark_cld_cl(&scan_mark_root_cl,
4387                                                                                false, // Process all klasses.
4388                                                                                true); // Need to claim CLDs.
4389       //    Weak roots closures.
4390       G1ParCopyClosure<G1BarrierNone, G1MarkPromotedFromRoot> scan_mark_weak_root_cl(_g1h, &pss, rp);
4391       G1CLDClosure<G1MarkPromotedFromRoot>                    scan_mark_weak_cld_cl(&scan_mark_weak_root_cl,
4392                                                                                     false, // Process all klasses.
4393                                                                                     true); // Need to claim CLDs.
4394 
4395       OopClosure* strong_root_cl;
4396       OopClosure* weak_root_cl;
4397       CLDClosure* strong_cld_cl;
4398       CLDClosure* weak_cld_cl;
4399 
4400       bool trace_metadata = false;
4401 
4402       if (_g1h->collector_state()->during_initial_mark_pause()) {
4403         // We also need to mark copied objects.
4404         strong_root_cl = &scan_mark_root_cl;
4405         strong_cld_cl  = &scan_mark_cld_cl;
4406         if (ClassUnloadingWithConcurrentMark) {
4407           weak_root_cl = &scan_mark_weak_root_cl;
4408           weak_cld_cl  = &scan_mark_weak_cld_cl;
4409           trace_metadata = true;
4410         } else {
4411           weak_root_cl = &scan_mark_root_cl;
4412           weak_cld_cl  = &scan_mark_cld_cl;
4413         }
4414       } else {
4415         strong_root_cl = &scan_only_root_cl;
4416         weak_root_cl   = &scan_only_root_cl;
4417         strong_cld_cl  = &scan_only_cld_cl;
4418         weak_cld_cl    = &scan_only_cld_cl;
4419       }
4420 
4421       pss.start_strong_roots();
4422 
4423       _root_processor->evacuate_roots(strong_root_cl,
4424                              weak_root_cl,
4425                              strong_cld_cl,
4426                              weak_cld_cl,
4427                                       trace_metadata,
4428                              worker_id);
4429 
4430       G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, &pss);
4431       _root_processor->scan_remembered_sets(&push_heap_rs_cl,
4432                                             weak_root_cl,
4433                                             worker_id);
4434       pss.end_strong_roots();
4435 
4436       {
4437         double start = os::elapsedTime();
4438         G1ParEvacuateFollowersClosure evac(_g1h, &pss, _queues, &_terminator);
4439         evac.do_void();
4440         double elapsed_sec = os::elapsedTime() - start;
4441         double term_sec = pss.term_time();
4442         _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec);
4443         _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec);
4444         _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, pss.term_attempts());
4445       }
4446       _g1h->g1_policy()->record_thread_age_table(pss.age_table());
4447       _g1h->update_surviving_young_words(pss.surviving_young_words()+1);
4448 
4449       if (PrintTerminationStats) {
4450         MutexLocker x(stats_lock());
4451         pss.print_termination_stats(worker_id);
4452       }
4453 
4454       assert(pss.queue_is_empty(), "should be empty");
4455 
4456       // Close the inner scope so that the ResourceMark and HandleMark
4457       // destructors are executed here and are included as part of the
4458       // "GC Worker Time".
4459     }
4460     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime());
4461   }
4462 };
4463 
4464 class G1StringSymbolTableUnlinkTask : public AbstractGangTask {
4465 private:
4466   BoolObjectClosure* _is_alive;
4467   int _initial_string_table_size;
4468   int _initial_symbol_table_size;
4469 
4470   bool  _process_strings;
4471   int _strings_processed;
4472   int _strings_removed;
4473 
4474   bool  _process_symbols;
4475   int _symbols_processed;
4476   int _symbols_removed;
4477 
4478 public:
4479   G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) :
4480     AbstractGangTask("String/Symbol Unlinking"),
4481     _is_alive(is_alive),
4482     _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
4483     _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) {
4484 
4485     _initial_string_table_size = StringTable::the_table()->table_size();
4486     _initial_symbol_table_size = SymbolTable::the_table()->table_size();
4487     if (process_strings) {
4488       StringTable::clear_parallel_claimed_index();
4489     }
4490     if (process_symbols) {
4491       SymbolTable::clear_parallel_claimed_index();
4492     }
4493   }
4494 
4495   ~G1StringSymbolTableUnlinkTask() {
4496     guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size,
4497               err_msg("claim value %d after unlink less than initial string table size %d",
4498                       StringTable::parallel_claimed_index(), _initial_string_table_size));
4499     guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
4500               err_msg("claim value %d after unlink less than initial symbol table size %d",
4501                       SymbolTable::parallel_claimed_index(), _initial_symbol_table_size));
4502 
4503     if (G1TraceStringSymbolTableScrubbing) {
4504       gclog_or_tty->print_cr("Cleaned string and symbol table, "
4505                              "strings: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed, "
4506                              "symbols: "SIZE_FORMAT" processed, "SIZE_FORMAT" removed",
4507                              strings_processed(), strings_removed(),
4508                              symbols_processed(), symbols_removed());
4509     }
4510   }
4511 
4512   void work(uint worker_id) {
4513     int strings_processed = 0;
4514     int strings_removed = 0;
4515     int symbols_processed = 0;
4516     int symbols_removed = 0;
4517     if (_process_strings) {
4518       StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
4519       Atomic::add(strings_processed, &_strings_processed);
4520       Atomic::add(strings_removed, &_strings_removed);
4521     }
4522     if (_process_symbols) {
4523       SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
4524       Atomic::add(symbols_processed, &_symbols_processed);
4525       Atomic::add(symbols_removed, &_symbols_removed);
4526     }
4527   }
4528 
4529   size_t strings_processed() const { return (size_t)_strings_processed; }
4530   size_t strings_removed()   const { return (size_t)_strings_removed; }
4531 
4532   size_t symbols_processed() const { return (size_t)_symbols_processed; }
4533   size_t symbols_removed()   const { return (size_t)_symbols_removed; }
4534 };
4535 
4536 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
4537 private:
4538   static Monitor* _lock;
4539 
4540   BoolObjectClosure* const _is_alive;
4541   const bool               _unloading_occurred;
4542   const uint               _num_workers;
4543 
4544   // Variables used to claim nmethods.
4545   nmethod* _first_nmethod;
4546   volatile nmethod* _claimed_nmethod;
4547 
4548   // The list of nmethods that need to be processed by the second pass.
4549   volatile nmethod* _postponed_list;
4550   volatile uint     _num_entered_barrier;
4551 
4552  public:
4553   G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
4554       _is_alive(is_alive),
4555       _unloading_occurred(unloading_occurred),
4556       _num_workers(num_workers),
4557       _first_nmethod(NULL),
4558       _claimed_nmethod(NULL),
4559       _postponed_list(NULL),
4560       _num_entered_barrier(0)
4561   {
4562     nmethod::increase_unloading_clock();
4563     // Get first alive nmethod
4564     NMethodIterator iter = NMethodIterator();
4565     if(iter.next_alive()) {
4566       _first_nmethod = iter.method();
4567     }
4568     _claimed_nmethod = (volatile nmethod*)_first_nmethod;
4569   }
4570 
4571   ~G1CodeCacheUnloadingTask() {
4572     CodeCache::verify_clean_inline_caches();
4573 
4574     CodeCache::set_needs_cache_clean(false);
4575     guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
4576 
4577     CodeCache::verify_icholder_relocations();
4578   }
4579 
4580  private:
4581   void add_to_postponed_list(nmethod* nm) {
4582       nmethod* old;
4583       do {
4584         old = (nmethod*)_postponed_list;
4585         nm->set_unloading_next(old);
4586       } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old);
4587   }
4588 
4589   void clean_nmethod(nmethod* nm) {
4590     bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
4591 
4592     if (postponed) {
4593       // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
4594       add_to_postponed_list(nm);
4595     }
4596 
4597     // Mark that this thread has been cleaned/unloaded.
4598     // After this call, it will be safe to ask if this nmethod was unloaded or not.
4599     nm->set_unloading_clock(nmethod::global_unloading_clock());
4600   }
4601 
4602   void clean_nmethod_postponed(nmethod* nm) {
4603     nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
4604   }
4605 
4606   static const int MaxClaimNmethods = 16;
4607 
4608   void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) {
4609     nmethod* first;
4610     NMethodIterator last;
4611 
4612     do {
4613       *num_claimed_nmethods = 0;
4614 
4615       first = (nmethod*)_claimed_nmethod;
4616       last = NMethodIterator(first);
4617 
4618       if (first != NULL) {
4619 
4620         for (int i = 0; i < MaxClaimNmethods; i++) {
4621           if (!last.next_alive()) {
4622             break;
4623           }
4624           claimed_nmethods[i] = last.method();
4625           (*num_claimed_nmethods)++;
4626         }
4627       }
4628 
4629     } while ((nmethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first);
4630   }
4631 
4632   nmethod* claim_postponed_nmethod() {
4633     nmethod* claim;
4634     nmethod* next;
4635 
4636     do {
4637       claim = (nmethod*)_postponed_list;
4638       if (claim == NULL) {
4639         return NULL;
4640       }
4641 
4642       next = claim->unloading_next();
4643 
4644     } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim);
4645 
4646     return claim;
4647   }
4648 
4649  public:
4650   // Mark that we're done with the first pass of nmethod cleaning.
4651   void barrier_mark(uint worker_id) {
4652     MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
4653     _num_entered_barrier++;
4654     if (_num_entered_barrier == _num_workers) {
4655       ml.notify_all();
4656     }
4657   }
4658 
4659   // See if we have to wait for the other workers to
4660   // finish their first-pass nmethod cleaning work.
4661   void barrier_wait(uint worker_id) {
4662     if (_num_entered_barrier < _num_workers) {
4663       MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
4664       while (_num_entered_barrier < _num_workers) {
4665           ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
4666       }
4667     }
4668   }
4669 
4670   // Cleaning and unloading of nmethods. Some work has to be postponed
4671   // to the second pass, when we know which nmethods survive.
4672   void work_first_pass(uint worker_id) {
4673     // The first nmethods is claimed by the first worker.
4674     if (worker_id == 0 && _first_nmethod != NULL) {
4675       clean_nmethod(_first_nmethod);
4676       _first_nmethod = NULL;
4677     }
4678 
4679     int num_claimed_nmethods;
4680     nmethod* claimed_nmethods[MaxClaimNmethods];
4681 
4682     while (true) {
4683       claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
4684 
4685       if (num_claimed_nmethods == 0) {
4686         break;
4687       }
4688 
4689       for (int i = 0; i < num_claimed_nmethods; i++) {
4690         clean_nmethod(claimed_nmethods[i]);
4691       }
4692     }
4693   }
4694 
4695   void work_second_pass(uint worker_id) {
4696     nmethod* nm;
4697     // Take care of postponed nmethods.
4698     while ((nm = claim_postponed_nmethod()) != NULL) {
4699       clean_nmethod_postponed(nm);
4700     }
4701   }
4702 };
4703 
4704 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never);
4705 
4706 class G1KlassCleaningTask : public StackObj {
4707   BoolObjectClosure*                      _is_alive;
4708   volatile jint                           _clean_klass_tree_claimed;
4709   ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
4710 
4711  public:
4712   G1KlassCleaningTask(BoolObjectClosure* is_alive) :
4713       _is_alive(is_alive),
4714       _clean_klass_tree_claimed(0),
4715       _klass_iterator() {
4716   }
4717 
4718  private:
4719   bool claim_clean_klass_tree_task() {
4720     if (_clean_klass_tree_claimed) {
4721       return false;
4722     }
4723 
4724     return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0;
4725   }
4726 
4727   InstanceKlass* claim_next_klass() {
4728     Klass* klass;
4729     do {
4730       klass =_klass_iterator.next_klass();
4731     } while (klass != NULL && !klass->oop_is_instance());
4732 
4733     return (InstanceKlass*)klass;
4734   }
4735 
4736 public:
4737 
4738   void clean_klass(InstanceKlass* ik) {
4739     ik->clean_implementors_list(_is_alive);
4740     ik->clean_method_data(_is_alive);
4741 
4742     // G1 specific cleanup work that has
4743     // been moved here to be done in parallel.
4744     ik->clean_dependent_nmethods();
4745   }
4746 
4747   void work() {
4748     ResourceMark rm;
4749 
4750     // One worker will clean the subklass/sibling klass tree.
4751     if (claim_clean_klass_tree_task()) {
4752       Klass::clean_subklass_tree(_is_alive);
4753     }
4754 
4755     // All workers will help cleaning the classes,
4756     InstanceKlass* klass;
4757     while ((klass = claim_next_klass()) != NULL) {
4758       clean_klass(klass);
4759     }
4760   }
4761 };
4762 
4763 // To minimize the remark pause times, the tasks below are done in parallel.
4764 class G1ParallelCleaningTask : public AbstractGangTask {
4765 private:
4766   G1StringSymbolTableUnlinkTask _string_symbol_task;
4767   G1CodeCacheUnloadingTask      _code_cache_task;
4768   G1KlassCleaningTask           _klass_cleaning_task;
4769 
4770 public:
4771   // The constructor is run in the VMThread.
4772   G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) :
4773       AbstractGangTask("Parallel Cleaning"),
4774       _string_symbol_task(is_alive, process_strings, process_symbols),
4775       _code_cache_task(num_workers, is_alive, unloading_occurred),
4776       _klass_cleaning_task(is_alive) {
4777   }
4778 
4779   // The parallel work done by all worker threads.
4780   void work(uint worker_id) {
4781     // Do first pass of code cache cleaning.
4782     _code_cache_task.work_first_pass(worker_id);
4783 
4784     // Let the threads mark that the first pass is done.
4785     _code_cache_task.barrier_mark(worker_id);
4786 
4787     // Clean the Strings and Symbols.
4788     _string_symbol_task.work(worker_id);
4789 
4790     // Wait for all workers to finish the first code cache cleaning pass.
4791     _code_cache_task.barrier_wait(worker_id);
4792 
4793     // Do the second code cache cleaning work, which realize on
4794     // the liveness information gathered during the first pass.
4795     _code_cache_task.work_second_pass(worker_id);
4796 
4797     // Clean all klasses that were not unloaded.
4798     _klass_cleaning_task.work();
4799   }
4800 };
4801 
4802 
4803 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive,
4804                                         bool process_strings,
4805                                         bool process_symbols,
4806                                         bool class_unloading_occurred) {
4807   uint n_workers = workers()->active_workers();
4808 
4809   G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols,
4810                                         n_workers, class_unloading_occurred);
4811   set_par_threads(n_workers);
4812   workers()->run_task(&g1_unlink_task);
4813   set_par_threads(0);
4814 }
4815 
4816 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive,
4817                                                      bool process_strings, bool process_symbols) {
4818   {
4819     uint n_workers = workers()->active_workers();
4820     G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols);
4821     set_par_threads(n_workers);
4822     workers()->run_task(&g1_unlink_task);
4823     set_par_threads(0);
4824   }
4825 
4826   if (G1StringDedup::is_enabled()) {
4827     G1StringDedup::unlink(is_alive);
4828   }
4829 }
4830 
4831 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
4832  private:
4833   DirtyCardQueueSet* _queue;
4834  public:
4835   G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue) : AbstractGangTask("Redirty Cards"), _queue(queue) { }
4836 
4837   virtual void work(uint worker_id) {
4838     G1GCPhaseTimes* phase_times = G1CollectedHeap::heap()->g1_policy()->phase_times();
4839     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id);
4840 
4841     RedirtyLoggedCardTableEntryClosure cl;
4842     _queue->par_apply_closure_to_all_completed_buffers(&cl);
4843 
4844     phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_processed());
4845   }
4846 };
4847 
4848 void G1CollectedHeap::redirty_logged_cards() {
4849   double redirty_logged_cards_start = os::elapsedTime();
4850 
4851   uint n_workers = workers()->active_workers();
4852 
4853   G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set());
4854   dirty_card_queue_set().reset_for_par_iteration();
4855   set_par_threads(n_workers);
4856   workers()->run_task(&redirty_task);
4857   set_par_threads(0);
4858 
4859   DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
4860   dcq.merge_bufferlists(&dirty_card_queue_set());
4861   assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
4862 
4863   g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
4864 }
4865 
4866 // Weak Reference Processing support
4867 
4868 // An always "is_alive" closure that is used to preserve referents.
4869 // If the object is non-null then it's alive.  Used in the preservation
4870 // of referent objects that are pointed to by reference objects
4871 // discovered by the CM ref processor.
4872 class G1AlwaysAliveClosure: public BoolObjectClosure {
4873   G1CollectedHeap* _g1;
4874 public:
4875   G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
4876   bool do_object_b(oop p) {
4877     if (p != NULL) {
4878       return true;
4879     }
4880     return false;
4881   }
4882 };
4883 
4884 bool G1STWIsAliveClosure::do_object_b(oop p) {
4885   // An object is reachable if it is outside the collection set,
4886   // or is inside and copied.
4887   return !_g1->obj_in_cs(p) || p->is_forwarded();
4888 }
4889 
4890 // Non Copying Keep Alive closure
4891 class G1KeepAliveClosure: public OopClosure {
4892   G1CollectedHeap* _g1;
4893 public:
4894   G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
4895   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
4896   void do_oop(oop* p) {
4897     oop obj = *p;
4898     assert(obj != NULL, "the caller should have filtered out NULL values");
4899 
4900     const InCSetState cset_state = _g1->in_cset_state(obj);
4901     if (!cset_state.is_in_cset_or_humongous()) {
4902       return;
4903     }
4904     if (cset_state.is_in_cset()) {
4905       assert( obj->is_forwarded(), "invariant" );
4906       *p = obj->forwardee();
4907     } else {
4908       assert(!obj->is_forwarded(), "invariant" );
4909       assert(cset_state.is_humongous(),
4910              err_msg("Only allowed InCSet state is IsHumongous, but is %d", cset_state.value()));
4911       _g1->set_humongous_is_live(obj);
4912     }
4913   }
4914 };
4915 
4916 // Copying Keep Alive closure - can be called from both
4917 // serial and parallel code as long as different worker
4918 // threads utilize different G1ParScanThreadState instances
4919 // and different queues.
4920 
4921 class G1CopyingKeepAliveClosure: public OopClosure {
4922   G1CollectedHeap*         _g1h;
4923   OopClosure*              _copy_non_heap_obj_cl;
4924   G1ParScanThreadState*    _par_scan_state;
4925 
4926 public:
4927   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
4928                             OopClosure* non_heap_obj_cl,
4929                             G1ParScanThreadState* pss):
4930     _g1h(g1h),
4931     _copy_non_heap_obj_cl(non_heap_obj_cl),
4932     _par_scan_state(pss)
4933   {}
4934 
4935   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
4936   virtual void do_oop(      oop* p) { do_oop_work(p); }
4937 
4938   template <class T> void do_oop_work(T* p) {
4939     oop obj = oopDesc::load_decode_heap_oop(p);
4940 
4941     if (_g1h->is_in_cset_or_humongous(obj)) {
4942       // If the referent object has been forwarded (either copied
4943       // to a new location or to itself in the event of an
4944       // evacuation failure) then we need to update the reference
4945       // field and, if both reference and referent are in the G1
4946       // heap, update the RSet for the referent.
4947       //
4948       // If the referent has not been forwarded then we have to keep
4949       // it alive by policy. Therefore we have copy the referent.
4950       //
4951       // If the reference field is in the G1 heap then we can push
4952       // on the PSS queue. When the queue is drained (after each
4953       // phase of reference processing) the object and it's followers
4954       // will be copied, the reference field set to point to the
4955       // new location, and the RSet updated. Otherwise we need to
4956       // use the the non-heap or metadata closures directly to copy
4957       // the referent object and update the pointer, while avoiding
4958       // updating the RSet.
4959 
4960       if (_g1h->is_in_g1_reserved(p)) {
4961         _par_scan_state->push_on_queue(p);
4962       } else {
4963         assert(!Metaspace::contains((const void*)p),
4964                err_msg("Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p)));
4965         _copy_non_heap_obj_cl->do_oop(p);
4966       }
4967     }
4968   }
4969 };
4970 
4971 // Serial drain queue closure. Called as the 'complete_gc'
4972 // closure for each discovered list in some of the
4973 // reference processing phases.
4974 
4975 class G1STWDrainQueueClosure: public VoidClosure {
4976 protected:
4977   G1CollectedHeap* _g1h;
4978   G1ParScanThreadState* _par_scan_state;
4979 
4980   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
4981 
4982 public:
4983   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
4984     _g1h(g1h),
4985     _par_scan_state(pss)
4986   { }
4987 
4988   void do_void() {
4989     G1ParScanThreadState* const pss = par_scan_state();
4990     pss->trim_queue();
4991   }
4992 };
4993 
4994 // Parallel Reference Processing closures
4995 
4996 // Implementation of AbstractRefProcTaskExecutor for parallel reference
4997 // processing during G1 evacuation pauses.
4998 
4999 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
5000 private:
5001   G1CollectedHeap*   _g1h;
5002   RefToScanQueueSet* _queues;
5003   FlexibleWorkGang*  _workers;
5004   uint               _active_workers;
5005 
5006 public:
5007   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
5008                         FlexibleWorkGang* workers,
5009                         RefToScanQueueSet *task_queues,
5010                            uint n_workers) :
5011     _g1h(g1h),
5012     _queues(task_queues),
5013     _workers(workers),
5014     _active_workers(n_workers)
5015   {
5016     assert(n_workers > 0, "shouldn't call this otherwise");
5017   }
5018 
5019   // Executes the given task using concurrent marking worker threads.
5020   virtual void execute(ProcessTask& task);
5021   virtual void execute(EnqueueTask& task);
5022 };
5023 
5024 // Gang task for possibly parallel reference processing
5025 
5026 class G1STWRefProcTaskProxy: public AbstractGangTask {
5027   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
5028   ProcessTask&     _proc_task;
5029   G1CollectedHeap* _g1h;
5030   RefToScanQueueSet *_task_queues;
5031   ParallelTaskTerminator* _terminator;
5032 
5033 public:
5034   G1STWRefProcTaskProxy(ProcessTask& proc_task,
5035                      G1CollectedHeap* g1h,
5036                      RefToScanQueueSet *task_queues,
5037                      ParallelTaskTerminator* terminator) :
5038     AbstractGangTask("Process reference objects in parallel"),
5039     _proc_task(proc_task),
5040     _g1h(g1h),
5041     _task_queues(task_queues),
5042     _terminator(terminator)
5043   {}
5044 
5045   virtual void work(uint worker_id) {
5046     // The reference processing task executed by a single worker.
5047     ResourceMark rm;
5048     HandleMark   hm;
5049 
5050     G1STWIsAliveClosure is_alive(_g1h);
5051 
5052     G1ParScanThreadState            pss(_g1h, worker_id, NULL);
5053     G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5054 
5055     pss.set_evac_failure_closure(&evac_failure_cl);
5056 
5057     G1ParScanExtRootClosure        only_copy_non_heap_cl(_g1h, &pss, NULL);
5058 
5059     G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5060 
5061     OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5062 
5063     if (_g1h->collector_state()->during_initial_mark_pause()) {
5064       // We also need to mark copied objects.
5065       copy_non_heap_cl = &copy_mark_non_heap_cl;
5066     }
5067 
5068     // Keep alive closure.
5069     G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5070 
5071     // Complete GC closure
5072     G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _task_queues, _terminator);
5073 
5074     // Call the reference processing task's work routine.
5075     _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
5076 
5077     // Note we cannot assert that the refs array is empty here as not all
5078     // of the processing tasks (specifically phase2 - pp2_work) execute
5079     // the complete_gc closure (which ordinarily would drain the queue) so
5080     // the queue may not be empty.
5081   }
5082 };
5083 
5084 // Driver routine for parallel reference processing.
5085 // Creates an instance of the ref processing gang
5086 // task and has the worker threads execute it.
5087 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
5088   assert(_workers != NULL, "Need parallel worker threads.");
5089 
5090   ParallelTaskTerminator terminator(_active_workers, _queues);
5091   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _queues, &terminator);
5092 
5093   _g1h->set_par_threads(_active_workers);
5094   _workers->run_task(&proc_task_proxy);
5095   _g1h->set_par_threads(0);
5096 }
5097 
5098 // Gang task for parallel reference enqueueing.
5099 
5100 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
5101   typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
5102   EnqueueTask& _enq_task;
5103 
5104 public:
5105   G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
5106     AbstractGangTask("Enqueue reference objects in parallel"),
5107     _enq_task(enq_task)
5108   { }
5109 
5110   virtual void work(uint worker_id) {
5111     _enq_task.work(worker_id);
5112   }
5113 };
5114 
5115 // Driver routine for parallel reference enqueueing.
5116 // Creates an instance of the ref enqueueing gang
5117 // task and has the worker threads execute it.
5118 
5119 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
5120   assert(_workers != NULL, "Need parallel worker threads.");
5121 
5122   G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
5123 
5124   _g1h->set_par_threads(_active_workers);
5125   _workers->run_task(&enq_task_proxy);
5126   _g1h->set_par_threads(0);
5127 }
5128 
5129 // End of weak reference support closures
5130 
5131 // Abstract task used to preserve (i.e. copy) any referent objects
5132 // that are in the collection set and are pointed to by reference
5133 // objects discovered by the CM ref processor.
5134 
5135 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
5136 protected:
5137   G1CollectedHeap* _g1h;
5138   RefToScanQueueSet      *_queues;
5139   ParallelTaskTerminator _terminator;
5140   uint _n_workers;
5141 
5142 public:
5143   G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, uint workers, RefToScanQueueSet *task_queues) :
5144     AbstractGangTask("ParPreserveCMReferents"),
5145     _g1h(g1h),
5146     _queues(task_queues),
5147     _terminator(workers, _queues),
5148     _n_workers(workers)
5149   { }
5150 
5151   void work(uint worker_id) {
5152     ResourceMark rm;
5153     HandleMark   hm;
5154 
5155     G1ParScanThreadState            pss(_g1h, worker_id, NULL);
5156     G1ParScanHeapEvacFailureClosure evac_failure_cl(_g1h, &pss, NULL);
5157 
5158     pss.set_evac_failure_closure(&evac_failure_cl);
5159 
5160     assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5161 
5162     G1ParScanExtRootClosure        only_copy_non_heap_cl(_g1h, &pss, NULL);
5163 
5164     G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(_g1h, &pss, NULL);
5165 
5166     OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5167 
5168     if (_g1h->collector_state()->during_initial_mark_pause()) {
5169       // We also need to mark copied objects.
5170       copy_non_heap_cl = &copy_mark_non_heap_cl;
5171     }
5172 
5173     // Is alive closure
5174     G1AlwaysAliveClosure always_alive(_g1h);
5175 
5176     // Copying keep alive closure. Applied to referent objects that need
5177     // to be copied.
5178     G1CopyingKeepAliveClosure keep_alive(_g1h, copy_non_heap_cl, &pss);
5179 
5180     ReferenceProcessor* rp = _g1h->ref_processor_cm();
5181 
5182     uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
5183     uint stride = MIN2(MAX2(_n_workers, 1U), limit);
5184 
5185     // limit is set using max_num_q() - which was set using ParallelGCThreads.
5186     // So this must be true - but assert just in case someone decides to
5187     // change the worker ids.
5188     assert(worker_id < limit, "sanity");
5189     assert(!rp->discovery_is_atomic(), "check this code");
5190 
5191     // Select discovered lists [i, i+stride, i+2*stride,...,limit)
5192     for (uint idx = worker_id; idx < limit; idx += stride) {
5193       DiscoveredList& ref_list = rp->discovered_refs()[idx];
5194 
5195       DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
5196       while (iter.has_next()) {
5197         // Since discovery is not atomic for the CM ref processor, we
5198         // can see some null referent objects.
5199         iter.load_ptrs(DEBUG_ONLY(true));
5200         oop ref = iter.obj();
5201 
5202         // This will filter nulls.
5203         if (iter.is_referent_alive()) {
5204           iter.make_referent_alive();
5205         }
5206         iter.move_to_next();
5207       }
5208     }
5209 
5210     // Drain the queue - which may cause stealing
5211     G1ParEvacuateFollowersClosure drain_queue(_g1h, &pss, _queues, &_terminator);
5212     drain_queue.do_void();
5213     // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
5214     assert(pss.queue_is_empty(), "should be");
5215   }
5216 };
5217 
5218 // Weak Reference processing during an evacuation pause (part 1).
5219 void G1CollectedHeap::process_discovered_references(uint no_of_gc_workers) {
5220   double ref_proc_start = os::elapsedTime();
5221 
5222   ReferenceProcessor* rp = _ref_processor_stw;
5223   assert(rp->discovery_enabled(), "should have been enabled");
5224 
5225   // Any reference objects, in the collection set, that were 'discovered'
5226   // by the CM ref processor should have already been copied (either by
5227   // applying the external root copy closure to the discovered lists, or
5228   // by following an RSet entry).
5229   //
5230   // But some of the referents, that are in the collection set, that these
5231   // reference objects point to may not have been copied: the STW ref
5232   // processor would have seen that the reference object had already
5233   // been 'discovered' and would have skipped discovering the reference,
5234   // but would not have treated the reference object as a regular oop.
5235   // As a result the copy closure would not have been applied to the
5236   // referent object.
5237   //
5238   // We need to explicitly copy these referent objects - the references
5239   // will be processed at the end of remarking.
5240   //
5241   // We also need to do this copying before we process the reference
5242   // objects discovered by the STW ref processor in case one of these
5243   // referents points to another object which is also referenced by an
5244   // object discovered by the STW ref processor.
5245 
5246   assert(no_of_gc_workers == workers()->active_workers(), "Need to reset active GC workers");
5247 
5248   set_par_threads(no_of_gc_workers);
5249   G1ParPreserveCMReferentsTask keep_cm_referents(this,
5250                                                  no_of_gc_workers,
5251                                                  _task_queues);
5252 
5253   workers()->run_task(&keep_cm_referents);
5254 
5255   set_par_threads(0);
5256 
5257   // Closure to test whether a referent is alive.
5258   G1STWIsAliveClosure is_alive(this);
5259 
5260   // Even when parallel reference processing is enabled, the processing
5261   // of JNI refs is serial and performed serially by the current thread
5262   // rather than by a worker. The following PSS will be used for processing
5263   // JNI refs.
5264 
5265   // Use only a single queue for this PSS.
5266   G1ParScanThreadState            pss(this, 0, NULL);
5267 
5268   // We do not embed a reference processor in the copying/scanning
5269   // closures while we're actually processing the discovered
5270   // reference objects.
5271   G1ParScanHeapEvacFailureClosure evac_failure_cl(this, &pss, NULL);
5272 
5273   pss.set_evac_failure_closure(&evac_failure_cl);
5274 
5275   assert(pss.queue_is_empty(), "pre-condition");
5276 
5277   G1ParScanExtRootClosure        only_copy_non_heap_cl(this, &pss, NULL);
5278 
5279   G1ParScanAndMarkExtRootClosure copy_mark_non_heap_cl(this, &pss, NULL);
5280 
5281   OopClosure*                    copy_non_heap_cl = &only_copy_non_heap_cl;
5282 
5283   if (collector_state()->during_initial_mark_pause()) {
5284     // We also need to mark copied objects.
5285     copy_non_heap_cl = &copy_mark_non_heap_cl;
5286   }
5287 
5288   // Keep alive closure.
5289   G1CopyingKeepAliveClosure keep_alive(this, copy_non_heap_cl, &pss);
5290 
5291   // Serial Complete GC closure
5292   G1STWDrainQueueClosure drain_queue(this, &pss);
5293 
5294   // Setup the soft refs policy...
5295   rp->setup_policy(false);
5296 
5297   ReferenceProcessorStats stats;
5298   if (!rp->processing_is_mt()) {
5299     // Serial reference processing...
5300     stats = rp->process_discovered_references(&is_alive,
5301                                               &keep_alive,
5302                                               &drain_queue,
5303                                               NULL,
5304                                               _gc_timer_stw,
5305                                               _gc_tracer_stw->gc_id());
5306   } else {
5307     // Parallel reference processing
5308     assert(rp->num_q() == no_of_gc_workers, "sanity");
5309     assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5310 
5311     G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5312     stats = rp->process_discovered_references(&is_alive,
5313                                               &keep_alive,
5314                                               &drain_queue,
5315                                               &par_task_executor,
5316                                               _gc_timer_stw,
5317                                               _gc_tracer_stw->gc_id());
5318   }
5319 
5320   _gc_tracer_stw->report_gc_reference_stats(stats);
5321 
5322   // We have completed copying any necessary live referent objects.
5323   assert(pss.queue_is_empty(), "both queue and overflow should be empty");
5324 
5325   double ref_proc_time = os::elapsedTime() - ref_proc_start;
5326   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
5327 }
5328 
5329 // Weak Reference processing during an evacuation pause (part 2).
5330 void G1CollectedHeap::enqueue_discovered_references(uint no_of_gc_workers) {
5331   double ref_enq_start = os::elapsedTime();
5332 
5333   ReferenceProcessor* rp = _ref_processor_stw;
5334   assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
5335 
5336   // Now enqueue any remaining on the discovered lists on to
5337   // the pending list.
5338   if (!rp->processing_is_mt()) {
5339     // Serial reference processing...
5340     rp->enqueue_discovered_references();
5341   } else {
5342     // Parallel reference enqueueing
5343 
5344     assert(no_of_gc_workers == workers()->active_workers(),
5345            "Need to reset active workers");
5346     assert(rp->num_q() == no_of_gc_workers, "sanity");
5347     assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
5348 
5349     G1STWRefProcTaskExecutor par_task_executor(this, workers(), _task_queues, no_of_gc_workers);
5350     rp->enqueue_discovered_references(&par_task_executor);
5351   }
5352 
5353   rp->verify_no_references_recorded();
5354   assert(!rp->discovery_enabled(), "should have been disabled");
5355 
5356   // FIXME
5357   // CM's reference processing also cleans up the string and symbol tables.
5358   // Should we do that here also? We could, but it is a serial operation
5359   // and could significantly increase the pause time.
5360 
5361   double ref_enq_time = os::elapsedTime() - ref_enq_start;
5362   g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
5363 }
5364 
5365 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info) {
5366   _expand_heap_after_alloc_failure = true;
5367   _evacuation_failed = false;
5368 
5369   // Should G1EvacuationFailureALot be in effect for this GC?
5370   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
5371 
5372   g1_rem_set()->prepare_for_oops_into_collection_set_do();
5373 
5374   // Disable the hot card cache.
5375   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
5376   hot_card_cache->reset_hot_cache_claimed_index();
5377   hot_card_cache->set_use_cache(false);
5378 
5379   const uint n_workers = workers()->active_workers();
5380   assert(UseDynamicNumberOfGCThreads ||
5381          n_workers == workers()->total_workers(),
5382          "If not dynamic should be using all the  workers");
5383   set_par_threads(n_workers);
5384 
5385 
5386   init_for_evac_failure(NULL);
5387 
5388   assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
5389   double start_par_time_sec = os::elapsedTime();
5390   double end_par_time_sec;
5391 
5392   {
5393     G1RootProcessor root_processor(this);
5394     G1ParTask g1_par_task(this, _task_queues, &root_processor);
5395     // InitialMark needs claim bits to keep track of the marked-through CLDs.
5396     if (collector_state()->during_initial_mark_pause()) {
5397       ClassLoaderDataGraph::clear_claimed_marks();
5398     }
5399 
5400      // The individual threads will set their evac-failure closures.
5401      if (PrintTerminationStats) G1ParScanThreadState::print_termination_stats_hdr();
5402      // These tasks use ShareHeap::_process_strong_tasks
5403      assert(UseDynamicNumberOfGCThreads ||
5404             workers()->active_workers() == workers()->total_workers(),
5405             "If not dynamic should be using all the  workers");
5406     workers()->run_task(&g1_par_task);
5407     end_par_time_sec = os::elapsedTime();
5408 
5409     // Closing the inner scope will execute the destructor
5410     // for the G1RootProcessor object. We record the current
5411     // elapsed time before closing the scope so that time
5412     // taken for the destructor is NOT included in the
5413     // reported parallel time.
5414   }
5415 
5416   G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
5417 
5418   double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
5419   phase_times->record_par_time(par_time_ms);
5420 
5421   double code_root_fixup_time_ms =
5422         (os::elapsedTime() - end_par_time_sec) * 1000.0;
5423   phase_times->record_code_root_fixup_time(code_root_fixup_time_ms);
5424 
5425   set_par_threads(0);
5426 
5427   // Process any discovered reference objects - we have
5428   // to do this _before_ we retire the GC alloc regions
5429   // as we may have to copy some 'reachable' referent
5430   // objects (and their reachable sub-graphs) that were
5431   // not copied during the pause.
5432   process_discovered_references(n_workers);
5433 
5434   if (G1StringDedup::is_enabled()) {
5435     double fixup_start = os::elapsedTime();
5436 
5437     G1STWIsAliveClosure is_alive(this);
5438     G1KeepAliveClosure keep_alive(this);
5439     G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, phase_times);
5440 
5441     double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
5442     phase_times->record_string_dedup_fixup_time(fixup_time_ms);
5443   }
5444 
5445   _allocator->release_gc_alloc_regions(n_workers, evacuation_info);
5446   g1_rem_set()->cleanup_after_oops_into_collection_set_do();
5447 
5448   // Reset and re-enable the hot card cache.
5449   // Note the counts for the cards in the regions in the
5450   // collection set are reset when the collection set is freed.
5451   hot_card_cache->reset_hot_cache();
5452   hot_card_cache->set_use_cache(true);
5453 
5454   purge_code_root_memory();
5455 
5456   finalize_for_evac_failure();
5457 
5458   if (evacuation_failed()) {
5459     remove_self_forwarding_pointers();
5460 
5461     // Reset the G1EvacuationFailureALot counters and flags
5462     // Note: the values are reset only when an actual
5463     // evacuation failure occurs.
5464     NOT_PRODUCT(reset_evacuation_should_fail();)
5465   }
5466 
5467   // Enqueue any remaining references remaining on the STW
5468   // reference processor's discovered lists. We need to do
5469   // this after the card table is cleaned (and verified) as
5470   // the act of enqueueing entries on to the pending list
5471   // will log these updates (and dirty their associated
5472   // cards). We need these updates logged to update any
5473   // RSets.
5474   enqueue_discovered_references(n_workers);
5475 
5476   redirty_logged_cards();
5477   COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
5478 }
5479 
5480 void G1CollectedHeap::free_region(HeapRegion* hr,
5481                                   FreeRegionList* free_list,
5482                                   bool par,
5483                                   bool locked) {
5484   assert(!hr->is_free(), "the region should not be free");
5485   assert(!hr->is_empty(), "the region should not be empty");
5486   assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
5487   assert(free_list != NULL, "pre-condition");
5488 
5489   if (G1VerifyBitmaps) {
5490     MemRegion mr(hr->bottom(), hr->end());
5491     concurrent_mark()->clearRangePrevBitmap(mr);
5492   }
5493 
5494   // Clear the card counts for this region.
5495   // Note: we only need to do this if the region is not young
5496   // (since we don't refine cards in young regions).
5497   if (!hr->is_young()) {
5498     _cg1r->hot_card_cache()->reset_card_counts(hr);
5499   }
5500   hr->hr_clear(par, true /* clear_space */, locked /* locked */);
5501   free_list->add_ordered(hr);
5502 }
5503 
5504 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
5505                                      FreeRegionList* free_list,
5506                                      bool par) {
5507   assert(hr->is_starts_humongous(), "this is only for starts humongous regions");
5508   assert(free_list != NULL, "pre-condition");
5509 
5510   size_t hr_capacity = hr->capacity();
5511   // We need to read this before we make the region non-humongous,
5512   // otherwise the information will be gone.
5513   uint last_index = hr->last_hc_index();
5514   hr->clear_humongous();
5515   free_region(hr, free_list, par);
5516 
5517   uint i = hr->hrm_index() + 1;
5518   while (i < last_index) {
5519     HeapRegion* curr_hr = region_at(i);
5520     assert(curr_hr->is_continues_humongous(), "invariant");
5521     curr_hr->clear_humongous();
5522     free_region(curr_hr, free_list, par);
5523     i += 1;
5524   }
5525 }
5526 
5527 void G1CollectedHeap::remove_from_old_sets(const HeapRegionSetCount& old_regions_removed,
5528                                        const HeapRegionSetCount& humongous_regions_removed) {
5529   if (old_regions_removed.length() > 0 || humongous_regions_removed.length() > 0) {
5530     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
5531     _old_set.bulk_remove(old_regions_removed);
5532     _humongous_set.bulk_remove(humongous_regions_removed);
5533   }
5534 
5535 }
5536 
5537 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
5538   assert(list != NULL, "list can't be null");
5539   if (!list->is_empty()) {
5540     MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
5541     _hrm.insert_list_into_free_list(list);
5542   }
5543 }
5544 
5545 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
5546   _allocator->decrease_used(bytes);
5547 }
5548 
5549 class G1ParCleanupCTTask : public AbstractGangTask {
5550   G1SATBCardTableModRefBS* _ct_bs;
5551   G1CollectedHeap* _g1h;
5552   HeapRegion* volatile _su_head;
5553 public:
5554   G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs,
5555                      G1CollectedHeap* g1h) :
5556     AbstractGangTask("G1 Par Cleanup CT Task"),
5557     _ct_bs(ct_bs), _g1h(g1h) { }
5558 
5559   void work(uint worker_id) {
5560     HeapRegion* r;
5561     while (r = _g1h->pop_dirty_cards_region()) {
5562       clear_cards(r);
5563     }
5564   }
5565 
5566   void clear_cards(HeapRegion* r) {
5567     // Cards of the survivors should have already been dirtied.
5568     if (!r->is_survivor()) {
5569       _ct_bs->clear(MemRegion(r->bottom(), r->end()));
5570     }
5571   }
5572 };
5573 
5574 #ifndef PRODUCT
5575 class G1VerifyCardTableCleanup: public HeapRegionClosure {
5576   G1CollectedHeap* _g1h;
5577   G1SATBCardTableModRefBS* _ct_bs;
5578 public:
5579   G1VerifyCardTableCleanup(G1CollectedHeap* g1h, G1SATBCardTableModRefBS* ct_bs)
5580     : _g1h(g1h), _ct_bs(ct_bs) { }
5581   virtual bool doHeapRegion(HeapRegion* r) {
5582     if (r->is_survivor()) {
5583       _g1h->verify_dirty_region(r);
5584     } else {
5585       _g1h->verify_not_dirty_region(r);
5586     }
5587     return false;
5588   }
5589 };
5590 
5591 void G1CollectedHeap::verify_not_dirty_region(HeapRegion* hr) {
5592   // All of the region should be clean.
5593   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5594   MemRegion mr(hr->bottom(), hr->end());
5595   ct_bs->verify_not_dirty_region(mr);
5596 }
5597 
5598 void G1CollectedHeap::verify_dirty_region(HeapRegion* hr) {
5599   // We cannot guarantee that [bottom(),end()] is dirty.  Threads
5600   // dirty allocated blocks as they allocate them. The thread that
5601   // retires each region and replaces it with a new one will do a
5602   // maximal allocation to fill in [pre_dummy_top(),end()] but will
5603   // not dirty that area (one less thing to have to do while holding
5604   // a lock). So we can only verify that [bottom(),pre_dummy_top()]
5605   // is dirty.
5606   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5607   MemRegion mr(hr->bottom(), hr->pre_dummy_top());
5608   if (hr->is_young()) {
5609     ct_bs->verify_g1_young_region(mr);
5610   } else {
5611     ct_bs->verify_dirty_region(mr);
5612   }
5613 }
5614 
5615 void G1CollectedHeap::verify_dirty_young_list(HeapRegion* head) {
5616   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5617   for (HeapRegion* hr = head; hr != NULL; hr = hr->get_next_young_region()) {
5618     verify_dirty_region(hr);
5619   }
5620 }
5621 
5622 void G1CollectedHeap::verify_dirty_young_regions() {
5623   verify_dirty_young_list(_young_list->first_region());
5624 }
5625 
5626 bool G1CollectedHeap::verify_no_bits_over_tams(const char* bitmap_name, CMBitMapRO* bitmap,
5627                                                HeapWord* tams, HeapWord* end) {
5628   guarantee(tams <= end,
5629             err_msg("tams: "PTR_FORMAT" end: "PTR_FORMAT, p2i(tams), p2i(end)));
5630   HeapWord* result = bitmap->getNextMarkedWordAddress(tams, end);
5631   if (result < end) {
5632     gclog_or_tty->cr();
5633     gclog_or_tty->print_cr("## wrong marked address on %s bitmap: "PTR_FORMAT,
5634                            bitmap_name, p2i(result));
5635     gclog_or_tty->print_cr("## %s tams: "PTR_FORMAT" end: "PTR_FORMAT,
5636                            bitmap_name, p2i(tams), p2i(end));
5637     return false;
5638   }
5639   return true;
5640 }
5641 
5642 bool G1CollectedHeap::verify_bitmaps(const char* caller, HeapRegion* hr) {
5643   CMBitMapRO* prev_bitmap = concurrent_mark()->prevMarkBitMap();
5644   CMBitMapRO* next_bitmap = (CMBitMapRO*) concurrent_mark()->nextMarkBitMap();
5645 
5646   HeapWord* bottom = hr->bottom();
5647   HeapWord* ptams  = hr->prev_top_at_mark_start();
5648   HeapWord* ntams  = hr->next_top_at_mark_start();
5649   HeapWord* end    = hr->end();
5650 
5651   bool res_p = verify_no_bits_over_tams("prev", prev_bitmap, ptams, end);
5652 
5653   bool res_n = true;
5654   // We reset mark_in_progress() before we reset _cmThread->in_progress() and in this window
5655   // we do the clearing of the next bitmap concurrently. Thus, we can not verify the bitmap
5656   // if we happen to be in that state.
5657   if (collector_state()->mark_in_progress() || !_cmThread->in_progress()) {
5658     res_n = verify_no_bits_over_tams("next", next_bitmap, ntams, end);
5659   }
5660   if (!res_p || !res_n) {
5661     gclog_or_tty->print_cr("#### Bitmap verification failed for "HR_FORMAT,
5662                            HR_FORMAT_PARAMS(hr));
5663     gclog_or_tty->print_cr("#### Caller: %s", caller);
5664     return false;
5665   }
5666   return true;
5667 }
5668 
5669 void G1CollectedHeap::check_bitmaps(const char* caller, HeapRegion* hr) {
5670   if (!G1VerifyBitmaps) return;
5671 
5672   guarantee(verify_bitmaps(caller, hr), "bitmap verification");
5673 }
5674 
5675 class G1VerifyBitmapClosure : public HeapRegionClosure {
5676 private:
5677   const char* _caller;
5678   G1CollectedHeap* _g1h;
5679   bool _failures;
5680 
5681 public:
5682   G1VerifyBitmapClosure(const char* caller, G1CollectedHeap* g1h) :
5683     _caller(caller), _g1h(g1h), _failures(false) { }
5684 
5685   bool failures() { return _failures; }
5686 
5687   virtual bool doHeapRegion(HeapRegion* hr) {
5688     if (hr->is_continues_humongous()) return false;
5689 
5690     bool result = _g1h->verify_bitmaps(_caller, hr);
5691     if (!result) {
5692       _failures = true;
5693     }
5694     return false;
5695   }
5696 };
5697 
5698 void G1CollectedHeap::check_bitmaps(const char* caller) {
5699   if (!G1VerifyBitmaps) return;
5700 
5701   G1VerifyBitmapClosure cl(caller, this);
5702   heap_region_iterate(&cl);
5703   guarantee(!cl.failures(), "bitmap verification");
5704 }
5705 
5706 class G1CheckCSetFastTableClosure : public HeapRegionClosure {
5707  private:
5708   bool _failures;
5709  public:
5710   G1CheckCSetFastTableClosure() : HeapRegionClosure(), _failures(false) { }
5711 
5712   virtual bool doHeapRegion(HeapRegion* hr) {
5713     uint i = hr->hrm_index();
5714     InCSetState cset_state = (InCSetState) G1CollectedHeap::heap()->_in_cset_fast_test.get_by_index(i);
5715     if (hr->is_humongous()) {
5716       if (hr->in_collection_set()) {
5717         gclog_or_tty->print_cr("\n## humongous region %u in CSet", i);
5718         _failures = true;
5719         return true;
5720       }
5721       if (cset_state.is_in_cset()) {
5722         gclog_or_tty->print_cr("\n## inconsistent cset state %d for humongous region %u", cset_state.value(), i);
5723         _failures = true;
5724         return true;
5725       }
5726       if (hr->is_continues_humongous() && cset_state.is_humongous()) {
5727         gclog_or_tty->print_cr("\n## inconsistent cset state %d for continues humongous region %u", cset_state.value(), i);
5728         _failures = true;
5729         return true;
5730       }
5731     } else {
5732       if (cset_state.is_humongous()) {
5733         gclog_or_tty->print_cr("\n## inconsistent cset state %d for non-humongous region %u", cset_state.value(), i);
5734         _failures = true;
5735         return true;
5736       }
5737       if (hr->in_collection_set() != cset_state.is_in_cset()) {
5738         gclog_or_tty->print_cr("\n## in CSet %d / cset state %d inconsistency for region %u",
5739                                hr->in_collection_set(), cset_state.value(), i);
5740         _failures = true;
5741         return true;
5742       }
5743       if (cset_state.is_in_cset()) {
5744         if (hr->is_young() != (cset_state.is_young())) {
5745           gclog_or_tty->print_cr("\n## is_young %d / cset state %d inconsistency for region %u",
5746                                  hr->is_young(), cset_state.value(), i);
5747           _failures = true;
5748           return true;
5749         }
5750         if (hr->is_old() != (cset_state.is_old())) {
5751           gclog_or_tty->print_cr("\n## is_old %d / cset state %d inconsistency for region %u",
5752                                  hr->is_old(), cset_state.value(), i);
5753           _failures = true;
5754           return true;
5755         }
5756       }
5757     }
5758     return false;
5759   }
5760 
5761   bool failures() const { return _failures; }
5762 };
5763 
5764 bool G1CollectedHeap::check_cset_fast_test() {
5765   G1CheckCSetFastTableClosure cl;
5766   _hrm.iterate(&cl);
5767   return !cl.failures();
5768 }
5769 #endif // PRODUCT
5770 
5771 void G1CollectedHeap::cleanUpCardTable() {
5772   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
5773   double start = os::elapsedTime();
5774 
5775   {
5776     // Iterate over the dirty cards region list.
5777     G1ParCleanupCTTask cleanup_task(ct_bs, this);
5778 
5779     set_par_threads();
5780     workers()->run_task(&cleanup_task);
5781     set_par_threads(0);
5782 #ifndef PRODUCT
5783     if (G1VerifyCTCleanup || VerifyAfterGC) {
5784       G1VerifyCardTableCleanup cleanup_verifier(this, ct_bs);
5785       heap_region_iterate(&cleanup_verifier);
5786     }
5787 #endif
5788   }
5789 
5790   double elapsed = os::elapsedTime() - start;
5791   g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
5792 }
5793 
5794 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info) {
5795   size_t pre_used = 0;
5796   FreeRegionList local_free_list("Local List for CSet Freeing");
5797 
5798   double young_time_ms     = 0.0;
5799   double non_young_time_ms = 0.0;
5800 
5801   // Since the collection set is a superset of the the young list,
5802   // all we need to do to clear the young list is clear its
5803   // head and length, and unlink any young regions in the code below
5804   _young_list->clear();
5805 
5806   G1CollectorPolicy* policy = g1_policy();
5807 
5808   double start_sec = os::elapsedTime();
5809   bool non_young = true;
5810 
5811   HeapRegion* cur = cs_head;
5812   int age_bound = -1;
5813   size_t rs_lengths = 0;
5814 
5815   while (cur != NULL) {
5816     assert(!is_on_master_free_list(cur), "sanity");
5817     if (non_young) {
5818       if (cur->is_young()) {
5819         double end_sec = os::elapsedTime();
5820         double elapsed_ms = (end_sec - start_sec) * 1000.0;
5821         non_young_time_ms += elapsed_ms;
5822 
5823         start_sec = os::elapsedTime();
5824         non_young = false;
5825       }
5826     } else {
5827       if (!cur->is_young()) {
5828         double end_sec = os::elapsedTime();
5829         double elapsed_ms = (end_sec - start_sec) * 1000.0;
5830         young_time_ms += elapsed_ms;
5831 
5832         start_sec = os::elapsedTime();
5833         non_young = true;
5834       }
5835     }
5836 
5837     rs_lengths += cur->rem_set()->occupied_locked();
5838 
5839     HeapRegion* next = cur->next_in_collection_set();
5840     assert(cur->in_collection_set(), "bad CS");
5841     cur->set_next_in_collection_set(NULL);
5842     clear_in_cset(cur);
5843 
5844     if (cur->is_young()) {
5845       int index = cur->young_index_in_cset();
5846       assert(index != -1, "invariant");
5847       assert((uint) index < policy->young_cset_region_length(), "invariant");
5848       size_t words_survived = _surviving_young_words[index];
5849       cur->record_surv_words_in_group(words_survived);
5850 
5851       // At this point the we have 'popped' cur from the collection set
5852       // (linked via next_in_collection_set()) but it is still in the
5853       // young list (linked via next_young_region()). Clear the
5854       // _next_young_region field.
5855       cur->set_next_young_region(NULL);
5856     } else {
5857       int index = cur->young_index_in_cset();
5858       assert(index == -1, "invariant");
5859     }
5860 
5861     assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
5862             (!cur->is_young() && cur->young_index_in_cset() == -1),
5863             "invariant" );
5864 
5865     if (!cur->evacuation_failed()) {
5866       MemRegion used_mr = cur->used_region();
5867 
5868       // And the region is empty.
5869       assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
5870       pre_used += cur->used();
5871       free_region(cur, &local_free_list, false /* par */, true /* locked */);
5872     } else {
5873       cur->uninstall_surv_rate_group();
5874       if (cur->is_young()) {
5875         cur->set_young_index_in_cset(-1);
5876       }
5877       cur->set_evacuation_failed(false);
5878       // The region is now considered to be old.
5879       cur->set_old();
5880       _old_set.add(cur);
5881       evacuation_info.increment_collectionset_used_after(cur->used());
5882     }
5883     cur = next;
5884   }
5885 
5886   evacuation_info.set_regions_freed(local_free_list.length());
5887   policy->record_max_rs_lengths(rs_lengths);
5888   policy->cset_regions_freed();
5889 
5890   double end_sec = os::elapsedTime();
5891   double elapsed_ms = (end_sec - start_sec) * 1000.0;
5892 
5893   if (non_young) {
5894     non_young_time_ms += elapsed_ms;
5895   } else {
5896     young_time_ms += elapsed_ms;
5897   }
5898 
5899   prepend_to_freelist(&local_free_list);
5900   decrement_summary_bytes(pre_used);
5901   policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
5902   policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
5903 }
5904 
5905 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
5906  private:
5907   FreeRegionList* _free_region_list;
5908   HeapRegionSet* _proxy_set;
5909   HeapRegionSetCount _humongous_regions_removed;
5910   size_t _freed_bytes;
5911  public:
5912 
5913   G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
5914     _free_region_list(free_region_list), _humongous_regions_removed(), _freed_bytes(0) {
5915   }
5916 
5917   virtual bool doHeapRegion(HeapRegion* r) {
5918     if (!r->is_starts_humongous()) {
5919       return false;
5920     }
5921 
5922     G1CollectedHeap* g1h = G1CollectedHeap::heap();
5923 
5924     oop obj = (oop)r->bottom();
5925     CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap();
5926 
5927     // The following checks whether the humongous object is live are sufficient.
5928     // The main additional check (in addition to having a reference from the roots
5929     // or the young gen) is whether the humongous object has a remembered set entry.
5930     //
5931     // A humongous object cannot be live if there is no remembered set for it
5932     // because:
5933     // - there can be no references from within humongous starts regions referencing
5934     // the object because we never allocate other objects into them.
5935     // (I.e. there are no intra-region references that may be missed by the
5936     // remembered set)
5937     // - as soon there is a remembered set entry to the humongous starts region
5938     // (i.e. it has "escaped" to an old object) this remembered set entry will stay
5939     // until the end of a concurrent mark.
5940     //
5941     // It is not required to check whether the object has been found dead by marking
5942     // or not, in fact it would prevent reclamation within a concurrent cycle, as
5943     // all objects allocated during that time are considered live.
5944     // SATB marking is even more conservative than the remembered set.
5945     // So if at this point in the collection there is no remembered set entry,
5946     // nobody has a reference to it.
5947     // At the start of collection we flush all refinement logs, and remembered sets
5948     // are completely up-to-date wrt to references to the humongous object.
5949     //
5950     // Other implementation considerations:
5951     // - never consider object arrays at this time because they would pose
5952     // considerable effort for cleaning up the the remembered sets. This is
5953     // required because stale remembered sets might reference locations that
5954     // are currently allocated into.
5955     uint region_idx = r->hrm_index();
5956     if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
5957         !r->rem_set()->is_empty()) {
5958 
5959       if (G1TraceEagerReclaimHumongousObjects) {
5960         gclog_or_tty->print_cr("Live humongous region %u size "SIZE_FORMAT" start "PTR_FORMAT" length %u with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is marked %d reclaim candidate %d type array %d",
5961                                region_idx,
5962                                (size_t)obj->size() * HeapWordSize,
5963                                p2i(r->bottom()),
5964                                r->region_num(),
5965                                r->rem_set()->occupied(),
5966                                r->rem_set()->strong_code_roots_list_length(),
5967                                next_bitmap->isMarked(r->bottom()),
5968                                g1h->is_humongous_reclaim_candidate(region_idx),
5969                                obj->is_typeArray()
5970                               );
5971       }
5972 
5973       return false;
5974     }
5975 
5976     guarantee(obj->is_typeArray(),
5977               err_msg("Only eagerly reclaiming type arrays is supported, but the object "
5978                       PTR_FORMAT " is not.",
5979                       p2i(r->bottom())));
5980 
5981     if (G1TraceEagerReclaimHumongousObjects) {
5982       gclog_or_tty->print_cr("Dead humongous region %u size "SIZE_FORMAT" start "PTR_FORMAT" length %u with remset "SIZE_FORMAT" code roots "SIZE_FORMAT" is marked %d reclaim candidate %d type array %d",
5983                              region_idx,
5984                              (size_t)obj->size() * HeapWordSize,
5985                              p2i(r->bottom()),
5986                              r->region_num(),
5987                              r->rem_set()->occupied(),
5988                              r->rem_set()->strong_code_roots_list_length(),
5989                              next_bitmap->isMarked(r->bottom()),
5990                              g1h->is_humongous_reclaim_candidate(region_idx),
5991                              obj->is_typeArray()
5992                             );
5993     }
5994     // Need to clear mark bit of the humongous object if already set.
5995     if (next_bitmap->isMarked(r->bottom())) {
5996       next_bitmap->clear(r->bottom());
5997     }
5998     _freed_bytes += r->used();
5999     r->set_containing_set(NULL);
6000     _humongous_regions_removed.increment(1u, r->capacity());
6001     g1h->free_humongous_region(r, _free_region_list, false);
6002 
6003     return false;
6004   }
6005 
6006   HeapRegionSetCount& humongous_free_count() {
6007     return _humongous_regions_removed;
6008   }
6009 
6010   size_t bytes_freed() const {
6011     return _freed_bytes;
6012   }
6013 
6014   size_t humongous_reclaimed() const {
6015     return _humongous_regions_removed.length();
6016   }
6017 };
6018 
6019 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
6020   assert_at_safepoint(true);
6021 
6022   if (!G1EagerReclaimHumongousObjects ||
6023       (!_has_humongous_reclaim_candidates && !G1TraceEagerReclaimHumongousObjects)) {
6024     g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
6025     return;
6026   }
6027 
6028   double start_time = os::elapsedTime();
6029 
6030   FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
6031 
6032   G1FreeHumongousRegionClosure cl(&local_cleanup_list);
6033   heap_region_iterate(&cl);
6034 
6035   HeapRegionSetCount empty_set;
6036   remove_from_old_sets(empty_set, cl.humongous_free_count());
6037 
6038   G1HRPrinter* hrp = hr_printer();
6039   if (hrp->is_active()) {
6040     FreeRegionListIterator iter(&local_cleanup_list);
6041     while (iter.more_available()) {
6042       HeapRegion* hr = iter.get_next();
6043       hrp->cleanup(hr);
6044     }
6045   }
6046 
6047   prepend_to_freelist(&local_cleanup_list);
6048   decrement_summary_bytes(cl.bytes_freed());
6049 
6050   g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
6051                                                                     cl.humongous_reclaimed());
6052 }
6053 
6054 // This routine is similar to the above but does not record
6055 // any policy statistics or update free lists; we are abandoning
6056 // the current incremental collection set in preparation of a
6057 // full collection. After the full GC we will start to build up
6058 // the incremental collection set again.
6059 // This is only called when we're doing a full collection
6060 // and is immediately followed by the tearing down of the young list.
6061 
6062 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
6063   HeapRegion* cur = cs_head;
6064 
6065   while (cur != NULL) {
6066     HeapRegion* next = cur->next_in_collection_set();
6067     assert(cur->in_collection_set(), "bad CS");
6068     cur->set_next_in_collection_set(NULL);
6069     clear_in_cset(cur);
6070     cur->set_young_index_in_cset(-1);
6071     cur = next;
6072   }
6073 }
6074 
6075 void G1CollectedHeap::set_free_regions_coming() {
6076   if (G1ConcRegionFreeingVerbose) {
6077     gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6078                            "setting free regions coming");
6079   }
6080 
6081   assert(!free_regions_coming(), "pre-condition");
6082   _free_regions_coming = true;
6083 }
6084 
6085 void G1CollectedHeap::reset_free_regions_coming() {
6086   assert(free_regions_coming(), "pre-condition");
6087 
6088   {
6089     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6090     _free_regions_coming = false;
6091     SecondaryFreeList_lock->notify_all();
6092   }
6093 
6094   if (G1ConcRegionFreeingVerbose) {
6095     gclog_or_tty->print_cr("G1ConcRegionFreeing [cm thread] : "
6096                            "reset free regions coming");
6097   }
6098 }
6099 
6100 void G1CollectedHeap::wait_while_free_regions_coming() {
6101   // Most of the time we won't have to wait, so let's do a quick test
6102   // first before we take the lock.
6103   if (!free_regions_coming()) {
6104     return;
6105   }
6106 
6107   if (G1ConcRegionFreeingVerbose) {
6108     gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6109                            "waiting for free regions");
6110   }
6111 
6112   {
6113     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6114     while (free_regions_coming()) {
6115       SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
6116     }
6117   }
6118 
6119   if (G1ConcRegionFreeingVerbose) {
6120     gclog_or_tty->print_cr("G1ConcRegionFreeing [other] : "
6121                            "done waiting for free regions");
6122   }
6123 }
6124 
6125 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
6126   _young_list->push_region(hr);
6127 }
6128 
6129 class NoYoungRegionsClosure: public HeapRegionClosure {
6130 private:
6131   bool _success;
6132 public:
6133   NoYoungRegionsClosure() : _success(true) { }
6134   bool doHeapRegion(HeapRegion* r) {
6135     if (r->is_young()) {
6136       gclog_or_tty->print_cr("Region ["PTR_FORMAT", "PTR_FORMAT") tagged as young",
6137                              p2i(r->bottom()), p2i(r->end()));
6138       _success = false;
6139     }
6140     return false;
6141   }
6142   bool success() { return _success; }
6143 };
6144 
6145 bool G1CollectedHeap::check_young_list_empty(bool check_heap, bool check_sample) {
6146   bool ret = _young_list->check_list_empty(check_sample);
6147 
6148   if (check_heap) {
6149     NoYoungRegionsClosure closure;
6150     heap_region_iterate(&closure);
6151     ret = ret && closure.success();
6152   }
6153 
6154   return ret;
6155 }
6156 
6157 class TearDownRegionSetsClosure : public HeapRegionClosure {
6158 private:
6159   HeapRegionSet *_old_set;
6160 
6161 public:
6162   TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
6163 
6164   bool doHeapRegion(HeapRegion* r) {
6165     if (r->is_old()) {
6166       _old_set->remove(r);
6167     } else {
6168       // We ignore free regions, we'll empty the free list afterwards.
6169       // We ignore young regions, we'll empty the young list afterwards.
6170       // We ignore humongous regions, we're not tearing down the
6171       // humongous regions set.
6172       assert(r->is_free() || r->is_young() || r->is_humongous(),
6173              "it cannot be another type");
6174     }
6175     return false;
6176   }
6177 
6178   ~TearDownRegionSetsClosure() {
6179     assert(_old_set->is_empty(), "post-condition");
6180   }
6181 };
6182 
6183 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
6184   assert_at_safepoint(true /* should_be_vm_thread */);
6185 
6186   if (!free_list_only) {
6187     TearDownRegionSetsClosure cl(&_old_set);
6188     heap_region_iterate(&cl);
6189 
6190     // Note that emptying the _young_list is postponed and instead done as
6191     // the first step when rebuilding the regions sets again. The reason for
6192     // this is that during a full GC string deduplication needs to know if
6193     // a collected region was young or old when the full GC was initiated.
6194   }
6195   _hrm.remove_all_free_regions();
6196 }
6197 
6198 class RebuildRegionSetsClosure : public HeapRegionClosure {
6199 private:
6200   bool            _free_list_only;
6201   HeapRegionSet*   _old_set;
6202   HeapRegionManager*   _hrm;
6203   size_t          _total_used;
6204 
6205 public:
6206   RebuildRegionSetsClosure(bool free_list_only,
6207                            HeapRegionSet* old_set, HeapRegionManager* hrm) :
6208     _free_list_only(free_list_only),
6209     _old_set(old_set), _hrm(hrm), _total_used(0) {
6210     assert(_hrm->num_free_regions() == 0, "pre-condition");
6211     if (!free_list_only) {
6212       assert(_old_set->is_empty(), "pre-condition");
6213     }
6214   }
6215 
6216   bool doHeapRegion(HeapRegion* r) {
6217     if (r->is_continues_humongous()) {
6218       return false;
6219     }
6220 
6221     if (r->is_empty()) {
6222       // Add free regions to the free list
6223       r->set_free();
6224       r->set_allocation_context(AllocationContext::system());
6225       _hrm->insert_into_free_list(r);
6226     } else if (!_free_list_only) {
6227       assert(!r->is_young(), "we should not come across young regions");
6228 
6229       if (r->is_humongous()) {
6230         // We ignore humongous regions, we left the humongous set unchanged
6231       } else {
6232         // Objects that were compacted would have ended up on regions
6233         // that were previously old or free.
6234         assert(r->is_free() || r->is_old(), "invariant");
6235         // We now consider them old, so register as such.
6236         r->set_old();
6237         _old_set->add(r);
6238       }
6239       _total_used += r->used();
6240     }
6241 
6242     return false;
6243   }
6244 
6245   size_t total_used() {
6246     return _total_used;
6247   }
6248 };
6249 
6250 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
6251   assert_at_safepoint(true /* should_be_vm_thread */);
6252 
6253   if (!free_list_only) {
6254     _young_list->empty_list();
6255   }
6256 
6257   RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
6258   heap_region_iterate(&cl);
6259 
6260   if (!free_list_only) {
6261     _allocator->set_used(cl.total_used());
6262   }
6263   assert(_allocator->used_unlocked() == recalculate_used(),
6264          err_msg("inconsistent _allocator->used_unlocked(), "
6265                  "value: "SIZE_FORMAT" recalculated: "SIZE_FORMAT,
6266                  _allocator->used_unlocked(), recalculate_used()));
6267 }
6268 
6269 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
6270   _refine_cte_cl->set_concurrent(concurrent);
6271 }
6272 
6273 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
6274   HeapRegion* hr = heap_region_containing(p);
6275   return hr->is_in(p);
6276 }
6277 
6278 // Methods for the mutator alloc region
6279 
6280 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
6281                                                       bool force) {
6282   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6283   assert(!force || g1_policy()->can_expand_young_list(),
6284          "if force is true we should be able to expand the young list");
6285   bool young_list_full = g1_policy()->is_young_list_full();
6286   if (force || !young_list_full) {
6287     HeapRegion* new_alloc_region = new_region(word_size,
6288                                               false /* is_old */,
6289                                               false /* do_expand */);
6290     if (new_alloc_region != NULL) {
6291       set_region_short_lived_locked(new_alloc_region);
6292       _hr_printer.alloc(new_alloc_region, G1HRPrinter::Eden, young_list_full);
6293       check_bitmaps("Mutator Region Allocation", new_alloc_region);
6294       return new_alloc_region;
6295     }
6296   }
6297   return NULL;
6298 }
6299 
6300 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
6301                                                   size_t allocated_bytes) {
6302   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6303   assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
6304 
6305   g1_policy()->add_region_to_incremental_cset_lhs(alloc_region);
6306   _allocator->increase_used(allocated_bytes);
6307   _hr_printer.retire(alloc_region);
6308   // We update the eden sizes here, when the region is retired,
6309   // instead of when it's allocated, since this is the point that its
6310   // used space has been recored in _summary_bytes_used.
6311   g1mm()->update_eden_size();
6312 }
6313 
6314 void G1CollectedHeap::set_par_threads() {
6315   // Don't change the number of workers.  Use the value previously set
6316   // in the workgroup.
6317   uint n_workers = workers()->active_workers();
6318   assert(UseDynamicNumberOfGCThreads ||
6319            n_workers == workers()->total_workers(),
6320       "Otherwise should be using the total number of workers");
6321   if (n_workers == 0) {
6322     assert(false, "Should have been set in prior evacuation pause.");
6323     n_workers = ParallelGCThreads;
6324     workers()->set_active_workers(n_workers);
6325   }
6326   set_par_threads(n_workers);
6327 }
6328 
6329 // Methods for the GC alloc regions
6330 
6331 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
6332                                                  uint count,
6333                                                  InCSetState dest) {
6334   assert(FreeList_lock->owned_by_self(), "pre-condition");
6335 
6336   if (count < g1_policy()->max_regions(dest)) {
6337     const bool is_survivor = (dest.is_young());
6338     HeapRegion* new_alloc_region = new_region(word_size,
6339                                               !is_survivor,
6340                                               true /* do_expand */);
6341     if (new_alloc_region != NULL) {
6342       // We really only need to do this for old regions given that we
6343       // should never scan survivors. But it doesn't hurt to do it
6344       // for survivors too.
6345       new_alloc_region->record_timestamp();
6346       if (is_survivor) {
6347         new_alloc_region->set_survivor();
6348         _hr_printer.alloc(new_alloc_region, G1HRPrinter::Survivor);
6349         check_bitmaps("Survivor Region Allocation", new_alloc_region);
6350       } else {
6351         new_alloc_region->set_old();
6352         _hr_printer.alloc(new_alloc_region, G1HRPrinter::Old);
6353         check_bitmaps("Old Region Allocation", new_alloc_region);
6354       }
6355       bool during_im = collector_state()->during_initial_mark_pause();
6356       new_alloc_region->note_start_of_copying(during_im);
6357       return new_alloc_region;
6358     }
6359   }
6360   return NULL;
6361 }
6362 
6363 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
6364                                              size_t allocated_bytes,
6365                                              InCSetState dest) {
6366   bool during_im = collector_state()->during_initial_mark_pause();
6367   alloc_region->note_end_of_copying(during_im);
6368   g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
6369   if (dest.is_young()) {
6370     young_list()->add_survivor_region(alloc_region);
6371   } else {
6372     _old_set.add(alloc_region);
6373   }
6374   _hr_printer.retire(alloc_region);
6375 }
6376 
6377 // Heap region set verification
6378 
6379 class VerifyRegionListsClosure : public HeapRegionClosure {
6380 private:
6381   HeapRegionSet*   _old_set;
6382   HeapRegionSet*   _humongous_set;
6383   HeapRegionManager*   _hrm;
6384 
6385 public:
6386   HeapRegionSetCount _old_count;
6387   HeapRegionSetCount _humongous_count;
6388   HeapRegionSetCount _free_count;
6389 
6390   VerifyRegionListsClosure(HeapRegionSet* old_set,
6391                            HeapRegionSet* humongous_set,
6392                            HeapRegionManager* hrm) :
6393     _old_set(old_set), _humongous_set(humongous_set), _hrm(hrm),
6394     _old_count(), _humongous_count(), _free_count(){ }
6395 
6396   bool doHeapRegion(HeapRegion* hr) {
6397     if (hr->is_continues_humongous()) {
6398       return false;
6399     }
6400 
6401     if (hr->is_young()) {
6402       // TODO
6403     } else if (hr->is_starts_humongous()) {
6404       assert(hr->containing_set() == _humongous_set, err_msg("Heap region %u is starts humongous but not in humongous set.", hr->hrm_index()));
6405       _humongous_count.increment(1u, hr->capacity());
6406     } else if (hr->is_empty()) {
6407       assert(_hrm->is_free(hr), err_msg("Heap region %u is empty but not on the free list.", hr->hrm_index()));
6408       _free_count.increment(1u, hr->capacity());
6409     } else if (hr->is_old()) {
6410       assert(hr->containing_set() == _old_set, err_msg("Heap region %u is old but not in the old set.", hr->hrm_index()));
6411       _old_count.increment(1u, hr->capacity());
6412     } else {
6413       ShouldNotReachHere();
6414     }
6415     return false;
6416   }
6417 
6418   void verify_counts(HeapRegionSet* old_set, HeapRegionSet* humongous_set, HeapRegionManager* free_list) {
6419     guarantee(old_set->length() == _old_count.length(), err_msg("Old set count mismatch. Expected %u, actual %u.", old_set->length(), _old_count.length()));
6420     guarantee(old_set->total_capacity_bytes() == _old_count.capacity(), err_msg("Old set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6421         old_set->total_capacity_bytes(), _old_count.capacity()));
6422 
6423     guarantee(humongous_set->length() == _humongous_count.length(), err_msg("Hum set count mismatch. Expected %u, actual %u.", humongous_set->length(), _humongous_count.length()));
6424     guarantee(humongous_set->total_capacity_bytes() == _humongous_count.capacity(), err_msg("Hum set capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6425         humongous_set->total_capacity_bytes(), _humongous_count.capacity()));
6426 
6427     guarantee(free_list->num_free_regions() == _free_count.length(), err_msg("Free list count mismatch. Expected %u, actual %u.", free_list->num_free_regions(), _free_count.length()));
6428     guarantee(free_list->total_capacity_bytes() == _free_count.capacity(), err_msg("Free list capacity mismatch. Expected " SIZE_FORMAT ", actual " SIZE_FORMAT,
6429         free_list->total_capacity_bytes(), _free_count.capacity()));
6430   }
6431 };
6432 
6433 void G1CollectedHeap::verify_region_sets() {
6434   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
6435 
6436   // First, check the explicit lists.
6437   _hrm.verify();
6438   {
6439     // Given that a concurrent operation might be adding regions to
6440     // the secondary free list we have to take the lock before
6441     // verifying it.
6442     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
6443     _secondary_free_list.verify_list();
6444   }
6445 
6446   // If a concurrent region freeing operation is in progress it will
6447   // be difficult to correctly attributed any free regions we come
6448   // across to the correct free list given that they might belong to
6449   // one of several (free_list, secondary_free_list, any local lists,
6450   // etc.). So, if that's the case we will skip the rest of the
6451   // verification operation. Alternatively, waiting for the concurrent
6452   // operation to complete will have a non-trivial effect on the GC's
6453   // operation (no concurrent operation will last longer than the
6454   // interval between two calls to verification) and it might hide
6455   // any issues that we would like to catch during testing.
6456   if (free_regions_coming()) {
6457     return;
6458   }
6459 
6460   // Make sure we append the secondary_free_list on the free_list so
6461   // that all free regions we will come across can be safely
6462   // attributed to the free_list.
6463   append_secondary_free_list_if_not_empty_with_lock();
6464 
6465   // Finally, make sure that the region accounting in the lists is
6466   // consistent with what we see in the heap.
6467 
6468   VerifyRegionListsClosure cl(&_old_set, &_humongous_set, &_hrm);
6469   heap_region_iterate(&cl);
6470   cl.verify_counts(&_old_set, &_humongous_set, &_hrm);
6471 }
6472 
6473 // Optimized nmethod scanning
6474 
6475 class RegisterNMethodOopClosure: public OopClosure {
6476   G1CollectedHeap* _g1h;
6477   nmethod* _nm;
6478 
6479   template <class T> void do_oop_work(T* p) {
6480     T heap_oop = oopDesc::load_heap_oop(p);
6481     if (!oopDesc::is_null(heap_oop)) {
6482       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6483       HeapRegion* hr = _g1h->heap_region_containing(obj);
6484       assert(!hr->is_continues_humongous(),
6485              err_msg("trying to add code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6486                      " starting at "HR_FORMAT,
6487                      p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6488 
6489       // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
6490       hr->add_strong_code_root_locked(_nm);
6491     }
6492   }
6493 
6494 public:
6495   RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6496     _g1h(g1h), _nm(nm) {}
6497 
6498   void do_oop(oop* p)       { do_oop_work(p); }
6499   void do_oop(narrowOop* p) { do_oop_work(p); }
6500 };
6501 
6502 class UnregisterNMethodOopClosure: public OopClosure {
6503   G1CollectedHeap* _g1h;
6504   nmethod* _nm;
6505 
6506   template <class T> void do_oop_work(T* p) {
6507     T heap_oop = oopDesc::load_heap_oop(p);
6508     if (!oopDesc::is_null(heap_oop)) {
6509       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
6510       HeapRegion* hr = _g1h->heap_region_containing(obj);
6511       assert(!hr->is_continues_humongous(),
6512              err_msg("trying to remove code root "PTR_FORMAT" in continuation of humongous region "HR_FORMAT
6513                      " starting at "HR_FORMAT,
6514                      p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region())));
6515 
6516       hr->remove_strong_code_root(_nm);
6517     }
6518   }
6519 
6520 public:
6521   UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
6522     _g1h(g1h), _nm(nm) {}
6523 
6524   void do_oop(oop* p)       { do_oop_work(p); }
6525   void do_oop(narrowOop* p) { do_oop_work(p); }
6526 };
6527 
6528 void G1CollectedHeap::register_nmethod(nmethod* nm) {
6529   CollectedHeap::register_nmethod(nm);
6530 
6531   guarantee(nm != NULL, "sanity");
6532   RegisterNMethodOopClosure reg_cl(this, nm);
6533   nm->oops_do(&reg_cl);
6534 }
6535 
6536 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
6537   CollectedHeap::unregister_nmethod(nm);
6538 
6539   guarantee(nm != NULL, "sanity");
6540   UnregisterNMethodOopClosure reg_cl(this, nm);
6541   nm->oops_do(&reg_cl, true);
6542 }
6543 
6544 void G1CollectedHeap::purge_code_root_memory() {
6545   double purge_start = os::elapsedTime();
6546   G1CodeRootSet::purge();
6547   double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
6548   g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
6549 }
6550 
6551 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
6552   G1CollectedHeap* _g1h;
6553 
6554 public:
6555   RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
6556     _g1h(g1h) {}
6557 
6558   void do_code_blob(CodeBlob* cb) {
6559     nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
6560     if (nm == NULL) {
6561       return;
6562     }
6563 
6564     if (ScavengeRootsInCode) {
6565       _g1h->register_nmethod(nm);
6566     }
6567   }
6568 };
6569 
6570 void G1CollectedHeap::rebuild_strong_code_roots() {
6571   RebuildStrongCodeRootClosure blob_cl(this);
6572   CodeCache::blobs_do(&blob_cl);
6573 }