1 /*
   2  * Copyright (c) 2001, 2016, 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 "classfile/symbolTable.hpp"
  29 #include "code/codeCache.hpp"
  30 #include "code/icBuffer.hpp"
  31 #include "gc/g1/bufferingOopClosure.hpp"
  32 #include "gc/g1/concurrentG1Refine.hpp"
  33 #include "gc/g1/concurrentG1RefineThread.hpp"
  34 #include "gc/g1/concurrentMarkThread.inline.hpp"
  35 #include "gc/g1/g1Allocator.inline.hpp"
  36 #include "gc/g1/g1CollectedHeap.inline.hpp"
  37 #include "gc/g1/g1CollectionSet.hpp"
  38 #include "gc/g1/g1CollectorPolicy.hpp"
  39 #include "gc/g1/g1CollectorState.hpp"
  40 #include "gc/g1/g1EvacStats.inline.hpp"
  41 #include "gc/g1/g1GCPhaseTimes.hpp"
  42 #include "gc/g1/g1HeapTransition.hpp"
  43 #include "gc/g1/g1HeapVerifier.hpp"
  44 #include "gc/g1/g1MarkSweep.hpp"
  45 #include "gc/g1/g1OopClosures.inline.hpp"
  46 #include "gc/g1/g1ParScanThreadState.inline.hpp"
  47 #include "gc/g1/g1RegionToSpaceMapper.hpp"
  48 #include "gc/g1/g1RemSet.inline.hpp"
  49 #include "gc/g1/g1RootClosures.hpp"
  50 #include "gc/g1/g1RootProcessor.hpp"
  51 #include "gc/g1/g1StringDedup.hpp"
  52 #include "gc/g1/g1YCTypes.hpp"
  53 #include "gc/g1/heapRegion.inline.hpp"
  54 #include "gc/g1/heapRegionRemSet.hpp"
  55 #include "gc/g1/heapRegionSet.inline.hpp"
  56 #include "gc/g1/suspendibleThreadSet.hpp"
  57 #include "gc/g1/vm_operations_g1.hpp"
  58 #include "gc/shared/gcHeapSummary.hpp"
  59 #include "gc/shared/gcId.hpp"
  60 #include "gc/shared/gcLocker.inline.hpp"
  61 #include "gc/shared/gcTimer.hpp"
  62 #include "gc/shared/gcTrace.hpp"
  63 #include "gc/shared/gcTraceTime.inline.hpp"
  64 #include "gc/shared/generationSpec.hpp"
  65 #include "gc/shared/isGCActiveMark.hpp"
  66 #include "gc/shared/referenceProcessor.inline.hpp"
  67 #include "gc/shared/taskqueue.inline.hpp"
  68 #include "logging/log.hpp"
  69 #include "memory/allocation.hpp"
  70 #include "memory/iterator.hpp"
  71 #include "memory/resourceArea.hpp"
  72 #include "oops/oop.inline.hpp"
  73 #include "runtime/atomic.inline.hpp"
  74 #include "runtime/init.hpp"
  75 #include "runtime/orderAccess.inline.hpp"
  76 #include "runtime/vmThread.hpp"
  77 #include "utilities/globalDefinitions.hpp"
  78 #include "utilities/stack.inline.hpp"
  79 
  80 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
  81 
  82 // INVARIANTS/NOTES
  83 //
  84 // All allocation activity covered by the G1CollectedHeap interface is
  85 // serialized by acquiring the HeapLock.  This happens in mem_allocate
  86 // and allocate_new_tlab, which are the "entry" points to the
  87 // allocation code from the rest of the JVM.  (Note that this does not
  88 // apply to TLAB allocation, which is not part of this interface: it
  89 // is done by clients of this interface.)
  90 
  91 // Local to this file.
  92 
  93 class RefineCardTableEntryClosure: public CardTableEntryClosure {
  94   bool _concurrent;
  95 public:
  96   RefineCardTableEntryClosure() : _concurrent(true) { }
  97 
  98   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
  99     bool oops_into_cset = G1CollectedHeap::heap()->g1_rem_set()->refine_card(card_ptr, worker_i, false);
 100     // This path is executed by the concurrent refine or mutator threads,
 101     // concurrently, and so we do not care if card_ptr contains references
 102     // that point into the collection set.
 103     assert(!oops_into_cset, "should be");
 104 
 105     if (_concurrent && SuspendibleThreadSet::should_yield()) {
 106       // Caller will actually yield.
 107       return false;
 108     }
 109     // Otherwise, we finished successfully; return true.
 110     return true;
 111   }
 112 
 113   void set_concurrent(bool b) { _concurrent = b; }
 114 };
 115 
 116 
 117 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
 118  private:
 119   size_t _num_dirtied;
 120   G1CollectedHeap* _g1h;
 121   G1SATBCardTableLoggingModRefBS* _g1_bs;
 122 
 123   HeapRegion* region_for_card(jbyte* card_ptr) const {
 124     return _g1h->heap_region_containing(_g1_bs->addr_for(card_ptr));
 125   }
 126 
 127   bool will_become_free(HeapRegion* hr) const {
 128     // A region will be freed by free_collection_set if the region is in the
 129     // collection set and has not had an evacuation failure.
 130     return _g1h->is_in_cset(hr) && !hr->evacuation_failed();
 131   }
 132 
 133  public:
 134   RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(),
 135     _num_dirtied(0), _g1h(g1h), _g1_bs(g1h->g1_barrier_set()) { }
 136 
 137   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
 138     HeapRegion* hr = region_for_card(card_ptr);
 139 
 140     // Should only dirty cards in regions that won't be freed.
 141     if (!will_become_free(hr)) {
 142       *card_ptr = CardTableModRefBS::dirty_card_val();
 143       _num_dirtied++;
 144     }
 145 
 146     return true;
 147   }
 148 
 149   size_t num_dirtied()   const { return _num_dirtied; }
 150 };
 151 
 152 
 153 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
 154   HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
 155 }
 156 
 157 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
 158   // The from card cache is not the memory that is actually committed. So we cannot
 159   // take advantage of the zero_filled parameter.
 160   reset_from_card_cache(start_idx, num_regions);
 161 }
 162 
 163 void G1CollectedHeap::push_dirty_cards_region(HeapRegion* hr)
 164 {
 165   // Claim the right to put the region on the dirty cards region list
 166   // by installing a self pointer.
 167   HeapRegion* next = hr->get_next_dirty_cards_region();
 168   if (next == NULL) {
 169     HeapRegion* res = (HeapRegion*)
 170       Atomic::cmpxchg_ptr(hr, hr->next_dirty_cards_region_addr(),
 171                           NULL);
 172     if (res == NULL) {
 173       HeapRegion* head;
 174       do {
 175         // Put the region to the dirty cards region list.
 176         head = _dirty_cards_region_list;
 177         next = (HeapRegion*)
 178           Atomic::cmpxchg_ptr(hr, &_dirty_cards_region_list, head);
 179         if (next == head) {
 180           assert(hr->get_next_dirty_cards_region() == hr,
 181                  "hr->get_next_dirty_cards_region() != hr");
 182           if (next == NULL) {
 183             // The last region in the list points to itself.
 184             hr->set_next_dirty_cards_region(hr);
 185           } else {
 186             hr->set_next_dirty_cards_region(next);
 187           }
 188         }
 189       } while (next != head);
 190     }
 191   }
 192 }
 193 
 194 HeapRegion* G1CollectedHeap::pop_dirty_cards_region()
 195 {
 196   HeapRegion* head;
 197   HeapRegion* hr;
 198   do {
 199     head = _dirty_cards_region_list;
 200     if (head == NULL) {
 201       return NULL;
 202     }
 203     HeapRegion* new_head = head->get_next_dirty_cards_region();
 204     if (head == new_head) {
 205       // The last region.
 206       new_head = NULL;
 207     }
 208     hr = (HeapRegion*)Atomic::cmpxchg_ptr(new_head, &_dirty_cards_region_list,
 209                                           head);
 210   } while (hr != head);
 211   assert(hr != NULL, "invariant");
 212   hr->set_next_dirty_cards_region(NULL);
 213   return hr;
 214 }
 215 
 216 // Returns true if the reference points to an object that
 217 // can move in an incremental collection.
 218 bool G1CollectedHeap::is_scavengable(const void* p) {
 219   HeapRegion* hr = heap_region_containing(p);
 220   return !hr->is_pinned();
 221 }
 222 
 223 // Private methods.
 224 
 225 HeapRegion*
 226 G1CollectedHeap::new_region_try_secondary_free_list(bool is_old) {
 227   MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
 228   while (!_secondary_free_list.is_empty() || free_regions_coming()) {
 229     if (!_secondary_free_list.is_empty()) {
 230       log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 231                                       "secondary_free_list has %u entries",
 232                                       _secondary_free_list.length());
 233       // It looks as if there are free regions available on the
 234       // secondary_free_list. Let's move them to the free_list and try
 235       // again to allocate from it.
 236       append_secondary_free_list();
 237 
 238       assert(_hrm.num_free_regions() > 0, "if the secondary_free_list was not "
 239              "empty we should have moved at least one entry to the free_list");
 240       HeapRegion* res = _hrm.allocate_free_region(is_old);
 241       log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 242                                       "allocated " HR_FORMAT " from secondary_free_list",
 243                                       HR_FORMAT_PARAMS(res));
 244       return res;
 245     }
 246 
 247     // Wait here until we get notified either when (a) there are no
 248     // more free regions coming or (b) some regions have been moved on
 249     // the secondary_free_list.
 250     SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
 251   }
 252 
 253   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 254                                   "could not allocate from secondary_free_list");
 255   return NULL;
 256 }
 257 
 258 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
 259   assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
 260          "the only time we use this to allocate a humongous region is "
 261          "when we are allocating a single humongous region");
 262 
 263   HeapRegion* res;
 264   if (G1StressConcRegionFreeing) {
 265     if (!_secondary_free_list.is_empty()) {
 266       log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 267                                       "forced to look at the secondary_free_list");
 268       res = new_region_try_secondary_free_list(is_old);
 269       if (res != NULL) {
 270         return res;
 271       }
 272     }
 273   }
 274 
 275   res = _hrm.allocate_free_region(is_old);
 276 
 277   if (res == NULL) {
 278     log_develop_trace(gc, freelist)("G1ConcRegionFreeing [region alloc] : "
 279                                     "res == NULL, trying the secondary_free_list");
 280     res = new_region_try_secondary_free_list(is_old);
 281   }
 282   if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
 283     // Currently, only attempts to allocate GC alloc regions set
 284     // do_expand to true. So, we should only reach here during a
 285     // safepoint. If this assumption changes we might have to
 286     // reconsider the use of _expand_heap_after_alloc_failure.
 287     assert(SafepointSynchronize::is_at_safepoint(), "invariant");
 288 
 289     log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B",
 290                               word_size * HeapWordSize);
 291 
 292     if (expand(word_size * HeapWordSize)) {
 293       // Given that expand() succeeded in expanding the heap, and we
 294       // always expand the heap by an amount aligned to the heap
 295       // region size, the free list should in theory not be empty.
 296       // In either case allocate_free_region() will check for NULL.
 297       res = _hrm.allocate_free_region(is_old);
 298     } else {
 299       _expand_heap_after_alloc_failure = false;
 300     }
 301   }
 302   return res;
 303 }
 304 
 305 HeapWord*
 306 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
 307                                                            uint num_regions,
 308                                                            size_t word_size,
 309                                                            AllocationContext_t context) {
 310   assert(first != G1_NO_HRM_INDEX, "pre-condition");
 311   assert(is_humongous(word_size), "word_size should be humongous");
 312   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 313 
 314   // Index of last region in the series.
 315   uint last = first + num_regions - 1;
 316 
 317   // We need to initialize the region(s) we just discovered. This is
 318   // a bit tricky given that it can happen concurrently with
 319   // refinement threads refining cards on these regions and
 320   // potentially wanting to refine the BOT as they are scanning
 321   // those cards (this can happen shortly after a cleanup; see CR
 322   // 6991377). So we have to set up the region(s) carefully and in
 323   // a specific order.
 324 
 325   // The word size sum of all the regions we will allocate.
 326   size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
 327   assert(word_size <= word_size_sum, "sanity");
 328 
 329   // This will be the "starts humongous" region.
 330   HeapRegion* first_hr = region_at(first);
 331   // The header of the new object will be placed at the bottom of
 332   // the first region.
 333   HeapWord* new_obj = first_hr->bottom();
 334   // This will be the new top of the new object.
 335   HeapWord* obj_top = new_obj + word_size;
 336 
 337   // First, we need to zero the header of the space that we will be
 338   // allocating. When we update top further down, some refinement
 339   // threads might try to scan the region. By zeroing the header we
 340   // ensure that any thread that will try to scan the region will
 341   // come across the zero klass word and bail out.
 342   //
 343   // NOTE: It would not have been correct to have used
 344   // CollectedHeap::fill_with_object() and make the space look like
 345   // an int array. The thread that is doing the allocation will
 346   // later update the object header to a potentially different array
 347   // type and, for a very short period of time, the klass and length
 348   // fields will be inconsistent. This could cause a refinement
 349   // thread to calculate the object size incorrectly.
 350   Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
 351 
 352   // How many words we use for filler objects.
 353   size_t word_fill_size = word_size_sum - word_size;
 354 
 355   // How many words memory we "waste" which cannot hold a filler object.
 356   size_t words_not_fillable = 0;
 357 
 358   if (word_fill_size >= min_fill_size()) {
 359     fill_with_objects(obj_top, word_fill_size);
 360   } else if (word_fill_size > 0) {
 361     // We have space to fill, but we cannot fit an object there.
 362     words_not_fillable = word_fill_size;
 363     word_fill_size = 0;
 364   }
 365 
 366   // We will set up the first region as "starts humongous". This
 367   // will also update the BOT covering all the regions to reflect
 368   // that there is a single object that starts at the bottom of the
 369   // first region.
 370   first_hr->set_starts_humongous(obj_top, word_fill_size);
 371   first_hr->set_allocation_context(context);
 372   // Then, if there are any, we will set up the "continues
 373   // humongous" regions.
 374   HeapRegion* hr = NULL;
 375   for (uint i = first + 1; i <= last; ++i) {
 376     hr = region_at(i);
 377     hr->set_continues_humongous(first_hr);
 378     hr->set_allocation_context(context);
 379   }
 380 
 381   // Up to this point no concurrent thread would have been able to
 382   // do any scanning on any region in this series. All the top
 383   // fields still point to bottom, so the intersection between
 384   // [bottom,top] and [card_start,card_end] will be empty. Before we
 385   // update the top fields, we'll do a storestore to make sure that
 386   // no thread sees the update to top before the zeroing of the
 387   // object header and the BOT initialization.
 388   OrderAccess::storestore();
 389 
 390   // Now, we will update the top fields of the "continues humongous"
 391   // regions except the last one.
 392   for (uint i = first; i < last; ++i) {
 393     hr = region_at(i);
 394     hr->set_top(hr->end());
 395   }
 396 
 397   hr = region_at(last);
 398   // If we cannot fit a filler object, we must set top to the end
 399   // of the humongous object, otherwise we cannot iterate the heap
 400   // and the BOT will not be complete.
 401   hr->set_top(hr->end() - words_not_fillable);
 402 
 403   assert(hr->bottom() < obj_top && obj_top <= hr->end(),
 404          "obj_top should be in last region");
 405 
 406   _verifier->check_bitmaps("Humongous Region Allocation", first_hr);
 407 
 408   assert(words_not_fillable == 0 ||
 409          first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(),
 410          "Miscalculation in humongous allocation");
 411 
 412   increase_used((word_size_sum - words_not_fillable) * HeapWordSize);
 413 
 414   for (uint i = first; i <= last; ++i) {
 415     hr = region_at(i);
 416     _humongous_set.add(hr);
 417     _hr_printer.alloc(hr);
 418   }
 419 
 420   return new_obj;
 421 }
 422 
 423 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) {
 424   assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size);
 425   return align_size_up_(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
 426 }
 427 
 428 // If could fit into free regions w/o expansion, try.
 429 // Otherwise, if can expand, do so.
 430 // Otherwise, if using ex regions might help, try with ex given back.
 431 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size, AllocationContext_t context) {
 432   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 433 
 434   _verifier->verify_region_sets_optional();
 435 
 436   uint first = G1_NO_HRM_INDEX;
 437   uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);
 438 
 439   if (obj_regions == 1) {
 440     // Only one region to allocate, try to use a fast path by directly allocating
 441     // from the free lists. Do not try to expand here, we will potentially do that
 442     // later.
 443     HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
 444     if (hr != NULL) {
 445       first = hr->hrm_index();
 446     }
 447   } else {
 448     // We can't allocate humongous regions spanning more than one region while
 449     // cleanupComplete() is running, since some of the regions we find to be
 450     // empty might not yet be added to the free list. It is not straightforward
 451     // to know in which list they are on so that we can remove them. We only
 452     // need to do this if we need to allocate more than one region to satisfy the
 453     // current humongous allocation request. If we are only allocating one region
 454     // we use the one-region region allocation code (see above), that already
 455     // potentially waits for regions from the secondary free list.
 456     wait_while_free_regions_coming();
 457     append_secondary_free_list_if_not_empty_with_lock();
 458 
 459     // Policy: Try only empty regions (i.e. already committed first). Maybe we
 460     // are lucky enough to find some.
 461     first = _hrm.find_contiguous_only_empty(obj_regions);
 462     if (first != G1_NO_HRM_INDEX) {
 463       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 464     }
 465   }
 466 
 467   if (first == G1_NO_HRM_INDEX) {
 468     // Policy: We could not find enough regions for the humongous object in the
 469     // free list. Look through the heap to find a mix of free and uncommitted regions.
 470     // If so, try expansion.
 471     first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
 472     if (first != G1_NO_HRM_INDEX) {
 473       // We found something. Make sure these regions are committed, i.e. expand
 474       // the heap. Alternatively we could do a defragmentation GC.
 475       log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B",
 476                                     word_size * HeapWordSize);
 477 
 478 
 479       _hrm.expand_at(first, obj_regions);
 480       g1_policy()->record_new_heap_size(num_regions());
 481 
 482 #ifdef ASSERT
 483       for (uint i = first; i < first + obj_regions; ++i) {
 484         HeapRegion* hr = region_at(i);
 485         assert(hr->is_free(), "sanity");
 486         assert(hr->is_empty(), "sanity");
 487         assert(is_on_master_free_list(hr), "sanity");
 488       }
 489 #endif
 490       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 491     } else {
 492       // Policy: Potentially trigger a defragmentation GC.
 493     }
 494   }
 495 
 496   HeapWord* result = NULL;
 497   if (first != G1_NO_HRM_INDEX) {
 498     result = humongous_obj_allocate_initialize_regions(first, obj_regions,
 499                                                        word_size, context);
 500     assert(result != NULL, "it should always return a valid result");
 501 
 502     // A successful humongous object allocation changes the used space
 503     // information of the old generation so we need to recalculate the
 504     // sizes and update the jstat counters here.
 505     g1mm()->update_sizes();
 506   }
 507 
 508   _verifier->verify_region_sets_optional();
 509 
 510   return result;
 511 }
 512 
 513 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
 514   assert_heap_not_locked_and_not_at_safepoint();
 515   assert(!is_humongous(word_size), "we do not allow humongous TLABs");
 516 
 517   uint dummy_gc_count_before;
 518   uint dummy_gclocker_retry_count = 0;
 519   return attempt_allocation(word_size, &dummy_gc_count_before, &dummy_gclocker_retry_count);
 520 }
 521 
 522 HeapWord*
 523 G1CollectedHeap::mem_allocate(size_t word_size,
 524                               bool*  gc_overhead_limit_was_exceeded) {
 525   assert_heap_not_locked_and_not_at_safepoint();
 526 
 527   // Loop until the allocation is satisfied, or unsatisfied after GC.
 528   for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 529     uint gc_count_before;
 530 
 531     HeapWord* result = NULL;
 532     if (!is_humongous(word_size)) {
 533       result = attempt_allocation(word_size, &gc_count_before, &gclocker_retry_count);
 534     } else {
 535       result = attempt_allocation_humongous(word_size, &gc_count_before, &gclocker_retry_count);
 536     }
 537     if (result != NULL) {
 538       return result;
 539     }
 540 
 541     // Create the garbage collection operation...
 542     VM_G1CollectForAllocation op(gc_count_before, word_size);
 543     op.set_allocation_context(AllocationContext::current());
 544 
 545     // ...and get the VM thread to execute it.
 546     VMThread::execute(&op);
 547 
 548     if (op.prologue_succeeded() && op.pause_succeeded()) {
 549       // If the operation was successful we'll return the result even
 550       // if it is NULL. If the allocation attempt failed immediately
 551       // after a Full GC, it's unlikely we'll be able to allocate now.
 552       HeapWord* result = op.result();
 553       if (result != NULL && !is_humongous(word_size)) {
 554         // Allocations that take place on VM operations do not do any
 555         // card dirtying and we have to do it here. We only have to do
 556         // this for non-humongous allocations, though.
 557         dirty_young_block(result, word_size);
 558       }
 559       return result;
 560     } else {
 561       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 562         return NULL;
 563       }
 564       assert(op.result() == NULL,
 565              "the result should be NULL if the VM op did not succeed");
 566     }
 567 
 568     // Give a warning if we seem to be looping forever.
 569     if ((QueuedAllocationWarningCount > 0) &&
 570         (try_count % QueuedAllocationWarningCount == 0)) {
 571       log_warning(gc)("G1CollectedHeap::mem_allocate retries %d times", try_count);
 572     }
 573   }
 574 
 575   ShouldNotReachHere();
 576   return NULL;
 577 }
 578 
 579 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size,
 580                                                    AllocationContext_t context,
 581                                                    uint* gc_count_before_ret,
 582                                                    uint* gclocker_retry_count_ret) {
 583   // Make sure you read the note in attempt_allocation_humongous().
 584 
 585   assert_heap_not_locked_and_not_at_safepoint();
 586   assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
 587          "be called for humongous allocation requests");
 588 
 589   // We should only get here after the first-level allocation attempt
 590   // (attempt_allocation()) failed to allocate.
 591 
 592   // We will loop until a) we manage to successfully perform the
 593   // allocation or b) we successfully schedule a collection which
 594   // fails to perform the allocation. b) is the only case when we'll
 595   // return NULL.
 596   HeapWord* result = NULL;
 597   for (int try_count = 1; /* we'll return */; try_count += 1) {
 598     bool should_try_gc;
 599     uint gc_count_before;
 600 
 601     {
 602       MutexLockerEx x(Heap_lock);
 603       result = _allocator->attempt_allocation_locked(word_size, context);
 604       if (result != NULL) {
 605         return result;
 606       }
 607 
 608       if (GCLocker::is_active_and_needs_gc()) {
 609         if (g1_policy()->can_expand_young_list()) {
 610           // No need for an ergo verbose message here,
 611           // can_expand_young_list() does this when it returns true.
 612           result = _allocator->attempt_allocation_force(word_size, context);
 613           if (result != NULL) {
 614             return result;
 615           }
 616         }
 617         should_try_gc = false;
 618       } else {
 619         // The GCLocker may not be active but the GCLocker initiated
 620         // GC may not yet have been performed (GCLocker::needs_gc()
 621         // returns true). In this case we do not try this GC and
 622         // wait until the GCLocker initiated GC is performed, and
 623         // then retry the allocation.
 624         if (GCLocker::needs_gc()) {
 625           should_try_gc = false;
 626         } else {
 627           // Read the GC count while still holding the Heap_lock.
 628           gc_count_before = total_collections();
 629           should_try_gc = true;
 630         }
 631       }
 632     }
 633 
 634     if (should_try_gc) {
 635       bool succeeded;
 636       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 637                                    GCCause::_g1_inc_collection_pause);
 638       if (result != NULL) {
 639         assert(succeeded, "only way to get back a non-NULL result");
 640         return result;
 641       }
 642 
 643       if (succeeded) {
 644         // If we get here we successfully scheduled a collection which
 645         // failed to allocate. No point in trying to allocate
 646         // further. We'll just return NULL.
 647         MutexLockerEx x(Heap_lock);
 648         *gc_count_before_ret = total_collections();
 649         return NULL;
 650       }
 651     } else {
 652       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
 653         MutexLockerEx x(Heap_lock);
 654         *gc_count_before_ret = total_collections();
 655         return NULL;
 656       }
 657       // The GCLocker is either active or the GCLocker initiated
 658       // GC has not yet been performed. Stall until it is and
 659       // then retry the allocation.
 660       GCLocker::stall_until_clear();
 661       (*gclocker_retry_count_ret) += 1;
 662     }
 663 
 664     // We can reach here if we were unsuccessful in scheduling a
 665     // collection (because another thread beat us to it) or if we were
 666     // stalled due to the GC locker. In either can we should retry the
 667     // allocation attempt in case another thread successfully
 668     // performed a collection and reclaimed enough space. We do the
 669     // first attempt (without holding the Heap_lock) here and the
 670     // follow-on attempt will be at the start of the next loop
 671     // iteration (after taking the Heap_lock).
 672     result = _allocator->attempt_allocation(word_size, context);
 673     if (result != NULL) {
 674       return result;
 675     }
 676 
 677     // Give a warning if we seem to be looping forever.
 678     if ((QueuedAllocationWarningCount > 0) &&
 679         (try_count % QueuedAllocationWarningCount == 0)) {
 680       log_warning(gc)("G1CollectedHeap::attempt_allocation_slow() "
 681                       "retries %d times", try_count);
 682     }
 683   }
 684 
 685   ShouldNotReachHere();
 686   return NULL;
 687 }
 688 
 689 void G1CollectedHeap::begin_archive_alloc_range() {
 690   assert_at_safepoint(true /* should_be_vm_thread */);
 691   if (_archive_allocator == NULL) {
 692     _archive_allocator = G1ArchiveAllocator::create_allocator(this);
 693   }
 694 }
 695 
 696 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) {
 697   // Allocations in archive regions cannot be of a size that would be considered
 698   // humongous even for a minimum-sized region, because G1 region sizes/boundaries
 699   // may be different at archive-restore time.
 700   return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words());
 701 }
 702 
 703 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) {
 704   assert_at_safepoint(true /* should_be_vm_thread */);
 705   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 706   if (is_archive_alloc_too_large(word_size)) {
 707     return NULL;
 708   }
 709   return _archive_allocator->archive_mem_allocate(word_size);
 710 }
 711 
 712 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
 713                                               size_t end_alignment_in_bytes) {
 714   assert_at_safepoint(true /* should_be_vm_thread */);
 715   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 716 
 717   // Call complete_archive to do the real work, filling in the MemRegion
 718   // array with the archive regions.
 719   _archive_allocator->complete_archive(ranges, end_alignment_in_bytes);
 720   delete _archive_allocator;
 721   _archive_allocator = NULL;
 722 }
 723 
 724 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) {
 725   assert(ranges != NULL, "MemRegion array NULL");
 726   assert(count != 0, "No MemRegions provided");
 727   MemRegion reserved = _hrm.reserved();
 728   for (size_t i = 0; i < count; i++) {
 729     if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) {
 730       return false;
 731     }
 732   }
 733   return true;
 734 }
 735 
 736 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges, size_t count) {
 737   assert(!is_init_completed(), "Expect to be called at JVM init time");
 738   assert(ranges != NULL, "MemRegion array NULL");
 739   assert(count != 0, "No MemRegions provided");
 740   MutexLockerEx x(Heap_lock);
 741 
 742   MemRegion reserved = _hrm.reserved();
 743   HeapWord* prev_last_addr = NULL;
 744   HeapRegion* prev_last_region = NULL;
 745 
 746   // Temporarily disable pretouching of heap pages. This interface is used
 747   // when mmap'ing archived heap data in, so pre-touching is wasted.
 748   FlagSetting fs(AlwaysPreTouch, false);
 749 
 750   // Enable archive object checking in G1MarkSweep. We have to let it know
 751   // about each archive range, so that objects in those ranges aren't marked.
 752   G1MarkSweep::enable_archive_object_check();
 753 
 754   // For each specified MemRegion range, allocate the corresponding G1
 755   // regions and mark them as archive regions. We expect the ranges in
 756   // ascending starting address order, without overlap.
 757   for (size_t i = 0; i < count; i++) {
 758     MemRegion curr_range = ranges[i];
 759     HeapWord* start_address = curr_range.start();
 760     size_t word_size = curr_range.word_size();
 761     HeapWord* last_address = curr_range.last();
 762     size_t commits = 0;
 763 
 764     guarantee(reserved.contains(start_address) && reserved.contains(last_address),
 765               "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 766               p2i(start_address), p2i(last_address));
 767     guarantee(start_address > prev_last_addr,
 768               "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 769               p2i(start_address), p2i(prev_last_addr));
 770     prev_last_addr = last_address;
 771 
 772     // Check for ranges that start in the same G1 region in which the previous
 773     // range ended, and adjust the start address so we don't try to allocate
 774     // the same region again. If the current range is entirely within that
 775     // region, skip it, just adjusting the recorded top.
 776     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 777     if ((prev_last_region != NULL) && (start_region == prev_last_region)) {
 778       start_address = start_region->end();
 779       if (start_address > last_address) {
 780         increase_used(word_size * HeapWordSize);
 781         start_region->set_top(last_address + 1);
 782         continue;
 783       }
 784       start_region->set_top(start_address);
 785       curr_range = MemRegion(start_address, last_address + 1);
 786       start_region = _hrm.addr_to_region(start_address);
 787     }
 788 
 789     // Perform the actual region allocation, exiting if it fails.
 790     // Then note how much new space we have allocated.
 791     if (!_hrm.allocate_containing_regions(curr_range, &commits)) {
 792       return false;
 793     }
 794     increase_used(word_size * HeapWordSize);
 795     if (commits != 0) {
 796       log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B",
 797                                 HeapRegion::GrainWords * HeapWordSize * commits);
 798 
 799     }
 800 
 801     // Mark each G1 region touched by the range as archive, add it to the old set,
 802     // and set the allocation context and top.
 803     HeapRegion* curr_region = _hrm.addr_to_region(start_address);
 804     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 805     prev_last_region = last_region;
 806 
 807     while (curr_region != NULL) {
 808       assert(curr_region->is_empty() && !curr_region->is_pinned(),
 809              "Region already in use (index %u)", curr_region->hrm_index());
 810       curr_region->set_allocation_context(AllocationContext::system());
 811       curr_region->set_archive();
 812       _hr_printer.alloc(curr_region);
 813       _old_set.add(curr_region);
 814       if (curr_region != last_region) {
 815         curr_region->set_top(curr_region->end());
 816         curr_region = _hrm.next_region_in_heap(curr_region);
 817       } else {
 818         curr_region->set_top(last_address + 1);
 819         curr_region = NULL;
 820       }
 821     }
 822 
 823     // Notify mark-sweep of the archive range.
 824     G1MarkSweep::set_range_archive(curr_range, true);
 825   }
 826   return true;
 827 }
 828 
 829 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) {
 830   assert(!is_init_completed(), "Expect to be called at JVM init time");
 831   assert(ranges != NULL, "MemRegion array NULL");
 832   assert(count != 0, "No MemRegions provided");
 833   MemRegion reserved = _hrm.reserved();
 834   HeapWord *prev_last_addr = NULL;
 835   HeapRegion* prev_last_region = NULL;
 836 
 837   // For each MemRegion, create filler objects, if needed, in the G1 regions
 838   // that contain the address range. The address range actually within the
 839   // MemRegion will not be modified. That is assumed to have been initialized
 840   // elsewhere, probably via an mmap of archived heap data.
 841   MutexLockerEx x(Heap_lock);
 842   for (size_t i = 0; i < count; i++) {
 843     HeapWord* start_address = ranges[i].start();
 844     HeapWord* last_address = ranges[i].last();
 845 
 846     assert(reserved.contains(start_address) && reserved.contains(last_address),
 847            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 848            p2i(start_address), p2i(last_address));
 849     assert(start_address > prev_last_addr,
 850            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 851            p2i(start_address), p2i(prev_last_addr));
 852 
 853     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 854     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 855     HeapWord* bottom_address = start_region->bottom();
 856 
 857     // Check for a range beginning in the same region in which the
 858     // previous one ended.
 859     if (start_region == prev_last_region) {
 860       bottom_address = prev_last_addr + 1;
 861     }
 862 
 863     // Verify that the regions were all marked as archive regions by
 864     // alloc_archive_regions.
 865     HeapRegion* curr_region = start_region;
 866     while (curr_region != NULL) {
 867       guarantee(curr_region->is_archive(),
 868                 "Expected archive region at index %u", curr_region->hrm_index());
 869       if (curr_region != last_region) {
 870         curr_region = _hrm.next_region_in_heap(curr_region);
 871       } else {
 872         curr_region = NULL;
 873       }
 874     }
 875 
 876     prev_last_addr = last_address;
 877     prev_last_region = last_region;
 878 
 879     // Fill the memory below the allocated range with dummy object(s),
 880     // if the region bottom does not match the range start, or if the previous
 881     // range ended within the same G1 region, and there is a gap.
 882     if (start_address != bottom_address) {
 883       size_t fill_size = pointer_delta(start_address, bottom_address);
 884       G1CollectedHeap::fill_with_objects(bottom_address, fill_size);
 885       increase_used(fill_size * HeapWordSize);
 886     }
 887   }
 888 }
 889 
 890 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size,
 891                                                      uint* gc_count_before_ret,
 892                                                      uint* gclocker_retry_count_ret) {
 893   assert_heap_not_locked_and_not_at_safepoint();
 894   assert(!is_humongous(word_size), "attempt_allocation() should not "
 895          "be called for humongous allocation requests");
 896 
 897   AllocationContext_t context = AllocationContext::current();
 898   HeapWord* result = _allocator->attempt_allocation(word_size, context);
 899 
 900   if (result == NULL) {
 901     result = attempt_allocation_slow(word_size,
 902                                      context,
 903                                      gc_count_before_ret,
 904                                      gclocker_retry_count_ret);
 905   }
 906   assert_heap_not_locked();
 907   if (result != NULL) {
 908     dirty_young_block(result, word_size);
 909   }
 910   return result;
 911 }
 912 
 913 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) {
 914   assert(!is_init_completed(), "Expect to be called at JVM init time");
 915   assert(ranges != NULL, "MemRegion array NULL");
 916   assert(count != 0, "No MemRegions provided");
 917   MemRegion reserved = _hrm.reserved();
 918   HeapWord* prev_last_addr = NULL;
 919   HeapRegion* prev_last_region = NULL;
 920   size_t size_used = 0;
 921   size_t uncommitted_regions = 0;
 922 
 923   // For each Memregion, free the G1 regions that constitute it, and
 924   // notify mark-sweep that the range is no longer to be considered 'archive.'
 925   MutexLockerEx x(Heap_lock);
 926   for (size_t i = 0; i < count; i++) {
 927     HeapWord* start_address = ranges[i].start();
 928     HeapWord* last_address = ranges[i].last();
 929 
 930     assert(reserved.contains(start_address) && reserved.contains(last_address),
 931            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 932            p2i(start_address), p2i(last_address));
 933     assert(start_address > prev_last_addr,
 934            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 935            p2i(start_address), p2i(prev_last_addr));
 936     size_used += ranges[i].byte_size();
 937     prev_last_addr = last_address;
 938 
 939     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 940     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 941 
 942     // Check for ranges that start in the same G1 region in which the previous
 943     // range ended, and adjust the start address so we don't try to free
 944     // the same region again. If the current range is entirely within that
 945     // region, skip it.
 946     if (start_region == prev_last_region) {
 947       start_address = start_region->end();
 948       if (start_address > last_address) {
 949         continue;
 950       }
 951       start_region = _hrm.addr_to_region(start_address);
 952     }
 953     prev_last_region = last_region;
 954 
 955     // After verifying that each region was marked as an archive region by
 956     // alloc_archive_regions, set it free and empty and uncommit it.
 957     HeapRegion* curr_region = start_region;
 958     while (curr_region != NULL) {
 959       guarantee(curr_region->is_archive(),
 960                 "Expected archive region at index %u", curr_region->hrm_index());
 961       uint curr_index = curr_region->hrm_index();
 962       _old_set.remove(curr_region);
 963       curr_region->set_free();
 964       curr_region->set_top(curr_region->bottom());
 965       if (curr_region != last_region) {
 966         curr_region = _hrm.next_region_in_heap(curr_region);
 967       } else {
 968         curr_region = NULL;
 969       }
 970       _hrm.shrink_at(curr_index, 1);
 971       uncommitted_regions++;
 972     }
 973 
 974     // Notify mark-sweep that this is no longer an archive range.
 975     G1MarkSweep::set_range_archive(ranges[i], false);
 976   }
 977 
 978   if (uncommitted_regions != 0) {
 979     log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B",
 980                               HeapRegion::GrainWords * HeapWordSize * uncommitted_regions);
 981   }
 982   decrease_used(size_used);
 983 }
 984 
 985 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size,
 986                                                         uint* gc_count_before_ret,
 987                                                         uint* gclocker_retry_count_ret) {
 988   // The structure of this method has a lot of similarities to
 989   // attempt_allocation_slow(). The reason these two were not merged
 990   // into a single one is that such a method would require several "if
 991   // allocation is not humongous do this, otherwise do that"
 992   // conditional paths which would obscure its flow. In fact, an early
 993   // version of this code did use a unified method which was harder to
 994   // follow and, as a result, it had subtle bugs that were hard to
 995   // track down. So keeping these two methods separate allows each to
 996   // be more readable. It will be good to keep these two in sync as
 997   // much as possible.
 998 
 999   assert_heap_not_locked_and_not_at_safepoint();
1000   assert(is_humongous(word_size), "attempt_allocation_humongous() "
1001          "should only be called for humongous allocations");
1002 
1003   // Humongous objects can exhaust the heap quickly, so we should check if we
1004   // need to start a marking cycle at each humongous object allocation. We do
1005   // the check before we do the actual allocation. The reason for doing it
1006   // before the allocation is that we avoid having to keep track of the newly
1007   // allocated memory while we do a GC.
1008   if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
1009                                            word_size)) {
1010     collect(GCCause::_g1_humongous_allocation);
1011   }
1012 
1013   // We will loop until a) we manage to successfully perform the
1014   // allocation or b) we successfully schedule a collection which
1015   // fails to perform the allocation. b) is the only case when we'll
1016   // return NULL.
1017   HeapWord* result = NULL;
1018   for (int try_count = 1; /* we'll return */; try_count += 1) {
1019     bool should_try_gc;
1020     uint gc_count_before;
1021 
1022     {
1023       MutexLockerEx x(Heap_lock);
1024 
1025       // Given that humongous objects are not allocated in young
1026       // regions, we'll first try to do the allocation without doing a
1027       // collection hoping that there's enough space in the heap.
1028       result = humongous_obj_allocate(word_size, AllocationContext::current());
1029       if (result != NULL) {
1030         size_t size_in_regions = humongous_obj_size_in_regions(word_size);
1031         g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
1032         return result;
1033       }
1034 
1035       if (GCLocker::is_active_and_needs_gc()) {
1036         should_try_gc = false;
1037       } else {
1038          // The GCLocker may not be active but the GCLocker initiated
1039         // GC may not yet have been performed (GCLocker::needs_gc()
1040         // returns true). In this case we do not try this GC and
1041         // wait until the GCLocker initiated GC is performed, and
1042         // then retry the allocation.
1043         if (GCLocker::needs_gc()) {
1044           should_try_gc = false;
1045         } else {
1046           // Read the GC count while still holding the Heap_lock.
1047           gc_count_before = total_collections();
1048           should_try_gc = true;
1049         }
1050       }
1051     }
1052 
1053     if (should_try_gc) {
1054       // If we failed to allocate the humongous object, we should try to
1055       // do a collection pause (if we're allowed) in case it reclaims
1056       // enough space for the allocation to succeed after the pause.
1057 
1058       bool succeeded;
1059       result = do_collection_pause(word_size, gc_count_before, &succeeded,
1060                                    GCCause::_g1_humongous_allocation);
1061       if (result != NULL) {
1062         assert(succeeded, "only way to get back a non-NULL result");
1063         return result;
1064       }
1065 
1066       if (succeeded) {
1067         // If we get here we successfully scheduled a collection which
1068         // failed to allocate. No point in trying to allocate
1069         // further. We'll just return NULL.
1070         MutexLockerEx x(Heap_lock);
1071         *gc_count_before_ret = total_collections();
1072         return NULL;
1073       }
1074     } else {
1075       if (*gclocker_retry_count_ret > GCLockerRetryAllocationCount) {
1076         MutexLockerEx x(Heap_lock);
1077         *gc_count_before_ret = total_collections();
1078         return NULL;
1079       }
1080       // The GCLocker is either active or the GCLocker initiated
1081       // GC has not yet been performed. Stall until it is and
1082       // then retry the allocation.
1083       GCLocker::stall_until_clear();
1084       (*gclocker_retry_count_ret) += 1;
1085     }
1086 
1087     // We can reach here if we were unsuccessful in scheduling a
1088     // collection (because another thread beat us to it) or if we were
1089     // stalled due to the GC locker. In either can we should retry the
1090     // allocation attempt in case another thread successfully
1091     // performed a collection and reclaimed enough space.  Give a
1092     // warning if we seem to be looping forever.
1093 
1094     if ((QueuedAllocationWarningCount > 0) &&
1095         (try_count % QueuedAllocationWarningCount == 0)) {
1096       log_warning(gc)("G1CollectedHeap::attempt_allocation_humongous() "
1097                       "retries %d times", try_count);
1098     }
1099   }
1100 
1101   ShouldNotReachHere();
1102   return NULL;
1103 }
1104 
1105 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
1106                                                            AllocationContext_t context,
1107                                                            bool expect_null_mutator_alloc_region) {
1108   assert_at_safepoint(true /* should_be_vm_thread */);
1109   assert(!_allocator->has_mutator_alloc_region(context) || !expect_null_mutator_alloc_region,
1110          "the current alloc region was unexpectedly found to be non-NULL");
1111 
1112   if (!is_humongous(word_size)) {
1113     return _allocator->attempt_allocation_locked(word_size, context);
1114   } else {
1115     HeapWord* result = humongous_obj_allocate(word_size, context);
1116     if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
1117       collector_state()->set_initiate_conc_mark_if_possible(true);
1118     }
1119     return result;
1120   }
1121 
1122   ShouldNotReachHere();
1123 }
1124 
1125 class PostMCRemSetClearClosure: public HeapRegionClosure {
1126   G1CollectedHeap* _g1h;
1127   ModRefBarrierSet* _mr_bs;
1128 public:
1129   PostMCRemSetClearClosure(G1CollectedHeap* g1h, ModRefBarrierSet* mr_bs) :
1130     _g1h(g1h), _mr_bs(mr_bs) {}
1131 
1132   bool doHeapRegion(HeapRegion* r) {
1133     HeapRegionRemSet* hrrs = r->rem_set();
1134 
1135     _g1h->reset_gc_time_stamps(r);
1136 
1137     if (r->is_continues_humongous()) {
1138       // We'll assert that the strong code root list and RSet is empty
1139       assert(hrrs->strong_code_roots_list_length() == 0, "sanity");
1140       assert(hrrs->occupied() == 0, "RSet should be empty");
1141     } else {
1142       hrrs->clear();
1143     }
1144     // You might think here that we could clear just the cards
1145     // corresponding to the used region.  But no: if we leave a dirty card
1146     // in a region we might allocate into, then it would prevent that card
1147     // from being enqueued, and cause it to be missed.
1148     // Re: the performance cost: we shouldn't be doing full GC anyway!
1149     _mr_bs->clear(MemRegion(r->bottom(), r->end()));
1150 
1151     return false;
1152   }
1153 };
1154 
1155 void G1CollectedHeap::clear_rsets_post_compaction() {
1156   PostMCRemSetClearClosure rs_clear(this, g1_barrier_set());
1157   heap_region_iterate(&rs_clear);
1158 }
1159 
1160 class RebuildRSOutOfRegionClosure: public HeapRegionClosure {
1161   G1CollectedHeap*   _g1h;
1162   UpdateRSOopClosure _cl;
1163 public:
1164   RebuildRSOutOfRegionClosure(G1CollectedHeap* g1, uint worker_i = 0) :
1165     _cl(g1->g1_rem_set(), worker_i),
1166     _g1h(g1)
1167   { }
1168 
1169   bool doHeapRegion(HeapRegion* r) {
1170     if (!r->is_continues_humongous()) {
1171       _cl.set_from(r);
1172       r->oop_iterate(&_cl);
1173     }
1174     return false;
1175   }
1176 };
1177 
1178 class ParRebuildRSTask: public AbstractGangTask {
1179   G1CollectedHeap* _g1;
1180   HeapRegionClaimer _hrclaimer;
1181 
1182 public:
1183   ParRebuildRSTask(G1CollectedHeap* g1) :
1184       AbstractGangTask("ParRebuildRSTask"), _g1(g1), _hrclaimer(g1->workers()->active_workers()) {}
1185 
1186   void work(uint worker_id) {
1187     RebuildRSOutOfRegionClosure rebuild_rs(_g1, worker_id);
1188     _g1->heap_region_par_iterate(&rebuild_rs, worker_id, &_hrclaimer);
1189   }
1190 };
1191 
1192 class PostCompactionPrinterClosure: public HeapRegionClosure {
1193 private:
1194   G1HRPrinter* _hr_printer;
1195 public:
1196   bool doHeapRegion(HeapRegion* hr) {
1197     assert(!hr->is_young(), "not expecting to find young regions");
1198     _hr_printer->post_compaction(hr);
1199     return false;
1200   }
1201 
1202   PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
1203     : _hr_printer(hr_printer) { }
1204 };
1205 
1206 void G1CollectedHeap::print_hrm_post_compaction() {
1207   if (_hr_printer.is_active()) {
1208     PostCompactionPrinterClosure cl(hr_printer());
1209     heap_region_iterate(&cl);
1210   }
1211 
1212 }
1213 
1214 bool G1CollectedHeap::do_full_collection(bool explicit_gc,
1215                                          bool clear_all_soft_refs) {
1216   assert_at_safepoint(true /* should_be_vm_thread */);
1217 
1218   if (GCLocker::check_active_before_gc()) {
1219     return false;
1220   }
1221 
1222   STWGCTimer* gc_timer = G1MarkSweep::gc_timer();
1223   gc_timer->register_gc_start();
1224 
1225   SerialOldTracer* gc_tracer = G1MarkSweep::gc_tracer();
1226   GCIdMark gc_id_mark;
1227   gc_tracer->report_gc_start(gc_cause(), gc_timer->gc_start());
1228 
1229   SvcGCMarker sgcm(SvcGCMarker::FULL);
1230   ResourceMark rm;
1231 
1232   print_heap_before_gc();
1233   print_heap_regions();
1234   trace_heap_before_gc(gc_tracer);
1235 
1236   size_t metadata_prev_used = MetaspaceAux::used_bytes();
1237 
1238   _verifier->verify_region_sets_optional();
1239 
1240   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1241                            collector_policy()->should_clear_all_soft_refs();
1242 
1243   ClearedAllSoftRefs casr(do_clear_all_soft_refs, collector_policy());
1244 
1245   {
1246     IsGCActiveMark x;
1247 
1248     // Timing
1249     assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant");
1250     GCTraceCPUTime tcpu;
1251 
1252     {
1253       GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true);
1254       TraceCollectorStats tcs(g1mm()->full_collection_counters());
1255       TraceMemoryManagerStats tms(true /* fullGC */, gc_cause());
1256 
1257       G1HeapTransition heap_transition(this);
1258       g1_policy()->record_full_collection_start();
1259 
1260       // Note: When we have a more flexible GC logging framework that
1261       // allows us to add optional attributes to a GC log record we
1262       // could consider timing and reporting how long we wait in the
1263       // following two methods.
1264       wait_while_free_regions_coming();
1265       // If we start the compaction before the CM threads finish
1266       // scanning the root regions we might trip them over as we'll
1267       // be moving objects / updating references. So let's wait until
1268       // they are done. By telling them to abort, they should complete
1269       // early.
1270       _cm->root_regions()->abort();
1271       _cm->root_regions()->wait_until_scan_finished();
1272       append_secondary_free_list_if_not_empty_with_lock();
1273 
1274       gc_prologue(true);
1275       increment_total_collections(true /* full gc */);
1276       increment_old_marking_cycles_started();
1277 
1278       assert(used() == recalculate_used(), "Should be equal");
1279 
1280       _verifier->verify_before_gc();
1281 
1282       _verifier->check_bitmaps("Full GC Start");
1283       pre_full_gc_dump(gc_timer);
1284 
1285 #if defined(COMPILER2) || INCLUDE_JVMCI
1286       DerivedPointerTable::clear();
1287 #endif
1288 
1289       // Disable discovery and empty the discovered lists
1290       // for the CM ref processor.
1291       ref_processor_cm()->disable_discovery();
1292       ref_processor_cm()->abandon_partial_discovery();
1293       ref_processor_cm()->verify_no_references_recorded();
1294 
1295       // Abandon current iterations of concurrent marking and concurrent
1296       // refinement, if any are in progress.
1297       concurrent_mark()->abort();
1298 
1299       // Make sure we'll choose a new allocation region afterwards.
1300       _allocator->release_mutator_alloc_region();
1301       _allocator->abandon_gc_alloc_regions();
1302       g1_rem_set()->cleanupHRRS();
1303 
1304       // We may have added regions to the current incremental collection
1305       // set between the last GC or pause and now. We need to clear the
1306       // incremental collection set and then start rebuilding it afresh
1307       // after this full GC.
1308       abandon_collection_set(collection_set()->inc_head());
1309       collection_set()->clear_incremental();
1310       collection_set()->stop_incremental_building();
1311 
1312       tear_down_region_sets(false /* free_list_only */);
1313       collector_state()->set_gcs_are_young(true);
1314 
1315       // See the comments in g1CollectedHeap.hpp and
1316       // G1CollectedHeap::ref_processing_init() about
1317       // how reference processing currently works in G1.
1318 
1319       // Temporarily make discovery by the STW ref processor single threaded (non-MT).
1320       ReferenceProcessorMTDiscoveryMutator stw_rp_disc_ser(ref_processor_stw(), false);
1321 
1322       // Temporarily clear the STW ref processor's _is_alive_non_header field.
1323       ReferenceProcessorIsAliveMutator stw_rp_is_alive_null(ref_processor_stw(), NULL);
1324 
1325       ref_processor_stw()->enable_discovery();
1326       ref_processor_stw()->setup_policy(do_clear_all_soft_refs);
1327 
1328       // Do collection work
1329       {
1330         HandleMark hm;  // Discard invalid handles created during gc
1331         G1MarkSweep::invoke_at_safepoint(ref_processor_stw(), do_clear_all_soft_refs);
1332       }
1333 
1334       assert(num_free_regions() == 0, "we should not have added any free regions");
1335       rebuild_region_sets(false /* free_list_only */);
1336 
1337       // Enqueue any discovered reference objects that have
1338       // not been removed from the discovered lists.
1339       ref_processor_stw()->enqueue_discovered_references();
1340 
1341 #if defined(COMPILER2) || INCLUDE_JVMCI
1342       DerivedPointerTable::update_pointers();
1343 #endif
1344 
1345       MemoryService::track_memory_usage();
1346 
1347       assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1348       ref_processor_stw()->verify_no_references_recorded();
1349 
1350       // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1351       ClassLoaderDataGraph::purge();
1352       MetaspaceAux::verify_metrics();
1353 
1354       // Note: since we've just done a full GC, concurrent
1355       // marking is no longer active. Therefore we need not
1356       // re-enable reference discovery for the CM ref processor.
1357       // That will be done at the start of the next marking cycle.
1358       assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1359       ref_processor_cm()->verify_no_references_recorded();
1360 
1361       reset_gc_time_stamp();
1362       // Since everything potentially moved, we will clear all remembered
1363       // sets, and clear all cards.  Later we will rebuild remembered
1364       // sets. We will also reset the GC time stamps of the regions.
1365       clear_rsets_post_compaction();
1366       check_gc_time_stamps();
1367 
1368       resize_if_necessary_after_full_collection();
1369 
1370       // We should do this after we potentially resize the heap so
1371       // that all the COMMIT / UNCOMMIT events are generated before
1372       // the compaction events.
1373       print_hrm_post_compaction();
1374 
1375       G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
1376       if (hot_card_cache->use_cache()) {
1377         hot_card_cache->reset_card_counts();
1378         hot_card_cache->reset_hot_cache();
1379       }
1380 
1381       // Rebuild remembered sets of all regions.
1382       uint n_workers =
1383         AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
1384                                                 workers()->active_workers(),
1385                                                 Threads::number_of_non_daemon_threads());
1386       workers()->set_active_workers(n_workers);
1387 
1388       ParRebuildRSTask rebuild_rs_task(this);
1389       workers()->run_task(&rebuild_rs_task);
1390 
1391       // Rebuild the strong code root lists for each region
1392       rebuild_strong_code_roots();
1393 
1394       if (true) { // FIXME
1395         MetaspaceGC::compute_new_size();
1396       }
1397 
1398 #ifdef TRACESPINNING
1399       ParallelTaskTerminator::print_termination_counts();
1400 #endif
1401 
1402       // Discard all rset updates
1403       JavaThread::dirty_card_queue_set().abandon_logs();
1404       assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1405 
1406       // At this point there should be no regions in the
1407       // entire heap tagged as young.
1408       assert(check_young_list_empty(true /* check_heap */),
1409              "young list should be empty at this point");
1410 
1411       // Update the number of full collections that have been completed.
1412       increment_old_marking_cycles_completed(false /* concurrent */);
1413 
1414       _hrm.verify_optional();
1415       _verifier->verify_region_sets_optional();
1416 
1417       _verifier->verify_after_gc();
1418 
1419       // Clear the previous marking bitmap, if needed for bitmap verification.
1420       // Note we cannot do this when we clear the next marking bitmap in
1421       // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the
1422       // objects marked during a full GC against the previous bitmap.
1423       // But we need to clear it before calling check_bitmaps below since
1424       // the full GC has compacted objects and updated TAMS but not updated
1425       // the prev bitmap.
1426       if (G1VerifyBitmaps) {
1427         ((G1CMBitMap*) concurrent_mark()->prevMarkBitMap())->clearAll();
1428       }
1429       _verifier->check_bitmaps("Full GC End");
1430 
1431       // Start a new incremental collection set for the next pause
1432       assert(collection_set()->head() == NULL, "must be");
1433       collection_set()->start_incremental_building();
1434 
1435       clear_cset_fast_test();
1436 
1437       _allocator->init_mutator_alloc_region();
1438 
1439       g1_policy()->record_full_collection_end();
1440 
1441       // We must call G1MonitoringSupport::update_sizes() in the same scoping level
1442       // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
1443       // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
1444       // before any GC notifications are raised.
1445       g1mm()->update_sizes();
1446 
1447       gc_epilogue(true);
1448 
1449       heap_transition.print();
1450 
1451       print_heap_after_gc();
1452       print_heap_regions();
1453       trace_heap_after_gc(gc_tracer);
1454 
1455       post_full_gc_dump(gc_timer);
1456     }
1457 
1458     gc_timer->register_gc_end();
1459     gc_tracer->report_gc_end(gc_timer->gc_end(), gc_timer->time_partitions());
1460   }
1461 
1462   return true;
1463 }
1464 
1465 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1466   // Currently, there is no facility in the do_full_collection(bool) API to notify
1467   // the caller that the collection did not succeed (e.g., because it was locked
1468   // out by the GC locker). So, right now, we'll ignore the return value.
1469   bool dummy = do_full_collection(true,                /* explicit_gc */
1470                                   clear_all_soft_refs);
1471 }
1472 
1473 void G1CollectedHeap::resize_if_necessary_after_full_collection() {
1474   // Include bytes that will be pre-allocated to support collections, as "used".
1475   const size_t used_after_gc = used();
1476   const size_t capacity_after_gc = capacity();
1477   const size_t free_after_gc = capacity_after_gc - used_after_gc;
1478 
1479   // This is enforced in arguments.cpp.
1480   assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1481          "otherwise the code below doesn't make sense");
1482 
1483   // We don't have floating point command-line arguments
1484   const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1485   const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1486   const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1487   const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1488 
1489   const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1490   const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1491 
1492   // We have to be careful here as these two calculations can overflow
1493   // 32-bit size_t's.
1494   double used_after_gc_d = (double) used_after_gc;
1495   double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1496   double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1497 
1498   // Let's make sure that they are both under the max heap size, which
1499   // by default will make them fit into a size_t.
1500   double desired_capacity_upper_bound = (double) max_heap_size;
1501   minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1502                                     desired_capacity_upper_bound);
1503   maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1504                                     desired_capacity_upper_bound);
1505 
1506   // We can now safely turn them into size_t's.
1507   size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1508   size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1509 
1510   // This assert only makes sense here, before we adjust them
1511   // with respect to the min and max heap size.
1512   assert(minimum_desired_capacity <= maximum_desired_capacity,
1513          "minimum_desired_capacity = " SIZE_FORMAT ", "
1514          "maximum_desired_capacity = " SIZE_FORMAT,
1515          minimum_desired_capacity, maximum_desired_capacity);
1516 
1517   // Should not be greater than the heap max size. No need to adjust
1518   // it with respect to the heap min size as it's a lower bound (i.e.,
1519   // we'll try to make the capacity larger than it, not smaller).
1520   minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1521   // Should not be less than the heap min size. No need to adjust it
1522   // with respect to the heap max size as it's an upper bound (i.e.,
1523   // we'll try to make the capacity smaller than it, not greater).
1524   maximum_desired_capacity =  MAX2(maximum_desired_capacity, min_heap_size);
1525 
1526   if (capacity_after_gc < minimum_desired_capacity) {
1527     // Don't expand unless it's significant
1528     size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1529 
1530     log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). "
1531                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1532                               capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio);
1533 
1534     expand(expand_bytes);
1535 
1536     // No expansion, now see if we want to shrink
1537   } else if (capacity_after_gc > maximum_desired_capacity) {
1538     // Capacity too large, compute shrinking size
1539     size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1540 
1541     log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). "
1542                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1543                               capacity_after_gc, used_after_gc, minimum_desired_capacity, MinHeapFreeRatio);
1544 
1545     shrink(shrink_bytes);
1546   }
1547 }
1548 
1549 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size,
1550                                                             AllocationContext_t context,
1551                                                             bool do_gc,
1552                                                             bool clear_all_soft_refs,
1553                                                             bool expect_null_mutator_alloc_region,
1554                                                             bool* gc_succeeded) {
1555   *gc_succeeded = true;
1556   // Let's attempt the allocation first.
1557   HeapWord* result =
1558     attempt_allocation_at_safepoint(word_size,
1559                                     context,
1560                                     expect_null_mutator_alloc_region);
1561   if (result != NULL) {
1562     assert(*gc_succeeded, "sanity");
1563     return result;
1564   }
1565 
1566   // In a G1 heap, we're supposed to keep allocation from failing by
1567   // incremental pauses.  Therefore, at least for now, we'll favor
1568   // expansion over collection.  (This might change in the future if we can
1569   // do something smarter than full collection to satisfy a failed alloc.)
1570   result = expand_and_allocate(word_size, context);
1571   if (result != NULL) {
1572     assert(*gc_succeeded, "sanity");
1573     return result;
1574   }
1575 
1576   if (do_gc) {
1577     // Expansion didn't work, we'll try to do a Full GC.
1578     *gc_succeeded = do_full_collection(false, /* explicit_gc */
1579                                        clear_all_soft_refs);
1580   }
1581 
1582   return NULL;
1583 }
1584 
1585 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1586                                                      AllocationContext_t context,
1587                                                      bool* succeeded) {
1588   assert_at_safepoint(true /* should_be_vm_thread */);
1589 
1590   // Attempts to allocate followed by Full GC.
1591   HeapWord* result =
1592     satisfy_failed_allocation_helper(word_size,
1593                                      context,
1594                                      true,  /* do_gc */
1595                                      false, /* clear_all_soft_refs */
1596                                      false, /* expect_null_mutator_alloc_region */
1597                                      succeeded);
1598 
1599   if (result != NULL || !*succeeded) {
1600     return result;
1601   }
1602 
1603   // Attempts to allocate followed by Full GC that will collect all soft references.
1604   result = satisfy_failed_allocation_helper(word_size,
1605                                             context,
1606                                             true, /* do_gc */
1607                                             true, /* clear_all_soft_refs */
1608                                             true, /* expect_null_mutator_alloc_region */
1609                                             succeeded);
1610 
1611   if (result != NULL || !*succeeded) {
1612     return result;
1613   }
1614 
1615   // Attempts to allocate, no GC
1616   result = satisfy_failed_allocation_helper(word_size,
1617                                             context,
1618                                             false, /* do_gc */
1619                                             false, /* clear_all_soft_refs */
1620                                             true,  /* expect_null_mutator_alloc_region */
1621                                             succeeded);
1622 
1623   if (result != NULL) {
1624     assert(*succeeded, "sanity");
1625     return result;
1626   }
1627 
1628   assert(!collector_policy()->should_clear_all_soft_refs(),
1629          "Flag should have been handled and cleared prior to this point");
1630 
1631   // What else?  We might try synchronous finalization later.  If the total
1632   // space available is large enough for the allocation, then a more
1633   // complete compaction phase than we've tried so far might be
1634   // appropriate.
1635   assert(*succeeded, "sanity");
1636   return NULL;
1637 }
1638 
1639 // Attempting to expand the heap sufficiently
1640 // to support an allocation of the given "word_size".  If
1641 // successful, perform the allocation and return the address of the
1642 // allocated block, or else "NULL".
1643 
1644 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size, AllocationContext_t context) {
1645   assert_at_safepoint(true /* should_be_vm_thread */);
1646 
1647   _verifier->verify_region_sets_optional();
1648 
1649   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1650   log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B",
1651                             word_size * HeapWordSize);
1652 
1653 
1654   if (expand(expand_bytes)) {
1655     _hrm.verify_optional();
1656     _verifier->verify_region_sets_optional();
1657     return attempt_allocation_at_safepoint(word_size,
1658                                            context,
1659                                            false /* expect_null_mutator_alloc_region */);
1660   }
1661   return NULL;
1662 }
1663 
1664 bool G1CollectedHeap::expand(size_t expand_bytes, double* expand_time_ms) {
1665   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1666   aligned_expand_bytes = align_size_up(aligned_expand_bytes,
1667                                        HeapRegion::GrainBytes);
1668 
1669   log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount:" SIZE_FORMAT "B expansion amount:" SIZE_FORMAT "B",
1670                             expand_bytes, aligned_expand_bytes);
1671 
1672   if (is_maximal_no_gc()) {
1673     log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1674     return false;
1675   }
1676 
1677   double expand_heap_start_time_sec = os::elapsedTime();
1678   uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1679   assert(regions_to_expand > 0, "Must expand by at least one region");
1680 
1681   uint expanded_by = _hrm.expand_by(regions_to_expand);
1682   if (expand_time_ms != NULL) {
1683     *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS;
1684   }
1685 
1686   if (expanded_by > 0) {
1687     size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1688     assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1689     g1_policy()->record_new_heap_size(num_regions());
1690   } else {
1691     log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)");
1692 
1693     // The expansion of the virtual storage space was unsuccessful.
1694     // Let's see if it was because we ran out of swap.
1695     if (G1ExitOnExpansionFailure &&
1696         _hrm.available() >= regions_to_expand) {
1697       // We had head room...
1698       vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1699     }
1700   }
1701   return regions_to_expand > 0;
1702 }
1703 
1704 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1705   size_t aligned_shrink_bytes =
1706     ReservedSpace::page_align_size_down(shrink_bytes);
1707   aligned_shrink_bytes = align_size_down(aligned_shrink_bytes,
1708                                          HeapRegion::GrainBytes);
1709   uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1710 
1711   uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1712   size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1713 
1714 
1715   log_debug(gc, ergo, heap)("Shrink the heap. requested shrinking amount: " SIZE_FORMAT "B aligned shrinking amount: " SIZE_FORMAT "B attempted shrinking amount: " SIZE_FORMAT "B",
1716                             shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1717   if (num_regions_removed > 0) {
1718     g1_policy()->record_new_heap_size(num_regions());
1719   } else {
1720     log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)");
1721   }
1722 }
1723 
1724 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1725   _verifier->verify_region_sets_optional();
1726 
1727   // We should only reach here at the end of a Full GC which means we
1728   // should not not be holding to any GC alloc regions. The method
1729   // below will make sure of that and do any remaining clean up.
1730   _allocator->abandon_gc_alloc_regions();
1731 
1732   // Instead of tearing down / rebuilding the free lists here, we
1733   // could instead use the remove_all_pending() method on free_list to
1734   // remove only the ones that we need to remove.
1735   tear_down_region_sets(true /* free_list_only */);
1736   shrink_helper(shrink_bytes);
1737   rebuild_region_sets(true /* free_list_only */);
1738 
1739   _hrm.verify_optional();
1740   _verifier->verify_region_sets_optional();
1741 }
1742 
1743 // Public methods.
1744 
1745 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* policy_) :
1746   CollectedHeap(),
1747   _g1_policy(policy_),
1748   _collection_set(this),
1749   _dirty_card_queue_set(false),
1750   _is_alive_closure_cm(this),
1751   _is_alive_closure_stw(this),
1752   _ref_processor_cm(NULL),
1753   _ref_processor_stw(NULL),
1754   _bot(NULL),
1755   _cg1r(NULL),
1756   _g1mm(NULL),
1757   _refine_cte_cl(NULL),
1758   _secondary_free_list("Secondary Free List", new SecondaryFreeRegionListMtSafeChecker()),
1759   _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1760   _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1761   _humongous_reclaim_candidates(),
1762   _has_humongous_reclaim_candidates(false),
1763   _archive_allocator(NULL),
1764   _free_regions_coming(false),
1765   _young_list(new YoungList(this)),
1766   _gc_time_stamp(0),
1767   _summary_bytes_used(0),
1768   _survivor_evac_stats("Young", YoungPLABSize, PLABWeight),
1769   _old_evac_stats("Old", OldPLABSize, PLABWeight),
1770   _expand_heap_after_alloc_failure(true),
1771   _old_marking_cycles_started(0),
1772   _old_marking_cycles_completed(0),
1773   _heap_summary_sent(false),
1774   _in_cset_fast_test(),
1775   _dirty_cards_region_list(NULL),
1776   _worker_cset_start_region(NULL),
1777   _worker_cset_start_region_time_stamp(NULL),
1778   _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1779   _gc_timer_cm(new (ResourceObj::C_HEAP, mtGC) ConcurrentGCTimer()),
1780   _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1781   _gc_tracer_cm(new (ResourceObj::C_HEAP, mtGC) G1OldTracer()) {
1782 
1783   _workers = new WorkGang("GC Thread", ParallelGCThreads,
1784                           /* are_GC_task_threads */true,
1785                           /* are_ConcurrentGC_threads */false);
1786   _workers->initialize_workers();
1787   _verifier = new G1HeapVerifier(this);
1788 
1789   _allocator = G1Allocator::create_allocator(this);
1790   _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);
1791 
1792   // Override the default _filler_array_max_size so that no humongous filler
1793   // objects are created.
1794   _filler_array_max_size = _humongous_object_threshold_in_words;
1795 
1796   uint n_queues = ParallelGCThreads;
1797   _task_queues = new RefToScanQueueSet(n_queues);
1798 
1799   _worker_cset_start_region = NEW_C_HEAP_ARRAY(HeapRegion*, n_queues, mtGC);
1800   _worker_cset_start_region_time_stamp = NEW_C_HEAP_ARRAY(uint, n_queues, mtGC);
1801   _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1802 
1803   for (uint i = 0; i < n_queues; i++) {
1804     RefToScanQueue* q = new RefToScanQueue();
1805     q->initialize();
1806     _task_queues->register_queue(i, q);
1807     ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1808   }
1809   clear_cset_start_regions();
1810 
1811   // Initialize the G1EvacuationFailureALot counters and flags.
1812   NOT_PRODUCT(reset_evacuation_should_fail();)
1813 
1814   guarantee(_task_queues != NULL, "task_queues allocation failure.");
1815 }
1816 
1817 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1818                                                                  size_t size,
1819                                                                  size_t translation_factor) {
1820   size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1821   // Allocate a new reserved space, preferring to use large pages.
1822   ReservedSpace rs(size, preferred_page_size);
1823   G1RegionToSpaceMapper* result  =
1824     G1RegionToSpaceMapper::create_mapper(rs,
1825                                          size,
1826                                          rs.alignment(),
1827                                          HeapRegion::GrainBytes,
1828                                          translation_factor,
1829                                          mtGC);
1830   if (TracePageSizes) {
1831     tty->print_cr("G1 '%s': pg_sz=" SIZE_FORMAT " base=" PTR_FORMAT " size=" SIZE_FORMAT " alignment=" SIZE_FORMAT " reqsize=" SIZE_FORMAT,
1832                   description, preferred_page_size, p2i(rs.base()), rs.size(), rs.alignment(), size);
1833   }
1834   return result;
1835 }
1836 
1837 jint G1CollectedHeap::initialize() {
1838   CollectedHeap::pre_initialize();
1839   os::enable_vtime();
1840 
1841   // Necessary to satisfy locking discipline assertions.
1842 
1843   MutexLocker x(Heap_lock);
1844 
1845   // While there are no constraints in the GC code that HeapWordSize
1846   // be any particular value, there are multiple other areas in the
1847   // system which believe this to be true (e.g. oop->object_size in some
1848   // cases incorrectly returns the size in wordSize units rather than
1849   // HeapWordSize).
1850   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1851 
1852   size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1853   size_t max_byte_size = collector_policy()->max_heap_byte_size();
1854   size_t heap_alignment = collector_policy()->heap_alignment();
1855 
1856   // Ensure that the sizes are properly aligned.
1857   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1858   Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1859   Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1860 
1861   _refine_cte_cl = new RefineCardTableEntryClosure();
1862 
1863   jint ecode = JNI_OK;
1864   _cg1r = ConcurrentG1Refine::create(this, _refine_cte_cl, &ecode);
1865   if (_cg1r == NULL) {
1866     return ecode;
1867   }
1868 
1869   // Reserve the maximum.
1870 
1871   // When compressed oops are enabled, the preferred heap base
1872   // is calculated by subtracting the requested size from the
1873   // 32Gb boundary and using the result as the base address for
1874   // heap reservation. If the requested size is not aligned to
1875   // HeapRegion::GrainBytes (i.e. the alignment that is passed
1876   // into the ReservedHeapSpace constructor) then the actual
1877   // base of the reserved heap may end up differing from the
1878   // address that was requested (i.e. the preferred heap base).
1879   // If this happens then we could end up using a non-optimal
1880   // compressed oops mode.
1881 
1882   ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1883                                                  heap_alignment);
1884 
1885   initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
1886 
1887   // Create the barrier set for the entire reserved region.
1888   G1SATBCardTableLoggingModRefBS* bs
1889     = new G1SATBCardTableLoggingModRefBS(reserved_region());
1890   bs->initialize();
1891   assert(bs->is_a(BarrierSet::G1SATBCTLogging), "sanity");
1892   set_barrier_set(bs);
1893 
1894   // Also create a G1 rem set.
1895   _g1_rem_set = new G1RemSet(this, g1_barrier_set());
1896 
1897   // Carve out the G1 part of the heap.
1898   ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1899   size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
1900   G1RegionToSpaceMapper* heap_storage =
1901     G1RegionToSpaceMapper::create_mapper(g1_rs,
1902                                          g1_rs.size(),
1903                                          page_size,
1904                                          HeapRegion::GrainBytes,
1905                                          1,
1906                                          mtJavaHeap);
1907   os::trace_page_sizes("G1 Heap", collector_policy()->min_heap_byte_size(),
1908                        max_byte_size, page_size,
1909                        heap_rs.base(),
1910                        heap_rs.size());
1911   heap_storage->set_mapping_changed_listener(&_listener);
1912 
1913   // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1914   G1RegionToSpaceMapper* bot_storage =
1915     create_aux_memory_mapper("Block offset table",
1916                              G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize),
1917                              G1BlockOffsetTable::heap_map_factor());
1918 
1919   ReservedSpace cardtable_rs(G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize));
1920   G1RegionToSpaceMapper* cardtable_storage =
1921     create_aux_memory_mapper("Card table",
1922                              G1SATBCardTableLoggingModRefBS::compute_size(g1_rs.size() / HeapWordSize),
1923                              G1SATBCardTableLoggingModRefBS::heap_map_factor());
1924 
1925   G1RegionToSpaceMapper* card_counts_storage =
1926     create_aux_memory_mapper("Card counts table",
1927                              G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1928                              G1CardCounts::heap_map_factor());
1929 
1930   size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size());
1931   G1RegionToSpaceMapper* prev_bitmap_storage =
1932     create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1933   G1RegionToSpaceMapper* next_bitmap_storage =
1934     create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1935 
1936   _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1937   g1_barrier_set()->initialize(cardtable_storage);
1938    // Do later initialization work for concurrent refinement.
1939   _cg1r->init(card_counts_storage);
1940 
1941   // 6843694 - ensure that the maximum region index can fit
1942   // in the remembered set structures.
1943   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1944   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1945 
1946   G1RemSet::initialize(max_regions());
1947 
1948   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1949   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1950   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1951             "too many cards per region");
1952 
1953   FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
1954 
1955   _bot = new G1BlockOffsetTable(reserved_region(), bot_storage);
1956 
1957   {
1958     HeapWord* start = _hrm.reserved().start();
1959     HeapWord* end = _hrm.reserved().end();
1960     size_t granularity = HeapRegion::GrainBytes;
1961 
1962     _in_cset_fast_test.initialize(start, end, granularity);
1963     _humongous_reclaim_candidates.initialize(start, end, granularity);
1964   }
1965 
1966   // Create the G1ConcurrentMark data structure and thread.
1967   // (Must do this late, so that "max_regions" is defined.)
1968   _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1969   if (_cm == NULL || !_cm->completed_initialization()) {
1970     vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark");
1971     return JNI_ENOMEM;
1972   }
1973   _cmThread = _cm->cmThread();
1974 
1975   // Now expand into the initial heap size.
1976   if (!expand(init_byte_size)) {
1977     vm_shutdown_during_initialization("Failed to allocate initial heap.");
1978     return JNI_ENOMEM;
1979   }
1980 
1981   // Perform any initialization actions delegated to the policy.
1982   g1_policy()->init();
1983 
1984   JavaThread::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
1985                                                SATB_Q_FL_lock,
1986                                                G1SATBProcessCompletedThreshold,
1987                                                Shared_SATB_Q_lock);
1988 
1989   JavaThread::dirty_card_queue_set().initialize(_refine_cte_cl,
1990                                                 DirtyCardQ_CBL_mon,
1991                                                 DirtyCardQ_FL_lock,
1992                                                 (int)concurrent_g1_refine()->yellow_zone(),
1993                                                 (int)concurrent_g1_refine()->red_zone(),
1994                                                 Shared_DirtyCardQ_lock,
1995                                                 NULL,  // fl_owner
1996                                                 true); // init_free_ids
1997 
1998   dirty_card_queue_set().initialize(NULL, // Should never be called by the Java code
1999                                     DirtyCardQ_CBL_mon,
2000                                     DirtyCardQ_FL_lock,
2001                                     -1, // never trigger processing
2002                                     -1, // no limit on length
2003                                     Shared_DirtyCardQ_lock,
2004                                     &JavaThread::dirty_card_queue_set());
2005 
2006   // Here we allocate the dummy HeapRegion that is required by the
2007   // G1AllocRegion class.
2008   HeapRegion* dummy_region = _hrm.get_dummy_region();
2009 
2010   // We'll re-use the same region whether the alloc region will
2011   // require BOT updates or not and, if it doesn't, then a non-young
2012   // region will complain that it cannot support allocations without
2013   // BOT updates. So we'll tag the dummy region as eden to avoid that.
2014   dummy_region->set_eden();
2015   // Make sure it's full.
2016   dummy_region->set_top(dummy_region->end());
2017   G1AllocRegion::setup(this, dummy_region);
2018 
2019   _allocator->init_mutator_alloc_region();
2020 
2021   // Do create of the monitoring and management support so that
2022   // values in the heap have been properly initialized.
2023   _g1mm = new G1MonitoringSupport(this);
2024 
2025   G1StringDedup::initialize();
2026 
2027   _preserved_objs = NEW_C_HEAP_ARRAY(OopAndMarkOopStack, ParallelGCThreads, mtGC);
2028   for (uint i = 0; i < ParallelGCThreads; i++) {
2029     new (&_preserved_objs[i]) OopAndMarkOopStack();
2030   }
2031 
2032   return JNI_OK;
2033 }
2034 
2035 void G1CollectedHeap::stop() {
2036   // Stop all concurrent threads. We do this to make sure these threads
2037   // do not continue to execute and access resources (e.g. logging)
2038   // that are destroyed during shutdown.
2039   _cg1r->stop();
2040   _cmThread->stop();
2041   if (G1StringDedup::is_enabled()) {
2042     G1StringDedup::stop();
2043   }
2044 }
2045 
2046 size_t G1CollectedHeap::conservative_max_heap_alignment() {
2047   return HeapRegion::max_region_size();
2048 }
2049 
2050 void G1CollectedHeap::post_initialize() {
2051   CollectedHeap::post_initialize();
2052   ref_processing_init();
2053 }
2054 
2055 void G1CollectedHeap::ref_processing_init() {
2056   // Reference processing in G1 currently works as follows:
2057   //
2058   // * There are two reference processor instances. One is
2059   //   used to record and process discovered references
2060   //   during concurrent marking; the other is used to
2061   //   record and process references during STW pauses
2062   //   (both full and incremental).
2063   // * Both ref processors need to 'span' the entire heap as
2064   //   the regions in the collection set may be dotted around.
2065   //
2066   // * For the concurrent marking ref processor:
2067   //   * Reference discovery is enabled at initial marking.
2068   //   * Reference discovery is disabled and the discovered
2069   //     references processed etc during remarking.
2070   //   * Reference discovery is MT (see below).
2071   //   * Reference discovery requires a barrier (see below).
2072   //   * Reference processing may or may not be MT
2073   //     (depending on the value of ParallelRefProcEnabled
2074   //     and ParallelGCThreads).
2075   //   * A full GC disables reference discovery by the CM
2076   //     ref processor and abandons any entries on it's
2077   //     discovered lists.
2078   //
2079   // * For the STW processor:
2080   //   * Non MT discovery is enabled at the start of a full GC.
2081   //   * Processing and enqueueing during a full GC is non-MT.
2082   //   * During a full GC, references are processed after marking.
2083   //
2084   //   * Discovery (may or may not be MT) is enabled at the start
2085   //     of an incremental evacuation pause.
2086   //   * References are processed near the end of a STW evacuation pause.
2087   //   * For both types of GC:
2088   //     * Discovery is atomic - i.e. not concurrent.
2089   //     * Reference discovery will not need a barrier.
2090 
2091   MemRegion mr = reserved_region();
2092 
2093   // Concurrent Mark ref processor
2094   _ref_processor_cm =
2095     new ReferenceProcessor(mr,    // span
2096                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2097                                 // mt processing
2098                            ParallelGCThreads,
2099                                 // degree of mt processing
2100                            (ParallelGCThreads > 1) || (ConcGCThreads > 1),
2101                                 // mt discovery
2102                            MAX2(ParallelGCThreads, ConcGCThreads),
2103                                 // degree of mt discovery
2104                            false,
2105                                 // Reference discovery is not atomic
2106                            &_is_alive_closure_cm);
2107                                 // is alive closure
2108                                 // (for efficiency/performance)
2109 
2110   // STW ref processor
2111   _ref_processor_stw =
2112     new ReferenceProcessor(mr,    // span
2113                            ParallelRefProcEnabled && (ParallelGCThreads > 1),
2114                                 // mt processing
2115                            ParallelGCThreads,
2116                                 // degree of mt processing
2117                            (ParallelGCThreads > 1),
2118                                 // mt discovery
2119                            ParallelGCThreads,
2120                                 // degree of mt discovery
2121                            true,
2122                                 // Reference discovery is atomic
2123                            &_is_alive_closure_stw);
2124                                 // is alive closure
2125                                 // (for efficiency/performance)
2126 }
2127 
2128 CollectorPolicy* G1CollectedHeap::collector_policy() const {
2129   return g1_policy();
2130 }
2131 
2132 size_t G1CollectedHeap::capacity() const {
2133   return _hrm.length() * HeapRegion::GrainBytes;
2134 }
2135 
2136 void G1CollectedHeap::reset_gc_time_stamps(HeapRegion* hr) {
2137   hr->reset_gc_time_stamp();
2138 }
2139 
2140 #ifndef PRODUCT
2141 
2142 class CheckGCTimeStampsHRClosure : public HeapRegionClosure {
2143 private:
2144   unsigned _gc_time_stamp;
2145   bool _failures;
2146 
2147 public:
2148   CheckGCTimeStampsHRClosure(unsigned gc_time_stamp) :
2149     _gc_time_stamp(gc_time_stamp), _failures(false) { }
2150 
2151   virtual bool doHeapRegion(HeapRegion* hr) {
2152     unsigned region_gc_time_stamp = hr->get_gc_time_stamp();
2153     if (_gc_time_stamp != region_gc_time_stamp) {
2154       log_error(gc, verify)("Region " HR_FORMAT " has GC time stamp = %d, expected %d", HR_FORMAT_PARAMS(hr),
2155                             region_gc_time_stamp, _gc_time_stamp);
2156       _failures = true;
2157     }
2158     return false;
2159   }
2160 
2161   bool failures() { return _failures; }
2162 };
2163 
2164 void G1CollectedHeap::check_gc_time_stamps() {
2165   CheckGCTimeStampsHRClosure cl(_gc_time_stamp);
2166   heap_region_iterate(&cl);
2167   guarantee(!cl.failures(), "all GC time stamps should have been reset");
2168 }
2169 #endif // PRODUCT
2170 
2171 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) {
2172   _cg1r->hot_card_cache()->drain(cl, worker_i);
2173 }
2174 
2175 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) {
2176   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2177   size_t n_completed_buffers = 0;
2178   while (dcqs.apply_closure_to_completed_buffer(cl, worker_i, 0, true)) {
2179     n_completed_buffers++;
2180   }
2181   g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers);
2182   dcqs.clear_n_completed_buffers();
2183   assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
2184 }
2185 
2186 // Computes the sum of the storage used by the various regions.
2187 size_t G1CollectedHeap::used() const {
2188   size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
2189   if (_archive_allocator != NULL) {
2190     result += _archive_allocator->used();
2191   }
2192   return result;
2193 }
2194 
2195 size_t G1CollectedHeap::used_unlocked() const {
2196   return _summary_bytes_used;
2197 }
2198 
2199 class SumUsedClosure: public HeapRegionClosure {
2200   size_t _used;
2201 public:
2202   SumUsedClosure() : _used(0) {}
2203   bool doHeapRegion(HeapRegion* r) {
2204     _used += r->used();
2205     return false;
2206   }
2207   size_t result() { return _used; }
2208 };
2209 
2210 size_t G1CollectedHeap::recalculate_used() const {
2211   double recalculate_used_start = os::elapsedTime();
2212 
2213   SumUsedClosure blk;
2214   heap_region_iterate(&blk);
2215 
2216   g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
2217   return blk.result();
2218 }
2219 
2220 bool  G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
2221   switch (cause) {
2222     case GCCause::_java_lang_system_gc:                 return ExplicitGCInvokesConcurrent;
2223     case GCCause::_dcmd_gc_run:                         return ExplicitGCInvokesConcurrent;
2224     case GCCause::_update_allocation_context_stats_inc: return true;
2225     case GCCause::_wb_conc_mark:                        return true;
2226     default :                                           return false;
2227   }
2228 }
2229 
2230 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2231   switch (cause) {
2232     case GCCause::_gc_locker:               return GCLockerInvokesConcurrent;
2233     case GCCause::_g1_humongous_allocation: return true;
2234     default:                                return is_user_requested_concurrent_full_gc(cause);
2235   }
2236 }
2237 
2238 #ifndef PRODUCT
2239 void G1CollectedHeap::allocate_dummy_regions() {
2240   // Let's fill up most of the region
2241   size_t word_size = HeapRegion::GrainWords - 1024;
2242   // And as a result the region we'll allocate will be humongous.
2243   guarantee(is_humongous(word_size), "sanity");
2244 
2245   // _filler_array_max_size is set to humongous object threshold
2246   // but temporarily change it to use CollectedHeap::fill_with_object().
2247   SizeTFlagSetting fs(_filler_array_max_size, word_size);
2248 
2249   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2250     // Let's use the existing mechanism for the allocation
2251     HeapWord* dummy_obj = humongous_obj_allocate(word_size,
2252                                                  AllocationContext::system());
2253     if (dummy_obj != NULL) {
2254       MemRegion mr(dummy_obj, word_size);
2255       CollectedHeap::fill_with_object(mr);
2256     } else {
2257       // If we can't allocate once, we probably cannot allocate
2258       // again. Let's get out of the loop.
2259       break;
2260     }
2261   }
2262 }
2263 #endif // !PRODUCT
2264 
2265 void G1CollectedHeap::increment_old_marking_cycles_started() {
2266   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2267          _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2268          "Wrong marking cycle count (started: %d, completed: %d)",
2269          _old_marking_cycles_started, _old_marking_cycles_completed);
2270 
2271   _old_marking_cycles_started++;
2272 }
2273 
2274 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2275   MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2276 
2277   // We assume that if concurrent == true, then the caller is a
2278   // concurrent thread that was joined the Suspendible Thread
2279   // Set. If there's ever a cheap way to check this, we should add an
2280   // assert here.
2281 
2282   // Given that this method is called at the end of a Full GC or of a
2283   // concurrent cycle, and those can be nested (i.e., a Full GC can
2284   // interrupt a concurrent cycle), the number of full collections
2285   // completed should be either one (in the case where there was no
2286   // nesting) or two (when a Full GC interrupted a concurrent cycle)
2287   // behind the number of full collections started.
2288 
2289   // This is the case for the inner caller, i.e. a Full GC.
2290   assert(concurrent ||
2291          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2292          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2293          "for inner caller (Full GC): _old_marking_cycles_started = %u "
2294          "is inconsistent with _old_marking_cycles_completed = %u",
2295          _old_marking_cycles_started, _old_marking_cycles_completed);
2296 
2297   // This is the case for the outer caller, i.e. the concurrent cycle.
2298   assert(!concurrent ||
2299          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2300          "for outer caller (concurrent cycle): "
2301          "_old_marking_cycles_started = %u "
2302          "is inconsistent with _old_marking_cycles_completed = %u",
2303          _old_marking_cycles_started, _old_marking_cycles_completed);
2304 
2305   _old_marking_cycles_completed += 1;
2306 
2307   // We need to clear the "in_progress" flag in the CM thread before
2308   // we wake up any waiters (especially when ExplicitInvokesConcurrent
2309   // is set) so that if a waiter requests another System.gc() it doesn't
2310   // incorrectly see that a marking cycle is still in progress.
2311   if (concurrent) {
2312     _cmThread->set_idle();
2313   }
2314 
2315   // This notify_all() will ensure that a thread that called
2316   // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2317   // and it's waiting for a full GC to finish will be woken up. It is
2318   // waiting in VM_G1IncCollectionPause::doit_epilogue().
2319   FullGCCount_lock->notify_all();
2320 }
2321 
2322 void G1CollectedHeap::register_concurrent_cycle_start(const Ticks& start_time) {
2323   GCIdMarkAndRestore conc_gc_id_mark;
2324   collector_state()->set_concurrent_cycle_started(true);
2325   _gc_timer_cm->register_gc_start(start_time);
2326 
2327   _gc_tracer_cm->report_gc_start(gc_cause(), _gc_timer_cm->gc_start());
2328   trace_heap_before_gc(_gc_tracer_cm);
2329   _cmThread->set_gc_id(GCId::current());
2330 }
2331 
2332 void G1CollectedHeap::register_concurrent_cycle_end() {
2333   if (collector_state()->concurrent_cycle_started()) {
2334     GCIdMarkAndRestore conc_gc_id_mark(_cmThread->gc_id());
2335     if (_cm->has_aborted()) {
2336       _gc_tracer_cm->report_concurrent_mode_failure();
2337 
2338       // ConcurrentGCTimer will be ended as well.
2339       _cm->register_concurrent_gc_end_and_stop_timer();
2340     } else {
2341       _gc_timer_cm->register_gc_end();
2342     }
2343 
2344     _gc_tracer_cm->report_gc_end(_gc_timer_cm->gc_end(), _gc_timer_cm->time_partitions());
2345 
2346     // Clear state variables to prepare for the next concurrent cycle.
2347     collector_state()->set_concurrent_cycle_started(false);
2348     _heap_summary_sent = false;
2349   }
2350 }
2351 
2352 void G1CollectedHeap::trace_heap_after_concurrent_cycle() {
2353   if (collector_state()->concurrent_cycle_started()) {
2354     // This function can be called when:
2355     //  the cleanup pause is run
2356     //  the concurrent cycle is aborted before the cleanup pause.
2357     //  the concurrent cycle is aborted after the cleanup pause,
2358     //   but before the concurrent cycle end has been registered.
2359     // Make sure that we only send the heap information once.
2360     if (!_heap_summary_sent) {
2361       GCIdMarkAndRestore conc_gc_id_mark(_cmThread->gc_id());
2362       trace_heap_after_gc(_gc_tracer_cm);
2363       _heap_summary_sent = true;
2364     }
2365   }
2366 }
2367 
2368 void G1CollectedHeap::collect(GCCause::Cause cause) {
2369   assert_heap_not_locked();
2370 
2371   uint gc_count_before;
2372   uint old_marking_count_before;
2373   uint full_gc_count_before;
2374   bool retry_gc;
2375 
2376   do {
2377     retry_gc = false;
2378 
2379     {
2380       MutexLocker ml(Heap_lock);
2381 
2382       // Read the GC count while holding the Heap_lock
2383       gc_count_before = total_collections();
2384       full_gc_count_before = total_full_collections();
2385       old_marking_count_before = _old_marking_cycles_started;
2386     }
2387 
2388     if (should_do_concurrent_full_gc(cause)) {
2389       // Schedule an initial-mark evacuation pause that will start a
2390       // concurrent cycle. We're setting word_size to 0 which means that
2391       // we are not requesting a post-GC allocation.
2392       VM_G1IncCollectionPause op(gc_count_before,
2393                                  0,     /* word_size */
2394                                  true,  /* should_initiate_conc_mark */
2395                                  g1_policy()->max_pause_time_ms(),
2396                                  cause);
2397       op.set_allocation_context(AllocationContext::current());
2398 
2399       VMThread::execute(&op);
2400       if (!op.pause_succeeded()) {
2401         if (old_marking_count_before == _old_marking_cycles_started) {
2402           retry_gc = op.should_retry_gc();
2403         } else {
2404           // A Full GC happened while we were trying to schedule the
2405           // initial-mark GC. No point in starting a new cycle given
2406           // that the whole heap was collected anyway.
2407         }
2408 
2409         if (retry_gc) {
2410           if (GCLocker::is_active_and_needs_gc()) {
2411             GCLocker::stall_until_clear();
2412           }
2413         }
2414       }
2415     } else {
2416       if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2417           DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2418 
2419         // Schedule a standard evacuation pause. We're setting word_size
2420         // to 0 which means that we are not requesting a post-GC allocation.
2421         VM_G1IncCollectionPause op(gc_count_before,
2422                                    0,     /* word_size */
2423                                    false, /* should_initiate_conc_mark */
2424                                    g1_policy()->max_pause_time_ms(),
2425                                    cause);
2426         VMThread::execute(&op);
2427       } else {
2428         // Schedule a Full GC.
2429         VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2430         VMThread::execute(&op);
2431       }
2432     }
2433   } while (retry_gc);
2434 }
2435 
2436 bool G1CollectedHeap::is_in(const void* p) const {
2437   if (_hrm.reserved().contains(p)) {
2438     // Given that we know that p is in the reserved space,
2439     // heap_region_containing() should successfully
2440     // return the containing region.
2441     HeapRegion* hr = heap_region_containing(p);
2442     return hr->is_in(p);
2443   } else {
2444     return false;
2445   }
2446 }
2447 
2448 #ifdef ASSERT
2449 bool G1CollectedHeap::is_in_exact(const void* p) const {
2450   bool contains = reserved_region().contains(p);
2451   bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2452   if (contains && available) {
2453     return true;
2454   } else {
2455     return false;
2456   }
2457 }
2458 #endif
2459 
2460 bool G1CollectedHeap::obj_in_cs(oop obj) {
2461   HeapRegion* r = _hrm.addr_to_region((HeapWord*) obj);
2462   return r != NULL && r->in_collection_set();
2463 }
2464 
2465 // Iteration functions.
2466 
2467 // Applies an ExtendedOopClosure onto all references of objects within a HeapRegion.
2468 
2469 class IterateOopClosureRegionClosure: public HeapRegionClosure {
2470   ExtendedOopClosure* _cl;
2471 public:
2472   IterateOopClosureRegionClosure(ExtendedOopClosure* cl) : _cl(cl) {}
2473   bool doHeapRegion(HeapRegion* r) {
2474     if (!r->is_continues_humongous()) {
2475       r->oop_iterate(_cl);
2476     }
2477     return false;
2478   }
2479 };
2480 
2481 // Iterates an ObjectClosure over all objects within a HeapRegion.
2482 
2483 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2484   ObjectClosure* _cl;
2485 public:
2486   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2487   bool doHeapRegion(HeapRegion* r) {
2488     if (!r->is_continues_humongous()) {
2489       r->object_iterate(_cl);
2490     }
2491     return false;
2492   }
2493 };
2494 
2495 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2496   IterateObjectClosureRegionClosure blk(cl);
2497   heap_region_iterate(&blk);
2498 }
2499 
2500 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2501   _hrm.iterate(cl);
2502 }
2503 
2504 void
2505 G1CollectedHeap::heap_region_par_iterate(HeapRegionClosure* cl,
2506                                          uint worker_id,
2507                                          HeapRegionClaimer *hrclaimer,
2508                                          bool concurrent) const {
2509   _hrm.par_iterate(cl, worker_id, hrclaimer, concurrent);
2510 }
2511 
2512 // Clear the cached CSet starting regions and (more importantly)
2513 // the time stamps. Called when we reset the GC time stamp.
2514 void G1CollectedHeap::clear_cset_start_regions() {
2515   assert(_worker_cset_start_region != NULL, "sanity");
2516   assert(_worker_cset_start_region_time_stamp != NULL, "sanity");
2517 
2518   for (uint i = 0; i < ParallelGCThreads; i++) {
2519     _worker_cset_start_region[i] = NULL;
2520     _worker_cset_start_region_time_stamp[i] = 0;
2521   }
2522 }
2523 
2524 // Given the id of a worker, obtain or calculate a suitable
2525 // starting region for iterating over the current collection set.
2526 HeapRegion* G1CollectedHeap::start_cset_region_for_worker(uint worker_i) {
2527   assert(get_gc_time_stamp() > 0, "should have been updated by now");
2528 
2529   HeapRegion* result = NULL;
2530   unsigned gc_time_stamp = get_gc_time_stamp();
2531 
2532   if (_worker_cset_start_region_time_stamp[worker_i] == gc_time_stamp) {
2533     // Cached starting region for current worker was set
2534     // during the current pause - so it's valid.
2535     // Note: the cached starting heap region may be NULL
2536     // (when the collection set is empty).
2537     result = _worker_cset_start_region[worker_i];
2538     assert(result == NULL || result->in_collection_set(), "sanity");
2539     return result;
2540   }
2541 
2542   // The cached entry was not valid so let's calculate
2543   // a suitable starting heap region for this worker.
2544 
2545   // We want the parallel threads to start their collection
2546   // set iteration at different collection set regions to
2547   // avoid contention.
2548   // If we have:
2549   //          n collection set regions
2550   //          p threads
2551   // Then thread t will start at region floor ((t * n) / p)
2552 
2553   result = collection_set()->head();
2554   uint cs_size = collection_set()->region_length();
2555   uint active_workers = workers()->active_workers();
2556 
2557   uint end_ind   = (cs_size * worker_i) / active_workers;
2558   uint start_ind = 0;
2559 
2560   if (worker_i > 0 &&
2561       _worker_cset_start_region_time_stamp[worker_i - 1] == gc_time_stamp) {
2562     // Previous workers starting region is valid
2563     // so let's iterate from there
2564     start_ind = (cs_size * (worker_i - 1)) / active_workers;
2565     OrderAccess::loadload();
2566     result = _worker_cset_start_region[worker_i - 1];
2567   }
2568 
2569   for (uint i = start_ind; i < end_ind; i++) {
2570     result = result->next_in_collection_set();
2571   }
2572 
2573   // Note: the calculated starting heap region may be NULL
2574   // (when the collection set is empty).
2575   assert(result == NULL || result->in_collection_set(), "sanity");
2576   assert(_worker_cset_start_region_time_stamp[worker_i] != gc_time_stamp,
2577          "should be updated only once per pause");
2578   _worker_cset_start_region[worker_i] = result;
2579   OrderAccess::storestore();
2580   _worker_cset_start_region_time_stamp[worker_i] = gc_time_stamp;
2581   return result;
2582 }
2583 
2584 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2585   HeapRegion* r = collection_set()->head();
2586   while (r != NULL) {
2587     HeapRegion* next = r->next_in_collection_set();
2588     if (cl->doHeapRegion(r)) {
2589       cl->incomplete();
2590       return;
2591     }
2592     r = next;
2593   }
2594 }
2595 
2596 void G1CollectedHeap::collection_set_iterate_from(HeapRegion* r,
2597                                                   HeapRegionClosure *cl) {
2598   if (r == NULL) {
2599     // The CSet is empty so there's nothing to do.
2600     return;
2601   }
2602 
2603   assert(r->in_collection_set(),
2604          "Start region must be a member of the collection set.");
2605   HeapRegion* cur = r;
2606   while (cur != NULL) {
2607     HeapRegion* next = cur->next_in_collection_set();
2608     if (cl->doHeapRegion(cur) && false) {
2609       cl->incomplete();
2610       return;
2611     }
2612     cur = next;
2613   }
2614   cur = collection_set()->head();
2615   while (cur != r) {
2616     HeapRegion* next = cur->next_in_collection_set();
2617     if (cl->doHeapRegion(cur) && false) {
2618       cl->incomplete();
2619       return;
2620     }
2621     cur = next;
2622   }
2623 }
2624 
2625 HeapRegion* G1CollectedHeap::next_compaction_region(const HeapRegion* from) const {
2626   HeapRegion* result = _hrm.next_region_in_heap(from);
2627   while (result != NULL && result->is_pinned()) {
2628     result = _hrm.next_region_in_heap(result);
2629   }
2630   return result;
2631 }
2632 
2633 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2634   HeapRegion* hr = heap_region_containing(addr);
2635   return hr->block_start(addr);
2636 }
2637 
2638 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2639   HeapRegion* hr = heap_region_containing(addr);
2640   return hr->block_size(addr);
2641 }
2642 
2643 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2644   HeapRegion* hr = heap_region_containing(addr);
2645   return hr->block_is_obj(addr);
2646 }
2647 
2648 bool G1CollectedHeap::supports_tlab_allocation() const {
2649   return true;
2650 }
2651 
2652 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2653   return (_g1_policy->young_list_target_length() - young_list()->survivor_length()) * HeapRegion::GrainBytes;
2654 }
2655 
2656 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2657   return young_list()->eden_used_bytes();
2658 }
2659 
2660 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2661 // must be equal to the humongous object limit.
2662 size_t G1CollectedHeap::max_tlab_size() const {
2663   return align_size_down(_humongous_object_threshold_in_words, MinObjAlignment);
2664 }
2665 
2666 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2667   AllocationContext_t context = AllocationContext::current();
2668   return _allocator->unsafe_max_tlab_alloc(context);
2669 }
2670 
2671 size_t G1CollectedHeap::max_capacity() const {
2672   return _hrm.reserved().byte_size();
2673 }
2674 
2675 jlong G1CollectedHeap::millis_since_last_gc() {
2676   // assert(false, "NYI");
2677   return 0;
2678 }
2679 
2680 void G1CollectedHeap::prepare_for_verify() {
2681   _verifier->prepare_for_verify();
2682 }
2683 
2684 void G1CollectedHeap::verify(VerifyOption vo) {
2685   _verifier->verify(vo);
2686 }
2687 
2688 class PrintRegionClosure: public HeapRegionClosure {
2689   outputStream* _st;
2690 public:
2691   PrintRegionClosure(outputStream* st) : _st(st) {}
2692   bool doHeapRegion(HeapRegion* r) {
2693     r->print_on(_st);
2694     return false;
2695   }
2696 };
2697 
2698 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2699                                        const HeapRegion* hr,
2700                                        const VerifyOption vo) const {
2701   switch (vo) {
2702   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
2703   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
2704   case VerifyOption_G1UseMarkWord:    return !obj->is_gc_marked() && !hr->is_archive();
2705   default:                            ShouldNotReachHere();
2706   }
2707   return false; // keep some compilers happy
2708 }
2709 
2710 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2711                                        const VerifyOption vo) const {
2712   switch (vo) {
2713   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
2714   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
2715   case VerifyOption_G1UseMarkWord: {
2716     HeapRegion* hr = _hrm.addr_to_region((HeapWord*)obj);
2717     return !obj->is_gc_marked() && !hr->is_archive();
2718   }
2719   default:                            ShouldNotReachHere();
2720   }
2721   return false; // keep some compilers happy
2722 }
2723 
2724 void G1CollectedHeap::print_heap_regions() const {
2725   LogHandle(gc, heap, region) log;
2726   if (log.is_trace()) {
2727     ResourceMark rm;
2728     print_regions_on(log.trace_stream());
2729   }
2730 }
2731 
2732 void G1CollectedHeap::print_on(outputStream* st) const {
2733   st->print(" %-20s", "garbage-first heap");
2734   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
2735             capacity()/K, used_unlocked()/K);
2736   st->print(" [" PTR_FORMAT ", " PTR_FORMAT ", " PTR_FORMAT ")",
2737             p2i(_hrm.reserved().start()),
2738             p2i(_hrm.reserved().start() + _hrm.length() + HeapRegion::GrainWords),
2739             p2i(_hrm.reserved().end()));
2740   st->cr();
2741   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
2742   uint young_regions = _young_list->length();
2743   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
2744             (size_t) young_regions * HeapRegion::GrainBytes / K);
2745   uint survivor_regions = _young_list->survivor_length();
2746   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
2747             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
2748   st->cr();
2749   MetaspaceAux::print_on(st);
2750 }
2751 
2752 void G1CollectedHeap::print_regions_on(outputStream* st) const {
2753   st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
2754                "HS=humongous(starts), HC=humongous(continues), "
2755                "CS=collection set, F=free, A=archive, TS=gc time stamp, "
2756                "AC=allocation context, "
2757                "TAMS=top-at-mark-start (previous, next)");
2758   PrintRegionClosure blk(st);
2759   heap_region_iterate(&blk);
2760 }
2761 
2762 void G1CollectedHeap::print_extended_on(outputStream* st) const {
2763   print_on(st);
2764 
2765   // Print the per-region information.
2766   print_regions_on(st);
2767 }
2768 
2769 void G1CollectedHeap::print_on_error(outputStream* st) const {
2770   this->CollectedHeap::print_on_error(st);
2771 
2772   if (_cm != NULL) {
2773     st->cr();
2774     _cm->print_on_error(st);
2775   }
2776 }
2777 
2778 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
2779   workers()->print_worker_threads_on(st);
2780   _cmThread->print_on(st);
2781   st->cr();
2782   _cm->print_worker_threads_on(st);
2783   _cg1r->print_worker_threads_on(st);
2784   if (G1StringDedup::is_enabled()) {
2785     G1StringDedup::print_worker_threads_on(st);
2786   }
2787 }
2788 
2789 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2790   workers()->threads_do(tc);
2791   tc->do_thread(_cmThread);
2792   _cg1r->threads_do(tc);
2793   if (G1StringDedup::is_enabled()) {
2794     G1StringDedup::threads_do(tc);
2795   }
2796 }
2797 
2798 void G1CollectedHeap::print_tracing_info() const {
2799   g1_rem_set()->print_summary_info();
2800   concurrent_mark()->print_summary_info();
2801   g1_policy()->print_yg_surv_rate_info();
2802 }
2803 
2804 #ifndef PRODUCT
2805 // Helpful for debugging RSet issues.
2806 
2807 class PrintRSetsClosure : public HeapRegionClosure {
2808 private:
2809   const char* _msg;
2810   size_t _occupied_sum;
2811 
2812 public:
2813   bool doHeapRegion(HeapRegion* r) {
2814     HeapRegionRemSet* hrrs = r->rem_set();
2815     size_t occupied = hrrs->occupied();
2816     _occupied_sum += occupied;
2817 
2818     tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r));
2819     if (occupied == 0) {
2820       tty->print_cr("  RSet is empty");
2821     } else {
2822       hrrs->print();
2823     }
2824     tty->print_cr("----------");
2825     return false;
2826   }
2827 
2828   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
2829     tty->cr();
2830     tty->print_cr("========================================");
2831     tty->print_cr("%s", msg);
2832     tty->cr();
2833   }
2834 
2835   ~PrintRSetsClosure() {
2836     tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
2837     tty->print_cr("========================================");
2838     tty->cr();
2839   }
2840 };
2841 
2842 void G1CollectedHeap::print_cset_rsets() {
2843   PrintRSetsClosure cl("Printing CSet RSets");
2844   collection_set_iterate(&cl);
2845 }
2846 
2847 void G1CollectedHeap::print_all_rsets() {
2848   PrintRSetsClosure cl("Printing All RSets");;
2849   heap_region_iterate(&cl);
2850 }
2851 #endif // PRODUCT
2852 
2853 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
2854   YoungList* young_list = heap()->young_list();
2855 
2856   size_t eden_used_bytes = young_list->eden_used_bytes();
2857   size_t survivor_used_bytes = young_list->survivor_used_bytes();
2858 
2859   size_t eden_capacity_bytes =
2860     (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
2861 
2862   VirtualSpaceSummary heap_summary = create_heap_space_summary();
2863   return G1HeapSummary(heap_summary, used(), eden_used_bytes, eden_capacity_bytes, survivor_used_bytes, num_regions());
2864 }
2865 
2866 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
2867   return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
2868                        stats->unused(), stats->used(), stats->region_end_waste(),
2869                        stats->regions_filled(), stats->direct_allocated(),
2870                        stats->failure_used(), stats->failure_waste());
2871 }
2872 
2873 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
2874   const G1HeapSummary& heap_summary = create_g1_heap_summary();
2875   gc_tracer->report_gc_heap_summary(when, heap_summary);
2876 
2877   const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
2878   gc_tracer->report_metaspace_summary(when, metaspace_summary);
2879 }
2880 
2881 
2882 G1CollectedHeap* G1CollectedHeap::heap() {
2883   CollectedHeap* heap = Universe::heap();
2884   assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
2885   assert(heap->kind() == CollectedHeap::G1CollectedHeap, "Not a G1CollectedHeap");
2886   return (G1CollectedHeap*)heap;
2887 }
2888 
2889 void G1CollectedHeap::gc_prologue(bool full /* Ignored */) {
2890   // always_do_update_barrier = false;
2891   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
2892   // Fill TLAB's and such
2893   accumulate_statistics_all_tlabs();
2894   ensure_parsability(true);
2895 
2896   g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections());
2897 }
2898 
2899 void G1CollectedHeap::gc_epilogue(bool full) {
2900   // we are at the end of the GC. Total collections has already been increased.
2901   g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1);
2902 
2903   // FIXME: what is this about?
2904   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
2905   // is set.
2906 #if defined(COMPILER2) || INCLUDE_JVMCI
2907   assert(DerivedPointerTable::is_empty(), "derived pointer present");
2908 #endif
2909   // always_do_update_barrier = true;
2910 
2911   resize_all_tlabs();
2912   allocation_context_stats().update(full);
2913 
2914   // We have just completed a GC. Update the soft reference
2915   // policy with the new heap occupancy
2916   Universe::update_heap_info_at_gc();
2917 }
2918 
2919 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2920                                                uint gc_count_before,
2921                                                bool* succeeded,
2922                                                GCCause::Cause gc_cause) {
2923   assert_heap_not_locked_and_not_at_safepoint();
2924   VM_G1IncCollectionPause op(gc_count_before,
2925                              word_size,
2926                              false, /* should_initiate_conc_mark */
2927                              g1_policy()->max_pause_time_ms(),
2928                              gc_cause);
2929 
2930   op.set_allocation_context(AllocationContext::current());
2931   VMThread::execute(&op);
2932 
2933   HeapWord* result = op.result();
2934   bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
2935   assert(result == NULL || ret_succeeded,
2936          "the result should be NULL if the VM did not succeed");
2937   *succeeded = ret_succeeded;
2938 
2939   assert_heap_not_locked();
2940   return result;
2941 }
2942 
2943 void
2944 G1CollectedHeap::doConcurrentMark() {
2945   MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
2946   if (!_cmThread->in_progress()) {
2947     _cmThread->set_started();
2948     CGC_lock->notify();
2949   }
2950 }
2951 
2952 size_t G1CollectedHeap::pending_card_num() {
2953   size_t extra_cards = 0;
2954   JavaThread *curr = Threads::first();
2955   while (curr != NULL) {
2956     DirtyCardQueue& dcq = curr->dirty_card_queue();
2957     extra_cards += dcq.size();
2958     curr = curr->next();
2959   }
2960   DirtyCardQueueSet& dcqs = JavaThread::dirty_card_queue_set();
2961   size_t buffer_size = dcqs.buffer_size();
2962   size_t buffer_num = dcqs.completed_buffers_num();
2963 
2964   // PtrQueueSet::buffer_size() and PtrQueue:size() return sizes
2965   // in bytes - not the number of 'entries'. We need to convert
2966   // into a number of cards.
2967   return (buffer_size * buffer_num + extra_cards) / oopSize;
2968 }
2969 
2970 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
2971  private:
2972   size_t _total_humongous;
2973   size_t _candidate_humongous;
2974 
2975   DirtyCardQueue _dcq;
2976 
2977   // We don't nominate objects with many remembered set entries, on
2978   // the assumption that such objects are likely still live.
2979   bool is_remset_small(HeapRegion* region) const {
2980     HeapRegionRemSet* const rset = region->rem_set();
2981     return G1EagerReclaimHumongousObjectsWithStaleRefs
2982       ? rset->occupancy_less_or_equal_than(G1RSetSparseRegionEntries)
2983       : rset->is_empty();
2984   }
2985 
2986   bool is_typeArray_region(HeapRegion* region) const {
2987     return oop(region->bottom())->is_typeArray();
2988   }
2989 
2990   bool humongous_region_is_candidate(G1CollectedHeap* heap, HeapRegion* region) const {
2991     assert(region->is_starts_humongous(), "Must start a humongous object");
2992 
2993     // Candidate selection must satisfy the following constraints
2994     // while concurrent marking is in progress:
2995     //
2996     // * In order to maintain SATB invariants, an object must not be
2997     // reclaimed if it was allocated before the start of marking and
2998     // has not had its references scanned.  Such an object must have
2999     // its references (including type metadata) scanned to ensure no
3000     // live objects are missed by the marking process.  Objects
3001     // allocated after the start of concurrent marking don't need to
3002     // be scanned.
3003     //
3004     // * An object must not be reclaimed if it is on the concurrent
3005     // mark stack.  Objects allocated after the start of concurrent
3006     // marking are never pushed on the mark stack.
3007     //
3008     // Nominating only objects allocated after the start of concurrent
3009     // marking is sufficient to meet both constraints.  This may miss
3010     // some objects that satisfy the constraints, but the marking data
3011     // structures don't support efficiently performing the needed
3012     // additional tests or scrubbing of the mark stack.
3013     //
3014     // However, we presently only nominate is_typeArray() objects.
3015     // A humongous object containing references induces remembered
3016     // set entries on other regions.  In order to reclaim such an
3017     // object, those remembered sets would need to be cleaned up.
3018     //
3019     // We also treat is_typeArray() objects specially, allowing them
3020     // to be reclaimed even if allocated before the start of
3021     // concurrent mark.  For this we rely on mark stack insertion to
3022     // exclude is_typeArray() objects, preventing reclaiming an object
3023     // that is in the mark stack.  We also rely on the metadata for
3024     // such objects to be built-in and so ensured to be kept live.
3025     // Frequent allocation and drop of large binary blobs is an
3026     // important use case for eager reclaim, and this special handling
3027     // may reduce needed headroom.
3028 
3029     return is_typeArray_region(region) && is_remset_small(region);
3030   }
3031 
3032  public:
3033   RegisterHumongousWithInCSetFastTestClosure()
3034   : _total_humongous(0),
3035     _candidate_humongous(0),
3036     _dcq(&JavaThread::dirty_card_queue_set()) {
3037   }
3038 
3039   virtual bool doHeapRegion(HeapRegion* r) {
3040     if (!r->is_starts_humongous()) {
3041       return false;
3042     }
3043     G1CollectedHeap* g1h = G1CollectedHeap::heap();
3044 
3045     bool is_candidate = humongous_region_is_candidate(g1h, r);
3046     uint rindex = r->hrm_index();
3047     g1h->set_humongous_reclaim_candidate(rindex, is_candidate);
3048     if (is_candidate) {
3049       _candidate_humongous++;
3050       g1h->register_humongous_region_with_cset(rindex);
3051       // Is_candidate already filters out humongous object with large remembered sets.
3052       // If we have a humongous object with a few remembered sets, we simply flush these
3053       // remembered set entries into the DCQS. That will result in automatic
3054       // re-evaluation of their remembered set entries during the following evacuation
3055       // phase.
3056       if (!r->rem_set()->is_empty()) {
3057         guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
3058                   "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
3059         G1SATBCardTableLoggingModRefBS* bs = g1h->g1_barrier_set();
3060         HeapRegionRemSetIterator hrrs(r->rem_set());
3061         size_t card_index;
3062         while (hrrs.has_next(card_index)) {
3063           jbyte* card_ptr = (jbyte*)bs->byte_for_index(card_index);
3064           // The remembered set might contain references to already freed
3065           // regions. Filter out such entries to avoid failing card table
3066           // verification.
3067           if (g1h->is_in_closed_subset(bs->addr_for(card_ptr))) {
3068             if (*card_ptr != CardTableModRefBS::dirty_card_val()) {
3069               *card_ptr = CardTableModRefBS::dirty_card_val();
3070               _dcq.enqueue(card_ptr);
3071             }
3072           }
3073         }
3074         assert(hrrs.n_yielded() == r->rem_set()->occupied(),
3075                "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries",
3076                hrrs.n_yielded(), r->rem_set()->occupied());
3077         r->rem_set()->clear_locked();
3078       }
3079       assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
3080     }
3081     _total_humongous++;
3082 
3083     return false;
3084   }
3085 
3086   size_t total_humongous() const { return _total_humongous; }
3087   size_t candidate_humongous() const { return _candidate_humongous; }
3088 
3089   void flush_rem_set_entries() { _dcq.flush(); }
3090 };
3091 
3092 void G1CollectedHeap::register_humongous_regions_with_cset() {
3093   if (!G1EagerReclaimHumongousObjects) {
3094     g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
3095     return;
3096   }
3097   double time = os::elapsed_counter();
3098 
3099   // Collect reclaim candidate information and register candidates with cset.
3100   RegisterHumongousWithInCSetFastTestClosure cl;
3101   heap_region_iterate(&cl);
3102 
3103   time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
3104   g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
3105                                                                   cl.total_humongous(),
3106                                                                   cl.candidate_humongous());
3107   _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
3108 
3109   // Finally flush all remembered set entries to re-check into the global DCQS.
3110   cl.flush_rem_set_entries();
3111 }
3112 
3113 class VerifyRegionRemSetClosure : public HeapRegionClosure {
3114   public:
3115     bool doHeapRegion(HeapRegion* hr) {
3116       if (!hr->is_archive() && !hr->is_continues_humongous()) {
3117         hr->verify_rem_set();
3118       }
3119       return false;
3120     }
3121 };
3122 
3123 #ifdef ASSERT
3124 class VerifyCSetClosure: public HeapRegionClosure {
3125 public:
3126   bool doHeapRegion(HeapRegion* hr) {
3127     // Here we check that the CSet region's RSet is ready for parallel
3128     // iteration. The fields that we'll verify are only manipulated
3129     // when the region is part of a CSet and is collected. Afterwards,
3130     // we reset these fields when we clear the region's RSet (when the
3131     // region is freed) so they are ready when the region is
3132     // re-allocated. The only exception to this is if there's an
3133     // evacuation failure and instead of freeing the region we leave
3134     // it in the heap. In that case, we reset these fields during
3135     // evacuation failure handling.
3136     guarantee(hr->rem_set()->verify_ready_for_par_iteration(), "verification");
3137 
3138     // Here's a good place to add any other checks we'd like to
3139     // perform on CSet regions.
3140     return false;
3141   }
3142 };
3143 #endif // ASSERT
3144 
3145 uint G1CollectedHeap::num_task_queues() const {
3146   return _task_queues->size();
3147 }
3148 
3149 #if TASKQUEUE_STATS
3150 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
3151   st->print_raw_cr("GC Task Stats");
3152   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
3153   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
3154 }
3155 
3156 void G1CollectedHeap::print_taskqueue_stats() const {
3157   if (!log_develop_is_enabled(Trace, gc, task, stats)) {
3158     return;
3159   }
3160   LogHandle(gc, task, stats) log;
3161   ResourceMark rm;
3162   outputStream* st = log.trace_stream();
3163 
3164   print_taskqueue_stats_hdr(st);
3165 
3166   TaskQueueStats totals;
3167   const uint n = num_task_queues();
3168   for (uint i = 0; i < n; ++i) {
3169     st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
3170     totals += task_queue(i)->stats;
3171   }
3172   st->print_raw("tot "); totals.print(st); st->cr();
3173 
3174   DEBUG_ONLY(totals.verify());
3175 }
3176 
3177 void G1CollectedHeap::reset_taskqueue_stats() {
3178   const uint n = num_task_queues();
3179   for (uint i = 0; i < n; ++i) {
3180     task_queue(i)->stats.reset();
3181   }
3182 }
3183 #endif // TASKQUEUE_STATS
3184 
3185 void G1CollectedHeap::wait_for_root_region_scanning() {
3186   double scan_wait_start = os::elapsedTime();
3187   // We have to wait until the CM threads finish scanning the
3188   // root regions as it's the only way to ensure that all the
3189   // objects on them have been correctly scanned before we start
3190   // moving them during the GC.
3191   bool waited = _cm->root_regions()->wait_until_scan_finished();
3192   double wait_time_ms = 0.0;
3193   if (waited) {
3194     double scan_wait_end = os::elapsedTime();
3195     wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
3196   }
3197   g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
3198 }
3199 
3200 bool
3201 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3202   assert_at_safepoint(true /* should_be_vm_thread */);
3203   guarantee(!is_gc_active(), "collection is not reentrant");
3204 
3205   if (GCLocker::check_active_before_gc()) {
3206     return false;
3207   }
3208 
3209   _gc_timer_stw->register_gc_start();
3210 
3211   GCIdMark gc_id_mark;
3212   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3213 
3214   SvcGCMarker sgcm(SvcGCMarker::MINOR);
3215   ResourceMark rm;
3216 
3217   wait_for_root_region_scanning();
3218 
3219   print_heap_before_gc();
3220   print_heap_regions();
3221   trace_heap_before_gc(_gc_tracer_stw);
3222 
3223   _verifier->verify_region_sets_optional();
3224   _verifier->verify_dirty_young_regions();
3225 
3226   // This call will decide whether this pause is an initial-mark
3227   // pause. If it is, during_initial_mark_pause() will return true
3228   // for the duration of this pause.
3229   g1_policy()->decide_on_conc_mark_initiation();
3230 
3231   // We do not allow initial-mark to be piggy-backed on a mixed GC.
3232   assert(!collector_state()->during_initial_mark_pause() ||
3233           collector_state()->gcs_are_young(), "sanity");
3234 
3235   // We also do not allow mixed GCs during marking.
3236   assert(!collector_state()->mark_in_progress() || collector_state()->gcs_are_young(), "sanity");
3237 
3238   // Record whether this pause is an initial mark. When the current
3239   // thread has completed its logging output and it's safe to signal
3240   // the CM thread, the flag's value in the policy has been reset.
3241   bool should_start_conc_mark = collector_state()->during_initial_mark_pause();
3242 
3243   // Inner scope for scope based logging, timers, and stats collection
3244   {
3245     EvacuationInfo evacuation_info;
3246 
3247     if (collector_state()->during_initial_mark_pause()) {
3248       // We are about to start a marking cycle, so we increment the
3249       // full collection counter.
3250       increment_old_marking_cycles_started();
3251       register_concurrent_cycle_start(_gc_timer_stw->gc_start());
3252     }
3253 
3254     _gc_tracer_stw->report_yc_type(collector_state()->yc_type());
3255 
3256     GCTraceCPUTime tcpu;
3257 
3258     FormatBuffer<> gc_string("Pause ");
3259     if (collector_state()->during_initial_mark_pause()) {
3260       gc_string.append("Initial Mark");
3261     } else if (collector_state()->gcs_are_young()) {
3262       gc_string.append("Young");
3263     } else {
3264       gc_string.append("Mixed");
3265     }
3266     GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true);
3267 
3268     uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
3269                                                                   workers()->active_workers(),
3270                                                                   Threads::number_of_non_daemon_threads());
3271     workers()->set_active_workers(active_workers);
3272 
3273     g1_policy()->note_gc_start(active_workers);
3274 
3275     TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
3276     TraceMemoryManagerStats tms(false /* fullGC */, gc_cause());
3277 
3278     // If the secondary_free_list is not empty, append it to the
3279     // free_list. No need to wait for the cleanup operation to finish;
3280     // the region allocation code will check the secondary_free_list
3281     // and wait if necessary. If the G1StressConcRegionFreeing flag is
3282     // set, skip this step so that the region allocation code has to
3283     // get entries from the secondary_free_list.
3284     if (!G1StressConcRegionFreeing) {
3285       append_secondary_free_list_if_not_empty_with_lock();
3286     }
3287 
3288     G1HeapTransition heap_transition(this);
3289     size_t heap_used_bytes_before_gc = used();
3290 
3291     assert(check_young_list_well_formed(), "young list should be well formed");
3292 
3293     // Don't dynamically change the number of GC threads this early.  A value of
3294     // 0 is used to indicate serial work.  When parallel work is done,
3295     // it will be set.
3296 
3297     { // Call to jvmpi::post_class_unload_events must occur outside of active GC
3298       IsGCActiveMark x;
3299 
3300       gc_prologue(false);
3301       increment_total_collections(false /* full gc */);
3302       increment_gc_time_stamp();
3303 
3304       if (VerifyRememberedSets) {
3305         log_info(gc, verify)("[Verifying RemSets before GC]");
3306         VerifyRegionRemSetClosure v_cl;
3307         heap_region_iterate(&v_cl);
3308       }
3309 
3310       _verifier->verify_before_gc();
3311 
3312       _verifier->check_bitmaps("GC Start");
3313 
3314 #if defined(COMPILER2) || INCLUDE_JVMCI
3315       DerivedPointerTable::clear();
3316 #endif
3317 
3318       // Please see comment in g1CollectedHeap.hpp and
3319       // G1CollectedHeap::ref_processing_init() to see how
3320       // reference processing currently works in G1.
3321 
3322       // Enable discovery in the STW reference processor
3323       if (g1_policy()->should_process_references()) {
3324         ref_processor_stw()->enable_discovery();
3325       } else {
3326         ref_processor_stw()->disable_discovery();
3327       }
3328 
3329       {
3330         // We want to temporarily turn off discovery by the
3331         // CM ref processor, if necessary, and turn it back on
3332         // on again later if we do. Using a scoped
3333         // NoRefDiscovery object will do this.
3334         NoRefDiscovery no_cm_discovery(ref_processor_cm());
3335 
3336         // Forget the current alloc region (we might even choose it to be part
3337         // of the collection set!).
3338         _allocator->release_mutator_alloc_region();
3339 
3340         // This timing is only used by the ergonomics to handle our pause target.
3341         // It is unclear why this should not include the full pause. We will
3342         // investigate this in CR 7178365.
3343         //
3344         // Preserving the old comment here if that helps the investigation:
3345         //
3346         // The elapsed time induced by the start time below deliberately elides
3347         // the possible verification above.
3348         double sample_start_time_sec = os::elapsedTime();
3349 
3350         g1_policy()->record_collection_pause_start(sample_start_time_sec);
3351 
3352         if (collector_state()->during_initial_mark_pause()) {
3353           concurrent_mark()->checkpointRootsInitialPre();
3354         }
3355 
3356         g1_policy()->finalize_collection_set(target_pause_time_ms);
3357 
3358         evacuation_info.set_collectionset_regions(collection_set()->region_length());
3359 
3360         // Make sure the remembered sets are up to date. This needs to be
3361         // done before register_humongous_regions_with_cset(), because the
3362         // remembered sets are used there to choose eager reclaim candidates.
3363         // If the remembered sets are not up to date we might miss some
3364         // entries that need to be handled.
3365         g1_rem_set()->cleanupHRRS();
3366 
3367         register_humongous_regions_with_cset();
3368 
3369         assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table.");
3370 
3371         _cm->note_start_of_gc();
3372         // We call this after finalize_cset() to
3373         // ensure that the CSet has been finalized.
3374         _cm->verify_no_cset_oops();
3375 
3376         if (_hr_printer.is_active()) {
3377           HeapRegion* hr = collection_set()->head();
3378           while (hr != NULL) {
3379             _hr_printer.cset(hr);
3380             hr = hr->next_in_collection_set();
3381           }
3382         }
3383 
3384 #ifdef ASSERT
3385         VerifyCSetClosure cl;
3386         collection_set_iterate(&cl);
3387 #endif // ASSERT
3388 
3389         // Initialize the GC alloc regions.
3390         _allocator->init_gc_alloc_regions(evacuation_info);
3391 
3392         G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length());
3393         pre_evacuate_collection_set();
3394 
3395         // Actually do the work...
3396         evacuate_collection_set(evacuation_info, &per_thread_states);
3397 
3398         post_evacuate_collection_set(evacuation_info, &per_thread_states);
3399 
3400         const size_t* surviving_young_words = per_thread_states.surviving_young_words();
3401         free_collection_set(collection_set()->head(), evacuation_info, surviving_young_words);
3402 
3403         eagerly_reclaim_humongous_regions();
3404 
3405         collection_set()->clear_head();
3406 
3407         record_obj_copy_mem_stats();
3408         _survivor_evac_stats.adjust_desired_plab_sz();
3409         _old_evac_stats.adjust_desired_plab_sz();
3410 
3411         // Start a new incremental collection set for the next pause.
3412         collection_set()->start_incremental_building();
3413 
3414         clear_cset_fast_test();
3415 
3416         // Don't check the whole heap at this point as the
3417         // GC alloc regions from this pause have been tagged
3418         // as survivors and moved on to the survivor list.
3419         // Survivor regions will fail the !is_young() check.
3420         assert(check_young_list_empty(false /* check_heap */),
3421           "young list should be empty");
3422 
3423         _young_list->reset_auxilary_lists();
3424 
3425         if (evacuation_failed()) {
3426           set_used(recalculate_used());
3427           if (_archive_allocator != NULL) {
3428             _archive_allocator->clear_used();
3429           }
3430           for (uint i = 0; i < ParallelGCThreads; i++) {
3431             if (_evacuation_failed_info_array[i].has_failed()) {
3432               _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
3433             }
3434           }
3435         } else {
3436           // The "used" of the the collection set have already been subtracted
3437           // when they were freed.  Add in the bytes evacuated.
3438           increase_used(g1_policy()->bytes_copied_during_gc());
3439         }
3440 
3441         if (collector_state()->during_initial_mark_pause()) {
3442           // We have to do this before we notify the CM threads that
3443           // they can start working to make sure that all the
3444           // appropriate initialization is done on the CM object.
3445           concurrent_mark()->checkpointRootsInitialPost();
3446           collector_state()->set_mark_in_progress(true);
3447           // Note that we don't actually trigger the CM thread at
3448           // this point. We do that later when we're sure that
3449           // the current thread has completed its logging output.
3450         }
3451 
3452         allocate_dummy_regions();
3453 
3454         _allocator->init_mutator_alloc_region();
3455 
3456         {
3457           size_t expand_bytes = g1_policy()->expansion_amount();
3458           if (expand_bytes > 0) {
3459             size_t bytes_before = capacity();
3460             // No need for an ergo logging here,
3461             // expansion_amount() does this when it returns a value > 0.
3462             double expand_ms;
3463             if (!expand(expand_bytes, &expand_ms)) {
3464               // We failed to expand the heap. Cannot do anything about it.
3465             }
3466             g1_policy()->phase_times()->record_expand_heap_time(expand_ms);
3467           }
3468         }
3469 
3470         // We redo the verification but now wrt to the new CSet which
3471         // has just got initialized after the previous CSet was freed.
3472         _cm->verify_no_cset_oops();
3473         _cm->note_end_of_gc();
3474 
3475         // This timing is only used by the ergonomics to handle our pause target.
3476         // It is unclear why this should not include the full pause. We will
3477         // investigate this in CR 7178365.
3478         double sample_end_time_sec = os::elapsedTime();
3479         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3480         size_t total_cards_scanned = per_thread_states.total_cards_scanned();
3481         g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc);
3482 
3483         evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before());
3484         evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc());
3485 
3486         MemoryService::track_memory_usage();
3487 
3488         // In prepare_for_verify() below we'll need to scan the deferred
3489         // update buffers to bring the RSets up-to-date if
3490         // G1HRRSFlushLogBuffersOnVerify has been set. While scanning
3491         // the update buffers we'll probably need to scan cards on the
3492         // regions we just allocated to (i.e., the GC alloc
3493         // regions). However, during the last GC we called
3494         // set_saved_mark() on all the GC alloc regions, so card
3495         // scanning might skip the [saved_mark_word()...top()] area of
3496         // those regions (i.e., the area we allocated objects into
3497         // during the last GC). But it shouldn't. Given that
3498         // saved_mark_word() is conditional on whether the GC time stamp
3499         // on the region is current or not, by incrementing the GC time
3500         // stamp here we invalidate all the GC time stamps on all the
3501         // regions and saved_mark_word() will simply return top() for
3502         // all the regions. This is a nicer way of ensuring this rather
3503         // than iterating over the regions and fixing them. In fact, the
3504         // GC time stamp increment here also ensures that
3505         // saved_mark_word() will return top() between pauses, i.e.,
3506         // during concurrent refinement. So we don't need the
3507         // is_gc_active() check to decided which top to use when
3508         // scanning cards (see CR 7039627).
3509         increment_gc_time_stamp();
3510 
3511         if (VerifyRememberedSets) {
3512           log_info(gc, verify)("[Verifying RemSets after GC]");
3513           VerifyRegionRemSetClosure v_cl;
3514           heap_region_iterate(&v_cl);
3515         }
3516 
3517         _verifier->verify_after_gc();
3518         _verifier->check_bitmaps("GC End");
3519 
3520         assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
3521         ref_processor_stw()->verify_no_references_recorded();
3522 
3523         // CM reference discovery will be re-enabled if necessary.
3524       }
3525 
3526 #ifdef TRACESPINNING
3527       ParallelTaskTerminator::print_termination_counts();
3528 #endif
3529 
3530       gc_epilogue(false);
3531     }
3532 
3533     // Print the remainder of the GC log output.
3534     if (evacuation_failed()) {
3535       log_info(gc)("To-space exhausted");
3536     }
3537 
3538     g1_policy()->print_phases();
3539     heap_transition.print();
3540 
3541     // It is not yet to safe to tell the concurrent mark to
3542     // start as we have some optional output below. We don't want the
3543     // output from the concurrent mark thread interfering with this
3544     // logging output either.
3545 
3546     _hrm.verify_optional();
3547     _verifier->verify_region_sets_optional();
3548 
3549     TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
3550     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3551 
3552     print_heap_after_gc();
3553     print_heap_regions();
3554     trace_heap_after_gc(_gc_tracer_stw);
3555 
3556     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3557     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3558     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3559     // before any GC notifications are raised.
3560     g1mm()->update_sizes();
3561 
3562     _gc_tracer_stw->report_evacuation_info(&evacuation_info);
3563     _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
3564     _gc_timer_stw->register_gc_end();
3565     _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
3566   }
3567   // It should now be safe to tell the concurrent mark thread to start
3568   // without its logging output interfering with the logging output
3569   // that came from the pause.
3570 
3571   if (should_start_conc_mark) {
3572     // CAUTION: after the doConcurrentMark() call below,
3573     // the concurrent marking thread(s) could be running
3574     // concurrently with us. Make sure that anything after
3575     // this point does not assume that we are the only GC thread
3576     // running. Note: of course, the actual marking work will
3577     // not start until the safepoint itself is released in
3578     // SuspendibleThreadSet::desynchronize().
3579     doConcurrentMark();
3580   }
3581 
3582   return true;
3583 }
3584 
3585 void G1CollectedHeap::restore_preserved_marks() {
3586   G1RestorePreservedMarksTask rpm_task(_preserved_objs);
3587   workers()->run_task(&rpm_task);
3588 }
3589 
3590 void G1CollectedHeap::remove_self_forwarding_pointers() {
3591   G1ParRemoveSelfForwardPtrsTask rsfp_task;
3592   workers()->run_task(&rsfp_task);
3593 }
3594 
3595 void G1CollectedHeap::restore_after_evac_failure() {
3596   double remove_self_forwards_start = os::elapsedTime();
3597 
3598   remove_self_forwarding_pointers();
3599   restore_preserved_marks();
3600 
3601   g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
3602 }
3603 
3604 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) {
3605   if (!_evacuation_failed) {
3606     _evacuation_failed = true;
3607   }
3608 
3609   _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size());
3610 
3611   // We want to call the "for_promotion_failure" version only in the
3612   // case of a promotion failure.
3613   if (m->must_be_preserved_for_promotion_failure(obj)) {
3614     OopAndMarkOop elem(obj, m);
3615     _preserved_objs[worker_id].push(elem);
3616   }
3617 }
3618 
3619 bool G1ParEvacuateFollowersClosure::offer_termination() {
3620   G1ParScanThreadState* const pss = par_scan_state();
3621   start_term_time();
3622   const bool res = terminator()->offer_termination();
3623   end_term_time();
3624   return res;
3625 }
3626 
3627 void G1ParEvacuateFollowersClosure::do_void() {
3628   G1ParScanThreadState* const pss = par_scan_state();
3629   pss->trim_queue();
3630   do {
3631     pss->steal_and_trim_queue(queues());
3632   } while (!offer_termination());
3633 }
3634 
3635 class G1ParTask : public AbstractGangTask {
3636 protected:
3637   G1CollectedHeap*         _g1h;
3638   G1ParScanThreadStateSet* _pss;
3639   RefToScanQueueSet*       _queues;
3640   G1RootProcessor*         _root_processor;
3641   ParallelTaskTerminator   _terminator;
3642   uint                     _n_workers;
3643 
3644 public:
3645   G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers)
3646     : AbstractGangTask("G1 collection"),
3647       _g1h(g1h),
3648       _pss(per_thread_states),
3649       _queues(task_queues),
3650       _root_processor(root_processor),
3651       _terminator(n_workers, _queues),
3652       _n_workers(n_workers)
3653   {}
3654 
3655   void work(uint worker_id) {
3656     if (worker_id >= _n_workers) return;  // no work needed this round
3657 
3658     double start_sec = os::elapsedTime();
3659     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec);
3660 
3661     {
3662       ResourceMark rm;
3663       HandleMark   hm;
3664 
3665       ReferenceProcessor*             rp = _g1h->ref_processor_stw();
3666 
3667       G1ParScanThreadState*           pss = _pss->state_for_worker(worker_id);
3668       pss->set_ref_processor(rp);
3669 
3670       double start_strong_roots_sec = os::elapsedTime();
3671 
3672       _root_processor->evacuate_roots(pss->closures(), worker_id);
3673 
3674       G1ParPushHeapRSClosure push_heap_rs_cl(_g1h, pss);
3675 
3676       // We pass a weak code blobs closure to the remembered set scanning because we want to avoid
3677       // treating the nmethods visited to act as roots for concurrent marking.
3678       // We only want to make sure that the oops in the nmethods are adjusted with regard to the
3679       // objects copied by the current evacuation.
3680       size_t cards_scanned = _g1h->g1_rem_set()->oops_into_collection_set_do(&push_heap_rs_cl,
3681                                                                              pss->closures()->weak_codeblobs(),
3682                                                                              worker_id);
3683 
3684       _pss->add_cards_scanned(worker_id, cards_scanned);
3685 
3686       double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec;
3687 
3688       double term_sec = 0.0;
3689       size_t evac_term_attempts = 0;
3690       {
3691         double start = os::elapsedTime();
3692         G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator);
3693         evac.do_void();
3694 
3695         evac_term_attempts = evac.term_attempts();
3696         term_sec = evac.term_time();
3697         double elapsed_sec = os::elapsedTime() - start;
3698         _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec);
3699         _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec);
3700         _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts);
3701       }
3702 
3703       assert(pss->queue_is_empty(), "should be empty");
3704 
3705       if (log_is_enabled(Debug, gc, task, stats)) {
3706         MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3707         size_t lab_waste;
3708         size_t lab_undo_waste;
3709         pss->waste(lab_waste, lab_undo_waste);
3710         _g1h->print_termination_stats(worker_id,
3711                                       (os::elapsedTime() - start_sec) * 1000.0,   /* elapsed time */
3712                                       strong_roots_sec * 1000.0,                  /* strong roots time */
3713                                       term_sec * 1000.0,                          /* evac term time */
3714                                       evac_term_attempts,                         /* evac term attempts */
3715                                       lab_waste,                                  /* alloc buffer waste */
3716                                       lab_undo_waste                              /* undo waste */
3717                                       );
3718       }
3719 
3720       // Close the inner scope so that the ResourceMark and HandleMark
3721       // destructors are executed here and are included as part of the
3722       // "GC Worker Time".
3723     }
3724     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime());
3725   }
3726 };
3727 
3728 void G1CollectedHeap::print_termination_stats_hdr() {
3729   log_debug(gc, task, stats)("GC Termination Stats");
3730   log_debug(gc, task, stats)("     elapsed  --strong roots-- -------termination------- ------waste (KiB)------");
3731   log_debug(gc, task, stats)("thr     ms        ms      %%        ms      %%    attempts  total   alloc    undo");
3732   log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------");
3733 }
3734 
3735 void G1CollectedHeap::print_termination_stats(uint worker_id,
3736                                               double elapsed_ms,
3737                                               double strong_roots_ms,
3738                                               double term_ms,
3739                                               size_t term_attempts,
3740                                               size_t alloc_buffer_waste,
3741                                               size_t undo_waste) const {
3742   log_debug(gc, task, stats)
3743               ("%3d %9.2f %9.2f %6.2f "
3744                "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
3745                SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
3746                worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms,
3747                term_ms, term_ms * 100 / elapsed_ms, term_attempts,
3748                (alloc_buffer_waste + undo_waste) * HeapWordSize / K,
3749                alloc_buffer_waste * HeapWordSize / K,
3750                undo_waste * HeapWordSize / K);
3751 }
3752 
3753 class G1StringSymbolTableUnlinkTask : public AbstractGangTask {
3754 private:
3755   BoolObjectClosure* _is_alive;
3756   int _initial_string_table_size;
3757   int _initial_symbol_table_size;
3758 
3759   bool  _process_strings;
3760   int _strings_processed;
3761   int _strings_removed;
3762 
3763   bool  _process_symbols;
3764   int _symbols_processed;
3765   int _symbols_removed;
3766 
3767 public:
3768   G1StringSymbolTableUnlinkTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols) :
3769     AbstractGangTask("String/Symbol Unlinking"),
3770     _is_alive(is_alive),
3771     _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
3772     _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0) {
3773 
3774     _initial_string_table_size = StringTable::the_table()->table_size();
3775     _initial_symbol_table_size = SymbolTable::the_table()->table_size();
3776     if (process_strings) {
3777       StringTable::clear_parallel_claimed_index();
3778     }
3779     if (process_symbols) {
3780       SymbolTable::clear_parallel_claimed_index();
3781     }
3782   }
3783 
3784   ~G1StringSymbolTableUnlinkTask() {
3785     guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size,
3786               "claim value %d after unlink less than initial string table size %d",
3787               StringTable::parallel_claimed_index(), _initial_string_table_size);
3788     guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
3789               "claim value %d after unlink less than initial symbol table size %d",
3790               SymbolTable::parallel_claimed_index(), _initial_symbol_table_size);
3791 
3792     log_debug(gc, stringdedup)("Cleaned string and symbol table, "
3793                                "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, "
3794                                "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed",
3795                                strings_processed(), strings_removed(),
3796                                symbols_processed(), symbols_removed());
3797   }
3798 
3799   void work(uint worker_id) {
3800     int strings_processed = 0;
3801     int strings_removed = 0;
3802     int symbols_processed = 0;
3803     int symbols_removed = 0;
3804     if (_process_strings) {
3805       StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
3806       Atomic::add(strings_processed, &_strings_processed);
3807       Atomic::add(strings_removed, &_strings_removed);
3808     }
3809     if (_process_symbols) {
3810       SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
3811       Atomic::add(symbols_processed, &_symbols_processed);
3812       Atomic::add(symbols_removed, &_symbols_removed);
3813     }
3814   }
3815 
3816   size_t strings_processed() const { return (size_t)_strings_processed; }
3817   size_t strings_removed()   const { return (size_t)_strings_removed; }
3818 
3819   size_t symbols_processed() const { return (size_t)_symbols_processed; }
3820   size_t symbols_removed()   const { return (size_t)_symbols_removed; }
3821 };
3822 
3823 class G1CodeCacheUnloadingTask VALUE_OBJ_CLASS_SPEC {
3824 private:
3825   static Monitor* _lock;
3826 
3827   BoolObjectClosure* const _is_alive;
3828   const bool               _unloading_occurred;
3829   const uint               _num_workers;
3830 
3831   // Variables used to claim nmethods.
3832   nmethod* _first_nmethod;
3833   volatile nmethod* _claimed_nmethod;
3834 
3835   // The list of nmethods that need to be processed by the second pass.
3836   volatile nmethod* _postponed_list;
3837   volatile uint     _num_entered_barrier;
3838 
3839  public:
3840   G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
3841       _is_alive(is_alive),
3842       _unloading_occurred(unloading_occurred),
3843       _num_workers(num_workers),
3844       _first_nmethod(NULL),
3845       _claimed_nmethod(NULL),
3846       _postponed_list(NULL),
3847       _num_entered_barrier(0)
3848   {
3849     nmethod::increase_unloading_clock();
3850     // Get first alive nmethod
3851     NMethodIterator iter = NMethodIterator();
3852     if(iter.next_alive()) {
3853       _first_nmethod = iter.method();
3854     }
3855     _claimed_nmethod = (volatile nmethod*)_first_nmethod;
3856   }
3857 
3858   ~G1CodeCacheUnloadingTask() {
3859     CodeCache::verify_clean_inline_caches();
3860 
3861     CodeCache::set_needs_cache_clean(false);
3862     guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
3863 
3864     CodeCache::verify_icholder_relocations();
3865   }
3866 
3867  private:
3868   void add_to_postponed_list(nmethod* nm) {
3869       nmethod* old;
3870       do {
3871         old = (nmethod*)_postponed_list;
3872         nm->set_unloading_next(old);
3873       } while ((nmethod*)Atomic::cmpxchg_ptr(nm, &_postponed_list, old) != old);
3874   }
3875 
3876   void clean_nmethod(nmethod* nm) {
3877     bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
3878 
3879     if (postponed) {
3880       // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
3881       add_to_postponed_list(nm);
3882     }
3883 
3884     // Mark that this thread has been cleaned/unloaded.
3885     // After this call, it will be safe to ask if this nmethod was unloaded or not.
3886     nm->set_unloading_clock(nmethod::global_unloading_clock());
3887   }
3888 
3889   void clean_nmethod_postponed(nmethod* nm) {
3890     nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
3891   }
3892 
3893   static const int MaxClaimNmethods = 16;
3894 
3895   void claim_nmethods(nmethod** claimed_nmethods, int *num_claimed_nmethods) {
3896     nmethod* first;
3897     NMethodIterator last;
3898 
3899     do {
3900       *num_claimed_nmethods = 0;
3901 
3902       first = (nmethod*)_claimed_nmethod;
3903       last = NMethodIterator(first);
3904 
3905       if (first != NULL) {
3906 
3907         for (int i = 0; i < MaxClaimNmethods; i++) {
3908           if (!last.next_alive()) {
3909             break;
3910           }
3911           claimed_nmethods[i] = last.method();
3912           (*num_claimed_nmethods)++;
3913         }
3914       }
3915 
3916     } while ((nmethod*)Atomic::cmpxchg_ptr(last.method(), &_claimed_nmethod, first) != first);
3917   }
3918 
3919   nmethod* claim_postponed_nmethod() {
3920     nmethod* claim;
3921     nmethod* next;
3922 
3923     do {
3924       claim = (nmethod*)_postponed_list;
3925       if (claim == NULL) {
3926         return NULL;
3927       }
3928 
3929       next = claim->unloading_next();
3930 
3931     } while ((nmethod*)Atomic::cmpxchg_ptr(next, &_postponed_list, claim) != claim);
3932 
3933     return claim;
3934   }
3935 
3936  public:
3937   // Mark that we're done with the first pass of nmethod cleaning.
3938   void barrier_mark(uint worker_id) {
3939     MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3940     _num_entered_barrier++;
3941     if (_num_entered_barrier == _num_workers) {
3942       ml.notify_all();
3943     }
3944   }
3945 
3946   // See if we have to wait for the other workers to
3947   // finish their first-pass nmethod cleaning work.
3948   void barrier_wait(uint worker_id) {
3949     if (_num_entered_barrier < _num_workers) {
3950       MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3951       while (_num_entered_barrier < _num_workers) {
3952           ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
3953       }
3954     }
3955   }
3956 
3957   // Cleaning and unloading of nmethods. Some work has to be postponed
3958   // to the second pass, when we know which nmethods survive.
3959   void work_first_pass(uint worker_id) {
3960     // The first nmethods is claimed by the first worker.
3961     if (worker_id == 0 && _first_nmethod != NULL) {
3962       clean_nmethod(_first_nmethod);
3963       _first_nmethod = NULL;
3964     }
3965 
3966     int num_claimed_nmethods;
3967     nmethod* claimed_nmethods[MaxClaimNmethods];
3968 
3969     while (true) {
3970       claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
3971 
3972       if (num_claimed_nmethods == 0) {
3973         break;
3974       }
3975 
3976       for (int i = 0; i < num_claimed_nmethods; i++) {
3977         clean_nmethod(claimed_nmethods[i]);
3978       }
3979     }
3980   }
3981 
3982   void work_second_pass(uint worker_id) {
3983     nmethod* nm;
3984     // Take care of postponed nmethods.
3985     while ((nm = claim_postponed_nmethod()) != NULL) {
3986       clean_nmethod_postponed(nm);
3987     }
3988   }
3989 };
3990 
3991 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never);
3992 
3993 class G1KlassCleaningTask : public StackObj {
3994   BoolObjectClosure*                      _is_alive;
3995   volatile jint                           _clean_klass_tree_claimed;
3996   ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
3997 
3998  public:
3999   G1KlassCleaningTask(BoolObjectClosure* is_alive) :
4000       _is_alive(is_alive),
4001       _clean_klass_tree_claimed(0),
4002       _klass_iterator() {
4003   }
4004 
4005  private:
4006   bool claim_clean_klass_tree_task() {
4007     if (_clean_klass_tree_claimed) {
4008       return false;
4009     }
4010 
4011     return Atomic::cmpxchg(1, (jint*)&_clean_klass_tree_claimed, 0) == 0;
4012   }
4013 
4014   InstanceKlass* claim_next_klass() {
4015     Klass* klass;
4016     do {
4017       klass =_klass_iterator.next_klass();
4018     } while (klass != NULL && !klass->is_instance_klass());
4019 
4020     // this can be null so don't call InstanceKlass::cast
4021     return static_cast<InstanceKlass*>(klass);
4022   }
4023 
4024 public:
4025 
4026   void clean_klass(InstanceKlass* ik) {
4027     ik->clean_weak_instanceklass_links(_is_alive);
4028   }
4029 
4030   void work() {
4031     ResourceMark rm;
4032 
4033     // One worker will clean the subklass/sibling klass tree.
4034     if (claim_clean_klass_tree_task()) {
4035       Klass::clean_subklass_tree(_is_alive);
4036     }
4037 
4038     // All workers will help cleaning the classes,
4039     InstanceKlass* klass;
4040     while ((klass = claim_next_klass()) != NULL) {
4041       clean_klass(klass);
4042     }
4043   }
4044 };
4045 
4046 // To minimize the remark pause times, the tasks below are done in parallel.
4047 class G1ParallelCleaningTask : public AbstractGangTask {
4048 private:
4049   G1StringSymbolTableUnlinkTask _string_symbol_task;
4050   G1CodeCacheUnloadingTask      _code_cache_task;
4051   G1KlassCleaningTask           _klass_cleaning_task;
4052 
4053 public:
4054   // The constructor is run in the VMThread.
4055   G1ParallelCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, uint num_workers, bool unloading_occurred) :
4056       AbstractGangTask("Parallel Cleaning"),
4057       _string_symbol_task(is_alive, process_strings, process_symbols),
4058       _code_cache_task(num_workers, is_alive, unloading_occurred),
4059       _klass_cleaning_task(is_alive) {
4060   }
4061 
4062   // The parallel work done by all worker threads.
4063   void work(uint worker_id) {
4064     // Do first pass of code cache cleaning.
4065     _code_cache_task.work_first_pass(worker_id);
4066 
4067     // Let the threads mark that the first pass is done.
4068     _code_cache_task.barrier_mark(worker_id);
4069 
4070     // Clean the Strings and Symbols.
4071     _string_symbol_task.work(worker_id);
4072 
4073     // Wait for all workers to finish the first code cache cleaning pass.
4074     _code_cache_task.barrier_wait(worker_id);
4075 
4076     // Do the second code cache cleaning work, which realize on
4077     // the liveness information gathered during the first pass.
4078     _code_cache_task.work_second_pass(worker_id);
4079 
4080     // Clean all klasses that were not unloaded.
4081     _klass_cleaning_task.work();
4082   }
4083 };
4084 
4085 
4086 void G1CollectedHeap::parallel_cleaning(BoolObjectClosure* is_alive,
4087                                         bool process_strings,
4088                                         bool process_symbols,
4089                                         bool class_unloading_occurred) {
4090   uint n_workers = workers()->active_workers();
4091 
4092   G1ParallelCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols,
4093                                         n_workers, class_unloading_occurred);
4094   workers()->run_task(&g1_unlink_task);
4095 }
4096 
4097 void G1CollectedHeap::unlink_string_and_symbol_table(BoolObjectClosure* is_alive,
4098                                                      bool process_strings, bool process_symbols) {
4099   {
4100     G1StringSymbolTableUnlinkTask g1_unlink_task(is_alive, process_strings, process_symbols);
4101     workers()->run_task(&g1_unlink_task);
4102   }
4103 
4104   if (G1StringDedup::is_enabled()) {
4105     G1StringDedup::unlink(is_alive);
4106   }
4107 }
4108 
4109 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
4110  private:
4111   DirtyCardQueueSet* _queue;
4112   G1CollectedHeap* _g1h;
4113  public:
4114   G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"),
4115     _queue(queue), _g1h(g1h) { }
4116 
4117   virtual void work(uint worker_id) {
4118     G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times();
4119     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id);
4120 
4121     RedirtyLoggedCardTableEntryClosure cl(_g1h);
4122     _queue->par_apply_closure_to_all_completed_buffers(&cl);
4123 
4124     phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied());
4125   }
4126 };
4127 
4128 void G1CollectedHeap::redirty_logged_cards() {
4129   double redirty_logged_cards_start = os::elapsedTime();
4130 
4131   G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this);
4132   dirty_card_queue_set().reset_for_par_iteration();
4133   workers()->run_task(&redirty_task);
4134 
4135   DirtyCardQueueSet& dcq = JavaThread::dirty_card_queue_set();
4136   dcq.merge_bufferlists(&dirty_card_queue_set());
4137   assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
4138 
4139   g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
4140 }
4141 
4142 // Weak Reference Processing support
4143 
4144 // An always "is_alive" closure that is used to preserve referents.
4145 // If the object is non-null then it's alive.  Used in the preservation
4146 // of referent objects that are pointed to by reference objects
4147 // discovered by the CM ref processor.
4148 class G1AlwaysAliveClosure: public BoolObjectClosure {
4149   G1CollectedHeap* _g1;
4150 public:
4151   G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
4152   bool do_object_b(oop p) {
4153     if (p != NULL) {
4154       return true;
4155     }
4156     return false;
4157   }
4158 };
4159 
4160 bool G1STWIsAliveClosure::do_object_b(oop p) {
4161   // An object is reachable if it is outside the collection set,
4162   // or is inside and copied.
4163   return !_g1->is_in_cset(p) || p->is_forwarded();
4164 }
4165 
4166 // Non Copying Keep Alive closure
4167 class G1KeepAliveClosure: public OopClosure {
4168   G1CollectedHeap* _g1;
4169 public:
4170   G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
4171   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
4172   void do_oop(oop* p) {
4173     oop obj = *p;
4174     assert(obj != NULL, "the caller should have filtered out NULL values");
4175 
4176     const InCSetState cset_state = _g1->in_cset_state(obj);
4177     if (!cset_state.is_in_cset_or_humongous()) {
4178       return;
4179     }
4180     if (cset_state.is_in_cset()) {
4181       assert( obj->is_forwarded(), "invariant" );
4182       *p = obj->forwardee();
4183     } else {
4184       assert(!obj->is_forwarded(), "invariant" );
4185       assert(cset_state.is_humongous(),
4186              "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value());
4187       _g1->set_humongous_is_live(obj);
4188     }
4189   }
4190 };
4191 
4192 // Copying Keep Alive closure - can be called from both
4193 // serial and parallel code as long as different worker
4194 // threads utilize different G1ParScanThreadState instances
4195 // and different queues.
4196 
4197 class G1CopyingKeepAliveClosure: public OopClosure {
4198   G1CollectedHeap*         _g1h;
4199   OopClosure*              _copy_non_heap_obj_cl;
4200   G1ParScanThreadState*    _par_scan_state;
4201 
4202 public:
4203   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
4204                             OopClosure* non_heap_obj_cl,
4205                             G1ParScanThreadState* pss):
4206     _g1h(g1h),
4207     _copy_non_heap_obj_cl(non_heap_obj_cl),
4208     _par_scan_state(pss)
4209   {}
4210 
4211   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
4212   virtual void do_oop(      oop* p) { do_oop_work(p); }
4213 
4214   template <class T> void do_oop_work(T* p) {
4215     oop obj = oopDesc::load_decode_heap_oop(p);
4216 
4217     if (_g1h->is_in_cset_or_humongous(obj)) {
4218       // If the referent object has been forwarded (either copied
4219       // to a new location or to itself in the event of an
4220       // evacuation failure) then we need to update the reference
4221       // field and, if both reference and referent are in the G1
4222       // heap, update the RSet for the referent.
4223       //
4224       // If the referent has not been forwarded then we have to keep
4225       // it alive by policy. Therefore we have copy the referent.
4226       //
4227       // If the reference field is in the G1 heap then we can push
4228       // on the PSS queue. When the queue is drained (after each
4229       // phase of reference processing) the object and it's followers
4230       // will be copied, the reference field set to point to the
4231       // new location, and the RSet updated. Otherwise we need to
4232       // use the the non-heap or metadata closures directly to copy
4233       // the referent object and update the pointer, while avoiding
4234       // updating the RSet.
4235 
4236       if (_g1h->is_in_g1_reserved(p)) {
4237         _par_scan_state->push_on_queue(p);
4238       } else {
4239         assert(!Metaspace::contains((const void*)p),
4240                "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p));
4241         _copy_non_heap_obj_cl->do_oop(p);
4242       }
4243     }
4244   }
4245 };
4246 
4247 // Serial drain queue closure. Called as the 'complete_gc'
4248 // closure for each discovered list in some of the
4249 // reference processing phases.
4250 
4251 class G1STWDrainQueueClosure: public VoidClosure {
4252 protected:
4253   G1CollectedHeap* _g1h;
4254   G1ParScanThreadState* _par_scan_state;
4255 
4256   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
4257 
4258 public:
4259   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
4260     _g1h(g1h),
4261     _par_scan_state(pss)
4262   { }
4263 
4264   void do_void() {
4265     G1ParScanThreadState* const pss = par_scan_state();
4266     pss->trim_queue();
4267   }
4268 };
4269 
4270 // Parallel Reference Processing closures
4271 
4272 // Implementation of AbstractRefProcTaskExecutor for parallel reference
4273 // processing during G1 evacuation pauses.
4274 
4275 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
4276 private:
4277   G1CollectedHeap*          _g1h;
4278   G1ParScanThreadStateSet*  _pss;
4279   RefToScanQueueSet*        _queues;
4280   WorkGang*                 _workers;
4281   uint                      _active_workers;
4282 
4283 public:
4284   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
4285                            G1ParScanThreadStateSet* per_thread_states,
4286                            WorkGang* workers,
4287                            RefToScanQueueSet *task_queues,
4288                            uint n_workers) :
4289     _g1h(g1h),
4290     _pss(per_thread_states),
4291     _queues(task_queues),
4292     _workers(workers),
4293     _active_workers(n_workers)
4294   {
4295     assert(n_workers > 0, "shouldn't call this otherwise");
4296   }
4297 
4298   // Executes the given task using concurrent marking worker threads.
4299   virtual void execute(ProcessTask& task);
4300   virtual void execute(EnqueueTask& task);
4301 };
4302 
4303 // Gang task for possibly parallel reference processing
4304 
4305 class G1STWRefProcTaskProxy: public AbstractGangTask {
4306   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
4307   ProcessTask&     _proc_task;
4308   G1CollectedHeap* _g1h;
4309   G1ParScanThreadStateSet* _pss;
4310   RefToScanQueueSet* _task_queues;
4311   ParallelTaskTerminator* _terminator;
4312 
4313 public:
4314   G1STWRefProcTaskProxy(ProcessTask& proc_task,
4315                         G1CollectedHeap* g1h,
4316                         G1ParScanThreadStateSet* per_thread_states,
4317                         RefToScanQueueSet *task_queues,
4318                         ParallelTaskTerminator* terminator) :
4319     AbstractGangTask("Process reference objects in parallel"),
4320     _proc_task(proc_task),
4321     _g1h(g1h),
4322     _pss(per_thread_states),
4323     _task_queues(task_queues),
4324     _terminator(terminator)
4325   {}
4326 
4327   virtual void work(uint worker_id) {
4328     // The reference processing task executed by a single worker.
4329     ResourceMark rm;
4330     HandleMark   hm;
4331 
4332     G1STWIsAliveClosure is_alive(_g1h);
4333 
4334     G1ParScanThreadState*          pss = _pss->state_for_worker(worker_id);
4335     pss->set_ref_processor(NULL);
4336 
4337     // Keep alive closure.
4338     G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
4339 
4340     // Complete GC closure
4341     G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator);
4342 
4343     // Call the reference processing task's work routine.
4344     _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
4345 
4346     // Note we cannot assert that the refs array is empty here as not all
4347     // of the processing tasks (specifically phase2 - pp2_work) execute
4348     // the complete_gc closure (which ordinarily would drain the queue) so
4349     // the queue may not be empty.
4350   }
4351 };
4352 
4353 // Driver routine for parallel reference processing.
4354 // Creates an instance of the ref processing gang
4355 // task and has the worker threads execute it.
4356 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
4357   assert(_workers != NULL, "Need parallel worker threads.");
4358 
4359   ParallelTaskTerminator terminator(_active_workers, _queues);
4360   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator);
4361 
4362   _workers->run_task(&proc_task_proxy);
4363 }
4364 
4365 // Gang task for parallel reference enqueueing.
4366 
4367 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
4368   typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
4369   EnqueueTask& _enq_task;
4370 
4371 public:
4372   G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
4373     AbstractGangTask("Enqueue reference objects in parallel"),
4374     _enq_task(enq_task)
4375   { }
4376 
4377   virtual void work(uint worker_id) {
4378     _enq_task.work(worker_id);
4379   }
4380 };
4381 
4382 // Driver routine for parallel reference enqueueing.
4383 // Creates an instance of the ref enqueueing gang
4384 // task and has the worker threads execute it.
4385 
4386 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
4387   assert(_workers != NULL, "Need parallel worker threads.");
4388 
4389   G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
4390 
4391   _workers->run_task(&enq_task_proxy);
4392 }
4393 
4394 // End of weak reference support closures
4395 
4396 // Abstract task used to preserve (i.e. copy) any referent objects
4397 // that are in the collection set and are pointed to by reference
4398 // objects discovered by the CM ref processor.
4399 
4400 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
4401 protected:
4402   G1CollectedHeap*         _g1h;
4403   G1ParScanThreadStateSet* _pss;
4404   RefToScanQueueSet*       _queues;
4405   ParallelTaskTerminator   _terminator;
4406   uint                     _n_workers;
4407 
4408 public:
4409   G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) :
4410     AbstractGangTask("ParPreserveCMReferents"),
4411     _g1h(g1h),
4412     _pss(per_thread_states),
4413     _queues(task_queues),
4414     _terminator(workers, _queues),
4415     _n_workers(workers)
4416   { }
4417 
4418   void work(uint worker_id) {
4419     G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id);
4420 
4421     ResourceMark rm;
4422     HandleMark   hm;
4423 
4424     G1ParScanThreadState*          pss = _pss->state_for_worker(worker_id);
4425     pss->set_ref_processor(NULL);
4426     assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4427 
4428     // Is alive closure
4429     G1AlwaysAliveClosure always_alive(_g1h);
4430 
4431     // Copying keep alive closure. Applied to referent objects that need
4432     // to be copied.
4433     G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
4434 
4435     ReferenceProcessor* rp = _g1h->ref_processor_cm();
4436 
4437     uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
4438     uint stride = MIN2(MAX2(_n_workers, 1U), limit);
4439 
4440     // limit is set using max_num_q() - which was set using ParallelGCThreads.
4441     // So this must be true - but assert just in case someone decides to
4442     // change the worker ids.
4443     assert(worker_id < limit, "sanity");
4444     assert(!rp->discovery_is_atomic(), "check this code");
4445 
4446     // Select discovered lists [i, i+stride, i+2*stride,...,limit)
4447     for (uint idx = worker_id; idx < limit; idx += stride) {
4448       DiscoveredList& ref_list = rp->discovered_refs()[idx];
4449 
4450       DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
4451       while (iter.has_next()) {
4452         // Since discovery is not atomic for the CM ref processor, we
4453         // can see some null referent objects.
4454         iter.load_ptrs(DEBUG_ONLY(true));
4455         oop ref = iter.obj();
4456 
4457         // This will filter nulls.
4458         if (iter.is_referent_alive()) {
4459           iter.make_referent_alive();
4460         }
4461         iter.move_to_next();
4462       }
4463     }
4464 
4465     // Drain the queue - which may cause stealing
4466     G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator);
4467     drain_queue.do_void();
4468     // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
4469     assert(pss->queue_is_empty(), "should be");
4470   }
4471 };
4472 
4473 void G1CollectedHeap::process_weak_jni_handles() {
4474   double ref_proc_start = os::elapsedTime();
4475 
4476   G1STWIsAliveClosure is_alive(this);
4477   G1KeepAliveClosure keep_alive(this);
4478   JNIHandles::weak_oops_do(&is_alive, &keep_alive);
4479 
4480   double ref_proc_time = os::elapsedTime() - ref_proc_start;
4481   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
4482 }
4483 
4484 void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) {
4485   double preserve_cm_referents_start = os::elapsedTime();
4486   // Any reference objects, in the collection set, that were 'discovered'
4487   // by the CM ref processor should have already been copied (either by
4488   // applying the external root copy closure to the discovered lists, or
4489   // by following an RSet entry).
4490   //
4491   // But some of the referents, that are in the collection set, that these
4492   // reference objects point to may not have been copied: the STW ref
4493   // processor would have seen that the reference object had already
4494   // been 'discovered' and would have skipped discovering the reference,
4495   // but would not have treated the reference object as a regular oop.
4496   // As a result the copy closure would not have been applied to the
4497   // referent object.
4498   //
4499   // We need to explicitly copy these referent objects - the references
4500   // will be processed at the end of remarking.
4501   //
4502   // We also need to do this copying before we process the reference
4503   // objects discovered by the STW ref processor in case one of these
4504   // referents points to another object which is also referenced by an
4505   // object discovered by the STW ref processor.
4506 
4507   uint no_of_gc_workers = workers()->active_workers();
4508 
4509   G1ParPreserveCMReferentsTask keep_cm_referents(this,
4510                                                  per_thread_states,
4511                                                  no_of_gc_workers,
4512                                                  _task_queues);
4513   workers()->run_task(&keep_cm_referents);
4514 
4515   g1_policy()->phase_times()->record_preserve_cm_referents_time_ms((os::elapsedTime() - preserve_cm_referents_start) * 1000.0);
4516 }
4517 
4518 // Weak Reference processing during an evacuation pause (part 1).
4519 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4520   double ref_proc_start = os::elapsedTime();
4521 
4522   ReferenceProcessor* rp = _ref_processor_stw;
4523   assert(rp->discovery_enabled(), "should have been enabled");
4524 
4525   // Closure to test whether a referent is alive.
4526   G1STWIsAliveClosure is_alive(this);
4527 
4528   // Even when parallel reference processing is enabled, the processing
4529   // of JNI refs is serial and performed serially by the current thread
4530   // rather than by a worker. The following PSS will be used for processing
4531   // JNI refs.
4532 
4533   // Use only a single queue for this PSS.
4534   G1ParScanThreadState*          pss = per_thread_states->state_for_worker(0);
4535   pss->set_ref_processor(NULL);
4536   assert(pss->queue_is_empty(), "pre-condition");
4537 
4538   // Keep alive closure.
4539   G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss);
4540 
4541   // Serial Complete GC closure
4542   G1STWDrainQueueClosure drain_queue(this, pss);
4543 
4544   // Setup the soft refs policy...
4545   rp->setup_policy(false);
4546 
4547   ReferenceProcessorStats stats;
4548   if (!rp->processing_is_mt()) {
4549     // Serial reference processing...
4550     stats = rp->process_discovered_references(&is_alive,
4551                                               &keep_alive,
4552                                               &drain_queue,
4553                                               NULL,
4554                                               _gc_timer_stw);
4555   } else {
4556     uint no_of_gc_workers = workers()->active_workers();
4557 
4558     // Parallel reference processing
4559     assert(rp->num_q() == no_of_gc_workers, "sanity");
4560     assert(no_of_gc_workers <= rp->max_num_q(), "sanity");
4561 
4562     G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers);
4563     stats = rp->process_discovered_references(&is_alive,
4564                                               &keep_alive,
4565                                               &drain_queue,
4566                                               &par_task_executor,
4567                                               _gc_timer_stw);
4568   }
4569 
4570   _gc_tracer_stw->report_gc_reference_stats(stats);
4571 
4572   // We have completed copying any necessary live referent objects.
4573   assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4574 
4575   double ref_proc_time = os::elapsedTime() - ref_proc_start;
4576   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
4577 }
4578 
4579 // Weak Reference processing during an evacuation pause (part 2).
4580 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4581   double ref_enq_start = os::elapsedTime();
4582 
4583   ReferenceProcessor* rp = _ref_processor_stw;
4584   assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
4585 
4586   // Now enqueue any remaining on the discovered lists on to
4587   // the pending list.
4588   if (!rp->processing_is_mt()) {
4589     // Serial reference processing...
4590     rp->enqueue_discovered_references();
4591   } else {
4592     // Parallel reference enqueueing
4593 
4594     uint n_workers = workers()->active_workers();
4595 
4596     assert(rp->num_q() == n_workers, "sanity");
4597     assert(n_workers <= rp->max_num_q(), "sanity");
4598 
4599     G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers);
4600     rp->enqueue_discovered_references(&par_task_executor);
4601   }
4602 
4603   rp->verify_no_references_recorded();
4604   assert(!rp->discovery_enabled(), "should have been disabled");
4605 
4606   // FIXME
4607   // CM's reference processing also cleans up the string and symbol tables.
4608   // Should we do that here also? We could, but it is a serial operation
4609   // and could significantly increase the pause time.
4610 
4611   double ref_enq_time = os::elapsedTime() - ref_enq_start;
4612   g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
4613 }
4614 
4615 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) {
4616   double merge_pss_time_start = os::elapsedTime();
4617   per_thread_states->flush();
4618   g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0);
4619 }
4620 
4621 void G1CollectedHeap::pre_evacuate_collection_set() {
4622   _expand_heap_after_alloc_failure = true;
4623   _evacuation_failed = false;
4624 
4625   // Disable the hot card cache.
4626   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
4627   hot_card_cache->reset_hot_cache_claimed_index();
4628   hot_card_cache->set_use_cache(false);
4629 
4630   g1_rem_set()->prepare_for_oops_into_collection_set_do();
4631 }
4632 
4633 void G1CollectedHeap::evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4634   // Should G1EvacuationFailureALot be in effect for this GC?
4635   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
4636 
4637   assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
4638   double start_par_time_sec = os::elapsedTime();
4639   double end_par_time_sec;
4640 
4641   {
4642     const uint n_workers = workers()->active_workers();
4643     G1RootProcessor root_processor(this, n_workers);
4644     G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers);
4645     // InitialMark needs claim bits to keep track of the marked-through CLDs.
4646     if (collector_state()->during_initial_mark_pause()) {
4647       ClassLoaderDataGraph::clear_claimed_marks();
4648     }
4649 
4650     print_termination_stats_hdr();
4651 
4652     workers()->run_task(&g1_par_task);
4653     end_par_time_sec = os::elapsedTime();
4654 
4655     // Closing the inner scope will execute the destructor
4656     // for the G1RootProcessor object. We record the current
4657     // elapsed time before closing the scope so that time
4658     // taken for the destructor is NOT included in the
4659     // reported parallel time.
4660   }
4661 
4662   G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
4663 
4664   double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
4665   phase_times->record_par_time(par_time_ms);
4666 
4667   double code_root_fixup_time_ms =
4668         (os::elapsedTime() - end_par_time_sec) * 1000.0;
4669   phase_times->record_code_root_fixup_time(code_root_fixup_time_ms);
4670 }
4671 
4672 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4673   // Process any discovered reference objects - we have
4674   // to do this _before_ we retire the GC alloc regions
4675   // as we may have to copy some 'reachable' referent
4676   // objects (and their reachable sub-graphs) that were
4677   // not copied during the pause.
4678   if (g1_policy()->should_process_references()) {
4679     preserve_cm_referents(per_thread_states);
4680     process_discovered_references(per_thread_states);
4681   } else {
4682     ref_processor_stw()->verify_no_references_recorded();
4683     process_weak_jni_handles();
4684   }
4685 
4686   if (G1StringDedup::is_enabled()) {
4687     double fixup_start = os::elapsedTime();
4688 
4689     G1STWIsAliveClosure is_alive(this);
4690     G1KeepAliveClosure keep_alive(this);
4691     G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times());
4692 
4693     double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
4694     g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms);
4695   }
4696 
4697   g1_rem_set()->cleanup_after_oops_into_collection_set_do();
4698 
4699   if (evacuation_failed()) {
4700     restore_after_evac_failure();
4701 
4702     // Reset the G1EvacuationFailureALot counters and flags
4703     // Note: the values are reset only when an actual
4704     // evacuation failure occurs.
4705     NOT_PRODUCT(reset_evacuation_should_fail();)
4706   }
4707 
4708   // Enqueue any remaining references remaining on the STW
4709   // reference processor's discovered lists. We need to do
4710   // this after the card table is cleaned (and verified) as
4711   // the act of enqueueing entries on to the pending list
4712   // will log these updates (and dirty their associated
4713   // cards). We need these updates logged to update any
4714   // RSets.
4715   if (g1_policy()->should_process_references()) {
4716     enqueue_discovered_references(per_thread_states);
4717   } else {
4718     g1_policy()->phase_times()->record_ref_enq_time(0);
4719   }
4720 
4721   _allocator->release_gc_alloc_regions(evacuation_info);
4722 
4723   merge_per_thread_state_info(per_thread_states);
4724 
4725   // Reset and re-enable the hot card cache.
4726   // Note the counts for the cards in the regions in the
4727   // collection set are reset when the collection set is freed.
4728   G1HotCardCache* hot_card_cache = _cg1r->hot_card_cache();
4729   hot_card_cache->reset_hot_cache();
4730   hot_card_cache->set_use_cache(true);
4731 
4732   purge_code_root_memory();
4733 
4734   redirty_logged_cards();
4735 #if defined(COMPILER2) || INCLUDE_JVMCI
4736   DerivedPointerTable::update_pointers();
4737 #endif
4738 }
4739 
4740 void G1CollectedHeap::record_obj_copy_mem_stats() {
4741   g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
4742 
4743   _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
4744                                                create_g1_evac_summary(&_old_evac_stats));
4745 }
4746 
4747 void G1CollectedHeap::free_region(HeapRegion* hr,
4748                                   FreeRegionList* free_list,
4749                                   bool par,
4750                                   bool locked) {
4751   assert(!hr->is_free(), "the region should not be free");
4752   assert(!hr->is_empty(), "the region should not be empty");
4753   assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
4754   assert(free_list != NULL, "pre-condition");
4755 
4756   if (G1VerifyBitmaps) {
4757     MemRegion mr(hr->bottom(), hr->end());
4758     concurrent_mark()->clearRangePrevBitmap(mr);
4759   }
4760 
4761   // Clear the card counts for this region.
4762   // Note: we only need to do this if the region is not young
4763   // (since we don't refine cards in young regions).
4764   if (!hr->is_young()) {
4765     _cg1r->hot_card_cache()->reset_card_counts(hr);
4766   }
4767   hr->hr_clear(par, true /* clear_space */, locked /* locked */);
4768   free_list->add_ordered(hr);
4769 }
4770 
4771 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
4772                                             FreeRegionList* free_list,
4773                                             bool par) {
4774   assert(hr->is_humongous(), "this is only for humongous regions");
4775   assert(free_list != NULL, "pre-condition");
4776   hr->clear_humongous();
4777   free_region(hr, free_list, par);
4778 }
4779 
4780 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed,
4781                                            const uint humongous_regions_removed) {
4782   if (old_regions_removed > 0 || humongous_regions_removed > 0) {
4783     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4784     _old_set.bulk_remove(old_regions_removed);
4785     _humongous_set.bulk_remove(humongous_regions_removed);
4786   }
4787 
4788 }
4789 
4790 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
4791   assert(list != NULL, "list can't be null");
4792   if (!list->is_empty()) {
4793     MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4794     _hrm.insert_list_into_free_list(list);
4795   }
4796 }
4797 
4798 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
4799   decrease_used(bytes);
4800 }
4801 
4802 class G1ParCleanupCTTask : public AbstractGangTask {
4803   G1SATBCardTableModRefBS* _ct_bs;
4804   G1CollectedHeap* _g1h;
4805   HeapRegion* volatile _su_head;
4806 public:
4807   G1ParCleanupCTTask(G1SATBCardTableModRefBS* ct_bs,
4808                      G1CollectedHeap* g1h) :
4809     AbstractGangTask("G1 Par Cleanup CT Task"),
4810     _ct_bs(ct_bs), _g1h(g1h) { }
4811 
4812   void work(uint worker_id) {
4813     HeapRegion* r;
4814     while (r = _g1h->pop_dirty_cards_region()) {
4815       clear_cards(r);
4816     }
4817   }
4818 
4819   void clear_cards(HeapRegion* r) {
4820     // Cards of the survivors should have already been dirtied.
4821     if (!r->is_survivor()) {
4822       _ct_bs->clear(MemRegion(r->bottom(), r->end()));
4823     }
4824   }
4825 };
4826 
4827 class G1ParScrubRemSetTask: public AbstractGangTask {
4828 protected:
4829   G1RemSet* _g1rs;
4830   BitMap* _region_bm;
4831   BitMap* _card_bm;
4832   HeapRegionClaimer _hrclaimer;
4833 
4834 public:
4835   G1ParScrubRemSetTask(G1RemSet* g1_rs, BitMap* region_bm, BitMap* card_bm, uint num_workers) :
4836     AbstractGangTask("G1 ScrubRS"),
4837     _g1rs(g1_rs),
4838     _region_bm(region_bm),
4839     _card_bm(card_bm),
4840     _hrclaimer(num_workers) {
4841   }
4842 
4843   void work(uint worker_id) {
4844     _g1rs->scrub(_region_bm, _card_bm, worker_id, &_hrclaimer);
4845   }
4846 };
4847 
4848 void G1CollectedHeap::scrub_rem_set(BitMap* region_bm, BitMap* card_bm) {
4849   uint num_workers = workers()->active_workers();
4850   G1ParScrubRemSetTask g1_par_scrub_rs_task(g1_rem_set(), region_bm, card_bm, num_workers);
4851   workers()->run_task(&g1_par_scrub_rs_task);
4852 }
4853 
4854 void G1CollectedHeap::cleanUpCardTable() {
4855   G1SATBCardTableModRefBS* ct_bs = g1_barrier_set();
4856   double start = os::elapsedTime();
4857 
4858   {
4859     // Iterate over the dirty cards region list.
4860     G1ParCleanupCTTask cleanup_task(ct_bs, this);
4861 
4862     workers()->run_task(&cleanup_task);
4863 #ifndef PRODUCT
4864     _verifier->verify_card_table_cleanup();
4865 #endif
4866   }
4867 
4868   double elapsed = os::elapsedTime() - start;
4869   g1_policy()->phase_times()->record_clear_ct_time(elapsed * 1000.0);
4870 }
4871 
4872 void G1CollectedHeap::free_collection_set(HeapRegion* cs_head, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) {
4873   size_t pre_used = 0;
4874   FreeRegionList local_free_list("Local List for CSet Freeing");
4875 
4876   double young_time_ms     = 0.0;
4877   double non_young_time_ms = 0.0;
4878 
4879   // Since the collection set is a superset of the the young list,
4880   // all we need to do to clear the young list is clear its
4881   // head and length, and unlink any young regions in the code below
4882   _young_list->clear();
4883 
4884   G1CollectorPolicy* policy = g1_policy();
4885 
4886   double start_sec = os::elapsedTime();
4887   bool non_young = true;
4888 
4889   HeapRegion* cur = cs_head;
4890   int age_bound = -1;
4891   size_t rs_lengths = 0;
4892 
4893   while (cur != NULL) {
4894     assert(!is_on_master_free_list(cur), "sanity");
4895     if (non_young) {
4896       if (cur->is_young()) {
4897         double end_sec = os::elapsedTime();
4898         double elapsed_ms = (end_sec - start_sec) * 1000.0;
4899         non_young_time_ms += elapsed_ms;
4900 
4901         start_sec = os::elapsedTime();
4902         non_young = false;
4903       }
4904     } else {
4905       if (!cur->is_young()) {
4906         double end_sec = os::elapsedTime();
4907         double elapsed_ms = (end_sec - start_sec) * 1000.0;
4908         young_time_ms += elapsed_ms;
4909 
4910         start_sec = os::elapsedTime();
4911         non_young = true;
4912       }
4913     }
4914 
4915     rs_lengths += cur->rem_set()->occupied_locked();
4916 
4917     HeapRegion* next = cur->next_in_collection_set();
4918     assert(cur->in_collection_set(), "bad CS");
4919     cur->set_next_in_collection_set(NULL);
4920     clear_in_cset(cur);
4921 
4922     if (cur->is_young()) {
4923       int index = cur->young_index_in_cset();
4924       assert(index != -1, "invariant");
4925       assert((uint) index < collection_set()->young_region_length(), "invariant");
4926       size_t words_survived = surviving_young_words[index];
4927       cur->record_surv_words_in_group(words_survived);
4928 
4929       // At this point the we have 'popped' cur from the collection set
4930       // (linked via next_in_collection_set()) but it is still in the
4931       // young list (linked via next_young_region()). Clear the
4932       // _next_young_region field.
4933       cur->set_next_young_region(NULL);
4934     } else {
4935       int index = cur->young_index_in_cset();
4936       assert(index == -1, "invariant");
4937     }
4938 
4939     assert( (cur->is_young() && cur->young_index_in_cset() > -1) ||
4940             (!cur->is_young() && cur->young_index_in_cset() == -1),
4941             "invariant" );
4942 
4943     if (!cur->evacuation_failed()) {
4944       MemRegion used_mr = cur->used_region();
4945 
4946       // And the region is empty.
4947       assert(!used_mr.is_empty(), "Should not have empty regions in a CS.");
4948       pre_used += cur->used();
4949       free_region(cur, &local_free_list, false /* par */, true /* locked */);
4950     } else {
4951       cur->uninstall_surv_rate_group();
4952       if (cur->is_young()) {
4953         cur->set_young_index_in_cset(-1);
4954       }
4955       cur->set_evacuation_failed(false);
4956       // When moving a young gen region to old gen, we "allocate" that whole region
4957       // there. This is in addition to any already evacuated objects. Notify the
4958       // policy about that.
4959       // Old gen regions do not cause an additional allocation: both the objects
4960       // still in the region and the ones already moved are accounted for elsewhere.
4961       if (cur->is_young()) {
4962         policy->add_bytes_allocated_in_old_since_last_gc(HeapRegion::GrainBytes);
4963       }
4964       // The region is now considered to be old.
4965       cur->set_old();
4966       // Do some allocation statistics accounting. Regions that failed evacuation
4967       // are always made old, so there is no need to update anything in the young
4968       // gen statistics, but we need to update old gen statistics.
4969       size_t used_words = cur->marked_bytes() / HeapWordSize;
4970       _old_evac_stats.add_failure_used_and_waste(used_words, HeapRegion::GrainWords - used_words);
4971       _old_set.add(cur);
4972       evacuation_info.increment_collectionset_used_after(cur->used());
4973     }
4974     cur = next;
4975   }
4976 
4977   evacuation_info.set_regions_freed(local_free_list.length());
4978   policy->record_max_rs_lengths(rs_lengths);
4979   policy->cset_regions_freed();
4980 
4981   double end_sec = os::elapsedTime();
4982   double elapsed_ms = (end_sec - start_sec) * 1000.0;
4983 
4984   if (non_young) {
4985     non_young_time_ms += elapsed_ms;
4986   } else {
4987     young_time_ms += elapsed_ms;
4988   }
4989 
4990   prepend_to_freelist(&local_free_list);
4991   decrement_summary_bytes(pre_used);
4992   policy->phase_times()->record_young_free_cset_time_ms(young_time_ms);
4993   policy->phase_times()->record_non_young_free_cset_time_ms(non_young_time_ms);
4994 }
4995 
4996 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
4997  private:
4998   FreeRegionList* _free_region_list;
4999   HeapRegionSet* _proxy_set;
5000   uint _humongous_regions_removed;
5001   size_t _freed_bytes;
5002  public:
5003 
5004   G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
5005     _free_region_list(free_region_list), _humongous_regions_removed(0), _freed_bytes(0) {
5006   }
5007 
5008   virtual bool doHeapRegion(HeapRegion* r) {
5009     if (!r->is_starts_humongous()) {
5010       return false;
5011     }
5012 
5013     G1CollectedHeap* g1h = G1CollectedHeap::heap();
5014 
5015     oop obj = (oop)r->bottom();
5016     G1CMBitMap* next_bitmap = g1h->concurrent_mark()->nextMarkBitMap();
5017 
5018     // The following checks whether the humongous object is live are sufficient.
5019     // The main additional check (in addition to having a reference from the roots
5020     // or the young gen) is whether the humongous object has a remembered set entry.
5021     //
5022     // A humongous object cannot be live if there is no remembered set for it
5023     // because:
5024     // - there can be no references from within humongous starts regions referencing
5025     // the object because we never allocate other objects into them.
5026     // (I.e. there are no intra-region references that may be missed by the
5027     // remembered set)
5028     // - as soon there is a remembered set entry to the humongous starts region
5029     // (i.e. it has "escaped" to an old object) this remembered set entry will stay
5030     // until the end of a concurrent mark.
5031     //
5032     // It is not required to check whether the object has been found dead by marking
5033     // or not, in fact it would prevent reclamation within a concurrent cycle, as
5034     // all objects allocated during that time are considered live.
5035     // SATB marking is even more conservative than the remembered set.
5036     // So if at this point in the collection there is no remembered set entry,
5037     // nobody has a reference to it.
5038     // At the start of collection we flush all refinement logs, and remembered sets
5039     // are completely up-to-date wrt to references to the humongous object.
5040     //
5041     // Other implementation considerations:
5042     // - never consider object arrays at this time because they would pose
5043     // considerable effort for cleaning up the the remembered sets. This is
5044     // required because stale remembered sets might reference locations that
5045     // are currently allocated into.
5046     uint region_idx = r->hrm_index();
5047     if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
5048         !r->rem_set()->is_empty()) {
5049       log_debug(gc, humongous)("Live humongous region %u object size " SIZE_FORMAT " start " PTR_FORMAT "  with remset " SIZE_FORMAT " code roots " SIZE_FORMAT " is marked %d reclaim candidate %d type array %d",
5050                                region_idx,
5051                                (size_t)obj->size() * HeapWordSize,
5052                                p2i(r->bottom()),
5053                                r->rem_set()->occupied(),
5054                                r->rem_set()->strong_code_roots_list_length(),
5055                                next_bitmap->isMarked(r->bottom()),
5056                                g1h->is_humongous_reclaim_candidate(region_idx),
5057                                obj->is_typeArray()
5058                               );
5059       return false;
5060     }
5061 
5062     guarantee(obj->is_typeArray(),
5063               "Only eagerly reclaiming type arrays is supported, but the object "
5064               PTR_FORMAT " is not.", p2i(r->bottom()));
5065 
5066     log_debug(gc, humongous)("Dead humongous region %u object size " SIZE_FORMAT " start " PTR_FORMAT " with remset " SIZE_FORMAT " code roots " SIZE_FORMAT " is marked %d reclaim candidate %d type array %d",
5067                              region_idx,
5068                              (size_t)obj->size() * HeapWordSize,
5069                              p2i(r->bottom()),
5070                              r->rem_set()->occupied(),
5071                              r->rem_set()->strong_code_roots_list_length(),
5072                              next_bitmap->isMarked(r->bottom()),
5073                              g1h->is_humongous_reclaim_candidate(region_idx),
5074                              obj->is_typeArray()
5075                             );
5076 
5077     // Need to clear mark bit of the humongous object if already set.
5078     if (next_bitmap->isMarked(r->bottom())) {
5079       next_bitmap->clear(r->bottom());
5080     }
5081     do {
5082       HeapRegion* next = g1h->next_region_in_humongous(r);
5083       _freed_bytes += r->used();
5084       r->set_containing_set(NULL);
5085       _humongous_regions_removed++;
5086       g1h->free_humongous_region(r, _free_region_list, false);
5087       r = next;
5088     } while (r != NULL);
5089 
5090     return false;
5091   }
5092 
5093   uint humongous_free_count() {
5094     return _humongous_regions_removed;
5095   }
5096 
5097   size_t bytes_freed() const {
5098     return _freed_bytes;
5099   }
5100 };
5101 
5102 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
5103   assert_at_safepoint(true);
5104 
5105   if (!G1EagerReclaimHumongousObjects ||
5106       (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) {
5107     g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
5108     return;
5109   }
5110 
5111   double start_time = os::elapsedTime();
5112 
5113   FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
5114 
5115   G1FreeHumongousRegionClosure cl(&local_cleanup_list);
5116   heap_region_iterate(&cl);
5117 
5118   remove_from_old_sets(0, cl.humongous_free_count());
5119 
5120   G1HRPrinter* hrp = hr_printer();
5121   if (hrp->is_active()) {
5122     FreeRegionListIterator iter(&local_cleanup_list);
5123     while (iter.more_available()) {
5124       HeapRegion* hr = iter.get_next();
5125       hrp->cleanup(hr);
5126     }
5127   }
5128 
5129   prepend_to_freelist(&local_cleanup_list);
5130   decrement_summary_bytes(cl.bytes_freed());
5131 
5132   g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
5133                                                                     cl.humongous_free_count());
5134 }
5135 
5136 // This routine is similar to the above but does not record
5137 // any policy statistics or update free lists; we are abandoning
5138 // the current incremental collection set in preparation of a
5139 // full collection. After the full GC we will start to build up
5140 // the incremental collection set again.
5141 // This is only called when we're doing a full collection
5142 // and is immediately followed by the tearing down of the young list.
5143 
5144 void G1CollectedHeap::abandon_collection_set(HeapRegion* cs_head) {
5145   HeapRegion* cur = cs_head;
5146 
5147   while (cur != NULL) {
5148     HeapRegion* next = cur->next_in_collection_set();
5149     assert(cur->in_collection_set(), "bad CS");
5150     cur->set_next_in_collection_set(NULL);
5151     clear_in_cset(cur);
5152     cur->set_young_index_in_cset(-1);
5153     cur = next;
5154   }
5155 }
5156 
5157 void G1CollectedHeap::set_free_regions_coming() {
5158   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : setting free regions coming");
5159 
5160   assert(!free_regions_coming(), "pre-condition");
5161   _free_regions_coming = true;
5162 }
5163 
5164 void G1CollectedHeap::reset_free_regions_coming() {
5165   assert(free_regions_coming(), "pre-condition");
5166 
5167   {
5168     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5169     _free_regions_coming = false;
5170     SecondaryFreeList_lock->notify_all();
5171   }
5172 
5173   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [cm thread] : reset free regions coming");
5174 }
5175 
5176 void G1CollectedHeap::wait_while_free_regions_coming() {
5177   // Most of the time we won't have to wait, so let's do a quick test
5178   // first before we take the lock.
5179   if (!free_regions_coming()) {
5180     return;
5181   }
5182 
5183   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : waiting for free regions");
5184 
5185   {
5186     MutexLockerEx x(SecondaryFreeList_lock, Mutex::_no_safepoint_check_flag);
5187     while (free_regions_coming()) {
5188       SecondaryFreeList_lock->wait(Mutex::_no_safepoint_check_flag);
5189     }
5190   }
5191 
5192   log_develop_trace(gc, freelist)("G1ConcRegionFreeing [other] : done waiting for free regions");
5193 }
5194 
5195 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
5196   return _allocator->is_retained_old_region(hr);
5197 }
5198 
5199 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
5200   _young_list->push_region(hr);
5201 }
5202 
5203 class NoYoungRegionsClosure: public HeapRegionClosure {
5204 private:
5205   bool _success;
5206 public:
5207   NoYoungRegionsClosure() : _success(true) { }
5208   bool doHeapRegion(HeapRegion* r) {
5209     if (r->is_young()) {
5210       log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
5211                             p2i(r->bottom()), p2i(r->end()));
5212       _success = false;
5213     }
5214     return false;
5215   }
5216   bool success() { return _success; }
5217 };
5218 
5219 bool G1CollectedHeap::check_young_list_empty(bool check_heap) {
5220   bool ret = _young_list->check_list_empty();
5221 
5222   if (check_heap) {
5223     NoYoungRegionsClosure closure;
5224     heap_region_iterate(&closure);
5225     ret = ret && closure.success();
5226   }
5227 
5228   return ret;
5229 }
5230 
5231 class TearDownRegionSetsClosure : public HeapRegionClosure {
5232 private:
5233   HeapRegionSet *_old_set;
5234 
5235 public:
5236   TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
5237 
5238   bool doHeapRegion(HeapRegion* r) {
5239     if (r->is_old()) {
5240       _old_set->remove(r);
5241     } else {
5242       // We ignore free regions, we'll empty the free list afterwards.
5243       // We ignore young regions, we'll empty the young list afterwards.
5244       // We ignore humongous regions, we're not tearing down the
5245       // humongous regions set.
5246       assert(r->is_free() || r->is_young() || r->is_humongous(),
5247              "it cannot be another type");
5248     }
5249     return false;
5250   }
5251 
5252   ~TearDownRegionSetsClosure() {
5253     assert(_old_set->is_empty(), "post-condition");
5254   }
5255 };
5256 
5257 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
5258   assert_at_safepoint(true /* should_be_vm_thread */);
5259 
5260   if (!free_list_only) {
5261     TearDownRegionSetsClosure cl(&_old_set);
5262     heap_region_iterate(&cl);
5263 
5264     // Note that emptying the _young_list is postponed and instead done as
5265     // the first step when rebuilding the regions sets again. The reason for
5266     // this is that during a full GC string deduplication needs to know if
5267     // a collected region was young or old when the full GC was initiated.
5268   }
5269   _hrm.remove_all_free_regions();
5270 }
5271 
5272 void G1CollectedHeap::increase_used(size_t bytes) {
5273   _summary_bytes_used += bytes;
5274 }
5275 
5276 void G1CollectedHeap::decrease_used(size_t bytes) {
5277   assert(_summary_bytes_used >= bytes,
5278          "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
5279          _summary_bytes_used, bytes);
5280   _summary_bytes_used -= bytes;
5281 }
5282 
5283 void G1CollectedHeap::set_used(size_t bytes) {
5284   _summary_bytes_used = bytes;
5285 }
5286 
5287 class RebuildRegionSetsClosure : public HeapRegionClosure {
5288 private:
5289   bool            _free_list_only;
5290   HeapRegionSet*   _old_set;
5291   HeapRegionManager*   _hrm;
5292   size_t          _total_used;
5293 
5294 public:
5295   RebuildRegionSetsClosure(bool free_list_only,
5296                            HeapRegionSet* old_set, HeapRegionManager* hrm) :
5297     _free_list_only(free_list_only),
5298     _old_set(old_set), _hrm(hrm), _total_used(0) {
5299     assert(_hrm->num_free_regions() == 0, "pre-condition");
5300     if (!free_list_only) {
5301       assert(_old_set->is_empty(), "pre-condition");
5302     }
5303   }
5304 
5305   bool doHeapRegion(HeapRegion* r) {
5306     if (r->is_empty()) {
5307       // Add free regions to the free list
5308       r->set_free();
5309       r->set_allocation_context(AllocationContext::system());
5310       _hrm->insert_into_free_list(r);
5311     } else if (!_free_list_only) {
5312       assert(!r->is_young(), "we should not come across young regions");
5313 
5314       if (r->is_humongous()) {
5315         // We ignore humongous regions. We left the humongous set unchanged.
5316       } else {
5317         // Objects that were compacted would have ended up on regions
5318         // that were previously old or free.  Archive regions (which are
5319         // old) will not have been touched.
5320         assert(r->is_free() || r->is_old(), "invariant");
5321         // We now consider them old, so register as such. Leave
5322         // archive regions set that way, however, while still adding
5323         // them to the old set.
5324         if (!r->is_archive()) {
5325           r->set_old();
5326         }
5327         _old_set->add(r);
5328       }
5329       _total_used += r->used();
5330     }
5331 
5332     return false;
5333   }
5334 
5335   size_t total_used() {
5336     return _total_used;
5337   }
5338 };
5339 
5340 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
5341   assert_at_safepoint(true /* should_be_vm_thread */);
5342 
5343   if (!free_list_only) {
5344     _young_list->empty_list();
5345   }
5346 
5347   RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
5348   heap_region_iterate(&cl);
5349 
5350   if (!free_list_only) {
5351     set_used(cl.total_used());
5352     if (_archive_allocator != NULL) {
5353       _archive_allocator->clear_used();
5354     }
5355   }
5356   assert(used_unlocked() == recalculate_used(),
5357          "inconsistent used_unlocked(), "
5358          "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT,
5359          used_unlocked(), recalculate_used());
5360 }
5361 
5362 void G1CollectedHeap::set_refine_cte_cl_concurrency(bool concurrent) {
5363   _refine_cte_cl->set_concurrent(concurrent);
5364 }
5365 
5366 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
5367   HeapRegion* hr = heap_region_containing(p);
5368   return hr->is_in(p);
5369 }
5370 
5371 // Methods for the mutator alloc region
5372 
5373 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
5374                                                       bool force) {
5375   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5376   assert(!force || g1_policy()->can_expand_young_list(),
5377          "if force is true we should be able to expand the young list");
5378   bool young_list_full = g1_policy()->is_young_list_full();
5379   if (force || !young_list_full) {
5380     HeapRegion* new_alloc_region = new_region(word_size,
5381                                               false /* is_old */,
5382                                               false /* do_expand */);
5383     if (new_alloc_region != NULL) {
5384       set_region_short_lived_locked(new_alloc_region);
5385       _hr_printer.alloc(new_alloc_region, young_list_full);
5386       _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region);
5387       return new_alloc_region;
5388     }
5389   }
5390   return NULL;
5391 }
5392 
5393 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
5394                                                   size_t allocated_bytes) {
5395   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
5396   assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
5397 
5398   collection_set()->add_eden_region(alloc_region);
5399   increase_used(allocated_bytes);
5400   _hr_printer.retire(alloc_region);
5401   // We update the eden sizes here, when the region is retired,
5402   // instead of when it's allocated, since this is the point that its
5403   // used space has been recored in _summary_bytes_used.
5404   g1mm()->update_eden_size();
5405 }
5406 
5407 // Methods for the GC alloc regions
5408 
5409 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size,
5410                                                  uint count,
5411                                                  InCSetState dest) {
5412   assert(FreeList_lock->owned_by_self(), "pre-condition");
5413 
5414   if (count < g1_policy()->max_regions(dest)) {
5415     const bool is_survivor = (dest.is_young());
5416     HeapRegion* new_alloc_region = new_region(word_size,
5417                                               !is_survivor,
5418                                               true /* do_expand */);
5419     if (new_alloc_region != NULL) {
5420       // We really only need to do this for old regions given that we
5421       // should never scan survivors. But it doesn't hurt to do it
5422       // for survivors too.
5423       new_alloc_region->record_timestamp();
5424       if (is_survivor) {
5425         new_alloc_region->set_survivor();
5426         _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region);
5427       } else {
5428         new_alloc_region->set_old();
5429         _verifier->check_bitmaps("Old Region Allocation", new_alloc_region);
5430       }
5431       _hr_printer.alloc(new_alloc_region);
5432       bool during_im = collector_state()->during_initial_mark_pause();
5433       new_alloc_region->note_start_of_copying(during_im);
5434       return new_alloc_region;
5435     }
5436   }
5437   return NULL;
5438 }
5439 
5440 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
5441                                              size_t allocated_bytes,
5442                                              InCSetState dest) {
5443   bool during_im = collector_state()->during_initial_mark_pause();
5444   alloc_region->note_end_of_copying(during_im);
5445   g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
5446   if (dest.is_young()) {
5447     young_list()->add_survivor_region(alloc_region);
5448   } else {
5449     _old_set.add(alloc_region);
5450   }
5451   _hr_printer.retire(alloc_region);
5452 }
5453 
5454 HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
5455   bool expanded = false;
5456   uint index = _hrm.find_highest_free(&expanded);
5457 
5458   if (index != G1_NO_HRM_INDEX) {
5459     if (expanded) {
5460       log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
5461                                 HeapRegion::GrainWords * HeapWordSize);
5462     }
5463     _hrm.allocate_free_regions_starting_at(index, 1);
5464     return region_at(index);
5465   }
5466   return NULL;
5467 }
5468 
5469 // Optimized nmethod scanning
5470 
5471 class RegisterNMethodOopClosure: public OopClosure {
5472   G1CollectedHeap* _g1h;
5473   nmethod* _nm;
5474 
5475   template <class T> void do_oop_work(T* p) {
5476     T heap_oop = oopDesc::load_heap_oop(p);
5477     if (!oopDesc::is_null(heap_oop)) {
5478       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5479       HeapRegion* hr = _g1h->heap_region_containing(obj);
5480       assert(!hr->is_continues_humongous(),
5481              "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5482              " starting at " HR_FORMAT,
5483              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5484 
5485       // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
5486       hr->add_strong_code_root_locked(_nm);
5487     }
5488   }
5489 
5490 public:
5491   RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5492     _g1h(g1h), _nm(nm) {}
5493 
5494   void do_oop(oop* p)       { do_oop_work(p); }
5495   void do_oop(narrowOop* p) { do_oop_work(p); }
5496 };
5497 
5498 class UnregisterNMethodOopClosure: public OopClosure {
5499   G1CollectedHeap* _g1h;
5500   nmethod* _nm;
5501 
5502   template <class T> void do_oop_work(T* p) {
5503     T heap_oop = oopDesc::load_heap_oop(p);
5504     if (!oopDesc::is_null(heap_oop)) {
5505       oop obj = oopDesc::decode_heap_oop_not_null(heap_oop);
5506       HeapRegion* hr = _g1h->heap_region_containing(obj);
5507       assert(!hr->is_continues_humongous(),
5508              "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5509              " starting at " HR_FORMAT,
5510              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5511 
5512       hr->remove_strong_code_root(_nm);
5513     }
5514   }
5515 
5516 public:
5517   UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5518     _g1h(g1h), _nm(nm) {}
5519 
5520   void do_oop(oop* p)       { do_oop_work(p); }
5521   void do_oop(narrowOop* p) { do_oop_work(p); }
5522 };
5523 
5524 void G1CollectedHeap::register_nmethod(nmethod* nm) {
5525   CollectedHeap::register_nmethod(nm);
5526 
5527   guarantee(nm != NULL, "sanity");
5528   RegisterNMethodOopClosure reg_cl(this, nm);
5529   nm->oops_do(&reg_cl);
5530 }
5531 
5532 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
5533   CollectedHeap::unregister_nmethod(nm);
5534 
5535   guarantee(nm != NULL, "sanity");
5536   UnregisterNMethodOopClosure reg_cl(this, nm);
5537   nm->oops_do(&reg_cl, true);
5538 }
5539 
5540 void G1CollectedHeap::purge_code_root_memory() {
5541   double purge_start = os::elapsedTime();
5542   G1CodeRootSet::purge();
5543   double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
5544   g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
5545 }
5546 
5547 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
5548   G1CollectedHeap* _g1h;
5549 
5550 public:
5551   RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
5552     _g1h(g1h) {}
5553 
5554   void do_code_blob(CodeBlob* cb) {
5555     nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
5556     if (nm == NULL) {
5557       return;
5558     }
5559 
5560     if (ScavengeRootsInCode) {
5561       _g1h->register_nmethod(nm);
5562     }
5563   }
5564 };
5565 
5566 void G1CollectedHeap::rebuild_strong_code_roots() {
5567   RebuildStrongCodeRootClosure blob_cl(this);
5568   CodeCache::blobs_do(&blob_cl);
5569 }
--- EOF ---