1 /*
   2  * Copyright (c) 2001, 2020, 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/classLoaderDataGraph.hpp"
  27 #include "classfile/metadataOnStackMark.hpp"
  28 #include "classfile/stringTable.hpp"
  29 #include "code/codeCache.hpp"
  30 #include "code/icBuffer.hpp"
  31 #include "gc/g1/g1Allocator.inline.hpp"
  32 #include "gc/g1/g1Arguments.hpp"
  33 #include "gc/g1/g1BarrierSet.hpp"
  34 #include "gc/g1/g1CardTableEntryClosure.hpp"
  35 #include "gc/g1/g1CollectedHeap.inline.hpp"
  36 #include "gc/g1/g1CollectionSet.hpp"
  37 #include "gc/g1/g1CollectorState.hpp"
  38 #include "gc/g1/g1ConcurrentRefine.hpp"
  39 #include "gc/g1/g1ConcurrentRefineThread.hpp"
  40 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp"
  41 #include "gc/g1/g1DirtyCardQueue.hpp"
  42 #include "gc/g1/g1EvacStats.inline.hpp"
  43 #include "gc/g1/g1FullCollector.hpp"
  44 #include "gc/g1/g1GCParPhaseTimesTracker.hpp"
  45 #include "gc/g1/g1GCPhaseTimes.hpp"
  46 #include "gc/g1/g1HeapSizingPolicy.hpp"
  47 #include "gc/g1/g1HeapTransition.hpp"
  48 #include "gc/g1/g1HeapVerifier.hpp"
  49 #include "gc/g1/g1HotCardCache.hpp"
  50 #include "gc/g1/g1InitLogger.hpp"
  51 #include "gc/g1/g1MemoryPool.hpp"
  52 #include "gc/g1/g1OopClosures.inline.hpp"
  53 #include "gc/g1/g1ParallelCleaning.hpp"
  54 #include "gc/g1/g1ParScanThreadState.inline.hpp"
  55 #include "gc/g1/g1Policy.hpp"
  56 #include "gc/g1/g1RedirtyCardsQueue.hpp"
  57 #include "gc/g1/g1RegionToSpaceMapper.hpp"
  58 #include "gc/g1/g1RemSet.hpp"
  59 #include "gc/g1/g1RootClosures.hpp"
  60 #include "gc/g1/g1RootProcessor.hpp"
  61 #include "gc/g1/g1SATBMarkQueueSet.hpp"
  62 #include "gc/g1/g1StringDedup.hpp"
  63 #include "gc/g1/g1ThreadLocalData.hpp"
  64 #include "gc/g1/g1Trace.hpp"
  65 #include "gc/g1/g1YCTypes.hpp"
  66 #include "gc/g1/g1YoungRemSetSamplingThread.hpp"
  67 #include "gc/g1/g1VMOperations.hpp"
  68 #include "gc/g1/heapRegion.inline.hpp"
  69 #include "gc/g1/heapRegionRemSet.hpp"
  70 #include "gc/g1/heapRegionSet.inline.hpp"
  71 #include "gc/shared/concurrentGCBreakpoints.hpp"
  72 #include "gc/shared/gcBehaviours.hpp"
  73 #include "gc/shared/gcHeapSummary.hpp"
  74 #include "gc/shared/gcId.hpp"
  75 #include "gc/shared/gcLocker.hpp"
  76 #include "gc/shared/gcTimer.hpp"
  77 #include "gc/shared/gcTraceTime.inline.hpp"
  78 #include "gc/shared/generationSpec.hpp"
  79 #include "gc/shared/isGCActiveMark.hpp"
  80 #include "gc/shared/locationPrinter.inline.hpp"
  81 #include "gc/shared/oopStorageParState.hpp"
  82 #include "gc/shared/preservedMarks.inline.hpp"
  83 #include "gc/shared/suspendibleThreadSet.hpp"
  84 #include "gc/shared/referenceProcessor.inline.hpp"
  85 #include "gc/shared/taskTerminator.hpp"
  86 #include "gc/shared/taskqueue.inline.hpp"
  87 #include "gc/shared/weakProcessor.inline.hpp"
  88 #include "gc/shared/workerPolicy.hpp"
  89 #include "logging/log.hpp"
  90 #include "memory/allocation.hpp"
  91 #include "memory/iterator.hpp"
  92 #include "memory/resourceArea.hpp"
  93 #include "memory/universe.hpp"
  94 #include "oops/access.inline.hpp"
  95 #include "oops/compressedOops.inline.hpp"
  96 #include "oops/oop.inline.hpp"
  97 #include "runtime/atomic.hpp"
  98 #include "runtime/flags/flagSetting.hpp"
  99 #include "runtime/handles.inline.hpp"
 100 #include "runtime/init.hpp"
 101 #include "runtime/orderAccess.hpp"
 102 #include "runtime/threadSMR.hpp"
 103 #include "runtime/vmThread.hpp"
 104 #include "utilities/align.hpp"
 105 #include "utilities/bitMap.inline.hpp"
 106 #include "utilities/globalDefinitions.hpp"
 107 #include "utilities/stack.inline.hpp"
 108 
 109 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
 110 
 111 // INVARIANTS/NOTES
 112 //
 113 // All allocation activity covered by the G1CollectedHeap interface is
 114 // serialized by acquiring the HeapLock.  This happens in mem_allocate
 115 // and allocate_new_tlab, which are the "entry" points to the
 116 // allocation code from the rest of the JVM.  (Note that this does not
 117 // apply to TLAB allocation, which is not part of this interface: it
 118 // is done by clients of this interface.)
 119 
 120 class RedirtyLoggedCardTableEntryClosure : public G1CardTableEntryClosure {
 121  private:
 122   size_t _num_dirtied;
 123   G1CollectedHeap* _g1h;
 124   G1CardTable* _g1_ct;
 125 
 126   HeapRegion* region_for_card(CardValue* card_ptr) const {
 127     return _g1h->heap_region_containing(_g1_ct->addr_for(card_ptr));
 128   }
 129 
 130   bool will_become_free(HeapRegion* hr) const {
 131     // A region will be freed by free_collection_set if the region is in the
 132     // collection set and has not had an evacuation failure.
 133     return _g1h->is_in_cset(hr) && !hr->evacuation_failed();
 134   }
 135 
 136  public:
 137   RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : G1CardTableEntryClosure(),
 138     _num_dirtied(0), _g1h(g1h), _g1_ct(g1h->card_table()) { }
 139 
 140   void do_card_ptr(CardValue* card_ptr, uint worker_id) {
 141     HeapRegion* hr = region_for_card(card_ptr);
 142 
 143     // Should only dirty cards in regions that won't be freed.
 144     if (!will_become_free(hr)) {
 145       *card_ptr = G1CardTable::dirty_card_val();
 146       _num_dirtied++;
 147     }
 148   }
 149 
 150   size_t num_dirtied()   const { return _num_dirtied; }
 151 };
 152 
 153 
 154 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
 155   HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
 156 }
 157 
 158 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
 159   // The from card cache is not the memory that is actually committed. So we cannot
 160   // take advantage of the zero_filled parameter.
 161   reset_from_card_cache(start_idx, num_regions);
 162 }
 163 
 164 Tickspan G1CollectedHeap::run_task(AbstractGangTask* task) {
 165   Ticks start = Ticks::now();
 166   workers()->run_task(task, workers()->active_workers());
 167   return Ticks::now() - start;
 168 }
 169 
 170 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
 171                                              MemRegion mr) {
 172   return new HeapRegion(hrs_index, bot(), mr);
 173 }
 174 
 175 // Private methods.
 176 
 177 HeapRegion* G1CollectedHeap::new_region(size_t word_size,
 178                                         HeapRegionType type,
 179                                         bool do_expand,
 180                                         uint node_index) {
 181   assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
 182          "the only time we use this to allocate a humongous region is "
 183          "when we are allocating a single humongous region");
 184 
 185   HeapRegion* res = _hrm->allocate_free_region(type, node_index);
 186 
 187   if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
 188     // Currently, only attempts to allocate GC alloc regions set
 189     // do_expand to true. So, we should only reach here during a
 190     // safepoint. If this assumption changes we might have to
 191     // reconsider the use of _expand_heap_after_alloc_failure.
 192     assert(SafepointSynchronize::is_at_safepoint(), "invariant");
 193 
 194     log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B",
 195                               word_size * HeapWordSize);
 196 
 197     assert(word_size * HeapWordSize < HeapRegion::GrainBytes,
 198            "This kind of expansion should never be more than one region. Size: " SIZE_FORMAT,
 199            word_size * HeapWordSize);
 200     if (expand_single_region(node_index)) {
 201       // Given that expand_single_region() succeeded in expanding the heap, and we
 202       // always expand the heap by an amount aligned to the heap
 203       // region size, the free list should in theory not be empty.
 204       // In either case allocate_free_region() will check for NULL.
 205       res = _hrm->allocate_free_region(type, node_index);
 206     } else {
 207       _expand_heap_after_alloc_failure = false;
 208     }
 209   }
 210   return res;
 211 }
 212 
 213 HeapWord*
 214 G1CollectedHeap::humongous_obj_allocate_initialize_regions(HeapRegion* first_hr,
 215                                                            uint num_regions,
 216                                                            size_t word_size) {
 217   assert(first_hr != NULL, "pre-condition");
 218   assert(is_humongous(word_size), "word_size should be humongous");
 219   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 220 
 221   // Index of last region in the series.
 222   uint first = first_hr->hrm_index();
 223   uint last = first + num_regions - 1;
 224 
 225   // We need to initialize the region(s) we just discovered. This is
 226   // a bit tricky given that it can happen concurrently with
 227   // refinement threads refining cards on these regions and
 228   // potentially wanting to refine the BOT as they are scanning
 229   // those cards (this can happen shortly after a cleanup; see CR
 230   // 6991377). So we have to set up the region(s) carefully and in
 231   // a specific order.
 232 
 233   // The word size sum of all the regions we will allocate.
 234   size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
 235   assert(word_size <= word_size_sum, "sanity");
 236 
 237   // The passed in hr will be the "starts humongous" region. The header
 238   // of the new object will be placed at the bottom of this region.
 239   HeapWord* new_obj = first_hr->bottom();
 240   // This will be the new top of the new object.
 241   HeapWord* obj_top = new_obj + word_size;
 242 
 243   // First, we need to zero the header of the space that we will be
 244   // allocating. When we update top further down, some refinement
 245   // threads might try to scan the region. By zeroing the header we
 246   // ensure that any thread that will try to scan the region will
 247   // come across the zero klass word and bail out.
 248   //
 249   // NOTE: It would not have been correct to have used
 250   // CollectedHeap::fill_with_object() and make the space look like
 251   // an int array. The thread that is doing the allocation will
 252   // later update the object header to a potentially different array
 253   // type and, for a very short period of time, the klass and length
 254   // fields will be inconsistent. This could cause a refinement
 255   // thread to calculate the object size incorrectly.
 256   Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
 257 
 258   // Next, pad out the unused tail of the last region with filler
 259   // objects, for improved usage accounting.
 260   // How many words we use for filler objects.
 261   size_t word_fill_size = word_size_sum - word_size;
 262 
 263   // How many words memory we "waste" which cannot hold a filler object.
 264   size_t words_not_fillable = 0;
 265 
 266   if (word_fill_size >= min_fill_size()) {
 267     fill_with_objects(obj_top, word_fill_size);
 268   } else if (word_fill_size > 0) {
 269     // We have space to fill, but we cannot fit an object there.
 270     words_not_fillable = word_fill_size;
 271     word_fill_size = 0;
 272   }
 273 
 274   // We will set up the first region as "starts humongous". This
 275   // will also update the BOT covering all the regions to reflect
 276   // that there is a single object that starts at the bottom of the
 277   // first region.
 278   first_hr->set_starts_humongous(obj_top, word_fill_size);
 279   _policy->remset_tracker()->update_at_allocate(first_hr);
 280   // Then, if there are any, we will set up the "continues
 281   // humongous" regions.
 282   HeapRegion* hr = NULL;
 283   for (uint i = first + 1; i <= last; ++i) {
 284     hr = region_at(i);
 285     hr->set_continues_humongous(first_hr);
 286     _policy->remset_tracker()->update_at_allocate(hr);
 287   }
 288 
 289   // Up to this point no concurrent thread would have been able to
 290   // do any scanning on any region in this series. All the top
 291   // fields still point to bottom, so the intersection between
 292   // [bottom,top] and [card_start,card_end] will be empty. Before we
 293   // update the top fields, we'll do a storestore to make sure that
 294   // no thread sees the update to top before the zeroing of the
 295   // object header and the BOT initialization.
 296   OrderAccess::storestore();
 297 
 298   // Now, we will update the top fields of the "continues humongous"
 299   // regions except the last one.
 300   for (uint i = first; i < last; ++i) {
 301     hr = region_at(i);
 302     hr->set_top(hr->end());
 303   }
 304 
 305   hr = region_at(last);
 306   // If we cannot fit a filler object, we must set top to the end
 307   // of the humongous object, otherwise we cannot iterate the heap
 308   // and the BOT will not be complete.
 309   hr->set_top(hr->end() - words_not_fillable);
 310 
 311   assert(hr->bottom() < obj_top && obj_top <= hr->end(),
 312          "obj_top should be in last region");
 313 
 314   _verifier->check_bitmaps("Humongous Region Allocation", first_hr);
 315 
 316   assert(words_not_fillable == 0 ||
 317          first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(),
 318          "Miscalculation in humongous allocation");
 319 
 320   increase_used((word_size_sum - words_not_fillable) * HeapWordSize);
 321 
 322   for (uint i = first; i <= last; ++i) {
 323     hr = region_at(i);
 324     _humongous_set.add(hr);
 325     _hr_printer.alloc(hr);
 326   }
 327 
 328   return new_obj;
 329 }
 330 
 331 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) {
 332   assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size);
 333   return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
 334 }
 335 
 336 // If could fit into free regions w/o expansion, try.
 337 // Otherwise, if can expand, do so.
 338 // Otherwise, if using ex regions might help, try with ex given back.
 339 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
 340   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 341 
 342   _verifier->verify_region_sets_optional();
 343 
 344   uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);
 345 
 346   // Policy: First try to allocate a humongous object in the free list.
 347   HeapRegion* humongous_start = _hrm->allocate_humongous(obj_regions);
 348   if (humongous_start == NULL) {
 349     // Policy: We could not find enough regions for the humongous object in the
 350     // free list. Look through the heap to find a mix of free and uncommitted regions.
 351     // If so, expand the heap and allocate the humongous object.
 352     humongous_start = _hrm->expand_and_allocate_humongous(obj_regions);
 353     if (humongous_start != NULL) {
 354       // We managed to find a region by expanding the heap.
 355       log_debug(gc, ergo, heap)("Heap expansion (humongous allocation request). Allocation request: " SIZE_FORMAT "B",
 356                                 word_size * HeapWordSize);
 357       policy()->record_new_heap_size(num_regions());
 358     } else {
 359       // Policy: Potentially trigger a defragmentation GC.
 360     }
 361   }
 362 
 363   HeapWord* result = NULL;
 364   if (humongous_start != NULL) {
 365     result = humongous_obj_allocate_initialize_regions(humongous_start, obj_regions, word_size);
 366     assert(result != NULL, "it should always return a valid result");
 367 
 368     // A successful humongous object allocation changes the used space
 369     // information of the old generation so we need to recalculate the
 370     // sizes and update the jstat counters here.
 371     g1mm()->update_sizes();
 372   }
 373 
 374   _verifier->verify_region_sets_optional();
 375 
 376   return result;
 377 }
 378 
 379 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t min_size,
 380                                              size_t requested_size,
 381                                              size_t* actual_size) {
 382   assert_heap_not_locked_and_not_at_safepoint();
 383   assert(!is_humongous(requested_size), "we do not allow humongous TLABs");
 384 
 385   return attempt_allocation(min_size, requested_size, actual_size);
 386 }
 387 
 388 HeapWord*
 389 G1CollectedHeap::mem_allocate(size_t word_size,
 390                               bool*  gc_overhead_limit_was_exceeded) {
 391   assert_heap_not_locked_and_not_at_safepoint();
 392 
 393   if (is_humongous(word_size)) {
 394     return attempt_allocation_humongous(word_size);
 395   }
 396   size_t dummy = 0;
 397   return attempt_allocation(word_size, word_size, &dummy);
 398 }
 399 
 400 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size) {
 401   ResourceMark rm; // For retrieving the thread names in log messages.
 402 
 403   // Make sure you read the note in attempt_allocation_humongous().
 404 
 405   assert_heap_not_locked_and_not_at_safepoint();
 406   assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
 407          "be called for humongous allocation requests");
 408 
 409   // We should only get here after the first-level allocation attempt
 410   // (attempt_allocation()) failed to allocate.
 411 
 412   // We will loop until a) we manage to successfully perform the
 413   // allocation or b) we successfully schedule a collection which
 414   // fails to perform the allocation. b) is the only case when we'll
 415   // return NULL.
 416   HeapWord* result = NULL;
 417   for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 418     bool should_try_gc;
 419     uint gc_count_before;
 420 
 421     {
 422       MutexLocker x(Heap_lock);
 423       result = _allocator->attempt_allocation_locked(word_size);
 424       if (result != NULL) {
 425         return result;
 426       }
 427 
 428       // If the GCLocker is active and we are bound for a GC, try expanding young gen.
 429       // This is different to when only GCLocker::needs_gc() is set: try to avoid
 430       // waiting because the GCLocker is active to not wait too long.
 431       if (GCLocker::is_active_and_needs_gc() && policy()->can_expand_young_list()) {
 432         // No need for an ergo message here, can_expand_young_list() does this when
 433         // it returns true.
 434         result = _allocator->attempt_allocation_force(word_size);
 435         if (result != NULL) {
 436           return result;
 437         }
 438       }
 439       // Only try a GC if the GCLocker does not signal the need for a GC. Wait until
 440       // the GCLocker initiated GC has been performed and then retry. This includes
 441       // the case when the GC Locker is not active but has not been performed.
 442       should_try_gc = !GCLocker::needs_gc();
 443       // Read the GC count while still holding the Heap_lock.
 444       gc_count_before = total_collections();
 445     }
 446 
 447     if (should_try_gc) {
 448       bool succeeded;
 449       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 450                                    GCCause::_g1_inc_collection_pause);
 451       if (result != NULL) {
 452         assert(succeeded, "only way to get back a non-NULL result");
 453         log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT,
 454                              Thread::current()->name(), p2i(result));
 455         return result;
 456       }
 457 
 458       if (succeeded) {
 459         // We successfully scheduled a collection which failed to allocate. No
 460         // point in trying to allocate further. We'll just return NULL.
 461         log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate "
 462                              SIZE_FORMAT " words", Thread::current()->name(), word_size);
 463         return NULL;
 464       }
 465       log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT " words",
 466                            Thread::current()->name(), word_size);
 467     } else {
 468       // Failed to schedule a collection.
 469       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 470         log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating "
 471                                SIZE_FORMAT " words", Thread::current()->name(), word_size);
 472         return NULL;
 473       }
 474       log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name());
 475       // The GCLocker is either active or the GCLocker initiated
 476       // GC has not yet been performed. Stall until it is and
 477       // then retry the allocation.
 478       GCLocker::stall_until_clear();
 479       gclocker_retry_count += 1;
 480     }
 481 
 482     // We can reach here if we were unsuccessful in scheduling a
 483     // collection (because another thread beat us to it) or if we were
 484     // stalled due to the GC locker. In either can we should retry the
 485     // allocation attempt in case another thread successfully
 486     // performed a collection and reclaimed enough space. We do the
 487     // first attempt (without holding the Heap_lock) here and the
 488     // follow-on attempt will be at the start of the next loop
 489     // iteration (after taking the Heap_lock).
 490     size_t dummy = 0;
 491     result = _allocator->attempt_allocation(word_size, word_size, &dummy);
 492     if (result != NULL) {
 493       return result;
 494     }
 495 
 496     // Give a warning if we seem to be looping forever.
 497     if ((QueuedAllocationWarningCount > 0) &&
 498         (try_count % QueuedAllocationWarningCount == 0)) {
 499       log_warning(gc, alloc)("%s:  Retried allocation %u times for " SIZE_FORMAT " words",
 500                              Thread::current()->name(), try_count, word_size);
 501     }
 502   }
 503 
 504   ShouldNotReachHere();
 505   return NULL;
 506 }
 507 
 508 void G1CollectedHeap::begin_archive_alloc_range(bool open) {
 509   assert_at_safepoint_on_vm_thread();
 510   if (_archive_allocator == NULL) {
 511     _archive_allocator = G1ArchiveAllocator::create_allocator(this, open);
 512   }
 513 }
 514 
 515 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) {
 516   // Allocations in archive regions cannot be of a size that would be considered
 517   // humongous even for a minimum-sized region, because G1 region sizes/boundaries
 518   // may be different at archive-restore time.
 519   return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words());
 520 }
 521 
 522 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) {
 523   assert_at_safepoint_on_vm_thread();
 524   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 525   if (is_archive_alloc_too_large(word_size)) {
 526     return NULL;
 527   }
 528   return _archive_allocator->archive_mem_allocate(word_size);
 529 }
 530 
 531 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
 532                                               size_t end_alignment_in_bytes) {
 533   assert_at_safepoint_on_vm_thread();
 534   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 535 
 536   // Call complete_archive to do the real work, filling in the MemRegion
 537   // array with the archive regions.
 538   _archive_allocator->complete_archive(ranges, end_alignment_in_bytes);
 539   delete _archive_allocator;
 540   _archive_allocator = NULL;
 541 }
 542 
 543 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) {
 544   assert(ranges != NULL, "MemRegion array NULL");
 545   assert(count != 0, "No MemRegions provided");
 546   MemRegion reserved = _hrm->reserved();
 547   for (size_t i = 0; i < count; i++) {
 548     if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) {
 549       return false;
 550     }
 551   }
 552   return true;
 553 }
 554 
 555 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges,
 556                                             size_t count,
 557                                             bool open) {
 558   assert(!is_init_completed(), "Expect to be called at JVM init time");
 559   assert(ranges != NULL, "MemRegion array NULL");
 560   assert(count != 0, "No MemRegions provided");
 561   MutexLocker x(Heap_lock);
 562 
 563   MemRegion reserved = _hrm->reserved();
 564   HeapWord* prev_last_addr = NULL;
 565   HeapRegion* prev_last_region = NULL;
 566 
 567   // Temporarily disable pretouching of heap pages. This interface is used
 568   // when mmap'ing archived heap data in, so pre-touching is wasted.
 569   FlagSetting fs(AlwaysPreTouch, false);
 570 
 571   // Enable archive object checking used by G1MarkSweep. We have to let it know
 572   // about each archive range, so that objects in those ranges aren't marked.
 573   G1ArchiveAllocator::enable_archive_object_check();
 574 
 575   // For each specified MemRegion range, allocate the corresponding G1
 576   // regions and mark them as archive regions. We expect the ranges
 577   // in ascending starting address order, without overlap.
 578   for (size_t i = 0; i < count; i++) {
 579     MemRegion curr_range = ranges[i];
 580     HeapWord* start_address = curr_range.start();
 581     size_t word_size = curr_range.word_size();
 582     HeapWord* last_address = curr_range.last();
 583     size_t commits = 0;
 584 
 585     guarantee(reserved.contains(start_address) && reserved.contains(last_address),
 586               "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 587               p2i(start_address), p2i(last_address));
 588     guarantee(start_address > prev_last_addr,
 589               "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 590               p2i(start_address), p2i(prev_last_addr));
 591     prev_last_addr = last_address;
 592 
 593     // Check for ranges that start in the same G1 region in which the previous
 594     // range ended, and adjust the start address so we don't try to allocate
 595     // the same region again. If the current range is entirely within that
 596     // region, skip it, just adjusting the recorded top.
 597     HeapRegion* start_region = _hrm->addr_to_region(start_address);
 598     if ((prev_last_region != NULL) && (start_region == prev_last_region)) {
 599       start_address = start_region->end();
 600       if (start_address > last_address) {
 601         increase_used(word_size * HeapWordSize);
 602         start_region->set_top(last_address + 1);
 603         continue;
 604       }
 605       start_region->set_top(start_address);
 606       curr_range = MemRegion(start_address, last_address + 1);
 607       start_region = _hrm->addr_to_region(start_address);
 608     }
 609 
 610     // Perform the actual region allocation, exiting if it fails.
 611     // Then note how much new space we have allocated.
 612     if (!_hrm->allocate_containing_regions(curr_range, &commits, workers())) {
 613       return false;
 614     }
 615     increase_used(word_size * HeapWordSize);
 616     if (commits != 0) {
 617       log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B",
 618                                 HeapRegion::GrainWords * HeapWordSize * commits);
 619 
 620     }
 621 
 622     // Mark each G1 region touched by the range as archive, add it to
 623     // the old set, and set top.
 624     HeapRegion* curr_region = _hrm->addr_to_region(start_address);
 625     HeapRegion* last_region = _hrm->addr_to_region(last_address);
 626     prev_last_region = last_region;
 627 
 628     while (curr_region != NULL) {
 629       assert(curr_region->is_empty() && !curr_region->is_pinned(),
 630              "Region already in use (index %u)", curr_region->hrm_index());
 631       if (open) {
 632         curr_region->set_open_archive();
 633       } else {
 634         curr_region->set_closed_archive();
 635       }
 636       _hr_printer.alloc(curr_region);
 637       _archive_set.add(curr_region);
 638       HeapWord* top;
 639       HeapRegion* next_region;
 640       if (curr_region != last_region) {
 641         top = curr_region->end();
 642         next_region = _hrm->next_region_in_heap(curr_region);
 643       } else {
 644         top = last_address + 1;
 645         next_region = NULL;
 646       }
 647       curr_region->set_top(top);
 648       curr_region = next_region;
 649     }
 650 
 651     // Notify mark-sweep of the archive
 652     G1ArchiveAllocator::set_range_archive(curr_range, open);
 653   }
 654   return true;
 655 }
 656 
 657 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) {
 658   assert(!is_init_completed(), "Expect to be called at JVM init time");
 659   assert(ranges != NULL, "MemRegion array NULL");
 660   assert(count != 0, "No MemRegions provided");
 661   MemRegion reserved = _hrm->reserved();
 662   HeapWord *prev_last_addr = NULL;
 663   HeapRegion* prev_last_region = NULL;
 664 
 665   // For each MemRegion, create filler objects, if needed, in the G1 regions
 666   // that contain the address range. The address range actually within the
 667   // MemRegion will not be modified. That is assumed to have been initialized
 668   // elsewhere, probably via an mmap of archived heap data.
 669   MutexLocker x(Heap_lock);
 670   for (size_t i = 0; i < count; i++) {
 671     HeapWord* start_address = ranges[i].start();
 672     HeapWord* last_address = ranges[i].last();
 673 
 674     assert(reserved.contains(start_address) && reserved.contains(last_address),
 675            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 676            p2i(start_address), p2i(last_address));
 677     assert(start_address > prev_last_addr,
 678            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 679            p2i(start_address), p2i(prev_last_addr));
 680 
 681     HeapRegion* start_region = _hrm->addr_to_region(start_address);
 682     HeapRegion* last_region = _hrm->addr_to_region(last_address);
 683     HeapWord* bottom_address = start_region->bottom();
 684 
 685     // Check for a range beginning in the same region in which the
 686     // previous one ended.
 687     if (start_region == prev_last_region) {
 688       bottom_address = prev_last_addr + 1;
 689     }
 690 
 691     // Verify that the regions were all marked as archive regions by
 692     // alloc_archive_regions.
 693     HeapRegion* curr_region = start_region;
 694     while (curr_region != NULL) {
 695       guarantee(curr_region->is_archive(),
 696                 "Expected archive region at index %u", curr_region->hrm_index());
 697       if (curr_region != last_region) {
 698         curr_region = _hrm->next_region_in_heap(curr_region);
 699       } else {
 700         curr_region = NULL;
 701       }
 702     }
 703 
 704     prev_last_addr = last_address;
 705     prev_last_region = last_region;
 706 
 707     // Fill the memory below the allocated range with dummy object(s),
 708     // if the region bottom does not match the range start, or if the previous
 709     // range ended within the same G1 region, and there is a gap.
 710     if (start_address != bottom_address) {
 711       size_t fill_size = pointer_delta(start_address, bottom_address);
 712       G1CollectedHeap::fill_with_objects(bottom_address, fill_size);
 713       increase_used(fill_size * HeapWordSize);
 714     }
 715   }
 716 }
 717 
 718 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t min_word_size,
 719                                                      size_t desired_word_size,
 720                                                      size_t* actual_word_size) {
 721   assert_heap_not_locked_and_not_at_safepoint();
 722   assert(!is_humongous(desired_word_size), "attempt_allocation() should not "
 723          "be called for humongous allocation requests");
 724 
 725   HeapWord* result = _allocator->attempt_allocation(min_word_size, desired_word_size, actual_word_size);
 726 
 727   if (result == NULL) {
 728     *actual_word_size = desired_word_size;
 729     result = attempt_allocation_slow(desired_word_size);
 730   }
 731 
 732   assert_heap_not_locked();
 733   if (result != NULL) {
 734     assert(*actual_word_size != 0, "Actual size must have been set here");
 735     dirty_young_block(result, *actual_word_size);
 736   } else {
 737     *actual_word_size = 0;
 738   }
 739 
 740   return result;
 741 }
 742 
 743 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) {
 744   assert(!is_init_completed(), "Expect to be called at JVM init time");
 745   assert(ranges != NULL, "MemRegion array NULL");
 746   assert(count != 0, "No MemRegions provided");
 747   MemRegion reserved = _hrm->reserved();
 748   HeapWord* prev_last_addr = NULL;
 749   HeapRegion* prev_last_region = NULL;
 750   size_t size_used = 0;
 751   size_t uncommitted_regions = 0;
 752 
 753   // For each Memregion, free the G1 regions that constitute it, and
 754   // notify mark-sweep that the range is no longer to be considered 'archive.'
 755   MutexLocker x(Heap_lock);
 756   for (size_t i = 0; i < count; i++) {
 757     HeapWord* start_address = ranges[i].start();
 758     HeapWord* last_address = ranges[i].last();
 759 
 760     assert(reserved.contains(start_address) && reserved.contains(last_address),
 761            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 762            p2i(start_address), p2i(last_address));
 763     assert(start_address > prev_last_addr,
 764            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 765            p2i(start_address), p2i(prev_last_addr));
 766     size_used += ranges[i].byte_size();
 767     prev_last_addr = last_address;
 768 
 769     HeapRegion* start_region = _hrm->addr_to_region(start_address);
 770     HeapRegion* last_region = _hrm->addr_to_region(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 free
 774     // the same region again. If the current range is entirely within that
 775     // region, skip it.
 776     if (start_region == prev_last_region) {
 777       start_address = start_region->end();
 778       if (start_address > last_address) {
 779         continue;
 780       }
 781       start_region = _hrm->addr_to_region(start_address);
 782     }
 783     prev_last_region = last_region;
 784 
 785     // After verifying that each region was marked as an archive region by
 786     // alloc_archive_regions, set it free and empty and uncommit it.
 787     HeapRegion* curr_region = start_region;
 788     while (curr_region != NULL) {
 789       guarantee(curr_region->is_archive(),
 790                 "Expected archive region at index %u", curr_region->hrm_index());
 791       uint curr_index = curr_region->hrm_index();
 792       _archive_set.remove(curr_region);
 793       curr_region->set_free();
 794       curr_region->set_top(curr_region->bottom());
 795       if (curr_region != last_region) {
 796         curr_region = _hrm->next_region_in_heap(curr_region);
 797       } else {
 798         curr_region = NULL;
 799       }
 800       _hrm->shrink_at(curr_index, 1);
 801       uncommitted_regions++;
 802     }
 803 
 804     // Notify mark-sweep that this is no longer an archive range.
 805     G1ArchiveAllocator::clear_range_archive(ranges[i]);
 806   }
 807 
 808   if (uncommitted_regions != 0) {
 809     log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B",
 810                               HeapRegion::GrainWords * HeapWordSize * uncommitted_regions);
 811   }
 812   decrease_used(size_used);
 813 }
 814 
 815 oop G1CollectedHeap::materialize_archived_object(oop obj) {
 816   assert(obj != NULL, "archived obj is NULL");
 817   assert(G1ArchiveAllocator::is_archived_object(obj), "must be archived object");
 818 
 819   // Loading an archived object makes it strongly reachable. If it is
 820   // loaded during concurrent marking, it must be enqueued to the SATB
 821   // queue, shading the previously white object gray.
 822   G1BarrierSet::enqueue(obj);
 823 
 824   return obj;
 825 }
 826 
 827 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size) {
 828   ResourceMark rm; // For retrieving the thread names in log messages.
 829 
 830   // The structure of this method has a lot of similarities to
 831   // attempt_allocation_slow(). The reason these two were not merged
 832   // into a single one is that such a method would require several "if
 833   // allocation is not humongous do this, otherwise do that"
 834   // conditional paths which would obscure its flow. In fact, an early
 835   // version of this code did use a unified method which was harder to
 836   // follow and, as a result, it had subtle bugs that were hard to
 837   // track down. So keeping these two methods separate allows each to
 838   // be more readable. It will be good to keep these two in sync as
 839   // much as possible.
 840 
 841   assert_heap_not_locked_and_not_at_safepoint();
 842   assert(is_humongous(word_size), "attempt_allocation_humongous() "
 843          "should only be called for humongous allocations");
 844 
 845   // Humongous objects can exhaust the heap quickly, so we should check if we
 846   // need to start a marking cycle at each humongous object allocation. We do
 847   // the check before we do the actual allocation. The reason for doing it
 848   // before the allocation is that we avoid having to keep track of the newly
 849   // allocated memory while we do a GC.
 850   if (policy()->need_to_start_conc_mark("concurrent humongous allocation",
 851                                            word_size)) {
 852     collect(GCCause::_g1_humongous_allocation);
 853   }
 854 
 855   // We will loop until a) we manage to successfully perform the
 856   // allocation or b) we successfully schedule a collection which
 857   // fails to perform the allocation. b) is the only case when we'll
 858   // return NULL.
 859   HeapWord* result = NULL;
 860   for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 861     bool should_try_gc;
 862     uint gc_count_before;
 863 
 864 
 865     {
 866       MutexLocker x(Heap_lock);
 867 
 868       // Given that humongous objects are not allocated in young
 869       // regions, we'll first try to do the allocation without doing a
 870       // collection hoping that there's enough space in the heap.
 871       result = humongous_obj_allocate(word_size);
 872       if (result != NULL) {
 873         size_t size_in_regions = humongous_obj_size_in_regions(word_size);
 874         policy()->old_gen_alloc_tracker()->
 875           add_allocated_bytes_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
 876         return result;
 877       }
 878 
 879       // Only try a GC if the GCLocker does not signal the need for a GC. Wait until
 880       // the GCLocker initiated GC has been performed and then retry. This includes
 881       // the case when the GC Locker is not active but has not been performed.
 882       should_try_gc = !GCLocker::needs_gc();
 883       // Read the GC count while still holding the Heap_lock.
 884       gc_count_before = total_collections();
 885     }
 886 
 887     if (should_try_gc) {
 888       bool succeeded;
 889       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 890                                    GCCause::_g1_humongous_allocation);
 891       if (result != NULL) {
 892         assert(succeeded, "only way to get back a non-NULL result");
 893         log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT,
 894                              Thread::current()->name(), p2i(result));
 895         return result;
 896       }
 897 
 898       if (succeeded) {
 899         // We successfully scheduled a collection which failed to allocate. No
 900         // point in trying to allocate further. We'll just return NULL.
 901         log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate "
 902                              SIZE_FORMAT " words", Thread::current()->name(), word_size);
 903         return NULL;
 904       }
 905       log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT "",
 906                            Thread::current()->name(), word_size);
 907     } else {
 908       // Failed to schedule a collection.
 909       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 910         log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating "
 911                                SIZE_FORMAT " words", Thread::current()->name(), word_size);
 912         return NULL;
 913       }
 914       log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name());
 915       // The GCLocker is either active or the GCLocker initiated
 916       // GC has not yet been performed. Stall until it is and
 917       // then retry the allocation.
 918       GCLocker::stall_until_clear();
 919       gclocker_retry_count += 1;
 920     }
 921 
 922 
 923     // We can reach here if we were unsuccessful in scheduling a
 924     // collection (because another thread beat us to it) or if we were
 925     // stalled due to the GC locker. In either can we should retry the
 926     // allocation attempt in case another thread successfully
 927     // performed a collection and reclaimed enough space.
 928     // Humongous object allocation always needs a lock, so we wait for the retry
 929     // in the next iteration of the loop, unlike for the regular iteration case.
 930     // Give a warning if we seem to be looping forever.
 931 
 932     if ((QueuedAllocationWarningCount > 0) &&
 933         (try_count % QueuedAllocationWarningCount == 0)) {
 934       log_warning(gc, alloc)("%s: Retried allocation %u times for " SIZE_FORMAT " words",
 935                              Thread::current()->name(), try_count, word_size);
 936     }
 937   }
 938 
 939   ShouldNotReachHere();
 940   return NULL;
 941 }
 942 
 943 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
 944                                                            bool expect_null_mutator_alloc_region) {
 945   assert_at_safepoint_on_vm_thread();
 946   assert(!_allocator->has_mutator_alloc_region() || !expect_null_mutator_alloc_region,
 947          "the current alloc region was unexpectedly found to be non-NULL");
 948 
 949   if (!is_humongous(word_size)) {
 950     return _allocator->attempt_allocation_locked(word_size);
 951   } else {
 952     HeapWord* result = humongous_obj_allocate(word_size);
 953     if (result != NULL && policy()->need_to_start_conc_mark("STW humongous allocation")) {
 954       collector_state()->set_initiate_conc_mark_if_possible(true);
 955     }
 956     return result;
 957   }
 958 
 959   ShouldNotReachHere();
 960 }
 961 
 962 class PostCompactionPrinterClosure: public HeapRegionClosure {
 963 private:
 964   G1HRPrinter* _hr_printer;
 965 public:
 966   bool do_heap_region(HeapRegion* hr) {
 967     assert(!hr->is_young(), "not expecting to find young regions");
 968     _hr_printer->post_compaction(hr);
 969     return false;
 970   }
 971 
 972   PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
 973     : _hr_printer(hr_printer) { }
 974 };
 975 
 976 void G1CollectedHeap::print_hrm_post_compaction() {
 977   if (_hr_printer.is_active()) {
 978     PostCompactionPrinterClosure cl(hr_printer());
 979     heap_region_iterate(&cl);
 980   }
 981 }
 982 
 983 void G1CollectedHeap::abort_concurrent_cycle() {
 984   // If we start the compaction before the CM threads finish
 985   // scanning the root regions we might trip them over as we'll
 986   // be moving objects / updating references. So let's wait until
 987   // they are done. By telling them to abort, they should complete
 988   // early.
 989   _cm->root_regions()->abort();
 990   _cm->root_regions()->wait_until_scan_finished();
 991 
 992   // Disable discovery and empty the discovered lists
 993   // for the CM ref processor.
 994   _ref_processor_cm->disable_discovery();
 995   _ref_processor_cm->abandon_partial_discovery();
 996   _ref_processor_cm->verify_no_references_recorded();
 997 
 998   // Abandon current iterations of concurrent marking and concurrent
 999   // refinement, if any are in progress.
1000   concurrent_mark()->concurrent_cycle_abort();
1001 }
1002 
1003 void G1CollectedHeap::prepare_heap_for_full_collection() {
1004   // Make sure we'll choose a new allocation region afterwards.
1005   _allocator->release_mutator_alloc_regions();
1006   _allocator->abandon_gc_alloc_regions();
1007 
1008   // We may have added regions to the current incremental collection
1009   // set between the last GC or pause and now. We need to clear the
1010   // incremental collection set and then start rebuilding it afresh
1011   // after this full GC.
1012   abandon_collection_set(collection_set());
1013 
1014   tear_down_region_sets(false /* free_list_only */);
1015 
1016   hrm()->prepare_for_full_collection_start();
1017 }
1018 
1019 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) {
1020   assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant");
1021   assert_used_and_recalculate_used_equal(this);
1022   _verifier->verify_region_sets_optional();
1023   _verifier->verify_before_gc(G1HeapVerifier::G1VerifyFull);
1024   _verifier->check_bitmaps("Full GC Start");
1025 }
1026 
1027 void G1CollectedHeap::prepare_heap_for_mutators() {
1028   hrm()->prepare_for_full_collection_end();
1029 
1030   // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1031   ClassLoaderDataGraph::purge();
1032   MetaspaceUtils::verify_metrics();
1033 
1034   // Prepare heap for normal collections.
1035   assert(num_free_regions() == 0, "we should not have added any free regions");
1036   rebuild_region_sets(false /* free_list_only */);
1037   abort_refinement();
1038   resize_heap_if_necessary();
1039 
1040   // Rebuild the strong code root lists for each region
1041   rebuild_strong_code_roots();
1042 
1043   // Purge code root memory
1044   purge_code_root_memory();
1045 
1046   // Start a new incremental collection set for the next pause
1047   start_new_collection_set();
1048 
1049   _allocator->init_mutator_alloc_regions();
1050 
1051   // Post collection state updates.
1052   MetaspaceGC::compute_new_size();
1053 }
1054 
1055 void G1CollectedHeap::abort_refinement() {
1056   if (_hot_card_cache->use_cache()) {
1057     _hot_card_cache->reset_hot_cache();
1058   }
1059 
1060   // Discard all remembered set updates and reset refinement statistics.
1061   G1BarrierSet::dirty_card_queue_set().abandon_logs();
1062   assert(G1BarrierSet::dirty_card_queue_set().num_cards() == 0,
1063          "DCQS should be empty");
1064   concurrent_refine()->get_and_reset_refinement_stats();
1065 }
1066 
1067 void G1CollectedHeap::verify_after_full_collection() {
1068   _hrm->verify_optional();
1069   _verifier->verify_region_sets_optional();
1070   _verifier->verify_after_gc(G1HeapVerifier::G1VerifyFull);
1071   // Clear the previous marking bitmap, if needed for bitmap verification.
1072   // Note we cannot do this when we clear the next marking bitmap in
1073   // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the
1074   // objects marked during a full GC against the previous bitmap.
1075   // But we need to clear it before calling check_bitmaps below since
1076   // the full GC has compacted objects and updated TAMS but not updated
1077   // the prev bitmap.
1078   if (G1VerifyBitmaps) {
1079     GCTraceTime(Debug, gc) tm("Clear Prev Bitmap for Verification");
1080     _cm->clear_prev_bitmap(workers());
1081   }
1082   // This call implicitly verifies that the next bitmap is clear after Full GC.
1083   _verifier->check_bitmaps("Full GC End");
1084 
1085   // At this point there should be no regions in the
1086   // entire heap tagged as young.
1087   assert(check_young_list_empty(), "young list should be empty at this point");
1088 
1089   // Note: since we've just done a full GC, concurrent
1090   // marking is no longer active. Therefore we need not
1091   // re-enable reference discovery for the CM ref processor.
1092   // That will be done at the start of the next marking cycle.
1093   // We also know that the STW processor should no longer
1094   // discover any new references.
1095   assert(!_ref_processor_stw->discovery_enabled(), "Postcondition");
1096   assert(!_ref_processor_cm->discovery_enabled(), "Postcondition");
1097   _ref_processor_stw->verify_no_references_recorded();
1098   _ref_processor_cm->verify_no_references_recorded();
1099 }
1100 
1101 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) {
1102   // Post collection logging.
1103   // We should do this after we potentially resize the heap so
1104   // that all the COMMIT / UNCOMMIT events are generated before
1105   // the compaction events.
1106   print_hrm_post_compaction();
1107   heap_transition->print();
1108   print_heap_after_gc();
1109   print_heap_regions();
1110 }
1111 
1112 bool G1CollectedHeap::do_full_collection(bool explicit_gc,
1113                                          bool clear_all_soft_refs) {
1114   assert_at_safepoint_on_vm_thread();
1115 
1116   if (GCLocker::check_active_before_gc()) {
1117     // Full GC was not completed.
1118     return false;
1119   }
1120 
1121   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1122       soft_ref_policy()->should_clear_all_soft_refs();
1123 
1124   G1FullCollector collector(this, explicit_gc, do_clear_all_soft_refs);
1125   GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true);
1126 
1127   collector.prepare_collection();
1128   collector.collect();
1129   collector.complete_collection();
1130 
1131   // Full collection was successfully completed.
1132   return true;
1133 }
1134 
1135 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1136   // Currently, there is no facility in the do_full_collection(bool) API to notify
1137   // the caller that the collection did not succeed (e.g., because it was locked
1138   // out by the GC locker). So, right now, we'll ignore the return value.
1139   bool dummy = do_full_collection(true,                /* explicit_gc */
1140                                   clear_all_soft_refs);
1141 }
1142 
1143 void G1CollectedHeap::resize_heap_if_necessary() {
1144   assert_at_safepoint_on_vm_thread();
1145 
1146   // Capacity, free and used after the GC counted as full regions to
1147   // include the waste in the following calculations.
1148   const size_t capacity_after_gc = capacity();
1149   const size_t used_after_gc = capacity_after_gc - unused_committed_regions_in_bytes();
1150 
1151   // This is enforced in arguments.cpp.
1152   assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1153          "otherwise the code below doesn't make sense");
1154 
1155   // We don't have floating point command-line arguments
1156   const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1157   const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1158   const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1159   const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1160 
1161   // We have to be careful here as these two calculations can overflow
1162   // 32-bit size_t's.
1163   double used_after_gc_d = (double) used_after_gc;
1164   double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1165   double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1166 
1167   // Let's make sure that they are both under the max heap size, which
1168   // by default will make them fit into a size_t.
1169   double desired_capacity_upper_bound = (double) MaxHeapSize;
1170   minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1171                                     desired_capacity_upper_bound);
1172   maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1173                                     desired_capacity_upper_bound);
1174 
1175   // We can now safely turn them into size_t's.
1176   size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1177   size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1178 
1179   // This assert only makes sense here, before we adjust them
1180   // with respect to the min and max heap size.
1181   assert(minimum_desired_capacity <= maximum_desired_capacity,
1182          "minimum_desired_capacity = " SIZE_FORMAT ", "
1183          "maximum_desired_capacity = " SIZE_FORMAT,
1184          minimum_desired_capacity, maximum_desired_capacity);
1185 
1186   // Should not be greater than the heap max size. No need to adjust
1187   // it with respect to the heap min size as it's a lower bound (i.e.,
1188   // we'll try to make the capacity larger than it, not smaller).
1189   minimum_desired_capacity = MIN2(minimum_desired_capacity, MaxHeapSize);
1190   // Should not be less than the heap min size. No need to adjust it
1191   // with respect to the heap max size as it's an upper bound (i.e.,
1192   // we'll try to make the capacity smaller than it, not greater).
1193   maximum_desired_capacity =  MAX2(maximum_desired_capacity, MinHeapSize);
1194 
1195   if (capacity_after_gc < minimum_desired_capacity) {
1196     // Don't expand unless it's significant
1197     size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1198 
1199     log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity). "
1200                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1201                               "min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1202                               capacity_after_gc, used_after_gc, used(), minimum_desired_capacity, MinHeapFreeRatio);
1203 
1204     expand(expand_bytes, _workers);
1205 
1206     // No expansion, now see if we want to shrink
1207   } else if (capacity_after_gc > maximum_desired_capacity) {
1208     // Capacity too large, compute shrinking size
1209     size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1210 
1211     log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity). "
1212                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1213                               "maximum_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1214                               capacity_after_gc, used_after_gc, used(), maximum_desired_capacity, MaxHeapFreeRatio);
1215 
1216     shrink(shrink_bytes);
1217   }
1218 }
1219 
1220 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size,
1221                                                             bool do_gc,
1222                                                             bool clear_all_soft_refs,
1223                                                             bool expect_null_mutator_alloc_region,
1224                                                             bool* gc_succeeded) {
1225   *gc_succeeded = true;
1226   // Let's attempt the allocation first.
1227   HeapWord* result =
1228     attempt_allocation_at_safepoint(word_size,
1229                                     expect_null_mutator_alloc_region);
1230   if (result != NULL) {
1231     return result;
1232   }
1233 
1234   // In a G1 heap, we're supposed to keep allocation from failing by
1235   // incremental pauses.  Therefore, at least for now, we'll favor
1236   // expansion over collection.  (This might change in the future if we can
1237   // do something smarter than full collection to satisfy a failed alloc.)
1238   result = expand_and_allocate(word_size);
1239   if (result != NULL) {
1240     return result;
1241   }
1242 
1243   if (do_gc) {
1244     // Expansion didn't work, we'll try to do a Full GC.
1245     *gc_succeeded = do_full_collection(false, /* explicit_gc */
1246                                        clear_all_soft_refs);
1247   }
1248 
1249   return NULL;
1250 }
1251 
1252 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1253                                                      bool* succeeded) {
1254   assert_at_safepoint_on_vm_thread();
1255 
1256   // Attempts to allocate followed by Full GC.
1257   HeapWord* result =
1258     satisfy_failed_allocation_helper(word_size,
1259                                      true,  /* do_gc */
1260                                      false, /* clear_all_soft_refs */
1261                                      false, /* expect_null_mutator_alloc_region */
1262                                      succeeded);
1263 
1264   if (result != NULL || !*succeeded) {
1265     return result;
1266   }
1267 
1268   // Attempts to allocate followed by Full GC that will collect all soft references.
1269   result = satisfy_failed_allocation_helper(word_size,
1270                                             true, /* do_gc */
1271                                             true, /* clear_all_soft_refs */
1272                                             true, /* expect_null_mutator_alloc_region */
1273                                             succeeded);
1274 
1275   if (result != NULL || !*succeeded) {
1276     return result;
1277   }
1278 
1279   // Attempts to allocate, no GC
1280   result = satisfy_failed_allocation_helper(word_size,
1281                                             false, /* do_gc */
1282                                             false, /* clear_all_soft_refs */
1283                                             true,  /* expect_null_mutator_alloc_region */
1284                                             succeeded);
1285 
1286   if (result != NULL) {
1287     return result;
1288   }
1289 
1290   assert(!soft_ref_policy()->should_clear_all_soft_refs(),
1291          "Flag should have been handled and cleared prior to this point");
1292 
1293   // What else?  We might try synchronous finalization later.  If the total
1294   // space available is large enough for the allocation, then a more
1295   // complete compaction phase than we've tried so far might be
1296   // appropriate.
1297   return NULL;
1298 }
1299 
1300 // Attempting to expand the heap sufficiently
1301 // to support an allocation of the given "word_size".  If
1302 // successful, perform the allocation and return the address of the
1303 // allocated block, or else "NULL".
1304 
1305 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1306   assert_at_safepoint_on_vm_thread();
1307 
1308   _verifier->verify_region_sets_optional();
1309 
1310   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1311   log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B",
1312                             word_size * HeapWordSize);
1313 
1314 
1315   if (expand(expand_bytes, _workers)) {
1316     _hrm->verify_optional();
1317     _verifier->verify_region_sets_optional();
1318     return attempt_allocation_at_safepoint(word_size,
1319                                            false /* expect_null_mutator_alloc_region */);
1320   }
1321   return NULL;
1322 }
1323 
1324 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) {
1325   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1326   aligned_expand_bytes = align_up(aligned_expand_bytes,
1327                                        HeapRegion::GrainBytes);
1328 
1329   log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B",
1330                             expand_bytes, aligned_expand_bytes);
1331 
1332   if (is_maximal_no_gc()) {
1333     log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1334     return false;
1335   }
1336 
1337   double expand_heap_start_time_sec = os::elapsedTime();
1338   uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1339   assert(regions_to_expand > 0, "Must expand by at least one region");
1340 
1341   uint expanded_by = _hrm->expand_by(regions_to_expand, pretouch_workers);
1342   if (expand_time_ms != NULL) {
1343     *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS;
1344   }
1345 
1346   if (expanded_by > 0) {
1347     size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1348     assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1349     policy()->record_new_heap_size(num_regions());
1350   } else {
1351     log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)");
1352 
1353     // The expansion of the virtual storage space was unsuccessful.
1354     // Let's see if it was because we ran out of swap.
1355     if (G1ExitOnExpansionFailure &&
1356         _hrm->available() >= regions_to_expand) {
1357       // We had head room...
1358       vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1359     }
1360   }
1361   return regions_to_expand > 0;
1362 }
1363 
1364 bool G1CollectedHeap::expand_single_region(uint node_index) {
1365   uint expanded_by = _hrm->expand_on_preferred_node(node_index);
1366 
1367   if (expanded_by == 0) {
1368     assert(is_maximal_no_gc(), "Should be no regions left, available: %u", _hrm->available());
1369     log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1370     return false;
1371   }
1372 
1373   policy()->record_new_heap_size(num_regions());
1374   return true;
1375 }
1376 
1377 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1378   size_t aligned_shrink_bytes =
1379     ReservedSpace::page_align_size_down(shrink_bytes);
1380   aligned_shrink_bytes = align_down(aligned_shrink_bytes,
1381                                          HeapRegion::GrainBytes);
1382   uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1383 
1384   uint num_regions_removed = _hrm->shrink_by(num_regions_to_remove);
1385   size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1386 
1387   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",
1388                             shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1389   if (num_regions_removed > 0) {
1390     policy()->record_new_heap_size(num_regions());
1391   } else {
1392     log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)");
1393   }
1394 }
1395 
1396 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1397   _verifier->verify_region_sets_optional();
1398 
1399   // We should only reach here at the end of a Full GC or during Remark which
1400   // means we should not not be holding to any GC alloc regions. The method
1401   // below will make sure of that and do any remaining clean up.
1402   _allocator->abandon_gc_alloc_regions();
1403 
1404   // Instead of tearing down / rebuilding the free lists here, we
1405   // could instead use the remove_all_pending() method on free_list to
1406   // remove only the ones that we need to remove.
1407   tear_down_region_sets(true /* free_list_only */);
1408   shrink_helper(shrink_bytes);
1409   rebuild_region_sets(true /* free_list_only */);
1410 
1411   _hrm->verify_optional();
1412   _verifier->verify_region_sets_optional();
1413 }
1414 
1415 class OldRegionSetChecker : public HeapRegionSetChecker {
1416 public:
1417   void check_mt_safety() {
1418     // Master Old Set MT safety protocol:
1419     // (a) If we're at a safepoint, operations on the master old set
1420     // should be invoked:
1421     // - by the VM thread (which will serialize them), or
1422     // - by the GC workers while holding the FreeList_lock, if we're
1423     //   at a safepoint for an evacuation pause (this lock is taken
1424     //   anyway when an GC alloc region is retired so that a new one
1425     //   is allocated from the free list), or
1426     // - by the GC workers while holding the OldSets_lock, if we're at a
1427     //   safepoint for a cleanup pause.
1428     // (b) If we're not at a safepoint, operations on the master old set
1429     // should be invoked while holding the Heap_lock.
1430 
1431     if (SafepointSynchronize::is_at_safepoint()) {
1432       guarantee(Thread::current()->is_VM_thread() ||
1433                 FreeList_lock->owned_by_self() || OldSets_lock->owned_by_self(),
1434                 "master old set MT safety protocol at a safepoint");
1435     } else {
1436       guarantee(Heap_lock->owned_by_self(), "master old set MT safety protocol outside a safepoint");
1437     }
1438   }
1439   bool is_correct_type(HeapRegion* hr) { return hr->is_old(); }
1440   const char* get_description() { return "Old Regions"; }
1441 };
1442 
1443 class ArchiveRegionSetChecker : public HeapRegionSetChecker {
1444 public:
1445   void check_mt_safety() {
1446     guarantee(!Universe::is_fully_initialized() || SafepointSynchronize::is_at_safepoint(),
1447               "May only change archive regions during initialization or safepoint.");
1448   }
1449   bool is_correct_type(HeapRegion* hr) { return hr->is_archive(); }
1450   const char* get_description() { return "Archive Regions"; }
1451 };
1452 
1453 class HumongousRegionSetChecker : public HeapRegionSetChecker {
1454 public:
1455   void check_mt_safety() {
1456     // Humongous Set MT safety protocol:
1457     // (a) If we're at a safepoint, operations on the master humongous
1458     // set should be invoked by either the VM thread (which will
1459     // serialize them) or by the GC workers while holding the
1460     // OldSets_lock.
1461     // (b) If we're not at a safepoint, operations on the master
1462     // humongous set should be invoked while holding the Heap_lock.
1463 
1464     if (SafepointSynchronize::is_at_safepoint()) {
1465       guarantee(Thread::current()->is_VM_thread() ||
1466                 OldSets_lock->owned_by_self(),
1467                 "master humongous set MT safety protocol at a safepoint");
1468     } else {
1469       guarantee(Heap_lock->owned_by_self(),
1470                 "master humongous set MT safety protocol outside a safepoint");
1471     }
1472   }
1473   bool is_correct_type(HeapRegion* hr) { return hr->is_humongous(); }
1474   const char* get_description() { return "Humongous Regions"; }
1475 };
1476 
1477 G1CollectedHeap::G1CollectedHeap() :
1478   CollectedHeap(),
1479   _young_gen_sampling_thread(NULL),
1480   _workers(NULL),
1481   _card_table(NULL),
1482   _soft_ref_policy(),
1483   _collection_pause_end(Ticks::now()),
1484   _time_of_last_gc_ns(os::javaTimeNanos()),
1485   _old_set("Old Region Set", new OldRegionSetChecker()),
1486   _archive_set("Archive Region Set", new ArchiveRegionSetChecker()),
1487   _humongous_set("Humongous Region Set", new HumongousRegionSetChecker()),
1488   _bot(NULL),
1489   _listener(),
1490   _numa(G1NUMA::create()),
1491   _hrm(NULL),
1492   _allocator(NULL),
1493   _verifier(NULL),
1494   _summary_bytes_used(0),
1495   _bytes_used_during_gc(0),
1496   _archive_allocator(NULL),
1497   _survivor_evac_stats("Young", YoungPLABSize, PLABWeight),
1498   _old_evac_stats("Old", OldPLABSize, PLABWeight),
1499   _expand_heap_after_alloc_failure(true),
1500   _g1mm(NULL),
1501   _humongous_reclaim_candidates(),
1502   _has_humongous_reclaim_candidates(false),
1503   _hr_printer(),
1504   _collector_state(),
1505   _old_marking_cycles_started(0),
1506   _old_marking_cycles_completed(0),
1507   _eden(),
1508   _survivor(),
1509   _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1510   _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1511   _policy(G1Policy::create_policy(_gc_timer_stw)),
1512   _heap_sizing_policy(NULL),
1513   _collection_set(this, _policy),
1514   _hot_card_cache(NULL),
1515   _rem_set(NULL),
1516   _cm(NULL),
1517   _cm_thread(NULL),
1518   _cr(NULL),
1519   _task_queues(NULL),
1520   _evacuation_failed(false),
1521   _evacuation_failed_info_array(NULL),
1522   _preserved_marks_set(true /* in_c_heap */),
1523 #ifndef PRODUCT
1524   _evacuation_failure_alot_for_current_gc(false),
1525   _evacuation_failure_alot_gc_number(0),
1526   _evacuation_failure_alot_count(0),
1527 #endif
1528   _ref_processor_stw(NULL),
1529   _is_alive_closure_stw(this),
1530   _is_subject_to_discovery_stw(this),
1531   _ref_processor_cm(NULL),
1532   _is_alive_closure_cm(this),
1533   _is_subject_to_discovery_cm(this),
1534   _region_attr() {
1535 
1536   _verifier = new G1HeapVerifier(this);
1537 
1538   _allocator = new G1Allocator(this);
1539 
1540   _heap_sizing_policy = G1HeapSizingPolicy::create(this, _policy->analytics());
1541 
1542   _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);
1543 
1544   // Override the default _filler_array_max_size so that no humongous filler
1545   // objects are created.
1546   _filler_array_max_size = _humongous_object_threshold_in_words;
1547 
1548   uint n_queues = ParallelGCThreads;
1549   _task_queues = new G1ScannerTasksQueueSet(n_queues);
1550 
1551   _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1552 
1553   for (uint i = 0; i < n_queues; i++) {
1554     G1ScannerTasksQueue* q = new G1ScannerTasksQueue();
1555     q->initialize();
1556     _task_queues->register_queue(i, q);
1557     ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1558   }
1559 
1560   // Initialize the G1EvacuationFailureALot counters and flags.
1561   NOT_PRODUCT(reset_evacuation_should_fail();)
1562   _gc_tracer_stw->initialize();
1563 
1564   guarantee(_task_queues != NULL, "task_queues allocation failure.");
1565 }
1566 
1567 static size_t actual_reserved_page_size(ReservedSpace rs) {
1568   size_t page_size = os::vm_page_size();
1569   if (UseLargePages) {
1570     // There are two ways to manage large page memory.
1571     // 1. OS supports committing large page memory.
1572     // 2. OS doesn't support committing large page memory so ReservedSpace manages it.
1573     //    And ReservedSpace calls it 'special'. If we failed to set 'special',
1574     //    we reserved memory without large page.
1575     if (os::can_commit_large_page_memory() || rs.special()) {
1576       // An alignment at ReservedSpace comes from preferred page size or
1577       // heap alignment, and if the alignment came from heap alignment, it could be
1578       // larger than large pages size. So need to cap with the large page size.
1579       page_size = MIN2(rs.alignment(), os::large_page_size());
1580     }
1581   }
1582 
1583   return page_size;
1584 }
1585 
1586 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1587                                                                  size_t size,
1588                                                                  size_t translation_factor) {
1589   size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1590   // Allocate a new reserved space, preferring to use large pages.
1591   ReservedSpace rs(size, preferred_page_size);
1592   size_t page_size = actual_reserved_page_size(rs);
1593   G1RegionToSpaceMapper* result  =
1594     G1RegionToSpaceMapper::create_mapper(rs,
1595                                          size,
1596                                          page_size,
1597                                          HeapRegion::GrainBytes,
1598                                          translation_factor,
1599                                          mtGC);
1600 
1601   os::trace_page_sizes_for_requested_size(description,
1602                                           size,
1603                                           preferred_page_size,
1604                                           page_size,
1605                                           rs.base(),
1606                                           rs.size());
1607 
1608   return result;
1609 }
1610 
1611 jint G1CollectedHeap::initialize_concurrent_refinement() {
1612   jint ecode = JNI_OK;
1613   _cr = G1ConcurrentRefine::create(&ecode);
1614   return ecode;
1615 }
1616 
1617 jint G1CollectedHeap::initialize_young_gen_sampling_thread() {
1618   _young_gen_sampling_thread = new G1YoungRemSetSamplingThread();
1619   if (_young_gen_sampling_thread->osthread() == NULL) {
1620     vm_shutdown_during_initialization("Could not create G1YoungRemSetSamplingThread");
1621     return JNI_ENOMEM;
1622   }
1623   return JNI_OK;
1624 }
1625 
1626 jint G1CollectedHeap::initialize() {
1627 
1628   // Necessary to satisfy locking discipline assertions.
1629 
1630   MutexLocker x(Heap_lock);
1631 
1632   // While there are no constraints in the GC code that HeapWordSize
1633   // be any particular value, there are multiple other areas in the
1634   // system which believe this to be true (e.g. oop->object_size in some
1635   // cases incorrectly returns the size in wordSize units rather than
1636   // HeapWordSize).
1637   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1638 
1639   size_t init_byte_size = InitialHeapSize;
1640   size_t reserved_byte_size = G1Arguments::heap_reserved_size_bytes();
1641 
1642   // Ensure that the sizes are properly aligned.
1643   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1644   Universe::check_alignment(reserved_byte_size, HeapRegion::GrainBytes, "g1 heap");
1645   Universe::check_alignment(reserved_byte_size, HeapAlignment, "g1 heap");
1646 
1647   // Reserve the maximum.
1648 
1649   // When compressed oops are enabled, the preferred heap base
1650   // is calculated by subtracting the requested size from the
1651   // 32Gb boundary and using the result as the base address for
1652   // heap reservation. If the requested size is not aligned to
1653   // HeapRegion::GrainBytes (i.e. the alignment that is passed
1654   // into the ReservedHeapSpace constructor) then the actual
1655   // base of the reserved heap may end up differing from the
1656   // address that was requested (i.e. the preferred heap base).
1657   // If this happens then we could end up using a non-optimal
1658   // compressed oops mode.
1659 
1660   ReservedHeapSpace heap_rs = Universe::reserve_heap(reserved_byte_size,
1661                                                      HeapAlignment);
1662 
1663   initialize_reserved_region(heap_rs);
1664 
1665   // Create the barrier set for the entire reserved region.
1666   G1CardTable* ct = new G1CardTable(heap_rs.region());
1667   ct->initialize();
1668   G1BarrierSet* bs = new G1BarrierSet(ct);
1669   bs->initialize();
1670   assert(bs->is_a(BarrierSet::G1BarrierSet), "sanity");
1671   BarrierSet::set_barrier_set(bs);
1672   _card_table = ct;
1673 
1674   {
1675     G1SATBMarkQueueSet& satbqs = bs->satb_mark_queue_set();
1676     satbqs.set_process_completed_buffers_threshold(G1SATBProcessCompletedThreshold);
1677     satbqs.set_buffer_enqueue_threshold_percentage(G1SATBBufferEnqueueingThresholdPercent);
1678   }
1679 
1680   // Create the hot card cache.
1681   _hot_card_cache = new G1HotCardCache(this);
1682 
1683   // Carve out the G1 part of the heap.
1684   ReservedSpace g1_rs = heap_rs.first_part(reserved_byte_size);
1685   size_t page_size = actual_reserved_page_size(heap_rs);
1686   G1RegionToSpaceMapper* heap_storage =
1687     G1RegionToSpaceMapper::create_heap_mapper(g1_rs,
1688                                               g1_rs.size(),
1689                                               page_size,
1690                                               HeapRegion::GrainBytes,
1691                                               1,
1692                                               mtJavaHeap);
1693   if(heap_storage == NULL) {
1694     vm_shutdown_during_initialization("Could not initialize G1 heap");
1695     return JNI_ERR;
1696   }
1697 
1698   os::trace_page_sizes("Heap",
1699                        MinHeapSize,
1700                        reserved_byte_size,
1701                        page_size,
1702                        heap_rs.base(),
1703                        heap_rs.size());
1704   heap_storage->set_mapping_changed_listener(&_listener);
1705 
1706   // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1707   G1RegionToSpaceMapper* bot_storage =
1708     create_aux_memory_mapper("Block Offset Table",
1709                              G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize),
1710                              G1BlockOffsetTable::heap_map_factor());
1711 
1712   G1RegionToSpaceMapper* cardtable_storage =
1713     create_aux_memory_mapper("Card Table",
1714                              G1CardTable::compute_size(g1_rs.size() / HeapWordSize),
1715                              G1CardTable::heap_map_factor());
1716 
1717   G1RegionToSpaceMapper* card_counts_storage =
1718     create_aux_memory_mapper("Card Counts Table",
1719                              G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1720                              G1CardCounts::heap_map_factor());
1721 
1722   size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size());
1723   G1RegionToSpaceMapper* prev_bitmap_storage =
1724     create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1725   G1RegionToSpaceMapper* next_bitmap_storage =
1726     create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1727 
1728   _hrm = HeapRegionManager::create_manager(this);
1729 
1730   _hrm->initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1731   _card_table->initialize(cardtable_storage);
1732 
1733   // Do later initialization work for concurrent refinement.
1734   _hot_card_cache->initialize(card_counts_storage);
1735 
1736   // 6843694 - ensure that the maximum region index can fit
1737   // in the remembered set structures.
1738   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1739   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1740 
1741   // The G1FromCardCache reserves card with value 0 as "invalid", so the heap must not
1742   // start within the first card.
1743   guarantee(g1_rs.base() >= (char*)G1CardTable::card_size, "Java heap must not start within the first card.");
1744   // Also create a G1 rem set.
1745   _rem_set = new G1RemSet(this, _card_table, _hot_card_cache);
1746   _rem_set->initialize(max_reserved_capacity(), max_regions());
1747 
1748   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1749   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1750   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1751             "too many cards per region");
1752 
1753   FreeRegionList::set_unrealistically_long_length(max_expandable_regions() + 1);
1754 
1755   _bot = new G1BlockOffsetTable(reserved_region(), bot_storage);
1756 
1757   {
1758     HeapWord* start = _hrm->reserved().start();
1759     HeapWord* end = _hrm->reserved().end();
1760     size_t granularity = HeapRegion::GrainBytes;
1761 
1762     _region_attr.initialize(start, end, granularity);
1763     _humongous_reclaim_candidates.initialize(start, end, granularity);
1764   }
1765 
1766   _workers = new WorkGang("GC Thread", ParallelGCThreads,
1767                           true /* are_GC_task_threads */,
1768                           false /* are_ConcurrentGC_threads */);
1769   if (_workers == NULL) {
1770     return JNI_ENOMEM;
1771   }
1772   _workers->initialize_workers();
1773 
1774   _numa->set_region_info(HeapRegion::GrainBytes, page_size);
1775 
1776   // Create the G1ConcurrentMark data structure and thread.
1777   // (Must do this late, so that "max_regions" is defined.)
1778   _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1779   _cm_thread = _cm->cm_thread();
1780 
1781   // Now expand into the initial heap size.
1782   if (!expand(init_byte_size, _workers)) {
1783     vm_shutdown_during_initialization("Failed to allocate initial heap.");
1784     return JNI_ENOMEM;
1785   }
1786 
1787   // Perform any initialization actions delegated to the policy.
1788   policy()->init(this, &_collection_set);
1789 
1790   jint ecode = initialize_concurrent_refinement();
1791   if (ecode != JNI_OK) {
1792     return ecode;
1793   }
1794 
1795   ecode = initialize_young_gen_sampling_thread();
1796   if (ecode != JNI_OK) {
1797     return ecode;
1798   }
1799 
1800   {
1801     G1DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
1802     dcqs.set_process_cards_threshold(concurrent_refine()->yellow_zone());
1803     dcqs.set_max_cards(concurrent_refine()->red_zone());
1804   }
1805 
1806   // Here we allocate the dummy HeapRegion that is required by the
1807   // G1AllocRegion class.
1808   HeapRegion* dummy_region = _hrm->get_dummy_region();
1809 
1810   // We'll re-use the same region whether the alloc region will
1811   // require BOT updates or not and, if it doesn't, then a non-young
1812   // region will complain that it cannot support allocations without
1813   // BOT updates. So we'll tag the dummy region as eden to avoid that.
1814   dummy_region->set_eden();
1815   // Make sure it's full.
1816   dummy_region->set_top(dummy_region->end());
1817   G1AllocRegion::setup(this, dummy_region);
1818 
1819   _allocator->init_mutator_alloc_regions();
1820 
1821   // Do create of the monitoring and management support so that
1822   // values in the heap have been properly initialized.
1823   _g1mm = new G1MonitoringSupport(this);
1824 
1825   G1StringDedup::initialize();
1826 
1827   _preserved_marks_set.init(ParallelGCThreads);
1828 
1829   _collection_set.initialize(max_regions());
1830 
1831   G1InitLogger::print();
1832 
1833   return JNI_OK;
1834 }
1835 
1836 void G1CollectedHeap::stop() {
1837   // Stop all concurrent threads. We do this to make sure these threads
1838   // do not continue to execute and access resources (e.g. logging)
1839   // that are destroyed during shutdown.
1840   _cr->stop();
1841   _young_gen_sampling_thread->stop();
1842   _cm_thread->stop();
1843   if (G1StringDedup::is_enabled()) {
1844     G1StringDedup::stop();
1845   }
1846 }
1847 
1848 void G1CollectedHeap::safepoint_synchronize_begin() {
1849   SuspendibleThreadSet::synchronize();
1850 }
1851 
1852 void G1CollectedHeap::safepoint_synchronize_end() {
1853   SuspendibleThreadSet::desynchronize();
1854 }
1855 
1856 void G1CollectedHeap::post_initialize() {
1857   CollectedHeap::post_initialize();
1858   ref_processing_init();
1859 }
1860 
1861 void G1CollectedHeap::ref_processing_init() {
1862   // Reference processing in G1 currently works as follows:
1863   //
1864   // * There are two reference processor instances. One is
1865   //   used to record and process discovered references
1866   //   during concurrent marking; the other is used to
1867   //   record and process references during STW pauses
1868   //   (both full and incremental).
1869   // * Both ref processors need to 'span' the entire heap as
1870   //   the regions in the collection set may be dotted around.
1871   //
1872   // * For the concurrent marking ref processor:
1873   //   * Reference discovery is enabled at initial marking.
1874   //   * Reference discovery is disabled and the discovered
1875   //     references processed etc during remarking.
1876   //   * Reference discovery is MT (see below).
1877   //   * Reference discovery requires a barrier (see below).
1878   //   * Reference processing may or may not be MT
1879   //     (depending on the value of ParallelRefProcEnabled
1880   //     and ParallelGCThreads).
1881   //   * A full GC disables reference discovery by the CM
1882   //     ref processor and abandons any entries on it's
1883   //     discovered lists.
1884   //
1885   // * For the STW processor:
1886   //   * Non MT discovery is enabled at the start of a full GC.
1887   //   * Processing and enqueueing during a full GC is non-MT.
1888   //   * During a full GC, references are processed after marking.
1889   //
1890   //   * Discovery (may or may not be MT) is enabled at the start
1891   //     of an incremental evacuation pause.
1892   //   * References are processed near the end of a STW evacuation pause.
1893   //   * For both types of GC:
1894   //     * Discovery is atomic - i.e. not concurrent.
1895   //     * Reference discovery will not need a barrier.
1896 
1897   bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1);
1898 
1899   // Concurrent Mark ref processor
1900   _ref_processor_cm =
1901     new ReferenceProcessor(&_is_subject_to_discovery_cm,
1902                            mt_processing,                                  // mt processing
1903                            ParallelGCThreads,                              // degree of mt processing
1904                            (ParallelGCThreads > 1) || (ConcGCThreads > 1), // mt discovery
1905                            MAX2(ParallelGCThreads, ConcGCThreads),         // degree of mt discovery
1906                            false,                                          // Reference discovery is not atomic
1907                            &_is_alive_closure_cm,                          // is alive closure
1908                            true);                                          // allow changes to number of processing threads
1909 
1910   // STW ref processor
1911   _ref_processor_stw =
1912     new ReferenceProcessor(&_is_subject_to_discovery_stw,
1913                            mt_processing,                        // mt processing
1914                            ParallelGCThreads,                    // degree of mt processing
1915                            (ParallelGCThreads > 1),              // mt discovery
1916                            ParallelGCThreads,                    // degree of mt discovery
1917                            true,                                 // Reference discovery is atomic
1918                            &_is_alive_closure_stw,               // is alive closure
1919                            true);                                // allow changes to number of processing threads
1920 }
1921 
1922 SoftRefPolicy* G1CollectedHeap::soft_ref_policy() {
1923   return &_soft_ref_policy;
1924 }
1925 
1926 size_t G1CollectedHeap::capacity() const {
1927   return _hrm->length() * HeapRegion::GrainBytes;
1928 }
1929 
1930 size_t G1CollectedHeap::unused_committed_regions_in_bytes() const {
1931   return _hrm->total_free_bytes();
1932 }
1933 
1934 void G1CollectedHeap::iterate_hcc_closure(G1CardTableEntryClosure* cl, uint worker_id) {
1935   _hot_card_cache->drain(cl, worker_id);
1936 }
1937 
1938 // Computes the sum of the storage used by the various regions.
1939 size_t G1CollectedHeap::used() const {
1940   size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
1941   if (_archive_allocator != NULL) {
1942     result += _archive_allocator->used();
1943   }
1944   return result;
1945 }
1946 
1947 size_t G1CollectedHeap::used_unlocked() const {
1948   return _summary_bytes_used;
1949 }
1950 
1951 class SumUsedClosure: public HeapRegionClosure {
1952   size_t _used;
1953 public:
1954   SumUsedClosure() : _used(0) {}
1955   bool do_heap_region(HeapRegion* r) {
1956     _used += r->used();
1957     return false;
1958   }
1959   size_t result() { return _used; }
1960 };
1961 
1962 size_t G1CollectedHeap::recalculate_used() const {
1963   SumUsedClosure blk;
1964   heap_region_iterate(&blk);
1965   return blk.result();
1966 }
1967 
1968 bool  G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
1969   switch (cause) {
1970     case GCCause::_java_lang_system_gc:                 return ExplicitGCInvokesConcurrent;
1971     case GCCause::_dcmd_gc_run:                         return ExplicitGCInvokesConcurrent;
1972     case GCCause::_wb_conc_mark:                        return true;
1973     default :                                           return false;
1974   }
1975 }
1976 
1977 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
1978   switch (cause) {
1979     case GCCause::_g1_humongous_allocation: return true;
1980     case GCCause::_g1_periodic_collection:  return G1PeriodicGCInvokesConcurrent;
1981     case GCCause::_wb_breakpoint:           return true;
1982     default:                                return is_user_requested_concurrent_full_gc(cause);
1983   }
1984 }
1985 
1986 bool G1CollectedHeap::should_upgrade_to_full_gc(GCCause::Cause cause) {
1987   if (policy()->force_upgrade_to_full()) {
1988     return true;
1989   } else if (should_do_concurrent_full_gc(_gc_cause)) {
1990     return false;
1991   } else if (has_regions_left_for_allocation()) {
1992     return false;
1993   } else {
1994     return true;
1995   }
1996 }
1997 
1998 #ifndef PRODUCT
1999 void G1CollectedHeap::allocate_dummy_regions() {
2000   // Let's fill up most of the region
2001   size_t word_size = HeapRegion::GrainWords - 1024;
2002   // And as a result the region we'll allocate will be humongous.
2003   guarantee(is_humongous(word_size), "sanity");
2004 
2005   // _filler_array_max_size is set to humongous object threshold
2006   // but temporarily change it to use CollectedHeap::fill_with_object().
2007   SizeTFlagSetting fs(_filler_array_max_size, word_size);
2008 
2009   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2010     // Let's use the existing mechanism for the allocation
2011     HeapWord* dummy_obj = humongous_obj_allocate(word_size);
2012     if (dummy_obj != NULL) {
2013       MemRegion mr(dummy_obj, word_size);
2014       CollectedHeap::fill_with_object(mr);
2015     } else {
2016       // If we can't allocate once, we probably cannot allocate
2017       // again. Let's get out of the loop.
2018       break;
2019     }
2020   }
2021 }
2022 #endif // !PRODUCT
2023 
2024 void G1CollectedHeap::increment_old_marking_cycles_started() {
2025   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2026          _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2027          "Wrong marking cycle count (started: %d, completed: %d)",
2028          _old_marking_cycles_started, _old_marking_cycles_completed);
2029 
2030   _old_marking_cycles_started++;
2031 }
2032 
2033 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2034   MonitorLocker ml(G1OldGCCount_lock, Mutex::_no_safepoint_check_flag);
2035 
2036   // We assume that if concurrent == true, then the caller is a
2037   // concurrent thread that was joined the Suspendible Thread
2038   // Set. If there's ever a cheap way to check this, we should add an
2039   // assert here.
2040 
2041   // Given that this method is called at the end of a Full GC or of a
2042   // concurrent cycle, and those can be nested (i.e., a Full GC can
2043   // interrupt a concurrent cycle), the number of full collections
2044   // completed should be either one (in the case where there was no
2045   // nesting) or two (when a Full GC interrupted a concurrent cycle)
2046   // behind the number of full collections started.
2047 
2048   // This is the case for the inner caller, i.e. a Full GC.
2049   assert(concurrent ||
2050          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2051          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2052          "for inner caller (Full GC): _old_marking_cycles_started = %u "
2053          "is inconsistent with _old_marking_cycles_completed = %u",
2054          _old_marking_cycles_started, _old_marking_cycles_completed);
2055 
2056   // This is the case for the outer caller, i.e. the concurrent cycle.
2057   assert(!concurrent ||
2058          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2059          "for outer caller (concurrent cycle): "
2060          "_old_marking_cycles_started = %u "
2061          "is inconsistent with _old_marking_cycles_completed = %u",
2062          _old_marking_cycles_started, _old_marking_cycles_completed);
2063 
2064   _old_marking_cycles_completed += 1;
2065 
2066   // We need to clear the "in_progress" flag in the CM thread before
2067   // we wake up any waiters (especially when ExplicitInvokesConcurrent
2068   // is set) so that if a waiter requests another System.gc() it doesn't
2069   // incorrectly see that a marking cycle is still in progress.
2070   if (concurrent) {
2071     _cm_thread->set_idle();
2072   }
2073 
2074   // Notify threads waiting in System.gc() (with ExplicitGCInvokesConcurrent)
2075   // for a full GC to finish that their wait is over.
2076   ml.notify_all();
2077 }
2078 
2079 void G1CollectedHeap::collect(GCCause::Cause cause) {
2080   try_collect(cause);
2081 }
2082 
2083 // Return true if (x < y) with allowance for wraparound.
2084 static bool gc_counter_less_than(uint x, uint y) {
2085   return (x - y) > (UINT_MAX/2);
2086 }
2087 
2088 // LOG_COLLECT_CONCURRENTLY(cause, msg, args...)
2089 // Macro so msg printing is format-checked.
2090 #define LOG_COLLECT_CONCURRENTLY(cause, ...)                            \
2091   do {                                                                  \
2092     LogTarget(Trace, gc) LOG_COLLECT_CONCURRENTLY_lt;                   \
2093     if (LOG_COLLECT_CONCURRENTLY_lt.is_enabled()) {                     \
2094       ResourceMark rm; /* For thread name. */                           \
2095       LogStream LOG_COLLECT_CONCURRENTLY_s(&LOG_COLLECT_CONCURRENTLY_lt); \
2096       LOG_COLLECT_CONCURRENTLY_s.print("%s: Try Collect Concurrently (%s): ", \
2097                                        Thread::current()->name(),       \
2098                                        GCCause::to_string(cause));      \
2099       LOG_COLLECT_CONCURRENTLY_s.print(__VA_ARGS__);                    \
2100     }                                                                   \
2101   } while (0)
2102 
2103 #define LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, result) \
2104   LOG_COLLECT_CONCURRENTLY(cause, "complete %s", BOOL_TO_STR(result))
2105 
2106 bool G1CollectedHeap::try_collect_concurrently(GCCause::Cause cause,
2107                                                uint gc_counter,
2108                                                uint old_marking_started_before) {
2109   assert_heap_not_locked();
2110   assert(should_do_concurrent_full_gc(cause),
2111          "Non-concurrent cause %s", GCCause::to_string(cause));
2112 
2113   for (uint i = 1; true; ++i) {
2114     // Try to schedule an initial-mark evacuation pause that will
2115     // start a concurrent cycle.
2116     LOG_COLLECT_CONCURRENTLY(cause, "attempt %u", i);
2117     VM_G1TryInitiateConcMark op(gc_counter,
2118                                 cause,
2119                                 policy()->max_pause_time_ms());
2120     VMThread::execute(&op);
2121 
2122     // Request is trivially finished.
2123     if (cause == GCCause::_g1_periodic_collection) {
2124       LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, op.gc_succeeded());
2125       return op.gc_succeeded();
2126     }
2127 
2128     // If VMOp skipped initiating concurrent marking cycle because
2129     // we're terminating, then we're done.
2130     if (op.terminating()) {
2131       LOG_COLLECT_CONCURRENTLY(cause, "skipped: terminating");
2132       return false;
2133     }
2134 
2135     // Lock to get consistent set of values.
2136     uint old_marking_started_after;
2137     uint old_marking_completed_after;
2138     {
2139       MutexLocker ml(Heap_lock);
2140       // Update gc_counter for retrying VMOp if needed. Captured here to be
2141       // consistent with the values we use below for termination tests.  If
2142       // a retry is needed after a possible wait, and another collection
2143       // occurs in the meantime, it will cause our retry to be skipped and
2144       // we'll recheck for termination with updated conditions from that
2145       // more recent collection.  That's what we want, rather than having
2146       // our retry possibly perform an unnecessary collection.
2147       gc_counter = total_collections();
2148       old_marking_started_after = _old_marking_cycles_started;
2149       old_marking_completed_after = _old_marking_cycles_completed;
2150     }
2151 
2152     if (cause == GCCause::_wb_breakpoint) {
2153       if (op.gc_succeeded()) {
2154         LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, true);
2155         return true;
2156       }
2157       // When _wb_breakpoint there can't be another cycle or deferred.
2158       assert(!op.cycle_already_in_progress(), "invariant");
2159       assert(!op.whitebox_attached(), "invariant");
2160       // Concurrent cycle attempt might have been cancelled by some other
2161       // collection, so retry.  Unlike other cases below, we want to retry
2162       // even if cancelled by a STW full collection, because we really want
2163       // to start a concurrent cycle.
2164       if (old_marking_started_before != old_marking_started_after) {
2165         LOG_COLLECT_CONCURRENTLY(cause, "ignoring STW full GC");
2166         old_marking_started_before = old_marking_started_after;
2167       }
2168     } else if (!GCCause::is_user_requested_gc(cause)) {
2169       // For an "automatic" (not user-requested) collection, we just need to
2170       // ensure that progress is made.
2171       //
2172       // Request is finished if any of
2173       // (1) the VMOp successfully performed a GC,
2174       // (2) a concurrent cycle was already in progress,
2175       // (3) whitebox is controlling concurrent cycles,
2176       // (4) a new cycle was started (by this thread or some other), or
2177       // (5) a Full GC was performed.
2178       // Cases (4) and (5) are detected together by a change to
2179       // _old_marking_cycles_started.
2180       //
2181       // Note that (1) does not imply (4).  If we're still in the mixed
2182       // phase of an earlier concurrent collection, the request to make the
2183       // collection an initial-mark won't be honored.  If we don't check for
2184       // both conditions we'll spin doing back-to-back collections.
2185       if (op.gc_succeeded() ||
2186           op.cycle_already_in_progress() ||
2187           op.whitebox_attached() ||
2188           (old_marking_started_before != old_marking_started_after)) {
2189         LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, true);
2190         return true;
2191       }
2192     } else {                    // User-requested GC.
2193       // For a user-requested collection, we want to ensure that a complete
2194       // full collection has been performed before returning, but without
2195       // waiting for more than needed.
2196 
2197       // For user-requested GCs (unlike non-UR), a successful VMOp implies a
2198       // new cycle was started.  That's good, because it's not clear what we
2199       // should do otherwise.  Trying again just does back to back GCs.
2200       // Can't wait for someone else to start a cycle.  And returning fails
2201       // to meet the goal of ensuring a full collection was performed.
2202       assert(!op.gc_succeeded() ||
2203              (old_marking_started_before != old_marking_started_after),
2204              "invariant: succeeded %s, started before %u, started after %u",
2205              BOOL_TO_STR(op.gc_succeeded()),
2206              old_marking_started_before, old_marking_started_after);
2207 
2208       // Request is finished if a full collection (concurrent or stw)
2209       // was started after this request and has completed, e.g.
2210       // started_before < completed_after.
2211       if (gc_counter_less_than(old_marking_started_before,
2212                                old_marking_completed_after)) {
2213         LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, true);
2214         return true;
2215       }
2216 
2217       if (old_marking_started_after != old_marking_completed_after) {
2218         // If there is an in-progress cycle (possibly started by us), then
2219         // wait for that cycle to complete, e.g.
2220         // while completed_now < started_after.
2221         LOG_COLLECT_CONCURRENTLY(cause, "wait");
2222         MonitorLocker ml(G1OldGCCount_lock);
2223         while (gc_counter_less_than(_old_marking_cycles_completed,
2224                                     old_marking_started_after)) {
2225           ml.wait();
2226         }
2227         // Request is finished if the collection we just waited for was
2228         // started after this request.
2229         if (old_marking_started_before != old_marking_started_after) {
2230           LOG_COLLECT_CONCURRENTLY(cause, "complete after wait");
2231           return true;
2232         }
2233       }
2234 
2235       // If VMOp was successful then it started a new cycle that the above
2236       // wait &etc should have recognized as finishing this request.  This
2237       // differs from a non-user-request, where gc_succeeded does not imply
2238       // a new cycle was started.
2239       assert(!op.gc_succeeded(), "invariant");
2240 
2241       if (op.cycle_already_in_progress()) {
2242         // If VMOp failed because a cycle was already in progress, it
2243         // is now complete.  But it didn't finish this user-requested
2244         // GC, so try again.
2245         LOG_COLLECT_CONCURRENTLY(cause, "retry after in-progress");
2246         continue;
2247       } else if (op.whitebox_attached()) {
2248         // If WhiteBox wants control, wait for notification of a state
2249         // change in the controller, then try again.  Don't wait for
2250         // release of control, since collections may complete while in
2251         // control.  Note: This won't recognize a STW full collection
2252         // while waiting; we can't wait on multiple monitors.
2253         LOG_COLLECT_CONCURRENTLY(cause, "whitebox control stall");
2254         MonitorLocker ml(ConcurrentGCBreakpoints::monitor());
2255         if (ConcurrentGCBreakpoints::is_controlled()) {
2256           ml.wait();
2257         }
2258         continue;
2259       }
2260     }
2261 
2262     // Collection failed and should be retried.
2263     assert(op.transient_failure(), "invariant");
2264 
2265     if (GCLocker::is_active_and_needs_gc()) {
2266       // If GCLocker is active, wait until clear before retrying.
2267       LOG_COLLECT_CONCURRENTLY(cause, "gc-locker stall");
2268       GCLocker::stall_until_clear();
2269     }
2270 
2271     LOG_COLLECT_CONCURRENTLY(cause, "retry");
2272   }
2273 }
2274 
2275 bool G1CollectedHeap::try_collect(GCCause::Cause cause) {
2276   assert_heap_not_locked();
2277 
2278   // Lock to get consistent set of values.
2279   uint gc_count_before;
2280   uint full_gc_count_before;
2281   uint old_marking_started_before;
2282   {
2283     MutexLocker ml(Heap_lock);
2284     gc_count_before = total_collections();
2285     full_gc_count_before = total_full_collections();
2286     old_marking_started_before = _old_marking_cycles_started;
2287   }
2288 
2289   if (should_do_concurrent_full_gc(cause)) {
2290     return try_collect_concurrently(cause,
2291                                     gc_count_before,
2292                                     old_marking_started_before);
2293   } else if (GCLocker::should_discard(cause, gc_count_before)) {
2294     // Indicate failure to be consistent with VMOp failure due to
2295     // another collection slipping in after our gc_count but before
2296     // our request is processed.
2297     return false;
2298   } else if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2299              DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2300 
2301     // Schedule a standard evacuation pause. We're setting word_size
2302     // to 0 which means that we are not requesting a post-GC allocation.
2303     VM_G1CollectForAllocation op(0,     /* word_size */
2304                                  gc_count_before,
2305                                  cause,
2306                                  policy()->max_pause_time_ms());
2307     VMThread::execute(&op);
2308     return op.gc_succeeded();
2309   } else {
2310     // Schedule a Full GC.
2311     VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2312     VMThread::execute(&op);
2313     return op.gc_succeeded();
2314   }
2315 }
2316 
2317 bool G1CollectedHeap::is_in(const void* p) const {
2318   if (_hrm->reserved().contains(p)) {
2319     // Given that we know that p is in the reserved space,
2320     // heap_region_containing() should successfully
2321     // return the containing region.
2322     HeapRegion* hr = heap_region_containing(p);
2323     return hr->is_in(p);
2324   } else {
2325     return false;
2326   }
2327 }
2328 
2329 #ifdef ASSERT
2330 bool G1CollectedHeap::is_in_exact(const void* p) const {
2331   bool contains = reserved_region().contains(p);
2332   bool available = _hrm->is_available(addr_to_region((HeapWord*)p));
2333   if (contains && available) {
2334     return true;
2335   } else {
2336     return false;
2337   }
2338 }
2339 #endif
2340 
2341 // Iteration functions.
2342 
2343 // Iterates an ObjectClosure over all objects within a HeapRegion.
2344 
2345 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2346   ObjectClosure* _cl;
2347 public:
2348   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2349   bool do_heap_region(HeapRegion* r) {
2350     if (!r->is_continues_humongous()) {
2351       r->object_iterate(_cl);
2352     }
2353     return false;
2354   }
2355 };
2356 
2357 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2358   IterateObjectClosureRegionClosure blk(cl);
2359   heap_region_iterate(&blk);
2360 }
2361 
2362 void G1CollectedHeap::keep_alive(oop obj) {
2363   G1BarrierSet::enqueue(obj);
2364 }
2365 
2366 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2367   _hrm->iterate(cl);
2368 }
2369 
2370 void G1CollectedHeap::heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl,
2371                                                                  HeapRegionClaimer *hrclaimer,
2372                                                                  uint worker_id) const {
2373   _hrm->par_iterate(cl, hrclaimer, hrclaimer->offset_for_worker(worker_id));
2374 }
2375 
2376 void G1CollectedHeap::heap_region_par_iterate_from_start(HeapRegionClosure* cl,
2377                                                          HeapRegionClaimer *hrclaimer) const {
2378   _hrm->par_iterate(cl, hrclaimer, 0);
2379 }
2380 
2381 void G1CollectedHeap::collection_set_iterate_all(HeapRegionClosure* cl) {
2382   _collection_set.iterate(cl);
2383 }
2384 
2385 void G1CollectedHeap::collection_set_par_iterate_all(HeapRegionClosure* cl, HeapRegionClaimer* hr_claimer, uint worker_id) {
2386   _collection_set.par_iterate(cl, hr_claimer, worker_id, workers()->active_workers());
2387 }
2388 
2389 void G1CollectedHeap::collection_set_iterate_increment_from(HeapRegionClosure *cl, HeapRegionClaimer* hr_claimer, uint worker_id) {
2390   _collection_set.iterate_incremental_part_from(cl, hr_claimer, worker_id, workers()->active_workers());
2391 }
2392 
2393 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2394   HeapRegion* hr = heap_region_containing(addr);
2395   return hr->block_start(addr);
2396 }
2397 
2398 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2399   HeapRegion* hr = heap_region_containing(addr);
2400   return hr->block_is_obj(addr);
2401 }
2402 
2403 bool G1CollectedHeap::supports_tlab_allocation() const {
2404   return true;
2405 }
2406 
2407 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2408   return (_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes;
2409 }
2410 
2411 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2412   return _eden.length() * HeapRegion::GrainBytes;
2413 }
2414 
2415 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2416 // must be equal to the humongous object limit.
2417 size_t G1CollectedHeap::max_tlab_size() const {
2418   return align_down(_humongous_object_threshold_in_words, MinObjAlignment);
2419 }
2420 
2421 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2422   return _allocator->unsafe_max_tlab_alloc();
2423 }
2424 
2425 size_t G1CollectedHeap::max_capacity() const {
2426   return _hrm->max_expandable_length() * HeapRegion::GrainBytes;
2427 }
2428 
2429 size_t G1CollectedHeap::max_reserved_capacity() const {
2430   return _hrm->max_length() * HeapRegion::GrainBytes;
2431 }
2432 
2433 jlong G1CollectedHeap::millis_since_last_gc() {
2434   // See the notes in GenCollectedHeap::millis_since_last_gc()
2435   // for more information about the implementation.
2436   jlong ret_val = (os::javaTimeNanos() - _time_of_last_gc_ns) /
2437                   NANOSECS_PER_MILLISEC;
2438   if (ret_val < 0) {
2439     NOT_PRODUCT(log_warning(gc)("time warp: " JLONG_FORMAT, ret_val);)
2440     return 0;
2441   }
2442   return ret_val;
2443 }
2444 
2445 void G1CollectedHeap::deduplicate_string(oop str) {
2446   assert(java_lang_String::is_instance(str), "invariant");
2447 
2448   if (G1StringDedup::is_enabled()) {
2449     G1StringDedup::deduplicate(str);
2450   }
2451 }
2452 
2453 void G1CollectedHeap::prepare_for_verify() {
2454   _verifier->prepare_for_verify();
2455 }
2456 
2457 void G1CollectedHeap::verify(VerifyOption vo) {
2458   _verifier->verify(vo);
2459 }
2460 
2461 bool G1CollectedHeap::supports_concurrent_gc_breakpoints() const {
2462   return true;
2463 }
2464 
2465 bool G1CollectedHeap::is_heterogeneous_heap() const {
2466   return G1Arguments::is_heterogeneous_heap();
2467 }
2468 
2469 class PrintRegionClosure: public HeapRegionClosure {
2470   outputStream* _st;
2471 public:
2472   PrintRegionClosure(outputStream* st) : _st(st) {}
2473   bool do_heap_region(HeapRegion* r) {
2474     r->print_on(_st);
2475     return false;
2476   }
2477 };
2478 
2479 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2480                                        const HeapRegion* hr,
2481                                        const VerifyOption vo) const {
2482   switch (vo) {
2483   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
2484   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
2485   case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj, hr);
2486   default:                            ShouldNotReachHere();
2487   }
2488   return false; // keep some compilers happy
2489 }
2490 
2491 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2492                                        const VerifyOption vo) const {
2493   switch (vo) {
2494   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
2495   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
2496   case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj);
2497   default:                            ShouldNotReachHere();
2498   }
2499   return false; // keep some compilers happy
2500 }
2501 
2502 void G1CollectedHeap::print_heap_regions() const {
2503   LogTarget(Trace, gc, heap, region) lt;
2504   if (lt.is_enabled()) {
2505     LogStream ls(lt);
2506     print_regions_on(&ls);
2507   }
2508 }
2509 
2510 void G1CollectedHeap::print_on(outputStream* st) const {
2511   st->print(" %-20s", "garbage-first heap");
2512   if (_hrm != NULL) {
2513     st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
2514               capacity()/K, used_unlocked()/K);
2515     st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")",
2516               p2i(_hrm->reserved().start()),
2517               p2i(_hrm->reserved().end()));
2518   }
2519   st->cr();
2520   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
2521   uint young_regions = young_regions_count();
2522   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
2523             (size_t) young_regions * HeapRegion::GrainBytes / K);
2524   uint survivor_regions = survivor_regions_count();
2525   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
2526             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
2527   st->cr();
2528   if (_numa->is_enabled()) {
2529     uint num_nodes = _numa->num_active_nodes();
2530     st->print("  remaining free region(s) on each NUMA node: ");
2531     const int* node_ids = _numa->node_ids();
2532     for (uint node_index = 0; node_index < num_nodes; node_index++) {
2533       uint num_free_regions = (_hrm != NULL ? _hrm->num_free_regions(node_index) : 0);
2534       st->print("%d=%u ", node_ids[node_index], num_free_regions);
2535     }
2536     st->cr();
2537   }
2538   MetaspaceUtils::print_on(st);
2539 }
2540 
2541 void G1CollectedHeap::print_regions_on(outputStream* st) const {
2542   if (_hrm == NULL) {
2543     return;
2544   }
2545 
2546   st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
2547                "HS=humongous(starts), HC=humongous(continues), "
2548                "CS=collection set, F=free, "
2549                "OA=open archive, CA=closed archive, "
2550                "TAMS=top-at-mark-start (previous, next)");
2551   PrintRegionClosure blk(st);
2552   heap_region_iterate(&blk);
2553 }
2554 
2555 void G1CollectedHeap::print_extended_on(outputStream* st) const {
2556   print_on(st);
2557 
2558   // Print the per-region information.
2559   if (_hrm != NULL) {
2560     st->cr();
2561     print_regions_on(st);
2562   }
2563 }
2564 
2565 void G1CollectedHeap::print_on_error(outputStream* st) const {
2566   this->CollectedHeap::print_on_error(st);
2567 
2568   if (_cm != NULL) {
2569     st->cr();
2570     _cm->print_on_error(st);
2571   }
2572 }
2573 
2574 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2575   workers()->threads_do(tc);
2576   tc->do_thread(_cm_thread);
2577   _cm->threads_do(tc);
2578   _cr->threads_do(tc);
2579   tc->do_thread(_young_gen_sampling_thread);
2580   if (G1StringDedup::is_enabled()) {
2581     G1StringDedup::threads_do(tc);
2582   }
2583 }
2584 
2585 void G1CollectedHeap::print_tracing_info() const {
2586   rem_set()->print_summary_info();
2587   concurrent_mark()->print_summary_info();
2588 }
2589 
2590 #ifndef PRODUCT
2591 // Helpful for debugging RSet issues.
2592 
2593 class PrintRSetsClosure : public HeapRegionClosure {
2594 private:
2595   const char* _msg;
2596   size_t _occupied_sum;
2597 
2598 public:
2599   bool do_heap_region(HeapRegion* r) {
2600     HeapRegionRemSet* hrrs = r->rem_set();
2601     size_t occupied = hrrs->occupied();
2602     _occupied_sum += occupied;
2603 
2604     tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r));
2605     if (occupied == 0) {
2606       tty->print_cr("  RSet is empty");
2607     } else {
2608       hrrs->print();
2609     }
2610     tty->print_cr("----------");
2611     return false;
2612   }
2613 
2614   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
2615     tty->cr();
2616     tty->print_cr("========================================");
2617     tty->print_cr("%s", msg);
2618     tty->cr();
2619   }
2620 
2621   ~PrintRSetsClosure() {
2622     tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
2623     tty->print_cr("========================================");
2624     tty->cr();
2625   }
2626 };
2627 
2628 void G1CollectedHeap::print_cset_rsets() {
2629   PrintRSetsClosure cl("Printing CSet RSets");
2630   collection_set_iterate_all(&cl);
2631 }
2632 
2633 void G1CollectedHeap::print_all_rsets() {
2634   PrintRSetsClosure cl("Printing All RSets");;
2635   heap_region_iterate(&cl);
2636 }
2637 #endif // PRODUCT
2638 
2639 bool G1CollectedHeap::print_location(outputStream* st, void* addr) const {
2640   return BlockLocationPrinter<G1CollectedHeap>::print_location(st, addr);
2641 }
2642 
2643 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
2644 
2645   size_t eden_used_bytes = _eden.used_bytes();
2646   size_t survivor_used_bytes = _survivor.used_bytes();
2647   size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
2648 
2649   size_t eden_capacity_bytes =
2650     (policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
2651 
2652   VirtualSpaceSummary heap_summary = create_heap_space_summary();
2653   return G1HeapSummary(heap_summary, heap_used, eden_used_bytes,
2654                        eden_capacity_bytes, survivor_used_bytes, num_regions());
2655 }
2656 
2657 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
2658   return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
2659                        stats->unused(), stats->used(), stats->region_end_waste(),
2660                        stats->regions_filled(), stats->direct_allocated(),
2661                        stats->failure_used(), stats->failure_waste());
2662 }
2663 
2664 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
2665   const G1HeapSummary& heap_summary = create_g1_heap_summary();
2666   gc_tracer->report_gc_heap_summary(when, heap_summary);
2667 
2668   const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
2669   gc_tracer->report_metaspace_summary(when, metaspace_summary);
2670 }
2671 
2672 void G1CollectedHeap::gc_prologue(bool full) {
2673   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
2674 
2675   // This summary needs to be printed before incrementing total collections.
2676   rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections());
2677 
2678   // Update common counters.
2679   increment_total_collections(full /* full gc */);
2680   if (full || collector_state()->in_initial_mark_gc()) {
2681     increment_old_marking_cycles_started();
2682   }
2683 
2684   // Fill TLAB's and such
2685   {
2686     Ticks start = Ticks::now();
2687     ensure_parsability(true);
2688     Tickspan dt = Ticks::now() - start;
2689     phase_times()->record_prepare_tlab_time_ms(dt.seconds() * MILLIUNITS);
2690   }
2691 
2692   if (!full) {
2693     // Flush dirty card queues to qset, so later phases don't need to account
2694     // for partially filled per-thread queues and such.  Not needed for full
2695     // collections, which ignore those logs.
2696     Ticks start = Ticks::now();
2697     G1BarrierSet::dirty_card_queue_set().concatenate_logs();
2698     Tickspan dt = Ticks::now() - start;
2699     phase_times()->record_concatenate_dirty_card_logs_time_ms(dt.seconds() * MILLIUNITS);
2700   }
2701 }
2702 
2703 void G1CollectedHeap::gc_epilogue(bool full) {
2704   // Update common counters.
2705   if (full) {
2706     // Update the number of full collections that have been completed.
2707     increment_old_marking_cycles_completed(false /* concurrent */);
2708   }
2709 
2710   // We are at the end of the GC. Total collections has already been increased.
2711   rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1);
2712 
2713   // FIXME: what is this about?
2714   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
2715   // is set.
2716 #if COMPILER2_OR_JVMCI
2717   assert(DerivedPointerTable::is_empty(), "derived pointer present");
2718 #endif
2719 
2720   double start = os::elapsedTime();
2721   resize_all_tlabs();
2722   phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2723 
2724   MemoryService::track_memory_usage();
2725   // We have just completed a GC. Update the soft reference
2726   // policy with the new heap occupancy
2727   Universe::update_heap_info_at_gc();
2728 
2729   // Print NUMA statistics.
2730   _numa->print_statistics();
2731 
2732   _collection_pause_end = Ticks::now();
2733 }
2734 
2735 void G1CollectedHeap::verify_numa_regions(const char* desc) {
2736   LogTarget(Trace, gc, heap, verify) lt;
2737 
2738   if (lt.is_enabled()) {
2739     LogStream ls(lt);
2740     // Iterate all heap regions to print matching between preferred numa id and actual numa id.
2741     G1NodeIndexCheckClosure cl(desc, _numa, &ls);
2742     heap_region_iterate(&cl);
2743   }
2744 }
2745 
2746 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2747                                                uint gc_count_before,
2748                                                bool* succeeded,
2749                                                GCCause::Cause gc_cause) {
2750   assert_heap_not_locked_and_not_at_safepoint();
2751   VM_G1CollectForAllocation op(word_size,
2752                                gc_count_before,
2753                                gc_cause,
2754                                policy()->max_pause_time_ms());
2755   VMThread::execute(&op);
2756 
2757   HeapWord* result = op.result();
2758   bool ret_succeeded = op.prologue_succeeded() && op.gc_succeeded();
2759   assert(result == NULL || ret_succeeded,
2760          "the result should be NULL if the VM did not succeed");
2761   *succeeded = ret_succeeded;
2762 
2763   assert_heap_not_locked();
2764   return result;
2765 }
2766 
2767 void G1CollectedHeap::do_concurrent_mark() {
2768   MutexLocker x(CGC_lock, Mutex::_no_safepoint_check_flag);
2769   if (!_cm_thread->in_progress()) {
2770     _cm_thread->set_started();
2771     CGC_lock->notify();
2772   }
2773 }
2774 
2775 bool G1CollectedHeap::is_potential_eager_reclaim_candidate(HeapRegion* r) const {
2776   // We don't nominate objects with many remembered set entries, on
2777   // the assumption that such objects are likely still live.
2778   HeapRegionRemSet* rem_set = r->rem_set();
2779 
2780   return G1EagerReclaimHumongousObjectsWithStaleRefs ?
2781          rem_set->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) :
2782          G1EagerReclaimHumongousObjects && rem_set->is_empty();
2783 }
2784 
2785 #ifndef PRODUCT
2786 void G1CollectedHeap::verify_region_attr_remset_update() {
2787   class VerifyRegionAttrRemSet : public HeapRegionClosure {
2788   public:
2789     virtual bool do_heap_region(HeapRegion* r) {
2790       G1CollectedHeap* g1h = G1CollectedHeap::heap();
2791       bool const needs_remset_update = g1h->region_attr(r->bottom()).needs_remset_update();
2792       assert(r->rem_set()->is_tracked() == needs_remset_update,
2793              "Region %u remset tracking status (%s) different to region attribute (%s)",
2794              r->hrm_index(), BOOL_TO_STR(r->rem_set()->is_tracked()), BOOL_TO_STR(needs_remset_update));
2795       return false;
2796     }
2797   } cl;
2798   heap_region_iterate(&cl);
2799 }
2800 #endif
2801 
2802 class VerifyRegionRemSetClosure : public HeapRegionClosure {
2803   public:
2804     bool do_heap_region(HeapRegion* hr) {
2805       if (!hr->is_archive() && !hr->is_continues_humongous()) {
2806         hr->verify_rem_set();
2807       }
2808       return false;
2809     }
2810 };
2811 
2812 uint G1CollectedHeap::num_task_queues() const {
2813   return _task_queues->size();
2814 }
2815 
2816 #if TASKQUEUE_STATS
2817 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
2818   st->print_raw_cr("GC Task Stats");
2819   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
2820   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
2821 }
2822 
2823 void G1CollectedHeap::print_taskqueue_stats() const {
2824   if (!log_is_enabled(Trace, gc, task, stats)) {
2825     return;
2826   }
2827   Log(gc, task, stats) log;
2828   ResourceMark rm;
2829   LogStream ls(log.trace());
2830   outputStream* st = &ls;
2831 
2832   print_taskqueue_stats_hdr(st);
2833 
2834   TaskQueueStats totals;
2835   const uint n = num_task_queues();
2836   for (uint i = 0; i < n; ++i) {
2837     st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
2838     totals += task_queue(i)->stats;
2839   }
2840   st->print_raw("tot "); totals.print(st); st->cr();
2841 
2842   DEBUG_ONLY(totals.verify());
2843 }
2844 
2845 void G1CollectedHeap::reset_taskqueue_stats() {
2846   const uint n = num_task_queues();
2847   for (uint i = 0; i < n; ++i) {
2848     task_queue(i)->stats.reset();
2849   }
2850 }
2851 #endif // TASKQUEUE_STATS
2852 
2853 void G1CollectedHeap::wait_for_root_region_scanning() {
2854   double scan_wait_start = os::elapsedTime();
2855   // We have to wait until the CM threads finish scanning the
2856   // root regions as it's the only way to ensure that all the
2857   // objects on them have been correctly scanned before we start
2858   // moving them during the GC.
2859   bool waited = _cm->root_regions()->wait_until_scan_finished();
2860   double wait_time_ms = 0.0;
2861   if (waited) {
2862     double scan_wait_end = os::elapsedTime();
2863     wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
2864   }
2865   phase_times()->record_root_region_scan_wait_time(wait_time_ms);
2866 }
2867 
2868 class G1PrintCollectionSetClosure : public HeapRegionClosure {
2869 private:
2870   G1HRPrinter* _hr_printer;
2871 public:
2872   G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { }
2873 
2874   virtual bool do_heap_region(HeapRegion* r) {
2875     _hr_printer->cset(r);
2876     return false;
2877   }
2878 };
2879 
2880 void G1CollectedHeap::start_new_collection_set() {
2881   double start = os::elapsedTime();
2882 
2883   collection_set()->start_incremental_building();
2884 
2885   clear_region_attr();
2886 
2887   guarantee(_eden.length() == 0, "eden should have been cleared");
2888   policy()->transfer_survivors_to_cset(survivor());
2889 
2890   // We redo the verification but now wrt to the new CSet which
2891   // has just got initialized after the previous CSet was freed.
2892   _cm->verify_no_collection_set_oops();
2893 
2894   phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0);
2895 }
2896 
2897 void G1CollectedHeap::calculate_collection_set(G1EvacuationInfo& evacuation_info, double target_pause_time_ms) {
2898 
2899   _collection_set.finalize_initial_collection_set(target_pause_time_ms, &_survivor);
2900   evacuation_info.set_collectionset_regions(collection_set()->region_length() +
2901                                             collection_set()->optional_region_length());
2902 
2903   _cm->verify_no_collection_set_oops();
2904 
2905   if (_hr_printer.is_active()) {
2906     G1PrintCollectionSetClosure cl(&_hr_printer);
2907     _collection_set.iterate(&cl);
2908     _collection_set.iterate_optional(&cl);
2909   }
2910 }
2911 
2912 G1HeapVerifier::G1VerifyType G1CollectedHeap::young_collection_verify_type() const {
2913   if (collector_state()->in_initial_mark_gc()) {
2914     return G1HeapVerifier::G1VerifyConcurrentStart;
2915   } else if (collector_state()->in_young_only_phase()) {
2916     return G1HeapVerifier::G1VerifyYoungNormal;
2917   } else {
2918     return G1HeapVerifier::G1VerifyMixed;
2919   }
2920 }
2921 
2922 void G1CollectedHeap::verify_before_young_collection(G1HeapVerifier::G1VerifyType type) {
2923   if (VerifyRememberedSets) {
2924     log_info(gc, verify)("[Verifying RemSets before GC]");
2925     VerifyRegionRemSetClosure v_cl;
2926     heap_region_iterate(&v_cl);
2927   }
2928   _verifier->verify_before_gc(type);
2929   _verifier->check_bitmaps("GC Start");
2930   verify_numa_regions("GC Start");
2931 }
2932 
2933 void G1CollectedHeap::verify_after_young_collection(G1HeapVerifier::G1VerifyType type) {
2934   if (VerifyRememberedSets) {
2935     log_info(gc, verify)("[Verifying RemSets after GC]");
2936     VerifyRegionRemSetClosure v_cl;
2937     heap_region_iterate(&v_cl);
2938   }
2939   _verifier->verify_after_gc(type);
2940   _verifier->check_bitmaps("GC End");
2941   verify_numa_regions("GC End");
2942 }
2943 
2944 void G1CollectedHeap::expand_heap_after_young_collection(){
2945   size_t expand_bytes = _heap_sizing_policy->expansion_amount();
2946   if (expand_bytes > 0) {
2947     // No need for an ergo logging here,
2948     // expansion_amount() does this when it returns a value > 0.
2949     double expand_ms;
2950     if (!expand(expand_bytes, _workers, &expand_ms)) {
2951       // We failed to expand the heap. Cannot do anything about it.
2952     }
2953     phase_times()->record_expand_heap_time(expand_ms);
2954   }
2955 }
2956 
2957 const char* G1CollectedHeap::young_gc_name() const {
2958   if (collector_state()->in_initial_mark_gc()) {
2959     return "Pause Young (Concurrent Start)";
2960   } else if (collector_state()->in_young_only_phase()) {
2961     if (collector_state()->in_young_gc_before_mixed()) {
2962       return "Pause Young (Prepare Mixed)";
2963     } else {
2964       return "Pause Young (Normal)";
2965     }
2966   } else {
2967     return "Pause Young (Mixed)";
2968   }
2969 }
2970 
2971 bool G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
2972   assert_at_safepoint_on_vm_thread();
2973   guarantee(!is_gc_active(), "collection is not reentrant");
2974 
2975   if (GCLocker::check_active_before_gc()) {
2976     return false;
2977   }
2978 
2979   do_collection_pause_at_safepoint_helper(target_pause_time_ms);
2980   if (should_upgrade_to_full_gc(gc_cause())) {
2981     log_info(gc, ergo)("Attempting maximally compacting collection");
2982     bool result = do_full_collection(false /* explicit gc */,
2983                                      true /* clear_all_soft_refs */);
2984     // do_full_collection only fails if blocked by GC locker, but
2985     // we've already checked for that above.
2986     assert(result, "invariant");
2987   }
2988   return true;
2989 }
2990 
2991 void G1CollectedHeap::do_collection_pause_at_safepoint_helper(double target_pause_time_ms) {
2992   GCIdMark gc_id_mark;
2993 
2994   SvcGCMarker sgcm(SvcGCMarker::MINOR);
2995   ResourceMark rm;
2996 
2997   policy()->note_gc_start();
2998 
2999   _gc_timer_stw->register_gc_start();
3000   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3001 
3002   wait_for_root_region_scanning();
3003 
3004   print_heap_before_gc();
3005   print_heap_regions();
3006   trace_heap_before_gc(_gc_tracer_stw);
3007 
3008   _verifier->verify_region_sets_optional();
3009   _verifier->verify_dirty_young_regions();
3010 
3011   // We should not be doing initial mark unless the conc mark thread is running
3012   if (!_cm_thread->should_terminate()) {
3013     // This call will decide whether this pause is an initial-mark
3014     // pause. If it is, in_initial_mark_gc() will return true
3015     // for the duration of this pause.
3016     policy()->decide_on_conc_mark_initiation();
3017   }
3018 
3019   // We do not allow initial-mark to be piggy-backed on a mixed GC.
3020   assert(!collector_state()->in_initial_mark_gc() ||
3021          collector_state()->in_young_only_phase(), "sanity");
3022   // We also do not allow mixed GCs during marking.
3023   assert(!collector_state()->mark_or_rebuild_in_progress() || collector_state()->in_young_only_phase(), "sanity");
3024 
3025   // Record whether this pause is an initial mark. When the current
3026   // thread has completed its logging output and it's safe to signal
3027   // the CM thread, the flag's value in the policy has been reset.
3028   bool should_start_conc_mark = collector_state()->in_initial_mark_gc();
3029   if (should_start_conc_mark) {
3030     _cm->gc_tracer_cm()->set_gc_cause(gc_cause());
3031   }
3032 
3033   // Inner scope for scope based logging, timers, and stats collection
3034   {
3035     G1EvacuationInfo evacuation_info;
3036 
3037     _gc_tracer_stw->report_yc_type(collector_state()->yc_type());
3038 
3039     GCTraceCPUTime tcpu;
3040 
3041     GCTraceTime(Info, gc) tm(young_gc_name(), NULL, gc_cause(), true);
3042 
3043     uint active_workers = WorkerPolicy::calc_active_workers(workers()->total_workers(),
3044                                                             workers()->active_workers(),
3045                                                             Threads::number_of_non_daemon_threads());
3046     active_workers = workers()->update_active_workers(active_workers);
3047     log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers());
3048 
3049     G1MonitoringScope ms(g1mm(),
3050                          false /* full_gc */,
3051                          collector_state()->yc_type() == Mixed /* all_memory_pools_affected */);
3052 
3053     G1HeapTransition heap_transition(this);
3054 
3055     {
3056       IsGCActiveMark x;
3057 
3058       gc_prologue(false);
3059 
3060       G1HeapVerifier::G1VerifyType verify_type = young_collection_verify_type();
3061       verify_before_young_collection(verify_type);
3062 
3063       {
3064         // The elapsed time induced by the start time below deliberately elides
3065         // the possible verification above.
3066         double sample_start_time_sec = os::elapsedTime();
3067 
3068         // Please see comment in g1CollectedHeap.hpp and
3069         // G1CollectedHeap::ref_processing_init() to see how
3070         // reference processing currently works in G1.
3071         _ref_processor_stw->enable_discovery();
3072 
3073         // We want to temporarily turn off discovery by the
3074         // CM ref processor, if necessary, and turn it back on
3075         // on again later if we do. Using a scoped
3076         // NoRefDiscovery object will do this.
3077         NoRefDiscovery no_cm_discovery(_ref_processor_cm);
3078 
3079         policy()->record_collection_pause_start(sample_start_time_sec);
3080 
3081         // Forget the current allocation region (we might even choose it to be part
3082         // of the collection set!).
3083         _allocator->release_mutator_alloc_regions();
3084 
3085         calculate_collection_set(evacuation_info, target_pause_time_ms);
3086 
3087         G1RedirtyCardsQueueSet rdcqs(G1BarrierSet::dirty_card_queue_set().allocator());
3088         G1ParScanThreadStateSet per_thread_states(this,
3089                                                   &rdcqs,
3090                                                   workers()->active_workers(),
3091                                                   collection_set()->young_region_length(),
3092                                                   collection_set()->optional_region_length());
3093         pre_evacuate_collection_set(evacuation_info, &per_thread_states);
3094 
3095         // Actually do the work...
3096         evacuate_initial_collection_set(&per_thread_states);
3097 
3098         if (_collection_set.optional_region_length() != 0) {
3099           evacuate_optional_collection_set(&per_thread_states);
3100         }
3101         post_evacuate_collection_set(evacuation_info, &rdcqs, &per_thread_states);
3102 
3103         start_new_collection_set();
3104 
3105         _survivor_evac_stats.adjust_desired_plab_sz();
3106         _old_evac_stats.adjust_desired_plab_sz();
3107 
3108         if (should_start_conc_mark) {
3109           // We have to do this before we notify the CM threads that
3110           // they can start working to make sure that all the
3111           // appropriate initialization is done on the CM object.
3112           concurrent_mark()->post_initial_mark();
3113           // Note that we don't actually trigger the CM thread at
3114           // this point. We do that later when we're sure that
3115           // the current thread has completed its logging output.
3116         }
3117 
3118         allocate_dummy_regions();
3119 
3120         _allocator->init_mutator_alloc_regions();
3121 
3122         expand_heap_after_young_collection();
3123 
3124         double sample_end_time_sec = os::elapsedTime();
3125         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3126         policy()->record_collection_pause_end(pause_time_ms);
3127 
3128         _time_of_last_gc_ns = os::javaTimeNanos();
3129       }
3130 
3131       verify_after_young_collection(verify_type);
3132 
3133       gc_epilogue(false);
3134     }
3135 
3136     // Print the remainder of the GC log output.
3137     if (evacuation_failed()) {
3138       log_info(gc)("To-space exhausted");
3139     }
3140 
3141     policy()->print_phases();
3142     heap_transition.print();
3143 
3144     _hrm->verify_optional();
3145     _verifier->verify_region_sets_optional();
3146 
3147     TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
3148     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3149 
3150     print_heap_after_gc();
3151     print_heap_regions();
3152     trace_heap_after_gc(_gc_tracer_stw);
3153 
3154     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3155     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3156     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3157     // before any GC notifications are raised.
3158     g1mm()->update_sizes();
3159 
3160     _gc_tracer_stw->report_evacuation_info(&evacuation_info);
3161     _gc_tracer_stw->report_tenuring_threshold(_policy->tenuring_threshold());
3162     _gc_timer_stw->register_gc_end();
3163     _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
3164   }
3165   // It should now be safe to tell the concurrent mark thread to start
3166   // without its logging output interfering with the logging output
3167   // that came from the pause.
3168 
3169   if (should_start_conc_mark) {
3170     // CAUTION: after the doConcurrentMark() call below, the concurrent marking
3171     // thread(s) could be running concurrently with us. Make sure that anything
3172     // after this point does not assume that we are the only GC thread running.
3173     // Note: of course, the actual marking work will not start until the safepoint
3174     // itself is released in SuspendibleThreadSet::desynchronize().
3175     do_concurrent_mark();
3176     ConcurrentGCBreakpoints::notify_idle_to_active();
3177   }
3178 }
3179 
3180 void G1CollectedHeap::remove_self_forwarding_pointers(G1RedirtyCardsQueueSet* rdcqs) {
3181   G1ParRemoveSelfForwardPtrsTask rsfp_task(rdcqs);
3182   workers()->run_task(&rsfp_task);
3183 }
3184 
3185 void G1CollectedHeap::restore_after_evac_failure(G1RedirtyCardsQueueSet* rdcqs) {
3186   double remove_self_forwards_start = os::elapsedTime();
3187 
3188   remove_self_forwarding_pointers(rdcqs);
3189   _preserved_marks_set.restore(workers());
3190 
3191   phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
3192 }
3193 
3194 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markWord m) {
3195   if (!_evacuation_failed) {
3196     _evacuation_failed = true;
3197   }
3198 
3199   _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size());
3200   _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m);
3201 }
3202 
3203 bool G1ParEvacuateFollowersClosure::offer_termination() {
3204   EventGCPhaseParallel event;
3205   G1ParScanThreadState* const pss = par_scan_state();
3206   start_term_time();
3207   const bool res = terminator()->offer_termination();
3208   end_term_time();
3209   event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(G1GCPhaseTimes::Termination));
3210   return res;
3211 }
3212 
3213 void G1ParEvacuateFollowersClosure::do_void() {
3214   EventGCPhaseParallel event;
3215   G1ParScanThreadState* const pss = par_scan_state();
3216   pss->trim_queue();
3217   event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(_phase));
3218   do {
3219     EventGCPhaseParallel event;
3220     pss->steal_and_trim_queue(queues());
3221     event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(_phase));
3222   } while (!offer_termination());
3223 }
3224 
3225 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive,
3226                                         bool class_unloading_occurred) {
3227   uint num_workers = workers()->active_workers();
3228   G1ParallelCleaningTask unlink_task(is_alive, num_workers, class_unloading_occurred, false);
3229   workers()->run_task(&unlink_task);
3230 }
3231 
3232 // Clean string dedup data structures.
3233 // Ideally we would prefer to use a StringDedupCleaningTask here, but we want to
3234 // record the durations of the phases. Hence the almost-copy.
3235 class G1StringDedupCleaningTask : public AbstractGangTask {
3236   BoolObjectClosure* _is_alive;
3237   OopClosure* _keep_alive;
3238   G1GCPhaseTimes* _phase_times;
3239 
3240 public:
3241   G1StringDedupCleaningTask(BoolObjectClosure* is_alive,
3242                             OopClosure* keep_alive,
3243                             G1GCPhaseTimes* phase_times) :
3244     AbstractGangTask("Partial Cleaning Task"),
3245     _is_alive(is_alive),
3246     _keep_alive(keep_alive),
3247     _phase_times(phase_times)
3248   {
3249     assert(G1StringDedup::is_enabled(), "String deduplication disabled.");
3250     StringDedup::gc_prologue(true);
3251   }
3252 
3253   ~G1StringDedupCleaningTask() {
3254     StringDedup::gc_epilogue();
3255   }
3256 
3257   void work(uint worker_id) {
3258     StringDedupUnlinkOrOopsDoClosure cl(_is_alive, _keep_alive);
3259     {
3260       G1GCParPhaseTimesTracker x(_phase_times, G1GCPhaseTimes::StringDedupQueueFixup, worker_id);
3261       StringDedupQueue::unlink_or_oops_do(&cl);
3262     }
3263     {
3264       G1GCParPhaseTimesTracker x(_phase_times, G1GCPhaseTimes::StringDedupTableFixup, worker_id);
3265       StringDedupTable::unlink_or_oops_do(&cl, worker_id);
3266     }
3267   }
3268 };
3269 
3270 void G1CollectedHeap::string_dedup_cleaning(BoolObjectClosure* is_alive,
3271                                             OopClosure* keep_alive,
3272                                             G1GCPhaseTimes* phase_times) {
3273   G1StringDedupCleaningTask cl(is_alive, keep_alive, phase_times);
3274   workers()->run_task(&cl);
3275 }
3276 
3277 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
3278  private:
3279   G1RedirtyCardsQueueSet* _qset;
3280   G1CollectedHeap* _g1h;
3281   BufferNode* volatile _nodes;
3282 
3283   void par_apply(RedirtyLoggedCardTableEntryClosure* cl, uint worker_id) {
3284     size_t buffer_size = _qset->buffer_size();
3285     BufferNode* next = Atomic::load(&_nodes);
3286     while (next != NULL) {
3287       BufferNode* node = next;
3288       next = Atomic::cmpxchg(&_nodes, node, node->next());
3289       if (next == node) {
3290         cl->apply_to_buffer(node, buffer_size, worker_id);
3291         next = node->next();
3292       }
3293     }
3294   }
3295 
3296  public:
3297   G1RedirtyLoggedCardsTask(G1RedirtyCardsQueueSet* qset, G1CollectedHeap* g1h) :
3298     AbstractGangTask("Redirty Cards"),
3299     _qset(qset), _g1h(g1h), _nodes(qset->all_completed_buffers()) { }
3300 
3301   virtual void work(uint worker_id) {
3302     G1GCPhaseTimes* p = _g1h->phase_times();
3303     G1GCParPhaseTimesTracker x(p, G1GCPhaseTimes::RedirtyCards, worker_id);
3304 
3305     RedirtyLoggedCardTableEntryClosure cl(_g1h);
3306     par_apply(&cl, worker_id);
3307 
3308     p->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied());
3309   }
3310 };
3311 
3312 void G1CollectedHeap::redirty_logged_cards(G1RedirtyCardsQueueSet* rdcqs) {
3313   double redirty_logged_cards_start = os::elapsedTime();
3314 
3315   G1RedirtyLoggedCardsTask redirty_task(rdcqs, this);
3316   workers()->run_task(&redirty_task);
3317 
3318   G1DirtyCardQueueSet& dcq = G1BarrierSet::dirty_card_queue_set();
3319   dcq.merge_bufferlists(rdcqs);
3320 
3321   phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
3322 }
3323 
3324 // Weak Reference Processing support
3325 
3326 bool G1STWIsAliveClosure::do_object_b(oop p) {
3327   // An object is reachable if it is outside the collection set,
3328   // or is inside and copied.
3329   return !_g1h->is_in_cset(p) || p->is_forwarded();
3330 }
3331 
3332 bool G1STWSubjectToDiscoveryClosure::do_object_b(oop obj) {
3333   assert(obj != NULL, "must not be NULL");
3334   assert(_g1h->is_in_reserved(obj), "Trying to discover obj " PTR_FORMAT " not in heap", p2i(obj));
3335   // The areas the CM and STW ref processor manage must be disjoint. The is_in_cset() below
3336   // may falsely indicate that this is not the case here: however the collection set only
3337   // contains old regions when concurrent mark is not running.
3338   return _g1h->is_in_cset(obj) || _g1h->heap_region_containing(obj)->is_survivor();
3339 }
3340 
3341 // Non Copying Keep Alive closure
3342 class G1KeepAliveClosure: public OopClosure {
3343   G1CollectedHeap*_g1h;
3344 public:
3345   G1KeepAliveClosure(G1CollectedHeap* g1h) :_g1h(g1h) {}
3346   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
3347   void do_oop(oop* p) {
3348     oop obj = *p;
3349     assert(obj != NULL, "the caller should have filtered out NULL values");
3350 
3351     const G1HeapRegionAttr region_attr =_g1h->region_attr(obj);
3352     if (!region_attr.is_in_cset_or_humongous()) {
3353       return;
3354     }
3355     if (region_attr.is_in_cset()) {
3356       assert( obj->is_forwarded(), "invariant" );
3357       *p = obj->forwardee();
3358     } else {
3359       assert(!obj->is_forwarded(), "invariant" );
3360       assert(region_attr.is_humongous(),
3361              "Only allowed G1HeapRegionAttr state is IsHumongous, but is %d", region_attr.type());
3362      _g1h->set_humongous_is_live(obj);
3363     }
3364   }
3365 };
3366 
3367 // Copying Keep Alive closure - can be called from both
3368 // serial and parallel code as long as different worker
3369 // threads utilize different G1ParScanThreadState instances
3370 // and different queues.
3371 
3372 class G1CopyingKeepAliveClosure: public OopClosure {
3373   G1CollectedHeap*         _g1h;
3374   G1ParScanThreadState*    _par_scan_state;
3375 
3376 public:
3377   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
3378                             G1ParScanThreadState* pss):
3379     _g1h(g1h),
3380     _par_scan_state(pss)
3381   {}
3382 
3383   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
3384   virtual void do_oop(      oop* p) { do_oop_work(p); }
3385 
3386   template <class T> void do_oop_work(T* p) {
3387     oop obj = RawAccess<>::oop_load(p);
3388 
3389     if (_g1h->is_in_cset_or_humongous(obj)) {
3390       // If the referent object has been forwarded (either copied
3391       // to a new location or to itself in the event of an
3392       // evacuation failure) then we need to update the reference
3393       // field and, if both reference and referent are in the G1
3394       // heap, update the RSet for the referent.
3395       //
3396       // If the referent has not been forwarded then we have to keep
3397       // it alive by policy. Therefore we have copy the referent.
3398       //
3399       // When the queue is drained (after each phase of reference processing)
3400       // the object and it's followers will be copied, the reference field set
3401       // to point to the new location, and the RSet updated.
3402       _par_scan_state->push_on_queue(ScannerTask(p));
3403     }
3404   }
3405 };
3406 
3407 // Serial drain queue closure. Called as the 'complete_gc'
3408 // closure for each discovered list in some of the
3409 // reference processing phases.
3410 
3411 class G1STWDrainQueueClosure: public VoidClosure {
3412 protected:
3413   G1CollectedHeap* _g1h;
3414   G1ParScanThreadState* _par_scan_state;
3415 
3416   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
3417 
3418 public:
3419   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
3420     _g1h(g1h),
3421     _par_scan_state(pss)
3422   { }
3423 
3424   void do_void() {
3425     G1ParScanThreadState* const pss = par_scan_state();
3426     pss->trim_queue();
3427   }
3428 };
3429 
3430 // Parallel Reference Processing closures
3431 
3432 // Implementation of AbstractRefProcTaskExecutor for parallel reference
3433 // processing during G1 evacuation pauses.
3434 
3435 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
3436 private:
3437   G1CollectedHeap*          _g1h;
3438   G1ParScanThreadStateSet*  _pss;
3439   G1ScannerTasksQueueSet*   _queues;
3440   WorkGang*                 _workers;
3441 
3442 public:
3443   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
3444                            G1ParScanThreadStateSet* per_thread_states,
3445                            WorkGang* workers,
3446                            G1ScannerTasksQueueSet *task_queues) :
3447     _g1h(g1h),
3448     _pss(per_thread_states),
3449     _queues(task_queues),
3450     _workers(workers)
3451   {
3452     g1h->ref_processor_stw()->set_active_mt_degree(workers->active_workers());
3453   }
3454 
3455   // Executes the given task using concurrent marking worker threads.
3456   virtual void execute(ProcessTask& task, uint ergo_workers);
3457 };
3458 
3459 // Gang task for possibly parallel reference processing
3460 
3461 class G1STWRefProcTaskProxy: public AbstractGangTask {
3462   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
3463   ProcessTask&     _proc_task;
3464   G1CollectedHeap* _g1h;
3465   G1ParScanThreadStateSet* _pss;
3466   G1ScannerTasksQueueSet* _task_queues;
3467   TaskTerminator* _terminator;
3468 
3469 public:
3470   G1STWRefProcTaskProxy(ProcessTask& proc_task,
3471                         G1CollectedHeap* g1h,
3472                         G1ParScanThreadStateSet* per_thread_states,
3473                         G1ScannerTasksQueueSet *task_queues,
3474                         TaskTerminator* terminator) :
3475     AbstractGangTask("Process reference objects in parallel"),
3476     _proc_task(proc_task),
3477     _g1h(g1h),
3478     _pss(per_thread_states),
3479     _task_queues(task_queues),
3480     _terminator(terminator)
3481   {}
3482 
3483   virtual void work(uint worker_id) {
3484     // The reference processing task executed by a single worker.
3485     ResourceMark rm;
3486     HandleMark   hm;
3487 
3488     G1STWIsAliveClosure is_alive(_g1h);
3489 
3490     G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
3491     pss->set_ref_discoverer(NULL);
3492 
3493     // Keep alive closure.
3494     G1CopyingKeepAliveClosure keep_alive(_g1h, pss);
3495 
3496     // Complete GC closure
3497     G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator, G1GCPhaseTimes::ObjCopy);
3498 
3499     // Call the reference processing task's work routine.
3500     _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
3501 
3502     // Note we cannot assert that the refs array is empty here as not all
3503     // of the processing tasks (specifically phase2 - pp2_work) execute
3504     // the complete_gc closure (which ordinarily would drain the queue) so
3505     // the queue may not be empty.
3506   }
3507 };
3508 
3509 // Driver routine for parallel reference processing.
3510 // Creates an instance of the ref processing gang
3511 // task and has the worker threads execute it.
3512 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task, uint ergo_workers) {
3513   assert(_workers != NULL, "Need parallel worker threads.");
3514 
3515   assert(_workers->active_workers() >= ergo_workers,
3516          "Ergonomically chosen workers (%u) should be less than or equal to active workers (%u)",
3517          ergo_workers, _workers->active_workers());
3518   TaskTerminator terminator(ergo_workers, _queues);
3519   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator);
3520 
3521   _workers->run_task(&proc_task_proxy, ergo_workers);
3522 }
3523 
3524 // End of weak reference support closures
3525 
3526 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
3527   double ref_proc_start = os::elapsedTime();
3528 
3529   ReferenceProcessor* rp = _ref_processor_stw;
3530   assert(rp->discovery_enabled(), "should have been enabled");
3531 
3532   // Closure to test whether a referent is alive.
3533   G1STWIsAliveClosure is_alive(this);
3534 
3535   // Even when parallel reference processing is enabled, the processing
3536   // of JNI refs is serial and performed serially by the current thread
3537   // rather than by a worker. The following PSS will be used for processing
3538   // JNI refs.
3539 
3540   // Use only a single queue for this PSS.
3541   G1ParScanThreadState*          pss = per_thread_states->state_for_worker(0);
3542   pss->set_ref_discoverer(NULL);
3543   assert(pss->queue_is_empty(), "pre-condition");
3544 
3545   // Keep alive closure.
3546   G1CopyingKeepAliveClosure keep_alive(this, pss);
3547 
3548   // Serial Complete GC closure
3549   G1STWDrainQueueClosure drain_queue(this, pss);
3550 
3551   // Setup the soft refs policy...
3552   rp->setup_policy(false);
3553 
3554   ReferenceProcessorPhaseTimes* pt = phase_times()->ref_phase_times();
3555 
3556   ReferenceProcessorStats stats;
3557   if (!rp->processing_is_mt()) {
3558     // Serial reference processing...
3559     stats = rp->process_discovered_references(&is_alive,
3560                                               &keep_alive,
3561                                               &drain_queue,
3562                                               NULL,
3563                                               pt);
3564   } else {
3565     uint no_of_gc_workers = workers()->active_workers();
3566 
3567     // Parallel reference processing
3568     assert(no_of_gc_workers <= rp->max_num_queues(),
3569            "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
3570            no_of_gc_workers,  rp->max_num_queues());
3571 
3572     G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues);
3573     stats = rp->process_discovered_references(&is_alive,
3574                                               &keep_alive,
3575                                               &drain_queue,
3576                                               &par_task_executor,
3577                                               pt);
3578   }
3579 
3580   _gc_tracer_stw->report_gc_reference_stats(stats);
3581 
3582   // We have completed copying any necessary live referent objects.
3583   assert(pss->queue_is_empty(), "both queue and overflow should be empty");
3584 
3585   make_pending_list_reachable();
3586 
3587   assert(!rp->discovery_enabled(), "Postcondition");
3588   rp->verify_no_references_recorded();
3589 
3590   double ref_proc_time = os::elapsedTime() - ref_proc_start;
3591   phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
3592 }
3593 
3594 void G1CollectedHeap::make_pending_list_reachable() {
3595   if (collector_state()->in_initial_mark_gc()) {
3596     oop pll_head = Universe::reference_pending_list();
3597     if (pll_head != NULL) {
3598       // Any valid worker id is fine here as we are in the VM thread and single-threaded.
3599       _cm->mark_in_next_bitmap(0 /* worker_id */, pll_head);
3600     }
3601   }
3602 }
3603 
3604 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) {
3605   Ticks start = Ticks::now();
3606   per_thread_states->flush();
3607   phase_times()->record_or_add_time_secs(G1GCPhaseTimes::MergePSS, 0 /* worker_id */, (Ticks::now() - start).seconds());
3608 }
3609 
3610 class G1PrepareEvacuationTask : public AbstractGangTask {
3611   class G1PrepareRegionsClosure : public HeapRegionClosure {
3612     G1CollectedHeap* _g1h;
3613     G1PrepareEvacuationTask* _parent_task;
3614     size_t _worker_humongous_total;
3615     size_t _worker_humongous_candidates;
3616 
3617     bool humongous_region_is_candidate(HeapRegion* region) const {
3618       assert(region->is_starts_humongous(), "Must start a humongous object");
3619 
3620       oop obj = oop(region->bottom());
3621 
3622       // Dead objects cannot be eager reclaim candidates. Due to class
3623       // unloading it is unsafe to query their classes so we return early.
3624       if (_g1h->is_obj_dead(obj, region)) {
3625         return false;
3626       }
3627 
3628       // If we do not have a complete remembered set for the region, then we can
3629       // not be sure that we have all references to it.
3630       if (!region->rem_set()->is_complete()) {
3631         return false;
3632       }
3633       // Candidate selection must satisfy the following constraints
3634       // while concurrent marking is in progress:
3635       //
3636       // * In order to maintain SATB invariants, an object must not be
3637       // reclaimed if it was allocated before the start of marking and
3638       // has not had its references scanned.  Such an object must have
3639       // its references (including type metadata) scanned to ensure no
3640       // live objects are missed by the marking process.  Objects
3641       // allocated after the start of concurrent marking don't need to
3642       // be scanned.
3643       //
3644       // * An object must not be reclaimed if it is on the concurrent
3645       // mark stack.  Objects allocated after the start of concurrent
3646       // marking are never pushed on the mark stack.
3647       //
3648       // Nominating only objects allocated after the start of concurrent
3649       // marking is sufficient to meet both constraints.  This may miss
3650       // some objects that satisfy the constraints, but the marking data
3651       // structures don't support efficiently performing the needed
3652       // additional tests or scrubbing of the mark stack.
3653       //
3654       // However, we presently only nominate is_typeArray() objects.
3655       // A humongous object containing references induces remembered
3656       // set entries on other regions.  In order to reclaim such an
3657       // object, those remembered sets would need to be cleaned up.
3658       //
3659       // We also treat is_typeArray() objects specially, allowing them
3660       // to be reclaimed even if allocated before the start of
3661       // concurrent mark.  For this we rely on mark stack insertion to
3662       // exclude is_typeArray() objects, preventing reclaiming an object
3663       // that is in the mark stack.  We also rely on the metadata for
3664       // such objects to be built-in and so ensured to be kept live.
3665       // Frequent allocation and drop of large binary blobs is an
3666       // important use case for eager reclaim, and this special handling
3667       // may reduce needed headroom.
3668 
3669       return obj->is_typeArray() &&
3670              _g1h->is_potential_eager_reclaim_candidate(region);
3671     }
3672 
3673   public:
3674     G1PrepareRegionsClosure(G1CollectedHeap* g1h, G1PrepareEvacuationTask* parent_task) :
3675       _g1h(g1h),
3676       _parent_task(parent_task),
3677       _worker_humongous_total(0),
3678       _worker_humongous_candidates(0) { }
3679 
3680     ~G1PrepareRegionsClosure() {
3681       _parent_task->add_humongous_candidates(_worker_humongous_candidates);
3682       _parent_task->add_humongous_total(_worker_humongous_total);
3683     }
3684 
3685     virtual bool do_heap_region(HeapRegion* hr) {
3686       // First prepare the region for scanning
3687       _g1h->rem_set()->prepare_region_for_scan(hr);
3688 
3689       // Now check if region is a humongous candidate
3690       if (!hr->is_starts_humongous()) {
3691         _g1h->register_region_with_region_attr(hr);
3692         return false;
3693       }
3694 
3695       uint index = hr->hrm_index();
3696       if (humongous_region_is_candidate(hr)) {
3697         _g1h->set_humongous_reclaim_candidate(index, true);
3698         _g1h->register_humongous_region_with_region_attr(index);
3699         _worker_humongous_candidates++;
3700         // We will later handle the remembered sets of these regions.
3701       } else {
3702         _g1h->set_humongous_reclaim_candidate(index, false);
3703         _g1h->register_region_with_region_attr(hr);
3704       }
3705       _worker_humongous_total++;
3706 
3707       return false;
3708     }
3709   };
3710 
3711   G1CollectedHeap* _g1h;
3712   HeapRegionClaimer _claimer;
3713   volatile size_t _humongous_total;
3714   volatile size_t _humongous_candidates;
3715 public:
3716   G1PrepareEvacuationTask(G1CollectedHeap* g1h) :
3717     AbstractGangTask("Prepare Evacuation"),
3718     _g1h(g1h),
3719     _claimer(_g1h->workers()->active_workers()),
3720     _humongous_total(0),
3721     _humongous_candidates(0) { }
3722 
3723   ~G1PrepareEvacuationTask() {
3724     _g1h->set_has_humongous_reclaim_candidate(_humongous_candidates > 0);
3725   }
3726 
3727   void work(uint worker_id) {
3728     G1PrepareRegionsClosure cl(_g1h, this);
3729     _g1h->heap_region_par_iterate_from_worker_offset(&cl, &_claimer, worker_id);
3730   }
3731 
3732   void add_humongous_candidates(size_t candidates) {
3733     Atomic::add(&_humongous_candidates, candidates);
3734   }
3735 
3736   void add_humongous_total(size_t total) {
3737     Atomic::add(&_humongous_total, total);
3738   }
3739 
3740   size_t humongous_candidates() {
3741     return _humongous_candidates;
3742   }
3743 
3744   size_t humongous_total() {
3745     return _humongous_total;
3746   }
3747 };
3748 
3749 void G1CollectedHeap::pre_evacuate_collection_set(G1EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
3750   _bytes_used_during_gc = 0;
3751 
3752   _expand_heap_after_alloc_failure = true;
3753   _evacuation_failed = false;
3754 
3755   // Disable the hot card cache.
3756   _hot_card_cache->reset_hot_cache_claimed_index();
3757   _hot_card_cache->set_use_cache(false);
3758 
3759   // Initialize the GC alloc regions.
3760   _allocator->init_gc_alloc_regions(evacuation_info);
3761 
3762   {
3763     Ticks start = Ticks::now();
3764     rem_set()->prepare_for_scan_heap_roots();
3765     phase_times()->record_prepare_heap_roots_time_ms((Ticks::now() - start).seconds() * 1000.0);
3766   }
3767 
3768   {
3769     G1PrepareEvacuationTask g1_prep_task(this);
3770     Tickspan task_time = run_task(&g1_prep_task);
3771 
3772     phase_times()->record_register_regions(task_time.seconds() * 1000.0,
3773                                            g1_prep_task.humongous_total(),
3774                                            g1_prep_task.humongous_candidates());
3775   }
3776 
3777   assert(_verifier->check_region_attr_table(), "Inconsistency in the region attributes table.");
3778   _preserved_marks_set.assert_empty();
3779 
3780 #if COMPILER2_OR_JVMCI
3781   DerivedPointerTable::clear();
3782 #endif
3783 
3784   // InitialMark needs claim bits to keep track of the marked-through CLDs.
3785   if (collector_state()->in_initial_mark_gc()) {
3786     concurrent_mark()->pre_initial_mark();
3787 
3788     double start_clear_claimed_marks = os::elapsedTime();
3789 
3790     ClassLoaderDataGraph::clear_claimed_marks();
3791 
3792     double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0;
3793     phase_times()->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms);
3794   }
3795 
3796   // Should G1EvacuationFailureALot be in effect for this GC?
3797   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
3798 }
3799 
3800 class G1EvacuateRegionsBaseTask : public AbstractGangTask {
3801 protected:
3802   G1CollectedHeap* _g1h;
3803   G1ParScanThreadStateSet* _per_thread_states;
3804   G1ScannerTasksQueueSet* _task_queues;
3805   TaskTerminator _terminator;
3806   uint _num_workers;
3807 
3808   void evacuate_live_objects(G1ParScanThreadState* pss,
3809                              uint worker_id,
3810                              G1GCPhaseTimes::GCParPhases objcopy_phase,
3811                              G1GCPhaseTimes::GCParPhases termination_phase) {
3812     G1GCPhaseTimes* p = _g1h->phase_times();
3813 
3814     Ticks start = Ticks::now();
3815     G1ParEvacuateFollowersClosure cl(_g1h, pss, _task_queues, &_terminator, objcopy_phase);
3816     cl.do_void();
3817 
3818     assert(pss->queue_is_empty(), "should be empty");
3819 
3820     Tickspan evac_time = (Ticks::now() - start);
3821     p->record_or_add_time_secs(objcopy_phase, worker_id, evac_time.seconds() - cl.term_time());
3822 
3823     if (termination_phase == G1GCPhaseTimes::Termination) {
3824       p->record_time_secs(termination_phase, worker_id, cl.term_time());
3825       p->record_thread_work_item(termination_phase, worker_id, cl.term_attempts());
3826     } else {
3827       p->record_or_add_time_secs(termination_phase, worker_id, cl.term_time());
3828       p->record_or_add_thread_work_item(termination_phase, worker_id, cl.term_attempts());
3829     }
3830     assert(pss->trim_ticks().seconds() == 0.0, "Unexpected partial trimming during evacuation");
3831   }
3832 
3833   virtual void start_work(uint worker_id) { }
3834 
3835   virtual void end_work(uint worker_id) { }
3836 
3837   virtual void scan_roots(G1ParScanThreadState* pss, uint worker_id) = 0;
3838 
3839   virtual void evacuate_live_objects(G1ParScanThreadState* pss, uint worker_id) = 0;
3840 
3841 public:
3842   G1EvacuateRegionsBaseTask(const char* name,
3843                             G1ParScanThreadStateSet* per_thread_states,
3844                             G1ScannerTasksQueueSet* task_queues,
3845                             uint num_workers) :
3846     AbstractGangTask(name),
3847     _g1h(G1CollectedHeap::heap()),
3848     _per_thread_states(per_thread_states),
3849     _task_queues(task_queues),
3850     _terminator(num_workers, _task_queues),
3851     _num_workers(num_workers)
3852   { }
3853 
3854   void work(uint worker_id) {
3855     start_work(worker_id);
3856 
3857     {
3858       ResourceMark rm;
3859       HandleMark   hm;
3860 
3861       G1ParScanThreadState* pss = _per_thread_states->state_for_worker(worker_id);
3862       pss->set_ref_discoverer(_g1h->ref_processor_stw());
3863 
3864       scan_roots(pss, worker_id);
3865       evacuate_live_objects(pss, worker_id);
3866     }
3867 
3868     end_work(worker_id);
3869   }
3870 };
3871 
3872 class G1EvacuateRegionsTask : public G1EvacuateRegionsBaseTask {
3873   G1RootProcessor* _root_processor;
3874 
3875   void scan_roots(G1ParScanThreadState* pss, uint worker_id) {
3876     _root_processor->evacuate_roots(pss, worker_id);
3877     _g1h->rem_set()->scan_heap_roots(pss, worker_id, G1GCPhaseTimes::ScanHR, G1GCPhaseTimes::ObjCopy);
3878     _g1h->rem_set()->scan_collection_set_regions(pss, worker_id, G1GCPhaseTimes::ScanHR, G1GCPhaseTimes::CodeRoots, G1GCPhaseTimes::ObjCopy);
3879   }
3880 
3881   void evacuate_live_objects(G1ParScanThreadState* pss, uint worker_id) {
3882     G1EvacuateRegionsBaseTask::evacuate_live_objects(pss, worker_id, G1GCPhaseTimes::ObjCopy, G1GCPhaseTimes::Termination);
3883   }
3884 
3885   void start_work(uint worker_id) {
3886     _g1h->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, Ticks::now().seconds());
3887   }
3888 
3889   void end_work(uint worker_id) {
3890     _g1h->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, Ticks::now().seconds());
3891   }
3892 
3893 public:
3894   G1EvacuateRegionsTask(G1CollectedHeap* g1h,
3895                         G1ParScanThreadStateSet* per_thread_states,
3896                         G1ScannerTasksQueueSet* task_queues,
3897                         G1RootProcessor* root_processor,
3898                         uint num_workers) :
3899     G1EvacuateRegionsBaseTask("G1 Evacuate Regions", per_thread_states, task_queues, num_workers),
3900     _root_processor(root_processor)
3901   { }
3902 };
3903 
3904 void G1CollectedHeap::evacuate_initial_collection_set(G1ParScanThreadStateSet* per_thread_states) {
3905   G1GCPhaseTimes* p = phase_times();
3906 
3907   {
3908     Ticks start = Ticks::now();
3909     rem_set()->merge_heap_roots(true /* initial_evacuation */);
3910     p->record_merge_heap_roots_time((Ticks::now() - start).seconds() * 1000.0);
3911   }
3912 
3913   Tickspan task_time;
3914   const uint num_workers = workers()->active_workers();
3915 
3916   Ticks start_processing = Ticks::now();
3917   {
3918     G1RootProcessor root_processor(this, num_workers);
3919     G1EvacuateRegionsTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, num_workers);
3920     task_time = run_task(&g1_par_task);
3921     // Closing the inner scope will execute the destructor for the G1RootProcessor object.
3922     // To extract its code root fixup time we measure total time of this scope and
3923     // subtract from the time the WorkGang task took.
3924   }
3925   Tickspan total_processing = Ticks::now() - start_processing;
3926 
3927   p->record_initial_evac_time(task_time.seconds() * 1000.0);
3928   p->record_or_add_code_root_fixup_time((total_processing - task_time).seconds() * 1000.0);
3929 }
3930 
3931 class G1EvacuateOptionalRegionsTask : public G1EvacuateRegionsBaseTask {
3932 
3933   void scan_roots(G1ParScanThreadState* pss, uint worker_id) {
3934     _g1h->rem_set()->scan_heap_roots(pss, worker_id, G1GCPhaseTimes::OptScanHR, G1GCPhaseTimes::OptObjCopy);
3935     _g1h->rem_set()->scan_collection_set_regions(pss, worker_id, G1GCPhaseTimes::OptScanHR, G1GCPhaseTimes::OptCodeRoots, G1GCPhaseTimes::OptObjCopy);
3936   }
3937 
3938   void evacuate_live_objects(G1ParScanThreadState* pss, uint worker_id) {
3939     G1EvacuateRegionsBaseTask::evacuate_live_objects(pss, worker_id, G1GCPhaseTimes::OptObjCopy, G1GCPhaseTimes::OptTermination);
3940   }
3941 
3942 public:
3943   G1EvacuateOptionalRegionsTask(G1ParScanThreadStateSet* per_thread_states,
3944                                 G1ScannerTasksQueueSet* queues,
3945                                 uint num_workers) :
3946     G1EvacuateRegionsBaseTask("G1 Evacuate Optional Regions", per_thread_states, queues, num_workers) {
3947   }
3948 };
3949 
3950 void G1CollectedHeap::evacuate_next_optional_regions(G1ParScanThreadStateSet* per_thread_states) {
3951   class G1MarkScope : public MarkScope { };
3952 
3953   Tickspan task_time;
3954 
3955   Ticks start_processing = Ticks::now();
3956   {
3957     G1MarkScope code_mark_scope;
3958     G1EvacuateOptionalRegionsTask task(per_thread_states, _task_queues, workers()->active_workers());
3959     task_time = run_task(&task);
3960     // See comment in evacuate_collection_set() for the reason of the scope.
3961   }
3962   Tickspan total_processing = Ticks::now() - start_processing;
3963 
3964   G1GCPhaseTimes* p = phase_times();
3965   p->record_or_add_code_root_fixup_time((total_processing - task_time).seconds() * 1000.0);
3966 }
3967 
3968 void G1CollectedHeap::evacuate_optional_collection_set(G1ParScanThreadStateSet* per_thread_states) {
3969   const double gc_start_time_ms = phase_times()->cur_collection_start_sec() * 1000.0;
3970 
3971   while (!evacuation_failed() && _collection_set.optional_region_length() > 0) {
3972 
3973     double time_used_ms = os::elapsedTime() * 1000.0 - gc_start_time_ms;
3974     double time_left_ms = MaxGCPauseMillis - time_used_ms;
3975 
3976     if (time_left_ms < 0 ||
3977         !_collection_set.finalize_optional_for_evacuation(time_left_ms * policy()->optional_evacuation_fraction())) {
3978       log_trace(gc, ergo, cset)("Skipping evacuation of %u optional regions, no more regions can be evacuated in %.3fms",
3979                                 _collection_set.optional_region_length(), time_left_ms);
3980       break;
3981     }
3982 
3983     {
3984       Ticks start = Ticks::now();
3985       rem_set()->merge_heap_roots(false /* initial_evacuation */);
3986       phase_times()->record_or_add_optional_merge_heap_roots_time((Ticks::now() - start).seconds() * 1000.0);
3987     }
3988 
3989     {
3990       Ticks start = Ticks::now();
3991       evacuate_next_optional_regions(per_thread_states);
3992       phase_times()->record_or_add_optional_evac_time((Ticks::now() - start).seconds() * 1000.0);
3993     }
3994   }
3995 
3996   _collection_set.abandon_optional_collection_set(per_thread_states);
3997 }
3998 
3999 void G1CollectedHeap::post_evacuate_collection_set(G1EvacuationInfo& evacuation_info,
4000                                                    G1RedirtyCardsQueueSet* rdcqs,
4001                                                    G1ParScanThreadStateSet* per_thread_states) {
4002   G1GCPhaseTimes* p = phase_times();
4003 
4004   rem_set()->cleanup_after_scan_heap_roots();
4005 
4006   // Process any discovered reference objects - we have
4007   // to do this _before_ we retire the GC alloc regions
4008   // as we may have to copy some 'reachable' referent
4009   // objects (and their reachable sub-graphs) that were
4010   // not copied during the pause.
4011   process_discovered_references(per_thread_states);
4012 
4013   G1STWIsAliveClosure is_alive(this);
4014   G1KeepAliveClosure keep_alive(this);
4015 
4016   WeakProcessor::weak_oops_do(workers(), &is_alive, &keep_alive, p->weak_phase_times());
4017 
4018   if (G1StringDedup::is_enabled()) {
4019     double string_dedup_time_ms = os::elapsedTime();
4020 
4021     string_dedup_cleaning(&is_alive, &keep_alive, p);
4022 
4023     double string_cleanup_time_ms = (os::elapsedTime() - string_dedup_time_ms) * 1000.0;
4024     p->record_string_deduplication_time(string_cleanup_time_ms);
4025   }
4026 
4027   _allocator->release_gc_alloc_regions(evacuation_info);
4028 
4029   if (evacuation_failed()) {
4030     restore_after_evac_failure(rdcqs);
4031 
4032     // Reset the G1EvacuationFailureALot counters and flags
4033     NOT_PRODUCT(reset_evacuation_should_fail();)
4034 
4035     double recalculate_used_start = os::elapsedTime();
4036     set_used(recalculate_used());
4037     p->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
4038 
4039     if (_archive_allocator != NULL) {
4040       _archive_allocator->clear_used();
4041     }
4042     for (uint i = 0; i < ParallelGCThreads; i++) {
4043       if (_evacuation_failed_info_array[i].has_failed()) {
4044         _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
4045       }
4046     }
4047   } else {
4048     // The "used" of the the collection set have already been subtracted
4049     // when they were freed.  Add in the bytes used.
4050     increase_used(_bytes_used_during_gc);
4051   }
4052 
4053   _preserved_marks_set.assert_empty();
4054 
4055   merge_per_thread_state_info(per_thread_states);
4056 
4057   // Reset and re-enable the hot card cache.
4058   // Note the counts for the cards in the regions in the
4059   // collection set are reset when the collection set is freed.
4060   _hot_card_cache->reset_hot_cache();
4061   _hot_card_cache->set_use_cache(true);
4062 
4063   purge_code_root_memory();
4064 
4065   redirty_logged_cards(rdcqs);
4066 
4067   free_collection_set(&_collection_set, evacuation_info, per_thread_states->surviving_young_words());
4068 
4069   eagerly_reclaim_humongous_regions();
4070 
4071   record_obj_copy_mem_stats();
4072 
4073   evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before());
4074   evacuation_info.set_bytes_used(_bytes_used_during_gc);
4075 
4076 #if COMPILER2_OR_JVMCI
4077   double start = os::elapsedTime();
4078   DerivedPointerTable::update_pointers();
4079   phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0);
4080 #endif
4081   policy()->print_age_table();
4082 }
4083 
4084 void G1CollectedHeap::record_obj_copy_mem_stats() {
4085   policy()->old_gen_alloc_tracker()->
4086     add_allocated_bytes_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
4087 
4088   _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
4089                                                create_g1_evac_summary(&_old_evac_stats));
4090 }
4091 
4092 void G1CollectedHeap::free_region(HeapRegion* hr, FreeRegionList* free_list) {
4093   assert(!hr->is_free(), "the region should not be free");
4094   assert(!hr->is_empty(), "the region should not be empty");
4095   assert(_hrm->is_available(hr->hrm_index()), "region should be committed");
4096 
4097   if (G1VerifyBitmaps) {
4098     MemRegion mr(hr->bottom(), hr->end());
4099     concurrent_mark()->clear_range_in_prev_bitmap(mr);
4100   }
4101 
4102   // Clear the card counts for this region.
4103   // Note: we only need to do this if the region is not young
4104   // (since we don't refine cards in young regions).
4105   if (!hr->is_young()) {
4106     _hot_card_cache->reset_card_counts(hr);
4107   }
4108 
4109   // Reset region metadata to allow reuse.
4110   hr->hr_clear(true /* clear_space */);
4111   _policy->remset_tracker()->update_at_free(hr);
4112 
4113   if (free_list != NULL) {
4114     free_list->add_ordered(hr);
4115   }
4116 }
4117 
4118 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
4119                                             FreeRegionList* free_list) {
4120   assert(hr->is_humongous(), "this is only for humongous regions");
4121   assert(free_list != NULL, "pre-condition");
4122   hr->clear_humongous();
4123   free_region(hr, free_list);
4124 }
4125 
4126 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed,
4127                                            const uint humongous_regions_removed) {
4128   if (old_regions_removed > 0 || humongous_regions_removed > 0) {
4129     MutexLocker x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4130     _old_set.bulk_remove(old_regions_removed);
4131     _humongous_set.bulk_remove(humongous_regions_removed);
4132   }
4133 
4134 }
4135 
4136 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
4137   assert(list != NULL, "list can't be null");
4138   if (!list->is_empty()) {
4139     MutexLocker x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4140     _hrm->insert_list_into_free_list(list);
4141   }
4142 }
4143 
4144 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
4145   decrease_used(bytes);
4146 }
4147 
4148 class G1FreeCollectionSetTask : public AbstractGangTask {
4149   // Helper class to keep statistics for the collection set freeing
4150   class FreeCSetStats {
4151     size_t _before_used_bytes;   // Usage in regions successfully evacutate
4152     size_t _after_used_bytes;    // Usage in regions failing evacuation
4153     size_t _bytes_allocated_in_old_since_last_gc; // Size of young regions turned into old
4154     size_t _failure_used_words;  // Live size in failed regions
4155     size_t _failure_waste_words; // Wasted size in failed regions
4156     size_t _rs_length;           // Remembered set size
4157     uint _regions_freed;         // Number of regions freed
4158   public:
4159     FreeCSetStats() :
4160         _before_used_bytes(0),
4161         _after_used_bytes(0),
4162         _bytes_allocated_in_old_since_last_gc(0),
4163         _failure_used_words(0),
4164         _failure_waste_words(0),
4165         _rs_length(0),
4166         _regions_freed(0) { }
4167 
4168     void merge_stats(FreeCSetStats* other) {
4169       assert(other != NULL, "invariant");
4170       _before_used_bytes += other->_before_used_bytes;
4171       _after_used_bytes += other->_after_used_bytes;
4172       _bytes_allocated_in_old_since_last_gc += other->_bytes_allocated_in_old_since_last_gc;
4173       _failure_used_words += other->_failure_used_words;
4174       _failure_waste_words += other->_failure_waste_words;
4175       _rs_length += other->_rs_length;
4176       _regions_freed += other->_regions_freed;
4177     }
4178 
4179     void report(G1CollectedHeap* g1h, G1EvacuationInfo* evacuation_info) {
4180       evacuation_info->set_regions_freed(_regions_freed);
4181       evacuation_info->increment_collectionset_used_after(_after_used_bytes);
4182 
4183       g1h->decrement_summary_bytes(_before_used_bytes);
4184       g1h->alloc_buffer_stats(G1HeapRegionAttr::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words);
4185 
4186       G1Policy *policy = g1h->policy();
4187       policy->old_gen_alloc_tracker()->add_allocated_bytes_since_last_gc(_bytes_allocated_in_old_since_last_gc);
4188       policy->record_rs_length(_rs_length);
4189       policy->cset_regions_freed();
4190     }
4191 
4192     void account_failed_region(HeapRegion* r) {
4193       size_t used_words = r->marked_bytes() / HeapWordSize;
4194       _failure_used_words += used_words;
4195       _failure_waste_words += HeapRegion::GrainWords - used_words;
4196       _after_used_bytes += r->used();
4197 
4198       // When moving a young gen region to old gen, we "allocate" that whole
4199       // region there. This is in addition to any already evacuated objects.
4200       // Notify the policy about that. Old gen regions do not cause an
4201       // additional allocation: both the objects still in the region and the
4202       // ones already moved are accounted for elsewhere.
4203       if (r->is_young()) {
4204         _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes;
4205       }
4206     }
4207 
4208     void account_evacuated_region(HeapRegion* r) {
4209       _before_used_bytes += r->used();
4210       _regions_freed += 1;
4211     }
4212 
4213     void account_rs_length(HeapRegion* r) {
4214       _rs_length += r->rem_set()->occupied();
4215     }
4216   };
4217 
4218   // Closure applied to all regions in the collection set.
4219   class FreeCSetClosure : public HeapRegionClosure {
4220     // Helper to send JFR events for regions.
4221     class JFREventForRegion {
4222       EventGCPhaseParallel _event;
4223     public:
4224       JFREventForRegion(HeapRegion* region, uint worker_id) : _event() {
4225         _event.set_gcId(GCId::current());
4226         _event.set_gcWorkerId(worker_id);
4227         if (region->is_young()) {
4228           _event.set_name(G1GCPhaseTimes::phase_name(G1GCPhaseTimes::YoungFreeCSet));
4229         } else {
4230           _event.set_name(G1GCPhaseTimes::phase_name(G1GCPhaseTimes::NonYoungFreeCSet));
4231         }
4232       }
4233 
4234       ~JFREventForRegion() {
4235         _event.commit();
4236       }
4237     };
4238 
4239     // Helper to do timing for region work.
4240     class TimerForRegion {
4241       Tickspan& _time;
4242       Ticks     _start_time;
4243     public:
4244       TimerForRegion(Tickspan& time) : _time(time), _start_time(Ticks::now()) { }
4245       ~TimerForRegion() {
4246         _time += Ticks::now() - _start_time;
4247       }
4248     };
4249 
4250     // FreeCSetClosure members
4251     G1CollectedHeap* _g1h;
4252     const size_t*    _surviving_young_words;
4253     uint             _worker_id;
4254     Tickspan         _young_time;
4255     Tickspan         _non_young_time;
4256     FreeCSetStats*   _stats;
4257 
4258     void assert_in_cset(HeapRegion* r) {
4259       assert(r->young_index_in_cset() != 0 &&
4260              (uint)r->young_index_in_cset() <= _g1h->collection_set()->young_region_length(),
4261              "Young index %u is wrong for region %u of type %s with %u young regions",
4262              r->young_index_in_cset(), r->hrm_index(), r->get_type_str(), _g1h->collection_set()->young_region_length());
4263     }
4264 
4265     void handle_evacuated_region(HeapRegion* r) {
4266       assert(!r->is_empty(), "Region %u is an empty region in the collection set.", r->hrm_index());
4267       stats()->account_evacuated_region(r);
4268 
4269       // Free the region and and its remembered set.
4270       _g1h->free_region(r, NULL);
4271     }
4272 
4273     void handle_failed_region(HeapRegion* r) {
4274       // Do some allocation statistics accounting. Regions that failed evacuation
4275       // are always made old, so there is no need to update anything in the young
4276       // gen statistics, but we need to update old gen statistics.
4277       stats()->account_failed_region(r);
4278 
4279       // Update the region state due to the failed evacuation.
4280       r->handle_evacuation_failure();
4281 
4282       // Add region to old set, need to hold lock.
4283       MutexLocker x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4284       _g1h->old_set_add(r);
4285     }
4286 
4287     Tickspan& timer_for_region(HeapRegion* r) {
4288       return r->is_young() ? _young_time : _non_young_time;
4289     }
4290 
4291     FreeCSetStats* stats() {
4292       return _stats;
4293     }
4294   public:
4295     FreeCSetClosure(const size_t* surviving_young_words,
4296                     uint worker_id,
4297                     FreeCSetStats* stats) :
4298         HeapRegionClosure(),
4299         _g1h(G1CollectedHeap::heap()),
4300         _surviving_young_words(surviving_young_words),
4301         _worker_id(worker_id),
4302         _young_time(),
4303         _non_young_time(),
4304         _stats(stats) { }
4305 
4306     virtual bool do_heap_region(HeapRegion* r) {
4307       assert(r->in_collection_set(), "Invariant: %u missing from CSet", r->hrm_index());
4308       JFREventForRegion event(r, _worker_id);
4309       TimerForRegion timer(timer_for_region(r));
4310 
4311       _g1h->clear_region_attr(r);
4312       stats()->account_rs_length(r);
4313 
4314       if (r->is_young()) {
4315         assert_in_cset(r);
4316         r->record_surv_words_in_group(_surviving_young_words[r->young_index_in_cset()]);
4317       }
4318 
4319       if (r->evacuation_failed()) {
4320         handle_failed_region(r);
4321       } else {
4322         handle_evacuated_region(r);
4323       }
4324       assert(!_g1h->is_on_master_free_list(r), "sanity");
4325 
4326       return false;
4327     }
4328 
4329     void report_timing(Tickspan parallel_time) {
4330       G1GCPhaseTimes* pt = _g1h->phase_times();
4331       pt->record_time_secs(G1GCPhaseTimes::ParFreeCSet, _worker_id, parallel_time.seconds());
4332       if (_young_time.value() > 0) {
4333         pt->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, _worker_id, _young_time.seconds());
4334       }
4335       if (_non_young_time.value() > 0) {
4336         pt->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, _worker_id, _non_young_time.seconds());
4337       }
4338     }
4339   };
4340 
4341   // G1FreeCollectionSetTask members
4342   G1CollectedHeap*  _g1h;
4343   G1EvacuationInfo* _evacuation_info;
4344   FreeCSetStats*    _worker_stats;
4345   HeapRegionClaimer _claimer;
4346   const size_t*     _surviving_young_words;
4347   uint              _active_workers;
4348 
4349   FreeCSetStats* worker_stats(uint worker) {
4350     return &_worker_stats[worker];
4351   }
4352 
4353   void report_statistics() {
4354     // Merge the accounting
4355     FreeCSetStats total_stats;
4356     for (uint worker = 0; worker < _active_workers; worker++) {
4357       total_stats.merge_stats(worker_stats(worker));
4358     }
4359     total_stats.report(_g1h, _evacuation_info);
4360   }
4361 
4362 public:
4363   G1FreeCollectionSetTask(G1EvacuationInfo* evacuation_info, const size_t* surviving_young_words, uint active_workers) :
4364       AbstractGangTask("G1 Free Collection Set"),
4365       _g1h(G1CollectedHeap::heap()),
4366       _evacuation_info(evacuation_info),
4367       _worker_stats(NEW_C_HEAP_ARRAY(FreeCSetStats, active_workers, mtGC)),
4368       _claimer(active_workers),
4369       _surviving_young_words(surviving_young_words),
4370       _active_workers(active_workers) {
4371     for (uint worker = 0; worker < active_workers; worker++) {
4372       ::new (&_worker_stats[worker]) FreeCSetStats();
4373     }
4374   }
4375 
4376   ~G1FreeCollectionSetTask() {
4377     Ticks serial_time = Ticks::now();
4378     report_statistics();
4379     for (uint worker = 0; worker < _active_workers; worker++) {
4380       _worker_stats[worker].~FreeCSetStats();
4381     }
4382     FREE_C_HEAP_ARRAY(FreeCSetStats, _worker_stats);
4383     _g1h->phase_times()->record_serial_free_cset_time_ms((Ticks::now() - serial_time).seconds() * 1000.0);
4384   }
4385 
4386   virtual void work(uint worker_id) {
4387     EventGCPhaseParallel event;
4388     Ticks start = Ticks::now();
4389     FreeCSetClosure cl(_surviving_young_words, worker_id, worker_stats(worker_id));
4390     _g1h->collection_set_par_iterate_all(&cl, &_claimer, worker_id);
4391 
4392     // Report the total parallel time along with some more detailed metrics.
4393     cl.report_timing(Ticks::now() - start);
4394     event.commit(GCId::current(), worker_id, G1GCPhaseTimes::phase_name(G1GCPhaseTimes::ParFreeCSet));
4395   }
4396 };
4397 
4398 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, G1EvacuationInfo& evacuation_info, const size_t* surviving_young_words) {
4399   _eden.clear();
4400 
4401   // The free collections set is split up in two tasks, the first
4402   // frees the collection set and records what regions are free,
4403   // and the second one rebuilds the free list. This proved to be
4404   // more efficient than adding a sorted list to another.
4405 
4406   Ticks free_cset_start_time = Ticks::now();
4407   {
4408     uint const num_cs_regions = _collection_set.region_length();
4409     uint const num_workers = clamp(num_cs_regions, 1u, workers()->active_workers());
4410     G1FreeCollectionSetTask cl(&evacuation_info, surviving_young_words, num_workers);
4411 
4412     log_debug(gc, ergo)("Running %s using %u workers for collection set length %u (%u)",
4413                         cl.name(), num_workers, num_cs_regions, num_regions());
4414     workers()->run_task(&cl, num_workers);
4415   }
4416 
4417   Ticks free_cset_end_time = Ticks::now();
4418   phase_times()->record_total_free_cset_time_ms((free_cset_end_time - free_cset_start_time).seconds() * 1000.0);
4419 
4420   // Now rebuild the free region list.
4421   hrm()->rebuild_free_list(workers());
4422   phase_times()->record_total_rebuild_freelist_time_ms((Ticks::now() - free_cset_end_time).seconds() * 1000.0);
4423 
4424   collection_set->clear();
4425 }
4426 
4427 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
4428  private:
4429   FreeRegionList* _free_region_list;
4430   HeapRegionSet* _proxy_set;
4431   uint _humongous_objects_reclaimed;
4432   uint _humongous_regions_reclaimed;
4433   size_t _freed_bytes;
4434  public:
4435 
4436   G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
4437     _free_region_list(free_region_list), _proxy_set(NULL), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) {
4438   }
4439 
4440   virtual bool do_heap_region(HeapRegion* r) {
4441     if (!r->is_starts_humongous()) {
4442       return false;
4443     }
4444 
4445     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4446 
4447     oop obj = (oop)r->bottom();
4448     G1CMBitMap* next_bitmap = g1h->concurrent_mark()->next_mark_bitmap();
4449 
4450     // The following checks whether the humongous object is live are sufficient.
4451     // The main additional check (in addition to having a reference from the roots
4452     // or the young gen) is whether the humongous object has a remembered set entry.
4453     //
4454     // A humongous object cannot be live if there is no remembered set for it
4455     // because:
4456     // - there can be no references from within humongous starts regions referencing
4457     // the object because we never allocate other objects into them.
4458     // (I.e. there are no intra-region references that may be missed by the
4459     // remembered set)
4460     // - as soon there is a remembered set entry to the humongous starts region
4461     // (i.e. it has "escaped" to an old object) this remembered set entry will stay
4462     // until the end of a concurrent mark.
4463     //
4464     // It is not required to check whether the object has been found dead by marking
4465     // or not, in fact it would prevent reclamation within a concurrent cycle, as
4466     // all objects allocated during that time are considered live.
4467     // SATB marking is even more conservative than the remembered set.
4468     // So if at this point in the collection there is no remembered set entry,
4469     // nobody has a reference to it.
4470     // At the start of collection we flush all refinement logs, and remembered sets
4471     // are completely up-to-date wrt to references to the humongous object.
4472     //
4473     // Other implementation considerations:
4474     // - never consider object arrays at this time because they would pose
4475     // considerable effort for cleaning up the the remembered sets. This is
4476     // required because stale remembered sets might reference locations that
4477     // are currently allocated into.
4478     uint region_idx = r->hrm_index();
4479     if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
4480         !r->rem_set()->is_empty()) {
4481       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",
4482                                region_idx,
4483                                (size_t)obj->size() * HeapWordSize,
4484                                p2i(r->bottom()),
4485                                r->rem_set()->occupied(),
4486                                r->rem_set()->strong_code_roots_list_length(),
4487                                next_bitmap->is_marked(r->bottom()),
4488                                g1h->is_humongous_reclaim_candidate(region_idx),
4489                                obj->is_typeArray()
4490                               );
4491       return false;
4492     }
4493 
4494     guarantee(obj->is_typeArray(),
4495               "Only eagerly reclaiming type arrays is supported, but the object "
4496               PTR_FORMAT " is not.", p2i(r->bottom()));
4497 
4498     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",
4499                              region_idx,
4500                              (size_t)obj->size() * HeapWordSize,
4501                              p2i(r->bottom()),
4502                              r->rem_set()->occupied(),
4503                              r->rem_set()->strong_code_roots_list_length(),
4504                              next_bitmap->is_marked(r->bottom()),
4505                              g1h->is_humongous_reclaim_candidate(region_idx),
4506                              obj->is_typeArray()
4507                             );
4508 
4509     G1ConcurrentMark* const cm = g1h->concurrent_mark();
4510     cm->humongous_object_eagerly_reclaimed(r);
4511     assert(!cm->is_marked_in_prev_bitmap(obj) && !cm->is_marked_in_next_bitmap(obj),
4512            "Eagerly reclaimed humongous region %u should not be marked at all but is in prev %s next %s",
4513            region_idx,
4514            BOOL_TO_STR(cm->is_marked_in_prev_bitmap(obj)),
4515            BOOL_TO_STR(cm->is_marked_in_next_bitmap(obj)));
4516     _humongous_objects_reclaimed++;
4517     do {
4518       HeapRegion* next = g1h->next_region_in_humongous(r);
4519       _freed_bytes += r->used();
4520       r->set_containing_set(NULL);
4521       _humongous_regions_reclaimed++;
4522       g1h->free_humongous_region(r, _free_region_list);
4523       r = next;
4524     } while (r != NULL);
4525 
4526     return false;
4527   }
4528 
4529   uint humongous_objects_reclaimed() {
4530     return _humongous_objects_reclaimed;
4531   }
4532 
4533   uint humongous_regions_reclaimed() {
4534     return _humongous_regions_reclaimed;
4535   }
4536 
4537   size_t bytes_freed() const {
4538     return _freed_bytes;
4539   }
4540 };
4541 
4542 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
4543   assert_at_safepoint_on_vm_thread();
4544 
4545   if (!G1EagerReclaimHumongousObjects ||
4546       (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) {
4547     phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
4548     return;
4549   }
4550 
4551   double start_time = os::elapsedTime();
4552 
4553   FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
4554 
4555   G1FreeHumongousRegionClosure cl(&local_cleanup_list);
4556   heap_region_iterate(&cl);
4557 
4558   remove_from_old_sets(0, cl.humongous_regions_reclaimed());
4559 
4560   G1HRPrinter* hrp = hr_printer();
4561   if (hrp->is_active()) {
4562     FreeRegionListIterator iter(&local_cleanup_list);
4563     while (iter.more_available()) {
4564       HeapRegion* hr = iter.get_next();
4565       hrp->cleanup(hr);
4566     }
4567   }
4568 
4569   prepend_to_freelist(&local_cleanup_list);
4570   decrement_summary_bytes(cl.bytes_freed());
4571 
4572   phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
4573                                                        cl.humongous_objects_reclaimed());
4574 }
4575 
4576 class G1AbandonCollectionSetClosure : public HeapRegionClosure {
4577 public:
4578   virtual bool do_heap_region(HeapRegion* r) {
4579     assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index());
4580     G1CollectedHeap::heap()->clear_region_attr(r);
4581     r->clear_young_index_in_cset();
4582     return false;
4583   }
4584 };
4585 
4586 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) {
4587   G1AbandonCollectionSetClosure cl;
4588   collection_set_iterate_all(&cl);
4589 
4590   collection_set->clear();
4591   collection_set->stop_incremental_building();
4592 }
4593 
4594 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
4595   return _allocator->is_retained_old_region(hr);
4596 }
4597 
4598 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
4599   _eden.add(hr);
4600   _policy->set_region_eden(hr);
4601 }
4602 
4603 #ifdef ASSERT
4604 
4605 class NoYoungRegionsClosure: public HeapRegionClosure {
4606 private:
4607   bool _success;
4608 public:
4609   NoYoungRegionsClosure() : _success(true) { }
4610   bool do_heap_region(HeapRegion* r) {
4611     if (r->is_young()) {
4612       log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
4613                             p2i(r->bottom()), p2i(r->end()));
4614       _success = false;
4615     }
4616     return false;
4617   }
4618   bool success() { return _success; }
4619 };
4620 
4621 bool G1CollectedHeap::check_young_list_empty() {
4622   bool ret = (young_regions_count() == 0);
4623 
4624   NoYoungRegionsClosure closure;
4625   heap_region_iterate(&closure);
4626   ret = ret && closure.success();
4627 
4628   return ret;
4629 }
4630 
4631 #endif // ASSERT
4632 
4633 class TearDownRegionSetsClosure : public HeapRegionClosure {
4634   HeapRegionSet *_old_set;
4635 
4636 public:
4637   TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
4638 
4639   bool do_heap_region(HeapRegion* r) {
4640     if (r->is_old()) {
4641       _old_set->remove(r);
4642     } else if(r->is_young()) {
4643       r->uninstall_surv_rate_group();
4644     } else {
4645       // We ignore free regions, we'll empty the free list afterwards.
4646       // We ignore humongous and archive regions, we're not tearing down these
4647       // sets.
4648       assert(r->is_archive() || r->is_free() || r->is_humongous(),
4649              "it cannot be another type");
4650     }
4651     return false;
4652   }
4653 
4654   ~TearDownRegionSetsClosure() {
4655     assert(_old_set->is_empty(), "post-condition");
4656   }
4657 };
4658 
4659 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
4660   assert_at_safepoint_on_vm_thread();
4661 
4662   if (!free_list_only) {
4663     TearDownRegionSetsClosure cl(&_old_set);
4664     heap_region_iterate(&cl);
4665 
4666     // Note that emptying the _young_list is postponed and instead done as
4667     // the first step when rebuilding the regions sets again. The reason for
4668     // this is that during a full GC string deduplication needs to know if
4669     // a collected region was young or old when the full GC was initiated.
4670   }
4671   _hrm->remove_all_free_regions();
4672 }
4673 
4674 void G1CollectedHeap::increase_used(size_t bytes) {
4675   _summary_bytes_used += bytes;
4676 }
4677 
4678 void G1CollectedHeap::decrease_used(size_t bytes) {
4679   assert(_summary_bytes_used >= bytes,
4680          "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
4681          _summary_bytes_used, bytes);
4682   _summary_bytes_used -= bytes;
4683 }
4684 
4685 void G1CollectedHeap::set_used(size_t bytes) {
4686   _summary_bytes_used = bytes;
4687 }
4688 
4689 class RebuildRegionSetsClosure : public HeapRegionClosure {
4690 private:
4691   bool _free_list_only;
4692 
4693   HeapRegionSet* _old_set;
4694   HeapRegionManager* _hrm;
4695 
4696   size_t _total_used;
4697 
4698 public:
4699   RebuildRegionSetsClosure(bool free_list_only,
4700                            HeapRegionSet* old_set,
4701                            HeapRegionManager* hrm) :
4702     _free_list_only(free_list_only),
4703     _old_set(old_set), _hrm(hrm), _total_used(0) {
4704     assert(_hrm->num_free_regions() == 0, "pre-condition");
4705     if (!free_list_only) {
4706       assert(_old_set->is_empty(), "pre-condition");
4707     }
4708   }
4709 
4710   bool do_heap_region(HeapRegion* r) {
4711     if (r->is_empty()) {
4712       assert(r->rem_set()->is_empty(), "Empty regions should have empty remembered sets.");
4713       // Add free regions to the free list
4714       r->set_free();
4715       _hrm->insert_into_free_list(r);
4716     } else if (!_free_list_only) {
4717       assert(r->rem_set()->is_empty(), "At this point remembered sets must have been cleared.");
4718 
4719       if (r->is_archive() || r->is_humongous()) {
4720         // We ignore archive and humongous regions. We left these sets unchanged.
4721       } else {
4722         assert(r->is_young() || r->is_free() || r->is_old(), "invariant");
4723         // We now move all (non-humongous, non-old, non-archive) regions to old gen, and register them as such.
4724         r->move_to_old();
4725         _old_set->add(r);
4726       }
4727       _total_used += r->used();
4728     }
4729 
4730     return false;
4731   }
4732 
4733   size_t total_used() {
4734     return _total_used;
4735   }
4736 };
4737 
4738 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
4739   assert_at_safepoint_on_vm_thread();
4740 
4741   if (!free_list_only) {
4742     _eden.clear();
4743     _survivor.clear();
4744   }
4745 
4746   RebuildRegionSetsClosure cl(free_list_only, &_old_set, _hrm);
4747   heap_region_iterate(&cl);
4748 
4749   if (!free_list_only) {
4750     set_used(cl.total_used());
4751     if (_archive_allocator != NULL) {
4752       _archive_allocator->clear_used();
4753     }
4754   }
4755   assert_used_and_recalculate_used_equal(this);
4756 }
4757 
4758 // Methods for the mutator alloc region
4759 
4760 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
4761                                                       bool force,
4762                                                       uint node_index) {
4763   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
4764   bool should_allocate = policy()->should_allocate_mutator_region();
4765   if (force || should_allocate) {
4766     HeapRegion* new_alloc_region = new_region(word_size,
4767                                               HeapRegionType::Eden,
4768                                               false /* do_expand */,
4769                                               node_index);
4770     if (new_alloc_region != NULL) {
4771       set_region_short_lived_locked(new_alloc_region);
4772       _hr_printer.alloc(new_alloc_region, !should_allocate);
4773       _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region);
4774       _policy->remset_tracker()->update_at_allocate(new_alloc_region);
4775       return new_alloc_region;
4776     }
4777   }
4778   return NULL;
4779 }
4780 
4781 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
4782                                                   size_t allocated_bytes) {
4783   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
4784   assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
4785 
4786   collection_set()->add_eden_region(alloc_region);
4787   increase_used(allocated_bytes);
4788   _eden.add_used_bytes(allocated_bytes);
4789   _hr_printer.retire(alloc_region);
4790 
4791   // We update the eden sizes here, when the region is retired,
4792   // instead of when it's allocated, since this is the point that its
4793   // used space has been recorded in _summary_bytes_used.
4794   g1mm()->update_eden_size();
4795 }
4796 
4797 // Methods for the GC alloc regions
4798 
4799 bool G1CollectedHeap::has_more_regions(G1HeapRegionAttr dest) {
4800   if (dest.is_old()) {
4801     return true;
4802   } else {
4803     return survivor_regions_count() < policy()->max_survivor_regions();
4804   }
4805 }
4806 
4807 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, G1HeapRegionAttr dest, uint node_index) {
4808   assert(FreeList_lock->owned_by_self(), "pre-condition");
4809 
4810   if (!has_more_regions(dest)) {
4811     return NULL;
4812   }
4813 
4814   HeapRegionType type;
4815   if (dest.is_young()) {
4816     type = HeapRegionType::Survivor;
4817   } else {
4818     type = HeapRegionType::Old;
4819   }
4820 
4821   HeapRegion* new_alloc_region = new_region(word_size,
4822                                             type,
4823                                             true /* do_expand */,
4824                                             node_index);
4825 
4826   if (new_alloc_region != NULL) {
4827     if (type.is_survivor()) {
4828       new_alloc_region->set_survivor();
4829       _survivor.add(new_alloc_region);
4830       _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region);
4831     } else {
4832       new_alloc_region->set_old();
4833       _verifier->check_bitmaps("Old Region Allocation", new_alloc_region);
4834     }
4835     _policy->remset_tracker()->update_at_allocate(new_alloc_region);
4836     register_region_with_region_attr(new_alloc_region);
4837     _hr_printer.alloc(new_alloc_region);
4838     return new_alloc_region;
4839   }
4840   return NULL;
4841 }
4842 
4843 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
4844                                              size_t allocated_bytes,
4845                                              G1HeapRegionAttr dest) {
4846   _bytes_used_during_gc += allocated_bytes;
4847   if (dest.is_old()) {
4848     old_set_add(alloc_region);
4849   } else {
4850     assert(dest.is_young(), "Retiring alloc region should be young (%d)", dest.type());
4851     _survivor.add_used_bytes(allocated_bytes);
4852   }
4853 
4854   bool const during_im = collector_state()->in_initial_mark_gc();
4855   if (during_im && allocated_bytes > 0) {
4856     _cm->root_regions()->add(alloc_region->next_top_at_mark_start(), alloc_region->top());
4857   }
4858   _hr_printer.retire(alloc_region);
4859 }
4860 
4861 HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
4862   bool expanded = false;
4863   uint index = _hrm->find_highest_free(&expanded);
4864 
4865   if (index != G1_NO_HRM_INDEX) {
4866     if (expanded) {
4867       log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
4868                                 HeapRegion::GrainWords * HeapWordSize);
4869     }
4870     return _hrm->allocate_free_regions_starting_at(index, 1);
4871   }
4872   return NULL;
4873 }
4874 
4875 // Optimized nmethod scanning
4876 
4877 class RegisterNMethodOopClosure: public OopClosure {
4878   G1CollectedHeap* _g1h;
4879   nmethod* _nm;
4880 
4881   template <class T> void do_oop_work(T* p) {
4882     T heap_oop = RawAccess<>::oop_load(p);
4883     if (!CompressedOops::is_null(heap_oop)) {
4884       oop obj = CompressedOops::decode_not_null(heap_oop);
4885       HeapRegion* hr = _g1h->heap_region_containing(obj);
4886       assert(!hr->is_continues_humongous(),
4887              "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
4888              " starting at " HR_FORMAT,
4889              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
4890 
4891       // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
4892       hr->add_strong_code_root_locked(_nm);
4893     }
4894   }
4895 
4896 public:
4897   RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
4898     _g1h(g1h), _nm(nm) {}
4899 
4900   void do_oop(oop* p)       { do_oop_work(p); }
4901   void do_oop(narrowOop* p) { do_oop_work(p); }
4902 };
4903 
4904 class UnregisterNMethodOopClosure: public OopClosure {
4905   G1CollectedHeap* _g1h;
4906   nmethod* _nm;
4907 
4908   template <class T> void do_oop_work(T* p) {
4909     T heap_oop = RawAccess<>::oop_load(p);
4910     if (!CompressedOops::is_null(heap_oop)) {
4911       oop obj = CompressedOops::decode_not_null(heap_oop);
4912       HeapRegion* hr = _g1h->heap_region_containing(obj);
4913       assert(!hr->is_continues_humongous(),
4914              "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
4915              " starting at " HR_FORMAT,
4916              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
4917 
4918       hr->remove_strong_code_root(_nm);
4919     }
4920   }
4921 
4922 public:
4923   UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
4924     _g1h(g1h), _nm(nm) {}
4925 
4926   void do_oop(oop* p)       { do_oop_work(p); }
4927   void do_oop(narrowOop* p) { do_oop_work(p); }
4928 };
4929 
4930 void G1CollectedHeap::register_nmethod(nmethod* nm) {
4931   guarantee(nm != NULL, "sanity");
4932   RegisterNMethodOopClosure reg_cl(this, nm);
4933   nm->oops_do(&reg_cl);
4934 }
4935 
4936 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
4937   guarantee(nm != NULL, "sanity");
4938   UnregisterNMethodOopClosure reg_cl(this, nm);
4939   nm->oops_do(&reg_cl, true);
4940 }
4941 
4942 void G1CollectedHeap::purge_code_root_memory() {
4943   double purge_start = os::elapsedTime();
4944   G1CodeRootSet::purge();
4945   double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
4946   phase_times()->record_strong_code_root_purge_time(purge_time_ms);
4947 }
4948 
4949 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
4950   G1CollectedHeap* _g1h;
4951 
4952 public:
4953   RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
4954     _g1h(g1h) {}
4955 
4956   void do_code_blob(CodeBlob* cb) {
4957     nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
4958     if (nm == NULL) {
4959       return;
4960     }
4961 
4962     _g1h->register_nmethod(nm);
4963   }
4964 };
4965 
4966 void G1CollectedHeap::rebuild_strong_code_roots() {
4967   RebuildStrongCodeRootClosure blob_cl(this);
4968   CodeCache::blobs_do(&blob_cl);
4969 }
4970 
4971 void G1CollectedHeap::initialize_serviceability() {
4972   _g1mm->initialize_serviceability();
4973 }
4974 
4975 MemoryUsage G1CollectedHeap::memory_usage() {
4976   return _g1mm->memory_usage();
4977 }
4978 
4979 GrowableArray<GCMemoryManager*> G1CollectedHeap::memory_managers() {
4980   return _g1mm->memory_managers();
4981 }
4982 
4983 GrowableArray<MemoryPool*> G1CollectedHeap::memory_pools() {
4984   return _g1mm->memory_pools();
4985 }