rev 59939 : [mq]: 8243974-investigate-millis-since-last-gc-move

   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   _old_set("Old Region Set", new OldRegionSetChecker()),
1484   _archive_set("Archive Region Set", new ArchiveRegionSetChecker()),
1485   _humongous_set("Humongous Region Set", new HumongousRegionSetChecker()),
1486   _bot(NULL),
1487   _listener(),
1488   _numa(G1NUMA::create()),
1489   _hrm(NULL),
1490   _allocator(NULL),
1491   _verifier(NULL),
1492   _summary_bytes_used(0),
1493   _bytes_used_during_gc(0),
1494   _archive_allocator(NULL),
1495   _survivor_evac_stats("Young", YoungPLABSize, PLABWeight),
1496   _old_evac_stats("Old", OldPLABSize, PLABWeight),
1497   _expand_heap_after_alloc_failure(true),
1498   _g1mm(NULL),
1499   _humongous_reclaim_candidates(),
1500   _has_humongous_reclaim_candidates(false),
1501   _hr_printer(),
1502   _collector_state(),
1503   _old_marking_cycles_started(0),
1504   _old_marking_cycles_completed(0),
1505   _eden(),
1506   _survivor(),
1507   _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1508   _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1509   _policy(G1Policy::create_policy(_gc_timer_stw)),
1510   _heap_sizing_policy(NULL),
1511   _collection_set(this, _policy),
1512   _hot_card_cache(NULL),
1513   _rem_set(NULL),
1514   _cm(NULL),
1515   _cm_thread(NULL),
1516   _cr(NULL),
1517   _task_queues(NULL),
1518   _evacuation_failed(false),
1519   _evacuation_failed_info_array(NULL),
1520   _preserved_marks_set(true /* in_c_heap */),
1521 #ifndef PRODUCT
1522   _evacuation_failure_alot_for_current_gc(false),
1523   _evacuation_failure_alot_gc_number(0),
1524   _evacuation_failure_alot_count(0),
1525 #endif
1526   _ref_processor_stw(NULL),
1527   _is_alive_closure_stw(this),
1528   _is_subject_to_discovery_stw(this),
1529   _ref_processor_cm(NULL),
1530   _is_alive_closure_cm(this),
1531   _is_subject_to_discovery_cm(this),
1532   _region_attr() {
1533 
1534   _verifier = new G1HeapVerifier(this);
1535 
1536   _allocator = new G1Allocator(this);
1537 
1538   _heap_sizing_policy = G1HeapSizingPolicy::create(this, _policy->analytics());
1539 
1540   _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);
1541 
1542   // Override the default _filler_array_max_size so that no humongous filler
1543   // objects are created.
1544   _filler_array_max_size = _humongous_object_threshold_in_words;
1545 
1546   uint n_queues = ParallelGCThreads;
1547   _task_queues = new G1ScannerTasksQueueSet(n_queues);
1548 
1549   _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1550 
1551   for (uint i = 0; i < n_queues; i++) {
1552     G1ScannerTasksQueue* q = new G1ScannerTasksQueue();
1553     q->initialize();
1554     _task_queues->register_queue(i, q);
1555     ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1556   }
1557 
1558   // Initialize the G1EvacuationFailureALot counters and flags.
1559   NOT_PRODUCT(reset_evacuation_should_fail();)
1560   _gc_tracer_stw->initialize();
1561 
1562   guarantee(_task_queues != NULL, "task_queues allocation failure.");
1563 }
1564 
1565 static size_t actual_reserved_page_size(ReservedSpace rs) {
1566   size_t page_size = os::vm_page_size();
1567   if (UseLargePages) {
1568     // There are two ways to manage large page memory.
1569     // 1. OS supports committing large page memory.
1570     // 2. OS doesn't support committing large page memory so ReservedSpace manages it.
1571     //    And ReservedSpace calls it 'special'. If we failed to set 'special',
1572     //    we reserved memory without large page.
1573     if (os::can_commit_large_page_memory() || rs.special()) {
1574       // An alignment at ReservedSpace comes from preferred page size or
1575       // heap alignment, and if the alignment came from heap alignment, it could be
1576       // larger than large pages size. So need to cap with the large page size.
1577       page_size = MIN2(rs.alignment(), os::large_page_size());
1578     }
1579   }
1580 
1581   return page_size;
1582 }
1583 
1584 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1585                                                                  size_t size,
1586                                                                  size_t translation_factor) {
1587   size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1588   // Allocate a new reserved space, preferring to use large pages.
1589   ReservedSpace rs(size, preferred_page_size);
1590   size_t page_size = actual_reserved_page_size(rs);
1591   G1RegionToSpaceMapper* result  =
1592     G1RegionToSpaceMapper::create_mapper(rs,
1593                                          size,
1594                                          page_size,
1595                                          HeapRegion::GrainBytes,
1596                                          translation_factor,
1597                                          mtGC);
1598 
1599   os::trace_page_sizes_for_requested_size(description,
1600                                           size,
1601                                           preferred_page_size,
1602                                           page_size,
1603                                           rs.base(),
1604                                           rs.size());
1605 
1606   return result;
1607 }
1608 
1609 jint G1CollectedHeap::initialize_concurrent_refinement() {
1610   jint ecode = JNI_OK;
1611   _cr = G1ConcurrentRefine::create(&ecode);
1612   return ecode;
1613 }
1614 
1615 jint G1CollectedHeap::initialize_young_gen_sampling_thread() {
1616   _young_gen_sampling_thread = new G1YoungRemSetSamplingThread();
1617   if (_young_gen_sampling_thread->osthread() == NULL) {
1618     vm_shutdown_during_initialization("Could not create G1YoungRemSetSamplingThread");
1619     return JNI_ENOMEM;
1620   }
1621   return JNI_OK;
1622 }
1623 
1624 jint G1CollectedHeap::initialize() {
1625 
1626   // Necessary to satisfy locking discipline assertions.
1627 
1628   MutexLocker x(Heap_lock);
1629 
1630   // While there are no constraints in the GC code that HeapWordSize
1631   // be any particular value, there are multiple other areas in the
1632   // system which believe this to be true (e.g. oop->object_size in some
1633   // cases incorrectly returns the size in wordSize units rather than
1634   // HeapWordSize).
1635   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1636 
1637   size_t init_byte_size = InitialHeapSize;
1638   size_t reserved_byte_size = G1Arguments::heap_reserved_size_bytes();
1639 
1640   // Ensure that the sizes are properly aligned.
1641   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1642   Universe::check_alignment(reserved_byte_size, HeapRegion::GrainBytes, "g1 heap");
1643   Universe::check_alignment(reserved_byte_size, HeapAlignment, "g1 heap");
1644 
1645   // Reserve the maximum.
1646 
1647   // When compressed oops are enabled, the preferred heap base
1648   // is calculated by subtracting the requested size from the
1649   // 32Gb boundary and using the result as the base address for
1650   // heap reservation. If the requested size is not aligned to
1651   // HeapRegion::GrainBytes (i.e. the alignment that is passed
1652   // into the ReservedHeapSpace constructor) then the actual
1653   // base of the reserved heap may end up differing from the
1654   // address that was requested (i.e. the preferred heap base).
1655   // If this happens then we could end up using a non-optimal
1656   // compressed oops mode.
1657 
1658   ReservedHeapSpace heap_rs = Universe::reserve_heap(reserved_byte_size,
1659                                                      HeapAlignment);
1660 
1661   initialize_reserved_region(heap_rs);
1662 
1663   // Create the barrier set for the entire reserved region.
1664   G1CardTable* ct = new G1CardTable(heap_rs.region());
1665   ct->initialize();
1666   G1BarrierSet* bs = new G1BarrierSet(ct);
1667   bs->initialize();
1668   assert(bs->is_a(BarrierSet::G1BarrierSet), "sanity");
1669   BarrierSet::set_barrier_set(bs);
1670   _card_table = ct;
1671 
1672   {
1673     G1SATBMarkQueueSet& satbqs = bs->satb_mark_queue_set();
1674     satbqs.set_process_completed_buffers_threshold(G1SATBProcessCompletedThreshold);
1675     satbqs.set_buffer_enqueue_threshold_percentage(G1SATBBufferEnqueueingThresholdPercent);
1676   }
1677 
1678   // Create the hot card cache.
1679   _hot_card_cache = new G1HotCardCache(this);
1680 
1681   // Carve out the G1 part of the heap.
1682   ReservedSpace g1_rs = heap_rs.first_part(reserved_byte_size);
1683   size_t page_size = actual_reserved_page_size(heap_rs);
1684   G1RegionToSpaceMapper* heap_storage =
1685     G1RegionToSpaceMapper::create_heap_mapper(g1_rs,
1686                                               g1_rs.size(),
1687                                               page_size,
1688                                               HeapRegion::GrainBytes,
1689                                               1,
1690                                               mtJavaHeap);
1691   if(heap_storage == NULL) {
1692     vm_shutdown_during_initialization("Could not initialize G1 heap");
1693     return JNI_ERR;
1694   }
1695 
1696   os::trace_page_sizes("Heap",
1697                        MinHeapSize,
1698                        reserved_byte_size,
1699                        page_size,
1700                        heap_rs.base(),
1701                        heap_rs.size());
1702   heap_storage->set_mapping_changed_listener(&_listener);
1703 
1704   // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1705   G1RegionToSpaceMapper* bot_storage =
1706     create_aux_memory_mapper("Block Offset Table",
1707                              G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize),
1708                              G1BlockOffsetTable::heap_map_factor());
1709 
1710   G1RegionToSpaceMapper* cardtable_storage =
1711     create_aux_memory_mapper("Card Table",
1712                              G1CardTable::compute_size(g1_rs.size() / HeapWordSize),
1713                              G1CardTable::heap_map_factor());
1714 
1715   G1RegionToSpaceMapper* card_counts_storage =
1716     create_aux_memory_mapper("Card Counts Table",
1717                              G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1718                              G1CardCounts::heap_map_factor());
1719 
1720   size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size());
1721   G1RegionToSpaceMapper* prev_bitmap_storage =
1722     create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1723   G1RegionToSpaceMapper* next_bitmap_storage =
1724     create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1725 
1726   _hrm = HeapRegionManager::create_manager(this);
1727 
1728   _hrm->initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1729   _card_table->initialize(cardtable_storage);
1730 
1731   // Do later initialization work for concurrent refinement.
1732   _hot_card_cache->initialize(card_counts_storage);
1733 
1734   // 6843694 - ensure that the maximum region index can fit
1735   // in the remembered set structures.
1736   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1737   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1738 
1739   // The G1FromCardCache reserves card with value 0 as "invalid", so the heap must not
1740   // start within the first card.
1741   guarantee(g1_rs.base() >= (char*)G1CardTable::card_size, "Java heap must not start within the first card.");
1742   // Also create a G1 rem set.
1743   _rem_set = new G1RemSet(this, _card_table, _hot_card_cache);
1744   _rem_set->initialize(max_reserved_capacity(), max_regions());
1745 
1746   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1747   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1748   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1749             "too many cards per region");
1750 
1751   FreeRegionList::set_unrealistically_long_length(max_expandable_regions() + 1);
1752 
1753   _bot = new G1BlockOffsetTable(reserved_region(), bot_storage);
1754 
1755   {
1756     HeapWord* start = _hrm->reserved().start();
1757     HeapWord* end = _hrm->reserved().end();
1758     size_t granularity = HeapRegion::GrainBytes;
1759 
1760     _region_attr.initialize(start, end, granularity);
1761     _humongous_reclaim_candidates.initialize(start, end, granularity);
1762   }
1763 
1764   _workers = new WorkGang("GC Thread", ParallelGCThreads,
1765                           true /* are_GC_task_threads */,
1766                           false /* are_ConcurrentGC_threads */);
1767   if (_workers == NULL) {
1768     return JNI_ENOMEM;
1769   }
1770   _workers->initialize_workers();
1771 
1772   _numa->set_region_info(HeapRegion::GrainBytes, page_size);
1773 
1774   // Create the G1ConcurrentMark data structure and thread.
1775   // (Must do this late, so that "max_regions" is defined.)
1776   _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1777   _cm_thread = _cm->cm_thread();
1778 
1779   // Now expand into the initial heap size.
1780   if (!expand(init_byte_size, _workers)) {
1781     vm_shutdown_during_initialization("Failed to allocate initial heap.");
1782     return JNI_ENOMEM;
1783   }
1784 
1785   // Perform any initialization actions delegated to the policy.
1786   policy()->init(this, &_collection_set);
1787 
1788   jint ecode = initialize_concurrent_refinement();
1789   if (ecode != JNI_OK) {
1790     return ecode;
1791   }
1792 
1793   ecode = initialize_young_gen_sampling_thread();
1794   if (ecode != JNI_OK) {
1795     return ecode;
1796   }
1797 
1798   {
1799     G1DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
1800     dcqs.set_process_cards_threshold(concurrent_refine()->yellow_zone());
1801     dcqs.set_max_cards(concurrent_refine()->red_zone());
1802   }
1803 
1804   // Here we allocate the dummy HeapRegion that is required by the
1805   // G1AllocRegion class.
1806   HeapRegion* dummy_region = _hrm->get_dummy_region();
1807 
1808   // We'll re-use the same region whether the alloc region will
1809   // require BOT updates or not and, if it doesn't, then a non-young
1810   // region will complain that it cannot support allocations without
1811   // BOT updates. So we'll tag the dummy region as eden to avoid that.
1812   dummy_region->set_eden();
1813   // Make sure it's full.
1814   dummy_region->set_top(dummy_region->end());
1815   G1AllocRegion::setup(this, dummy_region);
1816 
1817   _allocator->init_mutator_alloc_regions();
1818 
1819   // Do create of the monitoring and management support so that
1820   // values in the heap have been properly initialized.
1821   _g1mm = new G1MonitoringSupport(this);
1822 
1823   G1StringDedup::initialize();
1824 
1825   _preserved_marks_set.init(ParallelGCThreads);
1826 
1827   _collection_set.initialize(max_regions());
1828 
1829   G1InitLogger::print();
1830 
1831   return JNI_OK;
1832 }
1833 
1834 void G1CollectedHeap::stop() {
1835   // Stop all concurrent threads. We do this to make sure these threads
1836   // do not continue to execute and access resources (e.g. logging)
1837   // that are destroyed during shutdown.
1838   _cr->stop();
1839   _young_gen_sampling_thread->stop();
1840   _cm_thread->stop();
1841   if (G1StringDedup::is_enabled()) {
1842     G1StringDedup::stop();
1843   }
1844 }
1845 
1846 void G1CollectedHeap::safepoint_synchronize_begin() {
1847   SuspendibleThreadSet::synchronize();
1848 }
1849 
1850 void G1CollectedHeap::safepoint_synchronize_end() {
1851   SuspendibleThreadSet::desynchronize();
1852 }
1853 
1854 void G1CollectedHeap::post_initialize() {
1855   CollectedHeap::post_initialize();
1856   ref_processing_init();
1857 }
1858 
1859 void G1CollectedHeap::ref_processing_init() {
1860   // Reference processing in G1 currently works as follows:
1861   //
1862   // * There are two reference processor instances. One is
1863   //   used to record and process discovered references
1864   //   during concurrent marking; the other is used to
1865   //   record and process references during STW pauses
1866   //   (both full and incremental).
1867   // * Both ref processors need to 'span' the entire heap as
1868   //   the regions in the collection set may be dotted around.
1869   //
1870   // * For the concurrent marking ref processor:
1871   //   * Reference discovery is enabled at initial marking.
1872   //   * Reference discovery is disabled and the discovered
1873   //     references processed etc during remarking.
1874   //   * Reference discovery is MT (see below).
1875   //   * Reference discovery requires a barrier (see below).
1876   //   * Reference processing may or may not be MT
1877   //     (depending on the value of ParallelRefProcEnabled
1878   //     and ParallelGCThreads).
1879   //   * A full GC disables reference discovery by the CM
1880   //     ref processor and abandons any entries on it's
1881   //     discovered lists.
1882   //
1883   // * For the STW processor:
1884   //   * Non MT discovery is enabled at the start of a full GC.
1885   //   * Processing and enqueueing during a full GC is non-MT.
1886   //   * During a full GC, references are processed after marking.
1887   //
1888   //   * Discovery (may or may not be MT) is enabled at the start
1889   //     of an incremental evacuation pause.
1890   //   * References are processed near the end of a STW evacuation pause.
1891   //   * For both types of GC:
1892   //     * Discovery is atomic - i.e. not concurrent.
1893   //     * Reference discovery will not need a barrier.
1894 
1895   bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1);
1896 
1897   // Concurrent Mark ref processor
1898   _ref_processor_cm =
1899     new ReferenceProcessor(&_is_subject_to_discovery_cm,
1900                            mt_processing,                                  // mt processing
1901                            ParallelGCThreads,                              // degree of mt processing
1902                            (ParallelGCThreads > 1) || (ConcGCThreads > 1), // mt discovery
1903                            MAX2(ParallelGCThreads, ConcGCThreads),         // degree of mt discovery
1904                            false,                                          // Reference discovery is not atomic
1905                            &_is_alive_closure_cm,                          // is alive closure
1906                            true);                                          // allow changes to number of processing threads
1907 
1908   // STW ref processor
1909   _ref_processor_stw =
1910     new ReferenceProcessor(&_is_subject_to_discovery_stw,
1911                            mt_processing,                        // mt processing
1912                            ParallelGCThreads,                    // degree of mt processing
1913                            (ParallelGCThreads > 1),              // mt discovery
1914                            ParallelGCThreads,                    // degree of mt discovery
1915                            true,                                 // Reference discovery is atomic
1916                            &_is_alive_closure_stw,               // is alive closure
1917                            true);                                // allow changes to number of processing threads
1918 }
1919 
1920 SoftRefPolicy* G1CollectedHeap::soft_ref_policy() {
1921   return &_soft_ref_policy;
1922 }
1923 
1924 size_t G1CollectedHeap::capacity() const {
1925   return _hrm->length() * HeapRegion::GrainBytes;
1926 }
1927 
1928 size_t G1CollectedHeap::unused_committed_regions_in_bytes() const {
1929   return _hrm->total_free_bytes();
1930 }
1931 
1932 void G1CollectedHeap::iterate_hcc_closure(G1CardTableEntryClosure* cl, uint worker_id) {
1933   _hot_card_cache->drain(cl, worker_id);
1934 }
1935 
1936 // Computes the sum of the storage used by the various regions.
1937 size_t G1CollectedHeap::used() const {
1938   size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
1939   if (_archive_allocator != NULL) {
1940     result += _archive_allocator->used();
1941   }
1942   return result;
1943 }
1944 
1945 size_t G1CollectedHeap::used_unlocked() const {
1946   return _summary_bytes_used;
1947 }
1948 
1949 class SumUsedClosure: public HeapRegionClosure {
1950   size_t _used;
1951 public:
1952   SumUsedClosure() : _used(0) {}
1953   bool do_heap_region(HeapRegion* r) {
1954     _used += r->used();
1955     return false;
1956   }
1957   size_t result() { return _used; }
1958 };
1959 
1960 size_t G1CollectedHeap::recalculate_used() const {
1961   SumUsedClosure blk;
1962   heap_region_iterate(&blk);
1963   return blk.result();
1964 }
1965 
1966 bool  G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
1967   switch (cause) {
1968     case GCCause::_java_lang_system_gc:                 return ExplicitGCInvokesConcurrent;
1969     case GCCause::_dcmd_gc_run:                         return ExplicitGCInvokesConcurrent;
1970     case GCCause::_wb_conc_mark:                        return true;
1971     default :                                           return false;
1972   }
1973 }
1974 
1975 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
1976   switch (cause) {
1977     case GCCause::_g1_humongous_allocation: return true;
1978     case GCCause::_g1_periodic_collection:  return G1PeriodicGCInvokesConcurrent;
1979     case GCCause::_wb_breakpoint:           return true;
1980     default:                                return is_user_requested_concurrent_full_gc(cause);
1981   }
1982 }
1983 
1984 bool G1CollectedHeap::should_upgrade_to_full_gc(GCCause::Cause cause) {
1985   if (policy()->force_upgrade_to_full()) {
1986     return true;
1987   } else if (should_do_concurrent_full_gc(_gc_cause)) {
1988     return false;
1989   } else if (has_regions_left_for_allocation()) {
1990     return false;
1991   } else {
1992     return true;
1993   }
1994 }
1995 
1996 #ifndef PRODUCT
1997 void G1CollectedHeap::allocate_dummy_regions() {
1998   // Let's fill up most of the region
1999   size_t word_size = HeapRegion::GrainWords - 1024;
2000   // And as a result the region we'll allocate will be humongous.
2001   guarantee(is_humongous(word_size), "sanity");
2002 
2003   // _filler_array_max_size is set to humongous object threshold
2004   // but temporarily change it to use CollectedHeap::fill_with_object().
2005   SizeTFlagSetting fs(_filler_array_max_size, word_size);
2006 
2007   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2008     // Let's use the existing mechanism for the allocation
2009     HeapWord* dummy_obj = humongous_obj_allocate(word_size);
2010     if (dummy_obj != NULL) {
2011       MemRegion mr(dummy_obj, word_size);
2012       CollectedHeap::fill_with_object(mr);
2013     } else {
2014       // If we can't allocate once, we probably cannot allocate
2015       // again. Let's get out of the loop.
2016       break;
2017     }
2018   }
2019 }
2020 #endif // !PRODUCT
2021 
2022 void G1CollectedHeap::increment_old_marking_cycles_started() {
2023   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2024          _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2025          "Wrong marking cycle count (started: %d, completed: %d)",
2026          _old_marking_cycles_started, _old_marking_cycles_completed);
2027 
2028   _old_marking_cycles_started++;
2029 }
2030 
2031 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2032   MonitorLocker ml(G1OldGCCount_lock, Mutex::_no_safepoint_check_flag);
2033 
2034   // We assume that if concurrent == true, then the caller is a
2035   // concurrent thread that was joined the Suspendible Thread
2036   // Set. If there's ever a cheap way to check this, we should add an
2037   // assert here.
2038 
2039   // Given that this method is called at the end of a Full GC or of a
2040   // concurrent cycle, and those can be nested (i.e., a Full GC can
2041   // interrupt a concurrent cycle), the number of full collections
2042   // completed should be either one (in the case where there was no
2043   // nesting) or two (when a Full GC interrupted a concurrent cycle)
2044   // behind the number of full collections started.
2045 
2046   // This is the case for the inner caller, i.e. a Full GC.
2047   assert(concurrent ||
2048          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2049          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2050          "for inner caller (Full GC): _old_marking_cycles_started = %u "
2051          "is inconsistent with _old_marking_cycles_completed = %u",
2052          _old_marking_cycles_started, _old_marking_cycles_completed);
2053 
2054   // This is the case for the outer caller, i.e. the concurrent cycle.
2055   assert(!concurrent ||
2056          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2057          "for outer caller (concurrent cycle): "
2058          "_old_marking_cycles_started = %u "
2059          "is inconsistent with _old_marking_cycles_completed = %u",
2060          _old_marking_cycles_started, _old_marking_cycles_completed);
2061 
2062   _old_marking_cycles_completed += 1;
2063 
2064   // We need to clear the "in_progress" flag in the CM thread before
2065   // we wake up any waiters (especially when ExplicitInvokesConcurrent
2066   // is set) so that if a waiter requests another System.gc() it doesn't
2067   // incorrectly see that a marking cycle is still in progress.
2068   if (concurrent) {
2069     _cm_thread->set_idle();
2070   }
2071 
2072   // Notify threads waiting in System.gc() (with ExplicitGCInvokesConcurrent)
2073   // for a full GC to finish that their wait is over.
2074   ml.notify_all();
2075 }
2076 
2077 void G1CollectedHeap::collect(GCCause::Cause cause) {
2078   try_collect(cause);
2079 }
2080 
2081 // Return true if (x < y) with allowance for wraparound.
2082 static bool gc_counter_less_than(uint x, uint y) {
2083   return (x - y) > (UINT_MAX/2);
2084 }
2085 
2086 // LOG_COLLECT_CONCURRENTLY(cause, msg, args...)
2087 // Macro so msg printing is format-checked.
2088 #define LOG_COLLECT_CONCURRENTLY(cause, ...)                            \
2089   do {                                                                  \
2090     LogTarget(Trace, gc) LOG_COLLECT_CONCURRENTLY_lt;                   \
2091     if (LOG_COLLECT_CONCURRENTLY_lt.is_enabled()) {                     \
2092       ResourceMark rm; /* For thread name. */                           \
2093       LogStream LOG_COLLECT_CONCURRENTLY_s(&LOG_COLLECT_CONCURRENTLY_lt); \
2094       LOG_COLLECT_CONCURRENTLY_s.print("%s: Try Collect Concurrently (%s): ", \
2095                                        Thread::current()->name(),       \
2096                                        GCCause::to_string(cause));      \
2097       LOG_COLLECT_CONCURRENTLY_s.print(__VA_ARGS__);                    \
2098     }                                                                   \
2099   } while (0)
2100 
2101 #define LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, result) \
2102   LOG_COLLECT_CONCURRENTLY(cause, "complete %s", BOOL_TO_STR(result))
2103 
2104 bool G1CollectedHeap::try_collect_concurrently(GCCause::Cause cause,
2105                                                uint gc_counter,
2106                                                uint old_marking_started_before) {
2107   assert_heap_not_locked();
2108   assert(should_do_concurrent_full_gc(cause),
2109          "Non-concurrent cause %s", GCCause::to_string(cause));
2110 
2111   for (uint i = 1; true; ++i) {
2112     // Try to schedule an initial-mark evacuation pause that will
2113     // start a concurrent cycle.
2114     LOG_COLLECT_CONCURRENTLY(cause, "attempt %u", i);
2115     VM_G1TryInitiateConcMark op(gc_counter,
2116                                 cause,
2117                                 policy()->max_pause_time_ms());
2118     VMThread::execute(&op);
2119 
2120     // Request is trivially finished.
2121     if (cause == GCCause::_g1_periodic_collection) {
2122       LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, op.gc_succeeded());
2123       return op.gc_succeeded();
2124     }
2125 
2126     // If VMOp skipped initiating concurrent marking cycle because
2127     // we're terminating, then we're done.
2128     if (op.terminating()) {
2129       LOG_COLLECT_CONCURRENTLY(cause, "skipped: terminating");
2130       return false;
2131     }
2132 
2133     // Lock to get consistent set of values.
2134     uint old_marking_started_after;
2135     uint old_marking_completed_after;
2136     {
2137       MutexLocker ml(Heap_lock);
2138       // Update gc_counter for retrying VMOp if needed. Captured here to be
2139       // consistent with the values we use below for termination tests.  If
2140       // a retry is needed after a possible wait, and another collection
2141       // occurs in the meantime, it will cause our retry to be skipped and
2142       // we'll recheck for termination with updated conditions from that
2143       // more recent collection.  That's what we want, rather than having
2144       // our retry possibly perform an unnecessary collection.
2145       gc_counter = total_collections();
2146       old_marking_started_after = _old_marking_cycles_started;
2147       old_marking_completed_after = _old_marking_cycles_completed;
2148     }
2149 
2150     if (cause == GCCause::_wb_breakpoint) {
2151       if (op.gc_succeeded()) {
2152         LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, true);
2153         return true;
2154       }
2155       // When _wb_breakpoint there can't be another cycle or deferred.
2156       assert(!op.cycle_already_in_progress(), "invariant");
2157       assert(!op.whitebox_attached(), "invariant");
2158       // Concurrent cycle attempt might have been cancelled by some other
2159       // collection, so retry.  Unlike other cases below, we want to retry
2160       // even if cancelled by a STW full collection, because we really want
2161       // to start a concurrent cycle.
2162       if (old_marking_started_before != old_marking_started_after) {
2163         LOG_COLLECT_CONCURRENTLY(cause, "ignoring STW full GC");
2164         old_marking_started_before = old_marking_started_after;
2165       }
2166     } else if (!GCCause::is_user_requested_gc(cause)) {
2167       // For an "automatic" (not user-requested) collection, we just need to
2168       // ensure that progress is made.
2169       //
2170       // Request is finished if any of
2171       // (1) the VMOp successfully performed a GC,
2172       // (2) a concurrent cycle was already in progress,
2173       // (3) whitebox is controlling concurrent cycles,
2174       // (4) a new cycle was started (by this thread or some other), or
2175       // (5) a Full GC was performed.
2176       // Cases (4) and (5) are detected together by a change to
2177       // _old_marking_cycles_started.
2178       //
2179       // Note that (1) does not imply (4).  If we're still in the mixed
2180       // phase of an earlier concurrent collection, the request to make the
2181       // collection an initial-mark won't be honored.  If we don't check for
2182       // both conditions we'll spin doing back-to-back collections.
2183       if (op.gc_succeeded() ||
2184           op.cycle_already_in_progress() ||
2185           op.whitebox_attached() ||
2186           (old_marking_started_before != old_marking_started_after)) {
2187         LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, true);
2188         return true;
2189       }
2190     } else {                    // User-requested GC.
2191       // For a user-requested collection, we want to ensure that a complete
2192       // full collection has been performed before returning, but without
2193       // waiting for more than needed.
2194 
2195       // For user-requested GCs (unlike non-UR), a successful VMOp implies a
2196       // new cycle was started.  That's good, because it's not clear what we
2197       // should do otherwise.  Trying again just does back to back GCs.
2198       // Can't wait for someone else to start a cycle.  And returning fails
2199       // to meet the goal of ensuring a full collection was performed.
2200       assert(!op.gc_succeeded() ||
2201              (old_marking_started_before != old_marking_started_after),
2202              "invariant: succeeded %s, started before %u, started after %u",
2203              BOOL_TO_STR(op.gc_succeeded()),
2204              old_marking_started_before, old_marking_started_after);
2205 
2206       // Request is finished if a full collection (concurrent or stw)
2207       // was started after this request and has completed, e.g.
2208       // started_before < completed_after.
2209       if (gc_counter_less_than(old_marking_started_before,
2210                                old_marking_completed_after)) {
2211         LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, true);
2212         return true;
2213       }
2214 
2215       if (old_marking_started_after != old_marking_completed_after) {
2216         // If there is an in-progress cycle (possibly started by us), then
2217         // wait for that cycle to complete, e.g.
2218         // while completed_now < started_after.
2219         LOG_COLLECT_CONCURRENTLY(cause, "wait");
2220         MonitorLocker ml(G1OldGCCount_lock);
2221         while (gc_counter_less_than(_old_marking_cycles_completed,
2222                                     old_marking_started_after)) {
2223           ml.wait();
2224         }
2225         // Request is finished if the collection we just waited for was
2226         // started after this request.
2227         if (old_marking_started_before != old_marking_started_after) {
2228           LOG_COLLECT_CONCURRENTLY(cause, "complete after wait");
2229           return true;
2230         }
2231       }
2232 
2233       // If VMOp was successful then it started a new cycle that the above
2234       // wait &etc should have recognized as finishing this request.  This
2235       // differs from a non-user-request, where gc_succeeded does not imply
2236       // a new cycle was started.
2237       assert(!op.gc_succeeded(), "invariant");
2238 
2239       if (op.cycle_already_in_progress()) {
2240         // If VMOp failed because a cycle was already in progress, it
2241         // is now complete.  But it didn't finish this user-requested
2242         // GC, so try again.
2243         LOG_COLLECT_CONCURRENTLY(cause, "retry after in-progress");
2244         continue;
2245       } else if (op.whitebox_attached()) {
2246         // If WhiteBox wants control, wait for notification of a state
2247         // change in the controller, then try again.  Don't wait for
2248         // release of control, since collections may complete while in
2249         // control.  Note: This won't recognize a STW full collection
2250         // while waiting; we can't wait on multiple monitors.
2251         LOG_COLLECT_CONCURRENTLY(cause, "whitebox control stall");
2252         MonitorLocker ml(ConcurrentGCBreakpoints::monitor());
2253         if (ConcurrentGCBreakpoints::is_controlled()) {
2254           ml.wait();
2255         }
2256         continue;
2257       }
2258     }
2259 
2260     // Collection failed and should be retried.
2261     assert(op.transient_failure(), "invariant");
2262 
2263     if (GCLocker::is_active_and_needs_gc()) {
2264       // If GCLocker is active, wait until clear before retrying.
2265       LOG_COLLECT_CONCURRENTLY(cause, "gc-locker stall");
2266       GCLocker::stall_until_clear();
2267     }
2268 
2269     LOG_COLLECT_CONCURRENTLY(cause, "retry");
2270   }
2271 }
2272 
2273 bool G1CollectedHeap::try_collect(GCCause::Cause cause) {
2274   assert_heap_not_locked();
2275 
2276   // Lock to get consistent set of values.
2277   uint gc_count_before;
2278   uint full_gc_count_before;
2279   uint old_marking_started_before;
2280   {
2281     MutexLocker ml(Heap_lock);
2282     gc_count_before = total_collections();
2283     full_gc_count_before = total_full_collections();
2284     old_marking_started_before = _old_marking_cycles_started;
2285   }
2286 
2287   if (should_do_concurrent_full_gc(cause)) {
2288     return try_collect_concurrently(cause,
2289                                     gc_count_before,
2290                                     old_marking_started_before);
2291   } else if (GCLocker::should_discard(cause, gc_count_before)) {
2292     // Indicate failure to be consistent with VMOp failure due to
2293     // another collection slipping in after our gc_count but before
2294     // our request is processed.
2295     return false;
2296   } else if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2297              DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2298 
2299     // Schedule a standard evacuation pause. We're setting word_size
2300     // to 0 which means that we are not requesting a post-GC allocation.
2301     VM_G1CollectForAllocation op(0,     /* word_size */
2302                                  gc_count_before,
2303                                  cause,
2304                                  policy()->max_pause_time_ms());
2305     VMThread::execute(&op);
2306     return op.gc_succeeded();
2307   } else {
2308     // Schedule a Full GC.
2309     VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2310     VMThread::execute(&op);
2311     return op.gc_succeeded();
2312   }
2313 }
2314 
2315 bool G1CollectedHeap::is_in(const void* p) const {
2316   if (_hrm->reserved().contains(p)) {
2317     // Given that we know that p is in the reserved space,
2318     // heap_region_containing() should successfully
2319     // return the containing region.
2320     HeapRegion* hr = heap_region_containing(p);
2321     return hr->is_in(p);
2322   } else {
2323     return false;
2324   }
2325 }
2326 
2327 #ifdef ASSERT
2328 bool G1CollectedHeap::is_in_exact(const void* p) const {
2329   bool contains = reserved_region().contains(p);
2330   bool available = _hrm->is_available(addr_to_region((HeapWord*)p));
2331   if (contains && available) {
2332     return true;
2333   } else {
2334     return false;
2335   }
2336 }
2337 #endif
2338 
2339 // Iteration functions.
2340 
2341 // Iterates an ObjectClosure over all objects within a HeapRegion.
2342 
2343 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2344   ObjectClosure* _cl;
2345 public:
2346   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2347   bool do_heap_region(HeapRegion* r) {
2348     if (!r->is_continues_humongous()) {
2349       r->object_iterate(_cl);
2350     }
2351     return false;
2352   }
2353 };
2354 
2355 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2356   IterateObjectClosureRegionClosure blk(cl);
2357   heap_region_iterate(&blk);
2358 }
2359 
2360 void G1CollectedHeap::keep_alive(oop obj) {
2361   G1BarrierSet::enqueue(obj);
2362 }
2363 
2364 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2365   _hrm->iterate(cl);
2366 }
2367 
2368 void G1CollectedHeap::heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl,
2369                                                                  HeapRegionClaimer *hrclaimer,
2370                                                                  uint worker_id) const {
2371   _hrm->par_iterate(cl, hrclaimer, hrclaimer->offset_for_worker(worker_id));
2372 }
2373 
2374 void G1CollectedHeap::heap_region_par_iterate_from_start(HeapRegionClosure* cl,
2375                                                          HeapRegionClaimer *hrclaimer) const {
2376   _hrm->par_iterate(cl, hrclaimer, 0);
2377 }
2378 
2379 void G1CollectedHeap::collection_set_iterate_all(HeapRegionClosure* cl) {
2380   _collection_set.iterate(cl);
2381 }
2382 
2383 void G1CollectedHeap::collection_set_par_iterate_all(HeapRegionClosure* cl, HeapRegionClaimer* hr_claimer, uint worker_id) {
2384   _collection_set.par_iterate(cl, hr_claimer, worker_id, workers()->active_workers());
2385 }
2386 
2387 void G1CollectedHeap::collection_set_iterate_increment_from(HeapRegionClosure *cl, HeapRegionClaimer* hr_claimer, uint worker_id) {
2388   _collection_set.iterate_incremental_part_from(cl, hr_claimer, worker_id, workers()->active_workers());
2389 }
2390 
2391 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2392   HeapRegion* hr = heap_region_containing(addr);
2393   return hr->block_start(addr);
2394 }
2395 
2396 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2397   HeapRegion* hr = heap_region_containing(addr);
2398   return hr->block_is_obj(addr);
2399 }
2400 
2401 bool G1CollectedHeap::supports_tlab_allocation() const {
2402   return true;
2403 }
2404 
2405 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2406   return (_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes;
2407 }
2408 
2409 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2410   return _eden.length() * HeapRegion::GrainBytes;
2411 }
2412 
2413 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2414 // must be equal to the humongous object limit.
2415 size_t G1CollectedHeap::max_tlab_size() const {
2416   return align_down(_humongous_object_threshold_in_words, MinObjAlignment);
2417 }
2418 
2419 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2420   return _allocator->unsafe_max_tlab_alloc();
2421 }
2422 
2423 size_t G1CollectedHeap::max_capacity() const {
2424   return _hrm->max_expandable_length() * HeapRegion::GrainBytes;
2425 }
2426 
2427 size_t G1CollectedHeap::max_reserved_capacity() const {
2428   return _hrm->max_length() * HeapRegion::GrainBytes;
2429 }
2430 
2431 jlong G1CollectedHeap::millis_since_last_gc() {
2432   // See the notes in GenCollectedHeap::millis_since_last_gc()
2433   // for more information about the implementation.
2434   jlong ret_val = (os::javaTimeNanos() - _policy->time_of_last_gc()) /
2435                   NANOSECS_PER_MILLISEC;
2436   if (ret_val < 0) {
2437     NOT_PRODUCT(log_warning(gc)("time warp: " JLONG_FORMAT, ret_val);)
2438     return 0;
2439   }
2440   return ret_val;
2441 }
2442 
2443 void G1CollectedHeap::deduplicate_string(oop str) {
2444   assert(java_lang_String::is_instance(str), "invariant");
2445 
2446   if (G1StringDedup::is_enabled()) {
2447     G1StringDedup::deduplicate(str);
2448   }
2449 }
2450 
2451 void G1CollectedHeap::prepare_for_verify() {
2452   _verifier->prepare_for_verify();
2453 }
2454 
2455 void G1CollectedHeap::verify(VerifyOption vo) {
2456   _verifier->verify(vo);
2457 }
2458 
2459 bool G1CollectedHeap::supports_concurrent_gc_breakpoints() const {
2460   return true;
2461 }
2462 
2463 bool G1CollectedHeap::is_heterogeneous_heap() const {
2464   return G1Arguments::is_heterogeneous_heap();
2465 }
2466 
2467 class PrintRegionClosure: public HeapRegionClosure {
2468   outputStream* _st;
2469 public:
2470   PrintRegionClosure(outputStream* st) : _st(st) {}
2471   bool do_heap_region(HeapRegion* r) {
2472     r->print_on(_st);
2473     return false;
2474   }
2475 };
2476 
2477 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2478                                        const HeapRegion* hr,
2479                                        const VerifyOption vo) const {
2480   switch (vo) {
2481   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
2482   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
2483   case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj, hr);
2484   default:                            ShouldNotReachHere();
2485   }
2486   return false; // keep some compilers happy
2487 }
2488 
2489 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2490                                        const VerifyOption vo) const {
2491   switch (vo) {
2492   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
2493   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
2494   case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj);
2495   default:                            ShouldNotReachHere();
2496   }
2497   return false; // keep some compilers happy
2498 }
2499 
2500 void G1CollectedHeap::print_heap_regions() const {
2501   LogTarget(Trace, gc, heap, region) lt;
2502   if (lt.is_enabled()) {
2503     LogStream ls(lt);
2504     print_regions_on(&ls);
2505   }
2506 }
2507 
2508 void G1CollectedHeap::print_on(outputStream* st) const {
2509   st->print(" %-20s", "garbage-first heap");
2510   if (_hrm != NULL) {
2511     st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
2512               capacity()/K, used_unlocked()/K);
2513     st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")",
2514               p2i(_hrm->reserved().start()),
2515               p2i(_hrm->reserved().end()));
2516   }
2517   st->cr();
2518   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
2519   uint young_regions = young_regions_count();
2520   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
2521             (size_t) young_regions * HeapRegion::GrainBytes / K);
2522   uint survivor_regions = survivor_regions_count();
2523   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
2524             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
2525   st->cr();
2526   if (_numa->is_enabled()) {
2527     uint num_nodes = _numa->num_active_nodes();
2528     st->print("  remaining free region(s) on each NUMA node: ");
2529     const int* node_ids = _numa->node_ids();
2530     for (uint node_index = 0; node_index < num_nodes; node_index++) {
2531       uint num_free_regions = (_hrm != NULL ? _hrm->num_free_regions(node_index) : 0);
2532       st->print("%d=%u ", node_ids[node_index], num_free_regions);
2533     }
2534     st->cr();
2535   }
2536   MetaspaceUtils::print_on(st);
2537 }
2538 
2539 void G1CollectedHeap::print_regions_on(outputStream* st) const {
2540   if (_hrm == NULL) {
2541     return;
2542   }
2543 
2544   st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
2545                "HS=humongous(starts), HC=humongous(continues), "
2546                "CS=collection set, F=free, "
2547                "OA=open archive, CA=closed archive, "
2548                "TAMS=top-at-mark-start (previous, next)");
2549   PrintRegionClosure blk(st);
2550   heap_region_iterate(&blk);
2551 }
2552 
2553 void G1CollectedHeap::print_extended_on(outputStream* st) const {
2554   print_on(st);
2555 
2556   // Print the per-region information.
2557   if (_hrm != NULL) {
2558     st->cr();
2559     print_regions_on(st);
2560   }
2561 }
2562 
2563 void G1CollectedHeap::print_on_error(outputStream* st) const {
2564   this->CollectedHeap::print_on_error(st);
2565 
2566   if (_cm != NULL) {
2567     st->cr();
2568     _cm->print_on_error(st);
2569   }
2570 }
2571 
2572 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2573   workers()->threads_do(tc);
2574   tc->do_thread(_cm_thread);
2575   _cm->threads_do(tc);
2576   _cr->threads_do(tc);
2577   tc->do_thread(_young_gen_sampling_thread);
2578   if (G1StringDedup::is_enabled()) {
2579     G1StringDedup::threads_do(tc);
2580   }
2581 }
2582 
2583 void G1CollectedHeap::print_tracing_info() const {
2584   rem_set()->print_summary_info();
2585   concurrent_mark()->print_summary_info();
2586 }
2587 
2588 #ifndef PRODUCT
2589 // Helpful for debugging RSet issues.
2590 
2591 class PrintRSetsClosure : public HeapRegionClosure {
2592 private:
2593   const char* _msg;
2594   size_t _occupied_sum;
2595 
2596 public:
2597   bool do_heap_region(HeapRegion* r) {
2598     HeapRegionRemSet* hrrs = r->rem_set();
2599     size_t occupied = hrrs->occupied();
2600     _occupied_sum += occupied;
2601 
2602     tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r));
2603     if (occupied == 0) {
2604       tty->print_cr("  RSet is empty");
2605     } else {
2606       hrrs->print();
2607     }
2608     tty->print_cr("----------");
2609     return false;
2610   }
2611 
2612   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
2613     tty->cr();
2614     tty->print_cr("========================================");
2615     tty->print_cr("%s", msg);
2616     tty->cr();
2617   }
2618 
2619   ~PrintRSetsClosure() {
2620     tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
2621     tty->print_cr("========================================");
2622     tty->cr();
2623   }
2624 };
2625 
2626 void G1CollectedHeap::print_cset_rsets() {
2627   PrintRSetsClosure cl("Printing CSet RSets");
2628   collection_set_iterate_all(&cl);
2629 }
2630 
2631 void G1CollectedHeap::print_all_rsets() {
2632   PrintRSetsClosure cl("Printing All RSets");;
2633   heap_region_iterate(&cl);
2634 }
2635 #endif // PRODUCT
2636 
2637 bool G1CollectedHeap::print_location(outputStream* st, void* addr) const {
2638   return BlockLocationPrinter<G1CollectedHeap>::print_location(st, addr);
2639 }
2640 
2641 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
2642 
2643   size_t eden_used_bytes = _eden.used_bytes();
2644   size_t survivor_used_bytes = _survivor.used_bytes();
2645   size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
2646 
2647   size_t eden_capacity_bytes =
2648     (policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
2649 
2650   VirtualSpaceSummary heap_summary = create_heap_space_summary();
2651   return G1HeapSummary(heap_summary, heap_used, eden_used_bytes,
2652                        eden_capacity_bytes, survivor_used_bytes, num_regions());
2653 }
2654 
2655 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
2656   return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
2657                        stats->unused(), stats->used(), stats->region_end_waste(),
2658                        stats->regions_filled(), stats->direct_allocated(),
2659                        stats->failure_used(), stats->failure_waste());
2660 }
2661 
2662 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
2663   const G1HeapSummary& heap_summary = create_g1_heap_summary();
2664   gc_tracer->report_gc_heap_summary(when, heap_summary);
2665 
2666   const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
2667   gc_tracer->report_metaspace_summary(when, metaspace_summary);
2668 }
2669 
2670 void G1CollectedHeap::gc_prologue(bool full) {
2671   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
2672 
2673   // This summary needs to be printed before incrementing total collections.
2674   rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections());
2675 
2676   // Update common counters.
2677   increment_total_collections(full /* full gc */);
2678   if (full || collector_state()->in_initial_mark_gc()) {
2679     increment_old_marking_cycles_started();
2680   }
2681 
2682   // Fill TLAB's and such
2683   {
2684     Ticks start = Ticks::now();
2685     ensure_parsability(true);
2686     Tickspan dt = Ticks::now() - start;
2687     phase_times()->record_prepare_tlab_time_ms(dt.seconds() * MILLIUNITS);
2688   }
2689 
2690   if (!full) {
2691     // Flush dirty card queues to qset, so later phases don't need to account
2692     // for partially filled per-thread queues and such.  Not needed for full
2693     // collections, which ignore those logs.
2694     Ticks start = Ticks::now();
2695     G1BarrierSet::dirty_card_queue_set().concatenate_logs();
2696     Tickspan dt = Ticks::now() - start;
2697     phase_times()->record_concatenate_dirty_card_logs_time_ms(dt.seconds() * MILLIUNITS);
2698   }
2699 }
2700 
2701 void G1CollectedHeap::gc_epilogue(bool full) {
2702   // Update common counters.
2703   if (full) {
2704     // Update the number of full collections that have been completed.
2705     increment_old_marking_cycles_completed(false /* concurrent */);
2706   }
2707 
2708   // We are at the end of the GC. Total collections has already been increased.
2709   rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1);
2710 
2711   // FIXME: what is this about?
2712   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
2713   // is set.
2714 #if COMPILER2_OR_JVMCI
2715   assert(DerivedPointerTable::is_empty(), "derived pointer present");
2716 #endif
2717 
2718   double start = os::elapsedTime();
2719   resize_all_tlabs();
2720   phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2721 
2722   MemoryService::track_memory_usage();
2723   // We have just completed a GC. Update the soft reference
2724   // policy with the new heap occupancy
2725   Universe::update_heap_info_at_gc();
2726 
2727   // Print NUMA statistics.
2728   _numa->print_statistics();


2729 }
2730 
2731 void G1CollectedHeap::verify_numa_regions(const char* desc) {
2732   LogTarget(Trace, gc, heap, verify) lt;
2733 
2734   if (lt.is_enabled()) {
2735     LogStream ls(lt);
2736     // Iterate all heap regions to print matching between preferred numa id and actual numa id.
2737     G1NodeIndexCheckClosure cl(desc, _numa, &ls);
2738     heap_region_iterate(&cl);
2739   }
2740 }
2741 
2742 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2743                                                uint gc_count_before,
2744                                                bool* succeeded,
2745                                                GCCause::Cause gc_cause) {
2746   assert_heap_not_locked_and_not_at_safepoint();
2747   VM_G1CollectForAllocation op(word_size,
2748                                gc_count_before,
2749                                gc_cause,
2750                                policy()->max_pause_time_ms());
2751   VMThread::execute(&op);
2752 
2753   HeapWord* result = op.result();
2754   bool ret_succeeded = op.prologue_succeeded() && op.gc_succeeded();
2755   assert(result == NULL || ret_succeeded,
2756          "the result should be NULL if the VM did not succeed");
2757   *succeeded = ret_succeeded;
2758 
2759   assert_heap_not_locked();
2760   return result;
2761 }
2762 
2763 void G1CollectedHeap::do_concurrent_mark() {
2764   MutexLocker x(CGC_lock, Mutex::_no_safepoint_check_flag);
2765   if (!_cm_thread->in_progress()) {
2766     _cm_thread->set_started();
2767     CGC_lock->notify();
2768   }
2769 }
2770 
2771 bool G1CollectedHeap::is_potential_eager_reclaim_candidate(HeapRegion* r) const {
2772   // We don't nominate objects with many remembered set entries, on
2773   // the assumption that such objects are likely still live.
2774   HeapRegionRemSet* rem_set = r->rem_set();
2775 
2776   return G1EagerReclaimHumongousObjectsWithStaleRefs ?
2777          rem_set->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) :
2778          G1EagerReclaimHumongousObjects && rem_set->is_empty();
2779 }
2780 
2781 #ifndef PRODUCT
2782 void G1CollectedHeap::verify_region_attr_remset_update() {
2783   class VerifyRegionAttrRemSet : public HeapRegionClosure {
2784   public:
2785     virtual bool do_heap_region(HeapRegion* r) {
2786       G1CollectedHeap* g1h = G1CollectedHeap::heap();
2787       bool const needs_remset_update = g1h->region_attr(r->bottom()).needs_remset_update();
2788       assert(r->rem_set()->is_tracked() == needs_remset_update,
2789              "Region %u remset tracking status (%s) different to region attribute (%s)",
2790              r->hrm_index(), BOOL_TO_STR(r->rem_set()->is_tracked()), BOOL_TO_STR(needs_remset_update));
2791       return false;
2792     }
2793   } cl;
2794   heap_region_iterate(&cl);
2795 }
2796 #endif
2797 
2798 class VerifyRegionRemSetClosure : public HeapRegionClosure {
2799   public:
2800     bool do_heap_region(HeapRegion* hr) {
2801       if (!hr->is_archive() && !hr->is_continues_humongous()) {
2802         hr->verify_rem_set();
2803       }
2804       return false;
2805     }
2806 };
2807 
2808 uint G1CollectedHeap::num_task_queues() const {
2809   return _task_queues->size();
2810 }
2811 
2812 #if TASKQUEUE_STATS
2813 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
2814   st->print_raw_cr("GC Task Stats");
2815   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
2816   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
2817 }
2818 
2819 void G1CollectedHeap::print_taskqueue_stats() const {
2820   if (!log_is_enabled(Trace, gc, task, stats)) {
2821     return;
2822   }
2823   Log(gc, task, stats) log;
2824   ResourceMark rm;
2825   LogStream ls(log.trace());
2826   outputStream* st = &ls;
2827 
2828   print_taskqueue_stats_hdr(st);
2829 
2830   TaskQueueStats totals;
2831   const uint n = num_task_queues();
2832   for (uint i = 0; i < n; ++i) {
2833     st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
2834     totals += task_queue(i)->stats;
2835   }
2836   st->print_raw("tot "); totals.print(st); st->cr();
2837 
2838   DEBUG_ONLY(totals.verify());
2839 }
2840 
2841 void G1CollectedHeap::reset_taskqueue_stats() {
2842   const uint n = num_task_queues();
2843   for (uint i = 0; i < n; ++i) {
2844     task_queue(i)->stats.reset();
2845   }
2846 }
2847 #endif // TASKQUEUE_STATS
2848 
2849 void G1CollectedHeap::wait_for_root_region_scanning() {
2850   double scan_wait_start = os::elapsedTime();
2851   // We have to wait until the CM threads finish scanning the
2852   // root regions as it's the only way to ensure that all the
2853   // objects on them have been correctly scanned before we start
2854   // moving them during the GC.
2855   bool waited = _cm->root_regions()->wait_until_scan_finished();
2856   double wait_time_ms = 0.0;
2857   if (waited) {
2858     double scan_wait_end = os::elapsedTime();
2859     wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
2860   }
2861   phase_times()->record_root_region_scan_wait_time(wait_time_ms);
2862 }
2863 
2864 class G1PrintCollectionSetClosure : public HeapRegionClosure {
2865 private:
2866   G1HRPrinter* _hr_printer;
2867 public:
2868   G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { }
2869 
2870   virtual bool do_heap_region(HeapRegion* r) {
2871     _hr_printer->cset(r);
2872     return false;
2873   }
2874 };
2875 
2876 void G1CollectedHeap::start_new_collection_set() {
2877   double start = os::elapsedTime();
2878 
2879   collection_set()->start_incremental_building();
2880 
2881   clear_region_attr();
2882 
2883   guarantee(_eden.length() == 0, "eden should have been cleared");
2884   policy()->transfer_survivors_to_cset(survivor());
2885 
2886   // We redo the verification but now wrt to the new CSet which
2887   // has just got initialized after the previous CSet was freed.
2888   _cm->verify_no_collection_set_oops();
2889 
2890   phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0);
2891 }
2892 
2893 void G1CollectedHeap::calculate_collection_set(G1EvacuationInfo& evacuation_info, double target_pause_time_ms) {
2894 
2895   _collection_set.finalize_initial_collection_set(target_pause_time_ms, &_survivor);
2896   evacuation_info.set_collectionset_regions(collection_set()->region_length() +
2897                                             collection_set()->optional_region_length());
2898 
2899   _cm->verify_no_collection_set_oops();
2900 
2901   if (_hr_printer.is_active()) {
2902     G1PrintCollectionSetClosure cl(&_hr_printer);
2903     _collection_set.iterate(&cl);
2904     _collection_set.iterate_optional(&cl);
2905   }
2906 }
2907 
2908 G1HeapVerifier::G1VerifyType G1CollectedHeap::young_collection_verify_type() const {
2909   if (collector_state()->in_initial_mark_gc()) {
2910     return G1HeapVerifier::G1VerifyConcurrentStart;
2911   } else if (collector_state()->in_young_only_phase()) {
2912     return G1HeapVerifier::G1VerifyYoungNormal;
2913   } else {
2914     return G1HeapVerifier::G1VerifyMixed;
2915   }
2916 }
2917 
2918 void G1CollectedHeap::verify_before_young_collection(G1HeapVerifier::G1VerifyType type) {
2919   if (VerifyRememberedSets) {
2920     log_info(gc, verify)("[Verifying RemSets before GC]");
2921     VerifyRegionRemSetClosure v_cl;
2922     heap_region_iterate(&v_cl);
2923   }
2924   _verifier->verify_before_gc(type);
2925   _verifier->check_bitmaps("GC Start");
2926   verify_numa_regions("GC Start");
2927 }
2928 
2929 void G1CollectedHeap::verify_after_young_collection(G1HeapVerifier::G1VerifyType type) {
2930   if (VerifyRememberedSets) {
2931     log_info(gc, verify)("[Verifying RemSets after GC]");
2932     VerifyRegionRemSetClosure v_cl;
2933     heap_region_iterate(&v_cl);
2934   }
2935   _verifier->verify_after_gc(type);
2936   _verifier->check_bitmaps("GC End");
2937   verify_numa_regions("GC End");
2938 }
2939 
2940 void G1CollectedHeap::expand_heap_after_young_collection(){
2941   size_t expand_bytes = _heap_sizing_policy->expansion_amount();
2942   if (expand_bytes > 0) {
2943     // No need for an ergo logging here,
2944     // expansion_amount() does this when it returns a value > 0.
2945     double expand_ms;
2946     if (!expand(expand_bytes, _workers, &expand_ms)) {
2947       // We failed to expand the heap. Cannot do anything about it.
2948     }
2949     phase_times()->record_expand_heap_time(expand_ms);
2950   }
2951 }
2952 
2953 const char* G1CollectedHeap::young_gc_name() const {
2954   if (collector_state()->in_initial_mark_gc()) {
2955     return "Pause Young (Concurrent Start)";
2956   } else if (collector_state()->in_young_only_phase()) {
2957     if (collector_state()->in_young_gc_before_mixed()) {
2958       return "Pause Young (Prepare Mixed)";
2959     } else {
2960       return "Pause Young (Normal)";
2961     }
2962   } else {
2963     return "Pause Young (Mixed)";
2964   }
2965 }
2966 
2967 bool G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
2968   assert_at_safepoint_on_vm_thread();
2969   guarantee(!is_gc_active(), "collection is not reentrant");
2970 
2971   if (GCLocker::check_active_before_gc()) {
2972     return false;
2973   }
2974 
2975   do_collection_pause_at_safepoint_helper(target_pause_time_ms);
2976   if (should_upgrade_to_full_gc(gc_cause())) {
2977     log_info(gc, ergo)("Attempting maximally compacting collection");
2978     bool result = do_full_collection(false /* explicit gc */,
2979                                      true /* clear_all_soft_refs */);
2980     // do_full_collection only fails if blocked by GC locker, but
2981     // we've already checked for that above.
2982     assert(result, "invariant");
2983   }
2984   return true;
2985 }
2986 
2987 void G1CollectedHeap::do_collection_pause_at_safepoint_helper(double target_pause_time_ms) {
2988   GCIdMark gc_id_mark;
2989 
2990   SvcGCMarker sgcm(SvcGCMarker::MINOR);
2991   ResourceMark rm;
2992 
2993   policy()->note_gc_start();
2994 
2995   _gc_timer_stw->register_gc_start();
2996   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
2997 
2998   wait_for_root_region_scanning();
2999 
3000   print_heap_before_gc();
3001   print_heap_regions();
3002   trace_heap_before_gc(_gc_tracer_stw);
3003 
3004   _verifier->verify_region_sets_optional();
3005   _verifier->verify_dirty_young_regions();
3006 
3007   // We should not be doing initial mark unless the conc mark thread is running
3008   if (!_cm_thread->should_terminate()) {
3009     // This call will decide whether this pause is an initial-mark
3010     // pause. If it is, in_initial_mark_gc() will return true
3011     // for the duration of this pause.
3012     policy()->decide_on_conc_mark_initiation();
3013   }
3014 
3015   // We do not allow initial-mark to be piggy-backed on a mixed GC.
3016   assert(!collector_state()->in_initial_mark_gc() ||
3017          collector_state()->in_young_only_phase(), "sanity");
3018   // We also do not allow mixed GCs during marking.
3019   assert(!collector_state()->mark_or_rebuild_in_progress() || collector_state()->in_young_only_phase(), "sanity");
3020 
3021   // Record whether this pause is an initial mark. When the current
3022   // thread has completed its logging output and it's safe to signal
3023   // the CM thread, the flag's value in the policy has been reset.
3024   bool should_start_conc_mark = collector_state()->in_initial_mark_gc();
3025   if (should_start_conc_mark) {
3026     _cm->gc_tracer_cm()->set_gc_cause(gc_cause());
3027   }
3028 
3029   // Inner scope for scope based logging, timers, and stats collection
3030   {
3031     G1EvacuationInfo evacuation_info;
3032 
3033     _gc_tracer_stw->report_yc_type(collector_state()->yc_type());
3034 
3035     GCTraceCPUTime tcpu;
3036 
3037     GCTraceTime(Info, gc) tm(young_gc_name(), NULL, gc_cause(), true);
3038 
3039     uint active_workers = WorkerPolicy::calc_active_workers(workers()->total_workers(),
3040                                                             workers()->active_workers(),
3041                                                             Threads::number_of_non_daemon_threads());
3042     active_workers = workers()->update_active_workers(active_workers);
3043     log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers());
3044 
3045     G1MonitoringScope ms(g1mm(),
3046                          false /* full_gc */,
3047                          collector_state()->yc_type() == Mixed /* all_memory_pools_affected */);
3048 
3049     G1HeapTransition heap_transition(this);
3050 
3051     {
3052       IsGCActiveMark x;
3053 
3054       gc_prologue(false);
3055 
3056       G1HeapVerifier::G1VerifyType verify_type = young_collection_verify_type();
3057       verify_before_young_collection(verify_type);
3058 
3059       {
3060         // The elapsed time induced by the start time below deliberately elides
3061         // the possible verification above.
3062         double sample_start_time_sec = os::elapsedTime();
3063 
3064         // Please see comment in g1CollectedHeap.hpp and
3065         // G1CollectedHeap::ref_processing_init() to see how
3066         // reference processing currently works in G1.
3067         _ref_processor_stw->enable_discovery();
3068 
3069         // We want to temporarily turn off discovery by the
3070         // CM ref processor, if necessary, and turn it back on
3071         // on again later if we do. Using a scoped
3072         // NoRefDiscovery object will do this.
3073         NoRefDiscovery no_cm_discovery(_ref_processor_cm);
3074 
3075         policy()->record_collection_pause_start(sample_start_time_sec);
3076 
3077         // Forget the current allocation region (we might even choose it to be part
3078         // of the collection set!).
3079         _allocator->release_mutator_alloc_regions();
3080 
3081         calculate_collection_set(evacuation_info, target_pause_time_ms);
3082 
3083         G1RedirtyCardsQueueSet rdcqs(G1BarrierSet::dirty_card_queue_set().allocator());
3084         G1ParScanThreadStateSet per_thread_states(this,
3085                                                   &rdcqs,
3086                                                   workers()->active_workers(),
3087                                                   collection_set()->young_region_length(),
3088                                                   collection_set()->optional_region_length());
3089         pre_evacuate_collection_set(evacuation_info, &per_thread_states);
3090 
3091         // Actually do the work...
3092         evacuate_initial_collection_set(&per_thread_states);
3093 
3094         if (_collection_set.optional_region_length() != 0) {
3095           evacuate_optional_collection_set(&per_thread_states);
3096         }
3097         post_evacuate_collection_set(evacuation_info, &rdcqs, &per_thread_states);
3098 
3099         start_new_collection_set();
3100 
3101         _survivor_evac_stats.adjust_desired_plab_sz();
3102         _old_evac_stats.adjust_desired_plab_sz();
3103 
3104         if (should_start_conc_mark) {
3105           // We have to do this before we notify the CM threads that
3106           // they can start working to make sure that all the
3107           // appropriate initialization is done on the CM object.
3108           concurrent_mark()->post_initial_mark();
3109           // Note that we don't actually trigger the CM thread at
3110           // this point. We do that later when we're sure that
3111           // the current thread has completed its logging output.
3112         }
3113 
3114         allocate_dummy_regions();
3115 
3116         _allocator->init_mutator_alloc_regions();
3117 
3118         expand_heap_after_young_collection();
3119 
3120         double sample_end_time_sec = os::elapsedTime();
3121         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3122         policy()->record_collection_pause_end(pause_time_ms);


3123       }
3124 
3125       verify_after_young_collection(verify_type);
3126 
3127       gc_epilogue(false);
3128     }
3129 
3130     // Print the remainder of the GC log output.
3131     if (evacuation_failed()) {
3132       log_info(gc)("To-space exhausted");
3133     }
3134 
3135     policy()->print_phases();
3136     heap_transition.print();
3137 
3138     _hrm->verify_optional();
3139     _verifier->verify_region_sets_optional();
3140 
3141     TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
3142     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3143 
3144     print_heap_after_gc();
3145     print_heap_regions();
3146     trace_heap_after_gc(_gc_tracer_stw);
3147 
3148     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3149     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3150     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3151     // before any GC notifications are raised.
3152     g1mm()->update_sizes();
3153 
3154     _gc_tracer_stw->report_evacuation_info(&evacuation_info);
3155     _gc_tracer_stw->report_tenuring_threshold(_policy->tenuring_threshold());
3156     _gc_timer_stw->register_gc_end();
3157     _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
3158   }
3159   // It should now be safe to tell the concurrent mark thread to start
3160   // without its logging output interfering with the logging output
3161   // that came from the pause.
3162 
3163   if (should_start_conc_mark) {
3164     // CAUTION: after the doConcurrentMark() call below, the concurrent marking
3165     // thread(s) could be running concurrently with us. Make sure that anything
3166     // after this point does not assume that we are the only GC thread running.
3167     // Note: of course, the actual marking work will not start until the safepoint
3168     // itself is released in SuspendibleThreadSet::desynchronize().
3169     do_concurrent_mark();
3170     ConcurrentGCBreakpoints::notify_idle_to_active();
3171   }
3172 }
3173 
3174 void G1CollectedHeap::remove_self_forwarding_pointers(G1RedirtyCardsQueueSet* rdcqs) {
3175   G1ParRemoveSelfForwardPtrsTask rsfp_task(rdcqs);
3176   workers()->run_task(&rsfp_task);
3177 }
3178 
3179 void G1CollectedHeap::restore_after_evac_failure(G1RedirtyCardsQueueSet* rdcqs) {
3180   double remove_self_forwards_start = os::elapsedTime();
3181 
3182   remove_self_forwarding_pointers(rdcqs);
3183   _preserved_marks_set.restore(workers());
3184 
3185   phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
3186 }
3187 
3188 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markWord m) {
3189   if (!_evacuation_failed) {
3190     _evacuation_failed = true;
3191   }
3192 
3193   _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size());
3194   _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m);
3195 }
3196 
3197 bool G1ParEvacuateFollowersClosure::offer_termination() {
3198   EventGCPhaseParallel event;
3199   G1ParScanThreadState* const pss = par_scan_state();
3200   start_term_time();
3201   const bool res = terminator()->offer_termination();
3202   end_term_time();
3203   event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(G1GCPhaseTimes::Termination));
3204   return res;
3205 }
3206 
3207 void G1ParEvacuateFollowersClosure::do_void() {
3208   EventGCPhaseParallel event;
3209   G1ParScanThreadState* const pss = par_scan_state();
3210   pss->trim_queue();
3211   event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(_phase));
3212   do {
3213     EventGCPhaseParallel event;
3214     pss->steal_and_trim_queue(queues());
3215     event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(_phase));
3216   } while (!offer_termination());
3217 }
3218 
3219 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive,
3220                                         bool class_unloading_occurred) {
3221   uint num_workers = workers()->active_workers();
3222   G1ParallelCleaningTask unlink_task(is_alive, num_workers, class_unloading_occurred, false);
3223   workers()->run_task(&unlink_task);
3224 }
3225 
3226 // Clean string dedup data structures.
3227 // Ideally we would prefer to use a StringDedupCleaningTask here, but we want to
3228 // record the durations of the phases. Hence the almost-copy.
3229 class G1StringDedupCleaningTask : public AbstractGangTask {
3230   BoolObjectClosure* _is_alive;
3231   OopClosure* _keep_alive;
3232   G1GCPhaseTimes* _phase_times;
3233 
3234 public:
3235   G1StringDedupCleaningTask(BoolObjectClosure* is_alive,
3236                             OopClosure* keep_alive,
3237                             G1GCPhaseTimes* phase_times) :
3238     AbstractGangTask("Partial Cleaning Task"),
3239     _is_alive(is_alive),
3240     _keep_alive(keep_alive),
3241     _phase_times(phase_times)
3242   {
3243     assert(G1StringDedup::is_enabled(), "String deduplication disabled.");
3244     StringDedup::gc_prologue(true);
3245   }
3246 
3247   ~G1StringDedupCleaningTask() {
3248     StringDedup::gc_epilogue();
3249   }
3250 
3251   void work(uint worker_id) {
3252     StringDedupUnlinkOrOopsDoClosure cl(_is_alive, _keep_alive);
3253     {
3254       G1GCParPhaseTimesTracker x(_phase_times, G1GCPhaseTimes::StringDedupQueueFixup, worker_id);
3255       StringDedupQueue::unlink_or_oops_do(&cl);
3256     }
3257     {
3258       G1GCParPhaseTimesTracker x(_phase_times, G1GCPhaseTimes::StringDedupTableFixup, worker_id);
3259       StringDedupTable::unlink_or_oops_do(&cl, worker_id);
3260     }
3261   }
3262 };
3263 
3264 void G1CollectedHeap::string_dedup_cleaning(BoolObjectClosure* is_alive,
3265                                             OopClosure* keep_alive,
3266                                             G1GCPhaseTimes* phase_times) {
3267   G1StringDedupCleaningTask cl(is_alive, keep_alive, phase_times);
3268   workers()->run_task(&cl);
3269 }
3270 
3271 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
3272  private:
3273   G1RedirtyCardsQueueSet* _qset;
3274   G1CollectedHeap* _g1h;
3275   BufferNode* volatile _nodes;
3276 
3277   void par_apply(RedirtyLoggedCardTableEntryClosure* cl, uint worker_id) {
3278     size_t buffer_size = _qset->buffer_size();
3279     BufferNode* next = Atomic::load(&_nodes);
3280     while (next != NULL) {
3281       BufferNode* node = next;
3282       next = Atomic::cmpxchg(&_nodes, node, node->next());
3283       if (next == node) {
3284         cl->apply_to_buffer(node, buffer_size, worker_id);
3285         next = node->next();
3286       }
3287     }
3288   }
3289 
3290  public:
3291   G1RedirtyLoggedCardsTask(G1RedirtyCardsQueueSet* qset, G1CollectedHeap* g1h) :
3292     AbstractGangTask("Redirty Cards"),
3293     _qset(qset), _g1h(g1h), _nodes(qset->all_completed_buffers()) { }
3294 
3295   virtual void work(uint worker_id) {
3296     G1GCPhaseTimes* p = _g1h->phase_times();
3297     G1GCParPhaseTimesTracker x(p, G1GCPhaseTimes::RedirtyCards, worker_id);
3298 
3299     RedirtyLoggedCardTableEntryClosure cl(_g1h);
3300     par_apply(&cl, worker_id);
3301 
3302     p->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied());
3303   }
3304 };
3305 
3306 void G1CollectedHeap::redirty_logged_cards(G1RedirtyCardsQueueSet* rdcqs) {
3307   double redirty_logged_cards_start = os::elapsedTime();
3308 
3309   G1RedirtyLoggedCardsTask redirty_task(rdcqs, this);
3310   workers()->run_task(&redirty_task);
3311 
3312   G1DirtyCardQueueSet& dcq = G1BarrierSet::dirty_card_queue_set();
3313   dcq.merge_bufferlists(rdcqs);
3314 
3315   phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
3316 }
3317 
3318 // Weak Reference Processing support
3319 
3320 bool G1STWIsAliveClosure::do_object_b(oop p) {
3321   // An object is reachable if it is outside the collection set,
3322   // or is inside and copied.
3323   return !_g1h->is_in_cset(p) || p->is_forwarded();
3324 }
3325 
3326 bool G1STWSubjectToDiscoveryClosure::do_object_b(oop obj) {
3327   assert(obj != NULL, "must not be NULL");
3328   assert(_g1h->is_in_reserved(obj), "Trying to discover obj " PTR_FORMAT " not in heap", p2i(obj));
3329   // The areas the CM and STW ref processor manage must be disjoint. The is_in_cset() below
3330   // may falsely indicate that this is not the case here: however the collection set only
3331   // contains old regions when concurrent mark is not running.
3332   return _g1h->is_in_cset(obj) || _g1h->heap_region_containing(obj)->is_survivor();
3333 }
3334 
3335 // Non Copying Keep Alive closure
3336 class G1KeepAliveClosure: public OopClosure {
3337   G1CollectedHeap*_g1h;
3338 public:
3339   G1KeepAliveClosure(G1CollectedHeap* g1h) :_g1h(g1h) {}
3340   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
3341   void do_oop(oop* p) {
3342     oop obj = *p;
3343     assert(obj != NULL, "the caller should have filtered out NULL values");
3344 
3345     const G1HeapRegionAttr region_attr =_g1h->region_attr(obj);
3346     if (!region_attr.is_in_cset_or_humongous()) {
3347       return;
3348     }
3349     if (region_attr.is_in_cset()) {
3350       assert( obj->is_forwarded(), "invariant" );
3351       *p = obj->forwardee();
3352     } else {
3353       assert(!obj->is_forwarded(), "invariant" );
3354       assert(region_attr.is_humongous(),
3355              "Only allowed G1HeapRegionAttr state is IsHumongous, but is %d", region_attr.type());
3356      _g1h->set_humongous_is_live(obj);
3357     }
3358   }
3359 };
3360 
3361 // Copying Keep Alive closure - can be called from both
3362 // serial and parallel code as long as different worker
3363 // threads utilize different G1ParScanThreadState instances
3364 // and different queues.
3365 
3366 class G1CopyingKeepAliveClosure: public OopClosure {
3367   G1CollectedHeap*         _g1h;
3368   G1ParScanThreadState*    _par_scan_state;
3369 
3370 public:
3371   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
3372                             G1ParScanThreadState* pss):
3373     _g1h(g1h),
3374     _par_scan_state(pss)
3375   {}
3376 
3377   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
3378   virtual void do_oop(      oop* p) { do_oop_work(p); }
3379 
3380   template <class T> void do_oop_work(T* p) {
3381     oop obj = RawAccess<>::oop_load(p);
3382 
3383     if (_g1h->is_in_cset_or_humongous(obj)) {
3384       // If the referent object has been forwarded (either copied
3385       // to a new location or to itself in the event of an
3386       // evacuation failure) then we need to update the reference
3387       // field and, if both reference and referent are in the G1
3388       // heap, update the RSet for the referent.
3389       //
3390       // If the referent has not been forwarded then we have to keep
3391       // it alive by policy. Therefore we have copy the referent.
3392       //
3393       // When the queue is drained (after each phase of reference processing)
3394       // the object and it's followers will be copied, the reference field set
3395       // to point to the new location, and the RSet updated.
3396       _par_scan_state->push_on_queue(ScannerTask(p));
3397     }
3398   }
3399 };
3400 
3401 // Serial drain queue closure. Called as the 'complete_gc'
3402 // closure for each discovered list in some of the
3403 // reference processing phases.
3404 
3405 class G1STWDrainQueueClosure: public VoidClosure {
3406 protected:
3407   G1CollectedHeap* _g1h;
3408   G1ParScanThreadState* _par_scan_state;
3409 
3410   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
3411 
3412 public:
3413   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
3414     _g1h(g1h),
3415     _par_scan_state(pss)
3416   { }
3417 
3418   void do_void() {
3419     G1ParScanThreadState* const pss = par_scan_state();
3420     pss->trim_queue();
3421   }
3422 };
3423 
3424 // Parallel Reference Processing closures
3425 
3426 // Implementation of AbstractRefProcTaskExecutor for parallel reference
3427 // processing during G1 evacuation pauses.
3428 
3429 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
3430 private:
3431   G1CollectedHeap*          _g1h;
3432   G1ParScanThreadStateSet*  _pss;
3433   G1ScannerTasksQueueSet*   _queues;
3434   WorkGang*                 _workers;
3435 
3436 public:
3437   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
3438                            G1ParScanThreadStateSet* per_thread_states,
3439                            WorkGang* workers,
3440                            G1ScannerTasksQueueSet *task_queues) :
3441     _g1h(g1h),
3442     _pss(per_thread_states),
3443     _queues(task_queues),
3444     _workers(workers)
3445   {
3446     g1h->ref_processor_stw()->set_active_mt_degree(workers->active_workers());
3447   }
3448 
3449   // Executes the given task using concurrent marking worker threads.
3450   virtual void execute(ProcessTask& task, uint ergo_workers);
3451 };
3452 
3453 // Gang task for possibly parallel reference processing
3454 
3455 class G1STWRefProcTaskProxy: public AbstractGangTask {
3456   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
3457   ProcessTask&     _proc_task;
3458   G1CollectedHeap* _g1h;
3459   G1ParScanThreadStateSet* _pss;
3460   G1ScannerTasksQueueSet* _task_queues;
3461   TaskTerminator* _terminator;
3462 
3463 public:
3464   G1STWRefProcTaskProxy(ProcessTask& proc_task,
3465                         G1CollectedHeap* g1h,
3466                         G1ParScanThreadStateSet* per_thread_states,
3467                         G1ScannerTasksQueueSet *task_queues,
3468                         TaskTerminator* terminator) :
3469     AbstractGangTask("Process reference objects in parallel"),
3470     _proc_task(proc_task),
3471     _g1h(g1h),
3472     _pss(per_thread_states),
3473     _task_queues(task_queues),
3474     _terminator(terminator)
3475   {}
3476 
3477   virtual void work(uint worker_id) {
3478     // The reference processing task executed by a single worker.
3479     ResourceMark rm;
3480     HandleMark   hm;
3481 
3482     G1STWIsAliveClosure is_alive(_g1h);
3483 
3484     G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
3485     pss->set_ref_discoverer(NULL);
3486 
3487     // Keep alive closure.
3488     G1CopyingKeepAliveClosure keep_alive(_g1h, pss);
3489 
3490     // Complete GC closure
3491     G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator, G1GCPhaseTimes::ObjCopy);
3492 
3493     // Call the reference processing task's work routine.
3494     _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
3495 
3496     // Note we cannot assert that the refs array is empty here as not all
3497     // of the processing tasks (specifically phase2 - pp2_work) execute
3498     // the complete_gc closure (which ordinarily would drain the queue) so
3499     // the queue may not be empty.
3500   }
3501 };
3502 
3503 // Driver routine for parallel reference processing.
3504 // Creates an instance of the ref processing gang
3505 // task and has the worker threads execute it.
3506 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task, uint ergo_workers) {
3507   assert(_workers != NULL, "Need parallel worker threads.");
3508 
3509   assert(_workers->active_workers() >= ergo_workers,
3510          "Ergonomically chosen workers (%u) should be less than or equal to active workers (%u)",
3511          ergo_workers, _workers->active_workers());
3512   TaskTerminator terminator(ergo_workers, _queues);
3513   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator);
3514 
3515   _workers->run_task(&proc_task_proxy, ergo_workers);
3516 }
3517 
3518 // End of weak reference support closures
3519 
3520 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
3521   double ref_proc_start = os::elapsedTime();
3522 
3523   ReferenceProcessor* rp = _ref_processor_stw;
3524   assert(rp->discovery_enabled(), "should have been enabled");
3525 
3526   // Closure to test whether a referent is alive.
3527   G1STWIsAliveClosure is_alive(this);
3528 
3529   // Even when parallel reference processing is enabled, the processing
3530   // of JNI refs is serial and performed serially by the current thread
3531   // rather than by a worker. The following PSS will be used for processing
3532   // JNI refs.
3533 
3534   // Use only a single queue for this PSS.
3535   G1ParScanThreadState*          pss = per_thread_states->state_for_worker(0);
3536   pss->set_ref_discoverer(NULL);
3537   assert(pss->queue_is_empty(), "pre-condition");
3538 
3539   // Keep alive closure.
3540   G1CopyingKeepAliveClosure keep_alive(this, pss);
3541 
3542   // Serial Complete GC closure
3543   G1STWDrainQueueClosure drain_queue(this, pss);
3544 
3545   // Setup the soft refs policy...
3546   rp->setup_policy(false);
3547 
3548   ReferenceProcessorPhaseTimes* pt = phase_times()->ref_phase_times();
3549 
3550   ReferenceProcessorStats stats;
3551   if (!rp->processing_is_mt()) {
3552     // Serial reference processing...
3553     stats = rp->process_discovered_references(&is_alive,
3554                                               &keep_alive,
3555                                               &drain_queue,
3556                                               NULL,
3557                                               pt);
3558   } else {
3559     uint no_of_gc_workers = workers()->active_workers();
3560 
3561     // Parallel reference processing
3562     assert(no_of_gc_workers <= rp->max_num_queues(),
3563            "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
3564            no_of_gc_workers,  rp->max_num_queues());
3565 
3566     G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues);
3567     stats = rp->process_discovered_references(&is_alive,
3568                                               &keep_alive,
3569                                               &drain_queue,
3570                                               &par_task_executor,
3571                                               pt);
3572   }
3573 
3574   _gc_tracer_stw->report_gc_reference_stats(stats);
3575 
3576   // We have completed copying any necessary live referent objects.
3577   assert(pss->queue_is_empty(), "both queue and overflow should be empty");
3578 
3579   make_pending_list_reachable();
3580 
3581   assert(!rp->discovery_enabled(), "Postcondition");
3582   rp->verify_no_references_recorded();
3583 
3584   double ref_proc_time = os::elapsedTime() - ref_proc_start;
3585   phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
3586 }
3587 
3588 void G1CollectedHeap::make_pending_list_reachable() {
3589   if (collector_state()->in_initial_mark_gc()) {
3590     oop pll_head = Universe::reference_pending_list();
3591     if (pll_head != NULL) {
3592       // Any valid worker id is fine here as we are in the VM thread and single-threaded.
3593       _cm->mark_in_next_bitmap(0 /* worker_id */, pll_head);
3594     }
3595   }
3596 }
3597 
3598 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) {
3599   Ticks start = Ticks::now();
3600   per_thread_states->flush();
3601   phase_times()->record_or_add_time_secs(G1GCPhaseTimes::MergePSS, 0 /* worker_id */, (Ticks::now() - start).seconds());
3602 }
3603 
3604 class G1PrepareEvacuationTask : public AbstractGangTask {
3605   class G1PrepareRegionsClosure : public HeapRegionClosure {
3606     G1CollectedHeap* _g1h;
3607     G1PrepareEvacuationTask* _parent_task;
3608     size_t _worker_humongous_total;
3609     size_t _worker_humongous_candidates;
3610 
3611     bool humongous_region_is_candidate(HeapRegion* region) const {
3612       assert(region->is_starts_humongous(), "Must start a humongous object");
3613 
3614       oop obj = oop(region->bottom());
3615 
3616       // Dead objects cannot be eager reclaim candidates. Due to class
3617       // unloading it is unsafe to query their classes so we return early.
3618       if (_g1h->is_obj_dead(obj, region)) {
3619         return false;
3620       }
3621 
3622       // If we do not have a complete remembered set for the region, then we can
3623       // not be sure that we have all references to it.
3624       if (!region->rem_set()->is_complete()) {
3625         return false;
3626       }
3627       // Candidate selection must satisfy the following constraints
3628       // while concurrent marking is in progress:
3629       //
3630       // * In order to maintain SATB invariants, an object must not be
3631       // reclaimed if it was allocated before the start of marking and
3632       // has not had its references scanned.  Such an object must have
3633       // its references (including type metadata) scanned to ensure no
3634       // live objects are missed by the marking process.  Objects
3635       // allocated after the start of concurrent marking don't need to
3636       // be scanned.
3637       //
3638       // * An object must not be reclaimed if it is on the concurrent
3639       // mark stack.  Objects allocated after the start of concurrent
3640       // marking are never pushed on the mark stack.
3641       //
3642       // Nominating only objects allocated after the start of concurrent
3643       // marking is sufficient to meet both constraints.  This may miss
3644       // some objects that satisfy the constraints, but the marking data
3645       // structures don't support efficiently performing the needed
3646       // additional tests or scrubbing of the mark stack.
3647       //
3648       // However, we presently only nominate is_typeArray() objects.
3649       // A humongous object containing references induces remembered
3650       // set entries on other regions.  In order to reclaim such an
3651       // object, those remembered sets would need to be cleaned up.
3652       //
3653       // We also treat is_typeArray() objects specially, allowing them
3654       // to be reclaimed even if allocated before the start of
3655       // concurrent mark.  For this we rely on mark stack insertion to
3656       // exclude is_typeArray() objects, preventing reclaiming an object
3657       // that is in the mark stack.  We also rely on the metadata for
3658       // such objects to be built-in and so ensured to be kept live.
3659       // Frequent allocation and drop of large binary blobs is an
3660       // important use case for eager reclaim, and this special handling
3661       // may reduce needed headroom.
3662 
3663       return obj->is_typeArray() &&
3664              _g1h->is_potential_eager_reclaim_candidate(region);
3665     }
3666 
3667   public:
3668     G1PrepareRegionsClosure(G1CollectedHeap* g1h, G1PrepareEvacuationTask* parent_task) :
3669       _g1h(g1h),
3670       _parent_task(parent_task),
3671       _worker_humongous_total(0),
3672       _worker_humongous_candidates(0) { }
3673 
3674     ~G1PrepareRegionsClosure() {
3675       _parent_task->add_humongous_candidates(_worker_humongous_candidates);
3676       _parent_task->add_humongous_total(_worker_humongous_total);
3677     }
3678 
3679     virtual bool do_heap_region(HeapRegion* hr) {
3680       // First prepare the region for scanning
3681       _g1h->rem_set()->prepare_region_for_scan(hr);
3682 
3683       // Now check if region is a humongous candidate
3684       if (!hr->is_starts_humongous()) {
3685         _g1h->register_region_with_region_attr(hr);
3686         return false;
3687       }
3688 
3689       uint index = hr->hrm_index();
3690       if (humongous_region_is_candidate(hr)) {
3691         _g1h->set_humongous_reclaim_candidate(index, true);
3692         _g1h->register_humongous_region_with_region_attr(index);
3693         _worker_humongous_candidates++;
3694         // We will later handle the remembered sets of these regions.
3695       } else {
3696         _g1h->set_humongous_reclaim_candidate(index, false);
3697         _g1h->register_region_with_region_attr(hr);
3698       }
3699       _worker_humongous_total++;
3700 
3701       return false;
3702     }
3703   };
3704 
3705   G1CollectedHeap* _g1h;
3706   HeapRegionClaimer _claimer;
3707   volatile size_t _humongous_total;
3708   volatile size_t _humongous_candidates;
3709 public:
3710   G1PrepareEvacuationTask(G1CollectedHeap* g1h) :
3711     AbstractGangTask("Prepare Evacuation"),
3712     _g1h(g1h),
3713     _claimer(_g1h->workers()->active_workers()),
3714     _humongous_total(0),
3715     _humongous_candidates(0) { }
3716 
3717   ~G1PrepareEvacuationTask() {
3718     _g1h->set_has_humongous_reclaim_candidate(_humongous_candidates > 0);
3719   }
3720 
3721   void work(uint worker_id) {
3722     G1PrepareRegionsClosure cl(_g1h, this);
3723     _g1h->heap_region_par_iterate_from_worker_offset(&cl, &_claimer, worker_id);
3724   }
3725 
3726   void add_humongous_candidates(size_t candidates) {
3727     Atomic::add(&_humongous_candidates, candidates);
3728   }
3729 
3730   void add_humongous_total(size_t total) {
3731     Atomic::add(&_humongous_total, total);
3732   }
3733 
3734   size_t humongous_candidates() {
3735     return _humongous_candidates;
3736   }
3737 
3738   size_t humongous_total() {
3739     return _humongous_total;
3740   }
3741 };
3742 
3743 void G1CollectedHeap::pre_evacuate_collection_set(G1EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
3744   _bytes_used_during_gc = 0;
3745 
3746   _expand_heap_after_alloc_failure = true;
3747   _evacuation_failed = false;
3748 
3749   // Disable the hot card cache.
3750   _hot_card_cache->reset_hot_cache_claimed_index();
3751   _hot_card_cache->set_use_cache(false);
3752 
3753   // Initialize the GC alloc regions.
3754   _allocator->init_gc_alloc_regions(evacuation_info);
3755 
3756   {
3757     Ticks start = Ticks::now();
3758     rem_set()->prepare_for_scan_heap_roots();
3759     phase_times()->record_prepare_heap_roots_time_ms((Ticks::now() - start).seconds() * 1000.0);
3760   }
3761 
3762   {
3763     G1PrepareEvacuationTask g1_prep_task(this);
3764     Tickspan task_time = run_task(&g1_prep_task);
3765 
3766     phase_times()->record_register_regions(task_time.seconds() * 1000.0,
3767                                            g1_prep_task.humongous_total(),
3768                                            g1_prep_task.humongous_candidates());
3769   }
3770 
3771   assert(_verifier->check_region_attr_table(), "Inconsistency in the region attributes table.");
3772   _preserved_marks_set.assert_empty();
3773 
3774 #if COMPILER2_OR_JVMCI
3775   DerivedPointerTable::clear();
3776 #endif
3777 
3778   // InitialMark needs claim bits to keep track of the marked-through CLDs.
3779   if (collector_state()->in_initial_mark_gc()) {
3780     concurrent_mark()->pre_initial_mark();
3781 
3782     double start_clear_claimed_marks = os::elapsedTime();
3783 
3784     ClassLoaderDataGraph::clear_claimed_marks();
3785 
3786     double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0;
3787     phase_times()->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms);
3788   }
3789 
3790   // Should G1EvacuationFailureALot be in effect for this GC?
3791   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
3792 }
3793 
3794 class G1EvacuateRegionsBaseTask : public AbstractGangTask {
3795 protected:
3796   G1CollectedHeap* _g1h;
3797   G1ParScanThreadStateSet* _per_thread_states;
3798   G1ScannerTasksQueueSet* _task_queues;
3799   TaskTerminator _terminator;
3800   uint _num_workers;
3801 
3802   void evacuate_live_objects(G1ParScanThreadState* pss,
3803                              uint worker_id,
3804                              G1GCPhaseTimes::GCParPhases objcopy_phase,
3805                              G1GCPhaseTimes::GCParPhases termination_phase) {
3806     G1GCPhaseTimes* p = _g1h->phase_times();
3807 
3808     Ticks start = Ticks::now();
3809     G1ParEvacuateFollowersClosure cl(_g1h, pss, _task_queues, &_terminator, objcopy_phase);
3810     cl.do_void();
3811 
3812     assert(pss->queue_is_empty(), "should be empty");
3813 
3814     Tickspan evac_time = (Ticks::now() - start);
3815     p->record_or_add_time_secs(objcopy_phase, worker_id, evac_time.seconds() - cl.term_time());
3816 
3817     if (termination_phase == G1GCPhaseTimes::Termination) {
3818       p->record_time_secs(termination_phase, worker_id, cl.term_time());
3819       p->record_thread_work_item(termination_phase, worker_id, cl.term_attempts());
3820     } else {
3821       p->record_or_add_time_secs(termination_phase, worker_id, cl.term_time());
3822       p->record_or_add_thread_work_item(termination_phase, worker_id, cl.term_attempts());
3823     }
3824     assert(pss->trim_ticks().seconds() == 0.0, "Unexpected partial trimming during evacuation");
3825   }
3826 
3827   virtual void start_work(uint worker_id) { }
3828 
3829   virtual void end_work(uint worker_id) { }
3830 
3831   virtual void scan_roots(G1ParScanThreadState* pss, uint worker_id) = 0;
3832 
3833   virtual void evacuate_live_objects(G1ParScanThreadState* pss, uint worker_id) = 0;
3834 
3835 public:
3836   G1EvacuateRegionsBaseTask(const char* name,
3837                             G1ParScanThreadStateSet* per_thread_states,
3838                             G1ScannerTasksQueueSet* task_queues,
3839                             uint num_workers) :
3840     AbstractGangTask(name),
3841     _g1h(G1CollectedHeap::heap()),
3842     _per_thread_states(per_thread_states),
3843     _task_queues(task_queues),
3844     _terminator(num_workers, _task_queues),
3845     _num_workers(num_workers)
3846   { }
3847 
3848   void work(uint worker_id) {
3849     start_work(worker_id);
3850 
3851     {
3852       ResourceMark rm;
3853       HandleMark   hm;
3854 
3855       G1ParScanThreadState* pss = _per_thread_states->state_for_worker(worker_id);
3856       pss->set_ref_discoverer(_g1h->ref_processor_stw());
3857 
3858       scan_roots(pss, worker_id);
3859       evacuate_live_objects(pss, worker_id);
3860     }
3861 
3862     end_work(worker_id);
3863   }
3864 };
3865 
3866 class G1EvacuateRegionsTask : public G1EvacuateRegionsBaseTask {
3867   G1RootProcessor* _root_processor;
3868 
3869   void scan_roots(G1ParScanThreadState* pss, uint worker_id) {
3870     _root_processor->evacuate_roots(pss, worker_id);
3871     _g1h->rem_set()->scan_heap_roots(pss, worker_id, G1GCPhaseTimes::ScanHR, G1GCPhaseTimes::ObjCopy);
3872     _g1h->rem_set()->scan_collection_set_regions(pss, worker_id, G1GCPhaseTimes::ScanHR, G1GCPhaseTimes::CodeRoots, G1GCPhaseTimes::ObjCopy);
3873   }
3874 
3875   void evacuate_live_objects(G1ParScanThreadState* pss, uint worker_id) {
3876     G1EvacuateRegionsBaseTask::evacuate_live_objects(pss, worker_id, G1GCPhaseTimes::ObjCopy, G1GCPhaseTimes::Termination);
3877   }
3878 
3879   void start_work(uint worker_id) {
3880     _g1h->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, Ticks::now().seconds());
3881   }
3882 
3883   void end_work(uint worker_id) {
3884     _g1h->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, Ticks::now().seconds());
3885   }
3886 
3887 public:
3888   G1EvacuateRegionsTask(G1CollectedHeap* g1h,
3889                         G1ParScanThreadStateSet* per_thread_states,
3890                         G1ScannerTasksQueueSet* task_queues,
3891                         G1RootProcessor* root_processor,
3892                         uint num_workers) :
3893     G1EvacuateRegionsBaseTask("G1 Evacuate Regions", per_thread_states, task_queues, num_workers),
3894     _root_processor(root_processor)
3895   { }
3896 };
3897 
3898 void G1CollectedHeap::evacuate_initial_collection_set(G1ParScanThreadStateSet* per_thread_states) {
3899   G1GCPhaseTimes* p = phase_times();
3900 
3901   {
3902     Ticks start = Ticks::now();
3903     rem_set()->merge_heap_roots(true /* initial_evacuation */);
3904     p->record_merge_heap_roots_time((Ticks::now() - start).seconds() * 1000.0);
3905   }
3906 
3907   Tickspan task_time;
3908   const uint num_workers = workers()->active_workers();
3909 
3910   Ticks start_processing = Ticks::now();
3911   {
3912     G1RootProcessor root_processor(this, num_workers);
3913     G1EvacuateRegionsTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, num_workers);
3914     task_time = run_task(&g1_par_task);
3915     // Closing the inner scope will execute the destructor for the G1RootProcessor object.
3916     // To extract its code root fixup time we measure total time of this scope and
3917     // subtract from the time the WorkGang task took.
3918   }
3919   Tickspan total_processing = Ticks::now() - start_processing;
3920 
3921   p->record_initial_evac_time(task_time.seconds() * 1000.0);
3922   p->record_or_add_code_root_fixup_time((total_processing - task_time).seconds() * 1000.0);
3923 }
3924 
3925 class G1EvacuateOptionalRegionsTask : public G1EvacuateRegionsBaseTask {
3926 
3927   void scan_roots(G1ParScanThreadState* pss, uint worker_id) {
3928     _g1h->rem_set()->scan_heap_roots(pss, worker_id, G1GCPhaseTimes::OptScanHR, G1GCPhaseTimes::OptObjCopy);
3929     _g1h->rem_set()->scan_collection_set_regions(pss, worker_id, G1GCPhaseTimes::OptScanHR, G1GCPhaseTimes::OptCodeRoots, G1GCPhaseTimes::OptObjCopy);
3930   }
3931 
3932   void evacuate_live_objects(G1ParScanThreadState* pss, uint worker_id) {
3933     G1EvacuateRegionsBaseTask::evacuate_live_objects(pss, worker_id, G1GCPhaseTimes::OptObjCopy, G1GCPhaseTimes::OptTermination);
3934   }
3935 
3936 public:
3937   G1EvacuateOptionalRegionsTask(G1ParScanThreadStateSet* per_thread_states,
3938                                 G1ScannerTasksQueueSet* queues,
3939                                 uint num_workers) :
3940     G1EvacuateRegionsBaseTask("G1 Evacuate Optional Regions", per_thread_states, queues, num_workers) {
3941   }
3942 };
3943 
3944 void G1CollectedHeap::evacuate_next_optional_regions(G1ParScanThreadStateSet* per_thread_states) {
3945   class G1MarkScope : public MarkScope { };
3946 
3947   Tickspan task_time;
3948 
3949   Ticks start_processing = Ticks::now();
3950   {
3951     G1MarkScope code_mark_scope;
3952     G1EvacuateOptionalRegionsTask task(per_thread_states, _task_queues, workers()->active_workers());
3953     task_time = run_task(&task);
3954     // See comment in evacuate_collection_set() for the reason of the scope.
3955   }
3956   Tickspan total_processing = Ticks::now() - start_processing;
3957 
3958   G1GCPhaseTimes* p = phase_times();
3959   p->record_or_add_code_root_fixup_time((total_processing - task_time).seconds() * 1000.0);
3960 }
3961 
3962 void G1CollectedHeap::evacuate_optional_collection_set(G1ParScanThreadStateSet* per_thread_states) {
3963   const double gc_start_time_ms = phase_times()->cur_collection_start_sec() * 1000.0;
3964 
3965   while (!evacuation_failed() && _collection_set.optional_region_length() > 0) {
3966 
3967     double time_used_ms = os::elapsedTime() * 1000.0 - gc_start_time_ms;
3968     double time_left_ms = MaxGCPauseMillis - time_used_ms;
3969 
3970     if (time_left_ms < 0 ||
3971         !_collection_set.finalize_optional_for_evacuation(time_left_ms * policy()->optional_evacuation_fraction())) {
3972       log_trace(gc, ergo, cset)("Skipping evacuation of %u optional regions, no more regions can be evacuated in %.3fms",
3973                                 _collection_set.optional_region_length(), time_left_ms);
3974       break;
3975     }
3976 
3977     {
3978       Ticks start = Ticks::now();
3979       rem_set()->merge_heap_roots(false /* initial_evacuation */);
3980       phase_times()->record_or_add_optional_merge_heap_roots_time((Ticks::now() - start).seconds() * 1000.0);
3981     }
3982 
3983     {
3984       Ticks start = Ticks::now();
3985       evacuate_next_optional_regions(per_thread_states);
3986       phase_times()->record_or_add_optional_evac_time((Ticks::now() - start).seconds() * 1000.0);
3987     }
3988   }
3989 
3990   _collection_set.abandon_optional_collection_set(per_thread_states);
3991 }
3992 
3993 void G1CollectedHeap::post_evacuate_collection_set(G1EvacuationInfo& evacuation_info,
3994                                                    G1RedirtyCardsQueueSet* rdcqs,
3995                                                    G1ParScanThreadStateSet* per_thread_states) {
3996   G1GCPhaseTimes* p = phase_times();
3997 
3998   rem_set()->cleanup_after_scan_heap_roots();
3999 
4000   // Process any discovered reference objects - we have
4001   // to do this _before_ we retire the GC alloc regions
4002   // as we may have to copy some 'reachable' referent
4003   // objects (and their reachable sub-graphs) that were
4004   // not copied during the pause.
4005   process_discovered_references(per_thread_states);
4006 
4007   G1STWIsAliveClosure is_alive(this);
4008   G1KeepAliveClosure keep_alive(this);
4009 
4010   WeakProcessor::weak_oops_do(workers(), &is_alive, &keep_alive, p->weak_phase_times());
4011 
4012   if (G1StringDedup::is_enabled()) {
4013     double string_dedup_time_ms = os::elapsedTime();
4014 
4015     string_dedup_cleaning(&is_alive, &keep_alive, p);
4016 
4017     double string_cleanup_time_ms = (os::elapsedTime() - string_dedup_time_ms) * 1000.0;
4018     p->record_string_deduplication_time(string_cleanup_time_ms);
4019   }
4020 
4021   _allocator->release_gc_alloc_regions(evacuation_info);
4022 
4023   if (evacuation_failed()) {
4024     restore_after_evac_failure(rdcqs);
4025 
4026     // Reset the G1EvacuationFailureALot counters and flags
4027     NOT_PRODUCT(reset_evacuation_should_fail();)
4028 
4029     double recalculate_used_start = os::elapsedTime();
4030     set_used(recalculate_used());
4031     p->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
4032 
4033     if (_archive_allocator != NULL) {
4034       _archive_allocator->clear_used();
4035     }
4036     for (uint i = 0; i < ParallelGCThreads; i++) {
4037       if (_evacuation_failed_info_array[i].has_failed()) {
4038         _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
4039       }
4040     }
4041   } else {
4042     // The "used" of the the collection set have already been subtracted
4043     // when they were freed.  Add in the bytes used.
4044     increase_used(_bytes_used_during_gc);
4045   }
4046 
4047   _preserved_marks_set.assert_empty();
4048 
4049   merge_per_thread_state_info(per_thread_states);
4050 
4051   // Reset and re-enable the hot card cache.
4052   // Note the counts for the cards in the regions in the
4053   // collection set are reset when the collection set is freed.
4054   _hot_card_cache->reset_hot_cache();
4055   _hot_card_cache->set_use_cache(true);
4056 
4057   purge_code_root_memory();
4058 
4059   redirty_logged_cards(rdcqs);
4060 
4061   free_collection_set(&_collection_set, evacuation_info, per_thread_states->surviving_young_words());
4062 
4063   eagerly_reclaim_humongous_regions();
4064 
4065   record_obj_copy_mem_stats();
4066 
4067   evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before());
4068   evacuation_info.set_bytes_used(_bytes_used_during_gc);
4069 
4070 #if COMPILER2_OR_JVMCI
4071   double start = os::elapsedTime();
4072   DerivedPointerTable::update_pointers();
4073   phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0);
4074 #endif
4075   policy()->print_age_table();
4076 }
4077 
4078 void G1CollectedHeap::record_obj_copy_mem_stats() {
4079   policy()->old_gen_alloc_tracker()->
4080     add_allocated_bytes_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
4081 
4082   _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
4083                                                create_g1_evac_summary(&_old_evac_stats));
4084 }
4085 
4086 void G1CollectedHeap::free_region(HeapRegion* hr, FreeRegionList* free_list) {
4087   assert(!hr->is_free(), "the region should not be free");
4088   assert(!hr->is_empty(), "the region should not be empty");
4089   assert(_hrm->is_available(hr->hrm_index()), "region should be committed");
4090 
4091   if (G1VerifyBitmaps) {
4092     MemRegion mr(hr->bottom(), hr->end());
4093     concurrent_mark()->clear_range_in_prev_bitmap(mr);
4094   }
4095 
4096   // Clear the card counts for this region.
4097   // Note: we only need to do this if the region is not young
4098   // (since we don't refine cards in young regions).
4099   if (!hr->is_young()) {
4100     _hot_card_cache->reset_card_counts(hr);
4101   }
4102 
4103   // Reset region metadata to allow reuse.
4104   hr->hr_clear(true /* clear_space */);
4105   _policy->remset_tracker()->update_at_free(hr);
4106 
4107   if (free_list != NULL) {
4108     free_list->add_ordered(hr);
4109   }
4110 }
4111 
4112 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
4113                                             FreeRegionList* free_list) {
4114   assert(hr->is_humongous(), "this is only for humongous regions");
4115   assert(free_list != NULL, "pre-condition");
4116   hr->clear_humongous();
4117   free_region(hr, free_list);
4118 }
4119 
4120 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed,
4121                                            const uint humongous_regions_removed) {
4122   if (old_regions_removed > 0 || humongous_regions_removed > 0) {
4123     MutexLocker x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4124     _old_set.bulk_remove(old_regions_removed);
4125     _humongous_set.bulk_remove(humongous_regions_removed);
4126   }
4127 
4128 }
4129 
4130 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
4131   assert(list != NULL, "list can't be null");
4132   if (!list->is_empty()) {
4133     MutexLocker x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4134     _hrm->insert_list_into_free_list(list);
4135   }
4136 }
4137 
4138 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
4139   decrease_used(bytes);
4140 }
4141 
4142 class G1FreeCollectionSetTask : public AbstractGangTask {
4143   // Helper class to keep statistics for the collection set freeing
4144   class FreeCSetStats {
4145     size_t _before_used_bytes;   // Usage in regions successfully evacutate
4146     size_t _after_used_bytes;    // Usage in regions failing evacuation
4147     size_t _bytes_allocated_in_old_since_last_gc; // Size of young regions turned into old
4148     size_t _failure_used_words;  // Live size in failed regions
4149     size_t _failure_waste_words; // Wasted size in failed regions
4150     size_t _rs_length;           // Remembered set size
4151     uint _regions_freed;         // Number of regions freed
4152   public:
4153     FreeCSetStats() :
4154         _before_used_bytes(0),
4155         _after_used_bytes(0),
4156         _bytes_allocated_in_old_since_last_gc(0),
4157         _failure_used_words(0),
4158         _failure_waste_words(0),
4159         _rs_length(0),
4160         _regions_freed(0) { }
4161 
4162     void merge_stats(FreeCSetStats* other) {
4163       assert(other != NULL, "invariant");
4164       _before_used_bytes += other->_before_used_bytes;
4165       _after_used_bytes += other->_after_used_bytes;
4166       _bytes_allocated_in_old_since_last_gc += other->_bytes_allocated_in_old_since_last_gc;
4167       _failure_used_words += other->_failure_used_words;
4168       _failure_waste_words += other->_failure_waste_words;
4169       _rs_length += other->_rs_length;
4170       _regions_freed += other->_regions_freed;
4171     }
4172 
4173     void report(G1CollectedHeap* g1h, G1EvacuationInfo* evacuation_info) {
4174       evacuation_info->set_regions_freed(_regions_freed);
4175       evacuation_info->increment_collectionset_used_after(_after_used_bytes);
4176 
4177       g1h->decrement_summary_bytes(_before_used_bytes);
4178       g1h->alloc_buffer_stats(G1HeapRegionAttr::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words);
4179 
4180       G1Policy *policy = g1h->policy();
4181       policy->old_gen_alloc_tracker()->add_allocated_bytes_since_last_gc(_bytes_allocated_in_old_since_last_gc);
4182       policy->record_rs_length(_rs_length);
4183       policy->cset_regions_freed();
4184     }
4185 
4186     void account_failed_region(HeapRegion* r) {
4187       size_t used_words = r->marked_bytes() / HeapWordSize;
4188       _failure_used_words += used_words;
4189       _failure_waste_words += HeapRegion::GrainWords - used_words;
4190       _after_used_bytes += r->used();
4191 
4192       // When moving a young gen region to old gen, we "allocate" that whole
4193       // region there. This is in addition to any already evacuated objects.
4194       // Notify the policy about that. Old gen regions do not cause an
4195       // additional allocation: both the objects still in the region and the
4196       // ones already moved are accounted for elsewhere.
4197       if (r->is_young()) {
4198         _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes;
4199       }
4200     }
4201 
4202     void account_evacuated_region(HeapRegion* r) {
4203       _before_used_bytes += r->used();
4204       _regions_freed += 1;
4205     }
4206 
4207     void account_rs_length(HeapRegion* r) {
4208       _rs_length += r->rem_set()->occupied();
4209     }
4210   };
4211 
4212   // Closure applied to all regions in the collection set.
4213   class FreeCSetClosure : public HeapRegionClosure {
4214     // Helper to send JFR events for regions.
4215     class JFREventForRegion {
4216       EventGCPhaseParallel _event;
4217     public:
4218       JFREventForRegion(HeapRegion* region, uint worker_id) : _event() {
4219         _event.set_gcId(GCId::current());
4220         _event.set_gcWorkerId(worker_id);
4221         if (region->is_young()) {
4222           _event.set_name(G1GCPhaseTimes::phase_name(G1GCPhaseTimes::YoungFreeCSet));
4223         } else {
4224           _event.set_name(G1GCPhaseTimes::phase_name(G1GCPhaseTimes::NonYoungFreeCSet));
4225         }
4226       }
4227 
4228       ~JFREventForRegion() {
4229         _event.commit();
4230       }
4231     };
4232 
4233     // Helper to do timing for region work.
4234     class TimerForRegion {
4235       Tickspan& _time;
4236       Ticks     _start_time;
4237     public:
4238       TimerForRegion(Tickspan& time) : _time(time), _start_time(Ticks::now()) { }
4239       ~TimerForRegion() {
4240         _time += Ticks::now() - _start_time;
4241       }
4242     };
4243 
4244     // FreeCSetClosure members
4245     G1CollectedHeap* _g1h;
4246     const size_t*    _surviving_young_words;
4247     uint             _worker_id;
4248     Tickspan         _young_time;
4249     Tickspan         _non_young_time;
4250     FreeCSetStats*   _stats;
4251 
4252     void assert_in_cset(HeapRegion* r) {
4253       assert(r->young_index_in_cset() != 0 &&
4254              (uint)r->young_index_in_cset() <= _g1h->collection_set()->young_region_length(),
4255              "Young index %u is wrong for region %u of type %s with %u young regions",
4256              r->young_index_in_cset(), r->hrm_index(), r->get_type_str(), _g1h->collection_set()->young_region_length());
4257     }
4258 
4259     void handle_evacuated_region(HeapRegion* r) {
4260       assert(!r->is_empty(), "Region %u is an empty region in the collection set.", r->hrm_index());
4261       stats()->account_evacuated_region(r);
4262 
4263       // Free the region and and its remembered set.
4264       _g1h->free_region(r, NULL);
4265     }
4266 
4267     void handle_failed_region(HeapRegion* r) {
4268       // Do some allocation statistics accounting. Regions that failed evacuation
4269       // are always made old, so there is no need to update anything in the young
4270       // gen statistics, but we need to update old gen statistics.
4271       stats()->account_failed_region(r);
4272 
4273       // Update the region state due to the failed evacuation.
4274       r->handle_evacuation_failure();
4275 
4276       // Add region to old set, need to hold lock.
4277       MutexLocker x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4278       _g1h->old_set_add(r);
4279     }
4280 
4281     Tickspan& timer_for_region(HeapRegion* r) {
4282       return r->is_young() ? _young_time : _non_young_time;
4283     }
4284 
4285     FreeCSetStats* stats() {
4286       return _stats;
4287     }
4288   public:
4289     FreeCSetClosure(const size_t* surviving_young_words,
4290                     uint worker_id,
4291                     FreeCSetStats* stats) :
4292         HeapRegionClosure(),
4293         _g1h(G1CollectedHeap::heap()),
4294         _surviving_young_words(surviving_young_words),
4295         _worker_id(worker_id),
4296         _young_time(),
4297         _non_young_time(),
4298         _stats(stats) { }
4299 
4300     virtual bool do_heap_region(HeapRegion* r) {
4301       assert(r->in_collection_set(), "Invariant: %u missing from CSet", r->hrm_index());
4302       JFREventForRegion event(r, _worker_id);
4303       TimerForRegion timer(timer_for_region(r));
4304 
4305       _g1h->clear_region_attr(r);
4306       stats()->account_rs_length(r);
4307 
4308       if (r->is_young()) {
4309         assert_in_cset(r);
4310         r->record_surv_words_in_group(_surviving_young_words[r->young_index_in_cset()]);
4311       }
4312 
4313       if (r->evacuation_failed()) {
4314         handle_failed_region(r);
4315       } else {
4316         handle_evacuated_region(r);
4317       }
4318       assert(!_g1h->is_on_master_free_list(r), "sanity");
4319 
4320       return false;
4321     }
4322 
4323     void report_timing(Tickspan parallel_time) {
4324       G1GCPhaseTimes* pt = _g1h->phase_times();
4325       pt->record_time_secs(G1GCPhaseTimes::ParFreeCSet, _worker_id, parallel_time.seconds());
4326       if (_young_time.value() > 0) {
4327         pt->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, _worker_id, _young_time.seconds());
4328       }
4329       if (_non_young_time.value() > 0) {
4330         pt->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, _worker_id, _non_young_time.seconds());
4331       }
4332     }
4333   };
4334 
4335   // G1FreeCollectionSetTask members
4336   G1CollectedHeap*  _g1h;
4337   G1EvacuationInfo* _evacuation_info;
4338   FreeCSetStats*    _worker_stats;
4339   HeapRegionClaimer _claimer;
4340   const size_t*     _surviving_young_words;
4341   uint              _active_workers;
4342 
4343   FreeCSetStats* worker_stats(uint worker) {
4344     return &_worker_stats[worker];
4345   }
4346 
4347   void report_statistics() {
4348     // Merge the accounting
4349     FreeCSetStats total_stats;
4350     for (uint worker = 0; worker < _active_workers; worker++) {
4351       total_stats.merge_stats(worker_stats(worker));
4352     }
4353     total_stats.report(_g1h, _evacuation_info);
4354   }
4355 
4356 public:
4357   G1FreeCollectionSetTask(G1EvacuationInfo* evacuation_info, const size_t* surviving_young_words, uint active_workers) :
4358       AbstractGangTask("G1 Free Collection Set"),
4359       _g1h(G1CollectedHeap::heap()),
4360       _evacuation_info(evacuation_info),
4361       _worker_stats(NEW_C_HEAP_ARRAY(FreeCSetStats, active_workers, mtGC)),
4362       _claimer(active_workers),
4363       _surviving_young_words(surviving_young_words),
4364       _active_workers(active_workers) {
4365     for (uint worker = 0; worker < active_workers; worker++) {
4366       ::new (&_worker_stats[worker]) FreeCSetStats();
4367     }
4368   }
4369 
4370   ~G1FreeCollectionSetTask() {
4371     Ticks serial_time = Ticks::now();
4372     report_statistics();
4373     for (uint worker = 0; worker < _active_workers; worker++) {
4374       _worker_stats[worker].~FreeCSetStats();
4375     }
4376     FREE_C_HEAP_ARRAY(FreeCSetStats, _worker_stats);
4377     _g1h->phase_times()->record_serial_free_cset_time_ms((Ticks::now() - serial_time).seconds() * 1000.0);
4378   }
4379 
4380   virtual void work(uint worker_id) {
4381     EventGCPhaseParallel event;
4382     Ticks start = Ticks::now();
4383     FreeCSetClosure cl(_surviving_young_words, worker_id, worker_stats(worker_id));
4384     _g1h->collection_set_par_iterate_all(&cl, &_claimer, worker_id);
4385 
4386     // Report the total parallel time along with some more detailed metrics.
4387     cl.report_timing(Ticks::now() - start);
4388     event.commit(GCId::current(), worker_id, G1GCPhaseTimes::phase_name(G1GCPhaseTimes::ParFreeCSet));
4389   }
4390 };
4391 
4392 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, G1EvacuationInfo& evacuation_info, const size_t* surviving_young_words) {
4393   _eden.clear();
4394 
4395   // The free collections set is split up in two tasks, the first
4396   // frees the collection set and records what regions are free,
4397   // and the second one rebuilds the free list. This proved to be
4398   // more efficient than adding a sorted list to another.
4399 
4400   Ticks free_cset_start_time = Ticks::now();
4401   {
4402     uint const num_cs_regions = _collection_set.region_length();
4403     uint const num_workers = clamp(num_cs_regions, 1u, workers()->active_workers());
4404     G1FreeCollectionSetTask cl(&evacuation_info, surviving_young_words, num_workers);
4405 
4406     log_debug(gc, ergo)("Running %s using %u workers for collection set length %u (%u)",
4407                         cl.name(), num_workers, num_cs_regions, num_regions());
4408     workers()->run_task(&cl, num_workers);
4409   }
4410 
4411   Ticks free_cset_end_time = Ticks::now();
4412   phase_times()->record_total_free_cset_time_ms((free_cset_end_time - free_cset_start_time).seconds() * 1000.0);
4413 
4414   // Now rebuild the free region list.
4415   hrm()->rebuild_free_list(workers());
4416   phase_times()->record_total_rebuild_freelist_time_ms((Ticks::now() - free_cset_end_time).seconds() * 1000.0);
4417 
4418   collection_set->clear();
4419 }
4420 
4421 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
4422  private:
4423   FreeRegionList* _free_region_list;
4424   HeapRegionSet* _proxy_set;
4425   uint _humongous_objects_reclaimed;
4426   uint _humongous_regions_reclaimed;
4427   size_t _freed_bytes;
4428  public:
4429 
4430   G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
4431     _free_region_list(free_region_list), _proxy_set(NULL), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) {
4432   }
4433 
4434   virtual bool do_heap_region(HeapRegion* r) {
4435     if (!r->is_starts_humongous()) {
4436       return false;
4437     }
4438 
4439     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4440 
4441     oop obj = (oop)r->bottom();
4442     G1CMBitMap* next_bitmap = g1h->concurrent_mark()->next_mark_bitmap();
4443 
4444     // The following checks whether the humongous object is live are sufficient.
4445     // The main additional check (in addition to having a reference from the roots
4446     // or the young gen) is whether the humongous object has a remembered set entry.
4447     //
4448     // A humongous object cannot be live if there is no remembered set for it
4449     // because:
4450     // - there can be no references from within humongous starts regions referencing
4451     // the object because we never allocate other objects into them.
4452     // (I.e. there are no intra-region references that may be missed by the
4453     // remembered set)
4454     // - as soon there is a remembered set entry to the humongous starts region
4455     // (i.e. it has "escaped" to an old object) this remembered set entry will stay
4456     // until the end of a concurrent mark.
4457     //
4458     // It is not required to check whether the object has been found dead by marking
4459     // or not, in fact it would prevent reclamation within a concurrent cycle, as
4460     // all objects allocated during that time are considered live.
4461     // SATB marking is even more conservative than the remembered set.
4462     // So if at this point in the collection there is no remembered set entry,
4463     // nobody has a reference to it.
4464     // At the start of collection we flush all refinement logs, and remembered sets
4465     // are completely up-to-date wrt to references to the humongous object.
4466     //
4467     // Other implementation considerations:
4468     // - never consider object arrays at this time because they would pose
4469     // considerable effort for cleaning up the the remembered sets. This is
4470     // required because stale remembered sets might reference locations that
4471     // are currently allocated into.
4472     uint region_idx = r->hrm_index();
4473     if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
4474         !r->rem_set()->is_empty()) {
4475       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",
4476                                region_idx,
4477                                (size_t)obj->size() * HeapWordSize,
4478                                p2i(r->bottom()),
4479                                r->rem_set()->occupied(),
4480                                r->rem_set()->strong_code_roots_list_length(),
4481                                next_bitmap->is_marked(r->bottom()),
4482                                g1h->is_humongous_reclaim_candidate(region_idx),
4483                                obj->is_typeArray()
4484                               );
4485       return false;
4486     }
4487 
4488     guarantee(obj->is_typeArray(),
4489               "Only eagerly reclaiming type arrays is supported, but the object "
4490               PTR_FORMAT " is not.", p2i(r->bottom()));
4491 
4492     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",
4493                              region_idx,
4494                              (size_t)obj->size() * HeapWordSize,
4495                              p2i(r->bottom()),
4496                              r->rem_set()->occupied(),
4497                              r->rem_set()->strong_code_roots_list_length(),
4498                              next_bitmap->is_marked(r->bottom()),
4499                              g1h->is_humongous_reclaim_candidate(region_idx),
4500                              obj->is_typeArray()
4501                             );
4502 
4503     G1ConcurrentMark* const cm = g1h->concurrent_mark();
4504     cm->humongous_object_eagerly_reclaimed(r);
4505     assert(!cm->is_marked_in_prev_bitmap(obj) && !cm->is_marked_in_next_bitmap(obj),
4506            "Eagerly reclaimed humongous region %u should not be marked at all but is in prev %s next %s",
4507            region_idx,
4508            BOOL_TO_STR(cm->is_marked_in_prev_bitmap(obj)),
4509            BOOL_TO_STR(cm->is_marked_in_next_bitmap(obj)));
4510     _humongous_objects_reclaimed++;
4511     do {
4512       HeapRegion* next = g1h->next_region_in_humongous(r);
4513       _freed_bytes += r->used();
4514       r->set_containing_set(NULL);
4515       _humongous_regions_reclaimed++;
4516       g1h->free_humongous_region(r, _free_region_list);
4517       r = next;
4518     } while (r != NULL);
4519 
4520     return false;
4521   }
4522 
4523   uint humongous_objects_reclaimed() {
4524     return _humongous_objects_reclaimed;
4525   }
4526 
4527   uint humongous_regions_reclaimed() {
4528     return _humongous_regions_reclaimed;
4529   }
4530 
4531   size_t bytes_freed() const {
4532     return _freed_bytes;
4533   }
4534 };
4535 
4536 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
4537   assert_at_safepoint_on_vm_thread();
4538 
4539   if (!G1EagerReclaimHumongousObjects ||
4540       (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) {
4541     phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
4542     return;
4543   }
4544 
4545   double start_time = os::elapsedTime();
4546 
4547   FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
4548 
4549   G1FreeHumongousRegionClosure cl(&local_cleanup_list);
4550   heap_region_iterate(&cl);
4551 
4552   remove_from_old_sets(0, cl.humongous_regions_reclaimed());
4553 
4554   G1HRPrinter* hrp = hr_printer();
4555   if (hrp->is_active()) {
4556     FreeRegionListIterator iter(&local_cleanup_list);
4557     while (iter.more_available()) {
4558       HeapRegion* hr = iter.get_next();
4559       hrp->cleanup(hr);
4560     }
4561   }
4562 
4563   prepend_to_freelist(&local_cleanup_list);
4564   decrement_summary_bytes(cl.bytes_freed());
4565 
4566   phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
4567                                                        cl.humongous_objects_reclaimed());
4568 }
4569 
4570 class G1AbandonCollectionSetClosure : public HeapRegionClosure {
4571 public:
4572   virtual bool do_heap_region(HeapRegion* r) {
4573     assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index());
4574     G1CollectedHeap::heap()->clear_region_attr(r);
4575     r->clear_young_index_in_cset();
4576     return false;
4577   }
4578 };
4579 
4580 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) {
4581   G1AbandonCollectionSetClosure cl;
4582   collection_set_iterate_all(&cl);
4583 
4584   collection_set->clear();
4585   collection_set->stop_incremental_building();
4586 }
4587 
4588 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
4589   return _allocator->is_retained_old_region(hr);
4590 }
4591 
4592 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
4593   _eden.add(hr);
4594   _policy->set_region_eden(hr);
4595 }
4596 
4597 #ifdef ASSERT
4598 
4599 class NoYoungRegionsClosure: public HeapRegionClosure {
4600 private:
4601   bool _success;
4602 public:
4603   NoYoungRegionsClosure() : _success(true) { }
4604   bool do_heap_region(HeapRegion* r) {
4605     if (r->is_young()) {
4606       log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
4607                             p2i(r->bottom()), p2i(r->end()));
4608       _success = false;
4609     }
4610     return false;
4611   }
4612   bool success() { return _success; }
4613 };
4614 
4615 bool G1CollectedHeap::check_young_list_empty() {
4616   bool ret = (young_regions_count() == 0);
4617 
4618   NoYoungRegionsClosure closure;
4619   heap_region_iterate(&closure);
4620   ret = ret && closure.success();
4621 
4622   return ret;
4623 }
4624 
4625 #endif // ASSERT
4626 
4627 class TearDownRegionSetsClosure : public HeapRegionClosure {
4628   HeapRegionSet *_old_set;
4629 
4630 public:
4631   TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
4632 
4633   bool do_heap_region(HeapRegion* r) {
4634     if (r->is_old()) {
4635       _old_set->remove(r);
4636     } else if(r->is_young()) {
4637       r->uninstall_surv_rate_group();
4638     } else {
4639       // We ignore free regions, we'll empty the free list afterwards.
4640       // We ignore humongous and archive regions, we're not tearing down these
4641       // sets.
4642       assert(r->is_archive() || r->is_free() || r->is_humongous(),
4643              "it cannot be another type");
4644     }
4645     return false;
4646   }
4647 
4648   ~TearDownRegionSetsClosure() {
4649     assert(_old_set->is_empty(), "post-condition");
4650   }
4651 };
4652 
4653 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
4654   assert_at_safepoint_on_vm_thread();
4655 
4656   if (!free_list_only) {
4657     TearDownRegionSetsClosure cl(&_old_set);
4658     heap_region_iterate(&cl);
4659 
4660     // Note that emptying the _young_list is postponed and instead done as
4661     // the first step when rebuilding the regions sets again. The reason for
4662     // this is that during a full GC string deduplication needs to know if
4663     // a collected region was young or old when the full GC was initiated.
4664   }
4665   _hrm->remove_all_free_regions();
4666 }
4667 
4668 void G1CollectedHeap::increase_used(size_t bytes) {
4669   _summary_bytes_used += bytes;
4670 }
4671 
4672 void G1CollectedHeap::decrease_used(size_t bytes) {
4673   assert(_summary_bytes_used >= bytes,
4674          "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
4675          _summary_bytes_used, bytes);
4676   _summary_bytes_used -= bytes;
4677 }
4678 
4679 void G1CollectedHeap::set_used(size_t bytes) {
4680   _summary_bytes_used = bytes;
4681 }
4682 
4683 class RebuildRegionSetsClosure : public HeapRegionClosure {
4684 private:
4685   bool _free_list_only;
4686 
4687   HeapRegionSet* _old_set;
4688   HeapRegionManager* _hrm;
4689 
4690   size_t _total_used;
4691 
4692 public:
4693   RebuildRegionSetsClosure(bool free_list_only,
4694                            HeapRegionSet* old_set,
4695                            HeapRegionManager* hrm) :
4696     _free_list_only(free_list_only),
4697     _old_set(old_set), _hrm(hrm), _total_used(0) {
4698     assert(_hrm->num_free_regions() == 0, "pre-condition");
4699     if (!free_list_only) {
4700       assert(_old_set->is_empty(), "pre-condition");
4701     }
4702   }
4703 
4704   bool do_heap_region(HeapRegion* r) {
4705     if (r->is_empty()) {
4706       assert(r->rem_set()->is_empty(), "Empty regions should have empty remembered sets.");
4707       // Add free regions to the free list
4708       r->set_free();
4709       _hrm->insert_into_free_list(r);
4710     } else if (!_free_list_only) {
4711       assert(r->rem_set()->is_empty(), "At this point remembered sets must have been cleared.");
4712 
4713       if (r->is_archive() || r->is_humongous()) {
4714         // We ignore archive and humongous regions. We left these sets unchanged.
4715       } else {
4716         assert(r->is_young() || r->is_free() || r->is_old(), "invariant");
4717         // We now move all (non-humongous, non-old, non-archive) regions to old gen, and register them as such.
4718         r->move_to_old();
4719         _old_set->add(r);
4720       }
4721       _total_used += r->used();
4722     }
4723 
4724     return false;
4725   }
4726 
4727   size_t total_used() {
4728     return _total_used;
4729   }
4730 };
4731 
4732 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
4733   assert_at_safepoint_on_vm_thread();
4734 
4735   if (!free_list_only) {
4736     _eden.clear();
4737     _survivor.clear();
4738   }
4739 
4740   RebuildRegionSetsClosure cl(free_list_only, &_old_set, _hrm);
4741   heap_region_iterate(&cl);
4742 
4743   if (!free_list_only) {
4744     set_used(cl.total_used());
4745     if (_archive_allocator != NULL) {
4746       _archive_allocator->clear_used();
4747     }
4748   }
4749   assert_used_and_recalculate_used_equal(this);
4750 }
4751 
4752 // Methods for the mutator alloc region
4753 
4754 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
4755                                                       bool force,
4756                                                       uint node_index) {
4757   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
4758   bool should_allocate = policy()->should_allocate_mutator_region();
4759   if (force || should_allocate) {
4760     HeapRegion* new_alloc_region = new_region(word_size,
4761                                               HeapRegionType::Eden,
4762                                               false /* do_expand */,
4763                                               node_index);
4764     if (new_alloc_region != NULL) {
4765       set_region_short_lived_locked(new_alloc_region);
4766       _hr_printer.alloc(new_alloc_region, !should_allocate);
4767       _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region);
4768       _policy->remset_tracker()->update_at_allocate(new_alloc_region);
4769       return new_alloc_region;
4770     }
4771   }
4772   return NULL;
4773 }
4774 
4775 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
4776                                                   size_t allocated_bytes) {
4777   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
4778   assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
4779 
4780   collection_set()->add_eden_region(alloc_region);
4781   increase_used(allocated_bytes);
4782   _eden.add_used_bytes(allocated_bytes);
4783   _hr_printer.retire(alloc_region);
4784 
4785   // We update the eden sizes here, when the region is retired,
4786   // instead of when it's allocated, since this is the point that its
4787   // used space has been recorded in _summary_bytes_used.
4788   g1mm()->update_eden_size();
4789 }
4790 
4791 // Methods for the GC alloc regions
4792 
4793 bool G1CollectedHeap::has_more_regions(G1HeapRegionAttr dest) {
4794   if (dest.is_old()) {
4795     return true;
4796   } else {
4797     return survivor_regions_count() < policy()->max_survivor_regions();
4798   }
4799 }
4800 
4801 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, G1HeapRegionAttr dest, uint node_index) {
4802   assert(FreeList_lock->owned_by_self(), "pre-condition");
4803 
4804   if (!has_more_regions(dest)) {
4805     return NULL;
4806   }
4807 
4808   HeapRegionType type;
4809   if (dest.is_young()) {
4810     type = HeapRegionType::Survivor;
4811   } else {
4812     type = HeapRegionType::Old;
4813   }
4814 
4815   HeapRegion* new_alloc_region = new_region(word_size,
4816                                             type,
4817                                             true /* do_expand */,
4818                                             node_index);
4819 
4820   if (new_alloc_region != NULL) {
4821     if (type.is_survivor()) {
4822       new_alloc_region->set_survivor();
4823       _survivor.add(new_alloc_region);
4824       _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region);
4825     } else {
4826       new_alloc_region->set_old();
4827       _verifier->check_bitmaps("Old Region Allocation", new_alloc_region);
4828     }
4829     _policy->remset_tracker()->update_at_allocate(new_alloc_region);
4830     register_region_with_region_attr(new_alloc_region);
4831     _hr_printer.alloc(new_alloc_region);
4832     return new_alloc_region;
4833   }
4834   return NULL;
4835 }
4836 
4837 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
4838                                              size_t allocated_bytes,
4839                                              G1HeapRegionAttr dest) {
4840   _bytes_used_during_gc += allocated_bytes;
4841   if (dest.is_old()) {
4842     old_set_add(alloc_region);
4843   } else {
4844     assert(dest.is_young(), "Retiring alloc region should be young (%d)", dest.type());
4845     _survivor.add_used_bytes(allocated_bytes);
4846   }
4847 
4848   bool const during_im = collector_state()->in_initial_mark_gc();
4849   if (during_im && allocated_bytes > 0) {
4850     _cm->root_regions()->add(alloc_region->next_top_at_mark_start(), alloc_region->top());
4851   }
4852   _hr_printer.retire(alloc_region);
4853 }
4854 
4855 HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
4856   bool expanded = false;
4857   uint index = _hrm->find_highest_free(&expanded);
4858 
4859   if (index != G1_NO_HRM_INDEX) {
4860     if (expanded) {
4861       log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
4862                                 HeapRegion::GrainWords * HeapWordSize);
4863     }
4864     return _hrm->allocate_free_regions_starting_at(index, 1);
4865   }
4866   return NULL;
4867 }
4868 
4869 // Optimized nmethod scanning
4870 
4871 class RegisterNMethodOopClosure: public OopClosure {
4872   G1CollectedHeap* _g1h;
4873   nmethod* _nm;
4874 
4875   template <class T> void do_oop_work(T* p) {
4876     T heap_oop = RawAccess<>::oop_load(p);
4877     if (!CompressedOops::is_null(heap_oop)) {
4878       oop obj = CompressedOops::decode_not_null(heap_oop);
4879       HeapRegion* hr = _g1h->heap_region_containing(obj);
4880       assert(!hr->is_continues_humongous(),
4881              "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
4882              " starting at " HR_FORMAT,
4883              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
4884 
4885       // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
4886       hr->add_strong_code_root_locked(_nm);
4887     }
4888   }
4889 
4890 public:
4891   RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
4892     _g1h(g1h), _nm(nm) {}
4893 
4894   void do_oop(oop* p)       { do_oop_work(p); }
4895   void do_oop(narrowOop* p) { do_oop_work(p); }
4896 };
4897 
4898 class UnregisterNMethodOopClosure: public OopClosure {
4899   G1CollectedHeap* _g1h;
4900   nmethod* _nm;
4901 
4902   template <class T> void do_oop_work(T* p) {
4903     T heap_oop = RawAccess<>::oop_load(p);
4904     if (!CompressedOops::is_null(heap_oop)) {
4905       oop obj = CompressedOops::decode_not_null(heap_oop);
4906       HeapRegion* hr = _g1h->heap_region_containing(obj);
4907       assert(!hr->is_continues_humongous(),
4908              "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
4909              " starting at " HR_FORMAT,
4910              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
4911 
4912       hr->remove_strong_code_root(_nm);
4913     }
4914   }
4915 
4916 public:
4917   UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
4918     _g1h(g1h), _nm(nm) {}
4919 
4920   void do_oop(oop* p)       { do_oop_work(p); }
4921   void do_oop(narrowOop* p) { do_oop_work(p); }
4922 };
4923 
4924 void G1CollectedHeap::register_nmethod(nmethod* nm) {
4925   guarantee(nm != NULL, "sanity");
4926   RegisterNMethodOopClosure reg_cl(this, nm);
4927   nm->oops_do(&reg_cl);
4928 }
4929 
4930 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
4931   guarantee(nm != NULL, "sanity");
4932   UnregisterNMethodOopClosure reg_cl(this, nm);
4933   nm->oops_do(&reg_cl, true);
4934 }
4935 
4936 void G1CollectedHeap::purge_code_root_memory() {
4937   double purge_start = os::elapsedTime();
4938   G1CodeRootSet::purge();
4939   double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
4940   phase_times()->record_strong_code_root_purge_time(purge_time_ms);
4941 }
4942 
4943 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
4944   G1CollectedHeap* _g1h;
4945 
4946 public:
4947   RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
4948     _g1h(g1h) {}
4949 
4950   void do_code_blob(CodeBlob* cb) {
4951     nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
4952     if (nm == NULL) {
4953       return;
4954     }
4955 
4956     _g1h->register_nmethod(nm);
4957   }
4958 };
4959 
4960 void G1CollectedHeap::rebuild_strong_code_roots() {
4961   RebuildStrongCodeRootClosure blob_cl(this);
4962   CodeCache::blobs_do(&blob_cl);
4963 }
4964 
4965 void G1CollectedHeap::initialize_serviceability() {
4966   _g1mm->initialize_serviceability();
4967 }
4968 
4969 MemoryUsage G1CollectedHeap::memory_usage() {
4970   return _g1mm->memory_usage();
4971 }
4972 
4973 GrowableArray<GCMemoryManager*> G1CollectedHeap::memory_managers() {
4974   return _g1mm->memory_managers();
4975 }
4976 
4977 GrowableArray<MemoryPool*> G1CollectedHeap::memory_pools() {
4978   return _g1mm->memory_pools();
4979 }
--- EOF ---