1 /*
   2  * Copyright (c) 2001, 2019, 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/g1CollectedHeap.inline.hpp"
  35 #include "gc/g1/g1CollectionSet.hpp"
  36 #include "gc/g1/g1CollectorState.hpp"
  37 #include "gc/g1/g1ConcurrentRefine.hpp"
  38 #include "gc/g1/g1ConcurrentRefineThread.hpp"
  39 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp"
  40 #include "gc/g1/g1DirtyCardQueue.hpp"
  41 #include "gc/g1/g1EvacStats.inline.hpp"
  42 #include "gc/g1/g1FullCollector.hpp"
  43 #include "gc/g1/g1GCPhaseTimes.hpp"
  44 #include "gc/g1/g1HeapSizingPolicy.hpp"
  45 #include "gc/g1/g1HeapTransition.hpp"
  46 #include "gc/g1/g1HeapVerifier.hpp"
  47 #include "gc/g1/g1HotCardCache.hpp"
  48 #include "gc/g1/g1MemoryPool.hpp"
  49 #include "gc/g1/g1OopClosures.inline.hpp"
  50 #include "gc/g1/g1ParScanThreadState.inline.hpp"
  51 #include "gc/g1/g1Policy.hpp"
  52 #include "gc/g1/g1RegionToSpaceMapper.hpp"
  53 #include "gc/g1/g1RemSet.hpp"
  54 #include "gc/g1/g1RootClosures.hpp"
  55 #include "gc/g1/g1RootProcessor.hpp"
  56 #include "gc/g1/g1SATBMarkQueueSet.hpp"
  57 #include "gc/g1/g1StringDedup.hpp"
  58 #include "gc/g1/g1ThreadLocalData.hpp"
  59 #include "gc/g1/g1YCTypes.hpp"
  60 #include "gc/g1/g1YoungRemSetSamplingThread.hpp"
  61 #include "gc/g1/g1VMOperations.hpp"
  62 #include "gc/g1/heapRegion.inline.hpp"
  63 #include "gc/g1/heapRegionRemSet.hpp"
  64 #include "gc/g1/heapRegionSet.inline.hpp"
  65 #include "gc/shared/gcBehaviours.hpp"
  66 #include "gc/shared/gcHeapSummary.hpp"
  67 #include "gc/shared/gcId.hpp"
  68 #include "gc/shared/gcLocker.hpp"
  69 #include "gc/shared/gcTimer.hpp"
  70 #include "gc/shared/gcTrace.hpp"
  71 #include "gc/shared/gcTraceTime.inline.hpp"
  72 #include "gc/shared/generationSpec.hpp"
  73 #include "gc/shared/isGCActiveMark.hpp"
  74 #include "gc/shared/oopStorageParState.hpp"
  75 #include "gc/shared/parallelCleaning.hpp"
  76 #include "gc/shared/preservedMarks.inline.hpp"
  77 #include "gc/shared/suspendibleThreadSet.hpp"
  78 #include "gc/shared/referenceProcessor.inline.hpp"
  79 #include "gc/shared/taskqueue.inline.hpp"
  80 #include "gc/shared/weakProcessor.inline.hpp"
  81 #include "gc/shared/workerPolicy.hpp"
  82 #include "logging/log.hpp"
  83 #include "memory/allocation.hpp"
  84 #include "memory/iterator.hpp"
  85 #include "memory/resourceArea.hpp"
  86 #include "memory/universe.hpp"
  87 #include "oops/access.inline.hpp"
  88 #include "oops/compressedOops.inline.hpp"
  89 #include "oops/oop.inline.hpp"
  90 #include "runtime/atomic.hpp"
  91 #include "runtime/flags/flagSetting.hpp"
  92 #include "runtime/handles.inline.hpp"
  93 #include "runtime/init.hpp"
  94 #include "runtime/orderAccess.hpp"
  95 #include "runtime/threadSMR.hpp"
  96 #include "runtime/vmThread.hpp"
  97 #include "utilities/align.hpp"
  98 #include "utilities/globalDefinitions.hpp"
  99 #include "utilities/stack.inline.hpp"
 100 
 101 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
 102 
 103 // INVARIANTS/NOTES
 104 //
 105 // All allocation activity covered by the G1CollectedHeap interface is
 106 // serialized by acquiring the HeapLock.  This happens in mem_allocate
 107 // and allocate_new_tlab, which are the "entry" points to the
 108 // allocation code from the rest of the JVM.  (Note that this does not
 109 // apply to TLAB allocation, which is not part of this interface: it
 110 // is done by clients of this interface.)
 111 
 112 class RedirtyLoggedCardTableEntryClosure : public G1CardTableEntryClosure {
 113  private:
 114   size_t _num_dirtied;
 115   G1CollectedHeap* _g1h;
 116   G1CardTable* _g1_ct;
 117 
 118   HeapRegion* region_for_card(CardValue* card_ptr) const {
 119     return _g1h->heap_region_containing(_g1_ct->addr_for(card_ptr));
 120   }
 121 
 122   bool will_become_free(HeapRegion* hr) const {
 123     // A region will be freed by free_collection_set if the region is in the
 124     // collection set and has not had an evacuation failure.
 125     return _g1h->is_in_cset(hr) && !hr->evacuation_failed();
 126   }
 127 
 128  public:
 129   RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : G1CardTableEntryClosure(),
 130     _num_dirtied(0), _g1h(g1h), _g1_ct(g1h->card_table()) { }
 131 
 132   bool do_card_ptr(CardValue* card_ptr, uint worker_i) {
 133     HeapRegion* hr = region_for_card(card_ptr);
 134 
 135     // Should only dirty cards in regions that won't be freed.
 136     if (!will_become_free(hr)) {
 137       *card_ptr = G1CardTable::dirty_card_val();
 138       _num_dirtied++;
 139     }
 140 
 141     return true;
 142   }
 143 
 144   size_t num_dirtied()   const { return _num_dirtied; }
 145 };
 146 
 147 
 148 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
 149   HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
 150 }
 151 
 152 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
 153   // The from card cache is not the memory that is actually committed. So we cannot
 154   // take advantage of the zero_filled parameter.
 155   reset_from_card_cache(start_idx, num_regions);
 156 }
 157 
 158 Tickspan G1CollectedHeap::run_task(AbstractGangTask* task) {
 159   Ticks start = Ticks::now();
 160   workers()->run_task(task, workers()->active_workers());
 161   return Ticks::now() - start;
 162 }
 163 
 164 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
 165                                              MemRegion mr) {
 166   return new HeapRegion(hrs_index, bot(), mr);
 167 }
 168 
 169 // Private methods.
 170 
 171 HeapRegion* G1CollectedHeap::new_region(size_t word_size, HeapRegionType type, bool do_expand) {
 172   assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
 173          "the only time we use this to allocate a humongous region is "
 174          "when we are allocating a single humongous region");
 175 
 176   HeapRegion* res = _hrm->allocate_free_region(type);
 177 
 178   if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
 179     // Currently, only attempts to allocate GC alloc regions set
 180     // do_expand to true. So, we should only reach here during a
 181     // safepoint. If this assumption changes we might have to
 182     // reconsider the use of _expand_heap_after_alloc_failure.
 183     assert(SafepointSynchronize::is_at_safepoint(), "invariant");
 184 
 185     log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B",
 186                               word_size * HeapWordSize);
 187 
 188     if (expand(word_size * HeapWordSize)) {
 189       // Given that expand() succeeded in expanding the heap, and we
 190       // always expand the heap by an amount aligned to the heap
 191       // region size, the free list should in theory not be empty.
 192       // In either case allocate_free_region() will check for NULL.
 193       res = _hrm->allocate_free_region(type);
 194     } else {
 195       _expand_heap_after_alloc_failure = false;
 196     }
 197   }
 198   return res;
 199 }
 200 
 201 HeapWord*
 202 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
 203                                                            uint num_regions,
 204                                                            size_t word_size) {
 205   assert(first != G1_NO_HRM_INDEX, "pre-condition");
 206   assert(is_humongous(word_size), "word_size should be humongous");
 207   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 208 
 209   // Index of last region in the series.
 210   uint last = first + num_regions - 1;
 211 
 212   // We need to initialize the region(s) we just discovered. This is
 213   // a bit tricky given that it can happen concurrently with
 214   // refinement threads refining cards on these regions and
 215   // potentially wanting to refine the BOT as they are scanning
 216   // those cards (this can happen shortly after a cleanup; see CR
 217   // 6991377). So we have to set up the region(s) carefully and in
 218   // a specific order.
 219 
 220   // The word size sum of all the regions we will allocate.
 221   size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
 222   assert(word_size <= word_size_sum, "sanity");
 223 
 224   // This will be the "starts humongous" region.
 225   HeapRegion* first_hr = region_at(first);
 226   // The header of the new object will be placed at the bottom of
 227   // the first region.
 228   HeapWord* new_obj = first_hr->bottom();
 229   // This will be the new top of the new object.
 230   HeapWord* obj_top = new_obj + word_size;
 231 
 232   // First, we need to zero the header of the space that we will be
 233   // allocating. When we update top further down, some refinement
 234   // threads might try to scan the region. By zeroing the header we
 235   // ensure that any thread that will try to scan the region will
 236   // come across the zero klass word and bail out.
 237   //
 238   // NOTE: It would not have been correct to have used
 239   // CollectedHeap::fill_with_object() and make the space look like
 240   // an int array. The thread that is doing the allocation will
 241   // later update the object header to a potentially different array
 242   // type and, for a very short period of time, the klass and length
 243   // fields will be inconsistent. This could cause a refinement
 244   // thread to calculate the object size incorrectly.
 245   Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
 246 
 247   // Next, pad out the unused tail of the last region with filler
 248   // objects, for improved usage accounting.
 249   // How many words we use for filler objects.
 250   size_t word_fill_size = word_size_sum - word_size;
 251 
 252   // How many words memory we "waste" which cannot hold a filler object.
 253   size_t words_not_fillable = 0;
 254 
 255   if (word_fill_size >= min_fill_size()) {
 256     fill_with_objects(obj_top, word_fill_size);
 257   } else if (word_fill_size > 0) {
 258     // We have space to fill, but we cannot fit an object there.
 259     words_not_fillable = word_fill_size;
 260     word_fill_size = 0;
 261   }
 262 
 263   // We will set up the first region as "starts humongous". This
 264   // will also update the BOT covering all the regions to reflect
 265   // that there is a single object that starts at the bottom of the
 266   // first region.
 267   first_hr->set_starts_humongous(obj_top, word_fill_size);
 268   _policy->remset_tracker()->update_at_allocate(first_hr);
 269   // Then, if there are any, we will set up the "continues
 270   // humongous" regions.
 271   HeapRegion* hr = NULL;
 272   for (uint i = first + 1; i <= last; ++i) {
 273     hr = region_at(i);
 274     hr->set_continues_humongous(first_hr);
 275     _policy->remset_tracker()->update_at_allocate(hr);
 276   }
 277 
 278   // Up to this point no concurrent thread would have been able to
 279   // do any scanning on any region in this series. All the top
 280   // fields still point to bottom, so the intersection between
 281   // [bottom,top] and [card_start,card_end] will be empty. Before we
 282   // update the top fields, we'll do a storestore to make sure that
 283   // no thread sees the update to top before the zeroing of the
 284   // object header and the BOT initialization.
 285   OrderAccess::storestore();
 286 
 287   // Now, we will update the top fields of the "continues humongous"
 288   // regions except the last one.
 289   for (uint i = first; i < last; ++i) {
 290     hr = region_at(i);
 291     hr->set_top(hr->end());
 292   }
 293 
 294   hr = region_at(last);
 295   // If we cannot fit a filler object, we must set top to the end
 296   // of the humongous object, otherwise we cannot iterate the heap
 297   // and the BOT will not be complete.
 298   hr->set_top(hr->end() - words_not_fillable);
 299 
 300   assert(hr->bottom() < obj_top && obj_top <= hr->end(),
 301          "obj_top should be in last region");
 302 
 303   _verifier->check_bitmaps("Humongous Region Allocation", first_hr);
 304 
 305   assert(words_not_fillable == 0 ||
 306          first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(),
 307          "Miscalculation in humongous allocation");
 308 
 309   increase_used((word_size_sum - words_not_fillable) * HeapWordSize);
 310 
 311   for (uint i = first; i <= last; ++i) {
 312     hr = region_at(i);
 313     _humongous_set.add(hr);
 314     _hr_printer.alloc(hr);
 315   }
 316 
 317   return new_obj;
 318 }
 319 
 320 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) {
 321   assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size);
 322   return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
 323 }
 324 
 325 // If could fit into free regions w/o expansion, try.
 326 // Otherwise, if can expand, do so.
 327 // Otherwise, if using ex regions might help, try with ex given back.
 328 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
 329   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 330 
 331   _verifier->verify_region_sets_optional();
 332 
 333   uint first = G1_NO_HRM_INDEX;
 334   uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);
 335 
 336   if (obj_regions == 1) {
 337     // Only one region to allocate, try to use a fast path by directly allocating
 338     // from the free lists. Do not try to expand here, we will potentially do that
 339     // later.
 340     HeapRegion* hr = new_region(word_size, HeapRegionType::Humongous, false /* do_expand */);
 341     if (hr != NULL) {
 342       first = hr->hrm_index();
 343     }
 344   } else {
 345     // Policy: Try only empty regions (i.e. already committed first). Maybe we
 346     // are lucky enough to find some.
 347     first = _hrm->find_contiguous_only_empty(obj_regions);
 348     if (first != G1_NO_HRM_INDEX) {
 349       _hrm->allocate_free_regions_starting_at(first, obj_regions);
 350     }
 351   }
 352 
 353   if (first == G1_NO_HRM_INDEX) {
 354     // Policy: We could not find enough regions for the humongous object in the
 355     // free list. Look through the heap to find a mix of free and uncommitted regions.
 356     // If so, try expansion.
 357     first = _hrm->find_contiguous_empty_or_unavailable(obj_regions);
 358     if (first != G1_NO_HRM_INDEX) {
 359       // We found something. Make sure these regions are committed, i.e. expand
 360       // the heap. Alternatively we could do a defragmentation GC.
 361       log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B",
 362                                     word_size * HeapWordSize);
 363 
 364       _hrm->expand_at(first, obj_regions, workers());
 365       policy()->record_new_heap_size(num_regions());
 366 
 367 #ifdef ASSERT
 368       for (uint i = first; i < first + obj_regions; ++i) {
 369         HeapRegion* hr = region_at(i);
 370         assert(hr->is_free(), "sanity");
 371         assert(hr->is_empty(), "sanity");
 372         assert(is_on_master_free_list(hr), "sanity");
 373       }
 374 #endif
 375       _hrm->allocate_free_regions_starting_at(first, obj_regions);
 376     } else {
 377       // Policy: Potentially trigger a defragmentation GC.
 378     }
 379   }
 380 
 381   HeapWord* result = NULL;
 382   if (first != G1_NO_HRM_INDEX) {
 383     result = humongous_obj_allocate_initialize_regions(first, obj_regions, word_size);
 384     assert(result != NULL, "it should always return a valid result");
 385 
 386     // A successful humongous object allocation changes the used space
 387     // information of the old generation so we need to recalculate the
 388     // sizes and update the jstat counters here.
 389     g1mm()->update_sizes();
 390   }
 391 
 392   _verifier->verify_region_sets_optional();
 393 
 394   return result;
 395 }
 396 
 397 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t min_size,
 398                                              size_t requested_size,
 399                                              size_t* actual_size) {
 400   assert_heap_not_locked_and_not_at_safepoint();
 401   assert(!is_humongous(requested_size), "we do not allow humongous TLABs");
 402 
 403   return attempt_allocation(min_size, requested_size, actual_size);
 404 }
 405 
 406 HeapWord*
 407 G1CollectedHeap::mem_allocate(size_t word_size,
 408                               bool*  gc_overhead_limit_was_exceeded) {
 409   assert_heap_not_locked_and_not_at_safepoint();
 410 
 411   if (is_humongous(word_size)) {
 412     return attempt_allocation_humongous(word_size);
 413   }
 414   size_t dummy = 0;
 415   return attempt_allocation(word_size, word_size, &dummy);
 416 }
 417 
 418 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size) {
 419   ResourceMark rm; // For retrieving the thread names in log messages.
 420 
 421   // Make sure you read the note in attempt_allocation_humongous().
 422 
 423   assert_heap_not_locked_and_not_at_safepoint();
 424   assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
 425          "be called for humongous allocation requests");
 426 
 427   // We should only get here after the first-level allocation attempt
 428   // (attempt_allocation()) failed to allocate.
 429 
 430   // We will loop until a) we manage to successfully perform the
 431   // allocation or b) we successfully schedule a collection which
 432   // fails to perform the allocation. b) is the only case when we'll
 433   // return NULL.
 434   HeapWord* result = NULL;
 435   for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 436     bool should_try_gc;
 437     uint gc_count_before;
 438 
 439     {
 440       MutexLocker x(Heap_lock);
 441       result = _allocator->attempt_allocation_locked(word_size);
 442       if (result != NULL) {
 443         return result;
 444       }
 445 
 446       // If the GCLocker is active and we are bound for a GC, try expanding young gen.
 447       // This is different to when only GCLocker::needs_gc() is set: try to avoid
 448       // waiting because the GCLocker is active to not wait too long.
 449       if (GCLocker::is_active_and_needs_gc() && policy()->can_expand_young_list()) {
 450         // No need for an ergo message here, can_expand_young_list() does this when
 451         // it returns true.
 452         result = _allocator->attempt_allocation_force(word_size);
 453         if (result != NULL) {
 454           return result;
 455         }
 456       }
 457       // Only try a GC if the GCLocker does not signal the need for a GC. Wait until
 458       // the GCLocker initiated GC has been performed and then retry. This includes
 459       // the case when the GC Locker is not active but has not been performed.
 460       should_try_gc = !GCLocker::needs_gc();
 461       // Read the GC count while still holding the Heap_lock.
 462       gc_count_before = total_collections();
 463     }
 464 
 465     if (should_try_gc) {
 466       bool succeeded;
 467       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 468                                    GCCause::_g1_inc_collection_pause);
 469       if (result != NULL) {
 470         assert(succeeded, "only way to get back a non-NULL result");
 471         log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT,
 472                              Thread::current()->name(), p2i(result));
 473         return result;
 474       }
 475 
 476       if (succeeded) {
 477         // We successfully scheduled a collection which failed to allocate. No
 478         // point in trying to allocate further. We'll just return NULL.
 479         log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate "
 480                              SIZE_FORMAT " words", Thread::current()->name(), word_size);
 481         return NULL;
 482       }
 483       log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT " words",
 484                            Thread::current()->name(), word_size);
 485     } else {
 486       // Failed to schedule a collection.
 487       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 488         log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating "
 489                                SIZE_FORMAT " words", Thread::current()->name(), word_size);
 490         return NULL;
 491       }
 492       log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name());
 493       // The GCLocker is either active or the GCLocker initiated
 494       // GC has not yet been performed. Stall until it is and
 495       // then retry the allocation.
 496       GCLocker::stall_until_clear();
 497       gclocker_retry_count += 1;
 498     }
 499 
 500     // We can reach here if we were unsuccessful in scheduling a
 501     // collection (because another thread beat us to it) or if we were
 502     // stalled due to the GC locker. In either can we should retry the
 503     // allocation attempt in case another thread successfully
 504     // performed a collection and reclaimed enough space. We do the
 505     // first attempt (without holding the Heap_lock) here and the
 506     // follow-on attempt will be at the start of the next loop
 507     // iteration (after taking the Heap_lock).
 508     size_t dummy = 0;
 509     result = _allocator->attempt_allocation(word_size, word_size, &dummy);
 510     if (result != NULL) {
 511       return result;
 512     }
 513 
 514     // Give a warning if we seem to be looping forever.
 515     if ((QueuedAllocationWarningCount > 0) &&
 516         (try_count % QueuedAllocationWarningCount == 0)) {
 517       log_warning(gc, alloc)("%s:  Retried allocation %u times for " SIZE_FORMAT " words",
 518                              Thread::current()->name(), try_count, word_size);
 519     }
 520   }
 521 
 522   ShouldNotReachHere();
 523   return NULL;
 524 }
 525 
 526 void G1CollectedHeap::begin_archive_alloc_range(bool open) {
 527   assert_at_safepoint_on_vm_thread();
 528   if (_archive_allocator == NULL) {
 529     _archive_allocator = G1ArchiveAllocator::create_allocator(this, open);
 530   }
 531 }
 532 
 533 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) {
 534   // Allocations in archive regions cannot be of a size that would be considered
 535   // humongous even for a minimum-sized region, because G1 region sizes/boundaries
 536   // may be different at archive-restore time.
 537   return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words());
 538 }
 539 
 540 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) {
 541   assert_at_safepoint_on_vm_thread();
 542   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 543   if (is_archive_alloc_too_large(word_size)) {
 544     return NULL;
 545   }
 546   return _archive_allocator->archive_mem_allocate(word_size);
 547 }
 548 
 549 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
 550                                               size_t end_alignment_in_bytes) {
 551   assert_at_safepoint_on_vm_thread();
 552   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 553 
 554   // Call complete_archive to do the real work, filling in the MemRegion
 555   // array with the archive regions.
 556   _archive_allocator->complete_archive(ranges, end_alignment_in_bytes);
 557   delete _archive_allocator;
 558   _archive_allocator = NULL;
 559 }
 560 
 561 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) {
 562   assert(ranges != NULL, "MemRegion array NULL");
 563   assert(count != 0, "No MemRegions provided");
 564   MemRegion reserved = _hrm->reserved();
 565   for (size_t i = 0; i < count; i++) {
 566     if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) {
 567       return false;
 568     }
 569   }
 570   return true;
 571 }
 572 
 573 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges,
 574                                             size_t count,
 575                                             bool open) {
 576   assert(!is_init_completed(), "Expect to be called at JVM init time");
 577   assert(ranges != NULL, "MemRegion array NULL");
 578   assert(count != 0, "No MemRegions provided");
 579   MutexLocker x(Heap_lock);
 580 
 581   MemRegion reserved = _hrm->reserved();
 582   HeapWord* prev_last_addr = NULL;
 583   HeapRegion* prev_last_region = NULL;
 584 
 585   // Temporarily disable pretouching of heap pages. This interface is used
 586   // when mmap'ing archived heap data in, so pre-touching is wasted.
 587   FlagSetting fs(AlwaysPreTouch, false);
 588 
 589   // Enable archive object checking used by G1MarkSweep. We have to let it know
 590   // about each archive range, so that objects in those ranges aren't marked.
 591   G1ArchiveAllocator::enable_archive_object_check();
 592 
 593   // For each specified MemRegion range, allocate the corresponding G1
 594   // regions and mark them as archive regions. We expect the ranges
 595   // in ascending starting address order, without overlap.
 596   for (size_t i = 0; i < count; i++) {
 597     MemRegion curr_range = ranges[i];
 598     HeapWord* start_address = curr_range.start();
 599     size_t word_size = curr_range.word_size();
 600     HeapWord* last_address = curr_range.last();
 601     size_t commits = 0;
 602 
 603     guarantee(reserved.contains(start_address) && reserved.contains(last_address),
 604               "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 605               p2i(start_address), p2i(last_address));
 606     guarantee(start_address > prev_last_addr,
 607               "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 608               p2i(start_address), p2i(prev_last_addr));
 609     prev_last_addr = last_address;
 610 
 611     // Check for ranges that start in the same G1 region in which the previous
 612     // range ended, and adjust the start address so we don't try to allocate
 613     // the same region again. If the current range is entirely within that
 614     // region, skip it, just adjusting the recorded top.
 615     HeapRegion* start_region = _hrm->addr_to_region(start_address);
 616     if ((prev_last_region != NULL) && (start_region == prev_last_region)) {
 617       start_address = start_region->end();
 618       if (start_address > last_address) {
 619         increase_used(word_size * HeapWordSize);
 620         start_region->set_top(last_address + 1);
 621         continue;
 622       }
 623       start_region->set_top(start_address);
 624       curr_range = MemRegion(start_address, last_address + 1);
 625       start_region = _hrm->addr_to_region(start_address);
 626     }
 627 
 628     // Perform the actual region allocation, exiting if it fails.
 629     // Then note how much new space we have allocated.
 630     if (!_hrm->allocate_containing_regions(curr_range, &commits, workers())) {
 631       return false;
 632     }
 633     increase_used(word_size * HeapWordSize);
 634     if (commits != 0) {
 635       log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B",
 636                                 HeapRegion::GrainWords * HeapWordSize * commits);
 637 
 638     }
 639 
 640     // Mark each G1 region touched by the range as archive, add it to
 641     // the old set, and set top.
 642     HeapRegion* curr_region = _hrm->addr_to_region(start_address);
 643     HeapRegion* last_region = _hrm->addr_to_region(last_address);
 644     prev_last_region = last_region;
 645 
 646     while (curr_region != NULL) {
 647       assert(curr_region->is_empty() && !curr_region->is_pinned(),
 648              "Region already in use (index %u)", curr_region->hrm_index());
 649       if (open) {
 650         curr_region->set_open_archive();
 651       } else {
 652         curr_region->set_closed_archive();
 653       }
 654       _hr_printer.alloc(curr_region);
 655       _archive_set.add(curr_region);
 656       HeapWord* top;
 657       HeapRegion* next_region;
 658       if (curr_region != last_region) {
 659         top = curr_region->end();
 660         next_region = _hrm->next_region_in_heap(curr_region);
 661       } else {
 662         top = last_address + 1;
 663         next_region = NULL;
 664       }
 665       curr_region->set_top(top);
 666       curr_region->set_first_dead(top);
 667       curr_region->set_end_of_live(top);
 668       curr_region = next_region;
 669     }
 670 
 671     // Notify mark-sweep of the archive
 672     G1ArchiveAllocator::set_range_archive(curr_range, open);
 673   }
 674   return true;
 675 }
 676 
 677 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) {
 678   assert(!is_init_completed(), "Expect to be called at JVM init time");
 679   assert(ranges != NULL, "MemRegion array NULL");
 680   assert(count != 0, "No MemRegions provided");
 681   MemRegion reserved = _hrm->reserved();
 682   HeapWord *prev_last_addr = NULL;
 683   HeapRegion* prev_last_region = NULL;
 684 
 685   // For each MemRegion, create filler objects, if needed, in the G1 regions
 686   // that contain the address range. The address range actually within the
 687   // MemRegion will not be modified. That is assumed to have been initialized
 688   // elsewhere, probably via an mmap of archived heap data.
 689   MutexLocker x(Heap_lock);
 690   for (size_t i = 0; i < count; i++) {
 691     HeapWord* start_address = ranges[i].start();
 692     HeapWord* last_address = ranges[i].last();
 693 
 694     assert(reserved.contains(start_address) && reserved.contains(last_address),
 695            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 696            p2i(start_address), p2i(last_address));
 697     assert(start_address > prev_last_addr,
 698            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 699            p2i(start_address), p2i(prev_last_addr));
 700 
 701     HeapRegion* start_region = _hrm->addr_to_region(start_address);
 702     HeapRegion* last_region = _hrm->addr_to_region(last_address);
 703     HeapWord* bottom_address = start_region->bottom();
 704 
 705     // Check for a range beginning in the same region in which the
 706     // previous one ended.
 707     if (start_region == prev_last_region) {
 708       bottom_address = prev_last_addr + 1;
 709     }
 710 
 711     // Verify that the regions were all marked as archive regions by
 712     // alloc_archive_regions.
 713     HeapRegion* curr_region = start_region;
 714     while (curr_region != NULL) {
 715       guarantee(curr_region->is_archive(),
 716                 "Expected archive region at index %u", curr_region->hrm_index());
 717       if (curr_region != last_region) {
 718         curr_region = _hrm->next_region_in_heap(curr_region);
 719       } else {
 720         curr_region = NULL;
 721       }
 722     }
 723 
 724     prev_last_addr = last_address;
 725     prev_last_region = last_region;
 726 
 727     // Fill the memory below the allocated range with dummy object(s),
 728     // if the region bottom does not match the range start, or if the previous
 729     // range ended within the same G1 region, and there is a gap.
 730     if (start_address != bottom_address) {
 731       size_t fill_size = pointer_delta(start_address, bottom_address);
 732       G1CollectedHeap::fill_with_objects(bottom_address, fill_size);
 733       increase_used(fill_size * HeapWordSize);
 734     }
 735   }
 736 }
 737 
 738 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t min_word_size,
 739                                                      size_t desired_word_size,
 740                                                      size_t* actual_word_size) {
 741   assert_heap_not_locked_and_not_at_safepoint();
 742   assert(!is_humongous(desired_word_size), "attempt_allocation() should not "
 743          "be called for humongous allocation requests");
 744 
 745   HeapWord* result = _allocator->attempt_allocation(min_word_size, desired_word_size, actual_word_size);
 746 
 747   if (result == NULL) {
 748     *actual_word_size = desired_word_size;
 749     result = attempt_allocation_slow(desired_word_size);
 750   }
 751 
 752   assert_heap_not_locked();
 753   if (result != NULL) {
 754     assert(*actual_word_size != 0, "Actual size must have been set here");
 755     dirty_young_block(result, *actual_word_size);
 756   } else {
 757     *actual_word_size = 0;
 758   }
 759 
 760   return result;
 761 }
 762 
 763 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count, bool is_open) {
 764   assert(!is_init_completed(), "Expect to be called at JVM init time");
 765   assert(ranges != NULL, "MemRegion array NULL");
 766   assert(count != 0, "No MemRegions provided");
 767   MemRegion reserved = _hrm->reserved();
 768   HeapWord* prev_last_addr = NULL;
 769   HeapRegion* prev_last_region = NULL;
 770   size_t size_used = 0;
 771   size_t uncommitted_regions = 0;
 772 
 773   // For each Memregion, free the G1 regions that constitute it, and
 774   // notify mark-sweep that the range is no longer to be considered 'archive.'
 775   MutexLocker x(Heap_lock);
 776   for (size_t i = 0; i < count; i++) {
 777     HeapWord* start_address = ranges[i].start();
 778     HeapWord* last_address = ranges[i].last();
 779 
 780     assert(reserved.contains(start_address) && reserved.contains(last_address),
 781            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 782            p2i(start_address), p2i(last_address));
 783     assert(start_address > prev_last_addr,
 784            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 785            p2i(start_address), p2i(prev_last_addr));
 786     size_used += ranges[i].byte_size();
 787     prev_last_addr = last_address;
 788 
 789     HeapRegion* start_region = _hrm->addr_to_region(start_address);
 790     HeapRegion* last_region = _hrm->addr_to_region(last_address);
 791 
 792     // Check for ranges that start in the same G1 region in which the previous
 793     // range ended, and adjust the start address so we don't try to free
 794     // the same region again. If the current range is entirely within that
 795     // region, skip it.
 796     if (start_region == prev_last_region) {
 797       start_address = start_region->end();
 798       if (start_address > last_address) {
 799         continue;
 800       }
 801       start_region = _hrm->addr_to_region(start_address);
 802     }
 803     prev_last_region = last_region;
 804 
 805     // After verifying that each region was marked as an archive region by
 806     // alloc_archive_regions, set it free and empty and uncommit it.
 807     HeapRegion* curr_region = start_region;
 808     while (curr_region != NULL) {
 809       guarantee(curr_region->is_archive(),
 810                 "Expected archive region at index %u", curr_region->hrm_index());
 811       uint curr_index = curr_region->hrm_index();
 812       _archive_set.remove(curr_region);
 813       curr_region->set_free();
 814       curr_region->set_top(curr_region->bottom());
 815       if (curr_region != last_region) {
 816         curr_region = _hrm->next_region_in_heap(curr_region);
 817       } else {
 818         curr_region = NULL;
 819       }
 820       _hrm->shrink_at(curr_index, 1);
 821       uncommitted_regions++;
 822     }
 823 
 824     // Notify mark-sweep that this is no longer an archive range.
 825     G1ArchiveAllocator::clear_range_archive(ranges[i], is_open);
 826   }
 827 
 828   if (uncommitted_regions != 0) {
 829     log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B",
 830                               HeapRegion::GrainWords * HeapWordSize * uncommitted_regions);
 831   }
 832   decrease_used(size_used);
 833 }
 834 
 835 oop G1CollectedHeap::materialize_archived_object(oop obj) {
 836   assert(obj != NULL, "archived obj is NULL");
 837   assert(G1ArchiveAllocator::is_archived_object(obj), "must be archived object");
 838 
 839   // Loading an archived object makes it strongly reachable. If it is
 840   // loaded during concurrent marking, it must be enqueued to the SATB
 841   // queue, shading the previously white object gray.
 842   G1BarrierSet::enqueue(obj);
 843 
 844   return obj;
 845 }
 846 
 847 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size) {
 848   ResourceMark rm; // For retrieving the thread names in log messages.
 849 
 850   // The structure of this method has a lot of similarities to
 851   // attempt_allocation_slow(). The reason these two were not merged
 852   // into a single one is that such a method would require several "if
 853   // allocation is not humongous do this, otherwise do that"
 854   // conditional paths which would obscure its flow. In fact, an early
 855   // version of this code did use a unified method which was harder to
 856   // follow and, as a result, it had subtle bugs that were hard to
 857   // track down. So keeping these two methods separate allows each to
 858   // be more readable. It will be good to keep these two in sync as
 859   // much as possible.
 860 
 861   assert_heap_not_locked_and_not_at_safepoint();
 862   assert(is_humongous(word_size), "attempt_allocation_humongous() "
 863          "should only be called for humongous allocations");
 864 
 865   // Humongous objects can exhaust the heap quickly, so we should check if we
 866   // need to start a marking cycle at each humongous object allocation. We do
 867   // the check before we do the actual allocation. The reason for doing it
 868   // before the allocation is that we avoid having to keep track of the newly
 869   // allocated memory while we do a GC.
 870   if (policy()->need_to_start_conc_mark("concurrent humongous allocation",
 871                                            word_size)) {
 872     collect(GCCause::_g1_humongous_allocation);
 873   }
 874 
 875   // We will loop until a) we manage to successfully perform the
 876   // allocation or b) we successfully schedule a collection which
 877   // fails to perform the allocation. b) is the only case when we'll
 878   // return NULL.
 879   HeapWord* result = NULL;
 880   for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 881     bool should_try_gc;
 882     uint gc_count_before;
 883 
 884 
 885     {
 886       MutexLocker x(Heap_lock);
 887 
 888       // Given that humongous objects are not allocated in young
 889       // regions, we'll first try to do the allocation without doing a
 890       // collection hoping that there's enough space in the heap.
 891       result = humongous_obj_allocate(word_size);
 892       if (result != NULL) {
 893         size_t size_in_regions = humongous_obj_size_in_regions(word_size);
 894         policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
 895         return result;
 896       }
 897 
 898       // Only try a GC if the GCLocker does not signal the need for a GC. Wait until
 899       // the GCLocker initiated GC has been performed and then retry. This includes
 900       // the case when the GC Locker is not active but has not been performed.
 901       should_try_gc = !GCLocker::needs_gc();
 902       // Read the GC count while still holding the Heap_lock.
 903       gc_count_before = total_collections();
 904     }
 905 
 906     if (should_try_gc) {
 907       bool succeeded;
 908       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 909                                    GCCause::_g1_humongous_allocation);
 910       if (result != NULL) {
 911         assert(succeeded, "only way to get back a non-NULL result");
 912         log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT,
 913                              Thread::current()->name(), p2i(result));
 914         return result;
 915       }
 916 
 917       if (succeeded) {
 918         // We successfully scheduled a collection which failed to allocate. No
 919         // point in trying to allocate further. We'll just return NULL.
 920         log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate "
 921                              SIZE_FORMAT " words", Thread::current()->name(), word_size);
 922         return NULL;
 923       }
 924       log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT "",
 925                            Thread::current()->name(), word_size);
 926     } else {
 927       // Failed to schedule a collection.
 928       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 929         log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating "
 930                                SIZE_FORMAT " words", Thread::current()->name(), word_size);
 931         return NULL;
 932       }
 933       log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name());
 934       // The GCLocker is either active or the GCLocker initiated
 935       // GC has not yet been performed. Stall until it is and
 936       // then retry the allocation.
 937       GCLocker::stall_until_clear();
 938       gclocker_retry_count += 1;
 939     }
 940 
 941 
 942     // We can reach here if we were unsuccessful in scheduling a
 943     // collection (because another thread beat us to it) or if we were
 944     // stalled due to the GC locker. In either can we should retry the
 945     // allocation attempt in case another thread successfully
 946     // performed a collection and reclaimed enough space.
 947     // Humongous object allocation always needs a lock, so we wait for the retry
 948     // in the next iteration of the loop, unlike for the regular iteration case.
 949     // Give a warning if we seem to be looping forever.
 950 
 951     if ((QueuedAllocationWarningCount > 0) &&
 952         (try_count % QueuedAllocationWarningCount == 0)) {
 953       log_warning(gc, alloc)("%s: Retried allocation %u times for " SIZE_FORMAT " words",
 954                              Thread::current()->name(), try_count, word_size);
 955     }
 956   }
 957 
 958   ShouldNotReachHere();
 959   return NULL;
 960 }
 961 
 962 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
 963                                                            bool expect_null_mutator_alloc_region) {
 964   assert_at_safepoint_on_vm_thread();
 965   assert(!_allocator->has_mutator_alloc_region() || !expect_null_mutator_alloc_region,
 966          "the current alloc region was unexpectedly found to be non-NULL");
 967 
 968   if (!is_humongous(word_size)) {
 969     return _allocator->attempt_allocation_locked(word_size);
 970   } else {
 971     HeapWord* result = humongous_obj_allocate(word_size);
 972     if (result != NULL && policy()->need_to_start_conc_mark("STW humongous allocation")) {
 973       collector_state()->set_initiate_conc_mark_if_possible(true);
 974     }
 975     return result;
 976   }
 977 
 978   ShouldNotReachHere();
 979 }
 980 
 981 class PostCompactionPrinterClosure: public HeapRegionClosure {
 982 private:
 983   G1HRPrinter* _hr_printer;
 984 public:
 985   bool do_heap_region(HeapRegion* hr) {
 986     assert(!hr->is_young(), "not expecting to find young regions");
 987     _hr_printer->post_compaction(hr);
 988     return false;
 989   }
 990 
 991   PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
 992     : _hr_printer(hr_printer) { }
 993 };
 994 
 995 void G1CollectedHeap::print_hrm_post_compaction() {
 996   if (_hr_printer.is_active()) {
 997     PostCompactionPrinterClosure cl(hr_printer());
 998     heap_region_iterate(&cl);
 999   }
1000 }
1001 
1002 void G1CollectedHeap::abort_concurrent_cycle() {
1003   // If we start the compaction before the CM threads finish
1004   // scanning the root regions we might trip them over as we'll
1005   // be moving objects / updating references. So let's wait until
1006   // they are done. By telling them to abort, they should complete
1007   // early.
1008   _cm->root_regions()->abort();
1009   _cm->root_regions()->wait_until_scan_finished();
1010 
1011   // Disable discovery and empty the discovered lists
1012   // for the CM ref processor.
1013   _ref_processor_cm->disable_discovery();
1014   _ref_processor_cm->abandon_partial_discovery();
1015   _ref_processor_cm->verify_no_references_recorded();
1016 
1017   // Abandon current iterations of concurrent marking and concurrent
1018   // refinement, if any are in progress.
1019   concurrent_mark()->concurrent_cycle_abort();
1020 }
1021 
1022 void G1CollectedHeap::prepare_heap_for_full_collection() {
1023   // Make sure we'll choose a new allocation region afterwards.
1024   _allocator->release_mutator_alloc_region();
1025   _allocator->abandon_gc_alloc_regions();
1026 
1027   // We may have added regions to the current incremental collection
1028   // set between the last GC or pause and now. We need to clear the
1029   // incremental collection set and then start rebuilding it afresh
1030   // after this full GC.
1031   abandon_collection_set(collection_set());
1032 
1033   tear_down_region_sets(false /* free_list_only */);
1034 
1035   hrm()->prepare_for_full_collection_start();
1036 }
1037 
1038 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) {
1039   assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant");
1040   assert_used_and_recalculate_used_equal(this);
1041   _verifier->verify_region_sets_optional();
1042   _verifier->verify_before_gc(G1HeapVerifier::G1VerifyFull);
1043   _verifier->check_bitmaps("Full GC Start");
1044 }
1045 
1046 void G1CollectedHeap::prepare_heap_for_mutators() {
1047   hrm()->prepare_for_full_collection_end();
1048 
1049   // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1050   ClassLoaderDataGraph::purge();
1051   MetaspaceUtils::verify_metrics();
1052 
1053   // Prepare heap for normal collections.
1054   assert(num_free_regions() == 0, "we should not have added any free regions");
1055   rebuild_region_sets(false /* free_list_only */);
1056   abort_refinement();
1057   resize_heap_if_necessary();
1058 
1059   // Rebuild the strong code root lists for each region
1060   rebuild_strong_code_roots();
1061 
1062   // Purge code root memory
1063   purge_code_root_memory();
1064 
1065   // Start a new incremental collection set for the next pause
1066   start_new_collection_set();
1067 
1068   _allocator->init_mutator_alloc_region();
1069 
1070   // Post collection state updates.
1071   MetaspaceGC::compute_new_size();
1072 }
1073 
1074 void G1CollectedHeap::abort_refinement() {
1075   if (_hot_card_cache->use_cache()) {
1076     _hot_card_cache->reset_hot_cache();
1077   }
1078 
1079   // Discard all remembered set updates.
1080   G1BarrierSet::dirty_card_queue_set().abandon_logs();
1081   assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1082 }
1083 
1084 void G1CollectedHeap::verify_after_full_collection() {
1085   _hrm->verify_optional();
1086   _verifier->verify_region_sets_optional();
1087   _verifier->verify_after_gc(G1HeapVerifier::G1VerifyFull);
1088   // Clear the previous marking bitmap, if needed for bitmap verification.
1089   // Note we cannot do this when we clear the next marking bitmap in
1090   // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the
1091   // objects marked during a full GC against the previous bitmap.
1092   // But we need to clear it before calling check_bitmaps below since
1093   // the full GC has compacted objects and updated TAMS but not updated
1094   // the prev bitmap.
1095   if (G1VerifyBitmaps) {
1096     GCTraceTime(Debug, gc) tm("Clear Prev Bitmap for Verification");
1097     _cm->clear_prev_bitmap(workers());
1098   }
1099   // This call implicitly verifies that the next bitmap is clear after Full GC.
1100   _verifier->check_bitmaps("Full GC End");
1101 
1102   // At this point there should be no regions in the
1103   // entire heap tagged as young.
1104   assert(check_young_list_empty(), "young list should be empty at this point");
1105 
1106   // Note: since we've just done a full GC, concurrent
1107   // marking is no longer active. Therefore we need not
1108   // re-enable reference discovery for the CM ref processor.
1109   // That will be done at the start of the next marking cycle.
1110   // We also know that the STW processor should no longer
1111   // discover any new references.
1112   assert(!_ref_processor_stw->discovery_enabled(), "Postcondition");
1113   assert(!_ref_processor_cm->discovery_enabled(), "Postcondition");
1114   _ref_processor_stw->verify_no_references_recorded();
1115   _ref_processor_cm->verify_no_references_recorded();
1116 }
1117 
1118 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) {
1119   // Post collection logging.
1120   // We should do this after we potentially resize the heap so
1121   // that all the COMMIT / UNCOMMIT events are generated before
1122   // the compaction events.
1123   print_hrm_post_compaction();
1124   heap_transition->print();
1125   print_heap_after_gc();
1126   print_heap_regions();
1127 #ifdef TRACESPINNING
1128   ParallelTaskTerminator::print_termination_counts();
1129 #endif
1130 }
1131 
1132 bool G1CollectedHeap::do_full_collection(bool explicit_gc,
1133                                          bool clear_all_soft_refs) {
1134   assert_at_safepoint_on_vm_thread();
1135 
1136   if (GCLocker::check_active_before_gc()) {
1137     // Full GC was not completed.
1138     return false;
1139   }
1140 
1141   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1142       soft_ref_policy()->should_clear_all_soft_refs();
1143 
1144   G1FullCollector collector(this, explicit_gc, do_clear_all_soft_refs);
1145   GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true);
1146 
1147   collector.prepare_collection();
1148   collector.collect();
1149   collector.complete_collection();
1150 
1151   // Full collection was successfully completed.
1152   return true;
1153 }
1154 
1155 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1156   // Currently, there is no facility in the do_full_collection(bool) API to notify
1157   // the caller that the collection did not succeed (e.g., because it was locked
1158   // out by the GC locker). So, right now, we'll ignore the return value.
1159   bool dummy = do_full_collection(true,                /* explicit_gc */
1160                                   clear_all_soft_refs);
1161 }
1162 
1163 void G1CollectedHeap::resize_heap_if_necessary() {
1164   assert_at_safepoint_on_vm_thread();
1165 
1166   // Capacity, free and used after the GC counted as full regions to
1167   // include the waste in the following calculations.
1168   const size_t capacity_after_gc = capacity();
1169   const size_t used_after_gc = capacity_after_gc - unused_committed_regions_in_bytes();
1170 
1171   // This is enforced in arguments.cpp.
1172   assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1173          "otherwise the code below doesn't make sense");
1174 
1175   // We don't have floating point command-line arguments
1176   const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1177   const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1178   const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1179   const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1180 
1181   // We have to be careful here as these two calculations can overflow
1182   // 32-bit size_t's.
1183   double used_after_gc_d = (double) used_after_gc;
1184   double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1185   double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1186 
1187   // Let's make sure that they are both under the max heap size, which
1188   // by default will make them fit into a size_t.
1189   double desired_capacity_upper_bound = (double) MaxHeapSize;
1190   minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1191                                     desired_capacity_upper_bound);
1192   maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1193                                     desired_capacity_upper_bound);
1194 
1195   // We can now safely turn them into size_t's.
1196   size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1197   size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1198 
1199   // This assert only makes sense here, before we adjust them
1200   // with respect to the min and max heap size.
1201   assert(minimum_desired_capacity <= maximum_desired_capacity,
1202          "minimum_desired_capacity = " SIZE_FORMAT ", "
1203          "maximum_desired_capacity = " SIZE_FORMAT,
1204          minimum_desired_capacity, maximum_desired_capacity);
1205 
1206   // Should not be greater than the heap max size. No need to adjust
1207   // it with respect to the heap min size as it's a lower bound (i.e.,
1208   // we'll try to make the capacity larger than it, not smaller).
1209   minimum_desired_capacity = MIN2(minimum_desired_capacity, MaxHeapSize);
1210   // Should not be less than the heap min size. No need to adjust it
1211   // with respect to the heap max size as it's an upper bound (i.e.,
1212   // we'll try to make the capacity smaller than it, not greater).
1213   maximum_desired_capacity =  MAX2(maximum_desired_capacity, MinHeapSize);
1214 
1215   if (capacity_after_gc < minimum_desired_capacity) {
1216     // Don't expand unless it's significant
1217     size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1218 
1219     log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity). "
1220                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1221                               "min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1222                               capacity_after_gc, used_after_gc, used(), minimum_desired_capacity, MinHeapFreeRatio);
1223 
1224     expand(expand_bytes, _workers);
1225 
1226     // No expansion, now see if we want to shrink
1227   } else if (capacity_after_gc > maximum_desired_capacity) {
1228     // Capacity too large, compute shrinking size
1229     size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1230 
1231     log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity). "
1232                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1233                               "maximum_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1234                               capacity_after_gc, used_after_gc, used(), maximum_desired_capacity, MaxHeapFreeRatio);
1235 
1236     shrink(shrink_bytes);
1237   }
1238 }
1239 
1240 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size,
1241                                                             bool do_gc,
1242                                                             bool clear_all_soft_refs,
1243                                                             bool expect_null_mutator_alloc_region,
1244                                                             bool* gc_succeeded) {
1245   *gc_succeeded = true;
1246   // Let's attempt the allocation first.
1247   HeapWord* result =
1248     attempt_allocation_at_safepoint(word_size,
1249                                     expect_null_mutator_alloc_region);
1250   if (result != NULL) {
1251     return result;
1252   }
1253 
1254   // In a G1 heap, we're supposed to keep allocation from failing by
1255   // incremental pauses.  Therefore, at least for now, we'll favor
1256   // expansion over collection.  (This might change in the future if we can
1257   // do something smarter than full collection to satisfy a failed alloc.)
1258   result = expand_and_allocate(word_size);
1259   if (result != NULL) {
1260     return result;
1261   }
1262 
1263   if (do_gc) {
1264     // Expansion didn't work, we'll try to do a Full GC.
1265     *gc_succeeded = do_full_collection(false, /* explicit_gc */
1266                                        clear_all_soft_refs);
1267   }
1268 
1269   return NULL;
1270 }
1271 
1272 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1273                                                      bool* succeeded) {
1274   assert_at_safepoint_on_vm_thread();
1275 
1276   // Attempts to allocate followed by Full GC.
1277   HeapWord* result =
1278     satisfy_failed_allocation_helper(word_size,
1279                                      true,  /* do_gc */
1280                                      false, /* clear_all_soft_refs */
1281                                      false, /* expect_null_mutator_alloc_region */
1282                                      succeeded);
1283 
1284   if (result != NULL || !*succeeded) {
1285     return result;
1286   }
1287 
1288   // Attempts to allocate followed by Full GC that will collect all soft references.
1289   result = satisfy_failed_allocation_helper(word_size,
1290                                             true, /* do_gc */
1291                                             true, /* clear_all_soft_refs */
1292                                             true, /* expect_null_mutator_alloc_region */
1293                                             succeeded);
1294 
1295   if (result != NULL || !*succeeded) {
1296     return result;
1297   }
1298 
1299   // Attempts to allocate, no GC
1300   result = satisfy_failed_allocation_helper(word_size,
1301                                             false, /* do_gc */
1302                                             false, /* clear_all_soft_refs */
1303                                             true,  /* expect_null_mutator_alloc_region */
1304                                             succeeded);
1305 
1306   if (result != NULL) {
1307     return result;
1308   }
1309 
1310   assert(!soft_ref_policy()->should_clear_all_soft_refs(),
1311          "Flag should have been handled and cleared prior to this point");
1312 
1313   // What else?  We might try synchronous finalization later.  If the total
1314   // space available is large enough for the allocation, then a more
1315   // complete compaction phase than we've tried so far might be
1316   // appropriate.
1317   return NULL;
1318 }
1319 
1320 // Attempting to expand the heap sufficiently
1321 // to support an allocation of the given "word_size".  If
1322 // successful, perform the allocation and return the address of the
1323 // allocated block, or else "NULL".
1324 
1325 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1326   assert_at_safepoint_on_vm_thread();
1327 
1328   _verifier->verify_region_sets_optional();
1329 
1330   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1331   log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B",
1332                             word_size * HeapWordSize);
1333 
1334 
1335   if (expand(expand_bytes, _workers)) {
1336     _hrm->verify_optional();
1337     _verifier->verify_region_sets_optional();
1338     return attempt_allocation_at_safepoint(word_size,
1339                                            false /* expect_null_mutator_alloc_region */);
1340   }
1341   return NULL;
1342 }
1343 
1344 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) {
1345   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1346   aligned_expand_bytes = align_up(aligned_expand_bytes,
1347                                        HeapRegion::GrainBytes);
1348 
1349   log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B",
1350                             expand_bytes, aligned_expand_bytes);
1351 
1352   if (is_maximal_no_gc()) {
1353     log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1354     return false;
1355   }
1356 
1357   double expand_heap_start_time_sec = os::elapsedTime();
1358   uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1359   assert(regions_to_expand > 0, "Must expand by at least one region");
1360 
1361   uint expanded_by = _hrm->expand_by(regions_to_expand, pretouch_workers);
1362   if (expand_time_ms != NULL) {
1363     *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS;
1364   }
1365 
1366   if (expanded_by > 0) {
1367     size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1368     assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1369     policy()->record_new_heap_size(num_regions());
1370   } else {
1371     log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)");
1372 
1373     // The expansion of the virtual storage space was unsuccessful.
1374     // Let's see if it was because we ran out of swap.
1375     if (G1ExitOnExpansionFailure &&
1376         _hrm->available() >= regions_to_expand) {
1377       // We had head room...
1378       vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1379     }
1380   }
1381   return regions_to_expand > 0;
1382 }
1383 
1384 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1385   size_t aligned_shrink_bytes =
1386     ReservedSpace::page_align_size_down(shrink_bytes);
1387   aligned_shrink_bytes = align_down(aligned_shrink_bytes,
1388                                          HeapRegion::GrainBytes);
1389   uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1390 
1391   uint num_regions_removed = _hrm->shrink_by(num_regions_to_remove);
1392   size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1393 
1394 
1395   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",
1396                             shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1397   if (num_regions_removed > 0) {
1398     policy()->record_new_heap_size(num_regions());
1399   } else {
1400     log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)");
1401   }
1402 }
1403 
1404 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1405   _verifier->verify_region_sets_optional();
1406 
1407   // We should only reach here at the end of a Full GC or during Remark which
1408   // means we should not not be holding to any GC alloc regions. The method
1409   // below will make sure of that and do any remaining clean up.
1410   _allocator->abandon_gc_alloc_regions();
1411 
1412   // Instead of tearing down / rebuilding the free lists here, we
1413   // could instead use the remove_all_pending() method on free_list to
1414   // remove only the ones that we need to remove.
1415   tear_down_region_sets(true /* free_list_only */);
1416   shrink_helper(shrink_bytes);
1417   rebuild_region_sets(true /* free_list_only */);
1418 
1419   _hrm->verify_optional();
1420   _verifier->verify_region_sets_optional();
1421 }
1422 
1423 class OldRegionSetChecker : public HeapRegionSetChecker {
1424 public:
1425   void check_mt_safety() {
1426     // Master Old Set MT safety protocol:
1427     // (a) If we're at a safepoint, operations on the master old set
1428     // should be invoked:
1429     // - by the VM thread (which will serialize them), or
1430     // - by the GC workers while holding the FreeList_lock, if we're
1431     //   at a safepoint for an evacuation pause (this lock is taken
1432     //   anyway when an GC alloc region is retired so that a new one
1433     //   is allocated from the free list), or
1434     // - by the GC workers while holding the OldSets_lock, if we're at a
1435     //   safepoint for a cleanup pause.
1436     // (b) If we're not at a safepoint, operations on the master old set
1437     // should be invoked while holding the Heap_lock.
1438 
1439     if (SafepointSynchronize::is_at_safepoint()) {
1440       guarantee(Thread::current()->is_VM_thread() ||
1441                 FreeList_lock->owned_by_self() || OldSets_lock->owned_by_self(),
1442                 "master old set MT safety protocol at a safepoint");
1443     } else {
1444       guarantee(Heap_lock->owned_by_self(), "master old set MT safety protocol outside a safepoint");
1445     }
1446   }
1447   bool is_correct_type(HeapRegion* hr) { return hr->is_old(); }
1448   const char* get_description() { return "Old Regions"; }
1449 };
1450 
1451 class ArchiveRegionSetChecker : public HeapRegionSetChecker {
1452 public:
1453   void check_mt_safety() {
1454     guarantee(!Universe::is_fully_initialized() || SafepointSynchronize::is_at_safepoint(),
1455               "May only change archive regions during initialization or safepoint.");
1456   }
1457   bool is_correct_type(HeapRegion* hr) { return hr->is_archive(); }
1458   const char* get_description() { return "Archive Regions"; }
1459 };
1460 
1461 class HumongousRegionSetChecker : public HeapRegionSetChecker {
1462 public:
1463   void check_mt_safety() {
1464     // Humongous Set MT safety protocol:
1465     // (a) If we're at a safepoint, operations on the master humongous
1466     // set should be invoked by either the VM thread (which will
1467     // serialize them) or by the GC workers while holding the
1468     // OldSets_lock.
1469     // (b) If we're not at a safepoint, operations on the master
1470     // humongous set should be invoked while holding the Heap_lock.
1471 
1472     if (SafepointSynchronize::is_at_safepoint()) {
1473       guarantee(Thread::current()->is_VM_thread() ||
1474                 OldSets_lock->owned_by_self(),
1475                 "master humongous set MT safety protocol at a safepoint");
1476     } else {
1477       guarantee(Heap_lock->owned_by_self(),
1478                 "master humongous set MT safety protocol outside a safepoint");
1479     }
1480   }
1481   bool is_correct_type(HeapRegion* hr) { return hr->is_humongous(); }
1482   const char* get_description() { return "Humongous Regions"; }
1483 };
1484 
1485 G1CollectedHeap::G1CollectedHeap() :
1486   CollectedHeap(),
1487   _young_gen_sampling_thread(NULL),
1488   _workers(NULL),
1489   _card_table(NULL),
1490   _soft_ref_policy(),
1491   _old_set("Old Region Set", new OldRegionSetChecker()),
1492   _archive_set("Archive Region Set", new ArchiveRegionSetChecker()),
1493   _humongous_set("Humongous Region Set", new HumongousRegionSetChecker()),
1494   _bot(NULL),
1495   _listener(),
1496   _hrm(NULL),
1497   _allocator(NULL),
1498   _verifier(NULL),
1499   _summary_bytes_used(0),
1500   _archive_allocator(NULL),
1501   _survivor_evac_stats("Young", YoungPLABSize, PLABWeight),
1502   _old_evac_stats("Old", OldPLABSize, PLABWeight),
1503   _expand_heap_after_alloc_failure(true),
1504   _g1mm(NULL),
1505   _humongous_reclaim_candidates(),
1506   _has_humongous_reclaim_candidates(false),
1507   _hr_printer(),
1508   _collector_state(),
1509   _old_marking_cycles_started(0),
1510   _old_marking_cycles_completed(0),
1511   _eden(),
1512   _survivor(),
1513   _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1514   _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1515   _policy(G1Policy::create_policy(_gc_timer_stw)),
1516   _heap_sizing_policy(NULL),
1517   _collection_set(this, _policy),
1518   _hot_card_cache(NULL),
1519   _rem_set(NULL),
1520   _dirty_card_queue_set(false),
1521   _cm(NULL),
1522   _cm_thread(NULL),
1523   _cr(NULL),
1524   _task_queues(NULL),
1525   _evacuation_failed(false),
1526   _evacuation_failed_info_array(NULL),
1527   _preserved_marks_set(true /* in_c_heap */),
1528 #ifndef PRODUCT
1529   _evacuation_failure_alot_for_current_gc(false),
1530   _evacuation_failure_alot_gc_number(0),
1531   _evacuation_failure_alot_count(0),
1532 #endif
1533   _ref_processor_stw(NULL),
1534   _is_alive_closure_stw(this),
1535   _is_subject_to_discovery_stw(this),
1536   _ref_processor_cm(NULL),
1537   _is_alive_closure_cm(this),
1538   _is_subject_to_discovery_cm(this),
1539   _region_attr() {
1540 
1541   _verifier = new G1HeapVerifier(this);
1542 
1543   _allocator = new G1Allocator(this);
1544 
1545   _heap_sizing_policy = G1HeapSizingPolicy::create(this, _policy->analytics());
1546 
1547   _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);
1548 
1549   // Override the default _filler_array_max_size so that no humongous filler
1550   // objects are created.
1551   _filler_array_max_size = _humongous_object_threshold_in_words;
1552 
1553   uint n_queues = ParallelGCThreads;
1554   _task_queues = new RefToScanQueueSet(n_queues);
1555 
1556   _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1557 
1558   for (uint i = 0; i < n_queues; i++) {
1559     RefToScanQueue* q = new RefToScanQueue();
1560     q->initialize();
1561     _task_queues->register_queue(i, q);
1562     ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1563   }
1564 
1565   // Initialize the G1EvacuationFailureALot counters and flags.
1566   NOT_PRODUCT(reset_evacuation_should_fail();)
1567 
1568   guarantee(_task_queues != NULL, "task_queues allocation failure.");
1569 }
1570 
1571 static size_t actual_reserved_page_size(ReservedSpace rs) {
1572   size_t page_size = os::vm_page_size();
1573   if (UseLargePages) {
1574     // There are two ways to manage large page memory.
1575     // 1. OS supports committing large page memory.
1576     // 2. OS doesn't support committing large page memory so ReservedSpace manages it.
1577     //    And ReservedSpace calls it 'special'. If we failed to set 'special',
1578     //    we reserved memory without large page.
1579     if (os::can_commit_large_page_memory() || rs.special()) {
1580       // An alignment at ReservedSpace comes from preferred page size or
1581       // heap alignment, and if the alignment came from heap alignment, it could be
1582       // larger than large pages size. So need to cap with the large page size.
1583       page_size = MIN2(rs.alignment(), os::large_page_size());
1584     }
1585   }
1586 
1587   return page_size;
1588 }
1589 
1590 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1591                                                                  size_t size,
1592                                                                  size_t translation_factor) {
1593   size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1594   // Allocate a new reserved space, preferring to use large pages.
1595   ReservedSpace rs(size, preferred_page_size);
1596   size_t page_size = actual_reserved_page_size(rs);
1597   G1RegionToSpaceMapper* result  =
1598     G1RegionToSpaceMapper::create_mapper(rs,
1599                                          size,
1600                                          page_size,
1601                                          HeapRegion::GrainBytes,
1602                                          translation_factor,
1603                                          mtGC);
1604 
1605   os::trace_page_sizes_for_requested_size(description,
1606                                           size,
1607                                           preferred_page_size,
1608                                           page_size,
1609                                           rs.base(),
1610                                           rs.size());
1611 
1612   return result;
1613 }
1614 
1615 jint G1CollectedHeap::initialize_concurrent_refinement() {
1616   jint ecode = JNI_OK;
1617   _cr = G1ConcurrentRefine::create(&ecode);
1618   return ecode;
1619 }
1620 
1621 jint G1CollectedHeap::initialize_young_gen_sampling_thread() {
1622   _young_gen_sampling_thread = new G1YoungRemSetSamplingThread();
1623   if (_young_gen_sampling_thread->osthread() == NULL) {
1624     vm_shutdown_during_initialization("Could not create G1YoungRemSetSamplingThread");
1625     return JNI_ENOMEM;
1626   }
1627   return JNI_OK;
1628 }
1629 
1630 jint G1CollectedHeap::initialize() {
1631   os::enable_vtime();
1632 
1633   // Necessary to satisfy locking discipline assertions.
1634 
1635   MutexLocker x(Heap_lock);
1636 
1637   // While there are no constraints in the GC code that HeapWordSize
1638   // be any particular value, there are multiple other areas in the
1639   // system which believe this to be true (e.g. oop->object_size in some
1640   // cases incorrectly returns the size in wordSize units rather than
1641   // HeapWordSize).
1642   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1643 
1644   size_t init_byte_size = InitialHeapSize;
1645   size_t reserved_byte_size = G1Arguments::heap_reserved_size_bytes();
1646 
1647   // Ensure that the sizes are properly aligned.
1648   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1649   Universe::check_alignment(reserved_byte_size, HeapRegion::GrainBytes, "g1 heap");
1650   Universe::check_alignment(reserved_byte_size, HeapAlignment, "g1 heap");
1651 
1652   // Reserve the maximum.
1653 
1654   // When compressed oops are enabled, the preferred heap base
1655   // is calculated by subtracting the requested size from the
1656   // 32Gb boundary and using the result as the base address for
1657   // heap reservation. If the requested size is not aligned to
1658   // HeapRegion::GrainBytes (i.e. the alignment that is passed
1659   // into the ReservedHeapSpace constructor) then the actual
1660   // base of the reserved heap may end up differing from the
1661   // address that was requested (i.e. the preferred heap base).
1662   // If this happens then we could end up using a non-optimal
1663   // compressed oops mode.
1664 
1665   ReservedSpace heap_rs = Universe::reserve_heap(reserved_byte_size,
1666                                                  HeapAlignment);
1667 
1668   initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
1669 
1670   // Create the barrier set for the entire reserved region.
1671   G1CardTable* ct = new G1CardTable(reserved_region());
1672   ct->initialize();
1673   G1BarrierSet* bs = new G1BarrierSet(ct);
1674   bs->initialize();
1675   assert(bs->is_a(BarrierSet::G1BarrierSet), "sanity");
1676   BarrierSet::set_barrier_set(bs);
1677   _card_table = ct;
1678 
1679   G1BarrierSet::satb_mark_queue_set().initialize(this,
1680                                                  SATB_Q_CBL_mon,
1681                                                  &bs->satb_mark_queue_buffer_allocator(),
1682                                                  G1SATBProcessCompletedThreshold,
1683                                                  G1SATBBufferEnqueueingThresholdPercent);
1684 
1685   // process_completed_buffers_threshold and max_completed_buffers are updated
1686   // later, based on the concurrent refinement object.
1687   G1BarrierSet::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1688                                                   &bs->dirty_card_queue_buffer_allocator(),
1689                                                   true); // init_free_ids
1690 
1691   dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1692                                     &bs->dirty_card_queue_buffer_allocator());
1693 
1694   // Create the hot card cache.
1695   _hot_card_cache = new G1HotCardCache(this);
1696 
1697   // Carve out the G1 part of the heap.
1698   ReservedSpace g1_rs = heap_rs.first_part(reserved_byte_size);
1699   size_t page_size = actual_reserved_page_size(heap_rs);
1700   G1RegionToSpaceMapper* heap_storage =
1701     G1RegionToSpaceMapper::create_heap_mapper(g1_rs,
1702                                               g1_rs.size(),
1703                                               page_size,
1704                                               HeapRegion::GrainBytes,
1705                                               1,
1706                                               mtJavaHeap);
1707   if(heap_storage == NULL) {
1708     vm_shutdown_during_initialization("Could not initialize G1 heap");
1709     return JNI_ERR;
1710   }
1711 
1712   os::trace_page_sizes("Heap",
1713                        MinHeapSize,
1714                        reserved_byte_size,
1715                        page_size,
1716                        heap_rs.base(),
1717                        heap_rs.size());
1718   heap_storage->set_mapping_changed_listener(&_listener);
1719 
1720   // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1721   G1RegionToSpaceMapper* bot_storage =
1722     create_aux_memory_mapper("Block Offset Table",
1723                              G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize),
1724                              G1BlockOffsetTable::heap_map_factor());
1725 
1726   G1RegionToSpaceMapper* cardtable_storage =
1727     create_aux_memory_mapper("Card Table",
1728                              G1CardTable::compute_size(g1_rs.size() / HeapWordSize),
1729                              G1CardTable::heap_map_factor());
1730 
1731   G1RegionToSpaceMapper* card_counts_storage =
1732     create_aux_memory_mapper("Card Counts Table",
1733                              G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1734                              G1CardCounts::heap_map_factor());
1735 
1736   size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size());
1737   G1RegionToSpaceMapper* prev_bitmap_storage =
1738     create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1739   G1RegionToSpaceMapper* next_bitmap_storage =
1740     create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1741 
1742   _hrm = HeapRegionManager::create_manager(this);
1743 
1744   _hrm->initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1745   _card_table->initialize(cardtable_storage);
1746   // Do later initialization work for concurrent refinement.
1747   _hot_card_cache->initialize(card_counts_storage);
1748 
1749   // 6843694 - ensure that the maximum region index can fit
1750   // in the remembered set structures.
1751   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1752   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1753 
1754   // The G1FromCardCache reserves card with value 0 as "invalid", so the heap must not
1755   // start within the first card.
1756   guarantee(g1_rs.base() >= (char*)G1CardTable::card_size, "Java heap must not start within the first card.");
1757   // Also create a G1 rem set.
1758   _rem_set = new G1RemSet(this, _card_table, _hot_card_cache);
1759   _rem_set->initialize(max_reserved_capacity(), max_regions());
1760 
1761   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1762   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1763   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1764             "too many cards per region");
1765 
1766   FreeRegionList::set_unrealistically_long_length(max_expandable_regions() + 1);
1767 
1768   _bot = new G1BlockOffsetTable(reserved_region(), bot_storage);
1769 
1770   {
1771     HeapWord* start = _hrm->reserved().start();
1772     HeapWord* end = _hrm->reserved().end();
1773     size_t granularity = HeapRegion::GrainBytes;
1774 
1775     _region_attr.initialize(start, end, granularity);
1776     _humongous_reclaim_candidates.initialize(start, end, granularity);
1777   }
1778 
1779   _workers = new WorkGang("GC Thread", ParallelGCThreads,
1780                           true /* are_GC_task_threads */,
1781                           false /* are_ConcurrentGC_threads */);
1782   if (_workers == NULL) {
1783     return JNI_ENOMEM;
1784   }
1785   _workers->initialize_workers();
1786 
1787   // Create the G1ConcurrentMark data structure and thread.
1788   // (Must do this late, so that "max_regions" is defined.)
1789   _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1790   if (_cm == NULL || !_cm->completed_initialization()) {
1791     vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark");
1792     return JNI_ENOMEM;
1793   }
1794   _cm_thread = _cm->cm_thread();
1795 
1796   // Now expand into the initial heap size.
1797   if (!expand(init_byte_size, _workers)) {
1798     vm_shutdown_during_initialization("Failed to allocate initial heap.");
1799     return JNI_ENOMEM;
1800   }
1801 
1802   // Perform any initialization actions delegated to the policy.
1803   policy()->init(this, &_collection_set);
1804 
1805   jint ecode = initialize_concurrent_refinement();
1806   if (ecode != JNI_OK) {
1807     return ecode;
1808   }
1809 
1810   ecode = initialize_young_gen_sampling_thread();
1811   if (ecode != JNI_OK) {
1812     return ecode;
1813   }
1814 
1815   {
1816     G1DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
1817     dcqs.set_process_completed_buffers_threshold(concurrent_refine()->yellow_zone());
1818     dcqs.set_max_completed_buffers(concurrent_refine()->red_zone());
1819   }
1820 
1821   // Here we allocate the dummy HeapRegion that is required by the
1822   // G1AllocRegion class.
1823   HeapRegion* dummy_region = _hrm->get_dummy_region();
1824 
1825   // We'll re-use the same region whether the alloc region will
1826   // require BOT updates or not and, if it doesn't, then a non-young
1827   // region will complain that it cannot support allocations without
1828   // BOT updates. So we'll tag the dummy region as eden to avoid that.
1829   dummy_region->set_eden();
1830   // Make sure it's full.
1831   dummy_region->set_top(dummy_region->end());
1832   G1AllocRegion::setup(this, dummy_region);
1833 
1834   _allocator->init_mutator_alloc_region();
1835 
1836   // Do create of the monitoring and management support so that
1837   // values in the heap have been properly initialized.
1838   _g1mm = new G1MonitoringSupport(this);
1839 
1840   G1StringDedup::initialize();
1841 
1842   _preserved_marks_set.init(ParallelGCThreads);
1843 
1844   _collection_set.initialize(max_regions());
1845 
1846   return JNI_OK;
1847 }
1848 
1849 void G1CollectedHeap::stop() {
1850   // Stop all concurrent threads. We do this to make sure these threads
1851   // do not continue to execute and access resources (e.g. logging)
1852   // that are destroyed during shutdown.
1853   _cr->stop();
1854   _young_gen_sampling_thread->stop();
1855   _cm_thread->stop();
1856   if (G1StringDedup::is_enabled()) {
1857     G1StringDedup::stop();
1858   }
1859 }
1860 
1861 void G1CollectedHeap::safepoint_synchronize_begin() {
1862   SuspendibleThreadSet::synchronize();
1863 }
1864 
1865 void G1CollectedHeap::safepoint_synchronize_end() {
1866   SuspendibleThreadSet::desynchronize();
1867 }
1868 
1869 void G1CollectedHeap::post_initialize() {
1870   CollectedHeap::post_initialize();
1871   ref_processing_init();
1872 }
1873 
1874 void G1CollectedHeap::ref_processing_init() {
1875   // Reference processing in G1 currently works as follows:
1876   //
1877   // * There are two reference processor instances. One is
1878   //   used to record and process discovered references
1879   //   during concurrent marking; the other is used to
1880   //   record and process references during STW pauses
1881   //   (both full and incremental).
1882   // * Both ref processors need to 'span' the entire heap as
1883   //   the regions in the collection set may be dotted around.
1884   //
1885   // * For the concurrent marking ref processor:
1886   //   * Reference discovery is enabled at initial marking.
1887   //   * Reference discovery is disabled and the discovered
1888   //     references processed etc during remarking.
1889   //   * Reference discovery is MT (see below).
1890   //   * Reference discovery requires a barrier (see below).
1891   //   * Reference processing may or may not be MT
1892   //     (depending on the value of ParallelRefProcEnabled
1893   //     and ParallelGCThreads).
1894   //   * A full GC disables reference discovery by the CM
1895   //     ref processor and abandons any entries on it's
1896   //     discovered lists.
1897   //
1898   // * For the STW processor:
1899   //   * Non MT discovery is enabled at the start of a full GC.
1900   //   * Processing and enqueueing during a full GC is non-MT.
1901   //   * During a full GC, references are processed after marking.
1902   //
1903   //   * Discovery (may or may not be MT) is enabled at the start
1904   //     of an incremental evacuation pause.
1905   //   * References are processed near the end of a STW evacuation pause.
1906   //   * For both types of GC:
1907   //     * Discovery is atomic - i.e. not concurrent.
1908   //     * Reference discovery will not need a barrier.
1909 
1910   bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1);
1911 
1912   // Concurrent Mark ref processor
1913   _ref_processor_cm =
1914     new ReferenceProcessor(&_is_subject_to_discovery_cm,
1915                            mt_processing,                                  // mt processing
1916                            ParallelGCThreads,                              // degree of mt processing
1917                            (ParallelGCThreads > 1) || (ConcGCThreads > 1), // mt discovery
1918                            MAX2(ParallelGCThreads, ConcGCThreads),         // degree of mt discovery
1919                            false,                                          // Reference discovery is not atomic
1920                            &_is_alive_closure_cm,                          // is alive closure
1921                            true);                                          // allow changes to number of processing threads
1922 
1923   // STW ref processor
1924   _ref_processor_stw =
1925     new ReferenceProcessor(&_is_subject_to_discovery_stw,
1926                            mt_processing,                        // mt processing
1927                            ParallelGCThreads,                    // degree of mt processing
1928                            (ParallelGCThreads > 1),              // mt discovery
1929                            ParallelGCThreads,                    // degree of mt discovery
1930                            true,                                 // Reference discovery is atomic
1931                            &_is_alive_closure_stw,               // is alive closure
1932                            true);                                // allow changes to number of processing threads
1933 }
1934 
1935 SoftRefPolicy* G1CollectedHeap::soft_ref_policy() {
1936   return &_soft_ref_policy;
1937 }
1938 
1939 size_t G1CollectedHeap::capacity() const {
1940   return _hrm->length() * HeapRegion::GrainBytes;
1941 }
1942 
1943 size_t G1CollectedHeap::unused_committed_regions_in_bytes() const {
1944   return _hrm->total_free_bytes();
1945 }
1946 
1947 void G1CollectedHeap::iterate_hcc_closure(G1CardTableEntryClosure* cl, uint worker_i) {
1948   _hot_card_cache->drain(cl, worker_i);
1949 }
1950 
1951 void G1CollectedHeap::iterate_dirty_card_closure(G1CardTableEntryClosure* cl, uint worker_i) {
1952   G1DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
1953   size_t n_completed_buffers = 0;
1954   while (dcqs.apply_closure_during_gc(cl, worker_i)) {
1955     n_completed_buffers++;
1956   }
1957   assert(dcqs.completed_buffers_num() == 0, "Completed buffers exist!");
1958   phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers, G1GCPhaseTimes::UpdateRSProcessedBuffers);
1959 }
1960 
1961 // Computes the sum of the storage used by the various regions.
1962 size_t G1CollectedHeap::used() const {
1963   size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
1964   if (_archive_allocator != NULL) {
1965     result += _archive_allocator->used();
1966   }
1967   return result;
1968 }
1969 
1970 size_t G1CollectedHeap::used_unlocked() const {
1971   return _summary_bytes_used;
1972 }
1973 
1974 class SumUsedClosure: public HeapRegionClosure {
1975   size_t _used;
1976 public:
1977   SumUsedClosure() : _used(0) {}
1978   bool do_heap_region(HeapRegion* r) {
1979     _used += r->used();
1980     return false;
1981   }
1982   size_t result() { return _used; }
1983 };
1984 
1985 size_t G1CollectedHeap::recalculate_used() const {
1986   SumUsedClosure blk;
1987   heap_region_iterate(&blk);
1988   return blk.result();
1989 }
1990 
1991 bool  G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
1992   switch (cause) {
1993     case GCCause::_java_lang_system_gc:                 return ExplicitGCInvokesConcurrent;
1994     case GCCause::_dcmd_gc_run:                         return ExplicitGCInvokesConcurrent;
1995     case GCCause::_wb_conc_mark:                        return true;
1996     default :                                           return false;
1997   }
1998 }
1999 
2000 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2001   switch (cause) {
2002     case GCCause::_gc_locker:               return GCLockerInvokesConcurrent;
2003     case GCCause::_g1_humongous_allocation: return true;
2004     case GCCause::_g1_periodic_collection:  return G1PeriodicGCInvokesConcurrent;
2005     default:                                return is_user_requested_concurrent_full_gc(cause);
2006   }
2007 }
2008 
2009 bool G1CollectedHeap::should_upgrade_to_full_gc(GCCause::Cause cause) {
2010   if(policy()->force_upgrade_to_full()) {
2011     return true;
2012   } else if (should_do_concurrent_full_gc(_gc_cause)) {
2013     return false;
2014   } else if (has_regions_left_for_allocation()) {
2015     return false;
2016   } else {
2017     return true;
2018   }
2019 }
2020 
2021 #ifndef PRODUCT
2022 void G1CollectedHeap::allocate_dummy_regions() {
2023   // Let's fill up most of the region
2024   size_t word_size = HeapRegion::GrainWords - 1024;
2025   // And as a result the region we'll allocate will be humongous.
2026   guarantee(is_humongous(word_size), "sanity");
2027 
2028   // _filler_array_max_size is set to humongous object threshold
2029   // but temporarily change it to use CollectedHeap::fill_with_object().
2030   SizeTFlagSetting fs(_filler_array_max_size, word_size);
2031 
2032   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2033     // Let's use the existing mechanism for the allocation
2034     HeapWord* dummy_obj = humongous_obj_allocate(word_size);
2035     if (dummy_obj != NULL) {
2036       MemRegion mr(dummy_obj, word_size);
2037       CollectedHeap::fill_with_object(mr);
2038     } else {
2039       // If we can't allocate once, we probably cannot allocate
2040       // again. Let's get out of the loop.
2041       break;
2042     }
2043   }
2044 }
2045 #endif // !PRODUCT
2046 
2047 void G1CollectedHeap::increment_old_marking_cycles_started() {
2048   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2049          _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2050          "Wrong marking cycle count (started: %d, completed: %d)",
2051          _old_marking_cycles_started, _old_marking_cycles_completed);
2052 
2053   _old_marking_cycles_started++;
2054 }
2055 
2056 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2057   MonitorLocker x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2058 
2059   // We assume that if concurrent == true, then the caller is a
2060   // concurrent thread that was joined the Suspendible Thread
2061   // Set. If there's ever a cheap way to check this, we should add an
2062   // assert here.
2063 
2064   // Given that this method is called at the end of a Full GC or of a
2065   // concurrent cycle, and those can be nested (i.e., a Full GC can
2066   // interrupt a concurrent cycle), the number of full collections
2067   // completed should be either one (in the case where there was no
2068   // nesting) or two (when a Full GC interrupted a concurrent cycle)
2069   // behind the number of full collections started.
2070 
2071   // This is the case for the inner caller, i.e. a Full GC.
2072   assert(concurrent ||
2073          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2074          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2075          "for inner caller (Full GC): _old_marking_cycles_started = %u "
2076          "is inconsistent with _old_marking_cycles_completed = %u",
2077          _old_marking_cycles_started, _old_marking_cycles_completed);
2078 
2079   // This is the case for the outer caller, i.e. the concurrent cycle.
2080   assert(!concurrent ||
2081          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2082          "for outer caller (concurrent cycle): "
2083          "_old_marking_cycles_started = %u "
2084          "is inconsistent with _old_marking_cycles_completed = %u",
2085          _old_marking_cycles_started, _old_marking_cycles_completed);
2086 
2087   _old_marking_cycles_completed += 1;
2088 
2089   // We need to clear the "in_progress" flag in the CM thread before
2090   // we wake up any waiters (especially when ExplicitInvokesConcurrent
2091   // is set) so that if a waiter requests another System.gc() it doesn't
2092   // incorrectly see that a marking cycle is still in progress.
2093   if (concurrent) {
2094     _cm_thread->set_idle();
2095   }
2096 
2097   // This notify_all() will ensure that a thread that called
2098   // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2099   // and it's waiting for a full GC to finish will be woken up. It is
2100   // waiting in VM_G1CollectForAllocation::doit_epilogue().
2101   FullGCCount_lock->notify_all();
2102 }
2103 
2104 void G1CollectedHeap::collect(GCCause::Cause cause) {
2105   try_collect(cause, true);
2106 }
2107 
2108 bool G1CollectedHeap::try_collect(GCCause::Cause cause, bool retry_on_gc_failure) {
2109   assert_heap_not_locked();
2110 
2111   bool gc_succeeded;
2112   bool should_retry_gc;
2113 
2114   do {
2115     should_retry_gc = false;
2116 
2117     uint gc_count_before;
2118     uint old_marking_count_before;
2119     uint full_gc_count_before;
2120 
2121     {
2122       MutexLocker ml(Heap_lock);
2123 
2124       // Read the GC count while holding the Heap_lock
2125       gc_count_before = total_collections();
2126       full_gc_count_before = total_full_collections();
2127       old_marking_count_before = _old_marking_cycles_started;
2128     }
2129 
2130     if (should_do_concurrent_full_gc(cause)) {
2131       // Schedule an initial-mark evacuation pause that will start a
2132       // concurrent cycle. We're setting word_size to 0 which means that
2133       // we are not requesting a post-GC allocation.
2134       VM_G1CollectForAllocation op(0,     /* word_size */
2135                                    gc_count_before,
2136                                    cause,
2137                                    true,  /* should_initiate_conc_mark */
2138                                    policy()->max_pause_time_ms());
2139       VMThread::execute(&op);
2140       gc_succeeded = op.gc_succeeded();
2141       if (!gc_succeeded && retry_on_gc_failure) {
2142         if (old_marking_count_before == _old_marking_cycles_started) {
2143           should_retry_gc = op.should_retry_gc();
2144         } else {
2145           // A Full GC happened while we were trying to schedule the
2146           // concurrent cycle. No point in starting a new cycle given
2147           // that the whole heap was collected anyway.
2148         }
2149 
2150         if (should_retry_gc && GCLocker::is_active_and_needs_gc()) {
2151           GCLocker::stall_until_clear();
2152         }
2153       }
2154     } else {
2155       if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2156           DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2157 
2158         // Schedule a standard evacuation pause. We're setting word_size
2159         // to 0 which means that we are not requesting a post-GC allocation.
2160         VM_G1CollectForAllocation op(0,     /* word_size */
2161                                      gc_count_before,
2162                                      cause,
2163                                      false, /* should_initiate_conc_mark */
2164                                      policy()->max_pause_time_ms());
2165         VMThread::execute(&op);
2166         gc_succeeded = op.gc_succeeded();
2167       } else {
2168         // Schedule a Full GC.
2169         VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2170         VMThread::execute(&op);
2171         gc_succeeded = op.gc_succeeded();
2172       }
2173     }
2174   } while (should_retry_gc);
2175   return gc_succeeded;
2176 }
2177 
2178 bool G1CollectedHeap::is_in(const void* p) const {
2179   if (_hrm->reserved().contains(p)) {
2180     // Given that we know that p is in the reserved space,
2181     // heap_region_containing() should successfully
2182     // return the containing region.
2183     HeapRegion* hr = heap_region_containing(p);
2184     return hr->is_in(p);
2185   } else {
2186     return false;
2187   }
2188 }
2189 
2190 #ifdef ASSERT
2191 bool G1CollectedHeap::is_in_exact(const void* p) const {
2192   bool contains = reserved_region().contains(p);
2193   bool available = _hrm->is_available(addr_to_region((HeapWord*)p));
2194   if (contains && available) {
2195     return true;
2196   } else {
2197     return false;
2198   }
2199 }
2200 #endif
2201 
2202 // Iteration functions.
2203 
2204 // Iterates an ObjectClosure over all objects within a HeapRegion.
2205 
2206 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2207   ObjectClosure* _cl;
2208 public:
2209   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2210   bool do_heap_region(HeapRegion* r) {
2211     if (!r->is_continues_humongous()) {
2212       r->object_iterate(_cl);
2213     }
2214     return false;
2215   }
2216 };
2217 
2218 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2219   IterateObjectClosureRegionClosure blk(cl);
2220   heap_region_iterate(&blk);
2221 }
2222 
2223 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2224   _hrm->iterate(cl);
2225 }
2226 
2227 void G1CollectedHeap::heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl,
2228                                                                  HeapRegionClaimer *hrclaimer,
2229                                                                  uint worker_id) const {
2230   _hrm->par_iterate(cl, hrclaimer, hrclaimer->offset_for_worker(worker_id));
2231 }
2232 
2233 void G1CollectedHeap::heap_region_par_iterate_from_start(HeapRegionClosure* cl,
2234                                                          HeapRegionClaimer *hrclaimer) const {
2235   _hrm->par_iterate(cl, hrclaimer, 0);
2236 }
2237 
2238 void G1CollectedHeap::collection_set_iterate_all(HeapRegionClosure* cl) {
2239   _collection_set.iterate(cl);
2240 }
2241 
2242 void G1CollectedHeap::collection_set_iterate_increment_from(HeapRegionClosure *cl, uint worker_id) {
2243   _collection_set.iterate_incremental_part_from(cl, worker_id, workers()->active_workers());
2244 }
2245 
2246 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2247   HeapRegion* hr = heap_region_containing(addr);
2248   return hr->block_start(addr);
2249 }
2250 
2251 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2252   HeapRegion* hr = heap_region_containing(addr);
2253   return hr->block_is_obj(addr);
2254 }
2255 
2256 bool G1CollectedHeap::supports_tlab_allocation() const {
2257   return true;
2258 }
2259 
2260 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2261   return (_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes;
2262 }
2263 
2264 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2265   return _eden.length() * HeapRegion::GrainBytes;
2266 }
2267 
2268 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2269 // must be equal to the humongous object limit.
2270 size_t G1CollectedHeap::max_tlab_size() const {
2271   return align_down(_humongous_object_threshold_in_words, MinObjAlignment);
2272 }
2273 
2274 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2275   return _allocator->unsafe_max_tlab_alloc();
2276 }
2277 
2278 size_t G1CollectedHeap::max_capacity() const {
2279   return _hrm->max_expandable_length() * HeapRegion::GrainBytes;
2280 }
2281 
2282 size_t G1CollectedHeap::max_reserved_capacity() const {
2283   return _hrm->max_length() * HeapRegion::GrainBytes;
2284 }
2285 
2286 jlong G1CollectedHeap::millis_since_last_gc() {
2287   // See the notes in GenCollectedHeap::millis_since_last_gc()
2288   // for more information about the implementation.
2289   jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) -
2290                   _policy->collection_pause_end_millis();
2291   if (ret_val < 0) {
2292     log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT
2293       ". returning zero instead.", ret_val);
2294     return 0;
2295   }
2296   return ret_val;
2297 }
2298 
2299 void G1CollectedHeap::deduplicate_string(oop str) {
2300   assert(java_lang_String::is_instance(str), "invariant");
2301 
2302   if (G1StringDedup::is_enabled()) {
2303     G1StringDedup::deduplicate(str);
2304   }
2305 }
2306 
2307 void G1CollectedHeap::prepare_for_verify() {
2308   _verifier->prepare_for_verify();
2309 }
2310 
2311 void G1CollectedHeap::verify(VerifyOption vo) {
2312   _verifier->verify(vo);
2313 }
2314 
2315 bool G1CollectedHeap::supports_concurrent_phase_control() const {
2316   return true;
2317 }
2318 
2319 bool G1CollectedHeap::request_concurrent_phase(const char* phase) {
2320   return _cm_thread->request_concurrent_phase(phase);
2321 }
2322 
2323 bool G1CollectedHeap::is_heterogeneous_heap() const {
2324   return G1Arguments::is_heterogeneous_heap();
2325 }
2326 
2327 class PrintRegionClosure: public HeapRegionClosure {
2328   outputStream* _st;
2329 public:
2330   PrintRegionClosure(outputStream* st) : _st(st) {}
2331   bool do_heap_region(HeapRegion* r) {
2332     r->print_on(_st);
2333     return false;
2334   }
2335 };
2336 
2337 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2338                                        const HeapRegion* hr,
2339                                        const VerifyOption vo) const {
2340   switch (vo) {
2341   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
2342   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
2343   case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj, hr);
2344   default:                            ShouldNotReachHere();
2345   }
2346   return false; // keep some compilers happy
2347 }
2348 
2349 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2350                                        const VerifyOption vo) const {
2351   switch (vo) {
2352   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
2353   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
2354   case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj);
2355   default:                            ShouldNotReachHere();
2356   }
2357   return false; // keep some compilers happy
2358 }
2359 
2360 void G1CollectedHeap::print_heap_regions() const {
2361   LogTarget(Trace, gc, heap, region) lt;
2362   if (lt.is_enabled()) {
2363     LogStream ls(lt);
2364     print_regions_on(&ls);
2365   }
2366 }
2367 
2368 void G1CollectedHeap::print_on(outputStream* st) const {
2369   st->print(" %-20s", "garbage-first heap");
2370   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
2371             capacity()/K, used_unlocked()/K);
2372   st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")",
2373             p2i(_hrm->reserved().start()),
2374             p2i(_hrm->reserved().end()));
2375   st->cr();
2376   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
2377   uint young_regions = young_regions_count();
2378   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
2379             (size_t) young_regions * HeapRegion::GrainBytes / K);
2380   uint survivor_regions = survivor_regions_count();
2381   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
2382             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
2383   st->cr();
2384   MetaspaceUtils::print_on(st);
2385 }
2386 
2387 void G1CollectedHeap::print_regions_on(outputStream* st) const {
2388   st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
2389                "HS=humongous(starts), HC=humongous(continues), "
2390                "CS=collection set, F=free, A=archive, "
2391                "TAMS=top-at-mark-start (previous, next)");
2392   PrintRegionClosure blk(st);
2393   heap_region_iterate(&blk);
2394 }
2395 
2396 void G1CollectedHeap::print_extended_on(outputStream* st) const {
2397   print_on(st);
2398 
2399   // Print the per-region information.
2400   print_regions_on(st);
2401 }
2402 
2403 void G1CollectedHeap::print_on_error(outputStream* st) const {
2404   this->CollectedHeap::print_on_error(st);
2405 
2406   if (_cm != NULL) {
2407     st->cr();
2408     _cm->print_on_error(st);
2409   }
2410 }
2411 
2412 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
2413   workers()->print_worker_threads_on(st);
2414   _cm_thread->print_on(st);
2415   st->cr();
2416   _cm->print_worker_threads_on(st);
2417   _cr->print_threads_on(st);
2418   _young_gen_sampling_thread->print_on(st);
2419   if (G1StringDedup::is_enabled()) {
2420     G1StringDedup::print_worker_threads_on(st);
2421   }
2422 }
2423 
2424 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2425   workers()->threads_do(tc);
2426   tc->do_thread(_cm_thread);
2427   _cm->threads_do(tc);
2428   _cr->threads_do(tc);
2429   tc->do_thread(_young_gen_sampling_thread);
2430   if (G1StringDedup::is_enabled()) {
2431     G1StringDedup::threads_do(tc);
2432   }
2433 }
2434 
2435 void G1CollectedHeap::print_tracing_info() const {
2436   rem_set()->print_summary_info();
2437   concurrent_mark()->print_summary_info();
2438 }
2439 
2440 #ifndef PRODUCT
2441 // Helpful for debugging RSet issues.
2442 
2443 class PrintRSetsClosure : public HeapRegionClosure {
2444 private:
2445   const char* _msg;
2446   size_t _occupied_sum;
2447 
2448 public:
2449   bool do_heap_region(HeapRegion* r) {
2450     HeapRegionRemSet* hrrs = r->rem_set();
2451     size_t occupied = hrrs->occupied();
2452     _occupied_sum += occupied;
2453 
2454     tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r));
2455     if (occupied == 0) {
2456       tty->print_cr("  RSet is empty");
2457     } else {
2458       hrrs->print();
2459     }
2460     tty->print_cr("----------");
2461     return false;
2462   }
2463 
2464   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
2465     tty->cr();
2466     tty->print_cr("========================================");
2467     tty->print_cr("%s", msg);
2468     tty->cr();
2469   }
2470 
2471   ~PrintRSetsClosure() {
2472     tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
2473     tty->print_cr("========================================");
2474     tty->cr();
2475   }
2476 };
2477 
2478 void G1CollectedHeap::print_cset_rsets() {
2479   PrintRSetsClosure cl("Printing CSet RSets");
2480   collection_set_iterate_all(&cl);
2481 }
2482 
2483 void G1CollectedHeap::print_all_rsets() {
2484   PrintRSetsClosure cl("Printing All RSets");;
2485   heap_region_iterate(&cl);
2486 }
2487 #endif // PRODUCT
2488 
2489 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
2490 
2491   size_t eden_used_bytes = _eden.used_bytes();
2492   size_t survivor_used_bytes = _survivor.used_bytes();
2493   size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
2494 
2495   size_t eden_capacity_bytes =
2496     (policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
2497 
2498   VirtualSpaceSummary heap_summary = create_heap_space_summary();
2499   return G1HeapSummary(heap_summary, heap_used, eden_used_bytes,
2500                        eden_capacity_bytes, survivor_used_bytes, num_regions());
2501 }
2502 
2503 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
2504   return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
2505                        stats->unused(), stats->used(), stats->region_end_waste(),
2506                        stats->regions_filled(), stats->direct_allocated(),
2507                        stats->failure_used(), stats->failure_waste());
2508 }
2509 
2510 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
2511   const G1HeapSummary& heap_summary = create_g1_heap_summary();
2512   gc_tracer->report_gc_heap_summary(when, heap_summary);
2513 
2514   const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
2515   gc_tracer->report_metaspace_summary(when, metaspace_summary);
2516 }
2517 
2518 G1CollectedHeap* G1CollectedHeap::heap() {
2519   CollectedHeap* heap = Universe::heap();
2520   assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
2521   assert(heap->kind() == CollectedHeap::G1, "Invalid name");
2522   return (G1CollectedHeap*)heap;
2523 }
2524 
2525 void G1CollectedHeap::gc_prologue(bool full) {
2526   // always_do_update_barrier = false;
2527   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
2528 
2529   // This summary needs to be printed before incrementing total collections.
2530   rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections());
2531 
2532   // Update common counters.
2533   increment_total_collections(full /* full gc */);
2534   if (full || collector_state()->in_initial_mark_gc()) {
2535     increment_old_marking_cycles_started();
2536   }
2537 
2538   // Fill TLAB's and such
2539   double start = os::elapsedTime();
2540   ensure_parsability(true);
2541   phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2542 }
2543 
2544 void G1CollectedHeap::gc_epilogue(bool full) {
2545   // Update common counters.
2546   if (full) {
2547     // Update the number of full collections that have been completed.
2548     increment_old_marking_cycles_completed(false /* concurrent */);
2549   }
2550 
2551   // We are at the end of the GC. Total collections has already been increased.
2552   rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1);
2553 
2554   // FIXME: what is this about?
2555   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
2556   // is set.
2557 #if COMPILER2_OR_JVMCI
2558   assert(DerivedPointerTable::is_empty(), "derived pointer present");
2559 #endif
2560   // always_do_update_barrier = true;
2561 
2562   double start = os::elapsedTime();
2563   resize_all_tlabs();
2564   phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2565 
2566   MemoryService::track_memory_usage();
2567   // We have just completed a GC. Update the soft reference
2568   // policy with the new heap occupancy
2569   Universe::update_heap_info_at_gc();
2570 }
2571 
2572 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2573                                                uint gc_count_before,
2574                                                bool* succeeded,
2575                                                GCCause::Cause gc_cause) {
2576   assert_heap_not_locked_and_not_at_safepoint();
2577   VM_G1CollectForAllocation op(word_size,
2578                                gc_count_before,
2579                                gc_cause,
2580                                false, /* should_initiate_conc_mark */
2581                                policy()->max_pause_time_ms());
2582   VMThread::execute(&op);
2583 
2584   HeapWord* result = op.result();
2585   bool ret_succeeded = op.prologue_succeeded() && op.gc_succeeded();
2586   assert(result == NULL || ret_succeeded,
2587          "the result should be NULL if the VM did not succeed");
2588   *succeeded = ret_succeeded;
2589 
2590   assert_heap_not_locked();
2591   return result;
2592 }
2593 
2594 void G1CollectedHeap::do_concurrent_mark() {
2595   MutexLocker x(CGC_lock, Mutex::_no_safepoint_check_flag);
2596   if (!_cm_thread->in_progress()) {
2597     _cm_thread->set_started();
2598     CGC_lock->notify();
2599   }
2600 }
2601 
2602 size_t G1CollectedHeap::pending_card_num() {
2603   struct CountCardsClosure : public ThreadClosure {
2604     size_t _cards;
2605     CountCardsClosure() : _cards(0) {}
2606     virtual void do_thread(Thread* t) {
2607       _cards += G1ThreadLocalData::dirty_card_queue(t).size();
2608     }
2609   } count_from_threads;
2610   Threads::threads_do(&count_from_threads);
2611 
2612   G1DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
2613   size_t buffer_size = dcqs.buffer_size();
2614   size_t buffer_num = dcqs.completed_buffers_num();
2615 
2616   return buffer_size * buffer_num + count_from_threads._cards;
2617 }
2618 
2619 bool G1CollectedHeap::is_potential_eager_reclaim_candidate(HeapRegion* r) const {
2620   // We don't nominate objects with many remembered set entries, on
2621   // the assumption that such objects are likely still live.
2622   HeapRegionRemSet* rem_set = r->rem_set();
2623 
2624   return G1EagerReclaimHumongousObjectsWithStaleRefs ?
2625          rem_set->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) :
2626          G1EagerReclaimHumongousObjects && rem_set->is_empty();
2627 }
2628 
2629 class RegisterRegionsWithRegionAttrTableClosure : public HeapRegionClosure {
2630  private:
2631   size_t _total_humongous;
2632   size_t _candidate_humongous;
2633 
2634   G1DirtyCardQueue _dcq;
2635 
2636   bool humongous_region_is_candidate(G1CollectedHeap* g1h, HeapRegion* region) const {
2637     assert(region->is_starts_humongous(), "Must start a humongous object");
2638 
2639     oop obj = oop(region->bottom());
2640 
2641     // Dead objects cannot be eager reclaim candidates. Due to class
2642     // unloading it is unsafe to query their classes so we return early.
2643     if (g1h->is_obj_dead(obj, region)) {
2644       return false;
2645     }
2646 
2647     // If we do not have a complete remembered set for the region, then we can
2648     // not be sure that we have all references to it.
2649     if (!region->rem_set()->is_complete()) {
2650       return false;
2651     }
2652     // Candidate selection must satisfy the following constraints
2653     // while concurrent marking is in progress:
2654     //
2655     // * In order to maintain SATB invariants, an object must not be
2656     // reclaimed if it was allocated before the start of marking and
2657     // has not had its references scanned.  Such an object must have
2658     // its references (including type metadata) scanned to ensure no
2659     // live objects are missed by the marking process.  Objects
2660     // allocated after the start of concurrent marking don't need to
2661     // be scanned.
2662     //
2663     // * An object must not be reclaimed if it is on the concurrent
2664     // mark stack.  Objects allocated after the start of concurrent
2665     // marking are never pushed on the mark stack.
2666     //
2667     // Nominating only objects allocated after the start of concurrent
2668     // marking is sufficient to meet both constraints.  This may miss
2669     // some objects that satisfy the constraints, but the marking data
2670     // structures don't support efficiently performing the needed
2671     // additional tests or scrubbing of the mark stack.
2672     //
2673     // However, we presently only nominate is_typeArray() objects.
2674     // A humongous object containing references induces remembered
2675     // set entries on other regions.  In order to reclaim such an
2676     // object, those remembered sets would need to be cleaned up.
2677     //
2678     // We also treat is_typeArray() objects specially, allowing them
2679     // to be reclaimed even if allocated before the start of
2680     // concurrent mark.  For this we rely on mark stack insertion to
2681     // exclude is_typeArray() objects, preventing reclaiming an object
2682     // that is in the mark stack.  We also rely on the metadata for
2683     // such objects to be built-in and so ensured to be kept live.
2684     // Frequent allocation and drop of large binary blobs is an
2685     // important use case for eager reclaim, and this special handling
2686     // may reduce needed headroom.
2687 
2688     return obj->is_typeArray() &&
2689            g1h->is_potential_eager_reclaim_candidate(region);
2690   }
2691 
2692  public:
2693   RegisterRegionsWithRegionAttrTableClosure()
2694   : _total_humongous(0),
2695     _candidate_humongous(0),
2696     _dcq(&G1BarrierSet::dirty_card_queue_set()) {
2697   }
2698 
2699   virtual bool do_heap_region(HeapRegion* r) {
2700     G1CollectedHeap* g1h = G1CollectedHeap::heap();
2701 
2702     if (!r->is_starts_humongous()) {
2703       g1h->register_region_with_region_attr(r);
2704       return false;
2705     }
2706 
2707     bool is_candidate = humongous_region_is_candidate(g1h, r);
2708     uint rindex = r->hrm_index();
2709     g1h->set_humongous_reclaim_candidate(rindex, is_candidate);
2710     if (is_candidate) {
2711       _candidate_humongous++;
2712       g1h->register_humongous_region_with_region_attr(rindex);
2713       // Is_candidate already filters out humongous object with large remembered sets.
2714       // If we have a humongous object with a few remembered sets, we simply flush these
2715       // remembered set entries into the DCQS. That will result in automatic
2716       // re-evaluation of their remembered set entries during the following evacuation
2717       // phase.
2718       if (!r->rem_set()->is_empty()) {
2719         guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
2720                   "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
2721         G1CardTable* ct = g1h->card_table();
2722         HeapRegionRemSetIterator hrrs(r->rem_set());
2723         size_t card_index;
2724         while (hrrs.has_next(card_index)) {
2725           CardTable::CardValue* card_ptr = ct->byte_for_index(card_index);
2726           // The remembered set might contain references to already freed
2727           // regions. Filter out such entries to avoid failing card table
2728           // verification.
2729           if (g1h->is_in(ct->addr_for(card_ptr))) {
2730             if (*card_ptr != G1CardTable::dirty_card_val()) {
2731               *card_ptr = G1CardTable::dirty_card_val();
2732               _dcq.enqueue(card_ptr);
2733             }
2734           }
2735         }
2736         assert(hrrs.n_yielded() == r->rem_set()->occupied(),
2737                "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries",
2738                hrrs.n_yielded(), r->rem_set()->occupied());
2739         // We should only clear the card based remembered set here as we will not
2740         // implicitly rebuild anything else during eager reclaim. Note that at the moment
2741         // (and probably never) we do not enter this path if there are other kind of
2742         // remembered sets for this region.
2743         r->rem_set()->clear_locked(true /* only_cardset */);
2744         // Clear_locked() above sets the state to Empty. However we want to continue
2745         // collecting remembered set entries for humongous regions that were not
2746         // reclaimed.
2747         r->rem_set()->set_state_complete();
2748 #ifdef ASSERT
2749         G1HeapRegionAttr region_attr = g1h->region_attr(oop(r->bottom()));
2750         assert(region_attr.needs_remset_update(), "must be");
2751 #endif
2752       }
2753       assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
2754     } else {
2755       g1h->register_region_with_region_attr(r);
2756     }
2757     _total_humongous++;
2758 
2759     return false;
2760   }
2761 
2762   size_t total_humongous() const { return _total_humongous; }
2763   size_t candidate_humongous() const { return _candidate_humongous; }
2764 
2765   void flush_rem_set_entries() { _dcq.flush(); }
2766 };
2767 
2768 void G1CollectedHeap::register_regions_with_region_attr() {
2769   Ticks start = Ticks::now();
2770 
2771   RegisterRegionsWithRegionAttrTableClosure cl;
2772   heap_region_iterate(&cl);
2773 
2774   phase_times()->record_register_regions((Ticks::now() - start).seconds() * 1000.0,
2775                                          cl.total_humongous(),
2776                                          cl.candidate_humongous());
2777   _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
2778 
2779   // Finally flush all remembered set entries to re-check into the global DCQS.
2780   cl.flush_rem_set_entries();
2781 }
2782 
2783 #ifndef PRODUCT
2784 void G1CollectedHeap::verify_region_attr_remset_update() {
2785   class VerifyRegionAttrRemSet : public HeapRegionClosure {
2786   public:
2787     virtual bool do_heap_region(HeapRegion* r) {
2788       G1CollectedHeap* g1h = G1CollectedHeap::heap();
2789       bool const needs_remset_update = g1h->region_attr(r->bottom()).needs_remset_update();
2790       assert(r->rem_set()->is_tracked() == needs_remset_update,
2791              "Region %u remset tracking status (%s) different to region attribute (%s)",
2792              r->hrm_index(), BOOL_TO_STR(r->rem_set()->is_tracked()), BOOL_TO_STR(needs_remset_update));
2793       return false;
2794     }
2795   } cl;
2796   heap_region_iterate(&cl);
2797 }
2798 #endif
2799 
2800 class VerifyRegionRemSetClosure : public HeapRegionClosure {
2801   public:
2802     bool do_heap_region(HeapRegion* hr) {
2803       if (!hr->is_archive() && !hr->is_continues_humongous()) {
2804         hr->verify_rem_set();
2805       }
2806       return false;
2807     }
2808 };
2809 
2810 uint G1CollectedHeap::num_task_queues() const {
2811   return _task_queues->size();
2812 }
2813 
2814 #if TASKQUEUE_STATS
2815 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
2816   st->print_raw_cr("GC Task Stats");
2817   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
2818   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
2819 }
2820 
2821 void G1CollectedHeap::print_taskqueue_stats() const {
2822   if (!log_is_enabled(Trace, gc, task, stats)) {
2823     return;
2824   }
2825   Log(gc, task, stats) log;
2826   ResourceMark rm;
2827   LogStream ls(log.trace());
2828   outputStream* st = &ls;
2829 
2830   print_taskqueue_stats_hdr(st);
2831 
2832   TaskQueueStats totals;
2833   const uint n = num_task_queues();
2834   for (uint i = 0; i < n; ++i) {
2835     st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
2836     totals += task_queue(i)->stats;
2837   }
2838   st->print_raw("tot "); totals.print(st); st->cr();
2839 
2840   DEBUG_ONLY(totals.verify());
2841 }
2842 
2843 void G1CollectedHeap::reset_taskqueue_stats() {
2844   const uint n = num_task_queues();
2845   for (uint i = 0; i < n; ++i) {
2846     task_queue(i)->stats.reset();
2847   }
2848 }
2849 #endif // TASKQUEUE_STATS
2850 
2851 void G1CollectedHeap::wait_for_root_region_scanning() {
2852   double scan_wait_start = os::elapsedTime();
2853   // We have to wait until the CM threads finish scanning the
2854   // root regions as it's the only way to ensure that all the
2855   // objects on them have been correctly scanned before we start
2856   // moving them during the GC.
2857   bool waited = _cm->root_regions()->wait_until_scan_finished();
2858   double wait_time_ms = 0.0;
2859   if (waited) {
2860     double scan_wait_end = os::elapsedTime();
2861     wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
2862   }
2863   phase_times()->record_root_region_scan_wait_time(wait_time_ms);
2864 }
2865 
2866 class G1PrintCollectionSetClosure : public HeapRegionClosure {
2867 private:
2868   G1HRPrinter* _hr_printer;
2869 public:
2870   G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { }
2871 
2872   virtual bool do_heap_region(HeapRegion* r) {
2873     _hr_printer->cset(r);
2874     return false;
2875   }
2876 };
2877 
2878 void G1CollectedHeap::start_new_collection_set() {
2879   double start = os::elapsedTime();
2880 
2881   collection_set()->start_incremental_building();
2882 
2883   clear_region_attr();
2884 
2885   guarantee(_eden.length() == 0, "eden should have been cleared");
2886   policy()->transfer_survivors_to_cset(survivor());
2887 
2888   // We redo the verification but now wrt to the new CSet which
2889   // has just got initialized after the previous CSet was freed.
2890   _cm->verify_no_collection_set_oops();
2891 
2892   phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0);
2893 }
2894 
2895 void G1CollectedHeap::calculate_collection_set(G1EvacuationInfo& evacuation_info, double target_pause_time_ms) {
2896 
2897   _collection_set.finalize_initial_collection_set(target_pause_time_ms, &_survivor);
2898   evacuation_info.set_collectionset_regions(collection_set()->region_length() +
2899                                             collection_set()->optional_region_length());
2900 
2901   _cm->verify_no_collection_set_oops();
2902 
2903   if (_hr_printer.is_active()) {
2904     G1PrintCollectionSetClosure cl(&_hr_printer);
2905     _collection_set.iterate(&cl);
2906     _collection_set.iterate_optional(&cl);
2907   }
2908 }
2909 
2910 G1HeapVerifier::G1VerifyType G1CollectedHeap::young_collection_verify_type() const {
2911   if (collector_state()->in_initial_mark_gc()) {
2912     return G1HeapVerifier::G1VerifyConcurrentStart;
2913   } else if (collector_state()->in_young_only_phase()) {
2914     return G1HeapVerifier::G1VerifyYoungNormal;
2915   } else {
2916     return G1HeapVerifier::G1VerifyMixed;
2917   }
2918 }
2919 
2920 void G1CollectedHeap::verify_before_young_collection(G1HeapVerifier::G1VerifyType type) {
2921   if (VerifyRememberedSets) {
2922     log_info(gc, verify)("[Verifying RemSets before GC]");
2923     VerifyRegionRemSetClosure v_cl;
2924     heap_region_iterate(&v_cl);
2925   }
2926   _verifier->verify_before_gc(type);
2927   _verifier->check_bitmaps("GC Start");
2928 }
2929 
2930 void G1CollectedHeap::verify_after_young_collection(G1HeapVerifier::G1VerifyType type) {
2931   if (VerifyRememberedSets) {
2932     log_info(gc, verify)("[Verifying RemSets after GC]");
2933     VerifyRegionRemSetClosure v_cl;
2934     heap_region_iterate(&v_cl);
2935   }
2936   _verifier->verify_after_gc(type);
2937   _verifier->check_bitmaps("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   GCIdMark gc_id_mark;
2976 
2977   SvcGCMarker sgcm(SvcGCMarker::MINOR);
2978   ResourceMark rm;
2979 
2980   policy()->note_gc_start();
2981 
2982   _gc_timer_stw->register_gc_start();
2983   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
2984 
2985   wait_for_root_region_scanning();
2986 
2987   print_heap_before_gc();
2988   print_heap_regions();
2989   trace_heap_before_gc(_gc_tracer_stw);
2990 
2991   _verifier->verify_region_sets_optional();
2992   _verifier->verify_dirty_young_regions();
2993 
2994   // We should not be doing initial mark unless the conc mark thread is running
2995   if (!_cm_thread->should_terminate()) {
2996     // This call will decide whether this pause is an initial-mark
2997     // pause. If it is, in_initial_mark_gc() will return true
2998     // for the duration of this pause.
2999     policy()->decide_on_conc_mark_initiation();
3000   }
3001 
3002   // We do not allow initial-mark to be piggy-backed on a mixed GC.
3003   assert(!collector_state()->in_initial_mark_gc() ||
3004          collector_state()->in_young_only_phase(), "sanity");
3005   // We also do not allow mixed GCs during marking.
3006   assert(!collector_state()->mark_or_rebuild_in_progress() || collector_state()->in_young_only_phase(), "sanity");
3007 
3008   // Record whether this pause is an initial mark. When the current
3009   // thread has completed its logging output and it's safe to signal
3010   // the CM thread, the flag's value in the policy has been reset.
3011   bool should_start_conc_mark = collector_state()->in_initial_mark_gc();
3012   if (should_start_conc_mark) {
3013     _cm->gc_tracer_cm()->set_gc_cause(gc_cause());
3014   }
3015 
3016   // Inner scope for scope based logging, timers, and stats collection
3017   {
3018     G1EvacuationInfo evacuation_info;
3019 
3020     _gc_tracer_stw->report_yc_type(collector_state()->yc_type());
3021 
3022     GCTraceCPUTime tcpu;
3023 
3024     GCTraceTime(Info, gc) tm(young_gc_name(), NULL, gc_cause(), true);
3025 
3026     uint active_workers = WorkerPolicy::calc_active_workers(workers()->total_workers(),
3027                                                             workers()->active_workers(),
3028                                                             Threads::number_of_non_daemon_threads());
3029     active_workers = workers()->update_active_workers(active_workers);
3030     log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers());
3031 
3032     G1MonitoringScope ms(g1mm(),
3033                          false /* full_gc */,
3034                          collector_state()->yc_type() == Mixed /* all_memory_pools_affected */);
3035 
3036     G1HeapTransition heap_transition(this);
3037     size_t heap_used_bytes_before_gc = used();
3038 
3039     {
3040       IsGCActiveMark x;
3041 
3042       gc_prologue(false);
3043 
3044       G1HeapVerifier::G1VerifyType verify_type = young_collection_verify_type();
3045       verify_before_young_collection(verify_type);
3046 
3047       {
3048         // The elapsed time induced by the start time below deliberately elides
3049         // the possible verification above.
3050         double sample_start_time_sec = os::elapsedTime();
3051 
3052         // Please see comment in g1CollectedHeap.hpp and
3053         // G1CollectedHeap::ref_processing_init() to see how
3054         // reference processing currently works in G1.
3055         _ref_processor_stw->enable_discovery();
3056 
3057         // We want to temporarily turn off discovery by the
3058         // CM ref processor, if necessary, and turn it back on
3059         // on again later if we do. Using a scoped
3060         // NoRefDiscovery object will do this.
3061         NoRefDiscovery no_cm_discovery(_ref_processor_cm);
3062 
3063         policy()->record_collection_pause_start(sample_start_time_sec);
3064 
3065         // Forget the current allocation region (we might even choose it to be part
3066         // of the collection set!).
3067         _allocator->release_mutator_alloc_region();
3068 
3069         calculate_collection_set(evacuation_info, target_pause_time_ms);
3070 
3071         G1ParScanThreadStateSet per_thread_states(this,
3072                                                   workers()->active_workers(),
3073                                                   collection_set()->young_region_length(),
3074                                                   collection_set()->optional_region_length());
3075         pre_evacuate_collection_set(evacuation_info);
3076 
3077         // Actually do the work...
3078         evacuate_initial_collection_set(&per_thread_states);
3079 
3080         if (_collection_set.optional_region_length() != 0) {
3081           evacuate_optional_collection_set(&per_thread_states);
3082         }
3083         post_evacuate_collection_set(evacuation_info, &per_thread_states);
3084 
3085         start_new_collection_set();
3086 
3087         _survivor_evac_stats.adjust_desired_plab_sz();
3088         _old_evac_stats.adjust_desired_plab_sz();
3089 
3090         if (should_start_conc_mark) {
3091           // We have to do this before we notify the CM threads that
3092           // they can start working to make sure that all the
3093           // appropriate initialization is done on the CM object.
3094           concurrent_mark()->post_initial_mark();
3095           // Note that we don't actually trigger the CM thread at
3096           // this point. We do that later when we're sure that
3097           // the current thread has completed its logging output.
3098         }
3099 
3100         allocate_dummy_regions();
3101 
3102         _allocator->init_mutator_alloc_region();
3103 
3104         expand_heap_after_young_collection();
3105 
3106         double sample_end_time_sec = os::elapsedTime();
3107         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3108         size_t total_cards_scanned = phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanRS, G1GCPhaseTimes::ScanRSScannedCards) +
3109                                      phase_times()->sum_thread_work_items(G1GCPhaseTimes::OptScanRS, G1GCPhaseTimes::ScanRSScannedCards);
3110         policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc);
3111       }
3112 
3113       verify_after_young_collection(verify_type);
3114 
3115 #ifdef TRACESPINNING
3116       ParallelTaskTerminator::print_termination_counts();
3117 #endif
3118 
3119       gc_epilogue(false);
3120     }
3121 
3122     // Print the remainder of the GC log output.
3123     if (evacuation_failed()) {
3124       log_info(gc)("To-space exhausted");
3125     }
3126 
3127     policy()->print_phases();
3128     heap_transition.print();
3129 
3130     _hrm->verify_optional();
3131     _verifier->verify_region_sets_optional();
3132 
3133     TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
3134     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3135 
3136     print_heap_after_gc();
3137     print_heap_regions();
3138     trace_heap_after_gc(_gc_tracer_stw);
3139 
3140     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3141     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3142     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3143     // before any GC notifications are raised.
3144     g1mm()->update_sizes();
3145 
3146     _gc_tracer_stw->report_evacuation_info(&evacuation_info);
3147     _gc_tracer_stw->report_tenuring_threshold(_policy->tenuring_threshold());
3148     _gc_timer_stw->register_gc_end();
3149     _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
3150   }
3151   // It should now be safe to tell the concurrent mark thread to start
3152   // without its logging output interfering with the logging output
3153   // that came from the pause.
3154 
3155   if (should_start_conc_mark) {
3156     // CAUTION: after the doConcurrentMark() call below, the concurrent marking
3157     // thread(s) could be running concurrently with us. Make sure that anything
3158     // after this point does not assume that we are the only GC thread running.
3159     // Note: of course, the actual marking work will not start until the safepoint
3160     // itself is released in SuspendibleThreadSet::desynchronize().
3161     do_concurrent_mark();
3162   }
3163 
3164   return true;
3165 }
3166 
3167 void G1CollectedHeap::remove_self_forwarding_pointers() {
3168   G1ParRemoveSelfForwardPtrsTask rsfp_task;
3169   workers()->run_task(&rsfp_task);
3170 }
3171 
3172 void G1CollectedHeap::restore_after_evac_failure() {
3173   double remove_self_forwards_start = os::elapsedTime();
3174 
3175   remove_self_forwarding_pointers();
3176   SharedRestorePreservedMarksTaskExecutor task_executor(workers());
3177   _preserved_marks_set.restore(&task_executor);
3178 
3179   phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
3180 }
3181 
3182 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) {
3183   if (!_evacuation_failed) {
3184     _evacuation_failed = true;
3185   }
3186 
3187   _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size());
3188   _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m);
3189 }
3190 
3191 bool G1ParEvacuateFollowersClosure::offer_termination() {
3192   EventGCPhaseParallel event;
3193   G1ParScanThreadState* const pss = par_scan_state();
3194   start_term_time();
3195   const bool res = terminator()->offer_termination();
3196   end_term_time();
3197   event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(G1GCPhaseTimes::Termination));
3198   return res;
3199 }
3200 
3201 void G1ParEvacuateFollowersClosure::do_void() {
3202   EventGCPhaseParallel event;
3203   G1ParScanThreadState* const pss = par_scan_state();
3204   pss->trim_queue();
3205   event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(_phase));
3206   do {
3207     EventGCPhaseParallel event;
3208     pss->steal_and_trim_queue(queues());
3209     event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(_phase));
3210   } while (!offer_termination());
3211 }
3212 
3213 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive,
3214                                         bool class_unloading_occurred) {
3215   uint num_workers = workers()->active_workers();
3216   ParallelCleaningTask unlink_task(is_alive, num_workers, class_unloading_occurred, false);
3217   workers()->run_task(&unlink_task);
3218 }
3219 
3220 // Clean string dedup data structures.
3221 // Ideally we would prefer to use a StringDedupCleaningTask here, but we want to
3222 // record the durations of the phases. Hence the almost-copy.
3223 class G1StringDedupCleaningTask : public AbstractGangTask {
3224   BoolObjectClosure* _is_alive;
3225   OopClosure* _keep_alive;
3226   G1GCPhaseTimes* _phase_times;
3227 
3228 public:
3229   G1StringDedupCleaningTask(BoolObjectClosure* is_alive,
3230                             OopClosure* keep_alive,
3231                             G1GCPhaseTimes* phase_times) :
3232     AbstractGangTask("Partial Cleaning Task"),
3233     _is_alive(is_alive),
3234     _keep_alive(keep_alive),
3235     _phase_times(phase_times)
3236   {
3237     assert(G1StringDedup::is_enabled(), "String deduplication disabled.");
3238     StringDedup::gc_prologue(true);
3239   }
3240 
3241   ~G1StringDedupCleaningTask() {
3242     StringDedup::gc_epilogue();
3243   }
3244 
3245   void work(uint worker_id) {
3246     StringDedupUnlinkOrOopsDoClosure cl(_is_alive, _keep_alive);
3247     {
3248       G1GCParPhaseTimesTracker x(_phase_times, G1GCPhaseTimes::StringDedupQueueFixup, worker_id);
3249       StringDedupQueue::unlink_or_oops_do(&cl);
3250     }
3251     {
3252       G1GCParPhaseTimesTracker x(_phase_times, G1GCPhaseTimes::StringDedupTableFixup, worker_id);
3253       StringDedupTable::unlink_or_oops_do(&cl, worker_id);
3254     }
3255   }
3256 };
3257 
3258 void G1CollectedHeap::string_dedup_cleaning(BoolObjectClosure* is_alive,
3259                                             OopClosure* keep_alive,
3260                                             G1GCPhaseTimes* phase_times) {
3261   G1StringDedupCleaningTask cl(is_alive, keep_alive, phase_times);
3262   workers()->run_task(&cl);
3263 }
3264 
3265 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
3266  private:
3267   G1DirtyCardQueueSet* _queue;
3268   G1CollectedHeap* _g1h;
3269  public:
3270   G1RedirtyLoggedCardsTask(G1DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"),
3271     _queue(queue), _g1h(g1h) { }
3272 
3273   virtual void work(uint worker_id) {
3274     G1GCPhaseTimes* p = _g1h->phase_times();
3275     G1GCParPhaseTimesTracker x(p, G1GCPhaseTimes::RedirtyCards, worker_id);
3276 
3277     RedirtyLoggedCardTableEntryClosure cl(_g1h);
3278     _queue->par_apply_closure_to_all_completed_buffers(&cl);
3279 
3280     p->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied());
3281   }
3282 };
3283 
3284 void G1CollectedHeap::redirty_logged_cards() {
3285   double redirty_logged_cards_start = os::elapsedTime();
3286 
3287   G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this);
3288   dirty_card_queue_set().reset_for_par_iteration();
3289   workers()->run_task(&redirty_task);
3290 
3291   G1DirtyCardQueueSet& dcq = G1BarrierSet::dirty_card_queue_set();
3292   dcq.merge_bufferlists(&dirty_card_queue_set());
3293   assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
3294 
3295   phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
3296 }
3297 
3298 // Weak Reference Processing support
3299 
3300 bool G1STWIsAliveClosure::do_object_b(oop p) {
3301   // An object is reachable if it is outside the collection set,
3302   // or is inside and copied.
3303   return !_g1h->is_in_cset(p) || p->is_forwarded();
3304 }
3305 
3306 bool G1STWSubjectToDiscoveryClosure::do_object_b(oop obj) {
3307   assert(obj != NULL, "must not be NULL");
3308   assert(_g1h->is_in_reserved(obj), "Trying to discover obj " PTR_FORMAT " not in heap", p2i(obj));
3309   // The areas the CM and STW ref processor manage must be disjoint. The is_in_cset() below
3310   // may falsely indicate that this is not the case here: however the collection set only
3311   // contains old regions when concurrent mark is not running.
3312   return _g1h->is_in_cset(obj) || _g1h->heap_region_containing(obj)->is_survivor();
3313 }
3314 
3315 // Non Copying Keep Alive closure
3316 class G1KeepAliveClosure: public OopClosure {
3317   G1CollectedHeap*_g1h;
3318 public:
3319   G1KeepAliveClosure(G1CollectedHeap* g1h) :_g1h(g1h) {}
3320   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
3321   void do_oop(oop* p) {
3322     oop obj = *p;
3323     assert(obj != NULL, "the caller should have filtered out NULL values");
3324 
3325     const G1HeapRegionAttr region_attr =_g1h->region_attr(obj);
3326     if (!region_attr.is_in_cset_or_humongous()) {
3327       return;
3328     }
3329     if (region_attr.is_in_cset()) {
3330       assert( obj->is_forwarded(), "invariant" );
3331       *p = obj->forwardee();
3332     } else {
3333       assert(!obj->is_forwarded(), "invariant" );
3334       assert(region_attr.is_humongous(),
3335              "Only allowed G1HeapRegionAttr state is IsHumongous, but is %d", region_attr.type());
3336      _g1h->set_humongous_is_live(obj);
3337     }
3338   }
3339 };
3340 
3341 // Copying Keep Alive closure - can be called from both
3342 // serial and parallel code as long as different worker
3343 // threads utilize different G1ParScanThreadState instances
3344 // and different queues.
3345 
3346 class G1CopyingKeepAliveClosure: public OopClosure {
3347   G1CollectedHeap*         _g1h;
3348   G1ParScanThreadState*    _par_scan_state;
3349 
3350 public:
3351   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
3352                             G1ParScanThreadState* pss):
3353     _g1h(g1h),
3354     _par_scan_state(pss)
3355   {}
3356 
3357   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
3358   virtual void do_oop(      oop* p) { do_oop_work(p); }
3359 
3360   template <class T> void do_oop_work(T* p) {
3361     oop obj = RawAccess<>::oop_load(p);
3362 
3363     if (_g1h->is_in_cset_or_humongous(obj)) {
3364       // If the referent object has been forwarded (either copied
3365       // to a new location or to itself in the event of an
3366       // evacuation failure) then we need to update the reference
3367       // field and, if both reference and referent are in the G1
3368       // heap, update the RSet for the referent.
3369       //
3370       // If the referent has not been forwarded then we have to keep
3371       // it alive by policy. Therefore we have copy the referent.
3372       //
3373       // When the queue is drained (after each phase of reference processing)
3374       // the object and it's followers will be copied, the reference field set
3375       // to point to the new location, and the RSet updated.
3376       _par_scan_state->push_on_queue(p);
3377     }
3378   }
3379 };
3380 
3381 // Serial drain queue closure. Called as the 'complete_gc'
3382 // closure for each discovered list in some of the
3383 // reference processing phases.
3384 
3385 class G1STWDrainQueueClosure: public VoidClosure {
3386 protected:
3387   G1CollectedHeap* _g1h;
3388   G1ParScanThreadState* _par_scan_state;
3389 
3390   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
3391 
3392 public:
3393   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
3394     _g1h(g1h),
3395     _par_scan_state(pss)
3396   { }
3397 
3398   void do_void() {
3399     G1ParScanThreadState* const pss = par_scan_state();
3400     pss->trim_queue();
3401   }
3402 };
3403 
3404 // Parallel Reference Processing closures
3405 
3406 // Implementation of AbstractRefProcTaskExecutor for parallel reference
3407 // processing during G1 evacuation pauses.
3408 
3409 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
3410 private:
3411   G1CollectedHeap*          _g1h;
3412   G1ParScanThreadStateSet*  _pss;
3413   RefToScanQueueSet*        _queues;
3414   WorkGang*                 _workers;
3415 
3416 public:
3417   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
3418                            G1ParScanThreadStateSet* per_thread_states,
3419                            WorkGang* workers,
3420                            RefToScanQueueSet *task_queues) :
3421     _g1h(g1h),
3422     _pss(per_thread_states),
3423     _queues(task_queues),
3424     _workers(workers)
3425   {
3426     g1h->ref_processor_stw()->set_active_mt_degree(workers->active_workers());
3427   }
3428 
3429   // Executes the given task using concurrent marking worker threads.
3430   virtual void execute(ProcessTask& task, uint ergo_workers);
3431 };
3432 
3433 // Gang task for possibly parallel reference processing
3434 
3435 class G1STWRefProcTaskProxy: public AbstractGangTask {
3436   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
3437   ProcessTask&     _proc_task;
3438   G1CollectedHeap* _g1h;
3439   G1ParScanThreadStateSet* _pss;
3440   RefToScanQueueSet* _task_queues;
3441   ParallelTaskTerminator* _terminator;
3442 
3443 public:
3444   G1STWRefProcTaskProxy(ProcessTask& proc_task,
3445                         G1CollectedHeap* g1h,
3446                         G1ParScanThreadStateSet* per_thread_states,
3447                         RefToScanQueueSet *task_queues,
3448                         ParallelTaskTerminator* terminator) :
3449     AbstractGangTask("Process reference objects in parallel"),
3450     _proc_task(proc_task),
3451     _g1h(g1h),
3452     _pss(per_thread_states),
3453     _task_queues(task_queues),
3454     _terminator(terminator)
3455   {}
3456 
3457   virtual void work(uint worker_id) {
3458     // The reference processing task executed by a single worker.
3459     ResourceMark rm;
3460     HandleMark   hm;
3461 
3462     G1STWIsAliveClosure is_alive(_g1h);
3463 
3464     G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
3465     pss->set_ref_discoverer(NULL);
3466 
3467     // Keep alive closure.
3468     G1CopyingKeepAliveClosure keep_alive(_g1h, pss);
3469 
3470     // Complete GC closure
3471     G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator, G1GCPhaseTimes::ObjCopy);
3472 
3473     // Call the reference processing task's work routine.
3474     _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
3475 
3476     // Note we cannot assert that the refs array is empty here as not all
3477     // of the processing tasks (specifically phase2 - pp2_work) execute
3478     // the complete_gc closure (which ordinarily would drain the queue) so
3479     // the queue may not be empty.
3480   }
3481 };
3482 
3483 // Driver routine for parallel reference processing.
3484 // Creates an instance of the ref processing gang
3485 // task and has the worker threads execute it.
3486 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task, uint ergo_workers) {
3487   assert(_workers != NULL, "Need parallel worker threads.");
3488 
3489   assert(_workers->active_workers() >= ergo_workers,
3490          "Ergonomically chosen workers (%u) should be less than or equal to active workers (%u)",
3491          ergo_workers, _workers->active_workers());
3492   TaskTerminator terminator(ergo_workers, _queues);
3493   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, terminator.terminator());
3494 
3495   _workers->run_task(&proc_task_proxy, ergo_workers);
3496 }
3497 
3498 // End of weak reference support closures
3499 
3500 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
3501   double ref_proc_start = os::elapsedTime();
3502 
3503   ReferenceProcessor* rp = _ref_processor_stw;
3504   assert(rp->discovery_enabled(), "should have been enabled");
3505 
3506   // Closure to test whether a referent is alive.
3507   G1STWIsAliveClosure is_alive(this);
3508 
3509   // Even when parallel reference processing is enabled, the processing
3510   // of JNI refs is serial and performed serially by the current thread
3511   // rather than by a worker. The following PSS will be used for processing
3512   // JNI refs.
3513 
3514   // Use only a single queue for this PSS.
3515   G1ParScanThreadState*          pss = per_thread_states->state_for_worker(0);
3516   pss->set_ref_discoverer(NULL);
3517   assert(pss->queue_is_empty(), "pre-condition");
3518 
3519   // Keep alive closure.
3520   G1CopyingKeepAliveClosure keep_alive(this, pss);
3521 
3522   // Serial Complete GC closure
3523   G1STWDrainQueueClosure drain_queue(this, pss);
3524 
3525   // Setup the soft refs policy...
3526   rp->setup_policy(false);
3527 
3528   ReferenceProcessorPhaseTimes* pt = phase_times()->ref_phase_times();
3529 
3530   ReferenceProcessorStats stats;
3531   if (!rp->processing_is_mt()) {
3532     // Serial reference processing...
3533     stats = rp->process_discovered_references(&is_alive,
3534                                               &keep_alive,
3535                                               &drain_queue,
3536                                               NULL,
3537                                               pt);
3538   } else {
3539     uint no_of_gc_workers = workers()->active_workers();
3540 
3541     // Parallel reference processing
3542     assert(no_of_gc_workers <= rp->max_num_queues(),
3543            "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
3544            no_of_gc_workers,  rp->max_num_queues());
3545 
3546     G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues);
3547     stats = rp->process_discovered_references(&is_alive,
3548                                               &keep_alive,
3549                                               &drain_queue,
3550                                               &par_task_executor,
3551                                               pt);
3552   }
3553 
3554   _gc_tracer_stw->report_gc_reference_stats(stats);
3555 
3556   // We have completed copying any necessary live referent objects.
3557   assert(pss->queue_is_empty(), "both queue and overflow should be empty");
3558 
3559   make_pending_list_reachable();
3560 
3561   assert(!rp->discovery_enabled(), "Postcondition");
3562   rp->verify_no_references_recorded();
3563 
3564   double ref_proc_time = os::elapsedTime() - ref_proc_start;
3565   phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
3566 }
3567 
3568 void G1CollectedHeap::make_pending_list_reachable() {
3569   if (collector_state()->in_initial_mark_gc()) {
3570     oop pll_head = Universe::reference_pending_list();
3571     if (pll_head != NULL) {
3572       // Any valid worker id is fine here as we are in the VM thread and single-threaded.
3573       _cm->mark_in_next_bitmap(0 /* worker_id */, pll_head);
3574     }
3575   }
3576 }
3577 
3578 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) {
3579   double merge_pss_time_start = os::elapsedTime();
3580   per_thread_states->flush();
3581   phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0);
3582 }
3583 
3584 void G1CollectedHeap::pre_evacuate_collection_set(G1EvacuationInfo& evacuation_info) {
3585   _expand_heap_after_alloc_failure = true;
3586   _evacuation_failed = false;
3587 
3588   // Disable the hot card cache.
3589   _hot_card_cache->reset_hot_cache_claimed_index();
3590   _hot_card_cache->set_use_cache(false);
3591 
3592   // Initialize the GC alloc regions.
3593   _allocator->init_gc_alloc_regions(evacuation_info);
3594 
3595   register_regions_with_region_attr();
3596   assert(_verifier->check_region_attr_table(), "Inconsistency in the region attributes table.");
3597 
3598   rem_set()->prepare_for_scan_rem_set();
3599   _preserved_marks_set.assert_empty();
3600 
3601 #if COMPILER2_OR_JVMCI
3602   DerivedPointerTable::clear();
3603 #endif
3604 
3605   // InitialMark needs claim bits to keep track of the marked-through CLDs.
3606   if (collector_state()->in_initial_mark_gc()) {
3607     concurrent_mark()->pre_initial_mark();
3608 
3609     double start_clear_claimed_marks = os::elapsedTime();
3610 
3611     ClassLoaderDataGraph::clear_claimed_marks();
3612 
3613     double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0;
3614     phase_times()->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms);
3615   }
3616 
3617   // Should G1EvacuationFailureALot be in effect for this GC?
3618   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
3619 
3620   assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
3621 }
3622 
3623 class G1EvacuateRegionsBaseTask : public AbstractGangTask {
3624 protected:
3625   G1CollectedHeap* _g1h;
3626   G1ParScanThreadStateSet* _per_thread_states;
3627   RefToScanQueueSet* _task_queues;
3628   TaskTerminator _terminator;
3629   uint _num_workers;
3630 
3631   void evacuate_live_objects(G1ParScanThreadState* pss,
3632                              uint worker_id,
3633                              G1GCPhaseTimes::GCParPhases objcopy_phase,
3634                              G1GCPhaseTimes::GCParPhases termination_phase) {
3635     G1GCPhaseTimes* p = _g1h->phase_times();
3636 
3637     Ticks start = Ticks::now();
3638     G1ParEvacuateFollowersClosure cl(_g1h, pss, _task_queues, _terminator.terminator(), objcopy_phase);
3639     cl.do_void();
3640 
3641     assert(pss->queue_is_empty(), "should be empty");
3642 
3643     Tickspan evac_time = (Ticks::now() - start);
3644     p->record_or_add_time_secs(objcopy_phase, worker_id, evac_time.seconds() - cl.term_time());
3645 
3646     p->record_or_add_thread_work_item(objcopy_phase, worker_id, pss->lab_waste_words() * HeapWordSize, G1GCPhaseTimes::ObjCopyLABWaste);
3647     p->record_or_add_thread_work_item(objcopy_phase, worker_id, pss->lab_undo_waste_words() * HeapWordSize, G1GCPhaseTimes::ObjCopyLABUndoWaste);
3648 
3649     if (termination_phase == G1GCPhaseTimes::Termination) {
3650       p->record_time_secs(termination_phase, worker_id, cl.term_time());
3651       p->record_thread_work_item(termination_phase, worker_id, cl.term_attempts());
3652     } else {
3653       p->record_or_add_time_secs(termination_phase, worker_id, cl.term_time());
3654       p->record_or_add_thread_work_item(termination_phase, worker_id, cl.term_attempts());
3655     }
3656     assert(pss->trim_ticks().seconds() == 0.0, "Unexpected partial trimming during evacuation");
3657   }
3658 
3659   virtual void start_work(uint worker_id) { }
3660 
3661   virtual void end_work(uint worker_id) { }
3662 
3663   virtual void scan_roots(G1ParScanThreadState* pss, uint worker_id) = 0;
3664 
3665   virtual void evacuate_live_objects(G1ParScanThreadState* pss, uint worker_id) = 0;
3666 
3667 public:
3668   G1EvacuateRegionsBaseTask(const char* name, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet* task_queues, uint num_workers) :
3669     AbstractGangTask(name),
3670     _g1h(G1CollectedHeap::heap()),
3671     _per_thread_states(per_thread_states),
3672     _task_queues(task_queues),
3673     _terminator(num_workers, _task_queues),
3674     _num_workers(num_workers)
3675   { }
3676 
3677   void work(uint worker_id) {
3678     start_work(worker_id);
3679 
3680     {
3681       ResourceMark rm;
3682       HandleMark   hm;
3683 
3684       G1ParScanThreadState* pss = _per_thread_states->state_for_worker(worker_id);
3685       pss->set_ref_discoverer(_g1h->ref_processor_stw());
3686 
3687       scan_roots(pss, worker_id);
3688       evacuate_live_objects(pss, worker_id);
3689     }
3690 
3691     end_work(worker_id);
3692   }
3693 };
3694 
3695 class G1EvacuateRegionsTask : public G1EvacuateRegionsBaseTask {
3696   G1RootProcessor* _root_processor;
3697 
3698   void scan_roots(G1ParScanThreadState* pss, uint worker_id) {
3699     _root_processor->evacuate_roots(pss, worker_id);
3700     _g1h->rem_set()->update_rem_set(pss, worker_id);
3701     _g1h->rem_set()->scan_rem_set(pss, worker_id, G1GCPhaseTimes::ScanRS, G1GCPhaseTimes::ObjCopy, G1GCPhaseTimes::CodeRoots);
3702   }
3703 
3704   void evacuate_live_objects(G1ParScanThreadState* pss, uint worker_id) {
3705     G1EvacuateRegionsBaseTask::evacuate_live_objects(pss, worker_id, G1GCPhaseTimes::ObjCopy, G1GCPhaseTimes::Termination);
3706   }
3707 
3708   void start_work(uint worker_id) {
3709     _g1h->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, Ticks::now().seconds());
3710   }
3711 
3712   void end_work(uint worker_id) {
3713     _g1h->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, Ticks::now().seconds());
3714   }
3715 
3716 public:
3717   G1EvacuateRegionsTask(G1CollectedHeap* g1h,
3718                         G1ParScanThreadStateSet* per_thread_states,
3719                         RefToScanQueueSet* task_queues,
3720                         G1RootProcessor* root_processor,
3721                         uint num_workers) :
3722     G1EvacuateRegionsBaseTask("G1 Evacuate Regions", per_thread_states, task_queues, num_workers),
3723     _root_processor(root_processor)
3724   { }
3725 };
3726 
3727 void G1CollectedHeap::evacuate_initial_collection_set(G1ParScanThreadStateSet* per_thread_states) {
3728   Tickspan task_time;
3729   const uint num_workers = workers()->active_workers();
3730 
3731   Ticks start_processing = Ticks::now();
3732   {
3733     G1RootProcessor root_processor(this, num_workers);
3734     G1EvacuateRegionsTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, num_workers);
3735     task_time = run_task(&g1_par_task);
3736     // Closing the inner scope will execute the destructor for the G1RootProcessor object.
3737     // To extract its code root fixup time we measure total time of this scope and
3738     // subtract from the time the WorkGang task took.
3739   }
3740   Tickspan total_processing = Ticks::now() - start_processing;
3741 
3742   G1GCPhaseTimes* p = phase_times();
3743   p->record_initial_evac_time(task_time.seconds() * 1000.0);
3744   p->record_or_add_code_root_fixup_time((total_processing - task_time).seconds() * 1000.0);
3745 }
3746 
3747 class G1EvacuateOptionalRegionsTask : public G1EvacuateRegionsBaseTask {
3748 
3749   void scan_roots(G1ParScanThreadState* pss, uint worker_id) {
3750     _g1h->rem_set()->scan_rem_set(pss, worker_id, G1GCPhaseTimes::OptScanRS, G1GCPhaseTimes::OptObjCopy, G1GCPhaseTimes::OptCodeRoots);
3751   }
3752 
3753   void evacuate_live_objects(G1ParScanThreadState* pss, uint worker_id) {
3754     G1EvacuateRegionsBaseTask::evacuate_live_objects(pss, worker_id, G1GCPhaseTimes::OptObjCopy, G1GCPhaseTimes::OptTermination);
3755   }
3756 
3757 public:
3758   G1EvacuateOptionalRegionsTask(G1ParScanThreadStateSet* per_thread_states,
3759                                 RefToScanQueueSet* queues,
3760                                 uint num_workers) :
3761     G1EvacuateRegionsBaseTask("G1 Evacuate Optional Regions", per_thread_states, queues, num_workers) {
3762   }
3763 };
3764 
3765 void G1CollectedHeap::evacuate_next_optional_regions(G1ParScanThreadStateSet* per_thread_states) {
3766   class G1MarkScope : public MarkScope { };
3767 
3768   Tickspan task_time;
3769 
3770   Ticks start_processing = Ticks::now();
3771   {
3772     G1MarkScope code_mark_scope;
3773     G1EvacuateOptionalRegionsTask task(per_thread_states, _task_queues, workers()->active_workers());
3774     task_time = run_task(&task);
3775     // See comment in evacuate_collection_set() for the reason of the scope.
3776   }
3777   Tickspan total_processing = Ticks::now() - start_processing;
3778 
3779   G1GCPhaseTimes* p = phase_times();
3780   p->record_or_add_code_root_fixup_time((total_processing - task_time).seconds() * 1000.0);
3781 }
3782 
3783 void G1CollectedHeap::evacuate_optional_collection_set(G1ParScanThreadStateSet* per_thread_states) {
3784   const double gc_start_time_ms = phase_times()->cur_collection_start_sec() * 1000.0;
3785 
3786   Ticks start = Ticks::now();
3787 
3788   while (!evacuation_failed() && _collection_set.optional_region_length() > 0) {
3789 
3790     double time_used_ms = os::elapsedTime() * 1000.0 - gc_start_time_ms;
3791     double time_left_ms = MaxGCPauseMillis - time_used_ms;
3792 
3793     if (time_left_ms < 0 ||
3794         !_collection_set.finalize_optional_for_evacuation(time_left_ms * policy()->optional_evacuation_fraction())) {
3795       log_trace(gc, ergo, cset)("Skipping evacuation of %u optional regions, no more regions can be evacuated in %.3fms",
3796                                 _collection_set.optional_region_length(), time_left_ms);
3797       break;
3798     }
3799 
3800     evacuate_next_optional_regions(per_thread_states);
3801   }
3802 
3803   _collection_set.abandon_optional_collection_set(per_thread_states);
3804 
3805   phase_times()->record_or_add_optional_evac_time((Ticks::now() - start).seconds() * 1000.0);
3806 }
3807 
3808 void G1CollectedHeap::post_evacuate_collection_set(G1EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
3809   // Also cleans the card table from temporary duplicate detection information used
3810   // during UpdateRS/ScanRS.
3811   rem_set()->cleanup_after_scan_rem_set();
3812 
3813   // Process any discovered reference objects - we have
3814   // to do this _before_ we retire the GC alloc regions
3815   // as we may have to copy some 'reachable' referent
3816   // objects (and their reachable sub-graphs) that were
3817   // not copied during the pause.
3818   process_discovered_references(per_thread_states);
3819 
3820   G1STWIsAliveClosure is_alive(this);
3821   G1KeepAliveClosure keep_alive(this);
3822 
3823   WeakProcessor::weak_oops_do(workers(), &is_alive, &keep_alive,
3824                               phase_times()->weak_phase_times());
3825 
3826   if (G1StringDedup::is_enabled()) {
3827     double string_dedup_time_ms = os::elapsedTime();
3828 
3829     string_dedup_cleaning(&is_alive, &keep_alive, phase_times());
3830 
3831     double string_cleanup_time_ms = (os::elapsedTime() - string_dedup_time_ms) * 1000.0;
3832     phase_times()->record_string_deduplication_time(string_cleanup_time_ms);
3833   }
3834 
3835   _allocator->release_gc_alloc_regions(evacuation_info);
3836 
3837   if (evacuation_failed()) {
3838     restore_after_evac_failure();
3839 
3840     // Reset the G1EvacuationFailureALot counters and flags
3841     NOT_PRODUCT(reset_evacuation_should_fail();)
3842 
3843     double recalculate_used_start = os::elapsedTime();
3844     set_used(recalculate_used());
3845     phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
3846 
3847     if (_archive_allocator != NULL) {
3848       _archive_allocator->clear_used();
3849     }
3850     for (uint i = 0; i < ParallelGCThreads; i++) {
3851       if (_evacuation_failed_info_array[i].has_failed()) {
3852         _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
3853       }
3854     }
3855   } else {
3856     // The "used" of the the collection set have already been subtracted
3857     // when they were freed.  Add in the bytes evacuated.
3858     increase_used(policy()->bytes_copied_during_gc());
3859   }
3860 
3861   _preserved_marks_set.assert_empty();
3862 
3863   merge_per_thread_state_info(per_thread_states);
3864 
3865   // Reset and re-enable the hot card cache.
3866   // Note the counts for the cards in the regions in the
3867   // collection set are reset when the collection set is freed.
3868   _hot_card_cache->reset_hot_cache();
3869   _hot_card_cache->set_use_cache(true);
3870 
3871   purge_code_root_memory();
3872 
3873   redirty_logged_cards();
3874 
3875   free_collection_set(&_collection_set, evacuation_info, per_thread_states->surviving_young_words());
3876 
3877   eagerly_reclaim_humongous_regions();
3878 
3879   record_obj_copy_mem_stats();
3880 
3881   evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before());
3882   evacuation_info.set_bytes_copied(policy()->bytes_copied_during_gc());
3883 
3884 #if COMPILER2_OR_JVMCI
3885   double start = os::elapsedTime();
3886   DerivedPointerTable::update_pointers();
3887   phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0);
3888 #endif
3889   policy()->print_age_table();
3890 }
3891 
3892 void G1CollectedHeap::record_obj_copy_mem_stats() {
3893   policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
3894 
3895   _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
3896                                                create_g1_evac_summary(&_old_evac_stats));
3897 }
3898 
3899 void G1CollectedHeap::free_region(HeapRegion* hr,
3900                                   FreeRegionList* free_list,
3901                                   bool skip_remset,
3902                                   bool skip_hot_card_cache,
3903                                   bool locked) {
3904   assert(!hr->is_free(), "the region should not be free");
3905   assert(!hr->is_empty(), "the region should not be empty");
3906   assert(_hrm->is_available(hr->hrm_index()), "region should be committed");
3907   assert(free_list != NULL, "pre-condition");
3908 
3909   if (G1VerifyBitmaps) {
3910     MemRegion mr(hr->bottom(), hr->end());
3911     concurrent_mark()->clear_range_in_prev_bitmap(mr);
3912   }
3913 
3914   // Clear the card counts for this region.
3915   // Note: we only need to do this if the region is not young
3916   // (since we don't refine cards in young regions).
3917   if (!skip_hot_card_cache && !hr->is_young()) {
3918     _hot_card_cache->reset_card_counts(hr);
3919   }
3920   hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */);
3921   _policy->remset_tracker()->update_at_free(hr);
3922   free_list->add_ordered(hr);
3923 }
3924 
3925 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
3926                                             FreeRegionList* free_list) {
3927   assert(hr->is_humongous(), "this is only for humongous regions");
3928   assert(free_list != NULL, "pre-condition");
3929   hr->clear_humongous();
3930   free_region(hr, free_list, false /* skip_remset */, false /* skip_hcc */, true /* locked */);
3931 }
3932 
3933 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed,
3934                                            const uint humongous_regions_removed) {
3935   if (old_regions_removed > 0 || humongous_regions_removed > 0) {
3936     MutexLocker x(OldSets_lock, Mutex::_no_safepoint_check_flag);
3937     _old_set.bulk_remove(old_regions_removed);
3938     _humongous_set.bulk_remove(humongous_regions_removed);
3939   }
3940 
3941 }
3942 
3943 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
3944   assert(list != NULL, "list can't be null");
3945   if (!list->is_empty()) {
3946     MutexLocker x(FreeList_lock, Mutex::_no_safepoint_check_flag);
3947     _hrm->insert_list_into_free_list(list);
3948   }
3949 }
3950 
3951 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
3952   decrease_used(bytes);
3953 }
3954 
3955 class G1FreeCollectionSetTask : public AbstractGangTask {
3956 private:
3957 
3958   // Closure applied to all regions in the collection set to do work that needs to
3959   // be done serially in a single thread.
3960   class G1SerialFreeCollectionSetClosure : public HeapRegionClosure {
3961   private:
3962     G1EvacuationInfo* _evacuation_info;
3963     const size_t* _surviving_young_words;
3964 
3965     // Bytes used in successfully evacuated regions before the evacuation.
3966     size_t _before_used_bytes;
3967     // Bytes used in unsucessfully evacuated regions before the evacuation
3968     size_t _after_used_bytes;
3969 
3970     size_t _bytes_allocated_in_old_since_last_gc;
3971 
3972     size_t _failure_used_words;
3973     size_t _failure_waste_words;
3974 
3975     FreeRegionList _local_free_list;
3976   public:
3977     G1SerialFreeCollectionSetClosure(G1EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
3978       HeapRegionClosure(),
3979       _evacuation_info(evacuation_info),
3980       _surviving_young_words(surviving_young_words),
3981       _before_used_bytes(0),
3982       _after_used_bytes(0),
3983       _bytes_allocated_in_old_since_last_gc(0),
3984       _failure_used_words(0),
3985       _failure_waste_words(0),
3986       _local_free_list("Local Region List for CSet Freeing") {
3987     }
3988 
3989     virtual bool do_heap_region(HeapRegion* r) {
3990       G1CollectedHeap* g1h = G1CollectedHeap::heap();
3991 
3992       assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index());
3993       g1h->clear_region_attr(r);
3994 
3995       if (r->is_young()) {
3996         assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(),
3997                "Young index %d is wrong for region %u of type %s with %u young regions",
3998                r->young_index_in_cset(),
3999                r->hrm_index(),
4000                r->get_type_str(),
4001                g1h->collection_set()->young_region_length());
4002         size_t words_survived = _surviving_young_words[r->young_index_in_cset()];
4003         r->record_surv_words_in_group(words_survived);
4004       }
4005 
4006       if (!r->evacuation_failed()) {
4007         assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index());
4008         _before_used_bytes += r->used();
4009         g1h->free_region(r,
4010                          &_local_free_list,
4011                          true, /* skip_remset */
4012                          true, /* skip_hot_card_cache */
4013                          true  /* locked */);
4014       } else {
4015         r->uninstall_surv_rate_group();
4016         r->set_young_index_in_cset(-1);
4017         r->set_evacuation_failed(false);
4018         // When moving a young gen region to old gen, we "allocate" that whole region
4019         // there. This is in addition to any already evacuated objects. Notify the
4020         // policy about that.
4021         // Old gen regions do not cause an additional allocation: both the objects
4022         // still in the region and the ones already moved are accounted for elsewhere.
4023         if (r->is_young()) {
4024           _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes;
4025         }
4026         // The region is now considered to be old.
4027         r->set_old();
4028         // Do some allocation statistics accounting. Regions that failed evacuation
4029         // are always made old, so there is no need to update anything in the young
4030         // gen statistics, but we need to update old gen statistics.
4031         size_t used_words = r->marked_bytes() / HeapWordSize;
4032 
4033         _failure_used_words += used_words;
4034         _failure_waste_words += HeapRegion::GrainWords - used_words;
4035 
4036         g1h->old_set_add(r);
4037         _after_used_bytes += r->used();
4038       }
4039       return false;
4040     }
4041 
4042     void complete_work() {
4043       G1CollectedHeap* g1h = G1CollectedHeap::heap();
4044 
4045       _evacuation_info->set_regions_freed(_local_free_list.length());
4046       _evacuation_info->increment_collectionset_used_after(_after_used_bytes);
4047 
4048       g1h->prepend_to_freelist(&_local_free_list);
4049       g1h->decrement_summary_bytes(_before_used_bytes);
4050 
4051       G1Policy* policy = g1h->policy();
4052       policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc);
4053 
4054       g1h->alloc_buffer_stats(G1HeapRegionAttr::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words);
4055     }
4056   };
4057 
4058   G1CollectionSet* _collection_set;
4059   G1SerialFreeCollectionSetClosure _cl;
4060   const size_t* _surviving_young_words;
4061 
4062   size_t _rs_lengths;
4063 
4064   volatile jint _serial_work_claim;
4065 
4066   struct WorkItem {
4067     uint region_idx;
4068     bool is_young;
4069     bool evacuation_failed;
4070 
4071     WorkItem(HeapRegion* r) {
4072       region_idx = r->hrm_index();
4073       is_young = r->is_young();
4074       evacuation_failed = r->evacuation_failed();
4075     }
4076   };
4077 
4078   volatile size_t _parallel_work_claim;
4079   size_t _num_work_items;
4080   WorkItem* _work_items;
4081 
4082   void do_serial_work() {
4083     // Need to grab the lock to be allowed to modify the old region list.
4084     MutexLocker x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4085     _collection_set->iterate(&_cl);
4086   }
4087 
4088   void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) {
4089     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4090 
4091     HeapRegion* r = g1h->region_at(region_idx);
4092     assert(!g1h->is_on_master_free_list(r), "sanity");
4093 
4094     Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths);
4095 
4096     if (!is_young) {
4097       g1h->_hot_card_cache->reset_card_counts(r);
4098     }
4099 
4100     if (!evacuation_failed) {
4101       r->rem_set()->clear_locked();
4102     }
4103   }
4104 
4105   class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure {
4106   private:
4107     size_t _cur_idx;
4108     WorkItem* _work_items;
4109   public:
4110     G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { }
4111 
4112     virtual bool do_heap_region(HeapRegion* r) {
4113       _work_items[_cur_idx++] = WorkItem(r);
4114       return false;
4115     }
4116   };
4117 
4118   void prepare_work() {
4119     G1PrepareFreeCollectionSetClosure cl(_work_items);
4120     _collection_set->iterate(&cl);
4121   }
4122 
4123   void complete_work() {
4124     _cl.complete_work();
4125 
4126     G1Policy* policy = G1CollectedHeap::heap()->policy();
4127     policy->record_max_rs_lengths(_rs_lengths);
4128     policy->cset_regions_freed();
4129   }
4130 public:
4131   G1FreeCollectionSetTask(G1CollectionSet* collection_set, G1EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4132     AbstractGangTask("G1 Free Collection Set"),
4133     _collection_set(collection_set),
4134     _cl(evacuation_info, surviving_young_words),
4135     _surviving_young_words(surviving_young_words),
4136     _rs_lengths(0),
4137     _serial_work_claim(0),
4138     _parallel_work_claim(0),
4139     _num_work_items(collection_set->region_length()),
4140     _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) {
4141     prepare_work();
4142   }
4143 
4144   ~G1FreeCollectionSetTask() {
4145     complete_work();
4146     FREE_C_HEAP_ARRAY(WorkItem, _work_items);
4147   }
4148 
4149   // Chunk size for work distribution. The chosen value has been determined experimentally
4150   // to be a good tradeoff between overhead and achievable parallelism.
4151   static uint chunk_size() { return 32; }
4152 
4153   virtual void work(uint worker_id) {
4154     G1GCPhaseTimes* timer = G1CollectedHeap::heap()->phase_times();
4155 
4156     // Claim serial work.
4157     if (_serial_work_claim == 0) {
4158       jint value = Atomic::add(1, &_serial_work_claim) - 1;
4159       if (value == 0) {
4160         double serial_time = os::elapsedTime();
4161         do_serial_work();
4162         timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0);
4163       }
4164     }
4165 
4166     // Start parallel work.
4167     double young_time = 0.0;
4168     bool has_young_time = false;
4169     double non_young_time = 0.0;
4170     bool has_non_young_time = false;
4171 
4172     while (true) {
4173       size_t end = Atomic::add(chunk_size(), &_parallel_work_claim);
4174       size_t cur = end - chunk_size();
4175 
4176       if (cur >= _num_work_items) {
4177         break;
4178       }
4179 
4180       EventGCPhaseParallel event;
4181       double start_time = os::elapsedTime();
4182 
4183       end = MIN2(end, _num_work_items);
4184 
4185       for (; cur < end; cur++) {
4186         bool is_young = _work_items[cur].is_young;
4187 
4188         do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed);
4189 
4190         double end_time = os::elapsedTime();
4191         double time_taken = end_time - start_time;
4192         if (is_young) {
4193           young_time += time_taken;
4194           has_young_time = true;
4195           event.commit(GCId::current(), worker_id, G1GCPhaseTimes::phase_name(G1GCPhaseTimes::YoungFreeCSet));
4196         } else {
4197           non_young_time += time_taken;
4198           has_non_young_time = true;
4199           event.commit(GCId::current(), worker_id, G1GCPhaseTimes::phase_name(G1GCPhaseTimes::NonYoungFreeCSet));
4200         }
4201         start_time = end_time;
4202       }
4203     }
4204 
4205     if (has_young_time) {
4206       timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time);
4207     }
4208     if (has_non_young_time) {
4209       timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, non_young_time);
4210     }
4211   }
4212 };
4213 
4214 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, G1EvacuationInfo& evacuation_info, const size_t* surviving_young_words) {
4215   _eden.clear();
4216 
4217   double free_cset_start_time = os::elapsedTime();
4218 
4219   {
4220     uint const num_regions = _collection_set.region_length();
4221     uint const num_chunks = MAX2(num_regions / G1FreeCollectionSetTask::chunk_size(), 1U);
4222     uint const num_workers = MIN2(workers()->active_workers(), num_chunks);
4223 
4224     G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words);
4225 
4226     log_debug(gc, ergo)("Running %s using %u workers for collection set length %u",
4227                         cl.name(), num_workers, num_regions);
4228     workers()->run_task(&cl, num_workers);
4229   }
4230   phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0);
4231 
4232   collection_set->clear();
4233 }
4234 
4235 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
4236  private:
4237   FreeRegionList* _free_region_list;
4238   HeapRegionSet* _proxy_set;
4239   uint _humongous_objects_reclaimed;
4240   uint _humongous_regions_reclaimed;
4241   size_t _freed_bytes;
4242  public:
4243 
4244   G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
4245     _free_region_list(free_region_list), _proxy_set(NULL), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) {
4246   }
4247 
4248   virtual bool do_heap_region(HeapRegion* r) {
4249     if (!r->is_starts_humongous()) {
4250       return false;
4251     }
4252 
4253     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4254 
4255     oop obj = (oop)r->bottom();
4256     G1CMBitMap* next_bitmap = g1h->concurrent_mark()->next_mark_bitmap();
4257 
4258     // The following checks whether the humongous object is live are sufficient.
4259     // The main additional check (in addition to having a reference from the roots
4260     // or the young gen) is whether the humongous object has a remembered set entry.
4261     //
4262     // A humongous object cannot be live if there is no remembered set for it
4263     // because:
4264     // - there can be no references from within humongous starts regions referencing
4265     // the object because we never allocate other objects into them.
4266     // (I.e. there are no intra-region references that may be missed by the
4267     // remembered set)
4268     // - as soon there is a remembered set entry to the humongous starts region
4269     // (i.e. it has "escaped" to an old object) this remembered set entry will stay
4270     // until the end of a concurrent mark.
4271     //
4272     // It is not required to check whether the object has been found dead by marking
4273     // or not, in fact it would prevent reclamation within a concurrent cycle, as
4274     // all objects allocated during that time are considered live.
4275     // SATB marking is even more conservative than the remembered set.
4276     // So if at this point in the collection there is no remembered set entry,
4277     // nobody has a reference to it.
4278     // At the start of collection we flush all refinement logs, and remembered sets
4279     // are completely up-to-date wrt to references to the humongous object.
4280     //
4281     // Other implementation considerations:
4282     // - never consider object arrays at this time because they would pose
4283     // considerable effort for cleaning up the the remembered sets. This is
4284     // required because stale remembered sets might reference locations that
4285     // are currently allocated into.
4286     uint region_idx = r->hrm_index();
4287     if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
4288         !r->rem_set()->is_empty()) {
4289       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",
4290                                region_idx,
4291                                (size_t)obj->size() * HeapWordSize,
4292                                p2i(r->bottom()),
4293                                r->rem_set()->occupied(),
4294                                r->rem_set()->strong_code_roots_list_length(),
4295                                next_bitmap->is_marked(r->bottom()),
4296                                g1h->is_humongous_reclaim_candidate(region_idx),
4297                                obj->is_typeArray()
4298                               );
4299       return false;
4300     }
4301 
4302     guarantee(obj->is_typeArray(),
4303               "Only eagerly reclaiming type arrays is supported, but the object "
4304               PTR_FORMAT " is not.", p2i(r->bottom()));
4305 
4306     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",
4307                              region_idx,
4308                              (size_t)obj->size() * HeapWordSize,
4309                              p2i(r->bottom()),
4310                              r->rem_set()->occupied(),
4311                              r->rem_set()->strong_code_roots_list_length(),
4312                              next_bitmap->is_marked(r->bottom()),
4313                              g1h->is_humongous_reclaim_candidate(region_idx),
4314                              obj->is_typeArray()
4315                             );
4316 
4317     G1ConcurrentMark* const cm = g1h->concurrent_mark();
4318     cm->humongous_object_eagerly_reclaimed(r);
4319     assert(!cm->is_marked_in_prev_bitmap(obj) && !cm->is_marked_in_next_bitmap(obj),
4320            "Eagerly reclaimed humongous region %u should not be marked at all but is in prev %s next %s",
4321            region_idx,
4322            BOOL_TO_STR(cm->is_marked_in_prev_bitmap(obj)),
4323            BOOL_TO_STR(cm->is_marked_in_next_bitmap(obj)));
4324     _humongous_objects_reclaimed++;
4325     do {
4326       HeapRegion* next = g1h->next_region_in_humongous(r);
4327       _freed_bytes += r->used();
4328       r->set_containing_set(NULL);
4329       _humongous_regions_reclaimed++;
4330       g1h->free_humongous_region(r, _free_region_list);
4331       r = next;
4332     } while (r != NULL);
4333 
4334     return false;
4335   }
4336 
4337   uint humongous_objects_reclaimed() {
4338     return _humongous_objects_reclaimed;
4339   }
4340 
4341   uint humongous_regions_reclaimed() {
4342     return _humongous_regions_reclaimed;
4343   }
4344 
4345   size_t bytes_freed() const {
4346     return _freed_bytes;
4347   }
4348 };
4349 
4350 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
4351   assert_at_safepoint_on_vm_thread();
4352 
4353   if (!G1EagerReclaimHumongousObjects ||
4354       (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) {
4355     phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
4356     return;
4357   }
4358 
4359   double start_time = os::elapsedTime();
4360 
4361   FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
4362 
4363   G1FreeHumongousRegionClosure cl(&local_cleanup_list);
4364   heap_region_iterate(&cl);
4365 
4366   remove_from_old_sets(0, cl.humongous_regions_reclaimed());
4367 
4368   G1HRPrinter* hrp = hr_printer();
4369   if (hrp->is_active()) {
4370     FreeRegionListIterator iter(&local_cleanup_list);
4371     while (iter.more_available()) {
4372       HeapRegion* hr = iter.get_next();
4373       hrp->cleanup(hr);
4374     }
4375   }
4376 
4377   prepend_to_freelist(&local_cleanup_list);
4378   decrement_summary_bytes(cl.bytes_freed());
4379 
4380   phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
4381                                                        cl.humongous_objects_reclaimed());
4382 }
4383 
4384 class G1AbandonCollectionSetClosure : public HeapRegionClosure {
4385 public:
4386   virtual bool do_heap_region(HeapRegion* r) {
4387     assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index());
4388     G1CollectedHeap::heap()->clear_region_attr(r);
4389     r->set_young_index_in_cset(-1);
4390     return false;
4391   }
4392 };
4393 
4394 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) {
4395   G1AbandonCollectionSetClosure cl;
4396   collection_set_iterate_all(&cl);
4397 
4398   collection_set->clear();
4399   collection_set->stop_incremental_building();
4400 }
4401 
4402 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
4403   return _allocator->is_retained_old_region(hr);
4404 }
4405 
4406 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
4407   _eden.add(hr);
4408   _policy->set_region_eden(hr);
4409 }
4410 
4411 #ifdef ASSERT
4412 
4413 class NoYoungRegionsClosure: public HeapRegionClosure {
4414 private:
4415   bool _success;
4416 public:
4417   NoYoungRegionsClosure() : _success(true) { }
4418   bool do_heap_region(HeapRegion* r) {
4419     if (r->is_young()) {
4420       log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
4421                             p2i(r->bottom()), p2i(r->end()));
4422       _success = false;
4423     }
4424     return false;
4425   }
4426   bool success() { return _success; }
4427 };
4428 
4429 bool G1CollectedHeap::check_young_list_empty() {
4430   bool ret = (young_regions_count() == 0);
4431 
4432   NoYoungRegionsClosure closure;
4433   heap_region_iterate(&closure);
4434   ret = ret && closure.success();
4435 
4436   return ret;
4437 }
4438 
4439 #endif // ASSERT
4440 
4441 class TearDownRegionSetsClosure : public HeapRegionClosure {
4442   HeapRegionSet *_old_set;
4443 
4444 public:
4445   TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
4446 
4447   bool do_heap_region(HeapRegion* r) {
4448     if (r->is_old()) {
4449       _old_set->remove(r);
4450     } else if(r->is_young()) {
4451       r->uninstall_surv_rate_group();
4452     } else {
4453       // We ignore free regions, we'll empty the free list afterwards.
4454       // We ignore humongous and archive regions, we're not tearing down these
4455       // sets.
4456       assert(r->is_archive() || r->is_free() || r->is_humongous(),
4457              "it cannot be another type");
4458     }
4459     return false;
4460   }
4461 
4462   ~TearDownRegionSetsClosure() {
4463     assert(_old_set->is_empty(), "post-condition");
4464   }
4465 };
4466 
4467 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
4468   assert_at_safepoint_on_vm_thread();
4469 
4470   if (!free_list_only) {
4471     TearDownRegionSetsClosure cl(&_old_set);
4472     heap_region_iterate(&cl);
4473 
4474     // Note that emptying the _young_list is postponed and instead done as
4475     // the first step when rebuilding the regions sets again. The reason for
4476     // this is that during a full GC string deduplication needs to know if
4477     // a collected region was young or old when the full GC was initiated.
4478   }
4479   _hrm->remove_all_free_regions();
4480 }
4481 
4482 void G1CollectedHeap::increase_used(size_t bytes) {
4483   _summary_bytes_used += bytes;
4484 }
4485 
4486 void G1CollectedHeap::decrease_used(size_t bytes) {
4487   assert(_summary_bytes_used >= bytes,
4488          "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
4489          _summary_bytes_used, bytes);
4490   _summary_bytes_used -= bytes;
4491 }
4492 
4493 void G1CollectedHeap::set_used(size_t bytes) {
4494   _summary_bytes_used = bytes;
4495 }
4496 
4497 class RebuildRegionSetsClosure : public HeapRegionClosure {
4498 private:
4499   bool _free_list_only;
4500 
4501   HeapRegionSet* _old_set;
4502   HeapRegionManager* _hrm;
4503 
4504   size_t _total_used;
4505 
4506 public:
4507   RebuildRegionSetsClosure(bool free_list_only,
4508                            HeapRegionSet* old_set,
4509                            HeapRegionManager* hrm) :
4510     _free_list_only(free_list_only),
4511     _old_set(old_set), _hrm(hrm), _total_used(0) {
4512     assert(_hrm->num_free_regions() == 0, "pre-condition");
4513     if (!free_list_only) {
4514       assert(_old_set->is_empty(), "pre-condition");
4515     }
4516   }
4517 
4518   bool do_heap_region(HeapRegion* r) {
4519     if (r->is_empty()) {
4520       assert(r->rem_set()->is_empty(), "Empty regions should have empty remembered sets.");
4521       // Add free regions to the free list
4522       r->set_free();
4523       _hrm->insert_into_free_list(r);
4524     } else if (!_free_list_only) {
4525       assert(r->rem_set()->is_empty(), "At this point remembered sets must have been cleared.");
4526 
4527       if (r->is_archive() || r->is_humongous()) {
4528         // We ignore archive and humongous regions. We left these sets unchanged.
4529       } else {
4530         assert(r->is_young() || r->is_free() || r->is_old(), "invariant");
4531         // We now move all (non-humongous, non-old, non-archive) regions to old gen, and register them as such.
4532         r->move_to_old();
4533         _old_set->add(r);
4534       }
4535       _total_used += r->used();
4536     }
4537 
4538     return false;
4539   }
4540 
4541   size_t total_used() {
4542     return _total_used;
4543   }
4544 };
4545 
4546 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
4547   assert_at_safepoint_on_vm_thread();
4548 
4549   if (!free_list_only) {
4550     _eden.clear();
4551     _survivor.clear();
4552   }
4553 
4554   RebuildRegionSetsClosure cl(free_list_only, &_old_set, _hrm);
4555   heap_region_iterate(&cl);
4556 
4557   if (!free_list_only) {
4558     set_used(cl.total_used());
4559     if (_archive_allocator != NULL) {
4560       _archive_allocator->clear_used();
4561     }
4562   }
4563   assert_used_and_recalculate_used_equal(this);
4564 }
4565 
4566 // Methods for the mutator alloc region
4567 
4568 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
4569                                                       bool force) {
4570   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
4571   bool should_allocate = policy()->should_allocate_mutator_region();
4572   if (force || should_allocate) {
4573     HeapRegion* new_alloc_region = new_region(word_size,
4574                                               HeapRegionType::Eden,
4575                                               false /* do_expand */);
4576     if (new_alloc_region != NULL) {
4577       set_region_short_lived_locked(new_alloc_region);
4578       _hr_printer.alloc(new_alloc_region, !should_allocate);
4579       _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region);
4580       _policy->remset_tracker()->update_at_allocate(new_alloc_region);
4581       return new_alloc_region;
4582     }
4583   }
4584   return NULL;
4585 }
4586 
4587 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
4588                                                   size_t allocated_bytes) {
4589   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
4590   assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
4591 
4592   collection_set()->add_eden_region(alloc_region);
4593   increase_used(allocated_bytes);
4594   _eden.add_used_bytes(allocated_bytes);
4595   _hr_printer.retire(alloc_region);
4596 
4597   // We update the eden sizes here, when the region is retired,
4598   // instead of when it's allocated, since this is the point that its
4599   // used space has been recorded in _summary_bytes_used.
4600   g1mm()->update_eden_size();
4601 }
4602 
4603 // Methods for the GC alloc regions
4604 
4605 bool G1CollectedHeap::has_more_regions(G1HeapRegionAttr dest) {
4606   if (dest.is_old()) {
4607     return true;
4608   } else {
4609     return survivor_regions_count() < policy()->max_survivor_regions();
4610   }
4611 }
4612 
4613 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, G1HeapRegionAttr dest) {
4614   assert(FreeList_lock->owned_by_self(), "pre-condition");
4615 
4616   if (!has_more_regions(dest)) {
4617     return NULL;
4618   }
4619 
4620   HeapRegionType type;
4621   if (dest.is_young()) {
4622     type = HeapRegionType::Survivor;
4623   } else {
4624     type = HeapRegionType::Old;
4625   }
4626 
4627   HeapRegion* new_alloc_region = new_region(word_size,
4628                                             type,
4629                                             true /* do_expand */);
4630 
4631   if (new_alloc_region != NULL) {
4632     if (type.is_survivor()) {
4633       new_alloc_region->set_survivor();
4634       _survivor.add(new_alloc_region);
4635       _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region);
4636     } else {
4637       new_alloc_region->set_old();
4638       _verifier->check_bitmaps("Old Region Allocation", new_alloc_region);
4639     }
4640     _policy->remset_tracker()->update_at_allocate(new_alloc_region);
4641     register_region_with_region_attr(new_alloc_region);
4642     _hr_printer.alloc(new_alloc_region);
4643     return new_alloc_region;
4644   }
4645   return NULL;
4646 }
4647 
4648 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
4649                                              size_t allocated_bytes,
4650                                              G1HeapRegionAttr dest) {
4651   policy()->record_bytes_copied_during_gc(allocated_bytes);
4652   if (dest.is_old()) {
4653     old_set_add(alloc_region);
4654   } else {
4655     assert(dest.is_young(), "Retiring alloc region should be young (%d)", dest.type());
4656     _survivor.add_used_bytes(allocated_bytes);
4657   }
4658 
4659   bool const during_im = collector_state()->in_initial_mark_gc();
4660   if (during_im && allocated_bytes > 0) {
4661     _cm->root_regions()->add(alloc_region);
4662   }
4663   _hr_printer.retire(alloc_region);
4664 }
4665 
4666 HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
4667   bool expanded = false;
4668   uint index = _hrm->find_highest_free(&expanded);
4669 
4670   if (index != G1_NO_HRM_INDEX) {
4671     if (expanded) {
4672       log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
4673                                 HeapRegion::GrainWords * HeapWordSize);
4674     }
4675     _hrm->allocate_free_regions_starting_at(index, 1);
4676     return region_at(index);
4677   }
4678   return NULL;
4679 }
4680 
4681 // Optimized nmethod scanning
4682 
4683 class RegisterNMethodOopClosure: public OopClosure {
4684   G1CollectedHeap* _g1h;
4685   nmethod* _nm;
4686 
4687   template <class T> void do_oop_work(T* p) {
4688     T heap_oop = RawAccess<>::oop_load(p);
4689     if (!CompressedOops::is_null(heap_oop)) {
4690       oop obj = CompressedOops::decode_not_null(heap_oop);
4691       HeapRegion* hr = _g1h->heap_region_containing(obj);
4692       assert(!hr->is_continues_humongous(),
4693              "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
4694              " starting at " HR_FORMAT,
4695              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
4696 
4697       // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
4698       hr->add_strong_code_root_locked(_nm);
4699     }
4700   }
4701 
4702 public:
4703   RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
4704     _g1h(g1h), _nm(nm) {}
4705 
4706   void do_oop(oop* p)       { do_oop_work(p); }
4707   void do_oop(narrowOop* p) { do_oop_work(p); }
4708 };
4709 
4710 class UnregisterNMethodOopClosure: public OopClosure {
4711   G1CollectedHeap* _g1h;
4712   nmethod* _nm;
4713 
4714   template <class T> void do_oop_work(T* p) {
4715     T heap_oop = RawAccess<>::oop_load(p);
4716     if (!CompressedOops::is_null(heap_oop)) {
4717       oop obj = CompressedOops::decode_not_null(heap_oop);
4718       HeapRegion* hr = _g1h->heap_region_containing(obj);
4719       assert(!hr->is_continues_humongous(),
4720              "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
4721              " starting at " HR_FORMAT,
4722              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
4723 
4724       hr->remove_strong_code_root(_nm);
4725     }
4726   }
4727 
4728 public:
4729   UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
4730     _g1h(g1h), _nm(nm) {}
4731 
4732   void do_oop(oop* p)       { do_oop_work(p); }
4733   void do_oop(narrowOop* p) { do_oop_work(p); }
4734 };
4735 
4736 void G1CollectedHeap::register_nmethod(nmethod* nm) {
4737   guarantee(nm != NULL, "sanity");
4738   RegisterNMethodOopClosure reg_cl(this, nm);
4739   nm->oops_do(&reg_cl);
4740 }
4741 
4742 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
4743   guarantee(nm != NULL, "sanity");
4744   UnregisterNMethodOopClosure reg_cl(this, nm);
4745   nm->oops_do(&reg_cl, true);
4746 }
4747 
4748 void G1CollectedHeap::purge_code_root_memory() {
4749   double purge_start = os::elapsedTime();
4750   G1CodeRootSet::purge();
4751   double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
4752   phase_times()->record_strong_code_root_purge_time(purge_time_ms);
4753 }
4754 
4755 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
4756   G1CollectedHeap* _g1h;
4757 
4758 public:
4759   RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
4760     _g1h(g1h) {}
4761 
4762   void do_code_blob(CodeBlob* cb) {
4763     nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
4764     if (nm == NULL) {
4765       return;
4766     }
4767 
4768     _g1h->register_nmethod(nm);
4769   }
4770 };
4771 
4772 void G1CollectedHeap::rebuild_strong_code_roots() {
4773   RebuildStrongCodeRootClosure blob_cl(this);
4774   CodeCache::blobs_do(&blob_cl);
4775 }
4776 
4777 void G1CollectedHeap::initialize_serviceability() {
4778   _g1mm->initialize_serviceability();
4779 }
4780 
4781 MemoryUsage G1CollectedHeap::memory_usage() {
4782   return _g1mm->memory_usage();
4783 }
4784 
4785 GrowableArray<GCMemoryManager*> G1CollectedHeap::memory_managers() {
4786   return _g1mm->memory_managers();
4787 }
4788 
4789 GrowableArray<MemoryPool*> G1CollectedHeap::memory_pools() {
4790   return _g1mm->memory_pools();
4791 }