1 /*
   2  * Copyright (c) 2001, 2024, 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/systemDictionary.hpp"
  29 #include "code/codeCache.hpp"
  30 #include "compiler/oopMap.hpp"
  31 #include "gc/g1/g1Allocator.inline.hpp"
  32 #include "gc/g1/g1Arguments.hpp"
  33 #include "gc/g1/g1BarrierSet.hpp"
  34 #include "gc/g1/g1BatchedTask.hpp"
  35 #include "gc/g1/g1CollectedHeap.inline.hpp"
  36 #include "gc/g1/g1CollectionSet.hpp"
  37 #include "gc/g1/g1CollectionSetCandidates.hpp"
  38 #include "gc/g1/g1CollectorState.hpp"
  39 #include "gc/g1/g1ConcurrentRefine.hpp"
  40 #include "gc/g1/g1ConcurrentRefineThread.hpp"
  41 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp"
  42 #include "gc/g1/g1DirtyCardQueue.hpp"
  43 #include "gc/g1/g1EvacStats.inline.hpp"
  44 #include "gc/g1/g1FullCollector.hpp"
  45 #include "gc/g1/g1GCCounters.hpp"
  46 #include "gc/g1/g1GCParPhaseTimesTracker.hpp"
  47 #include "gc/g1/g1GCPhaseTimes.hpp"
  48 #include "gc/g1/g1GCPauseType.hpp"
  49 #include "gc/g1/g1HeapSizingPolicy.hpp"
  50 #include "gc/g1/g1HeapTransition.hpp"
  51 #include "gc/g1/g1HeapVerifier.hpp"
  52 #include "gc/g1/g1InitLogger.hpp"
  53 #include "gc/g1/g1MemoryPool.hpp"
  54 #include "gc/g1/g1MonotonicArenaFreeMemoryTask.hpp"
  55 #include "gc/g1/g1OopClosures.inline.hpp"
  56 #include "gc/g1/g1ParallelCleaning.hpp"
  57 #include "gc/g1/g1ParScanThreadState.inline.hpp"
  58 #include "gc/g1/g1PeriodicGCTask.hpp"
  59 #include "gc/g1/g1Policy.hpp"
  60 #include "gc/g1/g1RedirtyCardsQueue.hpp"
  61 #include "gc/g1/g1RegionPinCache.inline.hpp"
  62 #include "gc/g1/g1RegionToSpaceMapper.hpp"
  63 #include "gc/g1/g1RemSet.hpp"
  64 #include "gc/g1/g1RootClosures.hpp"
  65 #include "gc/g1/g1RootProcessor.hpp"
  66 #include "gc/g1/g1SATBMarkQueueSet.hpp"
  67 #include "gc/g1/g1ServiceThread.hpp"
  68 #include "gc/g1/g1ThreadLocalData.hpp"
  69 #include "gc/g1/g1Trace.hpp"
  70 #include "gc/g1/g1UncommitRegionTask.hpp"
  71 #include "gc/g1/g1VMOperations.hpp"
  72 #include "gc/g1/g1YoungCollector.hpp"
  73 #include "gc/g1/g1YoungGCAllocationFailureInjector.hpp"
  74 #include "gc/g1/heapRegion.inline.hpp"
  75 #include "gc/g1/heapRegionRemSet.inline.hpp"
  76 #include "gc/g1/heapRegionSet.inline.hpp"
  77 #include "gc/shared/classUnloadingContext.hpp"
  78 #include "gc/shared/concurrentGCBreakpoints.hpp"
  79 #include "gc/shared/gcBehaviours.hpp"
  80 #include "gc/shared/gcHeapSummary.hpp"
  81 #include "gc/shared/gcId.hpp"
  82 #include "gc/shared/gcTimer.hpp"
  83 #include "gc/shared/gcTraceTime.inline.hpp"
  84 #include "gc/shared/isGCActiveMark.hpp"
  85 #include "gc/shared/locationPrinter.inline.hpp"
  86 #include "gc/shared/oopStorageParState.hpp"
  87 #include "gc/shared/preservedMarks.inline.hpp"
  88 #include "gc/shared/referenceProcessor.inline.hpp"
  89 #include "gc/shared/slidingForwarding.hpp"
  90 #include "gc/shared/suspendibleThreadSet.hpp"
  91 #include "gc/shared/taskqueue.inline.hpp"
  92 #include "gc/shared/taskTerminator.hpp"
  93 #include "gc/shared/tlab_globals.hpp"
  94 #include "gc/shared/workerPolicy.hpp"
  95 #include "gc/shared/weakProcessor.inline.hpp"
  96 #include "logging/log.hpp"
  97 #include "memory/allocation.hpp"
  98 #include "memory/heapInspection.hpp"
  99 #include "memory/iterator.hpp"
 100 #include "memory/metaspaceUtils.hpp"
 101 #include "memory/resourceArea.hpp"
 102 #include "memory/universe.hpp"
 103 #include "oops/access.inline.hpp"
 104 #include "oops/compressedOops.inline.hpp"
 105 #include "oops/oop.inline.hpp"
 106 #include "runtime/atomic.hpp"
 107 #include "runtime/cpuTimeCounters.hpp"
 108 #include "runtime/handles.inline.hpp"
 109 #include "runtime/init.hpp"
 110 #include "runtime/java.hpp"
 111 #include "runtime/orderAccess.hpp"
 112 #include "runtime/threadSMR.hpp"
 113 #include "runtime/vmThread.hpp"
 114 #include "utilities/align.hpp"
 115 #include "utilities/autoRestore.hpp"
 116 #include "utilities/bitMap.inline.hpp"
 117 #include "utilities/globalDefinitions.hpp"
 118 #include "utilities/stack.inline.hpp"
 119 
 120 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
 121 
 122 // INVARIANTS/NOTES
 123 //
 124 // All allocation activity covered by the G1CollectedHeap interface is
 125 // serialized by acquiring the HeapLock.  This happens in mem_allocate
 126 // and allocate_new_tlab, which are the "entry" points to the
 127 // allocation code from the rest of the JVM.  (Note that this does not
 128 // apply to TLAB allocation, which is not part of this interface: it
 129 // is done by clients of this interface.)
 130 
 131 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
 132   HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
 133 }
 134 
 135 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
 136   // The from card cache is not the memory that is actually committed. So we cannot
 137   // take advantage of the zero_filled parameter.
 138   reset_from_card_cache(start_idx, num_regions);
 139 }
 140 
 141 void G1CollectedHeap::run_batch_task(G1BatchedTask* cl) {
 142   uint num_workers = MAX2(1u, MIN2(cl->num_workers_estimate(), workers()->active_workers()));
 143   cl->set_max_workers(num_workers);
 144   workers()->run_task(cl, num_workers);
 145 }
 146 
 147 uint G1CollectedHeap::get_chunks_per_region() {
 148   uint log_region_size = HeapRegion::LogOfHRGrainBytes;
 149   // Limit the expected input values to current known possible values of the
 150   // (log) region size. Adjust as necessary after testing if changing the permissible
 151   // values for region size.
 152   assert(log_region_size >= 20 && log_region_size <= 29,
 153          "expected value in [20,29], but got %u", log_region_size);
 154   return 1u << (log_region_size / 2 - 4);
 155 }
 156 
 157 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
 158                                              MemRegion mr) {
 159   return new HeapRegion(hrs_index, bot(), mr, &_card_set_config);
 160 }
 161 
 162 // Private methods.
 163 
 164 HeapRegion* G1CollectedHeap::new_region(size_t word_size,
 165                                         HeapRegionType type,
 166                                         bool do_expand,
 167                                         uint node_index) {
 168   assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
 169          "the only time we use this to allocate a humongous region is "
 170          "when we are allocating a single humongous region");
 171 
 172   HeapRegion* res = _hrm.allocate_free_region(type, node_index);
 173 
 174   if (res == nullptr && do_expand) {
 175     // Currently, only attempts to allocate GC alloc regions set
 176     // do_expand to true. So, we should only reach here during a
 177     // safepoint.
 178     assert(SafepointSynchronize::is_at_safepoint(), "invariant");
 179 
 180     log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B",
 181                               word_size * HeapWordSize);
 182 
 183     assert(word_size * HeapWordSize < HeapRegion::GrainBytes,
 184            "This kind of expansion should never be more than one region. Size: " SIZE_FORMAT,
 185            word_size * HeapWordSize);
 186     if (expand_single_region(node_index)) {
 187       // Given that expand_single_region() succeeded in expanding the heap, and we
 188       // always expand the heap by an amount aligned to the heap
 189       // region size, the free list should in theory not be empty.
 190       // In either case allocate_free_region() will check for null.
 191       res = _hrm.allocate_free_region(type, node_index);
 192     }
 193   }
 194   return res;
 195 }
 196 
 197 void G1CollectedHeap::set_humongous_metadata(HeapRegion* first_hr,
 198                                              uint num_regions,
 199                                              size_t word_size,
 200                                              bool update_remsets) {
 201   // Calculate the new top of the humongous object.
 202   HeapWord* obj_top = first_hr->bottom() + word_size;
 203   // The word size sum of all the regions used
 204   size_t word_size_sum = num_regions * HeapRegion::GrainWords;
 205   assert(word_size <= word_size_sum, "sanity");
 206 
 207   // How many words memory we "waste" which cannot hold a filler object.
 208   size_t words_not_fillable = 0;
 209 
 210   // Pad out the unused tail of the last region with filler
 211   // objects, for improved usage accounting.
 212 
 213   // How many words can we use for filler objects.
 214   size_t words_fillable = word_size_sum - word_size;
 215 
 216   if (words_fillable >= G1CollectedHeap::min_fill_size()) {
 217     G1CollectedHeap::fill_with_objects(obj_top, words_fillable);
 218   } else {
 219     // We have space to fill, but we cannot fit an object there.
 220     words_not_fillable = words_fillable;
 221     words_fillable = 0;
 222   }
 223 
 224   // We will set up the first region as "starts humongous". This
 225   // will also update the BOT covering all the regions to reflect
 226   // that there is a single object that starts at the bottom of the
 227   // first region.
 228   first_hr->hr_clear(false /* clear_space */);
 229   first_hr->set_starts_humongous(obj_top, words_fillable);
 230 
 231   if (update_remsets) {
 232     _policy->remset_tracker()->update_at_allocate(first_hr);
 233   }
 234 
 235   // Indices of first and last regions in the series.
 236   uint first = first_hr->hrm_index();
 237   uint last = first + num_regions - 1;
 238 
 239   HeapRegion* hr = nullptr;
 240   for (uint i = first + 1; i <= last; ++i) {
 241     hr = region_at(i);
 242     hr->hr_clear(false /* clear_space */);
 243     hr->set_continues_humongous(first_hr);
 244     if (update_remsets) {
 245       _policy->remset_tracker()->update_at_allocate(hr);
 246     }
 247   }
 248 
 249   // Up to this point no concurrent thread would have been able to
 250   // do any scanning on any region in this series. All the top
 251   // fields still point to bottom, so the intersection between
 252   // [bottom,top] and [card_start,card_end] will be empty. Before we
 253   // update the top fields, we'll do a storestore to make sure that
 254   // no thread sees the update to top before the zeroing of the
 255   // object header and the BOT initialization.
 256   OrderAccess::storestore();
 257 
 258   // Now, we will update the top fields of the "continues humongous"
 259   // regions except the last one.
 260   for (uint i = first; i < last; ++i) {
 261     hr = region_at(i);
 262     hr->set_top(hr->end());
 263   }
 264 
 265   hr = region_at(last);
 266   // If we cannot fit a filler object, we must set top to the end
 267   // of the humongous object, otherwise we cannot iterate the heap
 268   // and the BOT will not be complete.
 269   hr->set_top(hr->end() - words_not_fillable);
 270 
 271   assert(hr->bottom() < obj_top && obj_top <= hr->end(),
 272          "obj_top should be in last region");
 273 
 274   assert(words_not_fillable == 0 ||
 275          first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(),
 276          "Miscalculation in humongous allocation");
 277 }
 278 
 279 HeapWord*
 280 G1CollectedHeap::humongous_obj_allocate_initialize_regions(HeapRegion* first_hr,
 281                                                            uint num_regions,
 282                                                            size_t word_size) {
 283   assert(first_hr != nullptr, "pre-condition");
 284   assert(is_humongous(word_size), "word_size should be humongous");
 285   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 286 
 287   // Index of last region in the series.
 288   uint first = first_hr->hrm_index();
 289   uint last = first + num_regions - 1;
 290 
 291   // We need to initialize the region(s) we just discovered. This is
 292   // a bit tricky given that it can happen concurrently with
 293   // refinement threads refining cards on these regions and
 294   // potentially wanting to refine the BOT as they are scanning
 295   // those cards (this can happen shortly after a cleanup; see CR
 296   // 6991377). So we have to set up the region(s) carefully and in
 297   // a specific order.
 298 
 299   // The passed in hr will be the "starts humongous" region. The header
 300   // of the new object will be placed at the bottom of this region.
 301   HeapWord* new_obj = first_hr->bottom();
 302 
 303   // First, we need to zero the header of the space that we will be
 304   // allocating. When we update top further down, some refinement
 305   // threads might try to scan the region. By zeroing the header we
 306   // ensure that any thread that will try to scan the region will
 307   // come across the zero klass word and bail out.
 308   //
 309   // NOTE: It would not have been correct to have used
 310   // CollectedHeap::fill_with_object() and make the space look like
 311   // an int array. The thread that is doing the allocation will
 312   // later update the object header to a potentially different array
 313   // type and, for a very short period of time, the klass and length
 314   // fields will be inconsistent. This could cause a refinement
 315   // thread to calculate the object size incorrectly.
 316   Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
 317 
 318   // Next, update the metadata for the regions.
 319   set_humongous_metadata(first_hr, num_regions, word_size, true);
 320 
 321   HeapRegion* last_hr = region_at(last);
 322   size_t used = byte_size(first_hr->bottom(), last_hr->top());
 323 
 324   increase_used(used);
 325 
 326   for (uint i = first; i <= last; ++i) {
 327     HeapRegion *hr = region_at(i);
 328     _humongous_set.add(hr);
 329     _hr_printer.alloc(hr);
 330   }
 331 
 332   return new_obj;
 333 }
 334 
 335 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) {
 336   assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size);
 337   return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
 338 }
 339 
 340 // If could fit into free regions w/o expansion, try.
 341 // Otherwise, if can expand, do so.
 342 // Otherwise, if using ex regions might help, try with ex given back.
 343 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
 344   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 345 
 346   _verifier->verify_region_sets_optional();
 347 
 348   uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);
 349 
 350   // Policy: First try to allocate a humongous object in the free list.
 351   HeapRegion* humongous_start = _hrm.allocate_humongous(obj_regions);
 352   if (humongous_start == nullptr) {
 353     // Policy: We could not find enough regions for the humongous object in the
 354     // free list. Look through the heap to find a mix of free and uncommitted regions.
 355     // If so, expand the heap and allocate the humongous object.
 356     humongous_start = _hrm.expand_and_allocate_humongous(obj_regions);
 357     if (humongous_start != nullptr) {
 358       // We managed to find a region by expanding the heap.
 359       log_debug(gc, ergo, heap)("Heap expansion (humongous allocation request). Allocation request: " SIZE_FORMAT "B",
 360                                 word_size * HeapWordSize);
 361       policy()->record_new_heap_size(num_regions());
 362     } else {
 363       // Policy: Potentially trigger a defragmentation GC.
 364     }
 365   }
 366 
 367   HeapWord* result = nullptr;
 368   if (humongous_start != nullptr) {
 369     result = humongous_obj_allocate_initialize_regions(humongous_start, obj_regions, word_size);
 370     assert(result != nullptr, "it should always return a valid result");
 371 
 372     // A successful humongous object allocation changes the used space
 373     // information of the old generation so we need to recalculate the
 374     // sizes and update the jstat counters here.
 375     monitoring_support()->update_sizes();
 376   }
 377 
 378   _verifier->verify_region_sets_optional();
 379 
 380   return result;
 381 }
 382 
 383 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t min_size,
 384                                              size_t requested_size,
 385                                              size_t* actual_size) {
 386   assert_heap_not_locked_and_not_at_safepoint();
 387   assert(!is_humongous(requested_size), "we do not allow humongous TLABs");
 388 
 389   return attempt_allocation(min_size, requested_size, actual_size);
 390 }
 391 
 392 HeapWord*
 393 G1CollectedHeap::mem_allocate(size_t word_size,
 394                               bool*  gc_overhead_limit_was_exceeded) {
 395   assert_heap_not_locked_and_not_at_safepoint();
 396 
 397   if (is_humongous(word_size)) {
 398     return attempt_allocation_humongous(word_size);
 399   }
 400   size_t dummy = 0;
 401   return attempt_allocation(word_size, word_size, &dummy);
 402 }
 403 
 404 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size) {
 405   ResourceMark rm; // For retrieving the thread names in log messages.
 406 
 407   // Make sure you read the note in attempt_allocation_humongous().
 408 
 409   assert_heap_not_locked_and_not_at_safepoint();
 410   assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
 411          "be called for humongous allocation requests");
 412 
 413   // We should only get here after the first-level allocation attempt
 414   // (attempt_allocation()) failed to allocate.
 415 
 416   // We will loop until a) we manage to successfully perform the allocation or b)
 417   // successfully schedule a collection which fails to perform the allocation.
 418   // Case b) is the only case when we'll return null.
 419   HeapWord* result = nullptr;
 420   for (uint try_count = 1; /* we'll return */; try_count++) {
 421     uint gc_count_before;
 422 
 423     {
 424       MutexLocker x(Heap_lock);
 425 
 426       // Now that we have the lock, we first retry the allocation in case another
 427       // thread changed the region while we were waiting to acquire the lock.
 428       result = _allocator->attempt_allocation_locked(word_size);
 429       if (result != nullptr) {
 430         return result;
 431       }
 432 
 433       // Read the GC count while still holding the Heap_lock.
 434       gc_count_before = total_collections();
 435     }
 436 
 437     bool succeeded;
 438     result = do_collection_pause(word_size, gc_count_before, &succeeded, GCCause::_g1_inc_collection_pause);
 439     if (succeeded) {
 440       log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT,
 441                            Thread::current()->name(), p2i(result));
 442       return result;
 443     }
 444 
 445     log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT " words",
 446                          Thread::current()->name(), word_size);
 447 
 448     // We can reach here if we were unsuccessful in scheduling a collection (because
 449     // another thread beat us to it). In this case immeditealy retry the allocation
 450     // attempt because another thread successfully performed a collection and possibly
 451     // reclaimed enough space. The first attempt (without holding the Heap_lock) is
 452     // here and the follow-on attempt will be at the start of the next loop
 453     // iteration (after taking the Heap_lock).
 454     size_t dummy = 0;
 455     result = _allocator->attempt_allocation(word_size, word_size, &dummy);
 456     if (result != nullptr) {
 457       return result;
 458     }
 459 
 460     // Give a warning if we seem to be looping forever.
 461     if ((QueuedAllocationWarningCount > 0) &&
 462         (try_count % QueuedAllocationWarningCount == 0)) {
 463       log_warning(gc, alloc)("%s:  Retried allocation %u times for " SIZE_FORMAT " words",
 464                              Thread::current()->name(), try_count, word_size);
 465     }
 466   }
 467 
 468   ShouldNotReachHere();
 469   return nullptr;
 470 }
 471 
 472 template <typename Func>
 473 void G1CollectedHeap::iterate_regions_in_range(MemRegion range, const Func& func) {
 474   // Mark each G1 region touched by the range as old, add it to
 475   // the old set, and set top.
 476   HeapRegion* curr_region = _hrm.addr_to_region(range.start());
 477   HeapRegion* end_region = _hrm.addr_to_region(range.last());
 478 
 479   while (curr_region != nullptr) {
 480     bool is_last = curr_region == end_region;
 481     HeapRegion* next_region = is_last ? nullptr : _hrm.next_region_in_heap(curr_region);
 482 
 483     func(curr_region, is_last);
 484 
 485     curr_region = next_region;
 486   }
 487 }
 488 
 489 HeapWord* G1CollectedHeap::alloc_archive_region(size_t word_size, HeapWord* preferred_addr) {
 490   assert(!is_init_completed(), "Expect to be called at JVM init time");
 491   MutexLocker x(Heap_lock);
 492 
 493   MemRegion reserved = _hrm.reserved();
 494 
 495   if (reserved.word_size() <= word_size) {
 496     log_info(gc, heap)("Unable to allocate regions as archive heap is too large; size requested = " SIZE_FORMAT
 497                        " bytes, heap = " SIZE_FORMAT " bytes", word_size, reserved.word_size());
 498     return nullptr;
 499   }
 500 
 501   // Temporarily disable pretouching of heap pages. This interface is used
 502   // when mmap'ing archived heap data in, so pre-touching is wasted.
 503   FlagSetting fs(AlwaysPreTouch, false);
 504 
 505   size_t commits = 0;
 506   // Attempt to allocate towards the end of the heap.
 507   HeapWord* start_addr = reserved.end() - align_up(word_size, HeapRegion::GrainWords);
 508   MemRegion range = MemRegion(start_addr, word_size);
 509   HeapWord* last_address = range.last();
 510   if (!_hrm.allocate_containing_regions(range, &commits, workers())) {
 511     return nullptr;
 512   }
 513   increase_used(word_size * HeapWordSize);
 514   if (commits != 0) {
 515     log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B",
 516                               HeapRegion::GrainWords * HeapWordSize * commits);
 517   }
 518 
 519   // Mark each G1 region touched by the range as old, add it to
 520   // the old set, and set top.
 521   auto set_region_to_old = [&] (HeapRegion* r, bool is_last) {
 522     assert(r->is_empty(), "Region already in use (%u)", r->hrm_index());
 523 
 524     HeapWord* top = is_last ? last_address + 1 : r->end();
 525     r->set_top(top);
 526 
 527     r->set_old();
 528     _hr_printer.alloc(r);
 529     _old_set.add(r);
 530   };
 531 
 532   iterate_regions_in_range(range, set_region_to_old);
 533   return start_addr;
 534 }
 535 
 536 void G1CollectedHeap::populate_archive_regions_bot_part(MemRegion range) {
 537   assert(!is_init_completed(), "Expect to be called at JVM init time");
 538 
 539   iterate_regions_in_range(range,
 540                            [&] (HeapRegion* r, bool is_last) {
 541                              r->update_bot();
 542                            });
 543 }
 544 
 545 void G1CollectedHeap::dealloc_archive_regions(MemRegion range) {
 546   assert(!is_init_completed(), "Expect to be called at JVM init time");
 547   MemRegion reserved = _hrm.reserved();
 548   size_t size_used = 0;
 549   uint shrink_count = 0;
 550 
 551   // Free the G1 regions that are within the specified range.
 552   MutexLocker x(Heap_lock);
 553   HeapWord* start_address = range.start();
 554   HeapWord* last_address = range.last();
 555 
 556   assert(reserved.contains(start_address) && reserved.contains(last_address),
 557          "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 558          p2i(start_address), p2i(last_address));
 559   size_used += range.byte_size();
 560 
 561   // Free, empty and uncommit regions with CDS archive content.
 562   auto dealloc_archive_region = [&] (HeapRegion* r, bool is_last) {
 563     guarantee(r->is_old(), "Expected old region at index %u", r->hrm_index());
 564     _old_set.remove(r);
 565     r->set_free();
 566     r->set_top(r->bottom());
 567     _hrm.shrink_at(r->hrm_index(), 1);
 568     shrink_count++;
 569   };
 570 
 571   iterate_regions_in_range(range, dealloc_archive_region);
 572 
 573   if (shrink_count != 0) {
 574     log_debug(gc, ergo, heap)("Attempt heap shrinking (CDS archive regions). Total size: " SIZE_FORMAT "B",
 575                               HeapRegion::GrainWords * HeapWordSize * shrink_count);
 576     // Explicit uncommit.
 577     uncommit_regions(shrink_count);
 578   }
 579   decrease_used(size_used);
 580 }
 581 
 582 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t min_word_size,
 583                                                      size_t desired_word_size,
 584                                                      size_t* actual_word_size) {
 585   assert_heap_not_locked_and_not_at_safepoint();
 586   assert(!is_humongous(desired_word_size), "attempt_allocation() should not "
 587          "be called for humongous allocation requests");
 588 
 589   HeapWord* result = _allocator->attempt_allocation(min_word_size, desired_word_size, actual_word_size);
 590 
 591   if (result == nullptr) {
 592     *actual_word_size = desired_word_size;
 593     result = attempt_allocation_slow(desired_word_size);
 594   }
 595 
 596   assert_heap_not_locked();
 597   if (result != nullptr) {
 598     assert(*actual_word_size != 0, "Actual size must have been set here");
 599     dirty_young_block(result, *actual_word_size);
 600   } else {
 601     *actual_word_size = 0;
 602   }
 603 
 604   return result;
 605 }
 606 
 607 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size) {
 608   ResourceMark rm; // For retrieving the thread names in log messages.
 609 
 610   // The structure of this method has a lot of similarities to
 611   // attempt_allocation_slow(). The reason these two were not merged
 612   // into a single one is that such a method would require several "if
 613   // allocation is not humongous do this, otherwise do that"
 614   // conditional paths which would obscure its flow. In fact, an early
 615   // version of this code did use a unified method which was harder to
 616   // follow and, as a result, it had subtle bugs that were hard to
 617   // track down. So keeping these two methods separate allows each to
 618   // be more readable. It will be good to keep these two in sync as
 619   // much as possible.
 620 
 621   assert_heap_not_locked_and_not_at_safepoint();
 622   assert(is_humongous(word_size), "attempt_allocation_humongous() "
 623          "should only be called for humongous allocations");
 624 
 625   // Humongous objects can exhaust the heap quickly, so we should check if we
 626   // need to start a marking cycle at each humongous object allocation. We do
 627   // the check before we do the actual allocation. The reason for doing it
 628   // before the allocation is that we avoid having to keep track of the newly
 629   // allocated memory while we do a GC.
 630   if (policy()->need_to_start_conc_mark("concurrent humongous allocation",
 631                                         word_size)) {
 632     collect(GCCause::_g1_humongous_allocation);
 633   }
 634 
 635   // We will loop until a) we manage to successfully perform the allocation or b)
 636   // successfully schedule a collection which fails to perform the allocation.
 637   // Case b) is the only case when we'll return null.
 638   HeapWord* result = nullptr;
 639   for (uint try_count = 1; /* we'll return */; try_count++) {
 640     uint gc_count_before;
 641 
 642 
 643     {
 644       MutexLocker x(Heap_lock);
 645 
 646       size_t size_in_regions = humongous_obj_size_in_regions(word_size);
 647       // Given that humongous objects are not allocated in young
 648       // regions, we'll first try to do the allocation without doing a
 649       // collection hoping that there's enough space in the heap.
 650       result = humongous_obj_allocate(word_size);
 651       if (result != nullptr) {
 652         policy()->old_gen_alloc_tracker()->
 653           add_allocated_humongous_bytes_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
 654         return result;
 655       }
 656 
 657       // Read the GC count while still holding the Heap_lock.
 658       gc_count_before = total_collections();
 659     }
 660 
 661     bool succeeded;
 662     result = do_collection_pause(word_size, gc_count_before, &succeeded, GCCause::_g1_humongous_allocation);
 663     if (succeeded) {
 664       log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT,
 665                            Thread::current()->name(), p2i(result));
 666       if (result != nullptr) {
 667         size_t size_in_regions = humongous_obj_size_in_regions(word_size);
 668         policy()->old_gen_alloc_tracker()->
 669           record_collection_pause_humongous_allocation(size_in_regions * HeapRegion::GrainBytes);
 670       }
 671       return result;
 672     }
 673 
 674     log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT "",
 675                          Thread::current()->name(), word_size);
 676 
 677     // We can reach here if we were unsuccessful in scheduling a collection (because
 678     // another thread beat us to it).
 679     // Humongous object allocation always needs a lock, so we wait for the retry
 680     // in the next iteration of the loop, unlike for the regular iteration case.
 681     // Give a warning if we seem to be looping forever.
 682 
 683     if ((QueuedAllocationWarningCount > 0) &&
 684         (try_count % QueuedAllocationWarningCount == 0)) {
 685       log_warning(gc, alloc)("%s: Retried allocation %u times for %zu words",
 686                              Thread::current()->name(), try_count, word_size);
 687     }
 688   }
 689 
 690   ShouldNotReachHere();
 691   return nullptr;
 692 }
 693 
 694 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
 695                                                            bool expect_null_mutator_alloc_region) {
 696   assert_at_safepoint_on_vm_thread();
 697   assert(!_allocator->has_mutator_alloc_region() || !expect_null_mutator_alloc_region,
 698          "the current alloc region was unexpectedly found to be non-null");
 699 
 700   if (!is_humongous(word_size)) {
 701     return _allocator->attempt_allocation_locked(word_size);
 702   } else {
 703     HeapWord* result = humongous_obj_allocate(word_size);
 704     if (result != nullptr && policy()->need_to_start_conc_mark("STW humongous allocation")) {
 705       collector_state()->set_initiate_conc_mark_if_possible(true);
 706     }
 707     return result;
 708   }
 709 
 710   ShouldNotReachHere();
 711 }
 712 
 713 class PostCompactionPrinterClosure: public HeapRegionClosure {
 714 private:
 715   G1HRPrinter* _hr_printer;
 716 public:
 717   bool do_heap_region(HeapRegion* hr) {
 718     assert(!hr->is_young(), "not expecting to find young regions");
 719     _hr_printer->post_compaction(hr);
 720     return false;
 721   }
 722 
 723   PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
 724     : _hr_printer(hr_printer) { }
 725 };
 726 
 727 void G1CollectedHeap::print_heap_after_full_collection() {
 728   // Post collection region logging.
 729   // We should do this after we potentially resize the heap so
 730   // that all the COMMIT / UNCOMMIT events are generated before
 731   // the compaction events.
 732   if (_hr_printer.is_active()) {
 733     PostCompactionPrinterClosure cl(hr_printer());
 734     heap_region_iterate(&cl);
 735   }
 736 }
 737 
 738 bool G1CollectedHeap::abort_concurrent_cycle() {
 739   // Disable discovery and empty the discovered lists
 740   // for the CM ref processor.
 741   _ref_processor_cm->disable_discovery();
 742   _ref_processor_cm->abandon_partial_discovery();
 743   _ref_processor_cm->verify_no_references_recorded();
 744 
 745   // Abandon current iterations of concurrent marking and concurrent
 746   // refinement, if any are in progress.
 747   return concurrent_mark()->concurrent_cycle_abort();
 748 }
 749 
 750 void G1CollectedHeap::prepare_heap_for_full_collection() {
 751   // Make sure we'll choose a new allocation region afterwards.
 752   _allocator->release_mutator_alloc_regions();
 753   _allocator->abandon_gc_alloc_regions();
 754 
 755   // We may have added regions to the current incremental collection
 756   // set between the last GC or pause and now. We need to clear the
 757   // incremental collection set and then start rebuilding it afresh
 758   // after this full GC.
 759   abandon_collection_set(collection_set());
 760 
 761   _hrm.remove_all_free_regions();
 762 }
 763 
 764 void G1CollectedHeap::verify_before_full_collection() {
 765   assert_used_and_recalculate_used_equal(this);
 766   if (!VerifyBeforeGC) {
 767     return;
 768   }
 769   if (!G1HeapVerifier::should_verify(G1HeapVerifier::G1VerifyFull)) {
 770     return;
 771   }
 772   _verifier->verify_region_sets_optional();
 773   _verifier->verify_before_gc();
 774   _verifier->verify_bitmap_clear(true /* above_tams_only */);
 775 }
 776 
 777 void G1CollectedHeap::prepare_for_mutator_after_full_collection() {
 778   // Prepare heap for normal collections.
 779   assert(num_free_regions() == 0, "we should not have added any free regions");
 780   rebuild_region_sets(false /* free_list_only */);
 781   abort_refinement();
 782   resize_heap_if_necessary();
 783   uncommit_regions_if_necessary();
 784 
 785   // Rebuild the code root lists for each region
 786   rebuild_code_roots();
 787 
 788   start_new_collection_set();
 789   _allocator->init_mutator_alloc_regions();
 790 
 791   // Post collection state updates.
 792   MetaspaceGC::compute_new_size();
 793 }
 794 
 795 void G1CollectedHeap::abort_refinement() {
 796   // Discard all remembered set updates and reset refinement statistics.
 797   G1BarrierSet::dirty_card_queue_set().abandon_logs_and_stats();
 798   assert(G1BarrierSet::dirty_card_queue_set().num_cards() == 0,
 799          "DCQS should be empty");
 800   concurrent_refine()->get_and_reset_refinement_stats();
 801 }
 802 
 803 void G1CollectedHeap::verify_after_full_collection() {
 804   if (!VerifyAfterGC) {
 805     return;
 806   }
 807   if (!G1HeapVerifier::should_verify(G1HeapVerifier::G1VerifyFull)) {
 808     return;
 809   }
 810   _hrm.verify_optional();
 811   _verifier->verify_region_sets_optional();
 812   _verifier->verify_after_gc();
 813   _verifier->verify_bitmap_clear(false /* above_tams_only */);
 814 
 815   // At this point there should be no regions in the
 816   // entire heap tagged as young.
 817   assert(check_young_list_empty(), "young list should be empty at this point");
 818 
 819   // Note: since we've just done a full GC, concurrent
 820   // marking is no longer active. Therefore we need not
 821   // re-enable reference discovery for the CM ref processor.
 822   // That will be done at the start of the next marking cycle.
 823   // We also know that the STW processor should no longer
 824   // discover any new references.
 825   assert(!_ref_processor_stw->discovery_enabled(), "Postcondition");
 826   assert(!_ref_processor_cm->discovery_enabled(), "Postcondition");
 827   _ref_processor_stw->verify_no_references_recorded();
 828   _ref_processor_cm->verify_no_references_recorded();
 829 }
 830 
 831 bool G1CollectedHeap::do_full_collection(bool clear_all_soft_refs,
 832                                          bool do_maximal_compaction) {
 833   assert_at_safepoint_on_vm_thread();
 834 
 835   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
 836       soft_ref_policy()->should_clear_all_soft_refs();
 837 
 838   G1FullGCMark gc_mark;
 839   GCTraceTime(Info, gc) tm("Pause Full", nullptr, gc_cause(), true);
 840   G1FullCollector collector(this, do_clear_all_soft_refs, do_maximal_compaction, gc_mark.tracer());
 841 
 842   collector.prepare_collection();
 843   collector.collect();
 844   collector.complete_collection();
 845 
 846   // Full collection was successfully completed.
 847   return true;
 848 }
 849 
 850 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
 851   // Currently, there is no facility in the do_full_collection(bool) API to notify
 852   // the caller that the collection did not succeed (e.g., because it was locked
 853   // out by the GC locker). So, right now, we'll ignore the return value.
 854 
 855   do_full_collection(clear_all_soft_refs,
 856                      false /* do_maximal_compaction */);
 857 }
 858 
 859 bool G1CollectedHeap::upgrade_to_full_collection() {
 860   GCCauseSetter compaction(this, GCCause::_g1_compaction_pause);
 861   log_info(gc, ergo)("Attempting full compaction clearing soft references");
 862   bool success = do_full_collection(true  /* clear_all_soft_refs */,
 863                                     false /* do_maximal_compaction */);
 864   // do_full_collection only fails if blocked by GC locker and that can't
 865   // be the case here since we only call this when already completed one gc.
 866   assert(success, "invariant");
 867   return success;
 868 }
 869 
 870 void G1CollectedHeap::resize_heap_if_necessary() {
 871   assert_at_safepoint_on_vm_thread();
 872 
 873   bool should_expand;
 874   size_t resize_amount = _heap_sizing_policy->full_collection_resize_amount(should_expand);
 875 
 876   if (resize_amount == 0) {
 877     return;
 878   } else if (should_expand) {
 879     expand(resize_amount, _workers);
 880   } else {
 881     shrink(resize_amount);
 882   }
 883 }
 884 
 885 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size,
 886                                                             bool do_gc,
 887                                                             bool maximal_compaction,
 888                                                             bool expect_null_mutator_alloc_region,
 889                                                             bool* gc_succeeded) {
 890   *gc_succeeded = true;
 891   // Let's attempt the allocation first.
 892   HeapWord* result =
 893     attempt_allocation_at_safepoint(word_size,
 894                                     expect_null_mutator_alloc_region);
 895   if (result != nullptr) {
 896     return result;
 897   }
 898 
 899   // In a G1 heap, we're supposed to keep allocation from failing by
 900   // incremental pauses.  Therefore, at least for now, we'll favor
 901   // expansion over collection.  (This might change in the future if we can
 902   // do something smarter than full collection to satisfy a failed alloc.)
 903   result = expand_and_allocate(word_size);
 904   if (result != nullptr) {
 905     return result;
 906   }
 907 
 908   if (do_gc) {
 909     GCCauseSetter compaction(this, GCCause::_g1_compaction_pause);
 910     // Expansion didn't work, we'll try to do a Full GC.
 911     // If maximal_compaction is set we clear all soft references and don't
 912     // allow any dead wood to be left on the heap.
 913     if (maximal_compaction) {
 914       log_info(gc, ergo)("Attempting maximal full compaction clearing soft references");
 915     } else {
 916       log_info(gc, ergo)("Attempting full compaction");
 917     }
 918     *gc_succeeded = do_full_collection(maximal_compaction /* clear_all_soft_refs */ ,
 919                                        maximal_compaction /* do_maximal_compaction */);
 920   }
 921 
 922   return nullptr;
 923 }
 924 
 925 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
 926                                                      bool* succeeded) {
 927   assert_at_safepoint_on_vm_thread();
 928 
 929   // Attempts to allocate followed by Full GC.
 930   HeapWord* result =
 931     satisfy_failed_allocation_helper(word_size,
 932                                      true,  /* do_gc */
 933                                      false, /* maximum_collection */
 934                                      false, /* expect_null_mutator_alloc_region */
 935                                      succeeded);
 936 
 937   if (result != nullptr || !*succeeded) {
 938     return result;
 939   }
 940 
 941   // Attempts to allocate followed by Full GC that will collect all soft references.
 942   result = satisfy_failed_allocation_helper(word_size,
 943                                             true, /* do_gc */
 944                                             true, /* maximum_collection */
 945                                             true, /* expect_null_mutator_alloc_region */
 946                                             succeeded);
 947 
 948   if (result != nullptr || !*succeeded) {
 949     return result;
 950   }
 951 
 952   // Attempts to allocate, no GC
 953   result = satisfy_failed_allocation_helper(word_size,
 954                                             false, /* do_gc */
 955                                             false, /* maximum_collection */
 956                                             true,  /* expect_null_mutator_alloc_region */
 957                                             succeeded);
 958 
 959   if (result != nullptr) {
 960     return result;
 961   }
 962 
 963   assert(!soft_ref_policy()->should_clear_all_soft_refs(),
 964          "Flag should have been handled and cleared prior to this point");
 965 
 966   // What else?  We might try synchronous finalization later.  If the total
 967   // space available is large enough for the allocation, then a more
 968   // complete compaction phase than we've tried so far might be
 969   // appropriate.
 970   return nullptr;
 971 }
 972 
 973 // Attempting to expand the heap sufficiently
 974 // to support an allocation of the given "word_size".  If
 975 // successful, perform the allocation and return the address of the
 976 // allocated block, or else null.
 977 
 978 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
 979   assert_at_safepoint_on_vm_thread();
 980 
 981   _verifier->verify_region_sets_optional();
 982 
 983   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
 984   log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B",
 985                             word_size * HeapWordSize);
 986 
 987 
 988   if (expand(expand_bytes, _workers)) {
 989     _hrm.verify_optional();
 990     _verifier->verify_region_sets_optional();
 991     return attempt_allocation_at_safepoint(word_size,
 992                                            false /* expect_null_mutator_alloc_region */);
 993   }
 994   return nullptr;
 995 }
 996 
 997 bool G1CollectedHeap::expand(size_t expand_bytes, WorkerThreads* pretouch_workers, double* expand_time_ms) {
 998   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
 999   aligned_expand_bytes = align_up(aligned_expand_bytes,
1000                                        HeapRegion::GrainBytes);
1001 
1002   log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B",
1003                             expand_bytes, aligned_expand_bytes);
1004 
1005   if (is_maximal_no_gc()) {
1006     log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1007     return false;
1008   }
1009 
1010   double expand_heap_start_time_sec = os::elapsedTime();
1011   uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1012   assert(regions_to_expand > 0, "Must expand by at least one region");
1013 
1014   uint expanded_by = _hrm.expand_by(regions_to_expand, pretouch_workers);
1015   if (expand_time_ms != nullptr) {
1016     *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS;
1017   }
1018 
1019   assert(expanded_by > 0, "must have failed during commit.");
1020 
1021   size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1022   assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1023   policy()->record_new_heap_size(num_regions());
1024 
1025   return true;
1026 }
1027 
1028 bool G1CollectedHeap::expand_single_region(uint node_index) {
1029   uint expanded_by = _hrm.expand_on_preferred_node(node_index);
1030 
1031   if (expanded_by == 0) {
1032     assert(is_maximal_no_gc(), "Should be no regions left, available: %u", _hrm.available());
1033     log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1034     return false;
1035   }
1036 
1037   policy()->record_new_heap_size(num_regions());
1038   return true;
1039 }
1040 
1041 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1042   size_t aligned_shrink_bytes =
1043     ReservedSpace::page_align_size_down(shrink_bytes);
1044   aligned_shrink_bytes = align_down(aligned_shrink_bytes,
1045                                          HeapRegion::GrainBytes);
1046   uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1047 
1048   uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1049   size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1050 
1051   log_debug(gc, ergo, heap)("Shrink the heap. requested shrinking amount: " SIZE_FORMAT "B aligned shrinking amount: " SIZE_FORMAT "B actual amount shrunk: " SIZE_FORMAT "B",
1052                             shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1053   if (num_regions_removed > 0) {
1054     log_debug(gc, heap)("Uncommittable regions after shrink: %u", num_regions_removed);
1055     policy()->record_new_heap_size(num_regions());
1056   } else {
1057     log_debug(gc, ergo, heap)("Did not shrink the heap (heap shrinking operation failed)");
1058   }
1059 }
1060 
1061 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1062   _verifier->verify_region_sets_optional();
1063 
1064   // We should only reach here at the end of a Full GC or during Remark which
1065   // means we should not not be holding to any GC alloc regions. The method
1066   // below will make sure of that and do any remaining clean up.
1067   _allocator->abandon_gc_alloc_regions();
1068 
1069   // Instead of tearing down / rebuilding the free lists here, we
1070   // could instead use the remove_all_pending() method on free_list to
1071   // remove only the ones that we need to remove.
1072   _hrm.remove_all_free_regions();
1073   shrink_helper(shrink_bytes);
1074   rebuild_region_sets(true /* free_list_only */);
1075 
1076   _hrm.verify_optional();
1077   _verifier->verify_region_sets_optional();
1078 }
1079 
1080 class OldRegionSetChecker : public HeapRegionSetChecker {
1081 public:
1082   void check_mt_safety() {
1083     // Master Old Set MT safety protocol:
1084     // (a) If we're at a safepoint, operations on the master old set
1085     // should be invoked:
1086     // - by the VM thread (which will serialize them), or
1087     // - by the GC workers while holding the FreeList_lock, if we're
1088     //   at a safepoint for an evacuation pause (this lock is taken
1089     //   anyway when an GC alloc region is retired so that a new one
1090     //   is allocated from the free list), or
1091     // - by the GC workers while holding the OldSets_lock, if we're at a
1092     //   safepoint for a cleanup pause.
1093     // (b) If we're not at a safepoint, operations on the master old set
1094     // should be invoked while holding the Heap_lock.
1095 
1096     if (SafepointSynchronize::is_at_safepoint()) {
1097       guarantee(Thread::current()->is_VM_thread() ||
1098                 FreeList_lock->owned_by_self() || OldSets_lock->owned_by_self(),
1099                 "master old set MT safety protocol at a safepoint");
1100     } else {
1101       guarantee(Heap_lock->owned_by_self(), "master old set MT safety protocol outside a safepoint");
1102     }
1103   }
1104   bool is_correct_type(HeapRegion* hr) { return hr->is_old(); }
1105   const char* get_description() { return "Old Regions"; }
1106 };
1107 
1108 class HumongousRegionSetChecker : public HeapRegionSetChecker {
1109 public:
1110   void check_mt_safety() {
1111     // Humongous Set MT safety protocol:
1112     // (a) If we're at a safepoint, operations on the master humongous
1113     // set should be invoked by either the VM thread (which will
1114     // serialize them) or by the GC workers while holding the
1115     // OldSets_lock.
1116     // (b) If we're not at a safepoint, operations on the master
1117     // humongous set should be invoked while holding the Heap_lock.
1118 
1119     if (SafepointSynchronize::is_at_safepoint()) {
1120       guarantee(Thread::current()->is_VM_thread() ||
1121                 OldSets_lock->owned_by_self(),
1122                 "master humongous set MT safety protocol at a safepoint");
1123     } else {
1124       guarantee(Heap_lock->owned_by_self(),
1125                 "master humongous set MT safety protocol outside a safepoint");
1126     }
1127   }
1128   bool is_correct_type(HeapRegion* hr) { return hr->is_humongous(); }
1129   const char* get_description() { return "Humongous Regions"; }
1130 };
1131 
1132 G1CollectedHeap::G1CollectedHeap() :
1133   CollectedHeap(),
1134   _service_thread(nullptr),
1135   _periodic_gc_task(nullptr),
1136   _free_arena_memory_task(nullptr),
1137   _workers(nullptr),
1138   _card_table(nullptr),
1139   _collection_pause_end(Ticks::now()),
1140   _old_set("Old Region Set", new OldRegionSetChecker()),
1141   _humongous_set("Humongous Region Set", new HumongousRegionSetChecker()),
1142   _bot(nullptr),
1143   _listener(),
1144   _numa(G1NUMA::create()),
1145   _hrm(),
1146   _allocator(nullptr),
1147   _allocation_failure_injector(),
1148   _verifier(nullptr),
1149   _summary_bytes_used(0),
1150   _bytes_used_during_gc(0),
1151   _survivor_evac_stats("Young", YoungPLABSize, PLABWeight),
1152   _old_evac_stats("Old", OldPLABSize, PLABWeight),
1153   _monitoring_support(nullptr),
1154   _num_humongous_objects(0),
1155   _num_humongous_reclaim_candidates(0),
1156   _hr_printer(),
1157   _collector_state(),
1158   _old_marking_cycles_started(0),
1159   _old_marking_cycles_completed(0),
1160   _eden(),
1161   _survivor(),
1162   _gc_timer_stw(new STWGCTimer()),
1163   _gc_tracer_stw(new G1NewTracer()),
1164   _policy(new G1Policy(_gc_timer_stw)),
1165   _heap_sizing_policy(nullptr),
1166   _collection_set(this, _policy),
1167   _rem_set(nullptr),
1168   _card_set_config(),
1169   _card_set_freelist_pool(G1CardSetConfiguration::num_mem_object_types()),
1170   _cm(nullptr),
1171   _cm_thread(nullptr),
1172   _cr(nullptr),
1173   _task_queues(nullptr),
1174   _ref_processor_stw(nullptr),
1175   _is_alive_closure_stw(this),
1176   _is_subject_to_discovery_stw(this),
1177   _ref_processor_cm(nullptr),
1178   _is_alive_closure_cm(this),
1179   _is_subject_to_discovery_cm(this),
1180   _region_attr() {
1181 
1182   _verifier = new G1HeapVerifier(this);
1183 
1184   _allocator = new G1Allocator(this);
1185 
1186   _heap_sizing_policy = G1HeapSizingPolicy::create(this, _policy->analytics());
1187 
1188   _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);
1189 
1190   // Since filler arrays are never referenced, we can make them region sized.
1191   // This simplifies filling up the region in case we have some potentially
1192   // unreferenced (by Java code, but still in use by native code) pinned objects
1193   // in there.
1194   _filler_array_max_size = HeapRegion::GrainWords;
1195 
1196   // Override the default _stack_chunk_max_size so that no humongous stack chunks are created
1197   _stack_chunk_max_size = _humongous_object_threshold_in_words;
1198 
1199   uint n_queues = ParallelGCThreads;
1200   _task_queues = new G1ScannerTasksQueueSet(n_queues);
1201 
1202   for (uint i = 0; i < n_queues; i++) {
1203     G1ScannerTasksQueue* q = new G1ScannerTasksQueue();
1204     _task_queues->register_queue(i, q);
1205   }
1206 
1207   _gc_tracer_stw->initialize();
1208 
1209   guarantee(_task_queues != nullptr, "task_queues allocation failure.");
1210 }
1211 
1212 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1213                                                                  size_t size,
1214                                                                  size_t translation_factor) {
1215   size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1216   // Allocate a new reserved space, preferring to use large pages.
1217   ReservedSpace rs(size, preferred_page_size);
1218   size_t page_size = rs.page_size();
1219   G1RegionToSpaceMapper* result  =
1220     G1RegionToSpaceMapper::create_mapper(rs,
1221                                          size,
1222                                          page_size,
1223                                          HeapRegion::GrainBytes,
1224                                          translation_factor,
1225                                          mtGC);
1226 
1227   os::trace_page_sizes_for_requested_size(description,
1228                                           size,
1229                                           preferred_page_size,
1230                                           rs.base(),
1231                                           rs.size(),
1232                                           page_size);
1233 
1234   return result;
1235 }
1236 
1237 jint G1CollectedHeap::initialize_concurrent_refinement() {
1238   jint ecode = JNI_OK;
1239   _cr = G1ConcurrentRefine::create(policy(), &ecode);
1240   return ecode;
1241 }
1242 
1243 jint G1CollectedHeap::initialize_service_thread() {
1244   _service_thread = new G1ServiceThread();
1245   if (_service_thread->osthread() == nullptr) {
1246     vm_shutdown_during_initialization("Could not create G1ServiceThread");
1247     return JNI_ENOMEM;
1248   }
1249   return JNI_OK;
1250 }
1251 
1252 jint G1CollectedHeap::initialize() {
1253 
1254   // Necessary to satisfy locking discipline assertions.
1255 
1256   MutexLocker x(Heap_lock);
1257 
1258   // While there are no constraints in the GC code that HeapWordSize
1259   // be any particular value, there are multiple other areas in the
1260   // system which believe this to be true (e.g. oop->object_size in some
1261   // cases incorrectly returns the size in wordSize units rather than
1262   // HeapWordSize).
1263   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1264 
1265   size_t init_byte_size = InitialHeapSize;
1266   size_t reserved_byte_size = G1Arguments::heap_reserved_size_bytes();
1267 
1268   // Ensure that the sizes are properly aligned.
1269   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1270   Universe::check_alignment(reserved_byte_size, HeapRegion::GrainBytes, "g1 heap");
1271   Universe::check_alignment(reserved_byte_size, HeapAlignment, "g1 heap");
1272 
1273   // Reserve the maximum.
1274 
1275   // When compressed oops are enabled, the preferred heap base
1276   // is calculated by subtracting the requested size from the
1277   // 32Gb boundary and using the result as the base address for
1278   // heap reservation. If the requested size is not aligned to
1279   // HeapRegion::GrainBytes (i.e. the alignment that is passed
1280   // into the ReservedHeapSpace constructor) then the actual
1281   // base of the reserved heap may end up differing from the
1282   // address that was requested (i.e. the preferred heap base).
1283   // If this happens then we could end up using a non-optimal
1284   // compressed oops mode.
1285 
1286   ReservedHeapSpace heap_rs = Universe::reserve_heap(reserved_byte_size,
1287                                                      HeapAlignment);
1288 
1289   initialize_reserved_region(heap_rs);
1290 
1291   // Create the barrier set for the entire reserved region.
1292   G1CardTable* ct = new G1CardTable(heap_rs.region());
1293   G1BarrierSet* bs = new G1BarrierSet(ct);
1294   bs->initialize();
1295   assert(bs->is_a(BarrierSet::G1BarrierSet), "sanity");
1296   BarrierSet::set_barrier_set(bs);
1297   _card_table = ct;
1298 
1299   {
1300     G1SATBMarkQueueSet& satbqs = bs->satb_mark_queue_set();
1301     satbqs.set_process_completed_buffers_threshold(G1SATBProcessCompletedThreshold);
1302     satbqs.set_buffer_enqueue_threshold_percentage(G1SATBBufferEnqueueingThresholdPercent);
1303   }
1304 
1305   // Create space mappers.
1306   size_t page_size = heap_rs.page_size();
1307   G1RegionToSpaceMapper* heap_storage =
1308     G1RegionToSpaceMapper::create_mapper(heap_rs,
1309                                          heap_rs.size(),
1310                                          page_size,
1311                                          HeapRegion::GrainBytes,
1312                                          1,
1313                                          mtJavaHeap);
1314   if(heap_storage == nullptr) {
1315     vm_shutdown_during_initialization("Could not initialize G1 heap");
1316     return JNI_ERR;
1317   }
1318 
1319   os::trace_page_sizes("Heap",
1320                        MinHeapSize,
1321                        reserved_byte_size,
1322                        heap_rs.base(),
1323                        heap_rs.size(),
1324                        page_size);
1325   heap_storage->set_mapping_changed_listener(&_listener);
1326 
1327   // Create storage for the BOT, card table and the bitmap.
1328   G1RegionToSpaceMapper* bot_storage =
1329     create_aux_memory_mapper("Block Offset Table",
1330                              G1BlockOffsetTable::compute_size(heap_rs.size() / HeapWordSize),
1331                              G1BlockOffsetTable::heap_map_factor());
1332 
1333   G1RegionToSpaceMapper* cardtable_storage =
1334     create_aux_memory_mapper("Card Table",
1335                              G1CardTable::compute_size(heap_rs.size() / HeapWordSize),
1336                              G1CardTable::heap_map_factor());
1337 
1338   size_t bitmap_size = G1CMBitMap::compute_size(heap_rs.size());
1339   G1RegionToSpaceMapper* bitmap_storage =
1340     create_aux_memory_mapper("Mark Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1341 
1342   _hrm.initialize(heap_storage, bitmap_storage, bot_storage, cardtable_storage);
1343   _card_table->initialize(cardtable_storage);
1344 
1345   // 6843694 - ensure that the maximum region index can fit
1346   // in the remembered set structures.
1347   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1348   guarantee((max_reserved_regions() - 1) <= max_region_idx, "too many regions");
1349 
1350   // The G1FromCardCache reserves card with value 0 as "invalid", so the heap must not
1351   // start within the first card.
1352   guarantee((uintptr_t)(heap_rs.base()) >= G1CardTable::card_size(), "Java heap must not start within the first card.");
1353   G1FromCardCache::initialize(max_reserved_regions());
1354   // Also create a G1 rem set.
1355   _rem_set = new G1RemSet(this, _card_table);
1356   _rem_set->initialize(max_reserved_regions());
1357 
1358   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1359   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1360   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1361             "too many cards per region");
1362 
1363   HeapRegionRemSet::initialize(_reserved);
1364 
1365   FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
1366 
1367   _bot = new G1BlockOffsetTable(reserved(), bot_storage);
1368 
1369   {
1370     size_t granularity = HeapRegion::GrainBytes;
1371 
1372     _region_attr.initialize(reserved(), granularity);
1373   }
1374 
1375   _workers = new WorkerThreads("GC Thread", ParallelGCThreads);
1376   if (_workers == nullptr) {
1377     return JNI_ENOMEM;
1378   }
1379   _workers->initialize_workers();
1380 
1381   _numa->set_region_info(HeapRegion::GrainBytes, page_size);
1382 
1383   // Create the G1ConcurrentMark data structure and thread.
1384   // (Must do this late, so that "max_[reserved_]regions" is defined.)
1385   _cm = new G1ConcurrentMark(this, bitmap_storage);
1386   _cm_thread = _cm->cm_thread();
1387 
1388   // Now expand into the initial heap size.
1389   if (!expand(init_byte_size, _workers)) {
1390     vm_shutdown_during_initialization("Failed to allocate initial heap.");
1391     return JNI_ENOMEM;
1392   }
1393 
1394   // Perform any initialization actions delegated to the policy.
1395   policy()->init(this, &_collection_set);
1396 
1397   jint ecode = initialize_concurrent_refinement();
1398   if (ecode != JNI_OK) {
1399     return ecode;
1400   }
1401 
1402   ecode = initialize_service_thread();
1403   if (ecode != JNI_OK) {
1404     return ecode;
1405   }
1406 
1407   // Create and schedule the periodic gc task on the service thread.
1408   _periodic_gc_task = new G1PeriodicGCTask("Periodic GC Task");
1409   _service_thread->register_task(_periodic_gc_task);
1410 
1411   _free_arena_memory_task = new G1MonotonicArenaFreeMemoryTask("Card Set Free Memory Task");
1412   _service_thread->register_task(_free_arena_memory_task);
1413 
1414   // Here we allocate the dummy HeapRegion that is required by the
1415   // G1AllocRegion class.
1416   HeapRegion* dummy_region = _hrm.get_dummy_region();
1417 
1418   // We'll re-use the same region whether the alloc region will
1419   // require BOT updates or not and, if it doesn't, then a non-young
1420   // region will complain that it cannot support allocations without
1421   // BOT updates. So we'll tag the dummy region as eden to avoid that.
1422   dummy_region->set_eden();
1423   // Make sure it's full.
1424   dummy_region->set_top(dummy_region->end());
1425   G1AllocRegion::setup(this, dummy_region);
1426 
1427   _allocator->init_mutator_alloc_regions();
1428 
1429   // Do create of the monitoring and management support so that
1430   // values in the heap have been properly initialized.
1431   _monitoring_support = new G1MonitoringSupport(this);
1432 
1433   _collection_set.initialize(max_reserved_regions());
1434 
1435   allocation_failure_injector()->reset();
1436 
1437   CPUTimeCounters::create_counter(CPUTimeGroups::CPUTimeType::gc_parallel_workers);
1438   CPUTimeCounters::create_counter(CPUTimeGroups::CPUTimeType::gc_conc_mark);
1439   CPUTimeCounters::create_counter(CPUTimeGroups::CPUTimeType::gc_conc_refine);
1440   CPUTimeCounters::create_counter(CPUTimeGroups::CPUTimeType::gc_service);
1441 
1442   G1InitLogger::print();
1443 
1444   SlidingForwarding::initialize(heap_rs.region(), HeapRegion::GrainWords);
1445 
1446   return JNI_OK;
1447 }
1448 
1449 bool G1CollectedHeap::concurrent_mark_is_terminating() const {
1450   return _cm_thread->should_terminate();
1451 }
1452 
1453 void G1CollectedHeap::stop() {
1454   // Stop all concurrent threads. We do this to make sure these threads
1455   // do not continue to execute and access resources (e.g. logging)
1456   // that are destroyed during shutdown.
1457   _cr->stop();
1458   _service_thread->stop();
1459   _cm_thread->stop();
1460 }
1461 
1462 void G1CollectedHeap::safepoint_synchronize_begin() {
1463   SuspendibleThreadSet::synchronize();
1464 }
1465 
1466 void G1CollectedHeap::safepoint_synchronize_end() {
1467   SuspendibleThreadSet::desynchronize();
1468 }
1469 
1470 void G1CollectedHeap::post_initialize() {
1471   CollectedHeap::post_initialize();
1472   ref_processing_init();
1473 }
1474 
1475 void G1CollectedHeap::ref_processing_init() {
1476   // Reference processing in G1 currently works as follows:
1477   //
1478   // * There are two reference processor instances. One is
1479   //   used to record and process discovered references
1480   //   during concurrent marking; the other is used to
1481   //   record and process references during STW pauses
1482   //   (both full and incremental).
1483   // * Both ref processors need to 'span' the entire heap as
1484   //   the regions in the collection set may be dotted around.
1485   //
1486   // * For the concurrent marking ref processor:
1487   //   * Reference discovery is enabled at concurrent start.
1488   //   * Reference discovery is disabled and the discovered
1489   //     references processed etc during remarking.
1490   //   * Reference discovery is MT (see below).
1491   //   * Reference discovery requires a barrier (see below).
1492   //   * Reference processing may or may not be MT
1493   //     (depending on the value of ParallelRefProcEnabled
1494   //     and ParallelGCThreads).
1495   //   * A full GC disables reference discovery by the CM
1496   //     ref processor and abandons any entries on it's
1497   //     discovered lists.
1498   //
1499   // * For the STW processor:
1500   //   * Non MT discovery is enabled at the start of a full GC.
1501   //   * Processing and enqueueing during a full GC is non-MT.
1502   //   * During a full GC, references are processed after marking.
1503   //
1504   //   * Discovery (may or may not be MT) is enabled at the start
1505   //     of an incremental evacuation pause.
1506   //   * References are processed near the end of a STW evacuation pause.
1507   //   * For both types of GC:
1508   //     * Discovery is atomic - i.e. not concurrent.
1509   //     * Reference discovery will not need a barrier.
1510 
1511   // Concurrent Mark ref processor
1512   _ref_processor_cm =
1513     new ReferenceProcessor(&_is_subject_to_discovery_cm,
1514                            ParallelGCThreads,                              // degree of mt processing
1515                            // We discover with the gc worker threads during Remark, so both
1516                            // thread counts must be considered for discovery.
1517                            MAX2(ParallelGCThreads, ConcGCThreads),         // degree of mt discovery
1518                            true,                                           // Reference discovery is concurrent
1519                            &_is_alive_closure_cm);                         // is alive closure
1520 
1521   // STW ref processor
1522   _ref_processor_stw =
1523     new ReferenceProcessor(&_is_subject_to_discovery_stw,
1524                            ParallelGCThreads,                    // degree of mt processing
1525                            ParallelGCThreads,                    // degree of mt discovery
1526                            false,                                // Reference discovery is not concurrent
1527                            &_is_alive_closure_stw);              // is alive closure
1528 }
1529 
1530 size_t G1CollectedHeap::capacity() const {
1531   return _hrm.length() * HeapRegion::GrainBytes;
1532 }
1533 
1534 size_t G1CollectedHeap::unused_committed_regions_in_bytes() const {
1535   return _hrm.total_free_bytes();
1536 }
1537 
1538 // Computes the sum of the storage used by the various regions.
1539 size_t G1CollectedHeap::used() const {
1540   size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
1541   return result;
1542 }
1543 
1544 size_t G1CollectedHeap::used_unlocked() const {
1545   return _summary_bytes_used;
1546 }
1547 
1548 class SumUsedClosure: public HeapRegionClosure {
1549   size_t _used;
1550 public:
1551   SumUsedClosure() : _used(0) {}
1552   bool do_heap_region(HeapRegion* r) {
1553     _used += r->used();
1554     return false;
1555   }
1556   size_t result() { return _used; }
1557 };
1558 
1559 size_t G1CollectedHeap::recalculate_used() const {
1560   SumUsedClosure blk;
1561   heap_region_iterate(&blk);
1562   return blk.result();
1563 }
1564 
1565 bool  G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
1566   return GCCause::is_user_requested_gc(cause) && ExplicitGCInvokesConcurrent;
1567 }
1568 
1569 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
1570   switch (cause) {
1571     case GCCause::_g1_humongous_allocation: return true;
1572     case GCCause::_g1_periodic_collection:  return G1PeriodicGCInvokesConcurrent;
1573     case GCCause::_wb_breakpoint:           return true;
1574     case GCCause::_codecache_GC_aggressive: return true;
1575     case GCCause::_codecache_GC_threshold:  return true;
1576     default:                                return is_user_requested_concurrent_full_gc(cause);
1577   }
1578 }
1579 
1580 void G1CollectedHeap::increment_old_marking_cycles_started() {
1581   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
1582          _old_marking_cycles_started == _old_marking_cycles_completed + 1,
1583          "Wrong marking cycle count (started: %d, completed: %d)",
1584          _old_marking_cycles_started, _old_marking_cycles_completed);
1585 
1586   _old_marking_cycles_started++;
1587 }
1588 
1589 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent,
1590                                                              bool whole_heap_examined) {
1591   MonitorLocker ml(G1OldGCCount_lock, Mutex::_no_safepoint_check_flag);
1592 
1593   // We assume that if concurrent == true, then the caller is a
1594   // concurrent thread that was joined the Suspendible Thread
1595   // Set. If there's ever a cheap way to check this, we should add an
1596   // assert here.
1597 
1598   // Given that this method is called at the end of a Full GC or of a
1599   // concurrent cycle, and those can be nested (i.e., a Full GC can
1600   // interrupt a concurrent cycle), the number of full collections
1601   // completed should be either one (in the case where there was no
1602   // nesting) or two (when a Full GC interrupted a concurrent cycle)
1603   // behind the number of full collections started.
1604 
1605   // This is the case for the inner caller, i.e. a Full GC.
1606   assert(concurrent ||
1607          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
1608          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
1609          "for inner caller (Full GC): _old_marking_cycles_started = %u "
1610          "is inconsistent with _old_marking_cycles_completed = %u",
1611          _old_marking_cycles_started, _old_marking_cycles_completed);
1612 
1613   // This is the case for the outer caller, i.e. the concurrent cycle.
1614   assert(!concurrent ||
1615          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
1616          "for outer caller (concurrent cycle): "
1617          "_old_marking_cycles_started = %u "
1618          "is inconsistent with _old_marking_cycles_completed = %u",
1619          _old_marking_cycles_started, _old_marking_cycles_completed);
1620 
1621   _old_marking_cycles_completed += 1;
1622   if (whole_heap_examined) {
1623     // Signal that we have completed a visit to all live objects.
1624     record_whole_heap_examined_timestamp();
1625   }
1626 
1627   // We need to clear the "in_progress" flag in the CM thread before
1628   // we wake up any waiters (especially when ExplicitInvokesConcurrent
1629   // is set) so that if a waiter requests another System.gc() it doesn't
1630   // incorrectly see that a marking cycle is still in progress.
1631   if (concurrent) {
1632     _cm_thread->set_idle();
1633   }
1634 
1635   // Notify threads waiting in System.gc() (with ExplicitGCInvokesConcurrent)
1636   // for a full GC to finish that their wait is over.
1637   ml.notify_all();
1638 }
1639 
1640 // Helper for collect().
1641 static G1GCCounters collection_counters(G1CollectedHeap* g1h) {
1642   MutexLocker ml(Heap_lock);
1643   return G1GCCounters(g1h);
1644 }
1645 
1646 void G1CollectedHeap::collect(GCCause::Cause cause) {
1647   try_collect(cause, collection_counters(this));
1648 }
1649 
1650 // Return true if (x < y) with allowance for wraparound.
1651 static bool gc_counter_less_than(uint x, uint y) {
1652   return (x - y) > (UINT_MAX/2);
1653 }
1654 
1655 // LOG_COLLECT_CONCURRENTLY(cause, msg, args...)
1656 // Macro so msg printing is format-checked.
1657 #define LOG_COLLECT_CONCURRENTLY(cause, ...)                            \
1658   do {                                                                  \
1659     LogTarget(Trace, gc) LOG_COLLECT_CONCURRENTLY_lt;                   \
1660     if (LOG_COLLECT_CONCURRENTLY_lt.is_enabled()) {                     \
1661       ResourceMark rm; /* For thread name. */                           \
1662       LogStream LOG_COLLECT_CONCURRENTLY_s(&LOG_COLLECT_CONCURRENTLY_lt); \
1663       LOG_COLLECT_CONCURRENTLY_s.print("%s: Try Collect Concurrently (%s): ", \
1664                                        Thread::current()->name(),       \
1665                                        GCCause::to_string(cause));      \
1666       LOG_COLLECT_CONCURRENTLY_s.print(__VA_ARGS__);                    \
1667     }                                                                   \
1668   } while (0)
1669 
1670 #define LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, result) \
1671   LOG_COLLECT_CONCURRENTLY(cause, "complete %s", BOOL_TO_STR(result))
1672 
1673 bool G1CollectedHeap::try_collect_concurrently(GCCause::Cause cause,
1674                                                uint gc_counter,
1675                                                uint old_marking_started_before) {
1676   assert_heap_not_locked();
1677   assert(should_do_concurrent_full_gc(cause),
1678          "Non-concurrent cause %s", GCCause::to_string(cause));
1679 
1680   for (uint i = 1; true; ++i) {
1681     // Try to schedule concurrent start evacuation pause that will
1682     // start a concurrent cycle.
1683     LOG_COLLECT_CONCURRENTLY(cause, "attempt %u", i);
1684     VM_G1TryInitiateConcMark op(gc_counter, cause);
1685     VMThread::execute(&op);
1686 
1687     // Request is trivially finished.
1688     if (cause == GCCause::_g1_periodic_collection) {
1689       LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, op.gc_succeeded());
1690       return op.gc_succeeded();
1691     }
1692 
1693     // If VMOp skipped initiating concurrent marking cycle because
1694     // we're terminating, then we're done.
1695     if (op.terminating()) {
1696       LOG_COLLECT_CONCURRENTLY(cause, "skipped: terminating");
1697       return false;
1698     }
1699 
1700     // Lock to get consistent set of values.
1701     uint old_marking_started_after;
1702     uint old_marking_completed_after;
1703     {
1704       MutexLocker ml(Heap_lock);
1705       // Update gc_counter for retrying VMOp if needed. Captured here to be
1706       // consistent with the values we use below for termination tests.  If
1707       // a retry is needed after a possible wait, and another collection
1708       // occurs in the meantime, it will cause our retry to be skipped and
1709       // we'll recheck for termination with updated conditions from that
1710       // more recent collection.  That's what we want, rather than having
1711       // our retry possibly perform an unnecessary collection.
1712       gc_counter = total_collections();
1713       old_marking_started_after = _old_marking_cycles_started;
1714       old_marking_completed_after = _old_marking_cycles_completed;
1715     }
1716 
1717     if (cause == GCCause::_wb_breakpoint) {
1718       if (op.gc_succeeded()) {
1719         LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, true);
1720         return true;
1721       }
1722       // When _wb_breakpoint there can't be another cycle or deferred.
1723       assert(!op.cycle_already_in_progress(), "invariant");
1724       assert(!op.whitebox_attached(), "invariant");
1725       // Concurrent cycle attempt might have been cancelled by some other
1726       // collection, so retry.  Unlike other cases below, we want to retry
1727       // even if cancelled by a STW full collection, because we really want
1728       // to start a concurrent cycle.
1729       if (old_marking_started_before != old_marking_started_after) {
1730         LOG_COLLECT_CONCURRENTLY(cause, "ignoring STW full GC");
1731         old_marking_started_before = old_marking_started_after;
1732       }
1733     } else if (!GCCause::is_user_requested_gc(cause)) {
1734       // For an "automatic" (not user-requested) collection, we just need to
1735       // ensure that progress is made.
1736       //
1737       // Request is finished if any of
1738       // (1) the VMOp successfully performed a GC,
1739       // (2) a concurrent cycle was already in progress,
1740       // (3) whitebox is controlling concurrent cycles,
1741       // (4) a new cycle was started (by this thread or some other), or
1742       // (5) a Full GC was performed.
1743       // Cases (4) and (5) are detected together by a change to
1744       // _old_marking_cycles_started.
1745       //
1746       // Note that (1) does not imply (4).  If we're still in the mixed
1747       // phase of an earlier concurrent collection, the request to make the
1748       // collection a concurrent start won't be honored.  If we don't check for
1749       // both conditions we'll spin doing back-to-back collections.
1750       if (op.gc_succeeded() ||
1751           op.cycle_already_in_progress() ||
1752           op.whitebox_attached() ||
1753           (old_marking_started_before != old_marking_started_after)) {
1754         LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, true);
1755         return true;
1756       }
1757     } else {                    // User-requested GC.
1758       // For a user-requested collection, we want to ensure that a complete
1759       // full collection has been performed before returning, but without
1760       // waiting for more than needed.
1761 
1762       // For user-requested GCs (unlike non-UR), a successful VMOp implies a
1763       // new cycle was started.  That's good, because it's not clear what we
1764       // should do otherwise.  Trying again just does back to back GCs.
1765       // Can't wait for someone else to start a cycle.  And returning fails
1766       // to meet the goal of ensuring a full collection was performed.
1767       assert(!op.gc_succeeded() ||
1768              (old_marking_started_before != old_marking_started_after),
1769              "invariant: succeeded %s, started before %u, started after %u",
1770              BOOL_TO_STR(op.gc_succeeded()),
1771              old_marking_started_before, old_marking_started_after);
1772 
1773       // Request is finished if a full collection (concurrent or stw)
1774       // was started after this request and has completed, e.g.
1775       // started_before < completed_after.
1776       if (gc_counter_less_than(old_marking_started_before,
1777                                old_marking_completed_after)) {
1778         LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, true);
1779         return true;
1780       }
1781 
1782       if (old_marking_started_after != old_marking_completed_after) {
1783         // If there is an in-progress cycle (possibly started by us), then
1784         // wait for that cycle to complete, e.g.
1785         // while completed_now < started_after.
1786         LOG_COLLECT_CONCURRENTLY(cause, "wait");
1787         MonitorLocker ml(G1OldGCCount_lock);
1788         while (gc_counter_less_than(_old_marking_cycles_completed,
1789                                     old_marking_started_after)) {
1790           ml.wait();
1791         }
1792         // Request is finished if the collection we just waited for was
1793         // started after this request.
1794         if (old_marking_started_before != old_marking_started_after) {
1795           LOG_COLLECT_CONCURRENTLY(cause, "complete after wait");
1796           return true;
1797         }
1798       }
1799 
1800       // If VMOp was successful then it started a new cycle that the above
1801       // wait &etc should have recognized as finishing this request.  This
1802       // differs from a non-user-request, where gc_succeeded does not imply
1803       // a new cycle was started.
1804       assert(!op.gc_succeeded(), "invariant");
1805 
1806       if (op.cycle_already_in_progress()) {
1807         // If VMOp failed because a cycle was already in progress, it
1808         // is now complete.  But it didn't finish this user-requested
1809         // GC, so try again.
1810         LOG_COLLECT_CONCURRENTLY(cause, "retry after in-progress");
1811         continue;
1812       } else if (op.whitebox_attached()) {
1813         // If WhiteBox wants control, wait for notification of a state
1814         // change in the controller, then try again.  Don't wait for
1815         // release of control, since collections may complete while in
1816         // control.  Note: This won't recognize a STW full collection
1817         // while waiting; we can't wait on multiple monitors.
1818         LOG_COLLECT_CONCURRENTLY(cause, "whitebox control stall");
1819         MonitorLocker ml(ConcurrentGCBreakpoints::monitor());
1820         if (ConcurrentGCBreakpoints::is_controlled()) {
1821           ml.wait();
1822         }
1823         continue;
1824       }
1825     }
1826 
1827     // Collection failed and should be retried.
1828     assert(op.transient_failure(), "invariant");
1829 
1830     LOG_COLLECT_CONCURRENTLY(cause, "retry");
1831   }
1832 }
1833 
1834 bool G1CollectedHeap::try_collect_fullgc(GCCause::Cause cause,
1835                                          const G1GCCounters& counters_before) {
1836   assert_heap_not_locked();
1837 
1838   while(true) {
1839     VM_G1CollectFull op(counters_before.total_collections(),
1840                         counters_before.total_full_collections(),
1841                         cause);
1842     VMThread::execute(&op);
1843 
1844     // Request is trivially finished.
1845     if (!GCCause::is_explicit_full_gc(cause) || op.gc_succeeded()) {
1846       return op.gc_succeeded();
1847     }
1848 
1849     {
1850       MutexLocker ml(Heap_lock);
1851       if (counters_before.total_full_collections() != total_full_collections()) {
1852         return true;
1853       }
1854     }
1855   }
1856 }
1857 
1858 bool G1CollectedHeap::try_collect(GCCause::Cause cause,
1859                                   const G1GCCounters& counters_before) {
1860   if (should_do_concurrent_full_gc(cause)) {
1861     return try_collect_concurrently(cause,
1862                                     counters_before.total_collections(),
1863                                     counters_before.old_marking_cycles_started());
1864   } else if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
1865              DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
1866 
1867     // Schedule a standard evacuation pause. We're setting word_size
1868     // to 0 which means that we are not requesting a post-GC allocation.
1869     VM_G1CollectForAllocation op(0,     /* word_size */
1870                                  counters_before.total_collections(),
1871                                  cause);
1872     VMThread::execute(&op);
1873     return op.gc_succeeded();
1874   } else {
1875     // Schedule a Full GC.
1876     return try_collect_fullgc(cause, counters_before);
1877   }
1878 }
1879 
1880 void G1CollectedHeap::start_concurrent_gc_for_metadata_allocation(GCCause::Cause gc_cause) {
1881   GCCauseSetter x(this, gc_cause);
1882 
1883   // At this point we are supposed to start a concurrent cycle. We
1884   // will do so if one is not already in progress.
1885   bool should_start = policy()->force_concurrent_start_if_outside_cycle(gc_cause);
1886   if (should_start) {
1887     do_collection_pause_at_safepoint();
1888   }
1889 }
1890 
1891 bool G1CollectedHeap::is_in(const void* p) const {
1892   return is_in_reserved(p) && _hrm.is_available(addr_to_region(p));
1893 }
1894 
1895 // Iteration functions.
1896 
1897 // Iterates an ObjectClosure over all objects within a HeapRegion.
1898 
1899 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
1900   ObjectClosure* _cl;
1901 public:
1902   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
1903   bool do_heap_region(HeapRegion* r) {
1904     if (!r->is_continues_humongous()) {
1905       r->object_iterate(_cl);
1906     }
1907     return false;
1908   }
1909 };
1910 
1911 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
1912   IterateObjectClosureRegionClosure blk(cl);
1913   heap_region_iterate(&blk);
1914 }
1915 
1916 class G1ParallelObjectIterator : public ParallelObjectIteratorImpl {
1917 private:
1918   G1CollectedHeap*  _heap;
1919   HeapRegionClaimer _claimer;
1920 
1921 public:
1922   G1ParallelObjectIterator(uint thread_num) :
1923       _heap(G1CollectedHeap::heap()),
1924       _claimer(thread_num == 0 ? G1CollectedHeap::heap()->workers()->active_workers() : thread_num) {}
1925 
1926   virtual void object_iterate(ObjectClosure* cl, uint worker_id) {
1927     _heap->object_iterate_parallel(cl, worker_id, &_claimer);
1928   }
1929 };
1930 
1931 ParallelObjectIteratorImpl* G1CollectedHeap::parallel_object_iterator(uint thread_num) {
1932   return new G1ParallelObjectIterator(thread_num);
1933 }
1934 
1935 void G1CollectedHeap::object_iterate_parallel(ObjectClosure* cl, uint worker_id, HeapRegionClaimer* claimer) {
1936   IterateObjectClosureRegionClosure blk(cl);
1937   heap_region_par_iterate_from_worker_offset(&blk, claimer, worker_id);
1938 }
1939 
1940 void G1CollectedHeap::keep_alive(oop obj) {
1941   G1BarrierSet::enqueue_preloaded(obj);
1942 }
1943 
1944 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
1945   _hrm.iterate(cl);
1946 }
1947 
1948 void G1CollectedHeap::heap_region_iterate(HeapRegionIndexClosure* cl) const {
1949   _hrm.iterate(cl);
1950 }
1951 
1952 void G1CollectedHeap::heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl,
1953                                                                  HeapRegionClaimer *hrclaimer,
1954                                                                  uint worker_id) const {
1955   _hrm.par_iterate(cl, hrclaimer, hrclaimer->offset_for_worker(worker_id));
1956 }
1957 
1958 void G1CollectedHeap::heap_region_par_iterate_from_start(HeapRegionClosure* cl,
1959                                                          HeapRegionClaimer *hrclaimer) const {
1960   _hrm.par_iterate(cl, hrclaimer, 0);
1961 }
1962 
1963 void G1CollectedHeap::collection_set_iterate_all(HeapRegionClosure* cl) {
1964   _collection_set.iterate(cl);
1965 }
1966 
1967 void G1CollectedHeap::collection_set_par_iterate_all(HeapRegionClosure* cl,
1968                                                      HeapRegionClaimer* hr_claimer,
1969                                                      uint worker_id) {
1970   _collection_set.par_iterate(cl, hr_claimer, worker_id);
1971 }
1972 
1973 void G1CollectedHeap::collection_set_iterate_increment_from(HeapRegionClosure *cl,
1974                                                             HeapRegionClaimer* hr_claimer,
1975                                                             uint worker_id) {
1976   _collection_set.iterate_incremental_part_from(cl, hr_claimer, worker_id);
1977 }
1978 
1979 void G1CollectedHeap::par_iterate_regions_array(HeapRegionClosure* cl,
1980                                                 HeapRegionClaimer* hr_claimer,
1981                                                 const uint regions[],
1982                                                 size_t length,
1983                                                 uint worker_id) const {
1984   assert_at_safepoint();
1985   if (length == 0) {
1986     return;
1987   }
1988   uint total_workers = workers()->active_workers();
1989 
1990   size_t start_pos = (worker_id * length) / total_workers;
1991   size_t cur_pos = start_pos;
1992 
1993   do {
1994     uint region_idx = regions[cur_pos];
1995     if (hr_claimer == nullptr || hr_claimer->claim_region(region_idx)) {
1996       HeapRegion* r = region_at(region_idx);
1997       bool result = cl->do_heap_region(r);
1998       guarantee(!result, "Must not cancel iteration");
1999     }
2000 
2001     cur_pos++;
2002     if (cur_pos == length) {
2003       cur_pos = 0;
2004     }
2005   } while (cur_pos != start_pos);
2006 }
2007 
2008 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2009   HeapRegion* hr = heap_region_containing(addr);
2010   // The CollectedHeap API requires us to not fail for any given address within
2011   // the heap. HeapRegion::block_start() has been optimized to not accept addresses
2012   // outside of the allocated area.
2013   if (addr >= hr->top()) {
2014     return nullptr;
2015   }
2016   return hr->block_start(addr);
2017 }
2018 
2019 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2020   HeapRegion* hr = heap_region_containing(addr);
2021   return hr->block_is_obj(addr, hr->parsable_bottom_acquire());
2022 }
2023 
2024 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2025   return (_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes;
2026 }
2027 
2028 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2029   return _eden.length() * HeapRegion::GrainBytes;
2030 }
2031 
2032 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2033 // must be equal to the humongous object limit.
2034 size_t G1CollectedHeap::max_tlab_size() const {
2035   return align_down(_humongous_object_threshold_in_words, MinObjAlignment);
2036 }
2037 
2038 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2039   return _allocator->unsafe_max_tlab_alloc();
2040 }
2041 
2042 size_t G1CollectedHeap::max_capacity() const {
2043   return max_regions() * HeapRegion::GrainBytes;
2044 }
2045 
2046 void G1CollectedHeap::prepare_for_verify() {
2047   _verifier->prepare_for_verify();
2048 }
2049 
2050 void G1CollectedHeap::verify(VerifyOption vo) {
2051   _verifier->verify(vo);
2052 }
2053 
2054 bool G1CollectedHeap::supports_concurrent_gc_breakpoints() const {
2055   return true;
2056 }
2057 
2058 class PrintRegionClosure: public HeapRegionClosure {
2059   outputStream* _st;
2060 public:
2061   PrintRegionClosure(outputStream* st) : _st(st) {}
2062   bool do_heap_region(HeapRegion* r) {
2063     r->print_on(_st);
2064     return false;
2065   }
2066 };
2067 
2068 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2069                                        const HeapRegion* hr,
2070                                        const VerifyOption vo) const {
2071   switch (vo) {
2072     case VerifyOption::G1UseConcMarking: return is_obj_dead(obj, hr);
2073     case VerifyOption::G1UseFullMarking: return is_obj_dead_full(obj, hr);
2074     default:                             ShouldNotReachHere();
2075   }
2076   return false; // keep some compilers happy
2077 }
2078 
2079 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2080                                        const VerifyOption vo) const {
2081   switch (vo) {
2082     case VerifyOption::G1UseConcMarking: return is_obj_dead(obj);
2083     case VerifyOption::G1UseFullMarking: return is_obj_dead_full(obj);
2084     default:                             ShouldNotReachHere();
2085   }
2086   return false; // keep some compilers happy
2087 }
2088 
2089 void G1CollectedHeap::print_heap_regions() const {
2090   LogTarget(Trace, gc, heap, region) lt;
2091   if (lt.is_enabled()) {
2092     LogStream ls(lt);
2093     print_regions_on(&ls);
2094   }
2095 }
2096 
2097 void G1CollectedHeap::print_on(outputStream* st) const {
2098   size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
2099   st->print(" %-20s", "garbage-first heap");
2100   st->print(" total reserved %zuK, committed %zuK, used %zuK",
2101             _hrm.reserved().byte_size()/K, capacity()/K, heap_used/K);
2102   st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")",
2103             p2i(_hrm.reserved().start()),
2104             p2i(_hrm.reserved().end()));
2105   st->cr();
2106   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
2107   uint young_regions = young_regions_count();
2108   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
2109             (size_t) young_regions * HeapRegion::GrainBytes / K);
2110   uint survivor_regions = survivor_regions_count();
2111   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
2112             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
2113   st->cr();
2114   if (_numa->is_enabled()) {
2115     uint num_nodes = _numa->num_active_nodes();
2116     st->print("  remaining free region(s) on each NUMA node: ");
2117     const uint* node_ids = _numa->node_ids();
2118     for (uint node_index = 0; node_index < num_nodes; node_index++) {
2119       uint num_free_regions = _hrm.num_free_regions(node_index);
2120       st->print("%u=%u ", node_ids[node_index], num_free_regions);
2121     }
2122     st->cr();
2123   }
2124   MetaspaceUtils::print_on(st);
2125 }
2126 
2127 void G1CollectedHeap::print_regions_on(outputStream* st) const {
2128   st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
2129                "HS=humongous(starts), HC=humongous(continues), "
2130                "CS=collection set, F=free, "
2131                "TAMS=top-at-mark-start, "
2132                "PB=parsable bottom");
2133   PrintRegionClosure blk(st);
2134   heap_region_iterate(&blk);
2135 }
2136 
2137 void G1CollectedHeap::print_extended_on(outputStream* st) const {
2138   print_on(st);
2139 
2140   // Print the per-region information.
2141   st->cr();
2142   print_regions_on(st);
2143 }
2144 
2145 void G1CollectedHeap::print_on_error(outputStream* st) const {
2146   this->CollectedHeap::print_on_error(st);
2147 
2148   if (_cm != nullptr) {
2149     st->cr();
2150     _cm->print_on_error(st);
2151   }
2152 }
2153 
2154 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2155   workers()->threads_do(tc);
2156   tc->do_thread(_cm_thread);
2157   _cm->threads_do(tc);
2158   _cr->threads_do(tc);
2159   tc->do_thread(_service_thread);
2160 }
2161 
2162 void G1CollectedHeap::print_tracing_info() const {
2163   rem_set()->print_summary_info();
2164   concurrent_mark()->print_summary_info();
2165 }
2166 
2167 bool G1CollectedHeap::print_location(outputStream* st, void* addr) const {
2168   return BlockLocationPrinter<G1CollectedHeap>::print_location(st, addr);
2169 }
2170 
2171 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
2172 
2173   size_t eden_used_bytes = _monitoring_support->eden_space_used();
2174   size_t survivor_used_bytes = _monitoring_support->survivor_space_used();
2175   size_t old_gen_used_bytes = _monitoring_support->old_gen_used();
2176   size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
2177 
2178   size_t eden_capacity_bytes =
2179     (policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
2180 
2181   VirtualSpaceSummary heap_summary = create_heap_space_summary();
2182   return G1HeapSummary(heap_summary, heap_used, eden_used_bytes, eden_capacity_bytes,
2183                        survivor_used_bytes, old_gen_used_bytes, num_regions());
2184 }
2185 
2186 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
2187   return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
2188                        stats->unused(), stats->used(), stats->region_end_waste(),
2189                        stats->regions_filled(), stats->num_plab_filled(),
2190                        stats->direct_allocated(), stats->num_direct_allocated(),
2191                        stats->failure_used(), stats->failure_waste());
2192 }
2193 
2194 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
2195   const G1HeapSummary& heap_summary = create_g1_heap_summary();
2196   gc_tracer->report_gc_heap_summary(when, heap_summary);
2197 
2198   const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
2199   gc_tracer->report_metaspace_summary(when, metaspace_summary);
2200 }
2201 
2202 void G1CollectedHeap::gc_prologue(bool full) {
2203   // Update common counters.
2204   increment_total_collections(full /* full gc */);
2205   if (full || collector_state()->in_concurrent_start_gc()) {
2206     increment_old_marking_cycles_started();
2207   }
2208 }
2209 
2210 void G1CollectedHeap::gc_epilogue(bool full) {
2211   // Update common counters.
2212   if (full) {
2213     // Update the number of full collections that have been completed.
2214     increment_old_marking_cycles_completed(false /* concurrent */, true /* liveness_completed */);
2215   }
2216 
2217 #if COMPILER2_OR_JVMCI
2218   assert(DerivedPointerTable::is_empty(), "derived pointer present");
2219 #endif
2220 
2221   // We have just completed a GC. Update the soft reference
2222   // policy with the new heap occupancy
2223   Universe::heap()->update_capacity_and_used_at_gc();
2224 
2225   _collection_pause_end = Ticks::now();
2226 
2227   _free_arena_memory_task->notify_new_stats(&_young_gen_card_set_stats,
2228                                             &_collection_set_candidates_card_set_stats);
2229 
2230   update_parallel_gc_threads_cpu_time();
2231 }
2232 
2233 uint G1CollectedHeap::uncommit_regions(uint region_limit) {
2234   return _hrm.uncommit_inactive_regions(region_limit);
2235 }
2236 
2237 bool G1CollectedHeap::has_uncommittable_regions() {
2238   return _hrm.has_inactive_regions();
2239 }
2240 
2241 void G1CollectedHeap::uncommit_regions_if_necessary() {
2242   if (has_uncommittable_regions()) {
2243     G1UncommitRegionTask::enqueue();
2244   }
2245 }
2246 
2247 void G1CollectedHeap::verify_numa_regions(const char* desc) {
2248   LogTarget(Trace, gc, heap, verify) lt;
2249 
2250   if (lt.is_enabled()) {
2251     LogStream ls(lt);
2252     // Iterate all heap regions to print matching between preferred numa id and actual numa id.
2253     G1NodeIndexCheckClosure cl(desc, _numa, &ls);
2254     heap_region_iterate(&cl);
2255   }
2256 }
2257 
2258 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2259                                                uint gc_count_before,
2260                                                bool* succeeded,
2261                                                GCCause::Cause gc_cause) {
2262   assert_heap_not_locked_and_not_at_safepoint();
2263   VM_G1CollectForAllocation op(word_size, gc_count_before, gc_cause);
2264   VMThread::execute(&op);
2265 
2266   HeapWord* result = op.result();
2267   bool ret_succeeded = op.prologue_succeeded() && op.gc_succeeded();
2268   assert(result == nullptr || ret_succeeded,
2269          "the result should be null if the VM did not succeed");
2270   *succeeded = ret_succeeded;
2271 
2272   assert_heap_not_locked();
2273   return result;
2274 }
2275 
2276 void G1CollectedHeap::start_concurrent_cycle(bool concurrent_operation_is_full_mark) {
2277   assert(!_cm_thread->in_progress(), "Can not start concurrent operation while in progress");
2278 
2279   MutexLocker x(CGC_lock, Mutex::_no_safepoint_check_flag);
2280   if (concurrent_operation_is_full_mark) {
2281     _cm->post_concurrent_mark_start();
2282     _cm_thread->start_full_mark();
2283   } else {
2284     _cm->post_concurrent_undo_start();
2285     _cm_thread->start_undo_mark();
2286   }
2287   CGC_lock->notify();
2288 }
2289 
2290 bool G1CollectedHeap::is_potential_eager_reclaim_candidate(HeapRegion* r) const {
2291   // We don't nominate objects with many remembered set entries, on
2292   // the assumption that such objects are likely still live.
2293   HeapRegionRemSet* rem_set = r->rem_set();
2294 
2295   return rem_set->occupancy_less_or_equal_than(G1EagerReclaimRemSetThreshold);
2296 }
2297 
2298 #ifndef PRODUCT
2299 void G1CollectedHeap::verify_region_attr_remset_is_tracked() {
2300   class VerifyRegionAttrRemSet : public HeapRegionClosure {
2301   public:
2302     virtual bool do_heap_region(HeapRegion* r) {
2303       G1CollectedHeap* g1h = G1CollectedHeap::heap();
2304       bool const remset_is_tracked = g1h->region_attr(r->bottom()).remset_is_tracked();
2305       assert(r->rem_set()->is_tracked() == remset_is_tracked,
2306              "Region %u remset tracking status (%s) different to region attribute (%s)",
2307              r->hrm_index(), BOOL_TO_STR(r->rem_set()->is_tracked()), BOOL_TO_STR(remset_is_tracked));
2308       return false;
2309     }
2310   } cl;
2311   heap_region_iterate(&cl);
2312 }
2313 #endif
2314 
2315 void G1CollectedHeap::update_parallel_gc_threads_cpu_time() {
2316   assert(Thread::current()->is_VM_thread(),
2317          "Must be called from VM thread to avoid races");
2318   if (!UsePerfData || !os::is_thread_cpu_time_supported()) {
2319     return;
2320   }
2321 
2322   // Ensure ThreadTotalCPUTimeClosure destructor is called before publishing gc
2323   // time.
2324   {
2325     ThreadTotalCPUTimeClosure tttc(CPUTimeGroups::CPUTimeType::gc_parallel_workers);
2326     // Currently parallel worker threads never terminate (JDK-8081682), so it is
2327     // safe for VMThread to read their CPU times. However, if JDK-8087340 is
2328     // resolved so they terminate, we should rethink if it is still safe.
2329     workers()->threads_do(&tttc);
2330   }
2331 
2332   CPUTimeCounters::publish_gc_total_cpu_time();
2333 }
2334 
2335 void G1CollectedHeap::start_new_collection_set() {
2336   collection_set()->start_incremental_building();
2337 
2338   clear_region_attr();
2339 
2340   guarantee(_eden.length() == 0, "eden should have been cleared");
2341   policy()->transfer_survivors_to_cset(survivor());
2342 
2343   // We redo the verification but now wrt to the new CSet which
2344   // has just got initialized after the previous CSet was freed.
2345   _cm->verify_no_collection_set_oops();
2346 }
2347 
2348 G1HeapVerifier::G1VerifyType G1CollectedHeap::young_collection_verify_type() const {
2349   if (collector_state()->in_concurrent_start_gc()) {
2350     return G1HeapVerifier::G1VerifyConcurrentStart;
2351   } else if (collector_state()->in_young_only_phase()) {
2352     return G1HeapVerifier::G1VerifyYoungNormal;
2353   } else {
2354     return G1HeapVerifier::G1VerifyMixed;
2355   }
2356 }
2357 
2358 void G1CollectedHeap::verify_before_young_collection(G1HeapVerifier::G1VerifyType type) {
2359   if (!VerifyBeforeGC) {
2360     return;
2361   }
2362   if (!G1HeapVerifier::should_verify(type)) {
2363     return;
2364   }
2365   Ticks start = Ticks::now();
2366   _verifier->prepare_for_verify();
2367   _verifier->verify_region_sets_optional();
2368   _verifier->verify_dirty_young_regions();
2369   _verifier->verify_before_gc();
2370   verify_numa_regions("GC Start");
2371   phase_times()->record_verify_before_time_ms((Ticks::now() - start).seconds() * MILLIUNITS);
2372 }
2373 
2374 void G1CollectedHeap::verify_after_young_collection(G1HeapVerifier::G1VerifyType type) {
2375   if (!VerifyAfterGC) {
2376     return;
2377   }
2378   if (!G1HeapVerifier::should_verify(type)) {
2379     return;
2380   }
2381   Ticks start = Ticks::now();
2382   _verifier->verify_after_gc();
2383   verify_numa_regions("GC End");
2384   _verifier->verify_region_sets_optional();
2385 
2386   if (collector_state()->in_concurrent_start_gc()) {
2387     log_debug(gc, verify)("Marking state");
2388     _verifier->verify_marking_state();
2389   }
2390 
2391   phase_times()->record_verify_after_time_ms((Ticks::now() - start).seconds() * MILLIUNITS);
2392 }
2393 
2394 void G1CollectedHeap::expand_heap_after_young_collection(){
2395   size_t expand_bytes = _heap_sizing_policy->young_collection_expansion_amount();
2396   if (expand_bytes > 0) {
2397     // No need for an ergo logging here,
2398     // expansion_amount() does this when it returns a value > 0.
2399     double expand_ms = 0.0;
2400     if (!expand(expand_bytes, _workers, &expand_ms)) {
2401       // We failed to expand the heap. Cannot do anything about it.
2402     }
2403     phase_times()->record_expand_heap_time(expand_ms);
2404   }
2405 }
2406 
2407 bool G1CollectedHeap::do_collection_pause_at_safepoint() {
2408   assert_at_safepoint_on_vm_thread();
2409   guarantee(!is_gc_active(), "collection is not reentrant");
2410 
2411   do_collection_pause_at_safepoint_helper();
2412   return true;
2413 }
2414 
2415 G1HeapPrinterMark::G1HeapPrinterMark(G1CollectedHeap* g1h) : _g1h(g1h), _heap_transition(g1h) {
2416   // This summary needs to be printed before incrementing total collections.
2417   _g1h->rem_set()->print_periodic_summary_info("Before GC RS summary",
2418                                                _g1h->total_collections(),
2419                                                true /* show_thread_times */);
2420   _g1h->print_heap_before_gc();
2421   _g1h->print_heap_regions();
2422 }
2423 
2424 G1HeapPrinterMark::~G1HeapPrinterMark() {
2425   _g1h->policy()->print_age_table();
2426   _g1h->rem_set()->print_coarsen_stats();
2427   // We are at the end of the GC. Total collections has already been increased.
2428   _g1h->rem_set()->print_periodic_summary_info("After GC RS summary",
2429                                                _g1h->total_collections() - 1,
2430                                                false /* show_thread_times */);
2431 
2432   _heap_transition.print();
2433   _g1h->print_heap_regions();
2434   _g1h->print_heap_after_gc();
2435   // Print NUMA statistics.
2436   _g1h->numa()->print_statistics();
2437 }
2438 
2439 G1JFRTracerMark::G1JFRTracerMark(STWGCTimer* timer, GCTracer* tracer) :
2440   _timer(timer), _tracer(tracer) {
2441 
2442   _timer->register_gc_start();
2443   _tracer->report_gc_start(G1CollectedHeap::heap()->gc_cause(), _timer->gc_start());
2444   G1CollectedHeap::heap()->trace_heap_before_gc(_tracer);
2445 }
2446 
2447 G1JFRTracerMark::~G1JFRTracerMark() {
2448   G1CollectedHeap::heap()->trace_heap_after_gc(_tracer);
2449   _timer->register_gc_end();
2450   _tracer->report_gc_end(_timer->gc_end(), _timer->time_partitions());
2451 }
2452 
2453 void G1CollectedHeap::prepare_for_mutator_after_young_collection() {
2454   Ticks start = Ticks::now();
2455 
2456   _survivor_evac_stats.adjust_desired_plab_size();
2457   _old_evac_stats.adjust_desired_plab_size();
2458 
2459   // Start a new incremental collection set for the mutator phase.
2460   start_new_collection_set();
2461   _allocator->init_mutator_alloc_regions();
2462 
2463   phase_times()->record_prepare_for_mutator_time_ms((Ticks::now() - start).seconds() * 1000.0);
2464 }
2465 
2466 void G1CollectedHeap::retire_tlabs() {
2467   ensure_parsability(true);
2468 }
2469 
2470 void G1CollectedHeap::flush_region_pin_cache() {
2471   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *thread = jtiwh.next(); ) {
2472     G1ThreadLocalData::pin_count_cache(thread).flush();
2473   }
2474 }
2475 
2476 void G1CollectedHeap::do_collection_pause_at_safepoint_helper() {
2477   ResourceMark rm;
2478 
2479   IsGCActiveMark active_gc_mark;
2480   GCIdMark gc_id_mark;
2481   SvcGCMarker sgcm(SvcGCMarker::MINOR);
2482 
2483   GCTraceCPUTime tcpu(_gc_tracer_stw);
2484 
2485   _bytes_used_during_gc = 0;
2486 
2487   policy()->decide_on_concurrent_start_pause();
2488   // Record whether this pause may need to trigger a concurrent operation. Later,
2489   // when we signal the G1ConcurrentMarkThread, the collector state has already
2490   // been reset for the next pause.
2491   bool should_start_concurrent_mark_operation = collector_state()->in_concurrent_start_gc();
2492 
2493   // Perform the collection.
2494   G1YoungCollector collector(gc_cause());
2495   collector.collect();
2496 
2497   // It should now be safe to tell the concurrent mark thread to start
2498   // without its logging output interfering with the logging output
2499   // that came from the pause.
2500   if (should_start_concurrent_mark_operation) {
2501     verifier()->verify_bitmap_clear(true /* above_tams_only */);
2502     // CAUTION: after the start_concurrent_cycle() call below, the concurrent marking
2503     // thread(s) could be running concurrently with us. Make sure that anything
2504     // after this point does not assume that we are the only GC thread running.
2505     // Note: of course, the actual marking work will not start until the safepoint
2506     // itself is released in SuspendibleThreadSet::desynchronize().
2507     start_concurrent_cycle(collector.concurrent_operation_is_full_mark());
2508     ConcurrentGCBreakpoints::notify_idle_to_active();
2509   }
2510 }
2511 
2512 void G1CollectedHeap::complete_cleaning(bool class_unloading_occurred) {
2513   uint num_workers = workers()->active_workers();
2514   G1ParallelCleaningTask unlink_task(num_workers, class_unloading_occurred);
2515   workers()->run_task(&unlink_task);
2516 }
2517 
2518 void G1CollectedHeap::unload_classes_and_code(const char* description, BoolObjectClosure* is_alive, GCTimer* timer) {
2519   GCTraceTime(Debug, gc, phases) debug(description, timer);
2520 
2521   ClassUnloadingContext ctx(workers()->active_workers(),
2522                             false /* unregister_nmethods_during_purge */,
2523                             false /* lock_codeblob_free_separately */);
2524   {
2525     CodeCache::UnlinkingScope scope(is_alive);
2526     bool unloading_occurred = SystemDictionary::do_unloading(timer);
2527     GCTraceTime(Debug, gc, phases) t("G1 Complete Cleaning", timer);
2528     complete_cleaning(unloading_occurred);
2529   }
2530   {
2531     GCTraceTime(Debug, gc, phases) t("Purge Unlinked NMethods", timer);
2532     ctx.purge_nmethods();
2533   }
2534   {
2535     GCTraceTime(Debug, gc, phases) ur("Unregister NMethods", timer);
2536     G1CollectedHeap::heap()->bulk_unregister_nmethods();
2537   }
2538   {
2539     GCTraceTime(Debug, gc, phases) t("Free Code Blobs", timer);
2540     ctx.free_code_blobs();
2541   }
2542   {
2543     GCTraceTime(Debug, gc, phases) t("Purge Class Loader Data", timer);
2544     ClassLoaderDataGraph::purge(true /* at_safepoint */);
2545     DEBUG_ONLY(MetaspaceUtils::verify();)
2546   }
2547 }
2548 
2549 class G1BulkUnregisterNMethodTask : public WorkerTask {
2550   HeapRegionClaimer _hrclaimer;
2551 
2552   class UnregisterNMethodsHeapRegionClosure : public HeapRegionClosure {
2553   public:
2554 
2555     bool do_heap_region(HeapRegion* hr) {
2556       hr->rem_set()->bulk_remove_code_roots();
2557       return false;
2558     }
2559   } _cl;
2560 
2561 public:
2562   G1BulkUnregisterNMethodTask(uint num_workers)
2563   : WorkerTask("G1 Remove Unlinked NMethods From Code Root Set Task"),
2564     _hrclaimer(num_workers) { }
2565 
2566   void work(uint worker_id) {
2567     G1CollectedHeap::heap()->heap_region_par_iterate_from_worker_offset(&_cl, &_hrclaimer, worker_id);
2568   }
2569 };
2570 
2571 void G1CollectedHeap::bulk_unregister_nmethods() {
2572   uint num_workers = workers()->active_workers();
2573   G1BulkUnregisterNMethodTask t(num_workers);
2574   workers()->run_task(&t);
2575 }
2576 
2577 bool G1STWSubjectToDiscoveryClosure::do_object_b(oop obj) {
2578   assert(obj != nullptr, "must not be null");
2579   assert(_g1h->is_in_reserved(obj), "Trying to discover obj " PTR_FORMAT " not in heap", p2i(obj));
2580   // The areas the CM and STW ref processor manage must be disjoint. The is_in_cset() below
2581   // may falsely indicate that this is not the case here: however the collection set only
2582   // contains old regions when concurrent mark is not running.
2583   return _g1h->is_in_cset(obj) || _g1h->heap_region_containing(obj)->is_survivor();
2584 }
2585 
2586 void G1CollectedHeap::make_pending_list_reachable() {
2587   if (collector_state()->in_concurrent_start_gc()) {
2588     oop pll_head = Universe::reference_pending_list();
2589     if (pll_head != nullptr) {
2590       // Any valid worker id is fine here as we are in the VM thread and single-threaded.
2591       _cm->mark_in_bitmap(0 /* worker_id */, pll_head);
2592     }
2593   }
2594 }
2595 
2596 void G1CollectedHeap::set_humongous_stats(uint num_humongous_total, uint num_humongous_candidates) {
2597   _num_humongous_objects = num_humongous_total;
2598   _num_humongous_reclaim_candidates = num_humongous_candidates;
2599 }
2600 
2601 bool G1CollectedHeap::should_sample_collection_set_candidates() const {
2602   const G1CollectionSetCandidates* candidates = collection_set()->candidates();
2603   return !candidates->is_empty();
2604 }
2605 
2606 void G1CollectedHeap::set_collection_set_candidates_stats(G1MonotonicArenaMemoryStats& stats) {
2607   _collection_set_candidates_card_set_stats = stats;
2608 }
2609 
2610 void G1CollectedHeap::set_young_gen_card_set_stats(const G1MonotonicArenaMemoryStats& stats) {
2611   _young_gen_card_set_stats = stats;
2612 }
2613 
2614 void G1CollectedHeap::record_obj_copy_mem_stats() {
2615   policy()->old_gen_alloc_tracker()->
2616     add_allocated_bytes_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
2617 
2618   _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
2619                                                create_g1_evac_summary(&_old_evac_stats));
2620 }
2621 
2622 void G1CollectedHeap::clear_bitmap_for_region(HeapRegion* hr) {
2623   concurrent_mark()->clear_bitmap_for_region(hr);
2624 }
2625 
2626 void G1CollectedHeap::free_region(HeapRegion* hr, FreeRegionList* free_list) {
2627   assert(!hr->is_free(), "the region should not be free");
2628   assert(!hr->is_empty(), "the region should not be empty");
2629   assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
2630   assert(!hr->has_pinned_objects(),
2631          "must not free a region which contains pinned objects");
2632 
2633   // Reset region metadata to allow reuse.
2634   hr->hr_clear(true /* clear_space */);
2635   _policy->remset_tracker()->update_at_free(hr);
2636 
2637   if (free_list != nullptr) {
2638     free_list->add_ordered(hr);
2639   }
2640 }
2641 
2642 void G1CollectedHeap::retain_region(HeapRegion* hr) {
2643   MutexLocker x(G1RareEvent_lock, Mutex::_no_safepoint_check_flag);
2644   collection_set()->candidates()->add_retained_region_unsorted(hr);
2645 }
2646 
2647 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
2648                                             FreeRegionList* free_list) {
2649   assert(hr->is_humongous(), "this is only for humongous regions");
2650   hr->clear_humongous();
2651   free_region(hr, free_list);
2652 }
2653 
2654 void G1CollectedHeap::remove_from_old_gen_sets(const uint old_regions_removed,
2655                                                const uint humongous_regions_removed) {
2656   if (old_regions_removed > 0 || humongous_regions_removed > 0) {
2657     MutexLocker x(OldSets_lock, Mutex::_no_safepoint_check_flag);
2658     _old_set.bulk_remove(old_regions_removed);
2659     _humongous_set.bulk_remove(humongous_regions_removed);
2660   }
2661 
2662 }
2663 
2664 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
2665   assert(list != nullptr, "list can't be null");
2666   if (!list->is_empty()) {
2667     MutexLocker x(FreeList_lock, Mutex::_no_safepoint_check_flag);
2668     _hrm.insert_list_into_free_list(list);
2669   }
2670 }
2671 
2672 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
2673   decrease_used(bytes);
2674 }
2675 
2676 void G1CollectedHeap::clear_eden() {
2677   _eden.clear();
2678 }
2679 
2680 void G1CollectedHeap::clear_collection_set() {
2681   collection_set()->clear();
2682 }
2683 
2684 void G1CollectedHeap::rebuild_free_region_list() {
2685   Ticks start = Ticks::now();
2686   _hrm.rebuild_free_list(workers());
2687   phase_times()->record_total_rebuild_freelist_time_ms((Ticks::now() - start).seconds() * 1000.0);
2688 }
2689 
2690 class G1AbandonCollectionSetClosure : public HeapRegionClosure {
2691 public:
2692   virtual bool do_heap_region(HeapRegion* r) {
2693     assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index());
2694     G1CollectedHeap::heap()->clear_region_attr(r);
2695     r->clear_young_index_in_cset();
2696     return false;
2697   }
2698 };
2699 
2700 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) {
2701   G1AbandonCollectionSetClosure cl;
2702   collection_set_iterate_all(&cl);
2703 
2704   collection_set->clear();
2705   collection_set->stop_incremental_building();
2706 }
2707 
2708 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
2709   return _allocator->is_retained_old_region(hr);
2710 }
2711 
2712 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
2713   _eden.add(hr);
2714   _policy->set_region_eden(hr);
2715 }
2716 
2717 #ifdef ASSERT
2718 
2719 class NoYoungRegionsClosure: public HeapRegionClosure {
2720 private:
2721   bool _success;
2722 public:
2723   NoYoungRegionsClosure() : _success(true) { }
2724   bool do_heap_region(HeapRegion* r) {
2725     if (r->is_young()) {
2726       log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
2727                             p2i(r->bottom()), p2i(r->end()));
2728       _success = false;
2729     }
2730     return false;
2731   }
2732   bool success() { return _success; }
2733 };
2734 
2735 bool G1CollectedHeap::check_young_list_empty() {
2736   bool ret = (young_regions_count() == 0);
2737 
2738   NoYoungRegionsClosure closure;
2739   heap_region_iterate(&closure);
2740   ret = ret && closure.success();
2741 
2742   return ret;
2743 }
2744 
2745 #endif // ASSERT
2746 
2747 // Remove the given HeapRegion from the appropriate region set.
2748 void G1CollectedHeap::prepare_region_for_full_compaction(HeapRegion* hr) {
2749   if (hr->is_humongous()) {
2750     _humongous_set.remove(hr);
2751   } else if (hr->is_old()) {
2752     _old_set.remove(hr);
2753   } else if (hr->is_young()) {
2754     // Note that emptying the eden and survivor lists is postponed and instead
2755     // done as the first step when rebuilding the regions sets again. The reason
2756     // for this is that during a full GC string deduplication needs to know if
2757     // a collected region was young or old when the full GC was initiated.
2758     hr->uninstall_surv_rate_group();
2759   } else {
2760     // We ignore free regions, we'll empty the free list afterwards.
2761     assert(hr->is_free(), "it cannot be another type");
2762   }
2763 }
2764 
2765 void G1CollectedHeap::increase_used(size_t bytes) {
2766   _summary_bytes_used += bytes;
2767 }
2768 
2769 void G1CollectedHeap::decrease_used(size_t bytes) {
2770   assert(_summary_bytes_used >= bytes,
2771          "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
2772          _summary_bytes_used, bytes);
2773   _summary_bytes_used -= bytes;
2774 }
2775 
2776 void G1CollectedHeap::set_used(size_t bytes) {
2777   _summary_bytes_used = bytes;
2778 }
2779 
2780 class RebuildRegionSetsClosure : public HeapRegionClosure {
2781 private:
2782   bool _free_list_only;
2783 
2784   HeapRegionSet* _old_set;
2785   HeapRegionSet* _humongous_set;
2786 
2787   HeapRegionManager* _hrm;
2788 
2789   size_t _total_used;
2790 
2791 public:
2792   RebuildRegionSetsClosure(bool free_list_only,
2793                            HeapRegionSet* old_set,
2794                            HeapRegionSet* humongous_set,
2795                            HeapRegionManager* hrm) :
2796     _free_list_only(free_list_only), _old_set(old_set),
2797     _humongous_set(humongous_set), _hrm(hrm), _total_used(0) {
2798     assert(_hrm->num_free_regions() == 0, "pre-condition");
2799     if (!free_list_only) {
2800       assert(_old_set->is_empty(), "pre-condition");
2801       assert(_humongous_set->is_empty(), "pre-condition");
2802     }
2803   }
2804 
2805   bool do_heap_region(HeapRegion* r) {
2806     if (r->is_empty()) {
2807       assert(r->rem_set()->is_empty(), "Empty regions should have empty remembered sets.");
2808       // Add free regions to the free list
2809       r->set_free();
2810       _hrm->insert_into_free_list(r);
2811     } else if (!_free_list_only) {
2812       assert(r->rem_set()->is_empty(), "At this point remembered sets must have been cleared.");
2813 
2814       if (r->is_humongous()) {
2815         _humongous_set->add(r);
2816       } else {
2817         assert(r->is_young() || r->is_free() || r->is_old(), "invariant");
2818         // We now move all (non-humongous, non-old) regions to old gen,
2819         // and register them as such.
2820         r->move_to_old();
2821         _old_set->add(r);
2822       }
2823       _total_used += r->used();
2824     }
2825 
2826     return false;
2827   }
2828 
2829   size_t total_used() {
2830     return _total_used;
2831   }
2832 };
2833 
2834 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
2835   assert_at_safepoint_on_vm_thread();
2836 
2837   if (!free_list_only) {
2838     _eden.clear();
2839     _survivor.clear();
2840   }
2841 
2842   RebuildRegionSetsClosure cl(free_list_only,
2843                               &_old_set, &_humongous_set,
2844                               &_hrm);
2845   heap_region_iterate(&cl);
2846 
2847   if (!free_list_only) {
2848     set_used(cl.total_used());
2849   }
2850   assert_used_and_recalculate_used_equal(this);
2851 }
2852 
2853 // Methods for the mutator alloc region
2854 
2855 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
2856                                                       bool force,
2857                                                       uint node_index) {
2858   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
2859   bool should_allocate = policy()->should_allocate_mutator_region();
2860   if (force || should_allocate) {
2861     HeapRegion* new_alloc_region = new_region(word_size,
2862                                               HeapRegionType::Eden,
2863                                               false /* do_expand */,
2864                                               node_index);
2865     if (new_alloc_region != nullptr) {
2866       set_region_short_lived_locked(new_alloc_region);
2867       _hr_printer.alloc(new_alloc_region, !should_allocate);
2868       _policy->remset_tracker()->update_at_allocate(new_alloc_region);
2869       return new_alloc_region;
2870     }
2871   }
2872   return nullptr;
2873 }
2874 
2875 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
2876                                                   size_t allocated_bytes) {
2877   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
2878   assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
2879 
2880   collection_set()->add_eden_region(alloc_region);
2881   increase_used(allocated_bytes);
2882   _eden.add_used_bytes(allocated_bytes);
2883   _hr_printer.retire(alloc_region);
2884 
2885   // We update the eden sizes here, when the region is retired,
2886   // instead of when it's allocated, since this is the point that its
2887   // used space has been recorded in _summary_bytes_used.
2888   monitoring_support()->update_eden_size();
2889 }
2890 
2891 // Methods for the GC alloc regions
2892 
2893 bool G1CollectedHeap::has_more_regions(G1HeapRegionAttr dest) {
2894   if (dest.is_old()) {
2895     return true;
2896   } else {
2897     return survivor_regions_count() < policy()->max_survivor_regions();
2898   }
2899 }
2900 
2901 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, G1HeapRegionAttr dest, uint node_index) {
2902   assert(FreeList_lock->owned_by_self(), "pre-condition");
2903 
2904   if (!has_more_regions(dest)) {
2905     return nullptr;
2906   }
2907 
2908   HeapRegionType type;
2909   if (dest.is_young()) {
2910     type = HeapRegionType::Survivor;
2911   } else {
2912     type = HeapRegionType::Old;
2913   }
2914 
2915   HeapRegion* new_alloc_region = new_region(word_size,
2916                                             type,
2917                                             true /* do_expand */,
2918                                             node_index);
2919 
2920   if (new_alloc_region != nullptr) {
2921     if (type.is_survivor()) {
2922       new_alloc_region->set_survivor();
2923       _survivor.add(new_alloc_region);
2924       register_new_survivor_region_with_region_attr(new_alloc_region);
2925     } else {
2926       new_alloc_region->set_old();
2927     }
2928     _policy->remset_tracker()->update_at_allocate(new_alloc_region);
2929     register_region_with_region_attr(new_alloc_region);
2930     _hr_printer.alloc(new_alloc_region);
2931     return new_alloc_region;
2932   }
2933   return nullptr;
2934 }
2935 
2936 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
2937                                              size_t allocated_bytes,
2938                                              G1HeapRegionAttr dest) {
2939   _bytes_used_during_gc += allocated_bytes;
2940   if (dest.is_old()) {
2941     old_set_add(alloc_region);
2942   } else {
2943     assert(dest.is_young(), "Retiring alloc region should be young (%d)", dest.type());
2944     _survivor.add_used_bytes(allocated_bytes);
2945   }
2946 
2947   bool const during_im = collector_state()->in_concurrent_start_gc();
2948   if (during_im && allocated_bytes > 0) {
2949     _cm->add_root_region(alloc_region);
2950   }
2951   _hr_printer.retire(alloc_region);
2952 }
2953 
2954 HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
2955   bool expanded = false;
2956   uint index = _hrm.find_highest_free(&expanded);
2957 
2958   if (index != G1_NO_HRM_INDEX) {
2959     if (expanded) {
2960       log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
2961                                 HeapRegion::GrainWords * HeapWordSize);
2962     }
2963     return _hrm.allocate_free_regions_starting_at(index, 1);
2964   }
2965   return nullptr;
2966 }
2967 
2968 void G1CollectedHeap::mark_evac_failure_object(uint worker_id, const oop obj, size_t obj_size) const {
2969   assert(!_cm->is_marked_in_bitmap(obj), "must be");
2970 
2971   _cm->raw_mark_in_bitmap(obj);
2972 }
2973 
2974 // Optimized nmethod scanning
2975 class RegisterNMethodOopClosure: public OopClosure {
2976   G1CollectedHeap* _g1h;
2977   nmethod* _nm;
2978 
2979 public:
2980   RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
2981     _g1h(g1h), _nm(nm) {}
2982 
2983   void do_oop(oop* p) {
2984     oop heap_oop = RawAccess<>::oop_load(p);
2985     if (!CompressedOops::is_null(heap_oop)) {
2986       oop obj = CompressedOops::decode_not_null(heap_oop);
2987       HeapRegion* hr = _g1h->heap_region_containing(obj);
2988       assert(!hr->is_continues_humongous(),
2989              "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
2990              " starting at " HR_FORMAT,
2991              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
2992 
2993       hr->add_code_root(_nm);
2994     }
2995   }
2996 
2997   void do_oop(narrowOop* p) { ShouldNotReachHere(); }
2998 };
2999 
3000 void G1CollectedHeap::register_nmethod(nmethod* nm) {
3001   guarantee(nm != nullptr, "sanity");
3002   RegisterNMethodOopClosure reg_cl(this, nm);
3003   nm->oops_do(&reg_cl);
3004 }
3005 
3006 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
3007   // We always unregister nmethods in bulk during code unloading only.
3008   ShouldNotReachHere();
3009 }
3010 
3011 void G1CollectedHeap::update_used_after_gc(bool evacuation_failed) {
3012   if (evacuation_failed) {
3013     set_used(recalculate_used());
3014   } else {
3015     // The "used" of the collection set have already been subtracted
3016     // when they were freed.  Add in the bytes used.
3017     increase_used(_bytes_used_during_gc);
3018   }
3019 }
3020 
3021 class RebuildCodeRootClosure: public CodeBlobClosure {
3022   G1CollectedHeap* _g1h;
3023 
3024 public:
3025   RebuildCodeRootClosure(G1CollectedHeap* g1h) :
3026     _g1h(g1h) {}
3027 
3028   void do_code_blob(CodeBlob* cb) {
3029     nmethod* nm = cb->as_nmethod_or_null();
3030     if (nm != nullptr) {
3031       _g1h->register_nmethod(nm);
3032     }
3033   }
3034 };
3035 
3036 void G1CollectedHeap::rebuild_code_roots() {
3037   RebuildCodeRootClosure blob_cl(this);
3038   CodeCache::blobs_do(&blob_cl);
3039 }
3040 
3041 void G1CollectedHeap::initialize_serviceability() {
3042   _monitoring_support->initialize_serviceability();
3043 }
3044 
3045 MemoryUsage G1CollectedHeap::memory_usage() {
3046   return _monitoring_support->memory_usage();
3047 }
3048 
3049 GrowableArray<GCMemoryManager*> G1CollectedHeap::memory_managers() {
3050   return _monitoring_support->memory_managers();
3051 }
3052 
3053 GrowableArray<MemoryPool*> G1CollectedHeap::memory_pools() {
3054   return _monitoring_support->memory_pools();
3055 }
3056 
3057 void G1CollectedHeap::fill_with_dummy_object(HeapWord* start, HeapWord* end, bool zap) {
3058   HeapRegion* region = heap_region_containing(start);
3059   region->fill_with_dummy_object(start, pointer_delta(end, start), zap);
3060 }
3061 
3062 void G1CollectedHeap::start_codecache_marking_cycle_if_inactive(bool concurrent_mark_start) {
3063   // We can reach here with an active code cache marking cycle either because the
3064   // previous G1 concurrent marking cycle was undone (if heap occupancy after the
3065   // concurrent start young collection was below the threshold) or aborted. See
3066   // CodeCache::on_gc_marking_cycle_finish() why this is.  We must not start a new code
3067   // cache cycle then. If we are about to start a new g1 concurrent marking cycle we
3068   // still have to arm all nmethod entry barriers. They are needed for adding oop
3069   // constants to the SATB snapshot. Full GC does not need nmethods to be armed.
3070   if (!CodeCache::is_gc_marking_cycle_active()) {
3071     CodeCache::on_gc_marking_cycle_start();
3072   }
3073   if (concurrent_mark_start) {
3074     CodeCache::arm_all_nmethods();
3075   }
3076 }
3077 
3078 void G1CollectedHeap::finish_codecache_marking_cycle() {
3079   CodeCache::on_gc_marking_cycle_finish();
3080   CodeCache::arm_all_nmethods();
3081 }