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