1 /*
   2  * Copyright (c) 2001, 2020, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "classfile/classLoaderDataGraph.hpp"
  27 #include "classfile/metadataOnStackMark.hpp"
  28 #include "classfile/stringTable.hpp"
  29 #include "code/codeCache.hpp"
  30 #include "code/icBuffer.hpp"
  31 #include "gc/g1/g1Allocator.inline.hpp"
  32 #include "gc/g1/g1Arguments.hpp"
  33 #include "gc/g1/g1BarrierSet.hpp"
  34 #include "gc/g1/g1CardTableEntryClosure.hpp"
  35 #include "gc/g1/g1CollectedHeap.inline.hpp"
  36 #include "gc/g1/g1CollectionSet.hpp"
  37 #include "gc/g1/g1CollectorState.hpp"
  38 #include "gc/g1/g1ConcurrentRefine.hpp"
  39 #include "gc/g1/g1ConcurrentRefineThread.hpp"
  40 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp"
  41 #include "gc/g1/g1DirtyCardQueue.hpp"
  42 #include "gc/g1/g1EvacStats.inline.hpp"
  43 #include "gc/g1/g1FullCollector.hpp"
  44 #include "gc/g1/g1GCParPhaseTimesTracker.hpp"
  45 #include "gc/g1/g1GCPhaseTimes.hpp"
  46 #include "gc/g1/g1HeapSizingPolicy.hpp"
  47 #include "gc/g1/g1HeapTransition.hpp"
  48 #include "gc/g1/g1HeapVerifier.hpp"
  49 #include "gc/g1/g1HotCardCache.hpp"
  50 #include "gc/g1/g1InitLogger.hpp"
  51 #include "gc/g1/g1MemoryPool.hpp"
  52 #include "gc/g1/g1OopClosures.inline.hpp"
  53 #include "gc/g1/g1ParallelCleaning.hpp"
  54 #include "gc/g1/g1ParScanThreadState.inline.hpp"
  55 #include "gc/g1/g1Policy.hpp"
  56 #include "gc/g1/g1RedirtyCardsQueue.hpp"
  57 #include "gc/g1/g1RegionToSpaceMapper.hpp"
  58 #include "gc/g1/g1RemSet.hpp"
  59 #include "gc/g1/g1RootClosures.hpp"
  60 #include "gc/g1/g1RootProcessor.hpp"
  61 #include "gc/g1/g1SATBMarkQueueSet.hpp"
  62 #include "gc/g1/g1StringDedup.hpp"
  63 #include "gc/g1/g1ThreadLocalData.hpp"
  64 #include "gc/g1/g1Trace.hpp"
  65 #include "gc/g1/g1YCTypes.hpp"
  66 #include "gc/g1/g1YoungRemSetSamplingThread.hpp"
  67 #include "gc/g1/g1VMOperations.hpp"
  68 #include "gc/g1/heapRegion.inline.hpp"
  69 #include "gc/g1/heapRegionRemSet.hpp"
  70 #include "gc/g1/heapRegionSet.inline.hpp"
  71 #include "gc/shared/concurrentGCBreakpoints.hpp"
  72 #include "gc/shared/gcBehaviours.hpp"
  73 #include "gc/shared/gcHeapSummary.hpp"
  74 #include "gc/shared/gcId.hpp"
  75 #include "gc/shared/gcLocker.hpp"
  76 #include "gc/shared/gcTimer.hpp"
  77 #include "gc/shared/gcTraceTime.inline.hpp"
  78 #include "gc/shared/generationSpec.hpp"
  79 #include "gc/shared/isGCActiveMark.hpp"
  80 #include "gc/shared/locationPrinter.inline.hpp"
  81 #include "gc/shared/oopStorageParState.hpp"
  82 #include "gc/shared/preservedMarks.inline.hpp"
  83 #include "gc/shared/suspendibleThreadSet.hpp"
  84 #include "gc/shared/referenceProcessor.inline.hpp"
  85 #include "gc/shared/taskTerminator.hpp"
  86 #include "gc/shared/taskqueue.inline.hpp"
  87 #include "gc/shared/weakProcessor.inline.hpp"
  88 #include "gc/shared/workerPolicy.hpp"
  89 #include "logging/log.hpp"
  90 #include "memory/allocation.hpp"
  91 #include "memory/iterator.hpp"
  92 #include "memory/heapInspection.hpp"
  93 #include "memory/resourceArea.hpp"
  94 #include "memory/universe.hpp"
  95 #include "oops/access.inline.hpp"
  96 #include "oops/compressedOops.inline.hpp"
  97 #include "oops/oop.inline.hpp"
  98 #include "runtime/atomic.hpp"
  99 #include "runtime/handles.inline.hpp"
 100 #include "runtime/init.hpp"
 101 #include "runtime/orderAccess.hpp"
 102 #include "runtime/threadSMR.hpp"
 103 #include "runtime/vmThread.hpp"
 104 #include "utilities/align.hpp"
 105 #include "utilities/autoRestore.hpp"
 106 #include "utilities/bitMap.inline.hpp"
 107 #include "utilities/globalDefinitions.hpp"
 108 #include "utilities/stack.inline.hpp"
 109 
 110 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
 111 
 112 // INVARIANTS/NOTES
 113 //
 114 // All allocation activity covered by the G1CollectedHeap interface is
 115 // serialized by acquiring the HeapLock.  This happens in mem_allocate
 116 // and allocate_new_tlab, which are the "entry" points to the
 117 // allocation code from the rest of the JVM.  (Note that this does not
 118 // apply to TLAB allocation, which is not part of this interface: it
 119 // is done by clients of this interface.)
 120 
 121 class RedirtyLoggedCardTableEntryClosure : public G1CardTableEntryClosure {
 122  private:
 123   size_t _num_dirtied;
 124   G1CollectedHeap* _g1h;
 125   G1CardTable* _g1_ct;
 126 
 127   HeapRegion* region_for_card(CardValue* card_ptr) const {
 128     return _g1h->heap_region_containing(_g1_ct->addr_for(card_ptr));
 129   }
 130 
 131   bool will_become_free(HeapRegion* hr) const {
 132     // A region will be freed by free_collection_set if the region is in the
 133     // collection set and has not had an evacuation failure.
 134     return _g1h->is_in_cset(hr) && !hr->evacuation_failed();
 135   }
 136 
 137  public:
 138   RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : G1CardTableEntryClosure(),
 139     _num_dirtied(0), _g1h(g1h), _g1_ct(g1h->card_table()) { }
 140 
 141   void do_card_ptr(CardValue* card_ptr, uint worker_id) {
 142     HeapRegion* hr = region_for_card(card_ptr);
 143 
 144     // Should only dirty cards in regions that won't be freed.
 145     if (!will_become_free(hr)) {
 146       *card_ptr = G1CardTable::dirty_card_val();
 147       _num_dirtied++;
 148     }
 149   }
 150 
 151   size_t num_dirtied()   const { return _num_dirtied; }
 152 };
 153 
 154 
 155 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
 156   HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
 157 }
 158 
 159 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
 160   // The from card cache is not the memory that is actually committed. So we cannot
 161   // take advantage of the zero_filled parameter.
 162   reset_from_card_cache(start_idx, num_regions);
 163 }
 164 
 165 void G1CollectedHeap::run_task(AbstractGangTask* task) {
 166   workers()->run_task(task, workers()->active_workers());
 167 }
 168 
 169 Tickspan G1CollectedHeap::run_task_timed(AbstractGangTask* task) {
 170   Ticks start = Ticks::now();
 171   run_task(task);
 172   return Ticks::now() - start;
 173 }
 174 
 175 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
 176                                              MemRegion mr) {
 177   return new HeapRegion(hrs_index, bot(), mr);
 178 }
 179 
 180 // Private methods.
 181 
 182 HeapRegion* G1CollectedHeap::new_region(size_t word_size,
 183                                         HeapRegionType type,
 184                                         bool do_expand,
 185                                         uint node_index) {
 186   assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
 187          "the only time we use this to allocate a humongous region is "
 188          "when we are allocating a single humongous region");
 189 
 190   HeapRegion* res = _hrm->allocate_free_region(type, node_index);
 191 
 192   if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
 193     // Currently, only attempts to allocate GC alloc regions set
 194     // do_expand to true. So, we should only reach here during a
 195     // safepoint. If this assumption changes we might have to
 196     // reconsider the use of _expand_heap_after_alloc_failure.
 197     assert(SafepointSynchronize::is_at_safepoint(), "invariant");
 198 
 199     log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B",
 200                               word_size * HeapWordSize);
 201 
 202     assert(word_size * HeapWordSize < HeapRegion::GrainBytes,
 203            "This kind of expansion should never be more than one region. Size: " SIZE_FORMAT,
 204            word_size * HeapWordSize);
 205     if (expand_single_region(node_index)) {
 206       // Given that expand_single_region() succeeded in expanding the heap, and we
 207       // always expand the heap by an amount aligned to the heap
 208       // region size, the free list should in theory not be empty.
 209       // In either case allocate_free_region() will check for NULL.
 210       res = _hrm->allocate_free_region(type, node_index);
 211     } else {
 212       _expand_heap_after_alloc_failure = false;
 213     }
 214   }
 215   return res;
 216 }
 217 
 218 HeapWord*
 219 G1CollectedHeap::humongous_obj_allocate_initialize_regions(HeapRegion* first_hr,
 220                                                            uint num_regions,
 221                                                            size_t word_size) {
 222   assert(first_hr != NULL, "pre-condition");
 223   assert(is_humongous(word_size), "word_size should be humongous");
 224   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 225 
 226   // Index of last region in the series.
 227   uint first = first_hr->hrm_index();
 228   uint last = first + num_regions - 1;
 229 
 230   // We need to initialize the region(s) we just discovered. This is
 231   // a bit tricky given that it can happen concurrently with
 232   // refinement threads refining cards on these regions and
 233   // potentially wanting to refine the BOT as they are scanning
 234   // those cards (this can happen shortly after a cleanup; see CR
 235   // 6991377). So we have to set up the region(s) carefully and in
 236   // a specific order.
 237 
 238   // The word size sum of all the regions we will allocate.
 239   size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
 240   assert(word_size <= word_size_sum, "sanity");
 241 
 242   // The passed in hr will be the "starts humongous" region. The header
 243   // of the new object will be placed at the bottom of this region.
 244   HeapWord* new_obj = first_hr->bottom();
 245   // This will be the new top of the new object.
 246   HeapWord* obj_top = new_obj + word_size;
 247 
 248   // First, we need to zero the header of the space that we will be
 249   // allocating. When we update top further down, some refinement
 250   // threads might try to scan the region. By zeroing the header we
 251   // ensure that any thread that will try to scan the region will
 252   // come across the zero klass word and bail out.
 253   //
 254   // NOTE: It would not have been correct to have used
 255   // CollectedHeap::fill_with_object() and make the space look like
 256   // an int array. The thread that is doing the allocation will
 257   // later update the object header to a potentially different array
 258   // type and, for a very short period of time, the klass and length
 259   // fields will be inconsistent. This could cause a refinement
 260   // thread to calculate the object size incorrectly.
 261   Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
 262 
 263   // Next, pad out the unused tail of the last region with filler
 264   // objects, for improved usage accounting.
 265   // How many words we use for filler objects.
 266   size_t word_fill_size = word_size_sum - word_size;
 267 
 268   // How many words memory we "waste" which cannot hold a filler object.
 269   size_t words_not_fillable = 0;
 270 
 271   if (word_fill_size >= min_fill_size()) {
 272     fill_with_objects(obj_top, word_fill_size);
 273   } else if (word_fill_size > 0) {
 274     // We have space to fill, but we cannot fit an object there.
 275     words_not_fillable = word_fill_size;
 276     word_fill_size = 0;
 277   }
 278 
 279   // We will set up the first region as "starts humongous". This
 280   // will also update the BOT covering all the regions to reflect
 281   // that there is a single object that starts at the bottom of the
 282   // first region.
 283   first_hr->set_starts_humongous(obj_top, word_fill_size);
 284   _policy->remset_tracker()->update_at_allocate(first_hr);
 285   // Then, if there are any, we will set up the "continues
 286   // humongous" regions.
 287   HeapRegion* hr = NULL;
 288   for (uint i = first + 1; i <= last; ++i) {
 289     hr = region_at(i);
 290     hr->set_continues_humongous(first_hr);
 291     _policy->remset_tracker()->update_at_allocate(hr);
 292   }
 293 
 294   // Up to this point no concurrent thread would have been able to
 295   // do any scanning on any region in this series. All the top
 296   // fields still point to bottom, so the intersection between
 297   // [bottom,top] and [card_start,card_end] will be empty. Before we
 298   // update the top fields, we'll do a storestore to make sure that
 299   // no thread sees the update to top before the zeroing of the
 300   // object header and the BOT initialization.
 301   OrderAccess::storestore();
 302 
 303   // Now, we will update the top fields of the "continues humongous"
 304   // regions except the last one.
 305   for (uint i = first; i < last; ++i) {
 306     hr = region_at(i);
 307     hr->set_top(hr->end());
 308   }
 309 
 310   hr = region_at(last);
 311   // If we cannot fit a filler object, we must set top to the end
 312   // of the humongous object, otherwise we cannot iterate the heap
 313   // and the BOT will not be complete.
 314   hr->set_top(hr->end() - words_not_fillable);
 315 
 316   assert(hr->bottom() < obj_top && obj_top <= hr->end(),
 317          "obj_top should be in last region");
 318 
 319   _verifier->check_bitmaps("Humongous Region Allocation", first_hr);
 320 
 321   assert(words_not_fillable == 0 ||
 322          first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(),
 323          "Miscalculation in humongous allocation");
 324 
 325   increase_used((word_size_sum - words_not_fillable) * HeapWordSize);
 326 
 327   for (uint i = first; i <= last; ++i) {
 328     hr = region_at(i);
 329     _humongous_set.add(hr);
 330     _hr_printer.alloc(hr);
 331   }
 332 
 333   return new_obj;
 334 }
 335 
 336 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) {
 337   assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size);
 338   return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
 339 }
 340 
 341 // If could fit into free regions w/o expansion, try.
 342 // Otherwise, if can expand, do so.
 343 // Otherwise, if using ex regions might help, try with ex given back.
 344 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
 345   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 346 
 347   _verifier->verify_region_sets_optional();
 348 
 349   uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);
 350 
 351   // Policy: First try to allocate a humongous object in the free list.
 352   HeapRegion* humongous_start = _hrm->allocate_humongous(obj_regions);
 353   if (humongous_start == NULL) {
 354     // Policy: We could not find enough regions for the humongous object in the
 355     // free list. Look through the heap to find a mix of free and uncommitted regions.
 356     // If so, expand the heap and allocate the humongous object.
 357     humongous_start = _hrm->expand_and_allocate_humongous(obj_regions);
 358     if (humongous_start != NULL) {
 359       // We managed to find a region by expanding the heap.
 360       log_debug(gc, ergo, heap)("Heap expansion (humongous allocation request). Allocation request: " SIZE_FORMAT "B",
 361                                 word_size * HeapWordSize);
 362       policy()->record_new_heap_size(num_regions());
 363     } else {
 364       // Policy: Potentially trigger a defragmentation GC.
 365     }
 366   }
 367 
 368   HeapWord* result = NULL;
 369   if (humongous_start != NULL) {
 370     result = humongous_obj_allocate_initialize_regions(humongous_start, obj_regions, word_size);
 371     assert(result != NULL, "it should always return a valid result");
 372 
 373     // A successful humongous object allocation changes the used space
 374     // information of the old generation so we need to recalculate the
 375     // sizes and update the jstat counters here.
 376     g1mm()->update_sizes();
 377   }
 378 
 379   _verifier->verify_region_sets_optional();
 380 
 381   return result;
 382 }
 383 
 384 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t min_size,
 385                                              size_t requested_size,
 386                                              size_t* actual_size) {
 387   assert_heap_not_locked_and_not_at_safepoint();
 388   assert(!is_humongous(requested_size), "we do not allow humongous TLABs");
 389 
 390   return attempt_allocation(min_size, requested_size, actual_size);
 391 }
 392 
 393 HeapWord*
 394 G1CollectedHeap::mem_allocate(size_t word_size,
 395                               bool*  gc_overhead_limit_was_exceeded) {
 396   assert_heap_not_locked_and_not_at_safepoint();
 397 
 398   if (is_humongous(word_size)) {
 399     return attempt_allocation_humongous(word_size);
 400   }
 401   size_t dummy = 0;
 402   return attempt_allocation(word_size, word_size, &dummy);
 403 }
 404 
 405 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size) {
 406   ResourceMark rm; // For retrieving the thread names in log messages.
 407 
 408   // Make sure you read the note in attempt_allocation_humongous().
 409 
 410   assert_heap_not_locked_and_not_at_safepoint();
 411   assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
 412          "be called for humongous allocation requests");
 413 
 414   // We should only get here after the first-level allocation attempt
 415   // (attempt_allocation()) failed to allocate.
 416 
 417   // We will loop until a) we manage to successfully perform the
 418   // allocation or b) we successfully schedule a collection which
 419   // fails to perform the allocation. b) is the only case when we'll
 420   // return NULL.
 421   HeapWord* result = NULL;
 422   for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 423     bool should_try_gc;
 424     uint gc_count_before;
 425 
 426     {
 427       MutexLocker x(Heap_lock);
 428       result = _allocator->attempt_allocation_locked(word_size);
 429       if (result != NULL) {
 430         return result;
 431       }
 432 
 433       // If the GCLocker is active and we are bound for a GC, try expanding young gen.
 434       // This is different to when only GCLocker::needs_gc() is set: try to avoid
 435       // waiting because the GCLocker is active to not wait too long.
 436       if (GCLocker::is_active_and_needs_gc() && policy()->can_expand_young_list()) {
 437         // No need for an ergo message here, can_expand_young_list() does this when
 438         // it returns true.
 439         result = _allocator->attempt_allocation_force(word_size);
 440         if (result != NULL) {
 441           return result;
 442         }
 443       }
 444       // Only try a GC if the GCLocker does not signal the need for a GC. Wait until
 445       // the GCLocker initiated GC has been performed and then retry. This includes
 446       // the case when the GC Locker is not active but has not been performed.
 447       should_try_gc = !GCLocker::needs_gc();
 448       // Read the GC count while still holding the Heap_lock.
 449       gc_count_before = total_collections();
 450     }
 451 
 452     if (should_try_gc) {
 453       bool succeeded;
 454       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 455                                    GCCause::_g1_inc_collection_pause);
 456       if (result != NULL) {
 457         assert(succeeded, "only way to get back a non-NULL result");
 458         log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT,
 459                              Thread::current()->name(), p2i(result));
 460         return result;
 461       }
 462 
 463       if (succeeded) {
 464         // We successfully scheduled a collection which failed to allocate. No
 465         // point in trying to allocate further. We'll just return NULL.
 466         log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate "
 467                              SIZE_FORMAT " words", Thread::current()->name(), word_size);
 468         return NULL;
 469       }
 470       log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT " words",
 471                            Thread::current()->name(), word_size);
 472     } else {
 473       // Failed to schedule a collection.
 474       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 475         log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating "
 476                                SIZE_FORMAT " words", Thread::current()->name(), word_size);
 477         return NULL;
 478       }
 479       log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name());
 480       // The GCLocker is either active or the GCLocker initiated
 481       // GC has not yet been performed. Stall until it is and
 482       // then retry the allocation.
 483       GCLocker::stall_until_clear();
 484       gclocker_retry_count += 1;
 485     }
 486 
 487     // We can reach here if we were unsuccessful in scheduling a
 488     // collection (because another thread beat us to it) or if we were
 489     // stalled due to the GC locker. In either can we should retry the
 490     // allocation attempt in case another thread successfully
 491     // performed a collection and reclaimed enough space. We do the
 492     // first attempt (without holding the Heap_lock) here and the
 493     // follow-on attempt will be at the start of the next loop
 494     // iteration (after taking the Heap_lock).
 495     size_t dummy = 0;
 496     result = _allocator->attempt_allocation(word_size, word_size, &dummy);
 497     if (result != NULL) {
 498       return result;
 499     }
 500 
 501     // Give a warning if we seem to be looping forever.
 502     if ((QueuedAllocationWarningCount > 0) &&
 503         (try_count % QueuedAllocationWarningCount == 0)) {
 504       log_warning(gc, alloc)("%s:  Retried allocation %u times for " SIZE_FORMAT " words",
 505                              Thread::current()->name(), try_count, word_size);
 506     }
 507   }
 508 
 509   ShouldNotReachHere();
 510   return NULL;
 511 }
 512 
 513 void G1CollectedHeap::begin_archive_alloc_range(bool open) {
 514   assert_at_safepoint_on_vm_thread();
 515   if (_archive_allocator == NULL) {
 516     _archive_allocator = G1ArchiveAllocator::create_allocator(this, open);
 517   }
 518 }
 519 
 520 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) {
 521   // Allocations in archive regions cannot be of a size that would be considered
 522   // humongous even for a minimum-sized region, because G1 region sizes/boundaries
 523   // may be different at archive-restore time.
 524   return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words());
 525 }
 526 
 527 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) {
 528   assert_at_safepoint_on_vm_thread();
 529   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 530   if (is_archive_alloc_too_large(word_size)) {
 531     return NULL;
 532   }
 533   return _archive_allocator->archive_mem_allocate(word_size);
 534 }
 535 
 536 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
 537                                               size_t end_alignment_in_bytes) {
 538   assert_at_safepoint_on_vm_thread();
 539   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 540 
 541   // Call complete_archive to do the real work, filling in the MemRegion
 542   // array with the archive regions.
 543   _archive_allocator->complete_archive(ranges, end_alignment_in_bytes);
 544   delete _archive_allocator;
 545   _archive_allocator = NULL;
 546 }
 547 
 548 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) {
 549   assert(ranges != NULL, "MemRegion array NULL");
 550   assert(count != 0, "No MemRegions provided");
 551   MemRegion reserved = _hrm->reserved();
 552   for (size_t i = 0; i < count; i++) {
 553     if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) {
 554       return false;
 555     }
 556   }
 557   return true;
 558 }
 559 
 560 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges,
 561                                             size_t count,
 562                                             bool open) {
 563   assert(!is_init_completed(), "Expect to be called at JVM init time");
 564   assert(ranges != NULL, "MemRegion array NULL");
 565   assert(count != 0, "No MemRegions provided");
 566   MutexLocker x(Heap_lock);
 567 
 568   MemRegion reserved = _hrm->reserved();
 569   HeapWord* prev_last_addr = NULL;
 570   HeapRegion* prev_last_region = NULL;
 571 
 572   // Temporarily disable pretouching of heap pages. This interface is used
 573   // when mmap'ing archived heap data in, so pre-touching is wasted.
 574   FlagSetting fs(AlwaysPreTouch, false);
 575 
 576   // Enable archive object checking used by G1MarkSweep. We have to let it know
 577   // about each archive range, so that objects in those ranges aren't marked.
 578   G1ArchiveAllocator::enable_archive_object_check();
 579 
 580   // For each specified MemRegion range, allocate the corresponding G1
 581   // regions and mark them as archive regions. We expect the ranges
 582   // in ascending starting address order, without overlap.
 583   for (size_t i = 0; i < count; i++) {
 584     MemRegion curr_range = ranges[i];
 585     HeapWord* start_address = curr_range.start();
 586     size_t word_size = curr_range.word_size();
 587     HeapWord* last_address = curr_range.last();
 588     size_t commits = 0;
 589 
 590     guarantee(reserved.contains(start_address) && reserved.contains(last_address),
 591               "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 592               p2i(start_address), p2i(last_address));
 593     guarantee(start_address > prev_last_addr,
 594               "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 595               p2i(start_address), p2i(prev_last_addr));
 596     prev_last_addr = last_address;
 597 
 598     // Check for ranges that start in the same G1 region in which the previous
 599     // range ended, and adjust the start address so we don't try to allocate
 600     // the same region again. If the current range is entirely within that
 601     // region, skip it, just adjusting the recorded top.
 602     HeapRegion* start_region = _hrm->addr_to_region(start_address);
 603     if ((prev_last_region != NULL) && (start_region == prev_last_region)) {
 604       start_address = start_region->end();
 605       if (start_address > last_address) {
 606         increase_used(word_size * HeapWordSize);
 607         start_region->set_top(last_address + 1);
 608         continue;
 609       }
 610       start_region->set_top(start_address);
 611       curr_range = MemRegion(start_address, last_address + 1);
 612       start_region = _hrm->addr_to_region(start_address);
 613     }
 614 
 615     // Perform the actual region allocation, exiting if it fails.
 616     // Then note how much new space we have allocated.
 617     if (!_hrm->allocate_containing_regions(curr_range, &commits, workers())) {
 618       return false;
 619     }
 620     increase_used(word_size * HeapWordSize);
 621     if (commits != 0) {
 622       log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B",
 623                                 HeapRegion::GrainWords * HeapWordSize * commits);
 624 
 625     }
 626 
 627     // Mark each G1 region touched by the range as archive, add it to
 628     // the old set, and set top.
 629     HeapRegion* curr_region = _hrm->addr_to_region(start_address);
 630     HeapRegion* last_region = _hrm->addr_to_region(last_address);
 631     prev_last_region = last_region;
 632 
 633     while (curr_region != NULL) {
 634       assert(curr_region->is_empty() && !curr_region->is_pinned(),
 635              "Region already in use (index %u)", curr_region->hrm_index());
 636       if (open) {
 637         curr_region->set_open_archive();
 638       } else {
 639         curr_region->set_closed_archive();
 640       }
 641       _hr_printer.alloc(curr_region);
 642       _archive_set.add(curr_region);
 643       HeapWord* top;
 644       HeapRegion* next_region;
 645       if (curr_region != last_region) {
 646         top = curr_region->end();
 647         next_region = _hrm->next_region_in_heap(curr_region);
 648       } else {
 649         top = last_address + 1;
 650         next_region = NULL;
 651       }
 652       curr_region->set_top(top);
 653       curr_region = next_region;
 654     }
 655 
 656     // Notify mark-sweep of the archive
 657     G1ArchiveAllocator::set_range_archive(curr_range, open);
 658   }
 659   return true;
 660 }
 661 
 662 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) {
 663   assert(!is_init_completed(), "Expect to be called at JVM init time");
 664   assert(ranges != NULL, "MemRegion array NULL");
 665   assert(count != 0, "No MemRegions provided");
 666   MemRegion reserved = _hrm->reserved();
 667   HeapWord *prev_last_addr = NULL;
 668   HeapRegion* prev_last_region = NULL;
 669 
 670   // For each MemRegion, create filler objects, if needed, in the G1 regions
 671   // that contain the address range. The address range actually within the
 672   // MemRegion will not be modified. That is assumed to have been initialized
 673   // elsewhere, probably via an mmap of archived heap data.
 674   MutexLocker x(Heap_lock);
 675   for (size_t i = 0; i < count; i++) {
 676     HeapWord* start_address = ranges[i].start();
 677     HeapWord* last_address = ranges[i].last();
 678 
 679     assert(reserved.contains(start_address) && reserved.contains(last_address),
 680            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 681            p2i(start_address), p2i(last_address));
 682     assert(start_address > prev_last_addr,
 683            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 684            p2i(start_address), p2i(prev_last_addr));
 685 
 686     HeapRegion* start_region = _hrm->addr_to_region(start_address);
 687     HeapRegion* last_region = _hrm->addr_to_region(last_address);
 688     HeapWord* bottom_address = start_region->bottom();
 689 
 690     // Check for a range beginning in the same region in which the
 691     // previous one ended.
 692     if (start_region == prev_last_region) {
 693       bottom_address = prev_last_addr + 1;
 694     }
 695 
 696     // Verify that the regions were all marked as archive regions by
 697     // alloc_archive_regions.
 698     HeapRegion* curr_region = start_region;
 699     while (curr_region != NULL) {
 700       guarantee(curr_region->is_archive(),
 701                 "Expected archive region at index %u", curr_region->hrm_index());
 702       if (curr_region != last_region) {
 703         curr_region = _hrm->next_region_in_heap(curr_region);
 704       } else {
 705         curr_region = NULL;
 706       }
 707     }
 708 
 709     prev_last_addr = last_address;
 710     prev_last_region = last_region;
 711 
 712     // Fill the memory below the allocated range with dummy object(s),
 713     // if the region bottom does not match the range start, or if the previous
 714     // range ended within the same G1 region, and there is a gap.
 715     if (start_address != bottom_address) {
 716       size_t fill_size = pointer_delta(start_address, bottom_address);
 717       G1CollectedHeap::fill_with_objects(bottom_address, fill_size);
 718       increase_used(fill_size * HeapWordSize);
 719     }
 720   }
 721 }
 722 
 723 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t min_word_size,
 724                                                      size_t desired_word_size,
 725                                                      size_t* actual_word_size) {
 726   assert_heap_not_locked_and_not_at_safepoint();
 727   assert(!is_humongous(desired_word_size), "attempt_allocation() should not "
 728          "be called for humongous allocation requests");
 729 
 730   HeapWord* result = _allocator->attempt_allocation(min_word_size, desired_word_size, actual_word_size);
 731 
 732   if (result == NULL) {
 733     *actual_word_size = desired_word_size;
 734     result = attempt_allocation_slow(desired_word_size);
 735   }
 736 
 737   assert_heap_not_locked();
 738   if (result != NULL) {
 739     assert(*actual_word_size != 0, "Actual size must have been set here");
 740     dirty_young_block(result, *actual_word_size);
 741   } else {
 742     *actual_word_size = 0;
 743   }
 744 
 745   return result;
 746 }
 747 
 748 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) {
 749   assert(!is_init_completed(), "Expect to be called at JVM init time");
 750   assert(ranges != NULL, "MemRegion array NULL");
 751   assert(count != 0, "No MemRegions provided");
 752   MemRegion reserved = _hrm->reserved();
 753   HeapWord* prev_last_addr = NULL;
 754   HeapRegion* prev_last_region = NULL;
 755   size_t size_used = 0;
 756   size_t uncommitted_regions = 0;
 757 
 758   // For each Memregion, free the G1 regions that constitute it, and
 759   // notify mark-sweep that the range is no longer to be considered 'archive.'
 760   MutexLocker x(Heap_lock);
 761   for (size_t i = 0; i < count; i++) {
 762     HeapWord* start_address = ranges[i].start();
 763     HeapWord* last_address = ranges[i].last();
 764 
 765     assert(reserved.contains(start_address) && reserved.contains(last_address),
 766            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 767            p2i(start_address), p2i(last_address));
 768     assert(start_address > prev_last_addr,
 769            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 770            p2i(start_address), p2i(prev_last_addr));
 771     size_used += ranges[i].byte_size();
 772     prev_last_addr = last_address;
 773 
 774     HeapRegion* start_region = _hrm->addr_to_region(start_address);
 775     HeapRegion* last_region = _hrm->addr_to_region(last_address);
 776 
 777     // Check for ranges that start in the same G1 region in which the previous
 778     // range ended, and adjust the start address so we don't try to free
 779     // the same region again. If the current range is entirely within that
 780     // region, skip it.
 781     if (start_region == prev_last_region) {
 782       start_address = start_region->end();
 783       if (start_address > last_address) {
 784         continue;
 785       }
 786       start_region = _hrm->addr_to_region(start_address);
 787     }
 788     prev_last_region = last_region;
 789 
 790     // After verifying that each region was marked as an archive region by
 791     // alloc_archive_regions, set it free and empty and uncommit it.
 792     HeapRegion* curr_region = start_region;
 793     while (curr_region != NULL) {
 794       guarantee(curr_region->is_archive(),
 795                 "Expected archive region at index %u", curr_region->hrm_index());
 796       uint curr_index = curr_region->hrm_index();
 797       _archive_set.remove(curr_region);
 798       curr_region->set_free();
 799       curr_region->set_top(curr_region->bottom());
 800       if (curr_region != last_region) {
 801         curr_region = _hrm->next_region_in_heap(curr_region);
 802       } else {
 803         curr_region = NULL;
 804       }
 805       _hrm->shrink_at(curr_index, 1);
 806       uncommitted_regions++;
 807     }
 808 
 809     // Notify mark-sweep that this is no longer an archive range.
 810     G1ArchiveAllocator::clear_range_archive(ranges[i]);
 811   }
 812 
 813   if (uncommitted_regions != 0) {
 814     log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B",
 815                               HeapRegion::GrainWords * HeapWordSize * uncommitted_regions);
 816   }
 817   decrease_used(size_used);
 818 }
 819 
 820 oop G1CollectedHeap::materialize_archived_object(oop obj) {
 821   assert(obj != NULL, "archived obj is NULL");
 822   assert(G1ArchiveAllocator::is_archived_object(obj), "must be archived object");
 823 
 824   // Loading an archived object makes it strongly reachable. If it is
 825   // loaded during concurrent marking, it must be enqueued to the SATB
 826   // queue, shading the previously white object gray.
 827   G1BarrierSet::enqueue(obj);
 828 
 829   return obj;
 830 }
 831 
 832 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size) {
 833   ResourceMark rm; // For retrieving the thread names in log messages.
 834 
 835   // The structure of this method has a lot of similarities to
 836   // attempt_allocation_slow(). The reason these two were not merged
 837   // into a single one is that such a method would require several "if
 838   // allocation is not humongous do this, otherwise do that"
 839   // conditional paths which would obscure its flow. In fact, an early
 840   // version of this code did use a unified method which was harder to
 841   // follow and, as a result, it had subtle bugs that were hard to
 842   // track down. So keeping these two methods separate allows each to
 843   // be more readable. It will be good to keep these two in sync as
 844   // much as possible.
 845 
 846   assert_heap_not_locked_and_not_at_safepoint();
 847   assert(is_humongous(word_size), "attempt_allocation_humongous() "
 848          "should only be called for humongous allocations");
 849 
 850   // Humongous objects can exhaust the heap quickly, so we should check if we
 851   // need to start a marking cycle at each humongous object allocation. We do
 852   // the check before we do the actual allocation. The reason for doing it
 853   // before the allocation is that we avoid having to keep track of the newly
 854   // allocated memory while we do a GC.
 855   if (policy()->need_to_start_conc_mark("concurrent humongous allocation",
 856                                            word_size)) {
 857     collect(GCCause::_g1_humongous_allocation);
 858   }
 859 
 860   // We will loop until a) we manage to successfully perform the
 861   // allocation or b) we successfully schedule a collection which
 862   // fails to perform the allocation. b) is the only case when we'll
 863   // return NULL.
 864   HeapWord* result = NULL;
 865   for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 866     bool should_try_gc;
 867     uint gc_count_before;
 868 
 869 
 870     {
 871       MutexLocker x(Heap_lock);
 872 
 873       // Given that humongous objects are not allocated in young
 874       // regions, we'll first try to do the allocation without doing a
 875       // collection hoping that there's enough space in the heap.
 876       result = humongous_obj_allocate(word_size);
 877       if (result != NULL) {
 878         size_t size_in_regions = humongous_obj_size_in_regions(word_size);
 879         policy()->old_gen_alloc_tracker()->
 880           add_allocated_bytes_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
 881         return result;
 882       }
 883 
 884       // Only try a GC if the GCLocker does not signal the need for a GC. Wait until
 885       // the GCLocker initiated GC has been performed and then retry. This includes
 886       // the case when the GC Locker is not active but has not been performed.
 887       should_try_gc = !GCLocker::needs_gc();
 888       // Read the GC count while still holding the Heap_lock.
 889       gc_count_before = total_collections();
 890     }
 891 
 892     if (should_try_gc) {
 893       bool succeeded;
 894       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 895                                    GCCause::_g1_humongous_allocation);
 896       if (result != NULL) {
 897         assert(succeeded, "only way to get back a non-NULL result");
 898         log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT,
 899                              Thread::current()->name(), p2i(result));
 900         return result;
 901       }
 902 
 903       if (succeeded) {
 904         // We successfully scheduled a collection which failed to allocate. No
 905         // point in trying to allocate further. We'll just return NULL.
 906         log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate "
 907                              SIZE_FORMAT " words", Thread::current()->name(), word_size);
 908         return NULL;
 909       }
 910       log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT "",
 911                            Thread::current()->name(), word_size);
 912     } else {
 913       // Failed to schedule a collection.
 914       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 915         log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating "
 916                                SIZE_FORMAT " words", Thread::current()->name(), word_size);
 917         return NULL;
 918       }
 919       log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name());
 920       // The GCLocker is either active or the GCLocker initiated
 921       // GC has not yet been performed. Stall until it is and
 922       // then retry the allocation.
 923       GCLocker::stall_until_clear();
 924       gclocker_retry_count += 1;
 925     }
 926 
 927 
 928     // We can reach here if we were unsuccessful in scheduling a
 929     // collection (because another thread beat us to it) or if we were
 930     // stalled due to the GC locker. In either can we should retry the
 931     // allocation attempt in case another thread successfully
 932     // performed a collection and reclaimed enough space.
 933     // Humongous object allocation always needs a lock, so we wait for the retry
 934     // in the next iteration of the loop, unlike for the regular iteration case.
 935     // Give a warning if we seem to be looping forever.
 936 
 937     if ((QueuedAllocationWarningCount > 0) &&
 938         (try_count % QueuedAllocationWarningCount == 0)) {
 939       log_warning(gc, alloc)("%s: Retried allocation %u times for " SIZE_FORMAT " words",
 940                              Thread::current()->name(), try_count, word_size);
 941     }
 942   }
 943 
 944   ShouldNotReachHere();
 945   return NULL;
 946 }
 947 
 948 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
 949                                                            bool expect_null_mutator_alloc_region) {
 950   assert_at_safepoint_on_vm_thread();
 951   assert(!_allocator->has_mutator_alloc_region() || !expect_null_mutator_alloc_region,
 952          "the current alloc region was unexpectedly found to be non-NULL");
 953 
 954   if (!is_humongous(word_size)) {
 955     return _allocator->attempt_allocation_locked(word_size);
 956   } else {
 957     HeapWord* result = humongous_obj_allocate(word_size);
 958     if (result != NULL && policy()->need_to_start_conc_mark("STW humongous allocation")) {
 959       collector_state()->set_initiate_conc_mark_if_possible(true);
 960     }
 961     return result;
 962   }
 963 
 964   ShouldNotReachHere();
 965 }
 966 
 967 class PostCompactionPrinterClosure: public HeapRegionClosure {
 968 private:
 969   G1HRPrinter* _hr_printer;
 970 public:
 971   bool do_heap_region(HeapRegion* hr) {
 972     assert(!hr->is_young(), "not expecting to find young regions");
 973     _hr_printer->post_compaction(hr);
 974     return false;
 975   }
 976 
 977   PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
 978     : _hr_printer(hr_printer) { }
 979 };
 980 
 981 void G1CollectedHeap::print_hrm_post_compaction() {
 982   if (_hr_printer.is_active()) {
 983     PostCompactionPrinterClosure cl(hr_printer());
 984     heap_region_iterate(&cl);
 985   }
 986 }
 987 
 988 void G1CollectedHeap::abort_concurrent_cycle() {
 989   // If we start the compaction before the CM threads finish
 990   // scanning the root regions we might trip them over as we'll
 991   // be moving objects / updating references. So let's wait until
 992   // they are done. By telling them to abort, they should complete
 993   // early.
 994   _cm->root_regions()->abort();
 995   _cm->root_regions()->wait_until_scan_finished();
 996 
 997   // Disable discovery and empty the discovered lists
 998   // for the CM ref processor.
 999   _ref_processor_cm->disable_discovery();
1000   _ref_processor_cm->abandon_partial_discovery();
1001   _ref_processor_cm->verify_no_references_recorded();
1002 
1003   // Abandon current iterations of concurrent marking and concurrent
1004   // refinement, if any are in progress.
1005   concurrent_mark()->concurrent_cycle_abort();
1006 }
1007 
1008 void G1CollectedHeap::prepare_heap_for_full_collection() {
1009   // Make sure we'll choose a new allocation region afterwards.
1010   _allocator->release_mutator_alloc_regions();
1011   _allocator->abandon_gc_alloc_regions();
1012 
1013   // We may have added regions to the current incremental collection
1014   // set between the last GC or pause and now. We need to clear the
1015   // incremental collection set and then start rebuilding it afresh
1016   // after this full GC.
1017   abandon_collection_set(collection_set());
1018 
1019   tear_down_region_sets(false /* free_list_only */);
1020 
1021   hrm()->prepare_for_full_collection_start();
1022 }
1023 
1024 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) {
1025   assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant");
1026   assert_used_and_recalculate_used_equal(this);
1027   _verifier->verify_region_sets_optional();
1028   _verifier->verify_before_gc(G1HeapVerifier::G1VerifyFull);
1029   _verifier->check_bitmaps("Full GC Start");
1030 }
1031 
1032 void G1CollectedHeap::prepare_heap_for_mutators() {
1033   hrm()->prepare_for_full_collection_end();
1034 
1035   // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1036   ClassLoaderDataGraph::purge();
1037   MetaspaceUtils::verify_metrics();
1038 
1039   // Prepare heap for normal collections.
1040   assert(num_free_regions() == 0, "we should not have added any free regions");
1041   rebuild_region_sets(false /* free_list_only */);
1042   abort_refinement();
1043   resize_heap_if_necessary();
1044 
1045   // Rebuild the strong code root lists for each region
1046   rebuild_strong_code_roots();
1047 
1048   // Purge code root memory
1049   purge_code_root_memory();
1050 
1051   // Start a new incremental collection set for the next pause
1052   start_new_collection_set();
1053 
1054   _allocator->init_mutator_alloc_regions();
1055 
1056   // Post collection state updates.
1057   MetaspaceGC::compute_new_size();
1058 }
1059 
1060 void G1CollectedHeap::abort_refinement() {
1061   if (_hot_card_cache->use_cache()) {
1062     _hot_card_cache->reset_hot_cache();
1063   }
1064 
1065   // Discard all remembered set updates and reset refinement statistics.
1066   G1BarrierSet::dirty_card_queue_set().abandon_logs();
1067   assert(G1BarrierSet::dirty_card_queue_set().num_cards() == 0,
1068          "DCQS should be empty");
1069   concurrent_refine()->get_and_reset_refinement_stats();
1070 }
1071 
1072 void G1CollectedHeap::verify_after_full_collection() {
1073   _hrm->verify_optional();
1074   _verifier->verify_region_sets_optional();
1075   _verifier->verify_after_gc(G1HeapVerifier::G1VerifyFull);
1076   // Clear the previous marking bitmap, if needed for bitmap verification.
1077   // Note we cannot do this when we clear the next marking bitmap in
1078   // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the
1079   // objects marked during a full GC against the previous bitmap.
1080   // But we need to clear it before calling check_bitmaps below since
1081   // the full GC has compacted objects and updated TAMS but not updated
1082   // the prev bitmap.
1083   if (G1VerifyBitmaps) {
1084     GCTraceTime(Debug, gc) tm("Clear Prev Bitmap for Verification");
1085     _cm->clear_prev_bitmap(workers());
1086   }
1087   // This call implicitly verifies that the next bitmap is clear after Full GC.
1088   _verifier->check_bitmaps("Full GC End");
1089 
1090   // At this point there should be no regions in the
1091   // entire heap tagged as young.
1092   assert(check_young_list_empty(), "young list should be empty at this point");
1093 
1094   // Note: since we've just done a full GC, concurrent
1095   // marking is no longer active. Therefore we need not
1096   // re-enable reference discovery for the CM ref processor.
1097   // That will be done at the start of the next marking cycle.
1098   // We also know that the STW processor should no longer
1099   // discover any new references.
1100   assert(!_ref_processor_stw->discovery_enabled(), "Postcondition");
1101   assert(!_ref_processor_cm->discovery_enabled(), "Postcondition");
1102   _ref_processor_stw->verify_no_references_recorded();
1103   _ref_processor_cm->verify_no_references_recorded();
1104 }
1105 
1106 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) {
1107   // Post collection logging.
1108   // We should do this after we potentially resize the heap so
1109   // that all the COMMIT / UNCOMMIT events are generated before
1110   // the compaction events.
1111   print_hrm_post_compaction();
1112   heap_transition->print();
1113   print_heap_after_gc();
1114   print_heap_regions();
1115 }
1116 
1117 bool G1CollectedHeap::do_full_collection(bool explicit_gc,
1118                                          bool clear_all_soft_refs) {
1119   assert_at_safepoint_on_vm_thread();
1120 
1121   if (GCLocker::check_active_before_gc()) {
1122     // Full GC was not completed.
1123     return false;
1124   }
1125 
1126   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1127       soft_ref_policy()->should_clear_all_soft_refs();
1128 
1129   G1FullCollector collector(this, explicit_gc, do_clear_all_soft_refs);
1130   GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true);
1131 
1132   collector.prepare_collection();
1133   collector.collect();
1134   collector.complete_collection();
1135 
1136   // Full collection was successfully completed.
1137   return true;
1138 }
1139 
1140 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1141   // Currently, there is no facility in the do_full_collection(bool) API to notify
1142   // the caller that the collection did not succeed (e.g., because it was locked
1143   // out by the GC locker). So, right now, we'll ignore the return value.
1144   bool dummy = do_full_collection(true,                /* explicit_gc */
1145                                   clear_all_soft_refs);
1146 }
1147 
1148 void G1CollectedHeap::resize_heap_if_necessary() {
1149   assert_at_safepoint_on_vm_thread();
1150 
1151   bool should_expand;
1152   size_t resize_amount = _heap_sizing_policy->full_collection_resize_amount(should_expand);
1153 
1154   if (resize_amount == 0) {
1155     return;
1156   } else if (should_expand) {
1157     expand(resize_amount, _workers);
1158   } else {
1159     shrink(resize_amount);
1160   }
1161 }
1162 
1163 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size,
1164                                                             bool do_gc,
1165                                                             bool clear_all_soft_refs,
1166                                                             bool expect_null_mutator_alloc_region,
1167                                                             bool* gc_succeeded) {
1168   *gc_succeeded = true;
1169   // Let's attempt the allocation first.
1170   HeapWord* result =
1171     attempt_allocation_at_safepoint(word_size,
1172                                     expect_null_mutator_alloc_region);
1173   if (result != NULL) {
1174     return result;
1175   }
1176 
1177   // In a G1 heap, we're supposed to keep allocation from failing by
1178   // incremental pauses.  Therefore, at least for now, we'll favor
1179   // expansion over collection.  (This might change in the future if we can
1180   // do something smarter than full collection to satisfy a failed alloc.)
1181   result = expand_and_allocate(word_size);
1182   if (result != NULL) {
1183     return result;
1184   }
1185 
1186   if (do_gc) {
1187     // Expansion didn't work, we'll try to do a Full GC.
1188     *gc_succeeded = do_full_collection(false, /* explicit_gc */
1189                                        clear_all_soft_refs);
1190   }
1191 
1192   return NULL;
1193 }
1194 
1195 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1196                                                      bool* succeeded) {
1197   assert_at_safepoint_on_vm_thread();
1198 
1199   // Attempts to allocate followed by Full GC.
1200   HeapWord* result =
1201     satisfy_failed_allocation_helper(word_size,
1202                                      true,  /* do_gc */
1203                                      false, /* clear_all_soft_refs */
1204                                      false, /* expect_null_mutator_alloc_region */
1205                                      succeeded);
1206 
1207   if (result != NULL || !*succeeded) {
1208     return result;
1209   }
1210 
1211   // Attempts to allocate followed by Full GC that will collect all soft references.
1212   result = satisfy_failed_allocation_helper(word_size,
1213                                             true, /* do_gc */
1214                                             true, /* clear_all_soft_refs */
1215                                             true, /* expect_null_mutator_alloc_region */
1216                                             succeeded);
1217 
1218   if (result != NULL || !*succeeded) {
1219     return result;
1220   }
1221 
1222   // Attempts to allocate, no GC
1223   result = satisfy_failed_allocation_helper(word_size,
1224                                             false, /* do_gc */
1225                                             false, /* clear_all_soft_refs */
1226                                             true,  /* expect_null_mutator_alloc_region */
1227                                             succeeded);
1228 
1229   if (result != NULL) {
1230     return result;
1231   }
1232 
1233   assert(!soft_ref_policy()->should_clear_all_soft_refs(),
1234          "Flag should have been handled and cleared prior to this point");
1235 
1236   // What else?  We might try synchronous finalization later.  If the total
1237   // space available is large enough for the allocation, then a more
1238   // complete compaction phase than we've tried so far might be
1239   // appropriate.
1240   return NULL;
1241 }
1242 
1243 // Attempting to expand the heap sufficiently
1244 // to support an allocation of the given "word_size".  If
1245 // successful, perform the allocation and return the address of the
1246 // allocated block, or else "NULL".
1247 
1248 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1249   assert_at_safepoint_on_vm_thread();
1250 
1251   _verifier->verify_region_sets_optional();
1252 
1253   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1254   log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B",
1255                             word_size * HeapWordSize);
1256 
1257 
1258   if (expand(expand_bytes, _workers)) {
1259     _hrm->verify_optional();
1260     _verifier->verify_region_sets_optional();
1261     return attempt_allocation_at_safepoint(word_size,
1262                                            false /* expect_null_mutator_alloc_region */);
1263   }
1264   return NULL;
1265 }
1266 
1267 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) {
1268   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1269   aligned_expand_bytes = align_up(aligned_expand_bytes,
1270                                        HeapRegion::GrainBytes);
1271 
1272   log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B",
1273                             expand_bytes, aligned_expand_bytes);
1274 
1275   if (is_maximal_no_gc()) {
1276     log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1277     return false;
1278   }
1279 
1280   double expand_heap_start_time_sec = os::elapsedTime();
1281   uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1282   assert(regions_to_expand > 0, "Must expand by at least one region");
1283 
1284   uint expanded_by = _hrm->expand_by(regions_to_expand, pretouch_workers);
1285   if (expand_time_ms != NULL) {
1286     *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS;
1287   }
1288 
1289   if (expanded_by > 0) {
1290     size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1291     assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1292     policy()->record_new_heap_size(num_regions());
1293   } else {
1294     log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)");
1295 
1296     // The expansion of the virtual storage space was unsuccessful.
1297     // Let's see if it was because we ran out of swap.
1298     if (G1ExitOnExpansionFailure &&
1299         _hrm->available() >= regions_to_expand) {
1300       // We had head room...
1301       vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1302     }
1303   }
1304   return regions_to_expand > 0;
1305 }
1306 
1307 bool G1CollectedHeap::expand_single_region(uint node_index) {
1308   uint expanded_by = _hrm->expand_on_preferred_node(node_index);
1309 
1310   if (expanded_by == 0) {
1311     assert(is_maximal_no_gc(), "Should be no regions left, available: %u", _hrm->available());
1312     log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1313     return false;
1314   }
1315 
1316   policy()->record_new_heap_size(num_regions());
1317   return true;
1318 }
1319 
1320 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1321   size_t aligned_shrink_bytes =
1322     ReservedSpace::page_align_size_down(shrink_bytes);
1323   aligned_shrink_bytes = align_down(aligned_shrink_bytes,
1324                                          HeapRegion::GrainBytes);
1325   uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1326 
1327   uint num_regions_removed = _hrm->shrink_by(num_regions_to_remove);
1328   size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1329 
1330   log_debug(gc, ergo, heap)("Shrink the heap. requested shrinking amount: " SIZE_FORMAT "B aligned shrinking amount: " SIZE_FORMAT "B attempted shrinking amount: " SIZE_FORMAT "B",
1331                             shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1332   if (num_regions_removed > 0) {
1333     policy()->record_new_heap_size(num_regions());
1334   } else {
1335     log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)");
1336   }
1337 }
1338 
1339 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1340   _verifier->verify_region_sets_optional();
1341 
1342   // We should only reach here at the end of a Full GC or during Remark which
1343   // means we should not not be holding to any GC alloc regions. The method
1344   // below will make sure of that and do any remaining clean up.
1345   _allocator->abandon_gc_alloc_regions();
1346 
1347   // Instead of tearing down / rebuilding the free lists here, we
1348   // could instead use the remove_all_pending() method on free_list to
1349   // remove only the ones that we need to remove.
1350   tear_down_region_sets(true /* free_list_only */);
1351   shrink_helper(shrink_bytes);
1352   rebuild_region_sets(true /* free_list_only */);
1353 
1354   _hrm->verify_optional();
1355   _verifier->verify_region_sets_optional();
1356 }
1357 
1358 class OldRegionSetChecker : public HeapRegionSetChecker {
1359 public:
1360   void check_mt_safety() {
1361     // Master Old Set MT safety protocol:
1362     // (a) If we're at a safepoint, operations on the master old set
1363     // should be invoked:
1364     // - by the VM thread (which will serialize them), or
1365     // - by the GC workers while holding the FreeList_lock, if we're
1366     //   at a safepoint for an evacuation pause (this lock is taken
1367     //   anyway when an GC alloc region is retired so that a new one
1368     //   is allocated from the free list), or
1369     // - by the GC workers while holding the OldSets_lock, if we're at a
1370     //   safepoint for a cleanup pause.
1371     // (b) If we're not at a safepoint, operations on the master old set
1372     // should be invoked while holding the Heap_lock.
1373 
1374     if (SafepointSynchronize::is_at_safepoint()) {
1375       guarantee(Thread::current()->is_VM_thread() ||
1376                 FreeList_lock->owned_by_self() || OldSets_lock->owned_by_self(),
1377                 "master old set MT safety protocol at a safepoint");
1378     } else {
1379       guarantee(Heap_lock->owned_by_self(), "master old set MT safety protocol outside a safepoint");
1380     }
1381   }
1382   bool is_correct_type(HeapRegion* hr) { return hr->is_old(); }
1383   const char* get_description() { return "Old Regions"; }
1384 };
1385 
1386 class ArchiveRegionSetChecker : public HeapRegionSetChecker {
1387 public:
1388   void check_mt_safety() {
1389     guarantee(!Universe::is_fully_initialized() || SafepointSynchronize::is_at_safepoint(),
1390               "May only change archive regions during initialization or safepoint.");
1391   }
1392   bool is_correct_type(HeapRegion* hr) { return hr->is_archive(); }
1393   const char* get_description() { return "Archive Regions"; }
1394 };
1395 
1396 class HumongousRegionSetChecker : public HeapRegionSetChecker {
1397 public:
1398   void check_mt_safety() {
1399     // Humongous Set MT safety protocol:
1400     // (a) If we're at a safepoint, operations on the master humongous
1401     // set should be invoked by either the VM thread (which will
1402     // serialize them) or by the GC workers while holding the
1403     // OldSets_lock.
1404     // (b) If we're not at a safepoint, operations on the master
1405     // humongous set should be invoked while holding the Heap_lock.
1406 
1407     if (SafepointSynchronize::is_at_safepoint()) {
1408       guarantee(Thread::current()->is_VM_thread() ||
1409                 OldSets_lock->owned_by_self(),
1410                 "master humongous set MT safety protocol at a safepoint");
1411     } else {
1412       guarantee(Heap_lock->owned_by_self(),
1413                 "master humongous set MT safety protocol outside a safepoint");
1414     }
1415   }
1416   bool is_correct_type(HeapRegion* hr) { return hr->is_humongous(); }
1417   const char* get_description() { return "Humongous Regions"; }
1418 };
1419 
1420 G1CollectedHeap::G1CollectedHeap() :
1421   CollectedHeap(),
1422   _young_gen_sampling_thread(NULL),
1423   _workers(NULL),
1424   _card_table(NULL),
1425   _soft_ref_policy(),
1426   _old_set("Old Region Set", new OldRegionSetChecker()),
1427   _archive_set("Archive Region Set", new ArchiveRegionSetChecker()),
1428   _humongous_set("Humongous Region Set", new HumongousRegionSetChecker()),
1429   _bot(NULL),
1430   _listener(),
1431   _numa(G1NUMA::create()),
1432   _hrm(NULL),
1433   _allocator(NULL),
1434   _verifier(NULL),
1435   _summary_bytes_used(0),
1436   _bytes_used_during_gc(0),
1437   _archive_allocator(NULL),
1438   _survivor_evac_stats("Young", YoungPLABSize, PLABWeight),
1439   _old_evac_stats("Old", OldPLABSize, PLABWeight),
1440   _expand_heap_after_alloc_failure(true),
1441   _g1mm(NULL),
1442   _humongous_reclaim_candidates(),
1443   _has_humongous_reclaim_candidates(false),
1444   _hr_printer(),
1445   _collector_state(),
1446   _old_marking_cycles_started(0),
1447   _old_marking_cycles_completed(0),
1448   _eden(),
1449   _survivor(),
1450   _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1451   _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1452   _policy(G1Policy::create_policy(_gc_timer_stw)),
1453   _heap_sizing_policy(NULL),
1454   _collection_set(this, _policy),
1455   _hot_card_cache(NULL),
1456   _rem_set(NULL),
1457   _cm(NULL),
1458   _cm_thread(NULL),
1459   _cr(NULL),
1460   _task_queues(NULL),
1461   _evacuation_failed(false),
1462   _evacuation_failed_info_array(NULL),
1463   _preserved_marks_set(true /* in_c_heap */),
1464 #ifndef PRODUCT
1465   _evacuation_failure_alot_for_current_gc(false),
1466   _evacuation_failure_alot_gc_number(0),
1467   _evacuation_failure_alot_count(0),
1468 #endif
1469   _ref_processor_stw(NULL),
1470   _is_alive_closure_stw(this),
1471   _is_subject_to_discovery_stw(this),
1472   _ref_processor_cm(NULL),
1473   _is_alive_closure_cm(this),
1474   _is_subject_to_discovery_cm(this),
1475   _region_attr() {
1476 
1477   _verifier = new G1HeapVerifier(this);
1478 
1479   _allocator = new G1Allocator(this);
1480 
1481   _heap_sizing_policy = G1HeapSizingPolicy::create(this, _policy->analytics());
1482 
1483   _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);
1484 
1485   // Override the default _filler_array_max_size so that no humongous filler
1486   // objects are created.
1487   _filler_array_max_size = _humongous_object_threshold_in_words;
1488 
1489   uint n_queues = ParallelGCThreads;
1490   _task_queues = new G1ScannerTasksQueueSet(n_queues);
1491 
1492   _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1493 
1494   for (uint i = 0; i < n_queues; i++) {
1495     G1ScannerTasksQueue* q = new G1ScannerTasksQueue();
1496     q->initialize();
1497     _task_queues->register_queue(i, q);
1498     ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1499   }
1500 
1501   // Initialize the G1EvacuationFailureALot counters and flags.
1502   NOT_PRODUCT(reset_evacuation_should_fail();)
1503   _gc_tracer_stw->initialize();
1504 
1505   guarantee(_task_queues != NULL, "task_queues allocation failure.");
1506 }
1507 
1508 static size_t actual_reserved_page_size(ReservedSpace rs) {
1509   size_t page_size = os::vm_page_size();
1510   if (UseLargePages) {
1511     // There are two ways to manage large page memory.
1512     // 1. OS supports committing large page memory.
1513     // 2. OS doesn't support committing large page memory so ReservedSpace manages it.
1514     //    And ReservedSpace calls it 'special'. If we failed to set 'special',
1515     //    we reserved memory without large page.
1516     if (os::can_commit_large_page_memory() || rs.special()) {
1517       // An alignment at ReservedSpace comes from preferred page size or
1518       // heap alignment, and if the alignment came from heap alignment, it could be
1519       // larger than large pages size. So need to cap with the large page size.
1520       page_size = MIN2(rs.alignment(), os::large_page_size());
1521     }
1522   }
1523 
1524   return page_size;
1525 }
1526 
1527 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1528                                                                  size_t size,
1529                                                                  size_t translation_factor) {
1530   size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1531   // Allocate a new reserved space, preferring to use large pages.
1532   ReservedSpace rs(size, preferred_page_size);
1533   size_t page_size = actual_reserved_page_size(rs);
1534   G1RegionToSpaceMapper* result  =
1535     G1RegionToSpaceMapper::create_mapper(rs,
1536                                          size,
1537                                          page_size,
1538                                          HeapRegion::GrainBytes,
1539                                          translation_factor,
1540                                          mtGC);
1541 
1542   os::trace_page_sizes_for_requested_size(description,
1543                                           size,
1544                                           preferred_page_size,
1545                                           page_size,
1546                                           rs.base(),
1547                                           rs.size());
1548 
1549   return result;
1550 }
1551 
1552 jint G1CollectedHeap::initialize_concurrent_refinement() {
1553   jint ecode = JNI_OK;
1554   _cr = G1ConcurrentRefine::create(&ecode);
1555   return ecode;
1556 }
1557 
1558 jint G1CollectedHeap::initialize_young_gen_sampling_thread() {
1559   _young_gen_sampling_thread = new G1YoungRemSetSamplingThread();
1560   if (_young_gen_sampling_thread->osthread() == NULL) {
1561     vm_shutdown_during_initialization("Could not create G1YoungRemSetSamplingThread");
1562     return JNI_ENOMEM;
1563   }
1564   return JNI_OK;
1565 }
1566 
1567 jint G1CollectedHeap::initialize() {
1568 
1569   // Necessary to satisfy locking discipline assertions.
1570 
1571   MutexLocker x(Heap_lock);
1572 
1573   // While there are no constraints in the GC code that HeapWordSize
1574   // be any particular value, there are multiple other areas in the
1575   // system which believe this to be true (e.g. oop->object_size in some
1576   // cases incorrectly returns the size in wordSize units rather than
1577   // HeapWordSize).
1578   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1579 
1580   size_t init_byte_size = InitialHeapSize;
1581   size_t reserved_byte_size = G1Arguments::heap_reserved_size_bytes();
1582 
1583   // Ensure that the sizes are properly aligned.
1584   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1585   Universe::check_alignment(reserved_byte_size, HeapRegion::GrainBytes, "g1 heap");
1586   Universe::check_alignment(reserved_byte_size, HeapAlignment, "g1 heap");
1587 
1588   // Reserve the maximum.
1589 
1590   // When compressed oops are enabled, the preferred heap base
1591   // is calculated by subtracting the requested size from the
1592   // 32Gb boundary and using the result as the base address for
1593   // heap reservation. If the requested size is not aligned to
1594   // HeapRegion::GrainBytes (i.e. the alignment that is passed
1595   // into the ReservedHeapSpace constructor) then the actual
1596   // base of the reserved heap may end up differing from the
1597   // address that was requested (i.e. the preferred heap base).
1598   // If this happens then we could end up using a non-optimal
1599   // compressed oops mode.
1600 
1601   ReservedHeapSpace heap_rs = Universe::reserve_heap(reserved_byte_size,
1602                                                      HeapAlignment);
1603 
1604   initialize_reserved_region(heap_rs);
1605 
1606   // Create the barrier set for the entire reserved region.
1607   G1CardTable* ct = new G1CardTable(heap_rs.region());
1608   ct->initialize();
1609   G1BarrierSet* bs = new G1BarrierSet(ct);
1610   bs->initialize();
1611   assert(bs->is_a(BarrierSet::G1BarrierSet), "sanity");
1612   BarrierSet::set_barrier_set(bs);
1613   _card_table = ct;
1614 
1615   {
1616     G1SATBMarkQueueSet& satbqs = bs->satb_mark_queue_set();
1617     satbqs.set_process_completed_buffers_threshold(G1SATBProcessCompletedThreshold);
1618     satbqs.set_buffer_enqueue_threshold_percentage(G1SATBBufferEnqueueingThresholdPercent);
1619   }
1620 
1621   // Create the hot card cache.
1622   _hot_card_cache = new G1HotCardCache(this);
1623 
1624   // Carve out the G1 part of the heap.
1625   ReservedSpace g1_rs = heap_rs.first_part(reserved_byte_size);
1626   size_t page_size = actual_reserved_page_size(heap_rs);
1627   G1RegionToSpaceMapper* heap_storage =
1628     G1RegionToSpaceMapper::create_heap_mapper(g1_rs,
1629                                               g1_rs.size(),
1630                                               page_size,
1631                                               HeapRegion::GrainBytes,
1632                                               1,
1633                                               mtJavaHeap);
1634   if(heap_storage == NULL) {
1635     vm_shutdown_during_initialization("Could not initialize G1 heap");
1636     return JNI_ERR;
1637   }
1638 
1639   os::trace_page_sizes("Heap",
1640                        MinHeapSize,
1641                        reserved_byte_size,
1642                        page_size,
1643                        heap_rs.base(),
1644                        heap_rs.size());
1645   heap_storage->set_mapping_changed_listener(&_listener);
1646 
1647   // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1648   G1RegionToSpaceMapper* bot_storage =
1649     create_aux_memory_mapper("Block Offset Table",
1650                              G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize),
1651                              G1BlockOffsetTable::heap_map_factor());
1652 
1653   G1RegionToSpaceMapper* cardtable_storage =
1654     create_aux_memory_mapper("Card Table",
1655                              G1CardTable::compute_size(g1_rs.size() / HeapWordSize),
1656                              G1CardTable::heap_map_factor());
1657 
1658   G1RegionToSpaceMapper* card_counts_storage =
1659     create_aux_memory_mapper("Card Counts Table",
1660                              G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1661                              G1CardCounts::heap_map_factor());
1662 
1663   size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size());
1664   G1RegionToSpaceMapper* prev_bitmap_storage =
1665     create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1666   G1RegionToSpaceMapper* next_bitmap_storage =
1667     create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1668 
1669   _hrm = HeapRegionManager::create_manager(this);
1670 
1671   _hrm->initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1672   _card_table->initialize(cardtable_storage);
1673 
1674   // Do later initialization work for concurrent refinement.
1675   _hot_card_cache->initialize(card_counts_storage);
1676 
1677   // 6843694 - ensure that the maximum region index can fit
1678   // in the remembered set structures.
1679   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1680   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1681 
1682   // The G1FromCardCache reserves card with value 0 as "invalid", so the heap must not
1683   // start within the first card.
1684   guarantee(g1_rs.base() >= (char*)G1CardTable::card_size, "Java heap must not start within the first card.");
1685   // Also create a G1 rem set.
1686   _rem_set = new G1RemSet(this, _card_table, _hot_card_cache);
1687   _rem_set->initialize(max_reserved_capacity(), max_regions());
1688 
1689   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1690   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1691   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1692             "too many cards per region");
1693 
1694   FreeRegionList::set_unrealistically_long_length(max_expandable_regions() + 1);
1695 
1696   _bot = new G1BlockOffsetTable(reserved_region(), bot_storage);
1697 
1698   {
1699     HeapWord* start = _hrm->reserved().start();
1700     HeapWord* end = _hrm->reserved().end();
1701     size_t granularity = HeapRegion::GrainBytes;
1702 
1703     _region_attr.initialize(start, end, granularity);
1704     _humongous_reclaim_candidates.initialize(start, end, granularity);
1705   }
1706 
1707   _workers = new WorkGang("GC Thread", ParallelGCThreads,
1708                           true /* are_GC_task_threads */,
1709                           false /* are_ConcurrentGC_threads */);
1710   if (_workers == NULL) {
1711     return JNI_ENOMEM;
1712   }
1713   _workers->initialize_workers();
1714 
1715   _numa->set_region_info(HeapRegion::GrainBytes, page_size);
1716 
1717   // Create the G1ConcurrentMark data structure and thread.
1718   // (Must do this late, so that "max_regions" is defined.)
1719   _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1720   _cm_thread = _cm->cm_thread();
1721 
1722   // Now expand into the initial heap size.
1723   if (!expand(init_byte_size, _workers)) {
1724     vm_shutdown_during_initialization("Failed to allocate initial heap.");
1725     return JNI_ENOMEM;
1726   }
1727 
1728   // Perform any initialization actions delegated to the policy.
1729   policy()->init(this, &_collection_set);
1730 
1731   jint ecode = initialize_concurrent_refinement();
1732   if (ecode != JNI_OK) {
1733     return ecode;
1734   }
1735 
1736   ecode = initialize_young_gen_sampling_thread();
1737   if (ecode != JNI_OK) {
1738     return ecode;
1739   }
1740 
1741   {
1742     G1DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
1743     dcqs.set_process_cards_threshold(concurrent_refine()->yellow_zone());
1744     dcqs.set_max_cards(concurrent_refine()->red_zone());
1745   }
1746 
1747   // Here we allocate the dummy HeapRegion that is required by the
1748   // G1AllocRegion class.
1749   HeapRegion* dummy_region = _hrm->get_dummy_region();
1750 
1751   // We'll re-use the same region whether the alloc region will
1752   // require BOT updates or not and, if it doesn't, then a non-young
1753   // region will complain that it cannot support allocations without
1754   // BOT updates. So we'll tag the dummy region as eden to avoid that.
1755   dummy_region->set_eden();
1756   // Make sure it's full.
1757   dummy_region->set_top(dummy_region->end());
1758   G1AllocRegion::setup(this, dummy_region);
1759 
1760   _allocator->init_mutator_alloc_regions();
1761 
1762   // Do create of the monitoring and management support so that
1763   // values in the heap have been properly initialized.
1764   _g1mm = new G1MonitoringSupport(this);
1765 
1766   G1StringDedup::initialize();
1767 
1768   _preserved_marks_set.init(ParallelGCThreads);
1769 
1770   _collection_set.initialize(max_regions());
1771 
1772   G1InitLogger::print();
1773 
1774   return JNI_OK;
1775 }
1776 
1777 void G1CollectedHeap::stop() {
1778   // Stop all concurrent threads. We do this to make sure these threads
1779   // do not continue to execute and access resources (e.g. logging)
1780   // that are destroyed during shutdown.
1781   _cr->stop();
1782   _young_gen_sampling_thread->stop();
1783   _cm_thread->stop();
1784   if (G1StringDedup::is_enabled()) {
1785     G1StringDedup::stop();
1786   }
1787 }
1788 
1789 void G1CollectedHeap::safepoint_synchronize_begin() {
1790   SuspendibleThreadSet::synchronize();
1791 }
1792 
1793 void G1CollectedHeap::safepoint_synchronize_end() {
1794   SuspendibleThreadSet::desynchronize();
1795 }
1796 
1797 void G1CollectedHeap::post_initialize() {
1798   CollectedHeap::post_initialize();
1799   ref_processing_init();
1800 }
1801 
1802 void G1CollectedHeap::ref_processing_init() {
1803   // Reference processing in G1 currently works as follows:
1804   //
1805   // * There are two reference processor instances. One is
1806   //   used to record and process discovered references
1807   //   during concurrent marking; the other is used to
1808   //   record and process references during STW pauses
1809   //   (both full and incremental).
1810   // * Both ref processors need to 'span' the entire heap as
1811   //   the regions in the collection set may be dotted around.
1812   //
1813   // * For the concurrent marking ref processor:
1814   //   * Reference discovery is enabled at concurrent start.
1815   //   * Reference discovery is disabled and the discovered
1816   //     references processed etc during remarking.
1817   //   * Reference discovery is MT (see below).
1818   //   * Reference discovery requires a barrier (see below).
1819   //   * Reference processing may or may not be MT
1820   //     (depending on the value of ParallelRefProcEnabled
1821   //     and ParallelGCThreads).
1822   //   * A full GC disables reference discovery by the CM
1823   //     ref processor and abandons any entries on it's
1824   //     discovered lists.
1825   //
1826   // * For the STW processor:
1827   //   * Non MT discovery is enabled at the start of a full GC.
1828   //   * Processing and enqueueing during a full GC is non-MT.
1829   //   * During a full GC, references are processed after marking.
1830   //
1831   //   * Discovery (may or may not be MT) is enabled at the start
1832   //     of an incremental evacuation pause.
1833   //   * References are processed near the end of a STW evacuation pause.
1834   //   * For both types of GC:
1835   //     * Discovery is atomic - i.e. not concurrent.
1836   //     * Reference discovery will not need a barrier.
1837 
1838   bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1);
1839 
1840   // Concurrent Mark ref processor
1841   _ref_processor_cm =
1842     new ReferenceProcessor(&_is_subject_to_discovery_cm,
1843                            mt_processing,                                  // mt processing
1844                            ParallelGCThreads,                              // degree of mt processing
1845                            (ParallelGCThreads > 1) || (ConcGCThreads > 1), // mt discovery
1846                            MAX2(ParallelGCThreads, ConcGCThreads),         // degree of mt discovery
1847                            false,                                          // Reference discovery is not atomic
1848                            &_is_alive_closure_cm,                          // is alive closure
1849                            true);                                          // allow changes to number of processing threads
1850 
1851   // STW ref processor
1852   _ref_processor_stw =
1853     new ReferenceProcessor(&_is_subject_to_discovery_stw,
1854                            mt_processing,                        // mt processing
1855                            ParallelGCThreads,                    // degree of mt processing
1856                            (ParallelGCThreads > 1),              // mt discovery
1857                            ParallelGCThreads,                    // degree of mt discovery
1858                            true,                                 // Reference discovery is atomic
1859                            &_is_alive_closure_stw,               // is alive closure
1860                            true);                                // allow changes to number of processing threads
1861 }
1862 
1863 SoftRefPolicy* G1CollectedHeap::soft_ref_policy() {
1864   return &_soft_ref_policy;
1865 }
1866 
1867 size_t G1CollectedHeap::capacity() const {
1868   return _hrm->length() * HeapRegion::GrainBytes;
1869 }
1870 
1871 size_t G1CollectedHeap::unused_committed_regions_in_bytes() const {
1872   return _hrm->total_free_bytes();
1873 }
1874 
1875 void G1CollectedHeap::iterate_hcc_closure(G1CardTableEntryClosure* cl, uint worker_id) {
1876   _hot_card_cache->drain(cl, worker_id);
1877 }
1878 
1879 // Computes the sum of the storage used by the various regions.
1880 size_t G1CollectedHeap::used() const {
1881   size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
1882   if (_archive_allocator != NULL) {
1883     result += _archive_allocator->used();
1884   }
1885   return result;
1886 }
1887 
1888 size_t G1CollectedHeap::used_unlocked() const {
1889   return _summary_bytes_used;
1890 }
1891 
1892 class SumUsedClosure: public HeapRegionClosure {
1893   size_t _used;
1894 public:
1895   SumUsedClosure() : _used(0) {}
1896   bool do_heap_region(HeapRegion* r) {
1897     _used += r->used();
1898     return false;
1899   }
1900   size_t result() { return _used; }
1901 };
1902 
1903 size_t G1CollectedHeap::recalculate_used() const {
1904   SumUsedClosure blk;
1905   heap_region_iterate(&blk);
1906   return blk.result();
1907 }
1908 
1909 bool  G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
1910   switch (cause) {
1911     case GCCause::_java_lang_system_gc:                 return ExplicitGCInvokesConcurrent;
1912     case GCCause::_dcmd_gc_run:                         return ExplicitGCInvokesConcurrent;
1913     case GCCause::_wb_conc_mark:                        return true;
1914     default :                                           return false;
1915   }
1916 }
1917 
1918 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
1919   switch (cause) {
1920     case GCCause::_g1_humongous_allocation: return true;
1921     case GCCause::_g1_periodic_collection:  return G1PeriodicGCInvokesConcurrent;
1922     case GCCause::_wb_breakpoint:           return true;
1923     default:                                return is_user_requested_concurrent_full_gc(cause);
1924   }
1925 }
1926 
1927 bool G1CollectedHeap::should_upgrade_to_full_gc(GCCause::Cause cause) {
1928   if (policy()->force_upgrade_to_full()) {
1929     return true;
1930   } else if (should_do_concurrent_full_gc(_gc_cause)) {
1931     return false;
1932   } else if (has_regions_left_for_allocation()) {
1933     return false;
1934   } else {
1935     return true;
1936   }
1937 }
1938 
1939 #ifndef PRODUCT
1940 void G1CollectedHeap::allocate_dummy_regions() {
1941   // Let's fill up most of the region
1942   size_t word_size = HeapRegion::GrainWords - 1024;
1943   // And as a result the region we'll allocate will be humongous.
1944   guarantee(is_humongous(word_size), "sanity");
1945 
1946   // _filler_array_max_size is set to humongous object threshold
1947   // but temporarily change it to use CollectedHeap::fill_with_object().
1948   AutoModifyRestore<size_t> temporarily(_filler_array_max_size, word_size);
1949 
1950   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
1951     // Let's use the existing mechanism for the allocation
1952     HeapWord* dummy_obj = humongous_obj_allocate(word_size);
1953     if (dummy_obj != NULL) {
1954       MemRegion mr(dummy_obj, word_size);
1955       CollectedHeap::fill_with_object(mr);
1956     } else {
1957       // If we can't allocate once, we probably cannot allocate
1958       // again. Let's get out of the loop.
1959       break;
1960     }
1961   }
1962 }
1963 #endif // !PRODUCT
1964 
1965 void G1CollectedHeap::increment_old_marking_cycles_started() {
1966   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
1967          _old_marking_cycles_started == _old_marking_cycles_completed + 1,
1968          "Wrong marking cycle count (started: %d, completed: %d)",
1969          _old_marking_cycles_started, _old_marking_cycles_completed);
1970 
1971   _old_marking_cycles_started++;
1972 }
1973 
1974 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
1975   MonitorLocker ml(G1OldGCCount_lock, Mutex::_no_safepoint_check_flag);
1976 
1977   // We assume that if concurrent == true, then the caller is a
1978   // concurrent thread that was joined the Suspendible Thread
1979   // Set. If there's ever a cheap way to check this, we should add an
1980   // assert here.
1981 
1982   // Given that this method is called at the end of a Full GC or of a
1983   // concurrent cycle, and those can be nested (i.e., a Full GC can
1984   // interrupt a concurrent cycle), the number of full collections
1985   // completed should be either one (in the case where there was no
1986   // nesting) or two (when a Full GC interrupted a concurrent cycle)
1987   // behind the number of full collections started.
1988 
1989   // This is the case for the inner caller, i.e. a Full GC.
1990   assert(concurrent ||
1991          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
1992          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
1993          "for inner caller (Full GC): _old_marking_cycles_started = %u "
1994          "is inconsistent with _old_marking_cycles_completed = %u",
1995          _old_marking_cycles_started, _old_marking_cycles_completed);
1996 
1997   // This is the case for the outer caller, i.e. the concurrent cycle.
1998   assert(!concurrent ||
1999          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2000          "for outer caller (concurrent cycle): "
2001          "_old_marking_cycles_started = %u "
2002          "is inconsistent with _old_marking_cycles_completed = %u",
2003          _old_marking_cycles_started, _old_marking_cycles_completed);
2004 
2005   _old_marking_cycles_completed += 1;
2006 
2007   // We need to clear the "in_progress" flag in the CM thread before
2008   // we wake up any waiters (especially when ExplicitInvokesConcurrent
2009   // is set) so that if a waiter requests another System.gc() it doesn't
2010   // incorrectly see that a marking cycle is still in progress.
2011   if (concurrent) {
2012     _cm_thread->set_idle();
2013   }
2014 
2015   // Notify threads waiting in System.gc() (with ExplicitGCInvokesConcurrent)
2016   // for a full GC to finish that their wait is over.
2017   ml.notify_all();
2018 }
2019 
2020 void G1CollectedHeap::collect(GCCause::Cause cause) {
2021   try_collect(cause);
2022 }
2023 
2024 // Return true if (x < y) with allowance for wraparound.
2025 static bool gc_counter_less_than(uint x, uint y) {
2026   return (x - y) > (UINT_MAX/2);
2027 }
2028 
2029 // LOG_COLLECT_CONCURRENTLY(cause, msg, args...)
2030 // Macro so msg printing is format-checked.
2031 #define LOG_COLLECT_CONCURRENTLY(cause, ...)                            \
2032   do {                                                                  \
2033     LogTarget(Trace, gc) LOG_COLLECT_CONCURRENTLY_lt;                   \
2034     if (LOG_COLLECT_CONCURRENTLY_lt.is_enabled()) {                     \
2035       ResourceMark rm; /* For thread name. */                           \
2036       LogStream LOG_COLLECT_CONCURRENTLY_s(&LOG_COLLECT_CONCURRENTLY_lt); \
2037       LOG_COLLECT_CONCURRENTLY_s.print("%s: Try Collect Concurrently (%s): ", \
2038                                        Thread::current()->name(),       \
2039                                        GCCause::to_string(cause));      \
2040       LOG_COLLECT_CONCURRENTLY_s.print(__VA_ARGS__);                    \
2041     }                                                                   \
2042   } while (0)
2043 
2044 #define LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, result) \
2045   LOG_COLLECT_CONCURRENTLY(cause, "complete %s", BOOL_TO_STR(result))
2046 
2047 bool G1CollectedHeap::try_collect_concurrently(GCCause::Cause cause,
2048                                                uint gc_counter,
2049                                                uint old_marking_started_before) {
2050   assert_heap_not_locked();
2051   assert(should_do_concurrent_full_gc(cause),
2052          "Non-concurrent cause %s", GCCause::to_string(cause));
2053 
2054   for (uint i = 1; true; ++i) {
2055     // Try to schedule concurrent start evacuation pause that will
2056     // start a concurrent cycle.
2057     LOG_COLLECT_CONCURRENTLY(cause, "attempt %u", i);
2058     VM_G1TryInitiateConcMark op(gc_counter,
2059                                 cause,
2060                                 policy()->max_pause_time_ms());
2061     VMThread::execute(&op);
2062 
2063     // Request is trivially finished.
2064     if (cause == GCCause::_g1_periodic_collection) {
2065       LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, op.gc_succeeded());
2066       return op.gc_succeeded();
2067     }
2068 
2069     // If VMOp skipped initiating concurrent marking cycle because
2070     // we're terminating, then we're done.
2071     if (op.terminating()) {
2072       LOG_COLLECT_CONCURRENTLY(cause, "skipped: terminating");
2073       return false;
2074     }
2075 
2076     // Lock to get consistent set of values.
2077     uint old_marking_started_after;
2078     uint old_marking_completed_after;
2079     {
2080       MutexLocker ml(Heap_lock);
2081       // Update gc_counter for retrying VMOp if needed. Captured here to be
2082       // consistent with the values we use below for termination tests.  If
2083       // a retry is needed after a possible wait, and another collection
2084       // occurs in the meantime, it will cause our retry to be skipped and
2085       // we'll recheck for termination with updated conditions from that
2086       // more recent collection.  That's what we want, rather than having
2087       // our retry possibly perform an unnecessary collection.
2088       gc_counter = total_collections();
2089       old_marking_started_after = _old_marking_cycles_started;
2090       old_marking_completed_after = _old_marking_cycles_completed;
2091     }
2092 
2093     if (cause == GCCause::_wb_breakpoint) {
2094       if (op.gc_succeeded()) {
2095         LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, true);
2096         return true;
2097       }
2098       // When _wb_breakpoint there can't be another cycle or deferred.
2099       assert(!op.cycle_already_in_progress(), "invariant");
2100       assert(!op.whitebox_attached(), "invariant");
2101       // Concurrent cycle attempt might have been cancelled by some other
2102       // collection, so retry.  Unlike other cases below, we want to retry
2103       // even if cancelled by a STW full collection, because we really want
2104       // to start a concurrent cycle.
2105       if (old_marking_started_before != old_marking_started_after) {
2106         LOG_COLLECT_CONCURRENTLY(cause, "ignoring STW full GC");
2107         old_marking_started_before = old_marking_started_after;
2108       }
2109     } else if (!GCCause::is_user_requested_gc(cause)) {
2110       // For an "automatic" (not user-requested) collection, we just need to
2111       // ensure that progress is made.
2112       //
2113       // Request is finished if any of
2114       // (1) the VMOp successfully performed a GC,
2115       // (2) a concurrent cycle was already in progress,
2116       // (3) whitebox is controlling concurrent cycles,
2117       // (4) a new cycle was started (by this thread or some other), or
2118       // (5) a Full GC was performed.
2119       // Cases (4) and (5) are detected together by a change to
2120       // _old_marking_cycles_started.
2121       //
2122       // Note that (1) does not imply (4).  If we're still in the mixed
2123       // phase of an earlier concurrent collection, the request to make the
2124       // collection a concurrent start won't be honored.  If we don't check for
2125       // both conditions we'll spin doing back-to-back collections.
2126       if (op.gc_succeeded() ||
2127           op.cycle_already_in_progress() ||
2128           op.whitebox_attached() ||
2129           (old_marking_started_before != old_marking_started_after)) {
2130         LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, true);
2131         return true;
2132       }
2133     } else {                    // User-requested GC.
2134       // For a user-requested collection, we want to ensure that a complete
2135       // full collection has been performed before returning, but without
2136       // waiting for more than needed.
2137 
2138       // For user-requested GCs (unlike non-UR), a successful VMOp implies a
2139       // new cycle was started.  That's good, because it's not clear what we
2140       // should do otherwise.  Trying again just does back to back GCs.
2141       // Can't wait for someone else to start a cycle.  And returning fails
2142       // to meet the goal of ensuring a full collection was performed.
2143       assert(!op.gc_succeeded() ||
2144              (old_marking_started_before != old_marking_started_after),
2145              "invariant: succeeded %s, started before %u, started after %u",
2146              BOOL_TO_STR(op.gc_succeeded()),
2147              old_marking_started_before, old_marking_started_after);
2148 
2149       // Request is finished if a full collection (concurrent or stw)
2150       // was started after this request and has completed, e.g.
2151       // started_before < completed_after.
2152       if (gc_counter_less_than(old_marking_started_before,
2153                                old_marking_completed_after)) {
2154         LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, true);
2155         return true;
2156       }
2157 
2158       if (old_marking_started_after != old_marking_completed_after) {
2159         // If there is an in-progress cycle (possibly started by us), then
2160         // wait for that cycle to complete, e.g.
2161         // while completed_now < started_after.
2162         LOG_COLLECT_CONCURRENTLY(cause, "wait");
2163         MonitorLocker ml(G1OldGCCount_lock);
2164         while (gc_counter_less_than(_old_marking_cycles_completed,
2165                                     old_marking_started_after)) {
2166           ml.wait();
2167         }
2168         // Request is finished if the collection we just waited for was
2169         // started after this request.
2170         if (old_marking_started_before != old_marking_started_after) {
2171           LOG_COLLECT_CONCURRENTLY(cause, "complete after wait");
2172           return true;
2173         }
2174       }
2175 
2176       // If VMOp was successful then it started a new cycle that the above
2177       // wait &etc should have recognized as finishing this request.  This
2178       // differs from a non-user-request, where gc_succeeded does not imply
2179       // a new cycle was started.
2180       assert(!op.gc_succeeded(), "invariant");
2181 
2182       if (op.cycle_already_in_progress()) {
2183         // If VMOp failed because a cycle was already in progress, it
2184         // is now complete.  But it didn't finish this user-requested
2185         // GC, so try again.
2186         LOG_COLLECT_CONCURRENTLY(cause, "retry after in-progress");
2187         continue;
2188       } else if (op.whitebox_attached()) {
2189         // If WhiteBox wants control, wait for notification of a state
2190         // change in the controller, then try again.  Don't wait for
2191         // release of control, since collections may complete while in
2192         // control.  Note: This won't recognize a STW full collection
2193         // while waiting; we can't wait on multiple monitors.
2194         LOG_COLLECT_CONCURRENTLY(cause, "whitebox control stall");
2195         MonitorLocker ml(ConcurrentGCBreakpoints::monitor());
2196         if (ConcurrentGCBreakpoints::is_controlled()) {
2197           ml.wait();
2198         }
2199         continue;
2200       }
2201     }
2202 
2203     // Collection failed and should be retried.
2204     assert(op.transient_failure(), "invariant");
2205 
2206     if (GCLocker::is_active_and_needs_gc()) {
2207       // If GCLocker is active, wait until clear before retrying.
2208       LOG_COLLECT_CONCURRENTLY(cause, "gc-locker stall");
2209       GCLocker::stall_until_clear();
2210     }
2211 
2212     LOG_COLLECT_CONCURRENTLY(cause, "retry");
2213   }
2214 }
2215 
2216 bool G1CollectedHeap::try_collect(GCCause::Cause cause) {
2217   assert_heap_not_locked();
2218 
2219   // Lock to get consistent set of values.
2220   uint gc_count_before;
2221   uint full_gc_count_before;
2222   uint old_marking_started_before;
2223   {
2224     MutexLocker ml(Heap_lock);
2225     gc_count_before = total_collections();
2226     full_gc_count_before = total_full_collections();
2227     old_marking_started_before = _old_marking_cycles_started;
2228   }
2229 
2230   if (should_do_concurrent_full_gc(cause)) {
2231     return try_collect_concurrently(cause,
2232                                     gc_count_before,
2233                                     old_marking_started_before);
2234   } else if (GCLocker::should_discard(cause, gc_count_before)) {
2235     // Indicate failure to be consistent with VMOp failure due to
2236     // another collection slipping in after our gc_count but before
2237     // our request is processed.
2238     return false;
2239   } else if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2240              DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2241 
2242     // Schedule a standard evacuation pause. We're setting word_size
2243     // to 0 which means that we are not requesting a post-GC allocation.
2244     VM_G1CollectForAllocation op(0,     /* word_size */
2245                                  gc_count_before,
2246                                  cause,
2247                                  policy()->max_pause_time_ms());
2248     VMThread::execute(&op);
2249     return op.gc_succeeded();
2250   } else {
2251     // Schedule a Full GC.
2252     VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2253     VMThread::execute(&op);
2254     return op.gc_succeeded();
2255   }
2256 }
2257 
2258 bool G1CollectedHeap::is_in(const void* p) const {
2259   if (_hrm->reserved().contains(p)) {
2260     // Given that we know that p is in the reserved space,
2261     // heap_region_containing() should successfully
2262     // return the containing region.
2263     HeapRegion* hr = heap_region_containing(p);
2264     return hr->is_in(p);
2265   } else {
2266     return false;
2267   }
2268 }
2269 
2270 #ifdef ASSERT
2271 bool G1CollectedHeap::is_in_exact(const void* p) const {
2272   bool contains = reserved_region().contains(p);
2273   bool available = _hrm->is_available(addr_to_region((HeapWord*)p));
2274   if (contains && available) {
2275     return true;
2276   } else {
2277     return false;
2278   }
2279 }
2280 #endif
2281 
2282 // Iteration functions.
2283 
2284 // Iterates an ObjectClosure over all objects within a HeapRegion.
2285 
2286 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2287   ObjectClosure* _cl;
2288 public:
2289   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2290   bool do_heap_region(HeapRegion* r) {
2291     if (!r->is_continues_humongous()) {
2292       r->object_iterate(_cl);
2293     }
2294     return false;
2295   }
2296 };
2297 
2298 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2299   IterateObjectClosureRegionClosure blk(cl);
2300   heap_region_iterate(&blk);
2301 }
2302 
2303 void G1CollectedHeap::keep_alive(oop obj) {
2304   G1BarrierSet::enqueue(obj);
2305 }
2306 
2307 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2308   _hrm->iterate(cl);
2309 }
2310 
2311 void G1CollectedHeap::heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl,
2312                                                                  HeapRegionClaimer *hrclaimer,
2313                                                                  uint worker_id) const {
2314   _hrm->par_iterate(cl, hrclaimer, hrclaimer->offset_for_worker(worker_id));
2315 }
2316 
2317 void G1CollectedHeap::heap_region_par_iterate_from_start(HeapRegionClosure* cl,
2318                                                          HeapRegionClaimer *hrclaimer) const {
2319   _hrm->par_iterate(cl, hrclaimer, 0);
2320 }
2321 
2322 void G1CollectedHeap::collection_set_iterate_all(HeapRegionClosure* cl) {
2323   _collection_set.iterate(cl);
2324 }
2325 
2326 void G1CollectedHeap::collection_set_par_iterate_all(HeapRegionClosure* cl, HeapRegionClaimer* hr_claimer, uint worker_id) {
2327   _collection_set.par_iterate(cl, hr_claimer, worker_id, workers()->active_workers());
2328 }
2329 
2330 void G1CollectedHeap::collection_set_iterate_increment_from(HeapRegionClosure *cl, HeapRegionClaimer* hr_claimer, uint worker_id) {
2331   _collection_set.iterate_incremental_part_from(cl, hr_claimer, worker_id, workers()->active_workers());
2332 }
2333 
2334 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2335   HeapRegion* hr = heap_region_containing(addr);
2336   return hr->block_start(addr);
2337 }
2338 
2339 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2340   HeapRegion* hr = heap_region_containing(addr);
2341   return hr->block_is_obj(addr);
2342 }
2343 
2344 bool G1CollectedHeap::supports_tlab_allocation() const {
2345   return true;
2346 }
2347 
2348 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2349   return (_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes;
2350 }
2351 
2352 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2353   return _eden.length() * HeapRegion::GrainBytes;
2354 }
2355 
2356 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2357 // must be equal to the humongous object limit.
2358 size_t G1CollectedHeap::max_tlab_size() const {
2359   return align_down(_humongous_object_threshold_in_words, MinObjAlignment);
2360 }
2361 
2362 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2363   return _allocator->unsafe_max_tlab_alloc();
2364 }
2365 
2366 size_t G1CollectedHeap::max_capacity() const {
2367   return _hrm->max_expandable_length() * HeapRegion::GrainBytes;
2368 }
2369 
2370 size_t G1CollectedHeap::max_reserved_capacity() const {
2371   return _hrm->max_length() * HeapRegion::GrainBytes;
2372 }
2373 
2374 jlong G1CollectedHeap::millis_since_last_gc() {
2375   // See the notes in GenCollectedHeap::millis_since_last_gc()
2376   // for more information about the implementation.
2377   jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) -
2378                   _policy->collection_pause_end_millis();
2379   if (ret_val < 0) {
2380     log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT
2381       ". returning zero instead.", ret_val);
2382     return 0;
2383   }
2384   return ret_val;
2385 }
2386 
2387 void G1CollectedHeap::deduplicate_string(oop str) {
2388   assert(java_lang_String::is_instance(str), "invariant");
2389 
2390   if (G1StringDedup::is_enabled()) {
2391     G1StringDedup::deduplicate(str);
2392   }
2393 }
2394 
2395 void G1CollectedHeap::prepare_for_verify() {
2396   _verifier->prepare_for_verify();
2397 }
2398 
2399 void G1CollectedHeap::verify(VerifyOption vo) {
2400   _verifier->verify(vo);
2401 }
2402 
2403 bool G1CollectedHeap::supports_concurrent_gc_breakpoints() const {
2404   return true;
2405 }
2406 
2407 bool G1CollectedHeap::is_heterogeneous_heap() const {
2408   return G1Arguments::is_heterogeneous_heap();
2409 }
2410 
2411 class PrintRegionClosure: public HeapRegionClosure {
2412   outputStream* _st;
2413 public:
2414   PrintRegionClosure(outputStream* st) : _st(st) {}
2415   bool do_heap_region(HeapRegion* r) {
2416     r->print_on(_st);
2417     return false;
2418   }
2419 };
2420 
2421 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2422                                        const HeapRegion* hr,
2423                                        const VerifyOption vo) const {
2424   switch (vo) {
2425   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
2426   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
2427   case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj, hr);
2428   default:                            ShouldNotReachHere();
2429   }
2430   return false; // keep some compilers happy
2431 }
2432 
2433 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2434                                        const VerifyOption vo) const {
2435   switch (vo) {
2436   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
2437   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
2438   case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj);
2439   default:                            ShouldNotReachHere();
2440   }
2441   return false; // keep some compilers happy
2442 }
2443 
2444 void G1CollectedHeap::print_heap_regions() const {
2445   LogTarget(Trace, gc, heap, region) lt;
2446   if (lt.is_enabled()) {
2447     LogStream ls(lt);
2448     print_regions_on(&ls);
2449   }
2450 }
2451 
2452 void G1CollectedHeap::print_on(outputStream* st) const {
2453   st->print(" %-20s", "garbage-first heap");
2454   if (_hrm != NULL) {
2455     st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
2456               capacity()/K, used_unlocked()/K);
2457     st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")",
2458               p2i(_hrm->reserved().start()),
2459               p2i(_hrm->reserved().end()));
2460   }
2461   st->cr();
2462   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
2463   uint young_regions = young_regions_count();
2464   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
2465             (size_t) young_regions * HeapRegion::GrainBytes / K);
2466   uint survivor_regions = survivor_regions_count();
2467   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
2468             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
2469   st->cr();
2470   if (_numa->is_enabled()) {
2471     uint num_nodes = _numa->num_active_nodes();
2472     st->print("  remaining free region(s) on each NUMA node: ");
2473     const int* node_ids = _numa->node_ids();
2474     for (uint node_index = 0; node_index < num_nodes; node_index++) {
2475       uint num_free_regions = (_hrm != NULL ? _hrm->num_free_regions(node_index) : 0);
2476       st->print("%d=%u ", node_ids[node_index], num_free_regions);
2477     }
2478     st->cr();
2479   }
2480   MetaspaceUtils::print_on(st);
2481 }
2482 
2483 void G1CollectedHeap::print_regions_on(outputStream* st) const {
2484   if (_hrm == NULL) {
2485     return;
2486   }
2487 
2488   st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
2489                "HS=humongous(starts), HC=humongous(continues), "
2490                "CS=collection set, F=free, "
2491                "OA=open archive, CA=closed archive, "
2492                "TAMS=top-at-mark-start (previous, next)");
2493   PrintRegionClosure blk(st);
2494   heap_region_iterate(&blk);
2495 }
2496 
2497 void G1CollectedHeap::print_extended_on(outputStream* st) const {
2498   print_on(st);
2499 
2500   // Print the per-region information.
2501   if (_hrm != NULL) {
2502     st->cr();
2503     print_regions_on(st);
2504   }
2505 }
2506 
2507 void G1CollectedHeap::print_on_error(outputStream* st) const {
2508   this->CollectedHeap::print_on_error(st);
2509 
2510   if (_cm != NULL) {
2511     st->cr();
2512     _cm->print_on_error(st);
2513   }
2514 }
2515 
2516 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2517   workers()->threads_do(tc);
2518   tc->do_thread(_cm_thread);
2519   _cm->threads_do(tc);
2520   _cr->threads_do(tc);
2521   tc->do_thread(_young_gen_sampling_thread);
2522   if (G1StringDedup::is_enabled()) {
2523     G1StringDedup::threads_do(tc);
2524   }
2525 }
2526 
2527 void G1CollectedHeap::print_tracing_info() const {
2528   rem_set()->print_summary_info();
2529   concurrent_mark()->print_summary_info();
2530 }
2531 
2532 #ifndef PRODUCT
2533 // Helpful for debugging RSet issues.
2534 
2535 class PrintRSetsClosure : public HeapRegionClosure {
2536 private:
2537   const char* _msg;
2538   size_t _occupied_sum;
2539 
2540 public:
2541   bool do_heap_region(HeapRegion* r) {
2542     HeapRegionRemSet* hrrs = r->rem_set();
2543     size_t occupied = hrrs->occupied();
2544     _occupied_sum += occupied;
2545 
2546     tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r));
2547     if (occupied == 0) {
2548       tty->print_cr("  RSet is empty");
2549     } else {
2550       hrrs->print();
2551     }
2552     tty->print_cr("----------");
2553     return false;
2554   }
2555 
2556   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
2557     tty->cr();
2558     tty->print_cr("========================================");
2559     tty->print_cr("%s", msg);
2560     tty->cr();
2561   }
2562 
2563   ~PrintRSetsClosure() {
2564     tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
2565     tty->print_cr("========================================");
2566     tty->cr();
2567   }
2568 };
2569 
2570 void G1CollectedHeap::print_cset_rsets() {
2571   PrintRSetsClosure cl("Printing CSet RSets");
2572   collection_set_iterate_all(&cl);
2573 }
2574 
2575 void G1CollectedHeap::print_all_rsets() {
2576   PrintRSetsClosure cl("Printing All RSets");;
2577   heap_region_iterate(&cl);
2578 }
2579 #endif // PRODUCT
2580 
2581 bool G1CollectedHeap::print_location(outputStream* st, void* addr) const {
2582   return BlockLocationPrinter<G1CollectedHeap>::print_location(st, addr);
2583 }
2584 
2585 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
2586 
2587   size_t eden_used_bytes = _eden.used_bytes();
2588   size_t survivor_used_bytes = _survivor.used_bytes();
2589   size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
2590 
2591   size_t eden_capacity_bytes =
2592     (policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
2593 
2594   VirtualSpaceSummary heap_summary = create_heap_space_summary();
2595   return G1HeapSummary(heap_summary, heap_used, eden_used_bytes,
2596                        eden_capacity_bytes, survivor_used_bytes, num_regions());
2597 }
2598 
2599 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
2600   return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
2601                        stats->unused(), stats->used(), stats->region_end_waste(),
2602                        stats->regions_filled(), stats->direct_allocated(),
2603                        stats->failure_used(), stats->failure_waste());
2604 }
2605 
2606 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
2607   const G1HeapSummary& heap_summary = create_g1_heap_summary();
2608   gc_tracer->report_gc_heap_summary(when, heap_summary);
2609 
2610   const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
2611   gc_tracer->report_metaspace_summary(when, metaspace_summary);
2612 }
2613 
2614 void G1CollectedHeap::gc_prologue(bool full) {
2615   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
2616 
2617   // This summary needs to be printed before incrementing total collections.
2618   rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections());
2619 
2620   // Update common counters.
2621   increment_total_collections(full /* full gc */);
2622   if (full || collector_state()->in_concurrent_start_gc()) {
2623     increment_old_marking_cycles_started();
2624   }
2625 
2626   // Fill TLAB's and such
2627   {
2628     Ticks start = Ticks::now();
2629     ensure_parsability(true);
2630     Tickspan dt = Ticks::now() - start;
2631     phase_times()->record_prepare_tlab_time_ms(dt.seconds() * MILLIUNITS);
2632   }
2633 
2634   if (!full) {
2635     // Flush dirty card queues to qset, so later phases don't need to account
2636     // for partially filled per-thread queues and such.  Not needed for full
2637     // collections, which ignore those logs.
2638     Ticks start = Ticks::now();
2639     G1BarrierSet::dirty_card_queue_set().concatenate_logs();
2640     Tickspan dt = Ticks::now() - start;
2641     phase_times()->record_concatenate_dirty_card_logs_time_ms(dt.seconds() * MILLIUNITS);
2642   }
2643 }
2644 
2645 void G1CollectedHeap::gc_epilogue(bool full) {
2646   // Update common counters.
2647   if (full) {
2648     // Update the number of full collections that have been completed.
2649     increment_old_marking_cycles_completed(false /* concurrent */);
2650   }
2651 
2652   // We are at the end of the GC. Total collections has already been increased.
2653   rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1);
2654 
2655   // FIXME: what is this about?
2656   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
2657   // is set.
2658 #if COMPILER2_OR_JVMCI
2659   assert(DerivedPointerTable::is_empty(), "derived pointer present");
2660 #endif
2661 
2662   double start = os::elapsedTime();
2663   resize_all_tlabs();
2664   phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2665 
2666   MemoryService::track_memory_usage();
2667   // We have just completed a GC. Update the soft reference
2668   // policy with the new heap occupancy
2669   Universe::update_heap_info_at_gc();
2670 
2671   // Print NUMA statistics.
2672   _numa->print_statistics();
2673 }
2674 
2675 void G1CollectedHeap::verify_numa_regions(const char* desc) {
2676   LogTarget(Trace, gc, heap, verify) lt;
2677 
2678   if (lt.is_enabled()) {
2679     LogStream ls(lt);
2680     // Iterate all heap regions to print matching between preferred numa id and actual numa id.
2681     G1NodeIndexCheckClosure cl(desc, _numa, &ls);
2682     heap_region_iterate(&cl);
2683   }
2684 }
2685 
2686 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2687                                                uint gc_count_before,
2688                                                bool* succeeded,
2689                                                GCCause::Cause gc_cause) {
2690   assert_heap_not_locked_and_not_at_safepoint();
2691   VM_G1CollectForAllocation op(word_size,
2692                                gc_count_before,
2693                                gc_cause,
2694                                policy()->max_pause_time_ms());
2695   VMThread::execute(&op);
2696 
2697   HeapWord* result = op.result();
2698   bool ret_succeeded = op.prologue_succeeded() && op.gc_succeeded();
2699   assert(result == NULL || ret_succeeded,
2700          "the result should be NULL if the VM did not succeed");
2701   *succeeded = ret_succeeded;
2702 
2703   assert_heap_not_locked();
2704   return result;
2705 }
2706 
2707 void G1CollectedHeap::do_concurrent_mark() {
2708   MutexLocker x(CGC_lock, Mutex::_no_safepoint_check_flag);
2709   if (!_cm_thread->in_progress()) {
2710     _cm_thread->set_started();
2711     CGC_lock->notify();
2712   }
2713 }
2714 
2715 bool G1CollectedHeap::is_potential_eager_reclaim_candidate(HeapRegion* r) const {
2716   // We don't nominate objects with many remembered set entries, on
2717   // the assumption that such objects are likely still live.
2718   HeapRegionRemSet* rem_set = r->rem_set();
2719 
2720   return G1EagerReclaimHumongousObjectsWithStaleRefs ?
2721          rem_set->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) :
2722          G1EagerReclaimHumongousObjects && rem_set->is_empty();
2723 }
2724 
2725 #ifndef PRODUCT
2726 void G1CollectedHeap::verify_region_attr_remset_update() {
2727   class VerifyRegionAttrRemSet : public HeapRegionClosure {
2728   public:
2729     virtual bool do_heap_region(HeapRegion* r) {
2730       G1CollectedHeap* g1h = G1CollectedHeap::heap();
2731       bool const needs_remset_update = g1h->region_attr(r->bottom()).needs_remset_update();
2732       assert(r->rem_set()->is_tracked() == needs_remset_update,
2733              "Region %u remset tracking status (%s) different to region attribute (%s)",
2734              r->hrm_index(), BOOL_TO_STR(r->rem_set()->is_tracked()), BOOL_TO_STR(needs_remset_update));
2735       return false;
2736     }
2737   } cl;
2738   heap_region_iterate(&cl);
2739 }
2740 #endif
2741 
2742 class VerifyRegionRemSetClosure : public HeapRegionClosure {
2743   public:
2744     bool do_heap_region(HeapRegion* hr) {
2745       if (!hr->is_archive() && !hr->is_continues_humongous()) {
2746         hr->verify_rem_set();
2747       }
2748       return false;
2749     }
2750 };
2751 
2752 uint G1CollectedHeap::num_task_queues() const {
2753   return _task_queues->size();
2754 }
2755 
2756 #if TASKQUEUE_STATS
2757 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
2758   st->print_raw_cr("GC Task Stats");
2759   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
2760   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
2761 }
2762 
2763 void G1CollectedHeap::print_taskqueue_stats() const {
2764   if (!log_is_enabled(Trace, gc, task, stats)) {
2765     return;
2766   }
2767   Log(gc, task, stats) log;
2768   ResourceMark rm;
2769   LogStream ls(log.trace());
2770   outputStream* st = &ls;
2771 
2772   print_taskqueue_stats_hdr(st);
2773 
2774   TaskQueueStats totals;
2775   const uint n = num_task_queues();
2776   for (uint i = 0; i < n; ++i) {
2777     st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
2778     totals += task_queue(i)->stats;
2779   }
2780   st->print_raw("tot "); totals.print(st); st->cr();
2781 
2782   DEBUG_ONLY(totals.verify());
2783 }
2784 
2785 void G1CollectedHeap::reset_taskqueue_stats() {
2786   const uint n = num_task_queues();
2787   for (uint i = 0; i < n; ++i) {
2788     task_queue(i)->stats.reset();
2789   }
2790 }
2791 #endif // TASKQUEUE_STATS
2792 
2793 void G1CollectedHeap::wait_for_root_region_scanning() {
2794   double scan_wait_start = os::elapsedTime();
2795   // We have to wait until the CM threads finish scanning the
2796   // root regions as it's the only way to ensure that all the
2797   // objects on them have been correctly scanned before we start
2798   // moving them during the GC.
2799   bool waited = _cm->root_regions()->wait_until_scan_finished();
2800   double wait_time_ms = 0.0;
2801   if (waited) {
2802     double scan_wait_end = os::elapsedTime();
2803     wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
2804   }
2805   phase_times()->record_root_region_scan_wait_time(wait_time_ms);
2806 }
2807 
2808 class G1PrintCollectionSetClosure : public HeapRegionClosure {
2809 private:
2810   G1HRPrinter* _hr_printer;
2811 public:
2812   G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { }
2813 
2814   virtual bool do_heap_region(HeapRegion* r) {
2815     _hr_printer->cset(r);
2816     return false;
2817   }
2818 };
2819 
2820 void G1CollectedHeap::start_new_collection_set() {
2821   double start = os::elapsedTime();
2822 
2823   collection_set()->start_incremental_building();
2824 
2825   clear_region_attr();
2826 
2827   guarantee(_eden.length() == 0, "eden should have been cleared");
2828   policy()->transfer_survivors_to_cset(survivor());
2829 
2830   // We redo the verification but now wrt to the new CSet which
2831   // has just got initialized after the previous CSet was freed.
2832   _cm->verify_no_collection_set_oops();
2833 
2834   phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0);
2835 }
2836 
2837 void G1CollectedHeap::calculate_collection_set(G1EvacuationInfo& evacuation_info, double target_pause_time_ms) {
2838 
2839   _collection_set.finalize_initial_collection_set(target_pause_time_ms, &_survivor);
2840   evacuation_info.set_collectionset_regions(collection_set()->region_length() +
2841                                             collection_set()->optional_region_length());
2842 
2843   _cm->verify_no_collection_set_oops();
2844 
2845   if (_hr_printer.is_active()) {
2846     G1PrintCollectionSetClosure cl(&_hr_printer);
2847     _collection_set.iterate(&cl);
2848     _collection_set.iterate_optional(&cl);
2849   }
2850 }
2851 
2852 G1HeapVerifier::G1VerifyType G1CollectedHeap::young_collection_verify_type() const {
2853   if (collector_state()->in_concurrent_start_gc()) {
2854     return G1HeapVerifier::G1VerifyConcurrentStart;
2855   } else if (collector_state()->in_young_only_phase()) {
2856     return G1HeapVerifier::G1VerifyYoungNormal;
2857   } else {
2858     return G1HeapVerifier::G1VerifyMixed;
2859   }
2860 }
2861 
2862 void G1CollectedHeap::verify_before_young_collection(G1HeapVerifier::G1VerifyType type) {
2863   if (VerifyRememberedSets) {
2864     log_info(gc, verify)("[Verifying RemSets before GC]");
2865     VerifyRegionRemSetClosure v_cl;
2866     heap_region_iterate(&v_cl);
2867   }
2868   _verifier->verify_before_gc(type);
2869   _verifier->check_bitmaps("GC Start");
2870   verify_numa_regions("GC Start");
2871 }
2872 
2873 void G1CollectedHeap::verify_after_young_collection(G1HeapVerifier::G1VerifyType type) {
2874   if (VerifyRememberedSets) {
2875     log_info(gc, verify)("[Verifying RemSets after GC]");
2876     VerifyRegionRemSetClosure v_cl;
2877     heap_region_iterate(&v_cl);
2878   }
2879   _verifier->verify_after_gc(type);
2880   _verifier->check_bitmaps("GC End");
2881   verify_numa_regions("GC End");
2882 }
2883 
2884 void G1CollectedHeap::expand_heap_after_young_collection(){
2885   size_t expand_bytes = _heap_sizing_policy->young_collection_expansion_amount();
2886   if (expand_bytes > 0) {
2887     // No need for an ergo logging here,
2888     // expansion_amount() does this when it returns a value > 0.
2889     double expand_ms;
2890     if (!expand(expand_bytes, _workers, &expand_ms)) {
2891       // We failed to expand the heap. Cannot do anything about it.
2892     }
2893     phase_times()->record_expand_heap_time(expand_ms);
2894   }
2895 }
2896 
2897 const char* G1CollectedHeap::young_gc_name() const {
2898   if (collector_state()->in_concurrent_start_gc()) {
2899     return "Pause Young (Concurrent Start)";
2900   } else if (collector_state()->in_young_only_phase()) {
2901     if (collector_state()->in_young_gc_before_mixed()) {
2902       return "Pause Young (Prepare Mixed)";
2903     } else {
2904       return "Pause Young (Normal)";
2905     }
2906   } else {
2907     return "Pause Young (Mixed)";
2908   }
2909 }
2910 
2911 bool G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
2912   assert_at_safepoint_on_vm_thread();
2913   guarantee(!is_gc_active(), "collection is not reentrant");
2914 
2915   if (GCLocker::check_active_before_gc()) {
2916     return false;
2917   }
2918 
2919   do_collection_pause_at_safepoint_helper(target_pause_time_ms);
2920   if (should_upgrade_to_full_gc(gc_cause())) {
2921     log_info(gc, ergo)("Attempting maximally compacting collection");
2922     bool result = do_full_collection(false /* explicit gc */,
2923                                      true /* clear_all_soft_refs */);
2924     // do_full_collection only fails if blocked by GC locker, but
2925     // we've already checked for that above.
2926     assert(result, "invariant");
2927   }
2928   return true;
2929 }
2930 
2931 void G1CollectedHeap::do_collection_pause_at_safepoint_helper(double target_pause_time_ms) {
2932   GCIdMark gc_id_mark;
2933 
2934   SvcGCMarker sgcm(SvcGCMarker::MINOR);
2935   ResourceMark rm;
2936 
2937   policy()->note_gc_start();
2938 
2939   _gc_timer_stw->register_gc_start();
2940   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
2941 
2942   wait_for_root_region_scanning();
2943 
2944   print_heap_before_gc();
2945   print_heap_regions();
2946   trace_heap_before_gc(_gc_tracer_stw);
2947 
2948   _verifier->verify_region_sets_optional();
2949   _verifier->verify_dirty_young_regions();
2950 
2951   // We should not be doing concurrent start unless the concurrent mark thread is running
2952   if (!_cm_thread->should_terminate()) {
2953     // This call will decide whether this pause is a concurrent start
2954     // pause. If it is, in_concurrent_start_gc() will return true
2955     // for the duration of this pause.
2956     policy()->decide_on_conc_mark_initiation();
2957   }
2958 
2959   // We do not allow concurrent start to be piggy-backed on a mixed GC.
2960   assert(!collector_state()->in_concurrent_start_gc() ||
2961          collector_state()->in_young_only_phase(), "sanity");
2962   // We also do not allow mixed GCs during marking.
2963   assert(!collector_state()->mark_or_rebuild_in_progress() || collector_state()->in_young_only_phase(), "sanity");
2964 
2965   // Record whether this pause is a concurrent start. When the current
2966   // thread has completed its logging output and it's safe to signal
2967   // the CM thread, the flag's value in the policy has been reset.
2968   bool should_start_conc_mark = collector_state()->in_concurrent_start_gc();
2969   if (should_start_conc_mark) {
2970     _cm->gc_tracer_cm()->set_gc_cause(gc_cause());
2971   }
2972 
2973   // Inner scope for scope based logging, timers, and stats collection
2974   {
2975     G1EvacuationInfo evacuation_info;
2976 
2977     _gc_tracer_stw->report_yc_type(collector_state()->yc_type());
2978 
2979     GCTraceCPUTime tcpu;
2980 
2981     GCTraceTime(Info, gc) tm(young_gc_name(), NULL, gc_cause(), true);
2982 
2983     uint active_workers = WorkerPolicy::calc_active_workers(workers()->total_workers(),
2984                                                             workers()->active_workers(),
2985                                                             Threads::number_of_non_daemon_threads());
2986     active_workers = workers()->update_active_workers(active_workers);
2987     log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers());
2988 
2989     G1MonitoringScope ms(g1mm(),
2990                          false /* full_gc */,
2991                          collector_state()->yc_type() == Mixed /* all_memory_pools_affected */);
2992 
2993     G1HeapTransition heap_transition(this);
2994 
2995     {
2996       IsGCActiveMark x;
2997 
2998       gc_prologue(false);
2999 
3000       G1HeapVerifier::G1VerifyType verify_type = young_collection_verify_type();
3001       verify_before_young_collection(verify_type);
3002 
3003       {
3004         // The elapsed time induced by the start time below deliberately elides
3005         // the possible verification above.
3006         double sample_start_time_sec = os::elapsedTime();
3007 
3008         // Please see comment in g1CollectedHeap.hpp and
3009         // G1CollectedHeap::ref_processing_init() to see how
3010         // reference processing currently works in G1.
3011         _ref_processor_stw->enable_discovery();
3012 
3013         // We want to temporarily turn off discovery by the
3014         // CM ref processor, if necessary, and turn it back on
3015         // on again later if we do. Using a scoped
3016         // NoRefDiscovery object will do this.
3017         NoRefDiscovery no_cm_discovery(_ref_processor_cm);
3018 
3019         policy()->record_collection_pause_start(sample_start_time_sec);
3020 
3021         // Forget the current allocation region (we might even choose it to be part
3022         // of the collection set!).
3023         _allocator->release_mutator_alloc_regions();
3024 
3025         calculate_collection_set(evacuation_info, target_pause_time_ms);
3026 
3027         G1RedirtyCardsQueueSet rdcqs(G1BarrierSet::dirty_card_queue_set().allocator());
3028         G1ParScanThreadStateSet per_thread_states(this,
3029                                                   &rdcqs,
3030                                                   workers()->active_workers(),
3031                                                   collection_set()->young_region_length(),
3032                                                   collection_set()->optional_region_length());
3033         pre_evacuate_collection_set(evacuation_info, &per_thread_states);
3034 
3035         // Actually do the work...
3036         evacuate_initial_collection_set(&per_thread_states);
3037 
3038         if (_collection_set.optional_region_length() != 0) {
3039           evacuate_optional_collection_set(&per_thread_states);
3040         }
3041         post_evacuate_collection_set(evacuation_info, &rdcqs, &per_thread_states);
3042 
3043         start_new_collection_set();
3044 
3045         _survivor_evac_stats.adjust_desired_plab_sz();
3046         _old_evac_stats.adjust_desired_plab_sz();
3047 
3048         if (should_start_conc_mark) {
3049           // We have to do this before we notify the CM threads that
3050           // they can start working to make sure that all the
3051           // appropriate initialization is done on the CM object.
3052           concurrent_mark()->post_concurrent_start();
3053           // Note that we don't actually trigger the CM thread at
3054           // this point. We do that later when we're sure that
3055           // the current thread has completed its logging output.
3056         }
3057 
3058         allocate_dummy_regions();
3059 
3060         _allocator->init_mutator_alloc_regions();
3061 
3062         expand_heap_after_young_collection();
3063 
3064         double sample_end_time_sec = os::elapsedTime();
3065         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3066         policy()->record_collection_pause_end(pause_time_ms);
3067       }
3068 
3069       verify_after_young_collection(verify_type);
3070 
3071       gc_epilogue(false);
3072     }
3073 
3074     // Print the remainder of the GC log output.
3075     if (evacuation_failed()) {
3076       log_info(gc)("To-space exhausted");
3077     }
3078 
3079     policy()->print_phases();
3080     heap_transition.print();
3081 
3082     _hrm->verify_optional();
3083     _verifier->verify_region_sets_optional();
3084 
3085     TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
3086     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3087 
3088     print_heap_after_gc();
3089     print_heap_regions();
3090     trace_heap_after_gc(_gc_tracer_stw);
3091 
3092     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3093     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3094     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3095     // before any GC notifications are raised.
3096     g1mm()->update_sizes();
3097 
3098     _gc_tracer_stw->report_evacuation_info(&evacuation_info);
3099     _gc_tracer_stw->report_tenuring_threshold(_policy->tenuring_threshold());
3100     _gc_timer_stw->register_gc_end();
3101     _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
3102   }
3103   // It should now be safe to tell the concurrent mark thread to start
3104   // without its logging output interfering with the logging output
3105   // that came from the pause.
3106 
3107   if (should_start_conc_mark) {
3108     // CAUTION: after the doConcurrentMark() call below, the concurrent marking
3109     // thread(s) could be running concurrently with us. Make sure that anything
3110     // after this point does not assume that we are the only GC thread running.
3111     // Note: of course, the actual marking work will not start until the safepoint
3112     // itself is released in SuspendibleThreadSet::desynchronize().
3113     do_concurrent_mark();
3114     ConcurrentGCBreakpoints::notify_idle_to_active();
3115   }
3116 }
3117 
3118 void G1CollectedHeap::remove_self_forwarding_pointers(G1RedirtyCardsQueueSet* rdcqs) {
3119   G1ParRemoveSelfForwardPtrsTask rsfp_task(rdcqs);
3120   workers()->run_task(&rsfp_task);
3121 }
3122 
3123 void G1CollectedHeap::restore_after_evac_failure(G1RedirtyCardsQueueSet* rdcqs) {
3124   double remove_self_forwards_start = os::elapsedTime();
3125 
3126   remove_self_forwarding_pointers(rdcqs);
3127   _preserved_marks_set.restore(workers());
3128 
3129   phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
3130 }
3131 
3132 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markWord m) {
3133   if (!_evacuation_failed) {
3134     _evacuation_failed = true;
3135   }
3136 
3137   _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size());
3138   _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m);
3139 }
3140 
3141 bool G1ParEvacuateFollowersClosure::offer_termination() {
3142   EventGCPhaseParallel event;
3143   G1ParScanThreadState* const pss = par_scan_state();
3144   start_term_time();
3145   const bool res = terminator()->offer_termination();
3146   end_term_time();
3147   event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(G1GCPhaseTimes::Termination));
3148   return res;
3149 }
3150 
3151 void G1ParEvacuateFollowersClosure::do_void() {
3152   EventGCPhaseParallel event;
3153   G1ParScanThreadState* const pss = par_scan_state();
3154   pss->trim_queue();
3155   event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(_phase));
3156   do {
3157     EventGCPhaseParallel event;
3158     pss->steal_and_trim_queue(queues());
3159     event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(_phase));
3160   } while (!offer_termination());
3161 }
3162 
3163 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive,
3164                                         bool class_unloading_occurred) {
3165   uint num_workers = workers()->active_workers();
3166   G1ParallelCleaningTask unlink_task(is_alive, num_workers, class_unloading_occurred, false);
3167   workers()->run_task(&unlink_task);
3168 }
3169 
3170 // Clean string dedup data structures.
3171 // Ideally we would prefer to use a StringDedupCleaningTask here, but we want to
3172 // record the durations of the phases. Hence the almost-copy.
3173 class G1StringDedupCleaningTask : public AbstractGangTask {
3174   BoolObjectClosure* _is_alive;
3175   OopClosure* _keep_alive;
3176   G1GCPhaseTimes* _phase_times;
3177 
3178 public:
3179   G1StringDedupCleaningTask(BoolObjectClosure* is_alive,
3180                             OopClosure* keep_alive,
3181                             G1GCPhaseTimes* phase_times) :
3182     AbstractGangTask("Partial Cleaning Task"),
3183     _is_alive(is_alive),
3184     _keep_alive(keep_alive),
3185     _phase_times(phase_times)
3186   {
3187     assert(G1StringDedup::is_enabled(), "String deduplication disabled.");
3188     StringDedup::gc_prologue(true);
3189   }
3190 
3191   ~G1StringDedupCleaningTask() {
3192     StringDedup::gc_epilogue();
3193   }
3194 
3195   void work(uint worker_id) {
3196     StringDedupUnlinkOrOopsDoClosure cl(_is_alive, _keep_alive);
3197     {
3198       G1GCParPhaseTimesTracker x(_phase_times, G1GCPhaseTimes::StringDedupQueueFixup, worker_id);
3199       StringDedupQueue::unlink_or_oops_do(&cl);
3200     }
3201     {
3202       G1GCParPhaseTimesTracker x(_phase_times, G1GCPhaseTimes::StringDedupTableFixup, worker_id);
3203       StringDedupTable::unlink_or_oops_do(&cl, worker_id);
3204     }
3205   }
3206 };
3207 
3208 void G1CollectedHeap::string_dedup_cleaning(BoolObjectClosure* is_alive,
3209                                             OopClosure* keep_alive,
3210                                             G1GCPhaseTimes* phase_times) {
3211   G1StringDedupCleaningTask cl(is_alive, keep_alive, phase_times);
3212   workers()->run_task(&cl);
3213 }
3214 
3215 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
3216  private:
3217   G1RedirtyCardsQueueSet* _qset;
3218   G1CollectedHeap* _g1h;
3219   BufferNode* volatile _nodes;
3220 
3221   void par_apply(RedirtyLoggedCardTableEntryClosure* cl, uint worker_id) {
3222     size_t buffer_size = _qset->buffer_size();
3223     BufferNode* next = Atomic::load(&_nodes);
3224     while (next != NULL) {
3225       BufferNode* node = next;
3226       next = Atomic::cmpxchg(&_nodes, node, node->next());
3227       if (next == node) {
3228         cl->apply_to_buffer(node, buffer_size, worker_id);
3229         next = node->next();
3230       }
3231     }
3232   }
3233 
3234  public:
3235   G1RedirtyLoggedCardsTask(G1RedirtyCardsQueueSet* qset, G1CollectedHeap* g1h) :
3236     AbstractGangTask("Redirty Cards"),
3237     _qset(qset), _g1h(g1h), _nodes(qset->all_completed_buffers()) { }
3238 
3239   virtual void work(uint worker_id) {
3240     G1GCPhaseTimes* p = _g1h->phase_times();
3241     G1GCParPhaseTimesTracker x(p, G1GCPhaseTimes::RedirtyCards, worker_id);
3242 
3243     RedirtyLoggedCardTableEntryClosure cl(_g1h);
3244     par_apply(&cl, worker_id);
3245 
3246     p->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied());
3247   }
3248 };
3249 
3250 void G1CollectedHeap::redirty_logged_cards(G1RedirtyCardsQueueSet* rdcqs) {
3251   double redirty_logged_cards_start = os::elapsedTime();
3252 
3253   G1RedirtyLoggedCardsTask redirty_task(rdcqs, this);
3254   workers()->run_task(&redirty_task);
3255 
3256   G1DirtyCardQueueSet& dcq = G1BarrierSet::dirty_card_queue_set();
3257   dcq.merge_bufferlists(rdcqs);
3258 
3259   phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
3260 }
3261 
3262 // Weak Reference Processing support
3263 
3264 bool G1STWIsAliveClosure::do_object_b(oop p) {
3265   // An object is reachable if it is outside the collection set,
3266   // or is inside and copied.
3267   return !_g1h->is_in_cset(p) || p->is_forwarded();
3268 }
3269 
3270 bool G1STWSubjectToDiscoveryClosure::do_object_b(oop obj) {
3271   assert(obj != NULL, "must not be NULL");
3272   assert(_g1h->is_in_reserved(obj), "Trying to discover obj " PTR_FORMAT " not in heap", p2i(obj));
3273   // The areas the CM and STW ref processor manage must be disjoint. The is_in_cset() below
3274   // may falsely indicate that this is not the case here: however the collection set only
3275   // contains old regions when concurrent mark is not running.
3276   return _g1h->is_in_cset(obj) || _g1h->heap_region_containing(obj)->is_survivor();
3277 }
3278 
3279 // Non Copying Keep Alive closure
3280 class G1KeepAliveClosure: public OopClosure {
3281   G1CollectedHeap*_g1h;
3282 public:
3283   G1KeepAliveClosure(G1CollectedHeap* g1h) :_g1h(g1h) {}
3284   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
3285   void do_oop(oop* p) {
3286     oop obj = *p;
3287     assert(obj != NULL, "the caller should have filtered out NULL values");
3288 
3289     const G1HeapRegionAttr region_attr =_g1h->region_attr(obj);
3290     if (!region_attr.is_in_cset_or_humongous()) {
3291       return;
3292     }
3293     if (region_attr.is_in_cset()) {
3294       assert( obj->is_forwarded(), "invariant" );
3295       *p = obj->forwardee();
3296     } else {
3297       assert(!obj->is_forwarded(), "invariant" );
3298       assert(region_attr.is_humongous(),
3299              "Only allowed G1HeapRegionAttr state is IsHumongous, but is %d", region_attr.type());
3300      _g1h->set_humongous_is_live(obj);
3301     }
3302   }
3303 };
3304 
3305 // Copying Keep Alive closure - can be called from both
3306 // serial and parallel code as long as different worker
3307 // threads utilize different G1ParScanThreadState instances
3308 // and different queues.
3309 
3310 class G1CopyingKeepAliveClosure: public OopClosure {
3311   G1CollectedHeap*         _g1h;
3312   G1ParScanThreadState*    _par_scan_state;
3313 
3314 public:
3315   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
3316                             G1ParScanThreadState* pss):
3317     _g1h(g1h),
3318     _par_scan_state(pss)
3319   {}
3320 
3321   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
3322   virtual void do_oop(      oop* p) { do_oop_work(p); }
3323 
3324   template <class T> void do_oop_work(T* p) {
3325     oop obj = RawAccess<>::oop_load(p);
3326 
3327     if (_g1h->is_in_cset_or_humongous(obj)) {
3328       // If the referent object has been forwarded (either copied
3329       // to a new location or to itself in the event of an
3330       // evacuation failure) then we need to update the reference
3331       // field and, if both reference and referent are in the G1
3332       // heap, update the RSet for the referent.
3333       //
3334       // If the referent has not been forwarded then we have to keep
3335       // it alive by policy. Therefore we have copy the referent.
3336       //
3337       // When the queue is drained (after each phase of reference processing)
3338       // the object and it's followers will be copied, the reference field set
3339       // to point to the new location, and the RSet updated.
3340       _par_scan_state->push_on_queue(ScannerTask(p));
3341     }
3342   }
3343 };
3344 
3345 // Serial drain queue closure. Called as the 'complete_gc'
3346 // closure for each discovered list in some of the
3347 // reference processing phases.
3348 
3349 class G1STWDrainQueueClosure: public VoidClosure {
3350 protected:
3351   G1CollectedHeap* _g1h;
3352   G1ParScanThreadState* _par_scan_state;
3353 
3354   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
3355 
3356 public:
3357   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
3358     _g1h(g1h),
3359     _par_scan_state(pss)
3360   { }
3361 
3362   void do_void() {
3363     G1ParScanThreadState* const pss = par_scan_state();
3364     pss->trim_queue();
3365   }
3366 };
3367 
3368 // Parallel Reference Processing closures
3369 
3370 // Implementation of AbstractRefProcTaskExecutor for parallel reference
3371 // processing during G1 evacuation pauses.
3372 
3373 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
3374 private:
3375   G1CollectedHeap*          _g1h;
3376   G1ParScanThreadStateSet*  _pss;
3377   G1ScannerTasksQueueSet*   _queues;
3378   WorkGang*                 _workers;
3379 
3380 public:
3381   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
3382                            G1ParScanThreadStateSet* per_thread_states,
3383                            WorkGang* workers,
3384                            G1ScannerTasksQueueSet *task_queues) :
3385     _g1h(g1h),
3386     _pss(per_thread_states),
3387     _queues(task_queues),
3388     _workers(workers)
3389   {
3390     g1h->ref_processor_stw()->set_active_mt_degree(workers->active_workers());
3391   }
3392 
3393   // Executes the given task using concurrent marking worker threads.
3394   virtual void execute(ProcessTask& task, uint ergo_workers);
3395 };
3396 
3397 // Gang task for possibly parallel reference processing
3398 
3399 class G1STWRefProcTaskProxy: public AbstractGangTask {
3400   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
3401   ProcessTask&     _proc_task;
3402   G1CollectedHeap* _g1h;
3403   G1ParScanThreadStateSet* _pss;
3404   G1ScannerTasksQueueSet* _task_queues;
3405   TaskTerminator* _terminator;
3406 
3407 public:
3408   G1STWRefProcTaskProxy(ProcessTask& proc_task,
3409                         G1CollectedHeap* g1h,
3410                         G1ParScanThreadStateSet* per_thread_states,
3411                         G1ScannerTasksQueueSet *task_queues,
3412                         TaskTerminator* terminator) :
3413     AbstractGangTask("Process reference objects in parallel"),
3414     _proc_task(proc_task),
3415     _g1h(g1h),
3416     _pss(per_thread_states),
3417     _task_queues(task_queues),
3418     _terminator(terminator)
3419   {}
3420 
3421   virtual void work(uint worker_id) {
3422     // The reference processing task executed by a single worker.
3423     ResourceMark rm;
3424 
3425     G1STWIsAliveClosure is_alive(_g1h);
3426 
3427     G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
3428     pss->set_ref_discoverer(NULL);
3429 
3430     // Keep alive closure.
3431     G1CopyingKeepAliveClosure keep_alive(_g1h, pss);
3432 
3433     // Complete GC closure
3434     G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator, G1GCPhaseTimes::ObjCopy);
3435 
3436     // Call the reference processing task's work routine.
3437     _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
3438 
3439     // Note we cannot assert that the refs array is empty here as not all
3440     // of the processing tasks (specifically phase2 - pp2_work) execute
3441     // the complete_gc closure (which ordinarily would drain the queue) so
3442     // the queue may not be empty.
3443   }
3444 };
3445 
3446 // Driver routine for parallel reference processing.
3447 // Creates an instance of the ref processing gang
3448 // task and has the worker threads execute it.
3449 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task, uint ergo_workers) {
3450   assert(_workers != NULL, "Need parallel worker threads.");
3451 
3452   assert(_workers->active_workers() >= ergo_workers,
3453          "Ergonomically chosen workers (%u) should be less than or equal to active workers (%u)",
3454          ergo_workers, _workers->active_workers());
3455   TaskTerminator terminator(ergo_workers, _queues);
3456   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator);
3457 
3458   _workers->run_task(&proc_task_proxy, ergo_workers);
3459 }
3460 
3461 // End of weak reference support closures
3462 
3463 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
3464   double ref_proc_start = os::elapsedTime();
3465 
3466   ReferenceProcessor* rp = _ref_processor_stw;
3467   assert(rp->discovery_enabled(), "should have been enabled");
3468 
3469   // Closure to test whether a referent is alive.
3470   G1STWIsAliveClosure is_alive(this);
3471 
3472   // Even when parallel reference processing is enabled, the processing
3473   // of JNI refs is serial and performed serially by the current thread
3474   // rather than by a worker. The following PSS will be used for processing
3475   // JNI refs.
3476 
3477   // Use only a single queue for this PSS.
3478   G1ParScanThreadState*          pss = per_thread_states->state_for_worker(0);
3479   pss->set_ref_discoverer(NULL);
3480   assert(pss->queue_is_empty(), "pre-condition");
3481 
3482   // Keep alive closure.
3483   G1CopyingKeepAliveClosure keep_alive(this, pss);
3484 
3485   // Serial Complete GC closure
3486   G1STWDrainQueueClosure drain_queue(this, pss);
3487 
3488   // Setup the soft refs policy...
3489   rp->setup_policy(false);
3490 
3491   ReferenceProcessorPhaseTimes* pt = phase_times()->ref_phase_times();
3492 
3493   ReferenceProcessorStats stats;
3494   if (!rp->processing_is_mt()) {
3495     // Serial reference processing...
3496     stats = rp->process_discovered_references(&is_alive,
3497                                               &keep_alive,
3498                                               &drain_queue,
3499                                               NULL,
3500                                               pt);
3501   } else {
3502     uint no_of_gc_workers = workers()->active_workers();
3503 
3504     // Parallel reference processing
3505     assert(no_of_gc_workers <= rp->max_num_queues(),
3506            "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
3507            no_of_gc_workers,  rp->max_num_queues());
3508 
3509     G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues);
3510     stats = rp->process_discovered_references(&is_alive,
3511                                               &keep_alive,
3512                                               &drain_queue,
3513                                               &par_task_executor,
3514                                               pt);
3515   }
3516 
3517   _gc_tracer_stw->report_gc_reference_stats(stats);
3518 
3519   // We have completed copying any necessary live referent objects.
3520   assert(pss->queue_is_empty(), "both queue and overflow should be empty");
3521 
3522   make_pending_list_reachable();
3523 
3524   assert(!rp->discovery_enabled(), "Postcondition");
3525   rp->verify_no_references_recorded();
3526 
3527   double ref_proc_time = os::elapsedTime() - ref_proc_start;
3528   phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
3529 }
3530 
3531 void G1CollectedHeap::make_pending_list_reachable() {
3532   if (collector_state()->in_concurrent_start_gc()) {
3533     oop pll_head = Universe::reference_pending_list();
3534     if (pll_head != NULL) {
3535       // Any valid worker id is fine here as we are in the VM thread and single-threaded.
3536       _cm->mark_in_next_bitmap(0 /* worker_id */, pll_head);
3537     }
3538   }
3539 }
3540 
3541 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) {
3542   Ticks start = Ticks::now();
3543   per_thread_states->flush();
3544   phase_times()->record_or_add_time_secs(G1GCPhaseTimes::MergePSS, 0 /* worker_id */, (Ticks::now() - start).seconds());
3545 }
3546 
3547 class G1PrepareEvacuationTask : public AbstractGangTask {
3548   class G1PrepareRegionsClosure : public HeapRegionClosure {
3549     G1CollectedHeap* _g1h;
3550     G1PrepareEvacuationTask* _parent_task;
3551     size_t _worker_humongous_total;
3552     size_t _worker_humongous_candidates;
3553 
3554     bool humongous_region_is_candidate(HeapRegion* region) const {
3555       assert(region->is_starts_humongous(), "Must start a humongous object");
3556 
3557       oop obj = oop(region->bottom());
3558 
3559       // Dead objects cannot be eager reclaim candidates. Due to class
3560       // unloading it is unsafe to query their classes so we return early.
3561       if (_g1h->is_obj_dead(obj, region)) {
3562         return false;
3563       }
3564 
3565       // If we do not have a complete remembered set for the region, then we can
3566       // not be sure that we have all references to it.
3567       if (!region->rem_set()->is_complete()) {
3568         return false;
3569       }
3570       // Candidate selection must satisfy the following constraints
3571       // while concurrent marking is in progress:
3572       //
3573       // * In order to maintain SATB invariants, an object must not be
3574       // reclaimed if it was allocated before the start of marking and
3575       // has not had its references scanned.  Such an object must have
3576       // its references (including type metadata) scanned to ensure no
3577       // live objects are missed by the marking process.  Objects
3578       // allocated after the start of concurrent marking don't need to
3579       // be scanned.
3580       //
3581       // * An object must not be reclaimed if it is on the concurrent
3582       // mark stack.  Objects allocated after the start of concurrent
3583       // marking are never pushed on the mark stack.
3584       //
3585       // Nominating only objects allocated after the start of concurrent
3586       // marking is sufficient to meet both constraints.  This may miss
3587       // some objects that satisfy the constraints, but the marking data
3588       // structures don't support efficiently performing the needed
3589       // additional tests or scrubbing of the mark stack.
3590       //
3591       // However, we presently only nominate is_typeArray() objects.
3592       // A humongous object containing references induces remembered
3593       // set entries on other regions.  In order to reclaim such an
3594       // object, those remembered sets would need to be cleaned up.
3595       //
3596       // We also treat is_typeArray() objects specially, allowing them
3597       // to be reclaimed even if allocated before the start of
3598       // concurrent mark.  For this we rely on mark stack insertion to
3599       // exclude is_typeArray() objects, preventing reclaiming an object
3600       // that is in the mark stack.  We also rely on the metadata for
3601       // such objects to be built-in and so ensured to be kept live.
3602       // Frequent allocation and drop of large binary blobs is an
3603       // important use case for eager reclaim, and this special handling
3604       // may reduce needed headroom.
3605 
3606       return obj->is_typeArray() &&
3607              _g1h->is_potential_eager_reclaim_candidate(region);
3608     }
3609 
3610   public:
3611     G1PrepareRegionsClosure(G1CollectedHeap* g1h, G1PrepareEvacuationTask* parent_task) :
3612       _g1h(g1h),
3613       _parent_task(parent_task),
3614       _worker_humongous_total(0),
3615       _worker_humongous_candidates(0) { }
3616 
3617     ~G1PrepareRegionsClosure() {
3618       _parent_task->add_humongous_candidates(_worker_humongous_candidates);
3619       _parent_task->add_humongous_total(_worker_humongous_total);
3620     }
3621 
3622     virtual bool do_heap_region(HeapRegion* hr) {
3623       // First prepare the region for scanning
3624       _g1h->rem_set()->prepare_region_for_scan(hr);
3625 
3626       // Now check if region is a humongous candidate
3627       if (!hr->is_starts_humongous()) {
3628         _g1h->register_region_with_region_attr(hr);
3629         return false;
3630       }
3631 
3632       uint index = hr->hrm_index();
3633       if (humongous_region_is_candidate(hr)) {
3634         _g1h->set_humongous_reclaim_candidate(index, true);
3635         _g1h->register_humongous_region_with_region_attr(index);
3636         _worker_humongous_candidates++;
3637         // We will later handle the remembered sets of these regions.
3638       } else {
3639         _g1h->set_humongous_reclaim_candidate(index, false);
3640         _g1h->register_region_with_region_attr(hr);
3641       }
3642       _worker_humongous_total++;
3643 
3644       return false;
3645     }
3646   };
3647 
3648   G1CollectedHeap* _g1h;
3649   HeapRegionClaimer _claimer;
3650   volatile size_t _humongous_total;
3651   volatile size_t _humongous_candidates;
3652 public:
3653   G1PrepareEvacuationTask(G1CollectedHeap* g1h) :
3654     AbstractGangTask("Prepare Evacuation"),
3655     _g1h(g1h),
3656     _claimer(_g1h->workers()->active_workers()),
3657     _humongous_total(0),
3658     _humongous_candidates(0) { }
3659 
3660   ~G1PrepareEvacuationTask() {
3661     _g1h->set_has_humongous_reclaim_candidate(_humongous_candidates > 0);
3662   }
3663 
3664   void work(uint worker_id) {
3665     G1PrepareRegionsClosure cl(_g1h, this);
3666     _g1h->heap_region_par_iterate_from_worker_offset(&cl, &_claimer, worker_id);
3667   }
3668 
3669   void add_humongous_candidates(size_t candidates) {
3670     Atomic::add(&_humongous_candidates, candidates);
3671   }
3672 
3673   void add_humongous_total(size_t total) {
3674     Atomic::add(&_humongous_total, total);
3675   }
3676 
3677   size_t humongous_candidates() {
3678     return _humongous_candidates;
3679   }
3680 
3681   size_t humongous_total() {
3682     return _humongous_total;
3683   }
3684 };
3685 
3686 void G1CollectedHeap::pre_evacuate_collection_set(G1EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
3687   _bytes_used_during_gc = 0;
3688 
3689   _expand_heap_after_alloc_failure = true;
3690   _evacuation_failed = false;
3691 
3692   // Disable the hot card cache.
3693   _hot_card_cache->reset_hot_cache_claimed_index();
3694   _hot_card_cache->set_use_cache(false);
3695 
3696   // Initialize the GC alloc regions.
3697   _allocator->init_gc_alloc_regions(evacuation_info);
3698 
3699   {
3700     Ticks start = Ticks::now();
3701     rem_set()->prepare_for_scan_heap_roots();
3702     phase_times()->record_prepare_heap_roots_time_ms((Ticks::now() - start).seconds() * 1000.0);
3703   }
3704 
3705   {
3706     G1PrepareEvacuationTask g1_prep_task(this);
3707     Tickspan task_time = run_task_timed(&g1_prep_task);
3708 
3709     phase_times()->record_register_regions(task_time.seconds() * 1000.0,
3710                                            g1_prep_task.humongous_total(),
3711                                            g1_prep_task.humongous_candidates());
3712   }
3713 
3714   assert(_verifier->check_region_attr_table(), "Inconsistency in the region attributes table.");
3715   _preserved_marks_set.assert_empty();
3716 
3717 #if COMPILER2_OR_JVMCI
3718   DerivedPointerTable::clear();
3719 #endif
3720 
3721   // Concurrent start needs claim bits to keep track of the marked-through CLDs.
3722   if (collector_state()->in_concurrent_start_gc()) {
3723     concurrent_mark()->pre_concurrent_start();
3724 
3725     double start_clear_claimed_marks = os::elapsedTime();
3726 
3727     ClassLoaderDataGraph::clear_claimed_marks();
3728 
3729     double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0;
3730     phase_times()->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms);
3731   }
3732 
3733   // Should G1EvacuationFailureALot be in effect for this GC?
3734   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
3735 }
3736 
3737 class G1EvacuateRegionsBaseTask : public AbstractGangTask {
3738 protected:
3739   G1CollectedHeap* _g1h;
3740   G1ParScanThreadStateSet* _per_thread_states;
3741   G1ScannerTasksQueueSet* _task_queues;
3742   TaskTerminator _terminator;
3743   uint _num_workers;
3744 
3745   void evacuate_live_objects(G1ParScanThreadState* pss,
3746                              uint worker_id,
3747                              G1GCPhaseTimes::GCParPhases objcopy_phase,
3748                              G1GCPhaseTimes::GCParPhases termination_phase) {
3749     G1GCPhaseTimes* p = _g1h->phase_times();
3750 
3751     Ticks start = Ticks::now();
3752     G1ParEvacuateFollowersClosure cl(_g1h, pss, _task_queues, &_terminator, objcopy_phase);
3753     cl.do_void();
3754 
3755     assert(pss->queue_is_empty(), "should be empty");
3756 
3757     Tickspan evac_time = (Ticks::now() - start);
3758     p->record_or_add_time_secs(objcopy_phase, worker_id, evac_time.seconds() - cl.term_time());
3759 
3760     if (termination_phase == G1GCPhaseTimes::Termination) {
3761       p->record_time_secs(termination_phase, worker_id, cl.term_time());
3762       p->record_thread_work_item(termination_phase, worker_id, cl.term_attempts());
3763     } else {
3764       p->record_or_add_time_secs(termination_phase, worker_id, cl.term_time());
3765       p->record_or_add_thread_work_item(termination_phase, worker_id, cl.term_attempts());
3766     }
3767     assert(pss->trim_ticks().seconds() == 0.0, "Unexpected partial trimming during evacuation");
3768   }
3769 
3770   virtual void start_work(uint worker_id) { }
3771 
3772   virtual void end_work(uint worker_id) { }
3773 
3774   virtual void scan_roots(G1ParScanThreadState* pss, uint worker_id) = 0;
3775 
3776   virtual void evacuate_live_objects(G1ParScanThreadState* pss, uint worker_id) = 0;
3777 
3778 public:
3779   G1EvacuateRegionsBaseTask(const char* name,
3780                             G1ParScanThreadStateSet* per_thread_states,
3781                             G1ScannerTasksQueueSet* task_queues,
3782                             uint num_workers) :
3783     AbstractGangTask(name),
3784     _g1h(G1CollectedHeap::heap()),
3785     _per_thread_states(per_thread_states),
3786     _task_queues(task_queues),
3787     _terminator(num_workers, _task_queues),
3788     _num_workers(num_workers)
3789   { }
3790 
3791   void work(uint worker_id) {
3792     start_work(worker_id);
3793 
3794     {
3795       ResourceMark rm;
3796 
3797       G1ParScanThreadState* pss = _per_thread_states->state_for_worker(worker_id);
3798       pss->set_ref_discoverer(_g1h->ref_processor_stw());
3799 
3800       scan_roots(pss, worker_id);
3801       evacuate_live_objects(pss, worker_id);
3802     }
3803 
3804     end_work(worker_id);
3805   }
3806 };
3807 
3808 class G1EvacuateRegionsTask : public G1EvacuateRegionsBaseTask {
3809   G1RootProcessor* _root_processor;
3810 
3811   void scan_roots(G1ParScanThreadState* pss, uint worker_id) {
3812     _root_processor->evacuate_roots(pss, worker_id);
3813     _g1h->rem_set()->scan_heap_roots(pss, worker_id, G1GCPhaseTimes::ScanHR, G1GCPhaseTimes::ObjCopy);
3814     _g1h->rem_set()->scan_collection_set_regions(pss, worker_id, G1GCPhaseTimes::ScanHR, G1GCPhaseTimes::CodeRoots, G1GCPhaseTimes::ObjCopy);
3815   }
3816 
3817   void evacuate_live_objects(G1ParScanThreadState* pss, uint worker_id) {
3818     G1EvacuateRegionsBaseTask::evacuate_live_objects(pss, worker_id, G1GCPhaseTimes::ObjCopy, G1GCPhaseTimes::Termination);
3819   }
3820 
3821   void start_work(uint worker_id) {
3822     _g1h->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, Ticks::now().seconds());
3823   }
3824 
3825   void end_work(uint worker_id) {
3826     _g1h->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, Ticks::now().seconds());
3827   }
3828 
3829 public:
3830   G1EvacuateRegionsTask(G1CollectedHeap* g1h,
3831                         G1ParScanThreadStateSet* per_thread_states,
3832                         G1ScannerTasksQueueSet* task_queues,
3833                         G1RootProcessor* root_processor,
3834                         uint num_workers) :
3835     G1EvacuateRegionsBaseTask("G1 Evacuate Regions", per_thread_states, task_queues, num_workers),
3836     _root_processor(root_processor)
3837   { }
3838 };
3839 
3840 void G1CollectedHeap::evacuate_initial_collection_set(G1ParScanThreadStateSet* per_thread_states) {
3841   G1GCPhaseTimes* p = phase_times();
3842 
3843   {
3844     Ticks start = Ticks::now();
3845     rem_set()->merge_heap_roots(true /* initial_evacuation */);
3846     p->record_merge_heap_roots_time((Ticks::now() - start).seconds() * 1000.0);
3847   }
3848 
3849   Tickspan task_time;
3850   const uint num_workers = workers()->active_workers();
3851 
3852   Ticks start_processing = Ticks::now();
3853   {
3854     G1RootProcessor root_processor(this, num_workers);
3855     G1EvacuateRegionsTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, num_workers);
3856     task_time = run_task_timed(&g1_par_task);
3857     // Closing the inner scope will execute the destructor for the G1RootProcessor object.
3858     // To extract its code root fixup time we measure total time of this scope and
3859     // subtract from the time the WorkGang task took.
3860   }
3861   Tickspan total_processing = Ticks::now() - start_processing;
3862 
3863   p->record_initial_evac_time(task_time.seconds() * 1000.0);
3864   p->record_or_add_code_root_fixup_time((total_processing - task_time).seconds() * 1000.0);
3865 }
3866 
3867 class G1EvacuateOptionalRegionsTask : public G1EvacuateRegionsBaseTask {
3868 
3869   void scan_roots(G1ParScanThreadState* pss, uint worker_id) {
3870     _g1h->rem_set()->scan_heap_roots(pss, worker_id, G1GCPhaseTimes::OptScanHR, G1GCPhaseTimes::OptObjCopy);
3871     _g1h->rem_set()->scan_collection_set_regions(pss, worker_id, G1GCPhaseTimes::OptScanHR, G1GCPhaseTimes::OptCodeRoots, G1GCPhaseTimes::OptObjCopy);
3872   }
3873 
3874   void evacuate_live_objects(G1ParScanThreadState* pss, uint worker_id) {
3875     G1EvacuateRegionsBaseTask::evacuate_live_objects(pss, worker_id, G1GCPhaseTimes::OptObjCopy, G1GCPhaseTimes::OptTermination);
3876   }
3877 
3878 public:
3879   G1EvacuateOptionalRegionsTask(G1ParScanThreadStateSet* per_thread_states,
3880                                 G1ScannerTasksQueueSet* queues,
3881                                 uint num_workers) :
3882     G1EvacuateRegionsBaseTask("G1 Evacuate Optional Regions", per_thread_states, queues, num_workers) {
3883   }
3884 };
3885 
3886 void G1CollectedHeap::evacuate_next_optional_regions(G1ParScanThreadStateSet* per_thread_states) {
3887   class G1MarkScope : public MarkScope { };
3888 
3889   Tickspan task_time;
3890 
3891   Ticks start_processing = Ticks::now();
3892   {
3893     G1MarkScope code_mark_scope;
3894     G1EvacuateOptionalRegionsTask task(per_thread_states, _task_queues, workers()->active_workers());
3895     task_time = run_task_timed(&task);
3896     // See comment in evacuate_collection_set() for the reason of the scope.
3897   }
3898   Tickspan total_processing = Ticks::now() - start_processing;
3899 
3900   G1GCPhaseTimes* p = phase_times();
3901   p->record_or_add_code_root_fixup_time((total_processing - task_time).seconds() * 1000.0);
3902 }
3903 
3904 void G1CollectedHeap::evacuate_optional_collection_set(G1ParScanThreadStateSet* per_thread_states) {
3905   const double gc_start_time_ms = phase_times()->cur_collection_start_sec() * 1000.0;
3906 
3907   while (!evacuation_failed() && _collection_set.optional_region_length() > 0) {
3908 
3909     double time_used_ms = os::elapsedTime() * 1000.0 - gc_start_time_ms;
3910     double time_left_ms = MaxGCPauseMillis - time_used_ms;
3911 
3912     if (time_left_ms < 0 ||
3913         !_collection_set.finalize_optional_for_evacuation(time_left_ms * policy()->optional_evacuation_fraction())) {
3914       log_trace(gc, ergo, cset)("Skipping evacuation of %u optional regions, no more regions can be evacuated in %.3fms",
3915                                 _collection_set.optional_region_length(), time_left_ms);
3916       break;
3917     }
3918 
3919     {
3920       Ticks start = Ticks::now();
3921       rem_set()->merge_heap_roots(false /* initial_evacuation */);
3922       phase_times()->record_or_add_optional_merge_heap_roots_time((Ticks::now() - start).seconds() * 1000.0);
3923     }
3924 
3925     {
3926       Ticks start = Ticks::now();
3927       evacuate_next_optional_regions(per_thread_states);
3928       phase_times()->record_or_add_optional_evac_time((Ticks::now() - start).seconds() * 1000.0);
3929     }
3930   }
3931 
3932   _collection_set.abandon_optional_collection_set(per_thread_states);
3933 }
3934 
3935 void G1CollectedHeap::post_evacuate_collection_set(G1EvacuationInfo& evacuation_info,
3936                                                    G1RedirtyCardsQueueSet* rdcqs,
3937                                                    G1ParScanThreadStateSet* per_thread_states) {
3938   G1GCPhaseTimes* p = phase_times();
3939 
3940   rem_set()->cleanup_after_scan_heap_roots();
3941 
3942   // Process any discovered reference objects - we have
3943   // to do this _before_ we retire the GC alloc regions
3944   // as we may have to copy some 'reachable' referent
3945   // objects (and their reachable sub-graphs) that were
3946   // not copied during the pause.
3947   process_discovered_references(per_thread_states);
3948 
3949   G1STWIsAliveClosure is_alive(this);
3950   G1KeepAliveClosure keep_alive(this);
3951 
3952   WeakProcessor::weak_oops_do(workers(), &is_alive, &keep_alive, p->weak_phase_times());
3953 
3954   if (G1StringDedup::is_enabled()) {
3955     double string_dedup_time_ms = os::elapsedTime();
3956 
3957     string_dedup_cleaning(&is_alive, &keep_alive, p);
3958 
3959     double string_cleanup_time_ms = (os::elapsedTime() - string_dedup_time_ms) * 1000.0;
3960     p->record_string_deduplication_time(string_cleanup_time_ms);
3961   }
3962 
3963   _allocator->release_gc_alloc_regions(evacuation_info);
3964 
3965   if (evacuation_failed()) {
3966     restore_after_evac_failure(rdcqs);
3967 
3968     // Reset the G1EvacuationFailureALot counters and flags
3969     NOT_PRODUCT(reset_evacuation_should_fail();)
3970 
3971     double recalculate_used_start = os::elapsedTime();
3972     set_used(recalculate_used());
3973     p->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
3974 
3975     if (_archive_allocator != NULL) {
3976       _archive_allocator->clear_used();
3977     }
3978     for (uint i = 0; i < ParallelGCThreads; i++) {
3979       if (_evacuation_failed_info_array[i].has_failed()) {
3980         _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
3981       }
3982     }
3983   } else {
3984     // The "used" of the the collection set have already been subtracted
3985     // when they were freed.  Add in the bytes used.
3986     increase_used(_bytes_used_during_gc);
3987   }
3988 
3989   _preserved_marks_set.assert_empty();
3990 
3991   merge_per_thread_state_info(per_thread_states);
3992 
3993   // Reset and re-enable the hot card cache.
3994   // Note the counts for the cards in the regions in the
3995   // collection set are reset when the collection set is freed.
3996   _hot_card_cache->reset_hot_cache();
3997   _hot_card_cache->set_use_cache(true);
3998 
3999   purge_code_root_memory();
4000 
4001   redirty_logged_cards(rdcqs);
4002 
4003   free_collection_set(&_collection_set, evacuation_info, per_thread_states->surviving_young_words());
4004 
4005   eagerly_reclaim_humongous_regions();
4006 
4007   record_obj_copy_mem_stats();
4008 
4009   evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before());
4010   evacuation_info.set_bytes_used(_bytes_used_during_gc);
4011 
4012 #if COMPILER2_OR_JVMCI
4013   double start = os::elapsedTime();
4014   DerivedPointerTable::update_pointers();
4015   phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0);
4016 #endif
4017   policy()->print_age_table();
4018 }
4019 
4020 void G1CollectedHeap::record_obj_copy_mem_stats() {
4021   policy()->old_gen_alloc_tracker()->
4022     add_allocated_bytes_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
4023 
4024   _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
4025                                                create_g1_evac_summary(&_old_evac_stats));
4026 }
4027 
4028 void G1CollectedHeap::free_region(HeapRegion* hr, FreeRegionList* free_list) {
4029   assert(!hr->is_free(), "the region should not be free");
4030   assert(!hr->is_empty(), "the region should not be empty");
4031   assert(_hrm->is_available(hr->hrm_index()), "region should be committed");
4032 
4033   if (G1VerifyBitmaps) {
4034     MemRegion mr(hr->bottom(), hr->end());
4035     concurrent_mark()->clear_range_in_prev_bitmap(mr);
4036   }
4037 
4038   // Clear the card counts for this region.
4039   // Note: we only need to do this if the region is not young
4040   // (since we don't refine cards in young regions).
4041   if (!hr->is_young()) {
4042     _hot_card_cache->reset_card_counts(hr);
4043   }
4044 
4045   // Reset region metadata to allow reuse.
4046   hr->hr_clear(true /* clear_space */);
4047   _policy->remset_tracker()->update_at_free(hr);
4048 
4049   if (free_list != NULL) {
4050     free_list->add_ordered(hr);
4051   }
4052 }
4053 
4054 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
4055                                             FreeRegionList* free_list) {
4056   assert(hr->is_humongous(), "this is only for humongous regions");
4057   assert(free_list != NULL, "pre-condition");
4058   hr->clear_humongous();
4059   free_region(hr, free_list);
4060 }
4061 
4062 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed,
4063                                            const uint humongous_regions_removed) {
4064   if (old_regions_removed > 0 || humongous_regions_removed > 0) {
4065     MutexLocker x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4066     _old_set.bulk_remove(old_regions_removed);
4067     _humongous_set.bulk_remove(humongous_regions_removed);
4068   }
4069 
4070 }
4071 
4072 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
4073   assert(list != NULL, "list can't be null");
4074   if (!list->is_empty()) {
4075     MutexLocker x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4076     _hrm->insert_list_into_free_list(list);
4077   }
4078 }
4079 
4080 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
4081   decrease_used(bytes);
4082 }
4083 
4084 class G1FreeCollectionSetTask : public AbstractGangTask {
4085   // Helper class to keep statistics for the collection set freeing
4086   class FreeCSetStats {
4087     size_t _before_used_bytes;   // Usage in regions successfully evacutate
4088     size_t _after_used_bytes;    // Usage in regions failing evacuation
4089     size_t _bytes_allocated_in_old_since_last_gc; // Size of young regions turned into old
4090     size_t _failure_used_words;  // Live size in failed regions
4091     size_t _failure_waste_words; // Wasted size in failed regions
4092     size_t _rs_length;           // Remembered set size
4093     uint _regions_freed;         // Number of regions freed
4094   public:
4095     FreeCSetStats() :
4096         _before_used_bytes(0),
4097         _after_used_bytes(0),
4098         _bytes_allocated_in_old_since_last_gc(0),
4099         _failure_used_words(0),
4100         _failure_waste_words(0),
4101         _rs_length(0),
4102         _regions_freed(0) { }
4103 
4104     void merge_stats(FreeCSetStats* other) {
4105       assert(other != NULL, "invariant");
4106       _before_used_bytes += other->_before_used_bytes;
4107       _after_used_bytes += other->_after_used_bytes;
4108       _bytes_allocated_in_old_since_last_gc += other->_bytes_allocated_in_old_since_last_gc;
4109       _failure_used_words += other->_failure_used_words;
4110       _failure_waste_words += other->_failure_waste_words;
4111       _rs_length += other->_rs_length;
4112       _regions_freed += other->_regions_freed;
4113     }
4114 
4115     void report(G1CollectedHeap* g1h, G1EvacuationInfo* evacuation_info) {
4116       evacuation_info->set_regions_freed(_regions_freed);
4117       evacuation_info->increment_collectionset_used_after(_after_used_bytes);
4118 
4119       g1h->decrement_summary_bytes(_before_used_bytes);
4120       g1h->alloc_buffer_stats(G1HeapRegionAttr::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words);
4121 
4122       G1Policy *policy = g1h->policy();
4123       policy->old_gen_alloc_tracker()->add_allocated_bytes_since_last_gc(_bytes_allocated_in_old_since_last_gc);
4124       policy->record_rs_length(_rs_length);
4125       policy->cset_regions_freed();
4126     }
4127 
4128     void account_failed_region(HeapRegion* r) {
4129       size_t used_words = r->marked_bytes() / HeapWordSize;
4130       _failure_used_words += used_words;
4131       _failure_waste_words += HeapRegion::GrainWords - used_words;
4132       _after_used_bytes += r->used();
4133 
4134       // When moving a young gen region to old gen, we "allocate" that whole
4135       // region there. This is in addition to any already evacuated objects.
4136       // Notify the policy about that. Old gen regions do not cause an
4137       // additional allocation: both the objects still in the region and the
4138       // ones already moved are accounted for elsewhere.
4139       if (r->is_young()) {
4140         _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes;
4141       }
4142     }
4143 
4144     void account_evacuated_region(HeapRegion* r) {
4145       _before_used_bytes += r->used();
4146       _regions_freed += 1;
4147     }
4148 
4149     void account_rs_length(HeapRegion* r) {
4150       _rs_length += r->rem_set()->occupied();
4151     }
4152   };
4153 
4154   // Closure applied to all regions in the collection set.
4155   class FreeCSetClosure : public HeapRegionClosure {
4156     // Helper to send JFR events for regions.
4157     class JFREventForRegion {
4158       EventGCPhaseParallel _event;
4159     public:
4160       JFREventForRegion(HeapRegion* region, uint worker_id) : _event() {
4161         _event.set_gcId(GCId::current());
4162         _event.set_gcWorkerId(worker_id);
4163         if (region->is_young()) {
4164           _event.set_name(G1GCPhaseTimes::phase_name(G1GCPhaseTimes::YoungFreeCSet));
4165         } else {
4166           _event.set_name(G1GCPhaseTimes::phase_name(G1GCPhaseTimes::NonYoungFreeCSet));
4167         }
4168       }
4169 
4170       ~JFREventForRegion() {
4171         _event.commit();
4172       }
4173     };
4174 
4175     // Helper to do timing for region work.
4176     class TimerForRegion {
4177       Tickspan& _time;
4178       Ticks     _start_time;
4179     public:
4180       TimerForRegion(Tickspan& time) : _time(time), _start_time(Ticks::now()) { }
4181       ~TimerForRegion() {
4182         _time += Ticks::now() - _start_time;
4183       }
4184     };
4185 
4186     // FreeCSetClosure members
4187     G1CollectedHeap* _g1h;
4188     const size_t*    _surviving_young_words;
4189     uint             _worker_id;
4190     Tickspan         _young_time;
4191     Tickspan         _non_young_time;
4192     FreeCSetStats*   _stats;
4193 
4194     void assert_in_cset(HeapRegion* r) {
4195       assert(r->young_index_in_cset() != 0 &&
4196              (uint)r->young_index_in_cset() <= _g1h->collection_set()->young_region_length(),
4197              "Young index %u is wrong for region %u of type %s with %u young regions",
4198              r->young_index_in_cset(), r->hrm_index(), r->get_type_str(), _g1h->collection_set()->young_region_length());
4199     }
4200 
4201     void handle_evacuated_region(HeapRegion* r) {
4202       assert(!r->is_empty(), "Region %u is an empty region in the collection set.", r->hrm_index());
4203       stats()->account_evacuated_region(r);
4204 
4205       // Free the region and and its remembered set.
4206       _g1h->free_region(r, NULL);
4207     }
4208 
4209     void handle_failed_region(HeapRegion* r) {
4210       // Do some allocation statistics accounting. Regions that failed evacuation
4211       // are always made old, so there is no need to update anything in the young
4212       // gen statistics, but we need to update old gen statistics.
4213       stats()->account_failed_region(r);
4214 
4215       // Update the region state due to the failed evacuation.
4216       r->handle_evacuation_failure();
4217 
4218       // Add region to old set, need to hold lock.
4219       MutexLocker x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4220       _g1h->old_set_add(r);
4221     }
4222 
4223     Tickspan& timer_for_region(HeapRegion* r) {
4224       return r->is_young() ? _young_time : _non_young_time;
4225     }
4226 
4227     FreeCSetStats* stats() {
4228       return _stats;
4229     }
4230   public:
4231     FreeCSetClosure(const size_t* surviving_young_words,
4232                     uint worker_id,
4233                     FreeCSetStats* stats) :
4234         HeapRegionClosure(),
4235         _g1h(G1CollectedHeap::heap()),
4236         _surviving_young_words(surviving_young_words),
4237         _worker_id(worker_id),
4238         _young_time(),
4239         _non_young_time(),
4240         _stats(stats) { }
4241 
4242     virtual bool do_heap_region(HeapRegion* r) {
4243       assert(r->in_collection_set(), "Invariant: %u missing from CSet", r->hrm_index());
4244       JFREventForRegion event(r, _worker_id);
4245       TimerForRegion timer(timer_for_region(r));
4246 
4247       _g1h->clear_region_attr(r);
4248       stats()->account_rs_length(r);
4249 
4250       if (r->is_young()) {
4251         assert_in_cset(r);
4252         r->record_surv_words_in_group(_surviving_young_words[r->young_index_in_cset()]);
4253       }
4254 
4255       if (r->evacuation_failed()) {
4256         handle_failed_region(r);
4257       } else {
4258         handle_evacuated_region(r);
4259       }
4260       assert(!_g1h->is_on_master_free_list(r), "sanity");
4261 
4262       return false;
4263     }
4264 
4265     void report_timing(Tickspan parallel_time) {
4266       G1GCPhaseTimes* pt = _g1h->phase_times();
4267       pt->record_time_secs(G1GCPhaseTimes::ParFreeCSet, _worker_id, parallel_time.seconds());
4268       if (_young_time.value() > 0) {
4269         pt->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, _worker_id, _young_time.seconds());
4270       }
4271       if (_non_young_time.value() > 0) {
4272         pt->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, _worker_id, _non_young_time.seconds());
4273       }
4274     }
4275   };
4276 
4277   // G1FreeCollectionSetTask members
4278   G1CollectedHeap*  _g1h;
4279   G1EvacuationInfo* _evacuation_info;
4280   FreeCSetStats*    _worker_stats;
4281   HeapRegionClaimer _claimer;
4282   const size_t*     _surviving_young_words;
4283   uint              _active_workers;
4284 
4285   FreeCSetStats* worker_stats(uint worker) {
4286     return &_worker_stats[worker];
4287   }
4288 
4289   void report_statistics() {
4290     // Merge the accounting
4291     FreeCSetStats total_stats;
4292     for (uint worker = 0; worker < _active_workers; worker++) {
4293       total_stats.merge_stats(worker_stats(worker));
4294     }
4295     total_stats.report(_g1h, _evacuation_info);
4296   }
4297 
4298 public:
4299   G1FreeCollectionSetTask(G1EvacuationInfo* evacuation_info, const size_t* surviving_young_words, uint active_workers) :
4300       AbstractGangTask("G1 Free Collection Set"),
4301       _g1h(G1CollectedHeap::heap()),
4302       _evacuation_info(evacuation_info),
4303       _worker_stats(NEW_C_HEAP_ARRAY(FreeCSetStats, active_workers, mtGC)),
4304       _claimer(active_workers),
4305       _surviving_young_words(surviving_young_words),
4306       _active_workers(active_workers) {
4307     for (uint worker = 0; worker < active_workers; worker++) {
4308       ::new (&_worker_stats[worker]) FreeCSetStats();
4309     }
4310   }
4311 
4312   ~G1FreeCollectionSetTask() {
4313     Ticks serial_time = Ticks::now();
4314     report_statistics();
4315     for (uint worker = 0; worker < _active_workers; worker++) {
4316       _worker_stats[worker].~FreeCSetStats();
4317     }
4318     FREE_C_HEAP_ARRAY(FreeCSetStats, _worker_stats);
4319     _g1h->phase_times()->record_serial_free_cset_time_ms((Ticks::now() - serial_time).seconds() * 1000.0);
4320   }
4321 
4322   virtual void work(uint worker_id) {
4323     EventGCPhaseParallel event;
4324     Ticks start = Ticks::now();
4325     FreeCSetClosure cl(_surviving_young_words, worker_id, worker_stats(worker_id));
4326     _g1h->collection_set_par_iterate_all(&cl, &_claimer, worker_id);
4327 
4328     // Report the total parallel time along with some more detailed metrics.
4329     cl.report_timing(Ticks::now() - start);
4330     event.commit(GCId::current(), worker_id, G1GCPhaseTimes::phase_name(G1GCPhaseTimes::ParFreeCSet));
4331   }
4332 };
4333 
4334 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, G1EvacuationInfo& evacuation_info, const size_t* surviving_young_words) {
4335   _eden.clear();
4336 
4337   // The free collections set is split up in two tasks, the first
4338   // frees the collection set and records what regions are free,
4339   // and the second one rebuilds the free list. This proved to be
4340   // more efficient than adding a sorted list to another.
4341 
4342   Ticks free_cset_start_time = Ticks::now();
4343   {
4344     uint const num_cs_regions = _collection_set.region_length();
4345     uint const num_workers = clamp(num_cs_regions, 1u, workers()->active_workers());
4346     G1FreeCollectionSetTask cl(&evacuation_info, surviving_young_words, num_workers);
4347 
4348     log_debug(gc, ergo)("Running %s using %u workers for collection set length %u (%u)",
4349                         cl.name(), num_workers, num_cs_regions, num_regions());
4350     workers()->run_task(&cl, num_workers);
4351   }
4352 
4353   Ticks free_cset_end_time = Ticks::now();
4354   phase_times()->record_total_free_cset_time_ms((free_cset_end_time - free_cset_start_time).seconds() * 1000.0);
4355 
4356   // Now rebuild the free region list.
4357   hrm()->rebuild_free_list(workers());
4358   phase_times()->record_total_rebuild_freelist_time_ms((Ticks::now() - free_cset_end_time).seconds() * 1000.0);
4359 
4360   collection_set->clear();
4361 }
4362 
4363 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
4364  private:
4365   FreeRegionList* _free_region_list;
4366   HeapRegionSet* _proxy_set;
4367   uint _humongous_objects_reclaimed;
4368   uint _humongous_regions_reclaimed;
4369   size_t _freed_bytes;
4370  public:
4371 
4372   G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
4373     _free_region_list(free_region_list), _proxy_set(NULL), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) {
4374   }
4375 
4376   virtual bool do_heap_region(HeapRegion* r) {
4377     if (!r->is_starts_humongous()) {
4378       return false;
4379     }
4380 
4381     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4382 
4383     oop obj = (oop)r->bottom();
4384     G1CMBitMap* next_bitmap = g1h->concurrent_mark()->next_mark_bitmap();
4385 
4386     // The following checks whether the humongous object is live are sufficient.
4387     // The main additional check (in addition to having a reference from the roots
4388     // or the young gen) is whether the humongous object has a remembered set entry.
4389     //
4390     // A humongous object cannot be live if there is no remembered set for it
4391     // because:
4392     // - there can be no references from within humongous starts regions referencing
4393     // the object because we never allocate other objects into them.
4394     // (I.e. there are no intra-region references that may be missed by the
4395     // remembered set)
4396     // - as soon there is a remembered set entry to the humongous starts region
4397     // (i.e. it has "escaped" to an old object) this remembered set entry will stay
4398     // until the end of a concurrent mark.
4399     //
4400     // It is not required to check whether the object has been found dead by marking
4401     // or not, in fact it would prevent reclamation within a concurrent cycle, as
4402     // all objects allocated during that time are considered live.
4403     // SATB marking is even more conservative than the remembered set.
4404     // So if at this point in the collection there is no remembered set entry,
4405     // nobody has a reference to it.
4406     // At the start of collection we flush all refinement logs, and remembered sets
4407     // are completely up-to-date wrt to references to the humongous object.
4408     //
4409     // Other implementation considerations:
4410     // - never consider object arrays at this time because they would pose
4411     // considerable effort for cleaning up the the remembered sets. This is
4412     // required because stale remembered sets might reference locations that
4413     // are currently allocated into.
4414     uint region_idx = r->hrm_index();
4415     if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
4416         !r->rem_set()->is_empty()) {
4417       log_debug(gc, humongous)("Live humongous region %u object size " SIZE_FORMAT " start " PTR_FORMAT "  with remset " SIZE_FORMAT " code roots " SIZE_FORMAT " is marked %d reclaim candidate %d type array %d",
4418                                region_idx,
4419                                (size_t)obj->size() * HeapWordSize,
4420                                p2i(r->bottom()),
4421                                r->rem_set()->occupied(),
4422                                r->rem_set()->strong_code_roots_list_length(),
4423                                next_bitmap->is_marked(r->bottom()),
4424                                g1h->is_humongous_reclaim_candidate(region_idx),
4425                                obj->is_typeArray()
4426                               );
4427       return false;
4428     }
4429 
4430     guarantee(obj->is_typeArray(),
4431               "Only eagerly reclaiming type arrays is supported, but the object "
4432               PTR_FORMAT " is not.", p2i(r->bottom()));
4433 
4434     log_debug(gc, humongous)("Dead humongous region %u object size " SIZE_FORMAT " start " PTR_FORMAT " with remset " SIZE_FORMAT " code roots " SIZE_FORMAT " is marked %d reclaim candidate %d type array %d",
4435                              region_idx,
4436                              (size_t)obj->size() * HeapWordSize,
4437                              p2i(r->bottom()),
4438                              r->rem_set()->occupied(),
4439                              r->rem_set()->strong_code_roots_list_length(),
4440                              next_bitmap->is_marked(r->bottom()),
4441                              g1h->is_humongous_reclaim_candidate(region_idx),
4442                              obj->is_typeArray()
4443                             );
4444 
4445     G1ConcurrentMark* const cm = g1h->concurrent_mark();
4446     cm->humongous_object_eagerly_reclaimed(r);
4447     assert(!cm->is_marked_in_prev_bitmap(obj) && !cm->is_marked_in_next_bitmap(obj),
4448            "Eagerly reclaimed humongous region %u should not be marked at all but is in prev %s next %s",
4449            region_idx,
4450            BOOL_TO_STR(cm->is_marked_in_prev_bitmap(obj)),
4451            BOOL_TO_STR(cm->is_marked_in_next_bitmap(obj)));
4452     _humongous_objects_reclaimed++;
4453     do {
4454       HeapRegion* next = g1h->next_region_in_humongous(r);
4455       _freed_bytes += r->used();
4456       r->set_containing_set(NULL);
4457       _humongous_regions_reclaimed++;
4458       g1h->free_humongous_region(r, _free_region_list);
4459       r = next;
4460     } while (r != NULL);
4461 
4462     return false;
4463   }
4464 
4465   uint humongous_objects_reclaimed() {
4466     return _humongous_objects_reclaimed;
4467   }
4468 
4469   uint humongous_regions_reclaimed() {
4470     return _humongous_regions_reclaimed;
4471   }
4472 
4473   size_t bytes_freed() const {
4474     return _freed_bytes;
4475   }
4476 };
4477 
4478 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
4479   assert_at_safepoint_on_vm_thread();
4480 
4481   if (!G1EagerReclaimHumongousObjects ||
4482       (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) {
4483     phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
4484     return;
4485   }
4486 
4487   double start_time = os::elapsedTime();
4488 
4489   FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
4490 
4491   G1FreeHumongousRegionClosure cl(&local_cleanup_list);
4492   heap_region_iterate(&cl);
4493 
4494   remove_from_old_sets(0, cl.humongous_regions_reclaimed());
4495 
4496   G1HRPrinter* hrp = hr_printer();
4497   if (hrp->is_active()) {
4498     FreeRegionListIterator iter(&local_cleanup_list);
4499     while (iter.more_available()) {
4500       HeapRegion* hr = iter.get_next();
4501       hrp->cleanup(hr);
4502     }
4503   }
4504 
4505   prepend_to_freelist(&local_cleanup_list);
4506   decrement_summary_bytes(cl.bytes_freed());
4507 
4508   phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
4509                                                        cl.humongous_objects_reclaimed());
4510 }
4511 
4512 class G1AbandonCollectionSetClosure : public HeapRegionClosure {
4513 public:
4514   virtual bool do_heap_region(HeapRegion* r) {
4515     assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index());
4516     G1CollectedHeap::heap()->clear_region_attr(r);
4517     r->clear_young_index_in_cset();
4518     return false;
4519   }
4520 };
4521 
4522 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) {
4523   G1AbandonCollectionSetClosure cl;
4524   collection_set_iterate_all(&cl);
4525 
4526   collection_set->clear();
4527   collection_set->stop_incremental_building();
4528 }
4529 
4530 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
4531   return _allocator->is_retained_old_region(hr);
4532 }
4533 
4534 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
4535   _eden.add(hr);
4536   _policy->set_region_eden(hr);
4537 }
4538 
4539 #ifdef ASSERT
4540 
4541 class NoYoungRegionsClosure: public HeapRegionClosure {
4542 private:
4543   bool _success;
4544 public:
4545   NoYoungRegionsClosure() : _success(true) { }
4546   bool do_heap_region(HeapRegion* r) {
4547     if (r->is_young()) {
4548       log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
4549                             p2i(r->bottom()), p2i(r->end()));
4550       _success = false;
4551     }
4552     return false;
4553   }
4554   bool success() { return _success; }
4555 };
4556 
4557 bool G1CollectedHeap::check_young_list_empty() {
4558   bool ret = (young_regions_count() == 0);
4559 
4560   NoYoungRegionsClosure closure;
4561   heap_region_iterate(&closure);
4562   ret = ret && closure.success();
4563 
4564   return ret;
4565 }
4566 
4567 #endif // ASSERT
4568 
4569 class TearDownRegionSetsClosure : public HeapRegionClosure {
4570   HeapRegionSet *_old_set;
4571 
4572 public:
4573   TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
4574 
4575   bool do_heap_region(HeapRegion* r) {
4576     if (r->is_old()) {
4577       _old_set->remove(r);
4578     } else if(r->is_young()) {
4579       r->uninstall_surv_rate_group();
4580     } else {
4581       // We ignore free regions, we'll empty the free list afterwards.
4582       // We ignore humongous and archive regions, we're not tearing down these
4583       // sets.
4584       assert(r->is_archive() || r->is_free() || r->is_humongous(),
4585              "it cannot be another type");
4586     }
4587     return false;
4588   }
4589 
4590   ~TearDownRegionSetsClosure() {
4591     assert(_old_set->is_empty(), "post-condition");
4592   }
4593 };
4594 
4595 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
4596   assert_at_safepoint_on_vm_thread();
4597 
4598   if (!free_list_only) {
4599     TearDownRegionSetsClosure cl(&_old_set);
4600     heap_region_iterate(&cl);
4601 
4602     // Note that emptying the _young_list is postponed and instead done as
4603     // the first step when rebuilding the regions sets again. The reason for
4604     // this is that during a full GC string deduplication needs to know if
4605     // a collected region was young or old when the full GC was initiated.
4606   }
4607   _hrm->remove_all_free_regions();
4608 }
4609 
4610 void G1CollectedHeap::increase_used(size_t bytes) {
4611   _summary_bytes_used += bytes;
4612 }
4613 
4614 void G1CollectedHeap::decrease_used(size_t bytes) {
4615   assert(_summary_bytes_used >= bytes,
4616          "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
4617          _summary_bytes_used, bytes);
4618   _summary_bytes_used -= bytes;
4619 }
4620 
4621 void G1CollectedHeap::set_used(size_t bytes) {
4622   _summary_bytes_used = bytes;
4623 }
4624 
4625 class RebuildRegionSetsClosure : public HeapRegionClosure {
4626 private:
4627   bool _free_list_only;
4628 
4629   HeapRegionSet* _old_set;
4630   HeapRegionManager* _hrm;
4631 
4632   size_t _total_used;
4633 
4634 public:
4635   RebuildRegionSetsClosure(bool free_list_only,
4636                            HeapRegionSet* old_set,
4637                            HeapRegionManager* hrm) :
4638     _free_list_only(free_list_only),
4639     _old_set(old_set), _hrm(hrm), _total_used(0) {
4640     assert(_hrm->num_free_regions() == 0, "pre-condition");
4641     if (!free_list_only) {
4642       assert(_old_set->is_empty(), "pre-condition");
4643     }
4644   }
4645 
4646   bool do_heap_region(HeapRegion* r) {
4647     if (r->is_empty()) {
4648       assert(r->rem_set()->is_empty(), "Empty regions should have empty remembered sets.");
4649       // Add free regions to the free list
4650       r->set_free();
4651       _hrm->insert_into_free_list(r);
4652     } else if (!_free_list_only) {
4653       assert(r->rem_set()->is_empty(), "At this point remembered sets must have been cleared.");
4654 
4655       if (r->is_archive() || r->is_humongous()) {
4656         // We ignore archive and humongous regions. We left these sets unchanged.
4657       } else {
4658         assert(r->is_young() || r->is_free() || r->is_old(), "invariant");
4659         // We now move all (non-humongous, non-old, non-archive) regions to old gen, and register them as such.
4660         r->move_to_old();
4661         _old_set->add(r);
4662       }
4663       _total_used += r->used();
4664     }
4665 
4666     return false;
4667   }
4668 
4669   size_t total_used() {
4670     return _total_used;
4671   }
4672 };
4673 
4674 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
4675   assert_at_safepoint_on_vm_thread();
4676 
4677   if (!free_list_only) {
4678     _eden.clear();
4679     _survivor.clear();
4680   }
4681 
4682   RebuildRegionSetsClosure cl(free_list_only, &_old_set, _hrm);
4683   heap_region_iterate(&cl);
4684 
4685   if (!free_list_only) {
4686     set_used(cl.total_used());
4687     if (_archive_allocator != NULL) {
4688       _archive_allocator->clear_used();
4689     }
4690   }
4691   assert_used_and_recalculate_used_equal(this);
4692 }
4693 
4694 // Methods for the mutator alloc region
4695 
4696 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
4697                                                       bool force,
4698                                                       uint node_index) {
4699   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
4700   bool should_allocate = policy()->should_allocate_mutator_region();
4701   if (force || should_allocate) {
4702     HeapRegion* new_alloc_region = new_region(word_size,
4703                                               HeapRegionType::Eden,
4704                                               false /* do_expand */,
4705                                               node_index);
4706     if (new_alloc_region != NULL) {
4707       set_region_short_lived_locked(new_alloc_region);
4708       _hr_printer.alloc(new_alloc_region, !should_allocate);
4709       _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region);
4710       _policy->remset_tracker()->update_at_allocate(new_alloc_region);
4711       return new_alloc_region;
4712     }
4713   }
4714   return NULL;
4715 }
4716 
4717 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
4718                                                   size_t allocated_bytes) {
4719   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
4720   assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
4721 
4722   collection_set()->add_eden_region(alloc_region);
4723   increase_used(allocated_bytes);
4724   _eden.add_used_bytes(allocated_bytes);
4725   _hr_printer.retire(alloc_region);
4726 
4727   // We update the eden sizes here, when the region is retired,
4728   // instead of when it's allocated, since this is the point that its
4729   // used space has been recorded in _summary_bytes_used.
4730   g1mm()->update_eden_size();
4731 }
4732 
4733 // Methods for the GC alloc regions
4734 
4735 bool G1CollectedHeap::has_more_regions(G1HeapRegionAttr dest) {
4736   if (dest.is_old()) {
4737     return true;
4738   } else {
4739     return survivor_regions_count() < policy()->max_survivor_regions();
4740   }
4741 }
4742 
4743 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, G1HeapRegionAttr dest, uint node_index) {
4744   assert(FreeList_lock->owned_by_self(), "pre-condition");
4745 
4746   if (!has_more_regions(dest)) {
4747     return NULL;
4748   }
4749 
4750   HeapRegionType type;
4751   if (dest.is_young()) {
4752     type = HeapRegionType::Survivor;
4753   } else {
4754     type = HeapRegionType::Old;
4755   }
4756 
4757   HeapRegion* new_alloc_region = new_region(word_size,
4758                                             type,
4759                                             true /* do_expand */,
4760                                             node_index);
4761 
4762   if (new_alloc_region != NULL) {
4763     if (type.is_survivor()) {
4764       new_alloc_region->set_survivor();
4765       _survivor.add(new_alloc_region);
4766       _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region);
4767     } else {
4768       new_alloc_region->set_old();
4769       _verifier->check_bitmaps("Old Region Allocation", new_alloc_region);
4770     }
4771     _policy->remset_tracker()->update_at_allocate(new_alloc_region);
4772     register_region_with_region_attr(new_alloc_region);
4773     _hr_printer.alloc(new_alloc_region);
4774     return new_alloc_region;
4775   }
4776   return NULL;
4777 }
4778 
4779 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
4780                                              size_t allocated_bytes,
4781                                              G1HeapRegionAttr dest) {
4782   _bytes_used_during_gc += allocated_bytes;
4783   if (dest.is_old()) {
4784     old_set_add(alloc_region);
4785   } else {
4786     assert(dest.is_young(), "Retiring alloc region should be young (%d)", dest.type());
4787     _survivor.add_used_bytes(allocated_bytes);
4788   }
4789 
4790   bool const during_im = collector_state()->in_concurrent_start_gc();
4791   if (during_im && allocated_bytes > 0) {
4792     _cm->root_regions()->add(alloc_region->next_top_at_mark_start(), alloc_region->top());
4793   }
4794   _hr_printer.retire(alloc_region);
4795 }
4796 
4797 HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
4798   bool expanded = false;
4799   uint index = _hrm->find_highest_free(&expanded);
4800 
4801   if (index != G1_NO_HRM_INDEX) {
4802     if (expanded) {
4803       log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
4804                                 HeapRegion::GrainWords * HeapWordSize);
4805     }
4806     return _hrm->allocate_free_regions_starting_at(index, 1);
4807   }
4808   return NULL;
4809 }
4810 
4811 // Optimized nmethod scanning
4812 
4813 class RegisterNMethodOopClosure: public OopClosure {
4814   G1CollectedHeap* _g1h;
4815   nmethod* _nm;
4816 
4817   template <class T> void do_oop_work(T* p) {
4818     T heap_oop = RawAccess<>::oop_load(p);
4819     if (!CompressedOops::is_null(heap_oop)) {
4820       oop obj = CompressedOops::decode_not_null(heap_oop);
4821       HeapRegion* hr = _g1h->heap_region_containing(obj);
4822       assert(!hr->is_continues_humongous(),
4823              "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
4824              " starting at " HR_FORMAT,
4825              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
4826 
4827       // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
4828       hr->add_strong_code_root_locked(_nm);
4829     }
4830   }
4831 
4832 public:
4833   RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
4834     _g1h(g1h), _nm(nm) {}
4835 
4836   void do_oop(oop* p)       { do_oop_work(p); }
4837   void do_oop(narrowOop* p) { do_oop_work(p); }
4838 };
4839 
4840 class UnregisterNMethodOopClosure: public OopClosure {
4841   G1CollectedHeap* _g1h;
4842   nmethod* _nm;
4843 
4844   template <class T> void do_oop_work(T* p) {
4845     T heap_oop = RawAccess<>::oop_load(p);
4846     if (!CompressedOops::is_null(heap_oop)) {
4847       oop obj = CompressedOops::decode_not_null(heap_oop);
4848       HeapRegion* hr = _g1h->heap_region_containing(obj);
4849       assert(!hr->is_continues_humongous(),
4850              "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
4851              " starting at " HR_FORMAT,
4852              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
4853 
4854       hr->remove_strong_code_root(_nm);
4855     }
4856   }
4857 
4858 public:
4859   UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
4860     _g1h(g1h), _nm(nm) {}
4861 
4862   void do_oop(oop* p)       { do_oop_work(p); }
4863   void do_oop(narrowOop* p) { do_oop_work(p); }
4864 };
4865 
4866 void G1CollectedHeap::register_nmethod(nmethod* nm) {
4867   guarantee(nm != NULL, "sanity");
4868   RegisterNMethodOopClosure reg_cl(this, nm);
4869   nm->oops_do(&reg_cl);
4870 }
4871 
4872 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
4873   guarantee(nm != NULL, "sanity");
4874   UnregisterNMethodOopClosure reg_cl(this, nm);
4875   nm->oops_do(&reg_cl, true);
4876 }
4877 
4878 void G1CollectedHeap::purge_code_root_memory() {
4879   double purge_start = os::elapsedTime();
4880   G1CodeRootSet::purge();
4881   double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
4882   phase_times()->record_strong_code_root_purge_time(purge_time_ms);
4883 }
4884 
4885 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
4886   G1CollectedHeap* _g1h;
4887 
4888 public:
4889   RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
4890     _g1h(g1h) {}
4891 
4892   void do_code_blob(CodeBlob* cb) {
4893     nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
4894     if (nm == NULL) {
4895       return;
4896     }
4897 
4898     _g1h->register_nmethod(nm);
4899   }
4900 };
4901 
4902 void G1CollectedHeap::rebuild_strong_code_roots() {
4903   RebuildStrongCodeRootClosure blob_cl(this);
4904   CodeCache::blobs_do(&blob_cl);
4905 }
4906 
4907 void G1CollectedHeap::initialize_serviceability() {
4908   _g1mm->initialize_serviceability();
4909 }
4910 
4911 MemoryUsage G1CollectedHeap::memory_usage() {
4912   return _g1mm->memory_usage();
4913 }
4914 
4915 GrowableArray<GCMemoryManager*> G1CollectedHeap::memory_managers() {
4916   return _g1mm->memory_managers();
4917 }
4918 
4919 GrowableArray<MemoryPool*> G1CollectedHeap::memory_pools() {
4920   return _g1mm->memory_pools();
4921 }
4922 
4923 class G1ParallelObjectIterator : public ParallelObjectIterator {
4924 private:
4925   G1CollectedHeap*  _heap;
4926   HeapRegionClaimer _claimer;
4927 
4928 public:
4929   G1ParallelObjectIterator(uint thread_num) :
4930       _heap(G1CollectedHeap::heap()),
4931       _claimer(thread_num == 0 ? G1CollectedHeap::heap()->workers()->active_workers() : thread_num) {}
4932 
4933   virtual void object_iterate(ObjectClosure* cl, uint worker_id) {
4934     _heap->object_iterate_parallel(cl, worker_id, &_claimer);
4935   }
4936 };
4937 
4938 ParallelObjectIterator* G1CollectedHeap::parallel_object_iterator(uint thread_num) {
4939   return new G1ParallelObjectIterator(thread_num);
4940 }
4941 
4942 void G1CollectedHeap::object_iterate_parallel(ObjectClosure* cl, uint worker_id, HeapRegionClaimer* claimer) {
4943   IterateObjectClosureRegionClosure blk(cl);
4944   heap_region_par_iterate_from_worker_offset(&blk, claimer, worker_id);
4945 }