1  /*
   2  * Copyright (c) 2001, 2019, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "classfile/classLoaderDataGraph.hpp"
  27 #include "classfile/metadataOnStackMark.hpp"
  28 #include "classfile/stringTable.hpp"
  29 #include "code/codeCache.hpp"
  30 #include "code/icBuffer.hpp"
  31 #include "gc/g1/g1Allocator.inline.hpp"
  32 #include "gc/g1/g1Arguments.hpp"
  33 #include "gc/g1/g1BarrierSet.hpp"
  34 #include "gc/g1/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/g1GCPhaseTimes.hpp"
  45 #include "gc/g1/g1HeapSizingPolicy.hpp"
  46 #include "gc/g1/g1HeapTransition.hpp"
  47 #include "gc/g1/g1HeapVerifier.hpp"
  48 #include "gc/g1/g1HotCardCache.hpp"
  49 #include "gc/g1/g1MemoryPool.hpp"
  50 #include "gc/g1/g1OopClosures.inline.hpp"
  51 #include "gc/g1/g1ParallelCleaning.hpp"
  52 #include "gc/g1/g1ParScanThreadState.inline.hpp"
  53 #include "gc/g1/g1Policy.hpp"
  54 #include "gc/g1/g1RedirtyCardsQueue.hpp"
  55 #include "gc/g1/g1RegionToSpaceMapper.hpp"
  56 #include "gc/g1/g1RemSet.hpp"
  57 #include "gc/g1/g1RootClosures.hpp"
  58 #include "gc/g1/g1RootProcessor.hpp"
  59 #include "gc/g1/g1SATBMarkQueueSet.hpp"
  60 #include "gc/g1/g1StringDedup.hpp"
  61 #include "gc/g1/g1ThreadLocalData.hpp"
  62 #include "gc/g1/g1Trace.hpp"
  63 #include "gc/g1/g1YCTypes.hpp"
  64 #include "gc/g1/g1YoungRemSetSamplingThread.hpp"
  65 #include "gc/g1/g1VMOperations.hpp"
  66 #include "gc/g1/heapRegion.inline.hpp"
  67 #include "gc/g1/heapRegionRemSet.hpp"
  68 #include "gc/g1/heapRegionSet.inline.hpp"
  69 #include "gc/shared/gcBehaviours.hpp"
  70 #include "gc/shared/gcHeapSummary.hpp"
  71 #include "gc/shared/gcId.hpp"
  72 #include "gc/shared/gcLocker.hpp"
  73 #include "gc/shared/gcTimer.hpp"
  74 #include "gc/shared/gcTraceTime.inline.hpp"
  75 #include "gc/shared/generationSpec.hpp"
  76 #include "gc/shared/isGCActiveMark.hpp"
  77 #include "gc/shared/locationPrinter.inline.hpp"
  78 #include "gc/shared/oopStorageParState.hpp"
  79 #include "gc/shared/preservedMarks.inline.hpp"
  80 #include "gc/shared/suspendibleThreadSet.hpp"
  81 #include "gc/shared/referenceProcessor.inline.hpp"
  82 #include "gc/shared/taskqueue.inline.hpp"
  83 #include "gc/shared/weakProcessor.inline.hpp"
  84 #include "gc/shared/workerPolicy.hpp"
  85 #include "logging/log.hpp"
  86 #include "memory/allocation.hpp"
  87 #include "memory/iterator.hpp"
  88 #include "memory/resourceArea.hpp"
  89 #include "memory/universe.hpp"
  90 #include "oops/access.inline.hpp"
  91 #include "oops/compressedOops.inline.hpp"
  92 #include "oops/oop.inline.hpp"
  93 #include "runtime/atomic.hpp"
  94 #include "runtime/flags/flagSetting.hpp"
  95 #include "runtime/handles.inline.hpp"
  96 #include "runtime/init.hpp"
  97 #include "runtime/orderAccess.hpp"
  98 #include "runtime/threadSMR.hpp"
  99 #include "runtime/vmThread.hpp"
 100 #include "utilities/align.hpp"
 101 #include "utilities/bitMap.inline.hpp"
 102 #include "utilities/globalDefinitions.hpp"
 103 #include "utilities/stack.inline.hpp"
 104 
 105 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
 106 
 107 // INVARIANTS/NOTES
 108 //
 109 // All allocation activity covered by the G1CollectedHeap interface is
 110 // serialized by acquiring the HeapLock.  This happens in mem_allocate
 111 // and allocate_new_tlab, which are the "entry" points to the
 112 // allocation code from the rest of the JVM.  (Note that this does not
 113 // apply to TLAB allocation, which is not part of this interface: it
 114 // is done by clients of this interface.)
 115 
 116 class RedirtyLoggedCardTableEntryClosure : public G1CardTableEntryClosure {
 117  private:
 118   size_t _num_dirtied;
 119   G1CollectedHeap* _g1h;
 120   G1CardTable* _g1_ct;
 121 
 122   HeapRegion* region_for_card(CardValue* card_ptr) const {
 123     return _g1h->heap_region_containing(_g1_ct->addr_for(card_ptr));
 124   }
 125 
 126   bool will_become_free(HeapRegion* hr) const {
 127     // A region will be freed by free_collection_set if the region is in the
 128     // collection set and has not had an evacuation failure.
 129     return _g1h->is_in_cset(hr) && !hr->evacuation_failed();
 130   }
 131 
 132  public:
 133   RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : G1CardTableEntryClosure(),
 134     _num_dirtied(0), _g1h(g1h), _g1_ct(g1h->card_table()) { }
 135 
 136   void do_card_ptr(CardValue* card_ptr, uint worker_id) {
 137     HeapRegion* hr = region_for_card(card_ptr);
 138 
 139     // Should only dirty cards in regions that won't be freed.
 140     if (!will_become_free(hr)) {
 141       *card_ptr = G1CardTable::dirty_card_val();
 142       _num_dirtied++;
 143     }
 144   }
 145 
 146   size_t num_dirtied()   const { return _num_dirtied; }
 147 };
 148 
 149 
 150 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
 151   HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
 152 }
 153 
 154 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
 155   // The from card cache is not the memory that is actually committed. So we cannot
 156   // take advantage of the zero_filled parameter.
 157   reset_from_card_cache(start_idx, num_regions);
 158 }
 159 
 160 Tickspan G1CollectedHeap::run_task(AbstractGangTask* task) {
 161   Ticks start = Ticks::now();
 162   workers()->run_task(task, workers()->active_workers());
 163   return Ticks::now() - start;
 164 }
 165 
 166 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
 167                                              MemRegion mr) {
 168   return new HeapRegion(hrs_index, bot(), mr);
 169 }
 170 
 171 // Private methods.
 172 
 173 HeapRegion* G1CollectedHeap::new_region(size_t word_size,
 174                                         HeapRegionType type,
 175                                         bool do_expand,
 176                                         uint node_index) {
 177   assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
 178          "the only time we use this to allocate a humongous region is "
 179          "when we are allocating a single humongous region");
 180 
 181   HeapRegion* res = _hrm->allocate_free_region(type, node_index);
 182 
 183   if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
 184     // Currently, only attempts to allocate GC alloc regions set
 185     // do_expand to true. So, we should only reach here during a
 186     // safepoint. If this assumption changes we might have to
 187     // reconsider the use of _expand_heap_after_alloc_failure.
 188     assert(SafepointSynchronize::is_at_safepoint(), "invariant");
 189 
 190     log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B",
 191                               word_size * HeapWordSize);
 192 
 193     assert(word_size * HeapWordSize < HeapRegion::GrainBytes,
 194            "This kind of expansion should never be more than one region. Size: " SIZE_FORMAT,
 195            word_size * HeapWordSize);
 196     if (expand_single_region(node_index)) {
 197       // Given that expand_single_region() succeeded in expanding the heap, and we
 198       // always expand the heap by an amount aligned to the heap
 199       // region size, the free list should in theory not be empty.
 200       // In either case allocate_free_region() will check for NULL.
 201       res = _hrm->allocate_free_region(type, node_index);
 202     } else {
 203       _expand_heap_after_alloc_failure = false;
 204     }
 205   }
 206   return res;
 207 }
 208 
 209 HeapWord*
 210 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
 211                                                            uint num_regions,
 212                                                            size_t word_size) {
 213   assert(first != G1_NO_HRM_INDEX, "pre-condition");
 214   assert(is_humongous(word_size), "word_size should be humongous");
 215   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 216 
 217   // Index of last region in the series.
 218   uint last = first + num_regions - 1;
 219 
 220   // We need to initialize the region(s) we just discovered. This is
 221   // a bit tricky given that it can happen concurrently with
 222   // refinement threads refining cards on these regions and
 223   // potentially wanting to refine the BOT as they are scanning
 224   // those cards (this can happen shortly after a cleanup; see CR
 225   // 6991377). So we have to set up the region(s) carefully and in
 226   // a specific order.
 227 
 228   // The word size sum of all the regions we will allocate.
 229   size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
 230   assert(word_size <= word_size_sum, "sanity");
 231 
 232   // This will be the "starts humongous" region.
 233   HeapRegion* first_hr = region_at(first);
 234   // The header of the new object will be placed at the bottom of
 235   // the first region.
 236   HeapWord* new_obj = first_hr->bottom();
 237   // This will be the new top of the new object.
 238   HeapWord* obj_top = new_obj + word_size;
 239 
 240   // First, we need to zero the header of the space that we will be
 241   // allocating. When we update top further down, some refinement
 242   // threads might try to scan the region. By zeroing the header we
 243   // ensure that any thread that will try to scan the region will
 244   // come across the zero klass word and bail out.
 245   //
 246   // NOTE: It would not have been correct to have used
 247   // CollectedHeap::fill_with_object() and make the space look like
 248   // an int array. The thread that is doing the allocation will
 249   // later update the object header to a potentially different array
 250   // type and, for a very short period of time, the klass and length
 251   // fields will be inconsistent. This could cause a refinement
 252   // thread to calculate the object size incorrectly.
 253   Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
 254 
 255   // Next, pad out the unused tail of the last region with filler
 256   // objects, for improved usage accounting.
 257   // How many words we use for filler objects.
 258   size_t word_fill_size = word_size_sum - word_size;
 259 
 260   // How many words memory we "waste" which cannot hold a filler object.
 261   size_t words_not_fillable = 0;
 262 
 263   if (word_fill_size >= min_fill_size()) {
 264     fill_with_objects(obj_top, word_fill_size);
 265   } else if (word_fill_size > 0) {
 266     // We have space to fill, but we cannot fit an object there.
 267     words_not_fillable = word_fill_size;
 268     word_fill_size = 0;
 269   }
 270 
 271   // We will set up the first region as "starts humongous". This
 272   // will also update the BOT covering all the regions to reflect
 273   // that there is a single object that starts at the bottom of the
 274   // first region.
 275   first_hr->set_starts_humongous(obj_top, word_fill_size);
 276   _policy->remset_tracker()->update_at_allocate(first_hr);
 277   // Then, if there are any, we will set up the "continues
 278   // humongous" regions.
 279   HeapRegion* hr = NULL;
 280   for (uint i = first + 1; i <= last; ++i) {
 281     hr = region_at(i);
 282     hr->set_continues_humongous(first_hr);
 283     _policy->remset_tracker()->update_at_allocate(hr);
 284   }
 285 
 286   // Up to this point no concurrent thread would have been able to
 287   // do any scanning on any region in this series. All the top
 288   // fields still point to bottom, so the intersection between
 289   // [bottom,top] and [card_start,card_end] will be empty. Before we
 290   // update the top fields, we'll do a storestore to make sure that
 291   // no thread sees the update to top before the zeroing of the
 292   // object header and the BOT initialization.
 293   OrderAccess::storestore();
 294 
 295   // Now, we will update the top fields of the "continues humongous"
 296   // regions except the last one.
 297   for (uint i = first; i < last; ++i) {
 298     hr = region_at(i);
 299     hr->set_top(hr->end());
 300   }
 301 
 302   hr = region_at(last);
 303   // If we cannot fit a filler object, we must set top to the end
 304   // of the humongous object, otherwise we cannot iterate the heap
 305   // and the BOT will not be complete.
 306   hr->set_top(hr->end() - words_not_fillable);
 307 
 308   assert(hr->bottom() < obj_top && obj_top <= hr->end(),
 309          "obj_top should be in last region");
 310 
 311   _verifier->check_bitmaps("Humongous Region Allocation", first_hr);
 312 
 313   assert(words_not_fillable == 0 ||
 314          first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(),
 315          "Miscalculation in humongous allocation");
 316 
 317   increase_used((word_size_sum - words_not_fillable) * HeapWordSize);
 318 
 319   for (uint i = first; i <= last; ++i) {
 320     hr = region_at(i);
 321     _humongous_set.add(hr);
 322     _hr_printer.alloc(hr);
 323   }
 324 
 325   return new_obj;
 326 }
 327 
 328 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) {
 329   assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size);
 330   return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
 331 }
 332 
 333 // If could fit into free regions w/o expansion, try.
 334 // Otherwise, if can expand, do so.
 335 // Otherwise, if using ex regions might help, try with ex given back.
 336 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
 337   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 338 
 339   _verifier->verify_region_sets_optional();
 340 
 341   uint first = G1_NO_HRM_INDEX;
 342   uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);
 343 
 344   if (obj_regions == 1) {
 345     // Only one region to allocate, try to use a fast path by directly allocating
 346     // from the free lists. Do not try to expand here, we will potentially do that
 347     // later.
 348     HeapRegion* hr = new_region(word_size, HeapRegionType::Humongous, false /* do_expand */);
 349     if (hr != NULL) {
 350       first = hr->hrm_index();
 351     }
 352   } else {
 353     // Policy: Try only empty regions (i.e. already committed first). Maybe we
 354     // are lucky enough to find some.
 355     first = _hrm->find_contiguous_only_empty(obj_regions);
 356     if (first != G1_NO_HRM_INDEX) {
 357       _hrm->allocate_free_regions_starting_at(first, obj_regions);
 358     }
 359   }
 360 
 361   if (first == G1_NO_HRM_INDEX) {
 362     // Policy: We could not find enough regions for the humongous object in the
 363     // free list. Look through the heap to find a mix of free and uncommitted regions.
 364     // If so, try expansion.
 365     first = _hrm->find_contiguous_empty_or_unavailable(obj_regions);
 366     if (first != G1_NO_HRM_INDEX) {
 367       // We found something. Make sure these regions are committed, i.e. expand
 368       // the heap. Alternatively we could do a defragmentation GC.
 369       log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B",
 370                                     word_size * HeapWordSize);
 371 
 372       _hrm->expand_at(first, obj_regions, workers());
 373       policy()->record_new_heap_size(num_regions());
 374 
 375 #ifdef ASSERT
 376       for (uint i = first; i < first + obj_regions; ++i) {
 377         HeapRegion* hr = region_at(i);
 378         assert(hr->is_free(), "sanity");
 379         assert(hr->is_empty(), "sanity");
 380         assert(is_on_master_free_list(hr), "sanity");
 381       }
 382 #endif
 383       _hrm->allocate_free_regions_starting_at(first, obj_regions);
 384     } else {
 385       // Policy: Potentially trigger a defragmentation GC.
 386     }
 387   }
 388 
 389   HeapWord* result = NULL;
 390   if (first != G1_NO_HRM_INDEX) {
 391     result = humongous_obj_allocate_initialize_regions(first, obj_regions, word_size);
 392     assert(result != NULL, "it should always return a valid result");
 393 
 394     // A successful humongous object allocation changes the used space
 395     // information of the old generation so we need to recalculate the
 396     // sizes and update the jstat counters here.
 397     g1mm()->update_sizes();
 398   }
 399 
 400   _verifier->verify_region_sets_optional();
 401 
 402   return result;
 403 }
 404 
 405 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t min_size,
 406                                              size_t requested_size,
 407                                              size_t* actual_size) {
 408   assert_heap_not_locked_and_not_at_safepoint();
 409   assert(!is_humongous(requested_size), "we do not allow humongous TLABs");
 410 
 411   return attempt_allocation(min_size, requested_size, actual_size);
 412 }
 413 
 414 HeapWord*
 415 G1CollectedHeap::mem_allocate(size_t word_size,
 416                               bool*  gc_overhead_limit_was_exceeded) {
 417   assert_heap_not_locked_and_not_at_safepoint();
 418 
 419   if (is_humongous(word_size)) {
 420     return attempt_allocation_humongous(word_size);
 421   }
 422   size_t dummy = 0;
 423   return attempt_allocation(word_size, word_size, &dummy);
 424 }
 425 
 426 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size) {
 427   ResourceMark rm; // For retrieving the thread names in log messages.
 428 
 429   // Make sure you read the note in attempt_allocation_humongous().
 430 
 431   assert_heap_not_locked_and_not_at_safepoint();
 432   assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
 433          "be called for humongous allocation requests");
 434 
 435   // We should only get here after the first-level allocation attempt
 436   // (attempt_allocation()) failed to allocate.
 437 
 438   // We will loop until a) we manage to successfully perform the
 439   // allocation or b) we successfully schedule a collection which
 440   // fails to perform the allocation. b) is the only case when we'll
 441   // return NULL.
 442   HeapWord* result = NULL;
 443   for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 444     bool should_try_gc;
 445     uint gc_count_before;
 446 
 447     {
 448       MutexLocker x(Heap_lock);
 449       result = _allocator->attempt_allocation_locked(word_size);
 450       if (result != NULL) {
 451         return result;
 452       }
 453 
 454       // If the GCLocker is active and we are bound for a GC, try expanding young gen.
 455       // This is different to when only GCLocker::needs_gc() is set: try to avoid
 456       // waiting because the GCLocker is active to not wait too long.
 457       if (GCLocker::is_active_and_needs_gc() && policy()->can_expand_young_list()) {
 458         // No need for an ergo message here, can_expand_young_list() does this when
 459         // it returns true.
 460         result = _allocator->attempt_allocation_force(word_size);
 461         if (result != NULL) {
 462           return result;
 463         }
 464       }
 465       // Only try a GC if the GCLocker does not signal the need for a GC. Wait until
 466       // the GCLocker initiated GC has been performed and then retry. This includes
 467       // the case when the GC Locker is not active but has not been performed.
 468       should_try_gc = !GCLocker::needs_gc();
 469       // Read the GC count while still holding the Heap_lock.
 470       gc_count_before = total_collections();
 471     }
 472 
 473     if (should_try_gc) {
 474       bool succeeded;
 475       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 476                                    GCCause::_g1_inc_collection_pause);
 477       if (result != NULL) {
 478         assert(succeeded, "only way to get back a non-NULL result");
 479         log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT,
 480                              Thread::current()->name(), p2i(result));
 481         return result;
 482       }
 483 
 484       if (succeeded) {
 485         // We successfully scheduled a collection which failed to allocate. No
 486         // point in trying to allocate further. We'll just return NULL.
 487         log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate "
 488                              SIZE_FORMAT " words", Thread::current()->name(), word_size);
 489         return NULL;
 490       }
 491       log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT " words",
 492                            Thread::current()->name(), word_size);
 493     } else {
 494       // Failed to schedule a collection.
 495       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 496         log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating "
 497                                SIZE_FORMAT " words", Thread::current()->name(), word_size);
 498         return NULL;
 499       }
 500       log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name());
 501       // The GCLocker is either active or the GCLocker initiated
 502       // GC has not yet been performed. Stall until it is and
 503       // then retry the allocation.
 504       GCLocker::stall_until_clear();
 505       gclocker_retry_count += 1;
 506     }
 507 
 508     // We can reach here if we were unsuccessful in scheduling a
 509     // collection (because another thread beat us to it) or if we were
 510     // stalled due to the GC locker. In either can we should retry the
 511     // allocation attempt in case another thread successfully
 512     // performed a collection and reclaimed enough space. We do the
 513     // first attempt (without holding the Heap_lock) here and the
 514     // follow-on attempt will be at the start of the next loop
 515     // iteration (after taking the Heap_lock).
 516     size_t dummy = 0;
 517     result = _allocator->attempt_allocation(word_size, word_size, &dummy);
 518     if (result != NULL) {
 519       return result;
 520     }
 521 
 522     // Give a warning if we seem to be looping forever.
 523     if ((QueuedAllocationWarningCount > 0) &&
 524         (try_count % QueuedAllocationWarningCount == 0)) {
 525       log_warning(gc, alloc)("%s:  Retried allocation %u times for " SIZE_FORMAT " words",
 526                              Thread::current()->name(), try_count, word_size);
 527     }
 528   }
 529 
 530   ShouldNotReachHere();
 531   return NULL;
 532 }
 533 
 534 void G1CollectedHeap::begin_archive_alloc_range(bool open) {
 535   assert_at_safepoint_on_vm_thread();
 536   if (_archive_allocator == NULL) {
 537     _archive_allocator = G1ArchiveAllocator::create_allocator(this, open);
 538   }
 539 }
 540 
 541 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) {
 542   // Allocations in archive regions cannot be of a size that would be considered
 543   // humongous even for a minimum-sized region, because G1 region sizes/boundaries
 544   // may be different at archive-restore time.
 545   return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words());
 546 }
 547 
 548 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) {
 549   assert_at_safepoint_on_vm_thread();
 550   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 551   if (is_archive_alloc_too_large(word_size)) {
 552     return NULL;
 553   }
 554   return _archive_allocator->archive_mem_allocate(word_size);
 555 }
 556 
 557 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
 558                                               size_t end_alignment_in_bytes) {
 559   assert_at_safepoint_on_vm_thread();
 560   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 561 
 562   // Call complete_archive to do the real work, filling in the MemRegion
 563   // array with the archive regions.
 564   _archive_allocator->complete_archive(ranges, end_alignment_in_bytes);
 565   delete _archive_allocator;
 566   _archive_allocator = NULL;
 567 }
 568 
 569 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) {
 570   assert(ranges != NULL, "MemRegion array NULL");
 571   assert(count != 0, "No MemRegions provided");
 572   MemRegion reserved = _hrm->reserved();
 573   for (size_t i = 0; i < count; i++) {
 574     if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) {
 575       return false;
 576     }
 577   }
 578   return true;
 579 }
 580 
 581 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges,
 582                                             size_t count,
 583                                             bool open) {
 584   assert(!is_init_completed(), "Expect to be called at JVM init time");
 585   assert(ranges != NULL, "MemRegion array NULL");
 586   assert(count != 0, "No MemRegions provided");
 587   MutexLocker x(Heap_lock);
 588 
 589   MemRegion reserved = _hrm->reserved();
 590   HeapWord* prev_last_addr = NULL;
 591   HeapRegion* prev_last_region = NULL;
 592 
 593   // Temporarily disable pretouching of heap pages. This interface is used
 594   // when mmap'ing archived heap data in, so pre-touching is wasted.
 595   FlagSetting fs(AlwaysPreTouch, false);
 596 
 597   // Enable archive object checking used by G1MarkSweep. We have to let it know
 598   // about each archive range, so that objects in those ranges aren't marked.
 599   G1ArchiveAllocator::enable_archive_object_check();
 600 
 601   // For each specified MemRegion range, allocate the corresponding G1
 602   // regions and mark them as archive regions. We expect the ranges
 603   // in ascending starting address order, without overlap.
 604   for (size_t i = 0; i < count; i++) {
 605     MemRegion curr_range = ranges[i];
 606     HeapWord* start_address = curr_range.start();
 607     size_t word_size = curr_range.word_size();
 608     HeapWord* last_address = curr_range.last();
 609     size_t commits = 0;
 610 
 611     guarantee(reserved.contains(start_address) && reserved.contains(last_address),
 612               "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 613               p2i(start_address), p2i(last_address));
 614     guarantee(start_address > prev_last_addr,
 615               "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 616               p2i(start_address), p2i(prev_last_addr));
 617     prev_last_addr = last_address;
 618 
 619     // Check for ranges that start in the same G1 region in which the previous
 620     // range ended, and adjust the start address so we don't try to allocate
 621     // the same region again. If the current range is entirely within that
 622     // region, skip it, just adjusting the recorded top.
 623     HeapRegion* start_region = _hrm->addr_to_region(start_address);
 624     if ((prev_last_region != NULL) && (start_region == prev_last_region)) {
 625       start_address = start_region->end();
 626       if (start_address > last_address) {
 627         increase_used(word_size * HeapWordSize);
 628         start_region->set_top(last_address + 1);
 629         continue;
 630       }
 631       start_region->set_top(start_address);
 632       curr_range = MemRegion(start_address, last_address + 1);
 633       start_region = _hrm->addr_to_region(start_address);
 634     }
 635 
 636     // Perform the actual region allocation, exiting if it fails.
 637     // Then note how much new space we have allocated.
 638     if (!_hrm->allocate_containing_regions(curr_range, &commits, workers())) {
 639       return false;
 640     }
 641     increase_used(word_size * HeapWordSize);
 642     if (commits != 0) {
 643       log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B",
 644                                 HeapRegion::GrainWords * HeapWordSize * commits);
 645 
 646     }
 647 
 648     // Mark each G1 region touched by the range as archive, add it to
 649     // the old set, and set top.
 650     HeapRegion* curr_region = _hrm->addr_to_region(start_address);
 651     HeapRegion* last_region = _hrm->addr_to_region(last_address);
 652     prev_last_region = last_region;
 653 
 654     while (curr_region != NULL) {
 655       assert(curr_region->is_empty() && !curr_region->is_pinned(),
 656              "Region already in use (index %u)", curr_region->hrm_index());
 657       if (open) {
 658         curr_region->set_open_archive();
 659       } else {
 660         curr_region->set_closed_archive();
 661       }
 662       _hr_printer.alloc(curr_region);
 663       _archive_set.add(curr_region);
 664       HeapWord* top;
 665       HeapRegion* next_region;
 666       if (curr_region != last_region) {
 667         top = curr_region->end();
 668         next_region = _hrm->next_region_in_heap(curr_region);
 669       } else {
 670         top = last_address + 1;
 671         next_region = NULL;
 672       }
 673       curr_region->set_top(top);
 674       curr_region = next_region;
 675     }
 676 
 677     // Notify mark-sweep of the archive
 678     G1ArchiveAllocator::set_range_archive(curr_range, open);
 679   }
 680   return true;
 681 }
 682 
 683 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) {
 684   assert(!is_init_completed(), "Expect to be called at JVM init time");
 685   assert(ranges != NULL, "MemRegion array NULL");
 686   assert(count != 0, "No MemRegions provided");
 687   MemRegion reserved = _hrm->reserved();
 688   HeapWord *prev_last_addr = NULL;
 689   HeapRegion* prev_last_region = NULL;
 690 
 691   // For each MemRegion, create filler objects, if needed, in the G1 regions
 692   // that contain the address range. The address range actually within the
 693   // MemRegion will not be modified. That is assumed to have been initialized
 694   // elsewhere, probably via an mmap of archived heap data.
 695   MutexLocker x(Heap_lock);
 696   for (size_t i = 0; i < count; i++) {
 697     HeapWord* start_address = ranges[i].start();
 698     HeapWord* last_address = ranges[i].last();
 699 
 700     assert(reserved.contains(start_address) && reserved.contains(last_address),
 701            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 702            p2i(start_address), p2i(last_address));
 703     assert(start_address > prev_last_addr,
 704            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 705            p2i(start_address), p2i(prev_last_addr));
 706 
 707     HeapRegion* start_region = _hrm->addr_to_region(start_address);
 708     HeapRegion* last_region = _hrm->addr_to_region(last_address);
 709     HeapWord* bottom_address = start_region->bottom();
 710 
 711     // Check for a range beginning in the same region in which the
 712     // previous one ended.
 713     if (start_region == prev_last_region) {
 714       bottom_address = prev_last_addr + 1;
 715     }
 716 
 717     // Verify that the regions were all marked as archive regions by
 718     // alloc_archive_regions.
 719     HeapRegion* curr_region = start_region;
 720     while (curr_region != NULL) {
 721       guarantee(curr_region->is_archive(),
 722                 "Expected archive region at index %u", curr_region->hrm_index());
 723       if (curr_region != last_region) {
 724         curr_region = _hrm->next_region_in_heap(curr_region);
 725       } else {
 726         curr_region = NULL;
 727       }
 728     }
 729 
 730     prev_last_addr = last_address;
 731     prev_last_region = last_region;
 732 
 733     // Fill the memory below the allocated range with dummy object(s),
 734     // if the region bottom does not match the range start, or if the previous
 735     // range ended within the same G1 region, and there is a gap.
 736     if (start_address != bottom_address) {
 737       size_t fill_size = pointer_delta(start_address, bottom_address);
 738       G1CollectedHeap::fill_with_objects(bottom_address, fill_size);
 739       increase_used(fill_size * HeapWordSize);
 740     }
 741   }
 742 }
 743 
 744 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t min_word_size,
 745                                                      size_t desired_word_size,
 746                                                      size_t* actual_word_size) {
 747   assert_heap_not_locked_and_not_at_safepoint();
 748   assert(!is_humongous(desired_word_size), "attempt_allocation() should not "
 749          "be called for humongous allocation requests");
 750 
 751   HeapWord* result = _allocator->attempt_allocation(min_word_size, desired_word_size, actual_word_size);
 752 
 753   if (result == NULL) {
 754     *actual_word_size = desired_word_size;
 755     result = attempt_allocation_slow(desired_word_size);
 756   }
 757 
 758   assert_heap_not_locked();
 759   if (result != NULL) {
 760     assert(*actual_word_size != 0, "Actual size must have been set here");
 761     dirty_young_block(result, *actual_word_size);
 762   } else {
 763     *actual_word_size = 0;
 764   }
 765 
 766   return result;
 767 }
 768 
 769 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count, bool is_open) {
 770   assert(!is_init_completed(), "Expect to be called at JVM init time");
 771   assert(ranges != NULL, "MemRegion array NULL");
 772   assert(count != 0, "No MemRegions provided");
 773   MemRegion reserved = _hrm->reserved();
 774   HeapWord* prev_last_addr = NULL;
 775   HeapRegion* prev_last_region = NULL;
 776   size_t size_used = 0;
 777   size_t uncommitted_regions = 0;
 778 
 779   // For each Memregion, free the G1 regions that constitute it, and
 780   // notify mark-sweep that the range is no longer to be considered 'archive.'
 781   MutexLocker x(Heap_lock);
 782   for (size_t i = 0; i < count; i++) {
 783     HeapWord* start_address = ranges[i].start();
 784     HeapWord* last_address = ranges[i].last();
 785 
 786     assert(reserved.contains(start_address) && reserved.contains(last_address),
 787            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 788            p2i(start_address), p2i(last_address));
 789     assert(start_address > prev_last_addr,
 790            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 791            p2i(start_address), p2i(prev_last_addr));
 792     size_used += ranges[i].byte_size();
 793     prev_last_addr = last_address;
 794 
 795     HeapRegion* start_region = _hrm->addr_to_region(start_address);
 796     HeapRegion* last_region = _hrm->addr_to_region(last_address);
 797 
 798     // Check for ranges that start in the same G1 region in which the previous
 799     // range ended, and adjust the start address so we don't try to free
 800     // the same region again. If the current range is entirely within that
 801     // region, skip it.
 802     if (start_region == prev_last_region) {
 803       start_address = start_region->end();
 804       if (start_address > last_address) {
 805         continue;
 806       }
 807       start_region = _hrm->addr_to_region(start_address);
 808     }
 809     prev_last_region = last_region;
 810 
 811     // After verifying that each region was marked as an archive region by
 812     // alloc_archive_regions, set it free and empty and uncommit it.
 813     HeapRegion* curr_region = start_region;
 814     while (curr_region != NULL) {
 815       guarantee(curr_region->is_archive(),
 816                 "Expected archive region at index %u", curr_region->hrm_index());
 817       uint curr_index = curr_region->hrm_index();
 818       _archive_set.remove(curr_region);
 819       curr_region->set_free();
 820       curr_region->set_top(curr_region->bottom());
 821       if (curr_region != last_region) {
 822         curr_region = _hrm->next_region_in_heap(curr_region);
 823       } else {
 824         curr_region = NULL;
 825       }
 826       _hrm->shrink_at(curr_index, 1);
 827       uncommitted_regions++;
 828     }
 829 
 830     // Notify mark-sweep that this is no longer an archive range.
 831     G1ArchiveAllocator::clear_range_archive(ranges[i], is_open);
 832   }
 833 
 834   if (uncommitted_regions != 0) {
 835     log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B",
 836                               HeapRegion::GrainWords * HeapWordSize * uncommitted_regions);
 837   }
 838   decrease_used(size_used);
 839 }
 840 
 841 oop G1CollectedHeap::materialize_archived_object(oop obj) {
 842   assert(obj != NULL, "archived obj is NULL");
 843   assert(G1ArchiveAllocator::is_archived_object(obj), "must be archived object");
 844 
 845   // Loading an archived object makes it strongly reachable. If it is
 846   // loaded during concurrent marking, it must be enqueued to the SATB
 847   // queue, shading the previously white object gray.
 848   G1BarrierSet::enqueue(obj);
 849 
 850   return obj;
 851 }
 852 
 853 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size) {
 854   ResourceMark rm; // For retrieving the thread names in log messages.
 855 
 856   // The structure of this method has a lot of similarities to
 857   // attempt_allocation_slow(). The reason these two were not merged
 858   // into a single one is that such a method would require several "if
 859   // allocation is not humongous do this, otherwise do that"
 860   // conditional paths which would obscure its flow. In fact, an early
 861   // version of this code did use a unified method which was harder to
 862   // follow and, as a result, it had subtle bugs that were hard to
 863   // track down. So keeping these two methods separate allows each to
 864   // be more readable. It will be good to keep these two in sync as
 865   // much as possible.
 866 
 867   assert_heap_not_locked_and_not_at_safepoint();
 868   assert(is_humongous(word_size), "attempt_allocation_humongous() "
 869          "should only be called for humongous allocations");
 870 
 871   // Humongous objects can exhaust the heap quickly, so we should check if we
 872   // need to start a marking cycle at each humongous object allocation. We do
 873   // the check before we do the actual allocation. The reason for doing it
 874   // before the allocation is that we avoid having to keep track of the newly
 875   // allocated memory while we do a GC.
 876   if (policy()->need_to_start_conc_mark("concurrent humongous allocation",
 877                                            word_size)) {
 878     collect(GCCause::_g1_humongous_allocation);
 879   }
 880 
 881   // We will loop until a) we manage to successfully perform the
 882   // allocation or b) we successfully schedule a collection which
 883   // fails to perform the allocation. b) is the only case when we'll
 884   // return NULL.
 885   HeapWord* result = NULL;
 886   for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 887     bool should_try_gc;
 888     uint gc_count_before;
 889 
 890 
 891     {
 892       MutexLocker x(Heap_lock);
 893 
 894       // Given that humongous objects are not allocated in young
 895       // regions, we'll first try to do the allocation without doing a
 896       // collection hoping that there's enough space in the heap.
 897       result = humongous_obj_allocate(word_size);
 898       if (result != NULL) {
 899         size_t size_in_regions = humongous_obj_size_in_regions(word_size);
 900         policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
 901         return result;
 902       }
 903 
 904       // Only try a GC if the GCLocker does not signal the need for a GC. Wait until
 905       // the GCLocker initiated GC has been performed and then retry. This includes
 906       // the case when the GC Locker is not active but has not been performed.
 907       should_try_gc = !GCLocker::needs_gc();
 908       // Read the GC count while still holding the Heap_lock.
 909       gc_count_before = total_collections();
 910     }
 911 
 912     if (should_try_gc) {
 913       bool succeeded;
 914       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 915                                    GCCause::_g1_humongous_allocation);
 916       if (result != NULL) {
 917         assert(succeeded, "only way to get back a non-NULL result");
 918         log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT,
 919                              Thread::current()->name(), p2i(result));
 920         return result;
 921       }
 922 
 923       if (succeeded) {
 924         // We successfully scheduled a collection which failed to allocate. No
 925         // point in trying to allocate further. We'll just return NULL.
 926         log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate "
 927                              SIZE_FORMAT " words", Thread::current()->name(), word_size);
 928         return NULL;
 929       }
 930       log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT "",
 931                            Thread::current()->name(), word_size);
 932     } else {
 933       // Failed to schedule a collection.
 934       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 935         log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating "
 936                                SIZE_FORMAT " words", Thread::current()->name(), word_size);
 937         return NULL;
 938       }
 939       log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name());
 940       // The GCLocker is either active or the GCLocker initiated
 941       // GC has not yet been performed. Stall until it is and
 942       // then retry the allocation.
 943       GCLocker::stall_until_clear();
 944       gclocker_retry_count += 1;
 945     }
 946 
 947 
 948     // We can reach here if we were unsuccessful in scheduling a
 949     // collection (because another thread beat us to it) or if we were
 950     // stalled due to the GC locker. In either can we should retry the
 951     // allocation attempt in case another thread successfully
 952     // performed a collection and reclaimed enough space.
 953     // Humongous object allocation always needs a lock, so we wait for the retry
 954     // in the next iteration of the loop, unlike for the regular iteration case.
 955     // Give a warning if we seem to be looping forever.
 956 
 957     if ((QueuedAllocationWarningCount > 0) &&
 958         (try_count % QueuedAllocationWarningCount == 0)) {
 959       log_warning(gc, alloc)("%s: Retried allocation %u times for " SIZE_FORMAT " words",
 960                              Thread::current()->name(), try_count, word_size);
 961     }
 962   }
 963 
 964   ShouldNotReachHere();
 965   return NULL;
 966 }
 967 
 968 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
 969                                                            bool expect_null_mutator_alloc_region) {
 970   assert_at_safepoint_on_vm_thread();
 971   assert(!_allocator->has_mutator_alloc_region() || !expect_null_mutator_alloc_region,
 972          "the current alloc region was unexpectedly found to be non-NULL");
 973 
 974   if (!is_humongous(word_size)) {
 975     return _allocator->attempt_allocation_locked(word_size);
 976   } else {
 977     HeapWord* result = humongous_obj_allocate(word_size);
 978     if (result != NULL && policy()->need_to_start_conc_mark("STW humongous allocation")) {
 979       collector_state()->set_initiate_conc_mark_if_possible(true);
 980     }
 981     return result;
 982   }
 983 
 984   ShouldNotReachHere();
 985 }
 986 
 987 class PostCompactionPrinterClosure: public HeapRegionClosure {
 988 private:
 989   G1HRPrinter* _hr_printer;
 990 public:
 991   bool do_heap_region(HeapRegion* hr) {
 992     assert(!hr->is_young(), "not expecting to find young regions");
 993     _hr_printer->post_compaction(hr);
 994     return false;
 995   }
 996 
 997   PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
 998     : _hr_printer(hr_printer) { }
 999 };
1000 
1001 void G1CollectedHeap::print_hrm_post_compaction() {
1002   if (_hr_printer.is_active()) {
1003     PostCompactionPrinterClosure cl(hr_printer());
1004     heap_region_iterate(&cl);
1005   }
1006 }
1007 
1008 void G1CollectedHeap::abort_concurrent_cycle() {
1009   // If we start the compaction before the CM threads finish
1010   // scanning the root regions we might trip them over as we'll
1011   // be moving objects / updating references. So let's wait until
1012   // they are done. By telling them to abort, they should complete
1013   // early.
1014   _cm->root_regions()->abort();
1015   _cm->root_regions()->wait_until_scan_finished();
1016 
1017   // Disable discovery and empty the discovered lists
1018   // for the CM ref processor.
1019   _ref_processor_cm->disable_discovery();
1020   _ref_processor_cm->abandon_partial_discovery();
1021   _ref_processor_cm->verify_no_references_recorded();
1022 
1023   // Abandon current iterations of concurrent marking and concurrent
1024   // refinement, if any are in progress.
1025   concurrent_mark()->concurrent_cycle_abort();
1026 }
1027 
1028 void G1CollectedHeap::prepare_heap_for_full_collection() {
1029   // Make sure we'll choose a new allocation region afterwards.
1030   _allocator->release_mutator_alloc_regions();
1031   _allocator->abandon_gc_alloc_regions();
1032 
1033   // We may have added regions to the current incremental collection
1034   // set between the last GC or pause and now. We need to clear the
1035   // incremental collection set and then start rebuilding it afresh
1036   // after this full GC.
1037   abandon_collection_set(collection_set());
1038 
1039   tear_down_region_sets(false /* free_list_only */);
1040 
1041   hrm()->prepare_for_full_collection_start();
1042 }
1043 
1044 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) {
1045   assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant");
1046   assert_used_and_recalculate_used_equal(this);
1047   _verifier->verify_region_sets_optional();
1048   _verifier->verify_before_gc(G1HeapVerifier::G1VerifyFull);
1049   _verifier->check_bitmaps("Full GC Start");
1050 }
1051 
1052 void G1CollectedHeap::prepare_heap_for_mutators() {
1053   hrm()->prepare_for_full_collection_end();
1054 
1055   // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1056   ClassLoaderDataGraph::purge();
1057   MetaspaceUtils::verify_metrics();
1058 
1059   // Prepare heap for normal collections.
1060   assert(num_free_regions() == 0, "we should not have added any free regions");
1061   rebuild_region_sets(false /* free_list_only */);
1062   abort_refinement();
1063   resize_heap_if_necessary();
1064 
1065   // Rebuild the strong code root lists for each region
1066   rebuild_strong_code_roots();
1067 
1068   // Purge code root memory
1069   purge_code_root_memory();
1070 
1071   // Start a new incremental collection set for the next pause
1072   start_new_collection_set();
1073 
1074   _allocator->init_mutator_alloc_regions();
1075 
1076   // Post collection state updates.
1077   MetaspaceGC::compute_new_size();
1078 }
1079 
1080 void G1CollectedHeap::abort_refinement() {
1081   if (_hot_card_cache->use_cache()) {
1082     _hot_card_cache->reset_hot_cache();
1083   }
1084 
1085   // Discard all remembered set updates.
1086   G1BarrierSet::dirty_card_queue_set().abandon_logs();
1087   assert(G1BarrierSet::dirty_card_queue_set().num_cards() == 0,
1088          "DCQS should be empty");
1089 }
1090 
1091 void G1CollectedHeap::verify_after_full_collection() {
1092   _hrm->verify_optional();
1093   _verifier->verify_region_sets_optional();
1094   _verifier->verify_after_gc(G1HeapVerifier::G1VerifyFull);
1095   // Clear the previous marking bitmap, if needed for bitmap verification.
1096   // Note we cannot do this when we clear the next marking bitmap in
1097   // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the
1098   // objects marked during a full GC against the previous bitmap.
1099   // But we need to clear it before calling check_bitmaps below since
1100   // the full GC has compacted objects and updated TAMS but not updated
1101   // the prev bitmap.
1102   if (G1VerifyBitmaps) {
1103     GCTraceTime(Debug, gc) tm("Clear Prev Bitmap for Verification");
1104     _cm->clear_prev_bitmap(workers());
1105   }
1106   // This call implicitly verifies that the next bitmap is clear after Full GC.
1107   _verifier->check_bitmaps("Full GC End");
1108 
1109   // At this point there should be no regions in the
1110   // entire heap tagged as young.
1111   assert(check_young_list_empty(), "young list should be empty at this point");
1112 
1113   // Note: since we've just done a full GC, concurrent
1114   // marking is no longer active. Therefore we need not
1115   // re-enable reference discovery for the CM ref processor.
1116   // That will be done at the start of the next marking cycle.
1117   // We also know that the STW processor should no longer
1118   // discover any new references.
1119   assert(!_ref_processor_stw->discovery_enabled(), "Postcondition");
1120   assert(!_ref_processor_cm->discovery_enabled(), "Postcondition");
1121   _ref_processor_stw->verify_no_references_recorded();
1122   _ref_processor_cm->verify_no_references_recorded();
1123 }
1124 
1125 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) {
1126   // Post collection logging.
1127   // We should do this after we potentially resize the heap so
1128   // that all the COMMIT / UNCOMMIT events are generated before
1129   // the compaction events.
1130   print_hrm_post_compaction();
1131   heap_transition->print();
1132   print_heap_after_gc();
1133   print_heap_regions();
1134 #ifdef TRACESPINNING
1135   ParallelTaskTerminator::print_termination_counts();
1136 #endif
1137 }
1138 
1139 bool G1CollectedHeap::do_full_collection(bool explicit_gc,
1140                                          bool clear_all_soft_refs) {
1141   assert_at_safepoint_on_vm_thread();
1142 
1143   if (GCLocker::check_active_before_gc()) {
1144     // Full GC was not completed.
1145     return false;
1146   }
1147 
1148   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1149       soft_ref_policy()->should_clear_all_soft_refs();
1150 
1151   G1FullCollector collector(this, explicit_gc, do_clear_all_soft_refs);
1152   GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true);
1153 
1154   collector.prepare_collection();
1155   collector.collect();
1156   collector.complete_collection();
1157 
1158   // Full collection was successfully completed.
1159   return true;
1160 }
1161 
1162 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1163   // Currently, there is no facility in the do_full_collection(bool) API to notify
1164   // the caller that the collection did not succeed (e.g., because it was locked
1165   // out by the GC locker). So, right now, we'll ignore the return value.
1166   bool dummy = do_full_collection(true,                /* explicit_gc */
1167                                   clear_all_soft_refs);
1168 }
1169 
1170 void G1CollectedHeap::resize_heap_if_necessary() {
1171   assert_at_safepoint_on_vm_thread();
1172 
1173   // Capacity, free and used after the GC counted as full regions to
1174   // include the waste in the following calculations.
1175   const size_t capacity_after_gc = capacity();
1176   const size_t used_after_gc = capacity_after_gc - unused_committed_regions_in_bytes();
1177 
1178   // This is enforced in arguments.cpp.
1179   assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1180          "otherwise the code below doesn't make sense");
1181 
1182   // We don't have floating point command-line arguments
1183   const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1184   const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1185   const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1186   const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1187 
1188   // We have to be careful here as these two calculations can overflow
1189   // 32-bit size_t's.
1190   double used_after_gc_d = (double) used_after_gc;
1191   double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1192   double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1193 
1194   // Let's make sure that they are both under the max heap size, which
1195   // by default will make them fit into a size_t.
1196   double desired_capacity_upper_bound = (double) MaxHeapSize;
1197   minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1198                                     desired_capacity_upper_bound);
1199   maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1200                                     desired_capacity_upper_bound);
1201 
1202   // We can now safely turn them into size_t's.
1203   size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1204   size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1205 
1206   // This assert only makes sense here, before we adjust them
1207   // with respect to the min and max heap size.
1208   assert(minimum_desired_capacity <= maximum_desired_capacity,
1209          "minimum_desired_capacity = " SIZE_FORMAT ", "
1210          "maximum_desired_capacity = " SIZE_FORMAT,
1211          minimum_desired_capacity, maximum_desired_capacity);
1212 
1213   // Should not be greater than the heap max size. No need to adjust
1214   // it with respect to the heap min size as it's a lower bound (i.e.,
1215   // we'll try to make the capacity larger than it, not smaller).
1216   minimum_desired_capacity = MIN2(minimum_desired_capacity, MaxHeapSize);
1217   // Should not be less than the heap min size. No need to adjust it
1218   // with respect to the heap max size as it's an upper bound (i.e.,
1219   // we'll try to make the capacity smaller than it, not greater).
1220   maximum_desired_capacity =  MAX2(maximum_desired_capacity, MinHeapSize);
1221 
1222   if (capacity_after_gc < minimum_desired_capacity) {
1223     // Don't expand unless it's significant
1224     size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1225 
1226     log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity). "
1227                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1228                               "min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1229                               capacity_after_gc, used_after_gc, used(), minimum_desired_capacity, MinHeapFreeRatio);
1230 
1231     expand(expand_bytes, _workers);
1232 
1233     // No expansion, now see if we want to shrink
1234   } else if (capacity_after_gc > maximum_desired_capacity) {
1235     // Capacity too large, compute shrinking size
1236     size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1237 
1238     log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity). "
1239                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1240                               "maximum_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1241                               capacity_after_gc, used_after_gc, used(), maximum_desired_capacity, MaxHeapFreeRatio);
1242 
1243     shrink(shrink_bytes);
1244   }
1245 }
1246 
1247 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size,
1248                                                             bool do_gc,
1249                                                             bool clear_all_soft_refs,
1250                                                             bool expect_null_mutator_alloc_region,
1251                                                             bool* gc_succeeded) {
1252   *gc_succeeded = true;
1253   // Let's attempt the allocation first.
1254   HeapWord* result =
1255     attempt_allocation_at_safepoint(word_size,
1256                                     expect_null_mutator_alloc_region);
1257   if (result != NULL) {
1258     return result;
1259   }
1260 
1261   // In a G1 heap, we're supposed to keep allocation from failing by
1262   // incremental pauses.  Therefore, at least for now, we'll favor
1263   // expansion over collection.  (This might change in the future if we can
1264   // do something smarter than full collection to satisfy a failed alloc.)
1265   result = expand_and_allocate(word_size);
1266   if (result != NULL) {
1267     return result;
1268   }
1269 
1270   if (do_gc) {
1271     // Expansion didn't work, we'll try to do a Full GC.
1272     *gc_succeeded = do_full_collection(false, /* explicit_gc */
1273                                        clear_all_soft_refs);
1274   }
1275 
1276   return NULL;
1277 }
1278 
1279 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1280                                                      bool* succeeded) {
1281   assert_at_safepoint_on_vm_thread();
1282 
1283   // Attempts to allocate followed by Full GC.
1284   HeapWord* result =
1285     satisfy_failed_allocation_helper(word_size,
1286                                      true,  /* do_gc */
1287                                      false, /* clear_all_soft_refs */
1288                                      false, /* expect_null_mutator_alloc_region */
1289                                      succeeded);
1290 
1291   if (result != NULL || !*succeeded) {
1292     return result;
1293   }
1294 
1295   // Attempts to allocate followed by Full GC that will collect all soft references.
1296   result = satisfy_failed_allocation_helper(word_size,
1297                                             true, /* do_gc */
1298                                             true, /* clear_all_soft_refs */
1299                                             true, /* expect_null_mutator_alloc_region */
1300                                             succeeded);
1301 
1302   if (result != NULL || !*succeeded) {
1303     return result;
1304   }
1305 
1306   // Attempts to allocate, no GC
1307   result = satisfy_failed_allocation_helper(word_size,
1308                                             false, /* do_gc */
1309                                             false, /* clear_all_soft_refs */
1310                                             true,  /* expect_null_mutator_alloc_region */
1311                                             succeeded);
1312 
1313   if (result != NULL) {
1314     return result;
1315   }
1316 
1317   assert(!soft_ref_policy()->should_clear_all_soft_refs(),
1318          "Flag should have been handled and cleared prior to this point");
1319 
1320   // What else?  We might try synchronous finalization later.  If the total
1321   // space available is large enough for the allocation, then a more
1322   // complete compaction phase than we've tried so far might be
1323   // appropriate.
1324   return NULL;
1325 }
1326 
1327 // Attempting to expand the heap sufficiently
1328 // to support an allocation of the given "word_size".  If
1329 // successful, perform the allocation and return the address of the
1330 // allocated block, or else "NULL".
1331 
1332 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1333   assert_at_safepoint_on_vm_thread();
1334 
1335   _verifier->verify_region_sets_optional();
1336 
1337   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1338   log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B",
1339                             word_size * HeapWordSize);
1340 
1341 
1342   if (expand(expand_bytes, _workers)) {
1343     _hrm->verify_optional();
1344     _verifier->verify_region_sets_optional();
1345     return attempt_allocation_at_safepoint(word_size,
1346                                            false /* expect_null_mutator_alloc_region */);
1347   }
1348   return NULL;
1349 }
1350 
1351 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) {
1352   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1353   aligned_expand_bytes = align_up(aligned_expand_bytes,
1354                                        HeapRegion::GrainBytes);
1355 
1356   log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B",
1357                             expand_bytes, aligned_expand_bytes);
1358 
1359   if (is_maximal_no_gc()) {
1360     log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1361     return false;
1362   }
1363 
1364   double expand_heap_start_time_sec = os::elapsedTime();
1365   uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1366   assert(regions_to_expand > 0, "Must expand by at least one region");
1367 
1368   uint expanded_by = _hrm->expand_by(regions_to_expand, pretouch_workers);
1369   if (expand_time_ms != NULL) {
1370     *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS;
1371   }
1372 
1373   if (expanded_by > 0) {
1374     size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1375     assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1376     policy()->record_new_heap_size(num_regions());
1377   } else {
1378     log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)");
1379 
1380     // The expansion of the virtual storage space was unsuccessful.
1381     // Let's see if it was because we ran out of swap.
1382     if (G1ExitOnExpansionFailure &&
1383         _hrm->available() >= regions_to_expand) {
1384       // We had head room...
1385       vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1386     }
1387   }
1388   return regions_to_expand > 0;
1389 }
1390 
1391 bool G1CollectedHeap::expand_single_region(uint node_index) {
1392   uint expanded_by = _hrm->expand_on_preferred_node(node_index);
1393 
1394   if (expanded_by == 0) {
1395     assert(is_maximal_no_gc(), "Should be no regions left, available: %u", _hrm->available());
1396     log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1397     return false;
1398   }
1399 
1400   policy()->record_new_heap_size(num_regions());
1401   return true;
1402 }
1403 
1404 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1405   size_t aligned_shrink_bytes =
1406     ReservedSpace::page_align_size_down(shrink_bytes);
1407   aligned_shrink_bytes = align_down(aligned_shrink_bytes,
1408                                          HeapRegion::GrainBytes);
1409   uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1410 
1411   uint num_regions_removed = _hrm->shrink_by(num_regions_to_remove);
1412   size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1413 
1414   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",
1415                             shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1416   if (num_regions_removed > 0) {
1417     policy()->record_new_heap_size(num_regions());
1418   } else {
1419     log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)");
1420   }
1421 }
1422 
1423 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1424   _verifier->verify_region_sets_optional();
1425 
1426   // We should only reach here at the end of a Full GC or during Remark which
1427   // means we should not not be holding to any GC alloc regions. The method
1428   // below will make sure of that and do any remaining clean up.
1429   _allocator->abandon_gc_alloc_regions();
1430 
1431   // Instead of tearing down / rebuilding the free lists here, we
1432   // could instead use the remove_all_pending() method on free_list to
1433   // remove only the ones that we need to remove.
1434   tear_down_region_sets(true /* free_list_only */);
1435   shrink_helper(shrink_bytes);
1436   rebuild_region_sets(true /* free_list_only */);
1437 
1438   _hrm->verify_optional();
1439   _verifier->verify_region_sets_optional();
1440 }
1441 
1442 class OldRegionSetChecker : public HeapRegionSetChecker {
1443 public:
1444   void check_mt_safety() {
1445     // Master Old Set MT safety protocol:
1446     // (a) If we're at a safepoint, operations on the master old set
1447     // should be invoked:
1448     // - by the VM thread (which will serialize them), or
1449     // - by the GC workers while holding the FreeList_lock, if we're
1450     //   at a safepoint for an evacuation pause (this lock is taken
1451     //   anyway when an GC alloc region is retired so that a new one
1452     //   is allocated from the free list), or
1453     // - by the GC workers while holding the OldSets_lock, if we're at a
1454     //   safepoint for a cleanup pause.
1455     // (b) If we're not at a safepoint, operations on the master old set
1456     // should be invoked while holding the Heap_lock.
1457 
1458     if (SafepointSynchronize::is_at_safepoint()) {
1459       guarantee(Thread::current()->is_VM_thread() ||
1460                 FreeList_lock->owned_by_self() || OldSets_lock->owned_by_self(),
1461                 "master old set MT safety protocol at a safepoint");
1462     } else {
1463       guarantee(Heap_lock->owned_by_self(), "master old set MT safety protocol outside a safepoint");
1464     }
1465   }
1466   bool is_correct_type(HeapRegion* hr) { return hr->is_old(); }
1467   const char* get_description() { return "Old Regions"; }
1468 };
1469 
1470 class ArchiveRegionSetChecker : public HeapRegionSetChecker {
1471 public:
1472   void check_mt_safety() {
1473     guarantee(!Universe::is_fully_initialized() || SafepointSynchronize::is_at_safepoint(),
1474               "May only change archive regions during initialization or safepoint.");
1475   }
1476   bool is_correct_type(HeapRegion* hr) { return hr->is_archive(); }
1477   const char* get_description() { return "Archive Regions"; }
1478 };
1479 
1480 class HumongousRegionSetChecker : public HeapRegionSetChecker {
1481 public:
1482   void check_mt_safety() {
1483     // Humongous Set MT safety protocol:
1484     // (a) If we're at a safepoint, operations on the master humongous
1485     // set should be invoked by either the VM thread (which will
1486     // serialize them) or by the GC workers while holding the
1487     // OldSets_lock.
1488     // (b) If we're not at a safepoint, operations on the master
1489     // humongous set should be invoked while holding the Heap_lock.
1490 
1491     if (SafepointSynchronize::is_at_safepoint()) {
1492       guarantee(Thread::current()->is_VM_thread() ||
1493                 OldSets_lock->owned_by_self(),
1494                 "master humongous set MT safety protocol at a safepoint");
1495     } else {
1496       guarantee(Heap_lock->owned_by_self(),
1497                 "master humongous set MT safety protocol outside a safepoint");
1498     }
1499   }
1500   bool is_correct_type(HeapRegion* hr) { return hr->is_humongous(); }
1501   const char* get_description() { return "Humongous Regions"; }
1502 };
1503 
1504 G1CollectedHeap::G1CollectedHeap() :
1505   CollectedHeap(),
1506   _young_gen_sampling_thread(NULL),
1507   _workers(NULL),
1508   _card_table(NULL),
1509   _soft_ref_policy(),
1510   _old_set("Old Region Set", new OldRegionSetChecker()),
1511   _archive_set("Archive Region Set", new ArchiveRegionSetChecker()),
1512   _humongous_set("Humongous Region Set", new HumongousRegionSetChecker()),
1513   _bot(NULL),
1514   _listener(),
1515   _numa(G1NUMA::create()),
1516   _hrm(NULL),
1517   _allocator(NULL),
1518   _verifier(NULL),
1519   _summary_bytes_used(0),
1520   _bytes_used_during_gc(0),
1521   _archive_allocator(NULL),
1522   _survivor_evac_stats("Young", YoungPLABSize, PLABWeight),
1523   _old_evac_stats("Old", OldPLABSize, PLABWeight),
1524   _expand_heap_after_alloc_failure(true),
1525   _g1mm(NULL),
1526   _humongous_reclaim_candidates(),
1527   _has_humongous_reclaim_candidates(false),
1528   _hr_printer(),
1529   _collector_state(),
1530   _old_marking_cycles_started(0),
1531   _old_marking_cycles_completed(0),
1532   _eden(),
1533   _survivor(),
1534   _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1535   _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1536   _policy(G1Policy::create_policy(_gc_timer_stw)),
1537   _heap_sizing_policy(NULL),
1538   _collection_set(this, _policy),
1539   _hot_card_cache(NULL),
1540   _rem_set(NULL),
1541   _cm(NULL),
1542   _cm_thread(NULL),
1543   _cr(NULL),
1544   _task_queues(NULL),
1545   _evacuation_failed(false),
1546   _evacuation_failed_info_array(NULL),
1547   _preserved_marks_set(true /* in_c_heap */),
1548 #ifndef PRODUCT
1549   _evacuation_failure_alot_for_current_gc(false),
1550   _evacuation_failure_alot_gc_number(0),
1551   _evacuation_failure_alot_count(0),
1552 #endif
1553   _ref_processor_stw(NULL),
1554   _is_alive_closure_stw(this),
1555   _is_subject_to_discovery_stw(this),
1556   _ref_processor_cm(NULL),
1557   _is_alive_closure_cm(this),
1558   _is_subject_to_discovery_cm(this),
1559   _region_attr() {
1560 
1561   _verifier = new G1HeapVerifier(this);
1562 
1563   _allocator = new G1Allocator(this);
1564 
1565   _heap_sizing_policy = G1HeapSizingPolicy::create(this, _policy->analytics());
1566 
1567   _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);
1568 
1569   // Override the default _filler_array_max_size so that no humongous filler
1570   // objects are created.
1571   _filler_array_max_size = _humongous_object_threshold_in_words;
1572 
1573   uint n_queues = ParallelGCThreads;
1574   _task_queues = new RefToScanQueueSet(n_queues);
1575 
1576   _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1577 
1578   for (uint i = 0; i < n_queues; i++) {
1579     RefToScanQueue* q = new RefToScanQueue();
1580     q->initialize();
1581     _task_queues->register_queue(i, q);
1582     ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1583   }
1584 
1585   // Initialize the G1EvacuationFailureALot counters and flags.
1586   NOT_PRODUCT(reset_evacuation_should_fail();)
1587   _gc_tracer_stw->initialize();
1588 
1589   guarantee(_task_queues != NULL, "task_queues allocation failure.");
1590 }
1591 
1592 static size_t actual_reserved_page_size(ReservedSpace rs) {
1593   size_t page_size = os::vm_page_size();
1594   if (UseLargePages) {
1595     // There are two ways to manage large page memory.
1596     // 1. OS supports committing large page memory.
1597     // 2. OS doesn't support committing large page memory so ReservedSpace manages it.
1598     //    And ReservedSpace calls it 'special'. If we failed to set 'special',
1599     //    we reserved memory without large page.
1600     if (os::can_commit_large_page_memory() || rs.special()) {
1601       // An alignment at ReservedSpace comes from preferred page size or
1602       // heap alignment, and if the alignment came from heap alignment, it could be
1603       // larger than large pages size. So need to cap with the large page size.
1604       page_size = MIN2(rs.alignment(), os::large_page_size());
1605     }
1606   }
1607 
1608   return page_size;
1609 }
1610 
1611 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1612                                                                  size_t size,
1613                                                                  size_t translation_factor) {
1614   size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1615   // Allocate a new reserved space, preferring to use large pages.
1616   ReservedSpace rs(size, preferred_page_size);
1617   size_t page_size = actual_reserved_page_size(rs);
1618   G1RegionToSpaceMapper* result  =
1619     G1RegionToSpaceMapper::create_mapper(rs,
1620                                          size,
1621                                          page_size,
1622                                          HeapRegion::GrainBytes,
1623                                          translation_factor,
1624                                          mtGC);
1625 
1626   os::trace_page_sizes_for_requested_size(description,
1627                                           size,
1628                                           preferred_page_size,
1629                                           page_size,
1630                                           rs.base(),
1631                                           rs.size());
1632 
1633   return result;
1634 }
1635 
1636 jint G1CollectedHeap::initialize_concurrent_refinement() {
1637   jint ecode = JNI_OK;
1638   _cr = G1ConcurrentRefine::create(&ecode);
1639   return ecode;
1640 }
1641 
1642 jint G1CollectedHeap::initialize_young_gen_sampling_thread() {
1643   _young_gen_sampling_thread = new G1YoungRemSetSamplingThread();
1644   if (_young_gen_sampling_thread->osthread() == NULL) {
1645     vm_shutdown_during_initialization("Could not create G1YoungRemSetSamplingThread");
1646     return JNI_ENOMEM;
1647   }
1648   return JNI_OK;
1649 }
1650 
1651 jint G1CollectedHeap::initialize() {
1652 
1653   // Necessary to satisfy locking discipline assertions.
1654 
1655   MutexLocker x(Heap_lock);
1656 
1657   // While there are no constraints in the GC code that HeapWordSize
1658   // be any particular value, there are multiple other areas in the
1659   // system which believe this to be true (e.g. oop->object_size in some
1660   // cases incorrectly returns the size in wordSize units rather than
1661   // HeapWordSize).
1662   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1663 
1664   size_t init_byte_size = InitialHeapSize;
1665   size_t reserved_byte_size = G1Arguments::heap_reserved_size_bytes();
1666 
1667   // Ensure that the sizes are properly aligned.
1668   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1669   Universe::check_alignment(reserved_byte_size, HeapRegion::GrainBytes, "g1 heap");
1670   Universe::check_alignment(reserved_byte_size, HeapAlignment, "g1 heap");
1671 
1672   // Reserve the maximum.
1673 
1674   // When compressed oops are enabled, the preferred heap base
1675   // is calculated by subtracting the requested size from the
1676   // 32Gb boundary and using the result as the base address for
1677   // heap reservation. If the requested size is not aligned to
1678   // HeapRegion::GrainBytes (i.e. the alignment that is passed
1679   // into the ReservedHeapSpace constructor) then the actual
1680   // base of the reserved heap may end up differing from the
1681   // address that was requested (i.e. the preferred heap base).
1682   // If this happens then we could end up using a non-optimal
1683   // compressed oops mode.
1684 
1685   ReservedHeapSpace heap_rs = Universe::reserve_heap(reserved_byte_size,
1686                                                      HeapAlignment);
1687 
1688   initialize_reserved_region(heap_rs);
1689 
1690   // Create the barrier set for the entire reserved region.
1691   G1CardTable* ct = new G1CardTable(heap_rs.region());
1692   ct->initialize();
1693   G1BarrierSet* bs = new G1BarrierSet(ct);
1694   bs->initialize();
1695   assert(bs->is_a(BarrierSet::G1BarrierSet), "sanity");
1696   BarrierSet::set_barrier_set(bs);
1697   _card_table = ct;
1698 
1699   {
1700     G1SATBMarkQueueSet& satbqs = bs->satb_mark_queue_set();
1701     satbqs.set_process_completed_buffers_threshold(G1SATBProcessCompletedThreshold);
1702     satbqs.set_buffer_enqueue_threshold_percentage(G1SATBBufferEnqueueingThresholdPercent);
1703   }
1704 
1705   // Create the hot card cache.
1706   _hot_card_cache = new G1HotCardCache(this);
1707 
1708   // Carve out the G1 part of the heap.
1709   ReservedSpace g1_rs = heap_rs.first_part(reserved_byte_size);
1710   size_t page_size = actual_reserved_page_size(heap_rs);
1711   G1RegionToSpaceMapper* heap_storage =
1712     G1RegionToSpaceMapper::create_heap_mapper(g1_rs,
1713                                               g1_rs.size(),
1714                                               page_size,
1715                                               HeapRegion::GrainBytes,
1716                                               1,
1717                                               mtJavaHeap);
1718   if(heap_storage == NULL) {
1719     vm_shutdown_during_initialization("Could not initialize G1 heap");
1720     return JNI_ERR;
1721   }
1722 
1723   os::trace_page_sizes("Heap",
1724                        MinHeapSize,
1725                        reserved_byte_size,
1726                        page_size,
1727                        heap_rs.base(),
1728                        heap_rs.size());
1729   heap_storage->set_mapping_changed_listener(&_listener);
1730 
1731   // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1732   G1RegionToSpaceMapper* bot_storage =
1733     create_aux_memory_mapper("Block Offset Table",
1734                              G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize),
1735                              G1BlockOffsetTable::heap_map_factor());
1736 
1737   G1RegionToSpaceMapper* cardtable_storage =
1738     create_aux_memory_mapper("Card Table",
1739                              G1CardTable::compute_size(g1_rs.size() / HeapWordSize),
1740                              G1CardTable::heap_map_factor());
1741 
1742   G1RegionToSpaceMapper* card_counts_storage =
1743     create_aux_memory_mapper("Card Counts Table",
1744                              G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1745                              G1CardCounts::heap_map_factor());
1746 
1747   size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size());
1748   G1RegionToSpaceMapper* prev_bitmap_storage =
1749     create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1750   G1RegionToSpaceMapper* next_bitmap_storage =
1751     create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1752 
1753   _hrm = HeapRegionManager::create_manager(this);
1754 
1755   _hrm->initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1756   _card_table->initialize(cardtable_storage);
1757 
1758   // Do later initialization work for concurrent refinement.
1759   _hot_card_cache->initialize(card_counts_storage);
1760 
1761   // 6843694 - ensure that the maximum region index can fit
1762   // in the remembered set structures.
1763   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1764   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1765 
1766   // The G1FromCardCache reserves card with value 0 as "invalid", so the heap must not
1767   // start within the first card.
1768   guarantee(g1_rs.base() >= (char*)G1CardTable::card_size, "Java heap must not start within the first card.");
1769   // Also create a G1 rem set.
1770   _rem_set = new G1RemSet(this, _card_table, _hot_card_cache);
1771   _rem_set->initialize(max_reserved_capacity(), max_regions());
1772 
1773   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1774   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1775   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1776             "too many cards per region");
1777 
1778   FreeRegionList::set_unrealistically_long_length(max_expandable_regions() + 1);
1779 
1780   _bot = new G1BlockOffsetTable(reserved_region(), bot_storage);
1781 
1782   {
1783     HeapWord* start = _hrm->reserved().start();
1784     HeapWord* end = _hrm->reserved().end();
1785     size_t granularity = HeapRegion::GrainBytes;
1786 
1787     _region_attr.initialize(start, end, granularity);
1788     _humongous_reclaim_candidates.initialize(start, end, granularity);
1789   }
1790 
1791   _workers = new WorkGang("GC Thread", ParallelGCThreads,
1792                           true /* are_GC_task_threads */,
1793                           false /* are_ConcurrentGC_threads */);
1794   if (_workers == NULL) {
1795     return JNI_ENOMEM;
1796   }
1797   _workers->initialize_workers();
1798 
1799   _numa->set_region_info(HeapRegion::GrainBytes, page_size);
1800 
1801   // Create the G1ConcurrentMark data structure and thread.
1802   // (Must do this late, so that "max_regions" is defined.)
1803   _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1804   if (_cm == NULL || !_cm->completed_initialization()) {
1805     vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark");
1806     return JNI_ENOMEM;
1807   }
1808   _cm_thread = _cm->cm_thread();
1809 
1810   // Now expand into the initial heap size.
1811   if (!expand(init_byte_size, _workers)) {
1812     vm_shutdown_during_initialization("Failed to allocate initial heap.");
1813     return JNI_ENOMEM;
1814   }
1815 
1816   // Perform any initialization actions delegated to the policy.
1817   policy()->init(this, &_collection_set);
1818 
1819   jint ecode = initialize_concurrent_refinement();
1820   if (ecode != JNI_OK) {
1821     return ecode;
1822   }
1823 
1824   ecode = initialize_young_gen_sampling_thread();
1825   if (ecode != JNI_OK) {
1826     return ecode;
1827   }
1828 
1829   {
1830     G1DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
1831     dcqs.set_process_cards_threshold(concurrent_refine()->yellow_zone());
1832     dcqs.set_max_cards(concurrent_refine()->red_zone());
1833   }
1834 
1835   // Here we allocate the dummy HeapRegion that is required by the
1836   // G1AllocRegion class.
1837   HeapRegion* dummy_region = _hrm->get_dummy_region();
1838 
1839   // We'll re-use the same region whether the alloc region will
1840   // require BOT updates or not and, if it doesn't, then a non-young
1841   // region will complain that it cannot support allocations without
1842   // BOT updates. So we'll tag the dummy region as eden to avoid that.
1843   dummy_region->set_eden();
1844   // Make sure it's full.
1845   dummy_region->set_top(dummy_region->end());
1846   G1AllocRegion::setup(this, dummy_region);
1847 
1848   _allocator->init_mutator_alloc_regions();
1849 
1850   // Do create of the monitoring and management support so that
1851   // values in the heap have been properly initialized.
1852   _g1mm = new G1MonitoringSupport(this);
1853 
1854   G1StringDedup::initialize();
1855 
1856   _preserved_marks_set.init(ParallelGCThreads);
1857 
1858   _collection_set.initialize(max_regions());
1859 
1860   return JNI_OK;
1861 }
1862 
1863 void G1CollectedHeap::stop() {
1864   // Stop all concurrent threads. We do this to make sure these threads
1865   // do not continue to execute and access resources (e.g. logging)
1866   // that are destroyed during shutdown.
1867   _cr->stop();
1868   _young_gen_sampling_thread->stop();
1869   _cm_thread->stop();
1870   if (G1StringDedup::is_enabled()) {
1871     G1StringDedup::stop();
1872   }
1873 }
1874 
1875 void G1CollectedHeap::safepoint_synchronize_begin() {
1876   SuspendibleThreadSet::synchronize();
1877 }
1878 
1879 void G1CollectedHeap::safepoint_synchronize_end() {
1880   SuspendibleThreadSet::desynchronize();
1881 }
1882 
1883 void G1CollectedHeap::post_initialize() {
1884   CollectedHeap::post_initialize();
1885   ref_processing_init();
1886 }
1887 
1888 void G1CollectedHeap::ref_processing_init() {
1889   // Reference processing in G1 currently works as follows:
1890   //
1891   // * There are two reference processor instances. One is
1892   //   used to record and process discovered references
1893   //   during concurrent marking; the other is used to
1894   //   record and process references during STW pauses
1895   //   (both full and incremental).
1896   // * Both ref processors need to 'span' the entire heap as
1897   //   the regions in the collection set may be dotted around.
1898   //
1899   // * For the concurrent marking ref processor:
1900   //   * Reference discovery is enabled at initial marking.
1901   //   * Reference discovery is disabled and the discovered
1902   //     references processed etc during remarking.
1903   //   * Reference discovery is MT (see below).
1904   //   * Reference discovery requires a barrier (see below).
1905   //   * Reference processing may or may not be MT
1906   //     (depending on the value of ParallelRefProcEnabled
1907   //     and ParallelGCThreads).
1908   //   * A full GC disables reference discovery by the CM
1909   //     ref processor and abandons any entries on it's
1910   //     discovered lists.
1911   //
1912   // * For the STW processor:
1913   //   * Non MT discovery is enabled at the start of a full GC.
1914   //   * Processing and enqueueing during a full GC is non-MT.
1915   //   * During a full GC, references are processed after marking.
1916   //
1917   //   * Discovery (may or may not be MT) is enabled at the start
1918   //     of an incremental evacuation pause.
1919   //   * References are processed near the end of a STW evacuation pause.
1920   //   * For both types of GC:
1921   //     * Discovery is atomic - i.e. not concurrent.
1922   //     * Reference discovery will not need a barrier.
1923 
1924   bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1);
1925 
1926   // Concurrent Mark ref processor
1927   _ref_processor_cm =
1928     new ReferenceProcessor(&_is_subject_to_discovery_cm,
1929                            mt_processing,                                  // mt processing
1930                            ParallelGCThreads,                              // degree of mt processing
1931                            (ParallelGCThreads > 1) || (ConcGCThreads > 1), // mt discovery
1932                            MAX2(ParallelGCThreads, ConcGCThreads),         // degree of mt discovery
1933                            false,                                          // Reference discovery is not atomic
1934                            &_is_alive_closure_cm,                          // is alive closure
1935                            true);                                          // allow changes to number of processing threads
1936 
1937   // STW ref processor
1938   _ref_processor_stw =
1939     new ReferenceProcessor(&_is_subject_to_discovery_stw,
1940                            mt_processing,                        // mt processing
1941                            ParallelGCThreads,                    // degree of mt processing
1942                            (ParallelGCThreads > 1),              // mt discovery
1943                            ParallelGCThreads,                    // degree of mt discovery
1944                            true,                                 // Reference discovery is atomic
1945                            &_is_alive_closure_stw,               // is alive closure
1946                            true);                                // allow changes to number of processing threads
1947 }
1948 
1949 SoftRefPolicy* G1CollectedHeap::soft_ref_policy() {
1950   return &_soft_ref_policy;
1951 }
1952 
1953 size_t G1CollectedHeap::capacity() const {
1954   return _hrm->length() * HeapRegion::GrainBytes;
1955 }
1956 
1957 size_t G1CollectedHeap::unused_committed_regions_in_bytes() const {
1958   return _hrm->total_free_bytes();
1959 }
1960 
1961 void G1CollectedHeap::iterate_hcc_closure(G1CardTableEntryClosure* cl, uint worker_id) {
1962   _hot_card_cache->drain(cl, worker_id);
1963 }
1964 
1965 // Computes the sum of the storage used by the various regions.
1966 size_t G1CollectedHeap::used() const {
1967   size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
1968   if (_archive_allocator != NULL) {
1969     result += _archive_allocator->used();
1970   }
1971   return result;
1972 }
1973 
1974 size_t G1CollectedHeap::used_unlocked() const {
1975   return _summary_bytes_used;
1976 }
1977 
1978 class SumUsedClosure: public HeapRegionClosure {
1979   size_t _used;
1980 public:
1981   SumUsedClosure() : _used(0) {}
1982   bool do_heap_region(HeapRegion* r) {
1983     _used += r->used();
1984     return false;
1985   }
1986   size_t result() { return _used; }
1987 };
1988 
1989 size_t G1CollectedHeap::recalculate_used() const {
1990   SumUsedClosure blk;
1991   heap_region_iterate(&blk);
1992   return blk.result();
1993 }
1994 
1995 bool  G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
1996   switch (cause) {
1997     case GCCause::_java_lang_system_gc:                 return ExplicitGCInvokesConcurrent;
1998     case GCCause::_dcmd_gc_run:                         return ExplicitGCInvokesConcurrent;
1999     case GCCause::_wb_conc_mark:                        return true;
2000     default :                                           return false;
2001   }
2002 }
2003 
2004 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2005   switch (cause) {
2006     case GCCause::_g1_humongous_allocation: return true;
2007     case GCCause::_g1_periodic_collection:  return G1PeriodicGCInvokesConcurrent;
2008     default:                                return is_user_requested_concurrent_full_gc(cause);
2009   }
2010 }
2011 
2012 bool G1CollectedHeap::should_upgrade_to_full_gc(GCCause::Cause cause) {
2013   if (policy()->force_upgrade_to_full()) {
2014     return true;
2015   } else if (should_do_concurrent_full_gc(_gc_cause)) {
2016     return false;
2017   } else if (has_regions_left_for_allocation()) {
2018     return false;
2019   } else {
2020     return true;
2021   }
2022 }
2023 
2024 #ifndef PRODUCT
2025 void G1CollectedHeap::allocate_dummy_regions() {
2026   // Let's fill up most of the region
2027   size_t word_size = HeapRegion::GrainWords - 1024;
2028   // And as a result the region we'll allocate will be humongous.
2029   guarantee(is_humongous(word_size), "sanity");
2030 
2031   // _filler_array_max_size is set to humongous object threshold
2032   // but temporarily change it to use CollectedHeap::fill_with_object().
2033   SizeTFlagSetting fs(_filler_array_max_size, word_size);
2034 
2035   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2036     // Let's use the existing mechanism for the allocation
2037     HeapWord* dummy_obj = humongous_obj_allocate(word_size);
2038     if (dummy_obj != NULL) {
2039       MemRegion mr(dummy_obj, word_size);
2040       CollectedHeap::fill_with_object(mr);
2041     } else {
2042       // If we can't allocate once, we probably cannot allocate
2043       // again. Let's get out of the loop.
2044       break;
2045     }
2046   }
2047 }
2048 #endif // !PRODUCT
2049 
2050 void G1CollectedHeap::increment_old_marking_cycles_started() {
2051   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2052          _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2053          "Wrong marking cycle count (started: %d, completed: %d)",
2054          _old_marking_cycles_started, _old_marking_cycles_completed);
2055 
2056   _old_marking_cycles_started++;
2057 }
2058 
2059 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2060   MonitorLocker ml(G1OldGCCount_lock, Mutex::_no_safepoint_check_flag);
2061 
2062   // We assume that if concurrent == true, then the caller is a
2063   // concurrent thread that was joined the Suspendible Thread
2064   // Set. If there's ever a cheap way to check this, we should add an
2065   // assert here.
2066 
2067   // Given that this method is called at the end of a Full GC or of a
2068   // concurrent cycle, and those can be nested (i.e., a Full GC can
2069   // interrupt a concurrent cycle), the number of full collections
2070   // completed should be either one (in the case where there was no
2071   // nesting) or two (when a Full GC interrupted a concurrent cycle)
2072   // behind the number of full collections started.
2073 
2074   // This is the case for the inner caller, i.e. a Full GC.
2075   assert(concurrent ||
2076          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2077          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2078          "for inner caller (Full GC): _old_marking_cycles_started = %u "
2079          "is inconsistent with _old_marking_cycles_completed = %u",
2080          _old_marking_cycles_started, _old_marking_cycles_completed);
2081 
2082   // This is the case for the outer caller, i.e. the concurrent cycle.
2083   assert(!concurrent ||
2084          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2085          "for outer caller (concurrent cycle): "
2086          "_old_marking_cycles_started = %u "
2087          "is inconsistent with _old_marking_cycles_completed = %u",
2088          _old_marking_cycles_started, _old_marking_cycles_completed);
2089 
2090   _old_marking_cycles_completed += 1;
2091 
2092   // We need to clear the "in_progress" flag in the CM thread before
2093   // we wake up any waiters (especially when ExplicitInvokesConcurrent
2094   // is set) so that if a waiter requests another System.gc() it doesn't
2095   // incorrectly see that a marking cycle is still in progress.
2096   if (concurrent) {
2097     _cm_thread->set_idle();
2098   }
2099 
2100   // Notify threads waiting in System.gc() (with ExplicitGCInvokesConcurrent)
2101   // for a full GC to finish that their wait is over.
2102   ml.notify_all();
2103 }
2104 
2105 void G1CollectedHeap::collect(GCCause::Cause cause) {
2106   try_collect(cause);
2107 }
2108 
2109 // Return true if (x < y) with allowance for wraparound.
2110 static bool gc_counter_less_than(uint x, uint y) {
2111   return (x - y) > (UINT_MAX/2);
2112 }
2113 
2114 // LOG_COLLECT_CONCURRENTLY(cause, msg, args...)
2115 // Macro so msg printing is format-checked.
2116 #define LOG_COLLECT_CONCURRENTLY(cause, ...)                            \
2117   do {                                                                  \
2118     LogTarget(Trace, gc) LOG_COLLECT_CONCURRENTLY_lt;                   \
2119     if (LOG_COLLECT_CONCURRENTLY_lt.is_enabled()) {                     \
2120       ResourceMark rm; /* For thread name. */                           \
2121       LogStream LOG_COLLECT_CONCURRENTLY_s(&LOG_COLLECT_CONCURRENTLY_lt); \
2122       LOG_COLLECT_CONCURRENTLY_s.print("%s: Try Collect Concurrently (%s): ", \
2123                                        Thread::current()->name(),       \
2124                                        GCCause::to_string(cause));      \
2125       LOG_COLLECT_CONCURRENTLY_s.print(__VA_ARGS__);                    \
2126     }                                                                   \
2127   } while (0)
2128 
2129 #define LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, result) \
2130   LOG_COLLECT_CONCURRENTLY(cause, "complete %s", BOOL_TO_STR(result))
2131 
2132 bool G1CollectedHeap::try_collect_concurrently(GCCause::Cause cause,
2133                                                uint gc_counter,
2134                                                uint old_marking_started_before) {
2135   assert_heap_not_locked();
2136   assert(should_do_concurrent_full_gc(cause),
2137          "Non-concurrent cause %s", GCCause::to_string(cause));
2138 
2139   for (uint i = 1; true; ++i) {
2140     // Try to schedule an initial-mark evacuation pause that will
2141     // start a concurrent cycle.
2142     LOG_COLLECT_CONCURRENTLY(cause, "attempt %u", i);
2143     VM_G1TryInitiateConcMark op(gc_counter,
2144                                 cause,
2145                                 policy()->max_pause_time_ms());
2146     VMThread::execute(&op);
2147 
2148     // Request is trivially finished.
2149     if (cause == GCCause::_g1_periodic_collection) {
2150       LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, op.gc_succeeded());
2151       return op.gc_succeeded();
2152     }
2153 
2154     // Lock to get consistent set of values.
2155     uint old_marking_started_after;
2156     uint old_marking_completed_after;
2157     {
2158       MutexLocker ml(Heap_lock);
2159       // Update gc_counter for retrying VMOp if needed. Captured here to be
2160       // consistent with the values we use below for termination tests.  If
2161       // a retry is needed after a possible wait, and another collection
2162       // occurs in the meantime, it will cause our retry to be skipped and
2163       // we'll recheck for termination with updated conditions from that
2164       // more recent collection.  That's what we want, rather than having
2165       // our retry possibly perform an unnecessary collection.
2166       gc_counter = total_collections();
2167       old_marking_started_after = _old_marking_cycles_started;
2168       old_marking_completed_after = _old_marking_cycles_completed;
2169     }
2170 
2171     if (!GCCause::is_user_requested_gc(cause)) {
2172       // For an "automatic" (not user-requested) collection, we just need to
2173       // ensure that progress is made.
2174       //
2175       // Request is finished if any of
2176       // (1) the VMOp successfully performed a GC,
2177       // (2) a concurrent cycle was already in progress,
2178       // (3) a new cycle was started (by this thread or some other), or
2179       // (4) a Full GC was performed.
2180       // Cases (3) and (4) are detected together by a change to
2181       // _old_marking_cycles_started.
2182       //
2183       // Note that (1) does not imply (3).  If we're still in the mixed
2184       // phase of an earlier concurrent collection, the request to make the
2185       // collection an initial-mark won't be honored.  If we don't check for
2186       // both conditions we'll spin doing back-to-back collections.
2187       if (op.gc_succeeded() ||
2188           op.cycle_already_in_progress() ||
2189           (old_marking_started_before != old_marking_started_after)) {
2190         LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, true);
2191         return true;
2192       }
2193     } else {                    // User-requested GC.
2194       // For a user-requested collection, we want to ensure that a complete
2195       // full collection has been performed before returning, but without
2196       // waiting for more than needed.
2197 
2198       // For user-requested GCs (unlike non-UR), a successful VMOp implies a
2199       // new cycle was started.  That's good, because it's not clear what we
2200       // should do otherwise.  Trying again just does back to back GCs.
2201       // Can't wait for someone else to start a cycle.  And returning fails
2202       // to meet the goal of ensuring a full collection was performed.
2203       assert(!op.gc_succeeded() ||
2204              (old_marking_started_before != old_marking_started_after),
2205              "invariant: succeeded %s, started before %u, started after %u",
2206              BOOL_TO_STR(op.gc_succeeded()),
2207              old_marking_started_before, old_marking_started_after);
2208 
2209       // Request is finished if a full collection (concurrent or stw)
2210       // was started after this request and has completed, e.g.
2211       // started_before < completed_after.
2212       if (gc_counter_less_than(old_marking_started_before,
2213                                old_marking_completed_after)) {
2214         LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, true);
2215         return true;
2216       }
2217 
2218       if (old_marking_started_after != old_marking_completed_after) {
2219         // If there is an in-progress cycle (possibly started by us), then
2220         // wait for that cycle to complete, e.g.
2221         // while completed_now < started_after.
2222         LOG_COLLECT_CONCURRENTLY(cause, "wait");
2223         MonitorLocker ml(G1OldGCCount_lock);
2224         while (gc_counter_less_than(_old_marking_cycles_completed,
2225                                     old_marking_started_after)) {
2226           ml.wait();
2227         }
2228         // Request is finished if the collection we just waited for was
2229         // started after this request.
2230         if (old_marking_started_before != old_marking_started_after) {
2231           LOG_COLLECT_CONCURRENTLY(cause, "complete after wait");
2232           return true;
2233         }
2234       }
2235 
2236       // If VMOp was successful then it started a new cycle that the above
2237       // wait &etc should have recognized as finishing this request.  This
2238       // differs from a non-user-request, where gc_succeeded does not imply
2239       // a new cycle was started.
2240       assert(!op.gc_succeeded(), "invariant");
2241 
2242       // If VMOp failed because a cycle was already in progress, it is now
2243       // complete.  But it didn't finish this user-requested GC, so try
2244       // again.
2245       if (op.cycle_already_in_progress()) {
2246         LOG_COLLECT_CONCURRENTLY(cause, "retry after in-progress");
2247         continue;
2248       }
2249     }
2250 
2251     // Collection failed and should be retried.
2252     assert(op.transient_failure(), "invariant");
2253 
2254     // If GCLocker is active, wait until clear before retrying.
2255     if (GCLocker::is_active_and_needs_gc()) {
2256       LOG_COLLECT_CONCURRENTLY(cause, "gc-locker stall");
2257       GCLocker::stall_until_clear();
2258     }
2259 
2260     LOG_COLLECT_CONCURRENTLY(cause, "retry");
2261   }
2262 }
2263 
2264 bool G1CollectedHeap::try_collect(GCCause::Cause cause) {
2265   assert_heap_not_locked();
2266 
2267   // Lock to get consistent set of values.
2268   uint gc_count_before;
2269   uint full_gc_count_before;
2270   uint old_marking_started_before;
2271   {
2272     MutexLocker ml(Heap_lock);
2273     gc_count_before = total_collections();
2274     full_gc_count_before = total_full_collections();
2275     old_marking_started_before = _old_marking_cycles_started;
2276   }
2277 
2278   if (should_do_concurrent_full_gc(cause)) {
2279     return try_collect_concurrently(cause,
2280                                     gc_count_before,
2281                                     old_marking_started_before);
2282   } else if (GCLocker::should_discard(cause, gc_count_before)) {
2283     // Indicate failure to be consistent with VMOp failure due to
2284     // another collection slipping in after our gc_count but before
2285     // our request is processed.
2286     return false;
2287   } else if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2288              DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2289 
2290     // Schedule a standard evacuation pause. We're setting word_size
2291     // to 0 which means that we are not requesting a post-GC allocation.
2292     VM_G1CollectForAllocation op(0,     /* word_size */
2293                                  gc_count_before,
2294                                  cause,
2295                                  policy()->max_pause_time_ms());
2296     VMThread::execute(&op);
2297     return op.gc_succeeded();
2298   } else {
2299     // Schedule a Full GC.
2300     VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2301     VMThread::execute(&op);
2302     return op.gc_succeeded();
2303   }
2304 }
2305 
2306 bool G1CollectedHeap::is_in(const void* p) const {
2307   if (_hrm->reserved().contains(p)) {
2308     // Given that we know that p is in the reserved space,
2309     // heap_region_containing() should successfully
2310     // return the containing region.
2311     HeapRegion* hr = heap_region_containing(p);
2312     return hr->is_in(p);
2313   } else {
2314     return false;
2315   }
2316 }
2317 
2318 #ifdef ASSERT
2319 bool G1CollectedHeap::is_in_exact(const void* p) const {
2320   bool contains = reserved_region().contains(p);
2321   bool available = _hrm->is_available(addr_to_region((HeapWord*)p));
2322   if (contains && available) {
2323     return true;
2324   } else {
2325     return false;
2326   }
2327 }
2328 #endif
2329 
2330 // Iteration functions.
2331 
2332 // Iterates an ObjectClosure over all objects within a HeapRegion.
2333 
2334 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2335   ObjectClosure* _cl;
2336 public:
2337   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2338   bool do_heap_region(HeapRegion* r) {
2339     if (!r->is_continues_humongous()) {
2340       r->object_iterate(_cl);
2341     }
2342     return false;
2343   }
2344 };
2345 
2346 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2347   IterateObjectClosureRegionClosure blk(cl);
2348   heap_region_iterate(&blk);
2349 }
2350 
2351 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2352   _hrm->iterate(cl);
2353 }
2354 
2355 void G1CollectedHeap::heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl,
2356                                                                  HeapRegionClaimer *hrclaimer,
2357                                                                  uint worker_id) const {
2358   _hrm->par_iterate(cl, hrclaimer, hrclaimer->offset_for_worker(worker_id));
2359 }
2360 
2361 void G1CollectedHeap::heap_region_par_iterate_from_start(HeapRegionClosure* cl,
2362                                                          HeapRegionClaimer *hrclaimer) const {
2363   _hrm->par_iterate(cl, hrclaimer, 0);
2364 }
2365 
2366 void G1CollectedHeap::collection_set_iterate_all(HeapRegionClosure* cl) {
2367   _collection_set.iterate(cl);
2368 }
2369 
2370 void G1CollectedHeap::collection_set_par_iterate_all(HeapRegionClosure* cl, HeapRegionClaimer* hr_claimer, uint worker_id) {
2371   _collection_set.par_iterate(cl, hr_claimer, worker_id, workers()->active_workers());
2372 }
2373 
2374 void G1CollectedHeap::collection_set_iterate_increment_from(HeapRegionClosure *cl, HeapRegionClaimer* hr_claimer, uint worker_id) {
2375   _collection_set.iterate_incremental_part_from(cl, hr_claimer, worker_id, workers()->active_workers());
2376 }
2377 
2378 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2379   HeapRegion* hr = heap_region_containing(addr);
2380   return hr->block_start(addr);
2381 }
2382 
2383 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2384   HeapRegion* hr = heap_region_containing(addr);
2385   return hr->block_is_obj(addr);
2386 }
2387 
2388 bool G1CollectedHeap::supports_tlab_allocation() const {
2389   return true;
2390 }
2391 
2392 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2393   return (_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes;
2394 }
2395 
2396 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2397   return _eden.length() * HeapRegion::GrainBytes;
2398 }
2399 
2400 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2401 // must be equal to the humongous object limit.
2402 size_t G1CollectedHeap::max_tlab_size() const {
2403   return align_down(_humongous_object_threshold_in_words, MinObjAlignment);
2404 }
2405 
2406 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2407   return _allocator->unsafe_max_tlab_alloc();
2408 }
2409 
2410 size_t G1CollectedHeap::max_capacity() const {
2411   return _hrm->max_expandable_length() * HeapRegion::GrainBytes;
2412 }
2413 
2414 size_t G1CollectedHeap::max_reserved_capacity() const {
2415   return _hrm->max_length() * HeapRegion::GrainBytes;
2416 }
2417 
2418 jlong G1CollectedHeap::millis_since_last_gc() {
2419   // See the notes in GenCollectedHeap::millis_since_last_gc()
2420   // for more information about the implementation.
2421   jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) -
2422                   _policy->collection_pause_end_millis();
2423   if (ret_val < 0) {
2424     log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT
2425       ". returning zero instead.", ret_val);
2426     return 0;
2427   }
2428   return ret_val;
2429 }
2430 
2431 void G1CollectedHeap::deduplicate_string(oop str) {
2432   assert(java_lang_String::is_instance(str), "invariant");
2433 
2434   if (G1StringDedup::is_enabled()) {
2435     G1StringDedup::deduplicate(str);
2436   }
2437 }
2438 
2439 void G1CollectedHeap::prepare_for_verify() {
2440   _verifier->prepare_for_verify();
2441 }
2442 
2443 void G1CollectedHeap::verify(VerifyOption vo) {
2444   _verifier->verify(vo);
2445 }
2446 
2447 bool G1CollectedHeap::supports_concurrent_phase_control() const {
2448   return true;
2449 }
2450 
2451 bool G1CollectedHeap::request_concurrent_phase(const char* phase) {
2452   return _cm_thread->request_concurrent_phase(phase);
2453 }
2454 
2455 bool G1CollectedHeap::is_heterogeneous_heap() const {
2456   return G1Arguments::is_heterogeneous_heap();
2457 }
2458 
2459 class PrintRegionClosure: public HeapRegionClosure {
2460   outputStream* _st;
2461 public:
2462   PrintRegionClosure(outputStream* st) : _st(st) {}
2463   bool do_heap_region(HeapRegion* r) {
2464     r->print_on(_st);
2465     return false;
2466   }
2467 };
2468 
2469 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2470                                        const HeapRegion* hr,
2471                                        const VerifyOption vo) const {
2472   switch (vo) {
2473   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
2474   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
2475   case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj, hr);
2476   default:                            ShouldNotReachHere();
2477   }
2478   return false; // keep some compilers happy
2479 }
2480 
2481 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2482                                        const VerifyOption vo) const {
2483   switch (vo) {
2484   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
2485   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
2486   case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj);
2487   default:                            ShouldNotReachHere();
2488   }
2489   return false; // keep some compilers happy
2490 }
2491 
2492 void G1CollectedHeap::print_heap_regions() const {
2493   LogTarget(Trace, gc, heap, region) lt;
2494   if (lt.is_enabled()) {
2495     LogStream ls(lt);
2496     print_regions_on(&ls);
2497   }
2498 }
2499 
2500 void G1CollectedHeap::print_on(outputStream* st) const {
2501   st->print(" %-20s", "garbage-first heap");
2502   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
2503             capacity()/K, used_unlocked()/K);
2504   st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")",
2505             p2i(_hrm->reserved().start()),
2506             p2i(_hrm->reserved().end()));
2507   st->cr();
2508   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
2509   uint young_regions = young_regions_count();
2510   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
2511             (size_t) young_regions * HeapRegion::GrainBytes / K);
2512   uint survivor_regions = survivor_regions_count();
2513   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
2514             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
2515   st->cr();
2516   if (_numa->is_enabled()) {
2517     uint num_nodes = _numa->num_active_nodes();
2518     st->print("  remaining free region(s) on each NUMA node: ");
2519     const int* node_ids = _numa->node_ids();
2520     for (uint node_index = 0; node_index < num_nodes; node_index++) {
2521       st->print("%d=%u ", node_ids[node_index], _hrm->num_free_regions(node_index));
2522     }
2523     st->cr();
2524   }
2525   MetaspaceUtils::print_on(st);
2526 }
2527 
2528 void G1CollectedHeap::print_regions_on(outputStream* st) const {
2529   st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
2530                "HS=humongous(starts), HC=humongous(continues), "
2531                "CS=collection set, F=free, "
2532                "OA=open archive, CA=closed archive, "
2533                "TAMS=top-at-mark-start (previous, next)");
2534   PrintRegionClosure blk(st);
2535   heap_region_iterate(&blk);
2536 }
2537 
2538 void G1CollectedHeap::print_extended_on(outputStream* st) const {
2539   print_on(st);
2540 
2541   // Print the per-region information.
2542   print_regions_on(st);
2543 }
2544 
2545 void G1CollectedHeap::print_on_error(outputStream* st) const {
2546   this->CollectedHeap::print_on_error(st);
2547 
2548   if (_cm != NULL) {
2549     st->cr();
2550     _cm->print_on_error(st);
2551   }
2552 }
2553 
2554 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
2555   workers()->print_worker_threads_on(st);
2556   _cm_thread->print_on(st);
2557   st->cr();
2558   _cm->print_worker_threads_on(st);
2559   _cr->print_threads_on(st);
2560   _young_gen_sampling_thread->print_on(st);
2561   if (G1StringDedup::is_enabled()) {
2562     G1StringDedup::print_worker_threads_on(st);
2563   }
2564 }
2565 
2566 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2567   workers()->threads_do(tc);
2568   tc->do_thread(_cm_thread);
2569   _cm->threads_do(tc);
2570   _cr->threads_do(tc);
2571   tc->do_thread(_young_gen_sampling_thread);
2572   if (G1StringDedup::is_enabled()) {
2573     G1StringDedup::threads_do(tc);
2574   }
2575 }
2576 
2577 void G1CollectedHeap::print_tracing_info() const {
2578   rem_set()->print_summary_info();
2579   concurrent_mark()->print_summary_info();
2580 }
2581 
2582 #ifndef PRODUCT
2583 // Helpful for debugging RSet issues.
2584 
2585 class PrintRSetsClosure : public HeapRegionClosure {
2586 private:
2587   const char* _msg;
2588   size_t _occupied_sum;
2589 
2590 public:
2591   bool do_heap_region(HeapRegion* r) {
2592     HeapRegionRemSet* hrrs = r->rem_set();
2593     size_t occupied = hrrs->occupied();
2594     _occupied_sum += occupied;
2595 
2596     tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r));
2597     if (occupied == 0) {
2598       tty->print_cr("  RSet is empty");
2599     } else {
2600       hrrs->print();
2601     }
2602     tty->print_cr("----------");
2603     return false;
2604   }
2605 
2606   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
2607     tty->cr();
2608     tty->print_cr("========================================");
2609     tty->print_cr("%s", msg);
2610     tty->cr();
2611   }
2612 
2613   ~PrintRSetsClosure() {
2614     tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
2615     tty->print_cr("========================================");
2616     tty->cr();
2617   }
2618 };
2619 
2620 void G1CollectedHeap::print_cset_rsets() {
2621   PrintRSetsClosure cl("Printing CSet RSets");
2622   collection_set_iterate_all(&cl);
2623 }
2624 
2625 void G1CollectedHeap::print_all_rsets() {
2626   PrintRSetsClosure cl("Printing All RSets");;
2627   heap_region_iterate(&cl);
2628 }
2629 #endif // PRODUCT
2630 
2631 bool G1CollectedHeap::print_location(outputStream* st, void* addr) const {
2632   return BlockLocationPrinter<G1CollectedHeap>::print_location(st, addr);
2633 }
2634 
2635 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
2636 
2637   size_t eden_used_bytes = _eden.used_bytes();
2638   size_t survivor_used_bytes = _survivor.used_bytes();
2639   size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
2640 
2641   size_t eden_capacity_bytes =
2642     (policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
2643 
2644   VirtualSpaceSummary heap_summary = create_heap_space_summary();
2645   return G1HeapSummary(heap_summary, heap_used, eden_used_bytes,
2646                        eden_capacity_bytes, survivor_used_bytes, num_regions());
2647 }
2648 
2649 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
2650   return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
2651                        stats->unused(), stats->used(), stats->region_end_waste(),
2652                        stats->regions_filled(), stats->direct_allocated(),
2653                        stats->failure_used(), stats->failure_waste());
2654 }
2655 
2656 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
2657   const G1HeapSummary& heap_summary = create_g1_heap_summary();
2658   gc_tracer->report_gc_heap_summary(when, heap_summary);
2659 
2660   const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
2661   gc_tracer->report_metaspace_summary(when, metaspace_summary);
2662 }
2663 
2664 G1CollectedHeap* G1CollectedHeap::heap() {
2665   CollectedHeap* heap = Universe::heap();
2666   assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
2667   assert(heap->kind() == CollectedHeap::G1, "Invalid name");
2668   return (G1CollectedHeap*)heap;
2669 }
2670 
2671 void G1CollectedHeap::gc_prologue(bool full) {
2672   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
2673 
2674   // This summary needs to be printed before incrementing total collections.
2675   rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections());
2676 
2677   // Update common counters.
2678   increment_total_collections(full /* full gc */);
2679   if (full || collector_state()->in_initial_mark_gc()) {
2680     increment_old_marking_cycles_started();
2681   }
2682 
2683   // Fill TLAB's and such
2684   double start = os::elapsedTime();
2685   ensure_parsability(true);
2686   phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2687 }
2688 
2689 void G1CollectedHeap::gc_epilogue(bool full) {
2690   // Update common counters.
2691   if (full) {
2692     // Update the number of full collections that have been completed.
2693     increment_old_marking_cycles_completed(false /* concurrent */);
2694   }
2695 
2696   // We are at the end of the GC. Total collections has already been increased.
2697   rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1);
2698 
2699   // FIXME: what is this about?
2700   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
2701   // is set.
2702 #if COMPILER2_OR_JVMCI
2703   assert(DerivedPointerTable::is_empty(), "derived pointer present");
2704 #endif
2705 
2706   double start = os::elapsedTime();
2707   resize_all_tlabs();
2708   phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2709 
2710   MemoryService::track_memory_usage();
2711   // We have just completed a GC. Update the soft reference
2712   // policy with the new heap occupancy
2713   Universe::update_heap_info_at_gc();
2714 
2715   // Print NUMA statistics.
2716   _numa->print_statistics();
2717 }
2718 
2719 void G1CollectedHeap::verify_numa_regions(const char* desc) {
2720   LogTarget(Trace, gc, heap, verify) lt;
2721 
2722   if (lt.is_enabled()) {
2723     LogStream ls(lt);
2724     // Iterate all heap regions to print matching between preferred numa id and actual numa id.
2725     G1NodeIndexCheckClosure cl(desc, _numa, &ls);
2726     heap_region_iterate(&cl);
2727   }
2728 }
2729 
2730 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2731                                                uint gc_count_before,
2732                                                bool* succeeded,
2733                                                GCCause::Cause gc_cause) {
2734   assert_heap_not_locked_and_not_at_safepoint();
2735   VM_G1CollectForAllocation op(word_size,
2736                                gc_count_before,
2737                                gc_cause,
2738                                policy()->max_pause_time_ms());
2739   VMThread::execute(&op);
2740 
2741   HeapWord* result = op.result();
2742   bool ret_succeeded = op.prologue_succeeded() && op.gc_succeeded();
2743   assert(result == NULL || ret_succeeded,
2744          "the result should be NULL if the VM did not succeed");
2745   *succeeded = ret_succeeded;
2746 
2747   assert_heap_not_locked();
2748   return result;
2749 }
2750 
2751 void G1CollectedHeap::do_concurrent_mark() {
2752   MutexLocker x(CGC_lock, Mutex::_no_safepoint_check_flag);
2753   if (!_cm_thread->in_progress()) {
2754     _cm_thread->set_started();
2755     CGC_lock->notify();
2756   }
2757 }
2758 
2759 size_t G1CollectedHeap::pending_card_num() {
2760   struct CountCardsClosure : public ThreadClosure {
2761     size_t _cards;
2762     CountCardsClosure() : _cards(0) {}
2763     virtual void do_thread(Thread* t) {
2764       _cards += G1ThreadLocalData::dirty_card_queue(t).size();
2765     }
2766   } count_from_threads;
2767   Threads::threads_do(&count_from_threads);
2768 
2769   G1DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
2770   dcqs.verify_num_cards();
2771 
2772   return dcqs.num_cards() + count_from_threads._cards;
2773 }
2774 
2775 bool G1CollectedHeap::is_potential_eager_reclaim_candidate(HeapRegion* r) const {
2776   // We don't nominate objects with many remembered set entries, on
2777   // the assumption that such objects are likely still live.
2778   HeapRegionRemSet* rem_set = r->rem_set();
2779 
2780   return G1EagerReclaimHumongousObjectsWithStaleRefs ?
2781          rem_set->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) :
2782          G1EagerReclaimHumongousObjects && rem_set->is_empty();
2783 }
2784 
2785 #ifndef PRODUCT
2786 void G1CollectedHeap::verify_region_attr_remset_update() {
2787   class VerifyRegionAttrRemSet : public HeapRegionClosure {
2788   public:
2789     virtual bool do_heap_region(HeapRegion* r) {
2790       G1CollectedHeap* g1h = G1CollectedHeap::heap();
2791       bool const needs_remset_update = g1h->region_attr(r->bottom()).needs_remset_update();
2792       assert(r->rem_set()->is_tracked() == needs_remset_update,
2793              "Region %u remset tracking status (%s) different to region attribute (%s)",
2794              r->hrm_index(), BOOL_TO_STR(r->rem_set()->is_tracked()), BOOL_TO_STR(needs_remset_update));
2795       return false;
2796     }
2797   } cl;
2798   heap_region_iterate(&cl);
2799 }
2800 #endif
2801 
2802 class VerifyRegionRemSetClosure : public HeapRegionClosure {
2803   public:
2804     bool do_heap_region(HeapRegion* hr) {
2805       if (!hr->is_archive() && !hr->is_continues_humongous()) {
2806         hr->verify_rem_set();
2807       }
2808       return false;
2809     }
2810 };
2811 
2812 uint G1CollectedHeap::num_task_queues() const {
2813   return _task_queues->size();
2814 }
2815 
2816 #if TASKQUEUE_STATS
2817 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
2818   st->print_raw_cr("GC Task Stats");
2819   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
2820   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
2821 }
2822 
2823 void G1CollectedHeap::print_taskqueue_stats() const {
2824   if (!log_is_enabled(Trace, gc, task, stats)) {
2825     return;
2826   }
2827   Log(gc, task, stats) log;
2828   ResourceMark rm;
2829   LogStream ls(log.trace());
2830   outputStream* st = &ls;
2831 
2832   print_taskqueue_stats_hdr(st);
2833 
2834   TaskQueueStats totals;
2835   const uint n = num_task_queues();
2836   for (uint i = 0; i < n; ++i) {
2837     st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
2838     totals += task_queue(i)->stats;
2839   }
2840   st->print_raw("tot "); totals.print(st); st->cr();
2841 
2842   DEBUG_ONLY(totals.verify());
2843 }
2844 
2845 void G1CollectedHeap::reset_taskqueue_stats() {
2846   const uint n = num_task_queues();
2847   for (uint i = 0; i < n; ++i) {
2848     task_queue(i)->stats.reset();
2849   }
2850 }
2851 #endif // TASKQUEUE_STATS
2852 
2853 void G1CollectedHeap::wait_for_root_region_scanning() {
2854   double scan_wait_start = os::elapsedTime();
2855   // We have to wait until the CM threads finish scanning the
2856   // root regions as it's the only way to ensure that all the
2857   // objects on them have been correctly scanned before we start
2858   // moving them during the GC.
2859   bool waited = _cm->root_regions()->wait_until_scan_finished();
2860   double wait_time_ms = 0.0;
2861   if (waited) {
2862     double scan_wait_end = os::elapsedTime();
2863     wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
2864   }
2865   phase_times()->record_root_region_scan_wait_time(wait_time_ms);
2866 }
2867 
2868 class G1PrintCollectionSetClosure : public HeapRegionClosure {
2869 private:
2870   G1HRPrinter* _hr_printer;
2871 public:
2872   G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { }
2873 
2874   virtual bool do_heap_region(HeapRegion* r) {
2875     _hr_printer->cset(r);
2876     return false;
2877   }
2878 };
2879 
2880 void G1CollectedHeap::start_new_collection_set() {
2881   double start = os::elapsedTime();
2882 
2883   collection_set()->start_incremental_building();
2884 
2885   clear_region_attr();
2886 
2887   guarantee(_eden.length() == 0, "eden should have been cleared");
2888   policy()->transfer_survivors_to_cset(survivor());
2889 
2890   // We redo the verification but now wrt to the new CSet which
2891   // has just got initialized after the previous CSet was freed.
2892   _cm->verify_no_collection_set_oops();
2893 
2894   phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0);
2895 }
2896 
2897 void G1CollectedHeap::calculate_collection_set(G1EvacuationInfo& evacuation_info, double target_pause_time_ms) {
2898 
2899   _collection_set.finalize_initial_collection_set(target_pause_time_ms, &_survivor);
2900   evacuation_info.set_collectionset_regions(collection_set()->region_length() +
2901                                             collection_set()->optional_region_length());
2902 
2903   _cm->verify_no_collection_set_oops();
2904 
2905   if (_hr_printer.is_active()) {
2906     G1PrintCollectionSetClosure cl(&_hr_printer);
2907     _collection_set.iterate(&cl);
2908     _collection_set.iterate_optional(&cl);
2909   }
2910 }
2911 
2912 G1HeapVerifier::G1VerifyType G1CollectedHeap::young_collection_verify_type() const {
2913   if (collector_state()->in_initial_mark_gc()) {
2914     return G1HeapVerifier::G1VerifyConcurrentStart;
2915   } else if (collector_state()->in_young_only_phase()) {
2916     return G1HeapVerifier::G1VerifyYoungNormal;
2917   } else {
2918     return G1HeapVerifier::G1VerifyMixed;
2919   }
2920 }
2921 
2922 void G1CollectedHeap::verify_before_young_collection(G1HeapVerifier::G1VerifyType type) {
2923   if (VerifyRememberedSets) {
2924     log_info(gc, verify)("[Verifying RemSets before GC]");
2925     VerifyRegionRemSetClosure v_cl;
2926     heap_region_iterate(&v_cl);
2927   }
2928   _verifier->verify_before_gc(type);
2929   _verifier->check_bitmaps("GC Start");
2930   verify_numa_regions("GC Start");
2931 }
2932 
2933 void G1CollectedHeap::verify_after_young_collection(G1HeapVerifier::G1VerifyType type) {
2934   if (VerifyRememberedSets) {
2935     log_info(gc, verify)("[Verifying RemSets after GC]");
2936     VerifyRegionRemSetClosure v_cl;
2937     heap_region_iterate(&v_cl);
2938   }
2939   _verifier->verify_after_gc(type);
2940   _verifier->check_bitmaps("GC End");
2941   verify_numa_regions("GC End");
2942 }
2943 
2944 void G1CollectedHeap::expand_heap_after_young_collection(){
2945   size_t expand_bytes = _heap_sizing_policy->expansion_amount();
2946   if (expand_bytes > 0) {
2947     // No need for an ergo logging here,
2948     // expansion_amount() does this when it returns a value > 0.
2949     double expand_ms;
2950     if (!expand(expand_bytes, _workers, &expand_ms)) {
2951       // We failed to expand the heap. Cannot do anything about it.
2952     }
2953     phase_times()->record_expand_heap_time(expand_ms);
2954   }
2955 }
2956 
2957 const char* G1CollectedHeap::young_gc_name() const {
2958   if (collector_state()->in_initial_mark_gc()) {
2959     return "Pause Young (Concurrent Start)";
2960   } else if (collector_state()->in_young_only_phase()) {
2961     if (collector_state()->in_young_gc_before_mixed()) {
2962       return "Pause Young (Prepare Mixed)";
2963     } else {
2964       return "Pause Young (Normal)";
2965     }
2966   } else {
2967     return "Pause Young (Mixed)";
2968   }
2969 }
2970 
2971 bool G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
2972   assert_at_safepoint_on_vm_thread();
2973   guarantee(!is_gc_active(), "collection is not reentrant");
2974 
2975   if (GCLocker::check_active_before_gc()) {
2976     return false;
2977   }
2978 
2979   GCIdMark gc_id_mark;
2980 
2981   SvcGCMarker sgcm(SvcGCMarker::MINOR);
2982   ResourceMark rm;
2983 
2984   policy()->note_gc_start();
2985 
2986   _gc_timer_stw->register_gc_start();
2987   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
2988 
2989   wait_for_root_region_scanning();
2990 
2991   print_heap_before_gc();
2992   print_heap_regions();
2993   trace_heap_before_gc(_gc_tracer_stw);
2994 
2995   _verifier->verify_region_sets_optional();
2996   _verifier->verify_dirty_young_regions();
2997 
2998   // We should not be doing initial mark unless the conc mark thread is running
2999   if (!_cm_thread->should_terminate()) {
3000     // This call will decide whether this pause is an initial-mark
3001     // pause. If it is, in_initial_mark_gc() will return true
3002     // for the duration of this pause.
3003     policy()->decide_on_conc_mark_initiation();
3004   }
3005 
3006   // We do not allow initial-mark to be piggy-backed on a mixed GC.
3007   assert(!collector_state()->in_initial_mark_gc() ||
3008          collector_state()->in_young_only_phase(), "sanity");
3009   // We also do not allow mixed GCs during marking.
3010   assert(!collector_state()->mark_or_rebuild_in_progress() || collector_state()->in_young_only_phase(), "sanity");
3011 
3012   // Record whether this pause is an initial mark. When the current
3013   // thread has completed its logging output and it's safe to signal
3014   // the CM thread, the flag's value in the policy has been reset.
3015   bool should_start_conc_mark = collector_state()->in_initial_mark_gc();
3016   if (should_start_conc_mark) {
3017     _cm->gc_tracer_cm()->set_gc_cause(gc_cause());
3018   }
3019 
3020   // Inner scope for scope based logging, timers, and stats collection
3021   {
3022     G1EvacuationInfo evacuation_info;
3023 
3024     _gc_tracer_stw->report_yc_type(collector_state()->yc_type());
3025 
3026     GCTraceCPUTime tcpu;
3027 
3028     GCTraceTime(Info, gc) tm(young_gc_name(), NULL, gc_cause(), true);
3029 
3030     uint active_workers = WorkerPolicy::calc_active_workers(workers()->total_workers(),
3031                                                             workers()->active_workers(),
3032                                                             Threads::number_of_non_daemon_threads());
3033     active_workers = workers()->update_active_workers(active_workers);
3034     log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers());
3035 
3036     G1MonitoringScope ms(g1mm(),
3037                          false /* full_gc */,
3038                          collector_state()->yc_type() == Mixed /* all_memory_pools_affected */);
3039 
3040     G1HeapTransition heap_transition(this);
3041 
3042     {
3043       IsGCActiveMark x;
3044 
3045       gc_prologue(false);
3046 
3047       G1HeapVerifier::G1VerifyType verify_type = young_collection_verify_type();
3048       verify_before_young_collection(verify_type);
3049 
3050       {
3051         // The elapsed time induced by the start time below deliberately elides
3052         // the possible verification above.
3053         double sample_start_time_sec = os::elapsedTime();
3054 
3055         // Please see comment in g1CollectedHeap.hpp and
3056         // G1CollectedHeap::ref_processing_init() to see how
3057         // reference processing currently works in G1.
3058         _ref_processor_stw->enable_discovery();
3059 
3060         // We want to temporarily turn off discovery by the
3061         // CM ref processor, if necessary, and turn it back on
3062         // on again later if we do. Using a scoped
3063         // NoRefDiscovery object will do this.
3064         NoRefDiscovery no_cm_discovery(_ref_processor_cm);
3065 
3066         policy()->record_collection_pause_start(sample_start_time_sec);
3067 
3068         // Forget the current allocation region (we might even choose it to be part
3069         // of the collection set!).
3070         _allocator->release_mutator_alloc_regions();
3071 
3072         calculate_collection_set(evacuation_info, target_pause_time_ms);
3073 
3074         G1RedirtyCardsQueueSet rdcqs(G1BarrierSet::dirty_card_queue_set().allocator());
3075         G1ParScanThreadStateSet per_thread_states(this,
3076                                                   &rdcqs,
3077                                                   workers()->active_workers(),
3078                                                   collection_set()->young_region_length(),
3079                                                   collection_set()->optional_region_length());
3080         pre_evacuate_collection_set(evacuation_info, &per_thread_states);
3081 
3082         // Actually do the work...
3083         evacuate_initial_collection_set(&per_thread_states);
3084 
3085         if (_collection_set.optional_region_length() != 0) {
3086           evacuate_optional_collection_set(&per_thread_states);
3087         }
3088         post_evacuate_collection_set(evacuation_info, &rdcqs, &per_thread_states);
3089 
3090         start_new_collection_set();
3091 
3092         _survivor_evac_stats.adjust_desired_plab_sz();
3093         _old_evac_stats.adjust_desired_plab_sz();
3094 
3095         if (should_start_conc_mark) {
3096           // We have to do this before we notify the CM threads that
3097           // they can start working to make sure that all the
3098           // appropriate initialization is done on the CM object.
3099           concurrent_mark()->post_initial_mark();
3100           // Note that we don't actually trigger the CM thread at
3101           // this point. We do that later when we're sure that
3102           // the current thread has completed its logging output.
3103         }
3104 
3105         allocate_dummy_regions();
3106 
3107         _allocator->init_mutator_alloc_regions();
3108 
3109         expand_heap_after_young_collection();
3110 
3111         double sample_end_time_sec = os::elapsedTime();
3112         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3113         policy()->record_collection_pause_end(pause_time_ms);
3114       }
3115 
3116       verify_after_young_collection(verify_type);
3117 
3118 #ifdef TRACESPINNING
3119       ParallelTaskTerminator::print_termination_counts();
3120 #endif
3121 
3122       gc_epilogue(false);
3123     }
3124 
3125     // Print the remainder of the GC log output.
3126     if (evacuation_failed()) {
3127       log_info(gc)("To-space exhausted");
3128     }
3129 
3130     policy()->print_phases();
3131     heap_transition.print();
3132 
3133     _hrm->verify_optional();
3134     _verifier->verify_region_sets_optional();
3135 
3136     TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
3137     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3138 
3139     print_heap_after_gc();
3140     print_heap_regions();
3141     trace_heap_after_gc(_gc_tracer_stw);
3142 
3143     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3144     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3145     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3146     // before any GC notifications are raised.
3147     g1mm()->update_sizes();
3148 
3149     _gc_tracer_stw->report_evacuation_info(&evacuation_info);
3150     _gc_tracer_stw->report_tenuring_threshold(_policy->tenuring_threshold());
3151     _gc_timer_stw->register_gc_end();
3152     _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
3153   }
3154   // It should now be safe to tell the concurrent mark thread to start
3155   // without its logging output interfering with the logging output
3156   // that came from the pause.
3157 
3158   if (should_start_conc_mark) {
3159     // CAUTION: after the doConcurrentMark() call below, the concurrent marking
3160     // thread(s) could be running concurrently with us. Make sure that anything
3161     // after this point does not assume that we are the only GC thread running.
3162     // Note: of course, the actual marking work will not start until the safepoint
3163     // itself is released in SuspendibleThreadSet::desynchronize().
3164     do_concurrent_mark();
3165   }
3166 
3167   return true;
3168 }
3169 
3170 void G1CollectedHeap::remove_self_forwarding_pointers(G1RedirtyCardsQueueSet* rdcqs) {
3171   G1ParRemoveSelfForwardPtrsTask rsfp_task(rdcqs);
3172   workers()->run_task(&rsfp_task);
3173 }
3174 
3175 void G1CollectedHeap::restore_after_evac_failure(G1RedirtyCardsQueueSet* rdcqs) {
3176   double remove_self_forwards_start = os::elapsedTime();
3177 
3178   remove_self_forwarding_pointers(rdcqs);
3179   SharedRestorePreservedMarksTaskExecutor task_executor(workers());
3180   _preserved_marks_set.restore(&task_executor);
3181 
3182   phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
3183 }
3184 
3185 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markWord m) {
3186   if (!_evacuation_failed) {
3187     _evacuation_failed = true;
3188   }
3189 
3190   _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size());
3191   _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m);
3192 }
3193 
3194 bool G1ParEvacuateFollowersClosure::offer_termination() {
3195   EventGCPhaseParallel event;
3196   G1ParScanThreadState* const pss = par_scan_state();
3197   start_term_time();
3198   const bool res = terminator()->offer_termination();
3199   end_term_time();
3200   event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(G1GCPhaseTimes::Termination));
3201   return res;
3202 }
3203 
3204 void G1ParEvacuateFollowersClosure::do_void() {
3205   EventGCPhaseParallel event;
3206   G1ParScanThreadState* const pss = par_scan_state();
3207   pss->trim_queue();
3208   event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(_phase));
3209   do {
3210     EventGCPhaseParallel event;
3211     pss->steal_and_trim_queue(queues());
3212     event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(_phase));
3213   } while (!offer_termination());
3214 }
3215 
3216 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive,
3217                                         bool class_unloading_occurred) {
3218   uint num_workers = workers()->active_workers();
3219   G1ParallelCleaningTask unlink_task(is_alive, num_workers, class_unloading_occurred, false);
3220   workers()->run_task(&unlink_task);
3221 }
3222 
3223 // Clean string dedup data structures.
3224 // Ideally we would prefer to use a StringDedupCleaningTask here, but we want to
3225 // record the durations of the phases. Hence the almost-copy.
3226 class G1StringDedupCleaningTask : public AbstractGangTask {
3227   BoolObjectClosure* _is_alive;
3228   OopClosure* _keep_alive;
3229   G1GCPhaseTimes* _phase_times;
3230 
3231 public:
3232   G1StringDedupCleaningTask(BoolObjectClosure* is_alive,
3233                             OopClosure* keep_alive,
3234                             G1GCPhaseTimes* phase_times) :
3235     AbstractGangTask("Partial Cleaning Task"),
3236     _is_alive(is_alive),
3237     _keep_alive(keep_alive),
3238     _phase_times(phase_times)
3239   {
3240     assert(G1StringDedup::is_enabled(), "String deduplication disabled.");
3241     StringDedup::gc_prologue(true);
3242   }
3243 
3244   ~G1StringDedupCleaningTask() {
3245     StringDedup::gc_epilogue();
3246   }
3247 
3248   void work(uint worker_id) {
3249     StringDedupUnlinkOrOopsDoClosure cl(_is_alive, _keep_alive);
3250     {
3251       G1GCParPhaseTimesTracker x(_phase_times, G1GCPhaseTimes::StringDedupQueueFixup, worker_id);
3252       StringDedupQueue::unlink_or_oops_do(&cl);
3253     }
3254     {
3255       G1GCParPhaseTimesTracker x(_phase_times, G1GCPhaseTimes::StringDedupTableFixup, worker_id);
3256       StringDedupTable::unlink_or_oops_do(&cl, worker_id);
3257     }
3258   }
3259 };
3260 
3261 void G1CollectedHeap::string_dedup_cleaning(BoolObjectClosure* is_alive,
3262                                             OopClosure* keep_alive,
3263                                             G1GCPhaseTimes* phase_times) {
3264   G1StringDedupCleaningTask cl(is_alive, keep_alive, phase_times);
3265   workers()->run_task(&cl);
3266 }
3267 
3268 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
3269  private:
3270   G1RedirtyCardsQueueSet* _qset;
3271   G1CollectedHeap* _g1h;
3272   BufferNode* volatile _nodes;
3273 
3274   void par_apply(RedirtyLoggedCardTableEntryClosure* cl, uint worker_id) {
3275     size_t buffer_size = _qset->buffer_size();
3276     BufferNode* next = Atomic::load(&_nodes);
3277     while (next != NULL) {
3278       BufferNode* node = next;
3279       next = Atomic::cmpxchg(&_nodes, node, node->next());
3280       if (next == node) {
3281         cl->apply_to_buffer(node, buffer_size, worker_id);
3282         next = node->next();
3283       }
3284     }
3285   }
3286 
3287  public:
3288   G1RedirtyLoggedCardsTask(G1RedirtyCardsQueueSet* qset, G1CollectedHeap* g1h) :
3289     AbstractGangTask("Redirty Cards"),
3290     _qset(qset), _g1h(g1h), _nodes(qset->all_completed_buffers()) { }
3291 
3292   virtual void work(uint worker_id) {
3293     G1GCPhaseTimes* p = _g1h->phase_times();
3294     G1GCParPhaseTimesTracker x(p, G1GCPhaseTimes::RedirtyCards, worker_id);
3295 
3296     RedirtyLoggedCardTableEntryClosure cl(_g1h);
3297     par_apply(&cl, worker_id);
3298 
3299     p->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied());
3300   }
3301 };
3302 
3303 void G1CollectedHeap::redirty_logged_cards(G1RedirtyCardsQueueSet* rdcqs) {
3304   double redirty_logged_cards_start = os::elapsedTime();
3305 
3306   G1RedirtyLoggedCardsTask redirty_task(rdcqs, this);
3307   workers()->run_task(&redirty_task);
3308 
3309   G1DirtyCardQueueSet& dcq = G1BarrierSet::dirty_card_queue_set();
3310   dcq.merge_bufferlists(rdcqs);
3311 
3312   phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
3313 }
3314 
3315 // Weak Reference Processing support
3316 
3317 bool G1STWIsAliveClosure::do_object_b(oop p) {
3318   // An object is reachable if it is outside the collection set,
3319   // or is inside and copied.
3320   return !_g1h->is_in_cset(p) || p->is_forwarded();
3321 }
3322 
3323 bool G1STWSubjectToDiscoveryClosure::do_object_b(oop obj) {
3324   assert(obj != NULL, "must not be NULL");
3325   assert(_g1h->is_in_reserved(obj), "Trying to discover obj " PTR_FORMAT " not in heap", p2i(obj));
3326   // The areas the CM and STW ref processor manage must be disjoint. The is_in_cset() below
3327   // may falsely indicate that this is not the case here: however the collection set only
3328   // contains old regions when concurrent mark is not running.
3329   return _g1h->is_in_cset(obj) || _g1h->heap_region_containing(obj)->is_survivor();
3330 }
3331 
3332 // Non Copying Keep Alive closure
3333 class G1KeepAliveClosure: public OopClosure {
3334   G1CollectedHeap*_g1h;
3335 public:
3336   G1KeepAliveClosure(G1CollectedHeap* g1h) :_g1h(g1h) {}
3337   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
3338   void do_oop(oop* p) {
3339     oop obj = *p;
3340     assert(obj != NULL, "the caller should have filtered out NULL values");
3341 
3342     const G1HeapRegionAttr region_attr =_g1h->region_attr(obj);
3343     if (!region_attr.is_in_cset_or_humongous()) {
3344       return;
3345     }
3346     if (region_attr.is_in_cset()) {
3347       assert( obj->is_forwarded(), "invariant" );
3348       *p = obj->forwardee();
3349     } else {
3350       assert(!obj->is_forwarded(), "invariant" );
3351       assert(region_attr.is_humongous(),
3352              "Only allowed G1HeapRegionAttr state is IsHumongous, but is %d", region_attr.type());
3353      _g1h->set_humongous_is_live(obj);
3354     }
3355   }
3356 };
3357 
3358 // Copying Keep Alive closure - can be called from both
3359 // serial and parallel code as long as different worker
3360 // threads utilize different G1ParScanThreadState instances
3361 // and different queues.
3362 
3363 class G1CopyingKeepAliveClosure: public OopClosure {
3364   G1CollectedHeap*         _g1h;
3365   G1ParScanThreadState*    _par_scan_state;
3366 
3367 public:
3368   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
3369                             G1ParScanThreadState* pss):
3370     _g1h(g1h),
3371     _par_scan_state(pss)
3372   {}
3373 
3374   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
3375   virtual void do_oop(      oop* p) { do_oop_work(p); }
3376 
3377   template <class T> void do_oop_work(T* p) {
3378     oop obj = RawAccess<>::oop_load(p);
3379 
3380     if (_g1h->is_in_cset_or_humongous(obj)) {
3381       // If the referent object has been forwarded (either copied
3382       // to a new location or to itself in the event of an
3383       // evacuation failure) then we need to update the reference
3384       // field and, if both reference and referent are in the G1
3385       // heap, update the RSet for the referent.
3386       //
3387       // If the referent has not been forwarded then we have to keep
3388       // it alive by policy. Therefore we have copy the referent.
3389       //
3390       // When the queue is drained (after each phase of reference processing)
3391       // the object and it's followers will be copied, the reference field set
3392       // to point to the new location, and the RSet updated.
3393       _par_scan_state->push_on_queue(p);
3394     }
3395   }
3396 };
3397 
3398 // Serial drain queue closure. Called as the 'complete_gc'
3399 // closure for each discovered list in some of the
3400 // reference processing phases.
3401 
3402 class G1STWDrainQueueClosure: public VoidClosure {
3403 protected:
3404   G1CollectedHeap* _g1h;
3405   G1ParScanThreadState* _par_scan_state;
3406 
3407   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
3408 
3409 public:
3410   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
3411     _g1h(g1h),
3412     _par_scan_state(pss)
3413   { }
3414 
3415   void do_void() {
3416     G1ParScanThreadState* const pss = par_scan_state();
3417     pss->trim_queue();
3418   }
3419 };
3420 
3421 // Parallel Reference Processing closures
3422 
3423 // Implementation of AbstractRefProcTaskExecutor for parallel reference
3424 // processing during G1 evacuation pauses.
3425 
3426 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
3427 private:
3428   G1CollectedHeap*          _g1h;
3429   G1ParScanThreadStateSet*  _pss;
3430   RefToScanQueueSet*        _queues;
3431   WorkGang*                 _workers;
3432 
3433 public:
3434   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
3435                            G1ParScanThreadStateSet* per_thread_states,
3436                            WorkGang* workers,
3437                            RefToScanQueueSet *task_queues) :
3438     _g1h(g1h),
3439     _pss(per_thread_states),
3440     _queues(task_queues),
3441     _workers(workers)
3442   {
3443     g1h->ref_processor_stw()->set_active_mt_degree(workers->active_workers());
3444   }
3445 
3446   // Executes the given task using concurrent marking worker threads.
3447   virtual void execute(ProcessTask& task, uint ergo_workers);
3448 };
3449 
3450 // Gang task for possibly parallel reference processing
3451 
3452 class G1STWRefProcTaskProxy: public AbstractGangTask {
3453   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
3454   ProcessTask&     _proc_task;
3455   G1CollectedHeap* _g1h;
3456   G1ParScanThreadStateSet* _pss;
3457   RefToScanQueueSet* _task_queues;
3458   ParallelTaskTerminator* _terminator;
3459 
3460 public:
3461   G1STWRefProcTaskProxy(ProcessTask& proc_task,
3462                         G1CollectedHeap* g1h,
3463                         G1ParScanThreadStateSet* per_thread_states,
3464                         RefToScanQueueSet *task_queues,
3465                         ParallelTaskTerminator* terminator) :
3466     AbstractGangTask("Process reference objects in parallel"),
3467     _proc_task(proc_task),
3468     _g1h(g1h),
3469     _pss(per_thread_states),
3470     _task_queues(task_queues),
3471     _terminator(terminator)
3472   {}
3473 
3474   virtual void work(uint worker_id) {
3475     // The reference processing task executed by a single worker.
3476     ResourceMark rm;
3477     HandleMark   hm;
3478 
3479     G1STWIsAliveClosure is_alive(_g1h);
3480 
3481     G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
3482     pss->set_ref_discoverer(NULL);
3483 
3484     // Keep alive closure.
3485     G1CopyingKeepAliveClosure keep_alive(_g1h, pss);
3486 
3487     // Complete GC closure
3488     G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator, G1GCPhaseTimes::ObjCopy);
3489 
3490     // Call the reference processing task's work routine.
3491     _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
3492 
3493     // Note we cannot assert that the refs array is empty here as not all
3494     // of the processing tasks (specifically phase2 - pp2_work) execute
3495     // the complete_gc closure (which ordinarily would drain the queue) so
3496     // the queue may not be empty.
3497   }
3498 };
3499 
3500 // Driver routine for parallel reference processing.
3501 // Creates an instance of the ref processing gang
3502 // task and has the worker threads execute it.
3503 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task, uint ergo_workers) {
3504   assert(_workers != NULL, "Need parallel worker threads.");
3505 
3506   assert(_workers->active_workers() >= ergo_workers,
3507          "Ergonomically chosen workers (%u) should be less than or equal to active workers (%u)",
3508          ergo_workers, _workers->active_workers());
3509   TaskTerminator terminator(ergo_workers, _queues);
3510   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, terminator.terminator());
3511 
3512   _workers->run_task(&proc_task_proxy, ergo_workers);
3513 }
3514 
3515 // End of weak reference support closures
3516 
3517 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
3518   double ref_proc_start = os::elapsedTime();
3519 
3520   ReferenceProcessor* rp = _ref_processor_stw;
3521   assert(rp->discovery_enabled(), "should have been enabled");
3522 
3523   // Closure to test whether a referent is alive.
3524   G1STWIsAliveClosure is_alive(this);
3525 
3526   // Even when parallel reference processing is enabled, the processing
3527   // of JNI refs is serial and performed serially by the current thread
3528   // rather than by a worker. The following PSS will be used for processing
3529   // JNI refs.
3530 
3531   // Use only a single queue for this PSS.
3532   G1ParScanThreadState*          pss = per_thread_states->state_for_worker(0);
3533   pss->set_ref_discoverer(NULL);
3534   assert(pss->queue_is_empty(), "pre-condition");
3535 
3536   // Keep alive closure.
3537   G1CopyingKeepAliveClosure keep_alive(this, pss);
3538 
3539   // Serial Complete GC closure
3540   G1STWDrainQueueClosure drain_queue(this, pss);
3541 
3542   // Setup the soft refs policy...
3543   rp->setup_policy(false);
3544 
3545   ReferenceProcessorPhaseTimes* pt = phase_times()->ref_phase_times();
3546 
3547   ReferenceProcessorStats stats;
3548   if (!rp->processing_is_mt()) {
3549     // Serial reference processing...
3550     stats = rp->process_discovered_references(&is_alive,
3551                                               &keep_alive,
3552                                               &drain_queue,
3553                                               NULL,
3554                                               pt);
3555   } else {
3556     uint no_of_gc_workers = workers()->active_workers();
3557 
3558     // Parallel reference processing
3559     assert(no_of_gc_workers <= rp->max_num_queues(),
3560            "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
3561            no_of_gc_workers,  rp->max_num_queues());
3562 
3563     G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues);
3564     stats = rp->process_discovered_references(&is_alive,
3565                                               &keep_alive,
3566                                               &drain_queue,
3567                                               &par_task_executor,
3568                                               pt);
3569   }
3570 
3571   _gc_tracer_stw->report_gc_reference_stats(stats);
3572 
3573   // We have completed copying any necessary live referent objects.
3574   assert(pss->queue_is_empty(), "both queue and overflow should be empty");
3575 
3576   make_pending_list_reachable();
3577 
3578   assert(!rp->discovery_enabled(), "Postcondition");
3579   rp->verify_no_references_recorded();
3580 
3581   double ref_proc_time = os::elapsedTime() - ref_proc_start;
3582   phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
3583 }
3584 
3585 void G1CollectedHeap::make_pending_list_reachable() {
3586   if (collector_state()->in_initial_mark_gc()) {
3587     oop pll_head = Universe::reference_pending_list();
3588     if (pll_head != NULL) {
3589       // Any valid worker id is fine here as we are in the VM thread and single-threaded.
3590       _cm->mark_in_next_bitmap(0 /* worker_id */, pll_head);
3591     }
3592   }
3593 }
3594 
3595 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) {
3596   Ticks start = Ticks::now();
3597   per_thread_states->flush();
3598   phase_times()->record_or_add_time_secs(G1GCPhaseTimes::MergePSS, 0 /* worker_id */, (Ticks::now() - start).seconds());
3599 }
3600 
3601 class G1PrepareEvacuationTask : public AbstractGangTask {
3602   class G1PrepareRegionsClosure : public HeapRegionClosure {
3603     G1CollectedHeap* _g1h;
3604     G1PrepareEvacuationTask* _parent_task;
3605     size_t _worker_humongous_total;
3606     size_t _worker_humongous_candidates;
3607 
3608     bool humongous_region_is_candidate(HeapRegion* region) const {
3609       assert(region->is_starts_humongous(), "Must start a humongous object");
3610 
3611       oop obj = oop(region->bottom());
3612 
3613       // Dead objects cannot be eager reclaim candidates. Due to class
3614       // unloading it is unsafe to query their classes so we return early.
3615       if (_g1h->is_obj_dead(obj, region)) {
3616         return false;
3617       }
3618 
3619       // If we do not have a complete remembered set for the region, then we can
3620       // not be sure that we have all references to it.
3621       if (!region->rem_set()->is_complete()) {
3622         return false;
3623       }
3624       // Candidate selection must satisfy the following constraints
3625       // while concurrent marking is in progress:
3626       //
3627       // * In order to maintain SATB invariants, an object must not be
3628       // reclaimed if it was allocated before the start of marking and
3629       // has not had its references scanned.  Such an object must have
3630       // its references (including type metadata) scanned to ensure no
3631       // live objects are missed by the marking process.  Objects
3632       // allocated after the start of concurrent marking don't need to
3633       // be scanned.
3634       //
3635       // * An object must not be reclaimed if it is on the concurrent
3636       // mark stack.  Objects allocated after the start of concurrent
3637       // marking are never pushed on the mark stack.
3638       //
3639       // Nominating only objects allocated after the start of concurrent
3640       // marking is sufficient to meet both constraints.  This may miss
3641       // some objects that satisfy the constraints, but the marking data
3642       // structures don't support efficiently performing the needed
3643       // additional tests or scrubbing of the mark stack.
3644       //
3645       // However, we presently only nominate is_typeArray() objects.
3646       // A humongous object containing references induces remembered
3647       // set entries on other regions.  In order to reclaim such an
3648       // object, those remembered sets would need to be cleaned up.
3649       //
3650       // We also treat is_typeArray() objects specially, allowing them
3651       // to be reclaimed even if allocated before the start of
3652       // concurrent mark.  For this we rely on mark stack insertion to
3653       // exclude is_typeArray() objects, preventing reclaiming an object
3654       // that is in the mark stack.  We also rely on the metadata for
3655       // such objects to be built-in and so ensured to be kept live.
3656       // Frequent allocation and drop of large binary blobs is an
3657       // important use case for eager reclaim, and this special handling
3658       // may reduce needed headroom.
3659 
3660       return obj->is_typeArray() &&
3661              _g1h->is_potential_eager_reclaim_candidate(region);
3662     }
3663 
3664   public:
3665     G1PrepareRegionsClosure(G1CollectedHeap* g1h, G1PrepareEvacuationTask* parent_task) :
3666       _g1h(g1h),
3667       _parent_task(parent_task),
3668       _worker_humongous_total(0),
3669       _worker_humongous_candidates(0) { }
3670 
3671     ~G1PrepareRegionsClosure() {
3672       _parent_task->add_humongous_candidates(_worker_humongous_candidates);
3673       _parent_task->add_humongous_total(_worker_humongous_total);
3674     }
3675 
3676     virtual bool do_heap_region(HeapRegion* hr) {
3677       // First prepare the region for scanning
3678       _g1h->rem_set()->prepare_region_for_scan(hr);
3679 
3680       // Now check if region is a humongous candidate
3681       if (!hr->is_starts_humongous()) {
3682         _g1h->register_region_with_region_attr(hr);
3683         return false;
3684       }
3685 
3686       uint index = hr->hrm_index();
3687       if (humongous_region_is_candidate(hr)) {
3688         _g1h->set_humongous_reclaim_candidate(index, true);
3689         _g1h->register_humongous_region_with_region_attr(index);
3690         _worker_humongous_candidates++;
3691         // We will later handle the remembered sets of these regions.
3692       } else {
3693         _g1h->set_humongous_reclaim_candidate(index, false);
3694         _g1h->register_region_with_region_attr(hr);
3695       }
3696       _worker_humongous_total++;
3697 
3698       return false;
3699     }
3700   };
3701 
3702   G1CollectedHeap* _g1h;
3703   HeapRegionClaimer _claimer;
3704   volatile size_t _humongous_total;
3705   volatile size_t _humongous_candidates;
3706 public:
3707   G1PrepareEvacuationTask(G1CollectedHeap* g1h) :
3708     AbstractGangTask("Prepare Evacuation"),
3709     _g1h(g1h),
3710     _claimer(_g1h->workers()->active_workers()),
3711     _humongous_total(0),
3712     _humongous_candidates(0) { }
3713 
3714   ~G1PrepareEvacuationTask() {
3715     _g1h->set_has_humongous_reclaim_candidate(_humongous_candidates > 0);
3716   }
3717 
3718   void work(uint worker_id) {
3719     G1PrepareRegionsClosure cl(_g1h, this);
3720     _g1h->heap_region_par_iterate_from_worker_offset(&cl, &_claimer, worker_id);
3721   }
3722 
3723   void add_humongous_candidates(size_t candidates) {
3724     Atomic::add(&_humongous_candidates, candidates);
3725   }
3726 
3727   void add_humongous_total(size_t total) {
3728     Atomic::add(&_humongous_total, total);
3729   }
3730 
3731   size_t humongous_candidates() {
3732     return _humongous_candidates;
3733   }
3734 
3735   size_t humongous_total() {
3736     return _humongous_total;
3737   }
3738 };
3739 
3740 void G1CollectedHeap::pre_evacuate_collection_set(G1EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
3741   _bytes_used_during_gc = 0;
3742 
3743   _expand_heap_after_alloc_failure = true;
3744   _evacuation_failed = false;
3745 
3746   // Disable the hot card cache.
3747   _hot_card_cache->reset_hot_cache_claimed_index();
3748   _hot_card_cache->set_use_cache(false);
3749 
3750   // Initialize the GC alloc regions.
3751   _allocator->init_gc_alloc_regions(evacuation_info);
3752 
3753   {
3754     Ticks start = Ticks::now();
3755     rem_set()->prepare_for_scan_heap_roots();
3756     phase_times()->record_prepare_heap_roots_time_ms((Ticks::now() - start).seconds() * 1000.0);
3757   }
3758 
3759   {
3760     G1PrepareEvacuationTask g1_prep_task(this);
3761     Tickspan task_time = run_task(&g1_prep_task);
3762 
3763     phase_times()->record_register_regions(task_time.seconds() * 1000.0,
3764                                            g1_prep_task.humongous_total(),
3765                                            g1_prep_task.humongous_candidates());
3766   }
3767 
3768   assert(_verifier->check_region_attr_table(), "Inconsistency in the region attributes table.");
3769   _preserved_marks_set.assert_empty();
3770 
3771 #if COMPILER2_OR_JVMCI
3772   DerivedPointerTable::clear();
3773 #endif
3774 
3775   // InitialMark needs claim bits to keep track of the marked-through CLDs.
3776   if (collector_state()->in_initial_mark_gc()) {
3777     concurrent_mark()->pre_initial_mark();
3778 
3779     double start_clear_claimed_marks = os::elapsedTime();
3780 
3781     ClassLoaderDataGraph::clear_claimed_marks();
3782 
3783     double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0;
3784     phase_times()->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms);
3785   }
3786 
3787   // Should G1EvacuationFailureALot be in effect for this GC?
3788   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
3789 }
3790 
3791 class G1EvacuateRegionsBaseTask : public AbstractGangTask {
3792 protected:
3793   G1CollectedHeap* _g1h;
3794   G1ParScanThreadStateSet* _per_thread_states;
3795   RefToScanQueueSet* _task_queues;
3796   TaskTerminator _terminator;
3797   uint _num_workers;
3798 
3799   void evacuate_live_objects(G1ParScanThreadState* pss,
3800                              uint worker_id,
3801                              G1GCPhaseTimes::GCParPhases objcopy_phase,
3802                              G1GCPhaseTimes::GCParPhases termination_phase) {
3803     G1GCPhaseTimes* p = _g1h->phase_times();
3804 
3805     Ticks start = Ticks::now();
3806     G1ParEvacuateFollowersClosure cl(_g1h, pss, _task_queues, _terminator.terminator(), objcopy_phase);
3807     cl.do_void();
3808 
3809     assert(pss->queue_is_empty(), "should be empty");
3810 
3811     Tickspan evac_time = (Ticks::now() - start);
3812     p->record_or_add_time_secs(objcopy_phase, worker_id, evac_time.seconds() - cl.term_time());
3813 
3814     if (termination_phase == G1GCPhaseTimes::Termination) {
3815       p->record_time_secs(termination_phase, worker_id, cl.term_time());
3816       p->record_thread_work_item(termination_phase, worker_id, cl.term_attempts());
3817     } else {
3818       p->record_or_add_time_secs(termination_phase, worker_id, cl.term_time());
3819       p->record_or_add_thread_work_item(termination_phase, worker_id, cl.term_attempts());
3820     }
3821     assert(pss->trim_ticks().seconds() == 0.0, "Unexpected partial trimming during evacuation");
3822   }
3823 
3824   virtual void start_work(uint worker_id) { }
3825 
3826   virtual void end_work(uint worker_id) { }
3827 
3828   virtual void scan_roots(G1ParScanThreadState* pss, uint worker_id) = 0;
3829 
3830   virtual void evacuate_live_objects(G1ParScanThreadState* pss, uint worker_id) = 0;
3831 
3832 public:
3833   G1EvacuateRegionsBaseTask(const char* name, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet* task_queues, uint num_workers) :
3834     AbstractGangTask(name),
3835     _g1h(G1CollectedHeap::heap()),
3836     _per_thread_states(per_thread_states),
3837     _task_queues(task_queues),
3838     _terminator(num_workers, _task_queues),
3839     _num_workers(num_workers)
3840   { }
3841 
3842   void work(uint worker_id) {
3843     start_work(worker_id);
3844 
3845     {
3846       ResourceMark rm;
3847       HandleMark   hm;
3848 
3849       G1ParScanThreadState* pss = _per_thread_states->state_for_worker(worker_id);
3850       pss->set_ref_discoverer(_g1h->ref_processor_stw());
3851 
3852       scan_roots(pss, worker_id);
3853       evacuate_live_objects(pss, worker_id);
3854     }
3855 
3856     end_work(worker_id);
3857   }
3858 };
3859 
3860 class G1EvacuateRegionsTask : public G1EvacuateRegionsBaseTask {
3861   G1RootProcessor* _root_processor;
3862 
3863   void scan_roots(G1ParScanThreadState* pss, uint worker_id) {
3864     _root_processor->evacuate_roots(pss, worker_id);
3865     _g1h->rem_set()->scan_heap_roots(pss, worker_id, G1GCPhaseTimes::ScanHR, G1GCPhaseTimes::ObjCopy);
3866     _g1h->rem_set()->scan_collection_set_regions(pss, worker_id, G1GCPhaseTimes::ScanHR, G1GCPhaseTimes::CodeRoots, G1GCPhaseTimes::ObjCopy);
3867   }
3868 
3869   void evacuate_live_objects(G1ParScanThreadState* pss, uint worker_id) {
3870     G1EvacuateRegionsBaseTask::evacuate_live_objects(pss, worker_id, G1GCPhaseTimes::ObjCopy, G1GCPhaseTimes::Termination);
3871   }
3872 
3873   void start_work(uint worker_id) {
3874     _g1h->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, Ticks::now().seconds());
3875   }
3876 
3877   void end_work(uint worker_id) {
3878     _g1h->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, Ticks::now().seconds());
3879   }
3880 
3881 public:
3882   G1EvacuateRegionsTask(G1CollectedHeap* g1h,
3883                         G1ParScanThreadStateSet* per_thread_states,
3884                         RefToScanQueueSet* task_queues,
3885                         G1RootProcessor* root_processor,
3886                         uint num_workers) :
3887     G1EvacuateRegionsBaseTask("G1 Evacuate Regions", per_thread_states, task_queues, num_workers),
3888     _root_processor(root_processor)
3889   { }
3890 };
3891 
3892 void G1CollectedHeap::evacuate_initial_collection_set(G1ParScanThreadStateSet* per_thread_states) {
3893   G1GCPhaseTimes* p = phase_times();
3894 
3895   {
3896     Ticks start = Ticks::now();
3897     rem_set()->merge_heap_roots(true /* initial_evacuation */);
3898     p->record_merge_heap_roots_time((Ticks::now() - start).seconds() * 1000.0);
3899   }
3900 
3901   Tickspan task_time;
3902   const uint num_workers = workers()->active_workers();
3903 
3904   Ticks start_processing = Ticks::now();
3905   {
3906     G1RootProcessor root_processor(this, num_workers);
3907     G1EvacuateRegionsTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, num_workers);
3908     task_time = run_task(&g1_par_task);
3909     // Closing the inner scope will execute the destructor for the G1RootProcessor object.
3910     // To extract its code root fixup time we measure total time of this scope and
3911     // subtract from the time the WorkGang task took.
3912   }
3913   Tickspan total_processing = Ticks::now() - start_processing;
3914 
3915   p->record_initial_evac_time(task_time.seconds() * 1000.0);
3916   p->record_or_add_code_root_fixup_time((total_processing - task_time).seconds() * 1000.0);
3917 }
3918 
3919 class G1EvacuateOptionalRegionsTask : public G1EvacuateRegionsBaseTask {
3920 
3921   void scan_roots(G1ParScanThreadState* pss, uint worker_id) {
3922     _g1h->rem_set()->scan_heap_roots(pss, worker_id, G1GCPhaseTimes::OptScanHR, G1GCPhaseTimes::OptObjCopy);
3923     _g1h->rem_set()->scan_collection_set_regions(pss, worker_id, G1GCPhaseTimes::OptScanHR, G1GCPhaseTimes::OptCodeRoots, G1GCPhaseTimes::OptObjCopy);
3924   }
3925 
3926   void evacuate_live_objects(G1ParScanThreadState* pss, uint worker_id) {
3927     G1EvacuateRegionsBaseTask::evacuate_live_objects(pss, worker_id, G1GCPhaseTimes::OptObjCopy, G1GCPhaseTimes::OptTermination);
3928   }
3929 
3930 public:
3931   G1EvacuateOptionalRegionsTask(G1ParScanThreadStateSet* per_thread_states,
3932                                 RefToScanQueueSet* queues,
3933                                 uint num_workers) :
3934     G1EvacuateRegionsBaseTask("G1 Evacuate Optional Regions", per_thread_states, queues, num_workers) {
3935   }
3936 };
3937 
3938 void G1CollectedHeap::evacuate_next_optional_regions(G1ParScanThreadStateSet* per_thread_states) {
3939   class G1MarkScope : public MarkScope { };
3940 
3941   Tickspan task_time;
3942 
3943   Ticks start_processing = Ticks::now();
3944   {
3945     G1MarkScope code_mark_scope;
3946     G1EvacuateOptionalRegionsTask task(per_thread_states, _task_queues, workers()->active_workers());
3947     task_time = run_task(&task);
3948     // See comment in evacuate_collection_set() for the reason of the scope.
3949   }
3950   Tickspan total_processing = Ticks::now() - start_processing;
3951 
3952   G1GCPhaseTimes* p = phase_times();
3953   p->record_or_add_code_root_fixup_time((total_processing - task_time).seconds() * 1000.0);
3954 }
3955 
3956 void G1CollectedHeap::evacuate_optional_collection_set(G1ParScanThreadStateSet* per_thread_states) {
3957   const double gc_start_time_ms = phase_times()->cur_collection_start_sec() * 1000.0;
3958 
3959   while (!evacuation_failed() && _collection_set.optional_region_length() > 0) {
3960 
3961     double time_used_ms = os::elapsedTime() * 1000.0 - gc_start_time_ms;
3962     double time_left_ms = MaxGCPauseMillis - time_used_ms;
3963 
3964     if (time_left_ms < 0 ||
3965         !_collection_set.finalize_optional_for_evacuation(time_left_ms * policy()->optional_evacuation_fraction())) {
3966       log_trace(gc, ergo, cset)("Skipping evacuation of %u optional regions, no more regions can be evacuated in %.3fms",
3967                                 _collection_set.optional_region_length(), time_left_ms);
3968       break;
3969     }
3970 
3971     {
3972       Ticks start = Ticks::now();
3973       rem_set()->merge_heap_roots(false /* initial_evacuation */);
3974       phase_times()->record_or_add_optional_merge_heap_roots_time((Ticks::now() - start).seconds() * 1000.0);
3975     }
3976 
3977     {
3978       Ticks start = Ticks::now();
3979       evacuate_next_optional_regions(per_thread_states);
3980       phase_times()->record_or_add_optional_evac_time((Ticks::now() - start).seconds() * 1000.0);
3981     }
3982   }
3983 
3984   _collection_set.abandon_optional_collection_set(per_thread_states);
3985 }
3986 
3987 void G1CollectedHeap::post_evacuate_collection_set(G1EvacuationInfo& evacuation_info,
3988                                                    G1RedirtyCardsQueueSet* rdcqs,
3989                                                    G1ParScanThreadStateSet* per_thread_states) {
3990   G1GCPhaseTimes* p = phase_times();
3991 
3992   rem_set()->cleanup_after_scan_heap_roots();
3993 
3994   // Process any discovered reference objects - we have
3995   // to do this _before_ we retire the GC alloc regions
3996   // as we may have to copy some 'reachable' referent
3997   // objects (and their reachable sub-graphs) that were
3998   // not copied during the pause.
3999   process_discovered_references(per_thread_states);
4000 
4001   G1STWIsAliveClosure is_alive(this);
4002   G1KeepAliveClosure keep_alive(this);
4003 
4004   WeakProcessor::weak_oops_do(workers(), &is_alive, &keep_alive, p->weak_phase_times());
4005 
4006   if (G1StringDedup::is_enabled()) {
4007     double string_dedup_time_ms = os::elapsedTime();
4008 
4009     string_dedup_cleaning(&is_alive, &keep_alive, p);
4010 
4011     double string_cleanup_time_ms = (os::elapsedTime() - string_dedup_time_ms) * 1000.0;
4012     p->record_string_deduplication_time(string_cleanup_time_ms);
4013   }
4014 
4015   _allocator->release_gc_alloc_regions(evacuation_info);
4016 
4017   if (evacuation_failed()) {
4018     restore_after_evac_failure(rdcqs);
4019 
4020     // Reset the G1EvacuationFailureALot counters and flags
4021     NOT_PRODUCT(reset_evacuation_should_fail();)
4022 
4023     double recalculate_used_start = os::elapsedTime();
4024     set_used(recalculate_used());
4025     p->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
4026 
4027     if (_archive_allocator != NULL) {
4028       _archive_allocator->clear_used();
4029     }
4030     for (uint i = 0; i < ParallelGCThreads; i++) {
4031       if (_evacuation_failed_info_array[i].has_failed()) {
4032         _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
4033       }
4034     }
4035   } else {
4036     // The "used" of the the collection set have already been subtracted
4037     // when they were freed.  Add in the bytes used.
4038     increase_used(_bytes_used_during_gc);
4039   }
4040 
4041   _preserved_marks_set.assert_empty();
4042 
4043   merge_per_thread_state_info(per_thread_states);
4044 
4045   // Reset and re-enable the hot card cache.
4046   // Note the counts for the cards in the regions in the
4047   // collection set are reset when the collection set is freed.
4048   _hot_card_cache->reset_hot_cache();
4049   _hot_card_cache->set_use_cache(true);
4050 
4051   purge_code_root_memory();
4052 
4053   redirty_logged_cards(rdcqs);
4054 
4055   free_collection_set(&_collection_set, evacuation_info, per_thread_states->surviving_young_words());
4056 
4057   eagerly_reclaim_humongous_regions();
4058 
4059   record_obj_copy_mem_stats();
4060 
4061   evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before());
4062   evacuation_info.set_bytes_used(_bytes_used_during_gc);
4063 
4064 #if COMPILER2_OR_JVMCI
4065   double start = os::elapsedTime();
4066   DerivedPointerTable::update_pointers();
4067   phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0);
4068 #endif
4069   policy()->print_age_table();
4070 }
4071 
4072 void G1CollectedHeap::record_obj_copy_mem_stats() {
4073   policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
4074 
4075   _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
4076                                                create_g1_evac_summary(&_old_evac_stats));
4077 }
4078 
4079 void G1CollectedHeap::free_region(HeapRegion* hr,
4080                                   FreeRegionList* free_list,
4081                                   bool skip_remset,
4082                                   bool skip_hot_card_cache,
4083                                   bool locked) {
4084   assert(!hr->is_free(), "the region should not be free");
4085   assert(!hr->is_empty(), "the region should not be empty");
4086   assert(_hrm->is_available(hr->hrm_index()), "region should be committed");
4087 
4088   if (G1VerifyBitmaps) {
4089     MemRegion mr(hr->bottom(), hr->end());
4090     concurrent_mark()->clear_range_in_prev_bitmap(mr);
4091   }
4092 
4093   // Clear the card counts for this region.
4094   // Note: we only need to do this if the region is not young
4095   // (since we don't refine cards in young regions).
4096   if (!skip_hot_card_cache && !hr->is_young()) {
4097     _hot_card_cache->reset_card_counts(hr);
4098   }
4099   hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */);
4100   _policy->remset_tracker()->update_at_free(hr);
4101   if (free_list != NULL) {
4102     free_list->add_ordered(hr);
4103   }
4104 }
4105 
4106 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
4107                                             FreeRegionList* free_list) {
4108   assert(hr->is_humongous(), "this is only for humongous regions");
4109   assert(free_list != NULL, "pre-condition");
4110   hr->clear_humongous();
4111   free_region(hr, free_list, false /* skip_remset */, false /* skip_hcc */, true /* locked */);
4112 }
4113 
4114 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed,
4115                                            const uint humongous_regions_removed) {
4116   if (old_regions_removed > 0 || humongous_regions_removed > 0) {
4117     MutexLocker x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4118     _old_set.bulk_remove(old_regions_removed);
4119     _humongous_set.bulk_remove(humongous_regions_removed);
4120   }
4121 
4122 }
4123 
4124 void G1CollectedHeap::abandon_freelist() {
4125   MutexLocker x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4126   _hrm->abandon_free_list();
4127 }
4128 
4129 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
4130   assert(list != NULL, "list can't be null");
4131   if (!list->is_empty()) {
4132     MutexLocker x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4133     _hrm->insert_list_into_free_list(list);
4134   }
4135 }
4136 
4137 void G1CollectedHeap::append_to_freelist(FreeRegionList* list) {
4138   assert(list != NULL, "list can't be null");
4139   if (!list->is_empty()) {
4140     MutexLocker x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4141     _hrm->append_to_free_list(list);
4142   }
4143 }
4144 
4145 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
4146   decrease_used(bytes);
4147 }
4148 
4149 class G1FreeCollectionSetTask : public AbstractGangTask {
4150   // Helper class to keep statistics for the collection set freeing
4151   class FreeCSetStats {
4152     size_t _before_used_bytes;   // Usage in regions successfully evacutate
4153     size_t _after_used_bytes;    // Usage in regions failing evacuation
4154     size_t _bytes_allocated_in_old_since_last_gc; // Size of young regions turned into old
4155     size_t _failure_used_words;  // Live size in failed regions
4156     size_t _failure_waste_words; // Wasted size in failed regions
4157     size_t _rs_length;           // Remembered set size
4158     uint _regions_freed;         // Number of regions freed
4159   public:
4160     FreeCSetStats() :
4161         _before_used_bytes(0),
4162         _after_used_bytes(0),
4163         _bytes_allocated_in_old_since_last_gc(0),
4164         _failure_used_words(0),
4165         _failure_waste_words(0),
4166         _rs_length(0),
4167         _regions_freed(0) { }
4168 
4169     void merge_stats(FreeCSetStats* other) {
4170       assert(other != NULL, "invariant");
4171       _before_used_bytes += other->_before_used_bytes;
4172       _after_used_bytes += other->_after_used_bytes;
4173       _bytes_allocated_in_old_since_last_gc += other->_bytes_allocated_in_old_since_last_gc;
4174       _failure_used_words += other->_failure_used_words;
4175       _failure_waste_words += other->_failure_waste_words;
4176       _rs_length += other->_rs_length;
4177       _regions_freed += other->_regions_freed;
4178     }
4179 
4180     void report(G1CollectedHeap* g1h, G1EvacuationInfo* evacuation_info) {
4181       evacuation_info->set_regions_freed(_regions_freed);
4182       evacuation_info->increment_collectionset_used_after(_after_used_bytes);
4183 
4184       g1h->decrement_summary_bytes(_before_used_bytes);
4185       g1h->alloc_buffer_stats(G1HeapRegionAttr::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words);
4186 
4187       G1Policy *policy = g1h->policy();
4188       policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc);
4189       policy->record_rs_length(_rs_length);
4190       policy->cset_regions_freed();
4191     }
4192 
4193     void update_used_before(size_t value) { _before_used_bytes += value; }
4194     void update_used_after(size_t value) { _after_used_bytes += value; }
4195     void update_bytes_alloc_in_old(size_t value) { _bytes_allocated_in_old_since_last_gc += value; }
4196     void update_failure_used(size_t value) { _failure_used_words += value; }
4197     void update_failure_waste(size_t value) { _failure_waste_words += value; }
4198     void update_rs_length(size_t value) { _rs_length += value; }
4199     void increment_regions_freed() { _regions_freed += 1; }
4200   };
4201 
4202   // Closure applied to all regions in the collection set.
4203   class G1FreeCollectionSetClosure : public HeapRegionClosure {
4204     // Helper to send JFR events for regions.
4205     class EventForRegion {
4206       EventGCPhaseParallel _event;
4207     public:
4208       EventForRegion(HeapRegion* region, uint worker_id) : _event() {
4209         _event.set_gcId(GCId::current());
4210         _event.set_gcWorkerId(worker_id);
4211         if (region->is_young()) {
4212           _event.set_name(G1GCPhaseTimes::phase_name(G1GCPhaseTimes::YoungFreeCSet));
4213         } else {
4214           _event.set_name(G1GCPhaseTimes::phase_name(G1GCPhaseTimes::NonYoungFreeCSet));
4215         }
4216       }
4217 
4218       ~EventForRegion() {
4219         _event.commit();
4220       }
4221     };
4222 
4223     // Helper to do timing for region work.
4224     class TimerForRegion {
4225       double& _time;
4226       double  _start_time;
4227     public:
4228       TimerForRegion(double& time) : _time(time), _start_time(os::elapsedTime()) { }
4229       ~TimerForRegion() {
4230         _time += os::elapsedTime() - _start_time;
4231       }
4232     };
4233 
4234     // G1FreeCollectionSetClosure members
4235     G1CollectedHeap* _g1h;
4236     const size_t*    _surviving_young_words;
4237     uint             _worker_id;
4238     double           _young_time;
4239     double           _non_young_time;
4240     FreeCSetStats*   _stats;
4241 
4242     void assert_in_cset(HeapRegion* r) {
4243       assert(r->young_index_in_cset() != 0 &&
4244              (uint)r->young_index_in_cset() <= _g1h->collection_set()->young_region_length(),
4245              "Young index %u is wrong for region %u of type %s with %u young regions",
4246              r->young_index_in_cset(), r->hrm_index(), r->get_type_str(), _g1h->collection_set()->young_region_length());
4247     }
4248 
4249     void handle_evacuated_region(HeapRegion* r) {
4250       assert(!r->is_empty(), "Region %u is an empty region in the collection set.", r->hrm_index());
4251       // Update stats.
4252       stats()->update_used_before(r->used());
4253       stats()->increment_regions_freed();
4254 
4255       // Free the region and mark it in the bit map so it gets added to the new free list.
4256       r->rem_set()->clear_locked();
4257       _g1h->free_region(r, NULL, true /* skip_remset */, true /* skip_hot_card_cache */, true  /* locked */);
4258     }
4259 
4260     void handle_failed_region(HeapRegion* r) {
4261       // Do some allocation statistics accounting. Regions that failed evacuation
4262       // are always made old, so there is no need to update anything in the young
4263       // gen statistics, but we need to update old gen statistics.
4264       size_t used_words = r->marked_bytes() / HeapWordSize;
4265       stats()->update_failure_used(used_words);
4266       stats()->update_failure_waste(HeapRegion::GrainWords - used_words);
4267       stats()->update_used_after(r->used());
4268       // When moving a young gen region to old gen, we "allocate" that whole
4269       // region there. This is in addition to any already evacuated objects.
4270       // Notify the policy about that. Old gen regions do not cause an
4271       // additional allocation: both the objects still in the region and the
4272       // ones already moved are accounted for elsewhere.
4273       if (r->is_young()) {
4274         stats()->update_bytes_alloc_in_old(HeapRegion::GrainBytes);
4275       }
4276 
4277       // Update the region state due to the failed evacuation.
4278       r->handle_evacuation_failed();
4279 
4280       // Add region to old set, need to hold lock.
4281       MutexLocker x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4282       _g1h->old_set_add(r);
4283     }
4284 
4285     double& timer_for_region(HeapRegion* r) {
4286       return r->is_young() ? _young_time : _non_young_time;
4287     }
4288   public:
4289     G1FreeCollectionSetClosure(const size_t* surviving_young_words,
4290                                uint worker_id,
4291                                FreeCSetStats* stats) :
4292         HeapRegionClosure(),
4293         _g1h(G1CollectedHeap::heap()),
4294         _surviving_young_words(surviving_young_words),
4295         _worker_id(worker_id),
4296         _young_time(0.0),
4297         _non_young_time(0.0),
4298         _stats(stats) { }
4299 
4300     virtual bool do_heap_region(HeapRegion* r) {
4301       assert(r->in_collection_set(), "Invariant: %u missing from CSet", r->hrm_index());
4302       EventForRegion event(r, _worker_id);
4303       TimerForRegion timer(timer_for_region(r));
4304 
4305       _g1h->clear_region_attr(r);
4306       stats()->update_rs_length(r->rem_set()->occupied_locked());
4307 
4308       if (r->is_young()) {
4309         assert_in_cset(r);
4310         r->record_surv_words_in_group(_surviving_young_words[r->young_index_in_cset()]);
4311       } else {
4312         _g1h->hot_card_cache()->reset_card_counts(r);
4313       }
4314 
4315       if (r->evacuation_failed()) {
4316         handle_failed_region(r);
4317       } else {
4318         handle_evacuated_region(r);
4319       }
4320       assert(!_g1h->is_on_master_free_list(r), "sanity");
4321 
4322       return false;
4323     }
4324 
4325     FreeCSetStats* stats() {
4326       return _stats;
4327     }
4328 
4329     void report_timing(double parallel_time) {
4330       G1GCPhaseTimes* pt = _g1h->phase_times();
4331       pt->record_time_secs(G1GCPhaseTimes::ParFreeCSet, _worker_id, parallel_time);
4332       if (_young_time > 0.0) {
4333         pt->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, _worker_id, _young_time);
4334       }
4335       if (_non_young_time > 0.0) {
4336         pt->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, _worker_id, _non_young_time);
4337       }
4338     }
4339   };
4340 
4341   // G1FreeCollectionSetTask members
4342   G1CollectedHeap*  _g1h;
4343   G1EvacuationInfo* _evacuation_info;
4344   FreeCSetStats*    _worker_stats;
4345   HeapRegionClaimer _claimer;
4346   const size_t*     _surviving_young_words;
4347   uint              _active_workers;
4348 
4349   FreeCSetStats* worker_stats(uint worker) {
4350     return &_worker_stats[worker];
4351   }
4352 
4353   void report_statistics() {
4354     // Merge the accounting
4355     FreeCSetStats total_stats;
4356     for (uint worker = 0; worker < _active_workers; worker++) {
4357       total_stats.merge_stats(worker_stats(worker));
4358     }
4359     total_stats.report(_g1h, _evacuation_info);
4360   }
4361 
4362 public:
4363   G1FreeCollectionSetTask(G1EvacuationInfo* evacuation_info, const size_t* surviving_young_words, uint active_workers) :
4364       AbstractGangTask("G1 Free Collection Set"),
4365       _g1h(G1CollectedHeap::heap()),
4366       _evacuation_info(evacuation_info),
4367       _worker_stats(NEW_C_HEAP_ARRAY(FreeCSetStats, active_workers, mtGC)),
4368       _claimer(active_workers),
4369       _surviving_young_words(surviving_young_words),
4370       _active_workers(active_workers) {
4371     for (uint worker = 0; worker < active_workers; worker++) {
4372       ::new (&_worker_stats[worker]) FreeCSetStats();
4373     }
4374   }
4375 
4376   ~G1FreeCollectionSetTask() {
4377     double serial_time = os::elapsedTime();
4378     report_statistics();
4379     FREE_C_HEAP_ARRAY(FreeCSetStats, _worker_stats);
4380     _g1h->phase_times()->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0);
4381   }
4382 
4383   virtual void work(uint worker_id) {
4384     EventGCPhaseParallel event;
4385     double start = os::elapsedTime();
4386     G1FreeCollectionSetClosure cl(_surviving_young_words, worker_id, worker_stats(worker_id));
4387     _g1h->collection_set_par_iterate_all(&cl, &_claimer, worker_id);
4388 
4389     // Report the total parallel time along with some more detailed metrics.
4390     cl.report_timing(os::elapsedTime() - start);
4391     event.commit(GCId::current(), worker_id, G1GCPhaseTimes::phase_name(G1GCPhaseTimes::ParFreeCSet));
4392   }
4393 };
4394 
4395 class G1RebuildFreeListTask : public AbstractGangTask {
4396   G1CollectedHeap* _g1h;
4397   FreeRegionList*  _worker_freelists;
4398   uint             _worker_chunk_size;
4399   uint             _num_workers;
4400 
4401   FreeRegionList* worker_freelist(uint worker) { return &_worker_freelists[worker]; }
4402 
4403   // Take the partial free lists and link them together.
4404   void rebuild_freelist() {
4405     // Abandon current free list to allow a rebuild using the
4406     // workers chunked free lists.
4407     _g1h->abandon_freelist();
4408     for (uint worker = 0; worker < _num_workers; worker++) {
4409      _g1h->append_to_freelist(worker_freelist(worker));
4410     }
4411   }
4412 public:
4413   G1RebuildFreeListTask(G1CollectedHeap* g1, uint num_workers) :
4414       AbstractGangTask("G1 Rebuild Free List Task"),
4415       _g1h(g1),
4416       _worker_freelists(NEW_C_HEAP_ARRAY(FreeRegionList, num_workers, mtGC)),
4417       _worker_chunk_size((_g1h->max_regions() + num_workers - 1) / num_workers),
4418       _num_workers(num_workers) {
4419     for (uint worker = 0; worker < _num_workers; worker++) {
4420      ::new (&_worker_freelists[worker]) FreeRegionList("Appendable Worker Free List");
4421     }
4422   }
4423 
4424   ~G1RebuildFreeListTask() {
4425     double serial_time = os::elapsedTime();
4426     rebuild_freelist();
4427     FREE_C_HEAP_ARRAY(FreeRegionList, _worker_freelists);
4428     _g1h->phase_times()->record_serial_rebuild_freelist_time_ms((os::elapsedTime() - serial_time) * 1000.0);
4429   }
4430 
4431   // Each worker creates a free list for a chunk of the heap. The chunks won't
4432   // be overlapping so we don't need to do any claiming.
4433   virtual void work(uint worker_id) {
4434     double start_time = os::elapsedTime();
4435     EventGCPhaseParallel event;
4436 
4437     uint start = worker_id * _worker_chunk_size;
4438     uint end = MIN2(start + _worker_chunk_size, _g1h->max_regions());
4439 
4440     // If start is outside the heap, this worker has nothing to do.
4441     if (start > end) {
4442       return;
4443     }
4444 
4445     FreeRegionList* free_list = worker_freelist(worker_id);
4446     for (uint i = start; i < end; i++) {
4447       if (!_g1h->hrm()->is_available(i)) {
4448         continue;
4449       }
4450       HeapRegion* region = _g1h->region_at(i);
4451       if (region->is_free()) {
4452         region->unlink_from_list();
4453         free_list->add_to_tail(region);
4454       }
4455     }
4456 
4457     event.commit(GCId::current(), worker_id, G1GCPhaseTimes::phase_name(G1GCPhaseTimes::RebuildFreeList));
4458     _g1h->phase_times()->record_time_secs(G1GCPhaseTimes::RebuildFreeList, worker_id, os::elapsedTime() - start_time);
4459   }
4460 };
4461 
4462 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, G1EvacuationInfo& evacuation_info, const size_t* surviving_young_words) {
4463   _eden.clear();
4464 
4465   // The free collections set is split up in two tasks, the first
4466   // frees the collection set and records what regions are free,
4467   // and the second one rebuilds the free list. This proved to be
4468   // more efficient than adding a sorted list to another.
4469 
4470   double free_cset_start_time = os::elapsedTime();
4471   {
4472     uint const num_cs_regions = _collection_set.region_length();
4473     uint const num_workers = clamp(num_cs_regions, 1u, workers()->active_workers());
4474     G1FreeCollectionSetTask cl(&evacuation_info, surviving_young_words, num_workers);
4475 
4476     log_debug(gc, ergo)("Running %s using %u workers for collection set length %u (%u)",
4477                         cl.name(), num_workers, num_cs_regions, num_regions());
4478     workers()->run_task(&cl, num_workers);
4479   }
4480 
4481   double free_cset_end_time = os::elapsedTime();
4482   phase_times()->record_total_free_cset_time_ms((free_cset_end_time - free_cset_start_time) * 1000.0);
4483   {
4484     uint const num_workers = workers()->active_workers();
4485     G1RebuildFreeListTask cl(this, num_workers);
4486 
4487     log_debug(gc, ergo)("Running %s using %u workers for rebuilding free list of %u (%u) regions",
4488                         cl.name(), num_workers, num_free_regions(), num_regions());
4489     workers()->run_task(&cl, num_workers);
4490   }
4491   phase_times()->record_total_rebuild_freelist_time_ms((os::elapsedTime() - free_cset_end_time) * 1000.0);
4492 
4493   collection_set->clear();
4494 }
4495 
4496 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
4497  private:
4498   FreeRegionList* _free_region_list;
4499   HeapRegionSet* _proxy_set;
4500   uint _humongous_objects_reclaimed;
4501   uint _humongous_regions_reclaimed;
4502   size_t _freed_bytes;
4503  public:
4504 
4505   G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
4506     _free_region_list(free_region_list), _proxy_set(NULL), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) {
4507   }
4508 
4509   virtual bool do_heap_region(HeapRegion* r) {
4510     if (!r->is_starts_humongous()) {
4511       return false;
4512     }
4513 
4514     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4515 
4516     oop obj = (oop)r->bottom();
4517     G1CMBitMap* next_bitmap = g1h->concurrent_mark()->next_mark_bitmap();
4518 
4519     // The following checks whether the humongous object is live are sufficient.
4520     // The main additional check (in addition to having a reference from the roots
4521     // or the young gen) is whether the humongous object has a remembered set entry.
4522     //
4523     // A humongous object cannot be live if there is no remembered set for it
4524     // because:
4525     // - there can be no references from within humongous starts regions referencing
4526     // the object because we never allocate other objects into them.
4527     // (I.e. there are no intra-region references that may be missed by the
4528     // remembered set)
4529     // - as soon there is a remembered set entry to the humongous starts region
4530     // (i.e. it has "escaped" to an old object) this remembered set entry will stay
4531     // until the end of a concurrent mark.
4532     //
4533     // It is not required to check whether the object has been found dead by marking
4534     // or not, in fact it would prevent reclamation within a concurrent cycle, as
4535     // all objects allocated during that time are considered live.
4536     // SATB marking is even more conservative than the remembered set.
4537     // So if at this point in the collection there is no remembered set entry,
4538     // nobody has a reference to it.
4539     // At the start of collection we flush all refinement logs, and remembered sets
4540     // are completely up-to-date wrt to references to the humongous object.
4541     //
4542     // Other implementation considerations:
4543     // - never consider object arrays at this time because they would pose
4544     // considerable effort for cleaning up the the remembered sets. This is
4545     // required because stale remembered sets might reference locations that
4546     // are currently allocated into.
4547     uint region_idx = r->hrm_index();
4548     if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
4549         !r->rem_set()->is_empty()) {
4550       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",
4551                                region_idx,
4552                                (size_t)obj->size() * HeapWordSize,
4553                                p2i(r->bottom()),
4554                                r->rem_set()->occupied(),
4555                                r->rem_set()->strong_code_roots_list_length(),
4556                                next_bitmap->is_marked(r->bottom()),
4557                                g1h->is_humongous_reclaim_candidate(region_idx),
4558                                obj->is_typeArray()
4559                               );
4560       return false;
4561     }
4562 
4563     guarantee(obj->is_typeArray(),
4564               "Only eagerly reclaiming type arrays is supported, but the object "
4565               PTR_FORMAT " is not.", p2i(r->bottom()));
4566 
4567     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",
4568                              region_idx,
4569                              (size_t)obj->size() * HeapWordSize,
4570                              p2i(r->bottom()),
4571                              r->rem_set()->occupied(),
4572                              r->rem_set()->strong_code_roots_list_length(),
4573                              next_bitmap->is_marked(r->bottom()),
4574                              g1h->is_humongous_reclaim_candidate(region_idx),
4575                              obj->is_typeArray()
4576                             );
4577 
4578     G1ConcurrentMark* const cm = g1h->concurrent_mark();
4579     cm->humongous_object_eagerly_reclaimed(r);
4580     assert(!cm->is_marked_in_prev_bitmap(obj) && !cm->is_marked_in_next_bitmap(obj),
4581            "Eagerly reclaimed humongous region %u should not be marked at all but is in prev %s next %s",
4582            region_idx,
4583            BOOL_TO_STR(cm->is_marked_in_prev_bitmap(obj)),
4584            BOOL_TO_STR(cm->is_marked_in_next_bitmap(obj)));
4585     _humongous_objects_reclaimed++;
4586     do {
4587       HeapRegion* next = g1h->next_region_in_humongous(r);
4588       _freed_bytes += r->used();
4589       r->set_containing_set(NULL);
4590       _humongous_regions_reclaimed++;
4591       g1h->free_humongous_region(r, _free_region_list);
4592       r = next;
4593     } while (r != NULL);
4594 
4595     return false;
4596   }
4597 
4598   uint humongous_objects_reclaimed() {
4599     return _humongous_objects_reclaimed;
4600   }
4601 
4602   uint humongous_regions_reclaimed() {
4603     return _humongous_regions_reclaimed;
4604   }
4605 
4606   size_t bytes_freed() const {
4607     return _freed_bytes;
4608   }
4609 };
4610 
4611 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
4612   assert_at_safepoint_on_vm_thread();
4613 
4614   if (!G1EagerReclaimHumongousObjects ||
4615       (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) {
4616     phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
4617     return;
4618   }
4619 
4620   double start_time = os::elapsedTime();
4621 
4622   FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
4623 
4624   G1FreeHumongousRegionClosure cl(&local_cleanup_list);
4625   heap_region_iterate(&cl);
4626 
4627   remove_from_old_sets(0, cl.humongous_regions_reclaimed());
4628 
4629   G1HRPrinter* hrp = hr_printer();
4630   if (hrp->is_active()) {
4631     FreeRegionListIterator iter(&local_cleanup_list);
4632     while (iter.more_available()) {
4633       HeapRegion* hr = iter.get_next();
4634       hrp->cleanup(hr);
4635     }
4636   }
4637 
4638   prepend_to_freelist(&local_cleanup_list);
4639   decrement_summary_bytes(cl.bytes_freed());
4640 
4641   phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
4642                                                        cl.humongous_objects_reclaimed());
4643 }
4644 
4645 class G1AbandonCollectionSetClosure : public HeapRegionClosure {
4646 public:
4647   virtual bool do_heap_region(HeapRegion* r) {
4648     assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index());
4649     G1CollectedHeap::heap()->clear_region_attr(r);
4650     r->clear_young_index_in_cset();
4651     return false;
4652   }
4653 };
4654 
4655 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) {
4656   G1AbandonCollectionSetClosure cl;
4657   collection_set_iterate_all(&cl);
4658 
4659   collection_set->clear();
4660   collection_set->stop_incremental_building();
4661 }
4662 
4663 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
4664   return _allocator->is_retained_old_region(hr);
4665 }
4666 
4667 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
4668   _eden.add(hr);
4669   _policy->set_region_eden(hr);
4670 }
4671 
4672 #ifdef ASSERT
4673 
4674 class NoYoungRegionsClosure: public HeapRegionClosure {
4675 private:
4676   bool _success;
4677 public:
4678   NoYoungRegionsClosure() : _success(true) { }
4679   bool do_heap_region(HeapRegion* r) {
4680     if (r->is_young()) {
4681       log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
4682                             p2i(r->bottom()), p2i(r->end()));
4683       _success = false;
4684     }
4685     return false;
4686   }
4687   bool success() { return _success; }
4688 };
4689 
4690 bool G1CollectedHeap::check_young_list_empty() {
4691   bool ret = (young_regions_count() == 0);
4692 
4693   NoYoungRegionsClosure closure;
4694   heap_region_iterate(&closure);
4695   ret = ret && closure.success();
4696 
4697   return ret;
4698 }
4699 
4700 #endif // ASSERT
4701 
4702 class TearDownRegionSetsClosure : public HeapRegionClosure {
4703   HeapRegionSet *_old_set;
4704 
4705 public:
4706   TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
4707 
4708   bool do_heap_region(HeapRegion* r) {
4709     if (r->is_old()) {
4710       _old_set->remove(r);
4711     } else if(r->is_young()) {
4712       r->uninstall_surv_rate_group();
4713     } else {
4714       // We ignore free regions, we'll empty the free list afterwards.
4715       // We ignore humongous and archive regions, we're not tearing down these
4716       // sets.
4717       assert(r->is_archive() || r->is_free() || r->is_humongous(),
4718              "it cannot be another type");
4719     }
4720     return false;
4721   }
4722 
4723   ~TearDownRegionSetsClosure() {
4724     assert(_old_set->is_empty(), "post-condition");
4725   }
4726 };
4727 
4728 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
4729   assert_at_safepoint_on_vm_thread();
4730 
4731   if (!free_list_only) {
4732     TearDownRegionSetsClosure cl(&_old_set);
4733     heap_region_iterate(&cl);
4734 
4735     // Note that emptying the _young_list is postponed and instead done as
4736     // the first step when rebuilding the regions sets again. The reason for
4737     // this is that during a full GC string deduplication needs to know if
4738     // a collected region was young or old when the full GC was initiated.
4739   }
4740   _hrm->remove_all_free_regions();
4741 }
4742 
4743 void G1CollectedHeap::increase_used(size_t bytes) {
4744   _summary_bytes_used += bytes;
4745 }
4746 
4747 void G1CollectedHeap::decrease_used(size_t bytes) {
4748   assert(_summary_bytes_used >= bytes,
4749          "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
4750          _summary_bytes_used, bytes);
4751   _summary_bytes_used -= bytes;
4752 }
4753 
4754 void G1CollectedHeap::set_used(size_t bytes) {
4755   _summary_bytes_used = bytes;
4756 }
4757 
4758 class RebuildRegionSetsClosure : public HeapRegionClosure {
4759 private:
4760   bool _free_list_only;
4761 
4762   HeapRegionSet* _old_set;
4763   HeapRegionManager* _hrm;
4764 
4765   size_t _total_used;
4766 
4767 public:
4768   RebuildRegionSetsClosure(bool free_list_only,
4769                            HeapRegionSet* old_set,
4770                            HeapRegionManager* hrm) :
4771     _free_list_only(free_list_only),
4772     _old_set(old_set), _hrm(hrm), _total_used(0) {
4773     assert(_hrm->num_free_regions() == 0, "pre-condition");
4774     if (!free_list_only) {
4775       assert(_old_set->is_empty(), "pre-condition");
4776     }
4777   }
4778 
4779   bool do_heap_region(HeapRegion* r) {
4780     if (r->is_empty()) {
4781       assert(r->rem_set()->is_empty(), "Empty regions should have empty remembered sets.");
4782       // Add free regions to the free list
4783       r->set_free();
4784       _hrm->insert_into_free_list(r);
4785     } else if (!_free_list_only) {
4786       assert(r->rem_set()->is_empty(), "At this point remembered sets must have been cleared.");
4787 
4788       if (r->is_archive() || r->is_humongous()) {
4789         // We ignore archive and humongous regions. We left these sets unchanged.
4790       } else {
4791         assert(r->is_young() || r->is_free() || r->is_old(), "invariant");
4792         // We now move all (non-humongous, non-old, non-archive) regions to old gen, and register them as such.
4793         r->move_to_old();
4794         _old_set->add(r);
4795       }
4796       _total_used += r->used();
4797     }
4798 
4799     return false;
4800   }
4801 
4802   size_t total_used() {
4803     return _total_used;
4804   }
4805 };
4806 
4807 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
4808   assert_at_safepoint_on_vm_thread();
4809 
4810   if (!free_list_only) {
4811     _eden.clear();
4812     _survivor.clear();
4813   }
4814 
4815   RebuildRegionSetsClosure cl(free_list_only, &_old_set, _hrm);
4816   heap_region_iterate(&cl);
4817 
4818   if (!free_list_only) {
4819     set_used(cl.total_used());
4820     if (_archive_allocator != NULL) {
4821       _archive_allocator->clear_used();
4822     }
4823   }
4824   assert_used_and_recalculate_used_equal(this);
4825 }
4826 
4827 // Methods for the mutator alloc region
4828 
4829 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
4830                                                       bool force,
4831                                                       uint node_index) {
4832   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
4833   bool should_allocate = policy()->should_allocate_mutator_region();
4834   if (force || should_allocate) {
4835     HeapRegion* new_alloc_region = new_region(word_size,
4836                                               HeapRegionType::Eden,
4837                                               false /* do_expand */,
4838                                               node_index);
4839     if (new_alloc_region != NULL) {
4840       set_region_short_lived_locked(new_alloc_region);
4841       _hr_printer.alloc(new_alloc_region, !should_allocate);
4842       _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region);
4843       _policy->remset_tracker()->update_at_allocate(new_alloc_region);
4844       return new_alloc_region;
4845     }
4846   }
4847   return NULL;
4848 }
4849 
4850 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
4851                                                   size_t allocated_bytes) {
4852   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
4853   assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
4854 
4855   collection_set()->add_eden_region(alloc_region);
4856   increase_used(allocated_bytes);
4857   _eden.add_used_bytes(allocated_bytes);
4858   _hr_printer.retire(alloc_region);
4859 
4860   // We update the eden sizes here, when the region is retired,
4861   // instead of when it's allocated, since this is the point that its
4862   // used space has been recorded in _summary_bytes_used.
4863   g1mm()->update_eden_size();
4864 }
4865 
4866 // Methods for the GC alloc regions
4867 
4868 bool G1CollectedHeap::has_more_regions(G1HeapRegionAttr dest) {
4869   if (dest.is_old()) {
4870     return true;
4871   } else {
4872     return survivor_regions_count() < policy()->max_survivor_regions();
4873   }
4874 }
4875 
4876 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, G1HeapRegionAttr dest, uint node_index) {
4877   assert(FreeList_lock->owned_by_self(), "pre-condition");
4878 
4879   if (!has_more_regions(dest)) {
4880     return NULL;
4881   }
4882 
4883   HeapRegionType type;
4884   if (dest.is_young()) {
4885     type = HeapRegionType::Survivor;
4886   } else {
4887     type = HeapRegionType::Old;
4888   }
4889 
4890   HeapRegion* new_alloc_region = new_region(word_size,
4891                                             type,
4892                                             true /* do_expand */,
4893                                             node_index);
4894 
4895   if (new_alloc_region != NULL) {
4896     if (type.is_survivor()) {
4897       new_alloc_region->set_survivor();
4898       _survivor.add(new_alloc_region);
4899       _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region);
4900     } else {
4901       new_alloc_region->set_old();
4902       _verifier->check_bitmaps("Old Region Allocation", new_alloc_region);
4903     }
4904     _policy->remset_tracker()->update_at_allocate(new_alloc_region);
4905     register_region_with_region_attr(new_alloc_region);
4906     _hr_printer.alloc(new_alloc_region);
4907     return new_alloc_region;
4908   }
4909   return NULL;
4910 }
4911 
4912 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
4913                                              size_t allocated_bytes,
4914                                              G1HeapRegionAttr dest) {
4915   _bytes_used_during_gc += allocated_bytes;
4916   if (dest.is_old()) {
4917     old_set_add(alloc_region);
4918   } else {
4919     assert(dest.is_young(), "Retiring alloc region should be young (%d)", dest.type());
4920     _survivor.add_used_bytes(allocated_bytes);
4921   }
4922 
4923   bool const during_im = collector_state()->in_initial_mark_gc();
4924   if (during_im && allocated_bytes > 0) {
4925     _cm->root_regions()->add(alloc_region->next_top_at_mark_start(), alloc_region->top());
4926   }
4927   _hr_printer.retire(alloc_region);
4928 }
4929 
4930 HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
4931   bool expanded = false;
4932   uint index = _hrm->find_highest_free(&expanded);
4933 
4934   if (index != G1_NO_HRM_INDEX) {
4935     if (expanded) {
4936       log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
4937                                 HeapRegion::GrainWords * HeapWordSize);
4938     }
4939     _hrm->allocate_free_regions_starting_at(index, 1);
4940     return region_at(index);
4941   }
4942   return NULL;
4943 }
4944 
4945 // Optimized nmethod scanning
4946 
4947 class RegisterNMethodOopClosure: public OopClosure {
4948   G1CollectedHeap* _g1h;
4949   nmethod* _nm;
4950 
4951   template <class T> void do_oop_work(T* p) {
4952     T heap_oop = RawAccess<>::oop_load(p);
4953     if (!CompressedOops::is_null(heap_oop)) {
4954       oop obj = CompressedOops::decode_not_null(heap_oop);
4955       HeapRegion* hr = _g1h->heap_region_containing(obj);
4956       assert(!hr->is_continues_humongous(),
4957              "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
4958              " starting at " HR_FORMAT,
4959              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
4960 
4961       // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
4962       hr->add_strong_code_root_locked(_nm);
4963     }
4964   }
4965 
4966 public:
4967   RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
4968     _g1h(g1h), _nm(nm) {}
4969 
4970   void do_oop(oop* p)       { do_oop_work(p); }
4971   void do_oop(narrowOop* p) { do_oop_work(p); }
4972 };
4973 
4974 class UnregisterNMethodOopClosure: public OopClosure {
4975   G1CollectedHeap* _g1h;
4976   nmethod* _nm;
4977 
4978   template <class T> void do_oop_work(T* p) {
4979     T heap_oop = RawAccess<>::oop_load(p);
4980     if (!CompressedOops::is_null(heap_oop)) {
4981       oop obj = CompressedOops::decode_not_null(heap_oop);
4982       HeapRegion* hr = _g1h->heap_region_containing(obj);
4983       assert(!hr->is_continues_humongous(),
4984              "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
4985              " starting at " HR_FORMAT,
4986              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
4987 
4988       hr->remove_strong_code_root(_nm);
4989     }
4990   }
4991 
4992 public:
4993   UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
4994     _g1h(g1h), _nm(nm) {}
4995 
4996   void do_oop(oop* p)       { do_oop_work(p); }
4997   void do_oop(narrowOop* p) { do_oop_work(p); }
4998 };
4999 
5000 void G1CollectedHeap::register_nmethod(nmethod* nm) {
5001   guarantee(nm != NULL, "sanity");
5002   RegisterNMethodOopClosure reg_cl(this, nm);
5003   nm->oops_do(&reg_cl);
5004 }
5005 
5006 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
5007   guarantee(nm != NULL, "sanity");
5008   UnregisterNMethodOopClosure reg_cl(this, nm);
5009   nm->oops_do(&reg_cl, true);
5010 }
5011 
5012 void G1CollectedHeap::purge_code_root_memory() {
5013   double purge_start = os::elapsedTime();
5014   G1CodeRootSet::purge();
5015   double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
5016   phase_times()->record_strong_code_root_purge_time(purge_time_ms);
5017 }
5018 
5019 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
5020   G1CollectedHeap* _g1h;
5021 
5022 public:
5023   RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
5024     _g1h(g1h) {}
5025 
5026   void do_code_blob(CodeBlob* cb) {
5027     nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
5028     if (nm == NULL) {
5029       return;
5030     }
5031 
5032     _g1h->register_nmethod(nm);
5033   }
5034 };
5035 
5036 void G1CollectedHeap::rebuild_strong_code_roots() {
5037   RebuildStrongCodeRootClosure blob_cl(this);
5038   CodeCache::blobs_do(&blob_cl);
5039 }
5040 
5041 void G1CollectedHeap::initialize_serviceability() {
5042   _g1mm->initialize_serviceability();
5043 }
5044 
5045 MemoryUsage G1CollectedHeap::memory_usage() {
5046   return _g1mm->memory_usage();
5047 }
5048 
5049 GrowableArray<GCMemoryManager*> G1CollectedHeap::memory_managers() {
5050   return _g1mm->memory_managers();
5051 }
5052 
5053 GrowableArray<MemoryPool*> G1CollectedHeap::memory_pools() {
5054   return _g1mm->memory_pools();
5055 }