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/globalDefinitions.hpp"
 102 #include "utilities/stack.inline.hpp"
 103 
 104 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
 105 
 106 // INVARIANTS/NOTES
 107 //
 108 // All allocation activity covered by the G1CollectedHeap interface is
 109 // serialized by acquiring the HeapLock.  This happens in mem_allocate
 110 // and allocate_new_tlab, which are the "entry" points to the
 111 // allocation code from the rest of the JVM.  (Note that this does not
 112 // apply to TLAB allocation, which is not part of this interface: it
 113 // is done by clients of this interface.)
 114 
 115 class RedirtyLoggedCardTableEntryClosure : public G1CardTableEntryClosure {
 116  private:
 117   size_t _num_dirtied;
 118   G1CollectedHeap* _g1h;
 119   G1CardTable* _g1_ct;
 120 
 121   HeapRegion* region_for_card(CardValue* card_ptr) const {
 122     return _g1h->heap_region_containing(_g1_ct->addr_for(card_ptr));
 123   }
 124 
 125   bool will_become_free(HeapRegion* hr) const {
 126     // A region will be freed by free_collection_set if the region is in the
 127     // collection set and has not had an evacuation failure.
 128     return _g1h->is_in_cset(hr) && !hr->evacuation_failed();
 129   }
 130 
 131  public:
 132   RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : G1CardTableEntryClosure(),
 133     _num_dirtied(0), _g1h(g1h), _g1_ct(g1h->card_table()) { }
 134 
 135   void do_card_ptr(CardValue* card_ptr, uint worker_id) {
 136     HeapRegion* hr = region_for_card(card_ptr);
 137 
 138     // Should only dirty cards in regions that won't be freed.
 139     if (!will_become_free(hr)) {
 140       *card_ptr = G1CardTable::dirty_card_val();
 141       _num_dirtied++;
 142     }
 143   }
 144 
 145   size_t num_dirtied()   const { return _num_dirtied; }
 146 };
 147 
 148 
 149 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
 150   HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
 151 }
 152 
 153 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
 154   // The from card cache is not the memory that is actually committed. So we cannot
 155   // take advantage of the zero_filled parameter.
 156   reset_from_card_cache(start_idx, num_regions);
 157 }
 158 
 159 Tickspan G1CollectedHeap::run_task(AbstractGangTask* task) {
 160   Ticks start = Ticks::now();
 161   workers()->run_task(task, workers()->active_workers());
 162   return Ticks::now() - start;
 163 }
 164 
 165 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
 166                                              MemRegion mr) {
 167   return new HeapRegion(hrs_index, bot(), mr);
 168 }
 169 
 170 // Private methods.
 171 
 172 HeapRegion* G1CollectedHeap::new_region(size_t word_size,
 173                                         HeapRegionType type,
 174                                         bool do_expand,
 175                                         uint node_index) {
 176   assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
 177          "the only time we use this to allocate a humongous region is "
 178          "when we are allocating a single humongous region");
 179 
 180   HeapRegion* res = _hrm->allocate_free_region(type, node_index);
 181 
 182   if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
 183     // Currently, only attempts to allocate GC alloc regions set
 184     // do_expand to true. So, we should only reach here during a
 185     // safepoint. If this assumption changes we might have to
 186     // reconsider the use of _expand_heap_after_alloc_failure.
 187     assert(SafepointSynchronize::is_at_safepoint(), "invariant");
 188 
 189     log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B",
 190                               word_size * HeapWordSize);
 191 
 192     assert(word_size * HeapWordSize < HeapRegion::GrainBytes,
 193            "This kind of expansion should never be more than one region. Size: " SIZE_FORMAT,
 194            word_size * HeapWordSize);
 195     if (expand_single_region(node_index)) {
 196       // Given that expand_single_region() succeeded in expanding the heap, and we
 197       // always expand the heap by an amount aligned to the heap
 198       // region size, the free list should in theory not be empty.
 199       // In either case allocate_free_region() will check for NULL.
 200       res = _hrm->allocate_free_region(type, node_index);
 201     } else {
 202       _expand_heap_after_alloc_failure = false;
 203     }
 204   }
 205   return res;
 206 }
 207 
 208 HeapWord*
 209 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
 210                                                            uint num_regions,
 211                                                            size_t word_size) {
 212   assert(first != G1_NO_HRM_INDEX, "pre-condition");
 213   assert(is_humongous(word_size), "word_size should be humongous");
 214   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 215 
 216   // Index of last region in the series.
 217   uint last = first + num_regions - 1;
 218 
 219   // We need to initialize the region(s) we just discovered. This is
 220   // a bit tricky given that it can happen concurrently with
 221   // refinement threads refining cards on these regions and
 222   // potentially wanting to refine the BOT as they are scanning
 223   // those cards (this can happen shortly after a cleanup; see CR
 224   // 6991377). So we have to set up the region(s) carefully and in
 225   // a specific order.
 226 
 227   // The word size sum of all the regions we will allocate.
 228   size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
 229   assert(word_size <= word_size_sum, "sanity");
 230 
 231   // This will be the "starts humongous" region.
 232   HeapRegion* first_hr = region_at(first);
 233   // The header of the new object will be placed at the bottom of
 234   // the first region.
 235   HeapWord* new_obj = first_hr->bottom();
 236   // This will be the new top of the new object.
 237   HeapWord* obj_top = new_obj + word_size;
 238 
 239   // First, we need to zero the header of the space that we will be
 240   // allocating. When we update top further down, some refinement
 241   // threads might try to scan the region. By zeroing the header we
 242   // ensure that any thread that will try to scan the region will
 243   // come across the zero klass word and bail out.
 244   //
 245   // NOTE: It would not have been correct to have used
 246   // CollectedHeap::fill_with_object() and make the space look like
 247   // an int array. The thread that is doing the allocation will
 248   // later update the object header to a potentially different array
 249   // type and, for a very short period of time, the klass and length
 250   // fields will be inconsistent. This could cause a refinement
 251   // thread to calculate the object size incorrectly.
 252   Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
 253 
 254   // Next, pad out the unused tail of the last region with filler
 255   // objects, for improved usage accounting.
 256   // How many words we use for filler objects.
 257   size_t word_fill_size = word_size_sum - word_size;
 258 
 259   // How many words memory we "waste" which cannot hold a filler object.
 260   size_t words_not_fillable = 0;
 261 
 262   if (word_fill_size >= min_fill_size()) {
 263     fill_with_objects(obj_top, word_fill_size);
 264   } else if (word_fill_size > 0) {
 265     // We have space to fill, but we cannot fit an object there.
 266     words_not_fillable = word_fill_size;
 267     word_fill_size = 0;
 268   }
 269 
 270   // We will set up the first region as "starts humongous". This
 271   // will also update the BOT covering all the regions to reflect
 272   // that there is a single object that starts at the bottom of the
 273   // first region.
 274   first_hr->set_starts_humongous(obj_top, word_fill_size);
 275   _policy->remset_tracker()->update_at_allocate(first_hr);
 276   // Then, if there are any, we will set up the "continues
 277   // humongous" regions.
 278   HeapRegion* hr = NULL;
 279   for (uint i = first + 1; i <= last; ++i) {
 280     hr = region_at(i);
 281     hr->set_continues_humongous(first_hr);
 282     _policy->remset_tracker()->update_at_allocate(hr);
 283   }
 284 
 285   // Up to this point no concurrent thread would have been able to
 286   // do any scanning on any region in this series. All the top
 287   // fields still point to bottom, so the intersection between
 288   // [bottom,top] and [card_start,card_end] will be empty. Before we
 289   // update the top fields, we'll do a storestore to make sure that
 290   // no thread sees the update to top before the zeroing of the
 291   // object header and the BOT initialization.
 292   OrderAccess::storestore();
 293 
 294   // Now, we will update the top fields of the "continues humongous"
 295   // regions except the last one.
 296   for (uint i = first; i < last; ++i) {
 297     hr = region_at(i);
 298     hr->set_top(hr->end());
 299   }
 300 
 301   hr = region_at(last);
 302   // If we cannot fit a filler object, we must set top to the end
 303   // of the humongous object, otherwise we cannot iterate the heap
 304   // and the BOT will not be complete.
 305   hr->set_top(hr->end() - words_not_fillable);
 306 
 307   assert(hr->bottom() < obj_top && obj_top <= hr->end(),
 308          "obj_top should be in last region");
 309 
 310   _verifier->check_bitmaps("Humongous Region Allocation", first_hr);
 311 
 312   assert(words_not_fillable == 0 ||
 313          first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(),
 314          "Miscalculation in humongous allocation");
 315 
 316   increase_used((word_size_sum - words_not_fillable) * HeapWordSize);
 317 
 318   for (uint i = first; i <= last; ++i) {
 319     hr = region_at(i);
 320     _humongous_set.add(hr);
 321     _hr_printer.alloc(hr);
 322   }
 323 
 324   return new_obj;
 325 }
 326 
 327 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) {
 328   assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size);
 329   return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
 330 }
 331 
 332 // If could fit into free regions w/o expansion, try.
 333 // Otherwise, if can expand, do so.
 334 // Otherwise, if using ex regions might help, try with ex given back.
 335 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
 336   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 337 
 338   _verifier->verify_region_sets_optional();
 339 
 340   uint first = G1_NO_HRM_INDEX;
 341   uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);
 342 
 343   if (obj_regions == 1) {
 344     // Only one region to allocate, try to use a fast path by directly allocating
 345     // from the free lists. Do not try to expand here, we will potentially do that
 346     // later.
 347     HeapRegion* hr = new_region(word_size, HeapRegionType::Humongous, false /* do_expand */);
 348     if (hr != NULL) {
 349       first = hr->hrm_index();
 350     }
 351   } else {
 352     // Policy: Try only empty regions (i.e. already committed first). Maybe we
 353     // are lucky enough to find some.
 354     first = _hrm->find_contiguous_only_empty(obj_regions);
 355     if (first != G1_NO_HRM_INDEX) {
 356       _hrm->allocate_free_regions_starting_at(first, obj_regions);
 357     }
 358   }
 359 
 360   if (first == G1_NO_HRM_INDEX) {
 361     // Policy: We could not find enough regions for the humongous object in the
 362     // free list. Look through the heap to find a mix of free and uncommitted regions.
 363     // If so, try expansion.
 364     first = _hrm->find_contiguous_empty_or_unavailable(obj_regions);
 365     if (first != G1_NO_HRM_INDEX) {
 366       // We found something. Make sure these regions are committed, i.e. expand
 367       // the heap. Alternatively we could do a defragmentation GC.
 368       log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B",
 369                                     word_size * HeapWordSize);
 370 
 371       _hrm->expand_at(first, obj_regions, workers());
 372       policy()->record_new_heap_size(num_regions());
 373 
 374 #ifdef ASSERT
 375       for (uint i = first; i < first + obj_regions; ++i) {
 376         HeapRegion* hr = region_at(i);
 377         assert(hr->is_free(), "sanity");
 378         assert(hr->is_empty(), "sanity");
 379         assert(is_on_master_free_list(hr), "sanity");
 380       }
 381 #endif
 382       _hrm->allocate_free_regions_starting_at(first, obj_regions);
 383     } else {
 384       // Policy: Potentially trigger a defragmentation GC.
 385     }
 386   }
 387 
 388   HeapWord* result = NULL;
 389   if (first != G1_NO_HRM_INDEX) {
 390     result = humongous_obj_allocate_initialize_regions(first, obj_regions, word_size);
 391     assert(result != NULL, "it should always return a valid result");
 392 
 393     // A successful humongous object allocation changes the used space
 394     // information of the old generation so we need to recalculate the
 395     // sizes and update the jstat counters here.
 396     g1mm()->update_sizes();
 397   }
 398 
 399   _verifier->verify_region_sets_optional();
 400 
 401   return result;
 402 }
 403 
 404 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t min_size,
 405                                              size_t requested_size,
 406                                              size_t* actual_size) {
 407   assert_heap_not_locked_and_not_at_safepoint();
 408   assert(!is_humongous(requested_size), "we do not allow humongous TLABs");
 409 
 410   return attempt_allocation(min_size, requested_size, actual_size);
 411 }
 412 
 413 HeapWord*
 414 G1CollectedHeap::mem_allocate(size_t word_size,
 415                               bool*  gc_overhead_limit_was_exceeded) {
 416   assert_heap_not_locked_and_not_at_safepoint();
 417 
 418   if (is_humongous(word_size)) {
 419     return attempt_allocation_humongous(word_size);
 420   }
 421   size_t dummy = 0;
 422   return attempt_allocation(word_size, word_size, &dummy);
 423 }
 424 
 425 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size) {
 426   ResourceMark rm; // For retrieving the thread names in log messages.
 427 
 428   // Make sure you read the note in attempt_allocation_humongous().
 429 
 430   assert_heap_not_locked_and_not_at_safepoint();
 431   assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
 432          "be called for humongous allocation requests");
 433 
 434   // We should only get here after the first-level allocation attempt
 435   // (attempt_allocation()) failed to allocate.
 436 
 437   // We will loop until a) we manage to successfully perform the
 438   // allocation or b) we successfully schedule a collection which
 439   // fails to perform the allocation. b) is the only case when we'll
 440   // return NULL.
 441   HeapWord* result = NULL;
 442   for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 443     bool should_try_gc;
 444     uint gc_count_before;
 445 
 446     {
 447       MutexLocker x(Heap_lock);
 448       result = _allocator->attempt_allocation_locked(word_size);
 449       if (result != NULL) {
 450         return result;
 451       }
 452 
 453       // If the GCLocker is active and we are bound for a GC, try expanding young gen.
 454       // This is different to when only GCLocker::needs_gc() is set: try to avoid
 455       // waiting because the GCLocker is active to not wait too long.
 456       if (GCLocker::is_active_and_needs_gc() && policy()->can_expand_young_list()) {
 457         // No need for an ergo message here, can_expand_young_list() does this when
 458         // it returns true.
 459         result = _allocator->attempt_allocation_force(word_size);
 460         if (result != NULL) {
 461           return result;
 462         }
 463       }
 464       // Only try a GC if the GCLocker does not signal the need for a GC. Wait until
 465       // the GCLocker initiated GC has been performed and then retry. This includes
 466       // the case when the GC Locker is not active but has not been performed.
 467       should_try_gc = !GCLocker::needs_gc();
 468       // Read the GC count while still holding the Heap_lock.
 469       gc_count_before = total_collections();
 470     }
 471 
 472     if (should_try_gc) {
 473       bool succeeded;
 474       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 475                                    GCCause::_g1_inc_collection_pause);
 476       if (result != NULL) {
 477         assert(succeeded, "only way to get back a non-NULL result");
 478         log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT,
 479                              Thread::current()->name(), p2i(result));
 480         return result;
 481       }
 482 
 483       if (succeeded) {
 484         // We successfully scheduled a collection which failed to allocate. No
 485         // point in trying to allocate further. We'll just return NULL.
 486         log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate "
 487                              SIZE_FORMAT " words", Thread::current()->name(), word_size);
 488         return NULL;
 489       }
 490       log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT " words",
 491                            Thread::current()->name(), word_size);
 492     } else {
 493       // Failed to schedule a collection.
 494       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 495         log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating "
 496                                SIZE_FORMAT " words", Thread::current()->name(), word_size);
 497         return NULL;
 498       }
 499       log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name());
 500       // The GCLocker is either active or the GCLocker initiated
 501       // GC has not yet been performed. Stall until it is and
 502       // then retry the allocation.
 503       GCLocker::stall_until_clear();
 504       gclocker_retry_count += 1;
 505     }
 506 
 507     // We can reach here if we were unsuccessful in scheduling a
 508     // collection (because another thread beat us to it) or if we were
 509     // stalled due to the GC locker. In either can we should retry the
 510     // allocation attempt in case another thread successfully
 511     // performed a collection and reclaimed enough space. We do the
 512     // first attempt (without holding the Heap_lock) here and the
 513     // follow-on attempt will be at the start of the next loop
 514     // iteration (after taking the Heap_lock).
 515     size_t dummy = 0;
 516     result = _allocator->attempt_allocation(word_size, word_size, &dummy);
 517     if (result != NULL) {
 518       return result;
 519     }
 520 
 521     // Give a warning if we seem to be looping forever.
 522     if ((QueuedAllocationWarningCount > 0) &&
 523         (try_count % QueuedAllocationWarningCount == 0)) {
 524       log_warning(gc, alloc)("%s:  Retried allocation %u times for " SIZE_FORMAT " words",
 525                              Thread::current()->name(), try_count, word_size);
 526     }
 527   }
 528 
 529   ShouldNotReachHere();
 530   return NULL;
 531 }
 532 
 533 void G1CollectedHeap::begin_archive_alloc_range(bool open) {
 534   assert_at_safepoint_on_vm_thread();
 535   if (_archive_allocator == NULL) {
 536     _archive_allocator = G1ArchiveAllocator::create_allocator(this, open);
 537   }
 538 }
 539 
 540 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) {
 541   // Allocations in archive regions cannot be of a size that would be considered
 542   // humongous even for a minimum-sized region, because G1 region sizes/boundaries
 543   // may be different at archive-restore time.
 544   return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words());
 545 }
 546 
 547 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) {
 548   assert_at_safepoint_on_vm_thread();
 549   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 550   if (is_archive_alloc_too_large(word_size)) {
 551     return NULL;
 552   }
 553   return _archive_allocator->archive_mem_allocate(word_size);
 554 }
 555 
 556 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
 557                                               size_t end_alignment_in_bytes) {
 558   assert_at_safepoint_on_vm_thread();
 559   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 560 
 561   // Call complete_archive to do the real work, filling in the MemRegion
 562   // array with the archive regions.
 563   _archive_allocator->complete_archive(ranges, end_alignment_in_bytes);
 564   delete _archive_allocator;
 565   _archive_allocator = NULL;
 566 }
 567 
 568 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) {
 569   assert(ranges != NULL, "MemRegion array NULL");
 570   assert(count != 0, "No MemRegions provided");
 571   MemRegion reserved = _hrm->reserved();
 572   for (size_t i = 0; i < count; i++) {
 573     if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) {
 574       return false;
 575     }
 576   }
 577   return true;
 578 }
 579 
 580 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges,
 581                                             size_t count,
 582                                             bool open) {
 583   assert(!is_init_completed(), "Expect to be called at JVM init time");
 584   assert(ranges != NULL, "MemRegion array NULL");
 585   assert(count != 0, "No MemRegions provided");
 586   MutexLocker x(Heap_lock);
 587 
 588   MemRegion reserved = _hrm->reserved();
 589   HeapWord* prev_last_addr = NULL;
 590   HeapRegion* prev_last_region = NULL;
 591 
 592   // Temporarily disable pretouching of heap pages. This interface is used
 593   // when mmap'ing archived heap data in, so pre-touching is wasted.
 594   FlagSetting fs(AlwaysPreTouch, false);
 595 
 596   // Enable archive object checking used by G1MarkSweep. We have to let it know
 597   // about each archive range, so that objects in those ranges aren't marked.
 598   G1ArchiveAllocator::enable_archive_object_check();
 599 
 600   // For each specified MemRegion range, allocate the corresponding G1
 601   // regions and mark them as archive regions. We expect the ranges
 602   // in ascending starting address order, without overlap.
 603   for (size_t i = 0; i < count; i++) {
 604     MemRegion curr_range = ranges[i];
 605     HeapWord* start_address = curr_range.start();
 606     size_t word_size = curr_range.word_size();
 607     HeapWord* last_address = curr_range.last();
 608     size_t commits = 0;
 609 
 610     guarantee(reserved.contains(start_address) && reserved.contains(last_address),
 611               "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 612               p2i(start_address), p2i(last_address));
 613     guarantee(start_address > prev_last_addr,
 614               "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 615               p2i(start_address), p2i(prev_last_addr));
 616     prev_last_addr = last_address;
 617 
 618     // Check for ranges that start in the same G1 region in which the previous
 619     // range ended, and adjust the start address so we don't try to allocate
 620     // the same region again. If the current range is entirely within that
 621     // region, skip it, just adjusting the recorded top.
 622     HeapRegion* start_region = _hrm->addr_to_region(start_address);
 623     if ((prev_last_region != NULL) && (start_region == prev_last_region)) {
 624       start_address = start_region->end();
 625       if (start_address > last_address) {
 626         increase_used(word_size * HeapWordSize);
 627         start_region->set_top(last_address + 1);
 628         continue;
 629       }
 630       start_region->set_top(start_address);
 631       curr_range = MemRegion(start_address, last_address + 1);
 632       start_region = _hrm->addr_to_region(start_address);
 633     }
 634 
 635     // Perform the actual region allocation, exiting if it fails.
 636     // Then note how much new space we have allocated.
 637     if (!_hrm->allocate_containing_regions(curr_range, &commits, workers())) {
 638       return false;
 639     }
 640     increase_used(word_size * HeapWordSize);
 641     if (commits != 0) {
 642       log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B",
 643                                 HeapRegion::GrainWords * HeapWordSize * commits);
 644 
 645     }
 646 
 647     // Mark each G1 region touched by the range as archive, add it to
 648     // the old set, and set top.
 649     HeapRegion* curr_region = _hrm->addr_to_region(start_address);
 650     HeapRegion* last_region = _hrm->addr_to_region(last_address);
 651     prev_last_region = last_region;
 652 
 653     while (curr_region != NULL) {
 654       assert(curr_region->is_empty() && !curr_region->is_pinned(),
 655              "Region already in use (index %u)", curr_region->hrm_index());
 656       if (open) {
 657         curr_region->set_open_archive();
 658       } else {
 659         curr_region->set_closed_archive();
 660       }
 661       _hr_printer.alloc(curr_region);
 662       _archive_set.add(curr_region);
 663       HeapWord* top;
 664       HeapRegion* next_region;
 665       if (curr_region != last_region) {
 666         top = curr_region->end();
 667         next_region = _hrm->next_region_in_heap(curr_region);
 668       } else {
 669         top = last_address + 1;
 670         next_region = NULL;
 671       }
 672       curr_region->set_top(top);
 673       curr_region = next_region;
 674     }
 675 
 676     // Notify mark-sweep of the archive
 677     G1ArchiveAllocator::set_range_archive(curr_range, open);
 678   }
 679   return true;
 680 }
 681 
 682 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) {
 683   assert(!is_init_completed(), "Expect to be called at JVM init time");
 684   assert(ranges != NULL, "MemRegion array NULL");
 685   assert(count != 0, "No MemRegions provided");
 686   MemRegion reserved = _hrm->reserved();
 687   HeapWord *prev_last_addr = NULL;
 688   HeapRegion* prev_last_region = NULL;
 689 
 690   // For each MemRegion, create filler objects, if needed, in the G1 regions
 691   // that contain the address range. The address range actually within the
 692   // MemRegion will not be modified. That is assumed to have been initialized
 693   // elsewhere, probably via an mmap of archived heap data.
 694   MutexLocker x(Heap_lock);
 695   for (size_t i = 0; i < count; i++) {
 696     HeapWord* start_address = ranges[i].start();
 697     HeapWord* last_address = ranges[i].last();
 698 
 699     assert(reserved.contains(start_address) && reserved.contains(last_address),
 700            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 701            p2i(start_address), p2i(last_address));
 702     assert(start_address > prev_last_addr,
 703            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 704            p2i(start_address), p2i(prev_last_addr));
 705 
 706     HeapRegion* start_region = _hrm->addr_to_region(start_address);
 707     HeapRegion* last_region = _hrm->addr_to_region(last_address);
 708     HeapWord* bottom_address = start_region->bottom();
 709 
 710     // Check for a range beginning in the same region in which the
 711     // previous one ended.
 712     if (start_region == prev_last_region) {
 713       bottom_address = prev_last_addr + 1;
 714     }
 715 
 716     // Verify that the regions were all marked as archive regions by
 717     // alloc_archive_regions.
 718     HeapRegion* curr_region = start_region;
 719     while (curr_region != NULL) {
 720       guarantee(curr_region->is_archive(),
 721                 "Expected archive region at index %u", curr_region->hrm_index());
 722       if (curr_region != last_region) {
 723         curr_region = _hrm->next_region_in_heap(curr_region);
 724       } else {
 725         curr_region = NULL;
 726       }
 727     }
 728 
 729     prev_last_addr = last_address;
 730     prev_last_region = last_region;
 731 
 732     // Fill the memory below the allocated range with dummy object(s),
 733     // if the region bottom does not match the range start, or if the previous
 734     // range ended within the same G1 region, and there is a gap.
 735     if (start_address != bottom_address) {
 736       size_t fill_size = pointer_delta(start_address, bottom_address);
 737       G1CollectedHeap::fill_with_objects(bottom_address, fill_size);
 738       increase_used(fill_size * HeapWordSize);
 739     }
 740   }
 741 }
 742 
 743 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t min_word_size,
 744                                                      size_t desired_word_size,
 745                                                      size_t* actual_word_size) {
 746   assert_heap_not_locked_and_not_at_safepoint();
 747   assert(!is_humongous(desired_word_size), "attempt_allocation() should not "
 748          "be called for humongous allocation requests");
 749 
 750   HeapWord* result = _allocator->attempt_allocation(min_word_size, desired_word_size, actual_word_size);
 751 
 752   if (result == NULL) {
 753     *actual_word_size = desired_word_size;
 754     result = attempt_allocation_slow(desired_word_size);
 755   }
 756 
 757   assert_heap_not_locked();
 758   if (result != NULL) {
 759     assert(*actual_word_size != 0, "Actual size must have been set here");
 760     dirty_young_block(result, *actual_word_size);
 761   } else {
 762     *actual_word_size = 0;
 763   }
 764 
 765   return result;
 766 }
 767 
 768 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count, bool is_open) {
 769   assert(!is_init_completed(), "Expect to be called at JVM init time");
 770   assert(ranges != NULL, "MemRegion array NULL");
 771   assert(count != 0, "No MemRegions provided");
 772   MemRegion reserved = _hrm->reserved();
 773   HeapWord* prev_last_addr = NULL;
 774   HeapRegion* prev_last_region = NULL;
 775   size_t size_used = 0;
 776   size_t uncommitted_regions = 0;
 777 
 778   // For each Memregion, free the G1 regions that constitute it, and
 779   // notify mark-sweep that the range is no longer to be considered 'archive.'
 780   MutexLocker x(Heap_lock);
 781   for (size_t i = 0; i < count; i++) {
 782     HeapWord* start_address = ranges[i].start();
 783     HeapWord* last_address = ranges[i].last();
 784 
 785     assert(reserved.contains(start_address) && reserved.contains(last_address),
 786            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 787            p2i(start_address), p2i(last_address));
 788     assert(start_address > prev_last_addr,
 789            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 790            p2i(start_address), p2i(prev_last_addr));
 791     size_used += ranges[i].byte_size();
 792     prev_last_addr = last_address;
 793 
 794     HeapRegion* start_region = _hrm->addr_to_region(start_address);
 795     HeapRegion* last_region = _hrm->addr_to_region(last_address);
 796 
 797     // Check for ranges that start in the same G1 region in which the previous
 798     // range ended, and adjust the start address so we don't try to free
 799     // the same region again. If the current range is entirely within that
 800     // region, skip it.
 801     if (start_region == prev_last_region) {
 802       start_address = start_region->end();
 803       if (start_address > last_address) {
 804         continue;
 805       }
 806       start_region = _hrm->addr_to_region(start_address);
 807     }
 808     prev_last_region = last_region;
 809 
 810     // After verifying that each region was marked as an archive region by
 811     // alloc_archive_regions, set it free and empty and uncommit it.
 812     HeapRegion* curr_region = start_region;
 813     while (curr_region != NULL) {
 814       guarantee(curr_region->is_archive(),
 815                 "Expected archive region at index %u", curr_region->hrm_index());
 816       uint curr_index = curr_region->hrm_index();
 817       _archive_set.remove(curr_region);
 818       curr_region->set_free();
 819       curr_region->set_top(curr_region->bottom());
 820       if (curr_region != last_region) {
 821         curr_region = _hrm->next_region_in_heap(curr_region);
 822       } else {
 823         curr_region = NULL;
 824       }
 825       _hrm->shrink_at(curr_index, 1);
 826       uncommitted_regions++;
 827     }
 828 
 829     // Notify mark-sweep that this is no longer an archive range.
 830     G1ArchiveAllocator::clear_range_archive(ranges[i], is_open);
 831   }
 832 
 833   if (uncommitted_regions != 0) {
 834     log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B",
 835                               HeapRegion::GrainWords * HeapWordSize * uncommitted_regions);
 836   }
 837   decrease_used(size_used);
 838 }
 839 
 840 oop G1CollectedHeap::materialize_archived_object(oop obj) {
 841   assert(obj != NULL, "archived obj is NULL");
 842   assert(G1ArchiveAllocator::is_archived_object(obj), "must be archived object");
 843 
 844   // Loading an archived object makes it strongly reachable. If it is
 845   // loaded during concurrent marking, it must be enqueued to the SATB
 846   // queue, shading the previously white object gray.
 847   G1BarrierSet::enqueue(obj);
 848 
 849   return obj;
 850 }
 851 
 852 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size) {
 853   ResourceMark rm; // For retrieving the thread names in log messages.
 854 
 855   // The structure of this method has a lot of similarities to
 856   // attempt_allocation_slow(). The reason these two were not merged
 857   // into a single one is that such a method would require several "if
 858   // allocation is not humongous do this, otherwise do that"
 859   // conditional paths which would obscure its flow. In fact, an early
 860   // version of this code did use a unified method which was harder to
 861   // follow and, as a result, it had subtle bugs that were hard to
 862   // track down. So keeping these two methods separate allows each to
 863   // be more readable. It will be good to keep these two in sync as
 864   // much as possible.
 865 
 866   assert_heap_not_locked_and_not_at_safepoint();
 867   assert(is_humongous(word_size), "attempt_allocation_humongous() "
 868          "should only be called for humongous allocations");
 869 
 870   // Humongous objects can exhaust the heap quickly, so we should check if we
 871   // need to start a marking cycle at each humongous object allocation. We do
 872   // the check before we do the actual allocation. The reason for doing it
 873   // before the allocation is that we avoid having to keep track of the newly
 874   // allocated memory while we do a GC.
 875   if (policy()->need_to_start_conc_mark("concurrent humongous allocation",
 876                                            word_size)) {
 877     collect(GCCause::_g1_humongous_allocation);
 878   }
 879 
 880   // We will loop until a) we manage to successfully perform the
 881   // allocation or b) we successfully schedule a collection which
 882   // fails to perform the allocation. b) is the only case when we'll
 883   // return NULL.
 884   HeapWord* result = NULL;
 885   for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 886     bool should_try_gc;
 887     uint gc_count_before;
 888 
 889 
 890     {
 891       MutexLocker x(Heap_lock);
 892 
 893       // Given that humongous objects are not allocated in young
 894       // regions, we'll first try to do the allocation without doing a
 895       // collection hoping that there's enough space in the heap.
 896       result = humongous_obj_allocate(word_size);
 897       if (result != NULL) {
 898         size_t size_in_regions = humongous_obj_size_in_regions(word_size);
 899         policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
 900         return result;
 901       }
 902 
 903       // Only try a GC if the GCLocker does not signal the need for a GC. Wait until
 904       // the GCLocker initiated GC has been performed and then retry. This includes
 905       // the case when the GC Locker is not active but has not been performed.
 906       should_try_gc = !GCLocker::needs_gc();
 907       // Read the GC count while still holding the Heap_lock.
 908       gc_count_before = total_collections();
 909     }
 910 
 911     if (should_try_gc) {
 912       bool succeeded;
 913       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 914                                    GCCause::_g1_humongous_allocation);
 915       if (result != NULL) {
 916         assert(succeeded, "only way to get back a non-NULL result");
 917         log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT,
 918                              Thread::current()->name(), p2i(result));
 919         return result;
 920       }
 921 
 922       if (succeeded) {
 923         // We successfully scheduled a collection which failed to allocate. No
 924         // point in trying to allocate further. We'll just return NULL.
 925         log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate "
 926                              SIZE_FORMAT " words", Thread::current()->name(), word_size);
 927         return NULL;
 928       }
 929       log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT "",
 930                            Thread::current()->name(), word_size);
 931     } else {
 932       // Failed to schedule a collection.
 933       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 934         log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating "
 935                                SIZE_FORMAT " words", Thread::current()->name(), word_size);
 936         return NULL;
 937       }
 938       log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name());
 939       // The GCLocker is either active or the GCLocker initiated
 940       // GC has not yet been performed. Stall until it is and
 941       // then retry the allocation.
 942       GCLocker::stall_until_clear();
 943       gclocker_retry_count += 1;
 944     }
 945 
 946 
 947     // We can reach here if we were unsuccessful in scheduling a
 948     // collection (because another thread beat us to it) or if we were
 949     // stalled due to the GC locker. In either can we should retry the
 950     // allocation attempt in case another thread successfully
 951     // performed a collection and reclaimed enough space.
 952     // Humongous object allocation always needs a lock, so we wait for the retry
 953     // in the next iteration of the loop, unlike for the regular iteration case.
 954     // Give a warning if we seem to be looping forever.
 955 
 956     if ((QueuedAllocationWarningCount > 0) &&
 957         (try_count % QueuedAllocationWarningCount == 0)) {
 958       log_warning(gc, alloc)("%s: Retried allocation %u times for " SIZE_FORMAT " words",
 959                              Thread::current()->name(), try_count, word_size);
 960     }
 961   }
 962 
 963   ShouldNotReachHere();
 964   return NULL;
 965 }
 966 
 967 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
 968                                                            bool expect_null_mutator_alloc_region) {
 969   assert_at_safepoint_on_vm_thread();
 970   assert(!_allocator->has_mutator_alloc_region() || !expect_null_mutator_alloc_region,
 971          "the current alloc region was unexpectedly found to be non-NULL");
 972 
 973   if (!is_humongous(word_size)) {
 974     return _allocator->attempt_allocation_locked(word_size);
 975   } else {
 976     HeapWord* result = humongous_obj_allocate(word_size);
 977     if (result != NULL && policy()->need_to_start_conc_mark("STW humongous allocation")) {
 978       collector_state()->set_initiate_conc_mark_if_possible(true);
 979     }
 980     return result;
 981   }
 982 
 983   ShouldNotReachHere();
 984 }
 985 
 986 class PostCompactionPrinterClosure: public HeapRegionClosure {
 987 private:
 988   G1HRPrinter* _hr_printer;
 989 public:
 990   bool do_heap_region(HeapRegion* hr) {
 991     assert(!hr->is_young(), "not expecting to find young regions");
 992     _hr_printer->post_compaction(hr);
 993     return false;
 994   }
 995 
 996   PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
 997     : _hr_printer(hr_printer) { }
 998 };
 999 
1000 void G1CollectedHeap::print_hrm_post_compaction() {
1001   if (_hr_printer.is_active()) {
1002     PostCompactionPrinterClosure cl(hr_printer());
1003     heap_region_iterate(&cl);
1004   }
1005 }
1006 
1007 void G1CollectedHeap::abort_concurrent_cycle() {
1008   // If we start the compaction before the CM threads finish
1009   // scanning the root regions we might trip them over as we'll
1010   // be moving objects / updating references. So let's wait until
1011   // they are done. By telling them to abort, they should complete
1012   // early.
1013   _cm->root_regions()->abort();
1014   _cm->root_regions()->wait_until_scan_finished();
1015 
1016   // Disable discovery and empty the discovered lists
1017   // for the CM ref processor.
1018   _ref_processor_cm->disable_discovery();
1019   _ref_processor_cm->abandon_partial_discovery();
1020   _ref_processor_cm->verify_no_references_recorded();
1021 
1022   // Abandon current iterations of concurrent marking and concurrent
1023   // refinement, if any are in progress.
1024   concurrent_mark()->concurrent_cycle_abort();
1025 }
1026 
1027 void G1CollectedHeap::prepare_heap_for_full_collection() {
1028   // Make sure we'll choose a new allocation region afterwards.
1029   _allocator->release_mutator_alloc_regions();
1030   _allocator->abandon_gc_alloc_regions();
1031 
1032   // We may have added regions to the current incremental collection
1033   // set between the last GC or pause and now. We need to clear the
1034   // incremental collection set and then start rebuilding it afresh
1035   // after this full GC.
1036   abandon_collection_set(collection_set());
1037 
1038   tear_down_region_sets(false /* free_list_only */);
1039 
1040   hrm()->prepare_for_full_collection_start();
1041 }
1042 
1043 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) {
1044   assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant");
1045   assert_used_and_recalculate_used_equal(this);
1046   _verifier->verify_region_sets_optional();
1047   _verifier->verify_before_gc(G1HeapVerifier::G1VerifyFull);
1048   _verifier->check_bitmaps("Full GC Start");
1049 }
1050 
1051 void G1CollectedHeap::prepare_heap_for_mutators() {
1052   hrm()->prepare_for_full_collection_end();
1053 
1054   // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1055   ClassLoaderDataGraph::purge();
1056   MetaspaceUtils::verify_metrics();
1057 
1058   // Prepare heap for normal collections.
1059   assert(num_free_regions() == 0, "we should not have added any free regions");
1060   rebuild_region_sets(false /* free_list_only */);
1061   abort_refinement();
1062   resize_heap_if_necessary();
1063 
1064   // Rebuild the strong code root lists for each region
1065   rebuild_strong_code_roots();
1066 
1067   // Purge code root memory
1068   purge_code_root_memory();
1069 
1070   // Start a new incremental collection set for the next pause
1071   start_new_collection_set();
1072 
1073   _allocator->init_mutator_alloc_regions();
1074 
1075   // Post collection state updates.
1076   MetaspaceGC::compute_new_size();
1077 }
1078 
1079 void G1CollectedHeap::abort_refinement() {
1080   if (_hot_card_cache->use_cache()) {
1081     _hot_card_cache->reset_hot_cache();
1082   }
1083 
1084   // Discard all remembered set updates.
1085   G1BarrierSet::dirty_card_queue_set().abandon_logs();
1086   assert(G1BarrierSet::dirty_card_queue_set().num_cards() == 0,
1087          "DCQS should be empty");
1088 }
1089 
1090 void G1CollectedHeap::verify_after_full_collection() {
1091   _hrm->verify_optional();
1092   _verifier->verify_region_sets_optional();
1093   _verifier->verify_after_gc(G1HeapVerifier::G1VerifyFull);
1094   // Clear the previous marking bitmap, if needed for bitmap verification.
1095   // Note we cannot do this when we clear the next marking bitmap in
1096   // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the
1097   // objects marked during a full GC against the previous bitmap.
1098   // But we need to clear it before calling check_bitmaps below since
1099   // the full GC has compacted objects and updated TAMS but not updated
1100   // the prev bitmap.
1101   if (G1VerifyBitmaps) {
1102     GCTraceTime(Debug, gc) tm("Clear Prev Bitmap for Verification");
1103     _cm->clear_prev_bitmap(workers());
1104   }
1105   // This call implicitly verifies that the next bitmap is clear after Full GC.
1106   _verifier->check_bitmaps("Full GC End");
1107 
1108   // At this point there should be no regions in the
1109   // entire heap tagged as young.
1110   assert(check_young_list_empty(), "young list should be empty at this point");
1111 
1112   // Note: since we've just done a full GC, concurrent
1113   // marking is no longer active. Therefore we need not
1114   // re-enable reference discovery for the CM ref processor.
1115   // That will be done at the start of the next marking cycle.
1116   // We also know that the STW processor should no longer
1117   // discover any new references.
1118   assert(!_ref_processor_stw->discovery_enabled(), "Postcondition");
1119   assert(!_ref_processor_cm->discovery_enabled(), "Postcondition");
1120   _ref_processor_stw->verify_no_references_recorded();
1121   _ref_processor_cm->verify_no_references_recorded();
1122 }
1123 
1124 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) {
1125   // Post collection logging.
1126   // We should do this after we potentially resize the heap so
1127   // that all the COMMIT / UNCOMMIT events are generated before
1128   // the compaction events.
1129   print_hrm_post_compaction();
1130   heap_transition->print();
1131   print_heap_after_gc();
1132   print_heap_regions();
1133 #ifdef TRACESPINNING
1134   ParallelTaskTerminator::print_termination_counts();
1135 #endif
1136 }
1137 
1138 bool G1CollectedHeap::do_full_collection(bool explicit_gc,
1139                                          bool clear_all_soft_refs) {
1140   assert_at_safepoint_on_vm_thread();
1141 
1142   if (GCLocker::check_active_before_gc()) {
1143     // Full GC was not completed.
1144     return false;
1145   }
1146 
1147   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1148       soft_ref_policy()->should_clear_all_soft_refs();
1149 
1150   G1FullCollector collector(this, explicit_gc, do_clear_all_soft_refs);
1151   GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true);
1152 
1153   collector.prepare_collection();
1154   collector.collect();
1155   collector.complete_collection();
1156 
1157   // Full collection was successfully completed.
1158   return true;
1159 }
1160 
1161 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1162   // Currently, there is no facility in the do_full_collection(bool) API to notify
1163   // the caller that the collection did not succeed (e.g., because it was locked
1164   // out by the GC locker). So, right now, we'll ignore the return value.
1165   bool dummy = do_full_collection(true,                /* explicit_gc */
1166                                   clear_all_soft_refs);
1167 }
1168 
1169 void G1CollectedHeap::resize_heap_if_necessary() {
1170   assert_at_safepoint_on_vm_thread();
1171 
1172   // Capacity, free and used after the GC counted as full regions to
1173   // include the waste in the following calculations.
1174   const size_t capacity_after_gc = capacity();
1175   const size_t used_after_gc = capacity_after_gc - unused_committed_regions_in_bytes();
1176 
1177   // This is enforced in arguments.cpp.
1178   assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1179          "otherwise the code below doesn't make sense");
1180 
1181   // We don't have floating point command-line arguments
1182   const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1183   const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1184   const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1185   const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1186 
1187   // We have to be careful here as these two calculations can overflow
1188   // 32-bit size_t's.
1189   double used_after_gc_d = (double) used_after_gc;
1190   double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1191   double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1192 
1193   // Let's make sure that they are both under the max heap size, which
1194   // by default will make them fit into a size_t.
1195   double desired_capacity_upper_bound = (double) MaxHeapSize;
1196   minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1197                                     desired_capacity_upper_bound);
1198   maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1199                                     desired_capacity_upper_bound);
1200 
1201   // We can now safely turn them into size_t's.
1202   size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1203   size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1204 
1205   // This assert only makes sense here, before we adjust them
1206   // with respect to the min and max heap size.
1207   assert(minimum_desired_capacity <= maximum_desired_capacity,
1208          "minimum_desired_capacity = " SIZE_FORMAT ", "
1209          "maximum_desired_capacity = " SIZE_FORMAT,
1210          minimum_desired_capacity, maximum_desired_capacity);
1211 
1212   // Should not be greater than the heap max size. No need to adjust
1213   // it with respect to the heap min size as it's a lower bound (i.e.,
1214   // we'll try to make the capacity larger than it, not smaller).
1215   minimum_desired_capacity = MIN2(minimum_desired_capacity, MaxHeapSize);
1216   // Should not be less than the heap min size. No need to adjust it
1217   // with respect to the heap max size as it's an upper bound (i.e.,
1218   // we'll try to make the capacity smaller than it, not greater).
1219   maximum_desired_capacity =  MAX2(maximum_desired_capacity, MinHeapSize);
1220 
1221   if (capacity_after_gc < minimum_desired_capacity) {
1222     // Don't expand unless it's significant
1223     size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1224 
1225     log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity). "
1226                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1227                               "min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1228                               capacity_after_gc, used_after_gc, used(), minimum_desired_capacity, MinHeapFreeRatio);
1229 
1230     expand(expand_bytes, _workers);
1231 
1232     // No expansion, now see if we want to shrink
1233   } else if (capacity_after_gc > maximum_desired_capacity) {
1234     // Capacity too large, compute shrinking size
1235     size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1236 
1237     log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity). "
1238                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1239                               "maximum_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1240                               capacity_after_gc, used_after_gc, used(), maximum_desired_capacity, MaxHeapFreeRatio);
1241 
1242     shrink(shrink_bytes);
1243   }
1244 }
1245 
1246 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size,
1247                                                             bool do_gc,
1248                                                             bool clear_all_soft_refs,
1249                                                             bool expect_null_mutator_alloc_region,
1250                                                             bool* gc_succeeded) {
1251   *gc_succeeded = true;
1252   // Let's attempt the allocation first.
1253   HeapWord* result =
1254     attempt_allocation_at_safepoint(word_size,
1255                                     expect_null_mutator_alloc_region);
1256   if (result != NULL) {
1257     return result;
1258   }
1259 
1260   // In a G1 heap, we're supposed to keep allocation from failing by
1261   // incremental pauses.  Therefore, at least for now, we'll favor
1262   // expansion over collection.  (This might change in the future if we can
1263   // do something smarter than full collection to satisfy a failed alloc.)
1264   result = expand_and_allocate(word_size);
1265   if (result != NULL) {
1266     return result;
1267   }
1268 
1269   if (do_gc) {
1270     // Expansion didn't work, we'll try to do a Full GC.
1271     *gc_succeeded = do_full_collection(false, /* explicit_gc */
1272                                        clear_all_soft_refs);
1273   }
1274 
1275   return NULL;
1276 }
1277 
1278 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1279                                                      bool* succeeded) {
1280   assert_at_safepoint_on_vm_thread();
1281 
1282   // Attempts to allocate followed by Full GC.
1283   HeapWord* result =
1284     satisfy_failed_allocation_helper(word_size,
1285                                      true,  /* do_gc */
1286                                      false, /* clear_all_soft_refs */
1287                                      false, /* expect_null_mutator_alloc_region */
1288                                      succeeded);
1289 
1290   if (result != NULL || !*succeeded) {
1291     return result;
1292   }
1293 
1294   // Attempts to allocate followed by Full GC that will collect all soft references.
1295   result = satisfy_failed_allocation_helper(word_size,
1296                                             true, /* do_gc */
1297                                             true, /* clear_all_soft_refs */
1298                                             true, /* expect_null_mutator_alloc_region */
1299                                             succeeded);
1300 
1301   if (result != NULL || !*succeeded) {
1302     return result;
1303   }
1304 
1305   // Attempts to allocate, no GC
1306   result = satisfy_failed_allocation_helper(word_size,
1307                                             false, /* do_gc */
1308                                             false, /* clear_all_soft_refs */
1309                                             true,  /* expect_null_mutator_alloc_region */
1310                                             succeeded);
1311 
1312   if (result != NULL) {
1313     return result;
1314   }
1315 
1316   assert(!soft_ref_policy()->should_clear_all_soft_refs(),
1317          "Flag should have been handled and cleared prior to this point");
1318 
1319   // What else?  We might try synchronous finalization later.  If the total
1320   // space available is large enough for the allocation, then a more
1321   // complete compaction phase than we've tried so far might be
1322   // appropriate.
1323   return NULL;
1324 }
1325 
1326 // Attempting to expand the heap sufficiently
1327 // to support an allocation of the given "word_size".  If
1328 // successful, perform the allocation and return the address of the
1329 // allocated block, or else "NULL".
1330 
1331 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1332   assert_at_safepoint_on_vm_thread();
1333 
1334   _verifier->verify_region_sets_optional();
1335 
1336   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1337   log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B",
1338                             word_size * HeapWordSize);
1339 
1340 
1341   if (expand(expand_bytes, _workers)) {
1342     _hrm->verify_optional();
1343     _verifier->verify_region_sets_optional();
1344     return attempt_allocation_at_safepoint(word_size,
1345                                            false /* expect_null_mutator_alloc_region */);
1346   }
1347   return NULL;
1348 }
1349 
1350 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) {
1351   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1352   aligned_expand_bytes = align_up(aligned_expand_bytes,
1353                                        HeapRegion::GrainBytes);
1354 
1355   log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B",
1356                             expand_bytes, aligned_expand_bytes);
1357 
1358   if (is_maximal_no_gc()) {
1359     log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1360     return false;
1361   }
1362 
1363   double expand_heap_start_time_sec = os::elapsedTime();
1364   uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1365   assert(regions_to_expand > 0, "Must expand by at least one region");
1366 
1367   uint expanded_by = _hrm->expand_by(regions_to_expand, pretouch_workers);
1368   if (expand_time_ms != NULL) {
1369     *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS;
1370   }
1371 
1372   if (expanded_by > 0) {
1373     size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1374     assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1375     policy()->record_new_heap_size(num_regions());
1376   } else {
1377     log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)");
1378 
1379     // The expansion of the virtual storage space was unsuccessful.
1380     // Let's see if it was because we ran out of swap.
1381     if (G1ExitOnExpansionFailure &&
1382         _hrm->available() >= regions_to_expand) {
1383       // We had head room...
1384       vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1385     }
1386   }
1387   return regions_to_expand > 0;
1388 }
1389 
1390 bool G1CollectedHeap::expand_single_region(uint node_index) {
1391   uint expanded_by = _hrm->expand_on_preferred_node(node_index);
1392 
1393   if (expanded_by == 0) {
1394     assert(is_maximal_no_gc(), "Should be no regions left, available: %u", _hrm->available());
1395     log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1396     return false;
1397   }
1398 
1399   policy()->record_new_heap_size(num_regions());
1400   return true;
1401 }
1402 
1403 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1404   size_t aligned_shrink_bytes =
1405     ReservedSpace::page_align_size_down(shrink_bytes);
1406   aligned_shrink_bytes = align_down(aligned_shrink_bytes,
1407                                          HeapRegion::GrainBytes);
1408   uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1409 
1410   uint num_regions_removed = _hrm->shrink_by(num_regions_to_remove);
1411   size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1412 
1413   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",
1414                             shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1415   if (num_regions_removed > 0) {
1416     policy()->record_new_heap_size(num_regions());
1417   } else {
1418     log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)");
1419   }
1420 }
1421 
1422 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1423   _verifier->verify_region_sets_optional();
1424 
1425   // We should only reach here at the end of a Full GC or during Remark which
1426   // means we should not not be holding to any GC alloc regions. The method
1427   // below will make sure of that and do any remaining clean up.
1428   _allocator->abandon_gc_alloc_regions();
1429 
1430   // Instead of tearing down / rebuilding the free lists here, we
1431   // could instead use the remove_all_pending() method on free_list to
1432   // remove only the ones that we need to remove.
1433   tear_down_region_sets(true /* free_list_only */);
1434   shrink_helper(shrink_bytes);
1435   rebuild_region_sets(true /* free_list_only */);
1436 
1437   _hrm->verify_optional();
1438   _verifier->verify_region_sets_optional();
1439 }
1440 
1441 class OldRegionSetChecker : public HeapRegionSetChecker {
1442 public:
1443   void check_mt_safety() {
1444     // Master Old Set MT safety protocol:
1445     // (a) If we're at a safepoint, operations on the master old set
1446     // should be invoked:
1447     // - by the VM thread (which will serialize them), or
1448     // - by the GC workers while holding the FreeList_lock, if we're
1449     //   at a safepoint for an evacuation pause (this lock is taken
1450     //   anyway when an GC alloc region is retired so that a new one
1451     //   is allocated from the free list), or
1452     // - by the GC workers while holding the OldSets_lock, if we're at a
1453     //   safepoint for a cleanup pause.
1454     // (b) If we're not at a safepoint, operations on the master old set
1455     // should be invoked while holding the Heap_lock.
1456 
1457     if (SafepointSynchronize::is_at_safepoint()) {
1458       guarantee(Thread::current()->is_VM_thread() ||
1459                 FreeList_lock->owned_by_self() || OldSets_lock->owned_by_self(),
1460                 "master old set MT safety protocol at a safepoint");
1461     } else {
1462       guarantee(Heap_lock->owned_by_self(), "master old set MT safety protocol outside a safepoint");
1463     }
1464   }
1465   bool is_correct_type(HeapRegion* hr) { return hr->is_old(); }
1466   const char* get_description() { return "Old Regions"; }
1467 };
1468 
1469 class ArchiveRegionSetChecker : public HeapRegionSetChecker {
1470 public:
1471   void check_mt_safety() {
1472     guarantee(!Universe::is_fully_initialized() || SafepointSynchronize::is_at_safepoint(),
1473               "May only change archive regions during initialization or safepoint.");
1474   }
1475   bool is_correct_type(HeapRegion* hr) { return hr->is_archive(); }
1476   const char* get_description() { return "Archive Regions"; }
1477 };
1478 
1479 class HumongousRegionSetChecker : public HeapRegionSetChecker {
1480 public:
1481   void check_mt_safety() {
1482     // Humongous Set MT safety protocol:
1483     // (a) If we're at a safepoint, operations on the master humongous
1484     // set should be invoked by either the VM thread (which will
1485     // serialize them) or by the GC workers while holding the
1486     // OldSets_lock.
1487     // (b) If we're not at a safepoint, operations on the master
1488     // humongous set should be invoked while holding the Heap_lock.
1489 
1490     if (SafepointSynchronize::is_at_safepoint()) {
1491       guarantee(Thread::current()->is_VM_thread() ||
1492                 OldSets_lock->owned_by_self(),
1493                 "master humongous set MT safety protocol at a safepoint");
1494     } else {
1495       guarantee(Heap_lock->owned_by_self(),
1496                 "master humongous set MT safety protocol outside a safepoint");
1497     }
1498   }
1499   bool is_correct_type(HeapRegion* hr) { return hr->is_humongous(); }
1500   const char* get_description() { return "Humongous Regions"; }
1501 };
1502 
1503 G1CollectedHeap::G1CollectedHeap() :
1504   CollectedHeap(),
1505   _young_gen_sampling_thread(NULL),
1506   _workers(NULL),
1507   _card_table(NULL),
1508   _soft_ref_policy(),
1509   _old_set("Old Region Set", new OldRegionSetChecker()),
1510   _archive_set("Archive Region Set", new ArchiveRegionSetChecker()),
1511   _humongous_set("Humongous Region Set", new HumongousRegionSetChecker()),
1512   _bot(NULL),
1513   _listener(),
1514   _numa(G1NUMA::create()),
1515   _hrm(NULL),
1516   _allocator(NULL),
1517   _verifier(NULL),
1518   _summary_bytes_used(0),
1519   _bytes_used_during_gc(0),
1520   _archive_allocator(NULL),
1521   _survivor_evac_stats("Young", YoungPLABSize, PLABWeight),
1522   _old_evac_stats("Old", OldPLABSize, PLABWeight),
1523   _expand_heap_after_alloc_failure(true),
1524   _g1mm(NULL),
1525   _humongous_reclaim_candidates(),
1526   _has_humongous_reclaim_candidates(false),
1527   _hr_printer(),
1528   _collector_state(),
1529   _old_marking_cycles_started(0),
1530   _old_marking_cycles_completed(0),
1531   _eden(),
1532   _survivor(),
1533   _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1534   _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1535   _policy(G1Policy::create_policy(_gc_timer_stw)),
1536   _heap_sizing_policy(NULL),
1537   _collection_set(this, _policy),
1538   _hot_card_cache(NULL),
1539   _rem_set(NULL),
1540   _cm(NULL),
1541   _cm_thread(NULL),
1542   _cr(NULL),
1543   _task_queues(NULL),
1544   _evacuation_failed(false),
1545   _evacuation_failed_info_array(NULL),
1546   _preserved_marks_set(true /* in_c_heap */),
1547 #ifndef PRODUCT
1548   _evacuation_failure_alot_for_current_gc(false),
1549   _evacuation_failure_alot_gc_number(0),
1550   _evacuation_failure_alot_count(0),
1551 #endif
1552   _ref_processor_stw(NULL),
1553   _is_alive_closure_stw(this),
1554   _is_subject_to_discovery_stw(this),
1555   _ref_processor_cm(NULL),
1556   _is_alive_closure_cm(this),
1557   _is_subject_to_discovery_cm(this),
1558   _region_attr() {
1559 
1560   _verifier = new G1HeapVerifier(this);
1561 
1562   _allocator = new G1Allocator(this);
1563 
1564   _heap_sizing_policy = G1HeapSizingPolicy::create(this, _policy->analytics());
1565 
1566   _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);
1567 
1568   // Override the default _filler_array_max_size so that no humongous filler
1569   // objects are created.
1570   _filler_array_max_size = _humongous_object_threshold_in_words;
1571 
1572   uint n_queues = ParallelGCThreads;
1573   _task_queues = new RefToScanQueueSet(n_queues);
1574 
1575   _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1576 
1577   for (uint i = 0; i < n_queues; i++) {
1578     RefToScanQueue* q = new RefToScanQueue();
1579     q->initialize();
1580     _task_queues->register_queue(i, q);
1581     ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1582   }
1583 
1584   // Initialize the G1EvacuationFailureALot counters and flags.
1585   NOT_PRODUCT(reset_evacuation_should_fail();)
1586   _gc_tracer_stw->initialize();
1587 
1588   guarantee(_task_queues != NULL, "task_queues allocation failure.");
1589 }
1590 
1591 static size_t actual_reserved_page_size(ReservedSpace rs) {
1592   size_t page_size = os::vm_page_size();
1593   if (UseLargePages) {
1594     // There are two ways to manage large page memory.
1595     // 1. OS supports committing large page memory.
1596     // 2. OS doesn't support committing large page memory so ReservedSpace manages it.
1597     //    And ReservedSpace calls it 'special'. If we failed to set 'special',
1598     //    we reserved memory without large page.
1599     if (os::can_commit_large_page_memory() || rs.special()) {
1600       // An alignment at ReservedSpace comes from preferred page size or
1601       // heap alignment, and if the alignment came from heap alignment, it could be
1602       // larger than large pages size. So need to cap with the large page size.
1603       page_size = MIN2(rs.alignment(), os::large_page_size());
1604     }
1605   }
1606 
1607   return page_size;
1608 }
1609 
1610 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1611                                                                  size_t size,
1612                                                                  size_t translation_factor) {
1613   size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1614   // Allocate a new reserved space, preferring to use large pages.
1615   ReservedSpace rs(size, preferred_page_size);
1616   size_t page_size = actual_reserved_page_size(rs);
1617   G1RegionToSpaceMapper* result  =
1618     G1RegionToSpaceMapper::create_mapper(rs,
1619                                          size,
1620                                          page_size,
1621                                          HeapRegion::GrainBytes,
1622                                          translation_factor,
1623                                          mtGC);
1624 
1625   os::trace_page_sizes_for_requested_size(description,
1626                                           size,
1627                                           preferred_page_size,
1628                                           page_size,
1629                                           rs.base(),
1630                                           rs.size());
1631 
1632   return result;
1633 }
1634 
1635 jint G1CollectedHeap::initialize_concurrent_refinement() {
1636   jint ecode = JNI_OK;
1637   _cr = G1ConcurrentRefine::create(&ecode);
1638   return ecode;
1639 }
1640 
1641 jint G1CollectedHeap::initialize_young_gen_sampling_thread() {
1642   _young_gen_sampling_thread = new G1YoungRemSetSamplingThread();
1643   if (_young_gen_sampling_thread->osthread() == NULL) {
1644     vm_shutdown_during_initialization("Could not create G1YoungRemSetSamplingThread");
1645     return JNI_ENOMEM;
1646   }
1647   return JNI_OK;
1648 }
1649 
1650 jint G1CollectedHeap::initialize() {
1651 
1652   // Necessary to satisfy locking discipline assertions.
1653 
1654   MutexLocker x(Heap_lock);
1655 
1656   // While there are no constraints in the GC code that HeapWordSize
1657   // be any particular value, there are multiple other areas in the
1658   // system which believe this to be true (e.g. oop->object_size in some
1659   // cases incorrectly returns the size in wordSize units rather than
1660   // HeapWordSize).
1661   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1662 
1663   size_t init_byte_size = InitialHeapSize;
1664   size_t reserved_byte_size = G1Arguments::heap_reserved_size_bytes();
1665 
1666   // Ensure that the sizes are properly aligned.
1667   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1668   Universe::check_alignment(reserved_byte_size, HeapRegion::GrainBytes, "g1 heap");
1669   Universe::check_alignment(reserved_byte_size, HeapAlignment, "g1 heap");
1670 
1671   // Reserve the maximum.
1672 
1673   // When compressed oops are enabled, the preferred heap base
1674   // is calculated by subtracting the requested size from the
1675   // 32Gb boundary and using the result as the base address for
1676   // heap reservation. If the requested size is not aligned to
1677   // HeapRegion::GrainBytes (i.e. the alignment that is passed
1678   // into the ReservedHeapSpace constructor) then the actual
1679   // base of the reserved heap may end up differing from the
1680   // address that was requested (i.e. the preferred heap base).
1681   // If this happens then we could end up using a non-optimal
1682   // compressed oops mode.
1683 
1684   ReservedHeapSpace heap_rs = Universe::reserve_heap(reserved_byte_size,
1685                                                      HeapAlignment);
1686 
1687   initialize_reserved_region(heap_rs);
1688 
1689   // Create the barrier set for the entire reserved region.
1690   G1CardTable* ct = new G1CardTable(heap_rs.region());
1691   ct->initialize();
1692   G1BarrierSet* bs = new G1BarrierSet(ct);
1693   bs->initialize();
1694   assert(bs->is_a(BarrierSet::G1BarrierSet), "sanity");
1695   BarrierSet::set_barrier_set(bs);
1696   _card_table = ct;
1697 
1698   {
1699     G1SATBMarkQueueSet& satbqs = bs->satb_mark_queue_set();
1700     satbqs.set_process_completed_buffers_threshold(G1SATBProcessCompletedThreshold);
1701     satbqs.set_buffer_enqueue_threshold_percentage(G1SATBBufferEnqueueingThresholdPercent);
1702   }
1703 
1704   // Create the hot card cache.
1705   _hot_card_cache = new G1HotCardCache(this);
1706 
1707   // Carve out the G1 part of the heap.
1708   ReservedSpace g1_rs = heap_rs.first_part(reserved_byte_size);
1709   size_t page_size = actual_reserved_page_size(heap_rs);
1710   G1RegionToSpaceMapper* heap_storage =
1711     G1RegionToSpaceMapper::create_heap_mapper(g1_rs,
1712                                               g1_rs.size(),
1713                                               page_size,
1714                                               HeapRegion::GrainBytes,
1715                                               1,
1716                                               mtJavaHeap);
1717   if(heap_storage == NULL) {
1718     vm_shutdown_during_initialization("Could not initialize G1 heap");
1719     return JNI_ERR;
1720   }
1721 
1722   os::trace_page_sizes("Heap",
1723                        MinHeapSize,
1724                        reserved_byte_size,
1725                        page_size,
1726                        heap_rs.base(),
1727                        heap_rs.size());
1728   heap_storage->set_mapping_changed_listener(&_listener);
1729 
1730   // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1731   G1RegionToSpaceMapper* bot_storage =
1732     create_aux_memory_mapper("Block Offset Table",
1733                              G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize),
1734                              G1BlockOffsetTable::heap_map_factor());
1735 
1736   G1RegionToSpaceMapper* cardtable_storage =
1737     create_aux_memory_mapper("Card Table",
1738                              G1CardTable::compute_size(g1_rs.size() / HeapWordSize),
1739                              G1CardTable::heap_map_factor());
1740 
1741   G1RegionToSpaceMapper* card_counts_storage =
1742     create_aux_memory_mapper("Card Counts Table",
1743                              G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1744                              G1CardCounts::heap_map_factor());
1745 
1746   size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size());
1747   G1RegionToSpaceMapper* prev_bitmap_storage =
1748     create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1749   G1RegionToSpaceMapper* next_bitmap_storage =
1750     create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1751 
1752   _hrm = HeapRegionManager::create_manager(this);
1753 
1754   _hrm->initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1755   _card_table->initialize(cardtable_storage);
1756 
1757   // Do later initialization work for concurrent refinement.
1758   _hot_card_cache->initialize(card_counts_storage);
1759 
1760   // 6843694 - ensure that the maximum region index can fit
1761   // in the remembered set structures.
1762   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1763   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1764 
1765   // The G1FromCardCache reserves card with value 0 as "invalid", so the heap must not
1766   // start within the first card.
1767   guarantee(g1_rs.base() >= (char*)G1CardTable::card_size, "Java heap must not start within the first card.");
1768   // Also create a G1 rem set.
1769   _rem_set = new G1RemSet(this, _card_table, _hot_card_cache);
1770   _rem_set->initialize(max_reserved_capacity(), max_regions());
1771 
1772   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1773   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1774   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1775             "too many cards per region");
1776 
1777   FreeRegionList::set_unrealistically_long_length(max_expandable_regions() + 1);
1778 
1779   _bot = new G1BlockOffsetTable(reserved_region(), bot_storage);
1780 
1781   {
1782     HeapWord* start = _hrm->reserved().start();
1783     HeapWord* end = _hrm->reserved().end();
1784     size_t granularity = HeapRegion::GrainBytes;
1785 
1786     _region_attr.initialize(start, end, granularity);
1787     _humongous_reclaim_candidates.initialize(start, end, granularity);
1788   }
1789 
1790   _workers = new WorkGang("GC Thread", ParallelGCThreads,
1791                           true /* are_GC_task_threads */,
1792                           false /* are_ConcurrentGC_threads */);
1793   if (_workers == NULL) {
1794     return JNI_ENOMEM;
1795   }
1796   _workers->initialize_workers();
1797 
1798   _numa->set_region_info(HeapRegion::GrainBytes, page_size);
1799 
1800   // Create the G1ConcurrentMark data structure and thread.
1801   // (Must do this late, so that "max_regions" is defined.)
1802   _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1803   if (_cm == NULL || !_cm->completed_initialization()) {
1804     vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark");
1805     return JNI_ENOMEM;
1806   }
1807   _cm_thread = _cm->cm_thread();
1808 
1809   // Now expand into the initial heap size.
1810   if (!expand(init_byte_size, _workers)) {
1811     vm_shutdown_during_initialization("Failed to allocate initial heap.");
1812     return JNI_ENOMEM;
1813   }
1814 
1815   // Perform any initialization actions delegated to the policy.
1816   policy()->init(this, &_collection_set);
1817 
1818   jint ecode = initialize_concurrent_refinement();
1819   if (ecode != JNI_OK) {
1820     return ecode;
1821   }
1822 
1823   ecode = initialize_young_gen_sampling_thread();
1824   if (ecode != JNI_OK) {
1825     return ecode;
1826   }
1827 
1828   {
1829     G1DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
1830     dcqs.set_process_cards_threshold(concurrent_refine()->yellow_zone());
1831     dcqs.set_max_cards(concurrent_refine()->red_zone());
1832   }
1833 
1834   // Here we allocate the dummy HeapRegion that is required by the
1835   // G1AllocRegion class.
1836   HeapRegion* dummy_region = _hrm->get_dummy_region();
1837 
1838   // We'll re-use the same region whether the alloc region will
1839   // require BOT updates or not and, if it doesn't, then a non-young
1840   // region will complain that it cannot support allocations without
1841   // BOT updates. So we'll tag the dummy region as eden to avoid that.
1842   dummy_region->set_eden();
1843   // Make sure it's full.
1844   dummy_region->set_top(dummy_region->end());
1845   G1AllocRegion::setup(this, dummy_region);
1846 
1847   _allocator->init_mutator_alloc_regions();
1848 
1849   // Do create of the monitoring and management support so that
1850   // values in the heap have been properly initialized.
1851   _g1mm = new G1MonitoringSupport(this);
1852 
1853   G1StringDedup::initialize();
1854 
1855   _preserved_marks_set.init(ParallelGCThreads);
1856 
1857   _collection_set.initialize(max_regions());
1858 
1859   return JNI_OK;
1860 }
1861 
1862 void G1CollectedHeap::stop() {
1863   // Stop all concurrent threads. We do this to make sure these threads
1864   // do not continue to execute and access resources (e.g. logging)
1865   // that are destroyed during shutdown.
1866   _cr->stop();
1867   _young_gen_sampling_thread->stop();
1868   _cm_thread->stop();
1869   if (G1StringDedup::is_enabled()) {
1870     G1StringDedup::stop();
1871   }
1872 }
1873 
1874 void G1CollectedHeap::safepoint_synchronize_begin() {
1875   SuspendibleThreadSet::synchronize();
1876 }
1877 
1878 void G1CollectedHeap::safepoint_synchronize_end() {
1879   SuspendibleThreadSet::desynchronize();
1880 }
1881 
1882 void G1CollectedHeap::post_initialize() {
1883   CollectedHeap::post_initialize();
1884   ref_processing_init();
1885 }
1886 
1887 void G1CollectedHeap::ref_processing_init() {
1888   // Reference processing in G1 currently works as follows:
1889   //
1890   // * There are two reference processor instances. One is
1891   //   used to record and process discovered references
1892   //   during concurrent marking; the other is used to
1893   //   record and process references during STW pauses
1894   //   (both full and incremental).
1895   // * Both ref processors need to 'span' the entire heap as
1896   //   the regions in the collection set may be dotted around.
1897   //
1898   // * For the concurrent marking ref processor:
1899   //   * Reference discovery is enabled at initial marking.
1900   //   * Reference discovery is disabled and the discovered
1901   //     references processed etc during remarking.
1902   //   * Reference discovery is MT (see below).
1903   //   * Reference discovery requires a barrier (see below).
1904   //   * Reference processing may or may not be MT
1905   //     (depending on the value of ParallelRefProcEnabled
1906   //     and ParallelGCThreads).
1907   //   * A full GC disables reference discovery by the CM
1908   //     ref processor and abandons any entries on it's
1909   //     discovered lists.
1910   //
1911   // * For the STW processor:
1912   //   * Non MT discovery is enabled at the start of a full GC.
1913   //   * Processing and enqueueing during a full GC is non-MT.
1914   //   * During a full GC, references are processed after marking.
1915   //
1916   //   * Discovery (may or may not be MT) is enabled at the start
1917   //     of an incremental evacuation pause.
1918   //   * References are processed near the end of a STW evacuation pause.
1919   //   * For both types of GC:
1920   //     * Discovery is atomic - i.e. not concurrent.
1921   //     * Reference discovery will not need a barrier.
1922 
1923   bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1);
1924 
1925   // Concurrent Mark ref processor
1926   _ref_processor_cm =
1927     new ReferenceProcessor(&_is_subject_to_discovery_cm,
1928                            mt_processing,                                  // mt processing
1929                            ParallelGCThreads,                              // degree of mt processing
1930                            (ParallelGCThreads > 1) || (ConcGCThreads > 1), // mt discovery
1931                            MAX2(ParallelGCThreads, ConcGCThreads),         // degree of mt discovery
1932                            false,                                          // Reference discovery is not atomic
1933                            &_is_alive_closure_cm,                          // is alive closure
1934                            true);                                          // allow changes to number of processing threads
1935 
1936   // STW ref processor
1937   _ref_processor_stw =
1938     new ReferenceProcessor(&_is_subject_to_discovery_stw,
1939                            mt_processing,                        // mt processing
1940                            ParallelGCThreads,                    // degree of mt processing
1941                            (ParallelGCThreads > 1),              // mt discovery
1942                            ParallelGCThreads,                    // degree of mt discovery
1943                            true,                                 // Reference discovery is atomic
1944                            &_is_alive_closure_stw,               // is alive closure
1945                            true);                                // allow changes to number of processing threads
1946 }
1947 
1948 SoftRefPolicy* G1CollectedHeap::soft_ref_policy() {
1949   return &_soft_ref_policy;
1950 }
1951 
1952 size_t G1CollectedHeap::capacity() const {
1953   return _hrm->length() * HeapRegion::GrainBytes;
1954 }
1955 
1956 size_t G1CollectedHeap::unused_committed_regions_in_bytes() const {
1957   return _hrm->total_free_bytes();
1958 }
1959 
1960 void G1CollectedHeap::iterate_hcc_closure(G1CardTableEntryClosure* cl, uint worker_id) {
1961   _hot_card_cache->drain(cl, worker_id);
1962 }
1963 
1964 // Computes the sum of the storage used by the various regions.
1965 size_t G1CollectedHeap::used() const {
1966   size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
1967   if (_archive_allocator != NULL) {
1968     result += _archive_allocator->used();
1969   }
1970   return result;
1971 }
1972 
1973 size_t G1CollectedHeap::used_unlocked() const {
1974   return _summary_bytes_used;
1975 }
1976 
1977 class SumUsedClosure: public HeapRegionClosure {
1978   size_t _used;
1979 public:
1980   SumUsedClosure() : _used(0) {}
1981   bool do_heap_region(HeapRegion* r) {
1982     _used += r->used();
1983     return false;
1984   }
1985   size_t result() { return _used; }
1986 };
1987 
1988 size_t G1CollectedHeap::recalculate_used() const {
1989   SumUsedClosure blk;
1990   heap_region_iterate(&blk);
1991   return blk.result();
1992 }
1993 
1994 bool  G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
1995   switch (cause) {
1996     case GCCause::_java_lang_system_gc:                 return ExplicitGCInvokesConcurrent;
1997     case GCCause::_dcmd_gc_run:                         return ExplicitGCInvokesConcurrent;
1998     case GCCause::_wb_conc_mark:                        return true;
1999     default :                                           return false;
2000   }
2001 }
2002 
2003 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2004   switch (cause) {
2005     case GCCause::_g1_humongous_allocation: return true;
2006     case GCCause::_g1_periodic_collection:  return G1PeriodicGCInvokesConcurrent;
2007     default:                                return is_user_requested_concurrent_full_gc(cause);
2008   }
2009 }
2010 
2011 bool G1CollectedHeap::should_upgrade_to_full_gc(GCCause::Cause cause) {
2012   if (policy()->force_upgrade_to_full()) {
2013     return true;
2014   } else if (should_do_concurrent_full_gc(_gc_cause)) {
2015     return false;
2016   } else if (has_regions_left_for_allocation()) {
2017     return false;
2018   } else {
2019     return true;
2020   }
2021 }
2022 
2023 #ifndef PRODUCT
2024 void G1CollectedHeap::allocate_dummy_regions() {
2025   // Let's fill up most of the region
2026   size_t word_size = HeapRegion::GrainWords - 1024;
2027   // And as a result the region we'll allocate will be humongous.
2028   guarantee(is_humongous(word_size), "sanity");
2029 
2030   // _filler_array_max_size is set to humongous object threshold
2031   // but temporarily change it to use CollectedHeap::fill_with_object().
2032   SizeTFlagSetting fs(_filler_array_max_size, word_size);
2033 
2034   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2035     // Let's use the existing mechanism for the allocation
2036     HeapWord* dummy_obj = humongous_obj_allocate(word_size);
2037     if (dummy_obj != NULL) {
2038       MemRegion mr(dummy_obj, word_size);
2039       CollectedHeap::fill_with_object(mr);
2040     } else {
2041       // If we can't allocate once, we probably cannot allocate
2042       // again. Let's get out of the loop.
2043       break;
2044     }
2045   }
2046 }
2047 #endif // !PRODUCT
2048 
2049 void G1CollectedHeap::increment_old_marking_cycles_started() {
2050   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2051          _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2052          "Wrong marking cycle count (started: %d, completed: %d)",
2053          _old_marking_cycles_started, _old_marking_cycles_completed);
2054 
2055   _old_marking_cycles_started++;
2056 }
2057 
2058 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2059   MonitorLocker ml(G1OldGCCount_lock, Mutex::_no_safepoint_check_flag);
2060 
2061   // We assume that if concurrent == true, then the caller is a
2062   // concurrent thread that was joined the Suspendible Thread
2063   // Set. If there's ever a cheap way to check this, we should add an
2064   // assert here.
2065 
2066   // Given that this method is called at the end of a Full GC or of a
2067   // concurrent cycle, and those can be nested (i.e., a Full GC can
2068   // interrupt a concurrent cycle), the number of full collections
2069   // completed should be either one (in the case where there was no
2070   // nesting) or two (when a Full GC interrupted a concurrent cycle)
2071   // behind the number of full collections started.
2072 
2073   // This is the case for the inner caller, i.e. a Full GC.
2074   assert(concurrent ||
2075          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2076          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2077          "for inner caller (Full GC): _old_marking_cycles_started = %u "
2078          "is inconsistent with _old_marking_cycles_completed = %u",
2079          _old_marking_cycles_started, _old_marking_cycles_completed);
2080 
2081   // This is the case for the outer caller, i.e. the concurrent cycle.
2082   assert(!concurrent ||
2083          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2084          "for outer caller (concurrent cycle): "
2085          "_old_marking_cycles_started = %u "
2086          "is inconsistent with _old_marking_cycles_completed = %u",
2087          _old_marking_cycles_started, _old_marking_cycles_completed);
2088 
2089   _old_marking_cycles_completed += 1;
2090 
2091   // We need to clear the "in_progress" flag in the CM thread before
2092   // we wake up any waiters (especially when ExplicitInvokesConcurrent
2093   // is set) so that if a waiter requests another System.gc() it doesn't
2094   // incorrectly see that a marking cycle is still in progress.
2095   if (concurrent) {
2096     _cm_thread->set_idle();
2097   }
2098 
2099   // Notify threads waiting in System.gc() (with ExplicitGCInvokesConcurrent)
2100   // for a full GC to finish that their wait is over.
2101   ml.notify_all();
2102 }
2103 
2104 void G1CollectedHeap::collect(GCCause::Cause cause) {
2105   try_collect(cause);
2106 }
2107 
2108 // Return true if (x < y) with allowance for wraparound.
2109 static bool gc_counter_less_than(uint x, uint y) {
2110   return (x - y) > (UINT_MAX/2);
2111 }
2112 
2113 // LOG_COLLECT_CONCURRENTLY(cause, msg, args...)
2114 // Macro so msg printing is format-checked.
2115 #define LOG_COLLECT_CONCURRENTLY(cause, ...)                            \
2116   do {                                                                  \
2117     LogTarget(Trace, gc) LOG_COLLECT_CONCURRENTLY_lt;                   \
2118     if (LOG_COLLECT_CONCURRENTLY_lt.is_enabled()) {                     \
2119       ResourceMark rm; /* For thread name. */                           \
2120       LogStream LOG_COLLECT_CONCURRENTLY_s(&LOG_COLLECT_CONCURRENTLY_lt); \
2121       LOG_COLLECT_CONCURRENTLY_s.print("%s: Try Collect Concurrently (%s): ", \
2122                                        Thread::current()->name(),       \
2123                                        GCCause::to_string(cause));      \
2124       LOG_COLLECT_CONCURRENTLY_s.print(__VA_ARGS__);                    \
2125     }                                                                   \
2126   } while (0)
2127 
2128 #define LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, result) \
2129   LOG_COLLECT_CONCURRENTLY(cause, "complete %s", BOOL_TO_STR(result))
2130 
2131 bool G1CollectedHeap::try_collect_concurrently(GCCause::Cause cause,
2132                                                uint gc_counter,
2133                                                uint old_marking_started_before) {
2134   assert_heap_not_locked();
2135   assert(should_do_concurrent_full_gc(cause),
2136          "Non-concurrent cause %s", GCCause::to_string(cause));
2137 
2138   for (uint i = 1; true; ++i) {
2139     // Try to schedule an initial-mark evacuation pause that will
2140     // start a concurrent cycle.
2141     LOG_COLLECT_CONCURRENTLY(cause, "attempt %u", i);
2142     VM_G1TryInitiateConcMark op(gc_counter,
2143                                 cause,
2144                                 policy()->max_pause_time_ms());
2145     VMThread::execute(&op);
2146 
2147     // Request is trivially finished.
2148     if (cause == GCCause::_g1_periodic_collection) {
2149       LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, op.gc_succeeded());
2150       return op.gc_succeeded();
2151     }
2152 
2153     // Lock to get consistent set of values.
2154     uint old_marking_started_after;
2155     uint old_marking_completed_after;
2156     {
2157       MutexLocker ml(Heap_lock);
2158       // Update gc_counter for retrying VMOp if needed. Captured here to be
2159       // consistent with the values we use below for termination tests.  If
2160       // a retry is needed after a possible wait, and another collection
2161       // occurs in the meantime, it will cause our retry to be skipped and
2162       // we'll recheck for termination with updated conditions from that
2163       // more recent collection.  That's what we want, rather than having
2164       // our retry possibly perform an unnecessary collection.
2165       gc_counter = total_collections();
2166       old_marking_started_after = _old_marking_cycles_started;
2167       old_marking_completed_after = _old_marking_cycles_completed;
2168     }
2169 
2170     if (!GCCause::is_user_requested_gc(cause)) {
2171       // For an "automatic" (not user-requested) collection, we just need to
2172       // ensure that progress is made.
2173       //
2174       // Request is finished if any of
2175       // (1) the VMOp successfully performed a GC,
2176       // (2) a concurrent cycle was already in progress,
2177       // (3) a new cycle was started (by this thread or some other), or
2178       // (4) a Full GC was performed.
2179       // Cases (3) and (4) are detected together by a change to
2180       // _old_marking_cycles_started.
2181       //
2182       // Note that (1) does not imply (3).  If we're still in the mixed
2183       // phase of an earlier concurrent collection, the request to make the
2184       // collection an initial-mark won't be honored.  If we don't check for
2185       // both conditions we'll spin doing back-to-back collections.
2186       if (op.gc_succeeded() ||
2187           op.cycle_already_in_progress() ||
2188           (old_marking_started_before != old_marking_started_after)) {
2189         LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, true);
2190         return true;
2191       }
2192     } else {                    // User-requested GC.
2193       // For a user-requested collection, we want to ensure that a complete
2194       // full collection has been performed before returning, but without
2195       // waiting for more than needed.
2196 
2197       // For user-requested GCs (unlike non-UR), a successful VMOp implies a
2198       // new cycle was started.  That's good, because it's not clear what we
2199       // should do otherwise.  Trying again just does back to back GCs.
2200       // Can't wait for someone else to start a cycle.  And returning fails
2201       // to meet the goal of ensuring a full collection was performed.
2202       assert(!op.gc_succeeded() ||
2203              (old_marking_started_before != old_marking_started_after),
2204              "invariant: succeeded %s, started before %u, started after %u",
2205              BOOL_TO_STR(op.gc_succeeded()),
2206              old_marking_started_before, old_marking_started_after);
2207 
2208       // Request is finished if a full collection (concurrent or stw)
2209       // was started after this request and has completed, e.g.
2210       // started_before < completed_after.
2211       if (gc_counter_less_than(old_marking_started_before,
2212                                old_marking_completed_after)) {
2213         LOG_COLLECT_CONCURRENTLY_COMPLETE(cause, true);
2214         return true;
2215       }
2216 
2217       if (old_marking_started_after != old_marking_completed_after) {
2218         // If there is an in-progress cycle (possibly started by us), then
2219         // wait for that cycle to complete, e.g.
2220         // while completed_now < started_after.
2221         LOG_COLLECT_CONCURRENTLY(cause, "wait");
2222         MonitorLocker ml(G1OldGCCount_lock);
2223         while (gc_counter_less_than(_old_marking_cycles_completed,
2224                                     old_marking_started_after)) {
2225           ml.wait();
2226         }
2227         // Request is finished if the collection we just waited for was
2228         // started after this request.
2229         if (old_marking_started_before != old_marking_started_after) {
2230           LOG_COLLECT_CONCURRENTLY(cause, "complete after wait");
2231           return true;
2232         }
2233       }
2234 
2235       // If VMOp was successful then it started a new cycle that the above
2236       // wait &etc should have recognized as finishing this request.  This
2237       // differs from a non-user-request, where gc_succeeded does not imply
2238       // a new cycle was started.
2239       assert(!op.gc_succeeded(), "invariant");
2240 
2241       // If VMOp failed because a cycle was already in progress, it is now
2242       // complete.  But it didn't finish this user-requested GC, so try
2243       // again.
2244       if (op.cycle_already_in_progress()) {
2245         LOG_COLLECT_CONCURRENTLY(cause, "retry after in-progress");
2246         continue;
2247       }
2248     }
2249 
2250     // Collection failed and should be retried.
2251     assert(op.transient_failure(), "invariant");
2252 
2253     // If GCLocker is active, wait until clear before retrying.
2254     if (GCLocker::is_active_and_needs_gc()) {
2255       LOG_COLLECT_CONCURRENTLY(cause, "gc-locker stall");
2256       GCLocker::stall_until_clear();
2257     }
2258 
2259     LOG_COLLECT_CONCURRENTLY(cause, "retry");
2260   }
2261 }
2262 
2263 bool G1CollectedHeap::try_collect(GCCause::Cause cause) {
2264   assert_heap_not_locked();
2265 
2266   // Lock to get consistent set of values.
2267   uint gc_count_before;
2268   uint full_gc_count_before;
2269   uint old_marking_started_before;
2270   {
2271     MutexLocker ml(Heap_lock);
2272     gc_count_before = total_collections();
2273     full_gc_count_before = total_full_collections();
2274     old_marking_started_before = _old_marking_cycles_started;
2275   }
2276 
2277   if (should_do_concurrent_full_gc(cause)) {
2278     return try_collect_concurrently(cause,
2279                                     gc_count_before,
2280                                     old_marking_started_before);
2281   } else if (GCLocker::should_discard(cause, gc_count_before)) {
2282     // Indicate failure to be consistent with VMOp failure due to
2283     // another collection slipping in after our gc_count but before
2284     // our request is processed.
2285     return false;
2286   } else if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2287              DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2288 
2289     // Schedule a standard evacuation pause. We're setting word_size
2290     // to 0 which means that we are not requesting a post-GC allocation.
2291     VM_G1CollectForAllocation op(0,     /* word_size */
2292                                  gc_count_before,
2293                                  cause,
2294                                  policy()->max_pause_time_ms());
2295     VMThread::execute(&op);
2296     return op.gc_succeeded();
2297   } else {
2298     // Schedule a Full GC.
2299     VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2300     VMThread::execute(&op);
2301     return op.gc_succeeded();
2302   }
2303 }
2304 
2305 bool G1CollectedHeap::is_in(const void* p) const {
2306   if (_hrm->reserved().contains(p)) {
2307     // Given that we know that p is in the reserved space,
2308     // heap_region_containing() should successfully
2309     // return the containing region.
2310     HeapRegion* hr = heap_region_containing(p);
2311     return hr->is_in(p);
2312   } else {
2313     return false;
2314   }
2315 }
2316 
2317 #ifdef ASSERT
2318 bool G1CollectedHeap::is_in_exact(const void* p) const {
2319   bool contains = reserved_region().contains(p);
2320   bool available = _hrm->is_available(addr_to_region((HeapWord*)p));
2321   if (contains && available) {
2322     return true;
2323   } else {
2324     return false;
2325   }
2326 }
2327 #endif
2328 
2329 // Iteration functions.
2330 
2331 // Iterates an ObjectClosure over all objects within a HeapRegion.
2332 
2333 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2334   ObjectClosure* _cl;
2335 public:
2336   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2337   bool do_heap_region(HeapRegion* r) {
2338     if (!r->is_continues_humongous()) {
2339       r->object_iterate(_cl);
2340     }
2341     return false;
2342   }
2343 };
2344 
2345 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2346   IterateObjectClosureRegionClosure blk(cl);
2347   heap_region_iterate(&blk);
2348 }
2349 
2350 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2351   _hrm->iterate(cl);
2352 }
2353 
2354 void G1CollectedHeap::heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl,
2355                                                                  HeapRegionClaimer *hrclaimer,
2356                                                                  uint worker_id) const {
2357   _hrm->par_iterate(cl, hrclaimer, hrclaimer->offset_for_worker(worker_id));
2358 }
2359 
2360 void G1CollectedHeap::heap_region_par_iterate_from_start(HeapRegionClosure* cl,
2361                                                          HeapRegionClaimer *hrclaimer) const {
2362   _hrm->par_iterate(cl, hrclaimer, 0);
2363 }
2364 
2365 void G1CollectedHeap::collection_set_iterate_all(HeapRegionClosure* cl) {
2366   _collection_set.iterate(cl);
2367 }
2368 
2369 void G1CollectedHeap::collection_set_iterate_increment_from(HeapRegionClosure *cl, HeapRegionClaimer* hr_claimer, uint worker_id) {
2370   _collection_set.iterate_incremental_part_from(cl, hr_claimer, worker_id, workers()->active_workers());
2371 }
2372 
2373 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2374   HeapRegion* hr = heap_region_containing(addr);
2375   return hr->block_start(addr);
2376 }
2377 
2378 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2379   HeapRegion* hr = heap_region_containing(addr);
2380   return hr->block_is_obj(addr);
2381 }
2382 
2383 bool G1CollectedHeap::supports_tlab_allocation() const {
2384   return true;
2385 }
2386 
2387 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2388   return (_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes;
2389 }
2390 
2391 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2392   return _eden.length() * HeapRegion::GrainBytes;
2393 }
2394 
2395 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2396 // must be equal to the humongous object limit.
2397 size_t G1CollectedHeap::max_tlab_size() const {
2398   return align_down(_humongous_object_threshold_in_words, MinObjAlignment);
2399 }
2400 
2401 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2402   return _allocator->unsafe_max_tlab_alloc();
2403 }
2404 
2405 size_t G1CollectedHeap::max_capacity() const {
2406   return _hrm->max_expandable_length() * HeapRegion::GrainBytes;
2407 }
2408 
2409 size_t G1CollectedHeap::max_reserved_capacity() const {
2410   return _hrm->max_length() * HeapRegion::GrainBytes;
2411 }
2412 
2413 jlong G1CollectedHeap::millis_since_last_gc() {
2414   // See the notes in GenCollectedHeap::millis_since_last_gc()
2415   // for more information about the implementation.
2416   jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) -
2417                   _policy->collection_pause_end_millis();
2418   if (ret_val < 0) {
2419     log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT
2420       ". returning zero instead.", ret_val);
2421     return 0;
2422   }
2423   return ret_val;
2424 }
2425 
2426 void G1CollectedHeap::deduplicate_string(oop str) {
2427   assert(java_lang_String::is_instance(str), "invariant");
2428 
2429   if (G1StringDedup::is_enabled()) {
2430     G1StringDedup::deduplicate(str);
2431   }
2432 }
2433 
2434 void G1CollectedHeap::prepare_for_verify() {
2435   _verifier->prepare_for_verify();
2436 }
2437 
2438 void G1CollectedHeap::verify(VerifyOption vo) {
2439   _verifier->verify(vo);
2440 }
2441 
2442 bool G1CollectedHeap::supports_concurrent_phase_control() const {
2443   return true;
2444 }
2445 
2446 bool G1CollectedHeap::request_concurrent_phase(const char* phase) {
2447   return _cm_thread->request_concurrent_phase(phase);
2448 }
2449 
2450 bool G1CollectedHeap::is_heterogeneous_heap() const {
2451   return G1Arguments::is_heterogeneous_heap();
2452 }
2453 
2454 class PrintRegionClosure: public HeapRegionClosure {
2455   outputStream* _st;
2456 public:
2457   PrintRegionClosure(outputStream* st) : _st(st) {}
2458   bool do_heap_region(HeapRegion* r) {
2459     r->print_on(_st);
2460     return false;
2461   }
2462 };
2463 
2464 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2465                                        const HeapRegion* hr,
2466                                        const VerifyOption vo) const {
2467   switch (vo) {
2468   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
2469   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
2470   case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj, hr);
2471   default:                            ShouldNotReachHere();
2472   }
2473   return false; // keep some compilers happy
2474 }
2475 
2476 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2477                                        const VerifyOption vo) const {
2478   switch (vo) {
2479   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
2480   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
2481   case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj);
2482   default:                            ShouldNotReachHere();
2483   }
2484   return false; // keep some compilers happy
2485 }
2486 
2487 void G1CollectedHeap::print_heap_regions() const {
2488   LogTarget(Trace, gc, heap, region) lt;
2489   if (lt.is_enabled()) {
2490     LogStream ls(lt);
2491     print_regions_on(&ls);
2492   }
2493 }
2494 
2495 void G1CollectedHeap::print_on(outputStream* st) const {
2496   st->print(" %-20s", "garbage-first heap");
2497   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
2498             capacity()/K, used_unlocked()/K);
2499   st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")",
2500             p2i(_hrm->reserved().start()),
2501             p2i(_hrm->reserved().end()));
2502   st->cr();
2503   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
2504   uint young_regions = young_regions_count();
2505   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
2506             (size_t) young_regions * HeapRegion::GrainBytes / K);
2507   uint survivor_regions = survivor_regions_count();
2508   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
2509             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
2510   st->cr();
2511   if (_numa->is_enabled()) {
2512     uint num_nodes = _numa->num_active_nodes();
2513     st->print("  remaining free region(s) on each NUMA node: ");
2514     const int* node_ids = _numa->node_ids();
2515     for (uint node_index = 0; node_index < num_nodes; node_index++) {
2516       st->print("%d=%u ", node_ids[node_index], _hrm->num_free_regions(node_index));
2517     }
2518     st->cr();
2519   }
2520   MetaspaceUtils::print_on(st);
2521 }
2522 
2523 void G1CollectedHeap::print_regions_on(outputStream* st) const {
2524   st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
2525                "HS=humongous(starts), HC=humongous(continues), "
2526                "CS=collection set, F=free, "
2527                "OA=open archive, CA=closed archive, "
2528                "TAMS=top-at-mark-start (previous, next)");
2529   PrintRegionClosure blk(st);
2530   heap_region_iterate(&blk);
2531 }
2532 
2533 void G1CollectedHeap::print_extended_on(outputStream* st) const {
2534   print_on(st);
2535 
2536   // Print the per-region information.
2537   print_regions_on(st);
2538 }
2539 
2540 void G1CollectedHeap::print_on_error(outputStream* st) const {
2541   this->CollectedHeap::print_on_error(st);
2542 
2543   if (_cm != NULL) {
2544     st->cr();
2545     _cm->print_on_error(st);
2546   }
2547 }
2548 
2549 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
2550   workers()->print_worker_threads_on(st);
2551   _cm_thread->print_on(st);
2552   st->cr();
2553   _cm->print_worker_threads_on(st);
2554   _cr->print_threads_on(st);
2555   _young_gen_sampling_thread->print_on(st);
2556   if (G1StringDedup::is_enabled()) {
2557     G1StringDedup::print_worker_threads_on(st);
2558   }
2559 }
2560 
2561 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2562   workers()->threads_do(tc);
2563   tc->do_thread(_cm_thread);
2564   _cm->threads_do(tc);
2565   _cr->threads_do(tc);
2566   tc->do_thread(_young_gen_sampling_thread);
2567   if (G1StringDedup::is_enabled()) {
2568     G1StringDedup::threads_do(tc);
2569   }
2570 }
2571 
2572 void G1CollectedHeap::print_tracing_info() const {
2573   rem_set()->print_summary_info();
2574   concurrent_mark()->print_summary_info();
2575 }
2576 
2577 #ifndef PRODUCT
2578 // Helpful for debugging RSet issues.
2579 
2580 class PrintRSetsClosure : public HeapRegionClosure {
2581 private:
2582   const char* _msg;
2583   size_t _occupied_sum;
2584 
2585 public:
2586   bool do_heap_region(HeapRegion* r) {
2587     HeapRegionRemSet* hrrs = r->rem_set();
2588     size_t occupied = hrrs->occupied();
2589     _occupied_sum += occupied;
2590 
2591     tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r));
2592     if (occupied == 0) {
2593       tty->print_cr("  RSet is empty");
2594     } else {
2595       hrrs->print();
2596     }
2597     tty->print_cr("----------");
2598     return false;
2599   }
2600 
2601   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
2602     tty->cr();
2603     tty->print_cr("========================================");
2604     tty->print_cr("%s", msg);
2605     tty->cr();
2606   }
2607 
2608   ~PrintRSetsClosure() {
2609     tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
2610     tty->print_cr("========================================");
2611     tty->cr();
2612   }
2613 };
2614 
2615 void G1CollectedHeap::print_cset_rsets() {
2616   PrintRSetsClosure cl("Printing CSet RSets");
2617   collection_set_iterate_all(&cl);
2618 }
2619 
2620 void G1CollectedHeap::print_all_rsets() {
2621   PrintRSetsClosure cl("Printing All RSets");;
2622   heap_region_iterate(&cl);
2623 }
2624 #endif // PRODUCT
2625 
2626 bool G1CollectedHeap::print_location(outputStream* st, void* addr) const {
2627   return BlockLocationPrinter<G1CollectedHeap>::print_location(st, addr);
2628 }
2629 
2630 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
2631 
2632   size_t eden_used_bytes = _eden.used_bytes();
2633   size_t survivor_used_bytes = _survivor.used_bytes();
2634   size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
2635 
2636   size_t eden_capacity_bytes =
2637     (policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
2638 
2639   VirtualSpaceSummary heap_summary = create_heap_space_summary();
2640   return G1HeapSummary(heap_summary, heap_used, eden_used_bytes,
2641                        eden_capacity_bytes, survivor_used_bytes, num_regions());
2642 }
2643 
2644 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
2645   return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
2646                        stats->unused(), stats->used(), stats->region_end_waste(),
2647                        stats->regions_filled(), stats->direct_allocated(),
2648                        stats->failure_used(), stats->failure_waste());
2649 }
2650 
2651 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
2652   const G1HeapSummary& heap_summary = create_g1_heap_summary();
2653   gc_tracer->report_gc_heap_summary(when, heap_summary);
2654 
2655   const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
2656   gc_tracer->report_metaspace_summary(when, metaspace_summary);
2657 }
2658 
2659 G1CollectedHeap* G1CollectedHeap::heap() {
2660   CollectedHeap* heap = Universe::heap();
2661   assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
2662   assert(heap->kind() == CollectedHeap::G1, "Invalid name");
2663   return (G1CollectedHeap*)heap;
2664 }
2665 
2666 void G1CollectedHeap::gc_prologue(bool full) {
2667   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
2668 
2669   // This summary needs to be printed before incrementing total collections.
2670   rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections());
2671 
2672   // Update common counters.
2673   increment_total_collections(full /* full gc */);
2674   if (full || collector_state()->in_initial_mark_gc()) {
2675     increment_old_marking_cycles_started();
2676   }
2677 
2678   // Fill TLAB's and such
2679   double start = os::elapsedTime();
2680   ensure_parsability(true);
2681   phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2682 }
2683 
2684 void G1CollectedHeap::gc_epilogue(bool full) {
2685   // Update common counters.
2686   if (full) {
2687     // Update the number of full collections that have been completed.
2688     increment_old_marking_cycles_completed(false /* concurrent */);
2689   }
2690 
2691   // We are at the end of the GC. Total collections has already been increased.
2692   rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1);
2693 
2694   // FIXME: what is this about?
2695   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
2696   // is set.
2697 #if COMPILER2_OR_JVMCI
2698   assert(DerivedPointerTable::is_empty(), "derived pointer present");
2699 #endif
2700 
2701   double start = os::elapsedTime();
2702   resize_all_tlabs();
2703   phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2704 
2705   MemoryService::track_memory_usage();
2706   // We have just completed a GC. Update the soft reference
2707   // policy with the new heap occupancy
2708   Universe::update_heap_info_at_gc();
2709 
2710   // Print NUMA statistics.
2711   _numa->print_statistics();
2712 }
2713 
2714 void G1CollectedHeap::verify_numa_regions(const char* desc) {
2715   LogTarget(Trace, gc, heap, verify) lt;
2716 
2717   if (lt.is_enabled()) {
2718     LogStream ls(lt);
2719     // Iterate all heap regions to print matching between preferred numa id and actual numa id.
2720     G1NodeIndexCheckClosure cl(desc, _numa, &ls);
2721     heap_region_iterate(&cl);
2722   }
2723 }
2724 
2725 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2726                                                uint gc_count_before,
2727                                                bool* succeeded,
2728                                                GCCause::Cause gc_cause) {
2729   assert_heap_not_locked_and_not_at_safepoint();
2730   VM_G1CollectForAllocation op(word_size,
2731                                gc_count_before,
2732                                gc_cause,
2733                                policy()->max_pause_time_ms());
2734   VMThread::execute(&op);
2735 
2736   HeapWord* result = op.result();
2737   bool ret_succeeded = op.prologue_succeeded() && op.gc_succeeded();
2738   assert(result == NULL || ret_succeeded,
2739          "the result should be NULL if the VM did not succeed");
2740   *succeeded = ret_succeeded;
2741 
2742   assert_heap_not_locked();
2743   return result;
2744 }
2745 
2746 void G1CollectedHeap::do_concurrent_mark() {
2747   MutexLocker x(CGC_lock, Mutex::_no_safepoint_check_flag);
2748   if (!_cm_thread->in_progress()) {
2749     _cm_thread->set_started();
2750     CGC_lock->notify();
2751   }
2752 }
2753 
2754 size_t G1CollectedHeap::pending_card_num() {
2755   struct CountCardsClosure : public ThreadClosure {
2756     size_t _cards;
2757     CountCardsClosure() : _cards(0) {}
2758     virtual void do_thread(Thread* t) {
2759       _cards += G1ThreadLocalData::dirty_card_queue(t).size();
2760     }
2761   } count_from_threads;
2762   Threads::threads_do(&count_from_threads);
2763 
2764   G1DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
2765   dcqs.verify_num_cards();
2766 
2767   return dcqs.num_cards() + count_from_threads._cards;
2768 }
2769 
2770 bool G1CollectedHeap::is_potential_eager_reclaim_candidate(HeapRegion* r) const {
2771   // We don't nominate objects with many remembered set entries, on
2772   // the assumption that such objects are likely still live.
2773   HeapRegionRemSet* rem_set = r->rem_set();
2774 
2775   return G1EagerReclaimHumongousObjectsWithStaleRefs ?
2776          rem_set->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) :
2777          G1EagerReclaimHumongousObjects && rem_set->is_empty();
2778 }
2779 
2780 class RegisterRegionsWithRegionAttrTableClosure : public HeapRegionClosure {
2781  private:
2782   size_t _total_humongous;
2783   size_t _candidate_humongous;
2784 
2785   bool humongous_region_is_candidate(G1CollectedHeap* g1h, HeapRegion* region) const {
2786     assert(region->is_starts_humongous(), "Must start a humongous object");
2787 
2788     oop obj = oop(region->bottom());
2789 
2790     // Dead objects cannot be eager reclaim candidates. Due to class
2791     // unloading it is unsafe to query their classes so we return early.
2792     if (g1h->is_obj_dead(obj, region)) {
2793       return false;
2794     }
2795 
2796     // If we do not have a complete remembered set for the region, then we can
2797     // not be sure that we have all references to it.
2798     if (!region->rem_set()->is_complete()) {
2799       return false;
2800     }
2801     // Candidate selection must satisfy the following constraints
2802     // while concurrent marking is in progress:
2803     //
2804     // * In order to maintain SATB invariants, an object must not be
2805     // reclaimed if it was allocated before the start of marking and
2806     // has not had its references scanned.  Such an object must have
2807     // its references (including type metadata) scanned to ensure no
2808     // live objects are missed by the marking process.  Objects
2809     // allocated after the start of concurrent marking don't need to
2810     // be scanned.
2811     //
2812     // * An object must not be reclaimed if it is on the concurrent
2813     // mark stack.  Objects allocated after the start of concurrent
2814     // marking are never pushed on the mark stack.
2815     //
2816     // Nominating only objects allocated after the start of concurrent
2817     // marking is sufficient to meet both constraints.  This may miss
2818     // some objects that satisfy the constraints, but the marking data
2819     // structures don't support efficiently performing the needed
2820     // additional tests or scrubbing of the mark stack.
2821     //
2822     // However, we presently only nominate is_typeArray() objects.
2823     // A humongous object containing references induces remembered
2824     // set entries on other regions.  In order to reclaim such an
2825     // object, those remembered sets would need to be cleaned up.
2826     //
2827     // We also treat is_typeArray() objects specially, allowing them
2828     // to be reclaimed even if allocated before the start of
2829     // concurrent mark.  For this we rely on mark stack insertion to
2830     // exclude is_typeArray() objects, preventing reclaiming an object
2831     // that is in the mark stack.  We also rely on the metadata for
2832     // such objects to be built-in and so ensured to be kept live.
2833     // Frequent allocation and drop of large binary blobs is an
2834     // important use case for eager reclaim, and this special handling
2835     // may reduce needed headroom.
2836 
2837     return obj->is_typeArray() &&
2838            g1h->is_potential_eager_reclaim_candidate(region);
2839   }
2840 
2841  public:
2842   RegisterRegionsWithRegionAttrTableClosure()
2843   : _total_humongous(0),
2844     _candidate_humongous(0) {
2845   }
2846 
2847   virtual bool do_heap_region(HeapRegion* r) {
2848     G1CollectedHeap* g1h = G1CollectedHeap::heap();
2849 
2850     if (!r->is_starts_humongous()) {
2851       g1h->register_region_with_region_attr(r);
2852       return false;
2853     }
2854 
2855     bool is_candidate = humongous_region_is_candidate(g1h, r);
2856     uint rindex = r->hrm_index();
2857     g1h->set_humongous_reclaim_candidate(rindex, is_candidate);
2858     if (is_candidate) {
2859       g1h->register_humongous_region_with_region_attr(rindex);
2860       _candidate_humongous++;
2861       // We will later handle the remembered sets of these regions.
2862     } else {
2863       g1h->register_region_with_region_attr(r);
2864     }
2865     _total_humongous++;
2866 
2867     return false;
2868   }
2869 
2870   size_t total_humongous() const { return _total_humongous; }
2871   size_t candidate_humongous() const { return _candidate_humongous; }
2872 };
2873 
2874 void G1CollectedHeap::register_regions_with_region_attr() {
2875   Ticks start = Ticks::now();
2876 
2877   RegisterRegionsWithRegionAttrTableClosure cl;
2878   heap_region_iterate(&cl);
2879 
2880   phase_times()->record_register_regions((Ticks::now() - start).seconds() * 1000.0,
2881                                          cl.total_humongous(),
2882                                          cl.candidate_humongous());
2883   _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
2884 }
2885 
2886 #ifndef PRODUCT
2887 void G1CollectedHeap::verify_region_attr_remset_update() {
2888   class VerifyRegionAttrRemSet : public HeapRegionClosure {
2889   public:
2890     virtual bool do_heap_region(HeapRegion* r) {
2891       G1CollectedHeap* g1h = G1CollectedHeap::heap();
2892       bool const needs_remset_update = g1h->region_attr(r->bottom()).needs_remset_update();
2893       assert(r->rem_set()->is_tracked() == needs_remset_update,
2894              "Region %u remset tracking status (%s) different to region attribute (%s)",
2895              r->hrm_index(), BOOL_TO_STR(r->rem_set()->is_tracked()), BOOL_TO_STR(needs_remset_update));
2896       return false;
2897     }
2898   } cl;
2899   heap_region_iterate(&cl);
2900 }
2901 #endif
2902 
2903 class VerifyRegionRemSetClosure : public HeapRegionClosure {
2904   public:
2905     bool do_heap_region(HeapRegion* hr) {
2906       if (!hr->is_archive() && !hr->is_continues_humongous()) {
2907         hr->verify_rem_set();
2908       }
2909       return false;
2910     }
2911 };
2912 
2913 uint G1CollectedHeap::num_task_queues() const {
2914   return _task_queues->size();
2915 }
2916 
2917 #if TASKQUEUE_STATS
2918 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
2919   st->print_raw_cr("GC Task Stats");
2920   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
2921   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
2922 }
2923 
2924 void G1CollectedHeap::print_taskqueue_stats() const {
2925   if (!log_is_enabled(Trace, gc, task, stats)) {
2926     return;
2927   }
2928   Log(gc, task, stats) log;
2929   ResourceMark rm;
2930   LogStream ls(log.trace());
2931   outputStream* st = &ls;
2932 
2933   print_taskqueue_stats_hdr(st);
2934 
2935   TaskQueueStats totals;
2936   const uint n = num_task_queues();
2937   for (uint i = 0; i < n; ++i) {
2938     st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
2939     totals += task_queue(i)->stats;
2940   }
2941   st->print_raw("tot "); totals.print(st); st->cr();
2942 
2943   DEBUG_ONLY(totals.verify());
2944 }
2945 
2946 void G1CollectedHeap::reset_taskqueue_stats() {
2947   const uint n = num_task_queues();
2948   for (uint i = 0; i < n; ++i) {
2949     task_queue(i)->stats.reset();
2950   }
2951 }
2952 #endif // TASKQUEUE_STATS
2953 
2954 void G1CollectedHeap::wait_for_root_region_scanning() {
2955   double scan_wait_start = os::elapsedTime();
2956   // We have to wait until the CM threads finish scanning the
2957   // root regions as it's the only way to ensure that all the
2958   // objects on them have been correctly scanned before we start
2959   // moving them during the GC.
2960   bool waited = _cm->root_regions()->wait_until_scan_finished();
2961   double wait_time_ms = 0.0;
2962   if (waited) {
2963     double scan_wait_end = os::elapsedTime();
2964     wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
2965   }
2966   phase_times()->record_root_region_scan_wait_time(wait_time_ms);
2967 }
2968 
2969 class G1PrintCollectionSetClosure : public HeapRegionClosure {
2970 private:
2971   G1HRPrinter* _hr_printer;
2972 public:
2973   G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { }
2974 
2975   virtual bool do_heap_region(HeapRegion* r) {
2976     _hr_printer->cset(r);
2977     return false;
2978   }
2979 };
2980 
2981 void G1CollectedHeap::start_new_collection_set() {
2982   double start = os::elapsedTime();
2983 
2984   collection_set()->start_incremental_building();
2985 
2986   clear_region_attr();
2987 
2988   guarantee(_eden.length() == 0, "eden should have been cleared");
2989   policy()->transfer_survivors_to_cset(survivor());
2990 
2991   // We redo the verification but now wrt to the new CSet which
2992   // has just got initialized after the previous CSet was freed.
2993   _cm->verify_no_collection_set_oops();
2994 
2995   phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0);
2996 }
2997 
2998 void G1CollectedHeap::calculate_collection_set(G1EvacuationInfo& evacuation_info, double target_pause_time_ms) {
2999 
3000   _collection_set.finalize_initial_collection_set(target_pause_time_ms, &_survivor);
3001   evacuation_info.set_collectionset_regions(collection_set()->region_length() +
3002                                             collection_set()->optional_region_length());
3003 
3004   _cm->verify_no_collection_set_oops();
3005 
3006   if (_hr_printer.is_active()) {
3007     G1PrintCollectionSetClosure cl(&_hr_printer);
3008     _collection_set.iterate(&cl);
3009     _collection_set.iterate_optional(&cl);
3010   }
3011 }
3012 
3013 G1HeapVerifier::G1VerifyType G1CollectedHeap::young_collection_verify_type() const {
3014   if (collector_state()->in_initial_mark_gc()) {
3015     return G1HeapVerifier::G1VerifyConcurrentStart;
3016   } else if (collector_state()->in_young_only_phase()) {
3017     return G1HeapVerifier::G1VerifyYoungNormal;
3018   } else {
3019     return G1HeapVerifier::G1VerifyMixed;
3020   }
3021 }
3022 
3023 void G1CollectedHeap::verify_before_young_collection(G1HeapVerifier::G1VerifyType type) {
3024   if (VerifyRememberedSets) {
3025     log_info(gc, verify)("[Verifying RemSets before GC]");
3026     VerifyRegionRemSetClosure v_cl;
3027     heap_region_iterate(&v_cl);
3028   }
3029   _verifier->verify_before_gc(type);
3030   _verifier->check_bitmaps("GC Start");
3031   verify_numa_regions("GC Start");
3032 }
3033 
3034 void G1CollectedHeap::verify_after_young_collection(G1HeapVerifier::G1VerifyType type) {
3035   if (VerifyRememberedSets) {
3036     log_info(gc, verify)("[Verifying RemSets after GC]");
3037     VerifyRegionRemSetClosure v_cl;
3038     heap_region_iterate(&v_cl);
3039   }
3040   _verifier->verify_after_gc(type);
3041   _verifier->check_bitmaps("GC End");
3042   verify_numa_regions("GC End");
3043 }
3044 
3045 void G1CollectedHeap::expand_heap_after_young_collection(){
3046   size_t expand_bytes = _heap_sizing_policy->expansion_amount();
3047   if (expand_bytes > 0) {
3048     // No need for an ergo logging here,
3049     // expansion_amount() does this when it returns a value > 0.
3050     double expand_ms;
3051     if (!expand(expand_bytes, _workers, &expand_ms)) {
3052       // We failed to expand the heap. Cannot do anything about it.
3053     }
3054     phase_times()->record_expand_heap_time(expand_ms);
3055   }
3056 }
3057 
3058 const char* G1CollectedHeap::young_gc_name() const {
3059   if (collector_state()->in_initial_mark_gc()) {
3060     return "Pause Young (Concurrent Start)";
3061   } else if (collector_state()->in_young_only_phase()) {
3062     if (collector_state()->in_young_gc_before_mixed()) {
3063       return "Pause Young (Prepare Mixed)";
3064     } else {
3065       return "Pause Young (Normal)";
3066     }
3067   } else {
3068     return "Pause Young (Mixed)";
3069   }
3070 }
3071 
3072 bool G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
3073   assert_at_safepoint_on_vm_thread();
3074   guarantee(!is_gc_active(), "collection is not reentrant");
3075 
3076   if (GCLocker::check_active_before_gc()) {
3077     return false;
3078   }
3079 
3080   GCIdMark gc_id_mark;
3081 
3082   SvcGCMarker sgcm(SvcGCMarker::MINOR);
3083   ResourceMark rm;
3084 
3085   policy()->note_gc_start();
3086 
3087   _gc_timer_stw->register_gc_start();
3088   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
3089 
3090   wait_for_root_region_scanning();
3091 
3092   print_heap_before_gc();
3093   print_heap_regions();
3094   trace_heap_before_gc(_gc_tracer_stw);
3095 
3096   _verifier->verify_region_sets_optional();
3097   _verifier->verify_dirty_young_regions();
3098 
3099   // We should not be doing initial mark unless the conc mark thread is running
3100   if (!_cm_thread->should_terminate()) {
3101     // This call will decide whether this pause is an initial-mark
3102     // pause. If it is, in_initial_mark_gc() will return true
3103     // for the duration of this pause.
3104     policy()->decide_on_conc_mark_initiation();
3105   }
3106 
3107   // We do not allow initial-mark to be piggy-backed on a mixed GC.
3108   assert(!collector_state()->in_initial_mark_gc() ||
3109          collector_state()->in_young_only_phase(), "sanity");
3110   // We also do not allow mixed GCs during marking.
3111   assert(!collector_state()->mark_or_rebuild_in_progress() || collector_state()->in_young_only_phase(), "sanity");
3112 
3113   // Record whether this pause is an initial mark. When the current
3114   // thread has completed its logging output and it's safe to signal
3115   // the CM thread, the flag's value in the policy has been reset.
3116   bool should_start_conc_mark = collector_state()->in_initial_mark_gc();
3117   if (should_start_conc_mark) {
3118     _cm->gc_tracer_cm()->set_gc_cause(gc_cause());
3119   }
3120 
3121   // Inner scope for scope based logging, timers, and stats collection
3122   {
3123     G1EvacuationInfo evacuation_info;
3124 
3125     _gc_tracer_stw->report_yc_type(collector_state()->yc_type());
3126 
3127     GCTraceCPUTime tcpu;
3128 
3129     GCTraceTime(Info, gc) tm(young_gc_name(), NULL, gc_cause(), true);
3130 
3131     uint active_workers = WorkerPolicy::calc_active_workers(workers()->total_workers(),
3132                                                             workers()->active_workers(),
3133                                                             Threads::number_of_non_daemon_threads());
3134     active_workers = workers()->update_active_workers(active_workers);
3135     log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers());
3136 
3137     G1MonitoringScope ms(g1mm(),
3138                          false /* full_gc */,
3139                          collector_state()->yc_type() == Mixed /* all_memory_pools_affected */);
3140 
3141     G1HeapTransition heap_transition(this);
3142 
3143     {
3144       IsGCActiveMark x;
3145 
3146       gc_prologue(false);
3147 
3148       G1HeapVerifier::G1VerifyType verify_type = young_collection_verify_type();
3149       verify_before_young_collection(verify_type);
3150 
3151       {
3152         // The elapsed time induced by the start time below deliberately elides
3153         // the possible verification above.
3154         double sample_start_time_sec = os::elapsedTime();
3155 
3156         // Please see comment in g1CollectedHeap.hpp and
3157         // G1CollectedHeap::ref_processing_init() to see how
3158         // reference processing currently works in G1.
3159         _ref_processor_stw->enable_discovery();
3160 
3161         // We want to temporarily turn off discovery by the
3162         // CM ref processor, if necessary, and turn it back on
3163         // on again later if we do. Using a scoped
3164         // NoRefDiscovery object will do this.
3165         NoRefDiscovery no_cm_discovery(_ref_processor_cm);
3166 
3167         policy()->record_collection_pause_start(sample_start_time_sec);
3168 
3169         // Forget the current allocation region (we might even choose it to be part
3170         // of the collection set!).
3171         _allocator->release_mutator_alloc_regions();
3172 
3173         calculate_collection_set(evacuation_info, target_pause_time_ms);
3174 
3175         G1RedirtyCardsQueueSet rdcqs(G1BarrierSet::dirty_card_queue_set().allocator());
3176         G1ParScanThreadStateSet per_thread_states(this,
3177                                                   &rdcqs,
3178                                                   workers()->active_workers(),
3179                                                   collection_set()->young_region_length(),
3180                                                   collection_set()->optional_region_length());
3181         pre_evacuate_collection_set(evacuation_info, &per_thread_states);
3182 
3183         // Actually do the work...
3184         evacuate_initial_collection_set(&per_thread_states);
3185 
3186         if (_collection_set.optional_region_length() != 0) {
3187           evacuate_optional_collection_set(&per_thread_states);
3188         }
3189         post_evacuate_collection_set(evacuation_info, &rdcqs, &per_thread_states);
3190 
3191         start_new_collection_set();
3192 
3193         _survivor_evac_stats.adjust_desired_plab_sz();
3194         _old_evac_stats.adjust_desired_plab_sz();
3195 
3196         if (should_start_conc_mark) {
3197           // We have to do this before we notify the CM threads that
3198           // they can start working to make sure that all the
3199           // appropriate initialization is done on the CM object.
3200           concurrent_mark()->post_initial_mark();
3201           // Note that we don't actually trigger the CM thread at
3202           // this point. We do that later when we're sure that
3203           // the current thread has completed its logging output.
3204         }
3205 
3206         allocate_dummy_regions();
3207 
3208         _allocator->init_mutator_alloc_regions();
3209 
3210         expand_heap_after_young_collection();
3211 
3212         double sample_end_time_sec = os::elapsedTime();
3213         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3214         policy()->record_collection_pause_end(pause_time_ms);
3215       }
3216 
3217       verify_after_young_collection(verify_type);
3218 
3219 #ifdef TRACESPINNING
3220       ParallelTaskTerminator::print_termination_counts();
3221 #endif
3222 
3223       gc_epilogue(false);
3224     }
3225 
3226     // Print the remainder of the GC log output.
3227     if (evacuation_failed()) {
3228       log_info(gc)("To-space exhausted");
3229     }
3230 
3231     policy()->print_phases();
3232     heap_transition.print();
3233 
3234     _hrm->verify_optional();
3235     _verifier->verify_region_sets_optional();
3236 
3237     TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
3238     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3239 
3240     print_heap_after_gc();
3241     print_heap_regions();
3242     trace_heap_after_gc(_gc_tracer_stw);
3243 
3244     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3245     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3246     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3247     // before any GC notifications are raised.
3248     g1mm()->update_sizes();
3249 
3250     _gc_tracer_stw->report_evacuation_info(&evacuation_info);
3251     _gc_tracer_stw->report_tenuring_threshold(_policy->tenuring_threshold());
3252     _gc_timer_stw->register_gc_end();
3253     _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
3254   }
3255   // It should now be safe to tell the concurrent mark thread to start
3256   // without its logging output interfering with the logging output
3257   // that came from the pause.
3258 
3259   if (should_start_conc_mark) {
3260     // CAUTION: after the doConcurrentMark() call below, the concurrent marking
3261     // thread(s) could be running concurrently with us. Make sure that anything
3262     // after this point does not assume that we are the only GC thread running.
3263     // Note: of course, the actual marking work will not start until the safepoint
3264     // itself is released in SuspendibleThreadSet::desynchronize().
3265     do_concurrent_mark();
3266   }
3267 
3268   return true;
3269 }
3270 
3271 void G1CollectedHeap::remove_self_forwarding_pointers(G1RedirtyCardsQueueSet* rdcqs) {
3272   G1ParRemoveSelfForwardPtrsTask rsfp_task(rdcqs);
3273   workers()->run_task(&rsfp_task);
3274 }
3275 
3276 void G1CollectedHeap::restore_after_evac_failure(G1RedirtyCardsQueueSet* rdcqs) {
3277   double remove_self_forwards_start = os::elapsedTime();
3278 
3279   remove_self_forwarding_pointers(rdcqs);
3280   SharedRestorePreservedMarksTaskExecutor task_executor(workers());
3281   _preserved_marks_set.restore(&task_executor);
3282 
3283   phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
3284 }
3285 
3286 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markWord m) {
3287   if (!_evacuation_failed) {
3288     _evacuation_failed = true;
3289   }
3290 
3291   _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size());
3292   _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m);
3293 }
3294 
3295 bool G1ParEvacuateFollowersClosure::offer_termination() {
3296   EventGCPhaseParallel event;
3297   G1ParScanThreadState* const pss = par_scan_state();
3298   start_term_time();
3299   const bool res = terminator()->offer_termination();
3300   end_term_time();
3301   event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(G1GCPhaseTimes::Termination));
3302   return res;
3303 }
3304 
3305 void G1ParEvacuateFollowersClosure::do_void() {
3306   EventGCPhaseParallel event;
3307   G1ParScanThreadState* const pss = par_scan_state();
3308   pss->trim_queue();
3309   event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(_phase));
3310   do {
3311     EventGCPhaseParallel event;
3312     pss->steal_and_trim_queue(queues());
3313     event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(_phase));
3314   } while (!offer_termination());
3315 }
3316 
3317 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive,
3318                                         bool class_unloading_occurred) {
3319   uint num_workers = workers()->active_workers();
3320   G1ParallelCleaningTask unlink_task(is_alive, num_workers, class_unloading_occurred, false);
3321   workers()->run_task(&unlink_task);
3322 }
3323 
3324 // Clean string dedup data structures.
3325 // Ideally we would prefer to use a StringDedupCleaningTask here, but we want to
3326 // record the durations of the phases. Hence the almost-copy.
3327 class G1StringDedupCleaningTask : public AbstractGangTask {
3328   BoolObjectClosure* _is_alive;
3329   OopClosure* _keep_alive;
3330   G1GCPhaseTimes* _phase_times;
3331 
3332 public:
3333   G1StringDedupCleaningTask(BoolObjectClosure* is_alive,
3334                             OopClosure* keep_alive,
3335                             G1GCPhaseTimes* phase_times) :
3336     AbstractGangTask("Partial Cleaning Task"),
3337     _is_alive(is_alive),
3338     _keep_alive(keep_alive),
3339     _phase_times(phase_times)
3340   {
3341     assert(G1StringDedup::is_enabled(), "String deduplication disabled.");
3342     StringDedup::gc_prologue(true);
3343   }
3344 
3345   ~G1StringDedupCleaningTask() {
3346     StringDedup::gc_epilogue();
3347   }
3348 
3349   void work(uint worker_id) {
3350     StringDedupUnlinkOrOopsDoClosure cl(_is_alive, _keep_alive);
3351     {
3352       G1GCParPhaseTimesTracker x(_phase_times, G1GCPhaseTimes::StringDedupQueueFixup, worker_id);
3353       StringDedupQueue::unlink_or_oops_do(&cl);
3354     }
3355     {
3356       G1GCParPhaseTimesTracker x(_phase_times, G1GCPhaseTimes::StringDedupTableFixup, worker_id);
3357       StringDedupTable::unlink_or_oops_do(&cl, worker_id);
3358     }
3359   }
3360 };
3361 
3362 void G1CollectedHeap::string_dedup_cleaning(BoolObjectClosure* is_alive,
3363                                             OopClosure* keep_alive,
3364                                             G1GCPhaseTimes* phase_times) {
3365   G1StringDedupCleaningTask cl(is_alive, keep_alive, phase_times);
3366   workers()->run_task(&cl);
3367 }
3368 
3369 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
3370  private:
3371   G1RedirtyCardsQueueSet* _qset;
3372   G1CollectedHeap* _g1h;
3373   BufferNode* volatile _nodes;
3374 
3375   void par_apply(RedirtyLoggedCardTableEntryClosure* cl, uint worker_id) {
3376     size_t buffer_size = _qset->buffer_size();
3377     BufferNode* next = Atomic::load(&_nodes);
3378     while (next != NULL) {
3379       BufferNode* node = next;
3380       next = Atomic::cmpxchg(&_nodes, node, node->next());
3381       if (next == node) {
3382         cl->apply_to_buffer(node, buffer_size, worker_id);
3383         next = node->next();
3384       }
3385     }
3386   }
3387 
3388  public:
3389   G1RedirtyLoggedCardsTask(G1RedirtyCardsQueueSet* qset, G1CollectedHeap* g1h) :
3390     AbstractGangTask("Redirty Cards"),
3391     _qset(qset), _g1h(g1h), _nodes(qset->all_completed_buffers()) { }
3392 
3393   virtual void work(uint worker_id) {
3394     G1GCPhaseTimes* p = _g1h->phase_times();
3395     G1GCParPhaseTimesTracker x(p, G1GCPhaseTimes::RedirtyCards, worker_id);
3396 
3397     RedirtyLoggedCardTableEntryClosure cl(_g1h);
3398     par_apply(&cl, worker_id);
3399 
3400     p->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied());
3401   }
3402 };
3403 
3404 void G1CollectedHeap::redirty_logged_cards(G1RedirtyCardsQueueSet* rdcqs) {
3405   double redirty_logged_cards_start = os::elapsedTime();
3406 
3407   G1RedirtyLoggedCardsTask redirty_task(rdcqs, this);
3408   workers()->run_task(&redirty_task);
3409 
3410   G1DirtyCardQueueSet& dcq = G1BarrierSet::dirty_card_queue_set();
3411   dcq.merge_bufferlists(rdcqs);
3412 
3413   phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
3414 }
3415 
3416 // Weak Reference Processing support
3417 
3418 bool G1STWIsAliveClosure::do_object_b(oop p) {
3419   // An object is reachable if it is outside the collection set,
3420   // or is inside and copied.
3421   return !_g1h->is_in_cset(p) || p->is_forwarded();
3422 }
3423 
3424 bool G1STWSubjectToDiscoveryClosure::do_object_b(oop obj) {
3425   assert(obj != NULL, "must not be NULL");
3426   assert(_g1h->is_in_reserved(obj), "Trying to discover obj " PTR_FORMAT " not in heap", p2i(obj));
3427   // The areas the CM and STW ref processor manage must be disjoint. The is_in_cset() below
3428   // may falsely indicate that this is not the case here: however the collection set only
3429   // contains old regions when concurrent mark is not running.
3430   return _g1h->is_in_cset(obj) || _g1h->heap_region_containing(obj)->is_survivor();
3431 }
3432 
3433 // Non Copying Keep Alive closure
3434 class G1KeepAliveClosure: public OopClosure {
3435   G1CollectedHeap*_g1h;
3436 public:
3437   G1KeepAliveClosure(G1CollectedHeap* g1h) :_g1h(g1h) {}
3438   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
3439   void do_oop(oop* p) {
3440     oop obj = *p;
3441     assert(obj != NULL, "the caller should have filtered out NULL values");
3442 
3443     const G1HeapRegionAttr region_attr =_g1h->region_attr(obj);
3444     if (!region_attr.is_in_cset_or_humongous()) {
3445       return;
3446     }
3447     if (region_attr.is_in_cset()) {
3448       assert( obj->is_forwarded(), "invariant" );
3449       *p = obj->forwardee();
3450     } else {
3451       assert(!obj->is_forwarded(), "invariant" );
3452       assert(region_attr.is_humongous(),
3453              "Only allowed G1HeapRegionAttr state is IsHumongous, but is %d", region_attr.type());
3454      _g1h->set_humongous_is_live(obj);
3455     }
3456   }
3457 };
3458 
3459 // Copying Keep Alive closure - can be called from both
3460 // serial and parallel code as long as different worker
3461 // threads utilize different G1ParScanThreadState instances
3462 // and different queues.
3463 
3464 class G1CopyingKeepAliveClosure: public OopClosure {
3465   G1CollectedHeap*         _g1h;
3466   G1ParScanThreadState*    _par_scan_state;
3467 
3468 public:
3469   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
3470                             G1ParScanThreadState* pss):
3471     _g1h(g1h),
3472     _par_scan_state(pss)
3473   {}
3474 
3475   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
3476   virtual void do_oop(      oop* p) { do_oop_work(p); }
3477 
3478   template <class T> void do_oop_work(T* p) {
3479     oop obj = RawAccess<>::oop_load(p);
3480 
3481     if (_g1h->is_in_cset_or_humongous(obj)) {
3482       // If the referent object has been forwarded (either copied
3483       // to a new location or to itself in the event of an
3484       // evacuation failure) then we need to update the reference
3485       // field and, if both reference and referent are in the G1
3486       // heap, update the RSet for the referent.
3487       //
3488       // If the referent has not been forwarded then we have to keep
3489       // it alive by policy. Therefore we have copy the referent.
3490       //
3491       // When the queue is drained (after each phase of reference processing)
3492       // the object and it's followers will be copied, the reference field set
3493       // to point to the new location, and the RSet updated.
3494       _par_scan_state->push_on_queue(p);
3495     }
3496   }
3497 };
3498 
3499 // Serial drain queue closure. Called as the 'complete_gc'
3500 // closure for each discovered list in some of the
3501 // reference processing phases.
3502 
3503 class G1STWDrainQueueClosure: public VoidClosure {
3504 protected:
3505   G1CollectedHeap* _g1h;
3506   G1ParScanThreadState* _par_scan_state;
3507 
3508   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
3509 
3510 public:
3511   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
3512     _g1h(g1h),
3513     _par_scan_state(pss)
3514   { }
3515 
3516   void do_void() {
3517     G1ParScanThreadState* const pss = par_scan_state();
3518     pss->trim_queue();
3519   }
3520 };
3521 
3522 // Parallel Reference Processing closures
3523 
3524 // Implementation of AbstractRefProcTaskExecutor for parallel reference
3525 // processing during G1 evacuation pauses.
3526 
3527 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
3528 private:
3529   G1CollectedHeap*          _g1h;
3530   G1ParScanThreadStateSet*  _pss;
3531   RefToScanQueueSet*        _queues;
3532   WorkGang*                 _workers;
3533 
3534 public:
3535   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
3536                            G1ParScanThreadStateSet* per_thread_states,
3537                            WorkGang* workers,
3538                            RefToScanQueueSet *task_queues) :
3539     _g1h(g1h),
3540     _pss(per_thread_states),
3541     _queues(task_queues),
3542     _workers(workers)
3543   {
3544     g1h->ref_processor_stw()->set_active_mt_degree(workers->active_workers());
3545   }
3546 
3547   // Executes the given task using concurrent marking worker threads.
3548   virtual void execute(ProcessTask& task, uint ergo_workers);
3549 };
3550 
3551 // Gang task for possibly parallel reference processing
3552 
3553 class G1STWRefProcTaskProxy: public AbstractGangTask {
3554   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
3555   ProcessTask&     _proc_task;
3556   G1CollectedHeap* _g1h;
3557   G1ParScanThreadStateSet* _pss;
3558   RefToScanQueueSet* _task_queues;
3559   ParallelTaskTerminator* _terminator;
3560 
3561 public:
3562   G1STWRefProcTaskProxy(ProcessTask& proc_task,
3563                         G1CollectedHeap* g1h,
3564                         G1ParScanThreadStateSet* per_thread_states,
3565                         RefToScanQueueSet *task_queues,
3566                         ParallelTaskTerminator* terminator) :
3567     AbstractGangTask("Process reference objects in parallel"),
3568     _proc_task(proc_task),
3569     _g1h(g1h),
3570     _pss(per_thread_states),
3571     _task_queues(task_queues),
3572     _terminator(terminator)
3573   {}
3574 
3575   virtual void work(uint worker_id) {
3576     // The reference processing task executed by a single worker.
3577     ResourceMark rm;
3578     HandleMark   hm;
3579 
3580     G1STWIsAliveClosure is_alive(_g1h);
3581 
3582     G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
3583     pss->set_ref_discoverer(NULL);
3584 
3585     // Keep alive closure.
3586     G1CopyingKeepAliveClosure keep_alive(_g1h, pss);
3587 
3588     // Complete GC closure
3589     G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator, G1GCPhaseTimes::ObjCopy);
3590 
3591     // Call the reference processing task's work routine.
3592     _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
3593 
3594     // Note we cannot assert that the refs array is empty here as not all
3595     // of the processing tasks (specifically phase2 - pp2_work) execute
3596     // the complete_gc closure (which ordinarily would drain the queue) so
3597     // the queue may not be empty.
3598   }
3599 };
3600 
3601 // Driver routine for parallel reference processing.
3602 // Creates an instance of the ref processing gang
3603 // task and has the worker threads execute it.
3604 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task, uint ergo_workers) {
3605   assert(_workers != NULL, "Need parallel worker threads.");
3606 
3607   assert(_workers->active_workers() >= ergo_workers,
3608          "Ergonomically chosen workers (%u) should be less than or equal to active workers (%u)",
3609          ergo_workers, _workers->active_workers());
3610   TaskTerminator terminator(ergo_workers, _queues);
3611   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, terminator.terminator());
3612 
3613   _workers->run_task(&proc_task_proxy, ergo_workers);
3614 }
3615 
3616 // End of weak reference support closures
3617 
3618 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
3619   double ref_proc_start = os::elapsedTime();
3620 
3621   ReferenceProcessor* rp = _ref_processor_stw;
3622   assert(rp->discovery_enabled(), "should have been enabled");
3623 
3624   // Closure to test whether a referent is alive.
3625   G1STWIsAliveClosure is_alive(this);
3626 
3627   // Even when parallel reference processing is enabled, the processing
3628   // of JNI refs is serial and performed serially by the current thread
3629   // rather than by a worker. The following PSS will be used for processing
3630   // JNI refs.
3631 
3632   // Use only a single queue for this PSS.
3633   G1ParScanThreadState*          pss = per_thread_states->state_for_worker(0);
3634   pss->set_ref_discoverer(NULL);
3635   assert(pss->queue_is_empty(), "pre-condition");
3636 
3637   // Keep alive closure.
3638   G1CopyingKeepAliveClosure keep_alive(this, pss);
3639 
3640   // Serial Complete GC closure
3641   G1STWDrainQueueClosure drain_queue(this, pss);
3642 
3643   // Setup the soft refs policy...
3644   rp->setup_policy(false);
3645 
3646   ReferenceProcessorPhaseTimes* pt = phase_times()->ref_phase_times();
3647 
3648   ReferenceProcessorStats stats;
3649   if (!rp->processing_is_mt()) {
3650     // Serial reference processing...
3651     stats = rp->process_discovered_references(&is_alive,
3652                                               &keep_alive,
3653                                               &drain_queue,
3654                                               NULL,
3655                                               pt);
3656   } else {
3657     uint no_of_gc_workers = workers()->active_workers();
3658 
3659     // Parallel reference processing
3660     assert(no_of_gc_workers <= rp->max_num_queues(),
3661            "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
3662            no_of_gc_workers,  rp->max_num_queues());
3663 
3664     G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues);
3665     stats = rp->process_discovered_references(&is_alive,
3666                                               &keep_alive,
3667                                               &drain_queue,
3668                                               &par_task_executor,
3669                                               pt);
3670   }
3671 
3672   _gc_tracer_stw->report_gc_reference_stats(stats);
3673 
3674   // We have completed copying any necessary live referent objects.
3675   assert(pss->queue_is_empty(), "both queue and overflow should be empty");
3676 
3677   make_pending_list_reachable();
3678 
3679   assert(!rp->discovery_enabled(), "Postcondition");
3680   rp->verify_no_references_recorded();
3681 
3682   double ref_proc_time = os::elapsedTime() - ref_proc_start;
3683   phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
3684 }
3685 
3686 void G1CollectedHeap::make_pending_list_reachable() {
3687   if (collector_state()->in_initial_mark_gc()) {
3688     oop pll_head = Universe::reference_pending_list();
3689     if (pll_head != NULL) {
3690       // Any valid worker id is fine here as we are in the VM thread and single-threaded.
3691       _cm->mark_in_next_bitmap(0 /* worker_id */, pll_head);
3692     }
3693   }
3694 }
3695 
3696 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) {
3697   Ticks start = Ticks::now();
3698   per_thread_states->flush();
3699   phase_times()->record_or_add_time_secs(G1GCPhaseTimes::MergePSS, 0 /* worker_id */, (Ticks::now() - start).seconds());
3700 }
3701 
3702 void G1CollectedHeap::pre_evacuate_collection_set(G1EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
3703   _bytes_used_during_gc = 0;
3704 
3705   _expand_heap_after_alloc_failure = true;
3706   _evacuation_failed = false;
3707 
3708   // Disable the hot card cache.
3709   _hot_card_cache->reset_hot_cache_claimed_index();
3710   _hot_card_cache->set_use_cache(false);
3711 
3712   // Initialize the GC alloc regions.
3713   _allocator->init_gc_alloc_regions(evacuation_info);
3714 
3715   {
3716     Ticks start = Ticks::now();
3717     rem_set()->prepare_for_scan_heap_roots();
3718     phase_times()->record_prepare_heap_roots_time_ms((Ticks::now() - start).seconds() * 1000.0);
3719   }
3720 
3721   register_regions_with_region_attr();
3722   assert(_verifier->check_region_attr_table(), "Inconsistency in the region attributes table.");
3723 
3724   _preserved_marks_set.assert_empty();
3725 
3726 #if COMPILER2_OR_JVMCI
3727   DerivedPointerTable::clear();
3728 #endif
3729 
3730   // InitialMark needs claim bits to keep track of the marked-through CLDs.
3731   if (collector_state()->in_initial_mark_gc()) {
3732     concurrent_mark()->pre_initial_mark();
3733 
3734     double start_clear_claimed_marks = os::elapsedTime();
3735 
3736     ClassLoaderDataGraph::clear_claimed_marks();
3737 
3738     double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0;
3739     phase_times()->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms);
3740   }
3741 
3742   // Should G1EvacuationFailureALot be in effect for this GC?
3743   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
3744 }
3745 
3746 class G1EvacuateRegionsBaseTask : public AbstractGangTask {
3747 protected:
3748   G1CollectedHeap* _g1h;
3749   G1ParScanThreadStateSet* _per_thread_states;
3750   RefToScanQueueSet* _task_queues;
3751   TaskTerminator _terminator;
3752   uint _num_workers;
3753 
3754   void evacuate_live_objects(G1ParScanThreadState* pss,
3755                              uint worker_id,
3756                              G1GCPhaseTimes::GCParPhases objcopy_phase,
3757                              G1GCPhaseTimes::GCParPhases termination_phase) {
3758     G1GCPhaseTimes* p = _g1h->phase_times();
3759 
3760     Ticks start = Ticks::now();
3761     G1ParEvacuateFollowersClosure cl(_g1h, pss, _task_queues, _terminator.terminator(), objcopy_phase);
3762     cl.do_void();
3763 
3764     assert(pss->queue_is_empty(), "should be empty");
3765 
3766     Tickspan evac_time = (Ticks::now() - start);
3767     p->record_or_add_time_secs(objcopy_phase, worker_id, evac_time.seconds() - cl.term_time());
3768 
3769     if (termination_phase == G1GCPhaseTimes::Termination) {
3770       p->record_time_secs(termination_phase, worker_id, cl.term_time());
3771       p->record_thread_work_item(termination_phase, worker_id, cl.term_attempts());
3772     } else {
3773       p->record_or_add_time_secs(termination_phase, worker_id, cl.term_time());
3774       p->record_or_add_thread_work_item(termination_phase, worker_id, cl.term_attempts());
3775     }
3776     assert(pss->trim_ticks().seconds() == 0.0, "Unexpected partial trimming during evacuation");
3777   }
3778 
3779   virtual void start_work(uint worker_id) { }
3780 
3781   virtual void end_work(uint worker_id) { }
3782 
3783   virtual void scan_roots(G1ParScanThreadState* pss, uint worker_id) = 0;
3784 
3785   virtual void evacuate_live_objects(G1ParScanThreadState* pss, uint worker_id) = 0;
3786 
3787 public:
3788   G1EvacuateRegionsBaseTask(const char* name, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet* task_queues, uint num_workers) :
3789     AbstractGangTask(name),
3790     _g1h(G1CollectedHeap::heap()),
3791     _per_thread_states(per_thread_states),
3792     _task_queues(task_queues),
3793     _terminator(num_workers, _task_queues),
3794     _num_workers(num_workers)
3795   { }
3796 
3797   void work(uint worker_id) {
3798     start_work(worker_id);
3799 
3800     {
3801       ResourceMark rm;
3802       HandleMark   hm;
3803 
3804       G1ParScanThreadState* pss = _per_thread_states->state_for_worker(worker_id);
3805       pss->set_ref_discoverer(_g1h->ref_processor_stw());
3806 
3807       scan_roots(pss, worker_id);
3808       evacuate_live_objects(pss, worker_id);
3809     }
3810 
3811     end_work(worker_id);
3812   }
3813 };
3814 
3815 class G1EvacuateRegionsTask : public G1EvacuateRegionsBaseTask {
3816   G1RootProcessor* _root_processor;
3817 
3818   void scan_roots(G1ParScanThreadState* pss, uint worker_id) {
3819     _root_processor->evacuate_roots(pss, worker_id);
3820     _g1h->rem_set()->scan_heap_roots(pss, worker_id, G1GCPhaseTimes::ScanHR, G1GCPhaseTimes::ObjCopy);
3821     _g1h->rem_set()->scan_collection_set_regions(pss, worker_id, G1GCPhaseTimes::ScanHR, G1GCPhaseTimes::CodeRoots, G1GCPhaseTimes::ObjCopy);
3822   }
3823 
3824   void evacuate_live_objects(G1ParScanThreadState* pss, uint worker_id) {
3825     G1EvacuateRegionsBaseTask::evacuate_live_objects(pss, worker_id, G1GCPhaseTimes::ObjCopy, G1GCPhaseTimes::Termination);
3826   }
3827 
3828   void start_work(uint worker_id) {
3829     _g1h->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, Ticks::now().seconds());
3830   }
3831 
3832   void end_work(uint worker_id) {
3833     _g1h->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, Ticks::now().seconds());
3834   }
3835 
3836 public:
3837   G1EvacuateRegionsTask(G1CollectedHeap* g1h,
3838                         G1ParScanThreadStateSet* per_thread_states,
3839                         RefToScanQueueSet* task_queues,
3840                         G1RootProcessor* root_processor,
3841                         uint num_workers) :
3842     G1EvacuateRegionsBaseTask("G1 Evacuate Regions", per_thread_states, task_queues, num_workers),
3843     _root_processor(root_processor)
3844   { }
3845 };
3846 
3847 void G1CollectedHeap::evacuate_initial_collection_set(G1ParScanThreadStateSet* per_thread_states) {
3848   G1GCPhaseTimes* p = phase_times();
3849 
3850   {
3851     Ticks start = Ticks::now();
3852     rem_set()->merge_heap_roots(true /* initial_evacuation */);
3853     p->record_merge_heap_roots_time((Ticks::now() - start).seconds() * 1000.0);
3854   }
3855 
3856   Tickspan task_time;
3857   const uint num_workers = workers()->active_workers();
3858 
3859   Ticks start_processing = Ticks::now();
3860   {
3861     G1RootProcessor root_processor(this, num_workers);
3862     G1EvacuateRegionsTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, num_workers);
3863     task_time = run_task(&g1_par_task);
3864     // Closing the inner scope will execute the destructor for the G1RootProcessor object.
3865     // To extract its code root fixup time we measure total time of this scope and
3866     // subtract from the time the WorkGang task took.
3867   }
3868   Tickspan total_processing = Ticks::now() - start_processing;
3869 
3870   p->record_initial_evac_time(task_time.seconds() * 1000.0);
3871   p->record_or_add_code_root_fixup_time((total_processing - task_time).seconds() * 1000.0);
3872 }
3873 
3874 class G1EvacuateOptionalRegionsTask : public G1EvacuateRegionsBaseTask {
3875 
3876   void scan_roots(G1ParScanThreadState* pss, uint worker_id) {
3877     _g1h->rem_set()->scan_heap_roots(pss, worker_id, G1GCPhaseTimes::OptScanHR, G1GCPhaseTimes::OptObjCopy);
3878     _g1h->rem_set()->scan_collection_set_regions(pss, worker_id, G1GCPhaseTimes::OptScanHR, G1GCPhaseTimes::OptCodeRoots, G1GCPhaseTimes::OptObjCopy);
3879   }
3880 
3881   void evacuate_live_objects(G1ParScanThreadState* pss, uint worker_id) {
3882     G1EvacuateRegionsBaseTask::evacuate_live_objects(pss, worker_id, G1GCPhaseTimes::OptObjCopy, G1GCPhaseTimes::OptTermination);
3883   }
3884 
3885 public:
3886   G1EvacuateOptionalRegionsTask(G1ParScanThreadStateSet* per_thread_states,
3887                                 RefToScanQueueSet* queues,
3888                                 uint num_workers) :
3889     G1EvacuateRegionsBaseTask("G1 Evacuate Optional Regions", per_thread_states, queues, num_workers) {
3890   }
3891 };
3892 
3893 void G1CollectedHeap::evacuate_next_optional_regions(G1ParScanThreadStateSet* per_thread_states) {
3894   class G1MarkScope : public MarkScope { };
3895 
3896   Tickspan task_time;
3897 
3898   Ticks start_processing = Ticks::now();
3899   {
3900     G1MarkScope code_mark_scope;
3901     G1EvacuateOptionalRegionsTask task(per_thread_states, _task_queues, workers()->active_workers());
3902     task_time = run_task(&task);
3903     // See comment in evacuate_collection_set() for the reason of the scope.
3904   }
3905   Tickspan total_processing = Ticks::now() - start_processing;
3906 
3907   G1GCPhaseTimes* p = phase_times();
3908   p->record_or_add_code_root_fixup_time((total_processing - task_time).seconds() * 1000.0);
3909 }
3910 
3911 void G1CollectedHeap::evacuate_optional_collection_set(G1ParScanThreadStateSet* per_thread_states) {
3912   const double gc_start_time_ms = phase_times()->cur_collection_start_sec() * 1000.0;
3913 
3914   while (!evacuation_failed() && _collection_set.optional_region_length() > 0) {
3915 
3916     double time_used_ms = os::elapsedTime() * 1000.0 - gc_start_time_ms;
3917     double time_left_ms = MaxGCPauseMillis - time_used_ms;
3918 
3919     if (time_left_ms < 0 ||
3920         !_collection_set.finalize_optional_for_evacuation(time_left_ms * policy()->optional_evacuation_fraction())) {
3921       log_trace(gc, ergo, cset)("Skipping evacuation of %u optional regions, no more regions can be evacuated in %.3fms",
3922                                 _collection_set.optional_region_length(), time_left_ms);
3923       break;
3924     }
3925 
3926     {
3927       Ticks start = Ticks::now();
3928       rem_set()->merge_heap_roots(false /* initial_evacuation */);
3929       phase_times()->record_or_add_optional_merge_heap_roots_time((Ticks::now() - start).seconds() * 1000.0);
3930     }
3931 
3932     {
3933       Ticks start = Ticks::now();
3934       evacuate_next_optional_regions(per_thread_states);
3935       phase_times()->record_or_add_optional_evac_time((Ticks::now() - start).seconds() * 1000.0);
3936     }
3937   }
3938 
3939   _collection_set.abandon_optional_collection_set(per_thread_states);
3940 }
3941 
3942 void G1CollectedHeap::post_evacuate_collection_set(G1EvacuationInfo& evacuation_info,
3943                                                    G1RedirtyCardsQueueSet* rdcqs,
3944                                                    G1ParScanThreadStateSet* per_thread_states) {
3945   G1GCPhaseTimes* p = phase_times();
3946 
3947   rem_set()->cleanup_after_scan_heap_roots();
3948 
3949   // Process any discovered reference objects - we have
3950   // to do this _before_ we retire the GC alloc regions
3951   // as we may have to copy some 'reachable' referent
3952   // objects (and their reachable sub-graphs) that were
3953   // not copied during the pause.
3954   process_discovered_references(per_thread_states);
3955 
3956   G1STWIsAliveClosure is_alive(this);
3957   G1KeepAliveClosure keep_alive(this);
3958 
3959   WeakProcessor::weak_oops_do(workers(), &is_alive, &keep_alive, p->weak_phase_times());
3960 
3961   if (G1StringDedup::is_enabled()) {
3962     double string_dedup_time_ms = os::elapsedTime();
3963 
3964     string_dedup_cleaning(&is_alive, &keep_alive, p);
3965 
3966     double string_cleanup_time_ms = (os::elapsedTime() - string_dedup_time_ms) * 1000.0;
3967     p->record_string_deduplication_time(string_cleanup_time_ms);
3968   }
3969 
3970   _allocator->release_gc_alloc_regions(evacuation_info);
3971 
3972   if (evacuation_failed()) {
3973     restore_after_evac_failure(rdcqs);
3974 
3975     // Reset the G1EvacuationFailureALot counters and flags
3976     NOT_PRODUCT(reset_evacuation_should_fail();)
3977 
3978     double recalculate_used_start = os::elapsedTime();
3979     set_used(recalculate_used());
3980     p->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
3981 
3982     if (_archive_allocator != NULL) {
3983       _archive_allocator->clear_used();
3984     }
3985     for (uint i = 0; i < ParallelGCThreads; i++) {
3986       if (_evacuation_failed_info_array[i].has_failed()) {
3987         _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
3988       }
3989     }
3990   } else {
3991     // The "used" of the the collection set have already been subtracted
3992     // when they were freed.  Add in the bytes used.
3993     increase_used(_bytes_used_during_gc);
3994   }
3995 
3996   _preserved_marks_set.assert_empty();
3997 
3998   merge_per_thread_state_info(per_thread_states);
3999 
4000   // Reset and re-enable the hot card cache.
4001   // Note the counts for the cards in the regions in the
4002   // collection set are reset when the collection set is freed.
4003   _hot_card_cache->reset_hot_cache();
4004   _hot_card_cache->set_use_cache(true);
4005 
4006   purge_code_root_memory();
4007 
4008   redirty_logged_cards(rdcqs);
4009 
4010   free_collection_set(&_collection_set, evacuation_info, per_thread_states->surviving_young_words());
4011 
4012   eagerly_reclaim_humongous_regions();
4013 
4014   record_obj_copy_mem_stats();
4015 
4016   evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before());
4017   evacuation_info.set_bytes_used(_bytes_used_during_gc);
4018 
4019 #if COMPILER2_OR_JVMCI
4020   double start = os::elapsedTime();
4021   DerivedPointerTable::update_pointers();
4022   phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0);
4023 #endif
4024   policy()->print_age_table();
4025 }
4026 
4027 void G1CollectedHeap::record_obj_copy_mem_stats() {
4028   policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
4029 
4030   _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
4031                                                create_g1_evac_summary(&_old_evac_stats));
4032 }
4033 
4034 void G1CollectedHeap::free_region(HeapRegion* hr,
4035                                   FreeRegionList* free_list,
4036                                   bool skip_remset,
4037                                   bool skip_hot_card_cache,
4038                                   bool locked) {
4039   assert(!hr->is_free(), "the region should not be free");
4040   assert(!hr->is_empty(), "the region should not be empty");
4041   assert(_hrm->is_available(hr->hrm_index()), "region should be committed");
4042   assert(free_list != NULL, "pre-condition");
4043 
4044   if (G1VerifyBitmaps) {
4045     MemRegion mr(hr->bottom(), hr->end());
4046     concurrent_mark()->clear_range_in_prev_bitmap(mr);
4047   }
4048 
4049   // Clear the card counts for this region.
4050   // Note: we only need to do this if the region is not young
4051   // (since we don't refine cards in young regions).
4052   if (!skip_hot_card_cache && !hr->is_young()) {
4053     _hot_card_cache->reset_card_counts(hr);
4054   }
4055   hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */);
4056   _policy->remset_tracker()->update_at_free(hr);
4057   free_list->add_ordered(hr);
4058 }
4059 
4060 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
4061                                             FreeRegionList* free_list) {
4062   assert(hr->is_humongous(), "this is only for humongous regions");
4063   assert(free_list != NULL, "pre-condition");
4064   hr->clear_humongous();
4065   free_region(hr, free_list, false /* skip_remset */, false /* skip_hcc */, true /* locked */);
4066 }
4067 
4068 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed,
4069                                            const uint humongous_regions_removed) {
4070   if (old_regions_removed > 0 || humongous_regions_removed > 0) {
4071     MutexLocker x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4072     _old_set.bulk_remove(old_regions_removed);
4073     _humongous_set.bulk_remove(humongous_regions_removed);
4074   }
4075 
4076 }
4077 
4078 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
4079   assert(list != NULL, "list can't be null");
4080   if (!list->is_empty()) {
4081     MutexLocker x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4082     _hrm->insert_list_into_free_list(list);
4083   }
4084 }
4085 
4086 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
4087   decrease_used(bytes);
4088 }
4089 
4090 class G1FreeCollectionSetTask : public AbstractGangTask {
4091 private:
4092 
4093   // Closure applied to all regions in the collection set to do work that needs to
4094   // be done serially in a single thread.
4095   class G1SerialFreeCollectionSetClosure : public HeapRegionClosure {
4096   private:
4097     G1EvacuationInfo* _evacuation_info;
4098     const size_t* _surviving_young_words;
4099 
4100     // Bytes used in successfully evacuated regions before the evacuation.
4101     size_t _before_used_bytes;
4102     // Bytes used in unsucessfully evacuated regions before the evacuation
4103     size_t _after_used_bytes;
4104 
4105     size_t _bytes_allocated_in_old_since_last_gc;
4106 
4107     size_t _failure_used_words;
4108     size_t _failure_waste_words;
4109 
4110     FreeRegionList _local_free_list;
4111   public:
4112     G1SerialFreeCollectionSetClosure(G1EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4113       HeapRegionClosure(),
4114       _evacuation_info(evacuation_info),
4115       _surviving_young_words(surviving_young_words),
4116       _before_used_bytes(0),
4117       _after_used_bytes(0),
4118       _bytes_allocated_in_old_since_last_gc(0),
4119       _failure_used_words(0),
4120       _failure_waste_words(0),
4121       _local_free_list("Local Region List for CSet Freeing") {
4122     }
4123 
4124     virtual bool do_heap_region(HeapRegion* r) {
4125       G1CollectedHeap* g1h = G1CollectedHeap::heap();
4126 
4127       assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index());
4128       g1h->clear_region_attr(r);
4129 
4130       if (r->is_young()) {
4131         assert(r->young_index_in_cset() != 0 && (uint)r->young_index_in_cset() <= g1h->collection_set()->young_region_length(),
4132                "Young index %u is wrong for region %u of type %s with %u young regions",
4133                r->young_index_in_cset(),
4134                r->hrm_index(),
4135                r->get_type_str(),
4136                g1h->collection_set()->young_region_length());
4137         size_t words_survived = _surviving_young_words[r->young_index_in_cset()];
4138         r->record_surv_words_in_group(words_survived);
4139       }
4140 
4141       if (!r->evacuation_failed()) {
4142         assert(!r->is_empty(), "Region %u is an empty region in the collection set.", r->hrm_index());
4143         _before_used_bytes += r->used();
4144         g1h->free_region(r,
4145                          &_local_free_list,
4146                          true, /* skip_remset */
4147                          true, /* skip_hot_card_cache */
4148                          true  /* locked */);
4149       } else {
4150         r->uninstall_surv_rate_group();
4151         r->clear_young_index_in_cset();
4152         r->set_evacuation_failed(false);
4153         // When moving a young gen region to old gen, we "allocate" that whole region
4154         // there. This is in addition to any already evacuated objects. Notify the
4155         // policy about that.
4156         // Old gen regions do not cause an additional allocation: both the objects
4157         // still in the region and the ones already moved are accounted for elsewhere.
4158         if (r->is_young()) {
4159           _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes;
4160         }
4161         // The region is now considered to be old.
4162         r->set_old();
4163         // Do some allocation statistics accounting. Regions that failed evacuation
4164         // are always made old, so there is no need to update anything in the young
4165         // gen statistics, but we need to update old gen statistics.
4166         size_t used_words = r->marked_bytes() / HeapWordSize;
4167 
4168         _failure_used_words += used_words;
4169         _failure_waste_words += HeapRegion::GrainWords - used_words;
4170 
4171         g1h->old_set_add(r);
4172         _after_used_bytes += r->used();
4173       }
4174       return false;
4175     }
4176 
4177     void complete_work() {
4178       G1CollectedHeap* g1h = G1CollectedHeap::heap();
4179 
4180       _evacuation_info->set_regions_freed(_local_free_list.length());
4181       _evacuation_info->increment_collectionset_used_after(_after_used_bytes);
4182 
4183       g1h->prepend_to_freelist(&_local_free_list);
4184       g1h->decrement_summary_bytes(_before_used_bytes);
4185 
4186       G1Policy* policy = g1h->policy();
4187       policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc);
4188 
4189       g1h->alloc_buffer_stats(G1HeapRegionAttr::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words);
4190     }
4191   };
4192 
4193   G1CollectionSet* _collection_set;
4194   G1SerialFreeCollectionSetClosure _cl;
4195   const size_t* _surviving_young_words;
4196 
4197   size_t _rs_length;
4198 
4199   volatile jint _serial_work_claim;
4200 
4201   struct WorkItem {
4202     uint region_idx;
4203     bool is_young;
4204     bool evacuation_failed;
4205 
4206     WorkItem(HeapRegion* r) {
4207       region_idx = r->hrm_index();
4208       is_young = r->is_young();
4209       evacuation_failed = r->evacuation_failed();
4210     }
4211   };
4212 
4213   volatile size_t _parallel_work_claim;
4214   size_t _num_work_items;
4215   WorkItem* _work_items;
4216 
4217   void do_serial_work() {
4218     // Need to grab the lock to be allowed to modify the old region list.
4219     MutexLocker x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4220     _collection_set->iterate(&_cl);
4221   }
4222 
4223   void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) {
4224     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4225 
4226     HeapRegion* r = g1h->region_at(region_idx);
4227     assert(!g1h->is_on_master_free_list(r), "sanity");
4228 
4229     Atomic::add(&_rs_length, r->rem_set()->occupied_locked());
4230 
4231     if (!is_young) {
4232       g1h->hot_card_cache()->reset_card_counts(r);
4233     }
4234 
4235     if (!evacuation_failed) {
4236       r->rem_set()->clear_locked();
4237     }
4238   }
4239 
4240   class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure {
4241   private:
4242     size_t _cur_idx;
4243     WorkItem* _work_items;
4244   public:
4245     G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { }
4246 
4247     virtual bool do_heap_region(HeapRegion* r) {
4248       _work_items[_cur_idx++] = WorkItem(r);
4249       return false;
4250     }
4251   };
4252 
4253   void prepare_work() {
4254     G1PrepareFreeCollectionSetClosure cl(_work_items);
4255     _collection_set->iterate(&cl);
4256   }
4257 
4258   void complete_work() {
4259     _cl.complete_work();
4260 
4261     G1Policy* policy = G1CollectedHeap::heap()->policy();
4262     policy->record_rs_length(_rs_length);
4263     policy->cset_regions_freed();
4264   }
4265 public:
4266   G1FreeCollectionSetTask(G1CollectionSet* collection_set, G1EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4267     AbstractGangTask("G1 Free Collection Set"),
4268     _collection_set(collection_set),
4269     _cl(evacuation_info, surviving_young_words),
4270     _surviving_young_words(surviving_young_words),
4271     _rs_length(0),
4272     _serial_work_claim(0),
4273     _parallel_work_claim(0),
4274     _num_work_items(collection_set->region_length()),
4275     _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) {
4276     prepare_work();
4277   }
4278 
4279   ~G1FreeCollectionSetTask() {
4280     complete_work();
4281     FREE_C_HEAP_ARRAY(WorkItem, _work_items);
4282   }
4283 
4284   // Chunk size for work distribution. The chosen value has been determined experimentally
4285   // to be a good tradeoff between overhead and achievable parallelism.
4286   static uint chunk_size() { return 32; }
4287 
4288   virtual void work(uint worker_id) {
4289     G1GCPhaseTimes* timer = G1CollectedHeap::heap()->phase_times();
4290 
4291     // Claim serial work.
4292     if (_serial_work_claim == 0) {
4293       jint value = Atomic::add(&_serial_work_claim, 1) - 1;
4294       if (value == 0) {
4295         double serial_time = os::elapsedTime();
4296         do_serial_work();
4297         timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0);
4298       }
4299     }
4300 
4301     // Start parallel work.
4302     double young_time = 0.0;
4303     bool has_young_time = false;
4304     double non_young_time = 0.0;
4305     bool has_non_young_time = false;
4306 
4307     while (true) {
4308       size_t end = Atomic::add(&_parallel_work_claim, chunk_size());
4309       size_t cur = end - chunk_size();
4310 
4311       if (cur >= _num_work_items) {
4312         break;
4313       }
4314 
4315       EventGCPhaseParallel event;
4316       double start_time = os::elapsedTime();
4317 
4318       end = MIN2(end, _num_work_items);
4319 
4320       for (; cur < end; cur++) {
4321         bool is_young = _work_items[cur].is_young;
4322 
4323         do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed);
4324 
4325         double end_time = os::elapsedTime();
4326         double time_taken = end_time - start_time;
4327         if (is_young) {
4328           young_time += time_taken;
4329           has_young_time = true;
4330           event.commit(GCId::current(), worker_id, G1GCPhaseTimes::phase_name(G1GCPhaseTimes::YoungFreeCSet));
4331         } else {
4332           non_young_time += time_taken;
4333           has_non_young_time = true;
4334           event.commit(GCId::current(), worker_id, G1GCPhaseTimes::phase_name(G1GCPhaseTimes::NonYoungFreeCSet));
4335         }
4336         start_time = end_time;
4337       }
4338     }
4339 
4340     if (has_young_time) {
4341       timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time);
4342     }
4343     if (has_non_young_time) {
4344       timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, non_young_time);
4345     }
4346   }
4347 };
4348 
4349 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, G1EvacuationInfo& evacuation_info, const size_t* surviving_young_words) {
4350   _eden.clear();
4351 
4352   double free_cset_start_time = os::elapsedTime();
4353 
4354   {
4355     uint const num_regions = _collection_set.region_length();
4356     uint const num_chunks = MAX2(num_regions / G1FreeCollectionSetTask::chunk_size(), 1U);
4357     uint const num_workers = MIN2(workers()->active_workers(), num_chunks);
4358 
4359     G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words);
4360 
4361     log_debug(gc, ergo)("Running %s using %u workers for collection set length %u",
4362                         cl.name(), num_workers, num_regions);
4363     workers()->run_task(&cl, num_workers);
4364   }
4365   phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0);
4366 
4367   collection_set->clear();
4368 }
4369 
4370 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
4371  private:
4372   FreeRegionList* _free_region_list;
4373   HeapRegionSet* _proxy_set;
4374   uint _humongous_objects_reclaimed;
4375   uint _humongous_regions_reclaimed;
4376   size_t _freed_bytes;
4377  public:
4378 
4379   G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
4380     _free_region_list(free_region_list), _proxy_set(NULL), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) {
4381   }
4382 
4383   virtual bool do_heap_region(HeapRegion* r) {
4384     if (!r->is_starts_humongous()) {
4385       return false;
4386     }
4387 
4388     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4389 
4390     oop obj = (oop)r->bottom();
4391     G1CMBitMap* next_bitmap = g1h->concurrent_mark()->next_mark_bitmap();
4392 
4393     // The following checks whether the humongous object is live are sufficient.
4394     // The main additional check (in addition to having a reference from the roots
4395     // or the young gen) is whether the humongous object has a remembered set entry.
4396     //
4397     // A humongous object cannot be live if there is no remembered set for it
4398     // because:
4399     // - there can be no references from within humongous starts regions referencing
4400     // the object because we never allocate other objects into them.
4401     // (I.e. there are no intra-region references that may be missed by the
4402     // remembered set)
4403     // - as soon there is a remembered set entry to the humongous starts region
4404     // (i.e. it has "escaped" to an old object) this remembered set entry will stay
4405     // until the end of a concurrent mark.
4406     //
4407     // It is not required to check whether the object has been found dead by marking
4408     // or not, in fact it would prevent reclamation within a concurrent cycle, as
4409     // all objects allocated during that time are considered live.
4410     // SATB marking is even more conservative than the remembered set.
4411     // So if at this point in the collection there is no remembered set entry,
4412     // nobody has a reference to it.
4413     // At the start of collection we flush all refinement logs, and remembered sets
4414     // are completely up-to-date wrt to references to the humongous object.
4415     //
4416     // Other implementation considerations:
4417     // - never consider object arrays at this time because they would pose
4418     // considerable effort for cleaning up the the remembered sets. This is
4419     // required because stale remembered sets might reference locations that
4420     // are currently allocated into.
4421     uint region_idx = r->hrm_index();
4422     if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
4423         !r->rem_set()->is_empty()) {
4424       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",
4425                                region_idx,
4426                                (size_t)obj->size() * HeapWordSize,
4427                                p2i(r->bottom()),
4428                                r->rem_set()->occupied(),
4429                                r->rem_set()->strong_code_roots_list_length(),
4430                                next_bitmap->is_marked(r->bottom()),
4431                                g1h->is_humongous_reclaim_candidate(region_idx),
4432                                obj->is_typeArray()
4433                               );
4434       return false;
4435     }
4436 
4437     guarantee(obj->is_typeArray(),
4438               "Only eagerly reclaiming type arrays is supported, but the object "
4439               PTR_FORMAT " is not.", p2i(r->bottom()));
4440 
4441     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",
4442                              region_idx,
4443                              (size_t)obj->size() * HeapWordSize,
4444                              p2i(r->bottom()),
4445                              r->rem_set()->occupied(),
4446                              r->rem_set()->strong_code_roots_list_length(),
4447                              next_bitmap->is_marked(r->bottom()),
4448                              g1h->is_humongous_reclaim_candidate(region_idx),
4449                              obj->is_typeArray()
4450                             );
4451 
4452     G1ConcurrentMark* const cm = g1h->concurrent_mark();
4453     cm->humongous_object_eagerly_reclaimed(r);
4454     assert(!cm->is_marked_in_prev_bitmap(obj) && !cm->is_marked_in_next_bitmap(obj),
4455            "Eagerly reclaimed humongous region %u should not be marked at all but is in prev %s next %s",
4456            region_idx,
4457            BOOL_TO_STR(cm->is_marked_in_prev_bitmap(obj)),
4458            BOOL_TO_STR(cm->is_marked_in_next_bitmap(obj)));
4459     _humongous_objects_reclaimed++;
4460     do {
4461       HeapRegion* next = g1h->next_region_in_humongous(r);
4462       _freed_bytes += r->used();
4463       r->set_containing_set(NULL);
4464       _humongous_regions_reclaimed++;
4465       g1h->free_humongous_region(r, _free_region_list);
4466       r = next;
4467     } while (r != NULL);
4468 
4469     return false;
4470   }
4471 
4472   uint humongous_objects_reclaimed() {
4473     return _humongous_objects_reclaimed;
4474   }
4475 
4476   uint humongous_regions_reclaimed() {
4477     return _humongous_regions_reclaimed;
4478   }
4479 
4480   size_t bytes_freed() const {
4481     return _freed_bytes;
4482   }
4483 };
4484 
4485 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
4486   assert_at_safepoint_on_vm_thread();
4487 
4488   if (!G1EagerReclaimHumongousObjects ||
4489       (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) {
4490     phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
4491     return;
4492   }
4493 
4494   double start_time = os::elapsedTime();
4495 
4496   FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
4497 
4498   G1FreeHumongousRegionClosure cl(&local_cleanup_list);
4499   heap_region_iterate(&cl);
4500 
4501   remove_from_old_sets(0, cl.humongous_regions_reclaimed());
4502 
4503   G1HRPrinter* hrp = hr_printer();
4504   if (hrp->is_active()) {
4505     FreeRegionListIterator iter(&local_cleanup_list);
4506     while (iter.more_available()) {
4507       HeapRegion* hr = iter.get_next();
4508       hrp->cleanup(hr);
4509     }
4510   }
4511 
4512   prepend_to_freelist(&local_cleanup_list);
4513   decrement_summary_bytes(cl.bytes_freed());
4514 
4515   phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
4516                                                        cl.humongous_objects_reclaimed());
4517 }
4518 
4519 class G1AbandonCollectionSetClosure : public HeapRegionClosure {
4520 public:
4521   virtual bool do_heap_region(HeapRegion* r) {
4522     assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index());
4523     G1CollectedHeap::heap()->clear_region_attr(r);
4524     r->clear_young_index_in_cset();
4525     return false;
4526   }
4527 };
4528 
4529 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) {
4530   G1AbandonCollectionSetClosure cl;
4531   collection_set_iterate_all(&cl);
4532 
4533   collection_set->clear();
4534   collection_set->stop_incremental_building();
4535 }
4536 
4537 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
4538   return _allocator->is_retained_old_region(hr);
4539 }
4540 
4541 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
4542   _eden.add(hr);
4543   _policy->set_region_eden(hr);
4544 }
4545 
4546 #ifdef ASSERT
4547 
4548 class NoYoungRegionsClosure: public HeapRegionClosure {
4549 private:
4550   bool _success;
4551 public:
4552   NoYoungRegionsClosure() : _success(true) { }
4553   bool do_heap_region(HeapRegion* r) {
4554     if (r->is_young()) {
4555       log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
4556                             p2i(r->bottom()), p2i(r->end()));
4557       _success = false;
4558     }
4559     return false;
4560   }
4561   bool success() { return _success; }
4562 };
4563 
4564 bool G1CollectedHeap::check_young_list_empty() {
4565   bool ret = (young_regions_count() == 0);
4566 
4567   NoYoungRegionsClosure closure;
4568   heap_region_iterate(&closure);
4569   ret = ret && closure.success();
4570 
4571   return ret;
4572 }
4573 
4574 #endif // ASSERT
4575 
4576 class TearDownRegionSetsClosure : public HeapRegionClosure {
4577   HeapRegionSet *_old_set;
4578 
4579 public:
4580   TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
4581 
4582   bool do_heap_region(HeapRegion* r) {
4583     if (r->is_old()) {
4584       _old_set->remove(r);
4585     } else if(r->is_young()) {
4586       r->uninstall_surv_rate_group();
4587     } else {
4588       // We ignore free regions, we'll empty the free list afterwards.
4589       // We ignore humongous and archive regions, we're not tearing down these
4590       // sets.
4591       assert(r->is_archive() || r->is_free() || r->is_humongous(),
4592              "it cannot be another type");
4593     }
4594     return false;
4595   }
4596 
4597   ~TearDownRegionSetsClosure() {
4598     assert(_old_set->is_empty(), "post-condition");
4599   }
4600 };
4601 
4602 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
4603   assert_at_safepoint_on_vm_thread();
4604 
4605   if (!free_list_only) {
4606     TearDownRegionSetsClosure cl(&_old_set);
4607     heap_region_iterate(&cl);
4608 
4609     // Note that emptying the _young_list is postponed and instead done as
4610     // the first step when rebuilding the regions sets again. The reason for
4611     // this is that during a full GC string deduplication needs to know if
4612     // a collected region was young or old when the full GC was initiated.
4613   }
4614   _hrm->remove_all_free_regions();
4615 }
4616 
4617 void G1CollectedHeap::increase_used(size_t bytes) {
4618   _summary_bytes_used += bytes;
4619 }
4620 
4621 void G1CollectedHeap::decrease_used(size_t bytes) {
4622   assert(_summary_bytes_used >= bytes,
4623          "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
4624          _summary_bytes_used, bytes);
4625   _summary_bytes_used -= bytes;
4626 }
4627 
4628 void G1CollectedHeap::set_used(size_t bytes) {
4629   _summary_bytes_used = bytes;
4630 }
4631 
4632 class RebuildRegionSetsClosure : public HeapRegionClosure {
4633 private:
4634   bool _free_list_only;
4635 
4636   HeapRegionSet* _old_set;
4637   HeapRegionManager* _hrm;
4638 
4639   size_t _total_used;
4640 
4641 public:
4642   RebuildRegionSetsClosure(bool free_list_only,
4643                            HeapRegionSet* old_set,
4644                            HeapRegionManager* hrm) :
4645     _free_list_only(free_list_only),
4646     _old_set(old_set), _hrm(hrm), _total_used(0) {
4647     assert(_hrm->num_free_regions() == 0, "pre-condition");
4648     if (!free_list_only) {
4649       assert(_old_set->is_empty(), "pre-condition");
4650     }
4651   }
4652 
4653   bool do_heap_region(HeapRegion* r) {
4654     if (r->is_empty()) {
4655       assert(r->rem_set()->is_empty(), "Empty regions should have empty remembered sets.");
4656       // Add free regions to the free list
4657       r->set_free();
4658       _hrm->insert_into_free_list(r);
4659     } else if (!_free_list_only) {
4660       assert(r->rem_set()->is_empty(), "At this point remembered sets must have been cleared.");
4661 
4662       if (r->is_archive() || r->is_humongous()) {
4663         // We ignore archive and humongous regions. We left these sets unchanged.
4664       } else {
4665         assert(r->is_young() || r->is_free() || r->is_old(), "invariant");
4666         // We now move all (non-humongous, non-old, non-archive) regions to old gen, and register them as such.
4667         r->move_to_old();
4668         _old_set->add(r);
4669       }
4670       _total_used += r->used();
4671     }
4672 
4673     return false;
4674   }
4675 
4676   size_t total_used() {
4677     return _total_used;
4678   }
4679 };
4680 
4681 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
4682   assert_at_safepoint_on_vm_thread();
4683 
4684   if (!free_list_only) {
4685     _eden.clear();
4686     _survivor.clear();
4687   }
4688 
4689   RebuildRegionSetsClosure cl(free_list_only, &_old_set, _hrm);
4690   heap_region_iterate(&cl);
4691 
4692   if (!free_list_only) {
4693     set_used(cl.total_used());
4694     if (_archive_allocator != NULL) {
4695       _archive_allocator->clear_used();
4696     }
4697   }
4698   assert_used_and_recalculate_used_equal(this);
4699 }
4700 
4701 // Methods for the mutator alloc region
4702 
4703 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
4704                                                       bool force,
4705                                                       uint node_index) {
4706   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
4707   bool should_allocate = policy()->should_allocate_mutator_region();
4708   if (force || should_allocate) {
4709     HeapRegion* new_alloc_region = new_region(word_size,
4710                                               HeapRegionType::Eden,
4711                                               false /* do_expand */,
4712                                               node_index);
4713     if (new_alloc_region != NULL) {
4714       set_region_short_lived_locked(new_alloc_region);
4715       _hr_printer.alloc(new_alloc_region, !should_allocate);
4716       _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region);
4717       _policy->remset_tracker()->update_at_allocate(new_alloc_region);
4718       return new_alloc_region;
4719     }
4720   }
4721   return NULL;
4722 }
4723 
4724 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
4725                                                   size_t allocated_bytes) {
4726   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
4727   assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
4728 
4729   collection_set()->add_eden_region(alloc_region);
4730   increase_used(allocated_bytes);
4731   _eden.add_used_bytes(allocated_bytes);
4732   _hr_printer.retire(alloc_region);
4733 
4734   // We update the eden sizes here, when the region is retired,
4735   // instead of when it's allocated, since this is the point that its
4736   // used space has been recorded in _summary_bytes_used.
4737   g1mm()->update_eden_size();
4738 }
4739 
4740 // Methods for the GC alloc regions
4741 
4742 bool G1CollectedHeap::has_more_regions(G1HeapRegionAttr dest) {
4743   if (dest.is_old()) {
4744     return true;
4745   } else {
4746     return survivor_regions_count() < policy()->max_survivor_regions();
4747   }
4748 }
4749 
4750 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, G1HeapRegionAttr dest, uint node_index) {
4751   assert(FreeList_lock->owned_by_self(), "pre-condition");
4752 
4753   if (!has_more_regions(dest)) {
4754     return NULL;
4755   }
4756 
4757   HeapRegionType type;
4758   if (dest.is_young()) {
4759     type = HeapRegionType::Survivor;
4760   } else {
4761     type = HeapRegionType::Old;
4762   }
4763 
4764   HeapRegion* new_alloc_region = new_region(word_size,
4765                                             type,
4766                                             true /* do_expand */,
4767                                             node_index);
4768 
4769   if (new_alloc_region != NULL) {
4770     if (type.is_survivor()) {
4771       new_alloc_region->set_survivor();
4772       _survivor.add(new_alloc_region);
4773       _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region);
4774     } else {
4775       new_alloc_region->set_old();
4776       _verifier->check_bitmaps("Old Region Allocation", new_alloc_region);
4777     }
4778     _policy->remset_tracker()->update_at_allocate(new_alloc_region);
4779     register_region_with_region_attr(new_alloc_region);
4780     _hr_printer.alloc(new_alloc_region);
4781     return new_alloc_region;
4782   }
4783   return NULL;
4784 }
4785 
4786 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
4787                                              size_t allocated_bytes,
4788                                              G1HeapRegionAttr dest) {
4789   _bytes_used_during_gc += allocated_bytes;
4790   if (dest.is_old()) {
4791     old_set_add(alloc_region);
4792   } else {
4793     assert(dest.is_young(), "Retiring alloc region should be young (%d)", dest.type());
4794     _survivor.add_used_bytes(allocated_bytes);
4795   }
4796 
4797   bool const during_im = collector_state()->in_initial_mark_gc();
4798   if (during_im && allocated_bytes > 0) {
4799     _cm->root_regions()->add(alloc_region->next_top_at_mark_start(), alloc_region->top());
4800   }
4801   _hr_printer.retire(alloc_region);
4802 }
4803 
4804 HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
4805   bool expanded = false;
4806   uint index = _hrm->find_highest_free(&expanded);
4807 
4808   if (index != G1_NO_HRM_INDEX) {
4809     if (expanded) {
4810       log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
4811                                 HeapRegion::GrainWords * HeapWordSize);
4812     }
4813     _hrm->allocate_free_regions_starting_at(index, 1);
4814     return region_at(index);
4815   }
4816   return NULL;
4817 }
4818 
4819 // Optimized nmethod scanning
4820 
4821 class RegisterNMethodOopClosure: public OopClosure {
4822   G1CollectedHeap* _g1h;
4823   nmethod* _nm;
4824 
4825   template <class T> void do_oop_work(T* p) {
4826     T heap_oop = RawAccess<>::oop_load(p);
4827     if (!CompressedOops::is_null(heap_oop)) {
4828       oop obj = CompressedOops::decode_not_null(heap_oop);
4829       HeapRegion* hr = _g1h->heap_region_containing(obj);
4830       assert(!hr->is_continues_humongous(),
4831              "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
4832              " starting at " HR_FORMAT,
4833              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
4834 
4835       // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
4836       hr->add_strong_code_root_locked(_nm);
4837     }
4838   }
4839 
4840 public:
4841   RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
4842     _g1h(g1h), _nm(nm) {}
4843 
4844   void do_oop(oop* p)       { do_oop_work(p); }
4845   void do_oop(narrowOop* p) { do_oop_work(p); }
4846 };
4847 
4848 class UnregisterNMethodOopClosure: public OopClosure {
4849   G1CollectedHeap* _g1h;
4850   nmethod* _nm;
4851 
4852   template <class T> void do_oop_work(T* p) {
4853     T heap_oop = RawAccess<>::oop_load(p);
4854     if (!CompressedOops::is_null(heap_oop)) {
4855       oop obj = CompressedOops::decode_not_null(heap_oop);
4856       HeapRegion* hr = _g1h->heap_region_containing(obj);
4857       assert(!hr->is_continues_humongous(),
4858              "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
4859              " starting at " HR_FORMAT,
4860              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
4861 
4862       hr->remove_strong_code_root(_nm);
4863     }
4864   }
4865 
4866 public:
4867   UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
4868     _g1h(g1h), _nm(nm) {}
4869 
4870   void do_oop(oop* p)       { do_oop_work(p); }
4871   void do_oop(narrowOop* p) { do_oop_work(p); }
4872 };
4873 
4874 void G1CollectedHeap::register_nmethod(nmethod* nm) {
4875   guarantee(nm != NULL, "sanity");
4876   RegisterNMethodOopClosure reg_cl(this, nm);
4877   nm->oops_do(&reg_cl);
4878 }
4879 
4880 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
4881   guarantee(nm != NULL, "sanity");
4882   UnregisterNMethodOopClosure reg_cl(this, nm);
4883   nm->oops_do(&reg_cl, true);
4884 }
4885 
4886 void G1CollectedHeap::purge_code_root_memory() {
4887   double purge_start = os::elapsedTime();
4888   G1CodeRootSet::purge();
4889   double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
4890   phase_times()->record_strong_code_root_purge_time(purge_time_ms);
4891 }
4892 
4893 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
4894   G1CollectedHeap* _g1h;
4895 
4896 public:
4897   RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
4898     _g1h(g1h) {}
4899 
4900   void do_code_blob(CodeBlob* cb) {
4901     nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
4902     if (nm == NULL) {
4903       return;
4904     }
4905 
4906     _g1h->register_nmethod(nm);
4907   }
4908 };
4909 
4910 void G1CollectedHeap::rebuild_strong_code_roots() {
4911   RebuildStrongCodeRootClosure blob_cl(this);
4912   CodeCache::blobs_do(&blob_cl);
4913 }
4914 
4915 void G1CollectedHeap::initialize_serviceability() {
4916   _g1mm->initialize_serviceability();
4917 }
4918 
4919 MemoryUsage G1CollectedHeap::memory_usage() {
4920   return _g1mm->memory_usage();
4921 }
4922 
4923 GrowableArray<GCMemoryManager*> G1CollectedHeap::memory_managers() {
4924   return _g1mm->memory_managers();
4925 }
4926 
4927 GrowableArray<MemoryPool*> G1CollectedHeap::memory_pools() {
4928   return _g1mm->memory_pools();
4929 }