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/g1BarrierSet.hpp"
  33 #include "gc/g1/g1CollectedHeap.inline.hpp"
  34 #include "gc/g1/g1CollectionSet.hpp"
  35 #include "gc/g1/g1CollectorPolicy.hpp"
  36 #include "gc/g1/g1CollectorState.hpp"
  37 #include "gc/g1/g1ConcurrentRefine.hpp"
  38 #include "gc/g1/g1ConcurrentRefineThread.hpp"
  39 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp"
  40 #include "gc/g1/g1DirtyCardQueue.hpp"
  41 #include "gc/g1/g1EvacStats.inline.hpp"
  42 #include "gc/g1/g1FullCollector.hpp"
  43 #include "gc/g1/g1GCPhaseTimes.hpp"
  44 #include "gc/g1/g1HeapSizingPolicy.hpp"
  45 #include "gc/g1/g1HeapTransition.hpp"
  46 #include "gc/g1/g1HeapVerifier.hpp"
  47 #include "gc/g1/g1HotCardCache.hpp"
  48 #include "gc/g1/g1MemoryPool.hpp"
  49 #include "gc/g1/g1OopClosures.inline.hpp"
  50 #include "gc/g1/g1ParScanThreadState.inline.hpp"
  51 #include "gc/g1/g1Policy.hpp"
  52 #include "gc/g1/g1RegionToSpaceMapper.hpp"
  53 #include "gc/g1/g1RemSet.hpp"
  54 #include "gc/g1/g1RootClosures.hpp"
  55 #include "gc/g1/g1RootProcessor.hpp"
  56 #include "gc/g1/g1SATBMarkQueueSet.hpp"
  57 #include "gc/g1/g1StringDedup.hpp"
  58 #include "gc/g1/g1ThreadLocalData.hpp"
  59 #include "gc/g1/g1YCTypes.hpp"
  60 #include "gc/g1/g1YoungRemSetSamplingThread.hpp"
  61 #include "gc/g1/g1VMOperations.hpp"
  62 #include "gc/g1/heapRegion.inline.hpp"
  63 #include "gc/g1/heapRegionRemSet.hpp"
  64 #include "gc/g1/heapRegionSet.inline.hpp"
  65 #include "gc/shared/gcBehaviours.hpp"
  66 #include "gc/shared/gcHeapSummary.hpp"
  67 #include "gc/shared/gcId.hpp"
  68 #include "gc/shared/gcLocker.hpp"
  69 #include "gc/shared/gcTimer.hpp"
  70 #include "gc/shared/gcTrace.hpp"
  71 #include "gc/shared/gcTraceTime.inline.hpp"
  72 #include "gc/shared/generationSpec.hpp"
  73 #include "gc/shared/isGCActiveMark.hpp"
  74 #include "gc/shared/oopStorageParState.hpp"
  75 #include "gc/shared/parallelCleaning.hpp"
  76 #include "gc/shared/preservedMarks.inline.hpp"
  77 #include "gc/shared/suspendibleThreadSet.hpp"
  78 #include "gc/shared/referenceProcessor.inline.hpp"
  79 #include "gc/shared/taskqueue.inline.hpp"
  80 #include "gc/shared/weakProcessor.inline.hpp"
  81 #include "gc/shared/workerPolicy.hpp"
  82 #include "logging/log.hpp"
  83 #include "memory/allocation.hpp"
  84 #include "memory/iterator.hpp"
  85 #include "memory/resourceArea.hpp"
  86 #include "oops/access.inline.hpp"
  87 #include "oops/compressedOops.inline.hpp"
  88 #include "oops/oop.inline.hpp"
  89 #include "runtime/atomic.hpp"
  90 #include "runtime/flags/flagSetting.hpp"
  91 #include "runtime/handles.inline.hpp"
  92 #include "runtime/init.hpp"
  93 #include "runtime/orderAccess.hpp"
  94 #include "runtime/threadSMR.hpp"
  95 #include "runtime/vmThread.hpp"
  96 #include "utilities/align.hpp"
  97 #include "utilities/globalDefinitions.hpp"
  98 #include "utilities/stack.inline.hpp"
  99 
 100 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
 101 
 102 // INVARIANTS/NOTES
 103 //
 104 // All allocation activity covered by the G1CollectedHeap interface is
 105 // serialized by acquiring the HeapLock.  This happens in mem_allocate
 106 // and allocate_new_tlab, which are the "entry" points to the
 107 // allocation code from the rest of the JVM.  (Note that this does not
 108 // apply to TLAB allocation, which is not part of this interface: it
 109 // is done by clients of this interface.)
 110 
 111 class RedirtyLoggedCardTableEntryClosure : public G1CardTableEntryClosure {
 112  private:
 113   size_t _num_dirtied;
 114   G1CollectedHeap* _g1h;
 115   G1CardTable* _g1_ct;
 116 
 117   HeapRegion* region_for_card(jbyte* card_ptr) const {
 118     return _g1h->heap_region_containing(_g1_ct->addr_for(card_ptr));
 119   }
 120 
 121   bool will_become_free(HeapRegion* hr) const {
 122     // A region will be freed by free_collection_set if the region is in the
 123     // collection set and has not had an evacuation failure.
 124     return _g1h->is_in_cset(hr) && !hr->evacuation_failed();
 125   }
 126 
 127  public:
 128   RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : G1CardTableEntryClosure(),
 129     _num_dirtied(0), _g1h(g1h), _g1_ct(g1h->card_table()) { }
 130 
 131   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
 132     HeapRegion* hr = region_for_card(card_ptr);
 133 
 134     // Should only dirty cards in regions that won't be freed.
 135     if (!will_become_free(hr)) {
 136       *card_ptr = G1CardTable::dirty_card_val();
 137       _num_dirtied++;
 138     }
 139 
 140     return true;
 141   }
 142 
 143   size_t num_dirtied()   const { return _num_dirtied; }
 144 };
 145 
 146 
 147 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
 148   HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
 149 }
 150 
 151 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
 152   // The from card cache is not the memory that is actually committed. So we cannot
 153   // take advantage of the zero_filled parameter.
 154   reset_from_card_cache(start_idx, num_regions);
 155 }
 156 
 157 
 158 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
 159                                              MemRegion mr) {
 160   return new HeapRegion(hrs_index, bot(), mr);
 161 }
 162 
 163 // Private methods.
 164 
 165 HeapRegion* G1CollectedHeap::new_region(size_t word_size, HeapRegionType type, bool do_expand) {
 166   assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
 167          "the only time we use this to allocate a humongous region is "
 168          "when we are allocating a single humongous region");
 169 
 170   HeapRegion* res = _hrm->allocate_free_region(type);
 171 
 172   if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
 173     // Currently, only attempts to allocate GC alloc regions set
 174     // do_expand to true. So, we should only reach here during a
 175     // safepoint. If this assumption changes we might have to
 176     // reconsider the use of _expand_heap_after_alloc_failure.
 177     assert(SafepointSynchronize::is_at_safepoint(), "invariant");
 178 
 179     log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B",
 180                               word_size * HeapWordSize);
 181 
 182     if (expand(word_size * HeapWordSize)) {
 183       // Given that expand() succeeded in expanding the heap, and we
 184       // always expand the heap by an amount aligned to the heap
 185       // region size, the free list should in theory not be empty.
 186       // In either case allocate_free_region() will check for NULL.
 187       res = _hrm->allocate_free_region(type);
 188     } else {
 189       _expand_heap_after_alloc_failure = false;
 190     }
 191   }
 192   return res;
 193 }
 194 
 195 HeapWord*
 196 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
 197                                                            uint num_regions,
 198                                                            size_t word_size) {
 199   assert(first != G1_NO_HRM_INDEX, "pre-condition");
 200   assert(is_humongous(word_size), "word_size should be humongous");
 201   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 202 
 203   // Index of last region in the series.
 204   uint last = first + num_regions - 1;
 205 
 206   // We need to initialize the region(s) we just discovered. This is
 207   // a bit tricky given that it can happen concurrently with
 208   // refinement threads refining cards on these regions and
 209   // potentially wanting to refine the BOT as they are scanning
 210   // those cards (this can happen shortly after a cleanup; see CR
 211   // 6991377). So we have to set up the region(s) carefully and in
 212   // a specific order.
 213 
 214   // The word size sum of all the regions we will allocate.
 215   size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
 216   assert(word_size <= word_size_sum, "sanity");
 217 
 218   // This will be the "starts humongous" region.
 219   HeapRegion* first_hr = region_at(first);
 220   // The header of the new object will be placed at the bottom of
 221   // the first region.
 222   HeapWord* new_obj = first_hr->bottom();
 223   // This will be the new top of the new object.
 224   HeapWord* obj_top = new_obj + word_size;
 225 
 226   // First, we need to zero the header of the space that we will be
 227   // allocating. When we update top further down, some refinement
 228   // threads might try to scan the region. By zeroing the header we
 229   // ensure that any thread that will try to scan the region will
 230   // come across the zero klass word and bail out.
 231   //
 232   // NOTE: It would not have been correct to have used
 233   // CollectedHeap::fill_with_object() and make the space look like
 234   // an int array. The thread that is doing the allocation will
 235   // later update the object header to a potentially different array
 236   // type and, for a very short period of time, the klass and length
 237   // fields will be inconsistent. This could cause a refinement
 238   // thread to calculate the object size incorrectly.
 239   Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
 240 
 241   // Next, pad out the unused tail of the last region with filler
 242   // objects, for improved usage accounting.
 243   // How many words we use for filler objects.
 244   size_t word_fill_size = word_size_sum - word_size;
 245 
 246   // How many words memory we "waste" which cannot hold a filler object.
 247   size_t words_not_fillable = 0;
 248 
 249   if (word_fill_size >= min_fill_size()) {
 250     fill_with_objects(obj_top, word_fill_size);
 251   } else if (word_fill_size > 0) {
 252     // We have space to fill, but we cannot fit an object there.
 253     words_not_fillable = word_fill_size;
 254     word_fill_size = 0;
 255   }
 256 
 257   // We will set up the first region as "starts humongous". This
 258   // will also update the BOT covering all the regions to reflect
 259   // that there is a single object that starts at the bottom of the
 260   // first region.
 261   first_hr->set_starts_humongous(obj_top, word_fill_size);
 262   _g1_policy->remset_tracker()->update_at_allocate(first_hr);
 263   // Then, if there are any, we will set up the "continues
 264   // humongous" regions.
 265   HeapRegion* hr = NULL;
 266   for (uint i = first + 1; i <= last; ++i) {
 267     hr = region_at(i);
 268     hr->set_continues_humongous(first_hr);
 269     _g1_policy->remset_tracker()->update_at_allocate(hr);
 270   }
 271 
 272   // Up to this point no concurrent thread would have been able to
 273   // do any scanning on any region in this series. All the top
 274   // fields still point to bottom, so the intersection between
 275   // [bottom,top] and [card_start,card_end] will be empty. Before we
 276   // update the top fields, we'll do a storestore to make sure that
 277   // no thread sees the update to top before the zeroing of the
 278   // object header and the BOT initialization.
 279   OrderAccess::storestore();
 280 
 281   // Now, we will update the top fields of the "continues humongous"
 282   // regions except the last one.
 283   for (uint i = first; i < last; ++i) {
 284     hr = region_at(i);
 285     hr->set_top(hr->end());
 286   }
 287 
 288   hr = region_at(last);
 289   // If we cannot fit a filler object, we must set top to the end
 290   // of the humongous object, otherwise we cannot iterate the heap
 291   // and the BOT will not be complete.
 292   hr->set_top(hr->end() - words_not_fillable);
 293 
 294   assert(hr->bottom() < obj_top && obj_top <= hr->end(),
 295          "obj_top should be in last region");
 296 
 297   _verifier->check_bitmaps("Humongous Region Allocation", first_hr);
 298 
 299   assert(words_not_fillable == 0 ||
 300          first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(),
 301          "Miscalculation in humongous allocation");
 302 
 303   increase_used((word_size_sum - words_not_fillable) * HeapWordSize);
 304 
 305   for (uint i = first; i <= last; ++i) {
 306     hr = region_at(i);
 307     _humongous_set.add(hr);
 308     _hr_printer.alloc(hr);
 309   }
 310 
 311   return new_obj;
 312 }
 313 
 314 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) {
 315   assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size);
 316   return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
 317 }
 318 
 319 // If could fit into free regions w/o expansion, try.
 320 // Otherwise, if can expand, do so.
 321 // Otherwise, if using ex regions might help, try with ex given back.
 322 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
 323   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 324 
 325   _verifier->verify_region_sets_optional();
 326 
 327   uint first = G1_NO_HRM_INDEX;
 328   uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);
 329 
 330   if (obj_regions == 1) {
 331     // Only one region to allocate, try to use a fast path by directly allocating
 332     // from the free lists. Do not try to expand here, we will potentially do that
 333     // later.
 334     HeapRegion* hr = new_region(word_size, HeapRegionType::Humongous, false /* do_expand */);
 335     if (hr != NULL) {
 336       first = hr->hrm_index();
 337     }
 338   } else {
 339     // Policy: Try only empty regions (i.e. already committed first). Maybe we
 340     // are lucky enough to find some.
 341     first = _hrm->find_contiguous_only_empty(obj_regions);
 342     if (first != G1_NO_HRM_INDEX) {
 343       _hrm->allocate_free_regions_starting_at(first, obj_regions);
 344     }
 345   }
 346 
 347   if (first == G1_NO_HRM_INDEX) {
 348     // Policy: We could not find enough regions for the humongous object in the
 349     // free list. Look through the heap to find a mix of free and uncommitted regions.
 350     // If so, try expansion.
 351     first = _hrm->find_contiguous_empty_or_unavailable(obj_regions);
 352     if (first != G1_NO_HRM_INDEX) {
 353       // We found something. Make sure these regions are committed, i.e. expand
 354       // the heap. Alternatively we could do a defragmentation GC.
 355       log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B",
 356                                     word_size * HeapWordSize);
 357 
 358       _hrm->expand_at(first, obj_regions, workers());
 359       g1_policy()->record_new_heap_size(num_regions());
 360 
 361 #ifdef ASSERT
 362       for (uint i = first; i < first + obj_regions; ++i) {
 363         HeapRegion* hr = region_at(i);
 364         assert(hr->is_free(), "sanity");
 365         assert(hr->is_empty(), "sanity");
 366         assert(is_on_master_free_list(hr), "sanity");
 367       }
 368 #endif
 369       _hrm->allocate_free_regions_starting_at(first, obj_regions);
 370     } else {
 371       // Policy: Potentially trigger a defragmentation GC.
 372     }
 373   }
 374 
 375   HeapWord* result = NULL;
 376   if (first != G1_NO_HRM_INDEX) {
 377     result = humongous_obj_allocate_initialize_regions(first, obj_regions, word_size);
 378     assert(result != NULL, "it should always return a valid result");
 379 
 380     // A successful humongous object allocation changes the used space
 381     // information of the old generation so we need to recalculate the
 382     // sizes and update the jstat counters here.
 383     g1mm()->update_sizes();
 384   }
 385 
 386   _verifier->verify_region_sets_optional();
 387 
 388   return result;
 389 }
 390 
 391 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t min_size,
 392                                              size_t requested_size,
 393                                              size_t* actual_size) {
 394   assert_heap_not_locked_and_not_at_safepoint();
 395   assert(!is_humongous(requested_size), "we do not allow humongous TLABs");
 396 
 397   return attempt_allocation(min_size, requested_size, actual_size);
 398 }
 399 
 400 HeapWord*
 401 G1CollectedHeap::mem_allocate(size_t word_size,
 402                               bool*  gc_overhead_limit_was_exceeded) {
 403   assert_heap_not_locked_and_not_at_safepoint();
 404 
 405   if (is_humongous(word_size)) {
 406     return attempt_allocation_humongous(word_size);
 407   }
 408   size_t dummy = 0;
 409   return attempt_allocation(word_size, word_size, &dummy);
 410 }
 411 
 412 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size) {
 413   ResourceMark rm; // For retrieving the thread names in log messages.
 414 
 415   // Make sure you read the note in attempt_allocation_humongous().
 416 
 417   assert_heap_not_locked_and_not_at_safepoint();
 418   assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
 419          "be called for humongous allocation requests");
 420 
 421   // We should only get here after the first-level allocation attempt
 422   // (attempt_allocation()) failed to allocate.
 423 
 424   // We will loop until a) we manage to successfully perform the
 425   // allocation or b) we successfully schedule a collection which
 426   // fails to perform the allocation. b) is the only case when we'll
 427   // return NULL.
 428   HeapWord* result = NULL;
 429   for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 430     bool should_try_gc;
 431     uint gc_count_before;
 432 
 433     {
 434       MutexLockerEx x(Heap_lock);
 435       result = _allocator->attempt_allocation_locked(word_size);
 436       if (result != NULL) {
 437         return result;
 438       }
 439 
 440       // If the GCLocker is active and we are bound for a GC, try expanding young gen.
 441       // This is different to when only GCLocker::needs_gc() is set: try to avoid
 442       // waiting because the GCLocker is active to not wait too long.
 443       if (GCLocker::is_active_and_needs_gc() && g1_policy()->can_expand_young_list()) {
 444         // No need for an ergo message here, can_expand_young_list() does this when
 445         // it returns true.
 446         result = _allocator->attempt_allocation_force(word_size);
 447         if (result != NULL) {
 448           return result;
 449         }
 450       }
 451       // Only try a GC if the GCLocker does not signal the need for a GC. Wait until
 452       // the GCLocker initiated GC has been performed and then retry. This includes
 453       // the case when the GC Locker is not active but has not been performed.
 454       should_try_gc = !GCLocker::needs_gc();
 455       // Read the GC count while still holding the Heap_lock.
 456       gc_count_before = total_collections();
 457     }
 458 
 459     if (should_try_gc) {
 460       bool succeeded;
 461       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 462                                    GCCause::_g1_inc_collection_pause);
 463       if (result != NULL) {
 464         assert(succeeded, "only way to get back a non-NULL result");
 465         log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT,
 466                              Thread::current()->name(), p2i(result));
 467         return result;
 468       }
 469 
 470       if (succeeded) {
 471         // We successfully scheduled a collection which failed to allocate. No
 472         // point in trying to allocate further. We'll just return NULL.
 473         log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate "
 474                              SIZE_FORMAT " words", Thread::current()->name(), word_size);
 475         return NULL;
 476       }
 477       log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT " words",
 478                            Thread::current()->name(), word_size);
 479     } else {
 480       // Failed to schedule a collection.
 481       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 482         log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating "
 483                                SIZE_FORMAT " words", Thread::current()->name(), word_size);
 484         return NULL;
 485       }
 486       log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name());
 487       // The GCLocker is either active or the GCLocker initiated
 488       // GC has not yet been performed. Stall until it is and
 489       // then retry the allocation.
 490       GCLocker::stall_until_clear();
 491       gclocker_retry_count += 1;
 492     }
 493 
 494     // We can reach here if we were unsuccessful in scheduling a
 495     // collection (because another thread beat us to it) or if we were
 496     // stalled due to the GC locker. In either can we should retry the
 497     // allocation attempt in case another thread successfully
 498     // performed a collection and reclaimed enough space. We do the
 499     // first attempt (without holding the Heap_lock) here and the
 500     // follow-on attempt will be at the start of the next loop
 501     // iteration (after taking the Heap_lock).
 502     size_t dummy = 0;
 503     result = _allocator->attempt_allocation(word_size, word_size, &dummy);
 504     if (result != NULL) {
 505       return result;
 506     }
 507 
 508     // Give a warning if we seem to be looping forever.
 509     if ((QueuedAllocationWarningCount > 0) &&
 510         (try_count % QueuedAllocationWarningCount == 0)) {
 511       log_warning(gc, alloc)("%s:  Retried allocation %u times for " SIZE_FORMAT " words",
 512                              Thread::current()->name(), try_count, word_size);
 513     }
 514   }
 515 
 516   ShouldNotReachHere();
 517   return NULL;
 518 }
 519 
 520 void G1CollectedHeap::begin_archive_alloc_range(bool open) {
 521   assert_at_safepoint_on_vm_thread();
 522   if (_archive_allocator == NULL) {
 523     _archive_allocator = G1ArchiveAllocator::create_allocator(this, open);
 524   }
 525 }
 526 
 527 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) {
 528   // Allocations in archive regions cannot be of a size that would be considered
 529   // humongous even for a minimum-sized region, because G1 region sizes/boundaries
 530   // may be different at archive-restore time.
 531   return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words());
 532 }
 533 
 534 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) {
 535   assert_at_safepoint_on_vm_thread();
 536   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 537   if (is_archive_alloc_too_large(word_size)) {
 538     return NULL;
 539   }
 540   return _archive_allocator->archive_mem_allocate(word_size);
 541 }
 542 
 543 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
 544                                               size_t end_alignment_in_bytes) {
 545   assert_at_safepoint_on_vm_thread();
 546   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 547 
 548   // Call complete_archive to do the real work, filling in the MemRegion
 549   // array with the archive regions.
 550   _archive_allocator->complete_archive(ranges, end_alignment_in_bytes);
 551   delete _archive_allocator;
 552   _archive_allocator = NULL;
 553 }
 554 
 555 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) {
 556   assert(ranges != NULL, "MemRegion array NULL");
 557   assert(count != 0, "No MemRegions provided");
 558   MemRegion reserved = _hrm->reserved();
 559   for (size_t i = 0; i < count; i++) {
 560     if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) {
 561       return false;
 562     }
 563   }
 564   return true;
 565 }
 566 
 567 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges,
 568                                             size_t count,
 569                                             bool open) {
 570   assert(!is_init_completed(), "Expect to be called at JVM init time");
 571   assert(ranges != NULL, "MemRegion array NULL");
 572   assert(count != 0, "No MemRegions provided");
 573   MutexLockerEx x(Heap_lock);
 574 
 575   MemRegion reserved = _hrm->reserved();
 576   HeapWord* prev_last_addr = NULL;
 577   HeapRegion* prev_last_region = NULL;
 578 
 579   // Temporarily disable pretouching of heap pages. This interface is used
 580   // when mmap'ing archived heap data in, so pre-touching is wasted.
 581   FlagSetting fs(AlwaysPreTouch, false);
 582 
 583   // Enable archive object checking used by G1MarkSweep. We have to let it know
 584   // about each archive range, so that objects in those ranges aren't marked.
 585   G1ArchiveAllocator::enable_archive_object_check();
 586 
 587   // For each specified MemRegion range, allocate the corresponding G1
 588   // regions and mark them as archive regions. We expect the ranges
 589   // in ascending starting address order, without overlap.
 590   for (size_t i = 0; i < count; i++) {
 591     MemRegion curr_range = ranges[i];
 592     HeapWord* start_address = curr_range.start();
 593     size_t word_size = curr_range.word_size();
 594     HeapWord* last_address = curr_range.last();
 595     size_t commits = 0;
 596 
 597     guarantee(reserved.contains(start_address) && reserved.contains(last_address),
 598               "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 599               p2i(start_address), p2i(last_address));
 600     guarantee(start_address > prev_last_addr,
 601               "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 602               p2i(start_address), p2i(prev_last_addr));
 603     prev_last_addr = last_address;
 604 
 605     // Check for ranges that start in the same G1 region in which the previous
 606     // range ended, and adjust the start address so we don't try to allocate
 607     // the same region again. If the current range is entirely within that
 608     // region, skip it, just adjusting the recorded top.
 609     HeapRegion* start_region = _hrm->addr_to_region(start_address);
 610     if ((prev_last_region != NULL) && (start_region == prev_last_region)) {
 611       start_address = start_region->end();
 612       if (start_address > last_address) {
 613         increase_used(word_size * HeapWordSize);
 614         start_region->set_top(last_address + 1);
 615         continue;
 616       }
 617       start_region->set_top(start_address);
 618       curr_range = MemRegion(start_address, last_address + 1);
 619       start_region = _hrm->addr_to_region(start_address);
 620     }
 621 
 622     // Perform the actual region allocation, exiting if it fails.
 623     // Then note how much new space we have allocated.
 624     if (!_hrm->allocate_containing_regions(curr_range, &commits, workers())) {
 625       return false;
 626     }
 627     increase_used(word_size * HeapWordSize);
 628     if (commits != 0) {
 629       log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B",
 630                                 HeapRegion::GrainWords * HeapWordSize * commits);
 631 
 632     }
 633 
 634     // Mark each G1 region touched by the range as archive, add it to
 635     // the old set, and set top.
 636     HeapRegion* curr_region = _hrm->addr_to_region(start_address);
 637     HeapRegion* last_region = _hrm->addr_to_region(last_address);
 638     prev_last_region = last_region;
 639 
 640     while (curr_region != NULL) {
 641       assert(curr_region->is_empty() && !curr_region->is_pinned(),
 642              "Region already in use (index %u)", curr_region->hrm_index());
 643       if (open) {
 644         curr_region->set_open_archive();
 645       } else {
 646         curr_region->set_closed_archive();
 647       }
 648       _hr_printer.alloc(curr_region);
 649       _archive_set.add(curr_region);
 650       HeapWord* top;
 651       HeapRegion* next_region;
 652       if (curr_region != last_region) {
 653         top = curr_region->end();
 654         next_region = _hrm->next_region_in_heap(curr_region);
 655       } else {
 656         top = last_address + 1;
 657         next_region = NULL;
 658       }
 659       curr_region->set_top(top);
 660       curr_region->set_first_dead(top);
 661       curr_region->set_end_of_live(top);
 662       curr_region = next_region;
 663     }
 664 
 665     // Notify mark-sweep of the archive
 666     G1ArchiveAllocator::set_range_archive(curr_range, open);
 667   }
 668   return true;
 669 }
 670 
 671 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) {
 672   assert(!is_init_completed(), "Expect to be called at JVM init time");
 673   assert(ranges != NULL, "MemRegion array NULL");
 674   assert(count != 0, "No MemRegions provided");
 675   MemRegion reserved = _hrm->reserved();
 676   HeapWord *prev_last_addr = NULL;
 677   HeapRegion* prev_last_region = NULL;
 678 
 679   // For each MemRegion, create filler objects, if needed, in the G1 regions
 680   // that contain the address range. The address range actually within the
 681   // MemRegion will not be modified. That is assumed to have been initialized
 682   // elsewhere, probably via an mmap of archived heap data.
 683   MutexLockerEx x(Heap_lock);
 684   for (size_t i = 0; i < count; i++) {
 685     HeapWord* start_address = ranges[i].start();
 686     HeapWord* last_address = ranges[i].last();
 687 
 688     assert(reserved.contains(start_address) && reserved.contains(last_address),
 689            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 690            p2i(start_address), p2i(last_address));
 691     assert(start_address > prev_last_addr,
 692            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 693            p2i(start_address), p2i(prev_last_addr));
 694 
 695     HeapRegion* start_region = _hrm->addr_to_region(start_address);
 696     HeapRegion* last_region = _hrm->addr_to_region(last_address);
 697     HeapWord* bottom_address = start_region->bottom();
 698 
 699     // Check for a range beginning in the same region in which the
 700     // previous one ended.
 701     if (start_region == prev_last_region) {
 702       bottom_address = prev_last_addr + 1;
 703     }
 704 
 705     // Verify that the regions were all marked as archive regions by
 706     // alloc_archive_regions.
 707     HeapRegion* curr_region = start_region;
 708     while (curr_region != NULL) {
 709       guarantee(curr_region->is_archive(),
 710                 "Expected archive region at index %u", curr_region->hrm_index());
 711       if (curr_region != last_region) {
 712         curr_region = _hrm->next_region_in_heap(curr_region);
 713       } else {
 714         curr_region = NULL;
 715       }
 716     }
 717 
 718     prev_last_addr = last_address;
 719     prev_last_region = last_region;
 720 
 721     // Fill the memory below the allocated range with dummy object(s),
 722     // if the region bottom does not match the range start, or if the previous
 723     // range ended within the same G1 region, and there is a gap.
 724     if (start_address != bottom_address) {
 725       size_t fill_size = pointer_delta(start_address, bottom_address);
 726       G1CollectedHeap::fill_with_objects(bottom_address, fill_size);
 727       increase_used(fill_size * HeapWordSize);
 728     }
 729   }
 730 }
 731 
 732 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t min_word_size,
 733                                                      size_t desired_word_size,
 734                                                      size_t* actual_word_size) {
 735   assert_heap_not_locked_and_not_at_safepoint();
 736   assert(!is_humongous(desired_word_size), "attempt_allocation() should not "
 737          "be called for humongous allocation requests");
 738 
 739   HeapWord* result = _allocator->attempt_allocation(min_word_size, desired_word_size, actual_word_size);
 740 
 741   if (result == NULL) {
 742     *actual_word_size = desired_word_size;
 743     result = attempt_allocation_slow(desired_word_size);
 744   }
 745 
 746   assert_heap_not_locked();
 747   if (result != NULL) {
 748     assert(*actual_word_size != 0, "Actual size must have been set here");
 749     dirty_young_block(result, *actual_word_size);
 750   } else {
 751     *actual_word_size = 0;
 752   }
 753 
 754   return result;
 755 }
 756 
 757 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count, bool is_open) {
 758   assert(!is_init_completed(), "Expect to be called at JVM init time");
 759   assert(ranges != NULL, "MemRegion array NULL");
 760   assert(count != 0, "No MemRegions provided");
 761   MemRegion reserved = _hrm->reserved();
 762   HeapWord* prev_last_addr = NULL;
 763   HeapRegion* prev_last_region = NULL;
 764   size_t size_used = 0;
 765   size_t uncommitted_regions = 0;
 766 
 767   // For each Memregion, free the G1 regions that constitute it, and
 768   // notify mark-sweep that the range is no longer to be considered 'archive.'
 769   MutexLockerEx x(Heap_lock);
 770   for (size_t i = 0; i < count; i++) {
 771     HeapWord* start_address = ranges[i].start();
 772     HeapWord* last_address = ranges[i].last();
 773 
 774     assert(reserved.contains(start_address) && reserved.contains(last_address),
 775            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 776            p2i(start_address), p2i(last_address));
 777     assert(start_address > prev_last_addr,
 778            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 779            p2i(start_address), p2i(prev_last_addr));
 780     size_used += ranges[i].byte_size();
 781     prev_last_addr = last_address;
 782 
 783     HeapRegion* start_region = _hrm->addr_to_region(start_address);
 784     HeapRegion* last_region = _hrm->addr_to_region(last_address);
 785 
 786     // Check for ranges that start in the same G1 region in which the previous
 787     // range ended, and adjust the start address so we don't try to free
 788     // the same region again. If the current range is entirely within that
 789     // region, skip it.
 790     if (start_region == prev_last_region) {
 791       start_address = start_region->end();
 792       if (start_address > last_address) {
 793         continue;
 794       }
 795       start_region = _hrm->addr_to_region(start_address);
 796     }
 797     prev_last_region = last_region;
 798 
 799     // After verifying that each region was marked as an archive region by
 800     // alloc_archive_regions, set it free and empty and uncommit it.
 801     HeapRegion* curr_region = start_region;
 802     while (curr_region != NULL) {
 803       guarantee(curr_region->is_archive(),
 804                 "Expected archive region at index %u", curr_region->hrm_index());
 805       uint curr_index = curr_region->hrm_index();
 806       _archive_set.remove(curr_region);
 807       curr_region->set_free();
 808       curr_region->set_top(curr_region->bottom());
 809       if (curr_region != last_region) {
 810         curr_region = _hrm->next_region_in_heap(curr_region);
 811       } else {
 812         curr_region = NULL;
 813       }
 814       _hrm->shrink_at(curr_index, 1);
 815       uncommitted_regions++;
 816     }
 817 
 818     // Notify mark-sweep that this is no longer an archive range.
 819     G1ArchiveAllocator::clear_range_archive(ranges[i], is_open);
 820   }
 821 
 822   if (uncommitted_regions != 0) {
 823     log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B",
 824                               HeapRegion::GrainWords * HeapWordSize * uncommitted_regions);
 825   }
 826   decrease_used(size_used);
 827 }
 828 
 829 oop G1CollectedHeap::materialize_archived_object(oop obj) {
 830   assert(obj != NULL, "archived obj is NULL");
 831   assert(G1ArchiveAllocator::is_archived_object(obj), "must be archived object");
 832 
 833   // Loading an archived object makes it strongly reachable. If it is
 834   // loaded during concurrent marking, it must be enqueued to the SATB
 835   // queue, shading the previously white object gray.
 836   G1BarrierSet::enqueue(obj);
 837 
 838   return obj;
 839 }
 840 
 841 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size) {
 842   ResourceMark rm; // For retrieving the thread names in log messages.
 843 
 844   // The structure of this method has a lot of similarities to
 845   // attempt_allocation_slow(). The reason these two were not merged
 846   // into a single one is that such a method would require several "if
 847   // allocation is not humongous do this, otherwise do that"
 848   // conditional paths which would obscure its flow. In fact, an early
 849   // version of this code did use a unified method which was harder to
 850   // follow and, as a result, it had subtle bugs that were hard to
 851   // track down. So keeping these two methods separate allows each to
 852   // be more readable. It will be good to keep these two in sync as
 853   // much as possible.
 854 
 855   assert_heap_not_locked_and_not_at_safepoint();
 856   assert(is_humongous(word_size), "attempt_allocation_humongous() "
 857          "should only be called for humongous allocations");
 858 
 859   // Humongous objects can exhaust the heap quickly, so we should check if we
 860   // need to start a marking cycle at each humongous object allocation. We do
 861   // the check before we do the actual allocation. The reason for doing it
 862   // before the allocation is that we avoid having to keep track of the newly
 863   // allocated memory while we do a GC.
 864   if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
 865                                            word_size)) {
 866     collect(GCCause::_g1_humongous_allocation);
 867   }
 868 
 869   // We will loop until a) we manage to successfully perform the
 870   // allocation or b) we successfully schedule a collection which
 871   // fails to perform the allocation. b) is the only case when we'll
 872   // return NULL.
 873   HeapWord* result = NULL;
 874   for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 875     bool should_try_gc;
 876     uint gc_count_before;
 877 
 878 
 879     {
 880       MutexLockerEx x(Heap_lock);
 881 
 882       // Given that humongous objects are not allocated in young
 883       // regions, we'll first try to do the allocation without doing a
 884       // collection hoping that there's enough space in the heap.
 885       result = humongous_obj_allocate(word_size);
 886       if (result != NULL) {
 887         size_t size_in_regions = humongous_obj_size_in_regions(word_size);
 888         g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
 889         return result;
 890       }
 891 
 892       // Only try a GC if the GCLocker does not signal the need for a GC. Wait until
 893       // the GCLocker initiated GC has been performed and then retry. This includes
 894       // the case when the GC Locker is not active but has not been performed.
 895       should_try_gc = !GCLocker::needs_gc();
 896       // Read the GC count while still holding the Heap_lock.
 897       gc_count_before = total_collections();
 898     }
 899 
 900     if (should_try_gc) {
 901       bool succeeded;
 902       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 903                                    GCCause::_g1_humongous_allocation);
 904       if (result != NULL) {
 905         assert(succeeded, "only way to get back a non-NULL result");
 906         log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT,
 907                              Thread::current()->name(), p2i(result));
 908         return result;
 909       }
 910 
 911       if (succeeded) {
 912         // We successfully scheduled a collection which failed to allocate. No
 913         // point in trying to allocate further. We'll just return NULL.
 914         log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate "
 915                              SIZE_FORMAT " words", Thread::current()->name(), word_size);
 916         return NULL;
 917       }
 918       log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT "",
 919                            Thread::current()->name(), word_size);
 920     } else {
 921       // Failed to schedule a collection.
 922       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 923         log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating "
 924                                SIZE_FORMAT " words", Thread::current()->name(), word_size);
 925         return NULL;
 926       }
 927       log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name());
 928       // The GCLocker is either active or the GCLocker initiated
 929       // GC has not yet been performed. Stall until it is and
 930       // then retry the allocation.
 931       GCLocker::stall_until_clear();
 932       gclocker_retry_count += 1;
 933     }
 934 
 935 
 936     // We can reach here if we were unsuccessful in scheduling a
 937     // collection (because another thread beat us to it) or if we were
 938     // stalled due to the GC locker. In either can we should retry the
 939     // allocation attempt in case another thread successfully
 940     // performed a collection and reclaimed enough space.
 941     // Humongous object allocation always needs a lock, so we wait for the retry
 942     // in the next iteration of the loop, unlike for the regular iteration case.
 943     // Give a warning if we seem to be looping forever.
 944 
 945     if ((QueuedAllocationWarningCount > 0) &&
 946         (try_count % QueuedAllocationWarningCount == 0)) {
 947       log_warning(gc, alloc)("%s: Retried allocation %u times for " SIZE_FORMAT " words",
 948                              Thread::current()->name(), try_count, word_size);
 949     }
 950   }
 951 
 952   ShouldNotReachHere();
 953   return NULL;
 954 }
 955 
 956 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
 957                                                            bool expect_null_mutator_alloc_region) {
 958   assert_at_safepoint_on_vm_thread();
 959   assert(!_allocator->has_mutator_alloc_region() || !expect_null_mutator_alloc_region,
 960          "the current alloc region was unexpectedly found to be non-NULL");
 961 
 962   if (!is_humongous(word_size)) {
 963     return _allocator->attempt_allocation_locked(word_size);
 964   } else {
 965     HeapWord* result = humongous_obj_allocate(word_size);
 966     if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
 967       collector_state()->set_initiate_conc_mark_if_possible(true);
 968     }
 969     return result;
 970   }
 971 
 972   ShouldNotReachHere();
 973 }
 974 
 975 class PostCompactionPrinterClosure: public HeapRegionClosure {
 976 private:
 977   G1HRPrinter* _hr_printer;
 978 public:
 979   bool do_heap_region(HeapRegion* hr) {
 980     assert(!hr->is_young(), "not expecting to find young regions");
 981     _hr_printer->post_compaction(hr);
 982     return false;
 983   }
 984 
 985   PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
 986     : _hr_printer(hr_printer) { }
 987 };
 988 
 989 void G1CollectedHeap::print_hrm_post_compaction() {
 990   if (_hr_printer.is_active()) {
 991     PostCompactionPrinterClosure cl(hr_printer());
 992     heap_region_iterate(&cl);
 993   }
 994 }
 995 
 996 void G1CollectedHeap::abort_concurrent_cycle() {
 997   // If we start the compaction before the CM threads finish
 998   // scanning the root regions we might trip them over as we'll
 999   // be moving objects / updating references. So let's wait until
1000   // they are done. By telling them to abort, they should complete
1001   // early.
1002   _cm->root_regions()->abort();
1003   _cm->root_regions()->wait_until_scan_finished();
1004 
1005   // Disable discovery and empty the discovered lists
1006   // for the CM ref processor.
1007   _ref_processor_cm->disable_discovery();
1008   _ref_processor_cm->abandon_partial_discovery();
1009   _ref_processor_cm->verify_no_references_recorded();
1010 
1011   // Abandon current iterations of concurrent marking and concurrent
1012   // refinement, if any are in progress.
1013   concurrent_mark()->concurrent_cycle_abort();
1014 }
1015 
1016 void G1CollectedHeap::prepare_heap_for_full_collection() {
1017   // Make sure we'll choose a new allocation region afterwards.
1018   _allocator->release_mutator_alloc_region();
1019   _allocator->abandon_gc_alloc_regions();
1020 
1021   // We may have added regions to the current incremental collection
1022   // set between the last GC or pause and now. We need to clear the
1023   // incremental collection set and then start rebuilding it afresh
1024   // after this full GC.
1025   abandon_collection_set(collection_set());
1026 
1027   tear_down_region_sets(false /* free_list_only */);
1028 
1029   hrm()->prepare_for_full_collection_start();
1030 }
1031 
1032 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) {
1033   assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant");
1034   assert(used() == recalculate_used(), "Should be equal");
1035   _verifier->verify_region_sets_optional();
1036   _verifier->verify_before_gc(G1HeapVerifier::G1VerifyFull);
1037   _verifier->check_bitmaps("Full GC Start");
1038 }
1039 
1040 void G1CollectedHeap::prepare_heap_for_mutators() {
1041   hrm()->prepare_for_full_collection_end();
1042 
1043   // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1044   ClassLoaderDataGraph::purge();
1045   MetaspaceUtils::verify_metrics();
1046 
1047   // Prepare heap for normal collections.
1048   assert(num_free_regions() == 0, "we should not have added any free regions");
1049   rebuild_region_sets(false /* free_list_only */);
1050   abort_refinement();
1051   resize_heap_if_necessary();
1052 
1053   // Rebuild the strong code root lists for each region
1054   rebuild_strong_code_roots();
1055 
1056   // Purge code root memory
1057   purge_code_root_memory();
1058 
1059   // Start a new incremental collection set for the next pause
1060   start_new_collection_set();
1061 
1062   _allocator->init_mutator_alloc_region();
1063 
1064   // Post collection state updates.
1065   MetaspaceGC::compute_new_size();
1066 }
1067 
1068 void G1CollectedHeap::abort_refinement() {
1069   if (_hot_card_cache->use_cache()) {
1070     _hot_card_cache->reset_hot_cache();
1071   }
1072 
1073   // Discard all remembered set updates.
1074   G1BarrierSet::dirty_card_queue_set().abandon_logs();
1075   assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1076 }
1077 
1078 void G1CollectedHeap::verify_after_full_collection() {
1079   _hrm->verify_optional();
1080   _verifier->verify_region_sets_optional();
1081   _verifier->verify_after_gc(G1HeapVerifier::G1VerifyFull);
1082   // Clear the previous marking bitmap, if needed for bitmap verification.
1083   // Note we cannot do this when we clear the next marking bitmap in
1084   // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the
1085   // objects marked during a full GC against the previous bitmap.
1086   // But we need to clear it before calling check_bitmaps below since
1087   // the full GC has compacted objects and updated TAMS but not updated
1088   // the prev bitmap.
1089   if (G1VerifyBitmaps) {
1090     GCTraceTime(Debug, gc)("Clear Prev Bitmap for Verification");
1091     _cm->clear_prev_bitmap(workers());
1092   }
1093   // This call implicitly verifies that the next bitmap is clear after Full GC.
1094   _verifier->check_bitmaps("Full GC End");
1095 
1096   // At this point there should be no regions in the
1097   // entire heap tagged as young.
1098   assert(check_young_list_empty(), "young list should be empty at this point");
1099 
1100   // Note: since we've just done a full GC, concurrent
1101   // marking is no longer active. Therefore we need not
1102   // re-enable reference discovery for the CM ref processor.
1103   // That will be done at the start of the next marking cycle.
1104   // We also know that the STW processor should no longer
1105   // discover any new references.
1106   assert(!_ref_processor_stw->discovery_enabled(), "Postcondition");
1107   assert(!_ref_processor_cm->discovery_enabled(), "Postcondition");
1108   _ref_processor_stw->verify_no_references_recorded();
1109   _ref_processor_cm->verify_no_references_recorded();
1110 }
1111 
1112 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) {
1113   // Post collection logging.
1114   // We should do this after we potentially resize the heap so
1115   // that all the COMMIT / UNCOMMIT events are generated before
1116   // the compaction events.
1117   print_hrm_post_compaction();
1118   heap_transition->print();
1119   print_heap_after_gc();
1120   print_heap_regions();
1121 #ifdef TRACESPINNING
1122   ParallelTaskTerminator::print_termination_counts();
1123 #endif
1124 }
1125 
1126 bool G1CollectedHeap::do_full_collection(bool explicit_gc,
1127                                          bool clear_all_soft_refs) {
1128   assert_at_safepoint_on_vm_thread();
1129 
1130   if (GCLocker::check_active_before_gc()) {
1131     // Full GC was not completed.
1132     return false;
1133   }
1134 
1135   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1136       soft_ref_policy()->should_clear_all_soft_refs();
1137 
1138   G1FullCollector collector(this, explicit_gc, do_clear_all_soft_refs);
1139   GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true);
1140 
1141   collector.prepare_collection();
1142   collector.collect();
1143   collector.complete_collection();
1144 
1145   // Full collection was successfully completed.
1146   return true;
1147 }
1148 
1149 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1150   // Currently, there is no facility in the do_full_collection(bool) API to notify
1151   // the caller that the collection did not succeed (e.g., because it was locked
1152   // out by the GC locker). So, right now, we'll ignore the return value.
1153   bool dummy = do_full_collection(true,                /* explicit_gc */
1154                                   clear_all_soft_refs);
1155 }
1156 
1157 void G1CollectedHeap::resize_heap_if_necessary() {
1158   assert_at_safepoint_on_vm_thread();
1159 
1160   // Capacity, free and used after the GC counted as full regions to
1161   // include the waste in the following calculations.
1162   const size_t capacity_after_gc = capacity();
1163   const size_t used_after_gc = capacity_after_gc - unused_committed_regions_in_bytes();
1164 
1165   // This is enforced in arguments.cpp.
1166   assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1167          "otherwise the code below doesn't make sense");
1168 
1169   // We don't have floating point command-line arguments
1170   const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1171   const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1172   const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1173   const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1174 
1175   const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1176   const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1177 
1178   // We have to be careful here as these two calculations can overflow
1179   // 32-bit size_t's.
1180   double used_after_gc_d = (double) used_after_gc;
1181   double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1182   double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1183 
1184   // Let's make sure that they are both under the max heap size, which
1185   // by default will make them fit into a size_t.
1186   double desired_capacity_upper_bound = (double) max_heap_size;
1187   minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1188                                     desired_capacity_upper_bound);
1189   maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1190                                     desired_capacity_upper_bound);
1191 
1192   // We can now safely turn them into size_t's.
1193   size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1194   size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1195 
1196   // This assert only makes sense here, before we adjust them
1197   // with respect to the min and max heap size.
1198   assert(minimum_desired_capacity <= maximum_desired_capacity,
1199          "minimum_desired_capacity = " SIZE_FORMAT ", "
1200          "maximum_desired_capacity = " SIZE_FORMAT,
1201          minimum_desired_capacity, maximum_desired_capacity);
1202 
1203   // Should not be greater than the heap max size. No need to adjust
1204   // it with respect to the heap min size as it's a lower bound (i.e.,
1205   // we'll try to make the capacity larger than it, not smaller).
1206   minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1207   // Should not be less than the heap min size. No need to adjust it
1208   // with respect to the heap max size as it's an upper bound (i.e.,
1209   // we'll try to make the capacity smaller than it, not greater).
1210   maximum_desired_capacity =  MAX2(maximum_desired_capacity, min_heap_size);
1211 
1212   if (capacity_after_gc < minimum_desired_capacity) {
1213     // Don't expand unless it's significant
1214     size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1215 
1216     log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity). "
1217                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1218                               "min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1219                               capacity_after_gc, used_after_gc, used(), minimum_desired_capacity, MinHeapFreeRatio);
1220 
1221     expand(expand_bytes, _workers);
1222 
1223     // No expansion, now see if we want to shrink
1224   } else if (capacity_after_gc > maximum_desired_capacity) {
1225     // Capacity too large, compute shrinking size
1226     size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1227 
1228     log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity). "
1229                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1230                               "maximum_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1231                               capacity_after_gc, used_after_gc, used(), maximum_desired_capacity, MaxHeapFreeRatio);
1232 
1233     shrink(shrink_bytes);
1234   }
1235 }
1236 
1237 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size,
1238                                                             bool do_gc,
1239                                                             bool clear_all_soft_refs,
1240                                                             bool expect_null_mutator_alloc_region,
1241                                                             bool* gc_succeeded) {
1242   *gc_succeeded = true;
1243   // Let's attempt the allocation first.
1244   HeapWord* result =
1245     attempt_allocation_at_safepoint(word_size,
1246                                     expect_null_mutator_alloc_region);
1247   if (result != NULL) {
1248     return result;
1249   }
1250 
1251   // In a G1 heap, we're supposed to keep allocation from failing by
1252   // incremental pauses.  Therefore, at least for now, we'll favor
1253   // expansion over collection.  (This might change in the future if we can
1254   // do something smarter than full collection to satisfy a failed alloc.)
1255   result = expand_and_allocate(word_size);
1256   if (result != NULL) {
1257     return result;
1258   }
1259 
1260   if (do_gc) {
1261     // Expansion didn't work, we'll try to do a Full GC.
1262     *gc_succeeded = do_full_collection(false, /* explicit_gc */
1263                                        clear_all_soft_refs);
1264   }
1265 
1266   return NULL;
1267 }
1268 
1269 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1270                                                      bool* succeeded) {
1271   assert_at_safepoint_on_vm_thread();
1272 
1273   // Attempts to allocate followed by Full GC.
1274   HeapWord* result =
1275     satisfy_failed_allocation_helper(word_size,
1276                                      true,  /* do_gc */
1277                                      false, /* clear_all_soft_refs */
1278                                      false, /* expect_null_mutator_alloc_region */
1279                                      succeeded);
1280 
1281   if (result != NULL || !*succeeded) {
1282     return result;
1283   }
1284 
1285   // Attempts to allocate followed by Full GC that will collect all soft references.
1286   result = satisfy_failed_allocation_helper(word_size,
1287                                             true, /* do_gc */
1288                                             true, /* clear_all_soft_refs */
1289                                             true, /* expect_null_mutator_alloc_region */
1290                                             succeeded);
1291 
1292   if (result != NULL || !*succeeded) {
1293     return result;
1294   }
1295 
1296   // Attempts to allocate, no GC
1297   result = satisfy_failed_allocation_helper(word_size,
1298                                             false, /* do_gc */
1299                                             false, /* clear_all_soft_refs */
1300                                             true,  /* expect_null_mutator_alloc_region */
1301                                             succeeded);
1302 
1303   if (result != NULL) {
1304     return result;
1305   }
1306 
1307   assert(!soft_ref_policy()->should_clear_all_soft_refs(),
1308          "Flag should have been handled and cleared prior to this point");
1309 
1310   // What else?  We might try synchronous finalization later.  If the total
1311   // space available is large enough for the allocation, then a more
1312   // complete compaction phase than we've tried so far might be
1313   // appropriate.
1314   return NULL;
1315 }
1316 
1317 // Attempting to expand the heap sufficiently
1318 // to support an allocation of the given "word_size".  If
1319 // successful, perform the allocation and return the address of the
1320 // allocated block, or else "NULL".
1321 
1322 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1323   assert_at_safepoint_on_vm_thread();
1324 
1325   _verifier->verify_region_sets_optional();
1326 
1327   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1328   log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B",
1329                             word_size * HeapWordSize);
1330 
1331 
1332   if (expand(expand_bytes, _workers)) {
1333     _hrm->verify_optional();
1334     _verifier->verify_region_sets_optional();
1335     return attempt_allocation_at_safepoint(word_size,
1336                                            false /* expect_null_mutator_alloc_region */);
1337   }
1338   return NULL;
1339 }
1340 
1341 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) {
1342   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1343   aligned_expand_bytes = align_up(aligned_expand_bytes,
1344                                        HeapRegion::GrainBytes);
1345 
1346   log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B",
1347                             expand_bytes, aligned_expand_bytes);
1348 
1349   if (is_maximal_no_gc()) {
1350     log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1351     return false;
1352   }
1353 
1354   double expand_heap_start_time_sec = os::elapsedTime();
1355   uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1356   assert(regions_to_expand > 0, "Must expand by at least one region");
1357 
1358   uint expanded_by = _hrm->expand_by(regions_to_expand, pretouch_workers);
1359   if (expand_time_ms != NULL) {
1360     *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS;
1361   }
1362 
1363   if (expanded_by > 0) {
1364     size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1365     assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1366     g1_policy()->record_new_heap_size(num_regions());
1367   } else {
1368     log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)");
1369 
1370     // The expansion of the virtual storage space was unsuccessful.
1371     // Let's see if it was because we ran out of swap.
1372     if (G1ExitOnExpansionFailure &&
1373         _hrm->available() >= regions_to_expand) {
1374       // We had head room...
1375       vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1376     }
1377   }
1378   return regions_to_expand > 0;
1379 }
1380 
1381 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1382   size_t aligned_shrink_bytes =
1383     ReservedSpace::page_align_size_down(shrink_bytes);
1384   aligned_shrink_bytes = align_down(aligned_shrink_bytes,
1385                                          HeapRegion::GrainBytes);
1386   uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1387 
1388   uint num_regions_removed = _hrm->shrink_by(num_regions_to_remove);
1389   size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1390 
1391 
1392   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",
1393                             shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1394   if (num_regions_removed > 0) {
1395     g1_policy()->record_new_heap_size(num_regions());
1396   } else {
1397     log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)");
1398   }
1399 }
1400 
1401 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1402   _verifier->verify_region_sets_optional();
1403 
1404   // We should only reach here at the end of a Full GC or during Remark which
1405   // means we should not not be holding to any GC alloc regions. The method
1406   // below will make sure of that and do any remaining clean up.
1407   _allocator->abandon_gc_alloc_regions();
1408 
1409   // Instead of tearing down / rebuilding the free lists here, we
1410   // could instead use the remove_all_pending() method on free_list to
1411   // remove only the ones that we need to remove.
1412   tear_down_region_sets(true /* free_list_only */);
1413   shrink_helper(shrink_bytes);
1414   rebuild_region_sets(true /* free_list_only */);
1415 
1416   _hrm->verify_optional();
1417   _verifier->verify_region_sets_optional();
1418 }
1419 
1420 class OldRegionSetChecker : public HeapRegionSetChecker {
1421 public:
1422   void check_mt_safety() {
1423     // Master Old Set MT safety protocol:
1424     // (a) If we're at a safepoint, operations on the master old set
1425     // should be invoked:
1426     // - by the VM thread (which will serialize them), or
1427     // - by the GC workers while holding the FreeList_lock, if we're
1428     //   at a safepoint for an evacuation pause (this lock is taken
1429     //   anyway when an GC alloc region is retired so that a new one
1430     //   is allocated from the free list), or
1431     // - by the GC workers while holding the OldSets_lock, if we're at a
1432     //   safepoint for a cleanup pause.
1433     // (b) If we're not at a safepoint, operations on the master old set
1434     // should be invoked while holding the Heap_lock.
1435 
1436     if (SafepointSynchronize::is_at_safepoint()) {
1437       guarantee(Thread::current()->is_VM_thread() ||
1438                 FreeList_lock->owned_by_self() || OldSets_lock->owned_by_self(),
1439                 "master old set MT safety protocol at a safepoint");
1440     } else {
1441       guarantee(Heap_lock->owned_by_self(), "master old set MT safety protocol outside a safepoint");
1442     }
1443   }
1444   bool is_correct_type(HeapRegion* hr) { return hr->is_old(); }
1445   const char* get_description() { return "Old Regions"; }
1446 };
1447 
1448 class ArchiveRegionSetChecker : public HeapRegionSetChecker {
1449 public:
1450   void check_mt_safety() {
1451     guarantee(!Universe::is_fully_initialized() || SafepointSynchronize::is_at_safepoint(),
1452               "May only change archive regions during initialization or safepoint.");
1453   }
1454   bool is_correct_type(HeapRegion* hr) { return hr->is_archive(); }
1455   const char* get_description() { return "Archive Regions"; }
1456 };
1457 
1458 class HumongousRegionSetChecker : public HeapRegionSetChecker {
1459 public:
1460   void check_mt_safety() {
1461     // Humongous Set MT safety protocol:
1462     // (a) If we're at a safepoint, operations on the master humongous
1463     // set should be invoked by either the VM thread (which will
1464     // serialize them) or by the GC workers while holding the
1465     // OldSets_lock.
1466     // (b) If we're not at a safepoint, operations on the master
1467     // humongous set should be invoked while holding the Heap_lock.
1468 
1469     if (SafepointSynchronize::is_at_safepoint()) {
1470       guarantee(Thread::current()->is_VM_thread() ||
1471                 OldSets_lock->owned_by_self(),
1472                 "master humongous set MT safety protocol at a safepoint");
1473     } else {
1474       guarantee(Heap_lock->owned_by_self(),
1475                 "master humongous set MT safety protocol outside a safepoint");
1476     }
1477   }
1478   bool is_correct_type(HeapRegion* hr) { return hr->is_humongous(); }
1479   const char* get_description() { return "Humongous Regions"; }
1480 };
1481 
1482 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) :
1483   CollectedHeap(),
1484   _young_gen_sampling_thread(NULL),
1485   _workers(NULL),
1486   _collector_policy(collector_policy),
1487   _card_table(NULL),
1488   _soft_ref_policy(),
1489   _old_set("Old Region Set", new OldRegionSetChecker()),
1490   _archive_set("Archive Region Set", new ArchiveRegionSetChecker()),
1491   _humongous_set("Humongous Region Set", new HumongousRegionSetChecker()),
1492   _bot(NULL),
1493   _listener(),
1494   _hrm(NULL),
1495   _allocator(NULL),
1496   _verifier(NULL),
1497   _summary_bytes_used(0),
1498   _archive_allocator(NULL),
1499   _survivor_evac_stats("Young", YoungPLABSize, PLABWeight),
1500   _old_evac_stats("Old", OldPLABSize, PLABWeight),
1501   _expand_heap_after_alloc_failure(true),
1502   _g1mm(NULL),
1503   _humongous_reclaim_candidates(),
1504   _has_humongous_reclaim_candidates(false),
1505   _hr_printer(),
1506   _collector_state(),
1507   _old_marking_cycles_started(0),
1508   _old_marking_cycles_completed(0),
1509   _eden(),
1510   _survivor(),
1511   _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1512   _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1513   _g1_policy(G1Policy::create_policy(collector_policy, _gc_timer_stw)),
1514   _heap_sizing_policy(NULL),
1515   _collection_set(this, _g1_policy),
1516   _hot_card_cache(NULL),
1517   _g1_rem_set(NULL),
1518   _dirty_card_queue_set(false),
1519   _cm(NULL),
1520   _cm_thread(NULL),
1521   _cr(NULL),
1522   _task_queues(NULL),
1523   _evacuation_failed(false),
1524   _evacuation_failed_info_array(NULL),
1525   _preserved_marks_set(true /* in_c_heap */),
1526 #ifndef PRODUCT
1527   _evacuation_failure_alot_for_current_gc(false),
1528   _evacuation_failure_alot_gc_number(0),
1529   _evacuation_failure_alot_count(0),
1530 #endif
1531   _ref_processor_stw(NULL),
1532   _is_alive_closure_stw(this),
1533   _is_subject_to_discovery_stw(this),
1534   _ref_processor_cm(NULL),
1535   _is_alive_closure_cm(this),
1536   _is_subject_to_discovery_cm(this),
1537   _in_cset_fast_test() {
1538 
1539   _verifier = new G1HeapVerifier(this);
1540 
1541   _allocator = new G1Allocator(this);
1542 
1543   _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics());
1544 
1545   _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);
1546 
1547   // Override the default _filler_array_max_size so that no humongous filler
1548   // objects are created.
1549   _filler_array_max_size = _humongous_object_threshold_in_words;
1550 
1551   uint n_queues = ParallelGCThreads;
1552   _task_queues = new RefToScanQueueSet(n_queues);
1553 
1554   _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1555 
1556   for (uint i = 0; i < n_queues; i++) {
1557     RefToScanQueue* q = new RefToScanQueue();
1558     q->initialize();
1559     _task_queues->register_queue(i, q);
1560     ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1561   }
1562 
1563   // Initialize the G1EvacuationFailureALot counters and flags.
1564   NOT_PRODUCT(reset_evacuation_should_fail();)
1565 
1566   guarantee(_task_queues != NULL, "task_queues allocation failure.");
1567 }
1568 
1569 static size_t actual_reserved_page_size(ReservedSpace rs) {
1570   size_t page_size = os::vm_page_size();
1571   if (UseLargePages) {
1572     // There are two ways to manage large page memory.
1573     // 1. OS supports committing large page memory.
1574     // 2. OS doesn't support committing large page memory so ReservedSpace manages it.
1575     //    And ReservedSpace calls it 'special'. If we failed to set 'special',
1576     //    we reserved memory without large page.
1577     if (os::can_commit_large_page_memory() || rs.special()) {
1578       page_size = rs.alignment();
1579     }
1580   }
1581 
1582   return page_size;
1583 }
1584 
1585 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1586                                                                  size_t size,
1587                                                                  size_t translation_factor) {
1588   size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1589   // Allocate a new reserved space, preferring to use large pages.
1590   ReservedSpace rs(size, preferred_page_size);
1591   size_t page_size = actual_reserved_page_size(rs);
1592   G1RegionToSpaceMapper* result  =
1593     G1RegionToSpaceMapper::create_mapper(rs,
1594                                          size,
1595                                          page_size,
1596                                          HeapRegion::GrainBytes,
1597                                          translation_factor,
1598                                          mtGC);
1599 
1600   os::trace_page_sizes_for_requested_size(description,
1601                                           size,
1602                                           preferred_page_size,
1603                                           page_size,
1604                                           rs.base(),
1605                                           rs.size());
1606 
1607   return result;
1608 }
1609 
1610 jint G1CollectedHeap::initialize_concurrent_refinement() {
1611   jint ecode = JNI_OK;
1612   _cr = G1ConcurrentRefine::create(&ecode);
1613   return ecode;
1614 }
1615 
1616 jint G1CollectedHeap::initialize_young_gen_sampling_thread() {
1617   _young_gen_sampling_thread = new G1YoungRemSetSamplingThread();
1618   if (_young_gen_sampling_thread->osthread() == NULL) {
1619     vm_shutdown_during_initialization("Could not create G1YoungRemSetSamplingThread");
1620     return JNI_ENOMEM;
1621   }
1622   return JNI_OK;
1623 }
1624 
1625 jint G1CollectedHeap::initialize() {
1626   os::enable_vtime();
1627 
1628   // Necessary to satisfy locking discipline assertions.
1629 
1630   MutexLocker x(Heap_lock);
1631 
1632   // While there are no constraints in the GC code that HeapWordSize
1633   // be any particular value, there are multiple other areas in the
1634   // system which believe this to be true (e.g. oop->object_size in some
1635   // cases incorrectly returns the size in wordSize units rather than
1636   // HeapWordSize).
1637   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1638 
1639   size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1640   size_t max_byte_size = g1_collector_policy()->heap_reserved_size_bytes();
1641   size_t heap_alignment = collector_policy()->heap_alignment();
1642 
1643   // Ensure that the sizes are properly aligned.
1644   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1645   Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1646   Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1647 
1648   // Reserve the maximum.
1649 
1650   // When compressed oops are enabled, the preferred heap base
1651   // is calculated by subtracting the requested size from the
1652   // 32Gb boundary and using the result as the base address for
1653   // heap reservation. If the requested size is not aligned to
1654   // HeapRegion::GrainBytes (i.e. the alignment that is passed
1655   // into the ReservedHeapSpace constructor) then the actual
1656   // base of the reserved heap may end up differing from the
1657   // address that was requested (i.e. the preferred heap base).
1658   // If this happens then we could end up using a non-optimal
1659   // compressed oops mode.
1660 
1661   ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1662                                                  heap_alignment);
1663 
1664   initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
1665 
1666   // Create the barrier set for the entire reserved region.
1667   G1CardTable* ct = new G1CardTable(reserved_region());
1668   ct->initialize();
1669   G1BarrierSet* bs = new G1BarrierSet(ct);
1670   bs->initialize();
1671   assert(bs->is_a(BarrierSet::G1BarrierSet), "sanity");
1672   BarrierSet::set_barrier_set(bs);
1673   _card_table = ct;
1674 
1675   G1BarrierSet::satb_mark_queue_set().initialize(this,
1676                                                  SATB_Q_CBL_mon,
1677                                                  &bs->satb_mark_queue_buffer_allocator(),
1678                                                  G1SATBProcessCompletedThreshold,
1679                                                  G1SATBBufferEnqueueingThresholdPercent,
1680                                                  Shared_SATB_Q_lock);
1681 
1682   // process_completed_buffers_threshold and max_completed_buffers are updated
1683   // later, based on the concurrent refinement object.
1684   G1BarrierSet::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1685                                                   &bs->dirty_card_queue_buffer_allocator(),
1686                                                   Shared_DirtyCardQ_lock,
1687                                                   true); // init_free_ids
1688 
1689   dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1690                                     &bs->dirty_card_queue_buffer_allocator(),
1691                                     Shared_DirtyCardQ_lock);
1692 
1693   // Create the hot card cache.
1694   _hot_card_cache = new G1HotCardCache(this);
1695 
1696   // Carve out the G1 part of the heap.
1697   ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1698   size_t page_size = actual_reserved_page_size(heap_rs);
1699   G1RegionToSpaceMapper* heap_storage =
1700     G1RegionToSpaceMapper::create_heap_mapper(g1_rs,
1701                                               g1_rs.size(),
1702                                               page_size,
1703                                               HeapRegion::GrainBytes,
1704                                               1,
1705                                               mtJavaHeap);
1706   if(heap_storage == NULL) {
1707     vm_shutdown_during_initialization("Could not initialize G1 heap");
1708     return JNI_ERR;
1709   }
1710 
1711   os::trace_page_sizes("Heap",
1712                        collector_policy()->min_heap_byte_size(),
1713                        max_byte_size,
1714                        page_size,
1715                        heap_rs.base(),
1716                        heap_rs.size());
1717   heap_storage->set_mapping_changed_listener(&_listener);
1718 
1719   // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1720   G1RegionToSpaceMapper* bot_storage =
1721     create_aux_memory_mapper("Block Offset Table",
1722                              G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize),
1723                              G1BlockOffsetTable::heap_map_factor());
1724 
1725   G1RegionToSpaceMapper* cardtable_storage =
1726     create_aux_memory_mapper("Card Table",
1727                              G1CardTable::compute_size(g1_rs.size() / HeapWordSize),
1728                              G1CardTable::heap_map_factor());
1729 
1730   G1RegionToSpaceMapper* card_counts_storage =
1731     create_aux_memory_mapper("Card Counts Table",
1732                              G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1733                              G1CardCounts::heap_map_factor());
1734 
1735   size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size());
1736   G1RegionToSpaceMapper* prev_bitmap_storage =
1737     create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1738   G1RegionToSpaceMapper* next_bitmap_storage =
1739     create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1740 
1741   _hrm = HeapRegionManager::create_manager(this, g1_collector_policy());
1742 
1743   _hrm->initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1744   _card_table->initialize(cardtable_storage);
1745   // Do later initialization work for concurrent refinement.
1746   _hot_card_cache->initialize(card_counts_storage);
1747 
1748   // 6843694 - ensure that the maximum region index can fit
1749   // in the remembered set structures.
1750   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1751   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1752 
1753   // The G1FromCardCache reserves card with value 0 as "invalid", so the heap must not
1754   // start within the first card.
1755   guarantee(g1_rs.base() >= (char*)G1CardTable::card_size, "Java heap must not start within the first card.");
1756   // Also create a G1 rem set.
1757   _g1_rem_set = new G1RemSet(this, _card_table, _hot_card_cache);
1758   _g1_rem_set->initialize(max_reserved_capacity(), max_regions());
1759 
1760   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1761   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1762   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1763             "too many cards per region");
1764 
1765   FreeRegionList::set_unrealistically_long_length(max_expandable_regions() + 1);
1766 
1767   _bot = new G1BlockOffsetTable(reserved_region(), bot_storage);
1768 
1769   {
1770     HeapWord* start = _hrm->reserved().start();
1771     HeapWord* end = _hrm->reserved().end();
1772     size_t granularity = HeapRegion::GrainBytes;
1773 
1774     _in_cset_fast_test.initialize(start, end, granularity);
1775     _humongous_reclaim_candidates.initialize(start, end, granularity);
1776   }
1777 
1778   _workers = new WorkGang("GC Thread", ParallelGCThreads,
1779                           true /* are_GC_task_threads */,
1780                           false /* are_ConcurrentGC_threads */);
1781   if (_workers == NULL) {
1782     return JNI_ENOMEM;
1783   }
1784   _workers->initialize_workers();
1785 
1786   // Create the G1ConcurrentMark data structure and thread.
1787   // (Must do this late, so that "max_regions" is defined.)
1788   _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1789   if (_cm == NULL || !_cm->completed_initialization()) {
1790     vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark");
1791     return JNI_ENOMEM;
1792   }
1793   _cm_thread = _cm->cm_thread();
1794 
1795   // Now expand into the initial heap size.
1796   if (!expand(init_byte_size, _workers)) {
1797     vm_shutdown_during_initialization("Failed to allocate initial heap.");
1798     return JNI_ENOMEM;
1799   }
1800 
1801   // Perform any initialization actions delegated to the policy.
1802   g1_policy()->init(this, &_collection_set);
1803 
1804   jint ecode = initialize_concurrent_refinement();
1805   if (ecode != JNI_OK) {
1806     return ecode;
1807   }
1808 
1809   ecode = initialize_young_gen_sampling_thread();
1810   if (ecode != JNI_OK) {
1811     return ecode;
1812   }
1813 
1814   {
1815     G1DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
1816     dcqs.set_process_completed_buffers_threshold(concurrent_refine()->yellow_zone());
1817     dcqs.set_max_completed_buffers(concurrent_refine()->red_zone());
1818   }
1819 
1820   // Here we allocate the dummy HeapRegion that is required by the
1821   // G1AllocRegion class.
1822   HeapRegion* dummy_region = _hrm->get_dummy_region();
1823 
1824   // We'll re-use the same region whether the alloc region will
1825   // require BOT updates or not and, if it doesn't, then a non-young
1826   // region will complain that it cannot support allocations without
1827   // BOT updates. So we'll tag the dummy region as eden to avoid that.
1828   dummy_region->set_eden();
1829   // Make sure it's full.
1830   dummy_region->set_top(dummy_region->end());
1831   G1AllocRegion::setup(this, dummy_region);
1832 
1833   _allocator->init_mutator_alloc_region();
1834 
1835   // Do create of the monitoring and management support so that
1836   // values in the heap have been properly initialized.
1837   _g1mm = new G1MonitoringSupport(this);
1838 
1839   G1StringDedup::initialize();
1840 
1841   _preserved_marks_set.init(ParallelGCThreads);
1842 
1843   _collection_set.initialize(max_regions());
1844 
1845   return JNI_OK;
1846 }
1847 
1848 void G1CollectedHeap::stop() {
1849   // Stop all concurrent threads. We do this to make sure these threads
1850   // do not continue to execute and access resources (e.g. logging)
1851   // that are destroyed during shutdown.
1852   _cr->stop();
1853   _young_gen_sampling_thread->stop();
1854   _cm_thread->stop();
1855   if (G1StringDedup::is_enabled()) {
1856     G1StringDedup::stop();
1857   }
1858 }
1859 
1860 void G1CollectedHeap::safepoint_synchronize_begin() {
1861   SuspendibleThreadSet::synchronize();
1862 }
1863 
1864 void G1CollectedHeap::safepoint_synchronize_end() {
1865   SuspendibleThreadSet::desynchronize();
1866 }
1867 
1868 size_t G1CollectedHeap::conservative_max_heap_alignment() {
1869   return HeapRegion::max_region_size();
1870 }
1871 
1872 void G1CollectedHeap::post_initialize() {
1873   CollectedHeap::post_initialize();
1874   ref_processing_init();
1875 }
1876 
1877 void G1CollectedHeap::ref_processing_init() {
1878   // Reference processing in G1 currently works as follows:
1879   //
1880   // * There are two reference processor instances. One is
1881   //   used to record and process discovered references
1882   //   during concurrent marking; the other is used to
1883   //   record and process references during STW pauses
1884   //   (both full and incremental).
1885   // * Both ref processors need to 'span' the entire heap as
1886   //   the regions in the collection set may be dotted around.
1887   //
1888   // * For the concurrent marking ref processor:
1889   //   * Reference discovery is enabled at initial marking.
1890   //   * Reference discovery is disabled and the discovered
1891   //     references processed etc during remarking.
1892   //   * Reference discovery is MT (see below).
1893   //   * Reference discovery requires a barrier (see below).
1894   //   * Reference processing may or may not be MT
1895   //     (depending on the value of ParallelRefProcEnabled
1896   //     and ParallelGCThreads).
1897   //   * A full GC disables reference discovery by the CM
1898   //     ref processor and abandons any entries on it's
1899   //     discovered lists.
1900   //
1901   // * For the STW processor:
1902   //   * Non MT discovery is enabled at the start of a full GC.
1903   //   * Processing and enqueueing during a full GC is non-MT.
1904   //   * During a full GC, references are processed after marking.
1905   //
1906   //   * Discovery (may or may not be MT) is enabled at the start
1907   //     of an incremental evacuation pause.
1908   //   * References are processed near the end of a STW evacuation pause.
1909   //   * For both types of GC:
1910   //     * Discovery is atomic - i.e. not concurrent.
1911   //     * Reference discovery will not need a barrier.
1912 
1913   bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1);
1914 
1915   // Concurrent Mark ref processor
1916   _ref_processor_cm =
1917     new ReferenceProcessor(&_is_subject_to_discovery_cm,
1918                            mt_processing,                                  // mt processing
1919                            ParallelGCThreads,                              // degree of mt processing
1920                            (ParallelGCThreads > 1) || (ConcGCThreads > 1), // mt discovery
1921                            MAX2(ParallelGCThreads, ConcGCThreads),         // degree of mt discovery
1922                            false,                                          // Reference discovery is not atomic
1923                            &_is_alive_closure_cm,                          // is alive closure
1924                            true);                                          // allow changes to number of processing threads
1925 
1926   // STW ref processor
1927   _ref_processor_stw =
1928     new ReferenceProcessor(&_is_subject_to_discovery_stw,
1929                            mt_processing,                        // mt processing
1930                            ParallelGCThreads,                    // degree of mt processing
1931                            (ParallelGCThreads > 1),              // mt discovery
1932                            ParallelGCThreads,                    // degree of mt discovery
1933                            true,                                 // Reference discovery is atomic
1934                            &_is_alive_closure_stw,               // is alive closure
1935                            true);                                // allow changes to number of processing threads
1936 }
1937 
1938 CollectorPolicy* G1CollectedHeap::collector_policy() const {
1939   return _collector_policy;
1940 }
1941 
1942 G1CollectorPolicy* G1CollectedHeap::g1_collector_policy() const {
1943   return _collector_policy;
1944 }
1945 
1946 SoftRefPolicy* G1CollectedHeap::soft_ref_policy() {
1947   return &_soft_ref_policy;
1948 }
1949 
1950 size_t G1CollectedHeap::capacity() const {
1951   return _hrm->length() * HeapRegion::GrainBytes;
1952 }
1953 
1954 size_t G1CollectedHeap::unused_committed_regions_in_bytes() const {
1955   return _hrm->total_free_bytes();
1956 }
1957 
1958 void G1CollectedHeap::iterate_hcc_closure(G1CardTableEntryClosure* cl, uint worker_i) {
1959   _hot_card_cache->drain(cl, worker_i);
1960 }
1961 
1962 void G1CollectedHeap::iterate_dirty_card_closure(G1CardTableEntryClosure* cl, uint worker_i) {
1963   G1DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
1964   size_t n_completed_buffers = 0;
1965   while (dcqs.apply_closure_during_gc(cl, worker_i)) {
1966     n_completed_buffers++;
1967   }
1968   assert(dcqs.completed_buffers_num() == 0, "Completed buffers exist!");
1969   g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers, G1GCPhaseTimes::UpdateRSProcessedBuffers);
1970 }
1971 
1972 // Computes the sum of the storage used by the various regions.
1973 size_t G1CollectedHeap::used() const {
1974   size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
1975   if (_archive_allocator != NULL) {
1976     result += _archive_allocator->used();
1977   }
1978   return result;
1979 }
1980 
1981 size_t G1CollectedHeap::used_unlocked() const {
1982   return _summary_bytes_used;
1983 }
1984 
1985 class SumUsedClosure: public HeapRegionClosure {
1986   size_t _used;
1987 public:
1988   SumUsedClosure() : _used(0) {}
1989   bool do_heap_region(HeapRegion* r) {
1990     _used += r->used();
1991     return false;
1992   }
1993   size_t result() { return _used; }
1994 };
1995 
1996 size_t G1CollectedHeap::recalculate_used() const {
1997   SumUsedClosure blk;
1998   heap_region_iterate(&blk);
1999   return blk.result();
2000 }
2001 
2002 bool  G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
2003   switch (cause) {
2004     case GCCause::_java_lang_system_gc:                 return ExplicitGCInvokesConcurrent;
2005     case GCCause::_dcmd_gc_run:                         return ExplicitGCInvokesConcurrent;
2006     case GCCause::_wb_conc_mark:                        return true;
2007     default :                                           return false;
2008   }
2009 }
2010 
2011 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
2012   switch (cause) {
2013     case GCCause::_gc_locker:               return GCLockerInvokesConcurrent;
2014     case GCCause::_g1_humongous_allocation: return true;
2015     case GCCause::_g1_periodic_collection:  return G1PeriodicGCInvokesConcurrent;
2016     default:                                return is_user_requested_concurrent_full_gc(cause);
2017   }
2018 }
2019 
2020 bool G1CollectedHeap::should_upgrade_to_full_gc(GCCause::Cause cause) {
2021   if(g1_policy()->force_upgrade_to_full()) {
2022     return true;
2023   } else if (should_do_concurrent_full_gc(_gc_cause)) {
2024     return false;
2025   } else if (has_regions_left_for_allocation()) {
2026     return false;
2027   } else {
2028     return true;
2029   }
2030 }
2031 
2032 #ifndef PRODUCT
2033 void G1CollectedHeap::allocate_dummy_regions() {
2034   // Let's fill up most of the region
2035   size_t word_size = HeapRegion::GrainWords - 1024;
2036   // And as a result the region we'll allocate will be humongous.
2037   guarantee(is_humongous(word_size), "sanity");
2038 
2039   // _filler_array_max_size is set to humongous object threshold
2040   // but temporarily change it to use CollectedHeap::fill_with_object().
2041   SizeTFlagSetting fs(_filler_array_max_size, word_size);
2042 
2043   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2044     // Let's use the existing mechanism for the allocation
2045     HeapWord* dummy_obj = humongous_obj_allocate(word_size);
2046     if (dummy_obj != NULL) {
2047       MemRegion mr(dummy_obj, word_size);
2048       CollectedHeap::fill_with_object(mr);
2049     } else {
2050       // If we can't allocate once, we probably cannot allocate
2051       // again. Let's get out of the loop.
2052       break;
2053     }
2054   }
2055 }
2056 #endif // !PRODUCT
2057 
2058 void G1CollectedHeap::increment_old_marking_cycles_started() {
2059   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2060          _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2061          "Wrong marking cycle count (started: %d, completed: %d)",
2062          _old_marking_cycles_started, _old_marking_cycles_completed);
2063 
2064   _old_marking_cycles_started++;
2065 }
2066 
2067 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2068   MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2069 
2070   // We assume that if concurrent == true, then the caller is a
2071   // concurrent thread that was joined the Suspendible Thread
2072   // Set. If there's ever a cheap way to check this, we should add an
2073   // assert here.
2074 
2075   // Given that this method is called at the end of a Full GC or of a
2076   // concurrent cycle, and those can be nested (i.e., a Full GC can
2077   // interrupt a concurrent cycle), the number of full collections
2078   // completed should be either one (in the case where there was no
2079   // nesting) or two (when a Full GC interrupted a concurrent cycle)
2080   // behind the number of full collections started.
2081 
2082   // This is the case for the inner caller, i.e. a Full GC.
2083   assert(concurrent ||
2084          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2085          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2086          "for inner caller (Full GC): _old_marking_cycles_started = %u "
2087          "is inconsistent with _old_marking_cycles_completed = %u",
2088          _old_marking_cycles_started, _old_marking_cycles_completed);
2089 
2090   // This is the case for the outer caller, i.e. the concurrent cycle.
2091   assert(!concurrent ||
2092          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2093          "for outer caller (concurrent cycle): "
2094          "_old_marking_cycles_started = %u "
2095          "is inconsistent with _old_marking_cycles_completed = %u",
2096          _old_marking_cycles_started, _old_marking_cycles_completed);
2097 
2098   _old_marking_cycles_completed += 1;
2099 
2100   // We need to clear the "in_progress" flag in the CM thread before
2101   // we wake up any waiters (especially when ExplicitInvokesConcurrent
2102   // is set) so that if a waiter requests another System.gc() it doesn't
2103   // incorrectly see that a marking cycle is still in progress.
2104   if (concurrent) {
2105     _cm_thread->set_idle();
2106   }
2107 
2108   // This notify_all() will ensure that a thread that called
2109   // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2110   // and it's waiting for a full GC to finish will be woken up. It is
2111   // waiting in VM_G1CollectForAllocation::doit_epilogue().
2112   FullGCCount_lock->notify_all();
2113 }
2114 
2115 void G1CollectedHeap::collect(GCCause::Cause cause) {
2116   attempt_collect(cause, true);
2117 }
2118 
2119 bool G1CollectedHeap::attempt_collect(GCCause::Cause cause, bool retry_on_vmop_failure) {
2120   assert_heap_not_locked();
2121 
2122   bool vmop_succeeded;
2123   bool should_retry_vmop;
2124 
2125   do {
2126     should_retry_vmop = false;
2127 
2128     uint gc_count_before;
2129     uint old_marking_count_before;
2130     uint full_gc_count_before;
2131 
2132     {
2133       MutexLocker ml(Heap_lock);
2134 
2135       // Read the GC count while holding the Heap_lock
2136       gc_count_before = total_collections();
2137       full_gc_count_before = total_full_collections();
2138       old_marking_count_before = _old_marking_cycles_started;
2139     }
2140 
2141     if (should_do_concurrent_full_gc(cause)) {
2142       // Schedule an initial-mark evacuation pause that will start a
2143       // concurrent cycle. We're setting word_size to 0 which means that
2144       // we are not requesting a post-GC allocation.
2145       VM_G1CollectForAllocation op(0,     /* word_size */
2146                                    gc_count_before,
2147                                    cause,
2148                                    true,  /* should_initiate_conc_mark */
2149                                    g1_policy()->max_pause_time_ms());
2150       VMThread::execute(&op);
2151       vmop_succeeded = op.pause_succeeded();
2152       if (!vmop_succeeded && retry_on_vmop_failure) {
2153         if (old_marking_count_before == _old_marking_cycles_started) {
2154           should_retry_vmop = op.should_retry_gc();
2155         } else {
2156           // A Full GC happened while we were trying to schedule the
2157           // concurrent cycle. No point in starting a new cycle given
2158           // that the whole heap was collected anyway.
2159         }
2160 
2161         if (should_retry_vmop) {
2162           if (GCLocker::is_active_and_needs_gc()) {
2163             GCLocker::stall_until_clear();
2164           }
2165         }
2166       }
2167     } else {
2168       if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2169           DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2170 
2171         // Schedule a standard evacuation pause. We're setting word_size
2172         // to 0 which means that we are not requesting a post-GC allocation.
2173         VM_G1CollectForAllocation op(0,     /* word_size */
2174                                      gc_count_before,
2175                                      cause,
2176                                      false, /* should_initiate_conc_mark */
2177                                      g1_policy()->max_pause_time_ms());
2178         VMThread::execute(&op);
2179         vmop_succeeded = op.pause_succeeded();
2180       } else {
2181         // Schedule a Full GC.
2182         VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2183         VMThread::execute(&op);
2184         vmop_succeeded = op.pause_succeeded();
2185       }
2186     }
2187   } while (should_retry_vmop);
2188   return vmop_succeeded;
2189 }
2190 
2191 bool G1CollectedHeap::is_in(const void* p) const {
2192   if (_hrm->reserved().contains(p)) {
2193     // Given that we know that p is in the reserved space,
2194     // heap_region_containing() should successfully
2195     // return the containing region.
2196     HeapRegion* hr = heap_region_containing(p);
2197     return hr->is_in(p);
2198   } else {
2199     return false;
2200   }
2201 }
2202 
2203 #ifdef ASSERT
2204 bool G1CollectedHeap::is_in_exact(const void* p) const {
2205   bool contains = reserved_region().contains(p);
2206   bool available = _hrm->is_available(addr_to_region((HeapWord*)p));
2207   if (contains && available) {
2208     return true;
2209   } else {
2210     return false;
2211   }
2212 }
2213 #endif
2214 
2215 // Iteration functions.
2216 
2217 // Iterates an ObjectClosure over all objects within a HeapRegion.
2218 
2219 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2220   ObjectClosure* _cl;
2221 public:
2222   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2223   bool do_heap_region(HeapRegion* r) {
2224     if (!r->is_continues_humongous()) {
2225       r->object_iterate(_cl);
2226     }
2227     return false;
2228   }
2229 };
2230 
2231 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2232   IterateObjectClosureRegionClosure blk(cl);
2233   heap_region_iterate(&blk);
2234 }
2235 
2236 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2237   _hrm->iterate(cl);
2238 }
2239 
2240 void G1CollectedHeap::heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl,
2241                                                                  HeapRegionClaimer *hrclaimer,
2242                                                                  uint worker_id) const {
2243   _hrm->par_iterate(cl, hrclaimer, hrclaimer->offset_for_worker(worker_id));
2244 }
2245 
2246 void G1CollectedHeap::heap_region_par_iterate_from_start(HeapRegionClosure* cl,
2247                                                          HeapRegionClaimer *hrclaimer) const {
2248   _hrm->par_iterate(cl, hrclaimer, 0);
2249 }
2250 
2251 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2252   _collection_set.iterate(cl);
2253 }
2254 
2255 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) {
2256   _collection_set.iterate_from(cl, worker_id, workers()->active_workers());
2257 }
2258 
2259 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2260   HeapRegion* hr = heap_region_containing(addr);
2261   return hr->block_start(addr);
2262 }
2263 
2264 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2265   HeapRegion* hr = heap_region_containing(addr);
2266   return hr->block_size(addr);
2267 }
2268 
2269 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2270   HeapRegion* hr = heap_region_containing(addr);
2271   return hr->block_is_obj(addr);
2272 }
2273 
2274 bool G1CollectedHeap::supports_tlab_allocation() const {
2275   return true;
2276 }
2277 
2278 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2279   return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes;
2280 }
2281 
2282 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2283   return _eden.length() * HeapRegion::GrainBytes;
2284 }
2285 
2286 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2287 // must be equal to the humongous object limit.
2288 size_t G1CollectedHeap::max_tlab_size() const {
2289   return align_down(_humongous_object_threshold_in_words, MinObjAlignment);
2290 }
2291 
2292 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2293   return _allocator->unsafe_max_tlab_alloc();
2294 }
2295 
2296 size_t G1CollectedHeap::max_capacity() const {
2297   return _hrm->max_expandable_length() * HeapRegion::GrainBytes;
2298 }
2299 
2300 size_t G1CollectedHeap::max_reserved_capacity() const {
2301   return _hrm->max_length() * HeapRegion::GrainBytes;
2302 }
2303 
2304 jlong G1CollectedHeap::millis_since_last_gc() {
2305   // See the notes in GenCollectedHeap::millis_since_last_gc()
2306   // for more information about the implementation.
2307   jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) -
2308     _g1_policy->collection_pause_end_millis();
2309   if (ret_val < 0) {
2310     log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT
2311       ". returning zero instead.", ret_val);
2312     return 0;
2313   }
2314   return ret_val;
2315 }
2316 
2317 void G1CollectedHeap::deduplicate_string(oop str) {
2318   assert(java_lang_String::is_instance(str), "invariant");
2319 
2320   if (G1StringDedup::is_enabled()) {
2321     G1StringDedup::deduplicate(str);
2322   }
2323 }
2324 
2325 void G1CollectedHeap::prepare_for_verify() {
2326   _verifier->prepare_for_verify();
2327 }
2328 
2329 void G1CollectedHeap::verify(VerifyOption vo) {
2330   _verifier->verify(vo);
2331 }
2332 
2333 bool G1CollectedHeap::supports_concurrent_phase_control() const {
2334   return true;
2335 }
2336 
2337 bool G1CollectedHeap::request_concurrent_phase(const char* phase) {
2338   return _cm_thread->request_concurrent_phase(phase);
2339 }
2340 
2341 class PrintRegionClosure: public HeapRegionClosure {
2342   outputStream* _st;
2343 public:
2344   PrintRegionClosure(outputStream* st) : _st(st) {}
2345   bool do_heap_region(HeapRegion* r) {
2346     r->print_on(_st);
2347     return false;
2348   }
2349 };
2350 
2351 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2352                                        const HeapRegion* hr,
2353                                        const VerifyOption vo) const {
2354   switch (vo) {
2355   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
2356   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
2357   case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj, hr);
2358   default:                            ShouldNotReachHere();
2359   }
2360   return false; // keep some compilers happy
2361 }
2362 
2363 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2364                                        const VerifyOption vo) const {
2365   switch (vo) {
2366   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
2367   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
2368   case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj);
2369   default:                            ShouldNotReachHere();
2370   }
2371   return false; // keep some compilers happy
2372 }
2373 
2374 void G1CollectedHeap::print_heap_regions() const {
2375   LogTarget(Trace, gc, heap, region) lt;
2376   if (lt.is_enabled()) {
2377     LogStream ls(lt);
2378     print_regions_on(&ls);
2379   }
2380 }
2381 
2382 void G1CollectedHeap::print_on(outputStream* st) const {
2383   st->print(" %-20s", "garbage-first heap");
2384   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
2385             capacity()/K, used_unlocked()/K);
2386   st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")",
2387             p2i(_hrm->reserved().start()),
2388             p2i(_hrm->reserved().end()));
2389   st->cr();
2390   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
2391   uint young_regions = young_regions_count();
2392   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
2393             (size_t) young_regions * HeapRegion::GrainBytes / K);
2394   uint survivor_regions = survivor_regions_count();
2395   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
2396             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
2397   st->cr();
2398   MetaspaceUtils::print_on(st);
2399 }
2400 
2401 void G1CollectedHeap::print_regions_on(outputStream* st) const {
2402   st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
2403                "HS=humongous(starts), HC=humongous(continues), "
2404                "CS=collection set, F=free, A=archive, "
2405                "TAMS=top-at-mark-start (previous, next)");
2406   PrintRegionClosure blk(st);
2407   heap_region_iterate(&blk);
2408 }
2409 
2410 void G1CollectedHeap::print_extended_on(outputStream* st) const {
2411   print_on(st);
2412 
2413   // Print the per-region information.
2414   print_regions_on(st);
2415 }
2416 
2417 void G1CollectedHeap::print_on_error(outputStream* st) const {
2418   this->CollectedHeap::print_on_error(st);
2419 
2420   if (_cm != NULL) {
2421     st->cr();
2422     _cm->print_on_error(st);
2423   }
2424 }
2425 
2426 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
2427   workers()->print_worker_threads_on(st);
2428   _cm_thread->print_on(st);
2429   st->cr();
2430   _cm->print_worker_threads_on(st);
2431   _cr->print_threads_on(st);
2432   _young_gen_sampling_thread->print_on(st);
2433   if (G1StringDedup::is_enabled()) {
2434     G1StringDedup::print_worker_threads_on(st);
2435   }
2436 }
2437 
2438 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2439   workers()->threads_do(tc);
2440   tc->do_thread(_cm_thread);
2441   _cm->threads_do(tc);
2442   _cr->threads_do(tc);
2443   tc->do_thread(_young_gen_sampling_thread);
2444   if (G1StringDedup::is_enabled()) {
2445     G1StringDedup::threads_do(tc);
2446   }
2447 }
2448 
2449 void G1CollectedHeap::print_tracing_info() const {
2450   g1_rem_set()->print_summary_info();
2451   concurrent_mark()->print_summary_info();
2452 }
2453 
2454 #ifndef PRODUCT
2455 // Helpful for debugging RSet issues.
2456 
2457 class PrintRSetsClosure : public HeapRegionClosure {
2458 private:
2459   const char* _msg;
2460   size_t _occupied_sum;
2461 
2462 public:
2463   bool do_heap_region(HeapRegion* r) {
2464     HeapRegionRemSet* hrrs = r->rem_set();
2465     size_t occupied = hrrs->occupied();
2466     _occupied_sum += occupied;
2467 
2468     tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r));
2469     if (occupied == 0) {
2470       tty->print_cr("  RSet is empty");
2471     } else {
2472       hrrs->print();
2473     }
2474     tty->print_cr("----------");
2475     return false;
2476   }
2477 
2478   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
2479     tty->cr();
2480     tty->print_cr("========================================");
2481     tty->print_cr("%s", msg);
2482     tty->cr();
2483   }
2484 
2485   ~PrintRSetsClosure() {
2486     tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
2487     tty->print_cr("========================================");
2488     tty->cr();
2489   }
2490 };
2491 
2492 void G1CollectedHeap::print_cset_rsets() {
2493   PrintRSetsClosure cl("Printing CSet RSets");
2494   collection_set_iterate(&cl);
2495 }
2496 
2497 void G1CollectedHeap::print_all_rsets() {
2498   PrintRSetsClosure cl("Printing All RSets");;
2499   heap_region_iterate(&cl);
2500 }
2501 #endif // PRODUCT
2502 
2503 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
2504 
2505   size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes;
2506   size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes;
2507   size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
2508 
2509   size_t eden_capacity_bytes =
2510     (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
2511 
2512   VirtualSpaceSummary heap_summary = create_heap_space_summary();
2513   return G1HeapSummary(heap_summary, heap_used, eden_used_bytes,
2514                        eden_capacity_bytes, survivor_used_bytes, num_regions());
2515 }
2516 
2517 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
2518   return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
2519                        stats->unused(), stats->used(), stats->region_end_waste(),
2520                        stats->regions_filled(), stats->direct_allocated(),
2521                        stats->failure_used(), stats->failure_waste());
2522 }
2523 
2524 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
2525   const G1HeapSummary& heap_summary = create_g1_heap_summary();
2526   gc_tracer->report_gc_heap_summary(when, heap_summary);
2527 
2528   const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
2529   gc_tracer->report_metaspace_summary(when, metaspace_summary);
2530 }
2531 
2532 G1CollectedHeap* G1CollectedHeap::heap() {
2533   CollectedHeap* heap = Universe::heap();
2534   assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
2535   assert(heap->kind() == CollectedHeap::G1, "Invalid name");
2536   return (G1CollectedHeap*)heap;
2537 }
2538 
2539 void G1CollectedHeap::gc_prologue(bool full) {
2540   // always_do_update_barrier = false;
2541   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
2542 
2543   // This summary needs to be printed before incrementing total collections.
2544   g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections());
2545 
2546   // Update common counters.
2547   increment_total_collections(full /* full gc */);
2548   if (full) {
2549     increment_old_marking_cycles_started();
2550   }
2551 
2552   // Fill TLAB's and such
2553   double start = os::elapsedTime();
2554   ensure_parsability(true);
2555   g1_policy()->phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2556 }
2557 
2558 void G1CollectedHeap::gc_epilogue(bool full) {
2559   // Update common counters.
2560   if (full) {
2561     // Update the number of full collections that have been completed.
2562     increment_old_marking_cycles_completed(false /* concurrent */);
2563   }
2564 
2565   // We are at the end of the GC. Total collections has already been increased.
2566   g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1);
2567 
2568   // FIXME: what is this about?
2569   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
2570   // is set.
2571 #if COMPILER2_OR_JVMCI
2572   assert(DerivedPointerTable::is_empty(), "derived pointer present");
2573 #endif
2574   // always_do_update_barrier = true;
2575 
2576   double start = os::elapsedTime();
2577   resize_all_tlabs();
2578   g1_policy()->phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2579 
2580   MemoryService::track_memory_usage();
2581   // We have just completed a GC. Update the soft reference
2582   // policy with the new heap occupancy
2583   Universe::update_heap_info_at_gc();
2584 }
2585 
2586 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2587                                                uint gc_count_before,
2588                                                bool* succeeded,
2589                                                GCCause::Cause gc_cause) {
2590   assert_heap_not_locked_and_not_at_safepoint();
2591   VM_G1CollectForAllocation op(word_size,
2592                                gc_count_before,
2593                                gc_cause,
2594                                false, /* should_initiate_conc_mark */
2595                                g1_policy()->max_pause_time_ms());
2596   VMThread::execute(&op);
2597 
2598   HeapWord* result = op.result();
2599   bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
2600   assert(result == NULL || ret_succeeded,
2601          "the result should be NULL if the VM did not succeed");
2602   *succeeded = ret_succeeded;
2603 
2604   assert_heap_not_locked();
2605   return result;
2606 }
2607 
2608 void G1CollectedHeap::do_concurrent_mark() {
2609   MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
2610   if (!_cm_thread->in_progress()) {
2611     _cm_thread->set_started();
2612     CGC_lock->notify();
2613   }
2614 }
2615 
2616 size_t G1CollectedHeap::pending_card_num() {
2617   size_t extra_cards = 0;
2618   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *curr = jtiwh.next(); ) {
2619     G1DirtyCardQueue& dcq = G1ThreadLocalData::dirty_card_queue(curr);
2620     extra_cards += dcq.size();
2621   }
2622   G1DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
2623   size_t buffer_size = dcqs.buffer_size();
2624   size_t buffer_num = dcqs.completed_buffers_num();
2625 
2626   return buffer_size * buffer_num + extra_cards;
2627 }
2628 
2629 bool G1CollectedHeap::is_potential_eager_reclaim_candidate(HeapRegion* r) const {
2630   // We don't nominate objects with many remembered set entries, on
2631   // the assumption that such objects are likely still live.
2632   HeapRegionRemSet* rem_set = r->rem_set();
2633 
2634   return G1EagerReclaimHumongousObjectsWithStaleRefs ?
2635          rem_set->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) :
2636          G1EagerReclaimHumongousObjects && rem_set->is_empty();
2637 }
2638 
2639 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
2640  private:
2641   size_t _total_humongous;
2642   size_t _candidate_humongous;
2643 
2644   G1DirtyCardQueue _dcq;
2645 
2646   bool humongous_region_is_candidate(G1CollectedHeap* g1h, HeapRegion* region) const {
2647     assert(region->is_starts_humongous(), "Must start a humongous object");
2648 
2649     oop obj = oop(region->bottom());
2650 
2651     // Dead objects cannot be eager reclaim candidates. Due to class
2652     // unloading it is unsafe to query their classes so we return early.
2653     if (g1h->is_obj_dead(obj, region)) {
2654       return false;
2655     }
2656 
2657     // If we do not have a complete remembered set for the region, then we can
2658     // not be sure that we have all references to it.
2659     if (!region->rem_set()->is_complete()) {
2660       return false;
2661     }
2662     // Candidate selection must satisfy the following constraints
2663     // while concurrent marking is in progress:
2664     //
2665     // * In order to maintain SATB invariants, an object must not be
2666     // reclaimed if it was allocated before the start of marking and
2667     // has not had its references scanned.  Such an object must have
2668     // its references (including type metadata) scanned to ensure no
2669     // live objects are missed by the marking process.  Objects
2670     // allocated after the start of concurrent marking don't need to
2671     // be scanned.
2672     //
2673     // * An object must not be reclaimed if it is on the concurrent
2674     // mark stack.  Objects allocated after the start of concurrent
2675     // marking are never pushed on the mark stack.
2676     //
2677     // Nominating only objects allocated after the start of concurrent
2678     // marking is sufficient to meet both constraints.  This may miss
2679     // some objects that satisfy the constraints, but the marking data
2680     // structures don't support efficiently performing the needed
2681     // additional tests or scrubbing of the mark stack.
2682     //
2683     // However, we presently only nominate is_typeArray() objects.
2684     // A humongous object containing references induces remembered
2685     // set entries on other regions.  In order to reclaim such an
2686     // object, those remembered sets would need to be cleaned up.
2687     //
2688     // We also treat is_typeArray() objects specially, allowing them
2689     // to be reclaimed even if allocated before the start of
2690     // concurrent mark.  For this we rely on mark stack insertion to
2691     // exclude is_typeArray() objects, preventing reclaiming an object
2692     // that is in the mark stack.  We also rely on the metadata for
2693     // such objects to be built-in and so ensured to be kept live.
2694     // Frequent allocation and drop of large binary blobs is an
2695     // important use case for eager reclaim, and this special handling
2696     // may reduce needed headroom.
2697 
2698     return obj->is_typeArray() &&
2699            g1h->is_potential_eager_reclaim_candidate(region);
2700   }
2701 
2702  public:
2703   RegisterHumongousWithInCSetFastTestClosure()
2704   : _total_humongous(0),
2705     _candidate_humongous(0),
2706     _dcq(&G1BarrierSet::dirty_card_queue_set()) {
2707   }
2708 
2709   virtual bool do_heap_region(HeapRegion* r) {
2710     if (!r->is_starts_humongous()) {
2711       return false;
2712     }
2713     G1CollectedHeap* g1h = G1CollectedHeap::heap();
2714 
2715     bool is_candidate = humongous_region_is_candidate(g1h, r);
2716     uint rindex = r->hrm_index();
2717     g1h->set_humongous_reclaim_candidate(rindex, is_candidate);
2718     if (is_candidate) {
2719       _candidate_humongous++;
2720       g1h->register_humongous_region_with_cset(rindex);
2721       // Is_candidate already filters out humongous object with large remembered sets.
2722       // If we have a humongous object with a few remembered sets, we simply flush these
2723       // remembered set entries into the DCQS. That will result in automatic
2724       // re-evaluation of their remembered set entries during the following evacuation
2725       // phase.
2726       if (!r->rem_set()->is_empty()) {
2727         guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
2728                   "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
2729         G1CardTable* ct = g1h->card_table();
2730         HeapRegionRemSetIterator hrrs(r->rem_set());
2731         size_t card_index;
2732         while (hrrs.has_next(card_index)) {
2733           jbyte* card_ptr = (jbyte*)ct->byte_for_index(card_index);
2734           // The remembered set might contain references to already freed
2735           // regions. Filter out such entries to avoid failing card table
2736           // verification.
2737           if (g1h->is_in_closed_subset(ct->addr_for(card_ptr))) {
2738             if (*card_ptr != G1CardTable::dirty_card_val()) {
2739               *card_ptr = G1CardTable::dirty_card_val();
2740               _dcq.enqueue(card_ptr);
2741             }
2742           }
2743         }
2744         assert(hrrs.n_yielded() == r->rem_set()->occupied(),
2745                "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries",
2746                hrrs.n_yielded(), r->rem_set()->occupied());
2747         // We should only clear the card based remembered set here as we will not
2748         // implicitly rebuild anything else during eager reclaim. Note that at the moment
2749         // (and probably never) we do not enter this path if there are other kind of
2750         // remembered sets for this region.
2751         r->rem_set()->clear_locked(true /* only_cardset */);
2752         // Clear_locked() above sets the state to Empty. However we want to continue
2753         // collecting remembered set entries for humongous regions that were not
2754         // reclaimed.
2755         r->rem_set()->set_state_complete();
2756       }
2757       assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
2758     }
2759     _total_humongous++;
2760 
2761     return false;
2762   }
2763 
2764   size_t total_humongous() const { return _total_humongous; }
2765   size_t candidate_humongous() const { return _candidate_humongous; }
2766 
2767   void flush_rem_set_entries() { _dcq.flush(); }
2768 };
2769 
2770 void G1CollectedHeap::register_humongous_regions_with_cset() {
2771   if (!G1EagerReclaimHumongousObjects) {
2772     g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
2773     return;
2774   }
2775   double time = os::elapsed_counter();
2776 
2777   // Collect reclaim candidate information and register candidates with cset.
2778   RegisterHumongousWithInCSetFastTestClosure cl;
2779   heap_region_iterate(&cl);
2780 
2781   time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
2782   g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
2783                                                                   cl.total_humongous(),
2784                                                                   cl.candidate_humongous());
2785   _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
2786 
2787   // Finally flush all remembered set entries to re-check into the global DCQS.
2788   cl.flush_rem_set_entries();
2789 }
2790 
2791 class VerifyRegionRemSetClosure : public HeapRegionClosure {
2792   public:
2793     bool do_heap_region(HeapRegion* hr) {
2794       if (!hr->is_archive() && !hr->is_continues_humongous()) {
2795         hr->verify_rem_set();
2796       }
2797       return false;
2798     }
2799 };
2800 
2801 uint G1CollectedHeap::num_task_queues() const {
2802   return _task_queues->size();
2803 }
2804 
2805 #if TASKQUEUE_STATS
2806 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
2807   st->print_raw_cr("GC Task Stats");
2808   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
2809   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
2810 }
2811 
2812 void G1CollectedHeap::print_taskqueue_stats() const {
2813   if (!log_is_enabled(Trace, gc, task, stats)) {
2814     return;
2815   }
2816   Log(gc, task, stats) log;
2817   ResourceMark rm;
2818   LogStream ls(log.trace());
2819   outputStream* st = &ls;
2820 
2821   print_taskqueue_stats_hdr(st);
2822 
2823   TaskQueueStats totals;
2824   const uint n = num_task_queues();
2825   for (uint i = 0; i < n; ++i) {
2826     st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
2827     totals += task_queue(i)->stats;
2828   }
2829   st->print_raw("tot "); totals.print(st); st->cr();
2830 
2831   DEBUG_ONLY(totals.verify());
2832 }
2833 
2834 void G1CollectedHeap::reset_taskqueue_stats() {
2835   const uint n = num_task_queues();
2836   for (uint i = 0; i < n; ++i) {
2837     task_queue(i)->stats.reset();
2838   }
2839 }
2840 #endif // TASKQUEUE_STATS
2841 
2842 void G1CollectedHeap::wait_for_root_region_scanning() {
2843   double scan_wait_start = os::elapsedTime();
2844   // We have to wait until the CM threads finish scanning the
2845   // root regions as it's the only way to ensure that all the
2846   // objects on them have been correctly scanned before we start
2847   // moving them during the GC.
2848   bool waited = _cm->root_regions()->wait_until_scan_finished();
2849   double wait_time_ms = 0.0;
2850   if (waited) {
2851     double scan_wait_end = os::elapsedTime();
2852     wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
2853   }
2854   g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
2855 }
2856 
2857 class G1PrintCollectionSetClosure : public HeapRegionClosure {
2858 private:
2859   G1HRPrinter* _hr_printer;
2860 public:
2861   G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { }
2862 
2863   virtual bool do_heap_region(HeapRegion* r) {
2864     _hr_printer->cset(r);
2865     return false;
2866   }
2867 };
2868 
2869 void G1CollectedHeap::start_new_collection_set() {
2870   collection_set()->start_incremental_building();
2871 
2872   clear_cset_fast_test();
2873 
2874   guarantee(_eden.length() == 0, "eden should have been cleared");
2875   g1_policy()->transfer_survivors_to_cset(survivor());
2876 }
2877 
2878 bool
2879 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
2880   assert_at_safepoint_on_vm_thread();
2881   guarantee(!is_gc_active(), "collection is not reentrant");
2882 
2883   if (GCLocker::check_active_before_gc()) {
2884     return false;
2885   }
2886 
2887   _gc_timer_stw->register_gc_start();
2888 
2889   GCIdMark gc_id_mark;
2890   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
2891 
2892   SvcGCMarker sgcm(SvcGCMarker::MINOR);
2893   ResourceMark rm;
2894 
2895   g1_policy()->note_gc_start();
2896 
2897   wait_for_root_region_scanning();
2898 
2899   print_heap_before_gc();
2900   print_heap_regions();
2901   trace_heap_before_gc(_gc_tracer_stw);
2902 
2903   _verifier->verify_region_sets_optional();
2904   _verifier->verify_dirty_young_regions();
2905 
2906   // We should not be doing initial mark unless the conc mark thread is running
2907   if (!_cm_thread->should_terminate()) {
2908     // This call will decide whether this pause is an initial-mark
2909     // pause. If it is, in_initial_mark_gc() will return true
2910     // for the duration of this pause.
2911     g1_policy()->decide_on_conc_mark_initiation();
2912   }
2913 
2914   // We do not allow initial-mark to be piggy-backed on a mixed GC.
2915   assert(!collector_state()->in_initial_mark_gc() ||
2916           collector_state()->in_young_only_phase(), "sanity");
2917 
2918   // We also do not allow mixed GCs during marking.
2919   assert(!collector_state()->mark_or_rebuild_in_progress() || collector_state()->in_young_only_phase(), "sanity");
2920 
2921   // Record whether this pause is an initial mark. When the current
2922   // thread has completed its logging output and it's safe to signal
2923   // the CM thread, the flag's value in the policy has been reset.
2924   bool should_start_conc_mark = collector_state()->in_initial_mark_gc();
2925 
2926   // Inner scope for scope based logging, timers, and stats collection
2927   {
2928     G1EvacuationInfo evacuation_info;
2929 
2930     if (collector_state()->in_initial_mark_gc()) {
2931       // We are about to start a marking cycle, so we increment the
2932       // full collection counter.
2933       increment_old_marking_cycles_started();
2934       _cm->gc_tracer_cm()->set_gc_cause(gc_cause());
2935     }
2936 
2937     _gc_tracer_stw->report_yc_type(collector_state()->yc_type());
2938 
2939     GCTraceCPUTime tcpu;
2940 
2941     G1HeapVerifier::G1VerifyType verify_type;
2942     FormatBuffer<> gc_string("Pause Young ");
2943     if (collector_state()->in_initial_mark_gc()) {
2944       gc_string.append("(Concurrent Start)");
2945       verify_type = G1HeapVerifier::G1VerifyConcurrentStart;
2946     } else if (collector_state()->in_young_only_phase()) {
2947       if (collector_state()->in_young_gc_before_mixed()) {
2948         gc_string.append("(Prepare Mixed)");
2949       } else {
2950         gc_string.append("(Normal)");
2951       }
2952       verify_type = G1HeapVerifier::G1VerifyYoungNormal;
2953     } else {
2954       gc_string.append("(Mixed)");
2955       verify_type = G1HeapVerifier::G1VerifyMixed;
2956     }
2957     GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true);
2958 
2959     uint active_workers = WorkerPolicy::calc_active_workers(workers()->total_workers(),
2960                                                             workers()->active_workers(),
2961                                                             Threads::number_of_non_daemon_threads());
2962     active_workers = workers()->update_active_workers(active_workers);
2963     log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers());
2964 
2965     G1MonitoringScope ms(g1mm(),
2966                          false /* full_gc */,
2967                          collector_state()->yc_type() == Mixed /* all_memory_pools_affected */);
2968 
2969     G1HeapTransition heap_transition(this);
2970     size_t heap_used_bytes_before_gc = used();
2971 
2972     // Don't dynamically change the number of GC threads this early.  A value of
2973     // 0 is used to indicate serial work.  When parallel work is done,
2974     // it will be set.
2975 
2976     { // Call to jvmpi::post_class_unload_events must occur outside of active GC
2977       IsGCActiveMark x;
2978 
2979       gc_prologue(false);
2980 
2981       if (VerifyRememberedSets) {
2982         log_info(gc, verify)("[Verifying RemSets before GC]");
2983         VerifyRegionRemSetClosure v_cl;
2984         heap_region_iterate(&v_cl);
2985       }
2986 
2987       _verifier->verify_before_gc(verify_type);
2988 
2989       _verifier->check_bitmaps("GC Start");
2990 
2991 #if COMPILER2_OR_JVMCI
2992       DerivedPointerTable::clear();
2993 #endif
2994 
2995       // Please see comment in g1CollectedHeap.hpp and
2996       // G1CollectedHeap::ref_processing_init() to see how
2997       // reference processing currently works in G1.
2998 
2999       // Enable discovery in the STW reference processor
3000       _ref_processor_stw->enable_discovery();
3001 
3002       {
3003         // We want to temporarily turn off discovery by the
3004         // CM ref processor, if necessary, and turn it back on
3005         // on again later if we do. Using a scoped
3006         // NoRefDiscovery object will do this.
3007         NoRefDiscovery no_cm_discovery(_ref_processor_cm);
3008 
3009         // Forget the current alloc region (we might even choose it to be part
3010         // of the collection set!).
3011         _allocator->release_mutator_alloc_region();
3012 
3013         // This timing is only used by the ergonomics to handle our pause target.
3014         // It is unclear why this should not include the full pause. We will
3015         // investigate this in CR 7178365.
3016         //
3017         // Preserving the old comment here if that helps the investigation:
3018         //
3019         // The elapsed time induced by the start time below deliberately elides
3020         // the possible verification above.
3021         double sample_start_time_sec = os::elapsedTime();
3022 
3023         g1_policy()->record_collection_pause_start(sample_start_time_sec);
3024 
3025         if (collector_state()->in_initial_mark_gc()) {
3026           concurrent_mark()->pre_initial_mark();
3027         }
3028 
3029         g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor);
3030 
3031         evacuation_info.set_collectionset_regions(collection_set()->region_length());
3032 
3033         register_humongous_regions_with_cset();
3034 
3035         assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table.");
3036 
3037         // We call this after finalize_cset() to
3038         // ensure that the CSet has been finalized.
3039         _cm->verify_no_cset_oops();
3040 
3041         if (_hr_printer.is_active()) {
3042           G1PrintCollectionSetClosure cl(&_hr_printer);
3043           _collection_set.iterate(&cl);
3044         }
3045 
3046         // Initialize the GC alloc regions.
3047         _allocator->init_gc_alloc_regions(evacuation_info);
3048 
3049         G1ParScanThreadStateSet per_thread_states(this,
3050                                                   workers()->active_workers(),
3051                                                   collection_set()->young_region_length(),
3052                                                   collection_set()->optional_region_length());
3053         pre_evacuate_collection_set();
3054 
3055         // Actually do the work...
3056         evacuate_collection_set(&per_thread_states);
3057         evacuate_optional_collection_set(&per_thread_states);
3058 
3059         post_evacuate_collection_set(evacuation_info, &per_thread_states);
3060 
3061         const size_t* surviving_young_words = per_thread_states.surviving_young_words();
3062         free_collection_set(&_collection_set, evacuation_info, surviving_young_words);
3063 
3064         eagerly_reclaim_humongous_regions();
3065 
3066         record_obj_copy_mem_stats();
3067         _survivor_evac_stats.adjust_desired_plab_sz();
3068         _old_evac_stats.adjust_desired_plab_sz();
3069 
3070         double start = os::elapsedTime();
3071         start_new_collection_set();
3072         g1_policy()->phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0);
3073 
3074         if (evacuation_failed()) {
3075           double recalculate_used_start = os::elapsedTime();
3076           set_used(recalculate_used());
3077           g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
3078 
3079           if (_archive_allocator != NULL) {
3080             _archive_allocator->clear_used();
3081           }
3082           for (uint i = 0; i < ParallelGCThreads; i++) {
3083             if (_evacuation_failed_info_array[i].has_failed()) {
3084               _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
3085             }
3086           }
3087         } else {
3088           // The "used" of the the collection set have already been subtracted
3089           // when they were freed.  Add in the bytes evacuated.
3090           increase_used(g1_policy()->bytes_copied_during_gc());
3091         }
3092 
3093         if (collector_state()->in_initial_mark_gc()) {
3094           // We have to do this before we notify the CM threads that
3095           // they can start working to make sure that all the
3096           // appropriate initialization is done on the CM object.
3097           concurrent_mark()->post_initial_mark();
3098           // Note that we don't actually trigger the CM thread at
3099           // this point. We do that later when we're sure that
3100           // the current thread has completed its logging output.
3101         }
3102 
3103         allocate_dummy_regions();
3104 
3105         _allocator->init_mutator_alloc_region();
3106 
3107         {
3108           size_t expand_bytes = _heap_sizing_policy->expansion_amount();
3109           if (expand_bytes > 0) {
3110             size_t bytes_before = capacity();
3111             // No need for an ergo logging here,
3112             // expansion_amount() does this when it returns a value > 0.
3113             double expand_ms;
3114             if (!expand(expand_bytes, _workers, &expand_ms)) {
3115               // We failed to expand the heap. Cannot do anything about it.
3116             }
3117             g1_policy()->phase_times()->record_expand_heap_time(expand_ms);
3118           }
3119         }
3120 
3121         // We redo the verification but now wrt to the new CSet which
3122         // has just got initialized after the previous CSet was freed.
3123         _cm->verify_no_cset_oops();
3124 
3125         // This timing is only used by the ergonomics to handle our pause target.
3126         // It is unclear why this should not include the full pause. We will
3127         // investigate this in CR 7178365.
3128         double sample_end_time_sec = os::elapsedTime();
3129         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3130         size_t total_cards_scanned = g1_policy()->phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanRS, G1GCPhaseTimes::ScanRSScannedCards);
3131         g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc);
3132 
3133         evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before());
3134         evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc());
3135 
3136         if (VerifyRememberedSets) {
3137           log_info(gc, verify)("[Verifying RemSets after GC]");
3138           VerifyRegionRemSetClosure v_cl;
3139           heap_region_iterate(&v_cl);
3140         }
3141 
3142         _verifier->verify_after_gc(verify_type);
3143         _verifier->check_bitmaps("GC End");
3144 
3145         assert(!_ref_processor_stw->discovery_enabled(), "Postcondition");
3146         _ref_processor_stw->verify_no_references_recorded();
3147 
3148         // CM reference discovery will be re-enabled if necessary.
3149       }
3150 
3151 #ifdef TRACESPINNING
3152       ParallelTaskTerminator::print_termination_counts();
3153 #endif
3154 
3155       gc_epilogue(false);
3156     }
3157 
3158     // Print the remainder of the GC log output.
3159     if (evacuation_failed()) {
3160       log_info(gc)("To-space exhausted");
3161     }
3162 
3163     g1_policy()->print_phases();
3164     heap_transition.print();
3165 
3166     // It is not yet to safe to tell the concurrent mark to
3167     // start as we have some optional output below. We don't want the
3168     // output from the concurrent mark thread interfering with this
3169     // logging output either.
3170 
3171     _hrm->verify_optional();
3172     _verifier->verify_region_sets_optional();
3173 
3174     TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
3175     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3176 
3177     print_heap_after_gc();
3178     print_heap_regions();
3179     trace_heap_after_gc(_gc_tracer_stw);
3180 
3181     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3182     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3183     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3184     // before any GC notifications are raised.
3185     g1mm()->update_sizes();
3186 
3187     _gc_tracer_stw->report_evacuation_info(&evacuation_info);
3188     _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
3189     _gc_timer_stw->register_gc_end();
3190     _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
3191   }
3192   // It should now be safe to tell the concurrent mark thread to start
3193   // without its logging output interfering with the logging output
3194   // that came from the pause.
3195 
3196   if (should_start_conc_mark) {
3197     // CAUTION: after the doConcurrentMark() call below,
3198     // the concurrent marking thread(s) could be running
3199     // concurrently with us. Make sure that anything after
3200     // this point does not assume that we are the only GC thread
3201     // running. Note: of course, the actual marking work will
3202     // not start until the safepoint itself is released in
3203     // SuspendibleThreadSet::desynchronize().
3204     do_concurrent_mark();
3205   }
3206 
3207   return true;
3208 }
3209 
3210 void G1CollectedHeap::remove_self_forwarding_pointers() {
3211   G1ParRemoveSelfForwardPtrsTask rsfp_task;
3212   workers()->run_task(&rsfp_task);
3213 }
3214 
3215 void G1CollectedHeap::restore_after_evac_failure() {
3216   double remove_self_forwards_start = os::elapsedTime();
3217 
3218   remove_self_forwarding_pointers();
3219   SharedRestorePreservedMarksTaskExecutor task_executor(workers());
3220   _preserved_marks_set.restore(&task_executor);
3221 
3222   g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
3223 }
3224 
3225 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) {
3226   if (!_evacuation_failed) {
3227     _evacuation_failed = true;
3228   }
3229 
3230   _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size());
3231   _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m);
3232 }
3233 
3234 bool G1ParEvacuateFollowersClosure::offer_termination() {
3235   EventGCPhaseParallel event;
3236   G1ParScanThreadState* const pss = par_scan_state();
3237   start_term_time();
3238   const bool res = terminator()->offer_termination();
3239   end_term_time();
3240   event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(G1GCPhaseTimes::Termination));
3241   return res;
3242 }
3243 
3244 void G1ParEvacuateFollowersClosure::do_void() {
3245   EventGCPhaseParallel event;
3246   G1ParScanThreadState* const pss = par_scan_state();
3247   pss->trim_queue();
3248   event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(_phase));
3249   do {
3250     EventGCPhaseParallel event;
3251     pss->steal_and_trim_queue(queues());
3252     event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(_phase));
3253   } while (!offer_termination());
3254 }
3255 
3256 class G1ParTask : public AbstractGangTask {
3257 protected:
3258   G1CollectedHeap*         _g1h;
3259   G1ParScanThreadStateSet* _pss;
3260   RefToScanQueueSet*       _queues;
3261   G1RootProcessor*         _root_processor;
3262   TaskTerminator           _terminator;
3263   uint                     _n_workers;
3264 
3265 public:
3266   G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers)
3267     : AbstractGangTask("G1 collection"),
3268       _g1h(g1h),
3269       _pss(per_thread_states),
3270       _queues(task_queues),
3271       _root_processor(root_processor),
3272       _terminator(n_workers, _queues),
3273       _n_workers(n_workers)
3274   {}
3275 
3276   void work(uint worker_id) {
3277     if (worker_id >= _n_workers) return;  // no work needed this round
3278 
3279     double start_sec = os::elapsedTime();
3280     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec);
3281 
3282     {
3283       ResourceMark rm;
3284       HandleMark   hm;
3285 
3286       ReferenceProcessor*             rp = _g1h->ref_processor_stw();
3287 
3288       G1ParScanThreadState*           pss = _pss->state_for_worker(worker_id);
3289       pss->set_ref_discoverer(rp);
3290 
3291       double start_strong_roots_sec = os::elapsedTime();
3292 
3293       _root_processor->evacuate_roots(pss, worker_id);
3294 
3295       _g1h->g1_rem_set()->oops_into_collection_set_do(pss, worker_id);
3296 
3297       double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec;
3298 
3299       double term_sec = 0.0;
3300       size_t evac_term_attempts = 0;
3301       {
3302         double start = os::elapsedTime();
3303         G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, _terminator.terminator(), G1GCPhaseTimes::ObjCopy);
3304         evac.do_void();
3305 
3306         evac_term_attempts = evac.term_attempts();
3307         term_sec = evac.term_time();
3308         double elapsed_sec = os::elapsedTime() - start;
3309 
3310         G1GCPhaseTimes* p = _g1h->g1_policy()->phase_times();
3311         p->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec);
3312 
3313         p->record_or_add_thread_work_item(G1GCPhaseTimes::ObjCopy,
3314                                           worker_id,
3315                                           pss->lab_waste_words() * HeapWordSize,
3316                                           G1GCPhaseTimes::ObjCopyLABWaste);
3317         p->record_or_add_thread_work_item(G1GCPhaseTimes::ObjCopy,
3318                                           worker_id,
3319                                           pss->lab_undo_waste_words() * HeapWordSize,
3320                                           G1GCPhaseTimes::ObjCopyLABUndoWaste);
3321 
3322         p->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec);
3323         p->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts);
3324       }
3325 
3326       assert(pss->queue_is_empty(), "should be empty");
3327 
3328       // Close the inner scope so that the ResourceMark and HandleMark
3329       // destructors are executed here and are included as part of the
3330       // "GC Worker Time".
3331     }
3332     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime());
3333   }
3334 };
3335 
3336 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive,
3337                                         bool class_unloading_occurred) {
3338   uint num_workers = workers()->active_workers();
3339   ParallelCleaningTask unlink_task(is_alive, num_workers, class_unloading_occurred, false);
3340   workers()->run_task(&unlink_task);
3341 }
3342 
3343 // Clean string dedup data structures.
3344 // Ideally we would prefer to use a StringDedupCleaningTask here, but we want to
3345 // record the durations of the phases. Hence the almost-copy.
3346 class G1StringDedupCleaningTask : public AbstractGangTask {
3347   BoolObjectClosure* _is_alive;
3348   OopClosure* _keep_alive;
3349   G1GCPhaseTimes* _phase_times;
3350 
3351 public:
3352   G1StringDedupCleaningTask(BoolObjectClosure* is_alive,
3353                             OopClosure* keep_alive,
3354                             G1GCPhaseTimes* phase_times) :
3355     AbstractGangTask("Partial Cleaning Task"),
3356     _is_alive(is_alive),
3357     _keep_alive(keep_alive),
3358     _phase_times(phase_times)
3359   {
3360     assert(G1StringDedup::is_enabled(), "String deduplication disabled.");
3361     StringDedup::gc_prologue(true);
3362   }
3363 
3364   ~G1StringDedupCleaningTask() {
3365     StringDedup::gc_epilogue();
3366   }
3367 
3368   void work(uint worker_id) {
3369     StringDedupUnlinkOrOopsDoClosure cl(_is_alive, _keep_alive);
3370     {
3371       G1GCParPhaseTimesTracker x(_phase_times, G1GCPhaseTimes::StringDedupQueueFixup, worker_id);
3372       StringDedupQueue::unlink_or_oops_do(&cl);
3373     }
3374     {
3375       G1GCParPhaseTimesTracker x(_phase_times, G1GCPhaseTimes::StringDedupTableFixup, worker_id);
3376       StringDedupTable::unlink_or_oops_do(&cl, worker_id);
3377     }
3378   }
3379 };
3380 
3381 void G1CollectedHeap::string_dedup_cleaning(BoolObjectClosure* is_alive,
3382                                             OopClosure* keep_alive,
3383                                             G1GCPhaseTimes* phase_times) {
3384   G1StringDedupCleaningTask cl(is_alive, keep_alive, phase_times);
3385   workers()->run_task(&cl);
3386 }
3387 
3388 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
3389  private:
3390   G1DirtyCardQueueSet* _queue;
3391   G1CollectedHeap* _g1h;
3392  public:
3393   G1RedirtyLoggedCardsTask(G1DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"),
3394     _queue(queue), _g1h(g1h) { }
3395 
3396   virtual void work(uint worker_id) {
3397     G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times();
3398     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id);
3399 
3400     RedirtyLoggedCardTableEntryClosure cl(_g1h);
3401     _queue->par_apply_closure_to_all_completed_buffers(&cl);
3402 
3403     phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied());
3404   }
3405 };
3406 
3407 void G1CollectedHeap::redirty_logged_cards() {
3408   double redirty_logged_cards_start = os::elapsedTime();
3409 
3410   G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this);
3411   dirty_card_queue_set().reset_for_par_iteration();
3412   workers()->run_task(&redirty_task);
3413 
3414   G1DirtyCardQueueSet& dcq = G1BarrierSet::dirty_card_queue_set();
3415   dcq.merge_bufferlists(&dirty_card_queue_set());
3416   assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
3417 
3418   g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
3419 }
3420 
3421 // Weak Reference Processing support
3422 
3423 bool G1STWIsAliveClosure::do_object_b(oop p) {
3424   // An object is reachable if it is outside the collection set,
3425   // or is inside and copied.
3426   return !_g1h->is_in_cset(p) || p->is_forwarded();
3427 }
3428 
3429 bool G1STWSubjectToDiscoveryClosure::do_object_b(oop obj) {
3430   assert(obj != NULL, "must not be NULL");
3431   assert(_g1h->is_in_reserved(obj), "Trying to discover obj " PTR_FORMAT " not in heap", p2i(obj));
3432   // The areas the CM and STW ref processor manage must be disjoint. The is_in_cset() below
3433   // may falsely indicate that this is not the case here: however the collection set only
3434   // contains old regions when concurrent mark is not running.
3435   return _g1h->is_in_cset(obj) || _g1h->heap_region_containing(obj)->is_survivor();
3436 }
3437 
3438 // Non Copying Keep Alive closure
3439 class G1KeepAliveClosure: public OopClosure {
3440   G1CollectedHeap*_g1h;
3441 public:
3442   G1KeepAliveClosure(G1CollectedHeap* g1h) :_g1h(g1h) {}
3443   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
3444   void do_oop(oop* p) {
3445     oop obj = *p;
3446     assert(obj != NULL, "the caller should have filtered out NULL values");
3447 
3448     const InCSetState cset_state =_g1h->in_cset_state(obj);
3449     if (!cset_state.is_in_cset_or_humongous()) {
3450       return;
3451     }
3452     if (cset_state.is_in_cset()) {
3453       assert( obj->is_forwarded(), "invariant" );
3454       *p = obj->forwardee();
3455     } else {
3456       assert(!obj->is_forwarded(), "invariant" );
3457       assert(cset_state.is_humongous(),
3458              "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value());
3459      _g1h->set_humongous_is_live(obj);
3460     }
3461   }
3462 };
3463 
3464 // Copying Keep Alive closure - can be called from both
3465 // serial and parallel code as long as different worker
3466 // threads utilize different G1ParScanThreadState instances
3467 // and different queues.
3468 
3469 class G1CopyingKeepAliveClosure: public OopClosure {
3470   G1CollectedHeap*         _g1h;
3471   G1ParScanThreadState*    _par_scan_state;
3472 
3473 public:
3474   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
3475                             G1ParScanThreadState* pss):
3476     _g1h(g1h),
3477     _par_scan_state(pss)
3478   {}
3479 
3480   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
3481   virtual void do_oop(      oop* p) { do_oop_work(p); }
3482 
3483   template <class T> void do_oop_work(T* p) {
3484     oop obj = RawAccess<>::oop_load(p);
3485 
3486     if (_g1h->is_in_cset_or_humongous(obj)) {
3487       // If the referent object has been forwarded (either copied
3488       // to a new location or to itself in the event of an
3489       // evacuation failure) then we need to update the reference
3490       // field and, if both reference and referent are in the G1
3491       // heap, update the RSet for the referent.
3492       //
3493       // If the referent has not been forwarded then we have to keep
3494       // it alive by policy. Therefore we have copy the referent.
3495       //
3496       // When the queue is drained (after each phase of reference processing)
3497       // the object and it's followers will be copied, the reference field set
3498       // to point to the new location, and the RSet updated.
3499       _par_scan_state->push_on_queue(p);
3500     }
3501   }
3502 };
3503 
3504 // Serial drain queue closure. Called as the 'complete_gc'
3505 // closure for each discovered list in some of the
3506 // reference processing phases.
3507 
3508 class G1STWDrainQueueClosure: public VoidClosure {
3509 protected:
3510   G1CollectedHeap* _g1h;
3511   G1ParScanThreadState* _par_scan_state;
3512 
3513   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
3514 
3515 public:
3516   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
3517     _g1h(g1h),
3518     _par_scan_state(pss)
3519   { }
3520 
3521   void do_void() {
3522     G1ParScanThreadState* const pss = par_scan_state();
3523     pss->trim_queue();
3524   }
3525 };
3526 
3527 // Parallel Reference Processing closures
3528 
3529 // Implementation of AbstractRefProcTaskExecutor for parallel reference
3530 // processing during G1 evacuation pauses.
3531 
3532 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
3533 private:
3534   G1CollectedHeap*          _g1h;
3535   G1ParScanThreadStateSet*  _pss;
3536   RefToScanQueueSet*        _queues;
3537   WorkGang*                 _workers;
3538 
3539 public:
3540   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
3541                            G1ParScanThreadStateSet* per_thread_states,
3542                            WorkGang* workers,
3543                            RefToScanQueueSet *task_queues) :
3544     _g1h(g1h),
3545     _pss(per_thread_states),
3546     _queues(task_queues),
3547     _workers(workers)
3548   {
3549     g1h->ref_processor_stw()->set_active_mt_degree(workers->active_workers());
3550   }
3551 
3552   // Executes the given task using concurrent marking worker threads.
3553   virtual void execute(ProcessTask& task, uint ergo_workers);
3554 };
3555 
3556 // Gang task for possibly parallel reference processing
3557 
3558 class G1STWRefProcTaskProxy: public AbstractGangTask {
3559   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
3560   ProcessTask&     _proc_task;
3561   G1CollectedHeap* _g1h;
3562   G1ParScanThreadStateSet* _pss;
3563   RefToScanQueueSet* _task_queues;
3564   ParallelTaskTerminator* _terminator;
3565 
3566 public:
3567   G1STWRefProcTaskProxy(ProcessTask& proc_task,
3568                         G1CollectedHeap* g1h,
3569                         G1ParScanThreadStateSet* per_thread_states,
3570                         RefToScanQueueSet *task_queues,
3571                         ParallelTaskTerminator* terminator) :
3572     AbstractGangTask("Process reference objects in parallel"),
3573     _proc_task(proc_task),
3574     _g1h(g1h),
3575     _pss(per_thread_states),
3576     _task_queues(task_queues),
3577     _terminator(terminator)
3578   {}
3579 
3580   virtual void work(uint worker_id) {
3581     // The reference processing task executed by a single worker.
3582     ResourceMark rm;
3583     HandleMark   hm;
3584 
3585     G1STWIsAliveClosure is_alive(_g1h);
3586 
3587     G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
3588     pss->set_ref_discoverer(NULL);
3589 
3590     // Keep alive closure.
3591     G1CopyingKeepAliveClosure keep_alive(_g1h, pss);
3592 
3593     // Complete GC closure
3594     G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator, G1GCPhaseTimes::ObjCopy);
3595 
3596     // Call the reference processing task's work routine.
3597     _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
3598 
3599     // Note we cannot assert that the refs array is empty here as not all
3600     // of the processing tasks (specifically phase2 - pp2_work) execute
3601     // the complete_gc closure (which ordinarily would drain the queue) so
3602     // the queue may not be empty.
3603   }
3604 };
3605 
3606 // Driver routine for parallel reference processing.
3607 // Creates an instance of the ref processing gang
3608 // task and has the worker threads execute it.
3609 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task, uint ergo_workers) {
3610   assert(_workers != NULL, "Need parallel worker threads.");
3611 
3612   assert(_workers->active_workers() >= ergo_workers,
3613          "Ergonomically chosen workers (%u) should be less than or equal to active workers (%u)",
3614          ergo_workers, _workers->active_workers());
3615   TaskTerminator terminator(ergo_workers, _queues);
3616   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, terminator.terminator());
3617 
3618   _workers->run_task(&proc_task_proxy, ergo_workers);
3619 }
3620 
3621 // End of weak reference support closures
3622 
3623 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
3624   double ref_proc_start = os::elapsedTime();
3625 
3626   ReferenceProcessor* rp = _ref_processor_stw;
3627   assert(rp->discovery_enabled(), "should have been enabled");
3628 
3629   // Closure to test whether a referent is alive.
3630   G1STWIsAliveClosure is_alive(this);
3631 
3632   // Even when parallel reference processing is enabled, the processing
3633   // of JNI refs is serial and performed serially by the current thread
3634   // rather than by a worker. The following PSS will be used for processing
3635   // JNI refs.
3636 
3637   // Use only a single queue for this PSS.
3638   G1ParScanThreadState*          pss = per_thread_states->state_for_worker(0);
3639   pss->set_ref_discoverer(NULL);
3640   assert(pss->queue_is_empty(), "pre-condition");
3641 
3642   // Keep alive closure.
3643   G1CopyingKeepAliveClosure keep_alive(this, pss);
3644 
3645   // Serial Complete GC closure
3646   G1STWDrainQueueClosure drain_queue(this, pss);
3647 
3648   // Setup the soft refs policy...
3649   rp->setup_policy(false);
3650 
3651   ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times();
3652 
3653   ReferenceProcessorStats stats;
3654   if (!rp->processing_is_mt()) {
3655     // Serial reference processing...
3656     stats = rp->process_discovered_references(&is_alive,
3657                                               &keep_alive,
3658                                               &drain_queue,
3659                                               NULL,
3660                                               pt);
3661   } else {
3662     uint no_of_gc_workers = workers()->active_workers();
3663 
3664     // Parallel reference processing
3665     assert(no_of_gc_workers <= rp->max_num_queues(),
3666            "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
3667            no_of_gc_workers,  rp->max_num_queues());
3668 
3669     G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues);
3670     stats = rp->process_discovered_references(&is_alive,
3671                                               &keep_alive,
3672                                               &drain_queue,
3673                                               &par_task_executor,
3674                                               pt);
3675   }
3676 
3677   _gc_tracer_stw->report_gc_reference_stats(stats);
3678 
3679   // We have completed copying any necessary live referent objects.
3680   assert(pss->queue_is_empty(), "both queue and overflow should be empty");
3681 
3682   make_pending_list_reachable();
3683 
3684   rp->verify_no_references_recorded();
3685 
3686   double ref_proc_time = os::elapsedTime() - ref_proc_start;
3687   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
3688 }
3689 
3690 void G1CollectedHeap::make_pending_list_reachable() {
3691   if (collector_state()->in_initial_mark_gc()) {
3692     oop pll_head = Universe::reference_pending_list();
3693     if (pll_head != NULL) {
3694       // Any valid worker id is fine here as we are in the VM thread and single-threaded.
3695       _cm->mark_in_next_bitmap(0 /* worker_id */, pll_head);
3696     }
3697   }
3698 }
3699 
3700 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) {
3701   double merge_pss_time_start = os::elapsedTime();
3702   per_thread_states->flush();
3703   g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0);
3704 }
3705 
3706 void G1CollectedHeap::pre_evacuate_collection_set() {
3707   _expand_heap_after_alloc_failure = true;
3708   _evacuation_failed = false;
3709 
3710   // Disable the hot card cache.
3711   _hot_card_cache->reset_hot_cache_claimed_index();
3712   _hot_card_cache->set_use_cache(false);
3713 
3714   g1_rem_set()->prepare_for_oops_into_collection_set_do();
3715   _preserved_marks_set.assert_empty();
3716 
3717   G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
3718 
3719   // InitialMark needs claim bits to keep track of the marked-through CLDs.
3720   if (collector_state()->in_initial_mark_gc()) {
3721     double start_clear_claimed_marks = os::elapsedTime();
3722 
3723     ClassLoaderDataGraph::clear_claimed_marks();
3724 
3725     double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0;
3726     phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms);
3727   }
3728 }
3729 
3730 void G1CollectedHeap::evacuate_collection_set(G1ParScanThreadStateSet* per_thread_states) {
3731   // Should G1EvacuationFailureALot be in effect for this GC?
3732   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
3733 
3734   assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
3735 
3736   G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
3737 
3738   double start_par_time_sec = os::elapsedTime();
3739   double end_par_time_sec;
3740 
3741   {
3742     const uint n_workers = workers()->active_workers();
3743     G1RootProcessor root_processor(this, n_workers);
3744     G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers);
3745 
3746     workers()->run_task(&g1_par_task);
3747     end_par_time_sec = os::elapsedTime();
3748 
3749     // Closing the inner scope will execute the destructor
3750     // for the G1RootProcessor object. We record the current
3751     // elapsed time before closing the scope so that time
3752     // taken for the destructor is NOT included in the
3753     // reported parallel time.
3754   }
3755 
3756   double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
3757   phase_times->record_par_time(par_time_ms);
3758 
3759   double code_root_fixup_time_ms =
3760         (os::elapsedTime() - end_par_time_sec) * 1000.0;
3761   phase_times->record_code_root_fixup_time(code_root_fixup_time_ms);
3762 }
3763 
3764 class G1EvacuateOptionalRegionTask : public AbstractGangTask {
3765   G1CollectedHeap* _g1h;
3766   G1ParScanThreadStateSet* _per_thread_states;
3767   G1OptionalCSet* _optional;
3768   RefToScanQueueSet* _queues;
3769   ParallelTaskTerminator _terminator;
3770 
3771   Tickspan trim_ticks(G1ParScanThreadState* pss) {
3772     Tickspan copy_time = pss->trim_ticks();
3773     pss->reset_trim_ticks();
3774     return copy_time;
3775   }
3776 
3777   void scan_roots(G1ParScanThreadState* pss, uint worker_id) {
3778     G1EvacuationRootClosures* root_cls = pss->closures();
3779     G1ScanObjsDuringScanRSClosure obj_cl(_g1h, pss);
3780 
3781     size_t scanned = 0;
3782     size_t claimed = 0;
3783     size_t skipped = 0;
3784     size_t used_memory = 0;
3785 
3786     Ticks    start = Ticks::now();
3787     Tickspan copy_time;
3788 
3789     for (uint i = _optional->current_index(); i < _optional->current_limit(); i++) {
3790       HeapRegion* hr = _optional->region_at(i);
3791       G1ScanRSForOptionalClosure scan_opt_cl(&obj_cl);
3792       pss->oops_into_optional_region(hr)->oops_do(&scan_opt_cl, root_cls->raw_strong_oops());
3793       copy_time += trim_ticks(pss);
3794 
3795       G1ScanRSForRegionClosure scan_rs_cl(_g1h->g1_rem_set()->scan_state(), &obj_cl, pss, G1GCPhaseTimes::OptScanRS, worker_id);
3796       scan_rs_cl.do_heap_region(hr);
3797       copy_time += trim_ticks(pss);
3798       scanned += scan_rs_cl.cards_scanned();
3799       claimed += scan_rs_cl.cards_claimed();
3800       skipped += scan_rs_cl.cards_skipped();
3801 
3802       // Chunk lists for this region is no longer needed.
3803       used_memory += pss->oops_into_optional_region(hr)->used_memory();
3804     }
3805 
3806     Tickspan scan_time = (Ticks::now() - start) - copy_time;
3807     G1GCPhaseTimes* p = _g1h->g1_policy()->phase_times();
3808     p->record_or_add_time_secs(G1GCPhaseTimes::OptScanRS, worker_id, scan_time.seconds());
3809     p->record_or_add_time_secs(G1GCPhaseTimes::OptObjCopy, worker_id, copy_time.seconds());
3810 
3811     p->record_or_add_thread_work_item(G1GCPhaseTimes::OptScanRS, worker_id, scanned, G1GCPhaseTimes::OptCSetScannedCards);
3812     p->record_or_add_thread_work_item(G1GCPhaseTimes::OptScanRS, worker_id, claimed, G1GCPhaseTimes::OptCSetClaimedCards);
3813     p->record_or_add_thread_work_item(G1GCPhaseTimes::OptScanRS, worker_id, skipped, G1GCPhaseTimes::OptCSetSkippedCards);
3814     p->record_or_add_thread_work_item(G1GCPhaseTimes::OptScanRS, worker_id, used_memory, G1GCPhaseTimes::OptCSetUsedMemory);
3815   }
3816 
3817   void evacuate_live_objects(G1ParScanThreadState* pss, uint worker_id) {
3818     Ticks start = Ticks::now();
3819     G1ParEvacuateFollowersClosure cl(_g1h, pss, _queues, &_terminator, G1GCPhaseTimes::OptObjCopy);
3820     cl.do_void();
3821 
3822     Tickspan evac_time = (Ticks::now() - start);
3823     G1GCPhaseTimes* p = _g1h->g1_policy()->phase_times();
3824     p->record_or_add_time_secs(G1GCPhaseTimes::OptObjCopy, worker_id, evac_time.seconds());
3825     assert(pss->trim_ticks().seconds() == 0.0, "Unexpected partial trimming done during optional evacuation");
3826   }
3827 
3828  public:
3829   G1EvacuateOptionalRegionTask(G1CollectedHeap* g1h,
3830                                G1ParScanThreadStateSet* per_thread_states,
3831                                G1OptionalCSet* cset,
3832                                RefToScanQueueSet* queues,
3833                                uint n_workers) :
3834     AbstractGangTask("G1 Evacuation Optional Region Task"),
3835     _g1h(g1h),
3836     _per_thread_states(per_thread_states),
3837     _optional(cset),
3838     _queues(queues),
3839     _terminator(n_workers, _queues) {
3840   }
3841 
3842   void work(uint worker_id) {
3843     ResourceMark rm;
3844     HandleMark  hm;
3845 
3846     G1ParScanThreadState* pss = _per_thread_states->state_for_worker(worker_id);
3847     pss->set_ref_discoverer(_g1h->ref_processor_stw());
3848 
3849     scan_roots(pss, worker_id);
3850     evacuate_live_objects(pss, worker_id);
3851   }
3852 };
3853 
3854 void G1CollectedHeap::evacuate_optional_regions(G1ParScanThreadStateSet* per_thread_states, G1OptionalCSet* ocset) {
3855   class G1MarkScope : public MarkScope {};
3856   G1MarkScope code_mark_scope;
3857 
3858   G1EvacuateOptionalRegionTask task(this, per_thread_states, ocset, _task_queues, workers()->active_workers());
3859   workers()->run_task(&task);
3860 }
3861 
3862 void G1CollectedHeap::evacuate_optional_collection_set(G1ParScanThreadStateSet* per_thread_states) {
3863   G1OptionalCSet optional_cset(&_collection_set, per_thread_states);
3864   if (optional_cset.is_empty()) {
3865     return;
3866   }
3867 
3868   if (evacuation_failed()) {
3869     return;
3870   }
3871 
3872   G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
3873   const double gc_start_time_ms = phase_times->cur_collection_start_sec() * 1000.0;
3874 
3875   double start_time_sec = os::elapsedTime();
3876 
3877   do {
3878     double time_used_ms = os::elapsedTime() * 1000.0 - gc_start_time_ms;
3879     double time_left_ms = MaxGCPauseMillis - time_used_ms;
3880 
3881     if (time_left_ms < 0) {
3882       log_trace(gc, ergo, cset)("Skipping %u optional regions, pause time exceeded %.3fms", optional_cset.size(), time_used_ms);
3883       break;
3884     }
3885 
3886     optional_cset.prepare_evacuation(time_left_ms * _g1_policy->optional_evacuation_fraction());
3887     if (optional_cset.prepare_failed()) {
3888       log_trace(gc, ergo, cset)("Skipping %u optional regions, no regions can be evacuated in %.3fms", optional_cset.size(), time_left_ms);
3889       break;
3890     }
3891 
3892     evacuate_optional_regions(per_thread_states, &optional_cset);
3893 
3894     optional_cset.complete_evacuation();
3895     if (optional_cset.evacuation_failed()) {
3896       break;
3897     }
3898   } while (!optional_cset.is_empty());
3899 
3900   phase_times->record_optional_evacuation((os::elapsedTime() - start_time_sec) * 1000.0);
3901 }
3902 
3903 void G1CollectedHeap::post_evacuate_collection_set(G1EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
3904   // Also cleans the card table from temporary duplicate detection information used
3905   // during UpdateRS/ScanRS.
3906   g1_rem_set()->cleanup_after_oops_into_collection_set_do();
3907 
3908   // Process any discovered reference objects - we have
3909   // to do this _before_ we retire the GC alloc regions
3910   // as we may have to copy some 'reachable' referent
3911   // objects (and their reachable sub-graphs) that were
3912   // not copied during the pause.
3913   process_discovered_references(per_thread_states);
3914 
3915   G1STWIsAliveClosure is_alive(this);
3916   G1KeepAliveClosure keep_alive(this);
3917 
3918   WeakProcessor::weak_oops_do(workers(), &is_alive, &keep_alive,
3919                               g1_policy()->phase_times()->weak_phase_times());
3920 
3921   if (G1StringDedup::is_enabled()) {
3922     double string_dedup_time_ms = os::elapsedTime();
3923 
3924     string_dedup_cleaning(&is_alive, &keep_alive, g1_policy()->phase_times());
3925 
3926     double string_cleanup_time_ms = (os::elapsedTime() - string_dedup_time_ms) * 1000.0;
3927     g1_policy()->phase_times()->record_string_deduplication_time(string_cleanup_time_ms);
3928   }
3929 
3930   if (evacuation_failed()) {
3931     restore_after_evac_failure();
3932 
3933     // Reset the G1EvacuationFailureALot counters and flags
3934     // Note: the values are reset only when an actual
3935     // evacuation failure occurs.
3936     NOT_PRODUCT(reset_evacuation_should_fail();)
3937   }
3938 
3939   _preserved_marks_set.assert_empty();
3940 
3941   _allocator->release_gc_alloc_regions(evacuation_info);
3942 
3943   merge_per_thread_state_info(per_thread_states);
3944 
3945   // Reset and re-enable the hot card cache.
3946   // Note the counts for the cards in the regions in the
3947   // collection set are reset when the collection set is freed.
3948   _hot_card_cache->reset_hot_cache();
3949   _hot_card_cache->set_use_cache(true);
3950 
3951   purge_code_root_memory();
3952 
3953   redirty_logged_cards();
3954 #if COMPILER2_OR_JVMCI
3955   double start = os::elapsedTime();
3956   DerivedPointerTable::update_pointers();
3957   g1_policy()->phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0);
3958 #endif
3959   g1_policy()->print_age_table();
3960 }
3961 
3962 void G1CollectedHeap::record_obj_copy_mem_stats() {
3963   g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
3964 
3965   _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
3966                                                create_g1_evac_summary(&_old_evac_stats));
3967 }
3968 
3969 void G1CollectedHeap::free_region(HeapRegion* hr,
3970                                   FreeRegionList* free_list,
3971                                   bool skip_remset,
3972                                   bool skip_hot_card_cache,
3973                                   bool locked) {
3974   assert(!hr->is_free(), "the region should not be free");
3975   assert(!hr->is_empty(), "the region should not be empty");
3976   assert(_hrm->is_available(hr->hrm_index()), "region should be committed");
3977   assert(free_list != NULL, "pre-condition");
3978 
3979   if (G1VerifyBitmaps) {
3980     MemRegion mr(hr->bottom(), hr->end());
3981     concurrent_mark()->clear_range_in_prev_bitmap(mr);
3982   }
3983 
3984   // Clear the card counts for this region.
3985   // Note: we only need to do this if the region is not young
3986   // (since we don't refine cards in young regions).
3987   if (!skip_hot_card_cache && !hr->is_young()) {
3988     _hot_card_cache->reset_card_counts(hr);
3989   }
3990   hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */);
3991   _g1_policy->remset_tracker()->update_at_free(hr);
3992   free_list->add_ordered(hr);
3993 }
3994 
3995 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
3996                                             FreeRegionList* free_list) {
3997   assert(hr->is_humongous(), "this is only for humongous regions");
3998   assert(free_list != NULL, "pre-condition");
3999   hr->clear_humongous();
4000   free_region(hr, free_list, false /* skip_remset */, false /* skip_hcc */, true /* locked */);
4001 }
4002 
4003 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed,
4004                                            const uint humongous_regions_removed) {
4005   if (old_regions_removed > 0 || humongous_regions_removed > 0) {
4006     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4007     _old_set.bulk_remove(old_regions_removed);
4008     _humongous_set.bulk_remove(humongous_regions_removed);
4009   }
4010 
4011 }
4012 
4013 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
4014   assert(list != NULL, "list can't be null");
4015   if (!list->is_empty()) {
4016     MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4017     _hrm->insert_list_into_free_list(list);
4018   }
4019 }
4020 
4021 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
4022   decrease_used(bytes);
4023 }
4024 
4025 class G1FreeCollectionSetTask : public AbstractGangTask {
4026 private:
4027 
4028   // Closure applied to all regions in the collection set to do work that needs to
4029   // be done serially in a single thread.
4030   class G1SerialFreeCollectionSetClosure : public HeapRegionClosure {
4031   private:
4032     G1EvacuationInfo* _evacuation_info;
4033     const size_t* _surviving_young_words;
4034 
4035     // Bytes used in successfully evacuated regions before the evacuation.
4036     size_t _before_used_bytes;
4037     // Bytes used in unsucessfully evacuated regions before the evacuation
4038     size_t _after_used_bytes;
4039 
4040     size_t _bytes_allocated_in_old_since_last_gc;
4041 
4042     size_t _failure_used_words;
4043     size_t _failure_waste_words;
4044 
4045     FreeRegionList _local_free_list;
4046   public:
4047     G1SerialFreeCollectionSetClosure(G1EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4048       HeapRegionClosure(),
4049       _evacuation_info(evacuation_info),
4050       _surviving_young_words(surviving_young_words),
4051       _before_used_bytes(0),
4052       _after_used_bytes(0),
4053       _bytes_allocated_in_old_since_last_gc(0),
4054       _failure_used_words(0),
4055       _failure_waste_words(0),
4056       _local_free_list("Local Region List for CSet Freeing") {
4057     }
4058 
4059     virtual bool do_heap_region(HeapRegion* r) {
4060       G1CollectedHeap* g1h = G1CollectedHeap::heap();
4061 
4062       assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index());
4063       g1h->clear_in_cset(r);
4064 
4065       if (r->is_young()) {
4066         assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(),
4067                "Young index %d is wrong for region %u of type %s with %u young regions",
4068                r->young_index_in_cset(),
4069                r->hrm_index(),
4070                r->get_type_str(),
4071                g1h->collection_set()->young_region_length());
4072         size_t words_survived = _surviving_young_words[r->young_index_in_cset()];
4073         r->record_surv_words_in_group(words_survived);
4074       }
4075 
4076       if (!r->evacuation_failed()) {
4077         assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index());
4078         _before_used_bytes += r->used();
4079         g1h->free_region(r,
4080                          &_local_free_list,
4081                          true, /* skip_remset */
4082                          true, /* skip_hot_card_cache */
4083                          true  /* locked */);
4084       } else {
4085         r->uninstall_surv_rate_group();
4086         r->set_young_index_in_cset(-1);
4087         r->set_evacuation_failed(false);
4088         // When moving a young gen region to old gen, we "allocate" that whole region
4089         // there. This is in addition to any already evacuated objects. Notify the
4090         // policy about that.
4091         // Old gen regions do not cause an additional allocation: both the objects
4092         // still in the region and the ones already moved are accounted for elsewhere.
4093         if (r->is_young()) {
4094           _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes;
4095         }
4096         // The region is now considered to be old.
4097         r->set_old();
4098         // Do some allocation statistics accounting. Regions that failed evacuation
4099         // are always made old, so there is no need to update anything in the young
4100         // gen statistics, but we need to update old gen statistics.
4101         size_t used_words = r->marked_bytes() / HeapWordSize;
4102 
4103         _failure_used_words += used_words;
4104         _failure_waste_words += HeapRegion::GrainWords - used_words;
4105 
4106         g1h->old_set_add(r);
4107         _after_used_bytes += r->used();
4108       }
4109       return false;
4110     }
4111 
4112     void complete_work() {
4113       G1CollectedHeap* g1h = G1CollectedHeap::heap();
4114 
4115       _evacuation_info->set_regions_freed(_local_free_list.length());
4116       _evacuation_info->increment_collectionset_used_after(_after_used_bytes);
4117 
4118       g1h->prepend_to_freelist(&_local_free_list);
4119       g1h->decrement_summary_bytes(_before_used_bytes);
4120 
4121       G1Policy* policy = g1h->g1_policy();
4122       policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc);
4123 
4124       g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words);
4125     }
4126   };
4127 
4128   G1CollectionSet* _collection_set;
4129   G1SerialFreeCollectionSetClosure _cl;
4130   const size_t* _surviving_young_words;
4131 
4132   size_t _rs_lengths;
4133 
4134   volatile jint _serial_work_claim;
4135 
4136   struct WorkItem {
4137     uint region_idx;
4138     bool is_young;
4139     bool evacuation_failed;
4140 
4141     WorkItem(HeapRegion* r) {
4142       region_idx = r->hrm_index();
4143       is_young = r->is_young();
4144       evacuation_failed = r->evacuation_failed();
4145     }
4146   };
4147 
4148   volatile size_t _parallel_work_claim;
4149   size_t _num_work_items;
4150   WorkItem* _work_items;
4151 
4152   void do_serial_work() {
4153     // Need to grab the lock to be allowed to modify the old region list.
4154     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4155     _collection_set->iterate(&_cl);
4156   }
4157 
4158   void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) {
4159     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4160 
4161     HeapRegion* r = g1h->region_at(region_idx);
4162     assert(!g1h->is_on_master_free_list(r), "sanity");
4163 
4164     Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths);
4165 
4166     if (!is_young) {
4167       g1h->_hot_card_cache->reset_card_counts(r);
4168     }
4169 
4170     if (!evacuation_failed) {
4171       r->rem_set()->clear_locked();
4172     }
4173   }
4174 
4175   class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure {
4176   private:
4177     size_t _cur_idx;
4178     WorkItem* _work_items;
4179   public:
4180     G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { }
4181 
4182     virtual bool do_heap_region(HeapRegion* r) {
4183       _work_items[_cur_idx++] = WorkItem(r);
4184       return false;
4185     }
4186   };
4187 
4188   void prepare_work() {
4189     G1PrepareFreeCollectionSetClosure cl(_work_items);
4190     _collection_set->iterate(&cl);
4191   }
4192 
4193   void complete_work() {
4194     _cl.complete_work();
4195 
4196     G1Policy* policy = G1CollectedHeap::heap()->g1_policy();
4197     policy->record_max_rs_lengths(_rs_lengths);
4198     policy->cset_regions_freed();
4199   }
4200 public:
4201   G1FreeCollectionSetTask(G1CollectionSet* collection_set, G1EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4202     AbstractGangTask("G1 Free Collection Set"),
4203     _collection_set(collection_set),
4204     _cl(evacuation_info, surviving_young_words),
4205     _surviving_young_words(surviving_young_words),
4206     _rs_lengths(0),
4207     _serial_work_claim(0),
4208     _parallel_work_claim(0),
4209     _num_work_items(collection_set->region_length()),
4210     _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) {
4211     prepare_work();
4212   }
4213 
4214   ~G1FreeCollectionSetTask() {
4215     complete_work();
4216     FREE_C_HEAP_ARRAY(WorkItem, _work_items);
4217   }
4218 
4219   // Chunk size for work distribution. The chosen value has been determined experimentally
4220   // to be a good tradeoff between overhead and achievable parallelism.
4221   static uint chunk_size() { return 32; }
4222 
4223   virtual void work(uint worker_id) {
4224     G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
4225 
4226     // Claim serial work.
4227     if (_serial_work_claim == 0) {
4228       jint value = Atomic::add(1, &_serial_work_claim) - 1;
4229       if (value == 0) {
4230         double serial_time = os::elapsedTime();
4231         do_serial_work();
4232         timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0);
4233       }
4234     }
4235 
4236     // Start parallel work.
4237     double young_time = 0.0;
4238     bool has_young_time = false;
4239     double non_young_time = 0.0;
4240     bool has_non_young_time = false;
4241 
4242     while (true) {
4243       size_t end = Atomic::add(chunk_size(), &_parallel_work_claim);
4244       size_t cur = end - chunk_size();
4245 
4246       if (cur >= _num_work_items) {
4247         break;
4248       }
4249 
4250       EventGCPhaseParallel event;
4251       double start_time = os::elapsedTime();
4252 
4253       end = MIN2(end, _num_work_items);
4254 
4255       for (; cur < end; cur++) {
4256         bool is_young = _work_items[cur].is_young;
4257 
4258         do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed);
4259 
4260         double end_time = os::elapsedTime();
4261         double time_taken = end_time - start_time;
4262         if (is_young) {
4263           young_time += time_taken;
4264           has_young_time = true;
4265           event.commit(GCId::current(), worker_id, G1GCPhaseTimes::phase_name(G1GCPhaseTimes::YoungFreeCSet));
4266         } else {
4267           non_young_time += time_taken;
4268           has_non_young_time = true;
4269           event.commit(GCId::current(), worker_id, G1GCPhaseTimes::phase_name(G1GCPhaseTimes::NonYoungFreeCSet));
4270         }
4271         start_time = end_time;
4272       }
4273     }
4274 
4275     if (has_young_time) {
4276       timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time);
4277     }
4278     if (has_non_young_time) {
4279       timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, non_young_time);
4280     }
4281   }
4282 };
4283 
4284 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, G1EvacuationInfo& evacuation_info, const size_t* surviving_young_words) {
4285   _eden.clear();
4286 
4287   double free_cset_start_time = os::elapsedTime();
4288 
4289   {
4290     uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U);
4291     uint const num_workers = MIN2(workers()->active_workers(), num_chunks);
4292 
4293     G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words);
4294 
4295     log_debug(gc, ergo)("Running %s using %u workers for collection set length %u",
4296                         cl.name(),
4297                         num_workers,
4298                         _collection_set.region_length());
4299     workers()->run_task(&cl, num_workers);
4300   }
4301   g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0);
4302 
4303   collection_set->clear();
4304 }
4305 
4306 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
4307  private:
4308   FreeRegionList* _free_region_list;
4309   HeapRegionSet* _proxy_set;
4310   uint _humongous_objects_reclaimed;
4311   uint _humongous_regions_reclaimed;
4312   size_t _freed_bytes;
4313  public:
4314 
4315   G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
4316     _free_region_list(free_region_list), _proxy_set(NULL), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) {
4317   }
4318 
4319   virtual bool do_heap_region(HeapRegion* r) {
4320     if (!r->is_starts_humongous()) {
4321       return false;
4322     }
4323 
4324     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4325 
4326     oop obj = (oop)r->bottom();
4327     G1CMBitMap* next_bitmap = g1h->concurrent_mark()->next_mark_bitmap();
4328 
4329     // The following checks whether the humongous object is live are sufficient.
4330     // The main additional check (in addition to having a reference from the roots
4331     // or the young gen) is whether the humongous object has a remembered set entry.
4332     //
4333     // A humongous object cannot be live if there is no remembered set for it
4334     // because:
4335     // - there can be no references from within humongous starts regions referencing
4336     // the object because we never allocate other objects into them.
4337     // (I.e. there are no intra-region references that may be missed by the
4338     // remembered set)
4339     // - as soon there is a remembered set entry to the humongous starts region
4340     // (i.e. it has "escaped" to an old object) this remembered set entry will stay
4341     // until the end of a concurrent mark.
4342     //
4343     // It is not required to check whether the object has been found dead by marking
4344     // or not, in fact it would prevent reclamation within a concurrent cycle, as
4345     // all objects allocated during that time are considered live.
4346     // SATB marking is even more conservative than the remembered set.
4347     // So if at this point in the collection there is no remembered set entry,
4348     // nobody has a reference to it.
4349     // At the start of collection we flush all refinement logs, and remembered sets
4350     // are completely up-to-date wrt to references to the humongous object.
4351     //
4352     // Other implementation considerations:
4353     // - never consider object arrays at this time because they would pose
4354     // considerable effort for cleaning up the the remembered sets. This is
4355     // required because stale remembered sets might reference locations that
4356     // are currently allocated into.
4357     uint region_idx = r->hrm_index();
4358     if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
4359         !r->rem_set()->is_empty()) {
4360       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",
4361                                region_idx,
4362                                (size_t)obj->size() * HeapWordSize,
4363                                p2i(r->bottom()),
4364                                r->rem_set()->occupied(),
4365                                r->rem_set()->strong_code_roots_list_length(),
4366                                next_bitmap->is_marked(r->bottom()),
4367                                g1h->is_humongous_reclaim_candidate(region_idx),
4368                                obj->is_typeArray()
4369                               );
4370       return false;
4371     }
4372 
4373     guarantee(obj->is_typeArray(),
4374               "Only eagerly reclaiming type arrays is supported, but the object "
4375               PTR_FORMAT " is not.", p2i(r->bottom()));
4376 
4377     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",
4378                              region_idx,
4379                              (size_t)obj->size() * HeapWordSize,
4380                              p2i(r->bottom()),
4381                              r->rem_set()->occupied(),
4382                              r->rem_set()->strong_code_roots_list_length(),
4383                              next_bitmap->is_marked(r->bottom()),
4384                              g1h->is_humongous_reclaim_candidate(region_idx),
4385                              obj->is_typeArray()
4386                             );
4387 
4388     G1ConcurrentMark* const cm = g1h->concurrent_mark();
4389     cm->humongous_object_eagerly_reclaimed(r);
4390     assert(!cm->is_marked_in_prev_bitmap(obj) && !cm->is_marked_in_next_bitmap(obj),
4391            "Eagerly reclaimed humongous region %u should not be marked at all but is in prev %s next %s",
4392            region_idx,
4393            BOOL_TO_STR(cm->is_marked_in_prev_bitmap(obj)),
4394            BOOL_TO_STR(cm->is_marked_in_next_bitmap(obj)));
4395     _humongous_objects_reclaimed++;
4396     do {
4397       HeapRegion* next = g1h->next_region_in_humongous(r);
4398       _freed_bytes += r->used();
4399       r->set_containing_set(NULL);
4400       _humongous_regions_reclaimed++;
4401       g1h->free_humongous_region(r, _free_region_list);
4402       r = next;
4403     } while (r != NULL);
4404 
4405     return false;
4406   }
4407 
4408   uint humongous_objects_reclaimed() {
4409     return _humongous_objects_reclaimed;
4410   }
4411 
4412   uint humongous_regions_reclaimed() {
4413     return _humongous_regions_reclaimed;
4414   }
4415 
4416   size_t bytes_freed() const {
4417     return _freed_bytes;
4418   }
4419 };
4420 
4421 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
4422   assert_at_safepoint_on_vm_thread();
4423 
4424   if (!G1EagerReclaimHumongousObjects ||
4425       (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) {
4426     g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
4427     return;
4428   }
4429 
4430   double start_time = os::elapsedTime();
4431 
4432   FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
4433 
4434   G1FreeHumongousRegionClosure cl(&local_cleanup_list);
4435   heap_region_iterate(&cl);
4436 
4437   remove_from_old_sets(0, cl.humongous_regions_reclaimed());
4438 
4439   G1HRPrinter* hrp = hr_printer();
4440   if (hrp->is_active()) {
4441     FreeRegionListIterator iter(&local_cleanup_list);
4442     while (iter.more_available()) {
4443       HeapRegion* hr = iter.get_next();
4444       hrp->cleanup(hr);
4445     }
4446   }
4447 
4448   prepend_to_freelist(&local_cleanup_list);
4449   decrement_summary_bytes(cl.bytes_freed());
4450 
4451   g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
4452                                                                     cl.humongous_objects_reclaimed());
4453 }
4454 
4455 class G1AbandonCollectionSetClosure : public HeapRegionClosure {
4456 public:
4457   virtual bool do_heap_region(HeapRegion* r) {
4458     assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index());
4459     G1CollectedHeap::heap()->clear_in_cset(r);
4460     r->set_young_index_in_cset(-1);
4461     return false;
4462   }
4463 };
4464 
4465 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) {
4466   G1AbandonCollectionSetClosure cl;
4467   collection_set->iterate(&cl);
4468 
4469   collection_set->clear();
4470   collection_set->stop_incremental_building();
4471 }
4472 
4473 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
4474   return _allocator->is_retained_old_region(hr);
4475 }
4476 
4477 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
4478   _eden.add(hr);
4479   _g1_policy->set_region_eden(hr);
4480 }
4481 
4482 #ifdef ASSERT
4483 
4484 class NoYoungRegionsClosure: public HeapRegionClosure {
4485 private:
4486   bool _success;
4487 public:
4488   NoYoungRegionsClosure() : _success(true) { }
4489   bool do_heap_region(HeapRegion* r) {
4490     if (r->is_young()) {
4491       log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
4492                             p2i(r->bottom()), p2i(r->end()));
4493       _success = false;
4494     }
4495     return false;
4496   }
4497   bool success() { return _success; }
4498 };
4499 
4500 bool G1CollectedHeap::check_young_list_empty() {
4501   bool ret = (young_regions_count() == 0);
4502 
4503   NoYoungRegionsClosure closure;
4504   heap_region_iterate(&closure);
4505   ret = ret && closure.success();
4506 
4507   return ret;
4508 }
4509 
4510 #endif // ASSERT
4511 
4512 class TearDownRegionSetsClosure : public HeapRegionClosure {
4513   HeapRegionSet *_old_set;
4514 
4515 public:
4516   TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
4517 
4518   bool do_heap_region(HeapRegion* r) {
4519     if (r->is_old()) {
4520       _old_set->remove(r);
4521     } else if(r->is_young()) {
4522       r->uninstall_surv_rate_group();
4523     } else {
4524       // We ignore free regions, we'll empty the free list afterwards.
4525       // We ignore humongous and archive regions, we're not tearing down these
4526       // sets.
4527       assert(r->is_archive() || r->is_free() || r->is_humongous(),
4528              "it cannot be another type");
4529     }
4530     return false;
4531   }
4532 
4533   ~TearDownRegionSetsClosure() {
4534     assert(_old_set->is_empty(), "post-condition");
4535   }
4536 };
4537 
4538 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
4539   assert_at_safepoint_on_vm_thread();
4540 
4541   if (!free_list_only) {
4542     TearDownRegionSetsClosure cl(&_old_set);
4543     heap_region_iterate(&cl);
4544 
4545     // Note that emptying the _young_list is postponed and instead done as
4546     // the first step when rebuilding the regions sets again. The reason for
4547     // this is that during a full GC string deduplication needs to know if
4548     // a collected region was young or old when the full GC was initiated.
4549   }
4550   _hrm->remove_all_free_regions();
4551 }
4552 
4553 void G1CollectedHeap::increase_used(size_t bytes) {
4554   _summary_bytes_used += bytes;
4555 }
4556 
4557 void G1CollectedHeap::decrease_used(size_t bytes) {
4558   assert(_summary_bytes_used >= bytes,
4559          "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
4560          _summary_bytes_used, bytes);
4561   _summary_bytes_used -= bytes;
4562 }
4563 
4564 void G1CollectedHeap::set_used(size_t bytes) {
4565   _summary_bytes_used = bytes;
4566 }
4567 
4568 class RebuildRegionSetsClosure : public HeapRegionClosure {
4569 private:
4570   bool _free_list_only;
4571 
4572   HeapRegionSet* _old_set;
4573   HeapRegionManager* _hrm;
4574 
4575   size_t _total_used;
4576 
4577 public:
4578   RebuildRegionSetsClosure(bool free_list_only,
4579                            HeapRegionSet* old_set,
4580                            HeapRegionManager* hrm) :
4581     _free_list_only(free_list_only),
4582     _old_set(old_set), _hrm(hrm), _total_used(0) {
4583     assert(_hrm->num_free_regions() == 0, "pre-condition");
4584     if (!free_list_only) {
4585       assert(_old_set->is_empty(), "pre-condition");
4586     }
4587   }
4588 
4589   bool do_heap_region(HeapRegion* r) {
4590     if (r->is_empty()) {
4591       assert(r->rem_set()->is_empty(), "Empty regions should have empty remembered sets.");
4592       // Add free regions to the free list
4593       r->set_free();
4594       _hrm->insert_into_free_list(r);
4595     } else if (!_free_list_only) {
4596       assert(r->rem_set()->is_empty(), "At this point remembered sets must have been cleared.");
4597 
4598       if (r->is_archive() || r->is_humongous()) {
4599         // We ignore archive and humongous regions. We left these sets unchanged.
4600       } else {
4601         assert(r->is_young() || r->is_free() || r->is_old(), "invariant");
4602         // We now move all (non-humongous, non-old, non-archive) regions to old gen, and register them as such.
4603         r->move_to_old();
4604         _old_set->add(r);
4605       }
4606       _total_used += r->used();
4607     }
4608 
4609     return false;
4610   }
4611 
4612   size_t total_used() {
4613     return _total_used;
4614   }
4615 };
4616 
4617 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
4618   assert_at_safepoint_on_vm_thread();
4619 
4620   if (!free_list_only) {
4621     _eden.clear();
4622     _survivor.clear();
4623   }
4624 
4625   RebuildRegionSetsClosure cl(free_list_only, &_old_set, _hrm);
4626   heap_region_iterate(&cl);
4627 
4628   if (!free_list_only) {
4629     set_used(cl.total_used());
4630     if (_archive_allocator != NULL) {
4631       _archive_allocator->clear_used();
4632     }
4633   }
4634   assert(used() == recalculate_used(),
4635          "inconsistent used(), value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT,
4636          used(), recalculate_used());
4637 }
4638 
4639 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
4640   HeapRegion* hr = heap_region_containing(p);
4641   return hr->is_in(p);
4642 }
4643 
4644 // Methods for the mutator alloc region
4645 
4646 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
4647                                                       bool force) {
4648   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
4649   bool should_allocate = g1_policy()->should_allocate_mutator_region();
4650   if (force || should_allocate) {
4651     HeapRegion* new_alloc_region = new_region(word_size,
4652                                               HeapRegionType::Eden,
4653                                               false /* do_expand */);
4654     if (new_alloc_region != NULL) {
4655       set_region_short_lived_locked(new_alloc_region);
4656       _hr_printer.alloc(new_alloc_region, !should_allocate);
4657       _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region);
4658       _g1_policy->remset_tracker()->update_at_allocate(new_alloc_region);
4659       return new_alloc_region;
4660     }
4661   }
4662   return NULL;
4663 }
4664 
4665 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
4666                                                   size_t allocated_bytes) {
4667   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
4668   assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
4669 
4670   collection_set()->add_eden_region(alloc_region);
4671   increase_used(allocated_bytes);
4672   _hr_printer.retire(alloc_region);
4673   // We update the eden sizes here, when the region is retired,
4674   // instead of when it's allocated, since this is the point that its
4675   // used space has been recorded in _summary_bytes_used.
4676   g1mm()->update_eden_size();
4677 }
4678 
4679 // Methods for the GC alloc regions
4680 
4681 bool G1CollectedHeap::has_more_regions(InCSetState dest) {
4682   if (dest.is_old()) {
4683     return true;
4684   } else {
4685     return survivor_regions_count() < g1_policy()->max_survivor_regions();
4686   }
4687 }
4688 
4689 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) {
4690   assert(FreeList_lock->owned_by_self(), "pre-condition");
4691 
4692   if (!has_more_regions(dest)) {
4693     return NULL;
4694   }
4695 
4696   HeapRegionType type;
4697   if (dest.is_young()) {
4698     type = HeapRegionType::Survivor;
4699   } else {
4700     type = HeapRegionType::Old;
4701   }
4702 
4703   HeapRegion* new_alloc_region = new_region(word_size,
4704                                             type,
4705                                             true /* do_expand */);
4706 
4707   if (new_alloc_region != NULL) {
4708     if (type.is_survivor()) {
4709       new_alloc_region->set_survivor();
4710       _survivor.add(new_alloc_region);
4711       _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region);
4712     } else {
4713       new_alloc_region->set_old();
4714       _verifier->check_bitmaps("Old Region Allocation", new_alloc_region);
4715     }
4716     _g1_policy->remset_tracker()->update_at_allocate(new_alloc_region);
4717     _hr_printer.alloc(new_alloc_region);
4718     return new_alloc_region;
4719   }
4720   return NULL;
4721 }
4722 
4723 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
4724                                              size_t allocated_bytes,
4725                                              InCSetState dest) {
4726   g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
4727   if (dest.is_old()) {
4728     old_set_add(alloc_region);
4729   }
4730 
4731   bool const during_im = collector_state()->in_initial_mark_gc();
4732   if (during_im && allocated_bytes > 0) {
4733     _cm->root_regions()->add(alloc_region);
4734   }
4735   _hr_printer.retire(alloc_region);
4736 }
4737 
4738 HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
4739   bool expanded = false;
4740   uint index = _hrm->find_highest_free(&expanded);
4741 
4742   if (index != G1_NO_HRM_INDEX) {
4743     if (expanded) {
4744       log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
4745                                 HeapRegion::GrainWords * HeapWordSize);
4746     }
4747     _hrm->allocate_free_regions_starting_at(index, 1);
4748     return region_at(index);
4749   }
4750   return NULL;
4751 }
4752 
4753 // Optimized nmethod scanning
4754 
4755 class RegisterNMethodOopClosure: public OopClosure {
4756   G1CollectedHeap* _g1h;
4757   nmethod* _nm;
4758 
4759   template <class T> void do_oop_work(T* p) {
4760     T heap_oop = RawAccess<>::oop_load(p);
4761     if (!CompressedOops::is_null(heap_oop)) {
4762       oop obj = CompressedOops::decode_not_null(heap_oop);
4763       HeapRegion* hr = _g1h->heap_region_containing(obj);
4764       assert(!hr->is_continues_humongous(),
4765              "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
4766              " starting at " HR_FORMAT,
4767              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
4768 
4769       // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
4770       hr->add_strong_code_root_locked(_nm);
4771     }
4772   }
4773 
4774 public:
4775   RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
4776     _g1h(g1h), _nm(nm) {}
4777 
4778   void do_oop(oop* p)       { do_oop_work(p); }
4779   void do_oop(narrowOop* p) { do_oop_work(p); }
4780 };
4781 
4782 class UnregisterNMethodOopClosure: public OopClosure {
4783   G1CollectedHeap* _g1h;
4784   nmethod* _nm;
4785 
4786   template <class T> void do_oop_work(T* p) {
4787     T heap_oop = RawAccess<>::oop_load(p);
4788     if (!CompressedOops::is_null(heap_oop)) {
4789       oop obj = CompressedOops::decode_not_null(heap_oop);
4790       HeapRegion* hr = _g1h->heap_region_containing(obj);
4791       assert(!hr->is_continues_humongous(),
4792              "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
4793              " starting at " HR_FORMAT,
4794              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
4795 
4796       hr->remove_strong_code_root(_nm);
4797     }
4798   }
4799 
4800 public:
4801   UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
4802     _g1h(g1h), _nm(nm) {}
4803 
4804   void do_oop(oop* p)       { do_oop_work(p); }
4805   void do_oop(narrowOop* p) { do_oop_work(p); }
4806 };
4807 
4808 // Returns true if the reference points to an object that
4809 // can move in an incremental collection.
4810 bool G1CollectedHeap::is_scavengable(oop obj) {
4811   HeapRegion* hr = heap_region_containing(obj);
4812   return !hr->is_pinned();
4813 }
4814 
4815 void G1CollectedHeap::register_nmethod(nmethod* nm) {
4816   guarantee(nm != NULL, "sanity");
4817   RegisterNMethodOopClosure reg_cl(this, nm);
4818   nm->oops_do(&reg_cl);
4819 }
4820 
4821 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
4822   guarantee(nm != NULL, "sanity");
4823   UnregisterNMethodOopClosure reg_cl(this, nm);
4824   nm->oops_do(&reg_cl, true);
4825 }
4826 
4827 void G1CollectedHeap::purge_code_root_memory() {
4828   double purge_start = os::elapsedTime();
4829   G1CodeRootSet::purge();
4830   double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
4831   g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
4832 }
4833 
4834 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
4835   G1CollectedHeap* _g1h;
4836 
4837 public:
4838   RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
4839     _g1h(g1h) {}
4840 
4841   void do_code_blob(CodeBlob* cb) {
4842     nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
4843     if (nm == NULL) {
4844       return;
4845     }
4846 
4847     if (ScavengeRootsInCode) {
4848       _g1h->register_nmethod(nm);
4849     }
4850   }
4851 };
4852 
4853 void G1CollectedHeap::rebuild_strong_code_roots() {
4854   RebuildStrongCodeRootClosure blob_cl(this);
4855   CodeCache::blobs_do(&blob_cl);
4856 }
4857 
4858 void G1CollectedHeap::initialize_serviceability() {
4859   _g1mm->initialize_serviceability();
4860 }
4861 
4862 MemoryUsage G1CollectedHeap::memory_usage() {
4863   return _g1mm->memory_usage();
4864 }
4865 
4866 GrowableArray<GCMemoryManager*> G1CollectedHeap::memory_managers() {
4867   return _g1mm->memory_managers();
4868 }
4869 
4870 GrowableArray<MemoryPool*> G1CollectedHeap::memory_pools() {
4871   return _g1mm->memory_pools();
4872 }