1 /*
   2  * Copyright (c) 2001, 2018, 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/metadataOnStackMark.hpp"
  27 #include "classfile/stringTable.hpp"
  28 #include "classfile/symbolTable.hpp"
  29 #include "code/codeCache.hpp"
  30 #include "code/icBuffer.hpp"
  31 #include "gc/g1/bufferingOopClosure.hpp"
  32 #include "gc/g1/g1Allocator.inline.hpp"
  33 #include "gc/g1/g1BarrierSet.hpp"
  34 #include "gc/g1/g1CollectedHeap.inline.hpp"
  35 #include "gc/g1/g1CollectionSet.hpp"
  36 #include "gc/g1/g1CollectorPolicy.hpp"
  37 #include "gc/g1/g1CollectorState.hpp"
  38 #include "gc/g1/g1ConcurrentRefine.hpp"
  39 #include "gc/g1/g1ConcurrentRefineThread.hpp"
  40 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp"
  41 #include "gc/g1/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/g1StringDedup.hpp"
  57 #include "gc/g1/g1ThreadLocalData.hpp"
  58 #include "gc/g1/g1YCTypes.hpp"
  59 #include "gc/g1/g1YoungRemSetSamplingThread.hpp"
  60 #include "gc/g1/heapRegion.inline.hpp"
  61 #include "gc/g1/heapRegionRemSet.hpp"
  62 #include "gc/g1/heapRegionSet.inline.hpp"
  63 #include "gc/g1/vm_operations_g1.hpp"
  64 #include "gc/shared/adaptiveSizePolicy.hpp"
  65 #include "gc/shared/gcHeapSummary.hpp"
  66 #include "gc/shared/gcId.hpp"
  67 #include "gc/shared/gcLocker.hpp"
  68 #include "gc/shared/gcTimer.hpp"
  69 #include "gc/shared/gcTrace.hpp"
  70 #include "gc/shared/gcTraceTime.inline.hpp"
  71 #include "gc/shared/generationSpec.hpp"
  72 #include "gc/shared/isGCActiveMark.hpp"
  73 #include "gc/shared/preservedMarks.inline.hpp"
  74 #include "gc/shared/suspendibleThreadSet.hpp"
  75 #include "gc/shared/referenceProcessor.inline.hpp"
  76 #include "gc/shared/taskqueue.inline.hpp"
  77 #include "gc/shared/weakProcessor.hpp"
  78 #include "logging/log.hpp"
  79 #include "memory/allocation.hpp"
  80 #include "memory/iterator.hpp"
  81 #include "memory/resourceArea.hpp"
  82 #include "oops/access.inline.hpp"
  83 #include "oops/compressedOops.inline.hpp"
  84 #include "oops/oop.inline.hpp"
  85 #include "prims/resolvedMethodTable.hpp"
  86 #include "runtime/atomic.hpp"
  87 #include "runtime/handles.inline.hpp"
  88 #include "runtime/init.hpp"
  89 #include "runtime/orderAccess.inline.hpp"
  90 #include "runtime/threadSMR.hpp"
  91 #include "runtime/vmThread.hpp"
  92 #include "utilities/align.hpp"
  93 #include "utilities/globalDefinitions.hpp"
  94 #include "utilities/stack.inline.hpp"
  95 
  96 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
  97 
  98 // INVARIANTS/NOTES
  99 //
 100 // All allocation activity covered by the G1CollectedHeap interface is
 101 // serialized by acquiring the HeapLock.  This happens in mem_allocate
 102 // and allocate_new_tlab, which are the "entry" points to the
 103 // allocation code from the rest of the JVM.  (Note that this does not
 104 // apply to TLAB allocation, which is not part of this interface: it
 105 // is done by clients of this interface.)
 106 
 107 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
 108  private:
 109   size_t _num_dirtied;
 110   G1CollectedHeap* _g1h;
 111   G1CardTable* _g1_ct;
 112 
 113   HeapRegion* region_for_card(jbyte* card_ptr) const {
 114     return _g1h->heap_region_containing(_g1_ct->addr_for(card_ptr));
 115   }
 116 
 117   bool will_become_free(HeapRegion* hr) const {
 118     // A region will be freed by free_collection_set if the region is in the
 119     // collection set and has not had an evacuation failure.
 120     return _g1h->is_in_cset(hr) && !hr->evacuation_failed();
 121   }
 122 
 123  public:
 124   RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(),
 125     _num_dirtied(0), _g1h(g1h), _g1_ct(g1h->card_table()) { }
 126 
 127   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
 128     HeapRegion* hr = region_for_card(card_ptr);
 129 
 130     // Should only dirty cards in regions that won't be freed.
 131     if (!will_become_free(hr)) {
 132       *card_ptr = G1CardTable::dirty_card_val();
 133       _num_dirtied++;
 134     }
 135 
 136     return true;
 137   }
 138 
 139   size_t num_dirtied()   const { return _num_dirtied; }
 140 };
 141 
 142 
 143 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
 144   HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
 145 }
 146 
 147 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
 148   // The from card cache is not the memory that is actually committed. So we cannot
 149   // take advantage of the zero_filled parameter.
 150   reset_from_card_cache(start_idx, num_regions);
 151 }
 152 
 153 
 154 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
 155                                              MemRegion mr) {
 156   return new HeapRegion(hrs_index, bot(), mr);
 157 }
 158 
 159 // Private methods.
 160 
 161 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
 162   assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
 163          "the only time we use this to allocate a humongous region is "
 164          "when we are allocating a single humongous region");
 165 
 166   HeapRegion* res = _hrm.allocate_free_region(is_old);
 167 
 168   if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
 169     // Currently, only attempts to allocate GC alloc regions set
 170     // do_expand to true. So, we should only reach here during a
 171     // safepoint. If this assumption changes we might have to
 172     // reconsider the use of _expand_heap_after_alloc_failure.
 173     assert(SafepointSynchronize::is_at_safepoint(), "invariant");
 174 
 175     log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B",
 176                               word_size * HeapWordSize);
 177 
 178     if (expand(word_size * HeapWordSize)) {
 179       // Given that expand() succeeded in expanding the heap, and we
 180       // always expand the heap by an amount aligned to the heap
 181       // region size, the free list should in theory not be empty.
 182       // In either case allocate_free_region() will check for NULL.
 183       res = _hrm.allocate_free_region(is_old);
 184     } else {
 185       _expand_heap_after_alloc_failure = false;
 186     }
 187   }
 188   return res;
 189 }
 190 
 191 HeapWord*
 192 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
 193                                                            uint num_regions,
 194                                                            size_t word_size) {
 195   assert(first != G1_NO_HRM_INDEX, "pre-condition");
 196   assert(is_humongous(word_size), "word_size should be humongous");
 197   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 198 
 199   // Index of last region in the series.
 200   uint last = first + num_regions - 1;
 201 
 202   // We need to initialize the region(s) we just discovered. This is
 203   // a bit tricky given that it can happen concurrently with
 204   // refinement threads refining cards on these regions and
 205   // potentially wanting to refine the BOT as they are scanning
 206   // those cards (this can happen shortly after a cleanup; see CR
 207   // 6991377). So we have to set up the region(s) carefully and in
 208   // a specific order.
 209 
 210   // The word size sum of all the regions we will allocate.
 211   size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
 212   assert(word_size <= word_size_sum, "sanity");
 213 
 214   // This will be the "starts humongous" region.
 215   HeapRegion* first_hr = region_at(first);
 216   // The header of the new object will be placed at the bottom of
 217   // the first region.
 218   HeapWord* new_obj = first_hr->bottom();
 219   // This will be the new top of the new object.
 220   HeapWord* obj_top = new_obj + word_size;
 221 
 222   // First, we need to zero the header of the space that we will be
 223   // allocating. When we update top further down, some refinement
 224   // threads might try to scan the region. By zeroing the header we
 225   // ensure that any thread that will try to scan the region will
 226   // come across the zero klass word and bail out.
 227   //
 228   // NOTE: It would not have been correct to have used
 229   // CollectedHeap::fill_with_object() and make the space look like
 230   // an int array. The thread that is doing the allocation will
 231   // later update the object header to a potentially different array
 232   // type and, for a very short period of time, the klass and length
 233   // fields will be inconsistent. This could cause a refinement
 234   // thread to calculate the object size incorrectly.
 235   Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
 236 
 237   // Next, pad out the unused tail of the last region with filler
 238   // objects, for improved usage accounting.
 239   // How many words we use for filler objects.
 240   size_t word_fill_size = word_size_sum - word_size;
 241 
 242   // How many words memory we "waste" which cannot hold a filler object.
 243   size_t words_not_fillable = 0;
 244 
 245   if (word_fill_size >= min_fill_size()) {
 246     fill_with_objects(obj_top, word_fill_size);
 247   } else if (word_fill_size > 0) {
 248     // We have space to fill, but we cannot fit an object there.
 249     words_not_fillable = word_fill_size;
 250     word_fill_size = 0;
 251   }
 252 
 253   // We will set up the first region as "starts humongous". This
 254   // will also update the BOT covering all the regions to reflect
 255   // that there is a single object that starts at the bottom of the
 256   // first region.
 257   first_hr->set_starts_humongous(obj_top, word_fill_size);
 258   _g1_policy->remset_tracker()->update_at_allocate(first_hr);
 259   // Then, if there are any, we will set up the "continues
 260   // humongous" regions.
 261   HeapRegion* hr = NULL;
 262   for (uint i = first + 1; i <= last; ++i) {
 263     hr = region_at(i);
 264     hr->set_continues_humongous(first_hr);
 265     _g1_policy->remset_tracker()->update_at_allocate(hr);
 266   }
 267 
 268   // Up to this point no concurrent thread would have been able to
 269   // do any scanning on any region in this series. All the top
 270   // fields still point to bottom, so the intersection between
 271   // [bottom,top] and [card_start,card_end] will be empty. Before we
 272   // update the top fields, we'll do a storestore to make sure that
 273   // no thread sees the update to top before the zeroing of the
 274   // object header and the BOT initialization.
 275   OrderAccess::storestore();
 276 
 277   // Now, we will update the top fields of the "continues humongous"
 278   // regions except the last one.
 279   for (uint i = first; i < last; ++i) {
 280     hr = region_at(i);
 281     hr->set_top(hr->end());
 282   }
 283 
 284   hr = region_at(last);
 285   // If we cannot fit a filler object, we must set top to the end
 286   // of the humongous object, otherwise we cannot iterate the heap
 287   // and the BOT will not be complete.
 288   hr->set_top(hr->end() - words_not_fillable);
 289 
 290   assert(hr->bottom() < obj_top && obj_top <= hr->end(),
 291          "obj_top should be in last region");
 292 
 293   _verifier->check_bitmaps("Humongous Region Allocation", first_hr);
 294 
 295   assert(words_not_fillable == 0 ||
 296          first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(),
 297          "Miscalculation in humongous allocation");
 298 
 299   increase_used((word_size_sum - words_not_fillable) * HeapWordSize);
 300 
 301   for (uint i = first; i <= last; ++i) {
 302     hr = region_at(i);
 303     _humongous_set.add(hr);
 304     _hr_printer.alloc(hr);
 305   }
 306 
 307   return new_obj;
 308 }
 309 
 310 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) {
 311   assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size);
 312   return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
 313 }
 314 
 315 // If could fit into free regions w/o expansion, try.
 316 // Otherwise, if can expand, do so.
 317 // Otherwise, if using ex regions might help, try with ex given back.
 318 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
 319   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 320 
 321   _verifier->verify_region_sets_optional();
 322 
 323   uint first = G1_NO_HRM_INDEX;
 324   uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);
 325 
 326   if (obj_regions == 1) {
 327     // Only one region to allocate, try to use a fast path by directly allocating
 328     // from the free lists. Do not try to expand here, we will potentially do that
 329     // later.
 330     HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
 331     if (hr != NULL) {
 332       first = hr->hrm_index();
 333     }
 334   } else {
 335     // Policy: Try only empty regions (i.e. already committed first). Maybe we
 336     // are lucky enough to find some.
 337     first = _hrm.find_contiguous_only_empty(obj_regions);
 338     if (first != G1_NO_HRM_INDEX) {
 339       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 340     }
 341   }
 342 
 343   if (first == G1_NO_HRM_INDEX) {
 344     // Policy: We could not find enough regions for the humongous object in the
 345     // free list. Look through the heap to find a mix of free and uncommitted regions.
 346     // If so, try expansion.
 347     first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
 348     if (first != G1_NO_HRM_INDEX) {
 349       // We found something. Make sure these regions are committed, i.e. expand
 350       // the heap. Alternatively we could do a defragmentation GC.
 351       log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B",
 352                                     word_size * HeapWordSize);
 353 
 354       _hrm.expand_at(first, obj_regions, workers());
 355       g1_policy()->record_new_heap_size(num_regions());
 356 
 357 #ifdef ASSERT
 358       for (uint i = first; i < first + obj_regions; ++i) {
 359         HeapRegion* hr = region_at(i);
 360         assert(hr->is_free(), "sanity");
 361         assert(hr->is_empty(), "sanity");
 362         assert(is_on_master_free_list(hr), "sanity");
 363       }
 364 #endif
 365       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 366     } else {
 367       // Policy: Potentially trigger a defragmentation GC.
 368     }
 369   }
 370 
 371   HeapWord* result = NULL;
 372   if (first != G1_NO_HRM_INDEX) {
 373     result = humongous_obj_allocate_initialize_regions(first, obj_regions, word_size);
 374     assert(result != NULL, "it should always return a valid result");
 375 
 376     // A successful humongous object allocation changes the used space
 377     // information of the old generation so we need to recalculate the
 378     // sizes and update the jstat counters here.
 379     g1mm()->update_sizes();
 380   }
 381 
 382   _verifier->verify_region_sets_optional();
 383 
 384   return result;
 385 }
 386 
 387 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t word_size) {
 388   assert_heap_not_locked_and_not_at_safepoint();
 389   assert(!is_humongous(word_size), "we do not allow humongous TLABs");
 390 
 391   return attempt_allocation(word_size);
 392 }
 393 
 394 HeapWord*
 395 G1CollectedHeap::mem_allocate(size_t word_size,
 396                               bool*  gc_overhead_limit_was_exceeded) {
 397   assert_heap_not_locked_and_not_at_safepoint();
 398 
 399   if (is_humongous(word_size)) {
 400     return attempt_allocation_humongous(word_size);
 401   }
 402   return attempt_allocation(word_size);
 403 }
 404 
 405 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size) {
 406   ResourceMark rm; // For retrieving the thread names in log messages.
 407 
 408   // Make sure you read the note in attempt_allocation_humongous().
 409 
 410   assert_heap_not_locked_and_not_at_safepoint();
 411   assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
 412          "be called for humongous allocation requests");
 413 
 414   // We should only get here after the first-level allocation attempt
 415   // (attempt_allocation()) failed to allocate.
 416 
 417   // We will loop until a) we manage to successfully perform the
 418   // allocation or b) we successfully schedule a collection which
 419   // fails to perform the allocation. b) is the only case when we'll
 420   // return NULL.
 421   HeapWord* result = NULL;
 422   for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 423     bool should_try_gc;
 424     uint gc_count_before;
 425 
 426     {
 427       MutexLockerEx x(Heap_lock);
 428       result = _allocator->attempt_allocation_locked(word_size);
 429       if (result != NULL) {
 430         return result;
 431       }
 432 
 433       // If the GCLocker is active and we are bound for a GC, try expanding young gen.
 434       // This is different to when only GCLocker::needs_gc() is set: try to avoid
 435       // waiting because the GCLocker is active to not wait too long.
 436       if (GCLocker::is_active_and_needs_gc() && g1_policy()->can_expand_young_list()) {
 437         // No need for an ergo message here, can_expand_young_list() does this when
 438         // it returns true.
 439         result = _allocator->attempt_allocation_force(word_size);
 440         if (result != NULL) {
 441           return result;
 442         }
 443       }
 444       // Only try a GC if the GCLocker does not signal the need for a GC. Wait until
 445       // the GCLocker initiated GC has been performed and then retry. This includes
 446       // the case when the GC Locker is not active but has not been performed.
 447       should_try_gc = !GCLocker::needs_gc();
 448       // Read the GC count while still holding the Heap_lock.
 449       gc_count_before = total_collections();
 450     }
 451 
 452     if (should_try_gc) {
 453       bool succeeded;
 454       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 455                                    GCCause::_g1_inc_collection_pause);
 456       if (result != NULL) {
 457         assert(succeeded, "only way to get back a non-NULL result");
 458         log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT,
 459                              Thread::current()->name(), p2i(result));
 460         return result;
 461       }
 462 
 463       if (succeeded) {
 464         // We successfully scheduled a collection which failed to allocate. No
 465         // point in trying to allocate further. We'll just return NULL.
 466         log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate "
 467                              SIZE_FORMAT " words", Thread::current()->name(), word_size);
 468         return NULL;
 469       }
 470       log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT " words",
 471                            Thread::current()->name(), word_size);
 472     } else {
 473       // Failed to schedule a collection.
 474       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 475         log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating "
 476                                SIZE_FORMAT " words", Thread::current()->name(), word_size);
 477         return NULL;
 478       }
 479       log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name());
 480       // The GCLocker is either active or the GCLocker initiated
 481       // GC has not yet been performed. Stall until it is and
 482       // then retry the allocation.
 483       GCLocker::stall_until_clear();
 484       gclocker_retry_count += 1;
 485     }
 486 
 487     // We can reach here if we were unsuccessful in scheduling a
 488     // collection (because another thread beat us to it) or if we were
 489     // stalled due to the GC locker. In either can we should retry the
 490     // allocation attempt in case another thread successfully
 491     // performed a collection and reclaimed enough space. We do the
 492     // first attempt (without holding the Heap_lock) here and the
 493     // follow-on attempt will be at the start of the next loop
 494     // iteration (after taking the Heap_lock).
 495 
 496     result = _allocator->attempt_allocation(word_size);
 497     if (result != NULL) {
 498       return result;
 499     }
 500 
 501     // Give a warning if we seem to be looping forever.
 502     if ((QueuedAllocationWarningCount > 0) &&
 503         (try_count % QueuedAllocationWarningCount == 0)) {
 504       log_warning(gc, alloc)("%s:  Retried allocation %u times for " SIZE_FORMAT " words",
 505                              Thread::current()->name(), try_count, word_size);
 506     }
 507   }
 508 
 509   ShouldNotReachHere();
 510   return NULL;
 511 }
 512 
 513 void G1CollectedHeap::begin_archive_alloc_range(bool open) {
 514   assert_at_safepoint_on_vm_thread();
 515   if (_archive_allocator == NULL) {
 516     _archive_allocator = G1ArchiveAllocator::create_allocator(this, open);
 517   }
 518 }
 519 
 520 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) {
 521   // Allocations in archive regions cannot be of a size that would be considered
 522   // humongous even for a minimum-sized region, because G1 region sizes/boundaries
 523   // may be different at archive-restore time.
 524   return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words());
 525 }
 526 
 527 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) {
 528   assert_at_safepoint_on_vm_thread();
 529   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 530   if (is_archive_alloc_too_large(word_size)) {
 531     return NULL;
 532   }
 533   return _archive_allocator->archive_mem_allocate(word_size);
 534 }
 535 
 536 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
 537                                               size_t end_alignment_in_bytes) {
 538   assert_at_safepoint_on_vm_thread();
 539   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 540 
 541   // Call complete_archive to do the real work, filling in the MemRegion
 542   // array with the archive regions.
 543   _archive_allocator->complete_archive(ranges, end_alignment_in_bytes);
 544   delete _archive_allocator;
 545   _archive_allocator = NULL;
 546 }
 547 
 548 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) {
 549   assert(ranges != NULL, "MemRegion array NULL");
 550   assert(count != 0, "No MemRegions provided");
 551   MemRegion reserved = _hrm.reserved();
 552   for (size_t i = 0; i < count; i++) {
 553     if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) {
 554       return false;
 555     }
 556   }
 557   return true;
 558 }
 559 
 560 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges,
 561                                             size_t count,
 562                                             bool open) {
 563   assert(!is_init_completed(), "Expect to be called at JVM init time");
 564   assert(ranges != NULL, "MemRegion array NULL");
 565   assert(count != 0, "No MemRegions provided");
 566   MutexLockerEx x(Heap_lock);
 567 
 568   MemRegion reserved = _hrm.reserved();
 569   HeapWord* prev_last_addr = NULL;
 570   HeapRegion* prev_last_region = NULL;
 571 
 572   // Temporarily disable pretouching of heap pages. This interface is used
 573   // when mmap'ing archived heap data in, so pre-touching is wasted.
 574   FlagSetting fs(AlwaysPreTouch, false);
 575 
 576   // Enable archive object checking used by G1MarkSweep. We have to let it know
 577   // about each archive range, so that objects in those ranges aren't marked.
 578   G1ArchiveAllocator::enable_archive_object_check();
 579 
 580   // For each specified MemRegion range, allocate the corresponding G1
 581   // regions and mark them as archive regions. We expect the ranges
 582   // in ascending starting address order, without overlap.
 583   for (size_t i = 0; i < count; i++) {
 584     MemRegion curr_range = ranges[i];
 585     HeapWord* start_address = curr_range.start();
 586     size_t word_size = curr_range.word_size();
 587     HeapWord* last_address = curr_range.last();
 588     size_t commits = 0;
 589 
 590     guarantee(reserved.contains(start_address) && reserved.contains(last_address),
 591               "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 592               p2i(start_address), p2i(last_address));
 593     guarantee(start_address > prev_last_addr,
 594               "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 595               p2i(start_address), p2i(prev_last_addr));
 596     prev_last_addr = last_address;
 597 
 598     // Check for ranges that start in the same G1 region in which the previous
 599     // range ended, and adjust the start address so we don't try to allocate
 600     // the same region again. If the current range is entirely within that
 601     // region, skip it, just adjusting the recorded top.
 602     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 603     if ((prev_last_region != NULL) && (start_region == prev_last_region)) {
 604       start_address = start_region->end();
 605       if (start_address > last_address) {
 606         increase_used(word_size * HeapWordSize);
 607         start_region->set_top(last_address + 1);
 608         continue;
 609       }
 610       start_region->set_top(start_address);
 611       curr_range = MemRegion(start_address, last_address + 1);
 612       start_region = _hrm.addr_to_region(start_address);
 613     }
 614 
 615     // Perform the actual region allocation, exiting if it fails.
 616     // Then note how much new space we have allocated.
 617     if (!_hrm.allocate_containing_regions(curr_range, &commits, workers())) {
 618       return false;
 619     }
 620     increase_used(word_size * HeapWordSize);
 621     if (commits != 0) {
 622       log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B",
 623                                 HeapRegion::GrainWords * HeapWordSize * commits);
 624 
 625     }
 626 
 627     // Mark each G1 region touched by the range as archive, add it to
 628     // the old set, and set top.
 629     HeapRegion* curr_region = _hrm.addr_to_region(start_address);
 630     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 631     prev_last_region = last_region;
 632 
 633     while (curr_region != NULL) {
 634       assert(curr_region->is_empty() && !curr_region->is_pinned(),
 635              "Region already in use (index %u)", curr_region->hrm_index());
 636       if (open) {
 637         curr_region->set_open_archive();
 638       } else {
 639         curr_region->set_closed_archive();
 640       }
 641       _hr_printer.alloc(curr_region);
 642       _old_set.add(curr_region);
 643       HeapWord* top;
 644       HeapRegion* next_region;
 645       if (curr_region != last_region) {
 646         top = curr_region->end();
 647         next_region = _hrm.next_region_in_heap(curr_region);
 648       } else {
 649         top = last_address + 1;
 650         next_region = NULL;
 651       }
 652       curr_region->set_top(top);
 653       curr_region->set_first_dead(top);
 654       curr_region->set_end_of_live(top);
 655       curr_region = next_region;
 656     }
 657 
 658     // Notify mark-sweep of the archive
 659     G1ArchiveAllocator::set_range_archive(curr_range, open);
 660   }
 661   return true;
 662 }
 663 
 664 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) {
 665   assert(!is_init_completed(), "Expect to be called at JVM init time");
 666   assert(ranges != NULL, "MemRegion array NULL");
 667   assert(count != 0, "No MemRegions provided");
 668   MemRegion reserved = _hrm.reserved();
 669   HeapWord *prev_last_addr = NULL;
 670   HeapRegion* prev_last_region = NULL;
 671 
 672   // For each MemRegion, create filler objects, if needed, in the G1 regions
 673   // that contain the address range. The address range actually within the
 674   // MemRegion will not be modified. That is assumed to have been initialized
 675   // elsewhere, probably via an mmap of archived heap data.
 676   MutexLockerEx x(Heap_lock);
 677   for (size_t i = 0; i < count; i++) {
 678     HeapWord* start_address = ranges[i].start();
 679     HeapWord* last_address = ranges[i].last();
 680 
 681     assert(reserved.contains(start_address) && reserved.contains(last_address),
 682            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 683            p2i(start_address), p2i(last_address));
 684     assert(start_address > prev_last_addr,
 685            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 686            p2i(start_address), p2i(prev_last_addr));
 687 
 688     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 689     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 690     HeapWord* bottom_address = start_region->bottom();
 691 
 692     // Check for a range beginning in the same region in which the
 693     // previous one ended.
 694     if (start_region == prev_last_region) {
 695       bottom_address = prev_last_addr + 1;
 696     }
 697 
 698     // Verify that the regions were all marked as archive regions by
 699     // alloc_archive_regions.
 700     HeapRegion* curr_region = start_region;
 701     while (curr_region != NULL) {
 702       guarantee(curr_region->is_archive(),
 703                 "Expected archive region at index %u", curr_region->hrm_index());
 704       if (curr_region != last_region) {
 705         curr_region = _hrm.next_region_in_heap(curr_region);
 706       } else {
 707         curr_region = NULL;
 708       }
 709     }
 710 
 711     prev_last_addr = last_address;
 712     prev_last_region = last_region;
 713 
 714     // Fill the memory below the allocated range with dummy object(s),
 715     // if the region bottom does not match the range start, or if the previous
 716     // range ended within the same G1 region, and there is a gap.
 717     if (start_address != bottom_address) {
 718       size_t fill_size = pointer_delta(start_address, bottom_address);
 719       G1CollectedHeap::fill_with_objects(bottom_address, fill_size);
 720       increase_used(fill_size * HeapWordSize);
 721     }
 722   }
 723 }
 724 
 725 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t word_size) {
 726   assert_heap_not_locked_and_not_at_safepoint();
 727   assert(!is_humongous(word_size), "attempt_allocation() should not "
 728          "be called for humongous allocation requests");
 729 
 730   HeapWord* result = _allocator->attempt_allocation(word_size);
 731 
 732   if (result == NULL) {
 733     result = attempt_allocation_slow(word_size);
 734   }
 735   assert_heap_not_locked();
 736   if (result != NULL) {
 737     dirty_young_block(result, word_size);
 738   }
 739   return result;
 740 }
 741 
 742 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) {
 743   assert(!is_init_completed(), "Expect to be called at JVM init time");
 744   assert(ranges != NULL, "MemRegion array NULL");
 745   assert(count != 0, "No MemRegions provided");
 746   MemRegion reserved = _hrm.reserved();
 747   HeapWord* prev_last_addr = NULL;
 748   HeapRegion* prev_last_region = NULL;
 749   size_t size_used = 0;
 750   size_t uncommitted_regions = 0;
 751 
 752   // For each Memregion, free the G1 regions that constitute it, and
 753   // notify mark-sweep that the range is no longer to be considered 'archive.'
 754   MutexLockerEx x(Heap_lock);
 755   for (size_t i = 0; i < count; i++) {
 756     HeapWord* start_address = ranges[i].start();
 757     HeapWord* last_address = ranges[i].last();
 758 
 759     assert(reserved.contains(start_address) && reserved.contains(last_address),
 760            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 761            p2i(start_address), p2i(last_address));
 762     assert(start_address > prev_last_addr,
 763            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 764            p2i(start_address), p2i(prev_last_addr));
 765     size_used += ranges[i].byte_size();
 766     prev_last_addr = last_address;
 767 
 768     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 769     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 770 
 771     // Check for ranges that start in the same G1 region in which the previous
 772     // range ended, and adjust the start address so we don't try to free
 773     // the same region again. If the current range is entirely within that
 774     // region, skip it.
 775     if (start_region == prev_last_region) {
 776       start_address = start_region->end();
 777       if (start_address > last_address) {
 778         continue;
 779       }
 780       start_region = _hrm.addr_to_region(start_address);
 781     }
 782     prev_last_region = last_region;
 783 
 784     // After verifying that each region was marked as an archive region by
 785     // alloc_archive_regions, set it free and empty and uncommit it.
 786     HeapRegion* curr_region = start_region;
 787     while (curr_region != NULL) {
 788       guarantee(curr_region->is_archive(),
 789                 "Expected archive region at index %u", curr_region->hrm_index());
 790       uint curr_index = curr_region->hrm_index();
 791       _old_set.remove(curr_region);
 792       curr_region->set_free();
 793       curr_region->set_top(curr_region->bottom());
 794       if (curr_region != last_region) {
 795         curr_region = _hrm.next_region_in_heap(curr_region);
 796       } else {
 797         curr_region = NULL;
 798       }
 799       _hrm.shrink_at(curr_index, 1);
 800       uncommitted_regions++;
 801     }
 802 
 803     // Notify mark-sweep that this is no longer an archive range.
 804     G1ArchiveAllocator::set_range_archive(ranges[i], false);
 805   }
 806 
 807   if (uncommitted_regions != 0) {
 808     log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B",
 809                               HeapRegion::GrainWords * HeapWordSize * uncommitted_regions);
 810   }
 811   decrease_used(size_used);
 812 }
 813 
 814 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size) {
 815   ResourceMark rm; // For retrieving the thread names in log messages.
 816 
 817   // The structure of this method has a lot of similarities to
 818   // attempt_allocation_slow(). The reason these two were not merged
 819   // into a single one is that such a method would require several "if
 820   // allocation is not humongous do this, otherwise do that"
 821   // conditional paths which would obscure its flow. In fact, an early
 822   // version of this code did use a unified method which was harder to
 823   // follow and, as a result, it had subtle bugs that were hard to
 824   // track down. So keeping these two methods separate allows each to
 825   // be more readable. It will be good to keep these two in sync as
 826   // much as possible.
 827 
 828   assert_heap_not_locked_and_not_at_safepoint();
 829   assert(is_humongous(word_size), "attempt_allocation_humongous() "
 830          "should only be called for humongous allocations");
 831 
 832   // Humongous objects can exhaust the heap quickly, so we should check if we
 833   // need to start a marking cycle at each humongous object allocation. We do
 834   // the check before we do the actual allocation. The reason for doing it
 835   // before the allocation is that we avoid having to keep track of the newly
 836   // allocated memory while we do a GC.
 837   if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
 838                                            word_size)) {
 839     collect(GCCause::_g1_humongous_allocation);
 840   }
 841 
 842   // We will loop until a) we manage to successfully perform the
 843   // allocation or b) we successfully schedule a collection which
 844   // fails to perform the allocation. b) is the only case when we'll
 845   // return NULL.
 846   HeapWord* result = NULL;
 847   for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 848     bool should_try_gc;
 849     uint gc_count_before;
 850 
 851 
 852     {
 853       MutexLockerEx x(Heap_lock);
 854 
 855       // Given that humongous objects are not allocated in young
 856       // regions, we'll first try to do the allocation without doing a
 857       // collection hoping that there's enough space in the heap.
 858       result = humongous_obj_allocate(word_size);
 859       if (result != NULL) {
 860         size_t size_in_regions = humongous_obj_size_in_regions(word_size);
 861         g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
 862         return result;
 863       }
 864 
 865       // Only try a GC if the GCLocker does not signal the need for a GC. Wait until
 866       // the GCLocker initiated GC has been performed and then retry. This includes
 867       // the case when the GC Locker is not active but has not been performed.
 868       should_try_gc = !GCLocker::needs_gc();
 869       // Read the GC count while still holding the Heap_lock.
 870       gc_count_before = total_collections();
 871     }
 872 
 873     if (should_try_gc) {
 874       bool succeeded;
 875       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 876                                    GCCause::_g1_humongous_allocation);
 877       if (result != NULL) {
 878         assert(succeeded, "only way to get back a non-NULL result");
 879         log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT,
 880                              Thread::current()->name(), p2i(result));
 881         return result;
 882       }
 883 
 884       if (succeeded) {
 885         // We successfully scheduled a collection which failed to allocate. No
 886         // point in trying to allocate further. We'll just return NULL.
 887         log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate "
 888                              SIZE_FORMAT " words", Thread::current()->name(), word_size);
 889         return NULL;
 890       }
 891       log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT "",
 892                            Thread::current()->name(), word_size);
 893     } else {
 894       // Failed to schedule a collection.
 895       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 896         log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating "
 897                                SIZE_FORMAT " words", Thread::current()->name(), word_size);
 898         return NULL;
 899       }
 900       log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name());
 901       // The GCLocker is either active or the GCLocker initiated
 902       // GC has not yet been performed. Stall until it is and
 903       // then retry the allocation.
 904       GCLocker::stall_until_clear();
 905       gclocker_retry_count += 1;
 906     }
 907 
 908 
 909     // We can reach here if we were unsuccessful in scheduling a
 910     // collection (because another thread beat us to it) or if we were
 911     // stalled due to the GC locker. In either can we should retry the
 912     // allocation attempt in case another thread successfully
 913     // performed a collection and reclaimed enough space.
 914     // Humongous object allocation always needs a lock, so we wait for the retry
 915     // in the next iteration of the loop, unlike for the regular iteration case.
 916     // Give a warning if we seem to be looping forever.
 917 
 918     if ((QueuedAllocationWarningCount > 0) &&
 919         (try_count % QueuedAllocationWarningCount == 0)) {
 920       log_warning(gc, alloc)("%s: Retried allocation %u times for " SIZE_FORMAT " words",
 921                              Thread::current()->name(), try_count, word_size);
 922     }
 923   }
 924 
 925   ShouldNotReachHere();
 926   return NULL;
 927 }
 928 
 929 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
 930                                                            bool expect_null_mutator_alloc_region) {
 931   assert_at_safepoint_on_vm_thread();
 932   assert(!_allocator->has_mutator_alloc_region() || !expect_null_mutator_alloc_region,
 933          "the current alloc region was unexpectedly found to be non-NULL");
 934 
 935   if (!is_humongous(word_size)) {
 936     return _allocator->attempt_allocation_locked(word_size);
 937   } else {
 938     HeapWord* result = humongous_obj_allocate(word_size);
 939     if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
 940       collector_state()->set_initiate_conc_mark_if_possible(true);
 941     }
 942     return result;
 943   }
 944 
 945   ShouldNotReachHere();
 946 }
 947 
 948 class PostCompactionPrinterClosure: public HeapRegionClosure {
 949 private:
 950   G1HRPrinter* _hr_printer;
 951 public:
 952   bool do_heap_region(HeapRegion* hr) {
 953     assert(!hr->is_young(), "not expecting to find young regions");
 954     _hr_printer->post_compaction(hr);
 955     return false;
 956   }
 957 
 958   PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
 959     : _hr_printer(hr_printer) { }
 960 };
 961 
 962 void G1CollectedHeap::print_hrm_post_compaction() {
 963   if (_hr_printer.is_active()) {
 964     PostCompactionPrinterClosure cl(hr_printer());
 965     heap_region_iterate(&cl);
 966   }
 967 }
 968 
 969 void G1CollectedHeap::abort_concurrent_cycle() {
 970   // If we start the compaction before the CM threads finish
 971   // scanning the root regions we might trip them over as we'll
 972   // be moving objects / updating references. So let's wait until
 973   // they are done. By telling them to abort, they should complete
 974   // early.
 975   _cm->root_regions()->abort();
 976   _cm->root_regions()->wait_until_scan_finished();
 977 
 978   // Disable discovery and empty the discovered lists
 979   // for the CM ref processor.
 980   ref_processor_cm()->disable_discovery();
 981   ref_processor_cm()->abandon_partial_discovery();
 982   ref_processor_cm()->verify_no_references_recorded();
 983 
 984   // Abandon current iterations of concurrent marking and concurrent
 985   // refinement, if any are in progress.
 986   concurrent_mark()->concurrent_cycle_abort();
 987 }
 988 
 989 void G1CollectedHeap::prepare_heap_for_full_collection() {
 990   // Make sure we'll choose a new allocation region afterwards.
 991   _allocator->release_mutator_alloc_region();
 992   _allocator->abandon_gc_alloc_regions();
 993   g1_rem_set()->cleanupHRRS();
 994 
 995   // We may have added regions to the current incremental collection
 996   // set between the last GC or pause and now. We need to clear the
 997   // incremental collection set and then start rebuilding it afresh
 998   // after this full GC.
 999   abandon_collection_set(collection_set());
1000 
1001   tear_down_region_sets(false /* free_list_only */);
1002 }
1003 
1004 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) {
1005   assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant");
1006   assert(used() == recalculate_used(), "Should be equal");
1007   _verifier->verify_region_sets_optional();
1008   _verifier->verify_before_gc(G1HeapVerifier::G1VerifyFull);
1009   _verifier->check_bitmaps("Full GC Start");
1010 }
1011 
1012 void G1CollectedHeap::prepare_heap_for_mutators() {
1013   // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1014   ClassLoaderDataGraph::purge();
1015   MetaspaceUtils::verify_metrics();
1016 
1017   // Prepare heap for normal collections.
1018   assert(num_free_regions() == 0, "we should not have added any free regions");
1019   rebuild_region_sets(false /* free_list_only */);
1020   abort_refinement();
1021   resize_if_necessary_after_full_collection();
1022 
1023   // Rebuild the strong code root lists for each region
1024   rebuild_strong_code_roots();
1025 
1026   // Start a new incremental collection set for the next pause
1027   start_new_collection_set();
1028 
1029   _allocator->init_mutator_alloc_region();
1030 
1031   // Post collection state updates.
1032   MetaspaceGC::compute_new_size();
1033 }
1034 
1035 void G1CollectedHeap::abort_refinement() {
1036   if (_hot_card_cache->use_cache()) {
1037     _hot_card_cache->reset_hot_cache();
1038   }
1039 
1040   // Discard all remembered set updates.
1041   G1BarrierSet::dirty_card_queue_set().abandon_logs();
1042   assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1043 }
1044 
1045 void G1CollectedHeap::verify_after_full_collection() {
1046   _hrm.verify_optional();
1047   _verifier->verify_region_sets_optional();
1048   _verifier->verify_after_gc(G1HeapVerifier::G1VerifyFull);
1049   // Clear the previous marking bitmap, if needed for bitmap verification.
1050   // Note we cannot do this when we clear the next marking bitmap in
1051   // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the
1052   // objects marked during a full GC against the previous bitmap.
1053   // But we need to clear it before calling check_bitmaps below since
1054   // the full GC has compacted objects and updated TAMS but not updated
1055   // the prev bitmap.
1056   if (G1VerifyBitmaps) {
1057     GCTraceTime(Debug, gc)("Clear Bitmap for Verification");
1058     _cm->clear_prev_bitmap(workers());
1059   }
1060   _verifier->check_bitmaps("Full GC End");
1061 
1062   // At this point there should be no regions in the
1063   // entire heap tagged as young.
1064   assert(check_young_list_empty(), "young list should be empty at this point");
1065 
1066   // Note: since we've just done a full GC, concurrent
1067   // marking is no longer active. Therefore we need not
1068   // re-enable reference discovery for the CM ref processor.
1069   // That will be done at the start of the next marking cycle.
1070   // We also know that the STW processor should no longer
1071   // discover any new references.
1072   assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
1073   assert(!ref_processor_cm()->discovery_enabled(), "Postcondition");
1074   ref_processor_stw()->verify_no_references_recorded();
1075   ref_processor_cm()->verify_no_references_recorded();
1076 }
1077 
1078 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) {
1079   // Post collection logging.
1080   // We should do this after we potentially resize the heap so
1081   // that all the COMMIT / UNCOMMIT events are generated before
1082   // the compaction events.
1083   print_hrm_post_compaction();
1084   heap_transition->print();
1085   print_heap_after_gc();
1086   print_heap_regions();
1087 #ifdef TRACESPINNING
1088   ParallelTaskTerminator::print_termination_counts();
1089 #endif
1090 }
1091 
1092 bool G1CollectedHeap::do_full_collection(bool explicit_gc,
1093                                          bool clear_all_soft_refs) {
1094   assert_at_safepoint_on_vm_thread();
1095 
1096   if (GCLocker::check_active_before_gc()) {
1097     // Full GC was not completed.
1098     return false;
1099   }
1100 
1101   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1102       soft_ref_policy()->should_clear_all_soft_refs();
1103 
1104   G1FullCollector collector(this, &_full_gc_memory_manager, explicit_gc, do_clear_all_soft_refs);
1105   GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true);
1106 
1107   collector.prepare_collection();
1108   collector.collect();
1109   collector.complete_collection();
1110 
1111   // Full collection was successfully completed.
1112   return true;
1113 }
1114 
1115 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1116   // Currently, there is no facility in the do_full_collection(bool) API to notify
1117   // the caller that the collection did not succeed (e.g., because it was locked
1118   // out by the GC locker). So, right now, we'll ignore the return value.
1119   bool dummy = do_full_collection(true,                /* explicit_gc */
1120                                   clear_all_soft_refs);
1121 }
1122 
1123 void G1CollectedHeap::resize_if_necessary_after_full_collection() {
1124   // Capacity, free and used after the GC counted as full regions to
1125   // include the waste in the following calculations.
1126   const size_t capacity_after_gc = capacity();
1127   const size_t used_after_gc = capacity_after_gc - unused_committed_regions_in_bytes();
1128 
1129   // This is enforced in arguments.cpp.
1130   assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1131          "otherwise the code below doesn't make sense");
1132 
1133   // We don't have floating point command-line arguments
1134   const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1135   const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1136   const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1137   const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1138 
1139   const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1140   const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1141 
1142   // We have to be careful here as these two calculations can overflow
1143   // 32-bit size_t's.
1144   double used_after_gc_d = (double) used_after_gc;
1145   double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1146   double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1147 
1148   // Let's make sure that they are both under the max heap size, which
1149   // by default will make them fit into a size_t.
1150   double desired_capacity_upper_bound = (double) max_heap_size;
1151   minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1152                                     desired_capacity_upper_bound);
1153   maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1154                                     desired_capacity_upper_bound);
1155 
1156   // We can now safely turn them into size_t's.
1157   size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1158   size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1159 
1160   // This assert only makes sense here, before we adjust them
1161   // with respect to the min and max heap size.
1162   assert(minimum_desired_capacity <= maximum_desired_capacity,
1163          "minimum_desired_capacity = " SIZE_FORMAT ", "
1164          "maximum_desired_capacity = " SIZE_FORMAT,
1165          minimum_desired_capacity, maximum_desired_capacity);
1166 
1167   // Should not be greater than the heap max size. No need to adjust
1168   // it with respect to the heap min size as it's a lower bound (i.e.,
1169   // we'll try to make the capacity larger than it, not smaller).
1170   minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1171   // Should not be less than the heap min size. No need to adjust it
1172   // with respect to the heap max size as it's an upper bound (i.e.,
1173   // we'll try to make the capacity smaller than it, not greater).
1174   maximum_desired_capacity =  MAX2(maximum_desired_capacity, min_heap_size);
1175 
1176   if (capacity_after_gc < minimum_desired_capacity) {
1177     // Don't expand unless it's significant
1178     size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1179 
1180     log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). "
1181                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1182                               "min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1183                               capacity_after_gc, used_after_gc, used(), minimum_desired_capacity, MinHeapFreeRatio);
1184 
1185     expand(expand_bytes, _workers);
1186 
1187     // No expansion, now see if we want to shrink
1188   } else if (capacity_after_gc > maximum_desired_capacity) {
1189     // Capacity too large, compute shrinking size
1190     size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1191 
1192     log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). "
1193                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1194                               "maximum_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1195                               capacity_after_gc, used_after_gc, used(), maximum_desired_capacity, MaxHeapFreeRatio);
1196 
1197     shrink(shrink_bytes);
1198   }
1199 }
1200 
1201 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size,
1202                                                             bool do_gc,
1203                                                             bool clear_all_soft_refs,
1204                                                             bool expect_null_mutator_alloc_region,
1205                                                             bool* gc_succeeded) {
1206   *gc_succeeded = true;
1207   // Let's attempt the allocation first.
1208   HeapWord* result =
1209     attempt_allocation_at_safepoint(word_size,
1210                                     expect_null_mutator_alloc_region);
1211   if (result != NULL) {
1212     return result;
1213   }
1214 
1215   // In a G1 heap, we're supposed to keep allocation from failing by
1216   // incremental pauses.  Therefore, at least for now, we'll favor
1217   // expansion over collection.  (This might change in the future if we can
1218   // do something smarter than full collection to satisfy a failed alloc.)
1219   result = expand_and_allocate(word_size);
1220   if (result != NULL) {
1221     return result;
1222   }
1223 
1224   if (do_gc) {
1225     // Expansion didn't work, we'll try to do a Full GC.
1226     *gc_succeeded = do_full_collection(false, /* explicit_gc */
1227                                        clear_all_soft_refs);
1228   }
1229 
1230   return NULL;
1231 }
1232 
1233 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1234                                                      bool* succeeded) {
1235   assert_at_safepoint_on_vm_thread();
1236 
1237   // Attempts to allocate followed by Full GC.
1238   HeapWord* result =
1239     satisfy_failed_allocation_helper(word_size,
1240                                      true,  /* do_gc */
1241                                      false, /* clear_all_soft_refs */
1242                                      false, /* expect_null_mutator_alloc_region */
1243                                      succeeded);
1244 
1245   if (result != NULL || !*succeeded) {
1246     return result;
1247   }
1248 
1249   // Attempts to allocate followed by Full GC that will collect all soft references.
1250   result = satisfy_failed_allocation_helper(word_size,
1251                                             true, /* do_gc */
1252                                             true, /* clear_all_soft_refs */
1253                                             true, /* expect_null_mutator_alloc_region */
1254                                             succeeded);
1255 
1256   if (result != NULL || !*succeeded) {
1257     return result;
1258   }
1259 
1260   // Attempts to allocate, no GC
1261   result = satisfy_failed_allocation_helper(word_size,
1262                                             false, /* do_gc */
1263                                             false, /* clear_all_soft_refs */
1264                                             true,  /* expect_null_mutator_alloc_region */
1265                                             succeeded);
1266 
1267   if (result != NULL) {
1268     return result;
1269   }
1270 
1271   assert(!soft_ref_policy()->should_clear_all_soft_refs(),
1272          "Flag should have been handled and cleared prior to this point");
1273 
1274   // What else?  We might try synchronous finalization later.  If the total
1275   // space available is large enough for the allocation, then a more
1276   // complete compaction phase than we've tried so far might be
1277   // appropriate.
1278   return NULL;
1279 }
1280 
1281 // Attempting to expand the heap sufficiently
1282 // to support an allocation of the given "word_size".  If
1283 // successful, perform the allocation and return the address of the
1284 // allocated block, or else "NULL".
1285 
1286 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1287   assert_at_safepoint_on_vm_thread();
1288 
1289   _verifier->verify_region_sets_optional();
1290 
1291   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1292   log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B",
1293                             word_size * HeapWordSize);
1294 
1295 
1296   if (expand(expand_bytes, _workers)) {
1297     _hrm.verify_optional();
1298     _verifier->verify_region_sets_optional();
1299     return attempt_allocation_at_safepoint(word_size,
1300                                            false /* expect_null_mutator_alloc_region */);
1301   }
1302   return NULL;
1303 }
1304 
1305 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) {
1306   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1307   aligned_expand_bytes = align_up(aligned_expand_bytes,
1308                                        HeapRegion::GrainBytes);
1309 
1310   log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B",
1311                             expand_bytes, aligned_expand_bytes);
1312 
1313   if (is_maximal_no_gc()) {
1314     log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1315     return false;
1316   }
1317 
1318   double expand_heap_start_time_sec = os::elapsedTime();
1319   uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1320   assert(regions_to_expand > 0, "Must expand by at least one region");
1321 
1322   uint expanded_by = _hrm.expand_by(regions_to_expand, pretouch_workers);
1323   if (expand_time_ms != NULL) {
1324     *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS;
1325   }
1326 
1327   if (expanded_by > 0) {
1328     size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1329     assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1330     g1_policy()->record_new_heap_size(num_regions());
1331   } else {
1332     log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)");
1333 
1334     // The expansion of the virtual storage space was unsuccessful.
1335     // Let's see if it was because we ran out of swap.
1336     if (G1ExitOnExpansionFailure &&
1337         _hrm.available() >= regions_to_expand) {
1338       // We had head room...
1339       vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1340     }
1341   }
1342   return regions_to_expand > 0;
1343 }
1344 
1345 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1346   size_t aligned_shrink_bytes =
1347     ReservedSpace::page_align_size_down(shrink_bytes);
1348   aligned_shrink_bytes = align_down(aligned_shrink_bytes,
1349                                          HeapRegion::GrainBytes);
1350   uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1351 
1352   uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1353   size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1354 
1355 
1356   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",
1357                             shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1358   if (num_regions_removed > 0) {
1359     g1_policy()->record_new_heap_size(num_regions());
1360   } else {
1361     log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)");
1362   }
1363 }
1364 
1365 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1366   _verifier->verify_region_sets_optional();
1367 
1368   // We should only reach here at the end of a Full GC which means we
1369   // should not not be holding to any GC alloc regions. The method
1370   // below will make sure of that and do any remaining clean up.
1371   _allocator->abandon_gc_alloc_regions();
1372 
1373   // Instead of tearing down / rebuilding the free lists here, we
1374   // could instead use the remove_all_pending() method on free_list to
1375   // remove only the ones that we need to remove.
1376   tear_down_region_sets(true /* free_list_only */);
1377   shrink_helper(shrink_bytes);
1378   rebuild_region_sets(true /* free_list_only */);
1379 
1380   _hrm.verify_optional();
1381   _verifier->verify_region_sets_optional();
1382 }
1383 
1384 // Public methods.
1385 
1386 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) :
1387   CollectedHeap(),
1388   _young_gen_sampling_thread(NULL),
1389   _collector_policy(collector_policy),
1390   _soft_ref_policy(),
1391   _card_table(NULL),
1392   _memory_manager("G1 Young Generation", "end of minor GC"),
1393   _full_gc_memory_manager("G1 Old Generation", "end of major GC"),
1394   _eden_pool(NULL),
1395   _survivor_pool(NULL),
1396   _old_pool(NULL),
1397   _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1398   _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1399   _g1_policy(new G1Policy(_gc_timer_stw)),
1400   _collection_set(this, _g1_policy),
1401   _dirty_card_queue_set(false),
1402   _is_alive_closure_cm(this),
1403   _is_alive_closure_stw(this),
1404   _ref_processor_cm(NULL),
1405   _ref_processor_stw(NULL),
1406   _bot(NULL),
1407   _hot_card_cache(NULL),
1408   _g1_rem_set(NULL),
1409   _cr(NULL),
1410   _g1mm(NULL),
1411   _preserved_marks_set(true /* in_c_heap */),
1412   _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1413   _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1414   _humongous_reclaim_candidates(),
1415   _has_humongous_reclaim_candidates(false),
1416   _archive_allocator(NULL),
1417   _summary_bytes_used(0),
1418   _survivor_evac_stats("Young", YoungPLABSize, PLABWeight),
1419   _old_evac_stats("Old", OldPLABSize, PLABWeight),
1420   _expand_heap_after_alloc_failure(true),
1421   _old_marking_cycles_started(0),
1422   _old_marking_cycles_completed(0),
1423   _in_cset_fast_test() {
1424 
1425   _workers = new WorkGang("GC Thread", ParallelGCThreads,
1426                           /* are_GC_task_threads */true,
1427                           /* are_ConcurrentGC_threads */false);
1428   _workers->initialize_workers();
1429   _verifier = new G1HeapVerifier(this);
1430 
1431   _allocator = new G1Allocator(this);
1432 
1433   _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics());
1434 
1435   _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);
1436 
1437   // Override the default _filler_array_max_size so that no humongous filler
1438   // objects are created.
1439   _filler_array_max_size = _humongous_object_threshold_in_words;
1440 
1441   uint n_queues = ParallelGCThreads;
1442   _task_queues = new RefToScanQueueSet(n_queues);
1443 
1444   _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1445 
1446   for (uint i = 0; i < n_queues; i++) {
1447     RefToScanQueue* q = new RefToScanQueue();
1448     q->initialize();
1449     _task_queues->register_queue(i, q);
1450     ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1451   }
1452 
1453   // Initialize the G1EvacuationFailureALot counters and flags.
1454   NOT_PRODUCT(reset_evacuation_should_fail();)
1455 
1456   guarantee(_task_queues != NULL, "task_queues allocation failure.");
1457 }
1458 
1459 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1460                                                                  size_t size,
1461                                                                  size_t translation_factor) {
1462   size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1463   // Allocate a new reserved space, preferring to use large pages.
1464   ReservedSpace rs(size, preferred_page_size);
1465   G1RegionToSpaceMapper* result  =
1466     G1RegionToSpaceMapper::create_mapper(rs,
1467                                          size,
1468                                          rs.alignment(),
1469                                          HeapRegion::GrainBytes,
1470                                          translation_factor,
1471                                          mtGC);
1472 
1473   os::trace_page_sizes_for_requested_size(description,
1474                                           size,
1475                                           preferred_page_size,
1476                                           rs.alignment(),
1477                                           rs.base(),
1478                                           rs.size());
1479 
1480   return result;
1481 }
1482 
1483 jint G1CollectedHeap::initialize_concurrent_refinement() {
1484   jint ecode = JNI_OK;
1485   _cr = G1ConcurrentRefine::create(&ecode);
1486   return ecode;
1487 }
1488 
1489 jint G1CollectedHeap::initialize_young_gen_sampling_thread() {
1490   _young_gen_sampling_thread = new G1YoungRemSetSamplingThread();
1491   if (_young_gen_sampling_thread->osthread() == NULL) {
1492     vm_shutdown_during_initialization("Could not create G1YoungRemSetSamplingThread");
1493     return JNI_ENOMEM;
1494   }
1495   return JNI_OK;
1496 }
1497 
1498 jint G1CollectedHeap::initialize() {
1499   os::enable_vtime();
1500 
1501   // Necessary to satisfy locking discipline assertions.
1502 
1503   MutexLocker x(Heap_lock);
1504 
1505   // While there are no constraints in the GC code that HeapWordSize
1506   // be any particular value, there are multiple other areas in the
1507   // system which believe this to be true (e.g. oop->object_size in some
1508   // cases incorrectly returns the size in wordSize units rather than
1509   // HeapWordSize).
1510   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1511 
1512   size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1513   size_t max_byte_size = collector_policy()->max_heap_byte_size();
1514   size_t heap_alignment = collector_policy()->heap_alignment();
1515 
1516   // Ensure that the sizes are properly aligned.
1517   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1518   Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1519   Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1520 
1521   // Reserve the maximum.
1522 
1523   // When compressed oops are enabled, the preferred heap base
1524   // is calculated by subtracting the requested size from the
1525   // 32Gb boundary and using the result as the base address for
1526   // heap reservation. If the requested size is not aligned to
1527   // HeapRegion::GrainBytes (i.e. the alignment that is passed
1528   // into the ReservedHeapSpace constructor) then the actual
1529   // base of the reserved heap may end up differing from the
1530   // address that was requested (i.e. the preferred heap base).
1531   // If this happens then we could end up using a non-optimal
1532   // compressed oops mode.
1533 
1534   ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1535                                                  heap_alignment);
1536 
1537   initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
1538 
1539   // Create the barrier set for the entire reserved region.
1540   G1CardTable* ct = new G1CardTable(reserved_region());
1541   ct->initialize();
1542   G1BarrierSet* bs = new G1BarrierSet(ct);
1543   bs->initialize();
1544   assert(bs->is_a(BarrierSet::G1BarrierSet), "sanity");
1545   BarrierSet::set_barrier_set(bs);
1546   _card_table = ct;
1547 
1548   // Create the hot card cache.
1549   _hot_card_cache = new G1HotCardCache(this);
1550 
1551   // Carve out the G1 part of the heap.
1552   ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1553   size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
1554   G1RegionToSpaceMapper* heap_storage =
1555     G1RegionToSpaceMapper::create_mapper(g1_rs,
1556                                          g1_rs.size(),
1557                                          page_size,
1558                                          HeapRegion::GrainBytes,
1559                                          1,
1560                                          mtJavaHeap);
1561   os::trace_page_sizes("Heap",
1562                        collector_policy()->min_heap_byte_size(),
1563                        max_byte_size,
1564                        page_size,
1565                        heap_rs.base(),
1566                        heap_rs.size());
1567   heap_storage->set_mapping_changed_listener(&_listener);
1568 
1569   // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1570   G1RegionToSpaceMapper* bot_storage =
1571     create_aux_memory_mapper("Block Offset Table",
1572                              G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize),
1573                              G1BlockOffsetTable::heap_map_factor());
1574 
1575   G1RegionToSpaceMapper* cardtable_storage =
1576     create_aux_memory_mapper("Card Table",
1577                              G1CardTable::compute_size(g1_rs.size() / HeapWordSize),
1578                              G1CardTable::heap_map_factor());
1579 
1580   G1RegionToSpaceMapper* card_counts_storage =
1581     create_aux_memory_mapper("Card Counts Table",
1582                              G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1583                              G1CardCounts::heap_map_factor());
1584 
1585   size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size());
1586   G1RegionToSpaceMapper* prev_bitmap_storage =
1587     create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1588   G1RegionToSpaceMapper* next_bitmap_storage =
1589     create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1590 
1591   _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1592   _card_table->initialize(cardtable_storage);
1593   // Do later initialization work for concurrent refinement.
1594   _hot_card_cache->initialize(card_counts_storage);
1595 
1596   // 6843694 - ensure that the maximum region index can fit
1597   // in the remembered set structures.
1598   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1599   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1600 
1601   // Also create a G1 rem set.
1602   _g1_rem_set = new G1RemSet(this, _card_table, _hot_card_cache);
1603   _g1_rem_set->initialize(max_capacity(), max_regions());
1604 
1605   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1606   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1607   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1608             "too many cards per region");
1609 
1610   FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
1611 
1612   _bot = new G1BlockOffsetTable(reserved_region(), bot_storage);
1613 
1614   {
1615     HeapWord* start = _hrm.reserved().start();
1616     HeapWord* end = _hrm.reserved().end();
1617     size_t granularity = HeapRegion::GrainBytes;
1618 
1619     _in_cset_fast_test.initialize(start, end, granularity);
1620     _humongous_reclaim_candidates.initialize(start, end, granularity);
1621   }
1622 
1623   // Create the G1ConcurrentMark data structure and thread.
1624   // (Must do this late, so that "max_regions" is defined.)
1625   _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1626   if (_cm == NULL || !_cm->completed_initialization()) {
1627     vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark");
1628     return JNI_ENOMEM;
1629   }
1630   _cm_thread = _cm->cm_thread();
1631 
1632   // Now expand into the initial heap size.
1633   if (!expand(init_byte_size, _workers)) {
1634     vm_shutdown_during_initialization("Failed to allocate initial heap.");
1635     return JNI_ENOMEM;
1636   }
1637 
1638   // Perform any initialization actions delegated to the policy.
1639   g1_policy()->init(this, &_collection_set);
1640 
1641   G1BarrierSet::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
1642                                                  SATB_Q_FL_lock,
1643                                                  G1SATBProcessCompletedThreshold,
1644                                                  Shared_SATB_Q_lock);
1645 
1646   jint ecode = initialize_concurrent_refinement();
1647   if (ecode != JNI_OK) {
1648     return ecode;
1649   }
1650 
1651   ecode = initialize_young_gen_sampling_thread();
1652   if (ecode != JNI_OK) {
1653     return ecode;
1654   }
1655 
1656   G1BarrierSet::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1657                                                   DirtyCardQ_FL_lock,
1658                                                   (int)concurrent_refine()->yellow_zone(),
1659                                                   (int)concurrent_refine()->red_zone(),
1660                                                   Shared_DirtyCardQ_lock,
1661                                                   NULL,  // fl_owner
1662                                                   true); // init_free_ids
1663 
1664   dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1665                                     DirtyCardQ_FL_lock,
1666                                     -1, // never trigger processing
1667                                     -1, // no limit on length
1668                                     Shared_DirtyCardQ_lock,
1669                                     &G1BarrierSet::dirty_card_queue_set());
1670 
1671   // Here we allocate the dummy HeapRegion that is required by the
1672   // G1AllocRegion class.
1673   HeapRegion* dummy_region = _hrm.get_dummy_region();
1674 
1675   // We'll re-use the same region whether the alloc region will
1676   // require BOT updates or not and, if it doesn't, then a non-young
1677   // region will complain that it cannot support allocations without
1678   // BOT updates. So we'll tag the dummy region as eden to avoid that.
1679   dummy_region->set_eden();
1680   // Make sure it's full.
1681   dummy_region->set_top(dummy_region->end());
1682   G1AllocRegion::setup(this, dummy_region);
1683 
1684   _allocator->init_mutator_alloc_region();
1685 
1686   // Do create of the monitoring and management support so that
1687   // values in the heap have been properly initialized.
1688   _g1mm = new G1MonitoringSupport(this);
1689 
1690   G1StringDedup::initialize();
1691 
1692   _preserved_marks_set.init(ParallelGCThreads);
1693 
1694   _collection_set.initialize(max_regions());
1695 
1696   return JNI_OK;
1697 }
1698 
1699 void G1CollectedHeap::initialize_serviceability() {
1700   _eden_pool = new G1EdenPool(this);
1701   _survivor_pool = new G1SurvivorPool(this);
1702   _old_pool = new G1OldGenPool(this);
1703 
1704   _full_gc_memory_manager.add_pool(_eden_pool);
1705   _full_gc_memory_manager.add_pool(_survivor_pool);
1706   _full_gc_memory_manager.add_pool(_old_pool);
1707 
1708   _memory_manager.add_pool(_eden_pool);
1709   _memory_manager.add_pool(_survivor_pool);
1710 
1711 }
1712 
1713 void G1CollectedHeap::stop() {
1714   // Stop all concurrent threads. We do this to make sure these threads
1715   // do not continue to execute and access resources (e.g. logging)
1716   // that are destroyed during shutdown.
1717   _cr->stop();
1718   _young_gen_sampling_thread->stop();
1719   _cm_thread->stop();
1720   if (G1StringDedup::is_enabled()) {
1721     G1StringDedup::stop();
1722   }
1723 }
1724 
1725 void G1CollectedHeap::safepoint_synchronize_begin() {
1726   SuspendibleThreadSet::synchronize();
1727 }
1728 
1729 void G1CollectedHeap::safepoint_synchronize_end() {
1730   SuspendibleThreadSet::desynchronize();
1731 }
1732 
1733 size_t G1CollectedHeap::conservative_max_heap_alignment() {
1734   return HeapRegion::max_region_size();
1735 }
1736 
1737 void G1CollectedHeap::post_initialize() {
1738   CollectedHeap::post_initialize();
1739   ref_processing_init();
1740 }
1741 
1742 void G1CollectedHeap::ref_processing_init() {
1743   // Reference processing in G1 currently works as follows:
1744   //
1745   // * There are two reference processor instances. One is
1746   //   used to record and process discovered references
1747   //   during concurrent marking; the other is used to
1748   //   record and process references during STW pauses
1749   //   (both full and incremental).
1750   // * Both ref processors need to 'span' the entire heap as
1751   //   the regions in the collection set may be dotted around.
1752   //
1753   // * For the concurrent marking ref processor:
1754   //   * Reference discovery is enabled at initial marking.
1755   //   * Reference discovery is disabled and the discovered
1756   //     references processed etc during remarking.
1757   //   * Reference discovery is MT (see below).
1758   //   * Reference discovery requires a barrier (see below).
1759   //   * Reference processing may or may not be MT
1760   //     (depending on the value of ParallelRefProcEnabled
1761   //     and ParallelGCThreads).
1762   //   * A full GC disables reference discovery by the CM
1763   //     ref processor and abandons any entries on it's
1764   //     discovered lists.
1765   //
1766   // * For the STW processor:
1767   //   * Non MT discovery is enabled at the start of a full GC.
1768   //   * Processing and enqueueing during a full GC is non-MT.
1769   //   * During a full GC, references are processed after marking.
1770   //
1771   //   * Discovery (may or may not be MT) is enabled at the start
1772   //     of an incremental evacuation pause.
1773   //   * References are processed near the end of a STW evacuation pause.
1774   //   * For both types of GC:
1775   //     * Discovery is atomic - i.e. not concurrent.
1776   //     * Reference discovery will not need a barrier.
1777 
1778   MemRegion mr = reserved_region();
1779 
1780   bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1);
1781 
1782   // Concurrent Mark ref processor
1783   _ref_processor_cm =
1784     new ReferenceProcessor(mr,    // span
1785                            mt_processing,
1786                                 // mt processing
1787                            ParallelGCThreads,
1788                                 // degree of mt processing
1789                            (ParallelGCThreads > 1) || (ConcGCThreads > 1),
1790                                 // mt discovery
1791                            MAX2(ParallelGCThreads, ConcGCThreads),
1792                                 // degree of mt discovery
1793                            false,
1794                                 // Reference discovery is not atomic
1795                            &_is_alive_closure_cm);
1796                                 // is alive closure
1797                                 // (for efficiency/performance)
1798 
1799   // STW ref processor
1800   _ref_processor_stw =
1801     new ReferenceProcessor(mr,    // span
1802                            mt_processing,
1803                                 // mt processing
1804                            ParallelGCThreads,
1805                                 // degree of mt processing
1806                            (ParallelGCThreads > 1),
1807                                 // mt discovery
1808                            ParallelGCThreads,
1809                                 // degree of mt discovery
1810                            true,
1811                                 // Reference discovery is atomic
1812                            &_is_alive_closure_stw);
1813                                 // is alive closure
1814                                 // (for efficiency/performance)
1815 }
1816 
1817 CollectorPolicy* G1CollectedHeap::collector_policy() const {
1818   return _collector_policy;
1819 }
1820 
1821 SoftRefPolicy* G1CollectedHeap::soft_ref_policy() {
1822   return &_soft_ref_policy;
1823 }
1824 
1825 size_t G1CollectedHeap::capacity() const {
1826   return _hrm.length() * HeapRegion::GrainBytes;
1827 }
1828 
1829 size_t G1CollectedHeap::unused_committed_regions_in_bytes() const {
1830   return _hrm.total_free_bytes();
1831 }
1832 
1833 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) {
1834   _hot_card_cache->drain(cl, worker_i);
1835 }
1836 
1837 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) {
1838   DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
1839   size_t n_completed_buffers = 0;
1840   while (dcqs.apply_closure_during_gc(cl, worker_i)) {
1841     n_completed_buffers++;
1842   }
1843   g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers);
1844   dcqs.clear_n_completed_buffers();
1845   assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
1846 }
1847 
1848 // Computes the sum of the storage used by the various regions.
1849 size_t G1CollectedHeap::used() const {
1850   size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
1851   if (_archive_allocator != NULL) {
1852     result += _archive_allocator->used();
1853   }
1854   return result;
1855 }
1856 
1857 size_t G1CollectedHeap::used_unlocked() const {
1858   return _summary_bytes_used;
1859 }
1860 
1861 class SumUsedClosure: public HeapRegionClosure {
1862   size_t _used;
1863 public:
1864   SumUsedClosure() : _used(0) {}
1865   bool do_heap_region(HeapRegion* r) {
1866     _used += r->used();
1867     return false;
1868   }
1869   size_t result() { return _used; }
1870 };
1871 
1872 size_t G1CollectedHeap::recalculate_used() const {
1873   double recalculate_used_start = os::elapsedTime();
1874 
1875   SumUsedClosure blk;
1876   heap_region_iterate(&blk);
1877 
1878   g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
1879   return blk.result();
1880 }
1881 
1882 bool  G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
1883   switch (cause) {
1884     case GCCause::_java_lang_system_gc:                 return ExplicitGCInvokesConcurrent;
1885     case GCCause::_dcmd_gc_run:                         return ExplicitGCInvokesConcurrent;
1886     case GCCause::_wb_conc_mark:                        return true;
1887     default :                                           return false;
1888   }
1889 }
1890 
1891 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
1892   switch (cause) {
1893     case GCCause::_gc_locker:               return GCLockerInvokesConcurrent;
1894     case GCCause::_g1_humongous_allocation: return true;
1895     default:                                return is_user_requested_concurrent_full_gc(cause);
1896   }
1897 }
1898 
1899 #ifndef PRODUCT
1900 void G1CollectedHeap::allocate_dummy_regions() {
1901   // Let's fill up most of the region
1902   size_t word_size = HeapRegion::GrainWords - 1024;
1903   // And as a result the region we'll allocate will be humongous.
1904   guarantee(is_humongous(word_size), "sanity");
1905 
1906   // _filler_array_max_size is set to humongous object threshold
1907   // but temporarily change it to use CollectedHeap::fill_with_object().
1908   SizeTFlagSetting fs(_filler_array_max_size, word_size);
1909 
1910   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
1911     // Let's use the existing mechanism for the allocation
1912     HeapWord* dummy_obj = humongous_obj_allocate(word_size);
1913     if (dummy_obj != NULL) {
1914       MemRegion mr(dummy_obj, word_size);
1915       CollectedHeap::fill_with_object(mr);
1916     } else {
1917       // If we can't allocate once, we probably cannot allocate
1918       // again. Let's get out of the loop.
1919       break;
1920     }
1921   }
1922 }
1923 #endif // !PRODUCT
1924 
1925 void G1CollectedHeap::increment_old_marking_cycles_started() {
1926   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
1927          _old_marking_cycles_started == _old_marking_cycles_completed + 1,
1928          "Wrong marking cycle count (started: %d, completed: %d)",
1929          _old_marking_cycles_started, _old_marking_cycles_completed);
1930 
1931   _old_marking_cycles_started++;
1932 }
1933 
1934 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
1935   MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
1936 
1937   // We assume that if concurrent == true, then the caller is a
1938   // concurrent thread that was joined the Suspendible Thread
1939   // Set. If there's ever a cheap way to check this, we should add an
1940   // assert here.
1941 
1942   // Given that this method is called at the end of a Full GC or of a
1943   // concurrent cycle, and those can be nested (i.e., a Full GC can
1944   // interrupt a concurrent cycle), the number of full collections
1945   // completed should be either one (in the case where there was no
1946   // nesting) or two (when a Full GC interrupted a concurrent cycle)
1947   // behind the number of full collections started.
1948 
1949   // This is the case for the inner caller, i.e. a Full GC.
1950   assert(concurrent ||
1951          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
1952          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
1953          "for inner caller (Full GC): _old_marking_cycles_started = %u "
1954          "is inconsistent with _old_marking_cycles_completed = %u",
1955          _old_marking_cycles_started, _old_marking_cycles_completed);
1956 
1957   // This is the case for the outer caller, i.e. the concurrent cycle.
1958   assert(!concurrent ||
1959          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
1960          "for outer caller (concurrent cycle): "
1961          "_old_marking_cycles_started = %u "
1962          "is inconsistent with _old_marking_cycles_completed = %u",
1963          _old_marking_cycles_started, _old_marking_cycles_completed);
1964 
1965   _old_marking_cycles_completed += 1;
1966 
1967   // We need to clear the "in_progress" flag in the CM thread before
1968   // we wake up any waiters (especially when ExplicitInvokesConcurrent
1969   // is set) so that if a waiter requests another System.gc() it doesn't
1970   // incorrectly see that a marking cycle is still in progress.
1971   if (concurrent) {
1972     _cm_thread->set_idle();
1973   }
1974 
1975   // This notify_all() will ensure that a thread that called
1976   // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
1977   // and it's waiting for a full GC to finish will be woken up. It is
1978   // waiting in VM_G1CollectForAllocation::doit_epilogue().
1979   FullGCCount_lock->notify_all();
1980 }
1981 
1982 void G1CollectedHeap::collect(GCCause::Cause cause) {
1983   assert_heap_not_locked();
1984 
1985   uint gc_count_before;
1986   uint old_marking_count_before;
1987   uint full_gc_count_before;
1988   bool retry_gc;
1989 
1990   do {
1991     retry_gc = false;
1992 
1993     {
1994       MutexLocker ml(Heap_lock);
1995 
1996       // Read the GC count while holding the Heap_lock
1997       gc_count_before = total_collections();
1998       full_gc_count_before = total_full_collections();
1999       old_marking_count_before = _old_marking_cycles_started;
2000     }
2001 
2002     if (should_do_concurrent_full_gc(cause)) {
2003       // Schedule an initial-mark evacuation pause that will start a
2004       // concurrent cycle. We're setting word_size to 0 which means that
2005       // we are not requesting a post-GC allocation.
2006       VM_G1CollectForAllocation op(0,     /* word_size */
2007                                    gc_count_before,
2008                                    cause,
2009                                    true,  /* should_initiate_conc_mark */
2010                                    g1_policy()->max_pause_time_ms());
2011       VMThread::execute(&op);
2012       if (!op.pause_succeeded()) {
2013         if (old_marking_count_before == _old_marking_cycles_started) {
2014           retry_gc = op.should_retry_gc();
2015         } else {
2016           // A Full GC happened while we were trying to schedule the
2017           // initial-mark GC. No point in starting a new cycle given
2018           // that the whole heap was collected anyway.
2019         }
2020 
2021         if (retry_gc) {
2022           if (GCLocker::is_active_and_needs_gc()) {
2023             GCLocker::stall_until_clear();
2024           }
2025         }
2026       }
2027     } else {
2028       if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2029           DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2030 
2031         // Schedule a standard evacuation pause. We're setting word_size
2032         // to 0 which means that we are not requesting a post-GC allocation.
2033         VM_G1CollectForAllocation op(0,     /* word_size */
2034                                      gc_count_before,
2035                                      cause,
2036                                      false, /* should_initiate_conc_mark */
2037                                      g1_policy()->max_pause_time_ms());
2038         VMThread::execute(&op);
2039       } else {
2040         // Schedule a Full GC.
2041         VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2042         VMThread::execute(&op);
2043       }
2044     }
2045   } while (retry_gc);
2046 }
2047 
2048 bool G1CollectedHeap::is_in(const void* p) const {
2049   if (_hrm.reserved().contains(p)) {
2050     // Given that we know that p is in the reserved space,
2051     // heap_region_containing() should successfully
2052     // return the containing region.
2053     HeapRegion* hr = heap_region_containing(p);
2054     return hr->is_in(p);
2055   } else {
2056     return false;
2057   }
2058 }
2059 
2060 #ifdef ASSERT
2061 bool G1CollectedHeap::is_in_exact(const void* p) const {
2062   bool contains = reserved_region().contains(p);
2063   bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2064   if (contains && available) {
2065     return true;
2066   } else {
2067     return false;
2068   }
2069 }
2070 #endif
2071 
2072 // Iteration functions.
2073 
2074 // Iterates an ObjectClosure over all objects within a HeapRegion.
2075 
2076 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2077   ObjectClosure* _cl;
2078 public:
2079   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2080   bool do_heap_region(HeapRegion* r) {
2081     if (!r->is_continues_humongous()) {
2082       r->object_iterate(_cl);
2083     }
2084     return false;
2085   }
2086 };
2087 
2088 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2089   IterateObjectClosureRegionClosure blk(cl);
2090   heap_region_iterate(&blk);
2091 }
2092 
2093 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2094   _hrm.iterate(cl);
2095 }
2096 
2097 void G1CollectedHeap::heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl,
2098                                                                  HeapRegionClaimer *hrclaimer,
2099                                                                  uint worker_id) const {
2100   _hrm.par_iterate(cl, hrclaimer, hrclaimer->offset_for_worker(worker_id));
2101 }
2102 
2103 void G1CollectedHeap::heap_region_par_iterate_from_start(HeapRegionClosure* cl,
2104                                                          HeapRegionClaimer *hrclaimer) const {
2105   _hrm.par_iterate(cl, hrclaimer, 0);
2106 }
2107 
2108 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2109   _collection_set.iterate(cl);
2110 }
2111 
2112 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) {
2113   _collection_set.iterate_from(cl, worker_id, workers()->active_workers());
2114 }
2115 
2116 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2117   HeapRegion* hr = heap_region_containing(addr);
2118   return hr->block_start(addr);
2119 }
2120 
2121 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2122   HeapRegion* hr = heap_region_containing(addr);
2123   return hr->block_size(addr);
2124 }
2125 
2126 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2127   HeapRegion* hr = heap_region_containing(addr);
2128   return hr->block_is_obj(addr);
2129 }
2130 
2131 bool G1CollectedHeap::supports_tlab_allocation() const {
2132   return true;
2133 }
2134 
2135 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2136   return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes;
2137 }
2138 
2139 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2140   return _eden.length() * HeapRegion::GrainBytes;
2141 }
2142 
2143 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2144 // must be equal to the humongous object limit.
2145 size_t G1CollectedHeap::max_tlab_size() const {
2146   return align_down(_humongous_object_threshold_in_words, MinObjAlignment);
2147 }
2148 
2149 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2150   return _allocator->unsafe_max_tlab_alloc();
2151 }
2152 
2153 size_t G1CollectedHeap::max_capacity() const {
2154   return _hrm.reserved().byte_size();
2155 }
2156 
2157 jlong G1CollectedHeap::millis_since_last_gc() {
2158   // See the notes in GenCollectedHeap::millis_since_last_gc()
2159   // for more information about the implementation.
2160   jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) -
2161     _g1_policy->collection_pause_end_millis();
2162   if (ret_val < 0) {
2163     log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT
2164       ". returning zero instead.", ret_val);
2165     return 0;
2166   }
2167   return ret_val;
2168 }
2169 
2170 void G1CollectedHeap::prepare_for_verify() {
2171   _verifier->prepare_for_verify();
2172 }
2173 
2174 void G1CollectedHeap::verify(VerifyOption vo) {
2175   _verifier->verify(vo);
2176 }
2177 
2178 bool G1CollectedHeap::supports_concurrent_phase_control() const {
2179   return true;
2180 }
2181 
2182 const char* const* G1CollectedHeap::concurrent_phases() const {
2183   return _cm_thread->concurrent_phases();
2184 }
2185 
2186 bool G1CollectedHeap::request_concurrent_phase(const char* phase) {
2187   return _cm_thread->request_concurrent_phase(phase);
2188 }
2189 
2190 class PrintRegionClosure: public HeapRegionClosure {
2191   outputStream* _st;
2192 public:
2193   PrintRegionClosure(outputStream* st) : _st(st) {}
2194   bool do_heap_region(HeapRegion* r) {
2195     r->print_on(_st);
2196     return false;
2197   }
2198 };
2199 
2200 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2201                                        const HeapRegion* hr,
2202                                        const VerifyOption vo) const {
2203   switch (vo) {
2204   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
2205   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
2206   case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj, hr);
2207   default:                            ShouldNotReachHere();
2208   }
2209   return false; // keep some compilers happy
2210 }
2211 
2212 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2213                                        const VerifyOption vo) const {
2214   switch (vo) {
2215   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
2216   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
2217   case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj);
2218   default:                            ShouldNotReachHere();
2219   }
2220   return false; // keep some compilers happy
2221 }
2222 
2223 void G1CollectedHeap::print_heap_regions() const {
2224   LogTarget(Trace, gc, heap, region) lt;
2225   if (lt.is_enabled()) {
2226     LogStream ls(lt);
2227     print_regions_on(&ls);
2228   }
2229 }
2230 
2231 void G1CollectedHeap::print_on(outputStream* st) const {
2232   st->print(" %-20s", "garbage-first heap");
2233   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
2234             capacity()/K, used_unlocked()/K);
2235   st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")",
2236             p2i(_hrm.reserved().start()),
2237             p2i(_hrm.reserved().end()));
2238   st->cr();
2239   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
2240   uint young_regions = young_regions_count();
2241   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
2242             (size_t) young_regions * HeapRegion::GrainBytes / K);
2243   uint survivor_regions = survivor_regions_count();
2244   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
2245             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
2246   st->cr();
2247   MetaspaceUtils::print_on(st);
2248 }
2249 
2250 void G1CollectedHeap::print_regions_on(outputStream* st) const {
2251   st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
2252                "HS=humongous(starts), HC=humongous(continues), "
2253                "CS=collection set, F=free, A=archive, "
2254                "TAMS=top-at-mark-start (previous, next)");
2255   PrintRegionClosure blk(st);
2256   heap_region_iterate(&blk);
2257 }
2258 
2259 void G1CollectedHeap::print_extended_on(outputStream* st) const {
2260   print_on(st);
2261 
2262   // Print the per-region information.
2263   print_regions_on(st);
2264 }
2265 
2266 void G1CollectedHeap::print_on_error(outputStream* st) const {
2267   this->CollectedHeap::print_on_error(st);
2268 
2269   if (_cm != NULL) {
2270     st->cr();
2271     _cm->print_on_error(st);
2272   }
2273 }
2274 
2275 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
2276   workers()->print_worker_threads_on(st);
2277   _cm_thread->print_on(st);
2278   st->cr();
2279   _cm->print_worker_threads_on(st);
2280   _cr->print_threads_on(st);
2281   _young_gen_sampling_thread->print_on(st);
2282   if (G1StringDedup::is_enabled()) {
2283     G1StringDedup::print_worker_threads_on(st);
2284   }
2285 }
2286 
2287 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2288   workers()->threads_do(tc);
2289   tc->do_thread(_cm_thread);
2290   _cm->threads_do(tc);
2291   _cr->threads_do(tc);
2292   tc->do_thread(_young_gen_sampling_thread);
2293   if (G1StringDedup::is_enabled()) {
2294     G1StringDedup::threads_do(tc);
2295   }
2296 }
2297 
2298 void G1CollectedHeap::print_tracing_info() const {
2299   g1_rem_set()->print_summary_info();
2300   concurrent_mark()->print_summary_info();
2301 }
2302 
2303 #ifndef PRODUCT
2304 // Helpful for debugging RSet issues.
2305 
2306 class PrintRSetsClosure : public HeapRegionClosure {
2307 private:
2308   const char* _msg;
2309   size_t _occupied_sum;
2310 
2311 public:
2312   bool do_heap_region(HeapRegion* r) {
2313     HeapRegionRemSet* hrrs = r->rem_set();
2314     size_t occupied = hrrs->occupied();
2315     _occupied_sum += occupied;
2316 
2317     tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r));
2318     if (occupied == 0) {
2319       tty->print_cr("  RSet is empty");
2320     } else {
2321       hrrs->print();
2322     }
2323     tty->print_cr("----------");
2324     return false;
2325   }
2326 
2327   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
2328     tty->cr();
2329     tty->print_cr("========================================");
2330     tty->print_cr("%s", msg);
2331     tty->cr();
2332   }
2333 
2334   ~PrintRSetsClosure() {
2335     tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
2336     tty->print_cr("========================================");
2337     tty->cr();
2338   }
2339 };
2340 
2341 void G1CollectedHeap::print_cset_rsets() {
2342   PrintRSetsClosure cl("Printing CSet RSets");
2343   collection_set_iterate(&cl);
2344 }
2345 
2346 void G1CollectedHeap::print_all_rsets() {
2347   PrintRSetsClosure cl("Printing All RSets");;
2348   heap_region_iterate(&cl);
2349 }
2350 #endif // PRODUCT
2351 
2352 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
2353 
2354   size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes;
2355   size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes;
2356   size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
2357 
2358   size_t eden_capacity_bytes =
2359     (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
2360 
2361   VirtualSpaceSummary heap_summary = create_heap_space_summary();
2362   return G1HeapSummary(heap_summary, heap_used, eden_used_bytes,
2363                        eden_capacity_bytes, survivor_used_bytes, num_regions());
2364 }
2365 
2366 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
2367   return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
2368                        stats->unused(), stats->used(), stats->region_end_waste(),
2369                        stats->regions_filled(), stats->direct_allocated(),
2370                        stats->failure_used(), stats->failure_waste());
2371 }
2372 
2373 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
2374   const G1HeapSummary& heap_summary = create_g1_heap_summary();
2375   gc_tracer->report_gc_heap_summary(when, heap_summary);
2376 
2377   const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
2378   gc_tracer->report_metaspace_summary(when, metaspace_summary);
2379 }
2380 
2381 G1CollectedHeap* G1CollectedHeap::heap() {
2382   CollectedHeap* heap = Universe::heap();
2383   assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
2384   assert(heap->kind() == CollectedHeap::G1, "Invalid name");
2385   return (G1CollectedHeap*)heap;
2386 }
2387 
2388 void G1CollectedHeap::gc_prologue(bool full) {
2389   // always_do_update_barrier = false;
2390   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
2391 
2392   // This summary needs to be printed before incrementing total collections.
2393   g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections());
2394 
2395   // Update common counters.
2396   increment_total_collections(full /* full gc */);
2397   if (full) {
2398     increment_old_marking_cycles_started();
2399   }
2400 
2401   // Fill TLAB's and such
2402   double start = os::elapsedTime();
2403   accumulate_statistics_all_tlabs();
2404   ensure_parsability(true);
2405   g1_policy()->phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2406 }
2407 
2408 void G1CollectedHeap::gc_epilogue(bool full) {
2409   // Update common counters.
2410   if (full) {
2411     // Update the number of full collections that have been completed.
2412     increment_old_marking_cycles_completed(false /* concurrent */);
2413   }
2414 
2415   // We are at the end of the GC. Total collections has already been increased.
2416   g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1);
2417 
2418   // FIXME: what is this about?
2419   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
2420   // is set.
2421 #if COMPILER2_OR_JVMCI
2422   assert(DerivedPointerTable::is_empty(), "derived pointer present");
2423 #endif
2424   // always_do_update_barrier = true;
2425 
2426   double start = os::elapsedTime();
2427   resize_all_tlabs();
2428   g1_policy()->phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2429 
2430   MemoryService::track_memory_usage();
2431   // We have just completed a GC. Update the soft reference
2432   // policy with the new heap occupancy
2433   Universe::update_heap_info_at_gc();
2434 }
2435 
2436 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2437                                                uint gc_count_before,
2438                                                bool* succeeded,
2439                                                GCCause::Cause gc_cause) {
2440   assert_heap_not_locked_and_not_at_safepoint();
2441   VM_G1CollectForAllocation op(word_size,
2442                                gc_count_before,
2443                                gc_cause,
2444                                false, /* should_initiate_conc_mark */
2445                                g1_policy()->max_pause_time_ms());
2446   VMThread::execute(&op);
2447 
2448   HeapWord* result = op.result();
2449   bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
2450   assert(result == NULL || ret_succeeded,
2451          "the result should be NULL if the VM did not succeed");
2452   *succeeded = ret_succeeded;
2453 
2454   assert_heap_not_locked();
2455   return result;
2456 }
2457 
2458 void G1CollectedHeap::do_concurrent_mark() {
2459   MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
2460   if (!_cm_thread->in_progress()) {
2461     _cm_thread->set_started();
2462     CGC_lock->notify();
2463   }
2464 }
2465 
2466 size_t G1CollectedHeap::pending_card_num() {
2467   size_t extra_cards = 0;
2468   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *curr = jtiwh.next(); ) {
2469     DirtyCardQueue& dcq = G1ThreadLocalData::dirty_card_queue(curr);
2470     extra_cards += dcq.size();
2471   }
2472   DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
2473   size_t buffer_size = dcqs.buffer_size();
2474   size_t buffer_num = dcqs.completed_buffers_num();
2475 
2476   return buffer_size * buffer_num + extra_cards;
2477 }
2478 
2479 bool G1CollectedHeap::is_potential_eager_reclaim_candidate(HeapRegion* r) const {
2480   // We don't nominate objects with many remembered set entries, on
2481   // the assumption that such objects are likely still live.
2482   HeapRegionRemSet* rem_set = r->rem_set();
2483 
2484   return G1EagerReclaimHumongousObjectsWithStaleRefs ?
2485          rem_set->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) :
2486          G1EagerReclaimHumongousObjects && rem_set->is_empty();
2487 }
2488 
2489 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
2490  private:
2491   size_t _total_humongous;
2492   size_t _candidate_humongous;
2493 
2494   DirtyCardQueue _dcq;
2495 
2496   bool humongous_region_is_candidate(G1CollectedHeap* g1h, HeapRegion* region) const {
2497     assert(region->is_starts_humongous(), "Must start a humongous object");
2498 
2499     oop obj = oop(region->bottom());
2500 
2501     // Dead objects cannot be eager reclaim candidates. Due to class
2502     // unloading it is unsafe to query their classes so we return early.
2503     if (g1h->is_obj_dead(obj, region)) {
2504       return false;
2505     }
2506 
2507     // If we do not have a complete remembered set for the region, then we can
2508     // not be sure that we have all references to it.
2509     if (!region->rem_set()->is_complete()) {
2510       return false;
2511     }
2512     // Candidate selection must satisfy the following constraints
2513     // while concurrent marking is in progress:
2514     //
2515     // * In order to maintain SATB invariants, an object must not be
2516     // reclaimed if it was allocated before the start of marking and
2517     // has not had its references scanned.  Such an object must have
2518     // its references (including type metadata) scanned to ensure no
2519     // live objects are missed by the marking process.  Objects
2520     // allocated after the start of concurrent marking don't need to
2521     // be scanned.
2522     //
2523     // * An object must not be reclaimed if it is on the concurrent
2524     // mark stack.  Objects allocated after the start of concurrent
2525     // marking are never pushed on the mark stack.
2526     //
2527     // Nominating only objects allocated after the start of concurrent
2528     // marking is sufficient to meet both constraints.  This may miss
2529     // some objects that satisfy the constraints, but the marking data
2530     // structures don't support efficiently performing the needed
2531     // additional tests or scrubbing of the mark stack.
2532     //
2533     // However, we presently only nominate is_typeArray() objects.
2534     // A humongous object containing references induces remembered
2535     // set entries on other regions.  In order to reclaim such an
2536     // object, those remembered sets would need to be cleaned up.
2537     //
2538     // We also treat is_typeArray() objects specially, allowing them
2539     // to be reclaimed even if allocated before the start of
2540     // concurrent mark.  For this we rely on mark stack insertion to
2541     // exclude is_typeArray() objects, preventing reclaiming an object
2542     // that is in the mark stack.  We also rely on the metadata for
2543     // such objects to be built-in and so ensured to be kept live.
2544     // Frequent allocation and drop of large binary blobs is an
2545     // important use case for eager reclaim, and this special handling
2546     // may reduce needed headroom.
2547 
2548     return obj->is_typeArray() &&
2549            g1h->is_potential_eager_reclaim_candidate(region);
2550   }
2551 
2552  public:
2553   RegisterHumongousWithInCSetFastTestClosure()
2554   : _total_humongous(0),
2555     _candidate_humongous(0),
2556     _dcq(&G1BarrierSet::dirty_card_queue_set()) {
2557   }
2558 
2559   virtual bool do_heap_region(HeapRegion* r) {
2560     if (!r->is_starts_humongous()) {
2561       return false;
2562     }
2563     G1CollectedHeap* g1h = G1CollectedHeap::heap();
2564 
2565     bool is_candidate = humongous_region_is_candidate(g1h, r);
2566     uint rindex = r->hrm_index();
2567     g1h->set_humongous_reclaim_candidate(rindex, is_candidate);
2568     if (is_candidate) {
2569       _candidate_humongous++;
2570       g1h->register_humongous_region_with_cset(rindex);
2571       // Is_candidate already filters out humongous object with large remembered sets.
2572       // If we have a humongous object with a few remembered sets, we simply flush these
2573       // remembered set entries into the DCQS. That will result in automatic
2574       // re-evaluation of their remembered set entries during the following evacuation
2575       // phase.
2576       if (!r->rem_set()->is_empty()) {
2577         guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
2578                   "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
2579         G1CardTable* ct = g1h->card_table();
2580         HeapRegionRemSetIterator hrrs(r->rem_set());
2581         size_t card_index;
2582         while (hrrs.has_next(card_index)) {
2583           jbyte* card_ptr = (jbyte*)ct->byte_for_index(card_index);
2584           // The remembered set might contain references to already freed
2585           // regions. Filter out such entries to avoid failing card table
2586           // verification.
2587           if (g1h->is_in_closed_subset(ct->addr_for(card_ptr))) {
2588             if (*card_ptr != G1CardTable::dirty_card_val()) {
2589               *card_ptr = G1CardTable::dirty_card_val();
2590               _dcq.enqueue(card_ptr);
2591             }
2592           }
2593         }
2594         assert(hrrs.n_yielded() == r->rem_set()->occupied(),
2595                "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries",
2596                hrrs.n_yielded(), r->rem_set()->occupied());
2597         // We should only clear the card based remembered set here as we will not
2598         // implicitly rebuild anything else during eager reclaim. Note that at the moment
2599         // (and probably never) we do not enter this path if there are other kind of
2600         // remembered sets for this region.
2601         r->rem_set()->clear_locked(true /* only_cardset */);
2602         // Clear_locked() above sets the state to Empty. However we want to continue
2603         // collecting remembered set entries for humongous regions that were not
2604         // reclaimed.
2605         r->rem_set()->set_state_complete();
2606       }
2607       assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
2608     }
2609     _total_humongous++;
2610 
2611     return false;
2612   }
2613 
2614   size_t total_humongous() const { return _total_humongous; }
2615   size_t candidate_humongous() const { return _candidate_humongous; }
2616 
2617   void flush_rem_set_entries() { _dcq.flush(); }
2618 };
2619 
2620 void G1CollectedHeap::register_humongous_regions_with_cset() {
2621   if (!G1EagerReclaimHumongousObjects) {
2622     g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
2623     return;
2624   }
2625   double time = os::elapsed_counter();
2626 
2627   // Collect reclaim candidate information and register candidates with cset.
2628   RegisterHumongousWithInCSetFastTestClosure cl;
2629   heap_region_iterate(&cl);
2630 
2631   time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
2632   g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
2633                                                                   cl.total_humongous(),
2634                                                                   cl.candidate_humongous());
2635   _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
2636 
2637   // Finally flush all remembered set entries to re-check into the global DCQS.
2638   cl.flush_rem_set_entries();
2639 }
2640 
2641 class VerifyRegionRemSetClosure : public HeapRegionClosure {
2642   public:
2643     bool do_heap_region(HeapRegion* hr) {
2644       if (!hr->is_archive() && !hr->is_continues_humongous()) {
2645         hr->verify_rem_set();
2646       }
2647       return false;
2648     }
2649 };
2650 
2651 uint G1CollectedHeap::num_task_queues() const {
2652   return _task_queues->size();
2653 }
2654 
2655 #if TASKQUEUE_STATS
2656 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
2657   st->print_raw_cr("GC Task Stats");
2658   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
2659   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
2660 }
2661 
2662 void G1CollectedHeap::print_taskqueue_stats() const {
2663   if (!log_is_enabled(Trace, gc, task, stats)) {
2664     return;
2665   }
2666   Log(gc, task, stats) log;
2667   ResourceMark rm;
2668   LogStream ls(log.trace());
2669   outputStream* st = &ls;
2670 
2671   print_taskqueue_stats_hdr(st);
2672 
2673   TaskQueueStats totals;
2674   const uint n = num_task_queues();
2675   for (uint i = 0; i < n; ++i) {
2676     st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
2677     totals += task_queue(i)->stats;
2678   }
2679   st->print_raw("tot "); totals.print(st); st->cr();
2680 
2681   DEBUG_ONLY(totals.verify());
2682 }
2683 
2684 void G1CollectedHeap::reset_taskqueue_stats() {
2685   const uint n = num_task_queues();
2686   for (uint i = 0; i < n; ++i) {
2687     task_queue(i)->stats.reset();
2688   }
2689 }
2690 #endif // TASKQUEUE_STATS
2691 
2692 void G1CollectedHeap::wait_for_root_region_scanning() {
2693   double scan_wait_start = os::elapsedTime();
2694   // We have to wait until the CM threads finish scanning the
2695   // root regions as it's the only way to ensure that all the
2696   // objects on them have been correctly scanned before we start
2697   // moving them during the GC.
2698   bool waited = _cm->root_regions()->wait_until_scan_finished();
2699   double wait_time_ms = 0.0;
2700   if (waited) {
2701     double scan_wait_end = os::elapsedTime();
2702     wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
2703   }
2704   g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
2705 }
2706 
2707 class G1PrintCollectionSetClosure : public HeapRegionClosure {
2708 private:
2709   G1HRPrinter* _hr_printer;
2710 public:
2711   G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { }
2712 
2713   virtual bool do_heap_region(HeapRegion* r) {
2714     _hr_printer->cset(r);
2715     return false;
2716   }
2717 };
2718 
2719 void G1CollectedHeap::start_new_collection_set() {
2720   collection_set()->start_incremental_building();
2721 
2722   clear_cset_fast_test();
2723 
2724   guarantee(_eden.length() == 0, "eden should have been cleared");
2725   g1_policy()->transfer_survivors_to_cset(survivor());
2726 }
2727 
2728 bool
2729 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
2730   assert_at_safepoint_on_vm_thread();
2731   guarantee(!is_gc_active(), "collection is not reentrant");
2732 
2733   if (GCLocker::check_active_before_gc()) {
2734     return false;
2735   }
2736 
2737   _gc_timer_stw->register_gc_start();
2738 
2739   GCIdMark gc_id_mark;
2740   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
2741 
2742   SvcGCMarker sgcm(SvcGCMarker::MINOR);
2743   ResourceMark rm;
2744 
2745   g1_policy()->note_gc_start();
2746 
2747   wait_for_root_region_scanning();
2748 
2749   print_heap_before_gc();
2750   print_heap_regions();
2751   trace_heap_before_gc(_gc_tracer_stw);
2752 
2753   _verifier->verify_region_sets_optional();
2754   _verifier->verify_dirty_young_regions();
2755 
2756   // We should not be doing initial mark unless the conc mark thread is running
2757   if (!_cm_thread->should_terminate()) {
2758     // This call will decide whether this pause is an initial-mark
2759     // pause. If it is, in_initial_mark_gc() will return true
2760     // for the duration of this pause.
2761     g1_policy()->decide_on_conc_mark_initiation();
2762   }
2763 
2764   // We do not allow initial-mark to be piggy-backed on a mixed GC.
2765   assert(!collector_state()->in_initial_mark_gc() ||
2766           collector_state()->in_young_only_phase(), "sanity");
2767 
2768   // We also do not allow mixed GCs during marking.
2769   assert(!collector_state()->mark_or_rebuild_in_progress() || collector_state()->in_young_only_phase(), "sanity");
2770 
2771   // Record whether this pause is an initial mark. When the current
2772   // thread has completed its logging output and it's safe to signal
2773   // the CM thread, the flag's value in the policy has been reset.
2774   bool should_start_conc_mark = collector_state()->in_initial_mark_gc();
2775 
2776   // Inner scope for scope based logging, timers, and stats collection
2777   {
2778     EvacuationInfo evacuation_info;
2779 
2780     if (collector_state()->in_initial_mark_gc()) {
2781       // We are about to start a marking cycle, so we increment the
2782       // full collection counter.
2783       increment_old_marking_cycles_started();
2784       _cm->gc_tracer_cm()->set_gc_cause(gc_cause());
2785     }
2786 
2787     _gc_tracer_stw->report_yc_type(collector_state()->yc_type());
2788 
2789     GCTraceCPUTime tcpu;
2790 
2791     G1HeapVerifier::G1VerifyType verify_type;
2792     FormatBuffer<> gc_string("Pause ");
2793     if (collector_state()->in_initial_mark_gc()) {
2794       gc_string.append("Initial Mark");
2795       verify_type = G1HeapVerifier::G1VerifyInitialMark;
2796     } else if (collector_state()->in_young_only_phase()) {
2797       gc_string.append("Young");
2798       verify_type = G1HeapVerifier::G1VerifyYoungOnly;
2799     } else {
2800       gc_string.append("Mixed");
2801       verify_type = G1HeapVerifier::G1VerifyMixed;
2802     }
2803     GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true);
2804 
2805     uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
2806                                                                   workers()->active_workers(),
2807                                                                   Threads::number_of_non_daemon_threads());
2808     active_workers = workers()->update_active_workers(active_workers);
2809     log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers());
2810 
2811     TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
2812     TraceMemoryManagerStats tms(&_memory_manager, gc_cause());
2813 
2814     G1HeapTransition heap_transition(this);
2815     size_t heap_used_bytes_before_gc = used();
2816 
2817     // Don't dynamically change the number of GC threads this early.  A value of
2818     // 0 is used to indicate serial work.  When parallel work is done,
2819     // it will be set.
2820 
2821     { // Call to jvmpi::post_class_unload_events must occur outside of active GC
2822       IsGCActiveMark x;
2823 
2824       gc_prologue(false);
2825 
2826       if (VerifyRememberedSets) {
2827         log_info(gc, verify)("[Verifying RemSets before GC]");
2828         VerifyRegionRemSetClosure v_cl;
2829         heap_region_iterate(&v_cl);
2830       }
2831 
2832       _verifier->verify_before_gc(verify_type);
2833 
2834       _verifier->check_bitmaps("GC Start");
2835 
2836 #if COMPILER2_OR_JVMCI
2837       DerivedPointerTable::clear();
2838 #endif
2839 
2840       // Please see comment in g1CollectedHeap.hpp and
2841       // G1CollectedHeap::ref_processing_init() to see how
2842       // reference processing currently works in G1.
2843 
2844       // Enable discovery in the STW reference processor
2845       ref_processor_stw()->enable_discovery();
2846 
2847       {
2848         // We want to temporarily turn off discovery by the
2849         // CM ref processor, if necessary, and turn it back on
2850         // on again later if we do. Using a scoped
2851         // NoRefDiscovery object will do this.
2852         NoRefDiscovery no_cm_discovery(ref_processor_cm());
2853 
2854         // Forget the current alloc region (we might even choose it to be part
2855         // of the collection set!).
2856         _allocator->release_mutator_alloc_region();
2857 
2858         // This timing is only used by the ergonomics to handle our pause target.
2859         // It is unclear why this should not include the full pause. We will
2860         // investigate this in CR 7178365.
2861         //
2862         // Preserving the old comment here if that helps the investigation:
2863         //
2864         // The elapsed time induced by the start time below deliberately elides
2865         // the possible verification above.
2866         double sample_start_time_sec = os::elapsedTime();
2867 
2868         g1_policy()->record_collection_pause_start(sample_start_time_sec);
2869 
2870         if (collector_state()->in_initial_mark_gc()) {
2871           concurrent_mark()->pre_initial_mark();
2872         }
2873 
2874         g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor);
2875 
2876         evacuation_info.set_collectionset_regions(collection_set()->region_length());
2877 
2878         // Make sure the remembered sets are up to date. This needs to be
2879         // done before register_humongous_regions_with_cset(), because the
2880         // remembered sets are used there to choose eager reclaim candidates.
2881         // If the remembered sets are not up to date we might miss some
2882         // entries that need to be handled.
2883         g1_rem_set()->cleanupHRRS();
2884 
2885         register_humongous_regions_with_cset();
2886 
2887         assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table.");
2888 
2889         // We call this after finalize_cset() to
2890         // ensure that the CSet has been finalized.
2891         _cm->verify_no_cset_oops();
2892 
2893         if (_hr_printer.is_active()) {
2894           G1PrintCollectionSetClosure cl(&_hr_printer);
2895           _collection_set.iterate(&cl);
2896         }
2897 
2898         // Initialize the GC alloc regions.
2899         _allocator->init_gc_alloc_regions(evacuation_info);
2900 
2901         G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length());
2902         pre_evacuate_collection_set();
2903 
2904         // Actually do the work...
2905         evacuate_collection_set(&per_thread_states);
2906 
2907         post_evacuate_collection_set(evacuation_info, &per_thread_states);
2908 
2909         const size_t* surviving_young_words = per_thread_states.surviving_young_words();
2910         free_collection_set(&_collection_set, evacuation_info, surviving_young_words);
2911 
2912         eagerly_reclaim_humongous_regions();
2913 
2914         record_obj_copy_mem_stats();
2915         _survivor_evac_stats.adjust_desired_plab_sz();
2916         _old_evac_stats.adjust_desired_plab_sz();
2917 
2918         double start = os::elapsedTime();
2919         start_new_collection_set();
2920         g1_policy()->phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0);
2921 
2922         if (evacuation_failed()) {
2923           set_used(recalculate_used());
2924           if (_archive_allocator != NULL) {
2925             _archive_allocator->clear_used();
2926           }
2927           for (uint i = 0; i < ParallelGCThreads; i++) {
2928             if (_evacuation_failed_info_array[i].has_failed()) {
2929               _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
2930             }
2931           }
2932         } else {
2933           // The "used" of the the collection set have already been subtracted
2934           // when they were freed.  Add in the bytes evacuated.
2935           increase_used(g1_policy()->bytes_copied_during_gc());
2936         }
2937 
2938         if (collector_state()->in_initial_mark_gc()) {
2939           // We have to do this before we notify the CM threads that
2940           // they can start working to make sure that all the
2941           // appropriate initialization is done on the CM object.
2942           concurrent_mark()->post_initial_mark();
2943           // Note that we don't actually trigger the CM thread at
2944           // this point. We do that later when we're sure that
2945           // the current thread has completed its logging output.
2946         }
2947 
2948         allocate_dummy_regions();
2949 
2950         _allocator->init_mutator_alloc_region();
2951 
2952         {
2953           size_t expand_bytes = _heap_sizing_policy->expansion_amount();
2954           if (expand_bytes > 0) {
2955             size_t bytes_before = capacity();
2956             // No need for an ergo logging here,
2957             // expansion_amount() does this when it returns a value > 0.
2958             double expand_ms;
2959             if (!expand(expand_bytes, _workers, &expand_ms)) {
2960               // We failed to expand the heap. Cannot do anything about it.
2961             }
2962             g1_policy()->phase_times()->record_expand_heap_time(expand_ms);
2963           }
2964         }
2965 
2966         // We redo the verification but now wrt to the new CSet which
2967         // has just got initialized after the previous CSet was freed.
2968         _cm->verify_no_cset_oops();
2969 
2970         // This timing is only used by the ergonomics to handle our pause target.
2971         // It is unclear why this should not include the full pause. We will
2972         // investigate this in CR 7178365.
2973         double sample_end_time_sec = os::elapsedTime();
2974         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
2975         size_t total_cards_scanned = g1_policy()->phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanRS, G1GCPhaseTimes::ScanRSScannedCards);
2976         g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc);
2977 
2978         evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before());
2979         evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc());
2980 
2981         if (VerifyRememberedSets) {
2982           log_info(gc, verify)("[Verifying RemSets after GC]");
2983           VerifyRegionRemSetClosure v_cl;
2984           heap_region_iterate(&v_cl);
2985         }
2986 
2987         _verifier->verify_after_gc(verify_type);
2988         _verifier->check_bitmaps("GC End");
2989 
2990         assert(!ref_processor_stw()->discovery_enabled(), "Postcondition");
2991         ref_processor_stw()->verify_no_references_recorded();
2992 
2993         // CM reference discovery will be re-enabled if necessary.
2994       }
2995 
2996 #ifdef TRACESPINNING
2997       ParallelTaskTerminator::print_termination_counts();
2998 #endif
2999 
3000       gc_epilogue(false);
3001     }
3002 
3003     // Print the remainder of the GC log output.
3004     if (evacuation_failed()) {
3005       log_info(gc)("To-space exhausted");
3006     }
3007 
3008     g1_policy()->print_phases();
3009     heap_transition.print();
3010 
3011     // It is not yet to safe to tell the concurrent mark to
3012     // start as we have some optional output below. We don't want the
3013     // output from the concurrent mark thread interfering with this
3014     // logging output either.
3015 
3016     _hrm.verify_optional();
3017     _verifier->verify_region_sets_optional();
3018 
3019     TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
3020     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3021 
3022     print_heap_after_gc();
3023     print_heap_regions();
3024     trace_heap_after_gc(_gc_tracer_stw);
3025 
3026     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3027     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3028     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3029     // before any GC notifications are raised.
3030     g1mm()->update_sizes();
3031 
3032     _gc_tracer_stw->report_evacuation_info(&evacuation_info);
3033     _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
3034     _gc_timer_stw->register_gc_end();
3035     _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
3036   }
3037   // It should now be safe to tell the concurrent mark thread to start
3038   // without its logging output interfering with the logging output
3039   // that came from the pause.
3040 
3041   if (should_start_conc_mark) {
3042     // CAUTION: after the doConcurrentMark() call below,
3043     // the concurrent marking thread(s) could be running
3044     // concurrently with us. Make sure that anything after
3045     // this point does not assume that we are the only GC thread
3046     // running. Note: of course, the actual marking work will
3047     // not start until the safepoint itself is released in
3048     // SuspendibleThreadSet::desynchronize().
3049     do_concurrent_mark();
3050   }
3051 
3052   return true;
3053 }
3054 
3055 void G1CollectedHeap::remove_self_forwarding_pointers() {
3056   G1ParRemoveSelfForwardPtrsTask rsfp_task;
3057   workers()->run_task(&rsfp_task);
3058 }
3059 
3060 void G1CollectedHeap::restore_after_evac_failure() {
3061   double remove_self_forwards_start = os::elapsedTime();
3062 
3063   remove_self_forwarding_pointers();
3064   SharedRestorePreservedMarksTaskExecutor task_executor(workers());
3065   _preserved_marks_set.restore(&task_executor);
3066 
3067   g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
3068 }
3069 
3070 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) {
3071   if (!_evacuation_failed) {
3072     _evacuation_failed = true;
3073   }
3074 
3075   _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size());
3076   _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m);
3077 }
3078 
3079 bool G1ParEvacuateFollowersClosure::offer_termination() {
3080   G1ParScanThreadState* const pss = par_scan_state();
3081   start_term_time();
3082   const bool res = terminator()->offer_termination();
3083   end_term_time();
3084   return res;
3085 }
3086 
3087 void G1ParEvacuateFollowersClosure::do_void() {
3088   G1ParScanThreadState* const pss = par_scan_state();
3089   pss->trim_queue();
3090   do {
3091     pss->steal_and_trim_queue(queues());
3092   } while (!offer_termination());
3093 }
3094 
3095 class G1ParTask : public AbstractGangTask {
3096 protected:
3097   G1CollectedHeap*         _g1h;
3098   G1ParScanThreadStateSet* _pss;
3099   RefToScanQueueSet*       _queues;
3100   G1RootProcessor*         _root_processor;
3101   ParallelTaskTerminator   _terminator;
3102   uint                     _n_workers;
3103 
3104 public:
3105   G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers)
3106     : AbstractGangTask("G1 collection"),
3107       _g1h(g1h),
3108       _pss(per_thread_states),
3109       _queues(task_queues),
3110       _root_processor(root_processor),
3111       _terminator(n_workers, _queues),
3112       _n_workers(n_workers)
3113   {}
3114 
3115   void work(uint worker_id) {
3116     if (worker_id >= _n_workers) return;  // no work needed this round
3117 
3118     double start_sec = os::elapsedTime();
3119     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec);
3120 
3121     {
3122       ResourceMark rm;
3123       HandleMark   hm;
3124 
3125       ReferenceProcessor*             rp = _g1h->ref_processor_stw();
3126 
3127       G1ParScanThreadState*           pss = _pss->state_for_worker(worker_id);
3128       pss->set_ref_processor(rp);
3129 
3130       double start_strong_roots_sec = os::elapsedTime();
3131 
3132       _root_processor->evacuate_roots(pss->closures(), worker_id);
3133 
3134       // We pass a weak code blobs closure to the remembered set scanning because we want to avoid
3135       // treating the nmethods visited to act as roots for concurrent marking.
3136       // We only want to make sure that the oops in the nmethods are adjusted with regard to the
3137       // objects copied by the current evacuation.
3138       _g1h->g1_rem_set()->oops_into_collection_set_do(pss,
3139                                                       pss->closures()->weak_codeblobs(),
3140                                                       worker_id);
3141 
3142       double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec;
3143 
3144       double term_sec = 0.0;
3145       size_t evac_term_attempts = 0;
3146       {
3147         double start = os::elapsedTime();
3148         G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator);
3149         evac.do_void();
3150 
3151         evac_term_attempts = evac.term_attempts();
3152         term_sec = evac.term_time();
3153         double elapsed_sec = os::elapsedTime() - start;
3154         _g1h->g1_policy()->phase_times()->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec);
3155         _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec);
3156         _g1h->g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts);
3157       }
3158 
3159       assert(pss->queue_is_empty(), "should be empty");
3160 
3161       if (log_is_enabled(Debug, gc, task, stats)) {
3162         MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3163         size_t lab_waste;
3164         size_t lab_undo_waste;
3165         pss->waste(lab_waste, lab_undo_waste);
3166         _g1h->print_termination_stats(worker_id,
3167                                       (os::elapsedTime() - start_sec) * 1000.0,   /* elapsed time */
3168                                       strong_roots_sec * 1000.0,                  /* strong roots time */
3169                                       term_sec * 1000.0,                          /* evac term time */
3170                                       evac_term_attempts,                         /* evac term attempts */
3171                                       lab_waste,                                  /* alloc buffer waste */
3172                                       lab_undo_waste                              /* undo waste */
3173                                       );
3174       }
3175 
3176       // Close the inner scope so that the ResourceMark and HandleMark
3177       // destructors are executed here and are included as part of the
3178       // "GC Worker Time".
3179     }
3180     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime());
3181   }
3182 };
3183 
3184 void G1CollectedHeap::print_termination_stats_hdr() {
3185   log_debug(gc, task, stats)("GC Termination Stats");
3186   log_debug(gc, task, stats)("     elapsed  --strong roots-- -------termination------- ------waste (KiB)------");
3187   log_debug(gc, task, stats)("thr     ms        ms      %%        ms      %%    attempts  total   alloc    undo");
3188   log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------");
3189 }
3190 
3191 void G1CollectedHeap::print_termination_stats(uint worker_id,
3192                                               double elapsed_ms,
3193                                               double strong_roots_ms,
3194                                               double term_ms,
3195                                               size_t term_attempts,
3196                                               size_t alloc_buffer_waste,
3197                                               size_t undo_waste) const {
3198   log_debug(gc, task, stats)
3199               ("%3d %9.2f %9.2f %6.2f "
3200                "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
3201                SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
3202                worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms,
3203                term_ms, term_ms * 100 / elapsed_ms, term_attempts,
3204                (alloc_buffer_waste + undo_waste) * HeapWordSize / K,
3205                alloc_buffer_waste * HeapWordSize / K,
3206                undo_waste * HeapWordSize / K);
3207 }
3208 
3209 class G1StringAndSymbolCleaningTask : public AbstractGangTask {
3210 private:
3211   BoolObjectClosure* _is_alive;
3212   G1StringDedupUnlinkOrOopsDoClosure _dedup_closure;
3213 
3214   int _initial_string_table_size;
3215   int _initial_symbol_table_size;
3216 
3217   bool  _process_strings;
3218   int _strings_processed;
3219   int _strings_removed;
3220 
3221   bool  _process_symbols;
3222   int _symbols_processed;
3223   int _symbols_removed;
3224 
3225   bool _process_string_dedup;
3226 
3227 public:
3228   G1StringAndSymbolCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool process_string_dedup) :
3229     AbstractGangTask("String/Symbol Unlinking"),
3230     _is_alive(is_alive),
3231     _dedup_closure(is_alive, NULL, false),
3232     _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
3233     _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0),
3234     _process_string_dedup(process_string_dedup) {
3235 
3236     _initial_string_table_size = StringTable::the_table()->table_size();
3237     _initial_symbol_table_size = SymbolTable::the_table()->table_size();
3238     if (process_strings) {
3239       StringTable::clear_parallel_claimed_index();
3240     }
3241     if (process_symbols) {
3242       SymbolTable::clear_parallel_claimed_index();
3243     }
3244   }
3245 
3246   ~G1StringAndSymbolCleaningTask() {
3247     guarantee(!_process_strings || StringTable::parallel_claimed_index() >= _initial_string_table_size,
3248               "claim value %d after unlink less than initial string table size %d",
3249               StringTable::parallel_claimed_index(), _initial_string_table_size);
3250     guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
3251               "claim value %d after unlink less than initial symbol table size %d",
3252               SymbolTable::parallel_claimed_index(), _initial_symbol_table_size);
3253 
3254     log_info(gc, stringtable)(
3255         "Cleaned string and symbol table, "
3256         "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, "
3257         "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed",
3258         strings_processed(), strings_removed(),
3259         symbols_processed(), symbols_removed());
3260   }
3261 
3262   void work(uint worker_id) {
3263     int strings_processed = 0;
3264     int strings_removed = 0;
3265     int symbols_processed = 0;
3266     int symbols_removed = 0;
3267     if (_process_strings) {
3268       StringTable::possibly_parallel_unlink(_is_alive, &strings_processed, &strings_removed);
3269       Atomic::add(strings_processed, &_strings_processed);
3270       Atomic::add(strings_removed, &_strings_removed);
3271     }
3272     if (_process_symbols) {
3273       SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
3274       Atomic::add(symbols_processed, &_symbols_processed);
3275       Atomic::add(symbols_removed, &_symbols_removed);
3276     }
3277     if (_process_string_dedup) {
3278       G1StringDedup::parallel_unlink(&_dedup_closure, worker_id);
3279     }
3280   }
3281 
3282   size_t strings_processed() const { return (size_t)_strings_processed; }
3283   size_t strings_removed()   const { return (size_t)_strings_removed; }
3284 
3285   size_t symbols_processed() const { return (size_t)_symbols_processed; }
3286   size_t symbols_removed()   const { return (size_t)_symbols_removed; }
3287 };
3288 
3289 class G1CodeCacheUnloadingTask {
3290 private:
3291   static Monitor* _lock;
3292 
3293   BoolObjectClosure* const _is_alive;
3294   const bool               _unloading_occurred;
3295   const uint               _num_workers;
3296 
3297   // Variables used to claim nmethods.
3298   CompiledMethod* _first_nmethod;
3299   CompiledMethod* volatile _claimed_nmethod;
3300 
3301   // The list of nmethods that need to be processed by the second pass.
3302   CompiledMethod* volatile _postponed_list;
3303   volatile uint            _num_entered_barrier;
3304 
3305  public:
3306   G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
3307       _is_alive(is_alive),
3308       _unloading_occurred(unloading_occurred),
3309       _num_workers(num_workers),
3310       _first_nmethod(NULL),
3311       _claimed_nmethod(NULL),
3312       _postponed_list(NULL),
3313       _num_entered_barrier(0)
3314   {
3315     CompiledMethod::increase_unloading_clock();
3316     // Get first alive nmethod
3317     CompiledMethodIterator iter = CompiledMethodIterator();
3318     if(iter.next_alive()) {
3319       _first_nmethod = iter.method();
3320     }
3321     _claimed_nmethod = _first_nmethod;
3322   }
3323 
3324   ~G1CodeCacheUnloadingTask() {
3325     CodeCache::verify_clean_inline_caches();
3326 
3327     CodeCache::set_needs_cache_clean(false);
3328     guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
3329 
3330     CodeCache::verify_icholder_relocations();
3331   }
3332 
3333  private:
3334   void add_to_postponed_list(CompiledMethod* nm) {
3335       CompiledMethod* old;
3336       do {
3337         old = _postponed_list;
3338         nm->set_unloading_next(old);
3339       } while (Atomic::cmpxchg(nm, &_postponed_list, old) != old);
3340   }
3341 
3342   void clean_nmethod(CompiledMethod* nm) {
3343     bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
3344 
3345     if (postponed) {
3346       // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
3347       add_to_postponed_list(nm);
3348     }
3349 
3350     // Mark that this thread has been cleaned/unloaded.
3351     // After this call, it will be safe to ask if this nmethod was unloaded or not.
3352     nm->set_unloading_clock(CompiledMethod::global_unloading_clock());
3353   }
3354 
3355   void clean_nmethod_postponed(CompiledMethod* nm) {
3356     nm->do_unloading_parallel_postponed(_is_alive, _unloading_occurred);
3357   }
3358 
3359   static const int MaxClaimNmethods = 16;
3360 
3361   void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) {
3362     CompiledMethod* first;
3363     CompiledMethodIterator last;
3364 
3365     do {
3366       *num_claimed_nmethods = 0;
3367 
3368       first = _claimed_nmethod;
3369       last = CompiledMethodIterator(first);
3370 
3371       if (first != NULL) {
3372 
3373         for (int i = 0; i < MaxClaimNmethods; i++) {
3374           if (!last.next_alive()) {
3375             break;
3376           }
3377           claimed_nmethods[i] = last.method();
3378           (*num_claimed_nmethods)++;
3379         }
3380       }
3381 
3382     } while (Atomic::cmpxchg(last.method(), &_claimed_nmethod, first) != first);
3383   }
3384 
3385   CompiledMethod* claim_postponed_nmethod() {
3386     CompiledMethod* claim;
3387     CompiledMethod* next;
3388 
3389     do {
3390       claim = _postponed_list;
3391       if (claim == NULL) {
3392         return NULL;
3393       }
3394 
3395       next = claim->unloading_next();
3396 
3397     } while (Atomic::cmpxchg(next, &_postponed_list, claim) != claim);
3398 
3399     return claim;
3400   }
3401 
3402  public:
3403   // Mark that we're done with the first pass of nmethod cleaning.
3404   void barrier_mark(uint worker_id) {
3405     MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3406     _num_entered_barrier++;
3407     if (_num_entered_barrier == _num_workers) {
3408       ml.notify_all();
3409     }
3410   }
3411 
3412   // See if we have to wait for the other workers to
3413   // finish their first-pass nmethod cleaning work.
3414   void barrier_wait(uint worker_id) {
3415     if (_num_entered_barrier < _num_workers) {
3416       MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3417       while (_num_entered_barrier < _num_workers) {
3418           ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
3419       }
3420     }
3421   }
3422 
3423   // Cleaning and unloading of nmethods. Some work has to be postponed
3424   // to the second pass, when we know which nmethods survive.
3425   void work_first_pass(uint worker_id) {
3426     // The first nmethods is claimed by the first worker.
3427     if (worker_id == 0 && _first_nmethod != NULL) {
3428       clean_nmethod(_first_nmethod);
3429       _first_nmethod = NULL;
3430     }
3431 
3432     int num_claimed_nmethods;
3433     CompiledMethod* claimed_nmethods[MaxClaimNmethods];
3434 
3435     while (true) {
3436       claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
3437 
3438       if (num_claimed_nmethods == 0) {
3439         break;
3440       }
3441 
3442       for (int i = 0; i < num_claimed_nmethods; i++) {
3443         clean_nmethod(claimed_nmethods[i]);
3444       }
3445     }
3446   }
3447 
3448   void work_second_pass(uint worker_id) {
3449     CompiledMethod* nm;
3450     // Take care of postponed nmethods.
3451     while ((nm = claim_postponed_nmethod()) != NULL) {
3452       clean_nmethod_postponed(nm);
3453     }
3454   }
3455 };
3456 
3457 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never);
3458 
3459 class G1KlassCleaningTask : public StackObj {
3460   BoolObjectClosure*                      _is_alive;
3461   volatile int                            _clean_klass_tree_claimed;
3462   ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
3463 
3464  public:
3465   G1KlassCleaningTask(BoolObjectClosure* is_alive) :
3466       _is_alive(is_alive),
3467       _clean_klass_tree_claimed(0),
3468       _klass_iterator() {
3469   }
3470 
3471  private:
3472   bool claim_clean_klass_tree_task() {
3473     if (_clean_klass_tree_claimed) {
3474       return false;
3475     }
3476 
3477     return Atomic::cmpxchg(1, &_clean_klass_tree_claimed, 0) == 0;
3478   }
3479 
3480   InstanceKlass* claim_next_klass() {
3481     Klass* klass;
3482     do {
3483       klass =_klass_iterator.next_klass();
3484     } while (klass != NULL && !klass->is_instance_klass());
3485 
3486     // this can be null so don't call InstanceKlass::cast
3487     return static_cast<InstanceKlass*>(klass);
3488   }
3489 
3490 public:
3491 
3492   void clean_klass(InstanceKlass* ik) {
3493     ik->clean_weak_instanceklass_links(_is_alive);
3494   }
3495 
3496   void work() {
3497     ResourceMark rm;
3498 
3499     // One worker will clean the subklass/sibling klass tree.
3500     if (claim_clean_klass_tree_task()) {
3501       Klass::clean_subklass_tree(_is_alive);
3502     }
3503 
3504     // All workers will help cleaning the classes,
3505     InstanceKlass* klass;
3506     while ((klass = claim_next_klass()) != NULL) {
3507       clean_klass(klass);
3508     }
3509   }
3510 };
3511 
3512 class G1ResolvedMethodCleaningTask : public StackObj {
3513   BoolObjectClosure* _is_alive;
3514   volatile int       _resolved_method_task_claimed;
3515 public:
3516   G1ResolvedMethodCleaningTask(BoolObjectClosure* is_alive) :
3517       _is_alive(is_alive), _resolved_method_task_claimed(0) {}
3518 
3519   bool claim_resolved_method_task() {
3520     if (_resolved_method_task_claimed) {
3521       return false;
3522     }
3523     return Atomic::cmpxchg(1, &_resolved_method_task_claimed, 0) == 0;
3524   }
3525 
3526   // These aren't big, one thread can do it all.
3527   void work() {
3528     if (claim_resolved_method_task()) {
3529       ResolvedMethodTable::unlink(_is_alive);
3530     }
3531   }
3532 };
3533 
3534 
3535 // To minimize the remark pause times, the tasks below are done in parallel.
3536 class G1ParallelCleaningTask : public AbstractGangTask {
3537 private:
3538   G1StringAndSymbolCleaningTask _string_symbol_task;
3539   G1CodeCacheUnloadingTask      _code_cache_task;
3540   G1KlassCleaningTask           _klass_cleaning_task;
3541   G1ResolvedMethodCleaningTask  _resolved_method_cleaning_task;
3542 
3543 public:
3544   // The constructor is run in the VMThread.
3545   G1ParallelCleaningTask(BoolObjectClosure* is_alive, uint num_workers, bool unloading_occurred) :
3546       AbstractGangTask("Parallel Cleaning"),
3547       _string_symbol_task(is_alive, true, true, G1StringDedup::is_enabled()),
3548       _code_cache_task(num_workers, is_alive, unloading_occurred),
3549       _klass_cleaning_task(is_alive),
3550       _resolved_method_cleaning_task(is_alive) {
3551   }
3552 
3553   // The parallel work done by all worker threads.
3554   void work(uint worker_id) {
3555     // Do first pass of code cache cleaning.
3556     _code_cache_task.work_first_pass(worker_id);
3557 
3558     // Let the threads mark that the first pass is done.
3559     _code_cache_task.barrier_mark(worker_id);
3560 
3561     // Clean the Strings and Symbols.
3562     _string_symbol_task.work(worker_id);
3563 
3564     // Clean unreferenced things in the ResolvedMethodTable
3565     _resolved_method_cleaning_task.work();
3566 
3567     // Wait for all workers to finish the first code cache cleaning pass.
3568     _code_cache_task.barrier_wait(worker_id);
3569 
3570     // Do the second code cache cleaning work, which realize on
3571     // the liveness information gathered during the first pass.
3572     _code_cache_task.work_second_pass(worker_id);
3573 
3574     // Clean all klasses that were not unloaded.
3575     _klass_cleaning_task.work();
3576   }
3577 };
3578 
3579 
3580 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive,
3581                                         bool class_unloading_occurred) {
3582   uint n_workers = workers()->active_workers();
3583 
3584   G1ParallelCleaningTask g1_unlink_task(is_alive, n_workers, class_unloading_occurred);
3585   workers()->run_task(&g1_unlink_task);
3586 }
3587 
3588 void G1CollectedHeap::partial_cleaning(BoolObjectClosure* is_alive,
3589                                        bool process_strings,
3590                                        bool process_symbols,
3591                                        bool process_string_dedup) {
3592   if (!process_strings && !process_symbols && !process_string_dedup) {
3593     // Nothing to clean.
3594     return;
3595   }
3596 
3597   G1StringAndSymbolCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, process_string_dedup);
3598   workers()->run_task(&g1_unlink_task);
3599 
3600 }
3601 
3602 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
3603  private:
3604   DirtyCardQueueSet* _queue;
3605   G1CollectedHeap* _g1h;
3606  public:
3607   G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"),
3608     _queue(queue), _g1h(g1h) { }
3609 
3610   virtual void work(uint worker_id) {
3611     G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times();
3612     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id);
3613 
3614     RedirtyLoggedCardTableEntryClosure cl(_g1h);
3615     _queue->par_apply_closure_to_all_completed_buffers(&cl);
3616 
3617     phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied());
3618   }
3619 };
3620 
3621 void G1CollectedHeap::redirty_logged_cards() {
3622   double redirty_logged_cards_start = os::elapsedTime();
3623 
3624   G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this);
3625   dirty_card_queue_set().reset_for_par_iteration();
3626   workers()->run_task(&redirty_task);
3627 
3628   DirtyCardQueueSet& dcq = G1BarrierSet::dirty_card_queue_set();
3629   dcq.merge_bufferlists(&dirty_card_queue_set());
3630   assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
3631 
3632   g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
3633 }
3634 
3635 // Weak Reference Processing support
3636 
3637 // An always "is_alive" closure that is used to preserve referents.
3638 // If the object is non-null then it's alive.  Used in the preservation
3639 // of referent objects that are pointed to by reference objects
3640 // discovered by the CM ref processor.
3641 class G1AlwaysAliveClosure: public BoolObjectClosure {
3642   G1CollectedHeap* _g1;
3643 public:
3644   G1AlwaysAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3645   bool do_object_b(oop p) {
3646     if (p != NULL) {
3647       return true;
3648     }
3649     return false;
3650   }
3651 };
3652 
3653 bool G1STWIsAliveClosure::do_object_b(oop p) {
3654   // An object is reachable if it is outside the collection set,
3655   // or is inside and copied.
3656   return !_g1->is_in_cset(p) || p->is_forwarded();
3657 }
3658 
3659 // Non Copying Keep Alive closure
3660 class G1KeepAliveClosure: public OopClosure {
3661   G1CollectedHeap* _g1;
3662 public:
3663   G1KeepAliveClosure(G1CollectedHeap* g1) : _g1(g1) {}
3664   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
3665   void do_oop(oop* p) {
3666     oop obj = *p;
3667     assert(obj != NULL, "the caller should have filtered out NULL values");
3668 
3669     const InCSetState cset_state = _g1->in_cset_state(obj);
3670     if (!cset_state.is_in_cset_or_humongous()) {
3671       return;
3672     }
3673     if (cset_state.is_in_cset()) {
3674       assert( obj->is_forwarded(), "invariant" );
3675       *p = obj->forwardee();
3676     } else {
3677       assert(!obj->is_forwarded(), "invariant" );
3678       assert(cset_state.is_humongous(),
3679              "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value());
3680       _g1->set_humongous_is_live(obj);
3681     }
3682   }
3683 };
3684 
3685 // Copying Keep Alive closure - can be called from both
3686 // serial and parallel code as long as different worker
3687 // threads utilize different G1ParScanThreadState instances
3688 // and different queues.
3689 
3690 class G1CopyingKeepAliveClosure: public OopClosure {
3691   G1CollectedHeap*         _g1h;
3692   OopClosure*              _copy_non_heap_obj_cl;
3693   G1ParScanThreadState*    _par_scan_state;
3694 
3695 public:
3696   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
3697                             OopClosure* non_heap_obj_cl,
3698                             G1ParScanThreadState* pss):
3699     _g1h(g1h),
3700     _copy_non_heap_obj_cl(non_heap_obj_cl),
3701     _par_scan_state(pss)
3702   {}
3703 
3704   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
3705   virtual void do_oop(      oop* p) { do_oop_work(p); }
3706 
3707   template <class T> void do_oop_work(T* p) {
3708     oop obj = RawAccess<>::oop_load(p);
3709 
3710     if (_g1h->is_in_cset_or_humongous(obj)) {
3711       // If the referent object has been forwarded (either copied
3712       // to a new location or to itself in the event of an
3713       // evacuation failure) then we need to update the reference
3714       // field and, if both reference and referent are in the G1
3715       // heap, update the RSet for the referent.
3716       //
3717       // If the referent has not been forwarded then we have to keep
3718       // it alive by policy. Therefore we have copy the referent.
3719       //
3720       // If the reference field is in the G1 heap then we can push
3721       // on the PSS queue. When the queue is drained (after each
3722       // phase of reference processing) the object and it's followers
3723       // will be copied, the reference field set to point to the
3724       // new location, and the RSet updated. Otherwise we need to
3725       // use the the non-heap or metadata closures directly to copy
3726       // the referent object and update the pointer, while avoiding
3727       // updating the RSet.
3728 
3729       if (_g1h->is_in_g1_reserved(p)) {
3730         _par_scan_state->push_on_queue(p);
3731       } else {
3732         assert(!Metaspace::contains((const void*)p),
3733                "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p));
3734         _copy_non_heap_obj_cl->do_oop(p);
3735       }
3736     }
3737   }
3738 };
3739 
3740 // Serial drain queue closure. Called as the 'complete_gc'
3741 // closure for each discovered list in some of the
3742 // reference processing phases.
3743 
3744 class G1STWDrainQueueClosure: public VoidClosure {
3745 protected:
3746   G1CollectedHeap* _g1h;
3747   G1ParScanThreadState* _par_scan_state;
3748 
3749   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
3750 
3751 public:
3752   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
3753     _g1h(g1h),
3754     _par_scan_state(pss)
3755   { }
3756 
3757   void do_void() {
3758     G1ParScanThreadState* const pss = par_scan_state();
3759     pss->trim_queue();
3760   }
3761 };
3762 
3763 // Parallel Reference Processing closures
3764 
3765 // Implementation of AbstractRefProcTaskExecutor for parallel reference
3766 // processing during G1 evacuation pauses.
3767 
3768 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
3769 private:
3770   G1CollectedHeap*          _g1h;
3771   G1ParScanThreadStateSet*  _pss;
3772   RefToScanQueueSet*        _queues;
3773   WorkGang*                 _workers;
3774   uint                      _active_workers;
3775 
3776 public:
3777   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
3778                            G1ParScanThreadStateSet* per_thread_states,
3779                            WorkGang* workers,
3780                            RefToScanQueueSet *task_queues,
3781                            uint n_workers) :
3782     _g1h(g1h),
3783     _pss(per_thread_states),
3784     _queues(task_queues),
3785     _workers(workers),
3786     _active_workers(n_workers)
3787   {
3788     g1h->ref_processor_stw()->set_active_mt_degree(n_workers);
3789   }
3790 
3791   // Executes the given task using concurrent marking worker threads.
3792   virtual void execute(ProcessTask& task);
3793   virtual void execute(EnqueueTask& task);
3794 };
3795 
3796 // Gang task for possibly parallel reference processing
3797 
3798 class G1STWRefProcTaskProxy: public AbstractGangTask {
3799   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
3800   ProcessTask&     _proc_task;
3801   G1CollectedHeap* _g1h;
3802   G1ParScanThreadStateSet* _pss;
3803   RefToScanQueueSet* _task_queues;
3804   ParallelTaskTerminator* _terminator;
3805 
3806 public:
3807   G1STWRefProcTaskProxy(ProcessTask& proc_task,
3808                         G1CollectedHeap* g1h,
3809                         G1ParScanThreadStateSet* per_thread_states,
3810                         RefToScanQueueSet *task_queues,
3811                         ParallelTaskTerminator* terminator) :
3812     AbstractGangTask("Process reference objects in parallel"),
3813     _proc_task(proc_task),
3814     _g1h(g1h),
3815     _pss(per_thread_states),
3816     _task_queues(task_queues),
3817     _terminator(terminator)
3818   {}
3819 
3820   virtual void work(uint worker_id) {
3821     // The reference processing task executed by a single worker.
3822     ResourceMark rm;
3823     HandleMark   hm;
3824 
3825     G1STWIsAliveClosure is_alive(_g1h);
3826 
3827     G1ParScanThreadState*          pss = _pss->state_for_worker(worker_id);
3828     pss->set_ref_processor(NULL);
3829 
3830     // Keep alive closure.
3831     G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
3832 
3833     // Complete GC closure
3834     G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator);
3835 
3836     // Call the reference processing task's work routine.
3837     _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
3838 
3839     // Note we cannot assert that the refs array is empty here as not all
3840     // of the processing tasks (specifically phase2 - pp2_work) execute
3841     // the complete_gc closure (which ordinarily would drain the queue) so
3842     // the queue may not be empty.
3843   }
3844 };
3845 
3846 // Driver routine for parallel reference processing.
3847 // Creates an instance of the ref processing gang
3848 // task and has the worker threads execute it.
3849 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task) {
3850   assert(_workers != NULL, "Need parallel worker threads.");
3851 
3852   ParallelTaskTerminator terminator(_active_workers, _queues);
3853   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator);
3854 
3855   _workers->run_task(&proc_task_proxy);
3856 }
3857 
3858 // Gang task for parallel reference enqueueing.
3859 
3860 class G1STWRefEnqueueTaskProxy: public AbstractGangTask {
3861   typedef AbstractRefProcTaskExecutor::EnqueueTask EnqueueTask;
3862   EnqueueTask& _enq_task;
3863 
3864 public:
3865   G1STWRefEnqueueTaskProxy(EnqueueTask& enq_task) :
3866     AbstractGangTask("Enqueue reference objects in parallel"),
3867     _enq_task(enq_task)
3868   { }
3869 
3870   virtual void work(uint worker_id) {
3871     _enq_task.work(worker_id);
3872   }
3873 };
3874 
3875 // Driver routine for parallel reference enqueueing.
3876 // Creates an instance of the ref enqueueing gang
3877 // task and has the worker threads execute it.
3878 
3879 void G1STWRefProcTaskExecutor::execute(EnqueueTask& enq_task) {
3880   assert(_workers != NULL, "Need parallel worker threads.");
3881 
3882   G1STWRefEnqueueTaskProxy enq_task_proxy(enq_task);
3883 
3884   _workers->run_task(&enq_task_proxy);
3885 }
3886 
3887 // End of weak reference support closures
3888 
3889 // Abstract task used to preserve (i.e. copy) any referent objects
3890 // that are in the collection set and are pointed to by reference
3891 // objects discovered by the CM ref processor.
3892 
3893 class G1ParPreserveCMReferentsTask: public AbstractGangTask {
3894 protected:
3895   G1CollectedHeap*         _g1h;
3896   G1ParScanThreadStateSet* _pss;
3897   RefToScanQueueSet*       _queues;
3898   ParallelTaskTerminator   _terminator;
3899   uint                     _n_workers;
3900 
3901 public:
3902   G1ParPreserveCMReferentsTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, int workers, RefToScanQueueSet *task_queues) :
3903     AbstractGangTask("ParPreserveCMReferents"),
3904     _g1h(g1h),
3905     _pss(per_thread_states),
3906     _queues(task_queues),
3907     _terminator(workers, _queues),
3908     _n_workers(workers)
3909   {
3910     g1h->ref_processor_cm()->set_active_mt_degree(workers);
3911   }
3912 
3913   void work(uint worker_id) {
3914     G1GCParPhaseTimesTracker x(_g1h->g1_policy()->phase_times(), G1GCPhaseTimes::PreserveCMReferents, worker_id);
3915 
3916     ResourceMark rm;
3917     HandleMark   hm;
3918 
3919     G1ParScanThreadState*          pss = _pss->state_for_worker(worker_id);
3920     pss->set_ref_processor(NULL);
3921     assert(pss->queue_is_empty(), "both queue and overflow should be empty");
3922 
3923     // Is alive closure
3924     G1AlwaysAliveClosure always_alive(_g1h);
3925 
3926     // Copying keep alive closure. Applied to referent objects that need
3927     // to be copied.
3928     G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
3929 
3930     ReferenceProcessor* rp = _g1h->ref_processor_cm();
3931 
3932     uint limit = ReferenceProcessor::number_of_subclasses_of_ref() * rp->max_num_q();
3933     uint stride = MIN2(MAX2(_n_workers, 1U), limit);
3934 
3935     // limit is set using max_num_q() - which was set using ParallelGCThreads.
3936     // So this must be true - but assert just in case someone decides to
3937     // change the worker ids.
3938     assert(worker_id < limit, "sanity");
3939     assert(!rp->discovery_is_atomic(), "check this code");
3940 
3941     // Select discovered lists [i, i+stride, i+2*stride,...,limit)
3942     for (uint idx = worker_id; idx < limit; idx += stride) {
3943       DiscoveredList& ref_list = rp->discovered_refs()[idx];
3944 
3945       DiscoveredListIterator iter(ref_list, &keep_alive, &always_alive);
3946       while (iter.has_next()) {
3947         // Since discovery is not atomic for the CM ref processor, we
3948         // can see some null referent objects.
3949         iter.load_ptrs(DEBUG_ONLY(true));
3950         oop ref = iter.obj();
3951 
3952         // This will filter nulls.
3953         if (iter.is_referent_alive()) {
3954           iter.make_referent_alive();
3955         }
3956         iter.move_to_next();
3957       }
3958     }
3959 
3960     // Drain the queue - which may cause stealing
3961     G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _queues, &_terminator);
3962     drain_queue.do_void();
3963     // Allocation buffers were retired at the end of G1ParEvacuateFollowersClosure
3964     assert(pss->queue_is_empty(), "should be");
3965   }
3966 };
3967 
3968 void G1CollectedHeap::preserve_cm_referents(G1ParScanThreadStateSet* per_thread_states) {
3969   // Any reference objects, in the collection set, that were 'discovered'
3970   // by the CM ref processor should have already been copied (either by
3971   // applying the external root copy closure to the discovered lists, or
3972   // by following an RSet entry).
3973   //
3974   // But some of the referents, that are in the collection set, that these
3975   // reference objects point to may not have been copied: the STW ref
3976   // processor would have seen that the reference object had already
3977   // been 'discovered' and would have skipped discovering the reference,
3978   // but would not have treated the reference object as a regular oop.
3979   // As a result the copy closure would not have been applied to the
3980   // referent object.
3981   //
3982   // We need to explicitly copy these referent objects - the references
3983   // will be processed at the end of remarking.
3984   //
3985   // We also need to do this copying before we process the reference
3986   // objects discovered by the STW ref processor in case one of these
3987   // referents points to another object which is also referenced by an
3988   // object discovered by the STW ref processor.
3989   double preserve_cm_referents_time = 0.0;
3990 
3991   // To avoid spawning task when there is no work to do, check that
3992   // a concurrent cycle is active and that some references have been
3993   // discovered.
3994   if (concurrent_mark()->cm_thread()->during_cycle() &&
3995       ref_processor_cm()->has_discovered_references()) {
3996     double preserve_cm_referents_start = os::elapsedTime();
3997     uint no_of_gc_workers = workers()->active_workers();
3998     G1ParPreserveCMReferentsTask keep_cm_referents(this,
3999                                                    per_thread_states,
4000                                                    no_of_gc_workers,
4001                                                    _task_queues);
4002     workers()->run_task(&keep_cm_referents);
4003     preserve_cm_referents_time = os::elapsedTime() - preserve_cm_referents_start;
4004   }
4005 
4006   g1_policy()->phase_times()->record_preserve_cm_referents_time_ms(preserve_cm_referents_time * 1000.0);
4007 }
4008 
4009 // Weak Reference processing during an evacuation pause (part 1).
4010 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4011   double ref_proc_start = os::elapsedTime();
4012 
4013   ReferenceProcessor* rp = _ref_processor_stw;
4014   assert(rp->discovery_enabled(), "should have been enabled");
4015 
4016   // Closure to test whether a referent is alive.
4017   G1STWIsAliveClosure is_alive(this);
4018 
4019   // Even when parallel reference processing is enabled, the processing
4020   // of JNI refs is serial and performed serially by the current thread
4021   // rather than by a worker. The following PSS will be used for processing
4022   // JNI refs.
4023 
4024   // Use only a single queue for this PSS.
4025   G1ParScanThreadState*          pss = per_thread_states->state_for_worker(0);
4026   pss->set_ref_processor(NULL);
4027   assert(pss->queue_is_empty(), "pre-condition");
4028 
4029   // Keep alive closure.
4030   G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss);
4031 
4032   // Serial Complete GC closure
4033   G1STWDrainQueueClosure drain_queue(this, pss);
4034 
4035   // Setup the soft refs policy...
4036   rp->setup_policy(false);
4037 
4038   ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times();
4039 
4040   ReferenceProcessorStats stats;
4041   if (!rp->processing_is_mt()) {
4042     // Serial reference processing...
4043     stats = rp->process_discovered_references(&is_alive,
4044                                               &keep_alive,
4045                                               &drain_queue,
4046                                               NULL,
4047                                               pt);
4048   } else {
4049     uint no_of_gc_workers = workers()->active_workers();
4050 
4051     // Parallel reference processing
4052     assert(no_of_gc_workers <= rp->max_num_q(),
4053            "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
4054            no_of_gc_workers,  rp->max_num_q());
4055 
4056     G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, no_of_gc_workers);
4057     stats = rp->process_discovered_references(&is_alive,
4058                                               &keep_alive,
4059                                               &drain_queue,
4060                                               &par_task_executor,
4061                                               pt);
4062   }
4063 
4064   _gc_tracer_stw->report_gc_reference_stats(stats);
4065 
4066   // We have completed copying any necessary live referent objects.
4067   assert(pss->queue_is_empty(), "both queue and overflow should be empty");
4068 
4069   double ref_proc_time = os::elapsedTime() - ref_proc_start;
4070   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
4071 }
4072 
4073 // Weak Reference processing during an evacuation pause (part 2).
4074 void G1CollectedHeap::enqueue_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
4075   double ref_enq_start = os::elapsedTime();
4076 
4077   ReferenceProcessor* rp = _ref_processor_stw;
4078   assert(!rp->discovery_enabled(), "should have been disabled as part of processing");
4079 
4080   ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times();
4081 
4082   // Now enqueue any remaining on the discovered lists on to
4083   // the pending list.
4084   if (!rp->processing_is_mt()) {
4085     // Serial reference processing...
4086     rp->enqueue_discovered_references(NULL, pt);
4087   } else {
4088     // Parallel reference enqueueing
4089 
4090     uint n_workers = workers()->active_workers();
4091 
4092     assert(n_workers <= rp->max_num_q(),
4093            "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
4094            n_workers,  rp->max_num_q());
4095 
4096     G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues, n_workers);
4097     rp->enqueue_discovered_references(&par_task_executor, pt);
4098   }
4099 
4100   rp->verify_no_references_recorded();
4101   assert(!rp->discovery_enabled(), "should have been disabled");
4102 
4103   // If during an initial mark pause we install a pending list head which is not otherwise reachable
4104   // ensure that it is marked in the bitmap for concurrent marking to discover.
4105   if (collector_state()->in_initial_mark_gc()) {
4106     oop pll_head = Universe::reference_pending_list();
4107     if (pll_head != NULL) {
4108       // Any valid worker id is fine here as we are in the VM thread and single-threaded.
4109       _cm->mark_in_next_bitmap(0 /* worker_id */, pll_head);
4110     }
4111   }
4112 
4113   // FIXME
4114   // CM's reference processing also cleans up the string and symbol tables.
4115   // Should we do that here also? We could, but it is a serial operation
4116   // and could significantly increase the pause time.
4117 
4118   double ref_enq_time = os::elapsedTime() - ref_enq_start;
4119   g1_policy()->phase_times()->record_ref_enq_time(ref_enq_time * 1000.0);
4120 }
4121 
4122 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) {
4123   double merge_pss_time_start = os::elapsedTime();
4124   per_thread_states->flush();
4125   g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0);
4126 }
4127 
4128 void G1CollectedHeap::pre_evacuate_collection_set() {
4129   _expand_heap_after_alloc_failure = true;
4130   _evacuation_failed = false;
4131 
4132   // Disable the hot card cache.
4133   _hot_card_cache->reset_hot_cache_claimed_index();
4134   _hot_card_cache->set_use_cache(false);
4135 
4136   g1_rem_set()->prepare_for_oops_into_collection_set_do();
4137   _preserved_marks_set.assert_empty();
4138 
4139   G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
4140 
4141   // InitialMark needs claim bits to keep track of the marked-through CLDs.
4142   if (collector_state()->in_initial_mark_gc()) {
4143     double start_clear_claimed_marks = os::elapsedTime();
4144 
4145     ClassLoaderDataGraph::clear_claimed_marks();
4146 
4147     double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0;
4148     phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms);
4149   }
4150 }
4151 
4152 void G1CollectedHeap::evacuate_collection_set(G1ParScanThreadStateSet* per_thread_states) {
4153   // Should G1EvacuationFailureALot be in effect for this GC?
4154   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
4155 
4156   assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
4157 
4158   G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
4159 
4160   double start_par_time_sec = os::elapsedTime();
4161   double end_par_time_sec;
4162 
4163   {
4164     const uint n_workers = workers()->active_workers();
4165     G1RootProcessor root_processor(this, n_workers);
4166     G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers);
4167 
4168     print_termination_stats_hdr();
4169 
4170     workers()->run_task(&g1_par_task);
4171     end_par_time_sec = os::elapsedTime();
4172 
4173     // Closing the inner scope will execute the destructor
4174     // for the G1RootProcessor object. We record the current
4175     // elapsed time before closing the scope so that time
4176     // taken for the destructor is NOT included in the
4177     // reported parallel time.
4178   }
4179 
4180   double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
4181   phase_times->record_par_time(par_time_ms);
4182 
4183   double code_root_fixup_time_ms =
4184         (os::elapsedTime() - end_par_time_sec) * 1000.0;
4185   phase_times->record_code_root_fixup_time(code_root_fixup_time_ms);
4186 }
4187 
4188 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4189   // Process any discovered reference objects - we have
4190   // to do this _before_ we retire the GC alloc regions
4191   // as we may have to copy some 'reachable' referent
4192   // objects (and their reachable sub-graphs) that were
4193   // not copied during the pause.
4194   preserve_cm_referents(per_thread_states);
4195   process_discovered_references(per_thread_states);
4196 
4197   G1STWIsAliveClosure is_alive(this);
4198   G1KeepAliveClosure keep_alive(this);
4199 
4200   {
4201     double start = os::elapsedTime();
4202 
4203     WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
4204 
4205     double time_ms = (os::elapsedTime() - start) * 1000.0;
4206     g1_policy()->phase_times()->record_ref_proc_time(time_ms);
4207   }
4208 
4209   if (G1StringDedup::is_enabled()) {
4210     double fixup_start = os::elapsedTime();
4211 
4212     G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times());
4213 
4214     double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
4215     g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms);
4216   }
4217 
4218   g1_rem_set()->cleanup_after_oops_into_collection_set_do();
4219 
4220   if (evacuation_failed()) {
4221     restore_after_evac_failure();
4222 
4223     // Reset the G1EvacuationFailureALot counters and flags
4224     // Note: the values are reset only when an actual
4225     // evacuation failure occurs.
4226     NOT_PRODUCT(reset_evacuation_should_fail();)
4227   }
4228 
4229   _preserved_marks_set.assert_empty();
4230 
4231   // Enqueue any remaining references remaining on the STW
4232   // reference processor's discovered lists. We need to do
4233   // this after the card table is cleaned (and verified) as
4234   // the act of enqueueing entries on to the pending list
4235   // will log these updates (and dirty their associated
4236   // cards). We need these updates logged to update any
4237   // RSets.
4238   enqueue_discovered_references(per_thread_states);
4239 
4240   _allocator->release_gc_alloc_regions(evacuation_info);
4241 
4242   merge_per_thread_state_info(per_thread_states);
4243 
4244   // Reset and re-enable the hot card cache.
4245   // Note the counts for the cards in the regions in the
4246   // collection set are reset when the collection set is freed.
4247   _hot_card_cache->reset_hot_cache();
4248   _hot_card_cache->set_use_cache(true);
4249 
4250   purge_code_root_memory();
4251 
4252   redirty_logged_cards();
4253 #if COMPILER2_OR_JVMCI
4254   double start = os::elapsedTime();
4255   DerivedPointerTable::update_pointers();
4256   g1_policy()->phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0);
4257 #endif
4258   g1_policy()->print_age_table();
4259 }
4260 
4261 void G1CollectedHeap::record_obj_copy_mem_stats() {
4262   g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
4263 
4264   _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
4265                                                create_g1_evac_summary(&_old_evac_stats));
4266 }
4267 
4268 void G1CollectedHeap::free_region(HeapRegion* hr,
4269                                   FreeRegionList* free_list,
4270                                   bool skip_remset,
4271                                   bool skip_hot_card_cache,
4272                                   bool locked) {
4273   assert(!hr->is_free(), "the region should not be free");
4274   assert(!hr->is_empty(), "the region should not be empty");
4275   assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
4276   assert(free_list != NULL, "pre-condition");
4277 
4278   if (G1VerifyBitmaps) {
4279     MemRegion mr(hr->bottom(), hr->end());
4280     concurrent_mark()->clear_range_in_prev_bitmap(mr);
4281   }
4282 
4283   // Clear the card counts for this region.
4284   // Note: we only need to do this if the region is not young
4285   // (since we don't refine cards in young regions).
4286   if (!skip_hot_card_cache && !hr->is_young()) {
4287     _hot_card_cache->reset_card_counts(hr);
4288   }
4289   hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */);
4290   _g1_policy->remset_tracker()->update_at_free(hr);
4291   free_list->add_ordered(hr);
4292 }
4293 
4294 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
4295                                             FreeRegionList* free_list) {
4296   assert(hr->is_humongous(), "this is only for humongous regions");
4297   assert(free_list != NULL, "pre-condition");
4298   hr->clear_humongous();
4299   free_region(hr, free_list, false /* skip_remset */, false /* skip_hcc */, true /* locked */);
4300 }
4301 
4302 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed,
4303                                            const uint humongous_regions_removed) {
4304   if (old_regions_removed > 0 || humongous_regions_removed > 0) {
4305     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4306     _old_set.bulk_remove(old_regions_removed);
4307     _humongous_set.bulk_remove(humongous_regions_removed);
4308   }
4309 
4310 }
4311 
4312 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
4313   assert(list != NULL, "list can't be null");
4314   if (!list->is_empty()) {
4315     MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4316     _hrm.insert_list_into_free_list(list);
4317   }
4318 }
4319 
4320 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
4321   decrease_used(bytes);
4322 }
4323 
4324 class G1FreeCollectionSetTask : public AbstractGangTask {
4325 private:
4326 
4327   // Closure applied to all regions in the collection set to do work that needs to
4328   // be done serially in a single thread.
4329   class G1SerialFreeCollectionSetClosure : public HeapRegionClosure {
4330   private:
4331     EvacuationInfo* _evacuation_info;
4332     const size_t* _surviving_young_words;
4333 
4334     // Bytes used in successfully evacuated regions before the evacuation.
4335     size_t _before_used_bytes;
4336     // Bytes used in unsucessfully evacuated regions before the evacuation
4337     size_t _after_used_bytes;
4338 
4339     size_t _bytes_allocated_in_old_since_last_gc;
4340 
4341     size_t _failure_used_words;
4342     size_t _failure_waste_words;
4343 
4344     FreeRegionList _local_free_list;
4345   public:
4346     G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4347       HeapRegionClosure(),
4348       _evacuation_info(evacuation_info),
4349       _surviving_young_words(surviving_young_words),
4350       _before_used_bytes(0),
4351       _after_used_bytes(0),
4352       _bytes_allocated_in_old_since_last_gc(0),
4353       _failure_used_words(0),
4354       _failure_waste_words(0),
4355       _local_free_list("Local Region List for CSet Freeing") {
4356     }
4357 
4358     virtual bool do_heap_region(HeapRegion* r) {
4359       G1CollectedHeap* g1h = G1CollectedHeap::heap();
4360 
4361       assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index());
4362       g1h->clear_in_cset(r);
4363 
4364       if (r->is_young()) {
4365         assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(),
4366                "Young index %d is wrong for region %u of type %s with %u young regions",
4367                r->young_index_in_cset(),
4368                r->hrm_index(),
4369                r->get_type_str(),
4370                g1h->collection_set()->young_region_length());
4371         size_t words_survived = _surviving_young_words[r->young_index_in_cset()];
4372         r->record_surv_words_in_group(words_survived);
4373       }
4374 
4375       if (!r->evacuation_failed()) {
4376         assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index());
4377         _before_used_bytes += r->used();
4378         g1h->free_region(r,
4379                          &_local_free_list,
4380                          true, /* skip_remset */
4381                          true, /* skip_hot_card_cache */
4382                          true  /* locked */);
4383       } else {
4384         r->uninstall_surv_rate_group();
4385         r->set_young_index_in_cset(-1);
4386         r->set_evacuation_failed(false);
4387         // When moving a young gen region to old gen, we "allocate" that whole region
4388         // there. This is in addition to any already evacuated objects. Notify the
4389         // policy about that.
4390         // Old gen regions do not cause an additional allocation: both the objects
4391         // still in the region and the ones already moved are accounted for elsewhere.
4392         if (r->is_young()) {
4393           _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes;
4394         }
4395         // The region is now considered to be old.
4396         r->set_old();
4397         // Do some allocation statistics accounting. Regions that failed evacuation
4398         // are always made old, so there is no need to update anything in the young
4399         // gen statistics, but we need to update old gen statistics.
4400         size_t used_words = r->marked_bytes() / HeapWordSize;
4401 
4402         _failure_used_words += used_words;
4403         _failure_waste_words += HeapRegion::GrainWords - used_words;
4404 
4405         g1h->old_set_add(r);
4406         _after_used_bytes += r->used();
4407       }
4408       return false;
4409     }
4410 
4411     void complete_work() {
4412       G1CollectedHeap* g1h = G1CollectedHeap::heap();
4413 
4414       _evacuation_info->set_regions_freed(_local_free_list.length());
4415       _evacuation_info->increment_collectionset_used_after(_after_used_bytes);
4416 
4417       g1h->prepend_to_freelist(&_local_free_list);
4418       g1h->decrement_summary_bytes(_before_used_bytes);
4419 
4420       G1Policy* policy = g1h->g1_policy();
4421       policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc);
4422 
4423       g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words);
4424     }
4425   };
4426 
4427   G1CollectionSet* _collection_set;
4428   G1SerialFreeCollectionSetClosure _cl;
4429   const size_t* _surviving_young_words;
4430 
4431   size_t _rs_lengths;
4432 
4433   volatile jint _serial_work_claim;
4434 
4435   struct WorkItem {
4436     uint region_idx;
4437     bool is_young;
4438     bool evacuation_failed;
4439 
4440     WorkItem(HeapRegion* r) {
4441       region_idx = r->hrm_index();
4442       is_young = r->is_young();
4443       evacuation_failed = r->evacuation_failed();
4444     }
4445   };
4446 
4447   volatile size_t _parallel_work_claim;
4448   size_t _num_work_items;
4449   WorkItem* _work_items;
4450 
4451   void do_serial_work() {
4452     // Need to grab the lock to be allowed to modify the old region list.
4453     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4454     _collection_set->iterate(&_cl);
4455   }
4456 
4457   void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) {
4458     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4459 
4460     HeapRegion* r = g1h->region_at(region_idx);
4461     assert(!g1h->is_on_master_free_list(r), "sanity");
4462 
4463     Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths);
4464 
4465     if (!is_young) {
4466       g1h->_hot_card_cache->reset_card_counts(r);
4467     }
4468 
4469     if (!evacuation_failed) {
4470       r->rem_set()->clear_locked();
4471     }
4472   }
4473 
4474   class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure {
4475   private:
4476     size_t _cur_idx;
4477     WorkItem* _work_items;
4478   public:
4479     G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { }
4480 
4481     virtual bool do_heap_region(HeapRegion* r) {
4482       _work_items[_cur_idx++] = WorkItem(r);
4483       return false;
4484     }
4485   };
4486 
4487   void prepare_work() {
4488     G1PrepareFreeCollectionSetClosure cl(_work_items);
4489     _collection_set->iterate(&cl);
4490   }
4491 
4492   void complete_work() {
4493     _cl.complete_work();
4494 
4495     G1Policy* policy = G1CollectedHeap::heap()->g1_policy();
4496     policy->record_max_rs_lengths(_rs_lengths);
4497     policy->cset_regions_freed();
4498   }
4499 public:
4500   G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4501     AbstractGangTask("G1 Free Collection Set"),
4502     _cl(evacuation_info, surviving_young_words),
4503     _collection_set(collection_set),
4504     _surviving_young_words(surviving_young_words),
4505     _serial_work_claim(0),
4506     _rs_lengths(0),
4507     _parallel_work_claim(0),
4508     _num_work_items(collection_set->region_length()),
4509     _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) {
4510     prepare_work();
4511   }
4512 
4513   ~G1FreeCollectionSetTask() {
4514     complete_work();
4515     FREE_C_HEAP_ARRAY(WorkItem, _work_items);
4516   }
4517 
4518   // Chunk size for work distribution. The chosen value has been determined experimentally
4519   // to be a good tradeoff between overhead and achievable parallelism.
4520   static uint chunk_size() { return 32; }
4521 
4522   virtual void work(uint worker_id) {
4523     G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
4524 
4525     // Claim serial work.
4526     if (_serial_work_claim == 0) {
4527       jint value = Atomic::add(1, &_serial_work_claim) - 1;
4528       if (value == 0) {
4529         double serial_time = os::elapsedTime();
4530         do_serial_work();
4531         timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0);
4532       }
4533     }
4534 
4535     // Start parallel work.
4536     double young_time = 0.0;
4537     bool has_young_time = false;
4538     double non_young_time = 0.0;
4539     bool has_non_young_time = false;
4540 
4541     while (true) {
4542       size_t end = Atomic::add(chunk_size(), &_parallel_work_claim);
4543       size_t cur = end - chunk_size();
4544 
4545       if (cur >= _num_work_items) {
4546         break;
4547       }
4548 
4549       double start_time = os::elapsedTime();
4550 
4551       end = MIN2(end, _num_work_items);
4552 
4553       for (; cur < end; cur++) {
4554         bool is_young = _work_items[cur].is_young;
4555 
4556         do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed);
4557 
4558         double end_time = os::elapsedTime();
4559         double time_taken = end_time - start_time;
4560         if (is_young) {
4561           young_time += time_taken;
4562           has_young_time = true;
4563         } else {
4564           non_young_time += time_taken;
4565           has_non_young_time = true;
4566         }
4567         start_time = end_time;
4568       }
4569     }
4570 
4571     if (has_young_time) {
4572       timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time);
4573     }
4574     if (has_non_young_time) {
4575       timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, non_young_time);
4576     }
4577   }
4578 };
4579 
4580 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) {
4581   _eden.clear();
4582 
4583   double free_cset_start_time = os::elapsedTime();
4584 
4585   {
4586     uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U);
4587     uint const num_workers = MIN2(workers()->active_workers(), num_chunks);
4588 
4589     G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words);
4590 
4591     log_debug(gc, ergo)("Running %s using %u workers for collection set length %u",
4592                         cl.name(),
4593                         num_workers,
4594                         _collection_set.region_length());
4595     workers()->run_task(&cl, num_workers);
4596   }
4597   g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0);
4598 
4599   collection_set->clear();
4600 }
4601 
4602 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
4603  private:
4604   FreeRegionList* _free_region_list;
4605   HeapRegionSet* _proxy_set;
4606   uint _humongous_objects_reclaimed;
4607   uint _humongous_regions_reclaimed;
4608   size_t _freed_bytes;
4609  public:
4610 
4611   G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
4612     _free_region_list(free_region_list), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) {
4613   }
4614 
4615   virtual bool do_heap_region(HeapRegion* r) {
4616     if (!r->is_starts_humongous()) {
4617       return false;
4618     }
4619 
4620     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4621 
4622     oop obj = (oop)r->bottom();
4623     G1CMBitMap* next_bitmap = g1h->concurrent_mark()->next_mark_bitmap();
4624 
4625     // The following checks whether the humongous object is live are sufficient.
4626     // The main additional check (in addition to having a reference from the roots
4627     // or the young gen) is whether the humongous object has a remembered set entry.
4628     //
4629     // A humongous object cannot be live if there is no remembered set for it
4630     // because:
4631     // - there can be no references from within humongous starts regions referencing
4632     // the object because we never allocate other objects into them.
4633     // (I.e. there are no intra-region references that may be missed by the
4634     // remembered set)
4635     // - as soon there is a remembered set entry to the humongous starts region
4636     // (i.e. it has "escaped" to an old object) this remembered set entry will stay
4637     // until the end of a concurrent mark.
4638     //
4639     // It is not required to check whether the object has been found dead by marking
4640     // or not, in fact it would prevent reclamation within a concurrent cycle, as
4641     // all objects allocated during that time are considered live.
4642     // SATB marking is even more conservative than the remembered set.
4643     // So if at this point in the collection there is no remembered set entry,
4644     // nobody has a reference to it.
4645     // At the start of collection we flush all refinement logs, and remembered sets
4646     // are completely up-to-date wrt to references to the humongous object.
4647     //
4648     // Other implementation considerations:
4649     // - never consider object arrays at this time because they would pose
4650     // considerable effort for cleaning up the the remembered sets. This is
4651     // required because stale remembered sets might reference locations that
4652     // are currently allocated into.
4653     uint region_idx = r->hrm_index();
4654     if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
4655         !r->rem_set()->is_empty()) {
4656       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",
4657                                region_idx,
4658                                (size_t)obj->size() * HeapWordSize,
4659                                p2i(r->bottom()),
4660                                r->rem_set()->occupied(),
4661                                r->rem_set()->strong_code_roots_list_length(),
4662                                next_bitmap->is_marked(r->bottom()),
4663                                g1h->is_humongous_reclaim_candidate(region_idx),
4664                                obj->is_typeArray()
4665                               );
4666       return false;
4667     }
4668 
4669     guarantee(obj->is_typeArray(),
4670               "Only eagerly reclaiming type arrays is supported, but the object "
4671               PTR_FORMAT " is not.", p2i(r->bottom()));
4672 
4673     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",
4674                              region_idx,
4675                              (size_t)obj->size() * HeapWordSize,
4676                              p2i(r->bottom()),
4677                              r->rem_set()->occupied(),
4678                              r->rem_set()->strong_code_roots_list_length(),
4679                              next_bitmap->is_marked(r->bottom()),
4680                              g1h->is_humongous_reclaim_candidate(region_idx),
4681                              obj->is_typeArray()
4682                             );
4683 
4684     G1ConcurrentMark* const cm = g1h->concurrent_mark();
4685     cm->humongous_object_eagerly_reclaimed(r);
4686     assert(!cm->is_marked_in_prev_bitmap(obj) && !cm->is_marked_in_next_bitmap(obj),
4687            "Eagerly reclaimed humongous region %u should not be marked at all but is in prev %s next %s",
4688            region_idx,
4689            BOOL_TO_STR(cm->is_marked_in_prev_bitmap(obj)),
4690            BOOL_TO_STR(cm->is_marked_in_next_bitmap(obj)));
4691     _humongous_objects_reclaimed++;
4692     do {
4693       HeapRegion* next = g1h->next_region_in_humongous(r);
4694       _freed_bytes += r->used();
4695       r->set_containing_set(NULL);
4696       _humongous_regions_reclaimed++;
4697       g1h->free_humongous_region(r, _free_region_list);
4698       r = next;
4699     } while (r != NULL);
4700 
4701     return false;
4702   }
4703 
4704   uint humongous_objects_reclaimed() {
4705     return _humongous_objects_reclaimed;
4706   }
4707 
4708   uint humongous_regions_reclaimed() {
4709     return _humongous_regions_reclaimed;
4710   }
4711 
4712   size_t bytes_freed() const {
4713     return _freed_bytes;
4714   }
4715 };
4716 
4717 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
4718   assert_at_safepoint_on_vm_thread();
4719 
4720   if (!G1EagerReclaimHumongousObjects ||
4721       (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) {
4722     g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
4723     return;
4724   }
4725 
4726   double start_time = os::elapsedTime();
4727 
4728   FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
4729 
4730   G1FreeHumongousRegionClosure cl(&local_cleanup_list);
4731   heap_region_iterate(&cl);
4732 
4733   remove_from_old_sets(0, cl.humongous_regions_reclaimed());
4734 
4735   G1HRPrinter* hrp = hr_printer();
4736   if (hrp->is_active()) {
4737     FreeRegionListIterator iter(&local_cleanup_list);
4738     while (iter.more_available()) {
4739       HeapRegion* hr = iter.get_next();
4740       hrp->cleanup(hr);
4741     }
4742   }
4743 
4744   prepend_to_freelist(&local_cleanup_list);
4745   decrement_summary_bytes(cl.bytes_freed());
4746 
4747   g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
4748                                                                     cl.humongous_objects_reclaimed());
4749 }
4750 
4751 class G1AbandonCollectionSetClosure : public HeapRegionClosure {
4752 public:
4753   virtual bool do_heap_region(HeapRegion* r) {
4754     assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index());
4755     G1CollectedHeap::heap()->clear_in_cset(r);
4756     r->set_young_index_in_cset(-1);
4757     return false;
4758   }
4759 };
4760 
4761 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) {
4762   G1AbandonCollectionSetClosure cl;
4763   collection_set->iterate(&cl);
4764 
4765   collection_set->clear();
4766   collection_set->stop_incremental_building();
4767 }
4768 
4769 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
4770   return _allocator->is_retained_old_region(hr);
4771 }
4772 
4773 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
4774   _eden.add(hr);
4775   _g1_policy->set_region_eden(hr);
4776 }
4777 
4778 #ifdef ASSERT
4779 
4780 class NoYoungRegionsClosure: public HeapRegionClosure {
4781 private:
4782   bool _success;
4783 public:
4784   NoYoungRegionsClosure() : _success(true) { }
4785   bool do_heap_region(HeapRegion* r) {
4786     if (r->is_young()) {
4787       log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
4788                             p2i(r->bottom()), p2i(r->end()));
4789       _success = false;
4790     }
4791     return false;
4792   }
4793   bool success() { return _success; }
4794 };
4795 
4796 bool G1CollectedHeap::check_young_list_empty() {
4797   bool ret = (young_regions_count() == 0);
4798 
4799   NoYoungRegionsClosure closure;
4800   heap_region_iterate(&closure);
4801   ret = ret && closure.success();
4802 
4803   return ret;
4804 }
4805 
4806 #endif // ASSERT
4807 
4808 class TearDownRegionSetsClosure : public HeapRegionClosure {
4809 private:
4810   HeapRegionSet *_old_set;
4811 
4812 public:
4813   TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
4814 
4815   bool do_heap_region(HeapRegion* r) {
4816     if (r->is_old()) {
4817       _old_set->remove(r);
4818     } else if(r->is_young()) {
4819       r->uninstall_surv_rate_group();
4820     } else {
4821       // We ignore free regions, we'll empty the free list afterwards.
4822       // We ignore humongous regions, we're not tearing down the
4823       // humongous regions set.
4824       assert(r->is_free() || r->is_humongous(),
4825              "it cannot be another type");
4826     }
4827     return false;
4828   }
4829 
4830   ~TearDownRegionSetsClosure() {
4831     assert(_old_set->is_empty(), "post-condition");
4832   }
4833 };
4834 
4835 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
4836   assert_at_safepoint_on_vm_thread();
4837 
4838   if (!free_list_only) {
4839     TearDownRegionSetsClosure cl(&_old_set);
4840     heap_region_iterate(&cl);
4841 
4842     // Note that emptying the _young_list is postponed and instead done as
4843     // the first step when rebuilding the regions sets again. The reason for
4844     // this is that during a full GC string deduplication needs to know if
4845     // a collected region was young or old when the full GC was initiated.
4846   }
4847   _hrm.remove_all_free_regions();
4848 }
4849 
4850 void G1CollectedHeap::increase_used(size_t bytes) {
4851   _summary_bytes_used += bytes;
4852 }
4853 
4854 void G1CollectedHeap::decrease_used(size_t bytes) {
4855   assert(_summary_bytes_used >= bytes,
4856          "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
4857          _summary_bytes_used, bytes);
4858   _summary_bytes_used -= bytes;
4859 }
4860 
4861 void G1CollectedHeap::set_used(size_t bytes) {
4862   _summary_bytes_used = bytes;
4863 }
4864 
4865 class RebuildRegionSetsClosure : public HeapRegionClosure {
4866 private:
4867   bool            _free_list_only;
4868   HeapRegionSet*   _old_set;
4869   HeapRegionManager*   _hrm;
4870   size_t          _total_used;
4871 
4872 public:
4873   RebuildRegionSetsClosure(bool free_list_only,
4874                            HeapRegionSet* old_set, HeapRegionManager* hrm) :
4875     _free_list_only(free_list_only),
4876     _old_set(old_set), _hrm(hrm), _total_used(0) {
4877     assert(_hrm->num_free_regions() == 0, "pre-condition");
4878     if (!free_list_only) {
4879       assert(_old_set->is_empty(), "pre-condition");
4880     }
4881   }
4882 
4883   bool do_heap_region(HeapRegion* r) {
4884     // After full GC, no region should have a remembered set.
4885     r->rem_set()->clear(true);
4886     if (r->is_empty()) {
4887       // Add free regions to the free list
4888       r->set_free();
4889       _hrm->insert_into_free_list(r);
4890     } else if (!_free_list_only) {
4891 
4892       if (r->is_humongous()) {
4893         // We ignore humongous regions. We left the humongous set unchanged.
4894       } else {
4895         assert(r->is_young() || r->is_free() || r->is_old(), "invariant");
4896         // We now move all (non-humongous, non-old) regions to old gen, and register them as such.
4897         r->move_to_old();
4898         _old_set->add(r);
4899       }
4900       _total_used += r->used();
4901     }
4902 
4903     return false;
4904   }
4905 
4906   size_t total_used() {
4907     return _total_used;
4908   }
4909 };
4910 
4911 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
4912   assert_at_safepoint_on_vm_thread();
4913 
4914   if (!free_list_only) {
4915     _eden.clear();
4916     _survivor.clear();
4917   }
4918 
4919   RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
4920   heap_region_iterate(&cl);
4921 
4922   if (!free_list_only) {
4923     set_used(cl.total_used());
4924     if (_archive_allocator != NULL) {
4925       _archive_allocator->clear_used();
4926     }
4927   }
4928   assert(used_unlocked() == recalculate_used(),
4929          "inconsistent used_unlocked(), "
4930          "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT,
4931          used_unlocked(), recalculate_used());
4932 }
4933 
4934 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
4935   HeapRegion* hr = heap_region_containing(p);
4936   return hr->is_in(p);
4937 }
4938 
4939 // Methods for the mutator alloc region
4940 
4941 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
4942                                                       bool force) {
4943   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
4944   bool should_allocate = g1_policy()->should_allocate_mutator_region();
4945   if (force || should_allocate) {
4946     HeapRegion* new_alloc_region = new_region(word_size,
4947                                               false /* is_old */,
4948                                               false /* do_expand */);
4949     if (new_alloc_region != NULL) {
4950       set_region_short_lived_locked(new_alloc_region);
4951       _hr_printer.alloc(new_alloc_region, !should_allocate);
4952       _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region);
4953       _g1_policy->remset_tracker()->update_at_allocate(new_alloc_region);
4954       return new_alloc_region;
4955     }
4956   }
4957   return NULL;
4958 }
4959 
4960 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
4961                                                   size_t allocated_bytes) {
4962   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
4963   assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
4964 
4965   collection_set()->add_eden_region(alloc_region);
4966   increase_used(allocated_bytes);
4967   _hr_printer.retire(alloc_region);
4968   // We update the eden sizes here, when the region is retired,
4969   // instead of when it's allocated, since this is the point that its
4970   // used space has been recored in _summary_bytes_used.
4971   g1mm()->update_eden_size();
4972 }
4973 
4974 // Methods for the GC alloc regions
4975 
4976 bool G1CollectedHeap::has_more_regions(InCSetState dest) {
4977   if (dest.is_old()) {
4978     return true;
4979   } else {
4980     return survivor_regions_count() < g1_policy()->max_survivor_regions();
4981   }
4982 }
4983 
4984 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) {
4985   assert(FreeList_lock->owned_by_self(), "pre-condition");
4986 
4987   if (!has_more_regions(dest)) {
4988     return NULL;
4989   }
4990 
4991   const bool is_survivor = dest.is_young();
4992 
4993   HeapRegion* new_alloc_region = new_region(word_size,
4994                                             !is_survivor,
4995                                             true /* do_expand */);
4996   if (new_alloc_region != NULL) {
4997     if (is_survivor) {
4998       new_alloc_region->set_survivor();
4999       _survivor.add(new_alloc_region);
5000       _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region);
5001     } else {
5002       new_alloc_region->set_old();
5003       _verifier->check_bitmaps("Old Region Allocation", new_alloc_region);
5004     }
5005     _g1_policy->remset_tracker()->update_at_allocate(new_alloc_region);
5006     _hr_printer.alloc(new_alloc_region);
5007     bool during_im = collector_state()->in_initial_mark_gc();
5008     new_alloc_region->note_start_of_copying(during_im);
5009     return new_alloc_region;
5010   }
5011   return NULL;
5012 }
5013 
5014 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
5015                                              size_t allocated_bytes,
5016                                              InCSetState dest) {
5017   bool during_im = collector_state()->in_initial_mark_gc();
5018   alloc_region->note_end_of_copying(during_im);
5019   g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
5020   if (dest.is_old()) {
5021     _old_set.add(alloc_region);
5022   }
5023   _hr_printer.retire(alloc_region);
5024 }
5025 
5026 HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
5027   bool expanded = false;
5028   uint index = _hrm.find_highest_free(&expanded);
5029 
5030   if (index != G1_NO_HRM_INDEX) {
5031     if (expanded) {
5032       log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
5033                                 HeapRegion::GrainWords * HeapWordSize);
5034     }
5035     _hrm.allocate_free_regions_starting_at(index, 1);
5036     return region_at(index);
5037   }
5038   return NULL;
5039 }
5040 
5041 // Optimized nmethod scanning
5042 
5043 class RegisterNMethodOopClosure: public OopClosure {
5044   G1CollectedHeap* _g1h;
5045   nmethod* _nm;
5046 
5047   template <class T> void do_oop_work(T* p) {
5048     T heap_oop = RawAccess<>::oop_load(p);
5049     if (!CompressedOops::is_null(heap_oop)) {
5050       oop obj = CompressedOops::decode_not_null(heap_oop);
5051       HeapRegion* hr = _g1h->heap_region_containing(obj);
5052       assert(!hr->is_continues_humongous(),
5053              "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5054              " starting at " HR_FORMAT,
5055              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5056 
5057       // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
5058       hr->add_strong_code_root_locked(_nm);
5059     }
5060   }
5061 
5062 public:
5063   RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5064     _g1h(g1h), _nm(nm) {}
5065 
5066   void do_oop(oop* p)       { do_oop_work(p); }
5067   void do_oop(narrowOop* p) { do_oop_work(p); }
5068 };
5069 
5070 class UnregisterNMethodOopClosure: public OopClosure {
5071   G1CollectedHeap* _g1h;
5072   nmethod* _nm;
5073 
5074   template <class T> void do_oop_work(T* p) {
5075     T heap_oop = RawAccess<>::oop_load(p);
5076     if (!CompressedOops::is_null(heap_oop)) {
5077       oop obj = CompressedOops::decode_not_null(heap_oop);
5078       HeapRegion* hr = _g1h->heap_region_containing(obj);
5079       assert(!hr->is_continues_humongous(),
5080              "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
5081              " starting at " HR_FORMAT,
5082              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
5083 
5084       hr->remove_strong_code_root(_nm);
5085     }
5086   }
5087 
5088 public:
5089   UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
5090     _g1h(g1h), _nm(nm) {}
5091 
5092   void do_oop(oop* p)       { do_oop_work(p); }
5093   void do_oop(narrowOop* p) { do_oop_work(p); }
5094 };
5095 
5096 // Returns true if the reference points to an object that
5097 // can move in an incremental collection.
5098 bool G1CollectedHeap::is_scavengable(oop obj) {
5099   HeapRegion* hr = heap_region_containing(obj);
5100   return !hr->is_pinned();
5101 }
5102 
5103 void G1CollectedHeap::register_nmethod(nmethod* nm) {
5104   guarantee(nm != NULL, "sanity");
5105   RegisterNMethodOopClosure reg_cl(this, nm);
5106   nm->oops_do(&reg_cl);
5107 }
5108 
5109 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
5110   guarantee(nm != NULL, "sanity");
5111   UnregisterNMethodOopClosure reg_cl(this, nm);
5112   nm->oops_do(&reg_cl, true);
5113 }
5114 
5115 void G1CollectedHeap::purge_code_root_memory() {
5116   double purge_start = os::elapsedTime();
5117   G1CodeRootSet::purge();
5118   double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
5119   g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
5120 }
5121 
5122 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
5123   G1CollectedHeap* _g1h;
5124 
5125 public:
5126   RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
5127     _g1h(g1h) {}
5128 
5129   void do_code_blob(CodeBlob* cb) {
5130     nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
5131     if (nm == NULL) {
5132       return;
5133     }
5134 
5135     if (ScavengeRootsInCode) {
5136       _g1h->register_nmethod(nm);
5137     }
5138   }
5139 };
5140 
5141 void G1CollectedHeap::rebuild_strong_code_roots() {
5142   RebuildStrongCodeRootClosure blob_cl(this);
5143   CodeCache::blobs_do(&blob_cl);
5144 }
5145 
5146 GrowableArray<GCMemoryManager*> G1CollectedHeap::memory_managers() {
5147   GrowableArray<GCMemoryManager*> memory_managers(2);
5148   memory_managers.append(&_memory_manager);
5149   memory_managers.append(&_full_gc_memory_manager);
5150   return memory_managers;
5151 }
5152 
5153 GrowableArray<MemoryPool*> G1CollectedHeap::memory_pools() {
5154   GrowableArray<MemoryPool*> memory_pools(3);
5155   memory_pools.append(_eden_pool);
5156   memory_pools.append(_survivor_pool);
5157   memory_pools.append(_old_pool);
5158   return memory_pools;
5159 }