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 "code/codeCache.hpp"
  29 #include "code/icBuffer.hpp"
  30 #include "gc/g1/g1Allocator.inline.hpp"
  31 #include "gc/g1/g1BarrierSet.hpp"
  32 #include "gc/g1/g1CollectedHeap.inline.hpp"
  33 #include "gc/g1/g1CollectionSet.hpp"
  34 #include "gc/g1/g1CollectorPolicy.hpp"
  35 #include "gc/g1/g1CollectorState.hpp"
  36 #include "gc/g1/g1ConcurrentRefine.hpp"
  37 #include "gc/g1/g1ConcurrentRefineThread.hpp"
  38 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp"
  39 #include "gc/g1/g1EvacStats.inline.hpp"
  40 #include "gc/g1/g1FullCollector.hpp"
  41 #include "gc/g1/g1GCPhaseTimes.hpp"
  42 #include "gc/g1/g1HeapSizingPolicy.hpp"
  43 #include "gc/g1/g1HeapTransition.hpp"
  44 #include "gc/g1/g1HeapVerifier.hpp"
  45 #include "gc/g1/g1HotCardCache.hpp"
  46 #include "gc/g1/g1MemoryPool.hpp"
  47 #include "gc/g1/g1OopClosures.inline.hpp"
  48 #include "gc/g1/g1ParScanThreadState.inline.hpp"
  49 #include "gc/g1/g1Policy.hpp"
  50 #include "gc/g1/g1RegionToSpaceMapper.hpp"
  51 #include "gc/g1/g1RemSet.hpp"
  52 #include "gc/g1/g1RootClosures.hpp"
  53 #include "gc/g1/g1RootProcessor.hpp"
  54 #include "gc/g1/g1SATBMarkQueueSet.hpp"
  55 #include "gc/g1/g1StringDedup.hpp"
  56 #include "gc/g1/g1ThreadLocalData.hpp"
  57 #include "gc/g1/g1YCTypes.hpp"
  58 #include "gc/g1/g1YoungRemSetSamplingThread.hpp"
  59 #include "gc/g1/heapRegion.inline.hpp"
  60 #include "gc/g1/heapRegionRemSet.hpp"
  61 #include "gc/g1/heapRegionSet.inline.hpp"
  62 #include "gc/g1/vm_operations_g1.hpp"
  63 #include "gc/shared/adaptiveSizePolicy.hpp"
  64 #include "gc/shared/gcHeapSummary.hpp"
  65 #include "gc/shared/gcId.hpp"
  66 #include "gc/shared/gcLocker.hpp"
  67 #include "gc/shared/gcTimer.hpp"
  68 #include "gc/shared/gcTrace.hpp"
  69 #include "gc/shared/gcTraceTime.inline.hpp"
  70 #include "gc/shared/generationSpec.hpp"
  71 #include "gc/shared/isGCActiveMark.hpp"
  72 #include "gc/shared/oopStorageParState.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/metaspaceShared.hpp"
  82 #include "memory/resourceArea.hpp"
  83 #include "oops/access.inline.hpp"
  84 #include "oops/compressedOops.inline.hpp"
  85 #include "oops/oop.inline.hpp"
  86 #include "prims/resolvedMethodTable.hpp"
  87 #include "runtime/atomic.hpp"
  88 #include "runtime/flags/flagSetting.hpp"
  89 #include "runtime/handles.inline.hpp"
  90 #include "runtime/init.hpp"
  91 #include "runtime/orderAccess.hpp"
  92 #include "runtime/threadSMR.hpp"
  93 #include "runtime/vmThread.hpp"
  94 #include "utilities/align.hpp"
  95 #include "utilities/globalDefinitions.hpp"
  96 #include "utilities/stack.inline.hpp"
  97 
  98 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
  99 
 100 // INVARIANTS/NOTES
 101 //
 102 // All allocation activity covered by the G1CollectedHeap interface is
 103 // serialized by acquiring the HeapLock.  This happens in mem_allocate
 104 // and allocate_new_tlab, which are the "entry" points to the
 105 // allocation code from the rest of the JVM.  (Note that this does not
 106 // apply to TLAB allocation, which is not part of this interface: it
 107 // is done by clients of this interface.)
 108 
 109 class RedirtyLoggedCardTableEntryClosure : public CardTableEntryClosure {
 110  private:
 111   size_t _num_dirtied;
 112   G1CollectedHeap* _g1h;
 113   G1CardTable* _g1_ct;
 114 
 115   HeapRegion* region_for_card(jbyte* card_ptr) const {
 116     return _g1h->heap_region_containing(_g1_ct->addr_for(card_ptr));
 117   }
 118 
 119   bool will_become_free(HeapRegion* hr) const {
 120     // A region will be freed by free_collection_set if the region is in the
 121     // collection set and has not had an evacuation failure.
 122     return _g1h->is_in_cset(hr) && !hr->evacuation_failed();
 123   }
 124 
 125  public:
 126   RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : CardTableEntryClosure(),
 127     _num_dirtied(0), _g1h(g1h), _g1_ct(g1h->card_table()) { }
 128 
 129   bool do_card_ptr(jbyte* card_ptr, uint worker_i) {
 130     HeapRegion* hr = region_for_card(card_ptr);
 131 
 132     // Should only dirty cards in regions that won't be freed.
 133     if (!will_become_free(hr)) {
 134       *card_ptr = G1CardTable::dirty_card_val();
 135       _num_dirtied++;
 136     }
 137 
 138     return true;
 139   }
 140 
 141   size_t num_dirtied()   const { return _num_dirtied; }
 142 };
 143 
 144 
 145 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
 146   HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
 147 }
 148 
 149 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
 150   // The from card cache is not the memory that is actually committed. So we cannot
 151   // take advantage of the zero_filled parameter.
 152   reset_from_card_cache(start_idx, num_regions);
 153 }
 154 
 155 
 156 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
 157                                              MemRegion mr) {
 158   return new HeapRegion(hrs_index, bot(), mr);
 159 }
 160 
 161 // Private methods.
 162 
 163 HeapRegion* G1CollectedHeap::new_region(size_t word_size, bool is_old, bool do_expand) {
 164   assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
 165          "the only time we use this to allocate a humongous region is "
 166          "when we are allocating a single humongous region");
 167 
 168   HeapRegion* res = _hrm.allocate_free_region(is_old);
 169 
 170   if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
 171     // Currently, only attempts to allocate GC alloc regions set
 172     // do_expand to true. So, we should only reach here during a
 173     // safepoint. If this assumption changes we might have to
 174     // reconsider the use of _expand_heap_after_alloc_failure.
 175     assert(SafepointSynchronize::is_at_safepoint(), "invariant");
 176 
 177     log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B",
 178                               word_size * HeapWordSize);
 179 
 180     if (expand(word_size * HeapWordSize)) {
 181       // Given that expand() succeeded in expanding the heap, and we
 182       // always expand the heap by an amount aligned to the heap
 183       // region size, the free list should in theory not be empty.
 184       // In either case allocate_free_region() will check for NULL.
 185       res = _hrm.allocate_free_region(is_old);
 186     } else {
 187       _expand_heap_after_alloc_failure = false;
 188     }
 189   }
 190   return res;
 191 }
 192 
 193 HeapWord*
 194 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
 195                                                            uint num_regions,
 196                                                            size_t word_size) {
 197   assert(first != G1_NO_HRM_INDEX, "pre-condition");
 198   assert(is_humongous(word_size), "word_size should be humongous");
 199   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 200 
 201   // Index of last region in the series.
 202   uint last = first + num_regions - 1;
 203 
 204   // We need to initialize the region(s) we just discovered. This is
 205   // a bit tricky given that it can happen concurrently with
 206   // refinement threads refining cards on these regions and
 207   // potentially wanting to refine the BOT as they are scanning
 208   // those cards (this can happen shortly after a cleanup; see CR
 209   // 6991377). So we have to set up the region(s) carefully and in
 210   // a specific order.
 211 
 212   // The word size sum of all the regions we will allocate.
 213   size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
 214   assert(word_size <= word_size_sum, "sanity");
 215 
 216   // This will be the "starts humongous" region.
 217   HeapRegion* first_hr = region_at(first);
 218   // The header of the new object will be placed at the bottom of
 219   // the first region.
 220   HeapWord* new_obj = first_hr->bottom();
 221   // This will be the new top of the new object.
 222   HeapWord* obj_top = new_obj + word_size;
 223 
 224   // First, we need to zero the header of the space that we will be
 225   // allocating. When we update top further down, some refinement
 226   // threads might try to scan the region. By zeroing the header we
 227   // ensure that any thread that will try to scan the region will
 228   // come across the zero klass word and bail out.
 229   //
 230   // NOTE: It would not have been correct to have used
 231   // CollectedHeap::fill_with_object() and make the space look like
 232   // an int array. The thread that is doing the allocation will
 233   // later update the object header to a potentially different array
 234   // type and, for a very short period of time, the klass and length
 235   // fields will be inconsistent. This could cause a refinement
 236   // thread to calculate the object size incorrectly.
 237   Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
 238 
 239   // Next, pad out the unused tail of the last region with filler
 240   // objects, for improved usage accounting.
 241   // How many words we use for filler objects.
 242   size_t word_fill_size = word_size_sum - word_size;
 243 
 244   // How many words memory we "waste" which cannot hold a filler object.
 245   size_t words_not_fillable = 0;
 246 
 247   if (word_fill_size >= min_fill_size()) {
 248     fill_with_objects(obj_top, word_fill_size);
 249   } else if (word_fill_size > 0) {
 250     // We have space to fill, but we cannot fit an object there.
 251     words_not_fillable = word_fill_size;
 252     word_fill_size = 0;
 253   }
 254 
 255   // We will set up the first region as "starts humongous". This
 256   // will also update the BOT covering all the regions to reflect
 257   // that there is a single object that starts at the bottom of the
 258   // first region.
 259   first_hr->set_starts_humongous(obj_top, word_fill_size);
 260   _g1_policy->remset_tracker()->update_at_allocate(first_hr);
 261   // Then, if there are any, we will set up the "continues
 262   // humongous" regions.
 263   HeapRegion* hr = NULL;
 264   for (uint i = first + 1; i <= last; ++i) {
 265     hr = region_at(i);
 266     hr->set_continues_humongous(first_hr);
 267     _g1_policy->remset_tracker()->update_at_allocate(hr);
 268   }
 269 
 270   // Up to this point no concurrent thread would have been able to
 271   // do any scanning on any region in this series. All the top
 272   // fields still point to bottom, so the intersection between
 273   // [bottom,top] and [card_start,card_end] will be empty. Before we
 274   // update the top fields, we'll do a storestore to make sure that
 275   // no thread sees the update to top before the zeroing of the
 276   // object header and the BOT initialization.
 277   OrderAccess::storestore();
 278 
 279   // Now, we will update the top fields of the "continues humongous"
 280   // regions except the last one.
 281   for (uint i = first; i < last; ++i) {
 282     hr = region_at(i);
 283     hr->set_top(hr->end());
 284   }
 285 
 286   hr = region_at(last);
 287   // If we cannot fit a filler object, we must set top to the end
 288   // of the humongous object, otherwise we cannot iterate the heap
 289   // and the BOT will not be complete.
 290   hr->set_top(hr->end() - words_not_fillable);
 291 
 292   assert(hr->bottom() < obj_top && obj_top <= hr->end(),
 293          "obj_top should be in last region");
 294 
 295   _verifier->check_bitmaps("Humongous Region Allocation", first_hr);
 296 
 297   assert(words_not_fillable == 0 ||
 298          first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(),
 299          "Miscalculation in humongous allocation");
 300 
 301   increase_used((word_size_sum - words_not_fillable) * HeapWordSize);
 302 
 303   for (uint i = first; i <= last; ++i) {
 304     hr = region_at(i);
 305     _humongous_set.add(hr);
 306     _hr_printer.alloc(hr);
 307   }
 308 
 309   return new_obj;
 310 }
 311 
 312 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) {
 313   assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size);
 314   return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
 315 }
 316 
 317 // If could fit into free regions w/o expansion, try.
 318 // Otherwise, if can expand, do so.
 319 // Otherwise, if using ex regions might help, try with ex given back.
 320 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
 321   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 322 
 323   _verifier->verify_region_sets_optional();
 324 
 325   uint first = G1_NO_HRM_INDEX;
 326   uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);
 327 
 328   if (obj_regions == 1) {
 329     // Only one region to allocate, try to use a fast path by directly allocating
 330     // from the free lists. Do not try to expand here, we will potentially do that
 331     // later.
 332     HeapRegion* hr = new_region(word_size, true /* is_old */, false /* do_expand */);
 333     if (hr != NULL) {
 334       first = hr->hrm_index();
 335     }
 336   } else {
 337     // Policy: Try only empty regions (i.e. already committed first). Maybe we
 338     // are lucky enough to find some.
 339     first = _hrm.find_contiguous_only_empty(obj_regions);
 340     if (first != G1_NO_HRM_INDEX) {
 341       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 342     }
 343   }
 344 
 345   if (first == G1_NO_HRM_INDEX) {
 346     // Policy: We could not find enough regions for the humongous object in the
 347     // free list. Look through the heap to find a mix of free and uncommitted regions.
 348     // If so, try expansion.
 349     first = _hrm.find_contiguous_empty_or_unavailable(obj_regions);
 350     if (first != G1_NO_HRM_INDEX) {
 351       // We found something. Make sure these regions are committed, i.e. expand
 352       // the heap. Alternatively we could do a defragmentation GC.
 353       log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B",
 354                                     word_size * HeapWordSize);
 355 
 356       _hrm.expand_at(first, obj_regions, workers());
 357       g1_policy()->record_new_heap_size(num_regions());
 358 
 359 #ifdef ASSERT
 360       for (uint i = first; i < first + obj_regions; ++i) {
 361         HeapRegion* hr = region_at(i);
 362         assert(hr->is_free(), "sanity");
 363         assert(hr->is_empty(), "sanity");
 364         assert(is_on_master_free_list(hr), "sanity");
 365       }
 366 #endif
 367       _hrm.allocate_free_regions_starting_at(first, obj_regions);
 368     } else {
 369       // Policy: Potentially trigger a defragmentation GC.
 370     }
 371   }
 372 
 373   HeapWord* result = NULL;
 374   if (first != G1_NO_HRM_INDEX) {
 375     result = humongous_obj_allocate_initialize_regions(first, obj_regions, word_size);
 376     assert(result != NULL, "it should always return a valid result");
 377 
 378     // A successful humongous object allocation changes the used space
 379     // information of the old generation so we need to recalculate the
 380     // sizes and update the jstat counters here.
 381     g1mm()->update_sizes();
 382   }
 383 
 384   _verifier->verify_region_sets_optional();
 385 
 386   return result;
 387 }
 388 
 389 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t min_size,
 390                                              size_t requested_size,
 391                                              size_t* actual_size) {
 392   assert_heap_not_locked_and_not_at_safepoint();
 393   assert(!is_humongous(requested_size), "we do not allow humongous TLABs");
 394 
 395   return attempt_allocation(min_size, requested_size, actual_size);
 396 }
 397 
 398 HeapWord*
 399 G1CollectedHeap::mem_allocate(size_t word_size,
 400                               bool*  gc_overhead_limit_was_exceeded) {
 401   assert_heap_not_locked_and_not_at_safepoint();
 402 
 403   if (is_humongous(word_size)) {
 404     return attempt_allocation_humongous(word_size);
 405   }
 406   size_t dummy = 0;
 407   return attempt_allocation(word_size, word_size, &dummy);
 408 }
 409 
 410 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size) {
 411   ResourceMark rm; // For retrieving the thread names in log messages.
 412 
 413   // Make sure you read the note in attempt_allocation_humongous().
 414 
 415   assert_heap_not_locked_and_not_at_safepoint();
 416   assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
 417          "be called for humongous allocation requests");
 418 
 419   // We should only get here after the first-level allocation attempt
 420   // (attempt_allocation()) failed to allocate.
 421 
 422   // We will loop until a) we manage to successfully perform the
 423   // allocation or b) we successfully schedule a collection which
 424   // fails to perform the allocation. b) is the only case when we'll
 425   // return NULL.
 426   HeapWord* result = NULL;
 427   for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 428     bool should_try_gc;
 429     uint gc_count_before;
 430 
 431     {
 432       MutexLockerEx x(Heap_lock);
 433       result = _allocator->attempt_allocation_locked(word_size);
 434       if (result != NULL) {
 435         return result;
 436       }
 437 
 438       // If the GCLocker is active and we are bound for a GC, try expanding young gen.
 439       // This is different to when only GCLocker::needs_gc() is set: try to avoid
 440       // waiting because the GCLocker is active to not wait too long.
 441       if (GCLocker::is_active_and_needs_gc() && g1_policy()->can_expand_young_list()) {
 442         // No need for an ergo message here, can_expand_young_list() does this when
 443         // it returns true.
 444         result = _allocator->attempt_allocation_force(word_size);
 445         if (result != NULL) {
 446           return result;
 447         }
 448       }
 449       // Only try a GC if the GCLocker does not signal the need for a GC. Wait until
 450       // the GCLocker initiated GC has been performed and then retry. This includes
 451       // the case when the GC Locker is not active but has not been performed.
 452       should_try_gc = !GCLocker::needs_gc();
 453       // Read the GC count while still holding the Heap_lock.
 454       gc_count_before = total_collections();
 455     }
 456 
 457     if (should_try_gc) {
 458       bool succeeded;
 459       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 460                                    GCCause::_g1_inc_collection_pause);
 461       if (result != NULL) {
 462         assert(succeeded, "only way to get back a non-NULL result");
 463         log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT,
 464                              Thread::current()->name(), p2i(result));
 465         return result;
 466       }
 467 
 468       if (succeeded) {
 469         // We successfully scheduled a collection which failed to allocate. No
 470         // point in trying to allocate further. We'll just return NULL.
 471         log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate "
 472                              SIZE_FORMAT " words", Thread::current()->name(), word_size);
 473         return NULL;
 474       }
 475       log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT " words",
 476                            Thread::current()->name(), word_size);
 477     } else {
 478       // Failed to schedule a collection.
 479       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 480         log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating "
 481                                SIZE_FORMAT " words", Thread::current()->name(), word_size);
 482         return NULL;
 483       }
 484       log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name());
 485       // The GCLocker is either active or the GCLocker initiated
 486       // GC has not yet been performed. Stall until it is and
 487       // then retry the allocation.
 488       GCLocker::stall_until_clear();
 489       gclocker_retry_count += 1;
 490     }
 491 
 492     // We can reach here if we were unsuccessful in scheduling a
 493     // collection (because another thread beat us to it) or if we were
 494     // stalled due to the GC locker. In either can we should retry the
 495     // allocation attempt in case another thread successfully
 496     // performed a collection and reclaimed enough space. We do the
 497     // first attempt (without holding the Heap_lock) here and the
 498     // follow-on attempt will be at the start of the next loop
 499     // iteration (after taking the Heap_lock).
 500     size_t dummy = 0;
 501     result = _allocator->attempt_allocation(word_size, word_size, &dummy);
 502     if (result != NULL) {
 503       return result;
 504     }
 505 
 506     // Give a warning if we seem to be looping forever.
 507     if ((QueuedAllocationWarningCount > 0) &&
 508         (try_count % QueuedAllocationWarningCount == 0)) {
 509       log_warning(gc, alloc)("%s:  Retried allocation %u times for " SIZE_FORMAT " words",
 510                              Thread::current()->name(), try_count, word_size);
 511     }
 512   }
 513 
 514   ShouldNotReachHere();
 515   return NULL;
 516 }
 517 
 518 void G1CollectedHeap::begin_archive_alloc_range(bool open) {
 519   assert_at_safepoint_on_vm_thread();
 520   if (_archive_allocator == NULL) {
 521     _archive_allocator = G1ArchiveAllocator::create_allocator(this, open);
 522   }
 523 }
 524 
 525 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) {
 526   // Allocations in archive regions cannot be of a size that would be considered
 527   // humongous even for a minimum-sized region, because G1 region sizes/boundaries
 528   // may be different at archive-restore time.
 529   return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words());
 530 }
 531 
 532 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) {
 533   assert_at_safepoint_on_vm_thread();
 534   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 535   if (is_archive_alloc_too_large(word_size)) {
 536     return NULL;
 537   }
 538   return _archive_allocator->archive_mem_allocate(word_size);
 539 }
 540 
 541 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
 542                                               size_t end_alignment_in_bytes) {
 543   assert_at_safepoint_on_vm_thread();
 544   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 545 
 546   // Call complete_archive to do the real work, filling in the MemRegion
 547   // array with the archive regions.
 548   _archive_allocator->complete_archive(ranges, end_alignment_in_bytes);
 549   delete _archive_allocator;
 550   _archive_allocator = NULL;
 551 }
 552 
 553 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) {
 554   assert(ranges != NULL, "MemRegion array NULL");
 555   assert(count != 0, "No MemRegions provided");
 556   MemRegion reserved = _hrm.reserved();
 557   for (size_t i = 0; i < count; i++) {
 558     if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) {
 559       return false;
 560     }
 561   }
 562   return true;
 563 }
 564 
 565 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges,
 566                                             size_t count,
 567                                             bool open) {
 568   assert(!is_init_completed(), "Expect to be called at JVM init time");
 569   assert(ranges != NULL, "MemRegion array NULL");
 570   assert(count != 0, "No MemRegions provided");
 571   MutexLockerEx x(Heap_lock);
 572 
 573   MemRegion reserved = _hrm.reserved();
 574   HeapWord* prev_last_addr = NULL;
 575   HeapRegion* prev_last_region = NULL;
 576 
 577   // Temporarily disable pretouching of heap pages. This interface is used
 578   // when mmap'ing archived heap data in, so pre-touching is wasted.
 579   FlagSetting fs(AlwaysPreTouch, false);
 580 
 581   // Enable archive object checking used by G1MarkSweep. We have to let it know
 582   // about each archive range, so that objects in those ranges aren't marked.
 583   G1ArchiveAllocator::enable_archive_object_check();
 584 
 585   // For each specified MemRegion range, allocate the corresponding G1
 586   // regions and mark them as archive regions. We expect the ranges
 587   // in ascending starting address order, without overlap.
 588   for (size_t i = 0; i < count; i++) {
 589     MemRegion curr_range = ranges[i];
 590     HeapWord* start_address = curr_range.start();
 591     size_t word_size = curr_range.word_size();
 592     HeapWord* last_address = curr_range.last();
 593     size_t commits = 0;
 594 
 595     guarantee(reserved.contains(start_address) && reserved.contains(last_address),
 596               "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 597               p2i(start_address), p2i(last_address));
 598     guarantee(start_address > prev_last_addr,
 599               "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 600               p2i(start_address), p2i(prev_last_addr));
 601     prev_last_addr = last_address;
 602 
 603     // Check for ranges that start in the same G1 region in which the previous
 604     // range ended, and adjust the start address so we don't try to allocate
 605     // the same region again. If the current range is entirely within that
 606     // region, skip it, just adjusting the recorded top.
 607     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 608     if ((prev_last_region != NULL) && (start_region == prev_last_region)) {
 609       start_address = start_region->end();
 610       if (start_address > last_address) {
 611         increase_used(word_size * HeapWordSize);
 612         start_region->set_top(last_address + 1);
 613         continue;
 614       }
 615       start_region->set_top(start_address);
 616       curr_range = MemRegion(start_address, last_address + 1);
 617       start_region = _hrm.addr_to_region(start_address);
 618     }
 619 
 620     // Perform the actual region allocation, exiting if it fails.
 621     // Then note how much new space we have allocated.
 622     if (!_hrm.allocate_containing_regions(curr_range, &commits, workers())) {
 623       return false;
 624     }
 625     increase_used(word_size * HeapWordSize);
 626     if (commits != 0) {
 627       log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B",
 628                                 HeapRegion::GrainWords * HeapWordSize * commits);
 629 
 630     }
 631 
 632     // Mark each G1 region touched by the range as archive, add it to
 633     // the old set, and set top.
 634     HeapRegion* curr_region = _hrm.addr_to_region(start_address);
 635     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 636     prev_last_region = last_region;
 637 
 638     while (curr_region != NULL) {
 639       assert(curr_region->is_empty() && !curr_region->is_pinned(),
 640              "Region already in use (index %u)", curr_region->hrm_index());
 641       if (open) {
 642         curr_region->set_open_archive();
 643       } else {
 644         curr_region->set_closed_archive();
 645       }
 646       _hr_printer.alloc(curr_region);
 647       _old_set.add(curr_region);
 648       HeapWord* top;
 649       HeapRegion* next_region;
 650       if (curr_region != last_region) {
 651         top = curr_region->end();
 652         next_region = _hrm.next_region_in_heap(curr_region);
 653       } else {
 654         top = last_address + 1;
 655         next_region = NULL;
 656       }
 657       curr_region->set_top(top);
 658       curr_region->set_first_dead(top);
 659       curr_region->set_end_of_live(top);
 660       curr_region = next_region;
 661     }
 662 
 663     // Notify mark-sweep of the archive
 664     G1ArchiveAllocator::set_range_archive(curr_range, open);
 665   }
 666   return true;
 667 }
 668 
 669 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) {
 670   assert(!is_init_completed(), "Expect to be called at JVM init time");
 671   assert(ranges != NULL, "MemRegion array NULL");
 672   assert(count != 0, "No MemRegions provided");
 673   MemRegion reserved = _hrm.reserved();
 674   HeapWord *prev_last_addr = NULL;
 675   HeapRegion* prev_last_region = NULL;
 676 
 677   // For each MemRegion, create filler objects, if needed, in the G1 regions
 678   // that contain the address range. The address range actually within the
 679   // MemRegion will not be modified. That is assumed to have been initialized
 680   // elsewhere, probably via an mmap of archived heap data.
 681   MutexLockerEx x(Heap_lock);
 682   for (size_t i = 0; i < count; i++) {
 683     HeapWord* start_address = ranges[i].start();
 684     HeapWord* last_address = ranges[i].last();
 685 
 686     assert(reserved.contains(start_address) && reserved.contains(last_address),
 687            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 688            p2i(start_address), p2i(last_address));
 689     assert(start_address > prev_last_addr,
 690            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 691            p2i(start_address), p2i(prev_last_addr));
 692 
 693     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 694     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 695     HeapWord* bottom_address = start_region->bottom();
 696 
 697     // Check for a range beginning in the same region in which the
 698     // previous one ended.
 699     if (start_region == prev_last_region) {
 700       bottom_address = prev_last_addr + 1;
 701     }
 702 
 703     // Verify that the regions were all marked as archive regions by
 704     // alloc_archive_regions.
 705     HeapRegion* curr_region = start_region;
 706     while (curr_region != NULL) {
 707       guarantee(curr_region->is_archive(),
 708                 "Expected archive region at index %u", curr_region->hrm_index());
 709       if (curr_region != last_region) {
 710         curr_region = _hrm.next_region_in_heap(curr_region);
 711       } else {
 712         curr_region = NULL;
 713       }
 714     }
 715 
 716     prev_last_addr = last_address;
 717     prev_last_region = last_region;
 718 
 719     // Fill the memory below the allocated range with dummy object(s),
 720     // if the region bottom does not match the range start, or if the previous
 721     // range ended within the same G1 region, and there is a gap.
 722     if (start_address != bottom_address) {
 723       size_t fill_size = pointer_delta(start_address, bottom_address);
 724       G1CollectedHeap::fill_with_objects(bottom_address, fill_size);
 725       increase_used(fill_size * HeapWordSize);
 726     }
 727   }
 728 }
 729 
 730 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t min_word_size,
 731                                                      size_t desired_word_size,
 732                                                      size_t* actual_word_size) {
 733   assert_heap_not_locked_and_not_at_safepoint();
 734   assert(!is_humongous(desired_word_size), "attempt_allocation() should not "
 735          "be called for humongous allocation requests");
 736 
 737   HeapWord* result = _allocator->attempt_allocation(min_word_size, desired_word_size, actual_word_size);
 738 
 739   if (result == NULL) {
 740     *actual_word_size = desired_word_size;
 741     result = attempt_allocation_slow(desired_word_size);
 742   }
 743 
 744   assert_heap_not_locked();
 745   if (result != NULL) {
 746     assert(*actual_word_size != 0, "Actual size must have been set here");
 747     dirty_young_block(result, *actual_word_size);
 748   } else {
 749     *actual_word_size = 0;
 750   }
 751 
 752   return result;
 753 }
 754 
 755 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count) {
 756   assert(!is_init_completed(), "Expect to be called at JVM init time");
 757   assert(ranges != NULL, "MemRegion array NULL");
 758   assert(count != 0, "No MemRegions provided");
 759   MemRegion reserved = _hrm.reserved();
 760   HeapWord* prev_last_addr = NULL;
 761   HeapRegion* prev_last_region = NULL;
 762   size_t size_used = 0;
 763   size_t uncommitted_regions = 0;
 764 
 765   // For each Memregion, free the G1 regions that constitute it, and
 766   // notify mark-sweep that the range is no longer to be considered 'archive.'
 767   MutexLockerEx x(Heap_lock);
 768   for (size_t i = 0; i < count; i++) {
 769     HeapWord* start_address = ranges[i].start();
 770     HeapWord* last_address = ranges[i].last();
 771 
 772     assert(reserved.contains(start_address) && reserved.contains(last_address),
 773            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 774            p2i(start_address), p2i(last_address));
 775     assert(start_address > prev_last_addr,
 776            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 777            p2i(start_address), p2i(prev_last_addr));
 778     size_used += ranges[i].byte_size();
 779     prev_last_addr = last_address;
 780 
 781     HeapRegion* start_region = _hrm.addr_to_region(start_address);
 782     HeapRegion* last_region = _hrm.addr_to_region(last_address);
 783 
 784     // Check for ranges that start in the same G1 region in which the previous
 785     // range ended, and adjust the start address so we don't try to free
 786     // the same region again. If the current range is entirely within that
 787     // region, skip it.
 788     if (start_region == prev_last_region) {
 789       start_address = start_region->end();
 790       if (start_address > last_address) {
 791         continue;
 792       }
 793       start_region = _hrm.addr_to_region(start_address);
 794     }
 795     prev_last_region = last_region;
 796 
 797     // After verifying that each region was marked as an archive region by
 798     // alloc_archive_regions, set it free and empty and uncommit it.
 799     HeapRegion* curr_region = start_region;
 800     while (curr_region != NULL) {
 801       guarantee(curr_region->is_archive(),
 802                 "Expected archive region at index %u", curr_region->hrm_index());
 803       uint curr_index = curr_region->hrm_index();
 804       _old_set.remove(curr_region);
 805       curr_region->set_free();
 806       curr_region->set_top(curr_region->bottom());
 807       if (curr_region != last_region) {
 808         curr_region = _hrm.next_region_in_heap(curr_region);
 809       } else {
 810         curr_region = NULL;
 811       }
 812       _hrm.shrink_at(curr_index, 1);
 813       uncommitted_regions++;
 814     }
 815 
 816     // Notify mark-sweep that this is no longer an archive range.
 817     G1ArchiveAllocator::set_range_archive(ranges[i], false);
 818   }
 819 
 820   if (uncommitted_regions != 0) {
 821     log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B",
 822                               HeapRegion::GrainWords * HeapWordSize * uncommitted_regions);
 823   }
 824   decrease_used(size_used);
 825 }
 826 
 827 oop G1CollectedHeap::materialize_archived_object(oop obj) {
 828   assert(obj != NULL, "archived obj is NULL");
 829   assert(MetaspaceShared::is_archive_object(obj), "must be archived object");
 830 
 831   // Loading an archived object makes it strongly reachable. If it is
 832   // loaded during concurrent marking, it must be enqueued to the SATB
 833   // queue, shading the previously white object gray.
 834   G1BarrierSet::enqueue(obj);
 835 
 836   return obj;
 837 }
 838 
 839 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size) {
 840   ResourceMark rm; // For retrieving the thread names in log messages.
 841 
 842   // The structure of this method has a lot of similarities to
 843   // attempt_allocation_slow(). The reason these two were not merged
 844   // into a single one is that such a method would require several "if
 845   // allocation is not humongous do this, otherwise do that"
 846   // conditional paths which would obscure its flow. In fact, an early
 847   // version of this code did use a unified method which was harder to
 848   // follow and, as a result, it had subtle bugs that were hard to
 849   // track down. So keeping these two methods separate allows each to
 850   // be more readable. It will be good to keep these two in sync as
 851   // much as possible.
 852 
 853   assert_heap_not_locked_and_not_at_safepoint();
 854   assert(is_humongous(word_size), "attempt_allocation_humongous() "
 855          "should only be called for humongous allocations");
 856 
 857   // Humongous objects can exhaust the heap quickly, so we should check if we
 858   // need to start a marking cycle at each humongous object allocation. We do
 859   // the check before we do the actual allocation. The reason for doing it
 860   // before the allocation is that we avoid having to keep track of the newly
 861   // allocated memory while we do a GC.
 862   if (g1_policy()->need_to_start_conc_mark("concurrent humongous allocation",
 863                                            word_size)) {
 864     collect(GCCause::_g1_humongous_allocation);
 865   }
 866 
 867   // We will loop until a) we manage to successfully perform the
 868   // allocation or b) we successfully schedule a collection which
 869   // fails to perform the allocation. b) is the only case when we'll
 870   // return NULL.
 871   HeapWord* result = NULL;
 872   for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 873     bool should_try_gc;
 874     uint gc_count_before;
 875 
 876 
 877     {
 878       MutexLockerEx x(Heap_lock);
 879 
 880       // Given that humongous objects are not allocated in young
 881       // regions, we'll first try to do the allocation without doing a
 882       // collection hoping that there's enough space in the heap.
 883       result = humongous_obj_allocate(word_size);
 884       if (result != NULL) {
 885         size_t size_in_regions = humongous_obj_size_in_regions(word_size);
 886         g1_policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
 887         return result;
 888       }
 889 
 890       // Only try a GC if the GCLocker does not signal the need for a GC. Wait until
 891       // the GCLocker initiated GC has been performed and then retry. This includes
 892       // the case when the GC Locker is not active but has not been performed.
 893       should_try_gc = !GCLocker::needs_gc();
 894       // Read the GC count while still holding the Heap_lock.
 895       gc_count_before = total_collections();
 896     }
 897 
 898     if (should_try_gc) {
 899       bool succeeded;
 900       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 901                                    GCCause::_g1_humongous_allocation);
 902       if (result != NULL) {
 903         assert(succeeded, "only way to get back a non-NULL result");
 904         log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT,
 905                              Thread::current()->name(), p2i(result));
 906         return result;
 907       }
 908 
 909       if (succeeded) {
 910         // We successfully scheduled a collection which failed to allocate. No
 911         // point in trying to allocate further. We'll just return NULL.
 912         log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate "
 913                              SIZE_FORMAT " words", Thread::current()->name(), word_size);
 914         return NULL;
 915       }
 916       log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT "",
 917                            Thread::current()->name(), word_size);
 918     } else {
 919       // Failed to schedule a collection.
 920       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 921         log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating "
 922                                SIZE_FORMAT " words", Thread::current()->name(), word_size);
 923         return NULL;
 924       }
 925       log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name());
 926       // The GCLocker is either active or the GCLocker initiated
 927       // GC has not yet been performed. Stall until it is and
 928       // then retry the allocation.
 929       GCLocker::stall_until_clear();
 930       gclocker_retry_count += 1;
 931     }
 932 
 933 
 934     // We can reach here if we were unsuccessful in scheduling a
 935     // collection (because another thread beat us to it) or if we were
 936     // stalled due to the GC locker. In either can we should retry the
 937     // allocation attempt in case another thread successfully
 938     // performed a collection and reclaimed enough space.
 939     // Humongous object allocation always needs a lock, so we wait for the retry
 940     // in the next iteration of the loop, unlike for the regular iteration case.
 941     // Give a warning if we seem to be looping forever.
 942 
 943     if ((QueuedAllocationWarningCount > 0) &&
 944         (try_count % QueuedAllocationWarningCount == 0)) {
 945       log_warning(gc, alloc)("%s: Retried allocation %u times for " SIZE_FORMAT " words",
 946                              Thread::current()->name(), try_count, word_size);
 947     }
 948   }
 949 
 950   ShouldNotReachHere();
 951   return NULL;
 952 }
 953 
 954 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
 955                                                            bool expect_null_mutator_alloc_region) {
 956   assert_at_safepoint_on_vm_thread();
 957   assert(!_allocator->has_mutator_alloc_region() || !expect_null_mutator_alloc_region,
 958          "the current alloc region was unexpectedly found to be non-NULL");
 959 
 960   if (!is_humongous(word_size)) {
 961     return _allocator->attempt_allocation_locked(word_size);
 962   } else {
 963     HeapWord* result = humongous_obj_allocate(word_size);
 964     if (result != NULL && g1_policy()->need_to_start_conc_mark("STW humongous allocation")) {
 965       collector_state()->set_initiate_conc_mark_if_possible(true);
 966     }
 967     return result;
 968   }
 969 
 970   ShouldNotReachHere();
 971 }
 972 
 973 class PostCompactionPrinterClosure: public HeapRegionClosure {
 974 private:
 975   G1HRPrinter* _hr_printer;
 976 public:
 977   bool do_heap_region(HeapRegion* hr) {
 978     assert(!hr->is_young(), "not expecting to find young regions");
 979     _hr_printer->post_compaction(hr);
 980     return false;
 981   }
 982 
 983   PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
 984     : _hr_printer(hr_printer) { }
 985 };
 986 
 987 void G1CollectedHeap::print_hrm_post_compaction() {
 988   if (_hr_printer.is_active()) {
 989     PostCompactionPrinterClosure cl(hr_printer());
 990     heap_region_iterate(&cl);
 991   }
 992 }
 993 
 994 void G1CollectedHeap::abort_concurrent_cycle() {
 995   // If we start the compaction before the CM threads finish
 996   // scanning the root regions we might trip them over as we'll
 997   // be moving objects / updating references. So let's wait until
 998   // they are done. By telling them to abort, they should complete
 999   // early.
1000   _cm->root_regions()->abort();
1001   _cm->root_regions()->wait_until_scan_finished();
1002 
1003   // Disable discovery and empty the discovered lists
1004   // for the CM ref processor.
1005   _ref_processor_cm->disable_discovery();
1006   _ref_processor_cm->abandon_partial_discovery();
1007   _ref_processor_cm->verify_no_references_recorded();
1008 
1009   // Abandon current iterations of concurrent marking and concurrent
1010   // refinement, if any are in progress.
1011   concurrent_mark()->concurrent_cycle_abort();
1012 }
1013 
1014 void G1CollectedHeap::prepare_heap_for_full_collection() {
1015   // Make sure we'll choose a new allocation region afterwards.
1016   _allocator->release_mutator_alloc_region();
1017   _allocator->abandon_gc_alloc_regions();
1018   g1_rem_set()->cleanupHRRS();
1019 
1020   // We may have added regions to the current incremental collection
1021   // set between the last GC or pause and now. We need to clear the
1022   // incremental collection set and then start rebuilding it afresh
1023   // after this full GC.
1024   abandon_collection_set(collection_set());
1025 
1026   tear_down_region_sets(false /* free_list_only */);
1027 }
1028 
1029 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) {
1030   assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant");
1031   assert(used() == recalculate_used(), "Should be equal");
1032   _verifier->verify_region_sets_optional();
1033   _verifier->verify_before_gc(G1HeapVerifier::G1VerifyFull);
1034   _verifier->check_bitmaps("Full GC Start");
1035 }
1036 
1037 void G1CollectedHeap::prepare_heap_for_mutators() {
1038   // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1039   ClassLoaderDataGraph::purge();
1040   MetaspaceUtils::verify_metrics();
1041 
1042   // Prepare heap for normal collections.
1043   assert(num_free_regions() == 0, "we should not have added any free regions");
1044   rebuild_region_sets(false /* free_list_only */);
1045   abort_refinement();
1046   resize_if_necessary_after_full_collection();
1047 
1048   // Rebuild the strong code root lists for each region
1049   rebuild_strong_code_roots();
1050 
1051   // Start a new incremental collection set for the next pause
1052   start_new_collection_set();
1053 
1054   _allocator->init_mutator_alloc_region();
1055 
1056   // Post collection state updates.
1057   MetaspaceGC::compute_new_size();
1058 }
1059 
1060 void G1CollectedHeap::abort_refinement() {
1061   if (_hot_card_cache->use_cache()) {
1062     _hot_card_cache->reset_hot_cache();
1063   }
1064 
1065   // Discard all remembered set updates.
1066   G1BarrierSet::dirty_card_queue_set().abandon_logs();
1067   assert(dirty_card_queue_set().completed_buffers_num() == 0, "DCQS should be empty");
1068 }
1069 
1070 void G1CollectedHeap::verify_after_full_collection() {
1071   _hrm.verify_optional();
1072   _verifier->verify_region_sets_optional();
1073   _verifier->verify_after_gc(G1HeapVerifier::G1VerifyFull);
1074   // Clear the previous marking bitmap, if needed for bitmap verification.
1075   // Note we cannot do this when we clear the next marking bitmap in
1076   // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the
1077   // objects marked during a full GC against the previous bitmap.
1078   // But we need to clear it before calling check_bitmaps below since
1079   // the full GC has compacted objects and updated TAMS but not updated
1080   // the prev bitmap.
1081   if (G1VerifyBitmaps) {
1082     GCTraceTime(Debug, gc)("Clear Bitmap for Verification");
1083     _cm->clear_prev_bitmap(workers());
1084   }
1085   _verifier->check_bitmaps("Full GC End");
1086 
1087   // At this point there should be no regions in the
1088   // entire heap tagged as young.
1089   assert(check_young_list_empty(), "young list should be empty at this point");
1090 
1091   // Note: since we've just done a full GC, concurrent
1092   // marking is no longer active. Therefore we need not
1093   // re-enable reference discovery for the CM ref processor.
1094   // That will be done at the start of the next marking cycle.
1095   // We also know that the STW processor should no longer
1096   // discover any new references.
1097   assert(!_ref_processor_stw->discovery_enabled(), "Postcondition");
1098   assert(!_ref_processor_cm->discovery_enabled(), "Postcondition");
1099   _ref_processor_stw->verify_no_references_recorded();
1100   _ref_processor_cm->verify_no_references_recorded();
1101 }
1102 
1103 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) {
1104   // Post collection logging.
1105   // We should do this after we potentially resize the heap so
1106   // that all the COMMIT / UNCOMMIT events are generated before
1107   // the compaction events.
1108   print_hrm_post_compaction();
1109   heap_transition->print();
1110   print_heap_after_gc();
1111   print_heap_regions();
1112 #ifdef TRACESPINNING
1113   ParallelTaskTerminator::print_termination_counts();
1114 #endif
1115 }
1116 
1117 bool G1CollectedHeap::do_full_collection(bool explicit_gc,
1118                                          bool clear_all_soft_refs) {
1119   assert_at_safepoint_on_vm_thread();
1120 
1121   if (GCLocker::check_active_before_gc()) {
1122     // Full GC was not completed.
1123     return false;
1124   }
1125 
1126   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1127       soft_ref_policy()->should_clear_all_soft_refs();
1128 
1129   G1FullCollector collector(this, &_full_gc_memory_manager, explicit_gc, do_clear_all_soft_refs);
1130   GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true);
1131 
1132   collector.prepare_collection();
1133   collector.collect();
1134   collector.complete_collection();
1135 
1136   // Full collection was successfully completed.
1137   return true;
1138 }
1139 
1140 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1141   // Currently, there is no facility in the do_full_collection(bool) API to notify
1142   // the caller that the collection did not succeed (e.g., because it was locked
1143   // out by the GC locker). So, right now, we'll ignore the return value.
1144   bool dummy = do_full_collection(true,                /* explicit_gc */
1145                                   clear_all_soft_refs);
1146 }
1147 
1148 void G1CollectedHeap::resize_if_necessary_after_full_collection() {
1149   // Capacity, free and used after the GC counted as full regions to
1150   // include the waste in the following calculations.
1151   const size_t capacity_after_gc = capacity();
1152   const size_t used_after_gc = capacity_after_gc - unused_committed_regions_in_bytes();
1153 
1154   // This is enforced in arguments.cpp.
1155   assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1156          "otherwise the code below doesn't make sense");
1157 
1158   // We don't have floating point command-line arguments
1159   const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1160   const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1161   const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1162   const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1163 
1164   const size_t min_heap_size = collector_policy()->min_heap_byte_size();
1165   const size_t max_heap_size = collector_policy()->max_heap_byte_size();
1166 
1167   // We have to be careful here as these two calculations can overflow
1168   // 32-bit size_t's.
1169   double used_after_gc_d = (double) used_after_gc;
1170   double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1171   double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1172 
1173   // Let's make sure that they are both under the max heap size, which
1174   // by default will make them fit into a size_t.
1175   double desired_capacity_upper_bound = (double) max_heap_size;
1176   minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1177                                     desired_capacity_upper_bound);
1178   maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1179                                     desired_capacity_upper_bound);
1180 
1181   // We can now safely turn them into size_t's.
1182   size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1183   size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1184 
1185   // This assert only makes sense here, before we adjust them
1186   // with respect to the min and max heap size.
1187   assert(minimum_desired_capacity <= maximum_desired_capacity,
1188          "minimum_desired_capacity = " SIZE_FORMAT ", "
1189          "maximum_desired_capacity = " SIZE_FORMAT,
1190          minimum_desired_capacity, maximum_desired_capacity);
1191 
1192   // Should not be greater than the heap max size. No need to adjust
1193   // it with respect to the heap min size as it's a lower bound (i.e.,
1194   // we'll try to make the capacity larger than it, not smaller).
1195   minimum_desired_capacity = MIN2(minimum_desired_capacity, max_heap_size);
1196   // Should not be less than the heap min size. No need to adjust it
1197   // with respect to the heap max size as it's an upper bound (i.e.,
1198   // we'll try to make the capacity smaller than it, not greater).
1199   maximum_desired_capacity =  MAX2(maximum_desired_capacity, min_heap_size);
1200 
1201   if (capacity_after_gc < minimum_desired_capacity) {
1202     // Don't expand unless it's significant
1203     size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1204 
1205     log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity after Full GC). "
1206                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1207                               "min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1208                               capacity_after_gc, used_after_gc, used(), minimum_desired_capacity, MinHeapFreeRatio);
1209 
1210     expand(expand_bytes, _workers);
1211 
1212     // No expansion, now see if we want to shrink
1213   } else if (capacity_after_gc > maximum_desired_capacity) {
1214     // Capacity too large, compute shrinking size
1215     size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1216 
1217     log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity after Full GC). "
1218                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1219                               "maximum_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1220                               capacity_after_gc, used_after_gc, used(), maximum_desired_capacity, MaxHeapFreeRatio);
1221 
1222     shrink(shrink_bytes);
1223   }
1224 }
1225 
1226 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size,
1227                                                             bool do_gc,
1228                                                             bool clear_all_soft_refs,
1229                                                             bool expect_null_mutator_alloc_region,
1230                                                             bool* gc_succeeded) {
1231   *gc_succeeded = true;
1232   // Let's attempt the allocation first.
1233   HeapWord* result =
1234     attempt_allocation_at_safepoint(word_size,
1235                                     expect_null_mutator_alloc_region);
1236   if (result != NULL) {
1237     return result;
1238   }
1239 
1240   // In a G1 heap, we're supposed to keep allocation from failing by
1241   // incremental pauses.  Therefore, at least for now, we'll favor
1242   // expansion over collection.  (This might change in the future if we can
1243   // do something smarter than full collection to satisfy a failed alloc.)
1244   result = expand_and_allocate(word_size);
1245   if (result != NULL) {
1246     return result;
1247   }
1248 
1249   if (do_gc) {
1250     // Expansion didn't work, we'll try to do a Full GC.
1251     *gc_succeeded = do_full_collection(false, /* explicit_gc */
1252                                        clear_all_soft_refs);
1253   }
1254 
1255   return NULL;
1256 }
1257 
1258 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1259                                                      bool* succeeded) {
1260   assert_at_safepoint_on_vm_thread();
1261 
1262   // Attempts to allocate followed by Full GC.
1263   HeapWord* result =
1264     satisfy_failed_allocation_helper(word_size,
1265                                      true,  /* do_gc */
1266                                      false, /* clear_all_soft_refs */
1267                                      false, /* expect_null_mutator_alloc_region */
1268                                      succeeded);
1269 
1270   if (result != NULL || !*succeeded) {
1271     return result;
1272   }
1273 
1274   // Attempts to allocate followed by Full GC that will collect all soft references.
1275   result = satisfy_failed_allocation_helper(word_size,
1276                                             true, /* do_gc */
1277                                             true, /* clear_all_soft_refs */
1278                                             true, /* expect_null_mutator_alloc_region */
1279                                             succeeded);
1280 
1281   if (result != NULL || !*succeeded) {
1282     return result;
1283   }
1284 
1285   // Attempts to allocate, no GC
1286   result = satisfy_failed_allocation_helper(word_size,
1287                                             false, /* do_gc */
1288                                             false, /* clear_all_soft_refs */
1289                                             true,  /* expect_null_mutator_alloc_region */
1290                                             succeeded);
1291 
1292   if (result != NULL) {
1293     return result;
1294   }
1295 
1296   assert(!soft_ref_policy()->should_clear_all_soft_refs(),
1297          "Flag should have been handled and cleared prior to this point");
1298 
1299   // What else?  We might try synchronous finalization later.  If the total
1300   // space available is large enough for the allocation, then a more
1301   // complete compaction phase than we've tried so far might be
1302   // appropriate.
1303   return NULL;
1304 }
1305 
1306 // Attempting to expand the heap sufficiently
1307 // to support an allocation of the given "word_size".  If
1308 // successful, perform the allocation and return the address of the
1309 // allocated block, or else "NULL".
1310 
1311 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1312   assert_at_safepoint_on_vm_thread();
1313 
1314   _verifier->verify_region_sets_optional();
1315 
1316   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1317   log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B",
1318                             word_size * HeapWordSize);
1319 
1320 
1321   if (expand(expand_bytes, _workers)) {
1322     _hrm.verify_optional();
1323     _verifier->verify_region_sets_optional();
1324     return attempt_allocation_at_safepoint(word_size,
1325                                            false /* expect_null_mutator_alloc_region */);
1326   }
1327   return NULL;
1328 }
1329 
1330 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) {
1331   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1332   aligned_expand_bytes = align_up(aligned_expand_bytes,
1333                                        HeapRegion::GrainBytes);
1334 
1335   log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B",
1336                             expand_bytes, aligned_expand_bytes);
1337 
1338   if (is_maximal_no_gc()) {
1339     log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1340     return false;
1341   }
1342 
1343   double expand_heap_start_time_sec = os::elapsedTime();
1344   uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1345   assert(regions_to_expand > 0, "Must expand by at least one region");
1346 
1347   uint expanded_by = _hrm.expand_by(regions_to_expand, pretouch_workers);
1348   if (expand_time_ms != NULL) {
1349     *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS;
1350   }
1351 
1352   if (expanded_by > 0) {
1353     size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1354     assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1355     g1_policy()->record_new_heap_size(num_regions());
1356   } else {
1357     log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)");
1358 
1359     // The expansion of the virtual storage space was unsuccessful.
1360     // Let's see if it was because we ran out of swap.
1361     if (G1ExitOnExpansionFailure &&
1362         _hrm.available() >= regions_to_expand) {
1363       // We had head room...
1364       vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1365     }
1366   }
1367   return regions_to_expand > 0;
1368 }
1369 
1370 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1371   size_t aligned_shrink_bytes =
1372     ReservedSpace::page_align_size_down(shrink_bytes);
1373   aligned_shrink_bytes = align_down(aligned_shrink_bytes,
1374                                          HeapRegion::GrainBytes);
1375   uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1376 
1377   uint num_regions_removed = _hrm.shrink_by(num_regions_to_remove);
1378   size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1379 
1380 
1381   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",
1382                             shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1383   if (num_regions_removed > 0) {
1384     g1_policy()->record_new_heap_size(num_regions());
1385   } else {
1386     log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)");
1387   }
1388 }
1389 
1390 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1391   _verifier->verify_region_sets_optional();
1392 
1393   // We should only reach here at the end of a Full GC which means we
1394   // should not not be holding to any GC alloc regions. The method
1395   // below will make sure of that and do any remaining clean up.
1396   _allocator->abandon_gc_alloc_regions();
1397 
1398   // Instead of tearing down / rebuilding the free lists here, we
1399   // could instead use the remove_all_pending() method on free_list to
1400   // remove only the ones that we need to remove.
1401   tear_down_region_sets(true /* free_list_only */);
1402   shrink_helper(shrink_bytes);
1403   rebuild_region_sets(true /* free_list_only */);
1404 
1405   _hrm.verify_optional();
1406   _verifier->verify_region_sets_optional();
1407 }
1408 
1409 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) :
1410   CollectedHeap(),
1411   _young_gen_sampling_thread(NULL),
1412   _workers(NULL),
1413   _collector_policy(collector_policy),
1414   _card_table(NULL),
1415   _soft_ref_policy(),
1416   _memory_manager("G1 Young Generation", "end of minor GC"),
1417   _full_gc_memory_manager("G1 Old Generation", "end of major GC"),
1418   _eden_pool(NULL),
1419   _survivor_pool(NULL),
1420   _old_pool(NULL),
1421   _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1422   _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1423   _bot(NULL),
1424   _listener(),
1425   _hrm(),
1426   _allocator(NULL),
1427   _verifier(NULL),
1428   _summary_bytes_used(0),
1429   _archive_allocator(NULL),
1430   _survivor_evac_stats("Young", YoungPLABSize, PLABWeight),
1431   _old_evac_stats("Old", OldPLABSize, PLABWeight),
1432   _expand_heap_after_alloc_failure(true),
1433   _g1mm(NULL),
1434   _humongous_reclaim_candidates(),
1435   _has_humongous_reclaim_candidates(false),
1436   _hr_printer(),
1437   _collector_state(),
1438   _old_marking_cycles_started(0),
1439   _old_marking_cycles_completed(0),
1440   _eden(),
1441   _survivor(),
1442   _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1443   _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1444   _g1_policy(new G1Policy(_gc_timer_stw)),
1445   _heap_sizing_policy(NULL),
1446   _collection_set(this, _g1_policy),
1447   _hot_card_cache(NULL),
1448   _g1_rem_set(NULL),
1449   _dirty_card_queue_set(false),
1450   _cm(NULL),
1451   _cm_thread(NULL),
1452   _cr(NULL),
1453   _task_queues(NULL),
1454   _evacuation_failed(false),
1455   _evacuation_failed_info_array(NULL),
1456   _preserved_marks_set(true /* in_c_heap */),
1457 #ifndef PRODUCT
1458   _evacuation_failure_alot_for_current_gc(false),
1459   _evacuation_failure_alot_gc_number(0),
1460   _evacuation_failure_alot_count(0),
1461 #endif
1462   _ref_processor_stw(NULL),
1463   _is_alive_closure_stw(this),
1464   _is_subject_to_discovery_stw(this),
1465   _ref_processor_cm(NULL),
1466   _is_alive_closure_cm(this),
1467   _is_subject_to_discovery_cm(this),
1468   _in_cset_fast_test() {
1469 
1470   _workers = new WorkGang("GC Thread", ParallelGCThreads,
1471                           true /* are_GC_task_threads */,
1472                           false /* are_ConcurrentGC_threads */);
1473   _workers->initialize_workers();
1474   _verifier = new G1HeapVerifier(this);
1475 
1476   _allocator = new G1Allocator(this);
1477 
1478   _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics());
1479 
1480   _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);
1481 
1482   // Override the default _filler_array_max_size so that no humongous filler
1483   // objects are created.
1484   _filler_array_max_size = _humongous_object_threshold_in_words;
1485 
1486   uint n_queues = ParallelGCThreads;
1487   _task_queues = new RefToScanQueueSet(n_queues);
1488 
1489   _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1490 
1491   for (uint i = 0; i < n_queues; i++) {
1492     RefToScanQueue* q = new RefToScanQueue();
1493     q->initialize();
1494     _task_queues->register_queue(i, q);
1495     ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1496   }
1497 
1498   // Initialize the G1EvacuationFailureALot counters and flags.
1499   NOT_PRODUCT(reset_evacuation_should_fail();)
1500 
1501   guarantee(_task_queues != NULL, "task_queues allocation failure.");
1502 }
1503 
1504 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1505                                                                  size_t size,
1506                                                                  size_t translation_factor) {
1507   size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1508   // Allocate a new reserved space, preferring to use large pages.
1509   ReservedSpace rs(size, preferred_page_size);
1510   G1RegionToSpaceMapper* result  =
1511     G1RegionToSpaceMapper::create_mapper(rs,
1512                                          size,
1513                                          rs.alignment(),
1514                                          HeapRegion::GrainBytes,
1515                                          translation_factor,
1516                                          mtGC);
1517 
1518   os::trace_page_sizes_for_requested_size(description,
1519                                           size,
1520                                           preferred_page_size,
1521                                           rs.alignment(),
1522                                           rs.base(),
1523                                           rs.size());
1524 
1525   return result;
1526 }
1527 
1528 jint G1CollectedHeap::initialize_concurrent_refinement() {
1529   jint ecode = JNI_OK;
1530   _cr = G1ConcurrentRefine::create(&ecode);
1531   return ecode;
1532 }
1533 
1534 jint G1CollectedHeap::initialize_young_gen_sampling_thread() {
1535   _young_gen_sampling_thread = new G1YoungRemSetSamplingThread();
1536   if (_young_gen_sampling_thread->osthread() == NULL) {
1537     vm_shutdown_during_initialization("Could not create G1YoungRemSetSamplingThread");
1538     return JNI_ENOMEM;
1539   }
1540   return JNI_OK;
1541 }
1542 
1543 jint G1CollectedHeap::initialize() {
1544   os::enable_vtime();
1545 
1546   // Necessary to satisfy locking discipline assertions.
1547 
1548   MutexLocker x(Heap_lock);
1549 
1550   // While there are no constraints in the GC code that HeapWordSize
1551   // be any particular value, there are multiple other areas in the
1552   // system which believe this to be true (e.g. oop->object_size in some
1553   // cases incorrectly returns the size in wordSize units rather than
1554   // HeapWordSize).
1555   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1556 
1557   size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1558   size_t max_byte_size = collector_policy()->max_heap_byte_size();
1559   size_t heap_alignment = collector_policy()->heap_alignment();
1560 
1561   // Ensure that the sizes are properly aligned.
1562   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1563   Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1564   Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1565 
1566   // Reserve the maximum.
1567 
1568   // When compressed oops are enabled, the preferred heap base
1569   // is calculated by subtracting the requested size from the
1570   // 32Gb boundary and using the result as the base address for
1571   // heap reservation. If the requested size is not aligned to
1572   // HeapRegion::GrainBytes (i.e. the alignment that is passed
1573   // into the ReservedHeapSpace constructor) then the actual
1574   // base of the reserved heap may end up differing from the
1575   // address that was requested (i.e. the preferred heap base).
1576   // If this happens then we could end up using a non-optimal
1577   // compressed oops mode.
1578 
1579   ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1580                                                  heap_alignment);
1581 
1582   initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
1583 
1584   // Create the barrier set for the entire reserved region.
1585   G1CardTable* ct = new G1CardTable(reserved_region());
1586   ct->initialize();
1587   G1BarrierSet* bs = new G1BarrierSet(ct);
1588   bs->initialize();
1589   assert(bs->is_a(BarrierSet::G1BarrierSet), "sanity");
1590   BarrierSet::set_barrier_set(bs);
1591   _card_table = ct;
1592 
1593   // Create the hot card cache.
1594   _hot_card_cache = new G1HotCardCache(this);
1595 
1596   // Carve out the G1 part of the heap.
1597   ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1598   size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
1599   G1RegionToSpaceMapper* heap_storage =
1600     G1RegionToSpaceMapper::create_mapper(g1_rs,
1601                                          g1_rs.size(),
1602                                          page_size,
1603                                          HeapRegion::GrainBytes,
1604                                          1,
1605                                          mtJavaHeap);
1606   os::trace_page_sizes("Heap",
1607                        collector_policy()->min_heap_byte_size(),
1608                        max_byte_size,
1609                        page_size,
1610                        heap_rs.base(),
1611                        heap_rs.size());
1612   heap_storage->set_mapping_changed_listener(&_listener);
1613 
1614   // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1615   G1RegionToSpaceMapper* bot_storage =
1616     create_aux_memory_mapper("Block Offset Table",
1617                              G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize),
1618                              G1BlockOffsetTable::heap_map_factor());
1619 
1620   G1RegionToSpaceMapper* cardtable_storage =
1621     create_aux_memory_mapper("Card Table",
1622                              G1CardTable::compute_size(g1_rs.size() / HeapWordSize),
1623                              G1CardTable::heap_map_factor());
1624 
1625   G1RegionToSpaceMapper* card_counts_storage =
1626     create_aux_memory_mapper("Card Counts Table",
1627                              G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1628                              G1CardCounts::heap_map_factor());
1629 
1630   size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size());
1631   G1RegionToSpaceMapper* prev_bitmap_storage =
1632     create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1633   G1RegionToSpaceMapper* next_bitmap_storage =
1634     create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1635 
1636   _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1637   _card_table->initialize(cardtable_storage);
1638   // Do later initialization work for concurrent refinement.
1639   _hot_card_cache->initialize(card_counts_storage);
1640 
1641   // 6843694 - ensure that the maximum region index can fit
1642   // in the remembered set structures.
1643   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1644   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1645 
1646   // The G1FromCardCache reserves card with value 0 as "invalid", so the heap must not
1647   // start within the first card.
1648   guarantee(g1_rs.base() >= (char*)G1CardTable::card_size, "Java heap must not start within the first card.");
1649   // Also create a G1 rem set.
1650   _g1_rem_set = new G1RemSet(this, _card_table, _hot_card_cache);
1651   _g1_rem_set->initialize(max_capacity(), max_regions());
1652 
1653   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1654   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1655   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1656             "too many cards per region");
1657 
1658   FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
1659 
1660   _bot = new G1BlockOffsetTable(reserved_region(), bot_storage);
1661 
1662   {
1663     HeapWord* start = _hrm.reserved().start();
1664     HeapWord* end = _hrm.reserved().end();
1665     size_t granularity = HeapRegion::GrainBytes;
1666 
1667     _in_cset_fast_test.initialize(start, end, granularity);
1668     _humongous_reclaim_candidates.initialize(start, end, granularity);
1669   }
1670 
1671   // Create the G1ConcurrentMark data structure and thread.
1672   // (Must do this late, so that "max_regions" is defined.)
1673   _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1674   if (_cm == NULL || !_cm->completed_initialization()) {
1675     vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark");
1676     return JNI_ENOMEM;
1677   }
1678   _cm_thread = _cm->cm_thread();
1679 
1680   // Now expand into the initial heap size.
1681   if (!expand(init_byte_size, _workers)) {
1682     vm_shutdown_during_initialization("Failed to allocate initial heap.");
1683     return JNI_ENOMEM;
1684   }
1685 
1686   // Perform any initialization actions delegated to the policy.
1687   g1_policy()->init(this, &_collection_set);
1688 
1689   G1BarrierSet::satb_mark_queue_set().initialize(this,
1690                                                  SATB_Q_CBL_mon,
1691                                                  SATB_Q_FL_lock,
1692                                                  G1SATBProcessCompletedThreshold,
1693                                                  G1SATBBufferEnqueueingThresholdPercent,
1694                                                  Shared_SATB_Q_lock);
1695 
1696   jint ecode = initialize_concurrent_refinement();
1697   if (ecode != JNI_OK) {
1698     return ecode;
1699   }
1700 
1701   ecode = initialize_young_gen_sampling_thread();
1702   if (ecode != JNI_OK) {
1703     return ecode;
1704   }
1705 
1706   G1BarrierSet::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1707                                                   DirtyCardQ_FL_lock,
1708                                                   (int)concurrent_refine()->yellow_zone(),
1709                                                   (int)concurrent_refine()->red_zone(),
1710                                                   Shared_DirtyCardQ_lock,
1711                                                   NULL,  // fl_owner
1712                                                   true); // init_free_ids
1713 
1714   dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1715                                     DirtyCardQ_FL_lock,
1716                                     -1, // never trigger processing
1717                                     -1, // no limit on length
1718                                     Shared_DirtyCardQ_lock,
1719                                     &G1BarrierSet::dirty_card_queue_set());
1720 
1721   // Here we allocate the dummy HeapRegion that is required by the
1722   // G1AllocRegion class.
1723   HeapRegion* dummy_region = _hrm.get_dummy_region();
1724 
1725   // We'll re-use the same region whether the alloc region will
1726   // require BOT updates or not and, if it doesn't, then a non-young
1727   // region will complain that it cannot support allocations without
1728   // BOT updates. So we'll tag the dummy region as eden to avoid that.
1729   dummy_region->set_eden();
1730   // Make sure it's full.
1731   dummy_region->set_top(dummy_region->end());
1732   G1AllocRegion::setup(this, dummy_region);
1733 
1734   _allocator->init_mutator_alloc_region();
1735 
1736   // Do create of the monitoring and management support so that
1737   // values in the heap have been properly initialized.
1738   _g1mm = new G1MonitoringSupport(this);
1739 
1740   G1StringDedup::initialize();
1741 
1742   _preserved_marks_set.init(ParallelGCThreads);
1743 
1744   _collection_set.initialize(max_regions());
1745 
1746   return JNI_OK;
1747 }
1748 
1749 void G1CollectedHeap::initialize_serviceability() {
1750   _eden_pool = new G1EdenPool(this);
1751   _survivor_pool = new G1SurvivorPool(this);
1752   _old_pool = new G1OldGenPool(this);
1753 
1754   _full_gc_memory_manager.add_pool(_eden_pool);
1755   _full_gc_memory_manager.add_pool(_survivor_pool);
1756   _full_gc_memory_manager.add_pool(_old_pool);
1757 
1758   _memory_manager.add_pool(_eden_pool);
1759   _memory_manager.add_pool(_survivor_pool);
1760   _memory_manager.add_pool(_old_pool, false /* always_affected_by_gc */);
1761 }
1762 
1763 void G1CollectedHeap::stop() {
1764   // Stop all concurrent threads. We do this to make sure these threads
1765   // do not continue to execute and access resources (e.g. logging)
1766   // that are destroyed during shutdown.
1767   _cr->stop();
1768   _young_gen_sampling_thread->stop();
1769   _cm_thread->stop();
1770   if (G1StringDedup::is_enabled()) {
1771     G1StringDedup::stop();
1772   }
1773 }
1774 
1775 void G1CollectedHeap::safepoint_synchronize_begin() {
1776   SuspendibleThreadSet::synchronize();
1777 }
1778 
1779 void G1CollectedHeap::safepoint_synchronize_end() {
1780   SuspendibleThreadSet::desynchronize();
1781 }
1782 
1783 size_t G1CollectedHeap::conservative_max_heap_alignment() {
1784   return HeapRegion::max_region_size();
1785 }
1786 
1787 void G1CollectedHeap::post_initialize() {
1788   CollectedHeap::post_initialize();
1789   ref_processing_init();
1790 }
1791 
1792 void G1CollectedHeap::ref_processing_init() {
1793   // Reference processing in G1 currently works as follows:
1794   //
1795   // * There are two reference processor instances. One is
1796   //   used to record and process discovered references
1797   //   during concurrent marking; the other is used to
1798   //   record and process references during STW pauses
1799   //   (both full and incremental).
1800   // * Both ref processors need to 'span' the entire heap as
1801   //   the regions in the collection set may be dotted around.
1802   //
1803   // * For the concurrent marking ref processor:
1804   //   * Reference discovery is enabled at initial marking.
1805   //   * Reference discovery is disabled and the discovered
1806   //     references processed etc during remarking.
1807   //   * Reference discovery is MT (see below).
1808   //   * Reference discovery requires a barrier (see below).
1809   //   * Reference processing may or may not be MT
1810   //     (depending on the value of ParallelRefProcEnabled
1811   //     and ParallelGCThreads).
1812   //   * A full GC disables reference discovery by the CM
1813   //     ref processor and abandons any entries on it's
1814   //     discovered lists.
1815   //
1816   // * For the STW processor:
1817   //   * Non MT discovery is enabled at the start of a full GC.
1818   //   * Processing and enqueueing during a full GC is non-MT.
1819   //   * During a full GC, references are processed after marking.
1820   //
1821   //   * Discovery (may or may not be MT) is enabled at the start
1822   //     of an incremental evacuation pause.
1823   //   * References are processed near the end of a STW evacuation pause.
1824   //   * For both types of GC:
1825   //     * Discovery is atomic - i.e. not concurrent.
1826   //     * Reference discovery will not need a barrier.
1827 
1828   bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1);
1829 
1830   // Concurrent Mark ref processor
1831   _ref_processor_cm =
1832     new ReferenceProcessor(&_is_subject_to_discovery_cm,
1833                            mt_processing,                                  // mt processing
1834                            ParallelGCThreads,                              // degree of mt processing
1835                            (ParallelGCThreads > 1) || (ConcGCThreads > 1), // mt discovery
1836                            MAX2(ParallelGCThreads, ConcGCThreads),         // degree of mt discovery
1837                            false,                                          // Reference discovery is not atomic
1838                            &_is_alive_closure_cm,                          // is alive closure
1839                            true);                                          // allow changes to number of processing threads
1840 
1841   // STW ref processor
1842   _ref_processor_stw =
1843     new ReferenceProcessor(&_is_subject_to_discovery_stw,
1844                            mt_processing,                        // mt processing
1845                            ParallelGCThreads,                    // degree of mt processing
1846                            (ParallelGCThreads > 1),              // mt discovery
1847                            ParallelGCThreads,                    // degree of mt discovery
1848                            true,                                 // Reference discovery is atomic
1849                            &_is_alive_closure_stw,               // is alive closure
1850                            true);                                // allow changes to number of processing threads
1851 }
1852 
1853 CollectorPolicy* G1CollectedHeap::collector_policy() const {
1854   return _collector_policy;
1855 }
1856 
1857 SoftRefPolicy* G1CollectedHeap::soft_ref_policy() {
1858   return &_soft_ref_policy;
1859 }
1860 
1861 size_t G1CollectedHeap::capacity() const {
1862   return _hrm.length() * HeapRegion::GrainBytes;
1863 }
1864 
1865 size_t G1CollectedHeap::unused_committed_regions_in_bytes() const {
1866   return _hrm.total_free_bytes();
1867 }
1868 
1869 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) {
1870   _hot_card_cache->drain(cl, worker_i);
1871 }
1872 
1873 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) {
1874   DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
1875   size_t n_completed_buffers = 0;
1876   while (dcqs.apply_closure_during_gc(cl, worker_i)) {
1877     n_completed_buffers++;
1878   }
1879   g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers, G1GCPhaseTimes::UpdateRSProcessedBuffers);
1880   dcqs.clear_n_completed_buffers();
1881   assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
1882 }
1883 
1884 // Computes the sum of the storage used by the various regions.
1885 size_t G1CollectedHeap::used() const {
1886   size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
1887   if (_archive_allocator != NULL) {
1888     result += _archive_allocator->used();
1889   }
1890   return result;
1891 }
1892 
1893 size_t G1CollectedHeap::used_unlocked() const {
1894   return _summary_bytes_used;
1895 }
1896 
1897 class SumUsedClosure: public HeapRegionClosure {
1898   size_t _used;
1899 public:
1900   SumUsedClosure() : _used(0) {}
1901   bool do_heap_region(HeapRegion* r) {
1902     _used += r->used();
1903     return false;
1904   }
1905   size_t result() { return _used; }
1906 };
1907 
1908 size_t G1CollectedHeap::recalculate_used() const {
1909   double recalculate_used_start = os::elapsedTime();
1910 
1911   SumUsedClosure blk;
1912   heap_region_iterate(&blk);
1913 
1914   g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
1915   return blk.result();
1916 }
1917 
1918 bool  G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
1919   switch (cause) {
1920     case GCCause::_java_lang_system_gc:                 return ExplicitGCInvokesConcurrent;
1921     case GCCause::_dcmd_gc_run:                         return ExplicitGCInvokesConcurrent;
1922     case GCCause::_wb_conc_mark:                        return true;
1923     default :                                           return false;
1924   }
1925 }
1926 
1927 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
1928   switch (cause) {
1929     case GCCause::_gc_locker:               return GCLockerInvokesConcurrent;
1930     case GCCause::_g1_humongous_allocation: return true;
1931     default:                                return is_user_requested_concurrent_full_gc(cause);
1932   }
1933 }
1934 
1935 #ifndef PRODUCT
1936 void G1CollectedHeap::allocate_dummy_regions() {
1937   // Let's fill up most of the region
1938   size_t word_size = HeapRegion::GrainWords - 1024;
1939   // And as a result the region we'll allocate will be humongous.
1940   guarantee(is_humongous(word_size), "sanity");
1941 
1942   // _filler_array_max_size is set to humongous object threshold
1943   // but temporarily change it to use CollectedHeap::fill_with_object().
1944   SizeTFlagSetting fs(_filler_array_max_size, word_size);
1945 
1946   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
1947     // Let's use the existing mechanism for the allocation
1948     HeapWord* dummy_obj = humongous_obj_allocate(word_size);
1949     if (dummy_obj != NULL) {
1950       MemRegion mr(dummy_obj, word_size);
1951       CollectedHeap::fill_with_object(mr);
1952     } else {
1953       // If we can't allocate once, we probably cannot allocate
1954       // again. Let's get out of the loop.
1955       break;
1956     }
1957   }
1958 }
1959 #endif // !PRODUCT
1960 
1961 void G1CollectedHeap::increment_old_marking_cycles_started() {
1962   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
1963          _old_marking_cycles_started == _old_marking_cycles_completed + 1,
1964          "Wrong marking cycle count (started: %d, completed: %d)",
1965          _old_marking_cycles_started, _old_marking_cycles_completed);
1966 
1967   _old_marking_cycles_started++;
1968 }
1969 
1970 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
1971   MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
1972 
1973   // We assume that if concurrent == true, then the caller is a
1974   // concurrent thread that was joined the Suspendible Thread
1975   // Set. If there's ever a cheap way to check this, we should add an
1976   // assert here.
1977 
1978   // Given that this method is called at the end of a Full GC or of a
1979   // concurrent cycle, and those can be nested (i.e., a Full GC can
1980   // interrupt a concurrent cycle), the number of full collections
1981   // completed should be either one (in the case where there was no
1982   // nesting) or two (when a Full GC interrupted a concurrent cycle)
1983   // behind the number of full collections started.
1984 
1985   // This is the case for the inner caller, i.e. a Full GC.
1986   assert(concurrent ||
1987          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
1988          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
1989          "for inner caller (Full GC): _old_marking_cycles_started = %u "
1990          "is inconsistent with _old_marking_cycles_completed = %u",
1991          _old_marking_cycles_started, _old_marking_cycles_completed);
1992 
1993   // This is the case for the outer caller, i.e. the concurrent cycle.
1994   assert(!concurrent ||
1995          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
1996          "for outer caller (concurrent cycle): "
1997          "_old_marking_cycles_started = %u "
1998          "is inconsistent with _old_marking_cycles_completed = %u",
1999          _old_marking_cycles_started, _old_marking_cycles_completed);
2000 
2001   _old_marking_cycles_completed += 1;
2002 
2003   // We need to clear the "in_progress" flag in the CM thread before
2004   // we wake up any waiters (especially when ExplicitInvokesConcurrent
2005   // is set) so that if a waiter requests another System.gc() it doesn't
2006   // incorrectly see that a marking cycle is still in progress.
2007   if (concurrent) {
2008     _cm_thread->set_idle();
2009   }
2010 
2011   // This notify_all() will ensure that a thread that called
2012   // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2013   // and it's waiting for a full GC to finish will be woken up. It is
2014   // waiting in VM_G1CollectForAllocation::doit_epilogue().
2015   FullGCCount_lock->notify_all();
2016 }
2017 
2018 void G1CollectedHeap::collect(GCCause::Cause cause) {
2019   assert_heap_not_locked();
2020 
2021   uint gc_count_before;
2022   uint old_marking_count_before;
2023   uint full_gc_count_before;
2024   bool retry_gc;
2025 
2026   do {
2027     retry_gc = false;
2028 
2029     {
2030       MutexLocker ml(Heap_lock);
2031 
2032       // Read the GC count while holding the Heap_lock
2033       gc_count_before = total_collections();
2034       full_gc_count_before = total_full_collections();
2035       old_marking_count_before = _old_marking_cycles_started;
2036     }
2037 
2038     if (should_do_concurrent_full_gc(cause)) {
2039       // Schedule an initial-mark evacuation pause that will start a
2040       // concurrent cycle. We're setting word_size to 0 which means that
2041       // we are not requesting a post-GC allocation.
2042       VM_G1CollectForAllocation op(0,     /* word_size */
2043                                    gc_count_before,
2044                                    cause,
2045                                    true,  /* should_initiate_conc_mark */
2046                                    g1_policy()->max_pause_time_ms());
2047       VMThread::execute(&op);
2048       if (!op.pause_succeeded()) {
2049         if (old_marking_count_before == _old_marking_cycles_started) {
2050           retry_gc = op.should_retry_gc();
2051         } else {
2052           // A Full GC happened while we were trying to schedule the
2053           // initial-mark GC. No point in starting a new cycle given
2054           // that the whole heap was collected anyway.
2055         }
2056 
2057         if (retry_gc) {
2058           if (GCLocker::is_active_and_needs_gc()) {
2059             GCLocker::stall_until_clear();
2060           }
2061         }
2062       }
2063     } else {
2064       if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2065           DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2066 
2067         // Schedule a standard evacuation pause. We're setting word_size
2068         // to 0 which means that we are not requesting a post-GC allocation.
2069         VM_G1CollectForAllocation op(0,     /* word_size */
2070                                      gc_count_before,
2071                                      cause,
2072                                      false, /* should_initiate_conc_mark */
2073                                      g1_policy()->max_pause_time_ms());
2074         VMThread::execute(&op);
2075       } else {
2076         // Schedule a Full GC.
2077         VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2078         VMThread::execute(&op);
2079       }
2080     }
2081   } while (retry_gc);
2082 }
2083 
2084 bool G1CollectedHeap::is_in(const void* p) const {
2085   if (_hrm.reserved().contains(p)) {
2086     // Given that we know that p is in the reserved space,
2087     // heap_region_containing() should successfully
2088     // return the containing region.
2089     HeapRegion* hr = heap_region_containing(p);
2090     return hr->is_in(p);
2091   } else {
2092     return false;
2093   }
2094 }
2095 
2096 #ifdef ASSERT
2097 bool G1CollectedHeap::is_in_exact(const void* p) const {
2098   bool contains = reserved_region().contains(p);
2099   bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2100   if (contains && available) {
2101     return true;
2102   } else {
2103     return false;
2104   }
2105 }
2106 #endif
2107 
2108 // Iteration functions.
2109 
2110 // Iterates an ObjectClosure over all objects within a HeapRegion.
2111 
2112 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2113   ObjectClosure* _cl;
2114 public:
2115   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2116   bool do_heap_region(HeapRegion* r) {
2117     if (!r->is_continues_humongous()) {
2118       r->object_iterate(_cl);
2119     }
2120     return false;
2121   }
2122 };
2123 
2124 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2125   IterateObjectClosureRegionClosure blk(cl);
2126   heap_region_iterate(&blk);
2127 }
2128 
2129 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2130   _hrm.iterate(cl);
2131 }
2132 
2133 void G1CollectedHeap::heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl,
2134                                                                  HeapRegionClaimer *hrclaimer,
2135                                                                  uint worker_id) const {
2136   _hrm.par_iterate(cl, hrclaimer, hrclaimer->offset_for_worker(worker_id));
2137 }
2138 
2139 void G1CollectedHeap::heap_region_par_iterate_from_start(HeapRegionClosure* cl,
2140                                                          HeapRegionClaimer *hrclaimer) const {
2141   _hrm.par_iterate(cl, hrclaimer, 0);
2142 }
2143 
2144 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2145   _collection_set.iterate(cl);
2146 }
2147 
2148 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) {
2149   _collection_set.iterate_from(cl, worker_id, workers()->active_workers());
2150 }
2151 
2152 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2153   HeapRegion* hr = heap_region_containing(addr);
2154   return hr->block_start(addr);
2155 }
2156 
2157 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2158   HeapRegion* hr = heap_region_containing(addr);
2159   return hr->block_size(addr);
2160 }
2161 
2162 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2163   HeapRegion* hr = heap_region_containing(addr);
2164   return hr->block_is_obj(addr);
2165 }
2166 
2167 bool G1CollectedHeap::supports_tlab_allocation() const {
2168   return true;
2169 }
2170 
2171 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2172   return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes;
2173 }
2174 
2175 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2176   return _eden.length() * HeapRegion::GrainBytes;
2177 }
2178 
2179 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2180 // must be equal to the humongous object limit.
2181 size_t G1CollectedHeap::max_tlab_size() const {
2182   return align_down(_humongous_object_threshold_in_words, MinObjAlignment);
2183 }
2184 
2185 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2186   return _allocator->unsafe_max_tlab_alloc();
2187 }
2188 
2189 size_t G1CollectedHeap::max_capacity() const {
2190   return _hrm.reserved().byte_size();
2191 }
2192 
2193 jlong G1CollectedHeap::millis_since_last_gc() {
2194   // See the notes in GenCollectedHeap::millis_since_last_gc()
2195   // for more information about the implementation.
2196   jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) -
2197     _g1_policy->collection_pause_end_millis();
2198   if (ret_val < 0) {
2199     log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT
2200       ". returning zero instead.", ret_val);
2201     return 0;
2202   }
2203   return ret_val;
2204 }
2205 
2206 void G1CollectedHeap::deduplicate_string(oop str) {
2207   assert(java_lang_String::is_instance(str), "invariant");
2208 
2209   if (G1StringDedup::is_enabled()) {
2210     G1StringDedup::deduplicate(str);
2211   }
2212 }
2213 
2214 void G1CollectedHeap::prepare_for_verify() {
2215   _verifier->prepare_for_verify();
2216 }
2217 
2218 void G1CollectedHeap::verify(VerifyOption vo) {
2219   _verifier->verify(vo);
2220 }
2221 
2222 bool G1CollectedHeap::supports_concurrent_phase_control() const {
2223   return true;
2224 }
2225 
2226 const char* const* G1CollectedHeap::concurrent_phases() const {
2227   return _cm_thread->concurrent_phases();
2228 }
2229 
2230 bool G1CollectedHeap::request_concurrent_phase(const char* phase) {
2231   return _cm_thread->request_concurrent_phase(phase);
2232 }
2233 
2234 class PrintRegionClosure: public HeapRegionClosure {
2235   outputStream* _st;
2236 public:
2237   PrintRegionClosure(outputStream* st) : _st(st) {}
2238   bool do_heap_region(HeapRegion* r) {
2239     r->print_on(_st);
2240     return false;
2241   }
2242 };
2243 
2244 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2245                                        const HeapRegion* hr,
2246                                        const VerifyOption vo) const {
2247   switch (vo) {
2248   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
2249   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
2250   case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj, hr);
2251   default:                            ShouldNotReachHere();
2252   }
2253   return false; // keep some compilers happy
2254 }
2255 
2256 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2257                                        const VerifyOption vo) const {
2258   switch (vo) {
2259   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
2260   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
2261   case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj);
2262   default:                            ShouldNotReachHere();
2263   }
2264   return false; // keep some compilers happy
2265 }
2266 
2267 void G1CollectedHeap::print_heap_regions() const {
2268   LogTarget(Trace, gc, heap, region) lt;
2269   if (lt.is_enabled()) {
2270     LogStream ls(lt);
2271     print_regions_on(&ls);
2272   }
2273 }
2274 
2275 void G1CollectedHeap::print_on(outputStream* st) const {
2276   st->print(" %-20s", "garbage-first heap");
2277   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
2278             capacity()/K, used_unlocked()/K);
2279   st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")",
2280             p2i(_hrm.reserved().start()),
2281             p2i(_hrm.reserved().end()));
2282   st->cr();
2283   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
2284   uint young_regions = young_regions_count();
2285   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
2286             (size_t) young_regions * HeapRegion::GrainBytes / K);
2287   uint survivor_regions = survivor_regions_count();
2288   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
2289             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
2290   st->cr();
2291   MetaspaceUtils::print_on(st);
2292 }
2293 
2294 void G1CollectedHeap::print_regions_on(outputStream* st) const {
2295   st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
2296                "HS=humongous(starts), HC=humongous(continues), "
2297                "CS=collection set, F=free, A=archive, "
2298                "TAMS=top-at-mark-start (previous, next)");
2299   PrintRegionClosure blk(st);
2300   heap_region_iterate(&blk);
2301 }
2302 
2303 void G1CollectedHeap::print_extended_on(outputStream* st) const {
2304   print_on(st);
2305 
2306   // Print the per-region information.
2307   print_regions_on(st);
2308 }
2309 
2310 void G1CollectedHeap::print_on_error(outputStream* st) const {
2311   this->CollectedHeap::print_on_error(st);
2312 
2313   if (_cm != NULL) {
2314     st->cr();
2315     _cm->print_on_error(st);
2316   }
2317 }
2318 
2319 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
2320   workers()->print_worker_threads_on(st);
2321   _cm_thread->print_on(st);
2322   st->cr();
2323   _cm->print_worker_threads_on(st);
2324   _cr->print_threads_on(st);
2325   _young_gen_sampling_thread->print_on(st);
2326   if (G1StringDedup::is_enabled()) {
2327     G1StringDedup::print_worker_threads_on(st);
2328   }
2329 }
2330 
2331 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2332   workers()->threads_do(tc);
2333   tc->do_thread(_cm_thread);
2334   _cm->threads_do(tc);
2335   _cr->threads_do(tc);
2336   tc->do_thread(_young_gen_sampling_thread);
2337   if (G1StringDedup::is_enabled()) {
2338     G1StringDedup::threads_do(tc);
2339   }
2340 }
2341 
2342 void G1CollectedHeap::print_tracing_info() const {
2343   g1_rem_set()->print_summary_info();
2344   concurrent_mark()->print_summary_info();
2345 }
2346 
2347 #ifndef PRODUCT
2348 // Helpful for debugging RSet issues.
2349 
2350 class PrintRSetsClosure : public HeapRegionClosure {
2351 private:
2352   const char* _msg;
2353   size_t _occupied_sum;
2354 
2355 public:
2356   bool do_heap_region(HeapRegion* r) {
2357     HeapRegionRemSet* hrrs = r->rem_set();
2358     size_t occupied = hrrs->occupied();
2359     _occupied_sum += occupied;
2360 
2361     tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r));
2362     if (occupied == 0) {
2363       tty->print_cr("  RSet is empty");
2364     } else {
2365       hrrs->print();
2366     }
2367     tty->print_cr("----------");
2368     return false;
2369   }
2370 
2371   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
2372     tty->cr();
2373     tty->print_cr("========================================");
2374     tty->print_cr("%s", msg);
2375     tty->cr();
2376   }
2377 
2378   ~PrintRSetsClosure() {
2379     tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
2380     tty->print_cr("========================================");
2381     tty->cr();
2382   }
2383 };
2384 
2385 void G1CollectedHeap::print_cset_rsets() {
2386   PrintRSetsClosure cl("Printing CSet RSets");
2387   collection_set_iterate(&cl);
2388 }
2389 
2390 void G1CollectedHeap::print_all_rsets() {
2391   PrintRSetsClosure cl("Printing All RSets");;
2392   heap_region_iterate(&cl);
2393 }
2394 #endif // PRODUCT
2395 
2396 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
2397 
2398   size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes;
2399   size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes;
2400   size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
2401 
2402   size_t eden_capacity_bytes =
2403     (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
2404 
2405   VirtualSpaceSummary heap_summary = create_heap_space_summary();
2406   return G1HeapSummary(heap_summary, heap_used, eden_used_bytes,
2407                        eden_capacity_bytes, survivor_used_bytes, num_regions());
2408 }
2409 
2410 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
2411   return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
2412                        stats->unused(), stats->used(), stats->region_end_waste(),
2413                        stats->regions_filled(), stats->direct_allocated(),
2414                        stats->failure_used(), stats->failure_waste());
2415 }
2416 
2417 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
2418   const G1HeapSummary& heap_summary = create_g1_heap_summary();
2419   gc_tracer->report_gc_heap_summary(when, heap_summary);
2420 
2421   const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
2422   gc_tracer->report_metaspace_summary(when, metaspace_summary);
2423 }
2424 
2425 G1CollectedHeap* G1CollectedHeap::heap() {
2426   CollectedHeap* heap = Universe::heap();
2427   assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
2428   assert(heap->kind() == CollectedHeap::G1, "Invalid name");
2429   return (G1CollectedHeap*)heap;
2430 }
2431 
2432 void G1CollectedHeap::gc_prologue(bool full) {
2433   // always_do_update_barrier = false;
2434   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
2435 
2436   // This summary needs to be printed before incrementing total collections.
2437   g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections());
2438 
2439   // Update common counters.
2440   increment_total_collections(full /* full gc */);
2441   if (full) {
2442     increment_old_marking_cycles_started();
2443   }
2444 
2445   // Fill TLAB's and such
2446   double start = os::elapsedTime();
2447   accumulate_statistics_all_tlabs();
2448   ensure_parsability(true);
2449   g1_policy()->phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2450 }
2451 
2452 void G1CollectedHeap::gc_epilogue(bool full) {
2453   // Update common counters.
2454   if (full) {
2455     // Update the number of full collections that have been completed.
2456     increment_old_marking_cycles_completed(false /* concurrent */);
2457   }
2458 
2459   // We are at the end of the GC. Total collections has already been increased.
2460   g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1);
2461 
2462   // FIXME: what is this about?
2463   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
2464   // is set.
2465 #if COMPILER2_OR_JVMCI
2466   assert(DerivedPointerTable::is_empty(), "derived pointer present");
2467 #endif
2468   // always_do_update_barrier = true;
2469 
2470   double start = os::elapsedTime();
2471   resize_all_tlabs();
2472   g1_policy()->phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2473 
2474   MemoryService::track_memory_usage();
2475   // We have just completed a GC. Update the soft reference
2476   // policy with the new heap occupancy
2477   Universe::update_heap_info_at_gc();
2478 }
2479 
2480 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2481                                                uint gc_count_before,
2482                                                bool* succeeded,
2483                                                GCCause::Cause gc_cause) {
2484   assert_heap_not_locked_and_not_at_safepoint();
2485   VM_G1CollectForAllocation op(word_size,
2486                                gc_count_before,
2487                                gc_cause,
2488                                false, /* should_initiate_conc_mark */
2489                                g1_policy()->max_pause_time_ms());
2490   VMThread::execute(&op);
2491 
2492   HeapWord* result = op.result();
2493   bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
2494   assert(result == NULL || ret_succeeded,
2495          "the result should be NULL if the VM did not succeed");
2496   *succeeded = ret_succeeded;
2497 
2498   assert_heap_not_locked();
2499   return result;
2500 }
2501 
2502 void G1CollectedHeap::do_concurrent_mark() {
2503   MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
2504   if (!_cm_thread->in_progress()) {
2505     _cm_thread->set_started();
2506     CGC_lock->notify();
2507   }
2508 }
2509 
2510 size_t G1CollectedHeap::pending_card_num() {
2511   size_t extra_cards = 0;
2512   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *curr = jtiwh.next(); ) {
2513     DirtyCardQueue& dcq = G1ThreadLocalData::dirty_card_queue(curr);
2514     extra_cards += dcq.size();
2515   }
2516   DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
2517   size_t buffer_size = dcqs.buffer_size();
2518   size_t buffer_num = dcqs.completed_buffers_num();
2519 
2520   return buffer_size * buffer_num + extra_cards;
2521 }
2522 
2523 bool G1CollectedHeap::is_potential_eager_reclaim_candidate(HeapRegion* r) const {
2524   // We don't nominate objects with many remembered set entries, on
2525   // the assumption that such objects are likely still live.
2526   HeapRegionRemSet* rem_set = r->rem_set();
2527 
2528   return G1EagerReclaimHumongousObjectsWithStaleRefs ?
2529          rem_set->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) :
2530          G1EagerReclaimHumongousObjects && rem_set->is_empty();
2531 }
2532 
2533 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
2534  private:
2535   size_t _total_humongous;
2536   size_t _candidate_humongous;
2537 
2538   DirtyCardQueue _dcq;
2539 
2540   bool humongous_region_is_candidate(G1CollectedHeap* g1h, HeapRegion* region) const {
2541     assert(region->is_starts_humongous(), "Must start a humongous object");
2542 
2543     oop obj = oop(region->bottom());
2544 
2545     // Dead objects cannot be eager reclaim candidates. Due to class
2546     // unloading it is unsafe to query their classes so we return early.
2547     if (g1h->is_obj_dead(obj, region)) {
2548       return false;
2549     }
2550 
2551     // If we do not have a complete remembered set for the region, then we can
2552     // not be sure that we have all references to it.
2553     if (!region->rem_set()->is_complete()) {
2554       return false;
2555     }
2556     // Candidate selection must satisfy the following constraints
2557     // while concurrent marking is in progress:
2558     //
2559     // * In order to maintain SATB invariants, an object must not be
2560     // reclaimed if it was allocated before the start of marking and
2561     // has not had its references scanned.  Such an object must have
2562     // its references (including type metadata) scanned to ensure no
2563     // live objects are missed by the marking process.  Objects
2564     // allocated after the start of concurrent marking don't need to
2565     // be scanned.
2566     //
2567     // * An object must not be reclaimed if it is on the concurrent
2568     // mark stack.  Objects allocated after the start of concurrent
2569     // marking are never pushed on the mark stack.
2570     //
2571     // Nominating only objects allocated after the start of concurrent
2572     // marking is sufficient to meet both constraints.  This may miss
2573     // some objects that satisfy the constraints, but the marking data
2574     // structures don't support efficiently performing the needed
2575     // additional tests or scrubbing of the mark stack.
2576     //
2577     // However, we presently only nominate is_typeArray() objects.
2578     // A humongous object containing references induces remembered
2579     // set entries on other regions.  In order to reclaim such an
2580     // object, those remembered sets would need to be cleaned up.
2581     //
2582     // We also treat is_typeArray() objects specially, allowing them
2583     // to be reclaimed even if allocated before the start of
2584     // concurrent mark.  For this we rely on mark stack insertion to
2585     // exclude is_typeArray() objects, preventing reclaiming an object
2586     // that is in the mark stack.  We also rely on the metadata for
2587     // such objects to be built-in and so ensured to be kept live.
2588     // Frequent allocation and drop of large binary blobs is an
2589     // important use case for eager reclaim, and this special handling
2590     // may reduce needed headroom.
2591 
2592     return obj->is_typeArray() &&
2593            g1h->is_potential_eager_reclaim_candidate(region);
2594   }
2595 
2596  public:
2597   RegisterHumongousWithInCSetFastTestClosure()
2598   : _total_humongous(0),
2599     _candidate_humongous(0),
2600     _dcq(&G1BarrierSet::dirty_card_queue_set()) {
2601   }
2602 
2603   virtual bool do_heap_region(HeapRegion* r) {
2604     if (!r->is_starts_humongous()) {
2605       return false;
2606     }
2607     G1CollectedHeap* g1h = G1CollectedHeap::heap();
2608 
2609     bool is_candidate = humongous_region_is_candidate(g1h, r);
2610     uint rindex = r->hrm_index();
2611     g1h->set_humongous_reclaim_candidate(rindex, is_candidate);
2612     if (is_candidate) {
2613       _candidate_humongous++;
2614       g1h->register_humongous_region_with_cset(rindex);
2615       // Is_candidate already filters out humongous object with large remembered sets.
2616       // If we have a humongous object with a few remembered sets, we simply flush these
2617       // remembered set entries into the DCQS. That will result in automatic
2618       // re-evaluation of their remembered set entries during the following evacuation
2619       // phase.
2620       if (!r->rem_set()->is_empty()) {
2621         guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
2622                   "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
2623         G1CardTable* ct = g1h->card_table();
2624         HeapRegionRemSetIterator hrrs(r->rem_set());
2625         size_t card_index;
2626         while (hrrs.has_next(card_index)) {
2627           jbyte* card_ptr = (jbyte*)ct->byte_for_index(card_index);
2628           // The remembered set might contain references to already freed
2629           // regions. Filter out such entries to avoid failing card table
2630           // verification.
2631           if (g1h->is_in_closed_subset(ct->addr_for(card_ptr))) {
2632             if (*card_ptr != G1CardTable::dirty_card_val()) {
2633               *card_ptr = G1CardTable::dirty_card_val();
2634               _dcq.enqueue(card_ptr);
2635             }
2636           }
2637         }
2638         assert(hrrs.n_yielded() == r->rem_set()->occupied(),
2639                "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries",
2640                hrrs.n_yielded(), r->rem_set()->occupied());
2641         // We should only clear the card based remembered set here as we will not
2642         // implicitly rebuild anything else during eager reclaim. Note that at the moment
2643         // (and probably never) we do not enter this path if there are other kind of
2644         // remembered sets for this region.
2645         r->rem_set()->clear_locked(true /* only_cardset */);
2646         // Clear_locked() above sets the state to Empty. However we want to continue
2647         // collecting remembered set entries for humongous regions that were not
2648         // reclaimed.
2649         r->rem_set()->set_state_complete();
2650       }
2651       assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
2652     }
2653     _total_humongous++;
2654 
2655     return false;
2656   }
2657 
2658   size_t total_humongous() const { return _total_humongous; }
2659   size_t candidate_humongous() const { return _candidate_humongous; }
2660 
2661   void flush_rem_set_entries() { _dcq.flush(); }
2662 };
2663 
2664 void G1CollectedHeap::register_humongous_regions_with_cset() {
2665   if (!G1EagerReclaimHumongousObjects) {
2666     g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
2667     return;
2668   }
2669   double time = os::elapsed_counter();
2670 
2671   // Collect reclaim candidate information and register candidates with cset.
2672   RegisterHumongousWithInCSetFastTestClosure cl;
2673   heap_region_iterate(&cl);
2674 
2675   time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
2676   g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
2677                                                                   cl.total_humongous(),
2678                                                                   cl.candidate_humongous());
2679   _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
2680 
2681   // Finally flush all remembered set entries to re-check into the global DCQS.
2682   cl.flush_rem_set_entries();
2683 }
2684 
2685 class VerifyRegionRemSetClosure : public HeapRegionClosure {
2686   public:
2687     bool do_heap_region(HeapRegion* hr) {
2688       if (!hr->is_archive() && !hr->is_continues_humongous()) {
2689         hr->verify_rem_set();
2690       }
2691       return false;
2692     }
2693 };
2694 
2695 uint G1CollectedHeap::num_task_queues() const {
2696   return _task_queues->size();
2697 }
2698 
2699 #if TASKQUEUE_STATS
2700 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
2701   st->print_raw_cr("GC Task Stats");
2702   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
2703   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
2704 }
2705 
2706 void G1CollectedHeap::print_taskqueue_stats() const {
2707   if (!log_is_enabled(Trace, gc, task, stats)) {
2708     return;
2709   }
2710   Log(gc, task, stats) log;
2711   ResourceMark rm;
2712   LogStream ls(log.trace());
2713   outputStream* st = &ls;
2714 
2715   print_taskqueue_stats_hdr(st);
2716 
2717   TaskQueueStats totals;
2718   const uint n = num_task_queues();
2719   for (uint i = 0; i < n; ++i) {
2720     st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
2721     totals += task_queue(i)->stats;
2722   }
2723   st->print_raw("tot "); totals.print(st); st->cr();
2724 
2725   DEBUG_ONLY(totals.verify());
2726 }
2727 
2728 void G1CollectedHeap::reset_taskqueue_stats() {
2729   const uint n = num_task_queues();
2730   for (uint i = 0; i < n; ++i) {
2731     task_queue(i)->stats.reset();
2732   }
2733 }
2734 #endif // TASKQUEUE_STATS
2735 
2736 void G1CollectedHeap::wait_for_root_region_scanning() {
2737   double scan_wait_start = os::elapsedTime();
2738   // We have to wait until the CM threads finish scanning the
2739   // root regions as it's the only way to ensure that all the
2740   // objects on them have been correctly scanned before we start
2741   // moving them during the GC.
2742   bool waited = _cm->root_regions()->wait_until_scan_finished();
2743   double wait_time_ms = 0.0;
2744   if (waited) {
2745     double scan_wait_end = os::elapsedTime();
2746     wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
2747   }
2748   g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
2749 }
2750 
2751 class G1PrintCollectionSetClosure : public HeapRegionClosure {
2752 private:
2753   G1HRPrinter* _hr_printer;
2754 public:
2755   G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { }
2756 
2757   virtual bool do_heap_region(HeapRegion* r) {
2758     _hr_printer->cset(r);
2759     return false;
2760   }
2761 };
2762 
2763 void G1CollectedHeap::start_new_collection_set() {
2764   collection_set()->start_incremental_building();
2765 
2766   clear_cset_fast_test();
2767 
2768   guarantee(_eden.length() == 0, "eden should have been cleared");
2769   g1_policy()->transfer_survivors_to_cset(survivor());
2770 }
2771 
2772 bool
2773 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
2774   assert_at_safepoint_on_vm_thread();
2775   guarantee(!is_gc_active(), "collection is not reentrant");
2776 
2777   if (GCLocker::check_active_before_gc()) {
2778     return false;
2779   }
2780 
2781   _gc_timer_stw->register_gc_start();
2782 
2783   GCIdMark gc_id_mark;
2784   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
2785 
2786   SvcGCMarker sgcm(SvcGCMarker::MINOR);
2787   ResourceMark rm;
2788 
2789   g1_policy()->note_gc_start();
2790 
2791   wait_for_root_region_scanning();
2792 
2793   print_heap_before_gc();
2794   print_heap_regions();
2795   trace_heap_before_gc(_gc_tracer_stw);
2796 
2797   _verifier->verify_region_sets_optional();
2798   _verifier->verify_dirty_young_regions();
2799 
2800   // We should not be doing initial mark unless the conc mark thread is running
2801   if (!_cm_thread->should_terminate()) {
2802     // This call will decide whether this pause is an initial-mark
2803     // pause. If it is, in_initial_mark_gc() will return true
2804     // for the duration of this pause.
2805     g1_policy()->decide_on_conc_mark_initiation();
2806   }
2807 
2808   // We do not allow initial-mark to be piggy-backed on a mixed GC.
2809   assert(!collector_state()->in_initial_mark_gc() ||
2810           collector_state()->in_young_only_phase(), "sanity");
2811 
2812   // We also do not allow mixed GCs during marking.
2813   assert(!collector_state()->mark_or_rebuild_in_progress() || collector_state()->in_young_only_phase(), "sanity");
2814 
2815   // Record whether this pause is an initial mark. When the current
2816   // thread has completed its logging output and it's safe to signal
2817   // the CM thread, the flag's value in the policy has been reset.
2818   bool should_start_conc_mark = collector_state()->in_initial_mark_gc();
2819 
2820   // Inner scope for scope based logging, timers, and stats collection
2821   {
2822     EvacuationInfo evacuation_info;
2823 
2824     if (collector_state()->in_initial_mark_gc()) {
2825       // We are about to start a marking cycle, so we increment the
2826       // full collection counter.
2827       increment_old_marking_cycles_started();
2828       _cm->gc_tracer_cm()->set_gc_cause(gc_cause());
2829     }
2830 
2831     _gc_tracer_stw->report_yc_type(collector_state()->yc_type());
2832 
2833     GCTraceCPUTime tcpu;
2834 
2835     G1HeapVerifier::G1VerifyType verify_type;
2836     FormatBuffer<> gc_string("Pause Young ");
2837     if (collector_state()->in_initial_mark_gc()) {
2838       gc_string.append("(Concurrent Start)");
2839       verify_type = G1HeapVerifier::G1VerifyConcurrentStart;
2840     } else if (collector_state()->in_young_only_phase()) {
2841       if (collector_state()->in_young_gc_before_mixed()) {
2842         gc_string.append("(Prepare Mixed)");
2843       } else {
2844         gc_string.append("(Normal)");
2845       }
2846       verify_type = G1HeapVerifier::G1VerifyYoungNormal;
2847     } else {
2848       gc_string.append("(Mixed)");
2849       verify_type = G1HeapVerifier::G1VerifyMixed;
2850     }
2851     GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true);
2852 
2853     uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
2854                                                                   workers()->active_workers(),
2855                                                                   Threads::number_of_non_daemon_threads());
2856     active_workers = workers()->update_active_workers(active_workers);
2857     log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers());
2858 
2859     TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
2860     TraceMemoryManagerStats tms(&_memory_manager, gc_cause(),
2861                                 collector_state()->yc_type() == Mixed /* allMemoryPoolsAffected */);
2862 
2863     G1HeapTransition heap_transition(this);
2864     size_t heap_used_bytes_before_gc = used();
2865 
2866     // Don't dynamically change the number of GC threads this early.  A value of
2867     // 0 is used to indicate serial work.  When parallel work is done,
2868     // it will be set.
2869 
2870     { // Call to jvmpi::post_class_unload_events must occur outside of active GC
2871       IsGCActiveMark x;
2872 
2873       gc_prologue(false);
2874 
2875       if (VerifyRememberedSets) {
2876         log_info(gc, verify)("[Verifying RemSets before GC]");
2877         VerifyRegionRemSetClosure v_cl;
2878         heap_region_iterate(&v_cl);
2879       }
2880 
2881       _verifier->verify_before_gc(verify_type);
2882 
2883       _verifier->check_bitmaps("GC Start");
2884 
2885 #if COMPILER2_OR_JVMCI
2886       DerivedPointerTable::clear();
2887 #endif
2888 
2889       // Please see comment in g1CollectedHeap.hpp and
2890       // G1CollectedHeap::ref_processing_init() to see how
2891       // reference processing currently works in G1.
2892 
2893       // Enable discovery in the STW reference processor
2894       _ref_processor_stw->enable_discovery();
2895 
2896       {
2897         // We want to temporarily turn off discovery by the
2898         // CM ref processor, if necessary, and turn it back on
2899         // on again later if we do. Using a scoped
2900         // NoRefDiscovery object will do this.
2901         NoRefDiscovery no_cm_discovery(_ref_processor_cm);
2902 
2903         // Forget the current alloc region (we might even choose it to be part
2904         // of the collection set!).
2905         _allocator->release_mutator_alloc_region();
2906 
2907         // This timing is only used by the ergonomics to handle our pause target.
2908         // It is unclear why this should not include the full pause. We will
2909         // investigate this in CR 7178365.
2910         //
2911         // Preserving the old comment here if that helps the investigation:
2912         //
2913         // The elapsed time induced by the start time below deliberately elides
2914         // the possible verification above.
2915         double sample_start_time_sec = os::elapsedTime();
2916 
2917         g1_policy()->record_collection_pause_start(sample_start_time_sec);
2918 
2919         if (collector_state()->in_initial_mark_gc()) {
2920           concurrent_mark()->pre_initial_mark();
2921         }
2922 
2923         g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor);
2924 
2925         evacuation_info.set_collectionset_regions(collection_set()->region_length());
2926 
2927         // Make sure the remembered sets are up to date. This needs to be
2928         // done before register_humongous_regions_with_cset(), because the
2929         // remembered sets are used there to choose eager reclaim candidates.
2930         // If the remembered sets are not up to date we might miss some
2931         // entries that need to be handled.
2932         g1_rem_set()->cleanupHRRS();
2933 
2934         register_humongous_regions_with_cset();
2935 
2936         assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table.");
2937 
2938         // We call this after finalize_cset() to
2939         // ensure that the CSet has been finalized.
2940         _cm->verify_no_cset_oops();
2941 
2942         if (_hr_printer.is_active()) {
2943           G1PrintCollectionSetClosure cl(&_hr_printer);
2944           _collection_set.iterate(&cl);
2945         }
2946 
2947         // Initialize the GC alloc regions.
2948         _allocator->init_gc_alloc_regions(evacuation_info);
2949 
2950         G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length());
2951         pre_evacuate_collection_set();
2952 
2953         // Actually do the work...
2954         evacuate_collection_set(&per_thread_states);
2955 
2956         post_evacuate_collection_set(evacuation_info, &per_thread_states);
2957 
2958         const size_t* surviving_young_words = per_thread_states.surviving_young_words();
2959         free_collection_set(&_collection_set, evacuation_info, surviving_young_words);
2960 
2961         eagerly_reclaim_humongous_regions();
2962 
2963         record_obj_copy_mem_stats();
2964         _survivor_evac_stats.adjust_desired_plab_sz();
2965         _old_evac_stats.adjust_desired_plab_sz();
2966 
2967         double start = os::elapsedTime();
2968         start_new_collection_set();
2969         g1_policy()->phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0);
2970 
2971         if (evacuation_failed()) {
2972           set_used(recalculate_used());
2973           if (_archive_allocator != NULL) {
2974             _archive_allocator->clear_used();
2975           }
2976           for (uint i = 0; i < ParallelGCThreads; i++) {
2977             if (_evacuation_failed_info_array[i].has_failed()) {
2978               _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
2979             }
2980           }
2981         } else {
2982           // The "used" of the the collection set have already been subtracted
2983           // when they were freed.  Add in the bytes evacuated.
2984           increase_used(g1_policy()->bytes_copied_during_gc());
2985         }
2986 
2987         if (collector_state()->in_initial_mark_gc()) {
2988           // We have to do this before we notify the CM threads that
2989           // they can start working to make sure that all the
2990           // appropriate initialization is done on the CM object.
2991           concurrent_mark()->post_initial_mark();
2992           // Note that we don't actually trigger the CM thread at
2993           // this point. We do that later when we're sure that
2994           // the current thread has completed its logging output.
2995         }
2996 
2997         allocate_dummy_regions();
2998 
2999         _allocator->init_mutator_alloc_region();
3000 
3001         {
3002           size_t expand_bytes = _heap_sizing_policy->expansion_amount();
3003           if (expand_bytes > 0) {
3004             size_t bytes_before = capacity();
3005             // No need for an ergo logging here,
3006             // expansion_amount() does this when it returns a value > 0.
3007             double expand_ms;
3008             if (!expand(expand_bytes, _workers, &expand_ms)) {
3009               // We failed to expand the heap. Cannot do anything about it.
3010             }
3011             g1_policy()->phase_times()->record_expand_heap_time(expand_ms);
3012           }
3013         }
3014 
3015         // We redo the verification but now wrt to the new CSet which
3016         // has just got initialized after the previous CSet was freed.
3017         _cm->verify_no_cset_oops();
3018 
3019         // This timing is only used by the ergonomics to handle our pause target.
3020         // It is unclear why this should not include the full pause. We will
3021         // investigate this in CR 7178365.
3022         double sample_end_time_sec = os::elapsedTime();
3023         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3024         size_t total_cards_scanned = g1_policy()->phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanRS, G1GCPhaseTimes::ScanRSScannedCards);
3025         g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc);
3026 
3027         evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before());
3028         evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc());
3029 
3030         if (VerifyRememberedSets) {
3031           log_info(gc, verify)("[Verifying RemSets after GC]");
3032           VerifyRegionRemSetClosure v_cl;
3033           heap_region_iterate(&v_cl);
3034         }
3035 
3036         _verifier->verify_after_gc(verify_type);
3037         _verifier->check_bitmaps("GC End");
3038 
3039         assert(!_ref_processor_stw->discovery_enabled(), "Postcondition");
3040         _ref_processor_stw->verify_no_references_recorded();
3041 
3042         // CM reference discovery will be re-enabled if necessary.
3043       }
3044 
3045 #ifdef TRACESPINNING
3046       ParallelTaskTerminator::print_termination_counts();
3047 #endif
3048 
3049       gc_epilogue(false);
3050     }
3051 
3052     // Print the remainder of the GC log output.
3053     if (evacuation_failed()) {
3054       log_info(gc)("To-space exhausted");
3055     }
3056 
3057     g1_policy()->print_phases();
3058     heap_transition.print();
3059 
3060     // It is not yet to safe to tell the concurrent mark to
3061     // start as we have some optional output below. We don't want the
3062     // output from the concurrent mark thread interfering with this
3063     // logging output either.
3064 
3065     _hrm.verify_optional();
3066     _verifier->verify_region_sets_optional();
3067 
3068     TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
3069     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3070 
3071     print_heap_after_gc();
3072     print_heap_regions();
3073     trace_heap_after_gc(_gc_tracer_stw);
3074 
3075     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3076     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3077     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3078     // before any GC notifications are raised.
3079     g1mm()->update_sizes();
3080 
3081     _gc_tracer_stw->report_evacuation_info(&evacuation_info);
3082     _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
3083     _gc_timer_stw->register_gc_end();
3084     _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
3085   }
3086   // It should now be safe to tell the concurrent mark thread to start
3087   // without its logging output interfering with the logging output
3088   // that came from the pause.
3089 
3090   if (should_start_conc_mark) {
3091     // CAUTION: after the doConcurrentMark() call below,
3092     // the concurrent marking thread(s) could be running
3093     // concurrently with us. Make sure that anything after
3094     // this point does not assume that we are the only GC thread
3095     // running. Note: of course, the actual marking work will
3096     // not start until the safepoint itself is released in
3097     // SuspendibleThreadSet::desynchronize().
3098     do_concurrent_mark();
3099   }
3100 
3101   return true;
3102 }
3103 
3104 void G1CollectedHeap::remove_self_forwarding_pointers() {
3105   G1ParRemoveSelfForwardPtrsTask rsfp_task;
3106   workers()->run_task(&rsfp_task);
3107 }
3108 
3109 void G1CollectedHeap::restore_after_evac_failure() {
3110   double remove_self_forwards_start = os::elapsedTime();
3111 
3112   remove_self_forwarding_pointers();
3113   SharedRestorePreservedMarksTaskExecutor task_executor(workers());
3114   _preserved_marks_set.restore(&task_executor);
3115 
3116   g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
3117 }
3118 
3119 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) {
3120   if (!_evacuation_failed) {
3121     _evacuation_failed = true;
3122   }
3123 
3124   _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size());
3125   _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m);
3126 }
3127 
3128 bool G1ParEvacuateFollowersClosure::offer_termination() {
3129   G1ParScanThreadState* const pss = par_scan_state();
3130   start_term_time();
3131   const bool res = terminator()->offer_termination();
3132   end_term_time();
3133   return res;
3134 }
3135 
3136 void G1ParEvacuateFollowersClosure::do_void() {
3137   G1ParScanThreadState* const pss = par_scan_state();
3138   pss->trim_queue();
3139   do {
3140     pss->steal_and_trim_queue(queues());
3141   } while (!offer_termination());
3142 }
3143 
3144 class G1ParTask : public AbstractGangTask {
3145 protected:
3146   G1CollectedHeap*         _g1h;
3147   G1ParScanThreadStateSet* _pss;
3148   RefToScanQueueSet*       _queues;
3149   G1RootProcessor*         _root_processor;
3150   ParallelTaskTerminator   _terminator;
3151   uint                     _n_workers;
3152 
3153 public:
3154   G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers)
3155     : AbstractGangTask("G1 collection"),
3156       _g1h(g1h),
3157       _pss(per_thread_states),
3158       _queues(task_queues),
3159       _root_processor(root_processor),
3160       _terminator(n_workers, _queues),
3161       _n_workers(n_workers)
3162   {}
3163 
3164   void work(uint worker_id) {
3165     if (worker_id >= _n_workers) return;  // no work needed this round
3166 
3167     double start_sec = os::elapsedTime();
3168     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec);
3169 
3170     {
3171       ResourceMark rm;
3172       HandleMark   hm;
3173 
3174       ReferenceProcessor*             rp = _g1h->ref_processor_stw();
3175 
3176       G1ParScanThreadState*           pss = _pss->state_for_worker(worker_id);
3177       pss->set_ref_discoverer(rp);
3178 
3179       double start_strong_roots_sec = os::elapsedTime();
3180 
3181       _root_processor->evacuate_roots(pss, worker_id);
3182 
3183       // We pass a weak code blobs closure to the remembered set scanning because we want to avoid
3184       // treating the nmethods visited to act as roots for concurrent marking.
3185       // We only want to make sure that the oops in the nmethods are adjusted with regard to the
3186       // objects copied by the current evacuation.
3187       _g1h->g1_rem_set()->oops_into_collection_set_do(pss, worker_id);
3188 
3189       double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec;
3190 
3191       double term_sec = 0.0;
3192       size_t evac_term_attempts = 0;
3193       {
3194         double start = os::elapsedTime();
3195         G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator);
3196         evac.do_void();
3197 
3198         evac_term_attempts = evac.term_attempts();
3199         term_sec = evac.term_time();
3200         double elapsed_sec = os::elapsedTime() - start;
3201 
3202         G1GCPhaseTimes* p = _g1h->g1_policy()->phase_times();
3203         p->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec);
3204         p->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec);
3205         p->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts);
3206       }
3207 
3208       assert(pss->queue_is_empty(), "should be empty");
3209 
3210       if (log_is_enabled(Debug, gc, task, stats)) {
3211         MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3212         size_t lab_waste;
3213         size_t lab_undo_waste;
3214         pss->waste(lab_waste, lab_undo_waste);
3215         _g1h->print_termination_stats(worker_id,
3216                                       (os::elapsedTime() - start_sec) * 1000.0,   /* elapsed time */
3217                                       strong_roots_sec * 1000.0,                  /* strong roots time */
3218                                       term_sec * 1000.0,                          /* evac term time */
3219                                       evac_term_attempts,                         /* evac term attempts */
3220                                       lab_waste,                                  /* alloc buffer waste */
3221                                       lab_undo_waste                              /* undo waste */
3222                                       );
3223       }
3224 
3225       // Close the inner scope so that the ResourceMark and HandleMark
3226       // destructors are executed here and are included as part of the
3227       // "GC Worker Time".
3228     }
3229     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime());
3230   }
3231 };
3232 
3233 void G1CollectedHeap::print_termination_stats_hdr() {
3234   log_debug(gc, task, stats)("GC Termination Stats");
3235   log_debug(gc, task, stats)("     elapsed  --strong roots-- -------termination------- ------waste (KiB)------");
3236   log_debug(gc, task, stats)("thr     ms        ms      %%        ms      %%    attempts  total   alloc    undo");
3237   log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------");
3238 }
3239 
3240 void G1CollectedHeap::print_termination_stats(uint worker_id,
3241                                               double elapsed_ms,
3242                                               double strong_roots_ms,
3243                                               double term_ms,
3244                                               size_t term_attempts,
3245                                               size_t alloc_buffer_waste,
3246                                               size_t undo_waste) const {
3247   log_debug(gc, task, stats)
3248               ("%3d %9.2f %9.2f %6.2f "
3249                "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
3250                SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
3251                worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms,
3252                term_ms, term_ms * 100 / elapsed_ms, term_attempts,
3253                (alloc_buffer_waste + undo_waste) * HeapWordSize / K,
3254                alloc_buffer_waste * HeapWordSize / K,
3255                undo_waste * HeapWordSize / K);
3256 }
3257 
3258 class G1StringCleaningTask : public AbstractGangTask {
3259 private:
3260   BoolObjectClosure* _is_alive;
3261   G1StringDedupUnlinkOrOopsDoClosure _dedup_closure;
3262   OopStorage::ParState<false /* concurrent */, false /* const */> _par_state_string;
3263 
3264   int _initial_string_table_size;
3265 
3266   bool  _process_strings;
3267   int _strings_processed;
3268   int _strings_removed;
3269 
3270   bool _process_string_dedup;
3271 
3272 public:
3273   G1StringCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_string_dedup) :
3274     AbstractGangTask("String Unlinking"),
3275     _is_alive(is_alive),
3276     _dedup_closure(is_alive, NULL, false),
3277     _par_state_string(StringTable::weak_storage()),
3278     _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
3279     _process_string_dedup(process_string_dedup) {
3280 
3281     _initial_string_table_size = (int) StringTable::the_table()->table_size();
3282     if (process_strings) {
3283       StringTable::reset_dead_counter();
3284     }
3285   }
3286 
3287   ~G1StringCleaningTask() {
3288     log_info(gc, stringtable)(
3289         "Cleaned string table, "
3290         "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed",
3291         strings_processed(), strings_removed());
3292     if (_process_strings) {
3293       StringTable::finish_dead_counter();
3294     }
3295   }
3296 
3297   void work(uint worker_id) {
3298     int strings_processed = 0;
3299     int strings_removed = 0;
3300     if (_process_strings) {
3301       StringTable::possibly_parallel_unlink(&_par_state_string, _is_alive, &strings_processed, &strings_removed);
3302       Atomic::add(strings_processed, &_strings_processed);
3303       Atomic::add(strings_removed, &_strings_removed);
3304     }
3305     if (_process_string_dedup) {
3306       G1StringDedup::parallel_unlink(&_dedup_closure, worker_id);
3307     }
3308   }
3309 
3310   size_t strings_processed() const { return (size_t)_strings_processed; }
3311   size_t strings_removed()   const { return (size_t)_strings_removed; }
3312 };
3313 
3314 class G1CodeCacheUnloadingTask {
3315 private:
3316   static Monitor* _lock;
3317 
3318   BoolObjectClosure* const _is_alive;
3319   const bool               _unloading_occurred;
3320   const uint               _num_workers;
3321 
3322   // Variables used to claim nmethods.
3323   CompiledMethod* _first_nmethod;
3324   CompiledMethod* volatile _claimed_nmethod;
3325 
3326   // The list of nmethods that need to be processed by the second pass.
3327   CompiledMethod* volatile _postponed_list;
3328   volatile uint            _num_entered_barrier;
3329 
3330  public:
3331   G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
3332       _is_alive(is_alive),
3333       _unloading_occurred(unloading_occurred),
3334       _num_workers(num_workers),
3335       _first_nmethod(NULL),
3336       _claimed_nmethod(NULL),
3337       _postponed_list(NULL),
3338       _num_entered_barrier(0)
3339   {
3340     CompiledMethod::increase_unloading_clock();
3341     // Get first alive nmethod
3342     CompiledMethodIterator iter = CompiledMethodIterator();
3343     if(iter.next_alive()) {
3344       _first_nmethod = iter.method();
3345     }
3346     _claimed_nmethod = _first_nmethod;
3347   }
3348 
3349   ~G1CodeCacheUnloadingTask() {
3350     CodeCache::verify_clean_inline_caches();
3351 
3352     CodeCache::set_needs_cache_clean(false);
3353     guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
3354 
3355     CodeCache::verify_icholder_relocations();
3356   }
3357 
3358  private:
3359   void add_to_postponed_list(CompiledMethod* nm) {
3360       CompiledMethod* old;
3361       do {
3362         old = _postponed_list;
3363         nm->set_unloading_next(old);
3364       } while (Atomic::cmpxchg(nm, &_postponed_list, old) != old);
3365   }
3366 
3367   void clean_nmethod(CompiledMethod* nm) {
3368     bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
3369 
3370     if (postponed) {
3371       // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
3372       add_to_postponed_list(nm);
3373     }
3374 
3375     // Mark that this nmethod has been cleaned/unloaded.
3376     // After this call, it will be safe to ask if this nmethod was unloaded or not.
3377     nm->set_unloading_clock(CompiledMethod::global_unloading_clock());
3378   }
3379 
3380   void clean_nmethod_postponed(CompiledMethod* nm) {
3381     nm->do_unloading_parallel_postponed();
3382   }
3383 
3384   static const int MaxClaimNmethods = 16;
3385 
3386   void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) {
3387     CompiledMethod* first;
3388     CompiledMethodIterator last;
3389 
3390     do {
3391       *num_claimed_nmethods = 0;
3392 
3393       first = _claimed_nmethod;
3394       last = CompiledMethodIterator(first);
3395 
3396       if (first != NULL) {
3397 
3398         for (int i = 0; i < MaxClaimNmethods; i++) {
3399           if (!last.next_alive()) {
3400             break;
3401           }
3402           claimed_nmethods[i] = last.method();
3403           (*num_claimed_nmethods)++;
3404         }
3405       }
3406 
3407     } while (Atomic::cmpxchg(last.method(), &_claimed_nmethod, first) != first);
3408   }
3409 
3410   CompiledMethod* claim_postponed_nmethod() {
3411     CompiledMethod* claim;
3412     CompiledMethod* next;
3413 
3414     do {
3415       claim = _postponed_list;
3416       if (claim == NULL) {
3417         return NULL;
3418       }
3419 
3420       next = claim->unloading_next();
3421 
3422     } while (Atomic::cmpxchg(next, &_postponed_list, claim) != claim);
3423 
3424     return claim;
3425   }
3426 
3427  public:
3428   // Mark that we're done with the first pass of nmethod cleaning.
3429   void barrier_mark(uint worker_id) {
3430     MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3431     _num_entered_barrier++;
3432     if (_num_entered_barrier == _num_workers) {
3433       ml.notify_all();
3434     }
3435   }
3436 
3437   // See if we have to wait for the other workers to
3438   // finish their first-pass nmethod cleaning work.
3439   void barrier_wait(uint worker_id) {
3440     if (_num_entered_barrier < _num_workers) {
3441       MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3442       while (_num_entered_barrier < _num_workers) {
3443           ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
3444       }
3445     }
3446   }
3447 
3448   // Cleaning and unloading of nmethods. Some work has to be postponed
3449   // to the second pass, when we know which nmethods survive.
3450   void work_first_pass(uint worker_id) {
3451     // The first nmethods is claimed by the first worker.
3452     if (worker_id == 0 && _first_nmethod != NULL) {
3453       clean_nmethod(_first_nmethod);
3454       _first_nmethod = NULL;
3455     }
3456 
3457     int num_claimed_nmethods;
3458     CompiledMethod* claimed_nmethods[MaxClaimNmethods];
3459 
3460     while (true) {
3461       claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
3462 
3463       if (num_claimed_nmethods == 0) {
3464         break;
3465       }
3466 
3467       for (int i = 0; i < num_claimed_nmethods; i++) {
3468         clean_nmethod(claimed_nmethods[i]);
3469       }
3470     }
3471   }
3472 
3473   void work_second_pass(uint worker_id) {
3474     CompiledMethod* nm;
3475     // Take care of postponed nmethods.
3476     while ((nm = claim_postponed_nmethod()) != NULL) {
3477       clean_nmethod_postponed(nm);
3478     }
3479   }
3480 };
3481 
3482 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never);
3483 
3484 class G1KlassCleaningTask : public StackObj {
3485   volatile int                            _clean_klass_tree_claimed;
3486   ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
3487 
3488  public:
3489   G1KlassCleaningTask() :
3490       _clean_klass_tree_claimed(0),
3491       _klass_iterator() {
3492   }
3493 
3494  private:
3495   bool claim_clean_klass_tree_task() {
3496     if (_clean_klass_tree_claimed) {
3497       return false;
3498     }
3499 
3500     return Atomic::cmpxchg(1, &_clean_klass_tree_claimed, 0) == 0;
3501   }
3502 
3503   InstanceKlass* claim_next_klass() {
3504     Klass* klass;
3505     do {
3506       klass =_klass_iterator.next_klass();
3507     } while (klass != NULL && !klass->is_instance_klass());
3508 
3509     // this can be null so don't call InstanceKlass::cast
3510     return static_cast<InstanceKlass*>(klass);
3511   }
3512 
3513 public:
3514 
3515   void clean_klass(InstanceKlass* ik) {
3516     ik->clean_weak_instanceklass_links();
3517   }
3518 
3519   void work() {
3520     ResourceMark rm;
3521 
3522     // One worker will clean the subklass/sibling klass tree.
3523     if (claim_clean_klass_tree_task()) {
3524       Klass::clean_subklass_tree();
3525     }
3526 
3527     // All workers will help cleaning the classes,
3528     InstanceKlass* klass;
3529     while ((klass = claim_next_klass()) != NULL) {
3530       clean_klass(klass);
3531     }
3532   }
3533 };
3534 
3535 class G1ResolvedMethodCleaningTask : public StackObj {
3536   volatile int       _resolved_method_task_claimed;
3537 public:
3538   G1ResolvedMethodCleaningTask() :
3539       _resolved_method_task_claimed(0) {}
3540 
3541   bool claim_resolved_method_task() {
3542     if (_resolved_method_task_claimed) {
3543       return false;
3544     }
3545     return Atomic::cmpxchg(1, &_resolved_method_task_claimed, 0) == 0;
3546   }
3547 
3548   // These aren't big, one thread can do it all.
3549   void work() {
3550     if (claim_resolved_method_task()) {
3551       ResolvedMethodTable::unlink();
3552     }
3553   }
3554 };
3555 
3556 
3557 // To minimize the remark pause times, the tasks below are done in parallel.
3558 class G1ParallelCleaningTask : public AbstractGangTask {
3559 private:
3560   bool                          _unloading_occurred;
3561   G1StringCleaningTask          _string_task;
3562   G1CodeCacheUnloadingTask      _code_cache_task;
3563   G1KlassCleaningTask           _klass_cleaning_task;
3564   G1ResolvedMethodCleaningTask  _resolved_method_cleaning_task;
3565 
3566 public:
3567   // The constructor is run in the VMThread.
3568   G1ParallelCleaningTask(BoolObjectClosure* is_alive, uint num_workers, bool unloading_occurred) :
3569       AbstractGangTask("Parallel Cleaning"),
3570       _unloading_occurred(unloading_occurred),
3571       _string_task(is_alive, true, G1StringDedup::is_enabled()),
3572       _code_cache_task(num_workers, is_alive, unloading_occurred),
3573       _klass_cleaning_task(),
3574       _resolved_method_cleaning_task() {
3575   }
3576 
3577   // The parallel work done by all worker threads.
3578   void work(uint worker_id) {
3579     // Do first pass of code cache cleaning.
3580     _code_cache_task.work_first_pass(worker_id);
3581 
3582     // Let the threads mark that the first pass is done.
3583     _code_cache_task.barrier_mark(worker_id);
3584 
3585     // Clean the Strings.
3586     _string_task.work(worker_id);
3587 
3588     // Clean unreferenced things in the ResolvedMethodTable
3589     _resolved_method_cleaning_task.work();
3590 
3591     // Wait for all workers to finish the first code cache cleaning pass.
3592     _code_cache_task.barrier_wait(worker_id);
3593 
3594     // Do the second code cache cleaning work, which realize on
3595     // the liveness information gathered during the first pass.
3596     _code_cache_task.work_second_pass(worker_id);
3597 
3598     // Clean all klasses that were not unloaded.
3599     // The weak metadata in klass doesn't need to be
3600     // processed if there was no unloading.
3601     if (_unloading_occurred) {
3602       _klass_cleaning_task.work();
3603     }
3604   }
3605 };
3606 
3607 
3608 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive,
3609                                         bool class_unloading_occurred) {
3610   uint n_workers = workers()->active_workers();
3611 
3612   G1ParallelCleaningTask g1_unlink_task(is_alive, n_workers, class_unloading_occurred);
3613   workers()->run_task(&g1_unlink_task);
3614 }
3615 
3616 void G1CollectedHeap::partial_cleaning(BoolObjectClosure* is_alive,
3617                                        bool process_strings,
3618                                        bool process_string_dedup) {
3619   if (!process_strings && !process_string_dedup) {
3620     // Nothing to clean.
3621     return;
3622   }
3623 
3624   G1StringCleaningTask g1_unlink_task(is_alive, process_strings, process_string_dedup);
3625   workers()->run_task(&g1_unlink_task);
3626 }
3627 
3628 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
3629  private:
3630   DirtyCardQueueSet* _queue;
3631   G1CollectedHeap* _g1h;
3632  public:
3633   G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"),
3634     _queue(queue), _g1h(g1h) { }
3635 
3636   virtual void work(uint worker_id) {
3637     G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times();
3638     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id);
3639 
3640     RedirtyLoggedCardTableEntryClosure cl(_g1h);
3641     _queue->par_apply_closure_to_all_completed_buffers(&cl);
3642 
3643     phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied());
3644   }
3645 };
3646 
3647 void G1CollectedHeap::redirty_logged_cards() {
3648   double redirty_logged_cards_start = os::elapsedTime();
3649 
3650   G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this);
3651   dirty_card_queue_set().reset_for_par_iteration();
3652   workers()->run_task(&redirty_task);
3653 
3654   DirtyCardQueueSet& dcq = G1BarrierSet::dirty_card_queue_set();
3655   dcq.merge_bufferlists(&dirty_card_queue_set());
3656   assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
3657 
3658   g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
3659 }
3660 
3661 // Weak Reference Processing support
3662 
3663 bool G1STWIsAliveClosure::do_object_b(oop p) {
3664   // An object is reachable if it is outside the collection set,
3665   // or is inside and copied.
3666   return !_g1h->is_in_cset(p) || p->is_forwarded();
3667 }
3668 
3669 bool G1STWSubjectToDiscoveryClosure::do_object_b(oop obj) {
3670   assert(obj != NULL, "must not be NULL");
3671   assert(_g1h->is_in_reserved(obj), "Trying to discover obj " PTR_FORMAT " not in heap", p2i(obj));
3672   // The areas the CM and STW ref processor manage must be disjoint. The is_in_cset() below
3673   // may falsely indicate that this is not the case here: however the collection set only
3674   // contains old regions when concurrent mark is not running.
3675   return _g1h->is_in_cset(obj) || _g1h->heap_region_containing(obj)->is_survivor();
3676 }
3677 
3678 // Non Copying Keep Alive closure
3679 class G1KeepAliveClosure: public OopClosure {
3680   G1CollectedHeap*_g1h;
3681 public:
3682   G1KeepAliveClosure(G1CollectedHeap* g1h) :_g1h(g1h) {}
3683   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
3684   void do_oop(oop* p) {
3685     oop obj = *p;
3686     assert(obj != NULL, "the caller should have filtered out NULL values");
3687 
3688     const InCSetState cset_state =_g1h->in_cset_state(obj);
3689     if (!cset_state.is_in_cset_or_humongous()) {
3690       return;
3691     }
3692     if (cset_state.is_in_cset()) {
3693       assert( obj->is_forwarded(), "invariant" );
3694       *p = obj->forwardee();
3695     } else {
3696       assert(!obj->is_forwarded(), "invariant" );
3697       assert(cset_state.is_humongous(),
3698              "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value());
3699      _g1h->set_humongous_is_live(obj);
3700     }
3701   }
3702 };
3703 
3704 // Copying Keep Alive closure - can be called from both
3705 // serial and parallel code as long as different worker
3706 // threads utilize different G1ParScanThreadState instances
3707 // and different queues.
3708 
3709 class G1CopyingKeepAliveClosure: public OopClosure {
3710   G1CollectedHeap*         _g1h;
3711   G1ParScanThreadState*    _par_scan_state;
3712 
3713 public:
3714   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
3715                             G1ParScanThreadState* pss):
3716     _g1h(g1h),
3717     _par_scan_state(pss)
3718   {}
3719 
3720   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
3721   virtual void do_oop(      oop* p) { do_oop_work(p); }
3722 
3723   template <class T> void do_oop_work(T* p) {
3724     oop obj = RawAccess<>::oop_load(p);
3725 
3726     if (_g1h->is_in_cset_or_humongous(obj)) {
3727       // If the referent object has been forwarded (either copied
3728       // to a new location or to itself in the event of an
3729       // evacuation failure) then we need to update the reference
3730       // field and, if both reference and referent are in the G1
3731       // heap, update the RSet for the referent.
3732       //
3733       // If the referent has not been forwarded then we have to keep
3734       // it alive by policy. Therefore we have copy the referent.
3735       //
3736       // When the queue is drained (after each phase of reference processing)
3737       // the object and it's followers will be copied, the reference field set
3738       // to point to the new location, and the RSet updated.
3739       _par_scan_state->push_on_queue(p);
3740     }
3741   }
3742 };
3743 
3744 // Serial drain queue closure. Called as the 'complete_gc'
3745 // closure for each discovered list in some of the
3746 // reference processing phases.
3747 
3748 class G1STWDrainQueueClosure: public VoidClosure {
3749 protected:
3750   G1CollectedHeap* _g1h;
3751   G1ParScanThreadState* _par_scan_state;
3752 
3753   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
3754 
3755 public:
3756   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
3757     _g1h(g1h),
3758     _par_scan_state(pss)
3759   { }
3760 
3761   void do_void() {
3762     G1ParScanThreadState* const pss = par_scan_state();
3763     pss->trim_queue();
3764   }
3765 };
3766 
3767 // Parallel Reference Processing closures
3768 
3769 // Implementation of AbstractRefProcTaskExecutor for parallel reference
3770 // processing during G1 evacuation pauses.
3771 
3772 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
3773 private:
3774   G1CollectedHeap*          _g1h;
3775   G1ParScanThreadStateSet*  _pss;
3776   RefToScanQueueSet*        _queues;
3777   WorkGang*                 _workers;
3778 
3779 public:
3780   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
3781                            G1ParScanThreadStateSet* per_thread_states,
3782                            WorkGang* workers,
3783                            RefToScanQueueSet *task_queues) :
3784     _g1h(g1h),
3785     _pss(per_thread_states),
3786     _queues(task_queues),
3787     _workers(workers)
3788   {
3789     g1h->ref_processor_stw()->set_active_mt_degree(workers->active_workers());
3790   }
3791 
3792   // Executes the given task using concurrent marking worker threads.
3793   virtual void execute(ProcessTask& task, uint ergo_workers);
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_discoverer(NULL);
3829 
3830     // Keep alive closure.
3831     G1CopyingKeepAliveClosure keep_alive(_g1h, 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, uint ergo_workers) {
3850   assert(_workers != NULL, "Need parallel worker threads.");
3851 
3852   assert(_workers->active_workers() >= ergo_workers,
3853          "Ergonomically chosen workers (%u) should be less than or equal to active workers (%u)",
3854          ergo_workers, _workers->active_workers());
3855   ParallelTaskTerminator terminator(ergo_workers, _queues);
3856   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator);
3857 
3858   _workers->run_task(&proc_task_proxy, ergo_workers);
3859 }
3860 
3861 // End of weak reference support closures
3862 
3863 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
3864   double ref_proc_start = os::elapsedTime();
3865 
3866   ReferenceProcessor* rp = _ref_processor_stw;
3867   assert(rp->discovery_enabled(), "should have been enabled");
3868 
3869   // Closure to test whether a referent is alive.
3870   G1STWIsAliveClosure is_alive(this);
3871 
3872   // Even when parallel reference processing is enabled, the processing
3873   // of JNI refs is serial and performed serially by the current thread
3874   // rather than by a worker. The following PSS will be used for processing
3875   // JNI refs.
3876 
3877   // Use only a single queue for this PSS.
3878   G1ParScanThreadState*          pss = per_thread_states->state_for_worker(0);
3879   pss->set_ref_discoverer(NULL);
3880   assert(pss->queue_is_empty(), "pre-condition");
3881 
3882   // Keep alive closure.
3883   G1CopyingKeepAliveClosure keep_alive(this, pss);
3884 
3885   // Serial Complete GC closure
3886   G1STWDrainQueueClosure drain_queue(this, pss);
3887 
3888   // Setup the soft refs policy...
3889   rp->setup_policy(false);
3890 
3891   ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times();
3892 
3893   ReferenceProcessorStats stats;
3894   if (!rp->processing_is_mt()) {
3895     // Serial reference processing...
3896     stats = rp->process_discovered_references(&is_alive,
3897                                               &keep_alive,
3898                                               &drain_queue,
3899                                               NULL,
3900                                               pt);
3901   } else {
3902     uint no_of_gc_workers = workers()->active_workers();
3903 
3904     // Parallel reference processing
3905     assert(no_of_gc_workers <= rp->max_num_queues(),
3906            "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
3907            no_of_gc_workers,  rp->max_num_queues());
3908 
3909     G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues);
3910     stats = rp->process_discovered_references(&is_alive,
3911                                               &keep_alive,
3912                                               &drain_queue,
3913                                               &par_task_executor,
3914                                               pt);
3915   }
3916 
3917   _gc_tracer_stw->report_gc_reference_stats(stats);
3918 
3919   // We have completed copying any necessary live referent objects.
3920   assert(pss->queue_is_empty(), "both queue and overflow should be empty");
3921 
3922   make_pending_list_reachable();
3923 
3924   rp->verify_no_references_recorded();
3925 
3926   double ref_proc_time = os::elapsedTime() - ref_proc_start;
3927   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
3928 }
3929 
3930 void G1CollectedHeap::make_pending_list_reachable() {
3931   if (collector_state()->in_initial_mark_gc()) {
3932     oop pll_head = Universe::reference_pending_list();
3933     if (pll_head != NULL) {
3934       // Any valid worker id is fine here as we are in the VM thread and single-threaded.
3935       _cm->mark_in_next_bitmap(0 /* worker_id */, pll_head);
3936     }
3937   }
3938 }
3939 
3940 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) {
3941   double merge_pss_time_start = os::elapsedTime();
3942   per_thread_states->flush();
3943   g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0);
3944 }
3945 
3946 void G1CollectedHeap::pre_evacuate_collection_set() {
3947   _expand_heap_after_alloc_failure = true;
3948   _evacuation_failed = false;
3949 
3950   // Disable the hot card cache.
3951   _hot_card_cache->reset_hot_cache_claimed_index();
3952   _hot_card_cache->set_use_cache(false);
3953 
3954   g1_rem_set()->prepare_for_oops_into_collection_set_do();
3955   _preserved_marks_set.assert_empty();
3956 
3957   G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
3958 
3959   // InitialMark needs claim bits to keep track of the marked-through CLDs.
3960   if (collector_state()->in_initial_mark_gc()) {
3961     double start_clear_claimed_marks = os::elapsedTime();
3962 
3963     ClassLoaderDataGraph::clear_claimed_marks();
3964 
3965     double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0;
3966     phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms);
3967   }
3968 }
3969 
3970 void G1CollectedHeap::evacuate_collection_set(G1ParScanThreadStateSet* per_thread_states) {
3971   // Should G1EvacuationFailureALot be in effect for this GC?
3972   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
3973 
3974   assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
3975 
3976   G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
3977 
3978   double start_par_time_sec = os::elapsedTime();
3979   double end_par_time_sec;
3980 
3981   {
3982     const uint n_workers = workers()->active_workers();
3983     G1RootProcessor root_processor(this, n_workers);
3984     G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers);
3985 
3986     print_termination_stats_hdr();
3987 
3988     workers()->run_task(&g1_par_task);
3989     end_par_time_sec = os::elapsedTime();
3990 
3991     // Closing the inner scope will execute the destructor
3992     // for the G1RootProcessor object. We record the current
3993     // elapsed time before closing the scope so that time
3994     // taken for the destructor is NOT included in the
3995     // reported parallel time.
3996   }
3997 
3998   double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
3999   phase_times->record_par_time(par_time_ms);
4000 
4001   double code_root_fixup_time_ms =
4002         (os::elapsedTime() - end_par_time_sec) * 1000.0;
4003   phase_times->record_code_root_fixup_time(code_root_fixup_time_ms);
4004 }
4005 
4006 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4007   // Also cleans the card table from temporary duplicate detection information used
4008   // during UpdateRS/ScanRS.
4009   g1_rem_set()->cleanup_after_oops_into_collection_set_do();
4010 
4011   // Process any discovered reference objects - we have
4012   // to do this _before_ we retire the GC alloc regions
4013   // as we may have to copy some 'reachable' referent
4014   // objects (and their reachable sub-graphs) that were
4015   // not copied during the pause.
4016   process_discovered_references(per_thread_states);
4017 
4018   // FIXME
4019   // CM's reference processing also cleans up the string table.
4020   // Should we do that here also? We could, but it is a serial operation
4021   // and could significantly increase the pause time.
4022 
4023   G1STWIsAliveClosure is_alive(this);
4024   G1KeepAliveClosure keep_alive(this);
4025 
4026   {
4027     double start = os::elapsedTime();
4028 
4029     WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
4030 
4031     double time_ms = (os::elapsedTime() - start) * 1000.0;
4032     g1_policy()->phase_times()->record_weak_ref_proc_time(time_ms);
4033   }
4034 
4035   if (G1StringDedup::is_enabled()) {
4036     double fixup_start = os::elapsedTime();
4037 
4038     G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times());
4039 
4040     double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
4041     g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms);
4042   }
4043 
4044   if (evacuation_failed()) {
4045     restore_after_evac_failure();
4046 
4047     // Reset the G1EvacuationFailureALot counters and flags
4048     // Note: the values are reset only when an actual
4049     // evacuation failure occurs.
4050     NOT_PRODUCT(reset_evacuation_should_fail();)
4051   }
4052 
4053   _preserved_marks_set.assert_empty();
4054 
4055   _allocator->release_gc_alloc_regions(evacuation_info);
4056 
4057   merge_per_thread_state_info(per_thread_states);
4058 
4059   // Reset and re-enable the hot card cache.
4060   // Note the counts for the cards in the regions in the
4061   // collection set are reset when the collection set is freed.
4062   _hot_card_cache->reset_hot_cache();
4063   _hot_card_cache->set_use_cache(true);
4064 
4065   purge_code_root_memory();
4066 
4067   redirty_logged_cards();
4068 #if COMPILER2_OR_JVMCI
4069   double start = os::elapsedTime();
4070   DerivedPointerTable::update_pointers();
4071   g1_policy()->phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0);
4072 #endif
4073   g1_policy()->print_age_table();
4074 }
4075 
4076 void G1CollectedHeap::record_obj_copy_mem_stats() {
4077   g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
4078 
4079   _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
4080                                                create_g1_evac_summary(&_old_evac_stats));
4081 }
4082 
4083 void G1CollectedHeap::free_region(HeapRegion* hr,
4084                                   FreeRegionList* free_list,
4085                                   bool skip_remset,
4086                                   bool skip_hot_card_cache,
4087                                   bool locked) {
4088   assert(!hr->is_free(), "the region should not be free");
4089   assert(!hr->is_empty(), "the region should not be empty");
4090   assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
4091   assert(free_list != NULL, "pre-condition");
4092 
4093   if (G1VerifyBitmaps) {
4094     MemRegion mr(hr->bottom(), hr->end());
4095     concurrent_mark()->clear_range_in_prev_bitmap(mr);
4096   }
4097 
4098   // Clear the card counts for this region.
4099   // Note: we only need to do this if the region is not young
4100   // (since we don't refine cards in young regions).
4101   if (!skip_hot_card_cache && !hr->is_young()) {
4102     _hot_card_cache->reset_card_counts(hr);
4103   }
4104   hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */);
4105   _g1_policy->remset_tracker()->update_at_free(hr);
4106   free_list->add_ordered(hr);
4107 }
4108 
4109 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
4110                                             FreeRegionList* free_list) {
4111   assert(hr->is_humongous(), "this is only for humongous regions");
4112   assert(free_list != NULL, "pre-condition");
4113   hr->clear_humongous();
4114   free_region(hr, free_list, false /* skip_remset */, false /* skip_hcc */, true /* locked */);
4115 }
4116 
4117 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed,
4118                                            const uint humongous_regions_removed) {
4119   if (old_regions_removed > 0 || humongous_regions_removed > 0) {
4120     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4121     _old_set.bulk_remove(old_regions_removed);
4122     _humongous_set.bulk_remove(humongous_regions_removed);
4123   }
4124 
4125 }
4126 
4127 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
4128   assert(list != NULL, "list can't be null");
4129   if (!list->is_empty()) {
4130     MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4131     _hrm.insert_list_into_free_list(list);
4132   }
4133 }
4134 
4135 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
4136   decrease_used(bytes);
4137 }
4138 
4139 class G1FreeCollectionSetTask : public AbstractGangTask {
4140 private:
4141 
4142   // Closure applied to all regions in the collection set to do work that needs to
4143   // be done serially in a single thread.
4144   class G1SerialFreeCollectionSetClosure : public HeapRegionClosure {
4145   private:
4146     EvacuationInfo* _evacuation_info;
4147     const size_t* _surviving_young_words;
4148 
4149     // Bytes used in successfully evacuated regions before the evacuation.
4150     size_t _before_used_bytes;
4151     // Bytes used in unsucessfully evacuated regions before the evacuation
4152     size_t _after_used_bytes;
4153 
4154     size_t _bytes_allocated_in_old_since_last_gc;
4155 
4156     size_t _failure_used_words;
4157     size_t _failure_waste_words;
4158 
4159     FreeRegionList _local_free_list;
4160   public:
4161     G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4162       HeapRegionClosure(),
4163       _evacuation_info(evacuation_info),
4164       _surviving_young_words(surviving_young_words),
4165       _before_used_bytes(0),
4166       _after_used_bytes(0),
4167       _bytes_allocated_in_old_since_last_gc(0),
4168       _failure_used_words(0),
4169       _failure_waste_words(0),
4170       _local_free_list("Local Region List for CSet Freeing") {
4171     }
4172 
4173     virtual bool do_heap_region(HeapRegion* r) {
4174       G1CollectedHeap* g1h = G1CollectedHeap::heap();
4175 
4176       assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index());
4177       g1h->clear_in_cset(r);
4178 
4179       if (r->is_young()) {
4180         assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(),
4181                "Young index %d is wrong for region %u of type %s with %u young regions",
4182                r->young_index_in_cset(),
4183                r->hrm_index(),
4184                r->get_type_str(),
4185                g1h->collection_set()->young_region_length());
4186         size_t words_survived = _surviving_young_words[r->young_index_in_cset()];
4187         r->record_surv_words_in_group(words_survived);
4188       }
4189 
4190       if (!r->evacuation_failed()) {
4191         assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index());
4192         _before_used_bytes += r->used();
4193         g1h->free_region(r,
4194                          &_local_free_list,
4195                          true, /* skip_remset */
4196                          true, /* skip_hot_card_cache */
4197                          true  /* locked */);
4198       } else {
4199         r->uninstall_surv_rate_group();
4200         r->set_young_index_in_cset(-1);
4201         r->set_evacuation_failed(false);
4202         // When moving a young gen region to old gen, we "allocate" that whole region
4203         // there. This is in addition to any already evacuated objects. Notify the
4204         // policy about that.
4205         // Old gen regions do not cause an additional allocation: both the objects
4206         // still in the region and the ones already moved are accounted for elsewhere.
4207         if (r->is_young()) {
4208           _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes;
4209         }
4210         // The region is now considered to be old.
4211         r->set_old();
4212         // Do some allocation statistics accounting. Regions that failed evacuation
4213         // are always made old, so there is no need to update anything in the young
4214         // gen statistics, but we need to update old gen statistics.
4215         size_t used_words = r->marked_bytes() / HeapWordSize;
4216 
4217         _failure_used_words += used_words;
4218         _failure_waste_words += HeapRegion::GrainWords - used_words;
4219 
4220         g1h->old_set_add(r);
4221         _after_used_bytes += r->used();
4222       }
4223       return false;
4224     }
4225 
4226     void complete_work() {
4227       G1CollectedHeap* g1h = G1CollectedHeap::heap();
4228 
4229       _evacuation_info->set_regions_freed(_local_free_list.length());
4230       _evacuation_info->increment_collectionset_used_after(_after_used_bytes);
4231 
4232       g1h->prepend_to_freelist(&_local_free_list);
4233       g1h->decrement_summary_bytes(_before_used_bytes);
4234 
4235       G1Policy* policy = g1h->g1_policy();
4236       policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc);
4237 
4238       g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words);
4239     }
4240   };
4241 
4242   G1CollectionSet* _collection_set;
4243   G1SerialFreeCollectionSetClosure _cl;
4244   const size_t* _surviving_young_words;
4245 
4246   size_t _rs_lengths;
4247 
4248   volatile jint _serial_work_claim;
4249 
4250   struct WorkItem {
4251     uint region_idx;
4252     bool is_young;
4253     bool evacuation_failed;
4254 
4255     WorkItem(HeapRegion* r) {
4256       region_idx = r->hrm_index();
4257       is_young = r->is_young();
4258       evacuation_failed = r->evacuation_failed();
4259     }
4260   };
4261 
4262   volatile size_t _parallel_work_claim;
4263   size_t _num_work_items;
4264   WorkItem* _work_items;
4265 
4266   void do_serial_work() {
4267     // Need to grab the lock to be allowed to modify the old region list.
4268     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4269     _collection_set->iterate(&_cl);
4270   }
4271 
4272   void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) {
4273     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4274 
4275     HeapRegion* r = g1h->region_at(region_idx);
4276     assert(!g1h->is_on_master_free_list(r), "sanity");
4277 
4278     Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths);
4279 
4280     if (!is_young) {
4281       g1h->_hot_card_cache->reset_card_counts(r);
4282     }
4283 
4284     if (!evacuation_failed) {
4285       r->rem_set()->clear_locked();
4286     }
4287   }
4288 
4289   class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure {
4290   private:
4291     size_t _cur_idx;
4292     WorkItem* _work_items;
4293   public:
4294     G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { }
4295 
4296     virtual bool do_heap_region(HeapRegion* r) {
4297       _work_items[_cur_idx++] = WorkItem(r);
4298       return false;
4299     }
4300   };
4301 
4302   void prepare_work() {
4303     G1PrepareFreeCollectionSetClosure cl(_work_items);
4304     _collection_set->iterate(&cl);
4305   }
4306 
4307   void complete_work() {
4308     _cl.complete_work();
4309 
4310     G1Policy* policy = G1CollectedHeap::heap()->g1_policy();
4311     policy->record_max_rs_lengths(_rs_lengths);
4312     policy->cset_regions_freed();
4313   }
4314 public:
4315   G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4316     AbstractGangTask("G1 Free Collection Set"),
4317     _collection_set(collection_set),
4318     _cl(evacuation_info, surviving_young_words),
4319     _surviving_young_words(surviving_young_words),
4320     _rs_lengths(0),
4321     _serial_work_claim(0),
4322     _parallel_work_claim(0),
4323     _num_work_items(collection_set->region_length()),
4324     _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) {
4325     prepare_work();
4326   }
4327 
4328   ~G1FreeCollectionSetTask() {
4329     complete_work();
4330     FREE_C_HEAP_ARRAY(WorkItem, _work_items);
4331   }
4332 
4333   // Chunk size for work distribution. The chosen value has been determined experimentally
4334   // to be a good tradeoff between overhead and achievable parallelism.
4335   static uint chunk_size() { return 32; }
4336 
4337   virtual void work(uint worker_id) {
4338     G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
4339 
4340     // Claim serial work.
4341     if (_serial_work_claim == 0) {
4342       jint value = Atomic::add(1, &_serial_work_claim) - 1;
4343       if (value == 0) {
4344         double serial_time = os::elapsedTime();
4345         do_serial_work();
4346         timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0);
4347       }
4348     }
4349 
4350     // Start parallel work.
4351     double young_time = 0.0;
4352     bool has_young_time = false;
4353     double non_young_time = 0.0;
4354     bool has_non_young_time = false;
4355 
4356     while (true) {
4357       size_t end = Atomic::add(chunk_size(), &_parallel_work_claim);
4358       size_t cur = end - chunk_size();
4359 
4360       if (cur >= _num_work_items) {
4361         break;
4362       }
4363 
4364       double start_time = os::elapsedTime();
4365 
4366       end = MIN2(end, _num_work_items);
4367 
4368       for (; cur < end; cur++) {
4369         bool is_young = _work_items[cur].is_young;
4370 
4371         do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed);
4372 
4373         double end_time = os::elapsedTime();
4374         double time_taken = end_time - start_time;
4375         if (is_young) {
4376           young_time += time_taken;
4377           has_young_time = true;
4378         } else {
4379           non_young_time += time_taken;
4380           has_non_young_time = true;
4381         }
4382         start_time = end_time;
4383       }
4384     }
4385 
4386     if (has_young_time) {
4387       timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time);
4388     }
4389     if (has_non_young_time) {
4390       timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, non_young_time);
4391     }
4392   }
4393 };
4394 
4395 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) {
4396   _eden.clear();
4397 
4398   double free_cset_start_time = os::elapsedTime();
4399 
4400   {
4401     uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U);
4402     uint const num_workers = MIN2(workers()->active_workers(), num_chunks);
4403 
4404     G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words);
4405 
4406     log_debug(gc, ergo)("Running %s using %u workers for collection set length %u",
4407                         cl.name(),
4408                         num_workers,
4409                         _collection_set.region_length());
4410     workers()->run_task(&cl, num_workers);
4411   }
4412   g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0);
4413 
4414   collection_set->clear();
4415 }
4416 
4417 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
4418  private:
4419   FreeRegionList* _free_region_list;
4420   HeapRegionSet* _proxy_set;
4421   uint _humongous_objects_reclaimed;
4422   uint _humongous_regions_reclaimed;
4423   size_t _freed_bytes;
4424  public:
4425 
4426   G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
4427     _free_region_list(free_region_list), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) {
4428   }
4429 
4430   virtual bool do_heap_region(HeapRegion* r) {
4431     if (!r->is_starts_humongous()) {
4432       return false;
4433     }
4434 
4435     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4436 
4437     oop obj = (oop)r->bottom();
4438     G1CMBitMap* next_bitmap = g1h->concurrent_mark()->next_mark_bitmap();
4439 
4440     // The following checks whether the humongous object is live are sufficient.
4441     // The main additional check (in addition to having a reference from the roots
4442     // or the young gen) is whether the humongous object has a remembered set entry.
4443     //
4444     // A humongous object cannot be live if there is no remembered set for it
4445     // because:
4446     // - there can be no references from within humongous starts regions referencing
4447     // the object because we never allocate other objects into them.
4448     // (I.e. there are no intra-region references that may be missed by the
4449     // remembered set)
4450     // - as soon there is a remembered set entry to the humongous starts region
4451     // (i.e. it has "escaped" to an old object) this remembered set entry will stay
4452     // until the end of a concurrent mark.
4453     //
4454     // It is not required to check whether the object has been found dead by marking
4455     // or not, in fact it would prevent reclamation within a concurrent cycle, as
4456     // all objects allocated during that time are considered live.
4457     // SATB marking is even more conservative than the remembered set.
4458     // So if at this point in the collection there is no remembered set entry,
4459     // nobody has a reference to it.
4460     // At the start of collection we flush all refinement logs, and remembered sets
4461     // are completely up-to-date wrt to references to the humongous object.
4462     //
4463     // Other implementation considerations:
4464     // - never consider object arrays at this time because they would pose
4465     // considerable effort for cleaning up the the remembered sets. This is
4466     // required because stale remembered sets might reference locations that
4467     // are currently allocated into.
4468     uint region_idx = r->hrm_index();
4469     if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
4470         !r->rem_set()->is_empty()) {
4471       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",
4472                                region_idx,
4473                                (size_t)obj->size() * HeapWordSize,
4474                                p2i(r->bottom()),
4475                                r->rem_set()->occupied(),
4476                                r->rem_set()->strong_code_roots_list_length(),
4477                                next_bitmap->is_marked(r->bottom()),
4478                                g1h->is_humongous_reclaim_candidate(region_idx),
4479                                obj->is_typeArray()
4480                               );
4481       return false;
4482     }
4483 
4484     guarantee(obj->is_typeArray(),
4485               "Only eagerly reclaiming type arrays is supported, but the object "
4486               PTR_FORMAT " is not.", p2i(r->bottom()));
4487 
4488     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",
4489                              region_idx,
4490                              (size_t)obj->size() * HeapWordSize,
4491                              p2i(r->bottom()),
4492                              r->rem_set()->occupied(),
4493                              r->rem_set()->strong_code_roots_list_length(),
4494                              next_bitmap->is_marked(r->bottom()),
4495                              g1h->is_humongous_reclaim_candidate(region_idx),
4496                              obj->is_typeArray()
4497                             );
4498 
4499     G1ConcurrentMark* const cm = g1h->concurrent_mark();
4500     cm->humongous_object_eagerly_reclaimed(r);
4501     assert(!cm->is_marked_in_prev_bitmap(obj) && !cm->is_marked_in_next_bitmap(obj),
4502            "Eagerly reclaimed humongous region %u should not be marked at all but is in prev %s next %s",
4503            region_idx,
4504            BOOL_TO_STR(cm->is_marked_in_prev_bitmap(obj)),
4505            BOOL_TO_STR(cm->is_marked_in_next_bitmap(obj)));
4506     _humongous_objects_reclaimed++;
4507     do {
4508       HeapRegion* next = g1h->next_region_in_humongous(r);
4509       _freed_bytes += r->used();
4510       r->set_containing_set(NULL);
4511       _humongous_regions_reclaimed++;
4512       g1h->free_humongous_region(r, _free_region_list);
4513       r = next;
4514     } while (r != NULL);
4515 
4516     return false;
4517   }
4518 
4519   uint humongous_objects_reclaimed() {
4520     return _humongous_objects_reclaimed;
4521   }
4522 
4523   uint humongous_regions_reclaimed() {
4524     return _humongous_regions_reclaimed;
4525   }
4526 
4527   size_t bytes_freed() const {
4528     return _freed_bytes;
4529   }
4530 };
4531 
4532 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
4533   assert_at_safepoint_on_vm_thread();
4534 
4535   if (!G1EagerReclaimHumongousObjects ||
4536       (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) {
4537     g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
4538     return;
4539   }
4540 
4541   double start_time = os::elapsedTime();
4542 
4543   FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
4544 
4545   G1FreeHumongousRegionClosure cl(&local_cleanup_list);
4546   heap_region_iterate(&cl);
4547 
4548   remove_from_old_sets(0, cl.humongous_regions_reclaimed());
4549 
4550   G1HRPrinter* hrp = hr_printer();
4551   if (hrp->is_active()) {
4552     FreeRegionListIterator iter(&local_cleanup_list);
4553     while (iter.more_available()) {
4554       HeapRegion* hr = iter.get_next();
4555       hrp->cleanup(hr);
4556     }
4557   }
4558 
4559   prepend_to_freelist(&local_cleanup_list);
4560   decrement_summary_bytes(cl.bytes_freed());
4561 
4562   g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
4563                                                                     cl.humongous_objects_reclaimed());
4564 }
4565 
4566 class G1AbandonCollectionSetClosure : public HeapRegionClosure {
4567 public:
4568   virtual bool do_heap_region(HeapRegion* r) {
4569     assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index());
4570     G1CollectedHeap::heap()->clear_in_cset(r);
4571     r->set_young_index_in_cset(-1);
4572     return false;
4573   }
4574 };
4575 
4576 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) {
4577   G1AbandonCollectionSetClosure cl;
4578   collection_set->iterate(&cl);
4579 
4580   collection_set->clear();
4581   collection_set->stop_incremental_building();
4582 }
4583 
4584 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
4585   return _allocator->is_retained_old_region(hr);
4586 }
4587 
4588 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
4589   _eden.add(hr);
4590   _g1_policy->set_region_eden(hr);
4591 }
4592 
4593 #ifdef ASSERT
4594 
4595 class NoYoungRegionsClosure: public HeapRegionClosure {
4596 private:
4597   bool _success;
4598 public:
4599   NoYoungRegionsClosure() : _success(true) { }
4600   bool do_heap_region(HeapRegion* r) {
4601     if (r->is_young()) {
4602       log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
4603                             p2i(r->bottom()), p2i(r->end()));
4604       _success = false;
4605     }
4606     return false;
4607   }
4608   bool success() { return _success; }
4609 };
4610 
4611 bool G1CollectedHeap::check_young_list_empty() {
4612   bool ret = (young_regions_count() == 0);
4613 
4614   NoYoungRegionsClosure closure;
4615   heap_region_iterate(&closure);
4616   ret = ret && closure.success();
4617 
4618   return ret;
4619 }
4620 
4621 #endif // ASSERT
4622 
4623 class TearDownRegionSetsClosure : public HeapRegionClosure {
4624 private:
4625   HeapRegionSet *_old_set;
4626 
4627 public:
4628   TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
4629 
4630   bool do_heap_region(HeapRegion* r) {
4631     if (r->is_old()) {
4632       _old_set->remove(r);
4633     } else if(r->is_young()) {
4634       r->uninstall_surv_rate_group();
4635     } else {
4636       // We ignore free regions, we'll empty the free list afterwards.
4637       // We ignore humongous regions, we're not tearing down the
4638       // humongous regions set.
4639       assert(r->is_free() || r->is_humongous(),
4640              "it cannot be another type");
4641     }
4642     return false;
4643   }
4644 
4645   ~TearDownRegionSetsClosure() {
4646     assert(_old_set->is_empty(), "post-condition");
4647   }
4648 };
4649 
4650 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
4651   assert_at_safepoint_on_vm_thread();
4652 
4653   if (!free_list_only) {
4654     TearDownRegionSetsClosure cl(&_old_set);
4655     heap_region_iterate(&cl);
4656 
4657     // Note that emptying the _young_list is postponed and instead done as
4658     // the first step when rebuilding the regions sets again. The reason for
4659     // this is that during a full GC string deduplication needs to know if
4660     // a collected region was young or old when the full GC was initiated.
4661   }
4662   _hrm.remove_all_free_regions();
4663 }
4664 
4665 void G1CollectedHeap::increase_used(size_t bytes) {
4666   _summary_bytes_used += bytes;
4667 }
4668 
4669 void G1CollectedHeap::decrease_used(size_t bytes) {
4670   assert(_summary_bytes_used >= bytes,
4671          "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
4672          _summary_bytes_used, bytes);
4673   _summary_bytes_used -= bytes;
4674 }
4675 
4676 void G1CollectedHeap::set_used(size_t bytes) {
4677   _summary_bytes_used = bytes;
4678 }
4679 
4680 class RebuildRegionSetsClosure : public HeapRegionClosure {
4681 private:
4682   bool            _free_list_only;
4683   HeapRegionSet*   _old_set;
4684   HeapRegionManager*   _hrm;
4685   size_t          _total_used;
4686 
4687 public:
4688   RebuildRegionSetsClosure(bool free_list_only,
4689                            HeapRegionSet* old_set, HeapRegionManager* hrm) :
4690     _free_list_only(free_list_only),
4691     _old_set(old_set), _hrm(hrm), _total_used(0) {
4692     assert(_hrm->num_free_regions() == 0, "pre-condition");
4693     if (!free_list_only) {
4694       assert(_old_set->is_empty(), "pre-condition");
4695     }
4696   }
4697 
4698   bool do_heap_region(HeapRegion* r) {
4699     // After full GC, no region should have a remembered set.
4700     r->rem_set()->clear(true);
4701     if (r->is_empty()) {
4702       // Add free regions to the free list
4703       r->set_free();
4704       _hrm->insert_into_free_list(r);
4705     } else if (!_free_list_only) {
4706 
4707       if (r->is_humongous()) {
4708         // We ignore humongous regions. We left the humongous set unchanged.
4709       } else {
4710         assert(r->is_young() || r->is_free() || r->is_old(), "invariant");
4711         // We now move all (non-humongous, non-old) regions to old gen, and register them as such.
4712         r->move_to_old();
4713         _old_set->add(r);
4714       }
4715       _total_used += r->used();
4716     }
4717 
4718     return false;
4719   }
4720 
4721   size_t total_used() {
4722     return _total_used;
4723   }
4724 };
4725 
4726 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
4727   assert_at_safepoint_on_vm_thread();
4728 
4729   if (!free_list_only) {
4730     _eden.clear();
4731     _survivor.clear();
4732   }
4733 
4734   RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
4735   heap_region_iterate(&cl);
4736 
4737   if (!free_list_only) {
4738     set_used(cl.total_used());
4739     if (_archive_allocator != NULL) {
4740       _archive_allocator->clear_used();
4741     }
4742   }
4743   assert(used_unlocked() == recalculate_used(),
4744          "inconsistent used_unlocked(), "
4745          "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT,
4746          used_unlocked(), recalculate_used());
4747 }
4748 
4749 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
4750   HeapRegion* hr = heap_region_containing(p);
4751   return hr->is_in(p);
4752 }
4753 
4754 // Methods for the mutator alloc region
4755 
4756 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
4757                                                       bool force) {
4758   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
4759   bool should_allocate = g1_policy()->should_allocate_mutator_region();
4760   if (force || should_allocate) {
4761     HeapRegion* new_alloc_region = new_region(word_size,
4762                                               false /* is_old */,
4763                                               false /* do_expand */);
4764     if (new_alloc_region != NULL) {
4765       set_region_short_lived_locked(new_alloc_region);
4766       _hr_printer.alloc(new_alloc_region, !should_allocate);
4767       _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region);
4768       _g1_policy->remset_tracker()->update_at_allocate(new_alloc_region);
4769       return new_alloc_region;
4770     }
4771   }
4772   return NULL;
4773 }
4774 
4775 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
4776                                                   size_t allocated_bytes) {
4777   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
4778   assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
4779 
4780   collection_set()->add_eden_region(alloc_region);
4781   increase_used(allocated_bytes);
4782   _hr_printer.retire(alloc_region);
4783   // We update the eden sizes here, when the region is retired,
4784   // instead of when it's allocated, since this is the point that its
4785   // used space has been recored in _summary_bytes_used.
4786   g1mm()->update_eden_size();
4787 }
4788 
4789 // Methods for the GC alloc regions
4790 
4791 bool G1CollectedHeap::has_more_regions(InCSetState dest) {
4792   if (dest.is_old()) {
4793     return true;
4794   } else {
4795     return survivor_regions_count() < g1_policy()->max_survivor_regions();
4796   }
4797 }
4798 
4799 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) {
4800   assert(FreeList_lock->owned_by_self(), "pre-condition");
4801 
4802   if (!has_more_regions(dest)) {
4803     return NULL;
4804   }
4805 
4806   const bool is_survivor = dest.is_young();
4807 
4808   HeapRegion* new_alloc_region = new_region(word_size,
4809                                             !is_survivor,
4810                                             true /* do_expand */);
4811   if (new_alloc_region != NULL) {
4812     if (is_survivor) {
4813       new_alloc_region->set_survivor();
4814       _survivor.add(new_alloc_region);
4815       _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region);
4816     } else {
4817       new_alloc_region->set_old();
4818       _verifier->check_bitmaps("Old Region Allocation", new_alloc_region);
4819     }
4820     _g1_policy->remset_tracker()->update_at_allocate(new_alloc_region);
4821     _hr_printer.alloc(new_alloc_region);
4822     bool during_im = collector_state()->in_initial_mark_gc();
4823     new_alloc_region->note_start_of_copying(during_im);
4824     return new_alloc_region;
4825   }
4826   return NULL;
4827 }
4828 
4829 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
4830                                              size_t allocated_bytes,
4831                                              InCSetState dest) {
4832   bool during_im = collector_state()->in_initial_mark_gc();
4833   alloc_region->note_end_of_copying(during_im);
4834   g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
4835   if (dest.is_old()) {
4836     _old_set.add(alloc_region);
4837   }
4838   _hr_printer.retire(alloc_region);
4839 }
4840 
4841 HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
4842   bool expanded = false;
4843   uint index = _hrm.find_highest_free(&expanded);
4844 
4845   if (index != G1_NO_HRM_INDEX) {
4846     if (expanded) {
4847       log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
4848                                 HeapRegion::GrainWords * HeapWordSize);
4849     }
4850     _hrm.allocate_free_regions_starting_at(index, 1);
4851     return region_at(index);
4852   }
4853   return NULL;
4854 }
4855 
4856 // Optimized nmethod scanning
4857 
4858 class RegisterNMethodOopClosure: public OopClosure {
4859   G1CollectedHeap* _g1h;
4860   nmethod* _nm;
4861 
4862   template <class T> void do_oop_work(T* p) {
4863     T heap_oop = RawAccess<>::oop_load(p);
4864     if (!CompressedOops::is_null(heap_oop)) {
4865       oop obj = CompressedOops::decode_not_null(heap_oop);
4866       HeapRegion* hr = _g1h->heap_region_containing(obj);
4867       assert(!hr->is_continues_humongous(),
4868              "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
4869              " starting at " HR_FORMAT,
4870              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
4871 
4872       // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
4873       hr->add_strong_code_root_locked(_nm);
4874     }
4875   }
4876 
4877 public:
4878   RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
4879     _g1h(g1h), _nm(nm) {}
4880 
4881   void do_oop(oop* p)       { do_oop_work(p); }
4882   void do_oop(narrowOop* p) { do_oop_work(p); }
4883 };
4884 
4885 class UnregisterNMethodOopClosure: public OopClosure {
4886   G1CollectedHeap* _g1h;
4887   nmethod* _nm;
4888 
4889   template <class T> void do_oop_work(T* p) {
4890     T heap_oop = RawAccess<>::oop_load(p);
4891     if (!CompressedOops::is_null(heap_oop)) {
4892       oop obj = CompressedOops::decode_not_null(heap_oop);
4893       HeapRegion* hr = _g1h->heap_region_containing(obj);
4894       assert(!hr->is_continues_humongous(),
4895              "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
4896              " starting at " HR_FORMAT,
4897              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
4898 
4899       hr->remove_strong_code_root(_nm);
4900     }
4901   }
4902 
4903 public:
4904   UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
4905     _g1h(g1h), _nm(nm) {}
4906 
4907   void do_oop(oop* p)       { do_oop_work(p); }
4908   void do_oop(narrowOop* p) { do_oop_work(p); }
4909 };
4910 
4911 // Returns true if the reference points to an object that
4912 // can move in an incremental collection.
4913 bool G1CollectedHeap::is_scavengable(oop obj) {
4914   HeapRegion* hr = heap_region_containing(obj);
4915   return !hr->is_pinned();
4916 }
4917 
4918 void G1CollectedHeap::register_nmethod(nmethod* nm) {
4919   guarantee(nm != NULL, "sanity");
4920   RegisterNMethodOopClosure reg_cl(this, nm);
4921   nm->oops_do(&reg_cl);
4922 }
4923 
4924 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
4925   guarantee(nm != NULL, "sanity");
4926   UnregisterNMethodOopClosure reg_cl(this, nm);
4927   nm->oops_do(&reg_cl, true);
4928 }
4929 
4930 void G1CollectedHeap::purge_code_root_memory() {
4931   double purge_start = os::elapsedTime();
4932   G1CodeRootSet::purge();
4933   double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
4934   g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
4935 }
4936 
4937 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
4938   G1CollectedHeap* _g1h;
4939 
4940 public:
4941   RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
4942     _g1h(g1h) {}
4943 
4944   void do_code_blob(CodeBlob* cb) {
4945     nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
4946     if (nm == NULL) {
4947       return;
4948     }
4949 
4950     if (ScavengeRootsInCode) {
4951       _g1h->register_nmethod(nm);
4952     }
4953   }
4954 };
4955 
4956 void G1CollectedHeap::rebuild_strong_code_roots() {
4957   RebuildStrongCodeRootClosure blob_cl(this);
4958   CodeCache::blobs_do(&blob_cl);
4959 }
4960 
4961 GrowableArray<GCMemoryManager*> G1CollectedHeap::memory_managers() {
4962   GrowableArray<GCMemoryManager*> memory_managers(2);
4963   memory_managers.append(&_memory_manager);
4964   memory_managers.append(&_full_gc_memory_manager);
4965   return memory_managers;
4966 }
4967 
4968 GrowableArray<MemoryPool*> G1CollectedHeap::memory_pools() {
4969   GrowableArray<MemoryPool*> memory_pools(3);
4970   memory_pools.append(_eden_pool);
4971   memory_pools.append(_survivor_pool);
4972   memory_pools.append(_old_pool);
4973   return memory_pools;
4974 }