1 /*
   2  * Copyright (c) 2001, 2018, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "classfile/metadataOnStackMark.hpp"
  27 #include "classfile/stringTable.hpp"
  28 #include "classfile/symbolTable.hpp"
  29 #include "code/codeCache.hpp"
  30 #include "code/icBuffer.hpp"
  31 #include "gc/g1/g1Allocator.inline.hpp"
  32 #include "gc/g1/g1BarrierSet.hpp"
  33 #include "gc/g1/g1CollectedHeap.inline.hpp"
  34 #include "gc/g1/g1CollectionSet.hpp"
  35 #include "gc/g1/g1CollectorPolicy.hpp"
  36 #include "gc/g1/g1CollectorState.hpp"
  37 #include "gc/g1/g1ConcurrentRefine.hpp"
  38 #include "gc/g1/g1ConcurrentRefineThread.hpp"
  39 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp"
  40 #include "gc/g1/g1EvacStats.inline.hpp"
  41 #include "gc/g1/g1FullCollector.hpp"
  42 #include "gc/g1/g1GCPhaseTimes.hpp"
  43 #include "gc/g1/g1HeapSizingPolicy.hpp"
  44 #include "gc/g1/g1HeapTransition.hpp"
  45 #include "gc/g1/g1HeapVerifier.hpp"
  46 #include "gc/g1/g1HotCardCache.hpp"
  47 #include "gc/g1/g1MemoryPool.hpp"
  48 #include "gc/g1/g1OopClosures.inline.hpp"
  49 #include "gc/g1/g1ParScanThreadState.inline.hpp"
  50 #include "gc/g1/g1Policy.hpp"
  51 #include "gc/g1/g1RegionToSpaceMapper.hpp"
  52 #include "gc/g1/g1RemSet.hpp"
  53 #include "gc/g1/g1RootClosures.hpp"
  54 #include "gc/g1/g1RootProcessor.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, bool is_open) {
 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::clear_range_archive(ranges[i], is_open);
 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 // Public methods.
1410 
1411 G1CollectedHeap::G1CollectedHeap(G1CollectorPolicy* collector_policy) :
1412   CollectedHeap(),
1413   _young_gen_sampling_thread(NULL),
1414   _collector_policy(collector_policy),
1415   _soft_ref_policy(),
1416   _card_table(NULL),
1417   _memory_manager("G1 Young Generation", "end of minor GC"),
1418   _full_gc_memory_manager("G1 Old Generation", "end of major GC"),
1419   _eden_pool(NULL),
1420   _survivor_pool(NULL),
1421   _old_pool(NULL),
1422   _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1423   _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1424   _g1_policy(new G1Policy(_gc_timer_stw)),
1425   _collection_set(this, _g1_policy),
1426   _dirty_card_queue_set(false),
1427   _ref_processor_stw(NULL),
1428   _is_alive_closure_stw(this),
1429   _is_subject_to_discovery_stw(this),
1430   _ref_processor_cm(NULL),
1431   _is_alive_closure_cm(this),
1432   _is_subject_to_discovery_cm(this),
1433   _bot(NULL),
1434   _hot_card_cache(NULL),
1435   _g1_rem_set(NULL),
1436   _cr(NULL),
1437   _g1mm(NULL),
1438   _preserved_marks_set(true /* in_c_heap */),
1439   _old_set("Old Set", false /* humongous */, new OldRegionSetMtSafeChecker()),
1440   _humongous_set("Master Humongous Set", true /* humongous */, new HumongousRegionSetMtSafeChecker()),
1441   _humongous_reclaim_candidates(),
1442   _has_humongous_reclaim_candidates(false),
1443   _archive_allocator(NULL),
1444   _summary_bytes_used(0),
1445   _survivor_evac_stats("Young", YoungPLABSize, PLABWeight),
1446   _old_evac_stats("Old", OldPLABSize, PLABWeight),
1447   _expand_heap_after_alloc_failure(true),
1448   _old_marking_cycles_started(0),
1449   _old_marking_cycles_completed(0),
1450   _in_cset_fast_test() {
1451 
1452   _workers = new WorkGang("GC Thread", ParallelGCThreads,
1453                           /* are_GC_task_threads */true,
1454                           /* are_ConcurrentGC_threads */false);
1455   _workers->initialize_workers();
1456   _verifier = new G1HeapVerifier(this);
1457 
1458   _allocator = new G1Allocator(this);
1459 
1460   _heap_sizing_policy = G1HeapSizingPolicy::create(this, _g1_policy->analytics());
1461 
1462   _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);
1463 
1464   // Override the default _filler_array_max_size so that no humongous filler
1465   // objects are created.
1466   _filler_array_max_size = _humongous_object_threshold_in_words;
1467 
1468   uint n_queues = ParallelGCThreads;
1469   _task_queues = new RefToScanQueueSet(n_queues);
1470 
1471   _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1472 
1473   for (uint i = 0; i < n_queues; i++) {
1474     RefToScanQueue* q = new RefToScanQueue();
1475     q->initialize();
1476     _task_queues->register_queue(i, q);
1477     ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1478   }
1479 
1480   // Initialize the G1EvacuationFailureALot counters and flags.
1481   NOT_PRODUCT(reset_evacuation_should_fail();)
1482 
1483   guarantee(_task_queues != NULL, "task_queues allocation failure.");
1484 }
1485 
1486 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1487                                                                  size_t size,
1488                                                                  size_t translation_factor) {
1489   size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1490   // Allocate a new reserved space, preferring to use large pages.
1491   ReservedSpace rs(size, preferred_page_size);
1492   G1RegionToSpaceMapper* result  =
1493     G1RegionToSpaceMapper::create_mapper(rs,
1494                                          size,
1495                                          rs.alignment(),
1496                                          HeapRegion::GrainBytes,
1497                                          translation_factor,
1498                                          mtGC);
1499 
1500   os::trace_page_sizes_for_requested_size(description,
1501                                           size,
1502                                           preferred_page_size,
1503                                           rs.alignment(),
1504                                           rs.base(),
1505                                           rs.size());
1506 
1507   return result;
1508 }
1509 
1510 jint G1CollectedHeap::initialize_concurrent_refinement() {
1511   jint ecode = JNI_OK;
1512   _cr = G1ConcurrentRefine::create(&ecode);
1513   return ecode;
1514 }
1515 
1516 jint G1CollectedHeap::initialize_young_gen_sampling_thread() {
1517   _young_gen_sampling_thread = new G1YoungRemSetSamplingThread();
1518   if (_young_gen_sampling_thread->osthread() == NULL) {
1519     vm_shutdown_during_initialization("Could not create G1YoungRemSetSamplingThread");
1520     return JNI_ENOMEM;
1521   }
1522   return JNI_OK;
1523 }
1524 
1525 jint G1CollectedHeap::initialize() {
1526   os::enable_vtime();
1527 
1528   // Necessary to satisfy locking discipline assertions.
1529 
1530   MutexLocker x(Heap_lock);
1531 
1532   // While there are no constraints in the GC code that HeapWordSize
1533   // be any particular value, there are multiple other areas in the
1534   // system which believe this to be true (e.g. oop->object_size in some
1535   // cases incorrectly returns the size in wordSize units rather than
1536   // HeapWordSize).
1537   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1538 
1539   size_t init_byte_size = collector_policy()->initial_heap_byte_size();
1540   size_t max_byte_size = collector_policy()->max_heap_byte_size();
1541   size_t heap_alignment = collector_policy()->heap_alignment();
1542 
1543   // Ensure that the sizes are properly aligned.
1544   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1545   Universe::check_alignment(max_byte_size, HeapRegion::GrainBytes, "g1 heap");
1546   Universe::check_alignment(max_byte_size, heap_alignment, "g1 heap");
1547 
1548   // Reserve the maximum.
1549 
1550   // When compressed oops are enabled, the preferred heap base
1551   // is calculated by subtracting the requested size from the
1552   // 32Gb boundary and using the result as the base address for
1553   // heap reservation. If the requested size is not aligned to
1554   // HeapRegion::GrainBytes (i.e. the alignment that is passed
1555   // into the ReservedHeapSpace constructor) then the actual
1556   // base of the reserved heap may end up differing from the
1557   // address that was requested (i.e. the preferred heap base).
1558   // If this happens then we could end up using a non-optimal
1559   // compressed oops mode.
1560 
1561   ReservedSpace heap_rs = Universe::reserve_heap(max_byte_size,
1562                                                  heap_alignment);
1563 
1564   initialize_reserved_region((HeapWord*)heap_rs.base(), (HeapWord*)(heap_rs.base() + heap_rs.size()));
1565 
1566   // Create the barrier set for the entire reserved region.
1567   G1CardTable* ct = new G1CardTable(reserved_region());
1568   ct->initialize();
1569   G1BarrierSet* bs = new G1BarrierSet(ct);
1570   bs->initialize();
1571   assert(bs->is_a(BarrierSet::G1BarrierSet), "sanity");
1572   BarrierSet::set_barrier_set(bs);
1573   _card_table = ct;
1574 
1575   // Create the hot card cache.
1576   _hot_card_cache = new G1HotCardCache(this);
1577 
1578   // Carve out the G1 part of the heap.
1579   ReservedSpace g1_rs = heap_rs.first_part(max_byte_size);
1580   size_t page_size = UseLargePages ? os::large_page_size() : os::vm_page_size();
1581   G1RegionToSpaceMapper* heap_storage =
1582     G1RegionToSpaceMapper::create_mapper(g1_rs,
1583                                          g1_rs.size(),
1584                                          page_size,
1585                                          HeapRegion::GrainBytes,
1586                                          1,
1587                                          mtJavaHeap);
1588   os::trace_page_sizes("Heap",
1589                        collector_policy()->min_heap_byte_size(),
1590                        max_byte_size,
1591                        page_size,
1592                        heap_rs.base(),
1593                        heap_rs.size());
1594   heap_storage->set_mapping_changed_listener(&_listener);
1595 
1596   // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1597   G1RegionToSpaceMapper* bot_storage =
1598     create_aux_memory_mapper("Block Offset Table",
1599                              G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize),
1600                              G1BlockOffsetTable::heap_map_factor());
1601 
1602   G1RegionToSpaceMapper* cardtable_storage =
1603     create_aux_memory_mapper("Card Table",
1604                              G1CardTable::compute_size(g1_rs.size() / HeapWordSize),
1605                              G1CardTable::heap_map_factor());
1606 
1607   G1RegionToSpaceMapper* card_counts_storage =
1608     create_aux_memory_mapper("Card Counts Table",
1609                              G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1610                              G1CardCounts::heap_map_factor());
1611 
1612   size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size());
1613   G1RegionToSpaceMapper* prev_bitmap_storage =
1614     create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1615   G1RegionToSpaceMapper* next_bitmap_storage =
1616     create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1617 
1618   _hrm.initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1619   _card_table->initialize(cardtable_storage);
1620   // Do later initialization work for concurrent refinement.
1621   _hot_card_cache->initialize(card_counts_storage);
1622 
1623   // 6843694 - ensure that the maximum region index can fit
1624   // in the remembered set structures.
1625   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1626   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1627 
1628   // The G1FromCardCache reserves card with value 0 as "invalid", so the heap must not
1629   // start within the first card.
1630   guarantee(g1_rs.base() >= (char*)G1CardTable::card_size, "Java heap must not start within the first card.");
1631   // Also create a G1 rem set.
1632   _g1_rem_set = new G1RemSet(this, _card_table, _hot_card_cache);
1633   _g1_rem_set->initialize(max_capacity(), max_regions());
1634 
1635   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1636   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1637   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1638             "too many cards per region");
1639 
1640   FreeRegionList::set_unrealistically_long_length(max_regions() + 1);
1641 
1642   _bot = new G1BlockOffsetTable(reserved_region(), bot_storage);
1643 
1644   {
1645     HeapWord* start = _hrm.reserved().start();
1646     HeapWord* end = _hrm.reserved().end();
1647     size_t granularity = HeapRegion::GrainBytes;
1648 
1649     _in_cset_fast_test.initialize(start, end, granularity);
1650     _humongous_reclaim_candidates.initialize(start, end, granularity);
1651   }
1652 
1653   // Create the G1ConcurrentMark data structure and thread.
1654   // (Must do this late, so that "max_regions" is defined.)
1655   _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1656   if (_cm == NULL || !_cm->completed_initialization()) {
1657     vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark");
1658     return JNI_ENOMEM;
1659   }
1660   _cm_thread = _cm->cm_thread();
1661 
1662   // Now expand into the initial heap size.
1663   if (!expand(init_byte_size, _workers)) {
1664     vm_shutdown_during_initialization("Failed to allocate initial heap.");
1665     return JNI_ENOMEM;
1666   }
1667 
1668   // Perform any initialization actions delegated to the policy.
1669   g1_policy()->init(this, &_collection_set);
1670 
1671   G1BarrierSet::satb_mark_queue_set().initialize(SATB_Q_CBL_mon,
1672                                                  SATB_Q_FL_lock,
1673                                                  G1SATBProcessCompletedThreshold,
1674                                                  Shared_SATB_Q_lock);
1675 
1676   jint ecode = initialize_concurrent_refinement();
1677   if (ecode != JNI_OK) {
1678     return ecode;
1679   }
1680 
1681   ecode = initialize_young_gen_sampling_thread();
1682   if (ecode != JNI_OK) {
1683     return ecode;
1684   }
1685 
1686   G1BarrierSet::dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1687                                                   DirtyCardQ_FL_lock,
1688                                                   (int)concurrent_refine()->yellow_zone(),
1689                                                   (int)concurrent_refine()->red_zone(),
1690                                                   Shared_DirtyCardQ_lock,
1691                                                   NULL,  // fl_owner
1692                                                   true); // init_free_ids
1693 
1694   dirty_card_queue_set().initialize(DirtyCardQ_CBL_mon,
1695                                     DirtyCardQ_FL_lock,
1696                                     -1, // never trigger processing
1697                                     -1, // no limit on length
1698                                     Shared_DirtyCardQ_lock,
1699                                     &G1BarrierSet::dirty_card_queue_set());
1700 
1701   // Here we allocate the dummy HeapRegion that is required by the
1702   // G1AllocRegion class.
1703   HeapRegion* dummy_region = _hrm.get_dummy_region();
1704 
1705   // We'll re-use the same region whether the alloc region will
1706   // require BOT updates or not and, if it doesn't, then a non-young
1707   // region will complain that it cannot support allocations without
1708   // BOT updates. So we'll tag the dummy region as eden to avoid that.
1709   dummy_region->set_eden();
1710   // Make sure it's full.
1711   dummy_region->set_top(dummy_region->end());
1712   G1AllocRegion::setup(this, dummy_region);
1713 
1714   _allocator->init_mutator_alloc_region();
1715 
1716   // Do create of the monitoring and management support so that
1717   // values in the heap have been properly initialized.
1718   _g1mm = new G1MonitoringSupport(this);
1719 
1720   G1StringDedup::initialize();
1721 
1722   _preserved_marks_set.init(ParallelGCThreads);
1723 
1724   _collection_set.initialize(max_regions());
1725 
1726   return JNI_OK;
1727 }
1728 
1729 void G1CollectedHeap::initialize_serviceability() {
1730   _eden_pool = new G1EdenPool(this);
1731   _survivor_pool = new G1SurvivorPool(this);
1732   _old_pool = new G1OldGenPool(this);
1733 
1734   _full_gc_memory_manager.add_pool(_eden_pool);
1735   _full_gc_memory_manager.add_pool(_survivor_pool);
1736   _full_gc_memory_manager.add_pool(_old_pool);
1737 
1738   _memory_manager.add_pool(_eden_pool);
1739   _memory_manager.add_pool(_survivor_pool);
1740   _memory_manager.add_pool(_old_pool, false /* always_affected_by_gc */);
1741 }
1742 
1743 void G1CollectedHeap::stop() {
1744   // Stop all concurrent threads. We do this to make sure these threads
1745   // do not continue to execute and access resources (e.g. logging)
1746   // that are destroyed during shutdown.
1747   _cr->stop();
1748   _young_gen_sampling_thread->stop();
1749   _cm_thread->stop();
1750   if (G1StringDedup::is_enabled()) {
1751     G1StringDedup::stop();
1752   }
1753 }
1754 
1755 void G1CollectedHeap::safepoint_synchronize_begin() {
1756   SuspendibleThreadSet::synchronize();
1757 }
1758 
1759 void G1CollectedHeap::safepoint_synchronize_end() {
1760   SuspendibleThreadSet::desynchronize();
1761 }
1762 
1763 size_t G1CollectedHeap::conservative_max_heap_alignment() {
1764   return HeapRegion::max_region_size();
1765 }
1766 
1767 void G1CollectedHeap::post_initialize() {
1768   CollectedHeap::post_initialize();
1769   ref_processing_init();
1770 }
1771 
1772 void G1CollectedHeap::ref_processing_init() {
1773   // Reference processing in G1 currently works as follows:
1774   //
1775   // * There are two reference processor instances. One is
1776   //   used to record and process discovered references
1777   //   during concurrent marking; the other is used to
1778   //   record and process references during STW pauses
1779   //   (both full and incremental).
1780   // * Both ref processors need to 'span' the entire heap as
1781   //   the regions in the collection set may be dotted around.
1782   //
1783   // * For the concurrent marking ref processor:
1784   //   * Reference discovery is enabled at initial marking.
1785   //   * Reference discovery is disabled and the discovered
1786   //     references processed etc during remarking.
1787   //   * Reference discovery is MT (see below).
1788   //   * Reference discovery requires a barrier (see below).
1789   //   * Reference processing may or may not be MT
1790   //     (depending on the value of ParallelRefProcEnabled
1791   //     and ParallelGCThreads).
1792   //   * A full GC disables reference discovery by the CM
1793   //     ref processor and abandons any entries on it's
1794   //     discovered lists.
1795   //
1796   // * For the STW processor:
1797   //   * Non MT discovery is enabled at the start of a full GC.
1798   //   * Processing and enqueueing during a full GC is non-MT.
1799   //   * During a full GC, references are processed after marking.
1800   //
1801   //   * Discovery (may or may not be MT) is enabled at the start
1802   //     of an incremental evacuation pause.
1803   //   * References are processed near the end of a STW evacuation pause.
1804   //   * For both types of GC:
1805   //     * Discovery is atomic - i.e. not concurrent.
1806   //     * Reference discovery will not need a barrier.
1807 
1808   bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1);
1809 
1810   // Concurrent Mark ref processor
1811   _ref_processor_cm =
1812     new ReferenceProcessor(&_is_subject_to_discovery_cm,
1813                            mt_processing,                                  // mt processing
1814                            ParallelGCThreads,                              // degree of mt processing
1815                            (ParallelGCThreads > 1) || (ConcGCThreads > 1), // mt discovery
1816                            MAX2(ParallelGCThreads, ConcGCThreads),         // degree of mt discovery
1817                            false,                                          // Reference discovery is not atomic
1818                            &_is_alive_closure_cm,                          // is alive closure
1819                            true);                                          // allow changes to number of processing threads
1820 
1821   // STW ref processor
1822   _ref_processor_stw =
1823     new ReferenceProcessor(&_is_subject_to_discovery_stw,
1824                            mt_processing,                        // mt processing
1825                            ParallelGCThreads,                    // degree of mt processing
1826                            (ParallelGCThreads > 1),              // mt discovery
1827                            ParallelGCThreads,                    // degree of mt discovery
1828                            true,                                 // Reference discovery is atomic
1829                            &_is_alive_closure_stw,               // is alive closure
1830                            true);                                // allow changes to number of processing threads
1831 }
1832 
1833 CollectorPolicy* G1CollectedHeap::collector_policy() const {
1834   return _collector_policy;
1835 }
1836 
1837 SoftRefPolicy* G1CollectedHeap::soft_ref_policy() {
1838   return &_soft_ref_policy;
1839 }
1840 
1841 size_t G1CollectedHeap::capacity() const {
1842   return _hrm.length() * HeapRegion::GrainBytes;
1843 }
1844 
1845 size_t G1CollectedHeap::unused_committed_regions_in_bytes() const {
1846   return _hrm.total_free_bytes();
1847 }
1848 
1849 void G1CollectedHeap::iterate_hcc_closure(CardTableEntryClosure* cl, uint worker_i) {
1850   _hot_card_cache->drain(cl, worker_i);
1851 }
1852 
1853 void G1CollectedHeap::iterate_dirty_card_closure(CardTableEntryClosure* cl, uint worker_i) {
1854   DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
1855   size_t n_completed_buffers = 0;
1856   while (dcqs.apply_closure_during_gc(cl, worker_i)) {
1857     n_completed_buffers++;
1858   }
1859   g1_policy()->phase_times()->record_thread_work_item(G1GCPhaseTimes::UpdateRS, worker_i, n_completed_buffers, G1GCPhaseTimes::UpdateRSProcessedBuffers);
1860   dcqs.clear_n_completed_buffers();
1861   assert(!dcqs.completed_buffers_exist_dirty(), "Completed buffers exist!");
1862 }
1863 
1864 // Computes the sum of the storage used by the various regions.
1865 size_t G1CollectedHeap::used() const {
1866   size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
1867   if (_archive_allocator != NULL) {
1868     result += _archive_allocator->used();
1869   }
1870   return result;
1871 }
1872 
1873 size_t G1CollectedHeap::used_unlocked() const {
1874   return _summary_bytes_used;
1875 }
1876 
1877 class SumUsedClosure: public HeapRegionClosure {
1878   size_t _used;
1879 public:
1880   SumUsedClosure() : _used(0) {}
1881   bool do_heap_region(HeapRegion* r) {
1882     _used += r->used();
1883     return false;
1884   }
1885   size_t result() { return _used; }
1886 };
1887 
1888 size_t G1CollectedHeap::recalculate_used() const {
1889   double recalculate_used_start = os::elapsedTime();
1890 
1891   SumUsedClosure blk;
1892   heap_region_iterate(&blk);
1893 
1894   g1_policy()->phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
1895   return blk.result();
1896 }
1897 
1898 bool  G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
1899   switch (cause) {
1900     case GCCause::_java_lang_system_gc:                 return ExplicitGCInvokesConcurrent;
1901     case GCCause::_dcmd_gc_run:                         return ExplicitGCInvokesConcurrent;
1902     case GCCause::_wb_conc_mark:                        return true;
1903     default :                                           return false;
1904   }
1905 }
1906 
1907 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
1908   switch (cause) {
1909     case GCCause::_gc_locker:               return GCLockerInvokesConcurrent;
1910     case GCCause::_g1_humongous_allocation: return true;
1911     default:                                return is_user_requested_concurrent_full_gc(cause);
1912   }
1913 }
1914 
1915 #ifndef PRODUCT
1916 void G1CollectedHeap::allocate_dummy_regions() {
1917   // Let's fill up most of the region
1918   size_t word_size = HeapRegion::GrainWords - 1024;
1919   // And as a result the region we'll allocate will be humongous.
1920   guarantee(is_humongous(word_size), "sanity");
1921 
1922   // _filler_array_max_size is set to humongous object threshold
1923   // but temporarily change it to use CollectedHeap::fill_with_object().
1924   SizeTFlagSetting fs(_filler_array_max_size, word_size);
1925 
1926   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
1927     // Let's use the existing mechanism for the allocation
1928     HeapWord* dummy_obj = humongous_obj_allocate(word_size);
1929     if (dummy_obj != NULL) {
1930       MemRegion mr(dummy_obj, word_size);
1931       CollectedHeap::fill_with_object(mr);
1932     } else {
1933       // If we can't allocate once, we probably cannot allocate
1934       // again. Let's get out of the loop.
1935       break;
1936     }
1937   }
1938 }
1939 #endif // !PRODUCT
1940 
1941 void G1CollectedHeap::increment_old_marking_cycles_started() {
1942   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
1943          _old_marking_cycles_started == _old_marking_cycles_completed + 1,
1944          "Wrong marking cycle count (started: %d, completed: %d)",
1945          _old_marking_cycles_started, _old_marking_cycles_completed);
1946 
1947   _old_marking_cycles_started++;
1948 }
1949 
1950 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
1951   MonitorLockerEx x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
1952 
1953   // We assume that if concurrent == true, then the caller is a
1954   // concurrent thread that was joined the Suspendible Thread
1955   // Set. If there's ever a cheap way to check this, we should add an
1956   // assert here.
1957 
1958   // Given that this method is called at the end of a Full GC or of a
1959   // concurrent cycle, and those can be nested (i.e., a Full GC can
1960   // interrupt a concurrent cycle), the number of full collections
1961   // completed should be either one (in the case where there was no
1962   // nesting) or two (when a Full GC interrupted a concurrent cycle)
1963   // behind the number of full collections started.
1964 
1965   // This is the case for the inner caller, i.e. a Full GC.
1966   assert(concurrent ||
1967          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
1968          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
1969          "for inner caller (Full GC): _old_marking_cycles_started = %u "
1970          "is inconsistent with _old_marking_cycles_completed = %u",
1971          _old_marking_cycles_started, _old_marking_cycles_completed);
1972 
1973   // This is the case for the outer caller, i.e. the concurrent cycle.
1974   assert(!concurrent ||
1975          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
1976          "for outer caller (concurrent cycle): "
1977          "_old_marking_cycles_started = %u "
1978          "is inconsistent with _old_marking_cycles_completed = %u",
1979          _old_marking_cycles_started, _old_marking_cycles_completed);
1980 
1981   _old_marking_cycles_completed += 1;
1982 
1983   // We need to clear the "in_progress" flag in the CM thread before
1984   // we wake up any waiters (especially when ExplicitInvokesConcurrent
1985   // is set) so that if a waiter requests another System.gc() it doesn't
1986   // incorrectly see that a marking cycle is still in progress.
1987   if (concurrent) {
1988     _cm_thread->set_idle();
1989   }
1990 
1991   // This notify_all() will ensure that a thread that called
1992   // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
1993   // and it's waiting for a full GC to finish will be woken up. It is
1994   // waiting in VM_G1CollectForAllocation::doit_epilogue().
1995   FullGCCount_lock->notify_all();
1996 }
1997 
1998 void G1CollectedHeap::collect(GCCause::Cause cause) {
1999   assert_heap_not_locked();
2000 
2001   uint gc_count_before;
2002   uint old_marking_count_before;
2003   uint full_gc_count_before;
2004   bool retry_gc;
2005 
2006   do {
2007     retry_gc = false;
2008 
2009     {
2010       MutexLocker ml(Heap_lock);
2011 
2012       // Read the GC count while holding the Heap_lock
2013       gc_count_before = total_collections();
2014       full_gc_count_before = total_full_collections();
2015       old_marking_count_before = _old_marking_cycles_started;
2016     }
2017 
2018     if (should_do_concurrent_full_gc(cause)) {
2019       // Schedule an initial-mark evacuation pause that will start a
2020       // concurrent cycle. We're setting word_size to 0 which means that
2021       // we are not requesting a post-GC allocation.
2022       VM_G1CollectForAllocation op(0,     /* word_size */
2023                                    gc_count_before,
2024                                    cause,
2025                                    true,  /* should_initiate_conc_mark */
2026                                    g1_policy()->max_pause_time_ms());
2027       VMThread::execute(&op);
2028       if (!op.pause_succeeded()) {
2029         if (old_marking_count_before == _old_marking_cycles_started) {
2030           retry_gc = op.should_retry_gc();
2031         } else {
2032           // A Full GC happened while we were trying to schedule the
2033           // initial-mark GC. No point in starting a new cycle given
2034           // that the whole heap was collected anyway.
2035         }
2036 
2037         if (retry_gc) {
2038           if (GCLocker::is_active_and_needs_gc()) {
2039             GCLocker::stall_until_clear();
2040           }
2041         }
2042       }
2043     } else {
2044       if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2045           DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2046 
2047         // Schedule a standard evacuation pause. We're setting word_size
2048         // to 0 which means that we are not requesting a post-GC allocation.
2049         VM_G1CollectForAllocation op(0,     /* word_size */
2050                                      gc_count_before,
2051                                      cause,
2052                                      false, /* should_initiate_conc_mark */
2053                                      g1_policy()->max_pause_time_ms());
2054         VMThread::execute(&op);
2055       } else {
2056         // Schedule a Full GC.
2057         VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2058         VMThread::execute(&op);
2059       }
2060     }
2061   } while (retry_gc);
2062 }
2063 
2064 bool G1CollectedHeap::is_in(const void* p) const {
2065   if (_hrm.reserved().contains(p)) {
2066     // Given that we know that p is in the reserved space,
2067     // heap_region_containing() should successfully
2068     // return the containing region.
2069     HeapRegion* hr = heap_region_containing(p);
2070     return hr->is_in(p);
2071   } else {
2072     return false;
2073   }
2074 }
2075 
2076 #ifdef ASSERT
2077 bool G1CollectedHeap::is_in_exact(const void* p) const {
2078   bool contains = reserved_region().contains(p);
2079   bool available = _hrm.is_available(addr_to_region((HeapWord*)p));
2080   if (contains && available) {
2081     return true;
2082   } else {
2083     return false;
2084   }
2085 }
2086 #endif
2087 
2088 // Iteration functions.
2089 
2090 // Iterates an ObjectClosure over all objects within a HeapRegion.
2091 
2092 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2093   ObjectClosure* _cl;
2094 public:
2095   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2096   bool do_heap_region(HeapRegion* r) {
2097     if (!r->is_continues_humongous()) {
2098       r->object_iterate(_cl);
2099     }
2100     return false;
2101   }
2102 };
2103 
2104 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2105   IterateObjectClosureRegionClosure blk(cl);
2106   heap_region_iterate(&blk);
2107 }
2108 
2109 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2110   _hrm.iterate(cl);
2111 }
2112 
2113 void G1CollectedHeap::heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl,
2114                                                                  HeapRegionClaimer *hrclaimer,
2115                                                                  uint worker_id) const {
2116   _hrm.par_iterate(cl, hrclaimer, hrclaimer->offset_for_worker(worker_id));
2117 }
2118 
2119 void G1CollectedHeap::heap_region_par_iterate_from_start(HeapRegionClosure* cl,
2120                                                          HeapRegionClaimer *hrclaimer) const {
2121   _hrm.par_iterate(cl, hrclaimer, 0);
2122 }
2123 
2124 void G1CollectedHeap::collection_set_iterate(HeapRegionClosure* cl) {
2125   _collection_set.iterate(cl);
2126 }
2127 
2128 void G1CollectedHeap::collection_set_iterate_from(HeapRegionClosure *cl, uint worker_id) {
2129   _collection_set.iterate_from(cl, worker_id, workers()->active_workers());
2130 }
2131 
2132 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2133   HeapRegion* hr = heap_region_containing(addr);
2134   return hr->block_start(addr);
2135 }
2136 
2137 size_t G1CollectedHeap::block_size(const HeapWord* addr) const {
2138   HeapRegion* hr = heap_region_containing(addr);
2139   return hr->block_size(addr);
2140 }
2141 
2142 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2143   HeapRegion* hr = heap_region_containing(addr);
2144   return hr->block_is_obj(addr);
2145 }
2146 
2147 bool G1CollectedHeap::supports_tlab_allocation() const {
2148   return true;
2149 }
2150 
2151 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2152   return (_g1_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes;
2153 }
2154 
2155 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2156   return _eden.length() * HeapRegion::GrainBytes;
2157 }
2158 
2159 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2160 // must be equal to the humongous object limit.
2161 size_t G1CollectedHeap::max_tlab_size() const {
2162   return align_down(_humongous_object_threshold_in_words, MinObjAlignment);
2163 }
2164 
2165 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2166   return _allocator->unsafe_max_tlab_alloc();
2167 }
2168 
2169 size_t G1CollectedHeap::max_capacity() const {
2170   return _hrm.reserved().byte_size();
2171 }
2172 
2173 jlong G1CollectedHeap::millis_since_last_gc() {
2174   // See the notes in GenCollectedHeap::millis_since_last_gc()
2175   // for more information about the implementation.
2176   jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) -
2177     _g1_policy->collection_pause_end_millis();
2178   if (ret_val < 0) {
2179     log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT
2180       ". returning zero instead.", ret_val);
2181     return 0;
2182   }
2183   return ret_val;
2184 }
2185 
2186 void G1CollectedHeap::deduplicate_string(oop str) {
2187   assert(java_lang_String::is_instance(str), "invariant");
2188 
2189   if (G1StringDedup::is_enabled()) {
2190     G1StringDedup::deduplicate(str);
2191   }
2192 }
2193 
2194 void G1CollectedHeap::prepare_for_verify() {
2195   _verifier->prepare_for_verify();
2196 }
2197 
2198 void G1CollectedHeap::verify(VerifyOption vo) {
2199   _verifier->verify(vo);
2200 }
2201 
2202 bool G1CollectedHeap::supports_concurrent_phase_control() const {
2203   return true;
2204 }
2205 
2206 const char* const* G1CollectedHeap::concurrent_phases() const {
2207   return _cm_thread->concurrent_phases();
2208 }
2209 
2210 bool G1CollectedHeap::request_concurrent_phase(const char* phase) {
2211   return _cm_thread->request_concurrent_phase(phase);
2212 }
2213 
2214 class PrintRegionClosure: public HeapRegionClosure {
2215   outputStream* _st;
2216 public:
2217   PrintRegionClosure(outputStream* st) : _st(st) {}
2218   bool do_heap_region(HeapRegion* r) {
2219     r->print_on(_st);
2220     return false;
2221   }
2222 };
2223 
2224 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2225                                        const HeapRegion* hr,
2226                                        const VerifyOption vo) const {
2227   switch (vo) {
2228   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
2229   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
2230   case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj, hr);
2231   default:                            ShouldNotReachHere();
2232   }
2233   return false; // keep some compilers happy
2234 }
2235 
2236 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2237                                        const VerifyOption vo) const {
2238   switch (vo) {
2239   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
2240   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
2241   case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj);
2242   default:                            ShouldNotReachHere();
2243   }
2244   return false; // keep some compilers happy
2245 }
2246 
2247 void G1CollectedHeap::print_heap_regions() const {
2248   LogTarget(Trace, gc, heap, region) lt;
2249   if (lt.is_enabled()) {
2250     LogStream ls(lt);
2251     print_regions_on(&ls);
2252   }
2253 }
2254 
2255 void G1CollectedHeap::print_on(outputStream* st) const {
2256   st->print(" %-20s", "garbage-first heap");
2257   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
2258             capacity()/K, used_unlocked()/K);
2259   st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")",
2260             p2i(_hrm.reserved().start()),
2261             p2i(_hrm.reserved().end()));
2262   st->cr();
2263   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
2264   uint young_regions = young_regions_count();
2265   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
2266             (size_t) young_regions * HeapRegion::GrainBytes / K);
2267   uint survivor_regions = survivor_regions_count();
2268   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
2269             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
2270   st->cr();
2271   MetaspaceUtils::print_on(st);
2272 }
2273 
2274 void G1CollectedHeap::print_regions_on(outputStream* st) const {
2275   st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
2276                "HS=humongous(starts), HC=humongous(continues), "
2277                "CS=collection set, F=free, A=archive, "
2278                "TAMS=top-at-mark-start (previous, next)");
2279   PrintRegionClosure blk(st);
2280   heap_region_iterate(&blk);
2281 }
2282 
2283 void G1CollectedHeap::print_extended_on(outputStream* st) const {
2284   print_on(st);
2285 
2286   // Print the per-region information.
2287   print_regions_on(st);
2288 }
2289 
2290 void G1CollectedHeap::print_on_error(outputStream* st) const {
2291   this->CollectedHeap::print_on_error(st);
2292 
2293   if (_cm != NULL) {
2294     st->cr();
2295     _cm->print_on_error(st);
2296   }
2297 }
2298 
2299 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
2300   workers()->print_worker_threads_on(st);
2301   _cm_thread->print_on(st);
2302   st->cr();
2303   _cm->print_worker_threads_on(st);
2304   _cr->print_threads_on(st);
2305   _young_gen_sampling_thread->print_on(st);
2306   if (G1StringDedup::is_enabled()) {
2307     G1StringDedup::print_worker_threads_on(st);
2308   }
2309 }
2310 
2311 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2312   workers()->threads_do(tc);
2313   tc->do_thread(_cm_thread);
2314   _cm->threads_do(tc);
2315   _cr->threads_do(tc);
2316   tc->do_thread(_young_gen_sampling_thread);
2317   if (G1StringDedup::is_enabled()) {
2318     G1StringDedup::threads_do(tc);
2319   }
2320 }
2321 
2322 void G1CollectedHeap::print_tracing_info() const {
2323   g1_rem_set()->print_summary_info();
2324   concurrent_mark()->print_summary_info();
2325 }
2326 
2327 #ifndef PRODUCT
2328 // Helpful for debugging RSet issues.
2329 
2330 class PrintRSetsClosure : public HeapRegionClosure {
2331 private:
2332   const char* _msg;
2333   size_t _occupied_sum;
2334 
2335 public:
2336   bool do_heap_region(HeapRegion* r) {
2337     HeapRegionRemSet* hrrs = r->rem_set();
2338     size_t occupied = hrrs->occupied();
2339     _occupied_sum += occupied;
2340 
2341     tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r));
2342     if (occupied == 0) {
2343       tty->print_cr("  RSet is empty");
2344     } else {
2345       hrrs->print();
2346     }
2347     tty->print_cr("----------");
2348     return false;
2349   }
2350 
2351   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
2352     tty->cr();
2353     tty->print_cr("========================================");
2354     tty->print_cr("%s", msg);
2355     tty->cr();
2356   }
2357 
2358   ~PrintRSetsClosure() {
2359     tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
2360     tty->print_cr("========================================");
2361     tty->cr();
2362   }
2363 };
2364 
2365 void G1CollectedHeap::print_cset_rsets() {
2366   PrintRSetsClosure cl("Printing CSet RSets");
2367   collection_set_iterate(&cl);
2368 }
2369 
2370 void G1CollectedHeap::print_all_rsets() {
2371   PrintRSetsClosure cl("Printing All RSets");;
2372   heap_region_iterate(&cl);
2373 }
2374 #endif // PRODUCT
2375 
2376 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
2377 
2378   size_t eden_used_bytes = heap()->eden_regions_count() * HeapRegion::GrainBytes;
2379   size_t survivor_used_bytes = heap()->survivor_regions_count() * HeapRegion::GrainBytes;
2380   size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
2381 
2382   size_t eden_capacity_bytes =
2383     (g1_policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
2384 
2385   VirtualSpaceSummary heap_summary = create_heap_space_summary();
2386   return G1HeapSummary(heap_summary, heap_used, eden_used_bytes,
2387                        eden_capacity_bytes, survivor_used_bytes, num_regions());
2388 }
2389 
2390 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
2391   return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
2392                        stats->unused(), stats->used(), stats->region_end_waste(),
2393                        stats->regions_filled(), stats->direct_allocated(),
2394                        stats->failure_used(), stats->failure_waste());
2395 }
2396 
2397 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
2398   const G1HeapSummary& heap_summary = create_g1_heap_summary();
2399   gc_tracer->report_gc_heap_summary(when, heap_summary);
2400 
2401   const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
2402   gc_tracer->report_metaspace_summary(when, metaspace_summary);
2403 }
2404 
2405 G1CollectedHeap* G1CollectedHeap::heap() {
2406   CollectedHeap* heap = Universe::heap();
2407   assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
2408   assert(heap->kind() == CollectedHeap::G1, "Invalid name");
2409   return (G1CollectedHeap*)heap;
2410 }
2411 
2412 void G1CollectedHeap::gc_prologue(bool full) {
2413   // always_do_update_barrier = false;
2414   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
2415 
2416   // This summary needs to be printed before incrementing total collections.
2417   g1_rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections());
2418 
2419   // Update common counters.
2420   increment_total_collections(full /* full gc */);
2421   if (full) {
2422     increment_old_marking_cycles_started();
2423   }
2424 
2425   // Fill TLAB's and such
2426   double start = os::elapsedTime();
2427   accumulate_statistics_all_tlabs();
2428   ensure_parsability(true);
2429   g1_policy()->phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2430 }
2431 
2432 void G1CollectedHeap::gc_epilogue(bool full) {
2433   // Update common counters.
2434   if (full) {
2435     // Update the number of full collections that have been completed.
2436     increment_old_marking_cycles_completed(false /* concurrent */);
2437   }
2438 
2439   // We are at the end of the GC. Total collections has already been increased.
2440   g1_rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1);
2441 
2442   // FIXME: what is this about?
2443   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
2444   // is set.
2445 #if COMPILER2_OR_JVMCI
2446   assert(DerivedPointerTable::is_empty(), "derived pointer present");
2447 #endif
2448   // always_do_update_barrier = true;
2449 
2450   double start = os::elapsedTime();
2451   resize_all_tlabs();
2452   g1_policy()->phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2453 
2454   MemoryService::track_memory_usage();
2455   // We have just completed a GC. Update the soft reference
2456   // policy with the new heap occupancy
2457   Universe::update_heap_info_at_gc();
2458 }
2459 
2460 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2461                                                uint gc_count_before,
2462                                                bool* succeeded,
2463                                                GCCause::Cause gc_cause) {
2464   assert_heap_not_locked_and_not_at_safepoint();
2465   VM_G1CollectForAllocation op(word_size,
2466                                gc_count_before,
2467                                gc_cause,
2468                                false, /* should_initiate_conc_mark */
2469                                g1_policy()->max_pause_time_ms());
2470   VMThread::execute(&op);
2471 
2472   HeapWord* result = op.result();
2473   bool ret_succeeded = op.prologue_succeeded() && op.pause_succeeded();
2474   assert(result == NULL || ret_succeeded,
2475          "the result should be NULL if the VM did not succeed");
2476   *succeeded = ret_succeeded;
2477 
2478   assert_heap_not_locked();
2479   return result;
2480 }
2481 
2482 void G1CollectedHeap::do_concurrent_mark() {
2483   MutexLockerEx x(CGC_lock, Mutex::_no_safepoint_check_flag);
2484   if (!_cm_thread->in_progress()) {
2485     _cm_thread->set_started();
2486     CGC_lock->notify();
2487   }
2488 }
2489 
2490 size_t G1CollectedHeap::pending_card_num() {
2491   size_t extra_cards = 0;
2492   for (JavaThreadIteratorWithHandle jtiwh; JavaThread *curr = jtiwh.next(); ) {
2493     DirtyCardQueue& dcq = G1ThreadLocalData::dirty_card_queue(curr);
2494     extra_cards += dcq.size();
2495   }
2496   DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
2497   size_t buffer_size = dcqs.buffer_size();
2498   size_t buffer_num = dcqs.completed_buffers_num();
2499 
2500   return buffer_size * buffer_num + extra_cards;
2501 }
2502 
2503 bool G1CollectedHeap::is_potential_eager_reclaim_candidate(HeapRegion* r) const {
2504   // We don't nominate objects with many remembered set entries, on
2505   // the assumption that such objects are likely still live.
2506   HeapRegionRemSet* rem_set = r->rem_set();
2507 
2508   return G1EagerReclaimHumongousObjectsWithStaleRefs ?
2509          rem_set->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) :
2510          G1EagerReclaimHumongousObjects && rem_set->is_empty();
2511 }
2512 
2513 class RegisterHumongousWithInCSetFastTestClosure : public HeapRegionClosure {
2514  private:
2515   size_t _total_humongous;
2516   size_t _candidate_humongous;
2517 
2518   DirtyCardQueue _dcq;
2519 
2520   bool humongous_region_is_candidate(G1CollectedHeap* g1h, HeapRegion* region) const {
2521     assert(region->is_starts_humongous(), "Must start a humongous object");
2522 
2523     oop obj = oop(region->bottom());
2524 
2525     // Dead objects cannot be eager reclaim candidates. Due to class
2526     // unloading it is unsafe to query their classes so we return early.
2527     if (g1h->is_obj_dead(obj, region)) {
2528       return false;
2529     }
2530 
2531     // If we do not have a complete remembered set for the region, then we can
2532     // not be sure that we have all references to it.
2533     if (!region->rem_set()->is_complete()) {
2534       return false;
2535     }
2536     // Candidate selection must satisfy the following constraints
2537     // while concurrent marking is in progress:
2538     //
2539     // * In order to maintain SATB invariants, an object must not be
2540     // reclaimed if it was allocated before the start of marking and
2541     // has not had its references scanned.  Such an object must have
2542     // its references (including type metadata) scanned to ensure no
2543     // live objects are missed by the marking process.  Objects
2544     // allocated after the start of concurrent marking don't need to
2545     // be scanned.
2546     //
2547     // * An object must not be reclaimed if it is on the concurrent
2548     // mark stack.  Objects allocated after the start of concurrent
2549     // marking are never pushed on the mark stack.
2550     //
2551     // Nominating only objects allocated after the start of concurrent
2552     // marking is sufficient to meet both constraints.  This may miss
2553     // some objects that satisfy the constraints, but the marking data
2554     // structures don't support efficiently performing the needed
2555     // additional tests or scrubbing of the mark stack.
2556     //
2557     // However, we presently only nominate is_typeArray() objects.
2558     // A humongous object containing references induces remembered
2559     // set entries on other regions.  In order to reclaim such an
2560     // object, those remembered sets would need to be cleaned up.
2561     //
2562     // We also treat is_typeArray() objects specially, allowing them
2563     // to be reclaimed even if allocated before the start of
2564     // concurrent mark.  For this we rely on mark stack insertion to
2565     // exclude is_typeArray() objects, preventing reclaiming an object
2566     // that is in the mark stack.  We also rely on the metadata for
2567     // such objects to be built-in and so ensured to be kept live.
2568     // Frequent allocation and drop of large binary blobs is an
2569     // important use case for eager reclaim, and this special handling
2570     // may reduce needed headroom.
2571 
2572     return obj->is_typeArray() &&
2573            g1h->is_potential_eager_reclaim_candidate(region);
2574   }
2575 
2576  public:
2577   RegisterHumongousWithInCSetFastTestClosure()
2578   : _total_humongous(0),
2579     _candidate_humongous(0),
2580     _dcq(&G1BarrierSet::dirty_card_queue_set()) {
2581   }
2582 
2583   virtual bool do_heap_region(HeapRegion* r) {
2584     if (!r->is_starts_humongous()) {
2585       return false;
2586     }
2587     G1CollectedHeap* g1h = G1CollectedHeap::heap();
2588 
2589     bool is_candidate = humongous_region_is_candidate(g1h, r);
2590     uint rindex = r->hrm_index();
2591     g1h->set_humongous_reclaim_candidate(rindex, is_candidate);
2592     if (is_candidate) {
2593       _candidate_humongous++;
2594       g1h->register_humongous_region_with_cset(rindex);
2595       // Is_candidate already filters out humongous object with large remembered sets.
2596       // If we have a humongous object with a few remembered sets, we simply flush these
2597       // remembered set entries into the DCQS. That will result in automatic
2598       // re-evaluation of their remembered set entries during the following evacuation
2599       // phase.
2600       if (!r->rem_set()->is_empty()) {
2601         guarantee(r->rem_set()->occupancy_less_or_equal_than(G1RSetSparseRegionEntries),
2602                   "Found a not-small remembered set here. This is inconsistent with previous assumptions.");
2603         G1CardTable* ct = g1h->card_table();
2604         HeapRegionRemSetIterator hrrs(r->rem_set());
2605         size_t card_index;
2606         while (hrrs.has_next(card_index)) {
2607           jbyte* card_ptr = (jbyte*)ct->byte_for_index(card_index);
2608           // The remembered set might contain references to already freed
2609           // regions. Filter out such entries to avoid failing card table
2610           // verification.
2611           if (g1h->is_in_closed_subset(ct->addr_for(card_ptr))) {
2612             if (*card_ptr != G1CardTable::dirty_card_val()) {
2613               *card_ptr = G1CardTable::dirty_card_val();
2614               _dcq.enqueue(card_ptr);
2615             }
2616           }
2617         }
2618         assert(hrrs.n_yielded() == r->rem_set()->occupied(),
2619                "Remembered set hash maps out of sync, cur: " SIZE_FORMAT " entries, next: " SIZE_FORMAT " entries",
2620                hrrs.n_yielded(), r->rem_set()->occupied());
2621         // We should only clear the card based remembered set here as we will not
2622         // implicitly rebuild anything else during eager reclaim. Note that at the moment
2623         // (and probably never) we do not enter this path if there are other kind of
2624         // remembered sets for this region.
2625         r->rem_set()->clear_locked(true /* only_cardset */);
2626         // Clear_locked() above sets the state to Empty. However we want to continue
2627         // collecting remembered set entries for humongous regions that were not
2628         // reclaimed.
2629         r->rem_set()->set_state_complete();
2630       }
2631       assert(r->rem_set()->is_empty(), "At this point any humongous candidate remembered set must be empty.");
2632     }
2633     _total_humongous++;
2634 
2635     return false;
2636   }
2637 
2638   size_t total_humongous() const { return _total_humongous; }
2639   size_t candidate_humongous() const { return _candidate_humongous; }
2640 
2641   void flush_rem_set_entries() { _dcq.flush(); }
2642 };
2643 
2644 void G1CollectedHeap::register_humongous_regions_with_cset() {
2645   if (!G1EagerReclaimHumongousObjects) {
2646     g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(0.0, 0, 0);
2647     return;
2648   }
2649   double time = os::elapsed_counter();
2650 
2651   // Collect reclaim candidate information and register candidates with cset.
2652   RegisterHumongousWithInCSetFastTestClosure cl;
2653   heap_region_iterate(&cl);
2654 
2655   time = ((double)(os::elapsed_counter() - time) / os::elapsed_frequency()) * 1000.0;
2656   g1_policy()->phase_times()->record_fast_reclaim_humongous_stats(time,
2657                                                                   cl.total_humongous(),
2658                                                                   cl.candidate_humongous());
2659   _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
2660 
2661   // Finally flush all remembered set entries to re-check into the global DCQS.
2662   cl.flush_rem_set_entries();
2663 }
2664 
2665 class VerifyRegionRemSetClosure : public HeapRegionClosure {
2666   public:
2667     bool do_heap_region(HeapRegion* hr) {
2668       if (!hr->is_archive() && !hr->is_continues_humongous()) {
2669         hr->verify_rem_set();
2670       }
2671       return false;
2672     }
2673 };
2674 
2675 uint G1CollectedHeap::num_task_queues() const {
2676   return _task_queues->size();
2677 }
2678 
2679 #if TASKQUEUE_STATS
2680 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
2681   st->print_raw_cr("GC Task Stats");
2682   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
2683   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
2684 }
2685 
2686 void G1CollectedHeap::print_taskqueue_stats() const {
2687   if (!log_is_enabled(Trace, gc, task, stats)) {
2688     return;
2689   }
2690   Log(gc, task, stats) log;
2691   ResourceMark rm;
2692   LogStream ls(log.trace());
2693   outputStream* st = &ls;
2694 
2695   print_taskqueue_stats_hdr(st);
2696 
2697   TaskQueueStats totals;
2698   const uint n = num_task_queues();
2699   for (uint i = 0; i < n; ++i) {
2700     st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
2701     totals += task_queue(i)->stats;
2702   }
2703   st->print_raw("tot "); totals.print(st); st->cr();
2704 
2705   DEBUG_ONLY(totals.verify());
2706 }
2707 
2708 void G1CollectedHeap::reset_taskqueue_stats() {
2709   const uint n = num_task_queues();
2710   for (uint i = 0; i < n; ++i) {
2711     task_queue(i)->stats.reset();
2712   }
2713 }
2714 #endif // TASKQUEUE_STATS
2715 
2716 void G1CollectedHeap::wait_for_root_region_scanning() {
2717   double scan_wait_start = os::elapsedTime();
2718   // We have to wait until the CM threads finish scanning the
2719   // root regions as it's the only way to ensure that all the
2720   // objects on them have been correctly scanned before we start
2721   // moving them during the GC.
2722   bool waited = _cm->root_regions()->wait_until_scan_finished();
2723   double wait_time_ms = 0.0;
2724   if (waited) {
2725     double scan_wait_end = os::elapsedTime();
2726     wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
2727   }
2728   g1_policy()->phase_times()->record_root_region_scan_wait_time(wait_time_ms);
2729 }
2730 
2731 class G1PrintCollectionSetClosure : public HeapRegionClosure {
2732 private:
2733   G1HRPrinter* _hr_printer;
2734 public:
2735   G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { }
2736 
2737   virtual bool do_heap_region(HeapRegion* r) {
2738     _hr_printer->cset(r);
2739     return false;
2740   }
2741 };
2742 
2743 void G1CollectedHeap::start_new_collection_set() {
2744   collection_set()->start_incremental_building();
2745 
2746   clear_cset_fast_test();
2747 
2748   guarantee(_eden.length() == 0, "eden should have been cleared");
2749   g1_policy()->transfer_survivors_to_cset(survivor());
2750 }
2751 
2752 bool
2753 G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
2754   assert_at_safepoint_on_vm_thread();
2755   guarantee(!is_gc_active(), "collection is not reentrant");
2756 
2757   if (GCLocker::check_active_before_gc()) {
2758     return false;
2759   }
2760 
2761   _gc_timer_stw->register_gc_start();
2762 
2763   GCIdMark gc_id_mark;
2764   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
2765 
2766   SvcGCMarker sgcm(SvcGCMarker::MINOR);
2767   ResourceMark rm;
2768 
2769   g1_policy()->note_gc_start();
2770 
2771   wait_for_root_region_scanning();
2772 
2773   print_heap_before_gc();
2774   print_heap_regions();
2775   trace_heap_before_gc(_gc_tracer_stw);
2776 
2777   _verifier->verify_region_sets_optional();
2778   _verifier->verify_dirty_young_regions();
2779 
2780   // We should not be doing initial mark unless the conc mark thread is running
2781   if (!_cm_thread->should_terminate()) {
2782     // This call will decide whether this pause is an initial-mark
2783     // pause. If it is, in_initial_mark_gc() will return true
2784     // for the duration of this pause.
2785     g1_policy()->decide_on_conc_mark_initiation();
2786   }
2787 
2788   // We do not allow initial-mark to be piggy-backed on a mixed GC.
2789   assert(!collector_state()->in_initial_mark_gc() ||
2790           collector_state()->in_young_only_phase(), "sanity");
2791 
2792   // We also do not allow mixed GCs during marking.
2793   assert(!collector_state()->mark_or_rebuild_in_progress() || collector_state()->in_young_only_phase(), "sanity");
2794 
2795   // Record whether this pause is an initial mark. When the current
2796   // thread has completed its logging output and it's safe to signal
2797   // the CM thread, the flag's value in the policy has been reset.
2798   bool should_start_conc_mark = collector_state()->in_initial_mark_gc();
2799 
2800   // Inner scope for scope based logging, timers, and stats collection
2801   {
2802     EvacuationInfo evacuation_info;
2803 
2804     if (collector_state()->in_initial_mark_gc()) {
2805       // We are about to start a marking cycle, so we increment the
2806       // full collection counter.
2807       increment_old_marking_cycles_started();
2808       _cm->gc_tracer_cm()->set_gc_cause(gc_cause());
2809     }
2810 
2811     _gc_tracer_stw->report_yc_type(collector_state()->yc_type());
2812 
2813     GCTraceCPUTime tcpu;
2814 
2815     G1HeapVerifier::G1VerifyType verify_type;
2816     FormatBuffer<> gc_string("Pause Young ");
2817     if (collector_state()->in_initial_mark_gc()) {
2818       gc_string.append("(Concurrent Start)");
2819       verify_type = G1HeapVerifier::G1VerifyConcurrentStart;
2820     } else if (collector_state()->in_young_only_phase()) {
2821       if (collector_state()->in_young_gc_before_mixed()) {
2822         gc_string.append("(Prepare Mixed)");
2823       } else {
2824         gc_string.append("(Normal)");
2825       }
2826       verify_type = G1HeapVerifier::G1VerifyYoungNormal;
2827     } else {
2828       gc_string.append("(Mixed)");
2829       verify_type = G1HeapVerifier::G1VerifyMixed;
2830     }
2831     GCTraceTime(Info, gc) tm(gc_string, NULL, gc_cause(), true);
2832 
2833     uint active_workers = AdaptiveSizePolicy::calc_active_workers(workers()->total_workers(),
2834                                                                   workers()->active_workers(),
2835                                                                   Threads::number_of_non_daemon_threads());
2836     active_workers = workers()->update_active_workers(active_workers);
2837     log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers());
2838 
2839     TraceCollectorStats tcs(g1mm()->incremental_collection_counters());
2840     TraceMemoryManagerStats tms(&_memory_manager, gc_cause(),
2841                                 collector_state()->yc_type() == Mixed /* allMemoryPoolsAffected */);
2842 
2843     G1HeapTransition heap_transition(this);
2844     size_t heap_used_bytes_before_gc = used();
2845 
2846     // Don't dynamically change the number of GC threads this early.  A value of
2847     // 0 is used to indicate serial work.  When parallel work is done,
2848     // it will be set.
2849 
2850     { // Call to jvmpi::post_class_unload_events must occur outside of active GC
2851       IsGCActiveMark x;
2852 
2853       gc_prologue(false);
2854 
2855       if (VerifyRememberedSets) {
2856         log_info(gc, verify)("[Verifying RemSets before GC]");
2857         VerifyRegionRemSetClosure v_cl;
2858         heap_region_iterate(&v_cl);
2859       }
2860 
2861       _verifier->verify_before_gc(verify_type);
2862 
2863       _verifier->check_bitmaps("GC Start");
2864 
2865 #if COMPILER2_OR_JVMCI
2866       DerivedPointerTable::clear();
2867 #endif
2868 
2869       // Please see comment in g1CollectedHeap.hpp and
2870       // G1CollectedHeap::ref_processing_init() to see how
2871       // reference processing currently works in G1.
2872 
2873       // Enable discovery in the STW reference processor
2874       _ref_processor_stw->enable_discovery();
2875 
2876       {
2877         // We want to temporarily turn off discovery by the
2878         // CM ref processor, if necessary, and turn it back on
2879         // on again later if we do. Using a scoped
2880         // NoRefDiscovery object will do this.
2881         NoRefDiscovery no_cm_discovery(_ref_processor_cm);
2882 
2883         // Forget the current alloc region (we might even choose it to be part
2884         // of the collection set!).
2885         _allocator->release_mutator_alloc_region();
2886 
2887         // This timing is only used by the ergonomics to handle our pause target.
2888         // It is unclear why this should not include the full pause. We will
2889         // investigate this in CR 7178365.
2890         //
2891         // Preserving the old comment here if that helps the investigation:
2892         //
2893         // The elapsed time induced by the start time below deliberately elides
2894         // the possible verification above.
2895         double sample_start_time_sec = os::elapsedTime();
2896 
2897         g1_policy()->record_collection_pause_start(sample_start_time_sec);
2898 
2899         if (collector_state()->in_initial_mark_gc()) {
2900           concurrent_mark()->pre_initial_mark();
2901         }
2902 
2903         g1_policy()->finalize_collection_set(target_pause_time_ms, &_survivor);
2904 
2905         evacuation_info.set_collectionset_regions(collection_set()->region_length());
2906 
2907         // Make sure the remembered sets are up to date. This needs to be
2908         // done before register_humongous_regions_with_cset(), because the
2909         // remembered sets are used there to choose eager reclaim candidates.
2910         // If the remembered sets are not up to date we might miss some
2911         // entries that need to be handled.
2912         g1_rem_set()->cleanupHRRS();
2913 
2914         register_humongous_regions_with_cset();
2915 
2916         assert(_verifier->check_cset_fast_test(), "Inconsistency in the InCSetState table.");
2917 
2918         // We call this after finalize_cset() to
2919         // ensure that the CSet has been finalized.
2920         _cm->verify_no_cset_oops();
2921 
2922         if (_hr_printer.is_active()) {
2923           G1PrintCollectionSetClosure cl(&_hr_printer);
2924           _collection_set.iterate(&cl);
2925         }
2926 
2927         // Initialize the GC alloc regions.
2928         _allocator->init_gc_alloc_regions(evacuation_info);
2929 
2930         G1ParScanThreadStateSet per_thread_states(this, workers()->active_workers(), collection_set()->young_region_length());
2931         pre_evacuate_collection_set();
2932 
2933         // Actually do the work...
2934         evacuate_collection_set(&per_thread_states);
2935 
2936         post_evacuate_collection_set(evacuation_info, &per_thread_states);
2937 
2938         const size_t* surviving_young_words = per_thread_states.surviving_young_words();
2939         free_collection_set(&_collection_set, evacuation_info, surviving_young_words);
2940 
2941         eagerly_reclaim_humongous_regions();
2942 
2943         record_obj_copy_mem_stats();
2944         _survivor_evac_stats.adjust_desired_plab_sz();
2945         _old_evac_stats.adjust_desired_plab_sz();
2946 
2947         double start = os::elapsedTime();
2948         start_new_collection_set();
2949         g1_policy()->phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0);
2950 
2951         if (evacuation_failed()) {
2952           set_used(recalculate_used());
2953           if (_archive_allocator != NULL) {
2954             _archive_allocator->clear_used();
2955           }
2956           for (uint i = 0; i < ParallelGCThreads; i++) {
2957             if (_evacuation_failed_info_array[i].has_failed()) {
2958               _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
2959             }
2960           }
2961         } else {
2962           // The "used" of the the collection set have already been subtracted
2963           // when they were freed.  Add in the bytes evacuated.
2964           increase_used(g1_policy()->bytes_copied_during_gc());
2965         }
2966 
2967         if (collector_state()->in_initial_mark_gc()) {
2968           // We have to do this before we notify the CM threads that
2969           // they can start working to make sure that all the
2970           // appropriate initialization is done on the CM object.
2971           concurrent_mark()->post_initial_mark();
2972           // Note that we don't actually trigger the CM thread at
2973           // this point. We do that later when we're sure that
2974           // the current thread has completed its logging output.
2975         }
2976 
2977         allocate_dummy_regions();
2978 
2979         _allocator->init_mutator_alloc_region();
2980 
2981         {
2982           size_t expand_bytes = _heap_sizing_policy->expansion_amount();
2983           if (expand_bytes > 0) {
2984             size_t bytes_before = capacity();
2985             // No need for an ergo logging here,
2986             // expansion_amount() does this when it returns a value > 0.
2987             double expand_ms;
2988             if (!expand(expand_bytes, _workers, &expand_ms)) {
2989               // We failed to expand the heap. Cannot do anything about it.
2990             }
2991             g1_policy()->phase_times()->record_expand_heap_time(expand_ms);
2992           }
2993         }
2994 
2995         // We redo the verification but now wrt to the new CSet which
2996         // has just got initialized after the previous CSet was freed.
2997         _cm->verify_no_cset_oops();
2998 
2999         // This timing is only used by the ergonomics to handle our pause target.
3000         // It is unclear why this should not include the full pause. We will
3001         // investigate this in CR 7178365.
3002         double sample_end_time_sec = os::elapsedTime();
3003         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3004         size_t total_cards_scanned = g1_policy()->phase_times()->sum_thread_work_items(G1GCPhaseTimes::ScanRS, G1GCPhaseTimes::ScanRSScannedCards);
3005         g1_policy()->record_collection_pause_end(pause_time_ms, total_cards_scanned, heap_used_bytes_before_gc);
3006 
3007         evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before());
3008         evacuation_info.set_bytes_copied(g1_policy()->bytes_copied_during_gc());
3009 
3010         if (VerifyRememberedSets) {
3011           log_info(gc, verify)("[Verifying RemSets after GC]");
3012           VerifyRegionRemSetClosure v_cl;
3013           heap_region_iterate(&v_cl);
3014         }
3015 
3016         _verifier->verify_after_gc(verify_type);
3017         _verifier->check_bitmaps("GC End");
3018 
3019         assert(!_ref_processor_stw->discovery_enabled(), "Postcondition");
3020         _ref_processor_stw->verify_no_references_recorded();
3021 
3022         // CM reference discovery will be re-enabled if necessary.
3023       }
3024 
3025 #ifdef TRACESPINNING
3026       ParallelTaskTerminator::print_termination_counts();
3027 #endif
3028 
3029       gc_epilogue(false);
3030     }
3031 
3032     // Print the remainder of the GC log output.
3033     if (evacuation_failed()) {
3034       log_info(gc)("To-space exhausted");
3035     }
3036 
3037     g1_policy()->print_phases();
3038     heap_transition.print();
3039 
3040     // It is not yet to safe to tell the concurrent mark to
3041     // start as we have some optional output below. We don't want the
3042     // output from the concurrent mark thread interfering with this
3043     // logging output either.
3044 
3045     _hrm.verify_optional();
3046     _verifier->verify_region_sets_optional();
3047 
3048     TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
3049     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3050 
3051     print_heap_after_gc();
3052     print_heap_regions();
3053     trace_heap_after_gc(_gc_tracer_stw);
3054 
3055     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3056     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3057     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3058     // before any GC notifications are raised.
3059     g1mm()->update_sizes();
3060 
3061     _gc_tracer_stw->report_evacuation_info(&evacuation_info);
3062     _gc_tracer_stw->report_tenuring_threshold(_g1_policy->tenuring_threshold());
3063     _gc_timer_stw->register_gc_end();
3064     _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
3065   }
3066   // It should now be safe to tell the concurrent mark thread to start
3067   // without its logging output interfering with the logging output
3068   // that came from the pause.
3069 
3070   if (should_start_conc_mark) {
3071     // CAUTION: after the doConcurrentMark() call below,
3072     // the concurrent marking thread(s) could be running
3073     // concurrently with us. Make sure that anything after
3074     // this point does not assume that we are the only GC thread
3075     // running. Note: of course, the actual marking work will
3076     // not start until the safepoint itself is released in
3077     // SuspendibleThreadSet::desynchronize().
3078     do_concurrent_mark();
3079   }
3080 
3081   return true;
3082 }
3083 
3084 void G1CollectedHeap::remove_self_forwarding_pointers() {
3085   G1ParRemoveSelfForwardPtrsTask rsfp_task;
3086   workers()->run_task(&rsfp_task);
3087 }
3088 
3089 void G1CollectedHeap::restore_after_evac_failure() {
3090   double remove_self_forwards_start = os::elapsedTime();
3091 
3092   remove_self_forwarding_pointers();
3093   SharedRestorePreservedMarksTaskExecutor task_executor(workers());
3094   _preserved_marks_set.restore(&task_executor);
3095 
3096   g1_policy()->phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
3097 }
3098 
3099 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markOop m) {
3100   if (!_evacuation_failed) {
3101     _evacuation_failed = true;
3102   }
3103 
3104   _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size());
3105   _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m);
3106 }
3107 
3108 bool G1ParEvacuateFollowersClosure::offer_termination() {
3109   G1ParScanThreadState* const pss = par_scan_state();
3110   start_term_time();
3111   const bool res = terminator()->offer_termination();
3112   end_term_time();
3113   return res;
3114 }
3115 
3116 void G1ParEvacuateFollowersClosure::do_void() {
3117   G1ParScanThreadState* const pss = par_scan_state();
3118   pss->trim_queue();
3119   do {
3120     pss->steal_and_trim_queue(queues());
3121   } while (!offer_termination());
3122 }
3123 
3124 class G1ParTask : public AbstractGangTask {
3125 protected:
3126   G1CollectedHeap*         _g1h;
3127   G1ParScanThreadStateSet* _pss;
3128   RefToScanQueueSet*       _queues;
3129   G1RootProcessor*         _root_processor;
3130   ParallelTaskTerminator   _terminator;
3131   uint                     _n_workers;
3132 
3133 public:
3134   G1ParTask(G1CollectedHeap* g1h, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet *task_queues, G1RootProcessor* root_processor, uint n_workers)
3135     : AbstractGangTask("G1 collection"),
3136       _g1h(g1h),
3137       _pss(per_thread_states),
3138       _queues(task_queues),
3139       _root_processor(root_processor),
3140       _terminator(n_workers, _queues),
3141       _n_workers(n_workers)
3142   {}
3143 
3144   void work(uint worker_id) {
3145     if (worker_id >= _n_workers) return;  // no work needed this round
3146 
3147     double start_sec = os::elapsedTime();
3148     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, start_sec);
3149 
3150     {
3151       ResourceMark rm;
3152       HandleMark   hm;
3153 
3154       ReferenceProcessor*             rp = _g1h->ref_processor_stw();
3155 
3156       G1ParScanThreadState*           pss = _pss->state_for_worker(worker_id);
3157       pss->set_ref_discoverer(rp);
3158 
3159       double start_strong_roots_sec = os::elapsedTime();
3160 
3161       _root_processor->evacuate_roots(pss, worker_id);
3162 
3163       // We pass a weak code blobs closure to the remembered set scanning because we want to avoid
3164       // treating the nmethods visited to act as roots for concurrent marking.
3165       // We only want to make sure that the oops in the nmethods are adjusted with regard to the
3166       // objects copied by the current evacuation.
3167       _g1h->g1_rem_set()->oops_into_collection_set_do(pss, worker_id);
3168 
3169       double strong_roots_sec = os::elapsedTime() - start_strong_roots_sec;
3170 
3171       double term_sec = 0.0;
3172       size_t evac_term_attempts = 0;
3173       {
3174         double start = os::elapsedTime();
3175         G1ParEvacuateFollowersClosure evac(_g1h, pss, _queues, &_terminator);
3176         evac.do_void();
3177 
3178         evac_term_attempts = evac.term_attempts();
3179         term_sec = evac.term_time();
3180         double elapsed_sec = os::elapsedTime() - start;
3181 
3182         G1GCPhaseTimes* p = _g1h->g1_policy()->phase_times();
3183         p->add_time_secs(G1GCPhaseTimes::ObjCopy, worker_id, elapsed_sec - term_sec);
3184         p->record_time_secs(G1GCPhaseTimes::Termination, worker_id, term_sec);
3185         p->record_thread_work_item(G1GCPhaseTimes::Termination, worker_id, evac_term_attempts);
3186       }
3187 
3188       assert(pss->queue_is_empty(), "should be empty");
3189 
3190       if (log_is_enabled(Debug, gc, task, stats)) {
3191         MutexLockerEx x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
3192         size_t lab_waste;
3193         size_t lab_undo_waste;
3194         pss->waste(lab_waste, lab_undo_waste);
3195         _g1h->print_termination_stats(worker_id,
3196                                       (os::elapsedTime() - start_sec) * 1000.0,   /* elapsed time */
3197                                       strong_roots_sec * 1000.0,                  /* strong roots time */
3198                                       term_sec * 1000.0,                          /* evac term time */
3199                                       evac_term_attempts,                         /* evac term attempts */
3200                                       lab_waste,                                  /* alloc buffer waste */
3201                                       lab_undo_waste                              /* undo waste */
3202                                       );
3203       }
3204 
3205       // Close the inner scope so that the ResourceMark and HandleMark
3206       // destructors are executed here and are included as part of the
3207       // "GC Worker Time".
3208     }
3209     _g1h->g1_policy()->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, os::elapsedTime());
3210   }
3211 };
3212 
3213 void G1CollectedHeap::print_termination_stats_hdr() {
3214   log_debug(gc, task, stats)("GC Termination Stats");
3215   log_debug(gc, task, stats)("     elapsed  --strong roots-- -------termination------- ------waste (KiB)------");
3216   log_debug(gc, task, stats)("thr     ms        ms      %%        ms      %%    attempts  total   alloc    undo");
3217   log_debug(gc, task, stats)("--- --------- --------- ------ --------- ------ -------- ------- ------- -------");
3218 }
3219 
3220 void G1CollectedHeap::print_termination_stats(uint worker_id,
3221                                               double elapsed_ms,
3222                                               double strong_roots_ms,
3223                                               double term_ms,
3224                                               size_t term_attempts,
3225                                               size_t alloc_buffer_waste,
3226                                               size_t undo_waste) const {
3227   log_debug(gc, task, stats)
3228               ("%3d %9.2f %9.2f %6.2f "
3229                "%9.2f %6.2f " SIZE_FORMAT_W(8) " "
3230                SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7) " " SIZE_FORMAT_W(7),
3231                worker_id, elapsed_ms, strong_roots_ms, strong_roots_ms * 100 / elapsed_ms,
3232                term_ms, term_ms * 100 / elapsed_ms, term_attempts,
3233                (alloc_buffer_waste + undo_waste) * HeapWordSize / K,
3234                alloc_buffer_waste * HeapWordSize / K,
3235                undo_waste * HeapWordSize / K);
3236 }
3237 
3238 class G1StringAndSymbolCleaningTask : public AbstractGangTask {
3239 private:
3240   BoolObjectClosure* _is_alive;
3241   G1StringDedupUnlinkOrOopsDoClosure _dedup_closure;
3242   OopStorage::ParState<false /* concurrent */, false /* const */> _par_state_string;
3243 
3244   int _initial_string_table_size;
3245   int _initial_symbol_table_size;
3246 
3247   bool  _process_strings;
3248   int _strings_processed;
3249   int _strings_removed;
3250 
3251   bool  _process_symbols;
3252   int _symbols_processed;
3253   int _symbols_removed;
3254 
3255   bool _process_string_dedup;
3256 
3257 public:
3258   G1StringAndSymbolCleaningTask(BoolObjectClosure* is_alive, bool process_strings, bool process_symbols, bool process_string_dedup) :
3259     AbstractGangTask("String/Symbol Unlinking"),
3260     _is_alive(is_alive),
3261     _dedup_closure(is_alive, NULL, false),
3262     _par_state_string(StringTable::weak_storage()),
3263     _process_strings(process_strings), _strings_processed(0), _strings_removed(0),
3264     _process_symbols(process_symbols), _symbols_processed(0), _symbols_removed(0),
3265     _process_string_dedup(process_string_dedup) {
3266 
3267     _initial_string_table_size = (int) StringTable::the_table()->table_size();
3268     _initial_symbol_table_size = SymbolTable::the_table()->table_size();
3269     if (process_symbols) {
3270       SymbolTable::clear_parallel_claimed_index();
3271     }
3272     if (process_strings) {
3273       StringTable::reset_dead_counter();
3274     }
3275   }
3276 
3277   ~G1StringAndSymbolCleaningTask() {
3278     guarantee(!_process_symbols || SymbolTable::parallel_claimed_index() >= _initial_symbol_table_size,
3279               "claim value %d after unlink less than initial symbol table size %d",
3280               SymbolTable::parallel_claimed_index(), _initial_symbol_table_size);
3281 
3282     log_info(gc, stringtable)(
3283         "Cleaned string and symbol table, "
3284         "strings: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed, "
3285         "symbols: " SIZE_FORMAT " processed, " SIZE_FORMAT " removed",
3286         strings_processed(), strings_removed(),
3287         symbols_processed(), symbols_removed());
3288     if (_process_strings) {
3289       StringTable::finish_dead_counter();
3290     }
3291   }
3292 
3293   void work(uint worker_id) {
3294     int strings_processed = 0;
3295     int strings_removed = 0;
3296     int symbols_processed = 0;
3297     int symbols_removed = 0;
3298     if (_process_strings) {
3299       StringTable::possibly_parallel_unlink(&_par_state_string, _is_alive, &strings_processed, &strings_removed);
3300       Atomic::add(strings_processed, &_strings_processed);
3301       Atomic::add(strings_removed, &_strings_removed);
3302     }
3303     if (_process_symbols) {
3304       SymbolTable::possibly_parallel_unlink(&symbols_processed, &symbols_removed);
3305       Atomic::add(symbols_processed, &_symbols_processed);
3306       Atomic::add(symbols_removed, &_symbols_removed);
3307     }
3308     if (_process_string_dedup) {
3309       G1StringDedup::parallel_unlink(&_dedup_closure, worker_id);
3310     }
3311   }
3312 
3313   size_t strings_processed() const { return (size_t)_strings_processed; }
3314   size_t strings_removed()   const { return (size_t)_strings_removed; }
3315 
3316   size_t symbols_processed() const { return (size_t)_symbols_processed; }
3317   size_t symbols_removed()   const { return (size_t)_symbols_removed; }
3318 };
3319 
3320 class G1CodeCacheUnloadingTask {
3321 private:
3322   static Monitor* _lock;
3323 
3324   BoolObjectClosure* const _is_alive;
3325   const bool               _unloading_occurred;
3326   const uint               _num_workers;
3327 
3328   // Variables used to claim nmethods.
3329   CompiledMethod* _first_nmethod;
3330   CompiledMethod* volatile _claimed_nmethod;
3331 
3332   // The list of nmethods that need to be processed by the second pass.
3333   CompiledMethod* volatile _postponed_list;
3334   volatile uint            _num_entered_barrier;
3335 
3336  public:
3337   G1CodeCacheUnloadingTask(uint num_workers, BoolObjectClosure* is_alive, bool unloading_occurred) :
3338       _is_alive(is_alive),
3339       _unloading_occurred(unloading_occurred),
3340       _num_workers(num_workers),
3341       _first_nmethod(NULL),
3342       _claimed_nmethod(NULL),
3343       _postponed_list(NULL),
3344       _num_entered_barrier(0)
3345   {
3346     CompiledMethod::increase_unloading_clock();
3347     // Get first alive nmethod
3348     CompiledMethodIterator iter = CompiledMethodIterator();
3349     if(iter.next_alive()) {
3350       _first_nmethod = iter.method();
3351     }
3352     _claimed_nmethod = _first_nmethod;
3353   }
3354 
3355   ~G1CodeCacheUnloadingTask() {
3356     CodeCache::verify_clean_inline_caches();
3357 
3358     CodeCache::set_needs_cache_clean(false);
3359     guarantee(CodeCache::scavenge_root_nmethods() == NULL, "Must be");
3360 
3361     CodeCache::verify_icholder_relocations();
3362   }
3363 
3364  private:
3365   void add_to_postponed_list(CompiledMethod* nm) {
3366       CompiledMethod* old;
3367       do {
3368         old = _postponed_list;
3369         nm->set_unloading_next(old);
3370       } while (Atomic::cmpxchg(nm, &_postponed_list, old) != old);
3371   }
3372 
3373   void clean_nmethod(CompiledMethod* nm) {
3374     bool postponed = nm->do_unloading_parallel(_is_alive, _unloading_occurred);
3375 
3376     if (postponed) {
3377       // This nmethod referred to an nmethod that has not been cleaned/unloaded yet.
3378       add_to_postponed_list(nm);
3379     }
3380 
3381     // Mark that this nmethod has been cleaned/unloaded.
3382     // After this call, it will be safe to ask if this nmethod was unloaded or not.
3383     nm->set_unloading_clock(CompiledMethod::global_unloading_clock());
3384   }
3385 
3386   void clean_nmethod_postponed(CompiledMethod* nm) {
3387     nm->do_unloading_parallel_postponed();
3388   }
3389 
3390   static const int MaxClaimNmethods = 16;
3391 
3392   void claim_nmethods(CompiledMethod** claimed_nmethods, int *num_claimed_nmethods) {
3393     CompiledMethod* first;
3394     CompiledMethodIterator last;
3395 
3396     do {
3397       *num_claimed_nmethods = 0;
3398 
3399       first = _claimed_nmethod;
3400       last = CompiledMethodIterator(first);
3401 
3402       if (first != NULL) {
3403 
3404         for (int i = 0; i < MaxClaimNmethods; i++) {
3405           if (!last.next_alive()) {
3406             break;
3407           }
3408           claimed_nmethods[i] = last.method();
3409           (*num_claimed_nmethods)++;
3410         }
3411       }
3412 
3413     } while (Atomic::cmpxchg(last.method(), &_claimed_nmethod, first) != first);
3414   }
3415 
3416   CompiledMethod* claim_postponed_nmethod() {
3417     CompiledMethod* claim;
3418     CompiledMethod* next;
3419 
3420     do {
3421       claim = _postponed_list;
3422       if (claim == NULL) {
3423         return NULL;
3424       }
3425 
3426       next = claim->unloading_next();
3427 
3428     } while (Atomic::cmpxchg(next, &_postponed_list, claim) != claim);
3429 
3430     return claim;
3431   }
3432 
3433  public:
3434   // Mark that we're done with the first pass of nmethod cleaning.
3435   void barrier_mark(uint worker_id) {
3436     MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3437     _num_entered_barrier++;
3438     if (_num_entered_barrier == _num_workers) {
3439       ml.notify_all();
3440     }
3441   }
3442 
3443   // See if we have to wait for the other workers to
3444   // finish their first-pass nmethod cleaning work.
3445   void barrier_wait(uint worker_id) {
3446     if (_num_entered_barrier < _num_workers) {
3447       MonitorLockerEx ml(_lock, Mutex::_no_safepoint_check_flag);
3448       while (_num_entered_barrier < _num_workers) {
3449           ml.wait(Mutex::_no_safepoint_check_flag, 0, false);
3450       }
3451     }
3452   }
3453 
3454   // Cleaning and unloading of nmethods. Some work has to be postponed
3455   // to the second pass, when we know which nmethods survive.
3456   void work_first_pass(uint worker_id) {
3457     // The first nmethods is claimed by the first worker.
3458     if (worker_id == 0 && _first_nmethod != NULL) {
3459       clean_nmethod(_first_nmethod);
3460       _first_nmethod = NULL;
3461     }
3462 
3463     int num_claimed_nmethods;
3464     CompiledMethod* claimed_nmethods[MaxClaimNmethods];
3465 
3466     while (true) {
3467       claim_nmethods(claimed_nmethods, &num_claimed_nmethods);
3468 
3469       if (num_claimed_nmethods == 0) {
3470         break;
3471       }
3472 
3473       for (int i = 0; i < num_claimed_nmethods; i++) {
3474         clean_nmethod(claimed_nmethods[i]);
3475       }
3476     }
3477   }
3478 
3479   void work_second_pass(uint worker_id) {
3480     CompiledMethod* nm;
3481     // Take care of postponed nmethods.
3482     while ((nm = claim_postponed_nmethod()) != NULL) {
3483       clean_nmethod_postponed(nm);
3484     }
3485   }
3486 };
3487 
3488 Monitor* G1CodeCacheUnloadingTask::_lock = new Monitor(Mutex::leaf, "Code Cache Unload lock", false, Monitor::_safepoint_check_never);
3489 
3490 class G1KlassCleaningTask : public StackObj {
3491   volatile int                            _clean_klass_tree_claimed;
3492   ClassLoaderDataGraphKlassIteratorAtomic _klass_iterator;
3493 
3494  public:
3495   G1KlassCleaningTask() :
3496       _clean_klass_tree_claimed(0),
3497       _klass_iterator() {
3498   }
3499 
3500  private:
3501   bool claim_clean_klass_tree_task() {
3502     if (_clean_klass_tree_claimed) {
3503       return false;
3504     }
3505 
3506     return Atomic::cmpxchg(1, &_clean_klass_tree_claimed, 0) == 0;
3507   }
3508 
3509   InstanceKlass* claim_next_klass() {
3510     Klass* klass;
3511     do {
3512       klass =_klass_iterator.next_klass();
3513     } while (klass != NULL && !klass->is_instance_klass());
3514 
3515     // this can be null so don't call InstanceKlass::cast
3516     return static_cast<InstanceKlass*>(klass);
3517   }
3518 
3519 public:
3520 
3521   void clean_klass(InstanceKlass* ik) {
3522     ik->clean_weak_instanceklass_links();
3523   }
3524 
3525   void work() {
3526     ResourceMark rm;
3527 
3528     // One worker will clean the subklass/sibling klass tree.
3529     if (claim_clean_klass_tree_task()) {
3530       Klass::clean_subklass_tree();
3531     }
3532 
3533     // All workers will help cleaning the classes,
3534     InstanceKlass* klass;
3535     while ((klass = claim_next_klass()) != NULL) {
3536       clean_klass(klass);
3537     }
3538   }
3539 };
3540 
3541 class G1ResolvedMethodCleaningTask : public StackObj {
3542   volatile int       _resolved_method_task_claimed;
3543 public:
3544   G1ResolvedMethodCleaningTask() :
3545       _resolved_method_task_claimed(0) {}
3546 
3547   bool claim_resolved_method_task() {
3548     if (_resolved_method_task_claimed) {
3549       return false;
3550     }
3551     return Atomic::cmpxchg(1, &_resolved_method_task_claimed, 0) == 0;
3552   }
3553 
3554   // These aren't big, one thread can do it all.
3555   void work() {
3556     if (claim_resolved_method_task()) {
3557       ResolvedMethodTable::unlink();
3558     }
3559   }
3560 };
3561 
3562 
3563 // To minimize the remark pause times, the tasks below are done in parallel.
3564 class G1ParallelCleaningTask : public AbstractGangTask {
3565 private:
3566   bool                          _unloading_occurred;
3567   G1StringAndSymbolCleaningTask _string_symbol_task;
3568   G1CodeCacheUnloadingTask      _code_cache_task;
3569   G1KlassCleaningTask           _klass_cleaning_task;
3570   G1ResolvedMethodCleaningTask  _resolved_method_cleaning_task;
3571 
3572 public:
3573   // The constructor is run in the VMThread.
3574   G1ParallelCleaningTask(BoolObjectClosure* is_alive, uint num_workers, bool unloading_occurred) :
3575       AbstractGangTask("Parallel Cleaning"),
3576       _string_symbol_task(is_alive, true, true, G1StringDedup::is_enabled()),
3577       _code_cache_task(num_workers, is_alive, unloading_occurred),
3578       _klass_cleaning_task(),
3579       _unloading_occurred(unloading_occurred),
3580       _resolved_method_cleaning_task() {
3581   }
3582 
3583   // The parallel work done by all worker threads.
3584   void work(uint worker_id) {
3585     // Do first pass of code cache cleaning.
3586     _code_cache_task.work_first_pass(worker_id);
3587 
3588     // Let the threads mark that the first pass is done.
3589     _code_cache_task.barrier_mark(worker_id);
3590 
3591     // Clean the Strings and Symbols.
3592     _string_symbol_task.work(worker_id);
3593 
3594     // Clean unreferenced things in the ResolvedMethodTable
3595     _resolved_method_cleaning_task.work();
3596 
3597     // Wait for all workers to finish the first code cache cleaning pass.
3598     _code_cache_task.barrier_wait(worker_id);
3599 
3600     // Do the second code cache cleaning work, which realize on
3601     // the liveness information gathered during the first pass.
3602     _code_cache_task.work_second_pass(worker_id);
3603 
3604     // Clean all klasses that were not unloaded.
3605     // The weak metadata in klass doesn't need to be
3606     // processed if there was no unloading.
3607     if (_unloading_occurred) {
3608       _klass_cleaning_task.work();
3609     }
3610   }
3611 };
3612 
3613 
3614 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive,
3615                                         bool class_unloading_occurred) {
3616   uint n_workers = workers()->active_workers();
3617 
3618   G1ParallelCleaningTask g1_unlink_task(is_alive, n_workers, class_unloading_occurred);
3619   workers()->run_task(&g1_unlink_task);
3620 }
3621 
3622 void G1CollectedHeap::partial_cleaning(BoolObjectClosure* is_alive,
3623                                        bool process_strings,
3624                                        bool process_symbols,
3625                                        bool process_string_dedup) {
3626   if (!process_strings && !process_symbols && !process_string_dedup) {
3627     // Nothing to clean.
3628     return;
3629   }
3630 
3631   G1StringAndSymbolCleaningTask g1_unlink_task(is_alive, process_strings, process_symbols, process_string_dedup);
3632   workers()->run_task(&g1_unlink_task);
3633 
3634 }
3635 
3636 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
3637  private:
3638   DirtyCardQueueSet* _queue;
3639   G1CollectedHeap* _g1h;
3640  public:
3641   G1RedirtyLoggedCardsTask(DirtyCardQueueSet* queue, G1CollectedHeap* g1h) : AbstractGangTask("Redirty Cards"),
3642     _queue(queue), _g1h(g1h) { }
3643 
3644   virtual void work(uint worker_id) {
3645     G1GCPhaseTimes* phase_times = _g1h->g1_policy()->phase_times();
3646     G1GCParPhaseTimesTracker x(phase_times, G1GCPhaseTimes::RedirtyCards, worker_id);
3647 
3648     RedirtyLoggedCardTableEntryClosure cl(_g1h);
3649     _queue->par_apply_closure_to_all_completed_buffers(&cl);
3650 
3651     phase_times->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied());
3652   }
3653 };
3654 
3655 void G1CollectedHeap::redirty_logged_cards() {
3656   double redirty_logged_cards_start = os::elapsedTime();
3657 
3658   G1RedirtyLoggedCardsTask redirty_task(&dirty_card_queue_set(), this);
3659   dirty_card_queue_set().reset_for_par_iteration();
3660   workers()->run_task(&redirty_task);
3661 
3662   DirtyCardQueueSet& dcq = G1BarrierSet::dirty_card_queue_set();
3663   dcq.merge_bufferlists(&dirty_card_queue_set());
3664   assert(dirty_card_queue_set().completed_buffers_num() == 0, "All should be consumed");
3665 
3666   g1_policy()->phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
3667 }
3668 
3669 // Weak Reference Processing support
3670 
3671 bool G1STWIsAliveClosure::do_object_b(oop p) {
3672   // An object is reachable if it is outside the collection set,
3673   // or is inside and copied.
3674   return !_g1h->is_in_cset(p) || p->is_forwarded();
3675 }
3676 
3677 bool G1STWSubjectToDiscoveryClosure::do_object_b(oop obj) {
3678   assert(obj != NULL, "must not be NULL");
3679   assert(_g1h->is_in_reserved(obj), "Trying to discover obj " PTR_FORMAT " not in heap", p2i(obj));
3680   // The areas the CM and STW ref processor manage must be disjoint. The is_in_cset() below
3681   // may falsely indicate that this is not the case here: however the collection set only
3682   // contains old regions when concurrent mark is not running.
3683   return _g1h->is_in_cset(obj) || _g1h->heap_region_containing(obj)->is_survivor();
3684 }
3685 
3686 // Non Copying Keep Alive closure
3687 class G1KeepAliveClosure: public OopClosure {
3688   G1CollectedHeap*_g1h;
3689 public:
3690   G1KeepAliveClosure(G1CollectedHeap* g1h) :_g1h(g1h) {}
3691   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
3692   void do_oop(oop* p) {
3693     oop obj = *p;
3694     assert(obj != NULL, "the caller should have filtered out NULL values");
3695 
3696     const InCSetState cset_state =_g1h->in_cset_state(obj);
3697     if (!cset_state.is_in_cset_or_humongous()) {
3698       return;
3699     }
3700     if (cset_state.is_in_cset()) {
3701       assert( obj->is_forwarded(), "invariant" );
3702       *p = obj->forwardee();
3703     } else {
3704       assert(!obj->is_forwarded(), "invariant" );
3705       assert(cset_state.is_humongous(),
3706              "Only allowed InCSet state is IsHumongous, but is %d", cset_state.value());
3707      _g1h->set_humongous_is_live(obj);
3708     }
3709   }
3710 };
3711 
3712 // Copying Keep Alive closure - can be called from both
3713 // serial and parallel code as long as different worker
3714 // threads utilize different G1ParScanThreadState instances
3715 // and different queues.
3716 
3717 class G1CopyingKeepAliveClosure: public OopClosure {
3718   G1CollectedHeap*         _g1h;
3719   OopClosure*              _copy_non_heap_obj_cl;
3720   G1ParScanThreadState*    _par_scan_state;
3721 
3722 public:
3723   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
3724                             OopClosure* non_heap_obj_cl,
3725                             G1ParScanThreadState* pss):
3726     _g1h(g1h),
3727     _copy_non_heap_obj_cl(non_heap_obj_cl),
3728     _par_scan_state(pss)
3729   {}
3730 
3731   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
3732   virtual void do_oop(      oop* p) { do_oop_work(p); }
3733 
3734   template <class T> void do_oop_work(T* p) {
3735     oop obj = RawAccess<>::oop_load(p);
3736 
3737     if (_g1h->is_in_cset_or_humongous(obj)) {
3738       // If the referent object has been forwarded (either copied
3739       // to a new location or to itself in the event of an
3740       // evacuation failure) then we need to update the reference
3741       // field and, if both reference and referent are in the G1
3742       // heap, update the RSet for the referent.
3743       //
3744       // If the referent has not been forwarded then we have to keep
3745       // it alive by policy. Therefore we have copy the referent.
3746       //
3747       // If the reference field is in the G1 heap then we can push
3748       // on the PSS queue. When the queue is drained (after each
3749       // phase of reference processing) the object and it's followers
3750       // will be copied, the reference field set to point to the
3751       // new location, and the RSet updated. Otherwise we need to
3752       // use the the non-heap or metadata closures directly to copy
3753       // the referent object and update the pointer, while avoiding
3754       // updating the RSet.
3755 
3756       if (_g1h->is_in_g1_reserved(p)) {
3757         _par_scan_state->push_on_queue(p);
3758       } else {
3759         assert(!Metaspace::contains((const void*)p),
3760                "Unexpectedly found a pointer from metadata: " PTR_FORMAT, p2i(p));
3761         _copy_non_heap_obj_cl->do_oop(p);
3762       }
3763     }
3764   }
3765 };
3766 
3767 // Serial drain queue closure. Called as the 'complete_gc'
3768 // closure for each discovered list in some of the
3769 // reference processing phases.
3770 
3771 class G1STWDrainQueueClosure: public VoidClosure {
3772 protected:
3773   G1CollectedHeap* _g1h;
3774   G1ParScanThreadState* _par_scan_state;
3775 
3776   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
3777 
3778 public:
3779   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
3780     _g1h(g1h),
3781     _par_scan_state(pss)
3782   { }
3783 
3784   void do_void() {
3785     G1ParScanThreadState* const pss = par_scan_state();
3786     pss->trim_queue();
3787   }
3788 };
3789 
3790 // Parallel Reference Processing closures
3791 
3792 // Implementation of AbstractRefProcTaskExecutor for parallel reference
3793 // processing during G1 evacuation pauses.
3794 
3795 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
3796 private:
3797   G1CollectedHeap*          _g1h;
3798   G1ParScanThreadStateSet*  _pss;
3799   RefToScanQueueSet*        _queues;
3800   WorkGang*                 _workers;
3801 
3802 public:
3803   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
3804                            G1ParScanThreadStateSet* per_thread_states,
3805                            WorkGang* workers,
3806                            RefToScanQueueSet *task_queues) :
3807     _g1h(g1h),
3808     _pss(per_thread_states),
3809     _queues(task_queues),
3810     _workers(workers)
3811   {
3812     g1h->ref_processor_stw()->set_active_mt_degree(workers->active_workers());
3813   }
3814 
3815   // Executes the given task using concurrent marking worker threads.
3816   virtual void execute(ProcessTask& task, uint ergo_workers);
3817 };
3818 
3819 // Gang task for possibly parallel reference processing
3820 
3821 class G1STWRefProcTaskProxy: public AbstractGangTask {
3822   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
3823   ProcessTask&     _proc_task;
3824   G1CollectedHeap* _g1h;
3825   G1ParScanThreadStateSet* _pss;
3826   RefToScanQueueSet* _task_queues;
3827   ParallelTaskTerminator* _terminator;
3828 
3829 public:
3830   G1STWRefProcTaskProxy(ProcessTask& proc_task,
3831                         G1CollectedHeap* g1h,
3832                         G1ParScanThreadStateSet* per_thread_states,
3833                         RefToScanQueueSet *task_queues,
3834                         ParallelTaskTerminator* terminator) :
3835     AbstractGangTask("Process reference objects in parallel"),
3836     _proc_task(proc_task),
3837     _g1h(g1h),
3838     _pss(per_thread_states),
3839     _task_queues(task_queues),
3840     _terminator(terminator)
3841   {}
3842 
3843   virtual void work(uint worker_id) {
3844     // The reference processing task executed by a single worker.
3845     ResourceMark rm;
3846     HandleMark   hm;
3847 
3848     G1STWIsAliveClosure is_alive(_g1h);
3849 
3850     G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
3851     pss->set_ref_discoverer(NULL);
3852 
3853     // Keep alive closure.
3854     G1CopyingKeepAliveClosure keep_alive(_g1h, pss->closures()->raw_strong_oops(), pss);
3855 
3856     // Complete GC closure
3857     G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator);
3858 
3859     // Call the reference processing task's work routine.
3860     _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
3861 
3862     // Note we cannot assert that the refs array is empty here as not all
3863     // of the processing tasks (specifically phase2 - pp2_work) execute
3864     // the complete_gc closure (which ordinarily would drain the queue) so
3865     // the queue may not be empty.
3866   }
3867 };
3868 
3869 // Driver routine for parallel reference processing.
3870 // Creates an instance of the ref processing gang
3871 // task and has the worker threads execute it.
3872 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task, uint ergo_workers) {
3873   assert(_workers != NULL, "Need parallel worker threads.");
3874 
3875   assert(_workers->active_workers() >= ergo_workers,
3876          "Ergonomically chosen workers (%u) should be less than or equal to active workers (%u)",
3877          ergo_workers, _workers->active_workers());
3878   ParallelTaskTerminator terminator(ergo_workers, _queues);
3879   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, &terminator);
3880 
3881   _workers->run_task(&proc_task_proxy, ergo_workers);
3882 }
3883 
3884 // End of weak reference support closures
3885 
3886 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
3887   double ref_proc_start = os::elapsedTime();
3888 
3889   ReferenceProcessor* rp = _ref_processor_stw;
3890   assert(rp->discovery_enabled(), "should have been enabled");
3891 
3892   // Closure to test whether a referent is alive.
3893   G1STWIsAliveClosure is_alive(this);
3894 
3895   // Even when parallel reference processing is enabled, the processing
3896   // of JNI refs is serial and performed serially by the current thread
3897   // rather than by a worker. The following PSS will be used for processing
3898   // JNI refs.
3899 
3900   // Use only a single queue for this PSS.
3901   G1ParScanThreadState*          pss = per_thread_states->state_for_worker(0);
3902   pss->set_ref_discoverer(NULL);
3903   assert(pss->queue_is_empty(), "pre-condition");
3904 
3905   // Keep alive closure.
3906   G1CopyingKeepAliveClosure keep_alive(this, pss->closures()->raw_strong_oops(), pss);
3907 
3908   // Serial Complete GC closure
3909   G1STWDrainQueueClosure drain_queue(this, pss);
3910 
3911   // Setup the soft refs policy...
3912   rp->setup_policy(false);
3913 
3914   ReferenceProcessorPhaseTimes* pt = g1_policy()->phase_times()->ref_phase_times();
3915 
3916   ReferenceProcessorStats stats;
3917   if (!rp->processing_is_mt()) {
3918     // Serial reference processing...
3919     stats = rp->process_discovered_references(&is_alive,
3920                                               &keep_alive,
3921                                               &drain_queue,
3922                                               NULL,
3923                                               pt);
3924   } else {
3925     uint no_of_gc_workers = workers()->active_workers();
3926 
3927     // Parallel reference processing
3928     assert(no_of_gc_workers <= rp->max_num_queues(),
3929            "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
3930            no_of_gc_workers,  rp->max_num_queues());
3931 
3932     G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues);
3933     stats = rp->process_discovered_references(&is_alive,
3934                                               &keep_alive,
3935                                               &drain_queue,
3936                                               &par_task_executor,
3937                                               pt);
3938   }
3939 
3940   _gc_tracer_stw->report_gc_reference_stats(stats);
3941 
3942   // We have completed copying any necessary live referent objects.
3943   assert(pss->queue_is_empty(), "both queue and overflow should be empty");
3944 
3945   make_pending_list_reachable();
3946 
3947   rp->verify_no_references_recorded();
3948 
3949   double ref_proc_time = os::elapsedTime() - ref_proc_start;
3950   g1_policy()->phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
3951 }
3952 
3953 void G1CollectedHeap::make_pending_list_reachable() {
3954   if (collector_state()->in_initial_mark_gc()) {
3955     oop pll_head = Universe::reference_pending_list();
3956     if (pll_head != NULL) {
3957       // Any valid worker id is fine here as we are in the VM thread and single-threaded.
3958       _cm->mark_in_next_bitmap(0 /* worker_id */, pll_head);
3959     }
3960   }
3961 }
3962 
3963 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) {
3964   double merge_pss_time_start = os::elapsedTime();
3965   per_thread_states->flush();
3966   g1_policy()->phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0);
3967 }
3968 
3969 void G1CollectedHeap::pre_evacuate_collection_set() {
3970   _expand_heap_after_alloc_failure = true;
3971   _evacuation_failed = false;
3972 
3973   // Disable the hot card cache.
3974   _hot_card_cache->reset_hot_cache_claimed_index();
3975   _hot_card_cache->set_use_cache(false);
3976 
3977   g1_rem_set()->prepare_for_oops_into_collection_set_do();
3978   _preserved_marks_set.assert_empty();
3979 
3980   G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
3981 
3982   // InitialMark needs claim bits to keep track of the marked-through CLDs.
3983   if (collector_state()->in_initial_mark_gc()) {
3984     double start_clear_claimed_marks = os::elapsedTime();
3985 
3986     ClassLoaderDataGraph::clear_claimed_marks();
3987 
3988     double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0;
3989     phase_times->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms);
3990   }
3991 }
3992 
3993 void G1CollectedHeap::evacuate_collection_set(G1ParScanThreadStateSet* per_thread_states) {
3994   // Should G1EvacuationFailureALot be in effect for this GC?
3995   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
3996 
3997   assert(dirty_card_queue_set().completed_buffers_num() == 0, "Should be empty");
3998 
3999   G1GCPhaseTimes* phase_times = g1_policy()->phase_times();
4000 
4001   double start_par_time_sec = os::elapsedTime();
4002   double end_par_time_sec;
4003 
4004   {
4005     const uint n_workers = workers()->active_workers();
4006     G1RootProcessor root_processor(this, n_workers);
4007     G1ParTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, n_workers);
4008 
4009     print_termination_stats_hdr();
4010 
4011     workers()->run_task(&g1_par_task);
4012     end_par_time_sec = os::elapsedTime();
4013 
4014     // Closing the inner scope will execute the destructor
4015     // for the G1RootProcessor object. We record the current
4016     // elapsed time before closing the scope so that time
4017     // taken for the destructor is NOT included in the
4018     // reported parallel time.
4019   }
4020 
4021   double par_time_ms = (end_par_time_sec - start_par_time_sec) * 1000.0;
4022   phase_times->record_par_time(par_time_ms);
4023 
4024   double code_root_fixup_time_ms =
4025         (os::elapsedTime() - end_par_time_sec) * 1000.0;
4026   phase_times->record_code_root_fixup_time(code_root_fixup_time_ms);
4027 }
4028 
4029 void G1CollectedHeap::post_evacuate_collection_set(EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
4030   // Also cleans the card table from temporary duplicate detection information used
4031   // during UpdateRS/ScanRS.
4032   g1_rem_set()->cleanup_after_oops_into_collection_set_do();
4033 
4034   // Process any discovered reference objects - we have
4035   // to do this _before_ we retire the GC alloc regions
4036   // as we may have to copy some 'reachable' referent
4037   // objects (and their reachable sub-graphs) that were
4038   // not copied during the pause.
4039   process_discovered_references(per_thread_states);
4040 
4041   // FIXME
4042   // CM's reference processing also cleans up the string and symbol tables.
4043   // Should we do that here also? We could, but it is a serial operation
4044   // and could significantly increase the pause time.
4045 
4046   G1STWIsAliveClosure is_alive(this);
4047   G1KeepAliveClosure keep_alive(this);
4048 
4049   {
4050     double start = os::elapsedTime();
4051 
4052     WeakProcessor::weak_oops_do(&is_alive, &keep_alive);
4053 
4054     double time_ms = (os::elapsedTime() - start) * 1000.0;
4055     g1_policy()->phase_times()->record_weak_ref_proc_time(time_ms);
4056   }
4057 
4058   if (G1StringDedup::is_enabled()) {
4059     double fixup_start = os::elapsedTime();
4060 
4061     G1StringDedup::unlink_or_oops_do(&is_alive, &keep_alive, true, g1_policy()->phase_times());
4062 
4063     double fixup_time_ms = (os::elapsedTime() - fixup_start) * 1000.0;
4064     g1_policy()->phase_times()->record_string_dedup_fixup_time(fixup_time_ms);
4065   }
4066 
4067   if (evacuation_failed()) {
4068     restore_after_evac_failure();
4069 
4070     // Reset the G1EvacuationFailureALot counters and flags
4071     // Note: the values are reset only when an actual
4072     // evacuation failure occurs.
4073     NOT_PRODUCT(reset_evacuation_should_fail();)
4074   }
4075 
4076   _preserved_marks_set.assert_empty();
4077 
4078   _allocator->release_gc_alloc_regions(evacuation_info);
4079 
4080   merge_per_thread_state_info(per_thread_states);
4081 
4082   // Reset and re-enable the hot card cache.
4083   // Note the counts for the cards in the regions in the
4084   // collection set are reset when the collection set is freed.
4085   _hot_card_cache->reset_hot_cache();
4086   _hot_card_cache->set_use_cache(true);
4087 
4088   purge_code_root_memory();
4089 
4090   redirty_logged_cards();
4091 #if COMPILER2_OR_JVMCI
4092   double start = os::elapsedTime();
4093   DerivedPointerTable::update_pointers();
4094   g1_policy()->phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0);
4095 #endif
4096   g1_policy()->print_age_table();
4097 }
4098 
4099 void G1CollectedHeap::record_obj_copy_mem_stats() {
4100   g1_policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
4101 
4102   _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
4103                                                create_g1_evac_summary(&_old_evac_stats));
4104 }
4105 
4106 void G1CollectedHeap::free_region(HeapRegion* hr,
4107                                   FreeRegionList* free_list,
4108                                   bool skip_remset,
4109                                   bool skip_hot_card_cache,
4110                                   bool locked) {
4111   assert(!hr->is_free(), "the region should not be free");
4112   assert(!hr->is_empty(), "the region should not be empty");
4113   assert(_hrm.is_available(hr->hrm_index()), "region should be committed");
4114   assert(free_list != NULL, "pre-condition");
4115 
4116   if (G1VerifyBitmaps) {
4117     MemRegion mr(hr->bottom(), hr->end());
4118     concurrent_mark()->clear_range_in_prev_bitmap(mr);
4119   }
4120 
4121   // Clear the card counts for this region.
4122   // Note: we only need to do this if the region is not young
4123   // (since we don't refine cards in young regions).
4124   if (!skip_hot_card_cache && !hr->is_young()) {
4125     _hot_card_cache->reset_card_counts(hr);
4126   }
4127   hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */);
4128   _g1_policy->remset_tracker()->update_at_free(hr);
4129   free_list->add_ordered(hr);
4130 }
4131 
4132 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
4133                                             FreeRegionList* free_list) {
4134   assert(hr->is_humongous(), "this is only for humongous regions");
4135   assert(free_list != NULL, "pre-condition");
4136   hr->clear_humongous();
4137   free_region(hr, free_list, false /* skip_remset */, false /* skip_hcc */, true /* locked */);
4138 }
4139 
4140 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed,
4141                                            const uint humongous_regions_removed) {
4142   if (old_regions_removed > 0 || humongous_regions_removed > 0) {
4143     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4144     _old_set.bulk_remove(old_regions_removed);
4145     _humongous_set.bulk_remove(humongous_regions_removed);
4146   }
4147 
4148 }
4149 
4150 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
4151   assert(list != NULL, "list can't be null");
4152   if (!list->is_empty()) {
4153     MutexLockerEx x(FreeList_lock, Mutex::_no_safepoint_check_flag);
4154     _hrm.insert_list_into_free_list(list);
4155   }
4156 }
4157 
4158 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
4159   decrease_used(bytes);
4160 }
4161 
4162 class G1FreeCollectionSetTask : public AbstractGangTask {
4163 private:
4164 
4165   // Closure applied to all regions in the collection set to do work that needs to
4166   // be done serially in a single thread.
4167   class G1SerialFreeCollectionSetClosure : public HeapRegionClosure {
4168   private:
4169     EvacuationInfo* _evacuation_info;
4170     const size_t* _surviving_young_words;
4171 
4172     // Bytes used in successfully evacuated regions before the evacuation.
4173     size_t _before_used_bytes;
4174     // Bytes used in unsucessfully evacuated regions before the evacuation
4175     size_t _after_used_bytes;
4176 
4177     size_t _bytes_allocated_in_old_since_last_gc;
4178 
4179     size_t _failure_used_words;
4180     size_t _failure_waste_words;
4181 
4182     FreeRegionList _local_free_list;
4183   public:
4184     G1SerialFreeCollectionSetClosure(EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4185       HeapRegionClosure(),
4186       _evacuation_info(evacuation_info),
4187       _surviving_young_words(surviving_young_words),
4188       _before_used_bytes(0),
4189       _after_used_bytes(0),
4190       _bytes_allocated_in_old_since_last_gc(0),
4191       _failure_used_words(0),
4192       _failure_waste_words(0),
4193       _local_free_list("Local Region List for CSet Freeing") {
4194     }
4195 
4196     virtual bool do_heap_region(HeapRegion* r) {
4197       G1CollectedHeap* g1h = G1CollectedHeap::heap();
4198 
4199       assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index());
4200       g1h->clear_in_cset(r);
4201 
4202       if (r->is_young()) {
4203         assert(r->young_index_in_cset() != -1 && (uint)r->young_index_in_cset() < g1h->collection_set()->young_region_length(),
4204                "Young index %d is wrong for region %u of type %s with %u young regions",
4205                r->young_index_in_cset(),
4206                r->hrm_index(),
4207                r->get_type_str(),
4208                g1h->collection_set()->young_region_length());
4209         size_t words_survived = _surviving_young_words[r->young_index_in_cset()];
4210         r->record_surv_words_in_group(words_survived);
4211       }
4212 
4213       if (!r->evacuation_failed()) {
4214         assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index());
4215         _before_used_bytes += r->used();
4216         g1h->free_region(r,
4217                          &_local_free_list,
4218                          true, /* skip_remset */
4219                          true, /* skip_hot_card_cache */
4220                          true  /* locked */);
4221       } else {
4222         r->uninstall_surv_rate_group();
4223         r->set_young_index_in_cset(-1);
4224         r->set_evacuation_failed(false);
4225         // When moving a young gen region to old gen, we "allocate" that whole region
4226         // there. This is in addition to any already evacuated objects. Notify the
4227         // policy about that.
4228         // Old gen regions do not cause an additional allocation: both the objects
4229         // still in the region and the ones already moved are accounted for elsewhere.
4230         if (r->is_young()) {
4231           _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes;
4232         }
4233         // The region is now considered to be old.
4234         r->set_old();
4235         // Do some allocation statistics accounting. Regions that failed evacuation
4236         // are always made old, so there is no need to update anything in the young
4237         // gen statistics, but we need to update old gen statistics.
4238         size_t used_words = r->marked_bytes() / HeapWordSize;
4239 
4240         _failure_used_words += used_words;
4241         _failure_waste_words += HeapRegion::GrainWords - used_words;
4242 
4243         g1h->old_set_add(r);
4244         _after_used_bytes += r->used();
4245       }
4246       return false;
4247     }
4248 
4249     void complete_work() {
4250       G1CollectedHeap* g1h = G1CollectedHeap::heap();
4251 
4252       _evacuation_info->set_regions_freed(_local_free_list.length());
4253       _evacuation_info->increment_collectionset_used_after(_after_used_bytes);
4254 
4255       g1h->prepend_to_freelist(&_local_free_list);
4256       g1h->decrement_summary_bytes(_before_used_bytes);
4257 
4258       G1Policy* policy = g1h->g1_policy();
4259       policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc);
4260 
4261       g1h->alloc_buffer_stats(InCSetState::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words);
4262     }
4263   };
4264 
4265   G1CollectionSet* _collection_set;
4266   G1SerialFreeCollectionSetClosure _cl;
4267   const size_t* _surviving_young_words;
4268 
4269   size_t _rs_lengths;
4270 
4271   volatile jint _serial_work_claim;
4272 
4273   struct WorkItem {
4274     uint region_idx;
4275     bool is_young;
4276     bool evacuation_failed;
4277 
4278     WorkItem(HeapRegion* r) {
4279       region_idx = r->hrm_index();
4280       is_young = r->is_young();
4281       evacuation_failed = r->evacuation_failed();
4282     }
4283   };
4284 
4285   volatile size_t _parallel_work_claim;
4286   size_t _num_work_items;
4287   WorkItem* _work_items;
4288 
4289   void do_serial_work() {
4290     // Need to grab the lock to be allowed to modify the old region list.
4291     MutexLockerEx x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4292     _collection_set->iterate(&_cl);
4293   }
4294 
4295   void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) {
4296     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4297 
4298     HeapRegion* r = g1h->region_at(region_idx);
4299     assert(!g1h->is_on_master_free_list(r), "sanity");
4300 
4301     Atomic::add(r->rem_set()->occupied_locked(), &_rs_lengths);
4302 
4303     if (!is_young) {
4304       g1h->_hot_card_cache->reset_card_counts(r);
4305     }
4306 
4307     if (!evacuation_failed) {
4308       r->rem_set()->clear_locked();
4309     }
4310   }
4311 
4312   class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure {
4313   private:
4314     size_t _cur_idx;
4315     WorkItem* _work_items;
4316   public:
4317     G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { }
4318 
4319     virtual bool do_heap_region(HeapRegion* r) {
4320       _work_items[_cur_idx++] = WorkItem(r);
4321       return false;
4322     }
4323   };
4324 
4325   void prepare_work() {
4326     G1PrepareFreeCollectionSetClosure cl(_work_items);
4327     _collection_set->iterate(&cl);
4328   }
4329 
4330   void complete_work() {
4331     _cl.complete_work();
4332 
4333     G1Policy* policy = G1CollectedHeap::heap()->g1_policy();
4334     policy->record_max_rs_lengths(_rs_lengths);
4335     policy->cset_regions_freed();
4336   }
4337 public:
4338   G1FreeCollectionSetTask(G1CollectionSet* collection_set, EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4339     AbstractGangTask("G1 Free Collection Set"),
4340     _cl(evacuation_info, surviving_young_words),
4341     _collection_set(collection_set),
4342     _surviving_young_words(surviving_young_words),
4343     _serial_work_claim(0),
4344     _rs_lengths(0),
4345     _parallel_work_claim(0),
4346     _num_work_items(collection_set->region_length()),
4347     _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) {
4348     prepare_work();
4349   }
4350 
4351   ~G1FreeCollectionSetTask() {
4352     complete_work();
4353     FREE_C_HEAP_ARRAY(WorkItem, _work_items);
4354   }
4355 
4356   // Chunk size for work distribution. The chosen value has been determined experimentally
4357   // to be a good tradeoff between overhead and achievable parallelism.
4358   static uint chunk_size() { return 32; }
4359 
4360   virtual void work(uint worker_id) {
4361     G1GCPhaseTimes* timer = G1CollectedHeap::heap()->g1_policy()->phase_times();
4362 
4363     // Claim serial work.
4364     if (_serial_work_claim == 0) {
4365       jint value = Atomic::add(1, &_serial_work_claim) - 1;
4366       if (value == 0) {
4367         double serial_time = os::elapsedTime();
4368         do_serial_work();
4369         timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0);
4370       }
4371     }
4372 
4373     // Start parallel work.
4374     double young_time = 0.0;
4375     bool has_young_time = false;
4376     double non_young_time = 0.0;
4377     bool has_non_young_time = false;
4378 
4379     while (true) {
4380       size_t end = Atomic::add(chunk_size(), &_parallel_work_claim);
4381       size_t cur = end - chunk_size();
4382 
4383       if (cur >= _num_work_items) {
4384         break;
4385       }
4386 
4387       double start_time = os::elapsedTime();
4388 
4389       end = MIN2(end, _num_work_items);
4390 
4391       for (; cur < end; cur++) {
4392         bool is_young = _work_items[cur].is_young;
4393 
4394         do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed);
4395 
4396         double end_time = os::elapsedTime();
4397         double time_taken = end_time - start_time;
4398         if (is_young) {
4399           young_time += time_taken;
4400           has_young_time = true;
4401         } else {
4402           non_young_time += time_taken;
4403           has_non_young_time = true;
4404         }
4405         start_time = end_time;
4406       }
4407     }
4408 
4409     if (has_young_time) {
4410       timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time);
4411     }
4412     if (has_non_young_time) {
4413       timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, non_young_time);
4414     }
4415   }
4416 };
4417 
4418 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, EvacuationInfo& evacuation_info, const size_t* surviving_young_words) {
4419   _eden.clear();
4420 
4421   double free_cset_start_time = os::elapsedTime();
4422 
4423   {
4424     uint const num_chunks = MAX2(_collection_set.region_length() / G1FreeCollectionSetTask::chunk_size(), 1U);
4425     uint const num_workers = MIN2(workers()->active_workers(), num_chunks);
4426 
4427     G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words);
4428 
4429     log_debug(gc, ergo)("Running %s using %u workers for collection set length %u",
4430                         cl.name(),
4431                         num_workers,
4432                         _collection_set.region_length());
4433     workers()->run_task(&cl, num_workers);
4434   }
4435   g1_policy()->phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0);
4436 
4437   collection_set->clear();
4438 }
4439 
4440 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
4441  private:
4442   FreeRegionList* _free_region_list;
4443   HeapRegionSet* _proxy_set;
4444   uint _humongous_objects_reclaimed;
4445   uint _humongous_regions_reclaimed;
4446   size_t _freed_bytes;
4447  public:
4448 
4449   G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
4450     _free_region_list(free_region_list), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) {
4451   }
4452 
4453   virtual bool do_heap_region(HeapRegion* r) {
4454     if (!r->is_starts_humongous()) {
4455       return false;
4456     }
4457 
4458     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4459 
4460     oop obj = (oop)r->bottom();
4461     G1CMBitMap* next_bitmap = g1h->concurrent_mark()->next_mark_bitmap();
4462 
4463     // The following checks whether the humongous object is live are sufficient.
4464     // The main additional check (in addition to having a reference from the roots
4465     // or the young gen) is whether the humongous object has a remembered set entry.
4466     //
4467     // A humongous object cannot be live if there is no remembered set for it
4468     // because:
4469     // - there can be no references from within humongous starts regions referencing
4470     // the object because we never allocate other objects into them.
4471     // (I.e. there are no intra-region references that may be missed by the
4472     // remembered set)
4473     // - as soon there is a remembered set entry to the humongous starts region
4474     // (i.e. it has "escaped" to an old object) this remembered set entry will stay
4475     // until the end of a concurrent mark.
4476     //
4477     // It is not required to check whether the object has been found dead by marking
4478     // or not, in fact it would prevent reclamation within a concurrent cycle, as
4479     // all objects allocated during that time are considered live.
4480     // SATB marking is even more conservative than the remembered set.
4481     // So if at this point in the collection there is no remembered set entry,
4482     // nobody has a reference to it.
4483     // At the start of collection we flush all refinement logs, and remembered sets
4484     // are completely up-to-date wrt to references to the humongous object.
4485     //
4486     // Other implementation considerations:
4487     // - never consider object arrays at this time because they would pose
4488     // considerable effort for cleaning up the the remembered sets. This is
4489     // required because stale remembered sets might reference locations that
4490     // are currently allocated into.
4491     uint region_idx = r->hrm_index();
4492     if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
4493         !r->rem_set()->is_empty()) {
4494       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",
4495                                region_idx,
4496                                (size_t)obj->size() * HeapWordSize,
4497                                p2i(r->bottom()),
4498                                r->rem_set()->occupied(),
4499                                r->rem_set()->strong_code_roots_list_length(),
4500                                next_bitmap->is_marked(r->bottom()),
4501                                g1h->is_humongous_reclaim_candidate(region_idx),
4502                                obj->is_typeArray()
4503                               );
4504       return false;
4505     }
4506 
4507     guarantee(obj->is_typeArray(),
4508               "Only eagerly reclaiming type arrays is supported, but the object "
4509               PTR_FORMAT " is not.", p2i(r->bottom()));
4510 
4511     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",
4512                              region_idx,
4513                              (size_t)obj->size() * HeapWordSize,
4514                              p2i(r->bottom()),
4515                              r->rem_set()->occupied(),
4516                              r->rem_set()->strong_code_roots_list_length(),
4517                              next_bitmap->is_marked(r->bottom()),
4518                              g1h->is_humongous_reclaim_candidate(region_idx),
4519                              obj->is_typeArray()
4520                             );
4521 
4522     G1ConcurrentMark* const cm = g1h->concurrent_mark();
4523     cm->humongous_object_eagerly_reclaimed(r);
4524     assert(!cm->is_marked_in_prev_bitmap(obj) && !cm->is_marked_in_next_bitmap(obj),
4525            "Eagerly reclaimed humongous region %u should not be marked at all but is in prev %s next %s",
4526            region_idx,
4527            BOOL_TO_STR(cm->is_marked_in_prev_bitmap(obj)),
4528            BOOL_TO_STR(cm->is_marked_in_next_bitmap(obj)));
4529     _humongous_objects_reclaimed++;
4530     do {
4531       HeapRegion* next = g1h->next_region_in_humongous(r);
4532       _freed_bytes += r->used();
4533       r->set_containing_set(NULL);
4534       _humongous_regions_reclaimed++;
4535       g1h->free_humongous_region(r, _free_region_list);
4536       r = next;
4537     } while (r != NULL);
4538 
4539     return false;
4540   }
4541 
4542   uint humongous_objects_reclaimed() {
4543     return _humongous_objects_reclaimed;
4544   }
4545 
4546   uint humongous_regions_reclaimed() {
4547     return _humongous_regions_reclaimed;
4548   }
4549 
4550   size_t bytes_freed() const {
4551     return _freed_bytes;
4552   }
4553 };
4554 
4555 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
4556   assert_at_safepoint_on_vm_thread();
4557 
4558   if (!G1EagerReclaimHumongousObjects ||
4559       (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) {
4560     g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
4561     return;
4562   }
4563 
4564   double start_time = os::elapsedTime();
4565 
4566   FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
4567 
4568   G1FreeHumongousRegionClosure cl(&local_cleanup_list);
4569   heap_region_iterate(&cl);
4570 
4571   remove_from_old_sets(0, cl.humongous_regions_reclaimed());
4572 
4573   G1HRPrinter* hrp = hr_printer();
4574   if (hrp->is_active()) {
4575     FreeRegionListIterator iter(&local_cleanup_list);
4576     while (iter.more_available()) {
4577       HeapRegion* hr = iter.get_next();
4578       hrp->cleanup(hr);
4579     }
4580   }
4581 
4582   prepend_to_freelist(&local_cleanup_list);
4583   decrement_summary_bytes(cl.bytes_freed());
4584 
4585   g1_policy()->phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
4586                                                                     cl.humongous_objects_reclaimed());
4587 }
4588 
4589 class G1AbandonCollectionSetClosure : public HeapRegionClosure {
4590 public:
4591   virtual bool do_heap_region(HeapRegion* r) {
4592     assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index());
4593     G1CollectedHeap::heap()->clear_in_cset(r);
4594     r->set_young_index_in_cset(-1);
4595     return false;
4596   }
4597 };
4598 
4599 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) {
4600   G1AbandonCollectionSetClosure cl;
4601   collection_set->iterate(&cl);
4602 
4603   collection_set->clear();
4604   collection_set->stop_incremental_building();
4605 }
4606 
4607 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
4608   return _allocator->is_retained_old_region(hr);
4609 }
4610 
4611 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
4612   _eden.add(hr);
4613   _g1_policy->set_region_eden(hr);
4614 }
4615 
4616 #ifdef ASSERT
4617 
4618 class NoYoungRegionsClosure: public HeapRegionClosure {
4619 private:
4620   bool _success;
4621 public:
4622   NoYoungRegionsClosure() : _success(true) { }
4623   bool do_heap_region(HeapRegion* r) {
4624     if (r->is_young()) {
4625       log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
4626                             p2i(r->bottom()), p2i(r->end()));
4627       _success = false;
4628     }
4629     return false;
4630   }
4631   bool success() { return _success; }
4632 };
4633 
4634 bool G1CollectedHeap::check_young_list_empty() {
4635   bool ret = (young_regions_count() == 0);
4636 
4637   NoYoungRegionsClosure closure;
4638   heap_region_iterate(&closure);
4639   ret = ret && closure.success();
4640 
4641   return ret;
4642 }
4643 
4644 #endif // ASSERT
4645 
4646 class TearDownRegionSetsClosure : public HeapRegionClosure {
4647 private:
4648   HeapRegionSet *_old_set;
4649 
4650 public:
4651   TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
4652 
4653   bool do_heap_region(HeapRegion* r) {
4654     if (r->is_old()) {
4655       _old_set->remove(r);
4656     } else if(r->is_young()) {
4657       r->uninstall_surv_rate_group();
4658     } else {
4659       // We ignore free regions, we'll empty the free list afterwards.
4660       // We ignore humongous regions, we're not tearing down the
4661       // humongous regions set.
4662       assert(r->is_free() || r->is_humongous(),
4663              "it cannot be another type");
4664     }
4665     return false;
4666   }
4667 
4668   ~TearDownRegionSetsClosure() {
4669     assert(_old_set->is_empty(), "post-condition");
4670   }
4671 };
4672 
4673 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
4674   assert_at_safepoint_on_vm_thread();
4675 
4676   if (!free_list_only) {
4677     TearDownRegionSetsClosure cl(&_old_set);
4678     heap_region_iterate(&cl);
4679 
4680     // Note that emptying the _young_list is postponed and instead done as
4681     // the first step when rebuilding the regions sets again. The reason for
4682     // this is that during a full GC string deduplication needs to know if
4683     // a collected region was young or old when the full GC was initiated.
4684   }
4685   _hrm.remove_all_free_regions();
4686 }
4687 
4688 void G1CollectedHeap::increase_used(size_t bytes) {
4689   _summary_bytes_used += bytes;
4690 }
4691 
4692 void G1CollectedHeap::decrease_used(size_t bytes) {
4693   assert(_summary_bytes_used >= bytes,
4694          "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
4695          _summary_bytes_used, bytes);
4696   _summary_bytes_used -= bytes;
4697 }
4698 
4699 void G1CollectedHeap::set_used(size_t bytes) {
4700   _summary_bytes_used = bytes;
4701 }
4702 
4703 class RebuildRegionSetsClosure : public HeapRegionClosure {
4704 private:
4705   bool            _free_list_only;
4706   HeapRegionSet*   _old_set;
4707   HeapRegionManager*   _hrm;
4708   size_t          _total_used;
4709 
4710 public:
4711   RebuildRegionSetsClosure(bool free_list_only,
4712                            HeapRegionSet* old_set, HeapRegionManager* hrm) :
4713     _free_list_only(free_list_only),
4714     _old_set(old_set), _hrm(hrm), _total_used(0) {
4715     assert(_hrm->num_free_regions() == 0, "pre-condition");
4716     if (!free_list_only) {
4717       assert(_old_set->is_empty(), "pre-condition");
4718     }
4719   }
4720 
4721   bool do_heap_region(HeapRegion* r) {
4722     // After full GC, no region should have a remembered set.
4723     r->rem_set()->clear(true);
4724     if (r->is_empty()) {
4725       // Add free regions to the free list
4726       r->set_free();
4727       _hrm->insert_into_free_list(r);
4728     } else if (!_free_list_only) {
4729 
4730       if (r->is_humongous()) {
4731         // We ignore humongous regions. We left the humongous set unchanged.
4732       } else {
4733         assert(r->is_young() || r->is_free() || r->is_old(), "invariant");
4734         // We now move all (non-humongous, non-old) regions to old gen, and register them as such.
4735         r->move_to_old();
4736         _old_set->add(r);
4737       }
4738       _total_used += r->used();
4739     }
4740 
4741     return false;
4742   }
4743 
4744   size_t total_used() {
4745     return _total_used;
4746   }
4747 };
4748 
4749 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
4750   assert_at_safepoint_on_vm_thread();
4751 
4752   if (!free_list_only) {
4753     _eden.clear();
4754     _survivor.clear();
4755   }
4756 
4757   RebuildRegionSetsClosure cl(free_list_only, &_old_set, &_hrm);
4758   heap_region_iterate(&cl);
4759 
4760   if (!free_list_only) {
4761     set_used(cl.total_used());
4762     if (_archive_allocator != NULL) {
4763       _archive_allocator->clear_used();
4764     }
4765   }
4766   assert(used_unlocked() == recalculate_used(),
4767          "inconsistent used_unlocked(), "
4768          "value: " SIZE_FORMAT " recalculated: " SIZE_FORMAT,
4769          used_unlocked(), recalculate_used());
4770 }
4771 
4772 bool G1CollectedHeap::is_in_closed_subset(const void* p) const {
4773   HeapRegion* hr = heap_region_containing(p);
4774   return hr->is_in(p);
4775 }
4776 
4777 // Methods for the mutator alloc region
4778 
4779 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
4780                                                       bool force) {
4781   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
4782   bool should_allocate = g1_policy()->should_allocate_mutator_region();
4783   if (force || should_allocate) {
4784     HeapRegion* new_alloc_region = new_region(word_size,
4785                                               false /* is_old */,
4786                                               false /* do_expand */);
4787     if (new_alloc_region != NULL) {
4788       set_region_short_lived_locked(new_alloc_region);
4789       _hr_printer.alloc(new_alloc_region, !should_allocate);
4790       _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region);
4791       _g1_policy->remset_tracker()->update_at_allocate(new_alloc_region);
4792       return new_alloc_region;
4793     }
4794   }
4795   return NULL;
4796 }
4797 
4798 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
4799                                                   size_t allocated_bytes) {
4800   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
4801   assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
4802 
4803   collection_set()->add_eden_region(alloc_region);
4804   increase_used(allocated_bytes);
4805   _hr_printer.retire(alloc_region);
4806   // We update the eden sizes here, when the region is retired,
4807   // instead of when it's allocated, since this is the point that its
4808   // used space has been recored in _summary_bytes_used.
4809   g1mm()->update_eden_size();
4810 }
4811 
4812 // Methods for the GC alloc regions
4813 
4814 bool G1CollectedHeap::has_more_regions(InCSetState dest) {
4815   if (dest.is_old()) {
4816     return true;
4817   } else {
4818     return survivor_regions_count() < g1_policy()->max_survivor_regions();
4819   }
4820 }
4821 
4822 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, InCSetState dest) {
4823   assert(FreeList_lock->owned_by_self(), "pre-condition");
4824 
4825   if (!has_more_regions(dest)) {
4826     return NULL;
4827   }
4828 
4829   const bool is_survivor = dest.is_young();
4830 
4831   HeapRegion* new_alloc_region = new_region(word_size,
4832                                             !is_survivor,
4833                                             true /* do_expand */);
4834   if (new_alloc_region != NULL) {
4835     if (is_survivor) {
4836       new_alloc_region->set_survivor();
4837       _survivor.add(new_alloc_region);
4838       _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region);
4839     } else {
4840       new_alloc_region->set_old();
4841       _verifier->check_bitmaps("Old Region Allocation", new_alloc_region);
4842     }
4843     _g1_policy->remset_tracker()->update_at_allocate(new_alloc_region);
4844     _hr_printer.alloc(new_alloc_region);
4845     bool during_im = collector_state()->in_initial_mark_gc();
4846     new_alloc_region->note_start_of_copying(during_im);
4847     return new_alloc_region;
4848   }
4849   return NULL;
4850 }
4851 
4852 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
4853                                              size_t allocated_bytes,
4854                                              InCSetState dest) {
4855   bool during_im = collector_state()->in_initial_mark_gc();
4856   alloc_region->note_end_of_copying(during_im);
4857   g1_policy()->record_bytes_copied_during_gc(allocated_bytes);
4858   if (dest.is_old()) {
4859     _old_set.add(alloc_region);
4860   }
4861   _hr_printer.retire(alloc_region);
4862 }
4863 
4864 HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
4865   bool expanded = false;
4866   uint index = _hrm.find_highest_free(&expanded);
4867 
4868   if (index != G1_NO_HRM_INDEX) {
4869     if (expanded) {
4870       log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
4871                                 HeapRegion::GrainWords * HeapWordSize);
4872     }
4873     _hrm.allocate_free_regions_starting_at(index, 1);
4874     return region_at(index);
4875   }
4876   return NULL;
4877 }
4878 
4879 // Optimized nmethod scanning
4880 
4881 class RegisterNMethodOopClosure: public OopClosure {
4882   G1CollectedHeap* _g1h;
4883   nmethod* _nm;
4884 
4885   template <class T> void do_oop_work(T* p) {
4886     T heap_oop = RawAccess<>::oop_load(p);
4887     if (!CompressedOops::is_null(heap_oop)) {
4888       oop obj = CompressedOops::decode_not_null(heap_oop);
4889       HeapRegion* hr = _g1h->heap_region_containing(obj);
4890       assert(!hr->is_continues_humongous(),
4891              "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
4892              " starting at " HR_FORMAT,
4893              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
4894 
4895       // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
4896       hr->add_strong_code_root_locked(_nm);
4897     }
4898   }
4899 
4900 public:
4901   RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
4902     _g1h(g1h), _nm(nm) {}
4903 
4904   void do_oop(oop* p)       { do_oop_work(p); }
4905   void do_oop(narrowOop* p) { do_oop_work(p); }
4906 };
4907 
4908 class UnregisterNMethodOopClosure: public OopClosure {
4909   G1CollectedHeap* _g1h;
4910   nmethod* _nm;
4911 
4912   template <class T> void do_oop_work(T* p) {
4913     T heap_oop = RawAccess<>::oop_load(p);
4914     if (!CompressedOops::is_null(heap_oop)) {
4915       oop obj = CompressedOops::decode_not_null(heap_oop);
4916       HeapRegion* hr = _g1h->heap_region_containing(obj);
4917       assert(!hr->is_continues_humongous(),
4918              "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
4919              " starting at " HR_FORMAT,
4920              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
4921 
4922       hr->remove_strong_code_root(_nm);
4923     }
4924   }
4925 
4926 public:
4927   UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
4928     _g1h(g1h), _nm(nm) {}
4929 
4930   void do_oop(oop* p)       { do_oop_work(p); }
4931   void do_oop(narrowOop* p) { do_oop_work(p); }
4932 };
4933 
4934 // Returns true if the reference points to an object that
4935 // can move in an incremental collection.
4936 bool G1CollectedHeap::is_scavengable(oop obj) {
4937   HeapRegion* hr = heap_region_containing(obj);
4938   return !hr->is_pinned();
4939 }
4940 
4941 void G1CollectedHeap::register_nmethod(nmethod* nm) {
4942   guarantee(nm != NULL, "sanity");
4943   RegisterNMethodOopClosure reg_cl(this, nm);
4944   nm->oops_do(&reg_cl);
4945 }
4946 
4947 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
4948   guarantee(nm != NULL, "sanity");
4949   UnregisterNMethodOopClosure reg_cl(this, nm);
4950   nm->oops_do(&reg_cl, true);
4951 }
4952 
4953 void G1CollectedHeap::purge_code_root_memory() {
4954   double purge_start = os::elapsedTime();
4955   G1CodeRootSet::purge();
4956   double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
4957   g1_policy()->phase_times()->record_strong_code_root_purge_time(purge_time_ms);
4958 }
4959 
4960 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
4961   G1CollectedHeap* _g1h;
4962 
4963 public:
4964   RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
4965     _g1h(g1h) {}
4966 
4967   void do_code_blob(CodeBlob* cb) {
4968     nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
4969     if (nm == NULL) {
4970       return;
4971     }
4972 
4973     if (ScavengeRootsInCode) {
4974       _g1h->register_nmethod(nm);
4975     }
4976   }
4977 };
4978 
4979 void G1CollectedHeap::rebuild_strong_code_roots() {
4980   RebuildStrongCodeRootClosure blob_cl(this);
4981   CodeCache::blobs_do(&blob_cl);
4982 }
4983 
4984 GrowableArray<GCMemoryManager*> G1CollectedHeap::memory_managers() {
4985   GrowableArray<GCMemoryManager*> memory_managers(2);
4986   memory_managers.append(&_memory_manager);
4987   memory_managers.append(&_full_gc_memory_manager);
4988   return memory_managers;
4989 }
4990 
4991 GrowableArray<MemoryPool*> G1CollectedHeap::memory_pools() {
4992   GrowableArray<MemoryPool*> memory_pools(3);
4993   memory_pools.append(_eden_pool);
4994   memory_pools.append(_survivor_pool);
4995   memory_pools.append(_old_pool);
4996   return memory_pools;
4997 }