1 /*
   2  * Copyright (c) 2001, 2019, Oracle and/or its affiliates. All rights reserved.
   3  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   4  *
   5  * This code is free software; you can redistribute it and/or modify it
   6  * under the terms of the GNU General Public License version 2 only, as
   7  * published by the Free Software Foundation.
   8  *
   9  * This code is distributed in the hope that it will be useful, but WITHOUT
  10  * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
  11  * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
  12  * version 2 for more details (a copy is included in the LICENSE file that
  13  * accompanied this code).
  14  *
  15  * You should have received a copy of the GNU General Public License version
  16  * 2 along with this work; if not, write to the Free Software Foundation,
  17  * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
  18  *
  19  * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
  20  * or visit www.oracle.com if you need additional information or have any
  21  * questions.
  22  *
  23  */
  24 
  25 #include "precompiled.hpp"
  26 #include "classfile/classLoaderDataGraph.hpp"
  27 #include "classfile/metadataOnStackMark.hpp"
  28 #include "classfile/stringTable.hpp"
  29 #include "code/codeCache.hpp"
  30 #include "code/icBuffer.hpp"
  31 #include "gc/g1/g1Allocator.inline.hpp"
  32 #include "gc/g1/g1Arguments.hpp"
  33 #include "gc/g1/g1BarrierSet.hpp"
  34 #include "gc/g1/g1CardTableEntryClosure.hpp"
  35 #include "gc/g1/g1CollectedHeap.inline.hpp"
  36 #include "gc/g1/g1CollectionSet.hpp"
  37 #include "gc/g1/g1CollectorState.hpp"
  38 #include "gc/g1/g1ConcurrentRefine.hpp"
  39 #include "gc/g1/g1ConcurrentRefineThread.hpp"
  40 #include "gc/g1/g1ConcurrentMarkThread.inline.hpp"
  41 #include "gc/g1/g1DirtyCardQueue.hpp"
  42 #include "gc/g1/g1EvacStats.inline.hpp"
  43 #include "gc/g1/g1FullCollector.hpp"
  44 #include "gc/g1/g1GCPhaseTimes.hpp"
  45 #include "gc/g1/g1HeapSizingPolicy.hpp"
  46 #include "gc/g1/g1HeapTransition.hpp"
  47 #include "gc/g1/g1HeapVerifier.hpp"
  48 #include "gc/g1/g1HotCardCache.hpp"
  49 #include "gc/g1/g1MemoryPool.hpp"
  50 #include "gc/g1/g1OopClosures.inline.hpp"
  51 #include "gc/g1/g1ParallelCleaning.hpp"
  52 #include "gc/g1/g1ParScanThreadState.inline.hpp"
  53 #include "gc/g1/g1Policy.hpp"
  54 #include "gc/g1/g1RedirtyCardsQueue.hpp"
  55 #include "gc/g1/g1RegionToSpaceMapper.hpp"
  56 #include "gc/g1/g1RemSet.hpp"
  57 #include "gc/g1/g1RootClosures.hpp"
  58 #include "gc/g1/g1RootProcessor.hpp"
  59 #include "gc/g1/g1SATBMarkQueueSet.hpp"
  60 #include "gc/g1/g1StringDedup.hpp"
  61 #include "gc/g1/g1ThreadLocalData.hpp"
  62 #include "gc/g1/g1Trace.hpp"
  63 #include "gc/g1/g1YCTypes.hpp"
  64 #include "gc/g1/g1YoungRemSetSamplingThread.hpp"
  65 #include "gc/g1/g1VMOperations.hpp"
  66 #include "gc/g1/heapRegion.inline.hpp"
  67 #include "gc/g1/heapRegionRemSet.hpp"
  68 #include "gc/g1/heapRegionSet.inline.hpp"
  69 #include "gc/shared/gcBehaviours.hpp"
  70 #include "gc/shared/gcHeapSummary.hpp"
  71 #include "gc/shared/gcId.hpp"
  72 #include "gc/shared/gcLocker.hpp"
  73 #include "gc/shared/gcTimer.hpp"
  74 #include "gc/shared/gcTraceTime.inline.hpp"
  75 #include "gc/shared/generationSpec.hpp"
  76 #include "gc/shared/isGCActiveMark.hpp"
  77 #include "gc/shared/locationPrinter.inline.hpp"
  78 #include "gc/shared/oopStorageParState.hpp"
  79 #include "gc/shared/preservedMarks.inline.hpp"
  80 #include "gc/shared/suspendibleThreadSet.hpp"
  81 #include "gc/shared/referenceProcessor.inline.hpp"
  82 #include "gc/shared/taskqueue.inline.hpp"
  83 #include "gc/shared/weakProcessor.inline.hpp"
  84 #include "gc/shared/workerPolicy.hpp"
  85 #include "logging/log.hpp"
  86 #include "memory/allocation.hpp"
  87 #include "memory/iterator.hpp"
  88 #include "memory/resourceArea.hpp"
  89 #include "memory/universe.hpp"
  90 #include "oops/access.inline.hpp"
  91 #include "oops/compressedOops.inline.hpp"
  92 #include "oops/oop.inline.hpp"
  93 #include "runtime/atomic.hpp"
  94 #include "runtime/flags/flagSetting.hpp"
  95 #include "runtime/handles.inline.hpp"
  96 #include "runtime/init.hpp"
  97 #include "runtime/orderAccess.hpp"
  98 #include "runtime/threadSMR.hpp"
  99 #include "runtime/vmThread.hpp"
 100 #include "utilities/align.hpp"
 101 #include "utilities/globalDefinitions.hpp"
 102 #include "utilities/stack.inline.hpp"
 103 
 104 size_t G1CollectedHeap::_humongous_object_threshold_in_words = 0;
 105 
 106 // INVARIANTS/NOTES
 107 //
 108 // All allocation activity covered by the G1CollectedHeap interface is
 109 // serialized by acquiring the HeapLock.  This happens in mem_allocate
 110 // and allocate_new_tlab, which are the "entry" points to the
 111 // allocation code from the rest of the JVM.  (Note that this does not
 112 // apply to TLAB allocation, which is not part of this interface: it
 113 // is done by clients of this interface.)
 114 
 115 class RedirtyLoggedCardTableEntryClosure : public G1CardTableEntryClosure {
 116  private:
 117   size_t _num_dirtied;
 118   G1CollectedHeap* _g1h;
 119   G1CardTable* _g1_ct;
 120 
 121   HeapRegion* region_for_card(CardValue* card_ptr) const {
 122     return _g1h->heap_region_containing(_g1_ct->addr_for(card_ptr));
 123   }
 124 
 125   bool will_become_free(HeapRegion* hr) const {
 126     // A region will be freed by free_collection_set if the region is in the
 127     // collection set and has not had an evacuation failure.
 128     return _g1h->is_in_cset(hr) && !hr->evacuation_failed();
 129   }
 130 
 131  public:
 132   RedirtyLoggedCardTableEntryClosure(G1CollectedHeap* g1h) : G1CardTableEntryClosure(),
 133     _num_dirtied(0), _g1h(g1h), _g1_ct(g1h->card_table()) { }
 134 
 135   void do_card_ptr(CardValue* card_ptr, uint worker_id) {
 136     HeapRegion* hr = region_for_card(card_ptr);
 137 
 138     // Should only dirty cards in regions that won't be freed.
 139     if (!will_become_free(hr)) {
 140       *card_ptr = G1CardTable::dirty_card_val();
 141       _num_dirtied++;
 142     }
 143   }
 144 
 145   size_t num_dirtied()   const { return _num_dirtied; }
 146 };
 147 
 148 
 149 void G1RegionMappingChangedListener::reset_from_card_cache(uint start_idx, size_t num_regions) {
 150   HeapRegionRemSet::invalidate_from_card_cache(start_idx, num_regions);
 151 }
 152 
 153 void G1RegionMappingChangedListener::on_commit(uint start_idx, size_t num_regions, bool zero_filled) {
 154   // The from card cache is not the memory that is actually committed. So we cannot
 155   // take advantage of the zero_filled parameter.
 156   reset_from_card_cache(start_idx, num_regions);
 157 }
 158 
 159 Tickspan G1CollectedHeap::run_task(AbstractGangTask* task) {
 160   Ticks start = Ticks::now();
 161   workers()->run_task(task, workers()->active_workers());
 162   return Ticks::now() - start;
 163 }
 164 
 165 HeapRegion* G1CollectedHeap::new_heap_region(uint hrs_index,
 166                                              MemRegion mr) {
 167   return new HeapRegion(hrs_index, bot(), mr);
 168 }
 169 
 170 // Private methods.
 171 
 172 HeapRegion* G1CollectedHeap::new_region(size_t word_size, HeapRegionType type, bool do_expand) {
 173   assert(!is_humongous(word_size) || word_size <= HeapRegion::GrainWords,
 174          "the only time we use this to allocate a humongous region is "
 175          "when we are allocating a single humongous region");
 176 
 177   HeapRegion* res = _hrm->allocate_free_region(type);
 178 
 179   if (res == NULL && do_expand && _expand_heap_after_alloc_failure) {
 180     // Currently, only attempts to allocate GC alloc regions set
 181     // do_expand to true. So, we should only reach here during a
 182     // safepoint. If this assumption changes we might have to
 183     // reconsider the use of _expand_heap_after_alloc_failure.
 184     assert(SafepointSynchronize::is_at_safepoint(), "invariant");
 185 
 186     log_debug(gc, ergo, heap)("Attempt heap expansion (region allocation request failed). Allocation request: " SIZE_FORMAT "B",
 187                               word_size * HeapWordSize);
 188 
 189     if (expand(word_size * HeapWordSize)) {
 190       // Given that expand() succeeded in expanding the heap, and we
 191       // always expand the heap by an amount aligned to the heap
 192       // region size, the free list should in theory not be empty.
 193       // In either case allocate_free_region() will check for NULL.
 194       res = _hrm->allocate_free_region(type);
 195     } else {
 196       _expand_heap_after_alloc_failure = false;
 197     }
 198   }
 199   return res;
 200 }
 201 
 202 HeapWord*
 203 G1CollectedHeap::humongous_obj_allocate_initialize_regions(uint first,
 204                                                            uint num_regions,
 205                                                            size_t word_size) {
 206   assert(first != G1_NO_HRM_INDEX, "pre-condition");
 207   assert(is_humongous(word_size), "word_size should be humongous");
 208   assert(num_regions * HeapRegion::GrainWords >= word_size, "pre-condition");
 209 
 210   // Index of last region in the series.
 211   uint last = first + num_regions - 1;
 212 
 213   // We need to initialize the region(s) we just discovered. This is
 214   // a bit tricky given that it can happen concurrently with
 215   // refinement threads refining cards on these regions and
 216   // potentially wanting to refine the BOT as they are scanning
 217   // those cards (this can happen shortly after a cleanup; see CR
 218   // 6991377). So we have to set up the region(s) carefully and in
 219   // a specific order.
 220 
 221   // The word size sum of all the regions we will allocate.
 222   size_t word_size_sum = (size_t) num_regions * HeapRegion::GrainWords;
 223   assert(word_size <= word_size_sum, "sanity");
 224 
 225   // This will be the "starts humongous" region.
 226   HeapRegion* first_hr = region_at(first);
 227   // The header of the new object will be placed at the bottom of
 228   // the first region.
 229   HeapWord* new_obj = first_hr->bottom();
 230   // This will be the new top of the new object.
 231   HeapWord* obj_top = new_obj + word_size;
 232 
 233   // First, we need to zero the header of the space that we will be
 234   // allocating. When we update top further down, some refinement
 235   // threads might try to scan the region. By zeroing the header we
 236   // ensure that any thread that will try to scan the region will
 237   // come across the zero klass word and bail out.
 238   //
 239   // NOTE: It would not have been correct to have used
 240   // CollectedHeap::fill_with_object() and make the space look like
 241   // an int array. The thread that is doing the allocation will
 242   // later update the object header to a potentially different array
 243   // type and, for a very short period of time, the klass and length
 244   // fields will be inconsistent. This could cause a refinement
 245   // thread to calculate the object size incorrectly.
 246   Copy::fill_to_words(new_obj, oopDesc::header_size(), 0);
 247 
 248   // Next, pad out the unused tail of the last region with filler
 249   // objects, for improved usage accounting.
 250   // How many words we use for filler objects.
 251   size_t word_fill_size = word_size_sum - word_size;
 252 
 253   // How many words memory we "waste" which cannot hold a filler object.
 254   size_t words_not_fillable = 0;
 255 
 256   if (word_fill_size >= min_fill_size()) {
 257     fill_with_objects(obj_top, word_fill_size);
 258   } else if (word_fill_size > 0) {
 259     // We have space to fill, but we cannot fit an object there.
 260     words_not_fillable = word_fill_size;
 261     word_fill_size = 0;
 262   }
 263 
 264   // We will set up the first region as "starts humongous". This
 265   // will also update the BOT covering all the regions to reflect
 266   // that there is a single object that starts at the bottom of the
 267   // first region.
 268   first_hr->set_starts_humongous(obj_top, word_fill_size);
 269   _policy->remset_tracker()->update_at_allocate(first_hr);
 270   // Then, if there are any, we will set up the "continues
 271   // humongous" regions.
 272   HeapRegion* hr = NULL;
 273   for (uint i = first + 1; i <= last; ++i) {
 274     hr = region_at(i);
 275     hr->set_continues_humongous(first_hr);
 276     _policy->remset_tracker()->update_at_allocate(hr);
 277   }
 278 
 279   // Up to this point no concurrent thread would have been able to
 280   // do any scanning on any region in this series. All the top
 281   // fields still point to bottom, so the intersection between
 282   // [bottom,top] and [card_start,card_end] will be empty. Before we
 283   // update the top fields, we'll do a storestore to make sure that
 284   // no thread sees the update to top before the zeroing of the
 285   // object header and the BOT initialization.
 286   OrderAccess::storestore();
 287 
 288   // Now, we will update the top fields of the "continues humongous"
 289   // regions except the last one.
 290   for (uint i = first; i < last; ++i) {
 291     hr = region_at(i);
 292     hr->set_top(hr->end());
 293   }
 294 
 295   hr = region_at(last);
 296   // If we cannot fit a filler object, we must set top to the end
 297   // of the humongous object, otherwise we cannot iterate the heap
 298   // and the BOT will not be complete.
 299   hr->set_top(hr->end() - words_not_fillable);
 300 
 301   assert(hr->bottom() < obj_top && obj_top <= hr->end(),
 302          "obj_top should be in last region");
 303 
 304   _verifier->check_bitmaps("Humongous Region Allocation", first_hr);
 305 
 306   assert(words_not_fillable == 0 ||
 307          first_hr->bottom() + word_size_sum - words_not_fillable == hr->top(),
 308          "Miscalculation in humongous allocation");
 309 
 310   increase_used((word_size_sum - words_not_fillable) * HeapWordSize);
 311 
 312   for (uint i = first; i <= last; ++i) {
 313     hr = region_at(i);
 314     _humongous_set.add(hr);
 315     _hr_printer.alloc(hr);
 316   }
 317 
 318   return new_obj;
 319 }
 320 
 321 size_t G1CollectedHeap::humongous_obj_size_in_regions(size_t word_size) {
 322   assert(is_humongous(word_size), "Object of size " SIZE_FORMAT " must be humongous here", word_size);
 323   return align_up(word_size, HeapRegion::GrainWords) / HeapRegion::GrainWords;
 324 }
 325 
 326 // If could fit into free regions w/o expansion, try.
 327 // Otherwise, if can expand, do so.
 328 // Otherwise, if using ex regions might help, try with ex given back.
 329 HeapWord* G1CollectedHeap::humongous_obj_allocate(size_t word_size) {
 330   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
 331 
 332   _verifier->verify_region_sets_optional();
 333 
 334   uint first = G1_NO_HRM_INDEX;
 335   uint obj_regions = (uint) humongous_obj_size_in_regions(word_size);
 336 
 337   if (obj_regions == 1) {
 338     // Only one region to allocate, try to use a fast path by directly allocating
 339     // from the free lists. Do not try to expand here, we will potentially do that
 340     // later.
 341     HeapRegion* hr = new_region(word_size, HeapRegionType::Humongous, false /* do_expand */);
 342     if (hr != NULL) {
 343       first = hr->hrm_index();
 344     }
 345   } else {
 346     // Policy: Try only empty regions (i.e. already committed first). Maybe we
 347     // are lucky enough to find some.
 348     first = _hrm->find_contiguous_only_empty(obj_regions);
 349     if (first != G1_NO_HRM_INDEX) {
 350       _hrm->allocate_free_regions_starting_at(first, obj_regions);
 351     }
 352   }
 353 
 354   if (first == G1_NO_HRM_INDEX) {
 355     // Policy: We could not find enough regions for the humongous object in the
 356     // free list. Look through the heap to find a mix of free and uncommitted regions.
 357     // If so, try expansion.
 358     first = _hrm->find_contiguous_empty_or_unavailable(obj_regions);
 359     if (first != G1_NO_HRM_INDEX) {
 360       // We found something. Make sure these regions are committed, i.e. expand
 361       // the heap. Alternatively we could do a defragmentation GC.
 362       log_debug(gc, ergo, heap)("Attempt heap expansion (humongous allocation request failed). Allocation request: " SIZE_FORMAT "B",
 363                                     word_size * HeapWordSize);
 364 
 365       _hrm->expand_at(first, obj_regions, workers());
 366       policy()->record_new_heap_size(num_regions());
 367 
 368 #ifdef ASSERT
 369       for (uint i = first; i < first + obj_regions; ++i) {
 370         HeapRegion* hr = region_at(i);
 371         assert(hr->is_free(), "sanity");
 372         assert(hr->is_empty(), "sanity");
 373         assert(is_on_master_free_list(hr), "sanity");
 374       }
 375 #endif
 376       _hrm->allocate_free_regions_starting_at(first, obj_regions);
 377     } else {
 378       // Policy: Potentially trigger a defragmentation GC.
 379     }
 380   }
 381 
 382   HeapWord* result = NULL;
 383   if (first != G1_NO_HRM_INDEX) {
 384     result = humongous_obj_allocate_initialize_regions(first, obj_regions, word_size);
 385     assert(result != NULL, "it should always return a valid result");
 386 
 387     // A successful humongous object allocation changes the used space
 388     // information of the old generation so we need to recalculate the
 389     // sizes and update the jstat counters here.
 390     g1mm()->update_sizes();
 391   }
 392 
 393   _verifier->verify_region_sets_optional();
 394 
 395   return result;
 396 }
 397 
 398 HeapWord* G1CollectedHeap::allocate_new_tlab(size_t min_size,
 399                                              size_t requested_size,
 400                                              size_t* actual_size) {
 401   assert_heap_not_locked_and_not_at_safepoint();
 402   assert(!is_humongous(requested_size), "we do not allow humongous TLABs");
 403 
 404   return attempt_allocation(min_size, requested_size, actual_size);
 405 }
 406 
 407 HeapWord*
 408 G1CollectedHeap::mem_allocate(size_t word_size,
 409                               bool*  gc_overhead_limit_was_exceeded) {
 410   assert_heap_not_locked_and_not_at_safepoint();
 411 
 412   if (is_humongous(word_size)) {
 413     return attempt_allocation_humongous(word_size);
 414   }
 415   size_t dummy = 0;
 416   return attempt_allocation(word_size, word_size, &dummy);
 417 }
 418 
 419 HeapWord* G1CollectedHeap::attempt_allocation_slow(size_t word_size) {
 420   ResourceMark rm; // For retrieving the thread names in log messages.
 421 
 422   // Make sure you read the note in attempt_allocation_humongous().
 423 
 424   assert_heap_not_locked_and_not_at_safepoint();
 425   assert(!is_humongous(word_size), "attempt_allocation_slow() should not "
 426          "be called for humongous allocation requests");
 427 
 428   // We should only get here after the first-level allocation attempt
 429   // (attempt_allocation()) failed to allocate.
 430 
 431   // We will loop until a) we manage to successfully perform the
 432   // allocation or b) we successfully schedule a collection which
 433   // fails to perform the allocation. b) is the only case when we'll
 434   // return NULL.
 435   HeapWord* result = NULL;
 436   for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 437     bool should_try_gc;
 438     uint gc_count_before;
 439 
 440     {
 441       MutexLocker x(Heap_lock);
 442       result = _allocator->attempt_allocation_locked(word_size);
 443       if (result != NULL) {
 444         return result;
 445       }
 446 
 447       // If the GCLocker is active and we are bound for a GC, try expanding young gen.
 448       // This is different to when only GCLocker::needs_gc() is set: try to avoid
 449       // waiting because the GCLocker is active to not wait too long.
 450       if (GCLocker::is_active_and_needs_gc() && policy()->can_expand_young_list()) {
 451         // No need for an ergo message here, can_expand_young_list() does this when
 452         // it returns true.
 453         result = _allocator->attempt_allocation_force(word_size);
 454         if (result != NULL) {
 455           return result;
 456         }
 457       }
 458       // Only try a GC if the GCLocker does not signal the need for a GC. Wait until
 459       // the GCLocker initiated GC has been performed and then retry. This includes
 460       // the case when the GC Locker is not active but has not been performed.
 461       should_try_gc = !GCLocker::needs_gc();
 462       // Read the GC count while still holding the Heap_lock.
 463       gc_count_before = total_collections();
 464     }
 465 
 466     if (should_try_gc) {
 467       bool succeeded;
 468       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 469                                    GCCause::_g1_inc_collection_pause);
 470       if (result != NULL) {
 471         assert(succeeded, "only way to get back a non-NULL result");
 472         log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT,
 473                              Thread::current()->name(), p2i(result));
 474         return result;
 475       }
 476 
 477       if (succeeded) {
 478         // We successfully scheduled a collection which failed to allocate. No
 479         // point in trying to allocate further. We'll just return NULL.
 480         log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate "
 481                              SIZE_FORMAT " words", Thread::current()->name(), word_size);
 482         return NULL;
 483       }
 484       log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT " words",
 485                            Thread::current()->name(), word_size);
 486     } else {
 487       // Failed to schedule a collection.
 488       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 489         log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating "
 490                                SIZE_FORMAT " words", Thread::current()->name(), word_size);
 491         return NULL;
 492       }
 493       log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name());
 494       // The GCLocker is either active or the GCLocker initiated
 495       // GC has not yet been performed. Stall until it is and
 496       // then retry the allocation.
 497       GCLocker::stall_until_clear();
 498       gclocker_retry_count += 1;
 499     }
 500 
 501     // We can reach here if we were unsuccessful in scheduling a
 502     // collection (because another thread beat us to it) or if we were
 503     // stalled due to the GC locker. In either can we should retry the
 504     // allocation attempt in case another thread successfully
 505     // performed a collection and reclaimed enough space. We do the
 506     // first attempt (without holding the Heap_lock) here and the
 507     // follow-on attempt will be at the start of the next loop
 508     // iteration (after taking the Heap_lock).
 509     size_t dummy = 0;
 510     result = _allocator->attempt_allocation(word_size, word_size, &dummy);
 511     if (result != NULL) {
 512       return result;
 513     }
 514 
 515     // Give a warning if we seem to be looping forever.
 516     if ((QueuedAllocationWarningCount > 0) &&
 517         (try_count % QueuedAllocationWarningCount == 0)) {
 518       log_warning(gc, alloc)("%s:  Retried allocation %u times for " SIZE_FORMAT " words",
 519                              Thread::current()->name(), try_count, word_size);
 520     }
 521   }
 522 
 523   ShouldNotReachHere();
 524   return NULL;
 525 }
 526 
 527 void G1CollectedHeap::begin_archive_alloc_range(bool open) {
 528   assert_at_safepoint_on_vm_thread();
 529   if (_archive_allocator == NULL) {
 530     _archive_allocator = G1ArchiveAllocator::create_allocator(this, open);
 531   }
 532 }
 533 
 534 bool G1CollectedHeap::is_archive_alloc_too_large(size_t word_size) {
 535   // Allocations in archive regions cannot be of a size that would be considered
 536   // humongous even for a minimum-sized region, because G1 region sizes/boundaries
 537   // may be different at archive-restore time.
 538   return word_size >= humongous_threshold_for(HeapRegion::min_region_size_in_words());
 539 }
 540 
 541 HeapWord* G1CollectedHeap::archive_mem_allocate(size_t word_size) {
 542   assert_at_safepoint_on_vm_thread();
 543   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 544   if (is_archive_alloc_too_large(word_size)) {
 545     return NULL;
 546   }
 547   return _archive_allocator->archive_mem_allocate(word_size);
 548 }
 549 
 550 void G1CollectedHeap::end_archive_alloc_range(GrowableArray<MemRegion>* ranges,
 551                                               size_t end_alignment_in_bytes) {
 552   assert_at_safepoint_on_vm_thread();
 553   assert(_archive_allocator != NULL, "_archive_allocator not initialized");
 554 
 555   // Call complete_archive to do the real work, filling in the MemRegion
 556   // array with the archive regions.
 557   _archive_allocator->complete_archive(ranges, end_alignment_in_bytes);
 558   delete _archive_allocator;
 559   _archive_allocator = NULL;
 560 }
 561 
 562 bool G1CollectedHeap::check_archive_addresses(MemRegion* ranges, size_t count) {
 563   assert(ranges != NULL, "MemRegion array NULL");
 564   assert(count != 0, "No MemRegions provided");
 565   MemRegion reserved = _hrm->reserved();
 566   for (size_t i = 0; i < count; i++) {
 567     if (!reserved.contains(ranges[i].start()) || !reserved.contains(ranges[i].last())) {
 568       return false;
 569     }
 570   }
 571   return true;
 572 }
 573 
 574 bool G1CollectedHeap::alloc_archive_regions(MemRegion* ranges,
 575                                             size_t count,
 576                                             bool open) {
 577   assert(!is_init_completed(), "Expect to be called at JVM init time");
 578   assert(ranges != NULL, "MemRegion array NULL");
 579   assert(count != 0, "No MemRegions provided");
 580   MutexLocker x(Heap_lock);
 581 
 582   MemRegion reserved = _hrm->reserved();
 583   HeapWord* prev_last_addr = NULL;
 584   HeapRegion* prev_last_region = NULL;
 585 
 586   // Temporarily disable pretouching of heap pages. This interface is used
 587   // when mmap'ing archived heap data in, so pre-touching is wasted.
 588   FlagSetting fs(AlwaysPreTouch, false);
 589 
 590   // Enable archive object checking used by G1MarkSweep. We have to let it know
 591   // about each archive range, so that objects in those ranges aren't marked.
 592   G1ArchiveAllocator::enable_archive_object_check();
 593 
 594   // For each specified MemRegion range, allocate the corresponding G1
 595   // regions and mark them as archive regions. We expect the ranges
 596   // in ascending starting address order, without overlap.
 597   for (size_t i = 0; i < count; i++) {
 598     MemRegion curr_range = ranges[i];
 599     HeapWord* start_address = curr_range.start();
 600     size_t word_size = curr_range.word_size();
 601     HeapWord* last_address = curr_range.last();
 602     size_t commits = 0;
 603 
 604     guarantee(reserved.contains(start_address) && reserved.contains(last_address),
 605               "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 606               p2i(start_address), p2i(last_address));
 607     guarantee(start_address > prev_last_addr,
 608               "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 609               p2i(start_address), p2i(prev_last_addr));
 610     prev_last_addr = last_address;
 611 
 612     // Check for ranges that start in the same G1 region in which the previous
 613     // range ended, and adjust the start address so we don't try to allocate
 614     // the same region again. If the current range is entirely within that
 615     // region, skip it, just adjusting the recorded top.
 616     HeapRegion* start_region = _hrm->addr_to_region(start_address);
 617     if ((prev_last_region != NULL) && (start_region == prev_last_region)) {
 618       start_address = start_region->end();
 619       if (start_address > last_address) {
 620         increase_used(word_size * HeapWordSize);
 621         start_region->set_top(last_address + 1);
 622         continue;
 623       }
 624       start_region->set_top(start_address);
 625       curr_range = MemRegion(start_address, last_address + 1);
 626       start_region = _hrm->addr_to_region(start_address);
 627     }
 628 
 629     // Perform the actual region allocation, exiting if it fails.
 630     // Then note how much new space we have allocated.
 631     if (!_hrm->allocate_containing_regions(curr_range, &commits, workers())) {
 632       return false;
 633     }
 634     increase_used(word_size * HeapWordSize);
 635     if (commits != 0) {
 636       log_debug(gc, ergo, heap)("Attempt heap expansion (allocate archive regions). Total size: " SIZE_FORMAT "B",
 637                                 HeapRegion::GrainWords * HeapWordSize * commits);
 638 
 639     }
 640 
 641     // Mark each G1 region touched by the range as archive, add it to
 642     // the old set, and set top.
 643     HeapRegion* curr_region = _hrm->addr_to_region(start_address);
 644     HeapRegion* last_region = _hrm->addr_to_region(last_address);
 645     prev_last_region = last_region;
 646 
 647     while (curr_region != NULL) {
 648       assert(curr_region->is_empty() && !curr_region->is_pinned(),
 649              "Region already in use (index %u)", curr_region->hrm_index());
 650       if (open) {
 651         curr_region->set_open_archive();
 652       } else {
 653         curr_region->set_closed_archive();
 654       }
 655       _hr_printer.alloc(curr_region);
 656       _archive_set.add(curr_region);
 657       HeapWord* top;
 658       HeapRegion* next_region;
 659       if (curr_region != last_region) {
 660         top = curr_region->end();
 661         next_region = _hrm->next_region_in_heap(curr_region);
 662       } else {
 663         top = last_address + 1;
 664         next_region = NULL;
 665       }
 666       curr_region->set_top(top);
 667       curr_region->set_first_dead(top);
 668       curr_region->set_end_of_live(top);
 669       curr_region = next_region;
 670     }
 671 
 672     // Notify mark-sweep of the archive
 673     G1ArchiveAllocator::set_range_archive(curr_range, open);
 674   }
 675   return true;
 676 }
 677 
 678 void G1CollectedHeap::fill_archive_regions(MemRegion* ranges, size_t count) {
 679   assert(!is_init_completed(), "Expect to be called at JVM init time");
 680   assert(ranges != NULL, "MemRegion array NULL");
 681   assert(count != 0, "No MemRegions provided");
 682   MemRegion reserved = _hrm->reserved();
 683   HeapWord *prev_last_addr = NULL;
 684   HeapRegion* prev_last_region = NULL;
 685 
 686   // For each MemRegion, create filler objects, if needed, in the G1 regions
 687   // that contain the address range. The address range actually within the
 688   // MemRegion will not be modified. That is assumed to have been initialized
 689   // elsewhere, probably via an mmap of archived heap data.
 690   MutexLocker x(Heap_lock);
 691   for (size_t i = 0; i < count; i++) {
 692     HeapWord* start_address = ranges[i].start();
 693     HeapWord* last_address = ranges[i].last();
 694 
 695     assert(reserved.contains(start_address) && reserved.contains(last_address),
 696            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 697            p2i(start_address), p2i(last_address));
 698     assert(start_address > prev_last_addr,
 699            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 700            p2i(start_address), p2i(prev_last_addr));
 701 
 702     HeapRegion* start_region = _hrm->addr_to_region(start_address);
 703     HeapRegion* last_region = _hrm->addr_to_region(last_address);
 704     HeapWord* bottom_address = start_region->bottom();
 705 
 706     // Check for a range beginning in the same region in which the
 707     // previous one ended.
 708     if (start_region == prev_last_region) {
 709       bottom_address = prev_last_addr + 1;
 710     }
 711 
 712     // Verify that the regions were all marked as archive regions by
 713     // alloc_archive_regions.
 714     HeapRegion* curr_region = start_region;
 715     while (curr_region != NULL) {
 716       guarantee(curr_region->is_archive(),
 717                 "Expected archive region at index %u", curr_region->hrm_index());
 718       if (curr_region != last_region) {
 719         curr_region = _hrm->next_region_in_heap(curr_region);
 720       } else {
 721         curr_region = NULL;
 722       }
 723     }
 724 
 725     prev_last_addr = last_address;
 726     prev_last_region = last_region;
 727 
 728     // Fill the memory below the allocated range with dummy object(s),
 729     // if the region bottom does not match the range start, or if the previous
 730     // range ended within the same G1 region, and there is a gap.
 731     if (start_address != bottom_address) {
 732       size_t fill_size = pointer_delta(start_address, bottom_address);
 733       G1CollectedHeap::fill_with_objects(bottom_address, fill_size);
 734       increase_used(fill_size * HeapWordSize);
 735     }
 736   }
 737 }
 738 
 739 inline HeapWord* G1CollectedHeap::attempt_allocation(size_t min_word_size,
 740                                                      size_t desired_word_size,
 741                                                      size_t* actual_word_size) {
 742   assert_heap_not_locked_and_not_at_safepoint();
 743   assert(!is_humongous(desired_word_size), "attempt_allocation() should not "
 744          "be called for humongous allocation requests");
 745 
 746   HeapWord* result = _allocator->attempt_allocation(min_word_size, desired_word_size, actual_word_size);
 747 
 748   if (result == NULL) {
 749     *actual_word_size = desired_word_size;
 750     result = attempt_allocation_slow(desired_word_size);
 751   }
 752 
 753   assert_heap_not_locked();
 754   if (result != NULL) {
 755     assert(*actual_word_size != 0, "Actual size must have been set here");
 756     dirty_young_block(result, *actual_word_size);
 757   } else {
 758     *actual_word_size = 0;
 759   }
 760 
 761   return result;
 762 }
 763 
 764 void G1CollectedHeap::dealloc_archive_regions(MemRegion* ranges, size_t count, bool is_open) {
 765   assert(!is_init_completed(), "Expect to be called at JVM init time");
 766   assert(ranges != NULL, "MemRegion array NULL");
 767   assert(count != 0, "No MemRegions provided");
 768   MemRegion reserved = _hrm->reserved();
 769   HeapWord* prev_last_addr = NULL;
 770   HeapRegion* prev_last_region = NULL;
 771   size_t size_used = 0;
 772   size_t uncommitted_regions = 0;
 773 
 774   // For each Memregion, free the G1 regions that constitute it, and
 775   // notify mark-sweep that the range is no longer to be considered 'archive.'
 776   MutexLocker x(Heap_lock);
 777   for (size_t i = 0; i < count; i++) {
 778     HeapWord* start_address = ranges[i].start();
 779     HeapWord* last_address = ranges[i].last();
 780 
 781     assert(reserved.contains(start_address) && reserved.contains(last_address),
 782            "MemRegion outside of heap [" PTR_FORMAT ", " PTR_FORMAT "]",
 783            p2i(start_address), p2i(last_address));
 784     assert(start_address > prev_last_addr,
 785            "Ranges not in ascending order: " PTR_FORMAT " <= " PTR_FORMAT ,
 786            p2i(start_address), p2i(prev_last_addr));
 787     size_used += ranges[i].byte_size();
 788     prev_last_addr = last_address;
 789 
 790     HeapRegion* start_region = _hrm->addr_to_region(start_address);
 791     HeapRegion* last_region = _hrm->addr_to_region(last_address);
 792 
 793     // Check for ranges that start in the same G1 region in which the previous
 794     // range ended, and adjust the start address so we don't try to free
 795     // the same region again. If the current range is entirely within that
 796     // region, skip it.
 797     if (start_region == prev_last_region) {
 798       start_address = start_region->end();
 799       if (start_address > last_address) {
 800         continue;
 801       }
 802       start_region = _hrm->addr_to_region(start_address);
 803     }
 804     prev_last_region = last_region;
 805 
 806     // After verifying that each region was marked as an archive region by
 807     // alloc_archive_regions, set it free and empty and uncommit it.
 808     HeapRegion* curr_region = start_region;
 809     while (curr_region != NULL) {
 810       guarantee(curr_region->is_archive(),
 811                 "Expected archive region at index %u", curr_region->hrm_index());
 812       uint curr_index = curr_region->hrm_index();
 813       _archive_set.remove(curr_region);
 814       curr_region->set_free();
 815       curr_region->set_top(curr_region->bottom());
 816       if (curr_region != last_region) {
 817         curr_region = _hrm->next_region_in_heap(curr_region);
 818       } else {
 819         curr_region = NULL;
 820       }
 821       _hrm->shrink_at(curr_index, 1);
 822       uncommitted_regions++;
 823     }
 824 
 825     // Notify mark-sweep that this is no longer an archive range.
 826     G1ArchiveAllocator::clear_range_archive(ranges[i], is_open);
 827   }
 828 
 829   if (uncommitted_regions != 0) {
 830     log_debug(gc, ergo, heap)("Attempt heap shrinking (uncommitted archive regions). Total size: " SIZE_FORMAT "B",
 831                               HeapRegion::GrainWords * HeapWordSize * uncommitted_regions);
 832   }
 833   decrease_used(size_used);
 834 }
 835 
 836 oop G1CollectedHeap::materialize_archived_object(oop obj) {
 837   assert(obj != NULL, "archived obj is NULL");
 838   assert(G1ArchiveAllocator::is_archived_object(obj), "must be archived object");
 839 
 840   // Loading an archived object makes it strongly reachable. If it is
 841   // loaded during concurrent marking, it must be enqueued to the SATB
 842   // queue, shading the previously white object gray.
 843   G1BarrierSet::enqueue(obj);
 844 
 845   return obj;
 846 }
 847 
 848 HeapWord* G1CollectedHeap::attempt_allocation_humongous(size_t word_size) {
 849   ResourceMark rm; // For retrieving the thread names in log messages.
 850 
 851   // The structure of this method has a lot of similarities to
 852   // attempt_allocation_slow(). The reason these two were not merged
 853   // into a single one is that such a method would require several "if
 854   // allocation is not humongous do this, otherwise do that"
 855   // conditional paths which would obscure its flow. In fact, an early
 856   // version of this code did use a unified method which was harder to
 857   // follow and, as a result, it had subtle bugs that were hard to
 858   // track down. So keeping these two methods separate allows each to
 859   // be more readable. It will be good to keep these two in sync as
 860   // much as possible.
 861 
 862   assert_heap_not_locked_and_not_at_safepoint();
 863   assert(is_humongous(word_size), "attempt_allocation_humongous() "
 864          "should only be called for humongous allocations");
 865 
 866   // Humongous objects can exhaust the heap quickly, so we should check if we
 867   // need to start a marking cycle at each humongous object allocation. We do
 868   // the check before we do the actual allocation. The reason for doing it
 869   // before the allocation is that we avoid having to keep track of the newly
 870   // allocated memory while we do a GC.
 871   if (policy()->need_to_start_conc_mark("concurrent humongous allocation",
 872                                            word_size)) {
 873     collect(GCCause::_g1_humongous_allocation);
 874   }
 875 
 876   // We will loop until a) we manage to successfully perform the
 877   // allocation or b) we successfully schedule a collection which
 878   // fails to perform the allocation. b) is the only case when we'll
 879   // return NULL.
 880   HeapWord* result = NULL;
 881   for (uint try_count = 1, gclocker_retry_count = 0; /* we'll return */; try_count += 1) {
 882     bool should_try_gc;
 883     uint gc_count_before;
 884 
 885 
 886     {
 887       MutexLocker x(Heap_lock);
 888 
 889       // Given that humongous objects are not allocated in young
 890       // regions, we'll first try to do the allocation without doing a
 891       // collection hoping that there's enough space in the heap.
 892       result = humongous_obj_allocate(word_size);
 893       if (result != NULL) {
 894         size_t size_in_regions = humongous_obj_size_in_regions(word_size);
 895         policy()->add_bytes_allocated_in_old_since_last_gc(size_in_regions * HeapRegion::GrainBytes);
 896         return result;
 897       }
 898 
 899       // Only try a GC if the GCLocker does not signal the need for a GC. Wait until
 900       // the GCLocker initiated GC has been performed and then retry. This includes
 901       // the case when the GC Locker is not active but has not been performed.
 902       should_try_gc = !GCLocker::needs_gc();
 903       // Read the GC count while still holding the Heap_lock.
 904       gc_count_before = total_collections();
 905     }
 906 
 907     if (should_try_gc) {
 908       bool succeeded;
 909       result = do_collection_pause(word_size, gc_count_before, &succeeded,
 910                                    GCCause::_g1_humongous_allocation);
 911       if (result != NULL) {
 912         assert(succeeded, "only way to get back a non-NULL result");
 913         log_trace(gc, alloc)("%s: Successfully scheduled collection returning " PTR_FORMAT,
 914                              Thread::current()->name(), p2i(result));
 915         return result;
 916       }
 917 
 918       if (succeeded) {
 919         // We successfully scheduled a collection which failed to allocate. No
 920         // point in trying to allocate further. We'll just return NULL.
 921         log_trace(gc, alloc)("%s: Successfully scheduled collection failing to allocate "
 922                              SIZE_FORMAT " words", Thread::current()->name(), word_size);
 923         return NULL;
 924       }
 925       log_trace(gc, alloc)("%s: Unsuccessfully scheduled collection allocating " SIZE_FORMAT "",
 926                            Thread::current()->name(), word_size);
 927     } else {
 928       // Failed to schedule a collection.
 929       if (gclocker_retry_count > GCLockerRetryAllocationCount) {
 930         log_warning(gc, alloc)("%s: Retried waiting for GCLocker too often allocating "
 931                                SIZE_FORMAT " words", Thread::current()->name(), word_size);
 932         return NULL;
 933       }
 934       log_trace(gc, alloc)("%s: Stall until clear", Thread::current()->name());
 935       // The GCLocker is either active or the GCLocker initiated
 936       // GC has not yet been performed. Stall until it is and
 937       // then retry the allocation.
 938       GCLocker::stall_until_clear();
 939       gclocker_retry_count += 1;
 940     }
 941 
 942 
 943     // We can reach here if we were unsuccessful in scheduling a
 944     // collection (because another thread beat us to it) or if we were
 945     // stalled due to the GC locker. In either can we should retry the
 946     // allocation attempt in case another thread successfully
 947     // performed a collection and reclaimed enough space.
 948     // Humongous object allocation always needs a lock, so we wait for the retry
 949     // in the next iteration of the loop, unlike for the regular iteration case.
 950     // Give a warning if we seem to be looping forever.
 951 
 952     if ((QueuedAllocationWarningCount > 0) &&
 953         (try_count % QueuedAllocationWarningCount == 0)) {
 954       log_warning(gc, alloc)("%s: Retried allocation %u times for " SIZE_FORMAT " words",
 955                              Thread::current()->name(), try_count, word_size);
 956     }
 957   }
 958 
 959   ShouldNotReachHere();
 960   return NULL;
 961 }
 962 
 963 HeapWord* G1CollectedHeap::attempt_allocation_at_safepoint(size_t word_size,
 964                                                            bool expect_null_mutator_alloc_region) {
 965   assert_at_safepoint_on_vm_thread();
 966   assert(!_allocator->has_mutator_alloc_region() || !expect_null_mutator_alloc_region,
 967          "the current alloc region was unexpectedly found to be non-NULL");
 968 
 969   if (!is_humongous(word_size)) {
 970     return _allocator->attempt_allocation_locked(word_size);
 971   } else {
 972     HeapWord* result = humongous_obj_allocate(word_size);
 973     if (result != NULL && policy()->need_to_start_conc_mark("STW humongous allocation")) {
 974       collector_state()->set_initiate_conc_mark_if_possible(true);
 975     }
 976     return result;
 977   }
 978 
 979   ShouldNotReachHere();
 980 }
 981 
 982 class PostCompactionPrinterClosure: public HeapRegionClosure {
 983 private:
 984   G1HRPrinter* _hr_printer;
 985 public:
 986   bool do_heap_region(HeapRegion* hr) {
 987     assert(!hr->is_young(), "not expecting to find young regions");
 988     _hr_printer->post_compaction(hr);
 989     return false;
 990   }
 991 
 992   PostCompactionPrinterClosure(G1HRPrinter* hr_printer)
 993     : _hr_printer(hr_printer) { }
 994 };
 995 
 996 void G1CollectedHeap::print_hrm_post_compaction() {
 997   if (_hr_printer.is_active()) {
 998     PostCompactionPrinterClosure cl(hr_printer());
 999     heap_region_iterate(&cl);
1000   }
1001 }
1002 
1003 void G1CollectedHeap::abort_concurrent_cycle() {
1004   // If we start the compaction before the CM threads finish
1005   // scanning the root regions we might trip them over as we'll
1006   // be moving objects / updating references. So let's wait until
1007   // they are done. By telling them to abort, they should complete
1008   // early.
1009   _cm->root_regions()->abort();
1010   _cm->root_regions()->wait_until_scan_finished();
1011 
1012   // Disable discovery and empty the discovered lists
1013   // for the CM ref processor.
1014   _ref_processor_cm->disable_discovery();
1015   _ref_processor_cm->abandon_partial_discovery();
1016   _ref_processor_cm->verify_no_references_recorded();
1017 
1018   // Abandon current iterations of concurrent marking and concurrent
1019   // refinement, if any are in progress.
1020   concurrent_mark()->concurrent_cycle_abort();
1021 }
1022 
1023 void G1CollectedHeap::prepare_heap_for_full_collection() {
1024   // Make sure we'll choose a new allocation region afterwards.
1025   _allocator->release_mutator_alloc_region();
1026   _allocator->abandon_gc_alloc_regions();
1027 
1028   // We may have added regions to the current incremental collection
1029   // set between the last GC or pause and now. We need to clear the
1030   // incremental collection set and then start rebuilding it afresh
1031   // after this full GC.
1032   abandon_collection_set(collection_set());
1033 
1034   tear_down_region_sets(false /* free_list_only */);
1035 
1036   hrm()->prepare_for_full_collection_start();
1037 }
1038 
1039 void G1CollectedHeap::verify_before_full_collection(bool explicit_gc) {
1040   assert(!GCCause::is_user_requested_gc(gc_cause()) || explicit_gc, "invariant");
1041   assert_used_and_recalculate_used_equal(this);
1042   _verifier->verify_region_sets_optional();
1043   _verifier->verify_before_gc(G1HeapVerifier::G1VerifyFull);
1044   _verifier->check_bitmaps("Full GC Start");
1045 }
1046 
1047 void G1CollectedHeap::prepare_heap_for_mutators() {
1048   hrm()->prepare_for_full_collection_end();
1049 
1050   // Delete metaspaces for unloaded class loaders and clean up loader_data graph
1051   ClassLoaderDataGraph::purge();
1052   MetaspaceUtils::verify_metrics();
1053 
1054   // Prepare heap for normal collections.
1055   assert(num_free_regions() == 0, "we should not have added any free regions");
1056   rebuild_region_sets(false /* free_list_only */);
1057   abort_refinement();
1058   resize_heap_if_necessary();
1059 
1060   // Rebuild the strong code root lists for each region
1061   rebuild_strong_code_roots();
1062 
1063   // Purge code root memory
1064   purge_code_root_memory();
1065 
1066   // Start a new incremental collection set for the next pause
1067   start_new_collection_set();
1068 
1069   _allocator->init_mutator_alloc_region();
1070 
1071   // Post collection state updates.
1072   MetaspaceGC::compute_new_size();
1073 }
1074 
1075 void G1CollectedHeap::abort_refinement() {
1076   if (_hot_card_cache->use_cache()) {
1077     _hot_card_cache->reset_hot_cache();
1078   }
1079 
1080   // Discard all remembered set updates.
1081   G1BarrierSet::dirty_card_queue_set().abandon_logs();
1082   assert(G1BarrierSet::dirty_card_queue_set().num_cards() == 0,
1083          "DCQS should be empty");
1084 }
1085 
1086 void G1CollectedHeap::verify_after_full_collection() {
1087   _hrm->verify_optional();
1088   _verifier->verify_region_sets_optional();
1089   _verifier->verify_after_gc(G1HeapVerifier::G1VerifyFull);
1090   // Clear the previous marking bitmap, if needed for bitmap verification.
1091   // Note we cannot do this when we clear the next marking bitmap in
1092   // G1ConcurrentMark::abort() above since VerifyDuringGC verifies the
1093   // objects marked during a full GC against the previous bitmap.
1094   // But we need to clear it before calling check_bitmaps below since
1095   // the full GC has compacted objects and updated TAMS but not updated
1096   // the prev bitmap.
1097   if (G1VerifyBitmaps) {
1098     GCTraceTime(Debug, gc) tm("Clear Prev Bitmap for Verification");
1099     _cm->clear_prev_bitmap(workers());
1100   }
1101   // This call implicitly verifies that the next bitmap is clear after Full GC.
1102   _verifier->check_bitmaps("Full GC End");
1103 
1104   // At this point there should be no regions in the
1105   // entire heap tagged as young.
1106   assert(check_young_list_empty(), "young list should be empty at this point");
1107 
1108   // Note: since we've just done a full GC, concurrent
1109   // marking is no longer active. Therefore we need not
1110   // re-enable reference discovery for the CM ref processor.
1111   // That will be done at the start of the next marking cycle.
1112   // We also know that the STW processor should no longer
1113   // discover any new references.
1114   assert(!_ref_processor_stw->discovery_enabled(), "Postcondition");
1115   assert(!_ref_processor_cm->discovery_enabled(), "Postcondition");
1116   _ref_processor_stw->verify_no_references_recorded();
1117   _ref_processor_cm->verify_no_references_recorded();
1118 }
1119 
1120 void G1CollectedHeap::print_heap_after_full_collection(G1HeapTransition* heap_transition) {
1121   // Post collection logging.
1122   // We should do this after we potentially resize the heap so
1123   // that all the COMMIT / UNCOMMIT events are generated before
1124   // the compaction events.
1125   print_hrm_post_compaction();
1126   heap_transition->print();
1127   print_heap_after_gc();
1128   print_heap_regions();
1129 #ifdef TRACESPINNING
1130   ParallelTaskTerminator::print_termination_counts();
1131 #endif
1132 }
1133 
1134 bool G1CollectedHeap::do_full_collection(bool explicit_gc,
1135                                          bool clear_all_soft_refs) {
1136   assert_at_safepoint_on_vm_thread();
1137 
1138   if (GCLocker::check_active_before_gc()) {
1139     // Full GC was not completed.
1140     return false;
1141   }
1142 
1143   const bool do_clear_all_soft_refs = clear_all_soft_refs ||
1144       soft_ref_policy()->should_clear_all_soft_refs();
1145 
1146   G1FullCollector collector(this, explicit_gc, do_clear_all_soft_refs);
1147   GCTraceTime(Info, gc) tm("Pause Full", NULL, gc_cause(), true);
1148 
1149   collector.prepare_collection();
1150   collector.collect();
1151   collector.complete_collection();
1152 
1153   // Full collection was successfully completed.
1154   return true;
1155 }
1156 
1157 void G1CollectedHeap::do_full_collection(bool clear_all_soft_refs) {
1158   // Currently, there is no facility in the do_full_collection(bool) API to notify
1159   // the caller that the collection did not succeed (e.g., because it was locked
1160   // out by the GC locker). So, right now, we'll ignore the return value.
1161   bool dummy = do_full_collection(true,                /* explicit_gc */
1162                                   clear_all_soft_refs);
1163 }
1164 
1165 void G1CollectedHeap::resize_heap_if_necessary() {
1166   assert_at_safepoint_on_vm_thread();
1167 
1168   // Capacity, free and used after the GC counted as full regions to
1169   // include the waste in the following calculations.
1170   const size_t capacity_after_gc = capacity();
1171   const size_t used_after_gc = capacity_after_gc - unused_committed_regions_in_bytes();
1172 
1173   // This is enforced in arguments.cpp.
1174   assert(MinHeapFreeRatio <= MaxHeapFreeRatio,
1175          "otherwise the code below doesn't make sense");
1176 
1177   // We don't have floating point command-line arguments
1178   const double minimum_free_percentage = (double) MinHeapFreeRatio / 100.0;
1179   const double maximum_used_percentage = 1.0 - minimum_free_percentage;
1180   const double maximum_free_percentage = (double) MaxHeapFreeRatio / 100.0;
1181   const double minimum_used_percentage = 1.0 - maximum_free_percentage;
1182 
1183   // We have to be careful here as these two calculations can overflow
1184   // 32-bit size_t's.
1185   double used_after_gc_d = (double) used_after_gc;
1186   double minimum_desired_capacity_d = used_after_gc_d / maximum_used_percentage;
1187   double maximum_desired_capacity_d = used_after_gc_d / minimum_used_percentage;
1188 
1189   // Let's make sure that they are both under the max heap size, which
1190   // by default will make them fit into a size_t.
1191   double desired_capacity_upper_bound = (double) MaxHeapSize;
1192   minimum_desired_capacity_d = MIN2(minimum_desired_capacity_d,
1193                                     desired_capacity_upper_bound);
1194   maximum_desired_capacity_d = MIN2(maximum_desired_capacity_d,
1195                                     desired_capacity_upper_bound);
1196 
1197   // We can now safely turn them into size_t's.
1198   size_t minimum_desired_capacity = (size_t) minimum_desired_capacity_d;
1199   size_t maximum_desired_capacity = (size_t) maximum_desired_capacity_d;
1200 
1201   // This assert only makes sense here, before we adjust them
1202   // with respect to the min and max heap size.
1203   assert(minimum_desired_capacity <= maximum_desired_capacity,
1204          "minimum_desired_capacity = " SIZE_FORMAT ", "
1205          "maximum_desired_capacity = " SIZE_FORMAT,
1206          minimum_desired_capacity, maximum_desired_capacity);
1207 
1208   // Should not be greater than the heap max size. No need to adjust
1209   // it with respect to the heap min size as it's a lower bound (i.e.,
1210   // we'll try to make the capacity larger than it, not smaller).
1211   minimum_desired_capacity = MIN2(minimum_desired_capacity, MaxHeapSize);
1212   // Should not be less than the heap min size. No need to adjust it
1213   // with respect to the heap max size as it's an upper bound (i.e.,
1214   // we'll try to make the capacity smaller than it, not greater).
1215   maximum_desired_capacity =  MAX2(maximum_desired_capacity, MinHeapSize);
1216 
1217   if (capacity_after_gc < minimum_desired_capacity) {
1218     // Don't expand unless it's significant
1219     size_t expand_bytes = minimum_desired_capacity - capacity_after_gc;
1220 
1221     log_debug(gc, ergo, heap)("Attempt heap expansion (capacity lower than min desired capacity). "
1222                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1223                               "min_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1224                               capacity_after_gc, used_after_gc, used(), minimum_desired_capacity, MinHeapFreeRatio);
1225 
1226     expand(expand_bytes, _workers);
1227 
1228     // No expansion, now see if we want to shrink
1229   } else if (capacity_after_gc > maximum_desired_capacity) {
1230     // Capacity too large, compute shrinking size
1231     size_t shrink_bytes = capacity_after_gc - maximum_desired_capacity;
1232 
1233     log_debug(gc, ergo, heap)("Attempt heap shrinking (capacity higher than max desired capacity). "
1234                               "Capacity: " SIZE_FORMAT "B occupancy: " SIZE_FORMAT "B live: " SIZE_FORMAT "B "
1235                               "maximum_desired_capacity: " SIZE_FORMAT "B (" UINTX_FORMAT " %%)",
1236                               capacity_after_gc, used_after_gc, used(), maximum_desired_capacity, MaxHeapFreeRatio);
1237 
1238     shrink(shrink_bytes);
1239   }
1240 }
1241 
1242 HeapWord* G1CollectedHeap::satisfy_failed_allocation_helper(size_t word_size,
1243                                                             bool do_gc,
1244                                                             bool clear_all_soft_refs,
1245                                                             bool expect_null_mutator_alloc_region,
1246                                                             bool* gc_succeeded) {
1247   *gc_succeeded = true;
1248   // Let's attempt the allocation first.
1249   HeapWord* result =
1250     attempt_allocation_at_safepoint(word_size,
1251                                     expect_null_mutator_alloc_region);
1252   if (result != NULL) {
1253     return result;
1254   }
1255 
1256   // In a G1 heap, we're supposed to keep allocation from failing by
1257   // incremental pauses.  Therefore, at least for now, we'll favor
1258   // expansion over collection.  (This might change in the future if we can
1259   // do something smarter than full collection to satisfy a failed alloc.)
1260   result = expand_and_allocate(word_size);
1261   if (result != NULL) {
1262     return result;
1263   }
1264 
1265   if (do_gc) {
1266     // Expansion didn't work, we'll try to do a Full GC.
1267     *gc_succeeded = do_full_collection(false, /* explicit_gc */
1268                                        clear_all_soft_refs);
1269   }
1270 
1271   return NULL;
1272 }
1273 
1274 HeapWord* G1CollectedHeap::satisfy_failed_allocation(size_t word_size,
1275                                                      bool* succeeded) {
1276   assert_at_safepoint_on_vm_thread();
1277 
1278   // Attempts to allocate followed by Full GC.
1279   HeapWord* result =
1280     satisfy_failed_allocation_helper(word_size,
1281                                      true,  /* do_gc */
1282                                      false, /* clear_all_soft_refs */
1283                                      false, /* expect_null_mutator_alloc_region */
1284                                      succeeded);
1285 
1286   if (result != NULL || !*succeeded) {
1287     return result;
1288   }
1289 
1290   // Attempts to allocate followed by Full GC that will collect all soft references.
1291   result = satisfy_failed_allocation_helper(word_size,
1292                                             true, /* do_gc */
1293                                             true, /* clear_all_soft_refs */
1294                                             true, /* expect_null_mutator_alloc_region */
1295                                             succeeded);
1296 
1297   if (result != NULL || !*succeeded) {
1298     return result;
1299   }
1300 
1301   // Attempts to allocate, no GC
1302   result = satisfy_failed_allocation_helper(word_size,
1303                                             false, /* do_gc */
1304                                             false, /* clear_all_soft_refs */
1305                                             true,  /* expect_null_mutator_alloc_region */
1306                                             succeeded);
1307 
1308   if (result != NULL) {
1309     return result;
1310   }
1311 
1312   assert(!soft_ref_policy()->should_clear_all_soft_refs(),
1313          "Flag should have been handled and cleared prior to this point");
1314 
1315   // What else?  We might try synchronous finalization later.  If the total
1316   // space available is large enough for the allocation, then a more
1317   // complete compaction phase than we've tried so far might be
1318   // appropriate.
1319   return NULL;
1320 }
1321 
1322 // Attempting to expand the heap sufficiently
1323 // to support an allocation of the given "word_size".  If
1324 // successful, perform the allocation and return the address of the
1325 // allocated block, or else "NULL".
1326 
1327 HeapWord* G1CollectedHeap::expand_and_allocate(size_t word_size) {
1328   assert_at_safepoint_on_vm_thread();
1329 
1330   _verifier->verify_region_sets_optional();
1331 
1332   size_t expand_bytes = MAX2(word_size * HeapWordSize, MinHeapDeltaBytes);
1333   log_debug(gc, ergo, heap)("Attempt heap expansion (allocation request failed). Allocation request: " SIZE_FORMAT "B",
1334                             word_size * HeapWordSize);
1335 
1336 
1337   if (expand(expand_bytes, _workers)) {
1338     _hrm->verify_optional();
1339     _verifier->verify_region_sets_optional();
1340     return attempt_allocation_at_safepoint(word_size,
1341                                            false /* expect_null_mutator_alloc_region */);
1342   }
1343   return NULL;
1344 }
1345 
1346 bool G1CollectedHeap::expand(size_t expand_bytes, WorkGang* pretouch_workers, double* expand_time_ms) {
1347   size_t aligned_expand_bytes = ReservedSpace::page_align_size_up(expand_bytes);
1348   aligned_expand_bytes = align_up(aligned_expand_bytes,
1349                                        HeapRegion::GrainBytes);
1350 
1351   log_debug(gc, ergo, heap)("Expand the heap. requested expansion amount: " SIZE_FORMAT "B expansion amount: " SIZE_FORMAT "B",
1352                             expand_bytes, aligned_expand_bytes);
1353 
1354   if (is_maximal_no_gc()) {
1355     log_debug(gc, ergo, heap)("Did not expand the heap (heap already fully expanded)");
1356     return false;
1357   }
1358 
1359   double expand_heap_start_time_sec = os::elapsedTime();
1360   uint regions_to_expand = (uint)(aligned_expand_bytes / HeapRegion::GrainBytes);
1361   assert(regions_to_expand > 0, "Must expand by at least one region");
1362 
1363   uint expanded_by = _hrm->expand_by(regions_to_expand, pretouch_workers);
1364   if (expand_time_ms != NULL) {
1365     *expand_time_ms = (os::elapsedTime() - expand_heap_start_time_sec) * MILLIUNITS;
1366   }
1367 
1368   if (expanded_by > 0) {
1369     size_t actual_expand_bytes = expanded_by * HeapRegion::GrainBytes;
1370     assert(actual_expand_bytes <= aligned_expand_bytes, "post-condition");
1371     policy()->record_new_heap_size(num_regions());
1372   } else {
1373     log_debug(gc, ergo, heap)("Did not expand the heap (heap expansion operation failed)");
1374 
1375     // The expansion of the virtual storage space was unsuccessful.
1376     // Let's see if it was because we ran out of swap.
1377     if (G1ExitOnExpansionFailure &&
1378         _hrm->available() >= regions_to_expand) {
1379       // We had head room...
1380       vm_exit_out_of_memory(aligned_expand_bytes, OOM_MMAP_ERROR, "G1 heap expansion");
1381     }
1382   }
1383   return regions_to_expand > 0;
1384 }
1385 
1386 void G1CollectedHeap::shrink_helper(size_t shrink_bytes) {
1387   size_t aligned_shrink_bytes =
1388     ReservedSpace::page_align_size_down(shrink_bytes);
1389   aligned_shrink_bytes = align_down(aligned_shrink_bytes,
1390                                          HeapRegion::GrainBytes);
1391   uint num_regions_to_remove = (uint)(shrink_bytes / HeapRegion::GrainBytes);
1392 
1393   uint num_regions_removed = _hrm->shrink_by(num_regions_to_remove);
1394   size_t shrunk_bytes = num_regions_removed * HeapRegion::GrainBytes;
1395 
1396 
1397   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",
1398                             shrink_bytes, aligned_shrink_bytes, shrunk_bytes);
1399   if (num_regions_removed > 0) {
1400     policy()->record_new_heap_size(num_regions());
1401   } else {
1402     log_debug(gc, ergo, heap)("Did not expand the heap (heap shrinking operation failed)");
1403   }
1404 }
1405 
1406 void G1CollectedHeap::shrink(size_t shrink_bytes) {
1407   _verifier->verify_region_sets_optional();
1408 
1409   // We should only reach here at the end of a Full GC or during Remark which
1410   // means we should not not be holding to any GC alloc regions. The method
1411   // below will make sure of that and do any remaining clean up.
1412   _allocator->abandon_gc_alloc_regions();
1413 
1414   // Instead of tearing down / rebuilding the free lists here, we
1415   // could instead use the remove_all_pending() method on free_list to
1416   // remove only the ones that we need to remove.
1417   tear_down_region_sets(true /* free_list_only */);
1418   shrink_helper(shrink_bytes);
1419   rebuild_region_sets(true /* free_list_only */);
1420 
1421   _hrm->verify_optional();
1422   _verifier->verify_region_sets_optional();
1423 }
1424 
1425 class OldRegionSetChecker : public HeapRegionSetChecker {
1426 public:
1427   void check_mt_safety() {
1428     // Master Old Set MT safety protocol:
1429     // (a) If we're at a safepoint, operations on the master old set
1430     // should be invoked:
1431     // - by the VM thread (which will serialize them), or
1432     // - by the GC workers while holding the FreeList_lock, if we're
1433     //   at a safepoint for an evacuation pause (this lock is taken
1434     //   anyway when an GC alloc region is retired so that a new one
1435     //   is allocated from the free list), or
1436     // - by the GC workers while holding the OldSets_lock, if we're at a
1437     //   safepoint for a cleanup pause.
1438     // (b) If we're not at a safepoint, operations on the master old set
1439     // should be invoked while holding the Heap_lock.
1440 
1441     if (SafepointSynchronize::is_at_safepoint()) {
1442       guarantee(Thread::current()->is_VM_thread() ||
1443                 FreeList_lock->owned_by_self() || OldSets_lock->owned_by_self(),
1444                 "master old set MT safety protocol at a safepoint");
1445     } else {
1446       guarantee(Heap_lock->owned_by_self(), "master old set MT safety protocol outside a safepoint");
1447     }
1448   }
1449   bool is_correct_type(HeapRegion* hr) { return hr->is_old(); }
1450   const char* get_description() { return "Old Regions"; }
1451 };
1452 
1453 class ArchiveRegionSetChecker : public HeapRegionSetChecker {
1454 public:
1455   void check_mt_safety() {
1456     guarantee(!Universe::is_fully_initialized() || SafepointSynchronize::is_at_safepoint(),
1457               "May only change archive regions during initialization or safepoint.");
1458   }
1459   bool is_correct_type(HeapRegion* hr) { return hr->is_archive(); }
1460   const char* get_description() { return "Archive Regions"; }
1461 };
1462 
1463 class HumongousRegionSetChecker : public HeapRegionSetChecker {
1464 public:
1465   void check_mt_safety() {
1466     // Humongous Set MT safety protocol:
1467     // (a) If we're at a safepoint, operations on the master humongous
1468     // set should be invoked by either the VM thread (which will
1469     // serialize them) or by the GC workers while holding the
1470     // OldSets_lock.
1471     // (b) If we're not at a safepoint, operations on the master
1472     // humongous set should be invoked while holding the Heap_lock.
1473 
1474     if (SafepointSynchronize::is_at_safepoint()) {
1475       guarantee(Thread::current()->is_VM_thread() ||
1476                 OldSets_lock->owned_by_self(),
1477                 "master humongous set MT safety protocol at a safepoint");
1478     } else {
1479       guarantee(Heap_lock->owned_by_self(),
1480                 "master humongous set MT safety protocol outside a safepoint");
1481     }
1482   }
1483   bool is_correct_type(HeapRegion* hr) { return hr->is_humongous(); }
1484   const char* get_description() { return "Humongous Regions"; }
1485 };
1486 
1487 G1CollectedHeap::G1CollectedHeap() :
1488   CollectedHeap(),
1489   _young_gen_sampling_thread(NULL),
1490   _workers(NULL),
1491   _card_table(NULL),
1492   _soft_ref_policy(),
1493   _old_set("Old Region Set", new OldRegionSetChecker()),
1494   _archive_set("Archive Region Set", new ArchiveRegionSetChecker()),
1495   _humongous_set("Humongous Region Set", new HumongousRegionSetChecker()),
1496   _bot(NULL),
1497   _listener(),
1498   _hrm(NULL),
1499   _allocator(NULL),
1500   _verifier(NULL),
1501   _summary_bytes_used(0),
1502   _archive_allocator(NULL),
1503   _survivor_evac_stats("Young", YoungPLABSize, PLABWeight),
1504   _old_evac_stats("Old", OldPLABSize, PLABWeight),
1505   _expand_heap_after_alloc_failure(true),
1506   _g1mm(NULL),
1507   _humongous_reclaim_candidates(),
1508   _has_humongous_reclaim_candidates(false),
1509   _hr_printer(),
1510   _collector_state(),
1511   _old_marking_cycles_started(0),
1512   _old_marking_cycles_completed(0),
1513   _eden(),
1514   _survivor(),
1515   _gc_timer_stw(new (ResourceObj::C_HEAP, mtGC) STWGCTimer()),
1516   _gc_tracer_stw(new (ResourceObj::C_HEAP, mtGC) G1NewTracer()),
1517   _policy(G1Policy::create_policy(_gc_timer_stw)),
1518   _heap_sizing_policy(NULL),
1519   _collection_set(this, _policy),
1520   _hot_card_cache(NULL),
1521   _rem_set(NULL),
1522   _cm(NULL),
1523   _cm_thread(NULL),
1524   _cr(NULL),
1525   _task_queues(NULL),
1526   _evacuation_failed(false),
1527   _evacuation_failed_info_array(NULL),
1528   _preserved_marks_set(true /* in_c_heap */),
1529 #ifndef PRODUCT
1530   _evacuation_failure_alot_for_current_gc(false),
1531   _evacuation_failure_alot_gc_number(0),
1532   _evacuation_failure_alot_count(0),
1533 #endif
1534   _ref_processor_stw(NULL),
1535   _is_alive_closure_stw(this),
1536   _is_subject_to_discovery_stw(this),
1537   _ref_processor_cm(NULL),
1538   _is_alive_closure_cm(this),
1539   _is_subject_to_discovery_cm(this),
1540   _region_attr() {
1541 
1542   _verifier = new G1HeapVerifier(this);
1543 
1544   _allocator = new G1Allocator(this);
1545 
1546   _heap_sizing_policy = G1HeapSizingPolicy::create(this, _policy->analytics());
1547 
1548   _humongous_object_threshold_in_words = humongous_threshold_for(HeapRegion::GrainWords);
1549 
1550   // Override the default _filler_array_max_size so that no humongous filler
1551   // objects are created.
1552   _filler_array_max_size = _humongous_object_threshold_in_words;
1553 
1554   uint n_queues = ParallelGCThreads;
1555   _task_queues = new RefToScanQueueSet(n_queues);
1556 
1557   _evacuation_failed_info_array = NEW_C_HEAP_ARRAY(EvacuationFailedInfo, n_queues, mtGC);
1558 
1559   for (uint i = 0; i < n_queues; i++) {
1560     RefToScanQueue* q = new RefToScanQueue();
1561     q->initialize();
1562     _task_queues->register_queue(i, q);
1563     ::new (&_evacuation_failed_info_array[i]) EvacuationFailedInfo();
1564   }
1565 
1566   // Initialize the G1EvacuationFailureALot counters and flags.
1567   NOT_PRODUCT(reset_evacuation_should_fail();)
1568   _gc_tracer_stw->initialize();
1569 
1570   guarantee(_task_queues != NULL, "task_queues allocation failure.");
1571 }
1572 
1573 static size_t actual_reserved_page_size(ReservedSpace rs) {
1574   size_t page_size = os::vm_page_size();
1575   if (UseLargePages) {
1576     // There are two ways to manage large page memory.
1577     // 1. OS supports committing large page memory.
1578     // 2. OS doesn't support committing large page memory so ReservedSpace manages it.
1579     //    And ReservedSpace calls it 'special'. If we failed to set 'special',
1580     //    we reserved memory without large page.
1581     if (os::can_commit_large_page_memory() || rs.special()) {
1582       // An alignment at ReservedSpace comes from preferred page size or
1583       // heap alignment, and if the alignment came from heap alignment, it could be
1584       // larger than large pages size. So need to cap with the large page size.
1585       page_size = MIN2(rs.alignment(), os::large_page_size());
1586     }
1587   }
1588 
1589   return page_size;
1590 }
1591 
1592 G1RegionToSpaceMapper* G1CollectedHeap::create_aux_memory_mapper(const char* description,
1593                                                                  size_t size,
1594                                                                  size_t translation_factor) {
1595   size_t preferred_page_size = os::page_size_for_region_unaligned(size, 1);
1596   // Allocate a new reserved space, preferring to use large pages.
1597   ReservedSpace rs(size, preferred_page_size);
1598   size_t page_size = actual_reserved_page_size(rs);
1599   G1RegionToSpaceMapper* result  =
1600     G1RegionToSpaceMapper::create_mapper(rs,
1601                                          size,
1602                                          page_size,
1603                                          HeapRegion::GrainBytes,
1604                                          translation_factor,
1605                                          mtGC);
1606 
1607   os::trace_page_sizes_for_requested_size(description,
1608                                           size,
1609                                           preferred_page_size,
1610                                           page_size,
1611                                           rs.base(),
1612                                           rs.size());
1613 
1614   return result;
1615 }
1616 
1617 jint G1CollectedHeap::initialize_concurrent_refinement() {
1618   jint ecode = JNI_OK;
1619   _cr = G1ConcurrentRefine::create(&ecode);
1620   return ecode;
1621 }
1622 
1623 jint G1CollectedHeap::initialize_young_gen_sampling_thread() {
1624   _young_gen_sampling_thread = new G1YoungRemSetSamplingThread();
1625   if (_young_gen_sampling_thread->osthread() == NULL) {
1626     vm_shutdown_during_initialization("Could not create G1YoungRemSetSamplingThread");
1627     return JNI_ENOMEM;
1628   }
1629   return JNI_OK;
1630 }
1631 
1632 jint G1CollectedHeap::initialize() {
1633 
1634   // Necessary to satisfy locking discipline assertions.
1635 
1636   MutexLocker x(Heap_lock);
1637 
1638   // While there are no constraints in the GC code that HeapWordSize
1639   // be any particular value, there are multiple other areas in the
1640   // system which believe this to be true (e.g. oop->object_size in some
1641   // cases incorrectly returns the size in wordSize units rather than
1642   // HeapWordSize).
1643   guarantee(HeapWordSize == wordSize, "HeapWordSize must equal wordSize");
1644 
1645   size_t init_byte_size = InitialHeapSize;
1646   size_t reserved_byte_size = G1Arguments::heap_reserved_size_bytes();
1647 
1648   // Ensure that the sizes are properly aligned.
1649   Universe::check_alignment(init_byte_size, HeapRegion::GrainBytes, "g1 heap");
1650   Universe::check_alignment(reserved_byte_size, HeapRegion::GrainBytes, "g1 heap");
1651   Universe::check_alignment(reserved_byte_size, HeapAlignment, "g1 heap");
1652 
1653   // Reserve the maximum.
1654 
1655   // When compressed oops are enabled, the preferred heap base
1656   // is calculated by subtracting the requested size from the
1657   // 32Gb boundary and using the result as the base address for
1658   // heap reservation. If the requested size is not aligned to
1659   // HeapRegion::GrainBytes (i.e. the alignment that is passed
1660   // into the ReservedHeapSpace constructor) then the actual
1661   // base of the reserved heap may end up differing from the
1662   // address that was requested (i.e. the preferred heap base).
1663   // If this happens then we could end up using a non-optimal
1664   // compressed oops mode.
1665 
1666   ReservedHeapSpace heap_rs = Universe::reserve_heap(reserved_byte_size,
1667                                                      HeapAlignment);
1668 
1669   initialize_reserved_region(heap_rs);
1670 
1671   // Create the barrier set for the entire reserved region.
1672   G1CardTable* ct = new G1CardTable(heap_rs.region());
1673   ct->initialize();
1674   G1BarrierSet* bs = new G1BarrierSet(ct);
1675   bs->initialize();
1676   assert(bs->is_a(BarrierSet::G1BarrierSet), "sanity");
1677   BarrierSet::set_barrier_set(bs);
1678   _card_table = ct;
1679 
1680   {
1681     G1SATBMarkQueueSet& satbqs = bs->satb_mark_queue_set();
1682     satbqs.set_process_completed_buffers_threshold(G1SATBProcessCompletedThreshold);
1683     satbqs.set_buffer_enqueue_threshold_percentage(G1SATBBufferEnqueueingThresholdPercent);
1684   }
1685 
1686   // Create the hot card cache.
1687   _hot_card_cache = new G1HotCardCache(this);
1688 
1689   // Carve out the G1 part of the heap.
1690   ReservedSpace g1_rs = heap_rs.first_part(reserved_byte_size);
1691   size_t page_size = actual_reserved_page_size(heap_rs);
1692   G1RegionToSpaceMapper* heap_storage =
1693     G1RegionToSpaceMapper::create_heap_mapper(g1_rs,
1694                                               g1_rs.size(),
1695                                               page_size,
1696                                               HeapRegion::GrainBytes,
1697                                               1,
1698                                               mtJavaHeap);
1699   if(heap_storage == NULL) {
1700     vm_shutdown_during_initialization("Could not initialize G1 heap");
1701     return JNI_ERR;
1702   }
1703 
1704   os::trace_page_sizes("Heap",
1705                        MinHeapSize,
1706                        reserved_byte_size,
1707                        page_size,
1708                        heap_rs.base(),
1709                        heap_rs.size());
1710   heap_storage->set_mapping_changed_listener(&_listener);
1711 
1712   // Create storage for the BOT, card table, card counts table (hot card cache) and the bitmaps.
1713   G1RegionToSpaceMapper* bot_storage =
1714     create_aux_memory_mapper("Block Offset Table",
1715                              G1BlockOffsetTable::compute_size(g1_rs.size() / HeapWordSize),
1716                              G1BlockOffsetTable::heap_map_factor());
1717 
1718   G1RegionToSpaceMapper* cardtable_storage =
1719     create_aux_memory_mapper("Card Table",
1720                              G1CardTable::compute_size(g1_rs.size() / HeapWordSize),
1721                              G1CardTable::heap_map_factor());
1722 
1723   G1RegionToSpaceMapper* card_counts_storage =
1724     create_aux_memory_mapper("Card Counts Table",
1725                              G1CardCounts::compute_size(g1_rs.size() / HeapWordSize),
1726                              G1CardCounts::heap_map_factor());
1727 
1728   size_t bitmap_size = G1CMBitMap::compute_size(g1_rs.size());
1729   G1RegionToSpaceMapper* prev_bitmap_storage =
1730     create_aux_memory_mapper("Prev Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1731   G1RegionToSpaceMapper* next_bitmap_storage =
1732     create_aux_memory_mapper("Next Bitmap", bitmap_size, G1CMBitMap::heap_map_factor());
1733 
1734   _hrm = HeapRegionManager::create_manager(this);
1735 
1736   _hrm->initialize(heap_storage, prev_bitmap_storage, next_bitmap_storage, bot_storage, cardtable_storage, card_counts_storage);
1737   _card_table->initialize(cardtable_storage);
1738 
1739   // Do later initialization work for concurrent refinement.
1740   _hot_card_cache->initialize(card_counts_storage);
1741 
1742   // 6843694 - ensure that the maximum region index can fit
1743   // in the remembered set structures.
1744   const uint max_region_idx = (1U << (sizeof(RegionIdx_t)*BitsPerByte-1)) - 1;
1745   guarantee((max_regions() - 1) <= max_region_idx, "too many regions");
1746 
1747   // The G1FromCardCache reserves card with value 0 as "invalid", so the heap must not
1748   // start within the first card.
1749   guarantee(g1_rs.base() >= (char*)G1CardTable::card_size, "Java heap must not start within the first card.");
1750   // Also create a G1 rem set.
1751   _rem_set = new G1RemSet(this, _card_table, _hot_card_cache);
1752   _rem_set->initialize(max_reserved_capacity(), max_regions());
1753 
1754   size_t max_cards_per_region = ((size_t)1 << (sizeof(CardIdx_t)*BitsPerByte-1)) - 1;
1755   guarantee(HeapRegion::CardsPerRegion > 0, "make sure it's initialized");
1756   guarantee(HeapRegion::CardsPerRegion < max_cards_per_region,
1757             "too many cards per region");
1758 
1759   FreeRegionList::set_unrealistically_long_length(max_expandable_regions() + 1);
1760 
1761   _bot = new G1BlockOffsetTable(reserved_region(), bot_storage);
1762 
1763   {
1764     HeapWord* start = _hrm->reserved().start();
1765     HeapWord* end = _hrm->reserved().end();
1766     size_t granularity = HeapRegion::GrainBytes;
1767 
1768     _region_attr.initialize(start, end, granularity);
1769     _humongous_reclaim_candidates.initialize(start, end, granularity);
1770   }
1771 
1772   _workers = new WorkGang("GC Thread", ParallelGCThreads,
1773                           true /* are_GC_task_threads */,
1774                           false /* are_ConcurrentGC_threads */);
1775   if (_workers == NULL) {
1776     return JNI_ENOMEM;
1777   }
1778   _workers->initialize_workers();
1779 
1780   // Create the G1ConcurrentMark data structure and thread.
1781   // (Must do this late, so that "max_regions" is defined.)
1782   _cm = new G1ConcurrentMark(this, prev_bitmap_storage, next_bitmap_storage);
1783   if (_cm == NULL || !_cm->completed_initialization()) {
1784     vm_shutdown_during_initialization("Could not create/initialize G1ConcurrentMark");
1785     return JNI_ENOMEM;
1786   }
1787   _cm_thread = _cm->cm_thread();
1788 
1789   // Now expand into the initial heap size.
1790   if (!expand(init_byte_size, _workers)) {
1791     vm_shutdown_during_initialization("Failed to allocate initial heap.");
1792     return JNI_ENOMEM;
1793   }
1794 
1795   // Perform any initialization actions delegated to the policy.
1796   policy()->init(this, &_collection_set);
1797 
1798   jint ecode = initialize_concurrent_refinement();
1799   if (ecode != JNI_OK) {
1800     return ecode;
1801   }
1802 
1803   ecode = initialize_young_gen_sampling_thread();
1804   if (ecode != JNI_OK) {
1805     return ecode;
1806   }
1807 
1808   {
1809     G1DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
1810     dcqs.set_process_cards_threshold(concurrent_refine()->yellow_zone());
1811     dcqs.set_max_cards(concurrent_refine()->red_zone());
1812   }
1813 
1814   // Here we allocate the dummy HeapRegion that is required by the
1815   // G1AllocRegion class.
1816   HeapRegion* dummy_region = _hrm->get_dummy_region();
1817 
1818   // We'll re-use the same region whether the alloc region will
1819   // require BOT updates or not and, if it doesn't, then a non-young
1820   // region will complain that it cannot support allocations without
1821   // BOT updates. So we'll tag the dummy region as eden to avoid that.
1822   dummy_region->set_eden();
1823   // Make sure it's full.
1824   dummy_region->set_top(dummy_region->end());
1825   G1AllocRegion::setup(this, dummy_region);
1826 
1827   _allocator->init_mutator_alloc_region();
1828 
1829   // Do create of the monitoring and management support so that
1830   // values in the heap have been properly initialized.
1831   _g1mm = new G1MonitoringSupport(this);
1832 
1833   G1StringDedup::initialize();
1834 
1835   _preserved_marks_set.init(ParallelGCThreads);
1836 
1837   _collection_set.initialize(max_regions());
1838 
1839   return JNI_OK;
1840 }
1841 
1842 void G1CollectedHeap::stop() {
1843   // Stop all concurrent threads. We do this to make sure these threads
1844   // do not continue to execute and access resources (e.g. logging)
1845   // that are destroyed during shutdown.
1846   _cr->stop();
1847   _young_gen_sampling_thread->stop();
1848   _cm_thread->stop();
1849   if (G1StringDedup::is_enabled()) {
1850     G1StringDedup::stop();
1851   }
1852 }
1853 
1854 void G1CollectedHeap::safepoint_synchronize_begin() {
1855   SuspendibleThreadSet::synchronize();
1856 }
1857 
1858 void G1CollectedHeap::safepoint_synchronize_end() {
1859   SuspendibleThreadSet::desynchronize();
1860 }
1861 
1862 void G1CollectedHeap::post_initialize() {
1863   CollectedHeap::post_initialize();
1864   ref_processing_init();
1865 }
1866 
1867 void G1CollectedHeap::ref_processing_init() {
1868   // Reference processing in G1 currently works as follows:
1869   //
1870   // * There are two reference processor instances. One is
1871   //   used to record and process discovered references
1872   //   during concurrent marking; the other is used to
1873   //   record and process references during STW pauses
1874   //   (both full and incremental).
1875   // * Both ref processors need to 'span' the entire heap as
1876   //   the regions in the collection set may be dotted around.
1877   //
1878   // * For the concurrent marking ref processor:
1879   //   * Reference discovery is enabled at initial marking.
1880   //   * Reference discovery is disabled and the discovered
1881   //     references processed etc during remarking.
1882   //   * Reference discovery is MT (see below).
1883   //   * Reference discovery requires a barrier (see below).
1884   //   * Reference processing may or may not be MT
1885   //     (depending on the value of ParallelRefProcEnabled
1886   //     and ParallelGCThreads).
1887   //   * A full GC disables reference discovery by the CM
1888   //     ref processor and abandons any entries on it's
1889   //     discovered lists.
1890   //
1891   // * For the STW processor:
1892   //   * Non MT discovery is enabled at the start of a full GC.
1893   //   * Processing and enqueueing during a full GC is non-MT.
1894   //   * During a full GC, references are processed after marking.
1895   //
1896   //   * Discovery (may or may not be MT) is enabled at the start
1897   //     of an incremental evacuation pause.
1898   //   * References are processed near the end of a STW evacuation pause.
1899   //   * For both types of GC:
1900   //     * Discovery is atomic - i.e. not concurrent.
1901   //     * Reference discovery will not need a barrier.
1902 
1903   bool mt_processing = ParallelRefProcEnabled && (ParallelGCThreads > 1);
1904 
1905   // Concurrent Mark ref processor
1906   _ref_processor_cm =
1907     new ReferenceProcessor(&_is_subject_to_discovery_cm,
1908                            mt_processing,                                  // mt processing
1909                            ParallelGCThreads,                              // degree of mt processing
1910                            (ParallelGCThreads > 1) || (ConcGCThreads > 1), // mt discovery
1911                            MAX2(ParallelGCThreads, ConcGCThreads),         // degree of mt discovery
1912                            false,                                          // Reference discovery is not atomic
1913                            &_is_alive_closure_cm,                          // is alive closure
1914                            true);                                          // allow changes to number of processing threads
1915 
1916   // STW ref processor
1917   _ref_processor_stw =
1918     new ReferenceProcessor(&_is_subject_to_discovery_stw,
1919                            mt_processing,                        // mt processing
1920                            ParallelGCThreads,                    // degree of mt processing
1921                            (ParallelGCThreads > 1),              // mt discovery
1922                            ParallelGCThreads,                    // degree of mt discovery
1923                            true,                                 // Reference discovery is atomic
1924                            &_is_alive_closure_stw,               // is alive closure
1925                            true);                                // allow changes to number of processing threads
1926 }
1927 
1928 SoftRefPolicy* G1CollectedHeap::soft_ref_policy() {
1929   return &_soft_ref_policy;
1930 }
1931 
1932 size_t G1CollectedHeap::capacity() const {
1933   return _hrm->length() * HeapRegion::GrainBytes;
1934 }
1935 
1936 size_t G1CollectedHeap::unused_committed_regions_in_bytes() const {
1937   return _hrm->total_free_bytes();
1938 }
1939 
1940 void G1CollectedHeap::iterate_hcc_closure(G1CardTableEntryClosure* cl, uint worker_id) {
1941   _hot_card_cache->drain(cl, worker_id);
1942 }
1943 
1944 // Computes the sum of the storage used by the various regions.
1945 size_t G1CollectedHeap::used() const {
1946   size_t result = _summary_bytes_used + _allocator->used_in_alloc_regions();
1947   if (_archive_allocator != NULL) {
1948     result += _archive_allocator->used();
1949   }
1950   return result;
1951 }
1952 
1953 size_t G1CollectedHeap::used_unlocked() const {
1954   return _summary_bytes_used;
1955 }
1956 
1957 class SumUsedClosure: public HeapRegionClosure {
1958   size_t _used;
1959 public:
1960   SumUsedClosure() : _used(0) {}
1961   bool do_heap_region(HeapRegion* r) {
1962     _used += r->used();
1963     return false;
1964   }
1965   size_t result() { return _used; }
1966 };
1967 
1968 size_t G1CollectedHeap::recalculate_used() const {
1969   SumUsedClosure blk;
1970   heap_region_iterate(&blk);
1971   return blk.result();
1972 }
1973 
1974 bool  G1CollectedHeap::is_user_requested_concurrent_full_gc(GCCause::Cause cause) {
1975   switch (cause) {
1976     case GCCause::_java_lang_system_gc:                 return ExplicitGCInvokesConcurrent;
1977     case GCCause::_dcmd_gc_run:                         return ExplicitGCInvokesConcurrent;
1978     case GCCause::_wb_conc_mark:                        return true;
1979     default :                                           return false;
1980   }
1981 }
1982 
1983 bool G1CollectedHeap::should_do_concurrent_full_gc(GCCause::Cause cause) {
1984   switch (cause) {
1985     case GCCause::_gc_locker:               return GCLockerInvokesConcurrent;
1986     case GCCause::_g1_humongous_allocation: return true;
1987     case GCCause::_g1_periodic_collection:  return G1PeriodicGCInvokesConcurrent;
1988     default:                                return is_user_requested_concurrent_full_gc(cause);
1989   }
1990 }
1991 
1992 bool G1CollectedHeap::should_upgrade_to_full_gc(GCCause::Cause cause) {
1993   if(policy()->force_upgrade_to_full()) {
1994     return true;
1995   } else if (should_do_concurrent_full_gc(_gc_cause)) {
1996     return false;
1997   } else if (has_regions_left_for_allocation()) {
1998     return false;
1999   } else {
2000     return true;
2001   }
2002 }
2003 
2004 #ifndef PRODUCT
2005 void G1CollectedHeap::allocate_dummy_regions() {
2006   // Let's fill up most of the region
2007   size_t word_size = HeapRegion::GrainWords - 1024;
2008   // And as a result the region we'll allocate will be humongous.
2009   guarantee(is_humongous(word_size), "sanity");
2010 
2011   // _filler_array_max_size is set to humongous object threshold
2012   // but temporarily change it to use CollectedHeap::fill_with_object().
2013   SizeTFlagSetting fs(_filler_array_max_size, word_size);
2014 
2015   for (uintx i = 0; i < G1DummyRegionsPerGC; ++i) {
2016     // Let's use the existing mechanism for the allocation
2017     HeapWord* dummy_obj = humongous_obj_allocate(word_size);
2018     if (dummy_obj != NULL) {
2019       MemRegion mr(dummy_obj, word_size);
2020       CollectedHeap::fill_with_object(mr);
2021     } else {
2022       // If we can't allocate once, we probably cannot allocate
2023       // again. Let's get out of the loop.
2024       break;
2025     }
2026   }
2027 }
2028 #endif // !PRODUCT
2029 
2030 void G1CollectedHeap::increment_old_marking_cycles_started() {
2031   assert(_old_marking_cycles_started == _old_marking_cycles_completed ||
2032          _old_marking_cycles_started == _old_marking_cycles_completed + 1,
2033          "Wrong marking cycle count (started: %d, completed: %d)",
2034          _old_marking_cycles_started, _old_marking_cycles_completed);
2035 
2036   _old_marking_cycles_started++;
2037 }
2038 
2039 void G1CollectedHeap::increment_old_marking_cycles_completed(bool concurrent) {
2040   MonitorLocker x(FullGCCount_lock, Mutex::_no_safepoint_check_flag);
2041 
2042   // We assume that if concurrent == true, then the caller is a
2043   // concurrent thread that was joined the Suspendible Thread
2044   // Set. If there's ever a cheap way to check this, we should add an
2045   // assert here.
2046 
2047   // Given that this method is called at the end of a Full GC or of a
2048   // concurrent cycle, and those can be nested (i.e., a Full GC can
2049   // interrupt a concurrent cycle), the number of full collections
2050   // completed should be either one (in the case where there was no
2051   // nesting) or two (when a Full GC interrupted a concurrent cycle)
2052   // behind the number of full collections started.
2053 
2054   // This is the case for the inner caller, i.e. a Full GC.
2055   assert(concurrent ||
2056          (_old_marking_cycles_started == _old_marking_cycles_completed + 1) ||
2057          (_old_marking_cycles_started == _old_marking_cycles_completed + 2),
2058          "for inner caller (Full GC): _old_marking_cycles_started = %u "
2059          "is inconsistent with _old_marking_cycles_completed = %u",
2060          _old_marking_cycles_started, _old_marking_cycles_completed);
2061 
2062   // This is the case for the outer caller, i.e. the concurrent cycle.
2063   assert(!concurrent ||
2064          (_old_marking_cycles_started == _old_marking_cycles_completed + 1),
2065          "for outer caller (concurrent cycle): "
2066          "_old_marking_cycles_started = %u "
2067          "is inconsistent with _old_marking_cycles_completed = %u",
2068          _old_marking_cycles_started, _old_marking_cycles_completed);
2069 
2070   _old_marking_cycles_completed += 1;
2071 
2072   // We need to clear the "in_progress" flag in the CM thread before
2073   // we wake up any waiters (especially when ExplicitInvokesConcurrent
2074   // is set) so that if a waiter requests another System.gc() it doesn't
2075   // incorrectly see that a marking cycle is still in progress.
2076   if (concurrent) {
2077     _cm_thread->set_idle();
2078   }
2079 
2080   // This notify_all() will ensure that a thread that called
2081   // System.gc() with (with ExplicitGCInvokesConcurrent set or not)
2082   // and it's waiting for a full GC to finish will be woken up. It is
2083   // waiting in VM_G1CollectForAllocation::doit_epilogue().
2084   FullGCCount_lock->notify_all();
2085 }
2086 
2087 void G1CollectedHeap::collect(GCCause::Cause cause) {
2088   try_collect(cause, true);
2089 }
2090 
2091 bool G1CollectedHeap::try_collect(GCCause::Cause cause, bool retry_on_gc_failure) {
2092   assert_heap_not_locked();
2093 
2094   bool gc_succeeded;
2095   bool should_retry_gc;
2096 
2097   do {
2098     should_retry_gc = false;
2099 
2100     uint gc_count_before;
2101     uint old_marking_count_before;
2102     uint full_gc_count_before;
2103 
2104     {
2105       MutexLocker ml(Heap_lock);
2106 
2107       // Read the GC count while holding the Heap_lock
2108       gc_count_before = total_collections();
2109       full_gc_count_before = total_full_collections();
2110       old_marking_count_before = _old_marking_cycles_started;
2111     }
2112 
2113     if (should_do_concurrent_full_gc(cause)) {
2114       // Schedule an initial-mark evacuation pause that will start a
2115       // concurrent cycle. We're setting word_size to 0 which means that
2116       // we are not requesting a post-GC allocation.
2117       VM_G1CollectForAllocation op(0,     /* word_size */
2118                                    gc_count_before,
2119                                    cause,
2120                                    true,  /* should_initiate_conc_mark */
2121                                    policy()->max_pause_time_ms());
2122       VMThread::execute(&op);
2123       gc_succeeded = op.gc_succeeded();
2124       if (!gc_succeeded && retry_on_gc_failure) {
2125         if (old_marking_count_before == _old_marking_cycles_started) {
2126           should_retry_gc = op.should_retry_gc();
2127         } else {
2128           // A Full GC happened while we were trying to schedule the
2129           // concurrent cycle. No point in starting a new cycle given
2130           // that the whole heap was collected anyway.
2131         }
2132 
2133         if (should_retry_gc && GCLocker::is_active_and_needs_gc()) {
2134           GCLocker::stall_until_clear();
2135         }
2136       }
2137     } else if (GCLocker::should_discard(cause, gc_count_before)) {
2138       // Return false to be consistent with VMOp failure due to
2139       // another collection slipping in after our gc_count but before
2140       // our request is processed.  _gc_locker collections upgraded by
2141       // GCLockerInvokesConcurrent are handled above and never discarded.
2142       return false;
2143     } else {
2144       if (cause == GCCause::_gc_locker || cause == GCCause::_wb_young_gc
2145           DEBUG_ONLY(|| cause == GCCause::_scavenge_alot)) {
2146 
2147         // Schedule a standard evacuation pause. We're setting word_size
2148         // to 0 which means that we are not requesting a post-GC allocation.
2149         VM_G1CollectForAllocation op(0,     /* word_size */
2150                                      gc_count_before,
2151                                      cause,
2152                                      false, /* should_initiate_conc_mark */
2153                                      policy()->max_pause_time_ms());
2154         VMThread::execute(&op);
2155         gc_succeeded = op.gc_succeeded();
2156       } else {
2157         // Schedule a Full GC.
2158         VM_G1CollectFull op(gc_count_before, full_gc_count_before, cause);
2159         VMThread::execute(&op);
2160         gc_succeeded = op.gc_succeeded();
2161       }
2162     }
2163   } while (should_retry_gc);
2164   return gc_succeeded;
2165 }
2166 
2167 bool G1CollectedHeap::is_in(const void* p) const {
2168   if (_hrm->reserved().contains(p)) {
2169     // Given that we know that p is in the reserved space,
2170     // heap_region_containing() should successfully
2171     // return the containing region.
2172     HeapRegion* hr = heap_region_containing(p);
2173     return hr->is_in(p);
2174   } else {
2175     return false;
2176   }
2177 }
2178 
2179 #ifdef ASSERT
2180 bool G1CollectedHeap::is_in_exact(const void* p) const {
2181   bool contains = reserved_region().contains(p);
2182   bool available = _hrm->is_available(addr_to_region((HeapWord*)p));
2183   if (contains && available) {
2184     return true;
2185   } else {
2186     return false;
2187   }
2188 }
2189 #endif
2190 
2191 // Iteration functions.
2192 
2193 // Iterates an ObjectClosure over all objects within a HeapRegion.
2194 
2195 class IterateObjectClosureRegionClosure: public HeapRegionClosure {
2196   ObjectClosure* _cl;
2197 public:
2198   IterateObjectClosureRegionClosure(ObjectClosure* cl) : _cl(cl) {}
2199   bool do_heap_region(HeapRegion* r) {
2200     if (!r->is_continues_humongous()) {
2201       r->object_iterate(_cl);
2202     }
2203     return false;
2204   }
2205 };
2206 
2207 void G1CollectedHeap::object_iterate(ObjectClosure* cl) {
2208   IterateObjectClosureRegionClosure blk(cl);
2209   heap_region_iterate(&blk);
2210 }
2211 
2212 void G1CollectedHeap::heap_region_iterate(HeapRegionClosure* cl) const {
2213   _hrm->iterate(cl);
2214 }
2215 
2216 void G1CollectedHeap::heap_region_par_iterate_from_worker_offset(HeapRegionClosure* cl,
2217                                                                  HeapRegionClaimer *hrclaimer,
2218                                                                  uint worker_id) const {
2219   _hrm->par_iterate(cl, hrclaimer, hrclaimer->offset_for_worker(worker_id));
2220 }
2221 
2222 void G1CollectedHeap::heap_region_par_iterate_from_start(HeapRegionClosure* cl,
2223                                                          HeapRegionClaimer *hrclaimer) const {
2224   _hrm->par_iterate(cl, hrclaimer, 0);
2225 }
2226 
2227 void G1CollectedHeap::collection_set_iterate_all(HeapRegionClosure* cl) {
2228   _collection_set.iterate(cl);
2229 }
2230 
2231 void G1CollectedHeap::collection_set_iterate_increment_from(HeapRegionClosure *cl, HeapRegionClaimer* hr_claimer, uint worker_id) {
2232   _collection_set.iterate_incremental_part_from(cl, hr_claimer, worker_id, workers()->active_workers());
2233 }
2234 
2235 HeapWord* G1CollectedHeap::block_start(const void* addr) const {
2236   HeapRegion* hr = heap_region_containing(addr);
2237   return hr->block_start(addr);
2238 }
2239 
2240 bool G1CollectedHeap::block_is_obj(const HeapWord* addr) const {
2241   HeapRegion* hr = heap_region_containing(addr);
2242   return hr->block_is_obj(addr);
2243 }
2244 
2245 bool G1CollectedHeap::supports_tlab_allocation() const {
2246   return true;
2247 }
2248 
2249 size_t G1CollectedHeap::tlab_capacity(Thread* ignored) const {
2250   return (_policy->young_list_target_length() - _survivor.length()) * HeapRegion::GrainBytes;
2251 }
2252 
2253 size_t G1CollectedHeap::tlab_used(Thread* ignored) const {
2254   return _eden.length() * HeapRegion::GrainBytes;
2255 }
2256 
2257 // For G1 TLABs should not contain humongous objects, so the maximum TLAB size
2258 // must be equal to the humongous object limit.
2259 size_t G1CollectedHeap::max_tlab_size() const {
2260   return align_down(_humongous_object_threshold_in_words, MinObjAlignment);
2261 }
2262 
2263 size_t G1CollectedHeap::unsafe_max_tlab_alloc(Thread* ignored) const {
2264   return _allocator->unsafe_max_tlab_alloc();
2265 }
2266 
2267 size_t G1CollectedHeap::max_capacity() const {
2268   return _hrm->max_expandable_length() * HeapRegion::GrainBytes;
2269 }
2270 
2271 size_t G1CollectedHeap::max_reserved_capacity() const {
2272   return _hrm->max_length() * HeapRegion::GrainBytes;
2273 }
2274 
2275 jlong G1CollectedHeap::millis_since_last_gc() {
2276   // See the notes in GenCollectedHeap::millis_since_last_gc()
2277   // for more information about the implementation.
2278   jlong ret_val = (os::javaTimeNanos() / NANOSECS_PER_MILLISEC) -
2279                   _policy->collection_pause_end_millis();
2280   if (ret_val < 0) {
2281     log_warning(gc)("millis_since_last_gc() would return : " JLONG_FORMAT
2282       ". returning zero instead.", ret_val);
2283     return 0;
2284   }
2285   return ret_val;
2286 }
2287 
2288 void G1CollectedHeap::deduplicate_string(oop str) {
2289   assert(java_lang_String::is_instance(str), "invariant");
2290 
2291   if (G1StringDedup::is_enabled()) {
2292     G1StringDedup::deduplicate(str);
2293   }
2294 }
2295 
2296 void G1CollectedHeap::prepare_for_verify() {
2297   _verifier->prepare_for_verify();
2298 }
2299 
2300 void G1CollectedHeap::verify(VerifyOption vo) {
2301   _verifier->verify(vo);
2302 }
2303 
2304 bool G1CollectedHeap::supports_concurrent_phase_control() const {
2305   return true;
2306 }
2307 
2308 bool G1CollectedHeap::request_concurrent_phase(const char* phase) {
2309   return _cm_thread->request_concurrent_phase(phase);
2310 }
2311 
2312 bool G1CollectedHeap::is_heterogeneous_heap() const {
2313   return G1Arguments::is_heterogeneous_heap();
2314 }
2315 
2316 class PrintRegionClosure: public HeapRegionClosure {
2317   outputStream* _st;
2318 public:
2319   PrintRegionClosure(outputStream* st) : _st(st) {}
2320   bool do_heap_region(HeapRegion* r) {
2321     r->print_on(_st);
2322     return false;
2323   }
2324 };
2325 
2326 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2327                                        const HeapRegion* hr,
2328                                        const VerifyOption vo) const {
2329   switch (vo) {
2330   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj, hr);
2331   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj, hr);
2332   case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj, hr);
2333   default:                            ShouldNotReachHere();
2334   }
2335   return false; // keep some compilers happy
2336 }
2337 
2338 bool G1CollectedHeap::is_obj_dead_cond(const oop obj,
2339                                        const VerifyOption vo) const {
2340   switch (vo) {
2341   case VerifyOption_G1UsePrevMarking: return is_obj_dead(obj);
2342   case VerifyOption_G1UseNextMarking: return is_obj_ill(obj);
2343   case VerifyOption_G1UseFullMarking: return is_obj_dead_full(obj);
2344   default:                            ShouldNotReachHere();
2345   }
2346   return false; // keep some compilers happy
2347 }
2348 
2349 void G1CollectedHeap::print_heap_regions() const {
2350   LogTarget(Trace, gc, heap, region) lt;
2351   if (lt.is_enabled()) {
2352     LogStream ls(lt);
2353     print_regions_on(&ls);
2354   }
2355 }
2356 
2357 void G1CollectedHeap::print_on(outputStream* st) const {
2358   st->print(" %-20s", "garbage-first heap");
2359   st->print(" total " SIZE_FORMAT "K, used " SIZE_FORMAT "K",
2360             capacity()/K, used_unlocked()/K);
2361   st->print(" [" PTR_FORMAT ", " PTR_FORMAT ")",
2362             p2i(_hrm->reserved().start()),
2363             p2i(_hrm->reserved().end()));
2364   st->cr();
2365   st->print("  region size " SIZE_FORMAT "K, ", HeapRegion::GrainBytes / K);
2366   uint young_regions = young_regions_count();
2367   st->print("%u young (" SIZE_FORMAT "K), ", young_regions,
2368             (size_t) young_regions * HeapRegion::GrainBytes / K);
2369   uint survivor_regions = survivor_regions_count();
2370   st->print("%u survivors (" SIZE_FORMAT "K)", survivor_regions,
2371             (size_t) survivor_regions * HeapRegion::GrainBytes / K);
2372   st->cr();
2373   MetaspaceUtils::print_on(st);
2374 }
2375 
2376 void G1CollectedHeap::print_regions_on(outputStream* st) const {
2377   st->print_cr("Heap Regions: E=young(eden), S=young(survivor), O=old, "
2378                "HS=humongous(starts), HC=humongous(continues), "
2379                "CS=collection set, F=free, "
2380                "OA=open archive, CA=closed archive, "
2381                "TAMS=top-at-mark-start (previous, next)");
2382   PrintRegionClosure blk(st);
2383   heap_region_iterate(&blk);
2384 }
2385 
2386 void G1CollectedHeap::print_extended_on(outputStream* st) const {
2387   print_on(st);
2388 
2389   // Print the per-region information.
2390   print_regions_on(st);
2391 }
2392 
2393 void G1CollectedHeap::print_on_error(outputStream* st) const {
2394   this->CollectedHeap::print_on_error(st);
2395 
2396   if (_cm != NULL) {
2397     st->cr();
2398     _cm->print_on_error(st);
2399   }
2400 }
2401 
2402 void G1CollectedHeap::print_gc_threads_on(outputStream* st) const {
2403   workers()->print_worker_threads_on(st);
2404   _cm_thread->print_on(st);
2405   st->cr();
2406   _cm->print_worker_threads_on(st);
2407   _cr->print_threads_on(st);
2408   _young_gen_sampling_thread->print_on(st);
2409   if (G1StringDedup::is_enabled()) {
2410     G1StringDedup::print_worker_threads_on(st);
2411   }
2412 }
2413 
2414 void G1CollectedHeap::gc_threads_do(ThreadClosure* tc) const {
2415   workers()->threads_do(tc);
2416   tc->do_thread(_cm_thread);
2417   _cm->threads_do(tc);
2418   _cr->threads_do(tc);
2419   tc->do_thread(_young_gen_sampling_thread);
2420   if (G1StringDedup::is_enabled()) {
2421     G1StringDedup::threads_do(tc);
2422   }
2423 }
2424 
2425 void G1CollectedHeap::print_tracing_info() const {
2426   rem_set()->print_summary_info();
2427   concurrent_mark()->print_summary_info();
2428 }
2429 
2430 #ifndef PRODUCT
2431 // Helpful for debugging RSet issues.
2432 
2433 class PrintRSetsClosure : public HeapRegionClosure {
2434 private:
2435   const char* _msg;
2436   size_t _occupied_sum;
2437 
2438 public:
2439   bool do_heap_region(HeapRegion* r) {
2440     HeapRegionRemSet* hrrs = r->rem_set();
2441     size_t occupied = hrrs->occupied();
2442     _occupied_sum += occupied;
2443 
2444     tty->print_cr("Printing RSet for region " HR_FORMAT, HR_FORMAT_PARAMS(r));
2445     if (occupied == 0) {
2446       tty->print_cr("  RSet is empty");
2447     } else {
2448       hrrs->print();
2449     }
2450     tty->print_cr("----------");
2451     return false;
2452   }
2453 
2454   PrintRSetsClosure(const char* msg) : _msg(msg), _occupied_sum(0) {
2455     tty->cr();
2456     tty->print_cr("========================================");
2457     tty->print_cr("%s", msg);
2458     tty->cr();
2459   }
2460 
2461   ~PrintRSetsClosure() {
2462     tty->print_cr("Occupied Sum: " SIZE_FORMAT, _occupied_sum);
2463     tty->print_cr("========================================");
2464     tty->cr();
2465   }
2466 };
2467 
2468 void G1CollectedHeap::print_cset_rsets() {
2469   PrintRSetsClosure cl("Printing CSet RSets");
2470   collection_set_iterate_all(&cl);
2471 }
2472 
2473 void G1CollectedHeap::print_all_rsets() {
2474   PrintRSetsClosure cl("Printing All RSets");;
2475   heap_region_iterate(&cl);
2476 }
2477 #endif // PRODUCT
2478 
2479 bool G1CollectedHeap::print_location(outputStream* st, void* addr) const {
2480   return BlockLocationPrinter<G1CollectedHeap>::print_location(st, addr);
2481 }
2482 
2483 G1HeapSummary G1CollectedHeap::create_g1_heap_summary() {
2484 
2485   size_t eden_used_bytes = _eden.used_bytes();
2486   size_t survivor_used_bytes = _survivor.used_bytes();
2487   size_t heap_used = Heap_lock->owned_by_self() ? used() : used_unlocked();
2488 
2489   size_t eden_capacity_bytes =
2490     (policy()->young_list_target_length() * HeapRegion::GrainBytes) - survivor_used_bytes;
2491 
2492   VirtualSpaceSummary heap_summary = create_heap_space_summary();
2493   return G1HeapSummary(heap_summary, heap_used, eden_used_bytes,
2494                        eden_capacity_bytes, survivor_used_bytes, num_regions());
2495 }
2496 
2497 G1EvacSummary G1CollectedHeap::create_g1_evac_summary(G1EvacStats* stats) {
2498   return G1EvacSummary(stats->allocated(), stats->wasted(), stats->undo_wasted(),
2499                        stats->unused(), stats->used(), stats->region_end_waste(),
2500                        stats->regions_filled(), stats->direct_allocated(),
2501                        stats->failure_used(), stats->failure_waste());
2502 }
2503 
2504 void G1CollectedHeap::trace_heap(GCWhen::Type when, const GCTracer* gc_tracer) {
2505   const G1HeapSummary& heap_summary = create_g1_heap_summary();
2506   gc_tracer->report_gc_heap_summary(when, heap_summary);
2507 
2508   const MetaspaceSummary& metaspace_summary = create_metaspace_summary();
2509   gc_tracer->report_metaspace_summary(when, metaspace_summary);
2510 }
2511 
2512 G1CollectedHeap* G1CollectedHeap::heap() {
2513   CollectedHeap* heap = Universe::heap();
2514   assert(heap != NULL, "Uninitialized access to G1CollectedHeap::heap()");
2515   assert(heap->kind() == CollectedHeap::G1, "Invalid name");
2516   return (G1CollectedHeap*)heap;
2517 }
2518 
2519 void G1CollectedHeap::gc_prologue(bool full) {
2520   assert(InlineCacheBuffer::is_empty(), "should have cleaned up ICBuffer");
2521 
2522   // This summary needs to be printed before incrementing total collections.
2523   rem_set()->print_periodic_summary_info("Before GC RS summary", total_collections());
2524 
2525   // Update common counters.
2526   increment_total_collections(full /* full gc */);
2527   if (full || collector_state()->in_initial_mark_gc()) {
2528     increment_old_marking_cycles_started();
2529   }
2530 
2531   // Fill TLAB's and such
2532   double start = os::elapsedTime();
2533   ensure_parsability(true);
2534   phase_times()->record_prepare_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2535 }
2536 
2537 void G1CollectedHeap::gc_epilogue(bool full) {
2538   // Update common counters.
2539   if (full) {
2540     // Update the number of full collections that have been completed.
2541     increment_old_marking_cycles_completed(false /* concurrent */);
2542   }
2543 
2544   // We are at the end of the GC. Total collections has already been increased.
2545   rem_set()->print_periodic_summary_info("After GC RS summary", total_collections() - 1);
2546 
2547   // FIXME: what is this about?
2548   // I'm ignoring the "fill_newgen()" call if "alloc_event_enabled"
2549   // is set.
2550 #if COMPILER2_OR_JVMCI
2551   assert(DerivedPointerTable::is_empty(), "derived pointer present");
2552 #endif
2553 
2554   double start = os::elapsedTime();
2555   resize_all_tlabs();
2556   phase_times()->record_resize_tlab_time_ms((os::elapsedTime() - start) * 1000.0);
2557 
2558   MemoryService::track_memory_usage();
2559   // We have just completed a GC. Update the soft reference
2560   // policy with the new heap occupancy
2561   Universe::update_heap_info_at_gc();
2562 }
2563 
2564 HeapWord* G1CollectedHeap::do_collection_pause(size_t word_size,
2565                                                uint gc_count_before,
2566                                                bool* succeeded,
2567                                                GCCause::Cause gc_cause) {
2568   assert_heap_not_locked_and_not_at_safepoint();
2569   VM_G1CollectForAllocation op(word_size,
2570                                gc_count_before,
2571                                gc_cause,
2572                                false, /* should_initiate_conc_mark */
2573                                policy()->max_pause_time_ms());
2574   VMThread::execute(&op);
2575 
2576   HeapWord* result = op.result();
2577   bool ret_succeeded = op.prologue_succeeded() && op.gc_succeeded();
2578   assert(result == NULL || ret_succeeded,
2579          "the result should be NULL if the VM did not succeed");
2580   *succeeded = ret_succeeded;
2581 
2582   assert_heap_not_locked();
2583   return result;
2584 }
2585 
2586 void G1CollectedHeap::do_concurrent_mark() {
2587   MutexLocker x(CGC_lock, Mutex::_no_safepoint_check_flag);
2588   if (!_cm_thread->in_progress()) {
2589     _cm_thread->set_started();
2590     CGC_lock->notify();
2591   }
2592 }
2593 
2594 size_t G1CollectedHeap::pending_card_num() {
2595   struct CountCardsClosure : public ThreadClosure {
2596     size_t _cards;
2597     CountCardsClosure() : _cards(0) {}
2598     virtual void do_thread(Thread* t) {
2599       _cards += G1ThreadLocalData::dirty_card_queue(t).size();
2600     }
2601   } count_from_threads;
2602   Threads::threads_do(&count_from_threads);
2603 
2604   G1DirtyCardQueueSet& dcqs = G1BarrierSet::dirty_card_queue_set();
2605   dcqs.verify_num_cards();
2606 
2607   return dcqs.num_cards() + count_from_threads._cards;
2608 }
2609 
2610 bool G1CollectedHeap::is_potential_eager_reclaim_candidate(HeapRegion* r) const {
2611   // We don't nominate objects with many remembered set entries, on
2612   // the assumption that such objects are likely still live.
2613   HeapRegionRemSet* rem_set = r->rem_set();
2614 
2615   return G1EagerReclaimHumongousObjectsWithStaleRefs ?
2616          rem_set->occupancy_less_or_equal_than(G1RSetSparseRegionEntries) :
2617          G1EagerReclaimHumongousObjects && rem_set->is_empty();
2618 }
2619 
2620 class RegisterRegionsWithRegionAttrTableClosure : public HeapRegionClosure {
2621  private:
2622   size_t _total_humongous;
2623   size_t _candidate_humongous;
2624 
2625   bool humongous_region_is_candidate(G1CollectedHeap* g1h, HeapRegion* region) const {
2626     assert(region->is_starts_humongous(), "Must start a humongous object");
2627 
2628     oop obj = oop(region->bottom());
2629 
2630     // Dead objects cannot be eager reclaim candidates. Due to class
2631     // unloading it is unsafe to query their classes so we return early.
2632     if (g1h->is_obj_dead(obj, region)) {
2633       return false;
2634     }
2635 
2636     // If we do not have a complete remembered set for the region, then we can
2637     // not be sure that we have all references to it.
2638     if (!region->rem_set()->is_complete()) {
2639       return false;
2640     }
2641     // Candidate selection must satisfy the following constraints
2642     // while concurrent marking is in progress:
2643     //
2644     // * In order to maintain SATB invariants, an object must not be
2645     // reclaimed if it was allocated before the start of marking and
2646     // has not had its references scanned.  Such an object must have
2647     // its references (including type metadata) scanned to ensure no
2648     // live objects are missed by the marking process.  Objects
2649     // allocated after the start of concurrent marking don't need to
2650     // be scanned.
2651     //
2652     // * An object must not be reclaimed if it is on the concurrent
2653     // mark stack.  Objects allocated after the start of concurrent
2654     // marking are never pushed on the mark stack.
2655     //
2656     // Nominating only objects allocated after the start of concurrent
2657     // marking is sufficient to meet both constraints.  This may miss
2658     // some objects that satisfy the constraints, but the marking data
2659     // structures don't support efficiently performing the needed
2660     // additional tests or scrubbing of the mark stack.
2661     //
2662     // However, we presently only nominate is_typeArray() objects.
2663     // A humongous object containing references induces remembered
2664     // set entries on other regions.  In order to reclaim such an
2665     // object, those remembered sets would need to be cleaned up.
2666     //
2667     // We also treat is_typeArray() objects specially, allowing them
2668     // to be reclaimed even if allocated before the start of
2669     // concurrent mark.  For this we rely on mark stack insertion to
2670     // exclude is_typeArray() objects, preventing reclaiming an object
2671     // that is in the mark stack.  We also rely on the metadata for
2672     // such objects to be built-in and so ensured to be kept live.
2673     // Frequent allocation and drop of large binary blobs is an
2674     // important use case for eager reclaim, and this special handling
2675     // may reduce needed headroom.
2676 
2677     return obj->is_typeArray() &&
2678            g1h->is_potential_eager_reclaim_candidate(region);
2679   }
2680 
2681  public:
2682   RegisterRegionsWithRegionAttrTableClosure()
2683   : _total_humongous(0),
2684     _candidate_humongous(0) {
2685   }
2686 
2687   virtual bool do_heap_region(HeapRegion* r) {
2688     G1CollectedHeap* g1h = G1CollectedHeap::heap();
2689 
2690     if (!r->is_starts_humongous()) {
2691       g1h->register_region_with_region_attr(r);
2692       return false;
2693     }
2694 
2695     bool is_candidate = humongous_region_is_candidate(g1h, r);
2696     uint rindex = r->hrm_index();
2697     g1h->set_humongous_reclaim_candidate(rindex, is_candidate);
2698     if (is_candidate) {
2699       g1h->register_humongous_region_with_region_attr(rindex);
2700       _candidate_humongous++;
2701       // We will later handle the remembered sets of these regions.
2702     } else {
2703       g1h->register_region_with_region_attr(r);
2704     }
2705     _total_humongous++;
2706 
2707     return false;
2708   }
2709 
2710   size_t total_humongous() const { return _total_humongous; }
2711   size_t candidate_humongous() const { return _candidate_humongous; }
2712 };
2713 
2714 void G1CollectedHeap::register_regions_with_region_attr() {
2715   Ticks start = Ticks::now();
2716 
2717   RegisterRegionsWithRegionAttrTableClosure cl;
2718   heap_region_iterate(&cl);
2719 
2720   phase_times()->record_register_regions((Ticks::now() - start).seconds() * 1000.0,
2721                                          cl.total_humongous(),
2722                                          cl.candidate_humongous());
2723   _has_humongous_reclaim_candidates = cl.candidate_humongous() > 0;
2724 }
2725 
2726 #ifndef PRODUCT
2727 void G1CollectedHeap::verify_region_attr_remset_update() {
2728   class VerifyRegionAttrRemSet : public HeapRegionClosure {
2729   public:
2730     virtual bool do_heap_region(HeapRegion* r) {
2731       G1CollectedHeap* g1h = G1CollectedHeap::heap();
2732       bool const needs_remset_update = g1h->region_attr(r->bottom()).needs_remset_update();
2733       assert(r->rem_set()->is_tracked() == needs_remset_update,
2734              "Region %u remset tracking status (%s) different to region attribute (%s)",
2735              r->hrm_index(), BOOL_TO_STR(r->rem_set()->is_tracked()), BOOL_TO_STR(needs_remset_update));
2736       return false;
2737     }
2738   } cl;
2739   heap_region_iterate(&cl);
2740 }
2741 #endif
2742 
2743 class VerifyRegionRemSetClosure : public HeapRegionClosure {
2744   public:
2745     bool do_heap_region(HeapRegion* hr) {
2746       if (!hr->is_archive() && !hr->is_continues_humongous()) {
2747         hr->verify_rem_set();
2748       }
2749       return false;
2750     }
2751 };
2752 
2753 uint G1CollectedHeap::num_task_queues() const {
2754   return _task_queues->size();
2755 }
2756 
2757 #if TASKQUEUE_STATS
2758 void G1CollectedHeap::print_taskqueue_stats_hdr(outputStream* const st) {
2759   st->print_raw_cr("GC Task Stats");
2760   st->print_raw("thr "); TaskQueueStats::print_header(1, st); st->cr();
2761   st->print_raw("--- "); TaskQueueStats::print_header(2, st); st->cr();
2762 }
2763 
2764 void G1CollectedHeap::print_taskqueue_stats() const {
2765   if (!log_is_enabled(Trace, gc, task, stats)) {
2766     return;
2767   }
2768   Log(gc, task, stats) log;
2769   ResourceMark rm;
2770   LogStream ls(log.trace());
2771   outputStream* st = &ls;
2772 
2773   print_taskqueue_stats_hdr(st);
2774 
2775   TaskQueueStats totals;
2776   const uint n = num_task_queues();
2777   for (uint i = 0; i < n; ++i) {
2778     st->print("%3u ", i); task_queue(i)->stats.print(st); st->cr();
2779     totals += task_queue(i)->stats;
2780   }
2781   st->print_raw("tot "); totals.print(st); st->cr();
2782 
2783   DEBUG_ONLY(totals.verify());
2784 }
2785 
2786 void G1CollectedHeap::reset_taskqueue_stats() {
2787   const uint n = num_task_queues();
2788   for (uint i = 0; i < n; ++i) {
2789     task_queue(i)->stats.reset();
2790   }
2791 }
2792 #endif // TASKQUEUE_STATS
2793 
2794 void G1CollectedHeap::wait_for_root_region_scanning() {
2795   double scan_wait_start = os::elapsedTime();
2796   // We have to wait until the CM threads finish scanning the
2797   // root regions as it's the only way to ensure that all the
2798   // objects on them have been correctly scanned before we start
2799   // moving them during the GC.
2800   bool waited = _cm->root_regions()->wait_until_scan_finished();
2801   double wait_time_ms = 0.0;
2802   if (waited) {
2803     double scan_wait_end = os::elapsedTime();
2804     wait_time_ms = (scan_wait_end - scan_wait_start) * 1000.0;
2805   }
2806   phase_times()->record_root_region_scan_wait_time(wait_time_ms);
2807 }
2808 
2809 class G1PrintCollectionSetClosure : public HeapRegionClosure {
2810 private:
2811   G1HRPrinter* _hr_printer;
2812 public:
2813   G1PrintCollectionSetClosure(G1HRPrinter* hr_printer) : HeapRegionClosure(), _hr_printer(hr_printer) { }
2814 
2815   virtual bool do_heap_region(HeapRegion* r) {
2816     _hr_printer->cset(r);
2817     return false;
2818   }
2819 };
2820 
2821 void G1CollectedHeap::start_new_collection_set() {
2822   double start = os::elapsedTime();
2823 
2824   collection_set()->start_incremental_building();
2825 
2826   clear_region_attr();
2827 
2828   guarantee(_eden.length() == 0, "eden should have been cleared");
2829   policy()->transfer_survivors_to_cset(survivor());
2830 
2831   // We redo the verification but now wrt to the new CSet which
2832   // has just got initialized after the previous CSet was freed.
2833   _cm->verify_no_collection_set_oops();
2834 
2835   phase_times()->record_start_new_cset_time_ms((os::elapsedTime() - start) * 1000.0);
2836 }
2837 
2838 void G1CollectedHeap::calculate_collection_set(G1EvacuationInfo& evacuation_info, double target_pause_time_ms) {
2839 
2840   _collection_set.finalize_initial_collection_set(target_pause_time_ms, &_survivor);
2841   evacuation_info.set_collectionset_regions(collection_set()->region_length() +
2842                                             collection_set()->optional_region_length());
2843 
2844   _cm->verify_no_collection_set_oops();
2845 
2846   if (_hr_printer.is_active()) {
2847     G1PrintCollectionSetClosure cl(&_hr_printer);
2848     _collection_set.iterate(&cl);
2849     _collection_set.iterate_optional(&cl);
2850   }
2851 }
2852 
2853 G1HeapVerifier::G1VerifyType G1CollectedHeap::young_collection_verify_type() const {
2854   if (collector_state()->in_initial_mark_gc()) {
2855     return G1HeapVerifier::G1VerifyConcurrentStart;
2856   } else if (collector_state()->in_young_only_phase()) {
2857     return G1HeapVerifier::G1VerifyYoungNormal;
2858   } else {
2859     return G1HeapVerifier::G1VerifyMixed;
2860   }
2861 }
2862 
2863 void G1CollectedHeap::verify_before_young_collection(G1HeapVerifier::G1VerifyType type) {
2864   if (VerifyRememberedSets) {
2865     log_info(gc, verify)("[Verifying RemSets before GC]");
2866     VerifyRegionRemSetClosure v_cl;
2867     heap_region_iterate(&v_cl);
2868   }
2869   _verifier->verify_before_gc(type);
2870   _verifier->check_bitmaps("GC Start");
2871 }
2872 
2873 void G1CollectedHeap::verify_after_young_collection(G1HeapVerifier::G1VerifyType type) {
2874   if (VerifyRememberedSets) {
2875     log_info(gc, verify)("[Verifying RemSets after GC]");
2876     VerifyRegionRemSetClosure v_cl;
2877     heap_region_iterate(&v_cl);
2878   }
2879   _verifier->verify_after_gc(type);
2880   _verifier->check_bitmaps("GC End");
2881 }
2882 
2883 void G1CollectedHeap::expand_heap_after_young_collection(){
2884   size_t expand_bytes = _heap_sizing_policy->expansion_amount();
2885   if (expand_bytes > 0) {
2886     // No need for an ergo logging here,
2887     // expansion_amount() does this when it returns a value > 0.
2888     double expand_ms;
2889     if (!expand(expand_bytes, _workers, &expand_ms)) {
2890       // We failed to expand the heap. Cannot do anything about it.
2891     }
2892     phase_times()->record_expand_heap_time(expand_ms);
2893   }
2894 }
2895 
2896 const char* G1CollectedHeap::young_gc_name() const {
2897   if (collector_state()->in_initial_mark_gc()) {
2898     return "Pause Young (Concurrent Start)";
2899   } else if (collector_state()->in_young_only_phase()) {
2900     if (collector_state()->in_young_gc_before_mixed()) {
2901       return "Pause Young (Prepare Mixed)";
2902     } else {
2903       return "Pause Young (Normal)";
2904     }
2905   } else {
2906     return "Pause Young (Mixed)";
2907   }
2908 }
2909 
2910 bool G1CollectedHeap::do_collection_pause_at_safepoint(double target_pause_time_ms) {
2911   assert_at_safepoint_on_vm_thread();
2912   guarantee(!is_gc_active(), "collection is not reentrant");
2913 
2914   if (GCLocker::check_active_before_gc()) {
2915     return false;
2916   }
2917 
2918   GCIdMark gc_id_mark;
2919 
2920   SvcGCMarker sgcm(SvcGCMarker::MINOR);
2921   ResourceMark rm;
2922 
2923   policy()->note_gc_start();
2924 
2925   _gc_timer_stw->register_gc_start();
2926   _gc_tracer_stw->report_gc_start(gc_cause(), _gc_timer_stw->gc_start());
2927 
2928   wait_for_root_region_scanning();
2929 
2930   print_heap_before_gc();
2931   print_heap_regions();
2932   trace_heap_before_gc(_gc_tracer_stw);
2933 
2934   _verifier->verify_region_sets_optional();
2935   _verifier->verify_dirty_young_regions();
2936 
2937   // We should not be doing initial mark unless the conc mark thread is running
2938   if (!_cm_thread->should_terminate()) {
2939     // This call will decide whether this pause is an initial-mark
2940     // pause. If it is, in_initial_mark_gc() will return true
2941     // for the duration of this pause.
2942     policy()->decide_on_conc_mark_initiation();
2943   }
2944 
2945   // We do not allow initial-mark to be piggy-backed on a mixed GC.
2946   assert(!collector_state()->in_initial_mark_gc() ||
2947          collector_state()->in_young_only_phase(), "sanity");
2948   // We also do not allow mixed GCs during marking.
2949   assert(!collector_state()->mark_or_rebuild_in_progress() || collector_state()->in_young_only_phase(), "sanity");
2950 
2951   // Record whether this pause is an initial mark. When the current
2952   // thread has completed its logging output and it's safe to signal
2953   // the CM thread, the flag's value in the policy has been reset.
2954   bool should_start_conc_mark = collector_state()->in_initial_mark_gc();
2955   if (should_start_conc_mark) {
2956     _cm->gc_tracer_cm()->set_gc_cause(gc_cause());
2957   }
2958 
2959   // Inner scope for scope based logging, timers, and stats collection
2960   {
2961     G1EvacuationInfo evacuation_info;
2962 
2963     _gc_tracer_stw->report_yc_type(collector_state()->yc_type());
2964 
2965     GCTraceCPUTime tcpu;
2966 
2967     GCTraceTime(Info, gc) tm(young_gc_name(), NULL, gc_cause(), true);
2968 
2969     uint active_workers = WorkerPolicy::calc_active_workers(workers()->total_workers(),
2970                                                             workers()->active_workers(),
2971                                                             Threads::number_of_non_daemon_threads());
2972     active_workers = workers()->update_active_workers(active_workers);
2973     log_info(gc,task)("Using %u workers of %u for evacuation", active_workers, workers()->total_workers());
2974 
2975     G1MonitoringScope ms(g1mm(),
2976                          false /* full_gc */,
2977                          collector_state()->yc_type() == Mixed /* all_memory_pools_affected */);
2978 
2979     G1HeapTransition heap_transition(this);
2980     size_t heap_used_bytes_before_gc = used();
2981 
2982     {
2983       IsGCActiveMark x;
2984 
2985       gc_prologue(false);
2986 
2987       G1HeapVerifier::G1VerifyType verify_type = young_collection_verify_type();
2988       verify_before_young_collection(verify_type);
2989 
2990       {
2991         // The elapsed time induced by the start time below deliberately elides
2992         // the possible verification above.
2993         double sample_start_time_sec = os::elapsedTime();
2994 
2995         // Please see comment in g1CollectedHeap.hpp and
2996         // G1CollectedHeap::ref_processing_init() to see how
2997         // reference processing currently works in G1.
2998         _ref_processor_stw->enable_discovery();
2999 
3000         // We want to temporarily turn off discovery by the
3001         // CM ref processor, if necessary, and turn it back on
3002         // on again later if we do. Using a scoped
3003         // NoRefDiscovery object will do this.
3004         NoRefDiscovery no_cm_discovery(_ref_processor_cm);
3005 
3006         policy()->record_collection_pause_start(sample_start_time_sec);
3007 
3008         // Forget the current allocation region (we might even choose it to be part
3009         // of the collection set!).
3010         _allocator->release_mutator_alloc_region();
3011 
3012         calculate_collection_set(evacuation_info, target_pause_time_ms);
3013 
3014         G1RedirtyCardsQueueSet rdcqs(G1BarrierSet::dirty_card_queue_set().allocator());
3015         G1ParScanThreadStateSet per_thread_states(this,
3016                                                   &rdcqs,
3017                                                   workers()->active_workers(),
3018                                                   collection_set()->young_region_length(),
3019                                                   collection_set()->optional_region_length());
3020         pre_evacuate_collection_set(evacuation_info, &per_thread_states);
3021 
3022         // Actually do the work...
3023         evacuate_initial_collection_set(&per_thread_states);
3024 
3025         if (_collection_set.optional_region_length() != 0) {
3026           evacuate_optional_collection_set(&per_thread_states);
3027         }
3028         post_evacuate_collection_set(evacuation_info, &rdcqs, &per_thread_states);
3029 
3030         start_new_collection_set();
3031 
3032         _survivor_evac_stats.adjust_desired_plab_sz();
3033         _old_evac_stats.adjust_desired_plab_sz();
3034 
3035         if (should_start_conc_mark) {
3036           // We have to do this before we notify the CM threads that
3037           // they can start working to make sure that all the
3038           // appropriate initialization is done on the CM object.
3039           concurrent_mark()->post_initial_mark();
3040           // Note that we don't actually trigger the CM thread at
3041           // this point. We do that later when we're sure that
3042           // the current thread has completed its logging output.
3043         }
3044 
3045         allocate_dummy_regions();
3046 
3047         _allocator->init_mutator_alloc_region();
3048 
3049         expand_heap_after_young_collection();
3050 
3051         double sample_end_time_sec = os::elapsedTime();
3052         double pause_time_ms = (sample_end_time_sec - sample_start_time_sec) * MILLIUNITS;
3053         policy()->record_collection_pause_end(pause_time_ms, heap_used_bytes_before_gc);
3054       }
3055 
3056       verify_after_young_collection(verify_type);
3057 
3058 #ifdef TRACESPINNING
3059       ParallelTaskTerminator::print_termination_counts();
3060 #endif
3061 
3062       gc_epilogue(false);
3063     }
3064 
3065     // Print the remainder of the GC log output.
3066     if (evacuation_failed()) {
3067       log_info(gc)("To-space exhausted");
3068     }
3069 
3070     policy()->print_phases();
3071     heap_transition.print();
3072 
3073     _hrm->verify_optional();
3074     _verifier->verify_region_sets_optional();
3075 
3076     TASKQUEUE_STATS_ONLY(print_taskqueue_stats());
3077     TASKQUEUE_STATS_ONLY(reset_taskqueue_stats());
3078 
3079     print_heap_after_gc();
3080     print_heap_regions();
3081     trace_heap_after_gc(_gc_tracer_stw);
3082 
3083     // We must call G1MonitoringSupport::update_sizes() in the same scoping level
3084     // as an active TraceMemoryManagerStats object (i.e. before the destructor for the
3085     // TraceMemoryManagerStats is called) so that the G1 memory pools are updated
3086     // before any GC notifications are raised.
3087     g1mm()->update_sizes();
3088 
3089     _gc_tracer_stw->report_evacuation_info(&evacuation_info);
3090     _gc_tracer_stw->report_tenuring_threshold(_policy->tenuring_threshold());
3091     _gc_timer_stw->register_gc_end();
3092     _gc_tracer_stw->report_gc_end(_gc_timer_stw->gc_end(), _gc_timer_stw->time_partitions());
3093   }
3094   // It should now be safe to tell the concurrent mark thread to start
3095   // without its logging output interfering with the logging output
3096   // that came from the pause.
3097 
3098   if (should_start_conc_mark) {
3099     // CAUTION: after the doConcurrentMark() call below, the concurrent marking
3100     // thread(s) could be running concurrently with us. Make sure that anything
3101     // after this point does not assume that we are the only GC thread running.
3102     // Note: of course, the actual marking work will not start until the safepoint
3103     // itself is released in SuspendibleThreadSet::desynchronize().
3104     do_concurrent_mark();
3105   }
3106 
3107   return true;
3108 }
3109 
3110 void G1CollectedHeap::remove_self_forwarding_pointers(G1RedirtyCardsQueueSet* rdcqs) {
3111   G1ParRemoveSelfForwardPtrsTask rsfp_task(rdcqs);
3112   workers()->run_task(&rsfp_task);
3113 }
3114 
3115 void G1CollectedHeap::restore_after_evac_failure(G1RedirtyCardsQueueSet* rdcqs) {
3116   double remove_self_forwards_start = os::elapsedTime();
3117 
3118   remove_self_forwarding_pointers(rdcqs);
3119   SharedRestorePreservedMarksTaskExecutor task_executor(workers());
3120   _preserved_marks_set.restore(&task_executor);
3121 
3122   phase_times()->record_evac_fail_remove_self_forwards((os::elapsedTime() - remove_self_forwards_start) * 1000.0);
3123 }
3124 
3125 void G1CollectedHeap::preserve_mark_during_evac_failure(uint worker_id, oop obj, markWord m) {
3126   if (!_evacuation_failed) {
3127     _evacuation_failed = true;
3128   }
3129 
3130   _evacuation_failed_info_array[worker_id].register_copy_failure(obj->size());
3131   _preserved_marks_set.get(worker_id)->push_if_necessary(obj, m);
3132 }
3133 
3134 bool G1ParEvacuateFollowersClosure::offer_termination() {
3135   EventGCPhaseParallel event;
3136   G1ParScanThreadState* const pss = par_scan_state();
3137   start_term_time();
3138   const bool res = terminator()->offer_termination();
3139   end_term_time();
3140   event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(G1GCPhaseTimes::Termination));
3141   return res;
3142 }
3143 
3144 void G1ParEvacuateFollowersClosure::do_void() {
3145   EventGCPhaseParallel event;
3146   G1ParScanThreadState* const pss = par_scan_state();
3147   pss->trim_queue();
3148   event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(_phase));
3149   do {
3150     EventGCPhaseParallel event;
3151     pss->steal_and_trim_queue(queues());
3152     event.commit(GCId::current(), pss->worker_id(), G1GCPhaseTimes::phase_name(_phase));
3153   } while (!offer_termination());
3154 }
3155 
3156 void G1CollectedHeap::complete_cleaning(BoolObjectClosure* is_alive,
3157                                         bool class_unloading_occurred) {
3158   uint num_workers = workers()->active_workers();
3159   G1ParallelCleaningTask unlink_task(is_alive, num_workers, class_unloading_occurred, false);
3160   workers()->run_task(&unlink_task);
3161 }
3162 
3163 // Clean string dedup data structures.
3164 // Ideally we would prefer to use a StringDedupCleaningTask here, but we want to
3165 // record the durations of the phases. Hence the almost-copy.
3166 class G1StringDedupCleaningTask : public AbstractGangTask {
3167   BoolObjectClosure* _is_alive;
3168   OopClosure* _keep_alive;
3169   G1GCPhaseTimes* _phase_times;
3170 
3171 public:
3172   G1StringDedupCleaningTask(BoolObjectClosure* is_alive,
3173                             OopClosure* keep_alive,
3174                             G1GCPhaseTimes* phase_times) :
3175     AbstractGangTask("Partial Cleaning Task"),
3176     _is_alive(is_alive),
3177     _keep_alive(keep_alive),
3178     _phase_times(phase_times)
3179   {
3180     assert(G1StringDedup::is_enabled(), "String deduplication disabled.");
3181     StringDedup::gc_prologue(true);
3182   }
3183 
3184   ~G1StringDedupCleaningTask() {
3185     StringDedup::gc_epilogue();
3186   }
3187 
3188   void work(uint worker_id) {
3189     StringDedupUnlinkOrOopsDoClosure cl(_is_alive, _keep_alive);
3190     {
3191       G1GCParPhaseTimesTracker x(_phase_times, G1GCPhaseTimes::StringDedupQueueFixup, worker_id);
3192       StringDedupQueue::unlink_or_oops_do(&cl);
3193     }
3194     {
3195       G1GCParPhaseTimesTracker x(_phase_times, G1GCPhaseTimes::StringDedupTableFixup, worker_id);
3196       StringDedupTable::unlink_or_oops_do(&cl, worker_id);
3197     }
3198   }
3199 };
3200 
3201 void G1CollectedHeap::string_dedup_cleaning(BoolObjectClosure* is_alive,
3202                                             OopClosure* keep_alive,
3203                                             G1GCPhaseTimes* phase_times) {
3204   G1StringDedupCleaningTask cl(is_alive, keep_alive, phase_times);
3205   workers()->run_task(&cl);
3206 }
3207 
3208 class G1RedirtyLoggedCardsTask : public AbstractGangTask {
3209  private:
3210   G1RedirtyCardsQueueSet* _qset;
3211   G1CollectedHeap* _g1h;
3212   BufferNode* volatile _nodes;
3213 
3214   void par_apply(RedirtyLoggedCardTableEntryClosure* cl, uint worker_id) {
3215     size_t buffer_size = _qset->buffer_size();
3216     BufferNode* next = Atomic::load(&_nodes);
3217     while (next != NULL) {
3218       BufferNode* node = next;
3219       next = Atomic::cmpxchg(node->next(), &_nodes, node);
3220       if (next == node) {
3221         cl->apply_to_buffer(node, buffer_size, worker_id);
3222         next = node->next();
3223       }
3224     }
3225   }
3226 
3227  public:
3228   G1RedirtyLoggedCardsTask(G1RedirtyCardsQueueSet* qset, G1CollectedHeap* g1h) :
3229     AbstractGangTask("Redirty Cards"),
3230     _qset(qset), _g1h(g1h), _nodes(qset->all_completed_buffers()) { }
3231 
3232   virtual void work(uint worker_id) {
3233     G1GCPhaseTimes* p = _g1h->phase_times();
3234     G1GCParPhaseTimesTracker x(p, G1GCPhaseTimes::RedirtyCards, worker_id);
3235 
3236     RedirtyLoggedCardTableEntryClosure cl(_g1h);
3237     par_apply(&cl, worker_id);
3238 
3239     p->record_thread_work_item(G1GCPhaseTimes::RedirtyCards, worker_id, cl.num_dirtied());
3240   }
3241 };
3242 
3243 void G1CollectedHeap::redirty_logged_cards(G1RedirtyCardsQueueSet* rdcqs) {
3244   double redirty_logged_cards_start = os::elapsedTime();
3245 
3246   G1RedirtyLoggedCardsTask redirty_task(rdcqs, this);
3247   workers()->run_task(&redirty_task);
3248 
3249   G1DirtyCardQueueSet& dcq = G1BarrierSet::dirty_card_queue_set();
3250   dcq.merge_bufferlists(rdcqs);
3251 
3252   phase_times()->record_redirty_logged_cards_time_ms((os::elapsedTime() - redirty_logged_cards_start) * 1000.0);
3253 }
3254 
3255 // Weak Reference Processing support
3256 
3257 bool G1STWIsAliveClosure::do_object_b(oop p) {
3258   // An object is reachable if it is outside the collection set,
3259   // or is inside and copied.
3260   return !_g1h->is_in_cset(p) || p->is_forwarded();
3261 }
3262 
3263 bool G1STWSubjectToDiscoveryClosure::do_object_b(oop obj) {
3264   assert(obj != NULL, "must not be NULL");
3265   assert(_g1h->is_in_reserved(obj), "Trying to discover obj " PTR_FORMAT " not in heap", p2i(obj));
3266   // The areas the CM and STW ref processor manage must be disjoint. The is_in_cset() below
3267   // may falsely indicate that this is not the case here: however the collection set only
3268   // contains old regions when concurrent mark is not running.
3269   return _g1h->is_in_cset(obj) || _g1h->heap_region_containing(obj)->is_survivor();
3270 }
3271 
3272 // Non Copying Keep Alive closure
3273 class G1KeepAliveClosure: public OopClosure {
3274   G1CollectedHeap*_g1h;
3275 public:
3276   G1KeepAliveClosure(G1CollectedHeap* g1h) :_g1h(g1h) {}
3277   void do_oop(narrowOop* p) { guarantee(false, "Not needed"); }
3278   void do_oop(oop* p) {
3279     oop obj = *p;
3280     assert(obj != NULL, "the caller should have filtered out NULL values");
3281 
3282     const G1HeapRegionAttr region_attr =_g1h->region_attr(obj);
3283     if (!region_attr.is_in_cset_or_humongous()) {
3284       return;
3285     }
3286     if (region_attr.is_in_cset()) {
3287       assert( obj->is_forwarded(), "invariant" );
3288       *p = obj->forwardee();
3289     } else {
3290       assert(!obj->is_forwarded(), "invariant" );
3291       assert(region_attr.is_humongous(),
3292              "Only allowed G1HeapRegionAttr state is IsHumongous, but is %d", region_attr.type());
3293      _g1h->set_humongous_is_live(obj);
3294     }
3295   }
3296 };
3297 
3298 // Copying Keep Alive closure - can be called from both
3299 // serial and parallel code as long as different worker
3300 // threads utilize different G1ParScanThreadState instances
3301 // and different queues.
3302 
3303 class G1CopyingKeepAliveClosure: public OopClosure {
3304   G1CollectedHeap*         _g1h;
3305   G1ParScanThreadState*    _par_scan_state;
3306 
3307 public:
3308   G1CopyingKeepAliveClosure(G1CollectedHeap* g1h,
3309                             G1ParScanThreadState* pss):
3310     _g1h(g1h),
3311     _par_scan_state(pss)
3312   {}
3313 
3314   virtual void do_oop(narrowOop* p) { do_oop_work(p); }
3315   virtual void do_oop(      oop* p) { do_oop_work(p); }
3316 
3317   template <class T> void do_oop_work(T* p) {
3318     oop obj = RawAccess<>::oop_load(p);
3319 
3320     if (_g1h->is_in_cset_or_humongous(obj)) {
3321       // If the referent object has been forwarded (either copied
3322       // to a new location or to itself in the event of an
3323       // evacuation failure) then we need to update the reference
3324       // field and, if both reference and referent are in the G1
3325       // heap, update the RSet for the referent.
3326       //
3327       // If the referent has not been forwarded then we have to keep
3328       // it alive by policy. Therefore we have copy the referent.
3329       //
3330       // When the queue is drained (after each phase of reference processing)
3331       // the object and it's followers will be copied, the reference field set
3332       // to point to the new location, and the RSet updated.
3333       _par_scan_state->push_on_queue(p);
3334     }
3335   }
3336 };
3337 
3338 // Serial drain queue closure. Called as the 'complete_gc'
3339 // closure for each discovered list in some of the
3340 // reference processing phases.
3341 
3342 class G1STWDrainQueueClosure: public VoidClosure {
3343 protected:
3344   G1CollectedHeap* _g1h;
3345   G1ParScanThreadState* _par_scan_state;
3346 
3347   G1ParScanThreadState*   par_scan_state() { return _par_scan_state; }
3348 
3349 public:
3350   G1STWDrainQueueClosure(G1CollectedHeap* g1h, G1ParScanThreadState* pss) :
3351     _g1h(g1h),
3352     _par_scan_state(pss)
3353   { }
3354 
3355   void do_void() {
3356     G1ParScanThreadState* const pss = par_scan_state();
3357     pss->trim_queue();
3358   }
3359 };
3360 
3361 // Parallel Reference Processing closures
3362 
3363 // Implementation of AbstractRefProcTaskExecutor for parallel reference
3364 // processing during G1 evacuation pauses.
3365 
3366 class G1STWRefProcTaskExecutor: public AbstractRefProcTaskExecutor {
3367 private:
3368   G1CollectedHeap*          _g1h;
3369   G1ParScanThreadStateSet*  _pss;
3370   RefToScanQueueSet*        _queues;
3371   WorkGang*                 _workers;
3372 
3373 public:
3374   G1STWRefProcTaskExecutor(G1CollectedHeap* g1h,
3375                            G1ParScanThreadStateSet* per_thread_states,
3376                            WorkGang* workers,
3377                            RefToScanQueueSet *task_queues) :
3378     _g1h(g1h),
3379     _pss(per_thread_states),
3380     _queues(task_queues),
3381     _workers(workers)
3382   {
3383     g1h->ref_processor_stw()->set_active_mt_degree(workers->active_workers());
3384   }
3385 
3386   // Executes the given task using concurrent marking worker threads.
3387   virtual void execute(ProcessTask& task, uint ergo_workers);
3388 };
3389 
3390 // Gang task for possibly parallel reference processing
3391 
3392 class G1STWRefProcTaskProxy: public AbstractGangTask {
3393   typedef AbstractRefProcTaskExecutor::ProcessTask ProcessTask;
3394   ProcessTask&     _proc_task;
3395   G1CollectedHeap* _g1h;
3396   G1ParScanThreadStateSet* _pss;
3397   RefToScanQueueSet* _task_queues;
3398   ParallelTaskTerminator* _terminator;
3399 
3400 public:
3401   G1STWRefProcTaskProxy(ProcessTask& proc_task,
3402                         G1CollectedHeap* g1h,
3403                         G1ParScanThreadStateSet* per_thread_states,
3404                         RefToScanQueueSet *task_queues,
3405                         ParallelTaskTerminator* terminator) :
3406     AbstractGangTask("Process reference objects in parallel"),
3407     _proc_task(proc_task),
3408     _g1h(g1h),
3409     _pss(per_thread_states),
3410     _task_queues(task_queues),
3411     _terminator(terminator)
3412   {}
3413 
3414   virtual void work(uint worker_id) {
3415     // The reference processing task executed by a single worker.
3416     ResourceMark rm;
3417     HandleMark   hm;
3418 
3419     G1STWIsAliveClosure is_alive(_g1h);
3420 
3421     G1ParScanThreadState* pss = _pss->state_for_worker(worker_id);
3422     pss->set_ref_discoverer(NULL);
3423 
3424     // Keep alive closure.
3425     G1CopyingKeepAliveClosure keep_alive(_g1h, pss);
3426 
3427     // Complete GC closure
3428     G1ParEvacuateFollowersClosure drain_queue(_g1h, pss, _task_queues, _terminator, G1GCPhaseTimes::ObjCopy);
3429 
3430     // Call the reference processing task's work routine.
3431     _proc_task.work(worker_id, is_alive, keep_alive, drain_queue);
3432 
3433     // Note we cannot assert that the refs array is empty here as not all
3434     // of the processing tasks (specifically phase2 - pp2_work) execute
3435     // the complete_gc closure (which ordinarily would drain the queue) so
3436     // the queue may not be empty.
3437   }
3438 };
3439 
3440 // Driver routine for parallel reference processing.
3441 // Creates an instance of the ref processing gang
3442 // task and has the worker threads execute it.
3443 void G1STWRefProcTaskExecutor::execute(ProcessTask& proc_task, uint ergo_workers) {
3444   assert(_workers != NULL, "Need parallel worker threads.");
3445 
3446   assert(_workers->active_workers() >= ergo_workers,
3447          "Ergonomically chosen workers (%u) should be less than or equal to active workers (%u)",
3448          ergo_workers, _workers->active_workers());
3449   TaskTerminator terminator(ergo_workers, _queues);
3450   G1STWRefProcTaskProxy proc_task_proxy(proc_task, _g1h, _pss, _queues, terminator.terminator());
3451 
3452   _workers->run_task(&proc_task_proxy, ergo_workers);
3453 }
3454 
3455 // End of weak reference support closures
3456 
3457 void G1CollectedHeap::process_discovered_references(G1ParScanThreadStateSet* per_thread_states) {
3458   double ref_proc_start = os::elapsedTime();
3459 
3460   ReferenceProcessor* rp = _ref_processor_stw;
3461   assert(rp->discovery_enabled(), "should have been enabled");
3462 
3463   // Closure to test whether a referent is alive.
3464   G1STWIsAliveClosure is_alive(this);
3465 
3466   // Even when parallel reference processing is enabled, the processing
3467   // of JNI refs is serial and performed serially by the current thread
3468   // rather than by a worker. The following PSS will be used for processing
3469   // JNI refs.
3470 
3471   // Use only a single queue for this PSS.
3472   G1ParScanThreadState*          pss = per_thread_states->state_for_worker(0);
3473   pss->set_ref_discoverer(NULL);
3474   assert(pss->queue_is_empty(), "pre-condition");
3475 
3476   // Keep alive closure.
3477   G1CopyingKeepAliveClosure keep_alive(this, pss);
3478 
3479   // Serial Complete GC closure
3480   G1STWDrainQueueClosure drain_queue(this, pss);
3481 
3482   // Setup the soft refs policy...
3483   rp->setup_policy(false);
3484 
3485   ReferenceProcessorPhaseTimes* pt = phase_times()->ref_phase_times();
3486 
3487   ReferenceProcessorStats stats;
3488   if (!rp->processing_is_mt()) {
3489     // Serial reference processing...
3490     stats = rp->process_discovered_references(&is_alive,
3491                                               &keep_alive,
3492                                               &drain_queue,
3493                                               NULL,
3494                                               pt);
3495   } else {
3496     uint no_of_gc_workers = workers()->active_workers();
3497 
3498     // Parallel reference processing
3499     assert(no_of_gc_workers <= rp->max_num_queues(),
3500            "Mismatch between the number of GC workers %u and the maximum number of Reference process queues %u",
3501            no_of_gc_workers,  rp->max_num_queues());
3502 
3503     G1STWRefProcTaskExecutor par_task_executor(this, per_thread_states, workers(), _task_queues);
3504     stats = rp->process_discovered_references(&is_alive,
3505                                               &keep_alive,
3506                                               &drain_queue,
3507                                               &par_task_executor,
3508                                               pt);
3509   }
3510 
3511   _gc_tracer_stw->report_gc_reference_stats(stats);
3512 
3513   // We have completed copying any necessary live referent objects.
3514   assert(pss->queue_is_empty(), "both queue and overflow should be empty");
3515 
3516   make_pending_list_reachable();
3517 
3518   assert(!rp->discovery_enabled(), "Postcondition");
3519   rp->verify_no_references_recorded();
3520 
3521   double ref_proc_time = os::elapsedTime() - ref_proc_start;
3522   phase_times()->record_ref_proc_time(ref_proc_time * 1000.0);
3523 }
3524 
3525 void G1CollectedHeap::make_pending_list_reachable() {
3526   if (collector_state()->in_initial_mark_gc()) {
3527     oop pll_head = Universe::reference_pending_list();
3528     if (pll_head != NULL) {
3529       // Any valid worker id is fine here as we are in the VM thread and single-threaded.
3530       _cm->mark_in_next_bitmap(0 /* worker_id */, pll_head);
3531     }
3532   }
3533 }
3534 
3535 void G1CollectedHeap::merge_per_thread_state_info(G1ParScanThreadStateSet* per_thread_states) {
3536   double merge_pss_time_start = os::elapsedTime();
3537   per_thread_states->flush();
3538   phase_times()->record_merge_pss_time_ms((os::elapsedTime() - merge_pss_time_start) * 1000.0);
3539 }
3540 
3541 void G1CollectedHeap::pre_evacuate_collection_set(G1EvacuationInfo& evacuation_info, G1ParScanThreadStateSet* per_thread_states) {
3542   _expand_heap_after_alloc_failure = true;
3543   _evacuation_failed = false;
3544 
3545   // Disable the hot card cache.
3546   _hot_card_cache->reset_hot_cache_claimed_index();
3547   _hot_card_cache->set_use_cache(false);
3548 
3549   // Initialize the GC alloc regions.
3550   _allocator->init_gc_alloc_regions(evacuation_info);
3551 
3552   {
3553     Ticks start = Ticks::now();
3554     rem_set()->prepare_for_scan_heap_roots();
3555     phase_times()->record_prepare_heap_roots_time_ms((Ticks::now() - start).seconds() * 1000.0);
3556   }
3557 
3558   register_regions_with_region_attr();
3559   assert(_verifier->check_region_attr_table(), "Inconsistency in the region attributes table.");
3560 
3561   _preserved_marks_set.assert_empty();
3562 
3563 #if COMPILER2_OR_JVMCI
3564   DerivedPointerTable::clear();
3565 #endif
3566 
3567   // InitialMark needs claim bits to keep track of the marked-through CLDs.
3568   if (collector_state()->in_initial_mark_gc()) {
3569     concurrent_mark()->pre_initial_mark();
3570 
3571     double start_clear_claimed_marks = os::elapsedTime();
3572 
3573     ClassLoaderDataGraph::clear_claimed_marks();
3574 
3575     double recorded_clear_claimed_marks_time_ms = (os::elapsedTime() - start_clear_claimed_marks) * 1000.0;
3576     phase_times()->record_clear_claimed_marks_time_ms(recorded_clear_claimed_marks_time_ms);
3577   }
3578 
3579   // Should G1EvacuationFailureALot be in effect for this GC?
3580   NOT_PRODUCT(set_evacuation_failure_alot_for_current_gc();)
3581 }
3582 
3583 class G1EvacuateRegionsBaseTask : public AbstractGangTask {
3584 protected:
3585   G1CollectedHeap* _g1h;
3586   G1ParScanThreadStateSet* _per_thread_states;
3587   RefToScanQueueSet* _task_queues;
3588   TaskTerminator _terminator;
3589   uint _num_workers;
3590 
3591   void evacuate_live_objects(G1ParScanThreadState* pss,
3592                              uint worker_id,
3593                              G1GCPhaseTimes::GCParPhases objcopy_phase,
3594                              G1GCPhaseTimes::GCParPhases termination_phase) {
3595     G1GCPhaseTimes* p = _g1h->phase_times();
3596 
3597     Ticks start = Ticks::now();
3598     G1ParEvacuateFollowersClosure cl(_g1h, pss, _task_queues, _terminator.terminator(), objcopy_phase);
3599     cl.do_void();
3600 
3601     assert(pss->queue_is_empty(), "should be empty");
3602 
3603     Tickspan evac_time = (Ticks::now() - start);
3604     p->record_or_add_time_secs(objcopy_phase, worker_id, evac_time.seconds() - cl.term_time());
3605 
3606     p->record_or_add_thread_work_item(objcopy_phase, worker_id, pss->lab_waste_words() * HeapWordSize, G1GCPhaseTimes::ObjCopyLABWaste);
3607     p->record_or_add_thread_work_item(objcopy_phase, worker_id, pss->lab_undo_waste_words() * HeapWordSize, G1GCPhaseTimes::ObjCopyLABUndoWaste);
3608 
3609     if (termination_phase == G1GCPhaseTimes::Termination) {
3610       p->record_time_secs(termination_phase, worker_id, cl.term_time());
3611       p->record_thread_work_item(termination_phase, worker_id, cl.term_attempts());
3612     } else {
3613       p->record_or_add_time_secs(termination_phase, worker_id, cl.term_time());
3614       p->record_or_add_thread_work_item(termination_phase, worker_id, cl.term_attempts());
3615     }
3616     assert(pss->trim_ticks().seconds() == 0.0, "Unexpected partial trimming during evacuation");
3617   }
3618 
3619   virtual void start_work(uint worker_id) { }
3620 
3621   virtual void end_work(uint worker_id) { }
3622 
3623   virtual void scan_roots(G1ParScanThreadState* pss, uint worker_id) = 0;
3624 
3625   virtual void evacuate_live_objects(G1ParScanThreadState* pss, uint worker_id) = 0;
3626 
3627 public:
3628   G1EvacuateRegionsBaseTask(const char* name, G1ParScanThreadStateSet* per_thread_states, RefToScanQueueSet* task_queues, uint num_workers) :
3629     AbstractGangTask(name),
3630     _g1h(G1CollectedHeap::heap()),
3631     _per_thread_states(per_thread_states),
3632     _task_queues(task_queues),
3633     _terminator(num_workers, _task_queues),
3634     _num_workers(num_workers)
3635   { }
3636 
3637   void work(uint worker_id) {
3638     start_work(worker_id);
3639 
3640     {
3641       ResourceMark rm;
3642       HandleMark   hm;
3643 
3644       G1ParScanThreadState* pss = _per_thread_states->state_for_worker(worker_id);
3645       pss->set_ref_discoverer(_g1h->ref_processor_stw());
3646 
3647       scan_roots(pss, worker_id);
3648       evacuate_live_objects(pss, worker_id);
3649     }
3650 
3651     end_work(worker_id);
3652   }
3653 };
3654 
3655 class G1EvacuateRegionsTask : public G1EvacuateRegionsBaseTask {
3656   G1RootProcessor* _root_processor;
3657 
3658   void scan_roots(G1ParScanThreadState* pss, uint worker_id) {
3659     _root_processor->evacuate_roots(pss, worker_id);
3660     _g1h->rem_set()->scan_heap_roots(pss, worker_id, G1GCPhaseTimes::ScanHR, G1GCPhaseTimes::ObjCopy);
3661     _g1h->rem_set()->scan_collection_set_regions(pss, worker_id, G1GCPhaseTimes::ScanHR, G1GCPhaseTimes::CodeRoots, G1GCPhaseTimes::ObjCopy);
3662   }
3663 
3664   void evacuate_live_objects(G1ParScanThreadState* pss, uint worker_id) {
3665     G1EvacuateRegionsBaseTask::evacuate_live_objects(pss, worker_id, G1GCPhaseTimes::ObjCopy, G1GCPhaseTimes::Termination);
3666   }
3667 
3668   void start_work(uint worker_id) {
3669     _g1h->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerStart, worker_id, Ticks::now().seconds());
3670   }
3671 
3672   void end_work(uint worker_id) {
3673     _g1h->phase_times()->record_time_secs(G1GCPhaseTimes::GCWorkerEnd, worker_id, Ticks::now().seconds());
3674   }
3675 
3676 public:
3677   G1EvacuateRegionsTask(G1CollectedHeap* g1h,
3678                         G1ParScanThreadStateSet* per_thread_states,
3679                         RefToScanQueueSet* task_queues,
3680                         G1RootProcessor* root_processor,
3681                         uint num_workers) :
3682     G1EvacuateRegionsBaseTask("G1 Evacuate Regions", per_thread_states, task_queues, num_workers),
3683     _root_processor(root_processor)
3684   { }
3685 };
3686 
3687 void G1CollectedHeap::evacuate_initial_collection_set(G1ParScanThreadStateSet* per_thread_states) {
3688   G1GCPhaseTimes* p = phase_times();
3689 
3690   {
3691     Ticks start = Ticks::now();
3692     rem_set()->merge_heap_roots(true /* initial_evacuation */);
3693     p->record_merge_heap_roots_time((Ticks::now() - start).seconds() * 1000.0);
3694   }
3695 
3696   Tickspan task_time;
3697   const uint num_workers = workers()->active_workers();
3698 
3699   Ticks start_processing = Ticks::now();
3700   {
3701     G1RootProcessor root_processor(this, num_workers);
3702     G1EvacuateRegionsTask g1_par_task(this, per_thread_states, _task_queues, &root_processor, num_workers);
3703     task_time = run_task(&g1_par_task);
3704     // Closing the inner scope will execute the destructor for the G1RootProcessor object.
3705     // To extract its code root fixup time we measure total time of this scope and
3706     // subtract from the time the WorkGang task took.
3707   }
3708   Tickspan total_processing = Ticks::now() - start_processing;
3709 
3710   p->record_initial_evac_time(task_time.seconds() * 1000.0);
3711   p->record_or_add_code_root_fixup_time((total_processing - task_time).seconds() * 1000.0);
3712 }
3713 
3714 class G1EvacuateOptionalRegionsTask : public G1EvacuateRegionsBaseTask {
3715 
3716   void scan_roots(G1ParScanThreadState* pss, uint worker_id) {
3717     _g1h->rem_set()->scan_heap_roots(pss, worker_id, G1GCPhaseTimes::OptScanHR, G1GCPhaseTimes::OptObjCopy);
3718     _g1h->rem_set()->scan_collection_set_regions(pss, worker_id, G1GCPhaseTimes::OptScanHR, G1GCPhaseTimes::OptCodeRoots, G1GCPhaseTimes::OptObjCopy);
3719   }
3720 
3721   void evacuate_live_objects(G1ParScanThreadState* pss, uint worker_id) {
3722     G1EvacuateRegionsBaseTask::evacuate_live_objects(pss, worker_id, G1GCPhaseTimes::OptObjCopy, G1GCPhaseTimes::OptTermination);
3723   }
3724 
3725 public:
3726   G1EvacuateOptionalRegionsTask(G1ParScanThreadStateSet* per_thread_states,
3727                                 RefToScanQueueSet* queues,
3728                                 uint num_workers) :
3729     G1EvacuateRegionsBaseTask("G1 Evacuate Optional Regions", per_thread_states, queues, num_workers) {
3730   }
3731 };
3732 
3733 void G1CollectedHeap::evacuate_next_optional_regions(G1ParScanThreadStateSet* per_thread_states) {
3734   class G1MarkScope : public MarkScope { };
3735 
3736   Tickspan task_time;
3737 
3738   Ticks start_processing = Ticks::now();
3739   {
3740     G1MarkScope code_mark_scope;
3741     G1EvacuateOptionalRegionsTask task(per_thread_states, _task_queues, workers()->active_workers());
3742     task_time = run_task(&task);
3743     // See comment in evacuate_collection_set() for the reason of the scope.
3744   }
3745   Tickspan total_processing = Ticks::now() - start_processing;
3746 
3747   G1GCPhaseTimes* p = phase_times();
3748   p->record_or_add_code_root_fixup_time((total_processing - task_time).seconds() * 1000.0);
3749 }
3750 
3751 void G1CollectedHeap::evacuate_optional_collection_set(G1ParScanThreadStateSet* per_thread_states) {
3752   const double gc_start_time_ms = phase_times()->cur_collection_start_sec() * 1000.0;
3753 
3754   while (!evacuation_failed() && _collection_set.optional_region_length() > 0) {
3755 
3756     double time_used_ms = os::elapsedTime() * 1000.0 - gc_start_time_ms;
3757     double time_left_ms = MaxGCPauseMillis - time_used_ms;
3758 
3759     if (time_left_ms < 0 ||
3760         !_collection_set.finalize_optional_for_evacuation(time_left_ms * policy()->optional_evacuation_fraction())) {
3761       log_trace(gc, ergo, cset)("Skipping evacuation of %u optional regions, no more regions can be evacuated in %.3fms",
3762                                 _collection_set.optional_region_length(), time_left_ms);
3763       break;
3764     }
3765 
3766     {
3767       Ticks start = Ticks::now();
3768       rem_set()->merge_heap_roots(false /* initial_evacuation */);
3769       phase_times()->record_or_add_optional_merge_heap_roots_time((Ticks::now() - start).seconds() * 1000.0);
3770     }
3771 
3772     {
3773       Ticks start = Ticks::now();
3774       evacuate_next_optional_regions(per_thread_states);
3775       phase_times()->record_or_add_optional_evac_time((Ticks::now() - start).seconds() * 1000.0);
3776     }
3777   }
3778 
3779   _collection_set.abandon_optional_collection_set(per_thread_states);
3780 }
3781 
3782 void G1CollectedHeap::post_evacuate_collection_set(G1EvacuationInfo& evacuation_info,
3783                                                    G1RedirtyCardsQueueSet* rdcqs,
3784                                                    G1ParScanThreadStateSet* per_thread_states) {
3785   rem_set()->cleanup_after_scan_heap_roots();
3786 
3787   // Process any discovered reference objects - we have
3788   // to do this _before_ we retire the GC alloc regions
3789   // as we may have to copy some 'reachable' referent
3790   // objects (and their reachable sub-graphs) that were
3791   // not copied during the pause.
3792   process_discovered_references(per_thread_states);
3793 
3794   G1STWIsAliveClosure is_alive(this);
3795   G1KeepAliveClosure keep_alive(this);
3796 
3797   WeakProcessor::weak_oops_do(workers(), &is_alive, &keep_alive,
3798                               phase_times()->weak_phase_times());
3799 
3800   if (G1StringDedup::is_enabled()) {
3801     double string_dedup_time_ms = os::elapsedTime();
3802 
3803     string_dedup_cleaning(&is_alive, &keep_alive, phase_times());
3804 
3805     double string_cleanup_time_ms = (os::elapsedTime() - string_dedup_time_ms) * 1000.0;
3806     phase_times()->record_string_deduplication_time(string_cleanup_time_ms);
3807   }
3808 
3809   _allocator->release_gc_alloc_regions(evacuation_info);
3810 
3811   if (evacuation_failed()) {
3812     restore_after_evac_failure(rdcqs);
3813 
3814     // Reset the G1EvacuationFailureALot counters and flags
3815     NOT_PRODUCT(reset_evacuation_should_fail();)
3816 
3817     double recalculate_used_start = os::elapsedTime();
3818     set_used(recalculate_used());
3819     phase_times()->record_evac_fail_recalc_used_time((os::elapsedTime() - recalculate_used_start) * 1000.0);
3820 
3821     if (_archive_allocator != NULL) {
3822       _archive_allocator->clear_used();
3823     }
3824     for (uint i = 0; i < ParallelGCThreads; i++) {
3825       if (_evacuation_failed_info_array[i].has_failed()) {
3826         _gc_tracer_stw->report_evacuation_failed(_evacuation_failed_info_array[i]);
3827       }
3828     }
3829   } else {
3830     // The "used" of the the collection set have already been subtracted
3831     // when they were freed.  Add in the bytes evacuated.
3832     increase_used(policy()->bytes_copied_during_gc());
3833   }
3834 
3835   _preserved_marks_set.assert_empty();
3836 
3837   merge_per_thread_state_info(per_thread_states);
3838 
3839   // Reset and re-enable the hot card cache.
3840   // Note the counts for the cards in the regions in the
3841   // collection set are reset when the collection set is freed.
3842   _hot_card_cache->reset_hot_cache();
3843   _hot_card_cache->set_use_cache(true);
3844 
3845   purge_code_root_memory();
3846 
3847   redirty_logged_cards(rdcqs);
3848 
3849   free_collection_set(&_collection_set, evacuation_info, per_thread_states->surviving_young_words());
3850 
3851   eagerly_reclaim_humongous_regions();
3852 
3853   record_obj_copy_mem_stats();
3854 
3855   evacuation_info.set_collectionset_used_before(collection_set()->bytes_used_before());
3856   evacuation_info.set_bytes_copied(policy()->bytes_copied_during_gc());
3857 
3858 #if COMPILER2_OR_JVMCI
3859   double start = os::elapsedTime();
3860   DerivedPointerTable::update_pointers();
3861   phase_times()->record_derived_pointer_table_update_time((os::elapsedTime() - start) * 1000.0);
3862 #endif
3863   policy()->print_age_table();
3864 }
3865 
3866 void G1CollectedHeap::record_obj_copy_mem_stats() {
3867   policy()->add_bytes_allocated_in_old_since_last_gc(_old_evac_stats.allocated() * HeapWordSize);
3868 
3869   _gc_tracer_stw->report_evacuation_statistics(create_g1_evac_summary(&_survivor_evac_stats),
3870                                                create_g1_evac_summary(&_old_evac_stats));
3871 }
3872 
3873 void G1CollectedHeap::free_region(HeapRegion* hr,
3874                                   FreeRegionList* free_list,
3875                                   bool skip_remset,
3876                                   bool skip_hot_card_cache,
3877                                   bool locked) {
3878   assert(!hr->is_free(), "the region should not be free");
3879   assert(!hr->is_empty(), "the region should not be empty");
3880   assert(_hrm->is_available(hr->hrm_index()), "region should be committed");
3881   assert(free_list != NULL, "pre-condition");
3882 
3883   if (G1VerifyBitmaps) {
3884     MemRegion mr(hr->bottom(), hr->end());
3885     concurrent_mark()->clear_range_in_prev_bitmap(mr);
3886   }
3887 
3888   // Clear the card counts for this region.
3889   // Note: we only need to do this if the region is not young
3890   // (since we don't refine cards in young regions).
3891   if (!skip_hot_card_cache && !hr->is_young()) {
3892     _hot_card_cache->reset_card_counts(hr);
3893   }
3894   hr->hr_clear(skip_remset, true /* clear_space */, locked /* locked */);
3895   _policy->remset_tracker()->update_at_free(hr);
3896   free_list->add_ordered(hr);
3897 }
3898 
3899 void G1CollectedHeap::free_humongous_region(HeapRegion* hr,
3900                                             FreeRegionList* free_list) {
3901   assert(hr->is_humongous(), "this is only for humongous regions");
3902   assert(free_list != NULL, "pre-condition");
3903   hr->clear_humongous();
3904   free_region(hr, free_list, false /* skip_remset */, false /* skip_hcc */, true /* locked */);
3905 }
3906 
3907 void G1CollectedHeap::remove_from_old_sets(const uint old_regions_removed,
3908                                            const uint humongous_regions_removed) {
3909   if (old_regions_removed > 0 || humongous_regions_removed > 0) {
3910     MutexLocker x(OldSets_lock, Mutex::_no_safepoint_check_flag);
3911     _old_set.bulk_remove(old_regions_removed);
3912     _humongous_set.bulk_remove(humongous_regions_removed);
3913   }
3914 
3915 }
3916 
3917 void G1CollectedHeap::prepend_to_freelist(FreeRegionList* list) {
3918   assert(list != NULL, "list can't be null");
3919   if (!list->is_empty()) {
3920     MutexLocker x(FreeList_lock, Mutex::_no_safepoint_check_flag);
3921     _hrm->insert_list_into_free_list(list);
3922   }
3923 }
3924 
3925 void G1CollectedHeap::decrement_summary_bytes(size_t bytes) {
3926   decrease_used(bytes);
3927 }
3928 
3929 class G1FreeCollectionSetTask : public AbstractGangTask {
3930 private:
3931 
3932   // Closure applied to all regions in the collection set to do work that needs to
3933   // be done serially in a single thread.
3934   class G1SerialFreeCollectionSetClosure : public HeapRegionClosure {
3935   private:
3936     G1EvacuationInfo* _evacuation_info;
3937     const size_t* _surviving_young_words;
3938 
3939     // Bytes used in successfully evacuated regions before the evacuation.
3940     size_t _before_used_bytes;
3941     // Bytes used in unsucessfully evacuated regions before the evacuation
3942     size_t _after_used_bytes;
3943 
3944     size_t _bytes_allocated_in_old_since_last_gc;
3945 
3946     size_t _failure_used_words;
3947     size_t _failure_waste_words;
3948 
3949     FreeRegionList _local_free_list;
3950   public:
3951     G1SerialFreeCollectionSetClosure(G1EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
3952       HeapRegionClosure(),
3953       _evacuation_info(evacuation_info),
3954       _surviving_young_words(surviving_young_words),
3955       _before_used_bytes(0),
3956       _after_used_bytes(0),
3957       _bytes_allocated_in_old_since_last_gc(0),
3958       _failure_used_words(0),
3959       _failure_waste_words(0),
3960       _local_free_list("Local Region List for CSet Freeing") {
3961     }
3962 
3963     virtual bool do_heap_region(HeapRegion* r) {
3964       G1CollectedHeap* g1h = G1CollectedHeap::heap();
3965 
3966       assert(r->in_collection_set(), "Region %u should be in collection set.", r->hrm_index());
3967       g1h->clear_region_attr(r);
3968 
3969       if (r->is_young()) {
3970         assert(r->young_index_in_cset() != 0 && (uint)r->young_index_in_cset() <= g1h->collection_set()->young_region_length(),
3971                "Young index %u is wrong for region %u of type %s with %u young regions",
3972                r->young_index_in_cset(),
3973                r->hrm_index(),
3974                r->get_type_str(),
3975                g1h->collection_set()->young_region_length());
3976         size_t words_survived = _surviving_young_words[r->young_index_in_cset()];
3977         r->record_surv_words_in_group(words_survived);
3978       }
3979 
3980       if (!r->evacuation_failed()) {
3981         assert(r->not_empty(), "Region %u is an empty region in the collection set.", r->hrm_index());
3982         _before_used_bytes += r->used();
3983         g1h->free_region(r,
3984                          &_local_free_list,
3985                          true, /* skip_remset */
3986                          true, /* skip_hot_card_cache */
3987                          true  /* locked */);
3988       } else {
3989         r->uninstall_surv_rate_group();
3990         r->clear_young_index_in_cset();
3991         r->set_evacuation_failed(false);
3992         // When moving a young gen region to old gen, we "allocate" that whole region
3993         // there. This is in addition to any already evacuated objects. Notify the
3994         // policy about that.
3995         // Old gen regions do not cause an additional allocation: both the objects
3996         // still in the region and the ones already moved are accounted for elsewhere.
3997         if (r->is_young()) {
3998           _bytes_allocated_in_old_since_last_gc += HeapRegion::GrainBytes;
3999         }
4000         // The region is now considered to be old.
4001         r->set_old();
4002         // Do some allocation statistics accounting. Regions that failed evacuation
4003         // are always made old, so there is no need to update anything in the young
4004         // gen statistics, but we need to update old gen statistics.
4005         size_t used_words = r->marked_bytes() / HeapWordSize;
4006 
4007         _failure_used_words += used_words;
4008         _failure_waste_words += HeapRegion::GrainWords - used_words;
4009 
4010         g1h->old_set_add(r);
4011         _after_used_bytes += r->used();
4012       }
4013       return false;
4014     }
4015 
4016     void complete_work() {
4017       G1CollectedHeap* g1h = G1CollectedHeap::heap();
4018 
4019       _evacuation_info->set_regions_freed(_local_free_list.length());
4020       _evacuation_info->increment_collectionset_used_after(_after_used_bytes);
4021 
4022       g1h->prepend_to_freelist(&_local_free_list);
4023       g1h->decrement_summary_bytes(_before_used_bytes);
4024 
4025       G1Policy* policy = g1h->policy();
4026       policy->add_bytes_allocated_in_old_since_last_gc(_bytes_allocated_in_old_since_last_gc);
4027 
4028       g1h->alloc_buffer_stats(G1HeapRegionAttr::Old)->add_failure_used_and_waste(_failure_used_words, _failure_waste_words);
4029     }
4030   };
4031 
4032   G1CollectionSet* _collection_set;
4033   G1SerialFreeCollectionSetClosure _cl;
4034   const size_t* _surviving_young_words;
4035 
4036   size_t _rs_length;
4037 
4038   volatile jint _serial_work_claim;
4039 
4040   struct WorkItem {
4041     uint region_idx;
4042     bool is_young;
4043     bool evacuation_failed;
4044 
4045     WorkItem(HeapRegion* r) {
4046       region_idx = r->hrm_index();
4047       is_young = r->is_young();
4048       evacuation_failed = r->evacuation_failed();
4049     }
4050   };
4051 
4052   volatile size_t _parallel_work_claim;
4053   size_t _num_work_items;
4054   WorkItem* _work_items;
4055 
4056   void do_serial_work() {
4057     // Need to grab the lock to be allowed to modify the old region list.
4058     MutexLocker x(OldSets_lock, Mutex::_no_safepoint_check_flag);
4059     _collection_set->iterate(&_cl);
4060   }
4061 
4062   void do_parallel_work_for_region(uint region_idx, bool is_young, bool evacuation_failed) {
4063     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4064 
4065     HeapRegion* r = g1h->region_at(region_idx);
4066     assert(!g1h->is_on_master_free_list(r), "sanity");
4067 
4068     Atomic::add(r->rem_set()->occupied_locked(), &_rs_length);
4069 
4070     if (!is_young) {
4071       g1h->hot_card_cache()->reset_card_counts(r);
4072     }
4073 
4074     if (!evacuation_failed) {
4075       r->rem_set()->clear_locked();
4076     }
4077   }
4078 
4079   class G1PrepareFreeCollectionSetClosure : public HeapRegionClosure {
4080   private:
4081     size_t _cur_idx;
4082     WorkItem* _work_items;
4083   public:
4084     G1PrepareFreeCollectionSetClosure(WorkItem* work_items) : HeapRegionClosure(), _cur_idx(0), _work_items(work_items) { }
4085 
4086     virtual bool do_heap_region(HeapRegion* r) {
4087       _work_items[_cur_idx++] = WorkItem(r);
4088       return false;
4089     }
4090   };
4091 
4092   void prepare_work() {
4093     G1PrepareFreeCollectionSetClosure cl(_work_items);
4094     _collection_set->iterate(&cl);
4095   }
4096 
4097   void complete_work() {
4098     _cl.complete_work();
4099 
4100     G1Policy* policy = G1CollectedHeap::heap()->policy();
4101     policy->record_rs_length(_rs_length);
4102     policy->cset_regions_freed();
4103   }
4104 public:
4105   G1FreeCollectionSetTask(G1CollectionSet* collection_set, G1EvacuationInfo* evacuation_info, const size_t* surviving_young_words) :
4106     AbstractGangTask("G1 Free Collection Set"),
4107     _collection_set(collection_set),
4108     _cl(evacuation_info, surviving_young_words),
4109     _surviving_young_words(surviving_young_words),
4110     _rs_length(0),
4111     _serial_work_claim(0),
4112     _parallel_work_claim(0),
4113     _num_work_items(collection_set->region_length()),
4114     _work_items(NEW_C_HEAP_ARRAY(WorkItem, _num_work_items, mtGC)) {
4115     prepare_work();
4116   }
4117 
4118   ~G1FreeCollectionSetTask() {
4119     complete_work();
4120     FREE_C_HEAP_ARRAY(WorkItem, _work_items);
4121   }
4122 
4123   // Chunk size for work distribution. The chosen value has been determined experimentally
4124   // to be a good tradeoff between overhead and achievable parallelism.
4125   static uint chunk_size() { return 32; }
4126 
4127   virtual void work(uint worker_id) {
4128     G1GCPhaseTimes* timer = G1CollectedHeap::heap()->phase_times();
4129 
4130     // Claim serial work.
4131     if (_serial_work_claim == 0) {
4132       jint value = Atomic::add(1, &_serial_work_claim) - 1;
4133       if (value == 0) {
4134         double serial_time = os::elapsedTime();
4135         do_serial_work();
4136         timer->record_serial_free_cset_time_ms((os::elapsedTime() - serial_time) * 1000.0);
4137       }
4138     }
4139 
4140     // Start parallel work.
4141     double young_time = 0.0;
4142     bool has_young_time = false;
4143     double non_young_time = 0.0;
4144     bool has_non_young_time = false;
4145 
4146     while (true) {
4147       size_t end = Atomic::add(chunk_size(), &_parallel_work_claim);
4148       size_t cur = end - chunk_size();
4149 
4150       if (cur >= _num_work_items) {
4151         break;
4152       }
4153 
4154       EventGCPhaseParallel event;
4155       double start_time = os::elapsedTime();
4156 
4157       end = MIN2(end, _num_work_items);
4158 
4159       for (; cur < end; cur++) {
4160         bool is_young = _work_items[cur].is_young;
4161 
4162         do_parallel_work_for_region(_work_items[cur].region_idx, is_young, _work_items[cur].evacuation_failed);
4163 
4164         double end_time = os::elapsedTime();
4165         double time_taken = end_time - start_time;
4166         if (is_young) {
4167           young_time += time_taken;
4168           has_young_time = true;
4169           event.commit(GCId::current(), worker_id, G1GCPhaseTimes::phase_name(G1GCPhaseTimes::YoungFreeCSet));
4170         } else {
4171           non_young_time += time_taken;
4172           has_non_young_time = true;
4173           event.commit(GCId::current(), worker_id, G1GCPhaseTimes::phase_name(G1GCPhaseTimes::NonYoungFreeCSet));
4174         }
4175         start_time = end_time;
4176       }
4177     }
4178 
4179     if (has_young_time) {
4180       timer->record_time_secs(G1GCPhaseTimes::YoungFreeCSet, worker_id, young_time);
4181     }
4182     if (has_non_young_time) {
4183       timer->record_time_secs(G1GCPhaseTimes::NonYoungFreeCSet, worker_id, non_young_time);
4184     }
4185   }
4186 };
4187 
4188 void G1CollectedHeap::free_collection_set(G1CollectionSet* collection_set, G1EvacuationInfo& evacuation_info, const size_t* surviving_young_words) {
4189   _eden.clear();
4190 
4191   double free_cset_start_time = os::elapsedTime();
4192 
4193   {
4194     uint const num_regions = _collection_set.region_length();
4195     uint const num_chunks = MAX2(num_regions / G1FreeCollectionSetTask::chunk_size(), 1U);
4196     uint const num_workers = MIN2(workers()->active_workers(), num_chunks);
4197 
4198     G1FreeCollectionSetTask cl(collection_set, &evacuation_info, surviving_young_words);
4199 
4200     log_debug(gc, ergo)("Running %s using %u workers for collection set length %u",
4201                         cl.name(), num_workers, num_regions);
4202     workers()->run_task(&cl, num_workers);
4203   }
4204   phase_times()->record_total_free_cset_time_ms((os::elapsedTime() - free_cset_start_time) * 1000.0);
4205 
4206   collection_set->clear();
4207 }
4208 
4209 class G1FreeHumongousRegionClosure : public HeapRegionClosure {
4210  private:
4211   FreeRegionList* _free_region_list;
4212   HeapRegionSet* _proxy_set;
4213   uint _humongous_objects_reclaimed;
4214   uint _humongous_regions_reclaimed;
4215   size_t _freed_bytes;
4216  public:
4217 
4218   G1FreeHumongousRegionClosure(FreeRegionList* free_region_list) :
4219     _free_region_list(free_region_list), _proxy_set(NULL), _humongous_objects_reclaimed(0), _humongous_regions_reclaimed(0), _freed_bytes(0) {
4220   }
4221 
4222   virtual bool do_heap_region(HeapRegion* r) {
4223     if (!r->is_starts_humongous()) {
4224       return false;
4225     }
4226 
4227     G1CollectedHeap* g1h = G1CollectedHeap::heap();
4228 
4229     oop obj = (oop)r->bottom();
4230     G1CMBitMap* next_bitmap = g1h->concurrent_mark()->next_mark_bitmap();
4231 
4232     // The following checks whether the humongous object is live are sufficient.
4233     // The main additional check (in addition to having a reference from the roots
4234     // or the young gen) is whether the humongous object has a remembered set entry.
4235     //
4236     // A humongous object cannot be live if there is no remembered set for it
4237     // because:
4238     // - there can be no references from within humongous starts regions referencing
4239     // the object because we never allocate other objects into them.
4240     // (I.e. there are no intra-region references that may be missed by the
4241     // remembered set)
4242     // - as soon there is a remembered set entry to the humongous starts region
4243     // (i.e. it has "escaped" to an old object) this remembered set entry will stay
4244     // until the end of a concurrent mark.
4245     //
4246     // It is not required to check whether the object has been found dead by marking
4247     // or not, in fact it would prevent reclamation within a concurrent cycle, as
4248     // all objects allocated during that time are considered live.
4249     // SATB marking is even more conservative than the remembered set.
4250     // So if at this point in the collection there is no remembered set entry,
4251     // nobody has a reference to it.
4252     // At the start of collection we flush all refinement logs, and remembered sets
4253     // are completely up-to-date wrt to references to the humongous object.
4254     //
4255     // Other implementation considerations:
4256     // - never consider object arrays at this time because they would pose
4257     // considerable effort for cleaning up the the remembered sets. This is
4258     // required because stale remembered sets might reference locations that
4259     // are currently allocated into.
4260     uint region_idx = r->hrm_index();
4261     if (!g1h->is_humongous_reclaim_candidate(region_idx) ||
4262         !r->rem_set()->is_empty()) {
4263       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",
4264                                region_idx,
4265                                (size_t)obj->size() * HeapWordSize,
4266                                p2i(r->bottom()),
4267                                r->rem_set()->occupied(),
4268                                r->rem_set()->strong_code_roots_list_length(),
4269                                next_bitmap->is_marked(r->bottom()),
4270                                g1h->is_humongous_reclaim_candidate(region_idx),
4271                                obj->is_typeArray()
4272                               );
4273       return false;
4274     }
4275 
4276     guarantee(obj->is_typeArray(),
4277               "Only eagerly reclaiming type arrays is supported, but the object "
4278               PTR_FORMAT " is not.", p2i(r->bottom()));
4279 
4280     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",
4281                              region_idx,
4282                              (size_t)obj->size() * HeapWordSize,
4283                              p2i(r->bottom()),
4284                              r->rem_set()->occupied(),
4285                              r->rem_set()->strong_code_roots_list_length(),
4286                              next_bitmap->is_marked(r->bottom()),
4287                              g1h->is_humongous_reclaim_candidate(region_idx),
4288                              obj->is_typeArray()
4289                             );
4290 
4291     G1ConcurrentMark* const cm = g1h->concurrent_mark();
4292     cm->humongous_object_eagerly_reclaimed(r);
4293     assert(!cm->is_marked_in_prev_bitmap(obj) && !cm->is_marked_in_next_bitmap(obj),
4294            "Eagerly reclaimed humongous region %u should not be marked at all but is in prev %s next %s",
4295            region_idx,
4296            BOOL_TO_STR(cm->is_marked_in_prev_bitmap(obj)),
4297            BOOL_TO_STR(cm->is_marked_in_next_bitmap(obj)));
4298     _humongous_objects_reclaimed++;
4299     do {
4300       HeapRegion* next = g1h->next_region_in_humongous(r);
4301       _freed_bytes += r->used();
4302       r->set_containing_set(NULL);
4303       _humongous_regions_reclaimed++;
4304       g1h->free_humongous_region(r, _free_region_list);
4305       r = next;
4306     } while (r != NULL);
4307 
4308     return false;
4309   }
4310 
4311   uint humongous_objects_reclaimed() {
4312     return _humongous_objects_reclaimed;
4313   }
4314 
4315   uint humongous_regions_reclaimed() {
4316     return _humongous_regions_reclaimed;
4317   }
4318 
4319   size_t bytes_freed() const {
4320     return _freed_bytes;
4321   }
4322 };
4323 
4324 void G1CollectedHeap::eagerly_reclaim_humongous_regions() {
4325   assert_at_safepoint_on_vm_thread();
4326 
4327   if (!G1EagerReclaimHumongousObjects ||
4328       (!_has_humongous_reclaim_candidates && !log_is_enabled(Debug, gc, humongous))) {
4329     phase_times()->record_fast_reclaim_humongous_time_ms(0.0, 0);
4330     return;
4331   }
4332 
4333   double start_time = os::elapsedTime();
4334 
4335   FreeRegionList local_cleanup_list("Local Humongous Cleanup List");
4336 
4337   G1FreeHumongousRegionClosure cl(&local_cleanup_list);
4338   heap_region_iterate(&cl);
4339 
4340   remove_from_old_sets(0, cl.humongous_regions_reclaimed());
4341 
4342   G1HRPrinter* hrp = hr_printer();
4343   if (hrp->is_active()) {
4344     FreeRegionListIterator iter(&local_cleanup_list);
4345     while (iter.more_available()) {
4346       HeapRegion* hr = iter.get_next();
4347       hrp->cleanup(hr);
4348     }
4349   }
4350 
4351   prepend_to_freelist(&local_cleanup_list);
4352   decrement_summary_bytes(cl.bytes_freed());
4353 
4354   phase_times()->record_fast_reclaim_humongous_time_ms((os::elapsedTime() - start_time) * 1000.0,
4355                                                        cl.humongous_objects_reclaimed());
4356 }
4357 
4358 class G1AbandonCollectionSetClosure : public HeapRegionClosure {
4359 public:
4360   virtual bool do_heap_region(HeapRegion* r) {
4361     assert(r->in_collection_set(), "Region %u must have been in collection set", r->hrm_index());
4362     G1CollectedHeap::heap()->clear_region_attr(r);
4363     r->clear_young_index_in_cset();
4364     return false;
4365   }
4366 };
4367 
4368 void G1CollectedHeap::abandon_collection_set(G1CollectionSet* collection_set) {
4369   G1AbandonCollectionSetClosure cl;
4370   collection_set_iterate_all(&cl);
4371 
4372   collection_set->clear();
4373   collection_set->stop_incremental_building();
4374 }
4375 
4376 bool G1CollectedHeap::is_old_gc_alloc_region(HeapRegion* hr) {
4377   return _allocator->is_retained_old_region(hr);
4378 }
4379 
4380 void G1CollectedHeap::set_region_short_lived_locked(HeapRegion* hr) {
4381   _eden.add(hr);
4382   _policy->set_region_eden(hr);
4383 }
4384 
4385 #ifdef ASSERT
4386 
4387 class NoYoungRegionsClosure: public HeapRegionClosure {
4388 private:
4389   bool _success;
4390 public:
4391   NoYoungRegionsClosure() : _success(true) { }
4392   bool do_heap_region(HeapRegion* r) {
4393     if (r->is_young()) {
4394       log_error(gc, verify)("Region [" PTR_FORMAT ", " PTR_FORMAT ") tagged as young",
4395                             p2i(r->bottom()), p2i(r->end()));
4396       _success = false;
4397     }
4398     return false;
4399   }
4400   bool success() { return _success; }
4401 };
4402 
4403 bool G1CollectedHeap::check_young_list_empty() {
4404   bool ret = (young_regions_count() == 0);
4405 
4406   NoYoungRegionsClosure closure;
4407   heap_region_iterate(&closure);
4408   ret = ret && closure.success();
4409 
4410   return ret;
4411 }
4412 
4413 #endif // ASSERT
4414 
4415 class TearDownRegionSetsClosure : public HeapRegionClosure {
4416   HeapRegionSet *_old_set;
4417 
4418 public:
4419   TearDownRegionSetsClosure(HeapRegionSet* old_set) : _old_set(old_set) { }
4420 
4421   bool do_heap_region(HeapRegion* r) {
4422     if (r->is_old()) {
4423       _old_set->remove(r);
4424     } else if(r->is_young()) {
4425       r->uninstall_surv_rate_group();
4426     } else {
4427       // We ignore free regions, we'll empty the free list afterwards.
4428       // We ignore humongous and archive regions, we're not tearing down these
4429       // sets.
4430       assert(r->is_archive() || r->is_free() || r->is_humongous(),
4431              "it cannot be another type");
4432     }
4433     return false;
4434   }
4435 
4436   ~TearDownRegionSetsClosure() {
4437     assert(_old_set->is_empty(), "post-condition");
4438   }
4439 };
4440 
4441 void G1CollectedHeap::tear_down_region_sets(bool free_list_only) {
4442   assert_at_safepoint_on_vm_thread();
4443 
4444   if (!free_list_only) {
4445     TearDownRegionSetsClosure cl(&_old_set);
4446     heap_region_iterate(&cl);
4447 
4448     // Note that emptying the _young_list is postponed and instead done as
4449     // the first step when rebuilding the regions sets again. The reason for
4450     // this is that during a full GC string deduplication needs to know if
4451     // a collected region was young or old when the full GC was initiated.
4452   }
4453   _hrm->remove_all_free_regions();
4454 }
4455 
4456 void G1CollectedHeap::increase_used(size_t bytes) {
4457   _summary_bytes_used += bytes;
4458 }
4459 
4460 void G1CollectedHeap::decrease_used(size_t bytes) {
4461   assert(_summary_bytes_used >= bytes,
4462          "invariant: _summary_bytes_used: " SIZE_FORMAT " should be >= bytes: " SIZE_FORMAT,
4463          _summary_bytes_used, bytes);
4464   _summary_bytes_used -= bytes;
4465 }
4466 
4467 void G1CollectedHeap::set_used(size_t bytes) {
4468   _summary_bytes_used = bytes;
4469 }
4470 
4471 class RebuildRegionSetsClosure : public HeapRegionClosure {
4472 private:
4473   bool _free_list_only;
4474 
4475   HeapRegionSet* _old_set;
4476   HeapRegionManager* _hrm;
4477 
4478   size_t _total_used;
4479 
4480 public:
4481   RebuildRegionSetsClosure(bool free_list_only,
4482                            HeapRegionSet* old_set,
4483                            HeapRegionManager* hrm) :
4484     _free_list_only(free_list_only),
4485     _old_set(old_set), _hrm(hrm), _total_used(0) {
4486     assert(_hrm->num_free_regions() == 0, "pre-condition");
4487     if (!free_list_only) {
4488       assert(_old_set->is_empty(), "pre-condition");
4489     }
4490   }
4491 
4492   bool do_heap_region(HeapRegion* r) {
4493     if (r->is_empty()) {
4494       assert(r->rem_set()->is_empty(), "Empty regions should have empty remembered sets.");
4495       // Add free regions to the free list
4496       r->set_free();
4497       _hrm->insert_into_free_list(r);
4498     } else if (!_free_list_only) {
4499       assert(r->rem_set()->is_empty(), "At this point remembered sets must have been cleared.");
4500 
4501       if (r->is_archive() || r->is_humongous()) {
4502         // We ignore archive and humongous regions. We left these sets unchanged.
4503       } else {
4504         assert(r->is_young() || r->is_free() || r->is_old(), "invariant");
4505         // We now move all (non-humongous, non-old, non-archive) regions to old gen, and register them as such.
4506         r->move_to_old();
4507         _old_set->add(r);
4508       }
4509       _total_used += r->used();
4510     }
4511 
4512     return false;
4513   }
4514 
4515   size_t total_used() {
4516     return _total_used;
4517   }
4518 };
4519 
4520 void G1CollectedHeap::rebuild_region_sets(bool free_list_only) {
4521   assert_at_safepoint_on_vm_thread();
4522 
4523   if (!free_list_only) {
4524     _eden.clear();
4525     _survivor.clear();
4526   }
4527 
4528   RebuildRegionSetsClosure cl(free_list_only, &_old_set, _hrm);
4529   heap_region_iterate(&cl);
4530 
4531   if (!free_list_only) {
4532     set_used(cl.total_used());
4533     if (_archive_allocator != NULL) {
4534       _archive_allocator->clear_used();
4535     }
4536   }
4537   assert_used_and_recalculate_used_equal(this);
4538 }
4539 
4540 // Methods for the mutator alloc region
4541 
4542 HeapRegion* G1CollectedHeap::new_mutator_alloc_region(size_t word_size,
4543                                                       bool force) {
4544   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
4545   bool should_allocate = policy()->should_allocate_mutator_region();
4546   if (force || should_allocate) {
4547     HeapRegion* new_alloc_region = new_region(word_size,
4548                                               HeapRegionType::Eden,
4549                                               false /* do_expand */);
4550     if (new_alloc_region != NULL) {
4551       set_region_short_lived_locked(new_alloc_region);
4552       _hr_printer.alloc(new_alloc_region, !should_allocate);
4553       _verifier->check_bitmaps("Mutator Region Allocation", new_alloc_region);
4554       _policy->remset_tracker()->update_at_allocate(new_alloc_region);
4555       return new_alloc_region;
4556     }
4557   }
4558   return NULL;
4559 }
4560 
4561 void G1CollectedHeap::retire_mutator_alloc_region(HeapRegion* alloc_region,
4562                                                   size_t allocated_bytes) {
4563   assert_heap_locked_or_at_safepoint(true /* should_be_vm_thread */);
4564   assert(alloc_region->is_eden(), "all mutator alloc regions should be eden");
4565 
4566   collection_set()->add_eden_region(alloc_region);
4567   increase_used(allocated_bytes);
4568   _eden.add_used_bytes(allocated_bytes);
4569   _hr_printer.retire(alloc_region);
4570 
4571   // We update the eden sizes here, when the region is retired,
4572   // instead of when it's allocated, since this is the point that its
4573   // used space has been recorded in _summary_bytes_used.
4574   g1mm()->update_eden_size();
4575 }
4576 
4577 // Methods for the GC alloc regions
4578 
4579 bool G1CollectedHeap::has_more_regions(G1HeapRegionAttr dest) {
4580   if (dest.is_old()) {
4581     return true;
4582   } else {
4583     return survivor_regions_count() < policy()->max_survivor_regions();
4584   }
4585 }
4586 
4587 HeapRegion* G1CollectedHeap::new_gc_alloc_region(size_t word_size, G1HeapRegionAttr dest) {
4588   assert(FreeList_lock->owned_by_self(), "pre-condition");
4589 
4590   if (!has_more_regions(dest)) {
4591     return NULL;
4592   }
4593 
4594   HeapRegionType type;
4595   if (dest.is_young()) {
4596     type = HeapRegionType::Survivor;
4597   } else {
4598     type = HeapRegionType::Old;
4599   }
4600 
4601   HeapRegion* new_alloc_region = new_region(word_size,
4602                                             type,
4603                                             true /* do_expand */);
4604 
4605   if (new_alloc_region != NULL) {
4606     if (type.is_survivor()) {
4607       new_alloc_region->set_survivor();
4608       _survivor.add(new_alloc_region);
4609       _verifier->check_bitmaps("Survivor Region Allocation", new_alloc_region);
4610     } else {
4611       new_alloc_region->set_old();
4612       _verifier->check_bitmaps("Old Region Allocation", new_alloc_region);
4613     }
4614     _policy->remset_tracker()->update_at_allocate(new_alloc_region);
4615     register_region_with_region_attr(new_alloc_region);
4616     _hr_printer.alloc(new_alloc_region);
4617     return new_alloc_region;
4618   }
4619   return NULL;
4620 }
4621 
4622 void G1CollectedHeap::retire_gc_alloc_region(HeapRegion* alloc_region,
4623                                              size_t allocated_bytes,
4624                                              G1HeapRegionAttr dest) {
4625   policy()->record_bytes_copied_during_gc(allocated_bytes);
4626   if (dest.is_old()) {
4627     old_set_add(alloc_region);
4628   } else {
4629     assert(dest.is_young(), "Retiring alloc region should be young (%d)", dest.type());
4630     _survivor.add_used_bytes(allocated_bytes);
4631   }
4632 
4633   bool const during_im = collector_state()->in_initial_mark_gc();
4634   if (during_im && allocated_bytes > 0) {
4635     _cm->root_regions()->add(alloc_region->next_top_at_mark_start(), alloc_region->top());
4636   }
4637   _hr_printer.retire(alloc_region);
4638 }
4639 
4640 HeapRegion* G1CollectedHeap::alloc_highest_free_region() {
4641   bool expanded = false;
4642   uint index = _hrm->find_highest_free(&expanded);
4643 
4644   if (index != G1_NO_HRM_INDEX) {
4645     if (expanded) {
4646       log_debug(gc, ergo, heap)("Attempt heap expansion (requested address range outside heap bounds). region size: " SIZE_FORMAT "B",
4647                                 HeapRegion::GrainWords * HeapWordSize);
4648     }
4649     _hrm->allocate_free_regions_starting_at(index, 1);
4650     return region_at(index);
4651   }
4652   return NULL;
4653 }
4654 
4655 // Optimized nmethod scanning
4656 
4657 class RegisterNMethodOopClosure: public OopClosure {
4658   G1CollectedHeap* _g1h;
4659   nmethod* _nm;
4660 
4661   template <class T> void do_oop_work(T* p) {
4662     T heap_oop = RawAccess<>::oop_load(p);
4663     if (!CompressedOops::is_null(heap_oop)) {
4664       oop obj = CompressedOops::decode_not_null(heap_oop);
4665       HeapRegion* hr = _g1h->heap_region_containing(obj);
4666       assert(!hr->is_continues_humongous(),
4667              "trying to add code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
4668              " starting at " HR_FORMAT,
4669              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
4670 
4671       // HeapRegion::add_strong_code_root_locked() avoids adding duplicate entries.
4672       hr->add_strong_code_root_locked(_nm);
4673     }
4674   }
4675 
4676 public:
4677   RegisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
4678     _g1h(g1h), _nm(nm) {}
4679 
4680   void do_oop(oop* p)       { do_oop_work(p); }
4681   void do_oop(narrowOop* p) { do_oop_work(p); }
4682 };
4683 
4684 class UnregisterNMethodOopClosure: public OopClosure {
4685   G1CollectedHeap* _g1h;
4686   nmethod* _nm;
4687 
4688   template <class T> void do_oop_work(T* p) {
4689     T heap_oop = RawAccess<>::oop_load(p);
4690     if (!CompressedOops::is_null(heap_oop)) {
4691       oop obj = CompressedOops::decode_not_null(heap_oop);
4692       HeapRegion* hr = _g1h->heap_region_containing(obj);
4693       assert(!hr->is_continues_humongous(),
4694              "trying to remove code root " PTR_FORMAT " in continuation of humongous region " HR_FORMAT
4695              " starting at " HR_FORMAT,
4696              p2i(_nm), HR_FORMAT_PARAMS(hr), HR_FORMAT_PARAMS(hr->humongous_start_region()));
4697 
4698       hr->remove_strong_code_root(_nm);
4699     }
4700   }
4701 
4702 public:
4703   UnregisterNMethodOopClosure(G1CollectedHeap* g1h, nmethod* nm) :
4704     _g1h(g1h), _nm(nm) {}
4705 
4706   void do_oop(oop* p)       { do_oop_work(p); }
4707   void do_oop(narrowOop* p) { do_oop_work(p); }
4708 };
4709 
4710 void G1CollectedHeap::register_nmethod(nmethod* nm) {
4711   guarantee(nm != NULL, "sanity");
4712   RegisterNMethodOopClosure reg_cl(this, nm);
4713   nm->oops_do(&reg_cl);
4714 }
4715 
4716 void G1CollectedHeap::unregister_nmethod(nmethod* nm) {
4717   guarantee(nm != NULL, "sanity");
4718   UnregisterNMethodOopClosure reg_cl(this, nm);
4719   nm->oops_do(&reg_cl, true);
4720 }
4721 
4722 void G1CollectedHeap::purge_code_root_memory() {
4723   double purge_start = os::elapsedTime();
4724   G1CodeRootSet::purge();
4725   double purge_time_ms = (os::elapsedTime() - purge_start) * 1000.0;
4726   phase_times()->record_strong_code_root_purge_time(purge_time_ms);
4727 }
4728 
4729 class RebuildStrongCodeRootClosure: public CodeBlobClosure {
4730   G1CollectedHeap* _g1h;
4731 
4732 public:
4733   RebuildStrongCodeRootClosure(G1CollectedHeap* g1h) :
4734     _g1h(g1h) {}
4735 
4736   void do_code_blob(CodeBlob* cb) {
4737     nmethod* nm = (cb != NULL) ? cb->as_nmethod_or_null() : NULL;
4738     if (nm == NULL) {
4739       return;
4740     }
4741 
4742     _g1h->register_nmethod(nm);
4743   }
4744 };
4745 
4746 void G1CollectedHeap::rebuild_strong_code_roots() {
4747   RebuildStrongCodeRootClosure blob_cl(this);
4748   CodeCache::blobs_do(&blob_cl);
4749 }
4750 
4751 void G1CollectedHeap::initialize_serviceability() {
4752   _g1mm->initialize_serviceability();
4753 }
4754 
4755 MemoryUsage G1CollectedHeap::memory_usage() {
4756   return _g1mm->memory_usage();
4757 }
4758 
4759 GrowableArray<GCMemoryManager*> G1CollectedHeap::memory_managers() {
4760   return _g1mm->memory_managers();
4761 }
4762 
4763 GrowableArray<MemoryPool*> G1CollectedHeap::memory_pools() {
4764   return _g1mm->memory_pools();
4765 }